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  • Scandium in aluminium alloys - Atom probe · A considerable part of the available literature on scandium in aluminium alloys is reviewed. ... behaviour in Al Cu, Al Mg Si,
26
Scandium in aluminium alloys J. Røyset* and N. Ryum A considerable part of the available literature on scandium in aluminium alloys is reviewed. Experimental data and assessments of the binary Al–Sc phase diagram, a wide range of ternary Al–Sc–X phase diagrams and a few higher order phase diagrams are accounted for, with emphasis on the aluminium rich part of the diagrams. The phase which is in equilibrium with Al, Al 3 Sc, can form by several different mechanisms, all of which are described. The precipitation kinetics of Al 3 Sc in binary Al–Sc alloys are discussed, and an overview of the reported influences of ternary alloying elements on the precipitation of Al 3 Sc is given. The Al 3 Sc phase particles can serve as a grain refiner in the Al melt, a dispersoid for controlling the grain structure of the alloy and a strengthening precipitate. Several examples of these three effects are mentioned, both in binary Al–Sc alloys, and in more complex alloys. The reported effects of Sc on the precipitation behaviour in Al–Cu, Al–Mg–Si, Al–Zn–Mg and Al–Li alloys are also revised. A brief account of the effects of Sc additions on the corrosion behaviour of Al and Al-alloys is given. Finally, some views on the current and future use of Sc-containing Al alloys are given. Keywords: Al–Sc, Phase diagrams, Grain refinement, Precipitation, Dispersoids IMR/421 Some trivia about scandium Scandium is element no. 21 in the periodic system. It is a light metal, with density r<3 g cm 23 , and melting point 1541uC. 1 This is in itself an attractive combination of properties for special purposes, but owing to limited availability and high price, scandium metal has virtually no applications at the present time. Some of the areas where scandium is used as an additive or dopant, are (i) Addition as metal and iodide to high intensity halide lamps to make the emitted light spectrum resemble that of sunlight (ii) Dopant in garnets for lasers (iii) Alloying element in aluminium alloys. Scandium and yttrium bear many resemblances to the lanthanides (the elements 57 through 71 in the periodic table). In the technical literature, the term ‘rare earth metals’ (R.E.M.) sometimes means only the lanthanides and sometimes scandium, yttrium and the lanthanides. Throughout this paper, the latter definition is used. As can be seen in Fig. 1, Sc is located close to Ti, Y and Zr in the periodic table, and with respect to interactions with aluminium there are quite a few resemblances between these four elements. Binary aluminium–scandium system Al–Sc phase diagram Apparently, the first publication of the complete Al–Sc phase diagram in English was by Russian scientists at an international conference in the USA in 1964 (Fig. 2). 2 The same diagram appears in English translations of two Russian journals a year later, 3,4 and the phase diagram of these three publications is reproduced in various phase diagram handbooks. 5,6 With small excep- tions, the invariant points from this early investigation have been preserved in phase diagram assessments until recently. 7–10 As one can see, the two elements form four equilibrium intermetallic phases: Al 3 Sc, Al 2 Sc, AlSc and AlSc 2 . The phase which is in thermodynamic equilibrium with Al is Al 3 Sc. In the early work, 2–4 it was concluded that there was a peritectic reaction Liq:zAl 3 Sc~a(Al) occurring at 665uC. Later studies 11–14 have shown that Al and Al 3 Sc form eutectically from the melt Liq:~a(Al)zAl 3 Sc In spite of this, the peritectic temperature of the early work 2–4 has occasionally been used in assessing the Al– Sc phase diagram. 7,15 In the early work, 2–4 it was found that the Al 3 Sc and AlSc 2 phases form peritectically at approx. 1320 and 1195uC, respectively, whereas the Al 2 Sc and AlSc phases were found to form congruently from the melt at approx. 1420 and 1300uC, respectively. It was also found 2–4 that Al 2 Sc and AlSc form a eutectic at approx. 1150uC, and that AlSc 2 and Sc form a eutectic at approx. 945uC. In a later assesment, 9 it is argued that the AlSc 2 phase should be expected to melt congruently rather than peritectically. The phase diagram of Refs 2–4 indicates a melting point of Sc of 1535uC and a transition temperature of Department of Materials Technology, Norwegian University of Science and Technology, N-7491 Trondheim, Norway *Corresponding author. Present address: Hydro Aluminium, R&D Sunndal, PO Box 219, N-6601 Sunndalsøra, Norway, email [email protected] ß 2005 Institute of Materials, Minerals and Mining and ASM International Published by Maney for the Institute and ASM International DOI 10.1179/174328005X14311 International Materials Reviews 2005 VOL 50 NO 1 19

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Page 1: Scandium in aluminium alloys - Atom probe · A considerable part of the available literature on scandium in aluminium alloys is reviewed. ... behaviour in Al Cu, Al Mg Si,

Scandium in aluminium alloys

J Roslashyset and N Ryum

A considerable part of the available literature on scandium in aluminium alloys is reviewed

Experimental data and assessments of the binary AlndashSc phase diagram a wide range of ternary

AlndashScndashX phase diagrams and a few higher order phase diagrams are accounted for with

emphasis on the aluminium rich part of the diagrams The phase which is in equilibrium with Al

Al3Sc can form by several different mechanisms all of which are described The precipitation

kinetics of Al3Sc in binary AlndashSc alloys are discussed and an overview of the reported influences

of ternary alloying elements on the precipitation of Al3Sc is given The Al3Sc phase particles can

serve as a grain refiner in the Al melt a dispersoid for controlling the grain structure of the alloy

and a strengthening precipitate Several examples of these three effects are mentioned both in

binary AlndashSc alloys and in more complex alloys The reported effects of Sc on the precipitation

behaviour in AlndashCu AlndashMgndashSi AlndashZnndashMg and AlndashLi alloys are also revised A brief account of the

effects of Sc additions on the corrosion behaviour of Al and Al-alloys is given Finally some views

on the current and future use of Sc-containing Al alloys are given

Keywords AlndashSc Phase diagrams Grain refinement Precipitation Dispersoids IMR421

Some trivia about scandiumScandium is element no 21 in the periodic system It is alight metal with density rlt3 g cm23 and melting point1541uC1 This is in itself an attractive combination ofproperties for special purposes but owing to limitedavailability and high price scandium metal has virtuallyno applications at the present time Some of the areaswhere scandium is used as an additive or dopant are

(i) Addition as metal and iodide to high intensityhalide lamps to make the emitted light spectrumresemble that of sunlight

(ii) Dopant in garnets for lasers(iii) Alloying element in aluminium alloys

Scandium and yttrium bear many resemblances to thelanthanides (the elements 57 through 71 in the periodictable) In the technical literature the term lsquorare earthmetalsrsquo (REM) sometimes means only the lanthanidesand sometimes scandium yttrium and the lanthanidesThroughout this paper the latter definition is used Ascan be seen in Fig 1 Sc is located close to Ti Y and Zrin the periodic table and with respect to interactionswith aluminium there are quite a few resemblancesbetween these four elements

Binary aluminiumndashscandium system

AlndashSc phase diagramApparently the first publication of the complete AlndashScphase diagram in English was by Russian scientists at an

international conference in the USA in 1964 (Fig 2)2

The same diagram appears in English translations oftwo Russian journals a year later34 and the phasediagram of these three publications is reproduced invarious phase diagram handbooks56 With small excep-tions the invariant points from this early investigationhave been preserved in phase diagram assessments untilrecently7ndash10

As one can see the two elements form fourequilibrium intermetallic phases Al3Sc Al2Sc AlScand AlSc2 The phase which is in thermodynamicequilibrium with Al is Al3Sc In the early work2ndash4 itwas concluded that there was a peritectic reaction

LiqzAl3Sc~a(Al)

occurring at 665uC Later studies11ndash14 have shown thatAl and Al3Sc form eutectically from the melt

Liq~a(Al)zAl3Sc

In spite of this the peritectic temperature of the earlywork2ndash4 has occasionally been used in assessing the AlndashSc phase diagram715

In the early work2ndash4 it was found that the Al3Sc andAlSc2 phases form peritectically at approx 1320 and1195uC respectively whereas the Al2Sc and AlSc phaseswere found to form congruently from the melt atapprox 1420 and 1300uC respectively It was alsofound2ndash4 that Al2Sc and AlSc form a eutectic at approx1150uC and that AlSc2 and Sc form a eutectic at approx945uC In a later assesment9 it is argued that the AlSc2

phase should be expected to melt congruently ratherthan peritectically

The phase diagram of Refs 2ndash4 indicates a meltingpoint of Sc of 1535uC and a transition temperature of

Department of Materials Technology Norwegian University of Scienceand Technology N-7491 Trondheim Norway

Corresponding author Present address Hydro Aluminium RampDSunndal PO Box 219 N-6601 Sunndalsoslashra Norway emailJosteinRoysethydrocom

2005 Institute of Materials Minerals and Mining and ASM InternationalPublished by Maney for the Institute and ASM InternationalDOI 101179174328005X14311 International Materials Reviews 2005 VOL 50 NO 1 19

a-Sc to b-Sc of 1350uC In the phase diagram assessmentof Ref 8 these temperature are adjusted to 1541 and1337uC respectively

A recent experimental investigation of selected com-positions in the AlndashSc phase diagram1617 deviatessignificantly from the early work2ndash4 Most of thedetermined invariant temperatures are different It isalso found that the AlSc2 phase melts congruently assuggested previously9 and at a temperature of approx1300uC The most prominent difference however is thefinding of an extensive solid solubility of Al in b-Sc anda eutectoid transformation

b-Sc~AlSc2za-Sc

occurring at approx 970uC A sketch of the completephase diagram based on these new findings16 is shown inFig 3

The four intermetallic phases are drawn as stoichio-metric line-compounds in all the published phasediagrams However it has been suggested16 that theAlSc phase is slightly off-stoichiometric and that ithas a composition range of approximately 52ndash54Sc

Microstructural observations18 indicate that the Al3Scphase also has a solubility range An overview of thedifferent phases in the AlndashSc system is given in Table 18

Reported enthalpies of formation for the intermetallicphases are given in Table 2 There is a considerabledifference in the data reported in Refs 16 and 19 Acomparison between the two data sets as well as withother works (not included in the present review) done inRef 16 shows that the data of Ref 16 are more in linewith other reported results

Al rich side of AlndashSc phase diagramAs for the eutectic reaction

Liq~a(Al)zAl3Sc

the reported eutectic temperature varies between 655and 659uC11ndash142223 The eutectic composition is approx06 wt-1114 and the solid solubility of Sc in Al at theeutectic temperature is approx 035 wt-12

Table 1 Overview of phases in AlndashSc system8

Phase Pearson symbol Space group Strukturbericht designation Prototype Lattice parameter A Density g cm23

Al cF4 Fm3m A1 Cu a540496 2699Al3Sc cP4 Pm3m L12 AuCu3 a54103 3026Al2Sc cF24 Fd3m C15 Cu2Mg a57582 3015AlSc cP2 Pm3m B2 CsCl a53450 2909AlSc2 hP6 P63mmc B82 Ni2In a54888 c56166 3043b-Sc cI2 Im3m A2 W a5373 (estimated) 2880 (estimated)a-Sc hP2 P63mmc A3 Mg a533088 c552680 29890

Table 2 Some reported enthalpies of formation[kJ mol21] for intermetallic phases in AlndashScsystem

Reference Enthalpy Al3Sc Al2Sc AlSc AlSc2

19 2DH 0298 2395 2824 1240 847

20 2DH 00 193

16 2DH 0300 174 142 918 110

21 2DH 00 180

Calculated

1 Periodic table of elements with Al main alloying ele-

ments in Al-alloys and rare earth elements

2 Sketch of first reported AlndashSc phase diagram2ndash4

3 Sketch of AlndashSc binary phase diagram eutectic tem-

perature of AlzAl3Sc is adapted from Ref 10 peritec-

tic temperature of Al3Sc and temperature of congruent

melting of Al2Sc are calculated in Ref 16 all other bin-

ary invariant points are reported experimental values

in Ref 16

Roslashyset and Ryum Scandium in aluminium alloys

20 International Materials Reviews 2005 VOL 50 NO 1

The solvus line of Sc in Al has been estimated byseveral researchers and over a wide temperaturerange111224ndash31 All the reported measurements aresummarised in Fig 4 There is some spread in theresults most noticeably between data from Russian andnon-Russian papers

In most practical cases solidification of alloys occursunder non-equilibrium conditions Thus the finalmicrostructure might be different from what theequilibrium phase diagram predicts In the case of diluteAlndashSc alloys this is illustrated in a metastable statediagram for solidification at a cooling rate of approx100 K s2132 The temperature of the eutectic reactiondecreases by 3ndash4uC and the eutectic compositionincreases from approx 06 wt- to approx 07 wt-Also the maximum solid solubility of Sc in Al increasesto approx 06 wt-32

Ternary quaternary and higher orderAlndashScndashX(ndashX2ndashX3ndashhellip) phase diagramsA wide range of ternary quaternary and higher orderAlndashScndashX(ndashX2ndashX3ndashhellip) phase diagrams has been reportedin the literature the majority in Russian journals Someof the Russian journals do not have parallel Englishtranslations and thus these data are less accessible forthe non-Russian reader However a good overview ofthe majority of the published material is available33 Notall of the published phase diagrams comprise the fullcomposition ranges In the present review the emphasisis placed on phase diagrams of AlndashSc with elements thatare technologically important alloying elements withaluminium

Ternary phase diagrams withprecipitate-forming elementsAlndashMgndashSc

The AlndashMgndashSc phase diagram seems to be the AlndashScndashXdiagram that is best described in the technical literatureIn an investigation of AlndashMgndashSc alloys with up to

26 wt-Mg and 3 wt-Sc25 a ternary eutectic

Liq~aAlzAl3Mg2zAl3Sc

was observed at 447uC Two vertical cross-sections andone isothermal section at 430uC of the phase diagramwere constructed (Fig 5) It was found that Mg and Scmutually reduce each otherrsquos solid solubility in Al Thelsquocornerrsquo of the a-Al field was determined to be at105 wt-Mg and 0007 wt-Sc at 430uC No ternaryAlMgSc phases were observed

In another investigation a vertical cross-section of theAl rich corner at a constant Sc level of 03 wt- wasconstructed34 No ternary phases were reported Thisphase diagram suggests probably as a result of a lapseby the authors that 03 wt-Sc is a hypereutecticcomposition in binary AlndashSc

Odinaev and co-workers explored the AlndashMgndashScsystem for the whole AlndashMg range and for Sc contentsup to 333 at-Sc3536 An isothermal section at 400uC35

was constructed No ternary phases were observed in theregion examined A liquidus surface and three quasi-binary cross-sections were also constructed36 Threequasibinary eutectics three ternary eutectics and oneternary peritectic were observed in the examinedcomposition range The temperature for the eutecticreaction shown above was determined to be 435uCand the composition was found to be 625 at-Al366 at-Mg and 09 at-Sc

In a recent study37 the isothermal cross-section at350uC was determined experimentally in the regiondelimited by the phases Al3Mg2 Al3Sc AlSc2 MgScand Mg meaning that the Al- and Sc-corners of thephase diagram were not explored There are somediscrepancies between the phase relations found in thiswork37 and those found by Odinaev et al35 However noternary AlMgSc phases were found in Ref 37 either Allthe four intermetallic (AlSc) phases were found todissolve a few percent Mg seemingly by substituting AlFor Al3Sc this observation is sustained by othermeasurements38 where some Mg content in Al3Scprecipitates was found by three-dimensional atom probemicroscopy In Ref 37 a calculated liquidus surface and

4 Reported values of Al solvus line in AlndashSc phase dia-

gram full line is solvus estimate assuming regular

solution and applying maximum solubility as

assessed in Ref 10 and experimental data of Ref 31

5 Isothermal section of Al-corner of AlndashMgndashSc phase

diagram at 430uC redrawn from Ref 25

Roslashyset and Ryum Scandium in aluminium alloys

International Materials Reviews 2005 VOL 50 NO 1 21

several calculated vertical and isothermal cross-sectionsare also presented Additional phase diagram calcula-tions are reported in a separate paper39

The phase relations in a diffusion couple between Alndash177 wt-Sc and pure Mg at 430uC have also beenstudied40 No ternary phases were reported and the a-Alwas found to be in equilibrium with Al3Sc and Al3Mg2in accordance with earlier work253537 The maximumsolid solubility of Mg and Sc in a-Al at this temperaturewas reported to be 1527 at- (14 wt-) and 033 at-(055 wt-) respectively Both these solubilities and inparticular that of Sc is higher than what has been foundearlier25 Considering the binary AlndashSc system wherethe solubility of Sc in a-Al is only approx 0025 wt- at430uC the high solubility of Sc reported in Ref 40 forthe ternary system is rather unlikely It is possible thatfine-scale Al3Sc precipitates embedded in the a-Almatrix have been included in the electron probeanalyses and thus giving too high a value for the Sccontent in solid solution

AlndashCundashSc

Two ternary phases AlCuSc and AlCu2Sc werereported in an early investigation41 A later investigationof the Al-corner of the phase diagram42 revealed that aternary (AlCuSc) phase named the lsquoW-phasersquo couldbe in thermodynamic equilibrium with a-Al Thefollowing ternary invariant equilibria were found

LiqzAl3Sc~aAlzW(5720C)

Liq~aAlzAl2CuzW(5460C)

Isothermal sections of the Al-corner at 450 and 500uChave been constructed43 (Fig 6) The solid solubility ofCu in Al was found to decrease somewhat withincreasing Sc content whereas the solid solubility ofSc in Al was not found to be influenced by the Cucontent The W-phase was suggested to be the com-pound Al54ndash8Cu66ndash4Sc43 A liquidus surface of the Al-corner has also been constructed44

A more thorough review on the AlndashCundashSc system isavailable in the literature45

AlndashScndashSi

An isothermal section at 497uC has been constructed forthe entire system46 A ternary phase AlSc2Si2 wasidentified This phase frequently referred to as the lsquoV-phasersquo was found to be in thermodynamic equilibrium withAl3Sc Al Si and ScSi at this temperature A projection ofthe liquidus surface of the Al-corner has also been made47

Two ternary invariant reactions were reported

LiqzAl3Sc~aAlzV(6170C)

Liq~aAlzSizV(5740C)

Vertical cross-sections and isothermal sections of the Al-corner are reviewed in Ref 33 The 550uC isothermalsection is redrawn in Fig 7 It seems that the solidsolubility of Sc is not altered by an addition of Siwhereas the solubility of Si decreases somewhat with theSc content

AlndashScndashZn

A sketch of a lsquosemi-isothermalrsquo cross-section of the wholesystem partially at 300uC and partially at 500uC hasbeen reported48 No ternary phases were found in thisinvestigation The phase relations in the Al rich rangewere found to be limited by the subsystem AlndashZnndashAl3Sc

Another investigation of the subsystem AlndashZnndashAl2Scconfirmed that no ternary compounds are found in thiscomposition range49 The liquidus surface was con-structed It is suggested that the section ZnndashAl2Sc is aquasibinary simple eutectic A certain mutual solidsolubility of Zn and Al2Sc is indicated on the verticalcross-section although no measurements of the compo-sitions are presented In addition to the quasibinaryeutectic one ternary peritectic and one ternary eutecticreaction was found The ternary eutectic reaction

Liq~aAlzZnzAl3Sc

was found to occur at 367uC

AlndashLindashSc

An investigation of the phase relations in the Al-corner(up to 5 wt-Li and 3 wt-Sc) at 450uC revealed that

6 Isothermal section of Al-corner of AlndashCundashSc phase dia-

gram at 500uC redrawn from Ref 437 Isothermal section of Al-corner of AlndashScndashSi phase dia-

gram at 500uC redrawn from Ref 33

Roslashyset and Ryum Scandium in aluminium alloys

22 International Materials Reviews 2005 VOL 50 NO 1

a-Al could be in equilibrium with either Al3Sc or AlLi50

No ternary phases were observed Thermal analysesindicated that the ternary eutectic reaction

Liq~aAlzAl3SczAlLi

occurs at approximately 595uC It has been stated47 thatthere are only minor mutual effects of Sc and Li on theseelementsrsquo solid solubility in a-Al

This statement is confirmed in another investigation51

where the AlndashAlLindashAlSc subsystem is investigated At450uC it is found that the AlLi phase can be inequilibrium with Al3Sc Al2Sc and AlSc No significantsolubility of Li in Al3Sc was observed Several verticalcross-sections are constructed

It should be noted that the existence of a ternaryAl3(LiSc) phase has been reported52 which is indisagreement with the observations above

Ternary phase diagrams withdispersoid-forming elementsAlndashScndashZr

It has been shown53 that at 600uC the Al-corner consistsof the phase fields a-AlzAl3Sc a-AlzAl3SczAl3Zrand a-AlzAl3Zr Further it was discovered that there isa significant solid solubility of Zr in the Al3Sc phase(approx 35 wt-) and some solid solubility of Sc in theAl3Zr phase (approx 5 wt-) The lattice parameter ofAl3Sc was found to decrease when the phase dissolvesZr and likewise the lattice parameter of the Al3Zr wasfound to decrease when that phase dissolves Sc Foralloys in the a-AlzAl3Sc phase field the wt-Zrwt-Scratio in the Al3Sc particles was found to be approx 22times the wt-Zrwt-Sc ratio of the alloy53 Isothermalsections of the Al-corner at 550 and 600uC are alsoconstructed54 (Fig 8)

In another investigation55 two vertical cross-sectionsin the Al-corner were constructed and a ternaryperitectic reaction

LiqzAl3Zr~aAlzAl3Sc

was found to take place at 659uC

The 500uC isothermal section of the whole phasediagram has been investigated56 It is already knownthat Sc and Zr are completely miscible in the solid stateHere it was also found that the compounds AlSc2 andAlZr2 are completely miscible The extensions of theother single-phase fields are determined with variousdegrees of accuracy The solubility of Zr in Al3Sc wasfound to be 6 at- (approx 16 wt-) whereas thesolubility of Sc in Al3Zr was found to be 65 at-(approx 73 wt-) Contrary to Ref 53 the latticeparameter of Al3Sc was found to increase with increas-ing Zr content The lattice parameter of Al3Zr howeverwas found to decrease with increasing Sc content whichis in accordance with the findings of Ref 53

The section Al3ScndashAl3Zr at 1200uC has recently beeninvestigated57 The solubility of Sc in Al3Zr was reportedto be in the range 3ndash5 at- and the solubility of Zr inAl3Sc was found to be 122 at- In accordance withRef 53 the lattice parameters of Al3Sc and Al3Zr decreasewith increasing content of Zr and Sc respectively

AlndashFendashSc

The available data on this system is reviewed in Ref 33and an isothermal section at 500uC is reproduced Threeternary AlndashFendashSc phases are reported The Al-corner ofthe isothermal section however seems to be limited bythe subsystem AlndashAl3ScndashAl3Fe meaning that the a-Alcannot be in equilibrium with any of the ternary phases

AlndashMnndashSc

The Al-corner of the phase diagram has been investi-gated58 No ternary phases were observed meaning thatin the solid state only the Al3Sc and the Al6Mn phasecan be in equilibrium with a-Al An addition of Mn doesnot noticeably decrease the solid solubility of Scwhereas an addition of Sc causes a distinct decrease inthe solubility of Mn Two isothermal sections weremade one at 500uC (Fig 9) and one at 600uC Thelsquocornerrsquo of the a-phase field was reported to be at008 wt-Sc and 02 wt-Mn at 500uC and at 02 wt-Scand 055 wt-Mn at 600uC

8 Isothermal section of Al-corner of AlndashScndashZr phase dia-

gram at 600uC redrawn from Ref 54

9 Isothermal section of Al-corner of AlndashMnndashSc phase

diagram at 500uC redrawn from Ref 58

Roslashyset and Ryum Scandium in aluminium alloys

International Materials Reviews 2005 VOL 50 NO 1 23

Two vertical cross-sections were also constructed Aternary eutectic

Liq~aAlzAl6MnzAl3Sc

at 649uC was identified Several alloys in the sectionAl3ScndashAl6Mn have also been investigated59 and all werefound to comprise a mixture of the two binary phasesLattice parameter measurements of the Al3Sc phasewere interpreted as an indication of a slight solidsolubility of Mn in Al3Sc

AlndashCrndashSc

Alloys in the composition range 30ndash100 at-Al havebeen studied60 and an isothermal cross-section at 500uCwas constructed No ternary phases were identified Thephases that can be in equilibrium with the a-Al are thusAl7Cr and Al3Sc The solubility of Cr in the Al3Sc phasewas found to be considerable approximately 11 at-

Other ternary AlndashScndashX phase diagramsAlndashMondashSc

An isothermal cross-section at 550uC has been con-structed for the subsystem AlndashAl2ScndashAl2Mo61 Noternary phases were reported The phases in equilibriumwith a-Al were found to be Al3Sc and Al12Mo

AlndashScndashV

The section Al3ScndashAl21V2 has been studied62 and thevertical cross-section was constructed No ternaryphases were observed Solid solubilities of V in theAl3Sc phase of 14 at- and of Sc in Al21V2 of 25 at-are reported although a considerably higher maximumsolubility of V in Al3Sc is suggested in the vertical cross-section A quasibinary eutectic reaction

Liq~Al3SczAl21V2

is reported to occur at 917 K (644uC)The section Al3ScndashAl3V at 1200uC has also been

studied57 The solubilities of V in Al3Sc and Sc in Al3Vare reported to be 27 and 07 at- respectively WhenV was dissolved in Al3Sc the lattice parameter of Al3Scwas found to decrease

AlndashScndashTi

No ternary phase diagram is available The sectionAl3ScndashAl3Ti at 1200uC has been studied57 A solubilityof Ti in Al3Sc of almost 125 at- was found whichcorresponds to almost half of the Sc being substituted byTi The lattice parameter of Al3Sc was found to decreasesharply with increasing Ti content For the Al3Ti phasethe solubility of Sc was found to be approx 5 at-

AlndashCondashSc

The ternary system for 0ndash70 at-Sc has been investi-gated63 Three ternary (AlCoSc)-phases were identifiedThe only phases found to be in equilibrium with a-Alwere the binary phases Al3Sc and Al9Co2 An isothermalsection at 600uC and the vertical cross-sections Al3ScndashAl9Co2 and Al3ScndashAl9Co3Sc2 were constructed Thelsquocornerrsquo of the a-phase field was reported in the text to beat 15 at-Co and 05 at-Sc although in a tablethe numbers 02 at-Co and 01 at-Sc are reportedThe solubilities of Co in the Al3Sc phase and of Sc in theAl9Co2 phase were found to be 12 and 01 at-

respectively However in the vertical cross-sections it issuggested that the solubility of Co in Al3Sc may besignificantly higher at higher temperatures The latticeparameter of Al3Sc was not found to change withincreasing Co content

AlndashScndashSr

The subsystem AlndashAl2ScndashAl4Sr has been studied64 andan isothermal section at 500uC was constructed Noternary phases were detected meaning that the phases inequilibrium with a-Al were found to be Al3Sc and Al4SrThe solubility of Sc in Al4Sr and of Sr in Al3Sc wasfound to be low typically less than 15ndash2 at-

AlndashBendashSc

A study of the binary BendashSc system and the ternary AlndashBendashSc system for up to 20 at-Sc (or 30 wt-Sc) hasbeen reported65 The 600uC isothermal section for theinvestigated ternary composition range was constructedNo ternary phases were observed The a-Al can be inequilibrium with either Be Be13Sc or Al3Sc It is sug-gested that the section AlndashBe13Sc may be quasi-eutectic

AlndashBandashSc

An isothermal section at 500uC has been constructed66

No ternary phases were reported and a-Al is inequilibrium with Al4Ba and Al3Sc The solubility of Scin Al4Ba and of Ba in Al3Sc was reported to be less than2 at-

AlndashNndashSc

The region AlndashAlNndashScNndashSc has been investigated67 Aperovskite-type ternary phase AlN12xSc3 was reportedand an isothermal section at 1000uC was constructed Inthe Al-corner the Al melt was reported to be inequilibrium with AlN and Al3Sc

Quaternary and higher order AlndashScndashXndashX2(ndashX3hellip)phase diagramsAlndashMgndashScndashZr

The published material is limited to investigations onAl rich alloys A part of the liquidus surface of the6 wt-Mg section has been determined experimentallyfor the composition range 0ndash07 wt-Sc and 0ndash04 wt-Zr68 The 500uC isothermal phase relations inthe Al-corner of the 6 wt-Mg section has also beeninvestigated69 for Sc and Zr concentrations of up to3 wt- and 4 wt- respectively No ternary or qua-ternary phases were observed Likewise the 430uC iso-thermal phase relations of the 4 at-Mg (y35 wt-Mg)section have been investigated for up to 12 at-Sc(2 wt-Sc) and up to 25 at-Zr (8 wt-Zr)7071 Noternary or quaternary phases were observed in thepresent study either The Al3Sc phase was found todissolve an amount of 122 at-Zr corresponding to asubstitution of almost 50 of the Sc lattice positionswhereas the solubility of Sc in Al3Zr was 44 at-which corresponds to a substitution of almost 20 ofthe Zr lattice positions Figure 4 in Refs 70 and 71suggests that the Al content in the Al3Zr-phase increaseswith increasing Sc content however this is not sub-stantiated in the text

Roslashyset and Ryum Scandium in aluminium alloys

24 International Materials Reviews 2005 VOL 50 NO 1

AlndashMgndashScndashTindashZr

A vertical cross-section of the AlndashMgndashScndashTindashZr phasediagram for 03 wt-Sc 015 wt-Ti 015 wt-Zrand 0ndash10 wt-Mg has been constructed34 Accord-ing to this diagram the Al3Zr phase is the first andAl3Sc the last to form during solidification of thealloys No ternary quaternary or quinary phases arereported

AlndashZnndashMgndashCundashZrndashSc

A vertical cross-section of the full system as well asseveral sections of various sub-systems have beenconstructed72 For the full system a section at8 wt- Zn 2 wt-Cu 03 wt-Zr and 03 wt-Scwas constructed where Mg varies from 0 to 8 wt-The only reported Sc-containing sub-system is thatof AlndashZnndashMgndashCundashSc Here a vertical cross-sectionis constructed with the same levels of Zn Cu and Scas in the full system whereas Mg varies from 0 to65 wt-

No phases other than those known from the lowerorder systems were reported Amongst the findings it isinteresting to note that in the solid state Al3Sc isreported to be an equilibrium phase for all theinvestigated compositions It is also interesting to notethat the Sc-containing W-phase (Al54ndash8Cu66ndash4Sc see thesection on the AlndashCundashSc ternary system) is an equili-brium phase at low Mg content and disappears as theMg content increases

AlndashLindashMgndashSc

The 400uC isothermal phase relations of the 02 wt-Scsection have been investigated for the composition range0ndash6 wt-Mg and 0ndash5 wt-Li73 The a-Al was found tobe in equilibrium with AlLi Al2LiMg and Al3Sc Noquaternary phases were observed This investigation isalso summarised in Ref 50

AlndashCundashLindashSc

The aluminium rich corner of the system has beeninvestigated for alloys with 06 wt-Sc and with Cu andLi in the range 0ndash16 wt- and 0ndash4 wt- respectively74

No quaternary phases were reported Two sections ofthe phase diagram were constructed a section of the470uC isothermal tetrahedron at 06 wt-Sc and avertical section at 06 wt-Sc and 26 wt-Li Twoquaternary invariant equilibria were found and thetemperatures of the invariant points were estimated

Al3Sc phaseRechkin and co-workers were to the authorsrsquo knowl-edge the first to publish a paper in an internationaljournal identifying the Al3Sc phase75 The phase wasidentified as cubic with lattice parameter a5410 A Afew years later the lattice structure was reported to be ofthe Cu3Au type76 The atomic arrangement of the Al3Scphase is shown in Fig 10 The structure can bedescribed as ordered face-centred cubic (fcc) althoughin crystallographic terminology the Al3Sc structure isactually a simple cubic lattice with four atoms (one Scand three Al atoms) associated with each lattice pointThis particular atomic arrangement is nominated L12

and is found in several intermetallic compounds forinstance Ni3Al Ni3Fe and Cu3Au

Some efforts have been made in characterising theproperties of the Al3Sc phase A compilation of someresults is given in Table 3 The motivation for themajority of the investigations seems to be one of thethree following

(i) the Al3Sc phase has a density of 303 g cm23 andit melts peritectically at approx 1320uC This canmake the Al3Sc phase an attractive candidate asa material for lightweight high temperaturestructural applications205777ndash86

(ii) in order to understand the effect of Al3Scprecipitation in Al-alloys it is necessary to gainmore knowledge about the Al3Sc phase578187ndash91

(iii) the Al3Sc is an excellent model phase forstudying basic properties of intermetalliccompounds7990ndash98

10 Atomic arrangement of Al3Sc phase

Table 3 Some reported properties of Al3Sc phase

ReferenceE GPa(Youngrsquos modulus) n (Poissonrsquos ratio)

CTE (Coefficient ofthermal expansion) 1026 K21

(111) APB energymJ m22

(100) APB energymJ m22

88 Approx 11120 166 020 Max 670 45079 166 022 31399 1628 0204

1642iexcl19 0201iexcl000189 16

Reported to decrease linearly with increasing temperature to approx 97 GPa at 550uCCalculatedExperimental

Roslashyset and Ryum Scandium in aluminium alloys

International Materials Reviews 2005 VOL 50 NO 1 25

Formation of Al3Sc in AlndashSc alloysThere are at least four ways that the Al3Sc phase canform in dilute binary AlndashSc alloys

1 Upon solidification of hypereutectic alloys (Sc

approx 06 wt-) Al3Sc is the first phase to form

2 The solidification of hypo- and hypereutectic alloysends with formation of eutectic AlzAl3Sc

3 Al3Sc can precipitate discontinuously from super-saturated solid solution

4 Al3Sc can precipitate continuously (nucleation andgrowth) from supersaturated solid solution

Primary Al3ScAccording to the binary phase diagram primary Al3Scshould form during solidification of all alloys with Sccontent higher than approx 06 wt- ie higher thanthe eutectic composition Formation of primary Al3Sc inAlndash07 wt-Sc melts cooled at 102ndash103 K s21 has beenreported1832 According to the metastable state dia-gram32 this alloy composition is close to the eutectic oneat these cooling rates

Primary Al3Sc is reported to have a highly facetedmorphology1318100ndash102 The observation of a cubicmorphology in a slowly cooled Alndash87 wt-Sc alloyindicates that the facet planes in this case are thecrystallographic (100) planes13 Brodova et al100ndash102

have investigated the microstructure of rapidly cooledAlndash2 wt-Sc alloy They found that the dominantmorphology of primary Al3Sc was dependent on boththe cooling rate and the initial melt temperature A mapof primary Al3Sc morphologies as a function of theseparameters was constructed and is redrawn in Fig 11

The nucleation mechanism and growth morphologyof primary Al3Sc in an Alndash07 wt-Sc alloy solidified ata cooling rate of 100 K s21 were investigated by Hydeet al103104 Indications were found that the primaryAl3Sc particles nucleate heterogeneously on oxideparticles in the melt The primary Al3Sc particles werefound to grow with a dendritic morphology with theprimary dendrite arms in the crystallographic n110m

direction The overall shape is cubic which is inaccordance with earlier observations

Eutectic Al3ScEutectic AlzAl3Sc has been reported in hyper- as wellas hypoeutectic alloys11 but is scantily described in theliterature Given a eutectic composition of 06 wt- amaximum solid solubility of Sc in Al of 035 wt- andthe specific densities in Table 1 a eutectic formed underequilibrium conditions would contain a volume fractionof approx 063 vol-Al3Sc At high cooling rates thevolume fraction of Al3Sc in the eutectic is probablysomewhat smaller owing to the increased supersatura-tion of Sc in Al

The morphology of the eutectic in an Alndash2 wt-Scalloy is reported to depend on the temperature of themelt before solidification100 For low melt temperaturesthe eutectic is reported to be rodlike for a wide range ofcooling rates For intermediate melt temperatures andhigh cooling rates a lsquodiscontinuous eutecticrsquo is reportedwhereas for high melt temperatures and slow coolingrates a lsquoquasieutecticrsquo structure is reported with Al3Scparticles of almost spherical shape

Hyde et al have reported that during solidification ofan Alndash07 wt-Sc alloy some of the primary Al3Scparticles are pushed ahead of the Al solidification frontand end up at the grain boundaries103104 Thus primaryAl3Sc may be mixed with eutectic Al3Sc in themicrostructure A scanning electron microscopy (SEM)picture showing eutectic Al3Sc at the grain boundaries asdescribed in Refs 103 and 104 is given in Fig 12

Discontinuous precipitation of Al3ScDiscontinuous precipitation of Al3Sc from super-saturated solid solution is often observed in binary AlndashSc alloys131831105 This precipitation mechanism whichis sometimes referred to as cellular precipitation iscommonly described as a decomposition of super-saturated solid solution into a-Al and Al3Sc at a movinggrain boundary The driving force for the grainboundary migration is the volume free energy that isreleased during the precipitation As the grain boundarymoves it leaves behind a characteristic fan shaped array

11 Morphology of primary Al3Sc particles in Alndash2 wt-Sc

alloy as a function of melt overheating and cooling

rate during solidification redrawn from Ref 102

12 SEM image of particle structure of Alndash07 wt-Sc

alloy cooled at a rate of 100 K s21 during solidifica-

tion as described in Refs 103 and 104 primary Al3Sc

particle is seen in centre of grain whereas eutectic

Al3Sc is decorating grain boundaries image is kindly

provided by Dr Kristian Hyde UMIST Manchester UK

Roslashyset and Ryum Scandium in aluminium alloys

26 International Materials Reviews 2005 VOL 50 NO 1

of precipitates In the AlndashSc case the discontinuouslyprecipitated Al3Sc particles have been demonstrated tobe coherent with the aluminium matrix1318

The driving force for discontinuous precipitationincreases with increasing supersaturation of Sc in theAl matrix Thus discontinuous precipitation in binaryAlndashSc is most frequently reported in studies of alloyswith a Sc content of 04 wt- or higher1318106 Stilldiscontinuous precipitation has also occasionally beenreported to occur at lower alloy compositions In an Alndash027 wt-Sc alloy discontinuous precipitation wasobserved over a wide range of temperatures107 In arecent study31105 of precipitation kinetics and mechan-isms in Alndash02 wt-Sc discontinuous precipitation wasfound to take place when the specimens were quencheddirectly from a solutionising temperature in this case600uC to aging temperatures in the range 370ndash490uCFurther C-curves in a temperature-time-transformation(TTT) diagram were established (Fig 13) which showedthat the highest transformation rate of discontinuousprecipitation lies at a higher temperature than thehighest transformation rate of the continuous precipita-tion reaction ie the two precipitation reactions arerepresented by two separate lsquonosesrsquo on the C-curves

It has been shown that discontinuous precipitationcan be suppressed by continuous precipitation if thematerial is cold worked before the precipitation heattreatment13108

As a result of their rather coarse nature andinhomogeneous dispersion discontinuously precipitatedAl3Sc contributes but little to the strength of the alloyand also leads to a smaller amount of Sc in super-saturated solid solution being available for subsequentcontinuous precipitation Thus discontinuous precipita-tion is in general regarded as an undesired precipitationmode

Continuous precipitation of Al3ScContinuous precipitation of Al3Sc is a bulk decomposi-tion process of supersaturated solid solution of Sc in Aland can in the isothermal case be characterised by anucleation stage a growth stage and finally a coarsen-ing stage Apparently the continuous precipitation reac-tion occurs largely by homogeneous nucleation anddiffusion controlled growth and AlndashSc has occasionallybeen used as a model system for studying the mechan-isms of nucleation growth and coarsening107109ndash111

There have been several studies of the continuousprecipitation reaction in binary AlndashSc alloys and up tillnow there is no evidence that any metastable phases areforming before the L12 phase Al3Sc Thus it is assumedthat the equilibrium phase nucleates directly fromsupersaturated solid solution

Even though the nucleation of Al3Sc is frequentlyreported to occur homogeneously throughout the Almatrix there are some examples in the technical litera-ture of reported heterogeneous Al3Sc nucleation ondislocations110112ndash115 and grain boundaries110113115ndash118

In a recent numerical modelling study of continuousprecipitation in AlndashSc alloys111 the effect of hetero-geneous nucleation on dislocations is accounted for Themodel predicts that homogeneous nucleation dominatesat high Sc concentrations and low transformation tem-peratures whereas heterogeneous nucleation is predictedto dominate at low Sc concentrations and high trans-formation temperatures Figure 14 shows a sketch of anucleation map for AlndashSc The shift between homo-geneous and heterogeneous dominance in nucleation isdependent on the dislocation density as indicated in thefigure

The shape of continuously precipitated Al3Sc particlesis most frequently reported to be spherical29112113119ndash129

However it seems that under certain conditions theshape can differ from the spherical one Drits et al130

reported both spherical and star shaped morphologyThe star shaped precipitates had arms growing in thecrystallographic n110m-directions (Star shaped Al3Scprecipitates have also been found after some thermo-mechanical treatments of an AlndashMgndashScndashZr alloy131) InRef 128 precipitates of both cuboidal and sphericalmorphology are found to coexist after certain heattreatments Cauliflower shaped precipitates as well asprecipitates of spherical and cuboidal shapes arereported by Novotny and Ardell110 Bastow andCelotto132 found large oblong Al3Sc particles in an Alndash01 wt-Sc alloy after aging at 400uC for 24 h A facetedshape is suggested in a high-resolution image of anAl3(Sc Zr) precipitate in an AlndashMgndashMnndashZrndashSc alloy133

In a systematic high-resolution transmission electron

13 TTT diagram of precipitation in Alndash02 wt-Sc alloy

after solutionising at 600uC and direct quench to

aging temperature3114 Nucleation map for binary AlndashSc alloys which indi-

cates how the tendency towards heterogeneous ver-

sus homogeneous nucleation is predicted to depend

upon Sc concentration transformation temperature

and dislocation density redrawn from Ref 111

Roslashyset and Ryum Scandium in aluminium alloys

International Materials Reviews 2005 VOL 50 NO 1 27

microscopy (TEM) study of the Al3Sc particle morphol-ogy development during precipitation heat treatment ofbinary AlndashSc alloys by Marquis and Seidman114 it isdemonstrated that the precipitates can take a wide rangeof shapes as they grow depending on Sc content in thealloy transformation temperature and transformationtime Irregular shaped star shaped and cuboidalshaped precipitates were observed under someconditions It was however found that the equilibriumshape of the particles is an equiaxed multifaceted one(Fig 15) Supported by Wulffrsquos construction it wasconcluded that the shape was that of a GreatRhombicuboctahedron This equilibrium morphologyhas been reproduced by computer-simulations ofparticle growth87134 The multifaceted particles caneasily be taken for spherical in a conventional TEMpicture

Kinetics of precipitation of Al3Sc fromsupersaturated solid solutionThe precipitation kinetics of Al3Sc in binary AlndashScalloys is dependent on the precipitation heat treatmenttemperature and on the Sc content in the alloy Acomprehensive overview over the transformationkinetics in terms of C-curves is given by Zakharov135

The C-curves for 5 transformation for a range of AlndashSc alloys are redrawn in Fig 16

Hyland107 studied the homogeneous nucleationkinetics of Al3Sc in a Alndash018 wt-Sc alloy after directquench from 650uC to precipitation temperatures of 288and 343uC He found that after an incubation time t theAl3Sc particles nucleated at a constant rate until thediffusion fields of the individual particles started tooverlap At 288uC the incubation time and time tosignificant diffusion field overlap were estimated to beapprox 245 and 150 min respectively whereas thecorresponding values at 343uC were estimated to beapprox 7 and 20 min respectively

If one assumes that the JohnsonndashMehlndashAvramindashKomolgorov (JMAK) relationship is valid for thisprecipitation reaction one can express the fraction

transformed X as a function of the reaction time t bythe equation

X (t)~1expfrac12k(Dt)n (1)

where k is a constant D is the interdiffusion constant ofSc in Al and the exponent n is dependent on thenucleation rate For the situation described byHyland107 where the precipitates nucleate at a constantrate the value of n should theoretically136 be equal to52

Roslashyset and Ryum31105 applied an alloy and heattreatment method practically equal to that of Hyland107

One should thus expect that the precipitation kineticsshould also be quite similar However Roslashyset andRyum reported that the exponent n of the JMAKrelationship was approx 165ndash185 for the temperaturerange of concern31105 This does not point in thedirection of a constant nucleation rate but rather inthe direction of site saturation ie that all the particlesare nucleated simultaneously which in the JMAKequation would yield an exponent n of 32136 Anoverview of some reported values of n in the JMAKequation is given in Table 4 The majority of the valueslie closer to 32 than to 52 However it is important to

15 High resolution TEM picture along n100m axis of Al3Sc particle in Alndash03 wt-Sc alloy aged at 300uC for 350 h114

(reproduced with permission from Elsevier Science image kindly provided by Dr E A Marquis and Professor D N

Seidman) and various projections of a Great Rhombicuboctahedron

Table 4 Some reported values of n in JMAK equation

Reference n C 0Sc wt-Sc Ttrans uC Note

137 13 030 300 Solution heat treated (SHT) 500uC16026 030 300 SHT 600uC Low n at late stage20026 030 300 SHT 640uC Low n at late stage

29 130ndash149 015 260ndash370145ndash196 025 260ndash370

138 188ndash216 020 240ndash35031 165ndash185 023 270ndash350 SHT 600uC Direct quench to transformation temp

16 C-curves for 5 transformation in a range of binary

AlndashSc alloys redrawn from Ref 135

Roslashyset and Ryum Scandium in aluminium alloys

28 International Materials Reviews 2005 VOL 50 NO 1

note that an n value close to 32 is per se not evidence ofsite saturation

Hyland also showed that a water quench from thesolutionising temperature significantly altered thenucleation kinetics in the subsequent precipitation heattreatment107 The incubation time was dramaticallyshortened which is attributed to the quenched-in excessvacancies and it is also indicated that there might be ashift in the nucleation rate in the early stage ofprecipitation It is suggested that the vacancies mayenhance the diffusion of Sc in Al and that there is apossibility that vacancy clusters act as heterogeneousnucleation sites for Al3Sc precipitates107 Regardless ofwhich mechanism that is operative it is clearly demon-strated that the nucleation kinetics can be dependent onthe thermal history between solutionising and precipita-tion heat treatment

Loss of coherency during growth of Al3ScprecipitatesWhen an Al3Sc particle grows it will sooner or laterreach a critical size where it will be energetically morefavourable to introduce an interface dislocation at theAlAl3Sc interface than to increase the matrix strain Asimple approximation for the critical size can be derivedfrom the lattice parameters assuming that the criticalsize is reached when the misfit over the whole particlediameter equals the Burgers vector of the Al matrix

dcrit~b=d (2)

where b is the Burgers vector of Al and d is themisfit between Al and Al3Sc This approximation yieldsa critical diameter of approx 215 nm at ambienttemperature

The misfit d and thus also the critical diameter dcrit

will depend on the temperature owing to the differencesin thermal expansion between the Al matrix and the

Al3Sc particles The thermal expansion of Al3Sc hasrecently been measured89 and based on the differencesin thermal expansion between Al139 and Al3Sc the misfitas a function of temperature has been calculated89 Thiscalculation is reproduced and shown by the solid line inFig 17

It is however possible to refine this calculationsomewhat140 Whereas the thermal expansion of Al3Sc isexpected to be only because of lattice expansion there isa significant contribution from vacancies on thermalexpansion of Al at high temperatures141 Thus thetemperature effects on the misfit should be calculatedfrom the changes in lattice parameters rather than fromthe linear thermal expansion By subtracting the vacancyeffect on the thermal expansion one achieves atemperature-dependent misfit as represented by thedotted line in Fig 17

A second correction that should be taken into accountis the effect of Sc in solid solution on the latticeparameter of the Al matrix With increasing tempera-ture more Sc is brought into solid solution and it isreported that the lattice parameter of the Al matrixpresumably measured at room temperature increaseslinearly with the Sc content in solid solution142 Thesedata can be used to calculate the effect on the latticeparameter at elevated temperatures under the assump-tion that the relative increase in lattice parameter owingto Sc in solid solution is independent of temperature InRef 142 a figure is presented which shows the measuredlattice parameter as a function of Sc content in solidsolution and a value (dadc)a is reported where a is thelattice parameter of the Al matrix and c is the Sc contentin solid solution in at- The reported value for (dadc)a is 100 times larger than that indicated in thecorresponding figure possibly as a result of a decimalerror in the text Thus in the present exercise 1100th ofthe reported value for (dadc)a is used Using this incombination with the regular solution approximationfor the solvus line of Sc in Al1231 one obtains acorrection for Sc in solid solution on the temperature-dependent misfit as shown in Fig 18 This figure shows

17 Lattice mismatch between Al and Al3Sc as a function

of temperature solid line represents calculation

based on linear thermal expansion of the two phases

dotted line represents correction for vacancies in Al

lattice

18 Corrections of mismatch calculated from linear ther-

mal expansion data as a result of vacancies and to

Al lattice expansion from Sc in solid solution

Roslashyset and Ryum Scandium in aluminium alloys

International Materials Reviews 2005 VOL 50 NO 1 29

both the correction for vacancies and for Sc in solidsolution on the same graph The two corrections are ofapproximately the same magnitude but with oppositesigns Thus the resulting (net) correction is close to zeroand it turns out that the first hand approximation asapplied in Ref 89 is very good in this case

Applying the calculated temperature dependent misfitwith the simple approximation for a critical diameter forloss of coherency one obtains a temperature-dependentcritical diameter as shown in Fig 19

Some examples from the literature of experimentallyobserved critical diameters in binary AlndashSc alloys aresummarised in Table 5 along with some predictions forcritical diameters from Fig 19 There is a fairly goodconsistency between the observations and the measureddiameter is quite close to the simple predictions above

A more refined analysis on the transition fromcoherent to incoherent particles has recently beenperformed145 This analysis is based on the balancebetween the increase in particlematrix interface energyowing to interfacial dislocations and the relaxation inelastic energy in the Al matrix owing to the samedislocations This method yields a predicted criticaldiameter of 246 nm for transition from coherent to

semi-coherent particles at ambient temperature Thetemperature dependence of the critical diameter is nottreated in this analysis

The loss of coherency during isothermal annealing hasbeen reported to be accompanied by an increasedaverage coarsening rate119121137145 The increasedcoarsening rate has been attributed either to diffusionof Sc along dislocation lines119121 or to the increasedparticlematrix interface energy of a semicoherentparticle145 However there are also several data sets inthe literature that do not indicate an increased growthrate after the loss of coherency114128

Al3ScAl interface energyThe interface energy between Al3Sc and the Al matrix isone of the key parameters that governs the nucleationgrowth and coarsening behaviour of Al3Sc in Al and Alalloys The interface energy has been estimated in severalinvestigations either by fitting experimental data toequations that describe nucleation or coarsening or bycalculations A compilation of some of the results isgiven in Table 6 There is considerable spread in thereported values regardless of what approach has beenused for the estimation

Influence of other elements on precipitation ofAl3ScMagnesium

With regard to precipitation mechanism it has beenstated that Mg suppresses the tendency to discontinuousprecipitation of Al3Sc106 In an investigation of pre-cipitation kinetics of Al3Sc in the temperature range300ndash500uC only minor changes in the kinetics (Fig 20)were found when up to 5 wt-Mg was added to an Alndash04 wt-Sc alloy135 It seems that the precipitationreaction is slightly faster in the Mg-containing alloys

Several investigations on age hardening response alsoimply that there is only a small if any effect of Mg onthe precipitation kinetics of Al3Sc23148149 It is how-ever found that the hardness increase from theprecipitation of Al3Sc is somewhat reduced in AlndashMgndashSc alloys compared to binary AlndashSc alloys23148149 InRef 149 it is suggested that some of the Sc is dissolvedin the Al3Mg2 phase and thus the age hardeningpotential is reduced with increasing Mg contentSomewhat contradictory to these observations but

Table 5 Some reported critical diameters for coherencyloss in binary AlndashSc and correspondingtheoretical critical diameters from Fig 19

Reference dcrit nmC0

Scwt-Sc

TtransuC

Theoreticaldcrit nm

119 38ndash40 05137 28ndash30 03 400 308128 32 02 400 450 308 335129 50 02143 40 012 025115 40 025 450ndash500 335ndash37114 40 03 400 450 308 335144 40 02 400ndash460 308ndash341145 30ndash80 02 400ndash490 308ndash362

20 C-curves for 10 and 60 transformation in Alndash

04 wt-Sc and Alndash4 wt-Mgndash04 wt-Sc redrawn

from Ref 135

19 Simple approximation for temperature-dependent criti-

cal diameter for introduction of dislocations on Al

Al3Sc interface

Roslashyset and Ryum Scandium in aluminium alloys

30 International Materials Reviews 2005 VOL 50 NO 1

sustained by Ref 135 it has recently been reported150

that precipitation of Al3Sc at 300 and 350uC occursslightly faster in an Alndash2 wt-Mgndash02 wt-Sc alloythan in an Alndash02 wt-Sc alloy studied previously by thesame researchers117118 and that the correspondinghardness increase is highest in the AlndashMgndashSc alloyThe only reported difference in experimental procedureis the solutionising temperature which was higher forthe AlndashSc alloy (648uC) than for the AlndashMgndashSc alloy(617uC) However given that the nucleation time isshortened by quenched-in vacancies as suggested byHyland107 the difference in homogenisation tempera-ture should be in favour of a faster precipitation of thebinary AlndashSc alloy It should be worthwhile to probedeeper into this observation of different aging responses

Mg in solid solution increases the lattice parameter ofthe Al matrix This is in turn expected to influence thecritical diameter for AlAl3Sc coherency loss as discussedin the section on lsquoLoss of coherency during growth ofAl3Sc precipitatesrsquo above Such an influence on the criticaldiameter is also briefly discussed elsewhere150 A criticaldiameter of 80 nm in an Alndash3 wt-Mgndash02 wt-Sc alloyhas been observed compared to 40 nm in a binary Alndash02 wt-Sc alloy of the same investigation144 Otherresearchers have reported a critical diameter in excess of116 nm in an Alndash63 wt-Mgndash02 wt-Sc alloy151

Computer simulations predict that the AlAl3Scinterface should be enriched in Mg87 These predictionsare confirmed experimentally by three-dimensional atomprobe microscopy of an Alndash2 wt-Mgndash02 wt-Sc alloyaged at 300uC38 Here it was found that the Mg contentat the interface is approximately three times higher thanthe matrix concentration regardless of aging time

Copper

It has been claimed that Cu suppresses the tendencytowards discontinuous precipitation of Al3Sc106

Zakharov and Rostova152 have reported that additionsof up to 14 wt-Cu have only minor effects on theprecipitation kinetics in an Alndash04 wt-Sc alloy Themost noticeable effect is that for temperatures above400uC the late stage of the transformation is sloweddown for the highest Cu contents This does not show in

Fig 21 however where only the 10 and 60transformation curves are included

The W-phase (AlCuSc) was observed in the alloywith the highest Cu content which means that less Sc isavailable for the precipitation of Al3Sc in this alloyAnother investigation on the age hardening response ofAlndash023 wt-Sc and Alndash25 wt-Cundash023 wt-Sc at300uC also implies that the precipitation behaviour ofAl3Sc in the two alloys is similar153154 At 350uC alimited portion of the Al3Sc has been observed tonucleate heterogeneously on coarse hrsquo precipitates155

According to the isothermal sections of the phasediagram43 one should expect the ternary W-phase toform instead of the Al3Sc phase in an alloy with such ahigh CuSc ratio However no observations of the W-phase or other ternary phases were reported from TEMstudies of the Alndash25 wt-Cundash023 wt-Sc alloy thathad been heat treated in the temperature range 300ndash460uC153ndash156 A third investigation on the precipitationin Alndash048 wt-Sc alloys with up to 440 wt-Cu in thetemperature range 100ndash450uC also concludes that no W-phase or other ternary phase forms during the heattreatment157

Copper in solid solution decreases the lattice para-meter of the Al matrix Thus it is expected that the misfitbetween Al and Al3Sc precipitates should be higher in

21 C-curves for 10 and 60 transformation in Alndash

04 wt-Sc and Alndash14 wt-Cundash04 wt-Sc redrawn

from Ref 152

Table 6 Reported values of interphase energy cAlAl3Sc between coherent Al3Sc precipitates and Al matrix

Reference cAlAl3Sc mJ m22 Method of estimation

137 10 Fit of coarsening data to LifshitzndashSlezev equation107 78iexcl20 (288uC) Back-calculation of incubation time

93iexcl20 (343uC)107 123iexcl41 (288uC) Back-calculation of nucleation rate

125iexcl35 (343uC)29 542 (400uC) Fit of coarsening data to Ostwald ripening

632 (430uC)413 (460uC)

146 c(100) 192 (0 K) c(111) 226 (0 K) Pseudopotential calculations147 c(100) 325 (0 K) c(110) 513 (0 K) c(111)

782 (0 K) c(100) 315 (288uC) c(100) 325 (343uC)Atomistic simulation

110 105 Fit of coarsening data to LSW theory31 20ndash300 Fit of coarsening data to Ostwald ripening

for 16 different temperatures111 57 Fit of precipitation model to experimental data145 120 coherent particles Fit of coarsening data

170 semicoherent particles

It is argued in this study that c may be lower in the nucleation stage

Roslashyset and Ryum Scandium in aluminium alloys

International Materials Reviews 2005 VOL 50 NO 1 31

AlndashCundashSc alloys compared to AlndashSc alloys Howeveran experimental investigation of Alndash25 wt-Cundash023 wt-Sc alloy comes to a different conclusion Thelattice misfit strain is found to decrease compared to Alndash02 wt-Sc and the critical diameter for coherency losswas found to be the same in the ternary and the binaryalloy144 It is suggested that these observations may bebecause of the dissolution of some Cu in the Al3Sc phaseand thus that the lattice parameters of both the Al matrixand the Al3Sc precipitates decrease in the ternary alloy

Silicon

It has been found that the onset of precipitation in Alndash04 wt-Sc is only slightly altered when Si contents ofup to 04 wt are introduced in the alloy However thefinal stage of the precipitation reaction is considerablydelayed with increasing Si content135 Figure 22 showsthe effect of addition of a joint of 035 wt-Si and040 wt-Fe There are at least two possible explana-tions for why an Si-addition leads to this behaviour

1 Alloying with Si is known to promote discontin-uous precipitation of Al3Sc106158 It has been shown thatwhen isothermal precipitation of Al3Sc starts discon-tinuously the later stage of the overall transformationcan be very slow31

2 The isothermal section of the phase diagramsuggests that the V-phase (AlSc2Si2) should form inalloys of this composition46 If the V-phase forms lessSc is available for precipitation of Al3Sc

It has been shown157 that for an AlndashScndashSi alloy withsolid solution content of 010 wt-Sc an 110 wt-Sithe only phases to precipitate after heat treatment at200uC are Si and an (AlScSi)-phase possibly the V-phase On the other hand the Al3Sc phase has beenobserved to form in alloys with 04 wt-Sc and up to08 wt-Si159160

Zinc

It has been reported that additions of up to 5 wt- Znhave only minor effects on the precipitation kinetics ofan Alndash04 wt-Sc alloy135 (Fig 23) In Ref 106 it isclaimed that Zn promotes discontinuous precipitation ofAl3Sc

Lithium

A comparison of the age hardening response at 400uC inAlndash24 wt-Lindash019 wt-Sc and Alndash024 wt-Sc alloys

indicates that the onset of Al3Sc-precipitation is notaffected by the presence of Li161

Zirconium

As mentioned in the section on lsquoTernary phase diagramswith dispersoid-forming elementsrsquo earlier a considerableamount of Zr is dissolved in the Al3Sc phase and thus amore correct denotation of the precipitating phase isAl3(Sc12xZrx) In discussing the influence of the Zrcontent on the precipitation of Al3Sc one is thereforeactually discussing the difference in precipitation ofAl3Sc versus Al3(Sc12xZrx)

It is found that an addition of 015 wt-Zr to an Alndash04 wt-Sc alloy only marginally affects the initial stageof the precipitation reaction123135 while it slows downthe later stages of the transformation considerably(Fig 24)135 The coarsening rate of the Al3(Sc12xZrx)particles in AlndashScndashZr alloys is found to be much slowerthan that of Al3Sc particles in AlndashSc alloys123162

In three-dimensional atom probe field ion microscopy(3D-APFIM) of Al3(Sc12xZrx) particles formed at 475uCin a ternary AlndashScndashZr alloy163 it was found that the coreof the particles is almost pure Al3Sc whereas there is ashell of Al3(Sc12xZrx) with almost equal content of Scand Zr Such a behaviour has also been predicted bycomputer modelling of precipitation of Al3(Sc12xZrx) at480uC in an AlndashZnndashMgndashScndashZr alloy164 This modelpredicts that Zr starts to enter the growing

22 C-curves for 10 and 60 transformation in Alndash

04 wt-Sc and Alndash04 wt-Fendash035 wt-Sindash04 wt-Sc

redrawn from Ref 135

23 C-curves for 10 and 60 transformation in Alndash

04 wt-Sc and Alndash5 wt-Znndash04 wt-Sc redrawn

from Ref 135

24 C-curves for 10 and 60 transformation in Alndash

04 wt-Sc and Alndash04 wt-Scndash015 wt-Zr redrawn

from Ref 135

Roslashyset and Ryum Scandium in aluminium alloys

32 International Materials Reviews 2005 VOL 50 NO 1

Al3(Sc12xZrx) particles when approximately half of thesupersaturated Sc has been precipitated The Zr contentof the outer shell is predicted to be much higher thanwhat has been found experimentally163164

Another 3D-APFIM study of Al3(Sc12xZrx) particlesin a ternary AlndashScndashZr alloy has been reported165 Hereparticles grown at 300uC for various lengths of time werestudied The Zr content in these particles was muchlower than that reportedpredicted at higher tempera-tures163164 even after very long annealing times

Iron

The effect of adding up to 07 wt-Fe on the precipita-tion kinetics in an Alndash04 wt-Sc alloy has beeninvestigated135 The onset of precipitation was onlyslightly influenced by the Fe-level whereas the laterstages of the transformation however were significantlyslowed down as the Fe-level increased An example ofthe effect of a joint addition of Fe and Si is shown inFig 22

Manganese chromium and titanium

Small additions (03 wt-) of manganese or chromiumto Alndash040 wt-Sc alloys are reported to have onlyminor effects on the precipitation kinetics of Al3Sc135

According to Ref 106 Mn is reported to promote andCr and Ti to suppress discontinuous precipitation

Rare earth elements

An investigation of the precipitation behaviour of Alndash03 at-Sc and Alndash03 at-Scndash03 at-X alloyswhere X is either yttrium gadolinium holmium orerbium in the temperature range 235ndash310uC indicatedthat a Al3(Sc12xXx) phase with L12 structure wasformed in the ternary alloys22 Peak strength is reportedto occur after approx 10 h at 285uC in all alloys whichindicates that the precipitation kinetics up to peakstrength is practically unaltered by the ternary additions

Influence of Sc on microstructure andproperties of wrought aluminium alloysMost of the effects of Sc addition in wrought Al-alloysare linked to the formation of the Al3Sc phase In atypical processing route of a wrought aluminium alloyparticles of the Al3Sc phase can form under threedifferent conditions each of which influences themicrostructure and properties of the alloy in a specificway

1 During solidification after casting or weldingAl3Sc particles can form in the melt and act as nucleifor a-Al thus leading to grain refinement18166

2 High temperature processing of the alloy in therange 400ndash600uC for instance homogenisation hot-rolling or extrusion can give a dense distribution ofAl3Sc particles of typically 20ndash100 nm size The particledistributions formed under such conditions are reportedto lead to good recrystallisation resistance128148167168

and enhanced superplasticity52169170

3 Heat treatment in the range 250ndash350uC can lead tosignificant precipitation hardening of an alloy super-saturated in Sc148158171 The size of strengthening Al3Scprecipitates is typically in the range 2ndash6 nm121

Grain refinementA good grain refinement is almost always desired uponsolidification The formation of small equiaxed grainsrather than long dendrites in the melt facilitates thefeeding of the melt into cavities of the shrinkingsolidified metal and thus reduces the problem ofshrinkage porosity The tendency to hot cracking is alsoreduced and the second phase particles become morefinely and uniformly distributed

To the authorsrsquo knowledge the first effect of Sc in Al-alloys that was reported in an international scientificjournal was the grain refining action in pure Al and in anAlndashCu alloy upon solidification172 which was found tobe stronger for Sc than for other transition metals Inlater studies of Sc as a grain refiner in pure Al1832173 ithas been demonstrated that approx 07 wt-Sc issufficient to provide excellent grain refinement It hasalso been demonstrated that additions of 025 wt-Scz025 wt-Zr provide good grain refinement in pure Al18

In order for Sc to act as an effective grain refiner theAl3Sc phase has to form in the melt before thesolidification of a-Al The Al3Sc particles have a latticeparameter close to that of pure Al and whenhypereutectically formed the Al3Sc particles are veryeffective substrates for the nucleation of the a-Al phaseAs mentioned in the section on lsquoFormation of Al3Sc inAlndashSc alloysrsquo above this requires that the alloy ishypereutectic with respect to Sc ie in excess of approx06 wt- in a binary AlndashSc alloy In ternary and higherorder systems the eutectic Sc composition may dependon the other alloying elements present For instance theeutectic composition of Sc has been predicted todecrease with increasing Mg content in the ternary AlndashMgndashSc system39 This prediction is sustained by theobservation of good grain refinement by adding 05 wt-Sc to an Alndash7 wt-Mg alloy174 (Other examples ofgrain refinement at Sc concentrations lower than that ofthe binary eutectic are found in Ref 173)

Similarly the observation of good grain refinement inan Alndash025 wt-Scndash025 wt-Zr alloy18 may be as aresult of a lower Sc content of the eutectic in the ternarysystem ie less Sc is needed to make the alloy hyper-eutectic No literature data on the liquidus surface of theAlndashScndashZr system are available and thus this hypothesiscannot be confirmed In more complex alloy systems itis also observed that excellent grain refinement isachieved at low Sc contents when Sc is added togetherwith Zr It is reported that adding either 02 wt-Sc06 wt-Sc or 01 wt-Zr to an Alndash5Mg alloy givesmuch poorer grain refinement than adding 02 wt-Scz01 wt-Zr175 Similarly additions of 015 wt- ofeither Sc or Zr are reported to only marginally refinethe grain structure in an AlndashCundashLi alloy whereas a jointaddition of 015 wt-Sc and 015 wt-Zr gives excellentgrain refinement176 For an AA 3650 casting alloy (Alndash7 wt-Sindash04 wt-Mg) good grain refinement is achievedby adding 039 wt-Sc or 027 wt-Scz019 wt-Zr177

In some AlndashZnndashMgndashScndashZr alloys it is also found thatan addition of 02ndash03 wt-Sc can be sufficient for goodgrain refinement166169178179 Examples of the grainrefinement as a function of Sc addition in pure Al andin an AlndashZnndashMgndashZr alloy are shown in Fig 25

The nucleation of a-Al on Al3Sc particles in the melt isfacilitated by the close match in the lattice parameters ofthe two phases As shown in Fig 17 the mismatch at the

Roslashyset and Ryum Scandium in aluminium alloys

International Materials Reviews 2005 VOL 50 NO 1 33

eutectic temperature of binary AlndashSc alloys (660uC) isonly approx 047 In Refs 57 and 89 it is shown thatwhen Zr Hf and in particular Ti is dissolved in the Al3Scparticles this reduces the lattice parameter of the phaseIt appears that when 25 of the Sc atoms in Al3Sc aresubstituted by Ti the mismatch is zero at approx 550uCand becomes negative at higher temperatures89 Thissuggests that by carefully selecting the Ti content of thealloy it should be possible to obtain Al3(ScTi)substrates in the melt that match exactly the latticeparameter of the nucleating a-Al and thus furtherimprove the grain refinement of the alloy This appearsto have been achieved in a recent work180 where thegrain refinement of an Alndash07 wt-Sc alloy wascompared with that of an Alndash05 wt-Scndash02 wt-Tialloy At a cooling rate of 100 K s21 only an estimated2 of the primary Al3Sc particles of the binary AlndashScalloy were effective nuclei compared to practically 100for the primary Al3(ScTi) particles in the ternary AlndashScndashTi alloy leading to a much smaller grain size in theternary alloy Whereas the match of lattice parametersmay be of importance for these results the authors ofthis investigation180 draw attention to other factors suchas different growth restriction factors for Sc and Ti andthe possibility of a peritectic reaction in the ternaryalloy Nevertheless the principle of matching latticeparameters is worth looking into further in future work

Effects from dispersoidslsquoDispersoidsrsquo is a term which is commonly used aboutthe classes of second phase particles that are formedin an Al alloy during high temperature annealing orthermomechanical processing such as homogenisationhot rolling extrusion and forging A dense distributionof dispersoids can give a significant contribution to analloyrsquos strength owing to particle strengthening but thisis rarely the main strengthening mechanism A moreimportant contribution from the dispersoids is theirability to stabilise the grainsubgrain structure of analloy through the Zener-drag action and thus improvethe mechanical properties of the alloy

There are two noticeable dispersoid-related effectsthat have been reported for Sc-containing alloys Thefirst is the stabilising effect on a deformed microstruc-ture When a non-recrystallised structure is preserved inan alloy this can add considerably to the mechanical

strength of the material The second effect is thepreservation of a small grain size during hot deforma-tion at slow deformation rates which is necessary toobtain superplastic properties of an Al-alloy

Recrystallisation resistance

The anti-recrystallisation effect of Sc was first publishedin a patent171 where 03 wt-Sc was added to pure Aland to AlndashMg AlndashMn and AlndashZnndashMg alloys Both Sc-free and Sc-containing materials were cold worked andsubsequently annealed and it was found that theaddition of Sc increased the temperature for onset ofrecrystallisation by approx 220uC in pure Al andsomewhat less in the Al-alloys Although the author ofthe patent171 may have been well aware that the anti-recrystallisation effect is caused by Al3Sc dispersoidsthis is not mentioned in the text The first journal paperthat explicitly points out that the recrystallisationresistance is due to Al3Sc dispersoids was an investiga-tion of the effects of adding Sc to wrought AlndashMgalloys181 In this work it was found that the Al3Scdispersoids were very effective in preventing recrystalli-sation up to temperatures of approx 400ndash450uC Athigher temperatures the dispersoids coarsen consider-ably and the microstructure was partially recrystallised

It is established that the Zener-drag pZ that is imposedon an advancing grain boundary by randomly distrib-uted dispersoids can be expressed in the form

pZ~k f =r (3)

where k is a factor that includes the interface energybetween the dispersoids and the matrix f is the volumefraction and r is the mean radius of the dispersoids Thusthe Zener drag will decrease rapidly in the case where thedispersoids are coarsening

As mentioned in the section on lsquoInfluence of otherelements on precipitation of Al3Scrsquo above theAl3(Sc12xZrx) dispersoids in a ternary AlndashScndashZr alloycoarsen at a much slower rate than the Al3Sc dispersoidsin a binary AlndashSc alloy This effect was first reported inRef 123 (although also observed in Ref 182) andaccording to Ref 33 the same authors demonstratedsoon after that the denser dispersoid distributionachieved in an AlndashScndashZr alloy leads to superiorrecrystallisation resistance compared to a binary AlndashScalloy An example of the increased recrystallisationresistance by adding both Zr and Sc is shown in Fig 26

In isothermal sections of the ternary AlndashScndashZr phasediagram it is indicated that the solid solubility ofSczZr is somewhat higher than that of Sc alone54 Ithas also been demonstrated both by electrical con-ductivity measurements (Fig 27) and microstructuralobservations that the supersaturation of SczZr isgreater than that of only Sc or Zr in as cast Alndash15(SczZr) alloys183 This indicates that it should bepossible to increase the volume fraction of dispersoids inAlndashScndashZr compared to AlndashSc It is suggested162 that theincreased volume fraction that can be achieved byadding both Sc and Zr can be advantageous inconventional wrought Al-alloys

There are at least two different conditions underwhich Al3Sc or Al3(Sc12xZrx) dispersoids can form toprevent recrystallisation

1 Sc (or Sc and Zr) is in solid solution before thedeformation In the case of cold deformation and

25 Grain refinement as a function of Sc addition in pure

Al (redrawn from Ref 32) and AlndashZnndashMgndashZr (redrawn

from Ref 169) note that data points are plotted on

different ordinate axes

Roslashyset and Ryum Scandium in aluminium alloys

34 International Materials Reviews 2005 VOL 50 NO 1

subsequent annealing the Al3Sc or Al3(Sc12xZrx)dispersoids may nucleate and grow before the nucleationand growth of recrystallised grains takes placeDispersoids can form after a direct up-quench to theannealing temperature115143148184 during ramp-up tothe annealing temperature115 or by pre-annealing at anintermediate temperature129 In the case of hot deforma-tion the Al3Sc or Al3(Sc12xZrx) dispersoids maynucleate and grow during preheating of the materialand during the hot deformation itself184

2 The Al3Sc or Al3(Sc12xZrx) dispersoids are formedin the material before deformation184 Considering coldrolling and subsequent annealing the annealing tem-perature Tann may be either lower or higher than thetemperature Tdisp at which the dispersoids were formedIf TannTdisp only limited if any coarsening of thedispersoids is expected to take place and thus the Zenerdrag from the particles is expected to be practicallyconstant The driving force for recrystallisation how-ever is expected to decrease somewhat with theannealing time as a result of recovery processes Thusif recrystallisation does not occur within short annealingtimes the material is expected to remain unrecrystallisedfor infinite time at the annealing temperature IfTannTdisp there will be substantial coarsening of thedispersoids during annealing In order for the materialto remain unrecrystallised the decrease in driving forcefor recrystallisation owing to recovery has to be at leastas rapid as the decrease in Zener drag because of particlecoarsening

Experimental comparisons of the conditions abovepoint in the direction that the recrystallisation resistanceis poorest when Sc (or Sc and Zr) is in solid solutionbefore deformation and the deformed material is up-quenched to the annealing temperature148 or when Al3Scor Al3(Sc12xZrx) dispersoids are formed before defor-mation at TdispampTann184185 Excellent recrystallisationresistance is achieved if dispersoids are formed at anintermediate anneal of solutionised and deformedmaterial128 or if dispersoids are formed at TdispTann

before deformation148185ndash187 It seems that the decreasein Zener drag because of dispersoid coarsening in many

cases is slower than the decrease in driving force forrecrystallisation because of recovery processes Thusthere is an advantage in forming a high number densityof small dispersoids which for most practical casesmeans that they should be formed at TdispTann122

When an advancing high angle grain boundary iethe recrystallisation front is passing a coherent Al3Scdispersoid there are at least three possible grainboundarydispersoid interactions

1 The Al3Sc dispersoid retains its global orientationrelationship and thus loses its coherency with thesurrounding matrix

2 The Al3Sc dispersoid rotates as the grain boundarypasses either by diffusional processes at the dispersoidmatrix interface or by the grain boundary passingthrough the dispersoid and the Al3Sc dispersoidassumes the same crystallographic orientation as theAl matrix of the recrystallised grain

3 The Al3Sc dispersoid dissolves at the grainboundary and re-precipitates in the recrystallised grain

Which interactions that actually take place willprobably depend on the dispersoid size annealingtemperature and driving force for recrystallisation It isalso possible that alloy composition (other elementsthan Al) is of importance

It has been reported that large (Oslash about 100ndash150 nm)Al3Sc dispersoids in a deformed Alndash4 wt-Mgndash02 wt-Sc alloy annealed at 575uC lose the orientationrelationship with the matrix after being passed by therecrystallisation front148

A rotation of somewhat smaller Al3Sc dispersoids in arecrystallising binary Alndash025 wt-Sc alloy has beenreported115143 The rotation was reported to be accom-panied by substantial growth (from Oslash 30 nm to Oslash48 nm) as a result of enhanced Sc diffusion at the grainboundary Observations suggested that the grainboundaries were passing through the dispersoids andthus the Al3Sc dispersoids retained the orientationrelationship with the recrystallised Al matrix

Dissolution and re-precipitation of Al3Sc dispersoidshas been reported during recrystallisation of a 50 coldrolled Alndash02 wt-Sc alloy162 Large spherical partially

26 Fraction recrystallised structure in cold rolled sheets

of Alndash04 wt-Sc and Alndash04 wt-Scndash015 wt-Zr as a

function of annealing temperature redrawn from

Ref 183 27 Electrical conductivity in Alndash15(SczZr) alloys

redrawn from Ref 183

Roslashyset and Ryum Scandium in aluminium alloys

International Materials Reviews 2005 VOL 50 NO 1 35

coherent dispersoids were observed to dissolve at therecrystallisation front and re-precipitate as smallercoherent Al3Sc cuboids

Superplastic forming

It seems that the first publication on superplasticproperties of Sc-containing Al-alloys was a study of anAlndash35Cundash14Mgndash045Mnndash04(SczZr) alloy188

It was recognised that the superplastic properties are aresult of the stabilisation of the fine grain structure byAl3Sc dispersoids The Sc-containing Al alloys that havereceived most attention for their superplastic propertieshowever are those of the AlndashMgndashSc system which wasfirst published in a patent189 Here it was noted that anAlndash4 wt-Mgndash05 wt-Sc alloy had superior superplasticproperties compared to fine-grained 7475 (AlndashZnndashMgndashCu alloy) Binary Alndash05 wt-Sc and Alndash4 wt-Mgalloys did not behave superplastically The flow stress atthe hot forming temperature was found to be much (30ndash40) lower in the ternary alloy than that of the twobinary alloys

The superplastic properties of AlndashMgndashSc alloys havebeen explored by several research groups over the lastdecade190ndash196 It has frequently been found that thedeformation mechanism is dominated by grain bound-ary sliding190 However it has also been reported thatAlndashMgndashSc alloy may deform superplastically withoutnoticeable grain boundary sliding23 It is generallyrecognised that the grain boundary sliding mechanismis facilitated when the average grain size is very smalland grain boundaries are predominantly high-angleSuch a microstructure may be achieved by carefulthermomechanical processing of the starting mate-rial193194197198 It has however been shown that a finegrained structure with high angle boundaries maydevelop during superplastic forming of AlndashMgndashSc alloyseven if the starting microstructure is an entirely differentone for instance that of a cold rolled sheet192 It has alsobeen suggested that superplastic forming of as castmaterial may be possible189

One of the more efficient thermomechanical processesfor achieving an ultrafine grain structure with high anglegrain boundaries in Al-alloys is equal channel angularpressing (ECAP) A JapanesendashAmerican group ofscientists has published an impressive body of researchon improvements in superplastic properties in Al-alloys processed by ECAP over the last few years andseveral of the publications are from investigations onAlndashMgndashSc alloys170199ndash224 Maximum strains in excessof 2000 at a strain rate of 0033 s21 have beenachieved170201202217 which is an extraordinarily goodcombination of high strain and high strain rate for analuminium alloy

Superplastic properties of AlndashCundashMg(ndashMn)ndashSc(ndashZr)and AlndashMgndashSc(ndashZr) alloys have been mentionedNoticeable superplasticity in other Sc-containing Al-alloys has also been reported such as AlndashZnndashMg(ndashCu)ndashScndashZr169225ndash228 AlndashLindashSc229 AlndashMgndashLindashScndashZr229ndash234

AlndashLindashMgndashCundashScndashZr235236 and AlndashCundashLindashScndashZr233

Precipitation hardeningHardening by Al3Sc precipitates

It has been noted that when Al3Sc particles precipitate inthe temperature range 250ndash350uC they give a significanthardness increase in the alloy Some authors point out

that Sc is a more effective precipitation hardening elementper atomic fraction added than the elements that arecommonly used for precipitation hardening121130 (In onepaper29 it is claimed that only Au has a strongerstrengthening effect than Sc) However the amount ofSc that can be precipitated from supersaturated solidsolution is rather limited and thus the absolute values ofthe hardness increase from the precipitation hardening ismuch lower than what is normally associated withprecipitation hardened alloys Also the temperatureregime for age hardening by precipitation of Al3Sc issomewhere in between the temperature regimes for agehardening and solution heat treatments of commonprecipitation hardened alloys This makes a combinedprecipitation of Al3Sc and other strengthening precipi-tates unfeasible Thus precipitation strengthening byAl3Sc is most feasible in alloy systems that are non-heat-treatable The non-heat-treatable aluminium alloy sys-tems are according to the Aluminum Associationdesignations the 1xxx series (99 pure Al) the 3xxxseries (AlndashMn) and the 5xxx series (AlndashMg) The purposeof adding Sc to these alloys may be either to stabilise themicrostructure of wrought semiproducts (extrusionsrolled plates forgings etc) as discussed in the sectionon lsquoRecrystallisation resistancersquo above or to provideextra strength to the alloy through precipitation hard-ening In the latter case it is appropriate to considerwhether the Sc-containing alloy still should be classifiedas non-heat-treatable A heat treatment is applied thatbrings about a significant precipitation hardening On theother hand the hardness increase that is achieved throughthe heat treatment is lower than what is normallyassociated with heat-treatable alloy systems Hence eventhough it seems like a contradiction one chooses to keepusing the term lsquonon-heat-treatablersquo about these alloys

Table 7 gives an overview of some mechanicalproperties of Sc-containing non-heat-treatable alloysthat are reported in the literature Most of theexperimental work on Sc in 1xxx-types of alloys hasbeen done on binary AlndashSc alloys with much higherpurity than industrial alloys

Strengthening mechanisms

When the precipitates are larger than a critical size thestrengthening effect is due to the Orowan-mechanism iedislocations can only pass the precipitates by looping Inthis case the strengthening effect of the particles isapproximately inversely proportional to the mean parti-cle spacing When the precipitates can be sheared bydislocations there are a number of strengthening mechan-isms that apply It is proposed by Parker et al108 that thetwo major contributing mechanisms are coherency strainand anti-phase-boundary energy In a recent detailedstudy of strengthening mechanisms in binary AlndashSc alloysby Marquis and colleagues117118 the strengthening fromshear modulus mismatch between the matrix and theprecipitates is also accounted for A qualitatively goodmatch between theoretical strengthening and measuredvalues is achieved in this work both for deformation atroom temperature and at 300uC

Effect of Sc on precipitation strengthening in heat-treatablealloys

Following the AA designation system the traditionalheat-treatable Al-alloys are those that belong to the 2xxx

Roslashyset and Ryum Scandium in aluminium alloys

36 International Materials Reviews 2005 VOL 50 NO 1

series (AlndashCu) 6xxx series (AlndashMgndashSi) and 7xxx series(AlndashZnndashMg) AlndashLi alloys should also be mentionedSeveral investigations have been carried out in order toclarify the effects of Sc on the precipitation behaviour inthese alloy systems

AlndashCu alloys

The precipitation sequence in AlndashCu alloys is oftendescribed as follows

Supersaturated solid solutionRGP-zonesRh0Rh9Rh(Al2Cu)

The highest strength is normally achieved when the h0or h9 precipitates are predominant Typical precipitationheat treatment temperatures for AlndashCu alloys are in therange 160ndash190uC238 which is considerably lower thanthe typical precipitation temperature for Al3ScComparisons of the aging responses of AlndashCu and AlndashCundashSc alloys at 150 and 200uC indicate that there is nonoticeable effect of Sc on the precipitation kinetics ofh9153 It is observed that the h9 precipitates may nucleateon Al3Sc particles153 At 300uC it is observed that h9particles are somewhat smaller in AlndashCundashSc alloys thanin AlndashCu alloys156

AlndashMgndashSi alloys

The following precipitation sequence is commonlyreported for AlndashMgndashSi alloys

Supersaturated solid solutionRGP-zonesRb0Rb9Rb(Mg2Si)

For peak aged alloys the predominant precipitatetype is b0 for which the stoichiometric composition hasrecently been resolved to be Mg5Si6239 Temperatures inthe range 160ndash205uC are typically used for precipitationhardening of these alloys238 Adding both 03 wt-Scand 01 wt-Zr to an Alndash06 wt-Mgndash065 wt-Sialloy does not seem to alter the precipitation kineticsof b0 at 165uC However the hardness increase becauseof precipitation hardening appears to be smaller in theSczZr-containing alloy240 In another investigationadditions of 01 wt-Sc 015 wt-Sc 02 wt-Sc04 wt-Sc and 02 wt-Scz01 wt-Zr were made toan Alndash08 wt-Mgndash07 wt-Si alloy241 Here it wasalso observed that the precipitation kinetics of b0 wasseemingly independent of the Sc additions (Fig 28)TEM observations indicated that the b0 precipitateswere of comparable sizes in the investigated alloys andno interactions between Al3Sc and b0 were observed(Fig 29) In a third study242 where the effect of Sc onthe precipitation in an AlMgSindashSiC metal matrixcomposite was investigated there also does not seemto be any effect on the precipitation kinetics Howevercontrary to the findings of Ref 240 it is reported thatthe Sc addition leads to a higher hardness increase thanin the corresponding Sc free alloy

AlndashMgndashZn alloys

For these alloys the following precipitation sequence isoften ascribed

Table 7 Mechanical properties in non-heat-treatable Al-alloys with Sc

Reference Alloy wt- YS MPa UTS MPa Note

1xxx alloys171 000Sc 15 48 Cast material aged 288uC8 h

023Sc 159 185 Cast material aged 288uC8 h038Sc 199 220 Cast material aged 288uC8 h000Sc 14 49 Cold rolled material (89) aged 288uC8 h023Sc 198 208 Cold rolled material (89) aged 288uC8 h038Sc 240 264 Cold rolled material (89) aged 288uC8 h000Sc 8 34 Cold rolled material quenched from 649uC aged 288uC8 h023Sc 147 157 Cold rolled material quenched from 649uC aged 288uC8 h038Sc 193 199 Cold rolled material quenched from 649uC aged 288uC8 h

121 05Sc 160 ndash Forged material quenched from 635uC aged 250uC50 h23 05Sc 298 319 Hot rolled 288uC cold rolled 69ndash81 aged 288uC4 h112 01Sc 132 166 Hot z cold rolled material quenched from 630uC

aged 320uC133 h148 02Sc 138 ndash Cast material aged 300uC10 h compression test159 04Sc 196 ndash Cast material aged 300uC10 h compression test117 118 03Sc 209 ndash Cast material quenched from 648uC aged 300uC5 h

compression test3xxx alloys171 1Mn 015Sc 216 221 Cold rolled material (89) aged 288uC8 h

1Mn 05Sc 309 323 Cold rolled material (89) aged 288uC8 h186 05Mn 02Mg

026Sc 015Zr162 201 Extruded material solutionised 600uC aged 250uC

5xxx alloys171 1Mg 43 111 Cold rolled material (89) aged 288uC8 h

1Mg 03Sc 288 303 Cold rolled material (89) aged 288uC8 h53Mg 147 259 Cold rolled material (50) wintermediate anneals

at 343uC aged 288uC8 h53Mg 03Sc 368 401 Cold rolled material (50) wintermediate anneals

at 343uC aged 288uC8 h23 2Mg 05Sc 376 401 Hot rolled 288uC cold rolled 69ndash81 aged 288uC4 h

4Mg 05Sc 414 4606Mg 05Sc 433 503

237 4Mg 1Sc 420 525 Cold rolled material (83) aged 320uC1 h148 4Mg 02Sc 194 ndash Cast material aged 300uC10 h compression test

Tensile test data except where noted YS yield strength UTS ultimate tensile strength

Roslashyset and Ryum Scandium in aluminium alloys

International Materials Reviews 2005 VOL 50 NO 1 37

Supersaturated solid solutionRGP-zonesRg9Rg(Zn2Mg)

The maximum hardness is normally achieved whenthe g9 precipitates are predominant Common precipita-tion hardening temperatures are in the range 95ndash180uCand a two-step precipitation heat treatment within thistemperature regime is often used238 It has beenobserved in some investigations that Sc and SczZradditions to AlndashMgndashZn alloys slow down the precipita-tion of g9 somewhat243 Other investigations find thatthere is no effect of Sc on the precipitation behaviour ofg9244245 and yet others report that Sc additionssignificantly speed up the precipitation of g9246 In Ref247 it is found that an Sc addition leads to coarser g9precipitates and it is claimed that this gives an improvedductility of the alloy The strength-loss associated withlarger particle size is reported to be counterbalanced bystrengthening from Al3Sc precipitates

AlndashLi alloys

The precipitation sequence in binary AlndashLi alloys isapparently simple

Supersaturated solid solutionRd9Rd (AlLi)

where d9 is the metastable Al3Li phase which just likeAl3Sc has the L12 type of atomic arrangement Thetypical temperature regime for precipitation of d9 whichis the strengthening phase in this system is approx 150ndash200uC A comparison of the age hardening response ofan Alndash26 wt-Li and an Alndash24 wt-Lindash019 wt-Scalloy at 180uC248 and 200uC161 indicates that the onsetof d9 precipitation is not altered by the presence of ScThe hardness curves for the two alloys are practicallyidentical at 200uC whereas at 180uC the peak hardnesslevel is slightly higher in the AlndashLi than the AlndashLindashScalloy DSC measurements at constant heating ratesindicate that the addition of Sc to an AlndashLi alloysincreases the activation energy for d9 precipitation andmoves the exothermic peak associated with d9 precipita-tion to a higher temperature248 For specimens aged at

either 180uC or 200uC TEM observations reveal that thed9 precipitates are much smaller in the Sc containingalloy than in binary AlndashLi both in the peak agedcondition and in the overaged condition161248 Additionof Sc has also been observed to reduce the size of d9precipitates in other AlndashLi based alloys249ndash251 In an AlndashLindashCundashZr alloy an addition of Sc has been reported toslow down the homogeneous precipitation of d9252253 Ithas been claimed that Sc reduces the quench sensitivityand delays room temperature aging of AlndashLi basedalloys254ndash256

When present in the microstructure before the pre-cipitation of d9 the Al3Sc precipitates may act as effec-tive nucleation sites for d9 The resulting precipitates arespheres of d9 with a core of Al3Sc161249252ndash255257ndash261

Corrosion resistanceAn appreciable amount of data is available on the effectsof Sc on the corrosion behaviour of wrought Al-alloysSome of these effects are apparently derived from theeffects of Sc on the microstructure of the alloys It hasbeen reported that an addition of Sc increases thecorrosion potential (makes it less negative) in pureAl262ndash264 in AlndashZn alloys265266 AlndashMg alloys267 AlndashZnndashMgndashCu alloys264268 AlndashCundashMgndashMn alloys264 andin AlndashCundashLindashMgndashAg alloys264 Even though Sc alsohas been reported to decrease the corrosion potential in

28 Age hardening response at 175uC for Alndash08 wt-Mgndash

07 wt-Si alloy (Base) with additions of 02 wt-Sc

04 wt-Sc and 02 wt-Scz01 wt-Zr from Ref 241

29 TEM images of a b0 precipitates in Alndash08 wt-Mgndash

07 wt-Si alloy and b b0 and Al3(Sc1ndashxZrx) in a similar

alloy with addition of 02 wt-Scz01 wt-Zr from

Ref 241

Roslashyset and Ryum Scandium in aluminium alloys

38 International Materials Reviews 2005 VOL 50 NO 1

AlndashMg alloys269270 it seems that the general trend isthat adding Sc to an alloy makes it slightly more nobleThe change in corrosion potential is much morepronounced when Sc is added in amounts larger thanthe eutectic composition263 ie there is a considerablecontribution from primary or eutectic Al3Sc to theoverall potential It has also been demonstrated that thechange in corrosion potential caused by Sc can dependon the heat treatment applied to the alloy267268

Even though the corrosion potential is an essentialparameter in establishing the corrosion behaviour of analloy an increase in the corrosion potential does notnecessarily imply an improved self-corrosion resistanceHowever measurements of corrosion rates and passiva-tion current densities strongly suggest that the self-corrosion resistance in general is considerably improvedwhen Sc is added to wrought Al-alloys263264267 Someobserved variations in corrosion potential and passiva-tion current densities with Sc content in binary AlndashScalloys are plotted in Fig 30

Material failure in corrosive environments is often dueto localised corrosion attacks which may propagaterapidly even though the bulk material has a goodresistance against general corrosion It has been pointedout that hypereutectic additions of Sc may lead tomicrogalvanic corrosion beside primary Al3Sc parti-cles264 In AlndashMg alloys grain boundary precipitation ofAl8Mg5 can lead to localised corrosion attacks such asintergranular corrosion (IGC) exfoliation corrosion(EC) and stress corrosion cracking (SCC) In wroughtmaterial such precipitation may occur in the 60ndash180uCtemperature regime and heating in this temperaturerange is referred to as lsquosensitationrsquo An AlndashMgndashSc alloywas found to be immune against intergranular corrosionand have moderate susceptibility to exfoliation corro-sion after annealing at 350uC271 After sensitation heattreatments severe IGC and EC was observed but notquite as severe as in a corresponding alloy without ScAs for SCC the AlndashMgndashSc alloy was found to be highlyresistant271 In another study it was found that additionof 056 wt-Sc reduces the SCC susceptibility of an Alndash68 wt-Mg alloy in the as-rolled state and afterannealing at 250uC whereas in a sensitised specimenthe SCC susceptibility is somewhat increased by the Scaddition272 A third investigation found that Sc has nomeasurable detrimental effect on the SCC susceptibilityof sensitised Alndash5Mgndash015Zr alloy273 SCC is also a

severe problem in high strength AlndashZnndashMgndashCu alloys Ithas been shown that small Sc additions are effective inreducing the SCC sensitivity of these alloys244246268274

Use of Sc-containing Al alloysA systematic development of Sc-containing aluminiumalloys took place in the former USSR in the 1980s andthe interest for Sc as an alloying element in aluminiumalloys hit the western world approximately 10 yearslater Even though a number of improvements in Alalloys achieved by Sc addition have been demonstratedthe current uses of such alloys are very limited This isrelated to the very high price of scandium

In Russia some parts of military aircraft are made ofSc-containing AlndashLi alloys In the western world themain usage of Sc-containing alloys is for sportsequipment Ashurst Technology and Kaiser Aluminumdeveloped a Sc-containing 7xxx alloy for baseball andsoftball bats which was introduced to the Americanmarket in 1997 by Easton Alcoa soon followed with aSc-containing alloy for a competing brand of batsLouisville Slugger Since then several new and improvedSc-containing alloys for bats have been introduced tothe market The purpose of adding Sc is to increase theyield strength of the alloy allowing for a down-gaugingof the wall thickness which in turn gives a strongerlsquospring-rsquo or lsquotrampoline-rsquo effect when the ball hits thebat

Shortly after the introduction of the Sc containingbats Easton also launched Sc-containing 7xxx tubingfor bicycle frames Just as in the bats Sc increases theyield strength of the alloy allowing for down-gauging oftube wall thickness and a corresponding weight reduc-tion of the bicycle frame An Italian manufacturer ofbicycle tubing Dedacciai also delivers tubes in a Sc-containing 7xxx alloy

Other sports equipment made from Sc-containingaluminium alloys includes lacrosse sticks and tent polesSmith and Wesson has also introduced a series ofhandguns where the frame is made from a Sc-containingAl alloy

A common factor for the items mentioned above isthat the material cost is only a minor part of the totalmanufacturing cost of the end product and also thatthese products are aimed at a group of customers thathave a certain awareness of new materials Both baseballbats and bicycle frames have been marketed aslsquoscandium alloyrsquo even though the Sc content is muchlower than 1

Currently AlndashSc master alloys for the production ofSc-containing Al alloys are available at a price thatcorresponds to US$ 2000 per kg of Sc This means that ifone wants to add 02 wt-Sc to an alloy which is afairly common content one also increases the price ofthe alloy by US$ 4 per kg alloy Depending on the alloytype Sc is added to this represents a tripling orquadrupling of the price of the alloy There are notmany existing products where such an increase inmaterial cost can be justified In order to see awidespread use of Sc in high-volume products the Scprice has to come down considerably Actually the priceof adding Sc to Al alloys has gone down by a factor 3ndash10over the last 10ndash15 years and substantial price reduc-tions are also expected in the future

30 Observed variations in corrosion potential and passi-

vation current densities with Sc content in binary Alndash

Sc alloys based on data from Ref 263

Roslashyset and Ryum Scandium in aluminium alloys

International Materials Reviews 2005 VOL 50 NO 1 39

The current production of AlndashSc master alloys isbased upon and will continue to be based upon for theforeseeable future the reduction of Sc2O3 or other Sccompounds directly in molten aluminium It is notnecessary as many tend to believe to take the route viametallic Sc Thus the price of AlndashSc master alloy isgoverned by the price of Sc2O3 or other Sc compoundsin question and not by the price of metallic scandiumThe Sc2O3 which is the main source for todayrsquos AlndashScmaster alloy production comes from stockpiles in theformer USSR These stockpiles will be exhausted withina few years and new reliable sources of Sc2O3 or otherSc compound production are sought It turns out thatthe most economically viable option that has beendisclosed so far is the processing of Red Mud from theBayer process of extracting alumina from bauxiteScandium is enriched in the Red Mud and is extractedfrom a Red Mud aqueous slurry by selective leachingsubsequent ion-exchange procedure and finally a liquidndashliquid extraction procedure It is not required to build aseparate lsquoSc factoryrsquo to do this but rather build an lsquoadd-onrsquo to existing Bayer process plants Such a processroute is expected to bring down the price of Sc2O3

considerably which in turn means that AlndashSc masteralloy price should drop accordingly Preliminary ana-lyses suggest a price of approx US$ 400 per kg Sc in themaster alloy which translates to an added cost of 80cent per kilo when 02 wt-Sc is added to an aluminiumalloy This is also a considerable increase in the materialcost but with such prices one should expect to see Sccontaining alloys in many more applications than whatis the case at the present time

Concluding remarksThe body of published investigations on Al-based alloyswith Sc addition provides a sound basis of knowledgefor metallurgists that want to look into the possibility ofenhancing the performance of a wrought Al-alloy byadding Sc to it Ternary AlndashScndashX phase diagrams areavailable for practically every technologically importantalloying element in Al The effect of a wide range ofternary alloying elements on the precipitation behaviourof Al3Sc is accounted for It has been shown that theAl3Sc phase can be effective as a grain refiner adispersoid former and a precipitate hardening agentand some of the underlying conditions for achieving thedesired Al3Sc formation have been outlined Addingsome Zr together with Sc has proven to be beneficial Itmay lead to effective grain refinement at a lower Sc levelbut the most prominent effect is the refinement indispersoid distribution that can be achieved An addi-tion of Sc has little if any effect on precipitation in the2xxx 6xxx and 7xxx alloy systems and some effects onthe precipitation in AlndashLi based alloys With respect tocorrosion behaviour adding Sc to an Al-alloy does ingeneral seem to make the alloy slightly more noble andto increase its self-corrosion resistance Scandium-containing Al alloys have very few uses at the presenttime as a result of the high price of scandium The priceof Sc is expected to decrease significantly in the futureand this should lead to the disclosure of moreapplications where it is economically feasible to takeadvantage of the improved properties of some Sc-containing aluminium alloys

References1 D R Lide lsquoCRC handbook of chemistry and physicsrsquo 71st edn

4ndash29 1990 Boston USA CRC Press

2 E M Savitsky V F Terehova I V Burov and O P Naumkin

Proc Fourth Conf on lsquoRare earth researchrsquo Phoenix Arizona

USA April 1964 409ndash420

3 E M Savitskii V F Terekhova I V Burov O P Naumkin and

I A Markova Inorg Mater 1965 1 1503ndash1512

4 O P Naumkin V T Terekhova and E M Savitskiy Russ

Metall 1965 (4) 128ndash136

5 W G Moffatt lsquoThe handbook of binary phase diagramsrsquo 1981

Schenectady NY USA General Electric Co

6 E A Brandes (ed) lsquoSmithells metals reference bookrsquo 6th edn

1983 London UK Butterworths

7 R P Elliott and F A Shunk Bull Alloy Phase Diagrams 1981

2 (2) 222ndash223

8 K A Gschneider Jr and F W Calderwood Bull Alloy Phase

Diagrams 1989 10 34ndash36

9 H Okamoto J Phase Equil 1991 12 612ndash613

10 J L Murray J Phase Equil 1998 19 380ndash384

11 M E Drits E S Kadaner T V Dobatkina and N I Turkina

Russ Metall 1973 (4) 152ndash154

12 S-I Fujikawa M Sugaya H Takei and K-I Hirano J Less-

Common Met 1979 63 87ndash97

13 N Blake and M A Hopkins J Mater Sci 1985 20 2861ndash2867

14 V I Kononenko and S V Golubev Russ Metall 1990 (2) 193ndash

195

15 T B Massalski J L Murray L H Bennett and H Baker (eds)

lsquoBinary alloy phase diagramsrsquo 1986 Metals Park OH USA

ASM

16 G Cacciamani P Riani G Borzone N Parodi A Saccone

R Ferro A Pisch and R Schmid-Fetzer Intermetallics 1999 7

101ndash108

17 H Okamoto J Phase Equil 2000 21 310

18 A F Norman P B Pragnell and R S McEwen Acta Mater

1998 46 5715ndash5732

19 I N Pyagai and A V Vakhobov Russ Metall 1990 (5) 50ndash52

20 C L Fu J Mater Res 1990 5 971ndash979

21 X Lu and Y Wang Calphad 2002 26 555ndash561

22 R R Sawtell and J W Morris Jr Proc lsquoDispersion strengthened

aluminium alloysrsquo Phoenix Arizona USA January 1988 409ndash

420

23 R R Sawtell and C L Jensen Metall Trans A 1990 21A 421ndash

430

24 L A Willey Unpublished research Alcoa 1970 Data points are

extracted from Ref 10

25 N I Turkina and V I Kuzmina Russ Metall 1976 (4) 179ndash

183

26 T Torma E Kovacs-Csetenyi I Vitanyi M Butova and

J Stepanov Proc 6th Int Symp on lsquoHigh purity materials in

science and technologyrsquo Akademie der Wissenschaften der DDR

Dresden Germany May 1985 388ndash389

27 A L Berezina V A Volkov B P Domashnikov and K V

Chuistov Metallofizika 1987 9 (5) 43ndash47

28 H-H Jo J Korean Inst Metals 1990 28 499ndash504

29 H-H Jo and S-I Fujikawa Mater Sci Eng 1993 A 171 151ndash

161

30 S Celotto and T J Bastow Philos Mag A 2000 80 1111ndash1125

31 J Roslashyset and N Ryum submitted to Mater Sci Eng

32 M E Drits L S Toropova Yu G Bykov F L Gushchina V I

Elagin and Yu A Filatov Russ Metall 1983 (1) 150ndash153

33 L S Toropova D G Eskin M L Kharakterova and T V

Dobatkina lsquoAdvanced aluminum alloys containing scandium

structure and propertiesrsquo 1998 Amsterdam The Netherlands

Gordon and Breach Science Publishers

34 V V Cherkasov P P Pobezhimov L P Nefedova E V Belov

and G M Kuznetsov Met Sci Heat Treat 1996 (6) 268ndash270

35 Kh O Odinaev I N Ganiev V V Kinzhibalo and B Ya

Kotur Dokl Akad Nauk Tadzh SSR 1989 32 37ndash38

36 Kh O Odinaev I N Ganiev and A V Vakhobov Russ Metall

1991 (4) 200ndash203

37 J Grobner R Schmid-Fetzer A Pisch G Cacciamani P Riani

N Parodi G Borzone A Saccone and R Ferro Z Metallkd

1999 90 872ndash880

38 E A Marquis and D N Seidman Microsc Microanal 2002 8

(Suppl 2) 1100CDndash1101CD

39 A Pisch J Grobner and R Schmid-Fetzer Mater Sci Eng A

2000 A 289 123ndash129

Roslashyset and Ryum Scandium in aluminium alloys

40 International Materials Reviews 2005 VOL 50 NO 1

40 C Xia F Zeng and Y Gu Trans Nonferrous Met Soc China

2003 13 1124ndash1127

41 M Yu Teslyuk and V S Protasov Sov Phys Crystallogr 1966

10 470ndash471

42 M L Kharakterova and T V Dobatkina Russ Metall 1988

(6) 175ndash178

43 M L Kharakterova Russ Metall 1991 (4) 195ndash199

44 L S Toropova M L Kharakterova and D G Eskin Russ

Metall 1992 (3) 194ndash199

45 P Riani L Arrighi R Marazza D Mazzone G Zanicchi and

R Ferro J Phase Equil Diff 2004 25 22ndash52

46 A T Tyvanchuk T I Yanson B Ya Kotur O S Zarechnyuk

and M L Kharakterova Russ Metall 1988 (4) 190ndash192

47 L L Rokhlin T V Dobatkina and M L Kharakterova Powder

Metall Met Ceram 1997 36

48 A Z Ikromov I N Ganiev and V V Kinzhibalo Dokl Akad

Nauk Tadzh SSR 1990 (6) 391ndash392

49 I N Ganiev A Z Ikromov and V G Khudoiberdiev Russ

Metall 1995 (3) 125ndash127

50 I N Fridlyander L L Rokhlin T V Dobatkina and N I

Nikitina Met Sci Heat Treat 1993 (10) 567ndash571

51 I N Fridlyander L L Rokhlin T V Dobatkina V V

Kinzhibalo and A T Tyvanchuk Russ Metall 1998 (1) 161ndash

166

52 R A Emigh E L Bradley and J W Morris Jr in lsquoLight-weight

alloys for aerospace applications IIrsquo (ed E W Lee and N J

Kim) 27ndash43 1991 TMS

53 L S Toropova A N Kamardinkin V V Kindzhibalo and A T

Tyvanchuk Phys Met Metall 1990 70 (6) 106ndash110

54 A N Kamardinkin T V Dobatkina and T D Rostova Russ

Metall 1991 (4) 216ndash218

55 L S Torodskaya T V Dobatkina and A N Kamardinkin

Russ Metall 1992 (5) 128ndash131

56 E M Sokolovskaya E F Kazakova E I Poddyakova and A

A Ezhov Met Sci Heat Treat 1997 (5) 211ndash213

57 Y Harada and D C Dunand Mater Sci Eng 2002 A 329ndash331

686ndash695

58 N E Drits L S Toropova and F L Gushchina Russ Metall

1984 (4) 229ndash232

59 E M Sokolovskaya E F Kazakova V A Alikhanov and E V

Zhuravleva Moscow Univ Chem Bull 1997 52 (5) 70ndash72

60 E M Sokolovskaya E F Kazakova and E I Poddyakova Met

Sci Heat Treat 1989 (11) 837ndash839

61 G M Cheldieva E F Kazakova E M Sokolovskaya and N I

Kaloev Russ Metall 1990 (6) 87ndash90

62 E M Sokolovskaya E F Kazakova and O D-S Kendivan

Russ Metall 1998 (4) 135ndash137

63 N G Bukhanko E F Kazakova and E M Sokolovskaya Russ

Metall 2001 (4) 425ndash431

64 E D Trubnyakova O I Bodak I N Ganiev and A V

Vakhobov Russ Metall 1987 (3) 219ndash222

65 I N Fridlyander and L V Molchanova Russ Metall 2003 (5)

476ndash480

66 R A Altynbaev S Kh Khairidinov and A V Vakhobov Russ

Metall 1987 (4) 194ndash196

67 J C Schuster and J Bauer J Less-Common Met 1985 109

345ndash350

68 L L Rokhlin A S Fridman T V Dobatkina and D G Eskin

Russ Metall 1991 (6) 146ndash148

69 A S Fridman T V Dobatkina and E V Muratova Russ

Metall 1992 (1) 207ndash209

70 C Xia F Zeng and Y Gu Trans Nonferrous Met Soc China

2003 13 546ndash552

71 F Zeng C Xia and Y Gu J Alloys Comp 2004 363 175ndash181

72 L L Rokhlin T V Dobatkina N R Bochvar and E V Lysova

J Alloys Comp 2004 367 10ndash16

73 T V Dobatkina A S Fridman and E V Muratova Russ

Metall 1992 (5) 125ndash127

74 I N Fridlyander L L Rokhlin N R Bochvar E V Lysova

and O V Boteva Russ Metall 2001 (6) 661ndash666

75 V N Rechkin L K Lamikhov and T I Samsonova Sov Phys

Crystallogr 1964 9 325ndash327

76 I I Zalutskii and P I Kripyakevich Sov Phys Crystallogr

1967 12 341ndash343

77 T J Bastow C T Forwood M A Gibson and M E Smith

Phys Rev B 1998 58 2988ndash2997

78 K Fukunaga M Kolbe K Yamada and Y Miura Mater Sci

Eng 1997 A 234ndash236 594ndash597

79 E P George J A Horton W D Porter and J H Schneibel

J Mater Res 1990 5 1639ndash1648

80 E P George D P Pope C L Fu and J H Schneibel ISIJ Int

1991 31 1063ndash1075

81 Y Harada and D C Dunand Acta Mater 2000 48 3477ndash3487

82 J H Schneibel and E P George Scripta Metall Mater 1990 24

1069ndash1074

83 J H Schneibel and P M Hazzledine Mater Res Soc Symp

Proc 1991 213 323ndash328

84 J H Schneibel and P M Hazzledine J Mater Res 1992 7

868ndash875

85 C J Sparks E D Specht G E Ice P Zschack and J Schneibel

Mater Res Soc Symp Proc 1991 213 363ndash368

86 J Tarnacki and Y-W Kim Scripta Metall Mater 1989 23

1063ndash1068

87 M Asta V Ozolins and C Woodward JOM 2001 53 (9) 16ndash

19

88 M E Drits L S Toropova F L Gushchina and S G Fedotov

Sov Non-Ferrous Met Res 1984 12 83ndash85

89 Y Harada and D C Dunand Scripta Mater 2003 48 219ndash222

90 C Woodward M Asta G Kresse and J Hafner Phys Rev B

2001 63 094103-1-6

91 J-H Xu and A J Freeman Phys Rev B 1990 41 12553ndash12561

92 M F Bartholomeusz and J A Wert Acta Metall Mater 1992

40 673ndash682

93 G Bester and M Fahnle J Phys Condens Matter 2001 13

11551ndash11565

94 C L Fu and M H Yoo Proc lsquoOrdered intermetallics ndash physical

metallurgy and mechanical behaviorrsquo Irsee Germany June 1991

155ndash164

95 K Fukunaga T Shouji and Y Miura Mater Sci Eng 1997 A

239ndash240 202ndash205

96 D P Pope Proc lsquoOrdered intermetallics ndash physical metallurgy

and mechanical behaviorrsquo Irsee Germany June 1991 143ndash153

97 J-S Wang Acta Mater 1998 46 2663ndash2674

98 M H Yoo and C L Fu Mater Sci Eng 1992 A 153 470ndash478

99 R W Hyland Jr and R C Stiffler Scripta Metall Mater 1991

25 473ndash477

100 I G Brodova I V Polents O A Korzhavina P S Popelrsquo I P

Korshunov and V O Esin Melts 1992 4 392ndash397

101 I G Brodova O A Chikova I V Polents P S Popelrsquo and V O

Esin Casting Processes 1992 1 (2) 158ndash160

102 I G Brodova D V Bashlikov and I V Polents Mater Sci

Forum 1998 269ndash272 589ndash594

103 K B Hyde A F Norman and P B Pragnell Mater Sci Forum

2000 331ndash337 1013ndash1018

104 K B Hyde A F Norman and P B Pragnell Acta Mater 2001

49 1327ndash1337

105 J Roslashyset and N Ryum Proc 6th Int Conf on lsquoAluminum

alloysrsquo Toyohashi Japan July 1998 793ndash798

106 V I Elagin V V Zakharov and T D Rostova Met Sci Heat

Treat 1993 (6) 317ndash319

107 R W Hyland Jr Metall Trans A 1992 23A 1947ndash1955

108 B A Parker Z F Zhou and P Nolle J Mater Sci 1995 30

452ndash458

109 C L Rohrer M D Asta S M Foiles and R W Hyland Jr

Mater Res Soc Symp Proc 1996 398 477ndash482

110 G M Novotny and A J Ardell Mater Sci Eng 2001 A 318

144ndash154

111 J D Robson M J Jones and P B Pragnell Acta Mater 2003

51 1453ndash1468

112 C Tan Z Zheng and B Wang Proc 3rd Int Conf on

lsquoAluminium alloysrsquo Vol I NTH Trondheim Norway June

1992 290ndash294

113 M Nakayama A Furuta and Y Miura Mater Trans JIM

1997 38 852ndash857

114 E A Marquis and D N Seidman Acta Mater 2001 49 1909ndash

1919

115 M J Jones and F J Humphreys Acta Mater 2003 51 2149ndash

2159

116 E A Marquis D N Seidman and D C Dunand in lsquoCreep

deformation fundamentals and applicationsrsquo (ed R S Mishra

J C Earthman and S V Raj) 299ndash308 2002 TMS

117 D N Seidman E A Marquis and D C Dunand Acta Mater

2002 50 4021ndash4035

118 E A Marquis D N Seidman and D C Dunand Acta Mater

2003 51 285ndash287

119 M E Drits L S Toropova U G Bikov and G K Anastaseva

Proc lsquoDiffusion in metals and alloysrsquo Tihany Hungary Augustndash

September 1982 616ndash623

120 V I Elagin V V Zakharov and T D Rostova Met Sci Heat

Treat 1983 (7) 546ndash549

Roslashyset and Ryum Scandium in aluminium alloys

International Materials Reviews 2005 VOL 50 NO 1 41

121 M Ye Drits L B Ber Yu G Bykov L S Toropova and G K

Anastaseva Phys Met Metall 1984 57 (6) 118ndash126

122 M E Drits L S Toropova and Yu G Bykov Sov Non-Ferrous

Met Res 1985 13 309ndash314

123 V I Yelagin V V Zakharov S G Pavlenko and T D Rostova

Phys Met Metall 1985 60 (1) 88ndash92

124 N Sano Y Hasegawa K Hono H Jo K Hirano H W

Pickering and T Sakurai Journal de Physique 1987 48 C6 337ndash

342

125 N Sano H-H Jo K-I Hirano and T Sakurai J Jpn Inst

Metals 1989 39 444ndash450

126 N Sano H Jo K Hirano and T Sakurai Proc Second Int

Conf on lsquoAluminium alloysrsquo Beijing China October 1990 549ndash

554

127 Y Miura M Nakayama and A Furuta Proc lsquoAspects of high

temperature deformation and fracture in crystalline materialsrsquo

Nagoya Japan July 1993 255ndash262

128 Y W Riddle and T H Sanders Jr Mater Sci Forum 2000

331ndash337 939ndash944

129 Y W Riddle M McIntosh and T H Sanders Jr in lsquoLightweight

alloys for aerospace application VIrsquo (ed K Jata E W Lee

W Frazier and N J Kim) 25ndash39 2001 TMS

130 M E Drits J Dutkiewicz L S Toropova and J Salawa Crystal

Res Technol 1984 19 1325ndash1330

131 Y W Riddle MSc thesis Georgia Tech GA USA 1998

132 T J Bastow and S Celotto Mater Sci Eng 2003 C 23 757ndash

762

133 M C Carroll M J Mills G S Daehn P I Gouma M F

Savage and B R Dunbar in lsquoAutomotive Alloys 1999rsquo (ed

S Das) 239ndash246 2000 TMS

134 E Clouet M Nastar and C Sigli Phys Rev B 2004 69 064109-

1-14

135 V V Zakharov Met Sci Heat Treat 1997 (2) 61ndash66

136 J W Christian lsquoThe theory of transformation in metals and

alloysrsquo 2nd edn 1975 Pergamon Press Ltd

137 A L Berezina V A Volkov B P Domashnikov S V Ivanov

and K V Chuistov Phys Metals 1990 10 296ndash304

138 S-I Fujikawa and S Sakauchi Proc 6th Int Conf on

lsquoAluminum alloysrsquo Toyohashi Japan July 1998 805ndash810

139 Y S Touloukian R K Kirby R E Taylor and P D Desai

(eds) lsquoThermal expansion metallic elements and alloysrsquo 1975

New York Plenum

140 J Roslashyset and N Ryum submitted to Scripta Mater

141 R O Simmons and R W Balluffi Phys Rev 1960 117 52ndash61

142 M Ocko E Babic R Krsmik E Girt and B Leontic J Phys F

Metals Phys 1976 6 703ndash707

143 M J Jones and F J Humphreys Proc First Joint Int Conf on

lsquoRecrystallization and grain growthrsquo Aachen Germany August

2001 Springer Verlag 1287ndash1292

144 S Iwamura M Nakayama and Y Miura Mater Sci Forum

2002 396ndash402 1151ndash1156

145 S Iwamura and Y Miura Acta Mater 2004 52 591ndash600

146 M Asta S M Foiles and A A Quong Phys Rev B 1998 57

11265ndash11275

147 R W Hyland Jr M Asta S M Foiles and C L Rohrer Acta

Mater 1998 46 3667ndash3678

148 J Roslashyset and N Ryum Proc 4th Int Conf on lsquoAluminium

alloysrsquo Vol I Atlanta GA USA September 1994 194ndash201

149 M E Drits L S Toropova G K Anastaseva and G L

Nagornichnykh Russ Metall 1984 (3) 192ndash195

150 E A Marquis D N Seidman and D C Dunand Acta Mater

2003 51 4751ndash4760

151 M E Drits L S Toropova and Yu G Bykov Met Sci Heat

Treat 1983 (7) 550ndash554

152 V V Zakharov and T D Rostova Met Sci Heat Treat 1995

(2) 65ndash69

153 M Nakayama and Y Miura Proc 4th Int Conf on lsquoAluminium

alloysrsquo Vol I Atlanta GA USA September 1994 538ndash545

154 M Nakayama and Y Miura J Jpn Inst Light Metals 1996 46

275ndash279

155 M Nakayama T Okuyama and Y Miura Mater Sci Forum

2000 331ndash337 927ndash932

156 M Nakayama T Okuyama and Y Miura Proc 6th Int Conf

on lsquoAluminum alloysrsquo Toyohashi Japan July 1998 517ndash522

157 M L Kharakterova D G Eskin and L S Toropova Acta

Metall Mater 1994 42 2285ndash2290

158 V I Elagin V V Zakharov and T D Rostova Met Sci Heat

Treat 1992 (1) 37ndash45

159 H Wiik Siv Ing thesis NTH Institute of Metallurgy

Trondheim Norway 1995

160 J Roslashyset H Hovland and N Ryum Mater Sci Forum 2002

396ndash402 619ndash624

161 Y Miura K Horikawa K Yamada and M Nakayama Proc

4th Int Conf on lsquoAluminium alloysrsquo Vol II Atlanta GA USA

September 1994 161ndash168

162 Y W Riddle PhD thesis Georgia Tech GA USA 2000

163 B Forbord W Lefebvre F Danoix H Hallem and

K Marthinsen Scripta Mater 2004 51 333ndash337

164 J D Robson Acta Mater 2004 52 1409ndash1421

165 C B Fuller J L Murray and D N Seidman submitted to Acta

Mater 2004

166 M G Mousavi C E Cross and Oslash Grong Sci Technol Weld

Joining 1999 4 381ndash388

167 J S Vetrano S M Bruemmer L M Pawlowski and I M

Robertson Mater Sci Eng 1997 A 238 101ndash107

168 Y W Riddle and T H Sanders Jr Mater Sci Forum 2000

331ndash337 799ndash803

169 G M Khan A O Nikiforov V V Zakharov and I I Novikov

Tsvetnye Metally 1993 34 (11) 43ndash45

170 Z Horita M Furukawa M Nemoto A J Barnes and T G

Langdon Acta Mater 2000 48 3633ndash3640

171 L A Willey US Patent 3 619 181 9 November 1971

172 L K Lamikhov and G V Samsonov Tsvetnye Metally 1964 5

(8) 77ndash80

173 A L Berezina K V Chuistov N I Kolobnev L B

Khokhlatova and T A Monastyrskaya Mater Sci Forum

2002 396ndash402 741ndash746

174 F A Fasoyinu J Thomson D Cousineau T Castles and M

Sahoo Proc 6th Int AFS Conf on lsquoMolten aluminum

processingrsquo Orlando FL USA November 2001

175 Z Yin Q Pan Y Zhang and F Jiang Mater Sci Eng 2000

A 280 151ndash155

176 I I Novikov and O E Grushko Mater Sci Technol 1995 11

926ndash932

177 D Cousineau M Sahoo P D Newcombe T Castles and F A

Fasoyinu Proc lsquoAFS 105th casting congressrsquo Dallas TX USA

AprilndashMay 2001 157ndash184

178 C E Cross and Oslash Grong Proc 6th Int Conf on lsquoAluminum

alloysrsquo Toyohashi Japan July 1998 1441ndash1446

179 F A Costello J D Robson and P B Prangnell Mater Sci

Forum 2002 396ndash402 757ndash762

180 K B Hyde A F Norman and P B Prangnell Mater Sci

Forum 2002 396ndash402 39ndash44

181 M E Drits S G Pavlenko L S Toropova Yu G Bukov and

L B Ber Sov Phys Dokl 1981 26 (3) 344ndash346

182 A M Drits and B A Kopeliovich Russ Metall 1985 (4) 147ndash

151

183 V G Davydov V I Elagin V V Zakharov and T D Rostova

Met Sci Heat Treat 1996 (8) 347ndash352

184 M E Drits L S Toropova Yu G Bykov L B Ber and S G

Pavlenko Russ Metall 1982 (1) 148ndash152

185 T D Rostova V G Davydov V I Yelagin and V V Zakharov

Mater Sci Forum 2000 331ndash337 793ndash798

186 Y W Riddle H Hallem and N Ryum Mater Sci Forum 2002

396ndash402 563ndash568

187 J Roslashyset and Y W Riddle Proc 9th Int Conf on lsquoAluminium

alloysrsquo Brisbane Australia August 2004 1210ndash1215

188 A M Diskin V K Portnoi A M Drits and A A Alalykin Sov

Non-Ferrous Met Res 1986 14 499ndash500

189 R R Sawtell P E Bretz and C L Jensen US Patent 4 689 090

25 August 1987

190 G A Salishchev Yu B Timoshenko and R A Saitova Proc

Second Int Conf on lsquoAluminium alloysrsquo Beijing China October

1990 413ndash415

191 T G Nieh R Kaibyshev L M Hsiung N Nguyen and

J Wadsworth Scripta Mater 1997 36 1011ndash1016

192 T G Nieh L M Hsiung J Wadsworth and R Kaibyshev Acta

Mater 1998 46 2789ndash2800

193 J S Vetrano C H Henager Jr M T Smith and S M

Bruemmer in lsquoHot deformation of aluminum alloys IIrsquo (ed T R

Bieler L A Lalli and S R MacEwen) 407ndash418 1998 TMS

194 J S Vetrano C H Henager Jr S M Bruemmer Y Ge and

C H Hamilton in lsquoSuperplasticity and Superplastic Forming

1998rsquo (ed A K Gosh and T R Bieler) 89ndash97 1998 TMS

195 V Y Gertsman J S Vetrano C H Henager Jr and S M

Bruemmer Proc First Joint Int Conf on lsquoRecrystallization and

grain growthrsquo Aachen Germany August 2001 Springer Verlag

2001 837ndash842

196 Y Xiao C Gao H Ma and S Tian Trans Nonferrous Met Soc

China 2001 11 235ndash238

Roslashyset and Ryum Scandium in aluminium alloys

42 International Materials Reviews 2005 VOL 50 NO 1

197 A Gholinia F J Humphreys and P B Prangnell Acta Mater

2002 50 4461ndash4476

198 A Gholinia F J Humphreys and P B Prangnell Mater Sci

Forum 2002 408ndash412 1519ndash1524

199 S Komura P B Berbon M Furukawa Z Horita M Nemoto

and T G Langdon Scripta Mater 1998 38 1851ndash1856

200 S Komura P B Berbon A Utsunomiya M Furukawa

Z Horita M Nemoto and T G Langdon in lsquoHot deformation

of aluminum alloys IIrsquo (ed T R Bieler L A Lalli and S R

MacEwen) 125ndash138 1998 TMS

201 S Komura Z Horita M Furukawa M Nemoto and T G

Langdon J Mater Res 2000 15 2571ndash2576

202 S Komura M Furukawa Z Horita M Nemoto and T G

Langdon Mater Sci Eng 2001 A 297 111ndash118

203 S Komura Z Horita M Furukawa M Nemoto and T G

Langdon Metall Mater Trans A 2001 32A 707ndash716

204 Z Horita M Furukawa K Oh-ishi M Nemoto and T G

Langdon Proc Fourth Int Conf on lsquoRecrystallization and

related phenomenarsquo (ed T Sakai and H G Suzuki) 1999 The

Japan Institute of Metals 301ndash308

205 Z Horita S Komura P B Berbon A Utsunomiya

M Furukawa M Nemoto and T G Langdon Mater Sci

Forum 1999 304ndash306 91ndash96

206 Z Horita S Lee S Ota K Neishi and T G Langdon Mater

Sci Forum 2001 357ndash359 471ndash476

207 Z Horita T Fujinami K Sato S B Kang H W Kim and T G

Langdon in Proc James T Staley Honorary Symposium on

Aluminum Alloys lsquoAdvances in the metallurgy of aluminum

alloysrsquo (ed M Tiryakioglu) 271ndash275 2001 ASM

208 P B Berbon S Komura A Utsunomiya Z Horita

M Furukawa M Nemoto and T G Langdon Mater Trans

JIM 1999 40 772ndash778

209 M Nemoto Z Horita M Furukawa and T G Langdon Mater

Sci Forum 1999 304ndash306 59ndash66

210 M Furukawa Z Horita M Nemeto and T G Langdon Proc

lsquoLight Metals 1999rsquo Quebec City PQ Canada August 1999 583ndash

592

211 M Furukawa K Oh-ishi S Komura A Yamashita Z Horita

M Nemeto and T G Langdon Mater Sci Forum 1999 304ndash

306 97ndash102

212 M Furukawa A Utsunomiya K Matsubara Z Horita and

T G Langdon Acta Mater 2001 49 3829ndash3838

213 M Furukawa A Utsunomiya S Komura Z Horita M Nemoto

and T G Langdon Mater Sci Forum 2001 357ndash359 431ndash436

214 M Furukawa Z Horita and T G Langdon in Proc James T

Staley Honorary Symposium on Aluminum Alloys lsquoAdvances in

the metallurgy of aluminum alloysrsquo (ed M Tiryakioglu) 47ndash56

2001 ASM

215 M Furukawa Z Horita M Nemoto and T G Langdon Mater

Sci Eng 2002 A 324 82ndash89

216 M Furukawa Z Horita and T G Langdon in lsquoUltrafine grained

materials IIrsquo (ed Y T Zhu T G Langdon R S Mishra S L

Semiatin M J Saran and T C Lowe) 459ndash468 2002 TMS

217 T G Langdon M Furukawa Z Horita and M Nemoto Proc

NATO Advanced Research Workshop on lsquoInvestigations and

applications of severe plastic deformationrsquo Moscow August

1999 NATO Science Series Series 3 High Technology vol 80

Kluwer Academic Publishers The Netherlands 2000 149ndash154

218 S Lee H Akamatsu A Utsunomiya K Neishi M Furukawa

Z Horita and T G Langdon Proc Thermec 2000 Las Vegas

USA December 2000

219 S Lee A Utsunomiya H Akamatsu K Neishi M Furukawa

Z Horita and T G Langdon Acta Mater 2002 50 553ndash564

220 A Yamashita D Yamaguchi Z Horita and T G Langdon

Mater Sci Eng 2000 A 287 100ndash106

221 K Oh-ishi Z Horita D J Smith and T G Langdon J Mater

Res 2001 16 583ndash589

222 H Akamatsu T Fujinami Z Horita and T G Langdon Scripta

Mater 2001 44 759ndash764

223 S Ota H Akamatsu K Neishi M Furukawa Z Horita and

T G Langdon Mater Trans 2002 43 2364ndash2369

224 K Furuno H Akamatsu K Oh-ishi M Furukawa Z Horita

and T G Langdon Acta Mater 2004 52 2497ndash2507

225 I N Fridlyander O G Senatorova N A Ryazanova and A O

Nikiforov Mater Sci Forum 1994 170ndash172 345ndash349

226 J N Fridlyander and O G Senatorova Mater Sci Forum 1996

217ndash222 1813ndash1818

227 J Liu and D J Chakrabarti Acta Mater 1996 44 4647ndash4661

228 O G Senatorova A N Uksusnikov J N Fridlyander

J Koshorst R R Romanova N A Ryazanova A Galliot

and V V Cherkassov Proc 6th Int Conf on lsquoAluminum alloysrsquo

July 1998 Toyohashi Japan 589ndash593

229 R A Emigh E L Bradley and J W Morris Jr in

lsquoSuperplasticity in aerospace IIrsquo (ed T R McNelley and H C

Heikkenen) 303ndash315 1990 TMS

230 E L Bradley III R A Emigh and J W Morris Jr Scripta

Metall Mater 1991 25 717ndash721

231 N I Kolobnev L B Khokhlatova V D Makarov E Yu

Semenova and V V Redchits Proc Sixth Int Aluminiumndash

Lithium Conference Garmisch-Partenkirchen Germany October

1991 1053ndash1056

232 N K Tsenev R Z Valiev O V Obraztsov and I N Fridlander

Proc Sixth Int AluminiumndashLithium Conference Garmisch-

Partenkirchen Germany October 1991 1125ndash1132

233 A M Shammazov N K Tsenev R Z Valiev M M

Myshlyaev M M Bikbulatov and S P Lebedich Phys Met

Metall 2000 89 (3) 314ndash318

234 F Musin R Kaibyshev Y Motohashi T Sakuma and G Itoh

Mater Trans A 2002 43A 2370ndash2377

235 M Shagiev Y Motohashi F Musin R Kaibyshev and G Itoh

Mater Trans A 2003 44A 1694ndash1697

236 M Shagiev Y Motohashi F Musin R Kaibyshev and G Itoh

Mater Trans A 2003 44A 1698ndash1701

237 B A Parker and Z F Zhou Proc 3rd Int Conf on lsquoAluminium

alloysrsquo Vol I NTH Trondheim Norway June 1992 363ndash367

238 J R Davies lsquoASM specialty handbook aluminum and aluminum

alloysrsquo 1993 Materials Park OH USA ASM

239 S J Andersen H W Zandbergen J Jansen C Traeholt

U Tundal and O Reiso Acta Mater 1998 46 3283ndash3298

240 M L Kharakterova D G Eskin and L L Rokhlin Russ

Metall 1997 (1) 104ndash109

241 J Roslashyset Dr Ing thesis NTNU Trondheim Norway 2002

242 P P Chattopadhyay S Datta and M K Banerjee Mater Sci

Eng 2002 A 333 67ndash71

243 L I Kaigorodova E I Selnikhina E A Tkachenko and O G

Senatorova Phys Met Metall 1996 81 513ndash519

244 Y-L Wu F H Froes C Li and A Alvarez Metall Mater

Trans A 1999 30A 1017ndash1024

245 Z Yin L Yang Q Pan and F Jiang Trans Nonferrous Met

Soc China 2001 11 822ndash825

246 V I Elagin V V Zakharov and T D Rostova Met Sci Heat

Treat 1994 36 (7) 375ndash380

247 Y V Milman A I Sirko D V Lotsko O N Senkov and D B

Miracle Mater Sci Forum 2002 396ndash402 1217ndash1222

248 C-H Joh K Yamada and Y Miura Mater Trans JIM 1999

40 439ndash442

249 X J Jiang Q H Gui Y Y Li L M Ma G J Liang and C X

Shi Scr Metall Mater 1993 29 211ndash216

250 X J Jiang Y Y Li W Deng L Y Xiong W M Wu Y J Gao

and C X Shi Adv Cryogenic Eng (Mater) 1994 40 1369ndash

1376

251 C-H Joh T Katsube K Yamada and Y Miura Proc 6th Int

Conf on lsquoAluminum alloysrsquo Toyohashi Japan July 1998 799ndash

804

252 L I Kaygorodova A M Dritz T V Krymova and I N

Fridlyander Proc Sixth Int AluminiumndashLithium Conference

Garmisch-Partenkirchen Germany October 1991 363ndash367

253 L I Kaigorodova A M Drits Ya V Zhingel T V Krymova

and I N Fridlyander Phys Met Metall 1992 73 286ndash290

254 A L Berezina V A Volkov S V Ivanov N I Kolobnev and

K V Chuistov Phys Met Metall 1991 71 (2) 167ndash175

255 I N Fridlyander N I Kolobnev A L Berezina and K V

Chuistov Proc Sixth Int AluminiumndashLithium Conference

Garmisch-Partenkirchen Germany October 1991 107ndash112

256 L I Kaigorodova A M Drits Ya V Zhingel T V Krymova

and V A Rassokhin Phys Met Metall 1992 73 281ndash285

257 I N Fridlyander S F Danilov E N Malysheva T A

Gorokhova and N N Kirkina Proc Sixth Int Aluminiumndash

Lithium Conference Garmisch-Partenkirchen Germany October

1991 381ndash386

258 G Dlubek S Krause H Krause A L Beresina V S

Mikhalenkov and K V Chuistov J Phys Condens Matter

1992 4 6317ndash6328

259 S Krause H Krause G Dlubek A L Beresina and K S

Chuistov Mater Sci Forum 1992 105ndash110 1109ndash1112

260 C Y Tan Z Q Zheng and S Q Liang Proc 4th Int Conf on

lsquoAluminium alloysrsquo Vol II Atlanta GA USA September 1994

329ndash333

261 A L Beresina N I Kolobnev K V Chuistov A V Kotko and

O A Molebny Mater Sci Forum 2002 396ndash402 977ndash981

Roslashyset and Ryum Scandium in aluminium alloys

International Materials Reviews 2005 VOL 50 NO 1 43

262 I N Ganiev I Yunusov and V V Krasnoyarskii J Appl Chem

USSR 1986 60 1961ndash1965

263 I N Ganiev Prot Met 1995 31 543ndash546

264 N V Vyazovikina Prot Met 1999 35 448ndash453

265 G V Kharina and V P Kochergin Prot Met 1996 32 134ndash

136

266 G V Kharina M V Kuznetsov and V P Kochergin Russ J

Electrochem 1998 34 482ndash485

267 V S Sinyavskii V D Valrsquokov and E V Titkova Prot Met

1998 34 549ndash555

268 Y L Wu F H Froes C G Li and J Liu Proc lsquoSynthesis

processing of lightweight metallic materials IIrsquo Orlando FL

USA February 1997 73ndash81

269 Z Ahmad and B J Abdul-Aleem Proc EuroCorr 2000

270 Z Ahmad A Ul-Hamid and B J Abdul-Aleem Corros Sci

2001 43 1227ndash1243

271 R Braun B Lenczowski and G Tempus Mater Sci Forum

2000 331ndash337 1647ndash1652

272 T Torma E Kovacs-Csetenyi L Vitalis I Vitanyi

J Stepanov and M Butova Mater Sci Forum 1987 1314

497ndash503

273 Z Wang P Wang K S Kumar and C L Briant in lsquoChemistry

and electrochemistry of corrosion and stress corrosion crackingrsquo

(ed R H Jones) 573ndash582 2001 TMS

274 V I Elagin V V Zakharov A A Petrova and E V

Vyshegorodtseva Russ Metall 1983 (4) 143ndash146

Roslashyset and Ryum Scandium in aluminium alloys

44 International Materials Reviews 2005 VOL 50 NO 1

Page 2: Scandium in aluminium alloys - Atom probe · A considerable part of the available literature on scandium in aluminium alloys is reviewed. ... behaviour in Al Cu, Al Mg Si,

a-Sc to b-Sc of 1350uC In the phase diagram assessmentof Ref 8 these temperature are adjusted to 1541 and1337uC respectively

A recent experimental investigation of selected com-positions in the AlndashSc phase diagram1617 deviatessignificantly from the early work2ndash4 Most of thedetermined invariant temperatures are different It isalso found that the AlSc2 phase melts congruently assuggested previously9 and at a temperature of approx1300uC The most prominent difference however is thefinding of an extensive solid solubility of Al in b-Sc anda eutectoid transformation

b-Sc~AlSc2za-Sc

occurring at approx 970uC A sketch of the completephase diagram based on these new findings16 is shown inFig 3

The four intermetallic phases are drawn as stoichio-metric line-compounds in all the published phasediagrams However it has been suggested16 that theAlSc phase is slightly off-stoichiometric and that ithas a composition range of approximately 52ndash54Sc

Microstructural observations18 indicate that the Al3Scphase also has a solubility range An overview of thedifferent phases in the AlndashSc system is given in Table 18

Reported enthalpies of formation for the intermetallicphases are given in Table 2 There is a considerabledifference in the data reported in Refs 16 and 19 Acomparison between the two data sets as well as withother works (not included in the present review) done inRef 16 shows that the data of Ref 16 are more in linewith other reported results

Al rich side of AlndashSc phase diagramAs for the eutectic reaction

Liq~a(Al)zAl3Sc

the reported eutectic temperature varies between 655and 659uC11ndash142223 The eutectic composition is approx06 wt-1114 and the solid solubility of Sc in Al at theeutectic temperature is approx 035 wt-12

Table 1 Overview of phases in AlndashSc system8

Phase Pearson symbol Space group Strukturbericht designation Prototype Lattice parameter A Density g cm23

Al cF4 Fm3m A1 Cu a540496 2699Al3Sc cP4 Pm3m L12 AuCu3 a54103 3026Al2Sc cF24 Fd3m C15 Cu2Mg a57582 3015AlSc cP2 Pm3m B2 CsCl a53450 2909AlSc2 hP6 P63mmc B82 Ni2In a54888 c56166 3043b-Sc cI2 Im3m A2 W a5373 (estimated) 2880 (estimated)a-Sc hP2 P63mmc A3 Mg a533088 c552680 29890

Table 2 Some reported enthalpies of formation[kJ mol21] for intermetallic phases in AlndashScsystem

Reference Enthalpy Al3Sc Al2Sc AlSc AlSc2

19 2DH 0298 2395 2824 1240 847

20 2DH 00 193

16 2DH 0300 174 142 918 110

21 2DH 00 180

Calculated

1 Periodic table of elements with Al main alloying ele-

ments in Al-alloys and rare earth elements

2 Sketch of first reported AlndashSc phase diagram2ndash4

3 Sketch of AlndashSc binary phase diagram eutectic tem-

perature of AlzAl3Sc is adapted from Ref 10 peritec-

tic temperature of Al3Sc and temperature of congruent

melting of Al2Sc are calculated in Ref 16 all other bin-

ary invariant points are reported experimental values

in Ref 16

Roslashyset and Ryum Scandium in aluminium alloys

20 International Materials Reviews 2005 VOL 50 NO 1

The solvus line of Sc in Al has been estimated byseveral researchers and over a wide temperaturerange111224ndash31 All the reported measurements aresummarised in Fig 4 There is some spread in theresults most noticeably between data from Russian andnon-Russian papers

In most practical cases solidification of alloys occursunder non-equilibrium conditions Thus the finalmicrostructure might be different from what theequilibrium phase diagram predicts In the case of diluteAlndashSc alloys this is illustrated in a metastable statediagram for solidification at a cooling rate of approx100 K s2132 The temperature of the eutectic reactiondecreases by 3ndash4uC and the eutectic compositionincreases from approx 06 wt- to approx 07 wt-Also the maximum solid solubility of Sc in Al increasesto approx 06 wt-32

Ternary quaternary and higher orderAlndashScndashX(ndashX2ndashX3ndashhellip) phase diagramsA wide range of ternary quaternary and higher orderAlndashScndashX(ndashX2ndashX3ndashhellip) phase diagrams has been reportedin the literature the majority in Russian journals Someof the Russian journals do not have parallel Englishtranslations and thus these data are less accessible forthe non-Russian reader However a good overview ofthe majority of the published material is available33 Notall of the published phase diagrams comprise the fullcomposition ranges In the present review the emphasisis placed on phase diagrams of AlndashSc with elements thatare technologically important alloying elements withaluminium

Ternary phase diagrams withprecipitate-forming elementsAlndashMgndashSc

The AlndashMgndashSc phase diagram seems to be the AlndashScndashXdiagram that is best described in the technical literatureIn an investigation of AlndashMgndashSc alloys with up to

26 wt-Mg and 3 wt-Sc25 a ternary eutectic

Liq~aAlzAl3Mg2zAl3Sc

was observed at 447uC Two vertical cross-sections andone isothermal section at 430uC of the phase diagramwere constructed (Fig 5) It was found that Mg and Scmutually reduce each otherrsquos solid solubility in Al Thelsquocornerrsquo of the a-Al field was determined to be at105 wt-Mg and 0007 wt-Sc at 430uC No ternaryAlMgSc phases were observed

In another investigation a vertical cross-section of theAl rich corner at a constant Sc level of 03 wt- wasconstructed34 No ternary phases were reported Thisphase diagram suggests probably as a result of a lapseby the authors that 03 wt-Sc is a hypereutecticcomposition in binary AlndashSc

Odinaev and co-workers explored the AlndashMgndashScsystem for the whole AlndashMg range and for Sc contentsup to 333 at-Sc3536 An isothermal section at 400uC35

was constructed No ternary phases were observed in theregion examined A liquidus surface and three quasi-binary cross-sections were also constructed36 Threequasibinary eutectics three ternary eutectics and oneternary peritectic were observed in the examinedcomposition range The temperature for the eutecticreaction shown above was determined to be 435uCand the composition was found to be 625 at-Al366 at-Mg and 09 at-Sc

In a recent study37 the isothermal cross-section at350uC was determined experimentally in the regiondelimited by the phases Al3Mg2 Al3Sc AlSc2 MgScand Mg meaning that the Al- and Sc-corners of thephase diagram were not explored There are somediscrepancies between the phase relations found in thiswork37 and those found by Odinaev et al35 However noternary AlMgSc phases were found in Ref 37 either Allthe four intermetallic (AlSc) phases were found todissolve a few percent Mg seemingly by substituting AlFor Al3Sc this observation is sustained by othermeasurements38 where some Mg content in Al3Scprecipitates was found by three-dimensional atom probemicroscopy In Ref 37 a calculated liquidus surface and

4 Reported values of Al solvus line in AlndashSc phase dia-

gram full line is solvus estimate assuming regular

solution and applying maximum solubility as

assessed in Ref 10 and experimental data of Ref 31

5 Isothermal section of Al-corner of AlndashMgndashSc phase

diagram at 430uC redrawn from Ref 25

Roslashyset and Ryum Scandium in aluminium alloys

International Materials Reviews 2005 VOL 50 NO 1 21

several calculated vertical and isothermal cross-sectionsare also presented Additional phase diagram calcula-tions are reported in a separate paper39

The phase relations in a diffusion couple between Alndash177 wt-Sc and pure Mg at 430uC have also beenstudied40 No ternary phases were reported and the a-Alwas found to be in equilibrium with Al3Sc and Al3Mg2in accordance with earlier work253537 The maximumsolid solubility of Mg and Sc in a-Al at this temperaturewas reported to be 1527 at- (14 wt-) and 033 at-(055 wt-) respectively Both these solubilities and inparticular that of Sc is higher than what has been foundearlier25 Considering the binary AlndashSc system wherethe solubility of Sc in a-Al is only approx 0025 wt- at430uC the high solubility of Sc reported in Ref 40 forthe ternary system is rather unlikely It is possible thatfine-scale Al3Sc precipitates embedded in the a-Almatrix have been included in the electron probeanalyses and thus giving too high a value for the Sccontent in solid solution

AlndashCundashSc

Two ternary phases AlCuSc and AlCu2Sc werereported in an early investigation41 A later investigationof the Al-corner of the phase diagram42 revealed that aternary (AlCuSc) phase named the lsquoW-phasersquo couldbe in thermodynamic equilibrium with a-Al Thefollowing ternary invariant equilibria were found

LiqzAl3Sc~aAlzW(5720C)

Liq~aAlzAl2CuzW(5460C)

Isothermal sections of the Al-corner at 450 and 500uChave been constructed43 (Fig 6) The solid solubility ofCu in Al was found to decrease somewhat withincreasing Sc content whereas the solid solubility ofSc in Al was not found to be influenced by the Cucontent The W-phase was suggested to be the com-pound Al54ndash8Cu66ndash4Sc43 A liquidus surface of the Al-corner has also been constructed44

A more thorough review on the AlndashCundashSc system isavailable in the literature45

AlndashScndashSi

An isothermal section at 497uC has been constructed forthe entire system46 A ternary phase AlSc2Si2 wasidentified This phase frequently referred to as the lsquoV-phasersquo was found to be in thermodynamic equilibrium withAl3Sc Al Si and ScSi at this temperature A projection ofthe liquidus surface of the Al-corner has also been made47

Two ternary invariant reactions were reported

LiqzAl3Sc~aAlzV(6170C)

Liq~aAlzSizV(5740C)

Vertical cross-sections and isothermal sections of the Al-corner are reviewed in Ref 33 The 550uC isothermalsection is redrawn in Fig 7 It seems that the solidsolubility of Sc is not altered by an addition of Siwhereas the solubility of Si decreases somewhat with theSc content

AlndashScndashZn

A sketch of a lsquosemi-isothermalrsquo cross-section of the wholesystem partially at 300uC and partially at 500uC hasbeen reported48 No ternary phases were found in thisinvestigation The phase relations in the Al rich rangewere found to be limited by the subsystem AlndashZnndashAl3Sc

Another investigation of the subsystem AlndashZnndashAl2Scconfirmed that no ternary compounds are found in thiscomposition range49 The liquidus surface was con-structed It is suggested that the section ZnndashAl2Sc is aquasibinary simple eutectic A certain mutual solidsolubility of Zn and Al2Sc is indicated on the verticalcross-section although no measurements of the compo-sitions are presented In addition to the quasibinaryeutectic one ternary peritectic and one ternary eutecticreaction was found The ternary eutectic reaction

Liq~aAlzZnzAl3Sc

was found to occur at 367uC

AlndashLindashSc

An investigation of the phase relations in the Al-corner(up to 5 wt-Li and 3 wt-Sc) at 450uC revealed that

6 Isothermal section of Al-corner of AlndashCundashSc phase dia-

gram at 500uC redrawn from Ref 437 Isothermal section of Al-corner of AlndashScndashSi phase dia-

gram at 500uC redrawn from Ref 33

Roslashyset and Ryum Scandium in aluminium alloys

22 International Materials Reviews 2005 VOL 50 NO 1

a-Al could be in equilibrium with either Al3Sc or AlLi50

No ternary phases were observed Thermal analysesindicated that the ternary eutectic reaction

Liq~aAlzAl3SczAlLi

occurs at approximately 595uC It has been stated47 thatthere are only minor mutual effects of Sc and Li on theseelementsrsquo solid solubility in a-Al

This statement is confirmed in another investigation51

where the AlndashAlLindashAlSc subsystem is investigated At450uC it is found that the AlLi phase can be inequilibrium with Al3Sc Al2Sc and AlSc No significantsolubility of Li in Al3Sc was observed Several verticalcross-sections are constructed

It should be noted that the existence of a ternaryAl3(LiSc) phase has been reported52 which is indisagreement with the observations above

Ternary phase diagrams withdispersoid-forming elementsAlndashScndashZr

It has been shown53 that at 600uC the Al-corner consistsof the phase fields a-AlzAl3Sc a-AlzAl3SczAl3Zrand a-AlzAl3Zr Further it was discovered that there isa significant solid solubility of Zr in the Al3Sc phase(approx 35 wt-) and some solid solubility of Sc in theAl3Zr phase (approx 5 wt-) The lattice parameter ofAl3Sc was found to decrease when the phase dissolvesZr and likewise the lattice parameter of the Al3Zr wasfound to decrease when that phase dissolves Sc Foralloys in the a-AlzAl3Sc phase field the wt-Zrwt-Scratio in the Al3Sc particles was found to be approx 22times the wt-Zrwt-Sc ratio of the alloy53 Isothermalsections of the Al-corner at 550 and 600uC are alsoconstructed54 (Fig 8)

In another investigation55 two vertical cross-sectionsin the Al-corner were constructed and a ternaryperitectic reaction

LiqzAl3Zr~aAlzAl3Sc

was found to take place at 659uC

The 500uC isothermal section of the whole phasediagram has been investigated56 It is already knownthat Sc and Zr are completely miscible in the solid stateHere it was also found that the compounds AlSc2 andAlZr2 are completely miscible The extensions of theother single-phase fields are determined with variousdegrees of accuracy The solubility of Zr in Al3Sc wasfound to be 6 at- (approx 16 wt-) whereas thesolubility of Sc in Al3Zr was found to be 65 at-(approx 73 wt-) Contrary to Ref 53 the latticeparameter of Al3Sc was found to increase with increas-ing Zr content The lattice parameter of Al3Zr howeverwas found to decrease with increasing Sc content whichis in accordance with the findings of Ref 53

The section Al3ScndashAl3Zr at 1200uC has recently beeninvestigated57 The solubility of Sc in Al3Zr was reportedto be in the range 3ndash5 at- and the solubility of Zr inAl3Sc was found to be 122 at- In accordance withRef 53 the lattice parameters of Al3Sc and Al3Zr decreasewith increasing content of Zr and Sc respectively

AlndashFendashSc

The available data on this system is reviewed in Ref 33and an isothermal section at 500uC is reproduced Threeternary AlndashFendashSc phases are reported The Al-corner ofthe isothermal section however seems to be limited bythe subsystem AlndashAl3ScndashAl3Fe meaning that the a-Alcannot be in equilibrium with any of the ternary phases

AlndashMnndashSc

The Al-corner of the phase diagram has been investi-gated58 No ternary phases were observed meaning thatin the solid state only the Al3Sc and the Al6Mn phasecan be in equilibrium with a-Al An addition of Mn doesnot noticeably decrease the solid solubility of Scwhereas an addition of Sc causes a distinct decrease inthe solubility of Mn Two isothermal sections weremade one at 500uC (Fig 9) and one at 600uC Thelsquocornerrsquo of the a-phase field was reported to be at008 wt-Sc and 02 wt-Mn at 500uC and at 02 wt-Scand 055 wt-Mn at 600uC

8 Isothermal section of Al-corner of AlndashScndashZr phase dia-

gram at 600uC redrawn from Ref 54

9 Isothermal section of Al-corner of AlndashMnndashSc phase

diagram at 500uC redrawn from Ref 58

Roslashyset and Ryum Scandium in aluminium alloys

International Materials Reviews 2005 VOL 50 NO 1 23

Two vertical cross-sections were also constructed Aternary eutectic

Liq~aAlzAl6MnzAl3Sc

at 649uC was identified Several alloys in the sectionAl3ScndashAl6Mn have also been investigated59 and all werefound to comprise a mixture of the two binary phasesLattice parameter measurements of the Al3Sc phasewere interpreted as an indication of a slight solidsolubility of Mn in Al3Sc

AlndashCrndashSc

Alloys in the composition range 30ndash100 at-Al havebeen studied60 and an isothermal cross-section at 500uCwas constructed No ternary phases were identified Thephases that can be in equilibrium with the a-Al are thusAl7Cr and Al3Sc The solubility of Cr in the Al3Sc phasewas found to be considerable approximately 11 at-

Other ternary AlndashScndashX phase diagramsAlndashMondashSc

An isothermal cross-section at 550uC has been con-structed for the subsystem AlndashAl2ScndashAl2Mo61 Noternary phases were reported The phases in equilibriumwith a-Al were found to be Al3Sc and Al12Mo

AlndashScndashV

The section Al3ScndashAl21V2 has been studied62 and thevertical cross-section was constructed No ternaryphases were observed Solid solubilities of V in theAl3Sc phase of 14 at- and of Sc in Al21V2 of 25 at-are reported although a considerably higher maximumsolubility of V in Al3Sc is suggested in the vertical cross-section A quasibinary eutectic reaction

Liq~Al3SczAl21V2

is reported to occur at 917 K (644uC)The section Al3ScndashAl3V at 1200uC has also been

studied57 The solubilities of V in Al3Sc and Sc in Al3Vare reported to be 27 and 07 at- respectively WhenV was dissolved in Al3Sc the lattice parameter of Al3Scwas found to decrease

AlndashScndashTi

No ternary phase diagram is available The sectionAl3ScndashAl3Ti at 1200uC has been studied57 A solubilityof Ti in Al3Sc of almost 125 at- was found whichcorresponds to almost half of the Sc being substituted byTi The lattice parameter of Al3Sc was found to decreasesharply with increasing Ti content For the Al3Ti phasethe solubility of Sc was found to be approx 5 at-

AlndashCondashSc

The ternary system for 0ndash70 at-Sc has been investi-gated63 Three ternary (AlCoSc)-phases were identifiedThe only phases found to be in equilibrium with a-Alwere the binary phases Al3Sc and Al9Co2 An isothermalsection at 600uC and the vertical cross-sections Al3ScndashAl9Co2 and Al3ScndashAl9Co3Sc2 were constructed Thelsquocornerrsquo of the a-phase field was reported in the text to beat 15 at-Co and 05 at-Sc although in a tablethe numbers 02 at-Co and 01 at-Sc are reportedThe solubilities of Co in the Al3Sc phase and of Sc in theAl9Co2 phase were found to be 12 and 01 at-

respectively However in the vertical cross-sections it issuggested that the solubility of Co in Al3Sc may besignificantly higher at higher temperatures The latticeparameter of Al3Sc was not found to change withincreasing Co content

AlndashScndashSr

The subsystem AlndashAl2ScndashAl4Sr has been studied64 andan isothermal section at 500uC was constructed Noternary phases were detected meaning that the phases inequilibrium with a-Al were found to be Al3Sc and Al4SrThe solubility of Sc in Al4Sr and of Sr in Al3Sc wasfound to be low typically less than 15ndash2 at-

AlndashBendashSc

A study of the binary BendashSc system and the ternary AlndashBendashSc system for up to 20 at-Sc (or 30 wt-Sc) hasbeen reported65 The 600uC isothermal section for theinvestigated ternary composition range was constructedNo ternary phases were observed The a-Al can be inequilibrium with either Be Be13Sc or Al3Sc It is sug-gested that the section AlndashBe13Sc may be quasi-eutectic

AlndashBandashSc

An isothermal section at 500uC has been constructed66

No ternary phases were reported and a-Al is inequilibrium with Al4Ba and Al3Sc The solubility of Scin Al4Ba and of Ba in Al3Sc was reported to be less than2 at-

AlndashNndashSc

The region AlndashAlNndashScNndashSc has been investigated67 Aperovskite-type ternary phase AlN12xSc3 was reportedand an isothermal section at 1000uC was constructed Inthe Al-corner the Al melt was reported to be inequilibrium with AlN and Al3Sc

Quaternary and higher order AlndashScndashXndashX2(ndashX3hellip)phase diagramsAlndashMgndashScndashZr

The published material is limited to investigations onAl rich alloys A part of the liquidus surface of the6 wt-Mg section has been determined experimentallyfor the composition range 0ndash07 wt-Sc and 0ndash04 wt-Zr68 The 500uC isothermal phase relations inthe Al-corner of the 6 wt-Mg section has also beeninvestigated69 for Sc and Zr concentrations of up to3 wt- and 4 wt- respectively No ternary or qua-ternary phases were observed Likewise the 430uC iso-thermal phase relations of the 4 at-Mg (y35 wt-Mg)section have been investigated for up to 12 at-Sc(2 wt-Sc) and up to 25 at-Zr (8 wt-Zr)7071 Noternary or quaternary phases were observed in thepresent study either The Al3Sc phase was found todissolve an amount of 122 at-Zr corresponding to asubstitution of almost 50 of the Sc lattice positionswhereas the solubility of Sc in Al3Zr was 44 at-which corresponds to a substitution of almost 20 ofthe Zr lattice positions Figure 4 in Refs 70 and 71suggests that the Al content in the Al3Zr-phase increaseswith increasing Sc content however this is not sub-stantiated in the text

Roslashyset and Ryum Scandium in aluminium alloys

24 International Materials Reviews 2005 VOL 50 NO 1

AlndashMgndashScndashTindashZr

A vertical cross-section of the AlndashMgndashScndashTindashZr phasediagram for 03 wt-Sc 015 wt-Ti 015 wt-Zrand 0ndash10 wt-Mg has been constructed34 Accord-ing to this diagram the Al3Zr phase is the first andAl3Sc the last to form during solidification of thealloys No ternary quaternary or quinary phases arereported

AlndashZnndashMgndashCundashZrndashSc

A vertical cross-section of the full system as well asseveral sections of various sub-systems have beenconstructed72 For the full system a section at8 wt- Zn 2 wt-Cu 03 wt-Zr and 03 wt-Scwas constructed where Mg varies from 0 to 8 wt-The only reported Sc-containing sub-system is thatof AlndashZnndashMgndashCundashSc Here a vertical cross-sectionis constructed with the same levels of Zn Cu and Scas in the full system whereas Mg varies from 0 to65 wt-

No phases other than those known from the lowerorder systems were reported Amongst the findings it isinteresting to note that in the solid state Al3Sc isreported to be an equilibrium phase for all theinvestigated compositions It is also interesting to notethat the Sc-containing W-phase (Al54ndash8Cu66ndash4Sc see thesection on the AlndashCundashSc ternary system) is an equili-brium phase at low Mg content and disappears as theMg content increases

AlndashLindashMgndashSc

The 400uC isothermal phase relations of the 02 wt-Scsection have been investigated for the composition range0ndash6 wt-Mg and 0ndash5 wt-Li73 The a-Al was found tobe in equilibrium with AlLi Al2LiMg and Al3Sc Noquaternary phases were observed This investigation isalso summarised in Ref 50

AlndashCundashLindashSc

The aluminium rich corner of the system has beeninvestigated for alloys with 06 wt-Sc and with Cu andLi in the range 0ndash16 wt- and 0ndash4 wt- respectively74

No quaternary phases were reported Two sections ofthe phase diagram were constructed a section of the470uC isothermal tetrahedron at 06 wt-Sc and avertical section at 06 wt-Sc and 26 wt-Li Twoquaternary invariant equilibria were found and thetemperatures of the invariant points were estimated

Al3Sc phaseRechkin and co-workers were to the authorsrsquo knowl-edge the first to publish a paper in an internationaljournal identifying the Al3Sc phase75 The phase wasidentified as cubic with lattice parameter a5410 A Afew years later the lattice structure was reported to be ofthe Cu3Au type76 The atomic arrangement of the Al3Scphase is shown in Fig 10 The structure can bedescribed as ordered face-centred cubic (fcc) althoughin crystallographic terminology the Al3Sc structure isactually a simple cubic lattice with four atoms (one Scand three Al atoms) associated with each lattice pointThis particular atomic arrangement is nominated L12

and is found in several intermetallic compounds forinstance Ni3Al Ni3Fe and Cu3Au

Some efforts have been made in characterising theproperties of the Al3Sc phase A compilation of someresults is given in Table 3 The motivation for themajority of the investigations seems to be one of thethree following

(i) the Al3Sc phase has a density of 303 g cm23 andit melts peritectically at approx 1320uC This canmake the Al3Sc phase an attractive candidate asa material for lightweight high temperaturestructural applications205777ndash86

(ii) in order to understand the effect of Al3Scprecipitation in Al-alloys it is necessary to gainmore knowledge about the Al3Sc phase578187ndash91

(iii) the Al3Sc is an excellent model phase forstudying basic properties of intermetalliccompounds7990ndash98

10 Atomic arrangement of Al3Sc phase

Table 3 Some reported properties of Al3Sc phase

ReferenceE GPa(Youngrsquos modulus) n (Poissonrsquos ratio)

CTE (Coefficient ofthermal expansion) 1026 K21

(111) APB energymJ m22

(100) APB energymJ m22

88 Approx 11120 166 020 Max 670 45079 166 022 31399 1628 0204

1642iexcl19 0201iexcl000189 16

Reported to decrease linearly with increasing temperature to approx 97 GPa at 550uCCalculatedExperimental

Roslashyset and Ryum Scandium in aluminium alloys

International Materials Reviews 2005 VOL 50 NO 1 25

Formation of Al3Sc in AlndashSc alloysThere are at least four ways that the Al3Sc phase canform in dilute binary AlndashSc alloys

1 Upon solidification of hypereutectic alloys (Sc

approx 06 wt-) Al3Sc is the first phase to form

2 The solidification of hypo- and hypereutectic alloysends with formation of eutectic AlzAl3Sc

3 Al3Sc can precipitate discontinuously from super-saturated solid solution

4 Al3Sc can precipitate continuously (nucleation andgrowth) from supersaturated solid solution

Primary Al3ScAccording to the binary phase diagram primary Al3Scshould form during solidification of all alloys with Sccontent higher than approx 06 wt- ie higher thanthe eutectic composition Formation of primary Al3Sc inAlndash07 wt-Sc melts cooled at 102ndash103 K s21 has beenreported1832 According to the metastable state dia-gram32 this alloy composition is close to the eutectic oneat these cooling rates

Primary Al3Sc is reported to have a highly facetedmorphology1318100ndash102 The observation of a cubicmorphology in a slowly cooled Alndash87 wt-Sc alloyindicates that the facet planes in this case are thecrystallographic (100) planes13 Brodova et al100ndash102

have investigated the microstructure of rapidly cooledAlndash2 wt-Sc alloy They found that the dominantmorphology of primary Al3Sc was dependent on boththe cooling rate and the initial melt temperature A mapof primary Al3Sc morphologies as a function of theseparameters was constructed and is redrawn in Fig 11

The nucleation mechanism and growth morphologyof primary Al3Sc in an Alndash07 wt-Sc alloy solidified ata cooling rate of 100 K s21 were investigated by Hydeet al103104 Indications were found that the primaryAl3Sc particles nucleate heterogeneously on oxideparticles in the melt The primary Al3Sc particles werefound to grow with a dendritic morphology with theprimary dendrite arms in the crystallographic n110m

direction The overall shape is cubic which is inaccordance with earlier observations

Eutectic Al3ScEutectic AlzAl3Sc has been reported in hyper- as wellas hypoeutectic alloys11 but is scantily described in theliterature Given a eutectic composition of 06 wt- amaximum solid solubility of Sc in Al of 035 wt- andthe specific densities in Table 1 a eutectic formed underequilibrium conditions would contain a volume fractionof approx 063 vol-Al3Sc At high cooling rates thevolume fraction of Al3Sc in the eutectic is probablysomewhat smaller owing to the increased supersatura-tion of Sc in Al

The morphology of the eutectic in an Alndash2 wt-Scalloy is reported to depend on the temperature of themelt before solidification100 For low melt temperaturesthe eutectic is reported to be rodlike for a wide range ofcooling rates For intermediate melt temperatures andhigh cooling rates a lsquodiscontinuous eutecticrsquo is reportedwhereas for high melt temperatures and slow coolingrates a lsquoquasieutecticrsquo structure is reported with Al3Scparticles of almost spherical shape

Hyde et al have reported that during solidification ofan Alndash07 wt-Sc alloy some of the primary Al3Scparticles are pushed ahead of the Al solidification frontand end up at the grain boundaries103104 Thus primaryAl3Sc may be mixed with eutectic Al3Sc in themicrostructure A scanning electron microscopy (SEM)picture showing eutectic Al3Sc at the grain boundaries asdescribed in Refs 103 and 104 is given in Fig 12

Discontinuous precipitation of Al3ScDiscontinuous precipitation of Al3Sc from super-saturated solid solution is often observed in binary AlndashSc alloys131831105 This precipitation mechanism whichis sometimes referred to as cellular precipitation iscommonly described as a decomposition of super-saturated solid solution into a-Al and Al3Sc at a movinggrain boundary The driving force for the grainboundary migration is the volume free energy that isreleased during the precipitation As the grain boundarymoves it leaves behind a characteristic fan shaped array

11 Morphology of primary Al3Sc particles in Alndash2 wt-Sc

alloy as a function of melt overheating and cooling

rate during solidification redrawn from Ref 102

12 SEM image of particle structure of Alndash07 wt-Sc

alloy cooled at a rate of 100 K s21 during solidifica-

tion as described in Refs 103 and 104 primary Al3Sc

particle is seen in centre of grain whereas eutectic

Al3Sc is decorating grain boundaries image is kindly

provided by Dr Kristian Hyde UMIST Manchester UK

Roslashyset and Ryum Scandium in aluminium alloys

26 International Materials Reviews 2005 VOL 50 NO 1

of precipitates In the AlndashSc case the discontinuouslyprecipitated Al3Sc particles have been demonstrated tobe coherent with the aluminium matrix1318

The driving force for discontinuous precipitationincreases with increasing supersaturation of Sc in theAl matrix Thus discontinuous precipitation in binaryAlndashSc is most frequently reported in studies of alloyswith a Sc content of 04 wt- or higher1318106 Stilldiscontinuous precipitation has also occasionally beenreported to occur at lower alloy compositions In an Alndash027 wt-Sc alloy discontinuous precipitation wasobserved over a wide range of temperatures107 In arecent study31105 of precipitation kinetics and mechan-isms in Alndash02 wt-Sc discontinuous precipitation wasfound to take place when the specimens were quencheddirectly from a solutionising temperature in this case600uC to aging temperatures in the range 370ndash490uCFurther C-curves in a temperature-time-transformation(TTT) diagram were established (Fig 13) which showedthat the highest transformation rate of discontinuousprecipitation lies at a higher temperature than thehighest transformation rate of the continuous precipita-tion reaction ie the two precipitation reactions arerepresented by two separate lsquonosesrsquo on the C-curves

It has been shown that discontinuous precipitationcan be suppressed by continuous precipitation if thematerial is cold worked before the precipitation heattreatment13108

As a result of their rather coarse nature andinhomogeneous dispersion discontinuously precipitatedAl3Sc contributes but little to the strength of the alloyand also leads to a smaller amount of Sc in super-saturated solid solution being available for subsequentcontinuous precipitation Thus discontinuous precipita-tion is in general regarded as an undesired precipitationmode

Continuous precipitation of Al3ScContinuous precipitation of Al3Sc is a bulk decomposi-tion process of supersaturated solid solution of Sc in Aland can in the isothermal case be characterised by anucleation stage a growth stage and finally a coarsen-ing stage Apparently the continuous precipitation reac-tion occurs largely by homogeneous nucleation anddiffusion controlled growth and AlndashSc has occasionallybeen used as a model system for studying the mechan-isms of nucleation growth and coarsening107109ndash111

There have been several studies of the continuousprecipitation reaction in binary AlndashSc alloys and up tillnow there is no evidence that any metastable phases areforming before the L12 phase Al3Sc Thus it is assumedthat the equilibrium phase nucleates directly fromsupersaturated solid solution

Even though the nucleation of Al3Sc is frequentlyreported to occur homogeneously throughout the Almatrix there are some examples in the technical litera-ture of reported heterogeneous Al3Sc nucleation ondislocations110112ndash115 and grain boundaries110113115ndash118

In a recent numerical modelling study of continuousprecipitation in AlndashSc alloys111 the effect of hetero-geneous nucleation on dislocations is accounted for Themodel predicts that homogeneous nucleation dominatesat high Sc concentrations and low transformation tem-peratures whereas heterogeneous nucleation is predictedto dominate at low Sc concentrations and high trans-formation temperatures Figure 14 shows a sketch of anucleation map for AlndashSc The shift between homo-geneous and heterogeneous dominance in nucleation isdependent on the dislocation density as indicated in thefigure

The shape of continuously precipitated Al3Sc particlesis most frequently reported to be spherical29112113119ndash129

However it seems that under certain conditions theshape can differ from the spherical one Drits et al130

reported both spherical and star shaped morphologyThe star shaped precipitates had arms growing in thecrystallographic n110m-directions (Star shaped Al3Scprecipitates have also been found after some thermo-mechanical treatments of an AlndashMgndashScndashZr alloy131) InRef 128 precipitates of both cuboidal and sphericalmorphology are found to coexist after certain heattreatments Cauliflower shaped precipitates as well asprecipitates of spherical and cuboidal shapes arereported by Novotny and Ardell110 Bastow andCelotto132 found large oblong Al3Sc particles in an Alndash01 wt-Sc alloy after aging at 400uC for 24 h A facetedshape is suggested in a high-resolution image of anAl3(Sc Zr) precipitate in an AlndashMgndashMnndashZrndashSc alloy133

In a systematic high-resolution transmission electron

13 TTT diagram of precipitation in Alndash02 wt-Sc alloy

after solutionising at 600uC and direct quench to

aging temperature3114 Nucleation map for binary AlndashSc alloys which indi-

cates how the tendency towards heterogeneous ver-

sus homogeneous nucleation is predicted to depend

upon Sc concentration transformation temperature

and dislocation density redrawn from Ref 111

Roslashyset and Ryum Scandium in aluminium alloys

International Materials Reviews 2005 VOL 50 NO 1 27

microscopy (TEM) study of the Al3Sc particle morphol-ogy development during precipitation heat treatment ofbinary AlndashSc alloys by Marquis and Seidman114 it isdemonstrated that the precipitates can take a wide rangeof shapes as they grow depending on Sc content in thealloy transformation temperature and transformationtime Irregular shaped star shaped and cuboidalshaped precipitates were observed under someconditions It was however found that the equilibriumshape of the particles is an equiaxed multifaceted one(Fig 15) Supported by Wulffrsquos construction it wasconcluded that the shape was that of a GreatRhombicuboctahedron This equilibrium morphologyhas been reproduced by computer-simulations ofparticle growth87134 The multifaceted particles caneasily be taken for spherical in a conventional TEMpicture

Kinetics of precipitation of Al3Sc fromsupersaturated solid solutionThe precipitation kinetics of Al3Sc in binary AlndashScalloys is dependent on the precipitation heat treatmenttemperature and on the Sc content in the alloy Acomprehensive overview over the transformationkinetics in terms of C-curves is given by Zakharov135

The C-curves for 5 transformation for a range of AlndashSc alloys are redrawn in Fig 16

Hyland107 studied the homogeneous nucleationkinetics of Al3Sc in a Alndash018 wt-Sc alloy after directquench from 650uC to precipitation temperatures of 288and 343uC He found that after an incubation time t theAl3Sc particles nucleated at a constant rate until thediffusion fields of the individual particles started tooverlap At 288uC the incubation time and time tosignificant diffusion field overlap were estimated to beapprox 245 and 150 min respectively whereas thecorresponding values at 343uC were estimated to beapprox 7 and 20 min respectively

If one assumes that the JohnsonndashMehlndashAvramindashKomolgorov (JMAK) relationship is valid for thisprecipitation reaction one can express the fraction

transformed X as a function of the reaction time t bythe equation

X (t)~1expfrac12k(Dt)n (1)

where k is a constant D is the interdiffusion constant ofSc in Al and the exponent n is dependent on thenucleation rate For the situation described byHyland107 where the precipitates nucleate at a constantrate the value of n should theoretically136 be equal to52

Roslashyset and Ryum31105 applied an alloy and heattreatment method practically equal to that of Hyland107

One should thus expect that the precipitation kineticsshould also be quite similar However Roslashyset andRyum reported that the exponent n of the JMAKrelationship was approx 165ndash185 for the temperaturerange of concern31105 This does not point in thedirection of a constant nucleation rate but rather inthe direction of site saturation ie that all the particlesare nucleated simultaneously which in the JMAKequation would yield an exponent n of 32136 Anoverview of some reported values of n in the JMAKequation is given in Table 4 The majority of the valueslie closer to 32 than to 52 However it is important to

15 High resolution TEM picture along n100m axis of Al3Sc particle in Alndash03 wt-Sc alloy aged at 300uC for 350 h114

(reproduced with permission from Elsevier Science image kindly provided by Dr E A Marquis and Professor D N

Seidman) and various projections of a Great Rhombicuboctahedron

Table 4 Some reported values of n in JMAK equation

Reference n C 0Sc wt-Sc Ttrans uC Note

137 13 030 300 Solution heat treated (SHT) 500uC16026 030 300 SHT 600uC Low n at late stage20026 030 300 SHT 640uC Low n at late stage

29 130ndash149 015 260ndash370145ndash196 025 260ndash370

138 188ndash216 020 240ndash35031 165ndash185 023 270ndash350 SHT 600uC Direct quench to transformation temp

16 C-curves for 5 transformation in a range of binary

AlndashSc alloys redrawn from Ref 135

Roslashyset and Ryum Scandium in aluminium alloys

28 International Materials Reviews 2005 VOL 50 NO 1

note that an n value close to 32 is per se not evidence ofsite saturation

Hyland also showed that a water quench from thesolutionising temperature significantly altered thenucleation kinetics in the subsequent precipitation heattreatment107 The incubation time was dramaticallyshortened which is attributed to the quenched-in excessvacancies and it is also indicated that there might be ashift in the nucleation rate in the early stage ofprecipitation It is suggested that the vacancies mayenhance the diffusion of Sc in Al and that there is apossibility that vacancy clusters act as heterogeneousnucleation sites for Al3Sc precipitates107 Regardless ofwhich mechanism that is operative it is clearly demon-strated that the nucleation kinetics can be dependent onthe thermal history between solutionising and precipita-tion heat treatment

Loss of coherency during growth of Al3ScprecipitatesWhen an Al3Sc particle grows it will sooner or laterreach a critical size where it will be energetically morefavourable to introduce an interface dislocation at theAlAl3Sc interface than to increase the matrix strain Asimple approximation for the critical size can be derivedfrom the lattice parameters assuming that the criticalsize is reached when the misfit over the whole particlediameter equals the Burgers vector of the Al matrix

dcrit~b=d (2)

where b is the Burgers vector of Al and d is themisfit between Al and Al3Sc This approximation yieldsa critical diameter of approx 215 nm at ambienttemperature

The misfit d and thus also the critical diameter dcrit

will depend on the temperature owing to the differencesin thermal expansion between the Al matrix and the

Al3Sc particles The thermal expansion of Al3Sc hasrecently been measured89 and based on the differencesin thermal expansion between Al139 and Al3Sc the misfitas a function of temperature has been calculated89 Thiscalculation is reproduced and shown by the solid line inFig 17

It is however possible to refine this calculationsomewhat140 Whereas the thermal expansion of Al3Sc isexpected to be only because of lattice expansion there isa significant contribution from vacancies on thermalexpansion of Al at high temperatures141 Thus thetemperature effects on the misfit should be calculatedfrom the changes in lattice parameters rather than fromthe linear thermal expansion By subtracting the vacancyeffect on the thermal expansion one achieves atemperature-dependent misfit as represented by thedotted line in Fig 17

A second correction that should be taken into accountis the effect of Sc in solid solution on the latticeparameter of the Al matrix With increasing tempera-ture more Sc is brought into solid solution and it isreported that the lattice parameter of the Al matrixpresumably measured at room temperature increaseslinearly with the Sc content in solid solution142 Thesedata can be used to calculate the effect on the latticeparameter at elevated temperatures under the assump-tion that the relative increase in lattice parameter owingto Sc in solid solution is independent of temperature InRef 142 a figure is presented which shows the measuredlattice parameter as a function of Sc content in solidsolution and a value (dadc)a is reported where a is thelattice parameter of the Al matrix and c is the Sc contentin solid solution in at- The reported value for (dadc)a is 100 times larger than that indicated in thecorresponding figure possibly as a result of a decimalerror in the text Thus in the present exercise 1100th ofthe reported value for (dadc)a is used Using this incombination with the regular solution approximationfor the solvus line of Sc in Al1231 one obtains acorrection for Sc in solid solution on the temperature-dependent misfit as shown in Fig 18 This figure shows

17 Lattice mismatch between Al and Al3Sc as a function

of temperature solid line represents calculation

based on linear thermal expansion of the two phases

dotted line represents correction for vacancies in Al

lattice

18 Corrections of mismatch calculated from linear ther-

mal expansion data as a result of vacancies and to

Al lattice expansion from Sc in solid solution

Roslashyset and Ryum Scandium in aluminium alloys

International Materials Reviews 2005 VOL 50 NO 1 29

both the correction for vacancies and for Sc in solidsolution on the same graph The two corrections are ofapproximately the same magnitude but with oppositesigns Thus the resulting (net) correction is close to zeroand it turns out that the first hand approximation asapplied in Ref 89 is very good in this case

Applying the calculated temperature dependent misfitwith the simple approximation for a critical diameter forloss of coherency one obtains a temperature-dependentcritical diameter as shown in Fig 19

Some examples from the literature of experimentallyobserved critical diameters in binary AlndashSc alloys aresummarised in Table 5 along with some predictions forcritical diameters from Fig 19 There is a fairly goodconsistency between the observations and the measureddiameter is quite close to the simple predictions above

A more refined analysis on the transition fromcoherent to incoherent particles has recently beenperformed145 This analysis is based on the balancebetween the increase in particlematrix interface energyowing to interfacial dislocations and the relaxation inelastic energy in the Al matrix owing to the samedislocations This method yields a predicted criticaldiameter of 246 nm for transition from coherent to

semi-coherent particles at ambient temperature Thetemperature dependence of the critical diameter is nottreated in this analysis

The loss of coherency during isothermal annealing hasbeen reported to be accompanied by an increasedaverage coarsening rate119121137145 The increasedcoarsening rate has been attributed either to diffusionof Sc along dislocation lines119121 or to the increasedparticlematrix interface energy of a semicoherentparticle145 However there are also several data sets inthe literature that do not indicate an increased growthrate after the loss of coherency114128

Al3ScAl interface energyThe interface energy between Al3Sc and the Al matrix isone of the key parameters that governs the nucleationgrowth and coarsening behaviour of Al3Sc in Al and Alalloys The interface energy has been estimated in severalinvestigations either by fitting experimental data toequations that describe nucleation or coarsening or bycalculations A compilation of some of the results isgiven in Table 6 There is considerable spread in thereported values regardless of what approach has beenused for the estimation

Influence of other elements on precipitation ofAl3ScMagnesium

With regard to precipitation mechanism it has beenstated that Mg suppresses the tendency to discontinuousprecipitation of Al3Sc106 In an investigation of pre-cipitation kinetics of Al3Sc in the temperature range300ndash500uC only minor changes in the kinetics (Fig 20)were found when up to 5 wt-Mg was added to an Alndash04 wt-Sc alloy135 It seems that the precipitationreaction is slightly faster in the Mg-containing alloys

Several investigations on age hardening response alsoimply that there is only a small if any effect of Mg onthe precipitation kinetics of Al3Sc23148149 It is how-ever found that the hardness increase from theprecipitation of Al3Sc is somewhat reduced in AlndashMgndashSc alloys compared to binary AlndashSc alloys23148149 InRef 149 it is suggested that some of the Sc is dissolvedin the Al3Mg2 phase and thus the age hardeningpotential is reduced with increasing Mg contentSomewhat contradictory to these observations but

Table 5 Some reported critical diameters for coherencyloss in binary AlndashSc and correspondingtheoretical critical diameters from Fig 19

Reference dcrit nmC0

Scwt-Sc

TtransuC

Theoreticaldcrit nm

119 38ndash40 05137 28ndash30 03 400 308128 32 02 400 450 308 335129 50 02143 40 012 025115 40 025 450ndash500 335ndash37114 40 03 400 450 308 335144 40 02 400ndash460 308ndash341145 30ndash80 02 400ndash490 308ndash362

20 C-curves for 10 and 60 transformation in Alndash

04 wt-Sc and Alndash4 wt-Mgndash04 wt-Sc redrawn

from Ref 135

19 Simple approximation for temperature-dependent criti-

cal diameter for introduction of dislocations on Al

Al3Sc interface

Roslashyset and Ryum Scandium in aluminium alloys

30 International Materials Reviews 2005 VOL 50 NO 1

sustained by Ref 135 it has recently been reported150

that precipitation of Al3Sc at 300 and 350uC occursslightly faster in an Alndash2 wt-Mgndash02 wt-Sc alloythan in an Alndash02 wt-Sc alloy studied previously by thesame researchers117118 and that the correspondinghardness increase is highest in the AlndashMgndashSc alloyThe only reported difference in experimental procedureis the solutionising temperature which was higher forthe AlndashSc alloy (648uC) than for the AlndashMgndashSc alloy(617uC) However given that the nucleation time isshortened by quenched-in vacancies as suggested byHyland107 the difference in homogenisation tempera-ture should be in favour of a faster precipitation of thebinary AlndashSc alloy It should be worthwhile to probedeeper into this observation of different aging responses

Mg in solid solution increases the lattice parameter ofthe Al matrix This is in turn expected to influence thecritical diameter for AlAl3Sc coherency loss as discussedin the section on lsquoLoss of coherency during growth ofAl3Sc precipitatesrsquo above Such an influence on the criticaldiameter is also briefly discussed elsewhere150 A criticaldiameter of 80 nm in an Alndash3 wt-Mgndash02 wt-Sc alloyhas been observed compared to 40 nm in a binary Alndash02 wt-Sc alloy of the same investigation144 Otherresearchers have reported a critical diameter in excess of116 nm in an Alndash63 wt-Mgndash02 wt-Sc alloy151

Computer simulations predict that the AlAl3Scinterface should be enriched in Mg87 These predictionsare confirmed experimentally by three-dimensional atomprobe microscopy of an Alndash2 wt-Mgndash02 wt-Sc alloyaged at 300uC38 Here it was found that the Mg contentat the interface is approximately three times higher thanthe matrix concentration regardless of aging time

Copper

It has been claimed that Cu suppresses the tendencytowards discontinuous precipitation of Al3Sc106

Zakharov and Rostova152 have reported that additionsof up to 14 wt-Cu have only minor effects on theprecipitation kinetics in an Alndash04 wt-Sc alloy Themost noticeable effect is that for temperatures above400uC the late stage of the transformation is sloweddown for the highest Cu contents This does not show in

Fig 21 however where only the 10 and 60transformation curves are included

The W-phase (AlCuSc) was observed in the alloywith the highest Cu content which means that less Sc isavailable for the precipitation of Al3Sc in this alloyAnother investigation on the age hardening response ofAlndash023 wt-Sc and Alndash25 wt-Cundash023 wt-Sc at300uC also implies that the precipitation behaviour ofAl3Sc in the two alloys is similar153154 At 350uC alimited portion of the Al3Sc has been observed tonucleate heterogeneously on coarse hrsquo precipitates155

According to the isothermal sections of the phasediagram43 one should expect the ternary W-phase toform instead of the Al3Sc phase in an alloy with such ahigh CuSc ratio However no observations of the W-phase or other ternary phases were reported from TEMstudies of the Alndash25 wt-Cundash023 wt-Sc alloy thathad been heat treated in the temperature range 300ndash460uC153ndash156 A third investigation on the precipitationin Alndash048 wt-Sc alloys with up to 440 wt-Cu in thetemperature range 100ndash450uC also concludes that no W-phase or other ternary phase forms during the heattreatment157

Copper in solid solution decreases the lattice para-meter of the Al matrix Thus it is expected that the misfitbetween Al and Al3Sc precipitates should be higher in

21 C-curves for 10 and 60 transformation in Alndash

04 wt-Sc and Alndash14 wt-Cundash04 wt-Sc redrawn

from Ref 152

Table 6 Reported values of interphase energy cAlAl3Sc between coherent Al3Sc precipitates and Al matrix

Reference cAlAl3Sc mJ m22 Method of estimation

137 10 Fit of coarsening data to LifshitzndashSlezev equation107 78iexcl20 (288uC) Back-calculation of incubation time

93iexcl20 (343uC)107 123iexcl41 (288uC) Back-calculation of nucleation rate

125iexcl35 (343uC)29 542 (400uC) Fit of coarsening data to Ostwald ripening

632 (430uC)413 (460uC)

146 c(100) 192 (0 K) c(111) 226 (0 K) Pseudopotential calculations147 c(100) 325 (0 K) c(110) 513 (0 K) c(111)

782 (0 K) c(100) 315 (288uC) c(100) 325 (343uC)Atomistic simulation

110 105 Fit of coarsening data to LSW theory31 20ndash300 Fit of coarsening data to Ostwald ripening

for 16 different temperatures111 57 Fit of precipitation model to experimental data145 120 coherent particles Fit of coarsening data

170 semicoherent particles

It is argued in this study that c may be lower in the nucleation stage

Roslashyset and Ryum Scandium in aluminium alloys

International Materials Reviews 2005 VOL 50 NO 1 31

AlndashCundashSc alloys compared to AlndashSc alloys Howeveran experimental investigation of Alndash25 wt-Cundash023 wt-Sc alloy comes to a different conclusion Thelattice misfit strain is found to decrease compared to Alndash02 wt-Sc and the critical diameter for coherency losswas found to be the same in the ternary and the binaryalloy144 It is suggested that these observations may bebecause of the dissolution of some Cu in the Al3Sc phaseand thus that the lattice parameters of both the Al matrixand the Al3Sc precipitates decrease in the ternary alloy

Silicon

It has been found that the onset of precipitation in Alndash04 wt-Sc is only slightly altered when Si contents ofup to 04 wt are introduced in the alloy However thefinal stage of the precipitation reaction is considerablydelayed with increasing Si content135 Figure 22 showsthe effect of addition of a joint of 035 wt-Si and040 wt-Fe There are at least two possible explana-tions for why an Si-addition leads to this behaviour

1 Alloying with Si is known to promote discontin-uous precipitation of Al3Sc106158 It has been shown thatwhen isothermal precipitation of Al3Sc starts discon-tinuously the later stage of the overall transformationcan be very slow31

2 The isothermal section of the phase diagramsuggests that the V-phase (AlSc2Si2) should form inalloys of this composition46 If the V-phase forms lessSc is available for precipitation of Al3Sc

It has been shown157 that for an AlndashScndashSi alloy withsolid solution content of 010 wt-Sc an 110 wt-Sithe only phases to precipitate after heat treatment at200uC are Si and an (AlScSi)-phase possibly the V-phase On the other hand the Al3Sc phase has beenobserved to form in alloys with 04 wt-Sc and up to08 wt-Si159160

Zinc

It has been reported that additions of up to 5 wt- Znhave only minor effects on the precipitation kinetics ofan Alndash04 wt-Sc alloy135 (Fig 23) In Ref 106 it isclaimed that Zn promotes discontinuous precipitation ofAl3Sc

Lithium

A comparison of the age hardening response at 400uC inAlndash24 wt-Lindash019 wt-Sc and Alndash024 wt-Sc alloys

indicates that the onset of Al3Sc-precipitation is notaffected by the presence of Li161

Zirconium

As mentioned in the section on lsquoTernary phase diagramswith dispersoid-forming elementsrsquo earlier a considerableamount of Zr is dissolved in the Al3Sc phase and thus amore correct denotation of the precipitating phase isAl3(Sc12xZrx) In discussing the influence of the Zrcontent on the precipitation of Al3Sc one is thereforeactually discussing the difference in precipitation ofAl3Sc versus Al3(Sc12xZrx)

It is found that an addition of 015 wt-Zr to an Alndash04 wt-Sc alloy only marginally affects the initial stageof the precipitation reaction123135 while it slows downthe later stages of the transformation considerably(Fig 24)135 The coarsening rate of the Al3(Sc12xZrx)particles in AlndashScndashZr alloys is found to be much slowerthan that of Al3Sc particles in AlndashSc alloys123162

In three-dimensional atom probe field ion microscopy(3D-APFIM) of Al3(Sc12xZrx) particles formed at 475uCin a ternary AlndashScndashZr alloy163 it was found that the coreof the particles is almost pure Al3Sc whereas there is ashell of Al3(Sc12xZrx) with almost equal content of Scand Zr Such a behaviour has also been predicted bycomputer modelling of precipitation of Al3(Sc12xZrx) at480uC in an AlndashZnndashMgndashScndashZr alloy164 This modelpredicts that Zr starts to enter the growing

22 C-curves for 10 and 60 transformation in Alndash

04 wt-Sc and Alndash04 wt-Fendash035 wt-Sindash04 wt-Sc

redrawn from Ref 135

23 C-curves for 10 and 60 transformation in Alndash

04 wt-Sc and Alndash5 wt-Znndash04 wt-Sc redrawn

from Ref 135

24 C-curves for 10 and 60 transformation in Alndash

04 wt-Sc and Alndash04 wt-Scndash015 wt-Zr redrawn

from Ref 135

Roslashyset and Ryum Scandium in aluminium alloys

32 International Materials Reviews 2005 VOL 50 NO 1

Al3(Sc12xZrx) particles when approximately half of thesupersaturated Sc has been precipitated The Zr contentof the outer shell is predicted to be much higher thanwhat has been found experimentally163164

Another 3D-APFIM study of Al3(Sc12xZrx) particlesin a ternary AlndashScndashZr alloy has been reported165 Hereparticles grown at 300uC for various lengths of time werestudied The Zr content in these particles was muchlower than that reportedpredicted at higher tempera-tures163164 even after very long annealing times

Iron

The effect of adding up to 07 wt-Fe on the precipita-tion kinetics in an Alndash04 wt-Sc alloy has beeninvestigated135 The onset of precipitation was onlyslightly influenced by the Fe-level whereas the laterstages of the transformation however were significantlyslowed down as the Fe-level increased An example ofthe effect of a joint addition of Fe and Si is shown inFig 22

Manganese chromium and titanium

Small additions (03 wt-) of manganese or chromiumto Alndash040 wt-Sc alloys are reported to have onlyminor effects on the precipitation kinetics of Al3Sc135

According to Ref 106 Mn is reported to promote andCr and Ti to suppress discontinuous precipitation

Rare earth elements

An investigation of the precipitation behaviour of Alndash03 at-Sc and Alndash03 at-Scndash03 at-X alloyswhere X is either yttrium gadolinium holmium orerbium in the temperature range 235ndash310uC indicatedthat a Al3(Sc12xXx) phase with L12 structure wasformed in the ternary alloys22 Peak strength is reportedto occur after approx 10 h at 285uC in all alloys whichindicates that the precipitation kinetics up to peakstrength is practically unaltered by the ternary additions

Influence of Sc on microstructure andproperties of wrought aluminium alloysMost of the effects of Sc addition in wrought Al-alloysare linked to the formation of the Al3Sc phase In atypical processing route of a wrought aluminium alloyparticles of the Al3Sc phase can form under threedifferent conditions each of which influences themicrostructure and properties of the alloy in a specificway

1 During solidification after casting or weldingAl3Sc particles can form in the melt and act as nucleifor a-Al thus leading to grain refinement18166

2 High temperature processing of the alloy in therange 400ndash600uC for instance homogenisation hot-rolling or extrusion can give a dense distribution ofAl3Sc particles of typically 20ndash100 nm size The particledistributions formed under such conditions are reportedto lead to good recrystallisation resistance128148167168

and enhanced superplasticity52169170

3 Heat treatment in the range 250ndash350uC can lead tosignificant precipitation hardening of an alloy super-saturated in Sc148158171 The size of strengthening Al3Scprecipitates is typically in the range 2ndash6 nm121

Grain refinementA good grain refinement is almost always desired uponsolidification The formation of small equiaxed grainsrather than long dendrites in the melt facilitates thefeeding of the melt into cavities of the shrinkingsolidified metal and thus reduces the problem ofshrinkage porosity The tendency to hot cracking is alsoreduced and the second phase particles become morefinely and uniformly distributed

To the authorsrsquo knowledge the first effect of Sc in Al-alloys that was reported in an international scientificjournal was the grain refining action in pure Al and in anAlndashCu alloy upon solidification172 which was found tobe stronger for Sc than for other transition metals Inlater studies of Sc as a grain refiner in pure Al1832173 ithas been demonstrated that approx 07 wt-Sc issufficient to provide excellent grain refinement It hasalso been demonstrated that additions of 025 wt-Scz025 wt-Zr provide good grain refinement in pure Al18

In order for Sc to act as an effective grain refiner theAl3Sc phase has to form in the melt before thesolidification of a-Al The Al3Sc particles have a latticeparameter close to that of pure Al and whenhypereutectically formed the Al3Sc particles are veryeffective substrates for the nucleation of the a-Al phaseAs mentioned in the section on lsquoFormation of Al3Sc inAlndashSc alloysrsquo above this requires that the alloy ishypereutectic with respect to Sc ie in excess of approx06 wt- in a binary AlndashSc alloy In ternary and higherorder systems the eutectic Sc composition may dependon the other alloying elements present For instance theeutectic composition of Sc has been predicted todecrease with increasing Mg content in the ternary AlndashMgndashSc system39 This prediction is sustained by theobservation of good grain refinement by adding 05 wt-Sc to an Alndash7 wt-Mg alloy174 (Other examples ofgrain refinement at Sc concentrations lower than that ofthe binary eutectic are found in Ref 173)

Similarly the observation of good grain refinement inan Alndash025 wt-Scndash025 wt-Zr alloy18 may be as aresult of a lower Sc content of the eutectic in the ternarysystem ie less Sc is needed to make the alloy hyper-eutectic No literature data on the liquidus surface of theAlndashScndashZr system are available and thus this hypothesiscannot be confirmed In more complex alloy systems itis also observed that excellent grain refinement isachieved at low Sc contents when Sc is added togetherwith Zr It is reported that adding either 02 wt-Sc06 wt-Sc or 01 wt-Zr to an Alndash5Mg alloy givesmuch poorer grain refinement than adding 02 wt-Scz01 wt-Zr175 Similarly additions of 015 wt- ofeither Sc or Zr are reported to only marginally refinethe grain structure in an AlndashCundashLi alloy whereas a jointaddition of 015 wt-Sc and 015 wt-Zr gives excellentgrain refinement176 For an AA 3650 casting alloy (Alndash7 wt-Sindash04 wt-Mg) good grain refinement is achievedby adding 039 wt-Sc or 027 wt-Scz019 wt-Zr177

In some AlndashZnndashMgndashScndashZr alloys it is also found thatan addition of 02ndash03 wt-Sc can be sufficient for goodgrain refinement166169178179 Examples of the grainrefinement as a function of Sc addition in pure Al andin an AlndashZnndashMgndashZr alloy are shown in Fig 25

The nucleation of a-Al on Al3Sc particles in the melt isfacilitated by the close match in the lattice parameters ofthe two phases As shown in Fig 17 the mismatch at the

Roslashyset and Ryum Scandium in aluminium alloys

International Materials Reviews 2005 VOL 50 NO 1 33

eutectic temperature of binary AlndashSc alloys (660uC) isonly approx 047 In Refs 57 and 89 it is shown thatwhen Zr Hf and in particular Ti is dissolved in the Al3Scparticles this reduces the lattice parameter of the phaseIt appears that when 25 of the Sc atoms in Al3Sc aresubstituted by Ti the mismatch is zero at approx 550uCand becomes negative at higher temperatures89 Thissuggests that by carefully selecting the Ti content of thealloy it should be possible to obtain Al3(ScTi)substrates in the melt that match exactly the latticeparameter of the nucleating a-Al and thus furtherimprove the grain refinement of the alloy This appearsto have been achieved in a recent work180 where thegrain refinement of an Alndash07 wt-Sc alloy wascompared with that of an Alndash05 wt-Scndash02 wt-Tialloy At a cooling rate of 100 K s21 only an estimated2 of the primary Al3Sc particles of the binary AlndashScalloy were effective nuclei compared to practically 100for the primary Al3(ScTi) particles in the ternary AlndashScndashTi alloy leading to a much smaller grain size in theternary alloy Whereas the match of lattice parametersmay be of importance for these results the authors ofthis investigation180 draw attention to other factors suchas different growth restriction factors for Sc and Ti andthe possibility of a peritectic reaction in the ternaryalloy Nevertheless the principle of matching latticeparameters is worth looking into further in future work

Effects from dispersoidslsquoDispersoidsrsquo is a term which is commonly used aboutthe classes of second phase particles that are formedin an Al alloy during high temperature annealing orthermomechanical processing such as homogenisationhot rolling extrusion and forging A dense distributionof dispersoids can give a significant contribution to analloyrsquos strength owing to particle strengthening but thisis rarely the main strengthening mechanism A moreimportant contribution from the dispersoids is theirability to stabilise the grainsubgrain structure of analloy through the Zener-drag action and thus improvethe mechanical properties of the alloy

There are two noticeable dispersoid-related effectsthat have been reported for Sc-containing alloys Thefirst is the stabilising effect on a deformed microstruc-ture When a non-recrystallised structure is preserved inan alloy this can add considerably to the mechanical

strength of the material The second effect is thepreservation of a small grain size during hot deforma-tion at slow deformation rates which is necessary toobtain superplastic properties of an Al-alloy

Recrystallisation resistance

The anti-recrystallisation effect of Sc was first publishedin a patent171 where 03 wt-Sc was added to pure Aland to AlndashMg AlndashMn and AlndashZnndashMg alloys Both Sc-free and Sc-containing materials were cold worked andsubsequently annealed and it was found that theaddition of Sc increased the temperature for onset ofrecrystallisation by approx 220uC in pure Al andsomewhat less in the Al-alloys Although the author ofthe patent171 may have been well aware that the anti-recrystallisation effect is caused by Al3Sc dispersoidsthis is not mentioned in the text The first journal paperthat explicitly points out that the recrystallisationresistance is due to Al3Sc dispersoids was an investiga-tion of the effects of adding Sc to wrought AlndashMgalloys181 In this work it was found that the Al3Scdispersoids were very effective in preventing recrystalli-sation up to temperatures of approx 400ndash450uC Athigher temperatures the dispersoids coarsen consider-ably and the microstructure was partially recrystallised

It is established that the Zener-drag pZ that is imposedon an advancing grain boundary by randomly distrib-uted dispersoids can be expressed in the form

pZ~k f =r (3)

where k is a factor that includes the interface energybetween the dispersoids and the matrix f is the volumefraction and r is the mean radius of the dispersoids Thusthe Zener drag will decrease rapidly in the case where thedispersoids are coarsening

As mentioned in the section on lsquoInfluence of otherelements on precipitation of Al3Scrsquo above theAl3(Sc12xZrx) dispersoids in a ternary AlndashScndashZr alloycoarsen at a much slower rate than the Al3Sc dispersoidsin a binary AlndashSc alloy This effect was first reported inRef 123 (although also observed in Ref 182) andaccording to Ref 33 the same authors demonstratedsoon after that the denser dispersoid distributionachieved in an AlndashScndashZr alloy leads to superiorrecrystallisation resistance compared to a binary AlndashScalloy An example of the increased recrystallisationresistance by adding both Zr and Sc is shown in Fig 26

In isothermal sections of the ternary AlndashScndashZr phasediagram it is indicated that the solid solubility ofSczZr is somewhat higher than that of Sc alone54 Ithas also been demonstrated both by electrical con-ductivity measurements (Fig 27) and microstructuralobservations that the supersaturation of SczZr isgreater than that of only Sc or Zr in as cast Alndash15(SczZr) alloys183 This indicates that it should bepossible to increase the volume fraction of dispersoids inAlndashScndashZr compared to AlndashSc It is suggested162 that theincreased volume fraction that can be achieved byadding both Sc and Zr can be advantageous inconventional wrought Al-alloys

There are at least two different conditions underwhich Al3Sc or Al3(Sc12xZrx) dispersoids can form toprevent recrystallisation

1 Sc (or Sc and Zr) is in solid solution before thedeformation In the case of cold deformation and

25 Grain refinement as a function of Sc addition in pure

Al (redrawn from Ref 32) and AlndashZnndashMgndashZr (redrawn

from Ref 169) note that data points are plotted on

different ordinate axes

Roslashyset and Ryum Scandium in aluminium alloys

34 International Materials Reviews 2005 VOL 50 NO 1

subsequent annealing the Al3Sc or Al3(Sc12xZrx)dispersoids may nucleate and grow before the nucleationand growth of recrystallised grains takes placeDispersoids can form after a direct up-quench to theannealing temperature115143148184 during ramp-up tothe annealing temperature115 or by pre-annealing at anintermediate temperature129 In the case of hot deforma-tion the Al3Sc or Al3(Sc12xZrx) dispersoids maynucleate and grow during preheating of the materialand during the hot deformation itself184

2 The Al3Sc or Al3(Sc12xZrx) dispersoids are formedin the material before deformation184 Considering coldrolling and subsequent annealing the annealing tem-perature Tann may be either lower or higher than thetemperature Tdisp at which the dispersoids were formedIf TannTdisp only limited if any coarsening of thedispersoids is expected to take place and thus the Zenerdrag from the particles is expected to be practicallyconstant The driving force for recrystallisation how-ever is expected to decrease somewhat with theannealing time as a result of recovery processes Thusif recrystallisation does not occur within short annealingtimes the material is expected to remain unrecrystallisedfor infinite time at the annealing temperature IfTannTdisp there will be substantial coarsening of thedispersoids during annealing In order for the materialto remain unrecrystallised the decrease in driving forcefor recrystallisation owing to recovery has to be at leastas rapid as the decrease in Zener drag because of particlecoarsening

Experimental comparisons of the conditions abovepoint in the direction that the recrystallisation resistanceis poorest when Sc (or Sc and Zr) is in solid solutionbefore deformation and the deformed material is up-quenched to the annealing temperature148 or when Al3Scor Al3(Sc12xZrx) dispersoids are formed before defor-mation at TdispampTann184185 Excellent recrystallisationresistance is achieved if dispersoids are formed at anintermediate anneal of solutionised and deformedmaterial128 or if dispersoids are formed at TdispTann

before deformation148185ndash187 It seems that the decreasein Zener drag because of dispersoid coarsening in many

cases is slower than the decrease in driving force forrecrystallisation because of recovery processes Thusthere is an advantage in forming a high number densityof small dispersoids which for most practical casesmeans that they should be formed at TdispTann122

When an advancing high angle grain boundary iethe recrystallisation front is passing a coherent Al3Scdispersoid there are at least three possible grainboundarydispersoid interactions

1 The Al3Sc dispersoid retains its global orientationrelationship and thus loses its coherency with thesurrounding matrix

2 The Al3Sc dispersoid rotates as the grain boundarypasses either by diffusional processes at the dispersoidmatrix interface or by the grain boundary passingthrough the dispersoid and the Al3Sc dispersoidassumes the same crystallographic orientation as theAl matrix of the recrystallised grain

3 The Al3Sc dispersoid dissolves at the grainboundary and re-precipitates in the recrystallised grain

Which interactions that actually take place willprobably depend on the dispersoid size annealingtemperature and driving force for recrystallisation It isalso possible that alloy composition (other elementsthan Al) is of importance

It has been reported that large (Oslash about 100ndash150 nm)Al3Sc dispersoids in a deformed Alndash4 wt-Mgndash02 wt-Sc alloy annealed at 575uC lose the orientationrelationship with the matrix after being passed by therecrystallisation front148

A rotation of somewhat smaller Al3Sc dispersoids in arecrystallising binary Alndash025 wt-Sc alloy has beenreported115143 The rotation was reported to be accom-panied by substantial growth (from Oslash 30 nm to Oslash48 nm) as a result of enhanced Sc diffusion at the grainboundary Observations suggested that the grainboundaries were passing through the dispersoids andthus the Al3Sc dispersoids retained the orientationrelationship with the recrystallised Al matrix

Dissolution and re-precipitation of Al3Sc dispersoidshas been reported during recrystallisation of a 50 coldrolled Alndash02 wt-Sc alloy162 Large spherical partially

26 Fraction recrystallised structure in cold rolled sheets

of Alndash04 wt-Sc and Alndash04 wt-Scndash015 wt-Zr as a

function of annealing temperature redrawn from

Ref 183 27 Electrical conductivity in Alndash15(SczZr) alloys

redrawn from Ref 183

Roslashyset and Ryum Scandium in aluminium alloys

International Materials Reviews 2005 VOL 50 NO 1 35

coherent dispersoids were observed to dissolve at therecrystallisation front and re-precipitate as smallercoherent Al3Sc cuboids

Superplastic forming

It seems that the first publication on superplasticproperties of Sc-containing Al-alloys was a study of anAlndash35Cundash14Mgndash045Mnndash04(SczZr) alloy188

It was recognised that the superplastic properties are aresult of the stabilisation of the fine grain structure byAl3Sc dispersoids The Sc-containing Al alloys that havereceived most attention for their superplastic propertieshowever are those of the AlndashMgndashSc system which wasfirst published in a patent189 Here it was noted that anAlndash4 wt-Mgndash05 wt-Sc alloy had superior superplasticproperties compared to fine-grained 7475 (AlndashZnndashMgndashCu alloy) Binary Alndash05 wt-Sc and Alndash4 wt-Mgalloys did not behave superplastically The flow stress atthe hot forming temperature was found to be much (30ndash40) lower in the ternary alloy than that of the twobinary alloys

The superplastic properties of AlndashMgndashSc alloys havebeen explored by several research groups over the lastdecade190ndash196 It has frequently been found that thedeformation mechanism is dominated by grain bound-ary sliding190 However it has also been reported thatAlndashMgndashSc alloy may deform superplastically withoutnoticeable grain boundary sliding23 It is generallyrecognised that the grain boundary sliding mechanismis facilitated when the average grain size is very smalland grain boundaries are predominantly high-angleSuch a microstructure may be achieved by carefulthermomechanical processing of the starting mate-rial193194197198 It has however been shown that a finegrained structure with high angle boundaries maydevelop during superplastic forming of AlndashMgndashSc alloyseven if the starting microstructure is an entirely differentone for instance that of a cold rolled sheet192 It has alsobeen suggested that superplastic forming of as castmaterial may be possible189

One of the more efficient thermomechanical processesfor achieving an ultrafine grain structure with high anglegrain boundaries in Al-alloys is equal channel angularpressing (ECAP) A JapanesendashAmerican group ofscientists has published an impressive body of researchon improvements in superplastic properties in Al-alloys processed by ECAP over the last few years andseveral of the publications are from investigations onAlndashMgndashSc alloys170199ndash224 Maximum strains in excessof 2000 at a strain rate of 0033 s21 have beenachieved170201202217 which is an extraordinarily goodcombination of high strain and high strain rate for analuminium alloy

Superplastic properties of AlndashCundashMg(ndashMn)ndashSc(ndashZr)and AlndashMgndashSc(ndashZr) alloys have been mentionedNoticeable superplasticity in other Sc-containing Al-alloys has also been reported such as AlndashZnndashMg(ndashCu)ndashScndashZr169225ndash228 AlndashLindashSc229 AlndashMgndashLindashScndashZr229ndash234

AlndashLindashMgndashCundashScndashZr235236 and AlndashCundashLindashScndashZr233

Precipitation hardeningHardening by Al3Sc precipitates

It has been noted that when Al3Sc particles precipitate inthe temperature range 250ndash350uC they give a significanthardness increase in the alloy Some authors point out

that Sc is a more effective precipitation hardening elementper atomic fraction added than the elements that arecommonly used for precipitation hardening121130 (In onepaper29 it is claimed that only Au has a strongerstrengthening effect than Sc) However the amount ofSc that can be precipitated from supersaturated solidsolution is rather limited and thus the absolute values ofthe hardness increase from the precipitation hardening ismuch lower than what is normally associated withprecipitation hardened alloys Also the temperatureregime for age hardening by precipitation of Al3Sc issomewhere in between the temperature regimes for agehardening and solution heat treatments of commonprecipitation hardened alloys This makes a combinedprecipitation of Al3Sc and other strengthening precipi-tates unfeasible Thus precipitation strengthening byAl3Sc is most feasible in alloy systems that are non-heat-treatable The non-heat-treatable aluminium alloy sys-tems are according to the Aluminum Associationdesignations the 1xxx series (99 pure Al) the 3xxxseries (AlndashMn) and the 5xxx series (AlndashMg) The purposeof adding Sc to these alloys may be either to stabilise themicrostructure of wrought semiproducts (extrusionsrolled plates forgings etc) as discussed in the sectionon lsquoRecrystallisation resistancersquo above or to provideextra strength to the alloy through precipitation hard-ening In the latter case it is appropriate to considerwhether the Sc-containing alloy still should be classifiedas non-heat-treatable A heat treatment is applied thatbrings about a significant precipitation hardening On theother hand the hardness increase that is achieved throughthe heat treatment is lower than what is normallyassociated with heat-treatable alloy systems Hence eventhough it seems like a contradiction one chooses to keepusing the term lsquonon-heat-treatablersquo about these alloys

Table 7 gives an overview of some mechanicalproperties of Sc-containing non-heat-treatable alloysthat are reported in the literature Most of theexperimental work on Sc in 1xxx-types of alloys hasbeen done on binary AlndashSc alloys with much higherpurity than industrial alloys

Strengthening mechanisms

When the precipitates are larger than a critical size thestrengthening effect is due to the Orowan-mechanism iedislocations can only pass the precipitates by looping Inthis case the strengthening effect of the particles isapproximately inversely proportional to the mean parti-cle spacing When the precipitates can be sheared bydislocations there are a number of strengthening mechan-isms that apply It is proposed by Parker et al108 that thetwo major contributing mechanisms are coherency strainand anti-phase-boundary energy In a recent detailedstudy of strengthening mechanisms in binary AlndashSc alloysby Marquis and colleagues117118 the strengthening fromshear modulus mismatch between the matrix and theprecipitates is also accounted for A qualitatively goodmatch between theoretical strengthening and measuredvalues is achieved in this work both for deformation atroom temperature and at 300uC

Effect of Sc on precipitation strengthening in heat-treatablealloys

Following the AA designation system the traditionalheat-treatable Al-alloys are those that belong to the 2xxx

Roslashyset and Ryum Scandium in aluminium alloys

36 International Materials Reviews 2005 VOL 50 NO 1

series (AlndashCu) 6xxx series (AlndashMgndashSi) and 7xxx series(AlndashZnndashMg) AlndashLi alloys should also be mentionedSeveral investigations have been carried out in order toclarify the effects of Sc on the precipitation behaviour inthese alloy systems

AlndashCu alloys

The precipitation sequence in AlndashCu alloys is oftendescribed as follows

Supersaturated solid solutionRGP-zonesRh0Rh9Rh(Al2Cu)

The highest strength is normally achieved when the h0or h9 precipitates are predominant Typical precipitationheat treatment temperatures for AlndashCu alloys are in therange 160ndash190uC238 which is considerably lower thanthe typical precipitation temperature for Al3ScComparisons of the aging responses of AlndashCu and AlndashCundashSc alloys at 150 and 200uC indicate that there is nonoticeable effect of Sc on the precipitation kinetics ofh9153 It is observed that the h9 precipitates may nucleateon Al3Sc particles153 At 300uC it is observed that h9particles are somewhat smaller in AlndashCundashSc alloys thanin AlndashCu alloys156

AlndashMgndashSi alloys

The following precipitation sequence is commonlyreported for AlndashMgndashSi alloys

Supersaturated solid solutionRGP-zonesRb0Rb9Rb(Mg2Si)

For peak aged alloys the predominant precipitatetype is b0 for which the stoichiometric composition hasrecently been resolved to be Mg5Si6239 Temperatures inthe range 160ndash205uC are typically used for precipitationhardening of these alloys238 Adding both 03 wt-Scand 01 wt-Zr to an Alndash06 wt-Mgndash065 wt-Sialloy does not seem to alter the precipitation kineticsof b0 at 165uC However the hardness increase becauseof precipitation hardening appears to be smaller in theSczZr-containing alloy240 In another investigationadditions of 01 wt-Sc 015 wt-Sc 02 wt-Sc04 wt-Sc and 02 wt-Scz01 wt-Zr were made toan Alndash08 wt-Mgndash07 wt-Si alloy241 Here it wasalso observed that the precipitation kinetics of b0 wasseemingly independent of the Sc additions (Fig 28)TEM observations indicated that the b0 precipitateswere of comparable sizes in the investigated alloys andno interactions between Al3Sc and b0 were observed(Fig 29) In a third study242 where the effect of Sc onthe precipitation in an AlMgSindashSiC metal matrixcomposite was investigated there also does not seemto be any effect on the precipitation kinetics Howevercontrary to the findings of Ref 240 it is reported thatthe Sc addition leads to a higher hardness increase thanin the corresponding Sc free alloy

AlndashMgndashZn alloys

For these alloys the following precipitation sequence isoften ascribed

Table 7 Mechanical properties in non-heat-treatable Al-alloys with Sc

Reference Alloy wt- YS MPa UTS MPa Note

1xxx alloys171 000Sc 15 48 Cast material aged 288uC8 h

023Sc 159 185 Cast material aged 288uC8 h038Sc 199 220 Cast material aged 288uC8 h000Sc 14 49 Cold rolled material (89) aged 288uC8 h023Sc 198 208 Cold rolled material (89) aged 288uC8 h038Sc 240 264 Cold rolled material (89) aged 288uC8 h000Sc 8 34 Cold rolled material quenched from 649uC aged 288uC8 h023Sc 147 157 Cold rolled material quenched from 649uC aged 288uC8 h038Sc 193 199 Cold rolled material quenched from 649uC aged 288uC8 h

121 05Sc 160 ndash Forged material quenched from 635uC aged 250uC50 h23 05Sc 298 319 Hot rolled 288uC cold rolled 69ndash81 aged 288uC4 h112 01Sc 132 166 Hot z cold rolled material quenched from 630uC

aged 320uC133 h148 02Sc 138 ndash Cast material aged 300uC10 h compression test159 04Sc 196 ndash Cast material aged 300uC10 h compression test117 118 03Sc 209 ndash Cast material quenched from 648uC aged 300uC5 h

compression test3xxx alloys171 1Mn 015Sc 216 221 Cold rolled material (89) aged 288uC8 h

1Mn 05Sc 309 323 Cold rolled material (89) aged 288uC8 h186 05Mn 02Mg

026Sc 015Zr162 201 Extruded material solutionised 600uC aged 250uC

5xxx alloys171 1Mg 43 111 Cold rolled material (89) aged 288uC8 h

1Mg 03Sc 288 303 Cold rolled material (89) aged 288uC8 h53Mg 147 259 Cold rolled material (50) wintermediate anneals

at 343uC aged 288uC8 h53Mg 03Sc 368 401 Cold rolled material (50) wintermediate anneals

at 343uC aged 288uC8 h23 2Mg 05Sc 376 401 Hot rolled 288uC cold rolled 69ndash81 aged 288uC4 h

4Mg 05Sc 414 4606Mg 05Sc 433 503

237 4Mg 1Sc 420 525 Cold rolled material (83) aged 320uC1 h148 4Mg 02Sc 194 ndash Cast material aged 300uC10 h compression test

Tensile test data except where noted YS yield strength UTS ultimate tensile strength

Roslashyset and Ryum Scandium in aluminium alloys

International Materials Reviews 2005 VOL 50 NO 1 37

Supersaturated solid solutionRGP-zonesRg9Rg(Zn2Mg)

The maximum hardness is normally achieved whenthe g9 precipitates are predominant Common precipita-tion hardening temperatures are in the range 95ndash180uCand a two-step precipitation heat treatment within thistemperature regime is often used238 It has beenobserved in some investigations that Sc and SczZradditions to AlndashMgndashZn alloys slow down the precipita-tion of g9 somewhat243 Other investigations find thatthere is no effect of Sc on the precipitation behaviour ofg9244245 and yet others report that Sc additionssignificantly speed up the precipitation of g9246 In Ref247 it is found that an Sc addition leads to coarser g9precipitates and it is claimed that this gives an improvedductility of the alloy The strength-loss associated withlarger particle size is reported to be counterbalanced bystrengthening from Al3Sc precipitates

AlndashLi alloys

The precipitation sequence in binary AlndashLi alloys isapparently simple

Supersaturated solid solutionRd9Rd (AlLi)

where d9 is the metastable Al3Li phase which just likeAl3Sc has the L12 type of atomic arrangement Thetypical temperature regime for precipitation of d9 whichis the strengthening phase in this system is approx 150ndash200uC A comparison of the age hardening response ofan Alndash26 wt-Li and an Alndash24 wt-Lindash019 wt-Scalloy at 180uC248 and 200uC161 indicates that the onsetof d9 precipitation is not altered by the presence of ScThe hardness curves for the two alloys are practicallyidentical at 200uC whereas at 180uC the peak hardnesslevel is slightly higher in the AlndashLi than the AlndashLindashScalloy DSC measurements at constant heating ratesindicate that the addition of Sc to an AlndashLi alloysincreases the activation energy for d9 precipitation andmoves the exothermic peak associated with d9 precipita-tion to a higher temperature248 For specimens aged at

either 180uC or 200uC TEM observations reveal that thed9 precipitates are much smaller in the Sc containingalloy than in binary AlndashLi both in the peak agedcondition and in the overaged condition161248 Additionof Sc has also been observed to reduce the size of d9precipitates in other AlndashLi based alloys249ndash251 In an AlndashLindashCundashZr alloy an addition of Sc has been reported toslow down the homogeneous precipitation of d9252253 Ithas been claimed that Sc reduces the quench sensitivityand delays room temperature aging of AlndashLi basedalloys254ndash256

When present in the microstructure before the pre-cipitation of d9 the Al3Sc precipitates may act as effec-tive nucleation sites for d9 The resulting precipitates arespheres of d9 with a core of Al3Sc161249252ndash255257ndash261

Corrosion resistanceAn appreciable amount of data is available on the effectsof Sc on the corrosion behaviour of wrought Al-alloysSome of these effects are apparently derived from theeffects of Sc on the microstructure of the alloys It hasbeen reported that an addition of Sc increases thecorrosion potential (makes it less negative) in pureAl262ndash264 in AlndashZn alloys265266 AlndashMg alloys267 AlndashZnndashMgndashCu alloys264268 AlndashCundashMgndashMn alloys264 andin AlndashCundashLindashMgndashAg alloys264 Even though Sc alsohas been reported to decrease the corrosion potential in

28 Age hardening response at 175uC for Alndash08 wt-Mgndash

07 wt-Si alloy (Base) with additions of 02 wt-Sc

04 wt-Sc and 02 wt-Scz01 wt-Zr from Ref 241

29 TEM images of a b0 precipitates in Alndash08 wt-Mgndash

07 wt-Si alloy and b b0 and Al3(Sc1ndashxZrx) in a similar

alloy with addition of 02 wt-Scz01 wt-Zr from

Ref 241

Roslashyset and Ryum Scandium in aluminium alloys

38 International Materials Reviews 2005 VOL 50 NO 1

AlndashMg alloys269270 it seems that the general trend isthat adding Sc to an alloy makes it slightly more nobleThe change in corrosion potential is much morepronounced when Sc is added in amounts larger thanthe eutectic composition263 ie there is a considerablecontribution from primary or eutectic Al3Sc to theoverall potential It has also been demonstrated that thechange in corrosion potential caused by Sc can dependon the heat treatment applied to the alloy267268

Even though the corrosion potential is an essentialparameter in establishing the corrosion behaviour of analloy an increase in the corrosion potential does notnecessarily imply an improved self-corrosion resistanceHowever measurements of corrosion rates and passiva-tion current densities strongly suggest that the self-corrosion resistance in general is considerably improvedwhen Sc is added to wrought Al-alloys263264267 Someobserved variations in corrosion potential and passiva-tion current densities with Sc content in binary AlndashScalloys are plotted in Fig 30

Material failure in corrosive environments is often dueto localised corrosion attacks which may propagaterapidly even though the bulk material has a goodresistance against general corrosion It has been pointedout that hypereutectic additions of Sc may lead tomicrogalvanic corrosion beside primary Al3Sc parti-cles264 In AlndashMg alloys grain boundary precipitation ofAl8Mg5 can lead to localised corrosion attacks such asintergranular corrosion (IGC) exfoliation corrosion(EC) and stress corrosion cracking (SCC) In wroughtmaterial such precipitation may occur in the 60ndash180uCtemperature regime and heating in this temperaturerange is referred to as lsquosensitationrsquo An AlndashMgndashSc alloywas found to be immune against intergranular corrosionand have moderate susceptibility to exfoliation corro-sion after annealing at 350uC271 After sensitation heattreatments severe IGC and EC was observed but notquite as severe as in a corresponding alloy without ScAs for SCC the AlndashMgndashSc alloy was found to be highlyresistant271 In another study it was found that additionof 056 wt-Sc reduces the SCC susceptibility of an Alndash68 wt-Mg alloy in the as-rolled state and afterannealing at 250uC whereas in a sensitised specimenthe SCC susceptibility is somewhat increased by the Scaddition272 A third investigation found that Sc has nomeasurable detrimental effect on the SCC susceptibilityof sensitised Alndash5Mgndash015Zr alloy273 SCC is also a

severe problem in high strength AlndashZnndashMgndashCu alloys Ithas been shown that small Sc additions are effective inreducing the SCC sensitivity of these alloys244246268274

Use of Sc-containing Al alloysA systematic development of Sc-containing aluminiumalloys took place in the former USSR in the 1980s andthe interest for Sc as an alloying element in aluminiumalloys hit the western world approximately 10 yearslater Even though a number of improvements in Alalloys achieved by Sc addition have been demonstratedthe current uses of such alloys are very limited This isrelated to the very high price of scandium

In Russia some parts of military aircraft are made ofSc-containing AlndashLi alloys In the western world themain usage of Sc-containing alloys is for sportsequipment Ashurst Technology and Kaiser Aluminumdeveloped a Sc-containing 7xxx alloy for baseball andsoftball bats which was introduced to the Americanmarket in 1997 by Easton Alcoa soon followed with aSc-containing alloy for a competing brand of batsLouisville Slugger Since then several new and improvedSc-containing alloys for bats have been introduced tothe market The purpose of adding Sc is to increase theyield strength of the alloy allowing for a down-gaugingof the wall thickness which in turn gives a strongerlsquospring-rsquo or lsquotrampoline-rsquo effect when the ball hits thebat

Shortly after the introduction of the Sc containingbats Easton also launched Sc-containing 7xxx tubingfor bicycle frames Just as in the bats Sc increases theyield strength of the alloy allowing for down-gauging oftube wall thickness and a corresponding weight reduc-tion of the bicycle frame An Italian manufacturer ofbicycle tubing Dedacciai also delivers tubes in a Sc-containing 7xxx alloy

Other sports equipment made from Sc-containingaluminium alloys includes lacrosse sticks and tent polesSmith and Wesson has also introduced a series ofhandguns where the frame is made from a Sc-containingAl alloy

A common factor for the items mentioned above isthat the material cost is only a minor part of the totalmanufacturing cost of the end product and also thatthese products are aimed at a group of customers thathave a certain awareness of new materials Both baseballbats and bicycle frames have been marketed aslsquoscandium alloyrsquo even though the Sc content is muchlower than 1

Currently AlndashSc master alloys for the production ofSc-containing Al alloys are available at a price thatcorresponds to US$ 2000 per kg of Sc This means that ifone wants to add 02 wt-Sc to an alloy which is afairly common content one also increases the price ofthe alloy by US$ 4 per kg alloy Depending on the alloytype Sc is added to this represents a tripling orquadrupling of the price of the alloy There are notmany existing products where such an increase inmaterial cost can be justified In order to see awidespread use of Sc in high-volume products the Scprice has to come down considerably Actually the priceof adding Sc to Al alloys has gone down by a factor 3ndash10over the last 10ndash15 years and substantial price reduc-tions are also expected in the future

30 Observed variations in corrosion potential and passi-

vation current densities with Sc content in binary Alndash

Sc alloys based on data from Ref 263

Roslashyset and Ryum Scandium in aluminium alloys

International Materials Reviews 2005 VOL 50 NO 1 39

The current production of AlndashSc master alloys isbased upon and will continue to be based upon for theforeseeable future the reduction of Sc2O3 or other Sccompounds directly in molten aluminium It is notnecessary as many tend to believe to take the route viametallic Sc Thus the price of AlndashSc master alloy isgoverned by the price of Sc2O3 or other Sc compoundsin question and not by the price of metallic scandiumThe Sc2O3 which is the main source for todayrsquos AlndashScmaster alloy production comes from stockpiles in theformer USSR These stockpiles will be exhausted withina few years and new reliable sources of Sc2O3 or otherSc compound production are sought It turns out thatthe most economically viable option that has beendisclosed so far is the processing of Red Mud from theBayer process of extracting alumina from bauxiteScandium is enriched in the Red Mud and is extractedfrom a Red Mud aqueous slurry by selective leachingsubsequent ion-exchange procedure and finally a liquidndashliquid extraction procedure It is not required to build aseparate lsquoSc factoryrsquo to do this but rather build an lsquoadd-onrsquo to existing Bayer process plants Such a processroute is expected to bring down the price of Sc2O3

considerably which in turn means that AlndashSc masteralloy price should drop accordingly Preliminary ana-lyses suggest a price of approx US$ 400 per kg Sc in themaster alloy which translates to an added cost of 80cent per kilo when 02 wt-Sc is added to an aluminiumalloy This is also a considerable increase in the materialcost but with such prices one should expect to see Sccontaining alloys in many more applications than whatis the case at the present time

Concluding remarksThe body of published investigations on Al-based alloyswith Sc addition provides a sound basis of knowledgefor metallurgists that want to look into the possibility ofenhancing the performance of a wrought Al-alloy byadding Sc to it Ternary AlndashScndashX phase diagrams areavailable for practically every technologically importantalloying element in Al The effect of a wide range ofternary alloying elements on the precipitation behaviourof Al3Sc is accounted for It has been shown that theAl3Sc phase can be effective as a grain refiner adispersoid former and a precipitate hardening agentand some of the underlying conditions for achieving thedesired Al3Sc formation have been outlined Addingsome Zr together with Sc has proven to be beneficial Itmay lead to effective grain refinement at a lower Sc levelbut the most prominent effect is the refinement indispersoid distribution that can be achieved An addi-tion of Sc has little if any effect on precipitation in the2xxx 6xxx and 7xxx alloy systems and some effects onthe precipitation in AlndashLi based alloys With respect tocorrosion behaviour adding Sc to an Al-alloy does ingeneral seem to make the alloy slightly more noble andto increase its self-corrosion resistance Scandium-containing Al alloys have very few uses at the presenttime as a result of the high price of scandium The priceof Sc is expected to decrease significantly in the futureand this should lead to the disclosure of moreapplications where it is economically feasible to takeadvantage of the improved properties of some Sc-containing aluminium alloys

References1 D R Lide lsquoCRC handbook of chemistry and physicsrsquo 71st edn

4ndash29 1990 Boston USA CRC Press

2 E M Savitsky V F Terehova I V Burov and O P Naumkin

Proc Fourth Conf on lsquoRare earth researchrsquo Phoenix Arizona

USA April 1964 409ndash420

3 E M Savitskii V F Terekhova I V Burov O P Naumkin and

I A Markova Inorg Mater 1965 1 1503ndash1512

4 O P Naumkin V T Terekhova and E M Savitskiy Russ

Metall 1965 (4) 128ndash136

5 W G Moffatt lsquoThe handbook of binary phase diagramsrsquo 1981

Schenectady NY USA General Electric Co

6 E A Brandes (ed) lsquoSmithells metals reference bookrsquo 6th edn

1983 London UK Butterworths

7 R P Elliott and F A Shunk Bull Alloy Phase Diagrams 1981

2 (2) 222ndash223

8 K A Gschneider Jr and F W Calderwood Bull Alloy Phase

Diagrams 1989 10 34ndash36

9 H Okamoto J Phase Equil 1991 12 612ndash613

10 J L Murray J Phase Equil 1998 19 380ndash384

11 M E Drits E S Kadaner T V Dobatkina and N I Turkina

Russ Metall 1973 (4) 152ndash154

12 S-I Fujikawa M Sugaya H Takei and K-I Hirano J Less-

Common Met 1979 63 87ndash97

13 N Blake and M A Hopkins J Mater Sci 1985 20 2861ndash2867

14 V I Kononenko and S V Golubev Russ Metall 1990 (2) 193ndash

195

15 T B Massalski J L Murray L H Bennett and H Baker (eds)

lsquoBinary alloy phase diagramsrsquo 1986 Metals Park OH USA

ASM

16 G Cacciamani P Riani G Borzone N Parodi A Saccone

R Ferro A Pisch and R Schmid-Fetzer Intermetallics 1999 7

101ndash108

17 H Okamoto J Phase Equil 2000 21 310

18 A F Norman P B Pragnell and R S McEwen Acta Mater

1998 46 5715ndash5732

19 I N Pyagai and A V Vakhobov Russ Metall 1990 (5) 50ndash52

20 C L Fu J Mater Res 1990 5 971ndash979

21 X Lu and Y Wang Calphad 2002 26 555ndash561

22 R R Sawtell and J W Morris Jr Proc lsquoDispersion strengthened

aluminium alloysrsquo Phoenix Arizona USA January 1988 409ndash

420

23 R R Sawtell and C L Jensen Metall Trans A 1990 21A 421ndash

430

24 L A Willey Unpublished research Alcoa 1970 Data points are

extracted from Ref 10

25 N I Turkina and V I Kuzmina Russ Metall 1976 (4) 179ndash

183

26 T Torma E Kovacs-Csetenyi I Vitanyi M Butova and

J Stepanov Proc 6th Int Symp on lsquoHigh purity materials in

science and technologyrsquo Akademie der Wissenschaften der DDR

Dresden Germany May 1985 388ndash389

27 A L Berezina V A Volkov B P Domashnikov and K V

Chuistov Metallofizika 1987 9 (5) 43ndash47

28 H-H Jo J Korean Inst Metals 1990 28 499ndash504

29 H-H Jo and S-I Fujikawa Mater Sci Eng 1993 A 171 151ndash

161

30 S Celotto and T J Bastow Philos Mag A 2000 80 1111ndash1125

31 J Roslashyset and N Ryum submitted to Mater Sci Eng

32 M E Drits L S Toropova Yu G Bykov F L Gushchina V I

Elagin and Yu A Filatov Russ Metall 1983 (1) 150ndash153

33 L S Toropova D G Eskin M L Kharakterova and T V

Dobatkina lsquoAdvanced aluminum alloys containing scandium

structure and propertiesrsquo 1998 Amsterdam The Netherlands

Gordon and Breach Science Publishers

34 V V Cherkasov P P Pobezhimov L P Nefedova E V Belov

and G M Kuznetsov Met Sci Heat Treat 1996 (6) 268ndash270

35 Kh O Odinaev I N Ganiev V V Kinzhibalo and B Ya

Kotur Dokl Akad Nauk Tadzh SSR 1989 32 37ndash38

36 Kh O Odinaev I N Ganiev and A V Vakhobov Russ Metall

1991 (4) 200ndash203

37 J Grobner R Schmid-Fetzer A Pisch G Cacciamani P Riani

N Parodi G Borzone A Saccone and R Ferro Z Metallkd

1999 90 872ndash880

38 E A Marquis and D N Seidman Microsc Microanal 2002 8

(Suppl 2) 1100CDndash1101CD

39 A Pisch J Grobner and R Schmid-Fetzer Mater Sci Eng A

2000 A 289 123ndash129

Roslashyset and Ryum Scandium in aluminium alloys

40 International Materials Reviews 2005 VOL 50 NO 1

40 C Xia F Zeng and Y Gu Trans Nonferrous Met Soc China

2003 13 1124ndash1127

41 M Yu Teslyuk and V S Protasov Sov Phys Crystallogr 1966

10 470ndash471

42 M L Kharakterova and T V Dobatkina Russ Metall 1988

(6) 175ndash178

43 M L Kharakterova Russ Metall 1991 (4) 195ndash199

44 L S Toropova M L Kharakterova and D G Eskin Russ

Metall 1992 (3) 194ndash199

45 P Riani L Arrighi R Marazza D Mazzone G Zanicchi and

R Ferro J Phase Equil Diff 2004 25 22ndash52

46 A T Tyvanchuk T I Yanson B Ya Kotur O S Zarechnyuk

and M L Kharakterova Russ Metall 1988 (4) 190ndash192

47 L L Rokhlin T V Dobatkina and M L Kharakterova Powder

Metall Met Ceram 1997 36

48 A Z Ikromov I N Ganiev and V V Kinzhibalo Dokl Akad

Nauk Tadzh SSR 1990 (6) 391ndash392

49 I N Ganiev A Z Ikromov and V G Khudoiberdiev Russ

Metall 1995 (3) 125ndash127

50 I N Fridlyander L L Rokhlin T V Dobatkina and N I

Nikitina Met Sci Heat Treat 1993 (10) 567ndash571

51 I N Fridlyander L L Rokhlin T V Dobatkina V V

Kinzhibalo and A T Tyvanchuk Russ Metall 1998 (1) 161ndash

166

52 R A Emigh E L Bradley and J W Morris Jr in lsquoLight-weight

alloys for aerospace applications IIrsquo (ed E W Lee and N J

Kim) 27ndash43 1991 TMS

53 L S Toropova A N Kamardinkin V V Kindzhibalo and A T

Tyvanchuk Phys Met Metall 1990 70 (6) 106ndash110

54 A N Kamardinkin T V Dobatkina and T D Rostova Russ

Metall 1991 (4) 216ndash218

55 L S Torodskaya T V Dobatkina and A N Kamardinkin

Russ Metall 1992 (5) 128ndash131

56 E M Sokolovskaya E F Kazakova E I Poddyakova and A

A Ezhov Met Sci Heat Treat 1997 (5) 211ndash213

57 Y Harada and D C Dunand Mater Sci Eng 2002 A 329ndash331

686ndash695

58 N E Drits L S Toropova and F L Gushchina Russ Metall

1984 (4) 229ndash232

59 E M Sokolovskaya E F Kazakova V A Alikhanov and E V

Zhuravleva Moscow Univ Chem Bull 1997 52 (5) 70ndash72

60 E M Sokolovskaya E F Kazakova and E I Poddyakova Met

Sci Heat Treat 1989 (11) 837ndash839

61 G M Cheldieva E F Kazakova E M Sokolovskaya and N I

Kaloev Russ Metall 1990 (6) 87ndash90

62 E M Sokolovskaya E F Kazakova and O D-S Kendivan

Russ Metall 1998 (4) 135ndash137

63 N G Bukhanko E F Kazakova and E M Sokolovskaya Russ

Metall 2001 (4) 425ndash431

64 E D Trubnyakova O I Bodak I N Ganiev and A V

Vakhobov Russ Metall 1987 (3) 219ndash222

65 I N Fridlyander and L V Molchanova Russ Metall 2003 (5)

476ndash480

66 R A Altynbaev S Kh Khairidinov and A V Vakhobov Russ

Metall 1987 (4) 194ndash196

67 J C Schuster and J Bauer J Less-Common Met 1985 109

345ndash350

68 L L Rokhlin A S Fridman T V Dobatkina and D G Eskin

Russ Metall 1991 (6) 146ndash148

69 A S Fridman T V Dobatkina and E V Muratova Russ

Metall 1992 (1) 207ndash209

70 C Xia F Zeng and Y Gu Trans Nonferrous Met Soc China

2003 13 546ndash552

71 F Zeng C Xia and Y Gu J Alloys Comp 2004 363 175ndash181

72 L L Rokhlin T V Dobatkina N R Bochvar and E V Lysova

J Alloys Comp 2004 367 10ndash16

73 T V Dobatkina A S Fridman and E V Muratova Russ

Metall 1992 (5) 125ndash127

74 I N Fridlyander L L Rokhlin N R Bochvar E V Lysova

and O V Boteva Russ Metall 2001 (6) 661ndash666

75 V N Rechkin L K Lamikhov and T I Samsonova Sov Phys

Crystallogr 1964 9 325ndash327

76 I I Zalutskii and P I Kripyakevich Sov Phys Crystallogr

1967 12 341ndash343

77 T J Bastow C T Forwood M A Gibson and M E Smith

Phys Rev B 1998 58 2988ndash2997

78 K Fukunaga M Kolbe K Yamada and Y Miura Mater Sci

Eng 1997 A 234ndash236 594ndash597

79 E P George J A Horton W D Porter and J H Schneibel

J Mater Res 1990 5 1639ndash1648

80 E P George D P Pope C L Fu and J H Schneibel ISIJ Int

1991 31 1063ndash1075

81 Y Harada and D C Dunand Acta Mater 2000 48 3477ndash3487

82 J H Schneibel and E P George Scripta Metall Mater 1990 24

1069ndash1074

83 J H Schneibel and P M Hazzledine Mater Res Soc Symp

Proc 1991 213 323ndash328

84 J H Schneibel and P M Hazzledine J Mater Res 1992 7

868ndash875

85 C J Sparks E D Specht G E Ice P Zschack and J Schneibel

Mater Res Soc Symp Proc 1991 213 363ndash368

86 J Tarnacki and Y-W Kim Scripta Metall Mater 1989 23

1063ndash1068

87 M Asta V Ozolins and C Woodward JOM 2001 53 (9) 16ndash

19

88 M E Drits L S Toropova F L Gushchina and S G Fedotov

Sov Non-Ferrous Met Res 1984 12 83ndash85

89 Y Harada and D C Dunand Scripta Mater 2003 48 219ndash222

90 C Woodward M Asta G Kresse and J Hafner Phys Rev B

2001 63 094103-1-6

91 J-H Xu and A J Freeman Phys Rev B 1990 41 12553ndash12561

92 M F Bartholomeusz and J A Wert Acta Metall Mater 1992

40 673ndash682

93 G Bester and M Fahnle J Phys Condens Matter 2001 13

11551ndash11565

94 C L Fu and M H Yoo Proc lsquoOrdered intermetallics ndash physical

metallurgy and mechanical behaviorrsquo Irsee Germany June 1991

155ndash164

95 K Fukunaga T Shouji and Y Miura Mater Sci Eng 1997 A

239ndash240 202ndash205

96 D P Pope Proc lsquoOrdered intermetallics ndash physical metallurgy

and mechanical behaviorrsquo Irsee Germany June 1991 143ndash153

97 J-S Wang Acta Mater 1998 46 2663ndash2674

98 M H Yoo and C L Fu Mater Sci Eng 1992 A 153 470ndash478

99 R W Hyland Jr and R C Stiffler Scripta Metall Mater 1991

25 473ndash477

100 I G Brodova I V Polents O A Korzhavina P S Popelrsquo I P

Korshunov and V O Esin Melts 1992 4 392ndash397

101 I G Brodova O A Chikova I V Polents P S Popelrsquo and V O

Esin Casting Processes 1992 1 (2) 158ndash160

102 I G Brodova D V Bashlikov and I V Polents Mater Sci

Forum 1998 269ndash272 589ndash594

103 K B Hyde A F Norman and P B Pragnell Mater Sci Forum

2000 331ndash337 1013ndash1018

104 K B Hyde A F Norman and P B Pragnell Acta Mater 2001

49 1327ndash1337

105 J Roslashyset and N Ryum Proc 6th Int Conf on lsquoAluminum

alloysrsquo Toyohashi Japan July 1998 793ndash798

106 V I Elagin V V Zakharov and T D Rostova Met Sci Heat

Treat 1993 (6) 317ndash319

107 R W Hyland Jr Metall Trans A 1992 23A 1947ndash1955

108 B A Parker Z F Zhou and P Nolle J Mater Sci 1995 30

452ndash458

109 C L Rohrer M D Asta S M Foiles and R W Hyland Jr

Mater Res Soc Symp Proc 1996 398 477ndash482

110 G M Novotny and A J Ardell Mater Sci Eng 2001 A 318

144ndash154

111 J D Robson M J Jones and P B Pragnell Acta Mater 2003

51 1453ndash1468

112 C Tan Z Zheng and B Wang Proc 3rd Int Conf on

lsquoAluminium alloysrsquo Vol I NTH Trondheim Norway June

1992 290ndash294

113 M Nakayama A Furuta and Y Miura Mater Trans JIM

1997 38 852ndash857

114 E A Marquis and D N Seidman Acta Mater 2001 49 1909ndash

1919

115 M J Jones and F J Humphreys Acta Mater 2003 51 2149ndash

2159

116 E A Marquis D N Seidman and D C Dunand in lsquoCreep

deformation fundamentals and applicationsrsquo (ed R S Mishra

J C Earthman and S V Raj) 299ndash308 2002 TMS

117 D N Seidman E A Marquis and D C Dunand Acta Mater

2002 50 4021ndash4035

118 E A Marquis D N Seidman and D C Dunand Acta Mater

2003 51 285ndash287

119 M E Drits L S Toropova U G Bikov and G K Anastaseva

Proc lsquoDiffusion in metals and alloysrsquo Tihany Hungary Augustndash

September 1982 616ndash623

120 V I Elagin V V Zakharov and T D Rostova Met Sci Heat

Treat 1983 (7) 546ndash549

Roslashyset and Ryum Scandium in aluminium alloys

International Materials Reviews 2005 VOL 50 NO 1 41

121 M Ye Drits L B Ber Yu G Bykov L S Toropova and G K

Anastaseva Phys Met Metall 1984 57 (6) 118ndash126

122 M E Drits L S Toropova and Yu G Bykov Sov Non-Ferrous

Met Res 1985 13 309ndash314

123 V I Yelagin V V Zakharov S G Pavlenko and T D Rostova

Phys Met Metall 1985 60 (1) 88ndash92

124 N Sano Y Hasegawa K Hono H Jo K Hirano H W

Pickering and T Sakurai Journal de Physique 1987 48 C6 337ndash

342

125 N Sano H-H Jo K-I Hirano and T Sakurai J Jpn Inst

Metals 1989 39 444ndash450

126 N Sano H Jo K Hirano and T Sakurai Proc Second Int

Conf on lsquoAluminium alloysrsquo Beijing China October 1990 549ndash

554

127 Y Miura M Nakayama and A Furuta Proc lsquoAspects of high

temperature deformation and fracture in crystalline materialsrsquo

Nagoya Japan July 1993 255ndash262

128 Y W Riddle and T H Sanders Jr Mater Sci Forum 2000

331ndash337 939ndash944

129 Y W Riddle M McIntosh and T H Sanders Jr in lsquoLightweight

alloys for aerospace application VIrsquo (ed K Jata E W Lee

W Frazier and N J Kim) 25ndash39 2001 TMS

130 M E Drits J Dutkiewicz L S Toropova and J Salawa Crystal

Res Technol 1984 19 1325ndash1330

131 Y W Riddle MSc thesis Georgia Tech GA USA 1998

132 T J Bastow and S Celotto Mater Sci Eng 2003 C 23 757ndash

762

133 M C Carroll M J Mills G S Daehn P I Gouma M F

Savage and B R Dunbar in lsquoAutomotive Alloys 1999rsquo (ed

S Das) 239ndash246 2000 TMS

134 E Clouet M Nastar and C Sigli Phys Rev B 2004 69 064109-

1-14

135 V V Zakharov Met Sci Heat Treat 1997 (2) 61ndash66

136 J W Christian lsquoThe theory of transformation in metals and

alloysrsquo 2nd edn 1975 Pergamon Press Ltd

137 A L Berezina V A Volkov B P Domashnikov S V Ivanov

and K V Chuistov Phys Metals 1990 10 296ndash304

138 S-I Fujikawa and S Sakauchi Proc 6th Int Conf on

lsquoAluminum alloysrsquo Toyohashi Japan July 1998 805ndash810

139 Y S Touloukian R K Kirby R E Taylor and P D Desai

(eds) lsquoThermal expansion metallic elements and alloysrsquo 1975

New York Plenum

140 J Roslashyset and N Ryum submitted to Scripta Mater

141 R O Simmons and R W Balluffi Phys Rev 1960 117 52ndash61

142 M Ocko E Babic R Krsmik E Girt and B Leontic J Phys F

Metals Phys 1976 6 703ndash707

143 M J Jones and F J Humphreys Proc First Joint Int Conf on

lsquoRecrystallization and grain growthrsquo Aachen Germany August

2001 Springer Verlag 1287ndash1292

144 S Iwamura M Nakayama and Y Miura Mater Sci Forum

2002 396ndash402 1151ndash1156

145 S Iwamura and Y Miura Acta Mater 2004 52 591ndash600

146 M Asta S M Foiles and A A Quong Phys Rev B 1998 57

11265ndash11275

147 R W Hyland Jr M Asta S M Foiles and C L Rohrer Acta

Mater 1998 46 3667ndash3678

148 J Roslashyset and N Ryum Proc 4th Int Conf on lsquoAluminium

alloysrsquo Vol I Atlanta GA USA September 1994 194ndash201

149 M E Drits L S Toropova G K Anastaseva and G L

Nagornichnykh Russ Metall 1984 (3) 192ndash195

150 E A Marquis D N Seidman and D C Dunand Acta Mater

2003 51 4751ndash4760

151 M E Drits L S Toropova and Yu G Bykov Met Sci Heat

Treat 1983 (7) 550ndash554

152 V V Zakharov and T D Rostova Met Sci Heat Treat 1995

(2) 65ndash69

153 M Nakayama and Y Miura Proc 4th Int Conf on lsquoAluminium

alloysrsquo Vol I Atlanta GA USA September 1994 538ndash545

154 M Nakayama and Y Miura J Jpn Inst Light Metals 1996 46

275ndash279

155 M Nakayama T Okuyama and Y Miura Mater Sci Forum

2000 331ndash337 927ndash932

156 M Nakayama T Okuyama and Y Miura Proc 6th Int Conf

on lsquoAluminum alloysrsquo Toyohashi Japan July 1998 517ndash522

157 M L Kharakterova D G Eskin and L S Toropova Acta

Metall Mater 1994 42 2285ndash2290

158 V I Elagin V V Zakharov and T D Rostova Met Sci Heat

Treat 1992 (1) 37ndash45

159 H Wiik Siv Ing thesis NTH Institute of Metallurgy

Trondheim Norway 1995

160 J Roslashyset H Hovland and N Ryum Mater Sci Forum 2002

396ndash402 619ndash624

161 Y Miura K Horikawa K Yamada and M Nakayama Proc

4th Int Conf on lsquoAluminium alloysrsquo Vol II Atlanta GA USA

September 1994 161ndash168

162 Y W Riddle PhD thesis Georgia Tech GA USA 2000

163 B Forbord W Lefebvre F Danoix H Hallem and

K Marthinsen Scripta Mater 2004 51 333ndash337

164 J D Robson Acta Mater 2004 52 1409ndash1421

165 C B Fuller J L Murray and D N Seidman submitted to Acta

Mater 2004

166 M G Mousavi C E Cross and Oslash Grong Sci Technol Weld

Joining 1999 4 381ndash388

167 J S Vetrano S M Bruemmer L M Pawlowski and I M

Robertson Mater Sci Eng 1997 A 238 101ndash107

168 Y W Riddle and T H Sanders Jr Mater Sci Forum 2000

331ndash337 799ndash803

169 G M Khan A O Nikiforov V V Zakharov and I I Novikov

Tsvetnye Metally 1993 34 (11) 43ndash45

170 Z Horita M Furukawa M Nemoto A J Barnes and T G

Langdon Acta Mater 2000 48 3633ndash3640

171 L A Willey US Patent 3 619 181 9 November 1971

172 L K Lamikhov and G V Samsonov Tsvetnye Metally 1964 5

(8) 77ndash80

173 A L Berezina K V Chuistov N I Kolobnev L B

Khokhlatova and T A Monastyrskaya Mater Sci Forum

2002 396ndash402 741ndash746

174 F A Fasoyinu J Thomson D Cousineau T Castles and M

Sahoo Proc 6th Int AFS Conf on lsquoMolten aluminum

processingrsquo Orlando FL USA November 2001

175 Z Yin Q Pan Y Zhang and F Jiang Mater Sci Eng 2000

A 280 151ndash155

176 I I Novikov and O E Grushko Mater Sci Technol 1995 11

926ndash932

177 D Cousineau M Sahoo P D Newcombe T Castles and F A

Fasoyinu Proc lsquoAFS 105th casting congressrsquo Dallas TX USA

AprilndashMay 2001 157ndash184

178 C E Cross and Oslash Grong Proc 6th Int Conf on lsquoAluminum

alloysrsquo Toyohashi Japan July 1998 1441ndash1446

179 F A Costello J D Robson and P B Prangnell Mater Sci

Forum 2002 396ndash402 757ndash762

180 K B Hyde A F Norman and P B Prangnell Mater Sci

Forum 2002 396ndash402 39ndash44

181 M E Drits S G Pavlenko L S Toropova Yu G Bukov and

L B Ber Sov Phys Dokl 1981 26 (3) 344ndash346

182 A M Drits and B A Kopeliovich Russ Metall 1985 (4) 147ndash

151

183 V G Davydov V I Elagin V V Zakharov and T D Rostova

Met Sci Heat Treat 1996 (8) 347ndash352

184 M E Drits L S Toropova Yu G Bykov L B Ber and S G

Pavlenko Russ Metall 1982 (1) 148ndash152

185 T D Rostova V G Davydov V I Yelagin and V V Zakharov

Mater Sci Forum 2000 331ndash337 793ndash798

186 Y W Riddle H Hallem and N Ryum Mater Sci Forum 2002

396ndash402 563ndash568

187 J Roslashyset and Y W Riddle Proc 9th Int Conf on lsquoAluminium

alloysrsquo Brisbane Australia August 2004 1210ndash1215

188 A M Diskin V K Portnoi A M Drits and A A Alalykin Sov

Non-Ferrous Met Res 1986 14 499ndash500

189 R R Sawtell P E Bretz and C L Jensen US Patent 4 689 090

25 August 1987

190 G A Salishchev Yu B Timoshenko and R A Saitova Proc

Second Int Conf on lsquoAluminium alloysrsquo Beijing China October

1990 413ndash415

191 T G Nieh R Kaibyshev L M Hsiung N Nguyen and

J Wadsworth Scripta Mater 1997 36 1011ndash1016

192 T G Nieh L M Hsiung J Wadsworth and R Kaibyshev Acta

Mater 1998 46 2789ndash2800

193 J S Vetrano C H Henager Jr M T Smith and S M

Bruemmer in lsquoHot deformation of aluminum alloys IIrsquo (ed T R

Bieler L A Lalli and S R MacEwen) 407ndash418 1998 TMS

194 J S Vetrano C H Henager Jr S M Bruemmer Y Ge and

C H Hamilton in lsquoSuperplasticity and Superplastic Forming

1998rsquo (ed A K Gosh and T R Bieler) 89ndash97 1998 TMS

195 V Y Gertsman J S Vetrano C H Henager Jr and S M

Bruemmer Proc First Joint Int Conf on lsquoRecrystallization and

grain growthrsquo Aachen Germany August 2001 Springer Verlag

2001 837ndash842

196 Y Xiao C Gao H Ma and S Tian Trans Nonferrous Met Soc

China 2001 11 235ndash238

Roslashyset and Ryum Scandium in aluminium alloys

42 International Materials Reviews 2005 VOL 50 NO 1

197 A Gholinia F J Humphreys and P B Prangnell Acta Mater

2002 50 4461ndash4476

198 A Gholinia F J Humphreys and P B Prangnell Mater Sci

Forum 2002 408ndash412 1519ndash1524

199 S Komura P B Berbon M Furukawa Z Horita M Nemoto

and T G Langdon Scripta Mater 1998 38 1851ndash1856

200 S Komura P B Berbon A Utsunomiya M Furukawa

Z Horita M Nemoto and T G Langdon in lsquoHot deformation

of aluminum alloys IIrsquo (ed T R Bieler L A Lalli and S R

MacEwen) 125ndash138 1998 TMS

201 S Komura Z Horita M Furukawa M Nemoto and T G

Langdon J Mater Res 2000 15 2571ndash2576

202 S Komura M Furukawa Z Horita M Nemoto and T G

Langdon Mater Sci Eng 2001 A 297 111ndash118

203 S Komura Z Horita M Furukawa M Nemoto and T G

Langdon Metall Mater Trans A 2001 32A 707ndash716

204 Z Horita M Furukawa K Oh-ishi M Nemoto and T G

Langdon Proc Fourth Int Conf on lsquoRecrystallization and

related phenomenarsquo (ed T Sakai and H G Suzuki) 1999 The

Japan Institute of Metals 301ndash308

205 Z Horita S Komura P B Berbon A Utsunomiya

M Furukawa M Nemoto and T G Langdon Mater Sci

Forum 1999 304ndash306 91ndash96

206 Z Horita S Lee S Ota K Neishi and T G Langdon Mater

Sci Forum 2001 357ndash359 471ndash476

207 Z Horita T Fujinami K Sato S B Kang H W Kim and T G

Langdon in Proc James T Staley Honorary Symposium on

Aluminum Alloys lsquoAdvances in the metallurgy of aluminum

alloysrsquo (ed M Tiryakioglu) 271ndash275 2001 ASM

208 P B Berbon S Komura A Utsunomiya Z Horita

M Furukawa M Nemoto and T G Langdon Mater Trans

JIM 1999 40 772ndash778

209 M Nemoto Z Horita M Furukawa and T G Langdon Mater

Sci Forum 1999 304ndash306 59ndash66

210 M Furukawa Z Horita M Nemeto and T G Langdon Proc

lsquoLight Metals 1999rsquo Quebec City PQ Canada August 1999 583ndash

592

211 M Furukawa K Oh-ishi S Komura A Yamashita Z Horita

M Nemeto and T G Langdon Mater Sci Forum 1999 304ndash

306 97ndash102

212 M Furukawa A Utsunomiya K Matsubara Z Horita and

T G Langdon Acta Mater 2001 49 3829ndash3838

213 M Furukawa A Utsunomiya S Komura Z Horita M Nemoto

and T G Langdon Mater Sci Forum 2001 357ndash359 431ndash436

214 M Furukawa Z Horita and T G Langdon in Proc James T

Staley Honorary Symposium on Aluminum Alloys lsquoAdvances in

the metallurgy of aluminum alloysrsquo (ed M Tiryakioglu) 47ndash56

2001 ASM

215 M Furukawa Z Horita M Nemoto and T G Langdon Mater

Sci Eng 2002 A 324 82ndash89

216 M Furukawa Z Horita and T G Langdon in lsquoUltrafine grained

materials IIrsquo (ed Y T Zhu T G Langdon R S Mishra S L

Semiatin M J Saran and T C Lowe) 459ndash468 2002 TMS

217 T G Langdon M Furukawa Z Horita and M Nemoto Proc

NATO Advanced Research Workshop on lsquoInvestigations and

applications of severe plastic deformationrsquo Moscow August

1999 NATO Science Series Series 3 High Technology vol 80

Kluwer Academic Publishers The Netherlands 2000 149ndash154

218 S Lee H Akamatsu A Utsunomiya K Neishi M Furukawa

Z Horita and T G Langdon Proc Thermec 2000 Las Vegas

USA December 2000

219 S Lee A Utsunomiya H Akamatsu K Neishi M Furukawa

Z Horita and T G Langdon Acta Mater 2002 50 553ndash564

220 A Yamashita D Yamaguchi Z Horita and T G Langdon

Mater Sci Eng 2000 A 287 100ndash106

221 K Oh-ishi Z Horita D J Smith and T G Langdon J Mater

Res 2001 16 583ndash589

222 H Akamatsu T Fujinami Z Horita and T G Langdon Scripta

Mater 2001 44 759ndash764

223 S Ota H Akamatsu K Neishi M Furukawa Z Horita and

T G Langdon Mater Trans 2002 43 2364ndash2369

224 K Furuno H Akamatsu K Oh-ishi M Furukawa Z Horita

and T G Langdon Acta Mater 2004 52 2497ndash2507

225 I N Fridlyander O G Senatorova N A Ryazanova and A O

Nikiforov Mater Sci Forum 1994 170ndash172 345ndash349

226 J N Fridlyander and O G Senatorova Mater Sci Forum 1996

217ndash222 1813ndash1818

227 J Liu and D J Chakrabarti Acta Mater 1996 44 4647ndash4661

228 O G Senatorova A N Uksusnikov J N Fridlyander

J Koshorst R R Romanova N A Ryazanova A Galliot

and V V Cherkassov Proc 6th Int Conf on lsquoAluminum alloysrsquo

July 1998 Toyohashi Japan 589ndash593

229 R A Emigh E L Bradley and J W Morris Jr in

lsquoSuperplasticity in aerospace IIrsquo (ed T R McNelley and H C

Heikkenen) 303ndash315 1990 TMS

230 E L Bradley III R A Emigh and J W Morris Jr Scripta

Metall Mater 1991 25 717ndash721

231 N I Kolobnev L B Khokhlatova V D Makarov E Yu

Semenova and V V Redchits Proc Sixth Int Aluminiumndash

Lithium Conference Garmisch-Partenkirchen Germany October

1991 1053ndash1056

232 N K Tsenev R Z Valiev O V Obraztsov and I N Fridlander

Proc Sixth Int AluminiumndashLithium Conference Garmisch-

Partenkirchen Germany October 1991 1125ndash1132

233 A M Shammazov N K Tsenev R Z Valiev M M

Myshlyaev M M Bikbulatov and S P Lebedich Phys Met

Metall 2000 89 (3) 314ndash318

234 F Musin R Kaibyshev Y Motohashi T Sakuma and G Itoh

Mater Trans A 2002 43A 2370ndash2377

235 M Shagiev Y Motohashi F Musin R Kaibyshev and G Itoh

Mater Trans A 2003 44A 1694ndash1697

236 M Shagiev Y Motohashi F Musin R Kaibyshev and G Itoh

Mater Trans A 2003 44A 1698ndash1701

237 B A Parker and Z F Zhou Proc 3rd Int Conf on lsquoAluminium

alloysrsquo Vol I NTH Trondheim Norway June 1992 363ndash367

238 J R Davies lsquoASM specialty handbook aluminum and aluminum

alloysrsquo 1993 Materials Park OH USA ASM

239 S J Andersen H W Zandbergen J Jansen C Traeholt

U Tundal and O Reiso Acta Mater 1998 46 3283ndash3298

240 M L Kharakterova D G Eskin and L L Rokhlin Russ

Metall 1997 (1) 104ndash109

241 J Roslashyset Dr Ing thesis NTNU Trondheim Norway 2002

242 P P Chattopadhyay S Datta and M K Banerjee Mater Sci

Eng 2002 A 333 67ndash71

243 L I Kaigorodova E I Selnikhina E A Tkachenko and O G

Senatorova Phys Met Metall 1996 81 513ndash519

244 Y-L Wu F H Froes C Li and A Alvarez Metall Mater

Trans A 1999 30A 1017ndash1024

245 Z Yin L Yang Q Pan and F Jiang Trans Nonferrous Met

Soc China 2001 11 822ndash825

246 V I Elagin V V Zakharov and T D Rostova Met Sci Heat

Treat 1994 36 (7) 375ndash380

247 Y V Milman A I Sirko D V Lotsko O N Senkov and D B

Miracle Mater Sci Forum 2002 396ndash402 1217ndash1222

248 C-H Joh K Yamada and Y Miura Mater Trans JIM 1999

40 439ndash442

249 X J Jiang Q H Gui Y Y Li L M Ma G J Liang and C X

Shi Scr Metall Mater 1993 29 211ndash216

250 X J Jiang Y Y Li W Deng L Y Xiong W M Wu Y J Gao

and C X Shi Adv Cryogenic Eng (Mater) 1994 40 1369ndash

1376

251 C-H Joh T Katsube K Yamada and Y Miura Proc 6th Int

Conf on lsquoAluminum alloysrsquo Toyohashi Japan July 1998 799ndash

804

252 L I Kaygorodova A M Dritz T V Krymova and I N

Fridlyander Proc Sixth Int AluminiumndashLithium Conference

Garmisch-Partenkirchen Germany October 1991 363ndash367

253 L I Kaigorodova A M Drits Ya V Zhingel T V Krymova

and I N Fridlyander Phys Met Metall 1992 73 286ndash290

254 A L Berezina V A Volkov S V Ivanov N I Kolobnev and

K V Chuistov Phys Met Metall 1991 71 (2) 167ndash175

255 I N Fridlyander N I Kolobnev A L Berezina and K V

Chuistov Proc Sixth Int AluminiumndashLithium Conference

Garmisch-Partenkirchen Germany October 1991 107ndash112

256 L I Kaigorodova A M Drits Ya V Zhingel T V Krymova

and V A Rassokhin Phys Met Metall 1992 73 281ndash285

257 I N Fridlyander S F Danilov E N Malysheva T A

Gorokhova and N N Kirkina Proc Sixth Int Aluminiumndash

Lithium Conference Garmisch-Partenkirchen Germany October

1991 381ndash386

258 G Dlubek S Krause H Krause A L Beresina V S

Mikhalenkov and K V Chuistov J Phys Condens Matter

1992 4 6317ndash6328

259 S Krause H Krause G Dlubek A L Beresina and K S

Chuistov Mater Sci Forum 1992 105ndash110 1109ndash1112

260 C Y Tan Z Q Zheng and S Q Liang Proc 4th Int Conf on

lsquoAluminium alloysrsquo Vol II Atlanta GA USA September 1994

329ndash333

261 A L Beresina N I Kolobnev K V Chuistov A V Kotko and

O A Molebny Mater Sci Forum 2002 396ndash402 977ndash981

Roslashyset and Ryum Scandium in aluminium alloys

International Materials Reviews 2005 VOL 50 NO 1 43

262 I N Ganiev I Yunusov and V V Krasnoyarskii J Appl Chem

USSR 1986 60 1961ndash1965

263 I N Ganiev Prot Met 1995 31 543ndash546

264 N V Vyazovikina Prot Met 1999 35 448ndash453

265 G V Kharina and V P Kochergin Prot Met 1996 32 134ndash

136

266 G V Kharina M V Kuznetsov and V P Kochergin Russ J

Electrochem 1998 34 482ndash485

267 V S Sinyavskii V D Valrsquokov and E V Titkova Prot Met

1998 34 549ndash555

268 Y L Wu F H Froes C G Li and J Liu Proc lsquoSynthesis

processing of lightweight metallic materials IIrsquo Orlando FL

USA February 1997 73ndash81

269 Z Ahmad and B J Abdul-Aleem Proc EuroCorr 2000

270 Z Ahmad A Ul-Hamid and B J Abdul-Aleem Corros Sci

2001 43 1227ndash1243

271 R Braun B Lenczowski and G Tempus Mater Sci Forum

2000 331ndash337 1647ndash1652

272 T Torma E Kovacs-Csetenyi L Vitalis I Vitanyi

J Stepanov and M Butova Mater Sci Forum 1987 1314

497ndash503

273 Z Wang P Wang K S Kumar and C L Briant in lsquoChemistry

and electrochemistry of corrosion and stress corrosion crackingrsquo

(ed R H Jones) 573ndash582 2001 TMS

274 V I Elagin V V Zakharov A A Petrova and E V

Vyshegorodtseva Russ Metall 1983 (4) 143ndash146

Roslashyset and Ryum Scandium in aluminium alloys

44 International Materials Reviews 2005 VOL 50 NO 1

Page 3: Scandium in aluminium alloys - Atom probe · A considerable part of the available literature on scandium in aluminium alloys is reviewed. ... behaviour in Al Cu, Al Mg Si,

The solvus line of Sc in Al has been estimated byseveral researchers and over a wide temperaturerange111224ndash31 All the reported measurements aresummarised in Fig 4 There is some spread in theresults most noticeably between data from Russian andnon-Russian papers

In most practical cases solidification of alloys occursunder non-equilibrium conditions Thus the finalmicrostructure might be different from what theequilibrium phase diagram predicts In the case of diluteAlndashSc alloys this is illustrated in a metastable statediagram for solidification at a cooling rate of approx100 K s2132 The temperature of the eutectic reactiondecreases by 3ndash4uC and the eutectic compositionincreases from approx 06 wt- to approx 07 wt-Also the maximum solid solubility of Sc in Al increasesto approx 06 wt-32

Ternary quaternary and higher orderAlndashScndashX(ndashX2ndashX3ndashhellip) phase diagramsA wide range of ternary quaternary and higher orderAlndashScndashX(ndashX2ndashX3ndashhellip) phase diagrams has been reportedin the literature the majority in Russian journals Someof the Russian journals do not have parallel Englishtranslations and thus these data are less accessible forthe non-Russian reader However a good overview ofthe majority of the published material is available33 Notall of the published phase diagrams comprise the fullcomposition ranges In the present review the emphasisis placed on phase diagrams of AlndashSc with elements thatare technologically important alloying elements withaluminium

Ternary phase diagrams withprecipitate-forming elementsAlndashMgndashSc

The AlndashMgndashSc phase diagram seems to be the AlndashScndashXdiagram that is best described in the technical literatureIn an investigation of AlndashMgndashSc alloys with up to

26 wt-Mg and 3 wt-Sc25 a ternary eutectic

Liq~aAlzAl3Mg2zAl3Sc

was observed at 447uC Two vertical cross-sections andone isothermal section at 430uC of the phase diagramwere constructed (Fig 5) It was found that Mg and Scmutually reduce each otherrsquos solid solubility in Al Thelsquocornerrsquo of the a-Al field was determined to be at105 wt-Mg and 0007 wt-Sc at 430uC No ternaryAlMgSc phases were observed

In another investigation a vertical cross-section of theAl rich corner at a constant Sc level of 03 wt- wasconstructed34 No ternary phases were reported Thisphase diagram suggests probably as a result of a lapseby the authors that 03 wt-Sc is a hypereutecticcomposition in binary AlndashSc

Odinaev and co-workers explored the AlndashMgndashScsystem for the whole AlndashMg range and for Sc contentsup to 333 at-Sc3536 An isothermal section at 400uC35

was constructed No ternary phases were observed in theregion examined A liquidus surface and three quasi-binary cross-sections were also constructed36 Threequasibinary eutectics three ternary eutectics and oneternary peritectic were observed in the examinedcomposition range The temperature for the eutecticreaction shown above was determined to be 435uCand the composition was found to be 625 at-Al366 at-Mg and 09 at-Sc

In a recent study37 the isothermal cross-section at350uC was determined experimentally in the regiondelimited by the phases Al3Mg2 Al3Sc AlSc2 MgScand Mg meaning that the Al- and Sc-corners of thephase diagram were not explored There are somediscrepancies between the phase relations found in thiswork37 and those found by Odinaev et al35 However noternary AlMgSc phases were found in Ref 37 either Allthe four intermetallic (AlSc) phases were found todissolve a few percent Mg seemingly by substituting AlFor Al3Sc this observation is sustained by othermeasurements38 where some Mg content in Al3Scprecipitates was found by three-dimensional atom probemicroscopy In Ref 37 a calculated liquidus surface and

4 Reported values of Al solvus line in AlndashSc phase dia-

gram full line is solvus estimate assuming regular

solution and applying maximum solubility as

assessed in Ref 10 and experimental data of Ref 31

5 Isothermal section of Al-corner of AlndashMgndashSc phase

diagram at 430uC redrawn from Ref 25

Roslashyset and Ryum Scandium in aluminium alloys

International Materials Reviews 2005 VOL 50 NO 1 21

several calculated vertical and isothermal cross-sectionsare also presented Additional phase diagram calcula-tions are reported in a separate paper39

The phase relations in a diffusion couple between Alndash177 wt-Sc and pure Mg at 430uC have also beenstudied40 No ternary phases were reported and the a-Alwas found to be in equilibrium with Al3Sc and Al3Mg2in accordance with earlier work253537 The maximumsolid solubility of Mg and Sc in a-Al at this temperaturewas reported to be 1527 at- (14 wt-) and 033 at-(055 wt-) respectively Both these solubilities and inparticular that of Sc is higher than what has been foundearlier25 Considering the binary AlndashSc system wherethe solubility of Sc in a-Al is only approx 0025 wt- at430uC the high solubility of Sc reported in Ref 40 forthe ternary system is rather unlikely It is possible thatfine-scale Al3Sc precipitates embedded in the a-Almatrix have been included in the electron probeanalyses and thus giving too high a value for the Sccontent in solid solution

AlndashCundashSc

Two ternary phases AlCuSc and AlCu2Sc werereported in an early investigation41 A later investigationof the Al-corner of the phase diagram42 revealed that aternary (AlCuSc) phase named the lsquoW-phasersquo couldbe in thermodynamic equilibrium with a-Al Thefollowing ternary invariant equilibria were found

LiqzAl3Sc~aAlzW(5720C)

Liq~aAlzAl2CuzW(5460C)

Isothermal sections of the Al-corner at 450 and 500uChave been constructed43 (Fig 6) The solid solubility ofCu in Al was found to decrease somewhat withincreasing Sc content whereas the solid solubility ofSc in Al was not found to be influenced by the Cucontent The W-phase was suggested to be the com-pound Al54ndash8Cu66ndash4Sc43 A liquidus surface of the Al-corner has also been constructed44

A more thorough review on the AlndashCundashSc system isavailable in the literature45

AlndashScndashSi

An isothermal section at 497uC has been constructed forthe entire system46 A ternary phase AlSc2Si2 wasidentified This phase frequently referred to as the lsquoV-phasersquo was found to be in thermodynamic equilibrium withAl3Sc Al Si and ScSi at this temperature A projection ofthe liquidus surface of the Al-corner has also been made47

Two ternary invariant reactions were reported

LiqzAl3Sc~aAlzV(6170C)

Liq~aAlzSizV(5740C)

Vertical cross-sections and isothermal sections of the Al-corner are reviewed in Ref 33 The 550uC isothermalsection is redrawn in Fig 7 It seems that the solidsolubility of Sc is not altered by an addition of Siwhereas the solubility of Si decreases somewhat with theSc content

AlndashScndashZn

A sketch of a lsquosemi-isothermalrsquo cross-section of the wholesystem partially at 300uC and partially at 500uC hasbeen reported48 No ternary phases were found in thisinvestigation The phase relations in the Al rich rangewere found to be limited by the subsystem AlndashZnndashAl3Sc

Another investigation of the subsystem AlndashZnndashAl2Scconfirmed that no ternary compounds are found in thiscomposition range49 The liquidus surface was con-structed It is suggested that the section ZnndashAl2Sc is aquasibinary simple eutectic A certain mutual solidsolubility of Zn and Al2Sc is indicated on the verticalcross-section although no measurements of the compo-sitions are presented In addition to the quasibinaryeutectic one ternary peritectic and one ternary eutecticreaction was found The ternary eutectic reaction

Liq~aAlzZnzAl3Sc

was found to occur at 367uC

AlndashLindashSc

An investigation of the phase relations in the Al-corner(up to 5 wt-Li and 3 wt-Sc) at 450uC revealed that

6 Isothermal section of Al-corner of AlndashCundashSc phase dia-

gram at 500uC redrawn from Ref 437 Isothermal section of Al-corner of AlndashScndashSi phase dia-

gram at 500uC redrawn from Ref 33

Roslashyset and Ryum Scandium in aluminium alloys

22 International Materials Reviews 2005 VOL 50 NO 1

a-Al could be in equilibrium with either Al3Sc or AlLi50

No ternary phases were observed Thermal analysesindicated that the ternary eutectic reaction

Liq~aAlzAl3SczAlLi

occurs at approximately 595uC It has been stated47 thatthere are only minor mutual effects of Sc and Li on theseelementsrsquo solid solubility in a-Al

This statement is confirmed in another investigation51

where the AlndashAlLindashAlSc subsystem is investigated At450uC it is found that the AlLi phase can be inequilibrium with Al3Sc Al2Sc and AlSc No significantsolubility of Li in Al3Sc was observed Several verticalcross-sections are constructed

It should be noted that the existence of a ternaryAl3(LiSc) phase has been reported52 which is indisagreement with the observations above

Ternary phase diagrams withdispersoid-forming elementsAlndashScndashZr

It has been shown53 that at 600uC the Al-corner consistsof the phase fields a-AlzAl3Sc a-AlzAl3SczAl3Zrand a-AlzAl3Zr Further it was discovered that there isa significant solid solubility of Zr in the Al3Sc phase(approx 35 wt-) and some solid solubility of Sc in theAl3Zr phase (approx 5 wt-) The lattice parameter ofAl3Sc was found to decrease when the phase dissolvesZr and likewise the lattice parameter of the Al3Zr wasfound to decrease when that phase dissolves Sc Foralloys in the a-AlzAl3Sc phase field the wt-Zrwt-Scratio in the Al3Sc particles was found to be approx 22times the wt-Zrwt-Sc ratio of the alloy53 Isothermalsections of the Al-corner at 550 and 600uC are alsoconstructed54 (Fig 8)

In another investigation55 two vertical cross-sectionsin the Al-corner were constructed and a ternaryperitectic reaction

LiqzAl3Zr~aAlzAl3Sc

was found to take place at 659uC

The 500uC isothermal section of the whole phasediagram has been investigated56 It is already knownthat Sc and Zr are completely miscible in the solid stateHere it was also found that the compounds AlSc2 andAlZr2 are completely miscible The extensions of theother single-phase fields are determined with variousdegrees of accuracy The solubility of Zr in Al3Sc wasfound to be 6 at- (approx 16 wt-) whereas thesolubility of Sc in Al3Zr was found to be 65 at-(approx 73 wt-) Contrary to Ref 53 the latticeparameter of Al3Sc was found to increase with increas-ing Zr content The lattice parameter of Al3Zr howeverwas found to decrease with increasing Sc content whichis in accordance with the findings of Ref 53

The section Al3ScndashAl3Zr at 1200uC has recently beeninvestigated57 The solubility of Sc in Al3Zr was reportedto be in the range 3ndash5 at- and the solubility of Zr inAl3Sc was found to be 122 at- In accordance withRef 53 the lattice parameters of Al3Sc and Al3Zr decreasewith increasing content of Zr and Sc respectively

AlndashFendashSc

The available data on this system is reviewed in Ref 33and an isothermal section at 500uC is reproduced Threeternary AlndashFendashSc phases are reported The Al-corner ofthe isothermal section however seems to be limited bythe subsystem AlndashAl3ScndashAl3Fe meaning that the a-Alcannot be in equilibrium with any of the ternary phases

AlndashMnndashSc

The Al-corner of the phase diagram has been investi-gated58 No ternary phases were observed meaning thatin the solid state only the Al3Sc and the Al6Mn phasecan be in equilibrium with a-Al An addition of Mn doesnot noticeably decrease the solid solubility of Scwhereas an addition of Sc causes a distinct decrease inthe solubility of Mn Two isothermal sections weremade one at 500uC (Fig 9) and one at 600uC Thelsquocornerrsquo of the a-phase field was reported to be at008 wt-Sc and 02 wt-Mn at 500uC and at 02 wt-Scand 055 wt-Mn at 600uC

8 Isothermal section of Al-corner of AlndashScndashZr phase dia-

gram at 600uC redrawn from Ref 54

9 Isothermal section of Al-corner of AlndashMnndashSc phase

diagram at 500uC redrawn from Ref 58

Roslashyset and Ryum Scandium in aluminium alloys

International Materials Reviews 2005 VOL 50 NO 1 23

Two vertical cross-sections were also constructed Aternary eutectic

Liq~aAlzAl6MnzAl3Sc

at 649uC was identified Several alloys in the sectionAl3ScndashAl6Mn have also been investigated59 and all werefound to comprise a mixture of the two binary phasesLattice parameter measurements of the Al3Sc phasewere interpreted as an indication of a slight solidsolubility of Mn in Al3Sc

AlndashCrndashSc

Alloys in the composition range 30ndash100 at-Al havebeen studied60 and an isothermal cross-section at 500uCwas constructed No ternary phases were identified Thephases that can be in equilibrium with the a-Al are thusAl7Cr and Al3Sc The solubility of Cr in the Al3Sc phasewas found to be considerable approximately 11 at-

Other ternary AlndashScndashX phase diagramsAlndashMondashSc

An isothermal cross-section at 550uC has been con-structed for the subsystem AlndashAl2ScndashAl2Mo61 Noternary phases were reported The phases in equilibriumwith a-Al were found to be Al3Sc and Al12Mo

AlndashScndashV

The section Al3ScndashAl21V2 has been studied62 and thevertical cross-section was constructed No ternaryphases were observed Solid solubilities of V in theAl3Sc phase of 14 at- and of Sc in Al21V2 of 25 at-are reported although a considerably higher maximumsolubility of V in Al3Sc is suggested in the vertical cross-section A quasibinary eutectic reaction

Liq~Al3SczAl21V2

is reported to occur at 917 K (644uC)The section Al3ScndashAl3V at 1200uC has also been

studied57 The solubilities of V in Al3Sc and Sc in Al3Vare reported to be 27 and 07 at- respectively WhenV was dissolved in Al3Sc the lattice parameter of Al3Scwas found to decrease

AlndashScndashTi

No ternary phase diagram is available The sectionAl3ScndashAl3Ti at 1200uC has been studied57 A solubilityof Ti in Al3Sc of almost 125 at- was found whichcorresponds to almost half of the Sc being substituted byTi The lattice parameter of Al3Sc was found to decreasesharply with increasing Ti content For the Al3Ti phasethe solubility of Sc was found to be approx 5 at-

AlndashCondashSc

The ternary system for 0ndash70 at-Sc has been investi-gated63 Three ternary (AlCoSc)-phases were identifiedThe only phases found to be in equilibrium with a-Alwere the binary phases Al3Sc and Al9Co2 An isothermalsection at 600uC and the vertical cross-sections Al3ScndashAl9Co2 and Al3ScndashAl9Co3Sc2 were constructed Thelsquocornerrsquo of the a-phase field was reported in the text to beat 15 at-Co and 05 at-Sc although in a tablethe numbers 02 at-Co and 01 at-Sc are reportedThe solubilities of Co in the Al3Sc phase and of Sc in theAl9Co2 phase were found to be 12 and 01 at-

respectively However in the vertical cross-sections it issuggested that the solubility of Co in Al3Sc may besignificantly higher at higher temperatures The latticeparameter of Al3Sc was not found to change withincreasing Co content

AlndashScndashSr

The subsystem AlndashAl2ScndashAl4Sr has been studied64 andan isothermal section at 500uC was constructed Noternary phases were detected meaning that the phases inequilibrium with a-Al were found to be Al3Sc and Al4SrThe solubility of Sc in Al4Sr and of Sr in Al3Sc wasfound to be low typically less than 15ndash2 at-

AlndashBendashSc

A study of the binary BendashSc system and the ternary AlndashBendashSc system for up to 20 at-Sc (or 30 wt-Sc) hasbeen reported65 The 600uC isothermal section for theinvestigated ternary composition range was constructedNo ternary phases were observed The a-Al can be inequilibrium with either Be Be13Sc or Al3Sc It is sug-gested that the section AlndashBe13Sc may be quasi-eutectic

AlndashBandashSc

An isothermal section at 500uC has been constructed66

No ternary phases were reported and a-Al is inequilibrium with Al4Ba and Al3Sc The solubility of Scin Al4Ba and of Ba in Al3Sc was reported to be less than2 at-

AlndashNndashSc

The region AlndashAlNndashScNndashSc has been investigated67 Aperovskite-type ternary phase AlN12xSc3 was reportedand an isothermal section at 1000uC was constructed Inthe Al-corner the Al melt was reported to be inequilibrium with AlN and Al3Sc

Quaternary and higher order AlndashScndashXndashX2(ndashX3hellip)phase diagramsAlndashMgndashScndashZr

The published material is limited to investigations onAl rich alloys A part of the liquidus surface of the6 wt-Mg section has been determined experimentallyfor the composition range 0ndash07 wt-Sc and 0ndash04 wt-Zr68 The 500uC isothermal phase relations inthe Al-corner of the 6 wt-Mg section has also beeninvestigated69 for Sc and Zr concentrations of up to3 wt- and 4 wt- respectively No ternary or qua-ternary phases were observed Likewise the 430uC iso-thermal phase relations of the 4 at-Mg (y35 wt-Mg)section have been investigated for up to 12 at-Sc(2 wt-Sc) and up to 25 at-Zr (8 wt-Zr)7071 Noternary or quaternary phases were observed in thepresent study either The Al3Sc phase was found todissolve an amount of 122 at-Zr corresponding to asubstitution of almost 50 of the Sc lattice positionswhereas the solubility of Sc in Al3Zr was 44 at-which corresponds to a substitution of almost 20 ofthe Zr lattice positions Figure 4 in Refs 70 and 71suggests that the Al content in the Al3Zr-phase increaseswith increasing Sc content however this is not sub-stantiated in the text

Roslashyset and Ryum Scandium in aluminium alloys

24 International Materials Reviews 2005 VOL 50 NO 1

AlndashMgndashScndashTindashZr

A vertical cross-section of the AlndashMgndashScndashTindashZr phasediagram for 03 wt-Sc 015 wt-Ti 015 wt-Zrand 0ndash10 wt-Mg has been constructed34 Accord-ing to this diagram the Al3Zr phase is the first andAl3Sc the last to form during solidification of thealloys No ternary quaternary or quinary phases arereported

AlndashZnndashMgndashCundashZrndashSc

A vertical cross-section of the full system as well asseveral sections of various sub-systems have beenconstructed72 For the full system a section at8 wt- Zn 2 wt-Cu 03 wt-Zr and 03 wt-Scwas constructed where Mg varies from 0 to 8 wt-The only reported Sc-containing sub-system is thatof AlndashZnndashMgndashCundashSc Here a vertical cross-sectionis constructed with the same levels of Zn Cu and Scas in the full system whereas Mg varies from 0 to65 wt-

No phases other than those known from the lowerorder systems were reported Amongst the findings it isinteresting to note that in the solid state Al3Sc isreported to be an equilibrium phase for all theinvestigated compositions It is also interesting to notethat the Sc-containing W-phase (Al54ndash8Cu66ndash4Sc see thesection on the AlndashCundashSc ternary system) is an equili-brium phase at low Mg content and disappears as theMg content increases

AlndashLindashMgndashSc

The 400uC isothermal phase relations of the 02 wt-Scsection have been investigated for the composition range0ndash6 wt-Mg and 0ndash5 wt-Li73 The a-Al was found tobe in equilibrium with AlLi Al2LiMg and Al3Sc Noquaternary phases were observed This investigation isalso summarised in Ref 50

AlndashCundashLindashSc

The aluminium rich corner of the system has beeninvestigated for alloys with 06 wt-Sc and with Cu andLi in the range 0ndash16 wt- and 0ndash4 wt- respectively74

No quaternary phases were reported Two sections ofthe phase diagram were constructed a section of the470uC isothermal tetrahedron at 06 wt-Sc and avertical section at 06 wt-Sc and 26 wt-Li Twoquaternary invariant equilibria were found and thetemperatures of the invariant points were estimated

Al3Sc phaseRechkin and co-workers were to the authorsrsquo knowl-edge the first to publish a paper in an internationaljournal identifying the Al3Sc phase75 The phase wasidentified as cubic with lattice parameter a5410 A Afew years later the lattice structure was reported to be ofthe Cu3Au type76 The atomic arrangement of the Al3Scphase is shown in Fig 10 The structure can bedescribed as ordered face-centred cubic (fcc) althoughin crystallographic terminology the Al3Sc structure isactually a simple cubic lattice with four atoms (one Scand three Al atoms) associated with each lattice pointThis particular atomic arrangement is nominated L12

and is found in several intermetallic compounds forinstance Ni3Al Ni3Fe and Cu3Au

Some efforts have been made in characterising theproperties of the Al3Sc phase A compilation of someresults is given in Table 3 The motivation for themajority of the investigations seems to be one of thethree following

(i) the Al3Sc phase has a density of 303 g cm23 andit melts peritectically at approx 1320uC This canmake the Al3Sc phase an attractive candidate asa material for lightweight high temperaturestructural applications205777ndash86

(ii) in order to understand the effect of Al3Scprecipitation in Al-alloys it is necessary to gainmore knowledge about the Al3Sc phase578187ndash91

(iii) the Al3Sc is an excellent model phase forstudying basic properties of intermetalliccompounds7990ndash98

10 Atomic arrangement of Al3Sc phase

Table 3 Some reported properties of Al3Sc phase

ReferenceE GPa(Youngrsquos modulus) n (Poissonrsquos ratio)

CTE (Coefficient ofthermal expansion) 1026 K21

(111) APB energymJ m22

(100) APB energymJ m22

88 Approx 11120 166 020 Max 670 45079 166 022 31399 1628 0204

1642iexcl19 0201iexcl000189 16

Reported to decrease linearly with increasing temperature to approx 97 GPa at 550uCCalculatedExperimental

Roslashyset and Ryum Scandium in aluminium alloys

International Materials Reviews 2005 VOL 50 NO 1 25

Formation of Al3Sc in AlndashSc alloysThere are at least four ways that the Al3Sc phase canform in dilute binary AlndashSc alloys

1 Upon solidification of hypereutectic alloys (Sc

approx 06 wt-) Al3Sc is the first phase to form

2 The solidification of hypo- and hypereutectic alloysends with formation of eutectic AlzAl3Sc

3 Al3Sc can precipitate discontinuously from super-saturated solid solution

4 Al3Sc can precipitate continuously (nucleation andgrowth) from supersaturated solid solution

Primary Al3ScAccording to the binary phase diagram primary Al3Scshould form during solidification of all alloys with Sccontent higher than approx 06 wt- ie higher thanthe eutectic composition Formation of primary Al3Sc inAlndash07 wt-Sc melts cooled at 102ndash103 K s21 has beenreported1832 According to the metastable state dia-gram32 this alloy composition is close to the eutectic oneat these cooling rates

Primary Al3Sc is reported to have a highly facetedmorphology1318100ndash102 The observation of a cubicmorphology in a slowly cooled Alndash87 wt-Sc alloyindicates that the facet planes in this case are thecrystallographic (100) planes13 Brodova et al100ndash102

have investigated the microstructure of rapidly cooledAlndash2 wt-Sc alloy They found that the dominantmorphology of primary Al3Sc was dependent on boththe cooling rate and the initial melt temperature A mapof primary Al3Sc morphologies as a function of theseparameters was constructed and is redrawn in Fig 11

The nucleation mechanism and growth morphologyof primary Al3Sc in an Alndash07 wt-Sc alloy solidified ata cooling rate of 100 K s21 were investigated by Hydeet al103104 Indications were found that the primaryAl3Sc particles nucleate heterogeneously on oxideparticles in the melt The primary Al3Sc particles werefound to grow with a dendritic morphology with theprimary dendrite arms in the crystallographic n110m

direction The overall shape is cubic which is inaccordance with earlier observations

Eutectic Al3ScEutectic AlzAl3Sc has been reported in hyper- as wellas hypoeutectic alloys11 but is scantily described in theliterature Given a eutectic composition of 06 wt- amaximum solid solubility of Sc in Al of 035 wt- andthe specific densities in Table 1 a eutectic formed underequilibrium conditions would contain a volume fractionof approx 063 vol-Al3Sc At high cooling rates thevolume fraction of Al3Sc in the eutectic is probablysomewhat smaller owing to the increased supersatura-tion of Sc in Al

The morphology of the eutectic in an Alndash2 wt-Scalloy is reported to depend on the temperature of themelt before solidification100 For low melt temperaturesthe eutectic is reported to be rodlike for a wide range ofcooling rates For intermediate melt temperatures andhigh cooling rates a lsquodiscontinuous eutecticrsquo is reportedwhereas for high melt temperatures and slow coolingrates a lsquoquasieutecticrsquo structure is reported with Al3Scparticles of almost spherical shape

Hyde et al have reported that during solidification ofan Alndash07 wt-Sc alloy some of the primary Al3Scparticles are pushed ahead of the Al solidification frontand end up at the grain boundaries103104 Thus primaryAl3Sc may be mixed with eutectic Al3Sc in themicrostructure A scanning electron microscopy (SEM)picture showing eutectic Al3Sc at the grain boundaries asdescribed in Refs 103 and 104 is given in Fig 12

Discontinuous precipitation of Al3ScDiscontinuous precipitation of Al3Sc from super-saturated solid solution is often observed in binary AlndashSc alloys131831105 This precipitation mechanism whichis sometimes referred to as cellular precipitation iscommonly described as a decomposition of super-saturated solid solution into a-Al and Al3Sc at a movinggrain boundary The driving force for the grainboundary migration is the volume free energy that isreleased during the precipitation As the grain boundarymoves it leaves behind a characteristic fan shaped array

11 Morphology of primary Al3Sc particles in Alndash2 wt-Sc

alloy as a function of melt overheating and cooling

rate during solidification redrawn from Ref 102

12 SEM image of particle structure of Alndash07 wt-Sc

alloy cooled at a rate of 100 K s21 during solidifica-

tion as described in Refs 103 and 104 primary Al3Sc

particle is seen in centre of grain whereas eutectic

Al3Sc is decorating grain boundaries image is kindly

provided by Dr Kristian Hyde UMIST Manchester UK

Roslashyset and Ryum Scandium in aluminium alloys

26 International Materials Reviews 2005 VOL 50 NO 1

of precipitates In the AlndashSc case the discontinuouslyprecipitated Al3Sc particles have been demonstrated tobe coherent with the aluminium matrix1318

The driving force for discontinuous precipitationincreases with increasing supersaturation of Sc in theAl matrix Thus discontinuous precipitation in binaryAlndashSc is most frequently reported in studies of alloyswith a Sc content of 04 wt- or higher1318106 Stilldiscontinuous precipitation has also occasionally beenreported to occur at lower alloy compositions In an Alndash027 wt-Sc alloy discontinuous precipitation wasobserved over a wide range of temperatures107 In arecent study31105 of precipitation kinetics and mechan-isms in Alndash02 wt-Sc discontinuous precipitation wasfound to take place when the specimens were quencheddirectly from a solutionising temperature in this case600uC to aging temperatures in the range 370ndash490uCFurther C-curves in a temperature-time-transformation(TTT) diagram were established (Fig 13) which showedthat the highest transformation rate of discontinuousprecipitation lies at a higher temperature than thehighest transformation rate of the continuous precipita-tion reaction ie the two precipitation reactions arerepresented by two separate lsquonosesrsquo on the C-curves

It has been shown that discontinuous precipitationcan be suppressed by continuous precipitation if thematerial is cold worked before the precipitation heattreatment13108

As a result of their rather coarse nature andinhomogeneous dispersion discontinuously precipitatedAl3Sc contributes but little to the strength of the alloyand also leads to a smaller amount of Sc in super-saturated solid solution being available for subsequentcontinuous precipitation Thus discontinuous precipita-tion is in general regarded as an undesired precipitationmode

Continuous precipitation of Al3ScContinuous precipitation of Al3Sc is a bulk decomposi-tion process of supersaturated solid solution of Sc in Aland can in the isothermal case be characterised by anucleation stage a growth stage and finally a coarsen-ing stage Apparently the continuous precipitation reac-tion occurs largely by homogeneous nucleation anddiffusion controlled growth and AlndashSc has occasionallybeen used as a model system for studying the mechan-isms of nucleation growth and coarsening107109ndash111

There have been several studies of the continuousprecipitation reaction in binary AlndashSc alloys and up tillnow there is no evidence that any metastable phases areforming before the L12 phase Al3Sc Thus it is assumedthat the equilibrium phase nucleates directly fromsupersaturated solid solution

Even though the nucleation of Al3Sc is frequentlyreported to occur homogeneously throughout the Almatrix there are some examples in the technical litera-ture of reported heterogeneous Al3Sc nucleation ondislocations110112ndash115 and grain boundaries110113115ndash118

In a recent numerical modelling study of continuousprecipitation in AlndashSc alloys111 the effect of hetero-geneous nucleation on dislocations is accounted for Themodel predicts that homogeneous nucleation dominatesat high Sc concentrations and low transformation tem-peratures whereas heterogeneous nucleation is predictedto dominate at low Sc concentrations and high trans-formation temperatures Figure 14 shows a sketch of anucleation map for AlndashSc The shift between homo-geneous and heterogeneous dominance in nucleation isdependent on the dislocation density as indicated in thefigure

The shape of continuously precipitated Al3Sc particlesis most frequently reported to be spherical29112113119ndash129

However it seems that under certain conditions theshape can differ from the spherical one Drits et al130

reported both spherical and star shaped morphologyThe star shaped precipitates had arms growing in thecrystallographic n110m-directions (Star shaped Al3Scprecipitates have also been found after some thermo-mechanical treatments of an AlndashMgndashScndashZr alloy131) InRef 128 precipitates of both cuboidal and sphericalmorphology are found to coexist after certain heattreatments Cauliflower shaped precipitates as well asprecipitates of spherical and cuboidal shapes arereported by Novotny and Ardell110 Bastow andCelotto132 found large oblong Al3Sc particles in an Alndash01 wt-Sc alloy after aging at 400uC for 24 h A facetedshape is suggested in a high-resolution image of anAl3(Sc Zr) precipitate in an AlndashMgndashMnndashZrndashSc alloy133

In a systematic high-resolution transmission electron

13 TTT diagram of precipitation in Alndash02 wt-Sc alloy

after solutionising at 600uC and direct quench to

aging temperature3114 Nucleation map for binary AlndashSc alloys which indi-

cates how the tendency towards heterogeneous ver-

sus homogeneous nucleation is predicted to depend

upon Sc concentration transformation temperature

and dislocation density redrawn from Ref 111

Roslashyset and Ryum Scandium in aluminium alloys

International Materials Reviews 2005 VOL 50 NO 1 27

microscopy (TEM) study of the Al3Sc particle morphol-ogy development during precipitation heat treatment ofbinary AlndashSc alloys by Marquis and Seidman114 it isdemonstrated that the precipitates can take a wide rangeof shapes as they grow depending on Sc content in thealloy transformation temperature and transformationtime Irregular shaped star shaped and cuboidalshaped precipitates were observed under someconditions It was however found that the equilibriumshape of the particles is an equiaxed multifaceted one(Fig 15) Supported by Wulffrsquos construction it wasconcluded that the shape was that of a GreatRhombicuboctahedron This equilibrium morphologyhas been reproduced by computer-simulations ofparticle growth87134 The multifaceted particles caneasily be taken for spherical in a conventional TEMpicture

Kinetics of precipitation of Al3Sc fromsupersaturated solid solutionThe precipitation kinetics of Al3Sc in binary AlndashScalloys is dependent on the precipitation heat treatmenttemperature and on the Sc content in the alloy Acomprehensive overview over the transformationkinetics in terms of C-curves is given by Zakharov135

The C-curves for 5 transformation for a range of AlndashSc alloys are redrawn in Fig 16

Hyland107 studied the homogeneous nucleationkinetics of Al3Sc in a Alndash018 wt-Sc alloy after directquench from 650uC to precipitation temperatures of 288and 343uC He found that after an incubation time t theAl3Sc particles nucleated at a constant rate until thediffusion fields of the individual particles started tooverlap At 288uC the incubation time and time tosignificant diffusion field overlap were estimated to beapprox 245 and 150 min respectively whereas thecorresponding values at 343uC were estimated to beapprox 7 and 20 min respectively

If one assumes that the JohnsonndashMehlndashAvramindashKomolgorov (JMAK) relationship is valid for thisprecipitation reaction one can express the fraction

transformed X as a function of the reaction time t bythe equation

X (t)~1expfrac12k(Dt)n (1)

where k is a constant D is the interdiffusion constant ofSc in Al and the exponent n is dependent on thenucleation rate For the situation described byHyland107 where the precipitates nucleate at a constantrate the value of n should theoretically136 be equal to52

Roslashyset and Ryum31105 applied an alloy and heattreatment method practically equal to that of Hyland107

One should thus expect that the precipitation kineticsshould also be quite similar However Roslashyset andRyum reported that the exponent n of the JMAKrelationship was approx 165ndash185 for the temperaturerange of concern31105 This does not point in thedirection of a constant nucleation rate but rather inthe direction of site saturation ie that all the particlesare nucleated simultaneously which in the JMAKequation would yield an exponent n of 32136 Anoverview of some reported values of n in the JMAKequation is given in Table 4 The majority of the valueslie closer to 32 than to 52 However it is important to

15 High resolution TEM picture along n100m axis of Al3Sc particle in Alndash03 wt-Sc alloy aged at 300uC for 350 h114

(reproduced with permission from Elsevier Science image kindly provided by Dr E A Marquis and Professor D N

Seidman) and various projections of a Great Rhombicuboctahedron

Table 4 Some reported values of n in JMAK equation

Reference n C 0Sc wt-Sc Ttrans uC Note

137 13 030 300 Solution heat treated (SHT) 500uC16026 030 300 SHT 600uC Low n at late stage20026 030 300 SHT 640uC Low n at late stage

29 130ndash149 015 260ndash370145ndash196 025 260ndash370

138 188ndash216 020 240ndash35031 165ndash185 023 270ndash350 SHT 600uC Direct quench to transformation temp

16 C-curves for 5 transformation in a range of binary

AlndashSc alloys redrawn from Ref 135

Roslashyset and Ryum Scandium in aluminium alloys

28 International Materials Reviews 2005 VOL 50 NO 1

note that an n value close to 32 is per se not evidence ofsite saturation

Hyland also showed that a water quench from thesolutionising temperature significantly altered thenucleation kinetics in the subsequent precipitation heattreatment107 The incubation time was dramaticallyshortened which is attributed to the quenched-in excessvacancies and it is also indicated that there might be ashift in the nucleation rate in the early stage ofprecipitation It is suggested that the vacancies mayenhance the diffusion of Sc in Al and that there is apossibility that vacancy clusters act as heterogeneousnucleation sites for Al3Sc precipitates107 Regardless ofwhich mechanism that is operative it is clearly demon-strated that the nucleation kinetics can be dependent onthe thermal history between solutionising and precipita-tion heat treatment

Loss of coherency during growth of Al3ScprecipitatesWhen an Al3Sc particle grows it will sooner or laterreach a critical size where it will be energetically morefavourable to introduce an interface dislocation at theAlAl3Sc interface than to increase the matrix strain Asimple approximation for the critical size can be derivedfrom the lattice parameters assuming that the criticalsize is reached when the misfit over the whole particlediameter equals the Burgers vector of the Al matrix

dcrit~b=d (2)

where b is the Burgers vector of Al and d is themisfit between Al and Al3Sc This approximation yieldsa critical diameter of approx 215 nm at ambienttemperature

The misfit d and thus also the critical diameter dcrit

will depend on the temperature owing to the differencesin thermal expansion between the Al matrix and the

Al3Sc particles The thermal expansion of Al3Sc hasrecently been measured89 and based on the differencesin thermal expansion between Al139 and Al3Sc the misfitas a function of temperature has been calculated89 Thiscalculation is reproduced and shown by the solid line inFig 17

It is however possible to refine this calculationsomewhat140 Whereas the thermal expansion of Al3Sc isexpected to be only because of lattice expansion there isa significant contribution from vacancies on thermalexpansion of Al at high temperatures141 Thus thetemperature effects on the misfit should be calculatedfrom the changes in lattice parameters rather than fromthe linear thermal expansion By subtracting the vacancyeffect on the thermal expansion one achieves atemperature-dependent misfit as represented by thedotted line in Fig 17

A second correction that should be taken into accountis the effect of Sc in solid solution on the latticeparameter of the Al matrix With increasing tempera-ture more Sc is brought into solid solution and it isreported that the lattice parameter of the Al matrixpresumably measured at room temperature increaseslinearly with the Sc content in solid solution142 Thesedata can be used to calculate the effect on the latticeparameter at elevated temperatures under the assump-tion that the relative increase in lattice parameter owingto Sc in solid solution is independent of temperature InRef 142 a figure is presented which shows the measuredlattice parameter as a function of Sc content in solidsolution and a value (dadc)a is reported where a is thelattice parameter of the Al matrix and c is the Sc contentin solid solution in at- The reported value for (dadc)a is 100 times larger than that indicated in thecorresponding figure possibly as a result of a decimalerror in the text Thus in the present exercise 1100th ofthe reported value for (dadc)a is used Using this incombination with the regular solution approximationfor the solvus line of Sc in Al1231 one obtains acorrection for Sc in solid solution on the temperature-dependent misfit as shown in Fig 18 This figure shows

17 Lattice mismatch between Al and Al3Sc as a function

of temperature solid line represents calculation

based on linear thermal expansion of the two phases

dotted line represents correction for vacancies in Al

lattice

18 Corrections of mismatch calculated from linear ther-

mal expansion data as a result of vacancies and to

Al lattice expansion from Sc in solid solution

Roslashyset and Ryum Scandium in aluminium alloys

International Materials Reviews 2005 VOL 50 NO 1 29

both the correction for vacancies and for Sc in solidsolution on the same graph The two corrections are ofapproximately the same magnitude but with oppositesigns Thus the resulting (net) correction is close to zeroand it turns out that the first hand approximation asapplied in Ref 89 is very good in this case

Applying the calculated temperature dependent misfitwith the simple approximation for a critical diameter forloss of coherency one obtains a temperature-dependentcritical diameter as shown in Fig 19

Some examples from the literature of experimentallyobserved critical diameters in binary AlndashSc alloys aresummarised in Table 5 along with some predictions forcritical diameters from Fig 19 There is a fairly goodconsistency between the observations and the measureddiameter is quite close to the simple predictions above

A more refined analysis on the transition fromcoherent to incoherent particles has recently beenperformed145 This analysis is based on the balancebetween the increase in particlematrix interface energyowing to interfacial dislocations and the relaxation inelastic energy in the Al matrix owing to the samedislocations This method yields a predicted criticaldiameter of 246 nm for transition from coherent to

semi-coherent particles at ambient temperature Thetemperature dependence of the critical diameter is nottreated in this analysis

The loss of coherency during isothermal annealing hasbeen reported to be accompanied by an increasedaverage coarsening rate119121137145 The increasedcoarsening rate has been attributed either to diffusionof Sc along dislocation lines119121 or to the increasedparticlematrix interface energy of a semicoherentparticle145 However there are also several data sets inthe literature that do not indicate an increased growthrate after the loss of coherency114128

Al3ScAl interface energyThe interface energy between Al3Sc and the Al matrix isone of the key parameters that governs the nucleationgrowth and coarsening behaviour of Al3Sc in Al and Alalloys The interface energy has been estimated in severalinvestigations either by fitting experimental data toequations that describe nucleation or coarsening or bycalculations A compilation of some of the results isgiven in Table 6 There is considerable spread in thereported values regardless of what approach has beenused for the estimation

Influence of other elements on precipitation ofAl3ScMagnesium

With regard to precipitation mechanism it has beenstated that Mg suppresses the tendency to discontinuousprecipitation of Al3Sc106 In an investigation of pre-cipitation kinetics of Al3Sc in the temperature range300ndash500uC only minor changes in the kinetics (Fig 20)were found when up to 5 wt-Mg was added to an Alndash04 wt-Sc alloy135 It seems that the precipitationreaction is slightly faster in the Mg-containing alloys

Several investigations on age hardening response alsoimply that there is only a small if any effect of Mg onthe precipitation kinetics of Al3Sc23148149 It is how-ever found that the hardness increase from theprecipitation of Al3Sc is somewhat reduced in AlndashMgndashSc alloys compared to binary AlndashSc alloys23148149 InRef 149 it is suggested that some of the Sc is dissolvedin the Al3Mg2 phase and thus the age hardeningpotential is reduced with increasing Mg contentSomewhat contradictory to these observations but

Table 5 Some reported critical diameters for coherencyloss in binary AlndashSc and correspondingtheoretical critical diameters from Fig 19

Reference dcrit nmC0

Scwt-Sc

TtransuC

Theoreticaldcrit nm

119 38ndash40 05137 28ndash30 03 400 308128 32 02 400 450 308 335129 50 02143 40 012 025115 40 025 450ndash500 335ndash37114 40 03 400 450 308 335144 40 02 400ndash460 308ndash341145 30ndash80 02 400ndash490 308ndash362

20 C-curves for 10 and 60 transformation in Alndash

04 wt-Sc and Alndash4 wt-Mgndash04 wt-Sc redrawn

from Ref 135

19 Simple approximation for temperature-dependent criti-

cal diameter for introduction of dislocations on Al

Al3Sc interface

Roslashyset and Ryum Scandium in aluminium alloys

30 International Materials Reviews 2005 VOL 50 NO 1

sustained by Ref 135 it has recently been reported150

that precipitation of Al3Sc at 300 and 350uC occursslightly faster in an Alndash2 wt-Mgndash02 wt-Sc alloythan in an Alndash02 wt-Sc alloy studied previously by thesame researchers117118 and that the correspondinghardness increase is highest in the AlndashMgndashSc alloyThe only reported difference in experimental procedureis the solutionising temperature which was higher forthe AlndashSc alloy (648uC) than for the AlndashMgndashSc alloy(617uC) However given that the nucleation time isshortened by quenched-in vacancies as suggested byHyland107 the difference in homogenisation tempera-ture should be in favour of a faster precipitation of thebinary AlndashSc alloy It should be worthwhile to probedeeper into this observation of different aging responses

Mg in solid solution increases the lattice parameter ofthe Al matrix This is in turn expected to influence thecritical diameter for AlAl3Sc coherency loss as discussedin the section on lsquoLoss of coherency during growth ofAl3Sc precipitatesrsquo above Such an influence on the criticaldiameter is also briefly discussed elsewhere150 A criticaldiameter of 80 nm in an Alndash3 wt-Mgndash02 wt-Sc alloyhas been observed compared to 40 nm in a binary Alndash02 wt-Sc alloy of the same investigation144 Otherresearchers have reported a critical diameter in excess of116 nm in an Alndash63 wt-Mgndash02 wt-Sc alloy151

Computer simulations predict that the AlAl3Scinterface should be enriched in Mg87 These predictionsare confirmed experimentally by three-dimensional atomprobe microscopy of an Alndash2 wt-Mgndash02 wt-Sc alloyaged at 300uC38 Here it was found that the Mg contentat the interface is approximately three times higher thanthe matrix concentration regardless of aging time

Copper

It has been claimed that Cu suppresses the tendencytowards discontinuous precipitation of Al3Sc106

Zakharov and Rostova152 have reported that additionsof up to 14 wt-Cu have only minor effects on theprecipitation kinetics in an Alndash04 wt-Sc alloy Themost noticeable effect is that for temperatures above400uC the late stage of the transformation is sloweddown for the highest Cu contents This does not show in

Fig 21 however where only the 10 and 60transformation curves are included

The W-phase (AlCuSc) was observed in the alloywith the highest Cu content which means that less Sc isavailable for the precipitation of Al3Sc in this alloyAnother investigation on the age hardening response ofAlndash023 wt-Sc and Alndash25 wt-Cundash023 wt-Sc at300uC also implies that the precipitation behaviour ofAl3Sc in the two alloys is similar153154 At 350uC alimited portion of the Al3Sc has been observed tonucleate heterogeneously on coarse hrsquo precipitates155

According to the isothermal sections of the phasediagram43 one should expect the ternary W-phase toform instead of the Al3Sc phase in an alloy with such ahigh CuSc ratio However no observations of the W-phase or other ternary phases were reported from TEMstudies of the Alndash25 wt-Cundash023 wt-Sc alloy thathad been heat treated in the temperature range 300ndash460uC153ndash156 A third investigation on the precipitationin Alndash048 wt-Sc alloys with up to 440 wt-Cu in thetemperature range 100ndash450uC also concludes that no W-phase or other ternary phase forms during the heattreatment157

Copper in solid solution decreases the lattice para-meter of the Al matrix Thus it is expected that the misfitbetween Al and Al3Sc precipitates should be higher in

21 C-curves for 10 and 60 transformation in Alndash

04 wt-Sc and Alndash14 wt-Cundash04 wt-Sc redrawn

from Ref 152

Table 6 Reported values of interphase energy cAlAl3Sc between coherent Al3Sc precipitates and Al matrix

Reference cAlAl3Sc mJ m22 Method of estimation

137 10 Fit of coarsening data to LifshitzndashSlezev equation107 78iexcl20 (288uC) Back-calculation of incubation time

93iexcl20 (343uC)107 123iexcl41 (288uC) Back-calculation of nucleation rate

125iexcl35 (343uC)29 542 (400uC) Fit of coarsening data to Ostwald ripening

632 (430uC)413 (460uC)

146 c(100) 192 (0 K) c(111) 226 (0 K) Pseudopotential calculations147 c(100) 325 (0 K) c(110) 513 (0 K) c(111)

782 (0 K) c(100) 315 (288uC) c(100) 325 (343uC)Atomistic simulation

110 105 Fit of coarsening data to LSW theory31 20ndash300 Fit of coarsening data to Ostwald ripening

for 16 different temperatures111 57 Fit of precipitation model to experimental data145 120 coherent particles Fit of coarsening data

170 semicoherent particles

It is argued in this study that c may be lower in the nucleation stage

Roslashyset and Ryum Scandium in aluminium alloys

International Materials Reviews 2005 VOL 50 NO 1 31

AlndashCundashSc alloys compared to AlndashSc alloys Howeveran experimental investigation of Alndash25 wt-Cundash023 wt-Sc alloy comes to a different conclusion Thelattice misfit strain is found to decrease compared to Alndash02 wt-Sc and the critical diameter for coherency losswas found to be the same in the ternary and the binaryalloy144 It is suggested that these observations may bebecause of the dissolution of some Cu in the Al3Sc phaseand thus that the lattice parameters of both the Al matrixand the Al3Sc precipitates decrease in the ternary alloy

Silicon

It has been found that the onset of precipitation in Alndash04 wt-Sc is only slightly altered when Si contents ofup to 04 wt are introduced in the alloy However thefinal stage of the precipitation reaction is considerablydelayed with increasing Si content135 Figure 22 showsthe effect of addition of a joint of 035 wt-Si and040 wt-Fe There are at least two possible explana-tions for why an Si-addition leads to this behaviour

1 Alloying with Si is known to promote discontin-uous precipitation of Al3Sc106158 It has been shown thatwhen isothermal precipitation of Al3Sc starts discon-tinuously the later stage of the overall transformationcan be very slow31

2 The isothermal section of the phase diagramsuggests that the V-phase (AlSc2Si2) should form inalloys of this composition46 If the V-phase forms lessSc is available for precipitation of Al3Sc

It has been shown157 that for an AlndashScndashSi alloy withsolid solution content of 010 wt-Sc an 110 wt-Sithe only phases to precipitate after heat treatment at200uC are Si and an (AlScSi)-phase possibly the V-phase On the other hand the Al3Sc phase has beenobserved to form in alloys with 04 wt-Sc and up to08 wt-Si159160

Zinc

It has been reported that additions of up to 5 wt- Znhave only minor effects on the precipitation kinetics ofan Alndash04 wt-Sc alloy135 (Fig 23) In Ref 106 it isclaimed that Zn promotes discontinuous precipitation ofAl3Sc

Lithium

A comparison of the age hardening response at 400uC inAlndash24 wt-Lindash019 wt-Sc and Alndash024 wt-Sc alloys

indicates that the onset of Al3Sc-precipitation is notaffected by the presence of Li161

Zirconium

As mentioned in the section on lsquoTernary phase diagramswith dispersoid-forming elementsrsquo earlier a considerableamount of Zr is dissolved in the Al3Sc phase and thus amore correct denotation of the precipitating phase isAl3(Sc12xZrx) In discussing the influence of the Zrcontent on the precipitation of Al3Sc one is thereforeactually discussing the difference in precipitation ofAl3Sc versus Al3(Sc12xZrx)

It is found that an addition of 015 wt-Zr to an Alndash04 wt-Sc alloy only marginally affects the initial stageof the precipitation reaction123135 while it slows downthe later stages of the transformation considerably(Fig 24)135 The coarsening rate of the Al3(Sc12xZrx)particles in AlndashScndashZr alloys is found to be much slowerthan that of Al3Sc particles in AlndashSc alloys123162

In three-dimensional atom probe field ion microscopy(3D-APFIM) of Al3(Sc12xZrx) particles formed at 475uCin a ternary AlndashScndashZr alloy163 it was found that the coreof the particles is almost pure Al3Sc whereas there is ashell of Al3(Sc12xZrx) with almost equal content of Scand Zr Such a behaviour has also been predicted bycomputer modelling of precipitation of Al3(Sc12xZrx) at480uC in an AlndashZnndashMgndashScndashZr alloy164 This modelpredicts that Zr starts to enter the growing

22 C-curves for 10 and 60 transformation in Alndash

04 wt-Sc and Alndash04 wt-Fendash035 wt-Sindash04 wt-Sc

redrawn from Ref 135

23 C-curves for 10 and 60 transformation in Alndash

04 wt-Sc and Alndash5 wt-Znndash04 wt-Sc redrawn

from Ref 135

24 C-curves for 10 and 60 transformation in Alndash

04 wt-Sc and Alndash04 wt-Scndash015 wt-Zr redrawn

from Ref 135

Roslashyset and Ryum Scandium in aluminium alloys

32 International Materials Reviews 2005 VOL 50 NO 1

Al3(Sc12xZrx) particles when approximately half of thesupersaturated Sc has been precipitated The Zr contentof the outer shell is predicted to be much higher thanwhat has been found experimentally163164

Another 3D-APFIM study of Al3(Sc12xZrx) particlesin a ternary AlndashScndashZr alloy has been reported165 Hereparticles grown at 300uC for various lengths of time werestudied The Zr content in these particles was muchlower than that reportedpredicted at higher tempera-tures163164 even after very long annealing times

Iron

The effect of adding up to 07 wt-Fe on the precipita-tion kinetics in an Alndash04 wt-Sc alloy has beeninvestigated135 The onset of precipitation was onlyslightly influenced by the Fe-level whereas the laterstages of the transformation however were significantlyslowed down as the Fe-level increased An example ofthe effect of a joint addition of Fe and Si is shown inFig 22

Manganese chromium and titanium

Small additions (03 wt-) of manganese or chromiumto Alndash040 wt-Sc alloys are reported to have onlyminor effects on the precipitation kinetics of Al3Sc135

According to Ref 106 Mn is reported to promote andCr and Ti to suppress discontinuous precipitation

Rare earth elements

An investigation of the precipitation behaviour of Alndash03 at-Sc and Alndash03 at-Scndash03 at-X alloyswhere X is either yttrium gadolinium holmium orerbium in the temperature range 235ndash310uC indicatedthat a Al3(Sc12xXx) phase with L12 structure wasformed in the ternary alloys22 Peak strength is reportedto occur after approx 10 h at 285uC in all alloys whichindicates that the precipitation kinetics up to peakstrength is practically unaltered by the ternary additions

Influence of Sc on microstructure andproperties of wrought aluminium alloysMost of the effects of Sc addition in wrought Al-alloysare linked to the formation of the Al3Sc phase In atypical processing route of a wrought aluminium alloyparticles of the Al3Sc phase can form under threedifferent conditions each of which influences themicrostructure and properties of the alloy in a specificway

1 During solidification after casting or weldingAl3Sc particles can form in the melt and act as nucleifor a-Al thus leading to grain refinement18166

2 High temperature processing of the alloy in therange 400ndash600uC for instance homogenisation hot-rolling or extrusion can give a dense distribution ofAl3Sc particles of typically 20ndash100 nm size The particledistributions formed under such conditions are reportedto lead to good recrystallisation resistance128148167168

and enhanced superplasticity52169170

3 Heat treatment in the range 250ndash350uC can lead tosignificant precipitation hardening of an alloy super-saturated in Sc148158171 The size of strengthening Al3Scprecipitates is typically in the range 2ndash6 nm121

Grain refinementA good grain refinement is almost always desired uponsolidification The formation of small equiaxed grainsrather than long dendrites in the melt facilitates thefeeding of the melt into cavities of the shrinkingsolidified metal and thus reduces the problem ofshrinkage porosity The tendency to hot cracking is alsoreduced and the second phase particles become morefinely and uniformly distributed

To the authorsrsquo knowledge the first effect of Sc in Al-alloys that was reported in an international scientificjournal was the grain refining action in pure Al and in anAlndashCu alloy upon solidification172 which was found tobe stronger for Sc than for other transition metals Inlater studies of Sc as a grain refiner in pure Al1832173 ithas been demonstrated that approx 07 wt-Sc issufficient to provide excellent grain refinement It hasalso been demonstrated that additions of 025 wt-Scz025 wt-Zr provide good grain refinement in pure Al18

In order for Sc to act as an effective grain refiner theAl3Sc phase has to form in the melt before thesolidification of a-Al The Al3Sc particles have a latticeparameter close to that of pure Al and whenhypereutectically formed the Al3Sc particles are veryeffective substrates for the nucleation of the a-Al phaseAs mentioned in the section on lsquoFormation of Al3Sc inAlndashSc alloysrsquo above this requires that the alloy ishypereutectic with respect to Sc ie in excess of approx06 wt- in a binary AlndashSc alloy In ternary and higherorder systems the eutectic Sc composition may dependon the other alloying elements present For instance theeutectic composition of Sc has been predicted todecrease with increasing Mg content in the ternary AlndashMgndashSc system39 This prediction is sustained by theobservation of good grain refinement by adding 05 wt-Sc to an Alndash7 wt-Mg alloy174 (Other examples ofgrain refinement at Sc concentrations lower than that ofthe binary eutectic are found in Ref 173)

Similarly the observation of good grain refinement inan Alndash025 wt-Scndash025 wt-Zr alloy18 may be as aresult of a lower Sc content of the eutectic in the ternarysystem ie less Sc is needed to make the alloy hyper-eutectic No literature data on the liquidus surface of theAlndashScndashZr system are available and thus this hypothesiscannot be confirmed In more complex alloy systems itis also observed that excellent grain refinement isachieved at low Sc contents when Sc is added togetherwith Zr It is reported that adding either 02 wt-Sc06 wt-Sc or 01 wt-Zr to an Alndash5Mg alloy givesmuch poorer grain refinement than adding 02 wt-Scz01 wt-Zr175 Similarly additions of 015 wt- ofeither Sc or Zr are reported to only marginally refinethe grain structure in an AlndashCundashLi alloy whereas a jointaddition of 015 wt-Sc and 015 wt-Zr gives excellentgrain refinement176 For an AA 3650 casting alloy (Alndash7 wt-Sindash04 wt-Mg) good grain refinement is achievedby adding 039 wt-Sc or 027 wt-Scz019 wt-Zr177

In some AlndashZnndashMgndashScndashZr alloys it is also found thatan addition of 02ndash03 wt-Sc can be sufficient for goodgrain refinement166169178179 Examples of the grainrefinement as a function of Sc addition in pure Al andin an AlndashZnndashMgndashZr alloy are shown in Fig 25

The nucleation of a-Al on Al3Sc particles in the melt isfacilitated by the close match in the lattice parameters ofthe two phases As shown in Fig 17 the mismatch at the

Roslashyset and Ryum Scandium in aluminium alloys

International Materials Reviews 2005 VOL 50 NO 1 33

eutectic temperature of binary AlndashSc alloys (660uC) isonly approx 047 In Refs 57 and 89 it is shown thatwhen Zr Hf and in particular Ti is dissolved in the Al3Scparticles this reduces the lattice parameter of the phaseIt appears that when 25 of the Sc atoms in Al3Sc aresubstituted by Ti the mismatch is zero at approx 550uCand becomes negative at higher temperatures89 Thissuggests that by carefully selecting the Ti content of thealloy it should be possible to obtain Al3(ScTi)substrates in the melt that match exactly the latticeparameter of the nucleating a-Al and thus furtherimprove the grain refinement of the alloy This appearsto have been achieved in a recent work180 where thegrain refinement of an Alndash07 wt-Sc alloy wascompared with that of an Alndash05 wt-Scndash02 wt-Tialloy At a cooling rate of 100 K s21 only an estimated2 of the primary Al3Sc particles of the binary AlndashScalloy were effective nuclei compared to practically 100for the primary Al3(ScTi) particles in the ternary AlndashScndashTi alloy leading to a much smaller grain size in theternary alloy Whereas the match of lattice parametersmay be of importance for these results the authors ofthis investigation180 draw attention to other factors suchas different growth restriction factors for Sc and Ti andthe possibility of a peritectic reaction in the ternaryalloy Nevertheless the principle of matching latticeparameters is worth looking into further in future work

Effects from dispersoidslsquoDispersoidsrsquo is a term which is commonly used aboutthe classes of second phase particles that are formedin an Al alloy during high temperature annealing orthermomechanical processing such as homogenisationhot rolling extrusion and forging A dense distributionof dispersoids can give a significant contribution to analloyrsquos strength owing to particle strengthening but thisis rarely the main strengthening mechanism A moreimportant contribution from the dispersoids is theirability to stabilise the grainsubgrain structure of analloy through the Zener-drag action and thus improvethe mechanical properties of the alloy

There are two noticeable dispersoid-related effectsthat have been reported for Sc-containing alloys Thefirst is the stabilising effect on a deformed microstruc-ture When a non-recrystallised structure is preserved inan alloy this can add considerably to the mechanical

strength of the material The second effect is thepreservation of a small grain size during hot deforma-tion at slow deformation rates which is necessary toobtain superplastic properties of an Al-alloy

Recrystallisation resistance

The anti-recrystallisation effect of Sc was first publishedin a patent171 where 03 wt-Sc was added to pure Aland to AlndashMg AlndashMn and AlndashZnndashMg alloys Both Sc-free and Sc-containing materials were cold worked andsubsequently annealed and it was found that theaddition of Sc increased the temperature for onset ofrecrystallisation by approx 220uC in pure Al andsomewhat less in the Al-alloys Although the author ofthe patent171 may have been well aware that the anti-recrystallisation effect is caused by Al3Sc dispersoidsthis is not mentioned in the text The first journal paperthat explicitly points out that the recrystallisationresistance is due to Al3Sc dispersoids was an investiga-tion of the effects of adding Sc to wrought AlndashMgalloys181 In this work it was found that the Al3Scdispersoids were very effective in preventing recrystalli-sation up to temperatures of approx 400ndash450uC Athigher temperatures the dispersoids coarsen consider-ably and the microstructure was partially recrystallised

It is established that the Zener-drag pZ that is imposedon an advancing grain boundary by randomly distrib-uted dispersoids can be expressed in the form

pZ~k f =r (3)

where k is a factor that includes the interface energybetween the dispersoids and the matrix f is the volumefraction and r is the mean radius of the dispersoids Thusthe Zener drag will decrease rapidly in the case where thedispersoids are coarsening

As mentioned in the section on lsquoInfluence of otherelements on precipitation of Al3Scrsquo above theAl3(Sc12xZrx) dispersoids in a ternary AlndashScndashZr alloycoarsen at a much slower rate than the Al3Sc dispersoidsin a binary AlndashSc alloy This effect was first reported inRef 123 (although also observed in Ref 182) andaccording to Ref 33 the same authors demonstratedsoon after that the denser dispersoid distributionachieved in an AlndashScndashZr alloy leads to superiorrecrystallisation resistance compared to a binary AlndashScalloy An example of the increased recrystallisationresistance by adding both Zr and Sc is shown in Fig 26

In isothermal sections of the ternary AlndashScndashZr phasediagram it is indicated that the solid solubility ofSczZr is somewhat higher than that of Sc alone54 Ithas also been demonstrated both by electrical con-ductivity measurements (Fig 27) and microstructuralobservations that the supersaturation of SczZr isgreater than that of only Sc or Zr in as cast Alndash15(SczZr) alloys183 This indicates that it should bepossible to increase the volume fraction of dispersoids inAlndashScndashZr compared to AlndashSc It is suggested162 that theincreased volume fraction that can be achieved byadding both Sc and Zr can be advantageous inconventional wrought Al-alloys

There are at least two different conditions underwhich Al3Sc or Al3(Sc12xZrx) dispersoids can form toprevent recrystallisation

1 Sc (or Sc and Zr) is in solid solution before thedeformation In the case of cold deformation and

25 Grain refinement as a function of Sc addition in pure

Al (redrawn from Ref 32) and AlndashZnndashMgndashZr (redrawn

from Ref 169) note that data points are plotted on

different ordinate axes

Roslashyset and Ryum Scandium in aluminium alloys

34 International Materials Reviews 2005 VOL 50 NO 1

subsequent annealing the Al3Sc or Al3(Sc12xZrx)dispersoids may nucleate and grow before the nucleationand growth of recrystallised grains takes placeDispersoids can form after a direct up-quench to theannealing temperature115143148184 during ramp-up tothe annealing temperature115 or by pre-annealing at anintermediate temperature129 In the case of hot deforma-tion the Al3Sc or Al3(Sc12xZrx) dispersoids maynucleate and grow during preheating of the materialand during the hot deformation itself184

2 The Al3Sc or Al3(Sc12xZrx) dispersoids are formedin the material before deformation184 Considering coldrolling and subsequent annealing the annealing tem-perature Tann may be either lower or higher than thetemperature Tdisp at which the dispersoids were formedIf TannTdisp only limited if any coarsening of thedispersoids is expected to take place and thus the Zenerdrag from the particles is expected to be practicallyconstant The driving force for recrystallisation how-ever is expected to decrease somewhat with theannealing time as a result of recovery processes Thusif recrystallisation does not occur within short annealingtimes the material is expected to remain unrecrystallisedfor infinite time at the annealing temperature IfTannTdisp there will be substantial coarsening of thedispersoids during annealing In order for the materialto remain unrecrystallised the decrease in driving forcefor recrystallisation owing to recovery has to be at leastas rapid as the decrease in Zener drag because of particlecoarsening

Experimental comparisons of the conditions abovepoint in the direction that the recrystallisation resistanceis poorest when Sc (or Sc and Zr) is in solid solutionbefore deformation and the deformed material is up-quenched to the annealing temperature148 or when Al3Scor Al3(Sc12xZrx) dispersoids are formed before defor-mation at TdispampTann184185 Excellent recrystallisationresistance is achieved if dispersoids are formed at anintermediate anneal of solutionised and deformedmaterial128 or if dispersoids are formed at TdispTann

before deformation148185ndash187 It seems that the decreasein Zener drag because of dispersoid coarsening in many

cases is slower than the decrease in driving force forrecrystallisation because of recovery processes Thusthere is an advantage in forming a high number densityof small dispersoids which for most practical casesmeans that they should be formed at TdispTann122

When an advancing high angle grain boundary iethe recrystallisation front is passing a coherent Al3Scdispersoid there are at least three possible grainboundarydispersoid interactions

1 The Al3Sc dispersoid retains its global orientationrelationship and thus loses its coherency with thesurrounding matrix

2 The Al3Sc dispersoid rotates as the grain boundarypasses either by diffusional processes at the dispersoidmatrix interface or by the grain boundary passingthrough the dispersoid and the Al3Sc dispersoidassumes the same crystallographic orientation as theAl matrix of the recrystallised grain

3 The Al3Sc dispersoid dissolves at the grainboundary and re-precipitates in the recrystallised grain

Which interactions that actually take place willprobably depend on the dispersoid size annealingtemperature and driving force for recrystallisation It isalso possible that alloy composition (other elementsthan Al) is of importance

It has been reported that large (Oslash about 100ndash150 nm)Al3Sc dispersoids in a deformed Alndash4 wt-Mgndash02 wt-Sc alloy annealed at 575uC lose the orientationrelationship with the matrix after being passed by therecrystallisation front148

A rotation of somewhat smaller Al3Sc dispersoids in arecrystallising binary Alndash025 wt-Sc alloy has beenreported115143 The rotation was reported to be accom-panied by substantial growth (from Oslash 30 nm to Oslash48 nm) as a result of enhanced Sc diffusion at the grainboundary Observations suggested that the grainboundaries were passing through the dispersoids andthus the Al3Sc dispersoids retained the orientationrelationship with the recrystallised Al matrix

Dissolution and re-precipitation of Al3Sc dispersoidshas been reported during recrystallisation of a 50 coldrolled Alndash02 wt-Sc alloy162 Large spherical partially

26 Fraction recrystallised structure in cold rolled sheets

of Alndash04 wt-Sc and Alndash04 wt-Scndash015 wt-Zr as a

function of annealing temperature redrawn from

Ref 183 27 Electrical conductivity in Alndash15(SczZr) alloys

redrawn from Ref 183

Roslashyset and Ryum Scandium in aluminium alloys

International Materials Reviews 2005 VOL 50 NO 1 35

coherent dispersoids were observed to dissolve at therecrystallisation front and re-precipitate as smallercoherent Al3Sc cuboids

Superplastic forming

It seems that the first publication on superplasticproperties of Sc-containing Al-alloys was a study of anAlndash35Cundash14Mgndash045Mnndash04(SczZr) alloy188

It was recognised that the superplastic properties are aresult of the stabilisation of the fine grain structure byAl3Sc dispersoids The Sc-containing Al alloys that havereceived most attention for their superplastic propertieshowever are those of the AlndashMgndashSc system which wasfirst published in a patent189 Here it was noted that anAlndash4 wt-Mgndash05 wt-Sc alloy had superior superplasticproperties compared to fine-grained 7475 (AlndashZnndashMgndashCu alloy) Binary Alndash05 wt-Sc and Alndash4 wt-Mgalloys did not behave superplastically The flow stress atthe hot forming temperature was found to be much (30ndash40) lower in the ternary alloy than that of the twobinary alloys

The superplastic properties of AlndashMgndashSc alloys havebeen explored by several research groups over the lastdecade190ndash196 It has frequently been found that thedeformation mechanism is dominated by grain bound-ary sliding190 However it has also been reported thatAlndashMgndashSc alloy may deform superplastically withoutnoticeable grain boundary sliding23 It is generallyrecognised that the grain boundary sliding mechanismis facilitated when the average grain size is very smalland grain boundaries are predominantly high-angleSuch a microstructure may be achieved by carefulthermomechanical processing of the starting mate-rial193194197198 It has however been shown that a finegrained structure with high angle boundaries maydevelop during superplastic forming of AlndashMgndashSc alloyseven if the starting microstructure is an entirely differentone for instance that of a cold rolled sheet192 It has alsobeen suggested that superplastic forming of as castmaterial may be possible189

One of the more efficient thermomechanical processesfor achieving an ultrafine grain structure with high anglegrain boundaries in Al-alloys is equal channel angularpressing (ECAP) A JapanesendashAmerican group ofscientists has published an impressive body of researchon improvements in superplastic properties in Al-alloys processed by ECAP over the last few years andseveral of the publications are from investigations onAlndashMgndashSc alloys170199ndash224 Maximum strains in excessof 2000 at a strain rate of 0033 s21 have beenachieved170201202217 which is an extraordinarily goodcombination of high strain and high strain rate for analuminium alloy

Superplastic properties of AlndashCundashMg(ndashMn)ndashSc(ndashZr)and AlndashMgndashSc(ndashZr) alloys have been mentionedNoticeable superplasticity in other Sc-containing Al-alloys has also been reported such as AlndashZnndashMg(ndashCu)ndashScndashZr169225ndash228 AlndashLindashSc229 AlndashMgndashLindashScndashZr229ndash234

AlndashLindashMgndashCundashScndashZr235236 and AlndashCundashLindashScndashZr233

Precipitation hardeningHardening by Al3Sc precipitates

It has been noted that when Al3Sc particles precipitate inthe temperature range 250ndash350uC they give a significanthardness increase in the alloy Some authors point out

that Sc is a more effective precipitation hardening elementper atomic fraction added than the elements that arecommonly used for precipitation hardening121130 (In onepaper29 it is claimed that only Au has a strongerstrengthening effect than Sc) However the amount ofSc that can be precipitated from supersaturated solidsolution is rather limited and thus the absolute values ofthe hardness increase from the precipitation hardening ismuch lower than what is normally associated withprecipitation hardened alloys Also the temperatureregime for age hardening by precipitation of Al3Sc issomewhere in between the temperature regimes for agehardening and solution heat treatments of commonprecipitation hardened alloys This makes a combinedprecipitation of Al3Sc and other strengthening precipi-tates unfeasible Thus precipitation strengthening byAl3Sc is most feasible in alloy systems that are non-heat-treatable The non-heat-treatable aluminium alloy sys-tems are according to the Aluminum Associationdesignations the 1xxx series (99 pure Al) the 3xxxseries (AlndashMn) and the 5xxx series (AlndashMg) The purposeof adding Sc to these alloys may be either to stabilise themicrostructure of wrought semiproducts (extrusionsrolled plates forgings etc) as discussed in the sectionon lsquoRecrystallisation resistancersquo above or to provideextra strength to the alloy through precipitation hard-ening In the latter case it is appropriate to considerwhether the Sc-containing alloy still should be classifiedas non-heat-treatable A heat treatment is applied thatbrings about a significant precipitation hardening On theother hand the hardness increase that is achieved throughthe heat treatment is lower than what is normallyassociated with heat-treatable alloy systems Hence eventhough it seems like a contradiction one chooses to keepusing the term lsquonon-heat-treatablersquo about these alloys

Table 7 gives an overview of some mechanicalproperties of Sc-containing non-heat-treatable alloysthat are reported in the literature Most of theexperimental work on Sc in 1xxx-types of alloys hasbeen done on binary AlndashSc alloys with much higherpurity than industrial alloys

Strengthening mechanisms

When the precipitates are larger than a critical size thestrengthening effect is due to the Orowan-mechanism iedislocations can only pass the precipitates by looping Inthis case the strengthening effect of the particles isapproximately inversely proportional to the mean parti-cle spacing When the precipitates can be sheared bydislocations there are a number of strengthening mechan-isms that apply It is proposed by Parker et al108 that thetwo major contributing mechanisms are coherency strainand anti-phase-boundary energy In a recent detailedstudy of strengthening mechanisms in binary AlndashSc alloysby Marquis and colleagues117118 the strengthening fromshear modulus mismatch between the matrix and theprecipitates is also accounted for A qualitatively goodmatch between theoretical strengthening and measuredvalues is achieved in this work both for deformation atroom temperature and at 300uC

Effect of Sc on precipitation strengthening in heat-treatablealloys

Following the AA designation system the traditionalheat-treatable Al-alloys are those that belong to the 2xxx

Roslashyset and Ryum Scandium in aluminium alloys

36 International Materials Reviews 2005 VOL 50 NO 1

series (AlndashCu) 6xxx series (AlndashMgndashSi) and 7xxx series(AlndashZnndashMg) AlndashLi alloys should also be mentionedSeveral investigations have been carried out in order toclarify the effects of Sc on the precipitation behaviour inthese alloy systems

AlndashCu alloys

The precipitation sequence in AlndashCu alloys is oftendescribed as follows

Supersaturated solid solutionRGP-zonesRh0Rh9Rh(Al2Cu)

The highest strength is normally achieved when the h0or h9 precipitates are predominant Typical precipitationheat treatment temperatures for AlndashCu alloys are in therange 160ndash190uC238 which is considerably lower thanthe typical precipitation temperature for Al3ScComparisons of the aging responses of AlndashCu and AlndashCundashSc alloys at 150 and 200uC indicate that there is nonoticeable effect of Sc on the precipitation kinetics ofh9153 It is observed that the h9 precipitates may nucleateon Al3Sc particles153 At 300uC it is observed that h9particles are somewhat smaller in AlndashCundashSc alloys thanin AlndashCu alloys156

AlndashMgndashSi alloys

The following precipitation sequence is commonlyreported for AlndashMgndashSi alloys

Supersaturated solid solutionRGP-zonesRb0Rb9Rb(Mg2Si)

For peak aged alloys the predominant precipitatetype is b0 for which the stoichiometric composition hasrecently been resolved to be Mg5Si6239 Temperatures inthe range 160ndash205uC are typically used for precipitationhardening of these alloys238 Adding both 03 wt-Scand 01 wt-Zr to an Alndash06 wt-Mgndash065 wt-Sialloy does not seem to alter the precipitation kineticsof b0 at 165uC However the hardness increase becauseof precipitation hardening appears to be smaller in theSczZr-containing alloy240 In another investigationadditions of 01 wt-Sc 015 wt-Sc 02 wt-Sc04 wt-Sc and 02 wt-Scz01 wt-Zr were made toan Alndash08 wt-Mgndash07 wt-Si alloy241 Here it wasalso observed that the precipitation kinetics of b0 wasseemingly independent of the Sc additions (Fig 28)TEM observations indicated that the b0 precipitateswere of comparable sizes in the investigated alloys andno interactions between Al3Sc and b0 were observed(Fig 29) In a third study242 where the effect of Sc onthe precipitation in an AlMgSindashSiC metal matrixcomposite was investigated there also does not seemto be any effect on the precipitation kinetics Howevercontrary to the findings of Ref 240 it is reported thatthe Sc addition leads to a higher hardness increase thanin the corresponding Sc free alloy

AlndashMgndashZn alloys

For these alloys the following precipitation sequence isoften ascribed

Table 7 Mechanical properties in non-heat-treatable Al-alloys with Sc

Reference Alloy wt- YS MPa UTS MPa Note

1xxx alloys171 000Sc 15 48 Cast material aged 288uC8 h

023Sc 159 185 Cast material aged 288uC8 h038Sc 199 220 Cast material aged 288uC8 h000Sc 14 49 Cold rolled material (89) aged 288uC8 h023Sc 198 208 Cold rolled material (89) aged 288uC8 h038Sc 240 264 Cold rolled material (89) aged 288uC8 h000Sc 8 34 Cold rolled material quenched from 649uC aged 288uC8 h023Sc 147 157 Cold rolled material quenched from 649uC aged 288uC8 h038Sc 193 199 Cold rolled material quenched from 649uC aged 288uC8 h

121 05Sc 160 ndash Forged material quenched from 635uC aged 250uC50 h23 05Sc 298 319 Hot rolled 288uC cold rolled 69ndash81 aged 288uC4 h112 01Sc 132 166 Hot z cold rolled material quenched from 630uC

aged 320uC133 h148 02Sc 138 ndash Cast material aged 300uC10 h compression test159 04Sc 196 ndash Cast material aged 300uC10 h compression test117 118 03Sc 209 ndash Cast material quenched from 648uC aged 300uC5 h

compression test3xxx alloys171 1Mn 015Sc 216 221 Cold rolled material (89) aged 288uC8 h

1Mn 05Sc 309 323 Cold rolled material (89) aged 288uC8 h186 05Mn 02Mg

026Sc 015Zr162 201 Extruded material solutionised 600uC aged 250uC

5xxx alloys171 1Mg 43 111 Cold rolled material (89) aged 288uC8 h

1Mg 03Sc 288 303 Cold rolled material (89) aged 288uC8 h53Mg 147 259 Cold rolled material (50) wintermediate anneals

at 343uC aged 288uC8 h53Mg 03Sc 368 401 Cold rolled material (50) wintermediate anneals

at 343uC aged 288uC8 h23 2Mg 05Sc 376 401 Hot rolled 288uC cold rolled 69ndash81 aged 288uC4 h

4Mg 05Sc 414 4606Mg 05Sc 433 503

237 4Mg 1Sc 420 525 Cold rolled material (83) aged 320uC1 h148 4Mg 02Sc 194 ndash Cast material aged 300uC10 h compression test

Tensile test data except where noted YS yield strength UTS ultimate tensile strength

Roslashyset and Ryum Scandium in aluminium alloys

International Materials Reviews 2005 VOL 50 NO 1 37

Supersaturated solid solutionRGP-zonesRg9Rg(Zn2Mg)

The maximum hardness is normally achieved whenthe g9 precipitates are predominant Common precipita-tion hardening temperatures are in the range 95ndash180uCand a two-step precipitation heat treatment within thistemperature regime is often used238 It has beenobserved in some investigations that Sc and SczZradditions to AlndashMgndashZn alloys slow down the precipita-tion of g9 somewhat243 Other investigations find thatthere is no effect of Sc on the precipitation behaviour ofg9244245 and yet others report that Sc additionssignificantly speed up the precipitation of g9246 In Ref247 it is found that an Sc addition leads to coarser g9precipitates and it is claimed that this gives an improvedductility of the alloy The strength-loss associated withlarger particle size is reported to be counterbalanced bystrengthening from Al3Sc precipitates

AlndashLi alloys

The precipitation sequence in binary AlndashLi alloys isapparently simple

Supersaturated solid solutionRd9Rd (AlLi)

where d9 is the metastable Al3Li phase which just likeAl3Sc has the L12 type of atomic arrangement Thetypical temperature regime for precipitation of d9 whichis the strengthening phase in this system is approx 150ndash200uC A comparison of the age hardening response ofan Alndash26 wt-Li and an Alndash24 wt-Lindash019 wt-Scalloy at 180uC248 and 200uC161 indicates that the onsetof d9 precipitation is not altered by the presence of ScThe hardness curves for the two alloys are practicallyidentical at 200uC whereas at 180uC the peak hardnesslevel is slightly higher in the AlndashLi than the AlndashLindashScalloy DSC measurements at constant heating ratesindicate that the addition of Sc to an AlndashLi alloysincreases the activation energy for d9 precipitation andmoves the exothermic peak associated with d9 precipita-tion to a higher temperature248 For specimens aged at

either 180uC or 200uC TEM observations reveal that thed9 precipitates are much smaller in the Sc containingalloy than in binary AlndashLi both in the peak agedcondition and in the overaged condition161248 Additionof Sc has also been observed to reduce the size of d9precipitates in other AlndashLi based alloys249ndash251 In an AlndashLindashCundashZr alloy an addition of Sc has been reported toslow down the homogeneous precipitation of d9252253 Ithas been claimed that Sc reduces the quench sensitivityand delays room temperature aging of AlndashLi basedalloys254ndash256

When present in the microstructure before the pre-cipitation of d9 the Al3Sc precipitates may act as effec-tive nucleation sites for d9 The resulting precipitates arespheres of d9 with a core of Al3Sc161249252ndash255257ndash261

Corrosion resistanceAn appreciable amount of data is available on the effectsof Sc on the corrosion behaviour of wrought Al-alloysSome of these effects are apparently derived from theeffects of Sc on the microstructure of the alloys It hasbeen reported that an addition of Sc increases thecorrosion potential (makes it less negative) in pureAl262ndash264 in AlndashZn alloys265266 AlndashMg alloys267 AlndashZnndashMgndashCu alloys264268 AlndashCundashMgndashMn alloys264 andin AlndashCundashLindashMgndashAg alloys264 Even though Sc alsohas been reported to decrease the corrosion potential in

28 Age hardening response at 175uC for Alndash08 wt-Mgndash

07 wt-Si alloy (Base) with additions of 02 wt-Sc

04 wt-Sc and 02 wt-Scz01 wt-Zr from Ref 241

29 TEM images of a b0 precipitates in Alndash08 wt-Mgndash

07 wt-Si alloy and b b0 and Al3(Sc1ndashxZrx) in a similar

alloy with addition of 02 wt-Scz01 wt-Zr from

Ref 241

Roslashyset and Ryum Scandium in aluminium alloys

38 International Materials Reviews 2005 VOL 50 NO 1

AlndashMg alloys269270 it seems that the general trend isthat adding Sc to an alloy makes it slightly more nobleThe change in corrosion potential is much morepronounced when Sc is added in amounts larger thanthe eutectic composition263 ie there is a considerablecontribution from primary or eutectic Al3Sc to theoverall potential It has also been demonstrated that thechange in corrosion potential caused by Sc can dependon the heat treatment applied to the alloy267268

Even though the corrosion potential is an essentialparameter in establishing the corrosion behaviour of analloy an increase in the corrosion potential does notnecessarily imply an improved self-corrosion resistanceHowever measurements of corrosion rates and passiva-tion current densities strongly suggest that the self-corrosion resistance in general is considerably improvedwhen Sc is added to wrought Al-alloys263264267 Someobserved variations in corrosion potential and passiva-tion current densities with Sc content in binary AlndashScalloys are plotted in Fig 30

Material failure in corrosive environments is often dueto localised corrosion attacks which may propagaterapidly even though the bulk material has a goodresistance against general corrosion It has been pointedout that hypereutectic additions of Sc may lead tomicrogalvanic corrosion beside primary Al3Sc parti-cles264 In AlndashMg alloys grain boundary precipitation ofAl8Mg5 can lead to localised corrosion attacks such asintergranular corrosion (IGC) exfoliation corrosion(EC) and stress corrosion cracking (SCC) In wroughtmaterial such precipitation may occur in the 60ndash180uCtemperature regime and heating in this temperaturerange is referred to as lsquosensitationrsquo An AlndashMgndashSc alloywas found to be immune against intergranular corrosionand have moderate susceptibility to exfoliation corro-sion after annealing at 350uC271 After sensitation heattreatments severe IGC and EC was observed but notquite as severe as in a corresponding alloy without ScAs for SCC the AlndashMgndashSc alloy was found to be highlyresistant271 In another study it was found that additionof 056 wt-Sc reduces the SCC susceptibility of an Alndash68 wt-Mg alloy in the as-rolled state and afterannealing at 250uC whereas in a sensitised specimenthe SCC susceptibility is somewhat increased by the Scaddition272 A third investigation found that Sc has nomeasurable detrimental effect on the SCC susceptibilityof sensitised Alndash5Mgndash015Zr alloy273 SCC is also a

severe problem in high strength AlndashZnndashMgndashCu alloys Ithas been shown that small Sc additions are effective inreducing the SCC sensitivity of these alloys244246268274

Use of Sc-containing Al alloysA systematic development of Sc-containing aluminiumalloys took place in the former USSR in the 1980s andthe interest for Sc as an alloying element in aluminiumalloys hit the western world approximately 10 yearslater Even though a number of improvements in Alalloys achieved by Sc addition have been demonstratedthe current uses of such alloys are very limited This isrelated to the very high price of scandium

In Russia some parts of military aircraft are made ofSc-containing AlndashLi alloys In the western world themain usage of Sc-containing alloys is for sportsequipment Ashurst Technology and Kaiser Aluminumdeveloped a Sc-containing 7xxx alloy for baseball andsoftball bats which was introduced to the Americanmarket in 1997 by Easton Alcoa soon followed with aSc-containing alloy for a competing brand of batsLouisville Slugger Since then several new and improvedSc-containing alloys for bats have been introduced tothe market The purpose of adding Sc is to increase theyield strength of the alloy allowing for a down-gaugingof the wall thickness which in turn gives a strongerlsquospring-rsquo or lsquotrampoline-rsquo effect when the ball hits thebat

Shortly after the introduction of the Sc containingbats Easton also launched Sc-containing 7xxx tubingfor bicycle frames Just as in the bats Sc increases theyield strength of the alloy allowing for down-gauging oftube wall thickness and a corresponding weight reduc-tion of the bicycle frame An Italian manufacturer ofbicycle tubing Dedacciai also delivers tubes in a Sc-containing 7xxx alloy

Other sports equipment made from Sc-containingaluminium alloys includes lacrosse sticks and tent polesSmith and Wesson has also introduced a series ofhandguns where the frame is made from a Sc-containingAl alloy

A common factor for the items mentioned above isthat the material cost is only a minor part of the totalmanufacturing cost of the end product and also thatthese products are aimed at a group of customers thathave a certain awareness of new materials Both baseballbats and bicycle frames have been marketed aslsquoscandium alloyrsquo even though the Sc content is muchlower than 1

Currently AlndashSc master alloys for the production ofSc-containing Al alloys are available at a price thatcorresponds to US$ 2000 per kg of Sc This means that ifone wants to add 02 wt-Sc to an alloy which is afairly common content one also increases the price ofthe alloy by US$ 4 per kg alloy Depending on the alloytype Sc is added to this represents a tripling orquadrupling of the price of the alloy There are notmany existing products where such an increase inmaterial cost can be justified In order to see awidespread use of Sc in high-volume products the Scprice has to come down considerably Actually the priceof adding Sc to Al alloys has gone down by a factor 3ndash10over the last 10ndash15 years and substantial price reduc-tions are also expected in the future

30 Observed variations in corrosion potential and passi-

vation current densities with Sc content in binary Alndash

Sc alloys based on data from Ref 263

Roslashyset and Ryum Scandium in aluminium alloys

International Materials Reviews 2005 VOL 50 NO 1 39

The current production of AlndashSc master alloys isbased upon and will continue to be based upon for theforeseeable future the reduction of Sc2O3 or other Sccompounds directly in molten aluminium It is notnecessary as many tend to believe to take the route viametallic Sc Thus the price of AlndashSc master alloy isgoverned by the price of Sc2O3 or other Sc compoundsin question and not by the price of metallic scandiumThe Sc2O3 which is the main source for todayrsquos AlndashScmaster alloy production comes from stockpiles in theformer USSR These stockpiles will be exhausted withina few years and new reliable sources of Sc2O3 or otherSc compound production are sought It turns out thatthe most economically viable option that has beendisclosed so far is the processing of Red Mud from theBayer process of extracting alumina from bauxiteScandium is enriched in the Red Mud and is extractedfrom a Red Mud aqueous slurry by selective leachingsubsequent ion-exchange procedure and finally a liquidndashliquid extraction procedure It is not required to build aseparate lsquoSc factoryrsquo to do this but rather build an lsquoadd-onrsquo to existing Bayer process plants Such a processroute is expected to bring down the price of Sc2O3

considerably which in turn means that AlndashSc masteralloy price should drop accordingly Preliminary ana-lyses suggest a price of approx US$ 400 per kg Sc in themaster alloy which translates to an added cost of 80cent per kilo when 02 wt-Sc is added to an aluminiumalloy This is also a considerable increase in the materialcost but with such prices one should expect to see Sccontaining alloys in many more applications than whatis the case at the present time

Concluding remarksThe body of published investigations on Al-based alloyswith Sc addition provides a sound basis of knowledgefor metallurgists that want to look into the possibility ofenhancing the performance of a wrought Al-alloy byadding Sc to it Ternary AlndashScndashX phase diagrams areavailable for practically every technologically importantalloying element in Al The effect of a wide range ofternary alloying elements on the precipitation behaviourof Al3Sc is accounted for It has been shown that theAl3Sc phase can be effective as a grain refiner adispersoid former and a precipitate hardening agentand some of the underlying conditions for achieving thedesired Al3Sc formation have been outlined Addingsome Zr together with Sc has proven to be beneficial Itmay lead to effective grain refinement at a lower Sc levelbut the most prominent effect is the refinement indispersoid distribution that can be achieved An addi-tion of Sc has little if any effect on precipitation in the2xxx 6xxx and 7xxx alloy systems and some effects onthe precipitation in AlndashLi based alloys With respect tocorrosion behaviour adding Sc to an Al-alloy does ingeneral seem to make the alloy slightly more noble andto increase its self-corrosion resistance Scandium-containing Al alloys have very few uses at the presenttime as a result of the high price of scandium The priceof Sc is expected to decrease significantly in the futureand this should lead to the disclosure of moreapplications where it is economically feasible to takeadvantage of the improved properties of some Sc-containing aluminium alloys

References1 D R Lide lsquoCRC handbook of chemistry and physicsrsquo 71st edn

4ndash29 1990 Boston USA CRC Press

2 E M Savitsky V F Terehova I V Burov and O P Naumkin

Proc Fourth Conf on lsquoRare earth researchrsquo Phoenix Arizona

USA April 1964 409ndash420

3 E M Savitskii V F Terekhova I V Burov O P Naumkin and

I A Markova Inorg Mater 1965 1 1503ndash1512

4 O P Naumkin V T Terekhova and E M Savitskiy Russ

Metall 1965 (4) 128ndash136

5 W G Moffatt lsquoThe handbook of binary phase diagramsrsquo 1981

Schenectady NY USA General Electric Co

6 E A Brandes (ed) lsquoSmithells metals reference bookrsquo 6th edn

1983 London UK Butterworths

7 R P Elliott and F A Shunk Bull Alloy Phase Diagrams 1981

2 (2) 222ndash223

8 K A Gschneider Jr and F W Calderwood Bull Alloy Phase

Diagrams 1989 10 34ndash36

9 H Okamoto J Phase Equil 1991 12 612ndash613

10 J L Murray J Phase Equil 1998 19 380ndash384

11 M E Drits E S Kadaner T V Dobatkina and N I Turkina

Russ Metall 1973 (4) 152ndash154

12 S-I Fujikawa M Sugaya H Takei and K-I Hirano J Less-

Common Met 1979 63 87ndash97

13 N Blake and M A Hopkins J Mater Sci 1985 20 2861ndash2867

14 V I Kononenko and S V Golubev Russ Metall 1990 (2) 193ndash

195

15 T B Massalski J L Murray L H Bennett and H Baker (eds)

lsquoBinary alloy phase diagramsrsquo 1986 Metals Park OH USA

ASM

16 G Cacciamani P Riani G Borzone N Parodi A Saccone

R Ferro A Pisch and R Schmid-Fetzer Intermetallics 1999 7

101ndash108

17 H Okamoto J Phase Equil 2000 21 310

18 A F Norman P B Pragnell and R S McEwen Acta Mater

1998 46 5715ndash5732

19 I N Pyagai and A V Vakhobov Russ Metall 1990 (5) 50ndash52

20 C L Fu J Mater Res 1990 5 971ndash979

21 X Lu and Y Wang Calphad 2002 26 555ndash561

22 R R Sawtell and J W Morris Jr Proc lsquoDispersion strengthened

aluminium alloysrsquo Phoenix Arizona USA January 1988 409ndash

420

23 R R Sawtell and C L Jensen Metall Trans A 1990 21A 421ndash

430

24 L A Willey Unpublished research Alcoa 1970 Data points are

extracted from Ref 10

25 N I Turkina and V I Kuzmina Russ Metall 1976 (4) 179ndash

183

26 T Torma E Kovacs-Csetenyi I Vitanyi M Butova and

J Stepanov Proc 6th Int Symp on lsquoHigh purity materials in

science and technologyrsquo Akademie der Wissenschaften der DDR

Dresden Germany May 1985 388ndash389

27 A L Berezina V A Volkov B P Domashnikov and K V

Chuistov Metallofizika 1987 9 (5) 43ndash47

28 H-H Jo J Korean Inst Metals 1990 28 499ndash504

29 H-H Jo and S-I Fujikawa Mater Sci Eng 1993 A 171 151ndash

161

30 S Celotto and T J Bastow Philos Mag A 2000 80 1111ndash1125

31 J Roslashyset and N Ryum submitted to Mater Sci Eng

32 M E Drits L S Toropova Yu G Bykov F L Gushchina V I

Elagin and Yu A Filatov Russ Metall 1983 (1) 150ndash153

33 L S Toropova D G Eskin M L Kharakterova and T V

Dobatkina lsquoAdvanced aluminum alloys containing scandium

structure and propertiesrsquo 1998 Amsterdam The Netherlands

Gordon and Breach Science Publishers

34 V V Cherkasov P P Pobezhimov L P Nefedova E V Belov

and G M Kuznetsov Met Sci Heat Treat 1996 (6) 268ndash270

35 Kh O Odinaev I N Ganiev V V Kinzhibalo and B Ya

Kotur Dokl Akad Nauk Tadzh SSR 1989 32 37ndash38

36 Kh O Odinaev I N Ganiev and A V Vakhobov Russ Metall

1991 (4) 200ndash203

37 J Grobner R Schmid-Fetzer A Pisch G Cacciamani P Riani

N Parodi G Borzone A Saccone and R Ferro Z Metallkd

1999 90 872ndash880

38 E A Marquis and D N Seidman Microsc Microanal 2002 8

(Suppl 2) 1100CDndash1101CD

39 A Pisch J Grobner and R Schmid-Fetzer Mater Sci Eng A

2000 A 289 123ndash129

Roslashyset and Ryum Scandium in aluminium alloys

40 International Materials Reviews 2005 VOL 50 NO 1

40 C Xia F Zeng and Y Gu Trans Nonferrous Met Soc China

2003 13 1124ndash1127

41 M Yu Teslyuk and V S Protasov Sov Phys Crystallogr 1966

10 470ndash471

42 M L Kharakterova and T V Dobatkina Russ Metall 1988

(6) 175ndash178

43 M L Kharakterova Russ Metall 1991 (4) 195ndash199

44 L S Toropova M L Kharakterova and D G Eskin Russ

Metall 1992 (3) 194ndash199

45 P Riani L Arrighi R Marazza D Mazzone G Zanicchi and

R Ferro J Phase Equil Diff 2004 25 22ndash52

46 A T Tyvanchuk T I Yanson B Ya Kotur O S Zarechnyuk

and M L Kharakterova Russ Metall 1988 (4) 190ndash192

47 L L Rokhlin T V Dobatkina and M L Kharakterova Powder

Metall Met Ceram 1997 36

48 A Z Ikromov I N Ganiev and V V Kinzhibalo Dokl Akad

Nauk Tadzh SSR 1990 (6) 391ndash392

49 I N Ganiev A Z Ikromov and V G Khudoiberdiev Russ

Metall 1995 (3) 125ndash127

50 I N Fridlyander L L Rokhlin T V Dobatkina and N I

Nikitina Met Sci Heat Treat 1993 (10) 567ndash571

51 I N Fridlyander L L Rokhlin T V Dobatkina V V

Kinzhibalo and A T Tyvanchuk Russ Metall 1998 (1) 161ndash

166

52 R A Emigh E L Bradley and J W Morris Jr in lsquoLight-weight

alloys for aerospace applications IIrsquo (ed E W Lee and N J

Kim) 27ndash43 1991 TMS

53 L S Toropova A N Kamardinkin V V Kindzhibalo and A T

Tyvanchuk Phys Met Metall 1990 70 (6) 106ndash110

54 A N Kamardinkin T V Dobatkina and T D Rostova Russ

Metall 1991 (4) 216ndash218

55 L S Torodskaya T V Dobatkina and A N Kamardinkin

Russ Metall 1992 (5) 128ndash131

56 E M Sokolovskaya E F Kazakova E I Poddyakova and A

A Ezhov Met Sci Heat Treat 1997 (5) 211ndash213

57 Y Harada and D C Dunand Mater Sci Eng 2002 A 329ndash331

686ndash695

58 N E Drits L S Toropova and F L Gushchina Russ Metall

1984 (4) 229ndash232

59 E M Sokolovskaya E F Kazakova V A Alikhanov and E V

Zhuravleva Moscow Univ Chem Bull 1997 52 (5) 70ndash72

60 E M Sokolovskaya E F Kazakova and E I Poddyakova Met

Sci Heat Treat 1989 (11) 837ndash839

61 G M Cheldieva E F Kazakova E M Sokolovskaya and N I

Kaloev Russ Metall 1990 (6) 87ndash90

62 E M Sokolovskaya E F Kazakova and O D-S Kendivan

Russ Metall 1998 (4) 135ndash137

63 N G Bukhanko E F Kazakova and E M Sokolovskaya Russ

Metall 2001 (4) 425ndash431

64 E D Trubnyakova O I Bodak I N Ganiev and A V

Vakhobov Russ Metall 1987 (3) 219ndash222

65 I N Fridlyander and L V Molchanova Russ Metall 2003 (5)

476ndash480

66 R A Altynbaev S Kh Khairidinov and A V Vakhobov Russ

Metall 1987 (4) 194ndash196

67 J C Schuster and J Bauer J Less-Common Met 1985 109

345ndash350

68 L L Rokhlin A S Fridman T V Dobatkina and D G Eskin

Russ Metall 1991 (6) 146ndash148

69 A S Fridman T V Dobatkina and E V Muratova Russ

Metall 1992 (1) 207ndash209

70 C Xia F Zeng and Y Gu Trans Nonferrous Met Soc China

2003 13 546ndash552

71 F Zeng C Xia and Y Gu J Alloys Comp 2004 363 175ndash181

72 L L Rokhlin T V Dobatkina N R Bochvar and E V Lysova

J Alloys Comp 2004 367 10ndash16

73 T V Dobatkina A S Fridman and E V Muratova Russ

Metall 1992 (5) 125ndash127

74 I N Fridlyander L L Rokhlin N R Bochvar E V Lysova

and O V Boteva Russ Metall 2001 (6) 661ndash666

75 V N Rechkin L K Lamikhov and T I Samsonova Sov Phys

Crystallogr 1964 9 325ndash327

76 I I Zalutskii and P I Kripyakevich Sov Phys Crystallogr

1967 12 341ndash343

77 T J Bastow C T Forwood M A Gibson and M E Smith

Phys Rev B 1998 58 2988ndash2997

78 K Fukunaga M Kolbe K Yamada and Y Miura Mater Sci

Eng 1997 A 234ndash236 594ndash597

79 E P George J A Horton W D Porter and J H Schneibel

J Mater Res 1990 5 1639ndash1648

80 E P George D P Pope C L Fu and J H Schneibel ISIJ Int

1991 31 1063ndash1075

81 Y Harada and D C Dunand Acta Mater 2000 48 3477ndash3487

82 J H Schneibel and E P George Scripta Metall Mater 1990 24

1069ndash1074

83 J H Schneibel and P M Hazzledine Mater Res Soc Symp

Proc 1991 213 323ndash328

84 J H Schneibel and P M Hazzledine J Mater Res 1992 7

868ndash875

85 C J Sparks E D Specht G E Ice P Zschack and J Schneibel

Mater Res Soc Symp Proc 1991 213 363ndash368

86 J Tarnacki and Y-W Kim Scripta Metall Mater 1989 23

1063ndash1068

87 M Asta V Ozolins and C Woodward JOM 2001 53 (9) 16ndash

19

88 M E Drits L S Toropova F L Gushchina and S G Fedotov

Sov Non-Ferrous Met Res 1984 12 83ndash85

89 Y Harada and D C Dunand Scripta Mater 2003 48 219ndash222

90 C Woodward M Asta G Kresse and J Hafner Phys Rev B

2001 63 094103-1-6

91 J-H Xu and A J Freeman Phys Rev B 1990 41 12553ndash12561

92 M F Bartholomeusz and J A Wert Acta Metall Mater 1992

40 673ndash682

93 G Bester and M Fahnle J Phys Condens Matter 2001 13

11551ndash11565

94 C L Fu and M H Yoo Proc lsquoOrdered intermetallics ndash physical

metallurgy and mechanical behaviorrsquo Irsee Germany June 1991

155ndash164

95 K Fukunaga T Shouji and Y Miura Mater Sci Eng 1997 A

239ndash240 202ndash205

96 D P Pope Proc lsquoOrdered intermetallics ndash physical metallurgy

and mechanical behaviorrsquo Irsee Germany June 1991 143ndash153

97 J-S Wang Acta Mater 1998 46 2663ndash2674

98 M H Yoo and C L Fu Mater Sci Eng 1992 A 153 470ndash478

99 R W Hyland Jr and R C Stiffler Scripta Metall Mater 1991

25 473ndash477

100 I G Brodova I V Polents O A Korzhavina P S Popelrsquo I P

Korshunov and V O Esin Melts 1992 4 392ndash397

101 I G Brodova O A Chikova I V Polents P S Popelrsquo and V O

Esin Casting Processes 1992 1 (2) 158ndash160

102 I G Brodova D V Bashlikov and I V Polents Mater Sci

Forum 1998 269ndash272 589ndash594

103 K B Hyde A F Norman and P B Pragnell Mater Sci Forum

2000 331ndash337 1013ndash1018

104 K B Hyde A F Norman and P B Pragnell Acta Mater 2001

49 1327ndash1337

105 J Roslashyset and N Ryum Proc 6th Int Conf on lsquoAluminum

alloysrsquo Toyohashi Japan July 1998 793ndash798

106 V I Elagin V V Zakharov and T D Rostova Met Sci Heat

Treat 1993 (6) 317ndash319

107 R W Hyland Jr Metall Trans A 1992 23A 1947ndash1955

108 B A Parker Z F Zhou and P Nolle J Mater Sci 1995 30

452ndash458

109 C L Rohrer M D Asta S M Foiles and R W Hyland Jr

Mater Res Soc Symp Proc 1996 398 477ndash482

110 G M Novotny and A J Ardell Mater Sci Eng 2001 A 318

144ndash154

111 J D Robson M J Jones and P B Pragnell Acta Mater 2003

51 1453ndash1468

112 C Tan Z Zheng and B Wang Proc 3rd Int Conf on

lsquoAluminium alloysrsquo Vol I NTH Trondheim Norway June

1992 290ndash294

113 M Nakayama A Furuta and Y Miura Mater Trans JIM

1997 38 852ndash857

114 E A Marquis and D N Seidman Acta Mater 2001 49 1909ndash

1919

115 M J Jones and F J Humphreys Acta Mater 2003 51 2149ndash

2159

116 E A Marquis D N Seidman and D C Dunand in lsquoCreep

deformation fundamentals and applicationsrsquo (ed R S Mishra

J C Earthman and S V Raj) 299ndash308 2002 TMS

117 D N Seidman E A Marquis and D C Dunand Acta Mater

2002 50 4021ndash4035

118 E A Marquis D N Seidman and D C Dunand Acta Mater

2003 51 285ndash287

119 M E Drits L S Toropova U G Bikov and G K Anastaseva

Proc lsquoDiffusion in metals and alloysrsquo Tihany Hungary Augustndash

September 1982 616ndash623

120 V I Elagin V V Zakharov and T D Rostova Met Sci Heat

Treat 1983 (7) 546ndash549

Roslashyset and Ryum Scandium in aluminium alloys

International Materials Reviews 2005 VOL 50 NO 1 41

121 M Ye Drits L B Ber Yu G Bykov L S Toropova and G K

Anastaseva Phys Met Metall 1984 57 (6) 118ndash126

122 M E Drits L S Toropova and Yu G Bykov Sov Non-Ferrous

Met Res 1985 13 309ndash314

123 V I Yelagin V V Zakharov S G Pavlenko and T D Rostova

Phys Met Metall 1985 60 (1) 88ndash92

124 N Sano Y Hasegawa K Hono H Jo K Hirano H W

Pickering and T Sakurai Journal de Physique 1987 48 C6 337ndash

342

125 N Sano H-H Jo K-I Hirano and T Sakurai J Jpn Inst

Metals 1989 39 444ndash450

126 N Sano H Jo K Hirano and T Sakurai Proc Second Int

Conf on lsquoAluminium alloysrsquo Beijing China October 1990 549ndash

554

127 Y Miura M Nakayama and A Furuta Proc lsquoAspects of high

temperature deformation and fracture in crystalline materialsrsquo

Nagoya Japan July 1993 255ndash262

128 Y W Riddle and T H Sanders Jr Mater Sci Forum 2000

331ndash337 939ndash944

129 Y W Riddle M McIntosh and T H Sanders Jr in lsquoLightweight

alloys for aerospace application VIrsquo (ed K Jata E W Lee

W Frazier and N J Kim) 25ndash39 2001 TMS

130 M E Drits J Dutkiewicz L S Toropova and J Salawa Crystal

Res Technol 1984 19 1325ndash1330

131 Y W Riddle MSc thesis Georgia Tech GA USA 1998

132 T J Bastow and S Celotto Mater Sci Eng 2003 C 23 757ndash

762

133 M C Carroll M J Mills G S Daehn P I Gouma M F

Savage and B R Dunbar in lsquoAutomotive Alloys 1999rsquo (ed

S Das) 239ndash246 2000 TMS

134 E Clouet M Nastar and C Sigli Phys Rev B 2004 69 064109-

1-14

135 V V Zakharov Met Sci Heat Treat 1997 (2) 61ndash66

136 J W Christian lsquoThe theory of transformation in metals and

alloysrsquo 2nd edn 1975 Pergamon Press Ltd

137 A L Berezina V A Volkov B P Domashnikov S V Ivanov

and K V Chuistov Phys Metals 1990 10 296ndash304

138 S-I Fujikawa and S Sakauchi Proc 6th Int Conf on

lsquoAluminum alloysrsquo Toyohashi Japan July 1998 805ndash810

139 Y S Touloukian R K Kirby R E Taylor and P D Desai

(eds) lsquoThermal expansion metallic elements and alloysrsquo 1975

New York Plenum

140 J Roslashyset and N Ryum submitted to Scripta Mater

141 R O Simmons and R W Balluffi Phys Rev 1960 117 52ndash61

142 M Ocko E Babic R Krsmik E Girt and B Leontic J Phys F

Metals Phys 1976 6 703ndash707

143 M J Jones and F J Humphreys Proc First Joint Int Conf on

lsquoRecrystallization and grain growthrsquo Aachen Germany August

2001 Springer Verlag 1287ndash1292

144 S Iwamura M Nakayama and Y Miura Mater Sci Forum

2002 396ndash402 1151ndash1156

145 S Iwamura and Y Miura Acta Mater 2004 52 591ndash600

146 M Asta S M Foiles and A A Quong Phys Rev B 1998 57

11265ndash11275

147 R W Hyland Jr M Asta S M Foiles and C L Rohrer Acta

Mater 1998 46 3667ndash3678

148 J Roslashyset and N Ryum Proc 4th Int Conf on lsquoAluminium

alloysrsquo Vol I Atlanta GA USA September 1994 194ndash201

149 M E Drits L S Toropova G K Anastaseva and G L

Nagornichnykh Russ Metall 1984 (3) 192ndash195

150 E A Marquis D N Seidman and D C Dunand Acta Mater

2003 51 4751ndash4760

151 M E Drits L S Toropova and Yu G Bykov Met Sci Heat

Treat 1983 (7) 550ndash554

152 V V Zakharov and T D Rostova Met Sci Heat Treat 1995

(2) 65ndash69

153 M Nakayama and Y Miura Proc 4th Int Conf on lsquoAluminium

alloysrsquo Vol I Atlanta GA USA September 1994 538ndash545

154 M Nakayama and Y Miura J Jpn Inst Light Metals 1996 46

275ndash279

155 M Nakayama T Okuyama and Y Miura Mater Sci Forum

2000 331ndash337 927ndash932

156 M Nakayama T Okuyama and Y Miura Proc 6th Int Conf

on lsquoAluminum alloysrsquo Toyohashi Japan July 1998 517ndash522

157 M L Kharakterova D G Eskin and L S Toropova Acta

Metall Mater 1994 42 2285ndash2290

158 V I Elagin V V Zakharov and T D Rostova Met Sci Heat

Treat 1992 (1) 37ndash45

159 H Wiik Siv Ing thesis NTH Institute of Metallurgy

Trondheim Norway 1995

160 J Roslashyset H Hovland and N Ryum Mater Sci Forum 2002

396ndash402 619ndash624

161 Y Miura K Horikawa K Yamada and M Nakayama Proc

4th Int Conf on lsquoAluminium alloysrsquo Vol II Atlanta GA USA

September 1994 161ndash168

162 Y W Riddle PhD thesis Georgia Tech GA USA 2000

163 B Forbord W Lefebvre F Danoix H Hallem and

K Marthinsen Scripta Mater 2004 51 333ndash337

164 J D Robson Acta Mater 2004 52 1409ndash1421

165 C B Fuller J L Murray and D N Seidman submitted to Acta

Mater 2004

166 M G Mousavi C E Cross and Oslash Grong Sci Technol Weld

Joining 1999 4 381ndash388

167 J S Vetrano S M Bruemmer L M Pawlowski and I M

Robertson Mater Sci Eng 1997 A 238 101ndash107

168 Y W Riddle and T H Sanders Jr Mater Sci Forum 2000

331ndash337 799ndash803

169 G M Khan A O Nikiforov V V Zakharov and I I Novikov

Tsvetnye Metally 1993 34 (11) 43ndash45

170 Z Horita M Furukawa M Nemoto A J Barnes and T G

Langdon Acta Mater 2000 48 3633ndash3640

171 L A Willey US Patent 3 619 181 9 November 1971

172 L K Lamikhov and G V Samsonov Tsvetnye Metally 1964 5

(8) 77ndash80

173 A L Berezina K V Chuistov N I Kolobnev L B

Khokhlatova and T A Monastyrskaya Mater Sci Forum

2002 396ndash402 741ndash746

174 F A Fasoyinu J Thomson D Cousineau T Castles and M

Sahoo Proc 6th Int AFS Conf on lsquoMolten aluminum

processingrsquo Orlando FL USA November 2001

175 Z Yin Q Pan Y Zhang and F Jiang Mater Sci Eng 2000

A 280 151ndash155

176 I I Novikov and O E Grushko Mater Sci Technol 1995 11

926ndash932

177 D Cousineau M Sahoo P D Newcombe T Castles and F A

Fasoyinu Proc lsquoAFS 105th casting congressrsquo Dallas TX USA

AprilndashMay 2001 157ndash184

178 C E Cross and Oslash Grong Proc 6th Int Conf on lsquoAluminum

alloysrsquo Toyohashi Japan July 1998 1441ndash1446

179 F A Costello J D Robson and P B Prangnell Mater Sci

Forum 2002 396ndash402 757ndash762

180 K B Hyde A F Norman and P B Prangnell Mater Sci

Forum 2002 396ndash402 39ndash44

181 M E Drits S G Pavlenko L S Toropova Yu G Bukov and

L B Ber Sov Phys Dokl 1981 26 (3) 344ndash346

182 A M Drits and B A Kopeliovich Russ Metall 1985 (4) 147ndash

151

183 V G Davydov V I Elagin V V Zakharov and T D Rostova

Met Sci Heat Treat 1996 (8) 347ndash352

184 M E Drits L S Toropova Yu G Bykov L B Ber and S G

Pavlenko Russ Metall 1982 (1) 148ndash152

185 T D Rostova V G Davydov V I Yelagin and V V Zakharov

Mater Sci Forum 2000 331ndash337 793ndash798

186 Y W Riddle H Hallem and N Ryum Mater Sci Forum 2002

396ndash402 563ndash568

187 J Roslashyset and Y W Riddle Proc 9th Int Conf on lsquoAluminium

alloysrsquo Brisbane Australia August 2004 1210ndash1215

188 A M Diskin V K Portnoi A M Drits and A A Alalykin Sov

Non-Ferrous Met Res 1986 14 499ndash500

189 R R Sawtell P E Bretz and C L Jensen US Patent 4 689 090

25 August 1987

190 G A Salishchev Yu B Timoshenko and R A Saitova Proc

Second Int Conf on lsquoAluminium alloysrsquo Beijing China October

1990 413ndash415

191 T G Nieh R Kaibyshev L M Hsiung N Nguyen and

J Wadsworth Scripta Mater 1997 36 1011ndash1016

192 T G Nieh L M Hsiung J Wadsworth and R Kaibyshev Acta

Mater 1998 46 2789ndash2800

193 J S Vetrano C H Henager Jr M T Smith and S M

Bruemmer in lsquoHot deformation of aluminum alloys IIrsquo (ed T R

Bieler L A Lalli and S R MacEwen) 407ndash418 1998 TMS

194 J S Vetrano C H Henager Jr S M Bruemmer Y Ge and

C H Hamilton in lsquoSuperplasticity and Superplastic Forming

1998rsquo (ed A K Gosh and T R Bieler) 89ndash97 1998 TMS

195 V Y Gertsman J S Vetrano C H Henager Jr and S M

Bruemmer Proc First Joint Int Conf on lsquoRecrystallization and

grain growthrsquo Aachen Germany August 2001 Springer Verlag

2001 837ndash842

196 Y Xiao C Gao H Ma and S Tian Trans Nonferrous Met Soc

China 2001 11 235ndash238

Roslashyset and Ryum Scandium in aluminium alloys

42 International Materials Reviews 2005 VOL 50 NO 1

197 A Gholinia F J Humphreys and P B Prangnell Acta Mater

2002 50 4461ndash4476

198 A Gholinia F J Humphreys and P B Prangnell Mater Sci

Forum 2002 408ndash412 1519ndash1524

199 S Komura P B Berbon M Furukawa Z Horita M Nemoto

and T G Langdon Scripta Mater 1998 38 1851ndash1856

200 S Komura P B Berbon A Utsunomiya M Furukawa

Z Horita M Nemoto and T G Langdon in lsquoHot deformation

of aluminum alloys IIrsquo (ed T R Bieler L A Lalli and S R

MacEwen) 125ndash138 1998 TMS

201 S Komura Z Horita M Furukawa M Nemoto and T G

Langdon J Mater Res 2000 15 2571ndash2576

202 S Komura M Furukawa Z Horita M Nemoto and T G

Langdon Mater Sci Eng 2001 A 297 111ndash118

203 S Komura Z Horita M Furukawa M Nemoto and T G

Langdon Metall Mater Trans A 2001 32A 707ndash716

204 Z Horita M Furukawa K Oh-ishi M Nemoto and T G

Langdon Proc Fourth Int Conf on lsquoRecrystallization and

related phenomenarsquo (ed T Sakai and H G Suzuki) 1999 The

Japan Institute of Metals 301ndash308

205 Z Horita S Komura P B Berbon A Utsunomiya

M Furukawa M Nemoto and T G Langdon Mater Sci

Forum 1999 304ndash306 91ndash96

206 Z Horita S Lee S Ota K Neishi and T G Langdon Mater

Sci Forum 2001 357ndash359 471ndash476

207 Z Horita T Fujinami K Sato S B Kang H W Kim and T G

Langdon in Proc James T Staley Honorary Symposium on

Aluminum Alloys lsquoAdvances in the metallurgy of aluminum

alloysrsquo (ed M Tiryakioglu) 271ndash275 2001 ASM

208 P B Berbon S Komura A Utsunomiya Z Horita

M Furukawa M Nemoto and T G Langdon Mater Trans

JIM 1999 40 772ndash778

209 M Nemoto Z Horita M Furukawa and T G Langdon Mater

Sci Forum 1999 304ndash306 59ndash66

210 M Furukawa Z Horita M Nemeto and T G Langdon Proc

lsquoLight Metals 1999rsquo Quebec City PQ Canada August 1999 583ndash

592

211 M Furukawa K Oh-ishi S Komura A Yamashita Z Horita

M Nemeto and T G Langdon Mater Sci Forum 1999 304ndash

306 97ndash102

212 M Furukawa A Utsunomiya K Matsubara Z Horita and

T G Langdon Acta Mater 2001 49 3829ndash3838

213 M Furukawa A Utsunomiya S Komura Z Horita M Nemoto

and T G Langdon Mater Sci Forum 2001 357ndash359 431ndash436

214 M Furukawa Z Horita and T G Langdon in Proc James T

Staley Honorary Symposium on Aluminum Alloys lsquoAdvances in

the metallurgy of aluminum alloysrsquo (ed M Tiryakioglu) 47ndash56

2001 ASM

215 M Furukawa Z Horita M Nemoto and T G Langdon Mater

Sci Eng 2002 A 324 82ndash89

216 M Furukawa Z Horita and T G Langdon in lsquoUltrafine grained

materials IIrsquo (ed Y T Zhu T G Langdon R S Mishra S L

Semiatin M J Saran and T C Lowe) 459ndash468 2002 TMS

217 T G Langdon M Furukawa Z Horita and M Nemoto Proc

NATO Advanced Research Workshop on lsquoInvestigations and

applications of severe plastic deformationrsquo Moscow August

1999 NATO Science Series Series 3 High Technology vol 80

Kluwer Academic Publishers The Netherlands 2000 149ndash154

218 S Lee H Akamatsu A Utsunomiya K Neishi M Furukawa

Z Horita and T G Langdon Proc Thermec 2000 Las Vegas

USA December 2000

219 S Lee A Utsunomiya H Akamatsu K Neishi M Furukawa

Z Horita and T G Langdon Acta Mater 2002 50 553ndash564

220 A Yamashita D Yamaguchi Z Horita and T G Langdon

Mater Sci Eng 2000 A 287 100ndash106

221 K Oh-ishi Z Horita D J Smith and T G Langdon J Mater

Res 2001 16 583ndash589

222 H Akamatsu T Fujinami Z Horita and T G Langdon Scripta

Mater 2001 44 759ndash764

223 S Ota H Akamatsu K Neishi M Furukawa Z Horita and

T G Langdon Mater Trans 2002 43 2364ndash2369

224 K Furuno H Akamatsu K Oh-ishi M Furukawa Z Horita

and T G Langdon Acta Mater 2004 52 2497ndash2507

225 I N Fridlyander O G Senatorova N A Ryazanova and A O

Nikiforov Mater Sci Forum 1994 170ndash172 345ndash349

226 J N Fridlyander and O G Senatorova Mater Sci Forum 1996

217ndash222 1813ndash1818

227 J Liu and D J Chakrabarti Acta Mater 1996 44 4647ndash4661

228 O G Senatorova A N Uksusnikov J N Fridlyander

J Koshorst R R Romanova N A Ryazanova A Galliot

and V V Cherkassov Proc 6th Int Conf on lsquoAluminum alloysrsquo

July 1998 Toyohashi Japan 589ndash593

229 R A Emigh E L Bradley and J W Morris Jr in

lsquoSuperplasticity in aerospace IIrsquo (ed T R McNelley and H C

Heikkenen) 303ndash315 1990 TMS

230 E L Bradley III R A Emigh and J W Morris Jr Scripta

Metall Mater 1991 25 717ndash721

231 N I Kolobnev L B Khokhlatova V D Makarov E Yu

Semenova and V V Redchits Proc Sixth Int Aluminiumndash

Lithium Conference Garmisch-Partenkirchen Germany October

1991 1053ndash1056

232 N K Tsenev R Z Valiev O V Obraztsov and I N Fridlander

Proc Sixth Int AluminiumndashLithium Conference Garmisch-

Partenkirchen Germany October 1991 1125ndash1132

233 A M Shammazov N K Tsenev R Z Valiev M M

Myshlyaev M M Bikbulatov and S P Lebedich Phys Met

Metall 2000 89 (3) 314ndash318

234 F Musin R Kaibyshev Y Motohashi T Sakuma and G Itoh

Mater Trans A 2002 43A 2370ndash2377

235 M Shagiev Y Motohashi F Musin R Kaibyshev and G Itoh

Mater Trans A 2003 44A 1694ndash1697

236 M Shagiev Y Motohashi F Musin R Kaibyshev and G Itoh

Mater Trans A 2003 44A 1698ndash1701

237 B A Parker and Z F Zhou Proc 3rd Int Conf on lsquoAluminium

alloysrsquo Vol I NTH Trondheim Norway June 1992 363ndash367

238 J R Davies lsquoASM specialty handbook aluminum and aluminum

alloysrsquo 1993 Materials Park OH USA ASM

239 S J Andersen H W Zandbergen J Jansen C Traeholt

U Tundal and O Reiso Acta Mater 1998 46 3283ndash3298

240 M L Kharakterova D G Eskin and L L Rokhlin Russ

Metall 1997 (1) 104ndash109

241 J Roslashyset Dr Ing thesis NTNU Trondheim Norway 2002

242 P P Chattopadhyay S Datta and M K Banerjee Mater Sci

Eng 2002 A 333 67ndash71

243 L I Kaigorodova E I Selnikhina E A Tkachenko and O G

Senatorova Phys Met Metall 1996 81 513ndash519

244 Y-L Wu F H Froes C Li and A Alvarez Metall Mater

Trans A 1999 30A 1017ndash1024

245 Z Yin L Yang Q Pan and F Jiang Trans Nonferrous Met

Soc China 2001 11 822ndash825

246 V I Elagin V V Zakharov and T D Rostova Met Sci Heat

Treat 1994 36 (7) 375ndash380

247 Y V Milman A I Sirko D V Lotsko O N Senkov and D B

Miracle Mater Sci Forum 2002 396ndash402 1217ndash1222

248 C-H Joh K Yamada and Y Miura Mater Trans JIM 1999

40 439ndash442

249 X J Jiang Q H Gui Y Y Li L M Ma G J Liang and C X

Shi Scr Metall Mater 1993 29 211ndash216

250 X J Jiang Y Y Li W Deng L Y Xiong W M Wu Y J Gao

and C X Shi Adv Cryogenic Eng (Mater) 1994 40 1369ndash

1376

251 C-H Joh T Katsube K Yamada and Y Miura Proc 6th Int

Conf on lsquoAluminum alloysrsquo Toyohashi Japan July 1998 799ndash

804

252 L I Kaygorodova A M Dritz T V Krymova and I N

Fridlyander Proc Sixth Int AluminiumndashLithium Conference

Garmisch-Partenkirchen Germany October 1991 363ndash367

253 L I Kaigorodova A M Drits Ya V Zhingel T V Krymova

and I N Fridlyander Phys Met Metall 1992 73 286ndash290

254 A L Berezina V A Volkov S V Ivanov N I Kolobnev and

K V Chuistov Phys Met Metall 1991 71 (2) 167ndash175

255 I N Fridlyander N I Kolobnev A L Berezina and K V

Chuistov Proc Sixth Int AluminiumndashLithium Conference

Garmisch-Partenkirchen Germany October 1991 107ndash112

256 L I Kaigorodova A M Drits Ya V Zhingel T V Krymova

and V A Rassokhin Phys Met Metall 1992 73 281ndash285

257 I N Fridlyander S F Danilov E N Malysheva T A

Gorokhova and N N Kirkina Proc Sixth Int Aluminiumndash

Lithium Conference Garmisch-Partenkirchen Germany October

1991 381ndash386

258 G Dlubek S Krause H Krause A L Beresina V S

Mikhalenkov and K V Chuistov J Phys Condens Matter

1992 4 6317ndash6328

259 S Krause H Krause G Dlubek A L Beresina and K S

Chuistov Mater Sci Forum 1992 105ndash110 1109ndash1112

260 C Y Tan Z Q Zheng and S Q Liang Proc 4th Int Conf on

lsquoAluminium alloysrsquo Vol II Atlanta GA USA September 1994

329ndash333

261 A L Beresina N I Kolobnev K V Chuistov A V Kotko and

O A Molebny Mater Sci Forum 2002 396ndash402 977ndash981

Roslashyset and Ryum Scandium in aluminium alloys

International Materials Reviews 2005 VOL 50 NO 1 43

262 I N Ganiev I Yunusov and V V Krasnoyarskii J Appl Chem

USSR 1986 60 1961ndash1965

263 I N Ganiev Prot Met 1995 31 543ndash546

264 N V Vyazovikina Prot Met 1999 35 448ndash453

265 G V Kharina and V P Kochergin Prot Met 1996 32 134ndash

136

266 G V Kharina M V Kuznetsov and V P Kochergin Russ J

Electrochem 1998 34 482ndash485

267 V S Sinyavskii V D Valrsquokov and E V Titkova Prot Met

1998 34 549ndash555

268 Y L Wu F H Froes C G Li and J Liu Proc lsquoSynthesis

processing of lightweight metallic materials IIrsquo Orlando FL

USA February 1997 73ndash81

269 Z Ahmad and B J Abdul-Aleem Proc EuroCorr 2000

270 Z Ahmad A Ul-Hamid and B J Abdul-Aleem Corros Sci

2001 43 1227ndash1243

271 R Braun B Lenczowski and G Tempus Mater Sci Forum

2000 331ndash337 1647ndash1652

272 T Torma E Kovacs-Csetenyi L Vitalis I Vitanyi

J Stepanov and M Butova Mater Sci Forum 1987 1314

497ndash503

273 Z Wang P Wang K S Kumar and C L Briant in lsquoChemistry

and electrochemistry of corrosion and stress corrosion crackingrsquo

(ed R H Jones) 573ndash582 2001 TMS

274 V I Elagin V V Zakharov A A Petrova and E V

Vyshegorodtseva Russ Metall 1983 (4) 143ndash146

Roslashyset and Ryum Scandium in aluminium alloys

44 International Materials Reviews 2005 VOL 50 NO 1

Page 4: Scandium in aluminium alloys - Atom probe · A considerable part of the available literature on scandium in aluminium alloys is reviewed. ... behaviour in Al Cu, Al Mg Si,

several calculated vertical and isothermal cross-sectionsare also presented Additional phase diagram calcula-tions are reported in a separate paper39

The phase relations in a diffusion couple between Alndash177 wt-Sc and pure Mg at 430uC have also beenstudied40 No ternary phases were reported and the a-Alwas found to be in equilibrium with Al3Sc and Al3Mg2in accordance with earlier work253537 The maximumsolid solubility of Mg and Sc in a-Al at this temperaturewas reported to be 1527 at- (14 wt-) and 033 at-(055 wt-) respectively Both these solubilities and inparticular that of Sc is higher than what has been foundearlier25 Considering the binary AlndashSc system wherethe solubility of Sc in a-Al is only approx 0025 wt- at430uC the high solubility of Sc reported in Ref 40 forthe ternary system is rather unlikely It is possible thatfine-scale Al3Sc precipitates embedded in the a-Almatrix have been included in the electron probeanalyses and thus giving too high a value for the Sccontent in solid solution

AlndashCundashSc

Two ternary phases AlCuSc and AlCu2Sc werereported in an early investigation41 A later investigationof the Al-corner of the phase diagram42 revealed that aternary (AlCuSc) phase named the lsquoW-phasersquo couldbe in thermodynamic equilibrium with a-Al Thefollowing ternary invariant equilibria were found

LiqzAl3Sc~aAlzW(5720C)

Liq~aAlzAl2CuzW(5460C)

Isothermal sections of the Al-corner at 450 and 500uChave been constructed43 (Fig 6) The solid solubility ofCu in Al was found to decrease somewhat withincreasing Sc content whereas the solid solubility ofSc in Al was not found to be influenced by the Cucontent The W-phase was suggested to be the com-pound Al54ndash8Cu66ndash4Sc43 A liquidus surface of the Al-corner has also been constructed44

A more thorough review on the AlndashCundashSc system isavailable in the literature45

AlndashScndashSi

An isothermal section at 497uC has been constructed forthe entire system46 A ternary phase AlSc2Si2 wasidentified This phase frequently referred to as the lsquoV-phasersquo was found to be in thermodynamic equilibrium withAl3Sc Al Si and ScSi at this temperature A projection ofthe liquidus surface of the Al-corner has also been made47

Two ternary invariant reactions were reported

LiqzAl3Sc~aAlzV(6170C)

Liq~aAlzSizV(5740C)

Vertical cross-sections and isothermal sections of the Al-corner are reviewed in Ref 33 The 550uC isothermalsection is redrawn in Fig 7 It seems that the solidsolubility of Sc is not altered by an addition of Siwhereas the solubility of Si decreases somewhat with theSc content

AlndashScndashZn

A sketch of a lsquosemi-isothermalrsquo cross-section of the wholesystem partially at 300uC and partially at 500uC hasbeen reported48 No ternary phases were found in thisinvestigation The phase relations in the Al rich rangewere found to be limited by the subsystem AlndashZnndashAl3Sc

Another investigation of the subsystem AlndashZnndashAl2Scconfirmed that no ternary compounds are found in thiscomposition range49 The liquidus surface was con-structed It is suggested that the section ZnndashAl2Sc is aquasibinary simple eutectic A certain mutual solidsolubility of Zn and Al2Sc is indicated on the verticalcross-section although no measurements of the compo-sitions are presented In addition to the quasibinaryeutectic one ternary peritectic and one ternary eutecticreaction was found The ternary eutectic reaction

Liq~aAlzZnzAl3Sc

was found to occur at 367uC

AlndashLindashSc

An investigation of the phase relations in the Al-corner(up to 5 wt-Li and 3 wt-Sc) at 450uC revealed that

6 Isothermal section of Al-corner of AlndashCundashSc phase dia-

gram at 500uC redrawn from Ref 437 Isothermal section of Al-corner of AlndashScndashSi phase dia-

gram at 500uC redrawn from Ref 33

Roslashyset and Ryum Scandium in aluminium alloys

22 International Materials Reviews 2005 VOL 50 NO 1

a-Al could be in equilibrium with either Al3Sc or AlLi50

No ternary phases were observed Thermal analysesindicated that the ternary eutectic reaction

Liq~aAlzAl3SczAlLi

occurs at approximately 595uC It has been stated47 thatthere are only minor mutual effects of Sc and Li on theseelementsrsquo solid solubility in a-Al

This statement is confirmed in another investigation51

where the AlndashAlLindashAlSc subsystem is investigated At450uC it is found that the AlLi phase can be inequilibrium with Al3Sc Al2Sc and AlSc No significantsolubility of Li in Al3Sc was observed Several verticalcross-sections are constructed

It should be noted that the existence of a ternaryAl3(LiSc) phase has been reported52 which is indisagreement with the observations above

Ternary phase diagrams withdispersoid-forming elementsAlndashScndashZr

It has been shown53 that at 600uC the Al-corner consistsof the phase fields a-AlzAl3Sc a-AlzAl3SczAl3Zrand a-AlzAl3Zr Further it was discovered that there isa significant solid solubility of Zr in the Al3Sc phase(approx 35 wt-) and some solid solubility of Sc in theAl3Zr phase (approx 5 wt-) The lattice parameter ofAl3Sc was found to decrease when the phase dissolvesZr and likewise the lattice parameter of the Al3Zr wasfound to decrease when that phase dissolves Sc Foralloys in the a-AlzAl3Sc phase field the wt-Zrwt-Scratio in the Al3Sc particles was found to be approx 22times the wt-Zrwt-Sc ratio of the alloy53 Isothermalsections of the Al-corner at 550 and 600uC are alsoconstructed54 (Fig 8)

In another investigation55 two vertical cross-sectionsin the Al-corner were constructed and a ternaryperitectic reaction

LiqzAl3Zr~aAlzAl3Sc

was found to take place at 659uC

The 500uC isothermal section of the whole phasediagram has been investigated56 It is already knownthat Sc and Zr are completely miscible in the solid stateHere it was also found that the compounds AlSc2 andAlZr2 are completely miscible The extensions of theother single-phase fields are determined with variousdegrees of accuracy The solubility of Zr in Al3Sc wasfound to be 6 at- (approx 16 wt-) whereas thesolubility of Sc in Al3Zr was found to be 65 at-(approx 73 wt-) Contrary to Ref 53 the latticeparameter of Al3Sc was found to increase with increas-ing Zr content The lattice parameter of Al3Zr howeverwas found to decrease with increasing Sc content whichis in accordance with the findings of Ref 53

The section Al3ScndashAl3Zr at 1200uC has recently beeninvestigated57 The solubility of Sc in Al3Zr was reportedto be in the range 3ndash5 at- and the solubility of Zr inAl3Sc was found to be 122 at- In accordance withRef 53 the lattice parameters of Al3Sc and Al3Zr decreasewith increasing content of Zr and Sc respectively

AlndashFendashSc

The available data on this system is reviewed in Ref 33and an isothermal section at 500uC is reproduced Threeternary AlndashFendashSc phases are reported The Al-corner ofthe isothermal section however seems to be limited bythe subsystem AlndashAl3ScndashAl3Fe meaning that the a-Alcannot be in equilibrium with any of the ternary phases

AlndashMnndashSc

The Al-corner of the phase diagram has been investi-gated58 No ternary phases were observed meaning thatin the solid state only the Al3Sc and the Al6Mn phasecan be in equilibrium with a-Al An addition of Mn doesnot noticeably decrease the solid solubility of Scwhereas an addition of Sc causes a distinct decrease inthe solubility of Mn Two isothermal sections weremade one at 500uC (Fig 9) and one at 600uC Thelsquocornerrsquo of the a-phase field was reported to be at008 wt-Sc and 02 wt-Mn at 500uC and at 02 wt-Scand 055 wt-Mn at 600uC

8 Isothermal section of Al-corner of AlndashScndashZr phase dia-

gram at 600uC redrawn from Ref 54

9 Isothermal section of Al-corner of AlndashMnndashSc phase

diagram at 500uC redrawn from Ref 58

Roslashyset and Ryum Scandium in aluminium alloys

International Materials Reviews 2005 VOL 50 NO 1 23

Two vertical cross-sections were also constructed Aternary eutectic

Liq~aAlzAl6MnzAl3Sc

at 649uC was identified Several alloys in the sectionAl3ScndashAl6Mn have also been investigated59 and all werefound to comprise a mixture of the two binary phasesLattice parameter measurements of the Al3Sc phasewere interpreted as an indication of a slight solidsolubility of Mn in Al3Sc

AlndashCrndashSc

Alloys in the composition range 30ndash100 at-Al havebeen studied60 and an isothermal cross-section at 500uCwas constructed No ternary phases were identified Thephases that can be in equilibrium with the a-Al are thusAl7Cr and Al3Sc The solubility of Cr in the Al3Sc phasewas found to be considerable approximately 11 at-

Other ternary AlndashScndashX phase diagramsAlndashMondashSc

An isothermal cross-section at 550uC has been con-structed for the subsystem AlndashAl2ScndashAl2Mo61 Noternary phases were reported The phases in equilibriumwith a-Al were found to be Al3Sc and Al12Mo

AlndashScndashV

The section Al3ScndashAl21V2 has been studied62 and thevertical cross-section was constructed No ternaryphases were observed Solid solubilities of V in theAl3Sc phase of 14 at- and of Sc in Al21V2 of 25 at-are reported although a considerably higher maximumsolubility of V in Al3Sc is suggested in the vertical cross-section A quasibinary eutectic reaction

Liq~Al3SczAl21V2

is reported to occur at 917 K (644uC)The section Al3ScndashAl3V at 1200uC has also been

studied57 The solubilities of V in Al3Sc and Sc in Al3Vare reported to be 27 and 07 at- respectively WhenV was dissolved in Al3Sc the lattice parameter of Al3Scwas found to decrease

AlndashScndashTi

No ternary phase diagram is available The sectionAl3ScndashAl3Ti at 1200uC has been studied57 A solubilityof Ti in Al3Sc of almost 125 at- was found whichcorresponds to almost half of the Sc being substituted byTi The lattice parameter of Al3Sc was found to decreasesharply with increasing Ti content For the Al3Ti phasethe solubility of Sc was found to be approx 5 at-

AlndashCondashSc

The ternary system for 0ndash70 at-Sc has been investi-gated63 Three ternary (AlCoSc)-phases were identifiedThe only phases found to be in equilibrium with a-Alwere the binary phases Al3Sc and Al9Co2 An isothermalsection at 600uC and the vertical cross-sections Al3ScndashAl9Co2 and Al3ScndashAl9Co3Sc2 were constructed Thelsquocornerrsquo of the a-phase field was reported in the text to beat 15 at-Co and 05 at-Sc although in a tablethe numbers 02 at-Co and 01 at-Sc are reportedThe solubilities of Co in the Al3Sc phase and of Sc in theAl9Co2 phase were found to be 12 and 01 at-

respectively However in the vertical cross-sections it issuggested that the solubility of Co in Al3Sc may besignificantly higher at higher temperatures The latticeparameter of Al3Sc was not found to change withincreasing Co content

AlndashScndashSr

The subsystem AlndashAl2ScndashAl4Sr has been studied64 andan isothermal section at 500uC was constructed Noternary phases were detected meaning that the phases inequilibrium with a-Al were found to be Al3Sc and Al4SrThe solubility of Sc in Al4Sr and of Sr in Al3Sc wasfound to be low typically less than 15ndash2 at-

AlndashBendashSc

A study of the binary BendashSc system and the ternary AlndashBendashSc system for up to 20 at-Sc (or 30 wt-Sc) hasbeen reported65 The 600uC isothermal section for theinvestigated ternary composition range was constructedNo ternary phases were observed The a-Al can be inequilibrium with either Be Be13Sc or Al3Sc It is sug-gested that the section AlndashBe13Sc may be quasi-eutectic

AlndashBandashSc

An isothermal section at 500uC has been constructed66

No ternary phases were reported and a-Al is inequilibrium with Al4Ba and Al3Sc The solubility of Scin Al4Ba and of Ba in Al3Sc was reported to be less than2 at-

AlndashNndashSc

The region AlndashAlNndashScNndashSc has been investigated67 Aperovskite-type ternary phase AlN12xSc3 was reportedand an isothermal section at 1000uC was constructed Inthe Al-corner the Al melt was reported to be inequilibrium with AlN and Al3Sc

Quaternary and higher order AlndashScndashXndashX2(ndashX3hellip)phase diagramsAlndashMgndashScndashZr

The published material is limited to investigations onAl rich alloys A part of the liquidus surface of the6 wt-Mg section has been determined experimentallyfor the composition range 0ndash07 wt-Sc and 0ndash04 wt-Zr68 The 500uC isothermal phase relations inthe Al-corner of the 6 wt-Mg section has also beeninvestigated69 for Sc and Zr concentrations of up to3 wt- and 4 wt- respectively No ternary or qua-ternary phases were observed Likewise the 430uC iso-thermal phase relations of the 4 at-Mg (y35 wt-Mg)section have been investigated for up to 12 at-Sc(2 wt-Sc) and up to 25 at-Zr (8 wt-Zr)7071 Noternary or quaternary phases were observed in thepresent study either The Al3Sc phase was found todissolve an amount of 122 at-Zr corresponding to asubstitution of almost 50 of the Sc lattice positionswhereas the solubility of Sc in Al3Zr was 44 at-which corresponds to a substitution of almost 20 ofthe Zr lattice positions Figure 4 in Refs 70 and 71suggests that the Al content in the Al3Zr-phase increaseswith increasing Sc content however this is not sub-stantiated in the text

Roslashyset and Ryum Scandium in aluminium alloys

24 International Materials Reviews 2005 VOL 50 NO 1

AlndashMgndashScndashTindashZr

A vertical cross-section of the AlndashMgndashScndashTindashZr phasediagram for 03 wt-Sc 015 wt-Ti 015 wt-Zrand 0ndash10 wt-Mg has been constructed34 Accord-ing to this diagram the Al3Zr phase is the first andAl3Sc the last to form during solidification of thealloys No ternary quaternary or quinary phases arereported

AlndashZnndashMgndashCundashZrndashSc

A vertical cross-section of the full system as well asseveral sections of various sub-systems have beenconstructed72 For the full system a section at8 wt- Zn 2 wt-Cu 03 wt-Zr and 03 wt-Scwas constructed where Mg varies from 0 to 8 wt-The only reported Sc-containing sub-system is thatof AlndashZnndashMgndashCundashSc Here a vertical cross-sectionis constructed with the same levels of Zn Cu and Scas in the full system whereas Mg varies from 0 to65 wt-

No phases other than those known from the lowerorder systems were reported Amongst the findings it isinteresting to note that in the solid state Al3Sc isreported to be an equilibrium phase for all theinvestigated compositions It is also interesting to notethat the Sc-containing W-phase (Al54ndash8Cu66ndash4Sc see thesection on the AlndashCundashSc ternary system) is an equili-brium phase at low Mg content and disappears as theMg content increases

AlndashLindashMgndashSc

The 400uC isothermal phase relations of the 02 wt-Scsection have been investigated for the composition range0ndash6 wt-Mg and 0ndash5 wt-Li73 The a-Al was found tobe in equilibrium with AlLi Al2LiMg and Al3Sc Noquaternary phases were observed This investigation isalso summarised in Ref 50

AlndashCundashLindashSc

The aluminium rich corner of the system has beeninvestigated for alloys with 06 wt-Sc and with Cu andLi in the range 0ndash16 wt- and 0ndash4 wt- respectively74

No quaternary phases were reported Two sections ofthe phase diagram were constructed a section of the470uC isothermal tetrahedron at 06 wt-Sc and avertical section at 06 wt-Sc and 26 wt-Li Twoquaternary invariant equilibria were found and thetemperatures of the invariant points were estimated

Al3Sc phaseRechkin and co-workers were to the authorsrsquo knowl-edge the first to publish a paper in an internationaljournal identifying the Al3Sc phase75 The phase wasidentified as cubic with lattice parameter a5410 A Afew years later the lattice structure was reported to be ofthe Cu3Au type76 The atomic arrangement of the Al3Scphase is shown in Fig 10 The structure can bedescribed as ordered face-centred cubic (fcc) althoughin crystallographic terminology the Al3Sc structure isactually a simple cubic lattice with four atoms (one Scand three Al atoms) associated with each lattice pointThis particular atomic arrangement is nominated L12

and is found in several intermetallic compounds forinstance Ni3Al Ni3Fe and Cu3Au

Some efforts have been made in characterising theproperties of the Al3Sc phase A compilation of someresults is given in Table 3 The motivation for themajority of the investigations seems to be one of thethree following

(i) the Al3Sc phase has a density of 303 g cm23 andit melts peritectically at approx 1320uC This canmake the Al3Sc phase an attractive candidate asa material for lightweight high temperaturestructural applications205777ndash86

(ii) in order to understand the effect of Al3Scprecipitation in Al-alloys it is necessary to gainmore knowledge about the Al3Sc phase578187ndash91

(iii) the Al3Sc is an excellent model phase forstudying basic properties of intermetalliccompounds7990ndash98

10 Atomic arrangement of Al3Sc phase

Table 3 Some reported properties of Al3Sc phase

ReferenceE GPa(Youngrsquos modulus) n (Poissonrsquos ratio)

CTE (Coefficient ofthermal expansion) 1026 K21

(111) APB energymJ m22

(100) APB energymJ m22

88 Approx 11120 166 020 Max 670 45079 166 022 31399 1628 0204

1642iexcl19 0201iexcl000189 16

Reported to decrease linearly with increasing temperature to approx 97 GPa at 550uCCalculatedExperimental

Roslashyset and Ryum Scandium in aluminium alloys

International Materials Reviews 2005 VOL 50 NO 1 25

Formation of Al3Sc in AlndashSc alloysThere are at least four ways that the Al3Sc phase canform in dilute binary AlndashSc alloys

1 Upon solidification of hypereutectic alloys (Sc

approx 06 wt-) Al3Sc is the first phase to form

2 The solidification of hypo- and hypereutectic alloysends with formation of eutectic AlzAl3Sc

3 Al3Sc can precipitate discontinuously from super-saturated solid solution

4 Al3Sc can precipitate continuously (nucleation andgrowth) from supersaturated solid solution

Primary Al3ScAccording to the binary phase diagram primary Al3Scshould form during solidification of all alloys with Sccontent higher than approx 06 wt- ie higher thanthe eutectic composition Formation of primary Al3Sc inAlndash07 wt-Sc melts cooled at 102ndash103 K s21 has beenreported1832 According to the metastable state dia-gram32 this alloy composition is close to the eutectic oneat these cooling rates

Primary Al3Sc is reported to have a highly facetedmorphology1318100ndash102 The observation of a cubicmorphology in a slowly cooled Alndash87 wt-Sc alloyindicates that the facet planes in this case are thecrystallographic (100) planes13 Brodova et al100ndash102

have investigated the microstructure of rapidly cooledAlndash2 wt-Sc alloy They found that the dominantmorphology of primary Al3Sc was dependent on boththe cooling rate and the initial melt temperature A mapof primary Al3Sc morphologies as a function of theseparameters was constructed and is redrawn in Fig 11

The nucleation mechanism and growth morphologyof primary Al3Sc in an Alndash07 wt-Sc alloy solidified ata cooling rate of 100 K s21 were investigated by Hydeet al103104 Indications were found that the primaryAl3Sc particles nucleate heterogeneously on oxideparticles in the melt The primary Al3Sc particles werefound to grow with a dendritic morphology with theprimary dendrite arms in the crystallographic n110m

direction The overall shape is cubic which is inaccordance with earlier observations

Eutectic Al3ScEutectic AlzAl3Sc has been reported in hyper- as wellas hypoeutectic alloys11 but is scantily described in theliterature Given a eutectic composition of 06 wt- amaximum solid solubility of Sc in Al of 035 wt- andthe specific densities in Table 1 a eutectic formed underequilibrium conditions would contain a volume fractionof approx 063 vol-Al3Sc At high cooling rates thevolume fraction of Al3Sc in the eutectic is probablysomewhat smaller owing to the increased supersatura-tion of Sc in Al

The morphology of the eutectic in an Alndash2 wt-Scalloy is reported to depend on the temperature of themelt before solidification100 For low melt temperaturesthe eutectic is reported to be rodlike for a wide range ofcooling rates For intermediate melt temperatures andhigh cooling rates a lsquodiscontinuous eutecticrsquo is reportedwhereas for high melt temperatures and slow coolingrates a lsquoquasieutecticrsquo structure is reported with Al3Scparticles of almost spherical shape

Hyde et al have reported that during solidification ofan Alndash07 wt-Sc alloy some of the primary Al3Scparticles are pushed ahead of the Al solidification frontand end up at the grain boundaries103104 Thus primaryAl3Sc may be mixed with eutectic Al3Sc in themicrostructure A scanning electron microscopy (SEM)picture showing eutectic Al3Sc at the grain boundaries asdescribed in Refs 103 and 104 is given in Fig 12

Discontinuous precipitation of Al3ScDiscontinuous precipitation of Al3Sc from super-saturated solid solution is often observed in binary AlndashSc alloys131831105 This precipitation mechanism whichis sometimes referred to as cellular precipitation iscommonly described as a decomposition of super-saturated solid solution into a-Al and Al3Sc at a movinggrain boundary The driving force for the grainboundary migration is the volume free energy that isreleased during the precipitation As the grain boundarymoves it leaves behind a characteristic fan shaped array

11 Morphology of primary Al3Sc particles in Alndash2 wt-Sc

alloy as a function of melt overheating and cooling

rate during solidification redrawn from Ref 102

12 SEM image of particle structure of Alndash07 wt-Sc

alloy cooled at a rate of 100 K s21 during solidifica-

tion as described in Refs 103 and 104 primary Al3Sc

particle is seen in centre of grain whereas eutectic

Al3Sc is decorating grain boundaries image is kindly

provided by Dr Kristian Hyde UMIST Manchester UK

Roslashyset and Ryum Scandium in aluminium alloys

26 International Materials Reviews 2005 VOL 50 NO 1

of precipitates In the AlndashSc case the discontinuouslyprecipitated Al3Sc particles have been demonstrated tobe coherent with the aluminium matrix1318

The driving force for discontinuous precipitationincreases with increasing supersaturation of Sc in theAl matrix Thus discontinuous precipitation in binaryAlndashSc is most frequently reported in studies of alloyswith a Sc content of 04 wt- or higher1318106 Stilldiscontinuous precipitation has also occasionally beenreported to occur at lower alloy compositions In an Alndash027 wt-Sc alloy discontinuous precipitation wasobserved over a wide range of temperatures107 In arecent study31105 of precipitation kinetics and mechan-isms in Alndash02 wt-Sc discontinuous precipitation wasfound to take place when the specimens were quencheddirectly from a solutionising temperature in this case600uC to aging temperatures in the range 370ndash490uCFurther C-curves in a temperature-time-transformation(TTT) diagram were established (Fig 13) which showedthat the highest transformation rate of discontinuousprecipitation lies at a higher temperature than thehighest transformation rate of the continuous precipita-tion reaction ie the two precipitation reactions arerepresented by two separate lsquonosesrsquo on the C-curves

It has been shown that discontinuous precipitationcan be suppressed by continuous precipitation if thematerial is cold worked before the precipitation heattreatment13108

As a result of their rather coarse nature andinhomogeneous dispersion discontinuously precipitatedAl3Sc contributes but little to the strength of the alloyand also leads to a smaller amount of Sc in super-saturated solid solution being available for subsequentcontinuous precipitation Thus discontinuous precipita-tion is in general regarded as an undesired precipitationmode

Continuous precipitation of Al3ScContinuous precipitation of Al3Sc is a bulk decomposi-tion process of supersaturated solid solution of Sc in Aland can in the isothermal case be characterised by anucleation stage a growth stage and finally a coarsen-ing stage Apparently the continuous precipitation reac-tion occurs largely by homogeneous nucleation anddiffusion controlled growth and AlndashSc has occasionallybeen used as a model system for studying the mechan-isms of nucleation growth and coarsening107109ndash111

There have been several studies of the continuousprecipitation reaction in binary AlndashSc alloys and up tillnow there is no evidence that any metastable phases areforming before the L12 phase Al3Sc Thus it is assumedthat the equilibrium phase nucleates directly fromsupersaturated solid solution

Even though the nucleation of Al3Sc is frequentlyreported to occur homogeneously throughout the Almatrix there are some examples in the technical litera-ture of reported heterogeneous Al3Sc nucleation ondislocations110112ndash115 and grain boundaries110113115ndash118

In a recent numerical modelling study of continuousprecipitation in AlndashSc alloys111 the effect of hetero-geneous nucleation on dislocations is accounted for Themodel predicts that homogeneous nucleation dominatesat high Sc concentrations and low transformation tem-peratures whereas heterogeneous nucleation is predictedto dominate at low Sc concentrations and high trans-formation temperatures Figure 14 shows a sketch of anucleation map for AlndashSc The shift between homo-geneous and heterogeneous dominance in nucleation isdependent on the dislocation density as indicated in thefigure

The shape of continuously precipitated Al3Sc particlesis most frequently reported to be spherical29112113119ndash129

However it seems that under certain conditions theshape can differ from the spherical one Drits et al130

reported both spherical and star shaped morphologyThe star shaped precipitates had arms growing in thecrystallographic n110m-directions (Star shaped Al3Scprecipitates have also been found after some thermo-mechanical treatments of an AlndashMgndashScndashZr alloy131) InRef 128 precipitates of both cuboidal and sphericalmorphology are found to coexist after certain heattreatments Cauliflower shaped precipitates as well asprecipitates of spherical and cuboidal shapes arereported by Novotny and Ardell110 Bastow andCelotto132 found large oblong Al3Sc particles in an Alndash01 wt-Sc alloy after aging at 400uC for 24 h A facetedshape is suggested in a high-resolution image of anAl3(Sc Zr) precipitate in an AlndashMgndashMnndashZrndashSc alloy133

In a systematic high-resolution transmission electron

13 TTT diagram of precipitation in Alndash02 wt-Sc alloy

after solutionising at 600uC and direct quench to

aging temperature3114 Nucleation map for binary AlndashSc alloys which indi-

cates how the tendency towards heterogeneous ver-

sus homogeneous nucleation is predicted to depend

upon Sc concentration transformation temperature

and dislocation density redrawn from Ref 111

Roslashyset and Ryum Scandium in aluminium alloys

International Materials Reviews 2005 VOL 50 NO 1 27

microscopy (TEM) study of the Al3Sc particle morphol-ogy development during precipitation heat treatment ofbinary AlndashSc alloys by Marquis and Seidman114 it isdemonstrated that the precipitates can take a wide rangeof shapes as they grow depending on Sc content in thealloy transformation temperature and transformationtime Irregular shaped star shaped and cuboidalshaped precipitates were observed under someconditions It was however found that the equilibriumshape of the particles is an equiaxed multifaceted one(Fig 15) Supported by Wulffrsquos construction it wasconcluded that the shape was that of a GreatRhombicuboctahedron This equilibrium morphologyhas been reproduced by computer-simulations ofparticle growth87134 The multifaceted particles caneasily be taken for spherical in a conventional TEMpicture

Kinetics of precipitation of Al3Sc fromsupersaturated solid solutionThe precipitation kinetics of Al3Sc in binary AlndashScalloys is dependent on the precipitation heat treatmenttemperature and on the Sc content in the alloy Acomprehensive overview over the transformationkinetics in terms of C-curves is given by Zakharov135

The C-curves for 5 transformation for a range of AlndashSc alloys are redrawn in Fig 16

Hyland107 studied the homogeneous nucleationkinetics of Al3Sc in a Alndash018 wt-Sc alloy after directquench from 650uC to precipitation temperatures of 288and 343uC He found that after an incubation time t theAl3Sc particles nucleated at a constant rate until thediffusion fields of the individual particles started tooverlap At 288uC the incubation time and time tosignificant diffusion field overlap were estimated to beapprox 245 and 150 min respectively whereas thecorresponding values at 343uC were estimated to beapprox 7 and 20 min respectively

If one assumes that the JohnsonndashMehlndashAvramindashKomolgorov (JMAK) relationship is valid for thisprecipitation reaction one can express the fraction

transformed X as a function of the reaction time t bythe equation

X (t)~1expfrac12k(Dt)n (1)

where k is a constant D is the interdiffusion constant ofSc in Al and the exponent n is dependent on thenucleation rate For the situation described byHyland107 where the precipitates nucleate at a constantrate the value of n should theoretically136 be equal to52

Roslashyset and Ryum31105 applied an alloy and heattreatment method practically equal to that of Hyland107

One should thus expect that the precipitation kineticsshould also be quite similar However Roslashyset andRyum reported that the exponent n of the JMAKrelationship was approx 165ndash185 for the temperaturerange of concern31105 This does not point in thedirection of a constant nucleation rate but rather inthe direction of site saturation ie that all the particlesare nucleated simultaneously which in the JMAKequation would yield an exponent n of 32136 Anoverview of some reported values of n in the JMAKequation is given in Table 4 The majority of the valueslie closer to 32 than to 52 However it is important to

15 High resolution TEM picture along n100m axis of Al3Sc particle in Alndash03 wt-Sc alloy aged at 300uC for 350 h114

(reproduced with permission from Elsevier Science image kindly provided by Dr E A Marquis and Professor D N

Seidman) and various projections of a Great Rhombicuboctahedron

Table 4 Some reported values of n in JMAK equation

Reference n C 0Sc wt-Sc Ttrans uC Note

137 13 030 300 Solution heat treated (SHT) 500uC16026 030 300 SHT 600uC Low n at late stage20026 030 300 SHT 640uC Low n at late stage

29 130ndash149 015 260ndash370145ndash196 025 260ndash370

138 188ndash216 020 240ndash35031 165ndash185 023 270ndash350 SHT 600uC Direct quench to transformation temp

16 C-curves for 5 transformation in a range of binary

AlndashSc alloys redrawn from Ref 135

Roslashyset and Ryum Scandium in aluminium alloys

28 International Materials Reviews 2005 VOL 50 NO 1

note that an n value close to 32 is per se not evidence ofsite saturation

Hyland also showed that a water quench from thesolutionising temperature significantly altered thenucleation kinetics in the subsequent precipitation heattreatment107 The incubation time was dramaticallyshortened which is attributed to the quenched-in excessvacancies and it is also indicated that there might be ashift in the nucleation rate in the early stage ofprecipitation It is suggested that the vacancies mayenhance the diffusion of Sc in Al and that there is apossibility that vacancy clusters act as heterogeneousnucleation sites for Al3Sc precipitates107 Regardless ofwhich mechanism that is operative it is clearly demon-strated that the nucleation kinetics can be dependent onthe thermal history between solutionising and precipita-tion heat treatment

Loss of coherency during growth of Al3ScprecipitatesWhen an Al3Sc particle grows it will sooner or laterreach a critical size where it will be energetically morefavourable to introduce an interface dislocation at theAlAl3Sc interface than to increase the matrix strain Asimple approximation for the critical size can be derivedfrom the lattice parameters assuming that the criticalsize is reached when the misfit over the whole particlediameter equals the Burgers vector of the Al matrix

dcrit~b=d (2)

where b is the Burgers vector of Al and d is themisfit between Al and Al3Sc This approximation yieldsa critical diameter of approx 215 nm at ambienttemperature

The misfit d and thus also the critical diameter dcrit

will depend on the temperature owing to the differencesin thermal expansion between the Al matrix and the

Al3Sc particles The thermal expansion of Al3Sc hasrecently been measured89 and based on the differencesin thermal expansion between Al139 and Al3Sc the misfitas a function of temperature has been calculated89 Thiscalculation is reproduced and shown by the solid line inFig 17

It is however possible to refine this calculationsomewhat140 Whereas the thermal expansion of Al3Sc isexpected to be only because of lattice expansion there isa significant contribution from vacancies on thermalexpansion of Al at high temperatures141 Thus thetemperature effects on the misfit should be calculatedfrom the changes in lattice parameters rather than fromthe linear thermal expansion By subtracting the vacancyeffect on the thermal expansion one achieves atemperature-dependent misfit as represented by thedotted line in Fig 17

A second correction that should be taken into accountis the effect of Sc in solid solution on the latticeparameter of the Al matrix With increasing tempera-ture more Sc is brought into solid solution and it isreported that the lattice parameter of the Al matrixpresumably measured at room temperature increaseslinearly with the Sc content in solid solution142 Thesedata can be used to calculate the effect on the latticeparameter at elevated temperatures under the assump-tion that the relative increase in lattice parameter owingto Sc in solid solution is independent of temperature InRef 142 a figure is presented which shows the measuredlattice parameter as a function of Sc content in solidsolution and a value (dadc)a is reported where a is thelattice parameter of the Al matrix and c is the Sc contentin solid solution in at- The reported value for (dadc)a is 100 times larger than that indicated in thecorresponding figure possibly as a result of a decimalerror in the text Thus in the present exercise 1100th ofthe reported value for (dadc)a is used Using this incombination with the regular solution approximationfor the solvus line of Sc in Al1231 one obtains acorrection for Sc in solid solution on the temperature-dependent misfit as shown in Fig 18 This figure shows

17 Lattice mismatch between Al and Al3Sc as a function

of temperature solid line represents calculation

based on linear thermal expansion of the two phases

dotted line represents correction for vacancies in Al

lattice

18 Corrections of mismatch calculated from linear ther-

mal expansion data as a result of vacancies and to

Al lattice expansion from Sc in solid solution

Roslashyset and Ryum Scandium in aluminium alloys

International Materials Reviews 2005 VOL 50 NO 1 29

both the correction for vacancies and for Sc in solidsolution on the same graph The two corrections are ofapproximately the same magnitude but with oppositesigns Thus the resulting (net) correction is close to zeroand it turns out that the first hand approximation asapplied in Ref 89 is very good in this case

Applying the calculated temperature dependent misfitwith the simple approximation for a critical diameter forloss of coherency one obtains a temperature-dependentcritical diameter as shown in Fig 19

Some examples from the literature of experimentallyobserved critical diameters in binary AlndashSc alloys aresummarised in Table 5 along with some predictions forcritical diameters from Fig 19 There is a fairly goodconsistency between the observations and the measureddiameter is quite close to the simple predictions above

A more refined analysis on the transition fromcoherent to incoherent particles has recently beenperformed145 This analysis is based on the balancebetween the increase in particlematrix interface energyowing to interfacial dislocations and the relaxation inelastic energy in the Al matrix owing to the samedislocations This method yields a predicted criticaldiameter of 246 nm for transition from coherent to

semi-coherent particles at ambient temperature Thetemperature dependence of the critical diameter is nottreated in this analysis

The loss of coherency during isothermal annealing hasbeen reported to be accompanied by an increasedaverage coarsening rate119121137145 The increasedcoarsening rate has been attributed either to diffusionof Sc along dislocation lines119121 or to the increasedparticlematrix interface energy of a semicoherentparticle145 However there are also several data sets inthe literature that do not indicate an increased growthrate after the loss of coherency114128

Al3ScAl interface energyThe interface energy between Al3Sc and the Al matrix isone of the key parameters that governs the nucleationgrowth and coarsening behaviour of Al3Sc in Al and Alalloys The interface energy has been estimated in severalinvestigations either by fitting experimental data toequations that describe nucleation or coarsening or bycalculations A compilation of some of the results isgiven in Table 6 There is considerable spread in thereported values regardless of what approach has beenused for the estimation

Influence of other elements on precipitation ofAl3ScMagnesium

With regard to precipitation mechanism it has beenstated that Mg suppresses the tendency to discontinuousprecipitation of Al3Sc106 In an investigation of pre-cipitation kinetics of Al3Sc in the temperature range300ndash500uC only minor changes in the kinetics (Fig 20)were found when up to 5 wt-Mg was added to an Alndash04 wt-Sc alloy135 It seems that the precipitationreaction is slightly faster in the Mg-containing alloys

Several investigations on age hardening response alsoimply that there is only a small if any effect of Mg onthe precipitation kinetics of Al3Sc23148149 It is how-ever found that the hardness increase from theprecipitation of Al3Sc is somewhat reduced in AlndashMgndashSc alloys compared to binary AlndashSc alloys23148149 InRef 149 it is suggested that some of the Sc is dissolvedin the Al3Mg2 phase and thus the age hardeningpotential is reduced with increasing Mg contentSomewhat contradictory to these observations but

Table 5 Some reported critical diameters for coherencyloss in binary AlndashSc and correspondingtheoretical critical diameters from Fig 19

Reference dcrit nmC0

Scwt-Sc

TtransuC

Theoreticaldcrit nm

119 38ndash40 05137 28ndash30 03 400 308128 32 02 400 450 308 335129 50 02143 40 012 025115 40 025 450ndash500 335ndash37114 40 03 400 450 308 335144 40 02 400ndash460 308ndash341145 30ndash80 02 400ndash490 308ndash362

20 C-curves for 10 and 60 transformation in Alndash

04 wt-Sc and Alndash4 wt-Mgndash04 wt-Sc redrawn

from Ref 135

19 Simple approximation for temperature-dependent criti-

cal diameter for introduction of dislocations on Al

Al3Sc interface

Roslashyset and Ryum Scandium in aluminium alloys

30 International Materials Reviews 2005 VOL 50 NO 1

sustained by Ref 135 it has recently been reported150

that precipitation of Al3Sc at 300 and 350uC occursslightly faster in an Alndash2 wt-Mgndash02 wt-Sc alloythan in an Alndash02 wt-Sc alloy studied previously by thesame researchers117118 and that the correspondinghardness increase is highest in the AlndashMgndashSc alloyThe only reported difference in experimental procedureis the solutionising temperature which was higher forthe AlndashSc alloy (648uC) than for the AlndashMgndashSc alloy(617uC) However given that the nucleation time isshortened by quenched-in vacancies as suggested byHyland107 the difference in homogenisation tempera-ture should be in favour of a faster precipitation of thebinary AlndashSc alloy It should be worthwhile to probedeeper into this observation of different aging responses

Mg in solid solution increases the lattice parameter ofthe Al matrix This is in turn expected to influence thecritical diameter for AlAl3Sc coherency loss as discussedin the section on lsquoLoss of coherency during growth ofAl3Sc precipitatesrsquo above Such an influence on the criticaldiameter is also briefly discussed elsewhere150 A criticaldiameter of 80 nm in an Alndash3 wt-Mgndash02 wt-Sc alloyhas been observed compared to 40 nm in a binary Alndash02 wt-Sc alloy of the same investigation144 Otherresearchers have reported a critical diameter in excess of116 nm in an Alndash63 wt-Mgndash02 wt-Sc alloy151

Computer simulations predict that the AlAl3Scinterface should be enriched in Mg87 These predictionsare confirmed experimentally by three-dimensional atomprobe microscopy of an Alndash2 wt-Mgndash02 wt-Sc alloyaged at 300uC38 Here it was found that the Mg contentat the interface is approximately three times higher thanthe matrix concentration regardless of aging time

Copper

It has been claimed that Cu suppresses the tendencytowards discontinuous precipitation of Al3Sc106

Zakharov and Rostova152 have reported that additionsof up to 14 wt-Cu have only minor effects on theprecipitation kinetics in an Alndash04 wt-Sc alloy Themost noticeable effect is that for temperatures above400uC the late stage of the transformation is sloweddown for the highest Cu contents This does not show in

Fig 21 however where only the 10 and 60transformation curves are included

The W-phase (AlCuSc) was observed in the alloywith the highest Cu content which means that less Sc isavailable for the precipitation of Al3Sc in this alloyAnother investigation on the age hardening response ofAlndash023 wt-Sc and Alndash25 wt-Cundash023 wt-Sc at300uC also implies that the precipitation behaviour ofAl3Sc in the two alloys is similar153154 At 350uC alimited portion of the Al3Sc has been observed tonucleate heterogeneously on coarse hrsquo precipitates155

According to the isothermal sections of the phasediagram43 one should expect the ternary W-phase toform instead of the Al3Sc phase in an alloy with such ahigh CuSc ratio However no observations of the W-phase or other ternary phases were reported from TEMstudies of the Alndash25 wt-Cundash023 wt-Sc alloy thathad been heat treated in the temperature range 300ndash460uC153ndash156 A third investigation on the precipitationin Alndash048 wt-Sc alloys with up to 440 wt-Cu in thetemperature range 100ndash450uC also concludes that no W-phase or other ternary phase forms during the heattreatment157

Copper in solid solution decreases the lattice para-meter of the Al matrix Thus it is expected that the misfitbetween Al and Al3Sc precipitates should be higher in

21 C-curves for 10 and 60 transformation in Alndash

04 wt-Sc and Alndash14 wt-Cundash04 wt-Sc redrawn

from Ref 152

Table 6 Reported values of interphase energy cAlAl3Sc between coherent Al3Sc precipitates and Al matrix

Reference cAlAl3Sc mJ m22 Method of estimation

137 10 Fit of coarsening data to LifshitzndashSlezev equation107 78iexcl20 (288uC) Back-calculation of incubation time

93iexcl20 (343uC)107 123iexcl41 (288uC) Back-calculation of nucleation rate

125iexcl35 (343uC)29 542 (400uC) Fit of coarsening data to Ostwald ripening

632 (430uC)413 (460uC)

146 c(100) 192 (0 K) c(111) 226 (0 K) Pseudopotential calculations147 c(100) 325 (0 K) c(110) 513 (0 K) c(111)

782 (0 K) c(100) 315 (288uC) c(100) 325 (343uC)Atomistic simulation

110 105 Fit of coarsening data to LSW theory31 20ndash300 Fit of coarsening data to Ostwald ripening

for 16 different temperatures111 57 Fit of precipitation model to experimental data145 120 coherent particles Fit of coarsening data

170 semicoherent particles

It is argued in this study that c may be lower in the nucleation stage

Roslashyset and Ryum Scandium in aluminium alloys

International Materials Reviews 2005 VOL 50 NO 1 31

AlndashCundashSc alloys compared to AlndashSc alloys Howeveran experimental investigation of Alndash25 wt-Cundash023 wt-Sc alloy comes to a different conclusion Thelattice misfit strain is found to decrease compared to Alndash02 wt-Sc and the critical diameter for coherency losswas found to be the same in the ternary and the binaryalloy144 It is suggested that these observations may bebecause of the dissolution of some Cu in the Al3Sc phaseand thus that the lattice parameters of both the Al matrixand the Al3Sc precipitates decrease in the ternary alloy

Silicon

It has been found that the onset of precipitation in Alndash04 wt-Sc is only slightly altered when Si contents ofup to 04 wt are introduced in the alloy However thefinal stage of the precipitation reaction is considerablydelayed with increasing Si content135 Figure 22 showsthe effect of addition of a joint of 035 wt-Si and040 wt-Fe There are at least two possible explana-tions for why an Si-addition leads to this behaviour

1 Alloying with Si is known to promote discontin-uous precipitation of Al3Sc106158 It has been shown thatwhen isothermal precipitation of Al3Sc starts discon-tinuously the later stage of the overall transformationcan be very slow31

2 The isothermal section of the phase diagramsuggests that the V-phase (AlSc2Si2) should form inalloys of this composition46 If the V-phase forms lessSc is available for precipitation of Al3Sc

It has been shown157 that for an AlndashScndashSi alloy withsolid solution content of 010 wt-Sc an 110 wt-Sithe only phases to precipitate after heat treatment at200uC are Si and an (AlScSi)-phase possibly the V-phase On the other hand the Al3Sc phase has beenobserved to form in alloys with 04 wt-Sc and up to08 wt-Si159160

Zinc

It has been reported that additions of up to 5 wt- Znhave only minor effects on the precipitation kinetics ofan Alndash04 wt-Sc alloy135 (Fig 23) In Ref 106 it isclaimed that Zn promotes discontinuous precipitation ofAl3Sc

Lithium

A comparison of the age hardening response at 400uC inAlndash24 wt-Lindash019 wt-Sc and Alndash024 wt-Sc alloys

indicates that the onset of Al3Sc-precipitation is notaffected by the presence of Li161

Zirconium

As mentioned in the section on lsquoTernary phase diagramswith dispersoid-forming elementsrsquo earlier a considerableamount of Zr is dissolved in the Al3Sc phase and thus amore correct denotation of the precipitating phase isAl3(Sc12xZrx) In discussing the influence of the Zrcontent on the precipitation of Al3Sc one is thereforeactually discussing the difference in precipitation ofAl3Sc versus Al3(Sc12xZrx)

It is found that an addition of 015 wt-Zr to an Alndash04 wt-Sc alloy only marginally affects the initial stageof the precipitation reaction123135 while it slows downthe later stages of the transformation considerably(Fig 24)135 The coarsening rate of the Al3(Sc12xZrx)particles in AlndashScndashZr alloys is found to be much slowerthan that of Al3Sc particles in AlndashSc alloys123162

In three-dimensional atom probe field ion microscopy(3D-APFIM) of Al3(Sc12xZrx) particles formed at 475uCin a ternary AlndashScndashZr alloy163 it was found that the coreof the particles is almost pure Al3Sc whereas there is ashell of Al3(Sc12xZrx) with almost equal content of Scand Zr Such a behaviour has also been predicted bycomputer modelling of precipitation of Al3(Sc12xZrx) at480uC in an AlndashZnndashMgndashScndashZr alloy164 This modelpredicts that Zr starts to enter the growing

22 C-curves for 10 and 60 transformation in Alndash

04 wt-Sc and Alndash04 wt-Fendash035 wt-Sindash04 wt-Sc

redrawn from Ref 135

23 C-curves for 10 and 60 transformation in Alndash

04 wt-Sc and Alndash5 wt-Znndash04 wt-Sc redrawn

from Ref 135

24 C-curves for 10 and 60 transformation in Alndash

04 wt-Sc and Alndash04 wt-Scndash015 wt-Zr redrawn

from Ref 135

Roslashyset and Ryum Scandium in aluminium alloys

32 International Materials Reviews 2005 VOL 50 NO 1

Al3(Sc12xZrx) particles when approximately half of thesupersaturated Sc has been precipitated The Zr contentof the outer shell is predicted to be much higher thanwhat has been found experimentally163164

Another 3D-APFIM study of Al3(Sc12xZrx) particlesin a ternary AlndashScndashZr alloy has been reported165 Hereparticles grown at 300uC for various lengths of time werestudied The Zr content in these particles was muchlower than that reportedpredicted at higher tempera-tures163164 even after very long annealing times

Iron

The effect of adding up to 07 wt-Fe on the precipita-tion kinetics in an Alndash04 wt-Sc alloy has beeninvestigated135 The onset of precipitation was onlyslightly influenced by the Fe-level whereas the laterstages of the transformation however were significantlyslowed down as the Fe-level increased An example ofthe effect of a joint addition of Fe and Si is shown inFig 22

Manganese chromium and titanium

Small additions (03 wt-) of manganese or chromiumto Alndash040 wt-Sc alloys are reported to have onlyminor effects on the precipitation kinetics of Al3Sc135

According to Ref 106 Mn is reported to promote andCr and Ti to suppress discontinuous precipitation

Rare earth elements

An investigation of the precipitation behaviour of Alndash03 at-Sc and Alndash03 at-Scndash03 at-X alloyswhere X is either yttrium gadolinium holmium orerbium in the temperature range 235ndash310uC indicatedthat a Al3(Sc12xXx) phase with L12 structure wasformed in the ternary alloys22 Peak strength is reportedto occur after approx 10 h at 285uC in all alloys whichindicates that the precipitation kinetics up to peakstrength is practically unaltered by the ternary additions

Influence of Sc on microstructure andproperties of wrought aluminium alloysMost of the effects of Sc addition in wrought Al-alloysare linked to the formation of the Al3Sc phase In atypical processing route of a wrought aluminium alloyparticles of the Al3Sc phase can form under threedifferent conditions each of which influences themicrostructure and properties of the alloy in a specificway

1 During solidification after casting or weldingAl3Sc particles can form in the melt and act as nucleifor a-Al thus leading to grain refinement18166

2 High temperature processing of the alloy in therange 400ndash600uC for instance homogenisation hot-rolling or extrusion can give a dense distribution ofAl3Sc particles of typically 20ndash100 nm size The particledistributions formed under such conditions are reportedto lead to good recrystallisation resistance128148167168

and enhanced superplasticity52169170

3 Heat treatment in the range 250ndash350uC can lead tosignificant precipitation hardening of an alloy super-saturated in Sc148158171 The size of strengthening Al3Scprecipitates is typically in the range 2ndash6 nm121

Grain refinementA good grain refinement is almost always desired uponsolidification The formation of small equiaxed grainsrather than long dendrites in the melt facilitates thefeeding of the melt into cavities of the shrinkingsolidified metal and thus reduces the problem ofshrinkage porosity The tendency to hot cracking is alsoreduced and the second phase particles become morefinely and uniformly distributed

To the authorsrsquo knowledge the first effect of Sc in Al-alloys that was reported in an international scientificjournal was the grain refining action in pure Al and in anAlndashCu alloy upon solidification172 which was found tobe stronger for Sc than for other transition metals Inlater studies of Sc as a grain refiner in pure Al1832173 ithas been demonstrated that approx 07 wt-Sc issufficient to provide excellent grain refinement It hasalso been demonstrated that additions of 025 wt-Scz025 wt-Zr provide good grain refinement in pure Al18

In order for Sc to act as an effective grain refiner theAl3Sc phase has to form in the melt before thesolidification of a-Al The Al3Sc particles have a latticeparameter close to that of pure Al and whenhypereutectically formed the Al3Sc particles are veryeffective substrates for the nucleation of the a-Al phaseAs mentioned in the section on lsquoFormation of Al3Sc inAlndashSc alloysrsquo above this requires that the alloy ishypereutectic with respect to Sc ie in excess of approx06 wt- in a binary AlndashSc alloy In ternary and higherorder systems the eutectic Sc composition may dependon the other alloying elements present For instance theeutectic composition of Sc has been predicted todecrease with increasing Mg content in the ternary AlndashMgndashSc system39 This prediction is sustained by theobservation of good grain refinement by adding 05 wt-Sc to an Alndash7 wt-Mg alloy174 (Other examples ofgrain refinement at Sc concentrations lower than that ofthe binary eutectic are found in Ref 173)

Similarly the observation of good grain refinement inan Alndash025 wt-Scndash025 wt-Zr alloy18 may be as aresult of a lower Sc content of the eutectic in the ternarysystem ie less Sc is needed to make the alloy hyper-eutectic No literature data on the liquidus surface of theAlndashScndashZr system are available and thus this hypothesiscannot be confirmed In more complex alloy systems itis also observed that excellent grain refinement isachieved at low Sc contents when Sc is added togetherwith Zr It is reported that adding either 02 wt-Sc06 wt-Sc or 01 wt-Zr to an Alndash5Mg alloy givesmuch poorer grain refinement than adding 02 wt-Scz01 wt-Zr175 Similarly additions of 015 wt- ofeither Sc or Zr are reported to only marginally refinethe grain structure in an AlndashCundashLi alloy whereas a jointaddition of 015 wt-Sc and 015 wt-Zr gives excellentgrain refinement176 For an AA 3650 casting alloy (Alndash7 wt-Sindash04 wt-Mg) good grain refinement is achievedby adding 039 wt-Sc or 027 wt-Scz019 wt-Zr177

In some AlndashZnndashMgndashScndashZr alloys it is also found thatan addition of 02ndash03 wt-Sc can be sufficient for goodgrain refinement166169178179 Examples of the grainrefinement as a function of Sc addition in pure Al andin an AlndashZnndashMgndashZr alloy are shown in Fig 25

The nucleation of a-Al on Al3Sc particles in the melt isfacilitated by the close match in the lattice parameters ofthe two phases As shown in Fig 17 the mismatch at the

Roslashyset and Ryum Scandium in aluminium alloys

International Materials Reviews 2005 VOL 50 NO 1 33

eutectic temperature of binary AlndashSc alloys (660uC) isonly approx 047 In Refs 57 and 89 it is shown thatwhen Zr Hf and in particular Ti is dissolved in the Al3Scparticles this reduces the lattice parameter of the phaseIt appears that when 25 of the Sc atoms in Al3Sc aresubstituted by Ti the mismatch is zero at approx 550uCand becomes negative at higher temperatures89 Thissuggests that by carefully selecting the Ti content of thealloy it should be possible to obtain Al3(ScTi)substrates in the melt that match exactly the latticeparameter of the nucleating a-Al and thus furtherimprove the grain refinement of the alloy This appearsto have been achieved in a recent work180 where thegrain refinement of an Alndash07 wt-Sc alloy wascompared with that of an Alndash05 wt-Scndash02 wt-Tialloy At a cooling rate of 100 K s21 only an estimated2 of the primary Al3Sc particles of the binary AlndashScalloy were effective nuclei compared to practically 100for the primary Al3(ScTi) particles in the ternary AlndashScndashTi alloy leading to a much smaller grain size in theternary alloy Whereas the match of lattice parametersmay be of importance for these results the authors ofthis investigation180 draw attention to other factors suchas different growth restriction factors for Sc and Ti andthe possibility of a peritectic reaction in the ternaryalloy Nevertheless the principle of matching latticeparameters is worth looking into further in future work

Effects from dispersoidslsquoDispersoidsrsquo is a term which is commonly used aboutthe classes of second phase particles that are formedin an Al alloy during high temperature annealing orthermomechanical processing such as homogenisationhot rolling extrusion and forging A dense distributionof dispersoids can give a significant contribution to analloyrsquos strength owing to particle strengthening but thisis rarely the main strengthening mechanism A moreimportant contribution from the dispersoids is theirability to stabilise the grainsubgrain structure of analloy through the Zener-drag action and thus improvethe mechanical properties of the alloy

There are two noticeable dispersoid-related effectsthat have been reported for Sc-containing alloys Thefirst is the stabilising effect on a deformed microstruc-ture When a non-recrystallised structure is preserved inan alloy this can add considerably to the mechanical

strength of the material The second effect is thepreservation of a small grain size during hot deforma-tion at slow deformation rates which is necessary toobtain superplastic properties of an Al-alloy

Recrystallisation resistance

The anti-recrystallisation effect of Sc was first publishedin a patent171 where 03 wt-Sc was added to pure Aland to AlndashMg AlndashMn and AlndashZnndashMg alloys Both Sc-free and Sc-containing materials were cold worked andsubsequently annealed and it was found that theaddition of Sc increased the temperature for onset ofrecrystallisation by approx 220uC in pure Al andsomewhat less in the Al-alloys Although the author ofthe patent171 may have been well aware that the anti-recrystallisation effect is caused by Al3Sc dispersoidsthis is not mentioned in the text The first journal paperthat explicitly points out that the recrystallisationresistance is due to Al3Sc dispersoids was an investiga-tion of the effects of adding Sc to wrought AlndashMgalloys181 In this work it was found that the Al3Scdispersoids were very effective in preventing recrystalli-sation up to temperatures of approx 400ndash450uC Athigher temperatures the dispersoids coarsen consider-ably and the microstructure was partially recrystallised

It is established that the Zener-drag pZ that is imposedon an advancing grain boundary by randomly distrib-uted dispersoids can be expressed in the form

pZ~k f =r (3)

where k is a factor that includes the interface energybetween the dispersoids and the matrix f is the volumefraction and r is the mean radius of the dispersoids Thusthe Zener drag will decrease rapidly in the case where thedispersoids are coarsening

As mentioned in the section on lsquoInfluence of otherelements on precipitation of Al3Scrsquo above theAl3(Sc12xZrx) dispersoids in a ternary AlndashScndashZr alloycoarsen at a much slower rate than the Al3Sc dispersoidsin a binary AlndashSc alloy This effect was first reported inRef 123 (although also observed in Ref 182) andaccording to Ref 33 the same authors demonstratedsoon after that the denser dispersoid distributionachieved in an AlndashScndashZr alloy leads to superiorrecrystallisation resistance compared to a binary AlndashScalloy An example of the increased recrystallisationresistance by adding both Zr and Sc is shown in Fig 26

In isothermal sections of the ternary AlndashScndashZr phasediagram it is indicated that the solid solubility ofSczZr is somewhat higher than that of Sc alone54 Ithas also been demonstrated both by electrical con-ductivity measurements (Fig 27) and microstructuralobservations that the supersaturation of SczZr isgreater than that of only Sc or Zr in as cast Alndash15(SczZr) alloys183 This indicates that it should bepossible to increase the volume fraction of dispersoids inAlndashScndashZr compared to AlndashSc It is suggested162 that theincreased volume fraction that can be achieved byadding both Sc and Zr can be advantageous inconventional wrought Al-alloys

There are at least two different conditions underwhich Al3Sc or Al3(Sc12xZrx) dispersoids can form toprevent recrystallisation

1 Sc (or Sc and Zr) is in solid solution before thedeformation In the case of cold deformation and

25 Grain refinement as a function of Sc addition in pure

Al (redrawn from Ref 32) and AlndashZnndashMgndashZr (redrawn

from Ref 169) note that data points are plotted on

different ordinate axes

Roslashyset and Ryum Scandium in aluminium alloys

34 International Materials Reviews 2005 VOL 50 NO 1

subsequent annealing the Al3Sc or Al3(Sc12xZrx)dispersoids may nucleate and grow before the nucleationand growth of recrystallised grains takes placeDispersoids can form after a direct up-quench to theannealing temperature115143148184 during ramp-up tothe annealing temperature115 or by pre-annealing at anintermediate temperature129 In the case of hot deforma-tion the Al3Sc or Al3(Sc12xZrx) dispersoids maynucleate and grow during preheating of the materialand during the hot deformation itself184

2 The Al3Sc or Al3(Sc12xZrx) dispersoids are formedin the material before deformation184 Considering coldrolling and subsequent annealing the annealing tem-perature Tann may be either lower or higher than thetemperature Tdisp at which the dispersoids were formedIf TannTdisp only limited if any coarsening of thedispersoids is expected to take place and thus the Zenerdrag from the particles is expected to be practicallyconstant The driving force for recrystallisation how-ever is expected to decrease somewhat with theannealing time as a result of recovery processes Thusif recrystallisation does not occur within short annealingtimes the material is expected to remain unrecrystallisedfor infinite time at the annealing temperature IfTannTdisp there will be substantial coarsening of thedispersoids during annealing In order for the materialto remain unrecrystallised the decrease in driving forcefor recrystallisation owing to recovery has to be at leastas rapid as the decrease in Zener drag because of particlecoarsening

Experimental comparisons of the conditions abovepoint in the direction that the recrystallisation resistanceis poorest when Sc (or Sc and Zr) is in solid solutionbefore deformation and the deformed material is up-quenched to the annealing temperature148 or when Al3Scor Al3(Sc12xZrx) dispersoids are formed before defor-mation at TdispampTann184185 Excellent recrystallisationresistance is achieved if dispersoids are formed at anintermediate anneal of solutionised and deformedmaterial128 or if dispersoids are formed at TdispTann

before deformation148185ndash187 It seems that the decreasein Zener drag because of dispersoid coarsening in many

cases is slower than the decrease in driving force forrecrystallisation because of recovery processes Thusthere is an advantage in forming a high number densityof small dispersoids which for most practical casesmeans that they should be formed at TdispTann122

When an advancing high angle grain boundary iethe recrystallisation front is passing a coherent Al3Scdispersoid there are at least three possible grainboundarydispersoid interactions

1 The Al3Sc dispersoid retains its global orientationrelationship and thus loses its coherency with thesurrounding matrix

2 The Al3Sc dispersoid rotates as the grain boundarypasses either by diffusional processes at the dispersoidmatrix interface or by the grain boundary passingthrough the dispersoid and the Al3Sc dispersoidassumes the same crystallographic orientation as theAl matrix of the recrystallised grain

3 The Al3Sc dispersoid dissolves at the grainboundary and re-precipitates in the recrystallised grain

Which interactions that actually take place willprobably depend on the dispersoid size annealingtemperature and driving force for recrystallisation It isalso possible that alloy composition (other elementsthan Al) is of importance

It has been reported that large (Oslash about 100ndash150 nm)Al3Sc dispersoids in a deformed Alndash4 wt-Mgndash02 wt-Sc alloy annealed at 575uC lose the orientationrelationship with the matrix after being passed by therecrystallisation front148

A rotation of somewhat smaller Al3Sc dispersoids in arecrystallising binary Alndash025 wt-Sc alloy has beenreported115143 The rotation was reported to be accom-panied by substantial growth (from Oslash 30 nm to Oslash48 nm) as a result of enhanced Sc diffusion at the grainboundary Observations suggested that the grainboundaries were passing through the dispersoids andthus the Al3Sc dispersoids retained the orientationrelationship with the recrystallised Al matrix

Dissolution and re-precipitation of Al3Sc dispersoidshas been reported during recrystallisation of a 50 coldrolled Alndash02 wt-Sc alloy162 Large spherical partially

26 Fraction recrystallised structure in cold rolled sheets

of Alndash04 wt-Sc and Alndash04 wt-Scndash015 wt-Zr as a

function of annealing temperature redrawn from

Ref 183 27 Electrical conductivity in Alndash15(SczZr) alloys

redrawn from Ref 183

Roslashyset and Ryum Scandium in aluminium alloys

International Materials Reviews 2005 VOL 50 NO 1 35

coherent dispersoids were observed to dissolve at therecrystallisation front and re-precipitate as smallercoherent Al3Sc cuboids

Superplastic forming

It seems that the first publication on superplasticproperties of Sc-containing Al-alloys was a study of anAlndash35Cundash14Mgndash045Mnndash04(SczZr) alloy188

It was recognised that the superplastic properties are aresult of the stabilisation of the fine grain structure byAl3Sc dispersoids The Sc-containing Al alloys that havereceived most attention for their superplastic propertieshowever are those of the AlndashMgndashSc system which wasfirst published in a patent189 Here it was noted that anAlndash4 wt-Mgndash05 wt-Sc alloy had superior superplasticproperties compared to fine-grained 7475 (AlndashZnndashMgndashCu alloy) Binary Alndash05 wt-Sc and Alndash4 wt-Mgalloys did not behave superplastically The flow stress atthe hot forming temperature was found to be much (30ndash40) lower in the ternary alloy than that of the twobinary alloys

The superplastic properties of AlndashMgndashSc alloys havebeen explored by several research groups over the lastdecade190ndash196 It has frequently been found that thedeformation mechanism is dominated by grain bound-ary sliding190 However it has also been reported thatAlndashMgndashSc alloy may deform superplastically withoutnoticeable grain boundary sliding23 It is generallyrecognised that the grain boundary sliding mechanismis facilitated when the average grain size is very smalland grain boundaries are predominantly high-angleSuch a microstructure may be achieved by carefulthermomechanical processing of the starting mate-rial193194197198 It has however been shown that a finegrained structure with high angle boundaries maydevelop during superplastic forming of AlndashMgndashSc alloyseven if the starting microstructure is an entirely differentone for instance that of a cold rolled sheet192 It has alsobeen suggested that superplastic forming of as castmaterial may be possible189

One of the more efficient thermomechanical processesfor achieving an ultrafine grain structure with high anglegrain boundaries in Al-alloys is equal channel angularpressing (ECAP) A JapanesendashAmerican group ofscientists has published an impressive body of researchon improvements in superplastic properties in Al-alloys processed by ECAP over the last few years andseveral of the publications are from investigations onAlndashMgndashSc alloys170199ndash224 Maximum strains in excessof 2000 at a strain rate of 0033 s21 have beenachieved170201202217 which is an extraordinarily goodcombination of high strain and high strain rate for analuminium alloy

Superplastic properties of AlndashCundashMg(ndashMn)ndashSc(ndashZr)and AlndashMgndashSc(ndashZr) alloys have been mentionedNoticeable superplasticity in other Sc-containing Al-alloys has also been reported such as AlndashZnndashMg(ndashCu)ndashScndashZr169225ndash228 AlndashLindashSc229 AlndashMgndashLindashScndashZr229ndash234

AlndashLindashMgndashCundashScndashZr235236 and AlndashCundashLindashScndashZr233

Precipitation hardeningHardening by Al3Sc precipitates

It has been noted that when Al3Sc particles precipitate inthe temperature range 250ndash350uC they give a significanthardness increase in the alloy Some authors point out

that Sc is a more effective precipitation hardening elementper atomic fraction added than the elements that arecommonly used for precipitation hardening121130 (In onepaper29 it is claimed that only Au has a strongerstrengthening effect than Sc) However the amount ofSc that can be precipitated from supersaturated solidsolution is rather limited and thus the absolute values ofthe hardness increase from the precipitation hardening ismuch lower than what is normally associated withprecipitation hardened alloys Also the temperatureregime for age hardening by precipitation of Al3Sc issomewhere in between the temperature regimes for agehardening and solution heat treatments of commonprecipitation hardened alloys This makes a combinedprecipitation of Al3Sc and other strengthening precipi-tates unfeasible Thus precipitation strengthening byAl3Sc is most feasible in alloy systems that are non-heat-treatable The non-heat-treatable aluminium alloy sys-tems are according to the Aluminum Associationdesignations the 1xxx series (99 pure Al) the 3xxxseries (AlndashMn) and the 5xxx series (AlndashMg) The purposeof adding Sc to these alloys may be either to stabilise themicrostructure of wrought semiproducts (extrusionsrolled plates forgings etc) as discussed in the sectionon lsquoRecrystallisation resistancersquo above or to provideextra strength to the alloy through precipitation hard-ening In the latter case it is appropriate to considerwhether the Sc-containing alloy still should be classifiedas non-heat-treatable A heat treatment is applied thatbrings about a significant precipitation hardening On theother hand the hardness increase that is achieved throughthe heat treatment is lower than what is normallyassociated with heat-treatable alloy systems Hence eventhough it seems like a contradiction one chooses to keepusing the term lsquonon-heat-treatablersquo about these alloys

Table 7 gives an overview of some mechanicalproperties of Sc-containing non-heat-treatable alloysthat are reported in the literature Most of theexperimental work on Sc in 1xxx-types of alloys hasbeen done on binary AlndashSc alloys with much higherpurity than industrial alloys

Strengthening mechanisms

When the precipitates are larger than a critical size thestrengthening effect is due to the Orowan-mechanism iedislocations can only pass the precipitates by looping Inthis case the strengthening effect of the particles isapproximately inversely proportional to the mean parti-cle spacing When the precipitates can be sheared bydislocations there are a number of strengthening mechan-isms that apply It is proposed by Parker et al108 that thetwo major contributing mechanisms are coherency strainand anti-phase-boundary energy In a recent detailedstudy of strengthening mechanisms in binary AlndashSc alloysby Marquis and colleagues117118 the strengthening fromshear modulus mismatch between the matrix and theprecipitates is also accounted for A qualitatively goodmatch between theoretical strengthening and measuredvalues is achieved in this work both for deformation atroom temperature and at 300uC

Effect of Sc on precipitation strengthening in heat-treatablealloys

Following the AA designation system the traditionalheat-treatable Al-alloys are those that belong to the 2xxx

Roslashyset and Ryum Scandium in aluminium alloys

36 International Materials Reviews 2005 VOL 50 NO 1

series (AlndashCu) 6xxx series (AlndashMgndashSi) and 7xxx series(AlndashZnndashMg) AlndashLi alloys should also be mentionedSeveral investigations have been carried out in order toclarify the effects of Sc on the precipitation behaviour inthese alloy systems

AlndashCu alloys

The precipitation sequence in AlndashCu alloys is oftendescribed as follows

Supersaturated solid solutionRGP-zonesRh0Rh9Rh(Al2Cu)

The highest strength is normally achieved when the h0or h9 precipitates are predominant Typical precipitationheat treatment temperatures for AlndashCu alloys are in therange 160ndash190uC238 which is considerably lower thanthe typical precipitation temperature for Al3ScComparisons of the aging responses of AlndashCu and AlndashCundashSc alloys at 150 and 200uC indicate that there is nonoticeable effect of Sc on the precipitation kinetics ofh9153 It is observed that the h9 precipitates may nucleateon Al3Sc particles153 At 300uC it is observed that h9particles are somewhat smaller in AlndashCundashSc alloys thanin AlndashCu alloys156

AlndashMgndashSi alloys

The following precipitation sequence is commonlyreported for AlndashMgndashSi alloys

Supersaturated solid solutionRGP-zonesRb0Rb9Rb(Mg2Si)

For peak aged alloys the predominant precipitatetype is b0 for which the stoichiometric composition hasrecently been resolved to be Mg5Si6239 Temperatures inthe range 160ndash205uC are typically used for precipitationhardening of these alloys238 Adding both 03 wt-Scand 01 wt-Zr to an Alndash06 wt-Mgndash065 wt-Sialloy does not seem to alter the precipitation kineticsof b0 at 165uC However the hardness increase becauseof precipitation hardening appears to be smaller in theSczZr-containing alloy240 In another investigationadditions of 01 wt-Sc 015 wt-Sc 02 wt-Sc04 wt-Sc and 02 wt-Scz01 wt-Zr were made toan Alndash08 wt-Mgndash07 wt-Si alloy241 Here it wasalso observed that the precipitation kinetics of b0 wasseemingly independent of the Sc additions (Fig 28)TEM observations indicated that the b0 precipitateswere of comparable sizes in the investigated alloys andno interactions between Al3Sc and b0 were observed(Fig 29) In a third study242 where the effect of Sc onthe precipitation in an AlMgSindashSiC metal matrixcomposite was investigated there also does not seemto be any effect on the precipitation kinetics Howevercontrary to the findings of Ref 240 it is reported thatthe Sc addition leads to a higher hardness increase thanin the corresponding Sc free alloy

AlndashMgndashZn alloys

For these alloys the following precipitation sequence isoften ascribed

Table 7 Mechanical properties in non-heat-treatable Al-alloys with Sc

Reference Alloy wt- YS MPa UTS MPa Note

1xxx alloys171 000Sc 15 48 Cast material aged 288uC8 h

023Sc 159 185 Cast material aged 288uC8 h038Sc 199 220 Cast material aged 288uC8 h000Sc 14 49 Cold rolled material (89) aged 288uC8 h023Sc 198 208 Cold rolled material (89) aged 288uC8 h038Sc 240 264 Cold rolled material (89) aged 288uC8 h000Sc 8 34 Cold rolled material quenched from 649uC aged 288uC8 h023Sc 147 157 Cold rolled material quenched from 649uC aged 288uC8 h038Sc 193 199 Cold rolled material quenched from 649uC aged 288uC8 h

121 05Sc 160 ndash Forged material quenched from 635uC aged 250uC50 h23 05Sc 298 319 Hot rolled 288uC cold rolled 69ndash81 aged 288uC4 h112 01Sc 132 166 Hot z cold rolled material quenched from 630uC

aged 320uC133 h148 02Sc 138 ndash Cast material aged 300uC10 h compression test159 04Sc 196 ndash Cast material aged 300uC10 h compression test117 118 03Sc 209 ndash Cast material quenched from 648uC aged 300uC5 h

compression test3xxx alloys171 1Mn 015Sc 216 221 Cold rolled material (89) aged 288uC8 h

1Mn 05Sc 309 323 Cold rolled material (89) aged 288uC8 h186 05Mn 02Mg

026Sc 015Zr162 201 Extruded material solutionised 600uC aged 250uC

5xxx alloys171 1Mg 43 111 Cold rolled material (89) aged 288uC8 h

1Mg 03Sc 288 303 Cold rolled material (89) aged 288uC8 h53Mg 147 259 Cold rolled material (50) wintermediate anneals

at 343uC aged 288uC8 h53Mg 03Sc 368 401 Cold rolled material (50) wintermediate anneals

at 343uC aged 288uC8 h23 2Mg 05Sc 376 401 Hot rolled 288uC cold rolled 69ndash81 aged 288uC4 h

4Mg 05Sc 414 4606Mg 05Sc 433 503

237 4Mg 1Sc 420 525 Cold rolled material (83) aged 320uC1 h148 4Mg 02Sc 194 ndash Cast material aged 300uC10 h compression test

Tensile test data except where noted YS yield strength UTS ultimate tensile strength

Roslashyset and Ryum Scandium in aluminium alloys

International Materials Reviews 2005 VOL 50 NO 1 37

Supersaturated solid solutionRGP-zonesRg9Rg(Zn2Mg)

The maximum hardness is normally achieved whenthe g9 precipitates are predominant Common precipita-tion hardening temperatures are in the range 95ndash180uCand a two-step precipitation heat treatment within thistemperature regime is often used238 It has beenobserved in some investigations that Sc and SczZradditions to AlndashMgndashZn alloys slow down the precipita-tion of g9 somewhat243 Other investigations find thatthere is no effect of Sc on the precipitation behaviour ofg9244245 and yet others report that Sc additionssignificantly speed up the precipitation of g9246 In Ref247 it is found that an Sc addition leads to coarser g9precipitates and it is claimed that this gives an improvedductility of the alloy The strength-loss associated withlarger particle size is reported to be counterbalanced bystrengthening from Al3Sc precipitates

AlndashLi alloys

The precipitation sequence in binary AlndashLi alloys isapparently simple

Supersaturated solid solutionRd9Rd (AlLi)

where d9 is the metastable Al3Li phase which just likeAl3Sc has the L12 type of atomic arrangement Thetypical temperature regime for precipitation of d9 whichis the strengthening phase in this system is approx 150ndash200uC A comparison of the age hardening response ofan Alndash26 wt-Li and an Alndash24 wt-Lindash019 wt-Scalloy at 180uC248 and 200uC161 indicates that the onsetof d9 precipitation is not altered by the presence of ScThe hardness curves for the two alloys are practicallyidentical at 200uC whereas at 180uC the peak hardnesslevel is slightly higher in the AlndashLi than the AlndashLindashScalloy DSC measurements at constant heating ratesindicate that the addition of Sc to an AlndashLi alloysincreases the activation energy for d9 precipitation andmoves the exothermic peak associated with d9 precipita-tion to a higher temperature248 For specimens aged at

either 180uC or 200uC TEM observations reveal that thed9 precipitates are much smaller in the Sc containingalloy than in binary AlndashLi both in the peak agedcondition and in the overaged condition161248 Additionof Sc has also been observed to reduce the size of d9precipitates in other AlndashLi based alloys249ndash251 In an AlndashLindashCundashZr alloy an addition of Sc has been reported toslow down the homogeneous precipitation of d9252253 Ithas been claimed that Sc reduces the quench sensitivityand delays room temperature aging of AlndashLi basedalloys254ndash256

When present in the microstructure before the pre-cipitation of d9 the Al3Sc precipitates may act as effec-tive nucleation sites for d9 The resulting precipitates arespheres of d9 with a core of Al3Sc161249252ndash255257ndash261

Corrosion resistanceAn appreciable amount of data is available on the effectsof Sc on the corrosion behaviour of wrought Al-alloysSome of these effects are apparently derived from theeffects of Sc on the microstructure of the alloys It hasbeen reported that an addition of Sc increases thecorrosion potential (makes it less negative) in pureAl262ndash264 in AlndashZn alloys265266 AlndashMg alloys267 AlndashZnndashMgndashCu alloys264268 AlndashCundashMgndashMn alloys264 andin AlndashCundashLindashMgndashAg alloys264 Even though Sc alsohas been reported to decrease the corrosion potential in

28 Age hardening response at 175uC for Alndash08 wt-Mgndash

07 wt-Si alloy (Base) with additions of 02 wt-Sc

04 wt-Sc and 02 wt-Scz01 wt-Zr from Ref 241

29 TEM images of a b0 precipitates in Alndash08 wt-Mgndash

07 wt-Si alloy and b b0 and Al3(Sc1ndashxZrx) in a similar

alloy with addition of 02 wt-Scz01 wt-Zr from

Ref 241

Roslashyset and Ryum Scandium in aluminium alloys

38 International Materials Reviews 2005 VOL 50 NO 1

AlndashMg alloys269270 it seems that the general trend isthat adding Sc to an alloy makes it slightly more nobleThe change in corrosion potential is much morepronounced when Sc is added in amounts larger thanthe eutectic composition263 ie there is a considerablecontribution from primary or eutectic Al3Sc to theoverall potential It has also been demonstrated that thechange in corrosion potential caused by Sc can dependon the heat treatment applied to the alloy267268

Even though the corrosion potential is an essentialparameter in establishing the corrosion behaviour of analloy an increase in the corrosion potential does notnecessarily imply an improved self-corrosion resistanceHowever measurements of corrosion rates and passiva-tion current densities strongly suggest that the self-corrosion resistance in general is considerably improvedwhen Sc is added to wrought Al-alloys263264267 Someobserved variations in corrosion potential and passiva-tion current densities with Sc content in binary AlndashScalloys are plotted in Fig 30

Material failure in corrosive environments is often dueto localised corrosion attacks which may propagaterapidly even though the bulk material has a goodresistance against general corrosion It has been pointedout that hypereutectic additions of Sc may lead tomicrogalvanic corrosion beside primary Al3Sc parti-cles264 In AlndashMg alloys grain boundary precipitation ofAl8Mg5 can lead to localised corrosion attacks such asintergranular corrosion (IGC) exfoliation corrosion(EC) and stress corrosion cracking (SCC) In wroughtmaterial such precipitation may occur in the 60ndash180uCtemperature regime and heating in this temperaturerange is referred to as lsquosensitationrsquo An AlndashMgndashSc alloywas found to be immune against intergranular corrosionand have moderate susceptibility to exfoliation corro-sion after annealing at 350uC271 After sensitation heattreatments severe IGC and EC was observed but notquite as severe as in a corresponding alloy without ScAs for SCC the AlndashMgndashSc alloy was found to be highlyresistant271 In another study it was found that additionof 056 wt-Sc reduces the SCC susceptibility of an Alndash68 wt-Mg alloy in the as-rolled state and afterannealing at 250uC whereas in a sensitised specimenthe SCC susceptibility is somewhat increased by the Scaddition272 A third investigation found that Sc has nomeasurable detrimental effect on the SCC susceptibilityof sensitised Alndash5Mgndash015Zr alloy273 SCC is also a

severe problem in high strength AlndashZnndashMgndashCu alloys Ithas been shown that small Sc additions are effective inreducing the SCC sensitivity of these alloys244246268274

Use of Sc-containing Al alloysA systematic development of Sc-containing aluminiumalloys took place in the former USSR in the 1980s andthe interest for Sc as an alloying element in aluminiumalloys hit the western world approximately 10 yearslater Even though a number of improvements in Alalloys achieved by Sc addition have been demonstratedthe current uses of such alloys are very limited This isrelated to the very high price of scandium

In Russia some parts of military aircraft are made ofSc-containing AlndashLi alloys In the western world themain usage of Sc-containing alloys is for sportsequipment Ashurst Technology and Kaiser Aluminumdeveloped a Sc-containing 7xxx alloy for baseball andsoftball bats which was introduced to the Americanmarket in 1997 by Easton Alcoa soon followed with aSc-containing alloy for a competing brand of batsLouisville Slugger Since then several new and improvedSc-containing alloys for bats have been introduced tothe market The purpose of adding Sc is to increase theyield strength of the alloy allowing for a down-gaugingof the wall thickness which in turn gives a strongerlsquospring-rsquo or lsquotrampoline-rsquo effect when the ball hits thebat

Shortly after the introduction of the Sc containingbats Easton also launched Sc-containing 7xxx tubingfor bicycle frames Just as in the bats Sc increases theyield strength of the alloy allowing for down-gauging oftube wall thickness and a corresponding weight reduc-tion of the bicycle frame An Italian manufacturer ofbicycle tubing Dedacciai also delivers tubes in a Sc-containing 7xxx alloy

Other sports equipment made from Sc-containingaluminium alloys includes lacrosse sticks and tent polesSmith and Wesson has also introduced a series ofhandguns where the frame is made from a Sc-containingAl alloy

A common factor for the items mentioned above isthat the material cost is only a minor part of the totalmanufacturing cost of the end product and also thatthese products are aimed at a group of customers thathave a certain awareness of new materials Both baseballbats and bicycle frames have been marketed aslsquoscandium alloyrsquo even though the Sc content is muchlower than 1

Currently AlndashSc master alloys for the production ofSc-containing Al alloys are available at a price thatcorresponds to US$ 2000 per kg of Sc This means that ifone wants to add 02 wt-Sc to an alloy which is afairly common content one also increases the price ofthe alloy by US$ 4 per kg alloy Depending on the alloytype Sc is added to this represents a tripling orquadrupling of the price of the alloy There are notmany existing products where such an increase inmaterial cost can be justified In order to see awidespread use of Sc in high-volume products the Scprice has to come down considerably Actually the priceof adding Sc to Al alloys has gone down by a factor 3ndash10over the last 10ndash15 years and substantial price reduc-tions are also expected in the future

30 Observed variations in corrosion potential and passi-

vation current densities with Sc content in binary Alndash

Sc alloys based on data from Ref 263

Roslashyset and Ryum Scandium in aluminium alloys

International Materials Reviews 2005 VOL 50 NO 1 39

The current production of AlndashSc master alloys isbased upon and will continue to be based upon for theforeseeable future the reduction of Sc2O3 or other Sccompounds directly in molten aluminium It is notnecessary as many tend to believe to take the route viametallic Sc Thus the price of AlndashSc master alloy isgoverned by the price of Sc2O3 or other Sc compoundsin question and not by the price of metallic scandiumThe Sc2O3 which is the main source for todayrsquos AlndashScmaster alloy production comes from stockpiles in theformer USSR These stockpiles will be exhausted withina few years and new reliable sources of Sc2O3 or otherSc compound production are sought It turns out thatthe most economically viable option that has beendisclosed so far is the processing of Red Mud from theBayer process of extracting alumina from bauxiteScandium is enriched in the Red Mud and is extractedfrom a Red Mud aqueous slurry by selective leachingsubsequent ion-exchange procedure and finally a liquidndashliquid extraction procedure It is not required to build aseparate lsquoSc factoryrsquo to do this but rather build an lsquoadd-onrsquo to existing Bayer process plants Such a processroute is expected to bring down the price of Sc2O3

considerably which in turn means that AlndashSc masteralloy price should drop accordingly Preliminary ana-lyses suggest a price of approx US$ 400 per kg Sc in themaster alloy which translates to an added cost of 80cent per kilo when 02 wt-Sc is added to an aluminiumalloy This is also a considerable increase in the materialcost but with such prices one should expect to see Sccontaining alloys in many more applications than whatis the case at the present time

Concluding remarksThe body of published investigations on Al-based alloyswith Sc addition provides a sound basis of knowledgefor metallurgists that want to look into the possibility ofenhancing the performance of a wrought Al-alloy byadding Sc to it Ternary AlndashScndashX phase diagrams areavailable for practically every technologically importantalloying element in Al The effect of a wide range ofternary alloying elements on the precipitation behaviourof Al3Sc is accounted for It has been shown that theAl3Sc phase can be effective as a grain refiner adispersoid former and a precipitate hardening agentand some of the underlying conditions for achieving thedesired Al3Sc formation have been outlined Addingsome Zr together with Sc has proven to be beneficial Itmay lead to effective grain refinement at a lower Sc levelbut the most prominent effect is the refinement indispersoid distribution that can be achieved An addi-tion of Sc has little if any effect on precipitation in the2xxx 6xxx and 7xxx alloy systems and some effects onthe precipitation in AlndashLi based alloys With respect tocorrosion behaviour adding Sc to an Al-alloy does ingeneral seem to make the alloy slightly more noble andto increase its self-corrosion resistance Scandium-containing Al alloys have very few uses at the presenttime as a result of the high price of scandium The priceof Sc is expected to decrease significantly in the futureand this should lead to the disclosure of moreapplications where it is economically feasible to takeadvantage of the improved properties of some Sc-containing aluminium alloys

References1 D R Lide lsquoCRC handbook of chemistry and physicsrsquo 71st edn

4ndash29 1990 Boston USA CRC Press

2 E M Savitsky V F Terehova I V Burov and O P Naumkin

Proc Fourth Conf on lsquoRare earth researchrsquo Phoenix Arizona

USA April 1964 409ndash420

3 E M Savitskii V F Terekhova I V Burov O P Naumkin and

I A Markova Inorg Mater 1965 1 1503ndash1512

4 O P Naumkin V T Terekhova and E M Savitskiy Russ

Metall 1965 (4) 128ndash136

5 W G Moffatt lsquoThe handbook of binary phase diagramsrsquo 1981

Schenectady NY USA General Electric Co

6 E A Brandes (ed) lsquoSmithells metals reference bookrsquo 6th edn

1983 London UK Butterworths

7 R P Elliott and F A Shunk Bull Alloy Phase Diagrams 1981

2 (2) 222ndash223

8 K A Gschneider Jr and F W Calderwood Bull Alloy Phase

Diagrams 1989 10 34ndash36

9 H Okamoto J Phase Equil 1991 12 612ndash613

10 J L Murray J Phase Equil 1998 19 380ndash384

11 M E Drits E S Kadaner T V Dobatkina and N I Turkina

Russ Metall 1973 (4) 152ndash154

12 S-I Fujikawa M Sugaya H Takei and K-I Hirano J Less-

Common Met 1979 63 87ndash97

13 N Blake and M A Hopkins J Mater Sci 1985 20 2861ndash2867

14 V I Kononenko and S V Golubev Russ Metall 1990 (2) 193ndash

195

15 T B Massalski J L Murray L H Bennett and H Baker (eds)

lsquoBinary alloy phase diagramsrsquo 1986 Metals Park OH USA

ASM

16 G Cacciamani P Riani G Borzone N Parodi A Saccone

R Ferro A Pisch and R Schmid-Fetzer Intermetallics 1999 7

101ndash108

17 H Okamoto J Phase Equil 2000 21 310

18 A F Norman P B Pragnell and R S McEwen Acta Mater

1998 46 5715ndash5732

19 I N Pyagai and A V Vakhobov Russ Metall 1990 (5) 50ndash52

20 C L Fu J Mater Res 1990 5 971ndash979

21 X Lu and Y Wang Calphad 2002 26 555ndash561

22 R R Sawtell and J W Morris Jr Proc lsquoDispersion strengthened

aluminium alloysrsquo Phoenix Arizona USA January 1988 409ndash

420

23 R R Sawtell and C L Jensen Metall Trans A 1990 21A 421ndash

430

24 L A Willey Unpublished research Alcoa 1970 Data points are

extracted from Ref 10

25 N I Turkina and V I Kuzmina Russ Metall 1976 (4) 179ndash

183

26 T Torma E Kovacs-Csetenyi I Vitanyi M Butova and

J Stepanov Proc 6th Int Symp on lsquoHigh purity materials in

science and technologyrsquo Akademie der Wissenschaften der DDR

Dresden Germany May 1985 388ndash389

27 A L Berezina V A Volkov B P Domashnikov and K V

Chuistov Metallofizika 1987 9 (5) 43ndash47

28 H-H Jo J Korean Inst Metals 1990 28 499ndash504

29 H-H Jo and S-I Fujikawa Mater Sci Eng 1993 A 171 151ndash

161

30 S Celotto and T J Bastow Philos Mag A 2000 80 1111ndash1125

31 J Roslashyset and N Ryum submitted to Mater Sci Eng

32 M E Drits L S Toropova Yu G Bykov F L Gushchina V I

Elagin and Yu A Filatov Russ Metall 1983 (1) 150ndash153

33 L S Toropova D G Eskin M L Kharakterova and T V

Dobatkina lsquoAdvanced aluminum alloys containing scandium

structure and propertiesrsquo 1998 Amsterdam The Netherlands

Gordon and Breach Science Publishers

34 V V Cherkasov P P Pobezhimov L P Nefedova E V Belov

and G M Kuznetsov Met Sci Heat Treat 1996 (6) 268ndash270

35 Kh O Odinaev I N Ganiev V V Kinzhibalo and B Ya

Kotur Dokl Akad Nauk Tadzh SSR 1989 32 37ndash38

36 Kh O Odinaev I N Ganiev and A V Vakhobov Russ Metall

1991 (4) 200ndash203

37 J Grobner R Schmid-Fetzer A Pisch G Cacciamani P Riani

N Parodi G Borzone A Saccone and R Ferro Z Metallkd

1999 90 872ndash880

38 E A Marquis and D N Seidman Microsc Microanal 2002 8

(Suppl 2) 1100CDndash1101CD

39 A Pisch J Grobner and R Schmid-Fetzer Mater Sci Eng A

2000 A 289 123ndash129

Roslashyset and Ryum Scandium in aluminium alloys

40 International Materials Reviews 2005 VOL 50 NO 1

40 C Xia F Zeng and Y Gu Trans Nonferrous Met Soc China

2003 13 1124ndash1127

41 M Yu Teslyuk and V S Protasov Sov Phys Crystallogr 1966

10 470ndash471

42 M L Kharakterova and T V Dobatkina Russ Metall 1988

(6) 175ndash178

43 M L Kharakterova Russ Metall 1991 (4) 195ndash199

44 L S Toropova M L Kharakterova and D G Eskin Russ

Metall 1992 (3) 194ndash199

45 P Riani L Arrighi R Marazza D Mazzone G Zanicchi and

R Ferro J Phase Equil Diff 2004 25 22ndash52

46 A T Tyvanchuk T I Yanson B Ya Kotur O S Zarechnyuk

and M L Kharakterova Russ Metall 1988 (4) 190ndash192

47 L L Rokhlin T V Dobatkina and M L Kharakterova Powder

Metall Met Ceram 1997 36

48 A Z Ikromov I N Ganiev and V V Kinzhibalo Dokl Akad

Nauk Tadzh SSR 1990 (6) 391ndash392

49 I N Ganiev A Z Ikromov and V G Khudoiberdiev Russ

Metall 1995 (3) 125ndash127

50 I N Fridlyander L L Rokhlin T V Dobatkina and N I

Nikitina Met Sci Heat Treat 1993 (10) 567ndash571

51 I N Fridlyander L L Rokhlin T V Dobatkina V V

Kinzhibalo and A T Tyvanchuk Russ Metall 1998 (1) 161ndash

166

52 R A Emigh E L Bradley and J W Morris Jr in lsquoLight-weight

alloys for aerospace applications IIrsquo (ed E W Lee and N J

Kim) 27ndash43 1991 TMS

53 L S Toropova A N Kamardinkin V V Kindzhibalo and A T

Tyvanchuk Phys Met Metall 1990 70 (6) 106ndash110

54 A N Kamardinkin T V Dobatkina and T D Rostova Russ

Metall 1991 (4) 216ndash218

55 L S Torodskaya T V Dobatkina and A N Kamardinkin

Russ Metall 1992 (5) 128ndash131

56 E M Sokolovskaya E F Kazakova E I Poddyakova and A

A Ezhov Met Sci Heat Treat 1997 (5) 211ndash213

57 Y Harada and D C Dunand Mater Sci Eng 2002 A 329ndash331

686ndash695

58 N E Drits L S Toropova and F L Gushchina Russ Metall

1984 (4) 229ndash232

59 E M Sokolovskaya E F Kazakova V A Alikhanov and E V

Zhuravleva Moscow Univ Chem Bull 1997 52 (5) 70ndash72

60 E M Sokolovskaya E F Kazakova and E I Poddyakova Met

Sci Heat Treat 1989 (11) 837ndash839

61 G M Cheldieva E F Kazakova E M Sokolovskaya and N I

Kaloev Russ Metall 1990 (6) 87ndash90

62 E M Sokolovskaya E F Kazakova and O D-S Kendivan

Russ Metall 1998 (4) 135ndash137

63 N G Bukhanko E F Kazakova and E M Sokolovskaya Russ

Metall 2001 (4) 425ndash431

64 E D Trubnyakova O I Bodak I N Ganiev and A V

Vakhobov Russ Metall 1987 (3) 219ndash222

65 I N Fridlyander and L V Molchanova Russ Metall 2003 (5)

476ndash480

66 R A Altynbaev S Kh Khairidinov and A V Vakhobov Russ

Metall 1987 (4) 194ndash196

67 J C Schuster and J Bauer J Less-Common Met 1985 109

345ndash350

68 L L Rokhlin A S Fridman T V Dobatkina and D G Eskin

Russ Metall 1991 (6) 146ndash148

69 A S Fridman T V Dobatkina and E V Muratova Russ

Metall 1992 (1) 207ndash209

70 C Xia F Zeng and Y Gu Trans Nonferrous Met Soc China

2003 13 546ndash552

71 F Zeng C Xia and Y Gu J Alloys Comp 2004 363 175ndash181

72 L L Rokhlin T V Dobatkina N R Bochvar and E V Lysova

J Alloys Comp 2004 367 10ndash16

73 T V Dobatkina A S Fridman and E V Muratova Russ

Metall 1992 (5) 125ndash127

74 I N Fridlyander L L Rokhlin N R Bochvar E V Lysova

and O V Boteva Russ Metall 2001 (6) 661ndash666

75 V N Rechkin L K Lamikhov and T I Samsonova Sov Phys

Crystallogr 1964 9 325ndash327

76 I I Zalutskii and P I Kripyakevich Sov Phys Crystallogr

1967 12 341ndash343

77 T J Bastow C T Forwood M A Gibson and M E Smith

Phys Rev B 1998 58 2988ndash2997

78 K Fukunaga M Kolbe K Yamada and Y Miura Mater Sci

Eng 1997 A 234ndash236 594ndash597

79 E P George J A Horton W D Porter and J H Schneibel

J Mater Res 1990 5 1639ndash1648

80 E P George D P Pope C L Fu and J H Schneibel ISIJ Int

1991 31 1063ndash1075

81 Y Harada and D C Dunand Acta Mater 2000 48 3477ndash3487

82 J H Schneibel and E P George Scripta Metall Mater 1990 24

1069ndash1074

83 J H Schneibel and P M Hazzledine Mater Res Soc Symp

Proc 1991 213 323ndash328

84 J H Schneibel and P M Hazzledine J Mater Res 1992 7

868ndash875

85 C J Sparks E D Specht G E Ice P Zschack and J Schneibel

Mater Res Soc Symp Proc 1991 213 363ndash368

86 J Tarnacki and Y-W Kim Scripta Metall Mater 1989 23

1063ndash1068

87 M Asta V Ozolins and C Woodward JOM 2001 53 (9) 16ndash

19

88 M E Drits L S Toropova F L Gushchina and S G Fedotov

Sov Non-Ferrous Met Res 1984 12 83ndash85

89 Y Harada and D C Dunand Scripta Mater 2003 48 219ndash222

90 C Woodward M Asta G Kresse and J Hafner Phys Rev B

2001 63 094103-1-6

91 J-H Xu and A J Freeman Phys Rev B 1990 41 12553ndash12561

92 M F Bartholomeusz and J A Wert Acta Metall Mater 1992

40 673ndash682

93 G Bester and M Fahnle J Phys Condens Matter 2001 13

11551ndash11565

94 C L Fu and M H Yoo Proc lsquoOrdered intermetallics ndash physical

metallurgy and mechanical behaviorrsquo Irsee Germany June 1991

155ndash164

95 K Fukunaga T Shouji and Y Miura Mater Sci Eng 1997 A

239ndash240 202ndash205

96 D P Pope Proc lsquoOrdered intermetallics ndash physical metallurgy

and mechanical behaviorrsquo Irsee Germany June 1991 143ndash153

97 J-S Wang Acta Mater 1998 46 2663ndash2674

98 M H Yoo and C L Fu Mater Sci Eng 1992 A 153 470ndash478

99 R W Hyland Jr and R C Stiffler Scripta Metall Mater 1991

25 473ndash477

100 I G Brodova I V Polents O A Korzhavina P S Popelrsquo I P

Korshunov and V O Esin Melts 1992 4 392ndash397

101 I G Brodova O A Chikova I V Polents P S Popelrsquo and V O

Esin Casting Processes 1992 1 (2) 158ndash160

102 I G Brodova D V Bashlikov and I V Polents Mater Sci

Forum 1998 269ndash272 589ndash594

103 K B Hyde A F Norman and P B Pragnell Mater Sci Forum

2000 331ndash337 1013ndash1018

104 K B Hyde A F Norman and P B Pragnell Acta Mater 2001

49 1327ndash1337

105 J Roslashyset and N Ryum Proc 6th Int Conf on lsquoAluminum

alloysrsquo Toyohashi Japan July 1998 793ndash798

106 V I Elagin V V Zakharov and T D Rostova Met Sci Heat

Treat 1993 (6) 317ndash319

107 R W Hyland Jr Metall Trans A 1992 23A 1947ndash1955

108 B A Parker Z F Zhou and P Nolle J Mater Sci 1995 30

452ndash458

109 C L Rohrer M D Asta S M Foiles and R W Hyland Jr

Mater Res Soc Symp Proc 1996 398 477ndash482

110 G M Novotny and A J Ardell Mater Sci Eng 2001 A 318

144ndash154

111 J D Robson M J Jones and P B Pragnell Acta Mater 2003

51 1453ndash1468

112 C Tan Z Zheng and B Wang Proc 3rd Int Conf on

lsquoAluminium alloysrsquo Vol I NTH Trondheim Norway June

1992 290ndash294

113 M Nakayama A Furuta and Y Miura Mater Trans JIM

1997 38 852ndash857

114 E A Marquis and D N Seidman Acta Mater 2001 49 1909ndash

1919

115 M J Jones and F J Humphreys Acta Mater 2003 51 2149ndash

2159

116 E A Marquis D N Seidman and D C Dunand in lsquoCreep

deformation fundamentals and applicationsrsquo (ed R S Mishra

J C Earthman and S V Raj) 299ndash308 2002 TMS

117 D N Seidman E A Marquis and D C Dunand Acta Mater

2002 50 4021ndash4035

118 E A Marquis D N Seidman and D C Dunand Acta Mater

2003 51 285ndash287

119 M E Drits L S Toropova U G Bikov and G K Anastaseva

Proc lsquoDiffusion in metals and alloysrsquo Tihany Hungary Augustndash

September 1982 616ndash623

120 V I Elagin V V Zakharov and T D Rostova Met Sci Heat

Treat 1983 (7) 546ndash549

Roslashyset and Ryum Scandium in aluminium alloys

International Materials Reviews 2005 VOL 50 NO 1 41

121 M Ye Drits L B Ber Yu G Bykov L S Toropova and G K

Anastaseva Phys Met Metall 1984 57 (6) 118ndash126

122 M E Drits L S Toropova and Yu G Bykov Sov Non-Ferrous

Met Res 1985 13 309ndash314

123 V I Yelagin V V Zakharov S G Pavlenko and T D Rostova

Phys Met Metall 1985 60 (1) 88ndash92

124 N Sano Y Hasegawa K Hono H Jo K Hirano H W

Pickering and T Sakurai Journal de Physique 1987 48 C6 337ndash

342

125 N Sano H-H Jo K-I Hirano and T Sakurai J Jpn Inst

Metals 1989 39 444ndash450

126 N Sano H Jo K Hirano and T Sakurai Proc Second Int

Conf on lsquoAluminium alloysrsquo Beijing China October 1990 549ndash

554

127 Y Miura M Nakayama and A Furuta Proc lsquoAspects of high

temperature deformation and fracture in crystalline materialsrsquo

Nagoya Japan July 1993 255ndash262

128 Y W Riddle and T H Sanders Jr Mater Sci Forum 2000

331ndash337 939ndash944

129 Y W Riddle M McIntosh and T H Sanders Jr in lsquoLightweight

alloys for aerospace application VIrsquo (ed K Jata E W Lee

W Frazier and N J Kim) 25ndash39 2001 TMS

130 M E Drits J Dutkiewicz L S Toropova and J Salawa Crystal

Res Technol 1984 19 1325ndash1330

131 Y W Riddle MSc thesis Georgia Tech GA USA 1998

132 T J Bastow and S Celotto Mater Sci Eng 2003 C 23 757ndash

762

133 M C Carroll M J Mills G S Daehn P I Gouma M F

Savage and B R Dunbar in lsquoAutomotive Alloys 1999rsquo (ed

S Das) 239ndash246 2000 TMS

134 E Clouet M Nastar and C Sigli Phys Rev B 2004 69 064109-

1-14

135 V V Zakharov Met Sci Heat Treat 1997 (2) 61ndash66

136 J W Christian lsquoThe theory of transformation in metals and

alloysrsquo 2nd edn 1975 Pergamon Press Ltd

137 A L Berezina V A Volkov B P Domashnikov S V Ivanov

and K V Chuistov Phys Metals 1990 10 296ndash304

138 S-I Fujikawa and S Sakauchi Proc 6th Int Conf on

lsquoAluminum alloysrsquo Toyohashi Japan July 1998 805ndash810

139 Y S Touloukian R K Kirby R E Taylor and P D Desai

(eds) lsquoThermal expansion metallic elements and alloysrsquo 1975

New York Plenum

140 J Roslashyset and N Ryum submitted to Scripta Mater

141 R O Simmons and R W Balluffi Phys Rev 1960 117 52ndash61

142 M Ocko E Babic R Krsmik E Girt and B Leontic J Phys F

Metals Phys 1976 6 703ndash707

143 M J Jones and F J Humphreys Proc First Joint Int Conf on

lsquoRecrystallization and grain growthrsquo Aachen Germany August

2001 Springer Verlag 1287ndash1292

144 S Iwamura M Nakayama and Y Miura Mater Sci Forum

2002 396ndash402 1151ndash1156

145 S Iwamura and Y Miura Acta Mater 2004 52 591ndash600

146 M Asta S M Foiles and A A Quong Phys Rev B 1998 57

11265ndash11275

147 R W Hyland Jr M Asta S M Foiles and C L Rohrer Acta

Mater 1998 46 3667ndash3678

148 J Roslashyset and N Ryum Proc 4th Int Conf on lsquoAluminium

alloysrsquo Vol I Atlanta GA USA September 1994 194ndash201

149 M E Drits L S Toropova G K Anastaseva and G L

Nagornichnykh Russ Metall 1984 (3) 192ndash195

150 E A Marquis D N Seidman and D C Dunand Acta Mater

2003 51 4751ndash4760

151 M E Drits L S Toropova and Yu G Bykov Met Sci Heat

Treat 1983 (7) 550ndash554

152 V V Zakharov and T D Rostova Met Sci Heat Treat 1995

(2) 65ndash69

153 M Nakayama and Y Miura Proc 4th Int Conf on lsquoAluminium

alloysrsquo Vol I Atlanta GA USA September 1994 538ndash545

154 M Nakayama and Y Miura J Jpn Inst Light Metals 1996 46

275ndash279

155 M Nakayama T Okuyama and Y Miura Mater Sci Forum

2000 331ndash337 927ndash932

156 M Nakayama T Okuyama and Y Miura Proc 6th Int Conf

on lsquoAluminum alloysrsquo Toyohashi Japan July 1998 517ndash522

157 M L Kharakterova D G Eskin and L S Toropova Acta

Metall Mater 1994 42 2285ndash2290

158 V I Elagin V V Zakharov and T D Rostova Met Sci Heat

Treat 1992 (1) 37ndash45

159 H Wiik Siv Ing thesis NTH Institute of Metallurgy

Trondheim Norway 1995

160 J Roslashyset H Hovland and N Ryum Mater Sci Forum 2002

396ndash402 619ndash624

161 Y Miura K Horikawa K Yamada and M Nakayama Proc

4th Int Conf on lsquoAluminium alloysrsquo Vol II Atlanta GA USA

September 1994 161ndash168

162 Y W Riddle PhD thesis Georgia Tech GA USA 2000

163 B Forbord W Lefebvre F Danoix H Hallem and

K Marthinsen Scripta Mater 2004 51 333ndash337

164 J D Robson Acta Mater 2004 52 1409ndash1421

165 C B Fuller J L Murray and D N Seidman submitted to Acta

Mater 2004

166 M G Mousavi C E Cross and Oslash Grong Sci Technol Weld

Joining 1999 4 381ndash388

167 J S Vetrano S M Bruemmer L M Pawlowski and I M

Robertson Mater Sci Eng 1997 A 238 101ndash107

168 Y W Riddle and T H Sanders Jr Mater Sci Forum 2000

331ndash337 799ndash803

169 G M Khan A O Nikiforov V V Zakharov and I I Novikov

Tsvetnye Metally 1993 34 (11) 43ndash45

170 Z Horita M Furukawa M Nemoto A J Barnes and T G

Langdon Acta Mater 2000 48 3633ndash3640

171 L A Willey US Patent 3 619 181 9 November 1971

172 L K Lamikhov and G V Samsonov Tsvetnye Metally 1964 5

(8) 77ndash80

173 A L Berezina K V Chuistov N I Kolobnev L B

Khokhlatova and T A Monastyrskaya Mater Sci Forum

2002 396ndash402 741ndash746

174 F A Fasoyinu J Thomson D Cousineau T Castles and M

Sahoo Proc 6th Int AFS Conf on lsquoMolten aluminum

processingrsquo Orlando FL USA November 2001

175 Z Yin Q Pan Y Zhang and F Jiang Mater Sci Eng 2000

A 280 151ndash155

176 I I Novikov and O E Grushko Mater Sci Technol 1995 11

926ndash932

177 D Cousineau M Sahoo P D Newcombe T Castles and F A

Fasoyinu Proc lsquoAFS 105th casting congressrsquo Dallas TX USA

AprilndashMay 2001 157ndash184

178 C E Cross and Oslash Grong Proc 6th Int Conf on lsquoAluminum

alloysrsquo Toyohashi Japan July 1998 1441ndash1446

179 F A Costello J D Robson and P B Prangnell Mater Sci

Forum 2002 396ndash402 757ndash762

180 K B Hyde A F Norman and P B Prangnell Mater Sci

Forum 2002 396ndash402 39ndash44

181 M E Drits S G Pavlenko L S Toropova Yu G Bukov and

L B Ber Sov Phys Dokl 1981 26 (3) 344ndash346

182 A M Drits and B A Kopeliovich Russ Metall 1985 (4) 147ndash

151

183 V G Davydov V I Elagin V V Zakharov and T D Rostova

Met Sci Heat Treat 1996 (8) 347ndash352

184 M E Drits L S Toropova Yu G Bykov L B Ber and S G

Pavlenko Russ Metall 1982 (1) 148ndash152

185 T D Rostova V G Davydov V I Yelagin and V V Zakharov

Mater Sci Forum 2000 331ndash337 793ndash798

186 Y W Riddle H Hallem and N Ryum Mater Sci Forum 2002

396ndash402 563ndash568

187 J Roslashyset and Y W Riddle Proc 9th Int Conf on lsquoAluminium

alloysrsquo Brisbane Australia August 2004 1210ndash1215

188 A M Diskin V K Portnoi A M Drits and A A Alalykin Sov

Non-Ferrous Met Res 1986 14 499ndash500

189 R R Sawtell P E Bretz and C L Jensen US Patent 4 689 090

25 August 1987

190 G A Salishchev Yu B Timoshenko and R A Saitova Proc

Second Int Conf on lsquoAluminium alloysrsquo Beijing China October

1990 413ndash415

191 T G Nieh R Kaibyshev L M Hsiung N Nguyen and

J Wadsworth Scripta Mater 1997 36 1011ndash1016

192 T G Nieh L M Hsiung J Wadsworth and R Kaibyshev Acta

Mater 1998 46 2789ndash2800

193 J S Vetrano C H Henager Jr M T Smith and S M

Bruemmer in lsquoHot deformation of aluminum alloys IIrsquo (ed T R

Bieler L A Lalli and S R MacEwen) 407ndash418 1998 TMS

194 J S Vetrano C H Henager Jr S M Bruemmer Y Ge and

C H Hamilton in lsquoSuperplasticity and Superplastic Forming

1998rsquo (ed A K Gosh and T R Bieler) 89ndash97 1998 TMS

195 V Y Gertsman J S Vetrano C H Henager Jr and S M

Bruemmer Proc First Joint Int Conf on lsquoRecrystallization and

grain growthrsquo Aachen Germany August 2001 Springer Verlag

2001 837ndash842

196 Y Xiao C Gao H Ma and S Tian Trans Nonferrous Met Soc

China 2001 11 235ndash238

Roslashyset and Ryum Scandium in aluminium alloys

42 International Materials Reviews 2005 VOL 50 NO 1

197 A Gholinia F J Humphreys and P B Prangnell Acta Mater

2002 50 4461ndash4476

198 A Gholinia F J Humphreys and P B Prangnell Mater Sci

Forum 2002 408ndash412 1519ndash1524

199 S Komura P B Berbon M Furukawa Z Horita M Nemoto

and T G Langdon Scripta Mater 1998 38 1851ndash1856

200 S Komura P B Berbon A Utsunomiya M Furukawa

Z Horita M Nemoto and T G Langdon in lsquoHot deformation

of aluminum alloys IIrsquo (ed T R Bieler L A Lalli and S R

MacEwen) 125ndash138 1998 TMS

201 S Komura Z Horita M Furukawa M Nemoto and T G

Langdon J Mater Res 2000 15 2571ndash2576

202 S Komura M Furukawa Z Horita M Nemoto and T G

Langdon Mater Sci Eng 2001 A 297 111ndash118

203 S Komura Z Horita M Furukawa M Nemoto and T G

Langdon Metall Mater Trans A 2001 32A 707ndash716

204 Z Horita M Furukawa K Oh-ishi M Nemoto and T G

Langdon Proc Fourth Int Conf on lsquoRecrystallization and

related phenomenarsquo (ed T Sakai and H G Suzuki) 1999 The

Japan Institute of Metals 301ndash308

205 Z Horita S Komura P B Berbon A Utsunomiya

M Furukawa M Nemoto and T G Langdon Mater Sci

Forum 1999 304ndash306 91ndash96

206 Z Horita S Lee S Ota K Neishi and T G Langdon Mater

Sci Forum 2001 357ndash359 471ndash476

207 Z Horita T Fujinami K Sato S B Kang H W Kim and T G

Langdon in Proc James T Staley Honorary Symposium on

Aluminum Alloys lsquoAdvances in the metallurgy of aluminum

alloysrsquo (ed M Tiryakioglu) 271ndash275 2001 ASM

208 P B Berbon S Komura A Utsunomiya Z Horita

M Furukawa M Nemoto and T G Langdon Mater Trans

JIM 1999 40 772ndash778

209 M Nemoto Z Horita M Furukawa and T G Langdon Mater

Sci Forum 1999 304ndash306 59ndash66

210 M Furukawa Z Horita M Nemeto and T G Langdon Proc

lsquoLight Metals 1999rsquo Quebec City PQ Canada August 1999 583ndash

592

211 M Furukawa K Oh-ishi S Komura A Yamashita Z Horita

M Nemeto and T G Langdon Mater Sci Forum 1999 304ndash

306 97ndash102

212 M Furukawa A Utsunomiya K Matsubara Z Horita and

T G Langdon Acta Mater 2001 49 3829ndash3838

213 M Furukawa A Utsunomiya S Komura Z Horita M Nemoto

and T G Langdon Mater Sci Forum 2001 357ndash359 431ndash436

214 M Furukawa Z Horita and T G Langdon in Proc James T

Staley Honorary Symposium on Aluminum Alloys lsquoAdvances in

the metallurgy of aluminum alloysrsquo (ed M Tiryakioglu) 47ndash56

2001 ASM

215 M Furukawa Z Horita M Nemoto and T G Langdon Mater

Sci Eng 2002 A 324 82ndash89

216 M Furukawa Z Horita and T G Langdon in lsquoUltrafine grained

materials IIrsquo (ed Y T Zhu T G Langdon R S Mishra S L

Semiatin M J Saran and T C Lowe) 459ndash468 2002 TMS

217 T G Langdon M Furukawa Z Horita and M Nemoto Proc

NATO Advanced Research Workshop on lsquoInvestigations and

applications of severe plastic deformationrsquo Moscow August

1999 NATO Science Series Series 3 High Technology vol 80

Kluwer Academic Publishers The Netherlands 2000 149ndash154

218 S Lee H Akamatsu A Utsunomiya K Neishi M Furukawa

Z Horita and T G Langdon Proc Thermec 2000 Las Vegas

USA December 2000

219 S Lee A Utsunomiya H Akamatsu K Neishi M Furukawa

Z Horita and T G Langdon Acta Mater 2002 50 553ndash564

220 A Yamashita D Yamaguchi Z Horita and T G Langdon

Mater Sci Eng 2000 A 287 100ndash106

221 K Oh-ishi Z Horita D J Smith and T G Langdon J Mater

Res 2001 16 583ndash589

222 H Akamatsu T Fujinami Z Horita and T G Langdon Scripta

Mater 2001 44 759ndash764

223 S Ota H Akamatsu K Neishi M Furukawa Z Horita and

T G Langdon Mater Trans 2002 43 2364ndash2369

224 K Furuno H Akamatsu K Oh-ishi M Furukawa Z Horita

and T G Langdon Acta Mater 2004 52 2497ndash2507

225 I N Fridlyander O G Senatorova N A Ryazanova and A O

Nikiforov Mater Sci Forum 1994 170ndash172 345ndash349

226 J N Fridlyander and O G Senatorova Mater Sci Forum 1996

217ndash222 1813ndash1818

227 J Liu and D J Chakrabarti Acta Mater 1996 44 4647ndash4661

228 O G Senatorova A N Uksusnikov J N Fridlyander

J Koshorst R R Romanova N A Ryazanova A Galliot

and V V Cherkassov Proc 6th Int Conf on lsquoAluminum alloysrsquo

July 1998 Toyohashi Japan 589ndash593

229 R A Emigh E L Bradley and J W Morris Jr in

lsquoSuperplasticity in aerospace IIrsquo (ed T R McNelley and H C

Heikkenen) 303ndash315 1990 TMS

230 E L Bradley III R A Emigh and J W Morris Jr Scripta

Metall Mater 1991 25 717ndash721

231 N I Kolobnev L B Khokhlatova V D Makarov E Yu

Semenova and V V Redchits Proc Sixth Int Aluminiumndash

Lithium Conference Garmisch-Partenkirchen Germany October

1991 1053ndash1056

232 N K Tsenev R Z Valiev O V Obraztsov and I N Fridlander

Proc Sixth Int AluminiumndashLithium Conference Garmisch-

Partenkirchen Germany October 1991 1125ndash1132

233 A M Shammazov N K Tsenev R Z Valiev M M

Myshlyaev M M Bikbulatov and S P Lebedich Phys Met

Metall 2000 89 (3) 314ndash318

234 F Musin R Kaibyshev Y Motohashi T Sakuma and G Itoh

Mater Trans A 2002 43A 2370ndash2377

235 M Shagiev Y Motohashi F Musin R Kaibyshev and G Itoh

Mater Trans A 2003 44A 1694ndash1697

236 M Shagiev Y Motohashi F Musin R Kaibyshev and G Itoh

Mater Trans A 2003 44A 1698ndash1701

237 B A Parker and Z F Zhou Proc 3rd Int Conf on lsquoAluminium

alloysrsquo Vol I NTH Trondheim Norway June 1992 363ndash367

238 J R Davies lsquoASM specialty handbook aluminum and aluminum

alloysrsquo 1993 Materials Park OH USA ASM

239 S J Andersen H W Zandbergen J Jansen C Traeholt

U Tundal and O Reiso Acta Mater 1998 46 3283ndash3298

240 M L Kharakterova D G Eskin and L L Rokhlin Russ

Metall 1997 (1) 104ndash109

241 J Roslashyset Dr Ing thesis NTNU Trondheim Norway 2002

242 P P Chattopadhyay S Datta and M K Banerjee Mater Sci

Eng 2002 A 333 67ndash71

243 L I Kaigorodova E I Selnikhina E A Tkachenko and O G

Senatorova Phys Met Metall 1996 81 513ndash519

244 Y-L Wu F H Froes C Li and A Alvarez Metall Mater

Trans A 1999 30A 1017ndash1024

245 Z Yin L Yang Q Pan and F Jiang Trans Nonferrous Met

Soc China 2001 11 822ndash825

246 V I Elagin V V Zakharov and T D Rostova Met Sci Heat

Treat 1994 36 (7) 375ndash380

247 Y V Milman A I Sirko D V Lotsko O N Senkov and D B

Miracle Mater Sci Forum 2002 396ndash402 1217ndash1222

248 C-H Joh K Yamada and Y Miura Mater Trans JIM 1999

40 439ndash442

249 X J Jiang Q H Gui Y Y Li L M Ma G J Liang and C X

Shi Scr Metall Mater 1993 29 211ndash216

250 X J Jiang Y Y Li W Deng L Y Xiong W M Wu Y J Gao

and C X Shi Adv Cryogenic Eng (Mater) 1994 40 1369ndash

1376

251 C-H Joh T Katsube K Yamada and Y Miura Proc 6th Int

Conf on lsquoAluminum alloysrsquo Toyohashi Japan July 1998 799ndash

804

252 L I Kaygorodova A M Dritz T V Krymova and I N

Fridlyander Proc Sixth Int AluminiumndashLithium Conference

Garmisch-Partenkirchen Germany October 1991 363ndash367

253 L I Kaigorodova A M Drits Ya V Zhingel T V Krymova

and I N Fridlyander Phys Met Metall 1992 73 286ndash290

254 A L Berezina V A Volkov S V Ivanov N I Kolobnev and

K V Chuistov Phys Met Metall 1991 71 (2) 167ndash175

255 I N Fridlyander N I Kolobnev A L Berezina and K V

Chuistov Proc Sixth Int AluminiumndashLithium Conference

Garmisch-Partenkirchen Germany October 1991 107ndash112

256 L I Kaigorodova A M Drits Ya V Zhingel T V Krymova

and V A Rassokhin Phys Met Metall 1992 73 281ndash285

257 I N Fridlyander S F Danilov E N Malysheva T A

Gorokhova and N N Kirkina Proc Sixth Int Aluminiumndash

Lithium Conference Garmisch-Partenkirchen Germany October

1991 381ndash386

258 G Dlubek S Krause H Krause A L Beresina V S

Mikhalenkov and K V Chuistov J Phys Condens Matter

1992 4 6317ndash6328

259 S Krause H Krause G Dlubek A L Beresina and K S

Chuistov Mater Sci Forum 1992 105ndash110 1109ndash1112

260 C Y Tan Z Q Zheng and S Q Liang Proc 4th Int Conf on

lsquoAluminium alloysrsquo Vol II Atlanta GA USA September 1994

329ndash333

261 A L Beresina N I Kolobnev K V Chuistov A V Kotko and

O A Molebny Mater Sci Forum 2002 396ndash402 977ndash981

Roslashyset and Ryum Scandium in aluminium alloys

International Materials Reviews 2005 VOL 50 NO 1 43

262 I N Ganiev I Yunusov and V V Krasnoyarskii J Appl Chem

USSR 1986 60 1961ndash1965

263 I N Ganiev Prot Met 1995 31 543ndash546

264 N V Vyazovikina Prot Met 1999 35 448ndash453

265 G V Kharina and V P Kochergin Prot Met 1996 32 134ndash

136

266 G V Kharina M V Kuznetsov and V P Kochergin Russ J

Electrochem 1998 34 482ndash485

267 V S Sinyavskii V D Valrsquokov and E V Titkova Prot Met

1998 34 549ndash555

268 Y L Wu F H Froes C G Li and J Liu Proc lsquoSynthesis

processing of lightweight metallic materials IIrsquo Orlando FL

USA February 1997 73ndash81

269 Z Ahmad and B J Abdul-Aleem Proc EuroCorr 2000

270 Z Ahmad A Ul-Hamid and B J Abdul-Aleem Corros Sci

2001 43 1227ndash1243

271 R Braun B Lenczowski and G Tempus Mater Sci Forum

2000 331ndash337 1647ndash1652

272 T Torma E Kovacs-Csetenyi L Vitalis I Vitanyi

J Stepanov and M Butova Mater Sci Forum 1987 1314

497ndash503

273 Z Wang P Wang K S Kumar and C L Briant in lsquoChemistry

and electrochemistry of corrosion and stress corrosion crackingrsquo

(ed R H Jones) 573ndash582 2001 TMS

274 V I Elagin V V Zakharov A A Petrova and E V

Vyshegorodtseva Russ Metall 1983 (4) 143ndash146

Roslashyset and Ryum Scandium in aluminium alloys

44 International Materials Reviews 2005 VOL 50 NO 1

Page 5: Scandium in aluminium alloys - Atom probe · A considerable part of the available literature on scandium in aluminium alloys is reviewed. ... behaviour in Al Cu, Al Mg Si,

a-Al could be in equilibrium with either Al3Sc or AlLi50

No ternary phases were observed Thermal analysesindicated that the ternary eutectic reaction

Liq~aAlzAl3SczAlLi

occurs at approximately 595uC It has been stated47 thatthere are only minor mutual effects of Sc and Li on theseelementsrsquo solid solubility in a-Al

This statement is confirmed in another investigation51

where the AlndashAlLindashAlSc subsystem is investigated At450uC it is found that the AlLi phase can be inequilibrium with Al3Sc Al2Sc and AlSc No significantsolubility of Li in Al3Sc was observed Several verticalcross-sections are constructed

It should be noted that the existence of a ternaryAl3(LiSc) phase has been reported52 which is indisagreement with the observations above

Ternary phase diagrams withdispersoid-forming elementsAlndashScndashZr

It has been shown53 that at 600uC the Al-corner consistsof the phase fields a-AlzAl3Sc a-AlzAl3SczAl3Zrand a-AlzAl3Zr Further it was discovered that there isa significant solid solubility of Zr in the Al3Sc phase(approx 35 wt-) and some solid solubility of Sc in theAl3Zr phase (approx 5 wt-) The lattice parameter ofAl3Sc was found to decrease when the phase dissolvesZr and likewise the lattice parameter of the Al3Zr wasfound to decrease when that phase dissolves Sc Foralloys in the a-AlzAl3Sc phase field the wt-Zrwt-Scratio in the Al3Sc particles was found to be approx 22times the wt-Zrwt-Sc ratio of the alloy53 Isothermalsections of the Al-corner at 550 and 600uC are alsoconstructed54 (Fig 8)

In another investigation55 two vertical cross-sectionsin the Al-corner were constructed and a ternaryperitectic reaction

LiqzAl3Zr~aAlzAl3Sc

was found to take place at 659uC

The 500uC isothermal section of the whole phasediagram has been investigated56 It is already knownthat Sc and Zr are completely miscible in the solid stateHere it was also found that the compounds AlSc2 andAlZr2 are completely miscible The extensions of theother single-phase fields are determined with variousdegrees of accuracy The solubility of Zr in Al3Sc wasfound to be 6 at- (approx 16 wt-) whereas thesolubility of Sc in Al3Zr was found to be 65 at-(approx 73 wt-) Contrary to Ref 53 the latticeparameter of Al3Sc was found to increase with increas-ing Zr content The lattice parameter of Al3Zr howeverwas found to decrease with increasing Sc content whichis in accordance with the findings of Ref 53

The section Al3ScndashAl3Zr at 1200uC has recently beeninvestigated57 The solubility of Sc in Al3Zr was reportedto be in the range 3ndash5 at- and the solubility of Zr inAl3Sc was found to be 122 at- In accordance withRef 53 the lattice parameters of Al3Sc and Al3Zr decreasewith increasing content of Zr and Sc respectively

AlndashFendashSc

The available data on this system is reviewed in Ref 33and an isothermal section at 500uC is reproduced Threeternary AlndashFendashSc phases are reported The Al-corner ofthe isothermal section however seems to be limited bythe subsystem AlndashAl3ScndashAl3Fe meaning that the a-Alcannot be in equilibrium with any of the ternary phases

AlndashMnndashSc

The Al-corner of the phase diagram has been investi-gated58 No ternary phases were observed meaning thatin the solid state only the Al3Sc and the Al6Mn phasecan be in equilibrium with a-Al An addition of Mn doesnot noticeably decrease the solid solubility of Scwhereas an addition of Sc causes a distinct decrease inthe solubility of Mn Two isothermal sections weremade one at 500uC (Fig 9) and one at 600uC Thelsquocornerrsquo of the a-phase field was reported to be at008 wt-Sc and 02 wt-Mn at 500uC and at 02 wt-Scand 055 wt-Mn at 600uC

8 Isothermal section of Al-corner of AlndashScndashZr phase dia-

gram at 600uC redrawn from Ref 54

9 Isothermal section of Al-corner of AlndashMnndashSc phase

diagram at 500uC redrawn from Ref 58

Roslashyset and Ryum Scandium in aluminium alloys

International Materials Reviews 2005 VOL 50 NO 1 23

Two vertical cross-sections were also constructed Aternary eutectic

Liq~aAlzAl6MnzAl3Sc

at 649uC was identified Several alloys in the sectionAl3ScndashAl6Mn have also been investigated59 and all werefound to comprise a mixture of the two binary phasesLattice parameter measurements of the Al3Sc phasewere interpreted as an indication of a slight solidsolubility of Mn in Al3Sc

AlndashCrndashSc

Alloys in the composition range 30ndash100 at-Al havebeen studied60 and an isothermal cross-section at 500uCwas constructed No ternary phases were identified Thephases that can be in equilibrium with the a-Al are thusAl7Cr and Al3Sc The solubility of Cr in the Al3Sc phasewas found to be considerable approximately 11 at-

Other ternary AlndashScndashX phase diagramsAlndashMondashSc

An isothermal cross-section at 550uC has been con-structed for the subsystem AlndashAl2ScndashAl2Mo61 Noternary phases were reported The phases in equilibriumwith a-Al were found to be Al3Sc and Al12Mo

AlndashScndashV

The section Al3ScndashAl21V2 has been studied62 and thevertical cross-section was constructed No ternaryphases were observed Solid solubilities of V in theAl3Sc phase of 14 at- and of Sc in Al21V2 of 25 at-are reported although a considerably higher maximumsolubility of V in Al3Sc is suggested in the vertical cross-section A quasibinary eutectic reaction

Liq~Al3SczAl21V2

is reported to occur at 917 K (644uC)The section Al3ScndashAl3V at 1200uC has also been

studied57 The solubilities of V in Al3Sc and Sc in Al3Vare reported to be 27 and 07 at- respectively WhenV was dissolved in Al3Sc the lattice parameter of Al3Scwas found to decrease

AlndashScndashTi

No ternary phase diagram is available The sectionAl3ScndashAl3Ti at 1200uC has been studied57 A solubilityof Ti in Al3Sc of almost 125 at- was found whichcorresponds to almost half of the Sc being substituted byTi The lattice parameter of Al3Sc was found to decreasesharply with increasing Ti content For the Al3Ti phasethe solubility of Sc was found to be approx 5 at-

AlndashCondashSc

The ternary system for 0ndash70 at-Sc has been investi-gated63 Three ternary (AlCoSc)-phases were identifiedThe only phases found to be in equilibrium with a-Alwere the binary phases Al3Sc and Al9Co2 An isothermalsection at 600uC and the vertical cross-sections Al3ScndashAl9Co2 and Al3ScndashAl9Co3Sc2 were constructed Thelsquocornerrsquo of the a-phase field was reported in the text to beat 15 at-Co and 05 at-Sc although in a tablethe numbers 02 at-Co and 01 at-Sc are reportedThe solubilities of Co in the Al3Sc phase and of Sc in theAl9Co2 phase were found to be 12 and 01 at-

respectively However in the vertical cross-sections it issuggested that the solubility of Co in Al3Sc may besignificantly higher at higher temperatures The latticeparameter of Al3Sc was not found to change withincreasing Co content

AlndashScndashSr

The subsystem AlndashAl2ScndashAl4Sr has been studied64 andan isothermal section at 500uC was constructed Noternary phases were detected meaning that the phases inequilibrium with a-Al were found to be Al3Sc and Al4SrThe solubility of Sc in Al4Sr and of Sr in Al3Sc wasfound to be low typically less than 15ndash2 at-

AlndashBendashSc

A study of the binary BendashSc system and the ternary AlndashBendashSc system for up to 20 at-Sc (or 30 wt-Sc) hasbeen reported65 The 600uC isothermal section for theinvestigated ternary composition range was constructedNo ternary phases were observed The a-Al can be inequilibrium with either Be Be13Sc or Al3Sc It is sug-gested that the section AlndashBe13Sc may be quasi-eutectic

AlndashBandashSc

An isothermal section at 500uC has been constructed66

No ternary phases were reported and a-Al is inequilibrium with Al4Ba and Al3Sc The solubility of Scin Al4Ba and of Ba in Al3Sc was reported to be less than2 at-

AlndashNndashSc

The region AlndashAlNndashScNndashSc has been investigated67 Aperovskite-type ternary phase AlN12xSc3 was reportedand an isothermal section at 1000uC was constructed Inthe Al-corner the Al melt was reported to be inequilibrium with AlN and Al3Sc

Quaternary and higher order AlndashScndashXndashX2(ndashX3hellip)phase diagramsAlndashMgndashScndashZr

The published material is limited to investigations onAl rich alloys A part of the liquidus surface of the6 wt-Mg section has been determined experimentallyfor the composition range 0ndash07 wt-Sc and 0ndash04 wt-Zr68 The 500uC isothermal phase relations inthe Al-corner of the 6 wt-Mg section has also beeninvestigated69 for Sc and Zr concentrations of up to3 wt- and 4 wt- respectively No ternary or qua-ternary phases were observed Likewise the 430uC iso-thermal phase relations of the 4 at-Mg (y35 wt-Mg)section have been investigated for up to 12 at-Sc(2 wt-Sc) and up to 25 at-Zr (8 wt-Zr)7071 Noternary or quaternary phases were observed in thepresent study either The Al3Sc phase was found todissolve an amount of 122 at-Zr corresponding to asubstitution of almost 50 of the Sc lattice positionswhereas the solubility of Sc in Al3Zr was 44 at-which corresponds to a substitution of almost 20 ofthe Zr lattice positions Figure 4 in Refs 70 and 71suggests that the Al content in the Al3Zr-phase increaseswith increasing Sc content however this is not sub-stantiated in the text

Roslashyset and Ryum Scandium in aluminium alloys

24 International Materials Reviews 2005 VOL 50 NO 1

AlndashMgndashScndashTindashZr

A vertical cross-section of the AlndashMgndashScndashTindashZr phasediagram for 03 wt-Sc 015 wt-Ti 015 wt-Zrand 0ndash10 wt-Mg has been constructed34 Accord-ing to this diagram the Al3Zr phase is the first andAl3Sc the last to form during solidification of thealloys No ternary quaternary or quinary phases arereported

AlndashZnndashMgndashCundashZrndashSc

A vertical cross-section of the full system as well asseveral sections of various sub-systems have beenconstructed72 For the full system a section at8 wt- Zn 2 wt-Cu 03 wt-Zr and 03 wt-Scwas constructed where Mg varies from 0 to 8 wt-The only reported Sc-containing sub-system is thatof AlndashZnndashMgndashCundashSc Here a vertical cross-sectionis constructed with the same levels of Zn Cu and Scas in the full system whereas Mg varies from 0 to65 wt-

No phases other than those known from the lowerorder systems were reported Amongst the findings it isinteresting to note that in the solid state Al3Sc isreported to be an equilibrium phase for all theinvestigated compositions It is also interesting to notethat the Sc-containing W-phase (Al54ndash8Cu66ndash4Sc see thesection on the AlndashCundashSc ternary system) is an equili-brium phase at low Mg content and disappears as theMg content increases

AlndashLindashMgndashSc

The 400uC isothermal phase relations of the 02 wt-Scsection have been investigated for the composition range0ndash6 wt-Mg and 0ndash5 wt-Li73 The a-Al was found tobe in equilibrium with AlLi Al2LiMg and Al3Sc Noquaternary phases were observed This investigation isalso summarised in Ref 50

AlndashCundashLindashSc

The aluminium rich corner of the system has beeninvestigated for alloys with 06 wt-Sc and with Cu andLi in the range 0ndash16 wt- and 0ndash4 wt- respectively74

No quaternary phases were reported Two sections ofthe phase diagram were constructed a section of the470uC isothermal tetrahedron at 06 wt-Sc and avertical section at 06 wt-Sc and 26 wt-Li Twoquaternary invariant equilibria were found and thetemperatures of the invariant points were estimated

Al3Sc phaseRechkin and co-workers were to the authorsrsquo knowl-edge the first to publish a paper in an internationaljournal identifying the Al3Sc phase75 The phase wasidentified as cubic with lattice parameter a5410 A Afew years later the lattice structure was reported to be ofthe Cu3Au type76 The atomic arrangement of the Al3Scphase is shown in Fig 10 The structure can bedescribed as ordered face-centred cubic (fcc) althoughin crystallographic terminology the Al3Sc structure isactually a simple cubic lattice with four atoms (one Scand three Al atoms) associated with each lattice pointThis particular atomic arrangement is nominated L12

and is found in several intermetallic compounds forinstance Ni3Al Ni3Fe and Cu3Au

Some efforts have been made in characterising theproperties of the Al3Sc phase A compilation of someresults is given in Table 3 The motivation for themajority of the investigations seems to be one of thethree following

(i) the Al3Sc phase has a density of 303 g cm23 andit melts peritectically at approx 1320uC This canmake the Al3Sc phase an attractive candidate asa material for lightweight high temperaturestructural applications205777ndash86

(ii) in order to understand the effect of Al3Scprecipitation in Al-alloys it is necessary to gainmore knowledge about the Al3Sc phase578187ndash91

(iii) the Al3Sc is an excellent model phase forstudying basic properties of intermetalliccompounds7990ndash98

10 Atomic arrangement of Al3Sc phase

Table 3 Some reported properties of Al3Sc phase

ReferenceE GPa(Youngrsquos modulus) n (Poissonrsquos ratio)

CTE (Coefficient ofthermal expansion) 1026 K21

(111) APB energymJ m22

(100) APB energymJ m22

88 Approx 11120 166 020 Max 670 45079 166 022 31399 1628 0204

1642iexcl19 0201iexcl000189 16

Reported to decrease linearly with increasing temperature to approx 97 GPa at 550uCCalculatedExperimental

Roslashyset and Ryum Scandium in aluminium alloys

International Materials Reviews 2005 VOL 50 NO 1 25

Formation of Al3Sc in AlndashSc alloysThere are at least four ways that the Al3Sc phase canform in dilute binary AlndashSc alloys

1 Upon solidification of hypereutectic alloys (Sc

approx 06 wt-) Al3Sc is the first phase to form

2 The solidification of hypo- and hypereutectic alloysends with formation of eutectic AlzAl3Sc

3 Al3Sc can precipitate discontinuously from super-saturated solid solution

4 Al3Sc can precipitate continuously (nucleation andgrowth) from supersaturated solid solution

Primary Al3ScAccording to the binary phase diagram primary Al3Scshould form during solidification of all alloys with Sccontent higher than approx 06 wt- ie higher thanthe eutectic composition Formation of primary Al3Sc inAlndash07 wt-Sc melts cooled at 102ndash103 K s21 has beenreported1832 According to the metastable state dia-gram32 this alloy composition is close to the eutectic oneat these cooling rates

Primary Al3Sc is reported to have a highly facetedmorphology1318100ndash102 The observation of a cubicmorphology in a slowly cooled Alndash87 wt-Sc alloyindicates that the facet planes in this case are thecrystallographic (100) planes13 Brodova et al100ndash102

have investigated the microstructure of rapidly cooledAlndash2 wt-Sc alloy They found that the dominantmorphology of primary Al3Sc was dependent on boththe cooling rate and the initial melt temperature A mapof primary Al3Sc morphologies as a function of theseparameters was constructed and is redrawn in Fig 11

The nucleation mechanism and growth morphologyof primary Al3Sc in an Alndash07 wt-Sc alloy solidified ata cooling rate of 100 K s21 were investigated by Hydeet al103104 Indications were found that the primaryAl3Sc particles nucleate heterogeneously on oxideparticles in the melt The primary Al3Sc particles werefound to grow with a dendritic morphology with theprimary dendrite arms in the crystallographic n110m

direction The overall shape is cubic which is inaccordance with earlier observations

Eutectic Al3ScEutectic AlzAl3Sc has been reported in hyper- as wellas hypoeutectic alloys11 but is scantily described in theliterature Given a eutectic composition of 06 wt- amaximum solid solubility of Sc in Al of 035 wt- andthe specific densities in Table 1 a eutectic formed underequilibrium conditions would contain a volume fractionof approx 063 vol-Al3Sc At high cooling rates thevolume fraction of Al3Sc in the eutectic is probablysomewhat smaller owing to the increased supersatura-tion of Sc in Al

The morphology of the eutectic in an Alndash2 wt-Scalloy is reported to depend on the temperature of themelt before solidification100 For low melt temperaturesthe eutectic is reported to be rodlike for a wide range ofcooling rates For intermediate melt temperatures andhigh cooling rates a lsquodiscontinuous eutecticrsquo is reportedwhereas for high melt temperatures and slow coolingrates a lsquoquasieutecticrsquo structure is reported with Al3Scparticles of almost spherical shape

Hyde et al have reported that during solidification ofan Alndash07 wt-Sc alloy some of the primary Al3Scparticles are pushed ahead of the Al solidification frontand end up at the grain boundaries103104 Thus primaryAl3Sc may be mixed with eutectic Al3Sc in themicrostructure A scanning electron microscopy (SEM)picture showing eutectic Al3Sc at the grain boundaries asdescribed in Refs 103 and 104 is given in Fig 12

Discontinuous precipitation of Al3ScDiscontinuous precipitation of Al3Sc from super-saturated solid solution is often observed in binary AlndashSc alloys131831105 This precipitation mechanism whichis sometimes referred to as cellular precipitation iscommonly described as a decomposition of super-saturated solid solution into a-Al and Al3Sc at a movinggrain boundary The driving force for the grainboundary migration is the volume free energy that isreleased during the precipitation As the grain boundarymoves it leaves behind a characteristic fan shaped array

11 Morphology of primary Al3Sc particles in Alndash2 wt-Sc

alloy as a function of melt overheating and cooling

rate during solidification redrawn from Ref 102

12 SEM image of particle structure of Alndash07 wt-Sc

alloy cooled at a rate of 100 K s21 during solidifica-

tion as described in Refs 103 and 104 primary Al3Sc

particle is seen in centre of grain whereas eutectic

Al3Sc is decorating grain boundaries image is kindly

provided by Dr Kristian Hyde UMIST Manchester UK

Roslashyset and Ryum Scandium in aluminium alloys

26 International Materials Reviews 2005 VOL 50 NO 1

of precipitates In the AlndashSc case the discontinuouslyprecipitated Al3Sc particles have been demonstrated tobe coherent with the aluminium matrix1318

The driving force for discontinuous precipitationincreases with increasing supersaturation of Sc in theAl matrix Thus discontinuous precipitation in binaryAlndashSc is most frequently reported in studies of alloyswith a Sc content of 04 wt- or higher1318106 Stilldiscontinuous precipitation has also occasionally beenreported to occur at lower alloy compositions In an Alndash027 wt-Sc alloy discontinuous precipitation wasobserved over a wide range of temperatures107 In arecent study31105 of precipitation kinetics and mechan-isms in Alndash02 wt-Sc discontinuous precipitation wasfound to take place when the specimens were quencheddirectly from a solutionising temperature in this case600uC to aging temperatures in the range 370ndash490uCFurther C-curves in a temperature-time-transformation(TTT) diagram were established (Fig 13) which showedthat the highest transformation rate of discontinuousprecipitation lies at a higher temperature than thehighest transformation rate of the continuous precipita-tion reaction ie the two precipitation reactions arerepresented by two separate lsquonosesrsquo on the C-curves

It has been shown that discontinuous precipitationcan be suppressed by continuous precipitation if thematerial is cold worked before the precipitation heattreatment13108

As a result of their rather coarse nature andinhomogeneous dispersion discontinuously precipitatedAl3Sc contributes but little to the strength of the alloyand also leads to a smaller amount of Sc in super-saturated solid solution being available for subsequentcontinuous precipitation Thus discontinuous precipita-tion is in general regarded as an undesired precipitationmode

Continuous precipitation of Al3ScContinuous precipitation of Al3Sc is a bulk decomposi-tion process of supersaturated solid solution of Sc in Aland can in the isothermal case be characterised by anucleation stage a growth stage and finally a coarsen-ing stage Apparently the continuous precipitation reac-tion occurs largely by homogeneous nucleation anddiffusion controlled growth and AlndashSc has occasionallybeen used as a model system for studying the mechan-isms of nucleation growth and coarsening107109ndash111

There have been several studies of the continuousprecipitation reaction in binary AlndashSc alloys and up tillnow there is no evidence that any metastable phases areforming before the L12 phase Al3Sc Thus it is assumedthat the equilibrium phase nucleates directly fromsupersaturated solid solution

Even though the nucleation of Al3Sc is frequentlyreported to occur homogeneously throughout the Almatrix there are some examples in the technical litera-ture of reported heterogeneous Al3Sc nucleation ondislocations110112ndash115 and grain boundaries110113115ndash118

In a recent numerical modelling study of continuousprecipitation in AlndashSc alloys111 the effect of hetero-geneous nucleation on dislocations is accounted for Themodel predicts that homogeneous nucleation dominatesat high Sc concentrations and low transformation tem-peratures whereas heterogeneous nucleation is predictedto dominate at low Sc concentrations and high trans-formation temperatures Figure 14 shows a sketch of anucleation map for AlndashSc The shift between homo-geneous and heterogeneous dominance in nucleation isdependent on the dislocation density as indicated in thefigure

The shape of continuously precipitated Al3Sc particlesis most frequently reported to be spherical29112113119ndash129

However it seems that under certain conditions theshape can differ from the spherical one Drits et al130

reported both spherical and star shaped morphologyThe star shaped precipitates had arms growing in thecrystallographic n110m-directions (Star shaped Al3Scprecipitates have also been found after some thermo-mechanical treatments of an AlndashMgndashScndashZr alloy131) InRef 128 precipitates of both cuboidal and sphericalmorphology are found to coexist after certain heattreatments Cauliflower shaped precipitates as well asprecipitates of spherical and cuboidal shapes arereported by Novotny and Ardell110 Bastow andCelotto132 found large oblong Al3Sc particles in an Alndash01 wt-Sc alloy after aging at 400uC for 24 h A facetedshape is suggested in a high-resolution image of anAl3(Sc Zr) precipitate in an AlndashMgndashMnndashZrndashSc alloy133

In a systematic high-resolution transmission electron

13 TTT diagram of precipitation in Alndash02 wt-Sc alloy

after solutionising at 600uC and direct quench to

aging temperature3114 Nucleation map for binary AlndashSc alloys which indi-

cates how the tendency towards heterogeneous ver-

sus homogeneous nucleation is predicted to depend

upon Sc concentration transformation temperature

and dislocation density redrawn from Ref 111

Roslashyset and Ryum Scandium in aluminium alloys

International Materials Reviews 2005 VOL 50 NO 1 27

microscopy (TEM) study of the Al3Sc particle morphol-ogy development during precipitation heat treatment ofbinary AlndashSc alloys by Marquis and Seidman114 it isdemonstrated that the precipitates can take a wide rangeof shapes as they grow depending on Sc content in thealloy transformation temperature and transformationtime Irregular shaped star shaped and cuboidalshaped precipitates were observed under someconditions It was however found that the equilibriumshape of the particles is an equiaxed multifaceted one(Fig 15) Supported by Wulffrsquos construction it wasconcluded that the shape was that of a GreatRhombicuboctahedron This equilibrium morphologyhas been reproduced by computer-simulations ofparticle growth87134 The multifaceted particles caneasily be taken for spherical in a conventional TEMpicture

Kinetics of precipitation of Al3Sc fromsupersaturated solid solutionThe precipitation kinetics of Al3Sc in binary AlndashScalloys is dependent on the precipitation heat treatmenttemperature and on the Sc content in the alloy Acomprehensive overview over the transformationkinetics in terms of C-curves is given by Zakharov135

The C-curves for 5 transformation for a range of AlndashSc alloys are redrawn in Fig 16

Hyland107 studied the homogeneous nucleationkinetics of Al3Sc in a Alndash018 wt-Sc alloy after directquench from 650uC to precipitation temperatures of 288and 343uC He found that after an incubation time t theAl3Sc particles nucleated at a constant rate until thediffusion fields of the individual particles started tooverlap At 288uC the incubation time and time tosignificant diffusion field overlap were estimated to beapprox 245 and 150 min respectively whereas thecorresponding values at 343uC were estimated to beapprox 7 and 20 min respectively

If one assumes that the JohnsonndashMehlndashAvramindashKomolgorov (JMAK) relationship is valid for thisprecipitation reaction one can express the fraction

transformed X as a function of the reaction time t bythe equation

X (t)~1expfrac12k(Dt)n (1)

where k is a constant D is the interdiffusion constant ofSc in Al and the exponent n is dependent on thenucleation rate For the situation described byHyland107 where the precipitates nucleate at a constantrate the value of n should theoretically136 be equal to52

Roslashyset and Ryum31105 applied an alloy and heattreatment method practically equal to that of Hyland107

One should thus expect that the precipitation kineticsshould also be quite similar However Roslashyset andRyum reported that the exponent n of the JMAKrelationship was approx 165ndash185 for the temperaturerange of concern31105 This does not point in thedirection of a constant nucleation rate but rather inthe direction of site saturation ie that all the particlesare nucleated simultaneously which in the JMAKequation would yield an exponent n of 32136 Anoverview of some reported values of n in the JMAKequation is given in Table 4 The majority of the valueslie closer to 32 than to 52 However it is important to

15 High resolution TEM picture along n100m axis of Al3Sc particle in Alndash03 wt-Sc alloy aged at 300uC for 350 h114

(reproduced with permission from Elsevier Science image kindly provided by Dr E A Marquis and Professor D N

Seidman) and various projections of a Great Rhombicuboctahedron

Table 4 Some reported values of n in JMAK equation

Reference n C 0Sc wt-Sc Ttrans uC Note

137 13 030 300 Solution heat treated (SHT) 500uC16026 030 300 SHT 600uC Low n at late stage20026 030 300 SHT 640uC Low n at late stage

29 130ndash149 015 260ndash370145ndash196 025 260ndash370

138 188ndash216 020 240ndash35031 165ndash185 023 270ndash350 SHT 600uC Direct quench to transformation temp

16 C-curves for 5 transformation in a range of binary

AlndashSc alloys redrawn from Ref 135

Roslashyset and Ryum Scandium in aluminium alloys

28 International Materials Reviews 2005 VOL 50 NO 1

note that an n value close to 32 is per se not evidence ofsite saturation

Hyland also showed that a water quench from thesolutionising temperature significantly altered thenucleation kinetics in the subsequent precipitation heattreatment107 The incubation time was dramaticallyshortened which is attributed to the quenched-in excessvacancies and it is also indicated that there might be ashift in the nucleation rate in the early stage ofprecipitation It is suggested that the vacancies mayenhance the diffusion of Sc in Al and that there is apossibility that vacancy clusters act as heterogeneousnucleation sites for Al3Sc precipitates107 Regardless ofwhich mechanism that is operative it is clearly demon-strated that the nucleation kinetics can be dependent onthe thermal history between solutionising and precipita-tion heat treatment

Loss of coherency during growth of Al3ScprecipitatesWhen an Al3Sc particle grows it will sooner or laterreach a critical size where it will be energetically morefavourable to introduce an interface dislocation at theAlAl3Sc interface than to increase the matrix strain Asimple approximation for the critical size can be derivedfrom the lattice parameters assuming that the criticalsize is reached when the misfit over the whole particlediameter equals the Burgers vector of the Al matrix

dcrit~b=d (2)

where b is the Burgers vector of Al and d is themisfit between Al and Al3Sc This approximation yieldsa critical diameter of approx 215 nm at ambienttemperature

The misfit d and thus also the critical diameter dcrit

will depend on the temperature owing to the differencesin thermal expansion between the Al matrix and the

Al3Sc particles The thermal expansion of Al3Sc hasrecently been measured89 and based on the differencesin thermal expansion between Al139 and Al3Sc the misfitas a function of temperature has been calculated89 Thiscalculation is reproduced and shown by the solid line inFig 17

It is however possible to refine this calculationsomewhat140 Whereas the thermal expansion of Al3Sc isexpected to be only because of lattice expansion there isa significant contribution from vacancies on thermalexpansion of Al at high temperatures141 Thus thetemperature effects on the misfit should be calculatedfrom the changes in lattice parameters rather than fromthe linear thermal expansion By subtracting the vacancyeffect on the thermal expansion one achieves atemperature-dependent misfit as represented by thedotted line in Fig 17

A second correction that should be taken into accountis the effect of Sc in solid solution on the latticeparameter of the Al matrix With increasing tempera-ture more Sc is brought into solid solution and it isreported that the lattice parameter of the Al matrixpresumably measured at room temperature increaseslinearly with the Sc content in solid solution142 Thesedata can be used to calculate the effect on the latticeparameter at elevated temperatures under the assump-tion that the relative increase in lattice parameter owingto Sc in solid solution is independent of temperature InRef 142 a figure is presented which shows the measuredlattice parameter as a function of Sc content in solidsolution and a value (dadc)a is reported where a is thelattice parameter of the Al matrix and c is the Sc contentin solid solution in at- The reported value for (dadc)a is 100 times larger than that indicated in thecorresponding figure possibly as a result of a decimalerror in the text Thus in the present exercise 1100th ofthe reported value for (dadc)a is used Using this incombination with the regular solution approximationfor the solvus line of Sc in Al1231 one obtains acorrection for Sc in solid solution on the temperature-dependent misfit as shown in Fig 18 This figure shows

17 Lattice mismatch between Al and Al3Sc as a function

of temperature solid line represents calculation

based on linear thermal expansion of the two phases

dotted line represents correction for vacancies in Al

lattice

18 Corrections of mismatch calculated from linear ther-

mal expansion data as a result of vacancies and to

Al lattice expansion from Sc in solid solution

Roslashyset and Ryum Scandium in aluminium alloys

International Materials Reviews 2005 VOL 50 NO 1 29

both the correction for vacancies and for Sc in solidsolution on the same graph The two corrections are ofapproximately the same magnitude but with oppositesigns Thus the resulting (net) correction is close to zeroand it turns out that the first hand approximation asapplied in Ref 89 is very good in this case

Applying the calculated temperature dependent misfitwith the simple approximation for a critical diameter forloss of coherency one obtains a temperature-dependentcritical diameter as shown in Fig 19

Some examples from the literature of experimentallyobserved critical diameters in binary AlndashSc alloys aresummarised in Table 5 along with some predictions forcritical diameters from Fig 19 There is a fairly goodconsistency between the observations and the measureddiameter is quite close to the simple predictions above

A more refined analysis on the transition fromcoherent to incoherent particles has recently beenperformed145 This analysis is based on the balancebetween the increase in particlematrix interface energyowing to interfacial dislocations and the relaxation inelastic energy in the Al matrix owing to the samedislocations This method yields a predicted criticaldiameter of 246 nm for transition from coherent to

semi-coherent particles at ambient temperature Thetemperature dependence of the critical diameter is nottreated in this analysis

The loss of coherency during isothermal annealing hasbeen reported to be accompanied by an increasedaverage coarsening rate119121137145 The increasedcoarsening rate has been attributed either to diffusionof Sc along dislocation lines119121 or to the increasedparticlematrix interface energy of a semicoherentparticle145 However there are also several data sets inthe literature that do not indicate an increased growthrate after the loss of coherency114128

Al3ScAl interface energyThe interface energy between Al3Sc and the Al matrix isone of the key parameters that governs the nucleationgrowth and coarsening behaviour of Al3Sc in Al and Alalloys The interface energy has been estimated in severalinvestigations either by fitting experimental data toequations that describe nucleation or coarsening or bycalculations A compilation of some of the results isgiven in Table 6 There is considerable spread in thereported values regardless of what approach has beenused for the estimation

Influence of other elements on precipitation ofAl3ScMagnesium

With regard to precipitation mechanism it has beenstated that Mg suppresses the tendency to discontinuousprecipitation of Al3Sc106 In an investigation of pre-cipitation kinetics of Al3Sc in the temperature range300ndash500uC only minor changes in the kinetics (Fig 20)were found when up to 5 wt-Mg was added to an Alndash04 wt-Sc alloy135 It seems that the precipitationreaction is slightly faster in the Mg-containing alloys

Several investigations on age hardening response alsoimply that there is only a small if any effect of Mg onthe precipitation kinetics of Al3Sc23148149 It is how-ever found that the hardness increase from theprecipitation of Al3Sc is somewhat reduced in AlndashMgndashSc alloys compared to binary AlndashSc alloys23148149 InRef 149 it is suggested that some of the Sc is dissolvedin the Al3Mg2 phase and thus the age hardeningpotential is reduced with increasing Mg contentSomewhat contradictory to these observations but

Table 5 Some reported critical diameters for coherencyloss in binary AlndashSc and correspondingtheoretical critical diameters from Fig 19

Reference dcrit nmC0

Scwt-Sc

TtransuC

Theoreticaldcrit nm

119 38ndash40 05137 28ndash30 03 400 308128 32 02 400 450 308 335129 50 02143 40 012 025115 40 025 450ndash500 335ndash37114 40 03 400 450 308 335144 40 02 400ndash460 308ndash341145 30ndash80 02 400ndash490 308ndash362

20 C-curves for 10 and 60 transformation in Alndash

04 wt-Sc and Alndash4 wt-Mgndash04 wt-Sc redrawn

from Ref 135

19 Simple approximation for temperature-dependent criti-

cal diameter for introduction of dislocations on Al

Al3Sc interface

Roslashyset and Ryum Scandium in aluminium alloys

30 International Materials Reviews 2005 VOL 50 NO 1

sustained by Ref 135 it has recently been reported150

that precipitation of Al3Sc at 300 and 350uC occursslightly faster in an Alndash2 wt-Mgndash02 wt-Sc alloythan in an Alndash02 wt-Sc alloy studied previously by thesame researchers117118 and that the correspondinghardness increase is highest in the AlndashMgndashSc alloyThe only reported difference in experimental procedureis the solutionising temperature which was higher forthe AlndashSc alloy (648uC) than for the AlndashMgndashSc alloy(617uC) However given that the nucleation time isshortened by quenched-in vacancies as suggested byHyland107 the difference in homogenisation tempera-ture should be in favour of a faster precipitation of thebinary AlndashSc alloy It should be worthwhile to probedeeper into this observation of different aging responses

Mg in solid solution increases the lattice parameter ofthe Al matrix This is in turn expected to influence thecritical diameter for AlAl3Sc coherency loss as discussedin the section on lsquoLoss of coherency during growth ofAl3Sc precipitatesrsquo above Such an influence on the criticaldiameter is also briefly discussed elsewhere150 A criticaldiameter of 80 nm in an Alndash3 wt-Mgndash02 wt-Sc alloyhas been observed compared to 40 nm in a binary Alndash02 wt-Sc alloy of the same investigation144 Otherresearchers have reported a critical diameter in excess of116 nm in an Alndash63 wt-Mgndash02 wt-Sc alloy151

Computer simulations predict that the AlAl3Scinterface should be enriched in Mg87 These predictionsare confirmed experimentally by three-dimensional atomprobe microscopy of an Alndash2 wt-Mgndash02 wt-Sc alloyaged at 300uC38 Here it was found that the Mg contentat the interface is approximately three times higher thanthe matrix concentration regardless of aging time

Copper

It has been claimed that Cu suppresses the tendencytowards discontinuous precipitation of Al3Sc106

Zakharov and Rostova152 have reported that additionsof up to 14 wt-Cu have only minor effects on theprecipitation kinetics in an Alndash04 wt-Sc alloy Themost noticeable effect is that for temperatures above400uC the late stage of the transformation is sloweddown for the highest Cu contents This does not show in

Fig 21 however where only the 10 and 60transformation curves are included

The W-phase (AlCuSc) was observed in the alloywith the highest Cu content which means that less Sc isavailable for the precipitation of Al3Sc in this alloyAnother investigation on the age hardening response ofAlndash023 wt-Sc and Alndash25 wt-Cundash023 wt-Sc at300uC also implies that the precipitation behaviour ofAl3Sc in the two alloys is similar153154 At 350uC alimited portion of the Al3Sc has been observed tonucleate heterogeneously on coarse hrsquo precipitates155

According to the isothermal sections of the phasediagram43 one should expect the ternary W-phase toform instead of the Al3Sc phase in an alloy with such ahigh CuSc ratio However no observations of the W-phase or other ternary phases were reported from TEMstudies of the Alndash25 wt-Cundash023 wt-Sc alloy thathad been heat treated in the temperature range 300ndash460uC153ndash156 A third investigation on the precipitationin Alndash048 wt-Sc alloys with up to 440 wt-Cu in thetemperature range 100ndash450uC also concludes that no W-phase or other ternary phase forms during the heattreatment157

Copper in solid solution decreases the lattice para-meter of the Al matrix Thus it is expected that the misfitbetween Al and Al3Sc precipitates should be higher in

21 C-curves for 10 and 60 transformation in Alndash

04 wt-Sc and Alndash14 wt-Cundash04 wt-Sc redrawn

from Ref 152

Table 6 Reported values of interphase energy cAlAl3Sc between coherent Al3Sc precipitates and Al matrix

Reference cAlAl3Sc mJ m22 Method of estimation

137 10 Fit of coarsening data to LifshitzndashSlezev equation107 78iexcl20 (288uC) Back-calculation of incubation time

93iexcl20 (343uC)107 123iexcl41 (288uC) Back-calculation of nucleation rate

125iexcl35 (343uC)29 542 (400uC) Fit of coarsening data to Ostwald ripening

632 (430uC)413 (460uC)

146 c(100) 192 (0 K) c(111) 226 (0 K) Pseudopotential calculations147 c(100) 325 (0 K) c(110) 513 (0 K) c(111)

782 (0 K) c(100) 315 (288uC) c(100) 325 (343uC)Atomistic simulation

110 105 Fit of coarsening data to LSW theory31 20ndash300 Fit of coarsening data to Ostwald ripening

for 16 different temperatures111 57 Fit of precipitation model to experimental data145 120 coherent particles Fit of coarsening data

170 semicoherent particles

It is argued in this study that c may be lower in the nucleation stage

Roslashyset and Ryum Scandium in aluminium alloys

International Materials Reviews 2005 VOL 50 NO 1 31

AlndashCundashSc alloys compared to AlndashSc alloys Howeveran experimental investigation of Alndash25 wt-Cundash023 wt-Sc alloy comes to a different conclusion Thelattice misfit strain is found to decrease compared to Alndash02 wt-Sc and the critical diameter for coherency losswas found to be the same in the ternary and the binaryalloy144 It is suggested that these observations may bebecause of the dissolution of some Cu in the Al3Sc phaseand thus that the lattice parameters of both the Al matrixand the Al3Sc precipitates decrease in the ternary alloy

Silicon

It has been found that the onset of precipitation in Alndash04 wt-Sc is only slightly altered when Si contents ofup to 04 wt are introduced in the alloy However thefinal stage of the precipitation reaction is considerablydelayed with increasing Si content135 Figure 22 showsthe effect of addition of a joint of 035 wt-Si and040 wt-Fe There are at least two possible explana-tions for why an Si-addition leads to this behaviour

1 Alloying with Si is known to promote discontin-uous precipitation of Al3Sc106158 It has been shown thatwhen isothermal precipitation of Al3Sc starts discon-tinuously the later stage of the overall transformationcan be very slow31

2 The isothermal section of the phase diagramsuggests that the V-phase (AlSc2Si2) should form inalloys of this composition46 If the V-phase forms lessSc is available for precipitation of Al3Sc

It has been shown157 that for an AlndashScndashSi alloy withsolid solution content of 010 wt-Sc an 110 wt-Sithe only phases to precipitate after heat treatment at200uC are Si and an (AlScSi)-phase possibly the V-phase On the other hand the Al3Sc phase has beenobserved to form in alloys with 04 wt-Sc and up to08 wt-Si159160

Zinc

It has been reported that additions of up to 5 wt- Znhave only minor effects on the precipitation kinetics ofan Alndash04 wt-Sc alloy135 (Fig 23) In Ref 106 it isclaimed that Zn promotes discontinuous precipitation ofAl3Sc

Lithium

A comparison of the age hardening response at 400uC inAlndash24 wt-Lindash019 wt-Sc and Alndash024 wt-Sc alloys

indicates that the onset of Al3Sc-precipitation is notaffected by the presence of Li161

Zirconium

As mentioned in the section on lsquoTernary phase diagramswith dispersoid-forming elementsrsquo earlier a considerableamount of Zr is dissolved in the Al3Sc phase and thus amore correct denotation of the precipitating phase isAl3(Sc12xZrx) In discussing the influence of the Zrcontent on the precipitation of Al3Sc one is thereforeactually discussing the difference in precipitation ofAl3Sc versus Al3(Sc12xZrx)

It is found that an addition of 015 wt-Zr to an Alndash04 wt-Sc alloy only marginally affects the initial stageof the precipitation reaction123135 while it slows downthe later stages of the transformation considerably(Fig 24)135 The coarsening rate of the Al3(Sc12xZrx)particles in AlndashScndashZr alloys is found to be much slowerthan that of Al3Sc particles in AlndashSc alloys123162

In three-dimensional atom probe field ion microscopy(3D-APFIM) of Al3(Sc12xZrx) particles formed at 475uCin a ternary AlndashScndashZr alloy163 it was found that the coreof the particles is almost pure Al3Sc whereas there is ashell of Al3(Sc12xZrx) with almost equal content of Scand Zr Such a behaviour has also been predicted bycomputer modelling of precipitation of Al3(Sc12xZrx) at480uC in an AlndashZnndashMgndashScndashZr alloy164 This modelpredicts that Zr starts to enter the growing

22 C-curves for 10 and 60 transformation in Alndash

04 wt-Sc and Alndash04 wt-Fendash035 wt-Sindash04 wt-Sc

redrawn from Ref 135

23 C-curves for 10 and 60 transformation in Alndash

04 wt-Sc and Alndash5 wt-Znndash04 wt-Sc redrawn

from Ref 135

24 C-curves for 10 and 60 transformation in Alndash

04 wt-Sc and Alndash04 wt-Scndash015 wt-Zr redrawn

from Ref 135

Roslashyset and Ryum Scandium in aluminium alloys

32 International Materials Reviews 2005 VOL 50 NO 1

Al3(Sc12xZrx) particles when approximately half of thesupersaturated Sc has been precipitated The Zr contentof the outer shell is predicted to be much higher thanwhat has been found experimentally163164

Another 3D-APFIM study of Al3(Sc12xZrx) particlesin a ternary AlndashScndashZr alloy has been reported165 Hereparticles grown at 300uC for various lengths of time werestudied The Zr content in these particles was muchlower than that reportedpredicted at higher tempera-tures163164 even after very long annealing times

Iron

The effect of adding up to 07 wt-Fe on the precipita-tion kinetics in an Alndash04 wt-Sc alloy has beeninvestigated135 The onset of precipitation was onlyslightly influenced by the Fe-level whereas the laterstages of the transformation however were significantlyslowed down as the Fe-level increased An example ofthe effect of a joint addition of Fe and Si is shown inFig 22

Manganese chromium and titanium

Small additions (03 wt-) of manganese or chromiumto Alndash040 wt-Sc alloys are reported to have onlyminor effects on the precipitation kinetics of Al3Sc135

According to Ref 106 Mn is reported to promote andCr and Ti to suppress discontinuous precipitation

Rare earth elements

An investigation of the precipitation behaviour of Alndash03 at-Sc and Alndash03 at-Scndash03 at-X alloyswhere X is either yttrium gadolinium holmium orerbium in the temperature range 235ndash310uC indicatedthat a Al3(Sc12xXx) phase with L12 structure wasformed in the ternary alloys22 Peak strength is reportedto occur after approx 10 h at 285uC in all alloys whichindicates that the precipitation kinetics up to peakstrength is practically unaltered by the ternary additions

Influence of Sc on microstructure andproperties of wrought aluminium alloysMost of the effects of Sc addition in wrought Al-alloysare linked to the formation of the Al3Sc phase In atypical processing route of a wrought aluminium alloyparticles of the Al3Sc phase can form under threedifferent conditions each of which influences themicrostructure and properties of the alloy in a specificway

1 During solidification after casting or weldingAl3Sc particles can form in the melt and act as nucleifor a-Al thus leading to grain refinement18166

2 High temperature processing of the alloy in therange 400ndash600uC for instance homogenisation hot-rolling or extrusion can give a dense distribution ofAl3Sc particles of typically 20ndash100 nm size The particledistributions formed under such conditions are reportedto lead to good recrystallisation resistance128148167168

and enhanced superplasticity52169170

3 Heat treatment in the range 250ndash350uC can lead tosignificant precipitation hardening of an alloy super-saturated in Sc148158171 The size of strengthening Al3Scprecipitates is typically in the range 2ndash6 nm121

Grain refinementA good grain refinement is almost always desired uponsolidification The formation of small equiaxed grainsrather than long dendrites in the melt facilitates thefeeding of the melt into cavities of the shrinkingsolidified metal and thus reduces the problem ofshrinkage porosity The tendency to hot cracking is alsoreduced and the second phase particles become morefinely and uniformly distributed

To the authorsrsquo knowledge the first effect of Sc in Al-alloys that was reported in an international scientificjournal was the grain refining action in pure Al and in anAlndashCu alloy upon solidification172 which was found tobe stronger for Sc than for other transition metals Inlater studies of Sc as a grain refiner in pure Al1832173 ithas been demonstrated that approx 07 wt-Sc issufficient to provide excellent grain refinement It hasalso been demonstrated that additions of 025 wt-Scz025 wt-Zr provide good grain refinement in pure Al18

In order for Sc to act as an effective grain refiner theAl3Sc phase has to form in the melt before thesolidification of a-Al The Al3Sc particles have a latticeparameter close to that of pure Al and whenhypereutectically formed the Al3Sc particles are veryeffective substrates for the nucleation of the a-Al phaseAs mentioned in the section on lsquoFormation of Al3Sc inAlndashSc alloysrsquo above this requires that the alloy ishypereutectic with respect to Sc ie in excess of approx06 wt- in a binary AlndashSc alloy In ternary and higherorder systems the eutectic Sc composition may dependon the other alloying elements present For instance theeutectic composition of Sc has been predicted todecrease with increasing Mg content in the ternary AlndashMgndashSc system39 This prediction is sustained by theobservation of good grain refinement by adding 05 wt-Sc to an Alndash7 wt-Mg alloy174 (Other examples ofgrain refinement at Sc concentrations lower than that ofthe binary eutectic are found in Ref 173)

Similarly the observation of good grain refinement inan Alndash025 wt-Scndash025 wt-Zr alloy18 may be as aresult of a lower Sc content of the eutectic in the ternarysystem ie less Sc is needed to make the alloy hyper-eutectic No literature data on the liquidus surface of theAlndashScndashZr system are available and thus this hypothesiscannot be confirmed In more complex alloy systems itis also observed that excellent grain refinement isachieved at low Sc contents when Sc is added togetherwith Zr It is reported that adding either 02 wt-Sc06 wt-Sc or 01 wt-Zr to an Alndash5Mg alloy givesmuch poorer grain refinement than adding 02 wt-Scz01 wt-Zr175 Similarly additions of 015 wt- ofeither Sc or Zr are reported to only marginally refinethe grain structure in an AlndashCundashLi alloy whereas a jointaddition of 015 wt-Sc and 015 wt-Zr gives excellentgrain refinement176 For an AA 3650 casting alloy (Alndash7 wt-Sindash04 wt-Mg) good grain refinement is achievedby adding 039 wt-Sc or 027 wt-Scz019 wt-Zr177

In some AlndashZnndashMgndashScndashZr alloys it is also found thatan addition of 02ndash03 wt-Sc can be sufficient for goodgrain refinement166169178179 Examples of the grainrefinement as a function of Sc addition in pure Al andin an AlndashZnndashMgndashZr alloy are shown in Fig 25

The nucleation of a-Al on Al3Sc particles in the melt isfacilitated by the close match in the lattice parameters ofthe two phases As shown in Fig 17 the mismatch at the

Roslashyset and Ryum Scandium in aluminium alloys

International Materials Reviews 2005 VOL 50 NO 1 33

eutectic temperature of binary AlndashSc alloys (660uC) isonly approx 047 In Refs 57 and 89 it is shown thatwhen Zr Hf and in particular Ti is dissolved in the Al3Scparticles this reduces the lattice parameter of the phaseIt appears that when 25 of the Sc atoms in Al3Sc aresubstituted by Ti the mismatch is zero at approx 550uCand becomes negative at higher temperatures89 Thissuggests that by carefully selecting the Ti content of thealloy it should be possible to obtain Al3(ScTi)substrates in the melt that match exactly the latticeparameter of the nucleating a-Al and thus furtherimprove the grain refinement of the alloy This appearsto have been achieved in a recent work180 where thegrain refinement of an Alndash07 wt-Sc alloy wascompared with that of an Alndash05 wt-Scndash02 wt-Tialloy At a cooling rate of 100 K s21 only an estimated2 of the primary Al3Sc particles of the binary AlndashScalloy were effective nuclei compared to practically 100for the primary Al3(ScTi) particles in the ternary AlndashScndashTi alloy leading to a much smaller grain size in theternary alloy Whereas the match of lattice parametersmay be of importance for these results the authors ofthis investigation180 draw attention to other factors suchas different growth restriction factors for Sc and Ti andthe possibility of a peritectic reaction in the ternaryalloy Nevertheless the principle of matching latticeparameters is worth looking into further in future work

Effects from dispersoidslsquoDispersoidsrsquo is a term which is commonly used aboutthe classes of second phase particles that are formedin an Al alloy during high temperature annealing orthermomechanical processing such as homogenisationhot rolling extrusion and forging A dense distributionof dispersoids can give a significant contribution to analloyrsquos strength owing to particle strengthening but thisis rarely the main strengthening mechanism A moreimportant contribution from the dispersoids is theirability to stabilise the grainsubgrain structure of analloy through the Zener-drag action and thus improvethe mechanical properties of the alloy

There are two noticeable dispersoid-related effectsthat have been reported for Sc-containing alloys Thefirst is the stabilising effect on a deformed microstruc-ture When a non-recrystallised structure is preserved inan alloy this can add considerably to the mechanical

strength of the material The second effect is thepreservation of a small grain size during hot deforma-tion at slow deformation rates which is necessary toobtain superplastic properties of an Al-alloy

Recrystallisation resistance

The anti-recrystallisation effect of Sc was first publishedin a patent171 where 03 wt-Sc was added to pure Aland to AlndashMg AlndashMn and AlndashZnndashMg alloys Both Sc-free and Sc-containing materials were cold worked andsubsequently annealed and it was found that theaddition of Sc increased the temperature for onset ofrecrystallisation by approx 220uC in pure Al andsomewhat less in the Al-alloys Although the author ofthe patent171 may have been well aware that the anti-recrystallisation effect is caused by Al3Sc dispersoidsthis is not mentioned in the text The first journal paperthat explicitly points out that the recrystallisationresistance is due to Al3Sc dispersoids was an investiga-tion of the effects of adding Sc to wrought AlndashMgalloys181 In this work it was found that the Al3Scdispersoids were very effective in preventing recrystalli-sation up to temperatures of approx 400ndash450uC Athigher temperatures the dispersoids coarsen consider-ably and the microstructure was partially recrystallised

It is established that the Zener-drag pZ that is imposedon an advancing grain boundary by randomly distrib-uted dispersoids can be expressed in the form

pZ~k f =r (3)

where k is a factor that includes the interface energybetween the dispersoids and the matrix f is the volumefraction and r is the mean radius of the dispersoids Thusthe Zener drag will decrease rapidly in the case where thedispersoids are coarsening

As mentioned in the section on lsquoInfluence of otherelements on precipitation of Al3Scrsquo above theAl3(Sc12xZrx) dispersoids in a ternary AlndashScndashZr alloycoarsen at a much slower rate than the Al3Sc dispersoidsin a binary AlndashSc alloy This effect was first reported inRef 123 (although also observed in Ref 182) andaccording to Ref 33 the same authors demonstratedsoon after that the denser dispersoid distributionachieved in an AlndashScndashZr alloy leads to superiorrecrystallisation resistance compared to a binary AlndashScalloy An example of the increased recrystallisationresistance by adding both Zr and Sc is shown in Fig 26

In isothermal sections of the ternary AlndashScndashZr phasediagram it is indicated that the solid solubility ofSczZr is somewhat higher than that of Sc alone54 Ithas also been demonstrated both by electrical con-ductivity measurements (Fig 27) and microstructuralobservations that the supersaturation of SczZr isgreater than that of only Sc or Zr in as cast Alndash15(SczZr) alloys183 This indicates that it should bepossible to increase the volume fraction of dispersoids inAlndashScndashZr compared to AlndashSc It is suggested162 that theincreased volume fraction that can be achieved byadding both Sc and Zr can be advantageous inconventional wrought Al-alloys

There are at least two different conditions underwhich Al3Sc or Al3(Sc12xZrx) dispersoids can form toprevent recrystallisation

1 Sc (or Sc and Zr) is in solid solution before thedeformation In the case of cold deformation and

25 Grain refinement as a function of Sc addition in pure

Al (redrawn from Ref 32) and AlndashZnndashMgndashZr (redrawn

from Ref 169) note that data points are plotted on

different ordinate axes

Roslashyset and Ryum Scandium in aluminium alloys

34 International Materials Reviews 2005 VOL 50 NO 1

subsequent annealing the Al3Sc or Al3(Sc12xZrx)dispersoids may nucleate and grow before the nucleationand growth of recrystallised grains takes placeDispersoids can form after a direct up-quench to theannealing temperature115143148184 during ramp-up tothe annealing temperature115 or by pre-annealing at anintermediate temperature129 In the case of hot deforma-tion the Al3Sc or Al3(Sc12xZrx) dispersoids maynucleate and grow during preheating of the materialand during the hot deformation itself184

2 The Al3Sc or Al3(Sc12xZrx) dispersoids are formedin the material before deformation184 Considering coldrolling and subsequent annealing the annealing tem-perature Tann may be either lower or higher than thetemperature Tdisp at which the dispersoids were formedIf TannTdisp only limited if any coarsening of thedispersoids is expected to take place and thus the Zenerdrag from the particles is expected to be practicallyconstant The driving force for recrystallisation how-ever is expected to decrease somewhat with theannealing time as a result of recovery processes Thusif recrystallisation does not occur within short annealingtimes the material is expected to remain unrecrystallisedfor infinite time at the annealing temperature IfTannTdisp there will be substantial coarsening of thedispersoids during annealing In order for the materialto remain unrecrystallised the decrease in driving forcefor recrystallisation owing to recovery has to be at leastas rapid as the decrease in Zener drag because of particlecoarsening

Experimental comparisons of the conditions abovepoint in the direction that the recrystallisation resistanceis poorest when Sc (or Sc and Zr) is in solid solutionbefore deformation and the deformed material is up-quenched to the annealing temperature148 or when Al3Scor Al3(Sc12xZrx) dispersoids are formed before defor-mation at TdispampTann184185 Excellent recrystallisationresistance is achieved if dispersoids are formed at anintermediate anneal of solutionised and deformedmaterial128 or if dispersoids are formed at TdispTann

before deformation148185ndash187 It seems that the decreasein Zener drag because of dispersoid coarsening in many

cases is slower than the decrease in driving force forrecrystallisation because of recovery processes Thusthere is an advantage in forming a high number densityof small dispersoids which for most practical casesmeans that they should be formed at TdispTann122

When an advancing high angle grain boundary iethe recrystallisation front is passing a coherent Al3Scdispersoid there are at least three possible grainboundarydispersoid interactions

1 The Al3Sc dispersoid retains its global orientationrelationship and thus loses its coherency with thesurrounding matrix

2 The Al3Sc dispersoid rotates as the grain boundarypasses either by diffusional processes at the dispersoidmatrix interface or by the grain boundary passingthrough the dispersoid and the Al3Sc dispersoidassumes the same crystallographic orientation as theAl matrix of the recrystallised grain

3 The Al3Sc dispersoid dissolves at the grainboundary and re-precipitates in the recrystallised grain

Which interactions that actually take place willprobably depend on the dispersoid size annealingtemperature and driving force for recrystallisation It isalso possible that alloy composition (other elementsthan Al) is of importance

It has been reported that large (Oslash about 100ndash150 nm)Al3Sc dispersoids in a deformed Alndash4 wt-Mgndash02 wt-Sc alloy annealed at 575uC lose the orientationrelationship with the matrix after being passed by therecrystallisation front148

A rotation of somewhat smaller Al3Sc dispersoids in arecrystallising binary Alndash025 wt-Sc alloy has beenreported115143 The rotation was reported to be accom-panied by substantial growth (from Oslash 30 nm to Oslash48 nm) as a result of enhanced Sc diffusion at the grainboundary Observations suggested that the grainboundaries were passing through the dispersoids andthus the Al3Sc dispersoids retained the orientationrelationship with the recrystallised Al matrix

Dissolution and re-precipitation of Al3Sc dispersoidshas been reported during recrystallisation of a 50 coldrolled Alndash02 wt-Sc alloy162 Large spherical partially

26 Fraction recrystallised structure in cold rolled sheets

of Alndash04 wt-Sc and Alndash04 wt-Scndash015 wt-Zr as a

function of annealing temperature redrawn from

Ref 183 27 Electrical conductivity in Alndash15(SczZr) alloys

redrawn from Ref 183

Roslashyset and Ryum Scandium in aluminium alloys

International Materials Reviews 2005 VOL 50 NO 1 35

coherent dispersoids were observed to dissolve at therecrystallisation front and re-precipitate as smallercoherent Al3Sc cuboids

Superplastic forming

It seems that the first publication on superplasticproperties of Sc-containing Al-alloys was a study of anAlndash35Cundash14Mgndash045Mnndash04(SczZr) alloy188

It was recognised that the superplastic properties are aresult of the stabilisation of the fine grain structure byAl3Sc dispersoids The Sc-containing Al alloys that havereceived most attention for their superplastic propertieshowever are those of the AlndashMgndashSc system which wasfirst published in a patent189 Here it was noted that anAlndash4 wt-Mgndash05 wt-Sc alloy had superior superplasticproperties compared to fine-grained 7475 (AlndashZnndashMgndashCu alloy) Binary Alndash05 wt-Sc and Alndash4 wt-Mgalloys did not behave superplastically The flow stress atthe hot forming temperature was found to be much (30ndash40) lower in the ternary alloy than that of the twobinary alloys

The superplastic properties of AlndashMgndashSc alloys havebeen explored by several research groups over the lastdecade190ndash196 It has frequently been found that thedeformation mechanism is dominated by grain bound-ary sliding190 However it has also been reported thatAlndashMgndashSc alloy may deform superplastically withoutnoticeable grain boundary sliding23 It is generallyrecognised that the grain boundary sliding mechanismis facilitated when the average grain size is very smalland grain boundaries are predominantly high-angleSuch a microstructure may be achieved by carefulthermomechanical processing of the starting mate-rial193194197198 It has however been shown that a finegrained structure with high angle boundaries maydevelop during superplastic forming of AlndashMgndashSc alloyseven if the starting microstructure is an entirely differentone for instance that of a cold rolled sheet192 It has alsobeen suggested that superplastic forming of as castmaterial may be possible189

One of the more efficient thermomechanical processesfor achieving an ultrafine grain structure with high anglegrain boundaries in Al-alloys is equal channel angularpressing (ECAP) A JapanesendashAmerican group ofscientists has published an impressive body of researchon improvements in superplastic properties in Al-alloys processed by ECAP over the last few years andseveral of the publications are from investigations onAlndashMgndashSc alloys170199ndash224 Maximum strains in excessof 2000 at a strain rate of 0033 s21 have beenachieved170201202217 which is an extraordinarily goodcombination of high strain and high strain rate for analuminium alloy

Superplastic properties of AlndashCundashMg(ndashMn)ndashSc(ndashZr)and AlndashMgndashSc(ndashZr) alloys have been mentionedNoticeable superplasticity in other Sc-containing Al-alloys has also been reported such as AlndashZnndashMg(ndashCu)ndashScndashZr169225ndash228 AlndashLindashSc229 AlndashMgndashLindashScndashZr229ndash234

AlndashLindashMgndashCundashScndashZr235236 and AlndashCundashLindashScndashZr233

Precipitation hardeningHardening by Al3Sc precipitates

It has been noted that when Al3Sc particles precipitate inthe temperature range 250ndash350uC they give a significanthardness increase in the alloy Some authors point out

that Sc is a more effective precipitation hardening elementper atomic fraction added than the elements that arecommonly used for precipitation hardening121130 (In onepaper29 it is claimed that only Au has a strongerstrengthening effect than Sc) However the amount ofSc that can be precipitated from supersaturated solidsolution is rather limited and thus the absolute values ofthe hardness increase from the precipitation hardening ismuch lower than what is normally associated withprecipitation hardened alloys Also the temperatureregime for age hardening by precipitation of Al3Sc issomewhere in between the temperature regimes for agehardening and solution heat treatments of commonprecipitation hardened alloys This makes a combinedprecipitation of Al3Sc and other strengthening precipi-tates unfeasible Thus precipitation strengthening byAl3Sc is most feasible in alloy systems that are non-heat-treatable The non-heat-treatable aluminium alloy sys-tems are according to the Aluminum Associationdesignations the 1xxx series (99 pure Al) the 3xxxseries (AlndashMn) and the 5xxx series (AlndashMg) The purposeof adding Sc to these alloys may be either to stabilise themicrostructure of wrought semiproducts (extrusionsrolled plates forgings etc) as discussed in the sectionon lsquoRecrystallisation resistancersquo above or to provideextra strength to the alloy through precipitation hard-ening In the latter case it is appropriate to considerwhether the Sc-containing alloy still should be classifiedas non-heat-treatable A heat treatment is applied thatbrings about a significant precipitation hardening On theother hand the hardness increase that is achieved throughthe heat treatment is lower than what is normallyassociated with heat-treatable alloy systems Hence eventhough it seems like a contradiction one chooses to keepusing the term lsquonon-heat-treatablersquo about these alloys

Table 7 gives an overview of some mechanicalproperties of Sc-containing non-heat-treatable alloysthat are reported in the literature Most of theexperimental work on Sc in 1xxx-types of alloys hasbeen done on binary AlndashSc alloys with much higherpurity than industrial alloys

Strengthening mechanisms

When the precipitates are larger than a critical size thestrengthening effect is due to the Orowan-mechanism iedislocations can only pass the precipitates by looping Inthis case the strengthening effect of the particles isapproximately inversely proportional to the mean parti-cle spacing When the precipitates can be sheared bydislocations there are a number of strengthening mechan-isms that apply It is proposed by Parker et al108 that thetwo major contributing mechanisms are coherency strainand anti-phase-boundary energy In a recent detailedstudy of strengthening mechanisms in binary AlndashSc alloysby Marquis and colleagues117118 the strengthening fromshear modulus mismatch between the matrix and theprecipitates is also accounted for A qualitatively goodmatch between theoretical strengthening and measuredvalues is achieved in this work both for deformation atroom temperature and at 300uC

Effect of Sc on precipitation strengthening in heat-treatablealloys

Following the AA designation system the traditionalheat-treatable Al-alloys are those that belong to the 2xxx

Roslashyset and Ryum Scandium in aluminium alloys

36 International Materials Reviews 2005 VOL 50 NO 1

series (AlndashCu) 6xxx series (AlndashMgndashSi) and 7xxx series(AlndashZnndashMg) AlndashLi alloys should also be mentionedSeveral investigations have been carried out in order toclarify the effects of Sc on the precipitation behaviour inthese alloy systems

AlndashCu alloys

The precipitation sequence in AlndashCu alloys is oftendescribed as follows

Supersaturated solid solutionRGP-zonesRh0Rh9Rh(Al2Cu)

The highest strength is normally achieved when the h0or h9 precipitates are predominant Typical precipitationheat treatment temperatures for AlndashCu alloys are in therange 160ndash190uC238 which is considerably lower thanthe typical precipitation temperature for Al3ScComparisons of the aging responses of AlndashCu and AlndashCundashSc alloys at 150 and 200uC indicate that there is nonoticeable effect of Sc on the precipitation kinetics ofh9153 It is observed that the h9 precipitates may nucleateon Al3Sc particles153 At 300uC it is observed that h9particles are somewhat smaller in AlndashCundashSc alloys thanin AlndashCu alloys156

AlndashMgndashSi alloys

The following precipitation sequence is commonlyreported for AlndashMgndashSi alloys

Supersaturated solid solutionRGP-zonesRb0Rb9Rb(Mg2Si)

For peak aged alloys the predominant precipitatetype is b0 for which the stoichiometric composition hasrecently been resolved to be Mg5Si6239 Temperatures inthe range 160ndash205uC are typically used for precipitationhardening of these alloys238 Adding both 03 wt-Scand 01 wt-Zr to an Alndash06 wt-Mgndash065 wt-Sialloy does not seem to alter the precipitation kineticsof b0 at 165uC However the hardness increase becauseof precipitation hardening appears to be smaller in theSczZr-containing alloy240 In another investigationadditions of 01 wt-Sc 015 wt-Sc 02 wt-Sc04 wt-Sc and 02 wt-Scz01 wt-Zr were made toan Alndash08 wt-Mgndash07 wt-Si alloy241 Here it wasalso observed that the precipitation kinetics of b0 wasseemingly independent of the Sc additions (Fig 28)TEM observations indicated that the b0 precipitateswere of comparable sizes in the investigated alloys andno interactions between Al3Sc and b0 were observed(Fig 29) In a third study242 where the effect of Sc onthe precipitation in an AlMgSindashSiC metal matrixcomposite was investigated there also does not seemto be any effect on the precipitation kinetics Howevercontrary to the findings of Ref 240 it is reported thatthe Sc addition leads to a higher hardness increase thanin the corresponding Sc free alloy

AlndashMgndashZn alloys

For these alloys the following precipitation sequence isoften ascribed

Table 7 Mechanical properties in non-heat-treatable Al-alloys with Sc

Reference Alloy wt- YS MPa UTS MPa Note

1xxx alloys171 000Sc 15 48 Cast material aged 288uC8 h

023Sc 159 185 Cast material aged 288uC8 h038Sc 199 220 Cast material aged 288uC8 h000Sc 14 49 Cold rolled material (89) aged 288uC8 h023Sc 198 208 Cold rolled material (89) aged 288uC8 h038Sc 240 264 Cold rolled material (89) aged 288uC8 h000Sc 8 34 Cold rolled material quenched from 649uC aged 288uC8 h023Sc 147 157 Cold rolled material quenched from 649uC aged 288uC8 h038Sc 193 199 Cold rolled material quenched from 649uC aged 288uC8 h

121 05Sc 160 ndash Forged material quenched from 635uC aged 250uC50 h23 05Sc 298 319 Hot rolled 288uC cold rolled 69ndash81 aged 288uC4 h112 01Sc 132 166 Hot z cold rolled material quenched from 630uC

aged 320uC133 h148 02Sc 138 ndash Cast material aged 300uC10 h compression test159 04Sc 196 ndash Cast material aged 300uC10 h compression test117 118 03Sc 209 ndash Cast material quenched from 648uC aged 300uC5 h

compression test3xxx alloys171 1Mn 015Sc 216 221 Cold rolled material (89) aged 288uC8 h

1Mn 05Sc 309 323 Cold rolled material (89) aged 288uC8 h186 05Mn 02Mg

026Sc 015Zr162 201 Extruded material solutionised 600uC aged 250uC

5xxx alloys171 1Mg 43 111 Cold rolled material (89) aged 288uC8 h

1Mg 03Sc 288 303 Cold rolled material (89) aged 288uC8 h53Mg 147 259 Cold rolled material (50) wintermediate anneals

at 343uC aged 288uC8 h53Mg 03Sc 368 401 Cold rolled material (50) wintermediate anneals

at 343uC aged 288uC8 h23 2Mg 05Sc 376 401 Hot rolled 288uC cold rolled 69ndash81 aged 288uC4 h

4Mg 05Sc 414 4606Mg 05Sc 433 503

237 4Mg 1Sc 420 525 Cold rolled material (83) aged 320uC1 h148 4Mg 02Sc 194 ndash Cast material aged 300uC10 h compression test

Tensile test data except where noted YS yield strength UTS ultimate tensile strength

Roslashyset and Ryum Scandium in aluminium alloys

International Materials Reviews 2005 VOL 50 NO 1 37

Supersaturated solid solutionRGP-zonesRg9Rg(Zn2Mg)

The maximum hardness is normally achieved whenthe g9 precipitates are predominant Common precipita-tion hardening temperatures are in the range 95ndash180uCand a two-step precipitation heat treatment within thistemperature regime is often used238 It has beenobserved in some investigations that Sc and SczZradditions to AlndashMgndashZn alloys slow down the precipita-tion of g9 somewhat243 Other investigations find thatthere is no effect of Sc on the precipitation behaviour ofg9244245 and yet others report that Sc additionssignificantly speed up the precipitation of g9246 In Ref247 it is found that an Sc addition leads to coarser g9precipitates and it is claimed that this gives an improvedductility of the alloy The strength-loss associated withlarger particle size is reported to be counterbalanced bystrengthening from Al3Sc precipitates

AlndashLi alloys

The precipitation sequence in binary AlndashLi alloys isapparently simple

Supersaturated solid solutionRd9Rd (AlLi)

where d9 is the metastable Al3Li phase which just likeAl3Sc has the L12 type of atomic arrangement Thetypical temperature regime for precipitation of d9 whichis the strengthening phase in this system is approx 150ndash200uC A comparison of the age hardening response ofan Alndash26 wt-Li and an Alndash24 wt-Lindash019 wt-Scalloy at 180uC248 and 200uC161 indicates that the onsetof d9 precipitation is not altered by the presence of ScThe hardness curves for the two alloys are practicallyidentical at 200uC whereas at 180uC the peak hardnesslevel is slightly higher in the AlndashLi than the AlndashLindashScalloy DSC measurements at constant heating ratesindicate that the addition of Sc to an AlndashLi alloysincreases the activation energy for d9 precipitation andmoves the exothermic peak associated with d9 precipita-tion to a higher temperature248 For specimens aged at

either 180uC or 200uC TEM observations reveal that thed9 precipitates are much smaller in the Sc containingalloy than in binary AlndashLi both in the peak agedcondition and in the overaged condition161248 Additionof Sc has also been observed to reduce the size of d9precipitates in other AlndashLi based alloys249ndash251 In an AlndashLindashCundashZr alloy an addition of Sc has been reported toslow down the homogeneous precipitation of d9252253 Ithas been claimed that Sc reduces the quench sensitivityand delays room temperature aging of AlndashLi basedalloys254ndash256

When present in the microstructure before the pre-cipitation of d9 the Al3Sc precipitates may act as effec-tive nucleation sites for d9 The resulting precipitates arespheres of d9 with a core of Al3Sc161249252ndash255257ndash261

Corrosion resistanceAn appreciable amount of data is available on the effectsof Sc on the corrosion behaviour of wrought Al-alloysSome of these effects are apparently derived from theeffects of Sc on the microstructure of the alloys It hasbeen reported that an addition of Sc increases thecorrosion potential (makes it less negative) in pureAl262ndash264 in AlndashZn alloys265266 AlndashMg alloys267 AlndashZnndashMgndashCu alloys264268 AlndashCundashMgndashMn alloys264 andin AlndashCundashLindashMgndashAg alloys264 Even though Sc alsohas been reported to decrease the corrosion potential in

28 Age hardening response at 175uC for Alndash08 wt-Mgndash

07 wt-Si alloy (Base) with additions of 02 wt-Sc

04 wt-Sc and 02 wt-Scz01 wt-Zr from Ref 241

29 TEM images of a b0 precipitates in Alndash08 wt-Mgndash

07 wt-Si alloy and b b0 and Al3(Sc1ndashxZrx) in a similar

alloy with addition of 02 wt-Scz01 wt-Zr from

Ref 241

Roslashyset and Ryum Scandium in aluminium alloys

38 International Materials Reviews 2005 VOL 50 NO 1

AlndashMg alloys269270 it seems that the general trend isthat adding Sc to an alloy makes it slightly more nobleThe change in corrosion potential is much morepronounced when Sc is added in amounts larger thanthe eutectic composition263 ie there is a considerablecontribution from primary or eutectic Al3Sc to theoverall potential It has also been demonstrated that thechange in corrosion potential caused by Sc can dependon the heat treatment applied to the alloy267268

Even though the corrosion potential is an essentialparameter in establishing the corrosion behaviour of analloy an increase in the corrosion potential does notnecessarily imply an improved self-corrosion resistanceHowever measurements of corrosion rates and passiva-tion current densities strongly suggest that the self-corrosion resistance in general is considerably improvedwhen Sc is added to wrought Al-alloys263264267 Someobserved variations in corrosion potential and passiva-tion current densities with Sc content in binary AlndashScalloys are plotted in Fig 30

Material failure in corrosive environments is often dueto localised corrosion attacks which may propagaterapidly even though the bulk material has a goodresistance against general corrosion It has been pointedout that hypereutectic additions of Sc may lead tomicrogalvanic corrosion beside primary Al3Sc parti-cles264 In AlndashMg alloys grain boundary precipitation ofAl8Mg5 can lead to localised corrosion attacks such asintergranular corrosion (IGC) exfoliation corrosion(EC) and stress corrosion cracking (SCC) In wroughtmaterial such precipitation may occur in the 60ndash180uCtemperature regime and heating in this temperaturerange is referred to as lsquosensitationrsquo An AlndashMgndashSc alloywas found to be immune against intergranular corrosionand have moderate susceptibility to exfoliation corro-sion after annealing at 350uC271 After sensitation heattreatments severe IGC and EC was observed but notquite as severe as in a corresponding alloy without ScAs for SCC the AlndashMgndashSc alloy was found to be highlyresistant271 In another study it was found that additionof 056 wt-Sc reduces the SCC susceptibility of an Alndash68 wt-Mg alloy in the as-rolled state and afterannealing at 250uC whereas in a sensitised specimenthe SCC susceptibility is somewhat increased by the Scaddition272 A third investigation found that Sc has nomeasurable detrimental effect on the SCC susceptibilityof sensitised Alndash5Mgndash015Zr alloy273 SCC is also a

severe problem in high strength AlndashZnndashMgndashCu alloys Ithas been shown that small Sc additions are effective inreducing the SCC sensitivity of these alloys244246268274

Use of Sc-containing Al alloysA systematic development of Sc-containing aluminiumalloys took place in the former USSR in the 1980s andthe interest for Sc as an alloying element in aluminiumalloys hit the western world approximately 10 yearslater Even though a number of improvements in Alalloys achieved by Sc addition have been demonstratedthe current uses of such alloys are very limited This isrelated to the very high price of scandium

In Russia some parts of military aircraft are made ofSc-containing AlndashLi alloys In the western world themain usage of Sc-containing alloys is for sportsequipment Ashurst Technology and Kaiser Aluminumdeveloped a Sc-containing 7xxx alloy for baseball andsoftball bats which was introduced to the Americanmarket in 1997 by Easton Alcoa soon followed with aSc-containing alloy for a competing brand of batsLouisville Slugger Since then several new and improvedSc-containing alloys for bats have been introduced tothe market The purpose of adding Sc is to increase theyield strength of the alloy allowing for a down-gaugingof the wall thickness which in turn gives a strongerlsquospring-rsquo or lsquotrampoline-rsquo effect when the ball hits thebat

Shortly after the introduction of the Sc containingbats Easton also launched Sc-containing 7xxx tubingfor bicycle frames Just as in the bats Sc increases theyield strength of the alloy allowing for down-gauging oftube wall thickness and a corresponding weight reduc-tion of the bicycle frame An Italian manufacturer ofbicycle tubing Dedacciai also delivers tubes in a Sc-containing 7xxx alloy

Other sports equipment made from Sc-containingaluminium alloys includes lacrosse sticks and tent polesSmith and Wesson has also introduced a series ofhandguns where the frame is made from a Sc-containingAl alloy

A common factor for the items mentioned above isthat the material cost is only a minor part of the totalmanufacturing cost of the end product and also thatthese products are aimed at a group of customers thathave a certain awareness of new materials Both baseballbats and bicycle frames have been marketed aslsquoscandium alloyrsquo even though the Sc content is muchlower than 1

Currently AlndashSc master alloys for the production ofSc-containing Al alloys are available at a price thatcorresponds to US$ 2000 per kg of Sc This means that ifone wants to add 02 wt-Sc to an alloy which is afairly common content one also increases the price ofthe alloy by US$ 4 per kg alloy Depending on the alloytype Sc is added to this represents a tripling orquadrupling of the price of the alloy There are notmany existing products where such an increase inmaterial cost can be justified In order to see awidespread use of Sc in high-volume products the Scprice has to come down considerably Actually the priceof adding Sc to Al alloys has gone down by a factor 3ndash10over the last 10ndash15 years and substantial price reduc-tions are also expected in the future

30 Observed variations in corrosion potential and passi-

vation current densities with Sc content in binary Alndash

Sc alloys based on data from Ref 263

Roslashyset and Ryum Scandium in aluminium alloys

International Materials Reviews 2005 VOL 50 NO 1 39

The current production of AlndashSc master alloys isbased upon and will continue to be based upon for theforeseeable future the reduction of Sc2O3 or other Sccompounds directly in molten aluminium It is notnecessary as many tend to believe to take the route viametallic Sc Thus the price of AlndashSc master alloy isgoverned by the price of Sc2O3 or other Sc compoundsin question and not by the price of metallic scandiumThe Sc2O3 which is the main source for todayrsquos AlndashScmaster alloy production comes from stockpiles in theformer USSR These stockpiles will be exhausted withina few years and new reliable sources of Sc2O3 or otherSc compound production are sought It turns out thatthe most economically viable option that has beendisclosed so far is the processing of Red Mud from theBayer process of extracting alumina from bauxiteScandium is enriched in the Red Mud and is extractedfrom a Red Mud aqueous slurry by selective leachingsubsequent ion-exchange procedure and finally a liquidndashliquid extraction procedure It is not required to build aseparate lsquoSc factoryrsquo to do this but rather build an lsquoadd-onrsquo to existing Bayer process plants Such a processroute is expected to bring down the price of Sc2O3

considerably which in turn means that AlndashSc masteralloy price should drop accordingly Preliminary ana-lyses suggest a price of approx US$ 400 per kg Sc in themaster alloy which translates to an added cost of 80cent per kilo when 02 wt-Sc is added to an aluminiumalloy This is also a considerable increase in the materialcost but with such prices one should expect to see Sccontaining alloys in many more applications than whatis the case at the present time

Concluding remarksThe body of published investigations on Al-based alloyswith Sc addition provides a sound basis of knowledgefor metallurgists that want to look into the possibility ofenhancing the performance of a wrought Al-alloy byadding Sc to it Ternary AlndashScndashX phase diagrams areavailable for practically every technologically importantalloying element in Al The effect of a wide range ofternary alloying elements on the precipitation behaviourof Al3Sc is accounted for It has been shown that theAl3Sc phase can be effective as a grain refiner adispersoid former and a precipitate hardening agentand some of the underlying conditions for achieving thedesired Al3Sc formation have been outlined Addingsome Zr together with Sc has proven to be beneficial Itmay lead to effective grain refinement at a lower Sc levelbut the most prominent effect is the refinement indispersoid distribution that can be achieved An addi-tion of Sc has little if any effect on precipitation in the2xxx 6xxx and 7xxx alloy systems and some effects onthe precipitation in AlndashLi based alloys With respect tocorrosion behaviour adding Sc to an Al-alloy does ingeneral seem to make the alloy slightly more noble andto increase its self-corrosion resistance Scandium-containing Al alloys have very few uses at the presenttime as a result of the high price of scandium The priceof Sc is expected to decrease significantly in the futureand this should lead to the disclosure of moreapplications where it is economically feasible to takeadvantage of the improved properties of some Sc-containing aluminium alloys

References1 D R Lide lsquoCRC handbook of chemistry and physicsrsquo 71st edn

4ndash29 1990 Boston USA CRC Press

2 E M Savitsky V F Terehova I V Burov and O P Naumkin

Proc Fourth Conf on lsquoRare earth researchrsquo Phoenix Arizona

USA April 1964 409ndash420

3 E M Savitskii V F Terekhova I V Burov O P Naumkin and

I A Markova Inorg Mater 1965 1 1503ndash1512

4 O P Naumkin V T Terekhova and E M Savitskiy Russ

Metall 1965 (4) 128ndash136

5 W G Moffatt lsquoThe handbook of binary phase diagramsrsquo 1981

Schenectady NY USA General Electric Co

6 E A Brandes (ed) lsquoSmithells metals reference bookrsquo 6th edn

1983 London UK Butterworths

7 R P Elliott and F A Shunk Bull Alloy Phase Diagrams 1981

2 (2) 222ndash223

8 K A Gschneider Jr and F W Calderwood Bull Alloy Phase

Diagrams 1989 10 34ndash36

9 H Okamoto J Phase Equil 1991 12 612ndash613

10 J L Murray J Phase Equil 1998 19 380ndash384

11 M E Drits E S Kadaner T V Dobatkina and N I Turkina

Russ Metall 1973 (4) 152ndash154

12 S-I Fujikawa M Sugaya H Takei and K-I Hirano J Less-

Common Met 1979 63 87ndash97

13 N Blake and M A Hopkins J Mater Sci 1985 20 2861ndash2867

14 V I Kononenko and S V Golubev Russ Metall 1990 (2) 193ndash

195

15 T B Massalski J L Murray L H Bennett and H Baker (eds)

lsquoBinary alloy phase diagramsrsquo 1986 Metals Park OH USA

ASM

16 G Cacciamani P Riani G Borzone N Parodi A Saccone

R Ferro A Pisch and R Schmid-Fetzer Intermetallics 1999 7

101ndash108

17 H Okamoto J Phase Equil 2000 21 310

18 A F Norman P B Pragnell and R S McEwen Acta Mater

1998 46 5715ndash5732

19 I N Pyagai and A V Vakhobov Russ Metall 1990 (5) 50ndash52

20 C L Fu J Mater Res 1990 5 971ndash979

21 X Lu and Y Wang Calphad 2002 26 555ndash561

22 R R Sawtell and J W Morris Jr Proc lsquoDispersion strengthened

aluminium alloysrsquo Phoenix Arizona USA January 1988 409ndash

420

23 R R Sawtell and C L Jensen Metall Trans A 1990 21A 421ndash

430

24 L A Willey Unpublished research Alcoa 1970 Data points are

extracted from Ref 10

25 N I Turkina and V I Kuzmina Russ Metall 1976 (4) 179ndash

183

26 T Torma E Kovacs-Csetenyi I Vitanyi M Butova and

J Stepanov Proc 6th Int Symp on lsquoHigh purity materials in

science and technologyrsquo Akademie der Wissenschaften der DDR

Dresden Germany May 1985 388ndash389

27 A L Berezina V A Volkov B P Domashnikov and K V

Chuistov Metallofizika 1987 9 (5) 43ndash47

28 H-H Jo J Korean Inst Metals 1990 28 499ndash504

29 H-H Jo and S-I Fujikawa Mater Sci Eng 1993 A 171 151ndash

161

30 S Celotto and T J Bastow Philos Mag A 2000 80 1111ndash1125

31 J Roslashyset and N Ryum submitted to Mater Sci Eng

32 M E Drits L S Toropova Yu G Bykov F L Gushchina V I

Elagin and Yu A Filatov Russ Metall 1983 (1) 150ndash153

33 L S Toropova D G Eskin M L Kharakterova and T V

Dobatkina lsquoAdvanced aluminum alloys containing scandium

structure and propertiesrsquo 1998 Amsterdam The Netherlands

Gordon and Breach Science Publishers

34 V V Cherkasov P P Pobezhimov L P Nefedova E V Belov

and G M Kuznetsov Met Sci Heat Treat 1996 (6) 268ndash270

35 Kh O Odinaev I N Ganiev V V Kinzhibalo and B Ya

Kotur Dokl Akad Nauk Tadzh SSR 1989 32 37ndash38

36 Kh O Odinaev I N Ganiev and A V Vakhobov Russ Metall

1991 (4) 200ndash203

37 J Grobner R Schmid-Fetzer A Pisch G Cacciamani P Riani

N Parodi G Borzone A Saccone and R Ferro Z Metallkd

1999 90 872ndash880

38 E A Marquis and D N Seidman Microsc Microanal 2002 8

(Suppl 2) 1100CDndash1101CD

39 A Pisch J Grobner and R Schmid-Fetzer Mater Sci Eng A

2000 A 289 123ndash129

Roslashyset and Ryum Scandium in aluminium alloys

40 International Materials Reviews 2005 VOL 50 NO 1

40 C Xia F Zeng and Y Gu Trans Nonferrous Met Soc China

2003 13 1124ndash1127

41 M Yu Teslyuk and V S Protasov Sov Phys Crystallogr 1966

10 470ndash471

42 M L Kharakterova and T V Dobatkina Russ Metall 1988

(6) 175ndash178

43 M L Kharakterova Russ Metall 1991 (4) 195ndash199

44 L S Toropova M L Kharakterova and D G Eskin Russ

Metall 1992 (3) 194ndash199

45 P Riani L Arrighi R Marazza D Mazzone G Zanicchi and

R Ferro J Phase Equil Diff 2004 25 22ndash52

46 A T Tyvanchuk T I Yanson B Ya Kotur O S Zarechnyuk

and M L Kharakterova Russ Metall 1988 (4) 190ndash192

47 L L Rokhlin T V Dobatkina and M L Kharakterova Powder

Metall Met Ceram 1997 36

48 A Z Ikromov I N Ganiev and V V Kinzhibalo Dokl Akad

Nauk Tadzh SSR 1990 (6) 391ndash392

49 I N Ganiev A Z Ikromov and V G Khudoiberdiev Russ

Metall 1995 (3) 125ndash127

50 I N Fridlyander L L Rokhlin T V Dobatkina and N I

Nikitina Met Sci Heat Treat 1993 (10) 567ndash571

51 I N Fridlyander L L Rokhlin T V Dobatkina V V

Kinzhibalo and A T Tyvanchuk Russ Metall 1998 (1) 161ndash

166

52 R A Emigh E L Bradley and J W Morris Jr in lsquoLight-weight

alloys for aerospace applications IIrsquo (ed E W Lee and N J

Kim) 27ndash43 1991 TMS

53 L S Toropova A N Kamardinkin V V Kindzhibalo and A T

Tyvanchuk Phys Met Metall 1990 70 (6) 106ndash110

54 A N Kamardinkin T V Dobatkina and T D Rostova Russ

Metall 1991 (4) 216ndash218

55 L S Torodskaya T V Dobatkina and A N Kamardinkin

Russ Metall 1992 (5) 128ndash131

56 E M Sokolovskaya E F Kazakova E I Poddyakova and A

A Ezhov Met Sci Heat Treat 1997 (5) 211ndash213

57 Y Harada and D C Dunand Mater Sci Eng 2002 A 329ndash331

686ndash695

58 N E Drits L S Toropova and F L Gushchina Russ Metall

1984 (4) 229ndash232

59 E M Sokolovskaya E F Kazakova V A Alikhanov and E V

Zhuravleva Moscow Univ Chem Bull 1997 52 (5) 70ndash72

60 E M Sokolovskaya E F Kazakova and E I Poddyakova Met

Sci Heat Treat 1989 (11) 837ndash839

61 G M Cheldieva E F Kazakova E M Sokolovskaya and N I

Kaloev Russ Metall 1990 (6) 87ndash90

62 E M Sokolovskaya E F Kazakova and O D-S Kendivan

Russ Metall 1998 (4) 135ndash137

63 N G Bukhanko E F Kazakova and E M Sokolovskaya Russ

Metall 2001 (4) 425ndash431

64 E D Trubnyakova O I Bodak I N Ganiev and A V

Vakhobov Russ Metall 1987 (3) 219ndash222

65 I N Fridlyander and L V Molchanova Russ Metall 2003 (5)

476ndash480

66 R A Altynbaev S Kh Khairidinov and A V Vakhobov Russ

Metall 1987 (4) 194ndash196

67 J C Schuster and J Bauer J Less-Common Met 1985 109

345ndash350

68 L L Rokhlin A S Fridman T V Dobatkina and D G Eskin

Russ Metall 1991 (6) 146ndash148

69 A S Fridman T V Dobatkina and E V Muratova Russ

Metall 1992 (1) 207ndash209

70 C Xia F Zeng and Y Gu Trans Nonferrous Met Soc China

2003 13 546ndash552

71 F Zeng C Xia and Y Gu J Alloys Comp 2004 363 175ndash181

72 L L Rokhlin T V Dobatkina N R Bochvar and E V Lysova

J Alloys Comp 2004 367 10ndash16

73 T V Dobatkina A S Fridman and E V Muratova Russ

Metall 1992 (5) 125ndash127

74 I N Fridlyander L L Rokhlin N R Bochvar E V Lysova

and O V Boteva Russ Metall 2001 (6) 661ndash666

75 V N Rechkin L K Lamikhov and T I Samsonova Sov Phys

Crystallogr 1964 9 325ndash327

76 I I Zalutskii and P I Kripyakevich Sov Phys Crystallogr

1967 12 341ndash343

77 T J Bastow C T Forwood M A Gibson and M E Smith

Phys Rev B 1998 58 2988ndash2997

78 K Fukunaga M Kolbe K Yamada and Y Miura Mater Sci

Eng 1997 A 234ndash236 594ndash597

79 E P George J A Horton W D Porter and J H Schneibel

J Mater Res 1990 5 1639ndash1648

80 E P George D P Pope C L Fu and J H Schneibel ISIJ Int

1991 31 1063ndash1075

81 Y Harada and D C Dunand Acta Mater 2000 48 3477ndash3487

82 J H Schneibel and E P George Scripta Metall Mater 1990 24

1069ndash1074

83 J H Schneibel and P M Hazzledine Mater Res Soc Symp

Proc 1991 213 323ndash328

84 J H Schneibel and P M Hazzledine J Mater Res 1992 7

868ndash875

85 C J Sparks E D Specht G E Ice P Zschack and J Schneibel

Mater Res Soc Symp Proc 1991 213 363ndash368

86 J Tarnacki and Y-W Kim Scripta Metall Mater 1989 23

1063ndash1068

87 M Asta V Ozolins and C Woodward JOM 2001 53 (9) 16ndash

19

88 M E Drits L S Toropova F L Gushchina and S G Fedotov

Sov Non-Ferrous Met Res 1984 12 83ndash85

89 Y Harada and D C Dunand Scripta Mater 2003 48 219ndash222

90 C Woodward M Asta G Kresse and J Hafner Phys Rev B

2001 63 094103-1-6

91 J-H Xu and A J Freeman Phys Rev B 1990 41 12553ndash12561

92 M F Bartholomeusz and J A Wert Acta Metall Mater 1992

40 673ndash682

93 G Bester and M Fahnle J Phys Condens Matter 2001 13

11551ndash11565

94 C L Fu and M H Yoo Proc lsquoOrdered intermetallics ndash physical

metallurgy and mechanical behaviorrsquo Irsee Germany June 1991

155ndash164

95 K Fukunaga T Shouji and Y Miura Mater Sci Eng 1997 A

239ndash240 202ndash205

96 D P Pope Proc lsquoOrdered intermetallics ndash physical metallurgy

and mechanical behaviorrsquo Irsee Germany June 1991 143ndash153

97 J-S Wang Acta Mater 1998 46 2663ndash2674

98 M H Yoo and C L Fu Mater Sci Eng 1992 A 153 470ndash478

99 R W Hyland Jr and R C Stiffler Scripta Metall Mater 1991

25 473ndash477

100 I G Brodova I V Polents O A Korzhavina P S Popelrsquo I P

Korshunov and V O Esin Melts 1992 4 392ndash397

101 I G Brodova O A Chikova I V Polents P S Popelrsquo and V O

Esin Casting Processes 1992 1 (2) 158ndash160

102 I G Brodova D V Bashlikov and I V Polents Mater Sci

Forum 1998 269ndash272 589ndash594

103 K B Hyde A F Norman and P B Pragnell Mater Sci Forum

2000 331ndash337 1013ndash1018

104 K B Hyde A F Norman and P B Pragnell Acta Mater 2001

49 1327ndash1337

105 J Roslashyset and N Ryum Proc 6th Int Conf on lsquoAluminum

alloysrsquo Toyohashi Japan July 1998 793ndash798

106 V I Elagin V V Zakharov and T D Rostova Met Sci Heat

Treat 1993 (6) 317ndash319

107 R W Hyland Jr Metall Trans A 1992 23A 1947ndash1955

108 B A Parker Z F Zhou and P Nolle J Mater Sci 1995 30

452ndash458

109 C L Rohrer M D Asta S M Foiles and R W Hyland Jr

Mater Res Soc Symp Proc 1996 398 477ndash482

110 G M Novotny and A J Ardell Mater Sci Eng 2001 A 318

144ndash154

111 J D Robson M J Jones and P B Pragnell Acta Mater 2003

51 1453ndash1468

112 C Tan Z Zheng and B Wang Proc 3rd Int Conf on

lsquoAluminium alloysrsquo Vol I NTH Trondheim Norway June

1992 290ndash294

113 M Nakayama A Furuta and Y Miura Mater Trans JIM

1997 38 852ndash857

114 E A Marquis and D N Seidman Acta Mater 2001 49 1909ndash

1919

115 M J Jones and F J Humphreys Acta Mater 2003 51 2149ndash

2159

116 E A Marquis D N Seidman and D C Dunand in lsquoCreep

deformation fundamentals and applicationsrsquo (ed R S Mishra

J C Earthman and S V Raj) 299ndash308 2002 TMS

117 D N Seidman E A Marquis and D C Dunand Acta Mater

2002 50 4021ndash4035

118 E A Marquis D N Seidman and D C Dunand Acta Mater

2003 51 285ndash287

119 M E Drits L S Toropova U G Bikov and G K Anastaseva

Proc lsquoDiffusion in metals and alloysrsquo Tihany Hungary Augustndash

September 1982 616ndash623

120 V I Elagin V V Zakharov and T D Rostova Met Sci Heat

Treat 1983 (7) 546ndash549

Roslashyset and Ryum Scandium in aluminium alloys

International Materials Reviews 2005 VOL 50 NO 1 41

121 M Ye Drits L B Ber Yu G Bykov L S Toropova and G K

Anastaseva Phys Met Metall 1984 57 (6) 118ndash126

122 M E Drits L S Toropova and Yu G Bykov Sov Non-Ferrous

Met Res 1985 13 309ndash314

123 V I Yelagin V V Zakharov S G Pavlenko and T D Rostova

Phys Met Metall 1985 60 (1) 88ndash92

124 N Sano Y Hasegawa K Hono H Jo K Hirano H W

Pickering and T Sakurai Journal de Physique 1987 48 C6 337ndash

342

125 N Sano H-H Jo K-I Hirano and T Sakurai J Jpn Inst

Metals 1989 39 444ndash450

126 N Sano H Jo K Hirano and T Sakurai Proc Second Int

Conf on lsquoAluminium alloysrsquo Beijing China October 1990 549ndash

554

127 Y Miura M Nakayama and A Furuta Proc lsquoAspects of high

temperature deformation and fracture in crystalline materialsrsquo

Nagoya Japan July 1993 255ndash262

128 Y W Riddle and T H Sanders Jr Mater Sci Forum 2000

331ndash337 939ndash944

129 Y W Riddle M McIntosh and T H Sanders Jr in lsquoLightweight

alloys for aerospace application VIrsquo (ed K Jata E W Lee

W Frazier and N J Kim) 25ndash39 2001 TMS

130 M E Drits J Dutkiewicz L S Toropova and J Salawa Crystal

Res Technol 1984 19 1325ndash1330

131 Y W Riddle MSc thesis Georgia Tech GA USA 1998

132 T J Bastow and S Celotto Mater Sci Eng 2003 C 23 757ndash

762

133 M C Carroll M J Mills G S Daehn P I Gouma M F

Savage and B R Dunbar in lsquoAutomotive Alloys 1999rsquo (ed

S Das) 239ndash246 2000 TMS

134 E Clouet M Nastar and C Sigli Phys Rev B 2004 69 064109-

1-14

135 V V Zakharov Met Sci Heat Treat 1997 (2) 61ndash66

136 J W Christian lsquoThe theory of transformation in metals and

alloysrsquo 2nd edn 1975 Pergamon Press Ltd

137 A L Berezina V A Volkov B P Domashnikov S V Ivanov

and K V Chuistov Phys Metals 1990 10 296ndash304

138 S-I Fujikawa and S Sakauchi Proc 6th Int Conf on

lsquoAluminum alloysrsquo Toyohashi Japan July 1998 805ndash810

139 Y S Touloukian R K Kirby R E Taylor and P D Desai

(eds) lsquoThermal expansion metallic elements and alloysrsquo 1975

New York Plenum

140 J Roslashyset and N Ryum submitted to Scripta Mater

141 R O Simmons and R W Balluffi Phys Rev 1960 117 52ndash61

142 M Ocko E Babic R Krsmik E Girt and B Leontic J Phys F

Metals Phys 1976 6 703ndash707

143 M J Jones and F J Humphreys Proc First Joint Int Conf on

lsquoRecrystallization and grain growthrsquo Aachen Germany August

2001 Springer Verlag 1287ndash1292

144 S Iwamura M Nakayama and Y Miura Mater Sci Forum

2002 396ndash402 1151ndash1156

145 S Iwamura and Y Miura Acta Mater 2004 52 591ndash600

146 M Asta S M Foiles and A A Quong Phys Rev B 1998 57

11265ndash11275

147 R W Hyland Jr M Asta S M Foiles and C L Rohrer Acta

Mater 1998 46 3667ndash3678

148 J Roslashyset and N Ryum Proc 4th Int Conf on lsquoAluminium

alloysrsquo Vol I Atlanta GA USA September 1994 194ndash201

149 M E Drits L S Toropova G K Anastaseva and G L

Nagornichnykh Russ Metall 1984 (3) 192ndash195

150 E A Marquis D N Seidman and D C Dunand Acta Mater

2003 51 4751ndash4760

151 M E Drits L S Toropova and Yu G Bykov Met Sci Heat

Treat 1983 (7) 550ndash554

152 V V Zakharov and T D Rostova Met Sci Heat Treat 1995

(2) 65ndash69

153 M Nakayama and Y Miura Proc 4th Int Conf on lsquoAluminium

alloysrsquo Vol I Atlanta GA USA September 1994 538ndash545

154 M Nakayama and Y Miura J Jpn Inst Light Metals 1996 46

275ndash279

155 M Nakayama T Okuyama and Y Miura Mater Sci Forum

2000 331ndash337 927ndash932

156 M Nakayama T Okuyama and Y Miura Proc 6th Int Conf

on lsquoAluminum alloysrsquo Toyohashi Japan July 1998 517ndash522

157 M L Kharakterova D G Eskin and L S Toropova Acta

Metall Mater 1994 42 2285ndash2290

158 V I Elagin V V Zakharov and T D Rostova Met Sci Heat

Treat 1992 (1) 37ndash45

159 H Wiik Siv Ing thesis NTH Institute of Metallurgy

Trondheim Norway 1995

160 J Roslashyset H Hovland and N Ryum Mater Sci Forum 2002

396ndash402 619ndash624

161 Y Miura K Horikawa K Yamada and M Nakayama Proc

4th Int Conf on lsquoAluminium alloysrsquo Vol II Atlanta GA USA

September 1994 161ndash168

162 Y W Riddle PhD thesis Georgia Tech GA USA 2000

163 B Forbord W Lefebvre F Danoix H Hallem and

K Marthinsen Scripta Mater 2004 51 333ndash337

164 J D Robson Acta Mater 2004 52 1409ndash1421

165 C B Fuller J L Murray and D N Seidman submitted to Acta

Mater 2004

166 M G Mousavi C E Cross and Oslash Grong Sci Technol Weld

Joining 1999 4 381ndash388

167 J S Vetrano S M Bruemmer L M Pawlowski and I M

Robertson Mater Sci Eng 1997 A 238 101ndash107

168 Y W Riddle and T H Sanders Jr Mater Sci Forum 2000

331ndash337 799ndash803

169 G M Khan A O Nikiforov V V Zakharov and I I Novikov

Tsvetnye Metally 1993 34 (11) 43ndash45

170 Z Horita M Furukawa M Nemoto A J Barnes and T G

Langdon Acta Mater 2000 48 3633ndash3640

171 L A Willey US Patent 3 619 181 9 November 1971

172 L K Lamikhov and G V Samsonov Tsvetnye Metally 1964 5

(8) 77ndash80

173 A L Berezina K V Chuistov N I Kolobnev L B

Khokhlatova and T A Monastyrskaya Mater Sci Forum

2002 396ndash402 741ndash746

174 F A Fasoyinu J Thomson D Cousineau T Castles and M

Sahoo Proc 6th Int AFS Conf on lsquoMolten aluminum

processingrsquo Orlando FL USA November 2001

175 Z Yin Q Pan Y Zhang and F Jiang Mater Sci Eng 2000

A 280 151ndash155

176 I I Novikov and O E Grushko Mater Sci Technol 1995 11

926ndash932

177 D Cousineau M Sahoo P D Newcombe T Castles and F A

Fasoyinu Proc lsquoAFS 105th casting congressrsquo Dallas TX USA

AprilndashMay 2001 157ndash184

178 C E Cross and Oslash Grong Proc 6th Int Conf on lsquoAluminum

alloysrsquo Toyohashi Japan July 1998 1441ndash1446

179 F A Costello J D Robson and P B Prangnell Mater Sci

Forum 2002 396ndash402 757ndash762

180 K B Hyde A F Norman and P B Prangnell Mater Sci

Forum 2002 396ndash402 39ndash44

181 M E Drits S G Pavlenko L S Toropova Yu G Bukov and

L B Ber Sov Phys Dokl 1981 26 (3) 344ndash346

182 A M Drits and B A Kopeliovich Russ Metall 1985 (4) 147ndash

151

183 V G Davydov V I Elagin V V Zakharov and T D Rostova

Met Sci Heat Treat 1996 (8) 347ndash352

184 M E Drits L S Toropova Yu G Bykov L B Ber and S G

Pavlenko Russ Metall 1982 (1) 148ndash152

185 T D Rostova V G Davydov V I Yelagin and V V Zakharov

Mater Sci Forum 2000 331ndash337 793ndash798

186 Y W Riddle H Hallem and N Ryum Mater Sci Forum 2002

396ndash402 563ndash568

187 J Roslashyset and Y W Riddle Proc 9th Int Conf on lsquoAluminium

alloysrsquo Brisbane Australia August 2004 1210ndash1215

188 A M Diskin V K Portnoi A M Drits and A A Alalykin Sov

Non-Ferrous Met Res 1986 14 499ndash500

189 R R Sawtell P E Bretz and C L Jensen US Patent 4 689 090

25 August 1987

190 G A Salishchev Yu B Timoshenko and R A Saitova Proc

Second Int Conf on lsquoAluminium alloysrsquo Beijing China October

1990 413ndash415

191 T G Nieh R Kaibyshev L M Hsiung N Nguyen and

J Wadsworth Scripta Mater 1997 36 1011ndash1016

192 T G Nieh L M Hsiung J Wadsworth and R Kaibyshev Acta

Mater 1998 46 2789ndash2800

193 J S Vetrano C H Henager Jr M T Smith and S M

Bruemmer in lsquoHot deformation of aluminum alloys IIrsquo (ed T R

Bieler L A Lalli and S R MacEwen) 407ndash418 1998 TMS

194 J S Vetrano C H Henager Jr S M Bruemmer Y Ge and

C H Hamilton in lsquoSuperplasticity and Superplastic Forming

1998rsquo (ed A K Gosh and T R Bieler) 89ndash97 1998 TMS

195 V Y Gertsman J S Vetrano C H Henager Jr and S M

Bruemmer Proc First Joint Int Conf on lsquoRecrystallization and

grain growthrsquo Aachen Germany August 2001 Springer Verlag

2001 837ndash842

196 Y Xiao C Gao H Ma and S Tian Trans Nonferrous Met Soc

China 2001 11 235ndash238

Roslashyset and Ryum Scandium in aluminium alloys

42 International Materials Reviews 2005 VOL 50 NO 1

197 A Gholinia F J Humphreys and P B Prangnell Acta Mater

2002 50 4461ndash4476

198 A Gholinia F J Humphreys and P B Prangnell Mater Sci

Forum 2002 408ndash412 1519ndash1524

199 S Komura P B Berbon M Furukawa Z Horita M Nemoto

and T G Langdon Scripta Mater 1998 38 1851ndash1856

200 S Komura P B Berbon A Utsunomiya M Furukawa

Z Horita M Nemoto and T G Langdon in lsquoHot deformation

of aluminum alloys IIrsquo (ed T R Bieler L A Lalli and S R

MacEwen) 125ndash138 1998 TMS

201 S Komura Z Horita M Furukawa M Nemoto and T G

Langdon J Mater Res 2000 15 2571ndash2576

202 S Komura M Furukawa Z Horita M Nemoto and T G

Langdon Mater Sci Eng 2001 A 297 111ndash118

203 S Komura Z Horita M Furukawa M Nemoto and T G

Langdon Metall Mater Trans A 2001 32A 707ndash716

204 Z Horita M Furukawa K Oh-ishi M Nemoto and T G

Langdon Proc Fourth Int Conf on lsquoRecrystallization and

related phenomenarsquo (ed T Sakai and H G Suzuki) 1999 The

Japan Institute of Metals 301ndash308

205 Z Horita S Komura P B Berbon A Utsunomiya

M Furukawa M Nemoto and T G Langdon Mater Sci

Forum 1999 304ndash306 91ndash96

206 Z Horita S Lee S Ota K Neishi and T G Langdon Mater

Sci Forum 2001 357ndash359 471ndash476

207 Z Horita T Fujinami K Sato S B Kang H W Kim and T G

Langdon in Proc James T Staley Honorary Symposium on

Aluminum Alloys lsquoAdvances in the metallurgy of aluminum

alloysrsquo (ed M Tiryakioglu) 271ndash275 2001 ASM

208 P B Berbon S Komura A Utsunomiya Z Horita

M Furukawa M Nemoto and T G Langdon Mater Trans

JIM 1999 40 772ndash778

209 M Nemoto Z Horita M Furukawa and T G Langdon Mater

Sci Forum 1999 304ndash306 59ndash66

210 M Furukawa Z Horita M Nemeto and T G Langdon Proc

lsquoLight Metals 1999rsquo Quebec City PQ Canada August 1999 583ndash

592

211 M Furukawa K Oh-ishi S Komura A Yamashita Z Horita

M Nemeto and T G Langdon Mater Sci Forum 1999 304ndash

306 97ndash102

212 M Furukawa A Utsunomiya K Matsubara Z Horita and

T G Langdon Acta Mater 2001 49 3829ndash3838

213 M Furukawa A Utsunomiya S Komura Z Horita M Nemoto

and T G Langdon Mater Sci Forum 2001 357ndash359 431ndash436

214 M Furukawa Z Horita and T G Langdon in Proc James T

Staley Honorary Symposium on Aluminum Alloys lsquoAdvances in

the metallurgy of aluminum alloysrsquo (ed M Tiryakioglu) 47ndash56

2001 ASM

215 M Furukawa Z Horita M Nemoto and T G Langdon Mater

Sci Eng 2002 A 324 82ndash89

216 M Furukawa Z Horita and T G Langdon in lsquoUltrafine grained

materials IIrsquo (ed Y T Zhu T G Langdon R S Mishra S L

Semiatin M J Saran and T C Lowe) 459ndash468 2002 TMS

217 T G Langdon M Furukawa Z Horita and M Nemoto Proc

NATO Advanced Research Workshop on lsquoInvestigations and

applications of severe plastic deformationrsquo Moscow August

1999 NATO Science Series Series 3 High Technology vol 80

Kluwer Academic Publishers The Netherlands 2000 149ndash154

218 S Lee H Akamatsu A Utsunomiya K Neishi M Furukawa

Z Horita and T G Langdon Proc Thermec 2000 Las Vegas

USA December 2000

219 S Lee A Utsunomiya H Akamatsu K Neishi M Furukawa

Z Horita and T G Langdon Acta Mater 2002 50 553ndash564

220 A Yamashita D Yamaguchi Z Horita and T G Langdon

Mater Sci Eng 2000 A 287 100ndash106

221 K Oh-ishi Z Horita D J Smith and T G Langdon J Mater

Res 2001 16 583ndash589

222 H Akamatsu T Fujinami Z Horita and T G Langdon Scripta

Mater 2001 44 759ndash764

223 S Ota H Akamatsu K Neishi M Furukawa Z Horita and

T G Langdon Mater Trans 2002 43 2364ndash2369

224 K Furuno H Akamatsu K Oh-ishi M Furukawa Z Horita

and T G Langdon Acta Mater 2004 52 2497ndash2507

225 I N Fridlyander O G Senatorova N A Ryazanova and A O

Nikiforov Mater Sci Forum 1994 170ndash172 345ndash349

226 J N Fridlyander and O G Senatorova Mater Sci Forum 1996

217ndash222 1813ndash1818

227 J Liu and D J Chakrabarti Acta Mater 1996 44 4647ndash4661

228 O G Senatorova A N Uksusnikov J N Fridlyander

J Koshorst R R Romanova N A Ryazanova A Galliot

and V V Cherkassov Proc 6th Int Conf on lsquoAluminum alloysrsquo

July 1998 Toyohashi Japan 589ndash593

229 R A Emigh E L Bradley and J W Morris Jr in

lsquoSuperplasticity in aerospace IIrsquo (ed T R McNelley and H C

Heikkenen) 303ndash315 1990 TMS

230 E L Bradley III R A Emigh and J W Morris Jr Scripta

Metall Mater 1991 25 717ndash721

231 N I Kolobnev L B Khokhlatova V D Makarov E Yu

Semenova and V V Redchits Proc Sixth Int Aluminiumndash

Lithium Conference Garmisch-Partenkirchen Germany October

1991 1053ndash1056

232 N K Tsenev R Z Valiev O V Obraztsov and I N Fridlander

Proc Sixth Int AluminiumndashLithium Conference Garmisch-

Partenkirchen Germany October 1991 1125ndash1132

233 A M Shammazov N K Tsenev R Z Valiev M M

Myshlyaev M M Bikbulatov and S P Lebedich Phys Met

Metall 2000 89 (3) 314ndash318

234 F Musin R Kaibyshev Y Motohashi T Sakuma and G Itoh

Mater Trans A 2002 43A 2370ndash2377

235 M Shagiev Y Motohashi F Musin R Kaibyshev and G Itoh

Mater Trans A 2003 44A 1694ndash1697

236 M Shagiev Y Motohashi F Musin R Kaibyshev and G Itoh

Mater Trans A 2003 44A 1698ndash1701

237 B A Parker and Z F Zhou Proc 3rd Int Conf on lsquoAluminium

alloysrsquo Vol I NTH Trondheim Norway June 1992 363ndash367

238 J R Davies lsquoASM specialty handbook aluminum and aluminum

alloysrsquo 1993 Materials Park OH USA ASM

239 S J Andersen H W Zandbergen J Jansen C Traeholt

U Tundal and O Reiso Acta Mater 1998 46 3283ndash3298

240 M L Kharakterova D G Eskin and L L Rokhlin Russ

Metall 1997 (1) 104ndash109

241 J Roslashyset Dr Ing thesis NTNU Trondheim Norway 2002

242 P P Chattopadhyay S Datta and M K Banerjee Mater Sci

Eng 2002 A 333 67ndash71

243 L I Kaigorodova E I Selnikhina E A Tkachenko and O G

Senatorova Phys Met Metall 1996 81 513ndash519

244 Y-L Wu F H Froes C Li and A Alvarez Metall Mater

Trans A 1999 30A 1017ndash1024

245 Z Yin L Yang Q Pan and F Jiang Trans Nonferrous Met

Soc China 2001 11 822ndash825

246 V I Elagin V V Zakharov and T D Rostova Met Sci Heat

Treat 1994 36 (7) 375ndash380

247 Y V Milman A I Sirko D V Lotsko O N Senkov and D B

Miracle Mater Sci Forum 2002 396ndash402 1217ndash1222

248 C-H Joh K Yamada and Y Miura Mater Trans JIM 1999

40 439ndash442

249 X J Jiang Q H Gui Y Y Li L M Ma G J Liang and C X

Shi Scr Metall Mater 1993 29 211ndash216

250 X J Jiang Y Y Li W Deng L Y Xiong W M Wu Y J Gao

and C X Shi Adv Cryogenic Eng (Mater) 1994 40 1369ndash

1376

251 C-H Joh T Katsube K Yamada and Y Miura Proc 6th Int

Conf on lsquoAluminum alloysrsquo Toyohashi Japan July 1998 799ndash

804

252 L I Kaygorodova A M Dritz T V Krymova and I N

Fridlyander Proc Sixth Int AluminiumndashLithium Conference

Garmisch-Partenkirchen Germany October 1991 363ndash367

253 L I Kaigorodova A M Drits Ya V Zhingel T V Krymova

and I N Fridlyander Phys Met Metall 1992 73 286ndash290

254 A L Berezina V A Volkov S V Ivanov N I Kolobnev and

K V Chuistov Phys Met Metall 1991 71 (2) 167ndash175

255 I N Fridlyander N I Kolobnev A L Berezina and K V

Chuistov Proc Sixth Int AluminiumndashLithium Conference

Garmisch-Partenkirchen Germany October 1991 107ndash112

256 L I Kaigorodova A M Drits Ya V Zhingel T V Krymova

and V A Rassokhin Phys Met Metall 1992 73 281ndash285

257 I N Fridlyander S F Danilov E N Malysheva T A

Gorokhova and N N Kirkina Proc Sixth Int Aluminiumndash

Lithium Conference Garmisch-Partenkirchen Germany October

1991 381ndash386

258 G Dlubek S Krause H Krause A L Beresina V S

Mikhalenkov and K V Chuistov J Phys Condens Matter

1992 4 6317ndash6328

259 S Krause H Krause G Dlubek A L Beresina and K S

Chuistov Mater Sci Forum 1992 105ndash110 1109ndash1112

260 C Y Tan Z Q Zheng and S Q Liang Proc 4th Int Conf on

lsquoAluminium alloysrsquo Vol II Atlanta GA USA September 1994

329ndash333

261 A L Beresina N I Kolobnev K V Chuistov A V Kotko and

O A Molebny Mater Sci Forum 2002 396ndash402 977ndash981

Roslashyset and Ryum Scandium in aluminium alloys

International Materials Reviews 2005 VOL 50 NO 1 43

262 I N Ganiev I Yunusov and V V Krasnoyarskii J Appl Chem

USSR 1986 60 1961ndash1965

263 I N Ganiev Prot Met 1995 31 543ndash546

264 N V Vyazovikina Prot Met 1999 35 448ndash453

265 G V Kharina and V P Kochergin Prot Met 1996 32 134ndash

136

266 G V Kharina M V Kuznetsov and V P Kochergin Russ J

Electrochem 1998 34 482ndash485

267 V S Sinyavskii V D Valrsquokov and E V Titkova Prot Met

1998 34 549ndash555

268 Y L Wu F H Froes C G Li and J Liu Proc lsquoSynthesis

processing of lightweight metallic materials IIrsquo Orlando FL

USA February 1997 73ndash81

269 Z Ahmad and B J Abdul-Aleem Proc EuroCorr 2000

270 Z Ahmad A Ul-Hamid and B J Abdul-Aleem Corros Sci

2001 43 1227ndash1243

271 R Braun B Lenczowski and G Tempus Mater Sci Forum

2000 331ndash337 1647ndash1652

272 T Torma E Kovacs-Csetenyi L Vitalis I Vitanyi

J Stepanov and M Butova Mater Sci Forum 1987 1314

497ndash503

273 Z Wang P Wang K S Kumar and C L Briant in lsquoChemistry

and electrochemistry of corrosion and stress corrosion crackingrsquo

(ed R H Jones) 573ndash582 2001 TMS

274 V I Elagin V V Zakharov A A Petrova and E V

Vyshegorodtseva Russ Metall 1983 (4) 143ndash146

Roslashyset and Ryum Scandium in aluminium alloys

44 International Materials Reviews 2005 VOL 50 NO 1

Page 6: Scandium in aluminium alloys - Atom probe · A considerable part of the available literature on scandium in aluminium alloys is reviewed. ... behaviour in Al Cu, Al Mg Si,

Two vertical cross-sections were also constructed Aternary eutectic

Liq~aAlzAl6MnzAl3Sc

at 649uC was identified Several alloys in the sectionAl3ScndashAl6Mn have also been investigated59 and all werefound to comprise a mixture of the two binary phasesLattice parameter measurements of the Al3Sc phasewere interpreted as an indication of a slight solidsolubility of Mn in Al3Sc

AlndashCrndashSc

Alloys in the composition range 30ndash100 at-Al havebeen studied60 and an isothermal cross-section at 500uCwas constructed No ternary phases were identified Thephases that can be in equilibrium with the a-Al are thusAl7Cr and Al3Sc The solubility of Cr in the Al3Sc phasewas found to be considerable approximately 11 at-

Other ternary AlndashScndashX phase diagramsAlndashMondashSc

An isothermal cross-section at 550uC has been con-structed for the subsystem AlndashAl2ScndashAl2Mo61 Noternary phases were reported The phases in equilibriumwith a-Al were found to be Al3Sc and Al12Mo

AlndashScndashV

The section Al3ScndashAl21V2 has been studied62 and thevertical cross-section was constructed No ternaryphases were observed Solid solubilities of V in theAl3Sc phase of 14 at- and of Sc in Al21V2 of 25 at-are reported although a considerably higher maximumsolubility of V in Al3Sc is suggested in the vertical cross-section A quasibinary eutectic reaction

Liq~Al3SczAl21V2

is reported to occur at 917 K (644uC)The section Al3ScndashAl3V at 1200uC has also been

studied57 The solubilities of V in Al3Sc and Sc in Al3Vare reported to be 27 and 07 at- respectively WhenV was dissolved in Al3Sc the lattice parameter of Al3Scwas found to decrease

AlndashScndashTi

No ternary phase diagram is available The sectionAl3ScndashAl3Ti at 1200uC has been studied57 A solubilityof Ti in Al3Sc of almost 125 at- was found whichcorresponds to almost half of the Sc being substituted byTi The lattice parameter of Al3Sc was found to decreasesharply with increasing Ti content For the Al3Ti phasethe solubility of Sc was found to be approx 5 at-

AlndashCondashSc

The ternary system for 0ndash70 at-Sc has been investi-gated63 Three ternary (AlCoSc)-phases were identifiedThe only phases found to be in equilibrium with a-Alwere the binary phases Al3Sc and Al9Co2 An isothermalsection at 600uC and the vertical cross-sections Al3ScndashAl9Co2 and Al3ScndashAl9Co3Sc2 were constructed Thelsquocornerrsquo of the a-phase field was reported in the text to beat 15 at-Co and 05 at-Sc although in a tablethe numbers 02 at-Co and 01 at-Sc are reportedThe solubilities of Co in the Al3Sc phase and of Sc in theAl9Co2 phase were found to be 12 and 01 at-

respectively However in the vertical cross-sections it issuggested that the solubility of Co in Al3Sc may besignificantly higher at higher temperatures The latticeparameter of Al3Sc was not found to change withincreasing Co content

AlndashScndashSr

The subsystem AlndashAl2ScndashAl4Sr has been studied64 andan isothermal section at 500uC was constructed Noternary phases were detected meaning that the phases inequilibrium with a-Al were found to be Al3Sc and Al4SrThe solubility of Sc in Al4Sr and of Sr in Al3Sc wasfound to be low typically less than 15ndash2 at-

AlndashBendashSc

A study of the binary BendashSc system and the ternary AlndashBendashSc system for up to 20 at-Sc (or 30 wt-Sc) hasbeen reported65 The 600uC isothermal section for theinvestigated ternary composition range was constructedNo ternary phases were observed The a-Al can be inequilibrium with either Be Be13Sc or Al3Sc It is sug-gested that the section AlndashBe13Sc may be quasi-eutectic

AlndashBandashSc

An isothermal section at 500uC has been constructed66

No ternary phases were reported and a-Al is inequilibrium with Al4Ba and Al3Sc The solubility of Scin Al4Ba and of Ba in Al3Sc was reported to be less than2 at-

AlndashNndashSc

The region AlndashAlNndashScNndashSc has been investigated67 Aperovskite-type ternary phase AlN12xSc3 was reportedand an isothermal section at 1000uC was constructed Inthe Al-corner the Al melt was reported to be inequilibrium with AlN and Al3Sc

Quaternary and higher order AlndashScndashXndashX2(ndashX3hellip)phase diagramsAlndashMgndashScndashZr

The published material is limited to investigations onAl rich alloys A part of the liquidus surface of the6 wt-Mg section has been determined experimentallyfor the composition range 0ndash07 wt-Sc and 0ndash04 wt-Zr68 The 500uC isothermal phase relations inthe Al-corner of the 6 wt-Mg section has also beeninvestigated69 for Sc and Zr concentrations of up to3 wt- and 4 wt- respectively No ternary or qua-ternary phases were observed Likewise the 430uC iso-thermal phase relations of the 4 at-Mg (y35 wt-Mg)section have been investigated for up to 12 at-Sc(2 wt-Sc) and up to 25 at-Zr (8 wt-Zr)7071 Noternary or quaternary phases were observed in thepresent study either The Al3Sc phase was found todissolve an amount of 122 at-Zr corresponding to asubstitution of almost 50 of the Sc lattice positionswhereas the solubility of Sc in Al3Zr was 44 at-which corresponds to a substitution of almost 20 ofthe Zr lattice positions Figure 4 in Refs 70 and 71suggests that the Al content in the Al3Zr-phase increaseswith increasing Sc content however this is not sub-stantiated in the text

Roslashyset and Ryum Scandium in aluminium alloys

24 International Materials Reviews 2005 VOL 50 NO 1

AlndashMgndashScndashTindashZr

A vertical cross-section of the AlndashMgndashScndashTindashZr phasediagram for 03 wt-Sc 015 wt-Ti 015 wt-Zrand 0ndash10 wt-Mg has been constructed34 Accord-ing to this diagram the Al3Zr phase is the first andAl3Sc the last to form during solidification of thealloys No ternary quaternary or quinary phases arereported

AlndashZnndashMgndashCundashZrndashSc

A vertical cross-section of the full system as well asseveral sections of various sub-systems have beenconstructed72 For the full system a section at8 wt- Zn 2 wt-Cu 03 wt-Zr and 03 wt-Scwas constructed where Mg varies from 0 to 8 wt-The only reported Sc-containing sub-system is thatof AlndashZnndashMgndashCundashSc Here a vertical cross-sectionis constructed with the same levels of Zn Cu and Scas in the full system whereas Mg varies from 0 to65 wt-

No phases other than those known from the lowerorder systems were reported Amongst the findings it isinteresting to note that in the solid state Al3Sc isreported to be an equilibrium phase for all theinvestigated compositions It is also interesting to notethat the Sc-containing W-phase (Al54ndash8Cu66ndash4Sc see thesection on the AlndashCundashSc ternary system) is an equili-brium phase at low Mg content and disappears as theMg content increases

AlndashLindashMgndashSc

The 400uC isothermal phase relations of the 02 wt-Scsection have been investigated for the composition range0ndash6 wt-Mg and 0ndash5 wt-Li73 The a-Al was found tobe in equilibrium with AlLi Al2LiMg and Al3Sc Noquaternary phases were observed This investigation isalso summarised in Ref 50

AlndashCundashLindashSc

The aluminium rich corner of the system has beeninvestigated for alloys with 06 wt-Sc and with Cu andLi in the range 0ndash16 wt- and 0ndash4 wt- respectively74

No quaternary phases were reported Two sections ofthe phase diagram were constructed a section of the470uC isothermal tetrahedron at 06 wt-Sc and avertical section at 06 wt-Sc and 26 wt-Li Twoquaternary invariant equilibria were found and thetemperatures of the invariant points were estimated

Al3Sc phaseRechkin and co-workers were to the authorsrsquo knowl-edge the first to publish a paper in an internationaljournal identifying the Al3Sc phase75 The phase wasidentified as cubic with lattice parameter a5410 A Afew years later the lattice structure was reported to be ofthe Cu3Au type76 The atomic arrangement of the Al3Scphase is shown in Fig 10 The structure can bedescribed as ordered face-centred cubic (fcc) althoughin crystallographic terminology the Al3Sc structure isactually a simple cubic lattice with four atoms (one Scand three Al atoms) associated with each lattice pointThis particular atomic arrangement is nominated L12

and is found in several intermetallic compounds forinstance Ni3Al Ni3Fe and Cu3Au

Some efforts have been made in characterising theproperties of the Al3Sc phase A compilation of someresults is given in Table 3 The motivation for themajority of the investigations seems to be one of thethree following

(i) the Al3Sc phase has a density of 303 g cm23 andit melts peritectically at approx 1320uC This canmake the Al3Sc phase an attractive candidate asa material for lightweight high temperaturestructural applications205777ndash86

(ii) in order to understand the effect of Al3Scprecipitation in Al-alloys it is necessary to gainmore knowledge about the Al3Sc phase578187ndash91

(iii) the Al3Sc is an excellent model phase forstudying basic properties of intermetalliccompounds7990ndash98

10 Atomic arrangement of Al3Sc phase

Table 3 Some reported properties of Al3Sc phase

ReferenceE GPa(Youngrsquos modulus) n (Poissonrsquos ratio)

CTE (Coefficient ofthermal expansion) 1026 K21

(111) APB energymJ m22

(100) APB energymJ m22

88 Approx 11120 166 020 Max 670 45079 166 022 31399 1628 0204

1642iexcl19 0201iexcl000189 16

Reported to decrease linearly with increasing temperature to approx 97 GPa at 550uCCalculatedExperimental

Roslashyset and Ryum Scandium in aluminium alloys

International Materials Reviews 2005 VOL 50 NO 1 25

Formation of Al3Sc in AlndashSc alloysThere are at least four ways that the Al3Sc phase canform in dilute binary AlndashSc alloys

1 Upon solidification of hypereutectic alloys (Sc

approx 06 wt-) Al3Sc is the first phase to form

2 The solidification of hypo- and hypereutectic alloysends with formation of eutectic AlzAl3Sc

3 Al3Sc can precipitate discontinuously from super-saturated solid solution

4 Al3Sc can precipitate continuously (nucleation andgrowth) from supersaturated solid solution

Primary Al3ScAccording to the binary phase diagram primary Al3Scshould form during solidification of all alloys with Sccontent higher than approx 06 wt- ie higher thanthe eutectic composition Formation of primary Al3Sc inAlndash07 wt-Sc melts cooled at 102ndash103 K s21 has beenreported1832 According to the metastable state dia-gram32 this alloy composition is close to the eutectic oneat these cooling rates

Primary Al3Sc is reported to have a highly facetedmorphology1318100ndash102 The observation of a cubicmorphology in a slowly cooled Alndash87 wt-Sc alloyindicates that the facet planes in this case are thecrystallographic (100) planes13 Brodova et al100ndash102

have investigated the microstructure of rapidly cooledAlndash2 wt-Sc alloy They found that the dominantmorphology of primary Al3Sc was dependent on boththe cooling rate and the initial melt temperature A mapof primary Al3Sc morphologies as a function of theseparameters was constructed and is redrawn in Fig 11

The nucleation mechanism and growth morphologyof primary Al3Sc in an Alndash07 wt-Sc alloy solidified ata cooling rate of 100 K s21 were investigated by Hydeet al103104 Indications were found that the primaryAl3Sc particles nucleate heterogeneously on oxideparticles in the melt The primary Al3Sc particles werefound to grow with a dendritic morphology with theprimary dendrite arms in the crystallographic n110m

direction The overall shape is cubic which is inaccordance with earlier observations

Eutectic Al3ScEutectic AlzAl3Sc has been reported in hyper- as wellas hypoeutectic alloys11 but is scantily described in theliterature Given a eutectic composition of 06 wt- amaximum solid solubility of Sc in Al of 035 wt- andthe specific densities in Table 1 a eutectic formed underequilibrium conditions would contain a volume fractionof approx 063 vol-Al3Sc At high cooling rates thevolume fraction of Al3Sc in the eutectic is probablysomewhat smaller owing to the increased supersatura-tion of Sc in Al

The morphology of the eutectic in an Alndash2 wt-Scalloy is reported to depend on the temperature of themelt before solidification100 For low melt temperaturesthe eutectic is reported to be rodlike for a wide range ofcooling rates For intermediate melt temperatures andhigh cooling rates a lsquodiscontinuous eutecticrsquo is reportedwhereas for high melt temperatures and slow coolingrates a lsquoquasieutecticrsquo structure is reported with Al3Scparticles of almost spherical shape

Hyde et al have reported that during solidification ofan Alndash07 wt-Sc alloy some of the primary Al3Scparticles are pushed ahead of the Al solidification frontand end up at the grain boundaries103104 Thus primaryAl3Sc may be mixed with eutectic Al3Sc in themicrostructure A scanning electron microscopy (SEM)picture showing eutectic Al3Sc at the grain boundaries asdescribed in Refs 103 and 104 is given in Fig 12

Discontinuous precipitation of Al3ScDiscontinuous precipitation of Al3Sc from super-saturated solid solution is often observed in binary AlndashSc alloys131831105 This precipitation mechanism whichis sometimes referred to as cellular precipitation iscommonly described as a decomposition of super-saturated solid solution into a-Al and Al3Sc at a movinggrain boundary The driving force for the grainboundary migration is the volume free energy that isreleased during the precipitation As the grain boundarymoves it leaves behind a characteristic fan shaped array

11 Morphology of primary Al3Sc particles in Alndash2 wt-Sc

alloy as a function of melt overheating and cooling

rate during solidification redrawn from Ref 102

12 SEM image of particle structure of Alndash07 wt-Sc

alloy cooled at a rate of 100 K s21 during solidifica-

tion as described in Refs 103 and 104 primary Al3Sc

particle is seen in centre of grain whereas eutectic

Al3Sc is decorating grain boundaries image is kindly

provided by Dr Kristian Hyde UMIST Manchester UK

Roslashyset and Ryum Scandium in aluminium alloys

26 International Materials Reviews 2005 VOL 50 NO 1

of precipitates In the AlndashSc case the discontinuouslyprecipitated Al3Sc particles have been demonstrated tobe coherent with the aluminium matrix1318

The driving force for discontinuous precipitationincreases with increasing supersaturation of Sc in theAl matrix Thus discontinuous precipitation in binaryAlndashSc is most frequently reported in studies of alloyswith a Sc content of 04 wt- or higher1318106 Stilldiscontinuous precipitation has also occasionally beenreported to occur at lower alloy compositions In an Alndash027 wt-Sc alloy discontinuous precipitation wasobserved over a wide range of temperatures107 In arecent study31105 of precipitation kinetics and mechan-isms in Alndash02 wt-Sc discontinuous precipitation wasfound to take place when the specimens were quencheddirectly from a solutionising temperature in this case600uC to aging temperatures in the range 370ndash490uCFurther C-curves in a temperature-time-transformation(TTT) diagram were established (Fig 13) which showedthat the highest transformation rate of discontinuousprecipitation lies at a higher temperature than thehighest transformation rate of the continuous precipita-tion reaction ie the two precipitation reactions arerepresented by two separate lsquonosesrsquo on the C-curves

It has been shown that discontinuous precipitationcan be suppressed by continuous precipitation if thematerial is cold worked before the precipitation heattreatment13108

As a result of their rather coarse nature andinhomogeneous dispersion discontinuously precipitatedAl3Sc contributes but little to the strength of the alloyand also leads to a smaller amount of Sc in super-saturated solid solution being available for subsequentcontinuous precipitation Thus discontinuous precipita-tion is in general regarded as an undesired precipitationmode

Continuous precipitation of Al3ScContinuous precipitation of Al3Sc is a bulk decomposi-tion process of supersaturated solid solution of Sc in Aland can in the isothermal case be characterised by anucleation stage a growth stage and finally a coarsen-ing stage Apparently the continuous precipitation reac-tion occurs largely by homogeneous nucleation anddiffusion controlled growth and AlndashSc has occasionallybeen used as a model system for studying the mechan-isms of nucleation growth and coarsening107109ndash111

There have been several studies of the continuousprecipitation reaction in binary AlndashSc alloys and up tillnow there is no evidence that any metastable phases areforming before the L12 phase Al3Sc Thus it is assumedthat the equilibrium phase nucleates directly fromsupersaturated solid solution

Even though the nucleation of Al3Sc is frequentlyreported to occur homogeneously throughout the Almatrix there are some examples in the technical litera-ture of reported heterogeneous Al3Sc nucleation ondislocations110112ndash115 and grain boundaries110113115ndash118

In a recent numerical modelling study of continuousprecipitation in AlndashSc alloys111 the effect of hetero-geneous nucleation on dislocations is accounted for Themodel predicts that homogeneous nucleation dominatesat high Sc concentrations and low transformation tem-peratures whereas heterogeneous nucleation is predictedto dominate at low Sc concentrations and high trans-formation temperatures Figure 14 shows a sketch of anucleation map for AlndashSc The shift between homo-geneous and heterogeneous dominance in nucleation isdependent on the dislocation density as indicated in thefigure

The shape of continuously precipitated Al3Sc particlesis most frequently reported to be spherical29112113119ndash129

However it seems that under certain conditions theshape can differ from the spherical one Drits et al130

reported both spherical and star shaped morphologyThe star shaped precipitates had arms growing in thecrystallographic n110m-directions (Star shaped Al3Scprecipitates have also been found after some thermo-mechanical treatments of an AlndashMgndashScndashZr alloy131) InRef 128 precipitates of both cuboidal and sphericalmorphology are found to coexist after certain heattreatments Cauliflower shaped precipitates as well asprecipitates of spherical and cuboidal shapes arereported by Novotny and Ardell110 Bastow andCelotto132 found large oblong Al3Sc particles in an Alndash01 wt-Sc alloy after aging at 400uC for 24 h A facetedshape is suggested in a high-resolution image of anAl3(Sc Zr) precipitate in an AlndashMgndashMnndashZrndashSc alloy133

In a systematic high-resolution transmission electron

13 TTT diagram of precipitation in Alndash02 wt-Sc alloy

after solutionising at 600uC and direct quench to

aging temperature3114 Nucleation map for binary AlndashSc alloys which indi-

cates how the tendency towards heterogeneous ver-

sus homogeneous nucleation is predicted to depend

upon Sc concentration transformation temperature

and dislocation density redrawn from Ref 111

Roslashyset and Ryum Scandium in aluminium alloys

International Materials Reviews 2005 VOL 50 NO 1 27

microscopy (TEM) study of the Al3Sc particle morphol-ogy development during precipitation heat treatment ofbinary AlndashSc alloys by Marquis and Seidman114 it isdemonstrated that the precipitates can take a wide rangeof shapes as they grow depending on Sc content in thealloy transformation temperature and transformationtime Irregular shaped star shaped and cuboidalshaped precipitates were observed under someconditions It was however found that the equilibriumshape of the particles is an equiaxed multifaceted one(Fig 15) Supported by Wulffrsquos construction it wasconcluded that the shape was that of a GreatRhombicuboctahedron This equilibrium morphologyhas been reproduced by computer-simulations ofparticle growth87134 The multifaceted particles caneasily be taken for spherical in a conventional TEMpicture

Kinetics of precipitation of Al3Sc fromsupersaturated solid solutionThe precipitation kinetics of Al3Sc in binary AlndashScalloys is dependent on the precipitation heat treatmenttemperature and on the Sc content in the alloy Acomprehensive overview over the transformationkinetics in terms of C-curves is given by Zakharov135

The C-curves for 5 transformation for a range of AlndashSc alloys are redrawn in Fig 16

Hyland107 studied the homogeneous nucleationkinetics of Al3Sc in a Alndash018 wt-Sc alloy after directquench from 650uC to precipitation temperatures of 288and 343uC He found that after an incubation time t theAl3Sc particles nucleated at a constant rate until thediffusion fields of the individual particles started tooverlap At 288uC the incubation time and time tosignificant diffusion field overlap were estimated to beapprox 245 and 150 min respectively whereas thecorresponding values at 343uC were estimated to beapprox 7 and 20 min respectively

If one assumes that the JohnsonndashMehlndashAvramindashKomolgorov (JMAK) relationship is valid for thisprecipitation reaction one can express the fraction

transformed X as a function of the reaction time t bythe equation

X (t)~1expfrac12k(Dt)n (1)

where k is a constant D is the interdiffusion constant ofSc in Al and the exponent n is dependent on thenucleation rate For the situation described byHyland107 where the precipitates nucleate at a constantrate the value of n should theoretically136 be equal to52

Roslashyset and Ryum31105 applied an alloy and heattreatment method practically equal to that of Hyland107

One should thus expect that the precipitation kineticsshould also be quite similar However Roslashyset andRyum reported that the exponent n of the JMAKrelationship was approx 165ndash185 for the temperaturerange of concern31105 This does not point in thedirection of a constant nucleation rate but rather inthe direction of site saturation ie that all the particlesare nucleated simultaneously which in the JMAKequation would yield an exponent n of 32136 Anoverview of some reported values of n in the JMAKequation is given in Table 4 The majority of the valueslie closer to 32 than to 52 However it is important to

15 High resolution TEM picture along n100m axis of Al3Sc particle in Alndash03 wt-Sc alloy aged at 300uC for 350 h114

(reproduced with permission from Elsevier Science image kindly provided by Dr E A Marquis and Professor D N

Seidman) and various projections of a Great Rhombicuboctahedron

Table 4 Some reported values of n in JMAK equation

Reference n C 0Sc wt-Sc Ttrans uC Note

137 13 030 300 Solution heat treated (SHT) 500uC16026 030 300 SHT 600uC Low n at late stage20026 030 300 SHT 640uC Low n at late stage

29 130ndash149 015 260ndash370145ndash196 025 260ndash370

138 188ndash216 020 240ndash35031 165ndash185 023 270ndash350 SHT 600uC Direct quench to transformation temp

16 C-curves for 5 transformation in a range of binary

AlndashSc alloys redrawn from Ref 135

Roslashyset and Ryum Scandium in aluminium alloys

28 International Materials Reviews 2005 VOL 50 NO 1

note that an n value close to 32 is per se not evidence ofsite saturation

Hyland also showed that a water quench from thesolutionising temperature significantly altered thenucleation kinetics in the subsequent precipitation heattreatment107 The incubation time was dramaticallyshortened which is attributed to the quenched-in excessvacancies and it is also indicated that there might be ashift in the nucleation rate in the early stage ofprecipitation It is suggested that the vacancies mayenhance the diffusion of Sc in Al and that there is apossibility that vacancy clusters act as heterogeneousnucleation sites for Al3Sc precipitates107 Regardless ofwhich mechanism that is operative it is clearly demon-strated that the nucleation kinetics can be dependent onthe thermal history between solutionising and precipita-tion heat treatment

Loss of coherency during growth of Al3ScprecipitatesWhen an Al3Sc particle grows it will sooner or laterreach a critical size where it will be energetically morefavourable to introduce an interface dislocation at theAlAl3Sc interface than to increase the matrix strain Asimple approximation for the critical size can be derivedfrom the lattice parameters assuming that the criticalsize is reached when the misfit over the whole particlediameter equals the Burgers vector of the Al matrix

dcrit~b=d (2)

where b is the Burgers vector of Al and d is themisfit between Al and Al3Sc This approximation yieldsa critical diameter of approx 215 nm at ambienttemperature

The misfit d and thus also the critical diameter dcrit

will depend on the temperature owing to the differencesin thermal expansion between the Al matrix and the

Al3Sc particles The thermal expansion of Al3Sc hasrecently been measured89 and based on the differencesin thermal expansion between Al139 and Al3Sc the misfitas a function of temperature has been calculated89 Thiscalculation is reproduced and shown by the solid line inFig 17

It is however possible to refine this calculationsomewhat140 Whereas the thermal expansion of Al3Sc isexpected to be only because of lattice expansion there isa significant contribution from vacancies on thermalexpansion of Al at high temperatures141 Thus thetemperature effects on the misfit should be calculatedfrom the changes in lattice parameters rather than fromthe linear thermal expansion By subtracting the vacancyeffect on the thermal expansion one achieves atemperature-dependent misfit as represented by thedotted line in Fig 17

A second correction that should be taken into accountis the effect of Sc in solid solution on the latticeparameter of the Al matrix With increasing tempera-ture more Sc is brought into solid solution and it isreported that the lattice parameter of the Al matrixpresumably measured at room temperature increaseslinearly with the Sc content in solid solution142 Thesedata can be used to calculate the effect on the latticeparameter at elevated temperatures under the assump-tion that the relative increase in lattice parameter owingto Sc in solid solution is independent of temperature InRef 142 a figure is presented which shows the measuredlattice parameter as a function of Sc content in solidsolution and a value (dadc)a is reported where a is thelattice parameter of the Al matrix and c is the Sc contentin solid solution in at- The reported value for (dadc)a is 100 times larger than that indicated in thecorresponding figure possibly as a result of a decimalerror in the text Thus in the present exercise 1100th ofthe reported value for (dadc)a is used Using this incombination with the regular solution approximationfor the solvus line of Sc in Al1231 one obtains acorrection for Sc in solid solution on the temperature-dependent misfit as shown in Fig 18 This figure shows

17 Lattice mismatch between Al and Al3Sc as a function

of temperature solid line represents calculation

based on linear thermal expansion of the two phases

dotted line represents correction for vacancies in Al

lattice

18 Corrections of mismatch calculated from linear ther-

mal expansion data as a result of vacancies and to

Al lattice expansion from Sc in solid solution

Roslashyset and Ryum Scandium in aluminium alloys

International Materials Reviews 2005 VOL 50 NO 1 29

both the correction for vacancies and for Sc in solidsolution on the same graph The two corrections are ofapproximately the same magnitude but with oppositesigns Thus the resulting (net) correction is close to zeroand it turns out that the first hand approximation asapplied in Ref 89 is very good in this case

Applying the calculated temperature dependent misfitwith the simple approximation for a critical diameter forloss of coherency one obtains a temperature-dependentcritical diameter as shown in Fig 19

Some examples from the literature of experimentallyobserved critical diameters in binary AlndashSc alloys aresummarised in Table 5 along with some predictions forcritical diameters from Fig 19 There is a fairly goodconsistency between the observations and the measureddiameter is quite close to the simple predictions above

A more refined analysis on the transition fromcoherent to incoherent particles has recently beenperformed145 This analysis is based on the balancebetween the increase in particlematrix interface energyowing to interfacial dislocations and the relaxation inelastic energy in the Al matrix owing to the samedislocations This method yields a predicted criticaldiameter of 246 nm for transition from coherent to

semi-coherent particles at ambient temperature Thetemperature dependence of the critical diameter is nottreated in this analysis

The loss of coherency during isothermal annealing hasbeen reported to be accompanied by an increasedaverage coarsening rate119121137145 The increasedcoarsening rate has been attributed either to diffusionof Sc along dislocation lines119121 or to the increasedparticlematrix interface energy of a semicoherentparticle145 However there are also several data sets inthe literature that do not indicate an increased growthrate after the loss of coherency114128

Al3ScAl interface energyThe interface energy between Al3Sc and the Al matrix isone of the key parameters that governs the nucleationgrowth and coarsening behaviour of Al3Sc in Al and Alalloys The interface energy has been estimated in severalinvestigations either by fitting experimental data toequations that describe nucleation or coarsening or bycalculations A compilation of some of the results isgiven in Table 6 There is considerable spread in thereported values regardless of what approach has beenused for the estimation

Influence of other elements on precipitation ofAl3ScMagnesium

With regard to precipitation mechanism it has beenstated that Mg suppresses the tendency to discontinuousprecipitation of Al3Sc106 In an investigation of pre-cipitation kinetics of Al3Sc in the temperature range300ndash500uC only minor changes in the kinetics (Fig 20)were found when up to 5 wt-Mg was added to an Alndash04 wt-Sc alloy135 It seems that the precipitationreaction is slightly faster in the Mg-containing alloys

Several investigations on age hardening response alsoimply that there is only a small if any effect of Mg onthe precipitation kinetics of Al3Sc23148149 It is how-ever found that the hardness increase from theprecipitation of Al3Sc is somewhat reduced in AlndashMgndashSc alloys compared to binary AlndashSc alloys23148149 InRef 149 it is suggested that some of the Sc is dissolvedin the Al3Mg2 phase and thus the age hardeningpotential is reduced with increasing Mg contentSomewhat contradictory to these observations but

Table 5 Some reported critical diameters for coherencyloss in binary AlndashSc and correspondingtheoretical critical diameters from Fig 19

Reference dcrit nmC0

Scwt-Sc

TtransuC

Theoreticaldcrit nm

119 38ndash40 05137 28ndash30 03 400 308128 32 02 400 450 308 335129 50 02143 40 012 025115 40 025 450ndash500 335ndash37114 40 03 400 450 308 335144 40 02 400ndash460 308ndash341145 30ndash80 02 400ndash490 308ndash362

20 C-curves for 10 and 60 transformation in Alndash

04 wt-Sc and Alndash4 wt-Mgndash04 wt-Sc redrawn

from Ref 135

19 Simple approximation for temperature-dependent criti-

cal diameter for introduction of dislocations on Al

Al3Sc interface

Roslashyset and Ryum Scandium in aluminium alloys

30 International Materials Reviews 2005 VOL 50 NO 1

sustained by Ref 135 it has recently been reported150

that precipitation of Al3Sc at 300 and 350uC occursslightly faster in an Alndash2 wt-Mgndash02 wt-Sc alloythan in an Alndash02 wt-Sc alloy studied previously by thesame researchers117118 and that the correspondinghardness increase is highest in the AlndashMgndashSc alloyThe only reported difference in experimental procedureis the solutionising temperature which was higher forthe AlndashSc alloy (648uC) than for the AlndashMgndashSc alloy(617uC) However given that the nucleation time isshortened by quenched-in vacancies as suggested byHyland107 the difference in homogenisation tempera-ture should be in favour of a faster precipitation of thebinary AlndashSc alloy It should be worthwhile to probedeeper into this observation of different aging responses

Mg in solid solution increases the lattice parameter ofthe Al matrix This is in turn expected to influence thecritical diameter for AlAl3Sc coherency loss as discussedin the section on lsquoLoss of coherency during growth ofAl3Sc precipitatesrsquo above Such an influence on the criticaldiameter is also briefly discussed elsewhere150 A criticaldiameter of 80 nm in an Alndash3 wt-Mgndash02 wt-Sc alloyhas been observed compared to 40 nm in a binary Alndash02 wt-Sc alloy of the same investigation144 Otherresearchers have reported a critical diameter in excess of116 nm in an Alndash63 wt-Mgndash02 wt-Sc alloy151

Computer simulations predict that the AlAl3Scinterface should be enriched in Mg87 These predictionsare confirmed experimentally by three-dimensional atomprobe microscopy of an Alndash2 wt-Mgndash02 wt-Sc alloyaged at 300uC38 Here it was found that the Mg contentat the interface is approximately three times higher thanthe matrix concentration regardless of aging time

Copper

It has been claimed that Cu suppresses the tendencytowards discontinuous precipitation of Al3Sc106

Zakharov and Rostova152 have reported that additionsof up to 14 wt-Cu have only minor effects on theprecipitation kinetics in an Alndash04 wt-Sc alloy Themost noticeable effect is that for temperatures above400uC the late stage of the transformation is sloweddown for the highest Cu contents This does not show in

Fig 21 however where only the 10 and 60transformation curves are included

The W-phase (AlCuSc) was observed in the alloywith the highest Cu content which means that less Sc isavailable for the precipitation of Al3Sc in this alloyAnother investigation on the age hardening response ofAlndash023 wt-Sc and Alndash25 wt-Cundash023 wt-Sc at300uC also implies that the precipitation behaviour ofAl3Sc in the two alloys is similar153154 At 350uC alimited portion of the Al3Sc has been observed tonucleate heterogeneously on coarse hrsquo precipitates155

According to the isothermal sections of the phasediagram43 one should expect the ternary W-phase toform instead of the Al3Sc phase in an alloy with such ahigh CuSc ratio However no observations of the W-phase or other ternary phases were reported from TEMstudies of the Alndash25 wt-Cundash023 wt-Sc alloy thathad been heat treated in the temperature range 300ndash460uC153ndash156 A third investigation on the precipitationin Alndash048 wt-Sc alloys with up to 440 wt-Cu in thetemperature range 100ndash450uC also concludes that no W-phase or other ternary phase forms during the heattreatment157

Copper in solid solution decreases the lattice para-meter of the Al matrix Thus it is expected that the misfitbetween Al and Al3Sc precipitates should be higher in

21 C-curves for 10 and 60 transformation in Alndash

04 wt-Sc and Alndash14 wt-Cundash04 wt-Sc redrawn

from Ref 152

Table 6 Reported values of interphase energy cAlAl3Sc between coherent Al3Sc precipitates and Al matrix

Reference cAlAl3Sc mJ m22 Method of estimation

137 10 Fit of coarsening data to LifshitzndashSlezev equation107 78iexcl20 (288uC) Back-calculation of incubation time

93iexcl20 (343uC)107 123iexcl41 (288uC) Back-calculation of nucleation rate

125iexcl35 (343uC)29 542 (400uC) Fit of coarsening data to Ostwald ripening

632 (430uC)413 (460uC)

146 c(100) 192 (0 K) c(111) 226 (0 K) Pseudopotential calculations147 c(100) 325 (0 K) c(110) 513 (0 K) c(111)

782 (0 K) c(100) 315 (288uC) c(100) 325 (343uC)Atomistic simulation

110 105 Fit of coarsening data to LSW theory31 20ndash300 Fit of coarsening data to Ostwald ripening

for 16 different temperatures111 57 Fit of precipitation model to experimental data145 120 coherent particles Fit of coarsening data

170 semicoherent particles

It is argued in this study that c may be lower in the nucleation stage

Roslashyset and Ryum Scandium in aluminium alloys

International Materials Reviews 2005 VOL 50 NO 1 31

AlndashCundashSc alloys compared to AlndashSc alloys Howeveran experimental investigation of Alndash25 wt-Cundash023 wt-Sc alloy comes to a different conclusion Thelattice misfit strain is found to decrease compared to Alndash02 wt-Sc and the critical diameter for coherency losswas found to be the same in the ternary and the binaryalloy144 It is suggested that these observations may bebecause of the dissolution of some Cu in the Al3Sc phaseand thus that the lattice parameters of both the Al matrixand the Al3Sc precipitates decrease in the ternary alloy

Silicon

It has been found that the onset of precipitation in Alndash04 wt-Sc is only slightly altered when Si contents ofup to 04 wt are introduced in the alloy However thefinal stage of the precipitation reaction is considerablydelayed with increasing Si content135 Figure 22 showsthe effect of addition of a joint of 035 wt-Si and040 wt-Fe There are at least two possible explana-tions for why an Si-addition leads to this behaviour

1 Alloying with Si is known to promote discontin-uous precipitation of Al3Sc106158 It has been shown thatwhen isothermal precipitation of Al3Sc starts discon-tinuously the later stage of the overall transformationcan be very slow31

2 The isothermal section of the phase diagramsuggests that the V-phase (AlSc2Si2) should form inalloys of this composition46 If the V-phase forms lessSc is available for precipitation of Al3Sc

It has been shown157 that for an AlndashScndashSi alloy withsolid solution content of 010 wt-Sc an 110 wt-Sithe only phases to precipitate after heat treatment at200uC are Si and an (AlScSi)-phase possibly the V-phase On the other hand the Al3Sc phase has beenobserved to form in alloys with 04 wt-Sc and up to08 wt-Si159160

Zinc

It has been reported that additions of up to 5 wt- Znhave only minor effects on the precipitation kinetics ofan Alndash04 wt-Sc alloy135 (Fig 23) In Ref 106 it isclaimed that Zn promotes discontinuous precipitation ofAl3Sc

Lithium

A comparison of the age hardening response at 400uC inAlndash24 wt-Lindash019 wt-Sc and Alndash024 wt-Sc alloys

indicates that the onset of Al3Sc-precipitation is notaffected by the presence of Li161

Zirconium

As mentioned in the section on lsquoTernary phase diagramswith dispersoid-forming elementsrsquo earlier a considerableamount of Zr is dissolved in the Al3Sc phase and thus amore correct denotation of the precipitating phase isAl3(Sc12xZrx) In discussing the influence of the Zrcontent on the precipitation of Al3Sc one is thereforeactually discussing the difference in precipitation ofAl3Sc versus Al3(Sc12xZrx)

It is found that an addition of 015 wt-Zr to an Alndash04 wt-Sc alloy only marginally affects the initial stageof the precipitation reaction123135 while it slows downthe later stages of the transformation considerably(Fig 24)135 The coarsening rate of the Al3(Sc12xZrx)particles in AlndashScndashZr alloys is found to be much slowerthan that of Al3Sc particles in AlndashSc alloys123162

In three-dimensional atom probe field ion microscopy(3D-APFIM) of Al3(Sc12xZrx) particles formed at 475uCin a ternary AlndashScndashZr alloy163 it was found that the coreof the particles is almost pure Al3Sc whereas there is ashell of Al3(Sc12xZrx) with almost equal content of Scand Zr Such a behaviour has also been predicted bycomputer modelling of precipitation of Al3(Sc12xZrx) at480uC in an AlndashZnndashMgndashScndashZr alloy164 This modelpredicts that Zr starts to enter the growing

22 C-curves for 10 and 60 transformation in Alndash

04 wt-Sc and Alndash04 wt-Fendash035 wt-Sindash04 wt-Sc

redrawn from Ref 135

23 C-curves for 10 and 60 transformation in Alndash

04 wt-Sc and Alndash5 wt-Znndash04 wt-Sc redrawn

from Ref 135

24 C-curves for 10 and 60 transformation in Alndash

04 wt-Sc and Alndash04 wt-Scndash015 wt-Zr redrawn

from Ref 135

Roslashyset and Ryum Scandium in aluminium alloys

32 International Materials Reviews 2005 VOL 50 NO 1

Al3(Sc12xZrx) particles when approximately half of thesupersaturated Sc has been precipitated The Zr contentof the outer shell is predicted to be much higher thanwhat has been found experimentally163164

Another 3D-APFIM study of Al3(Sc12xZrx) particlesin a ternary AlndashScndashZr alloy has been reported165 Hereparticles grown at 300uC for various lengths of time werestudied The Zr content in these particles was muchlower than that reportedpredicted at higher tempera-tures163164 even after very long annealing times

Iron

The effect of adding up to 07 wt-Fe on the precipita-tion kinetics in an Alndash04 wt-Sc alloy has beeninvestigated135 The onset of precipitation was onlyslightly influenced by the Fe-level whereas the laterstages of the transformation however were significantlyslowed down as the Fe-level increased An example ofthe effect of a joint addition of Fe and Si is shown inFig 22

Manganese chromium and titanium

Small additions (03 wt-) of manganese or chromiumto Alndash040 wt-Sc alloys are reported to have onlyminor effects on the precipitation kinetics of Al3Sc135

According to Ref 106 Mn is reported to promote andCr and Ti to suppress discontinuous precipitation

Rare earth elements

An investigation of the precipitation behaviour of Alndash03 at-Sc and Alndash03 at-Scndash03 at-X alloyswhere X is either yttrium gadolinium holmium orerbium in the temperature range 235ndash310uC indicatedthat a Al3(Sc12xXx) phase with L12 structure wasformed in the ternary alloys22 Peak strength is reportedto occur after approx 10 h at 285uC in all alloys whichindicates that the precipitation kinetics up to peakstrength is practically unaltered by the ternary additions

Influence of Sc on microstructure andproperties of wrought aluminium alloysMost of the effects of Sc addition in wrought Al-alloysare linked to the formation of the Al3Sc phase In atypical processing route of a wrought aluminium alloyparticles of the Al3Sc phase can form under threedifferent conditions each of which influences themicrostructure and properties of the alloy in a specificway

1 During solidification after casting or weldingAl3Sc particles can form in the melt and act as nucleifor a-Al thus leading to grain refinement18166

2 High temperature processing of the alloy in therange 400ndash600uC for instance homogenisation hot-rolling or extrusion can give a dense distribution ofAl3Sc particles of typically 20ndash100 nm size The particledistributions formed under such conditions are reportedto lead to good recrystallisation resistance128148167168

and enhanced superplasticity52169170

3 Heat treatment in the range 250ndash350uC can lead tosignificant precipitation hardening of an alloy super-saturated in Sc148158171 The size of strengthening Al3Scprecipitates is typically in the range 2ndash6 nm121

Grain refinementA good grain refinement is almost always desired uponsolidification The formation of small equiaxed grainsrather than long dendrites in the melt facilitates thefeeding of the melt into cavities of the shrinkingsolidified metal and thus reduces the problem ofshrinkage porosity The tendency to hot cracking is alsoreduced and the second phase particles become morefinely and uniformly distributed

To the authorsrsquo knowledge the first effect of Sc in Al-alloys that was reported in an international scientificjournal was the grain refining action in pure Al and in anAlndashCu alloy upon solidification172 which was found tobe stronger for Sc than for other transition metals Inlater studies of Sc as a grain refiner in pure Al1832173 ithas been demonstrated that approx 07 wt-Sc issufficient to provide excellent grain refinement It hasalso been demonstrated that additions of 025 wt-Scz025 wt-Zr provide good grain refinement in pure Al18

In order for Sc to act as an effective grain refiner theAl3Sc phase has to form in the melt before thesolidification of a-Al The Al3Sc particles have a latticeparameter close to that of pure Al and whenhypereutectically formed the Al3Sc particles are veryeffective substrates for the nucleation of the a-Al phaseAs mentioned in the section on lsquoFormation of Al3Sc inAlndashSc alloysrsquo above this requires that the alloy ishypereutectic with respect to Sc ie in excess of approx06 wt- in a binary AlndashSc alloy In ternary and higherorder systems the eutectic Sc composition may dependon the other alloying elements present For instance theeutectic composition of Sc has been predicted todecrease with increasing Mg content in the ternary AlndashMgndashSc system39 This prediction is sustained by theobservation of good grain refinement by adding 05 wt-Sc to an Alndash7 wt-Mg alloy174 (Other examples ofgrain refinement at Sc concentrations lower than that ofthe binary eutectic are found in Ref 173)

Similarly the observation of good grain refinement inan Alndash025 wt-Scndash025 wt-Zr alloy18 may be as aresult of a lower Sc content of the eutectic in the ternarysystem ie less Sc is needed to make the alloy hyper-eutectic No literature data on the liquidus surface of theAlndashScndashZr system are available and thus this hypothesiscannot be confirmed In more complex alloy systems itis also observed that excellent grain refinement isachieved at low Sc contents when Sc is added togetherwith Zr It is reported that adding either 02 wt-Sc06 wt-Sc or 01 wt-Zr to an Alndash5Mg alloy givesmuch poorer grain refinement than adding 02 wt-Scz01 wt-Zr175 Similarly additions of 015 wt- ofeither Sc or Zr are reported to only marginally refinethe grain structure in an AlndashCundashLi alloy whereas a jointaddition of 015 wt-Sc and 015 wt-Zr gives excellentgrain refinement176 For an AA 3650 casting alloy (Alndash7 wt-Sindash04 wt-Mg) good grain refinement is achievedby adding 039 wt-Sc or 027 wt-Scz019 wt-Zr177

In some AlndashZnndashMgndashScndashZr alloys it is also found thatan addition of 02ndash03 wt-Sc can be sufficient for goodgrain refinement166169178179 Examples of the grainrefinement as a function of Sc addition in pure Al andin an AlndashZnndashMgndashZr alloy are shown in Fig 25

The nucleation of a-Al on Al3Sc particles in the melt isfacilitated by the close match in the lattice parameters ofthe two phases As shown in Fig 17 the mismatch at the

Roslashyset and Ryum Scandium in aluminium alloys

International Materials Reviews 2005 VOL 50 NO 1 33

eutectic temperature of binary AlndashSc alloys (660uC) isonly approx 047 In Refs 57 and 89 it is shown thatwhen Zr Hf and in particular Ti is dissolved in the Al3Scparticles this reduces the lattice parameter of the phaseIt appears that when 25 of the Sc atoms in Al3Sc aresubstituted by Ti the mismatch is zero at approx 550uCand becomes negative at higher temperatures89 Thissuggests that by carefully selecting the Ti content of thealloy it should be possible to obtain Al3(ScTi)substrates in the melt that match exactly the latticeparameter of the nucleating a-Al and thus furtherimprove the grain refinement of the alloy This appearsto have been achieved in a recent work180 where thegrain refinement of an Alndash07 wt-Sc alloy wascompared with that of an Alndash05 wt-Scndash02 wt-Tialloy At a cooling rate of 100 K s21 only an estimated2 of the primary Al3Sc particles of the binary AlndashScalloy were effective nuclei compared to practically 100for the primary Al3(ScTi) particles in the ternary AlndashScndashTi alloy leading to a much smaller grain size in theternary alloy Whereas the match of lattice parametersmay be of importance for these results the authors ofthis investigation180 draw attention to other factors suchas different growth restriction factors for Sc and Ti andthe possibility of a peritectic reaction in the ternaryalloy Nevertheless the principle of matching latticeparameters is worth looking into further in future work

Effects from dispersoidslsquoDispersoidsrsquo is a term which is commonly used aboutthe classes of second phase particles that are formedin an Al alloy during high temperature annealing orthermomechanical processing such as homogenisationhot rolling extrusion and forging A dense distributionof dispersoids can give a significant contribution to analloyrsquos strength owing to particle strengthening but thisis rarely the main strengthening mechanism A moreimportant contribution from the dispersoids is theirability to stabilise the grainsubgrain structure of analloy through the Zener-drag action and thus improvethe mechanical properties of the alloy

There are two noticeable dispersoid-related effectsthat have been reported for Sc-containing alloys Thefirst is the stabilising effect on a deformed microstruc-ture When a non-recrystallised structure is preserved inan alloy this can add considerably to the mechanical

strength of the material The second effect is thepreservation of a small grain size during hot deforma-tion at slow deformation rates which is necessary toobtain superplastic properties of an Al-alloy

Recrystallisation resistance

The anti-recrystallisation effect of Sc was first publishedin a patent171 where 03 wt-Sc was added to pure Aland to AlndashMg AlndashMn and AlndashZnndashMg alloys Both Sc-free and Sc-containing materials were cold worked andsubsequently annealed and it was found that theaddition of Sc increased the temperature for onset ofrecrystallisation by approx 220uC in pure Al andsomewhat less in the Al-alloys Although the author ofthe patent171 may have been well aware that the anti-recrystallisation effect is caused by Al3Sc dispersoidsthis is not mentioned in the text The first journal paperthat explicitly points out that the recrystallisationresistance is due to Al3Sc dispersoids was an investiga-tion of the effects of adding Sc to wrought AlndashMgalloys181 In this work it was found that the Al3Scdispersoids were very effective in preventing recrystalli-sation up to temperatures of approx 400ndash450uC Athigher temperatures the dispersoids coarsen consider-ably and the microstructure was partially recrystallised

It is established that the Zener-drag pZ that is imposedon an advancing grain boundary by randomly distrib-uted dispersoids can be expressed in the form

pZ~k f =r (3)

where k is a factor that includes the interface energybetween the dispersoids and the matrix f is the volumefraction and r is the mean radius of the dispersoids Thusthe Zener drag will decrease rapidly in the case where thedispersoids are coarsening

As mentioned in the section on lsquoInfluence of otherelements on precipitation of Al3Scrsquo above theAl3(Sc12xZrx) dispersoids in a ternary AlndashScndashZr alloycoarsen at a much slower rate than the Al3Sc dispersoidsin a binary AlndashSc alloy This effect was first reported inRef 123 (although also observed in Ref 182) andaccording to Ref 33 the same authors demonstratedsoon after that the denser dispersoid distributionachieved in an AlndashScndashZr alloy leads to superiorrecrystallisation resistance compared to a binary AlndashScalloy An example of the increased recrystallisationresistance by adding both Zr and Sc is shown in Fig 26

In isothermal sections of the ternary AlndashScndashZr phasediagram it is indicated that the solid solubility ofSczZr is somewhat higher than that of Sc alone54 Ithas also been demonstrated both by electrical con-ductivity measurements (Fig 27) and microstructuralobservations that the supersaturation of SczZr isgreater than that of only Sc or Zr in as cast Alndash15(SczZr) alloys183 This indicates that it should bepossible to increase the volume fraction of dispersoids inAlndashScndashZr compared to AlndashSc It is suggested162 that theincreased volume fraction that can be achieved byadding both Sc and Zr can be advantageous inconventional wrought Al-alloys

There are at least two different conditions underwhich Al3Sc or Al3(Sc12xZrx) dispersoids can form toprevent recrystallisation

1 Sc (or Sc and Zr) is in solid solution before thedeformation In the case of cold deformation and

25 Grain refinement as a function of Sc addition in pure

Al (redrawn from Ref 32) and AlndashZnndashMgndashZr (redrawn

from Ref 169) note that data points are plotted on

different ordinate axes

Roslashyset and Ryum Scandium in aluminium alloys

34 International Materials Reviews 2005 VOL 50 NO 1

subsequent annealing the Al3Sc or Al3(Sc12xZrx)dispersoids may nucleate and grow before the nucleationand growth of recrystallised grains takes placeDispersoids can form after a direct up-quench to theannealing temperature115143148184 during ramp-up tothe annealing temperature115 or by pre-annealing at anintermediate temperature129 In the case of hot deforma-tion the Al3Sc or Al3(Sc12xZrx) dispersoids maynucleate and grow during preheating of the materialand during the hot deformation itself184

2 The Al3Sc or Al3(Sc12xZrx) dispersoids are formedin the material before deformation184 Considering coldrolling and subsequent annealing the annealing tem-perature Tann may be either lower or higher than thetemperature Tdisp at which the dispersoids were formedIf TannTdisp only limited if any coarsening of thedispersoids is expected to take place and thus the Zenerdrag from the particles is expected to be practicallyconstant The driving force for recrystallisation how-ever is expected to decrease somewhat with theannealing time as a result of recovery processes Thusif recrystallisation does not occur within short annealingtimes the material is expected to remain unrecrystallisedfor infinite time at the annealing temperature IfTannTdisp there will be substantial coarsening of thedispersoids during annealing In order for the materialto remain unrecrystallised the decrease in driving forcefor recrystallisation owing to recovery has to be at leastas rapid as the decrease in Zener drag because of particlecoarsening

Experimental comparisons of the conditions abovepoint in the direction that the recrystallisation resistanceis poorest when Sc (or Sc and Zr) is in solid solutionbefore deformation and the deformed material is up-quenched to the annealing temperature148 or when Al3Scor Al3(Sc12xZrx) dispersoids are formed before defor-mation at TdispampTann184185 Excellent recrystallisationresistance is achieved if dispersoids are formed at anintermediate anneal of solutionised and deformedmaterial128 or if dispersoids are formed at TdispTann

before deformation148185ndash187 It seems that the decreasein Zener drag because of dispersoid coarsening in many

cases is slower than the decrease in driving force forrecrystallisation because of recovery processes Thusthere is an advantage in forming a high number densityof small dispersoids which for most practical casesmeans that they should be formed at TdispTann122

When an advancing high angle grain boundary iethe recrystallisation front is passing a coherent Al3Scdispersoid there are at least three possible grainboundarydispersoid interactions

1 The Al3Sc dispersoid retains its global orientationrelationship and thus loses its coherency with thesurrounding matrix

2 The Al3Sc dispersoid rotates as the grain boundarypasses either by diffusional processes at the dispersoidmatrix interface or by the grain boundary passingthrough the dispersoid and the Al3Sc dispersoidassumes the same crystallographic orientation as theAl matrix of the recrystallised grain

3 The Al3Sc dispersoid dissolves at the grainboundary and re-precipitates in the recrystallised grain

Which interactions that actually take place willprobably depend on the dispersoid size annealingtemperature and driving force for recrystallisation It isalso possible that alloy composition (other elementsthan Al) is of importance

It has been reported that large (Oslash about 100ndash150 nm)Al3Sc dispersoids in a deformed Alndash4 wt-Mgndash02 wt-Sc alloy annealed at 575uC lose the orientationrelationship with the matrix after being passed by therecrystallisation front148

A rotation of somewhat smaller Al3Sc dispersoids in arecrystallising binary Alndash025 wt-Sc alloy has beenreported115143 The rotation was reported to be accom-panied by substantial growth (from Oslash 30 nm to Oslash48 nm) as a result of enhanced Sc diffusion at the grainboundary Observations suggested that the grainboundaries were passing through the dispersoids andthus the Al3Sc dispersoids retained the orientationrelationship with the recrystallised Al matrix

Dissolution and re-precipitation of Al3Sc dispersoidshas been reported during recrystallisation of a 50 coldrolled Alndash02 wt-Sc alloy162 Large spherical partially

26 Fraction recrystallised structure in cold rolled sheets

of Alndash04 wt-Sc and Alndash04 wt-Scndash015 wt-Zr as a

function of annealing temperature redrawn from

Ref 183 27 Electrical conductivity in Alndash15(SczZr) alloys

redrawn from Ref 183

Roslashyset and Ryum Scandium in aluminium alloys

International Materials Reviews 2005 VOL 50 NO 1 35

coherent dispersoids were observed to dissolve at therecrystallisation front and re-precipitate as smallercoherent Al3Sc cuboids

Superplastic forming

It seems that the first publication on superplasticproperties of Sc-containing Al-alloys was a study of anAlndash35Cundash14Mgndash045Mnndash04(SczZr) alloy188

It was recognised that the superplastic properties are aresult of the stabilisation of the fine grain structure byAl3Sc dispersoids The Sc-containing Al alloys that havereceived most attention for their superplastic propertieshowever are those of the AlndashMgndashSc system which wasfirst published in a patent189 Here it was noted that anAlndash4 wt-Mgndash05 wt-Sc alloy had superior superplasticproperties compared to fine-grained 7475 (AlndashZnndashMgndashCu alloy) Binary Alndash05 wt-Sc and Alndash4 wt-Mgalloys did not behave superplastically The flow stress atthe hot forming temperature was found to be much (30ndash40) lower in the ternary alloy than that of the twobinary alloys

The superplastic properties of AlndashMgndashSc alloys havebeen explored by several research groups over the lastdecade190ndash196 It has frequently been found that thedeformation mechanism is dominated by grain bound-ary sliding190 However it has also been reported thatAlndashMgndashSc alloy may deform superplastically withoutnoticeable grain boundary sliding23 It is generallyrecognised that the grain boundary sliding mechanismis facilitated when the average grain size is very smalland grain boundaries are predominantly high-angleSuch a microstructure may be achieved by carefulthermomechanical processing of the starting mate-rial193194197198 It has however been shown that a finegrained structure with high angle boundaries maydevelop during superplastic forming of AlndashMgndashSc alloyseven if the starting microstructure is an entirely differentone for instance that of a cold rolled sheet192 It has alsobeen suggested that superplastic forming of as castmaterial may be possible189

One of the more efficient thermomechanical processesfor achieving an ultrafine grain structure with high anglegrain boundaries in Al-alloys is equal channel angularpressing (ECAP) A JapanesendashAmerican group ofscientists has published an impressive body of researchon improvements in superplastic properties in Al-alloys processed by ECAP over the last few years andseveral of the publications are from investigations onAlndashMgndashSc alloys170199ndash224 Maximum strains in excessof 2000 at a strain rate of 0033 s21 have beenachieved170201202217 which is an extraordinarily goodcombination of high strain and high strain rate for analuminium alloy

Superplastic properties of AlndashCundashMg(ndashMn)ndashSc(ndashZr)and AlndashMgndashSc(ndashZr) alloys have been mentionedNoticeable superplasticity in other Sc-containing Al-alloys has also been reported such as AlndashZnndashMg(ndashCu)ndashScndashZr169225ndash228 AlndashLindashSc229 AlndashMgndashLindashScndashZr229ndash234

AlndashLindashMgndashCundashScndashZr235236 and AlndashCundashLindashScndashZr233

Precipitation hardeningHardening by Al3Sc precipitates

It has been noted that when Al3Sc particles precipitate inthe temperature range 250ndash350uC they give a significanthardness increase in the alloy Some authors point out

that Sc is a more effective precipitation hardening elementper atomic fraction added than the elements that arecommonly used for precipitation hardening121130 (In onepaper29 it is claimed that only Au has a strongerstrengthening effect than Sc) However the amount ofSc that can be precipitated from supersaturated solidsolution is rather limited and thus the absolute values ofthe hardness increase from the precipitation hardening ismuch lower than what is normally associated withprecipitation hardened alloys Also the temperatureregime for age hardening by precipitation of Al3Sc issomewhere in between the temperature regimes for agehardening and solution heat treatments of commonprecipitation hardened alloys This makes a combinedprecipitation of Al3Sc and other strengthening precipi-tates unfeasible Thus precipitation strengthening byAl3Sc is most feasible in alloy systems that are non-heat-treatable The non-heat-treatable aluminium alloy sys-tems are according to the Aluminum Associationdesignations the 1xxx series (99 pure Al) the 3xxxseries (AlndashMn) and the 5xxx series (AlndashMg) The purposeof adding Sc to these alloys may be either to stabilise themicrostructure of wrought semiproducts (extrusionsrolled plates forgings etc) as discussed in the sectionon lsquoRecrystallisation resistancersquo above or to provideextra strength to the alloy through precipitation hard-ening In the latter case it is appropriate to considerwhether the Sc-containing alloy still should be classifiedas non-heat-treatable A heat treatment is applied thatbrings about a significant precipitation hardening On theother hand the hardness increase that is achieved throughthe heat treatment is lower than what is normallyassociated with heat-treatable alloy systems Hence eventhough it seems like a contradiction one chooses to keepusing the term lsquonon-heat-treatablersquo about these alloys

Table 7 gives an overview of some mechanicalproperties of Sc-containing non-heat-treatable alloysthat are reported in the literature Most of theexperimental work on Sc in 1xxx-types of alloys hasbeen done on binary AlndashSc alloys with much higherpurity than industrial alloys

Strengthening mechanisms

When the precipitates are larger than a critical size thestrengthening effect is due to the Orowan-mechanism iedislocations can only pass the precipitates by looping Inthis case the strengthening effect of the particles isapproximately inversely proportional to the mean parti-cle spacing When the precipitates can be sheared bydislocations there are a number of strengthening mechan-isms that apply It is proposed by Parker et al108 that thetwo major contributing mechanisms are coherency strainand anti-phase-boundary energy In a recent detailedstudy of strengthening mechanisms in binary AlndashSc alloysby Marquis and colleagues117118 the strengthening fromshear modulus mismatch between the matrix and theprecipitates is also accounted for A qualitatively goodmatch between theoretical strengthening and measuredvalues is achieved in this work both for deformation atroom temperature and at 300uC

Effect of Sc on precipitation strengthening in heat-treatablealloys

Following the AA designation system the traditionalheat-treatable Al-alloys are those that belong to the 2xxx

Roslashyset and Ryum Scandium in aluminium alloys

36 International Materials Reviews 2005 VOL 50 NO 1

series (AlndashCu) 6xxx series (AlndashMgndashSi) and 7xxx series(AlndashZnndashMg) AlndashLi alloys should also be mentionedSeveral investigations have been carried out in order toclarify the effects of Sc on the precipitation behaviour inthese alloy systems

AlndashCu alloys

The precipitation sequence in AlndashCu alloys is oftendescribed as follows

Supersaturated solid solutionRGP-zonesRh0Rh9Rh(Al2Cu)

The highest strength is normally achieved when the h0or h9 precipitates are predominant Typical precipitationheat treatment temperatures for AlndashCu alloys are in therange 160ndash190uC238 which is considerably lower thanthe typical precipitation temperature for Al3ScComparisons of the aging responses of AlndashCu and AlndashCundashSc alloys at 150 and 200uC indicate that there is nonoticeable effect of Sc on the precipitation kinetics ofh9153 It is observed that the h9 precipitates may nucleateon Al3Sc particles153 At 300uC it is observed that h9particles are somewhat smaller in AlndashCundashSc alloys thanin AlndashCu alloys156

AlndashMgndashSi alloys

The following precipitation sequence is commonlyreported for AlndashMgndashSi alloys

Supersaturated solid solutionRGP-zonesRb0Rb9Rb(Mg2Si)

For peak aged alloys the predominant precipitatetype is b0 for which the stoichiometric composition hasrecently been resolved to be Mg5Si6239 Temperatures inthe range 160ndash205uC are typically used for precipitationhardening of these alloys238 Adding both 03 wt-Scand 01 wt-Zr to an Alndash06 wt-Mgndash065 wt-Sialloy does not seem to alter the precipitation kineticsof b0 at 165uC However the hardness increase becauseof precipitation hardening appears to be smaller in theSczZr-containing alloy240 In another investigationadditions of 01 wt-Sc 015 wt-Sc 02 wt-Sc04 wt-Sc and 02 wt-Scz01 wt-Zr were made toan Alndash08 wt-Mgndash07 wt-Si alloy241 Here it wasalso observed that the precipitation kinetics of b0 wasseemingly independent of the Sc additions (Fig 28)TEM observations indicated that the b0 precipitateswere of comparable sizes in the investigated alloys andno interactions between Al3Sc and b0 were observed(Fig 29) In a third study242 where the effect of Sc onthe precipitation in an AlMgSindashSiC metal matrixcomposite was investigated there also does not seemto be any effect on the precipitation kinetics Howevercontrary to the findings of Ref 240 it is reported thatthe Sc addition leads to a higher hardness increase thanin the corresponding Sc free alloy

AlndashMgndashZn alloys

For these alloys the following precipitation sequence isoften ascribed

Table 7 Mechanical properties in non-heat-treatable Al-alloys with Sc

Reference Alloy wt- YS MPa UTS MPa Note

1xxx alloys171 000Sc 15 48 Cast material aged 288uC8 h

023Sc 159 185 Cast material aged 288uC8 h038Sc 199 220 Cast material aged 288uC8 h000Sc 14 49 Cold rolled material (89) aged 288uC8 h023Sc 198 208 Cold rolled material (89) aged 288uC8 h038Sc 240 264 Cold rolled material (89) aged 288uC8 h000Sc 8 34 Cold rolled material quenched from 649uC aged 288uC8 h023Sc 147 157 Cold rolled material quenched from 649uC aged 288uC8 h038Sc 193 199 Cold rolled material quenched from 649uC aged 288uC8 h

121 05Sc 160 ndash Forged material quenched from 635uC aged 250uC50 h23 05Sc 298 319 Hot rolled 288uC cold rolled 69ndash81 aged 288uC4 h112 01Sc 132 166 Hot z cold rolled material quenched from 630uC

aged 320uC133 h148 02Sc 138 ndash Cast material aged 300uC10 h compression test159 04Sc 196 ndash Cast material aged 300uC10 h compression test117 118 03Sc 209 ndash Cast material quenched from 648uC aged 300uC5 h

compression test3xxx alloys171 1Mn 015Sc 216 221 Cold rolled material (89) aged 288uC8 h

1Mn 05Sc 309 323 Cold rolled material (89) aged 288uC8 h186 05Mn 02Mg

026Sc 015Zr162 201 Extruded material solutionised 600uC aged 250uC

5xxx alloys171 1Mg 43 111 Cold rolled material (89) aged 288uC8 h

1Mg 03Sc 288 303 Cold rolled material (89) aged 288uC8 h53Mg 147 259 Cold rolled material (50) wintermediate anneals

at 343uC aged 288uC8 h53Mg 03Sc 368 401 Cold rolled material (50) wintermediate anneals

at 343uC aged 288uC8 h23 2Mg 05Sc 376 401 Hot rolled 288uC cold rolled 69ndash81 aged 288uC4 h

4Mg 05Sc 414 4606Mg 05Sc 433 503

237 4Mg 1Sc 420 525 Cold rolled material (83) aged 320uC1 h148 4Mg 02Sc 194 ndash Cast material aged 300uC10 h compression test

Tensile test data except where noted YS yield strength UTS ultimate tensile strength

Roslashyset and Ryum Scandium in aluminium alloys

International Materials Reviews 2005 VOL 50 NO 1 37

Supersaturated solid solutionRGP-zonesRg9Rg(Zn2Mg)

The maximum hardness is normally achieved whenthe g9 precipitates are predominant Common precipita-tion hardening temperatures are in the range 95ndash180uCand a two-step precipitation heat treatment within thistemperature regime is often used238 It has beenobserved in some investigations that Sc and SczZradditions to AlndashMgndashZn alloys slow down the precipita-tion of g9 somewhat243 Other investigations find thatthere is no effect of Sc on the precipitation behaviour ofg9244245 and yet others report that Sc additionssignificantly speed up the precipitation of g9246 In Ref247 it is found that an Sc addition leads to coarser g9precipitates and it is claimed that this gives an improvedductility of the alloy The strength-loss associated withlarger particle size is reported to be counterbalanced bystrengthening from Al3Sc precipitates

AlndashLi alloys

The precipitation sequence in binary AlndashLi alloys isapparently simple

Supersaturated solid solutionRd9Rd (AlLi)

where d9 is the metastable Al3Li phase which just likeAl3Sc has the L12 type of atomic arrangement Thetypical temperature regime for precipitation of d9 whichis the strengthening phase in this system is approx 150ndash200uC A comparison of the age hardening response ofan Alndash26 wt-Li and an Alndash24 wt-Lindash019 wt-Scalloy at 180uC248 and 200uC161 indicates that the onsetof d9 precipitation is not altered by the presence of ScThe hardness curves for the two alloys are practicallyidentical at 200uC whereas at 180uC the peak hardnesslevel is slightly higher in the AlndashLi than the AlndashLindashScalloy DSC measurements at constant heating ratesindicate that the addition of Sc to an AlndashLi alloysincreases the activation energy for d9 precipitation andmoves the exothermic peak associated with d9 precipita-tion to a higher temperature248 For specimens aged at

either 180uC or 200uC TEM observations reveal that thed9 precipitates are much smaller in the Sc containingalloy than in binary AlndashLi both in the peak agedcondition and in the overaged condition161248 Additionof Sc has also been observed to reduce the size of d9precipitates in other AlndashLi based alloys249ndash251 In an AlndashLindashCundashZr alloy an addition of Sc has been reported toslow down the homogeneous precipitation of d9252253 Ithas been claimed that Sc reduces the quench sensitivityand delays room temperature aging of AlndashLi basedalloys254ndash256

When present in the microstructure before the pre-cipitation of d9 the Al3Sc precipitates may act as effec-tive nucleation sites for d9 The resulting precipitates arespheres of d9 with a core of Al3Sc161249252ndash255257ndash261

Corrosion resistanceAn appreciable amount of data is available on the effectsof Sc on the corrosion behaviour of wrought Al-alloysSome of these effects are apparently derived from theeffects of Sc on the microstructure of the alloys It hasbeen reported that an addition of Sc increases thecorrosion potential (makes it less negative) in pureAl262ndash264 in AlndashZn alloys265266 AlndashMg alloys267 AlndashZnndashMgndashCu alloys264268 AlndashCundashMgndashMn alloys264 andin AlndashCundashLindashMgndashAg alloys264 Even though Sc alsohas been reported to decrease the corrosion potential in

28 Age hardening response at 175uC for Alndash08 wt-Mgndash

07 wt-Si alloy (Base) with additions of 02 wt-Sc

04 wt-Sc and 02 wt-Scz01 wt-Zr from Ref 241

29 TEM images of a b0 precipitates in Alndash08 wt-Mgndash

07 wt-Si alloy and b b0 and Al3(Sc1ndashxZrx) in a similar

alloy with addition of 02 wt-Scz01 wt-Zr from

Ref 241

Roslashyset and Ryum Scandium in aluminium alloys

38 International Materials Reviews 2005 VOL 50 NO 1

AlndashMg alloys269270 it seems that the general trend isthat adding Sc to an alloy makes it slightly more nobleThe change in corrosion potential is much morepronounced when Sc is added in amounts larger thanthe eutectic composition263 ie there is a considerablecontribution from primary or eutectic Al3Sc to theoverall potential It has also been demonstrated that thechange in corrosion potential caused by Sc can dependon the heat treatment applied to the alloy267268

Even though the corrosion potential is an essentialparameter in establishing the corrosion behaviour of analloy an increase in the corrosion potential does notnecessarily imply an improved self-corrosion resistanceHowever measurements of corrosion rates and passiva-tion current densities strongly suggest that the self-corrosion resistance in general is considerably improvedwhen Sc is added to wrought Al-alloys263264267 Someobserved variations in corrosion potential and passiva-tion current densities with Sc content in binary AlndashScalloys are plotted in Fig 30

Material failure in corrosive environments is often dueto localised corrosion attacks which may propagaterapidly even though the bulk material has a goodresistance against general corrosion It has been pointedout that hypereutectic additions of Sc may lead tomicrogalvanic corrosion beside primary Al3Sc parti-cles264 In AlndashMg alloys grain boundary precipitation ofAl8Mg5 can lead to localised corrosion attacks such asintergranular corrosion (IGC) exfoliation corrosion(EC) and stress corrosion cracking (SCC) In wroughtmaterial such precipitation may occur in the 60ndash180uCtemperature regime and heating in this temperaturerange is referred to as lsquosensitationrsquo An AlndashMgndashSc alloywas found to be immune against intergranular corrosionand have moderate susceptibility to exfoliation corro-sion after annealing at 350uC271 After sensitation heattreatments severe IGC and EC was observed but notquite as severe as in a corresponding alloy without ScAs for SCC the AlndashMgndashSc alloy was found to be highlyresistant271 In another study it was found that additionof 056 wt-Sc reduces the SCC susceptibility of an Alndash68 wt-Mg alloy in the as-rolled state and afterannealing at 250uC whereas in a sensitised specimenthe SCC susceptibility is somewhat increased by the Scaddition272 A third investigation found that Sc has nomeasurable detrimental effect on the SCC susceptibilityof sensitised Alndash5Mgndash015Zr alloy273 SCC is also a

severe problem in high strength AlndashZnndashMgndashCu alloys Ithas been shown that small Sc additions are effective inreducing the SCC sensitivity of these alloys244246268274

Use of Sc-containing Al alloysA systematic development of Sc-containing aluminiumalloys took place in the former USSR in the 1980s andthe interest for Sc as an alloying element in aluminiumalloys hit the western world approximately 10 yearslater Even though a number of improvements in Alalloys achieved by Sc addition have been demonstratedthe current uses of such alloys are very limited This isrelated to the very high price of scandium

In Russia some parts of military aircraft are made ofSc-containing AlndashLi alloys In the western world themain usage of Sc-containing alloys is for sportsequipment Ashurst Technology and Kaiser Aluminumdeveloped a Sc-containing 7xxx alloy for baseball andsoftball bats which was introduced to the Americanmarket in 1997 by Easton Alcoa soon followed with aSc-containing alloy for a competing brand of batsLouisville Slugger Since then several new and improvedSc-containing alloys for bats have been introduced tothe market The purpose of adding Sc is to increase theyield strength of the alloy allowing for a down-gaugingof the wall thickness which in turn gives a strongerlsquospring-rsquo or lsquotrampoline-rsquo effect when the ball hits thebat

Shortly after the introduction of the Sc containingbats Easton also launched Sc-containing 7xxx tubingfor bicycle frames Just as in the bats Sc increases theyield strength of the alloy allowing for down-gauging oftube wall thickness and a corresponding weight reduc-tion of the bicycle frame An Italian manufacturer ofbicycle tubing Dedacciai also delivers tubes in a Sc-containing 7xxx alloy

Other sports equipment made from Sc-containingaluminium alloys includes lacrosse sticks and tent polesSmith and Wesson has also introduced a series ofhandguns where the frame is made from a Sc-containingAl alloy

A common factor for the items mentioned above isthat the material cost is only a minor part of the totalmanufacturing cost of the end product and also thatthese products are aimed at a group of customers thathave a certain awareness of new materials Both baseballbats and bicycle frames have been marketed aslsquoscandium alloyrsquo even though the Sc content is muchlower than 1

Currently AlndashSc master alloys for the production ofSc-containing Al alloys are available at a price thatcorresponds to US$ 2000 per kg of Sc This means that ifone wants to add 02 wt-Sc to an alloy which is afairly common content one also increases the price ofthe alloy by US$ 4 per kg alloy Depending on the alloytype Sc is added to this represents a tripling orquadrupling of the price of the alloy There are notmany existing products where such an increase inmaterial cost can be justified In order to see awidespread use of Sc in high-volume products the Scprice has to come down considerably Actually the priceof adding Sc to Al alloys has gone down by a factor 3ndash10over the last 10ndash15 years and substantial price reduc-tions are also expected in the future

30 Observed variations in corrosion potential and passi-

vation current densities with Sc content in binary Alndash

Sc alloys based on data from Ref 263

Roslashyset and Ryum Scandium in aluminium alloys

International Materials Reviews 2005 VOL 50 NO 1 39

The current production of AlndashSc master alloys isbased upon and will continue to be based upon for theforeseeable future the reduction of Sc2O3 or other Sccompounds directly in molten aluminium It is notnecessary as many tend to believe to take the route viametallic Sc Thus the price of AlndashSc master alloy isgoverned by the price of Sc2O3 or other Sc compoundsin question and not by the price of metallic scandiumThe Sc2O3 which is the main source for todayrsquos AlndashScmaster alloy production comes from stockpiles in theformer USSR These stockpiles will be exhausted withina few years and new reliable sources of Sc2O3 or otherSc compound production are sought It turns out thatthe most economically viable option that has beendisclosed so far is the processing of Red Mud from theBayer process of extracting alumina from bauxiteScandium is enriched in the Red Mud and is extractedfrom a Red Mud aqueous slurry by selective leachingsubsequent ion-exchange procedure and finally a liquidndashliquid extraction procedure It is not required to build aseparate lsquoSc factoryrsquo to do this but rather build an lsquoadd-onrsquo to existing Bayer process plants Such a processroute is expected to bring down the price of Sc2O3

considerably which in turn means that AlndashSc masteralloy price should drop accordingly Preliminary ana-lyses suggest a price of approx US$ 400 per kg Sc in themaster alloy which translates to an added cost of 80cent per kilo when 02 wt-Sc is added to an aluminiumalloy This is also a considerable increase in the materialcost but with such prices one should expect to see Sccontaining alloys in many more applications than whatis the case at the present time

Concluding remarksThe body of published investigations on Al-based alloyswith Sc addition provides a sound basis of knowledgefor metallurgists that want to look into the possibility ofenhancing the performance of a wrought Al-alloy byadding Sc to it Ternary AlndashScndashX phase diagrams areavailable for practically every technologically importantalloying element in Al The effect of a wide range ofternary alloying elements on the precipitation behaviourof Al3Sc is accounted for It has been shown that theAl3Sc phase can be effective as a grain refiner adispersoid former and a precipitate hardening agentand some of the underlying conditions for achieving thedesired Al3Sc formation have been outlined Addingsome Zr together with Sc has proven to be beneficial Itmay lead to effective grain refinement at a lower Sc levelbut the most prominent effect is the refinement indispersoid distribution that can be achieved An addi-tion of Sc has little if any effect on precipitation in the2xxx 6xxx and 7xxx alloy systems and some effects onthe precipitation in AlndashLi based alloys With respect tocorrosion behaviour adding Sc to an Al-alloy does ingeneral seem to make the alloy slightly more noble andto increase its self-corrosion resistance Scandium-containing Al alloys have very few uses at the presenttime as a result of the high price of scandium The priceof Sc is expected to decrease significantly in the futureand this should lead to the disclosure of moreapplications where it is economically feasible to takeadvantage of the improved properties of some Sc-containing aluminium alloys

References1 D R Lide lsquoCRC handbook of chemistry and physicsrsquo 71st edn

4ndash29 1990 Boston USA CRC Press

2 E M Savitsky V F Terehova I V Burov and O P Naumkin

Proc Fourth Conf on lsquoRare earth researchrsquo Phoenix Arizona

USA April 1964 409ndash420

3 E M Savitskii V F Terekhova I V Burov O P Naumkin and

I A Markova Inorg Mater 1965 1 1503ndash1512

4 O P Naumkin V T Terekhova and E M Savitskiy Russ

Metall 1965 (4) 128ndash136

5 W G Moffatt lsquoThe handbook of binary phase diagramsrsquo 1981

Schenectady NY USA General Electric Co

6 E A Brandes (ed) lsquoSmithells metals reference bookrsquo 6th edn

1983 London UK Butterworths

7 R P Elliott and F A Shunk Bull Alloy Phase Diagrams 1981

2 (2) 222ndash223

8 K A Gschneider Jr and F W Calderwood Bull Alloy Phase

Diagrams 1989 10 34ndash36

9 H Okamoto J Phase Equil 1991 12 612ndash613

10 J L Murray J Phase Equil 1998 19 380ndash384

11 M E Drits E S Kadaner T V Dobatkina and N I Turkina

Russ Metall 1973 (4) 152ndash154

12 S-I Fujikawa M Sugaya H Takei and K-I Hirano J Less-

Common Met 1979 63 87ndash97

13 N Blake and M A Hopkins J Mater Sci 1985 20 2861ndash2867

14 V I Kononenko and S V Golubev Russ Metall 1990 (2) 193ndash

195

15 T B Massalski J L Murray L H Bennett and H Baker (eds)

lsquoBinary alloy phase diagramsrsquo 1986 Metals Park OH USA

ASM

16 G Cacciamani P Riani G Borzone N Parodi A Saccone

R Ferro A Pisch and R Schmid-Fetzer Intermetallics 1999 7

101ndash108

17 H Okamoto J Phase Equil 2000 21 310

18 A F Norman P B Pragnell and R S McEwen Acta Mater

1998 46 5715ndash5732

19 I N Pyagai and A V Vakhobov Russ Metall 1990 (5) 50ndash52

20 C L Fu J Mater Res 1990 5 971ndash979

21 X Lu and Y Wang Calphad 2002 26 555ndash561

22 R R Sawtell and J W Morris Jr Proc lsquoDispersion strengthened

aluminium alloysrsquo Phoenix Arizona USA January 1988 409ndash

420

23 R R Sawtell and C L Jensen Metall Trans A 1990 21A 421ndash

430

24 L A Willey Unpublished research Alcoa 1970 Data points are

extracted from Ref 10

25 N I Turkina and V I Kuzmina Russ Metall 1976 (4) 179ndash

183

26 T Torma E Kovacs-Csetenyi I Vitanyi M Butova and

J Stepanov Proc 6th Int Symp on lsquoHigh purity materials in

science and technologyrsquo Akademie der Wissenschaften der DDR

Dresden Germany May 1985 388ndash389

27 A L Berezina V A Volkov B P Domashnikov and K V

Chuistov Metallofizika 1987 9 (5) 43ndash47

28 H-H Jo J Korean Inst Metals 1990 28 499ndash504

29 H-H Jo and S-I Fujikawa Mater Sci Eng 1993 A 171 151ndash

161

30 S Celotto and T J Bastow Philos Mag A 2000 80 1111ndash1125

31 J Roslashyset and N Ryum submitted to Mater Sci Eng

32 M E Drits L S Toropova Yu G Bykov F L Gushchina V I

Elagin and Yu A Filatov Russ Metall 1983 (1) 150ndash153

33 L S Toropova D G Eskin M L Kharakterova and T V

Dobatkina lsquoAdvanced aluminum alloys containing scandium

structure and propertiesrsquo 1998 Amsterdam The Netherlands

Gordon and Breach Science Publishers

34 V V Cherkasov P P Pobezhimov L P Nefedova E V Belov

and G M Kuznetsov Met Sci Heat Treat 1996 (6) 268ndash270

35 Kh O Odinaev I N Ganiev V V Kinzhibalo and B Ya

Kotur Dokl Akad Nauk Tadzh SSR 1989 32 37ndash38

36 Kh O Odinaev I N Ganiev and A V Vakhobov Russ Metall

1991 (4) 200ndash203

37 J Grobner R Schmid-Fetzer A Pisch G Cacciamani P Riani

N Parodi G Borzone A Saccone and R Ferro Z Metallkd

1999 90 872ndash880

38 E A Marquis and D N Seidman Microsc Microanal 2002 8

(Suppl 2) 1100CDndash1101CD

39 A Pisch J Grobner and R Schmid-Fetzer Mater Sci Eng A

2000 A 289 123ndash129

Roslashyset and Ryum Scandium in aluminium alloys

40 International Materials Reviews 2005 VOL 50 NO 1

40 C Xia F Zeng and Y Gu Trans Nonferrous Met Soc China

2003 13 1124ndash1127

41 M Yu Teslyuk and V S Protasov Sov Phys Crystallogr 1966

10 470ndash471

42 M L Kharakterova and T V Dobatkina Russ Metall 1988

(6) 175ndash178

43 M L Kharakterova Russ Metall 1991 (4) 195ndash199

44 L S Toropova M L Kharakterova and D G Eskin Russ

Metall 1992 (3) 194ndash199

45 P Riani L Arrighi R Marazza D Mazzone G Zanicchi and

R Ferro J Phase Equil Diff 2004 25 22ndash52

46 A T Tyvanchuk T I Yanson B Ya Kotur O S Zarechnyuk

and M L Kharakterova Russ Metall 1988 (4) 190ndash192

47 L L Rokhlin T V Dobatkina and M L Kharakterova Powder

Metall Met Ceram 1997 36

48 A Z Ikromov I N Ganiev and V V Kinzhibalo Dokl Akad

Nauk Tadzh SSR 1990 (6) 391ndash392

49 I N Ganiev A Z Ikromov and V G Khudoiberdiev Russ

Metall 1995 (3) 125ndash127

50 I N Fridlyander L L Rokhlin T V Dobatkina and N I

Nikitina Met Sci Heat Treat 1993 (10) 567ndash571

51 I N Fridlyander L L Rokhlin T V Dobatkina V V

Kinzhibalo and A T Tyvanchuk Russ Metall 1998 (1) 161ndash

166

52 R A Emigh E L Bradley and J W Morris Jr in lsquoLight-weight

alloys for aerospace applications IIrsquo (ed E W Lee and N J

Kim) 27ndash43 1991 TMS

53 L S Toropova A N Kamardinkin V V Kindzhibalo and A T

Tyvanchuk Phys Met Metall 1990 70 (6) 106ndash110

54 A N Kamardinkin T V Dobatkina and T D Rostova Russ

Metall 1991 (4) 216ndash218

55 L S Torodskaya T V Dobatkina and A N Kamardinkin

Russ Metall 1992 (5) 128ndash131

56 E M Sokolovskaya E F Kazakova E I Poddyakova and A

A Ezhov Met Sci Heat Treat 1997 (5) 211ndash213

57 Y Harada and D C Dunand Mater Sci Eng 2002 A 329ndash331

686ndash695

58 N E Drits L S Toropova and F L Gushchina Russ Metall

1984 (4) 229ndash232

59 E M Sokolovskaya E F Kazakova V A Alikhanov and E V

Zhuravleva Moscow Univ Chem Bull 1997 52 (5) 70ndash72

60 E M Sokolovskaya E F Kazakova and E I Poddyakova Met

Sci Heat Treat 1989 (11) 837ndash839

61 G M Cheldieva E F Kazakova E M Sokolovskaya and N I

Kaloev Russ Metall 1990 (6) 87ndash90

62 E M Sokolovskaya E F Kazakova and O D-S Kendivan

Russ Metall 1998 (4) 135ndash137

63 N G Bukhanko E F Kazakova and E M Sokolovskaya Russ

Metall 2001 (4) 425ndash431

64 E D Trubnyakova O I Bodak I N Ganiev and A V

Vakhobov Russ Metall 1987 (3) 219ndash222

65 I N Fridlyander and L V Molchanova Russ Metall 2003 (5)

476ndash480

66 R A Altynbaev S Kh Khairidinov and A V Vakhobov Russ

Metall 1987 (4) 194ndash196

67 J C Schuster and J Bauer J Less-Common Met 1985 109

345ndash350

68 L L Rokhlin A S Fridman T V Dobatkina and D G Eskin

Russ Metall 1991 (6) 146ndash148

69 A S Fridman T V Dobatkina and E V Muratova Russ

Metall 1992 (1) 207ndash209

70 C Xia F Zeng and Y Gu Trans Nonferrous Met Soc China

2003 13 546ndash552

71 F Zeng C Xia and Y Gu J Alloys Comp 2004 363 175ndash181

72 L L Rokhlin T V Dobatkina N R Bochvar and E V Lysova

J Alloys Comp 2004 367 10ndash16

73 T V Dobatkina A S Fridman and E V Muratova Russ

Metall 1992 (5) 125ndash127

74 I N Fridlyander L L Rokhlin N R Bochvar E V Lysova

and O V Boteva Russ Metall 2001 (6) 661ndash666

75 V N Rechkin L K Lamikhov and T I Samsonova Sov Phys

Crystallogr 1964 9 325ndash327

76 I I Zalutskii and P I Kripyakevich Sov Phys Crystallogr

1967 12 341ndash343

77 T J Bastow C T Forwood M A Gibson and M E Smith

Phys Rev B 1998 58 2988ndash2997

78 K Fukunaga M Kolbe K Yamada and Y Miura Mater Sci

Eng 1997 A 234ndash236 594ndash597

79 E P George J A Horton W D Porter and J H Schneibel

J Mater Res 1990 5 1639ndash1648

80 E P George D P Pope C L Fu and J H Schneibel ISIJ Int

1991 31 1063ndash1075

81 Y Harada and D C Dunand Acta Mater 2000 48 3477ndash3487

82 J H Schneibel and E P George Scripta Metall Mater 1990 24

1069ndash1074

83 J H Schneibel and P M Hazzledine Mater Res Soc Symp

Proc 1991 213 323ndash328

84 J H Schneibel and P M Hazzledine J Mater Res 1992 7

868ndash875

85 C J Sparks E D Specht G E Ice P Zschack and J Schneibel

Mater Res Soc Symp Proc 1991 213 363ndash368

86 J Tarnacki and Y-W Kim Scripta Metall Mater 1989 23

1063ndash1068

87 M Asta V Ozolins and C Woodward JOM 2001 53 (9) 16ndash

19

88 M E Drits L S Toropova F L Gushchina and S G Fedotov

Sov Non-Ferrous Met Res 1984 12 83ndash85

89 Y Harada and D C Dunand Scripta Mater 2003 48 219ndash222

90 C Woodward M Asta G Kresse and J Hafner Phys Rev B

2001 63 094103-1-6

91 J-H Xu and A J Freeman Phys Rev B 1990 41 12553ndash12561

92 M F Bartholomeusz and J A Wert Acta Metall Mater 1992

40 673ndash682

93 G Bester and M Fahnle J Phys Condens Matter 2001 13

11551ndash11565

94 C L Fu and M H Yoo Proc lsquoOrdered intermetallics ndash physical

metallurgy and mechanical behaviorrsquo Irsee Germany June 1991

155ndash164

95 K Fukunaga T Shouji and Y Miura Mater Sci Eng 1997 A

239ndash240 202ndash205

96 D P Pope Proc lsquoOrdered intermetallics ndash physical metallurgy

and mechanical behaviorrsquo Irsee Germany June 1991 143ndash153

97 J-S Wang Acta Mater 1998 46 2663ndash2674

98 M H Yoo and C L Fu Mater Sci Eng 1992 A 153 470ndash478

99 R W Hyland Jr and R C Stiffler Scripta Metall Mater 1991

25 473ndash477

100 I G Brodova I V Polents O A Korzhavina P S Popelrsquo I P

Korshunov and V O Esin Melts 1992 4 392ndash397

101 I G Brodova O A Chikova I V Polents P S Popelrsquo and V O

Esin Casting Processes 1992 1 (2) 158ndash160

102 I G Brodova D V Bashlikov and I V Polents Mater Sci

Forum 1998 269ndash272 589ndash594

103 K B Hyde A F Norman and P B Pragnell Mater Sci Forum

2000 331ndash337 1013ndash1018

104 K B Hyde A F Norman and P B Pragnell Acta Mater 2001

49 1327ndash1337

105 J Roslashyset and N Ryum Proc 6th Int Conf on lsquoAluminum

alloysrsquo Toyohashi Japan July 1998 793ndash798

106 V I Elagin V V Zakharov and T D Rostova Met Sci Heat

Treat 1993 (6) 317ndash319

107 R W Hyland Jr Metall Trans A 1992 23A 1947ndash1955

108 B A Parker Z F Zhou and P Nolle J Mater Sci 1995 30

452ndash458

109 C L Rohrer M D Asta S M Foiles and R W Hyland Jr

Mater Res Soc Symp Proc 1996 398 477ndash482

110 G M Novotny and A J Ardell Mater Sci Eng 2001 A 318

144ndash154

111 J D Robson M J Jones and P B Pragnell Acta Mater 2003

51 1453ndash1468

112 C Tan Z Zheng and B Wang Proc 3rd Int Conf on

lsquoAluminium alloysrsquo Vol I NTH Trondheim Norway June

1992 290ndash294

113 M Nakayama A Furuta and Y Miura Mater Trans JIM

1997 38 852ndash857

114 E A Marquis and D N Seidman Acta Mater 2001 49 1909ndash

1919

115 M J Jones and F J Humphreys Acta Mater 2003 51 2149ndash

2159

116 E A Marquis D N Seidman and D C Dunand in lsquoCreep

deformation fundamentals and applicationsrsquo (ed R S Mishra

J C Earthman and S V Raj) 299ndash308 2002 TMS

117 D N Seidman E A Marquis and D C Dunand Acta Mater

2002 50 4021ndash4035

118 E A Marquis D N Seidman and D C Dunand Acta Mater

2003 51 285ndash287

119 M E Drits L S Toropova U G Bikov and G K Anastaseva

Proc lsquoDiffusion in metals and alloysrsquo Tihany Hungary Augustndash

September 1982 616ndash623

120 V I Elagin V V Zakharov and T D Rostova Met Sci Heat

Treat 1983 (7) 546ndash549

Roslashyset and Ryum Scandium in aluminium alloys

International Materials Reviews 2005 VOL 50 NO 1 41

121 M Ye Drits L B Ber Yu G Bykov L S Toropova and G K

Anastaseva Phys Met Metall 1984 57 (6) 118ndash126

122 M E Drits L S Toropova and Yu G Bykov Sov Non-Ferrous

Met Res 1985 13 309ndash314

123 V I Yelagin V V Zakharov S G Pavlenko and T D Rostova

Phys Met Metall 1985 60 (1) 88ndash92

124 N Sano Y Hasegawa K Hono H Jo K Hirano H W

Pickering and T Sakurai Journal de Physique 1987 48 C6 337ndash

342

125 N Sano H-H Jo K-I Hirano and T Sakurai J Jpn Inst

Metals 1989 39 444ndash450

126 N Sano H Jo K Hirano and T Sakurai Proc Second Int

Conf on lsquoAluminium alloysrsquo Beijing China October 1990 549ndash

554

127 Y Miura M Nakayama and A Furuta Proc lsquoAspects of high

temperature deformation and fracture in crystalline materialsrsquo

Nagoya Japan July 1993 255ndash262

128 Y W Riddle and T H Sanders Jr Mater Sci Forum 2000

331ndash337 939ndash944

129 Y W Riddle M McIntosh and T H Sanders Jr in lsquoLightweight

alloys for aerospace application VIrsquo (ed K Jata E W Lee

W Frazier and N J Kim) 25ndash39 2001 TMS

130 M E Drits J Dutkiewicz L S Toropova and J Salawa Crystal

Res Technol 1984 19 1325ndash1330

131 Y W Riddle MSc thesis Georgia Tech GA USA 1998

132 T J Bastow and S Celotto Mater Sci Eng 2003 C 23 757ndash

762

133 M C Carroll M J Mills G S Daehn P I Gouma M F

Savage and B R Dunbar in lsquoAutomotive Alloys 1999rsquo (ed

S Das) 239ndash246 2000 TMS

134 E Clouet M Nastar and C Sigli Phys Rev B 2004 69 064109-

1-14

135 V V Zakharov Met Sci Heat Treat 1997 (2) 61ndash66

136 J W Christian lsquoThe theory of transformation in metals and

alloysrsquo 2nd edn 1975 Pergamon Press Ltd

137 A L Berezina V A Volkov B P Domashnikov S V Ivanov

and K V Chuistov Phys Metals 1990 10 296ndash304

138 S-I Fujikawa and S Sakauchi Proc 6th Int Conf on

lsquoAluminum alloysrsquo Toyohashi Japan July 1998 805ndash810

139 Y S Touloukian R K Kirby R E Taylor and P D Desai

(eds) lsquoThermal expansion metallic elements and alloysrsquo 1975

New York Plenum

140 J Roslashyset and N Ryum submitted to Scripta Mater

141 R O Simmons and R W Balluffi Phys Rev 1960 117 52ndash61

142 M Ocko E Babic R Krsmik E Girt and B Leontic J Phys F

Metals Phys 1976 6 703ndash707

143 M J Jones and F J Humphreys Proc First Joint Int Conf on

lsquoRecrystallization and grain growthrsquo Aachen Germany August

2001 Springer Verlag 1287ndash1292

144 S Iwamura M Nakayama and Y Miura Mater Sci Forum

2002 396ndash402 1151ndash1156

145 S Iwamura and Y Miura Acta Mater 2004 52 591ndash600

146 M Asta S M Foiles and A A Quong Phys Rev B 1998 57

11265ndash11275

147 R W Hyland Jr M Asta S M Foiles and C L Rohrer Acta

Mater 1998 46 3667ndash3678

148 J Roslashyset and N Ryum Proc 4th Int Conf on lsquoAluminium

alloysrsquo Vol I Atlanta GA USA September 1994 194ndash201

149 M E Drits L S Toropova G K Anastaseva and G L

Nagornichnykh Russ Metall 1984 (3) 192ndash195

150 E A Marquis D N Seidman and D C Dunand Acta Mater

2003 51 4751ndash4760

151 M E Drits L S Toropova and Yu G Bykov Met Sci Heat

Treat 1983 (7) 550ndash554

152 V V Zakharov and T D Rostova Met Sci Heat Treat 1995

(2) 65ndash69

153 M Nakayama and Y Miura Proc 4th Int Conf on lsquoAluminium

alloysrsquo Vol I Atlanta GA USA September 1994 538ndash545

154 M Nakayama and Y Miura J Jpn Inst Light Metals 1996 46

275ndash279

155 M Nakayama T Okuyama and Y Miura Mater Sci Forum

2000 331ndash337 927ndash932

156 M Nakayama T Okuyama and Y Miura Proc 6th Int Conf

on lsquoAluminum alloysrsquo Toyohashi Japan July 1998 517ndash522

157 M L Kharakterova D G Eskin and L S Toropova Acta

Metall Mater 1994 42 2285ndash2290

158 V I Elagin V V Zakharov and T D Rostova Met Sci Heat

Treat 1992 (1) 37ndash45

159 H Wiik Siv Ing thesis NTH Institute of Metallurgy

Trondheim Norway 1995

160 J Roslashyset H Hovland and N Ryum Mater Sci Forum 2002

396ndash402 619ndash624

161 Y Miura K Horikawa K Yamada and M Nakayama Proc

4th Int Conf on lsquoAluminium alloysrsquo Vol II Atlanta GA USA

September 1994 161ndash168

162 Y W Riddle PhD thesis Georgia Tech GA USA 2000

163 B Forbord W Lefebvre F Danoix H Hallem and

K Marthinsen Scripta Mater 2004 51 333ndash337

164 J D Robson Acta Mater 2004 52 1409ndash1421

165 C B Fuller J L Murray and D N Seidman submitted to Acta

Mater 2004

166 M G Mousavi C E Cross and Oslash Grong Sci Technol Weld

Joining 1999 4 381ndash388

167 J S Vetrano S M Bruemmer L M Pawlowski and I M

Robertson Mater Sci Eng 1997 A 238 101ndash107

168 Y W Riddle and T H Sanders Jr Mater Sci Forum 2000

331ndash337 799ndash803

169 G M Khan A O Nikiforov V V Zakharov and I I Novikov

Tsvetnye Metally 1993 34 (11) 43ndash45

170 Z Horita M Furukawa M Nemoto A J Barnes and T G

Langdon Acta Mater 2000 48 3633ndash3640

171 L A Willey US Patent 3 619 181 9 November 1971

172 L K Lamikhov and G V Samsonov Tsvetnye Metally 1964 5

(8) 77ndash80

173 A L Berezina K V Chuistov N I Kolobnev L B

Khokhlatova and T A Monastyrskaya Mater Sci Forum

2002 396ndash402 741ndash746

174 F A Fasoyinu J Thomson D Cousineau T Castles and M

Sahoo Proc 6th Int AFS Conf on lsquoMolten aluminum

processingrsquo Orlando FL USA November 2001

175 Z Yin Q Pan Y Zhang and F Jiang Mater Sci Eng 2000

A 280 151ndash155

176 I I Novikov and O E Grushko Mater Sci Technol 1995 11

926ndash932

177 D Cousineau M Sahoo P D Newcombe T Castles and F A

Fasoyinu Proc lsquoAFS 105th casting congressrsquo Dallas TX USA

AprilndashMay 2001 157ndash184

178 C E Cross and Oslash Grong Proc 6th Int Conf on lsquoAluminum

alloysrsquo Toyohashi Japan July 1998 1441ndash1446

179 F A Costello J D Robson and P B Prangnell Mater Sci

Forum 2002 396ndash402 757ndash762

180 K B Hyde A F Norman and P B Prangnell Mater Sci

Forum 2002 396ndash402 39ndash44

181 M E Drits S G Pavlenko L S Toropova Yu G Bukov and

L B Ber Sov Phys Dokl 1981 26 (3) 344ndash346

182 A M Drits and B A Kopeliovich Russ Metall 1985 (4) 147ndash

151

183 V G Davydov V I Elagin V V Zakharov and T D Rostova

Met Sci Heat Treat 1996 (8) 347ndash352

184 M E Drits L S Toropova Yu G Bykov L B Ber and S G

Pavlenko Russ Metall 1982 (1) 148ndash152

185 T D Rostova V G Davydov V I Yelagin and V V Zakharov

Mater Sci Forum 2000 331ndash337 793ndash798

186 Y W Riddle H Hallem and N Ryum Mater Sci Forum 2002

396ndash402 563ndash568

187 J Roslashyset and Y W Riddle Proc 9th Int Conf on lsquoAluminium

alloysrsquo Brisbane Australia August 2004 1210ndash1215

188 A M Diskin V K Portnoi A M Drits and A A Alalykin Sov

Non-Ferrous Met Res 1986 14 499ndash500

189 R R Sawtell P E Bretz and C L Jensen US Patent 4 689 090

25 August 1987

190 G A Salishchev Yu B Timoshenko and R A Saitova Proc

Second Int Conf on lsquoAluminium alloysrsquo Beijing China October

1990 413ndash415

191 T G Nieh R Kaibyshev L M Hsiung N Nguyen and

J Wadsworth Scripta Mater 1997 36 1011ndash1016

192 T G Nieh L M Hsiung J Wadsworth and R Kaibyshev Acta

Mater 1998 46 2789ndash2800

193 J S Vetrano C H Henager Jr M T Smith and S M

Bruemmer in lsquoHot deformation of aluminum alloys IIrsquo (ed T R

Bieler L A Lalli and S R MacEwen) 407ndash418 1998 TMS

194 J S Vetrano C H Henager Jr S M Bruemmer Y Ge and

C H Hamilton in lsquoSuperplasticity and Superplastic Forming

1998rsquo (ed A K Gosh and T R Bieler) 89ndash97 1998 TMS

195 V Y Gertsman J S Vetrano C H Henager Jr and S M

Bruemmer Proc First Joint Int Conf on lsquoRecrystallization and

grain growthrsquo Aachen Germany August 2001 Springer Verlag

2001 837ndash842

196 Y Xiao C Gao H Ma and S Tian Trans Nonferrous Met Soc

China 2001 11 235ndash238

Roslashyset and Ryum Scandium in aluminium alloys

42 International Materials Reviews 2005 VOL 50 NO 1

197 A Gholinia F J Humphreys and P B Prangnell Acta Mater

2002 50 4461ndash4476

198 A Gholinia F J Humphreys and P B Prangnell Mater Sci

Forum 2002 408ndash412 1519ndash1524

199 S Komura P B Berbon M Furukawa Z Horita M Nemoto

and T G Langdon Scripta Mater 1998 38 1851ndash1856

200 S Komura P B Berbon A Utsunomiya M Furukawa

Z Horita M Nemoto and T G Langdon in lsquoHot deformation

of aluminum alloys IIrsquo (ed T R Bieler L A Lalli and S R

MacEwen) 125ndash138 1998 TMS

201 S Komura Z Horita M Furukawa M Nemoto and T G

Langdon J Mater Res 2000 15 2571ndash2576

202 S Komura M Furukawa Z Horita M Nemoto and T G

Langdon Mater Sci Eng 2001 A 297 111ndash118

203 S Komura Z Horita M Furukawa M Nemoto and T G

Langdon Metall Mater Trans A 2001 32A 707ndash716

204 Z Horita M Furukawa K Oh-ishi M Nemoto and T G

Langdon Proc Fourth Int Conf on lsquoRecrystallization and

related phenomenarsquo (ed T Sakai and H G Suzuki) 1999 The

Japan Institute of Metals 301ndash308

205 Z Horita S Komura P B Berbon A Utsunomiya

M Furukawa M Nemoto and T G Langdon Mater Sci

Forum 1999 304ndash306 91ndash96

206 Z Horita S Lee S Ota K Neishi and T G Langdon Mater

Sci Forum 2001 357ndash359 471ndash476

207 Z Horita T Fujinami K Sato S B Kang H W Kim and T G

Langdon in Proc James T Staley Honorary Symposium on

Aluminum Alloys lsquoAdvances in the metallurgy of aluminum

alloysrsquo (ed M Tiryakioglu) 271ndash275 2001 ASM

208 P B Berbon S Komura A Utsunomiya Z Horita

M Furukawa M Nemoto and T G Langdon Mater Trans

JIM 1999 40 772ndash778

209 M Nemoto Z Horita M Furukawa and T G Langdon Mater

Sci Forum 1999 304ndash306 59ndash66

210 M Furukawa Z Horita M Nemeto and T G Langdon Proc

lsquoLight Metals 1999rsquo Quebec City PQ Canada August 1999 583ndash

592

211 M Furukawa K Oh-ishi S Komura A Yamashita Z Horita

M Nemeto and T G Langdon Mater Sci Forum 1999 304ndash

306 97ndash102

212 M Furukawa A Utsunomiya K Matsubara Z Horita and

T G Langdon Acta Mater 2001 49 3829ndash3838

213 M Furukawa A Utsunomiya S Komura Z Horita M Nemoto

and T G Langdon Mater Sci Forum 2001 357ndash359 431ndash436

214 M Furukawa Z Horita and T G Langdon in Proc James T

Staley Honorary Symposium on Aluminum Alloys lsquoAdvances in

the metallurgy of aluminum alloysrsquo (ed M Tiryakioglu) 47ndash56

2001 ASM

215 M Furukawa Z Horita M Nemoto and T G Langdon Mater

Sci Eng 2002 A 324 82ndash89

216 M Furukawa Z Horita and T G Langdon in lsquoUltrafine grained

materials IIrsquo (ed Y T Zhu T G Langdon R S Mishra S L

Semiatin M J Saran and T C Lowe) 459ndash468 2002 TMS

217 T G Langdon M Furukawa Z Horita and M Nemoto Proc

NATO Advanced Research Workshop on lsquoInvestigations and

applications of severe plastic deformationrsquo Moscow August

1999 NATO Science Series Series 3 High Technology vol 80

Kluwer Academic Publishers The Netherlands 2000 149ndash154

218 S Lee H Akamatsu A Utsunomiya K Neishi M Furukawa

Z Horita and T G Langdon Proc Thermec 2000 Las Vegas

USA December 2000

219 S Lee A Utsunomiya H Akamatsu K Neishi M Furukawa

Z Horita and T G Langdon Acta Mater 2002 50 553ndash564

220 A Yamashita D Yamaguchi Z Horita and T G Langdon

Mater Sci Eng 2000 A 287 100ndash106

221 K Oh-ishi Z Horita D J Smith and T G Langdon J Mater

Res 2001 16 583ndash589

222 H Akamatsu T Fujinami Z Horita and T G Langdon Scripta

Mater 2001 44 759ndash764

223 S Ota H Akamatsu K Neishi M Furukawa Z Horita and

T G Langdon Mater Trans 2002 43 2364ndash2369

224 K Furuno H Akamatsu K Oh-ishi M Furukawa Z Horita

and T G Langdon Acta Mater 2004 52 2497ndash2507

225 I N Fridlyander O G Senatorova N A Ryazanova and A O

Nikiforov Mater Sci Forum 1994 170ndash172 345ndash349

226 J N Fridlyander and O G Senatorova Mater Sci Forum 1996

217ndash222 1813ndash1818

227 J Liu and D J Chakrabarti Acta Mater 1996 44 4647ndash4661

228 O G Senatorova A N Uksusnikov J N Fridlyander

J Koshorst R R Romanova N A Ryazanova A Galliot

and V V Cherkassov Proc 6th Int Conf on lsquoAluminum alloysrsquo

July 1998 Toyohashi Japan 589ndash593

229 R A Emigh E L Bradley and J W Morris Jr in

lsquoSuperplasticity in aerospace IIrsquo (ed T R McNelley and H C

Heikkenen) 303ndash315 1990 TMS

230 E L Bradley III R A Emigh and J W Morris Jr Scripta

Metall Mater 1991 25 717ndash721

231 N I Kolobnev L B Khokhlatova V D Makarov E Yu

Semenova and V V Redchits Proc Sixth Int Aluminiumndash

Lithium Conference Garmisch-Partenkirchen Germany October

1991 1053ndash1056

232 N K Tsenev R Z Valiev O V Obraztsov and I N Fridlander

Proc Sixth Int AluminiumndashLithium Conference Garmisch-

Partenkirchen Germany October 1991 1125ndash1132

233 A M Shammazov N K Tsenev R Z Valiev M M

Myshlyaev M M Bikbulatov and S P Lebedich Phys Met

Metall 2000 89 (3) 314ndash318

234 F Musin R Kaibyshev Y Motohashi T Sakuma and G Itoh

Mater Trans A 2002 43A 2370ndash2377

235 M Shagiev Y Motohashi F Musin R Kaibyshev and G Itoh

Mater Trans A 2003 44A 1694ndash1697

236 M Shagiev Y Motohashi F Musin R Kaibyshev and G Itoh

Mater Trans A 2003 44A 1698ndash1701

237 B A Parker and Z F Zhou Proc 3rd Int Conf on lsquoAluminium

alloysrsquo Vol I NTH Trondheim Norway June 1992 363ndash367

238 J R Davies lsquoASM specialty handbook aluminum and aluminum

alloysrsquo 1993 Materials Park OH USA ASM

239 S J Andersen H W Zandbergen J Jansen C Traeholt

U Tundal and O Reiso Acta Mater 1998 46 3283ndash3298

240 M L Kharakterova D G Eskin and L L Rokhlin Russ

Metall 1997 (1) 104ndash109

241 J Roslashyset Dr Ing thesis NTNU Trondheim Norway 2002

242 P P Chattopadhyay S Datta and M K Banerjee Mater Sci

Eng 2002 A 333 67ndash71

243 L I Kaigorodova E I Selnikhina E A Tkachenko and O G

Senatorova Phys Met Metall 1996 81 513ndash519

244 Y-L Wu F H Froes C Li and A Alvarez Metall Mater

Trans A 1999 30A 1017ndash1024

245 Z Yin L Yang Q Pan and F Jiang Trans Nonferrous Met

Soc China 2001 11 822ndash825

246 V I Elagin V V Zakharov and T D Rostova Met Sci Heat

Treat 1994 36 (7) 375ndash380

247 Y V Milman A I Sirko D V Lotsko O N Senkov and D B

Miracle Mater Sci Forum 2002 396ndash402 1217ndash1222

248 C-H Joh K Yamada and Y Miura Mater Trans JIM 1999

40 439ndash442

249 X J Jiang Q H Gui Y Y Li L M Ma G J Liang and C X

Shi Scr Metall Mater 1993 29 211ndash216

250 X J Jiang Y Y Li W Deng L Y Xiong W M Wu Y J Gao

and C X Shi Adv Cryogenic Eng (Mater) 1994 40 1369ndash

1376

251 C-H Joh T Katsube K Yamada and Y Miura Proc 6th Int

Conf on lsquoAluminum alloysrsquo Toyohashi Japan July 1998 799ndash

804

252 L I Kaygorodova A M Dritz T V Krymova and I N

Fridlyander Proc Sixth Int AluminiumndashLithium Conference

Garmisch-Partenkirchen Germany October 1991 363ndash367

253 L I Kaigorodova A M Drits Ya V Zhingel T V Krymova

and I N Fridlyander Phys Met Metall 1992 73 286ndash290

254 A L Berezina V A Volkov S V Ivanov N I Kolobnev and

K V Chuistov Phys Met Metall 1991 71 (2) 167ndash175

255 I N Fridlyander N I Kolobnev A L Berezina and K V

Chuistov Proc Sixth Int AluminiumndashLithium Conference

Garmisch-Partenkirchen Germany October 1991 107ndash112

256 L I Kaigorodova A M Drits Ya V Zhingel T V Krymova

and V A Rassokhin Phys Met Metall 1992 73 281ndash285

257 I N Fridlyander S F Danilov E N Malysheva T A

Gorokhova and N N Kirkina Proc Sixth Int Aluminiumndash

Lithium Conference Garmisch-Partenkirchen Germany October

1991 381ndash386

258 G Dlubek S Krause H Krause A L Beresina V S

Mikhalenkov and K V Chuistov J Phys Condens Matter

1992 4 6317ndash6328

259 S Krause H Krause G Dlubek A L Beresina and K S

Chuistov Mater Sci Forum 1992 105ndash110 1109ndash1112

260 C Y Tan Z Q Zheng and S Q Liang Proc 4th Int Conf on

lsquoAluminium alloysrsquo Vol II Atlanta GA USA September 1994

329ndash333

261 A L Beresina N I Kolobnev K V Chuistov A V Kotko and

O A Molebny Mater Sci Forum 2002 396ndash402 977ndash981

Roslashyset and Ryum Scandium in aluminium alloys

International Materials Reviews 2005 VOL 50 NO 1 43

262 I N Ganiev I Yunusov and V V Krasnoyarskii J Appl Chem

USSR 1986 60 1961ndash1965

263 I N Ganiev Prot Met 1995 31 543ndash546

264 N V Vyazovikina Prot Met 1999 35 448ndash453

265 G V Kharina and V P Kochergin Prot Met 1996 32 134ndash

136

266 G V Kharina M V Kuznetsov and V P Kochergin Russ J

Electrochem 1998 34 482ndash485

267 V S Sinyavskii V D Valrsquokov and E V Titkova Prot Met

1998 34 549ndash555

268 Y L Wu F H Froes C G Li and J Liu Proc lsquoSynthesis

processing of lightweight metallic materials IIrsquo Orlando FL

USA February 1997 73ndash81

269 Z Ahmad and B J Abdul-Aleem Proc EuroCorr 2000

270 Z Ahmad A Ul-Hamid and B J Abdul-Aleem Corros Sci

2001 43 1227ndash1243

271 R Braun B Lenczowski and G Tempus Mater Sci Forum

2000 331ndash337 1647ndash1652

272 T Torma E Kovacs-Csetenyi L Vitalis I Vitanyi

J Stepanov and M Butova Mater Sci Forum 1987 1314

497ndash503

273 Z Wang P Wang K S Kumar and C L Briant in lsquoChemistry

and electrochemistry of corrosion and stress corrosion crackingrsquo

(ed R H Jones) 573ndash582 2001 TMS

274 V I Elagin V V Zakharov A A Petrova and E V

Vyshegorodtseva Russ Metall 1983 (4) 143ndash146

Roslashyset and Ryum Scandium in aluminium alloys

44 International Materials Reviews 2005 VOL 50 NO 1

Page 7: Scandium in aluminium alloys - Atom probe · A considerable part of the available literature on scandium in aluminium alloys is reviewed. ... behaviour in Al Cu, Al Mg Si,

AlndashMgndashScndashTindashZr

A vertical cross-section of the AlndashMgndashScndashTindashZr phasediagram for 03 wt-Sc 015 wt-Ti 015 wt-Zrand 0ndash10 wt-Mg has been constructed34 Accord-ing to this diagram the Al3Zr phase is the first andAl3Sc the last to form during solidification of thealloys No ternary quaternary or quinary phases arereported

AlndashZnndashMgndashCundashZrndashSc

A vertical cross-section of the full system as well asseveral sections of various sub-systems have beenconstructed72 For the full system a section at8 wt- Zn 2 wt-Cu 03 wt-Zr and 03 wt-Scwas constructed where Mg varies from 0 to 8 wt-The only reported Sc-containing sub-system is thatof AlndashZnndashMgndashCundashSc Here a vertical cross-sectionis constructed with the same levels of Zn Cu and Scas in the full system whereas Mg varies from 0 to65 wt-

No phases other than those known from the lowerorder systems were reported Amongst the findings it isinteresting to note that in the solid state Al3Sc isreported to be an equilibrium phase for all theinvestigated compositions It is also interesting to notethat the Sc-containing W-phase (Al54ndash8Cu66ndash4Sc see thesection on the AlndashCundashSc ternary system) is an equili-brium phase at low Mg content and disappears as theMg content increases

AlndashLindashMgndashSc

The 400uC isothermal phase relations of the 02 wt-Scsection have been investigated for the composition range0ndash6 wt-Mg and 0ndash5 wt-Li73 The a-Al was found tobe in equilibrium with AlLi Al2LiMg and Al3Sc Noquaternary phases were observed This investigation isalso summarised in Ref 50

AlndashCundashLindashSc

The aluminium rich corner of the system has beeninvestigated for alloys with 06 wt-Sc and with Cu andLi in the range 0ndash16 wt- and 0ndash4 wt- respectively74

No quaternary phases were reported Two sections ofthe phase diagram were constructed a section of the470uC isothermal tetrahedron at 06 wt-Sc and avertical section at 06 wt-Sc and 26 wt-Li Twoquaternary invariant equilibria were found and thetemperatures of the invariant points were estimated

Al3Sc phaseRechkin and co-workers were to the authorsrsquo knowl-edge the first to publish a paper in an internationaljournal identifying the Al3Sc phase75 The phase wasidentified as cubic with lattice parameter a5410 A Afew years later the lattice structure was reported to be ofthe Cu3Au type76 The atomic arrangement of the Al3Scphase is shown in Fig 10 The structure can bedescribed as ordered face-centred cubic (fcc) althoughin crystallographic terminology the Al3Sc structure isactually a simple cubic lattice with four atoms (one Scand three Al atoms) associated with each lattice pointThis particular atomic arrangement is nominated L12

and is found in several intermetallic compounds forinstance Ni3Al Ni3Fe and Cu3Au

Some efforts have been made in characterising theproperties of the Al3Sc phase A compilation of someresults is given in Table 3 The motivation for themajority of the investigations seems to be one of thethree following

(i) the Al3Sc phase has a density of 303 g cm23 andit melts peritectically at approx 1320uC This canmake the Al3Sc phase an attractive candidate asa material for lightweight high temperaturestructural applications205777ndash86

(ii) in order to understand the effect of Al3Scprecipitation in Al-alloys it is necessary to gainmore knowledge about the Al3Sc phase578187ndash91

(iii) the Al3Sc is an excellent model phase forstudying basic properties of intermetalliccompounds7990ndash98

10 Atomic arrangement of Al3Sc phase

Table 3 Some reported properties of Al3Sc phase

ReferenceE GPa(Youngrsquos modulus) n (Poissonrsquos ratio)

CTE (Coefficient ofthermal expansion) 1026 K21

(111) APB energymJ m22

(100) APB energymJ m22

88 Approx 11120 166 020 Max 670 45079 166 022 31399 1628 0204

1642iexcl19 0201iexcl000189 16

Reported to decrease linearly with increasing temperature to approx 97 GPa at 550uCCalculatedExperimental

Roslashyset and Ryum Scandium in aluminium alloys

International Materials Reviews 2005 VOL 50 NO 1 25

Formation of Al3Sc in AlndashSc alloysThere are at least four ways that the Al3Sc phase canform in dilute binary AlndashSc alloys

1 Upon solidification of hypereutectic alloys (Sc

approx 06 wt-) Al3Sc is the first phase to form

2 The solidification of hypo- and hypereutectic alloysends with formation of eutectic AlzAl3Sc

3 Al3Sc can precipitate discontinuously from super-saturated solid solution

4 Al3Sc can precipitate continuously (nucleation andgrowth) from supersaturated solid solution

Primary Al3ScAccording to the binary phase diagram primary Al3Scshould form during solidification of all alloys with Sccontent higher than approx 06 wt- ie higher thanthe eutectic composition Formation of primary Al3Sc inAlndash07 wt-Sc melts cooled at 102ndash103 K s21 has beenreported1832 According to the metastable state dia-gram32 this alloy composition is close to the eutectic oneat these cooling rates

Primary Al3Sc is reported to have a highly facetedmorphology1318100ndash102 The observation of a cubicmorphology in a slowly cooled Alndash87 wt-Sc alloyindicates that the facet planes in this case are thecrystallographic (100) planes13 Brodova et al100ndash102

have investigated the microstructure of rapidly cooledAlndash2 wt-Sc alloy They found that the dominantmorphology of primary Al3Sc was dependent on boththe cooling rate and the initial melt temperature A mapof primary Al3Sc morphologies as a function of theseparameters was constructed and is redrawn in Fig 11

The nucleation mechanism and growth morphologyof primary Al3Sc in an Alndash07 wt-Sc alloy solidified ata cooling rate of 100 K s21 were investigated by Hydeet al103104 Indications were found that the primaryAl3Sc particles nucleate heterogeneously on oxideparticles in the melt The primary Al3Sc particles werefound to grow with a dendritic morphology with theprimary dendrite arms in the crystallographic n110m

direction The overall shape is cubic which is inaccordance with earlier observations

Eutectic Al3ScEutectic AlzAl3Sc has been reported in hyper- as wellas hypoeutectic alloys11 but is scantily described in theliterature Given a eutectic composition of 06 wt- amaximum solid solubility of Sc in Al of 035 wt- andthe specific densities in Table 1 a eutectic formed underequilibrium conditions would contain a volume fractionof approx 063 vol-Al3Sc At high cooling rates thevolume fraction of Al3Sc in the eutectic is probablysomewhat smaller owing to the increased supersatura-tion of Sc in Al

The morphology of the eutectic in an Alndash2 wt-Scalloy is reported to depend on the temperature of themelt before solidification100 For low melt temperaturesthe eutectic is reported to be rodlike for a wide range ofcooling rates For intermediate melt temperatures andhigh cooling rates a lsquodiscontinuous eutecticrsquo is reportedwhereas for high melt temperatures and slow coolingrates a lsquoquasieutecticrsquo structure is reported with Al3Scparticles of almost spherical shape

Hyde et al have reported that during solidification ofan Alndash07 wt-Sc alloy some of the primary Al3Scparticles are pushed ahead of the Al solidification frontand end up at the grain boundaries103104 Thus primaryAl3Sc may be mixed with eutectic Al3Sc in themicrostructure A scanning electron microscopy (SEM)picture showing eutectic Al3Sc at the grain boundaries asdescribed in Refs 103 and 104 is given in Fig 12

Discontinuous precipitation of Al3ScDiscontinuous precipitation of Al3Sc from super-saturated solid solution is often observed in binary AlndashSc alloys131831105 This precipitation mechanism whichis sometimes referred to as cellular precipitation iscommonly described as a decomposition of super-saturated solid solution into a-Al and Al3Sc at a movinggrain boundary The driving force for the grainboundary migration is the volume free energy that isreleased during the precipitation As the grain boundarymoves it leaves behind a characteristic fan shaped array

11 Morphology of primary Al3Sc particles in Alndash2 wt-Sc

alloy as a function of melt overheating and cooling

rate during solidification redrawn from Ref 102

12 SEM image of particle structure of Alndash07 wt-Sc

alloy cooled at a rate of 100 K s21 during solidifica-

tion as described in Refs 103 and 104 primary Al3Sc

particle is seen in centre of grain whereas eutectic

Al3Sc is decorating grain boundaries image is kindly

provided by Dr Kristian Hyde UMIST Manchester UK

Roslashyset and Ryum Scandium in aluminium alloys

26 International Materials Reviews 2005 VOL 50 NO 1

of precipitates In the AlndashSc case the discontinuouslyprecipitated Al3Sc particles have been demonstrated tobe coherent with the aluminium matrix1318

The driving force for discontinuous precipitationincreases with increasing supersaturation of Sc in theAl matrix Thus discontinuous precipitation in binaryAlndashSc is most frequently reported in studies of alloyswith a Sc content of 04 wt- or higher1318106 Stilldiscontinuous precipitation has also occasionally beenreported to occur at lower alloy compositions In an Alndash027 wt-Sc alloy discontinuous precipitation wasobserved over a wide range of temperatures107 In arecent study31105 of precipitation kinetics and mechan-isms in Alndash02 wt-Sc discontinuous precipitation wasfound to take place when the specimens were quencheddirectly from a solutionising temperature in this case600uC to aging temperatures in the range 370ndash490uCFurther C-curves in a temperature-time-transformation(TTT) diagram were established (Fig 13) which showedthat the highest transformation rate of discontinuousprecipitation lies at a higher temperature than thehighest transformation rate of the continuous precipita-tion reaction ie the two precipitation reactions arerepresented by two separate lsquonosesrsquo on the C-curves

It has been shown that discontinuous precipitationcan be suppressed by continuous precipitation if thematerial is cold worked before the precipitation heattreatment13108

As a result of their rather coarse nature andinhomogeneous dispersion discontinuously precipitatedAl3Sc contributes but little to the strength of the alloyand also leads to a smaller amount of Sc in super-saturated solid solution being available for subsequentcontinuous precipitation Thus discontinuous precipita-tion is in general regarded as an undesired precipitationmode

Continuous precipitation of Al3ScContinuous precipitation of Al3Sc is a bulk decomposi-tion process of supersaturated solid solution of Sc in Aland can in the isothermal case be characterised by anucleation stage a growth stage and finally a coarsen-ing stage Apparently the continuous precipitation reac-tion occurs largely by homogeneous nucleation anddiffusion controlled growth and AlndashSc has occasionallybeen used as a model system for studying the mechan-isms of nucleation growth and coarsening107109ndash111

There have been several studies of the continuousprecipitation reaction in binary AlndashSc alloys and up tillnow there is no evidence that any metastable phases areforming before the L12 phase Al3Sc Thus it is assumedthat the equilibrium phase nucleates directly fromsupersaturated solid solution

Even though the nucleation of Al3Sc is frequentlyreported to occur homogeneously throughout the Almatrix there are some examples in the technical litera-ture of reported heterogeneous Al3Sc nucleation ondislocations110112ndash115 and grain boundaries110113115ndash118

In a recent numerical modelling study of continuousprecipitation in AlndashSc alloys111 the effect of hetero-geneous nucleation on dislocations is accounted for Themodel predicts that homogeneous nucleation dominatesat high Sc concentrations and low transformation tem-peratures whereas heterogeneous nucleation is predictedto dominate at low Sc concentrations and high trans-formation temperatures Figure 14 shows a sketch of anucleation map for AlndashSc The shift between homo-geneous and heterogeneous dominance in nucleation isdependent on the dislocation density as indicated in thefigure

The shape of continuously precipitated Al3Sc particlesis most frequently reported to be spherical29112113119ndash129

However it seems that under certain conditions theshape can differ from the spherical one Drits et al130

reported both spherical and star shaped morphologyThe star shaped precipitates had arms growing in thecrystallographic n110m-directions (Star shaped Al3Scprecipitates have also been found after some thermo-mechanical treatments of an AlndashMgndashScndashZr alloy131) InRef 128 precipitates of both cuboidal and sphericalmorphology are found to coexist after certain heattreatments Cauliflower shaped precipitates as well asprecipitates of spherical and cuboidal shapes arereported by Novotny and Ardell110 Bastow andCelotto132 found large oblong Al3Sc particles in an Alndash01 wt-Sc alloy after aging at 400uC for 24 h A facetedshape is suggested in a high-resolution image of anAl3(Sc Zr) precipitate in an AlndashMgndashMnndashZrndashSc alloy133

In a systematic high-resolution transmission electron

13 TTT diagram of precipitation in Alndash02 wt-Sc alloy

after solutionising at 600uC and direct quench to

aging temperature3114 Nucleation map for binary AlndashSc alloys which indi-

cates how the tendency towards heterogeneous ver-

sus homogeneous nucleation is predicted to depend

upon Sc concentration transformation temperature

and dislocation density redrawn from Ref 111

Roslashyset and Ryum Scandium in aluminium alloys

International Materials Reviews 2005 VOL 50 NO 1 27

microscopy (TEM) study of the Al3Sc particle morphol-ogy development during precipitation heat treatment ofbinary AlndashSc alloys by Marquis and Seidman114 it isdemonstrated that the precipitates can take a wide rangeof shapes as they grow depending on Sc content in thealloy transformation temperature and transformationtime Irregular shaped star shaped and cuboidalshaped precipitates were observed under someconditions It was however found that the equilibriumshape of the particles is an equiaxed multifaceted one(Fig 15) Supported by Wulffrsquos construction it wasconcluded that the shape was that of a GreatRhombicuboctahedron This equilibrium morphologyhas been reproduced by computer-simulations ofparticle growth87134 The multifaceted particles caneasily be taken for spherical in a conventional TEMpicture

Kinetics of precipitation of Al3Sc fromsupersaturated solid solutionThe precipitation kinetics of Al3Sc in binary AlndashScalloys is dependent on the precipitation heat treatmenttemperature and on the Sc content in the alloy Acomprehensive overview over the transformationkinetics in terms of C-curves is given by Zakharov135

The C-curves for 5 transformation for a range of AlndashSc alloys are redrawn in Fig 16

Hyland107 studied the homogeneous nucleationkinetics of Al3Sc in a Alndash018 wt-Sc alloy after directquench from 650uC to precipitation temperatures of 288and 343uC He found that after an incubation time t theAl3Sc particles nucleated at a constant rate until thediffusion fields of the individual particles started tooverlap At 288uC the incubation time and time tosignificant diffusion field overlap were estimated to beapprox 245 and 150 min respectively whereas thecorresponding values at 343uC were estimated to beapprox 7 and 20 min respectively

If one assumes that the JohnsonndashMehlndashAvramindashKomolgorov (JMAK) relationship is valid for thisprecipitation reaction one can express the fraction

transformed X as a function of the reaction time t bythe equation

X (t)~1expfrac12k(Dt)n (1)

where k is a constant D is the interdiffusion constant ofSc in Al and the exponent n is dependent on thenucleation rate For the situation described byHyland107 where the precipitates nucleate at a constantrate the value of n should theoretically136 be equal to52

Roslashyset and Ryum31105 applied an alloy and heattreatment method practically equal to that of Hyland107

One should thus expect that the precipitation kineticsshould also be quite similar However Roslashyset andRyum reported that the exponent n of the JMAKrelationship was approx 165ndash185 for the temperaturerange of concern31105 This does not point in thedirection of a constant nucleation rate but rather inthe direction of site saturation ie that all the particlesare nucleated simultaneously which in the JMAKequation would yield an exponent n of 32136 Anoverview of some reported values of n in the JMAKequation is given in Table 4 The majority of the valueslie closer to 32 than to 52 However it is important to

15 High resolution TEM picture along n100m axis of Al3Sc particle in Alndash03 wt-Sc alloy aged at 300uC for 350 h114

(reproduced with permission from Elsevier Science image kindly provided by Dr E A Marquis and Professor D N

Seidman) and various projections of a Great Rhombicuboctahedron

Table 4 Some reported values of n in JMAK equation

Reference n C 0Sc wt-Sc Ttrans uC Note

137 13 030 300 Solution heat treated (SHT) 500uC16026 030 300 SHT 600uC Low n at late stage20026 030 300 SHT 640uC Low n at late stage

29 130ndash149 015 260ndash370145ndash196 025 260ndash370

138 188ndash216 020 240ndash35031 165ndash185 023 270ndash350 SHT 600uC Direct quench to transformation temp

16 C-curves for 5 transformation in a range of binary

AlndashSc alloys redrawn from Ref 135

Roslashyset and Ryum Scandium in aluminium alloys

28 International Materials Reviews 2005 VOL 50 NO 1

note that an n value close to 32 is per se not evidence ofsite saturation

Hyland also showed that a water quench from thesolutionising temperature significantly altered thenucleation kinetics in the subsequent precipitation heattreatment107 The incubation time was dramaticallyshortened which is attributed to the quenched-in excessvacancies and it is also indicated that there might be ashift in the nucleation rate in the early stage ofprecipitation It is suggested that the vacancies mayenhance the diffusion of Sc in Al and that there is apossibility that vacancy clusters act as heterogeneousnucleation sites for Al3Sc precipitates107 Regardless ofwhich mechanism that is operative it is clearly demon-strated that the nucleation kinetics can be dependent onthe thermal history between solutionising and precipita-tion heat treatment

Loss of coherency during growth of Al3ScprecipitatesWhen an Al3Sc particle grows it will sooner or laterreach a critical size where it will be energetically morefavourable to introduce an interface dislocation at theAlAl3Sc interface than to increase the matrix strain Asimple approximation for the critical size can be derivedfrom the lattice parameters assuming that the criticalsize is reached when the misfit over the whole particlediameter equals the Burgers vector of the Al matrix

dcrit~b=d (2)

where b is the Burgers vector of Al and d is themisfit between Al and Al3Sc This approximation yieldsa critical diameter of approx 215 nm at ambienttemperature

The misfit d and thus also the critical diameter dcrit

will depend on the temperature owing to the differencesin thermal expansion between the Al matrix and the

Al3Sc particles The thermal expansion of Al3Sc hasrecently been measured89 and based on the differencesin thermal expansion between Al139 and Al3Sc the misfitas a function of temperature has been calculated89 Thiscalculation is reproduced and shown by the solid line inFig 17

It is however possible to refine this calculationsomewhat140 Whereas the thermal expansion of Al3Sc isexpected to be only because of lattice expansion there isa significant contribution from vacancies on thermalexpansion of Al at high temperatures141 Thus thetemperature effects on the misfit should be calculatedfrom the changes in lattice parameters rather than fromthe linear thermal expansion By subtracting the vacancyeffect on the thermal expansion one achieves atemperature-dependent misfit as represented by thedotted line in Fig 17

A second correction that should be taken into accountis the effect of Sc in solid solution on the latticeparameter of the Al matrix With increasing tempera-ture more Sc is brought into solid solution and it isreported that the lattice parameter of the Al matrixpresumably measured at room temperature increaseslinearly with the Sc content in solid solution142 Thesedata can be used to calculate the effect on the latticeparameter at elevated temperatures under the assump-tion that the relative increase in lattice parameter owingto Sc in solid solution is independent of temperature InRef 142 a figure is presented which shows the measuredlattice parameter as a function of Sc content in solidsolution and a value (dadc)a is reported where a is thelattice parameter of the Al matrix and c is the Sc contentin solid solution in at- The reported value for (dadc)a is 100 times larger than that indicated in thecorresponding figure possibly as a result of a decimalerror in the text Thus in the present exercise 1100th ofthe reported value for (dadc)a is used Using this incombination with the regular solution approximationfor the solvus line of Sc in Al1231 one obtains acorrection for Sc in solid solution on the temperature-dependent misfit as shown in Fig 18 This figure shows

17 Lattice mismatch between Al and Al3Sc as a function

of temperature solid line represents calculation

based on linear thermal expansion of the two phases

dotted line represents correction for vacancies in Al

lattice

18 Corrections of mismatch calculated from linear ther-

mal expansion data as a result of vacancies and to

Al lattice expansion from Sc in solid solution

Roslashyset and Ryum Scandium in aluminium alloys

International Materials Reviews 2005 VOL 50 NO 1 29

both the correction for vacancies and for Sc in solidsolution on the same graph The two corrections are ofapproximately the same magnitude but with oppositesigns Thus the resulting (net) correction is close to zeroand it turns out that the first hand approximation asapplied in Ref 89 is very good in this case

Applying the calculated temperature dependent misfitwith the simple approximation for a critical diameter forloss of coherency one obtains a temperature-dependentcritical diameter as shown in Fig 19

Some examples from the literature of experimentallyobserved critical diameters in binary AlndashSc alloys aresummarised in Table 5 along with some predictions forcritical diameters from Fig 19 There is a fairly goodconsistency between the observations and the measureddiameter is quite close to the simple predictions above

A more refined analysis on the transition fromcoherent to incoherent particles has recently beenperformed145 This analysis is based on the balancebetween the increase in particlematrix interface energyowing to interfacial dislocations and the relaxation inelastic energy in the Al matrix owing to the samedislocations This method yields a predicted criticaldiameter of 246 nm for transition from coherent to

semi-coherent particles at ambient temperature Thetemperature dependence of the critical diameter is nottreated in this analysis

The loss of coherency during isothermal annealing hasbeen reported to be accompanied by an increasedaverage coarsening rate119121137145 The increasedcoarsening rate has been attributed either to diffusionof Sc along dislocation lines119121 or to the increasedparticlematrix interface energy of a semicoherentparticle145 However there are also several data sets inthe literature that do not indicate an increased growthrate after the loss of coherency114128

Al3ScAl interface energyThe interface energy between Al3Sc and the Al matrix isone of the key parameters that governs the nucleationgrowth and coarsening behaviour of Al3Sc in Al and Alalloys The interface energy has been estimated in severalinvestigations either by fitting experimental data toequations that describe nucleation or coarsening or bycalculations A compilation of some of the results isgiven in Table 6 There is considerable spread in thereported values regardless of what approach has beenused for the estimation

Influence of other elements on precipitation ofAl3ScMagnesium

With regard to precipitation mechanism it has beenstated that Mg suppresses the tendency to discontinuousprecipitation of Al3Sc106 In an investigation of pre-cipitation kinetics of Al3Sc in the temperature range300ndash500uC only minor changes in the kinetics (Fig 20)were found when up to 5 wt-Mg was added to an Alndash04 wt-Sc alloy135 It seems that the precipitationreaction is slightly faster in the Mg-containing alloys

Several investigations on age hardening response alsoimply that there is only a small if any effect of Mg onthe precipitation kinetics of Al3Sc23148149 It is how-ever found that the hardness increase from theprecipitation of Al3Sc is somewhat reduced in AlndashMgndashSc alloys compared to binary AlndashSc alloys23148149 InRef 149 it is suggested that some of the Sc is dissolvedin the Al3Mg2 phase and thus the age hardeningpotential is reduced with increasing Mg contentSomewhat contradictory to these observations but

Table 5 Some reported critical diameters for coherencyloss in binary AlndashSc and correspondingtheoretical critical diameters from Fig 19

Reference dcrit nmC0

Scwt-Sc

TtransuC

Theoreticaldcrit nm

119 38ndash40 05137 28ndash30 03 400 308128 32 02 400 450 308 335129 50 02143 40 012 025115 40 025 450ndash500 335ndash37114 40 03 400 450 308 335144 40 02 400ndash460 308ndash341145 30ndash80 02 400ndash490 308ndash362

20 C-curves for 10 and 60 transformation in Alndash

04 wt-Sc and Alndash4 wt-Mgndash04 wt-Sc redrawn

from Ref 135

19 Simple approximation for temperature-dependent criti-

cal diameter for introduction of dislocations on Al

Al3Sc interface

Roslashyset and Ryum Scandium in aluminium alloys

30 International Materials Reviews 2005 VOL 50 NO 1

sustained by Ref 135 it has recently been reported150

that precipitation of Al3Sc at 300 and 350uC occursslightly faster in an Alndash2 wt-Mgndash02 wt-Sc alloythan in an Alndash02 wt-Sc alloy studied previously by thesame researchers117118 and that the correspondinghardness increase is highest in the AlndashMgndashSc alloyThe only reported difference in experimental procedureis the solutionising temperature which was higher forthe AlndashSc alloy (648uC) than for the AlndashMgndashSc alloy(617uC) However given that the nucleation time isshortened by quenched-in vacancies as suggested byHyland107 the difference in homogenisation tempera-ture should be in favour of a faster precipitation of thebinary AlndashSc alloy It should be worthwhile to probedeeper into this observation of different aging responses

Mg in solid solution increases the lattice parameter ofthe Al matrix This is in turn expected to influence thecritical diameter for AlAl3Sc coherency loss as discussedin the section on lsquoLoss of coherency during growth ofAl3Sc precipitatesrsquo above Such an influence on the criticaldiameter is also briefly discussed elsewhere150 A criticaldiameter of 80 nm in an Alndash3 wt-Mgndash02 wt-Sc alloyhas been observed compared to 40 nm in a binary Alndash02 wt-Sc alloy of the same investigation144 Otherresearchers have reported a critical diameter in excess of116 nm in an Alndash63 wt-Mgndash02 wt-Sc alloy151

Computer simulations predict that the AlAl3Scinterface should be enriched in Mg87 These predictionsare confirmed experimentally by three-dimensional atomprobe microscopy of an Alndash2 wt-Mgndash02 wt-Sc alloyaged at 300uC38 Here it was found that the Mg contentat the interface is approximately three times higher thanthe matrix concentration regardless of aging time

Copper

It has been claimed that Cu suppresses the tendencytowards discontinuous precipitation of Al3Sc106

Zakharov and Rostova152 have reported that additionsof up to 14 wt-Cu have only minor effects on theprecipitation kinetics in an Alndash04 wt-Sc alloy Themost noticeable effect is that for temperatures above400uC the late stage of the transformation is sloweddown for the highest Cu contents This does not show in

Fig 21 however where only the 10 and 60transformation curves are included

The W-phase (AlCuSc) was observed in the alloywith the highest Cu content which means that less Sc isavailable for the precipitation of Al3Sc in this alloyAnother investigation on the age hardening response ofAlndash023 wt-Sc and Alndash25 wt-Cundash023 wt-Sc at300uC also implies that the precipitation behaviour ofAl3Sc in the two alloys is similar153154 At 350uC alimited portion of the Al3Sc has been observed tonucleate heterogeneously on coarse hrsquo precipitates155

According to the isothermal sections of the phasediagram43 one should expect the ternary W-phase toform instead of the Al3Sc phase in an alloy with such ahigh CuSc ratio However no observations of the W-phase or other ternary phases were reported from TEMstudies of the Alndash25 wt-Cundash023 wt-Sc alloy thathad been heat treated in the temperature range 300ndash460uC153ndash156 A third investigation on the precipitationin Alndash048 wt-Sc alloys with up to 440 wt-Cu in thetemperature range 100ndash450uC also concludes that no W-phase or other ternary phase forms during the heattreatment157

Copper in solid solution decreases the lattice para-meter of the Al matrix Thus it is expected that the misfitbetween Al and Al3Sc precipitates should be higher in

21 C-curves for 10 and 60 transformation in Alndash

04 wt-Sc and Alndash14 wt-Cundash04 wt-Sc redrawn

from Ref 152

Table 6 Reported values of interphase energy cAlAl3Sc between coherent Al3Sc precipitates and Al matrix

Reference cAlAl3Sc mJ m22 Method of estimation

137 10 Fit of coarsening data to LifshitzndashSlezev equation107 78iexcl20 (288uC) Back-calculation of incubation time

93iexcl20 (343uC)107 123iexcl41 (288uC) Back-calculation of nucleation rate

125iexcl35 (343uC)29 542 (400uC) Fit of coarsening data to Ostwald ripening

632 (430uC)413 (460uC)

146 c(100) 192 (0 K) c(111) 226 (0 K) Pseudopotential calculations147 c(100) 325 (0 K) c(110) 513 (0 K) c(111)

782 (0 K) c(100) 315 (288uC) c(100) 325 (343uC)Atomistic simulation

110 105 Fit of coarsening data to LSW theory31 20ndash300 Fit of coarsening data to Ostwald ripening

for 16 different temperatures111 57 Fit of precipitation model to experimental data145 120 coherent particles Fit of coarsening data

170 semicoherent particles

It is argued in this study that c may be lower in the nucleation stage

Roslashyset and Ryum Scandium in aluminium alloys

International Materials Reviews 2005 VOL 50 NO 1 31

AlndashCundashSc alloys compared to AlndashSc alloys Howeveran experimental investigation of Alndash25 wt-Cundash023 wt-Sc alloy comes to a different conclusion Thelattice misfit strain is found to decrease compared to Alndash02 wt-Sc and the critical diameter for coherency losswas found to be the same in the ternary and the binaryalloy144 It is suggested that these observations may bebecause of the dissolution of some Cu in the Al3Sc phaseand thus that the lattice parameters of both the Al matrixand the Al3Sc precipitates decrease in the ternary alloy

Silicon

It has been found that the onset of precipitation in Alndash04 wt-Sc is only slightly altered when Si contents ofup to 04 wt are introduced in the alloy However thefinal stage of the precipitation reaction is considerablydelayed with increasing Si content135 Figure 22 showsthe effect of addition of a joint of 035 wt-Si and040 wt-Fe There are at least two possible explana-tions for why an Si-addition leads to this behaviour

1 Alloying with Si is known to promote discontin-uous precipitation of Al3Sc106158 It has been shown thatwhen isothermal precipitation of Al3Sc starts discon-tinuously the later stage of the overall transformationcan be very slow31

2 The isothermal section of the phase diagramsuggests that the V-phase (AlSc2Si2) should form inalloys of this composition46 If the V-phase forms lessSc is available for precipitation of Al3Sc

It has been shown157 that for an AlndashScndashSi alloy withsolid solution content of 010 wt-Sc an 110 wt-Sithe only phases to precipitate after heat treatment at200uC are Si and an (AlScSi)-phase possibly the V-phase On the other hand the Al3Sc phase has beenobserved to form in alloys with 04 wt-Sc and up to08 wt-Si159160

Zinc

It has been reported that additions of up to 5 wt- Znhave only minor effects on the precipitation kinetics ofan Alndash04 wt-Sc alloy135 (Fig 23) In Ref 106 it isclaimed that Zn promotes discontinuous precipitation ofAl3Sc

Lithium

A comparison of the age hardening response at 400uC inAlndash24 wt-Lindash019 wt-Sc and Alndash024 wt-Sc alloys

indicates that the onset of Al3Sc-precipitation is notaffected by the presence of Li161

Zirconium

As mentioned in the section on lsquoTernary phase diagramswith dispersoid-forming elementsrsquo earlier a considerableamount of Zr is dissolved in the Al3Sc phase and thus amore correct denotation of the precipitating phase isAl3(Sc12xZrx) In discussing the influence of the Zrcontent on the precipitation of Al3Sc one is thereforeactually discussing the difference in precipitation ofAl3Sc versus Al3(Sc12xZrx)

It is found that an addition of 015 wt-Zr to an Alndash04 wt-Sc alloy only marginally affects the initial stageof the precipitation reaction123135 while it slows downthe later stages of the transformation considerably(Fig 24)135 The coarsening rate of the Al3(Sc12xZrx)particles in AlndashScndashZr alloys is found to be much slowerthan that of Al3Sc particles in AlndashSc alloys123162

In three-dimensional atom probe field ion microscopy(3D-APFIM) of Al3(Sc12xZrx) particles formed at 475uCin a ternary AlndashScndashZr alloy163 it was found that the coreof the particles is almost pure Al3Sc whereas there is ashell of Al3(Sc12xZrx) with almost equal content of Scand Zr Such a behaviour has also been predicted bycomputer modelling of precipitation of Al3(Sc12xZrx) at480uC in an AlndashZnndashMgndashScndashZr alloy164 This modelpredicts that Zr starts to enter the growing

22 C-curves for 10 and 60 transformation in Alndash

04 wt-Sc and Alndash04 wt-Fendash035 wt-Sindash04 wt-Sc

redrawn from Ref 135

23 C-curves for 10 and 60 transformation in Alndash

04 wt-Sc and Alndash5 wt-Znndash04 wt-Sc redrawn

from Ref 135

24 C-curves for 10 and 60 transformation in Alndash

04 wt-Sc and Alndash04 wt-Scndash015 wt-Zr redrawn

from Ref 135

Roslashyset and Ryum Scandium in aluminium alloys

32 International Materials Reviews 2005 VOL 50 NO 1

Al3(Sc12xZrx) particles when approximately half of thesupersaturated Sc has been precipitated The Zr contentof the outer shell is predicted to be much higher thanwhat has been found experimentally163164

Another 3D-APFIM study of Al3(Sc12xZrx) particlesin a ternary AlndashScndashZr alloy has been reported165 Hereparticles grown at 300uC for various lengths of time werestudied The Zr content in these particles was muchlower than that reportedpredicted at higher tempera-tures163164 even after very long annealing times

Iron

The effect of adding up to 07 wt-Fe on the precipita-tion kinetics in an Alndash04 wt-Sc alloy has beeninvestigated135 The onset of precipitation was onlyslightly influenced by the Fe-level whereas the laterstages of the transformation however were significantlyslowed down as the Fe-level increased An example ofthe effect of a joint addition of Fe and Si is shown inFig 22

Manganese chromium and titanium

Small additions (03 wt-) of manganese or chromiumto Alndash040 wt-Sc alloys are reported to have onlyminor effects on the precipitation kinetics of Al3Sc135

According to Ref 106 Mn is reported to promote andCr and Ti to suppress discontinuous precipitation

Rare earth elements

An investigation of the precipitation behaviour of Alndash03 at-Sc and Alndash03 at-Scndash03 at-X alloyswhere X is either yttrium gadolinium holmium orerbium in the temperature range 235ndash310uC indicatedthat a Al3(Sc12xXx) phase with L12 structure wasformed in the ternary alloys22 Peak strength is reportedto occur after approx 10 h at 285uC in all alloys whichindicates that the precipitation kinetics up to peakstrength is practically unaltered by the ternary additions

Influence of Sc on microstructure andproperties of wrought aluminium alloysMost of the effects of Sc addition in wrought Al-alloysare linked to the formation of the Al3Sc phase In atypical processing route of a wrought aluminium alloyparticles of the Al3Sc phase can form under threedifferent conditions each of which influences themicrostructure and properties of the alloy in a specificway

1 During solidification after casting or weldingAl3Sc particles can form in the melt and act as nucleifor a-Al thus leading to grain refinement18166

2 High temperature processing of the alloy in therange 400ndash600uC for instance homogenisation hot-rolling or extrusion can give a dense distribution ofAl3Sc particles of typically 20ndash100 nm size The particledistributions formed under such conditions are reportedto lead to good recrystallisation resistance128148167168

and enhanced superplasticity52169170

3 Heat treatment in the range 250ndash350uC can lead tosignificant precipitation hardening of an alloy super-saturated in Sc148158171 The size of strengthening Al3Scprecipitates is typically in the range 2ndash6 nm121

Grain refinementA good grain refinement is almost always desired uponsolidification The formation of small equiaxed grainsrather than long dendrites in the melt facilitates thefeeding of the melt into cavities of the shrinkingsolidified metal and thus reduces the problem ofshrinkage porosity The tendency to hot cracking is alsoreduced and the second phase particles become morefinely and uniformly distributed

To the authorsrsquo knowledge the first effect of Sc in Al-alloys that was reported in an international scientificjournal was the grain refining action in pure Al and in anAlndashCu alloy upon solidification172 which was found tobe stronger for Sc than for other transition metals Inlater studies of Sc as a grain refiner in pure Al1832173 ithas been demonstrated that approx 07 wt-Sc issufficient to provide excellent grain refinement It hasalso been demonstrated that additions of 025 wt-Scz025 wt-Zr provide good grain refinement in pure Al18

In order for Sc to act as an effective grain refiner theAl3Sc phase has to form in the melt before thesolidification of a-Al The Al3Sc particles have a latticeparameter close to that of pure Al and whenhypereutectically formed the Al3Sc particles are veryeffective substrates for the nucleation of the a-Al phaseAs mentioned in the section on lsquoFormation of Al3Sc inAlndashSc alloysrsquo above this requires that the alloy ishypereutectic with respect to Sc ie in excess of approx06 wt- in a binary AlndashSc alloy In ternary and higherorder systems the eutectic Sc composition may dependon the other alloying elements present For instance theeutectic composition of Sc has been predicted todecrease with increasing Mg content in the ternary AlndashMgndashSc system39 This prediction is sustained by theobservation of good grain refinement by adding 05 wt-Sc to an Alndash7 wt-Mg alloy174 (Other examples ofgrain refinement at Sc concentrations lower than that ofthe binary eutectic are found in Ref 173)

Similarly the observation of good grain refinement inan Alndash025 wt-Scndash025 wt-Zr alloy18 may be as aresult of a lower Sc content of the eutectic in the ternarysystem ie less Sc is needed to make the alloy hyper-eutectic No literature data on the liquidus surface of theAlndashScndashZr system are available and thus this hypothesiscannot be confirmed In more complex alloy systems itis also observed that excellent grain refinement isachieved at low Sc contents when Sc is added togetherwith Zr It is reported that adding either 02 wt-Sc06 wt-Sc or 01 wt-Zr to an Alndash5Mg alloy givesmuch poorer grain refinement than adding 02 wt-Scz01 wt-Zr175 Similarly additions of 015 wt- ofeither Sc or Zr are reported to only marginally refinethe grain structure in an AlndashCundashLi alloy whereas a jointaddition of 015 wt-Sc and 015 wt-Zr gives excellentgrain refinement176 For an AA 3650 casting alloy (Alndash7 wt-Sindash04 wt-Mg) good grain refinement is achievedby adding 039 wt-Sc or 027 wt-Scz019 wt-Zr177

In some AlndashZnndashMgndashScndashZr alloys it is also found thatan addition of 02ndash03 wt-Sc can be sufficient for goodgrain refinement166169178179 Examples of the grainrefinement as a function of Sc addition in pure Al andin an AlndashZnndashMgndashZr alloy are shown in Fig 25

The nucleation of a-Al on Al3Sc particles in the melt isfacilitated by the close match in the lattice parameters ofthe two phases As shown in Fig 17 the mismatch at the

Roslashyset and Ryum Scandium in aluminium alloys

International Materials Reviews 2005 VOL 50 NO 1 33

eutectic temperature of binary AlndashSc alloys (660uC) isonly approx 047 In Refs 57 and 89 it is shown thatwhen Zr Hf and in particular Ti is dissolved in the Al3Scparticles this reduces the lattice parameter of the phaseIt appears that when 25 of the Sc atoms in Al3Sc aresubstituted by Ti the mismatch is zero at approx 550uCand becomes negative at higher temperatures89 Thissuggests that by carefully selecting the Ti content of thealloy it should be possible to obtain Al3(ScTi)substrates in the melt that match exactly the latticeparameter of the nucleating a-Al and thus furtherimprove the grain refinement of the alloy This appearsto have been achieved in a recent work180 where thegrain refinement of an Alndash07 wt-Sc alloy wascompared with that of an Alndash05 wt-Scndash02 wt-Tialloy At a cooling rate of 100 K s21 only an estimated2 of the primary Al3Sc particles of the binary AlndashScalloy were effective nuclei compared to practically 100for the primary Al3(ScTi) particles in the ternary AlndashScndashTi alloy leading to a much smaller grain size in theternary alloy Whereas the match of lattice parametersmay be of importance for these results the authors ofthis investigation180 draw attention to other factors suchas different growth restriction factors for Sc and Ti andthe possibility of a peritectic reaction in the ternaryalloy Nevertheless the principle of matching latticeparameters is worth looking into further in future work

Effects from dispersoidslsquoDispersoidsrsquo is a term which is commonly used aboutthe classes of second phase particles that are formedin an Al alloy during high temperature annealing orthermomechanical processing such as homogenisationhot rolling extrusion and forging A dense distributionof dispersoids can give a significant contribution to analloyrsquos strength owing to particle strengthening but thisis rarely the main strengthening mechanism A moreimportant contribution from the dispersoids is theirability to stabilise the grainsubgrain structure of analloy through the Zener-drag action and thus improvethe mechanical properties of the alloy

There are two noticeable dispersoid-related effectsthat have been reported for Sc-containing alloys Thefirst is the stabilising effect on a deformed microstruc-ture When a non-recrystallised structure is preserved inan alloy this can add considerably to the mechanical

strength of the material The second effect is thepreservation of a small grain size during hot deforma-tion at slow deformation rates which is necessary toobtain superplastic properties of an Al-alloy

Recrystallisation resistance

The anti-recrystallisation effect of Sc was first publishedin a patent171 where 03 wt-Sc was added to pure Aland to AlndashMg AlndashMn and AlndashZnndashMg alloys Both Sc-free and Sc-containing materials were cold worked andsubsequently annealed and it was found that theaddition of Sc increased the temperature for onset ofrecrystallisation by approx 220uC in pure Al andsomewhat less in the Al-alloys Although the author ofthe patent171 may have been well aware that the anti-recrystallisation effect is caused by Al3Sc dispersoidsthis is not mentioned in the text The first journal paperthat explicitly points out that the recrystallisationresistance is due to Al3Sc dispersoids was an investiga-tion of the effects of adding Sc to wrought AlndashMgalloys181 In this work it was found that the Al3Scdispersoids were very effective in preventing recrystalli-sation up to temperatures of approx 400ndash450uC Athigher temperatures the dispersoids coarsen consider-ably and the microstructure was partially recrystallised

It is established that the Zener-drag pZ that is imposedon an advancing grain boundary by randomly distrib-uted dispersoids can be expressed in the form

pZ~k f =r (3)

where k is a factor that includes the interface energybetween the dispersoids and the matrix f is the volumefraction and r is the mean radius of the dispersoids Thusthe Zener drag will decrease rapidly in the case where thedispersoids are coarsening

As mentioned in the section on lsquoInfluence of otherelements on precipitation of Al3Scrsquo above theAl3(Sc12xZrx) dispersoids in a ternary AlndashScndashZr alloycoarsen at a much slower rate than the Al3Sc dispersoidsin a binary AlndashSc alloy This effect was first reported inRef 123 (although also observed in Ref 182) andaccording to Ref 33 the same authors demonstratedsoon after that the denser dispersoid distributionachieved in an AlndashScndashZr alloy leads to superiorrecrystallisation resistance compared to a binary AlndashScalloy An example of the increased recrystallisationresistance by adding both Zr and Sc is shown in Fig 26

In isothermal sections of the ternary AlndashScndashZr phasediagram it is indicated that the solid solubility ofSczZr is somewhat higher than that of Sc alone54 Ithas also been demonstrated both by electrical con-ductivity measurements (Fig 27) and microstructuralobservations that the supersaturation of SczZr isgreater than that of only Sc or Zr in as cast Alndash15(SczZr) alloys183 This indicates that it should bepossible to increase the volume fraction of dispersoids inAlndashScndashZr compared to AlndashSc It is suggested162 that theincreased volume fraction that can be achieved byadding both Sc and Zr can be advantageous inconventional wrought Al-alloys

There are at least two different conditions underwhich Al3Sc or Al3(Sc12xZrx) dispersoids can form toprevent recrystallisation

1 Sc (or Sc and Zr) is in solid solution before thedeformation In the case of cold deformation and

25 Grain refinement as a function of Sc addition in pure

Al (redrawn from Ref 32) and AlndashZnndashMgndashZr (redrawn

from Ref 169) note that data points are plotted on

different ordinate axes

Roslashyset and Ryum Scandium in aluminium alloys

34 International Materials Reviews 2005 VOL 50 NO 1

subsequent annealing the Al3Sc or Al3(Sc12xZrx)dispersoids may nucleate and grow before the nucleationand growth of recrystallised grains takes placeDispersoids can form after a direct up-quench to theannealing temperature115143148184 during ramp-up tothe annealing temperature115 or by pre-annealing at anintermediate temperature129 In the case of hot deforma-tion the Al3Sc or Al3(Sc12xZrx) dispersoids maynucleate and grow during preheating of the materialand during the hot deformation itself184

2 The Al3Sc or Al3(Sc12xZrx) dispersoids are formedin the material before deformation184 Considering coldrolling and subsequent annealing the annealing tem-perature Tann may be either lower or higher than thetemperature Tdisp at which the dispersoids were formedIf TannTdisp only limited if any coarsening of thedispersoids is expected to take place and thus the Zenerdrag from the particles is expected to be practicallyconstant The driving force for recrystallisation how-ever is expected to decrease somewhat with theannealing time as a result of recovery processes Thusif recrystallisation does not occur within short annealingtimes the material is expected to remain unrecrystallisedfor infinite time at the annealing temperature IfTannTdisp there will be substantial coarsening of thedispersoids during annealing In order for the materialto remain unrecrystallised the decrease in driving forcefor recrystallisation owing to recovery has to be at leastas rapid as the decrease in Zener drag because of particlecoarsening

Experimental comparisons of the conditions abovepoint in the direction that the recrystallisation resistanceis poorest when Sc (or Sc and Zr) is in solid solutionbefore deformation and the deformed material is up-quenched to the annealing temperature148 or when Al3Scor Al3(Sc12xZrx) dispersoids are formed before defor-mation at TdispampTann184185 Excellent recrystallisationresistance is achieved if dispersoids are formed at anintermediate anneal of solutionised and deformedmaterial128 or if dispersoids are formed at TdispTann

before deformation148185ndash187 It seems that the decreasein Zener drag because of dispersoid coarsening in many

cases is slower than the decrease in driving force forrecrystallisation because of recovery processes Thusthere is an advantage in forming a high number densityof small dispersoids which for most practical casesmeans that they should be formed at TdispTann122

When an advancing high angle grain boundary iethe recrystallisation front is passing a coherent Al3Scdispersoid there are at least three possible grainboundarydispersoid interactions

1 The Al3Sc dispersoid retains its global orientationrelationship and thus loses its coherency with thesurrounding matrix

2 The Al3Sc dispersoid rotates as the grain boundarypasses either by diffusional processes at the dispersoidmatrix interface or by the grain boundary passingthrough the dispersoid and the Al3Sc dispersoidassumes the same crystallographic orientation as theAl matrix of the recrystallised grain

3 The Al3Sc dispersoid dissolves at the grainboundary and re-precipitates in the recrystallised grain

Which interactions that actually take place willprobably depend on the dispersoid size annealingtemperature and driving force for recrystallisation It isalso possible that alloy composition (other elementsthan Al) is of importance

It has been reported that large (Oslash about 100ndash150 nm)Al3Sc dispersoids in a deformed Alndash4 wt-Mgndash02 wt-Sc alloy annealed at 575uC lose the orientationrelationship with the matrix after being passed by therecrystallisation front148

A rotation of somewhat smaller Al3Sc dispersoids in arecrystallising binary Alndash025 wt-Sc alloy has beenreported115143 The rotation was reported to be accom-panied by substantial growth (from Oslash 30 nm to Oslash48 nm) as a result of enhanced Sc diffusion at the grainboundary Observations suggested that the grainboundaries were passing through the dispersoids andthus the Al3Sc dispersoids retained the orientationrelationship with the recrystallised Al matrix

Dissolution and re-precipitation of Al3Sc dispersoidshas been reported during recrystallisation of a 50 coldrolled Alndash02 wt-Sc alloy162 Large spherical partially

26 Fraction recrystallised structure in cold rolled sheets

of Alndash04 wt-Sc and Alndash04 wt-Scndash015 wt-Zr as a

function of annealing temperature redrawn from

Ref 183 27 Electrical conductivity in Alndash15(SczZr) alloys

redrawn from Ref 183

Roslashyset and Ryum Scandium in aluminium alloys

International Materials Reviews 2005 VOL 50 NO 1 35

coherent dispersoids were observed to dissolve at therecrystallisation front and re-precipitate as smallercoherent Al3Sc cuboids

Superplastic forming

It seems that the first publication on superplasticproperties of Sc-containing Al-alloys was a study of anAlndash35Cundash14Mgndash045Mnndash04(SczZr) alloy188

It was recognised that the superplastic properties are aresult of the stabilisation of the fine grain structure byAl3Sc dispersoids The Sc-containing Al alloys that havereceived most attention for their superplastic propertieshowever are those of the AlndashMgndashSc system which wasfirst published in a patent189 Here it was noted that anAlndash4 wt-Mgndash05 wt-Sc alloy had superior superplasticproperties compared to fine-grained 7475 (AlndashZnndashMgndashCu alloy) Binary Alndash05 wt-Sc and Alndash4 wt-Mgalloys did not behave superplastically The flow stress atthe hot forming temperature was found to be much (30ndash40) lower in the ternary alloy than that of the twobinary alloys

The superplastic properties of AlndashMgndashSc alloys havebeen explored by several research groups over the lastdecade190ndash196 It has frequently been found that thedeformation mechanism is dominated by grain bound-ary sliding190 However it has also been reported thatAlndashMgndashSc alloy may deform superplastically withoutnoticeable grain boundary sliding23 It is generallyrecognised that the grain boundary sliding mechanismis facilitated when the average grain size is very smalland grain boundaries are predominantly high-angleSuch a microstructure may be achieved by carefulthermomechanical processing of the starting mate-rial193194197198 It has however been shown that a finegrained structure with high angle boundaries maydevelop during superplastic forming of AlndashMgndashSc alloyseven if the starting microstructure is an entirely differentone for instance that of a cold rolled sheet192 It has alsobeen suggested that superplastic forming of as castmaterial may be possible189

One of the more efficient thermomechanical processesfor achieving an ultrafine grain structure with high anglegrain boundaries in Al-alloys is equal channel angularpressing (ECAP) A JapanesendashAmerican group ofscientists has published an impressive body of researchon improvements in superplastic properties in Al-alloys processed by ECAP over the last few years andseveral of the publications are from investigations onAlndashMgndashSc alloys170199ndash224 Maximum strains in excessof 2000 at a strain rate of 0033 s21 have beenachieved170201202217 which is an extraordinarily goodcombination of high strain and high strain rate for analuminium alloy

Superplastic properties of AlndashCundashMg(ndashMn)ndashSc(ndashZr)and AlndashMgndashSc(ndashZr) alloys have been mentionedNoticeable superplasticity in other Sc-containing Al-alloys has also been reported such as AlndashZnndashMg(ndashCu)ndashScndashZr169225ndash228 AlndashLindashSc229 AlndashMgndashLindashScndashZr229ndash234

AlndashLindashMgndashCundashScndashZr235236 and AlndashCundashLindashScndashZr233

Precipitation hardeningHardening by Al3Sc precipitates

It has been noted that when Al3Sc particles precipitate inthe temperature range 250ndash350uC they give a significanthardness increase in the alloy Some authors point out

that Sc is a more effective precipitation hardening elementper atomic fraction added than the elements that arecommonly used for precipitation hardening121130 (In onepaper29 it is claimed that only Au has a strongerstrengthening effect than Sc) However the amount ofSc that can be precipitated from supersaturated solidsolution is rather limited and thus the absolute values ofthe hardness increase from the precipitation hardening ismuch lower than what is normally associated withprecipitation hardened alloys Also the temperatureregime for age hardening by precipitation of Al3Sc issomewhere in between the temperature regimes for agehardening and solution heat treatments of commonprecipitation hardened alloys This makes a combinedprecipitation of Al3Sc and other strengthening precipi-tates unfeasible Thus precipitation strengthening byAl3Sc is most feasible in alloy systems that are non-heat-treatable The non-heat-treatable aluminium alloy sys-tems are according to the Aluminum Associationdesignations the 1xxx series (99 pure Al) the 3xxxseries (AlndashMn) and the 5xxx series (AlndashMg) The purposeof adding Sc to these alloys may be either to stabilise themicrostructure of wrought semiproducts (extrusionsrolled plates forgings etc) as discussed in the sectionon lsquoRecrystallisation resistancersquo above or to provideextra strength to the alloy through precipitation hard-ening In the latter case it is appropriate to considerwhether the Sc-containing alloy still should be classifiedas non-heat-treatable A heat treatment is applied thatbrings about a significant precipitation hardening On theother hand the hardness increase that is achieved throughthe heat treatment is lower than what is normallyassociated with heat-treatable alloy systems Hence eventhough it seems like a contradiction one chooses to keepusing the term lsquonon-heat-treatablersquo about these alloys

Table 7 gives an overview of some mechanicalproperties of Sc-containing non-heat-treatable alloysthat are reported in the literature Most of theexperimental work on Sc in 1xxx-types of alloys hasbeen done on binary AlndashSc alloys with much higherpurity than industrial alloys

Strengthening mechanisms

When the precipitates are larger than a critical size thestrengthening effect is due to the Orowan-mechanism iedislocations can only pass the precipitates by looping Inthis case the strengthening effect of the particles isapproximately inversely proportional to the mean parti-cle spacing When the precipitates can be sheared bydislocations there are a number of strengthening mechan-isms that apply It is proposed by Parker et al108 that thetwo major contributing mechanisms are coherency strainand anti-phase-boundary energy In a recent detailedstudy of strengthening mechanisms in binary AlndashSc alloysby Marquis and colleagues117118 the strengthening fromshear modulus mismatch between the matrix and theprecipitates is also accounted for A qualitatively goodmatch between theoretical strengthening and measuredvalues is achieved in this work both for deformation atroom temperature and at 300uC

Effect of Sc on precipitation strengthening in heat-treatablealloys

Following the AA designation system the traditionalheat-treatable Al-alloys are those that belong to the 2xxx

Roslashyset and Ryum Scandium in aluminium alloys

36 International Materials Reviews 2005 VOL 50 NO 1

series (AlndashCu) 6xxx series (AlndashMgndashSi) and 7xxx series(AlndashZnndashMg) AlndashLi alloys should also be mentionedSeveral investigations have been carried out in order toclarify the effects of Sc on the precipitation behaviour inthese alloy systems

AlndashCu alloys

The precipitation sequence in AlndashCu alloys is oftendescribed as follows

Supersaturated solid solutionRGP-zonesRh0Rh9Rh(Al2Cu)

The highest strength is normally achieved when the h0or h9 precipitates are predominant Typical precipitationheat treatment temperatures for AlndashCu alloys are in therange 160ndash190uC238 which is considerably lower thanthe typical precipitation temperature for Al3ScComparisons of the aging responses of AlndashCu and AlndashCundashSc alloys at 150 and 200uC indicate that there is nonoticeable effect of Sc on the precipitation kinetics ofh9153 It is observed that the h9 precipitates may nucleateon Al3Sc particles153 At 300uC it is observed that h9particles are somewhat smaller in AlndashCundashSc alloys thanin AlndashCu alloys156

AlndashMgndashSi alloys

The following precipitation sequence is commonlyreported for AlndashMgndashSi alloys

Supersaturated solid solutionRGP-zonesRb0Rb9Rb(Mg2Si)

For peak aged alloys the predominant precipitatetype is b0 for which the stoichiometric composition hasrecently been resolved to be Mg5Si6239 Temperatures inthe range 160ndash205uC are typically used for precipitationhardening of these alloys238 Adding both 03 wt-Scand 01 wt-Zr to an Alndash06 wt-Mgndash065 wt-Sialloy does not seem to alter the precipitation kineticsof b0 at 165uC However the hardness increase becauseof precipitation hardening appears to be smaller in theSczZr-containing alloy240 In another investigationadditions of 01 wt-Sc 015 wt-Sc 02 wt-Sc04 wt-Sc and 02 wt-Scz01 wt-Zr were made toan Alndash08 wt-Mgndash07 wt-Si alloy241 Here it wasalso observed that the precipitation kinetics of b0 wasseemingly independent of the Sc additions (Fig 28)TEM observations indicated that the b0 precipitateswere of comparable sizes in the investigated alloys andno interactions between Al3Sc and b0 were observed(Fig 29) In a third study242 where the effect of Sc onthe precipitation in an AlMgSindashSiC metal matrixcomposite was investigated there also does not seemto be any effect on the precipitation kinetics Howevercontrary to the findings of Ref 240 it is reported thatthe Sc addition leads to a higher hardness increase thanin the corresponding Sc free alloy

AlndashMgndashZn alloys

For these alloys the following precipitation sequence isoften ascribed

Table 7 Mechanical properties in non-heat-treatable Al-alloys with Sc

Reference Alloy wt- YS MPa UTS MPa Note

1xxx alloys171 000Sc 15 48 Cast material aged 288uC8 h

023Sc 159 185 Cast material aged 288uC8 h038Sc 199 220 Cast material aged 288uC8 h000Sc 14 49 Cold rolled material (89) aged 288uC8 h023Sc 198 208 Cold rolled material (89) aged 288uC8 h038Sc 240 264 Cold rolled material (89) aged 288uC8 h000Sc 8 34 Cold rolled material quenched from 649uC aged 288uC8 h023Sc 147 157 Cold rolled material quenched from 649uC aged 288uC8 h038Sc 193 199 Cold rolled material quenched from 649uC aged 288uC8 h

121 05Sc 160 ndash Forged material quenched from 635uC aged 250uC50 h23 05Sc 298 319 Hot rolled 288uC cold rolled 69ndash81 aged 288uC4 h112 01Sc 132 166 Hot z cold rolled material quenched from 630uC

aged 320uC133 h148 02Sc 138 ndash Cast material aged 300uC10 h compression test159 04Sc 196 ndash Cast material aged 300uC10 h compression test117 118 03Sc 209 ndash Cast material quenched from 648uC aged 300uC5 h

compression test3xxx alloys171 1Mn 015Sc 216 221 Cold rolled material (89) aged 288uC8 h

1Mn 05Sc 309 323 Cold rolled material (89) aged 288uC8 h186 05Mn 02Mg

026Sc 015Zr162 201 Extruded material solutionised 600uC aged 250uC

5xxx alloys171 1Mg 43 111 Cold rolled material (89) aged 288uC8 h

1Mg 03Sc 288 303 Cold rolled material (89) aged 288uC8 h53Mg 147 259 Cold rolled material (50) wintermediate anneals

at 343uC aged 288uC8 h53Mg 03Sc 368 401 Cold rolled material (50) wintermediate anneals

at 343uC aged 288uC8 h23 2Mg 05Sc 376 401 Hot rolled 288uC cold rolled 69ndash81 aged 288uC4 h

4Mg 05Sc 414 4606Mg 05Sc 433 503

237 4Mg 1Sc 420 525 Cold rolled material (83) aged 320uC1 h148 4Mg 02Sc 194 ndash Cast material aged 300uC10 h compression test

Tensile test data except where noted YS yield strength UTS ultimate tensile strength

Roslashyset and Ryum Scandium in aluminium alloys

International Materials Reviews 2005 VOL 50 NO 1 37

Supersaturated solid solutionRGP-zonesRg9Rg(Zn2Mg)

The maximum hardness is normally achieved whenthe g9 precipitates are predominant Common precipita-tion hardening temperatures are in the range 95ndash180uCand a two-step precipitation heat treatment within thistemperature regime is often used238 It has beenobserved in some investigations that Sc and SczZradditions to AlndashMgndashZn alloys slow down the precipita-tion of g9 somewhat243 Other investigations find thatthere is no effect of Sc on the precipitation behaviour ofg9244245 and yet others report that Sc additionssignificantly speed up the precipitation of g9246 In Ref247 it is found that an Sc addition leads to coarser g9precipitates and it is claimed that this gives an improvedductility of the alloy The strength-loss associated withlarger particle size is reported to be counterbalanced bystrengthening from Al3Sc precipitates

AlndashLi alloys

The precipitation sequence in binary AlndashLi alloys isapparently simple

Supersaturated solid solutionRd9Rd (AlLi)

where d9 is the metastable Al3Li phase which just likeAl3Sc has the L12 type of atomic arrangement Thetypical temperature regime for precipitation of d9 whichis the strengthening phase in this system is approx 150ndash200uC A comparison of the age hardening response ofan Alndash26 wt-Li and an Alndash24 wt-Lindash019 wt-Scalloy at 180uC248 and 200uC161 indicates that the onsetof d9 precipitation is not altered by the presence of ScThe hardness curves for the two alloys are practicallyidentical at 200uC whereas at 180uC the peak hardnesslevel is slightly higher in the AlndashLi than the AlndashLindashScalloy DSC measurements at constant heating ratesindicate that the addition of Sc to an AlndashLi alloysincreases the activation energy for d9 precipitation andmoves the exothermic peak associated with d9 precipita-tion to a higher temperature248 For specimens aged at

either 180uC or 200uC TEM observations reveal that thed9 precipitates are much smaller in the Sc containingalloy than in binary AlndashLi both in the peak agedcondition and in the overaged condition161248 Additionof Sc has also been observed to reduce the size of d9precipitates in other AlndashLi based alloys249ndash251 In an AlndashLindashCundashZr alloy an addition of Sc has been reported toslow down the homogeneous precipitation of d9252253 Ithas been claimed that Sc reduces the quench sensitivityand delays room temperature aging of AlndashLi basedalloys254ndash256

When present in the microstructure before the pre-cipitation of d9 the Al3Sc precipitates may act as effec-tive nucleation sites for d9 The resulting precipitates arespheres of d9 with a core of Al3Sc161249252ndash255257ndash261

Corrosion resistanceAn appreciable amount of data is available on the effectsof Sc on the corrosion behaviour of wrought Al-alloysSome of these effects are apparently derived from theeffects of Sc on the microstructure of the alloys It hasbeen reported that an addition of Sc increases thecorrosion potential (makes it less negative) in pureAl262ndash264 in AlndashZn alloys265266 AlndashMg alloys267 AlndashZnndashMgndashCu alloys264268 AlndashCundashMgndashMn alloys264 andin AlndashCundashLindashMgndashAg alloys264 Even though Sc alsohas been reported to decrease the corrosion potential in

28 Age hardening response at 175uC for Alndash08 wt-Mgndash

07 wt-Si alloy (Base) with additions of 02 wt-Sc

04 wt-Sc and 02 wt-Scz01 wt-Zr from Ref 241

29 TEM images of a b0 precipitates in Alndash08 wt-Mgndash

07 wt-Si alloy and b b0 and Al3(Sc1ndashxZrx) in a similar

alloy with addition of 02 wt-Scz01 wt-Zr from

Ref 241

Roslashyset and Ryum Scandium in aluminium alloys

38 International Materials Reviews 2005 VOL 50 NO 1

AlndashMg alloys269270 it seems that the general trend isthat adding Sc to an alloy makes it slightly more nobleThe change in corrosion potential is much morepronounced when Sc is added in amounts larger thanthe eutectic composition263 ie there is a considerablecontribution from primary or eutectic Al3Sc to theoverall potential It has also been demonstrated that thechange in corrosion potential caused by Sc can dependon the heat treatment applied to the alloy267268

Even though the corrosion potential is an essentialparameter in establishing the corrosion behaviour of analloy an increase in the corrosion potential does notnecessarily imply an improved self-corrosion resistanceHowever measurements of corrosion rates and passiva-tion current densities strongly suggest that the self-corrosion resistance in general is considerably improvedwhen Sc is added to wrought Al-alloys263264267 Someobserved variations in corrosion potential and passiva-tion current densities with Sc content in binary AlndashScalloys are plotted in Fig 30

Material failure in corrosive environments is often dueto localised corrosion attacks which may propagaterapidly even though the bulk material has a goodresistance against general corrosion It has been pointedout that hypereutectic additions of Sc may lead tomicrogalvanic corrosion beside primary Al3Sc parti-cles264 In AlndashMg alloys grain boundary precipitation ofAl8Mg5 can lead to localised corrosion attacks such asintergranular corrosion (IGC) exfoliation corrosion(EC) and stress corrosion cracking (SCC) In wroughtmaterial such precipitation may occur in the 60ndash180uCtemperature regime and heating in this temperaturerange is referred to as lsquosensitationrsquo An AlndashMgndashSc alloywas found to be immune against intergranular corrosionand have moderate susceptibility to exfoliation corro-sion after annealing at 350uC271 After sensitation heattreatments severe IGC and EC was observed but notquite as severe as in a corresponding alloy without ScAs for SCC the AlndashMgndashSc alloy was found to be highlyresistant271 In another study it was found that additionof 056 wt-Sc reduces the SCC susceptibility of an Alndash68 wt-Mg alloy in the as-rolled state and afterannealing at 250uC whereas in a sensitised specimenthe SCC susceptibility is somewhat increased by the Scaddition272 A third investigation found that Sc has nomeasurable detrimental effect on the SCC susceptibilityof sensitised Alndash5Mgndash015Zr alloy273 SCC is also a

severe problem in high strength AlndashZnndashMgndashCu alloys Ithas been shown that small Sc additions are effective inreducing the SCC sensitivity of these alloys244246268274

Use of Sc-containing Al alloysA systematic development of Sc-containing aluminiumalloys took place in the former USSR in the 1980s andthe interest for Sc as an alloying element in aluminiumalloys hit the western world approximately 10 yearslater Even though a number of improvements in Alalloys achieved by Sc addition have been demonstratedthe current uses of such alloys are very limited This isrelated to the very high price of scandium

In Russia some parts of military aircraft are made ofSc-containing AlndashLi alloys In the western world themain usage of Sc-containing alloys is for sportsequipment Ashurst Technology and Kaiser Aluminumdeveloped a Sc-containing 7xxx alloy for baseball andsoftball bats which was introduced to the Americanmarket in 1997 by Easton Alcoa soon followed with aSc-containing alloy for a competing brand of batsLouisville Slugger Since then several new and improvedSc-containing alloys for bats have been introduced tothe market The purpose of adding Sc is to increase theyield strength of the alloy allowing for a down-gaugingof the wall thickness which in turn gives a strongerlsquospring-rsquo or lsquotrampoline-rsquo effect when the ball hits thebat

Shortly after the introduction of the Sc containingbats Easton also launched Sc-containing 7xxx tubingfor bicycle frames Just as in the bats Sc increases theyield strength of the alloy allowing for down-gauging oftube wall thickness and a corresponding weight reduc-tion of the bicycle frame An Italian manufacturer ofbicycle tubing Dedacciai also delivers tubes in a Sc-containing 7xxx alloy

Other sports equipment made from Sc-containingaluminium alloys includes lacrosse sticks and tent polesSmith and Wesson has also introduced a series ofhandguns where the frame is made from a Sc-containingAl alloy

A common factor for the items mentioned above isthat the material cost is only a minor part of the totalmanufacturing cost of the end product and also thatthese products are aimed at a group of customers thathave a certain awareness of new materials Both baseballbats and bicycle frames have been marketed aslsquoscandium alloyrsquo even though the Sc content is muchlower than 1

Currently AlndashSc master alloys for the production ofSc-containing Al alloys are available at a price thatcorresponds to US$ 2000 per kg of Sc This means that ifone wants to add 02 wt-Sc to an alloy which is afairly common content one also increases the price ofthe alloy by US$ 4 per kg alloy Depending on the alloytype Sc is added to this represents a tripling orquadrupling of the price of the alloy There are notmany existing products where such an increase inmaterial cost can be justified In order to see awidespread use of Sc in high-volume products the Scprice has to come down considerably Actually the priceof adding Sc to Al alloys has gone down by a factor 3ndash10over the last 10ndash15 years and substantial price reduc-tions are also expected in the future

30 Observed variations in corrosion potential and passi-

vation current densities with Sc content in binary Alndash

Sc alloys based on data from Ref 263

Roslashyset and Ryum Scandium in aluminium alloys

International Materials Reviews 2005 VOL 50 NO 1 39

The current production of AlndashSc master alloys isbased upon and will continue to be based upon for theforeseeable future the reduction of Sc2O3 or other Sccompounds directly in molten aluminium It is notnecessary as many tend to believe to take the route viametallic Sc Thus the price of AlndashSc master alloy isgoverned by the price of Sc2O3 or other Sc compoundsin question and not by the price of metallic scandiumThe Sc2O3 which is the main source for todayrsquos AlndashScmaster alloy production comes from stockpiles in theformer USSR These stockpiles will be exhausted withina few years and new reliable sources of Sc2O3 or otherSc compound production are sought It turns out thatthe most economically viable option that has beendisclosed so far is the processing of Red Mud from theBayer process of extracting alumina from bauxiteScandium is enriched in the Red Mud and is extractedfrom a Red Mud aqueous slurry by selective leachingsubsequent ion-exchange procedure and finally a liquidndashliquid extraction procedure It is not required to build aseparate lsquoSc factoryrsquo to do this but rather build an lsquoadd-onrsquo to existing Bayer process plants Such a processroute is expected to bring down the price of Sc2O3

considerably which in turn means that AlndashSc masteralloy price should drop accordingly Preliminary ana-lyses suggest a price of approx US$ 400 per kg Sc in themaster alloy which translates to an added cost of 80cent per kilo when 02 wt-Sc is added to an aluminiumalloy This is also a considerable increase in the materialcost but with such prices one should expect to see Sccontaining alloys in many more applications than whatis the case at the present time

Concluding remarksThe body of published investigations on Al-based alloyswith Sc addition provides a sound basis of knowledgefor metallurgists that want to look into the possibility ofenhancing the performance of a wrought Al-alloy byadding Sc to it Ternary AlndashScndashX phase diagrams areavailable for practically every technologically importantalloying element in Al The effect of a wide range ofternary alloying elements on the precipitation behaviourof Al3Sc is accounted for It has been shown that theAl3Sc phase can be effective as a grain refiner adispersoid former and a precipitate hardening agentand some of the underlying conditions for achieving thedesired Al3Sc formation have been outlined Addingsome Zr together with Sc has proven to be beneficial Itmay lead to effective grain refinement at a lower Sc levelbut the most prominent effect is the refinement indispersoid distribution that can be achieved An addi-tion of Sc has little if any effect on precipitation in the2xxx 6xxx and 7xxx alloy systems and some effects onthe precipitation in AlndashLi based alloys With respect tocorrosion behaviour adding Sc to an Al-alloy does ingeneral seem to make the alloy slightly more noble andto increase its self-corrosion resistance Scandium-containing Al alloys have very few uses at the presenttime as a result of the high price of scandium The priceof Sc is expected to decrease significantly in the futureand this should lead to the disclosure of moreapplications where it is economically feasible to takeadvantage of the improved properties of some Sc-containing aluminium alloys

References1 D R Lide lsquoCRC handbook of chemistry and physicsrsquo 71st edn

4ndash29 1990 Boston USA CRC Press

2 E M Savitsky V F Terehova I V Burov and O P Naumkin

Proc Fourth Conf on lsquoRare earth researchrsquo Phoenix Arizona

USA April 1964 409ndash420

3 E M Savitskii V F Terekhova I V Burov O P Naumkin and

I A Markova Inorg Mater 1965 1 1503ndash1512

4 O P Naumkin V T Terekhova and E M Savitskiy Russ

Metall 1965 (4) 128ndash136

5 W G Moffatt lsquoThe handbook of binary phase diagramsrsquo 1981

Schenectady NY USA General Electric Co

6 E A Brandes (ed) lsquoSmithells metals reference bookrsquo 6th edn

1983 London UK Butterworths

7 R P Elliott and F A Shunk Bull Alloy Phase Diagrams 1981

2 (2) 222ndash223

8 K A Gschneider Jr and F W Calderwood Bull Alloy Phase

Diagrams 1989 10 34ndash36

9 H Okamoto J Phase Equil 1991 12 612ndash613

10 J L Murray J Phase Equil 1998 19 380ndash384

11 M E Drits E S Kadaner T V Dobatkina and N I Turkina

Russ Metall 1973 (4) 152ndash154

12 S-I Fujikawa M Sugaya H Takei and K-I Hirano J Less-

Common Met 1979 63 87ndash97

13 N Blake and M A Hopkins J Mater Sci 1985 20 2861ndash2867

14 V I Kononenko and S V Golubev Russ Metall 1990 (2) 193ndash

195

15 T B Massalski J L Murray L H Bennett and H Baker (eds)

lsquoBinary alloy phase diagramsrsquo 1986 Metals Park OH USA

ASM

16 G Cacciamani P Riani G Borzone N Parodi A Saccone

R Ferro A Pisch and R Schmid-Fetzer Intermetallics 1999 7

101ndash108

17 H Okamoto J Phase Equil 2000 21 310

18 A F Norman P B Pragnell and R S McEwen Acta Mater

1998 46 5715ndash5732

19 I N Pyagai and A V Vakhobov Russ Metall 1990 (5) 50ndash52

20 C L Fu J Mater Res 1990 5 971ndash979

21 X Lu and Y Wang Calphad 2002 26 555ndash561

22 R R Sawtell and J W Morris Jr Proc lsquoDispersion strengthened

aluminium alloysrsquo Phoenix Arizona USA January 1988 409ndash

420

23 R R Sawtell and C L Jensen Metall Trans A 1990 21A 421ndash

430

24 L A Willey Unpublished research Alcoa 1970 Data points are

extracted from Ref 10

25 N I Turkina and V I Kuzmina Russ Metall 1976 (4) 179ndash

183

26 T Torma E Kovacs-Csetenyi I Vitanyi M Butova and

J Stepanov Proc 6th Int Symp on lsquoHigh purity materials in

science and technologyrsquo Akademie der Wissenschaften der DDR

Dresden Germany May 1985 388ndash389

27 A L Berezina V A Volkov B P Domashnikov and K V

Chuistov Metallofizika 1987 9 (5) 43ndash47

28 H-H Jo J Korean Inst Metals 1990 28 499ndash504

29 H-H Jo and S-I Fujikawa Mater Sci Eng 1993 A 171 151ndash

161

30 S Celotto and T J Bastow Philos Mag A 2000 80 1111ndash1125

31 J Roslashyset and N Ryum submitted to Mater Sci Eng

32 M E Drits L S Toropova Yu G Bykov F L Gushchina V I

Elagin and Yu A Filatov Russ Metall 1983 (1) 150ndash153

33 L S Toropova D G Eskin M L Kharakterova and T V

Dobatkina lsquoAdvanced aluminum alloys containing scandium

structure and propertiesrsquo 1998 Amsterdam The Netherlands

Gordon and Breach Science Publishers

34 V V Cherkasov P P Pobezhimov L P Nefedova E V Belov

and G M Kuznetsov Met Sci Heat Treat 1996 (6) 268ndash270

35 Kh O Odinaev I N Ganiev V V Kinzhibalo and B Ya

Kotur Dokl Akad Nauk Tadzh SSR 1989 32 37ndash38

36 Kh O Odinaev I N Ganiev and A V Vakhobov Russ Metall

1991 (4) 200ndash203

37 J Grobner R Schmid-Fetzer A Pisch G Cacciamani P Riani

N Parodi G Borzone A Saccone and R Ferro Z Metallkd

1999 90 872ndash880

38 E A Marquis and D N Seidman Microsc Microanal 2002 8

(Suppl 2) 1100CDndash1101CD

39 A Pisch J Grobner and R Schmid-Fetzer Mater Sci Eng A

2000 A 289 123ndash129

Roslashyset and Ryum Scandium in aluminium alloys

40 International Materials Reviews 2005 VOL 50 NO 1

40 C Xia F Zeng and Y Gu Trans Nonferrous Met Soc China

2003 13 1124ndash1127

41 M Yu Teslyuk and V S Protasov Sov Phys Crystallogr 1966

10 470ndash471

42 M L Kharakterova and T V Dobatkina Russ Metall 1988

(6) 175ndash178

43 M L Kharakterova Russ Metall 1991 (4) 195ndash199

44 L S Toropova M L Kharakterova and D G Eskin Russ

Metall 1992 (3) 194ndash199

45 P Riani L Arrighi R Marazza D Mazzone G Zanicchi and

R Ferro J Phase Equil Diff 2004 25 22ndash52

46 A T Tyvanchuk T I Yanson B Ya Kotur O S Zarechnyuk

and M L Kharakterova Russ Metall 1988 (4) 190ndash192

47 L L Rokhlin T V Dobatkina and M L Kharakterova Powder

Metall Met Ceram 1997 36

48 A Z Ikromov I N Ganiev and V V Kinzhibalo Dokl Akad

Nauk Tadzh SSR 1990 (6) 391ndash392

49 I N Ganiev A Z Ikromov and V G Khudoiberdiev Russ

Metall 1995 (3) 125ndash127

50 I N Fridlyander L L Rokhlin T V Dobatkina and N I

Nikitina Met Sci Heat Treat 1993 (10) 567ndash571

51 I N Fridlyander L L Rokhlin T V Dobatkina V V

Kinzhibalo and A T Tyvanchuk Russ Metall 1998 (1) 161ndash

166

52 R A Emigh E L Bradley and J W Morris Jr in lsquoLight-weight

alloys for aerospace applications IIrsquo (ed E W Lee and N J

Kim) 27ndash43 1991 TMS

53 L S Toropova A N Kamardinkin V V Kindzhibalo and A T

Tyvanchuk Phys Met Metall 1990 70 (6) 106ndash110

54 A N Kamardinkin T V Dobatkina and T D Rostova Russ

Metall 1991 (4) 216ndash218

55 L S Torodskaya T V Dobatkina and A N Kamardinkin

Russ Metall 1992 (5) 128ndash131

56 E M Sokolovskaya E F Kazakova E I Poddyakova and A

A Ezhov Met Sci Heat Treat 1997 (5) 211ndash213

57 Y Harada and D C Dunand Mater Sci Eng 2002 A 329ndash331

686ndash695

58 N E Drits L S Toropova and F L Gushchina Russ Metall

1984 (4) 229ndash232

59 E M Sokolovskaya E F Kazakova V A Alikhanov and E V

Zhuravleva Moscow Univ Chem Bull 1997 52 (5) 70ndash72

60 E M Sokolovskaya E F Kazakova and E I Poddyakova Met

Sci Heat Treat 1989 (11) 837ndash839

61 G M Cheldieva E F Kazakova E M Sokolovskaya and N I

Kaloev Russ Metall 1990 (6) 87ndash90

62 E M Sokolovskaya E F Kazakova and O D-S Kendivan

Russ Metall 1998 (4) 135ndash137

63 N G Bukhanko E F Kazakova and E M Sokolovskaya Russ

Metall 2001 (4) 425ndash431

64 E D Trubnyakova O I Bodak I N Ganiev and A V

Vakhobov Russ Metall 1987 (3) 219ndash222

65 I N Fridlyander and L V Molchanova Russ Metall 2003 (5)

476ndash480

66 R A Altynbaev S Kh Khairidinov and A V Vakhobov Russ

Metall 1987 (4) 194ndash196

67 J C Schuster and J Bauer J Less-Common Met 1985 109

345ndash350

68 L L Rokhlin A S Fridman T V Dobatkina and D G Eskin

Russ Metall 1991 (6) 146ndash148

69 A S Fridman T V Dobatkina and E V Muratova Russ

Metall 1992 (1) 207ndash209

70 C Xia F Zeng and Y Gu Trans Nonferrous Met Soc China

2003 13 546ndash552

71 F Zeng C Xia and Y Gu J Alloys Comp 2004 363 175ndash181

72 L L Rokhlin T V Dobatkina N R Bochvar and E V Lysova

J Alloys Comp 2004 367 10ndash16

73 T V Dobatkina A S Fridman and E V Muratova Russ

Metall 1992 (5) 125ndash127

74 I N Fridlyander L L Rokhlin N R Bochvar E V Lysova

and O V Boteva Russ Metall 2001 (6) 661ndash666

75 V N Rechkin L K Lamikhov and T I Samsonova Sov Phys

Crystallogr 1964 9 325ndash327

76 I I Zalutskii and P I Kripyakevich Sov Phys Crystallogr

1967 12 341ndash343

77 T J Bastow C T Forwood M A Gibson and M E Smith

Phys Rev B 1998 58 2988ndash2997

78 K Fukunaga M Kolbe K Yamada and Y Miura Mater Sci

Eng 1997 A 234ndash236 594ndash597

79 E P George J A Horton W D Porter and J H Schneibel

J Mater Res 1990 5 1639ndash1648

80 E P George D P Pope C L Fu and J H Schneibel ISIJ Int

1991 31 1063ndash1075

81 Y Harada and D C Dunand Acta Mater 2000 48 3477ndash3487

82 J H Schneibel and E P George Scripta Metall Mater 1990 24

1069ndash1074

83 J H Schneibel and P M Hazzledine Mater Res Soc Symp

Proc 1991 213 323ndash328

84 J H Schneibel and P M Hazzledine J Mater Res 1992 7

868ndash875

85 C J Sparks E D Specht G E Ice P Zschack and J Schneibel

Mater Res Soc Symp Proc 1991 213 363ndash368

86 J Tarnacki and Y-W Kim Scripta Metall Mater 1989 23

1063ndash1068

87 M Asta V Ozolins and C Woodward JOM 2001 53 (9) 16ndash

19

88 M E Drits L S Toropova F L Gushchina and S G Fedotov

Sov Non-Ferrous Met Res 1984 12 83ndash85

89 Y Harada and D C Dunand Scripta Mater 2003 48 219ndash222

90 C Woodward M Asta G Kresse and J Hafner Phys Rev B

2001 63 094103-1-6

91 J-H Xu and A J Freeman Phys Rev B 1990 41 12553ndash12561

92 M F Bartholomeusz and J A Wert Acta Metall Mater 1992

40 673ndash682

93 G Bester and M Fahnle J Phys Condens Matter 2001 13

11551ndash11565

94 C L Fu and M H Yoo Proc lsquoOrdered intermetallics ndash physical

metallurgy and mechanical behaviorrsquo Irsee Germany June 1991

155ndash164

95 K Fukunaga T Shouji and Y Miura Mater Sci Eng 1997 A

239ndash240 202ndash205

96 D P Pope Proc lsquoOrdered intermetallics ndash physical metallurgy

and mechanical behaviorrsquo Irsee Germany June 1991 143ndash153

97 J-S Wang Acta Mater 1998 46 2663ndash2674

98 M H Yoo and C L Fu Mater Sci Eng 1992 A 153 470ndash478

99 R W Hyland Jr and R C Stiffler Scripta Metall Mater 1991

25 473ndash477

100 I G Brodova I V Polents O A Korzhavina P S Popelrsquo I P

Korshunov and V O Esin Melts 1992 4 392ndash397

101 I G Brodova O A Chikova I V Polents P S Popelrsquo and V O

Esin Casting Processes 1992 1 (2) 158ndash160

102 I G Brodova D V Bashlikov and I V Polents Mater Sci

Forum 1998 269ndash272 589ndash594

103 K B Hyde A F Norman and P B Pragnell Mater Sci Forum

2000 331ndash337 1013ndash1018

104 K B Hyde A F Norman and P B Pragnell Acta Mater 2001

49 1327ndash1337

105 J Roslashyset and N Ryum Proc 6th Int Conf on lsquoAluminum

alloysrsquo Toyohashi Japan July 1998 793ndash798

106 V I Elagin V V Zakharov and T D Rostova Met Sci Heat

Treat 1993 (6) 317ndash319

107 R W Hyland Jr Metall Trans A 1992 23A 1947ndash1955

108 B A Parker Z F Zhou and P Nolle J Mater Sci 1995 30

452ndash458

109 C L Rohrer M D Asta S M Foiles and R W Hyland Jr

Mater Res Soc Symp Proc 1996 398 477ndash482

110 G M Novotny and A J Ardell Mater Sci Eng 2001 A 318

144ndash154

111 J D Robson M J Jones and P B Pragnell Acta Mater 2003

51 1453ndash1468

112 C Tan Z Zheng and B Wang Proc 3rd Int Conf on

lsquoAluminium alloysrsquo Vol I NTH Trondheim Norway June

1992 290ndash294

113 M Nakayama A Furuta and Y Miura Mater Trans JIM

1997 38 852ndash857

114 E A Marquis and D N Seidman Acta Mater 2001 49 1909ndash

1919

115 M J Jones and F J Humphreys Acta Mater 2003 51 2149ndash

2159

116 E A Marquis D N Seidman and D C Dunand in lsquoCreep

deformation fundamentals and applicationsrsquo (ed R S Mishra

J C Earthman and S V Raj) 299ndash308 2002 TMS

117 D N Seidman E A Marquis and D C Dunand Acta Mater

2002 50 4021ndash4035

118 E A Marquis D N Seidman and D C Dunand Acta Mater

2003 51 285ndash287

119 M E Drits L S Toropova U G Bikov and G K Anastaseva

Proc lsquoDiffusion in metals and alloysrsquo Tihany Hungary Augustndash

September 1982 616ndash623

120 V I Elagin V V Zakharov and T D Rostova Met Sci Heat

Treat 1983 (7) 546ndash549

Roslashyset and Ryum Scandium in aluminium alloys

International Materials Reviews 2005 VOL 50 NO 1 41

121 M Ye Drits L B Ber Yu G Bykov L S Toropova and G K

Anastaseva Phys Met Metall 1984 57 (6) 118ndash126

122 M E Drits L S Toropova and Yu G Bykov Sov Non-Ferrous

Met Res 1985 13 309ndash314

123 V I Yelagin V V Zakharov S G Pavlenko and T D Rostova

Phys Met Metall 1985 60 (1) 88ndash92

124 N Sano Y Hasegawa K Hono H Jo K Hirano H W

Pickering and T Sakurai Journal de Physique 1987 48 C6 337ndash

342

125 N Sano H-H Jo K-I Hirano and T Sakurai J Jpn Inst

Metals 1989 39 444ndash450

126 N Sano H Jo K Hirano and T Sakurai Proc Second Int

Conf on lsquoAluminium alloysrsquo Beijing China October 1990 549ndash

554

127 Y Miura M Nakayama and A Furuta Proc lsquoAspects of high

temperature deformation and fracture in crystalline materialsrsquo

Nagoya Japan July 1993 255ndash262

128 Y W Riddle and T H Sanders Jr Mater Sci Forum 2000

331ndash337 939ndash944

129 Y W Riddle M McIntosh and T H Sanders Jr in lsquoLightweight

alloys for aerospace application VIrsquo (ed K Jata E W Lee

W Frazier and N J Kim) 25ndash39 2001 TMS

130 M E Drits J Dutkiewicz L S Toropova and J Salawa Crystal

Res Technol 1984 19 1325ndash1330

131 Y W Riddle MSc thesis Georgia Tech GA USA 1998

132 T J Bastow and S Celotto Mater Sci Eng 2003 C 23 757ndash

762

133 M C Carroll M J Mills G S Daehn P I Gouma M F

Savage and B R Dunbar in lsquoAutomotive Alloys 1999rsquo (ed

S Das) 239ndash246 2000 TMS

134 E Clouet M Nastar and C Sigli Phys Rev B 2004 69 064109-

1-14

135 V V Zakharov Met Sci Heat Treat 1997 (2) 61ndash66

136 J W Christian lsquoThe theory of transformation in metals and

alloysrsquo 2nd edn 1975 Pergamon Press Ltd

137 A L Berezina V A Volkov B P Domashnikov S V Ivanov

and K V Chuistov Phys Metals 1990 10 296ndash304

138 S-I Fujikawa and S Sakauchi Proc 6th Int Conf on

lsquoAluminum alloysrsquo Toyohashi Japan July 1998 805ndash810

139 Y S Touloukian R K Kirby R E Taylor and P D Desai

(eds) lsquoThermal expansion metallic elements and alloysrsquo 1975

New York Plenum

140 J Roslashyset and N Ryum submitted to Scripta Mater

141 R O Simmons and R W Balluffi Phys Rev 1960 117 52ndash61

142 M Ocko E Babic R Krsmik E Girt and B Leontic J Phys F

Metals Phys 1976 6 703ndash707

143 M J Jones and F J Humphreys Proc First Joint Int Conf on

lsquoRecrystallization and grain growthrsquo Aachen Germany August

2001 Springer Verlag 1287ndash1292

144 S Iwamura M Nakayama and Y Miura Mater Sci Forum

2002 396ndash402 1151ndash1156

145 S Iwamura and Y Miura Acta Mater 2004 52 591ndash600

146 M Asta S M Foiles and A A Quong Phys Rev B 1998 57

11265ndash11275

147 R W Hyland Jr M Asta S M Foiles and C L Rohrer Acta

Mater 1998 46 3667ndash3678

148 J Roslashyset and N Ryum Proc 4th Int Conf on lsquoAluminium

alloysrsquo Vol I Atlanta GA USA September 1994 194ndash201

149 M E Drits L S Toropova G K Anastaseva and G L

Nagornichnykh Russ Metall 1984 (3) 192ndash195

150 E A Marquis D N Seidman and D C Dunand Acta Mater

2003 51 4751ndash4760

151 M E Drits L S Toropova and Yu G Bykov Met Sci Heat

Treat 1983 (7) 550ndash554

152 V V Zakharov and T D Rostova Met Sci Heat Treat 1995

(2) 65ndash69

153 M Nakayama and Y Miura Proc 4th Int Conf on lsquoAluminium

alloysrsquo Vol I Atlanta GA USA September 1994 538ndash545

154 M Nakayama and Y Miura J Jpn Inst Light Metals 1996 46

275ndash279

155 M Nakayama T Okuyama and Y Miura Mater Sci Forum

2000 331ndash337 927ndash932

156 M Nakayama T Okuyama and Y Miura Proc 6th Int Conf

on lsquoAluminum alloysrsquo Toyohashi Japan July 1998 517ndash522

157 M L Kharakterova D G Eskin and L S Toropova Acta

Metall Mater 1994 42 2285ndash2290

158 V I Elagin V V Zakharov and T D Rostova Met Sci Heat

Treat 1992 (1) 37ndash45

159 H Wiik Siv Ing thesis NTH Institute of Metallurgy

Trondheim Norway 1995

160 J Roslashyset H Hovland and N Ryum Mater Sci Forum 2002

396ndash402 619ndash624

161 Y Miura K Horikawa K Yamada and M Nakayama Proc

4th Int Conf on lsquoAluminium alloysrsquo Vol II Atlanta GA USA

September 1994 161ndash168

162 Y W Riddle PhD thesis Georgia Tech GA USA 2000

163 B Forbord W Lefebvre F Danoix H Hallem and

K Marthinsen Scripta Mater 2004 51 333ndash337

164 J D Robson Acta Mater 2004 52 1409ndash1421

165 C B Fuller J L Murray and D N Seidman submitted to Acta

Mater 2004

166 M G Mousavi C E Cross and Oslash Grong Sci Technol Weld

Joining 1999 4 381ndash388

167 J S Vetrano S M Bruemmer L M Pawlowski and I M

Robertson Mater Sci Eng 1997 A 238 101ndash107

168 Y W Riddle and T H Sanders Jr Mater Sci Forum 2000

331ndash337 799ndash803

169 G M Khan A O Nikiforov V V Zakharov and I I Novikov

Tsvetnye Metally 1993 34 (11) 43ndash45

170 Z Horita M Furukawa M Nemoto A J Barnes and T G

Langdon Acta Mater 2000 48 3633ndash3640

171 L A Willey US Patent 3 619 181 9 November 1971

172 L K Lamikhov and G V Samsonov Tsvetnye Metally 1964 5

(8) 77ndash80

173 A L Berezina K V Chuistov N I Kolobnev L B

Khokhlatova and T A Monastyrskaya Mater Sci Forum

2002 396ndash402 741ndash746

174 F A Fasoyinu J Thomson D Cousineau T Castles and M

Sahoo Proc 6th Int AFS Conf on lsquoMolten aluminum

processingrsquo Orlando FL USA November 2001

175 Z Yin Q Pan Y Zhang and F Jiang Mater Sci Eng 2000

A 280 151ndash155

176 I I Novikov and O E Grushko Mater Sci Technol 1995 11

926ndash932

177 D Cousineau M Sahoo P D Newcombe T Castles and F A

Fasoyinu Proc lsquoAFS 105th casting congressrsquo Dallas TX USA

AprilndashMay 2001 157ndash184

178 C E Cross and Oslash Grong Proc 6th Int Conf on lsquoAluminum

alloysrsquo Toyohashi Japan July 1998 1441ndash1446

179 F A Costello J D Robson and P B Prangnell Mater Sci

Forum 2002 396ndash402 757ndash762

180 K B Hyde A F Norman and P B Prangnell Mater Sci

Forum 2002 396ndash402 39ndash44

181 M E Drits S G Pavlenko L S Toropova Yu G Bukov and

L B Ber Sov Phys Dokl 1981 26 (3) 344ndash346

182 A M Drits and B A Kopeliovich Russ Metall 1985 (4) 147ndash

151

183 V G Davydov V I Elagin V V Zakharov and T D Rostova

Met Sci Heat Treat 1996 (8) 347ndash352

184 M E Drits L S Toropova Yu G Bykov L B Ber and S G

Pavlenko Russ Metall 1982 (1) 148ndash152

185 T D Rostova V G Davydov V I Yelagin and V V Zakharov

Mater Sci Forum 2000 331ndash337 793ndash798

186 Y W Riddle H Hallem and N Ryum Mater Sci Forum 2002

396ndash402 563ndash568

187 J Roslashyset and Y W Riddle Proc 9th Int Conf on lsquoAluminium

alloysrsquo Brisbane Australia August 2004 1210ndash1215

188 A M Diskin V K Portnoi A M Drits and A A Alalykin Sov

Non-Ferrous Met Res 1986 14 499ndash500

189 R R Sawtell P E Bretz and C L Jensen US Patent 4 689 090

25 August 1987

190 G A Salishchev Yu B Timoshenko and R A Saitova Proc

Second Int Conf on lsquoAluminium alloysrsquo Beijing China October

1990 413ndash415

191 T G Nieh R Kaibyshev L M Hsiung N Nguyen and

J Wadsworth Scripta Mater 1997 36 1011ndash1016

192 T G Nieh L M Hsiung J Wadsworth and R Kaibyshev Acta

Mater 1998 46 2789ndash2800

193 J S Vetrano C H Henager Jr M T Smith and S M

Bruemmer in lsquoHot deformation of aluminum alloys IIrsquo (ed T R

Bieler L A Lalli and S R MacEwen) 407ndash418 1998 TMS

194 J S Vetrano C H Henager Jr S M Bruemmer Y Ge and

C H Hamilton in lsquoSuperplasticity and Superplastic Forming

1998rsquo (ed A K Gosh and T R Bieler) 89ndash97 1998 TMS

195 V Y Gertsman J S Vetrano C H Henager Jr and S M

Bruemmer Proc First Joint Int Conf on lsquoRecrystallization and

grain growthrsquo Aachen Germany August 2001 Springer Verlag

2001 837ndash842

196 Y Xiao C Gao H Ma and S Tian Trans Nonferrous Met Soc

China 2001 11 235ndash238

Roslashyset and Ryum Scandium in aluminium alloys

42 International Materials Reviews 2005 VOL 50 NO 1

197 A Gholinia F J Humphreys and P B Prangnell Acta Mater

2002 50 4461ndash4476

198 A Gholinia F J Humphreys and P B Prangnell Mater Sci

Forum 2002 408ndash412 1519ndash1524

199 S Komura P B Berbon M Furukawa Z Horita M Nemoto

and T G Langdon Scripta Mater 1998 38 1851ndash1856

200 S Komura P B Berbon A Utsunomiya M Furukawa

Z Horita M Nemoto and T G Langdon in lsquoHot deformation

of aluminum alloys IIrsquo (ed T R Bieler L A Lalli and S R

MacEwen) 125ndash138 1998 TMS

201 S Komura Z Horita M Furukawa M Nemoto and T G

Langdon J Mater Res 2000 15 2571ndash2576

202 S Komura M Furukawa Z Horita M Nemoto and T G

Langdon Mater Sci Eng 2001 A 297 111ndash118

203 S Komura Z Horita M Furukawa M Nemoto and T G

Langdon Metall Mater Trans A 2001 32A 707ndash716

204 Z Horita M Furukawa K Oh-ishi M Nemoto and T G

Langdon Proc Fourth Int Conf on lsquoRecrystallization and

related phenomenarsquo (ed T Sakai and H G Suzuki) 1999 The

Japan Institute of Metals 301ndash308

205 Z Horita S Komura P B Berbon A Utsunomiya

M Furukawa M Nemoto and T G Langdon Mater Sci

Forum 1999 304ndash306 91ndash96

206 Z Horita S Lee S Ota K Neishi and T G Langdon Mater

Sci Forum 2001 357ndash359 471ndash476

207 Z Horita T Fujinami K Sato S B Kang H W Kim and T G

Langdon in Proc James T Staley Honorary Symposium on

Aluminum Alloys lsquoAdvances in the metallurgy of aluminum

alloysrsquo (ed M Tiryakioglu) 271ndash275 2001 ASM

208 P B Berbon S Komura A Utsunomiya Z Horita

M Furukawa M Nemoto and T G Langdon Mater Trans

JIM 1999 40 772ndash778

209 M Nemoto Z Horita M Furukawa and T G Langdon Mater

Sci Forum 1999 304ndash306 59ndash66

210 M Furukawa Z Horita M Nemeto and T G Langdon Proc

lsquoLight Metals 1999rsquo Quebec City PQ Canada August 1999 583ndash

592

211 M Furukawa K Oh-ishi S Komura A Yamashita Z Horita

M Nemeto and T G Langdon Mater Sci Forum 1999 304ndash

306 97ndash102

212 M Furukawa A Utsunomiya K Matsubara Z Horita and

T G Langdon Acta Mater 2001 49 3829ndash3838

213 M Furukawa A Utsunomiya S Komura Z Horita M Nemoto

and T G Langdon Mater Sci Forum 2001 357ndash359 431ndash436

214 M Furukawa Z Horita and T G Langdon in Proc James T

Staley Honorary Symposium on Aluminum Alloys lsquoAdvances in

the metallurgy of aluminum alloysrsquo (ed M Tiryakioglu) 47ndash56

2001 ASM

215 M Furukawa Z Horita M Nemoto and T G Langdon Mater

Sci Eng 2002 A 324 82ndash89

216 M Furukawa Z Horita and T G Langdon in lsquoUltrafine grained

materials IIrsquo (ed Y T Zhu T G Langdon R S Mishra S L

Semiatin M J Saran and T C Lowe) 459ndash468 2002 TMS

217 T G Langdon M Furukawa Z Horita and M Nemoto Proc

NATO Advanced Research Workshop on lsquoInvestigations and

applications of severe plastic deformationrsquo Moscow August

1999 NATO Science Series Series 3 High Technology vol 80

Kluwer Academic Publishers The Netherlands 2000 149ndash154

218 S Lee H Akamatsu A Utsunomiya K Neishi M Furukawa

Z Horita and T G Langdon Proc Thermec 2000 Las Vegas

USA December 2000

219 S Lee A Utsunomiya H Akamatsu K Neishi M Furukawa

Z Horita and T G Langdon Acta Mater 2002 50 553ndash564

220 A Yamashita D Yamaguchi Z Horita and T G Langdon

Mater Sci Eng 2000 A 287 100ndash106

221 K Oh-ishi Z Horita D J Smith and T G Langdon J Mater

Res 2001 16 583ndash589

222 H Akamatsu T Fujinami Z Horita and T G Langdon Scripta

Mater 2001 44 759ndash764

223 S Ota H Akamatsu K Neishi M Furukawa Z Horita and

T G Langdon Mater Trans 2002 43 2364ndash2369

224 K Furuno H Akamatsu K Oh-ishi M Furukawa Z Horita

and T G Langdon Acta Mater 2004 52 2497ndash2507

225 I N Fridlyander O G Senatorova N A Ryazanova and A O

Nikiforov Mater Sci Forum 1994 170ndash172 345ndash349

226 J N Fridlyander and O G Senatorova Mater Sci Forum 1996

217ndash222 1813ndash1818

227 J Liu and D J Chakrabarti Acta Mater 1996 44 4647ndash4661

228 O G Senatorova A N Uksusnikov J N Fridlyander

J Koshorst R R Romanova N A Ryazanova A Galliot

and V V Cherkassov Proc 6th Int Conf on lsquoAluminum alloysrsquo

July 1998 Toyohashi Japan 589ndash593

229 R A Emigh E L Bradley and J W Morris Jr in

lsquoSuperplasticity in aerospace IIrsquo (ed T R McNelley and H C

Heikkenen) 303ndash315 1990 TMS

230 E L Bradley III R A Emigh and J W Morris Jr Scripta

Metall Mater 1991 25 717ndash721

231 N I Kolobnev L B Khokhlatova V D Makarov E Yu

Semenova and V V Redchits Proc Sixth Int Aluminiumndash

Lithium Conference Garmisch-Partenkirchen Germany October

1991 1053ndash1056

232 N K Tsenev R Z Valiev O V Obraztsov and I N Fridlander

Proc Sixth Int AluminiumndashLithium Conference Garmisch-

Partenkirchen Germany October 1991 1125ndash1132

233 A M Shammazov N K Tsenev R Z Valiev M M

Myshlyaev M M Bikbulatov and S P Lebedich Phys Met

Metall 2000 89 (3) 314ndash318

234 F Musin R Kaibyshev Y Motohashi T Sakuma and G Itoh

Mater Trans A 2002 43A 2370ndash2377

235 M Shagiev Y Motohashi F Musin R Kaibyshev and G Itoh

Mater Trans A 2003 44A 1694ndash1697

236 M Shagiev Y Motohashi F Musin R Kaibyshev and G Itoh

Mater Trans A 2003 44A 1698ndash1701

237 B A Parker and Z F Zhou Proc 3rd Int Conf on lsquoAluminium

alloysrsquo Vol I NTH Trondheim Norway June 1992 363ndash367

238 J R Davies lsquoASM specialty handbook aluminum and aluminum

alloysrsquo 1993 Materials Park OH USA ASM

239 S J Andersen H W Zandbergen J Jansen C Traeholt

U Tundal and O Reiso Acta Mater 1998 46 3283ndash3298

240 M L Kharakterova D G Eskin and L L Rokhlin Russ

Metall 1997 (1) 104ndash109

241 J Roslashyset Dr Ing thesis NTNU Trondheim Norway 2002

242 P P Chattopadhyay S Datta and M K Banerjee Mater Sci

Eng 2002 A 333 67ndash71

243 L I Kaigorodova E I Selnikhina E A Tkachenko and O G

Senatorova Phys Met Metall 1996 81 513ndash519

244 Y-L Wu F H Froes C Li and A Alvarez Metall Mater

Trans A 1999 30A 1017ndash1024

245 Z Yin L Yang Q Pan and F Jiang Trans Nonferrous Met

Soc China 2001 11 822ndash825

246 V I Elagin V V Zakharov and T D Rostova Met Sci Heat

Treat 1994 36 (7) 375ndash380

247 Y V Milman A I Sirko D V Lotsko O N Senkov and D B

Miracle Mater Sci Forum 2002 396ndash402 1217ndash1222

248 C-H Joh K Yamada and Y Miura Mater Trans JIM 1999

40 439ndash442

249 X J Jiang Q H Gui Y Y Li L M Ma G J Liang and C X

Shi Scr Metall Mater 1993 29 211ndash216

250 X J Jiang Y Y Li W Deng L Y Xiong W M Wu Y J Gao

and C X Shi Adv Cryogenic Eng (Mater) 1994 40 1369ndash

1376

251 C-H Joh T Katsube K Yamada and Y Miura Proc 6th Int

Conf on lsquoAluminum alloysrsquo Toyohashi Japan July 1998 799ndash

804

252 L I Kaygorodova A M Dritz T V Krymova and I N

Fridlyander Proc Sixth Int AluminiumndashLithium Conference

Garmisch-Partenkirchen Germany October 1991 363ndash367

253 L I Kaigorodova A M Drits Ya V Zhingel T V Krymova

and I N Fridlyander Phys Met Metall 1992 73 286ndash290

254 A L Berezina V A Volkov S V Ivanov N I Kolobnev and

K V Chuistov Phys Met Metall 1991 71 (2) 167ndash175

255 I N Fridlyander N I Kolobnev A L Berezina and K V

Chuistov Proc Sixth Int AluminiumndashLithium Conference

Garmisch-Partenkirchen Germany October 1991 107ndash112

256 L I Kaigorodova A M Drits Ya V Zhingel T V Krymova

and V A Rassokhin Phys Met Metall 1992 73 281ndash285

257 I N Fridlyander S F Danilov E N Malysheva T A

Gorokhova and N N Kirkina Proc Sixth Int Aluminiumndash

Lithium Conference Garmisch-Partenkirchen Germany October

1991 381ndash386

258 G Dlubek S Krause H Krause A L Beresina V S

Mikhalenkov and K V Chuistov J Phys Condens Matter

1992 4 6317ndash6328

259 S Krause H Krause G Dlubek A L Beresina and K S

Chuistov Mater Sci Forum 1992 105ndash110 1109ndash1112

260 C Y Tan Z Q Zheng and S Q Liang Proc 4th Int Conf on

lsquoAluminium alloysrsquo Vol II Atlanta GA USA September 1994

329ndash333

261 A L Beresina N I Kolobnev K V Chuistov A V Kotko and

O A Molebny Mater Sci Forum 2002 396ndash402 977ndash981

Roslashyset and Ryum Scandium in aluminium alloys

International Materials Reviews 2005 VOL 50 NO 1 43

262 I N Ganiev I Yunusov and V V Krasnoyarskii J Appl Chem

USSR 1986 60 1961ndash1965

263 I N Ganiev Prot Met 1995 31 543ndash546

264 N V Vyazovikina Prot Met 1999 35 448ndash453

265 G V Kharina and V P Kochergin Prot Met 1996 32 134ndash

136

266 G V Kharina M V Kuznetsov and V P Kochergin Russ J

Electrochem 1998 34 482ndash485

267 V S Sinyavskii V D Valrsquokov and E V Titkova Prot Met

1998 34 549ndash555

268 Y L Wu F H Froes C G Li and J Liu Proc lsquoSynthesis

processing of lightweight metallic materials IIrsquo Orlando FL

USA February 1997 73ndash81

269 Z Ahmad and B J Abdul-Aleem Proc EuroCorr 2000

270 Z Ahmad A Ul-Hamid and B J Abdul-Aleem Corros Sci

2001 43 1227ndash1243

271 R Braun B Lenczowski and G Tempus Mater Sci Forum

2000 331ndash337 1647ndash1652

272 T Torma E Kovacs-Csetenyi L Vitalis I Vitanyi

J Stepanov and M Butova Mater Sci Forum 1987 1314

497ndash503

273 Z Wang P Wang K S Kumar and C L Briant in lsquoChemistry

and electrochemistry of corrosion and stress corrosion crackingrsquo

(ed R H Jones) 573ndash582 2001 TMS

274 V I Elagin V V Zakharov A A Petrova and E V

Vyshegorodtseva Russ Metall 1983 (4) 143ndash146

Roslashyset and Ryum Scandium in aluminium alloys

44 International Materials Reviews 2005 VOL 50 NO 1

Page 8: Scandium in aluminium alloys - Atom probe · A considerable part of the available literature on scandium in aluminium alloys is reviewed. ... behaviour in Al Cu, Al Mg Si,

Formation of Al3Sc in AlndashSc alloysThere are at least four ways that the Al3Sc phase canform in dilute binary AlndashSc alloys

1 Upon solidification of hypereutectic alloys (Sc

approx 06 wt-) Al3Sc is the first phase to form

2 The solidification of hypo- and hypereutectic alloysends with formation of eutectic AlzAl3Sc

3 Al3Sc can precipitate discontinuously from super-saturated solid solution

4 Al3Sc can precipitate continuously (nucleation andgrowth) from supersaturated solid solution

Primary Al3ScAccording to the binary phase diagram primary Al3Scshould form during solidification of all alloys with Sccontent higher than approx 06 wt- ie higher thanthe eutectic composition Formation of primary Al3Sc inAlndash07 wt-Sc melts cooled at 102ndash103 K s21 has beenreported1832 According to the metastable state dia-gram32 this alloy composition is close to the eutectic oneat these cooling rates

Primary Al3Sc is reported to have a highly facetedmorphology1318100ndash102 The observation of a cubicmorphology in a slowly cooled Alndash87 wt-Sc alloyindicates that the facet planes in this case are thecrystallographic (100) planes13 Brodova et al100ndash102

have investigated the microstructure of rapidly cooledAlndash2 wt-Sc alloy They found that the dominantmorphology of primary Al3Sc was dependent on boththe cooling rate and the initial melt temperature A mapof primary Al3Sc morphologies as a function of theseparameters was constructed and is redrawn in Fig 11

The nucleation mechanism and growth morphologyof primary Al3Sc in an Alndash07 wt-Sc alloy solidified ata cooling rate of 100 K s21 were investigated by Hydeet al103104 Indications were found that the primaryAl3Sc particles nucleate heterogeneously on oxideparticles in the melt The primary Al3Sc particles werefound to grow with a dendritic morphology with theprimary dendrite arms in the crystallographic n110m

direction The overall shape is cubic which is inaccordance with earlier observations

Eutectic Al3ScEutectic AlzAl3Sc has been reported in hyper- as wellas hypoeutectic alloys11 but is scantily described in theliterature Given a eutectic composition of 06 wt- amaximum solid solubility of Sc in Al of 035 wt- andthe specific densities in Table 1 a eutectic formed underequilibrium conditions would contain a volume fractionof approx 063 vol-Al3Sc At high cooling rates thevolume fraction of Al3Sc in the eutectic is probablysomewhat smaller owing to the increased supersatura-tion of Sc in Al

The morphology of the eutectic in an Alndash2 wt-Scalloy is reported to depend on the temperature of themelt before solidification100 For low melt temperaturesthe eutectic is reported to be rodlike for a wide range ofcooling rates For intermediate melt temperatures andhigh cooling rates a lsquodiscontinuous eutecticrsquo is reportedwhereas for high melt temperatures and slow coolingrates a lsquoquasieutecticrsquo structure is reported with Al3Scparticles of almost spherical shape

Hyde et al have reported that during solidification ofan Alndash07 wt-Sc alloy some of the primary Al3Scparticles are pushed ahead of the Al solidification frontand end up at the grain boundaries103104 Thus primaryAl3Sc may be mixed with eutectic Al3Sc in themicrostructure A scanning electron microscopy (SEM)picture showing eutectic Al3Sc at the grain boundaries asdescribed in Refs 103 and 104 is given in Fig 12

Discontinuous precipitation of Al3ScDiscontinuous precipitation of Al3Sc from super-saturated solid solution is often observed in binary AlndashSc alloys131831105 This precipitation mechanism whichis sometimes referred to as cellular precipitation iscommonly described as a decomposition of super-saturated solid solution into a-Al and Al3Sc at a movinggrain boundary The driving force for the grainboundary migration is the volume free energy that isreleased during the precipitation As the grain boundarymoves it leaves behind a characteristic fan shaped array

11 Morphology of primary Al3Sc particles in Alndash2 wt-Sc

alloy as a function of melt overheating and cooling

rate during solidification redrawn from Ref 102

12 SEM image of particle structure of Alndash07 wt-Sc

alloy cooled at a rate of 100 K s21 during solidifica-

tion as described in Refs 103 and 104 primary Al3Sc

particle is seen in centre of grain whereas eutectic

Al3Sc is decorating grain boundaries image is kindly

provided by Dr Kristian Hyde UMIST Manchester UK

Roslashyset and Ryum Scandium in aluminium alloys

26 International Materials Reviews 2005 VOL 50 NO 1

of precipitates In the AlndashSc case the discontinuouslyprecipitated Al3Sc particles have been demonstrated tobe coherent with the aluminium matrix1318

The driving force for discontinuous precipitationincreases with increasing supersaturation of Sc in theAl matrix Thus discontinuous precipitation in binaryAlndashSc is most frequently reported in studies of alloyswith a Sc content of 04 wt- or higher1318106 Stilldiscontinuous precipitation has also occasionally beenreported to occur at lower alloy compositions In an Alndash027 wt-Sc alloy discontinuous precipitation wasobserved over a wide range of temperatures107 In arecent study31105 of precipitation kinetics and mechan-isms in Alndash02 wt-Sc discontinuous precipitation wasfound to take place when the specimens were quencheddirectly from a solutionising temperature in this case600uC to aging temperatures in the range 370ndash490uCFurther C-curves in a temperature-time-transformation(TTT) diagram were established (Fig 13) which showedthat the highest transformation rate of discontinuousprecipitation lies at a higher temperature than thehighest transformation rate of the continuous precipita-tion reaction ie the two precipitation reactions arerepresented by two separate lsquonosesrsquo on the C-curves

It has been shown that discontinuous precipitationcan be suppressed by continuous precipitation if thematerial is cold worked before the precipitation heattreatment13108

As a result of their rather coarse nature andinhomogeneous dispersion discontinuously precipitatedAl3Sc contributes but little to the strength of the alloyand also leads to a smaller amount of Sc in super-saturated solid solution being available for subsequentcontinuous precipitation Thus discontinuous precipita-tion is in general regarded as an undesired precipitationmode

Continuous precipitation of Al3ScContinuous precipitation of Al3Sc is a bulk decomposi-tion process of supersaturated solid solution of Sc in Aland can in the isothermal case be characterised by anucleation stage a growth stage and finally a coarsen-ing stage Apparently the continuous precipitation reac-tion occurs largely by homogeneous nucleation anddiffusion controlled growth and AlndashSc has occasionallybeen used as a model system for studying the mechan-isms of nucleation growth and coarsening107109ndash111

There have been several studies of the continuousprecipitation reaction in binary AlndashSc alloys and up tillnow there is no evidence that any metastable phases areforming before the L12 phase Al3Sc Thus it is assumedthat the equilibrium phase nucleates directly fromsupersaturated solid solution

Even though the nucleation of Al3Sc is frequentlyreported to occur homogeneously throughout the Almatrix there are some examples in the technical litera-ture of reported heterogeneous Al3Sc nucleation ondislocations110112ndash115 and grain boundaries110113115ndash118

In a recent numerical modelling study of continuousprecipitation in AlndashSc alloys111 the effect of hetero-geneous nucleation on dislocations is accounted for Themodel predicts that homogeneous nucleation dominatesat high Sc concentrations and low transformation tem-peratures whereas heterogeneous nucleation is predictedto dominate at low Sc concentrations and high trans-formation temperatures Figure 14 shows a sketch of anucleation map for AlndashSc The shift between homo-geneous and heterogeneous dominance in nucleation isdependent on the dislocation density as indicated in thefigure

The shape of continuously precipitated Al3Sc particlesis most frequently reported to be spherical29112113119ndash129

However it seems that under certain conditions theshape can differ from the spherical one Drits et al130

reported both spherical and star shaped morphologyThe star shaped precipitates had arms growing in thecrystallographic n110m-directions (Star shaped Al3Scprecipitates have also been found after some thermo-mechanical treatments of an AlndashMgndashScndashZr alloy131) InRef 128 precipitates of both cuboidal and sphericalmorphology are found to coexist after certain heattreatments Cauliflower shaped precipitates as well asprecipitates of spherical and cuboidal shapes arereported by Novotny and Ardell110 Bastow andCelotto132 found large oblong Al3Sc particles in an Alndash01 wt-Sc alloy after aging at 400uC for 24 h A facetedshape is suggested in a high-resolution image of anAl3(Sc Zr) precipitate in an AlndashMgndashMnndashZrndashSc alloy133

In a systematic high-resolution transmission electron

13 TTT diagram of precipitation in Alndash02 wt-Sc alloy

after solutionising at 600uC and direct quench to

aging temperature3114 Nucleation map for binary AlndashSc alloys which indi-

cates how the tendency towards heterogeneous ver-

sus homogeneous nucleation is predicted to depend

upon Sc concentration transformation temperature

and dislocation density redrawn from Ref 111

Roslashyset and Ryum Scandium in aluminium alloys

International Materials Reviews 2005 VOL 50 NO 1 27

microscopy (TEM) study of the Al3Sc particle morphol-ogy development during precipitation heat treatment ofbinary AlndashSc alloys by Marquis and Seidman114 it isdemonstrated that the precipitates can take a wide rangeof shapes as they grow depending on Sc content in thealloy transformation temperature and transformationtime Irregular shaped star shaped and cuboidalshaped precipitates were observed under someconditions It was however found that the equilibriumshape of the particles is an equiaxed multifaceted one(Fig 15) Supported by Wulffrsquos construction it wasconcluded that the shape was that of a GreatRhombicuboctahedron This equilibrium morphologyhas been reproduced by computer-simulations ofparticle growth87134 The multifaceted particles caneasily be taken for spherical in a conventional TEMpicture

Kinetics of precipitation of Al3Sc fromsupersaturated solid solutionThe precipitation kinetics of Al3Sc in binary AlndashScalloys is dependent on the precipitation heat treatmenttemperature and on the Sc content in the alloy Acomprehensive overview over the transformationkinetics in terms of C-curves is given by Zakharov135

The C-curves for 5 transformation for a range of AlndashSc alloys are redrawn in Fig 16

Hyland107 studied the homogeneous nucleationkinetics of Al3Sc in a Alndash018 wt-Sc alloy after directquench from 650uC to precipitation temperatures of 288and 343uC He found that after an incubation time t theAl3Sc particles nucleated at a constant rate until thediffusion fields of the individual particles started tooverlap At 288uC the incubation time and time tosignificant diffusion field overlap were estimated to beapprox 245 and 150 min respectively whereas thecorresponding values at 343uC were estimated to beapprox 7 and 20 min respectively

If one assumes that the JohnsonndashMehlndashAvramindashKomolgorov (JMAK) relationship is valid for thisprecipitation reaction one can express the fraction

transformed X as a function of the reaction time t bythe equation

X (t)~1expfrac12k(Dt)n (1)

where k is a constant D is the interdiffusion constant ofSc in Al and the exponent n is dependent on thenucleation rate For the situation described byHyland107 where the precipitates nucleate at a constantrate the value of n should theoretically136 be equal to52

Roslashyset and Ryum31105 applied an alloy and heattreatment method practically equal to that of Hyland107

One should thus expect that the precipitation kineticsshould also be quite similar However Roslashyset andRyum reported that the exponent n of the JMAKrelationship was approx 165ndash185 for the temperaturerange of concern31105 This does not point in thedirection of a constant nucleation rate but rather inthe direction of site saturation ie that all the particlesare nucleated simultaneously which in the JMAKequation would yield an exponent n of 32136 Anoverview of some reported values of n in the JMAKequation is given in Table 4 The majority of the valueslie closer to 32 than to 52 However it is important to

15 High resolution TEM picture along n100m axis of Al3Sc particle in Alndash03 wt-Sc alloy aged at 300uC for 350 h114

(reproduced with permission from Elsevier Science image kindly provided by Dr E A Marquis and Professor D N

Seidman) and various projections of a Great Rhombicuboctahedron

Table 4 Some reported values of n in JMAK equation

Reference n C 0Sc wt-Sc Ttrans uC Note

137 13 030 300 Solution heat treated (SHT) 500uC16026 030 300 SHT 600uC Low n at late stage20026 030 300 SHT 640uC Low n at late stage

29 130ndash149 015 260ndash370145ndash196 025 260ndash370

138 188ndash216 020 240ndash35031 165ndash185 023 270ndash350 SHT 600uC Direct quench to transformation temp

16 C-curves for 5 transformation in a range of binary

AlndashSc alloys redrawn from Ref 135

Roslashyset and Ryum Scandium in aluminium alloys

28 International Materials Reviews 2005 VOL 50 NO 1

note that an n value close to 32 is per se not evidence ofsite saturation

Hyland also showed that a water quench from thesolutionising temperature significantly altered thenucleation kinetics in the subsequent precipitation heattreatment107 The incubation time was dramaticallyshortened which is attributed to the quenched-in excessvacancies and it is also indicated that there might be ashift in the nucleation rate in the early stage ofprecipitation It is suggested that the vacancies mayenhance the diffusion of Sc in Al and that there is apossibility that vacancy clusters act as heterogeneousnucleation sites for Al3Sc precipitates107 Regardless ofwhich mechanism that is operative it is clearly demon-strated that the nucleation kinetics can be dependent onthe thermal history between solutionising and precipita-tion heat treatment

Loss of coherency during growth of Al3ScprecipitatesWhen an Al3Sc particle grows it will sooner or laterreach a critical size where it will be energetically morefavourable to introduce an interface dislocation at theAlAl3Sc interface than to increase the matrix strain Asimple approximation for the critical size can be derivedfrom the lattice parameters assuming that the criticalsize is reached when the misfit over the whole particlediameter equals the Burgers vector of the Al matrix

dcrit~b=d (2)

where b is the Burgers vector of Al and d is themisfit between Al and Al3Sc This approximation yieldsa critical diameter of approx 215 nm at ambienttemperature

The misfit d and thus also the critical diameter dcrit

will depend on the temperature owing to the differencesin thermal expansion between the Al matrix and the

Al3Sc particles The thermal expansion of Al3Sc hasrecently been measured89 and based on the differencesin thermal expansion between Al139 and Al3Sc the misfitas a function of temperature has been calculated89 Thiscalculation is reproduced and shown by the solid line inFig 17

It is however possible to refine this calculationsomewhat140 Whereas the thermal expansion of Al3Sc isexpected to be only because of lattice expansion there isa significant contribution from vacancies on thermalexpansion of Al at high temperatures141 Thus thetemperature effects on the misfit should be calculatedfrom the changes in lattice parameters rather than fromthe linear thermal expansion By subtracting the vacancyeffect on the thermal expansion one achieves atemperature-dependent misfit as represented by thedotted line in Fig 17

A second correction that should be taken into accountis the effect of Sc in solid solution on the latticeparameter of the Al matrix With increasing tempera-ture more Sc is brought into solid solution and it isreported that the lattice parameter of the Al matrixpresumably measured at room temperature increaseslinearly with the Sc content in solid solution142 Thesedata can be used to calculate the effect on the latticeparameter at elevated temperatures under the assump-tion that the relative increase in lattice parameter owingto Sc in solid solution is independent of temperature InRef 142 a figure is presented which shows the measuredlattice parameter as a function of Sc content in solidsolution and a value (dadc)a is reported where a is thelattice parameter of the Al matrix and c is the Sc contentin solid solution in at- The reported value for (dadc)a is 100 times larger than that indicated in thecorresponding figure possibly as a result of a decimalerror in the text Thus in the present exercise 1100th ofthe reported value for (dadc)a is used Using this incombination with the regular solution approximationfor the solvus line of Sc in Al1231 one obtains acorrection for Sc in solid solution on the temperature-dependent misfit as shown in Fig 18 This figure shows

17 Lattice mismatch between Al and Al3Sc as a function

of temperature solid line represents calculation

based on linear thermal expansion of the two phases

dotted line represents correction for vacancies in Al

lattice

18 Corrections of mismatch calculated from linear ther-

mal expansion data as a result of vacancies and to

Al lattice expansion from Sc in solid solution

Roslashyset and Ryum Scandium in aluminium alloys

International Materials Reviews 2005 VOL 50 NO 1 29

both the correction for vacancies and for Sc in solidsolution on the same graph The two corrections are ofapproximately the same magnitude but with oppositesigns Thus the resulting (net) correction is close to zeroand it turns out that the first hand approximation asapplied in Ref 89 is very good in this case

Applying the calculated temperature dependent misfitwith the simple approximation for a critical diameter forloss of coherency one obtains a temperature-dependentcritical diameter as shown in Fig 19

Some examples from the literature of experimentallyobserved critical diameters in binary AlndashSc alloys aresummarised in Table 5 along with some predictions forcritical diameters from Fig 19 There is a fairly goodconsistency between the observations and the measureddiameter is quite close to the simple predictions above

A more refined analysis on the transition fromcoherent to incoherent particles has recently beenperformed145 This analysis is based on the balancebetween the increase in particlematrix interface energyowing to interfacial dislocations and the relaxation inelastic energy in the Al matrix owing to the samedislocations This method yields a predicted criticaldiameter of 246 nm for transition from coherent to

semi-coherent particles at ambient temperature Thetemperature dependence of the critical diameter is nottreated in this analysis

The loss of coherency during isothermal annealing hasbeen reported to be accompanied by an increasedaverage coarsening rate119121137145 The increasedcoarsening rate has been attributed either to diffusionof Sc along dislocation lines119121 or to the increasedparticlematrix interface energy of a semicoherentparticle145 However there are also several data sets inthe literature that do not indicate an increased growthrate after the loss of coherency114128

Al3ScAl interface energyThe interface energy between Al3Sc and the Al matrix isone of the key parameters that governs the nucleationgrowth and coarsening behaviour of Al3Sc in Al and Alalloys The interface energy has been estimated in severalinvestigations either by fitting experimental data toequations that describe nucleation or coarsening or bycalculations A compilation of some of the results isgiven in Table 6 There is considerable spread in thereported values regardless of what approach has beenused for the estimation

Influence of other elements on precipitation ofAl3ScMagnesium

With regard to precipitation mechanism it has beenstated that Mg suppresses the tendency to discontinuousprecipitation of Al3Sc106 In an investigation of pre-cipitation kinetics of Al3Sc in the temperature range300ndash500uC only minor changes in the kinetics (Fig 20)were found when up to 5 wt-Mg was added to an Alndash04 wt-Sc alloy135 It seems that the precipitationreaction is slightly faster in the Mg-containing alloys

Several investigations on age hardening response alsoimply that there is only a small if any effect of Mg onthe precipitation kinetics of Al3Sc23148149 It is how-ever found that the hardness increase from theprecipitation of Al3Sc is somewhat reduced in AlndashMgndashSc alloys compared to binary AlndashSc alloys23148149 InRef 149 it is suggested that some of the Sc is dissolvedin the Al3Mg2 phase and thus the age hardeningpotential is reduced with increasing Mg contentSomewhat contradictory to these observations but

Table 5 Some reported critical diameters for coherencyloss in binary AlndashSc and correspondingtheoretical critical diameters from Fig 19

Reference dcrit nmC0

Scwt-Sc

TtransuC

Theoreticaldcrit nm

119 38ndash40 05137 28ndash30 03 400 308128 32 02 400 450 308 335129 50 02143 40 012 025115 40 025 450ndash500 335ndash37114 40 03 400 450 308 335144 40 02 400ndash460 308ndash341145 30ndash80 02 400ndash490 308ndash362

20 C-curves for 10 and 60 transformation in Alndash

04 wt-Sc and Alndash4 wt-Mgndash04 wt-Sc redrawn

from Ref 135

19 Simple approximation for temperature-dependent criti-

cal diameter for introduction of dislocations on Al

Al3Sc interface

Roslashyset and Ryum Scandium in aluminium alloys

30 International Materials Reviews 2005 VOL 50 NO 1

sustained by Ref 135 it has recently been reported150

that precipitation of Al3Sc at 300 and 350uC occursslightly faster in an Alndash2 wt-Mgndash02 wt-Sc alloythan in an Alndash02 wt-Sc alloy studied previously by thesame researchers117118 and that the correspondinghardness increase is highest in the AlndashMgndashSc alloyThe only reported difference in experimental procedureis the solutionising temperature which was higher forthe AlndashSc alloy (648uC) than for the AlndashMgndashSc alloy(617uC) However given that the nucleation time isshortened by quenched-in vacancies as suggested byHyland107 the difference in homogenisation tempera-ture should be in favour of a faster precipitation of thebinary AlndashSc alloy It should be worthwhile to probedeeper into this observation of different aging responses

Mg in solid solution increases the lattice parameter ofthe Al matrix This is in turn expected to influence thecritical diameter for AlAl3Sc coherency loss as discussedin the section on lsquoLoss of coherency during growth ofAl3Sc precipitatesrsquo above Such an influence on the criticaldiameter is also briefly discussed elsewhere150 A criticaldiameter of 80 nm in an Alndash3 wt-Mgndash02 wt-Sc alloyhas been observed compared to 40 nm in a binary Alndash02 wt-Sc alloy of the same investigation144 Otherresearchers have reported a critical diameter in excess of116 nm in an Alndash63 wt-Mgndash02 wt-Sc alloy151

Computer simulations predict that the AlAl3Scinterface should be enriched in Mg87 These predictionsare confirmed experimentally by three-dimensional atomprobe microscopy of an Alndash2 wt-Mgndash02 wt-Sc alloyaged at 300uC38 Here it was found that the Mg contentat the interface is approximately three times higher thanthe matrix concentration regardless of aging time

Copper

It has been claimed that Cu suppresses the tendencytowards discontinuous precipitation of Al3Sc106

Zakharov and Rostova152 have reported that additionsof up to 14 wt-Cu have only minor effects on theprecipitation kinetics in an Alndash04 wt-Sc alloy Themost noticeable effect is that for temperatures above400uC the late stage of the transformation is sloweddown for the highest Cu contents This does not show in

Fig 21 however where only the 10 and 60transformation curves are included

The W-phase (AlCuSc) was observed in the alloywith the highest Cu content which means that less Sc isavailable for the precipitation of Al3Sc in this alloyAnother investigation on the age hardening response ofAlndash023 wt-Sc and Alndash25 wt-Cundash023 wt-Sc at300uC also implies that the precipitation behaviour ofAl3Sc in the two alloys is similar153154 At 350uC alimited portion of the Al3Sc has been observed tonucleate heterogeneously on coarse hrsquo precipitates155

According to the isothermal sections of the phasediagram43 one should expect the ternary W-phase toform instead of the Al3Sc phase in an alloy with such ahigh CuSc ratio However no observations of the W-phase or other ternary phases were reported from TEMstudies of the Alndash25 wt-Cundash023 wt-Sc alloy thathad been heat treated in the temperature range 300ndash460uC153ndash156 A third investigation on the precipitationin Alndash048 wt-Sc alloys with up to 440 wt-Cu in thetemperature range 100ndash450uC also concludes that no W-phase or other ternary phase forms during the heattreatment157

Copper in solid solution decreases the lattice para-meter of the Al matrix Thus it is expected that the misfitbetween Al and Al3Sc precipitates should be higher in

21 C-curves for 10 and 60 transformation in Alndash

04 wt-Sc and Alndash14 wt-Cundash04 wt-Sc redrawn

from Ref 152

Table 6 Reported values of interphase energy cAlAl3Sc between coherent Al3Sc precipitates and Al matrix

Reference cAlAl3Sc mJ m22 Method of estimation

137 10 Fit of coarsening data to LifshitzndashSlezev equation107 78iexcl20 (288uC) Back-calculation of incubation time

93iexcl20 (343uC)107 123iexcl41 (288uC) Back-calculation of nucleation rate

125iexcl35 (343uC)29 542 (400uC) Fit of coarsening data to Ostwald ripening

632 (430uC)413 (460uC)

146 c(100) 192 (0 K) c(111) 226 (0 K) Pseudopotential calculations147 c(100) 325 (0 K) c(110) 513 (0 K) c(111)

782 (0 K) c(100) 315 (288uC) c(100) 325 (343uC)Atomistic simulation

110 105 Fit of coarsening data to LSW theory31 20ndash300 Fit of coarsening data to Ostwald ripening

for 16 different temperatures111 57 Fit of precipitation model to experimental data145 120 coherent particles Fit of coarsening data

170 semicoherent particles

It is argued in this study that c may be lower in the nucleation stage

Roslashyset and Ryum Scandium in aluminium alloys

International Materials Reviews 2005 VOL 50 NO 1 31

AlndashCundashSc alloys compared to AlndashSc alloys Howeveran experimental investigation of Alndash25 wt-Cundash023 wt-Sc alloy comes to a different conclusion Thelattice misfit strain is found to decrease compared to Alndash02 wt-Sc and the critical diameter for coherency losswas found to be the same in the ternary and the binaryalloy144 It is suggested that these observations may bebecause of the dissolution of some Cu in the Al3Sc phaseand thus that the lattice parameters of both the Al matrixand the Al3Sc precipitates decrease in the ternary alloy

Silicon

It has been found that the onset of precipitation in Alndash04 wt-Sc is only slightly altered when Si contents ofup to 04 wt are introduced in the alloy However thefinal stage of the precipitation reaction is considerablydelayed with increasing Si content135 Figure 22 showsthe effect of addition of a joint of 035 wt-Si and040 wt-Fe There are at least two possible explana-tions for why an Si-addition leads to this behaviour

1 Alloying with Si is known to promote discontin-uous precipitation of Al3Sc106158 It has been shown thatwhen isothermal precipitation of Al3Sc starts discon-tinuously the later stage of the overall transformationcan be very slow31

2 The isothermal section of the phase diagramsuggests that the V-phase (AlSc2Si2) should form inalloys of this composition46 If the V-phase forms lessSc is available for precipitation of Al3Sc

It has been shown157 that for an AlndashScndashSi alloy withsolid solution content of 010 wt-Sc an 110 wt-Sithe only phases to precipitate after heat treatment at200uC are Si and an (AlScSi)-phase possibly the V-phase On the other hand the Al3Sc phase has beenobserved to form in alloys with 04 wt-Sc and up to08 wt-Si159160

Zinc

It has been reported that additions of up to 5 wt- Znhave only minor effects on the precipitation kinetics ofan Alndash04 wt-Sc alloy135 (Fig 23) In Ref 106 it isclaimed that Zn promotes discontinuous precipitation ofAl3Sc

Lithium

A comparison of the age hardening response at 400uC inAlndash24 wt-Lindash019 wt-Sc and Alndash024 wt-Sc alloys

indicates that the onset of Al3Sc-precipitation is notaffected by the presence of Li161

Zirconium

As mentioned in the section on lsquoTernary phase diagramswith dispersoid-forming elementsrsquo earlier a considerableamount of Zr is dissolved in the Al3Sc phase and thus amore correct denotation of the precipitating phase isAl3(Sc12xZrx) In discussing the influence of the Zrcontent on the precipitation of Al3Sc one is thereforeactually discussing the difference in precipitation ofAl3Sc versus Al3(Sc12xZrx)

It is found that an addition of 015 wt-Zr to an Alndash04 wt-Sc alloy only marginally affects the initial stageof the precipitation reaction123135 while it slows downthe later stages of the transformation considerably(Fig 24)135 The coarsening rate of the Al3(Sc12xZrx)particles in AlndashScndashZr alloys is found to be much slowerthan that of Al3Sc particles in AlndashSc alloys123162

In three-dimensional atom probe field ion microscopy(3D-APFIM) of Al3(Sc12xZrx) particles formed at 475uCin a ternary AlndashScndashZr alloy163 it was found that the coreof the particles is almost pure Al3Sc whereas there is ashell of Al3(Sc12xZrx) with almost equal content of Scand Zr Such a behaviour has also been predicted bycomputer modelling of precipitation of Al3(Sc12xZrx) at480uC in an AlndashZnndashMgndashScndashZr alloy164 This modelpredicts that Zr starts to enter the growing

22 C-curves for 10 and 60 transformation in Alndash

04 wt-Sc and Alndash04 wt-Fendash035 wt-Sindash04 wt-Sc

redrawn from Ref 135

23 C-curves for 10 and 60 transformation in Alndash

04 wt-Sc and Alndash5 wt-Znndash04 wt-Sc redrawn

from Ref 135

24 C-curves for 10 and 60 transformation in Alndash

04 wt-Sc and Alndash04 wt-Scndash015 wt-Zr redrawn

from Ref 135

Roslashyset and Ryum Scandium in aluminium alloys

32 International Materials Reviews 2005 VOL 50 NO 1

Al3(Sc12xZrx) particles when approximately half of thesupersaturated Sc has been precipitated The Zr contentof the outer shell is predicted to be much higher thanwhat has been found experimentally163164

Another 3D-APFIM study of Al3(Sc12xZrx) particlesin a ternary AlndashScndashZr alloy has been reported165 Hereparticles grown at 300uC for various lengths of time werestudied The Zr content in these particles was muchlower than that reportedpredicted at higher tempera-tures163164 even after very long annealing times

Iron

The effect of adding up to 07 wt-Fe on the precipita-tion kinetics in an Alndash04 wt-Sc alloy has beeninvestigated135 The onset of precipitation was onlyslightly influenced by the Fe-level whereas the laterstages of the transformation however were significantlyslowed down as the Fe-level increased An example ofthe effect of a joint addition of Fe and Si is shown inFig 22

Manganese chromium and titanium

Small additions (03 wt-) of manganese or chromiumto Alndash040 wt-Sc alloys are reported to have onlyminor effects on the precipitation kinetics of Al3Sc135

According to Ref 106 Mn is reported to promote andCr and Ti to suppress discontinuous precipitation

Rare earth elements

An investigation of the precipitation behaviour of Alndash03 at-Sc and Alndash03 at-Scndash03 at-X alloyswhere X is either yttrium gadolinium holmium orerbium in the temperature range 235ndash310uC indicatedthat a Al3(Sc12xXx) phase with L12 structure wasformed in the ternary alloys22 Peak strength is reportedto occur after approx 10 h at 285uC in all alloys whichindicates that the precipitation kinetics up to peakstrength is practically unaltered by the ternary additions

Influence of Sc on microstructure andproperties of wrought aluminium alloysMost of the effects of Sc addition in wrought Al-alloysare linked to the formation of the Al3Sc phase In atypical processing route of a wrought aluminium alloyparticles of the Al3Sc phase can form under threedifferent conditions each of which influences themicrostructure and properties of the alloy in a specificway

1 During solidification after casting or weldingAl3Sc particles can form in the melt and act as nucleifor a-Al thus leading to grain refinement18166

2 High temperature processing of the alloy in therange 400ndash600uC for instance homogenisation hot-rolling or extrusion can give a dense distribution ofAl3Sc particles of typically 20ndash100 nm size The particledistributions formed under such conditions are reportedto lead to good recrystallisation resistance128148167168

and enhanced superplasticity52169170

3 Heat treatment in the range 250ndash350uC can lead tosignificant precipitation hardening of an alloy super-saturated in Sc148158171 The size of strengthening Al3Scprecipitates is typically in the range 2ndash6 nm121

Grain refinementA good grain refinement is almost always desired uponsolidification The formation of small equiaxed grainsrather than long dendrites in the melt facilitates thefeeding of the melt into cavities of the shrinkingsolidified metal and thus reduces the problem ofshrinkage porosity The tendency to hot cracking is alsoreduced and the second phase particles become morefinely and uniformly distributed

To the authorsrsquo knowledge the first effect of Sc in Al-alloys that was reported in an international scientificjournal was the grain refining action in pure Al and in anAlndashCu alloy upon solidification172 which was found tobe stronger for Sc than for other transition metals Inlater studies of Sc as a grain refiner in pure Al1832173 ithas been demonstrated that approx 07 wt-Sc issufficient to provide excellent grain refinement It hasalso been demonstrated that additions of 025 wt-Scz025 wt-Zr provide good grain refinement in pure Al18

In order for Sc to act as an effective grain refiner theAl3Sc phase has to form in the melt before thesolidification of a-Al The Al3Sc particles have a latticeparameter close to that of pure Al and whenhypereutectically formed the Al3Sc particles are veryeffective substrates for the nucleation of the a-Al phaseAs mentioned in the section on lsquoFormation of Al3Sc inAlndashSc alloysrsquo above this requires that the alloy ishypereutectic with respect to Sc ie in excess of approx06 wt- in a binary AlndashSc alloy In ternary and higherorder systems the eutectic Sc composition may dependon the other alloying elements present For instance theeutectic composition of Sc has been predicted todecrease with increasing Mg content in the ternary AlndashMgndashSc system39 This prediction is sustained by theobservation of good grain refinement by adding 05 wt-Sc to an Alndash7 wt-Mg alloy174 (Other examples ofgrain refinement at Sc concentrations lower than that ofthe binary eutectic are found in Ref 173)

Similarly the observation of good grain refinement inan Alndash025 wt-Scndash025 wt-Zr alloy18 may be as aresult of a lower Sc content of the eutectic in the ternarysystem ie less Sc is needed to make the alloy hyper-eutectic No literature data on the liquidus surface of theAlndashScndashZr system are available and thus this hypothesiscannot be confirmed In more complex alloy systems itis also observed that excellent grain refinement isachieved at low Sc contents when Sc is added togetherwith Zr It is reported that adding either 02 wt-Sc06 wt-Sc or 01 wt-Zr to an Alndash5Mg alloy givesmuch poorer grain refinement than adding 02 wt-Scz01 wt-Zr175 Similarly additions of 015 wt- ofeither Sc or Zr are reported to only marginally refinethe grain structure in an AlndashCundashLi alloy whereas a jointaddition of 015 wt-Sc and 015 wt-Zr gives excellentgrain refinement176 For an AA 3650 casting alloy (Alndash7 wt-Sindash04 wt-Mg) good grain refinement is achievedby adding 039 wt-Sc or 027 wt-Scz019 wt-Zr177

In some AlndashZnndashMgndashScndashZr alloys it is also found thatan addition of 02ndash03 wt-Sc can be sufficient for goodgrain refinement166169178179 Examples of the grainrefinement as a function of Sc addition in pure Al andin an AlndashZnndashMgndashZr alloy are shown in Fig 25

The nucleation of a-Al on Al3Sc particles in the melt isfacilitated by the close match in the lattice parameters ofthe two phases As shown in Fig 17 the mismatch at the

Roslashyset and Ryum Scandium in aluminium alloys

International Materials Reviews 2005 VOL 50 NO 1 33

eutectic temperature of binary AlndashSc alloys (660uC) isonly approx 047 In Refs 57 and 89 it is shown thatwhen Zr Hf and in particular Ti is dissolved in the Al3Scparticles this reduces the lattice parameter of the phaseIt appears that when 25 of the Sc atoms in Al3Sc aresubstituted by Ti the mismatch is zero at approx 550uCand becomes negative at higher temperatures89 Thissuggests that by carefully selecting the Ti content of thealloy it should be possible to obtain Al3(ScTi)substrates in the melt that match exactly the latticeparameter of the nucleating a-Al and thus furtherimprove the grain refinement of the alloy This appearsto have been achieved in a recent work180 where thegrain refinement of an Alndash07 wt-Sc alloy wascompared with that of an Alndash05 wt-Scndash02 wt-Tialloy At a cooling rate of 100 K s21 only an estimated2 of the primary Al3Sc particles of the binary AlndashScalloy were effective nuclei compared to practically 100for the primary Al3(ScTi) particles in the ternary AlndashScndashTi alloy leading to a much smaller grain size in theternary alloy Whereas the match of lattice parametersmay be of importance for these results the authors ofthis investigation180 draw attention to other factors suchas different growth restriction factors for Sc and Ti andthe possibility of a peritectic reaction in the ternaryalloy Nevertheless the principle of matching latticeparameters is worth looking into further in future work

Effects from dispersoidslsquoDispersoidsrsquo is a term which is commonly used aboutthe classes of second phase particles that are formedin an Al alloy during high temperature annealing orthermomechanical processing such as homogenisationhot rolling extrusion and forging A dense distributionof dispersoids can give a significant contribution to analloyrsquos strength owing to particle strengthening but thisis rarely the main strengthening mechanism A moreimportant contribution from the dispersoids is theirability to stabilise the grainsubgrain structure of analloy through the Zener-drag action and thus improvethe mechanical properties of the alloy

There are two noticeable dispersoid-related effectsthat have been reported for Sc-containing alloys Thefirst is the stabilising effect on a deformed microstruc-ture When a non-recrystallised structure is preserved inan alloy this can add considerably to the mechanical

strength of the material The second effect is thepreservation of a small grain size during hot deforma-tion at slow deformation rates which is necessary toobtain superplastic properties of an Al-alloy

Recrystallisation resistance

The anti-recrystallisation effect of Sc was first publishedin a patent171 where 03 wt-Sc was added to pure Aland to AlndashMg AlndashMn and AlndashZnndashMg alloys Both Sc-free and Sc-containing materials were cold worked andsubsequently annealed and it was found that theaddition of Sc increased the temperature for onset ofrecrystallisation by approx 220uC in pure Al andsomewhat less in the Al-alloys Although the author ofthe patent171 may have been well aware that the anti-recrystallisation effect is caused by Al3Sc dispersoidsthis is not mentioned in the text The first journal paperthat explicitly points out that the recrystallisationresistance is due to Al3Sc dispersoids was an investiga-tion of the effects of adding Sc to wrought AlndashMgalloys181 In this work it was found that the Al3Scdispersoids were very effective in preventing recrystalli-sation up to temperatures of approx 400ndash450uC Athigher temperatures the dispersoids coarsen consider-ably and the microstructure was partially recrystallised

It is established that the Zener-drag pZ that is imposedon an advancing grain boundary by randomly distrib-uted dispersoids can be expressed in the form

pZ~k f =r (3)

where k is a factor that includes the interface energybetween the dispersoids and the matrix f is the volumefraction and r is the mean radius of the dispersoids Thusthe Zener drag will decrease rapidly in the case where thedispersoids are coarsening

As mentioned in the section on lsquoInfluence of otherelements on precipitation of Al3Scrsquo above theAl3(Sc12xZrx) dispersoids in a ternary AlndashScndashZr alloycoarsen at a much slower rate than the Al3Sc dispersoidsin a binary AlndashSc alloy This effect was first reported inRef 123 (although also observed in Ref 182) andaccording to Ref 33 the same authors demonstratedsoon after that the denser dispersoid distributionachieved in an AlndashScndashZr alloy leads to superiorrecrystallisation resistance compared to a binary AlndashScalloy An example of the increased recrystallisationresistance by adding both Zr and Sc is shown in Fig 26

In isothermal sections of the ternary AlndashScndashZr phasediagram it is indicated that the solid solubility ofSczZr is somewhat higher than that of Sc alone54 Ithas also been demonstrated both by electrical con-ductivity measurements (Fig 27) and microstructuralobservations that the supersaturation of SczZr isgreater than that of only Sc or Zr in as cast Alndash15(SczZr) alloys183 This indicates that it should bepossible to increase the volume fraction of dispersoids inAlndashScndashZr compared to AlndashSc It is suggested162 that theincreased volume fraction that can be achieved byadding both Sc and Zr can be advantageous inconventional wrought Al-alloys

There are at least two different conditions underwhich Al3Sc or Al3(Sc12xZrx) dispersoids can form toprevent recrystallisation

1 Sc (or Sc and Zr) is in solid solution before thedeformation In the case of cold deformation and

25 Grain refinement as a function of Sc addition in pure

Al (redrawn from Ref 32) and AlndashZnndashMgndashZr (redrawn

from Ref 169) note that data points are plotted on

different ordinate axes

Roslashyset and Ryum Scandium in aluminium alloys

34 International Materials Reviews 2005 VOL 50 NO 1

subsequent annealing the Al3Sc or Al3(Sc12xZrx)dispersoids may nucleate and grow before the nucleationand growth of recrystallised grains takes placeDispersoids can form after a direct up-quench to theannealing temperature115143148184 during ramp-up tothe annealing temperature115 or by pre-annealing at anintermediate temperature129 In the case of hot deforma-tion the Al3Sc or Al3(Sc12xZrx) dispersoids maynucleate and grow during preheating of the materialand during the hot deformation itself184

2 The Al3Sc or Al3(Sc12xZrx) dispersoids are formedin the material before deformation184 Considering coldrolling and subsequent annealing the annealing tem-perature Tann may be either lower or higher than thetemperature Tdisp at which the dispersoids were formedIf TannTdisp only limited if any coarsening of thedispersoids is expected to take place and thus the Zenerdrag from the particles is expected to be practicallyconstant The driving force for recrystallisation how-ever is expected to decrease somewhat with theannealing time as a result of recovery processes Thusif recrystallisation does not occur within short annealingtimes the material is expected to remain unrecrystallisedfor infinite time at the annealing temperature IfTannTdisp there will be substantial coarsening of thedispersoids during annealing In order for the materialto remain unrecrystallised the decrease in driving forcefor recrystallisation owing to recovery has to be at leastas rapid as the decrease in Zener drag because of particlecoarsening

Experimental comparisons of the conditions abovepoint in the direction that the recrystallisation resistanceis poorest when Sc (or Sc and Zr) is in solid solutionbefore deformation and the deformed material is up-quenched to the annealing temperature148 or when Al3Scor Al3(Sc12xZrx) dispersoids are formed before defor-mation at TdispampTann184185 Excellent recrystallisationresistance is achieved if dispersoids are formed at anintermediate anneal of solutionised and deformedmaterial128 or if dispersoids are formed at TdispTann

before deformation148185ndash187 It seems that the decreasein Zener drag because of dispersoid coarsening in many

cases is slower than the decrease in driving force forrecrystallisation because of recovery processes Thusthere is an advantage in forming a high number densityof small dispersoids which for most practical casesmeans that they should be formed at TdispTann122

When an advancing high angle grain boundary iethe recrystallisation front is passing a coherent Al3Scdispersoid there are at least three possible grainboundarydispersoid interactions

1 The Al3Sc dispersoid retains its global orientationrelationship and thus loses its coherency with thesurrounding matrix

2 The Al3Sc dispersoid rotates as the grain boundarypasses either by diffusional processes at the dispersoidmatrix interface or by the grain boundary passingthrough the dispersoid and the Al3Sc dispersoidassumes the same crystallographic orientation as theAl matrix of the recrystallised grain

3 The Al3Sc dispersoid dissolves at the grainboundary and re-precipitates in the recrystallised grain

Which interactions that actually take place willprobably depend on the dispersoid size annealingtemperature and driving force for recrystallisation It isalso possible that alloy composition (other elementsthan Al) is of importance

It has been reported that large (Oslash about 100ndash150 nm)Al3Sc dispersoids in a deformed Alndash4 wt-Mgndash02 wt-Sc alloy annealed at 575uC lose the orientationrelationship with the matrix after being passed by therecrystallisation front148

A rotation of somewhat smaller Al3Sc dispersoids in arecrystallising binary Alndash025 wt-Sc alloy has beenreported115143 The rotation was reported to be accom-panied by substantial growth (from Oslash 30 nm to Oslash48 nm) as a result of enhanced Sc diffusion at the grainboundary Observations suggested that the grainboundaries were passing through the dispersoids andthus the Al3Sc dispersoids retained the orientationrelationship with the recrystallised Al matrix

Dissolution and re-precipitation of Al3Sc dispersoidshas been reported during recrystallisation of a 50 coldrolled Alndash02 wt-Sc alloy162 Large spherical partially

26 Fraction recrystallised structure in cold rolled sheets

of Alndash04 wt-Sc and Alndash04 wt-Scndash015 wt-Zr as a

function of annealing temperature redrawn from

Ref 183 27 Electrical conductivity in Alndash15(SczZr) alloys

redrawn from Ref 183

Roslashyset and Ryum Scandium in aluminium alloys

International Materials Reviews 2005 VOL 50 NO 1 35

coherent dispersoids were observed to dissolve at therecrystallisation front and re-precipitate as smallercoherent Al3Sc cuboids

Superplastic forming

It seems that the first publication on superplasticproperties of Sc-containing Al-alloys was a study of anAlndash35Cundash14Mgndash045Mnndash04(SczZr) alloy188

It was recognised that the superplastic properties are aresult of the stabilisation of the fine grain structure byAl3Sc dispersoids The Sc-containing Al alloys that havereceived most attention for their superplastic propertieshowever are those of the AlndashMgndashSc system which wasfirst published in a patent189 Here it was noted that anAlndash4 wt-Mgndash05 wt-Sc alloy had superior superplasticproperties compared to fine-grained 7475 (AlndashZnndashMgndashCu alloy) Binary Alndash05 wt-Sc and Alndash4 wt-Mgalloys did not behave superplastically The flow stress atthe hot forming temperature was found to be much (30ndash40) lower in the ternary alloy than that of the twobinary alloys

The superplastic properties of AlndashMgndashSc alloys havebeen explored by several research groups over the lastdecade190ndash196 It has frequently been found that thedeformation mechanism is dominated by grain bound-ary sliding190 However it has also been reported thatAlndashMgndashSc alloy may deform superplastically withoutnoticeable grain boundary sliding23 It is generallyrecognised that the grain boundary sliding mechanismis facilitated when the average grain size is very smalland grain boundaries are predominantly high-angleSuch a microstructure may be achieved by carefulthermomechanical processing of the starting mate-rial193194197198 It has however been shown that a finegrained structure with high angle boundaries maydevelop during superplastic forming of AlndashMgndashSc alloyseven if the starting microstructure is an entirely differentone for instance that of a cold rolled sheet192 It has alsobeen suggested that superplastic forming of as castmaterial may be possible189

One of the more efficient thermomechanical processesfor achieving an ultrafine grain structure with high anglegrain boundaries in Al-alloys is equal channel angularpressing (ECAP) A JapanesendashAmerican group ofscientists has published an impressive body of researchon improvements in superplastic properties in Al-alloys processed by ECAP over the last few years andseveral of the publications are from investigations onAlndashMgndashSc alloys170199ndash224 Maximum strains in excessof 2000 at a strain rate of 0033 s21 have beenachieved170201202217 which is an extraordinarily goodcombination of high strain and high strain rate for analuminium alloy

Superplastic properties of AlndashCundashMg(ndashMn)ndashSc(ndashZr)and AlndashMgndashSc(ndashZr) alloys have been mentionedNoticeable superplasticity in other Sc-containing Al-alloys has also been reported such as AlndashZnndashMg(ndashCu)ndashScndashZr169225ndash228 AlndashLindashSc229 AlndashMgndashLindashScndashZr229ndash234

AlndashLindashMgndashCundashScndashZr235236 and AlndashCundashLindashScndashZr233

Precipitation hardeningHardening by Al3Sc precipitates

It has been noted that when Al3Sc particles precipitate inthe temperature range 250ndash350uC they give a significanthardness increase in the alloy Some authors point out

that Sc is a more effective precipitation hardening elementper atomic fraction added than the elements that arecommonly used for precipitation hardening121130 (In onepaper29 it is claimed that only Au has a strongerstrengthening effect than Sc) However the amount ofSc that can be precipitated from supersaturated solidsolution is rather limited and thus the absolute values ofthe hardness increase from the precipitation hardening ismuch lower than what is normally associated withprecipitation hardened alloys Also the temperatureregime for age hardening by precipitation of Al3Sc issomewhere in between the temperature regimes for agehardening and solution heat treatments of commonprecipitation hardened alloys This makes a combinedprecipitation of Al3Sc and other strengthening precipi-tates unfeasible Thus precipitation strengthening byAl3Sc is most feasible in alloy systems that are non-heat-treatable The non-heat-treatable aluminium alloy sys-tems are according to the Aluminum Associationdesignations the 1xxx series (99 pure Al) the 3xxxseries (AlndashMn) and the 5xxx series (AlndashMg) The purposeof adding Sc to these alloys may be either to stabilise themicrostructure of wrought semiproducts (extrusionsrolled plates forgings etc) as discussed in the sectionon lsquoRecrystallisation resistancersquo above or to provideextra strength to the alloy through precipitation hard-ening In the latter case it is appropriate to considerwhether the Sc-containing alloy still should be classifiedas non-heat-treatable A heat treatment is applied thatbrings about a significant precipitation hardening On theother hand the hardness increase that is achieved throughthe heat treatment is lower than what is normallyassociated with heat-treatable alloy systems Hence eventhough it seems like a contradiction one chooses to keepusing the term lsquonon-heat-treatablersquo about these alloys

Table 7 gives an overview of some mechanicalproperties of Sc-containing non-heat-treatable alloysthat are reported in the literature Most of theexperimental work on Sc in 1xxx-types of alloys hasbeen done on binary AlndashSc alloys with much higherpurity than industrial alloys

Strengthening mechanisms

When the precipitates are larger than a critical size thestrengthening effect is due to the Orowan-mechanism iedislocations can only pass the precipitates by looping Inthis case the strengthening effect of the particles isapproximately inversely proportional to the mean parti-cle spacing When the precipitates can be sheared bydislocations there are a number of strengthening mechan-isms that apply It is proposed by Parker et al108 that thetwo major contributing mechanisms are coherency strainand anti-phase-boundary energy In a recent detailedstudy of strengthening mechanisms in binary AlndashSc alloysby Marquis and colleagues117118 the strengthening fromshear modulus mismatch between the matrix and theprecipitates is also accounted for A qualitatively goodmatch between theoretical strengthening and measuredvalues is achieved in this work both for deformation atroom temperature and at 300uC

Effect of Sc on precipitation strengthening in heat-treatablealloys

Following the AA designation system the traditionalheat-treatable Al-alloys are those that belong to the 2xxx

Roslashyset and Ryum Scandium in aluminium alloys

36 International Materials Reviews 2005 VOL 50 NO 1

series (AlndashCu) 6xxx series (AlndashMgndashSi) and 7xxx series(AlndashZnndashMg) AlndashLi alloys should also be mentionedSeveral investigations have been carried out in order toclarify the effects of Sc on the precipitation behaviour inthese alloy systems

AlndashCu alloys

The precipitation sequence in AlndashCu alloys is oftendescribed as follows

Supersaturated solid solutionRGP-zonesRh0Rh9Rh(Al2Cu)

The highest strength is normally achieved when the h0or h9 precipitates are predominant Typical precipitationheat treatment temperatures for AlndashCu alloys are in therange 160ndash190uC238 which is considerably lower thanthe typical precipitation temperature for Al3ScComparisons of the aging responses of AlndashCu and AlndashCundashSc alloys at 150 and 200uC indicate that there is nonoticeable effect of Sc on the precipitation kinetics ofh9153 It is observed that the h9 precipitates may nucleateon Al3Sc particles153 At 300uC it is observed that h9particles are somewhat smaller in AlndashCundashSc alloys thanin AlndashCu alloys156

AlndashMgndashSi alloys

The following precipitation sequence is commonlyreported for AlndashMgndashSi alloys

Supersaturated solid solutionRGP-zonesRb0Rb9Rb(Mg2Si)

For peak aged alloys the predominant precipitatetype is b0 for which the stoichiometric composition hasrecently been resolved to be Mg5Si6239 Temperatures inthe range 160ndash205uC are typically used for precipitationhardening of these alloys238 Adding both 03 wt-Scand 01 wt-Zr to an Alndash06 wt-Mgndash065 wt-Sialloy does not seem to alter the precipitation kineticsof b0 at 165uC However the hardness increase becauseof precipitation hardening appears to be smaller in theSczZr-containing alloy240 In another investigationadditions of 01 wt-Sc 015 wt-Sc 02 wt-Sc04 wt-Sc and 02 wt-Scz01 wt-Zr were made toan Alndash08 wt-Mgndash07 wt-Si alloy241 Here it wasalso observed that the precipitation kinetics of b0 wasseemingly independent of the Sc additions (Fig 28)TEM observations indicated that the b0 precipitateswere of comparable sizes in the investigated alloys andno interactions between Al3Sc and b0 were observed(Fig 29) In a third study242 where the effect of Sc onthe precipitation in an AlMgSindashSiC metal matrixcomposite was investigated there also does not seemto be any effect on the precipitation kinetics Howevercontrary to the findings of Ref 240 it is reported thatthe Sc addition leads to a higher hardness increase thanin the corresponding Sc free alloy

AlndashMgndashZn alloys

For these alloys the following precipitation sequence isoften ascribed

Table 7 Mechanical properties in non-heat-treatable Al-alloys with Sc

Reference Alloy wt- YS MPa UTS MPa Note

1xxx alloys171 000Sc 15 48 Cast material aged 288uC8 h

023Sc 159 185 Cast material aged 288uC8 h038Sc 199 220 Cast material aged 288uC8 h000Sc 14 49 Cold rolled material (89) aged 288uC8 h023Sc 198 208 Cold rolled material (89) aged 288uC8 h038Sc 240 264 Cold rolled material (89) aged 288uC8 h000Sc 8 34 Cold rolled material quenched from 649uC aged 288uC8 h023Sc 147 157 Cold rolled material quenched from 649uC aged 288uC8 h038Sc 193 199 Cold rolled material quenched from 649uC aged 288uC8 h

121 05Sc 160 ndash Forged material quenched from 635uC aged 250uC50 h23 05Sc 298 319 Hot rolled 288uC cold rolled 69ndash81 aged 288uC4 h112 01Sc 132 166 Hot z cold rolled material quenched from 630uC

aged 320uC133 h148 02Sc 138 ndash Cast material aged 300uC10 h compression test159 04Sc 196 ndash Cast material aged 300uC10 h compression test117 118 03Sc 209 ndash Cast material quenched from 648uC aged 300uC5 h

compression test3xxx alloys171 1Mn 015Sc 216 221 Cold rolled material (89) aged 288uC8 h

1Mn 05Sc 309 323 Cold rolled material (89) aged 288uC8 h186 05Mn 02Mg

026Sc 015Zr162 201 Extruded material solutionised 600uC aged 250uC

5xxx alloys171 1Mg 43 111 Cold rolled material (89) aged 288uC8 h

1Mg 03Sc 288 303 Cold rolled material (89) aged 288uC8 h53Mg 147 259 Cold rolled material (50) wintermediate anneals

at 343uC aged 288uC8 h53Mg 03Sc 368 401 Cold rolled material (50) wintermediate anneals

at 343uC aged 288uC8 h23 2Mg 05Sc 376 401 Hot rolled 288uC cold rolled 69ndash81 aged 288uC4 h

4Mg 05Sc 414 4606Mg 05Sc 433 503

237 4Mg 1Sc 420 525 Cold rolled material (83) aged 320uC1 h148 4Mg 02Sc 194 ndash Cast material aged 300uC10 h compression test

Tensile test data except where noted YS yield strength UTS ultimate tensile strength

Roslashyset and Ryum Scandium in aluminium alloys

International Materials Reviews 2005 VOL 50 NO 1 37

Supersaturated solid solutionRGP-zonesRg9Rg(Zn2Mg)

The maximum hardness is normally achieved whenthe g9 precipitates are predominant Common precipita-tion hardening temperatures are in the range 95ndash180uCand a two-step precipitation heat treatment within thistemperature regime is often used238 It has beenobserved in some investigations that Sc and SczZradditions to AlndashMgndashZn alloys slow down the precipita-tion of g9 somewhat243 Other investigations find thatthere is no effect of Sc on the precipitation behaviour ofg9244245 and yet others report that Sc additionssignificantly speed up the precipitation of g9246 In Ref247 it is found that an Sc addition leads to coarser g9precipitates and it is claimed that this gives an improvedductility of the alloy The strength-loss associated withlarger particle size is reported to be counterbalanced bystrengthening from Al3Sc precipitates

AlndashLi alloys

The precipitation sequence in binary AlndashLi alloys isapparently simple

Supersaturated solid solutionRd9Rd (AlLi)

where d9 is the metastable Al3Li phase which just likeAl3Sc has the L12 type of atomic arrangement Thetypical temperature regime for precipitation of d9 whichis the strengthening phase in this system is approx 150ndash200uC A comparison of the age hardening response ofan Alndash26 wt-Li and an Alndash24 wt-Lindash019 wt-Scalloy at 180uC248 and 200uC161 indicates that the onsetof d9 precipitation is not altered by the presence of ScThe hardness curves for the two alloys are practicallyidentical at 200uC whereas at 180uC the peak hardnesslevel is slightly higher in the AlndashLi than the AlndashLindashScalloy DSC measurements at constant heating ratesindicate that the addition of Sc to an AlndashLi alloysincreases the activation energy for d9 precipitation andmoves the exothermic peak associated with d9 precipita-tion to a higher temperature248 For specimens aged at

either 180uC or 200uC TEM observations reveal that thed9 precipitates are much smaller in the Sc containingalloy than in binary AlndashLi both in the peak agedcondition and in the overaged condition161248 Additionof Sc has also been observed to reduce the size of d9precipitates in other AlndashLi based alloys249ndash251 In an AlndashLindashCundashZr alloy an addition of Sc has been reported toslow down the homogeneous precipitation of d9252253 Ithas been claimed that Sc reduces the quench sensitivityand delays room temperature aging of AlndashLi basedalloys254ndash256

When present in the microstructure before the pre-cipitation of d9 the Al3Sc precipitates may act as effec-tive nucleation sites for d9 The resulting precipitates arespheres of d9 with a core of Al3Sc161249252ndash255257ndash261

Corrosion resistanceAn appreciable amount of data is available on the effectsof Sc on the corrosion behaviour of wrought Al-alloysSome of these effects are apparently derived from theeffects of Sc on the microstructure of the alloys It hasbeen reported that an addition of Sc increases thecorrosion potential (makes it less negative) in pureAl262ndash264 in AlndashZn alloys265266 AlndashMg alloys267 AlndashZnndashMgndashCu alloys264268 AlndashCundashMgndashMn alloys264 andin AlndashCundashLindashMgndashAg alloys264 Even though Sc alsohas been reported to decrease the corrosion potential in

28 Age hardening response at 175uC for Alndash08 wt-Mgndash

07 wt-Si alloy (Base) with additions of 02 wt-Sc

04 wt-Sc and 02 wt-Scz01 wt-Zr from Ref 241

29 TEM images of a b0 precipitates in Alndash08 wt-Mgndash

07 wt-Si alloy and b b0 and Al3(Sc1ndashxZrx) in a similar

alloy with addition of 02 wt-Scz01 wt-Zr from

Ref 241

Roslashyset and Ryum Scandium in aluminium alloys

38 International Materials Reviews 2005 VOL 50 NO 1

AlndashMg alloys269270 it seems that the general trend isthat adding Sc to an alloy makes it slightly more nobleThe change in corrosion potential is much morepronounced when Sc is added in amounts larger thanthe eutectic composition263 ie there is a considerablecontribution from primary or eutectic Al3Sc to theoverall potential It has also been demonstrated that thechange in corrosion potential caused by Sc can dependon the heat treatment applied to the alloy267268

Even though the corrosion potential is an essentialparameter in establishing the corrosion behaviour of analloy an increase in the corrosion potential does notnecessarily imply an improved self-corrosion resistanceHowever measurements of corrosion rates and passiva-tion current densities strongly suggest that the self-corrosion resistance in general is considerably improvedwhen Sc is added to wrought Al-alloys263264267 Someobserved variations in corrosion potential and passiva-tion current densities with Sc content in binary AlndashScalloys are plotted in Fig 30

Material failure in corrosive environments is often dueto localised corrosion attacks which may propagaterapidly even though the bulk material has a goodresistance against general corrosion It has been pointedout that hypereutectic additions of Sc may lead tomicrogalvanic corrosion beside primary Al3Sc parti-cles264 In AlndashMg alloys grain boundary precipitation ofAl8Mg5 can lead to localised corrosion attacks such asintergranular corrosion (IGC) exfoliation corrosion(EC) and stress corrosion cracking (SCC) In wroughtmaterial such precipitation may occur in the 60ndash180uCtemperature regime and heating in this temperaturerange is referred to as lsquosensitationrsquo An AlndashMgndashSc alloywas found to be immune against intergranular corrosionand have moderate susceptibility to exfoliation corro-sion after annealing at 350uC271 After sensitation heattreatments severe IGC and EC was observed but notquite as severe as in a corresponding alloy without ScAs for SCC the AlndashMgndashSc alloy was found to be highlyresistant271 In another study it was found that additionof 056 wt-Sc reduces the SCC susceptibility of an Alndash68 wt-Mg alloy in the as-rolled state and afterannealing at 250uC whereas in a sensitised specimenthe SCC susceptibility is somewhat increased by the Scaddition272 A third investigation found that Sc has nomeasurable detrimental effect on the SCC susceptibilityof sensitised Alndash5Mgndash015Zr alloy273 SCC is also a

severe problem in high strength AlndashZnndashMgndashCu alloys Ithas been shown that small Sc additions are effective inreducing the SCC sensitivity of these alloys244246268274

Use of Sc-containing Al alloysA systematic development of Sc-containing aluminiumalloys took place in the former USSR in the 1980s andthe interest for Sc as an alloying element in aluminiumalloys hit the western world approximately 10 yearslater Even though a number of improvements in Alalloys achieved by Sc addition have been demonstratedthe current uses of such alloys are very limited This isrelated to the very high price of scandium

In Russia some parts of military aircraft are made ofSc-containing AlndashLi alloys In the western world themain usage of Sc-containing alloys is for sportsequipment Ashurst Technology and Kaiser Aluminumdeveloped a Sc-containing 7xxx alloy for baseball andsoftball bats which was introduced to the Americanmarket in 1997 by Easton Alcoa soon followed with aSc-containing alloy for a competing brand of batsLouisville Slugger Since then several new and improvedSc-containing alloys for bats have been introduced tothe market The purpose of adding Sc is to increase theyield strength of the alloy allowing for a down-gaugingof the wall thickness which in turn gives a strongerlsquospring-rsquo or lsquotrampoline-rsquo effect when the ball hits thebat

Shortly after the introduction of the Sc containingbats Easton also launched Sc-containing 7xxx tubingfor bicycle frames Just as in the bats Sc increases theyield strength of the alloy allowing for down-gauging oftube wall thickness and a corresponding weight reduc-tion of the bicycle frame An Italian manufacturer ofbicycle tubing Dedacciai also delivers tubes in a Sc-containing 7xxx alloy

Other sports equipment made from Sc-containingaluminium alloys includes lacrosse sticks and tent polesSmith and Wesson has also introduced a series ofhandguns where the frame is made from a Sc-containingAl alloy

A common factor for the items mentioned above isthat the material cost is only a minor part of the totalmanufacturing cost of the end product and also thatthese products are aimed at a group of customers thathave a certain awareness of new materials Both baseballbats and bicycle frames have been marketed aslsquoscandium alloyrsquo even though the Sc content is muchlower than 1

Currently AlndashSc master alloys for the production ofSc-containing Al alloys are available at a price thatcorresponds to US$ 2000 per kg of Sc This means that ifone wants to add 02 wt-Sc to an alloy which is afairly common content one also increases the price ofthe alloy by US$ 4 per kg alloy Depending on the alloytype Sc is added to this represents a tripling orquadrupling of the price of the alloy There are notmany existing products where such an increase inmaterial cost can be justified In order to see awidespread use of Sc in high-volume products the Scprice has to come down considerably Actually the priceof adding Sc to Al alloys has gone down by a factor 3ndash10over the last 10ndash15 years and substantial price reduc-tions are also expected in the future

30 Observed variations in corrosion potential and passi-

vation current densities with Sc content in binary Alndash

Sc alloys based on data from Ref 263

Roslashyset and Ryum Scandium in aluminium alloys

International Materials Reviews 2005 VOL 50 NO 1 39

The current production of AlndashSc master alloys isbased upon and will continue to be based upon for theforeseeable future the reduction of Sc2O3 or other Sccompounds directly in molten aluminium It is notnecessary as many tend to believe to take the route viametallic Sc Thus the price of AlndashSc master alloy isgoverned by the price of Sc2O3 or other Sc compoundsin question and not by the price of metallic scandiumThe Sc2O3 which is the main source for todayrsquos AlndashScmaster alloy production comes from stockpiles in theformer USSR These stockpiles will be exhausted withina few years and new reliable sources of Sc2O3 or otherSc compound production are sought It turns out thatthe most economically viable option that has beendisclosed so far is the processing of Red Mud from theBayer process of extracting alumina from bauxiteScandium is enriched in the Red Mud and is extractedfrom a Red Mud aqueous slurry by selective leachingsubsequent ion-exchange procedure and finally a liquidndashliquid extraction procedure It is not required to build aseparate lsquoSc factoryrsquo to do this but rather build an lsquoadd-onrsquo to existing Bayer process plants Such a processroute is expected to bring down the price of Sc2O3

considerably which in turn means that AlndashSc masteralloy price should drop accordingly Preliminary ana-lyses suggest a price of approx US$ 400 per kg Sc in themaster alloy which translates to an added cost of 80cent per kilo when 02 wt-Sc is added to an aluminiumalloy This is also a considerable increase in the materialcost but with such prices one should expect to see Sccontaining alloys in many more applications than whatis the case at the present time

Concluding remarksThe body of published investigations on Al-based alloyswith Sc addition provides a sound basis of knowledgefor metallurgists that want to look into the possibility ofenhancing the performance of a wrought Al-alloy byadding Sc to it Ternary AlndashScndashX phase diagrams areavailable for practically every technologically importantalloying element in Al The effect of a wide range ofternary alloying elements on the precipitation behaviourof Al3Sc is accounted for It has been shown that theAl3Sc phase can be effective as a grain refiner adispersoid former and a precipitate hardening agentand some of the underlying conditions for achieving thedesired Al3Sc formation have been outlined Addingsome Zr together with Sc has proven to be beneficial Itmay lead to effective grain refinement at a lower Sc levelbut the most prominent effect is the refinement indispersoid distribution that can be achieved An addi-tion of Sc has little if any effect on precipitation in the2xxx 6xxx and 7xxx alloy systems and some effects onthe precipitation in AlndashLi based alloys With respect tocorrosion behaviour adding Sc to an Al-alloy does ingeneral seem to make the alloy slightly more noble andto increase its self-corrosion resistance Scandium-containing Al alloys have very few uses at the presenttime as a result of the high price of scandium The priceof Sc is expected to decrease significantly in the futureand this should lead to the disclosure of moreapplications where it is economically feasible to takeadvantage of the improved properties of some Sc-containing aluminium alloys

References1 D R Lide lsquoCRC handbook of chemistry and physicsrsquo 71st edn

4ndash29 1990 Boston USA CRC Press

2 E M Savitsky V F Terehova I V Burov and O P Naumkin

Proc Fourth Conf on lsquoRare earth researchrsquo Phoenix Arizona

USA April 1964 409ndash420

3 E M Savitskii V F Terekhova I V Burov O P Naumkin and

I A Markova Inorg Mater 1965 1 1503ndash1512

4 O P Naumkin V T Terekhova and E M Savitskiy Russ

Metall 1965 (4) 128ndash136

5 W G Moffatt lsquoThe handbook of binary phase diagramsrsquo 1981

Schenectady NY USA General Electric Co

6 E A Brandes (ed) lsquoSmithells metals reference bookrsquo 6th edn

1983 London UK Butterworths

7 R P Elliott and F A Shunk Bull Alloy Phase Diagrams 1981

2 (2) 222ndash223

8 K A Gschneider Jr and F W Calderwood Bull Alloy Phase

Diagrams 1989 10 34ndash36

9 H Okamoto J Phase Equil 1991 12 612ndash613

10 J L Murray J Phase Equil 1998 19 380ndash384

11 M E Drits E S Kadaner T V Dobatkina and N I Turkina

Russ Metall 1973 (4) 152ndash154

12 S-I Fujikawa M Sugaya H Takei and K-I Hirano J Less-

Common Met 1979 63 87ndash97

13 N Blake and M A Hopkins J Mater Sci 1985 20 2861ndash2867

14 V I Kononenko and S V Golubev Russ Metall 1990 (2) 193ndash

195

15 T B Massalski J L Murray L H Bennett and H Baker (eds)

lsquoBinary alloy phase diagramsrsquo 1986 Metals Park OH USA

ASM

16 G Cacciamani P Riani G Borzone N Parodi A Saccone

R Ferro A Pisch and R Schmid-Fetzer Intermetallics 1999 7

101ndash108

17 H Okamoto J Phase Equil 2000 21 310

18 A F Norman P B Pragnell and R S McEwen Acta Mater

1998 46 5715ndash5732

19 I N Pyagai and A V Vakhobov Russ Metall 1990 (5) 50ndash52

20 C L Fu J Mater Res 1990 5 971ndash979

21 X Lu and Y Wang Calphad 2002 26 555ndash561

22 R R Sawtell and J W Morris Jr Proc lsquoDispersion strengthened

aluminium alloysrsquo Phoenix Arizona USA January 1988 409ndash

420

23 R R Sawtell and C L Jensen Metall Trans A 1990 21A 421ndash

430

24 L A Willey Unpublished research Alcoa 1970 Data points are

extracted from Ref 10

25 N I Turkina and V I Kuzmina Russ Metall 1976 (4) 179ndash

183

26 T Torma E Kovacs-Csetenyi I Vitanyi M Butova and

J Stepanov Proc 6th Int Symp on lsquoHigh purity materials in

science and technologyrsquo Akademie der Wissenschaften der DDR

Dresden Germany May 1985 388ndash389

27 A L Berezina V A Volkov B P Domashnikov and K V

Chuistov Metallofizika 1987 9 (5) 43ndash47

28 H-H Jo J Korean Inst Metals 1990 28 499ndash504

29 H-H Jo and S-I Fujikawa Mater Sci Eng 1993 A 171 151ndash

161

30 S Celotto and T J Bastow Philos Mag A 2000 80 1111ndash1125

31 J Roslashyset and N Ryum submitted to Mater Sci Eng

32 M E Drits L S Toropova Yu G Bykov F L Gushchina V I

Elagin and Yu A Filatov Russ Metall 1983 (1) 150ndash153

33 L S Toropova D G Eskin M L Kharakterova and T V

Dobatkina lsquoAdvanced aluminum alloys containing scandium

structure and propertiesrsquo 1998 Amsterdam The Netherlands

Gordon and Breach Science Publishers

34 V V Cherkasov P P Pobezhimov L P Nefedova E V Belov

and G M Kuznetsov Met Sci Heat Treat 1996 (6) 268ndash270

35 Kh O Odinaev I N Ganiev V V Kinzhibalo and B Ya

Kotur Dokl Akad Nauk Tadzh SSR 1989 32 37ndash38

36 Kh O Odinaev I N Ganiev and A V Vakhobov Russ Metall

1991 (4) 200ndash203

37 J Grobner R Schmid-Fetzer A Pisch G Cacciamani P Riani

N Parodi G Borzone A Saccone and R Ferro Z Metallkd

1999 90 872ndash880

38 E A Marquis and D N Seidman Microsc Microanal 2002 8

(Suppl 2) 1100CDndash1101CD

39 A Pisch J Grobner and R Schmid-Fetzer Mater Sci Eng A

2000 A 289 123ndash129

Roslashyset and Ryum Scandium in aluminium alloys

40 International Materials Reviews 2005 VOL 50 NO 1

40 C Xia F Zeng and Y Gu Trans Nonferrous Met Soc China

2003 13 1124ndash1127

41 M Yu Teslyuk and V S Protasov Sov Phys Crystallogr 1966

10 470ndash471

42 M L Kharakterova and T V Dobatkina Russ Metall 1988

(6) 175ndash178

43 M L Kharakterova Russ Metall 1991 (4) 195ndash199

44 L S Toropova M L Kharakterova and D G Eskin Russ

Metall 1992 (3) 194ndash199

45 P Riani L Arrighi R Marazza D Mazzone G Zanicchi and

R Ferro J Phase Equil Diff 2004 25 22ndash52

46 A T Tyvanchuk T I Yanson B Ya Kotur O S Zarechnyuk

and M L Kharakterova Russ Metall 1988 (4) 190ndash192

47 L L Rokhlin T V Dobatkina and M L Kharakterova Powder

Metall Met Ceram 1997 36

48 A Z Ikromov I N Ganiev and V V Kinzhibalo Dokl Akad

Nauk Tadzh SSR 1990 (6) 391ndash392

49 I N Ganiev A Z Ikromov and V G Khudoiberdiev Russ

Metall 1995 (3) 125ndash127

50 I N Fridlyander L L Rokhlin T V Dobatkina and N I

Nikitina Met Sci Heat Treat 1993 (10) 567ndash571

51 I N Fridlyander L L Rokhlin T V Dobatkina V V

Kinzhibalo and A T Tyvanchuk Russ Metall 1998 (1) 161ndash

166

52 R A Emigh E L Bradley and J W Morris Jr in lsquoLight-weight

alloys for aerospace applications IIrsquo (ed E W Lee and N J

Kim) 27ndash43 1991 TMS

53 L S Toropova A N Kamardinkin V V Kindzhibalo and A T

Tyvanchuk Phys Met Metall 1990 70 (6) 106ndash110

54 A N Kamardinkin T V Dobatkina and T D Rostova Russ

Metall 1991 (4) 216ndash218

55 L S Torodskaya T V Dobatkina and A N Kamardinkin

Russ Metall 1992 (5) 128ndash131

56 E M Sokolovskaya E F Kazakova E I Poddyakova and A

A Ezhov Met Sci Heat Treat 1997 (5) 211ndash213

57 Y Harada and D C Dunand Mater Sci Eng 2002 A 329ndash331

686ndash695

58 N E Drits L S Toropova and F L Gushchina Russ Metall

1984 (4) 229ndash232

59 E M Sokolovskaya E F Kazakova V A Alikhanov and E V

Zhuravleva Moscow Univ Chem Bull 1997 52 (5) 70ndash72

60 E M Sokolovskaya E F Kazakova and E I Poddyakova Met

Sci Heat Treat 1989 (11) 837ndash839

61 G M Cheldieva E F Kazakova E M Sokolovskaya and N I

Kaloev Russ Metall 1990 (6) 87ndash90

62 E M Sokolovskaya E F Kazakova and O D-S Kendivan

Russ Metall 1998 (4) 135ndash137

63 N G Bukhanko E F Kazakova and E M Sokolovskaya Russ

Metall 2001 (4) 425ndash431

64 E D Trubnyakova O I Bodak I N Ganiev and A V

Vakhobov Russ Metall 1987 (3) 219ndash222

65 I N Fridlyander and L V Molchanova Russ Metall 2003 (5)

476ndash480

66 R A Altynbaev S Kh Khairidinov and A V Vakhobov Russ

Metall 1987 (4) 194ndash196

67 J C Schuster and J Bauer J Less-Common Met 1985 109

345ndash350

68 L L Rokhlin A S Fridman T V Dobatkina and D G Eskin

Russ Metall 1991 (6) 146ndash148

69 A S Fridman T V Dobatkina and E V Muratova Russ

Metall 1992 (1) 207ndash209

70 C Xia F Zeng and Y Gu Trans Nonferrous Met Soc China

2003 13 546ndash552

71 F Zeng C Xia and Y Gu J Alloys Comp 2004 363 175ndash181

72 L L Rokhlin T V Dobatkina N R Bochvar and E V Lysova

J Alloys Comp 2004 367 10ndash16

73 T V Dobatkina A S Fridman and E V Muratova Russ

Metall 1992 (5) 125ndash127

74 I N Fridlyander L L Rokhlin N R Bochvar E V Lysova

and O V Boteva Russ Metall 2001 (6) 661ndash666

75 V N Rechkin L K Lamikhov and T I Samsonova Sov Phys

Crystallogr 1964 9 325ndash327

76 I I Zalutskii and P I Kripyakevich Sov Phys Crystallogr

1967 12 341ndash343

77 T J Bastow C T Forwood M A Gibson and M E Smith

Phys Rev B 1998 58 2988ndash2997

78 K Fukunaga M Kolbe K Yamada and Y Miura Mater Sci

Eng 1997 A 234ndash236 594ndash597

79 E P George J A Horton W D Porter and J H Schneibel

J Mater Res 1990 5 1639ndash1648

80 E P George D P Pope C L Fu and J H Schneibel ISIJ Int

1991 31 1063ndash1075

81 Y Harada and D C Dunand Acta Mater 2000 48 3477ndash3487

82 J H Schneibel and E P George Scripta Metall Mater 1990 24

1069ndash1074

83 J H Schneibel and P M Hazzledine Mater Res Soc Symp

Proc 1991 213 323ndash328

84 J H Schneibel and P M Hazzledine J Mater Res 1992 7

868ndash875

85 C J Sparks E D Specht G E Ice P Zschack and J Schneibel

Mater Res Soc Symp Proc 1991 213 363ndash368

86 J Tarnacki and Y-W Kim Scripta Metall Mater 1989 23

1063ndash1068

87 M Asta V Ozolins and C Woodward JOM 2001 53 (9) 16ndash

19

88 M E Drits L S Toropova F L Gushchina and S G Fedotov

Sov Non-Ferrous Met Res 1984 12 83ndash85

89 Y Harada and D C Dunand Scripta Mater 2003 48 219ndash222

90 C Woodward M Asta G Kresse and J Hafner Phys Rev B

2001 63 094103-1-6

91 J-H Xu and A J Freeman Phys Rev B 1990 41 12553ndash12561

92 M F Bartholomeusz and J A Wert Acta Metall Mater 1992

40 673ndash682

93 G Bester and M Fahnle J Phys Condens Matter 2001 13

11551ndash11565

94 C L Fu and M H Yoo Proc lsquoOrdered intermetallics ndash physical

metallurgy and mechanical behaviorrsquo Irsee Germany June 1991

155ndash164

95 K Fukunaga T Shouji and Y Miura Mater Sci Eng 1997 A

239ndash240 202ndash205

96 D P Pope Proc lsquoOrdered intermetallics ndash physical metallurgy

and mechanical behaviorrsquo Irsee Germany June 1991 143ndash153

97 J-S Wang Acta Mater 1998 46 2663ndash2674

98 M H Yoo and C L Fu Mater Sci Eng 1992 A 153 470ndash478

99 R W Hyland Jr and R C Stiffler Scripta Metall Mater 1991

25 473ndash477

100 I G Brodova I V Polents O A Korzhavina P S Popelrsquo I P

Korshunov and V O Esin Melts 1992 4 392ndash397

101 I G Brodova O A Chikova I V Polents P S Popelrsquo and V O

Esin Casting Processes 1992 1 (2) 158ndash160

102 I G Brodova D V Bashlikov and I V Polents Mater Sci

Forum 1998 269ndash272 589ndash594

103 K B Hyde A F Norman and P B Pragnell Mater Sci Forum

2000 331ndash337 1013ndash1018

104 K B Hyde A F Norman and P B Pragnell Acta Mater 2001

49 1327ndash1337

105 J Roslashyset and N Ryum Proc 6th Int Conf on lsquoAluminum

alloysrsquo Toyohashi Japan July 1998 793ndash798

106 V I Elagin V V Zakharov and T D Rostova Met Sci Heat

Treat 1993 (6) 317ndash319

107 R W Hyland Jr Metall Trans A 1992 23A 1947ndash1955

108 B A Parker Z F Zhou and P Nolle J Mater Sci 1995 30

452ndash458

109 C L Rohrer M D Asta S M Foiles and R W Hyland Jr

Mater Res Soc Symp Proc 1996 398 477ndash482

110 G M Novotny and A J Ardell Mater Sci Eng 2001 A 318

144ndash154

111 J D Robson M J Jones and P B Pragnell Acta Mater 2003

51 1453ndash1468

112 C Tan Z Zheng and B Wang Proc 3rd Int Conf on

lsquoAluminium alloysrsquo Vol I NTH Trondheim Norway June

1992 290ndash294

113 M Nakayama A Furuta and Y Miura Mater Trans JIM

1997 38 852ndash857

114 E A Marquis and D N Seidman Acta Mater 2001 49 1909ndash

1919

115 M J Jones and F J Humphreys Acta Mater 2003 51 2149ndash

2159

116 E A Marquis D N Seidman and D C Dunand in lsquoCreep

deformation fundamentals and applicationsrsquo (ed R S Mishra

J C Earthman and S V Raj) 299ndash308 2002 TMS

117 D N Seidman E A Marquis and D C Dunand Acta Mater

2002 50 4021ndash4035

118 E A Marquis D N Seidman and D C Dunand Acta Mater

2003 51 285ndash287

119 M E Drits L S Toropova U G Bikov and G K Anastaseva

Proc lsquoDiffusion in metals and alloysrsquo Tihany Hungary Augustndash

September 1982 616ndash623

120 V I Elagin V V Zakharov and T D Rostova Met Sci Heat

Treat 1983 (7) 546ndash549

Roslashyset and Ryum Scandium in aluminium alloys

International Materials Reviews 2005 VOL 50 NO 1 41

121 M Ye Drits L B Ber Yu G Bykov L S Toropova and G K

Anastaseva Phys Met Metall 1984 57 (6) 118ndash126

122 M E Drits L S Toropova and Yu G Bykov Sov Non-Ferrous

Met Res 1985 13 309ndash314

123 V I Yelagin V V Zakharov S G Pavlenko and T D Rostova

Phys Met Metall 1985 60 (1) 88ndash92

124 N Sano Y Hasegawa K Hono H Jo K Hirano H W

Pickering and T Sakurai Journal de Physique 1987 48 C6 337ndash

342

125 N Sano H-H Jo K-I Hirano and T Sakurai J Jpn Inst

Metals 1989 39 444ndash450

126 N Sano H Jo K Hirano and T Sakurai Proc Second Int

Conf on lsquoAluminium alloysrsquo Beijing China October 1990 549ndash

554

127 Y Miura M Nakayama and A Furuta Proc lsquoAspects of high

temperature deformation and fracture in crystalline materialsrsquo

Nagoya Japan July 1993 255ndash262

128 Y W Riddle and T H Sanders Jr Mater Sci Forum 2000

331ndash337 939ndash944

129 Y W Riddle M McIntosh and T H Sanders Jr in lsquoLightweight

alloys for aerospace application VIrsquo (ed K Jata E W Lee

W Frazier and N J Kim) 25ndash39 2001 TMS

130 M E Drits J Dutkiewicz L S Toropova and J Salawa Crystal

Res Technol 1984 19 1325ndash1330

131 Y W Riddle MSc thesis Georgia Tech GA USA 1998

132 T J Bastow and S Celotto Mater Sci Eng 2003 C 23 757ndash

762

133 M C Carroll M J Mills G S Daehn P I Gouma M F

Savage and B R Dunbar in lsquoAutomotive Alloys 1999rsquo (ed

S Das) 239ndash246 2000 TMS

134 E Clouet M Nastar and C Sigli Phys Rev B 2004 69 064109-

1-14

135 V V Zakharov Met Sci Heat Treat 1997 (2) 61ndash66

136 J W Christian lsquoThe theory of transformation in metals and

alloysrsquo 2nd edn 1975 Pergamon Press Ltd

137 A L Berezina V A Volkov B P Domashnikov S V Ivanov

and K V Chuistov Phys Metals 1990 10 296ndash304

138 S-I Fujikawa and S Sakauchi Proc 6th Int Conf on

lsquoAluminum alloysrsquo Toyohashi Japan July 1998 805ndash810

139 Y S Touloukian R K Kirby R E Taylor and P D Desai

(eds) lsquoThermal expansion metallic elements and alloysrsquo 1975

New York Plenum

140 J Roslashyset and N Ryum submitted to Scripta Mater

141 R O Simmons and R W Balluffi Phys Rev 1960 117 52ndash61

142 M Ocko E Babic R Krsmik E Girt and B Leontic J Phys F

Metals Phys 1976 6 703ndash707

143 M J Jones and F J Humphreys Proc First Joint Int Conf on

lsquoRecrystallization and grain growthrsquo Aachen Germany August

2001 Springer Verlag 1287ndash1292

144 S Iwamura M Nakayama and Y Miura Mater Sci Forum

2002 396ndash402 1151ndash1156

145 S Iwamura and Y Miura Acta Mater 2004 52 591ndash600

146 M Asta S M Foiles and A A Quong Phys Rev B 1998 57

11265ndash11275

147 R W Hyland Jr M Asta S M Foiles and C L Rohrer Acta

Mater 1998 46 3667ndash3678

148 J Roslashyset and N Ryum Proc 4th Int Conf on lsquoAluminium

alloysrsquo Vol I Atlanta GA USA September 1994 194ndash201

149 M E Drits L S Toropova G K Anastaseva and G L

Nagornichnykh Russ Metall 1984 (3) 192ndash195

150 E A Marquis D N Seidman and D C Dunand Acta Mater

2003 51 4751ndash4760

151 M E Drits L S Toropova and Yu G Bykov Met Sci Heat

Treat 1983 (7) 550ndash554

152 V V Zakharov and T D Rostova Met Sci Heat Treat 1995

(2) 65ndash69

153 M Nakayama and Y Miura Proc 4th Int Conf on lsquoAluminium

alloysrsquo Vol I Atlanta GA USA September 1994 538ndash545

154 M Nakayama and Y Miura J Jpn Inst Light Metals 1996 46

275ndash279

155 M Nakayama T Okuyama and Y Miura Mater Sci Forum

2000 331ndash337 927ndash932

156 M Nakayama T Okuyama and Y Miura Proc 6th Int Conf

on lsquoAluminum alloysrsquo Toyohashi Japan July 1998 517ndash522

157 M L Kharakterova D G Eskin and L S Toropova Acta

Metall Mater 1994 42 2285ndash2290

158 V I Elagin V V Zakharov and T D Rostova Met Sci Heat

Treat 1992 (1) 37ndash45

159 H Wiik Siv Ing thesis NTH Institute of Metallurgy

Trondheim Norway 1995

160 J Roslashyset H Hovland and N Ryum Mater Sci Forum 2002

396ndash402 619ndash624

161 Y Miura K Horikawa K Yamada and M Nakayama Proc

4th Int Conf on lsquoAluminium alloysrsquo Vol II Atlanta GA USA

September 1994 161ndash168

162 Y W Riddle PhD thesis Georgia Tech GA USA 2000

163 B Forbord W Lefebvre F Danoix H Hallem and

K Marthinsen Scripta Mater 2004 51 333ndash337

164 J D Robson Acta Mater 2004 52 1409ndash1421

165 C B Fuller J L Murray and D N Seidman submitted to Acta

Mater 2004

166 M G Mousavi C E Cross and Oslash Grong Sci Technol Weld

Joining 1999 4 381ndash388

167 J S Vetrano S M Bruemmer L M Pawlowski and I M

Robertson Mater Sci Eng 1997 A 238 101ndash107

168 Y W Riddle and T H Sanders Jr Mater Sci Forum 2000

331ndash337 799ndash803

169 G M Khan A O Nikiforov V V Zakharov and I I Novikov

Tsvetnye Metally 1993 34 (11) 43ndash45

170 Z Horita M Furukawa M Nemoto A J Barnes and T G

Langdon Acta Mater 2000 48 3633ndash3640

171 L A Willey US Patent 3 619 181 9 November 1971

172 L K Lamikhov and G V Samsonov Tsvetnye Metally 1964 5

(8) 77ndash80

173 A L Berezina K V Chuistov N I Kolobnev L B

Khokhlatova and T A Monastyrskaya Mater Sci Forum

2002 396ndash402 741ndash746

174 F A Fasoyinu J Thomson D Cousineau T Castles and M

Sahoo Proc 6th Int AFS Conf on lsquoMolten aluminum

processingrsquo Orlando FL USA November 2001

175 Z Yin Q Pan Y Zhang and F Jiang Mater Sci Eng 2000

A 280 151ndash155

176 I I Novikov and O E Grushko Mater Sci Technol 1995 11

926ndash932

177 D Cousineau M Sahoo P D Newcombe T Castles and F A

Fasoyinu Proc lsquoAFS 105th casting congressrsquo Dallas TX USA

AprilndashMay 2001 157ndash184

178 C E Cross and Oslash Grong Proc 6th Int Conf on lsquoAluminum

alloysrsquo Toyohashi Japan July 1998 1441ndash1446

179 F A Costello J D Robson and P B Prangnell Mater Sci

Forum 2002 396ndash402 757ndash762

180 K B Hyde A F Norman and P B Prangnell Mater Sci

Forum 2002 396ndash402 39ndash44

181 M E Drits S G Pavlenko L S Toropova Yu G Bukov and

L B Ber Sov Phys Dokl 1981 26 (3) 344ndash346

182 A M Drits and B A Kopeliovich Russ Metall 1985 (4) 147ndash

151

183 V G Davydov V I Elagin V V Zakharov and T D Rostova

Met Sci Heat Treat 1996 (8) 347ndash352

184 M E Drits L S Toropova Yu G Bykov L B Ber and S G

Pavlenko Russ Metall 1982 (1) 148ndash152

185 T D Rostova V G Davydov V I Yelagin and V V Zakharov

Mater Sci Forum 2000 331ndash337 793ndash798

186 Y W Riddle H Hallem and N Ryum Mater Sci Forum 2002

396ndash402 563ndash568

187 J Roslashyset and Y W Riddle Proc 9th Int Conf on lsquoAluminium

alloysrsquo Brisbane Australia August 2004 1210ndash1215

188 A M Diskin V K Portnoi A M Drits and A A Alalykin Sov

Non-Ferrous Met Res 1986 14 499ndash500

189 R R Sawtell P E Bretz and C L Jensen US Patent 4 689 090

25 August 1987

190 G A Salishchev Yu B Timoshenko and R A Saitova Proc

Second Int Conf on lsquoAluminium alloysrsquo Beijing China October

1990 413ndash415

191 T G Nieh R Kaibyshev L M Hsiung N Nguyen and

J Wadsworth Scripta Mater 1997 36 1011ndash1016

192 T G Nieh L M Hsiung J Wadsworth and R Kaibyshev Acta

Mater 1998 46 2789ndash2800

193 J S Vetrano C H Henager Jr M T Smith and S M

Bruemmer in lsquoHot deformation of aluminum alloys IIrsquo (ed T R

Bieler L A Lalli and S R MacEwen) 407ndash418 1998 TMS

194 J S Vetrano C H Henager Jr S M Bruemmer Y Ge and

C H Hamilton in lsquoSuperplasticity and Superplastic Forming

1998rsquo (ed A K Gosh and T R Bieler) 89ndash97 1998 TMS

195 V Y Gertsman J S Vetrano C H Henager Jr and S M

Bruemmer Proc First Joint Int Conf on lsquoRecrystallization and

grain growthrsquo Aachen Germany August 2001 Springer Verlag

2001 837ndash842

196 Y Xiao C Gao H Ma and S Tian Trans Nonferrous Met Soc

China 2001 11 235ndash238

Roslashyset and Ryum Scandium in aluminium alloys

42 International Materials Reviews 2005 VOL 50 NO 1

197 A Gholinia F J Humphreys and P B Prangnell Acta Mater

2002 50 4461ndash4476

198 A Gholinia F J Humphreys and P B Prangnell Mater Sci

Forum 2002 408ndash412 1519ndash1524

199 S Komura P B Berbon M Furukawa Z Horita M Nemoto

and T G Langdon Scripta Mater 1998 38 1851ndash1856

200 S Komura P B Berbon A Utsunomiya M Furukawa

Z Horita M Nemoto and T G Langdon in lsquoHot deformation

of aluminum alloys IIrsquo (ed T R Bieler L A Lalli and S R

MacEwen) 125ndash138 1998 TMS

201 S Komura Z Horita M Furukawa M Nemoto and T G

Langdon J Mater Res 2000 15 2571ndash2576

202 S Komura M Furukawa Z Horita M Nemoto and T G

Langdon Mater Sci Eng 2001 A 297 111ndash118

203 S Komura Z Horita M Furukawa M Nemoto and T G

Langdon Metall Mater Trans A 2001 32A 707ndash716

204 Z Horita M Furukawa K Oh-ishi M Nemoto and T G

Langdon Proc Fourth Int Conf on lsquoRecrystallization and

related phenomenarsquo (ed T Sakai and H G Suzuki) 1999 The

Japan Institute of Metals 301ndash308

205 Z Horita S Komura P B Berbon A Utsunomiya

M Furukawa M Nemoto and T G Langdon Mater Sci

Forum 1999 304ndash306 91ndash96

206 Z Horita S Lee S Ota K Neishi and T G Langdon Mater

Sci Forum 2001 357ndash359 471ndash476

207 Z Horita T Fujinami K Sato S B Kang H W Kim and T G

Langdon in Proc James T Staley Honorary Symposium on

Aluminum Alloys lsquoAdvances in the metallurgy of aluminum

alloysrsquo (ed M Tiryakioglu) 271ndash275 2001 ASM

208 P B Berbon S Komura A Utsunomiya Z Horita

M Furukawa M Nemoto and T G Langdon Mater Trans

JIM 1999 40 772ndash778

209 M Nemoto Z Horita M Furukawa and T G Langdon Mater

Sci Forum 1999 304ndash306 59ndash66

210 M Furukawa Z Horita M Nemeto and T G Langdon Proc

lsquoLight Metals 1999rsquo Quebec City PQ Canada August 1999 583ndash

592

211 M Furukawa K Oh-ishi S Komura A Yamashita Z Horita

M Nemeto and T G Langdon Mater Sci Forum 1999 304ndash

306 97ndash102

212 M Furukawa A Utsunomiya K Matsubara Z Horita and

T G Langdon Acta Mater 2001 49 3829ndash3838

213 M Furukawa A Utsunomiya S Komura Z Horita M Nemoto

and T G Langdon Mater Sci Forum 2001 357ndash359 431ndash436

214 M Furukawa Z Horita and T G Langdon in Proc James T

Staley Honorary Symposium on Aluminum Alloys lsquoAdvances in

the metallurgy of aluminum alloysrsquo (ed M Tiryakioglu) 47ndash56

2001 ASM

215 M Furukawa Z Horita M Nemoto and T G Langdon Mater

Sci Eng 2002 A 324 82ndash89

216 M Furukawa Z Horita and T G Langdon in lsquoUltrafine grained

materials IIrsquo (ed Y T Zhu T G Langdon R S Mishra S L

Semiatin M J Saran and T C Lowe) 459ndash468 2002 TMS

217 T G Langdon M Furukawa Z Horita and M Nemoto Proc

NATO Advanced Research Workshop on lsquoInvestigations and

applications of severe plastic deformationrsquo Moscow August

1999 NATO Science Series Series 3 High Technology vol 80

Kluwer Academic Publishers The Netherlands 2000 149ndash154

218 S Lee H Akamatsu A Utsunomiya K Neishi M Furukawa

Z Horita and T G Langdon Proc Thermec 2000 Las Vegas

USA December 2000

219 S Lee A Utsunomiya H Akamatsu K Neishi M Furukawa

Z Horita and T G Langdon Acta Mater 2002 50 553ndash564

220 A Yamashita D Yamaguchi Z Horita and T G Langdon

Mater Sci Eng 2000 A 287 100ndash106

221 K Oh-ishi Z Horita D J Smith and T G Langdon J Mater

Res 2001 16 583ndash589

222 H Akamatsu T Fujinami Z Horita and T G Langdon Scripta

Mater 2001 44 759ndash764

223 S Ota H Akamatsu K Neishi M Furukawa Z Horita and

T G Langdon Mater Trans 2002 43 2364ndash2369

224 K Furuno H Akamatsu K Oh-ishi M Furukawa Z Horita

and T G Langdon Acta Mater 2004 52 2497ndash2507

225 I N Fridlyander O G Senatorova N A Ryazanova and A O

Nikiforov Mater Sci Forum 1994 170ndash172 345ndash349

226 J N Fridlyander and O G Senatorova Mater Sci Forum 1996

217ndash222 1813ndash1818

227 J Liu and D J Chakrabarti Acta Mater 1996 44 4647ndash4661

228 O G Senatorova A N Uksusnikov J N Fridlyander

J Koshorst R R Romanova N A Ryazanova A Galliot

and V V Cherkassov Proc 6th Int Conf on lsquoAluminum alloysrsquo

July 1998 Toyohashi Japan 589ndash593

229 R A Emigh E L Bradley and J W Morris Jr in

lsquoSuperplasticity in aerospace IIrsquo (ed T R McNelley and H C

Heikkenen) 303ndash315 1990 TMS

230 E L Bradley III R A Emigh and J W Morris Jr Scripta

Metall Mater 1991 25 717ndash721

231 N I Kolobnev L B Khokhlatova V D Makarov E Yu

Semenova and V V Redchits Proc Sixth Int Aluminiumndash

Lithium Conference Garmisch-Partenkirchen Germany October

1991 1053ndash1056

232 N K Tsenev R Z Valiev O V Obraztsov and I N Fridlander

Proc Sixth Int AluminiumndashLithium Conference Garmisch-

Partenkirchen Germany October 1991 1125ndash1132

233 A M Shammazov N K Tsenev R Z Valiev M M

Myshlyaev M M Bikbulatov and S P Lebedich Phys Met

Metall 2000 89 (3) 314ndash318

234 F Musin R Kaibyshev Y Motohashi T Sakuma and G Itoh

Mater Trans A 2002 43A 2370ndash2377

235 M Shagiev Y Motohashi F Musin R Kaibyshev and G Itoh

Mater Trans A 2003 44A 1694ndash1697

236 M Shagiev Y Motohashi F Musin R Kaibyshev and G Itoh

Mater Trans A 2003 44A 1698ndash1701

237 B A Parker and Z F Zhou Proc 3rd Int Conf on lsquoAluminium

alloysrsquo Vol I NTH Trondheim Norway June 1992 363ndash367

238 J R Davies lsquoASM specialty handbook aluminum and aluminum

alloysrsquo 1993 Materials Park OH USA ASM

239 S J Andersen H W Zandbergen J Jansen C Traeholt

U Tundal and O Reiso Acta Mater 1998 46 3283ndash3298

240 M L Kharakterova D G Eskin and L L Rokhlin Russ

Metall 1997 (1) 104ndash109

241 J Roslashyset Dr Ing thesis NTNU Trondheim Norway 2002

242 P P Chattopadhyay S Datta and M K Banerjee Mater Sci

Eng 2002 A 333 67ndash71

243 L I Kaigorodova E I Selnikhina E A Tkachenko and O G

Senatorova Phys Met Metall 1996 81 513ndash519

244 Y-L Wu F H Froes C Li and A Alvarez Metall Mater

Trans A 1999 30A 1017ndash1024

245 Z Yin L Yang Q Pan and F Jiang Trans Nonferrous Met

Soc China 2001 11 822ndash825

246 V I Elagin V V Zakharov and T D Rostova Met Sci Heat

Treat 1994 36 (7) 375ndash380

247 Y V Milman A I Sirko D V Lotsko O N Senkov and D B

Miracle Mater Sci Forum 2002 396ndash402 1217ndash1222

248 C-H Joh K Yamada and Y Miura Mater Trans JIM 1999

40 439ndash442

249 X J Jiang Q H Gui Y Y Li L M Ma G J Liang and C X

Shi Scr Metall Mater 1993 29 211ndash216

250 X J Jiang Y Y Li W Deng L Y Xiong W M Wu Y J Gao

and C X Shi Adv Cryogenic Eng (Mater) 1994 40 1369ndash

1376

251 C-H Joh T Katsube K Yamada and Y Miura Proc 6th Int

Conf on lsquoAluminum alloysrsquo Toyohashi Japan July 1998 799ndash

804

252 L I Kaygorodova A M Dritz T V Krymova and I N

Fridlyander Proc Sixth Int AluminiumndashLithium Conference

Garmisch-Partenkirchen Germany October 1991 363ndash367

253 L I Kaigorodova A M Drits Ya V Zhingel T V Krymova

and I N Fridlyander Phys Met Metall 1992 73 286ndash290

254 A L Berezina V A Volkov S V Ivanov N I Kolobnev and

K V Chuistov Phys Met Metall 1991 71 (2) 167ndash175

255 I N Fridlyander N I Kolobnev A L Berezina and K V

Chuistov Proc Sixth Int AluminiumndashLithium Conference

Garmisch-Partenkirchen Germany October 1991 107ndash112

256 L I Kaigorodova A M Drits Ya V Zhingel T V Krymova

and V A Rassokhin Phys Met Metall 1992 73 281ndash285

257 I N Fridlyander S F Danilov E N Malysheva T A

Gorokhova and N N Kirkina Proc Sixth Int Aluminiumndash

Lithium Conference Garmisch-Partenkirchen Germany October

1991 381ndash386

258 G Dlubek S Krause H Krause A L Beresina V S

Mikhalenkov and K V Chuistov J Phys Condens Matter

1992 4 6317ndash6328

259 S Krause H Krause G Dlubek A L Beresina and K S

Chuistov Mater Sci Forum 1992 105ndash110 1109ndash1112

260 C Y Tan Z Q Zheng and S Q Liang Proc 4th Int Conf on

lsquoAluminium alloysrsquo Vol II Atlanta GA USA September 1994

329ndash333

261 A L Beresina N I Kolobnev K V Chuistov A V Kotko and

O A Molebny Mater Sci Forum 2002 396ndash402 977ndash981

Roslashyset and Ryum Scandium in aluminium alloys

International Materials Reviews 2005 VOL 50 NO 1 43

262 I N Ganiev I Yunusov and V V Krasnoyarskii J Appl Chem

USSR 1986 60 1961ndash1965

263 I N Ganiev Prot Met 1995 31 543ndash546

264 N V Vyazovikina Prot Met 1999 35 448ndash453

265 G V Kharina and V P Kochergin Prot Met 1996 32 134ndash

136

266 G V Kharina M V Kuznetsov and V P Kochergin Russ J

Electrochem 1998 34 482ndash485

267 V S Sinyavskii V D Valrsquokov and E V Titkova Prot Met

1998 34 549ndash555

268 Y L Wu F H Froes C G Li and J Liu Proc lsquoSynthesis

processing of lightweight metallic materials IIrsquo Orlando FL

USA February 1997 73ndash81

269 Z Ahmad and B J Abdul-Aleem Proc EuroCorr 2000

270 Z Ahmad A Ul-Hamid and B J Abdul-Aleem Corros Sci

2001 43 1227ndash1243

271 R Braun B Lenczowski and G Tempus Mater Sci Forum

2000 331ndash337 1647ndash1652

272 T Torma E Kovacs-Csetenyi L Vitalis I Vitanyi

J Stepanov and M Butova Mater Sci Forum 1987 1314

497ndash503

273 Z Wang P Wang K S Kumar and C L Briant in lsquoChemistry

and electrochemistry of corrosion and stress corrosion crackingrsquo

(ed R H Jones) 573ndash582 2001 TMS

274 V I Elagin V V Zakharov A A Petrova and E V

Vyshegorodtseva Russ Metall 1983 (4) 143ndash146

Roslashyset and Ryum Scandium in aluminium alloys

44 International Materials Reviews 2005 VOL 50 NO 1

Page 9: Scandium in aluminium alloys - Atom probe · A considerable part of the available literature on scandium in aluminium alloys is reviewed. ... behaviour in Al Cu, Al Mg Si,

of precipitates In the AlndashSc case the discontinuouslyprecipitated Al3Sc particles have been demonstrated tobe coherent with the aluminium matrix1318

The driving force for discontinuous precipitationincreases with increasing supersaturation of Sc in theAl matrix Thus discontinuous precipitation in binaryAlndashSc is most frequently reported in studies of alloyswith a Sc content of 04 wt- or higher1318106 Stilldiscontinuous precipitation has also occasionally beenreported to occur at lower alloy compositions In an Alndash027 wt-Sc alloy discontinuous precipitation wasobserved over a wide range of temperatures107 In arecent study31105 of precipitation kinetics and mechan-isms in Alndash02 wt-Sc discontinuous precipitation wasfound to take place when the specimens were quencheddirectly from a solutionising temperature in this case600uC to aging temperatures in the range 370ndash490uCFurther C-curves in a temperature-time-transformation(TTT) diagram were established (Fig 13) which showedthat the highest transformation rate of discontinuousprecipitation lies at a higher temperature than thehighest transformation rate of the continuous precipita-tion reaction ie the two precipitation reactions arerepresented by two separate lsquonosesrsquo on the C-curves

It has been shown that discontinuous precipitationcan be suppressed by continuous precipitation if thematerial is cold worked before the precipitation heattreatment13108

As a result of their rather coarse nature andinhomogeneous dispersion discontinuously precipitatedAl3Sc contributes but little to the strength of the alloyand also leads to a smaller amount of Sc in super-saturated solid solution being available for subsequentcontinuous precipitation Thus discontinuous precipita-tion is in general regarded as an undesired precipitationmode

Continuous precipitation of Al3ScContinuous precipitation of Al3Sc is a bulk decomposi-tion process of supersaturated solid solution of Sc in Aland can in the isothermal case be characterised by anucleation stage a growth stage and finally a coarsen-ing stage Apparently the continuous precipitation reac-tion occurs largely by homogeneous nucleation anddiffusion controlled growth and AlndashSc has occasionallybeen used as a model system for studying the mechan-isms of nucleation growth and coarsening107109ndash111

There have been several studies of the continuousprecipitation reaction in binary AlndashSc alloys and up tillnow there is no evidence that any metastable phases areforming before the L12 phase Al3Sc Thus it is assumedthat the equilibrium phase nucleates directly fromsupersaturated solid solution

Even though the nucleation of Al3Sc is frequentlyreported to occur homogeneously throughout the Almatrix there are some examples in the technical litera-ture of reported heterogeneous Al3Sc nucleation ondislocations110112ndash115 and grain boundaries110113115ndash118

In a recent numerical modelling study of continuousprecipitation in AlndashSc alloys111 the effect of hetero-geneous nucleation on dislocations is accounted for Themodel predicts that homogeneous nucleation dominatesat high Sc concentrations and low transformation tem-peratures whereas heterogeneous nucleation is predictedto dominate at low Sc concentrations and high trans-formation temperatures Figure 14 shows a sketch of anucleation map for AlndashSc The shift between homo-geneous and heterogeneous dominance in nucleation isdependent on the dislocation density as indicated in thefigure

The shape of continuously precipitated Al3Sc particlesis most frequently reported to be spherical29112113119ndash129

However it seems that under certain conditions theshape can differ from the spherical one Drits et al130

reported both spherical and star shaped morphologyThe star shaped precipitates had arms growing in thecrystallographic n110m-directions (Star shaped Al3Scprecipitates have also been found after some thermo-mechanical treatments of an AlndashMgndashScndashZr alloy131) InRef 128 precipitates of both cuboidal and sphericalmorphology are found to coexist after certain heattreatments Cauliflower shaped precipitates as well asprecipitates of spherical and cuboidal shapes arereported by Novotny and Ardell110 Bastow andCelotto132 found large oblong Al3Sc particles in an Alndash01 wt-Sc alloy after aging at 400uC for 24 h A facetedshape is suggested in a high-resolution image of anAl3(Sc Zr) precipitate in an AlndashMgndashMnndashZrndashSc alloy133

In a systematic high-resolution transmission electron

13 TTT diagram of precipitation in Alndash02 wt-Sc alloy

after solutionising at 600uC and direct quench to

aging temperature3114 Nucleation map for binary AlndashSc alloys which indi-

cates how the tendency towards heterogeneous ver-

sus homogeneous nucleation is predicted to depend

upon Sc concentration transformation temperature

and dislocation density redrawn from Ref 111

Roslashyset and Ryum Scandium in aluminium alloys

International Materials Reviews 2005 VOL 50 NO 1 27

microscopy (TEM) study of the Al3Sc particle morphol-ogy development during precipitation heat treatment ofbinary AlndashSc alloys by Marquis and Seidman114 it isdemonstrated that the precipitates can take a wide rangeof shapes as they grow depending on Sc content in thealloy transformation temperature and transformationtime Irregular shaped star shaped and cuboidalshaped precipitates were observed under someconditions It was however found that the equilibriumshape of the particles is an equiaxed multifaceted one(Fig 15) Supported by Wulffrsquos construction it wasconcluded that the shape was that of a GreatRhombicuboctahedron This equilibrium morphologyhas been reproduced by computer-simulations ofparticle growth87134 The multifaceted particles caneasily be taken for spherical in a conventional TEMpicture

Kinetics of precipitation of Al3Sc fromsupersaturated solid solutionThe precipitation kinetics of Al3Sc in binary AlndashScalloys is dependent on the precipitation heat treatmenttemperature and on the Sc content in the alloy Acomprehensive overview over the transformationkinetics in terms of C-curves is given by Zakharov135

The C-curves for 5 transformation for a range of AlndashSc alloys are redrawn in Fig 16

Hyland107 studied the homogeneous nucleationkinetics of Al3Sc in a Alndash018 wt-Sc alloy after directquench from 650uC to precipitation temperatures of 288and 343uC He found that after an incubation time t theAl3Sc particles nucleated at a constant rate until thediffusion fields of the individual particles started tooverlap At 288uC the incubation time and time tosignificant diffusion field overlap were estimated to beapprox 245 and 150 min respectively whereas thecorresponding values at 343uC were estimated to beapprox 7 and 20 min respectively

If one assumes that the JohnsonndashMehlndashAvramindashKomolgorov (JMAK) relationship is valid for thisprecipitation reaction one can express the fraction

transformed X as a function of the reaction time t bythe equation

X (t)~1expfrac12k(Dt)n (1)

where k is a constant D is the interdiffusion constant ofSc in Al and the exponent n is dependent on thenucleation rate For the situation described byHyland107 where the precipitates nucleate at a constantrate the value of n should theoretically136 be equal to52

Roslashyset and Ryum31105 applied an alloy and heattreatment method practically equal to that of Hyland107

One should thus expect that the precipitation kineticsshould also be quite similar However Roslashyset andRyum reported that the exponent n of the JMAKrelationship was approx 165ndash185 for the temperaturerange of concern31105 This does not point in thedirection of a constant nucleation rate but rather inthe direction of site saturation ie that all the particlesare nucleated simultaneously which in the JMAKequation would yield an exponent n of 32136 Anoverview of some reported values of n in the JMAKequation is given in Table 4 The majority of the valueslie closer to 32 than to 52 However it is important to

15 High resolution TEM picture along n100m axis of Al3Sc particle in Alndash03 wt-Sc alloy aged at 300uC for 350 h114

(reproduced with permission from Elsevier Science image kindly provided by Dr E A Marquis and Professor D N

Seidman) and various projections of a Great Rhombicuboctahedron

Table 4 Some reported values of n in JMAK equation

Reference n C 0Sc wt-Sc Ttrans uC Note

137 13 030 300 Solution heat treated (SHT) 500uC16026 030 300 SHT 600uC Low n at late stage20026 030 300 SHT 640uC Low n at late stage

29 130ndash149 015 260ndash370145ndash196 025 260ndash370

138 188ndash216 020 240ndash35031 165ndash185 023 270ndash350 SHT 600uC Direct quench to transformation temp

16 C-curves for 5 transformation in a range of binary

AlndashSc alloys redrawn from Ref 135

Roslashyset and Ryum Scandium in aluminium alloys

28 International Materials Reviews 2005 VOL 50 NO 1

note that an n value close to 32 is per se not evidence ofsite saturation

Hyland also showed that a water quench from thesolutionising temperature significantly altered thenucleation kinetics in the subsequent precipitation heattreatment107 The incubation time was dramaticallyshortened which is attributed to the quenched-in excessvacancies and it is also indicated that there might be ashift in the nucleation rate in the early stage ofprecipitation It is suggested that the vacancies mayenhance the diffusion of Sc in Al and that there is apossibility that vacancy clusters act as heterogeneousnucleation sites for Al3Sc precipitates107 Regardless ofwhich mechanism that is operative it is clearly demon-strated that the nucleation kinetics can be dependent onthe thermal history between solutionising and precipita-tion heat treatment

Loss of coherency during growth of Al3ScprecipitatesWhen an Al3Sc particle grows it will sooner or laterreach a critical size where it will be energetically morefavourable to introduce an interface dislocation at theAlAl3Sc interface than to increase the matrix strain Asimple approximation for the critical size can be derivedfrom the lattice parameters assuming that the criticalsize is reached when the misfit over the whole particlediameter equals the Burgers vector of the Al matrix

dcrit~b=d (2)

where b is the Burgers vector of Al and d is themisfit between Al and Al3Sc This approximation yieldsa critical diameter of approx 215 nm at ambienttemperature

The misfit d and thus also the critical diameter dcrit

will depend on the temperature owing to the differencesin thermal expansion between the Al matrix and the

Al3Sc particles The thermal expansion of Al3Sc hasrecently been measured89 and based on the differencesin thermal expansion between Al139 and Al3Sc the misfitas a function of temperature has been calculated89 Thiscalculation is reproduced and shown by the solid line inFig 17

It is however possible to refine this calculationsomewhat140 Whereas the thermal expansion of Al3Sc isexpected to be only because of lattice expansion there isa significant contribution from vacancies on thermalexpansion of Al at high temperatures141 Thus thetemperature effects on the misfit should be calculatedfrom the changes in lattice parameters rather than fromthe linear thermal expansion By subtracting the vacancyeffect on the thermal expansion one achieves atemperature-dependent misfit as represented by thedotted line in Fig 17

A second correction that should be taken into accountis the effect of Sc in solid solution on the latticeparameter of the Al matrix With increasing tempera-ture more Sc is brought into solid solution and it isreported that the lattice parameter of the Al matrixpresumably measured at room temperature increaseslinearly with the Sc content in solid solution142 Thesedata can be used to calculate the effect on the latticeparameter at elevated temperatures under the assump-tion that the relative increase in lattice parameter owingto Sc in solid solution is independent of temperature InRef 142 a figure is presented which shows the measuredlattice parameter as a function of Sc content in solidsolution and a value (dadc)a is reported where a is thelattice parameter of the Al matrix and c is the Sc contentin solid solution in at- The reported value for (dadc)a is 100 times larger than that indicated in thecorresponding figure possibly as a result of a decimalerror in the text Thus in the present exercise 1100th ofthe reported value for (dadc)a is used Using this incombination with the regular solution approximationfor the solvus line of Sc in Al1231 one obtains acorrection for Sc in solid solution on the temperature-dependent misfit as shown in Fig 18 This figure shows

17 Lattice mismatch between Al and Al3Sc as a function

of temperature solid line represents calculation

based on linear thermal expansion of the two phases

dotted line represents correction for vacancies in Al

lattice

18 Corrections of mismatch calculated from linear ther-

mal expansion data as a result of vacancies and to

Al lattice expansion from Sc in solid solution

Roslashyset and Ryum Scandium in aluminium alloys

International Materials Reviews 2005 VOL 50 NO 1 29

both the correction for vacancies and for Sc in solidsolution on the same graph The two corrections are ofapproximately the same magnitude but with oppositesigns Thus the resulting (net) correction is close to zeroand it turns out that the first hand approximation asapplied in Ref 89 is very good in this case

Applying the calculated temperature dependent misfitwith the simple approximation for a critical diameter forloss of coherency one obtains a temperature-dependentcritical diameter as shown in Fig 19

Some examples from the literature of experimentallyobserved critical diameters in binary AlndashSc alloys aresummarised in Table 5 along with some predictions forcritical diameters from Fig 19 There is a fairly goodconsistency between the observations and the measureddiameter is quite close to the simple predictions above

A more refined analysis on the transition fromcoherent to incoherent particles has recently beenperformed145 This analysis is based on the balancebetween the increase in particlematrix interface energyowing to interfacial dislocations and the relaxation inelastic energy in the Al matrix owing to the samedislocations This method yields a predicted criticaldiameter of 246 nm for transition from coherent to

semi-coherent particles at ambient temperature Thetemperature dependence of the critical diameter is nottreated in this analysis

The loss of coherency during isothermal annealing hasbeen reported to be accompanied by an increasedaverage coarsening rate119121137145 The increasedcoarsening rate has been attributed either to diffusionof Sc along dislocation lines119121 or to the increasedparticlematrix interface energy of a semicoherentparticle145 However there are also several data sets inthe literature that do not indicate an increased growthrate after the loss of coherency114128

Al3ScAl interface energyThe interface energy between Al3Sc and the Al matrix isone of the key parameters that governs the nucleationgrowth and coarsening behaviour of Al3Sc in Al and Alalloys The interface energy has been estimated in severalinvestigations either by fitting experimental data toequations that describe nucleation or coarsening or bycalculations A compilation of some of the results isgiven in Table 6 There is considerable spread in thereported values regardless of what approach has beenused for the estimation

Influence of other elements on precipitation ofAl3ScMagnesium

With regard to precipitation mechanism it has beenstated that Mg suppresses the tendency to discontinuousprecipitation of Al3Sc106 In an investigation of pre-cipitation kinetics of Al3Sc in the temperature range300ndash500uC only minor changes in the kinetics (Fig 20)were found when up to 5 wt-Mg was added to an Alndash04 wt-Sc alloy135 It seems that the precipitationreaction is slightly faster in the Mg-containing alloys

Several investigations on age hardening response alsoimply that there is only a small if any effect of Mg onthe precipitation kinetics of Al3Sc23148149 It is how-ever found that the hardness increase from theprecipitation of Al3Sc is somewhat reduced in AlndashMgndashSc alloys compared to binary AlndashSc alloys23148149 InRef 149 it is suggested that some of the Sc is dissolvedin the Al3Mg2 phase and thus the age hardeningpotential is reduced with increasing Mg contentSomewhat contradictory to these observations but

Table 5 Some reported critical diameters for coherencyloss in binary AlndashSc and correspondingtheoretical critical diameters from Fig 19

Reference dcrit nmC0

Scwt-Sc

TtransuC

Theoreticaldcrit nm

119 38ndash40 05137 28ndash30 03 400 308128 32 02 400 450 308 335129 50 02143 40 012 025115 40 025 450ndash500 335ndash37114 40 03 400 450 308 335144 40 02 400ndash460 308ndash341145 30ndash80 02 400ndash490 308ndash362

20 C-curves for 10 and 60 transformation in Alndash

04 wt-Sc and Alndash4 wt-Mgndash04 wt-Sc redrawn

from Ref 135

19 Simple approximation for temperature-dependent criti-

cal diameter for introduction of dislocations on Al

Al3Sc interface

Roslashyset and Ryum Scandium in aluminium alloys

30 International Materials Reviews 2005 VOL 50 NO 1

sustained by Ref 135 it has recently been reported150

that precipitation of Al3Sc at 300 and 350uC occursslightly faster in an Alndash2 wt-Mgndash02 wt-Sc alloythan in an Alndash02 wt-Sc alloy studied previously by thesame researchers117118 and that the correspondinghardness increase is highest in the AlndashMgndashSc alloyThe only reported difference in experimental procedureis the solutionising temperature which was higher forthe AlndashSc alloy (648uC) than for the AlndashMgndashSc alloy(617uC) However given that the nucleation time isshortened by quenched-in vacancies as suggested byHyland107 the difference in homogenisation tempera-ture should be in favour of a faster precipitation of thebinary AlndashSc alloy It should be worthwhile to probedeeper into this observation of different aging responses

Mg in solid solution increases the lattice parameter ofthe Al matrix This is in turn expected to influence thecritical diameter for AlAl3Sc coherency loss as discussedin the section on lsquoLoss of coherency during growth ofAl3Sc precipitatesrsquo above Such an influence on the criticaldiameter is also briefly discussed elsewhere150 A criticaldiameter of 80 nm in an Alndash3 wt-Mgndash02 wt-Sc alloyhas been observed compared to 40 nm in a binary Alndash02 wt-Sc alloy of the same investigation144 Otherresearchers have reported a critical diameter in excess of116 nm in an Alndash63 wt-Mgndash02 wt-Sc alloy151

Computer simulations predict that the AlAl3Scinterface should be enriched in Mg87 These predictionsare confirmed experimentally by three-dimensional atomprobe microscopy of an Alndash2 wt-Mgndash02 wt-Sc alloyaged at 300uC38 Here it was found that the Mg contentat the interface is approximately three times higher thanthe matrix concentration regardless of aging time

Copper

It has been claimed that Cu suppresses the tendencytowards discontinuous precipitation of Al3Sc106

Zakharov and Rostova152 have reported that additionsof up to 14 wt-Cu have only minor effects on theprecipitation kinetics in an Alndash04 wt-Sc alloy Themost noticeable effect is that for temperatures above400uC the late stage of the transformation is sloweddown for the highest Cu contents This does not show in

Fig 21 however where only the 10 and 60transformation curves are included

The W-phase (AlCuSc) was observed in the alloywith the highest Cu content which means that less Sc isavailable for the precipitation of Al3Sc in this alloyAnother investigation on the age hardening response ofAlndash023 wt-Sc and Alndash25 wt-Cundash023 wt-Sc at300uC also implies that the precipitation behaviour ofAl3Sc in the two alloys is similar153154 At 350uC alimited portion of the Al3Sc has been observed tonucleate heterogeneously on coarse hrsquo precipitates155

According to the isothermal sections of the phasediagram43 one should expect the ternary W-phase toform instead of the Al3Sc phase in an alloy with such ahigh CuSc ratio However no observations of the W-phase or other ternary phases were reported from TEMstudies of the Alndash25 wt-Cundash023 wt-Sc alloy thathad been heat treated in the temperature range 300ndash460uC153ndash156 A third investigation on the precipitationin Alndash048 wt-Sc alloys with up to 440 wt-Cu in thetemperature range 100ndash450uC also concludes that no W-phase or other ternary phase forms during the heattreatment157

Copper in solid solution decreases the lattice para-meter of the Al matrix Thus it is expected that the misfitbetween Al and Al3Sc precipitates should be higher in

21 C-curves for 10 and 60 transformation in Alndash

04 wt-Sc and Alndash14 wt-Cundash04 wt-Sc redrawn

from Ref 152

Table 6 Reported values of interphase energy cAlAl3Sc between coherent Al3Sc precipitates and Al matrix

Reference cAlAl3Sc mJ m22 Method of estimation

137 10 Fit of coarsening data to LifshitzndashSlezev equation107 78iexcl20 (288uC) Back-calculation of incubation time

93iexcl20 (343uC)107 123iexcl41 (288uC) Back-calculation of nucleation rate

125iexcl35 (343uC)29 542 (400uC) Fit of coarsening data to Ostwald ripening

632 (430uC)413 (460uC)

146 c(100) 192 (0 K) c(111) 226 (0 K) Pseudopotential calculations147 c(100) 325 (0 K) c(110) 513 (0 K) c(111)

782 (0 K) c(100) 315 (288uC) c(100) 325 (343uC)Atomistic simulation

110 105 Fit of coarsening data to LSW theory31 20ndash300 Fit of coarsening data to Ostwald ripening

for 16 different temperatures111 57 Fit of precipitation model to experimental data145 120 coherent particles Fit of coarsening data

170 semicoherent particles

It is argued in this study that c may be lower in the nucleation stage

Roslashyset and Ryum Scandium in aluminium alloys

International Materials Reviews 2005 VOL 50 NO 1 31

AlndashCundashSc alloys compared to AlndashSc alloys Howeveran experimental investigation of Alndash25 wt-Cundash023 wt-Sc alloy comes to a different conclusion Thelattice misfit strain is found to decrease compared to Alndash02 wt-Sc and the critical diameter for coherency losswas found to be the same in the ternary and the binaryalloy144 It is suggested that these observations may bebecause of the dissolution of some Cu in the Al3Sc phaseand thus that the lattice parameters of both the Al matrixand the Al3Sc precipitates decrease in the ternary alloy

Silicon

It has been found that the onset of precipitation in Alndash04 wt-Sc is only slightly altered when Si contents ofup to 04 wt are introduced in the alloy However thefinal stage of the precipitation reaction is considerablydelayed with increasing Si content135 Figure 22 showsthe effect of addition of a joint of 035 wt-Si and040 wt-Fe There are at least two possible explana-tions for why an Si-addition leads to this behaviour

1 Alloying with Si is known to promote discontin-uous precipitation of Al3Sc106158 It has been shown thatwhen isothermal precipitation of Al3Sc starts discon-tinuously the later stage of the overall transformationcan be very slow31

2 The isothermal section of the phase diagramsuggests that the V-phase (AlSc2Si2) should form inalloys of this composition46 If the V-phase forms lessSc is available for precipitation of Al3Sc

It has been shown157 that for an AlndashScndashSi alloy withsolid solution content of 010 wt-Sc an 110 wt-Sithe only phases to precipitate after heat treatment at200uC are Si and an (AlScSi)-phase possibly the V-phase On the other hand the Al3Sc phase has beenobserved to form in alloys with 04 wt-Sc and up to08 wt-Si159160

Zinc

It has been reported that additions of up to 5 wt- Znhave only minor effects on the precipitation kinetics ofan Alndash04 wt-Sc alloy135 (Fig 23) In Ref 106 it isclaimed that Zn promotes discontinuous precipitation ofAl3Sc

Lithium

A comparison of the age hardening response at 400uC inAlndash24 wt-Lindash019 wt-Sc and Alndash024 wt-Sc alloys

indicates that the onset of Al3Sc-precipitation is notaffected by the presence of Li161

Zirconium

As mentioned in the section on lsquoTernary phase diagramswith dispersoid-forming elementsrsquo earlier a considerableamount of Zr is dissolved in the Al3Sc phase and thus amore correct denotation of the precipitating phase isAl3(Sc12xZrx) In discussing the influence of the Zrcontent on the precipitation of Al3Sc one is thereforeactually discussing the difference in precipitation ofAl3Sc versus Al3(Sc12xZrx)

It is found that an addition of 015 wt-Zr to an Alndash04 wt-Sc alloy only marginally affects the initial stageof the precipitation reaction123135 while it slows downthe later stages of the transformation considerably(Fig 24)135 The coarsening rate of the Al3(Sc12xZrx)particles in AlndashScndashZr alloys is found to be much slowerthan that of Al3Sc particles in AlndashSc alloys123162

In three-dimensional atom probe field ion microscopy(3D-APFIM) of Al3(Sc12xZrx) particles formed at 475uCin a ternary AlndashScndashZr alloy163 it was found that the coreof the particles is almost pure Al3Sc whereas there is ashell of Al3(Sc12xZrx) with almost equal content of Scand Zr Such a behaviour has also been predicted bycomputer modelling of precipitation of Al3(Sc12xZrx) at480uC in an AlndashZnndashMgndashScndashZr alloy164 This modelpredicts that Zr starts to enter the growing

22 C-curves for 10 and 60 transformation in Alndash

04 wt-Sc and Alndash04 wt-Fendash035 wt-Sindash04 wt-Sc

redrawn from Ref 135

23 C-curves for 10 and 60 transformation in Alndash

04 wt-Sc and Alndash5 wt-Znndash04 wt-Sc redrawn

from Ref 135

24 C-curves for 10 and 60 transformation in Alndash

04 wt-Sc and Alndash04 wt-Scndash015 wt-Zr redrawn

from Ref 135

Roslashyset and Ryum Scandium in aluminium alloys

32 International Materials Reviews 2005 VOL 50 NO 1

Al3(Sc12xZrx) particles when approximately half of thesupersaturated Sc has been precipitated The Zr contentof the outer shell is predicted to be much higher thanwhat has been found experimentally163164

Another 3D-APFIM study of Al3(Sc12xZrx) particlesin a ternary AlndashScndashZr alloy has been reported165 Hereparticles grown at 300uC for various lengths of time werestudied The Zr content in these particles was muchlower than that reportedpredicted at higher tempera-tures163164 even after very long annealing times

Iron

The effect of adding up to 07 wt-Fe on the precipita-tion kinetics in an Alndash04 wt-Sc alloy has beeninvestigated135 The onset of precipitation was onlyslightly influenced by the Fe-level whereas the laterstages of the transformation however were significantlyslowed down as the Fe-level increased An example ofthe effect of a joint addition of Fe and Si is shown inFig 22

Manganese chromium and titanium

Small additions (03 wt-) of manganese or chromiumto Alndash040 wt-Sc alloys are reported to have onlyminor effects on the precipitation kinetics of Al3Sc135

According to Ref 106 Mn is reported to promote andCr and Ti to suppress discontinuous precipitation

Rare earth elements

An investigation of the precipitation behaviour of Alndash03 at-Sc and Alndash03 at-Scndash03 at-X alloyswhere X is either yttrium gadolinium holmium orerbium in the temperature range 235ndash310uC indicatedthat a Al3(Sc12xXx) phase with L12 structure wasformed in the ternary alloys22 Peak strength is reportedto occur after approx 10 h at 285uC in all alloys whichindicates that the precipitation kinetics up to peakstrength is practically unaltered by the ternary additions

Influence of Sc on microstructure andproperties of wrought aluminium alloysMost of the effects of Sc addition in wrought Al-alloysare linked to the formation of the Al3Sc phase In atypical processing route of a wrought aluminium alloyparticles of the Al3Sc phase can form under threedifferent conditions each of which influences themicrostructure and properties of the alloy in a specificway

1 During solidification after casting or weldingAl3Sc particles can form in the melt and act as nucleifor a-Al thus leading to grain refinement18166

2 High temperature processing of the alloy in therange 400ndash600uC for instance homogenisation hot-rolling or extrusion can give a dense distribution ofAl3Sc particles of typically 20ndash100 nm size The particledistributions formed under such conditions are reportedto lead to good recrystallisation resistance128148167168

and enhanced superplasticity52169170

3 Heat treatment in the range 250ndash350uC can lead tosignificant precipitation hardening of an alloy super-saturated in Sc148158171 The size of strengthening Al3Scprecipitates is typically in the range 2ndash6 nm121

Grain refinementA good grain refinement is almost always desired uponsolidification The formation of small equiaxed grainsrather than long dendrites in the melt facilitates thefeeding of the melt into cavities of the shrinkingsolidified metal and thus reduces the problem ofshrinkage porosity The tendency to hot cracking is alsoreduced and the second phase particles become morefinely and uniformly distributed

To the authorsrsquo knowledge the first effect of Sc in Al-alloys that was reported in an international scientificjournal was the grain refining action in pure Al and in anAlndashCu alloy upon solidification172 which was found tobe stronger for Sc than for other transition metals Inlater studies of Sc as a grain refiner in pure Al1832173 ithas been demonstrated that approx 07 wt-Sc issufficient to provide excellent grain refinement It hasalso been demonstrated that additions of 025 wt-Scz025 wt-Zr provide good grain refinement in pure Al18

In order for Sc to act as an effective grain refiner theAl3Sc phase has to form in the melt before thesolidification of a-Al The Al3Sc particles have a latticeparameter close to that of pure Al and whenhypereutectically formed the Al3Sc particles are veryeffective substrates for the nucleation of the a-Al phaseAs mentioned in the section on lsquoFormation of Al3Sc inAlndashSc alloysrsquo above this requires that the alloy ishypereutectic with respect to Sc ie in excess of approx06 wt- in a binary AlndashSc alloy In ternary and higherorder systems the eutectic Sc composition may dependon the other alloying elements present For instance theeutectic composition of Sc has been predicted todecrease with increasing Mg content in the ternary AlndashMgndashSc system39 This prediction is sustained by theobservation of good grain refinement by adding 05 wt-Sc to an Alndash7 wt-Mg alloy174 (Other examples ofgrain refinement at Sc concentrations lower than that ofthe binary eutectic are found in Ref 173)

Similarly the observation of good grain refinement inan Alndash025 wt-Scndash025 wt-Zr alloy18 may be as aresult of a lower Sc content of the eutectic in the ternarysystem ie less Sc is needed to make the alloy hyper-eutectic No literature data on the liquidus surface of theAlndashScndashZr system are available and thus this hypothesiscannot be confirmed In more complex alloy systems itis also observed that excellent grain refinement isachieved at low Sc contents when Sc is added togetherwith Zr It is reported that adding either 02 wt-Sc06 wt-Sc or 01 wt-Zr to an Alndash5Mg alloy givesmuch poorer grain refinement than adding 02 wt-Scz01 wt-Zr175 Similarly additions of 015 wt- ofeither Sc or Zr are reported to only marginally refinethe grain structure in an AlndashCundashLi alloy whereas a jointaddition of 015 wt-Sc and 015 wt-Zr gives excellentgrain refinement176 For an AA 3650 casting alloy (Alndash7 wt-Sindash04 wt-Mg) good grain refinement is achievedby adding 039 wt-Sc or 027 wt-Scz019 wt-Zr177

In some AlndashZnndashMgndashScndashZr alloys it is also found thatan addition of 02ndash03 wt-Sc can be sufficient for goodgrain refinement166169178179 Examples of the grainrefinement as a function of Sc addition in pure Al andin an AlndashZnndashMgndashZr alloy are shown in Fig 25

The nucleation of a-Al on Al3Sc particles in the melt isfacilitated by the close match in the lattice parameters ofthe two phases As shown in Fig 17 the mismatch at the

Roslashyset and Ryum Scandium in aluminium alloys

International Materials Reviews 2005 VOL 50 NO 1 33

eutectic temperature of binary AlndashSc alloys (660uC) isonly approx 047 In Refs 57 and 89 it is shown thatwhen Zr Hf and in particular Ti is dissolved in the Al3Scparticles this reduces the lattice parameter of the phaseIt appears that when 25 of the Sc atoms in Al3Sc aresubstituted by Ti the mismatch is zero at approx 550uCand becomes negative at higher temperatures89 Thissuggests that by carefully selecting the Ti content of thealloy it should be possible to obtain Al3(ScTi)substrates in the melt that match exactly the latticeparameter of the nucleating a-Al and thus furtherimprove the grain refinement of the alloy This appearsto have been achieved in a recent work180 where thegrain refinement of an Alndash07 wt-Sc alloy wascompared with that of an Alndash05 wt-Scndash02 wt-Tialloy At a cooling rate of 100 K s21 only an estimated2 of the primary Al3Sc particles of the binary AlndashScalloy were effective nuclei compared to practically 100for the primary Al3(ScTi) particles in the ternary AlndashScndashTi alloy leading to a much smaller grain size in theternary alloy Whereas the match of lattice parametersmay be of importance for these results the authors ofthis investigation180 draw attention to other factors suchas different growth restriction factors for Sc and Ti andthe possibility of a peritectic reaction in the ternaryalloy Nevertheless the principle of matching latticeparameters is worth looking into further in future work

Effects from dispersoidslsquoDispersoidsrsquo is a term which is commonly used aboutthe classes of second phase particles that are formedin an Al alloy during high temperature annealing orthermomechanical processing such as homogenisationhot rolling extrusion and forging A dense distributionof dispersoids can give a significant contribution to analloyrsquos strength owing to particle strengthening but thisis rarely the main strengthening mechanism A moreimportant contribution from the dispersoids is theirability to stabilise the grainsubgrain structure of analloy through the Zener-drag action and thus improvethe mechanical properties of the alloy

There are two noticeable dispersoid-related effectsthat have been reported for Sc-containing alloys Thefirst is the stabilising effect on a deformed microstruc-ture When a non-recrystallised structure is preserved inan alloy this can add considerably to the mechanical

strength of the material The second effect is thepreservation of a small grain size during hot deforma-tion at slow deformation rates which is necessary toobtain superplastic properties of an Al-alloy

Recrystallisation resistance

The anti-recrystallisation effect of Sc was first publishedin a patent171 where 03 wt-Sc was added to pure Aland to AlndashMg AlndashMn and AlndashZnndashMg alloys Both Sc-free and Sc-containing materials were cold worked andsubsequently annealed and it was found that theaddition of Sc increased the temperature for onset ofrecrystallisation by approx 220uC in pure Al andsomewhat less in the Al-alloys Although the author ofthe patent171 may have been well aware that the anti-recrystallisation effect is caused by Al3Sc dispersoidsthis is not mentioned in the text The first journal paperthat explicitly points out that the recrystallisationresistance is due to Al3Sc dispersoids was an investiga-tion of the effects of adding Sc to wrought AlndashMgalloys181 In this work it was found that the Al3Scdispersoids were very effective in preventing recrystalli-sation up to temperatures of approx 400ndash450uC Athigher temperatures the dispersoids coarsen consider-ably and the microstructure was partially recrystallised

It is established that the Zener-drag pZ that is imposedon an advancing grain boundary by randomly distrib-uted dispersoids can be expressed in the form

pZ~k f =r (3)

where k is a factor that includes the interface energybetween the dispersoids and the matrix f is the volumefraction and r is the mean radius of the dispersoids Thusthe Zener drag will decrease rapidly in the case where thedispersoids are coarsening

As mentioned in the section on lsquoInfluence of otherelements on precipitation of Al3Scrsquo above theAl3(Sc12xZrx) dispersoids in a ternary AlndashScndashZr alloycoarsen at a much slower rate than the Al3Sc dispersoidsin a binary AlndashSc alloy This effect was first reported inRef 123 (although also observed in Ref 182) andaccording to Ref 33 the same authors demonstratedsoon after that the denser dispersoid distributionachieved in an AlndashScndashZr alloy leads to superiorrecrystallisation resistance compared to a binary AlndashScalloy An example of the increased recrystallisationresistance by adding both Zr and Sc is shown in Fig 26

In isothermal sections of the ternary AlndashScndashZr phasediagram it is indicated that the solid solubility ofSczZr is somewhat higher than that of Sc alone54 Ithas also been demonstrated both by electrical con-ductivity measurements (Fig 27) and microstructuralobservations that the supersaturation of SczZr isgreater than that of only Sc or Zr in as cast Alndash15(SczZr) alloys183 This indicates that it should bepossible to increase the volume fraction of dispersoids inAlndashScndashZr compared to AlndashSc It is suggested162 that theincreased volume fraction that can be achieved byadding both Sc and Zr can be advantageous inconventional wrought Al-alloys

There are at least two different conditions underwhich Al3Sc or Al3(Sc12xZrx) dispersoids can form toprevent recrystallisation

1 Sc (or Sc and Zr) is in solid solution before thedeformation In the case of cold deformation and

25 Grain refinement as a function of Sc addition in pure

Al (redrawn from Ref 32) and AlndashZnndashMgndashZr (redrawn

from Ref 169) note that data points are plotted on

different ordinate axes

Roslashyset and Ryum Scandium in aluminium alloys

34 International Materials Reviews 2005 VOL 50 NO 1

subsequent annealing the Al3Sc or Al3(Sc12xZrx)dispersoids may nucleate and grow before the nucleationand growth of recrystallised grains takes placeDispersoids can form after a direct up-quench to theannealing temperature115143148184 during ramp-up tothe annealing temperature115 or by pre-annealing at anintermediate temperature129 In the case of hot deforma-tion the Al3Sc or Al3(Sc12xZrx) dispersoids maynucleate and grow during preheating of the materialand during the hot deformation itself184

2 The Al3Sc or Al3(Sc12xZrx) dispersoids are formedin the material before deformation184 Considering coldrolling and subsequent annealing the annealing tem-perature Tann may be either lower or higher than thetemperature Tdisp at which the dispersoids were formedIf TannTdisp only limited if any coarsening of thedispersoids is expected to take place and thus the Zenerdrag from the particles is expected to be practicallyconstant The driving force for recrystallisation how-ever is expected to decrease somewhat with theannealing time as a result of recovery processes Thusif recrystallisation does not occur within short annealingtimes the material is expected to remain unrecrystallisedfor infinite time at the annealing temperature IfTannTdisp there will be substantial coarsening of thedispersoids during annealing In order for the materialto remain unrecrystallised the decrease in driving forcefor recrystallisation owing to recovery has to be at leastas rapid as the decrease in Zener drag because of particlecoarsening

Experimental comparisons of the conditions abovepoint in the direction that the recrystallisation resistanceis poorest when Sc (or Sc and Zr) is in solid solutionbefore deformation and the deformed material is up-quenched to the annealing temperature148 or when Al3Scor Al3(Sc12xZrx) dispersoids are formed before defor-mation at TdispampTann184185 Excellent recrystallisationresistance is achieved if dispersoids are formed at anintermediate anneal of solutionised and deformedmaterial128 or if dispersoids are formed at TdispTann

before deformation148185ndash187 It seems that the decreasein Zener drag because of dispersoid coarsening in many

cases is slower than the decrease in driving force forrecrystallisation because of recovery processes Thusthere is an advantage in forming a high number densityof small dispersoids which for most practical casesmeans that they should be formed at TdispTann122

When an advancing high angle grain boundary iethe recrystallisation front is passing a coherent Al3Scdispersoid there are at least three possible grainboundarydispersoid interactions

1 The Al3Sc dispersoid retains its global orientationrelationship and thus loses its coherency with thesurrounding matrix

2 The Al3Sc dispersoid rotates as the grain boundarypasses either by diffusional processes at the dispersoidmatrix interface or by the grain boundary passingthrough the dispersoid and the Al3Sc dispersoidassumes the same crystallographic orientation as theAl matrix of the recrystallised grain

3 The Al3Sc dispersoid dissolves at the grainboundary and re-precipitates in the recrystallised grain

Which interactions that actually take place willprobably depend on the dispersoid size annealingtemperature and driving force for recrystallisation It isalso possible that alloy composition (other elementsthan Al) is of importance

It has been reported that large (Oslash about 100ndash150 nm)Al3Sc dispersoids in a deformed Alndash4 wt-Mgndash02 wt-Sc alloy annealed at 575uC lose the orientationrelationship with the matrix after being passed by therecrystallisation front148

A rotation of somewhat smaller Al3Sc dispersoids in arecrystallising binary Alndash025 wt-Sc alloy has beenreported115143 The rotation was reported to be accom-panied by substantial growth (from Oslash 30 nm to Oslash48 nm) as a result of enhanced Sc diffusion at the grainboundary Observations suggested that the grainboundaries were passing through the dispersoids andthus the Al3Sc dispersoids retained the orientationrelationship with the recrystallised Al matrix

Dissolution and re-precipitation of Al3Sc dispersoidshas been reported during recrystallisation of a 50 coldrolled Alndash02 wt-Sc alloy162 Large spherical partially

26 Fraction recrystallised structure in cold rolled sheets

of Alndash04 wt-Sc and Alndash04 wt-Scndash015 wt-Zr as a

function of annealing temperature redrawn from

Ref 183 27 Electrical conductivity in Alndash15(SczZr) alloys

redrawn from Ref 183

Roslashyset and Ryum Scandium in aluminium alloys

International Materials Reviews 2005 VOL 50 NO 1 35

coherent dispersoids were observed to dissolve at therecrystallisation front and re-precipitate as smallercoherent Al3Sc cuboids

Superplastic forming

It seems that the first publication on superplasticproperties of Sc-containing Al-alloys was a study of anAlndash35Cundash14Mgndash045Mnndash04(SczZr) alloy188

It was recognised that the superplastic properties are aresult of the stabilisation of the fine grain structure byAl3Sc dispersoids The Sc-containing Al alloys that havereceived most attention for their superplastic propertieshowever are those of the AlndashMgndashSc system which wasfirst published in a patent189 Here it was noted that anAlndash4 wt-Mgndash05 wt-Sc alloy had superior superplasticproperties compared to fine-grained 7475 (AlndashZnndashMgndashCu alloy) Binary Alndash05 wt-Sc and Alndash4 wt-Mgalloys did not behave superplastically The flow stress atthe hot forming temperature was found to be much (30ndash40) lower in the ternary alloy than that of the twobinary alloys

The superplastic properties of AlndashMgndashSc alloys havebeen explored by several research groups over the lastdecade190ndash196 It has frequently been found that thedeformation mechanism is dominated by grain bound-ary sliding190 However it has also been reported thatAlndashMgndashSc alloy may deform superplastically withoutnoticeable grain boundary sliding23 It is generallyrecognised that the grain boundary sliding mechanismis facilitated when the average grain size is very smalland grain boundaries are predominantly high-angleSuch a microstructure may be achieved by carefulthermomechanical processing of the starting mate-rial193194197198 It has however been shown that a finegrained structure with high angle boundaries maydevelop during superplastic forming of AlndashMgndashSc alloyseven if the starting microstructure is an entirely differentone for instance that of a cold rolled sheet192 It has alsobeen suggested that superplastic forming of as castmaterial may be possible189

One of the more efficient thermomechanical processesfor achieving an ultrafine grain structure with high anglegrain boundaries in Al-alloys is equal channel angularpressing (ECAP) A JapanesendashAmerican group ofscientists has published an impressive body of researchon improvements in superplastic properties in Al-alloys processed by ECAP over the last few years andseveral of the publications are from investigations onAlndashMgndashSc alloys170199ndash224 Maximum strains in excessof 2000 at a strain rate of 0033 s21 have beenachieved170201202217 which is an extraordinarily goodcombination of high strain and high strain rate for analuminium alloy

Superplastic properties of AlndashCundashMg(ndashMn)ndashSc(ndashZr)and AlndashMgndashSc(ndashZr) alloys have been mentionedNoticeable superplasticity in other Sc-containing Al-alloys has also been reported such as AlndashZnndashMg(ndashCu)ndashScndashZr169225ndash228 AlndashLindashSc229 AlndashMgndashLindashScndashZr229ndash234

AlndashLindashMgndashCundashScndashZr235236 and AlndashCundashLindashScndashZr233

Precipitation hardeningHardening by Al3Sc precipitates

It has been noted that when Al3Sc particles precipitate inthe temperature range 250ndash350uC they give a significanthardness increase in the alloy Some authors point out

that Sc is a more effective precipitation hardening elementper atomic fraction added than the elements that arecommonly used for precipitation hardening121130 (In onepaper29 it is claimed that only Au has a strongerstrengthening effect than Sc) However the amount ofSc that can be precipitated from supersaturated solidsolution is rather limited and thus the absolute values ofthe hardness increase from the precipitation hardening ismuch lower than what is normally associated withprecipitation hardened alloys Also the temperatureregime for age hardening by precipitation of Al3Sc issomewhere in between the temperature regimes for agehardening and solution heat treatments of commonprecipitation hardened alloys This makes a combinedprecipitation of Al3Sc and other strengthening precipi-tates unfeasible Thus precipitation strengthening byAl3Sc is most feasible in alloy systems that are non-heat-treatable The non-heat-treatable aluminium alloy sys-tems are according to the Aluminum Associationdesignations the 1xxx series (99 pure Al) the 3xxxseries (AlndashMn) and the 5xxx series (AlndashMg) The purposeof adding Sc to these alloys may be either to stabilise themicrostructure of wrought semiproducts (extrusionsrolled plates forgings etc) as discussed in the sectionon lsquoRecrystallisation resistancersquo above or to provideextra strength to the alloy through precipitation hard-ening In the latter case it is appropriate to considerwhether the Sc-containing alloy still should be classifiedas non-heat-treatable A heat treatment is applied thatbrings about a significant precipitation hardening On theother hand the hardness increase that is achieved throughthe heat treatment is lower than what is normallyassociated with heat-treatable alloy systems Hence eventhough it seems like a contradiction one chooses to keepusing the term lsquonon-heat-treatablersquo about these alloys

Table 7 gives an overview of some mechanicalproperties of Sc-containing non-heat-treatable alloysthat are reported in the literature Most of theexperimental work on Sc in 1xxx-types of alloys hasbeen done on binary AlndashSc alloys with much higherpurity than industrial alloys

Strengthening mechanisms

When the precipitates are larger than a critical size thestrengthening effect is due to the Orowan-mechanism iedislocations can only pass the precipitates by looping Inthis case the strengthening effect of the particles isapproximately inversely proportional to the mean parti-cle spacing When the precipitates can be sheared bydislocations there are a number of strengthening mechan-isms that apply It is proposed by Parker et al108 that thetwo major contributing mechanisms are coherency strainand anti-phase-boundary energy In a recent detailedstudy of strengthening mechanisms in binary AlndashSc alloysby Marquis and colleagues117118 the strengthening fromshear modulus mismatch between the matrix and theprecipitates is also accounted for A qualitatively goodmatch between theoretical strengthening and measuredvalues is achieved in this work both for deformation atroom temperature and at 300uC

Effect of Sc on precipitation strengthening in heat-treatablealloys

Following the AA designation system the traditionalheat-treatable Al-alloys are those that belong to the 2xxx

Roslashyset and Ryum Scandium in aluminium alloys

36 International Materials Reviews 2005 VOL 50 NO 1

series (AlndashCu) 6xxx series (AlndashMgndashSi) and 7xxx series(AlndashZnndashMg) AlndashLi alloys should also be mentionedSeveral investigations have been carried out in order toclarify the effects of Sc on the precipitation behaviour inthese alloy systems

AlndashCu alloys

The precipitation sequence in AlndashCu alloys is oftendescribed as follows

Supersaturated solid solutionRGP-zonesRh0Rh9Rh(Al2Cu)

The highest strength is normally achieved when the h0or h9 precipitates are predominant Typical precipitationheat treatment temperatures for AlndashCu alloys are in therange 160ndash190uC238 which is considerably lower thanthe typical precipitation temperature for Al3ScComparisons of the aging responses of AlndashCu and AlndashCundashSc alloys at 150 and 200uC indicate that there is nonoticeable effect of Sc on the precipitation kinetics ofh9153 It is observed that the h9 precipitates may nucleateon Al3Sc particles153 At 300uC it is observed that h9particles are somewhat smaller in AlndashCundashSc alloys thanin AlndashCu alloys156

AlndashMgndashSi alloys

The following precipitation sequence is commonlyreported for AlndashMgndashSi alloys

Supersaturated solid solutionRGP-zonesRb0Rb9Rb(Mg2Si)

For peak aged alloys the predominant precipitatetype is b0 for which the stoichiometric composition hasrecently been resolved to be Mg5Si6239 Temperatures inthe range 160ndash205uC are typically used for precipitationhardening of these alloys238 Adding both 03 wt-Scand 01 wt-Zr to an Alndash06 wt-Mgndash065 wt-Sialloy does not seem to alter the precipitation kineticsof b0 at 165uC However the hardness increase becauseof precipitation hardening appears to be smaller in theSczZr-containing alloy240 In another investigationadditions of 01 wt-Sc 015 wt-Sc 02 wt-Sc04 wt-Sc and 02 wt-Scz01 wt-Zr were made toan Alndash08 wt-Mgndash07 wt-Si alloy241 Here it wasalso observed that the precipitation kinetics of b0 wasseemingly independent of the Sc additions (Fig 28)TEM observations indicated that the b0 precipitateswere of comparable sizes in the investigated alloys andno interactions between Al3Sc and b0 were observed(Fig 29) In a third study242 where the effect of Sc onthe precipitation in an AlMgSindashSiC metal matrixcomposite was investigated there also does not seemto be any effect on the precipitation kinetics Howevercontrary to the findings of Ref 240 it is reported thatthe Sc addition leads to a higher hardness increase thanin the corresponding Sc free alloy

AlndashMgndashZn alloys

For these alloys the following precipitation sequence isoften ascribed

Table 7 Mechanical properties in non-heat-treatable Al-alloys with Sc

Reference Alloy wt- YS MPa UTS MPa Note

1xxx alloys171 000Sc 15 48 Cast material aged 288uC8 h

023Sc 159 185 Cast material aged 288uC8 h038Sc 199 220 Cast material aged 288uC8 h000Sc 14 49 Cold rolled material (89) aged 288uC8 h023Sc 198 208 Cold rolled material (89) aged 288uC8 h038Sc 240 264 Cold rolled material (89) aged 288uC8 h000Sc 8 34 Cold rolled material quenched from 649uC aged 288uC8 h023Sc 147 157 Cold rolled material quenched from 649uC aged 288uC8 h038Sc 193 199 Cold rolled material quenched from 649uC aged 288uC8 h

121 05Sc 160 ndash Forged material quenched from 635uC aged 250uC50 h23 05Sc 298 319 Hot rolled 288uC cold rolled 69ndash81 aged 288uC4 h112 01Sc 132 166 Hot z cold rolled material quenched from 630uC

aged 320uC133 h148 02Sc 138 ndash Cast material aged 300uC10 h compression test159 04Sc 196 ndash Cast material aged 300uC10 h compression test117 118 03Sc 209 ndash Cast material quenched from 648uC aged 300uC5 h

compression test3xxx alloys171 1Mn 015Sc 216 221 Cold rolled material (89) aged 288uC8 h

1Mn 05Sc 309 323 Cold rolled material (89) aged 288uC8 h186 05Mn 02Mg

026Sc 015Zr162 201 Extruded material solutionised 600uC aged 250uC

5xxx alloys171 1Mg 43 111 Cold rolled material (89) aged 288uC8 h

1Mg 03Sc 288 303 Cold rolled material (89) aged 288uC8 h53Mg 147 259 Cold rolled material (50) wintermediate anneals

at 343uC aged 288uC8 h53Mg 03Sc 368 401 Cold rolled material (50) wintermediate anneals

at 343uC aged 288uC8 h23 2Mg 05Sc 376 401 Hot rolled 288uC cold rolled 69ndash81 aged 288uC4 h

4Mg 05Sc 414 4606Mg 05Sc 433 503

237 4Mg 1Sc 420 525 Cold rolled material (83) aged 320uC1 h148 4Mg 02Sc 194 ndash Cast material aged 300uC10 h compression test

Tensile test data except where noted YS yield strength UTS ultimate tensile strength

Roslashyset and Ryum Scandium in aluminium alloys

International Materials Reviews 2005 VOL 50 NO 1 37

Supersaturated solid solutionRGP-zonesRg9Rg(Zn2Mg)

The maximum hardness is normally achieved whenthe g9 precipitates are predominant Common precipita-tion hardening temperatures are in the range 95ndash180uCand a two-step precipitation heat treatment within thistemperature regime is often used238 It has beenobserved in some investigations that Sc and SczZradditions to AlndashMgndashZn alloys slow down the precipita-tion of g9 somewhat243 Other investigations find thatthere is no effect of Sc on the precipitation behaviour ofg9244245 and yet others report that Sc additionssignificantly speed up the precipitation of g9246 In Ref247 it is found that an Sc addition leads to coarser g9precipitates and it is claimed that this gives an improvedductility of the alloy The strength-loss associated withlarger particle size is reported to be counterbalanced bystrengthening from Al3Sc precipitates

AlndashLi alloys

The precipitation sequence in binary AlndashLi alloys isapparently simple

Supersaturated solid solutionRd9Rd (AlLi)

where d9 is the metastable Al3Li phase which just likeAl3Sc has the L12 type of atomic arrangement Thetypical temperature regime for precipitation of d9 whichis the strengthening phase in this system is approx 150ndash200uC A comparison of the age hardening response ofan Alndash26 wt-Li and an Alndash24 wt-Lindash019 wt-Scalloy at 180uC248 and 200uC161 indicates that the onsetof d9 precipitation is not altered by the presence of ScThe hardness curves for the two alloys are practicallyidentical at 200uC whereas at 180uC the peak hardnesslevel is slightly higher in the AlndashLi than the AlndashLindashScalloy DSC measurements at constant heating ratesindicate that the addition of Sc to an AlndashLi alloysincreases the activation energy for d9 precipitation andmoves the exothermic peak associated with d9 precipita-tion to a higher temperature248 For specimens aged at

either 180uC or 200uC TEM observations reveal that thed9 precipitates are much smaller in the Sc containingalloy than in binary AlndashLi both in the peak agedcondition and in the overaged condition161248 Additionof Sc has also been observed to reduce the size of d9precipitates in other AlndashLi based alloys249ndash251 In an AlndashLindashCundashZr alloy an addition of Sc has been reported toslow down the homogeneous precipitation of d9252253 Ithas been claimed that Sc reduces the quench sensitivityand delays room temperature aging of AlndashLi basedalloys254ndash256

When present in the microstructure before the pre-cipitation of d9 the Al3Sc precipitates may act as effec-tive nucleation sites for d9 The resulting precipitates arespheres of d9 with a core of Al3Sc161249252ndash255257ndash261

Corrosion resistanceAn appreciable amount of data is available on the effectsof Sc on the corrosion behaviour of wrought Al-alloysSome of these effects are apparently derived from theeffects of Sc on the microstructure of the alloys It hasbeen reported that an addition of Sc increases thecorrosion potential (makes it less negative) in pureAl262ndash264 in AlndashZn alloys265266 AlndashMg alloys267 AlndashZnndashMgndashCu alloys264268 AlndashCundashMgndashMn alloys264 andin AlndashCundashLindashMgndashAg alloys264 Even though Sc alsohas been reported to decrease the corrosion potential in

28 Age hardening response at 175uC for Alndash08 wt-Mgndash

07 wt-Si alloy (Base) with additions of 02 wt-Sc

04 wt-Sc and 02 wt-Scz01 wt-Zr from Ref 241

29 TEM images of a b0 precipitates in Alndash08 wt-Mgndash

07 wt-Si alloy and b b0 and Al3(Sc1ndashxZrx) in a similar

alloy with addition of 02 wt-Scz01 wt-Zr from

Ref 241

Roslashyset and Ryum Scandium in aluminium alloys

38 International Materials Reviews 2005 VOL 50 NO 1

AlndashMg alloys269270 it seems that the general trend isthat adding Sc to an alloy makes it slightly more nobleThe change in corrosion potential is much morepronounced when Sc is added in amounts larger thanthe eutectic composition263 ie there is a considerablecontribution from primary or eutectic Al3Sc to theoverall potential It has also been demonstrated that thechange in corrosion potential caused by Sc can dependon the heat treatment applied to the alloy267268

Even though the corrosion potential is an essentialparameter in establishing the corrosion behaviour of analloy an increase in the corrosion potential does notnecessarily imply an improved self-corrosion resistanceHowever measurements of corrosion rates and passiva-tion current densities strongly suggest that the self-corrosion resistance in general is considerably improvedwhen Sc is added to wrought Al-alloys263264267 Someobserved variations in corrosion potential and passiva-tion current densities with Sc content in binary AlndashScalloys are plotted in Fig 30

Material failure in corrosive environments is often dueto localised corrosion attacks which may propagaterapidly even though the bulk material has a goodresistance against general corrosion It has been pointedout that hypereutectic additions of Sc may lead tomicrogalvanic corrosion beside primary Al3Sc parti-cles264 In AlndashMg alloys grain boundary precipitation ofAl8Mg5 can lead to localised corrosion attacks such asintergranular corrosion (IGC) exfoliation corrosion(EC) and stress corrosion cracking (SCC) In wroughtmaterial such precipitation may occur in the 60ndash180uCtemperature regime and heating in this temperaturerange is referred to as lsquosensitationrsquo An AlndashMgndashSc alloywas found to be immune against intergranular corrosionand have moderate susceptibility to exfoliation corro-sion after annealing at 350uC271 After sensitation heattreatments severe IGC and EC was observed but notquite as severe as in a corresponding alloy without ScAs for SCC the AlndashMgndashSc alloy was found to be highlyresistant271 In another study it was found that additionof 056 wt-Sc reduces the SCC susceptibility of an Alndash68 wt-Mg alloy in the as-rolled state and afterannealing at 250uC whereas in a sensitised specimenthe SCC susceptibility is somewhat increased by the Scaddition272 A third investigation found that Sc has nomeasurable detrimental effect on the SCC susceptibilityof sensitised Alndash5Mgndash015Zr alloy273 SCC is also a

severe problem in high strength AlndashZnndashMgndashCu alloys Ithas been shown that small Sc additions are effective inreducing the SCC sensitivity of these alloys244246268274

Use of Sc-containing Al alloysA systematic development of Sc-containing aluminiumalloys took place in the former USSR in the 1980s andthe interest for Sc as an alloying element in aluminiumalloys hit the western world approximately 10 yearslater Even though a number of improvements in Alalloys achieved by Sc addition have been demonstratedthe current uses of such alloys are very limited This isrelated to the very high price of scandium

In Russia some parts of military aircraft are made ofSc-containing AlndashLi alloys In the western world themain usage of Sc-containing alloys is for sportsequipment Ashurst Technology and Kaiser Aluminumdeveloped a Sc-containing 7xxx alloy for baseball andsoftball bats which was introduced to the Americanmarket in 1997 by Easton Alcoa soon followed with aSc-containing alloy for a competing brand of batsLouisville Slugger Since then several new and improvedSc-containing alloys for bats have been introduced tothe market The purpose of adding Sc is to increase theyield strength of the alloy allowing for a down-gaugingof the wall thickness which in turn gives a strongerlsquospring-rsquo or lsquotrampoline-rsquo effect when the ball hits thebat

Shortly after the introduction of the Sc containingbats Easton also launched Sc-containing 7xxx tubingfor bicycle frames Just as in the bats Sc increases theyield strength of the alloy allowing for down-gauging oftube wall thickness and a corresponding weight reduc-tion of the bicycle frame An Italian manufacturer ofbicycle tubing Dedacciai also delivers tubes in a Sc-containing 7xxx alloy

Other sports equipment made from Sc-containingaluminium alloys includes lacrosse sticks and tent polesSmith and Wesson has also introduced a series ofhandguns where the frame is made from a Sc-containingAl alloy

A common factor for the items mentioned above isthat the material cost is only a minor part of the totalmanufacturing cost of the end product and also thatthese products are aimed at a group of customers thathave a certain awareness of new materials Both baseballbats and bicycle frames have been marketed aslsquoscandium alloyrsquo even though the Sc content is muchlower than 1

Currently AlndashSc master alloys for the production ofSc-containing Al alloys are available at a price thatcorresponds to US$ 2000 per kg of Sc This means that ifone wants to add 02 wt-Sc to an alloy which is afairly common content one also increases the price ofthe alloy by US$ 4 per kg alloy Depending on the alloytype Sc is added to this represents a tripling orquadrupling of the price of the alloy There are notmany existing products where such an increase inmaterial cost can be justified In order to see awidespread use of Sc in high-volume products the Scprice has to come down considerably Actually the priceof adding Sc to Al alloys has gone down by a factor 3ndash10over the last 10ndash15 years and substantial price reduc-tions are also expected in the future

30 Observed variations in corrosion potential and passi-

vation current densities with Sc content in binary Alndash

Sc alloys based on data from Ref 263

Roslashyset and Ryum Scandium in aluminium alloys

International Materials Reviews 2005 VOL 50 NO 1 39

The current production of AlndashSc master alloys isbased upon and will continue to be based upon for theforeseeable future the reduction of Sc2O3 or other Sccompounds directly in molten aluminium It is notnecessary as many tend to believe to take the route viametallic Sc Thus the price of AlndashSc master alloy isgoverned by the price of Sc2O3 or other Sc compoundsin question and not by the price of metallic scandiumThe Sc2O3 which is the main source for todayrsquos AlndashScmaster alloy production comes from stockpiles in theformer USSR These stockpiles will be exhausted withina few years and new reliable sources of Sc2O3 or otherSc compound production are sought It turns out thatthe most economically viable option that has beendisclosed so far is the processing of Red Mud from theBayer process of extracting alumina from bauxiteScandium is enriched in the Red Mud and is extractedfrom a Red Mud aqueous slurry by selective leachingsubsequent ion-exchange procedure and finally a liquidndashliquid extraction procedure It is not required to build aseparate lsquoSc factoryrsquo to do this but rather build an lsquoadd-onrsquo to existing Bayer process plants Such a processroute is expected to bring down the price of Sc2O3

considerably which in turn means that AlndashSc masteralloy price should drop accordingly Preliminary ana-lyses suggest a price of approx US$ 400 per kg Sc in themaster alloy which translates to an added cost of 80cent per kilo when 02 wt-Sc is added to an aluminiumalloy This is also a considerable increase in the materialcost but with such prices one should expect to see Sccontaining alloys in many more applications than whatis the case at the present time

Concluding remarksThe body of published investigations on Al-based alloyswith Sc addition provides a sound basis of knowledgefor metallurgists that want to look into the possibility ofenhancing the performance of a wrought Al-alloy byadding Sc to it Ternary AlndashScndashX phase diagrams areavailable for practically every technologically importantalloying element in Al The effect of a wide range ofternary alloying elements on the precipitation behaviourof Al3Sc is accounted for It has been shown that theAl3Sc phase can be effective as a grain refiner adispersoid former and a precipitate hardening agentand some of the underlying conditions for achieving thedesired Al3Sc formation have been outlined Addingsome Zr together with Sc has proven to be beneficial Itmay lead to effective grain refinement at a lower Sc levelbut the most prominent effect is the refinement indispersoid distribution that can be achieved An addi-tion of Sc has little if any effect on precipitation in the2xxx 6xxx and 7xxx alloy systems and some effects onthe precipitation in AlndashLi based alloys With respect tocorrosion behaviour adding Sc to an Al-alloy does ingeneral seem to make the alloy slightly more noble andto increase its self-corrosion resistance Scandium-containing Al alloys have very few uses at the presenttime as a result of the high price of scandium The priceof Sc is expected to decrease significantly in the futureand this should lead to the disclosure of moreapplications where it is economically feasible to takeadvantage of the improved properties of some Sc-containing aluminium alloys

References1 D R Lide lsquoCRC handbook of chemistry and physicsrsquo 71st edn

4ndash29 1990 Boston USA CRC Press

2 E M Savitsky V F Terehova I V Burov and O P Naumkin

Proc Fourth Conf on lsquoRare earth researchrsquo Phoenix Arizona

USA April 1964 409ndash420

3 E M Savitskii V F Terekhova I V Burov O P Naumkin and

I A Markova Inorg Mater 1965 1 1503ndash1512

4 O P Naumkin V T Terekhova and E M Savitskiy Russ

Metall 1965 (4) 128ndash136

5 W G Moffatt lsquoThe handbook of binary phase diagramsrsquo 1981

Schenectady NY USA General Electric Co

6 E A Brandes (ed) lsquoSmithells metals reference bookrsquo 6th edn

1983 London UK Butterworths

7 R P Elliott and F A Shunk Bull Alloy Phase Diagrams 1981

2 (2) 222ndash223

8 K A Gschneider Jr and F W Calderwood Bull Alloy Phase

Diagrams 1989 10 34ndash36

9 H Okamoto J Phase Equil 1991 12 612ndash613

10 J L Murray J Phase Equil 1998 19 380ndash384

11 M E Drits E S Kadaner T V Dobatkina and N I Turkina

Russ Metall 1973 (4) 152ndash154

12 S-I Fujikawa M Sugaya H Takei and K-I Hirano J Less-

Common Met 1979 63 87ndash97

13 N Blake and M A Hopkins J Mater Sci 1985 20 2861ndash2867

14 V I Kononenko and S V Golubev Russ Metall 1990 (2) 193ndash

195

15 T B Massalski J L Murray L H Bennett and H Baker (eds)

lsquoBinary alloy phase diagramsrsquo 1986 Metals Park OH USA

ASM

16 G Cacciamani P Riani G Borzone N Parodi A Saccone

R Ferro A Pisch and R Schmid-Fetzer Intermetallics 1999 7

101ndash108

17 H Okamoto J Phase Equil 2000 21 310

18 A F Norman P B Pragnell and R S McEwen Acta Mater

1998 46 5715ndash5732

19 I N Pyagai and A V Vakhobov Russ Metall 1990 (5) 50ndash52

20 C L Fu J Mater Res 1990 5 971ndash979

21 X Lu and Y Wang Calphad 2002 26 555ndash561

22 R R Sawtell and J W Morris Jr Proc lsquoDispersion strengthened

aluminium alloysrsquo Phoenix Arizona USA January 1988 409ndash

420

23 R R Sawtell and C L Jensen Metall Trans A 1990 21A 421ndash

430

24 L A Willey Unpublished research Alcoa 1970 Data points are

extracted from Ref 10

25 N I Turkina and V I Kuzmina Russ Metall 1976 (4) 179ndash

183

26 T Torma E Kovacs-Csetenyi I Vitanyi M Butova and

J Stepanov Proc 6th Int Symp on lsquoHigh purity materials in

science and technologyrsquo Akademie der Wissenschaften der DDR

Dresden Germany May 1985 388ndash389

27 A L Berezina V A Volkov B P Domashnikov and K V

Chuistov Metallofizika 1987 9 (5) 43ndash47

28 H-H Jo J Korean Inst Metals 1990 28 499ndash504

29 H-H Jo and S-I Fujikawa Mater Sci Eng 1993 A 171 151ndash

161

30 S Celotto and T J Bastow Philos Mag A 2000 80 1111ndash1125

31 J Roslashyset and N Ryum submitted to Mater Sci Eng

32 M E Drits L S Toropova Yu G Bykov F L Gushchina V I

Elagin and Yu A Filatov Russ Metall 1983 (1) 150ndash153

33 L S Toropova D G Eskin M L Kharakterova and T V

Dobatkina lsquoAdvanced aluminum alloys containing scandium

structure and propertiesrsquo 1998 Amsterdam The Netherlands

Gordon and Breach Science Publishers

34 V V Cherkasov P P Pobezhimov L P Nefedova E V Belov

and G M Kuznetsov Met Sci Heat Treat 1996 (6) 268ndash270

35 Kh O Odinaev I N Ganiev V V Kinzhibalo and B Ya

Kotur Dokl Akad Nauk Tadzh SSR 1989 32 37ndash38

36 Kh O Odinaev I N Ganiev and A V Vakhobov Russ Metall

1991 (4) 200ndash203

37 J Grobner R Schmid-Fetzer A Pisch G Cacciamani P Riani

N Parodi G Borzone A Saccone and R Ferro Z Metallkd

1999 90 872ndash880

38 E A Marquis and D N Seidman Microsc Microanal 2002 8

(Suppl 2) 1100CDndash1101CD

39 A Pisch J Grobner and R Schmid-Fetzer Mater Sci Eng A

2000 A 289 123ndash129

Roslashyset and Ryum Scandium in aluminium alloys

40 International Materials Reviews 2005 VOL 50 NO 1

40 C Xia F Zeng and Y Gu Trans Nonferrous Met Soc China

2003 13 1124ndash1127

41 M Yu Teslyuk and V S Protasov Sov Phys Crystallogr 1966

10 470ndash471

42 M L Kharakterova and T V Dobatkina Russ Metall 1988

(6) 175ndash178

43 M L Kharakterova Russ Metall 1991 (4) 195ndash199

44 L S Toropova M L Kharakterova and D G Eskin Russ

Metall 1992 (3) 194ndash199

45 P Riani L Arrighi R Marazza D Mazzone G Zanicchi and

R Ferro J Phase Equil Diff 2004 25 22ndash52

46 A T Tyvanchuk T I Yanson B Ya Kotur O S Zarechnyuk

and M L Kharakterova Russ Metall 1988 (4) 190ndash192

47 L L Rokhlin T V Dobatkina and M L Kharakterova Powder

Metall Met Ceram 1997 36

48 A Z Ikromov I N Ganiev and V V Kinzhibalo Dokl Akad

Nauk Tadzh SSR 1990 (6) 391ndash392

49 I N Ganiev A Z Ikromov and V G Khudoiberdiev Russ

Metall 1995 (3) 125ndash127

50 I N Fridlyander L L Rokhlin T V Dobatkina and N I

Nikitina Met Sci Heat Treat 1993 (10) 567ndash571

51 I N Fridlyander L L Rokhlin T V Dobatkina V V

Kinzhibalo and A T Tyvanchuk Russ Metall 1998 (1) 161ndash

166

52 R A Emigh E L Bradley and J W Morris Jr in lsquoLight-weight

alloys for aerospace applications IIrsquo (ed E W Lee and N J

Kim) 27ndash43 1991 TMS

53 L S Toropova A N Kamardinkin V V Kindzhibalo and A T

Tyvanchuk Phys Met Metall 1990 70 (6) 106ndash110

54 A N Kamardinkin T V Dobatkina and T D Rostova Russ

Metall 1991 (4) 216ndash218

55 L S Torodskaya T V Dobatkina and A N Kamardinkin

Russ Metall 1992 (5) 128ndash131

56 E M Sokolovskaya E F Kazakova E I Poddyakova and A

A Ezhov Met Sci Heat Treat 1997 (5) 211ndash213

57 Y Harada and D C Dunand Mater Sci Eng 2002 A 329ndash331

686ndash695

58 N E Drits L S Toropova and F L Gushchina Russ Metall

1984 (4) 229ndash232

59 E M Sokolovskaya E F Kazakova V A Alikhanov and E V

Zhuravleva Moscow Univ Chem Bull 1997 52 (5) 70ndash72

60 E M Sokolovskaya E F Kazakova and E I Poddyakova Met

Sci Heat Treat 1989 (11) 837ndash839

61 G M Cheldieva E F Kazakova E M Sokolovskaya and N I

Kaloev Russ Metall 1990 (6) 87ndash90

62 E M Sokolovskaya E F Kazakova and O D-S Kendivan

Russ Metall 1998 (4) 135ndash137

63 N G Bukhanko E F Kazakova and E M Sokolovskaya Russ

Metall 2001 (4) 425ndash431

64 E D Trubnyakova O I Bodak I N Ganiev and A V

Vakhobov Russ Metall 1987 (3) 219ndash222

65 I N Fridlyander and L V Molchanova Russ Metall 2003 (5)

476ndash480

66 R A Altynbaev S Kh Khairidinov and A V Vakhobov Russ

Metall 1987 (4) 194ndash196

67 J C Schuster and J Bauer J Less-Common Met 1985 109

345ndash350

68 L L Rokhlin A S Fridman T V Dobatkina and D G Eskin

Russ Metall 1991 (6) 146ndash148

69 A S Fridman T V Dobatkina and E V Muratova Russ

Metall 1992 (1) 207ndash209

70 C Xia F Zeng and Y Gu Trans Nonferrous Met Soc China

2003 13 546ndash552

71 F Zeng C Xia and Y Gu J Alloys Comp 2004 363 175ndash181

72 L L Rokhlin T V Dobatkina N R Bochvar and E V Lysova

J Alloys Comp 2004 367 10ndash16

73 T V Dobatkina A S Fridman and E V Muratova Russ

Metall 1992 (5) 125ndash127

74 I N Fridlyander L L Rokhlin N R Bochvar E V Lysova

and O V Boteva Russ Metall 2001 (6) 661ndash666

75 V N Rechkin L K Lamikhov and T I Samsonova Sov Phys

Crystallogr 1964 9 325ndash327

76 I I Zalutskii and P I Kripyakevich Sov Phys Crystallogr

1967 12 341ndash343

77 T J Bastow C T Forwood M A Gibson and M E Smith

Phys Rev B 1998 58 2988ndash2997

78 K Fukunaga M Kolbe K Yamada and Y Miura Mater Sci

Eng 1997 A 234ndash236 594ndash597

79 E P George J A Horton W D Porter and J H Schneibel

J Mater Res 1990 5 1639ndash1648

80 E P George D P Pope C L Fu and J H Schneibel ISIJ Int

1991 31 1063ndash1075

81 Y Harada and D C Dunand Acta Mater 2000 48 3477ndash3487

82 J H Schneibel and E P George Scripta Metall Mater 1990 24

1069ndash1074

83 J H Schneibel and P M Hazzledine Mater Res Soc Symp

Proc 1991 213 323ndash328

84 J H Schneibel and P M Hazzledine J Mater Res 1992 7

868ndash875

85 C J Sparks E D Specht G E Ice P Zschack and J Schneibel

Mater Res Soc Symp Proc 1991 213 363ndash368

86 J Tarnacki and Y-W Kim Scripta Metall Mater 1989 23

1063ndash1068

87 M Asta V Ozolins and C Woodward JOM 2001 53 (9) 16ndash

19

88 M E Drits L S Toropova F L Gushchina and S G Fedotov

Sov Non-Ferrous Met Res 1984 12 83ndash85

89 Y Harada and D C Dunand Scripta Mater 2003 48 219ndash222

90 C Woodward M Asta G Kresse and J Hafner Phys Rev B

2001 63 094103-1-6

91 J-H Xu and A J Freeman Phys Rev B 1990 41 12553ndash12561

92 M F Bartholomeusz and J A Wert Acta Metall Mater 1992

40 673ndash682

93 G Bester and M Fahnle J Phys Condens Matter 2001 13

11551ndash11565

94 C L Fu and M H Yoo Proc lsquoOrdered intermetallics ndash physical

metallurgy and mechanical behaviorrsquo Irsee Germany June 1991

155ndash164

95 K Fukunaga T Shouji and Y Miura Mater Sci Eng 1997 A

239ndash240 202ndash205

96 D P Pope Proc lsquoOrdered intermetallics ndash physical metallurgy

and mechanical behaviorrsquo Irsee Germany June 1991 143ndash153

97 J-S Wang Acta Mater 1998 46 2663ndash2674

98 M H Yoo and C L Fu Mater Sci Eng 1992 A 153 470ndash478

99 R W Hyland Jr and R C Stiffler Scripta Metall Mater 1991

25 473ndash477

100 I G Brodova I V Polents O A Korzhavina P S Popelrsquo I P

Korshunov and V O Esin Melts 1992 4 392ndash397

101 I G Brodova O A Chikova I V Polents P S Popelrsquo and V O

Esin Casting Processes 1992 1 (2) 158ndash160

102 I G Brodova D V Bashlikov and I V Polents Mater Sci

Forum 1998 269ndash272 589ndash594

103 K B Hyde A F Norman and P B Pragnell Mater Sci Forum

2000 331ndash337 1013ndash1018

104 K B Hyde A F Norman and P B Pragnell Acta Mater 2001

49 1327ndash1337

105 J Roslashyset and N Ryum Proc 6th Int Conf on lsquoAluminum

alloysrsquo Toyohashi Japan July 1998 793ndash798

106 V I Elagin V V Zakharov and T D Rostova Met Sci Heat

Treat 1993 (6) 317ndash319

107 R W Hyland Jr Metall Trans A 1992 23A 1947ndash1955

108 B A Parker Z F Zhou and P Nolle J Mater Sci 1995 30

452ndash458

109 C L Rohrer M D Asta S M Foiles and R W Hyland Jr

Mater Res Soc Symp Proc 1996 398 477ndash482

110 G M Novotny and A J Ardell Mater Sci Eng 2001 A 318

144ndash154

111 J D Robson M J Jones and P B Pragnell Acta Mater 2003

51 1453ndash1468

112 C Tan Z Zheng and B Wang Proc 3rd Int Conf on

lsquoAluminium alloysrsquo Vol I NTH Trondheim Norway June

1992 290ndash294

113 M Nakayama A Furuta and Y Miura Mater Trans JIM

1997 38 852ndash857

114 E A Marquis and D N Seidman Acta Mater 2001 49 1909ndash

1919

115 M J Jones and F J Humphreys Acta Mater 2003 51 2149ndash

2159

116 E A Marquis D N Seidman and D C Dunand in lsquoCreep

deformation fundamentals and applicationsrsquo (ed R S Mishra

J C Earthman and S V Raj) 299ndash308 2002 TMS

117 D N Seidman E A Marquis and D C Dunand Acta Mater

2002 50 4021ndash4035

118 E A Marquis D N Seidman and D C Dunand Acta Mater

2003 51 285ndash287

119 M E Drits L S Toropova U G Bikov and G K Anastaseva

Proc lsquoDiffusion in metals and alloysrsquo Tihany Hungary Augustndash

September 1982 616ndash623

120 V I Elagin V V Zakharov and T D Rostova Met Sci Heat

Treat 1983 (7) 546ndash549

Roslashyset and Ryum Scandium in aluminium alloys

International Materials Reviews 2005 VOL 50 NO 1 41

121 M Ye Drits L B Ber Yu G Bykov L S Toropova and G K

Anastaseva Phys Met Metall 1984 57 (6) 118ndash126

122 M E Drits L S Toropova and Yu G Bykov Sov Non-Ferrous

Met Res 1985 13 309ndash314

123 V I Yelagin V V Zakharov S G Pavlenko and T D Rostova

Phys Met Metall 1985 60 (1) 88ndash92

124 N Sano Y Hasegawa K Hono H Jo K Hirano H W

Pickering and T Sakurai Journal de Physique 1987 48 C6 337ndash

342

125 N Sano H-H Jo K-I Hirano and T Sakurai J Jpn Inst

Metals 1989 39 444ndash450

126 N Sano H Jo K Hirano and T Sakurai Proc Second Int

Conf on lsquoAluminium alloysrsquo Beijing China October 1990 549ndash

554

127 Y Miura M Nakayama and A Furuta Proc lsquoAspects of high

temperature deformation and fracture in crystalline materialsrsquo

Nagoya Japan July 1993 255ndash262

128 Y W Riddle and T H Sanders Jr Mater Sci Forum 2000

331ndash337 939ndash944

129 Y W Riddle M McIntosh and T H Sanders Jr in lsquoLightweight

alloys for aerospace application VIrsquo (ed K Jata E W Lee

W Frazier and N J Kim) 25ndash39 2001 TMS

130 M E Drits J Dutkiewicz L S Toropova and J Salawa Crystal

Res Technol 1984 19 1325ndash1330

131 Y W Riddle MSc thesis Georgia Tech GA USA 1998

132 T J Bastow and S Celotto Mater Sci Eng 2003 C 23 757ndash

762

133 M C Carroll M J Mills G S Daehn P I Gouma M F

Savage and B R Dunbar in lsquoAutomotive Alloys 1999rsquo (ed

S Das) 239ndash246 2000 TMS

134 E Clouet M Nastar and C Sigli Phys Rev B 2004 69 064109-

1-14

135 V V Zakharov Met Sci Heat Treat 1997 (2) 61ndash66

136 J W Christian lsquoThe theory of transformation in metals and

alloysrsquo 2nd edn 1975 Pergamon Press Ltd

137 A L Berezina V A Volkov B P Domashnikov S V Ivanov

and K V Chuistov Phys Metals 1990 10 296ndash304

138 S-I Fujikawa and S Sakauchi Proc 6th Int Conf on

lsquoAluminum alloysrsquo Toyohashi Japan July 1998 805ndash810

139 Y S Touloukian R K Kirby R E Taylor and P D Desai

(eds) lsquoThermal expansion metallic elements and alloysrsquo 1975

New York Plenum

140 J Roslashyset and N Ryum submitted to Scripta Mater

141 R O Simmons and R W Balluffi Phys Rev 1960 117 52ndash61

142 M Ocko E Babic R Krsmik E Girt and B Leontic J Phys F

Metals Phys 1976 6 703ndash707

143 M J Jones and F J Humphreys Proc First Joint Int Conf on

lsquoRecrystallization and grain growthrsquo Aachen Germany August

2001 Springer Verlag 1287ndash1292

144 S Iwamura M Nakayama and Y Miura Mater Sci Forum

2002 396ndash402 1151ndash1156

145 S Iwamura and Y Miura Acta Mater 2004 52 591ndash600

146 M Asta S M Foiles and A A Quong Phys Rev B 1998 57

11265ndash11275

147 R W Hyland Jr M Asta S M Foiles and C L Rohrer Acta

Mater 1998 46 3667ndash3678

148 J Roslashyset and N Ryum Proc 4th Int Conf on lsquoAluminium

alloysrsquo Vol I Atlanta GA USA September 1994 194ndash201

149 M E Drits L S Toropova G K Anastaseva and G L

Nagornichnykh Russ Metall 1984 (3) 192ndash195

150 E A Marquis D N Seidman and D C Dunand Acta Mater

2003 51 4751ndash4760

151 M E Drits L S Toropova and Yu G Bykov Met Sci Heat

Treat 1983 (7) 550ndash554

152 V V Zakharov and T D Rostova Met Sci Heat Treat 1995

(2) 65ndash69

153 M Nakayama and Y Miura Proc 4th Int Conf on lsquoAluminium

alloysrsquo Vol I Atlanta GA USA September 1994 538ndash545

154 M Nakayama and Y Miura J Jpn Inst Light Metals 1996 46

275ndash279

155 M Nakayama T Okuyama and Y Miura Mater Sci Forum

2000 331ndash337 927ndash932

156 M Nakayama T Okuyama and Y Miura Proc 6th Int Conf

on lsquoAluminum alloysrsquo Toyohashi Japan July 1998 517ndash522

157 M L Kharakterova D G Eskin and L S Toropova Acta

Metall Mater 1994 42 2285ndash2290

158 V I Elagin V V Zakharov and T D Rostova Met Sci Heat

Treat 1992 (1) 37ndash45

159 H Wiik Siv Ing thesis NTH Institute of Metallurgy

Trondheim Norway 1995

160 J Roslashyset H Hovland and N Ryum Mater Sci Forum 2002

396ndash402 619ndash624

161 Y Miura K Horikawa K Yamada and M Nakayama Proc

4th Int Conf on lsquoAluminium alloysrsquo Vol II Atlanta GA USA

September 1994 161ndash168

162 Y W Riddle PhD thesis Georgia Tech GA USA 2000

163 B Forbord W Lefebvre F Danoix H Hallem and

K Marthinsen Scripta Mater 2004 51 333ndash337

164 J D Robson Acta Mater 2004 52 1409ndash1421

165 C B Fuller J L Murray and D N Seidman submitted to Acta

Mater 2004

166 M G Mousavi C E Cross and Oslash Grong Sci Technol Weld

Joining 1999 4 381ndash388

167 J S Vetrano S M Bruemmer L M Pawlowski and I M

Robertson Mater Sci Eng 1997 A 238 101ndash107

168 Y W Riddle and T H Sanders Jr Mater Sci Forum 2000

331ndash337 799ndash803

169 G M Khan A O Nikiforov V V Zakharov and I I Novikov

Tsvetnye Metally 1993 34 (11) 43ndash45

170 Z Horita M Furukawa M Nemoto A J Barnes and T G

Langdon Acta Mater 2000 48 3633ndash3640

171 L A Willey US Patent 3 619 181 9 November 1971

172 L K Lamikhov and G V Samsonov Tsvetnye Metally 1964 5

(8) 77ndash80

173 A L Berezina K V Chuistov N I Kolobnev L B

Khokhlatova and T A Monastyrskaya Mater Sci Forum

2002 396ndash402 741ndash746

174 F A Fasoyinu J Thomson D Cousineau T Castles and M

Sahoo Proc 6th Int AFS Conf on lsquoMolten aluminum

processingrsquo Orlando FL USA November 2001

175 Z Yin Q Pan Y Zhang and F Jiang Mater Sci Eng 2000

A 280 151ndash155

176 I I Novikov and O E Grushko Mater Sci Technol 1995 11

926ndash932

177 D Cousineau M Sahoo P D Newcombe T Castles and F A

Fasoyinu Proc lsquoAFS 105th casting congressrsquo Dallas TX USA

AprilndashMay 2001 157ndash184

178 C E Cross and Oslash Grong Proc 6th Int Conf on lsquoAluminum

alloysrsquo Toyohashi Japan July 1998 1441ndash1446

179 F A Costello J D Robson and P B Prangnell Mater Sci

Forum 2002 396ndash402 757ndash762

180 K B Hyde A F Norman and P B Prangnell Mater Sci

Forum 2002 396ndash402 39ndash44

181 M E Drits S G Pavlenko L S Toropova Yu G Bukov and

L B Ber Sov Phys Dokl 1981 26 (3) 344ndash346

182 A M Drits and B A Kopeliovich Russ Metall 1985 (4) 147ndash

151

183 V G Davydov V I Elagin V V Zakharov and T D Rostova

Met Sci Heat Treat 1996 (8) 347ndash352

184 M E Drits L S Toropova Yu G Bykov L B Ber and S G

Pavlenko Russ Metall 1982 (1) 148ndash152

185 T D Rostova V G Davydov V I Yelagin and V V Zakharov

Mater Sci Forum 2000 331ndash337 793ndash798

186 Y W Riddle H Hallem and N Ryum Mater Sci Forum 2002

396ndash402 563ndash568

187 J Roslashyset and Y W Riddle Proc 9th Int Conf on lsquoAluminium

alloysrsquo Brisbane Australia August 2004 1210ndash1215

188 A M Diskin V K Portnoi A M Drits and A A Alalykin Sov

Non-Ferrous Met Res 1986 14 499ndash500

189 R R Sawtell P E Bretz and C L Jensen US Patent 4 689 090

25 August 1987

190 G A Salishchev Yu B Timoshenko and R A Saitova Proc

Second Int Conf on lsquoAluminium alloysrsquo Beijing China October

1990 413ndash415

191 T G Nieh R Kaibyshev L M Hsiung N Nguyen and

J Wadsworth Scripta Mater 1997 36 1011ndash1016

192 T G Nieh L M Hsiung J Wadsworth and R Kaibyshev Acta

Mater 1998 46 2789ndash2800

193 J S Vetrano C H Henager Jr M T Smith and S M

Bruemmer in lsquoHot deformation of aluminum alloys IIrsquo (ed T R

Bieler L A Lalli and S R MacEwen) 407ndash418 1998 TMS

194 J S Vetrano C H Henager Jr S M Bruemmer Y Ge and

C H Hamilton in lsquoSuperplasticity and Superplastic Forming

1998rsquo (ed A K Gosh and T R Bieler) 89ndash97 1998 TMS

195 V Y Gertsman J S Vetrano C H Henager Jr and S M

Bruemmer Proc First Joint Int Conf on lsquoRecrystallization and

grain growthrsquo Aachen Germany August 2001 Springer Verlag

2001 837ndash842

196 Y Xiao C Gao H Ma and S Tian Trans Nonferrous Met Soc

China 2001 11 235ndash238

Roslashyset and Ryum Scandium in aluminium alloys

42 International Materials Reviews 2005 VOL 50 NO 1

197 A Gholinia F J Humphreys and P B Prangnell Acta Mater

2002 50 4461ndash4476

198 A Gholinia F J Humphreys and P B Prangnell Mater Sci

Forum 2002 408ndash412 1519ndash1524

199 S Komura P B Berbon M Furukawa Z Horita M Nemoto

and T G Langdon Scripta Mater 1998 38 1851ndash1856

200 S Komura P B Berbon A Utsunomiya M Furukawa

Z Horita M Nemoto and T G Langdon in lsquoHot deformation

of aluminum alloys IIrsquo (ed T R Bieler L A Lalli and S R

MacEwen) 125ndash138 1998 TMS

201 S Komura Z Horita M Furukawa M Nemoto and T G

Langdon J Mater Res 2000 15 2571ndash2576

202 S Komura M Furukawa Z Horita M Nemoto and T G

Langdon Mater Sci Eng 2001 A 297 111ndash118

203 S Komura Z Horita M Furukawa M Nemoto and T G

Langdon Metall Mater Trans A 2001 32A 707ndash716

204 Z Horita M Furukawa K Oh-ishi M Nemoto and T G

Langdon Proc Fourth Int Conf on lsquoRecrystallization and

related phenomenarsquo (ed T Sakai and H G Suzuki) 1999 The

Japan Institute of Metals 301ndash308

205 Z Horita S Komura P B Berbon A Utsunomiya

M Furukawa M Nemoto and T G Langdon Mater Sci

Forum 1999 304ndash306 91ndash96

206 Z Horita S Lee S Ota K Neishi and T G Langdon Mater

Sci Forum 2001 357ndash359 471ndash476

207 Z Horita T Fujinami K Sato S B Kang H W Kim and T G

Langdon in Proc James T Staley Honorary Symposium on

Aluminum Alloys lsquoAdvances in the metallurgy of aluminum

alloysrsquo (ed M Tiryakioglu) 271ndash275 2001 ASM

208 P B Berbon S Komura A Utsunomiya Z Horita

M Furukawa M Nemoto and T G Langdon Mater Trans

JIM 1999 40 772ndash778

209 M Nemoto Z Horita M Furukawa and T G Langdon Mater

Sci Forum 1999 304ndash306 59ndash66

210 M Furukawa Z Horita M Nemeto and T G Langdon Proc

lsquoLight Metals 1999rsquo Quebec City PQ Canada August 1999 583ndash

592

211 M Furukawa K Oh-ishi S Komura A Yamashita Z Horita

M Nemeto and T G Langdon Mater Sci Forum 1999 304ndash

306 97ndash102

212 M Furukawa A Utsunomiya K Matsubara Z Horita and

T G Langdon Acta Mater 2001 49 3829ndash3838

213 M Furukawa A Utsunomiya S Komura Z Horita M Nemoto

and T G Langdon Mater Sci Forum 2001 357ndash359 431ndash436

214 M Furukawa Z Horita and T G Langdon in Proc James T

Staley Honorary Symposium on Aluminum Alloys lsquoAdvances in

the metallurgy of aluminum alloysrsquo (ed M Tiryakioglu) 47ndash56

2001 ASM

215 M Furukawa Z Horita M Nemoto and T G Langdon Mater

Sci Eng 2002 A 324 82ndash89

216 M Furukawa Z Horita and T G Langdon in lsquoUltrafine grained

materials IIrsquo (ed Y T Zhu T G Langdon R S Mishra S L

Semiatin M J Saran and T C Lowe) 459ndash468 2002 TMS

217 T G Langdon M Furukawa Z Horita and M Nemoto Proc

NATO Advanced Research Workshop on lsquoInvestigations and

applications of severe plastic deformationrsquo Moscow August

1999 NATO Science Series Series 3 High Technology vol 80

Kluwer Academic Publishers The Netherlands 2000 149ndash154

218 S Lee H Akamatsu A Utsunomiya K Neishi M Furukawa

Z Horita and T G Langdon Proc Thermec 2000 Las Vegas

USA December 2000

219 S Lee A Utsunomiya H Akamatsu K Neishi M Furukawa

Z Horita and T G Langdon Acta Mater 2002 50 553ndash564

220 A Yamashita D Yamaguchi Z Horita and T G Langdon

Mater Sci Eng 2000 A 287 100ndash106

221 K Oh-ishi Z Horita D J Smith and T G Langdon J Mater

Res 2001 16 583ndash589

222 H Akamatsu T Fujinami Z Horita and T G Langdon Scripta

Mater 2001 44 759ndash764

223 S Ota H Akamatsu K Neishi M Furukawa Z Horita and

T G Langdon Mater Trans 2002 43 2364ndash2369

224 K Furuno H Akamatsu K Oh-ishi M Furukawa Z Horita

and T G Langdon Acta Mater 2004 52 2497ndash2507

225 I N Fridlyander O G Senatorova N A Ryazanova and A O

Nikiforov Mater Sci Forum 1994 170ndash172 345ndash349

226 J N Fridlyander and O G Senatorova Mater Sci Forum 1996

217ndash222 1813ndash1818

227 J Liu and D J Chakrabarti Acta Mater 1996 44 4647ndash4661

228 O G Senatorova A N Uksusnikov J N Fridlyander

J Koshorst R R Romanova N A Ryazanova A Galliot

and V V Cherkassov Proc 6th Int Conf on lsquoAluminum alloysrsquo

July 1998 Toyohashi Japan 589ndash593

229 R A Emigh E L Bradley and J W Morris Jr in

lsquoSuperplasticity in aerospace IIrsquo (ed T R McNelley and H C

Heikkenen) 303ndash315 1990 TMS

230 E L Bradley III R A Emigh and J W Morris Jr Scripta

Metall Mater 1991 25 717ndash721

231 N I Kolobnev L B Khokhlatova V D Makarov E Yu

Semenova and V V Redchits Proc Sixth Int Aluminiumndash

Lithium Conference Garmisch-Partenkirchen Germany October

1991 1053ndash1056

232 N K Tsenev R Z Valiev O V Obraztsov and I N Fridlander

Proc Sixth Int AluminiumndashLithium Conference Garmisch-

Partenkirchen Germany October 1991 1125ndash1132

233 A M Shammazov N K Tsenev R Z Valiev M M

Myshlyaev M M Bikbulatov and S P Lebedich Phys Met

Metall 2000 89 (3) 314ndash318

234 F Musin R Kaibyshev Y Motohashi T Sakuma and G Itoh

Mater Trans A 2002 43A 2370ndash2377

235 M Shagiev Y Motohashi F Musin R Kaibyshev and G Itoh

Mater Trans A 2003 44A 1694ndash1697

236 M Shagiev Y Motohashi F Musin R Kaibyshev and G Itoh

Mater Trans A 2003 44A 1698ndash1701

237 B A Parker and Z F Zhou Proc 3rd Int Conf on lsquoAluminium

alloysrsquo Vol I NTH Trondheim Norway June 1992 363ndash367

238 J R Davies lsquoASM specialty handbook aluminum and aluminum

alloysrsquo 1993 Materials Park OH USA ASM

239 S J Andersen H W Zandbergen J Jansen C Traeholt

U Tundal and O Reiso Acta Mater 1998 46 3283ndash3298

240 M L Kharakterova D G Eskin and L L Rokhlin Russ

Metall 1997 (1) 104ndash109

241 J Roslashyset Dr Ing thesis NTNU Trondheim Norway 2002

242 P P Chattopadhyay S Datta and M K Banerjee Mater Sci

Eng 2002 A 333 67ndash71

243 L I Kaigorodova E I Selnikhina E A Tkachenko and O G

Senatorova Phys Met Metall 1996 81 513ndash519

244 Y-L Wu F H Froes C Li and A Alvarez Metall Mater

Trans A 1999 30A 1017ndash1024

245 Z Yin L Yang Q Pan and F Jiang Trans Nonferrous Met

Soc China 2001 11 822ndash825

246 V I Elagin V V Zakharov and T D Rostova Met Sci Heat

Treat 1994 36 (7) 375ndash380

247 Y V Milman A I Sirko D V Lotsko O N Senkov and D B

Miracle Mater Sci Forum 2002 396ndash402 1217ndash1222

248 C-H Joh K Yamada and Y Miura Mater Trans JIM 1999

40 439ndash442

249 X J Jiang Q H Gui Y Y Li L M Ma G J Liang and C X

Shi Scr Metall Mater 1993 29 211ndash216

250 X J Jiang Y Y Li W Deng L Y Xiong W M Wu Y J Gao

and C X Shi Adv Cryogenic Eng (Mater) 1994 40 1369ndash

1376

251 C-H Joh T Katsube K Yamada and Y Miura Proc 6th Int

Conf on lsquoAluminum alloysrsquo Toyohashi Japan July 1998 799ndash

804

252 L I Kaygorodova A M Dritz T V Krymova and I N

Fridlyander Proc Sixth Int AluminiumndashLithium Conference

Garmisch-Partenkirchen Germany October 1991 363ndash367

253 L I Kaigorodova A M Drits Ya V Zhingel T V Krymova

and I N Fridlyander Phys Met Metall 1992 73 286ndash290

254 A L Berezina V A Volkov S V Ivanov N I Kolobnev and

K V Chuistov Phys Met Metall 1991 71 (2) 167ndash175

255 I N Fridlyander N I Kolobnev A L Berezina and K V

Chuistov Proc Sixth Int AluminiumndashLithium Conference

Garmisch-Partenkirchen Germany October 1991 107ndash112

256 L I Kaigorodova A M Drits Ya V Zhingel T V Krymova

and V A Rassokhin Phys Met Metall 1992 73 281ndash285

257 I N Fridlyander S F Danilov E N Malysheva T A

Gorokhova and N N Kirkina Proc Sixth Int Aluminiumndash

Lithium Conference Garmisch-Partenkirchen Germany October

1991 381ndash386

258 G Dlubek S Krause H Krause A L Beresina V S

Mikhalenkov and K V Chuistov J Phys Condens Matter

1992 4 6317ndash6328

259 S Krause H Krause G Dlubek A L Beresina and K S

Chuistov Mater Sci Forum 1992 105ndash110 1109ndash1112

260 C Y Tan Z Q Zheng and S Q Liang Proc 4th Int Conf on

lsquoAluminium alloysrsquo Vol II Atlanta GA USA September 1994

329ndash333

261 A L Beresina N I Kolobnev K V Chuistov A V Kotko and

O A Molebny Mater Sci Forum 2002 396ndash402 977ndash981

Roslashyset and Ryum Scandium in aluminium alloys

International Materials Reviews 2005 VOL 50 NO 1 43

262 I N Ganiev I Yunusov and V V Krasnoyarskii J Appl Chem

USSR 1986 60 1961ndash1965

263 I N Ganiev Prot Met 1995 31 543ndash546

264 N V Vyazovikina Prot Met 1999 35 448ndash453

265 G V Kharina and V P Kochergin Prot Met 1996 32 134ndash

136

266 G V Kharina M V Kuznetsov and V P Kochergin Russ J

Electrochem 1998 34 482ndash485

267 V S Sinyavskii V D Valrsquokov and E V Titkova Prot Met

1998 34 549ndash555

268 Y L Wu F H Froes C G Li and J Liu Proc lsquoSynthesis

processing of lightweight metallic materials IIrsquo Orlando FL

USA February 1997 73ndash81

269 Z Ahmad and B J Abdul-Aleem Proc EuroCorr 2000

270 Z Ahmad A Ul-Hamid and B J Abdul-Aleem Corros Sci

2001 43 1227ndash1243

271 R Braun B Lenczowski and G Tempus Mater Sci Forum

2000 331ndash337 1647ndash1652

272 T Torma E Kovacs-Csetenyi L Vitalis I Vitanyi

J Stepanov and M Butova Mater Sci Forum 1987 1314

497ndash503

273 Z Wang P Wang K S Kumar and C L Briant in lsquoChemistry

and electrochemistry of corrosion and stress corrosion crackingrsquo

(ed R H Jones) 573ndash582 2001 TMS

274 V I Elagin V V Zakharov A A Petrova and E V

Vyshegorodtseva Russ Metall 1983 (4) 143ndash146

Roslashyset and Ryum Scandium in aluminium alloys

44 International Materials Reviews 2005 VOL 50 NO 1

Page 10: Scandium in aluminium alloys - Atom probe · A considerable part of the available literature on scandium in aluminium alloys is reviewed. ... behaviour in Al Cu, Al Mg Si,

microscopy (TEM) study of the Al3Sc particle morphol-ogy development during precipitation heat treatment ofbinary AlndashSc alloys by Marquis and Seidman114 it isdemonstrated that the precipitates can take a wide rangeof shapes as they grow depending on Sc content in thealloy transformation temperature and transformationtime Irregular shaped star shaped and cuboidalshaped precipitates were observed under someconditions It was however found that the equilibriumshape of the particles is an equiaxed multifaceted one(Fig 15) Supported by Wulffrsquos construction it wasconcluded that the shape was that of a GreatRhombicuboctahedron This equilibrium morphologyhas been reproduced by computer-simulations ofparticle growth87134 The multifaceted particles caneasily be taken for spherical in a conventional TEMpicture

Kinetics of precipitation of Al3Sc fromsupersaturated solid solutionThe precipitation kinetics of Al3Sc in binary AlndashScalloys is dependent on the precipitation heat treatmenttemperature and on the Sc content in the alloy Acomprehensive overview over the transformationkinetics in terms of C-curves is given by Zakharov135

The C-curves for 5 transformation for a range of AlndashSc alloys are redrawn in Fig 16

Hyland107 studied the homogeneous nucleationkinetics of Al3Sc in a Alndash018 wt-Sc alloy after directquench from 650uC to precipitation temperatures of 288and 343uC He found that after an incubation time t theAl3Sc particles nucleated at a constant rate until thediffusion fields of the individual particles started tooverlap At 288uC the incubation time and time tosignificant diffusion field overlap were estimated to beapprox 245 and 150 min respectively whereas thecorresponding values at 343uC were estimated to beapprox 7 and 20 min respectively

If one assumes that the JohnsonndashMehlndashAvramindashKomolgorov (JMAK) relationship is valid for thisprecipitation reaction one can express the fraction

transformed X as a function of the reaction time t bythe equation

X (t)~1expfrac12k(Dt)n (1)

where k is a constant D is the interdiffusion constant ofSc in Al and the exponent n is dependent on thenucleation rate For the situation described byHyland107 where the precipitates nucleate at a constantrate the value of n should theoretically136 be equal to52

Roslashyset and Ryum31105 applied an alloy and heattreatment method practically equal to that of Hyland107

One should thus expect that the precipitation kineticsshould also be quite similar However Roslashyset andRyum reported that the exponent n of the JMAKrelationship was approx 165ndash185 for the temperaturerange of concern31105 This does not point in thedirection of a constant nucleation rate but rather inthe direction of site saturation ie that all the particlesare nucleated simultaneously which in the JMAKequation would yield an exponent n of 32136 Anoverview of some reported values of n in the JMAKequation is given in Table 4 The majority of the valueslie closer to 32 than to 52 However it is important to

15 High resolution TEM picture along n100m axis of Al3Sc particle in Alndash03 wt-Sc alloy aged at 300uC for 350 h114

(reproduced with permission from Elsevier Science image kindly provided by Dr E A Marquis and Professor D N

Seidman) and various projections of a Great Rhombicuboctahedron

Table 4 Some reported values of n in JMAK equation

Reference n C 0Sc wt-Sc Ttrans uC Note

137 13 030 300 Solution heat treated (SHT) 500uC16026 030 300 SHT 600uC Low n at late stage20026 030 300 SHT 640uC Low n at late stage

29 130ndash149 015 260ndash370145ndash196 025 260ndash370

138 188ndash216 020 240ndash35031 165ndash185 023 270ndash350 SHT 600uC Direct quench to transformation temp

16 C-curves for 5 transformation in a range of binary

AlndashSc alloys redrawn from Ref 135

Roslashyset and Ryum Scandium in aluminium alloys

28 International Materials Reviews 2005 VOL 50 NO 1

note that an n value close to 32 is per se not evidence ofsite saturation

Hyland also showed that a water quench from thesolutionising temperature significantly altered thenucleation kinetics in the subsequent precipitation heattreatment107 The incubation time was dramaticallyshortened which is attributed to the quenched-in excessvacancies and it is also indicated that there might be ashift in the nucleation rate in the early stage ofprecipitation It is suggested that the vacancies mayenhance the diffusion of Sc in Al and that there is apossibility that vacancy clusters act as heterogeneousnucleation sites for Al3Sc precipitates107 Regardless ofwhich mechanism that is operative it is clearly demon-strated that the nucleation kinetics can be dependent onthe thermal history between solutionising and precipita-tion heat treatment

Loss of coherency during growth of Al3ScprecipitatesWhen an Al3Sc particle grows it will sooner or laterreach a critical size where it will be energetically morefavourable to introduce an interface dislocation at theAlAl3Sc interface than to increase the matrix strain Asimple approximation for the critical size can be derivedfrom the lattice parameters assuming that the criticalsize is reached when the misfit over the whole particlediameter equals the Burgers vector of the Al matrix

dcrit~b=d (2)

where b is the Burgers vector of Al and d is themisfit between Al and Al3Sc This approximation yieldsa critical diameter of approx 215 nm at ambienttemperature

The misfit d and thus also the critical diameter dcrit

will depend on the temperature owing to the differencesin thermal expansion between the Al matrix and the

Al3Sc particles The thermal expansion of Al3Sc hasrecently been measured89 and based on the differencesin thermal expansion between Al139 and Al3Sc the misfitas a function of temperature has been calculated89 Thiscalculation is reproduced and shown by the solid line inFig 17

It is however possible to refine this calculationsomewhat140 Whereas the thermal expansion of Al3Sc isexpected to be only because of lattice expansion there isa significant contribution from vacancies on thermalexpansion of Al at high temperatures141 Thus thetemperature effects on the misfit should be calculatedfrom the changes in lattice parameters rather than fromthe linear thermal expansion By subtracting the vacancyeffect on the thermal expansion one achieves atemperature-dependent misfit as represented by thedotted line in Fig 17

A second correction that should be taken into accountis the effect of Sc in solid solution on the latticeparameter of the Al matrix With increasing tempera-ture more Sc is brought into solid solution and it isreported that the lattice parameter of the Al matrixpresumably measured at room temperature increaseslinearly with the Sc content in solid solution142 Thesedata can be used to calculate the effect on the latticeparameter at elevated temperatures under the assump-tion that the relative increase in lattice parameter owingto Sc in solid solution is independent of temperature InRef 142 a figure is presented which shows the measuredlattice parameter as a function of Sc content in solidsolution and a value (dadc)a is reported where a is thelattice parameter of the Al matrix and c is the Sc contentin solid solution in at- The reported value for (dadc)a is 100 times larger than that indicated in thecorresponding figure possibly as a result of a decimalerror in the text Thus in the present exercise 1100th ofthe reported value for (dadc)a is used Using this incombination with the regular solution approximationfor the solvus line of Sc in Al1231 one obtains acorrection for Sc in solid solution on the temperature-dependent misfit as shown in Fig 18 This figure shows

17 Lattice mismatch between Al and Al3Sc as a function

of temperature solid line represents calculation

based on linear thermal expansion of the two phases

dotted line represents correction for vacancies in Al

lattice

18 Corrections of mismatch calculated from linear ther-

mal expansion data as a result of vacancies and to

Al lattice expansion from Sc in solid solution

Roslashyset and Ryum Scandium in aluminium alloys

International Materials Reviews 2005 VOL 50 NO 1 29

both the correction for vacancies and for Sc in solidsolution on the same graph The two corrections are ofapproximately the same magnitude but with oppositesigns Thus the resulting (net) correction is close to zeroand it turns out that the first hand approximation asapplied in Ref 89 is very good in this case

Applying the calculated temperature dependent misfitwith the simple approximation for a critical diameter forloss of coherency one obtains a temperature-dependentcritical diameter as shown in Fig 19

Some examples from the literature of experimentallyobserved critical diameters in binary AlndashSc alloys aresummarised in Table 5 along with some predictions forcritical diameters from Fig 19 There is a fairly goodconsistency between the observations and the measureddiameter is quite close to the simple predictions above

A more refined analysis on the transition fromcoherent to incoherent particles has recently beenperformed145 This analysis is based on the balancebetween the increase in particlematrix interface energyowing to interfacial dislocations and the relaxation inelastic energy in the Al matrix owing to the samedislocations This method yields a predicted criticaldiameter of 246 nm for transition from coherent to

semi-coherent particles at ambient temperature Thetemperature dependence of the critical diameter is nottreated in this analysis

The loss of coherency during isothermal annealing hasbeen reported to be accompanied by an increasedaverage coarsening rate119121137145 The increasedcoarsening rate has been attributed either to diffusionof Sc along dislocation lines119121 or to the increasedparticlematrix interface energy of a semicoherentparticle145 However there are also several data sets inthe literature that do not indicate an increased growthrate after the loss of coherency114128

Al3ScAl interface energyThe interface energy between Al3Sc and the Al matrix isone of the key parameters that governs the nucleationgrowth and coarsening behaviour of Al3Sc in Al and Alalloys The interface energy has been estimated in severalinvestigations either by fitting experimental data toequations that describe nucleation or coarsening or bycalculations A compilation of some of the results isgiven in Table 6 There is considerable spread in thereported values regardless of what approach has beenused for the estimation

Influence of other elements on precipitation ofAl3ScMagnesium

With regard to precipitation mechanism it has beenstated that Mg suppresses the tendency to discontinuousprecipitation of Al3Sc106 In an investigation of pre-cipitation kinetics of Al3Sc in the temperature range300ndash500uC only minor changes in the kinetics (Fig 20)were found when up to 5 wt-Mg was added to an Alndash04 wt-Sc alloy135 It seems that the precipitationreaction is slightly faster in the Mg-containing alloys

Several investigations on age hardening response alsoimply that there is only a small if any effect of Mg onthe precipitation kinetics of Al3Sc23148149 It is how-ever found that the hardness increase from theprecipitation of Al3Sc is somewhat reduced in AlndashMgndashSc alloys compared to binary AlndashSc alloys23148149 InRef 149 it is suggested that some of the Sc is dissolvedin the Al3Mg2 phase and thus the age hardeningpotential is reduced with increasing Mg contentSomewhat contradictory to these observations but

Table 5 Some reported critical diameters for coherencyloss in binary AlndashSc and correspondingtheoretical critical diameters from Fig 19

Reference dcrit nmC0

Scwt-Sc

TtransuC

Theoreticaldcrit nm

119 38ndash40 05137 28ndash30 03 400 308128 32 02 400 450 308 335129 50 02143 40 012 025115 40 025 450ndash500 335ndash37114 40 03 400 450 308 335144 40 02 400ndash460 308ndash341145 30ndash80 02 400ndash490 308ndash362

20 C-curves for 10 and 60 transformation in Alndash

04 wt-Sc and Alndash4 wt-Mgndash04 wt-Sc redrawn

from Ref 135

19 Simple approximation for temperature-dependent criti-

cal diameter for introduction of dislocations on Al

Al3Sc interface

Roslashyset and Ryum Scandium in aluminium alloys

30 International Materials Reviews 2005 VOL 50 NO 1

sustained by Ref 135 it has recently been reported150

that precipitation of Al3Sc at 300 and 350uC occursslightly faster in an Alndash2 wt-Mgndash02 wt-Sc alloythan in an Alndash02 wt-Sc alloy studied previously by thesame researchers117118 and that the correspondinghardness increase is highest in the AlndashMgndashSc alloyThe only reported difference in experimental procedureis the solutionising temperature which was higher forthe AlndashSc alloy (648uC) than for the AlndashMgndashSc alloy(617uC) However given that the nucleation time isshortened by quenched-in vacancies as suggested byHyland107 the difference in homogenisation tempera-ture should be in favour of a faster precipitation of thebinary AlndashSc alloy It should be worthwhile to probedeeper into this observation of different aging responses

Mg in solid solution increases the lattice parameter ofthe Al matrix This is in turn expected to influence thecritical diameter for AlAl3Sc coherency loss as discussedin the section on lsquoLoss of coherency during growth ofAl3Sc precipitatesrsquo above Such an influence on the criticaldiameter is also briefly discussed elsewhere150 A criticaldiameter of 80 nm in an Alndash3 wt-Mgndash02 wt-Sc alloyhas been observed compared to 40 nm in a binary Alndash02 wt-Sc alloy of the same investigation144 Otherresearchers have reported a critical diameter in excess of116 nm in an Alndash63 wt-Mgndash02 wt-Sc alloy151

Computer simulations predict that the AlAl3Scinterface should be enriched in Mg87 These predictionsare confirmed experimentally by three-dimensional atomprobe microscopy of an Alndash2 wt-Mgndash02 wt-Sc alloyaged at 300uC38 Here it was found that the Mg contentat the interface is approximately three times higher thanthe matrix concentration regardless of aging time

Copper

It has been claimed that Cu suppresses the tendencytowards discontinuous precipitation of Al3Sc106

Zakharov and Rostova152 have reported that additionsof up to 14 wt-Cu have only minor effects on theprecipitation kinetics in an Alndash04 wt-Sc alloy Themost noticeable effect is that for temperatures above400uC the late stage of the transformation is sloweddown for the highest Cu contents This does not show in

Fig 21 however where only the 10 and 60transformation curves are included

The W-phase (AlCuSc) was observed in the alloywith the highest Cu content which means that less Sc isavailable for the precipitation of Al3Sc in this alloyAnother investigation on the age hardening response ofAlndash023 wt-Sc and Alndash25 wt-Cundash023 wt-Sc at300uC also implies that the precipitation behaviour ofAl3Sc in the two alloys is similar153154 At 350uC alimited portion of the Al3Sc has been observed tonucleate heterogeneously on coarse hrsquo precipitates155

According to the isothermal sections of the phasediagram43 one should expect the ternary W-phase toform instead of the Al3Sc phase in an alloy with such ahigh CuSc ratio However no observations of the W-phase or other ternary phases were reported from TEMstudies of the Alndash25 wt-Cundash023 wt-Sc alloy thathad been heat treated in the temperature range 300ndash460uC153ndash156 A third investigation on the precipitationin Alndash048 wt-Sc alloys with up to 440 wt-Cu in thetemperature range 100ndash450uC also concludes that no W-phase or other ternary phase forms during the heattreatment157

Copper in solid solution decreases the lattice para-meter of the Al matrix Thus it is expected that the misfitbetween Al and Al3Sc precipitates should be higher in

21 C-curves for 10 and 60 transformation in Alndash

04 wt-Sc and Alndash14 wt-Cundash04 wt-Sc redrawn

from Ref 152

Table 6 Reported values of interphase energy cAlAl3Sc between coherent Al3Sc precipitates and Al matrix

Reference cAlAl3Sc mJ m22 Method of estimation

137 10 Fit of coarsening data to LifshitzndashSlezev equation107 78iexcl20 (288uC) Back-calculation of incubation time

93iexcl20 (343uC)107 123iexcl41 (288uC) Back-calculation of nucleation rate

125iexcl35 (343uC)29 542 (400uC) Fit of coarsening data to Ostwald ripening

632 (430uC)413 (460uC)

146 c(100) 192 (0 K) c(111) 226 (0 K) Pseudopotential calculations147 c(100) 325 (0 K) c(110) 513 (0 K) c(111)

782 (0 K) c(100) 315 (288uC) c(100) 325 (343uC)Atomistic simulation

110 105 Fit of coarsening data to LSW theory31 20ndash300 Fit of coarsening data to Ostwald ripening

for 16 different temperatures111 57 Fit of precipitation model to experimental data145 120 coherent particles Fit of coarsening data

170 semicoherent particles

It is argued in this study that c may be lower in the nucleation stage

Roslashyset and Ryum Scandium in aluminium alloys

International Materials Reviews 2005 VOL 50 NO 1 31

AlndashCundashSc alloys compared to AlndashSc alloys Howeveran experimental investigation of Alndash25 wt-Cundash023 wt-Sc alloy comes to a different conclusion Thelattice misfit strain is found to decrease compared to Alndash02 wt-Sc and the critical diameter for coherency losswas found to be the same in the ternary and the binaryalloy144 It is suggested that these observations may bebecause of the dissolution of some Cu in the Al3Sc phaseand thus that the lattice parameters of both the Al matrixand the Al3Sc precipitates decrease in the ternary alloy

Silicon

It has been found that the onset of precipitation in Alndash04 wt-Sc is only slightly altered when Si contents ofup to 04 wt are introduced in the alloy However thefinal stage of the precipitation reaction is considerablydelayed with increasing Si content135 Figure 22 showsthe effect of addition of a joint of 035 wt-Si and040 wt-Fe There are at least two possible explana-tions for why an Si-addition leads to this behaviour

1 Alloying with Si is known to promote discontin-uous precipitation of Al3Sc106158 It has been shown thatwhen isothermal precipitation of Al3Sc starts discon-tinuously the later stage of the overall transformationcan be very slow31

2 The isothermal section of the phase diagramsuggests that the V-phase (AlSc2Si2) should form inalloys of this composition46 If the V-phase forms lessSc is available for precipitation of Al3Sc

It has been shown157 that for an AlndashScndashSi alloy withsolid solution content of 010 wt-Sc an 110 wt-Sithe only phases to precipitate after heat treatment at200uC are Si and an (AlScSi)-phase possibly the V-phase On the other hand the Al3Sc phase has beenobserved to form in alloys with 04 wt-Sc and up to08 wt-Si159160

Zinc

It has been reported that additions of up to 5 wt- Znhave only minor effects on the precipitation kinetics ofan Alndash04 wt-Sc alloy135 (Fig 23) In Ref 106 it isclaimed that Zn promotes discontinuous precipitation ofAl3Sc

Lithium

A comparison of the age hardening response at 400uC inAlndash24 wt-Lindash019 wt-Sc and Alndash024 wt-Sc alloys

indicates that the onset of Al3Sc-precipitation is notaffected by the presence of Li161

Zirconium

As mentioned in the section on lsquoTernary phase diagramswith dispersoid-forming elementsrsquo earlier a considerableamount of Zr is dissolved in the Al3Sc phase and thus amore correct denotation of the precipitating phase isAl3(Sc12xZrx) In discussing the influence of the Zrcontent on the precipitation of Al3Sc one is thereforeactually discussing the difference in precipitation ofAl3Sc versus Al3(Sc12xZrx)

It is found that an addition of 015 wt-Zr to an Alndash04 wt-Sc alloy only marginally affects the initial stageof the precipitation reaction123135 while it slows downthe later stages of the transformation considerably(Fig 24)135 The coarsening rate of the Al3(Sc12xZrx)particles in AlndashScndashZr alloys is found to be much slowerthan that of Al3Sc particles in AlndashSc alloys123162

In three-dimensional atom probe field ion microscopy(3D-APFIM) of Al3(Sc12xZrx) particles formed at 475uCin a ternary AlndashScndashZr alloy163 it was found that the coreof the particles is almost pure Al3Sc whereas there is ashell of Al3(Sc12xZrx) with almost equal content of Scand Zr Such a behaviour has also been predicted bycomputer modelling of precipitation of Al3(Sc12xZrx) at480uC in an AlndashZnndashMgndashScndashZr alloy164 This modelpredicts that Zr starts to enter the growing

22 C-curves for 10 and 60 transformation in Alndash

04 wt-Sc and Alndash04 wt-Fendash035 wt-Sindash04 wt-Sc

redrawn from Ref 135

23 C-curves for 10 and 60 transformation in Alndash

04 wt-Sc and Alndash5 wt-Znndash04 wt-Sc redrawn

from Ref 135

24 C-curves for 10 and 60 transformation in Alndash

04 wt-Sc and Alndash04 wt-Scndash015 wt-Zr redrawn

from Ref 135

Roslashyset and Ryum Scandium in aluminium alloys

32 International Materials Reviews 2005 VOL 50 NO 1

Al3(Sc12xZrx) particles when approximately half of thesupersaturated Sc has been precipitated The Zr contentof the outer shell is predicted to be much higher thanwhat has been found experimentally163164

Another 3D-APFIM study of Al3(Sc12xZrx) particlesin a ternary AlndashScndashZr alloy has been reported165 Hereparticles grown at 300uC for various lengths of time werestudied The Zr content in these particles was muchlower than that reportedpredicted at higher tempera-tures163164 even after very long annealing times

Iron

The effect of adding up to 07 wt-Fe on the precipita-tion kinetics in an Alndash04 wt-Sc alloy has beeninvestigated135 The onset of precipitation was onlyslightly influenced by the Fe-level whereas the laterstages of the transformation however were significantlyslowed down as the Fe-level increased An example ofthe effect of a joint addition of Fe and Si is shown inFig 22

Manganese chromium and titanium

Small additions (03 wt-) of manganese or chromiumto Alndash040 wt-Sc alloys are reported to have onlyminor effects on the precipitation kinetics of Al3Sc135

According to Ref 106 Mn is reported to promote andCr and Ti to suppress discontinuous precipitation

Rare earth elements

An investigation of the precipitation behaviour of Alndash03 at-Sc and Alndash03 at-Scndash03 at-X alloyswhere X is either yttrium gadolinium holmium orerbium in the temperature range 235ndash310uC indicatedthat a Al3(Sc12xXx) phase with L12 structure wasformed in the ternary alloys22 Peak strength is reportedto occur after approx 10 h at 285uC in all alloys whichindicates that the precipitation kinetics up to peakstrength is practically unaltered by the ternary additions

Influence of Sc on microstructure andproperties of wrought aluminium alloysMost of the effects of Sc addition in wrought Al-alloysare linked to the formation of the Al3Sc phase In atypical processing route of a wrought aluminium alloyparticles of the Al3Sc phase can form under threedifferent conditions each of which influences themicrostructure and properties of the alloy in a specificway

1 During solidification after casting or weldingAl3Sc particles can form in the melt and act as nucleifor a-Al thus leading to grain refinement18166

2 High temperature processing of the alloy in therange 400ndash600uC for instance homogenisation hot-rolling or extrusion can give a dense distribution ofAl3Sc particles of typically 20ndash100 nm size The particledistributions formed under such conditions are reportedto lead to good recrystallisation resistance128148167168

and enhanced superplasticity52169170

3 Heat treatment in the range 250ndash350uC can lead tosignificant precipitation hardening of an alloy super-saturated in Sc148158171 The size of strengthening Al3Scprecipitates is typically in the range 2ndash6 nm121

Grain refinementA good grain refinement is almost always desired uponsolidification The formation of small equiaxed grainsrather than long dendrites in the melt facilitates thefeeding of the melt into cavities of the shrinkingsolidified metal and thus reduces the problem ofshrinkage porosity The tendency to hot cracking is alsoreduced and the second phase particles become morefinely and uniformly distributed

To the authorsrsquo knowledge the first effect of Sc in Al-alloys that was reported in an international scientificjournal was the grain refining action in pure Al and in anAlndashCu alloy upon solidification172 which was found tobe stronger for Sc than for other transition metals Inlater studies of Sc as a grain refiner in pure Al1832173 ithas been demonstrated that approx 07 wt-Sc issufficient to provide excellent grain refinement It hasalso been demonstrated that additions of 025 wt-Scz025 wt-Zr provide good grain refinement in pure Al18

In order for Sc to act as an effective grain refiner theAl3Sc phase has to form in the melt before thesolidification of a-Al The Al3Sc particles have a latticeparameter close to that of pure Al and whenhypereutectically formed the Al3Sc particles are veryeffective substrates for the nucleation of the a-Al phaseAs mentioned in the section on lsquoFormation of Al3Sc inAlndashSc alloysrsquo above this requires that the alloy ishypereutectic with respect to Sc ie in excess of approx06 wt- in a binary AlndashSc alloy In ternary and higherorder systems the eutectic Sc composition may dependon the other alloying elements present For instance theeutectic composition of Sc has been predicted todecrease with increasing Mg content in the ternary AlndashMgndashSc system39 This prediction is sustained by theobservation of good grain refinement by adding 05 wt-Sc to an Alndash7 wt-Mg alloy174 (Other examples ofgrain refinement at Sc concentrations lower than that ofthe binary eutectic are found in Ref 173)

Similarly the observation of good grain refinement inan Alndash025 wt-Scndash025 wt-Zr alloy18 may be as aresult of a lower Sc content of the eutectic in the ternarysystem ie less Sc is needed to make the alloy hyper-eutectic No literature data on the liquidus surface of theAlndashScndashZr system are available and thus this hypothesiscannot be confirmed In more complex alloy systems itis also observed that excellent grain refinement isachieved at low Sc contents when Sc is added togetherwith Zr It is reported that adding either 02 wt-Sc06 wt-Sc or 01 wt-Zr to an Alndash5Mg alloy givesmuch poorer grain refinement than adding 02 wt-Scz01 wt-Zr175 Similarly additions of 015 wt- ofeither Sc or Zr are reported to only marginally refinethe grain structure in an AlndashCundashLi alloy whereas a jointaddition of 015 wt-Sc and 015 wt-Zr gives excellentgrain refinement176 For an AA 3650 casting alloy (Alndash7 wt-Sindash04 wt-Mg) good grain refinement is achievedby adding 039 wt-Sc or 027 wt-Scz019 wt-Zr177

In some AlndashZnndashMgndashScndashZr alloys it is also found thatan addition of 02ndash03 wt-Sc can be sufficient for goodgrain refinement166169178179 Examples of the grainrefinement as a function of Sc addition in pure Al andin an AlndashZnndashMgndashZr alloy are shown in Fig 25

The nucleation of a-Al on Al3Sc particles in the melt isfacilitated by the close match in the lattice parameters ofthe two phases As shown in Fig 17 the mismatch at the

Roslashyset and Ryum Scandium in aluminium alloys

International Materials Reviews 2005 VOL 50 NO 1 33

eutectic temperature of binary AlndashSc alloys (660uC) isonly approx 047 In Refs 57 and 89 it is shown thatwhen Zr Hf and in particular Ti is dissolved in the Al3Scparticles this reduces the lattice parameter of the phaseIt appears that when 25 of the Sc atoms in Al3Sc aresubstituted by Ti the mismatch is zero at approx 550uCand becomes negative at higher temperatures89 Thissuggests that by carefully selecting the Ti content of thealloy it should be possible to obtain Al3(ScTi)substrates in the melt that match exactly the latticeparameter of the nucleating a-Al and thus furtherimprove the grain refinement of the alloy This appearsto have been achieved in a recent work180 where thegrain refinement of an Alndash07 wt-Sc alloy wascompared with that of an Alndash05 wt-Scndash02 wt-Tialloy At a cooling rate of 100 K s21 only an estimated2 of the primary Al3Sc particles of the binary AlndashScalloy were effective nuclei compared to practically 100for the primary Al3(ScTi) particles in the ternary AlndashScndashTi alloy leading to a much smaller grain size in theternary alloy Whereas the match of lattice parametersmay be of importance for these results the authors ofthis investigation180 draw attention to other factors suchas different growth restriction factors for Sc and Ti andthe possibility of a peritectic reaction in the ternaryalloy Nevertheless the principle of matching latticeparameters is worth looking into further in future work

Effects from dispersoidslsquoDispersoidsrsquo is a term which is commonly used aboutthe classes of second phase particles that are formedin an Al alloy during high temperature annealing orthermomechanical processing such as homogenisationhot rolling extrusion and forging A dense distributionof dispersoids can give a significant contribution to analloyrsquos strength owing to particle strengthening but thisis rarely the main strengthening mechanism A moreimportant contribution from the dispersoids is theirability to stabilise the grainsubgrain structure of analloy through the Zener-drag action and thus improvethe mechanical properties of the alloy

There are two noticeable dispersoid-related effectsthat have been reported for Sc-containing alloys Thefirst is the stabilising effect on a deformed microstruc-ture When a non-recrystallised structure is preserved inan alloy this can add considerably to the mechanical

strength of the material The second effect is thepreservation of a small grain size during hot deforma-tion at slow deformation rates which is necessary toobtain superplastic properties of an Al-alloy

Recrystallisation resistance

The anti-recrystallisation effect of Sc was first publishedin a patent171 where 03 wt-Sc was added to pure Aland to AlndashMg AlndashMn and AlndashZnndashMg alloys Both Sc-free and Sc-containing materials were cold worked andsubsequently annealed and it was found that theaddition of Sc increased the temperature for onset ofrecrystallisation by approx 220uC in pure Al andsomewhat less in the Al-alloys Although the author ofthe patent171 may have been well aware that the anti-recrystallisation effect is caused by Al3Sc dispersoidsthis is not mentioned in the text The first journal paperthat explicitly points out that the recrystallisationresistance is due to Al3Sc dispersoids was an investiga-tion of the effects of adding Sc to wrought AlndashMgalloys181 In this work it was found that the Al3Scdispersoids were very effective in preventing recrystalli-sation up to temperatures of approx 400ndash450uC Athigher temperatures the dispersoids coarsen consider-ably and the microstructure was partially recrystallised

It is established that the Zener-drag pZ that is imposedon an advancing grain boundary by randomly distrib-uted dispersoids can be expressed in the form

pZ~k f =r (3)

where k is a factor that includes the interface energybetween the dispersoids and the matrix f is the volumefraction and r is the mean radius of the dispersoids Thusthe Zener drag will decrease rapidly in the case where thedispersoids are coarsening

As mentioned in the section on lsquoInfluence of otherelements on precipitation of Al3Scrsquo above theAl3(Sc12xZrx) dispersoids in a ternary AlndashScndashZr alloycoarsen at a much slower rate than the Al3Sc dispersoidsin a binary AlndashSc alloy This effect was first reported inRef 123 (although also observed in Ref 182) andaccording to Ref 33 the same authors demonstratedsoon after that the denser dispersoid distributionachieved in an AlndashScndashZr alloy leads to superiorrecrystallisation resistance compared to a binary AlndashScalloy An example of the increased recrystallisationresistance by adding both Zr and Sc is shown in Fig 26

In isothermal sections of the ternary AlndashScndashZr phasediagram it is indicated that the solid solubility ofSczZr is somewhat higher than that of Sc alone54 Ithas also been demonstrated both by electrical con-ductivity measurements (Fig 27) and microstructuralobservations that the supersaturation of SczZr isgreater than that of only Sc or Zr in as cast Alndash15(SczZr) alloys183 This indicates that it should bepossible to increase the volume fraction of dispersoids inAlndashScndashZr compared to AlndashSc It is suggested162 that theincreased volume fraction that can be achieved byadding both Sc and Zr can be advantageous inconventional wrought Al-alloys

There are at least two different conditions underwhich Al3Sc or Al3(Sc12xZrx) dispersoids can form toprevent recrystallisation

1 Sc (or Sc and Zr) is in solid solution before thedeformation In the case of cold deformation and

25 Grain refinement as a function of Sc addition in pure

Al (redrawn from Ref 32) and AlndashZnndashMgndashZr (redrawn

from Ref 169) note that data points are plotted on

different ordinate axes

Roslashyset and Ryum Scandium in aluminium alloys

34 International Materials Reviews 2005 VOL 50 NO 1

subsequent annealing the Al3Sc or Al3(Sc12xZrx)dispersoids may nucleate and grow before the nucleationand growth of recrystallised grains takes placeDispersoids can form after a direct up-quench to theannealing temperature115143148184 during ramp-up tothe annealing temperature115 or by pre-annealing at anintermediate temperature129 In the case of hot deforma-tion the Al3Sc or Al3(Sc12xZrx) dispersoids maynucleate and grow during preheating of the materialand during the hot deformation itself184

2 The Al3Sc or Al3(Sc12xZrx) dispersoids are formedin the material before deformation184 Considering coldrolling and subsequent annealing the annealing tem-perature Tann may be either lower or higher than thetemperature Tdisp at which the dispersoids were formedIf TannTdisp only limited if any coarsening of thedispersoids is expected to take place and thus the Zenerdrag from the particles is expected to be practicallyconstant The driving force for recrystallisation how-ever is expected to decrease somewhat with theannealing time as a result of recovery processes Thusif recrystallisation does not occur within short annealingtimes the material is expected to remain unrecrystallisedfor infinite time at the annealing temperature IfTannTdisp there will be substantial coarsening of thedispersoids during annealing In order for the materialto remain unrecrystallised the decrease in driving forcefor recrystallisation owing to recovery has to be at leastas rapid as the decrease in Zener drag because of particlecoarsening

Experimental comparisons of the conditions abovepoint in the direction that the recrystallisation resistanceis poorest when Sc (or Sc and Zr) is in solid solutionbefore deformation and the deformed material is up-quenched to the annealing temperature148 or when Al3Scor Al3(Sc12xZrx) dispersoids are formed before defor-mation at TdispampTann184185 Excellent recrystallisationresistance is achieved if dispersoids are formed at anintermediate anneal of solutionised and deformedmaterial128 or if dispersoids are formed at TdispTann

before deformation148185ndash187 It seems that the decreasein Zener drag because of dispersoid coarsening in many

cases is slower than the decrease in driving force forrecrystallisation because of recovery processes Thusthere is an advantage in forming a high number densityof small dispersoids which for most practical casesmeans that they should be formed at TdispTann122

When an advancing high angle grain boundary iethe recrystallisation front is passing a coherent Al3Scdispersoid there are at least three possible grainboundarydispersoid interactions

1 The Al3Sc dispersoid retains its global orientationrelationship and thus loses its coherency with thesurrounding matrix

2 The Al3Sc dispersoid rotates as the grain boundarypasses either by diffusional processes at the dispersoidmatrix interface or by the grain boundary passingthrough the dispersoid and the Al3Sc dispersoidassumes the same crystallographic orientation as theAl matrix of the recrystallised grain

3 The Al3Sc dispersoid dissolves at the grainboundary and re-precipitates in the recrystallised grain

Which interactions that actually take place willprobably depend on the dispersoid size annealingtemperature and driving force for recrystallisation It isalso possible that alloy composition (other elementsthan Al) is of importance

It has been reported that large (Oslash about 100ndash150 nm)Al3Sc dispersoids in a deformed Alndash4 wt-Mgndash02 wt-Sc alloy annealed at 575uC lose the orientationrelationship with the matrix after being passed by therecrystallisation front148

A rotation of somewhat smaller Al3Sc dispersoids in arecrystallising binary Alndash025 wt-Sc alloy has beenreported115143 The rotation was reported to be accom-panied by substantial growth (from Oslash 30 nm to Oslash48 nm) as a result of enhanced Sc diffusion at the grainboundary Observations suggested that the grainboundaries were passing through the dispersoids andthus the Al3Sc dispersoids retained the orientationrelationship with the recrystallised Al matrix

Dissolution and re-precipitation of Al3Sc dispersoidshas been reported during recrystallisation of a 50 coldrolled Alndash02 wt-Sc alloy162 Large spherical partially

26 Fraction recrystallised structure in cold rolled sheets

of Alndash04 wt-Sc and Alndash04 wt-Scndash015 wt-Zr as a

function of annealing temperature redrawn from

Ref 183 27 Electrical conductivity in Alndash15(SczZr) alloys

redrawn from Ref 183

Roslashyset and Ryum Scandium in aluminium alloys

International Materials Reviews 2005 VOL 50 NO 1 35

coherent dispersoids were observed to dissolve at therecrystallisation front and re-precipitate as smallercoherent Al3Sc cuboids

Superplastic forming

It seems that the first publication on superplasticproperties of Sc-containing Al-alloys was a study of anAlndash35Cundash14Mgndash045Mnndash04(SczZr) alloy188

It was recognised that the superplastic properties are aresult of the stabilisation of the fine grain structure byAl3Sc dispersoids The Sc-containing Al alloys that havereceived most attention for their superplastic propertieshowever are those of the AlndashMgndashSc system which wasfirst published in a patent189 Here it was noted that anAlndash4 wt-Mgndash05 wt-Sc alloy had superior superplasticproperties compared to fine-grained 7475 (AlndashZnndashMgndashCu alloy) Binary Alndash05 wt-Sc and Alndash4 wt-Mgalloys did not behave superplastically The flow stress atthe hot forming temperature was found to be much (30ndash40) lower in the ternary alloy than that of the twobinary alloys

The superplastic properties of AlndashMgndashSc alloys havebeen explored by several research groups over the lastdecade190ndash196 It has frequently been found that thedeformation mechanism is dominated by grain bound-ary sliding190 However it has also been reported thatAlndashMgndashSc alloy may deform superplastically withoutnoticeable grain boundary sliding23 It is generallyrecognised that the grain boundary sliding mechanismis facilitated when the average grain size is very smalland grain boundaries are predominantly high-angleSuch a microstructure may be achieved by carefulthermomechanical processing of the starting mate-rial193194197198 It has however been shown that a finegrained structure with high angle boundaries maydevelop during superplastic forming of AlndashMgndashSc alloyseven if the starting microstructure is an entirely differentone for instance that of a cold rolled sheet192 It has alsobeen suggested that superplastic forming of as castmaterial may be possible189

One of the more efficient thermomechanical processesfor achieving an ultrafine grain structure with high anglegrain boundaries in Al-alloys is equal channel angularpressing (ECAP) A JapanesendashAmerican group ofscientists has published an impressive body of researchon improvements in superplastic properties in Al-alloys processed by ECAP over the last few years andseveral of the publications are from investigations onAlndashMgndashSc alloys170199ndash224 Maximum strains in excessof 2000 at a strain rate of 0033 s21 have beenachieved170201202217 which is an extraordinarily goodcombination of high strain and high strain rate for analuminium alloy

Superplastic properties of AlndashCundashMg(ndashMn)ndashSc(ndashZr)and AlndashMgndashSc(ndashZr) alloys have been mentionedNoticeable superplasticity in other Sc-containing Al-alloys has also been reported such as AlndashZnndashMg(ndashCu)ndashScndashZr169225ndash228 AlndashLindashSc229 AlndashMgndashLindashScndashZr229ndash234

AlndashLindashMgndashCundashScndashZr235236 and AlndashCundashLindashScndashZr233

Precipitation hardeningHardening by Al3Sc precipitates

It has been noted that when Al3Sc particles precipitate inthe temperature range 250ndash350uC they give a significanthardness increase in the alloy Some authors point out

that Sc is a more effective precipitation hardening elementper atomic fraction added than the elements that arecommonly used for precipitation hardening121130 (In onepaper29 it is claimed that only Au has a strongerstrengthening effect than Sc) However the amount ofSc that can be precipitated from supersaturated solidsolution is rather limited and thus the absolute values ofthe hardness increase from the precipitation hardening ismuch lower than what is normally associated withprecipitation hardened alloys Also the temperatureregime for age hardening by precipitation of Al3Sc issomewhere in between the temperature regimes for agehardening and solution heat treatments of commonprecipitation hardened alloys This makes a combinedprecipitation of Al3Sc and other strengthening precipi-tates unfeasible Thus precipitation strengthening byAl3Sc is most feasible in alloy systems that are non-heat-treatable The non-heat-treatable aluminium alloy sys-tems are according to the Aluminum Associationdesignations the 1xxx series (99 pure Al) the 3xxxseries (AlndashMn) and the 5xxx series (AlndashMg) The purposeof adding Sc to these alloys may be either to stabilise themicrostructure of wrought semiproducts (extrusionsrolled plates forgings etc) as discussed in the sectionon lsquoRecrystallisation resistancersquo above or to provideextra strength to the alloy through precipitation hard-ening In the latter case it is appropriate to considerwhether the Sc-containing alloy still should be classifiedas non-heat-treatable A heat treatment is applied thatbrings about a significant precipitation hardening On theother hand the hardness increase that is achieved throughthe heat treatment is lower than what is normallyassociated with heat-treatable alloy systems Hence eventhough it seems like a contradiction one chooses to keepusing the term lsquonon-heat-treatablersquo about these alloys

Table 7 gives an overview of some mechanicalproperties of Sc-containing non-heat-treatable alloysthat are reported in the literature Most of theexperimental work on Sc in 1xxx-types of alloys hasbeen done on binary AlndashSc alloys with much higherpurity than industrial alloys

Strengthening mechanisms

When the precipitates are larger than a critical size thestrengthening effect is due to the Orowan-mechanism iedislocations can only pass the precipitates by looping Inthis case the strengthening effect of the particles isapproximately inversely proportional to the mean parti-cle spacing When the precipitates can be sheared bydislocations there are a number of strengthening mechan-isms that apply It is proposed by Parker et al108 that thetwo major contributing mechanisms are coherency strainand anti-phase-boundary energy In a recent detailedstudy of strengthening mechanisms in binary AlndashSc alloysby Marquis and colleagues117118 the strengthening fromshear modulus mismatch between the matrix and theprecipitates is also accounted for A qualitatively goodmatch between theoretical strengthening and measuredvalues is achieved in this work both for deformation atroom temperature and at 300uC

Effect of Sc on precipitation strengthening in heat-treatablealloys

Following the AA designation system the traditionalheat-treatable Al-alloys are those that belong to the 2xxx

Roslashyset and Ryum Scandium in aluminium alloys

36 International Materials Reviews 2005 VOL 50 NO 1

series (AlndashCu) 6xxx series (AlndashMgndashSi) and 7xxx series(AlndashZnndashMg) AlndashLi alloys should also be mentionedSeveral investigations have been carried out in order toclarify the effects of Sc on the precipitation behaviour inthese alloy systems

AlndashCu alloys

The precipitation sequence in AlndashCu alloys is oftendescribed as follows

Supersaturated solid solutionRGP-zonesRh0Rh9Rh(Al2Cu)

The highest strength is normally achieved when the h0or h9 precipitates are predominant Typical precipitationheat treatment temperatures for AlndashCu alloys are in therange 160ndash190uC238 which is considerably lower thanthe typical precipitation temperature for Al3ScComparisons of the aging responses of AlndashCu and AlndashCundashSc alloys at 150 and 200uC indicate that there is nonoticeable effect of Sc on the precipitation kinetics ofh9153 It is observed that the h9 precipitates may nucleateon Al3Sc particles153 At 300uC it is observed that h9particles are somewhat smaller in AlndashCundashSc alloys thanin AlndashCu alloys156

AlndashMgndashSi alloys

The following precipitation sequence is commonlyreported for AlndashMgndashSi alloys

Supersaturated solid solutionRGP-zonesRb0Rb9Rb(Mg2Si)

For peak aged alloys the predominant precipitatetype is b0 for which the stoichiometric composition hasrecently been resolved to be Mg5Si6239 Temperatures inthe range 160ndash205uC are typically used for precipitationhardening of these alloys238 Adding both 03 wt-Scand 01 wt-Zr to an Alndash06 wt-Mgndash065 wt-Sialloy does not seem to alter the precipitation kineticsof b0 at 165uC However the hardness increase becauseof precipitation hardening appears to be smaller in theSczZr-containing alloy240 In another investigationadditions of 01 wt-Sc 015 wt-Sc 02 wt-Sc04 wt-Sc and 02 wt-Scz01 wt-Zr were made toan Alndash08 wt-Mgndash07 wt-Si alloy241 Here it wasalso observed that the precipitation kinetics of b0 wasseemingly independent of the Sc additions (Fig 28)TEM observations indicated that the b0 precipitateswere of comparable sizes in the investigated alloys andno interactions between Al3Sc and b0 were observed(Fig 29) In a third study242 where the effect of Sc onthe precipitation in an AlMgSindashSiC metal matrixcomposite was investigated there also does not seemto be any effect on the precipitation kinetics Howevercontrary to the findings of Ref 240 it is reported thatthe Sc addition leads to a higher hardness increase thanin the corresponding Sc free alloy

AlndashMgndashZn alloys

For these alloys the following precipitation sequence isoften ascribed

Table 7 Mechanical properties in non-heat-treatable Al-alloys with Sc

Reference Alloy wt- YS MPa UTS MPa Note

1xxx alloys171 000Sc 15 48 Cast material aged 288uC8 h

023Sc 159 185 Cast material aged 288uC8 h038Sc 199 220 Cast material aged 288uC8 h000Sc 14 49 Cold rolled material (89) aged 288uC8 h023Sc 198 208 Cold rolled material (89) aged 288uC8 h038Sc 240 264 Cold rolled material (89) aged 288uC8 h000Sc 8 34 Cold rolled material quenched from 649uC aged 288uC8 h023Sc 147 157 Cold rolled material quenched from 649uC aged 288uC8 h038Sc 193 199 Cold rolled material quenched from 649uC aged 288uC8 h

121 05Sc 160 ndash Forged material quenched from 635uC aged 250uC50 h23 05Sc 298 319 Hot rolled 288uC cold rolled 69ndash81 aged 288uC4 h112 01Sc 132 166 Hot z cold rolled material quenched from 630uC

aged 320uC133 h148 02Sc 138 ndash Cast material aged 300uC10 h compression test159 04Sc 196 ndash Cast material aged 300uC10 h compression test117 118 03Sc 209 ndash Cast material quenched from 648uC aged 300uC5 h

compression test3xxx alloys171 1Mn 015Sc 216 221 Cold rolled material (89) aged 288uC8 h

1Mn 05Sc 309 323 Cold rolled material (89) aged 288uC8 h186 05Mn 02Mg

026Sc 015Zr162 201 Extruded material solutionised 600uC aged 250uC

5xxx alloys171 1Mg 43 111 Cold rolled material (89) aged 288uC8 h

1Mg 03Sc 288 303 Cold rolled material (89) aged 288uC8 h53Mg 147 259 Cold rolled material (50) wintermediate anneals

at 343uC aged 288uC8 h53Mg 03Sc 368 401 Cold rolled material (50) wintermediate anneals

at 343uC aged 288uC8 h23 2Mg 05Sc 376 401 Hot rolled 288uC cold rolled 69ndash81 aged 288uC4 h

4Mg 05Sc 414 4606Mg 05Sc 433 503

237 4Mg 1Sc 420 525 Cold rolled material (83) aged 320uC1 h148 4Mg 02Sc 194 ndash Cast material aged 300uC10 h compression test

Tensile test data except where noted YS yield strength UTS ultimate tensile strength

Roslashyset and Ryum Scandium in aluminium alloys

International Materials Reviews 2005 VOL 50 NO 1 37

Supersaturated solid solutionRGP-zonesRg9Rg(Zn2Mg)

The maximum hardness is normally achieved whenthe g9 precipitates are predominant Common precipita-tion hardening temperatures are in the range 95ndash180uCand a two-step precipitation heat treatment within thistemperature regime is often used238 It has beenobserved in some investigations that Sc and SczZradditions to AlndashMgndashZn alloys slow down the precipita-tion of g9 somewhat243 Other investigations find thatthere is no effect of Sc on the precipitation behaviour ofg9244245 and yet others report that Sc additionssignificantly speed up the precipitation of g9246 In Ref247 it is found that an Sc addition leads to coarser g9precipitates and it is claimed that this gives an improvedductility of the alloy The strength-loss associated withlarger particle size is reported to be counterbalanced bystrengthening from Al3Sc precipitates

AlndashLi alloys

The precipitation sequence in binary AlndashLi alloys isapparently simple

Supersaturated solid solutionRd9Rd (AlLi)

where d9 is the metastable Al3Li phase which just likeAl3Sc has the L12 type of atomic arrangement Thetypical temperature regime for precipitation of d9 whichis the strengthening phase in this system is approx 150ndash200uC A comparison of the age hardening response ofan Alndash26 wt-Li and an Alndash24 wt-Lindash019 wt-Scalloy at 180uC248 and 200uC161 indicates that the onsetof d9 precipitation is not altered by the presence of ScThe hardness curves for the two alloys are practicallyidentical at 200uC whereas at 180uC the peak hardnesslevel is slightly higher in the AlndashLi than the AlndashLindashScalloy DSC measurements at constant heating ratesindicate that the addition of Sc to an AlndashLi alloysincreases the activation energy for d9 precipitation andmoves the exothermic peak associated with d9 precipita-tion to a higher temperature248 For specimens aged at

either 180uC or 200uC TEM observations reveal that thed9 precipitates are much smaller in the Sc containingalloy than in binary AlndashLi both in the peak agedcondition and in the overaged condition161248 Additionof Sc has also been observed to reduce the size of d9precipitates in other AlndashLi based alloys249ndash251 In an AlndashLindashCundashZr alloy an addition of Sc has been reported toslow down the homogeneous precipitation of d9252253 Ithas been claimed that Sc reduces the quench sensitivityand delays room temperature aging of AlndashLi basedalloys254ndash256

When present in the microstructure before the pre-cipitation of d9 the Al3Sc precipitates may act as effec-tive nucleation sites for d9 The resulting precipitates arespheres of d9 with a core of Al3Sc161249252ndash255257ndash261

Corrosion resistanceAn appreciable amount of data is available on the effectsof Sc on the corrosion behaviour of wrought Al-alloysSome of these effects are apparently derived from theeffects of Sc on the microstructure of the alloys It hasbeen reported that an addition of Sc increases thecorrosion potential (makes it less negative) in pureAl262ndash264 in AlndashZn alloys265266 AlndashMg alloys267 AlndashZnndashMgndashCu alloys264268 AlndashCundashMgndashMn alloys264 andin AlndashCundashLindashMgndashAg alloys264 Even though Sc alsohas been reported to decrease the corrosion potential in

28 Age hardening response at 175uC for Alndash08 wt-Mgndash

07 wt-Si alloy (Base) with additions of 02 wt-Sc

04 wt-Sc and 02 wt-Scz01 wt-Zr from Ref 241

29 TEM images of a b0 precipitates in Alndash08 wt-Mgndash

07 wt-Si alloy and b b0 and Al3(Sc1ndashxZrx) in a similar

alloy with addition of 02 wt-Scz01 wt-Zr from

Ref 241

Roslashyset and Ryum Scandium in aluminium alloys

38 International Materials Reviews 2005 VOL 50 NO 1

AlndashMg alloys269270 it seems that the general trend isthat adding Sc to an alloy makes it slightly more nobleThe change in corrosion potential is much morepronounced when Sc is added in amounts larger thanthe eutectic composition263 ie there is a considerablecontribution from primary or eutectic Al3Sc to theoverall potential It has also been demonstrated that thechange in corrosion potential caused by Sc can dependon the heat treatment applied to the alloy267268

Even though the corrosion potential is an essentialparameter in establishing the corrosion behaviour of analloy an increase in the corrosion potential does notnecessarily imply an improved self-corrosion resistanceHowever measurements of corrosion rates and passiva-tion current densities strongly suggest that the self-corrosion resistance in general is considerably improvedwhen Sc is added to wrought Al-alloys263264267 Someobserved variations in corrosion potential and passiva-tion current densities with Sc content in binary AlndashScalloys are plotted in Fig 30

Material failure in corrosive environments is often dueto localised corrosion attacks which may propagaterapidly even though the bulk material has a goodresistance against general corrosion It has been pointedout that hypereutectic additions of Sc may lead tomicrogalvanic corrosion beside primary Al3Sc parti-cles264 In AlndashMg alloys grain boundary precipitation ofAl8Mg5 can lead to localised corrosion attacks such asintergranular corrosion (IGC) exfoliation corrosion(EC) and stress corrosion cracking (SCC) In wroughtmaterial such precipitation may occur in the 60ndash180uCtemperature regime and heating in this temperaturerange is referred to as lsquosensitationrsquo An AlndashMgndashSc alloywas found to be immune against intergranular corrosionand have moderate susceptibility to exfoliation corro-sion after annealing at 350uC271 After sensitation heattreatments severe IGC and EC was observed but notquite as severe as in a corresponding alloy without ScAs for SCC the AlndashMgndashSc alloy was found to be highlyresistant271 In another study it was found that additionof 056 wt-Sc reduces the SCC susceptibility of an Alndash68 wt-Mg alloy in the as-rolled state and afterannealing at 250uC whereas in a sensitised specimenthe SCC susceptibility is somewhat increased by the Scaddition272 A third investigation found that Sc has nomeasurable detrimental effect on the SCC susceptibilityof sensitised Alndash5Mgndash015Zr alloy273 SCC is also a

severe problem in high strength AlndashZnndashMgndashCu alloys Ithas been shown that small Sc additions are effective inreducing the SCC sensitivity of these alloys244246268274

Use of Sc-containing Al alloysA systematic development of Sc-containing aluminiumalloys took place in the former USSR in the 1980s andthe interest for Sc as an alloying element in aluminiumalloys hit the western world approximately 10 yearslater Even though a number of improvements in Alalloys achieved by Sc addition have been demonstratedthe current uses of such alloys are very limited This isrelated to the very high price of scandium

In Russia some parts of military aircraft are made ofSc-containing AlndashLi alloys In the western world themain usage of Sc-containing alloys is for sportsequipment Ashurst Technology and Kaiser Aluminumdeveloped a Sc-containing 7xxx alloy for baseball andsoftball bats which was introduced to the Americanmarket in 1997 by Easton Alcoa soon followed with aSc-containing alloy for a competing brand of batsLouisville Slugger Since then several new and improvedSc-containing alloys for bats have been introduced tothe market The purpose of adding Sc is to increase theyield strength of the alloy allowing for a down-gaugingof the wall thickness which in turn gives a strongerlsquospring-rsquo or lsquotrampoline-rsquo effect when the ball hits thebat

Shortly after the introduction of the Sc containingbats Easton also launched Sc-containing 7xxx tubingfor bicycle frames Just as in the bats Sc increases theyield strength of the alloy allowing for down-gauging oftube wall thickness and a corresponding weight reduc-tion of the bicycle frame An Italian manufacturer ofbicycle tubing Dedacciai also delivers tubes in a Sc-containing 7xxx alloy

Other sports equipment made from Sc-containingaluminium alloys includes lacrosse sticks and tent polesSmith and Wesson has also introduced a series ofhandguns where the frame is made from a Sc-containingAl alloy

A common factor for the items mentioned above isthat the material cost is only a minor part of the totalmanufacturing cost of the end product and also thatthese products are aimed at a group of customers thathave a certain awareness of new materials Both baseballbats and bicycle frames have been marketed aslsquoscandium alloyrsquo even though the Sc content is muchlower than 1

Currently AlndashSc master alloys for the production ofSc-containing Al alloys are available at a price thatcorresponds to US$ 2000 per kg of Sc This means that ifone wants to add 02 wt-Sc to an alloy which is afairly common content one also increases the price ofthe alloy by US$ 4 per kg alloy Depending on the alloytype Sc is added to this represents a tripling orquadrupling of the price of the alloy There are notmany existing products where such an increase inmaterial cost can be justified In order to see awidespread use of Sc in high-volume products the Scprice has to come down considerably Actually the priceof adding Sc to Al alloys has gone down by a factor 3ndash10over the last 10ndash15 years and substantial price reduc-tions are also expected in the future

30 Observed variations in corrosion potential and passi-

vation current densities with Sc content in binary Alndash

Sc alloys based on data from Ref 263

Roslashyset and Ryum Scandium in aluminium alloys

International Materials Reviews 2005 VOL 50 NO 1 39

The current production of AlndashSc master alloys isbased upon and will continue to be based upon for theforeseeable future the reduction of Sc2O3 or other Sccompounds directly in molten aluminium It is notnecessary as many tend to believe to take the route viametallic Sc Thus the price of AlndashSc master alloy isgoverned by the price of Sc2O3 or other Sc compoundsin question and not by the price of metallic scandiumThe Sc2O3 which is the main source for todayrsquos AlndashScmaster alloy production comes from stockpiles in theformer USSR These stockpiles will be exhausted withina few years and new reliable sources of Sc2O3 or otherSc compound production are sought It turns out thatthe most economically viable option that has beendisclosed so far is the processing of Red Mud from theBayer process of extracting alumina from bauxiteScandium is enriched in the Red Mud and is extractedfrom a Red Mud aqueous slurry by selective leachingsubsequent ion-exchange procedure and finally a liquidndashliquid extraction procedure It is not required to build aseparate lsquoSc factoryrsquo to do this but rather build an lsquoadd-onrsquo to existing Bayer process plants Such a processroute is expected to bring down the price of Sc2O3

considerably which in turn means that AlndashSc masteralloy price should drop accordingly Preliminary ana-lyses suggest a price of approx US$ 400 per kg Sc in themaster alloy which translates to an added cost of 80cent per kilo when 02 wt-Sc is added to an aluminiumalloy This is also a considerable increase in the materialcost but with such prices one should expect to see Sccontaining alloys in many more applications than whatis the case at the present time

Concluding remarksThe body of published investigations on Al-based alloyswith Sc addition provides a sound basis of knowledgefor metallurgists that want to look into the possibility ofenhancing the performance of a wrought Al-alloy byadding Sc to it Ternary AlndashScndashX phase diagrams areavailable for practically every technologically importantalloying element in Al The effect of a wide range ofternary alloying elements on the precipitation behaviourof Al3Sc is accounted for It has been shown that theAl3Sc phase can be effective as a grain refiner adispersoid former and a precipitate hardening agentand some of the underlying conditions for achieving thedesired Al3Sc formation have been outlined Addingsome Zr together with Sc has proven to be beneficial Itmay lead to effective grain refinement at a lower Sc levelbut the most prominent effect is the refinement indispersoid distribution that can be achieved An addi-tion of Sc has little if any effect on precipitation in the2xxx 6xxx and 7xxx alloy systems and some effects onthe precipitation in AlndashLi based alloys With respect tocorrosion behaviour adding Sc to an Al-alloy does ingeneral seem to make the alloy slightly more noble andto increase its self-corrosion resistance Scandium-containing Al alloys have very few uses at the presenttime as a result of the high price of scandium The priceof Sc is expected to decrease significantly in the futureand this should lead to the disclosure of moreapplications where it is economically feasible to takeadvantage of the improved properties of some Sc-containing aluminium alloys

References1 D R Lide lsquoCRC handbook of chemistry and physicsrsquo 71st edn

4ndash29 1990 Boston USA CRC Press

2 E M Savitsky V F Terehova I V Burov and O P Naumkin

Proc Fourth Conf on lsquoRare earth researchrsquo Phoenix Arizona

USA April 1964 409ndash420

3 E M Savitskii V F Terekhova I V Burov O P Naumkin and

I A Markova Inorg Mater 1965 1 1503ndash1512

4 O P Naumkin V T Terekhova and E M Savitskiy Russ

Metall 1965 (4) 128ndash136

5 W G Moffatt lsquoThe handbook of binary phase diagramsrsquo 1981

Schenectady NY USA General Electric Co

6 E A Brandes (ed) lsquoSmithells metals reference bookrsquo 6th edn

1983 London UK Butterworths

7 R P Elliott and F A Shunk Bull Alloy Phase Diagrams 1981

2 (2) 222ndash223

8 K A Gschneider Jr and F W Calderwood Bull Alloy Phase

Diagrams 1989 10 34ndash36

9 H Okamoto J Phase Equil 1991 12 612ndash613

10 J L Murray J Phase Equil 1998 19 380ndash384

11 M E Drits E S Kadaner T V Dobatkina and N I Turkina

Russ Metall 1973 (4) 152ndash154

12 S-I Fujikawa M Sugaya H Takei and K-I Hirano J Less-

Common Met 1979 63 87ndash97

13 N Blake and M A Hopkins J Mater Sci 1985 20 2861ndash2867

14 V I Kononenko and S V Golubev Russ Metall 1990 (2) 193ndash

195

15 T B Massalski J L Murray L H Bennett and H Baker (eds)

lsquoBinary alloy phase diagramsrsquo 1986 Metals Park OH USA

ASM

16 G Cacciamani P Riani G Borzone N Parodi A Saccone

R Ferro A Pisch and R Schmid-Fetzer Intermetallics 1999 7

101ndash108

17 H Okamoto J Phase Equil 2000 21 310

18 A F Norman P B Pragnell and R S McEwen Acta Mater

1998 46 5715ndash5732

19 I N Pyagai and A V Vakhobov Russ Metall 1990 (5) 50ndash52

20 C L Fu J Mater Res 1990 5 971ndash979

21 X Lu and Y Wang Calphad 2002 26 555ndash561

22 R R Sawtell and J W Morris Jr Proc lsquoDispersion strengthened

aluminium alloysrsquo Phoenix Arizona USA January 1988 409ndash

420

23 R R Sawtell and C L Jensen Metall Trans A 1990 21A 421ndash

430

24 L A Willey Unpublished research Alcoa 1970 Data points are

extracted from Ref 10

25 N I Turkina and V I Kuzmina Russ Metall 1976 (4) 179ndash

183

26 T Torma E Kovacs-Csetenyi I Vitanyi M Butova and

J Stepanov Proc 6th Int Symp on lsquoHigh purity materials in

science and technologyrsquo Akademie der Wissenschaften der DDR

Dresden Germany May 1985 388ndash389

27 A L Berezina V A Volkov B P Domashnikov and K V

Chuistov Metallofizika 1987 9 (5) 43ndash47

28 H-H Jo J Korean Inst Metals 1990 28 499ndash504

29 H-H Jo and S-I Fujikawa Mater Sci Eng 1993 A 171 151ndash

161

30 S Celotto and T J Bastow Philos Mag A 2000 80 1111ndash1125

31 J Roslashyset and N Ryum submitted to Mater Sci Eng

32 M E Drits L S Toropova Yu G Bykov F L Gushchina V I

Elagin and Yu A Filatov Russ Metall 1983 (1) 150ndash153

33 L S Toropova D G Eskin M L Kharakterova and T V

Dobatkina lsquoAdvanced aluminum alloys containing scandium

structure and propertiesrsquo 1998 Amsterdam The Netherlands

Gordon and Breach Science Publishers

34 V V Cherkasov P P Pobezhimov L P Nefedova E V Belov

and G M Kuznetsov Met Sci Heat Treat 1996 (6) 268ndash270

35 Kh O Odinaev I N Ganiev V V Kinzhibalo and B Ya

Kotur Dokl Akad Nauk Tadzh SSR 1989 32 37ndash38

36 Kh O Odinaev I N Ganiev and A V Vakhobov Russ Metall

1991 (4) 200ndash203

37 J Grobner R Schmid-Fetzer A Pisch G Cacciamani P Riani

N Parodi G Borzone A Saccone and R Ferro Z Metallkd

1999 90 872ndash880

38 E A Marquis and D N Seidman Microsc Microanal 2002 8

(Suppl 2) 1100CDndash1101CD

39 A Pisch J Grobner and R Schmid-Fetzer Mater Sci Eng A

2000 A 289 123ndash129

Roslashyset and Ryum Scandium in aluminium alloys

40 International Materials Reviews 2005 VOL 50 NO 1

40 C Xia F Zeng and Y Gu Trans Nonferrous Met Soc China

2003 13 1124ndash1127

41 M Yu Teslyuk and V S Protasov Sov Phys Crystallogr 1966

10 470ndash471

42 M L Kharakterova and T V Dobatkina Russ Metall 1988

(6) 175ndash178

43 M L Kharakterova Russ Metall 1991 (4) 195ndash199

44 L S Toropova M L Kharakterova and D G Eskin Russ

Metall 1992 (3) 194ndash199

45 P Riani L Arrighi R Marazza D Mazzone G Zanicchi and

R Ferro J Phase Equil Diff 2004 25 22ndash52

46 A T Tyvanchuk T I Yanson B Ya Kotur O S Zarechnyuk

and M L Kharakterova Russ Metall 1988 (4) 190ndash192

47 L L Rokhlin T V Dobatkina and M L Kharakterova Powder

Metall Met Ceram 1997 36

48 A Z Ikromov I N Ganiev and V V Kinzhibalo Dokl Akad

Nauk Tadzh SSR 1990 (6) 391ndash392

49 I N Ganiev A Z Ikromov and V G Khudoiberdiev Russ

Metall 1995 (3) 125ndash127

50 I N Fridlyander L L Rokhlin T V Dobatkina and N I

Nikitina Met Sci Heat Treat 1993 (10) 567ndash571

51 I N Fridlyander L L Rokhlin T V Dobatkina V V

Kinzhibalo and A T Tyvanchuk Russ Metall 1998 (1) 161ndash

166

52 R A Emigh E L Bradley and J W Morris Jr in lsquoLight-weight

alloys for aerospace applications IIrsquo (ed E W Lee and N J

Kim) 27ndash43 1991 TMS

53 L S Toropova A N Kamardinkin V V Kindzhibalo and A T

Tyvanchuk Phys Met Metall 1990 70 (6) 106ndash110

54 A N Kamardinkin T V Dobatkina and T D Rostova Russ

Metall 1991 (4) 216ndash218

55 L S Torodskaya T V Dobatkina and A N Kamardinkin

Russ Metall 1992 (5) 128ndash131

56 E M Sokolovskaya E F Kazakova E I Poddyakova and A

A Ezhov Met Sci Heat Treat 1997 (5) 211ndash213

57 Y Harada and D C Dunand Mater Sci Eng 2002 A 329ndash331

686ndash695

58 N E Drits L S Toropova and F L Gushchina Russ Metall

1984 (4) 229ndash232

59 E M Sokolovskaya E F Kazakova V A Alikhanov and E V

Zhuravleva Moscow Univ Chem Bull 1997 52 (5) 70ndash72

60 E M Sokolovskaya E F Kazakova and E I Poddyakova Met

Sci Heat Treat 1989 (11) 837ndash839

61 G M Cheldieva E F Kazakova E M Sokolovskaya and N I

Kaloev Russ Metall 1990 (6) 87ndash90

62 E M Sokolovskaya E F Kazakova and O D-S Kendivan

Russ Metall 1998 (4) 135ndash137

63 N G Bukhanko E F Kazakova and E M Sokolovskaya Russ

Metall 2001 (4) 425ndash431

64 E D Trubnyakova O I Bodak I N Ganiev and A V

Vakhobov Russ Metall 1987 (3) 219ndash222

65 I N Fridlyander and L V Molchanova Russ Metall 2003 (5)

476ndash480

66 R A Altynbaev S Kh Khairidinov and A V Vakhobov Russ

Metall 1987 (4) 194ndash196

67 J C Schuster and J Bauer J Less-Common Met 1985 109

345ndash350

68 L L Rokhlin A S Fridman T V Dobatkina and D G Eskin

Russ Metall 1991 (6) 146ndash148

69 A S Fridman T V Dobatkina and E V Muratova Russ

Metall 1992 (1) 207ndash209

70 C Xia F Zeng and Y Gu Trans Nonferrous Met Soc China

2003 13 546ndash552

71 F Zeng C Xia and Y Gu J Alloys Comp 2004 363 175ndash181

72 L L Rokhlin T V Dobatkina N R Bochvar and E V Lysova

J Alloys Comp 2004 367 10ndash16

73 T V Dobatkina A S Fridman and E V Muratova Russ

Metall 1992 (5) 125ndash127

74 I N Fridlyander L L Rokhlin N R Bochvar E V Lysova

and O V Boteva Russ Metall 2001 (6) 661ndash666

75 V N Rechkin L K Lamikhov and T I Samsonova Sov Phys

Crystallogr 1964 9 325ndash327

76 I I Zalutskii and P I Kripyakevich Sov Phys Crystallogr

1967 12 341ndash343

77 T J Bastow C T Forwood M A Gibson and M E Smith

Phys Rev B 1998 58 2988ndash2997

78 K Fukunaga M Kolbe K Yamada and Y Miura Mater Sci

Eng 1997 A 234ndash236 594ndash597

79 E P George J A Horton W D Porter and J H Schneibel

J Mater Res 1990 5 1639ndash1648

80 E P George D P Pope C L Fu and J H Schneibel ISIJ Int

1991 31 1063ndash1075

81 Y Harada and D C Dunand Acta Mater 2000 48 3477ndash3487

82 J H Schneibel and E P George Scripta Metall Mater 1990 24

1069ndash1074

83 J H Schneibel and P M Hazzledine Mater Res Soc Symp

Proc 1991 213 323ndash328

84 J H Schneibel and P M Hazzledine J Mater Res 1992 7

868ndash875

85 C J Sparks E D Specht G E Ice P Zschack and J Schneibel

Mater Res Soc Symp Proc 1991 213 363ndash368

86 J Tarnacki and Y-W Kim Scripta Metall Mater 1989 23

1063ndash1068

87 M Asta V Ozolins and C Woodward JOM 2001 53 (9) 16ndash

19

88 M E Drits L S Toropova F L Gushchina and S G Fedotov

Sov Non-Ferrous Met Res 1984 12 83ndash85

89 Y Harada and D C Dunand Scripta Mater 2003 48 219ndash222

90 C Woodward M Asta G Kresse and J Hafner Phys Rev B

2001 63 094103-1-6

91 J-H Xu and A J Freeman Phys Rev B 1990 41 12553ndash12561

92 M F Bartholomeusz and J A Wert Acta Metall Mater 1992

40 673ndash682

93 G Bester and M Fahnle J Phys Condens Matter 2001 13

11551ndash11565

94 C L Fu and M H Yoo Proc lsquoOrdered intermetallics ndash physical

metallurgy and mechanical behaviorrsquo Irsee Germany June 1991

155ndash164

95 K Fukunaga T Shouji and Y Miura Mater Sci Eng 1997 A

239ndash240 202ndash205

96 D P Pope Proc lsquoOrdered intermetallics ndash physical metallurgy

and mechanical behaviorrsquo Irsee Germany June 1991 143ndash153

97 J-S Wang Acta Mater 1998 46 2663ndash2674

98 M H Yoo and C L Fu Mater Sci Eng 1992 A 153 470ndash478

99 R W Hyland Jr and R C Stiffler Scripta Metall Mater 1991

25 473ndash477

100 I G Brodova I V Polents O A Korzhavina P S Popelrsquo I P

Korshunov and V O Esin Melts 1992 4 392ndash397

101 I G Brodova O A Chikova I V Polents P S Popelrsquo and V O

Esin Casting Processes 1992 1 (2) 158ndash160

102 I G Brodova D V Bashlikov and I V Polents Mater Sci

Forum 1998 269ndash272 589ndash594

103 K B Hyde A F Norman and P B Pragnell Mater Sci Forum

2000 331ndash337 1013ndash1018

104 K B Hyde A F Norman and P B Pragnell Acta Mater 2001

49 1327ndash1337

105 J Roslashyset and N Ryum Proc 6th Int Conf on lsquoAluminum

alloysrsquo Toyohashi Japan July 1998 793ndash798

106 V I Elagin V V Zakharov and T D Rostova Met Sci Heat

Treat 1993 (6) 317ndash319

107 R W Hyland Jr Metall Trans A 1992 23A 1947ndash1955

108 B A Parker Z F Zhou and P Nolle J Mater Sci 1995 30

452ndash458

109 C L Rohrer M D Asta S M Foiles and R W Hyland Jr

Mater Res Soc Symp Proc 1996 398 477ndash482

110 G M Novotny and A J Ardell Mater Sci Eng 2001 A 318

144ndash154

111 J D Robson M J Jones and P B Pragnell Acta Mater 2003

51 1453ndash1468

112 C Tan Z Zheng and B Wang Proc 3rd Int Conf on

lsquoAluminium alloysrsquo Vol I NTH Trondheim Norway June

1992 290ndash294

113 M Nakayama A Furuta and Y Miura Mater Trans JIM

1997 38 852ndash857

114 E A Marquis and D N Seidman Acta Mater 2001 49 1909ndash

1919

115 M J Jones and F J Humphreys Acta Mater 2003 51 2149ndash

2159

116 E A Marquis D N Seidman and D C Dunand in lsquoCreep

deformation fundamentals and applicationsrsquo (ed R S Mishra

J C Earthman and S V Raj) 299ndash308 2002 TMS

117 D N Seidman E A Marquis and D C Dunand Acta Mater

2002 50 4021ndash4035

118 E A Marquis D N Seidman and D C Dunand Acta Mater

2003 51 285ndash287

119 M E Drits L S Toropova U G Bikov and G K Anastaseva

Proc lsquoDiffusion in metals and alloysrsquo Tihany Hungary Augustndash

September 1982 616ndash623

120 V I Elagin V V Zakharov and T D Rostova Met Sci Heat

Treat 1983 (7) 546ndash549

Roslashyset and Ryum Scandium in aluminium alloys

International Materials Reviews 2005 VOL 50 NO 1 41

121 M Ye Drits L B Ber Yu G Bykov L S Toropova and G K

Anastaseva Phys Met Metall 1984 57 (6) 118ndash126

122 M E Drits L S Toropova and Yu G Bykov Sov Non-Ferrous

Met Res 1985 13 309ndash314

123 V I Yelagin V V Zakharov S G Pavlenko and T D Rostova

Phys Met Metall 1985 60 (1) 88ndash92

124 N Sano Y Hasegawa K Hono H Jo K Hirano H W

Pickering and T Sakurai Journal de Physique 1987 48 C6 337ndash

342

125 N Sano H-H Jo K-I Hirano and T Sakurai J Jpn Inst

Metals 1989 39 444ndash450

126 N Sano H Jo K Hirano and T Sakurai Proc Second Int

Conf on lsquoAluminium alloysrsquo Beijing China October 1990 549ndash

554

127 Y Miura M Nakayama and A Furuta Proc lsquoAspects of high

temperature deformation and fracture in crystalline materialsrsquo

Nagoya Japan July 1993 255ndash262

128 Y W Riddle and T H Sanders Jr Mater Sci Forum 2000

331ndash337 939ndash944

129 Y W Riddle M McIntosh and T H Sanders Jr in lsquoLightweight

alloys for aerospace application VIrsquo (ed K Jata E W Lee

W Frazier and N J Kim) 25ndash39 2001 TMS

130 M E Drits J Dutkiewicz L S Toropova and J Salawa Crystal

Res Technol 1984 19 1325ndash1330

131 Y W Riddle MSc thesis Georgia Tech GA USA 1998

132 T J Bastow and S Celotto Mater Sci Eng 2003 C 23 757ndash

762

133 M C Carroll M J Mills G S Daehn P I Gouma M F

Savage and B R Dunbar in lsquoAutomotive Alloys 1999rsquo (ed

S Das) 239ndash246 2000 TMS

134 E Clouet M Nastar and C Sigli Phys Rev B 2004 69 064109-

1-14

135 V V Zakharov Met Sci Heat Treat 1997 (2) 61ndash66

136 J W Christian lsquoThe theory of transformation in metals and

alloysrsquo 2nd edn 1975 Pergamon Press Ltd

137 A L Berezina V A Volkov B P Domashnikov S V Ivanov

and K V Chuistov Phys Metals 1990 10 296ndash304

138 S-I Fujikawa and S Sakauchi Proc 6th Int Conf on

lsquoAluminum alloysrsquo Toyohashi Japan July 1998 805ndash810

139 Y S Touloukian R K Kirby R E Taylor and P D Desai

(eds) lsquoThermal expansion metallic elements and alloysrsquo 1975

New York Plenum

140 J Roslashyset and N Ryum submitted to Scripta Mater

141 R O Simmons and R W Balluffi Phys Rev 1960 117 52ndash61

142 M Ocko E Babic R Krsmik E Girt and B Leontic J Phys F

Metals Phys 1976 6 703ndash707

143 M J Jones and F J Humphreys Proc First Joint Int Conf on

lsquoRecrystallization and grain growthrsquo Aachen Germany August

2001 Springer Verlag 1287ndash1292

144 S Iwamura M Nakayama and Y Miura Mater Sci Forum

2002 396ndash402 1151ndash1156

145 S Iwamura and Y Miura Acta Mater 2004 52 591ndash600

146 M Asta S M Foiles and A A Quong Phys Rev B 1998 57

11265ndash11275

147 R W Hyland Jr M Asta S M Foiles and C L Rohrer Acta

Mater 1998 46 3667ndash3678

148 J Roslashyset and N Ryum Proc 4th Int Conf on lsquoAluminium

alloysrsquo Vol I Atlanta GA USA September 1994 194ndash201

149 M E Drits L S Toropova G K Anastaseva and G L

Nagornichnykh Russ Metall 1984 (3) 192ndash195

150 E A Marquis D N Seidman and D C Dunand Acta Mater

2003 51 4751ndash4760

151 M E Drits L S Toropova and Yu G Bykov Met Sci Heat

Treat 1983 (7) 550ndash554

152 V V Zakharov and T D Rostova Met Sci Heat Treat 1995

(2) 65ndash69

153 M Nakayama and Y Miura Proc 4th Int Conf on lsquoAluminium

alloysrsquo Vol I Atlanta GA USA September 1994 538ndash545

154 M Nakayama and Y Miura J Jpn Inst Light Metals 1996 46

275ndash279

155 M Nakayama T Okuyama and Y Miura Mater Sci Forum

2000 331ndash337 927ndash932

156 M Nakayama T Okuyama and Y Miura Proc 6th Int Conf

on lsquoAluminum alloysrsquo Toyohashi Japan July 1998 517ndash522

157 M L Kharakterova D G Eskin and L S Toropova Acta

Metall Mater 1994 42 2285ndash2290

158 V I Elagin V V Zakharov and T D Rostova Met Sci Heat

Treat 1992 (1) 37ndash45

159 H Wiik Siv Ing thesis NTH Institute of Metallurgy

Trondheim Norway 1995

160 J Roslashyset H Hovland and N Ryum Mater Sci Forum 2002

396ndash402 619ndash624

161 Y Miura K Horikawa K Yamada and M Nakayama Proc

4th Int Conf on lsquoAluminium alloysrsquo Vol II Atlanta GA USA

September 1994 161ndash168

162 Y W Riddle PhD thesis Georgia Tech GA USA 2000

163 B Forbord W Lefebvre F Danoix H Hallem and

K Marthinsen Scripta Mater 2004 51 333ndash337

164 J D Robson Acta Mater 2004 52 1409ndash1421

165 C B Fuller J L Murray and D N Seidman submitted to Acta

Mater 2004

166 M G Mousavi C E Cross and Oslash Grong Sci Technol Weld

Joining 1999 4 381ndash388

167 J S Vetrano S M Bruemmer L M Pawlowski and I M

Robertson Mater Sci Eng 1997 A 238 101ndash107

168 Y W Riddle and T H Sanders Jr Mater Sci Forum 2000

331ndash337 799ndash803

169 G M Khan A O Nikiforov V V Zakharov and I I Novikov

Tsvetnye Metally 1993 34 (11) 43ndash45

170 Z Horita M Furukawa M Nemoto A J Barnes and T G

Langdon Acta Mater 2000 48 3633ndash3640

171 L A Willey US Patent 3 619 181 9 November 1971

172 L K Lamikhov and G V Samsonov Tsvetnye Metally 1964 5

(8) 77ndash80

173 A L Berezina K V Chuistov N I Kolobnev L B

Khokhlatova and T A Monastyrskaya Mater Sci Forum

2002 396ndash402 741ndash746

174 F A Fasoyinu J Thomson D Cousineau T Castles and M

Sahoo Proc 6th Int AFS Conf on lsquoMolten aluminum

processingrsquo Orlando FL USA November 2001

175 Z Yin Q Pan Y Zhang and F Jiang Mater Sci Eng 2000

A 280 151ndash155

176 I I Novikov and O E Grushko Mater Sci Technol 1995 11

926ndash932

177 D Cousineau M Sahoo P D Newcombe T Castles and F A

Fasoyinu Proc lsquoAFS 105th casting congressrsquo Dallas TX USA

AprilndashMay 2001 157ndash184

178 C E Cross and Oslash Grong Proc 6th Int Conf on lsquoAluminum

alloysrsquo Toyohashi Japan July 1998 1441ndash1446

179 F A Costello J D Robson and P B Prangnell Mater Sci

Forum 2002 396ndash402 757ndash762

180 K B Hyde A F Norman and P B Prangnell Mater Sci

Forum 2002 396ndash402 39ndash44

181 M E Drits S G Pavlenko L S Toropova Yu G Bukov and

L B Ber Sov Phys Dokl 1981 26 (3) 344ndash346

182 A M Drits and B A Kopeliovich Russ Metall 1985 (4) 147ndash

151

183 V G Davydov V I Elagin V V Zakharov and T D Rostova

Met Sci Heat Treat 1996 (8) 347ndash352

184 M E Drits L S Toropova Yu G Bykov L B Ber and S G

Pavlenko Russ Metall 1982 (1) 148ndash152

185 T D Rostova V G Davydov V I Yelagin and V V Zakharov

Mater Sci Forum 2000 331ndash337 793ndash798

186 Y W Riddle H Hallem and N Ryum Mater Sci Forum 2002

396ndash402 563ndash568

187 J Roslashyset and Y W Riddle Proc 9th Int Conf on lsquoAluminium

alloysrsquo Brisbane Australia August 2004 1210ndash1215

188 A M Diskin V K Portnoi A M Drits and A A Alalykin Sov

Non-Ferrous Met Res 1986 14 499ndash500

189 R R Sawtell P E Bretz and C L Jensen US Patent 4 689 090

25 August 1987

190 G A Salishchev Yu B Timoshenko and R A Saitova Proc

Second Int Conf on lsquoAluminium alloysrsquo Beijing China October

1990 413ndash415

191 T G Nieh R Kaibyshev L M Hsiung N Nguyen and

J Wadsworth Scripta Mater 1997 36 1011ndash1016

192 T G Nieh L M Hsiung J Wadsworth and R Kaibyshev Acta

Mater 1998 46 2789ndash2800

193 J S Vetrano C H Henager Jr M T Smith and S M

Bruemmer in lsquoHot deformation of aluminum alloys IIrsquo (ed T R

Bieler L A Lalli and S R MacEwen) 407ndash418 1998 TMS

194 J S Vetrano C H Henager Jr S M Bruemmer Y Ge and

C H Hamilton in lsquoSuperplasticity and Superplastic Forming

1998rsquo (ed A K Gosh and T R Bieler) 89ndash97 1998 TMS

195 V Y Gertsman J S Vetrano C H Henager Jr and S M

Bruemmer Proc First Joint Int Conf on lsquoRecrystallization and

grain growthrsquo Aachen Germany August 2001 Springer Verlag

2001 837ndash842

196 Y Xiao C Gao H Ma and S Tian Trans Nonferrous Met Soc

China 2001 11 235ndash238

Roslashyset and Ryum Scandium in aluminium alloys

42 International Materials Reviews 2005 VOL 50 NO 1

197 A Gholinia F J Humphreys and P B Prangnell Acta Mater

2002 50 4461ndash4476

198 A Gholinia F J Humphreys and P B Prangnell Mater Sci

Forum 2002 408ndash412 1519ndash1524

199 S Komura P B Berbon M Furukawa Z Horita M Nemoto

and T G Langdon Scripta Mater 1998 38 1851ndash1856

200 S Komura P B Berbon A Utsunomiya M Furukawa

Z Horita M Nemoto and T G Langdon in lsquoHot deformation

of aluminum alloys IIrsquo (ed T R Bieler L A Lalli and S R

MacEwen) 125ndash138 1998 TMS

201 S Komura Z Horita M Furukawa M Nemoto and T G

Langdon J Mater Res 2000 15 2571ndash2576

202 S Komura M Furukawa Z Horita M Nemoto and T G

Langdon Mater Sci Eng 2001 A 297 111ndash118

203 S Komura Z Horita M Furukawa M Nemoto and T G

Langdon Metall Mater Trans A 2001 32A 707ndash716

204 Z Horita M Furukawa K Oh-ishi M Nemoto and T G

Langdon Proc Fourth Int Conf on lsquoRecrystallization and

related phenomenarsquo (ed T Sakai and H G Suzuki) 1999 The

Japan Institute of Metals 301ndash308

205 Z Horita S Komura P B Berbon A Utsunomiya

M Furukawa M Nemoto and T G Langdon Mater Sci

Forum 1999 304ndash306 91ndash96

206 Z Horita S Lee S Ota K Neishi and T G Langdon Mater

Sci Forum 2001 357ndash359 471ndash476

207 Z Horita T Fujinami K Sato S B Kang H W Kim and T G

Langdon in Proc James T Staley Honorary Symposium on

Aluminum Alloys lsquoAdvances in the metallurgy of aluminum

alloysrsquo (ed M Tiryakioglu) 271ndash275 2001 ASM

208 P B Berbon S Komura A Utsunomiya Z Horita

M Furukawa M Nemoto and T G Langdon Mater Trans

JIM 1999 40 772ndash778

209 M Nemoto Z Horita M Furukawa and T G Langdon Mater

Sci Forum 1999 304ndash306 59ndash66

210 M Furukawa Z Horita M Nemeto and T G Langdon Proc

lsquoLight Metals 1999rsquo Quebec City PQ Canada August 1999 583ndash

592

211 M Furukawa K Oh-ishi S Komura A Yamashita Z Horita

M Nemeto and T G Langdon Mater Sci Forum 1999 304ndash

306 97ndash102

212 M Furukawa A Utsunomiya K Matsubara Z Horita and

T G Langdon Acta Mater 2001 49 3829ndash3838

213 M Furukawa A Utsunomiya S Komura Z Horita M Nemoto

and T G Langdon Mater Sci Forum 2001 357ndash359 431ndash436

214 M Furukawa Z Horita and T G Langdon in Proc James T

Staley Honorary Symposium on Aluminum Alloys lsquoAdvances in

the metallurgy of aluminum alloysrsquo (ed M Tiryakioglu) 47ndash56

2001 ASM

215 M Furukawa Z Horita M Nemoto and T G Langdon Mater

Sci Eng 2002 A 324 82ndash89

216 M Furukawa Z Horita and T G Langdon in lsquoUltrafine grained

materials IIrsquo (ed Y T Zhu T G Langdon R S Mishra S L

Semiatin M J Saran and T C Lowe) 459ndash468 2002 TMS

217 T G Langdon M Furukawa Z Horita and M Nemoto Proc

NATO Advanced Research Workshop on lsquoInvestigations and

applications of severe plastic deformationrsquo Moscow August

1999 NATO Science Series Series 3 High Technology vol 80

Kluwer Academic Publishers The Netherlands 2000 149ndash154

218 S Lee H Akamatsu A Utsunomiya K Neishi M Furukawa

Z Horita and T G Langdon Proc Thermec 2000 Las Vegas

USA December 2000

219 S Lee A Utsunomiya H Akamatsu K Neishi M Furukawa

Z Horita and T G Langdon Acta Mater 2002 50 553ndash564

220 A Yamashita D Yamaguchi Z Horita and T G Langdon

Mater Sci Eng 2000 A 287 100ndash106

221 K Oh-ishi Z Horita D J Smith and T G Langdon J Mater

Res 2001 16 583ndash589

222 H Akamatsu T Fujinami Z Horita and T G Langdon Scripta

Mater 2001 44 759ndash764

223 S Ota H Akamatsu K Neishi M Furukawa Z Horita and

T G Langdon Mater Trans 2002 43 2364ndash2369

224 K Furuno H Akamatsu K Oh-ishi M Furukawa Z Horita

and T G Langdon Acta Mater 2004 52 2497ndash2507

225 I N Fridlyander O G Senatorova N A Ryazanova and A O

Nikiforov Mater Sci Forum 1994 170ndash172 345ndash349

226 J N Fridlyander and O G Senatorova Mater Sci Forum 1996

217ndash222 1813ndash1818

227 J Liu and D J Chakrabarti Acta Mater 1996 44 4647ndash4661

228 O G Senatorova A N Uksusnikov J N Fridlyander

J Koshorst R R Romanova N A Ryazanova A Galliot

and V V Cherkassov Proc 6th Int Conf on lsquoAluminum alloysrsquo

July 1998 Toyohashi Japan 589ndash593

229 R A Emigh E L Bradley and J W Morris Jr in

lsquoSuperplasticity in aerospace IIrsquo (ed T R McNelley and H C

Heikkenen) 303ndash315 1990 TMS

230 E L Bradley III R A Emigh and J W Morris Jr Scripta

Metall Mater 1991 25 717ndash721

231 N I Kolobnev L B Khokhlatova V D Makarov E Yu

Semenova and V V Redchits Proc Sixth Int Aluminiumndash

Lithium Conference Garmisch-Partenkirchen Germany October

1991 1053ndash1056

232 N K Tsenev R Z Valiev O V Obraztsov and I N Fridlander

Proc Sixth Int AluminiumndashLithium Conference Garmisch-

Partenkirchen Germany October 1991 1125ndash1132

233 A M Shammazov N K Tsenev R Z Valiev M M

Myshlyaev M M Bikbulatov and S P Lebedich Phys Met

Metall 2000 89 (3) 314ndash318

234 F Musin R Kaibyshev Y Motohashi T Sakuma and G Itoh

Mater Trans A 2002 43A 2370ndash2377

235 M Shagiev Y Motohashi F Musin R Kaibyshev and G Itoh

Mater Trans A 2003 44A 1694ndash1697

236 M Shagiev Y Motohashi F Musin R Kaibyshev and G Itoh

Mater Trans A 2003 44A 1698ndash1701

237 B A Parker and Z F Zhou Proc 3rd Int Conf on lsquoAluminium

alloysrsquo Vol I NTH Trondheim Norway June 1992 363ndash367

238 J R Davies lsquoASM specialty handbook aluminum and aluminum

alloysrsquo 1993 Materials Park OH USA ASM

239 S J Andersen H W Zandbergen J Jansen C Traeholt

U Tundal and O Reiso Acta Mater 1998 46 3283ndash3298

240 M L Kharakterova D G Eskin and L L Rokhlin Russ

Metall 1997 (1) 104ndash109

241 J Roslashyset Dr Ing thesis NTNU Trondheim Norway 2002

242 P P Chattopadhyay S Datta and M K Banerjee Mater Sci

Eng 2002 A 333 67ndash71

243 L I Kaigorodova E I Selnikhina E A Tkachenko and O G

Senatorova Phys Met Metall 1996 81 513ndash519

244 Y-L Wu F H Froes C Li and A Alvarez Metall Mater

Trans A 1999 30A 1017ndash1024

245 Z Yin L Yang Q Pan and F Jiang Trans Nonferrous Met

Soc China 2001 11 822ndash825

246 V I Elagin V V Zakharov and T D Rostova Met Sci Heat

Treat 1994 36 (7) 375ndash380

247 Y V Milman A I Sirko D V Lotsko O N Senkov and D B

Miracle Mater Sci Forum 2002 396ndash402 1217ndash1222

248 C-H Joh K Yamada and Y Miura Mater Trans JIM 1999

40 439ndash442

249 X J Jiang Q H Gui Y Y Li L M Ma G J Liang and C X

Shi Scr Metall Mater 1993 29 211ndash216

250 X J Jiang Y Y Li W Deng L Y Xiong W M Wu Y J Gao

and C X Shi Adv Cryogenic Eng (Mater) 1994 40 1369ndash

1376

251 C-H Joh T Katsube K Yamada and Y Miura Proc 6th Int

Conf on lsquoAluminum alloysrsquo Toyohashi Japan July 1998 799ndash

804

252 L I Kaygorodova A M Dritz T V Krymova and I N

Fridlyander Proc Sixth Int AluminiumndashLithium Conference

Garmisch-Partenkirchen Germany October 1991 363ndash367

253 L I Kaigorodova A M Drits Ya V Zhingel T V Krymova

and I N Fridlyander Phys Met Metall 1992 73 286ndash290

254 A L Berezina V A Volkov S V Ivanov N I Kolobnev and

K V Chuistov Phys Met Metall 1991 71 (2) 167ndash175

255 I N Fridlyander N I Kolobnev A L Berezina and K V

Chuistov Proc Sixth Int AluminiumndashLithium Conference

Garmisch-Partenkirchen Germany October 1991 107ndash112

256 L I Kaigorodova A M Drits Ya V Zhingel T V Krymova

and V A Rassokhin Phys Met Metall 1992 73 281ndash285

257 I N Fridlyander S F Danilov E N Malysheva T A

Gorokhova and N N Kirkina Proc Sixth Int Aluminiumndash

Lithium Conference Garmisch-Partenkirchen Germany October

1991 381ndash386

258 G Dlubek S Krause H Krause A L Beresina V S

Mikhalenkov and K V Chuistov J Phys Condens Matter

1992 4 6317ndash6328

259 S Krause H Krause G Dlubek A L Beresina and K S

Chuistov Mater Sci Forum 1992 105ndash110 1109ndash1112

260 C Y Tan Z Q Zheng and S Q Liang Proc 4th Int Conf on

lsquoAluminium alloysrsquo Vol II Atlanta GA USA September 1994

329ndash333

261 A L Beresina N I Kolobnev K V Chuistov A V Kotko and

O A Molebny Mater Sci Forum 2002 396ndash402 977ndash981

Roslashyset and Ryum Scandium in aluminium alloys

International Materials Reviews 2005 VOL 50 NO 1 43

262 I N Ganiev I Yunusov and V V Krasnoyarskii J Appl Chem

USSR 1986 60 1961ndash1965

263 I N Ganiev Prot Met 1995 31 543ndash546

264 N V Vyazovikina Prot Met 1999 35 448ndash453

265 G V Kharina and V P Kochergin Prot Met 1996 32 134ndash

136

266 G V Kharina M V Kuznetsov and V P Kochergin Russ J

Electrochem 1998 34 482ndash485

267 V S Sinyavskii V D Valrsquokov and E V Titkova Prot Met

1998 34 549ndash555

268 Y L Wu F H Froes C G Li and J Liu Proc lsquoSynthesis

processing of lightweight metallic materials IIrsquo Orlando FL

USA February 1997 73ndash81

269 Z Ahmad and B J Abdul-Aleem Proc EuroCorr 2000

270 Z Ahmad A Ul-Hamid and B J Abdul-Aleem Corros Sci

2001 43 1227ndash1243

271 R Braun B Lenczowski and G Tempus Mater Sci Forum

2000 331ndash337 1647ndash1652

272 T Torma E Kovacs-Csetenyi L Vitalis I Vitanyi

J Stepanov and M Butova Mater Sci Forum 1987 1314

497ndash503

273 Z Wang P Wang K S Kumar and C L Briant in lsquoChemistry

and electrochemistry of corrosion and stress corrosion crackingrsquo

(ed R H Jones) 573ndash582 2001 TMS

274 V I Elagin V V Zakharov A A Petrova and E V

Vyshegorodtseva Russ Metall 1983 (4) 143ndash146

Roslashyset and Ryum Scandium in aluminium alloys

44 International Materials Reviews 2005 VOL 50 NO 1

Page 11: Scandium in aluminium alloys - Atom probe · A considerable part of the available literature on scandium in aluminium alloys is reviewed. ... behaviour in Al Cu, Al Mg Si,

note that an n value close to 32 is per se not evidence ofsite saturation

Hyland also showed that a water quench from thesolutionising temperature significantly altered thenucleation kinetics in the subsequent precipitation heattreatment107 The incubation time was dramaticallyshortened which is attributed to the quenched-in excessvacancies and it is also indicated that there might be ashift in the nucleation rate in the early stage ofprecipitation It is suggested that the vacancies mayenhance the diffusion of Sc in Al and that there is apossibility that vacancy clusters act as heterogeneousnucleation sites for Al3Sc precipitates107 Regardless ofwhich mechanism that is operative it is clearly demon-strated that the nucleation kinetics can be dependent onthe thermal history between solutionising and precipita-tion heat treatment

Loss of coherency during growth of Al3ScprecipitatesWhen an Al3Sc particle grows it will sooner or laterreach a critical size where it will be energetically morefavourable to introduce an interface dislocation at theAlAl3Sc interface than to increase the matrix strain Asimple approximation for the critical size can be derivedfrom the lattice parameters assuming that the criticalsize is reached when the misfit over the whole particlediameter equals the Burgers vector of the Al matrix

dcrit~b=d (2)

where b is the Burgers vector of Al and d is themisfit between Al and Al3Sc This approximation yieldsa critical diameter of approx 215 nm at ambienttemperature

The misfit d and thus also the critical diameter dcrit

will depend on the temperature owing to the differencesin thermal expansion between the Al matrix and the

Al3Sc particles The thermal expansion of Al3Sc hasrecently been measured89 and based on the differencesin thermal expansion between Al139 and Al3Sc the misfitas a function of temperature has been calculated89 Thiscalculation is reproduced and shown by the solid line inFig 17

It is however possible to refine this calculationsomewhat140 Whereas the thermal expansion of Al3Sc isexpected to be only because of lattice expansion there isa significant contribution from vacancies on thermalexpansion of Al at high temperatures141 Thus thetemperature effects on the misfit should be calculatedfrom the changes in lattice parameters rather than fromthe linear thermal expansion By subtracting the vacancyeffect on the thermal expansion one achieves atemperature-dependent misfit as represented by thedotted line in Fig 17

A second correction that should be taken into accountis the effect of Sc in solid solution on the latticeparameter of the Al matrix With increasing tempera-ture more Sc is brought into solid solution and it isreported that the lattice parameter of the Al matrixpresumably measured at room temperature increaseslinearly with the Sc content in solid solution142 Thesedata can be used to calculate the effect on the latticeparameter at elevated temperatures under the assump-tion that the relative increase in lattice parameter owingto Sc in solid solution is independent of temperature InRef 142 a figure is presented which shows the measuredlattice parameter as a function of Sc content in solidsolution and a value (dadc)a is reported where a is thelattice parameter of the Al matrix and c is the Sc contentin solid solution in at- The reported value for (dadc)a is 100 times larger than that indicated in thecorresponding figure possibly as a result of a decimalerror in the text Thus in the present exercise 1100th ofthe reported value for (dadc)a is used Using this incombination with the regular solution approximationfor the solvus line of Sc in Al1231 one obtains acorrection for Sc in solid solution on the temperature-dependent misfit as shown in Fig 18 This figure shows

17 Lattice mismatch between Al and Al3Sc as a function

of temperature solid line represents calculation

based on linear thermal expansion of the two phases

dotted line represents correction for vacancies in Al

lattice

18 Corrections of mismatch calculated from linear ther-

mal expansion data as a result of vacancies and to

Al lattice expansion from Sc in solid solution

Roslashyset and Ryum Scandium in aluminium alloys

International Materials Reviews 2005 VOL 50 NO 1 29

both the correction for vacancies and for Sc in solidsolution on the same graph The two corrections are ofapproximately the same magnitude but with oppositesigns Thus the resulting (net) correction is close to zeroand it turns out that the first hand approximation asapplied in Ref 89 is very good in this case

Applying the calculated temperature dependent misfitwith the simple approximation for a critical diameter forloss of coherency one obtains a temperature-dependentcritical diameter as shown in Fig 19

Some examples from the literature of experimentallyobserved critical diameters in binary AlndashSc alloys aresummarised in Table 5 along with some predictions forcritical diameters from Fig 19 There is a fairly goodconsistency between the observations and the measureddiameter is quite close to the simple predictions above

A more refined analysis on the transition fromcoherent to incoherent particles has recently beenperformed145 This analysis is based on the balancebetween the increase in particlematrix interface energyowing to interfacial dislocations and the relaxation inelastic energy in the Al matrix owing to the samedislocations This method yields a predicted criticaldiameter of 246 nm for transition from coherent to

semi-coherent particles at ambient temperature Thetemperature dependence of the critical diameter is nottreated in this analysis

The loss of coherency during isothermal annealing hasbeen reported to be accompanied by an increasedaverage coarsening rate119121137145 The increasedcoarsening rate has been attributed either to diffusionof Sc along dislocation lines119121 or to the increasedparticlematrix interface energy of a semicoherentparticle145 However there are also several data sets inthe literature that do not indicate an increased growthrate after the loss of coherency114128

Al3ScAl interface energyThe interface energy between Al3Sc and the Al matrix isone of the key parameters that governs the nucleationgrowth and coarsening behaviour of Al3Sc in Al and Alalloys The interface energy has been estimated in severalinvestigations either by fitting experimental data toequations that describe nucleation or coarsening or bycalculations A compilation of some of the results isgiven in Table 6 There is considerable spread in thereported values regardless of what approach has beenused for the estimation

Influence of other elements on precipitation ofAl3ScMagnesium

With regard to precipitation mechanism it has beenstated that Mg suppresses the tendency to discontinuousprecipitation of Al3Sc106 In an investigation of pre-cipitation kinetics of Al3Sc in the temperature range300ndash500uC only minor changes in the kinetics (Fig 20)were found when up to 5 wt-Mg was added to an Alndash04 wt-Sc alloy135 It seems that the precipitationreaction is slightly faster in the Mg-containing alloys

Several investigations on age hardening response alsoimply that there is only a small if any effect of Mg onthe precipitation kinetics of Al3Sc23148149 It is how-ever found that the hardness increase from theprecipitation of Al3Sc is somewhat reduced in AlndashMgndashSc alloys compared to binary AlndashSc alloys23148149 InRef 149 it is suggested that some of the Sc is dissolvedin the Al3Mg2 phase and thus the age hardeningpotential is reduced with increasing Mg contentSomewhat contradictory to these observations but

Table 5 Some reported critical diameters for coherencyloss in binary AlndashSc and correspondingtheoretical critical diameters from Fig 19

Reference dcrit nmC0

Scwt-Sc

TtransuC

Theoreticaldcrit nm

119 38ndash40 05137 28ndash30 03 400 308128 32 02 400 450 308 335129 50 02143 40 012 025115 40 025 450ndash500 335ndash37114 40 03 400 450 308 335144 40 02 400ndash460 308ndash341145 30ndash80 02 400ndash490 308ndash362

20 C-curves for 10 and 60 transformation in Alndash

04 wt-Sc and Alndash4 wt-Mgndash04 wt-Sc redrawn

from Ref 135

19 Simple approximation for temperature-dependent criti-

cal diameter for introduction of dislocations on Al

Al3Sc interface

Roslashyset and Ryum Scandium in aluminium alloys

30 International Materials Reviews 2005 VOL 50 NO 1

sustained by Ref 135 it has recently been reported150

that precipitation of Al3Sc at 300 and 350uC occursslightly faster in an Alndash2 wt-Mgndash02 wt-Sc alloythan in an Alndash02 wt-Sc alloy studied previously by thesame researchers117118 and that the correspondinghardness increase is highest in the AlndashMgndashSc alloyThe only reported difference in experimental procedureis the solutionising temperature which was higher forthe AlndashSc alloy (648uC) than for the AlndashMgndashSc alloy(617uC) However given that the nucleation time isshortened by quenched-in vacancies as suggested byHyland107 the difference in homogenisation tempera-ture should be in favour of a faster precipitation of thebinary AlndashSc alloy It should be worthwhile to probedeeper into this observation of different aging responses

Mg in solid solution increases the lattice parameter ofthe Al matrix This is in turn expected to influence thecritical diameter for AlAl3Sc coherency loss as discussedin the section on lsquoLoss of coherency during growth ofAl3Sc precipitatesrsquo above Such an influence on the criticaldiameter is also briefly discussed elsewhere150 A criticaldiameter of 80 nm in an Alndash3 wt-Mgndash02 wt-Sc alloyhas been observed compared to 40 nm in a binary Alndash02 wt-Sc alloy of the same investigation144 Otherresearchers have reported a critical diameter in excess of116 nm in an Alndash63 wt-Mgndash02 wt-Sc alloy151

Computer simulations predict that the AlAl3Scinterface should be enriched in Mg87 These predictionsare confirmed experimentally by three-dimensional atomprobe microscopy of an Alndash2 wt-Mgndash02 wt-Sc alloyaged at 300uC38 Here it was found that the Mg contentat the interface is approximately three times higher thanthe matrix concentration regardless of aging time

Copper

It has been claimed that Cu suppresses the tendencytowards discontinuous precipitation of Al3Sc106

Zakharov and Rostova152 have reported that additionsof up to 14 wt-Cu have only minor effects on theprecipitation kinetics in an Alndash04 wt-Sc alloy Themost noticeable effect is that for temperatures above400uC the late stage of the transformation is sloweddown for the highest Cu contents This does not show in

Fig 21 however where only the 10 and 60transformation curves are included

The W-phase (AlCuSc) was observed in the alloywith the highest Cu content which means that less Sc isavailable for the precipitation of Al3Sc in this alloyAnother investigation on the age hardening response ofAlndash023 wt-Sc and Alndash25 wt-Cundash023 wt-Sc at300uC also implies that the precipitation behaviour ofAl3Sc in the two alloys is similar153154 At 350uC alimited portion of the Al3Sc has been observed tonucleate heterogeneously on coarse hrsquo precipitates155

According to the isothermal sections of the phasediagram43 one should expect the ternary W-phase toform instead of the Al3Sc phase in an alloy with such ahigh CuSc ratio However no observations of the W-phase or other ternary phases were reported from TEMstudies of the Alndash25 wt-Cundash023 wt-Sc alloy thathad been heat treated in the temperature range 300ndash460uC153ndash156 A third investigation on the precipitationin Alndash048 wt-Sc alloys with up to 440 wt-Cu in thetemperature range 100ndash450uC also concludes that no W-phase or other ternary phase forms during the heattreatment157

Copper in solid solution decreases the lattice para-meter of the Al matrix Thus it is expected that the misfitbetween Al and Al3Sc precipitates should be higher in

21 C-curves for 10 and 60 transformation in Alndash

04 wt-Sc and Alndash14 wt-Cundash04 wt-Sc redrawn

from Ref 152

Table 6 Reported values of interphase energy cAlAl3Sc between coherent Al3Sc precipitates and Al matrix

Reference cAlAl3Sc mJ m22 Method of estimation

137 10 Fit of coarsening data to LifshitzndashSlezev equation107 78iexcl20 (288uC) Back-calculation of incubation time

93iexcl20 (343uC)107 123iexcl41 (288uC) Back-calculation of nucleation rate

125iexcl35 (343uC)29 542 (400uC) Fit of coarsening data to Ostwald ripening

632 (430uC)413 (460uC)

146 c(100) 192 (0 K) c(111) 226 (0 K) Pseudopotential calculations147 c(100) 325 (0 K) c(110) 513 (0 K) c(111)

782 (0 K) c(100) 315 (288uC) c(100) 325 (343uC)Atomistic simulation

110 105 Fit of coarsening data to LSW theory31 20ndash300 Fit of coarsening data to Ostwald ripening

for 16 different temperatures111 57 Fit of precipitation model to experimental data145 120 coherent particles Fit of coarsening data

170 semicoherent particles

It is argued in this study that c may be lower in the nucleation stage

Roslashyset and Ryum Scandium in aluminium alloys

International Materials Reviews 2005 VOL 50 NO 1 31

AlndashCundashSc alloys compared to AlndashSc alloys Howeveran experimental investigation of Alndash25 wt-Cundash023 wt-Sc alloy comes to a different conclusion Thelattice misfit strain is found to decrease compared to Alndash02 wt-Sc and the critical diameter for coherency losswas found to be the same in the ternary and the binaryalloy144 It is suggested that these observations may bebecause of the dissolution of some Cu in the Al3Sc phaseand thus that the lattice parameters of both the Al matrixand the Al3Sc precipitates decrease in the ternary alloy

Silicon

It has been found that the onset of precipitation in Alndash04 wt-Sc is only slightly altered when Si contents ofup to 04 wt are introduced in the alloy However thefinal stage of the precipitation reaction is considerablydelayed with increasing Si content135 Figure 22 showsthe effect of addition of a joint of 035 wt-Si and040 wt-Fe There are at least two possible explana-tions for why an Si-addition leads to this behaviour

1 Alloying with Si is known to promote discontin-uous precipitation of Al3Sc106158 It has been shown thatwhen isothermal precipitation of Al3Sc starts discon-tinuously the later stage of the overall transformationcan be very slow31

2 The isothermal section of the phase diagramsuggests that the V-phase (AlSc2Si2) should form inalloys of this composition46 If the V-phase forms lessSc is available for precipitation of Al3Sc

It has been shown157 that for an AlndashScndashSi alloy withsolid solution content of 010 wt-Sc an 110 wt-Sithe only phases to precipitate after heat treatment at200uC are Si and an (AlScSi)-phase possibly the V-phase On the other hand the Al3Sc phase has beenobserved to form in alloys with 04 wt-Sc and up to08 wt-Si159160

Zinc

It has been reported that additions of up to 5 wt- Znhave only minor effects on the precipitation kinetics ofan Alndash04 wt-Sc alloy135 (Fig 23) In Ref 106 it isclaimed that Zn promotes discontinuous precipitation ofAl3Sc

Lithium

A comparison of the age hardening response at 400uC inAlndash24 wt-Lindash019 wt-Sc and Alndash024 wt-Sc alloys

indicates that the onset of Al3Sc-precipitation is notaffected by the presence of Li161

Zirconium

As mentioned in the section on lsquoTernary phase diagramswith dispersoid-forming elementsrsquo earlier a considerableamount of Zr is dissolved in the Al3Sc phase and thus amore correct denotation of the precipitating phase isAl3(Sc12xZrx) In discussing the influence of the Zrcontent on the precipitation of Al3Sc one is thereforeactually discussing the difference in precipitation ofAl3Sc versus Al3(Sc12xZrx)

It is found that an addition of 015 wt-Zr to an Alndash04 wt-Sc alloy only marginally affects the initial stageof the precipitation reaction123135 while it slows downthe later stages of the transformation considerably(Fig 24)135 The coarsening rate of the Al3(Sc12xZrx)particles in AlndashScndashZr alloys is found to be much slowerthan that of Al3Sc particles in AlndashSc alloys123162

In three-dimensional atom probe field ion microscopy(3D-APFIM) of Al3(Sc12xZrx) particles formed at 475uCin a ternary AlndashScndashZr alloy163 it was found that the coreof the particles is almost pure Al3Sc whereas there is ashell of Al3(Sc12xZrx) with almost equal content of Scand Zr Such a behaviour has also been predicted bycomputer modelling of precipitation of Al3(Sc12xZrx) at480uC in an AlndashZnndashMgndashScndashZr alloy164 This modelpredicts that Zr starts to enter the growing

22 C-curves for 10 and 60 transformation in Alndash

04 wt-Sc and Alndash04 wt-Fendash035 wt-Sindash04 wt-Sc

redrawn from Ref 135

23 C-curves for 10 and 60 transformation in Alndash

04 wt-Sc and Alndash5 wt-Znndash04 wt-Sc redrawn

from Ref 135

24 C-curves for 10 and 60 transformation in Alndash

04 wt-Sc and Alndash04 wt-Scndash015 wt-Zr redrawn

from Ref 135

Roslashyset and Ryum Scandium in aluminium alloys

32 International Materials Reviews 2005 VOL 50 NO 1

Al3(Sc12xZrx) particles when approximately half of thesupersaturated Sc has been precipitated The Zr contentof the outer shell is predicted to be much higher thanwhat has been found experimentally163164

Another 3D-APFIM study of Al3(Sc12xZrx) particlesin a ternary AlndashScndashZr alloy has been reported165 Hereparticles grown at 300uC for various lengths of time werestudied The Zr content in these particles was muchlower than that reportedpredicted at higher tempera-tures163164 even after very long annealing times

Iron

The effect of adding up to 07 wt-Fe on the precipita-tion kinetics in an Alndash04 wt-Sc alloy has beeninvestigated135 The onset of precipitation was onlyslightly influenced by the Fe-level whereas the laterstages of the transformation however were significantlyslowed down as the Fe-level increased An example ofthe effect of a joint addition of Fe and Si is shown inFig 22

Manganese chromium and titanium

Small additions (03 wt-) of manganese or chromiumto Alndash040 wt-Sc alloys are reported to have onlyminor effects on the precipitation kinetics of Al3Sc135

According to Ref 106 Mn is reported to promote andCr and Ti to suppress discontinuous precipitation

Rare earth elements

An investigation of the precipitation behaviour of Alndash03 at-Sc and Alndash03 at-Scndash03 at-X alloyswhere X is either yttrium gadolinium holmium orerbium in the temperature range 235ndash310uC indicatedthat a Al3(Sc12xXx) phase with L12 structure wasformed in the ternary alloys22 Peak strength is reportedto occur after approx 10 h at 285uC in all alloys whichindicates that the precipitation kinetics up to peakstrength is practically unaltered by the ternary additions

Influence of Sc on microstructure andproperties of wrought aluminium alloysMost of the effects of Sc addition in wrought Al-alloysare linked to the formation of the Al3Sc phase In atypical processing route of a wrought aluminium alloyparticles of the Al3Sc phase can form under threedifferent conditions each of which influences themicrostructure and properties of the alloy in a specificway

1 During solidification after casting or weldingAl3Sc particles can form in the melt and act as nucleifor a-Al thus leading to grain refinement18166

2 High temperature processing of the alloy in therange 400ndash600uC for instance homogenisation hot-rolling or extrusion can give a dense distribution ofAl3Sc particles of typically 20ndash100 nm size The particledistributions formed under such conditions are reportedto lead to good recrystallisation resistance128148167168

and enhanced superplasticity52169170

3 Heat treatment in the range 250ndash350uC can lead tosignificant precipitation hardening of an alloy super-saturated in Sc148158171 The size of strengthening Al3Scprecipitates is typically in the range 2ndash6 nm121

Grain refinementA good grain refinement is almost always desired uponsolidification The formation of small equiaxed grainsrather than long dendrites in the melt facilitates thefeeding of the melt into cavities of the shrinkingsolidified metal and thus reduces the problem ofshrinkage porosity The tendency to hot cracking is alsoreduced and the second phase particles become morefinely and uniformly distributed

To the authorsrsquo knowledge the first effect of Sc in Al-alloys that was reported in an international scientificjournal was the grain refining action in pure Al and in anAlndashCu alloy upon solidification172 which was found tobe stronger for Sc than for other transition metals Inlater studies of Sc as a grain refiner in pure Al1832173 ithas been demonstrated that approx 07 wt-Sc issufficient to provide excellent grain refinement It hasalso been demonstrated that additions of 025 wt-Scz025 wt-Zr provide good grain refinement in pure Al18

In order for Sc to act as an effective grain refiner theAl3Sc phase has to form in the melt before thesolidification of a-Al The Al3Sc particles have a latticeparameter close to that of pure Al and whenhypereutectically formed the Al3Sc particles are veryeffective substrates for the nucleation of the a-Al phaseAs mentioned in the section on lsquoFormation of Al3Sc inAlndashSc alloysrsquo above this requires that the alloy ishypereutectic with respect to Sc ie in excess of approx06 wt- in a binary AlndashSc alloy In ternary and higherorder systems the eutectic Sc composition may dependon the other alloying elements present For instance theeutectic composition of Sc has been predicted todecrease with increasing Mg content in the ternary AlndashMgndashSc system39 This prediction is sustained by theobservation of good grain refinement by adding 05 wt-Sc to an Alndash7 wt-Mg alloy174 (Other examples ofgrain refinement at Sc concentrations lower than that ofthe binary eutectic are found in Ref 173)

Similarly the observation of good grain refinement inan Alndash025 wt-Scndash025 wt-Zr alloy18 may be as aresult of a lower Sc content of the eutectic in the ternarysystem ie less Sc is needed to make the alloy hyper-eutectic No literature data on the liquidus surface of theAlndashScndashZr system are available and thus this hypothesiscannot be confirmed In more complex alloy systems itis also observed that excellent grain refinement isachieved at low Sc contents when Sc is added togetherwith Zr It is reported that adding either 02 wt-Sc06 wt-Sc or 01 wt-Zr to an Alndash5Mg alloy givesmuch poorer grain refinement than adding 02 wt-Scz01 wt-Zr175 Similarly additions of 015 wt- ofeither Sc or Zr are reported to only marginally refinethe grain structure in an AlndashCundashLi alloy whereas a jointaddition of 015 wt-Sc and 015 wt-Zr gives excellentgrain refinement176 For an AA 3650 casting alloy (Alndash7 wt-Sindash04 wt-Mg) good grain refinement is achievedby adding 039 wt-Sc or 027 wt-Scz019 wt-Zr177

In some AlndashZnndashMgndashScndashZr alloys it is also found thatan addition of 02ndash03 wt-Sc can be sufficient for goodgrain refinement166169178179 Examples of the grainrefinement as a function of Sc addition in pure Al andin an AlndashZnndashMgndashZr alloy are shown in Fig 25

The nucleation of a-Al on Al3Sc particles in the melt isfacilitated by the close match in the lattice parameters ofthe two phases As shown in Fig 17 the mismatch at the

Roslashyset and Ryum Scandium in aluminium alloys

International Materials Reviews 2005 VOL 50 NO 1 33

eutectic temperature of binary AlndashSc alloys (660uC) isonly approx 047 In Refs 57 and 89 it is shown thatwhen Zr Hf and in particular Ti is dissolved in the Al3Scparticles this reduces the lattice parameter of the phaseIt appears that when 25 of the Sc atoms in Al3Sc aresubstituted by Ti the mismatch is zero at approx 550uCand becomes negative at higher temperatures89 Thissuggests that by carefully selecting the Ti content of thealloy it should be possible to obtain Al3(ScTi)substrates in the melt that match exactly the latticeparameter of the nucleating a-Al and thus furtherimprove the grain refinement of the alloy This appearsto have been achieved in a recent work180 where thegrain refinement of an Alndash07 wt-Sc alloy wascompared with that of an Alndash05 wt-Scndash02 wt-Tialloy At a cooling rate of 100 K s21 only an estimated2 of the primary Al3Sc particles of the binary AlndashScalloy were effective nuclei compared to practically 100for the primary Al3(ScTi) particles in the ternary AlndashScndashTi alloy leading to a much smaller grain size in theternary alloy Whereas the match of lattice parametersmay be of importance for these results the authors ofthis investigation180 draw attention to other factors suchas different growth restriction factors for Sc and Ti andthe possibility of a peritectic reaction in the ternaryalloy Nevertheless the principle of matching latticeparameters is worth looking into further in future work

Effects from dispersoidslsquoDispersoidsrsquo is a term which is commonly used aboutthe classes of second phase particles that are formedin an Al alloy during high temperature annealing orthermomechanical processing such as homogenisationhot rolling extrusion and forging A dense distributionof dispersoids can give a significant contribution to analloyrsquos strength owing to particle strengthening but thisis rarely the main strengthening mechanism A moreimportant contribution from the dispersoids is theirability to stabilise the grainsubgrain structure of analloy through the Zener-drag action and thus improvethe mechanical properties of the alloy

There are two noticeable dispersoid-related effectsthat have been reported for Sc-containing alloys Thefirst is the stabilising effect on a deformed microstruc-ture When a non-recrystallised structure is preserved inan alloy this can add considerably to the mechanical

strength of the material The second effect is thepreservation of a small grain size during hot deforma-tion at slow deformation rates which is necessary toobtain superplastic properties of an Al-alloy

Recrystallisation resistance

The anti-recrystallisation effect of Sc was first publishedin a patent171 where 03 wt-Sc was added to pure Aland to AlndashMg AlndashMn and AlndashZnndashMg alloys Both Sc-free and Sc-containing materials were cold worked andsubsequently annealed and it was found that theaddition of Sc increased the temperature for onset ofrecrystallisation by approx 220uC in pure Al andsomewhat less in the Al-alloys Although the author ofthe patent171 may have been well aware that the anti-recrystallisation effect is caused by Al3Sc dispersoidsthis is not mentioned in the text The first journal paperthat explicitly points out that the recrystallisationresistance is due to Al3Sc dispersoids was an investiga-tion of the effects of adding Sc to wrought AlndashMgalloys181 In this work it was found that the Al3Scdispersoids were very effective in preventing recrystalli-sation up to temperatures of approx 400ndash450uC Athigher temperatures the dispersoids coarsen consider-ably and the microstructure was partially recrystallised

It is established that the Zener-drag pZ that is imposedon an advancing grain boundary by randomly distrib-uted dispersoids can be expressed in the form

pZ~k f =r (3)

where k is a factor that includes the interface energybetween the dispersoids and the matrix f is the volumefraction and r is the mean radius of the dispersoids Thusthe Zener drag will decrease rapidly in the case where thedispersoids are coarsening

As mentioned in the section on lsquoInfluence of otherelements on precipitation of Al3Scrsquo above theAl3(Sc12xZrx) dispersoids in a ternary AlndashScndashZr alloycoarsen at a much slower rate than the Al3Sc dispersoidsin a binary AlndashSc alloy This effect was first reported inRef 123 (although also observed in Ref 182) andaccording to Ref 33 the same authors demonstratedsoon after that the denser dispersoid distributionachieved in an AlndashScndashZr alloy leads to superiorrecrystallisation resistance compared to a binary AlndashScalloy An example of the increased recrystallisationresistance by adding both Zr and Sc is shown in Fig 26

In isothermal sections of the ternary AlndashScndashZr phasediagram it is indicated that the solid solubility ofSczZr is somewhat higher than that of Sc alone54 Ithas also been demonstrated both by electrical con-ductivity measurements (Fig 27) and microstructuralobservations that the supersaturation of SczZr isgreater than that of only Sc or Zr in as cast Alndash15(SczZr) alloys183 This indicates that it should bepossible to increase the volume fraction of dispersoids inAlndashScndashZr compared to AlndashSc It is suggested162 that theincreased volume fraction that can be achieved byadding both Sc and Zr can be advantageous inconventional wrought Al-alloys

There are at least two different conditions underwhich Al3Sc or Al3(Sc12xZrx) dispersoids can form toprevent recrystallisation

1 Sc (or Sc and Zr) is in solid solution before thedeformation In the case of cold deformation and

25 Grain refinement as a function of Sc addition in pure

Al (redrawn from Ref 32) and AlndashZnndashMgndashZr (redrawn

from Ref 169) note that data points are plotted on

different ordinate axes

Roslashyset and Ryum Scandium in aluminium alloys

34 International Materials Reviews 2005 VOL 50 NO 1

subsequent annealing the Al3Sc or Al3(Sc12xZrx)dispersoids may nucleate and grow before the nucleationand growth of recrystallised grains takes placeDispersoids can form after a direct up-quench to theannealing temperature115143148184 during ramp-up tothe annealing temperature115 or by pre-annealing at anintermediate temperature129 In the case of hot deforma-tion the Al3Sc or Al3(Sc12xZrx) dispersoids maynucleate and grow during preheating of the materialand during the hot deformation itself184

2 The Al3Sc or Al3(Sc12xZrx) dispersoids are formedin the material before deformation184 Considering coldrolling and subsequent annealing the annealing tem-perature Tann may be either lower or higher than thetemperature Tdisp at which the dispersoids were formedIf TannTdisp only limited if any coarsening of thedispersoids is expected to take place and thus the Zenerdrag from the particles is expected to be practicallyconstant The driving force for recrystallisation how-ever is expected to decrease somewhat with theannealing time as a result of recovery processes Thusif recrystallisation does not occur within short annealingtimes the material is expected to remain unrecrystallisedfor infinite time at the annealing temperature IfTannTdisp there will be substantial coarsening of thedispersoids during annealing In order for the materialto remain unrecrystallised the decrease in driving forcefor recrystallisation owing to recovery has to be at leastas rapid as the decrease in Zener drag because of particlecoarsening

Experimental comparisons of the conditions abovepoint in the direction that the recrystallisation resistanceis poorest when Sc (or Sc and Zr) is in solid solutionbefore deformation and the deformed material is up-quenched to the annealing temperature148 or when Al3Scor Al3(Sc12xZrx) dispersoids are formed before defor-mation at TdispampTann184185 Excellent recrystallisationresistance is achieved if dispersoids are formed at anintermediate anneal of solutionised and deformedmaterial128 or if dispersoids are formed at TdispTann

before deformation148185ndash187 It seems that the decreasein Zener drag because of dispersoid coarsening in many

cases is slower than the decrease in driving force forrecrystallisation because of recovery processes Thusthere is an advantage in forming a high number densityof small dispersoids which for most practical casesmeans that they should be formed at TdispTann122

When an advancing high angle grain boundary iethe recrystallisation front is passing a coherent Al3Scdispersoid there are at least three possible grainboundarydispersoid interactions

1 The Al3Sc dispersoid retains its global orientationrelationship and thus loses its coherency with thesurrounding matrix

2 The Al3Sc dispersoid rotates as the grain boundarypasses either by diffusional processes at the dispersoidmatrix interface or by the grain boundary passingthrough the dispersoid and the Al3Sc dispersoidassumes the same crystallographic orientation as theAl matrix of the recrystallised grain

3 The Al3Sc dispersoid dissolves at the grainboundary and re-precipitates in the recrystallised grain

Which interactions that actually take place willprobably depend on the dispersoid size annealingtemperature and driving force for recrystallisation It isalso possible that alloy composition (other elementsthan Al) is of importance

It has been reported that large (Oslash about 100ndash150 nm)Al3Sc dispersoids in a deformed Alndash4 wt-Mgndash02 wt-Sc alloy annealed at 575uC lose the orientationrelationship with the matrix after being passed by therecrystallisation front148

A rotation of somewhat smaller Al3Sc dispersoids in arecrystallising binary Alndash025 wt-Sc alloy has beenreported115143 The rotation was reported to be accom-panied by substantial growth (from Oslash 30 nm to Oslash48 nm) as a result of enhanced Sc diffusion at the grainboundary Observations suggested that the grainboundaries were passing through the dispersoids andthus the Al3Sc dispersoids retained the orientationrelationship with the recrystallised Al matrix

Dissolution and re-precipitation of Al3Sc dispersoidshas been reported during recrystallisation of a 50 coldrolled Alndash02 wt-Sc alloy162 Large spherical partially

26 Fraction recrystallised structure in cold rolled sheets

of Alndash04 wt-Sc and Alndash04 wt-Scndash015 wt-Zr as a

function of annealing temperature redrawn from

Ref 183 27 Electrical conductivity in Alndash15(SczZr) alloys

redrawn from Ref 183

Roslashyset and Ryum Scandium in aluminium alloys

International Materials Reviews 2005 VOL 50 NO 1 35

coherent dispersoids were observed to dissolve at therecrystallisation front and re-precipitate as smallercoherent Al3Sc cuboids

Superplastic forming

It seems that the first publication on superplasticproperties of Sc-containing Al-alloys was a study of anAlndash35Cundash14Mgndash045Mnndash04(SczZr) alloy188

It was recognised that the superplastic properties are aresult of the stabilisation of the fine grain structure byAl3Sc dispersoids The Sc-containing Al alloys that havereceived most attention for their superplastic propertieshowever are those of the AlndashMgndashSc system which wasfirst published in a patent189 Here it was noted that anAlndash4 wt-Mgndash05 wt-Sc alloy had superior superplasticproperties compared to fine-grained 7475 (AlndashZnndashMgndashCu alloy) Binary Alndash05 wt-Sc and Alndash4 wt-Mgalloys did not behave superplastically The flow stress atthe hot forming temperature was found to be much (30ndash40) lower in the ternary alloy than that of the twobinary alloys

The superplastic properties of AlndashMgndashSc alloys havebeen explored by several research groups over the lastdecade190ndash196 It has frequently been found that thedeformation mechanism is dominated by grain bound-ary sliding190 However it has also been reported thatAlndashMgndashSc alloy may deform superplastically withoutnoticeable grain boundary sliding23 It is generallyrecognised that the grain boundary sliding mechanismis facilitated when the average grain size is very smalland grain boundaries are predominantly high-angleSuch a microstructure may be achieved by carefulthermomechanical processing of the starting mate-rial193194197198 It has however been shown that a finegrained structure with high angle boundaries maydevelop during superplastic forming of AlndashMgndashSc alloyseven if the starting microstructure is an entirely differentone for instance that of a cold rolled sheet192 It has alsobeen suggested that superplastic forming of as castmaterial may be possible189

One of the more efficient thermomechanical processesfor achieving an ultrafine grain structure with high anglegrain boundaries in Al-alloys is equal channel angularpressing (ECAP) A JapanesendashAmerican group ofscientists has published an impressive body of researchon improvements in superplastic properties in Al-alloys processed by ECAP over the last few years andseveral of the publications are from investigations onAlndashMgndashSc alloys170199ndash224 Maximum strains in excessof 2000 at a strain rate of 0033 s21 have beenachieved170201202217 which is an extraordinarily goodcombination of high strain and high strain rate for analuminium alloy

Superplastic properties of AlndashCundashMg(ndashMn)ndashSc(ndashZr)and AlndashMgndashSc(ndashZr) alloys have been mentionedNoticeable superplasticity in other Sc-containing Al-alloys has also been reported such as AlndashZnndashMg(ndashCu)ndashScndashZr169225ndash228 AlndashLindashSc229 AlndashMgndashLindashScndashZr229ndash234

AlndashLindashMgndashCundashScndashZr235236 and AlndashCundashLindashScndashZr233

Precipitation hardeningHardening by Al3Sc precipitates

It has been noted that when Al3Sc particles precipitate inthe temperature range 250ndash350uC they give a significanthardness increase in the alloy Some authors point out

that Sc is a more effective precipitation hardening elementper atomic fraction added than the elements that arecommonly used for precipitation hardening121130 (In onepaper29 it is claimed that only Au has a strongerstrengthening effect than Sc) However the amount ofSc that can be precipitated from supersaturated solidsolution is rather limited and thus the absolute values ofthe hardness increase from the precipitation hardening ismuch lower than what is normally associated withprecipitation hardened alloys Also the temperatureregime for age hardening by precipitation of Al3Sc issomewhere in between the temperature regimes for agehardening and solution heat treatments of commonprecipitation hardened alloys This makes a combinedprecipitation of Al3Sc and other strengthening precipi-tates unfeasible Thus precipitation strengthening byAl3Sc is most feasible in alloy systems that are non-heat-treatable The non-heat-treatable aluminium alloy sys-tems are according to the Aluminum Associationdesignations the 1xxx series (99 pure Al) the 3xxxseries (AlndashMn) and the 5xxx series (AlndashMg) The purposeof adding Sc to these alloys may be either to stabilise themicrostructure of wrought semiproducts (extrusionsrolled plates forgings etc) as discussed in the sectionon lsquoRecrystallisation resistancersquo above or to provideextra strength to the alloy through precipitation hard-ening In the latter case it is appropriate to considerwhether the Sc-containing alloy still should be classifiedas non-heat-treatable A heat treatment is applied thatbrings about a significant precipitation hardening On theother hand the hardness increase that is achieved throughthe heat treatment is lower than what is normallyassociated with heat-treatable alloy systems Hence eventhough it seems like a contradiction one chooses to keepusing the term lsquonon-heat-treatablersquo about these alloys

Table 7 gives an overview of some mechanicalproperties of Sc-containing non-heat-treatable alloysthat are reported in the literature Most of theexperimental work on Sc in 1xxx-types of alloys hasbeen done on binary AlndashSc alloys with much higherpurity than industrial alloys

Strengthening mechanisms

When the precipitates are larger than a critical size thestrengthening effect is due to the Orowan-mechanism iedislocations can only pass the precipitates by looping Inthis case the strengthening effect of the particles isapproximately inversely proportional to the mean parti-cle spacing When the precipitates can be sheared bydislocations there are a number of strengthening mechan-isms that apply It is proposed by Parker et al108 that thetwo major contributing mechanisms are coherency strainand anti-phase-boundary energy In a recent detailedstudy of strengthening mechanisms in binary AlndashSc alloysby Marquis and colleagues117118 the strengthening fromshear modulus mismatch between the matrix and theprecipitates is also accounted for A qualitatively goodmatch between theoretical strengthening and measuredvalues is achieved in this work both for deformation atroom temperature and at 300uC

Effect of Sc on precipitation strengthening in heat-treatablealloys

Following the AA designation system the traditionalheat-treatable Al-alloys are those that belong to the 2xxx

Roslashyset and Ryum Scandium in aluminium alloys

36 International Materials Reviews 2005 VOL 50 NO 1

series (AlndashCu) 6xxx series (AlndashMgndashSi) and 7xxx series(AlndashZnndashMg) AlndashLi alloys should also be mentionedSeveral investigations have been carried out in order toclarify the effects of Sc on the precipitation behaviour inthese alloy systems

AlndashCu alloys

The precipitation sequence in AlndashCu alloys is oftendescribed as follows

Supersaturated solid solutionRGP-zonesRh0Rh9Rh(Al2Cu)

The highest strength is normally achieved when the h0or h9 precipitates are predominant Typical precipitationheat treatment temperatures for AlndashCu alloys are in therange 160ndash190uC238 which is considerably lower thanthe typical precipitation temperature for Al3ScComparisons of the aging responses of AlndashCu and AlndashCundashSc alloys at 150 and 200uC indicate that there is nonoticeable effect of Sc on the precipitation kinetics ofh9153 It is observed that the h9 precipitates may nucleateon Al3Sc particles153 At 300uC it is observed that h9particles are somewhat smaller in AlndashCundashSc alloys thanin AlndashCu alloys156

AlndashMgndashSi alloys

The following precipitation sequence is commonlyreported for AlndashMgndashSi alloys

Supersaturated solid solutionRGP-zonesRb0Rb9Rb(Mg2Si)

For peak aged alloys the predominant precipitatetype is b0 for which the stoichiometric composition hasrecently been resolved to be Mg5Si6239 Temperatures inthe range 160ndash205uC are typically used for precipitationhardening of these alloys238 Adding both 03 wt-Scand 01 wt-Zr to an Alndash06 wt-Mgndash065 wt-Sialloy does not seem to alter the precipitation kineticsof b0 at 165uC However the hardness increase becauseof precipitation hardening appears to be smaller in theSczZr-containing alloy240 In another investigationadditions of 01 wt-Sc 015 wt-Sc 02 wt-Sc04 wt-Sc and 02 wt-Scz01 wt-Zr were made toan Alndash08 wt-Mgndash07 wt-Si alloy241 Here it wasalso observed that the precipitation kinetics of b0 wasseemingly independent of the Sc additions (Fig 28)TEM observations indicated that the b0 precipitateswere of comparable sizes in the investigated alloys andno interactions between Al3Sc and b0 were observed(Fig 29) In a third study242 where the effect of Sc onthe precipitation in an AlMgSindashSiC metal matrixcomposite was investigated there also does not seemto be any effect on the precipitation kinetics Howevercontrary to the findings of Ref 240 it is reported thatthe Sc addition leads to a higher hardness increase thanin the corresponding Sc free alloy

AlndashMgndashZn alloys

For these alloys the following precipitation sequence isoften ascribed

Table 7 Mechanical properties in non-heat-treatable Al-alloys with Sc

Reference Alloy wt- YS MPa UTS MPa Note

1xxx alloys171 000Sc 15 48 Cast material aged 288uC8 h

023Sc 159 185 Cast material aged 288uC8 h038Sc 199 220 Cast material aged 288uC8 h000Sc 14 49 Cold rolled material (89) aged 288uC8 h023Sc 198 208 Cold rolled material (89) aged 288uC8 h038Sc 240 264 Cold rolled material (89) aged 288uC8 h000Sc 8 34 Cold rolled material quenched from 649uC aged 288uC8 h023Sc 147 157 Cold rolled material quenched from 649uC aged 288uC8 h038Sc 193 199 Cold rolled material quenched from 649uC aged 288uC8 h

121 05Sc 160 ndash Forged material quenched from 635uC aged 250uC50 h23 05Sc 298 319 Hot rolled 288uC cold rolled 69ndash81 aged 288uC4 h112 01Sc 132 166 Hot z cold rolled material quenched from 630uC

aged 320uC133 h148 02Sc 138 ndash Cast material aged 300uC10 h compression test159 04Sc 196 ndash Cast material aged 300uC10 h compression test117 118 03Sc 209 ndash Cast material quenched from 648uC aged 300uC5 h

compression test3xxx alloys171 1Mn 015Sc 216 221 Cold rolled material (89) aged 288uC8 h

1Mn 05Sc 309 323 Cold rolled material (89) aged 288uC8 h186 05Mn 02Mg

026Sc 015Zr162 201 Extruded material solutionised 600uC aged 250uC

5xxx alloys171 1Mg 43 111 Cold rolled material (89) aged 288uC8 h

1Mg 03Sc 288 303 Cold rolled material (89) aged 288uC8 h53Mg 147 259 Cold rolled material (50) wintermediate anneals

at 343uC aged 288uC8 h53Mg 03Sc 368 401 Cold rolled material (50) wintermediate anneals

at 343uC aged 288uC8 h23 2Mg 05Sc 376 401 Hot rolled 288uC cold rolled 69ndash81 aged 288uC4 h

4Mg 05Sc 414 4606Mg 05Sc 433 503

237 4Mg 1Sc 420 525 Cold rolled material (83) aged 320uC1 h148 4Mg 02Sc 194 ndash Cast material aged 300uC10 h compression test

Tensile test data except where noted YS yield strength UTS ultimate tensile strength

Roslashyset and Ryum Scandium in aluminium alloys

International Materials Reviews 2005 VOL 50 NO 1 37

Supersaturated solid solutionRGP-zonesRg9Rg(Zn2Mg)

The maximum hardness is normally achieved whenthe g9 precipitates are predominant Common precipita-tion hardening temperatures are in the range 95ndash180uCand a two-step precipitation heat treatment within thistemperature regime is often used238 It has beenobserved in some investigations that Sc and SczZradditions to AlndashMgndashZn alloys slow down the precipita-tion of g9 somewhat243 Other investigations find thatthere is no effect of Sc on the precipitation behaviour ofg9244245 and yet others report that Sc additionssignificantly speed up the precipitation of g9246 In Ref247 it is found that an Sc addition leads to coarser g9precipitates and it is claimed that this gives an improvedductility of the alloy The strength-loss associated withlarger particle size is reported to be counterbalanced bystrengthening from Al3Sc precipitates

AlndashLi alloys

The precipitation sequence in binary AlndashLi alloys isapparently simple

Supersaturated solid solutionRd9Rd (AlLi)

where d9 is the metastable Al3Li phase which just likeAl3Sc has the L12 type of atomic arrangement Thetypical temperature regime for precipitation of d9 whichis the strengthening phase in this system is approx 150ndash200uC A comparison of the age hardening response ofan Alndash26 wt-Li and an Alndash24 wt-Lindash019 wt-Scalloy at 180uC248 and 200uC161 indicates that the onsetof d9 precipitation is not altered by the presence of ScThe hardness curves for the two alloys are practicallyidentical at 200uC whereas at 180uC the peak hardnesslevel is slightly higher in the AlndashLi than the AlndashLindashScalloy DSC measurements at constant heating ratesindicate that the addition of Sc to an AlndashLi alloysincreases the activation energy for d9 precipitation andmoves the exothermic peak associated with d9 precipita-tion to a higher temperature248 For specimens aged at

either 180uC or 200uC TEM observations reveal that thed9 precipitates are much smaller in the Sc containingalloy than in binary AlndashLi both in the peak agedcondition and in the overaged condition161248 Additionof Sc has also been observed to reduce the size of d9precipitates in other AlndashLi based alloys249ndash251 In an AlndashLindashCundashZr alloy an addition of Sc has been reported toslow down the homogeneous precipitation of d9252253 Ithas been claimed that Sc reduces the quench sensitivityand delays room temperature aging of AlndashLi basedalloys254ndash256

When present in the microstructure before the pre-cipitation of d9 the Al3Sc precipitates may act as effec-tive nucleation sites for d9 The resulting precipitates arespheres of d9 with a core of Al3Sc161249252ndash255257ndash261

Corrosion resistanceAn appreciable amount of data is available on the effectsof Sc on the corrosion behaviour of wrought Al-alloysSome of these effects are apparently derived from theeffects of Sc on the microstructure of the alloys It hasbeen reported that an addition of Sc increases thecorrosion potential (makes it less negative) in pureAl262ndash264 in AlndashZn alloys265266 AlndashMg alloys267 AlndashZnndashMgndashCu alloys264268 AlndashCundashMgndashMn alloys264 andin AlndashCundashLindashMgndashAg alloys264 Even though Sc alsohas been reported to decrease the corrosion potential in

28 Age hardening response at 175uC for Alndash08 wt-Mgndash

07 wt-Si alloy (Base) with additions of 02 wt-Sc

04 wt-Sc and 02 wt-Scz01 wt-Zr from Ref 241

29 TEM images of a b0 precipitates in Alndash08 wt-Mgndash

07 wt-Si alloy and b b0 and Al3(Sc1ndashxZrx) in a similar

alloy with addition of 02 wt-Scz01 wt-Zr from

Ref 241

Roslashyset and Ryum Scandium in aluminium alloys

38 International Materials Reviews 2005 VOL 50 NO 1

AlndashMg alloys269270 it seems that the general trend isthat adding Sc to an alloy makes it slightly more nobleThe change in corrosion potential is much morepronounced when Sc is added in amounts larger thanthe eutectic composition263 ie there is a considerablecontribution from primary or eutectic Al3Sc to theoverall potential It has also been demonstrated that thechange in corrosion potential caused by Sc can dependon the heat treatment applied to the alloy267268

Even though the corrosion potential is an essentialparameter in establishing the corrosion behaviour of analloy an increase in the corrosion potential does notnecessarily imply an improved self-corrosion resistanceHowever measurements of corrosion rates and passiva-tion current densities strongly suggest that the self-corrosion resistance in general is considerably improvedwhen Sc is added to wrought Al-alloys263264267 Someobserved variations in corrosion potential and passiva-tion current densities with Sc content in binary AlndashScalloys are plotted in Fig 30

Material failure in corrosive environments is often dueto localised corrosion attacks which may propagaterapidly even though the bulk material has a goodresistance against general corrosion It has been pointedout that hypereutectic additions of Sc may lead tomicrogalvanic corrosion beside primary Al3Sc parti-cles264 In AlndashMg alloys grain boundary precipitation ofAl8Mg5 can lead to localised corrosion attacks such asintergranular corrosion (IGC) exfoliation corrosion(EC) and stress corrosion cracking (SCC) In wroughtmaterial such precipitation may occur in the 60ndash180uCtemperature regime and heating in this temperaturerange is referred to as lsquosensitationrsquo An AlndashMgndashSc alloywas found to be immune against intergranular corrosionand have moderate susceptibility to exfoliation corro-sion after annealing at 350uC271 After sensitation heattreatments severe IGC and EC was observed but notquite as severe as in a corresponding alloy without ScAs for SCC the AlndashMgndashSc alloy was found to be highlyresistant271 In another study it was found that additionof 056 wt-Sc reduces the SCC susceptibility of an Alndash68 wt-Mg alloy in the as-rolled state and afterannealing at 250uC whereas in a sensitised specimenthe SCC susceptibility is somewhat increased by the Scaddition272 A third investigation found that Sc has nomeasurable detrimental effect on the SCC susceptibilityof sensitised Alndash5Mgndash015Zr alloy273 SCC is also a

severe problem in high strength AlndashZnndashMgndashCu alloys Ithas been shown that small Sc additions are effective inreducing the SCC sensitivity of these alloys244246268274

Use of Sc-containing Al alloysA systematic development of Sc-containing aluminiumalloys took place in the former USSR in the 1980s andthe interest for Sc as an alloying element in aluminiumalloys hit the western world approximately 10 yearslater Even though a number of improvements in Alalloys achieved by Sc addition have been demonstratedthe current uses of such alloys are very limited This isrelated to the very high price of scandium

In Russia some parts of military aircraft are made ofSc-containing AlndashLi alloys In the western world themain usage of Sc-containing alloys is for sportsequipment Ashurst Technology and Kaiser Aluminumdeveloped a Sc-containing 7xxx alloy for baseball andsoftball bats which was introduced to the Americanmarket in 1997 by Easton Alcoa soon followed with aSc-containing alloy for a competing brand of batsLouisville Slugger Since then several new and improvedSc-containing alloys for bats have been introduced tothe market The purpose of adding Sc is to increase theyield strength of the alloy allowing for a down-gaugingof the wall thickness which in turn gives a strongerlsquospring-rsquo or lsquotrampoline-rsquo effect when the ball hits thebat

Shortly after the introduction of the Sc containingbats Easton also launched Sc-containing 7xxx tubingfor bicycle frames Just as in the bats Sc increases theyield strength of the alloy allowing for down-gauging oftube wall thickness and a corresponding weight reduc-tion of the bicycle frame An Italian manufacturer ofbicycle tubing Dedacciai also delivers tubes in a Sc-containing 7xxx alloy

Other sports equipment made from Sc-containingaluminium alloys includes lacrosse sticks and tent polesSmith and Wesson has also introduced a series ofhandguns where the frame is made from a Sc-containingAl alloy

A common factor for the items mentioned above isthat the material cost is only a minor part of the totalmanufacturing cost of the end product and also thatthese products are aimed at a group of customers thathave a certain awareness of new materials Both baseballbats and bicycle frames have been marketed aslsquoscandium alloyrsquo even though the Sc content is muchlower than 1

Currently AlndashSc master alloys for the production ofSc-containing Al alloys are available at a price thatcorresponds to US$ 2000 per kg of Sc This means that ifone wants to add 02 wt-Sc to an alloy which is afairly common content one also increases the price ofthe alloy by US$ 4 per kg alloy Depending on the alloytype Sc is added to this represents a tripling orquadrupling of the price of the alloy There are notmany existing products where such an increase inmaterial cost can be justified In order to see awidespread use of Sc in high-volume products the Scprice has to come down considerably Actually the priceof adding Sc to Al alloys has gone down by a factor 3ndash10over the last 10ndash15 years and substantial price reduc-tions are also expected in the future

30 Observed variations in corrosion potential and passi-

vation current densities with Sc content in binary Alndash

Sc alloys based on data from Ref 263

Roslashyset and Ryum Scandium in aluminium alloys

International Materials Reviews 2005 VOL 50 NO 1 39

The current production of AlndashSc master alloys isbased upon and will continue to be based upon for theforeseeable future the reduction of Sc2O3 or other Sccompounds directly in molten aluminium It is notnecessary as many tend to believe to take the route viametallic Sc Thus the price of AlndashSc master alloy isgoverned by the price of Sc2O3 or other Sc compoundsin question and not by the price of metallic scandiumThe Sc2O3 which is the main source for todayrsquos AlndashScmaster alloy production comes from stockpiles in theformer USSR These stockpiles will be exhausted withina few years and new reliable sources of Sc2O3 or otherSc compound production are sought It turns out thatthe most economically viable option that has beendisclosed so far is the processing of Red Mud from theBayer process of extracting alumina from bauxiteScandium is enriched in the Red Mud and is extractedfrom a Red Mud aqueous slurry by selective leachingsubsequent ion-exchange procedure and finally a liquidndashliquid extraction procedure It is not required to build aseparate lsquoSc factoryrsquo to do this but rather build an lsquoadd-onrsquo to existing Bayer process plants Such a processroute is expected to bring down the price of Sc2O3

considerably which in turn means that AlndashSc masteralloy price should drop accordingly Preliminary ana-lyses suggest a price of approx US$ 400 per kg Sc in themaster alloy which translates to an added cost of 80cent per kilo when 02 wt-Sc is added to an aluminiumalloy This is also a considerable increase in the materialcost but with such prices one should expect to see Sccontaining alloys in many more applications than whatis the case at the present time

Concluding remarksThe body of published investigations on Al-based alloyswith Sc addition provides a sound basis of knowledgefor metallurgists that want to look into the possibility ofenhancing the performance of a wrought Al-alloy byadding Sc to it Ternary AlndashScndashX phase diagrams areavailable for practically every technologically importantalloying element in Al The effect of a wide range ofternary alloying elements on the precipitation behaviourof Al3Sc is accounted for It has been shown that theAl3Sc phase can be effective as a grain refiner adispersoid former and a precipitate hardening agentand some of the underlying conditions for achieving thedesired Al3Sc formation have been outlined Addingsome Zr together with Sc has proven to be beneficial Itmay lead to effective grain refinement at a lower Sc levelbut the most prominent effect is the refinement indispersoid distribution that can be achieved An addi-tion of Sc has little if any effect on precipitation in the2xxx 6xxx and 7xxx alloy systems and some effects onthe precipitation in AlndashLi based alloys With respect tocorrosion behaviour adding Sc to an Al-alloy does ingeneral seem to make the alloy slightly more noble andto increase its self-corrosion resistance Scandium-containing Al alloys have very few uses at the presenttime as a result of the high price of scandium The priceof Sc is expected to decrease significantly in the futureand this should lead to the disclosure of moreapplications where it is economically feasible to takeadvantage of the improved properties of some Sc-containing aluminium alloys

References1 D R Lide lsquoCRC handbook of chemistry and physicsrsquo 71st edn

4ndash29 1990 Boston USA CRC Press

2 E M Savitsky V F Terehova I V Burov and O P Naumkin

Proc Fourth Conf on lsquoRare earth researchrsquo Phoenix Arizona

USA April 1964 409ndash420

3 E M Savitskii V F Terekhova I V Burov O P Naumkin and

I A Markova Inorg Mater 1965 1 1503ndash1512

4 O P Naumkin V T Terekhova and E M Savitskiy Russ

Metall 1965 (4) 128ndash136

5 W G Moffatt lsquoThe handbook of binary phase diagramsrsquo 1981

Schenectady NY USA General Electric Co

6 E A Brandes (ed) lsquoSmithells metals reference bookrsquo 6th edn

1983 London UK Butterworths

7 R P Elliott and F A Shunk Bull Alloy Phase Diagrams 1981

2 (2) 222ndash223

8 K A Gschneider Jr and F W Calderwood Bull Alloy Phase

Diagrams 1989 10 34ndash36

9 H Okamoto J Phase Equil 1991 12 612ndash613

10 J L Murray J Phase Equil 1998 19 380ndash384

11 M E Drits E S Kadaner T V Dobatkina and N I Turkina

Russ Metall 1973 (4) 152ndash154

12 S-I Fujikawa M Sugaya H Takei and K-I Hirano J Less-

Common Met 1979 63 87ndash97

13 N Blake and M A Hopkins J Mater Sci 1985 20 2861ndash2867

14 V I Kononenko and S V Golubev Russ Metall 1990 (2) 193ndash

195

15 T B Massalski J L Murray L H Bennett and H Baker (eds)

lsquoBinary alloy phase diagramsrsquo 1986 Metals Park OH USA

ASM

16 G Cacciamani P Riani G Borzone N Parodi A Saccone

R Ferro A Pisch and R Schmid-Fetzer Intermetallics 1999 7

101ndash108

17 H Okamoto J Phase Equil 2000 21 310

18 A F Norman P B Pragnell and R S McEwen Acta Mater

1998 46 5715ndash5732

19 I N Pyagai and A V Vakhobov Russ Metall 1990 (5) 50ndash52

20 C L Fu J Mater Res 1990 5 971ndash979

21 X Lu and Y Wang Calphad 2002 26 555ndash561

22 R R Sawtell and J W Morris Jr Proc lsquoDispersion strengthened

aluminium alloysrsquo Phoenix Arizona USA January 1988 409ndash

420

23 R R Sawtell and C L Jensen Metall Trans A 1990 21A 421ndash

430

24 L A Willey Unpublished research Alcoa 1970 Data points are

extracted from Ref 10

25 N I Turkina and V I Kuzmina Russ Metall 1976 (4) 179ndash

183

26 T Torma E Kovacs-Csetenyi I Vitanyi M Butova and

J Stepanov Proc 6th Int Symp on lsquoHigh purity materials in

science and technologyrsquo Akademie der Wissenschaften der DDR

Dresden Germany May 1985 388ndash389

27 A L Berezina V A Volkov B P Domashnikov and K V

Chuistov Metallofizika 1987 9 (5) 43ndash47

28 H-H Jo J Korean Inst Metals 1990 28 499ndash504

29 H-H Jo and S-I Fujikawa Mater Sci Eng 1993 A 171 151ndash

161

30 S Celotto and T J Bastow Philos Mag A 2000 80 1111ndash1125

31 J Roslashyset and N Ryum submitted to Mater Sci Eng

32 M E Drits L S Toropova Yu G Bykov F L Gushchina V I

Elagin and Yu A Filatov Russ Metall 1983 (1) 150ndash153

33 L S Toropova D G Eskin M L Kharakterova and T V

Dobatkina lsquoAdvanced aluminum alloys containing scandium

structure and propertiesrsquo 1998 Amsterdam The Netherlands

Gordon and Breach Science Publishers

34 V V Cherkasov P P Pobezhimov L P Nefedova E V Belov

and G M Kuznetsov Met Sci Heat Treat 1996 (6) 268ndash270

35 Kh O Odinaev I N Ganiev V V Kinzhibalo and B Ya

Kotur Dokl Akad Nauk Tadzh SSR 1989 32 37ndash38

36 Kh O Odinaev I N Ganiev and A V Vakhobov Russ Metall

1991 (4) 200ndash203

37 J Grobner R Schmid-Fetzer A Pisch G Cacciamani P Riani

N Parodi G Borzone A Saccone and R Ferro Z Metallkd

1999 90 872ndash880

38 E A Marquis and D N Seidman Microsc Microanal 2002 8

(Suppl 2) 1100CDndash1101CD

39 A Pisch J Grobner and R Schmid-Fetzer Mater Sci Eng A

2000 A 289 123ndash129

Roslashyset and Ryum Scandium in aluminium alloys

40 International Materials Reviews 2005 VOL 50 NO 1

40 C Xia F Zeng and Y Gu Trans Nonferrous Met Soc China

2003 13 1124ndash1127

41 M Yu Teslyuk and V S Protasov Sov Phys Crystallogr 1966

10 470ndash471

42 M L Kharakterova and T V Dobatkina Russ Metall 1988

(6) 175ndash178

43 M L Kharakterova Russ Metall 1991 (4) 195ndash199

44 L S Toropova M L Kharakterova and D G Eskin Russ

Metall 1992 (3) 194ndash199

45 P Riani L Arrighi R Marazza D Mazzone G Zanicchi and

R Ferro J Phase Equil Diff 2004 25 22ndash52

46 A T Tyvanchuk T I Yanson B Ya Kotur O S Zarechnyuk

and M L Kharakterova Russ Metall 1988 (4) 190ndash192

47 L L Rokhlin T V Dobatkina and M L Kharakterova Powder

Metall Met Ceram 1997 36

48 A Z Ikromov I N Ganiev and V V Kinzhibalo Dokl Akad

Nauk Tadzh SSR 1990 (6) 391ndash392

49 I N Ganiev A Z Ikromov and V G Khudoiberdiev Russ

Metall 1995 (3) 125ndash127

50 I N Fridlyander L L Rokhlin T V Dobatkina and N I

Nikitina Met Sci Heat Treat 1993 (10) 567ndash571

51 I N Fridlyander L L Rokhlin T V Dobatkina V V

Kinzhibalo and A T Tyvanchuk Russ Metall 1998 (1) 161ndash

166

52 R A Emigh E L Bradley and J W Morris Jr in lsquoLight-weight

alloys for aerospace applications IIrsquo (ed E W Lee and N J

Kim) 27ndash43 1991 TMS

53 L S Toropova A N Kamardinkin V V Kindzhibalo and A T

Tyvanchuk Phys Met Metall 1990 70 (6) 106ndash110

54 A N Kamardinkin T V Dobatkina and T D Rostova Russ

Metall 1991 (4) 216ndash218

55 L S Torodskaya T V Dobatkina and A N Kamardinkin

Russ Metall 1992 (5) 128ndash131

56 E M Sokolovskaya E F Kazakova E I Poddyakova and A

A Ezhov Met Sci Heat Treat 1997 (5) 211ndash213

57 Y Harada and D C Dunand Mater Sci Eng 2002 A 329ndash331

686ndash695

58 N E Drits L S Toropova and F L Gushchina Russ Metall

1984 (4) 229ndash232

59 E M Sokolovskaya E F Kazakova V A Alikhanov and E V

Zhuravleva Moscow Univ Chem Bull 1997 52 (5) 70ndash72

60 E M Sokolovskaya E F Kazakova and E I Poddyakova Met

Sci Heat Treat 1989 (11) 837ndash839

61 G M Cheldieva E F Kazakova E M Sokolovskaya and N I

Kaloev Russ Metall 1990 (6) 87ndash90

62 E M Sokolovskaya E F Kazakova and O D-S Kendivan

Russ Metall 1998 (4) 135ndash137

63 N G Bukhanko E F Kazakova and E M Sokolovskaya Russ

Metall 2001 (4) 425ndash431

64 E D Trubnyakova O I Bodak I N Ganiev and A V

Vakhobov Russ Metall 1987 (3) 219ndash222

65 I N Fridlyander and L V Molchanova Russ Metall 2003 (5)

476ndash480

66 R A Altynbaev S Kh Khairidinov and A V Vakhobov Russ

Metall 1987 (4) 194ndash196

67 J C Schuster and J Bauer J Less-Common Met 1985 109

345ndash350

68 L L Rokhlin A S Fridman T V Dobatkina and D G Eskin

Russ Metall 1991 (6) 146ndash148

69 A S Fridman T V Dobatkina and E V Muratova Russ

Metall 1992 (1) 207ndash209

70 C Xia F Zeng and Y Gu Trans Nonferrous Met Soc China

2003 13 546ndash552

71 F Zeng C Xia and Y Gu J Alloys Comp 2004 363 175ndash181

72 L L Rokhlin T V Dobatkina N R Bochvar and E V Lysova

J Alloys Comp 2004 367 10ndash16

73 T V Dobatkina A S Fridman and E V Muratova Russ

Metall 1992 (5) 125ndash127

74 I N Fridlyander L L Rokhlin N R Bochvar E V Lysova

and O V Boteva Russ Metall 2001 (6) 661ndash666

75 V N Rechkin L K Lamikhov and T I Samsonova Sov Phys

Crystallogr 1964 9 325ndash327

76 I I Zalutskii and P I Kripyakevich Sov Phys Crystallogr

1967 12 341ndash343

77 T J Bastow C T Forwood M A Gibson and M E Smith

Phys Rev B 1998 58 2988ndash2997

78 K Fukunaga M Kolbe K Yamada and Y Miura Mater Sci

Eng 1997 A 234ndash236 594ndash597

79 E P George J A Horton W D Porter and J H Schneibel

J Mater Res 1990 5 1639ndash1648

80 E P George D P Pope C L Fu and J H Schneibel ISIJ Int

1991 31 1063ndash1075

81 Y Harada and D C Dunand Acta Mater 2000 48 3477ndash3487

82 J H Schneibel and E P George Scripta Metall Mater 1990 24

1069ndash1074

83 J H Schneibel and P M Hazzledine Mater Res Soc Symp

Proc 1991 213 323ndash328

84 J H Schneibel and P M Hazzledine J Mater Res 1992 7

868ndash875

85 C J Sparks E D Specht G E Ice P Zschack and J Schneibel

Mater Res Soc Symp Proc 1991 213 363ndash368

86 J Tarnacki and Y-W Kim Scripta Metall Mater 1989 23

1063ndash1068

87 M Asta V Ozolins and C Woodward JOM 2001 53 (9) 16ndash

19

88 M E Drits L S Toropova F L Gushchina and S G Fedotov

Sov Non-Ferrous Met Res 1984 12 83ndash85

89 Y Harada and D C Dunand Scripta Mater 2003 48 219ndash222

90 C Woodward M Asta G Kresse and J Hafner Phys Rev B

2001 63 094103-1-6

91 J-H Xu and A J Freeman Phys Rev B 1990 41 12553ndash12561

92 M F Bartholomeusz and J A Wert Acta Metall Mater 1992

40 673ndash682

93 G Bester and M Fahnle J Phys Condens Matter 2001 13

11551ndash11565

94 C L Fu and M H Yoo Proc lsquoOrdered intermetallics ndash physical

metallurgy and mechanical behaviorrsquo Irsee Germany June 1991

155ndash164

95 K Fukunaga T Shouji and Y Miura Mater Sci Eng 1997 A

239ndash240 202ndash205

96 D P Pope Proc lsquoOrdered intermetallics ndash physical metallurgy

and mechanical behaviorrsquo Irsee Germany June 1991 143ndash153

97 J-S Wang Acta Mater 1998 46 2663ndash2674

98 M H Yoo and C L Fu Mater Sci Eng 1992 A 153 470ndash478

99 R W Hyland Jr and R C Stiffler Scripta Metall Mater 1991

25 473ndash477

100 I G Brodova I V Polents O A Korzhavina P S Popelrsquo I P

Korshunov and V O Esin Melts 1992 4 392ndash397

101 I G Brodova O A Chikova I V Polents P S Popelrsquo and V O

Esin Casting Processes 1992 1 (2) 158ndash160

102 I G Brodova D V Bashlikov and I V Polents Mater Sci

Forum 1998 269ndash272 589ndash594

103 K B Hyde A F Norman and P B Pragnell Mater Sci Forum

2000 331ndash337 1013ndash1018

104 K B Hyde A F Norman and P B Pragnell Acta Mater 2001

49 1327ndash1337

105 J Roslashyset and N Ryum Proc 6th Int Conf on lsquoAluminum

alloysrsquo Toyohashi Japan July 1998 793ndash798

106 V I Elagin V V Zakharov and T D Rostova Met Sci Heat

Treat 1993 (6) 317ndash319

107 R W Hyland Jr Metall Trans A 1992 23A 1947ndash1955

108 B A Parker Z F Zhou and P Nolle J Mater Sci 1995 30

452ndash458

109 C L Rohrer M D Asta S M Foiles and R W Hyland Jr

Mater Res Soc Symp Proc 1996 398 477ndash482

110 G M Novotny and A J Ardell Mater Sci Eng 2001 A 318

144ndash154

111 J D Robson M J Jones and P B Pragnell Acta Mater 2003

51 1453ndash1468

112 C Tan Z Zheng and B Wang Proc 3rd Int Conf on

lsquoAluminium alloysrsquo Vol I NTH Trondheim Norway June

1992 290ndash294

113 M Nakayama A Furuta and Y Miura Mater Trans JIM

1997 38 852ndash857

114 E A Marquis and D N Seidman Acta Mater 2001 49 1909ndash

1919

115 M J Jones and F J Humphreys Acta Mater 2003 51 2149ndash

2159

116 E A Marquis D N Seidman and D C Dunand in lsquoCreep

deformation fundamentals and applicationsrsquo (ed R S Mishra

J C Earthman and S V Raj) 299ndash308 2002 TMS

117 D N Seidman E A Marquis and D C Dunand Acta Mater

2002 50 4021ndash4035

118 E A Marquis D N Seidman and D C Dunand Acta Mater

2003 51 285ndash287

119 M E Drits L S Toropova U G Bikov and G K Anastaseva

Proc lsquoDiffusion in metals and alloysrsquo Tihany Hungary Augustndash

September 1982 616ndash623

120 V I Elagin V V Zakharov and T D Rostova Met Sci Heat

Treat 1983 (7) 546ndash549

Roslashyset and Ryum Scandium in aluminium alloys

International Materials Reviews 2005 VOL 50 NO 1 41

121 M Ye Drits L B Ber Yu G Bykov L S Toropova and G K

Anastaseva Phys Met Metall 1984 57 (6) 118ndash126

122 M E Drits L S Toropova and Yu G Bykov Sov Non-Ferrous

Met Res 1985 13 309ndash314

123 V I Yelagin V V Zakharov S G Pavlenko and T D Rostova

Phys Met Metall 1985 60 (1) 88ndash92

124 N Sano Y Hasegawa K Hono H Jo K Hirano H W

Pickering and T Sakurai Journal de Physique 1987 48 C6 337ndash

342

125 N Sano H-H Jo K-I Hirano and T Sakurai J Jpn Inst

Metals 1989 39 444ndash450

126 N Sano H Jo K Hirano and T Sakurai Proc Second Int

Conf on lsquoAluminium alloysrsquo Beijing China October 1990 549ndash

554

127 Y Miura M Nakayama and A Furuta Proc lsquoAspects of high

temperature deformation and fracture in crystalline materialsrsquo

Nagoya Japan July 1993 255ndash262

128 Y W Riddle and T H Sanders Jr Mater Sci Forum 2000

331ndash337 939ndash944

129 Y W Riddle M McIntosh and T H Sanders Jr in lsquoLightweight

alloys for aerospace application VIrsquo (ed K Jata E W Lee

W Frazier and N J Kim) 25ndash39 2001 TMS

130 M E Drits J Dutkiewicz L S Toropova and J Salawa Crystal

Res Technol 1984 19 1325ndash1330

131 Y W Riddle MSc thesis Georgia Tech GA USA 1998

132 T J Bastow and S Celotto Mater Sci Eng 2003 C 23 757ndash

762

133 M C Carroll M J Mills G S Daehn P I Gouma M F

Savage and B R Dunbar in lsquoAutomotive Alloys 1999rsquo (ed

S Das) 239ndash246 2000 TMS

134 E Clouet M Nastar and C Sigli Phys Rev B 2004 69 064109-

1-14

135 V V Zakharov Met Sci Heat Treat 1997 (2) 61ndash66

136 J W Christian lsquoThe theory of transformation in metals and

alloysrsquo 2nd edn 1975 Pergamon Press Ltd

137 A L Berezina V A Volkov B P Domashnikov S V Ivanov

and K V Chuistov Phys Metals 1990 10 296ndash304

138 S-I Fujikawa and S Sakauchi Proc 6th Int Conf on

lsquoAluminum alloysrsquo Toyohashi Japan July 1998 805ndash810

139 Y S Touloukian R K Kirby R E Taylor and P D Desai

(eds) lsquoThermal expansion metallic elements and alloysrsquo 1975

New York Plenum

140 J Roslashyset and N Ryum submitted to Scripta Mater

141 R O Simmons and R W Balluffi Phys Rev 1960 117 52ndash61

142 M Ocko E Babic R Krsmik E Girt and B Leontic J Phys F

Metals Phys 1976 6 703ndash707

143 M J Jones and F J Humphreys Proc First Joint Int Conf on

lsquoRecrystallization and grain growthrsquo Aachen Germany August

2001 Springer Verlag 1287ndash1292

144 S Iwamura M Nakayama and Y Miura Mater Sci Forum

2002 396ndash402 1151ndash1156

145 S Iwamura and Y Miura Acta Mater 2004 52 591ndash600

146 M Asta S M Foiles and A A Quong Phys Rev B 1998 57

11265ndash11275

147 R W Hyland Jr M Asta S M Foiles and C L Rohrer Acta

Mater 1998 46 3667ndash3678

148 J Roslashyset and N Ryum Proc 4th Int Conf on lsquoAluminium

alloysrsquo Vol I Atlanta GA USA September 1994 194ndash201

149 M E Drits L S Toropova G K Anastaseva and G L

Nagornichnykh Russ Metall 1984 (3) 192ndash195

150 E A Marquis D N Seidman and D C Dunand Acta Mater

2003 51 4751ndash4760

151 M E Drits L S Toropova and Yu G Bykov Met Sci Heat

Treat 1983 (7) 550ndash554

152 V V Zakharov and T D Rostova Met Sci Heat Treat 1995

(2) 65ndash69

153 M Nakayama and Y Miura Proc 4th Int Conf on lsquoAluminium

alloysrsquo Vol I Atlanta GA USA September 1994 538ndash545

154 M Nakayama and Y Miura J Jpn Inst Light Metals 1996 46

275ndash279

155 M Nakayama T Okuyama and Y Miura Mater Sci Forum

2000 331ndash337 927ndash932

156 M Nakayama T Okuyama and Y Miura Proc 6th Int Conf

on lsquoAluminum alloysrsquo Toyohashi Japan July 1998 517ndash522

157 M L Kharakterova D G Eskin and L S Toropova Acta

Metall Mater 1994 42 2285ndash2290

158 V I Elagin V V Zakharov and T D Rostova Met Sci Heat

Treat 1992 (1) 37ndash45

159 H Wiik Siv Ing thesis NTH Institute of Metallurgy

Trondheim Norway 1995

160 J Roslashyset H Hovland and N Ryum Mater Sci Forum 2002

396ndash402 619ndash624

161 Y Miura K Horikawa K Yamada and M Nakayama Proc

4th Int Conf on lsquoAluminium alloysrsquo Vol II Atlanta GA USA

September 1994 161ndash168

162 Y W Riddle PhD thesis Georgia Tech GA USA 2000

163 B Forbord W Lefebvre F Danoix H Hallem and

K Marthinsen Scripta Mater 2004 51 333ndash337

164 J D Robson Acta Mater 2004 52 1409ndash1421

165 C B Fuller J L Murray and D N Seidman submitted to Acta

Mater 2004

166 M G Mousavi C E Cross and Oslash Grong Sci Technol Weld

Joining 1999 4 381ndash388

167 J S Vetrano S M Bruemmer L M Pawlowski and I M

Robertson Mater Sci Eng 1997 A 238 101ndash107

168 Y W Riddle and T H Sanders Jr Mater Sci Forum 2000

331ndash337 799ndash803

169 G M Khan A O Nikiforov V V Zakharov and I I Novikov

Tsvetnye Metally 1993 34 (11) 43ndash45

170 Z Horita M Furukawa M Nemoto A J Barnes and T G

Langdon Acta Mater 2000 48 3633ndash3640

171 L A Willey US Patent 3 619 181 9 November 1971

172 L K Lamikhov and G V Samsonov Tsvetnye Metally 1964 5

(8) 77ndash80

173 A L Berezina K V Chuistov N I Kolobnev L B

Khokhlatova and T A Monastyrskaya Mater Sci Forum

2002 396ndash402 741ndash746

174 F A Fasoyinu J Thomson D Cousineau T Castles and M

Sahoo Proc 6th Int AFS Conf on lsquoMolten aluminum

processingrsquo Orlando FL USA November 2001

175 Z Yin Q Pan Y Zhang and F Jiang Mater Sci Eng 2000

A 280 151ndash155

176 I I Novikov and O E Grushko Mater Sci Technol 1995 11

926ndash932

177 D Cousineau M Sahoo P D Newcombe T Castles and F A

Fasoyinu Proc lsquoAFS 105th casting congressrsquo Dallas TX USA

AprilndashMay 2001 157ndash184

178 C E Cross and Oslash Grong Proc 6th Int Conf on lsquoAluminum

alloysrsquo Toyohashi Japan July 1998 1441ndash1446

179 F A Costello J D Robson and P B Prangnell Mater Sci

Forum 2002 396ndash402 757ndash762

180 K B Hyde A F Norman and P B Prangnell Mater Sci

Forum 2002 396ndash402 39ndash44

181 M E Drits S G Pavlenko L S Toropova Yu G Bukov and

L B Ber Sov Phys Dokl 1981 26 (3) 344ndash346

182 A M Drits and B A Kopeliovich Russ Metall 1985 (4) 147ndash

151

183 V G Davydov V I Elagin V V Zakharov and T D Rostova

Met Sci Heat Treat 1996 (8) 347ndash352

184 M E Drits L S Toropova Yu G Bykov L B Ber and S G

Pavlenko Russ Metall 1982 (1) 148ndash152

185 T D Rostova V G Davydov V I Yelagin and V V Zakharov

Mater Sci Forum 2000 331ndash337 793ndash798

186 Y W Riddle H Hallem and N Ryum Mater Sci Forum 2002

396ndash402 563ndash568

187 J Roslashyset and Y W Riddle Proc 9th Int Conf on lsquoAluminium

alloysrsquo Brisbane Australia August 2004 1210ndash1215

188 A M Diskin V K Portnoi A M Drits and A A Alalykin Sov

Non-Ferrous Met Res 1986 14 499ndash500

189 R R Sawtell P E Bretz and C L Jensen US Patent 4 689 090

25 August 1987

190 G A Salishchev Yu B Timoshenko and R A Saitova Proc

Second Int Conf on lsquoAluminium alloysrsquo Beijing China October

1990 413ndash415

191 T G Nieh R Kaibyshev L M Hsiung N Nguyen and

J Wadsworth Scripta Mater 1997 36 1011ndash1016

192 T G Nieh L M Hsiung J Wadsworth and R Kaibyshev Acta

Mater 1998 46 2789ndash2800

193 J S Vetrano C H Henager Jr M T Smith and S M

Bruemmer in lsquoHot deformation of aluminum alloys IIrsquo (ed T R

Bieler L A Lalli and S R MacEwen) 407ndash418 1998 TMS

194 J S Vetrano C H Henager Jr S M Bruemmer Y Ge and

C H Hamilton in lsquoSuperplasticity and Superplastic Forming

1998rsquo (ed A K Gosh and T R Bieler) 89ndash97 1998 TMS

195 V Y Gertsman J S Vetrano C H Henager Jr and S M

Bruemmer Proc First Joint Int Conf on lsquoRecrystallization and

grain growthrsquo Aachen Germany August 2001 Springer Verlag

2001 837ndash842

196 Y Xiao C Gao H Ma and S Tian Trans Nonferrous Met Soc

China 2001 11 235ndash238

Roslashyset and Ryum Scandium in aluminium alloys

42 International Materials Reviews 2005 VOL 50 NO 1

197 A Gholinia F J Humphreys and P B Prangnell Acta Mater

2002 50 4461ndash4476

198 A Gholinia F J Humphreys and P B Prangnell Mater Sci

Forum 2002 408ndash412 1519ndash1524

199 S Komura P B Berbon M Furukawa Z Horita M Nemoto

and T G Langdon Scripta Mater 1998 38 1851ndash1856

200 S Komura P B Berbon A Utsunomiya M Furukawa

Z Horita M Nemoto and T G Langdon in lsquoHot deformation

of aluminum alloys IIrsquo (ed T R Bieler L A Lalli and S R

MacEwen) 125ndash138 1998 TMS

201 S Komura Z Horita M Furukawa M Nemoto and T G

Langdon J Mater Res 2000 15 2571ndash2576

202 S Komura M Furukawa Z Horita M Nemoto and T G

Langdon Mater Sci Eng 2001 A 297 111ndash118

203 S Komura Z Horita M Furukawa M Nemoto and T G

Langdon Metall Mater Trans A 2001 32A 707ndash716

204 Z Horita M Furukawa K Oh-ishi M Nemoto and T G

Langdon Proc Fourth Int Conf on lsquoRecrystallization and

related phenomenarsquo (ed T Sakai and H G Suzuki) 1999 The

Japan Institute of Metals 301ndash308

205 Z Horita S Komura P B Berbon A Utsunomiya

M Furukawa M Nemoto and T G Langdon Mater Sci

Forum 1999 304ndash306 91ndash96

206 Z Horita S Lee S Ota K Neishi and T G Langdon Mater

Sci Forum 2001 357ndash359 471ndash476

207 Z Horita T Fujinami K Sato S B Kang H W Kim and T G

Langdon in Proc James T Staley Honorary Symposium on

Aluminum Alloys lsquoAdvances in the metallurgy of aluminum

alloysrsquo (ed M Tiryakioglu) 271ndash275 2001 ASM

208 P B Berbon S Komura A Utsunomiya Z Horita

M Furukawa M Nemoto and T G Langdon Mater Trans

JIM 1999 40 772ndash778

209 M Nemoto Z Horita M Furukawa and T G Langdon Mater

Sci Forum 1999 304ndash306 59ndash66

210 M Furukawa Z Horita M Nemeto and T G Langdon Proc

lsquoLight Metals 1999rsquo Quebec City PQ Canada August 1999 583ndash

592

211 M Furukawa K Oh-ishi S Komura A Yamashita Z Horita

M Nemeto and T G Langdon Mater Sci Forum 1999 304ndash

306 97ndash102

212 M Furukawa A Utsunomiya K Matsubara Z Horita and

T G Langdon Acta Mater 2001 49 3829ndash3838

213 M Furukawa A Utsunomiya S Komura Z Horita M Nemoto

and T G Langdon Mater Sci Forum 2001 357ndash359 431ndash436

214 M Furukawa Z Horita and T G Langdon in Proc James T

Staley Honorary Symposium on Aluminum Alloys lsquoAdvances in

the metallurgy of aluminum alloysrsquo (ed M Tiryakioglu) 47ndash56

2001 ASM

215 M Furukawa Z Horita M Nemoto and T G Langdon Mater

Sci Eng 2002 A 324 82ndash89

216 M Furukawa Z Horita and T G Langdon in lsquoUltrafine grained

materials IIrsquo (ed Y T Zhu T G Langdon R S Mishra S L

Semiatin M J Saran and T C Lowe) 459ndash468 2002 TMS

217 T G Langdon M Furukawa Z Horita and M Nemoto Proc

NATO Advanced Research Workshop on lsquoInvestigations and

applications of severe plastic deformationrsquo Moscow August

1999 NATO Science Series Series 3 High Technology vol 80

Kluwer Academic Publishers The Netherlands 2000 149ndash154

218 S Lee H Akamatsu A Utsunomiya K Neishi M Furukawa

Z Horita and T G Langdon Proc Thermec 2000 Las Vegas

USA December 2000

219 S Lee A Utsunomiya H Akamatsu K Neishi M Furukawa

Z Horita and T G Langdon Acta Mater 2002 50 553ndash564

220 A Yamashita D Yamaguchi Z Horita and T G Langdon

Mater Sci Eng 2000 A 287 100ndash106

221 K Oh-ishi Z Horita D J Smith and T G Langdon J Mater

Res 2001 16 583ndash589

222 H Akamatsu T Fujinami Z Horita and T G Langdon Scripta

Mater 2001 44 759ndash764

223 S Ota H Akamatsu K Neishi M Furukawa Z Horita and

T G Langdon Mater Trans 2002 43 2364ndash2369

224 K Furuno H Akamatsu K Oh-ishi M Furukawa Z Horita

and T G Langdon Acta Mater 2004 52 2497ndash2507

225 I N Fridlyander O G Senatorova N A Ryazanova and A O

Nikiforov Mater Sci Forum 1994 170ndash172 345ndash349

226 J N Fridlyander and O G Senatorova Mater Sci Forum 1996

217ndash222 1813ndash1818

227 J Liu and D J Chakrabarti Acta Mater 1996 44 4647ndash4661

228 O G Senatorova A N Uksusnikov J N Fridlyander

J Koshorst R R Romanova N A Ryazanova A Galliot

and V V Cherkassov Proc 6th Int Conf on lsquoAluminum alloysrsquo

July 1998 Toyohashi Japan 589ndash593

229 R A Emigh E L Bradley and J W Morris Jr in

lsquoSuperplasticity in aerospace IIrsquo (ed T R McNelley and H C

Heikkenen) 303ndash315 1990 TMS

230 E L Bradley III R A Emigh and J W Morris Jr Scripta

Metall Mater 1991 25 717ndash721

231 N I Kolobnev L B Khokhlatova V D Makarov E Yu

Semenova and V V Redchits Proc Sixth Int Aluminiumndash

Lithium Conference Garmisch-Partenkirchen Germany October

1991 1053ndash1056

232 N K Tsenev R Z Valiev O V Obraztsov and I N Fridlander

Proc Sixth Int AluminiumndashLithium Conference Garmisch-

Partenkirchen Germany October 1991 1125ndash1132

233 A M Shammazov N K Tsenev R Z Valiev M M

Myshlyaev M M Bikbulatov and S P Lebedich Phys Met

Metall 2000 89 (3) 314ndash318

234 F Musin R Kaibyshev Y Motohashi T Sakuma and G Itoh

Mater Trans A 2002 43A 2370ndash2377

235 M Shagiev Y Motohashi F Musin R Kaibyshev and G Itoh

Mater Trans A 2003 44A 1694ndash1697

236 M Shagiev Y Motohashi F Musin R Kaibyshev and G Itoh

Mater Trans A 2003 44A 1698ndash1701

237 B A Parker and Z F Zhou Proc 3rd Int Conf on lsquoAluminium

alloysrsquo Vol I NTH Trondheim Norway June 1992 363ndash367

238 J R Davies lsquoASM specialty handbook aluminum and aluminum

alloysrsquo 1993 Materials Park OH USA ASM

239 S J Andersen H W Zandbergen J Jansen C Traeholt

U Tundal and O Reiso Acta Mater 1998 46 3283ndash3298

240 M L Kharakterova D G Eskin and L L Rokhlin Russ

Metall 1997 (1) 104ndash109

241 J Roslashyset Dr Ing thesis NTNU Trondheim Norway 2002

242 P P Chattopadhyay S Datta and M K Banerjee Mater Sci

Eng 2002 A 333 67ndash71

243 L I Kaigorodova E I Selnikhina E A Tkachenko and O G

Senatorova Phys Met Metall 1996 81 513ndash519

244 Y-L Wu F H Froes C Li and A Alvarez Metall Mater

Trans A 1999 30A 1017ndash1024

245 Z Yin L Yang Q Pan and F Jiang Trans Nonferrous Met

Soc China 2001 11 822ndash825

246 V I Elagin V V Zakharov and T D Rostova Met Sci Heat

Treat 1994 36 (7) 375ndash380

247 Y V Milman A I Sirko D V Lotsko O N Senkov and D B

Miracle Mater Sci Forum 2002 396ndash402 1217ndash1222

248 C-H Joh K Yamada and Y Miura Mater Trans JIM 1999

40 439ndash442

249 X J Jiang Q H Gui Y Y Li L M Ma G J Liang and C X

Shi Scr Metall Mater 1993 29 211ndash216

250 X J Jiang Y Y Li W Deng L Y Xiong W M Wu Y J Gao

and C X Shi Adv Cryogenic Eng (Mater) 1994 40 1369ndash

1376

251 C-H Joh T Katsube K Yamada and Y Miura Proc 6th Int

Conf on lsquoAluminum alloysrsquo Toyohashi Japan July 1998 799ndash

804

252 L I Kaygorodova A M Dritz T V Krymova and I N

Fridlyander Proc Sixth Int AluminiumndashLithium Conference

Garmisch-Partenkirchen Germany October 1991 363ndash367

253 L I Kaigorodova A M Drits Ya V Zhingel T V Krymova

and I N Fridlyander Phys Met Metall 1992 73 286ndash290

254 A L Berezina V A Volkov S V Ivanov N I Kolobnev and

K V Chuistov Phys Met Metall 1991 71 (2) 167ndash175

255 I N Fridlyander N I Kolobnev A L Berezina and K V

Chuistov Proc Sixth Int AluminiumndashLithium Conference

Garmisch-Partenkirchen Germany October 1991 107ndash112

256 L I Kaigorodova A M Drits Ya V Zhingel T V Krymova

and V A Rassokhin Phys Met Metall 1992 73 281ndash285

257 I N Fridlyander S F Danilov E N Malysheva T A

Gorokhova and N N Kirkina Proc Sixth Int Aluminiumndash

Lithium Conference Garmisch-Partenkirchen Germany October

1991 381ndash386

258 G Dlubek S Krause H Krause A L Beresina V S

Mikhalenkov and K V Chuistov J Phys Condens Matter

1992 4 6317ndash6328

259 S Krause H Krause G Dlubek A L Beresina and K S

Chuistov Mater Sci Forum 1992 105ndash110 1109ndash1112

260 C Y Tan Z Q Zheng and S Q Liang Proc 4th Int Conf on

lsquoAluminium alloysrsquo Vol II Atlanta GA USA September 1994

329ndash333

261 A L Beresina N I Kolobnev K V Chuistov A V Kotko and

O A Molebny Mater Sci Forum 2002 396ndash402 977ndash981

Roslashyset and Ryum Scandium in aluminium alloys

International Materials Reviews 2005 VOL 50 NO 1 43

262 I N Ganiev I Yunusov and V V Krasnoyarskii J Appl Chem

USSR 1986 60 1961ndash1965

263 I N Ganiev Prot Met 1995 31 543ndash546

264 N V Vyazovikina Prot Met 1999 35 448ndash453

265 G V Kharina and V P Kochergin Prot Met 1996 32 134ndash

136

266 G V Kharina M V Kuznetsov and V P Kochergin Russ J

Electrochem 1998 34 482ndash485

267 V S Sinyavskii V D Valrsquokov and E V Titkova Prot Met

1998 34 549ndash555

268 Y L Wu F H Froes C G Li and J Liu Proc lsquoSynthesis

processing of lightweight metallic materials IIrsquo Orlando FL

USA February 1997 73ndash81

269 Z Ahmad and B J Abdul-Aleem Proc EuroCorr 2000

270 Z Ahmad A Ul-Hamid and B J Abdul-Aleem Corros Sci

2001 43 1227ndash1243

271 R Braun B Lenczowski and G Tempus Mater Sci Forum

2000 331ndash337 1647ndash1652

272 T Torma E Kovacs-Csetenyi L Vitalis I Vitanyi

J Stepanov and M Butova Mater Sci Forum 1987 1314

497ndash503

273 Z Wang P Wang K S Kumar and C L Briant in lsquoChemistry

and electrochemistry of corrosion and stress corrosion crackingrsquo

(ed R H Jones) 573ndash582 2001 TMS

274 V I Elagin V V Zakharov A A Petrova and E V

Vyshegorodtseva Russ Metall 1983 (4) 143ndash146

Roslashyset and Ryum Scandium in aluminium alloys

44 International Materials Reviews 2005 VOL 50 NO 1

Page 12: Scandium in aluminium alloys - Atom probe · A considerable part of the available literature on scandium in aluminium alloys is reviewed. ... behaviour in Al Cu, Al Mg Si,

both the correction for vacancies and for Sc in solidsolution on the same graph The two corrections are ofapproximately the same magnitude but with oppositesigns Thus the resulting (net) correction is close to zeroand it turns out that the first hand approximation asapplied in Ref 89 is very good in this case

Applying the calculated temperature dependent misfitwith the simple approximation for a critical diameter forloss of coherency one obtains a temperature-dependentcritical diameter as shown in Fig 19

Some examples from the literature of experimentallyobserved critical diameters in binary AlndashSc alloys aresummarised in Table 5 along with some predictions forcritical diameters from Fig 19 There is a fairly goodconsistency between the observations and the measureddiameter is quite close to the simple predictions above

A more refined analysis on the transition fromcoherent to incoherent particles has recently beenperformed145 This analysis is based on the balancebetween the increase in particlematrix interface energyowing to interfacial dislocations and the relaxation inelastic energy in the Al matrix owing to the samedislocations This method yields a predicted criticaldiameter of 246 nm for transition from coherent to

semi-coherent particles at ambient temperature Thetemperature dependence of the critical diameter is nottreated in this analysis

The loss of coherency during isothermal annealing hasbeen reported to be accompanied by an increasedaverage coarsening rate119121137145 The increasedcoarsening rate has been attributed either to diffusionof Sc along dislocation lines119121 or to the increasedparticlematrix interface energy of a semicoherentparticle145 However there are also several data sets inthe literature that do not indicate an increased growthrate after the loss of coherency114128

Al3ScAl interface energyThe interface energy between Al3Sc and the Al matrix isone of the key parameters that governs the nucleationgrowth and coarsening behaviour of Al3Sc in Al and Alalloys The interface energy has been estimated in severalinvestigations either by fitting experimental data toequations that describe nucleation or coarsening or bycalculations A compilation of some of the results isgiven in Table 6 There is considerable spread in thereported values regardless of what approach has beenused for the estimation

Influence of other elements on precipitation ofAl3ScMagnesium

With regard to precipitation mechanism it has beenstated that Mg suppresses the tendency to discontinuousprecipitation of Al3Sc106 In an investigation of pre-cipitation kinetics of Al3Sc in the temperature range300ndash500uC only minor changes in the kinetics (Fig 20)were found when up to 5 wt-Mg was added to an Alndash04 wt-Sc alloy135 It seems that the precipitationreaction is slightly faster in the Mg-containing alloys

Several investigations on age hardening response alsoimply that there is only a small if any effect of Mg onthe precipitation kinetics of Al3Sc23148149 It is how-ever found that the hardness increase from theprecipitation of Al3Sc is somewhat reduced in AlndashMgndashSc alloys compared to binary AlndashSc alloys23148149 InRef 149 it is suggested that some of the Sc is dissolvedin the Al3Mg2 phase and thus the age hardeningpotential is reduced with increasing Mg contentSomewhat contradictory to these observations but

Table 5 Some reported critical diameters for coherencyloss in binary AlndashSc and correspondingtheoretical critical diameters from Fig 19

Reference dcrit nmC0

Scwt-Sc

TtransuC

Theoreticaldcrit nm

119 38ndash40 05137 28ndash30 03 400 308128 32 02 400 450 308 335129 50 02143 40 012 025115 40 025 450ndash500 335ndash37114 40 03 400 450 308 335144 40 02 400ndash460 308ndash341145 30ndash80 02 400ndash490 308ndash362

20 C-curves for 10 and 60 transformation in Alndash

04 wt-Sc and Alndash4 wt-Mgndash04 wt-Sc redrawn

from Ref 135

19 Simple approximation for temperature-dependent criti-

cal diameter for introduction of dislocations on Al

Al3Sc interface

Roslashyset and Ryum Scandium in aluminium alloys

30 International Materials Reviews 2005 VOL 50 NO 1

sustained by Ref 135 it has recently been reported150

that precipitation of Al3Sc at 300 and 350uC occursslightly faster in an Alndash2 wt-Mgndash02 wt-Sc alloythan in an Alndash02 wt-Sc alloy studied previously by thesame researchers117118 and that the correspondinghardness increase is highest in the AlndashMgndashSc alloyThe only reported difference in experimental procedureis the solutionising temperature which was higher forthe AlndashSc alloy (648uC) than for the AlndashMgndashSc alloy(617uC) However given that the nucleation time isshortened by quenched-in vacancies as suggested byHyland107 the difference in homogenisation tempera-ture should be in favour of a faster precipitation of thebinary AlndashSc alloy It should be worthwhile to probedeeper into this observation of different aging responses

Mg in solid solution increases the lattice parameter ofthe Al matrix This is in turn expected to influence thecritical diameter for AlAl3Sc coherency loss as discussedin the section on lsquoLoss of coherency during growth ofAl3Sc precipitatesrsquo above Such an influence on the criticaldiameter is also briefly discussed elsewhere150 A criticaldiameter of 80 nm in an Alndash3 wt-Mgndash02 wt-Sc alloyhas been observed compared to 40 nm in a binary Alndash02 wt-Sc alloy of the same investigation144 Otherresearchers have reported a critical diameter in excess of116 nm in an Alndash63 wt-Mgndash02 wt-Sc alloy151

Computer simulations predict that the AlAl3Scinterface should be enriched in Mg87 These predictionsare confirmed experimentally by three-dimensional atomprobe microscopy of an Alndash2 wt-Mgndash02 wt-Sc alloyaged at 300uC38 Here it was found that the Mg contentat the interface is approximately three times higher thanthe matrix concentration regardless of aging time

Copper

It has been claimed that Cu suppresses the tendencytowards discontinuous precipitation of Al3Sc106

Zakharov and Rostova152 have reported that additionsof up to 14 wt-Cu have only minor effects on theprecipitation kinetics in an Alndash04 wt-Sc alloy Themost noticeable effect is that for temperatures above400uC the late stage of the transformation is sloweddown for the highest Cu contents This does not show in

Fig 21 however where only the 10 and 60transformation curves are included

The W-phase (AlCuSc) was observed in the alloywith the highest Cu content which means that less Sc isavailable for the precipitation of Al3Sc in this alloyAnother investigation on the age hardening response ofAlndash023 wt-Sc and Alndash25 wt-Cundash023 wt-Sc at300uC also implies that the precipitation behaviour ofAl3Sc in the two alloys is similar153154 At 350uC alimited portion of the Al3Sc has been observed tonucleate heterogeneously on coarse hrsquo precipitates155

According to the isothermal sections of the phasediagram43 one should expect the ternary W-phase toform instead of the Al3Sc phase in an alloy with such ahigh CuSc ratio However no observations of the W-phase or other ternary phases were reported from TEMstudies of the Alndash25 wt-Cundash023 wt-Sc alloy thathad been heat treated in the temperature range 300ndash460uC153ndash156 A third investigation on the precipitationin Alndash048 wt-Sc alloys with up to 440 wt-Cu in thetemperature range 100ndash450uC also concludes that no W-phase or other ternary phase forms during the heattreatment157

Copper in solid solution decreases the lattice para-meter of the Al matrix Thus it is expected that the misfitbetween Al and Al3Sc precipitates should be higher in

21 C-curves for 10 and 60 transformation in Alndash

04 wt-Sc and Alndash14 wt-Cundash04 wt-Sc redrawn

from Ref 152

Table 6 Reported values of interphase energy cAlAl3Sc between coherent Al3Sc precipitates and Al matrix

Reference cAlAl3Sc mJ m22 Method of estimation

137 10 Fit of coarsening data to LifshitzndashSlezev equation107 78iexcl20 (288uC) Back-calculation of incubation time

93iexcl20 (343uC)107 123iexcl41 (288uC) Back-calculation of nucleation rate

125iexcl35 (343uC)29 542 (400uC) Fit of coarsening data to Ostwald ripening

632 (430uC)413 (460uC)

146 c(100) 192 (0 K) c(111) 226 (0 K) Pseudopotential calculations147 c(100) 325 (0 K) c(110) 513 (0 K) c(111)

782 (0 K) c(100) 315 (288uC) c(100) 325 (343uC)Atomistic simulation

110 105 Fit of coarsening data to LSW theory31 20ndash300 Fit of coarsening data to Ostwald ripening

for 16 different temperatures111 57 Fit of precipitation model to experimental data145 120 coherent particles Fit of coarsening data

170 semicoherent particles

It is argued in this study that c may be lower in the nucleation stage

Roslashyset and Ryum Scandium in aluminium alloys

International Materials Reviews 2005 VOL 50 NO 1 31

AlndashCundashSc alloys compared to AlndashSc alloys Howeveran experimental investigation of Alndash25 wt-Cundash023 wt-Sc alloy comes to a different conclusion Thelattice misfit strain is found to decrease compared to Alndash02 wt-Sc and the critical diameter for coherency losswas found to be the same in the ternary and the binaryalloy144 It is suggested that these observations may bebecause of the dissolution of some Cu in the Al3Sc phaseand thus that the lattice parameters of both the Al matrixand the Al3Sc precipitates decrease in the ternary alloy

Silicon

It has been found that the onset of precipitation in Alndash04 wt-Sc is only slightly altered when Si contents ofup to 04 wt are introduced in the alloy However thefinal stage of the precipitation reaction is considerablydelayed with increasing Si content135 Figure 22 showsthe effect of addition of a joint of 035 wt-Si and040 wt-Fe There are at least two possible explana-tions for why an Si-addition leads to this behaviour

1 Alloying with Si is known to promote discontin-uous precipitation of Al3Sc106158 It has been shown thatwhen isothermal precipitation of Al3Sc starts discon-tinuously the later stage of the overall transformationcan be very slow31

2 The isothermal section of the phase diagramsuggests that the V-phase (AlSc2Si2) should form inalloys of this composition46 If the V-phase forms lessSc is available for precipitation of Al3Sc

It has been shown157 that for an AlndashScndashSi alloy withsolid solution content of 010 wt-Sc an 110 wt-Sithe only phases to precipitate after heat treatment at200uC are Si and an (AlScSi)-phase possibly the V-phase On the other hand the Al3Sc phase has beenobserved to form in alloys with 04 wt-Sc and up to08 wt-Si159160

Zinc

It has been reported that additions of up to 5 wt- Znhave only minor effects on the precipitation kinetics ofan Alndash04 wt-Sc alloy135 (Fig 23) In Ref 106 it isclaimed that Zn promotes discontinuous precipitation ofAl3Sc

Lithium

A comparison of the age hardening response at 400uC inAlndash24 wt-Lindash019 wt-Sc and Alndash024 wt-Sc alloys

indicates that the onset of Al3Sc-precipitation is notaffected by the presence of Li161

Zirconium

As mentioned in the section on lsquoTernary phase diagramswith dispersoid-forming elementsrsquo earlier a considerableamount of Zr is dissolved in the Al3Sc phase and thus amore correct denotation of the precipitating phase isAl3(Sc12xZrx) In discussing the influence of the Zrcontent on the precipitation of Al3Sc one is thereforeactually discussing the difference in precipitation ofAl3Sc versus Al3(Sc12xZrx)

It is found that an addition of 015 wt-Zr to an Alndash04 wt-Sc alloy only marginally affects the initial stageof the precipitation reaction123135 while it slows downthe later stages of the transformation considerably(Fig 24)135 The coarsening rate of the Al3(Sc12xZrx)particles in AlndashScndashZr alloys is found to be much slowerthan that of Al3Sc particles in AlndashSc alloys123162

In three-dimensional atom probe field ion microscopy(3D-APFIM) of Al3(Sc12xZrx) particles formed at 475uCin a ternary AlndashScndashZr alloy163 it was found that the coreof the particles is almost pure Al3Sc whereas there is ashell of Al3(Sc12xZrx) with almost equal content of Scand Zr Such a behaviour has also been predicted bycomputer modelling of precipitation of Al3(Sc12xZrx) at480uC in an AlndashZnndashMgndashScndashZr alloy164 This modelpredicts that Zr starts to enter the growing

22 C-curves for 10 and 60 transformation in Alndash

04 wt-Sc and Alndash04 wt-Fendash035 wt-Sindash04 wt-Sc

redrawn from Ref 135

23 C-curves for 10 and 60 transformation in Alndash

04 wt-Sc and Alndash5 wt-Znndash04 wt-Sc redrawn

from Ref 135

24 C-curves for 10 and 60 transformation in Alndash

04 wt-Sc and Alndash04 wt-Scndash015 wt-Zr redrawn

from Ref 135

Roslashyset and Ryum Scandium in aluminium alloys

32 International Materials Reviews 2005 VOL 50 NO 1

Al3(Sc12xZrx) particles when approximately half of thesupersaturated Sc has been precipitated The Zr contentof the outer shell is predicted to be much higher thanwhat has been found experimentally163164

Another 3D-APFIM study of Al3(Sc12xZrx) particlesin a ternary AlndashScndashZr alloy has been reported165 Hereparticles grown at 300uC for various lengths of time werestudied The Zr content in these particles was muchlower than that reportedpredicted at higher tempera-tures163164 even after very long annealing times

Iron

The effect of adding up to 07 wt-Fe on the precipita-tion kinetics in an Alndash04 wt-Sc alloy has beeninvestigated135 The onset of precipitation was onlyslightly influenced by the Fe-level whereas the laterstages of the transformation however were significantlyslowed down as the Fe-level increased An example ofthe effect of a joint addition of Fe and Si is shown inFig 22

Manganese chromium and titanium

Small additions (03 wt-) of manganese or chromiumto Alndash040 wt-Sc alloys are reported to have onlyminor effects on the precipitation kinetics of Al3Sc135

According to Ref 106 Mn is reported to promote andCr and Ti to suppress discontinuous precipitation

Rare earth elements

An investigation of the precipitation behaviour of Alndash03 at-Sc and Alndash03 at-Scndash03 at-X alloyswhere X is either yttrium gadolinium holmium orerbium in the temperature range 235ndash310uC indicatedthat a Al3(Sc12xXx) phase with L12 structure wasformed in the ternary alloys22 Peak strength is reportedto occur after approx 10 h at 285uC in all alloys whichindicates that the precipitation kinetics up to peakstrength is practically unaltered by the ternary additions

Influence of Sc on microstructure andproperties of wrought aluminium alloysMost of the effects of Sc addition in wrought Al-alloysare linked to the formation of the Al3Sc phase In atypical processing route of a wrought aluminium alloyparticles of the Al3Sc phase can form under threedifferent conditions each of which influences themicrostructure and properties of the alloy in a specificway

1 During solidification after casting or weldingAl3Sc particles can form in the melt and act as nucleifor a-Al thus leading to grain refinement18166

2 High temperature processing of the alloy in therange 400ndash600uC for instance homogenisation hot-rolling or extrusion can give a dense distribution ofAl3Sc particles of typically 20ndash100 nm size The particledistributions formed under such conditions are reportedto lead to good recrystallisation resistance128148167168

and enhanced superplasticity52169170

3 Heat treatment in the range 250ndash350uC can lead tosignificant precipitation hardening of an alloy super-saturated in Sc148158171 The size of strengthening Al3Scprecipitates is typically in the range 2ndash6 nm121

Grain refinementA good grain refinement is almost always desired uponsolidification The formation of small equiaxed grainsrather than long dendrites in the melt facilitates thefeeding of the melt into cavities of the shrinkingsolidified metal and thus reduces the problem ofshrinkage porosity The tendency to hot cracking is alsoreduced and the second phase particles become morefinely and uniformly distributed

To the authorsrsquo knowledge the first effect of Sc in Al-alloys that was reported in an international scientificjournal was the grain refining action in pure Al and in anAlndashCu alloy upon solidification172 which was found tobe stronger for Sc than for other transition metals Inlater studies of Sc as a grain refiner in pure Al1832173 ithas been demonstrated that approx 07 wt-Sc issufficient to provide excellent grain refinement It hasalso been demonstrated that additions of 025 wt-Scz025 wt-Zr provide good grain refinement in pure Al18

In order for Sc to act as an effective grain refiner theAl3Sc phase has to form in the melt before thesolidification of a-Al The Al3Sc particles have a latticeparameter close to that of pure Al and whenhypereutectically formed the Al3Sc particles are veryeffective substrates for the nucleation of the a-Al phaseAs mentioned in the section on lsquoFormation of Al3Sc inAlndashSc alloysrsquo above this requires that the alloy ishypereutectic with respect to Sc ie in excess of approx06 wt- in a binary AlndashSc alloy In ternary and higherorder systems the eutectic Sc composition may dependon the other alloying elements present For instance theeutectic composition of Sc has been predicted todecrease with increasing Mg content in the ternary AlndashMgndashSc system39 This prediction is sustained by theobservation of good grain refinement by adding 05 wt-Sc to an Alndash7 wt-Mg alloy174 (Other examples ofgrain refinement at Sc concentrations lower than that ofthe binary eutectic are found in Ref 173)

Similarly the observation of good grain refinement inan Alndash025 wt-Scndash025 wt-Zr alloy18 may be as aresult of a lower Sc content of the eutectic in the ternarysystem ie less Sc is needed to make the alloy hyper-eutectic No literature data on the liquidus surface of theAlndashScndashZr system are available and thus this hypothesiscannot be confirmed In more complex alloy systems itis also observed that excellent grain refinement isachieved at low Sc contents when Sc is added togetherwith Zr It is reported that adding either 02 wt-Sc06 wt-Sc or 01 wt-Zr to an Alndash5Mg alloy givesmuch poorer grain refinement than adding 02 wt-Scz01 wt-Zr175 Similarly additions of 015 wt- ofeither Sc or Zr are reported to only marginally refinethe grain structure in an AlndashCundashLi alloy whereas a jointaddition of 015 wt-Sc and 015 wt-Zr gives excellentgrain refinement176 For an AA 3650 casting alloy (Alndash7 wt-Sindash04 wt-Mg) good grain refinement is achievedby adding 039 wt-Sc or 027 wt-Scz019 wt-Zr177

In some AlndashZnndashMgndashScndashZr alloys it is also found thatan addition of 02ndash03 wt-Sc can be sufficient for goodgrain refinement166169178179 Examples of the grainrefinement as a function of Sc addition in pure Al andin an AlndashZnndashMgndashZr alloy are shown in Fig 25

The nucleation of a-Al on Al3Sc particles in the melt isfacilitated by the close match in the lattice parameters ofthe two phases As shown in Fig 17 the mismatch at the

Roslashyset and Ryum Scandium in aluminium alloys

International Materials Reviews 2005 VOL 50 NO 1 33

eutectic temperature of binary AlndashSc alloys (660uC) isonly approx 047 In Refs 57 and 89 it is shown thatwhen Zr Hf and in particular Ti is dissolved in the Al3Scparticles this reduces the lattice parameter of the phaseIt appears that when 25 of the Sc atoms in Al3Sc aresubstituted by Ti the mismatch is zero at approx 550uCand becomes negative at higher temperatures89 Thissuggests that by carefully selecting the Ti content of thealloy it should be possible to obtain Al3(ScTi)substrates in the melt that match exactly the latticeparameter of the nucleating a-Al and thus furtherimprove the grain refinement of the alloy This appearsto have been achieved in a recent work180 where thegrain refinement of an Alndash07 wt-Sc alloy wascompared with that of an Alndash05 wt-Scndash02 wt-Tialloy At a cooling rate of 100 K s21 only an estimated2 of the primary Al3Sc particles of the binary AlndashScalloy were effective nuclei compared to practically 100for the primary Al3(ScTi) particles in the ternary AlndashScndashTi alloy leading to a much smaller grain size in theternary alloy Whereas the match of lattice parametersmay be of importance for these results the authors ofthis investigation180 draw attention to other factors suchas different growth restriction factors for Sc and Ti andthe possibility of a peritectic reaction in the ternaryalloy Nevertheless the principle of matching latticeparameters is worth looking into further in future work

Effects from dispersoidslsquoDispersoidsrsquo is a term which is commonly used aboutthe classes of second phase particles that are formedin an Al alloy during high temperature annealing orthermomechanical processing such as homogenisationhot rolling extrusion and forging A dense distributionof dispersoids can give a significant contribution to analloyrsquos strength owing to particle strengthening but thisis rarely the main strengthening mechanism A moreimportant contribution from the dispersoids is theirability to stabilise the grainsubgrain structure of analloy through the Zener-drag action and thus improvethe mechanical properties of the alloy

There are two noticeable dispersoid-related effectsthat have been reported for Sc-containing alloys Thefirst is the stabilising effect on a deformed microstruc-ture When a non-recrystallised structure is preserved inan alloy this can add considerably to the mechanical

strength of the material The second effect is thepreservation of a small grain size during hot deforma-tion at slow deformation rates which is necessary toobtain superplastic properties of an Al-alloy

Recrystallisation resistance

The anti-recrystallisation effect of Sc was first publishedin a patent171 where 03 wt-Sc was added to pure Aland to AlndashMg AlndashMn and AlndashZnndashMg alloys Both Sc-free and Sc-containing materials were cold worked andsubsequently annealed and it was found that theaddition of Sc increased the temperature for onset ofrecrystallisation by approx 220uC in pure Al andsomewhat less in the Al-alloys Although the author ofthe patent171 may have been well aware that the anti-recrystallisation effect is caused by Al3Sc dispersoidsthis is not mentioned in the text The first journal paperthat explicitly points out that the recrystallisationresistance is due to Al3Sc dispersoids was an investiga-tion of the effects of adding Sc to wrought AlndashMgalloys181 In this work it was found that the Al3Scdispersoids were very effective in preventing recrystalli-sation up to temperatures of approx 400ndash450uC Athigher temperatures the dispersoids coarsen consider-ably and the microstructure was partially recrystallised

It is established that the Zener-drag pZ that is imposedon an advancing grain boundary by randomly distrib-uted dispersoids can be expressed in the form

pZ~k f =r (3)

where k is a factor that includes the interface energybetween the dispersoids and the matrix f is the volumefraction and r is the mean radius of the dispersoids Thusthe Zener drag will decrease rapidly in the case where thedispersoids are coarsening

As mentioned in the section on lsquoInfluence of otherelements on precipitation of Al3Scrsquo above theAl3(Sc12xZrx) dispersoids in a ternary AlndashScndashZr alloycoarsen at a much slower rate than the Al3Sc dispersoidsin a binary AlndashSc alloy This effect was first reported inRef 123 (although also observed in Ref 182) andaccording to Ref 33 the same authors demonstratedsoon after that the denser dispersoid distributionachieved in an AlndashScndashZr alloy leads to superiorrecrystallisation resistance compared to a binary AlndashScalloy An example of the increased recrystallisationresistance by adding both Zr and Sc is shown in Fig 26

In isothermal sections of the ternary AlndashScndashZr phasediagram it is indicated that the solid solubility ofSczZr is somewhat higher than that of Sc alone54 Ithas also been demonstrated both by electrical con-ductivity measurements (Fig 27) and microstructuralobservations that the supersaturation of SczZr isgreater than that of only Sc or Zr in as cast Alndash15(SczZr) alloys183 This indicates that it should bepossible to increase the volume fraction of dispersoids inAlndashScndashZr compared to AlndashSc It is suggested162 that theincreased volume fraction that can be achieved byadding both Sc and Zr can be advantageous inconventional wrought Al-alloys

There are at least two different conditions underwhich Al3Sc or Al3(Sc12xZrx) dispersoids can form toprevent recrystallisation

1 Sc (or Sc and Zr) is in solid solution before thedeformation In the case of cold deformation and

25 Grain refinement as a function of Sc addition in pure

Al (redrawn from Ref 32) and AlndashZnndashMgndashZr (redrawn

from Ref 169) note that data points are plotted on

different ordinate axes

Roslashyset and Ryum Scandium in aluminium alloys

34 International Materials Reviews 2005 VOL 50 NO 1

subsequent annealing the Al3Sc or Al3(Sc12xZrx)dispersoids may nucleate and grow before the nucleationand growth of recrystallised grains takes placeDispersoids can form after a direct up-quench to theannealing temperature115143148184 during ramp-up tothe annealing temperature115 or by pre-annealing at anintermediate temperature129 In the case of hot deforma-tion the Al3Sc or Al3(Sc12xZrx) dispersoids maynucleate and grow during preheating of the materialand during the hot deformation itself184

2 The Al3Sc or Al3(Sc12xZrx) dispersoids are formedin the material before deformation184 Considering coldrolling and subsequent annealing the annealing tem-perature Tann may be either lower or higher than thetemperature Tdisp at which the dispersoids were formedIf TannTdisp only limited if any coarsening of thedispersoids is expected to take place and thus the Zenerdrag from the particles is expected to be practicallyconstant The driving force for recrystallisation how-ever is expected to decrease somewhat with theannealing time as a result of recovery processes Thusif recrystallisation does not occur within short annealingtimes the material is expected to remain unrecrystallisedfor infinite time at the annealing temperature IfTannTdisp there will be substantial coarsening of thedispersoids during annealing In order for the materialto remain unrecrystallised the decrease in driving forcefor recrystallisation owing to recovery has to be at leastas rapid as the decrease in Zener drag because of particlecoarsening

Experimental comparisons of the conditions abovepoint in the direction that the recrystallisation resistanceis poorest when Sc (or Sc and Zr) is in solid solutionbefore deformation and the deformed material is up-quenched to the annealing temperature148 or when Al3Scor Al3(Sc12xZrx) dispersoids are formed before defor-mation at TdispampTann184185 Excellent recrystallisationresistance is achieved if dispersoids are formed at anintermediate anneal of solutionised and deformedmaterial128 or if dispersoids are formed at TdispTann

before deformation148185ndash187 It seems that the decreasein Zener drag because of dispersoid coarsening in many

cases is slower than the decrease in driving force forrecrystallisation because of recovery processes Thusthere is an advantage in forming a high number densityof small dispersoids which for most practical casesmeans that they should be formed at TdispTann122

When an advancing high angle grain boundary iethe recrystallisation front is passing a coherent Al3Scdispersoid there are at least three possible grainboundarydispersoid interactions

1 The Al3Sc dispersoid retains its global orientationrelationship and thus loses its coherency with thesurrounding matrix

2 The Al3Sc dispersoid rotates as the grain boundarypasses either by diffusional processes at the dispersoidmatrix interface or by the grain boundary passingthrough the dispersoid and the Al3Sc dispersoidassumes the same crystallographic orientation as theAl matrix of the recrystallised grain

3 The Al3Sc dispersoid dissolves at the grainboundary and re-precipitates in the recrystallised grain

Which interactions that actually take place willprobably depend on the dispersoid size annealingtemperature and driving force for recrystallisation It isalso possible that alloy composition (other elementsthan Al) is of importance

It has been reported that large (Oslash about 100ndash150 nm)Al3Sc dispersoids in a deformed Alndash4 wt-Mgndash02 wt-Sc alloy annealed at 575uC lose the orientationrelationship with the matrix after being passed by therecrystallisation front148

A rotation of somewhat smaller Al3Sc dispersoids in arecrystallising binary Alndash025 wt-Sc alloy has beenreported115143 The rotation was reported to be accom-panied by substantial growth (from Oslash 30 nm to Oslash48 nm) as a result of enhanced Sc diffusion at the grainboundary Observations suggested that the grainboundaries were passing through the dispersoids andthus the Al3Sc dispersoids retained the orientationrelationship with the recrystallised Al matrix

Dissolution and re-precipitation of Al3Sc dispersoidshas been reported during recrystallisation of a 50 coldrolled Alndash02 wt-Sc alloy162 Large spherical partially

26 Fraction recrystallised structure in cold rolled sheets

of Alndash04 wt-Sc and Alndash04 wt-Scndash015 wt-Zr as a

function of annealing temperature redrawn from

Ref 183 27 Electrical conductivity in Alndash15(SczZr) alloys

redrawn from Ref 183

Roslashyset and Ryum Scandium in aluminium alloys

International Materials Reviews 2005 VOL 50 NO 1 35

coherent dispersoids were observed to dissolve at therecrystallisation front and re-precipitate as smallercoherent Al3Sc cuboids

Superplastic forming

It seems that the first publication on superplasticproperties of Sc-containing Al-alloys was a study of anAlndash35Cundash14Mgndash045Mnndash04(SczZr) alloy188

It was recognised that the superplastic properties are aresult of the stabilisation of the fine grain structure byAl3Sc dispersoids The Sc-containing Al alloys that havereceived most attention for their superplastic propertieshowever are those of the AlndashMgndashSc system which wasfirst published in a patent189 Here it was noted that anAlndash4 wt-Mgndash05 wt-Sc alloy had superior superplasticproperties compared to fine-grained 7475 (AlndashZnndashMgndashCu alloy) Binary Alndash05 wt-Sc and Alndash4 wt-Mgalloys did not behave superplastically The flow stress atthe hot forming temperature was found to be much (30ndash40) lower in the ternary alloy than that of the twobinary alloys

The superplastic properties of AlndashMgndashSc alloys havebeen explored by several research groups over the lastdecade190ndash196 It has frequently been found that thedeformation mechanism is dominated by grain bound-ary sliding190 However it has also been reported thatAlndashMgndashSc alloy may deform superplastically withoutnoticeable grain boundary sliding23 It is generallyrecognised that the grain boundary sliding mechanismis facilitated when the average grain size is very smalland grain boundaries are predominantly high-angleSuch a microstructure may be achieved by carefulthermomechanical processing of the starting mate-rial193194197198 It has however been shown that a finegrained structure with high angle boundaries maydevelop during superplastic forming of AlndashMgndashSc alloyseven if the starting microstructure is an entirely differentone for instance that of a cold rolled sheet192 It has alsobeen suggested that superplastic forming of as castmaterial may be possible189

One of the more efficient thermomechanical processesfor achieving an ultrafine grain structure with high anglegrain boundaries in Al-alloys is equal channel angularpressing (ECAP) A JapanesendashAmerican group ofscientists has published an impressive body of researchon improvements in superplastic properties in Al-alloys processed by ECAP over the last few years andseveral of the publications are from investigations onAlndashMgndashSc alloys170199ndash224 Maximum strains in excessof 2000 at a strain rate of 0033 s21 have beenachieved170201202217 which is an extraordinarily goodcombination of high strain and high strain rate for analuminium alloy

Superplastic properties of AlndashCundashMg(ndashMn)ndashSc(ndashZr)and AlndashMgndashSc(ndashZr) alloys have been mentionedNoticeable superplasticity in other Sc-containing Al-alloys has also been reported such as AlndashZnndashMg(ndashCu)ndashScndashZr169225ndash228 AlndashLindashSc229 AlndashMgndashLindashScndashZr229ndash234

AlndashLindashMgndashCundashScndashZr235236 and AlndashCundashLindashScndashZr233

Precipitation hardeningHardening by Al3Sc precipitates

It has been noted that when Al3Sc particles precipitate inthe temperature range 250ndash350uC they give a significanthardness increase in the alloy Some authors point out

that Sc is a more effective precipitation hardening elementper atomic fraction added than the elements that arecommonly used for precipitation hardening121130 (In onepaper29 it is claimed that only Au has a strongerstrengthening effect than Sc) However the amount ofSc that can be precipitated from supersaturated solidsolution is rather limited and thus the absolute values ofthe hardness increase from the precipitation hardening ismuch lower than what is normally associated withprecipitation hardened alloys Also the temperatureregime for age hardening by precipitation of Al3Sc issomewhere in between the temperature regimes for agehardening and solution heat treatments of commonprecipitation hardened alloys This makes a combinedprecipitation of Al3Sc and other strengthening precipi-tates unfeasible Thus precipitation strengthening byAl3Sc is most feasible in alloy systems that are non-heat-treatable The non-heat-treatable aluminium alloy sys-tems are according to the Aluminum Associationdesignations the 1xxx series (99 pure Al) the 3xxxseries (AlndashMn) and the 5xxx series (AlndashMg) The purposeof adding Sc to these alloys may be either to stabilise themicrostructure of wrought semiproducts (extrusionsrolled plates forgings etc) as discussed in the sectionon lsquoRecrystallisation resistancersquo above or to provideextra strength to the alloy through precipitation hard-ening In the latter case it is appropriate to considerwhether the Sc-containing alloy still should be classifiedas non-heat-treatable A heat treatment is applied thatbrings about a significant precipitation hardening On theother hand the hardness increase that is achieved throughthe heat treatment is lower than what is normallyassociated with heat-treatable alloy systems Hence eventhough it seems like a contradiction one chooses to keepusing the term lsquonon-heat-treatablersquo about these alloys

Table 7 gives an overview of some mechanicalproperties of Sc-containing non-heat-treatable alloysthat are reported in the literature Most of theexperimental work on Sc in 1xxx-types of alloys hasbeen done on binary AlndashSc alloys with much higherpurity than industrial alloys

Strengthening mechanisms

When the precipitates are larger than a critical size thestrengthening effect is due to the Orowan-mechanism iedislocations can only pass the precipitates by looping Inthis case the strengthening effect of the particles isapproximately inversely proportional to the mean parti-cle spacing When the precipitates can be sheared bydislocations there are a number of strengthening mechan-isms that apply It is proposed by Parker et al108 that thetwo major contributing mechanisms are coherency strainand anti-phase-boundary energy In a recent detailedstudy of strengthening mechanisms in binary AlndashSc alloysby Marquis and colleagues117118 the strengthening fromshear modulus mismatch between the matrix and theprecipitates is also accounted for A qualitatively goodmatch between theoretical strengthening and measuredvalues is achieved in this work both for deformation atroom temperature and at 300uC

Effect of Sc on precipitation strengthening in heat-treatablealloys

Following the AA designation system the traditionalheat-treatable Al-alloys are those that belong to the 2xxx

Roslashyset and Ryum Scandium in aluminium alloys

36 International Materials Reviews 2005 VOL 50 NO 1

series (AlndashCu) 6xxx series (AlndashMgndashSi) and 7xxx series(AlndashZnndashMg) AlndashLi alloys should also be mentionedSeveral investigations have been carried out in order toclarify the effects of Sc on the precipitation behaviour inthese alloy systems

AlndashCu alloys

The precipitation sequence in AlndashCu alloys is oftendescribed as follows

Supersaturated solid solutionRGP-zonesRh0Rh9Rh(Al2Cu)

The highest strength is normally achieved when the h0or h9 precipitates are predominant Typical precipitationheat treatment temperatures for AlndashCu alloys are in therange 160ndash190uC238 which is considerably lower thanthe typical precipitation temperature for Al3ScComparisons of the aging responses of AlndashCu and AlndashCundashSc alloys at 150 and 200uC indicate that there is nonoticeable effect of Sc on the precipitation kinetics ofh9153 It is observed that the h9 precipitates may nucleateon Al3Sc particles153 At 300uC it is observed that h9particles are somewhat smaller in AlndashCundashSc alloys thanin AlndashCu alloys156

AlndashMgndashSi alloys

The following precipitation sequence is commonlyreported for AlndashMgndashSi alloys

Supersaturated solid solutionRGP-zonesRb0Rb9Rb(Mg2Si)

For peak aged alloys the predominant precipitatetype is b0 for which the stoichiometric composition hasrecently been resolved to be Mg5Si6239 Temperatures inthe range 160ndash205uC are typically used for precipitationhardening of these alloys238 Adding both 03 wt-Scand 01 wt-Zr to an Alndash06 wt-Mgndash065 wt-Sialloy does not seem to alter the precipitation kineticsof b0 at 165uC However the hardness increase becauseof precipitation hardening appears to be smaller in theSczZr-containing alloy240 In another investigationadditions of 01 wt-Sc 015 wt-Sc 02 wt-Sc04 wt-Sc and 02 wt-Scz01 wt-Zr were made toan Alndash08 wt-Mgndash07 wt-Si alloy241 Here it wasalso observed that the precipitation kinetics of b0 wasseemingly independent of the Sc additions (Fig 28)TEM observations indicated that the b0 precipitateswere of comparable sizes in the investigated alloys andno interactions between Al3Sc and b0 were observed(Fig 29) In a third study242 where the effect of Sc onthe precipitation in an AlMgSindashSiC metal matrixcomposite was investigated there also does not seemto be any effect on the precipitation kinetics Howevercontrary to the findings of Ref 240 it is reported thatthe Sc addition leads to a higher hardness increase thanin the corresponding Sc free alloy

AlndashMgndashZn alloys

For these alloys the following precipitation sequence isoften ascribed

Table 7 Mechanical properties in non-heat-treatable Al-alloys with Sc

Reference Alloy wt- YS MPa UTS MPa Note

1xxx alloys171 000Sc 15 48 Cast material aged 288uC8 h

023Sc 159 185 Cast material aged 288uC8 h038Sc 199 220 Cast material aged 288uC8 h000Sc 14 49 Cold rolled material (89) aged 288uC8 h023Sc 198 208 Cold rolled material (89) aged 288uC8 h038Sc 240 264 Cold rolled material (89) aged 288uC8 h000Sc 8 34 Cold rolled material quenched from 649uC aged 288uC8 h023Sc 147 157 Cold rolled material quenched from 649uC aged 288uC8 h038Sc 193 199 Cold rolled material quenched from 649uC aged 288uC8 h

121 05Sc 160 ndash Forged material quenched from 635uC aged 250uC50 h23 05Sc 298 319 Hot rolled 288uC cold rolled 69ndash81 aged 288uC4 h112 01Sc 132 166 Hot z cold rolled material quenched from 630uC

aged 320uC133 h148 02Sc 138 ndash Cast material aged 300uC10 h compression test159 04Sc 196 ndash Cast material aged 300uC10 h compression test117 118 03Sc 209 ndash Cast material quenched from 648uC aged 300uC5 h

compression test3xxx alloys171 1Mn 015Sc 216 221 Cold rolled material (89) aged 288uC8 h

1Mn 05Sc 309 323 Cold rolled material (89) aged 288uC8 h186 05Mn 02Mg

026Sc 015Zr162 201 Extruded material solutionised 600uC aged 250uC

5xxx alloys171 1Mg 43 111 Cold rolled material (89) aged 288uC8 h

1Mg 03Sc 288 303 Cold rolled material (89) aged 288uC8 h53Mg 147 259 Cold rolled material (50) wintermediate anneals

at 343uC aged 288uC8 h53Mg 03Sc 368 401 Cold rolled material (50) wintermediate anneals

at 343uC aged 288uC8 h23 2Mg 05Sc 376 401 Hot rolled 288uC cold rolled 69ndash81 aged 288uC4 h

4Mg 05Sc 414 4606Mg 05Sc 433 503

237 4Mg 1Sc 420 525 Cold rolled material (83) aged 320uC1 h148 4Mg 02Sc 194 ndash Cast material aged 300uC10 h compression test

Tensile test data except where noted YS yield strength UTS ultimate tensile strength

Roslashyset and Ryum Scandium in aluminium alloys

International Materials Reviews 2005 VOL 50 NO 1 37

Supersaturated solid solutionRGP-zonesRg9Rg(Zn2Mg)

The maximum hardness is normally achieved whenthe g9 precipitates are predominant Common precipita-tion hardening temperatures are in the range 95ndash180uCand a two-step precipitation heat treatment within thistemperature regime is often used238 It has beenobserved in some investigations that Sc and SczZradditions to AlndashMgndashZn alloys slow down the precipita-tion of g9 somewhat243 Other investigations find thatthere is no effect of Sc on the precipitation behaviour ofg9244245 and yet others report that Sc additionssignificantly speed up the precipitation of g9246 In Ref247 it is found that an Sc addition leads to coarser g9precipitates and it is claimed that this gives an improvedductility of the alloy The strength-loss associated withlarger particle size is reported to be counterbalanced bystrengthening from Al3Sc precipitates

AlndashLi alloys

The precipitation sequence in binary AlndashLi alloys isapparently simple

Supersaturated solid solutionRd9Rd (AlLi)

where d9 is the metastable Al3Li phase which just likeAl3Sc has the L12 type of atomic arrangement Thetypical temperature regime for precipitation of d9 whichis the strengthening phase in this system is approx 150ndash200uC A comparison of the age hardening response ofan Alndash26 wt-Li and an Alndash24 wt-Lindash019 wt-Scalloy at 180uC248 and 200uC161 indicates that the onsetof d9 precipitation is not altered by the presence of ScThe hardness curves for the two alloys are practicallyidentical at 200uC whereas at 180uC the peak hardnesslevel is slightly higher in the AlndashLi than the AlndashLindashScalloy DSC measurements at constant heating ratesindicate that the addition of Sc to an AlndashLi alloysincreases the activation energy for d9 precipitation andmoves the exothermic peak associated with d9 precipita-tion to a higher temperature248 For specimens aged at

either 180uC or 200uC TEM observations reveal that thed9 precipitates are much smaller in the Sc containingalloy than in binary AlndashLi both in the peak agedcondition and in the overaged condition161248 Additionof Sc has also been observed to reduce the size of d9precipitates in other AlndashLi based alloys249ndash251 In an AlndashLindashCundashZr alloy an addition of Sc has been reported toslow down the homogeneous precipitation of d9252253 Ithas been claimed that Sc reduces the quench sensitivityand delays room temperature aging of AlndashLi basedalloys254ndash256

When present in the microstructure before the pre-cipitation of d9 the Al3Sc precipitates may act as effec-tive nucleation sites for d9 The resulting precipitates arespheres of d9 with a core of Al3Sc161249252ndash255257ndash261

Corrosion resistanceAn appreciable amount of data is available on the effectsof Sc on the corrosion behaviour of wrought Al-alloysSome of these effects are apparently derived from theeffects of Sc on the microstructure of the alloys It hasbeen reported that an addition of Sc increases thecorrosion potential (makes it less negative) in pureAl262ndash264 in AlndashZn alloys265266 AlndashMg alloys267 AlndashZnndashMgndashCu alloys264268 AlndashCundashMgndashMn alloys264 andin AlndashCundashLindashMgndashAg alloys264 Even though Sc alsohas been reported to decrease the corrosion potential in

28 Age hardening response at 175uC for Alndash08 wt-Mgndash

07 wt-Si alloy (Base) with additions of 02 wt-Sc

04 wt-Sc and 02 wt-Scz01 wt-Zr from Ref 241

29 TEM images of a b0 precipitates in Alndash08 wt-Mgndash

07 wt-Si alloy and b b0 and Al3(Sc1ndashxZrx) in a similar

alloy with addition of 02 wt-Scz01 wt-Zr from

Ref 241

Roslashyset and Ryum Scandium in aluminium alloys

38 International Materials Reviews 2005 VOL 50 NO 1

AlndashMg alloys269270 it seems that the general trend isthat adding Sc to an alloy makes it slightly more nobleThe change in corrosion potential is much morepronounced when Sc is added in amounts larger thanthe eutectic composition263 ie there is a considerablecontribution from primary or eutectic Al3Sc to theoverall potential It has also been demonstrated that thechange in corrosion potential caused by Sc can dependon the heat treatment applied to the alloy267268

Even though the corrosion potential is an essentialparameter in establishing the corrosion behaviour of analloy an increase in the corrosion potential does notnecessarily imply an improved self-corrosion resistanceHowever measurements of corrosion rates and passiva-tion current densities strongly suggest that the self-corrosion resistance in general is considerably improvedwhen Sc is added to wrought Al-alloys263264267 Someobserved variations in corrosion potential and passiva-tion current densities with Sc content in binary AlndashScalloys are plotted in Fig 30

Material failure in corrosive environments is often dueto localised corrosion attacks which may propagaterapidly even though the bulk material has a goodresistance against general corrosion It has been pointedout that hypereutectic additions of Sc may lead tomicrogalvanic corrosion beside primary Al3Sc parti-cles264 In AlndashMg alloys grain boundary precipitation ofAl8Mg5 can lead to localised corrosion attacks such asintergranular corrosion (IGC) exfoliation corrosion(EC) and stress corrosion cracking (SCC) In wroughtmaterial such precipitation may occur in the 60ndash180uCtemperature regime and heating in this temperaturerange is referred to as lsquosensitationrsquo An AlndashMgndashSc alloywas found to be immune against intergranular corrosionand have moderate susceptibility to exfoliation corro-sion after annealing at 350uC271 After sensitation heattreatments severe IGC and EC was observed but notquite as severe as in a corresponding alloy without ScAs for SCC the AlndashMgndashSc alloy was found to be highlyresistant271 In another study it was found that additionof 056 wt-Sc reduces the SCC susceptibility of an Alndash68 wt-Mg alloy in the as-rolled state and afterannealing at 250uC whereas in a sensitised specimenthe SCC susceptibility is somewhat increased by the Scaddition272 A third investigation found that Sc has nomeasurable detrimental effect on the SCC susceptibilityof sensitised Alndash5Mgndash015Zr alloy273 SCC is also a

severe problem in high strength AlndashZnndashMgndashCu alloys Ithas been shown that small Sc additions are effective inreducing the SCC sensitivity of these alloys244246268274

Use of Sc-containing Al alloysA systematic development of Sc-containing aluminiumalloys took place in the former USSR in the 1980s andthe interest for Sc as an alloying element in aluminiumalloys hit the western world approximately 10 yearslater Even though a number of improvements in Alalloys achieved by Sc addition have been demonstratedthe current uses of such alloys are very limited This isrelated to the very high price of scandium

In Russia some parts of military aircraft are made ofSc-containing AlndashLi alloys In the western world themain usage of Sc-containing alloys is for sportsequipment Ashurst Technology and Kaiser Aluminumdeveloped a Sc-containing 7xxx alloy for baseball andsoftball bats which was introduced to the Americanmarket in 1997 by Easton Alcoa soon followed with aSc-containing alloy for a competing brand of batsLouisville Slugger Since then several new and improvedSc-containing alloys for bats have been introduced tothe market The purpose of adding Sc is to increase theyield strength of the alloy allowing for a down-gaugingof the wall thickness which in turn gives a strongerlsquospring-rsquo or lsquotrampoline-rsquo effect when the ball hits thebat

Shortly after the introduction of the Sc containingbats Easton also launched Sc-containing 7xxx tubingfor bicycle frames Just as in the bats Sc increases theyield strength of the alloy allowing for down-gauging oftube wall thickness and a corresponding weight reduc-tion of the bicycle frame An Italian manufacturer ofbicycle tubing Dedacciai also delivers tubes in a Sc-containing 7xxx alloy

Other sports equipment made from Sc-containingaluminium alloys includes lacrosse sticks and tent polesSmith and Wesson has also introduced a series ofhandguns where the frame is made from a Sc-containingAl alloy

A common factor for the items mentioned above isthat the material cost is only a minor part of the totalmanufacturing cost of the end product and also thatthese products are aimed at a group of customers thathave a certain awareness of new materials Both baseballbats and bicycle frames have been marketed aslsquoscandium alloyrsquo even though the Sc content is muchlower than 1

Currently AlndashSc master alloys for the production ofSc-containing Al alloys are available at a price thatcorresponds to US$ 2000 per kg of Sc This means that ifone wants to add 02 wt-Sc to an alloy which is afairly common content one also increases the price ofthe alloy by US$ 4 per kg alloy Depending on the alloytype Sc is added to this represents a tripling orquadrupling of the price of the alloy There are notmany existing products where such an increase inmaterial cost can be justified In order to see awidespread use of Sc in high-volume products the Scprice has to come down considerably Actually the priceof adding Sc to Al alloys has gone down by a factor 3ndash10over the last 10ndash15 years and substantial price reduc-tions are also expected in the future

30 Observed variations in corrosion potential and passi-

vation current densities with Sc content in binary Alndash

Sc alloys based on data from Ref 263

Roslashyset and Ryum Scandium in aluminium alloys

International Materials Reviews 2005 VOL 50 NO 1 39

The current production of AlndashSc master alloys isbased upon and will continue to be based upon for theforeseeable future the reduction of Sc2O3 or other Sccompounds directly in molten aluminium It is notnecessary as many tend to believe to take the route viametallic Sc Thus the price of AlndashSc master alloy isgoverned by the price of Sc2O3 or other Sc compoundsin question and not by the price of metallic scandiumThe Sc2O3 which is the main source for todayrsquos AlndashScmaster alloy production comes from stockpiles in theformer USSR These stockpiles will be exhausted withina few years and new reliable sources of Sc2O3 or otherSc compound production are sought It turns out thatthe most economically viable option that has beendisclosed so far is the processing of Red Mud from theBayer process of extracting alumina from bauxiteScandium is enriched in the Red Mud and is extractedfrom a Red Mud aqueous slurry by selective leachingsubsequent ion-exchange procedure and finally a liquidndashliquid extraction procedure It is not required to build aseparate lsquoSc factoryrsquo to do this but rather build an lsquoadd-onrsquo to existing Bayer process plants Such a processroute is expected to bring down the price of Sc2O3

considerably which in turn means that AlndashSc masteralloy price should drop accordingly Preliminary ana-lyses suggest a price of approx US$ 400 per kg Sc in themaster alloy which translates to an added cost of 80cent per kilo when 02 wt-Sc is added to an aluminiumalloy This is also a considerable increase in the materialcost but with such prices one should expect to see Sccontaining alloys in many more applications than whatis the case at the present time

Concluding remarksThe body of published investigations on Al-based alloyswith Sc addition provides a sound basis of knowledgefor metallurgists that want to look into the possibility ofenhancing the performance of a wrought Al-alloy byadding Sc to it Ternary AlndashScndashX phase diagrams areavailable for practically every technologically importantalloying element in Al The effect of a wide range ofternary alloying elements on the precipitation behaviourof Al3Sc is accounted for It has been shown that theAl3Sc phase can be effective as a grain refiner adispersoid former and a precipitate hardening agentand some of the underlying conditions for achieving thedesired Al3Sc formation have been outlined Addingsome Zr together with Sc has proven to be beneficial Itmay lead to effective grain refinement at a lower Sc levelbut the most prominent effect is the refinement indispersoid distribution that can be achieved An addi-tion of Sc has little if any effect on precipitation in the2xxx 6xxx and 7xxx alloy systems and some effects onthe precipitation in AlndashLi based alloys With respect tocorrosion behaviour adding Sc to an Al-alloy does ingeneral seem to make the alloy slightly more noble andto increase its self-corrosion resistance Scandium-containing Al alloys have very few uses at the presenttime as a result of the high price of scandium The priceof Sc is expected to decrease significantly in the futureand this should lead to the disclosure of moreapplications where it is economically feasible to takeadvantage of the improved properties of some Sc-containing aluminium alloys

References1 D R Lide lsquoCRC handbook of chemistry and physicsrsquo 71st edn

4ndash29 1990 Boston USA CRC Press

2 E M Savitsky V F Terehova I V Burov and O P Naumkin

Proc Fourth Conf on lsquoRare earth researchrsquo Phoenix Arizona

USA April 1964 409ndash420

3 E M Savitskii V F Terekhova I V Burov O P Naumkin and

I A Markova Inorg Mater 1965 1 1503ndash1512

4 O P Naumkin V T Terekhova and E M Savitskiy Russ

Metall 1965 (4) 128ndash136

5 W G Moffatt lsquoThe handbook of binary phase diagramsrsquo 1981

Schenectady NY USA General Electric Co

6 E A Brandes (ed) lsquoSmithells metals reference bookrsquo 6th edn

1983 London UK Butterworths

7 R P Elliott and F A Shunk Bull Alloy Phase Diagrams 1981

2 (2) 222ndash223

8 K A Gschneider Jr and F W Calderwood Bull Alloy Phase

Diagrams 1989 10 34ndash36

9 H Okamoto J Phase Equil 1991 12 612ndash613

10 J L Murray J Phase Equil 1998 19 380ndash384

11 M E Drits E S Kadaner T V Dobatkina and N I Turkina

Russ Metall 1973 (4) 152ndash154

12 S-I Fujikawa M Sugaya H Takei and K-I Hirano J Less-

Common Met 1979 63 87ndash97

13 N Blake and M A Hopkins J Mater Sci 1985 20 2861ndash2867

14 V I Kononenko and S V Golubev Russ Metall 1990 (2) 193ndash

195

15 T B Massalski J L Murray L H Bennett and H Baker (eds)

lsquoBinary alloy phase diagramsrsquo 1986 Metals Park OH USA

ASM

16 G Cacciamani P Riani G Borzone N Parodi A Saccone

R Ferro A Pisch and R Schmid-Fetzer Intermetallics 1999 7

101ndash108

17 H Okamoto J Phase Equil 2000 21 310

18 A F Norman P B Pragnell and R S McEwen Acta Mater

1998 46 5715ndash5732

19 I N Pyagai and A V Vakhobov Russ Metall 1990 (5) 50ndash52

20 C L Fu J Mater Res 1990 5 971ndash979

21 X Lu and Y Wang Calphad 2002 26 555ndash561

22 R R Sawtell and J W Morris Jr Proc lsquoDispersion strengthened

aluminium alloysrsquo Phoenix Arizona USA January 1988 409ndash

420

23 R R Sawtell and C L Jensen Metall Trans A 1990 21A 421ndash

430

24 L A Willey Unpublished research Alcoa 1970 Data points are

extracted from Ref 10

25 N I Turkina and V I Kuzmina Russ Metall 1976 (4) 179ndash

183

26 T Torma E Kovacs-Csetenyi I Vitanyi M Butova and

J Stepanov Proc 6th Int Symp on lsquoHigh purity materials in

science and technologyrsquo Akademie der Wissenschaften der DDR

Dresden Germany May 1985 388ndash389

27 A L Berezina V A Volkov B P Domashnikov and K V

Chuistov Metallofizika 1987 9 (5) 43ndash47

28 H-H Jo J Korean Inst Metals 1990 28 499ndash504

29 H-H Jo and S-I Fujikawa Mater Sci Eng 1993 A 171 151ndash

161

30 S Celotto and T J Bastow Philos Mag A 2000 80 1111ndash1125

31 J Roslashyset and N Ryum submitted to Mater Sci Eng

32 M E Drits L S Toropova Yu G Bykov F L Gushchina V I

Elagin and Yu A Filatov Russ Metall 1983 (1) 150ndash153

33 L S Toropova D G Eskin M L Kharakterova and T V

Dobatkina lsquoAdvanced aluminum alloys containing scandium

structure and propertiesrsquo 1998 Amsterdam The Netherlands

Gordon and Breach Science Publishers

34 V V Cherkasov P P Pobezhimov L P Nefedova E V Belov

and G M Kuznetsov Met Sci Heat Treat 1996 (6) 268ndash270

35 Kh O Odinaev I N Ganiev V V Kinzhibalo and B Ya

Kotur Dokl Akad Nauk Tadzh SSR 1989 32 37ndash38

36 Kh O Odinaev I N Ganiev and A V Vakhobov Russ Metall

1991 (4) 200ndash203

37 J Grobner R Schmid-Fetzer A Pisch G Cacciamani P Riani

N Parodi G Borzone A Saccone and R Ferro Z Metallkd

1999 90 872ndash880

38 E A Marquis and D N Seidman Microsc Microanal 2002 8

(Suppl 2) 1100CDndash1101CD

39 A Pisch J Grobner and R Schmid-Fetzer Mater Sci Eng A

2000 A 289 123ndash129

Roslashyset and Ryum Scandium in aluminium alloys

40 International Materials Reviews 2005 VOL 50 NO 1

40 C Xia F Zeng and Y Gu Trans Nonferrous Met Soc China

2003 13 1124ndash1127

41 M Yu Teslyuk and V S Protasov Sov Phys Crystallogr 1966

10 470ndash471

42 M L Kharakterova and T V Dobatkina Russ Metall 1988

(6) 175ndash178

43 M L Kharakterova Russ Metall 1991 (4) 195ndash199

44 L S Toropova M L Kharakterova and D G Eskin Russ

Metall 1992 (3) 194ndash199

45 P Riani L Arrighi R Marazza D Mazzone G Zanicchi and

R Ferro J Phase Equil Diff 2004 25 22ndash52

46 A T Tyvanchuk T I Yanson B Ya Kotur O S Zarechnyuk

and M L Kharakterova Russ Metall 1988 (4) 190ndash192

47 L L Rokhlin T V Dobatkina and M L Kharakterova Powder

Metall Met Ceram 1997 36

48 A Z Ikromov I N Ganiev and V V Kinzhibalo Dokl Akad

Nauk Tadzh SSR 1990 (6) 391ndash392

49 I N Ganiev A Z Ikromov and V G Khudoiberdiev Russ

Metall 1995 (3) 125ndash127

50 I N Fridlyander L L Rokhlin T V Dobatkina and N I

Nikitina Met Sci Heat Treat 1993 (10) 567ndash571

51 I N Fridlyander L L Rokhlin T V Dobatkina V V

Kinzhibalo and A T Tyvanchuk Russ Metall 1998 (1) 161ndash

166

52 R A Emigh E L Bradley and J W Morris Jr in lsquoLight-weight

alloys for aerospace applications IIrsquo (ed E W Lee and N J

Kim) 27ndash43 1991 TMS

53 L S Toropova A N Kamardinkin V V Kindzhibalo and A T

Tyvanchuk Phys Met Metall 1990 70 (6) 106ndash110

54 A N Kamardinkin T V Dobatkina and T D Rostova Russ

Metall 1991 (4) 216ndash218

55 L S Torodskaya T V Dobatkina and A N Kamardinkin

Russ Metall 1992 (5) 128ndash131

56 E M Sokolovskaya E F Kazakova E I Poddyakova and A

A Ezhov Met Sci Heat Treat 1997 (5) 211ndash213

57 Y Harada and D C Dunand Mater Sci Eng 2002 A 329ndash331

686ndash695

58 N E Drits L S Toropova and F L Gushchina Russ Metall

1984 (4) 229ndash232

59 E M Sokolovskaya E F Kazakova V A Alikhanov and E V

Zhuravleva Moscow Univ Chem Bull 1997 52 (5) 70ndash72

60 E M Sokolovskaya E F Kazakova and E I Poddyakova Met

Sci Heat Treat 1989 (11) 837ndash839

61 G M Cheldieva E F Kazakova E M Sokolovskaya and N I

Kaloev Russ Metall 1990 (6) 87ndash90

62 E M Sokolovskaya E F Kazakova and O D-S Kendivan

Russ Metall 1998 (4) 135ndash137

63 N G Bukhanko E F Kazakova and E M Sokolovskaya Russ

Metall 2001 (4) 425ndash431

64 E D Trubnyakova O I Bodak I N Ganiev and A V

Vakhobov Russ Metall 1987 (3) 219ndash222

65 I N Fridlyander and L V Molchanova Russ Metall 2003 (5)

476ndash480

66 R A Altynbaev S Kh Khairidinov and A V Vakhobov Russ

Metall 1987 (4) 194ndash196

67 J C Schuster and J Bauer J Less-Common Met 1985 109

345ndash350

68 L L Rokhlin A S Fridman T V Dobatkina and D G Eskin

Russ Metall 1991 (6) 146ndash148

69 A S Fridman T V Dobatkina and E V Muratova Russ

Metall 1992 (1) 207ndash209

70 C Xia F Zeng and Y Gu Trans Nonferrous Met Soc China

2003 13 546ndash552

71 F Zeng C Xia and Y Gu J Alloys Comp 2004 363 175ndash181

72 L L Rokhlin T V Dobatkina N R Bochvar and E V Lysova

J Alloys Comp 2004 367 10ndash16

73 T V Dobatkina A S Fridman and E V Muratova Russ

Metall 1992 (5) 125ndash127

74 I N Fridlyander L L Rokhlin N R Bochvar E V Lysova

and O V Boteva Russ Metall 2001 (6) 661ndash666

75 V N Rechkin L K Lamikhov and T I Samsonova Sov Phys

Crystallogr 1964 9 325ndash327

76 I I Zalutskii and P I Kripyakevich Sov Phys Crystallogr

1967 12 341ndash343

77 T J Bastow C T Forwood M A Gibson and M E Smith

Phys Rev B 1998 58 2988ndash2997

78 K Fukunaga M Kolbe K Yamada and Y Miura Mater Sci

Eng 1997 A 234ndash236 594ndash597

79 E P George J A Horton W D Porter and J H Schneibel

J Mater Res 1990 5 1639ndash1648

80 E P George D P Pope C L Fu and J H Schneibel ISIJ Int

1991 31 1063ndash1075

81 Y Harada and D C Dunand Acta Mater 2000 48 3477ndash3487

82 J H Schneibel and E P George Scripta Metall Mater 1990 24

1069ndash1074

83 J H Schneibel and P M Hazzledine Mater Res Soc Symp

Proc 1991 213 323ndash328

84 J H Schneibel and P M Hazzledine J Mater Res 1992 7

868ndash875

85 C J Sparks E D Specht G E Ice P Zschack and J Schneibel

Mater Res Soc Symp Proc 1991 213 363ndash368

86 J Tarnacki and Y-W Kim Scripta Metall Mater 1989 23

1063ndash1068

87 M Asta V Ozolins and C Woodward JOM 2001 53 (9) 16ndash

19

88 M E Drits L S Toropova F L Gushchina and S G Fedotov

Sov Non-Ferrous Met Res 1984 12 83ndash85

89 Y Harada and D C Dunand Scripta Mater 2003 48 219ndash222

90 C Woodward M Asta G Kresse and J Hafner Phys Rev B

2001 63 094103-1-6

91 J-H Xu and A J Freeman Phys Rev B 1990 41 12553ndash12561

92 M F Bartholomeusz and J A Wert Acta Metall Mater 1992

40 673ndash682

93 G Bester and M Fahnle J Phys Condens Matter 2001 13

11551ndash11565

94 C L Fu and M H Yoo Proc lsquoOrdered intermetallics ndash physical

metallurgy and mechanical behaviorrsquo Irsee Germany June 1991

155ndash164

95 K Fukunaga T Shouji and Y Miura Mater Sci Eng 1997 A

239ndash240 202ndash205

96 D P Pope Proc lsquoOrdered intermetallics ndash physical metallurgy

and mechanical behaviorrsquo Irsee Germany June 1991 143ndash153

97 J-S Wang Acta Mater 1998 46 2663ndash2674

98 M H Yoo and C L Fu Mater Sci Eng 1992 A 153 470ndash478

99 R W Hyland Jr and R C Stiffler Scripta Metall Mater 1991

25 473ndash477

100 I G Brodova I V Polents O A Korzhavina P S Popelrsquo I P

Korshunov and V O Esin Melts 1992 4 392ndash397

101 I G Brodova O A Chikova I V Polents P S Popelrsquo and V O

Esin Casting Processes 1992 1 (2) 158ndash160

102 I G Brodova D V Bashlikov and I V Polents Mater Sci

Forum 1998 269ndash272 589ndash594

103 K B Hyde A F Norman and P B Pragnell Mater Sci Forum

2000 331ndash337 1013ndash1018

104 K B Hyde A F Norman and P B Pragnell Acta Mater 2001

49 1327ndash1337

105 J Roslashyset and N Ryum Proc 6th Int Conf on lsquoAluminum

alloysrsquo Toyohashi Japan July 1998 793ndash798

106 V I Elagin V V Zakharov and T D Rostova Met Sci Heat

Treat 1993 (6) 317ndash319

107 R W Hyland Jr Metall Trans A 1992 23A 1947ndash1955

108 B A Parker Z F Zhou and P Nolle J Mater Sci 1995 30

452ndash458

109 C L Rohrer M D Asta S M Foiles and R W Hyland Jr

Mater Res Soc Symp Proc 1996 398 477ndash482

110 G M Novotny and A J Ardell Mater Sci Eng 2001 A 318

144ndash154

111 J D Robson M J Jones and P B Pragnell Acta Mater 2003

51 1453ndash1468

112 C Tan Z Zheng and B Wang Proc 3rd Int Conf on

lsquoAluminium alloysrsquo Vol I NTH Trondheim Norway June

1992 290ndash294

113 M Nakayama A Furuta and Y Miura Mater Trans JIM

1997 38 852ndash857

114 E A Marquis and D N Seidman Acta Mater 2001 49 1909ndash

1919

115 M J Jones and F J Humphreys Acta Mater 2003 51 2149ndash

2159

116 E A Marquis D N Seidman and D C Dunand in lsquoCreep

deformation fundamentals and applicationsrsquo (ed R S Mishra

J C Earthman and S V Raj) 299ndash308 2002 TMS

117 D N Seidman E A Marquis and D C Dunand Acta Mater

2002 50 4021ndash4035

118 E A Marquis D N Seidman and D C Dunand Acta Mater

2003 51 285ndash287

119 M E Drits L S Toropova U G Bikov and G K Anastaseva

Proc lsquoDiffusion in metals and alloysrsquo Tihany Hungary Augustndash

September 1982 616ndash623

120 V I Elagin V V Zakharov and T D Rostova Met Sci Heat

Treat 1983 (7) 546ndash549

Roslashyset and Ryum Scandium in aluminium alloys

International Materials Reviews 2005 VOL 50 NO 1 41

121 M Ye Drits L B Ber Yu G Bykov L S Toropova and G K

Anastaseva Phys Met Metall 1984 57 (6) 118ndash126

122 M E Drits L S Toropova and Yu G Bykov Sov Non-Ferrous

Met Res 1985 13 309ndash314

123 V I Yelagin V V Zakharov S G Pavlenko and T D Rostova

Phys Met Metall 1985 60 (1) 88ndash92

124 N Sano Y Hasegawa K Hono H Jo K Hirano H W

Pickering and T Sakurai Journal de Physique 1987 48 C6 337ndash

342

125 N Sano H-H Jo K-I Hirano and T Sakurai J Jpn Inst

Metals 1989 39 444ndash450

126 N Sano H Jo K Hirano and T Sakurai Proc Second Int

Conf on lsquoAluminium alloysrsquo Beijing China October 1990 549ndash

554

127 Y Miura M Nakayama and A Furuta Proc lsquoAspects of high

temperature deformation and fracture in crystalline materialsrsquo

Nagoya Japan July 1993 255ndash262

128 Y W Riddle and T H Sanders Jr Mater Sci Forum 2000

331ndash337 939ndash944

129 Y W Riddle M McIntosh and T H Sanders Jr in lsquoLightweight

alloys for aerospace application VIrsquo (ed K Jata E W Lee

W Frazier and N J Kim) 25ndash39 2001 TMS

130 M E Drits J Dutkiewicz L S Toropova and J Salawa Crystal

Res Technol 1984 19 1325ndash1330

131 Y W Riddle MSc thesis Georgia Tech GA USA 1998

132 T J Bastow and S Celotto Mater Sci Eng 2003 C 23 757ndash

762

133 M C Carroll M J Mills G S Daehn P I Gouma M F

Savage and B R Dunbar in lsquoAutomotive Alloys 1999rsquo (ed

S Das) 239ndash246 2000 TMS

134 E Clouet M Nastar and C Sigli Phys Rev B 2004 69 064109-

1-14

135 V V Zakharov Met Sci Heat Treat 1997 (2) 61ndash66

136 J W Christian lsquoThe theory of transformation in metals and

alloysrsquo 2nd edn 1975 Pergamon Press Ltd

137 A L Berezina V A Volkov B P Domashnikov S V Ivanov

and K V Chuistov Phys Metals 1990 10 296ndash304

138 S-I Fujikawa and S Sakauchi Proc 6th Int Conf on

lsquoAluminum alloysrsquo Toyohashi Japan July 1998 805ndash810

139 Y S Touloukian R K Kirby R E Taylor and P D Desai

(eds) lsquoThermal expansion metallic elements and alloysrsquo 1975

New York Plenum

140 J Roslashyset and N Ryum submitted to Scripta Mater

141 R O Simmons and R W Balluffi Phys Rev 1960 117 52ndash61

142 M Ocko E Babic R Krsmik E Girt and B Leontic J Phys F

Metals Phys 1976 6 703ndash707

143 M J Jones and F J Humphreys Proc First Joint Int Conf on

lsquoRecrystallization and grain growthrsquo Aachen Germany August

2001 Springer Verlag 1287ndash1292

144 S Iwamura M Nakayama and Y Miura Mater Sci Forum

2002 396ndash402 1151ndash1156

145 S Iwamura and Y Miura Acta Mater 2004 52 591ndash600

146 M Asta S M Foiles and A A Quong Phys Rev B 1998 57

11265ndash11275

147 R W Hyland Jr M Asta S M Foiles and C L Rohrer Acta

Mater 1998 46 3667ndash3678

148 J Roslashyset and N Ryum Proc 4th Int Conf on lsquoAluminium

alloysrsquo Vol I Atlanta GA USA September 1994 194ndash201

149 M E Drits L S Toropova G K Anastaseva and G L

Nagornichnykh Russ Metall 1984 (3) 192ndash195

150 E A Marquis D N Seidman and D C Dunand Acta Mater

2003 51 4751ndash4760

151 M E Drits L S Toropova and Yu G Bykov Met Sci Heat

Treat 1983 (7) 550ndash554

152 V V Zakharov and T D Rostova Met Sci Heat Treat 1995

(2) 65ndash69

153 M Nakayama and Y Miura Proc 4th Int Conf on lsquoAluminium

alloysrsquo Vol I Atlanta GA USA September 1994 538ndash545

154 M Nakayama and Y Miura J Jpn Inst Light Metals 1996 46

275ndash279

155 M Nakayama T Okuyama and Y Miura Mater Sci Forum

2000 331ndash337 927ndash932

156 M Nakayama T Okuyama and Y Miura Proc 6th Int Conf

on lsquoAluminum alloysrsquo Toyohashi Japan July 1998 517ndash522

157 M L Kharakterova D G Eskin and L S Toropova Acta

Metall Mater 1994 42 2285ndash2290

158 V I Elagin V V Zakharov and T D Rostova Met Sci Heat

Treat 1992 (1) 37ndash45

159 H Wiik Siv Ing thesis NTH Institute of Metallurgy

Trondheim Norway 1995

160 J Roslashyset H Hovland and N Ryum Mater Sci Forum 2002

396ndash402 619ndash624

161 Y Miura K Horikawa K Yamada and M Nakayama Proc

4th Int Conf on lsquoAluminium alloysrsquo Vol II Atlanta GA USA

September 1994 161ndash168

162 Y W Riddle PhD thesis Georgia Tech GA USA 2000

163 B Forbord W Lefebvre F Danoix H Hallem and

K Marthinsen Scripta Mater 2004 51 333ndash337

164 J D Robson Acta Mater 2004 52 1409ndash1421

165 C B Fuller J L Murray and D N Seidman submitted to Acta

Mater 2004

166 M G Mousavi C E Cross and Oslash Grong Sci Technol Weld

Joining 1999 4 381ndash388

167 J S Vetrano S M Bruemmer L M Pawlowski and I M

Robertson Mater Sci Eng 1997 A 238 101ndash107

168 Y W Riddle and T H Sanders Jr Mater Sci Forum 2000

331ndash337 799ndash803

169 G M Khan A O Nikiforov V V Zakharov and I I Novikov

Tsvetnye Metally 1993 34 (11) 43ndash45

170 Z Horita M Furukawa M Nemoto A J Barnes and T G

Langdon Acta Mater 2000 48 3633ndash3640

171 L A Willey US Patent 3 619 181 9 November 1971

172 L K Lamikhov and G V Samsonov Tsvetnye Metally 1964 5

(8) 77ndash80

173 A L Berezina K V Chuistov N I Kolobnev L B

Khokhlatova and T A Monastyrskaya Mater Sci Forum

2002 396ndash402 741ndash746

174 F A Fasoyinu J Thomson D Cousineau T Castles and M

Sahoo Proc 6th Int AFS Conf on lsquoMolten aluminum

processingrsquo Orlando FL USA November 2001

175 Z Yin Q Pan Y Zhang and F Jiang Mater Sci Eng 2000

A 280 151ndash155

176 I I Novikov and O E Grushko Mater Sci Technol 1995 11

926ndash932

177 D Cousineau M Sahoo P D Newcombe T Castles and F A

Fasoyinu Proc lsquoAFS 105th casting congressrsquo Dallas TX USA

AprilndashMay 2001 157ndash184

178 C E Cross and Oslash Grong Proc 6th Int Conf on lsquoAluminum

alloysrsquo Toyohashi Japan July 1998 1441ndash1446

179 F A Costello J D Robson and P B Prangnell Mater Sci

Forum 2002 396ndash402 757ndash762

180 K B Hyde A F Norman and P B Prangnell Mater Sci

Forum 2002 396ndash402 39ndash44

181 M E Drits S G Pavlenko L S Toropova Yu G Bukov and

L B Ber Sov Phys Dokl 1981 26 (3) 344ndash346

182 A M Drits and B A Kopeliovich Russ Metall 1985 (4) 147ndash

151

183 V G Davydov V I Elagin V V Zakharov and T D Rostova

Met Sci Heat Treat 1996 (8) 347ndash352

184 M E Drits L S Toropova Yu G Bykov L B Ber and S G

Pavlenko Russ Metall 1982 (1) 148ndash152

185 T D Rostova V G Davydov V I Yelagin and V V Zakharov

Mater Sci Forum 2000 331ndash337 793ndash798

186 Y W Riddle H Hallem and N Ryum Mater Sci Forum 2002

396ndash402 563ndash568

187 J Roslashyset and Y W Riddle Proc 9th Int Conf on lsquoAluminium

alloysrsquo Brisbane Australia August 2004 1210ndash1215

188 A M Diskin V K Portnoi A M Drits and A A Alalykin Sov

Non-Ferrous Met Res 1986 14 499ndash500

189 R R Sawtell P E Bretz and C L Jensen US Patent 4 689 090

25 August 1987

190 G A Salishchev Yu B Timoshenko and R A Saitova Proc

Second Int Conf on lsquoAluminium alloysrsquo Beijing China October

1990 413ndash415

191 T G Nieh R Kaibyshev L M Hsiung N Nguyen and

J Wadsworth Scripta Mater 1997 36 1011ndash1016

192 T G Nieh L M Hsiung J Wadsworth and R Kaibyshev Acta

Mater 1998 46 2789ndash2800

193 J S Vetrano C H Henager Jr M T Smith and S M

Bruemmer in lsquoHot deformation of aluminum alloys IIrsquo (ed T R

Bieler L A Lalli and S R MacEwen) 407ndash418 1998 TMS

194 J S Vetrano C H Henager Jr S M Bruemmer Y Ge and

C H Hamilton in lsquoSuperplasticity and Superplastic Forming

1998rsquo (ed A K Gosh and T R Bieler) 89ndash97 1998 TMS

195 V Y Gertsman J S Vetrano C H Henager Jr and S M

Bruemmer Proc First Joint Int Conf on lsquoRecrystallization and

grain growthrsquo Aachen Germany August 2001 Springer Verlag

2001 837ndash842

196 Y Xiao C Gao H Ma and S Tian Trans Nonferrous Met Soc

China 2001 11 235ndash238

Roslashyset and Ryum Scandium in aluminium alloys

42 International Materials Reviews 2005 VOL 50 NO 1

197 A Gholinia F J Humphreys and P B Prangnell Acta Mater

2002 50 4461ndash4476

198 A Gholinia F J Humphreys and P B Prangnell Mater Sci

Forum 2002 408ndash412 1519ndash1524

199 S Komura P B Berbon M Furukawa Z Horita M Nemoto

and T G Langdon Scripta Mater 1998 38 1851ndash1856

200 S Komura P B Berbon A Utsunomiya M Furukawa

Z Horita M Nemoto and T G Langdon in lsquoHot deformation

of aluminum alloys IIrsquo (ed T R Bieler L A Lalli and S R

MacEwen) 125ndash138 1998 TMS

201 S Komura Z Horita M Furukawa M Nemoto and T G

Langdon J Mater Res 2000 15 2571ndash2576

202 S Komura M Furukawa Z Horita M Nemoto and T G

Langdon Mater Sci Eng 2001 A 297 111ndash118

203 S Komura Z Horita M Furukawa M Nemoto and T G

Langdon Metall Mater Trans A 2001 32A 707ndash716

204 Z Horita M Furukawa K Oh-ishi M Nemoto and T G

Langdon Proc Fourth Int Conf on lsquoRecrystallization and

related phenomenarsquo (ed T Sakai and H G Suzuki) 1999 The

Japan Institute of Metals 301ndash308

205 Z Horita S Komura P B Berbon A Utsunomiya

M Furukawa M Nemoto and T G Langdon Mater Sci

Forum 1999 304ndash306 91ndash96

206 Z Horita S Lee S Ota K Neishi and T G Langdon Mater

Sci Forum 2001 357ndash359 471ndash476

207 Z Horita T Fujinami K Sato S B Kang H W Kim and T G

Langdon in Proc James T Staley Honorary Symposium on

Aluminum Alloys lsquoAdvances in the metallurgy of aluminum

alloysrsquo (ed M Tiryakioglu) 271ndash275 2001 ASM

208 P B Berbon S Komura A Utsunomiya Z Horita

M Furukawa M Nemoto and T G Langdon Mater Trans

JIM 1999 40 772ndash778

209 M Nemoto Z Horita M Furukawa and T G Langdon Mater

Sci Forum 1999 304ndash306 59ndash66

210 M Furukawa Z Horita M Nemeto and T G Langdon Proc

lsquoLight Metals 1999rsquo Quebec City PQ Canada August 1999 583ndash

592

211 M Furukawa K Oh-ishi S Komura A Yamashita Z Horita

M Nemeto and T G Langdon Mater Sci Forum 1999 304ndash

306 97ndash102

212 M Furukawa A Utsunomiya K Matsubara Z Horita and

T G Langdon Acta Mater 2001 49 3829ndash3838

213 M Furukawa A Utsunomiya S Komura Z Horita M Nemoto

and T G Langdon Mater Sci Forum 2001 357ndash359 431ndash436

214 M Furukawa Z Horita and T G Langdon in Proc James T

Staley Honorary Symposium on Aluminum Alloys lsquoAdvances in

the metallurgy of aluminum alloysrsquo (ed M Tiryakioglu) 47ndash56

2001 ASM

215 M Furukawa Z Horita M Nemoto and T G Langdon Mater

Sci Eng 2002 A 324 82ndash89

216 M Furukawa Z Horita and T G Langdon in lsquoUltrafine grained

materials IIrsquo (ed Y T Zhu T G Langdon R S Mishra S L

Semiatin M J Saran and T C Lowe) 459ndash468 2002 TMS

217 T G Langdon M Furukawa Z Horita and M Nemoto Proc

NATO Advanced Research Workshop on lsquoInvestigations and

applications of severe plastic deformationrsquo Moscow August

1999 NATO Science Series Series 3 High Technology vol 80

Kluwer Academic Publishers The Netherlands 2000 149ndash154

218 S Lee H Akamatsu A Utsunomiya K Neishi M Furukawa

Z Horita and T G Langdon Proc Thermec 2000 Las Vegas

USA December 2000

219 S Lee A Utsunomiya H Akamatsu K Neishi M Furukawa

Z Horita and T G Langdon Acta Mater 2002 50 553ndash564

220 A Yamashita D Yamaguchi Z Horita and T G Langdon

Mater Sci Eng 2000 A 287 100ndash106

221 K Oh-ishi Z Horita D J Smith and T G Langdon J Mater

Res 2001 16 583ndash589

222 H Akamatsu T Fujinami Z Horita and T G Langdon Scripta

Mater 2001 44 759ndash764

223 S Ota H Akamatsu K Neishi M Furukawa Z Horita and

T G Langdon Mater Trans 2002 43 2364ndash2369

224 K Furuno H Akamatsu K Oh-ishi M Furukawa Z Horita

and T G Langdon Acta Mater 2004 52 2497ndash2507

225 I N Fridlyander O G Senatorova N A Ryazanova and A O

Nikiforov Mater Sci Forum 1994 170ndash172 345ndash349

226 J N Fridlyander and O G Senatorova Mater Sci Forum 1996

217ndash222 1813ndash1818

227 J Liu and D J Chakrabarti Acta Mater 1996 44 4647ndash4661

228 O G Senatorova A N Uksusnikov J N Fridlyander

J Koshorst R R Romanova N A Ryazanova A Galliot

and V V Cherkassov Proc 6th Int Conf on lsquoAluminum alloysrsquo

July 1998 Toyohashi Japan 589ndash593

229 R A Emigh E L Bradley and J W Morris Jr in

lsquoSuperplasticity in aerospace IIrsquo (ed T R McNelley and H C

Heikkenen) 303ndash315 1990 TMS

230 E L Bradley III R A Emigh and J W Morris Jr Scripta

Metall Mater 1991 25 717ndash721

231 N I Kolobnev L B Khokhlatova V D Makarov E Yu

Semenova and V V Redchits Proc Sixth Int Aluminiumndash

Lithium Conference Garmisch-Partenkirchen Germany October

1991 1053ndash1056

232 N K Tsenev R Z Valiev O V Obraztsov and I N Fridlander

Proc Sixth Int AluminiumndashLithium Conference Garmisch-

Partenkirchen Germany October 1991 1125ndash1132

233 A M Shammazov N K Tsenev R Z Valiev M M

Myshlyaev M M Bikbulatov and S P Lebedich Phys Met

Metall 2000 89 (3) 314ndash318

234 F Musin R Kaibyshev Y Motohashi T Sakuma and G Itoh

Mater Trans A 2002 43A 2370ndash2377

235 M Shagiev Y Motohashi F Musin R Kaibyshev and G Itoh

Mater Trans A 2003 44A 1694ndash1697

236 M Shagiev Y Motohashi F Musin R Kaibyshev and G Itoh

Mater Trans A 2003 44A 1698ndash1701

237 B A Parker and Z F Zhou Proc 3rd Int Conf on lsquoAluminium

alloysrsquo Vol I NTH Trondheim Norway June 1992 363ndash367

238 J R Davies lsquoASM specialty handbook aluminum and aluminum

alloysrsquo 1993 Materials Park OH USA ASM

239 S J Andersen H W Zandbergen J Jansen C Traeholt

U Tundal and O Reiso Acta Mater 1998 46 3283ndash3298

240 M L Kharakterova D G Eskin and L L Rokhlin Russ

Metall 1997 (1) 104ndash109

241 J Roslashyset Dr Ing thesis NTNU Trondheim Norway 2002

242 P P Chattopadhyay S Datta and M K Banerjee Mater Sci

Eng 2002 A 333 67ndash71

243 L I Kaigorodova E I Selnikhina E A Tkachenko and O G

Senatorova Phys Met Metall 1996 81 513ndash519

244 Y-L Wu F H Froes C Li and A Alvarez Metall Mater

Trans A 1999 30A 1017ndash1024

245 Z Yin L Yang Q Pan and F Jiang Trans Nonferrous Met

Soc China 2001 11 822ndash825

246 V I Elagin V V Zakharov and T D Rostova Met Sci Heat

Treat 1994 36 (7) 375ndash380

247 Y V Milman A I Sirko D V Lotsko O N Senkov and D B

Miracle Mater Sci Forum 2002 396ndash402 1217ndash1222

248 C-H Joh K Yamada and Y Miura Mater Trans JIM 1999

40 439ndash442

249 X J Jiang Q H Gui Y Y Li L M Ma G J Liang and C X

Shi Scr Metall Mater 1993 29 211ndash216

250 X J Jiang Y Y Li W Deng L Y Xiong W M Wu Y J Gao

and C X Shi Adv Cryogenic Eng (Mater) 1994 40 1369ndash

1376

251 C-H Joh T Katsube K Yamada and Y Miura Proc 6th Int

Conf on lsquoAluminum alloysrsquo Toyohashi Japan July 1998 799ndash

804

252 L I Kaygorodova A M Dritz T V Krymova and I N

Fridlyander Proc Sixth Int AluminiumndashLithium Conference

Garmisch-Partenkirchen Germany October 1991 363ndash367

253 L I Kaigorodova A M Drits Ya V Zhingel T V Krymova

and I N Fridlyander Phys Met Metall 1992 73 286ndash290

254 A L Berezina V A Volkov S V Ivanov N I Kolobnev and

K V Chuistov Phys Met Metall 1991 71 (2) 167ndash175

255 I N Fridlyander N I Kolobnev A L Berezina and K V

Chuistov Proc Sixth Int AluminiumndashLithium Conference

Garmisch-Partenkirchen Germany October 1991 107ndash112

256 L I Kaigorodova A M Drits Ya V Zhingel T V Krymova

and V A Rassokhin Phys Met Metall 1992 73 281ndash285

257 I N Fridlyander S F Danilov E N Malysheva T A

Gorokhova and N N Kirkina Proc Sixth Int Aluminiumndash

Lithium Conference Garmisch-Partenkirchen Germany October

1991 381ndash386

258 G Dlubek S Krause H Krause A L Beresina V S

Mikhalenkov and K V Chuistov J Phys Condens Matter

1992 4 6317ndash6328

259 S Krause H Krause G Dlubek A L Beresina and K S

Chuistov Mater Sci Forum 1992 105ndash110 1109ndash1112

260 C Y Tan Z Q Zheng and S Q Liang Proc 4th Int Conf on

lsquoAluminium alloysrsquo Vol II Atlanta GA USA September 1994

329ndash333

261 A L Beresina N I Kolobnev K V Chuistov A V Kotko and

O A Molebny Mater Sci Forum 2002 396ndash402 977ndash981

Roslashyset and Ryum Scandium in aluminium alloys

International Materials Reviews 2005 VOL 50 NO 1 43

262 I N Ganiev I Yunusov and V V Krasnoyarskii J Appl Chem

USSR 1986 60 1961ndash1965

263 I N Ganiev Prot Met 1995 31 543ndash546

264 N V Vyazovikina Prot Met 1999 35 448ndash453

265 G V Kharina and V P Kochergin Prot Met 1996 32 134ndash

136

266 G V Kharina M V Kuznetsov and V P Kochergin Russ J

Electrochem 1998 34 482ndash485

267 V S Sinyavskii V D Valrsquokov and E V Titkova Prot Met

1998 34 549ndash555

268 Y L Wu F H Froes C G Li and J Liu Proc lsquoSynthesis

processing of lightweight metallic materials IIrsquo Orlando FL

USA February 1997 73ndash81

269 Z Ahmad and B J Abdul-Aleem Proc EuroCorr 2000

270 Z Ahmad A Ul-Hamid and B J Abdul-Aleem Corros Sci

2001 43 1227ndash1243

271 R Braun B Lenczowski and G Tempus Mater Sci Forum

2000 331ndash337 1647ndash1652

272 T Torma E Kovacs-Csetenyi L Vitalis I Vitanyi

J Stepanov and M Butova Mater Sci Forum 1987 1314

497ndash503

273 Z Wang P Wang K S Kumar and C L Briant in lsquoChemistry

and electrochemistry of corrosion and stress corrosion crackingrsquo

(ed R H Jones) 573ndash582 2001 TMS

274 V I Elagin V V Zakharov A A Petrova and E V

Vyshegorodtseva Russ Metall 1983 (4) 143ndash146

Roslashyset and Ryum Scandium in aluminium alloys

44 International Materials Reviews 2005 VOL 50 NO 1

Page 13: Scandium in aluminium alloys - Atom probe · A considerable part of the available literature on scandium in aluminium alloys is reviewed. ... behaviour in Al Cu, Al Mg Si,

sustained by Ref 135 it has recently been reported150

that precipitation of Al3Sc at 300 and 350uC occursslightly faster in an Alndash2 wt-Mgndash02 wt-Sc alloythan in an Alndash02 wt-Sc alloy studied previously by thesame researchers117118 and that the correspondinghardness increase is highest in the AlndashMgndashSc alloyThe only reported difference in experimental procedureis the solutionising temperature which was higher forthe AlndashSc alloy (648uC) than for the AlndashMgndashSc alloy(617uC) However given that the nucleation time isshortened by quenched-in vacancies as suggested byHyland107 the difference in homogenisation tempera-ture should be in favour of a faster precipitation of thebinary AlndashSc alloy It should be worthwhile to probedeeper into this observation of different aging responses

Mg in solid solution increases the lattice parameter ofthe Al matrix This is in turn expected to influence thecritical diameter for AlAl3Sc coherency loss as discussedin the section on lsquoLoss of coherency during growth ofAl3Sc precipitatesrsquo above Such an influence on the criticaldiameter is also briefly discussed elsewhere150 A criticaldiameter of 80 nm in an Alndash3 wt-Mgndash02 wt-Sc alloyhas been observed compared to 40 nm in a binary Alndash02 wt-Sc alloy of the same investigation144 Otherresearchers have reported a critical diameter in excess of116 nm in an Alndash63 wt-Mgndash02 wt-Sc alloy151

Computer simulations predict that the AlAl3Scinterface should be enriched in Mg87 These predictionsare confirmed experimentally by three-dimensional atomprobe microscopy of an Alndash2 wt-Mgndash02 wt-Sc alloyaged at 300uC38 Here it was found that the Mg contentat the interface is approximately three times higher thanthe matrix concentration regardless of aging time

Copper

It has been claimed that Cu suppresses the tendencytowards discontinuous precipitation of Al3Sc106

Zakharov and Rostova152 have reported that additionsof up to 14 wt-Cu have only minor effects on theprecipitation kinetics in an Alndash04 wt-Sc alloy Themost noticeable effect is that for temperatures above400uC the late stage of the transformation is sloweddown for the highest Cu contents This does not show in

Fig 21 however where only the 10 and 60transformation curves are included

The W-phase (AlCuSc) was observed in the alloywith the highest Cu content which means that less Sc isavailable for the precipitation of Al3Sc in this alloyAnother investigation on the age hardening response ofAlndash023 wt-Sc and Alndash25 wt-Cundash023 wt-Sc at300uC also implies that the precipitation behaviour ofAl3Sc in the two alloys is similar153154 At 350uC alimited portion of the Al3Sc has been observed tonucleate heterogeneously on coarse hrsquo precipitates155

According to the isothermal sections of the phasediagram43 one should expect the ternary W-phase toform instead of the Al3Sc phase in an alloy with such ahigh CuSc ratio However no observations of the W-phase or other ternary phases were reported from TEMstudies of the Alndash25 wt-Cundash023 wt-Sc alloy thathad been heat treated in the temperature range 300ndash460uC153ndash156 A third investigation on the precipitationin Alndash048 wt-Sc alloys with up to 440 wt-Cu in thetemperature range 100ndash450uC also concludes that no W-phase or other ternary phase forms during the heattreatment157

Copper in solid solution decreases the lattice para-meter of the Al matrix Thus it is expected that the misfitbetween Al and Al3Sc precipitates should be higher in

21 C-curves for 10 and 60 transformation in Alndash

04 wt-Sc and Alndash14 wt-Cundash04 wt-Sc redrawn

from Ref 152

Table 6 Reported values of interphase energy cAlAl3Sc between coherent Al3Sc precipitates and Al matrix

Reference cAlAl3Sc mJ m22 Method of estimation

137 10 Fit of coarsening data to LifshitzndashSlezev equation107 78iexcl20 (288uC) Back-calculation of incubation time

93iexcl20 (343uC)107 123iexcl41 (288uC) Back-calculation of nucleation rate

125iexcl35 (343uC)29 542 (400uC) Fit of coarsening data to Ostwald ripening

632 (430uC)413 (460uC)

146 c(100) 192 (0 K) c(111) 226 (0 K) Pseudopotential calculations147 c(100) 325 (0 K) c(110) 513 (0 K) c(111)

782 (0 K) c(100) 315 (288uC) c(100) 325 (343uC)Atomistic simulation

110 105 Fit of coarsening data to LSW theory31 20ndash300 Fit of coarsening data to Ostwald ripening

for 16 different temperatures111 57 Fit of precipitation model to experimental data145 120 coherent particles Fit of coarsening data

170 semicoherent particles

It is argued in this study that c may be lower in the nucleation stage

Roslashyset and Ryum Scandium in aluminium alloys

International Materials Reviews 2005 VOL 50 NO 1 31

AlndashCundashSc alloys compared to AlndashSc alloys Howeveran experimental investigation of Alndash25 wt-Cundash023 wt-Sc alloy comes to a different conclusion Thelattice misfit strain is found to decrease compared to Alndash02 wt-Sc and the critical diameter for coherency losswas found to be the same in the ternary and the binaryalloy144 It is suggested that these observations may bebecause of the dissolution of some Cu in the Al3Sc phaseand thus that the lattice parameters of both the Al matrixand the Al3Sc precipitates decrease in the ternary alloy

Silicon

It has been found that the onset of precipitation in Alndash04 wt-Sc is only slightly altered when Si contents ofup to 04 wt are introduced in the alloy However thefinal stage of the precipitation reaction is considerablydelayed with increasing Si content135 Figure 22 showsthe effect of addition of a joint of 035 wt-Si and040 wt-Fe There are at least two possible explana-tions for why an Si-addition leads to this behaviour

1 Alloying with Si is known to promote discontin-uous precipitation of Al3Sc106158 It has been shown thatwhen isothermal precipitation of Al3Sc starts discon-tinuously the later stage of the overall transformationcan be very slow31

2 The isothermal section of the phase diagramsuggests that the V-phase (AlSc2Si2) should form inalloys of this composition46 If the V-phase forms lessSc is available for precipitation of Al3Sc

It has been shown157 that for an AlndashScndashSi alloy withsolid solution content of 010 wt-Sc an 110 wt-Sithe only phases to precipitate after heat treatment at200uC are Si and an (AlScSi)-phase possibly the V-phase On the other hand the Al3Sc phase has beenobserved to form in alloys with 04 wt-Sc and up to08 wt-Si159160

Zinc

It has been reported that additions of up to 5 wt- Znhave only minor effects on the precipitation kinetics ofan Alndash04 wt-Sc alloy135 (Fig 23) In Ref 106 it isclaimed that Zn promotes discontinuous precipitation ofAl3Sc

Lithium

A comparison of the age hardening response at 400uC inAlndash24 wt-Lindash019 wt-Sc and Alndash024 wt-Sc alloys

indicates that the onset of Al3Sc-precipitation is notaffected by the presence of Li161

Zirconium

As mentioned in the section on lsquoTernary phase diagramswith dispersoid-forming elementsrsquo earlier a considerableamount of Zr is dissolved in the Al3Sc phase and thus amore correct denotation of the precipitating phase isAl3(Sc12xZrx) In discussing the influence of the Zrcontent on the precipitation of Al3Sc one is thereforeactually discussing the difference in precipitation ofAl3Sc versus Al3(Sc12xZrx)

It is found that an addition of 015 wt-Zr to an Alndash04 wt-Sc alloy only marginally affects the initial stageof the precipitation reaction123135 while it slows downthe later stages of the transformation considerably(Fig 24)135 The coarsening rate of the Al3(Sc12xZrx)particles in AlndashScndashZr alloys is found to be much slowerthan that of Al3Sc particles in AlndashSc alloys123162

In three-dimensional atom probe field ion microscopy(3D-APFIM) of Al3(Sc12xZrx) particles formed at 475uCin a ternary AlndashScndashZr alloy163 it was found that the coreof the particles is almost pure Al3Sc whereas there is ashell of Al3(Sc12xZrx) with almost equal content of Scand Zr Such a behaviour has also been predicted bycomputer modelling of precipitation of Al3(Sc12xZrx) at480uC in an AlndashZnndashMgndashScndashZr alloy164 This modelpredicts that Zr starts to enter the growing

22 C-curves for 10 and 60 transformation in Alndash

04 wt-Sc and Alndash04 wt-Fendash035 wt-Sindash04 wt-Sc

redrawn from Ref 135

23 C-curves for 10 and 60 transformation in Alndash

04 wt-Sc and Alndash5 wt-Znndash04 wt-Sc redrawn

from Ref 135

24 C-curves for 10 and 60 transformation in Alndash

04 wt-Sc and Alndash04 wt-Scndash015 wt-Zr redrawn

from Ref 135

Roslashyset and Ryum Scandium in aluminium alloys

32 International Materials Reviews 2005 VOL 50 NO 1

Al3(Sc12xZrx) particles when approximately half of thesupersaturated Sc has been precipitated The Zr contentof the outer shell is predicted to be much higher thanwhat has been found experimentally163164

Another 3D-APFIM study of Al3(Sc12xZrx) particlesin a ternary AlndashScndashZr alloy has been reported165 Hereparticles grown at 300uC for various lengths of time werestudied The Zr content in these particles was muchlower than that reportedpredicted at higher tempera-tures163164 even after very long annealing times

Iron

The effect of adding up to 07 wt-Fe on the precipita-tion kinetics in an Alndash04 wt-Sc alloy has beeninvestigated135 The onset of precipitation was onlyslightly influenced by the Fe-level whereas the laterstages of the transformation however were significantlyslowed down as the Fe-level increased An example ofthe effect of a joint addition of Fe and Si is shown inFig 22

Manganese chromium and titanium

Small additions (03 wt-) of manganese or chromiumto Alndash040 wt-Sc alloys are reported to have onlyminor effects on the precipitation kinetics of Al3Sc135

According to Ref 106 Mn is reported to promote andCr and Ti to suppress discontinuous precipitation

Rare earth elements

An investigation of the precipitation behaviour of Alndash03 at-Sc and Alndash03 at-Scndash03 at-X alloyswhere X is either yttrium gadolinium holmium orerbium in the temperature range 235ndash310uC indicatedthat a Al3(Sc12xXx) phase with L12 structure wasformed in the ternary alloys22 Peak strength is reportedto occur after approx 10 h at 285uC in all alloys whichindicates that the precipitation kinetics up to peakstrength is practically unaltered by the ternary additions

Influence of Sc on microstructure andproperties of wrought aluminium alloysMost of the effects of Sc addition in wrought Al-alloysare linked to the formation of the Al3Sc phase In atypical processing route of a wrought aluminium alloyparticles of the Al3Sc phase can form under threedifferent conditions each of which influences themicrostructure and properties of the alloy in a specificway

1 During solidification after casting or weldingAl3Sc particles can form in the melt and act as nucleifor a-Al thus leading to grain refinement18166

2 High temperature processing of the alloy in therange 400ndash600uC for instance homogenisation hot-rolling or extrusion can give a dense distribution ofAl3Sc particles of typically 20ndash100 nm size The particledistributions formed under such conditions are reportedto lead to good recrystallisation resistance128148167168

and enhanced superplasticity52169170

3 Heat treatment in the range 250ndash350uC can lead tosignificant precipitation hardening of an alloy super-saturated in Sc148158171 The size of strengthening Al3Scprecipitates is typically in the range 2ndash6 nm121

Grain refinementA good grain refinement is almost always desired uponsolidification The formation of small equiaxed grainsrather than long dendrites in the melt facilitates thefeeding of the melt into cavities of the shrinkingsolidified metal and thus reduces the problem ofshrinkage porosity The tendency to hot cracking is alsoreduced and the second phase particles become morefinely and uniformly distributed

To the authorsrsquo knowledge the first effect of Sc in Al-alloys that was reported in an international scientificjournal was the grain refining action in pure Al and in anAlndashCu alloy upon solidification172 which was found tobe stronger for Sc than for other transition metals Inlater studies of Sc as a grain refiner in pure Al1832173 ithas been demonstrated that approx 07 wt-Sc issufficient to provide excellent grain refinement It hasalso been demonstrated that additions of 025 wt-Scz025 wt-Zr provide good grain refinement in pure Al18

In order for Sc to act as an effective grain refiner theAl3Sc phase has to form in the melt before thesolidification of a-Al The Al3Sc particles have a latticeparameter close to that of pure Al and whenhypereutectically formed the Al3Sc particles are veryeffective substrates for the nucleation of the a-Al phaseAs mentioned in the section on lsquoFormation of Al3Sc inAlndashSc alloysrsquo above this requires that the alloy ishypereutectic with respect to Sc ie in excess of approx06 wt- in a binary AlndashSc alloy In ternary and higherorder systems the eutectic Sc composition may dependon the other alloying elements present For instance theeutectic composition of Sc has been predicted todecrease with increasing Mg content in the ternary AlndashMgndashSc system39 This prediction is sustained by theobservation of good grain refinement by adding 05 wt-Sc to an Alndash7 wt-Mg alloy174 (Other examples ofgrain refinement at Sc concentrations lower than that ofthe binary eutectic are found in Ref 173)

Similarly the observation of good grain refinement inan Alndash025 wt-Scndash025 wt-Zr alloy18 may be as aresult of a lower Sc content of the eutectic in the ternarysystem ie less Sc is needed to make the alloy hyper-eutectic No literature data on the liquidus surface of theAlndashScndashZr system are available and thus this hypothesiscannot be confirmed In more complex alloy systems itis also observed that excellent grain refinement isachieved at low Sc contents when Sc is added togetherwith Zr It is reported that adding either 02 wt-Sc06 wt-Sc or 01 wt-Zr to an Alndash5Mg alloy givesmuch poorer grain refinement than adding 02 wt-Scz01 wt-Zr175 Similarly additions of 015 wt- ofeither Sc or Zr are reported to only marginally refinethe grain structure in an AlndashCundashLi alloy whereas a jointaddition of 015 wt-Sc and 015 wt-Zr gives excellentgrain refinement176 For an AA 3650 casting alloy (Alndash7 wt-Sindash04 wt-Mg) good grain refinement is achievedby adding 039 wt-Sc or 027 wt-Scz019 wt-Zr177

In some AlndashZnndashMgndashScndashZr alloys it is also found thatan addition of 02ndash03 wt-Sc can be sufficient for goodgrain refinement166169178179 Examples of the grainrefinement as a function of Sc addition in pure Al andin an AlndashZnndashMgndashZr alloy are shown in Fig 25

The nucleation of a-Al on Al3Sc particles in the melt isfacilitated by the close match in the lattice parameters ofthe two phases As shown in Fig 17 the mismatch at the

Roslashyset and Ryum Scandium in aluminium alloys

International Materials Reviews 2005 VOL 50 NO 1 33

eutectic temperature of binary AlndashSc alloys (660uC) isonly approx 047 In Refs 57 and 89 it is shown thatwhen Zr Hf and in particular Ti is dissolved in the Al3Scparticles this reduces the lattice parameter of the phaseIt appears that when 25 of the Sc atoms in Al3Sc aresubstituted by Ti the mismatch is zero at approx 550uCand becomes negative at higher temperatures89 Thissuggests that by carefully selecting the Ti content of thealloy it should be possible to obtain Al3(ScTi)substrates in the melt that match exactly the latticeparameter of the nucleating a-Al and thus furtherimprove the grain refinement of the alloy This appearsto have been achieved in a recent work180 where thegrain refinement of an Alndash07 wt-Sc alloy wascompared with that of an Alndash05 wt-Scndash02 wt-Tialloy At a cooling rate of 100 K s21 only an estimated2 of the primary Al3Sc particles of the binary AlndashScalloy were effective nuclei compared to practically 100for the primary Al3(ScTi) particles in the ternary AlndashScndashTi alloy leading to a much smaller grain size in theternary alloy Whereas the match of lattice parametersmay be of importance for these results the authors ofthis investigation180 draw attention to other factors suchas different growth restriction factors for Sc and Ti andthe possibility of a peritectic reaction in the ternaryalloy Nevertheless the principle of matching latticeparameters is worth looking into further in future work

Effects from dispersoidslsquoDispersoidsrsquo is a term which is commonly used aboutthe classes of second phase particles that are formedin an Al alloy during high temperature annealing orthermomechanical processing such as homogenisationhot rolling extrusion and forging A dense distributionof dispersoids can give a significant contribution to analloyrsquos strength owing to particle strengthening but thisis rarely the main strengthening mechanism A moreimportant contribution from the dispersoids is theirability to stabilise the grainsubgrain structure of analloy through the Zener-drag action and thus improvethe mechanical properties of the alloy

There are two noticeable dispersoid-related effectsthat have been reported for Sc-containing alloys Thefirst is the stabilising effect on a deformed microstruc-ture When a non-recrystallised structure is preserved inan alloy this can add considerably to the mechanical

strength of the material The second effect is thepreservation of a small grain size during hot deforma-tion at slow deformation rates which is necessary toobtain superplastic properties of an Al-alloy

Recrystallisation resistance

The anti-recrystallisation effect of Sc was first publishedin a patent171 where 03 wt-Sc was added to pure Aland to AlndashMg AlndashMn and AlndashZnndashMg alloys Both Sc-free and Sc-containing materials were cold worked andsubsequently annealed and it was found that theaddition of Sc increased the temperature for onset ofrecrystallisation by approx 220uC in pure Al andsomewhat less in the Al-alloys Although the author ofthe patent171 may have been well aware that the anti-recrystallisation effect is caused by Al3Sc dispersoidsthis is not mentioned in the text The first journal paperthat explicitly points out that the recrystallisationresistance is due to Al3Sc dispersoids was an investiga-tion of the effects of adding Sc to wrought AlndashMgalloys181 In this work it was found that the Al3Scdispersoids were very effective in preventing recrystalli-sation up to temperatures of approx 400ndash450uC Athigher temperatures the dispersoids coarsen consider-ably and the microstructure was partially recrystallised

It is established that the Zener-drag pZ that is imposedon an advancing grain boundary by randomly distrib-uted dispersoids can be expressed in the form

pZ~k f =r (3)

where k is a factor that includes the interface energybetween the dispersoids and the matrix f is the volumefraction and r is the mean radius of the dispersoids Thusthe Zener drag will decrease rapidly in the case where thedispersoids are coarsening

As mentioned in the section on lsquoInfluence of otherelements on precipitation of Al3Scrsquo above theAl3(Sc12xZrx) dispersoids in a ternary AlndashScndashZr alloycoarsen at a much slower rate than the Al3Sc dispersoidsin a binary AlndashSc alloy This effect was first reported inRef 123 (although also observed in Ref 182) andaccording to Ref 33 the same authors demonstratedsoon after that the denser dispersoid distributionachieved in an AlndashScndashZr alloy leads to superiorrecrystallisation resistance compared to a binary AlndashScalloy An example of the increased recrystallisationresistance by adding both Zr and Sc is shown in Fig 26

In isothermal sections of the ternary AlndashScndashZr phasediagram it is indicated that the solid solubility ofSczZr is somewhat higher than that of Sc alone54 Ithas also been demonstrated both by electrical con-ductivity measurements (Fig 27) and microstructuralobservations that the supersaturation of SczZr isgreater than that of only Sc or Zr in as cast Alndash15(SczZr) alloys183 This indicates that it should bepossible to increase the volume fraction of dispersoids inAlndashScndashZr compared to AlndashSc It is suggested162 that theincreased volume fraction that can be achieved byadding both Sc and Zr can be advantageous inconventional wrought Al-alloys

There are at least two different conditions underwhich Al3Sc or Al3(Sc12xZrx) dispersoids can form toprevent recrystallisation

1 Sc (or Sc and Zr) is in solid solution before thedeformation In the case of cold deformation and

25 Grain refinement as a function of Sc addition in pure

Al (redrawn from Ref 32) and AlndashZnndashMgndashZr (redrawn

from Ref 169) note that data points are plotted on

different ordinate axes

Roslashyset and Ryum Scandium in aluminium alloys

34 International Materials Reviews 2005 VOL 50 NO 1

subsequent annealing the Al3Sc or Al3(Sc12xZrx)dispersoids may nucleate and grow before the nucleationand growth of recrystallised grains takes placeDispersoids can form after a direct up-quench to theannealing temperature115143148184 during ramp-up tothe annealing temperature115 or by pre-annealing at anintermediate temperature129 In the case of hot deforma-tion the Al3Sc or Al3(Sc12xZrx) dispersoids maynucleate and grow during preheating of the materialand during the hot deformation itself184

2 The Al3Sc or Al3(Sc12xZrx) dispersoids are formedin the material before deformation184 Considering coldrolling and subsequent annealing the annealing tem-perature Tann may be either lower or higher than thetemperature Tdisp at which the dispersoids were formedIf TannTdisp only limited if any coarsening of thedispersoids is expected to take place and thus the Zenerdrag from the particles is expected to be practicallyconstant The driving force for recrystallisation how-ever is expected to decrease somewhat with theannealing time as a result of recovery processes Thusif recrystallisation does not occur within short annealingtimes the material is expected to remain unrecrystallisedfor infinite time at the annealing temperature IfTannTdisp there will be substantial coarsening of thedispersoids during annealing In order for the materialto remain unrecrystallised the decrease in driving forcefor recrystallisation owing to recovery has to be at leastas rapid as the decrease in Zener drag because of particlecoarsening

Experimental comparisons of the conditions abovepoint in the direction that the recrystallisation resistanceis poorest when Sc (or Sc and Zr) is in solid solutionbefore deformation and the deformed material is up-quenched to the annealing temperature148 or when Al3Scor Al3(Sc12xZrx) dispersoids are formed before defor-mation at TdispampTann184185 Excellent recrystallisationresistance is achieved if dispersoids are formed at anintermediate anneal of solutionised and deformedmaterial128 or if dispersoids are formed at TdispTann

before deformation148185ndash187 It seems that the decreasein Zener drag because of dispersoid coarsening in many

cases is slower than the decrease in driving force forrecrystallisation because of recovery processes Thusthere is an advantage in forming a high number densityof small dispersoids which for most practical casesmeans that they should be formed at TdispTann122

When an advancing high angle grain boundary iethe recrystallisation front is passing a coherent Al3Scdispersoid there are at least three possible grainboundarydispersoid interactions

1 The Al3Sc dispersoid retains its global orientationrelationship and thus loses its coherency with thesurrounding matrix

2 The Al3Sc dispersoid rotates as the grain boundarypasses either by diffusional processes at the dispersoidmatrix interface or by the grain boundary passingthrough the dispersoid and the Al3Sc dispersoidassumes the same crystallographic orientation as theAl matrix of the recrystallised grain

3 The Al3Sc dispersoid dissolves at the grainboundary and re-precipitates in the recrystallised grain

Which interactions that actually take place willprobably depend on the dispersoid size annealingtemperature and driving force for recrystallisation It isalso possible that alloy composition (other elementsthan Al) is of importance

It has been reported that large (Oslash about 100ndash150 nm)Al3Sc dispersoids in a deformed Alndash4 wt-Mgndash02 wt-Sc alloy annealed at 575uC lose the orientationrelationship with the matrix after being passed by therecrystallisation front148

A rotation of somewhat smaller Al3Sc dispersoids in arecrystallising binary Alndash025 wt-Sc alloy has beenreported115143 The rotation was reported to be accom-panied by substantial growth (from Oslash 30 nm to Oslash48 nm) as a result of enhanced Sc diffusion at the grainboundary Observations suggested that the grainboundaries were passing through the dispersoids andthus the Al3Sc dispersoids retained the orientationrelationship with the recrystallised Al matrix

Dissolution and re-precipitation of Al3Sc dispersoidshas been reported during recrystallisation of a 50 coldrolled Alndash02 wt-Sc alloy162 Large spherical partially

26 Fraction recrystallised structure in cold rolled sheets

of Alndash04 wt-Sc and Alndash04 wt-Scndash015 wt-Zr as a

function of annealing temperature redrawn from

Ref 183 27 Electrical conductivity in Alndash15(SczZr) alloys

redrawn from Ref 183

Roslashyset and Ryum Scandium in aluminium alloys

International Materials Reviews 2005 VOL 50 NO 1 35

coherent dispersoids were observed to dissolve at therecrystallisation front and re-precipitate as smallercoherent Al3Sc cuboids

Superplastic forming

It seems that the first publication on superplasticproperties of Sc-containing Al-alloys was a study of anAlndash35Cundash14Mgndash045Mnndash04(SczZr) alloy188

It was recognised that the superplastic properties are aresult of the stabilisation of the fine grain structure byAl3Sc dispersoids The Sc-containing Al alloys that havereceived most attention for their superplastic propertieshowever are those of the AlndashMgndashSc system which wasfirst published in a patent189 Here it was noted that anAlndash4 wt-Mgndash05 wt-Sc alloy had superior superplasticproperties compared to fine-grained 7475 (AlndashZnndashMgndashCu alloy) Binary Alndash05 wt-Sc and Alndash4 wt-Mgalloys did not behave superplastically The flow stress atthe hot forming temperature was found to be much (30ndash40) lower in the ternary alloy than that of the twobinary alloys

The superplastic properties of AlndashMgndashSc alloys havebeen explored by several research groups over the lastdecade190ndash196 It has frequently been found that thedeformation mechanism is dominated by grain bound-ary sliding190 However it has also been reported thatAlndashMgndashSc alloy may deform superplastically withoutnoticeable grain boundary sliding23 It is generallyrecognised that the grain boundary sliding mechanismis facilitated when the average grain size is very smalland grain boundaries are predominantly high-angleSuch a microstructure may be achieved by carefulthermomechanical processing of the starting mate-rial193194197198 It has however been shown that a finegrained structure with high angle boundaries maydevelop during superplastic forming of AlndashMgndashSc alloyseven if the starting microstructure is an entirely differentone for instance that of a cold rolled sheet192 It has alsobeen suggested that superplastic forming of as castmaterial may be possible189

One of the more efficient thermomechanical processesfor achieving an ultrafine grain structure with high anglegrain boundaries in Al-alloys is equal channel angularpressing (ECAP) A JapanesendashAmerican group ofscientists has published an impressive body of researchon improvements in superplastic properties in Al-alloys processed by ECAP over the last few years andseveral of the publications are from investigations onAlndashMgndashSc alloys170199ndash224 Maximum strains in excessof 2000 at a strain rate of 0033 s21 have beenachieved170201202217 which is an extraordinarily goodcombination of high strain and high strain rate for analuminium alloy

Superplastic properties of AlndashCundashMg(ndashMn)ndashSc(ndashZr)and AlndashMgndashSc(ndashZr) alloys have been mentionedNoticeable superplasticity in other Sc-containing Al-alloys has also been reported such as AlndashZnndashMg(ndashCu)ndashScndashZr169225ndash228 AlndashLindashSc229 AlndashMgndashLindashScndashZr229ndash234

AlndashLindashMgndashCundashScndashZr235236 and AlndashCundashLindashScndashZr233

Precipitation hardeningHardening by Al3Sc precipitates

It has been noted that when Al3Sc particles precipitate inthe temperature range 250ndash350uC they give a significanthardness increase in the alloy Some authors point out

that Sc is a more effective precipitation hardening elementper atomic fraction added than the elements that arecommonly used for precipitation hardening121130 (In onepaper29 it is claimed that only Au has a strongerstrengthening effect than Sc) However the amount ofSc that can be precipitated from supersaturated solidsolution is rather limited and thus the absolute values ofthe hardness increase from the precipitation hardening ismuch lower than what is normally associated withprecipitation hardened alloys Also the temperatureregime for age hardening by precipitation of Al3Sc issomewhere in between the temperature regimes for agehardening and solution heat treatments of commonprecipitation hardened alloys This makes a combinedprecipitation of Al3Sc and other strengthening precipi-tates unfeasible Thus precipitation strengthening byAl3Sc is most feasible in alloy systems that are non-heat-treatable The non-heat-treatable aluminium alloy sys-tems are according to the Aluminum Associationdesignations the 1xxx series (99 pure Al) the 3xxxseries (AlndashMn) and the 5xxx series (AlndashMg) The purposeof adding Sc to these alloys may be either to stabilise themicrostructure of wrought semiproducts (extrusionsrolled plates forgings etc) as discussed in the sectionon lsquoRecrystallisation resistancersquo above or to provideextra strength to the alloy through precipitation hard-ening In the latter case it is appropriate to considerwhether the Sc-containing alloy still should be classifiedas non-heat-treatable A heat treatment is applied thatbrings about a significant precipitation hardening On theother hand the hardness increase that is achieved throughthe heat treatment is lower than what is normallyassociated with heat-treatable alloy systems Hence eventhough it seems like a contradiction one chooses to keepusing the term lsquonon-heat-treatablersquo about these alloys

Table 7 gives an overview of some mechanicalproperties of Sc-containing non-heat-treatable alloysthat are reported in the literature Most of theexperimental work on Sc in 1xxx-types of alloys hasbeen done on binary AlndashSc alloys with much higherpurity than industrial alloys

Strengthening mechanisms

When the precipitates are larger than a critical size thestrengthening effect is due to the Orowan-mechanism iedislocations can only pass the precipitates by looping Inthis case the strengthening effect of the particles isapproximately inversely proportional to the mean parti-cle spacing When the precipitates can be sheared bydislocations there are a number of strengthening mechan-isms that apply It is proposed by Parker et al108 that thetwo major contributing mechanisms are coherency strainand anti-phase-boundary energy In a recent detailedstudy of strengthening mechanisms in binary AlndashSc alloysby Marquis and colleagues117118 the strengthening fromshear modulus mismatch between the matrix and theprecipitates is also accounted for A qualitatively goodmatch between theoretical strengthening and measuredvalues is achieved in this work both for deformation atroom temperature and at 300uC

Effect of Sc on precipitation strengthening in heat-treatablealloys

Following the AA designation system the traditionalheat-treatable Al-alloys are those that belong to the 2xxx

Roslashyset and Ryum Scandium in aluminium alloys

36 International Materials Reviews 2005 VOL 50 NO 1

series (AlndashCu) 6xxx series (AlndashMgndashSi) and 7xxx series(AlndashZnndashMg) AlndashLi alloys should also be mentionedSeveral investigations have been carried out in order toclarify the effects of Sc on the precipitation behaviour inthese alloy systems

AlndashCu alloys

The precipitation sequence in AlndashCu alloys is oftendescribed as follows

Supersaturated solid solutionRGP-zonesRh0Rh9Rh(Al2Cu)

The highest strength is normally achieved when the h0or h9 precipitates are predominant Typical precipitationheat treatment temperatures for AlndashCu alloys are in therange 160ndash190uC238 which is considerably lower thanthe typical precipitation temperature for Al3ScComparisons of the aging responses of AlndashCu and AlndashCundashSc alloys at 150 and 200uC indicate that there is nonoticeable effect of Sc on the precipitation kinetics ofh9153 It is observed that the h9 precipitates may nucleateon Al3Sc particles153 At 300uC it is observed that h9particles are somewhat smaller in AlndashCundashSc alloys thanin AlndashCu alloys156

AlndashMgndashSi alloys

The following precipitation sequence is commonlyreported for AlndashMgndashSi alloys

Supersaturated solid solutionRGP-zonesRb0Rb9Rb(Mg2Si)

For peak aged alloys the predominant precipitatetype is b0 for which the stoichiometric composition hasrecently been resolved to be Mg5Si6239 Temperatures inthe range 160ndash205uC are typically used for precipitationhardening of these alloys238 Adding both 03 wt-Scand 01 wt-Zr to an Alndash06 wt-Mgndash065 wt-Sialloy does not seem to alter the precipitation kineticsof b0 at 165uC However the hardness increase becauseof precipitation hardening appears to be smaller in theSczZr-containing alloy240 In another investigationadditions of 01 wt-Sc 015 wt-Sc 02 wt-Sc04 wt-Sc and 02 wt-Scz01 wt-Zr were made toan Alndash08 wt-Mgndash07 wt-Si alloy241 Here it wasalso observed that the precipitation kinetics of b0 wasseemingly independent of the Sc additions (Fig 28)TEM observations indicated that the b0 precipitateswere of comparable sizes in the investigated alloys andno interactions between Al3Sc and b0 were observed(Fig 29) In a third study242 where the effect of Sc onthe precipitation in an AlMgSindashSiC metal matrixcomposite was investigated there also does not seemto be any effect on the precipitation kinetics Howevercontrary to the findings of Ref 240 it is reported thatthe Sc addition leads to a higher hardness increase thanin the corresponding Sc free alloy

AlndashMgndashZn alloys

For these alloys the following precipitation sequence isoften ascribed

Table 7 Mechanical properties in non-heat-treatable Al-alloys with Sc

Reference Alloy wt- YS MPa UTS MPa Note

1xxx alloys171 000Sc 15 48 Cast material aged 288uC8 h

023Sc 159 185 Cast material aged 288uC8 h038Sc 199 220 Cast material aged 288uC8 h000Sc 14 49 Cold rolled material (89) aged 288uC8 h023Sc 198 208 Cold rolled material (89) aged 288uC8 h038Sc 240 264 Cold rolled material (89) aged 288uC8 h000Sc 8 34 Cold rolled material quenched from 649uC aged 288uC8 h023Sc 147 157 Cold rolled material quenched from 649uC aged 288uC8 h038Sc 193 199 Cold rolled material quenched from 649uC aged 288uC8 h

121 05Sc 160 ndash Forged material quenched from 635uC aged 250uC50 h23 05Sc 298 319 Hot rolled 288uC cold rolled 69ndash81 aged 288uC4 h112 01Sc 132 166 Hot z cold rolled material quenched from 630uC

aged 320uC133 h148 02Sc 138 ndash Cast material aged 300uC10 h compression test159 04Sc 196 ndash Cast material aged 300uC10 h compression test117 118 03Sc 209 ndash Cast material quenched from 648uC aged 300uC5 h

compression test3xxx alloys171 1Mn 015Sc 216 221 Cold rolled material (89) aged 288uC8 h

1Mn 05Sc 309 323 Cold rolled material (89) aged 288uC8 h186 05Mn 02Mg

026Sc 015Zr162 201 Extruded material solutionised 600uC aged 250uC

5xxx alloys171 1Mg 43 111 Cold rolled material (89) aged 288uC8 h

1Mg 03Sc 288 303 Cold rolled material (89) aged 288uC8 h53Mg 147 259 Cold rolled material (50) wintermediate anneals

at 343uC aged 288uC8 h53Mg 03Sc 368 401 Cold rolled material (50) wintermediate anneals

at 343uC aged 288uC8 h23 2Mg 05Sc 376 401 Hot rolled 288uC cold rolled 69ndash81 aged 288uC4 h

4Mg 05Sc 414 4606Mg 05Sc 433 503

237 4Mg 1Sc 420 525 Cold rolled material (83) aged 320uC1 h148 4Mg 02Sc 194 ndash Cast material aged 300uC10 h compression test

Tensile test data except where noted YS yield strength UTS ultimate tensile strength

Roslashyset and Ryum Scandium in aluminium alloys

International Materials Reviews 2005 VOL 50 NO 1 37

Supersaturated solid solutionRGP-zonesRg9Rg(Zn2Mg)

The maximum hardness is normally achieved whenthe g9 precipitates are predominant Common precipita-tion hardening temperatures are in the range 95ndash180uCand a two-step precipitation heat treatment within thistemperature regime is often used238 It has beenobserved in some investigations that Sc and SczZradditions to AlndashMgndashZn alloys slow down the precipita-tion of g9 somewhat243 Other investigations find thatthere is no effect of Sc on the precipitation behaviour ofg9244245 and yet others report that Sc additionssignificantly speed up the precipitation of g9246 In Ref247 it is found that an Sc addition leads to coarser g9precipitates and it is claimed that this gives an improvedductility of the alloy The strength-loss associated withlarger particle size is reported to be counterbalanced bystrengthening from Al3Sc precipitates

AlndashLi alloys

The precipitation sequence in binary AlndashLi alloys isapparently simple

Supersaturated solid solutionRd9Rd (AlLi)

where d9 is the metastable Al3Li phase which just likeAl3Sc has the L12 type of atomic arrangement Thetypical temperature regime for precipitation of d9 whichis the strengthening phase in this system is approx 150ndash200uC A comparison of the age hardening response ofan Alndash26 wt-Li and an Alndash24 wt-Lindash019 wt-Scalloy at 180uC248 and 200uC161 indicates that the onsetof d9 precipitation is not altered by the presence of ScThe hardness curves for the two alloys are practicallyidentical at 200uC whereas at 180uC the peak hardnesslevel is slightly higher in the AlndashLi than the AlndashLindashScalloy DSC measurements at constant heating ratesindicate that the addition of Sc to an AlndashLi alloysincreases the activation energy for d9 precipitation andmoves the exothermic peak associated with d9 precipita-tion to a higher temperature248 For specimens aged at

either 180uC or 200uC TEM observations reveal that thed9 precipitates are much smaller in the Sc containingalloy than in binary AlndashLi both in the peak agedcondition and in the overaged condition161248 Additionof Sc has also been observed to reduce the size of d9precipitates in other AlndashLi based alloys249ndash251 In an AlndashLindashCundashZr alloy an addition of Sc has been reported toslow down the homogeneous precipitation of d9252253 Ithas been claimed that Sc reduces the quench sensitivityand delays room temperature aging of AlndashLi basedalloys254ndash256

When present in the microstructure before the pre-cipitation of d9 the Al3Sc precipitates may act as effec-tive nucleation sites for d9 The resulting precipitates arespheres of d9 with a core of Al3Sc161249252ndash255257ndash261

Corrosion resistanceAn appreciable amount of data is available on the effectsof Sc on the corrosion behaviour of wrought Al-alloysSome of these effects are apparently derived from theeffects of Sc on the microstructure of the alloys It hasbeen reported that an addition of Sc increases thecorrosion potential (makes it less negative) in pureAl262ndash264 in AlndashZn alloys265266 AlndashMg alloys267 AlndashZnndashMgndashCu alloys264268 AlndashCundashMgndashMn alloys264 andin AlndashCundashLindashMgndashAg alloys264 Even though Sc alsohas been reported to decrease the corrosion potential in

28 Age hardening response at 175uC for Alndash08 wt-Mgndash

07 wt-Si alloy (Base) with additions of 02 wt-Sc

04 wt-Sc and 02 wt-Scz01 wt-Zr from Ref 241

29 TEM images of a b0 precipitates in Alndash08 wt-Mgndash

07 wt-Si alloy and b b0 and Al3(Sc1ndashxZrx) in a similar

alloy with addition of 02 wt-Scz01 wt-Zr from

Ref 241

Roslashyset and Ryum Scandium in aluminium alloys

38 International Materials Reviews 2005 VOL 50 NO 1

AlndashMg alloys269270 it seems that the general trend isthat adding Sc to an alloy makes it slightly more nobleThe change in corrosion potential is much morepronounced when Sc is added in amounts larger thanthe eutectic composition263 ie there is a considerablecontribution from primary or eutectic Al3Sc to theoverall potential It has also been demonstrated that thechange in corrosion potential caused by Sc can dependon the heat treatment applied to the alloy267268

Even though the corrosion potential is an essentialparameter in establishing the corrosion behaviour of analloy an increase in the corrosion potential does notnecessarily imply an improved self-corrosion resistanceHowever measurements of corrosion rates and passiva-tion current densities strongly suggest that the self-corrosion resistance in general is considerably improvedwhen Sc is added to wrought Al-alloys263264267 Someobserved variations in corrosion potential and passiva-tion current densities with Sc content in binary AlndashScalloys are plotted in Fig 30

Material failure in corrosive environments is often dueto localised corrosion attacks which may propagaterapidly even though the bulk material has a goodresistance against general corrosion It has been pointedout that hypereutectic additions of Sc may lead tomicrogalvanic corrosion beside primary Al3Sc parti-cles264 In AlndashMg alloys grain boundary precipitation ofAl8Mg5 can lead to localised corrosion attacks such asintergranular corrosion (IGC) exfoliation corrosion(EC) and stress corrosion cracking (SCC) In wroughtmaterial such precipitation may occur in the 60ndash180uCtemperature regime and heating in this temperaturerange is referred to as lsquosensitationrsquo An AlndashMgndashSc alloywas found to be immune against intergranular corrosionand have moderate susceptibility to exfoliation corro-sion after annealing at 350uC271 After sensitation heattreatments severe IGC and EC was observed but notquite as severe as in a corresponding alloy without ScAs for SCC the AlndashMgndashSc alloy was found to be highlyresistant271 In another study it was found that additionof 056 wt-Sc reduces the SCC susceptibility of an Alndash68 wt-Mg alloy in the as-rolled state and afterannealing at 250uC whereas in a sensitised specimenthe SCC susceptibility is somewhat increased by the Scaddition272 A third investigation found that Sc has nomeasurable detrimental effect on the SCC susceptibilityof sensitised Alndash5Mgndash015Zr alloy273 SCC is also a

severe problem in high strength AlndashZnndashMgndashCu alloys Ithas been shown that small Sc additions are effective inreducing the SCC sensitivity of these alloys244246268274

Use of Sc-containing Al alloysA systematic development of Sc-containing aluminiumalloys took place in the former USSR in the 1980s andthe interest for Sc as an alloying element in aluminiumalloys hit the western world approximately 10 yearslater Even though a number of improvements in Alalloys achieved by Sc addition have been demonstratedthe current uses of such alloys are very limited This isrelated to the very high price of scandium

In Russia some parts of military aircraft are made ofSc-containing AlndashLi alloys In the western world themain usage of Sc-containing alloys is for sportsequipment Ashurst Technology and Kaiser Aluminumdeveloped a Sc-containing 7xxx alloy for baseball andsoftball bats which was introduced to the Americanmarket in 1997 by Easton Alcoa soon followed with aSc-containing alloy for a competing brand of batsLouisville Slugger Since then several new and improvedSc-containing alloys for bats have been introduced tothe market The purpose of adding Sc is to increase theyield strength of the alloy allowing for a down-gaugingof the wall thickness which in turn gives a strongerlsquospring-rsquo or lsquotrampoline-rsquo effect when the ball hits thebat

Shortly after the introduction of the Sc containingbats Easton also launched Sc-containing 7xxx tubingfor bicycle frames Just as in the bats Sc increases theyield strength of the alloy allowing for down-gauging oftube wall thickness and a corresponding weight reduc-tion of the bicycle frame An Italian manufacturer ofbicycle tubing Dedacciai also delivers tubes in a Sc-containing 7xxx alloy

Other sports equipment made from Sc-containingaluminium alloys includes lacrosse sticks and tent polesSmith and Wesson has also introduced a series ofhandguns where the frame is made from a Sc-containingAl alloy

A common factor for the items mentioned above isthat the material cost is only a minor part of the totalmanufacturing cost of the end product and also thatthese products are aimed at a group of customers thathave a certain awareness of new materials Both baseballbats and bicycle frames have been marketed aslsquoscandium alloyrsquo even though the Sc content is muchlower than 1

Currently AlndashSc master alloys for the production ofSc-containing Al alloys are available at a price thatcorresponds to US$ 2000 per kg of Sc This means that ifone wants to add 02 wt-Sc to an alloy which is afairly common content one also increases the price ofthe alloy by US$ 4 per kg alloy Depending on the alloytype Sc is added to this represents a tripling orquadrupling of the price of the alloy There are notmany existing products where such an increase inmaterial cost can be justified In order to see awidespread use of Sc in high-volume products the Scprice has to come down considerably Actually the priceof adding Sc to Al alloys has gone down by a factor 3ndash10over the last 10ndash15 years and substantial price reduc-tions are also expected in the future

30 Observed variations in corrosion potential and passi-

vation current densities with Sc content in binary Alndash

Sc alloys based on data from Ref 263

Roslashyset and Ryum Scandium in aluminium alloys

International Materials Reviews 2005 VOL 50 NO 1 39

The current production of AlndashSc master alloys isbased upon and will continue to be based upon for theforeseeable future the reduction of Sc2O3 or other Sccompounds directly in molten aluminium It is notnecessary as many tend to believe to take the route viametallic Sc Thus the price of AlndashSc master alloy isgoverned by the price of Sc2O3 or other Sc compoundsin question and not by the price of metallic scandiumThe Sc2O3 which is the main source for todayrsquos AlndashScmaster alloy production comes from stockpiles in theformer USSR These stockpiles will be exhausted withina few years and new reliable sources of Sc2O3 or otherSc compound production are sought It turns out thatthe most economically viable option that has beendisclosed so far is the processing of Red Mud from theBayer process of extracting alumina from bauxiteScandium is enriched in the Red Mud and is extractedfrom a Red Mud aqueous slurry by selective leachingsubsequent ion-exchange procedure and finally a liquidndashliquid extraction procedure It is not required to build aseparate lsquoSc factoryrsquo to do this but rather build an lsquoadd-onrsquo to existing Bayer process plants Such a processroute is expected to bring down the price of Sc2O3

considerably which in turn means that AlndashSc masteralloy price should drop accordingly Preliminary ana-lyses suggest a price of approx US$ 400 per kg Sc in themaster alloy which translates to an added cost of 80cent per kilo when 02 wt-Sc is added to an aluminiumalloy This is also a considerable increase in the materialcost but with such prices one should expect to see Sccontaining alloys in many more applications than whatis the case at the present time

Concluding remarksThe body of published investigations on Al-based alloyswith Sc addition provides a sound basis of knowledgefor metallurgists that want to look into the possibility ofenhancing the performance of a wrought Al-alloy byadding Sc to it Ternary AlndashScndashX phase diagrams areavailable for practically every technologically importantalloying element in Al The effect of a wide range ofternary alloying elements on the precipitation behaviourof Al3Sc is accounted for It has been shown that theAl3Sc phase can be effective as a grain refiner adispersoid former and a precipitate hardening agentand some of the underlying conditions for achieving thedesired Al3Sc formation have been outlined Addingsome Zr together with Sc has proven to be beneficial Itmay lead to effective grain refinement at a lower Sc levelbut the most prominent effect is the refinement indispersoid distribution that can be achieved An addi-tion of Sc has little if any effect on precipitation in the2xxx 6xxx and 7xxx alloy systems and some effects onthe precipitation in AlndashLi based alloys With respect tocorrosion behaviour adding Sc to an Al-alloy does ingeneral seem to make the alloy slightly more noble andto increase its self-corrosion resistance Scandium-containing Al alloys have very few uses at the presenttime as a result of the high price of scandium The priceof Sc is expected to decrease significantly in the futureand this should lead to the disclosure of moreapplications where it is economically feasible to takeadvantage of the improved properties of some Sc-containing aluminium alloys

References1 D R Lide lsquoCRC handbook of chemistry and physicsrsquo 71st edn

4ndash29 1990 Boston USA CRC Press

2 E M Savitsky V F Terehova I V Burov and O P Naumkin

Proc Fourth Conf on lsquoRare earth researchrsquo Phoenix Arizona

USA April 1964 409ndash420

3 E M Savitskii V F Terekhova I V Burov O P Naumkin and

I A Markova Inorg Mater 1965 1 1503ndash1512

4 O P Naumkin V T Terekhova and E M Savitskiy Russ

Metall 1965 (4) 128ndash136

5 W G Moffatt lsquoThe handbook of binary phase diagramsrsquo 1981

Schenectady NY USA General Electric Co

6 E A Brandes (ed) lsquoSmithells metals reference bookrsquo 6th edn

1983 London UK Butterworths

7 R P Elliott and F A Shunk Bull Alloy Phase Diagrams 1981

2 (2) 222ndash223

8 K A Gschneider Jr and F W Calderwood Bull Alloy Phase

Diagrams 1989 10 34ndash36

9 H Okamoto J Phase Equil 1991 12 612ndash613

10 J L Murray J Phase Equil 1998 19 380ndash384

11 M E Drits E S Kadaner T V Dobatkina and N I Turkina

Russ Metall 1973 (4) 152ndash154

12 S-I Fujikawa M Sugaya H Takei and K-I Hirano J Less-

Common Met 1979 63 87ndash97

13 N Blake and M A Hopkins J Mater Sci 1985 20 2861ndash2867

14 V I Kononenko and S V Golubev Russ Metall 1990 (2) 193ndash

195

15 T B Massalski J L Murray L H Bennett and H Baker (eds)

lsquoBinary alloy phase diagramsrsquo 1986 Metals Park OH USA

ASM

16 G Cacciamani P Riani G Borzone N Parodi A Saccone

R Ferro A Pisch and R Schmid-Fetzer Intermetallics 1999 7

101ndash108

17 H Okamoto J Phase Equil 2000 21 310

18 A F Norman P B Pragnell and R S McEwen Acta Mater

1998 46 5715ndash5732

19 I N Pyagai and A V Vakhobov Russ Metall 1990 (5) 50ndash52

20 C L Fu J Mater Res 1990 5 971ndash979

21 X Lu and Y Wang Calphad 2002 26 555ndash561

22 R R Sawtell and J W Morris Jr Proc lsquoDispersion strengthened

aluminium alloysrsquo Phoenix Arizona USA January 1988 409ndash

420

23 R R Sawtell and C L Jensen Metall Trans A 1990 21A 421ndash

430

24 L A Willey Unpublished research Alcoa 1970 Data points are

extracted from Ref 10

25 N I Turkina and V I Kuzmina Russ Metall 1976 (4) 179ndash

183

26 T Torma E Kovacs-Csetenyi I Vitanyi M Butova and

J Stepanov Proc 6th Int Symp on lsquoHigh purity materials in

science and technologyrsquo Akademie der Wissenschaften der DDR

Dresden Germany May 1985 388ndash389

27 A L Berezina V A Volkov B P Domashnikov and K V

Chuistov Metallofizika 1987 9 (5) 43ndash47

28 H-H Jo J Korean Inst Metals 1990 28 499ndash504

29 H-H Jo and S-I Fujikawa Mater Sci Eng 1993 A 171 151ndash

161

30 S Celotto and T J Bastow Philos Mag A 2000 80 1111ndash1125

31 J Roslashyset and N Ryum submitted to Mater Sci Eng

32 M E Drits L S Toropova Yu G Bykov F L Gushchina V I

Elagin and Yu A Filatov Russ Metall 1983 (1) 150ndash153

33 L S Toropova D G Eskin M L Kharakterova and T V

Dobatkina lsquoAdvanced aluminum alloys containing scandium

structure and propertiesrsquo 1998 Amsterdam The Netherlands

Gordon and Breach Science Publishers

34 V V Cherkasov P P Pobezhimov L P Nefedova E V Belov

and G M Kuznetsov Met Sci Heat Treat 1996 (6) 268ndash270

35 Kh O Odinaev I N Ganiev V V Kinzhibalo and B Ya

Kotur Dokl Akad Nauk Tadzh SSR 1989 32 37ndash38

36 Kh O Odinaev I N Ganiev and A V Vakhobov Russ Metall

1991 (4) 200ndash203

37 J Grobner R Schmid-Fetzer A Pisch G Cacciamani P Riani

N Parodi G Borzone A Saccone and R Ferro Z Metallkd

1999 90 872ndash880

38 E A Marquis and D N Seidman Microsc Microanal 2002 8

(Suppl 2) 1100CDndash1101CD

39 A Pisch J Grobner and R Schmid-Fetzer Mater Sci Eng A

2000 A 289 123ndash129

Roslashyset and Ryum Scandium in aluminium alloys

40 International Materials Reviews 2005 VOL 50 NO 1

40 C Xia F Zeng and Y Gu Trans Nonferrous Met Soc China

2003 13 1124ndash1127

41 M Yu Teslyuk and V S Protasov Sov Phys Crystallogr 1966

10 470ndash471

42 M L Kharakterova and T V Dobatkina Russ Metall 1988

(6) 175ndash178

43 M L Kharakterova Russ Metall 1991 (4) 195ndash199

44 L S Toropova M L Kharakterova and D G Eskin Russ

Metall 1992 (3) 194ndash199

45 P Riani L Arrighi R Marazza D Mazzone G Zanicchi and

R Ferro J Phase Equil Diff 2004 25 22ndash52

46 A T Tyvanchuk T I Yanson B Ya Kotur O S Zarechnyuk

and M L Kharakterova Russ Metall 1988 (4) 190ndash192

47 L L Rokhlin T V Dobatkina and M L Kharakterova Powder

Metall Met Ceram 1997 36

48 A Z Ikromov I N Ganiev and V V Kinzhibalo Dokl Akad

Nauk Tadzh SSR 1990 (6) 391ndash392

49 I N Ganiev A Z Ikromov and V G Khudoiberdiev Russ

Metall 1995 (3) 125ndash127

50 I N Fridlyander L L Rokhlin T V Dobatkina and N I

Nikitina Met Sci Heat Treat 1993 (10) 567ndash571

51 I N Fridlyander L L Rokhlin T V Dobatkina V V

Kinzhibalo and A T Tyvanchuk Russ Metall 1998 (1) 161ndash

166

52 R A Emigh E L Bradley and J W Morris Jr in lsquoLight-weight

alloys for aerospace applications IIrsquo (ed E W Lee and N J

Kim) 27ndash43 1991 TMS

53 L S Toropova A N Kamardinkin V V Kindzhibalo and A T

Tyvanchuk Phys Met Metall 1990 70 (6) 106ndash110

54 A N Kamardinkin T V Dobatkina and T D Rostova Russ

Metall 1991 (4) 216ndash218

55 L S Torodskaya T V Dobatkina and A N Kamardinkin

Russ Metall 1992 (5) 128ndash131

56 E M Sokolovskaya E F Kazakova E I Poddyakova and A

A Ezhov Met Sci Heat Treat 1997 (5) 211ndash213

57 Y Harada and D C Dunand Mater Sci Eng 2002 A 329ndash331

686ndash695

58 N E Drits L S Toropova and F L Gushchina Russ Metall

1984 (4) 229ndash232

59 E M Sokolovskaya E F Kazakova V A Alikhanov and E V

Zhuravleva Moscow Univ Chem Bull 1997 52 (5) 70ndash72

60 E M Sokolovskaya E F Kazakova and E I Poddyakova Met

Sci Heat Treat 1989 (11) 837ndash839

61 G M Cheldieva E F Kazakova E M Sokolovskaya and N I

Kaloev Russ Metall 1990 (6) 87ndash90

62 E M Sokolovskaya E F Kazakova and O D-S Kendivan

Russ Metall 1998 (4) 135ndash137

63 N G Bukhanko E F Kazakova and E M Sokolovskaya Russ

Metall 2001 (4) 425ndash431

64 E D Trubnyakova O I Bodak I N Ganiev and A V

Vakhobov Russ Metall 1987 (3) 219ndash222

65 I N Fridlyander and L V Molchanova Russ Metall 2003 (5)

476ndash480

66 R A Altynbaev S Kh Khairidinov and A V Vakhobov Russ

Metall 1987 (4) 194ndash196

67 J C Schuster and J Bauer J Less-Common Met 1985 109

345ndash350

68 L L Rokhlin A S Fridman T V Dobatkina and D G Eskin

Russ Metall 1991 (6) 146ndash148

69 A S Fridman T V Dobatkina and E V Muratova Russ

Metall 1992 (1) 207ndash209

70 C Xia F Zeng and Y Gu Trans Nonferrous Met Soc China

2003 13 546ndash552

71 F Zeng C Xia and Y Gu J Alloys Comp 2004 363 175ndash181

72 L L Rokhlin T V Dobatkina N R Bochvar and E V Lysova

J Alloys Comp 2004 367 10ndash16

73 T V Dobatkina A S Fridman and E V Muratova Russ

Metall 1992 (5) 125ndash127

74 I N Fridlyander L L Rokhlin N R Bochvar E V Lysova

and O V Boteva Russ Metall 2001 (6) 661ndash666

75 V N Rechkin L K Lamikhov and T I Samsonova Sov Phys

Crystallogr 1964 9 325ndash327

76 I I Zalutskii and P I Kripyakevich Sov Phys Crystallogr

1967 12 341ndash343

77 T J Bastow C T Forwood M A Gibson and M E Smith

Phys Rev B 1998 58 2988ndash2997

78 K Fukunaga M Kolbe K Yamada and Y Miura Mater Sci

Eng 1997 A 234ndash236 594ndash597

79 E P George J A Horton W D Porter and J H Schneibel

J Mater Res 1990 5 1639ndash1648

80 E P George D P Pope C L Fu and J H Schneibel ISIJ Int

1991 31 1063ndash1075

81 Y Harada and D C Dunand Acta Mater 2000 48 3477ndash3487

82 J H Schneibel and E P George Scripta Metall Mater 1990 24

1069ndash1074

83 J H Schneibel and P M Hazzledine Mater Res Soc Symp

Proc 1991 213 323ndash328

84 J H Schneibel and P M Hazzledine J Mater Res 1992 7

868ndash875

85 C J Sparks E D Specht G E Ice P Zschack and J Schneibel

Mater Res Soc Symp Proc 1991 213 363ndash368

86 J Tarnacki and Y-W Kim Scripta Metall Mater 1989 23

1063ndash1068

87 M Asta V Ozolins and C Woodward JOM 2001 53 (9) 16ndash

19

88 M E Drits L S Toropova F L Gushchina and S G Fedotov

Sov Non-Ferrous Met Res 1984 12 83ndash85

89 Y Harada and D C Dunand Scripta Mater 2003 48 219ndash222

90 C Woodward M Asta G Kresse and J Hafner Phys Rev B

2001 63 094103-1-6

91 J-H Xu and A J Freeman Phys Rev B 1990 41 12553ndash12561

92 M F Bartholomeusz and J A Wert Acta Metall Mater 1992

40 673ndash682

93 G Bester and M Fahnle J Phys Condens Matter 2001 13

11551ndash11565

94 C L Fu and M H Yoo Proc lsquoOrdered intermetallics ndash physical

metallurgy and mechanical behaviorrsquo Irsee Germany June 1991

155ndash164

95 K Fukunaga T Shouji and Y Miura Mater Sci Eng 1997 A

239ndash240 202ndash205

96 D P Pope Proc lsquoOrdered intermetallics ndash physical metallurgy

and mechanical behaviorrsquo Irsee Germany June 1991 143ndash153

97 J-S Wang Acta Mater 1998 46 2663ndash2674

98 M H Yoo and C L Fu Mater Sci Eng 1992 A 153 470ndash478

99 R W Hyland Jr and R C Stiffler Scripta Metall Mater 1991

25 473ndash477

100 I G Brodova I V Polents O A Korzhavina P S Popelrsquo I P

Korshunov and V O Esin Melts 1992 4 392ndash397

101 I G Brodova O A Chikova I V Polents P S Popelrsquo and V O

Esin Casting Processes 1992 1 (2) 158ndash160

102 I G Brodova D V Bashlikov and I V Polents Mater Sci

Forum 1998 269ndash272 589ndash594

103 K B Hyde A F Norman and P B Pragnell Mater Sci Forum

2000 331ndash337 1013ndash1018

104 K B Hyde A F Norman and P B Pragnell Acta Mater 2001

49 1327ndash1337

105 J Roslashyset and N Ryum Proc 6th Int Conf on lsquoAluminum

alloysrsquo Toyohashi Japan July 1998 793ndash798

106 V I Elagin V V Zakharov and T D Rostova Met Sci Heat

Treat 1993 (6) 317ndash319

107 R W Hyland Jr Metall Trans A 1992 23A 1947ndash1955

108 B A Parker Z F Zhou and P Nolle J Mater Sci 1995 30

452ndash458

109 C L Rohrer M D Asta S M Foiles and R W Hyland Jr

Mater Res Soc Symp Proc 1996 398 477ndash482

110 G M Novotny and A J Ardell Mater Sci Eng 2001 A 318

144ndash154

111 J D Robson M J Jones and P B Pragnell Acta Mater 2003

51 1453ndash1468

112 C Tan Z Zheng and B Wang Proc 3rd Int Conf on

lsquoAluminium alloysrsquo Vol I NTH Trondheim Norway June

1992 290ndash294

113 M Nakayama A Furuta and Y Miura Mater Trans JIM

1997 38 852ndash857

114 E A Marquis and D N Seidman Acta Mater 2001 49 1909ndash

1919

115 M J Jones and F J Humphreys Acta Mater 2003 51 2149ndash

2159

116 E A Marquis D N Seidman and D C Dunand in lsquoCreep

deformation fundamentals and applicationsrsquo (ed R S Mishra

J C Earthman and S V Raj) 299ndash308 2002 TMS

117 D N Seidman E A Marquis and D C Dunand Acta Mater

2002 50 4021ndash4035

118 E A Marquis D N Seidman and D C Dunand Acta Mater

2003 51 285ndash287

119 M E Drits L S Toropova U G Bikov and G K Anastaseva

Proc lsquoDiffusion in metals and alloysrsquo Tihany Hungary Augustndash

September 1982 616ndash623

120 V I Elagin V V Zakharov and T D Rostova Met Sci Heat

Treat 1983 (7) 546ndash549

Roslashyset and Ryum Scandium in aluminium alloys

International Materials Reviews 2005 VOL 50 NO 1 41

121 M Ye Drits L B Ber Yu G Bykov L S Toropova and G K

Anastaseva Phys Met Metall 1984 57 (6) 118ndash126

122 M E Drits L S Toropova and Yu G Bykov Sov Non-Ferrous

Met Res 1985 13 309ndash314

123 V I Yelagin V V Zakharov S G Pavlenko and T D Rostova

Phys Met Metall 1985 60 (1) 88ndash92

124 N Sano Y Hasegawa K Hono H Jo K Hirano H W

Pickering and T Sakurai Journal de Physique 1987 48 C6 337ndash

342

125 N Sano H-H Jo K-I Hirano and T Sakurai J Jpn Inst

Metals 1989 39 444ndash450

126 N Sano H Jo K Hirano and T Sakurai Proc Second Int

Conf on lsquoAluminium alloysrsquo Beijing China October 1990 549ndash

554

127 Y Miura M Nakayama and A Furuta Proc lsquoAspects of high

temperature deformation and fracture in crystalline materialsrsquo

Nagoya Japan July 1993 255ndash262

128 Y W Riddle and T H Sanders Jr Mater Sci Forum 2000

331ndash337 939ndash944

129 Y W Riddle M McIntosh and T H Sanders Jr in lsquoLightweight

alloys for aerospace application VIrsquo (ed K Jata E W Lee

W Frazier and N J Kim) 25ndash39 2001 TMS

130 M E Drits J Dutkiewicz L S Toropova and J Salawa Crystal

Res Technol 1984 19 1325ndash1330

131 Y W Riddle MSc thesis Georgia Tech GA USA 1998

132 T J Bastow and S Celotto Mater Sci Eng 2003 C 23 757ndash

762

133 M C Carroll M J Mills G S Daehn P I Gouma M F

Savage and B R Dunbar in lsquoAutomotive Alloys 1999rsquo (ed

S Das) 239ndash246 2000 TMS

134 E Clouet M Nastar and C Sigli Phys Rev B 2004 69 064109-

1-14

135 V V Zakharov Met Sci Heat Treat 1997 (2) 61ndash66

136 J W Christian lsquoThe theory of transformation in metals and

alloysrsquo 2nd edn 1975 Pergamon Press Ltd

137 A L Berezina V A Volkov B P Domashnikov S V Ivanov

and K V Chuistov Phys Metals 1990 10 296ndash304

138 S-I Fujikawa and S Sakauchi Proc 6th Int Conf on

lsquoAluminum alloysrsquo Toyohashi Japan July 1998 805ndash810

139 Y S Touloukian R K Kirby R E Taylor and P D Desai

(eds) lsquoThermal expansion metallic elements and alloysrsquo 1975

New York Plenum

140 J Roslashyset and N Ryum submitted to Scripta Mater

141 R O Simmons and R W Balluffi Phys Rev 1960 117 52ndash61

142 M Ocko E Babic R Krsmik E Girt and B Leontic J Phys F

Metals Phys 1976 6 703ndash707

143 M J Jones and F J Humphreys Proc First Joint Int Conf on

lsquoRecrystallization and grain growthrsquo Aachen Germany August

2001 Springer Verlag 1287ndash1292

144 S Iwamura M Nakayama and Y Miura Mater Sci Forum

2002 396ndash402 1151ndash1156

145 S Iwamura and Y Miura Acta Mater 2004 52 591ndash600

146 M Asta S M Foiles and A A Quong Phys Rev B 1998 57

11265ndash11275

147 R W Hyland Jr M Asta S M Foiles and C L Rohrer Acta

Mater 1998 46 3667ndash3678

148 J Roslashyset and N Ryum Proc 4th Int Conf on lsquoAluminium

alloysrsquo Vol I Atlanta GA USA September 1994 194ndash201

149 M E Drits L S Toropova G K Anastaseva and G L

Nagornichnykh Russ Metall 1984 (3) 192ndash195

150 E A Marquis D N Seidman and D C Dunand Acta Mater

2003 51 4751ndash4760

151 M E Drits L S Toropova and Yu G Bykov Met Sci Heat

Treat 1983 (7) 550ndash554

152 V V Zakharov and T D Rostova Met Sci Heat Treat 1995

(2) 65ndash69

153 M Nakayama and Y Miura Proc 4th Int Conf on lsquoAluminium

alloysrsquo Vol I Atlanta GA USA September 1994 538ndash545

154 M Nakayama and Y Miura J Jpn Inst Light Metals 1996 46

275ndash279

155 M Nakayama T Okuyama and Y Miura Mater Sci Forum

2000 331ndash337 927ndash932

156 M Nakayama T Okuyama and Y Miura Proc 6th Int Conf

on lsquoAluminum alloysrsquo Toyohashi Japan July 1998 517ndash522

157 M L Kharakterova D G Eskin and L S Toropova Acta

Metall Mater 1994 42 2285ndash2290

158 V I Elagin V V Zakharov and T D Rostova Met Sci Heat

Treat 1992 (1) 37ndash45

159 H Wiik Siv Ing thesis NTH Institute of Metallurgy

Trondheim Norway 1995

160 J Roslashyset H Hovland and N Ryum Mater Sci Forum 2002

396ndash402 619ndash624

161 Y Miura K Horikawa K Yamada and M Nakayama Proc

4th Int Conf on lsquoAluminium alloysrsquo Vol II Atlanta GA USA

September 1994 161ndash168

162 Y W Riddle PhD thesis Georgia Tech GA USA 2000

163 B Forbord W Lefebvre F Danoix H Hallem and

K Marthinsen Scripta Mater 2004 51 333ndash337

164 J D Robson Acta Mater 2004 52 1409ndash1421

165 C B Fuller J L Murray and D N Seidman submitted to Acta

Mater 2004

166 M G Mousavi C E Cross and Oslash Grong Sci Technol Weld

Joining 1999 4 381ndash388

167 J S Vetrano S M Bruemmer L M Pawlowski and I M

Robertson Mater Sci Eng 1997 A 238 101ndash107

168 Y W Riddle and T H Sanders Jr Mater Sci Forum 2000

331ndash337 799ndash803

169 G M Khan A O Nikiforov V V Zakharov and I I Novikov

Tsvetnye Metally 1993 34 (11) 43ndash45

170 Z Horita M Furukawa M Nemoto A J Barnes and T G

Langdon Acta Mater 2000 48 3633ndash3640

171 L A Willey US Patent 3 619 181 9 November 1971

172 L K Lamikhov and G V Samsonov Tsvetnye Metally 1964 5

(8) 77ndash80

173 A L Berezina K V Chuistov N I Kolobnev L B

Khokhlatova and T A Monastyrskaya Mater Sci Forum

2002 396ndash402 741ndash746

174 F A Fasoyinu J Thomson D Cousineau T Castles and M

Sahoo Proc 6th Int AFS Conf on lsquoMolten aluminum

processingrsquo Orlando FL USA November 2001

175 Z Yin Q Pan Y Zhang and F Jiang Mater Sci Eng 2000

A 280 151ndash155

176 I I Novikov and O E Grushko Mater Sci Technol 1995 11

926ndash932

177 D Cousineau M Sahoo P D Newcombe T Castles and F A

Fasoyinu Proc lsquoAFS 105th casting congressrsquo Dallas TX USA

AprilndashMay 2001 157ndash184

178 C E Cross and Oslash Grong Proc 6th Int Conf on lsquoAluminum

alloysrsquo Toyohashi Japan July 1998 1441ndash1446

179 F A Costello J D Robson and P B Prangnell Mater Sci

Forum 2002 396ndash402 757ndash762

180 K B Hyde A F Norman and P B Prangnell Mater Sci

Forum 2002 396ndash402 39ndash44

181 M E Drits S G Pavlenko L S Toropova Yu G Bukov and

L B Ber Sov Phys Dokl 1981 26 (3) 344ndash346

182 A M Drits and B A Kopeliovich Russ Metall 1985 (4) 147ndash

151

183 V G Davydov V I Elagin V V Zakharov and T D Rostova

Met Sci Heat Treat 1996 (8) 347ndash352

184 M E Drits L S Toropova Yu G Bykov L B Ber and S G

Pavlenko Russ Metall 1982 (1) 148ndash152

185 T D Rostova V G Davydov V I Yelagin and V V Zakharov

Mater Sci Forum 2000 331ndash337 793ndash798

186 Y W Riddle H Hallem and N Ryum Mater Sci Forum 2002

396ndash402 563ndash568

187 J Roslashyset and Y W Riddle Proc 9th Int Conf on lsquoAluminium

alloysrsquo Brisbane Australia August 2004 1210ndash1215

188 A M Diskin V K Portnoi A M Drits and A A Alalykin Sov

Non-Ferrous Met Res 1986 14 499ndash500

189 R R Sawtell P E Bretz and C L Jensen US Patent 4 689 090

25 August 1987

190 G A Salishchev Yu B Timoshenko and R A Saitova Proc

Second Int Conf on lsquoAluminium alloysrsquo Beijing China October

1990 413ndash415

191 T G Nieh R Kaibyshev L M Hsiung N Nguyen and

J Wadsworth Scripta Mater 1997 36 1011ndash1016

192 T G Nieh L M Hsiung J Wadsworth and R Kaibyshev Acta

Mater 1998 46 2789ndash2800

193 J S Vetrano C H Henager Jr M T Smith and S M

Bruemmer in lsquoHot deformation of aluminum alloys IIrsquo (ed T R

Bieler L A Lalli and S R MacEwen) 407ndash418 1998 TMS

194 J S Vetrano C H Henager Jr S M Bruemmer Y Ge and

C H Hamilton in lsquoSuperplasticity and Superplastic Forming

1998rsquo (ed A K Gosh and T R Bieler) 89ndash97 1998 TMS

195 V Y Gertsman J S Vetrano C H Henager Jr and S M

Bruemmer Proc First Joint Int Conf on lsquoRecrystallization and

grain growthrsquo Aachen Germany August 2001 Springer Verlag

2001 837ndash842

196 Y Xiao C Gao H Ma and S Tian Trans Nonferrous Met Soc

China 2001 11 235ndash238

Roslashyset and Ryum Scandium in aluminium alloys

42 International Materials Reviews 2005 VOL 50 NO 1

197 A Gholinia F J Humphreys and P B Prangnell Acta Mater

2002 50 4461ndash4476

198 A Gholinia F J Humphreys and P B Prangnell Mater Sci

Forum 2002 408ndash412 1519ndash1524

199 S Komura P B Berbon M Furukawa Z Horita M Nemoto

and T G Langdon Scripta Mater 1998 38 1851ndash1856

200 S Komura P B Berbon A Utsunomiya M Furukawa

Z Horita M Nemoto and T G Langdon in lsquoHot deformation

of aluminum alloys IIrsquo (ed T R Bieler L A Lalli and S R

MacEwen) 125ndash138 1998 TMS

201 S Komura Z Horita M Furukawa M Nemoto and T G

Langdon J Mater Res 2000 15 2571ndash2576

202 S Komura M Furukawa Z Horita M Nemoto and T G

Langdon Mater Sci Eng 2001 A 297 111ndash118

203 S Komura Z Horita M Furukawa M Nemoto and T G

Langdon Metall Mater Trans A 2001 32A 707ndash716

204 Z Horita M Furukawa K Oh-ishi M Nemoto and T G

Langdon Proc Fourth Int Conf on lsquoRecrystallization and

related phenomenarsquo (ed T Sakai and H G Suzuki) 1999 The

Japan Institute of Metals 301ndash308

205 Z Horita S Komura P B Berbon A Utsunomiya

M Furukawa M Nemoto and T G Langdon Mater Sci

Forum 1999 304ndash306 91ndash96

206 Z Horita S Lee S Ota K Neishi and T G Langdon Mater

Sci Forum 2001 357ndash359 471ndash476

207 Z Horita T Fujinami K Sato S B Kang H W Kim and T G

Langdon in Proc James T Staley Honorary Symposium on

Aluminum Alloys lsquoAdvances in the metallurgy of aluminum

alloysrsquo (ed M Tiryakioglu) 271ndash275 2001 ASM

208 P B Berbon S Komura A Utsunomiya Z Horita

M Furukawa M Nemoto and T G Langdon Mater Trans

JIM 1999 40 772ndash778

209 M Nemoto Z Horita M Furukawa and T G Langdon Mater

Sci Forum 1999 304ndash306 59ndash66

210 M Furukawa Z Horita M Nemeto and T G Langdon Proc

lsquoLight Metals 1999rsquo Quebec City PQ Canada August 1999 583ndash

592

211 M Furukawa K Oh-ishi S Komura A Yamashita Z Horita

M Nemeto and T G Langdon Mater Sci Forum 1999 304ndash

306 97ndash102

212 M Furukawa A Utsunomiya K Matsubara Z Horita and

T G Langdon Acta Mater 2001 49 3829ndash3838

213 M Furukawa A Utsunomiya S Komura Z Horita M Nemoto

and T G Langdon Mater Sci Forum 2001 357ndash359 431ndash436

214 M Furukawa Z Horita and T G Langdon in Proc James T

Staley Honorary Symposium on Aluminum Alloys lsquoAdvances in

the metallurgy of aluminum alloysrsquo (ed M Tiryakioglu) 47ndash56

2001 ASM

215 M Furukawa Z Horita M Nemoto and T G Langdon Mater

Sci Eng 2002 A 324 82ndash89

216 M Furukawa Z Horita and T G Langdon in lsquoUltrafine grained

materials IIrsquo (ed Y T Zhu T G Langdon R S Mishra S L

Semiatin M J Saran and T C Lowe) 459ndash468 2002 TMS

217 T G Langdon M Furukawa Z Horita and M Nemoto Proc

NATO Advanced Research Workshop on lsquoInvestigations and

applications of severe plastic deformationrsquo Moscow August

1999 NATO Science Series Series 3 High Technology vol 80

Kluwer Academic Publishers The Netherlands 2000 149ndash154

218 S Lee H Akamatsu A Utsunomiya K Neishi M Furukawa

Z Horita and T G Langdon Proc Thermec 2000 Las Vegas

USA December 2000

219 S Lee A Utsunomiya H Akamatsu K Neishi M Furukawa

Z Horita and T G Langdon Acta Mater 2002 50 553ndash564

220 A Yamashita D Yamaguchi Z Horita and T G Langdon

Mater Sci Eng 2000 A 287 100ndash106

221 K Oh-ishi Z Horita D J Smith and T G Langdon J Mater

Res 2001 16 583ndash589

222 H Akamatsu T Fujinami Z Horita and T G Langdon Scripta

Mater 2001 44 759ndash764

223 S Ota H Akamatsu K Neishi M Furukawa Z Horita and

T G Langdon Mater Trans 2002 43 2364ndash2369

224 K Furuno H Akamatsu K Oh-ishi M Furukawa Z Horita

and T G Langdon Acta Mater 2004 52 2497ndash2507

225 I N Fridlyander O G Senatorova N A Ryazanova and A O

Nikiforov Mater Sci Forum 1994 170ndash172 345ndash349

226 J N Fridlyander and O G Senatorova Mater Sci Forum 1996

217ndash222 1813ndash1818

227 J Liu and D J Chakrabarti Acta Mater 1996 44 4647ndash4661

228 O G Senatorova A N Uksusnikov J N Fridlyander

J Koshorst R R Romanova N A Ryazanova A Galliot

and V V Cherkassov Proc 6th Int Conf on lsquoAluminum alloysrsquo

July 1998 Toyohashi Japan 589ndash593

229 R A Emigh E L Bradley and J W Morris Jr in

lsquoSuperplasticity in aerospace IIrsquo (ed T R McNelley and H C

Heikkenen) 303ndash315 1990 TMS

230 E L Bradley III R A Emigh and J W Morris Jr Scripta

Metall Mater 1991 25 717ndash721

231 N I Kolobnev L B Khokhlatova V D Makarov E Yu

Semenova and V V Redchits Proc Sixth Int Aluminiumndash

Lithium Conference Garmisch-Partenkirchen Germany October

1991 1053ndash1056

232 N K Tsenev R Z Valiev O V Obraztsov and I N Fridlander

Proc Sixth Int AluminiumndashLithium Conference Garmisch-

Partenkirchen Germany October 1991 1125ndash1132

233 A M Shammazov N K Tsenev R Z Valiev M M

Myshlyaev M M Bikbulatov and S P Lebedich Phys Met

Metall 2000 89 (3) 314ndash318

234 F Musin R Kaibyshev Y Motohashi T Sakuma and G Itoh

Mater Trans A 2002 43A 2370ndash2377

235 M Shagiev Y Motohashi F Musin R Kaibyshev and G Itoh

Mater Trans A 2003 44A 1694ndash1697

236 M Shagiev Y Motohashi F Musin R Kaibyshev and G Itoh

Mater Trans A 2003 44A 1698ndash1701

237 B A Parker and Z F Zhou Proc 3rd Int Conf on lsquoAluminium

alloysrsquo Vol I NTH Trondheim Norway June 1992 363ndash367

238 J R Davies lsquoASM specialty handbook aluminum and aluminum

alloysrsquo 1993 Materials Park OH USA ASM

239 S J Andersen H W Zandbergen J Jansen C Traeholt

U Tundal and O Reiso Acta Mater 1998 46 3283ndash3298

240 M L Kharakterova D G Eskin and L L Rokhlin Russ

Metall 1997 (1) 104ndash109

241 J Roslashyset Dr Ing thesis NTNU Trondheim Norway 2002

242 P P Chattopadhyay S Datta and M K Banerjee Mater Sci

Eng 2002 A 333 67ndash71

243 L I Kaigorodova E I Selnikhina E A Tkachenko and O G

Senatorova Phys Met Metall 1996 81 513ndash519

244 Y-L Wu F H Froes C Li and A Alvarez Metall Mater

Trans A 1999 30A 1017ndash1024

245 Z Yin L Yang Q Pan and F Jiang Trans Nonferrous Met

Soc China 2001 11 822ndash825

246 V I Elagin V V Zakharov and T D Rostova Met Sci Heat

Treat 1994 36 (7) 375ndash380

247 Y V Milman A I Sirko D V Lotsko O N Senkov and D B

Miracle Mater Sci Forum 2002 396ndash402 1217ndash1222

248 C-H Joh K Yamada and Y Miura Mater Trans JIM 1999

40 439ndash442

249 X J Jiang Q H Gui Y Y Li L M Ma G J Liang and C X

Shi Scr Metall Mater 1993 29 211ndash216

250 X J Jiang Y Y Li W Deng L Y Xiong W M Wu Y J Gao

and C X Shi Adv Cryogenic Eng (Mater) 1994 40 1369ndash

1376

251 C-H Joh T Katsube K Yamada and Y Miura Proc 6th Int

Conf on lsquoAluminum alloysrsquo Toyohashi Japan July 1998 799ndash

804

252 L I Kaygorodova A M Dritz T V Krymova and I N

Fridlyander Proc Sixth Int AluminiumndashLithium Conference

Garmisch-Partenkirchen Germany October 1991 363ndash367

253 L I Kaigorodova A M Drits Ya V Zhingel T V Krymova

and I N Fridlyander Phys Met Metall 1992 73 286ndash290

254 A L Berezina V A Volkov S V Ivanov N I Kolobnev and

K V Chuistov Phys Met Metall 1991 71 (2) 167ndash175

255 I N Fridlyander N I Kolobnev A L Berezina and K V

Chuistov Proc Sixth Int AluminiumndashLithium Conference

Garmisch-Partenkirchen Germany October 1991 107ndash112

256 L I Kaigorodova A M Drits Ya V Zhingel T V Krymova

and V A Rassokhin Phys Met Metall 1992 73 281ndash285

257 I N Fridlyander S F Danilov E N Malysheva T A

Gorokhova and N N Kirkina Proc Sixth Int Aluminiumndash

Lithium Conference Garmisch-Partenkirchen Germany October

1991 381ndash386

258 G Dlubek S Krause H Krause A L Beresina V S

Mikhalenkov and K V Chuistov J Phys Condens Matter

1992 4 6317ndash6328

259 S Krause H Krause G Dlubek A L Beresina and K S

Chuistov Mater Sci Forum 1992 105ndash110 1109ndash1112

260 C Y Tan Z Q Zheng and S Q Liang Proc 4th Int Conf on

lsquoAluminium alloysrsquo Vol II Atlanta GA USA September 1994

329ndash333

261 A L Beresina N I Kolobnev K V Chuistov A V Kotko and

O A Molebny Mater Sci Forum 2002 396ndash402 977ndash981

Roslashyset and Ryum Scandium in aluminium alloys

International Materials Reviews 2005 VOL 50 NO 1 43

262 I N Ganiev I Yunusov and V V Krasnoyarskii J Appl Chem

USSR 1986 60 1961ndash1965

263 I N Ganiev Prot Met 1995 31 543ndash546

264 N V Vyazovikina Prot Met 1999 35 448ndash453

265 G V Kharina and V P Kochergin Prot Met 1996 32 134ndash

136

266 G V Kharina M V Kuznetsov and V P Kochergin Russ J

Electrochem 1998 34 482ndash485

267 V S Sinyavskii V D Valrsquokov and E V Titkova Prot Met

1998 34 549ndash555

268 Y L Wu F H Froes C G Li and J Liu Proc lsquoSynthesis

processing of lightweight metallic materials IIrsquo Orlando FL

USA February 1997 73ndash81

269 Z Ahmad and B J Abdul-Aleem Proc EuroCorr 2000

270 Z Ahmad A Ul-Hamid and B J Abdul-Aleem Corros Sci

2001 43 1227ndash1243

271 R Braun B Lenczowski and G Tempus Mater Sci Forum

2000 331ndash337 1647ndash1652

272 T Torma E Kovacs-Csetenyi L Vitalis I Vitanyi

J Stepanov and M Butova Mater Sci Forum 1987 1314

497ndash503

273 Z Wang P Wang K S Kumar and C L Briant in lsquoChemistry

and electrochemistry of corrosion and stress corrosion crackingrsquo

(ed R H Jones) 573ndash582 2001 TMS

274 V I Elagin V V Zakharov A A Petrova and E V

Vyshegorodtseva Russ Metall 1983 (4) 143ndash146

Roslashyset and Ryum Scandium in aluminium alloys

44 International Materials Reviews 2005 VOL 50 NO 1

Page 14: Scandium in aluminium alloys - Atom probe · A considerable part of the available literature on scandium in aluminium alloys is reviewed. ... behaviour in Al Cu, Al Mg Si,

AlndashCundashSc alloys compared to AlndashSc alloys Howeveran experimental investigation of Alndash25 wt-Cundash023 wt-Sc alloy comes to a different conclusion Thelattice misfit strain is found to decrease compared to Alndash02 wt-Sc and the critical diameter for coherency losswas found to be the same in the ternary and the binaryalloy144 It is suggested that these observations may bebecause of the dissolution of some Cu in the Al3Sc phaseand thus that the lattice parameters of both the Al matrixand the Al3Sc precipitates decrease in the ternary alloy

Silicon

It has been found that the onset of precipitation in Alndash04 wt-Sc is only slightly altered when Si contents ofup to 04 wt are introduced in the alloy However thefinal stage of the precipitation reaction is considerablydelayed with increasing Si content135 Figure 22 showsthe effect of addition of a joint of 035 wt-Si and040 wt-Fe There are at least two possible explana-tions for why an Si-addition leads to this behaviour

1 Alloying with Si is known to promote discontin-uous precipitation of Al3Sc106158 It has been shown thatwhen isothermal precipitation of Al3Sc starts discon-tinuously the later stage of the overall transformationcan be very slow31

2 The isothermal section of the phase diagramsuggests that the V-phase (AlSc2Si2) should form inalloys of this composition46 If the V-phase forms lessSc is available for precipitation of Al3Sc

It has been shown157 that for an AlndashScndashSi alloy withsolid solution content of 010 wt-Sc an 110 wt-Sithe only phases to precipitate after heat treatment at200uC are Si and an (AlScSi)-phase possibly the V-phase On the other hand the Al3Sc phase has beenobserved to form in alloys with 04 wt-Sc and up to08 wt-Si159160

Zinc

It has been reported that additions of up to 5 wt- Znhave only minor effects on the precipitation kinetics ofan Alndash04 wt-Sc alloy135 (Fig 23) In Ref 106 it isclaimed that Zn promotes discontinuous precipitation ofAl3Sc

Lithium

A comparison of the age hardening response at 400uC inAlndash24 wt-Lindash019 wt-Sc and Alndash024 wt-Sc alloys

indicates that the onset of Al3Sc-precipitation is notaffected by the presence of Li161

Zirconium

As mentioned in the section on lsquoTernary phase diagramswith dispersoid-forming elementsrsquo earlier a considerableamount of Zr is dissolved in the Al3Sc phase and thus amore correct denotation of the precipitating phase isAl3(Sc12xZrx) In discussing the influence of the Zrcontent on the precipitation of Al3Sc one is thereforeactually discussing the difference in precipitation ofAl3Sc versus Al3(Sc12xZrx)

It is found that an addition of 015 wt-Zr to an Alndash04 wt-Sc alloy only marginally affects the initial stageof the precipitation reaction123135 while it slows downthe later stages of the transformation considerably(Fig 24)135 The coarsening rate of the Al3(Sc12xZrx)particles in AlndashScndashZr alloys is found to be much slowerthan that of Al3Sc particles in AlndashSc alloys123162

In three-dimensional atom probe field ion microscopy(3D-APFIM) of Al3(Sc12xZrx) particles formed at 475uCin a ternary AlndashScndashZr alloy163 it was found that the coreof the particles is almost pure Al3Sc whereas there is ashell of Al3(Sc12xZrx) with almost equal content of Scand Zr Such a behaviour has also been predicted bycomputer modelling of precipitation of Al3(Sc12xZrx) at480uC in an AlndashZnndashMgndashScndashZr alloy164 This modelpredicts that Zr starts to enter the growing

22 C-curves for 10 and 60 transformation in Alndash

04 wt-Sc and Alndash04 wt-Fendash035 wt-Sindash04 wt-Sc

redrawn from Ref 135

23 C-curves for 10 and 60 transformation in Alndash

04 wt-Sc and Alndash5 wt-Znndash04 wt-Sc redrawn

from Ref 135

24 C-curves for 10 and 60 transformation in Alndash

04 wt-Sc and Alndash04 wt-Scndash015 wt-Zr redrawn

from Ref 135

Roslashyset and Ryum Scandium in aluminium alloys

32 International Materials Reviews 2005 VOL 50 NO 1

Al3(Sc12xZrx) particles when approximately half of thesupersaturated Sc has been precipitated The Zr contentof the outer shell is predicted to be much higher thanwhat has been found experimentally163164

Another 3D-APFIM study of Al3(Sc12xZrx) particlesin a ternary AlndashScndashZr alloy has been reported165 Hereparticles grown at 300uC for various lengths of time werestudied The Zr content in these particles was muchlower than that reportedpredicted at higher tempera-tures163164 even after very long annealing times

Iron

The effect of adding up to 07 wt-Fe on the precipita-tion kinetics in an Alndash04 wt-Sc alloy has beeninvestigated135 The onset of precipitation was onlyslightly influenced by the Fe-level whereas the laterstages of the transformation however were significantlyslowed down as the Fe-level increased An example ofthe effect of a joint addition of Fe and Si is shown inFig 22

Manganese chromium and titanium

Small additions (03 wt-) of manganese or chromiumto Alndash040 wt-Sc alloys are reported to have onlyminor effects on the precipitation kinetics of Al3Sc135

According to Ref 106 Mn is reported to promote andCr and Ti to suppress discontinuous precipitation

Rare earth elements

An investigation of the precipitation behaviour of Alndash03 at-Sc and Alndash03 at-Scndash03 at-X alloyswhere X is either yttrium gadolinium holmium orerbium in the temperature range 235ndash310uC indicatedthat a Al3(Sc12xXx) phase with L12 structure wasformed in the ternary alloys22 Peak strength is reportedto occur after approx 10 h at 285uC in all alloys whichindicates that the precipitation kinetics up to peakstrength is practically unaltered by the ternary additions

Influence of Sc on microstructure andproperties of wrought aluminium alloysMost of the effects of Sc addition in wrought Al-alloysare linked to the formation of the Al3Sc phase In atypical processing route of a wrought aluminium alloyparticles of the Al3Sc phase can form under threedifferent conditions each of which influences themicrostructure and properties of the alloy in a specificway

1 During solidification after casting or weldingAl3Sc particles can form in the melt and act as nucleifor a-Al thus leading to grain refinement18166

2 High temperature processing of the alloy in therange 400ndash600uC for instance homogenisation hot-rolling or extrusion can give a dense distribution ofAl3Sc particles of typically 20ndash100 nm size The particledistributions formed under such conditions are reportedto lead to good recrystallisation resistance128148167168

and enhanced superplasticity52169170

3 Heat treatment in the range 250ndash350uC can lead tosignificant precipitation hardening of an alloy super-saturated in Sc148158171 The size of strengthening Al3Scprecipitates is typically in the range 2ndash6 nm121

Grain refinementA good grain refinement is almost always desired uponsolidification The formation of small equiaxed grainsrather than long dendrites in the melt facilitates thefeeding of the melt into cavities of the shrinkingsolidified metal and thus reduces the problem ofshrinkage porosity The tendency to hot cracking is alsoreduced and the second phase particles become morefinely and uniformly distributed

To the authorsrsquo knowledge the first effect of Sc in Al-alloys that was reported in an international scientificjournal was the grain refining action in pure Al and in anAlndashCu alloy upon solidification172 which was found tobe stronger for Sc than for other transition metals Inlater studies of Sc as a grain refiner in pure Al1832173 ithas been demonstrated that approx 07 wt-Sc issufficient to provide excellent grain refinement It hasalso been demonstrated that additions of 025 wt-Scz025 wt-Zr provide good grain refinement in pure Al18

In order for Sc to act as an effective grain refiner theAl3Sc phase has to form in the melt before thesolidification of a-Al The Al3Sc particles have a latticeparameter close to that of pure Al and whenhypereutectically formed the Al3Sc particles are veryeffective substrates for the nucleation of the a-Al phaseAs mentioned in the section on lsquoFormation of Al3Sc inAlndashSc alloysrsquo above this requires that the alloy ishypereutectic with respect to Sc ie in excess of approx06 wt- in a binary AlndashSc alloy In ternary and higherorder systems the eutectic Sc composition may dependon the other alloying elements present For instance theeutectic composition of Sc has been predicted todecrease with increasing Mg content in the ternary AlndashMgndashSc system39 This prediction is sustained by theobservation of good grain refinement by adding 05 wt-Sc to an Alndash7 wt-Mg alloy174 (Other examples ofgrain refinement at Sc concentrations lower than that ofthe binary eutectic are found in Ref 173)

Similarly the observation of good grain refinement inan Alndash025 wt-Scndash025 wt-Zr alloy18 may be as aresult of a lower Sc content of the eutectic in the ternarysystem ie less Sc is needed to make the alloy hyper-eutectic No literature data on the liquidus surface of theAlndashScndashZr system are available and thus this hypothesiscannot be confirmed In more complex alloy systems itis also observed that excellent grain refinement isachieved at low Sc contents when Sc is added togetherwith Zr It is reported that adding either 02 wt-Sc06 wt-Sc or 01 wt-Zr to an Alndash5Mg alloy givesmuch poorer grain refinement than adding 02 wt-Scz01 wt-Zr175 Similarly additions of 015 wt- ofeither Sc or Zr are reported to only marginally refinethe grain structure in an AlndashCundashLi alloy whereas a jointaddition of 015 wt-Sc and 015 wt-Zr gives excellentgrain refinement176 For an AA 3650 casting alloy (Alndash7 wt-Sindash04 wt-Mg) good grain refinement is achievedby adding 039 wt-Sc or 027 wt-Scz019 wt-Zr177

In some AlndashZnndashMgndashScndashZr alloys it is also found thatan addition of 02ndash03 wt-Sc can be sufficient for goodgrain refinement166169178179 Examples of the grainrefinement as a function of Sc addition in pure Al andin an AlndashZnndashMgndashZr alloy are shown in Fig 25

The nucleation of a-Al on Al3Sc particles in the melt isfacilitated by the close match in the lattice parameters ofthe two phases As shown in Fig 17 the mismatch at the

Roslashyset and Ryum Scandium in aluminium alloys

International Materials Reviews 2005 VOL 50 NO 1 33

eutectic temperature of binary AlndashSc alloys (660uC) isonly approx 047 In Refs 57 and 89 it is shown thatwhen Zr Hf and in particular Ti is dissolved in the Al3Scparticles this reduces the lattice parameter of the phaseIt appears that when 25 of the Sc atoms in Al3Sc aresubstituted by Ti the mismatch is zero at approx 550uCand becomes negative at higher temperatures89 Thissuggests that by carefully selecting the Ti content of thealloy it should be possible to obtain Al3(ScTi)substrates in the melt that match exactly the latticeparameter of the nucleating a-Al and thus furtherimprove the grain refinement of the alloy This appearsto have been achieved in a recent work180 where thegrain refinement of an Alndash07 wt-Sc alloy wascompared with that of an Alndash05 wt-Scndash02 wt-Tialloy At a cooling rate of 100 K s21 only an estimated2 of the primary Al3Sc particles of the binary AlndashScalloy were effective nuclei compared to practically 100for the primary Al3(ScTi) particles in the ternary AlndashScndashTi alloy leading to a much smaller grain size in theternary alloy Whereas the match of lattice parametersmay be of importance for these results the authors ofthis investigation180 draw attention to other factors suchas different growth restriction factors for Sc and Ti andthe possibility of a peritectic reaction in the ternaryalloy Nevertheless the principle of matching latticeparameters is worth looking into further in future work

Effects from dispersoidslsquoDispersoidsrsquo is a term which is commonly used aboutthe classes of second phase particles that are formedin an Al alloy during high temperature annealing orthermomechanical processing such as homogenisationhot rolling extrusion and forging A dense distributionof dispersoids can give a significant contribution to analloyrsquos strength owing to particle strengthening but thisis rarely the main strengthening mechanism A moreimportant contribution from the dispersoids is theirability to stabilise the grainsubgrain structure of analloy through the Zener-drag action and thus improvethe mechanical properties of the alloy

There are two noticeable dispersoid-related effectsthat have been reported for Sc-containing alloys Thefirst is the stabilising effect on a deformed microstruc-ture When a non-recrystallised structure is preserved inan alloy this can add considerably to the mechanical

strength of the material The second effect is thepreservation of a small grain size during hot deforma-tion at slow deformation rates which is necessary toobtain superplastic properties of an Al-alloy

Recrystallisation resistance

The anti-recrystallisation effect of Sc was first publishedin a patent171 where 03 wt-Sc was added to pure Aland to AlndashMg AlndashMn and AlndashZnndashMg alloys Both Sc-free and Sc-containing materials were cold worked andsubsequently annealed and it was found that theaddition of Sc increased the temperature for onset ofrecrystallisation by approx 220uC in pure Al andsomewhat less in the Al-alloys Although the author ofthe patent171 may have been well aware that the anti-recrystallisation effect is caused by Al3Sc dispersoidsthis is not mentioned in the text The first journal paperthat explicitly points out that the recrystallisationresistance is due to Al3Sc dispersoids was an investiga-tion of the effects of adding Sc to wrought AlndashMgalloys181 In this work it was found that the Al3Scdispersoids were very effective in preventing recrystalli-sation up to temperatures of approx 400ndash450uC Athigher temperatures the dispersoids coarsen consider-ably and the microstructure was partially recrystallised

It is established that the Zener-drag pZ that is imposedon an advancing grain boundary by randomly distrib-uted dispersoids can be expressed in the form

pZ~k f =r (3)

where k is a factor that includes the interface energybetween the dispersoids and the matrix f is the volumefraction and r is the mean radius of the dispersoids Thusthe Zener drag will decrease rapidly in the case where thedispersoids are coarsening

As mentioned in the section on lsquoInfluence of otherelements on precipitation of Al3Scrsquo above theAl3(Sc12xZrx) dispersoids in a ternary AlndashScndashZr alloycoarsen at a much slower rate than the Al3Sc dispersoidsin a binary AlndashSc alloy This effect was first reported inRef 123 (although also observed in Ref 182) andaccording to Ref 33 the same authors demonstratedsoon after that the denser dispersoid distributionachieved in an AlndashScndashZr alloy leads to superiorrecrystallisation resistance compared to a binary AlndashScalloy An example of the increased recrystallisationresistance by adding both Zr and Sc is shown in Fig 26

In isothermal sections of the ternary AlndashScndashZr phasediagram it is indicated that the solid solubility ofSczZr is somewhat higher than that of Sc alone54 Ithas also been demonstrated both by electrical con-ductivity measurements (Fig 27) and microstructuralobservations that the supersaturation of SczZr isgreater than that of only Sc or Zr in as cast Alndash15(SczZr) alloys183 This indicates that it should bepossible to increase the volume fraction of dispersoids inAlndashScndashZr compared to AlndashSc It is suggested162 that theincreased volume fraction that can be achieved byadding both Sc and Zr can be advantageous inconventional wrought Al-alloys

There are at least two different conditions underwhich Al3Sc or Al3(Sc12xZrx) dispersoids can form toprevent recrystallisation

1 Sc (or Sc and Zr) is in solid solution before thedeformation In the case of cold deformation and

25 Grain refinement as a function of Sc addition in pure

Al (redrawn from Ref 32) and AlndashZnndashMgndashZr (redrawn

from Ref 169) note that data points are plotted on

different ordinate axes

Roslashyset and Ryum Scandium in aluminium alloys

34 International Materials Reviews 2005 VOL 50 NO 1

subsequent annealing the Al3Sc or Al3(Sc12xZrx)dispersoids may nucleate and grow before the nucleationand growth of recrystallised grains takes placeDispersoids can form after a direct up-quench to theannealing temperature115143148184 during ramp-up tothe annealing temperature115 or by pre-annealing at anintermediate temperature129 In the case of hot deforma-tion the Al3Sc or Al3(Sc12xZrx) dispersoids maynucleate and grow during preheating of the materialand during the hot deformation itself184

2 The Al3Sc or Al3(Sc12xZrx) dispersoids are formedin the material before deformation184 Considering coldrolling and subsequent annealing the annealing tem-perature Tann may be either lower or higher than thetemperature Tdisp at which the dispersoids were formedIf TannTdisp only limited if any coarsening of thedispersoids is expected to take place and thus the Zenerdrag from the particles is expected to be practicallyconstant The driving force for recrystallisation how-ever is expected to decrease somewhat with theannealing time as a result of recovery processes Thusif recrystallisation does not occur within short annealingtimes the material is expected to remain unrecrystallisedfor infinite time at the annealing temperature IfTannTdisp there will be substantial coarsening of thedispersoids during annealing In order for the materialto remain unrecrystallised the decrease in driving forcefor recrystallisation owing to recovery has to be at leastas rapid as the decrease in Zener drag because of particlecoarsening

Experimental comparisons of the conditions abovepoint in the direction that the recrystallisation resistanceis poorest when Sc (or Sc and Zr) is in solid solutionbefore deformation and the deformed material is up-quenched to the annealing temperature148 or when Al3Scor Al3(Sc12xZrx) dispersoids are formed before defor-mation at TdispampTann184185 Excellent recrystallisationresistance is achieved if dispersoids are formed at anintermediate anneal of solutionised and deformedmaterial128 or if dispersoids are formed at TdispTann

before deformation148185ndash187 It seems that the decreasein Zener drag because of dispersoid coarsening in many

cases is slower than the decrease in driving force forrecrystallisation because of recovery processes Thusthere is an advantage in forming a high number densityof small dispersoids which for most practical casesmeans that they should be formed at TdispTann122

When an advancing high angle grain boundary iethe recrystallisation front is passing a coherent Al3Scdispersoid there are at least three possible grainboundarydispersoid interactions

1 The Al3Sc dispersoid retains its global orientationrelationship and thus loses its coherency with thesurrounding matrix

2 The Al3Sc dispersoid rotates as the grain boundarypasses either by diffusional processes at the dispersoidmatrix interface or by the grain boundary passingthrough the dispersoid and the Al3Sc dispersoidassumes the same crystallographic orientation as theAl matrix of the recrystallised grain

3 The Al3Sc dispersoid dissolves at the grainboundary and re-precipitates in the recrystallised grain

Which interactions that actually take place willprobably depend on the dispersoid size annealingtemperature and driving force for recrystallisation It isalso possible that alloy composition (other elementsthan Al) is of importance

It has been reported that large (Oslash about 100ndash150 nm)Al3Sc dispersoids in a deformed Alndash4 wt-Mgndash02 wt-Sc alloy annealed at 575uC lose the orientationrelationship with the matrix after being passed by therecrystallisation front148

A rotation of somewhat smaller Al3Sc dispersoids in arecrystallising binary Alndash025 wt-Sc alloy has beenreported115143 The rotation was reported to be accom-panied by substantial growth (from Oslash 30 nm to Oslash48 nm) as a result of enhanced Sc diffusion at the grainboundary Observations suggested that the grainboundaries were passing through the dispersoids andthus the Al3Sc dispersoids retained the orientationrelationship with the recrystallised Al matrix

Dissolution and re-precipitation of Al3Sc dispersoidshas been reported during recrystallisation of a 50 coldrolled Alndash02 wt-Sc alloy162 Large spherical partially

26 Fraction recrystallised structure in cold rolled sheets

of Alndash04 wt-Sc and Alndash04 wt-Scndash015 wt-Zr as a

function of annealing temperature redrawn from

Ref 183 27 Electrical conductivity in Alndash15(SczZr) alloys

redrawn from Ref 183

Roslashyset and Ryum Scandium in aluminium alloys

International Materials Reviews 2005 VOL 50 NO 1 35

coherent dispersoids were observed to dissolve at therecrystallisation front and re-precipitate as smallercoherent Al3Sc cuboids

Superplastic forming

It seems that the first publication on superplasticproperties of Sc-containing Al-alloys was a study of anAlndash35Cundash14Mgndash045Mnndash04(SczZr) alloy188

It was recognised that the superplastic properties are aresult of the stabilisation of the fine grain structure byAl3Sc dispersoids The Sc-containing Al alloys that havereceived most attention for their superplastic propertieshowever are those of the AlndashMgndashSc system which wasfirst published in a patent189 Here it was noted that anAlndash4 wt-Mgndash05 wt-Sc alloy had superior superplasticproperties compared to fine-grained 7475 (AlndashZnndashMgndashCu alloy) Binary Alndash05 wt-Sc and Alndash4 wt-Mgalloys did not behave superplastically The flow stress atthe hot forming temperature was found to be much (30ndash40) lower in the ternary alloy than that of the twobinary alloys

The superplastic properties of AlndashMgndashSc alloys havebeen explored by several research groups over the lastdecade190ndash196 It has frequently been found that thedeformation mechanism is dominated by grain bound-ary sliding190 However it has also been reported thatAlndashMgndashSc alloy may deform superplastically withoutnoticeable grain boundary sliding23 It is generallyrecognised that the grain boundary sliding mechanismis facilitated when the average grain size is very smalland grain boundaries are predominantly high-angleSuch a microstructure may be achieved by carefulthermomechanical processing of the starting mate-rial193194197198 It has however been shown that a finegrained structure with high angle boundaries maydevelop during superplastic forming of AlndashMgndashSc alloyseven if the starting microstructure is an entirely differentone for instance that of a cold rolled sheet192 It has alsobeen suggested that superplastic forming of as castmaterial may be possible189

One of the more efficient thermomechanical processesfor achieving an ultrafine grain structure with high anglegrain boundaries in Al-alloys is equal channel angularpressing (ECAP) A JapanesendashAmerican group ofscientists has published an impressive body of researchon improvements in superplastic properties in Al-alloys processed by ECAP over the last few years andseveral of the publications are from investigations onAlndashMgndashSc alloys170199ndash224 Maximum strains in excessof 2000 at a strain rate of 0033 s21 have beenachieved170201202217 which is an extraordinarily goodcombination of high strain and high strain rate for analuminium alloy

Superplastic properties of AlndashCundashMg(ndashMn)ndashSc(ndashZr)and AlndashMgndashSc(ndashZr) alloys have been mentionedNoticeable superplasticity in other Sc-containing Al-alloys has also been reported such as AlndashZnndashMg(ndashCu)ndashScndashZr169225ndash228 AlndashLindashSc229 AlndashMgndashLindashScndashZr229ndash234

AlndashLindashMgndashCundashScndashZr235236 and AlndashCundashLindashScndashZr233

Precipitation hardeningHardening by Al3Sc precipitates

It has been noted that when Al3Sc particles precipitate inthe temperature range 250ndash350uC they give a significanthardness increase in the alloy Some authors point out

that Sc is a more effective precipitation hardening elementper atomic fraction added than the elements that arecommonly used for precipitation hardening121130 (In onepaper29 it is claimed that only Au has a strongerstrengthening effect than Sc) However the amount ofSc that can be precipitated from supersaturated solidsolution is rather limited and thus the absolute values ofthe hardness increase from the precipitation hardening ismuch lower than what is normally associated withprecipitation hardened alloys Also the temperatureregime for age hardening by precipitation of Al3Sc issomewhere in between the temperature regimes for agehardening and solution heat treatments of commonprecipitation hardened alloys This makes a combinedprecipitation of Al3Sc and other strengthening precipi-tates unfeasible Thus precipitation strengthening byAl3Sc is most feasible in alloy systems that are non-heat-treatable The non-heat-treatable aluminium alloy sys-tems are according to the Aluminum Associationdesignations the 1xxx series (99 pure Al) the 3xxxseries (AlndashMn) and the 5xxx series (AlndashMg) The purposeof adding Sc to these alloys may be either to stabilise themicrostructure of wrought semiproducts (extrusionsrolled plates forgings etc) as discussed in the sectionon lsquoRecrystallisation resistancersquo above or to provideextra strength to the alloy through precipitation hard-ening In the latter case it is appropriate to considerwhether the Sc-containing alloy still should be classifiedas non-heat-treatable A heat treatment is applied thatbrings about a significant precipitation hardening On theother hand the hardness increase that is achieved throughthe heat treatment is lower than what is normallyassociated with heat-treatable alloy systems Hence eventhough it seems like a contradiction one chooses to keepusing the term lsquonon-heat-treatablersquo about these alloys

Table 7 gives an overview of some mechanicalproperties of Sc-containing non-heat-treatable alloysthat are reported in the literature Most of theexperimental work on Sc in 1xxx-types of alloys hasbeen done on binary AlndashSc alloys with much higherpurity than industrial alloys

Strengthening mechanisms

When the precipitates are larger than a critical size thestrengthening effect is due to the Orowan-mechanism iedislocations can only pass the precipitates by looping Inthis case the strengthening effect of the particles isapproximately inversely proportional to the mean parti-cle spacing When the precipitates can be sheared bydislocations there are a number of strengthening mechan-isms that apply It is proposed by Parker et al108 that thetwo major contributing mechanisms are coherency strainand anti-phase-boundary energy In a recent detailedstudy of strengthening mechanisms in binary AlndashSc alloysby Marquis and colleagues117118 the strengthening fromshear modulus mismatch between the matrix and theprecipitates is also accounted for A qualitatively goodmatch between theoretical strengthening and measuredvalues is achieved in this work both for deformation atroom temperature and at 300uC

Effect of Sc on precipitation strengthening in heat-treatablealloys

Following the AA designation system the traditionalheat-treatable Al-alloys are those that belong to the 2xxx

Roslashyset and Ryum Scandium in aluminium alloys

36 International Materials Reviews 2005 VOL 50 NO 1

series (AlndashCu) 6xxx series (AlndashMgndashSi) and 7xxx series(AlndashZnndashMg) AlndashLi alloys should also be mentionedSeveral investigations have been carried out in order toclarify the effects of Sc on the precipitation behaviour inthese alloy systems

AlndashCu alloys

The precipitation sequence in AlndashCu alloys is oftendescribed as follows

Supersaturated solid solutionRGP-zonesRh0Rh9Rh(Al2Cu)

The highest strength is normally achieved when the h0or h9 precipitates are predominant Typical precipitationheat treatment temperatures for AlndashCu alloys are in therange 160ndash190uC238 which is considerably lower thanthe typical precipitation temperature for Al3ScComparisons of the aging responses of AlndashCu and AlndashCundashSc alloys at 150 and 200uC indicate that there is nonoticeable effect of Sc on the precipitation kinetics ofh9153 It is observed that the h9 precipitates may nucleateon Al3Sc particles153 At 300uC it is observed that h9particles are somewhat smaller in AlndashCundashSc alloys thanin AlndashCu alloys156

AlndashMgndashSi alloys

The following precipitation sequence is commonlyreported for AlndashMgndashSi alloys

Supersaturated solid solutionRGP-zonesRb0Rb9Rb(Mg2Si)

For peak aged alloys the predominant precipitatetype is b0 for which the stoichiometric composition hasrecently been resolved to be Mg5Si6239 Temperatures inthe range 160ndash205uC are typically used for precipitationhardening of these alloys238 Adding both 03 wt-Scand 01 wt-Zr to an Alndash06 wt-Mgndash065 wt-Sialloy does not seem to alter the precipitation kineticsof b0 at 165uC However the hardness increase becauseof precipitation hardening appears to be smaller in theSczZr-containing alloy240 In another investigationadditions of 01 wt-Sc 015 wt-Sc 02 wt-Sc04 wt-Sc and 02 wt-Scz01 wt-Zr were made toan Alndash08 wt-Mgndash07 wt-Si alloy241 Here it wasalso observed that the precipitation kinetics of b0 wasseemingly independent of the Sc additions (Fig 28)TEM observations indicated that the b0 precipitateswere of comparable sizes in the investigated alloys andno interactions between Al3Sc and b0 were observed(Fig 29) In a third study242 where the effect of Sc onthe precipitation in an AlMgSindashSiC metal matrixcomposite was investigated there also does not seemto be any effect on the precipitation kinetics Howevercontrary to the findings of Ref 240 it is reported thatthe Sc addition leads to a higher hardness increase thanin the corresponding Sc free alloy

AlndashMgndashZn alloys

For these alloys the following precipitation sequence isoften ascribed

Table 7 Mechanical properties in non-heat-treatable Al-alloys with Sc

Reference Alloy wt- YS MPa UTS MPa Note

1xxx alloys171 000Sc 15 48 Cast material aged 288uC8 h

023Sc 159 185 Cast material aged 288uC8 h038Sc 199 220 Cast material aged 288uC8 h000Sc 14 49 Cold rolled material (89) aged 288uC8 h023Sc 198 208 Cold rolled material (89) aged 288uC8 h038Sc 240 264 Cold rolled material (89) aged 288uC8 h000Sc 8 34 Cold rolled material quenched from 649uC aged 288uC8 h023Sc 147 157 Cold rolled material quenched from 649uC aged 288uC8 h038Sc 193 199 Cold rolled material quenched from 649uC aged 288uC8 h

121 05Sc 160 ndash Forged material quenched from 635uC aged 250uC50 h23 05Sc 298 319 Hot rolled 288uC cold rolled 69ndash81 aged 288uC4 h112 01Sc 132 166 Hot z cold rolled material quenched from 630uC

aged 320uC133 h148 02Sc 138 ndash Cast material aged 300uC10 h compression test159 04Sc 196 ndash Cast material aged 300uC10 h compression test117 118 03Sc 209 ndash Cast material quenched from 648uC aged 300uC5 h

compression test3xxx alloys171 1Mn 015Sc 216 221 Cold rolled material (89) aged 288uC8 h

1Mn 05Sc 309 323 Cold rolled material (89) aged 288uC8 h186 05Mn 02Mg

026Sc 015Zr162 201 Extruded material solutionised 600uC aged 250uC

5xxx alloys171 1Mg 43 111 Cold rolled material (89) aged 288uC8 h

1Mg 03Sc 288 303 Cold rolled material (89) aged 288uC8 h53Mg 147 259 Cold rolled material (50) wintermediate anneals

at 343uC aged 288uC8 h53Mg 03Sc 368 401 Cold rolled material (50) wintermediate anneals

at 343uC aged 288uC8 h23 2Mg 05Sc 376 401 Hot rolled 288uC cold rolled 69ndash81 aged 288uC4 h

4Mg 05Sc 414 4606Mg 05Sc 433 503

237 4Mg 1Sc 420 525 Cold rolled material (83) aged 320uC1 h148 4Mg 02Sc 194 ndash Cast material aged 300uC10 h compression test

Tensile test data except where noted YS yield strength UTS ultimate tensile strength

Roslashyset and Ryum Scandium in aluminium alloys

International Materials Reviews 2005 VOL 50 NO 1 37

Supersaturated solid solutionRGP-zonesRg9Rg(Zn2Mg)

The maximum hardness is normally achieved whenthe g9 precipitates are predominant Common precipita-tion hardening temperatures are in the range 95ndash180uCand a two-step precipitation heat treatment within thistemperature regime is often used238 It has beenobserved in some investigations that Sc and SczZradditions to AlndashMgndashZn alloys slow down the precipita-tion of g9 somewhat243 Other investigations find thatthere is no effect of Sc on the precipitation behaviour ofg9244245 and yet others report that Sc additionssignificantly speed up the precipitation of g9246 In Ref247 it is found that an Sc addition leads to coarser g9precipitates and it is claimed that this gives an improvedductility of the alloy The strength-loss associated withlarger particle size is reported to be counterbalanced bystrengthening from Al3Sc precipitates

AlndashLi alloys

The precipitation sequence in binary AlndashLi alloys isapparently simple

Supersaturated solid solutionRd9Rd (AlLi)

where d9 is the metastable Al3Li phase which just likeAl3Sc has the L12 type of atomic arrangement Thetypical temperature regime for precipitation of d9 whichis the strengthening phase in this system is approx 150ndash200uC A comparison of the age hardening response ofan Alndash26 wt-Li and an Alndash24 wt-Lindash019 wt-Scalloy at 180uC248 and 200uC161 indicates that the onsetof d9 precipitation is not altered by the presence of ScThe hardness curves for the two alloys are practicallyidentical at 200uC whereas at 180uC the peak hardnesslevel is slightly higher in the AlndashLi than the AlndashLindashScalloy DSC measurements at constant heating ratesindicate that the addition of Sc to an AlndashLi alloysincreases the activation energy for d9 precipitation andmoves the exothermic peak associated with d9 precipita-tion to a higher temperature248 For specimens aged at

either 180uC or 200uC TEM observations reveal that thed9 precipitates are much smaller in the Sc containingalloy than in binary AlndashLi both in the peak agedcondition and in the overaged condition161248 Additionof Sc has also been observed to reduce the size of d9precipitates in other AlndashLi based alloys249ndash251 In an AlndashLindashCundashZr alloy an addition of Sc has been reported toslow down the homogeneous precipitation of d9252253 Ithas been claimed that Sc reduces the quench sensitivityand delays room temperature aging of AlndashLi basedalloys254ndash256

When present in the microstructure before the pre-cipitation of d9 the Al3Sc precipitates may act as effec-tive nucleation sites for d9 The resulting precipitates arespheres of d9 with a core of Al3Sc161249252ndash255257ndash261

Corrosion resistanceAn appreciable amount of data is available on the effectsof Sc on the corrosion behaviour of wrought Al-alloysSome of these effects are apparently derived from theeffects of Sc on the microstructure of the alloys It hasbeen reported that an addition of Sc increases thecorrosion potential (makes it less negative) in pureAl262ndash264 in AlndashZn alloys265266 AlndashMg alloys267 AlndashZnndashMgndashCu alloys264268 AlndashCundashMgndashMn alloys264 andin AlndashCundashLindashMgndashAg alloys264 Even though Sc alsohas been reported to decrease the corrosion potential in

28 Age hardening response at 175uC for Alndash08 wt-Mgndash

07 wt-Si alloy (Base) with additions of 02 wt-Sc

04 wt-Sc and 02 wt-Scz01 wt-Zr from Ref 241

29 TEM images of a b0 precipitates in Alndash08 wt-Mgndash

07 wt-Si alloy and b b0 and Al3(Sc1ndashxZrx) in a similar

alloy with addition of 02 wt-Scz01 wt-Zr from

Ref 241

Roslashyset and Ryum Scandium in aluminium alloys

38 International Materials Reviews 2005 VOL 50 NO 1

AlndashMg alloys269270 it seems that the general trend isthat adding Sc to an alloy makes it slightly more nobleThe change in corrosion potential is much morepronounced when Sc is added in amounts larger thanthe eutectic composition263 ie there is a considerablecontribution from primary or eutectic Al3Sc to theoverall potential It has also been demonstrated that thechange in corrosion potential caused by Sc can dependon the heat treatment applied to the alloy267268

Even though the corrosion potential is an essentialparameter in establishing the corrosion behaviour of analloy an increase in the corrosion potential does notnecessarily imply an improved self-corrosion resistanceHowever measurements of corrosion rates and passiva-tion current densities strongly suggest that the self-corrosion resistance in general is considerably improvedwhen Sc is added to wrought Al-alloys263264267 Someobserved variations in corrosion potential and passiva-tion current densities with Sc content in binary AlndashScalloys are plotted in Fig 30

Material failure in corrosive environments is often dueto localised corrosion attacks which may propagaterapidly even though the bulk material has a goodresistance against general corrosion It has been pointedout that hypereutectic additions of Sc may lead tomicrogalvanic corrosion beside primary Al3Sc parti-cles264 In AlndashMg alloys grain boundary precipitation ofAl8Mg5 can lead to localised corrosion attacks such asintergranular corrosion (IGC) exfoliation corrosion(EC) and stress corrosion cracking (SCC) In wroughtmaterial such precipitation may occur in the 60ndash180uCtemperature regime and heating in this temperaturerange is referred to as lsquosensitationrsquo An AlndashMgndashSc alloywas found to be immune against intergranular corrosionand have moderate susceptibility to exfoliation corro-sion after annealing at 350uC271 After sensitation heattreatments severe IGC and EC was observed but notquite as severe as in a corresponding alloy without ScAs for SCC the AlndashMgndashSc alloy was found to be highlyresistant271 In another study it was found that additionof 056 wt-Sc reduces the SCC susceptibility of an Alndash68 wt-Mg alloy in the as-rolled state and afterannealing at 250uC whereas in a sensitised specimenthe SCC susceptibility is somewhat increased by the Scaddition272 A third investigation found that Sc has nomeasurable detrimental effect on the SCC susceptibilityof sensitised Alndash5Mgndash015Zr alloy273 SCC is also a

severe problem in high strength AlndashZnndashMgndashCu alloys Ithas been shown that small Sc additions are effective inreducing the SCC sensitivity of these alloys244246268274

Use of Sc-containing Al alloysA systematic development of Sc-containing aluminiumalloys took place in the former USSR in the 1980s andthe interest for Sc as an alloying element in aluminiumalloys hit the western world approximately 10 yearslater Even though a number of improvements in Alalloys achieved by Sc addition have been demonstratedthe current uses of such alloys are very limited This isrelated to the very high price of scandium

In Russia some parts of military aircraft are made ofSc-containing AlndashLi alloys In the western world themain usage of Sc-containing alloys is for sportsequipment Ashurst Technology and Kaiser Aluminumdeveloped a Sc-containing 7xxx alloy for baseball andsoftball bats which was introduced to the Americanmarket in 1997 by Easton Alcoa soon followed with aSc-containing alloy for a competing brand of batsLouisville Slugger Since then several new and improvedSc-containing alloys for bats have been introduced tothe market The purpose of adding Sc is to increase theyield strength of the alloy allowing for a down-gaugingof the wall thickness which in turn gives a strongerlsquospring-rsquo or lsquotrampoline-rsquo effect when the ball hits thebat

Shortly after the introduction of the Sc containingbats Easton also launched Sc-containing 7xxx tubingfor bicycle frames Just as in the bats Sc increases theyield strength of the alloy allowing for down-gauging oftube wall thickness and a corresponding weight reduc-tion of the bicycle frame An Italian manufacturer ofbicycle tubing Dedacciai also delivers tubes in a Sc-containing 7xxx alloy

Other sports equipment made from Sc-containingaluminium alloys includes lacrosse sticks and tent polesSmith and Wesson has also introduced a series ofhandguns where the frame is made from a Sc-containingAl alloy

A common factor for the items mentioned above isthat the material cost is only a minor part of the totalmanufacturing cost of the end product and also thatthese products are aimed at a group of customers thathave a certain awareness of new materials Both baseballbats and bicycle frames have been marketed aslsquoscandium alloyrsquo even though the Sc content is muchlower than 1

Currently AlndashSc master alloys for the production ofSc-containing Al alloys are available at a price thatcorresponds to US$ 2000 per kg of Sc This means that ifone wants to add 02 wt-Sc to an alloy which is afairly common content one also increases the price ofthe alloy by US$ 4 per kg alloy Depending on the alloytype Sc is added to this represents a tripling orquadrupling of the price of the alloy There are notmany existing products where such an increase inmaterial cost can be justified In order to see awidespread use of Sc in high-volume products the Scprice has to come down considerably Actually the priceof adding Sc to Al alloys has gone down by a factor 3ndash10over the last 10ndash15 years and substantial price reduc-tions are also expected in the future

30 Observed variations in corrosion potential and passi-

vation current densities with Sc content in binary Alndash

Sc alloys based on data from Ref 263

Roslashyset and Ryum Scandium in aluminium alloys

International Materials Reviews 2005 VOL 50 NO 1 39

The current production of AlndashSc master alloys isbased upon and will continue to be based upon for theforeseeable future the reduction of Sc2O3 or other Sccompounds directly in molten aluminium It is notnecessary as many tend to believe to take the route viametallic Sc Thus the price of AlndashSc master alloy isgoverned by the price of Sc2O3 or other Sc compoundsin question and not by the price of metallic scandiumThe Sc2O3 which is the main source for todayrsquos AlndashScmaster alloy production comes from stockpiles in theformer USSR These stockpiles will be exhausted withina few years and new reliable sources of Sc2O3 or otherSc compound production are sought It turns out thatthe most economically viable option that has beendisclosed so far is the processing of Red Mud from theBayer process of extracting alumina from bauxiteScandium is enriched in the Red Mud and is extractedfrom a Red Mud aqueous slurry by selective leachingsubsequent ion-exchange procedure and finally a liquidndashliquid extraction procedure It is not required to build aseparate lsquoSc factoryrsquo to do this but rather build an lsquoadd-onrsquo to existing Bayer process plants Such a processroute is expected to bring down the price of Sc2O3

considerably which in turn means that AlndashSc masteralloy price should drop accordingly Preliminary ana-lyses suggest a price of approx US$ 400 per kg Sc in themaster alloy which translates to an added cost of 80cent per kilo when 02 wt-Sc is added to an aluminiumalloy This is also a considerable increase in the materialcost but with such prices one should expect to see Sccontaining alloys in many more applications than whatis the case at the present time

Concluding remarksThe body of published investigations on Al-based alloyswith Sc addition provides a sound basis of knowledgefor metallurgists that want to look into the possibility ofenhancing the performance of a wrought Al-alloy byadding Sc to it Ternary AlndashScndashX phase diagrams areavailable for practically every technologically importantalloying element in Al The effect of a wide range ofternary alloying elements on the precipitation behaviourof Al3Sc is accounted for It has been shown that theAl3Sc phase can be effective as a grain refiner adispersoid former and a precipitate hardening agentand some of the underlying conditions for achieving thedesired Al3Sc formation have been outlined Addingsome Zr together with Sc has proven to be beneficial Itmay lead to effective grain refinement at a lower Sc levelbut the most prominent effect is the refinement indispersoid distribution that can be achieved An addi-tion of Sc has little if any effect on precipitation in the2xxx 6xxx and 7xxx alloy systems and some effects onthe precipitation in AlndashLi based alloys With respect tocorrosion behaviour adding Sc to an Al-alloy does ingeneral seem to make the alloy slightly more noble andto increase its self-corrosion resistance Scandium-containing Al alloys have very few uses at the presenttime as a result of the high price of scandium The priceof Sc is expected to decrease significantly in the futureand this should lead to the disclosure of moreapplications where it is economically feasible to takeadvantage of the improved properties of some Sc-containing aluminium alloys

References1 D R Lide lsquoCRC handbook of chemistry and physicsrsquo 71st edn

4ndash29 1990 Boston USA CRC Press

2 E M Savitsky V F Terehova I V Burov and O P Naumkin

Proc Fourth Conf on lsquoRare earth researchrsquo Phoenix Arizona

USA April 1964 409ndash420

3 E M Savitskii V F Terekhova I V Burov O P Naumkin and

I A Markova Inorg Mater 1965 1 1503ndash1512

4 O P Naumkin V T Terekhova and E M Savitskiy Russ

Metall 1965 (4) 128ndash136

5 W G Moffatt lsquoThe handbook of binary phase diagramsrsquo 1981

Schenectady NY USA General Electric Co

6 E A Brandes (ed) lsquoSmithells metals reference bookrsquo 6th edn

1983 London UK Butterworths

7 R P Elliott and F A Shunk Bull Alloy Phase Diagrams 1981

2 (2) 222ndash223

8 K A Gschneider Jr and F W Calderwood Bull Alloy Phase

Diagrams 1989 10 34ndash36

9 H Okamoto J Phase Equil 1991 12 612ndash613

10 J L Murray J Phase Equil 1998 19 380ndash384

11 M E Drits E S Kadaner T V Dobatkina and N I Turkina

Russ Metall 1973 (4) 152ndash154

12 S-I Fujikawa M Sugaya H Takei and K-I Hirano J Less-

Common Met 1979 63 87ndash97

13 N Blake and M A Hopkins J Mater Sci 1985 20 2861ndash2867

14 V I Kononenko and S V Golubev Russ Metall 1990 (2) 193ndash

195

15 T B Massalski J L Murray L H Bennett and H Baker (eds)

lsquoBinary alloy phase diagramsrsquo 1986 Metals Park OH USA

ASM

16 G Cacciamani P Riani G Borzone N Parodi A Saccone

R Ferro A Pisch and R Schmid-Fetzer Intermetallics 1999 7

101ndash108

17 H Okamoto J Phase Equil 2000 21 310

18 A F Norman P B Pragnell and R S McEwen Acta Mater

1998 46 5715ndash5732

19 I N Pyagai and A V Vakhobov Russ Metall 1990 (5) 50ndash52

20 C L Fu J Mater Res 1990 5 971ndash979

21 X Lu and Y Wang Calphad 2002 26 555ndash561

22 R R Sawtell and J W Morris Jr Proc lsquoDispersion strengthened

aluminium alloysrsquo Phoenix Arizona USA January 1988 409ndash

420

23 R R Sawtell and C L Jensen Metall Trans A 1990 21A 421ndash

430

24 L A Willey Unpublished research Alcoa 1970 Data points are

extracted from Ref 10

25 N I Turkina and V I Kuzmina Russ Metall 1976 (4) 179ndash

183

26 T Torma E Kovacs-Csetenyi I Vitanyi M Butova and

J Stepanov Proc 6th Int Symp on lsquoHigh purity materials in

science and technologyrsquo Akademie der Wissenschaften der DDR

Dresden Germany May 1985 388ndash389

27 A L Berezina V A Volkov B P Domashnikov and K V

Chuistov Metallofizika 1987 9 (5) 43ndash47

28 H-H Jo J Korean Inst Metals 1990 28 499ndash504

29 H-H Jo and S-I Fujikawa Mater Sci Eng 1993 A 171 151ndash

161

30 S Celotto and T J Bastow Philos Mag A 2000 80 1111ndash1125

31 J Roslashyset and N Ryum submitted to Mater Sci Eng

32 M E Drits L S Toropova Yu G Bykov F L Gushchina V I

Elagin and Yu A Filatov Russ Metall 1983 (1) 150ndash153

33 L S Toropova D G Eskin M L Kharakterova and T V

Dobatkina lsquoAdvanced aluminum alloys containing scandium

structure and propertiesrsquo 1998 Amsterdam The Netherlands

Gordon and Breach Science Publishers

34 V V Cherkasov P P Pobezhimov L P Nefedova E V Belov

and G M Kuznetsov Met Sci Heat Treat 1996 (6) 268ndash270

35 Kh O Odinaev I N Ganiev V V Kinzhibalo and B Ya

Kotur Dokl Akad Nauk Tadzh SSR 1989 32 37ndash38

36 Kh O Odinaev I N Ganiev and A V Vakhobov Russ Metall

1991 (4) 200ndash203

37 J Grobner R Schmid-Fetzer A Pisch G Cacciamani P Riani

N Parodi G Borzone A Saccone and R Ferro Z Metallkd

1999 90 872ndash880

38 E A Marquis and D N Seidman Microsc Microanal 2002 8

(Suppl 2) 1100CDndash1101CD

39 A Pisch J Grobner and R Schmid-Fetzer Mater Sci Eng A

2000 A 289 123ndash129

Roslashyset and Ryum Scandium in aluminium alloys

40 International Materials Reviews 2005 VOL 50 NO 1

40 C Xia F Zeng and Y Gu Trans Nonferrous Met Soc China

2003 13 1124ndash1127

41 M Yu Teslyuk and V S Protasov Sov Phys Crystallogr 1966

10 470ndash471

42 M L Kharakterova and T V Dobatkina Russ Metall 1988

(6) 175ndash178

43 M L Kharakterova Russ Metall 1991 (4) 195ndash199

44 L S Toropova M L Kharakterova and D G Eskin Russ

Metall 1992 (3) 194ndash199

45 P Riani L Arrighi R Marazza D Mazzone G Zanicchi and

R Ferro J Phase Equil Diff 2004 25 22ndash52

46 A T Tyvanchuk T I Yanson B Ya Kotur O S Zarechnyuk

and M L Kharakterova Russ Metall 1988 (4) 190ndash192

47 L L Rokhlin T V Dobatkina and M L Kharakterova Powder

Metall Met Ceram 1997 36

48 A Z Ikromov I N Ganiev and V V Kinzhibalo Dokl Akad

Nauk Tadzh SSR 1990 (6) 391ndash392

49 I N Ganiev A Z Ikromov and V G Khudoiberdiev Russ

Metall 1995 (3) 125ndash127

50 I N Fridlyander L L Rokhlin T V Dobatkina and N I

Nikitina Met Sci Heat Treat 1993 (10) 567ndash571

51 I N Fridlyander L L Rokhlin T V Dobatkina V V

Kinzhibalo and A T Tyvanchuk Russ Metall 1998 (1) 161ndash

166

52 R A Emigh E L Bradley and J W Morris Jr in lsquoLight-weight

alloys for aerospace applications IIrsquo (ed E W Lee and N J

Kim) 27ndash43 1991 TMS

53 L S Toropova A N Kamardinkin V V Kindzhibalo and A T

Tyvanchuk Phys Met Metall 1990 70 (6) 106ndash110

54 A N Kamardinkin T V Dobatkina and T D Rostova Russ

Metall 1991 (4) 216ndash218

55 L S Torodskaya T V Dobatkina and A N Kamardinkin

Russ Metall 1992 (5) 128ndash131

56 E M Sokolovskaya E F Kazakova E I Poddyakova and A

A Ezhov Met Sci Heat Treat 1997 (5) 211ndash213

57 Y Harada and D C Dunand Mater Sci Eng 2002 A 329ndash331

686ndash695

58 N E Drits L S Toropova and F L Gushchina Russ Metall

1984 (4) 229ndash232

59 E M Sokolovskaya E F Kazakova V A Alikhanov and E V

Zhuravleva Moscow Univ Chem Bull 1997 52 (5) 70ndash72

60 E M Sokolovskaya E F Kazakova and E I Poddyakova Met

Sci Heat Treat 1989 (11) 837ndash839

61 G M Cheldieva E F Kazakova E M Sokolovskaya and N I

Kaloev Russ Metall 1990 (6) 87ndash90

62 E M Sokolovskaya E F Kazakova and O D-S Kendivan

Russ Metall 1998 (4) 135ndash137

63 N G Bukhanko E F Kazakova and E M Sokolovskaya Russ

Metall 2001 (4) 425ndash431

64 E D Trubnyakova O I Bodak I N Ganiev and A V

Vakhobov Russ Metall 1987 (3) 219ndash222

65 I N Fridlyander and L V Molchanova Russ Metall 2003 (5)

476ndash480

66 R A Altynbaev S Kh Khairidinov and A V Vakhobov Russ

Metall 1987 (4) 194ndash196

67 J C Schuster and J Bauer J Less-Common Met 1985 109

345ndash350

68 L L Rokhlin A S Fridman T V Dobatkina and D G Eskin

Russ Metall 1991 (6) 146ndash148

69 A S Fridman T V Dobatkina and E V Muratova Russ

Metall 1992 (1) 207ndash209

70 C Xia F Zeng and Y Gu Trans Nonferrous Met Soc China

2003 13 546ndash552

71 F Zeng C Xia and Y Gu J Alloys Comp 2004 363 175ndash181

72 L L Rokhlin T V Dobatkina N R Bochvar and E V Lysova

J Alloys Comp 2004 367 10ndash16

73 T V Dobatkina A S Fridman and E V Muratova Russ

Metall 1992 (5) 125ndash127

74 I N Fridlyander L L Rokhlin N R Bochvar E V Lysova

and O V Boteva Russ Metall 2001 (6) 661ndash666

75 V N Rechkin L K Lamikhov and T I Samsonova Sov Phys

Crystallogr 1964 9 325ndash327

76 I I Zalutskii and P I Kripyakevich Sov Phys Crystallogr

1967 12 341ndash343

77 T J Bastow C T Forwood M A Gibson and M E Smith

Phys Rev B 1998 58 2988ndash2997

78 K Fukunaga M Kolbe K Yamada and Y Miura Mater Sci

Eng 1997 A 234ndash236 594ndash597

79 E P George J A Horton W D Porter and J H Schneibel

J Mater Res 1990 5 1639ndash1648

80 E P George D P Pope C L Fu and J H Schneibel ISIJ Int

1991 31 1063ndash1075

81 Y Harada and D C Dunand Acta Mater 2000 48 3477ndash3487

82 J H Schneibel and E P George Scripta Metall Mater 1990 24

1069ndash1074

83 J H Schneibel and P M Hazzledine Mater Res Soc Symp

Proc 1991 213 323ndash328

84 J H Schneibel and P M Hazzledine J Mater Res 1992 7

868ndash875

85 C J Sparks E D Specht G E Ice P Zschack and J Schneibel

Mater Res Soc Symp Proc 1991 213 363ndash368

86 J Tarnacki and Y-W Kim Scripta Metall Mater 1989 23

1063ndash1068

87 M Asta V Ozolins and C Woodward JOM 2001 53 (9) 16ndash

19

88 M E Drits L S Toropova F L Gushchina and S G Fedotov

Sov Non-Ferrous Met Res 1984 12 83ndash85

89 Y Harada and D C Dunand Scripta Mater 2003 48 219ndash222

90 C Woodward M Asta G Kresse and J Hafner Phys Rev B

2001 63 094103-1-6

91 J-H Xu and A J Freeman Phys Rev B 1990 41 12553ndash12561

92 M F Bartholomeusz and J A Wert Acta Metall Mater 1992

40 673ndash682

93 G Bester and M Fahnle J Phys Condens Matter 2001 13

11551ndash11565

94 C L Fu and M H Yoo Proc lsquoOrdered intermetallics ndash physical

metallurgy and mechanical behaviorrsquo Irsee Germany June 1991

155ndash164

95 K Fukunaga T Shouji and Y Miura Mater Sci Eng 1997 A

239ndash240 202ndash205

96 D P Pope Proc lsquoOrdered intermetallics ndash physical metallurgy

and mechanical behaviorrsquo Irsee Germany June 1991 143ndash153

97 J-S Wang Acta Mater 1998 46 2663ndash2674

98 M H Yoo and C L Fu Mater Sci Eng 1992 A 153 470ndash478

99 R W Hyland Jr and R C Stiffler Scripta Metall Mater 1991

25 473ndash477

100 I G Brodova I V Polents O A Korzhavina P S Popelrsquo I P

Korshunov and V O Esin Melts 1992 4 392ndash397

101 I G Brodova O A Chikova I V Polents P S Popelrsquo and V O

Esin Casting Processes 1992 1 (2) 158ndash160

102 I G Brodova D V Bashlikov and I V Polents Mater Sci

Forum 1998 269ndash272 589ndash594

103 K B Hyde A F Norman and P B Pragnell Mater Sci Forum

2000 331ndash337 1013ndash1018

104 K B Hyde A F Norman and P B Pragnell Acta Mater 2001

49 1327ndash1337

105 J Roslashyset and N Ryum Proc 6th Int Conf on lsquoAluminum

alloysrsquo Toyohashi Japan July 1998 793ndash798

106 V I Elagin V V Zakharov and T D Rostova Met Sci Heat

Treat 1993 (6) 317ndash319

107 R W Hyland Jr Metall Trans A 1992 23A 1947ndash1955

108 B A Parker Z F Zhou and P Nolle J Mater Sci 1995 30

452ndash458

109 C L Rohrer M D Asta S M Foiles and R W Hyland Jr

Mater Res Soc Symp Proc 1996 398 477ndash482

110 G M Novotny and A J Ardell Mater Sci Eng 2001 A 318

144ndash154

111 J D Robson M J Jones and P B Pragnell Acta Mater 2003

51 1453ndash1468

112 C Tan Z Zheng and B Wang Proc 3rd Int Conf on

lsquoAluminium alloysrsquo Vol I NTH Trondheim Norway June

1992 290ndash294

113 M Nakayama A Furuta and Y Miura Mater Trans JIM

1997 38 852ndash857

114 E A Marquis and D N Seidman Acta Mater 2001 49 1909ndash

1919

115 M J Jones and F J Humphreys Acta Mater 2003 51 2149ndash

2159

116 E A Marquis D N Seidman and D C Dunand in lsquoCreep

deformation fundamentals and applicationsrsquo (ed R S Mishra

J C Earthman and S V Raj) 299ndash308 2002 TMS

117 D N Seidman E A Marquis and D C Dunand Acta Mater

2002 50 4021ndash4035

118 E A Marquis D N Seidman and D C Dunand Acta Mater

2003 51 285ndash287

119 M E Drits L S Toropova U G Bikov and G K Anastaseva

Proc lsquoDiffusion in metals and alloysrsquo Tihany Hungary Augustndash

September 1982 616ndash623

120 V I Elagin V V Zakharov and T D Rostova Met Sci Heat

Treat 1983 (7) 546ndash549

Roslashyset and Ryum Scandium in aluminium alloys

International Materials Reviews 2005 VOL 50 NO 1 41

121 M Ye Drits L B Ber Yu G Bykov L S Toropova and G K

Anastaseva Phys Met Metall 1984 57 (6) 118ndash126

122 M E Drits L S Toropova and Yu G Bykov Sov Non-Ferrous

Met Res 1985 13 309ndash314

123 V I Yelagin V V Zakharov S G Pavlenko and T D Rostova

Phys Met Metall 1985 60 (1) 88ndash92

124 N Sano Y Hasegawa K Hono H Jo K Hirano H W

Pickering and T Sakurai Journal de Physique 1987 48 C6 337ndash

342

125 N Sano H-H Jo K-I Hirano and T Sakurai J Jpn Inst

Metals 1989 39 444ndash450

126 N Sano H Jo K Hirano and T Sakurai Proc Second Int

Conf on lsquoAluminium alloysrsquo Beijing China October 1990 549ndash

554

127 Y Miura M Nakayama and A Furuta Proc lsquoAspects of high

temperature deformation and fracture in crystalline materialsrsquo

Nagoya Japan July 1993 255ndash262

128 Y W Riddle and T H Sanders Jr Mater Sci Forum 2000

331ndash337 939ndash944

129 Y W Riddle M McIntosh and T H Sanders Jr in lsquoLightweight

alloys for aerospace application VIrsquo (ed K Jata E W Lee

W Frazier and N J Kim) 25ndash39 2001 TMS

130 M E Drits J Dutkiewicz L S Toropova and J Salawa Crystal

Res Technol 1984 19 1325ndash1330

131 Y W Riddle MSc thesis Georgia Tech GA USA 1998

132 T J Bastow and S Celotto Mater Sci Eng 2003 C 23 757ndash

762

133 M C Carroll M J Mills G S Daehn P I Gouma M F

Savage and B R Dunbar in lsquoAutomotive Alloys 1999rsquo (ed

S Das) 239ndash246 2000 TMS

134 E Clouet M Nastar and C Sigli Phys Rev B 2004 69 064109-

1-14

135 V V Zakharov Met Sci Heat Treat 1997 (2) 61ndash66

136 J W Christian lsquoThe theory of transformation in metals and

alloysrsquo 2nd edn 1975 Pergamon Press Ltd

137 A L Berezina V A Volkov B P Domashnikov S V Ivanov

and K V Chuistov Phys Metals 1990 10 296ndash304

138 S-I Fujikawa and S Sakauchi Proc 6th Int Conf on

lsquoAluminum alloysrsquo Toyohashi Japan July 1998 805ndash810

139 Y S Touloukian R K Kirby R E Taylor and P D Desai

(eds) lsquoThermal expansion metallic elements and alloysrsquo 1975

New York Plenum

140 J Roslashyset and N Ryum submitted to Scripta Mater

141 R O Simmons and R W Balluffi Phys Rev 1960 117 52ndash61

142 M Ocko E Babic R Krsmik E Girt and B Leontic J Phys F

Metals Phys 1976 6 703ndash707

143 M J Jones and F J Humphreys Proc First Joint Int Conf on

lsquoRecrystallization and grain growthrsquo Aachen Germany August

2001 Springer Verlag 1287ndash1292

144 S Iwamura M Nakayama and Y Miura Mater Sci Forum

2002 396ndash402 1151ndash1156

145 S Iwamura and Y Miura Acta Mater 2004 52 591ndash600

146 M Asta S M Foiles and A A Quong Phys Rev B 1998 57

11265ndash11275

147 R W Hyland Jr M Asta S M Foiles and C L Rohrer Acta

Mater 1998 46 3667ndash3678

148 J Roslashyset and N Ryum Proc 4th Int Conf on lsquoAluminium

alloysrsquo Vol I Atlanta GA USA September 1994 194ndash201

149 M E Drits L S Toropova G K Anastaseva and G L

Nagornichnykh Russ Metall 1984 (3) 192ndash195

150 E A Marquis D N Seidman and D C Dunand Acta Mater

2003 51 4751ndash4760

151 M E Drits L S Toropova and Yu G Bykov Met Sci Heat

Treat 1983 (7) 550ndash554

152 V V Zakharov and T D Rostova Met Sci Heat Treat 1995

(2) 65ndash69

153 M Nakayama and Y Miura Proc 4th Int Conf on lsquoAluminium

alloysrsquo Vol I Atlanta GA USA September 1994 538ndash545

154 M Nakayama and Y Miura J Jpn Inst Light Metals 1996 46

275ndash279

155 M Nakayama T Okuyama and Y Miura Mater Sci Forum

2000 331ndash337 927ndash932

156 M Nakayama T Okuyama and Y Miura Proc 6th Int Conf

on lsquoAluminum alloysrsquo Toyohashi Japan July 1998 517ndash522

157 M L Kharakterova D G Eskin and L S Toropova Acta

Metall Mater 1994 42 2285ndash2290

158 V I Elagin V V Zakharov and T D Rostova Met Sci Heat

Treat 1992 (1) 37ndash45

159 H Wiik Siv Ing thesis NTH Institute of Metallurgy

Trondheim Norway 1995

160 J Roslashyset H Hovland and N Ryum Mater Sci Forum 2002

396ndash402 619ndash624

161 Y Miura K Horikawa K Yamada and M Nakayama Proc

4th Int Conf on lsquoAluminium alloysrsquo Vol II Atlanta GA USA

September 1994 161ndash168

162 Y W Riddle PhD thesis Georgia Tech GA USA 2000

163 B Forbord W Lefebvre F Danoix H Hallem and

K Marthinsen Scripta Mater 2004 51 333ndash337

164 J D Robson Acta Mater 2004 52 1409ndash1421

165 C B Fuller J L Murray and D N Seidman submitted to Acta

Mater 2004

166 M G Mousavi C E Cross and Oslash Grong Sci Technol Weld

Joining 1999 4 381ndash388

167 J S Vetrano S M Bruemmer L M Pawlowski and I M

Robertson Mater Sci Eng 1997 A 238 101ndash107

168 Y W Riddle and T H Sanders Jr Mater Sci Forum 2000

331ndash337 799ndash803

169 G M Khan A O Nikiforov V V Zakharov and I I Novikov

Tsvetnye Metally 1993 34 (11) 43ndash45

170 Z Horita M Furukawa M Nemoto A J Barnes and T G

Langdon Acta Mater 2000 48 3633ndash3640

171 L A Willey US Patent 3 619 181 9 November 1971

172 L K Lamikhov and G V Samsonov Tsvetnye Metally 1964 5

(8) 77ndash80

173 A L Berezina K V Chuistov N I Kolobnev L B

Khokhlatova and T A Monastyrskaya Mater Sci Forum

2002 396ndash402 741ndash746

174 F A Fasoyinu J Thomson D Cousineau T Castles and M

Sahoo Proc 6th Int AFS Conf on lsquoMolten aluminum

processingrsquo Orlando FL USA November 2001

175 Z Yin Q Pan Y Zhang and F Jiang Mater Sci Eng 2000

A 280 151ndash155

176 I I Novikov and O E Grushko Mater Sci Technol 1995 11

926ndash932

177 D Cousineau M Sahoo P D Newcombe T Castles and F A

Fasoyinu Proc lsquoAFS 105th casting congressrsquo Dallas TX USA

AprilndashMay 2001 157ndash184

178 C E Cross and Oslash Grong Proc 6th Int Conf on lsquoAluminum

alloysrsquo Toyohashi Japan July 1998 1441ndash1446

179 F A Costello J D Robson and P B Prangnell Mater Sci

Forum 2002 396ndash402 757ndash762

180 K B Hyde A F Norman and P B Prangnell Mater Sci

Forum 2002 396ndash402 39ndash44

181 M E Drits S G Pavlenko L S Toropova Yu G Bukov and

L B Ber Sov Phys Dokl 1981 26 (3) 344ndash346

182 A M Drits and B A Kopeliovich Russ Metall 1985 (4) 147ndash

151

183 V G Davydov V I Elagin V V Zakharov and T D Rostova

Met Sci Heat Treat 1996 (8) 347ndash352

184 M E Drits L S Toropova Yu G Bykov L B Ber and S G

Pavlenko Russ Metall 1982 (1) 148ndash152

185 T D Rostova V G Davydov V I Yelagin and V V Zakharov

Mater Sci Forum 2000 331ndash337 793ndash798

186 Y W Riddle H Hallem and N Ryum Mater Sci Forum 2002

396ndash402 563ndash568

187 J Roslashyset and Y W Riddle Proc 9th Int Conf on lsquoAluminium

alloysrsquo Brisbane Australia August 2004 1210ndash1215

188 A M Diskin V K Portnoi A M Drits and A A Alalykin Sov

Non-Ferrous Met Res 1986 14 499ndash500

189 R R Sawtell P E Bretz and C L Jensen US Patent 4 689 090

25 August 1987

190 G A Salishchev Yu B Timoshenko and R A Saitova Proc

Second Int Conf on lsquoAluminium alloysrsquo Beijing China October

1990 413ndash415

191 T G Nieh R Kaibyshev L M Hsiung N Nguyen and

J Wadsworth Scripta Mater 1997 36 1011ndash1016

192 T G Nieh L M Hsiung J Wadsworth and R Kaibyshev Acta

Mater 1998 46 2789ndash2800

193 J S Vetrano C H Henager Jr M T Smith and S M

Bruemmer in lsquoHot deformation of aluminum alloys IIrsquo (ed T R

Bieler L A Lalli and S R MacEwen) 407ndash418 1998 TMS

194 J S Vetrano C H Henager Jr S M Bruemmer Y Ge and

C H Hamilton in lsquoSuperplasticity and Superplastic Forming

1998rsquo (ed A K Gosh and T R Bieler) 89ndash97 1998 TMS

195 V Y Gertsman J S Vetrano C H Henager Jr and S M

Bruemmer Proc First Joint Int Conf on lsquoRecrystallization and

grain growthrsquo Aachen Germany August 2001 Springer Verlag

2001 837ndash842

196 Y Xiao C Gao H Ma and S Tian Trans Nonferrous Met Soc

China 2001 11 235ndash238

Roslashyset and Ryum Scandium in aluminium alloys

42 International Materials Reviews 2005 VOL 50 NO 1

197 A Gholinia F J Humphreys and P B Prangnell Acta Mater

2002 50 4461ndash4476

198 A Gholinia F J Humphreys and P B Prangnell Mater Sci

Forum 2002 408ndash412 1519ndash1524

199 S Komura P B Berbon M Furukawa Z Horita M Nemoto

and T G Langdon Scripta Mater 1998 38 1851ndash1856

200 S Komura P B Berbon A Utsunomiya M Furukawa

Z Horita M Nemoto and T G Langdon in lsquoHot deformation

of aluminum alloys IIrsquo (ed T R Bieler L A Lalli and S R

MacEwen) 125ndash138 1998 TMS

201 S Komura Z Horita M Furukawa M Nemoto and T G

Langdon J Mater Res 2000 15 2571ndash2576

202 S Komura M Furukawa Z Horita M Nemoto and T G

Langdon Mater Sci Eng 2001 A 297 111ndash118

203 S Komura Z Horita M Furukawa M Nemoto and T G

Langdon Metall Mater Trans A 2001 32A 707ndash716

204 Z Horita M Furukawa K Oh-ishi M Nemoto and T G

Langdon Proc Fourth Int Conf on lsquoRecrystallization and

related phenomenarsquo (ed T Sakai and H G Suzuki) 1999 The

Japan Institute of Metals 301ndash308

205 Z Horita S Komura P B Berbon A Utsunomiya

M Furukawa M Nemoto and T G Langdon Mater Sci

Forum 1999 304ndash306 91ndash96

206 Z Horita S Lee S Ota K Neishi and T G Langdon Mater

Sci Forum 2001 357ndash359 471ndash476

207 Z Horita T Fujinami K Sato S B Kang H W Kim and T G

Langdon in Proc James T Staley Honorary Symposium on

Aluminum Alloys lsquoAdvances in the metallurgy of aluminum

alloysrsquo (ed M Tiryakioglu) 271ndash275 2001 ASM

208 P B Berbon S Komura A Utsunomiya Z Horita

M Furukawa M Nemoto and T G Langdon Mater Trans

JIM 1999 40 772ndash778

209 M Nemoto Z Horita M Furukawa and T G Langdon Mater

Sci Forum 1999 304ndash306 59ndash66

210 M Furukawa Z Horita M Nemeto and T G Langdon Proc

lsquoLight Metals 1999rsquo Quebec City PQ Canada August 1999 583ndash

592

211 M Furukawa K Oh-ishi S Komura A Yamashita Z Horita

M Nemeto and T G Langdon Mater Sci Forum 1999 304ndash

306 97ndash102

212 M Furukawa A Utsunomiya K Matsubara Z Horita and

T G Langdon Acta Mater 2001 49 3829ndash3838

213 M Furukawa A Utsunomiya S Komura Z Horita M Nemoto

and T G Langdon Mater Sci Forum 2001 357ndash359 431ndash436

214 M Furukawa Z Horita and T G Langdon in Proc James T

Staley Honorary Symposium on Aluminum Alloys lsquoAdvances in

the metallurgy of aluminum alloysrsquo (ed M Tiryakioglu) 47ndash56

2001 ASM

215 M Furukawa Z Horita M Nemoto and T G Langdon Mater

Sci Eng 2002 A 324 82ndash89

216 M Furukawa Z Horita and T G Langdon in lsquoUltrafine grained

materials IIrsquo (ed Y T Zhu T G Langdon R S Mishra S L

Semiatin M J Saran and T C Lowe) 459ndash468 2002 TMS

217 T G Langdon M Furukawa Z Horita and M Nemoto Proc

NATO Advanced Research Workshop on lsquoInvestigations and

applications of severe plastic deformationrsquo Moscow August

1999 NATO Science Series Series 3 High Technology vol 80

Kluwer Academic Publishers The Netherlands 2000 149ndash154

218 S Lee H Akamatsu A Utsunomiya K Neishi M Furukawa

Z Horita and T G Langdon Proc Thermec 2000 Las Vegas

USA December 2000

219 S Lee A Utsunomiya H Akamatsu K Neishi M Furukawa

Z Horita and T G Langdon Acta Mater 2002 50 553ndash564

220 A Yamashita D Yamaguchi Z Horita and T G Langdon

Mater Sci Eng 2000 A 287 100ndash106

221 K Oh-ishi Z Horita D J Smith and T G Langdon J Mater

Res 2001 16 583ndash589

222 H Akamatsu T Fujinami Z Horita and T G Langdon Scripta

Mater 2001 44 759ndash764

223 S Ota H Akamatsu K Neishi M Furukawa Z Horita and

T G Langdon Mater Trans 2002 43 2364ndash2369

224 K Furuno H Akamatsu K Oh-ishi M Furukawa Z Horita

and T G Langdon Acta Mater 2004 52 2497ndash2507

225 I N Fridlyander O G Senatorova N A Ryazanova and A O

Nikiforov Mater Sci Forum 1994 170ndash172 345ndash349

226 J N Fridlyander and O G Senatorova Mater Sci Forum 1996

217ndash222 1813ndash1818

227 J Liu and D J Chakrabarti Acta Mater 1996 44 4647ndash4661

228 O G Senatorova A N Uksusnikov J N Fridlyander

J Koshorst R R Romanova N A Ryazanova A Galliot

and V V Cherkassov Proc 6th Int Conf on lsquoAluminum alloysrsquo

July 1998 Toyohashi Japan 589ndash593

229 R A Emigh E L Bradley and J W Morris Jr in

lsquoSuperplasticity in aerospace IIrsquo (ed T R McNelley and H C

Heikkenen) 303ndash315 1990 TMS

230 E L Bradley III R A Emigh and J W Morris Jr Scripta

Metall Mater 1991 25 717ndash721

231 N I Kolobnev L B Khokhlatova V D Makarov E Yu

Semenova and V V Redchits Proc Sixth Int Aluminiumndash

Lithium Conference Garmisch-Partenkirchen Germany October

1991 1053ndash1056

232 N K Tsenev R Z Valiev O V Obraztsov and I N Fridlander

Proc Sixth Int AluminiumndashLithium Conference Garmisch-

Partenkirchen Germany October 1991 1125ndash1132

233 A M Shammazov N K Tsenev R Z Valiev M M

Myshlyaev M M Bikbulatov and S P Lebedich Phys Met

Metall 2000 89 (3) 314ndash318

234 F Musin R Kaibyshev Y Motohashi T Sakuma and G Itoh

Mater Trans A 2002 43A 2370ndash2377

235 M Shagiev Y Motohashi F Musin R Kaibyshev and G Itoh

Mater Trans A 2003 44A 1694ndash1697

236 M Shagiev Y Motohashi F Musin R Kaibyshev and G Itoh

Mater Trans A 2003 44A 1698ndash1701

237 B A Parker and Z F Zhou Proc 3rd Int Conf on lsquoAluminium

alloysrsquo Vol I NTH Trondheim Norway June 1992 363ndash367

238 J R Davies lsquoASM specialty handbook aluminum and aluminum

alloysrsquo 1993 Materials Park OH USA ASM

239 S J Andersen H W Zandbergen J Jansen C Traeholt

U Tundal and O Reiso Acta Mater 1998 46 3283ndash3298

240 M L Kharakterova D G Eskin and L L Rokhlin Russ

Metall 1997 (1) 104ndash109

241 J Roslashyset Dr Ing thesis NTNU Trondheim Norway 2002

242 P P Chattopadhyay S Datta and M K Banerjee Mater Sci

Eng 2002 A 333 67ndash71

243 L I Kaigorodova E I Selnikhina E A Tkachenko and O G

Senatorova Phys Met Metall 1996 81 513ndash519

244 Y-L Wu F H Froes C Li and A Alvarez Metall Mater

Trans A 1999 30A 1017ndash1024

245 Z Yin L Yang Q Pan and F Jiang Trans Nonferrous Met

Soc China 2001 11 822ndash825

246 V I Elagin V V Zakharov and T D Rostova Met Sci Heat

Treat 1994 36 (7) 375ndash380

247 Y V Milman A I Sirko D V Lotsko O N Senkov and D B

Miracle Mater Sci Forum 2002 396ndash402 1217ndash1222

248 C-H Joh K Yamada and Y Miura Mater Trans JIM 1999

40 439ndash442

249 X J Jiang Q H Gui Y Y Li L M Ma G J Liang and C X

Shi Scr Metall Mater 1993 29 211ndash216

250 X J Jiang Y Y Li W Deng L Y Xiong W M Wu Y J Gao

and C X Shi Adv Cryogenic Eng (Mater) 1994 40 1369ndash

1376

251 C-H Joh T Katsube K Yamada and Y Miura Proc 6th Int

Conf on lsquoAluminum alloysrsquo Toyohashi Japan July 1998 799ndash

804

252 L I Kaygorodova A M Dritz T V Krymova and I N

Fridlyander Proc Sixth Int AluminiumndashLithium Conference

Garmisch-Partenkirchen Germany October 1991 363ndash367

253 L I Kaigorodova A M Drits Ya V Zhingel T V Krymova

and I N Fridlyander Phys Met Metall 1992 73 286ndash290

254 A L Berezina V A Volkov S V Ivanov N I Kolobnev and

K V Chuistov Phys Met Metall 1991 71 (2) 167ndash175

255 I N Fridlyander N I Kolobnev A L Berezina and K V

Chuistov Proc Sixth Int AluminiumndashLithium Conference

Garmisch-Partenkirchen Germany October 1991 107ndash112

256 L I Kaigorodova A M Drits Ya V Zhingel T V Krymova

and V A Rassokhin Phys Met Metall 1992 73 281ndash285

257 I N Fridlyander S F Danilov E N Malysheva T A

Gorokhova and N N Kirkina Proc Sixth Int Aluminiumndash

Lithium Conference Garmisch-Partenkirchen Germany October

1991 381ndash386

258 G Dlubek S Krause H Krause A L Beresina V S

Mikhalenkov and K V Chuistov J Phys Condens Matter

1992 4 6317ndash6328

259 S Krause H Krause G Dlubek A L Beresina and K S

Chuistov Mater Sci Forum 1992 105ndash110 1109ndash1112

260 C Y Tan Z Q Zheng and S Q Liang Proc 4th Int Conf on

lsquoAluminium alloysrsquo Vol II Atlanta GA USA September 1994

329ndash333

261 A L Beresina N I Kolobnev K V Chuistov A V Kotko and

O A Molebny Mater Sci Forum 2002 396ndash402 977ndash981

Roslashyset and Ryum Scandium in aluminium alloys

International Materials Reviews 2005 VOL 50 NO 1 43

262 I N Ganiev I Yunusov and V V Krasnoyarskii J Appl Chem

USSR 1986 60 1961ndash1965

263 I N Ganiev Prot Met 1995 31 543ndash546

264 N V Vyazovikina Prot Met 1999 35 448ndash453

265 G V Kharina and V P Kochergin Prot Met 1996 32 134ndash

136

266 G V Kharina M V Kuznetsov and V P Kochergin Russ J

Electrochem 1998 34 482ndash485

267 V S Sinyavskii V D Valrsquokov and E V Titkova Prot Met

1998 34 549ndash555

268 Y L Wu F H Froes C G Li and J Liu Proc lsquoSynthesis

processing of lightweight metallic materials IIrsquo Orlando FL

USA February 1997 73ndash81

269 Z Ahmad and B J Abdul-Aleem Proc EuroCorr 2000

270 Z Ahmad A Ul-Hamid and B J Abdul-Aleem Corros Sci

2001 43 1227ndash1243

271 R Braun B Lenczowski and G Tempus Mater Sci Forum

2000 331ndash337 1647ndash1652

272 T Torma E Kovacs-Csetenyi L Vitalis I Vitanyi

J Stepanov and M Butova Mater Sci Forum 1987 1314

497ndash503

273 Z Wang P Wang K S Kumar and C L Briant in lsquoChemistry

and electrochemistry of corrosion and stress corrosion crackingrsquo

(ed R H Jones) 573ndash582 2001 TMS

274 V I Elagin V V Zakharov A A Petrova and E V

Vyshegorodtseva Russ Metall 1983 (4) 143ndash146

Roslashyset and Ryum Scandium in aluminium alloys

44 International Materials Reviews 2005 VOL 50 NO 1

Page 15: Scandium in aluminium alloys - Atom probe · A considerable part of the available literature on scandium in aluminium alloys is reviewed. ... behaviour in Al Cu, Al Mg Si,

Al3(Sc12xZrx) particles when approximately half of thesupersaturated Sc has been precipitated The Zr contentof the outer shell is predicted to be much higher thanwhat has been found experimentally163164

Another 3D-APFIM study of Al3(Sc12xZrx) particlesin a ternary AlndashScndashZr alloy has been reported165 Hereparticles grown at 300uC for various lengths of time werestudied The Zr content in these particles was muchlower than that reportedpredicted at higher tempera-tures163164 even after very long annealing times

Iron

The effect of adding up to 07 wt-Fe on the precipita-tion kinetics in an Alndash04 wt-Sc alloy has beeninvestigated135 The onset of precipitation was onlyslightly influenced by the Fe-level whereas the laterstages of the transformation however were significantlyslowed down as the Fe-level increased An example ofthe effect of a joint addition of Fe and Si is shown inFig 22

Manganese chromium and titanium

Small additions (03 wt-) of manganese or chromiumto Alndash040 wt-Sc alloys are reported to have onlyminor effects on the precipitation kinetics of Al3Sc135

According to Ref 106 Mn is reported to promote andCr and Ti to suppress discontinuous precipitation

Rare earth elements

An investigation of the precipitation behaviour of Alndash03 at-Sc and Alndash03 at-Scndash03 at-X alloyswhere X is either yttrium gadolinium holmium orerbium in the temperature range 235ndash310uC indicatedthat a Al3(Sc12xXx) phase with L12 structure wasformed in the ternary alloys22 Peak strength is reportedto occur after approx 10 h at 285uC in all alloys whichindicates that the precipitation kinetics up to peakstrength is practically unaltered by the ternary additions

Influence of Sc on microstructure andproperties of wrought aluminium alloysMost of the effects of Sc addition in wrought Al-alloysare linked to the formation of the Al3Sc phase In atypical processing route of a wrought aluminium alloyparticles of the Al3Sc phase can form under threedifferent conditions each of which influences themicrostructure and properties of the alloy in a specificway

1 During solidification after casting or weldingAl3Sc particles can form in the melt and act as nucleifor a-Al thus leading to grain refinement18166

2 High temperature processing of the alloy in therange 400ndash600uC for instance homogenisation hot-rolling or extrusion can give a dense distribution ofAl3Sc particles of typically 20ndash100 nm size The particledistributions formed under such conditions are reportedto lead to good recrystallisation resistance128148167168

and enhanced superplasticity52169170

3 Heat treatment in the range 250ndash350uC can lead tosignificant precipitation hardening of an alloy super-saturated in Sc148158171 The size of strengthening Al3Scprecipitates is typically in the range 2ndash6 nm121

Grain refinementA good grain refinement is almost always desired uponsolidification The formation of small equiaxed grainsrather than long dendrites in the melt facilitates thefeeding of the melt into cavities of the shrinkingsolidified metal and thus reduces the problem ofshrinkage porosity The tendency to hot cracking is alsoreduced and the second phase particles become morefinely and uniformly distributed

To the authorsrsquo knowledge the first effect of Sc in Al-alloys that was reported in an international scientificjournal was the grain refining action in pure Al and in anAlndashCu alloy upon solidification172 which was found tobe stronger for Sc than for other transition metals Inlater studies of Sc as a grain refiner in pure Al1832173 ithas been demonstrated that approx 07 wt-Sc issufficient to provide excellent grain refinement It hasalso been demonstrated that additions of 025 wt-Scz025 wt-Zr provide good grain refinement in pure Al18

In order for Sc to act as an effective grain refiner theAl3Sc phase has to form in the melt before thesolidification of a-Al The Al3Sc particles have a latticeparameter close to that of pure Al and whenhypereutectically formed the Al3Sc particles are veryeffective substrates for the nucleation of the a-Al phaseAs mentioned in the section on lsquoFormation of Al3Sc inAlndashSc alloysrsquo above this requires that the alloy ishypereutectic with respect to Sc ie in excess of approx06 wt- in a binary AlndashSc alloy In ternary and higherorder systems the eutectic Sc composition may dependon the other alloying elements present For instance theeutectic composition of Sc has been predicted todecrease with increasing Mg content in the ternary AlndashMgndashSc system39 This prediction is sustained by theobservation of good grain refinement by adding 05 wt-Sc to an Alndash7 wt-Mg alloy174 (Other examples ofgrain refinement at Sc concentrations lower than that ofthe binary eutectic are found in Ref 173)

Similarly the observation of good grain refinement inan Alndash025 wt-Scndash025 wt-Zr alloy18 may be as aresult of a lower Sc content of the eutectic in the ternarysystem ie less Sc is needed to make the alloy hyper-eutectic No literature data on the liquidus surface of theAlndashScndashZr system are available and thus this hypothesiscannot be confirmed In more complex alloy systems itis also observed that excellent grain refinement isachieved at low Sc contents when Sc is added togetherwith Zr It is reported that adding either 02 wt-Sc06 wt-Sc or 01 wt-Zr to an Alndash5Mg alloy givesmuch poorer grain refinement than adding 02 wt-Scz01 wt-Zr175 Similarly additions of 015 wt- ofeither Sc or Zr are reported to only marginally refinethe grain structure in an AlndashCundashLi alloy whereas a jointaddition of 015 wt-Sc and 015 wt-Zr gives excellentgrain refinement176 For an AA 3650 casting alloy (Alndash7 wt-Sindash04 wt-Mg) good grain refinement is achievedby adding 039 wt-Sc or 027 wt-Scz019 wt-Zr177

In some AlndashZnndashMgndashScndashZr alloys it is also found thatan addition of 02ndash03 wt-Sc can be sufficient for goodgrain refinement166169178179 Examples of the grainrefinement as a function of Sc addition in pure Al andin an AlndashZnndashMgndashZr alloy are shown in Fig 25

The nucleation of a-Al on Al3Sc particles in the melt isfacilitated by the close match in the lattice parameters ofthe two phases As shown in Fig 17 the mismatch at the

Roslashyset and Ryum Scandium in aluminium alloys

International Materials Reviews 2005 VOL 50 NO 1 33

eutectic temperature of binary AlndashSc alloys (660uC) isonly approx 047 In Refs 57 and 89 it is shown thatwhen Zr Hf and in particular Ti is dissolved in the Al3Scparticles this reduces the lattice parameter of the phaseIt appears that when 25 of the Sc atoms in Al3Sc aresubstituted by Ti the mismatch is zero at approx 550uCand becomes negative at higher temperatures89 Thissuggests that by carefully selecting the Ti content of thealloy it should be possible to obtain Al3(ScTi)substrates in the melt that match exactly the latticeparameter of the nucleating a-Al and thus furtherimprove the grain refinement of the alloy This appearsto have been achieved in a recent work180 where thegrain refinement of an Alndash07 wt-Sc alloy wascompared with that of an Alndash05 wt-Scndash02 wt-Tialloy At a cooling rate of 100 K s21 only an estimated2 of the primary Al3Sc particles of the binary AlndashScalloy were effective nuclei compared to practically 100for the primary Al3(ScTi) particles in the ternary AlndashScndashTi alloy leading to a much smaller grain size in theternary alloy Whereas the match of lattice parametersmay be of importance for these results the authors ofthis investigation180 draw attention to other factors suchas different growth restriction factors for Sc and Ti andthe possibility of a peritectic reaction in the ternaryalloy Nevertheless the principle of matching latticeparameters is worth looking into further in future work

Effects from dispersoidslsquoDispersoidsrsquo is a term which is commonly used aboutthe classes of second phase particles that are formedin an Al alloy during high temperature annealing orthermomechanical processing such as homogenisationhot rolling extrusion and forging A dense distributionof dispersoids can give a significant contribution to analloyrsquos strength owing to particle strengthening but thisis rarely the main strengthening mechanism A moreimportant contribution from the dispersoids is theirability to stabilise the grainsubgrain structure of analloy through the Zener-drag action and thus improvethe mechanical properties of the alloy

There are two noticeable dispersoid-related effectsthat have been reported for Sc-containing alloys Thefirst is the stabilising effect on a deformed microstruc-ture When a non-recrystallised structure is preserved inan alloy this can add considerably to the mechanical

strength of the material The second effect is thepreservation of a small grain size during hot deforma-tion at slow deformation rates which is necessary toobtain superplastic properties of an Al-alloy

Recrystallisation resistance

The anti-recrystallisation effect of Sc was first publishedin a patent171 where 03 wt-Sc was added to pure Aland to AlndashMg AlndashMn and AlndashZnndashMg alloys Both Sc-free and Sc-containing materials were cold worked andsubsequently annealed and it was found that theaddition of Sc increased the temperature for onset ofrecrystallisation by approx 220uC in pure Al andsomewhat less in the Al-alloys Although the author ofthe patent171 may have been well aware that the anti-recrystallisation effect is caused by Al3Sc dispersoidsthis is not mentioned in the text The first journal paperthat explicitly points out that the recrystallisationresistance is due to Al3Sc dispersoids was an investiga-tion of the effects of adding Sc to wrought AlndashMgalloys181 In this work it was found that the Al3Scdispersoids were very effective in preventing recrystalli-sation up to temperatures of approx 400ndash450uC Athigher temperatures the dispersoids coarsen consider-ably and the microstructure was partially recrystallised

It is established that the Zener-drag pZ that is imposedon an advancing grain boundary by randomly distrib-uted dispersoids can be expressed in the form

pZ~k f =r (3)

where k is a factor that includes the interface energybetween the dispersoids and the matrix f is the volumefraction and r is the mean radius of the dispersoids Thusthe Zener drag will decrease rapidly in the case where thedispersoids are coarsening

As mentioned in the section on lsquoInfluence of otherelements on precipitation of Al3Scrsquo above theAl3(Sc12xZrx) dispersoids in a ternary AlndashScndashZr alloycoarsen at a much slower rate than the Al3Sc dispersoidsin a binary AlndashSc alloy This effect was first reported inRef 123 (although also observed in Ref 182) andaccording to Ref 33 the same authors demonstratedsoon after that the denser dispersoid distributionachieved in an AlndashScndashZr alloy leads to superiorrecrystallisation resistance compared to a binary AlndashScalloy An example of the increased recrystallisationresistance by adding both Zr and Sc is shown in Fig 26

In isothermal sections of the ternary AlndashScndashZr phasediagram it is indicated that the solid solubility ofSczZr is somewhat higher than that of Sc alone54 Ithas also been demonstrated both by electrical con-ductivity measurements (Fig 27) and microstructuralobservations that the supersaturation of SczZr isgreater than that of only Sc or Zr in as cast Alndash15(SczZr) alloys183 This indicates that it should bepossible to increase the volume fraction of dispersoids inAlndashScndashZr compared to AlndashSc It is suggested162 that theincreased volume fraction that can be achieved byadding both Sc and Zr can be advantageous inconventional wrought Al-alloys

There are at least two different conditions underwhich Al3Sc or Al3(Sc12xZrx) dispersoids can form toprevent recrystallisation

1 Sc (or Sc and Zr) is in solid solution before thedeformation In the case of cold deformation and

25 Grain refinement as a function of Sc addition in pure

Al (redrawn from Ref 32) and AlndashZnndashMgndashZr (redrawn

from Ref 169) note that data points are plotted on

different ordinate axes

Roslashyset and Ryum Scandium in aluminium alloys

34 International Materials Reviews 2005 VOL 50 NO 1

subsequent annealing the Al3Sc or Al3(Sc12xZrx)dispersoids may nucleate and grow before the nucleationand growth of recrystallised grains takes placeDispersoids can form after a direct up-quench to theannealing temperature115143148184 during ramp-up tothe annealing temperature115 or by pre-annealing at anintermediate temperature129 In the case of hot deforma-tion the Al3Sc or Al3(Sc12xZrx) dispersoids maynucleate and grow during preheating of the materialand during the hot deformation itself184

2 The Al3Sc or Al3(Sc12xZrx) dispersoids are formedin the material before deformation184 Considering coldrolling and subsequent annealing the annealing tem-perature Tann may be either lower or higher than thetemperature Tdisp at which the dispersoids were formedIf TannTdisp only limited if any coarsening of thedispersoids is expected to take place and thus the Zenerdrag from the particles is expected to be practicallyconstant The driving force for recrystallisation how-ever is expected to decrease somewhat with theannealing time as a result of recovery processes Thusif recrystallisation does not occur within short annealingtimes the material is expected to remain unrecrystallisedfor infinite time at the annealing temperature IfTannTdisp there will be substantial coarsening of thedispersoids during annealing In order for the materialto remain unrecrystallised the decrease in driving forcefor recrystallisation owing to recovery has to be at leastas rapid as the decrease in Zener drag because of particlecoarsening

Experimental comparisons of the conditions abovepoint in the direction that the recrystallisation resistanceis poorest when Sc (or Sc and Zr) is in solid solutionbefore deformation and the deformed material is up-quenched to the annealing temperature148 or when Al3Scor Al3(Sc12xZrx) dispersoids are formed before defor-mation at TdispampTann184185 Excellent recrystallisationresistance is achieved if dispersoids are formed at anintermediate anneal of solutionised and deformedmaterial128 or if dispersoids are formed at TdispTann

before deformation148185ndash187 It seems that the decreasein Zener drag because of dispersoid coarsening in many

cases is slower than the decrease in driving force forrecrystallisation because of recovery processes Thusthere is an advantage in forming a high number densityof small dispersoids which for most practical casesmeans that they should be formed at TdispTann122

When an advancing high angle grain boundary iethe recrystallisation front is passing a coherent Al3Scdispersoid there are at least three possible grainboundarydispersoid interactions

1 The Al3Sc dispersoid retains its global orientationrelationship and thus loses its coherency with thesurrounding matrix

2 The Al3Sc dispersoid rotates as the grain boundarypasses either by diffusional processes at the dispersoidmatrix interface or by the grain boundary passingthrough the dispersoid and the Al3Sc dispersoidassumes the same crystallographic orientation as theAl matrix of the recrystallised grain

3 The Al3Sc dispersoid dissolves at the grainboundary and re-precipitates in the recrystallised grain

Which interactions that actually take place willprobably depend on the dispersoid size annealingtemperature and driving force for recrystallisation It isalso possible that alloy composition (other elementsthan Al) is of importance

It has been reported that large (Oslash about 100ndash150 nm)Al3Sc dispersoids in a deformed Alndash4 wt-Mgndash02 wt-Sc alloy annealed at 575uC lose the orientationrelationship with the matrix after being passed by therecrystallisation front148

A rotation of somewhat smaller Al3Sc dispersoids in arecrystallising binary Alndash025 wt-Sc alloy has beenreported115143 The rotation was reported to be accom-panied by substantial growth (from Oslash 30 nm to Oslash48 nm) as a result of enhanced Sc diffusion at the grainboundary Observations suggested that the grainboundaries were passing through the dispersoids andthus the Al3Sc dispersoids retained the orientationrelationship with the recrystallised Al matrix

Dissolution and re-precipitation of Al3Sc dispersoidshas been reported during recrystallisation of a 50 coldrolled Alndash02 wt-Sc alloy162 Large spherical partially

26 Fraction recrystallised structure in cold rolled sheets

of Alndash04 wt-Sc and Alndash04 wt-Scndash015 wt-Zr as a

function of annealing temperature redrawn from

Ref 183 27 Electrical conductivity in Alndash15(SczZr) alloys

redrawn from Ref 183

Roslashyset and Ryum Scandium in aluminium alloys

International Materials Reviews 2005 VOL 50 NO 1 35

coherent dispersoids were observed to dissolve at therecrystallisation front and re-precipitate as smallercoherent Al3Sc cuboids

Superplastic forming

It seems that the first publication on superplasticproperties of Sc-containing Al-alloys was a study of anAlndash35Cundash14Mgndash045Mnndash04(SczZr) alloy188

It was recognised that the superplastic properties are aresult of the stabilisation of the fine grain structure byAl3Sc dispersoids The Sc-containing Al alloys that havereceived most attention for their superplastic propertieshowever are those of the AlndashMgndashSc system which wasfirst published in a patent189 Here it was noted that anAlndash4 wt-Mgndash05 wt-Sc alloy had superior superplasticproperties compared to fine-grained 7475 (AlndashZnndashMgndashCu alloy) Binary Alndash05 wt-Sc and Alndash4 wt-Mgalloys did not behave superplastically The flow stress atthe hot forming temperature was found to be much (30ndash40) lower in the ternary alloy than that of the twobinary alloys

The superplastic properties of AlndashMgndashSc alloys havebeen explored by several research groups over the lastdecade190ndash196 It has frequently been found that thedeformation mechanism is dominated by grain bound-ary sliding190 However it has also been reported thatAlndashMgndashSc alloy may deform superplastically withoutnoticeable grain boundary sliding23 It is generallyrecognised that the grain boundary sliding mechanismis facilitated when the average grain size is very smalland grain boundaries are predominantly high-angleSuch a microstructure may be achieved by carefulthermomechanical processing of the starting mate-rial193194197198 It has however been shown that a finegrained structure with high angle boundaries maydevelop during superplastic forming of AlndashMgndashSc alloyseven if the starting microstructure is an entirely differentone for instance that of a cold rolled sheet192 It has alsobeen suggested that superplastic forming of as castmaterial may be possible189

One of the more efficient thermomechanical processesfor achieving an ultrafine grain structure with high anglegrain boundaries in Al-alloys is equal channel angularpressing (ECAP) A JapanesendashAmerican group ofscientists has published an impressive body of researchon improvements in superplastic properties in Al-alloys processed by ECAP over the last few years andseveral of the publications are from investigations onAlndashMgndashSc alloys170199ndash224 Maximum strains in excessof 2000 at a strain rate of 0033 s21 have beenachieved170201202217 which is an extraordinarily goodcombination of high strain and high strain rate for analuminium alloy

Superplastic properties of AlndashCundashMg(ndashMn)ndashSc(ndashZr)and AlndashMgndashSc(ndashZr) alloys have been mentionedNoticeable superplasticity in other Sc-containing Al-alloys has also been reported such as AlndashZnndashMg(ndashCu)ndashScndashZr169225ndash228 AlndashLindashSc229 AlndashMgndashLindashScndashZr229ndash234

AlndashLindashMgndashCundashScndashZr235236 and AlndashCundashLindashScndashZr233

Precipitation hardeningHardening by Al3Sc precipitates

It has been noted that when Al3Sc particles precipitate inthe temperature range 250ndash350uC they give a significanthardness increase in the alloy Some authors point out

that Sc is a more effective precipitation hardening elementper atomic fraction added than the elements that arecommonly used for precipitation hardening121130 (In onepaper29 it is claimed that only Au has a strongerstrengthening effect than Sc) However the amount ofSc that can be precipitated from supersaturated solidsolution is rather limited and thus the absolute values ofthe hardness increase from the precipitation hardening ismuch lower than what is normally associated withprecipitation hardened alloys Also the temperatureregime for age hardening by precipitation of Al3Sc issomewhere in between the temperature regimes for agehardening and solution heat treatments of commonprecipitation hardened alloys This makes a combinedprecipitation of Al3Sc and other strengthening precipi-tates unfeasible Thus precipitation strengthening byAl3Sc is most feasible in alloy systems that are non-heat-treatable The non-heat-treatable aluminium alloy sys-tems are according to the Aluminum Associationdesignations the 1xxx series (99 pure Al) the 3xxxseries (AlndashMn) and the 5xxx series (AlndashMg) The purposeof adding Sc to these alloys may be either to stabilise themicrostructure of wrought semiproducts (extrusionsrolled plates forgings etc) as discussed in the sectionon lsquoRecrystallisation resistancersquo above or to provideextra strength to the alloy through precipitation hard-ening In the latter case it is appropriate to considerwhether the Sc-containing alloy still should be classifiedas non-heat-treatable A heat treatment is applied thatbrings about a significant precipitation hardening On theother hand the hardness increase that is achieved throughthe heat treatment is lower than what is normallyassociated with heat-treatable alloy systems Hence eventhough it seems like a contradiction one chooses to keepusing the term lsquonon-heat-treatablersquo about these alloys

Table 7 gives an overview of some mechanicalproperties of Sc-containing non-heat-treatable alloysthat are reported in the literature Most of theexperimental work on Sc in 1xxx-types of alloys hasbeen done on binary AlndashSc alloys with much higherpurity than industrial alloys

Strengthening mechanisms

When the precipitates are larger than a critical size thestrengthening effect is due to the Orowan-mechanism iedislocations can only pass the precipitates by looping Inthis case the strengthening effect of the particles isapproximately inversely proportional to the mean parti-cle spacing When the precipitates can be sheared bydislocations there are a number of strengthening mechan-isms that apply It is proposed by Parker et al108 that thetwo major contributing mechanisms are coherency strainand anti-phase-boundary energy In a recent detailedstudy of strengthening mechanisms in binary AlndashSc alloysby Marquis and colleagues117118 the strengthening fromshear modulus mismatch between the matrix and theprecipitates is also accounted for A qualitatively goodmatch between theoretical strengthening and measuredvalues is achieved in this work both for deformation atroom temperature and at 300uC

Effect of Sc on precipitation strengthening in heat-treatablealloys

Following the AA designation system the traditionalheat-treatable Al-alloys are those that belong to the 2xxx

Roslashyset and Ryum Scandium in aluminium alloys

36 International Materials Reviews 2005 VOL 50 NO 1

series (AlndashCu) 6xxx series (AlndashMgndashSi) and 7xxx series(AlndashZnndashMg) AlndashLi alloys should also be mentionedSeveral investigations have been carried out in order toclarify the effects of Sc on the precipitation behaviour inthese alloy systems

AlndashCu alloys

The precipitation sequence in AlndashCu alloys is oftendescribed as follows

Supersaturated solid solutionRGP-zonesRh0Rh9Rh(Al2Cu)

The highest strength is normally achieved when the h0or h9 precipitates are predominant Typical precipitationheat treatment temperatures for AlndashCu alloys are in therange 160ndash190uC238 which is considerably lower thanthe typical precipitation temperature for Al3ScComparisons of the aging responses of AlndashCu and AlndashCundashSc alloys at 150 and 200uC indicate that there is nonoticeable effect of Sc on the precipitation kinetics ofh9153 It is observed that the h9 precipitates may nucleateon Al3Sc particles153 At 300uC it is observed that h9particles are somewhat smaller in AlndashCundashSc alloys thanin AlndashCu alloys156

AlndashMgndashSi alloys

The following precipitation sequence is commonlyreported for AlndashMgndashSi alloys

Supersaturated solid solutionRGP-zonesRb0Rb9Rb(Mg2Si)

For peak aged alloys the predominant precipitatetype is b0 for which the stoichiometric composition hasrecently been resolved to be Mg5Si6239 Temperatures inthe range 160ndash205uC are typically used for precipitationhardening of these alloys238 Adding both 03 wt-Scand 01 wt-Zr to an Alndash06 wt-Mgndash065 wt-Sialloy does not seem to alter the precipitation kineticsof b0 at 165uC However the hardness increase becauseof precipitation hardening appears to be smaller in theSczZr-containing alloy240 In another investigationadditions of 01 wt-Sc 015 wt-Sc 02 wt-Sc04 wt-Sc and 02 wt-Scz01 wt-Zr were made toan Alndash08 wt-Mgndash07 wt-Si alloy241 Here it wasalso observed that the precipitation kinetics of b0 wasseemingly independent of the Sc additions (Fig 28)TEM observations indicated that the b0 precipitateswere of comparable sizes in the investigated alloys andno interactions between Al3Sc and b0 were observed(Fig 29) In a third study242 where the effect of Sc onthe precipitation in an AlMgSindashSiC metal matrixcomposite was investigated there also does not seemto be any effect on the precipitation kinetics Howevercontrary to the findings of Ref 240 it is reported thatthe Sc addition leads to a higher hardness increase thanin the corresponding Sc free alloy

AlndashMgndashZn alloys

For these alloys the following precipitation sequence isoften ascribed

Table 7 Mechanical properties in non-heat-treatable Al-alloys with Sc

Reference Alloy wt- YS MPa UTS MPa Note

1xxx alloys171 000Sc 15 48 Cast material aged 288uC8 h

023Sc 159 185 Cast material aged 288uC8 h038Sc 199 220 Cast material aged 288uC8 h000Sc 14 49 Cold rolled material (89) aged 288uC8 h023Sc 198 208 Cold rolled material (89) aged 288uC8 h038Sc 240 264 Cold rolled material (89) aged 288uC8 h000Sc 8 34 Cold rolled material quenched from 649uC aged 288uC8 h023Sc 147 157 Cold rolled material quenched from 649uC aged 288uC8 h038Sc 193 199 Cold rolled material quenched from 649uC aged 288uC8 h

121 05Sc 160 ndash Forged material quenched from 635uC aged 250uC50 h23 05Sc 298 319 Hot rolled 288uC cold rolled 69ndash81 aged 288uC4 h112 01Sc 132 166 Hot z cold rolled material quenched from 630uC

aged 320uC133 h148 02Sc 138 ndash Cast material aged 300uC10 h compression test159 04Sc 196 ndash Cast material aged 300uC10 h compression test117 118 03Sc 209 ndash Cast material quenched from 648uC aged 300uC5 h

compression test3xxx alloys171 1Mn 015Sc 216 221 Cold rolled material (89) aged 288uC8 h

1Mn 05Sc 309 323 Cold rolled material (89) aged 288uC8 h186 05Mn 02Mg

026Sc 015Zr162 201 Extruded material solutionised 600uC aged 250uC

5xxx alloys171 1Mg 43 111 Cold rolled material (89) aged 288uC8 h

1Mg 03Sc 288 303 Cold rolled material (89) aged 288uC8 h53Mg 147 259 Cold rolled material (50) wintermediate anneals

at 343uC aged 288uC8 h53Mg 03Sc 368 401 Cold rolled material (50) wintermediate anneals

at 343uC aged 288uC8 h23 2Mg 05Sc 376 401 Hot rolled 288uC cold rolled 69ndash81 aged 288uC4 h

4Mg 05Sc 414 4606Mg 05Sc 433 503

237 4Mg 1Sc 420 525 Cold rolled material (83) aged 320uC1 h148 4Mg 02Sc 194 ndash Cast material aged 300uC10 h compression test

Tensile test data except where noted YS yield strength UTS ultimate tensile strength

Roslashyset and Ryum Scandium in aluminium alloys

International Materials Reviews 2005 VOL 50 NO 1 37

Supersaturated solid solutionRGP-zonesRg9Rg(Zn2Mg)

The maximum hardness is normally achieved whenthe g9 precipitates are predominant Common precipita-tion hardening temperatures are in the range 95ndash180uCand a two-step precipitation heat treatment within thistemperature regime is often used238 It has beenobserved in some investigations that Sc and SczZradditions to AlndashMgndashZn alloys slow down the precipita-tion of g9 somewhat243 Other investigations find thatthere is no effect of Sc on the precipitation behaviour ofg9244245 and yet others report that Sc additionssignificantly speed up the precipitation of g9246 In Ref247 it is found that an Sc addition leads to coarser g9precipitates and it is claimed that this gives an improvedductility of the alloy The strength-loss associated withlarger particle size is reported to be counterbalanced bystrengthening from Al3Sc precipitates

AlndashLi alloys

The precipitation sequence in binary AlndashLi alloys isapparently simple

Supersaturated solid solutionRd9Rd (AlLi)

where d9 is the metastable Al3Li phase which just likeAl3Sc has the L12 type of atomic arrangement Thetypical temperature regime for precipitation of d9 whichis the strengthening phase in this system is approx 150ndash200uC A comparison of the age hardening response ofan Alndash26 wt-Li and an Alndash24 wt-Lindash019 wt-Scalloy at 180uC248 and 200uC161 indicates that the onsetof d9 precipitation is not altered by the presence of ScThe hardness curves for the two alloys are practicallyidentical at 200uC whereas at 180uC the peak hardnesslevel is slightly higher in the AlndashLi than the AlndashLindashScalloy DSC measurements at constant heating ratesindicate that the addition of Sc to an AlndashLi alloysincreases the activation energy for d9 precipitation andmoves the exothermic peak associated with d9 precipita-tion to a higher temperature248 For specimens aged at

either 180uC or 200uC TEM observations reveal that thed9 precipitates are much smaller in the Sc containingalloy than in binary AlndashLi both in the peak agedcondition and in the overaged condition161248 Additionof Sc has also been observed to reduce the size of d9precipitates in other AlndashLi based alloys249ndash251 In an AlndashLindashCundashZr alloy an addition of Sc has been reported toslow down the homogeneous precipitation of d9252253 Ithas been claimed that Sc reduces the quench sensitivityand delays room temperature aging of AlndashLi basedalloys254ndash256

When present in the microstructure before the pre-cipitation of d9 the Al3Sc precipitates may act as effec-tive nucleation sites for d9 The resulting precipitates arespheres of d9 with a core of Al3Sc161249252ndash255257ndash261

Corrosion resistanceAn appreciable amount of data is available on the effectsof Sc on the corrosion behaviour of wrought Al-alloysSome of these effects are apparently derived from theeffects of Sc on the microstructure of the alloys It hasbeen reported that an addition of Sc increases thecorrosion potential (makes it less negative) in pureAl262ndash264 in AlndashZn alloys265266 AlndashMg alloys267 AlndashZnndashMgndashCu alloys264268 AlndashCundashMgndashMn alloys264 andin AlndashCundashLindashMgndashAg alloys264 Even though Sc alsohas been reported to decrease the corrosion potential in

28 Age hardening response at 175uC for Alndash08 wt-Mgndash

07 wt-Si alloy (Base) with additions of 02 wt-Sc

04 wt-Sc and 02 wt-Scz01 wt-Zr from Ref 241

29 TEM images of a b0 precipitates in Alndash08 wt-Mgndash

07 wt-Si alloy and b b0 and Al3(Sc1ndashxZrx) in a similar

alloy with addition of 02 wt-Scz01 wt-Zr from

Ref 241

Roslashyset and Ryum Scandium in aluminium alloys

38 International Materials Reviews 2005 VOL 50 NO 1

AlndashMg alloys269270 it seems that the general trend isthat adding Sc to an alloy makes it slightly more nobleThe change in corrosion potential is much morepronounced when Sc is added in amounts larger thanthe eutectic composition263 ie there is a considerablecontribution from primary or eutectic Al3Sc to theoverall potential It has also been demonstrated that thechange in corrosion potential caused by Sc can dependon the heat treatment applied to the alloy267268

Even though the corrosion potential is an essentialparameter in establishing the corrosion behaviour of analloy an increase in the corrosion potential does notnecessarily imply an improved self-corrosion resistanceHowever measurements of corrosion rates and passiva-tion current densities strongly suggest that the self-corrosion resistance in general is considerably improvedwhen Sc is added to wrought Al-alloys263264267 Someobserved variations in corrosion potential and passiva-tion current densities with Sc content in binary AlndashScalloys are plotted in Fig 30

Material failure in corrosive environments is often dueto localised corrosion attacks which may propagaterapidly even though the bulk material has a goodresistance against general corrosion It has been pointedout that hypereutectic additions of Sc may lead tomicrogalvanic corrosion beside primary Al3Sc parti-cles264 In AlndashMg alloys grain boundary precipitation ofAl8Mg5 can lead to localised corrosion attacks such asintergranular corrosion (IGC) exfoliation corrosion(EC) and stress corrosion cracking (SCC) In wroughtmaterial such precipitation may occur in the 60ndash180uCtemperature regime and heating in this temperaturerange is referred to as lsquosensitationrsquo An AlndashMgndashSc alloywas found to be immune against intergranular corrosionand have moderate susceptibility to exfoliation corro-sion after annealing at 350uC271 After sensitation heattreatments severe IGC and EC was observed but notquite as severe as in a corresponding alloy without ScAs for SCC the AlndashMgndashSc alloy was found to be highlyresistant271 In another study it was found that additionof 056 wt-Sc reduces the SCC susceptibility of an Alndash68 wt-Mg alloy in the as-rolled state and afterannealing at 250uC whereas in a sensitised specimenthe SCC susceptibility is somewhat increased by the Scaddition272 A third investigation found that Sc has nomeasurable detrimental effect on the SCC susceptibilityof sensitised Alndash5Mgndash015Zr alloy273 SCC is also a

severe problem in high strength AlndashZnndashMgndashCu alloys Ithas been shown that small Sc additions are effective inreducing the SCC sensitivity of these alloys244246268274

Use of Sc-containing Al alloysA systematic development of Sc-containing aluminiumalloys took place in the former USSR in the 1980s andthe interest for Sc as an alloying element in aluminiumalloys hit the western world approximately 10 yearslater Even though a number of improvements in Alalloys achieved by Sc addition have been demonstratedthe current uses of such alloys are very limited This isrelated to the very high price of scandium

In Russia some parts of military aircraft are made ofSc-containing AlndashLi alloys In the western world themain usage of Sc-containing alloys is for sportsequipment Ashurst Technology and Kaiser Aluminumdeveloped a Sc-containing 7xxx alloy for baseball andsoftball bats which was introduced to the Americanmarket in 1997 by Easton Alcoa soon followed with aSc-containing alloy for a competing brand of batsLouisville Slugger Since then several new and improvedSc-containing alloys for bats have been introduced tothe market The purpose of adding Sc is to increase theyield strength of the alloy allowing for a down-gaugingof the wall thickness which in turn gives a strongerlsquospring-rsquo or lsquotrampoline-rsquo effect when the ball hits thebat

Shortly after the introduction of the Sc containingbats Easton also launched Sc-containing 7xxx tubingfor bicycle frames Just as in the bats Sc increases theyield strength of the alloy allowing for down-gauging oftube wall thickness and a corresponding weight reduc-tion of the bicycle frame An Italian manufacturer ofbicycle tubing Dedacciai also delivers tubes in a Sc-containing 7xxx alloy

Other sports equipment made from Sc-containingaluminium alloys includes lacrosse sticks and tent polesSmith and Wesson has also introduced a series ofhandguns where the frame is made from a Sc-containingAl alloy

A common factor for the items mentioned above isthat the material cost is only a minor part of the totalmanufacturing cost of the end product and also thatthese products are aimed at a group of customers thathave a certain awareness of new materials Both baseballbats and bicycle frames have been marketed aslsquoscandium alloyrsquo even though the Sc content is muchlower than 1

Currently AlndashSc master alloys for the production ofSc-containing Al alloys are available at a price thatcorresponds to US$ 2000 per kg of Sc This means that ifone wants to add 02 wt-Sc to an alloy which is afairly common content one also increases the price ofthe alloy by US$ 4 per kg alloy Depending on the alloytype Sc is added to this represents a tripling orquadrupling of the price of the alloy There are notmany existing products where such an increase inmaterial cost can be justified In order to see awidespread use of Sc in high-volume products the Scprice has to come down considerably Actually the priceof adding Sc to Al alloys has gone down by a factor 3ndash10over the last 10ndash15 years and substantial price reduc-tions are also expected in the future

30 Observed variations in corrosion potential and passi-

vation current densities with Sc content in binary Alndash

Sc alloys based on data from Ref 263

Roslashyset and Ryum Scandium in aluminium alloys

International Materials Reviews 2005 VOL 50 NO 1 39

The current production of AlndashSc master alloys isbased upon and will continue to be based upon for theforeseeable future the reduction of Sc2O3 or other Sccompounds directly in molten aluminium It is notnecessary as many tend to believe to take the route viametallic Sc Thus the price of AlndashSc master alloy isgoverned by the price of Sc2O3 or other Sc compoundsin question and not by the price of metallic scandiumThe Sc2O3 which is the main source for todayrsquos AlndashScmaster alloy production comes from stockpiles in theformer USSR These stockpiles will be exhausted withina few years and new reliable sources of Sc2O3 or otherSc compound production are sought It turns out thatthe most economically viable option that has beendisclosed so far is the processing of Red Mud from theBayer process of extracting alumina from bauxiteScandium is enriched in the Red Mud and is extractedfrom a Red Mud aqueous slurry by selective leachingsubsequent ion-exchange procedure and finally a liquidndashliquid extraction procedure It is not required to build aseparate lsquoSc factoryrsquo to do this but rather build an lsquoadd-onrsquo to existing Bayer process plants Such a processroute is expected to bring down the price of Sc2O3

considerably which in turn means that AlndashSc masteralloy price should drop accordingly Preliminary ana-lyses suggest a price of approx US$ 400 per kg Sc in themaster alloy which translates to an added cost of 80cent per kilo when 02 wt-Sc is added to an aluminiumalloy This is also a considerable increase in the materialcost but with such prices one should expect to see Sccontaining alloys in many more applications than whatis the case at the present time

Concluding remarksThe body of published investigations on Al-based alloyswith Sc addition provides a sound basis of knowledgefor metallurgists that want to look into the possibility ofenhancing the performance of a wrought Al-alloy byadding Sc to it Ternary AlndashScndashX phase diagrams areavailable for practically every technologically importantalloying element in Al The effect of a wide range ofternary alloying elements on the precipitation behaviourof Al3Sc is accounted for It has been shown that theAl3Sc phase can be effective as a grain refiner adispersoid former and a precipitate hardening agentand some of the underlying conditions for achieving thedesired Al3Sc formation have been outlined Addingsome Zr together with Sc has proven to be beneficial Itmay lead to effective grain refinement at a lower Sc levelbut the most prominent effect is the refinement indispersoid distribution that can be achieved An addi-tion of Sc has little if any effect on precipitation in the2xxx 6xxx and 7xxx alloy systems and some effects onthe precipitation in AlndashLi based alloys With respect tocorrosion behaviour adding Sc to an Al-alloy does ingeneral seem to make the alloy slightly more noble andto increase its self-corrosion resistance Scandium-containing Al alloys have very few uses at the presenttime as a result of the high price of scandium The priceof Sc is expected to decrease significantly in the futureand this should lead to the disclosure of moreapplications where it is economically feasible to takeadvantage of the improved properties of some Sc-containing aluminium alloys

References1 D R Lide lsquoCRC handbook of chemistry and physicsrsquo 71st edn

4ndash29 1990 Boston USA CRC Press

2 E M Savitsky V F Terehova I V Burov and O P Naumkin

Proc Fourth Conf on lsquoRare earth researchrsquo Phoenix Arizona

USA April 1964 409ndash420

3 E M Savitskii V F Terekhova I V Burov O P Naumkin and

I A Markova Inorg Mater 1965 1 1503ndash1512

4 O P Naumkin V T Terekhova and E M Savitskiy Russ

Metall 1965 (4) 128ndash136

5 W G Moffatt lsquoThe handbook of binary phase diagramsrsquo 1981

Schenectady NY USA General Electric Co

6 E A Brandes (ed) lsquoSmithells metals reference bookrsquo 6th edn

1983 London UK Butterworths

7 R P Elliott and F A Shunk Bull Alloy Phase Diagrams 1981

2 (2) 222ndash223

8 K A Gschneider Jr and F W Calderwood Bull Alloy Phase

Diagrams 1989 10 34ndash36

9 H Okamoto J Phase Equil 1991 12 612ndash613

10 J L Murray J Phase Equil 1998 19 380ndash384

11 M E Drits E S Kadaner T V Dobatkina and N I Turkina

Russ Metall 1973 (4) 152ndash154

12 S-I Fujikawa M Sugaya H Takei and K-I Hirano J Less-

Common Met 1979 63 87ndash97

13 N Blake and M A Hopkins J Mater Sci 1985 20 2861ndash2867

14 V I Kononenko and S V Golubev Russ Metall 1990 (2) 193ndash

195

15 T B Massalski J L Murray L H Bennett and H Baker (eds)

lsquoBinary alloy phase diagramsrsquo 1986 Metals Park OH USA

ASM

16 G Cacciamani P Riani G Borzone N Parodi A Saccone

R Ferro A Pisch and R Schmid-Fetzer Intermetallics 1999 7

101ndash108

17 H Okamoto J Phase Equil 2000 21 310

18 A F Norman P B Pragnell and R S McEwen Acta Mater

1998 46 5715ndash5732

19 I N Pyagai and A V Vakhobov Russ Metall 1990 (5) 50ndash52

20 C L Fu J Mater Res 1990 5 971ndash979

21 X Lu and Y Wang Calphad 2002 26 555ndash561

22 R R Sawtell and J W Morris Jr Proc lsquoDispersion strengthened

aluminium alloysrsquo Phoenix Arizona USA January 1988 409ndash

420

23 R R Sawtell and C L Jensen Metall Trans A 1990 21A 421ndash

430

24 L A Willey Unpublished research Alcoa 1970 Data points are

extracted from Ref 10

25 N I Turkina and V I Kuzmina Russ Metall 1976 (4) 179ndash

183

26 T Torma E Kovacs-Csetenyi I Vitanyi M Butova and

J Stepanov Proc 6th Int Symp on lsquoHigh purity materials in

science and technologyrsquo Akademie der Wissenschaften der DDR

Dresden Germany May 1985 388ndash389

27 A L Berezina V A Volkov B P Domashnikov and K V

Chuistov Metallofizika 1987 9 (5) 43ndash47

28 H-H Jo J Korean Inst Metals 1990 28 499ndash504

29 H-H Jo and S-I Fujikawa Mater Sci Eng 1993 A 171 151ndash

161

30 S Celotto and T J Bastow Philos Mag A 2000 80 1111ndash1125

31 J Roslashyset and N Ryum submitted to Mater Sci Eng

32 M E Drits L S Toropova Yu G Bykov F L Gushchina V I

Elagin and Yu A Filatov Russ Metall 1983 (1) 150ndash153

33 L S Toropova D G Eskin M L Kharakterova and T V

Dobatkina lsquoAdvanced aluminum alloys containing scandium

structure and propertiesrsquo 1998 Amsterdam The Netherlands

Gordon and Breach Science Publishers

34 V V Cherkasov P P Pobezhimov L P Nefedova E V Belov

and G M Kuznetsov Met Sci Heat Treat 1996 (6) 268ndash270

35 Kh O Odinaev I N Ganiev V V Kinzhibalo and B Ya

Kotur Dokl Akad Nauk Tadzh SSR 1989 32 37ndash38

36 Kh O Odinaev I N Ganiev and A V Vakhobov Russ Metall

1991 (4) 200ndash203

37 J Grobner R Schmid-Fetzer A Pisch G Cacciamani P Riani

N Parodi G Borzone A Saccone and R Ferro Z Metallkd

1999 90 872ndash880

38 E A Marquis and D N Seidman Microsc Microanal 2002 8

(Suppl 2) 1100CDndash1101CD

39 A Pisch J Grobner and R Schmid-Fetzer Mater Sci Eng A

2000 A 289 123ndash129

Roslashyset and Ryum Scandium in aluminium alloys

40 International Materials Reviews 2005 VOL 50 NO 1

40 C Xia F Zeng and Y Gu Trans Nonferrous Met Soc China

2003 13 1124ndash1127

41 M Yu Teslyuk and V S Protasov Sov Phys Crystallogr 1966

10 470ndash471

42 M L Kharakterova and T V Dobatkina Russ Metall 1988

(6) 175ndash178

43 M L Kharakterova Russ Metall 1991 (4) 195ndash199

44 L S Toropova M L Kharakterova and D G Eskin Russ

Metall 1992 (3) 194ndash199

45 P Riani L Arrighi R Marazza D Mazzone G Zanicchi and

R Ferro J Phase Equil Diff 2004 25 22ndash52

46 A T Tyvanchuk T I Yanson B Ya Kotur O S Zarechnyuk

and M L Kharakterova Russ Metall 1988 (4) 190ndash192

47 L L Rokhlin T V Dobatkina and M L Kharakterova Powder

Metall Met Ceram 1997 36

48 A Z Ikromov I N Ganiev and V V Kinzhibalo Dokl Akad

Nauk Tadzh SSR 1990 (6) 391ndash392

49 I N Ganiev A Z Ikromov and V G Khudoiberdiev Russ

Metall 1995 (3) 125ndash127

50 I N Fridlyander L L Rokhlin T V Dobatkina and N I

Nikitina Met Sci Heat Treat 1993 (10) 567ndash571

51 I N Fridlyander L L Rokhlin T V Dobatkina V V

Kinzhibalo and A T Tyvanchuk Russ Metall 1998 (1) 161ndash

166

52 R A Emigh E L Bradley and J W Morris Jr in lsquoLight-weight

alloys for aerospace applications IIrsquo (ed E W Lee and N J

Kim) 27ndash43 1991 TMS

53 L S Toropova A N Kamardinkin V V Kindzhibalo and A T

Tyvanchuk Phys Met Metall 1990 70 (6) 106ndash110

54 A N Kamardinkin T V Dobatkina and T D Rostova Russ

Metall 1991 (4) 216ndash218

55 L S Torodskaya T V Dobatkina and A N Kamardinkin

Russ Metall 1992 (5) 128ndash131

56 E M Sokolovskaya E F Kazakova E I Poddyakova and A

A Ezhov Met Sci Heat Treat 1997 (5) 211ndash213

57 Y Harada and D C Dunand Mater Sci Eng 2002 A 329ndash331

686ndash695

58 N E Drits L S Toropova and F L Gushchina Russ Metall

1984 (4) 229ndash232

59 E M Sokolovskaya E F Kazakova V A Alikhanov and E V

Zhuravleva Moscow Univ Chem Bull 1997 52 (5) 70ndash72

60 E M Sokolovskaya E F Kazakova and E I Poddyakova Met

Sci Heat Treat 1989 (11) 837ndash839

61 G M Cheldieva E F Kazakova E M Sokolovskaya and N I

Kaloev Russ Metall 1990 (6) 87ndash90

62 E M Sokolovskaya E F Kazakova and O D-S Kendivan

Russ Metall 1998 (4) 135ndash137

63 N G Bukhanko E F Kazakova and E M Sokolovskaya Russ

Metall 2001 (4) 425ndash431

64 E D Trubnyakova O I Bodak I N Ganiev and A V

Vakhobov Russ Metall 1987 (3) 219ndash222

65 I N Fridlyander and L V Molchanova Russ Metall 2003 (5)

476ndash480

66 R A Altynbaev S Kh Khairidinov and A V Vakhobov Russ

Metall 1987 (4) 194ndash196

67 J C Schuster and J Bauer J Less-Common Met 1985 109

345ndash350

68 L L Rokhlin A S Fridman T V Dobatkina and D G Eskin

Russ Metall 1991 (6) 146ndash148

69 A S Fridman T V Dobatkina and E V Muratova Russ

Metall 1992 (1) 207ndash209

70 C Xia F Zeng and Y Gu Trans Nonferrous Met Soc China

2003 13 546ndash552

71 F Zeng C Xia and Y Gu J Alloys Comp 2004 363 175ndash181

72 L L Rokhlin T V Dobatkina N R Bochvar and E V Lysova

J Alloys Comp 2004 367 10ndash16

73 T V Dobatkina A S Fridman and E V Muratova Russ

Metall 1992 (5) 125ndash127

74 I N Fridlyander L L Rokhlin N R Bochvar E V Lysova

and O V Boteva Russ Metall 2001 (6) 661ndash666

75 V N Rechkin L K Lamikhov and T I Samsonova Sov Phys

Crystallogr 1964 9 325ndash327

76 I I Zalutskii and P I Kripyakevich Sov Phys Crystallogr

1967 12 341ndash343

77 T J Bastow C T Forwood M A Gibson and M E Smith

Phys Rev B 1998 58 2988ndash2997

78 K Fukunaga M Kolbe K Yamada and Y Miura Mater Sci

Eng 1997 A 234ndash236 594ndash597

79 E P George J A Horton W D Porter and J H Schneibel

J Mater Res 1990 5 1639ndash1648

80 E P George D P Pope C L Fu and J H Schneibel ISIJ Int

1991 31 1063ndash1075

81 Y Harada and D C Dunand Acta Mater 2000 48 3477ndash3487

82 J H Schneibel and E P George Scripta Metall Mater 1990 24

1069ndash1074

83 J H Schneibel and P M Hazzledine Mater Res Soc Symp

Proc 1991 213 323ndash328

84 J H Schneibel and P M Hazzledine J Mater Res 1992 7

868ndash875

85 C J Sparks E D Specht G E Ice P Zschack and J Schneibel

Mater Res Soc Symp Proc 1991 213 363ndash368

86 J Tarnacki and Y-W Kim Scripta Metall Mater 1989 23

1063ndash1068

87 M Asta V Ozolins and C Woodward JOM 2001 53 (9) 16ndash

19

88 M E Drits L S Toropova F L Gushchina and S G Fedotov

Sov Non-Ferrous Met Res 1984 12 83ndash85

89 Y Harada and D C Dunand Scripta Mater 2003 48 219ndash222

90 C Woodward M Asta G Kresse and J Hafner Phys Rev B

2001 63 094103-1-6

91 J-H Xu and A J Freeman Phys Rev B 1990 41 12553ndash12561

92 M F Bartholomeusz and J A Wert Acta Metall Mater 1992

40 673ndash682

93 G Bester and M Fahnle J Phys Condens Matter 2001 13

11551ndash11565

94 C L Fu and M H Yoo Proc lsquoOrdered intermetallics ndash physical

metallurgy and mechanical behaviorrsquo Irsee Germany June 1991

155ndash164

95 K Fukunaga T Shouji and Y Miura Mater Sci Eng 1997 A

239ndash240 202ndash205

96 D P Pope Proc lsquoOrdered intermetallics ndash physical metallurgy

and mechanical behaviorrsquo Irsee Germany June 1991 143ndash153

97 J-S Wang Acta Mater 1998 46 2663ndash2674

98 M H Yoo and C L Fu Mater Sci Eng 1992 A 153 470ndash478

99 R W Hyland Jr and R C Stiffler Scripta Metall Mater 1991

25 473ndash477

100 I G Brodova I V Polents O A Korzhavina P S Popelrsquo I P

Korshunov and V O Esin Melts 1992 4 392ndash397

101 I G Brodova O A Chikova I V Polents P S Popelrsquo and V O

Esin Casting Processes 1992 1 (2) 158ndash160

102 I G Brodova D V Bashlikov and I V Polents Mater Sci

Forum 1998 269ndash272 589ndash594

103 K B Hyde A F Norman and P B Pragnell Mater Sci Forum

2000 331ndash337 1013ndash1018

104 K B Hyde A F Norman and P B Pragnell Acta Mater 2001

49 1327ndash1337

105 J Roslashyset and N Ryum Proc 6th Int Conf on lsquoAluminum

alloysrsquo Toyohashi Japan July 1998 793ndash798

106 V I Elagin V V Zakharov and T D Rostova Met Sci Heat

Treat 1993 (6) 317ndash319

107 R W Hyland Jr Metall Trans A 1992 23A 1947ndash1955

108 B A Parker Z F Zhou and P Nolle J Mater Sci 1995 30

452ndash458

109 C L Rohrer M D Asta S M Foiles and R W Hyland Jr

Mater Res Soc Symp Proc 1996 398 477ndash482

110 G M Novotny and A J Ardell Mater Sci Eng 2001 A 318

144ndash154

111 J D Robson M J Jones and P B Pragnell Acta Mater 2003

51 1453ndash1468

112 C Tan Z Zheng and B Wang Proc 3rd Int Conf on

lsquoAluminium alloysrsquo Vol I NTH Trondheim Norway June

1992 290ndash294

113 M Nakayama A Furuta and Y Miura Mater Trans JIM

1997 38 852ndash857

114 E A Marquis and D N Seidman Acta Mater 2001 49 1909ndash

1919

115 M J Jones and F J Humphreys Acta Mater 2003 51 2149ndash

2159

116 E A Marquis D N Seidman and D C Dunand in lsquoCreep

deformation fundamentals and applicationsrsquo (ed R S Mishra

J C Earthman and S V Raj) 299ndash308 2002 TMS

117 D N Seidman E A Marquis and D C Dunand Acta Mater

2002 50 4021ndash4035

118 E A Marquis D N Seidman and D C Dunand Acta Mater

2003 51 285ndash287

119 M E Drits L S Toropova U G Bikov and G K Anastaseva

Proc lsquoDiffusion in metals and alloysrsquo Tihany Hungary Augustndash

September 1982 616ndash623

120 V I Elagin V V Zakharov and T D Rostova Met Sci Heat

Treat 1983 (7) 546ndash549

Roslashyset and Ryum Scandium in aluminium alloys

International Materials Reviews 2005 VOL 50 NO 1 41

121 M Ye Drits L B Ber Yu G Bykov L S Toropova and G K

Anastaseva Phys Met Metall 1984 57 (6) 118ndash126

122 M E Drits L S Toropova and Yu G Bykov Sov Non-Ferrous

Met Res 1985 13 309ndash314

123 V I Yelagin V V Zakharov S G Pavlenko and T D Rostova

Phys Met Metall 1985 60 (1) 88ndash92

124 N Sano Y Hasegawa K Hono H Jo K Hirano H W

Pickering and T Sakurai Journal de Physique 1987 48 C6 337ndash

342

125 N Sano H-H Jo K-I Hirano and T Sakurai J Jpn Inst

Metals 1989 39 444ndash450

126 N Sano H Jo K Hirano and T Sakurai Proc Second Int

Conf on lsquoAluminium alloysrsquo Beijing China October 1990 549ndash

554

127 Y Miura M Nakayama and A Furuta Proc lsquoAspects of high

temperature deformation and fracture in crystalline materialsrsquo

Nagoya Japan July 1993 255ndash262

128 Y W Riddle and T H Sanders Jr Mater Sci Forum 2000

331ndash337 939ndash944

129 Y W Riddle M McIntosh and T H Sanders Jr in lsquoLightweight

alloys for aerospace application VIrsquo (ed K Jata E W Lee

W Frazier and N J Kim) 25ndash39 2001 TMS

130 M E Drits J Dutkiewicz L S Toropova and J Salawa Crystal

Res Technol 1984 19 1325ndash1330

131 Y W Riddle MSc thesis Georgia Tech GA USA 1998

132 T J Bastow and S Celotto Mater Sci Eng 2003 C 23 757ndash

762

133 M C Carroll M J Mills G S Daehn P I Gouma M F

Savage and B R Dunbar in lsquoAutomotive Alloys 1999rsquo (ed

S Das) 239ndash246 2000 TMS

134 E Clouet M Nastar and C Sigli Phys Rev B 2004 69 064109-

1-14

135 V V Zakharov Met Sci Heat Treat 1997 (2) 61ndash66

136 J W Christian lsquoThe theory of transformation in metals and

alloysrsquo 2nd edn 1975 Pergamon Press Ltd

137 A L Berezina V A Volkov B P Domashnikov S V Ivanov

and K V Chuistov Phys Metals 1990 10 296ndash304

138 S-I Fujikawa and S Sakauchi Proc 6th Int Conf on

lsquoAluminum alloysrsquo Toyohashi Japan July 1998 805ndash810

139 Y S Touloukian R K Kirby R E Taylor and P D Desai

(eds) lsquoThermal expansion metallic elements and alloysrsquo 1975

New York Plenum

140 J Roslashyset and N Ryum submitted to Scripta Mater

141 R O Simmons and R W Balluffi Phys Rev 1960 117 52ndash61

142 M Ocko E Babic R Krsmik E Girt and B Leontic J Phys F

Metals Phys 1976 6 703ndash707

143 M J Jones and F J Humphreys Proc First Joint Int Conf on

lsquoRecrystallization and grain growthrsquo Aachen Germany August

2001 Springer Verlag 1287ndash1292

144 S Iwamura M Nakayama and Y Miura Mater Sci Forum

2002 396ndash402 1151ndash1156

145 S Iwamura and Y Miura Acta Mater 2004 52 591ndash600

146 M Asta S M Foiles and A A Quong Phys Rev B 1998 57

11265ndash11275

147 R W Hyland Jr M Asta S M Foiles and C L Rohrer Acta

Mater 1998 46 3667ndash3678

148 J Roslashyset and N Ryum Proc 4th Int Conf on lsquoAluminium

alloysrsquo Vol I Atlanta GA USA September 1994 194ndash201

149 M E Drits L S Toropova G K Anastaseva and G L

Nagornichnykh Russ Metall 1984 (3) 192ndash195

150 E A Marquis D N Seidman and D C Dunand Acta Mater

2003 51 4751ndash4760

151 M E Drits L S Toropova and Yu G Bykov Met Sci Heat

Treat 1983 (7) 550ndash554

152 V V Zakharov and T D Rostova Met Sci Heat Treat 1995

(2) 65ndash69

153 M Nakayama and Y Miura Proc 4th Int Conf on lsquoAluminium

alloysrsquo Vol I Atlanta GA USA September 1994 538ndash545

154 M Nakayama and Y Miura J Jpn Inst Light Metals 1996 46

275ndash279

155 M Nakayama T Okuyama and Y Miura Mater Sci Forum

2000 331ndash337 927ndash932

156 M Nakayama T Okuyama and Y Miura Proc 6th Int Conf

on lsquoAluminum alloysrsquo Toyohashi Japan July 1998 517ndash522

157 M L Kharakterova D G Eskin and L S Toropova Acta

Metall Mater 1994 42 2285ndash2290

158 V I Elagin V V Zakharov and T D Rostova Met Sci Heat

Treat 1992 (1) 37ndash45

159 H Wiik Siv Ing thesis NTH Institute of Metallurgy

Trondheim Norway 1995

160 J Roslashyset H Hovland and N Ryum Mater Sci Forum 2002

396ndash402 619ndash624

161 Y Miura K Horikawa K Yamada and M Nakayama Proc

4th Int Conf on lsquoAluminium alloysrsquo Vol II Atlanta GA USA

September 1994 161ndash168

162 Y W Riddle PhD thesis Georgia Tech GA USA 2000

163 B Forbord W Lefebvre F Danoix H Hallem and

K Marthinsen Scripta Mater 2004 51 333ndash337

164 J D Robson Acta Mater 2004 52 1409ndash1421

165 C B Fuller J L Murray and D N Seidman submitted to Acta

Mater 2004

166 M G Mousavi C E Cross and Oslash Grong Sci Technol Weld

Joining 1999 4 381ndash388

167 J S Vetrano S M Bruemmer L M Pawlowski and I M

Robertson Mater Sci Eng 1997 A 238 101ndash107

168 Y W Riddle and T H Sanders Jr Mater Sci Forum 2000

331ndash337 799ndash803

169 G M Khan A O Nikiforov V V Zakharov and I I Novikov

Tsvetnye Metally 1993 34 (11) 43ndash45

170 Z Horita M Furukawa M Nemoto A J Barnes and T G

Langdon Acta Mater 2000 48 3633ndash3640

171 L A Willey US Patent 3 619 181 9 November 1971

172 L K Lamikhov and G V Samsonov Tsvetnye Metally 1964 5

(8) 77ndash80

173 A L Berezina K V Chuistov N I Kolobnev L B

Khokhlatova and T A Monastyrskaya Mater Sci Forum

2002 396ndash402 741ndash746

174 F A Fasoyinu J Thomson D Cousineau T Castles and M

Sahoo Proc 6th Int AFS Conf on lsquoMolten aluminum

processingrsquo Orlando FL USA November 2001

175 Z Yin Q Pan Y Zhang and F Jiang Mater Sci Eng 2000

A 280 151ndash155

176 I I Novikov and O E Grushko Mater Sci Technol 1995 11

926ndash932

177 D Cousineau M Sahoo P D Newcombe T Castles and F A

Fasoyinu Proc lsquoAFS 105th casting congressrsquo Dallas TX USA

AprilndashMay 2001 157ndash184

178 C E Cross and Oslash Grong Proc 6th Int Conf on lsquoAluminum

alloysrsquo Toyohashi Japan July 1998 1441ndash1446

179 F A Costello J D Robson and P B Prangnell Mater Sci

Forum 2002 396ndash402 757ndash762

180 K B Hyde A F Norman and P B Prangnell Mater Sci

Forum 2002 396ndash402 39ndash44

181 M E Drits S G Pavlenko L S Toropova Yu G Bukov and

L B Ber Sov Phys Dokl 1981 26 (3) 344ndash346

182 A M Drits and B A Kopeliovich Russ Metall 1985 (4) 147ndash

151

183 V G Davydov V I Elagin V V Zakharov and T D Rostova

Met Sci Heat Treat 1996 (8) 347ndash352

184 M E Drits L S Toropova Yu G Bykov L B Ber and S G

Pavlenko Russ Metall 1982 (1) 148ndash152

185 T D Rostova V G Davydov V I Yelagin and V V Zakharov

Mater Sci Forum 2000 331ndash337 793ndash798

186 Y W Riddle H Hallem and N Ryum Mater Sci Forum 2002

396ndash402 563ndash568

187 J Roslashyset and Y W Riddle Proc 9th Int Conf on lsquoAluminium

alloysrsquo Brisbane Australia August 2004 1210ndash1215

188 A M Diskin V K Portnoi A M Drits and A A Alalykin Sov

Non-Ferrous Met Res 1986 14 499ndash500

189 R R Sawtell P E Bretz and C L Jensen US Patent 4 689 090

25 August 1987

190 G A Salishchev Yu B Timoshenko and R A Saitova Proc

Second Int Conf on lsquoAluminium alloysrsquo Beijing China October

1990 413ndash415

191 T G Nieh R Kaibyshev L M Hsiung N Nguyen and

J Wadsworth Scripta Mater 1997 36 1011ndash1016

192 T G Nieh L M Hsiung J Wadsworth and R Kaibyshev Acta

Mater 1998 46 2789ndash2800

193 J S Vetrano C H Henager Jr M T Smith and S M

Bruemmer in lsquoHot deformation of aluminum alloys IIrsquo (ed T R

Bieler L A Lalli and S R MacEwen) 407ndash418 1998 TMS

194 J S Vetrano C H Henager Jr S M Bruemmer Y Ge and

C H Hamilton in lsquoSuperplasticity and Superplastic Forming

1998rsquo (ed A K Gosh and T R Bieler) 89ndash97 1998 TMS

195 V Y Gertsman J S Vetrano C H Henager Jr and S M

Bruemmer Proc First Joint Int Conf on lsquoRecrystallization and

grain growthrsquo Aachen Germany August 2001 Springer Verlag

2001 837ndash842

196 Y Xiao C Gao H Ma and S Tian Trans Nonferrous Met Soc

China 2001 11 235ndash238

Roslashyset and Ryum Scandium in aluminium alloys

42 International Materials Reviews 2005 VOL 50 NO 1

197 A Gholinia F J Humphreys and P B Prangnell Acta Mater

2002 50 4461ndash4476

198 A Gholinia F J Humphreys and P B Prangnell Mater Sci

Forum 2002 408ndash412 1519ndash1524

199 S Komura P B Berbon M Furukawa Z Horita M Nemoto

and T G Langdon Scripta Mater 1998 38 1851ndash1856

200 S Komura P B Berbon A Utsunomiya M Furukawa

Z Horita M Nemoto and T G Langdon in lsquoHot deformation

of aluminum alloys IIrsquo (ed T R Bieler L A Lalli and S R

MacEwen) 125ndash138 1998 TMS

201 S Komura Z Horita M Furukawa M Nemoto and T G

Langdon J Mater Res 2000 15 2571ndash2576

202 S Komura M Furukawa Z Horita M Nemoto and T G

Langdon Mater Sci Eng 2001 A 297 111ndash118

203 S Komura Z Horita M Furukawa M Nemoto and T G

Langdon Metall Mater Trans A 2001 32A 707ndash716

204 Z Horita M Furukawa K Oh-ishi M Nemoto and T G

Langdon Proc Fourth Int Conf on lsquoRecrystallization and

related phenomenarsquo (ed T Sakai and H G Suzuki) 1999 The

Japan Institute of Metals 301ndash308

205 Z Horita S Komura P B Berbon A Utsunomiya

M Furukawa M Nemoto and T G Langdon Mater Sci

Forum 1999 304ndash306 91ndash96

206 Z Horita S Lee S Ota K Neishi and T G Langdon Mater

Sci Forum 2001 357ndash359 471ndash476

207 Z Horita T Fujinami K Sato S B Kang H W Kim and T G

Langdon in Proc James T Staley Honorary Symposium on

Aluminum Alloys lsquoAdvances in the metallurgy of aluminum

alloysrsquo (ed M Tiryakioglu) 271ndash275 2001 ASM

208 P B Berbon S Komura A Utsunomiya Z Horita

M Furukawa M Nemoto and T G Langdon Mater Trans

JIM 1999 40 772ndash778

209 M Nemoto Z Horita M Furukawa and T G Langdon Mater

Sci Forum 1999 304ndash306 59ndash66

210 M Furukawa Z Horita M Nemeto and T G Langdon Proc

lsquoLight Metals 1999rsquo Quebec City PQ Canada August 1999 583ndash

592

211 M Furukawa K Oh-ishi S Komura A Yamashita Z Horita

M Nemeto and T G Langdon Mater Sci Forum 1999 304ndash

306 97ndash102

212 M Furukawa A Utsunomiya K Matsubara Z Horita and

T G Langdon Acta Mater 2001 49 3829ndash3838

213 M Furukawa A Utsunomiya S Komura Z Horita M Nemoto

and T G Langdon Mater Sci Forum 2001 357ndash359 431ndash436

214 M Furukawa Z Horita and T G Langdon in Proc James T

Staley Honorary Symposium on Aluminum Alloys lsquoAdvances in

the metallurgy of aluminum alloysrsquo (ed M Tiryakioglu) 47ndash56

2001 ASM

215 M Furukawa Z Horita M Nemoto and T G Langdon Mater

Sci Eng 2002 A 324 82ndash89

216 M Furukawa Z Horita and T G Langdon in lsquoUltrafine grained

materials IIrsquo (ed Y T Zhu T G Langdon R S Mishra S L

Semiatin M J Saran and T C Lowe) 459ndash468 2002 TMS

217 T G Langdon M Furukawa Z Horita and M Nemoto Proc

NATO Advanced Research Workshop on lsquoInvestigations and

applications of severe plastic deformationrsquo Moscow August

1999 NATO Science Series Series 3 High Technology vol 80

Kluwer Academic Publishers The Netherlands 2000 149ndash154

218 S Lee H Akamatsu A Utsunomiya K Neishi M Furukawa

Z Horita and T G Langdon Proc Thermec 2000 Las Vegas

USA December 2000

219 S Lee A Utsunomiya H Akamatsu K Neishi M Furukawa

Z Horita and T G Langdon Acta Mater 2002 50 553ndash564

220 A Yamashita D Yamaguchi Z Horita and T G Langdon

Mater Sci Eng 2000 A 287 100ndash106

221 K Oh-ishi Z Horita D J Smith and T G Langdon J Mater

Res 2001 16 583ndash589

222 H Akamatsu T Fujinami Z Horita and T G Langdon Scripta

Mater 2001 44 759ndash764

223 S Ota H Akamatsu K Neishi M Furukawa Z Horita and

T G Langdon Mater Trans 2002 43 2364ndash2369

224 K Furuno H Akamatsu K Oh-ishi M Furukawa Z Horita

and T G Langdon Acta Mater 2004 52 2497ndash2507

225 I N Fridlyander O G Senatorova N A Ryazanova and A O

Nikiforov Mater Sci Forum 1994 170ndash172 345ndash349

226 J N Fridlyander and O G Senatorova Mater Sci Forum 1996

217ndash222 1813ndash1818

227 J Liu and D J Chakrabarti Acta Mater 1996 44 4647ndash4661

228 O G Senatorova A N Uksusnikov J N Fridlyander

J Koshorst R R Romanova N A Ryazanova A Galliot

and V V Cherkassov Proc 6th Int Conf on lsquoAluminum alloysrsquo

July 1998 Toyohashi Japan 589ndash593

229 R A Emigh E L Bradley and J W Morris Jr in

lsquoSuperplasticity in aerospace IIrsquo (ed T R McNelley and H C

Heikkenen) 303ndash315 1990 TMS

230 E L Bradley III R A Emigh and J W Morris Jr Scripta

Metall Mater 1991 25 717ndash721

231 N I Kolobnev L B Khokhlatova V D Makarov E Yu

Semenova and V V Redchits Proc Sixth Int Aluminiumndash

Lithium Conference Garmisch-Partenkirchen Germany October

1991 1053ndash1056

232 N K Tsenev R Z Valiev O V Obraztsov and I N Fridlander

Proc Sixth Int AluminiumndashLithium Conference Garmisch-

Partenkirchen Germany October 1991 1125ndash1132

233 A M Shammazov N K Tsenev R Z Valiev M M

Myshlyaev M M Bikbulatov and S P Lebedich Phys Met

Metall 2000 89 (3) 314ndash318

234 F Musin R Kaibyshev Y Motohashi T Sakuma and G Itoh

Mater Trans A 2002 43A 2370ndash2377

235 M Shagiev Y Motohashi F Musin R Kaibyshev and G Itoh

Mater Trans A 2003 44A 1694ndash1697

236 M Shagiev Y Motohashi F Musin R Kaibyshev and G Itoh

Mater Trans A 2003 44A 1698ndash1701

237 B A Parker and Z F Zhou Proc 3rd Int Conf on lsquoAluminium

alloysrsquo Vol I NTH Trondheim Norway June 1992 363ndash367

238 J R Davies lsquoASM specialty handbook aluminum and aluminum

alloysrsquo 1993 Materials Park OH USA ASM

239 S J Andersen H W Zandbergen J Jansen C Traeholt

U Tundal and O Reiso Acta Mater 1998 46 3283ndash3298

240 M L Kharakterova D G Eskin and L L Rokhlin Russ

Metall 1997 (1) 104ndash109

241 J Roslashyset Dr Ing thesis NTNU Trondheim Norway 2002

242 P P Chattopadhyay S Datta and M K Banerjee Mater Sci

Eng 2002 A 333 67ndash71

243 L I Kaigorodova E I Selnikhina E A Tkachenko and O G

Senatorova Phys Met Metall 1996 81 513ndash519

244 Y-L Wu F H Froes C Li and A Alvarez Metall Mater

Trans A 1999 30A 1017ndash1024

245 Z Yin L Yang Q Pan and F Jiang Trans Nonferrous Met

Soc China 2001 11 822ndash825

246 V I Elagin V V Zakharov and T D Rostova Met Sci Heat

Treat 1994 36 (7) 375ndash380

247 Y V Milman A I Sirko D V Lotsko O N Senkov and D B

Miracle Mater Sci Forum 2002 396ndash402 1217ndash1222

248 C-H Joh K Yamada and Y Miura Mater Trans JIM 1999

40 439ndash442

249 X J Jiang Q H Gui Y Y Li L M Ma G J Liang and C X

Shi Scr Metall Mater 1993 29 211ndash216

250 X J Jiang Y Y Li W Deng L Y Xiong W M Wu Y J Gao

and C X Shi Adv Cryogenic Eng (Mater) 1994 40 1369ndash

1376

251 C-H Joh T Katsube K Yamada and Y Miura Proc 6th Int

Conf on lsquoAluminum alloysrsquo Toyohashi Japan July 1998 799ndash

804

252 L I Kaygorodova A M Dritz T V Krymova and I N

Fridlyander Proc Sixth Int AluminiumndashLithium Conference

Garmisch-Partenkirchen Germany October 1991 363ndash367

253 L I Kaigorodova A M Drits Ya V Zhingel T V Krymova

and I N Fridlyander Phys Met Metall 1992 73 286ndash290

254 A L Berezina V A Volkov S V Ivanov N I Kolobnev and

K V Chuistov Phys Met Metall 1991 71 (2) 167ndash175

255 I N Fridlyander N I Kolobnev A L Berezina and K V

Chuistov Proc Sixth Int AluminiumndashLithium Conference

Garmisch-Partenkirchen Germany October 1991 107ndash112

256 L I Kaigorodova A M Drits Ya V Zhingel T V Krymova

and V A Rassokhin Phys Met Metall 1992 73 281ndash285

257 I N Fridlyander S F Danilov E N Malysheva T A

Gorokhova and N N Kirkina Proc Sixth Int Aluminiumndash

Lithium Conference Garmisch-Partenkirchen Germany October

1991 381ndash386

258 G Dlubek S Krause H Krause A L Beresina V S

Mikhalenkov and K V Chuistov J Phys Condens Matter

1992 4 6317ndash6328

259 S Krause H Krause G Dlubek A L Beresina and K S

Chuistov Mater Sci Forum 1992 105ndash110 1109ndash1112

260 C Y Tan Z Q Zheng and S Q Liang Proc 4th Int Conf on

lsquoAluminium alloysrsquo Vol II Atlanta GA USA September 1994

329ndash333

261 A L Beresina N I Kolobnev K V Chuistov A V Kotko and

O A Molebny Mater Sci Forum 2002 396ndash402 977ndash981

Roslashyset and Ryum Scandium in aluminium alloys

International Materials Reviews 2005 VOL 50 NO 1 43

262 I N Ganiev I Yunusov and V V Krasnoyarskii J Appl Chem

USSR 1986 60 1961ndash1965

263 I N Ganiev Prot Met 1995 31 543ndash546

264 N V Vyazovikina Prot Met 1999 35 448ndash453

265 G V Kharina and V P Kochergin Prot Met 1996 32 134ndash

136

266 G V Kharina M V Kuznetsov and V P Kochergin Russ J

Electrochem 1998 34 482ndash485

267 V S Sinyavskii V D Valrsquokov and E V Titkova Prot Met

1998 34 549ndash555

268 Y L Wu F H Froes C G Li and J Liu Proc lsquoSynthesis

processing of lightweight metallic materials IIrsquo Orlando FL

USA February 1997 73ndash81

269 Z Ahmad and B J Abdul-Aleem Proc EuroCorr 2000

270 Z Ahmad A Ul-Hamid and B J Abdul-Aleem Corros Sci

2001 43 1227ndash1243

271 R Braun B Lenczowski and G Tempus Mater Sci Forum

2000 331ndash337 1647ndash1652

272 T Torma E Kovacs-Csetenyi L Vitalis I Vitanyi

J Stepanov and M Butova Mater Sci Forum 1987 1314

497ndash503

273 Z Wang P Wang K S Kumar and C L Briant in lsquoChemistry

and electrochemistry of corrosion and stress corrosion crackingrsquo

(ed R H Jones) 573ndash582 2001 TMS

274 V I Elagin V V Zakharov A A Petrova and E V

Vyshegorodtseva Russ Metall 1983 (4) 143ndash146

Roslashyset and Ryum Scandium in aluminium alloys

44 International Materials Reviews 2005 VOL 50 NO 1

Page 16: Scandium in aluminium alloys - Atom probe · A considerable part of the available literature on scandium in aluminium alloys is reviewed. ... behaviour in Al Cu, Al Mg Si,

eutectic temperature of binary AlndashSc alloys (660uC) isonly approx 047 In Refs 57 and 89 it is shown thatwhen Zr Hf and in particular Ti is dissolved in the Al3Scparticles this reduces the lattice parameter of the phaseIt appears that when 25 of the Sc atoms in Al3Sc aresubstituted by Ti the mismatch is zero at approx 550uCand becomes negative at higher temperatures89 Thissuggests that by carefully selecting the Ti content of thealloy it should be possible to obtain Al3(ScTi)substrates in the melt that match exactly the latticeparameter of the nucleating a-Al and thus furtherimprove the grain refinement of the alloy This appearsto have been achieved in a recent work180 where thegrain refinement of an Alndash07 wt-Sc alloy wascompared with that of an Alndash05 wt-Scndash02 wt-Tialloy At a cooling rate of 100 K s21 only an estimated2 of the primary Al3Sc particles of the binary AlndashScalloy were effective nuclei compared to practically 100for the primary Al3(ScTi) particles in the ternary AlndashScndashTi alloy leading to a much smaller grain size in theternary alloy Whereas the match of lattice parametersmay be of importance for these results the authors ofthis investigation180 draw attention to other factors suchas different growth restriction factors for Sc and Ti andthe possibility of a peritectic reaction in the ternaryalloy Nevertheless the principle of matching latticeparameters is worth looking into further in future work

Effects from dispersoidslsquoDispersoidsrsquo is a term which is commonly used aboutthe classes of second phase particles that are formedin an Al alloy during high temperature annealing orthermomechanical processing such as homogenisationhot rolling extrusion and forging A dense distributionof dispersoids can give a significant contribution to analloyrsquos strength owing to particle strengthening but thisis rarely the main strengthening mechanism A moreimportant contribution from the dispersoids is theirability to stabilise the grainsubgrain structure of analloy through the Zener-drag action and thus improvethe mechanical properties of the alloy

There are two noticeable dispersoid-related effectsthat have been reported for Sc-containing alloys Thefirst is the stabilising effect on a deformed microstruc-ture When a non-recrystallised structure is preserved inan alloy this can add considerably to the mechanical

strength of the material The second effect is thepreservation of a small grain size during hot deforma-tion at slow deformation rates which is necessary toobtain superplastic properties of an Al-alloy

Recrystallisation resistance

The anti-recrystallisation effect of Sc was first publishedin a patent171 where 03 wt-Sc was added to pure Aland to AlndashMg AlndashMn and AlndashZnndashMg alloys Both Sc-free and Sc-containing materials were cold worked andsubsequently annealed and it was found that theaddition of Sc increased the temperature for onset ofrecrystallisation by approx 220uC in pure Al andsomewhat less in the Al-alloys Although the author ofthe patent171 may have been well aware that the anti-recrystallisation effect is caused by Al3Sc dispersoidsthis is not mentioned in the text The first journal paperthat explicitly points out that the recrystallisationresistance is due to Al3Sc dispersoids was an investiga-tion of the effects of adding Sc to wrought AlndashMgalloys181 In this work it was found that the Al3Scdispersoids were very effective in preventing recrystalli-sation up to temperatures of approx 400ndash450uC Athigher temperatures the dispersoids coarsen consider-ably and the microstructure was partially recrystallised

It is established that the Zener-drag pZ that is imposedon an advancing grain boundary by randomly distrib-uted dispersoids can be expressed in the form

pZ~k f =r (3)

where k is a factor that includes the interface energybetween the dispersoids and the matrix f is the volumefraction and r is the mean radius of the dispersoids Thusthe Zener drag will decrease rapidly in the case where thedispersoids are coarsening

As mentioned in the section on lsquoInfluence of otherelements on precipitation of Al3Scrsquo above theAl3(Sc12xZrx) dispersoids in a ternary AlndashScndashZr alloycoarsen at a much slower rate than the Al3Sc dispersoidsin a binary AlndashSc alloy This effect was first reported inRef 123 (although also observed in Ref 182) andaccording to Ref 33 the same authors demonstratedsoon after that the denser dispersoid distributionachieved in an AlndashScndashZr alloy leads to superiorrecrystallisation resistance compared to a binary AlndashScalloy An example of the increased recrystallisationresistance by adding both Zr and Sc is shown in Fig 26

In isothermal sections of the ternary AlndashScndashZr phasediagram it is indicated that the solid solubility ofSczZr is somewhat higher than that of Sc alone54 Ithas also been demonstrated both by electrical con-ductivity measurements (Fig 27) and microstructuralobservations that the supersaturation of SczZr isgreater than that of only Sc or Zr in as cast Alndash15(SczZr) alloys183 This indicates that it should bepossible to increase the volume fraction of dispersoids inAlndashScndashZr compared to AlndashSc It is suggested162 that theincreased volume fraction that can be achieved byadding both Sc and Zr can be advantageous inconventional wrought Al-alloys

There are at least two different conditions underwhich Al3Sc or Al3(Sc12xZrx) dispersoids can form toprevent recrystallisation

1 Sc (or Sc and Zr) is in solid solution before thedeformation In the case of cold deformation and

25 Grain refinement as a function of Sc addition in pure

Al (redrawn from Ref 32) and AlndashZnndashMgndashZr (redrawn

from Ref 169) note that data points are plotted on

different ordinate axes

Roslashyset and Ryum Scandium in aluminium alloys

34 International Materials Reviews 2005 VOL 50 NO 1

subsequent annealing the Al3Sc or Al3(Sc12xZrx)dispersoids may nucleate and grow before the nucleationand growth of recrystallised grains takes placeDispersoids can form after a direct up-quench to theannealing temperature115143148184 during ramp-up tothe annealing temperature115 or by pre-annealing at anintermediate temperature129 In the case of hot deforma-tion the Al3Sc or Al3(Sc12xZrx) dispersoids maynucleate and grow during preheating of the materialand during the hot deformation itself184

2 The Al3Sc or Al3(Sc12xZrx) dispersoids are formedin the material before deformation184 Considering coldrolling and subsequent annealing the annealing tem-perature Tann may be either lower or higher than thetemperature Tdisp at which the dispersoids were formedIf TannTdisp only limited if any coarsening of thedispersoids is expected to take place and thus the Zenerdrag from the particles is expected to be practicallyconstant The driving force for recrystallisation how-ever is expected to decrease somewhat with theannealing time as a result of recovery processes Thusif recrystallisation does not occur within short annealingtimes the material is expected to remain unrecrystallisedfor infinite time at the annealing temperature IfTannTdisp there will be substantial coarsening of thedispersoids during annealing In order for the materialto remain unrecrystallised the decrease in driving forcefor recrystallisation owing to recovery has to be at leastas rapid as the decrease in Zener drag because of particlecoarsening

Experimental comparisons of the conditions abovepoint in the direction that the recrystallisation resistanceis poorest when Sc (or Sc and Zr) is in solid solutionbefore deformation and the deformed material is up-quenched to the annealing temperature148 or when Al3Scor Al3(Sc12xZrx) dispersoids are formed before defor-mation at TdispampTann184185 Excellent recrystallisationresistance is achieved if dispersoids are formed at anintermediate anneal of solutionised and deformedmaterial128 or if dispersoids are formed at TdispTann

before deformation148185ndash187 It seems that the decreasein Zener drag because of dispersoid coarsening in many

cases is slower than the decrease in driving force forrecrystallisation because of recovery processes Thusthere is an advantage in forming a high number densityof small dispersoids which for most practical casesmeans that they should be formed at TdispTann122

When an advancing high angle grain boundary iethe recrystallisation front is passing a coherent Al3Scdispersoid there are at least three possible grainboundarydispersoid interactions

1 The Al3Sc dispersoid retains its global orientationrelationship and thus loses its coherency with thesurrounding matrix

2 The Al3Sc dispersoid rotates as the grain boundarypasses either by diffusional processes at the dispersoidmatrix interface or by the grain boundary passingthrough the dispersoid and the Al3Sc dispersoidassumes the same crystallographic orientation as theAl matrix of the recrystallised grain

3 The Al3Sc dispersoid dissolves at the grainboundary and re-precipitates in the recrystallised grain

Which interactions that actually take place willprobably depend on the dispersoid size annealingtemperature and driving force for recrystallisation It isalso possible that alloy composition (other elementsthan Al) is of importance

It has been reported that large (Oslash about 100ndash150 nm)Al3Sc dispersoids in a deformed Alndash4 wt-Mgndash02 wt-Sc alloy annealed at 575uC lose the orientationrelationship with the matrix after being passed by therecrystallisation front148

A rotation of somewhat smaller Al3Sc dispersoids in arecrystallising binary Alndash025 wt-Sc alloy has beenreported115143 The rotation was reported to be accom-panied by substantial growth (from Oslash 30 nm to Oslash48 nm) as a result of enhanced Sc diffusion at the grainboundary Observations suggested that the grainboundaries were passing through the dispersoids andthus the Al3Sc dispersoids retained the orientationrelationship with the recrystallised Al matrix

Dissolution and re-precipitation of Al3Sc dispersoidshas been reported during recrystallisation of a 50 coldrolled Alndash02 wt-Sc alloy162 Large spherical partially

26 Fraction recrystallised structure in cold rolled sheets

of Alndash04 wt-Sc and Alndash04 wt-Scndash015 wt-Zr as a

function of annealing temperature redrawn from

Ref 183 27 Electrical conductivity in Alndash15(SczZr) alloys

redrawn from Ref 183

Roslashyset and Ryum Scandium in aluminium alloys

International Materials Reviews 2005 VOL 50 NO 1 35

coherent dispersoids were observed to dissolve at therecrystallisation front and re-precipitate as smallercoherent Al3Sc cuboids

Superplastic forming

It seems that the first publication on superplasticproperties of Sc-containing Al-alloys was a study of anAlndash35Cundash14Mgndash045Mnndash04(SczZr) alloy188

It was recognised that the superplastic properties are aresult of the stabilisation of the fine grain structure byAl3Sc dispersoids The Sc-containing Al alloys that havereceived most attention for their superplastic propertieshowever are those of the AlndashMgndashSc system which wasfirst published in a patent189 Here it was noted that anAlndash4 wt-Mgndash05 wt-Sc alloy had superior superplasticproperties compared to fine-grained 7475 (AlndashZnndashMgndashCu alloy) Binary Alndash05 wt-Sc and Alndash4 wt-Mgalloys did not behave superplastically The flow stress atthe hot forming temperature was found to be much (30ndash40) lower in the ternary alloy than that of the twobinary alloys

The superplastic properties of AlndashMgndashSc alloys havebeen explored by several research groups over the lastdecade190ndash196 It has frequently been found that thedeformation mechanism is dominated by grain bound-ary sliding190 However it has also been reported thatAlndashMgndashSc alloy may deform superplastically withoutnoticeable grain boundary sliding23 It is generallyrecognised that the grain boundary sliding mechanismis facilitated when the average grain size is very smalland grain boundaries are predominantly high-angleSuch a microstructure may be achieved by carefulthermomechanical processing of the starting mate-rial193194197198 It has however been shown that a finegrained structure with high angle boundaries maydevelop during superplastic forming of AlndashMgndashSc alloyseven if the starting microstructure is an entirely differentone for instance that of a cold rolled sheet192 It has alsobeen suggested that superplastic forming of as castmaterial may be possible189

One of the more efficient thermomechanical processesfor achieving an ultrafine grain structure with high anglegrain boundaries in Al-alloys is equal channel angularpressing (ECAP) A JapanesendashAmerican group ofscientists has published an impressive body of researchon improvements in superplastic properties in Al-alloys processed by ECAP over the last few years andseveral of the publications are from investigations onAlndashMgndashSc alloys170199ndash224 Maximum strains in excessof 2000 at a strain rate of 0033 s21 have beenachieved170201202217 which is an extraordinarily goodcombination of high strain and high strain rate for analuminium alloy

Superplastic properties of AlndashCundashMg(ndashMn)ndashSc(ndashZr)and AlndashMgndashSc(ndashZr) alloys have been mentionedNoticeable superplasticity in other Sc-containing Al-alloys has also been reported such as AlndashZnndashMg(ndashCu)ndashScndashZr169225ndash228 AlndashLindashSc229 AlndashMgndashLindashScndashZr229ndash234

AlndashLindashMgndashCundashScndashZr235236 and AlndashCundashLindashScndashZr233

Precipitation hardeningHardening by Al3Sc precipitates

It has been noted that when Al3Sc particles precipitate inthe temperature range 250ndash350uC they give a significanthardness increase in the alloy Some authors point out

that Sc is a more effective precipitation hardening elementper atomic fraction added than the elements that arecommonly used for precipitation hardening121130 (In onepaper29 it is claimed that only Au has a strongerstrengthening effect than Sc) However the amount ofSc that can be precipitated from supersaturated solidsolution is rather limited and thus the absolute values ofthe hardness increase from the precipitation hardening ismuch lower than what is normally associated withprecipitation hardened alloys Also the temperatureregime for age hardening by precipitation of Al3Sc issomewhere in between the temperature regimes for agehardening and solution heat treatments of commonprecipitation hardened alloys This makes a combinedprecipitation of Al3Sc and other strengthening precipi-tates unfeasible Thus precipitation strengthening byAl3Sc is most feasible in alloy systems that are non-heat-treatable The non-heat-treatable aluminium alloy sys-tems are according to the Aluminum Associationdesignations the 1xxx series (99 pure Al) the 3xxxseries (AlndashMn) and the 5xxx series (AlndashMg) The purposeof adding Sc to these alloys may be either to stabilise themicrostructure of wrought semiproducts (extrusionsrolled plates forgings etc) as discussed in the sectionon lsquoRecrystallisation resistancersquo above or to provideextra strength to the alloy through precipitation hard-ening In the latter case it is appropriate to considerwhether the Sc-containing alloy still should be classifiedas non-heat-treatable A heat treatment is applied thatbrings about a significant precipitation hardening On theother hand the hardness increase that is achieved throughthe heat treatment is lower than what is normallyassociated with heat-treatable alloy systems Hence eventhough it seems like a contradiction one chooses to keepusing the term lsquonon-heat-treatablersquo about these alloys

Table 7 gives an overview of some mechanicalproperties of Sc-containing non-heat-treatable alloysthat are reported in the literature Most of theexperimental work on Sc in 1xxx-types of alloys hasbeen done on binary AlndashSc alloys with much higherpurity than industrial alloys

Strengthening mechanisms

When the precipitates are larger than a critical size thestrengthening effect is due to the Orowan-mechanism iedislocations can only pass the precipitates by looping Inthis case the strengthening effect of the particles isapproximately inversely proportional to the mean parti-cle spacing When the precipitates can be sheared bydislocations there are a number of strengthening mechan-isms that apply It is proposed by Parker et al108 that thetwo major contributing mechanisms are coherency strainand anti-phase-boundary energy In a recent detailedstudy of strengthening mechanisms in binary AlndashSc alloysby Marquis and colleagues117118 the strengthening fromshear modulus mismatch between the matrix and theprecipitates is also accounted for A qualitatively goodmatch between theoretical strengthening and measuredvalues is achieved in this work both for deformation atroom temperature and at 300uC

Effect of Sc on precipitation strengthening in heat-treatablealloys

Following the AA designation system the traditionalheat-treatable Al-alloys are those that belong to the 2xxx

Roslashyset and Ryum Scandium in aluminium alloys

36 International Materials Reviews 2005 VOL 50 NO 1

series (AlndashCu) 6xxx series (AlndashMgndashSi) and 7xxx series(AlndashZnndashMg) AlndashLi alloys should also be mentionedSeveral investigations have been carried out in order toclarify the effects of Sc on the precipitation behaviour inthese alloy systems

AlndashCu alloys

The precipitation sequence in AlndashCu alloys is oftendescribed as follows

Supersaturated solid solutionRGP-zonesRh0Rh9Rh(Al2Cu)

The highest strength is normally achieved when the h0or h9 precipitates are predominant Typical precipitationheat treatment temperatures for AlndashCu alloys are in therange 160ndash190uC238 which is considerably lower thanthe typical precipitation temperature for Al3ScComparisons of the aging responses of AlndashCu and AlndashCundashSc alloys at 150 and 200uC indicate that there is nonoticeable effect of Sc on the precipitation kinetics ofh9153 It is observed that the h9 precipitates may nucleateon Al3Sc particles153 At 300uC it is observed that h9particles are somewhat smaller in AlndashCundashSc alloys thanin AlndashCu alloys156

AlndashMgndashSi alloys

The following precipitation sequence is commonlyreported for AlndashMgndashSi alloys

Supersaturated solid solutionRGP-zonesRb0Rb9Rb(Mg2Si)

For peak aged alloys the predominant precipitatetype is b0 for which the stoichiometric composition hasrecently been resolved to be Mg5Si6239 Temperatures inthe range 160ndash205uC are typically used for precipitationhardening of these alloys238 Adding both 03 wt-Scand 01 wt-Zr to an Alndash06 wt-Mgndash065 wt-Sialloy does not seem to alter the precipitation kineticsof b0 at 165uC However the hardness increase becauseof precipitation hardening appears to be smaller in theSczZr-containing alloy240 In another investigationadditions of 01 wt-Sc 015 wt-Sc 02 wt-Sc04 wt-Sc and 02 wt-Scz01 wt-Zr were made toan Alndash08 wt-Mgndash07 wt-Si alloy241 Here it wasalso observed that the precipitation kinetics of b0 wasseemingly independent of the Sc additions (Fig 28)TEM observations indicated that the b0 precipitateswere of comparable sizes in the investigated alloys andno interactions between Al3Sc and b0 were observed(Fig 29) In a third study242 where the effect of Sc onthe precipitation in an AlMgSindashSiC metal matrixcomposite was investigated there also does not seemto be any effect on the precipitation kinetics Howevercontrary to the findings of Ref 240 it is reported thatthe Sc addition leads to a higher hardness increase thanin the corresponding Sc free alloy

AlndashMgndashZn alloys

For these alloys the following precipitation sequence isoften ascribed

Table 7 Mechanical properties in non-heat-treatable Al-alloys with Sc

Reference Alloy wt- YS MPa UTS MPa Note

1xxx alloys171 000Sc 15 48 Cast material aged 288uC8 h

023Sc 159 185 Cast material aged 288uC8 h038Sc 199 220 Cast material aged 288uC8 h000Sc 14 49 Cold rolled material (89) aged 288uC8 h023Sc 198 208 Cold rolled material (89) aged 288uC8 h038Sc 240 264 Cold rolled material (89) aged 288uC8 h000Sc 8 34 Cold rolled material quenched from 649uC aged 288uC8 h023Sc 147 157 Cold rolled material quenched from 649uC aged 288uC8 h038Sc 193 199 Cold rolled material quenched from 649uC aged 288uC8 h

121 05Sc 160 ndash Forged material quenched from 635uC aged 250uC50 h23 05Sc 298 319 Hot rolled 288uC cold rolled 69ndash81 aged 288uC4 h112 01Sc 132 166 Hot z cold rolled material quenched from 630uC

aged 320uC133 h148 02Sc 138 ndash Cast material aged 300uC10 h compression test159 04Sc 196 ndash Cast material aged 300uC10 h compression test117 118 03Sc 209 ndash Cast material quenched from 648uC aged 300uC5 h

compression test3xxx alloys171 1Mn 015Sc 216 221 Cold rolled material (89) aged 288uC8 h

1Mn 05Sc 309 323 Cold rolled material (89) aged 288uC8 h186 05Mn 02Mg

026Sc 015Zr162 201 Extruded material solutionised 600uC aged 250uC

5xxx alloys171 1Mg 43 111 Cold rolled material (89) aged 288uC8 h

1Mg 03Sc 288 303 Cold rolled material (89) aged 288uC8 h53Mg 147 259 Cold rolled material (50) wintermediate anneals

at 343uC aged 288uC8 h53Mg 03Sc 368 401 Cold rolled material (50) wintermediate anneals

at 343uC aged 288uC8 h23 2Mg 05Sc 376 401 Hot rolled 288uC cold rolled 69ndash81 aged 288uC4 h

4Mg 05Sc 414 4606Mg 05Sc 433 503

237 4Mg 1Sc 420 525 Cold rolled material (83) aged 320uC1 h148 4Mg 02Sc 194 ndash Cast material aged 300uC10 h compression test

Tensile test data except where noted YS yield strength UTS ultimate tensile strength

Roslashyset and Ryum Scandium in aluminium alloys

International Materials Reviews 2005 VOL 50 NO 1 37

Supersaturated solid solutionRGP-zonesRg9Rg(Zn2Mg)

The maximum hardness is normally achieved whenthe g9 precipitates are predominant Common precipita-tion hardening temperatures are in the range 95ndash180uCand a two-step precipitation heat treatment within thistemperature regime is often used238 It has beenobserved in some investigations that Sc and SczZradditions to AlndashMgndashZn alloys slow down the precipita-tion of g9 somewhat243 Other investigations find thatthere is no effect of Sc on the precipitation behaviour ofg9244245 and yet others report that Sc additionssignificantly speed up the precipitation of g9246 In Ref247 it is found that an Sc addition leads to coarser g9precipitates and it is claimed that this gives an improvedductility of the alloy The strength-loss associated withlarger particle size is reported to be counterbalanced bystrengthening from Al3Sc precipitates

AlndashLi alloys

The precipitation sequence in binary AlndashLi alloys isapparently simple

Supersaturated solid solutionRd9Rd (AlLi)

where d9 is the metastable Al3Li phase which just likeAl3Sc has the L12 type of atomic arrangement Thetypical temperature regime for precipitation of d9 whichis the strengthening phase in this system is approx 150ndash200uC A comparison of the age hardening response ofan Alndash26 wt-Li and an Alndash24 wt-Lindash019 wt-Scalloy at 180uC248 and 200uC161 indicates that the onsetof d9 precipitation is not altered by the presence of ScThe hardness curves for the two alloys are practicallyidentical at 200uC whereas at 180uC the peak hardnesslevel is slightly higher in the AlndashLi than the AlndashLindashScalloy DSC measurements at constant heating ratesindicate that the addition of Sc to an AlndashLi alloysincreases the activation energy for d9 precipitation andmoves the exothermic peak associated with d9 precipita-tion to a higher temperature248 For specimens aged at

either 180uC or 200uC TEM observations reveal that thed9 precipitates are much smaller in the Sc containingalloy than in binary AlndashLi both in the peak agedcondition and in the overaged condition161248 Additionof Sc has also been observed to reduce the size of d9precipitates in other AlndashLi based alloys249ndash251 In an AlndashLindashCundashZr alloy an addition of Sc has been reported toslow down the homogeneous precipitation of d9252253 Ithas been claimed that Sc reduces the quench sensitivityand delays room temperature aging of AlndashLi basedalloys254ndash256

When present in the microstructure before the pre-cipitation of d9 the Al3Sc precipitates may act as effec-tive nucleation sites for d9 The resulting precipitates arespheres of d9 with a core of Al3Sc161249252ndash255257ndash261

Corrosion resistanceAn appreciable amount of data is available on the effectsof Sc on the corrosion behaviour of wrought Al-alloysSome of these effects are apparently derived from theeffects of Sc on the microstructure of the alloys It hasbeen reported that an addition of Sc increases thecorrosion potential (makes it less negative) in pureAl262ndash264 in AlndashZn alloys265266 AlndashMg alloys267 AlndashZnndashMgndashCu alloys264268 AlndashCundashMgndashMn alloys264 andin AlndashCundashLindashMgndashAg alloys264 Even though Sc alsohas been reported to decrease the corrosion potential in

28 Age hardening response at 175uC for Alndash08 wt-Mgndash

07 wt-Si alloy (Base) with additions of 02 wt-Sc

04 wt-Sc and 02 wt-Scz01 wt-Zr from Ref 241

29 TEM images of a b0 precipitates in Alndash08 wt-Mgndash

07 wt-Si alloy and b b0 and Al3(Sc1ndashxZrx) in a similar

alloy with addition of 02 wt-Scz01 wt-Zr from

Ref 241

Roslashyset and Ryum Scandium in aluminium alloys

38 International Materials Reviews 2005 VOL 50 NO 1

AlndashMg alloys269270 it seems that the general trend isthat adding Sc to an alloy makes it slightly more nobleThe change in corrosion potential is much morepronounced when Sc is added in amounts larger thanthe eutectic composition263 ie there is a considerablecontribution from primary or eutectic Al3Sc to theoverall potential It has also been demonstrated that thechange in corrosion potential caused by Sc can dependon the heat treatment applied to the alloy267268

Even though the corrosion potential is an essentialparameter in establishing the corrosion behaviour of analloy an increase in the corrosion potential does notnecessarily imply an improved self-corrosion resistanceHowever measurements of corrosion rates and passiva-tion current densities strongly suggest that the self-corrosion resistance in general is considerably improvedwhen Sc is added to wrought Al-alloys263264267 Someobserved variations in corrosion potential and passiva-tion current densities with Sc content in binary AlndashScalloys are plotted in Fig 30

Material failure in corrosive environments is often dueto localised corrosion attacks which may propagaterapidly even though the bulk material has a goodresistance against general corrosion It has been pointedout that hypereutectic additions of Sc may lead tomicrogalvanic corrosion beside primary Al3Sc parti-cles264 In AlndashMg alloys grain boundary precipitation ofAl8Mg5 can lead to localised corrosion attacks such asintergranular corrosion (IGC) exfoliation corrosion(EC) and stress corrosion cracking (SCC) In wroughtmaterial such precipitation may occur in the 60ndash180uCtemperature regime and heating in this temperaturerange is referred to as lsquosensitationrsquo An AlndashMgndashSc alloywas found to be immune against intergranular corrosionand have moderate susceptibility to exfoliation corro-sion after annealing at 350uC271 After sensitation heattreatments severe IGC and EC was observed but notquite as severe as in a corresponding alloy without ScAs for SCC the AlndashMgndashSc alloy was found to be highlyresistant271 In another study it was found that additionof 056 wt-Sc reduces the SCC susceptibility of an Alndash68 wt-Mg alloy in the as-rolled state and afterannealing at 250uC whereas in a sensitised specimenthe SCC susceptibility is somewhat increased by the Scaddition272 A third investigation found that Sc has nomeasurable detrimental effect on the SCC susceptibilityof sensitised Alndash5Mgndash015Zr alloy273 SCC is also a

severe problem in high strength AlndashZnndashMgndashCu alloys Ithas been shown that small Sc additions are effective inreducing the SCC sensitivity of these alloys244246268274

Use of Sc-containing Al alloysA systematic development of Sc-containing aluminiumalloys took place in the former USSR in the 1980s andthe interest for Sc as an alloying element in aluminiumalloys hit the western world approximately 10 yearslater Even though a number of improvements in Alalloys achieved by Sc addition have been demonstratedthe current uses of such alloys are very limited This isrelated to the very high price of scandium

In Russia some parts of military aircraft are made ofSc-containing AlndashLi alloys In the western world themain usage of Sc-containing alloys is for sportsequipment Ashurst Technology and Kaiser Aluminumdeveloped a Sc-containing 7xxx alloy for baseball andsoftball bats which was introduced to the Americanmarket in 1997 by Easton Alcoa soon followed with aSc-containing alloy for a competing brand of batsLouisville Slugger Since then several new and improvedSc-containing alloys for bats have been introduced tothe market The purpose of adding Sc is to increase theyield strength of the alloy allowing for a down-gaugingof the wall thickness which in turn gives a strongerlsquospring-rsquo or lsquotrampoline-rsquo effect when the ball hits thebat

Shortly after the introduction of the Sc containingbats Easton also launched Sc-containing 7xxx tubingfor bicycle frames Just as in the bats Sc increases theyield strength of the alloy allowing for down-gauging oftube wall thickness and a corresponding weight reduc-tion of the bicycle frame An Italian manufacturer ofbicycle tubing Dedacciai also delivers tubes in a Sc-containing 7xxx alloy

Other sports equipment made from Sc-containingaluminium alloys includes lacrosse sticks and tent polesSmith and Wesson has also introduced a series ofhandguns where the frame is made from a Sc-containingAl alloy

A common factor for the items mentioned above isthat the material cost is only a minor part of the totalmanufacturing cost of the end product and also thatthese products are aimed at a group of customers thathave a certain awareness of new materials Both baseballbats and bicycle frames have been marketed aslsquoscandium alloyrsquo even though the Sc content is muchlower than 1

Currently AlndashSc master alloys for the production ofSc-containing Al alloys are available at a price thatcorresponds to US$ 2000 per kg of Sc This means that ifone wants to add 02 wt-Sc to an alloy which is afairly common content one also increases the price ofthe alloy by US$ 4 per kg alloy Depending on the alloytype Sc is added to this represents a tripling orquadrupling of the price of the alloy There are notmany existing products where such an increase inmaterial cost can be justified In order to see awidespread use of Sc in high-volume products the Scprice has to come down considerably Actually the priceof adding Sc to Al alloys has gone down by a factor 3ndash10over the last 10ndash15 years and substantial price reduc-tions are also expected in the future

30 Observed variations in corrosion potential and passi-

vation current densities with Sc content in binary Alndash

Sc alloys based on data from Ref 263

Roslashyset and Ryum Scandium in aluminium alloys

International Materials Reviews 2005 VOL 50 NO 1 39

The current production of AlndashSc master alloys isbased upon and will continue to be based upon for theforeseeable future the reduction of Sc2O3 or other Sccompounds directly in molten aluminium It is notnecessary as many tend to believe to take the route viametallic Sc Thus the price of AlndashSc master alloy isgoverned by the price of Sc2O3 or other Sc compoundsin question and not by the price of metallic scandiumThe Sc2O3 which is the main source for todayrsquos AlndashScmaster alloy production comes from stockpiles in theformer USSR These stockpiles will be exhausted withina few years and new reliable sources of Sc2O3 or otherSc compound production are sought It turns out thatthe most economically viable option that has beendisclosed so far is the processing of Red Mud from theBayer process of extracting alumina from bauxiteScandium is enriched in the Red Mud and is extractedfrom a Red Mud aqueous slurry by selective leachingsubsequent ion-exchange procedure and finally a liquidndashliquid extraction procedure It is not required to build aseparate lsquoSc factoryrsquo to do this but rather build an lsquoadd-onrsquo to existing Bayer process plants Such a processroute is expected to bring down the price of Sc2O3

considerably which in turn means that AlndashSc masteralloy price should drop accordingly Preliminary ana-lyses suggest a price of approx US$ 400 per kg Sc in themaster alloy which translates to an added cost of 80cent per kilo when 02 wt-Sc is added to an aluminiumalloy This is also a considerable increase in the materialcost but with such prices one should expect to see Sccontaining alloys in many more applications than whatis the case at the present time

Concluding remarksThe body of published investigations on Al-based alloyswith Sc addition provides a sound basis of knowledgefor metallurgists that want to look into the possibility ofenhancing the performance of a wrought Al-alloy byadding Sc to it Ternary AlndashScndashX phase diagrams areavailable for practically every technologically importantalloying element in Al The effect of a wide range ofternary alloying elements on the precipitation behaviourof Al3Sc is accounted for It has been shown that theAl3Sc phase can be effective as a grain refiner adispersoid former and a precipitate hardening agentand some of the underlying conditions for achieving thedesired Al3Sc formation have been outlined Addingsome Zr together with Sc has proven to be beneficial Itmay lead to effective grain refinement at a lower Sc levelbut the most prominent effect is the refinement indispersoid distribution that can be achieved An addi-tion of Sc has little if any effect on precipitation in the2xxx 6xxx and 7xxx alloy systems and some effects onthe precipitation in AlndashLi based alloys With respect tocorrosion behaviour adding Sc to an Al-alloy does ingeneral seem to make the alloy slightly more noble andto increase its self-corrosion resistance Scandium-containing Al alloys have very few uses at the presenttime as a result of the high price of scandium The priceof Sc is expected to decrease significantly in the futureand this should lead to the disclosure of moreapplications where it is economically feasible to takeadvantage of the improved properties of some Sc-containing aluminium alloys

References1 D R Lide lsquoCRC handbook of chemistry and physicsrsquo 71st edn

4ndash29 1990 Boston USA CRC Press

2 E M Savitsky V F Terehova I V Burov and O P Naumkin

Proc Fourth Conf on lsquoRare earth researchrsquo Phoenix Arizona

USA April 1964 409ndash420

3 E M Savitskii V F Terekhova I V Burov O P Naumkin and

I A Markova Inorg Mater 1965 1 1503ndash1512

4 O P Naumkin V T Terekhova and E M Savitskiy Russ

Metall 1965 (4) 128ndash136

5 W G Moffatt lsquoThe handbook of binary phase diagramsrsquo 1981

Schenectady NY USA General Electric Co

6 E A Brandes (ed) lsquoSmithells metals reference bookrsquo 6th edn

1983 London UK Butterworths

7 R P Elliott and F A Shunk Bull Alloy Phase Diagrams 1981

2 (2) 222ndash223

8 K A Gschneider Jr and F W Calderwood Bull Alloy Phase

Diagrams 1989 10 34ndash36

9 H Okamoto J Phase Equil 1991 12 612ndash613

10 J L Murray J Phase Equil 1998 19 380ndash384

11 M E Drits E S Kadaner T V Dobatkina and N I Turkina

Russ Metall 1973 (4) 152ndash154

12 S-I Fujikawa M Sugaya H Takei and K-I Hirano J Less-

Common Met 1979 63 87ndash97

13 N Blake and M A Hopkins J Mater Sci 1985 20 2861ndash2867

14 V I Kononenko and S V Golubev Russ Metall 1990 (2) 193ndash

195

15 T B Massalski J L Murray L H Bennett and H Baker (eds)

lsquoBinary alloy phase diagramsrsquo 1986 Metals Park OH USA

ASM

16 G Cacciamani P Riani G Borzone N Parodi A Saccone

R Ferro A Pisch and R Schmid-Fetzer Intermetallics 1999 7

101ndash108

17 H Okamoto J Phase Equil 2000 21 310

18 A F Norman P B Pragnell and R S McEwen Acta Mater

1998 46 5715ndash5732

19 I N Pyagai and A V Vakhobov Russ Metall 1990 (5) 50ndash52

20 C L Fu J Mater Res 1990 5 971ndash979

21 X Lu and Y Wang Calphad 2002 26 555ndash561

22 R R Sawtell and J W Morris Jr Proc lsquoDispersion strengthened

aluminium alloysrsquo Phoenix Arizona USA January 1988 409ndash

420

23 R R Sawtell and C L Jensen Metall Trans A 1990 21A 421ndash

430

24 L A Willey Unpublished research Alcoa 1970 Data points are

extracted from Ref 10

25 N I Turkina and V I Kuzmina Russ Metall 1976 (4) 179ndash

183

26 T Torma E Kovacs-Csetenyi I Vitanyi M Butova and

J Stepanov Proc 6th Int Symp on lsquoHigh purity materials in

science and technologyrsquo Akademie der Wissenschaften der DDR

Dresden Germany May 1985 388ndash389

27 A L Berezina V A Volkov B P Domashnikov and K V

Chuistov Metallofizika 1987 9 (5) 43ndash47

28 H-H Jo J Korean Inst Metals 1990 28 499ndash504

29 H-H Jo and S-I Fujikawa Mater Sci Eng 1993 A 171 151ndash

161

30 S Celotto and T J Bastow Philos Mag A 2000 80 1111ndash1125

31 J Roslashyset and N Ryum submitted to Mater Sci Eng

32 M E Drits L S Toropova Yu G Bykov F L Gushchina V I

Elagin and Yu A Filatov Russ Metall 1983 (1) 150ndash153

33 L S Toropova D G Eskin M L Kharakterova and T V

Dobatkina lsquoAdvanced aluminum alloys containing scandium

structure and propertiesrsquo 1998 Amsterdam The Netherlands

Gordon and Breach Science Publishers

34 V V Cherkasov P P Pobezhimov L P Nefedova E V Belov

and G M Kuznetsov Met Sci Heat Treat 1996 (6) 268ndash270

35 Kh O Odinaev I N Ganiev V V Kinzhibalo and B Ya

Kotur Dokl Akad Nauk Tadzh SSR 1989 32 37ndash38

36 Kh O Odinaev I N Ganiev and A V Vakhobov Russ Metall

1991 (4) 200ndash203

37 J Grobner R Schmid-Fetzer A Pisch G Cacciamani P Riani

N Parodi G Borzone A Saccone and R Ferro Z Metallkd

1999 90 872ndash880

38 E A Marquis and D N Seidman Microsc Microanal 2002 8

(Suppl 2) 1100CDndash1101CD

39 A Pisch J Grobner and R Schmid-Fetzer Mater Sci Eng A

2000 A 289 123ndash129

Roslashyset and Ryum Scandium in aluminium alloys

40 International Materials Reviews 2005 VOL 50 NO 1

40 C Xia F Zeng and Y Gu Trans Nonferrous Met Soc China

2003 13 1124ndash1127

41 M Yu Teslyuk and V S Protasov Sov Phys Crystallogr 1966

10 470ndash471

42 M L Kharakterova and T V Dobatkina Russ Metall 1988

(6) 175ndash178

43 M L Kharakterova Russ Metall 1991 (4) 195ndash199

44 L S Toropova M L Kharakterova and D G Eskin Russ

Metall 1992 (3) 194ndash199

45 P Riani L Arrighi R Marazza D Mazzone G Zanicchi and

R Ferro J Phase Equil Diff 2004 25 22ndash52

46 A T Tyvanchuk T I Yanson B Ya Kotur O S Zarechnyuk

and M L Kharakterova Russ Metall 1988 (4) 190ndash192

47 L L Rokhlin T V Dobatkina and M L Kharakterova Powder

Metall Met Ceram 1997 36

48 A Z Ikromov I N Ganiev and V V Kinzhibalo Dokl Akad

Nauk Tadzh SSR 1990 (6) 391ndash392

49 I N Ganiev A Z Ikromov and V G Khudoiberdiev Russ

Metall 1995 (3) 125ndash127

50 I N Fridlyander L L Rokhlin T V Dobatkina and N I

Nikitina Met Sci Heat Treat 1993 (10) 567ndash571

51 I N Fridlyander L L Rokhlin T V Dobatkina V V

Kinzhibalo and A T Tyvanchuk Russ Metall 1998 (1) 161ndash

166

52 R A Emigh E L Bradley and J W Morris Jr in lsquoLight-weight

alloys for aerospace applications IIrsquo (ed E W Lee and N J

Kim) 27ndash43 1991 TMS

53 L S Toropova A N Kamardinkin V V Kindzhibalo and A T

Tyvanchuk Phys Met Metall 1990 70 (6) 106ndash110

54 A N Kamardinkin T V Dobatkina and T D Rostova Russ

Metall 1991 (4) 216ndash218

55 L S Torodskaya T V Dobatkina and A N Kamardinkin

Russ Metall 1992 (5) 128ndash131

56 E M Sokolovskaya E F Kazakova E I Poddyakova and A

A Ezhov Met Sci Heat Treat 1997 (5) 211ndash213

57 Y Harada and D C Dunand Mater Sci Eng 2002 A 329ndash331

686ndash695

58 N E Drits L S Toropova and F L Gushchina Russ Metall

1984 (4) 229ndash232

59 E M Sokolovskaya E F Kazakova V A Alikhanov and E V

Zhuravleva Moscow Univ Chem Bull 1997 52 (5) 70ndash72

60 E M Sokolovskaya E F Kazakova and E I Poddyakova Met

Sci Heat Treat 1989 (11) 837ndash839

61 G M Cheldieva E F Kazakova E M Sokolovskaya and N I

Kaloev Russ Metall 1990 (6) 87ndash90

62 E M Sokolovskaya E F Kazakova and O D-S Kendivan

Russ Metall 1998 (4) 135ndash137

63 N G Bukhanko E F Kazakova and E M Sokolovskaya Russ

Metall 2001 (4) 425ndash431

64 E D Trubnyakova O I Bodak I N Ganiev and A V

Vakhobov Russ Metall 1987 (3) 219ndash222

65 I N Fridlyander and L V Molchanova Russ Metall 2003 (5)

476ndash480

66 R A Altynbaev S Kh Khairidinov and A V Vakhobov Russ

Metall 1987 (4) 194ndash196

67 J C Schuster and J Bauer J Less-Common Met 1985 109

345ndash350

68 L L Rokhlin A S Fridman T V Dobatkina and D G Eskin

Russ Metall 1991 (6) 146ndash148

69 A S Fridman T V Dobatkina and E V Muratova Russ

Metall 1992 (1) 207ndash209

70 C Xia F Zeng and Y Gu Trans Nonferrous Met Soc China

2003 13 546ndash552

71 F Zeng C Xia and Y Gu J Alloys Comp 2004 363 175ndash181

72 L L Rokhlin T V Dobatkina N R Bochvar and E V Lysova

J Alloys Comp 2004 367 10ndash16

73 T V Dobatkina A S Fridman and E V Muratova Russ

Metall 1992 (5) 125ndash127

74 I N Fridlyander L L Rokhlin N R Bochvar E V Lysova

and O V Boteva Russ Metall 2001 (6) 661ndash666

75 V N Rechkin L K Lamikhov and T I Samsonova Sov Phys

Crystallogr 1964 9 325ndash327

76 I I Zalutskii and P I Kripyakevich Sov Phys Crystallogr

1967 12 341ndash343

77 T J Bastow C T Forwood M A Gibson and M E Smith

Phys Rev B 1998 58 2988ndash2997

78 K Fukunaga M Kolbe K Yamada and Y Miura Mater Sci

Eng 1997 A 234ndash236 594ndash597

79 E P George J A Horton W D Porter and J H Schneibel

J Mater Res 1990 5 1639ndash1648

80 E P George D P Pope C L Fu and J H Schneibel ISIJ Int

1991 31 1063ndash1075

81 Y Harada and D C Dunand Acta Mater 2000 48 3477ndash3487

82 J H Schneibel and E P George Scripta Metall Mater 1990 24

1069ndash1074

83 J H Schneibel and P M Hazzledine Mater Res Soc Symp

Proc 1991 213 323ndash328

84 J H Schneibel and P M Hazzledine J Mater Res 1992 7

868ndash875

85 C J Sparks E D Specht G E Ice P Zschack and J Schneibel

Mater Res Soc Symp Proc 1991 213 363ndash368

86 J Tarnacki and Y-W Kim Scripta Metall Mater 1989 23

1063ndash1068

87 M Asta V Ozolins and C Woodward JOM 2001 53 (9) 16ndash

19

88 M E Drits L S Toropova F L Gushchina and S G Fedotov

Sov Non-Ferrous Met Res 1984 12 83ndash85

89 Y Harada and D C Dunand Scripta Mater 2003 48 219ndash222

90 C Woodward M Asta G Kresse and J Hafner Phys Rev B

2001 63 094103-1-6

91 J-H Xu and A J Freeman Phys Rev B 1990 41 12553ndash12561

92 M F Bartholomeusz and J A Wert Acta Metall Mater 1992

40 673ndash682

93 G Bester and M Fahnle J Phys Condens Matter 2001 13

11551ndash11565

94 C L Fu and M H Yoo Proc lsquoOrdered intermetallics ndash physical

metallurgy and mechanical behaviorrsquo Irsee Germany June 1991

155ndash164

95 K Fukunaga T Shouji and Y Miura Mater Sci Eng 1997 A

239ndash240 202ndash205

96 D P Pope Proc lsquoOrdered intermetallics ndash physical metallurgy

and mechanical behaviorrsquo Irsee Germany June 1991 143ndash153

97 J-S Wang Acta Mater 1998 46 2663ndash2674

98 M H Yoo and C L Fu Mater Sci Eng 1992 A 153 470ndash478

99 R W Hyland Jr and R C Stiffler Scripta Metall Mater 1991

25 473ndash477

100 I G Brodova I V Polents O A Korzhavina P S Popelrsquo I P

Korshunov and V O Esin Melts 1992 4 392ndash397

101 I G Brodova O A Chikova I V Polents P S Popelrsquo and V O

Esin Casting Processes 1992 1 (2) 158ndash160

102 I G Brodova D V Bashlikov and I V Polents Mater Sci

Forum 1998 269ndash272 589ndash594

103 K B Hyde A F Norman and P B Pragnell Mater Sci Forum

2000 331ndash337 1013ndash1018

104 K B Hyde A F Norman and P B Pragnell Acta Mater 2001

49 1327ndash1337

105 J Roslashyset and N Ryum Proc 6th Int Conf on lsquoAluminum

alloysrsquo Toyohashi Japan July 1998 793ndash798

106 V I Elagin V V Zakharov and T D Rostova Met Sci Heat

Treat 1993 (6) 317ndash319

107 R W Hyland Jr Metall Trans A 1992 23A 1947ndash1955

108 B A Parker Z F Zhou and P Nolle J Mater Sci 1995 30

452ndash458

109 C L Rohrer M D Asta S M Foiles and R W Hyland Jr

Mater Res Soc Symp Proc 1996 398 477ndash482

110 G M Novotny and A J Ardell Mater Sci Eng 2001 A 318

144ndash154

111 J D Robson M J Jones and P B Pragnell Acta Mater 2003

51 1453ndash1468

112 C Tan Z Zheng and B Wang Proc 3rd Int Conf on

lsquoAluminium alloysrsquo Vol I NTH Trondheim Norway June

1992 290ndash294

113 M Nakayama A Furuta and Y Miura Mater Trans JIM

1997 38 852ndash857

114 E A Marquis and D N Seidman Acta Mater 2001 49 1909ndash

1919

115 M J Jones and F J Humphreys Acta Mater 2003 51 2149ndash

2159

116 E A Marquis D N Seidman and D C Dunand in lsquoCreep

deformation fundamentals and applicationsrsquo (ed R S Mishra

J C Earthman and S V Raj) 299ndash308 2002 TMS

117 D N Seidman E A Marquis and D C Dunand Acta Mater

2002 50 4021ndash4035

118 E A Marquis D N Seidman and D C Dunand Acta Mater

2003 51 285ndash287

119 M E Drits L S Toropova U G Bikov and G K Anastaseva

Proc lsquoDiffusion in metals and alloysrsquo Tihany Hungary Augustndash

September 1982 616ndash623

120 V I Elagin V V Zakharov and T D Rostova Met Sci Heat

Treat 1983 (7) 546ndash549

Roslashyset and Ryum Scandium in aluminium alloys

International Materials Reviews 2005 VOL 50 NO 1 41

121 M Ye Drits L B Ber Yu G Bykov L S Toropova and G K

Anastaseva Phys Met Metall 1984 57 (6) 118ndash126

122 M E Drits L S Toropova and Yu G Bykov Sov Non-Ferrous

Met Res 1985 13 309ndash314

123 V I Yelagin V V Zakharov S G Pavlenko and T D Rostova

Phys Met Metall 1985 60 (1) 88ndash92

124 N Sano Y Hasegawa K Hono H Jo K Hirano H W

Pickering and T Sakurai Journal de Physique 1987 48 C6 337ndash

342

125 N Sano H-H Jo K-I Hirano and T Sakurai J Jpn Inst

Metals 1989 39 444ndash450

126 N Sano H Jo K Hirano and T Sakurai Proc Second Int

Conf on lsquoAluminium alloysrsquo Beijing China October 1990 549ndash

554

127 Y Miura M Nakayama and A Furuta Proc lsquoAspects of high

temperature deformation and fracture in crystalline materialsrsquo

Nagoya Japan July 1993 255ndash262

128 Y W Riddle and T H Sanders Jr Mater Sci Forum 2000

331ndash337 939ndash944

129 Y W Riddle M McIntosh and T H Sanders Jr in lsquoLightweight

alloys for aerospace application VIrsquo (ed K Jata E W Lee

W Frazier and N J Kim) 25ndash39 2001 TMS

130 M E Drits J Dutkiewicz L S Toropova and J Salawa Crystal

Res Technol 1984 19 1325ndash1330

131 Y W Riddle MSc thesis Georgia Tech GA USA 1998

132 T J Bastow and S Celotto Mater Sci Eng 2003 C 23 757ndash

762

133 M C Carroll M J Mills G S Daehn P I Gouma M F

Savage and B R Dunbar in lsquoAutomotive Alloys 1999rsquo (ed

S Das) 239ndash246 2000 TMS

134 E Clouet M Nastar and C Sigli Phys Rev B 2004 69 064109-

1-14

135 V V Zakharov Met Sci Heat Treat 1997 (2) 61ndash66

136 J W Christian lsquoThe theory of transformation in metals and

alloysrsquo 2nd edn 1975 Pergamon Press Ltd

137 A L Berezina V A Volkov B P Domashnikov S V Ivanov

and K V Chuistov Phys Metals 1990 10 296ndash304

138 S-I Fujikawa and S Sakauchi Proc 6th Int Conf on

lsquoAluminum alloysrsquo Toyohashi Japan July 1998 805ndash810

139 Y S Touloukian R K Kirby R E Taylor and P D Desai

(eds) lsquoThermal expansion metallic elements and alloysrsquo 1975

New York Plenum

140 J Roslashyset and N Ryum submitted to Scripta Mater

141 R O Simmons and R W Balluffi Phys Rev 1960 117 52ndash61

142 M Ocko E Babic R Krsmik E Girt and B Leontic J Phys F

Metals Phys 1976 6 703ndash707

143 M J Jones and F J Humphreys Proc First Joint Int Conf on

lsquoRecrystallization and grain growthrsquo Aachen Germany August

2001 Springer Verlag 1287ndash1292

144 S Iwamura M Nakayama and Y Miura Mater Sci Forum

2002 396ndash402 1151ndash1156

145 S Iwamura and Y Miura Acta Mater 2004 52 591ndash600

146 M Asta S M Foiles and A A Quong Phys Rev B 1998 57

11265ndash11275

147 R W Hyland Jr M Asta S M Foiles and C L Rohrer Acta

Mater 1998 46 3667ndash3678

148 J Roslashyset and N Ryum Proc 4th Int Conf on lsquoAluminium

alloysrsquo Vol I Atlanta GA USA September 1994 194ndash201

149 M E Drits L S Toropova G K Anastaseva and G L

Nagornichnykh Russ Metall 1984 (3) 192ndash195

150 E A Marquis D N Seidman and D C Dunand Acta Mater

2003 51 4751ndash4760

151 M E Drits L S Toropova and Yu G Bykov Met Sci Heat

Treat 1983 (7) 550ndash554

152 V V Zakharov and T D Rostova Met Sci Heat Treat 1995

(2) 65ndash69

153 M Nakayama and Y Miura Proc 4th Int Conf on lsquoAluminium

alloysrsquo Vol I Atlanta GA USA September 1994 538ndash545

154 M Nakayama and Y Miura J Jpn Inst Light Metals 1996 46

275ndash279

155 M Nakayama T Okuyama and Y Miura Mater Sci Forum

2000 331ndash337 927ndash932

156 M Nakayama T Okuyama and Y Miura Proc 6th Int Conf

on lsquoAluminum alloysrsquo Toyohashi Japan July 1998 517ndash522

157 M L Kharakterova D G Eskin and L S Toropova Acta

Metall Mater 1994 42 2285ndash2290

158 V I Elagin V V Zakharov and T D Rostova Met Sci Heat

Treat 1992 (1) 37ndash45

159 H Wiik Siv Ing thesis NTH Institute of Metallurgy

Trondheim Norway 1995

160 J Roslashyset H Hovland and N Ryum Mater Sci Forum 2002

396ndash402 619ndash624

161 Y Miura K Horikawa K Yamada and M Nakayama Proc

4th Int Conf on lsquoAluminium alloysrsquo Vol II Atlanta GA USA

September 1994 161ndash168

162 Y W Riddle PhD thesis Georgia Tech GA USA 2000

163 B Forbord W Lefebvre F Danoix H Hallem and

K Marthinsen Scripta Mater 2004 51 333ndash337

164 J D Robson Acta Mater 2004 52 1409ndash1421

165 C B Fuller J L Murray and D N Seidman submitted to Acta

Mater 2004

166 M G Mousavi C E Cross and Oslash Grong Sci Technol Weld

Joining 1999 4 381ndash388

167 J S Vetrano S M Bruemmer L M Pawlowski and I M

Robertson Mater Sci Eng 1997 A 238 101ndash107

168 Y W Riddle and T H Sanders Jr Mater Sci Forum 2000

331ndash337 799ndash803

169 G M Khan A O Nikiforov V V Zakharov and I I Novikov

Tsvetnye Metally 1993 34 (11) 43ndash45

170 Z Horita M Furukawa M Nemoto A J Barnes and T G

Langdon Acta Mater 2000 48 3633ndash3640

171 L A Willey US Patent 3 619 181 9 November 1971

172 L K Lamikhov and G V Samsonov Tsvetnye Metally 1964 5

(8) 77ndash80

173 A L Berezina K V Chuistov N I Kolobnev L B

Khokhlatova and T A Monastyrskaya Mater Sci Forum

2002 396ndash402 741ndash746

174 F A Fasoyinu J Thomson D Cousineau T Castles and M

Sahoo Proc 6th Int AFS Conf on lsquoMolten aluminum

processingrsquo Orlando FL USA November 2001

175 Z Yin Q Pan Y Zhang and F Jiang Mater Sci Eng 2000

A 280 151ndash155

176 I I Novikov and O E Grushko Mater Sci Technol 1995 11

926ndash932

177 D Cousineau M Sahoo P D Newcombe T Castles and F A

Fasoyinu Proc lsquoAFS 105th casting congressrsquo Dallas TX USA

AprilndashMay 2001 157ndash184

178 C E Cross and Oslash Grong Proc 6th Int Conf on lsquoAluminum

alloysrsquo Toyohashi Japan July 1998 1441ndash1446

179 F A Costello J D Robson and P B Prangnell Mater Sci

Forum 2002 396ndash402 757ndash762

180 K B Hyde A F Norman and P B Prangnell Mater Sci

Forum 2002 396ndash402 39ndash44

181 M E Drits S G Pavlenko L S Toropova Yu G Bukov and

L B Ber Sov Phys Dokl 1981 26 (3) 344ndash346

182 A M Drits and B A Kopeliovich Russ Metall 1985 (4) 147ndash

151

183 V G Davydov V I Elagin V V Zakharov and T D Rostova

Met Sci Heat Treat 1996 (8) 347ndash352

184 M E Drits L S Toropova Yu G Bykov L B Ber and S G

Pavlenko Russ Metall 1982 (1) 148ndash152

185 T D Rostova V G Davydov V I Yelagin and V V Zakharov

Mater Sci Forum 2000 331ndash337 793ndash798

186 Y W Riddle H Hallem and N Ryum Mater Sci Forum 2002

396ndash402 563ndash568

187 J Roslashyset and Y W Riddle Proc 9th Int Conf on lsquoAluminium

alloysrsquo Brisbane Australia August 2004 1210ndash1215

188 A M Diskin V K Portnoi A M Drits and A A Alalykin Sov

Non-Ferrous Met Res 1986 14 499ndash500

189 R R Sawtell P E Bretz and C L Jensen US Patent 4 689 090

25 August 1987

190 G A Salishchev Yu B Timoshenko and R A Saitova Proc

Second Int Conf on lsquoAluminium alloysrsquo Beijing China October

1990 413ndash415

191 T G Nieh R Kaibyshev L M Hsiung N Nguyen and

J Wadsworth Scripta Mater 1997 36 1011ndash1016

192 T G Nieh L M Hsiung J Wadsworth and R Kaibyshev Acta

Mater 1998 46 2789ndash2800

193 J S Vetrano C H Henager Jr M T Smith and S M

Bruemmer in lsquoHot deformation of aluminum alloys IIrsquo (ed T R

Bieler L A Lalli and S R MacEwen) 407ndash418 1998 TMS

194 J S Vetrano C H Henager Jr S M Bruemmer Y Ge and

C H Hamilton in lsquoSuperplasticity and Superplastic Forming

1998rsquo (ed A K Gosh and T R Bieler) 89ndash97 1998 TMS

195 V Y Gertsman J S Vetrano C H Henager Jr and S M

Bruemmer Proc First Joint Int Conf on lsquoRecrystallization and

grain growthrsquo Aachen Germany August 2001 Springer Verlag

2001 837ndash842

196 Y Xiao C Gao H Ma and S Tian Trans Nonferrous Met Soc

China 2001 11 235ndash238

Roslashyset and Ryum Scandium in aluminium alloys

42 International Materials Reviews 2005 VOL 50 NO 1

197 A Gholinia F J Humphreys and P B Prangnell Acta Mater

2002 50 4461ndash4476

198 A Gholinia F J Humphreys and P B Prangnell Mater Sci

Forum 2002 408ndash412 1519ndash1524

199 S Komura P B Berbon M Furukawa Z Horita M Nemoto

and T G Langdon Scripta Mater 1998 38 1851ndash1856

200 S Komura P B Berbon A Utsunomiya M Furukawa

Z Horita M Nemoto and T G Langdon in lsquoHot deformation

of aluminum alloys IIrsquo (ed T R Bieler L A Lalli and S R

MacEwen) 125ndash138 1998 TMS

201 S Komura Z Horita M Furukawa M Nemoto and T G

Langdon J Mater Res 2000 15 2571ndash2576

202 S Komura M Furukawa Z Horita M Nemoto and T G

Langdon Mater Sci Eng 2001 A 297 111ndash118

203 S Komura Z Horita M Furukawa M Nemoto and T G

Langdon Metall Mater Trans A 2001 32A 707ndash716

204 Z Horita M Furukawa K Oh-ishi M Nemoto and T G

Langdon Proc Fourth Int Conf on lsquoRecrystallization and

related phenomenarsquo (ed T Sakai and H G Suzuki) 1999 The

Japan Institute of Metals 301ndash308

205 Z Horita S Komura P B Berbon A Utsunomiya

M Furukawa M Nemoto and T G Langdon Mater Sci

Forum 1999 304ndash306 91ndash96

206 Z Horita S Lee S Ota K Neishi and T G Langdon Mater

Sci Forum 2001 357ndash359 471ndash476

207 Z Horita T Fujinami K Sato S B Kang H W Kim and T G

Langdon in Proc James T Staley Honorary Symposium on

Aluminum Alloys lsquoAdvances in the metallurgy of aluminum

alloysrsquo (ed M Tiryakioglu) 271ndash275 2001 ASM

208 P B Berbon S Komura A Utsunomiya Z Horita

M Furukawa M Nemoto and T G Langdon Mater Trans

JIM 1999 40 772ndash778

209 M Nemoto Z Horita M Furukawa and T G Langdon Mater

Sci Forum 1999 304ndash306 59ndash66

210 M Furukawa Z Horita M Nemeto and T G Langdon Proc

lsquoLight Metals 1999rsquo Quebec City PQ Canada August 1999 583ndash

592

211 M Furukawa K Oh-ishi S Komura A Yamashita Z Horita

M Nemeto and T G Langdon Mater Sci Forum 1999 304ndash

306 97ndash102

212 M Furukawa A Utsunomiya K Matsubara Z Horita and

T G Langdon Acta Mater 2001 49 3829ndash3838

213 M Furukawa A Utsunomiya S Komura Z Horita M Nemoto

and T G Langdon Mater Sci Forum 2001 357ndash359 431ndash436

214 M Furukawa Z Horita and T G Langdon in Proc James T

Staley Honorary Symposium on Aluminum Alloys lsquoAdvances in

the metallurgy of aluminum alloysrsquo (ed M Tiryakioglu) 47ndash56

2001 ASM

215 M Furukawa Z Horita M Nemoto and T G Langdon Mater

Sci Eng 2002 A 324 82ndash89

216 M Furukawa Z Horita and T G Langdon in lsquoUltrafine grained

materials IIrsquo (ed Y T Zhu T G Langdon R S Mishra S L

Semiatin M J Saran and T C Lowe) 459ndash468 2002 TMS

217 T G Langdon M Furukawa Z Horita and M Nemoto Proc

NATO Advanced Research Workshop on lsquoInvestigations and

applications of severe plastic deformationrsquo Moscow August

1999 NATO Science Series Series 3 High Technology vol 80

Kluwer Academic Publishers The Netherlands 2000 149ndash154

218 S Lee H Akamatsu A Utsunomiya K Neishi M Furukawa

Z Horita and T G Langdon Proc Thermec 2000 Las Vegas

USA December 2000

219 S Lee A Utsunomiya H Akamatsu K Neishi M Furukawa

Z Horita and T G Langdon Acta Mater 2002 50 553ndash564

220 A Yamashita D Yamaguchi Z Horita and T G Langdon

Mater Sci Eng 2000 A 287 100ndash106

221 K Oh-ishi Z Horita D J Smith and T G Langdon J Mater

Res 2001 16 583ndash589

222 H Akamatsu T Fujinami Z Horita and T G Langdon Scripta

Mater 2001 44 759ndash764

223 S Ota H Akamatsu K Neishi M Furukawa Z Horita and

T G Langdon Mater Trans 2002 43 2364ndash2369

224 K Furuno H Akamatsu K Oh-ishi M Furukawa Z Horita

and T G Langdon Acta Mater 2004 52 2497ndash2507

225 I N Fridlyander O G Senatorova N A Ryazanova and A O

Nikiforov Mater Sci Forum 1994 170ndash172 345ndash349

226 J N Fridlyander and O G Senatorova Mater Sci Forum 1996

217ndash222 1813ndash1818

227 J Liu and D J Chakrabarti Acta Mater 1996 44 4647ndash4661

228 O G Senatorova A N Uksusnikov J N Fridlyander

J Koshorst R R Romanova N A Ryazanova A Galliot

and V V Cherkassov Proc 6th Int Conf on lsquoAluminum alloysrsquo

July 1998 Toyohashi Japan 589ndash593

229 R A Emigh E L Bradley and J W Morris Jr in

lsquoSuperplasticity in aerospace IIrsquo (ed T R McNelley and H C

Heikkenen) 303ndash315 1990 TMS

230 E L Bradley III R A Emigh and J W Morris Jr Scripta

Metall Mater 1991 25 717ndash721

231 N I Kolobnev L B Khokhlatova V D Makarov E Yu

Semenova and V V Redchits Proc Sixth Int Aluminiumndash

Lithium Conference Garmisch-Partenkirchen Germany October

1991 1053ndash1056

232 N K Tsenev R Z Valiev O V Obraztsov and I N Fridlander

Proc Sixth Int AluminiumndashLithium Conference Garmisch-

Partenkirchen Germany October 1991 1125ndash1132

233 A M Shammazov N K Tsenev R Z Valiev M M

Myshlyaev M M Bikbulatov and S P Lebedich Phys Met

Metall 2000 89 (3) 314ndash318

234 F Musin R Kaibyshev Y Motohashi T Sakuma and G Itoh

Mater Trans A 2002 43A 2370ndash2377

235 M Shagiev Y Motohashi F Musin R Kaibyshev and G Itoh

Mater Trans A 2003 44A 1694ndash1697

236 M Shagiev Y Motohashi F Musin R Kaibyshev and G Itoh

Mater Trans A 2003 44A 1698ndash1701

237 B A Parker and Z F Zhou Proc 3rd Int Conf on lsquoAluminium

alloysrsquo Vol I NTH Trondheim Norway June 1992 363ndash367

238 J R Davies lsquoASM specialty handbook aluminum and aluminum

alloysrsquo 1993 Materials Park OH USA ASM

239 S J Andersen H W Zandbergen J Jansen C Traeholt

U Tundal and O Reiso Acta Mater 1998 46 3283ndash3298

240 M L Kharakterova D G Eskin and L L Rokhlin Russ

Metall 1997 (1) 104ndash109

241 J Roslashyset Dr Ing thesis NTNU Trondheim Norway 2002

242 P P Chattopadhyay S Datta and M K Banerjee Mater Sci

Eng 2002 A 333 67ndash71

243 L I Kaigorodova E I Selnikhina E A Tkachenko and O G

Senatorova Phys Met Metall 1996 81 513ndash519

244 Y-L Wu F H Froes C Li and A Alvarez Metall Mater

Trans A 1999 30A 1017ndash1024

245 Z Yin L Yang Q Pan and F Jiang Trans Nonferrous Met

Soc China 2001 11 822ndash825

246 V I Elagin V V Zakharov and T D Rostova Met Sci Heat

Treat 1994 36 (7) 375ndash380

247 Y V Milman A I Sirko D V Lotsko O N Senkov and D B

Miracle Mater Sci Forum 2002 396ndash402 1217ndash1222

248 C-H Joh K Yamada and Y Miura Mater Trans JIM 1999

40 439ndash442

249 X J Jiang Q H Gui Y Y Li L M Ma G J Liang and C X

Shi Scr Metall Mater 1993 29 211ndash216

250 X J Jiang Y Y Li W Deng L Y Xiong W M Wu Y J Gao

and C X Shi Adv Cryogenic Eng (Mater) 1994 40 1369ndash

1376

251 C-H Joh T Katsube K Yamada and Y Miura Proc 6th Int

Conf on lsquoAluminum alloysrsquo Toyohashi Japan July 1998 799ndash

804

252 L I Kaygorodova A M Dritz T V Krymova and I N

Fridlyander Proc Sixth Int AluminiumndashLithium Conference

Garmisch-Partenkirchen Germany October 1991 363ndash367

253 L I Kaigorodova A M Drits Ya V Zhingel T V Krymova

and I N Fridlyander Phys Met Metall 1992 73 286ndash290

254 A L Berezina V A Volkov S V Ivanov N I Kolobnev and

K V Chuistov Phys Met Metall 1991 71 (2) 167ndash175

255 I N Fridlyander N I Kolobnev A L Berezina and K V

Chuistov Proc Sixth Int AluminiumndashLithium Conference

Garmisch-Partenkirchen Germany October 1991 107ndash112

256 L I Kaigorodova A M Drits Ya V Zhingel T V Krymova

and V A Rassokhin Phys Met Metall 1992 73 281ndash285

257 I N Fridlyander S F Danilov E N Malysheva T A

Gorokhova and N N Kirkina Proc Sixth Int Aluminiumndash

Lithium Conference Garmisch-Partenkirchen Germany October

1991 381ndash386

258 G Dlubek S Krause H Krause A L Beresina V S

Mikhalenkov and K V Chuistov J Phys Condens Matter

1992 4 6317ndash6328

259 S Krause H Krause G Dlubek A L Beresina and K S

Chuistov Mater Sci Forum 1992 105ndash110 1109ndash1112

260 C Y Tan Z Q Zheng and S Q Liang Proc 4th Int Conf on

lsquoAluminium alloysrsquo Vol II Atlanta GA USA September 1994

329ndash333

261 A L Beresina N I Kolobnev K V Chuistov A V Kotko and

O A Molebny Mater Sci Forum 2002 396ndash402 977ndash981

Roslashyset and Ryum Scandium in aluminium alloys

International Materials Reviews 2005 VOL 50 NO 1 43

262 I N Ganiev I Yunusov and V V Krasnoyarskii J Appl Chem

USSR 1986 60 1961ndash1965

263 I N Ganiev Prot Met 1995 31 543ndash546

264 N V Vyazovikina Prot Met 1999 35 448ndash453

265 G V Kharina and V P Kochergin Prot Met 1996 32 134ndash

136

266 G V Kharina M V Kuznetsov and V P Kochergin Russ J

Electrochem 1998 34 482ndash485

267 V S Sinyavskii V D Valrsquokov and E V Titkova Prot Met

1998 34 549ndash555

268 Y L Wu F H Froes C G Li and J Liu Proc lsquoSynthesis

processing of lightweight metallic materials IIrsquo Orlando FL

USA February 1997 73ndash81

269 Z Ahmad and B J Abdul-Aleem Proc EuroCorr 2000

270 Z Ahmad A Ul-Hamid and B J Abdul-Aleem Corros Sci

2001 43 1227ndash1243

271 R Braun B Lenczowski and G Tempus Mater Sci Forum

2000 331ndash337 1647ndash1652

272 T Torma E Kovacs-Csetenyi L Vitalis I Vitanyi

J Stepanov and M Butova Mater Sci Forum 1987 1314

497ndash503

273 Z Wang P Wang K S Kumar and C L Briant in lsquoChemistry

and electrochemistry of corrosion and stress corrosion crackingrsquo

(ed R H Jones) 573ndash582 2001 TMS

274 V I Elagin V V Zakharov A A Petrova and E V

Vyshegorodtseva Russ Metall 1983 (4) 143ndash146

Roslashyset and Ryum Scandium in aluminium alloys

44 International Materials Reviews 2005 VOL 50 NO 1

Page 17: Scandium in aluminium alloys - Atom probe · A considerable part of the available literature on scandium in aluminium alloys is reviewed. ... behaviour in Al Cu, Al Mg Si,

subsequent annealing the Al3Sc or Al3(Sc12xZrx)dispersoids may nucleate and grow before the nucleationand growth of recrystallised grains takes placeDispersoids can form after a direct up-quench to theannealing temperature115143148184 during ramp-up tothe annealing temperature115 or by pre-annealing at anintermediate temperature129 In the case of hot deforma-tion the Al3Sc or Al3(Sc12xZrx) dispersoids maynucleate and grow during preheating of the materialand during the hot deformation itself184

2 The Al3Sc or Al3(Sc12xZrx) dispersoids are formedin the material before deformation184 Considering coldrolling and subsequent annealing the annealing tem-perature Tann may be either lower or higher than thetemperature Tdisp at which the dispersoids were formedIf TannTdisp only limited if any coarsening of thedispersoids is expected to take place and thus the Zenerdrag from the particles is expected to be practicallyconstant The driving force for recrystallisation how-ever is expected to decrease somewhat with theannealing time as a result of recovery processes Thusif recrystallisation does not occur within short annealingtimes the material is expected to remain unrecrystallisedfor infinite time at the annealing temperature IfTannTdisp there will be substantial coarsening of thedispersoids during annealing In order for the materialto remain unrecrystallised the decrease in driving forcefor recrystallisation owing to recovery has to be at leastas rapid as the decrease in Zener drag because of particlecoarsening

Experimental comparisons of the conditions abovepoint in the direction that the recrystallisation resistanceis poorest when Sc (or Sc and Zr) is in solid solutionbefore deformation and the deformed material is up-quenched to the annealing temperature148 or when Al3Scor Al3(Sc12xZrx) dispersoids are formed before defor-mation at TdispampTann184185 Excellent recrystallisationresistance is achieved if dispersoids are formed at anintermediate anneal of solutionised and deformedmaterial128 or if dispersoids are formed at TdispTann

before deformation148185ndash187 It seems that the decreasein Zener drag because of dispersoid coarsening in many

cases is slower than the decrease in driving force forrecrystallisation because of recovery processes Thusthere is an advantage in forming a high number densityof small dispersoids which for most practical casesmeans that they should be formed at TdispTann122

When an advancing high angle grain boundary iethe recrystallisation front is passing a coherent Al3Scdispersoid there are at least three possible grainboundarydispersoid interactions

1 The Al3Sc dispersoid retains its global orientationrelationship and thus loses its coherency with thesurrounding matrix

2 The Al3Sc dispersoid rotates as the grain boundarypasses either by diffusional processes at the dispersoidmatrix interface or by the grain boundary passingthrough the dispersoid and the Al3Sc dispersoidassumes the same crystallographic orientation as theAl matrix of the recrystallised grain

3 The Al3Sc dispersoid dissolves at the grainboundary and re-precipitates in the recrystallised grain

Which interactions that actually take place willprobably depend on the dispersoid size annealingtemperature and driving force for recrystallisation It isalso possible that alloy composition (other elementsthan Al) is of importance

It has been reported that large (Oslash about 100ndash150 nm)Al3Sc dispersoids in a deformed Alndash4 wt-Mgndash02 wt-Sc alloy annealed at 575uC lose the orientationrelationship with the matrix after being passed by therecrystallisation front148

A rotation of somewhat smaller Al3Sc dispersoids in arecrystallising binary Alndash025 wt-Sc alloy has beenreported115143 The rotation was reported to be accom-panied by substantial growth (from Oslash 30 nm to Oslash48 nm) as a result of enhanced Sc diffusion at the grainboundary Observations suggested that the grainboundaries were passing through the dispersoids andthus the Al3Sc dispersoids retained the orientationrelationship with the recrystallised Al matrix

Dissolution and re-precipitation of Al3Sc dispersoidshas been reported during recrystallisation of a 50 coldrolled Alndash02 wt-Sc alloy162 Large spherical partially

26 Fraction recrystallised structure in cold rolled sheets

of Alndash04 wt-Sc and Alndash04 wt-Scndash015 wt-Zr as a

function of annealing temperature redrawn from

Ref 183 27 Electrical conductivity in Alndash15(SczZr) alloys

redrawn from Ref 183

Roslashyset and Ryum Scandium in aluminium alloys

International Materials Reviews 2005 VOL 50 NO 1 35

coherent dispersoids were observed to dissolve at therecrystallisation front and re-precipitate as smallercoherent Al3Sc cuboids

Superplastic forming

It seems that the first publication on superplasticproperties of Sc-containing Al-alloys was a study of anAlndash35Cundash14Mgndash045Mnndash04(SczZr) alloy188

It was recognised that the superplastic properties are aresult of the stabilisation of the fine grain structure byAl3Sc dispersoids The Sc-containing Al alloys that havereceived most attention for their superplastic propertieshowever are those of the AlndashMgndashSc system which wasfirst published in a patent189 Here it was noted that anAlndash4 wt-Mgndash05 wt-Sc alloy had superior superplasticproperties compared to fine-grained 7475 (AlndashZnndashMgndashCu alloy) Binary Alndash05 wt-Sc and Alndash4 wt-Mgalloys did not behave superplastically The flow stress atthe hot forming temperature was found to be much (30ndash40) lower in the ternary alloy than that of the twobinary alloys

The superplastic properties of AlndashMgndashSc alloys havebeen explored by several research groups over the lastdecade190ndash196 It has frequently been found that thedeformation mechanism is dominated by grain bound-ary sliding190 However it has also been reported thatAlndashMgndashSc alloy may deform superplastically withoutnoticeable grain boundary sliding23 It is generallyrecognised that the grain boundary sliding mechanismis facilitated when the average grain size is very smalland grain boundaries are predominantly high-angleSuch a microstructure may be achieved by carefulthermomechanical processing of the starting mate-rial193194197198 It has however been shown that a finegrained structure with high angle boundaries maydevelop during superplastic forming of AlndashMgndashSc alloyseven if the starting microstructure is an entirely differentone for instance that of a cold rolled sheet192 It has alsobeen suggested that superplastic forming of as castmaterial may be possible189

One of the more efficient thermomechanical processesfor achieving an ultrafine grain structure with high anglegrain boundaries in Al-alloys is equal channel angularpressing (ECAP) A JapanesendashAmerican group ofscientists has published an impressive body of researchon improvements in superplastic properties in Al-alloys processed by ECAP over the last few years andseveral of the publications are from investigations onAlndashMgndashSc alloys170199ndash224 Maximum strains in excessof 2000 at a strain rate of 0033 s21 have beenachieved170201202217 which is an extraordinarily goodcombination of high strain and high strain rate for analuminium alloy

Superplastic properties of AlndashCundashMg(ndashMn)ndashSc(ndashZr)and AlndashMgndashSc(ndashZr) alloys have been mentionedNoticeable superplasticity in other Sc-containing Al-alloys has also been reported such as AlndashZnndashMg(ndashCu)ndashScndashZr169225ndash228 AlndashLindashSc229 AlndashMgndashLindashScndashZr229ndash234

AlndashLindashMgndashCundashScndashZr235236 and AlndashCundashLindashScndashZr233

Precipitation hardeningHardening by Al3Sc precipitates

It has been noted that when Al3Sc particles precipitate inthe temperature range 250ndash350uC they give a significanthardness increase in the alloy Some authors point out

that Sc is a more effective precipitation hardening elementper atomic fraction added than the elements that arecommonly used for precipitation hardening121130 (In onepaper29 it is claimed that only Au has a strongerstrengthening effect than Sc) However the amount ofSc that can be precipitated from supersaturated solidsolution is rather limited and thus the absolute values ofthe hardness increase from the precipitation hardening ismuch lower than what is normally associated withprecipitation hardened alloys Also the temperatureregime for age hardening by precipitation of Al3Sc issomewhere in between the temperature regimes for agehardening and solution heat treatments of commonprecipitation hardened alloys This makes a combinedprecipitation of Al3Sc and other strengthening precipi-tates unfeasible Thus precipitation strengthening byAl3Sc is most feasible in alloy systems that are non-heat-treatable The non-heat-treatable aluminium alloy sys-tems are according to the Aluminum Associationdesignations the 1xxx series (99 pure Al) the 3xxxseries (AlndashMn) and the 5xxx series (AlndashMg) The purposeof adding Sc to these alloys may be either to stabilise themicrostructure of wrought semiproducts (extrusionsrolled plates forgings etc) as discussed in the sectionon lsquoRecrystallisation resistancersquo above or to provideextra strength to the alloy through precipitation hard-ening In the latter case it is appropriate to considerwhether the Sc-containing alloy still should be classifiedas non-heat-treatable A heat treatment is applied thatbrings about a significant precipitation hardening On theother hand the hardness increase that is achieved throughthe heat treatment is lower than what is normallyassociated with heat-treatable alloy systems Hence eventhough it seems like a contradiction one chooses to keepusing the term lsquonon-heat-treatablersquo about these alloys

Table 7 gives an overview of some mechanicalproperties of Sc-containing non-heat-treatable alloysthat are reported in the literature Most of theexperimental work on Sc in 1xxx-types of alloys hasbeen done on binary AlndashSc alloys with much higherpurity than industrial alloys

Strengthening mechanisms

When the precipitates are larger than a critical size thestrengthening effect is due to the Orowan-mechanism iedislocations can only pass the precipitates by looping Inthis case the strengthening effect of the particles isapproximately inversely proportional to the mean parti-cle spacing When the precipitates can be sheared bydislocations there are a number of strengthening mechan-isms that apply It is proposed by Parker et al108 that thetwo major contributing mechanisms are coherency strainand anti-phase-boundary energy In a recent detailedstudy of strengthening mechanisms in binary AlndashSc alloysby Marquis and colleagues117118 the strengthening fromshear modulus mismatch between the matrix and theprecipitates is also accounted for A qualitatively goodmatch between theoretical strengthening and measuredvalues is achieved in this work both for deformation atroom temperature and at 300uC

Effect of Sc on precipitation strengthening in heat-treatablealloys

Following the AA designation system the traditionalheat-treatable Al-alloys are those that belong to the 2xxx

Roslashyset and Ryum Scandium in aluminium alloys

36 International Materials Reviews 2005 VOL 50 NO 1

series (AlndashCu) 6xxx series (AlndashMgndashSi) and 7xxx series(AlndashZnndashMg) AlndashLi alloys should also be mentionedSeveral investigations have been carried out in order toclarify the effects of Sc on the precipitation behaviour inthese alloy systems

AlndashCu alloys

The precipitation sequence in AlndashCu alloys is oftendescribed as follows

Supersaturated solid solutionRGP-zonesRh0Rh9Rh(Al2Cu)

The highest strength is normally achieved when the h0or h9 precipitates are predominant Typical precipitationheat treatment temperatures for AlndashCu alloys are in therange 160ndash190uC238 which is considerably lower thanthe typical precipitation temperature for Al3ScComparisons of the aging responses of AlndashCu and AlndashCundashSc alloys at 150 and 200uC indicate that there is nonoticeable effect of Sc on the precipitation kinetics ofh9153 It is observed that the h9 precipitates may nucleateon Al3Sc particles153 At 300uC it is observed that h9particles are somewhat smaller in AlndashCundashSc alloys thanin AlndashCu alloys156

AlndashMgndashSi alloys

The following precipitation sequence is commonlyreported for AlndashMgndashSi alloys

Supersaturated solid solutionRGP-zonesRb0Rb9Rb(Mg2Si)

For peak aged alloys the predominant precipitatetype is b0 for which the stoichiometric composition hasrecently been resolved to be Mg5Si6239 Temperatures inthe range 160ndash205uC are typically used for precipitationhardening of these alloys238 Adding both 03 wt-Scand 01 wt-Zr to an Alndash06 wt-Mgndash065 wt-Sialloy does not seem to alter the precipitation kineticsof b0 at 165uC However the hardness increase becauseof precipitation hardening appears to be smaller in theSczZr-containing alloy240 In another investigationadditions of 01 wt-Sc 015 wt-Sc 02 wt-Sc04 wt-Sc and 02 wt-Scz01 wt-Zr were made toan Alndash08 wt-Mgndash07 wt-Si alloy241 Here it wasalso observed that the precipitation kinetics of b0 wasseemingly independent of the Sc additions (Fig 28)TEM observations indicated that the b0 precipitateswere of comparable sizes in the investigated alloys andno interactions between Al3Sc and b0 were observed(Fig 29) In a third study242 where the effect of Sc onthe precipitation in an AlMgSindashSiC metal matrixcomposite was investigated there also does not seemto be any effect on the precipitation kinetics Howevercontrary to the findings of Ref 240 it is reported thatthe Sc addition leads to a higher hardness increase thanin the corresponding Sc free alloy

AlndashMgndashZn alloys

For these alloys the following precipitation sequence isoften ascribed

Table 7 Mechanical properties in non-heat-treatable Al-alloys with Sc

Reference Alloy wt- YS MPa UTS MPa Note

1xxx alloys171 000Sc 15 48 Cast material aged 288uC8 h

023Sc 159 185 Cast material aged 288uC8 h038Sc 199 220 Cast material aged 288uC8 h000Sc 14 49 Cold rolled material (89) aged 288uC8 h023Sc 198 208 Cold rolled material (89) aged 288uC8 h038Sc 240 264 Cold rolled material (89) aged 288uC8 h000Sc 8 34 Cold rolled material quenched from 649uC aged 288uC8 h023Sc 147 157 Cold rolled material quenched from 649uC aged 288uC8 h038Sc 193 199 Cold rolled material quenched from 649uC aged 288uC8 h

121 05Sc 160 ndash Forged material quenched from 635uC aged 250uC50 h23 05Sc 298 319 Hot rolled 288uC cold rolled 69ndash81 aged 288uC4 h112 01Sc 132 166 Hot z cold rolled material quenched from 630uC

aged 320uC133 h148 02Sc 138 ndash Cast material aged 300uC10 h compression test159 04Sc 196 ndash Cast material aged 300uC10 h compression test117 118 03Sc 209 ndash Cast material quenched from 648uC aged 300uC5 h

compression test3xxx alloys171 1Mn 015Sc 216 221 Cold rolled material (89) aged 288uC8 h

1Mn 05Sc 309 323 Cold rolled material (89) aged 288uC8 h186 05Mn 02Mg

026Sc 015Zr162 201 Extruded material solutionised 600uC aged 250uC

5xxx alloys171 1Mg 43 111 Cold rolled material (89) aged 288uC8 h

1Mg 03Sc 288 303 Cold rolled material (89) aged 288uC8 h53Mg 147 259 Cold rolled material (50) wintermediate anneals

at 343uC aged 288uC8 h53Mg 03Sc 368 401 Cold rolled material (50) wintermediate anneals

at 343uC aged 288uC8 h23 2Mg 05Sc 376 401 Hot rolled 288uC cold rolled 69ndash81 aged 288uC4 h

4Mg 05Sc 414 4606Mg 05Sc 433 503

237 4Mg 1Sc 420 525 Cold rolled material (83) aged 320uC1 h148 4Mg 02Sc 194 ndash Cast material aged 300uC10 h compression test

Tensile test data except where noted YS yield strength UTS ultimate tensile strength

Roslashyset and Ryum Scandium in aluminium alloys

International Materials Reviews 2005 VOL 50 NO 1 37

Supersaturated solid solutionRGP-zonesRg9Rg(Zn2Mg)

The maximum hardness is normally achieved whenthe g9 precipitates are predominant Common precipita-tion hardening temperatures are in the range 95ndash180uCand a two-step precipitation heat treatment within thistemperature regime is often used238 It has beenobserved in some investigations that Sc and SczZradditions to AlndashMgndashZn alloys slow down the precipita-tion of g9 somewhat243 Other investigations find thatthere is no effect of Sc on the precipitation behaviour ofg9244245 and yet others report that Sc additionssignificantly speed up the precipitation of g9246 In Ref247 it is found that an Sc addition leads to coarser g9precipitates and it is claimed that this gives an improvedductility of the alloy The strength-loss associated withlarger particle size is reported to be counterbalanced bystrengthening from Al3Sc precipitates

AlndashLi alloys

The precipitation sequence in binary AlndashLi alloys isapparently simple

Supersaturated solid solutionRd9Rd (AlLi)

where d9 is the metastable Al3Li phase which just likeAl3Sc has the L12 type of atomic arrangement Thetypical temperature regime for precipitation of d9 whichis the strengthening phase in this system is approx 150ndash200uC A comparison of the age hardening response ofan Alndash26 wt-Li and an Alndash24 wt-Lindash019 wt-Scalloy at 180uC248 and 200uC161 indicates that the onsetof d9 precipitation is not altered by the presence of ScThe hardness curves for the two alloys are practicallyidentical at 200uC whereas at 180uC the peak hardnesslevel is slightly higher in the AlndashLi than the AlndashLindashScalloy DSC measurements at constant heating ratesindicate that the addition of Sc to an AlndashLi alloysincreases the activation energy for d9 precipitation andmoves the exothermic peak associated with d9 precipita-tion to a higher temperature248 For specimens aged at

either 180uC or 200uC TEM observations reveal that thed9 precipitates are much smaller in the Sc containingalloy than in binary AlndashLi both in the peak agedcondition and in the overaged condition161248 Additionof Sc has also been observed to reduce the size of d9precipitates in other AlndashLi based alloys249ndash251 In an AlndashLindashCundashZr alloy an addition of Sc has been reported toslow down the homogeneous precipitation of d9252253 Ithas been claimed that Sc reduces the quench sensitivityand delays room temperature aging of AlndashLi basedalloys254ndash256

When present in the microstructure before the pre-cipitation of d9 the Al3Sc precipitates may act as effec-tive nucleation sites for d9 The resulting precipitates arespheres of d9 with a core of Al3Sc161249252ndash255257ndash261

Corrosion resistanceAn appreciable amount of data is available on the effectsof Sc on the corrosion behaviour of wrought Al-alloysSome of these effects are apparently derived from theeffects of Sc on the microstructure of the alloys It hasbeen reported that an addition of Sc increases thecorrosion potential (makes it less negative) in pureAl262ndash264 in AlndashZn alloys265266 AlndashMg alloys267 AlndashZnndashMgndashCu alloys264268 AlndashCundashMgndashMn alloys264 andin AlndashCundashLindashMgndashAg alloys264 Even though Sc alsohas been reported to decrease the corrosion potential in

28 Age hardening response at 175uC for Alndash08 wt-Mgndash

07 wt-Si alloy (Base) with additions of 02 wt-Sc

04 wt-Sc and 02 wt-Scz01 wt-Zr from Ref 241

29 TEM images of a b0 precipitates in Alndash08 wt-Mgndash

07 wt-Si alloy and b b0 and Al3(Sc1ndashxZrx) in a similar

alloy with addition of 02 wt-Scz01 wt-Zr from

Ref 241

Roslashyset and Ryum Scandium in aluminium alloys

38 International Materials Reviews 2005 VOL 50 NO 1

AlndashMg alloys269270 it seems that the general trend isthat adding Sc to an alloy makes it slightly more nobleThe change in corrosion potential is much morepronounced when Sc is added in amounts larger thanthe eutectic composition263 ie there is a considerablecontribution from primary or eutectic Al3Sc to theoverall potential It has also been demonstrated that thechange in corrosion potential caused by Sc can dependon the heat treatment applied to the alloy267268

Even though the corrosion potential is an essentialparameter in establishing the corrosion behaviour of analloy an increase in the corrosion potential does notnecessarily imply an improved self-corrosion resistanceHowever measurements of corrosion rates and passiva-tion current densities strongly suggest that the self-corrosion resistance in general is considerably improvedwhen Sc is added to wrought Al-alloys263264267 Someobserved variations in corrosion potential and passiva-tion current densities with Sc content in binary AlndashScalloys are plotted in Fig 30

Material failure in corrosive environments is often dueto localised corrosion attacks which may propagaterapidly even though the bulk material has a goodresistance against general corrosion It has been pointedout that hypereutectic additions of Sc may lead tomicrogalvanic corrosion beside primary Al3Sc parti-cles264 In AlndashMg alloys grain boundary precipitation ofAl8Mg5 can lead to localised corrosion attacks such asintergranular corrosion (IGC) exfoliation corrosion(EC) and stress corrosion cracking (SCC) In wroughtmaterial such precipitation may occur in the 60ndash180uCtemperature regime and heating in this temperaturerange is referred to as lsquosensitationrsquo An AlndashMgndashSc alloywas found to be immune against intergranular corrosionand have moderate susceptibility to exfoliation corro-sion after annealing at 350uC271 After sensitation heattreatments severe IGC and EC was observed but notquite as severe as in a corresponding alloy without ScAs for SCC the AlndashMgndashSc alloy was found to be highlyresistant271 In another study it was found that additionof 056 wt-Sc reduces the SCC susceptibility of an Alndash68 wt-Mg alloy in the as-rolled state and afterannealing at 250uC whereas in a sensitised specimenthe SCC susceptibility is somewhat increased by the Scaddition272 A third investigation found that Sc has nomeasurable detrimental effect on the SCC susceptibilityof sensitised Alndash5Mgndash015Zr alloy273 SCC is also a

severe problem in high strength AlndashZnndashMgndashCu alloys Ithas been shown that small Sc additions are effective inreducing the SCC sensitivity of these alloys244246268274

Use of Sc-containing Al alloysA systematic development of Sc-containing aluminiumalloys took place in the former USSR in the 1980s andthe interest for Sc as an alloying element in aluminiumalloys hit the western world approximately 10 yearslater Even though a number of improvements in Alalloys achieved by Sc addition have been demonstratedthe current uses of such alloys are very limited This isrelated to the very high price of scandium

In Russia some parts of military aircraft are made ofSc-containing AlndashLi alloys In the western world themain usage of Sc-containing alloys is for sportsequipment Ashurst Technology and Kaiser Aluminumdeveloped a Sc-containing 7xxx alloy for baseball andsoftball bats which was introduced to the Americanmarket in 1997 by Easton Alcoa soon followed with aSc-containing alloy for a competing brand of batsLouisville Slugger Since then several new and improvedSc-containing alloys for bats have been introduced tothe market The purpose of adding Sc is to increase theyield strength of the alloy allowing for a down-gaugingof the wall thickness which in turn gives a strongerlsquospring-rsquo or lsquotrampoline-rsquo effect when the ball hits thebat

Shortly after the introduction of the Sc containingbats Easton also launched Sc-containing 7xxx tubingfor bicycle frames Just as in the bats Sc increases theyield strength of the alloy allowing for down-gauging oftube wall thickness and a corresponding weight reduc-tion of the bicycle frame An Italian manufacturer ofbicycle tubing Dedacciai also delivers tubes in a Sc-containing 7xxx alloy

Other sports equipment made from Sc-containingaluminium alloys includes lacrosse sticks and tent polesSmith and Wesson has also introduced a series ofhandguns where the frame is made from a Sc-containingAl alloy

A common factor for the items mentioned above isthat the material cost is only a minor part of the totalmanufacturing cost of the end product and also thatthese products are aimed at a group of customers thathave a certain awareness of new materials Both baseballbats and bicycle frames have been marketed aslsquoscandium alloyrsquo even though the Sc content is muchlower than 1

Currently AlndashSc master alloys for the production ofSc-containing Al alloys are available at a price thatcorresponds to US$ 2000 per kg of Sc This means that ifone wants to add 02 wt-Sc to an alloy which is afairly common content one also increases the price ofthe alloy by US$ 4 per kg alloy Depending on the alloytype Sc is added to this represents a tripling orquadrupling of the price of the alloy There are notmany existing products where such an increase inmaterial cost can be justified In order to see awidespread use of Sc in high-volume products the Scprice has to come down considerably Actually the priceof adding Sc to Al alloys has gone down by a factor 3ndash10over the last 10ndash15 years and substantial price reduc-tions are also expected in the future

30 Observed variations in corrosion potential and passi-

vation current densities with Sc content in binary Alndash

Sc alloys based on data from Ref 263

Roslashyset and Ryum Scandium in aluminium alloys

International Materials Reviews 2005 VOL 50 NO 1 39

The current production of AlndashSc master alloys isbased upon and will continue to be based upon for theforeseeable future the reduction of Sc2O3 or other Sccompounds directly in molten aluminium It is notnecessary as many tend to believe to take the route viametallic Sc Thus the price of AlndashSc master alloy isgoverned by the price of Sc2O3 or other Sc compoundsin question and not by the price of metallic scandiumThe Sc2O3 which is the main source for todayrsquos AlndashScmaster alloy production comes from stockpiles in theformer USSR These stockpiles will be exhausted withina few years and new reliable sources of Sc2O3 or otherSc compound production are sought It turns out thatthe most economically viable option that has beendisclosed so far is the processing of Red Mud from theBayer process of extracting alumina from bauxiteScandium is enriched in the Red Mud and is extractedfrom a Red Mud aqueous slurry by selective leachingsubsequent ion-exchange procedure and finally a liquidndashliquid extraction procedure It is not required to build aseparate lsquoSc factoryrsquo to do this but rather build an lsquoadd-onrsquo to existing Bayer process plants Such a processroute is expected to bring down the price of Sc2O3

considerably which in turn means that AlndashSc masteralloy price should drop accordingly Preliminary ana-lyses suggest a price of approx US$ 400 per kg Sc in themaster alloy which translates to an added cost of 80cent per kilo when 02 wt-Sc is added to an aluminiumalloy This is also a considerable increase in the materialcost but with such prices one should expect to see Sccontaining alloys in many more applications than whatis the case at the present time

Concluding remarksThe body of published investigations on Al-based alloyswith Sc addition provides a sound basis of knowledgefor metallurgists that want to look into the possibility ofenhancing the performance of a wrought Al-alloy byadding Sc to it Ternary AlndashScndashX phase diagrams areavailable for practically every technologically importantalloying element in Al The effect of a wide range ofternary alloying elements on the precipitation behaviourof Al3Sc is accounted for It has been shown that theAl3Sc phase can be effective as a grain refiner adispersoid former and a precipitate hardening agentand some of the underlying conditions for achieving thedesired Al3Sc formation have been outlined Addingsome Zr together with Sc has proven to be beneficial Itmay lead to effective grain refinement at a lower Sc levelbut the most prominent effect is the refinement indispersoid distribution that can be achieved An addi-tion of Sc has little if any effect on precipitation in the2xxx 6xxx and 7xxx alloy systems and some effects onthe precipitation in AlndashLi based alloys With respect tocorrosion behaviour adding Sc to an Al-alloy does ingeneral seem to make the alloy slightly more noble andto increase its self-corrosion resistance Scandium-containing Al alloys have very few uses at the presenttime as a result of the high price of scandium The priceof Sc is expected to decrease significantly in the futureand this should lead to the disclosure of moreapplications where it is economically feasible to takeadvantage of the improved properties of some Sc-containing aluminium alloys

References1 D R Lide lsquoCRC handbook of chemistry and physicsrsquo 71st edn

4ndash29 1990 Boston USA CRC Press

2 E M Savitsky V F Terehova I V Burov and O P Naumkin

Proc Fourth Conf on lsquoRare earth researchrsquo Phoenix Arizona

USA April 1964 409ndash420

3 E M Savitskii V F Terekhova I V Burov O P Naumkin and

I A Markova Inorg Mater 1965 1 1503ndash1512

4 O P Naumkin V T Terekhova and E M Savitskiy Russ

Metall 1965 (4) 128ndash136

5 W G Moffatt lsquoThe handbook of binary phase diagramsrsquo 1981

Schenectady NY USA General Electric Co

6 E A Brandes (ed) lsquoSmithells metals reference bookrsquo 6th edn

1983 London UK Butterworths

7 R P Elliott and F A Shunk Bull Alloy Phase Diagrams 1981

2 (2) 222ndash223

8 K A Gschneider Jr and F W Calderwood Bull Alloy Phase

Diagrams 1989 10 34ndash36

9 H Okamoto J Phase Equil 1991 12 612ndash613

10 J L Murray J Phase Equil 1998 19 380ndash384

11 M E Drits E S Kadaner T V Dobatkina and N I Turkina

Russ Metall 1973 (4) 152ndash154

12 S-I Fujikawa M Sugaya H Takei and K-I Hirano J Less-

Common Met 1979 63 87ndash97

13 N Blake and M A Hopkins J Mater Sci 1985 20 2861ndash2867

14 V I Kononenko and S V Golubev Russ Metall 1990 (2) 193ndash

195

15 T B Massalski J L Murray L H Bennett and H Baker (eds)

lsquoBinary alloy phase diagramsrsquo 1986 Metals Park OH USA

ASM

16 G Cacciamani P Riani G Borzone N Parodi A Saccone

R Ferro A Pisch and R Schmid-Fetzer Intermetallics 1999 7

101ndash108

17 H Okamoto J Phase Equil 2000 21 310

18 A F Norman P B Pragnell and R S McEwen Acta Mater

1998 46 5715ndash5732

19 I N Pyagai and A V Vakhobov Russ Metall 1990 (5) 50ndash52

20 C L Fu J Mater Res 1990 5 971ndash979

21 X Lu and Y Wang Calphad 2002 26 555ndash561

22 R R Sawtell and J W Morris Jr Proc lsquoDispersion strengthened

aluminium alloysrsquo Phoenix Arizona USA January 1988 409ndash

420

23 R R Sawtell and C L Jensen Metall Trans A 1990 21A 421ndash

430

24 L A Willey Unpublished research Alcoa 1970 Data points are

extracted from Ref 10

25 N I Turkina and V I Kuzmina Russ Metall 1976 (4) 179ndash

183

26 T Torma E Kovacs-Csetenyi I Vitanyi M Butova and

J Stepanov Proc 6th Int Symp on lsquoHigh purity materials in

science and technologyrsquo Akademie der Wissenschaften der DDR

Dresden Germany May 1985 388ndash389

27 A L Berezina V A Volkov B P Domashnikov and K V

Chuistov Metallofizika 1987 9 (5) 43ndash47

28 H-H Jo J Korean Inst Metals 1990 28 499ndash504

29 H-H Jo and S-I Fujikawa Mater Sci Eng 1993 A 171 151ndash

161

30 S Celotto and T J Bastow Philos Mag A 2000 80 1111ndash1125

31 J Roslashyset and N Ryum submitted to Mater Sci Eng

32 M E Drits L S Toropova Yu G Bykov F L Gushchina V I

Elagin and Yu A Filatov Russ Metall 1983 (1) 150ndash153

33 L S Toropova D G Eskin M L Kharakterova and T V

Dobatkina lsquoAdvanced aluminum alloys containing scandium

structure and propertiesrsquo 1998 Amsterdam The Netherlands

Gordon and Breach Science Publishers

34 V V Cherkasov P P Pobezhimov L P Nefedova E V Belov

and G M Kuznetsov Met Sci Heat Treat 1996 (6) 268ndash270

35 Kh O Odinaev I N Ganiev V V Kinzhibalo and B Ya

Kotur Dokl Akad Nauk Tadzh SSR 1989 32 37ndash38

36 Kh O Odinaev I N Ganiev and A V Vakhobov Russ Metall

1991 (4) 200ndash203

37 J Grobner R Schmid-Fetzer A Pisch G Cacciamani P Riani

N Parodi G Borzone A Saccone and R Ferro Z Metallkd

1999 90 872ndash880

38 E A Marquis and D N Seidman Microsc Microanal 2002 8

(Suppl 2) 1100CDndash1101CD

39 A Pisch J Grobner and R Schmid-Fetzer Mater Sci Eng A

2000 A 289 123ndash129

Roslashyset and Ryum Scandium in aluminium alloys

40 International Materials Reviews 2005 VOL 50 NO 1

40 C Xia F Zeng and Y Gu Trans Nonferrous Met Soc China

2003 13 1124ndash1127

41 M Yu Teslyuk and V S Protasov Sov Phys Crystallogr 1966

10 470ndash471

42 M L Kharakterova and T V Dobatkina Russ Metall 1988

(6) 175ndash178

43 M L Kharakterova Russ Metall 1991 (4) 195ndash199

44 L S Toropova M L Kharakterova and D G Eskin Russ

Metall 1992 (3) 194ndash199

45 P Riani L Arrighi R Marazza D Mazzone G Zanicchi and

R Ferro J Phase Equil Diff 2004 25 22ndash52

46 A T Tyvanchuk T I Yanson B Ya Kotur O S Zarechnyuk

and M L Kharakterova Russ Metall 1988 (4) 190ndash192

47 L L Rokhlin T V Dobatkina and M L Kharakterova Powder

Metall Met Ceram 1997 36

48 A Z Ikromov I N Ganiev and V V Kinzhibalo Dokl Akad

Nauk Tadzh SSR 1990 (6) 391ndash392

49 I N Ganiev A Z Ikromov and V G Khudoiberdiev Russ

Metall 1995 (3) 125ndash127

50 I N Fridlyander L L Rokhlin T V Dobatkina and N I

Nikitina Met Sci Heat Treat 1993 (10) 567ndash571

51 I N Fridlyander L L Rokhlin T V Dobatkina V V

Kinzhibalo and A T Tyvanchuk Russ Metall 1998 (1) 161ndash

166

52 R A Emigh E L Bradley and J W Morris Jr in lsquoLight-weight

alloys for aerospace applications IIrsquo (ed E W Lee and N J

Kim) 27ndash43 1991 TMS

53 L S Toropova A N Kamardinkin V V Kindzhibalo and A T

Tyvanchuk Phys Met Metall 1990 70 (6) 106ndash110

54 A N Kamardinkin T V Dobatkina and T D Rostova Russ

Metall 1991 (4) 216ndash218

55 L S Torodskaya T V Dobatkina and A N Kamardinkin

Russ Metall 1992 (5) 128ndash131

56 E M Sokolovskaya E F Kazakova E I Poddyakova and A

A Ezhov Met Sci Heat Treat 1997 (5) 211ndash213

57 Y Harada and D C Dunand Mater Sci Eng 2002 A 329ndash331

686ndash695

58 N E Drits L S Toropova and F L Gushchina Russ Metall

1984 (4) 229ndash232

59 E M Sokolovskaya E F Kazakova V A Alikhanov and E V

Zhuravleva Moscow Univ Chem Bull 1997 52 (5) 70ndash72

60 E M Sokolovskaya E F Kazakova and E I Poddyakova Met

Sci Heat Treat 1989 (11) 837ndash839

61 G M Cheldieva E F Kazakova E M Sokolovskaya and N I

Kaloev Russ Metall 1990 (6) 87ndash90

62 E M Sokolovskaya E F Kazakova and O D-S Kendivan

Russ Metall 1998 (4) 135ndash137

63 N G Bukhanko E F Kazakova and E M Sokolovskaya Russ

Metall 2001 (4) 425ndash431

64 E D Trubnyakova O I Bodak I N Ganiev and A V

Vakhobov Russ Metall 1987 (3) 219ndash222

65 I N Fridlyander and L V Molchanova Russ Metall 2003 (5)

476ndash480

66 R A Altynbaev S Kh Khairidinov and A V Vakhobov Russ

Metall 1987 (4) 194ndash196

67 J C Schuster and J Bauer J Less-Common Met 1985 109

345ndash350

68 L L Rokhlin A S Fridman T V Dobatkina and D G Eskin

Russ Metall 1991 (6) 146ndash148

69 A S Fridman T V Dobatkina and E V Muratova Russ

Metall 1992 (1) 207ndash209

70 C Xia F Zeng and Y Gu Trans Nonferrous Met Soc China

2003 13 546ndash552

71 F Zeng C Xia and Y Gu J Alloys Comp 2004 363 175ndash181

72 L L Rokhlin T V Dobatkina N R Bochvar and E V Lysova

J Alloys Comp 2004 367 10ndash16

73 T V Dobatkina A S Fridman and E V Muratova Russ

Metall 1992 (5) 125ndash127

74 I N Fridlyander L L Rokhlin N R Bochvar E V Lysova

and O V Boteva Russ Metall 2001 (6) 661ndash666

75 V N Rechkin L K Lamikhov and T I Samsonova Sov Phys

Crystallogr 1964 9 325ndash327

76 I I Zalutskii and P I Kripyakevich Sov Phys Crystallogr

1967 12 341ndash343

77 T J Bastow C T Forwood M A Gibson and M E Smith

Phys Rev B 1998 58 2988ndash2997

78 K Fukunaga M Kolbe K Yamada and Y Miura Mater Sci

Eng 1997 A 234ndash236 594ndash597

79 E P George J A Horton W D Porter and J H Schneibel

J Mater Res 1990 5 1639ndash1648

80 E P George D P Pope C L Fu and J H Schneibel ISIJ Int

1991 31 1063ndash1075

81 Y Harada and D C Dunand Acta Mater 2000 48 3477ndash3487

82 J H Schneibel and E P George Scripta Metall Mater 1990 24

1069ndash1074

83 J H Schneibel and P M Hazzledine Mater Res Soc Symp

Proc 1991 213 323ndash328

84 J H Schneibel and P M Hazzledine J Mater Res 1992 7

868ndash875

85 C J Sparks E D Specht G E Ice P Zschack and J Schneibel

Mater Res Soc Symp Proc 1991 213 363ndash368

86 J Tarnacki and Y-W Kim Scripta Metall Mater 1989 23

1063ndash1068

87 M Asta V Ozolins and C Woodward JOM 2001 53 (9) 16ndash

19

88 M E Drits L S Toropova F L Gushchina and S G Fedotov

Sov Non-Ferrous Met Res 1984 12 83ndash85

89 Y Harada and D C Dunand Scripta Mater 2003 48 219ndash222

90 C Woodward M Asta G Kresse and J Hafner Phys Rev B

2001 63 094103-1-6

91 J-H Xu and A J Freeman Phys Rev B 1990 41 12553ndash12561

92 M F Bartholomeusz and J A Wert Acta Metall Mater 1992

40 673ndash682

93 G Bester and M Fahnle J Phys Condens Matter 2001 13

11551ndash11565

94 C L Fu and M H Yoo Proc lsquoOrdered intermetallics ndash physical

metallurgy and mechanical behaviorrsquo Irsee Germany June 1991

155ndash164

95 K Fukunaga T Shouji and Y Miura Mater Sci Eng 1997 A

239ndash240 202ndash205

96 D P Pope Proc lsquoOrdered intermetallics ndash physical metallurgy

and mechanical behaviorrsquo Irsee Germany June 1991 143ndash153

97 J-S Wang Acta Mater 1998 46 2663ndash2674

98 M H Yoo and C L Fu Mater Sci Eng 1992 A 153 470ndash478

99 R W Hyland Jr and R C Stiffler Scripta Metall Mater 1991

25 473ndash477

100 I G Brodova I V Polents O A Korzhavina P S Popelrsquo I P

Korshunov and V O Esin Melts 1992 4 392ndash397

101 I G Brodova O A Chikova I V Polents P S Popelrsquo and V O

Esin Casting Processes 1992 1 (2) 158ndash160

102 I G Brodova D V Bashlikov and I V Polents Mater Sci

Forum 1998 269ndash272 589ndash594

103 K B Hyde A F Norman and P B Pragnell Mater Sci Forum

2000 331ndash337 1013ndash1018

104 K B Hyde A F Norman and P B Pragnell Acta Mater 2001

49 1327ndash1337

105 J Roslashyset and N Ryum Proc 6th Int Conf on lsquoAluminum

alloysrsquo Toyohashi Japan July 1998 793ndash798

106 V I Elagin V V Zakharov and T D Rostova Met Sci Heat

Treat 1993 (6) 317ndash319

107 R W Hyland Jr Metall Trans A 1992 23A 1947ndash1955

108 B A Parker Z F Zhou and P Nolle J Mater Sci 1995 30

452ndash458

109 C L Rohrer M D Asta S M Foiles and R W Hyland Jr

Mater Res Soc Symp Proc 1996 398 477ndash482

110 G M Novotny and A J Ardell Mater Sci Eng 2001 A 318

144ndash154

111 J D Robson M J Jones and P B Pragnell Acta Mater 2003

51 1453ndash1468

112 C Tan Z Zheng and B Wang Proc 3rd Int Conf on

lsquoAluminium alloysrsquo Vol I NTH Trondheim Norway June

1992 290ndash294

113 M Nakayama A Furuta and Y Miura Mater Trans JIM

1997 38 852ndash857

114 E A Marquis and D N Seidman Acta Mater 2001 49 1909ndash

1919

115 M J Jones and F J Humphreys Acta Mater 2003 51 2149ndash

2159

116 E A Marquis D N Seidman and D C Dunand in lsquoCreep

deformation fundamentals and applicationsrsquo (ed R S Mishra

J C Earthman and S V Raj) 299ndash308 2002 TMS

117 D N Seidman E A Marquis and D C Dunand Acta Mater

2002 50 4021ndash4035

118 E A Marquis D N Seidman and D C Dunand Acta Mater

2003 51 285ndash287

119 M E Drits L S Toropova U G Bikov and G K Anastaseva

Proc lsquoDiffusion in metals and alloysrsquo Tihany Hungary Augustndash

September 1982 616ndash623

120 V I Elagin V V Zakharov and T D Rostova Met Sci Heat

Treat 1983 (7) 546ndash549

Roslashyset and Ryum Scandium in aluminium alloys

International Materials Reviews 2005 VOL 50 NO 1 41

121 M Ye Drits L B Ber Yu G Bykov L S Toropova and G K

Anastaseva Phys Met Metall 1984 57 (6) 118ndash126

122 M E Drits L S Toropova and Yu G Bykov Sov Non-Ferrous

Met Res 1985 13 309ndash314

123 V I Yelagin V V Zakharov S G Pavlenko and T D Rostova

Phys Met Metall 1985 60 (1) 88ndash92

124 N Sano Y Hasegawa K Hono H Jo K Hirano H W

Pickering and T Sakurai Journal de Physique 1987 48 C6 337ndash

342

125 N Sano H-H Jo K-I Hirano and T Sakurai J Jpn Inst

Metals 1989 39 444ndash450

126 N Sano H Jo K Hirano and T Sakurai Proc Second Int

Conf on lsquoAluminium alloysrsquo Beijing China October 1990 549ndash

554

127 Y Miura M Nakayama and A Furuta Proc lsquoAspects of high

temperature deformation and fracture in crystalline materialsrsquo

Nagoya Japan July 1993 255ndash262

128 Y W Riddle and T H Sanders Jr Mater Sci Forum 2000

331ndash337 939ndash944

129 Y W Riddle M McIntosh and T H Sanders Jr in lsquoLightweight

alloys for aerospace application VIrsquo (ed K Jata E W Lee

W Frazier and N J Kim) 25ndash39 2001 TMS

130 M E Drits J Dutkiewicz L S Toropova and J Salawa Crystal

Res Technol 1984 19 1325ndash1330

131 Y W Riddle MSc thesis Georgia Tech GA USA 1998

132 T J Bastow and S Celotto Mater Sci Eng 2003 C 23 757ndash

762

133 M C Carroll M J Mills G S Daehn P I Gouma M F

Savage and B R Dunbar in lsquoAutomotive Alloys 1999rsquo (ed

S Das) 239ndash246 2000 TMS

134 E Clouet M Nastar and C Sigli Phys Rev B 2004 69 064109-

1-14

135 V V Zakharov Met Sci Heat Treat 1997 (2) 61ndash66

136 J W Christian lsquoThe theory of transformation in metals and

alloysrsquo 2nd edn 1975 Pergamon Press Ltd

137 A L Berezina V A Volkov B P Domashnikov S V Ivanov

and K V Chuistov Phys Metals 1990 10 296ndash304

138 S-I Fujikawa and S Sakauchi Proc 6th Int Conf on

lsquoAluminum alloysrsquo Toyohashi Japan July 1998 805ndash810

139 Y S Touloukian R K Kirby R E Taylor and P D Desai

(eds) lsquoThermal expansion metallic elements and alloysrsquo 1975

New York Plenum

140 J Roslashyset and N Ryum submitted to Scripta Mater

141 R O Simmons and R W Balluffi Phys Rev 1960 117 52ndash61

142 M Ocko E Babic R Krsmik E Girt and B Leontic J Phys F

Metals Phys 1976 6 703ndash707

143 M J Jones and F J Humphreys Proc First Joint Int Conf on

lsquoRecrystallization and grain growthrsquo Aachen Germany August

2001 Springer Verlag 1287ndash1292

144 S Iwamura M Nakayama and Y Miura Mater Sci Forum

2002 396ndash402 1151ndash1156

145 S Iwamura and Y Miura Acta Mater 2004 52 591ndash600

146 M Asta S M Foiles and A A Quong Phys Rev B 1998 57

11265ndash11275

147 R W Hyland Jr M Asta S M Foiles and C L Rohrer Acta

Mater 1998 46 3667ndash3678

148 J Roslashyset and N Ryum Proc 4th Int Conf on lsquoAluminium

alloysrsquo Vol I Atlanta GA USA September 1994 194ndash201

149 M E Drits L S Toropova G K Anastaseva and G L

Nagornichnykh Russ Metall 1984 (3) 192ndash195

150 E A Marquis D N Seidman and D C Dunand Acta Mater

2003 51 4751ndash4760

151 M E Drits L S Toropova and Yu G Bykov Met Sci Heat

Treat 1983 (7) 550ndash554

152 V V Zakharov and T D Rostova Met Sci Heat Treat 1995

(2) 65ndash69

153 M Nakayama and Y Miura Proc 4th Int Conf on lsquoAluminium

alloysrsquo Vol I Atlanta GA USA September 1994 538ndash545

154 M Nakayama and Y Miura J Jpn Inst Light Metals 1996 46

275ndash279

155 M Nakayama T Okuyama and Y Miura Mater Sci Forum

2000 331ndash337 927ndash932

156 M Nakayama T Okuyama and Y Miura Proc 6th Int Conf

on lsquoAluminum alloysrsquo Toyohashi Japan July 1998 517ndash522

157 M L Kharakterova D G Eskin and L S Toropova Acta

Metall Mater 1994 42 2285ndash2290

158 V I Elagin V V Zakharov and T D Rostova Met Sci Heat

Treat 1992 (1) 37ndash45

159 H Wiik Siv Ing thesis NTH Institute of Metallurgy

Trondheim Norway 1995

160 J Roslashyset H Hovland and N Ryum Mater Sci Forum 2002

396ndash402 619ndash624

161 Y Miura K Horikawa K Yamada and M Nakayama Proc

4th Int Conf on lsquoAluminium alloysrsquo Vol II Atlanta GA USA

September 1994 161ndash168

162 Y W Riddle PhD thesis Georgia Tech GA USA 2000

163 B Forbord W Lefebvre F Danoix H Hallem and

K Marthinsen Scripta Mater 2004 51 333ndash337

164 J D Robson Acta Mater 2004 52 1409ndash1421

165 C B Fuller J L Murray and D N Seidman submitted to Acta

Mater 2004

166 M G Mousavi C E Cross and Oslash Grong Sci Technol Weld

Joining 1999 4 381ndash388

167 J S Vetrano S M Bruemmer L M Pawlowski and I M

Robertson Mater Sci Eng 1997 A 238 101ndash107

168 Y W Riddle and T H Sanders Jr Mater Sci Forum 2000

331ndash337 799ndash803

169 G M Khan A O Nikiforov V V Zakharov and I I Novikov

Tsvetnye Metally 1993 34 (11) 43ndash45

170 Z Horita M Furukawa M Nemoto A J Barnes and T G

Langdon Acta Mater 2000 48 3633ndash3640

171 L A Willey US Patent 3 619 181 9 November 1971

172 L K Lamikhov and G V Samsonov Tsvetnye Metally 1964 5

(8) 77ndash80

173 A L Berezina K V Chuistov N I Kolobnev L B

Khokhlatova and T A Monastyrskaya Mater Sci Forum

2002 396ndash402 741ndash746

174 F A Fasoyinu J Thomson D Cousineau T Castles and M

Sahoo Proc 6th Int AFS Conf on lsquoMolten aluminum

processingrsquo Orlando FL USA November 2001

175 Z Yin Q Pan Y Zhang and F Jiang Mater Sci Eng 2000

A 280 151ndash155

176 I I Novikov and O E Grushko Mater Sci Technol 1995 11

926ndash932

177 D Cousineau M Sahoo P D Newcombe T Castles and F A

Fasoyinu Proc lsquoAFS 105th casting congressrsquo Dallas TX USA

AprilndashMay 2001 157ndash184

178 C E Cross and Oslash Grong Proc 6th Int Conf on lsquoAluminum

alloysrsquo Toyohashi Japan July 1998 1441ndash1446

179 F A Costello J D Robson and P B Prangnell Mater Sci

Forum 2002 396ndash402 757ndash762

180 K B Hyde A F Norman and P B Prangnell Mater Sci

Forum 2002 396ndash402 39ndash44

181 M E Drits S G Pavlenko L S Toropova Yu G Bukov and

L B Ber Sov Phys Dokl 1981 26 (3) 344ndash346

182 A M Drits and B A Kopeliovich Russ Metall 1985 (4) 147ndash

151

183 V G Davydov V I Elagin V V Zakharov and T D Rostova

Met Sci Heat Treat 1996 (8) 347ndash352

184 M E Drits L S Toropova Yu G Bykov L B Ber and S G

Pavlenko Russ Metall 1982 (1) 148ndash152

185 T D Rostova V G Davydov V I Yelagin and V V Zakharov

Mater Sci Forum 2000 331ndash337 793ndash798

186 Y W Riddle H Hallem and N Ryum Mater Sci Forum 2002

396ndash402 563ndash568

187 J Roslashyset and Y W Riddle Proc 9th Int Conf on lsquoAluminium

alloysrsquo Brisbane Australia August 2004 1210ndash1215

188 A M Diskin V K Portnoi A M Drits and A A Alalykin Sov

Non-Ferrous Met Res 1986 14 499ndash500

189 R R Sawtell P E Bretz and C L Jensen US Patent 4 689 090

25 August 1987

190 G A Salishchev Yu B Timoshenko and R A Saitova Proc

Second Int Conf on lsquoAluminium alloysrsquo Beijing China October

1990 413ndash415

191 T G Nieh R Kaibyshev L M Hsiung N Nguyen and

J Wadsworth Scripta Mater 1997 36 1011ndash1016

192 T G Nieh L M Hsiung J Wadsworth and R Kaibyshev Acta

Mater 1998 46 2789ndash2800

193 J S Vetrano C H Henager Jr M T Smith and S M

Bruemmer in lsquoHot deformation of aluminum alloys IIrsquo (ed T R

Bieler L A Lalli and S R MacEwen) 407ndash418 1998 TMS

194 J S Vetrano C H Henager Jr S M Bruemmer Y Ge and

C H Hamilton in lsquoSuperplasticity and Superplastic Forming

1998rsquo (ed A K Gosh and T R Bieler) 89ndash97 1998 TMS

195 V Y Gertsman J S Vetrano C H Henager Jr and S M

Bruemmer Proc First Joint Int Conf on lsquoRecrystallization and

grain growthrsquo Aachen Germany August 2001 Springer Verlag

2001 837ndash842

196 Y Xiao C Gao H Ma and S Tian Trans Nonferrous Met Soc

China 2001 11 235ndash238

Roslashyset and Ryum Scandium in aluminium alloys

42 International Materials Reviews 2005 VOL 50 NO 1

197 A Gholinia F J Humphreys and P B Prangnell Acta Mater

2002 50 4461ndash4476

198 A Gholinia F J Humphreys and P B Prangnell Mater Sci

Forum 2002 408ndash412 1519ndash1524

199 S Komura P B Berbon M Furukawa Z Horita M Nemoto

and T G Langdon Scripta Mater 1998 38 1851ndash1856

200 S Komura P B Berbon A Utsunomiya M Furukawa

Z Horita M Nemoto and T G Langdon in lsquoHot deformation

of aluminum alloys IIrsquo (ed T R Bieler L A Lalli and S R

MacEwen) 125ndash138 1998 TMS

201 S Komura Z Horita M Furukawa M Nemoto and T G

Langdon J Mater Res 2000 15 2571ndash2576

202 S Komura M Furukawa Z Horita M Nemoto and T G

Langdon Mater Sci Eng 2001 A 297 111ndash118

203 S Komura Z Horita M Furukawa M Nemoto and T G

Langdon Metall Mater Trans A 2001 32A 707ndash716

204 Z Horita M Furukawa K Oh-ishi M Nemoto and T G

Langdon Proc Fourth Int Conf on lsquoRecrystallization and

related phenomenarsquo (ed T Sakai and H G Suzuki) 1999 The

Japan Institute of Metals 301ndash308

205 Z Horita S Komura P B Berbon A Utsunomiya

M Furukawa M Nemoto and T G Langdon Mater Sci

Forum 1999 304ndash306 91ndash96

206 Z Horita S Lee S Ota K Neishi and T G Langdon Mater

Sci Forum 2001 357ndash359 471ndash476

207 Z Horita T Fujinami K Sato S B Kang H W Kim and T G

Langdon in Proc James T Staley Honorary Symposium on

Aluminum Alloys lsquoAdvances in the metallurgy of aluminum

alloysrsquo (ed M Tiryakioglu) 271ndash275 2001 ASM

208 P B Berbon S Komura A Utsunomiya Z Horita

M Furukawa M Nemoto and T G Langdon Mater Trans

JIM 1999 40 772ndash778

209 M Nemoto Z Horita M Furukawa and T G Langdon Mater

Sci Forum 1999 304ndash306 59ndash66

210 M Furukawa Z Horita M Nemeto and T G Langdon Proc

lsquoLight Metals 1999rsquo Quebec City PQ Canada August 1999 583ndash

592

211 M Furukawa K Oh-ishi S Komura A Yamashita Z Horita

M Nemeto and T G Langdon Mater Sci Forum 1999 304ndash

306 97ndash102

212 M Furukawa A Utsunomiya K Matsubara Z Horita and

T G Langdon Acta Mater 2001 49 3829ndash3838

213 M Furukawa A Utsunomiya S Komura Z Horita M Nemoto

and T G Langdon Mater Sci Forum 2001 357ndash359 431ndash436

214 M Furukawa Z Horita and T G Langdon in Proc James T

Staley Honorary Symposium on Aluminum Alloys lsquoAdvances in

the metallurgy of aluminum alloysrsquo (ed M Tiryakioglu) 47ndash56

2001 ASM

215 M Furukawa Z Horita M Nemoto and T G Langdon Mater

Sci Eng 2002 A 324 82ndash89

216 M Furukawa Z Horita and T G Langdon in lsquoUltrafine grained

materials IIrsquo (ed Y T Zhu T G Langdon R S Mishra S L

Semiatin M J Saran and T C Lowe) 459ndash468 2002 TMS

217 T G Langdon M Furukawa Z Horita and M Nemoto Proc

NATO Advanced Research Workshop on lsquoInvestigations and

applications of severe plastic deformationrsquo Moscow August

1999 NATO Science Series Series 3 High Technology vol 80

Kluwer Academic Publishers The Netherlands 2000 149ndash154

218 S Lee H Akamatsu A Utsunomiya K Neishi M Furukawa

Z Horita and T G Langdon Proc Thermec 2000 Las Vegas

USA December 2000

219 S Lee A Utsunomiya H Akamatsu K Neishi M Furukawa

Z Horita and T G Langdon Acta Mater 2002 50 553ndash564

220 A Yamashita D Yamaguchi Z Horita and T G Langdon

Mater Sci Eng 2000 A 287 100ndash106

221 K Oh-ishi Z Horita D J Smith and T G Langdon J Mater

Res 2001 16 583ndash589

222 H Akamatsu T Fujinami Z Horita and T G Langdon Scripta

Mater 2001 44 759ndash764

223 S Ota H Akamatsu K Neishi M Furukawa Z Horita and

T G Langdon Mater Trans 2002 43 2364ndash2369

224 K Furuno H Akamatsu K Oh-ishi M Furukawa Z Horita

and T G Langdon Acta Mater 2004 52 2497ndash2507

225 I N Fridlyander O G Senatorova N A Ryazanova and A O

Nikiforov Mater Sci Forum 1994 170ndash172 345ndash349

226 J N Fridlyander and O G Senatorova Mater Sci Forum 1996

217ndash222 1813ndash1818

227 J Liu and D J Chakrabarti Acta Mater 1996 44 4647ndash4661

228 O G Senatorova A N Uksusnikov J N Fridlyander

J Koshorst R R Romanova N A Ryazanova A Galliot

and V V Cherkassov Proc 6th Int Conf on lsquoAluminum alloysrsquo

July 1998 Toyohashi Japan 589ndash593

229 R A Emigh E L Bradley and J W Morris Jr in

lsquoSuperplasticity in aerospace IIrsquo (ed T R McNelley and H C

Heikkenen) 303ndash315 1990 TMS

230 E L Bradley III R A Emigh and J W Morris Jr Scripta

Metall Mater 1991 25 717ndash721

231 N I Kolobnev L B Khokhlatova V D Makarov E Yu

Semenova and V V Redchits Proc Sixth Int Aluminiumndash

Lithium Conference Garmisch-Partenkirchen Germany October

1991 1053ndash1056

232 N K Tsenev R Z Valiev O V Obraztsov and I N Fridlander

Proc Sixth Int AluminiumndashLithium Conference Garmisch-

Partenkirchen Germany October 1991 1125ndash1132

233 A M Shammazov N K Tsenev R Z Valiev M M

Myshlyaev M M Bikbulatov and S P Lebedich Phys Met

Metall 2000 89 (3) 314ndash318

234 F Musin R Kaibyshev Y Motohashi T Sakuma and G Itoh

Mater Trans A 2002 43A 2370ndash2377

235 M Shagiev Y Motohashi F Musin R Kaibyshev and G Itoh

Mater Trans A 2003 44A 1694ndash1697

236 M Shagiev Y Motohashi F Musin R Kaibyshev and G Itoh

Mater Trans A 2003 44A 1698ndash1701

237 B A Parker and Z F Zhou Proc 3rd Int Conf on lsquoAluminium

alloysrsquo Vol I NTH Trondheim Norway June 1992 363ndash367

238 J R Davies lsquoASM specialty handbook aluminum and aluminum

alloysrsquo 1993 Materials Park OH USA ASM

239 S J Andersen H W Zandbergen J Jansen C Traeholt

U Tundal and O Reiso Acta Mater 1998 46 3283ndash3298

240 M L Kharakterova D G Eskin and L L Rokhlin Russ

Metall 1997 (1) 104ndash109

241 J Roslashyset Dr Ing thesis NTNU Trondheim Norway 2002

242 P P Chattopadhyay S Datta and M K Banerjee Mater Sci

Eng 2002 A 333 67ndash71

243 L I Kaigorodova E I Selnikhina E A Tkachenko and O G

Senatorova Phys Met Metall 1996 81 513ndash519

244 Y-L Wu F H Froes C Li and A Alvarez Metall Mater

Trans A 1999 30A 1017ndash1024

245 Z Yin L Yang Q Pan and F Jiang Trans Nonferrous Met

Soc China 2001 11 822ndash825

246 V I Elagin V V Zakharov and T D Rostova Met Sci Heat

Treat 1994 36 (7) 375ndash380

247 Y V Milman A I Sirko D V Lotsko O N Senkov and D B

Miracle Mater Sci Forum 2002 396ndash402 1217ndash1222

248 C-H Joh K Yamada and Y Miura Mater Trans JIM 1999

40 439ndash442

249 X J Jiang Q H Gui Y Y Li L M Ma G J Liang and C X

Shi Scr Metall Mater 1993 29 211ndash216

250 X J Jiang Y Y Li W Deng L Y Xiong W M Wu Y J Gao

and C X Shi Adv Cryogenic Eng (Mater) 1994 40 1369ndash

1376

251 C-H Joh T Katsube K Yamada and Y Miura Proc 6th Int

Conf on lsquoAluminum alloysrsquo Toyohashi Japan July 1998 799ndash

804

252 L I Kaygorodova A M Dritz T V Krymova and I N

Fridlyander Proc Sixth Int AluminiumndashLithium Conference

Garmisch-Partenkirchen Germany October 1991 363ndash367

253 L I Kaigorodova A M Drits Ya V Zhingel T V Krymova

and I N Fridlyander Phys Met Metall 1992 73 286ndash290

254 A L Berezina V A Volkov S V Ivanov N I Kolobnev and

K V Chuistov Phys Met Metall 1991 71 (2) 167ndash175

255 I N Fridlyander N I Kolobnev A L Berezina and K V

Chuistov Proc Sixth Int AluminiumndashLithium Conference

Garmisch-Partenkirchen Germany October 1991 107ndash112

256 L I Kaigorodova A M Drits Ya V Zhingel T V Krymova

and V A Rassokhin Phys Met Metall 1992 73 281ndash285

257 I N Fridlyander S F Danilov E N Malysheva T A

Gorokhova and N N Kirkina Proc Sixth Int Aluminiumndash

Lithium Conference Garmisch-Partenkirchen Germany October

1991 381ndash386

258 G Dlubek S Krause H Krause A L Beresina V S

Mikhalenkov and K V Chuistov J Phys Condens Matter

1992 4 6317ndash6328

259 S Krause H Krause G Dlubek A L Beresina and K S

Chuistov Mater Sci Forum 1992 105ndash110 1109ndash1112

260 C Y Tan Z Q Zheng and S Q Liang Proc 4th Int Conf on

lsquoAluminium alloysrsquo Vol II Atlanta GA USA September 1994

329ndash333

261 A L Beresina N I Kolobnev K V Chuistov A V Kotko and

O A Molebny Mater Sci Forum 2002 396ndash402 977ndash981

Roslashyset and Ryum Scandium in aluminium alloys

International Materials Reviews 2005 VOL 50 NO 1 43

262 I N Ganiev I Yunusov and V V Krasnoyarskii J Appl Chem

USSR 1986 60 1961ndash1965

263 I N Ganiev Prot Met 1995 31 543ndash546

264 N V Vyazovikina Prot Met 1999 35 448ndash453

265 G V Kharina and V P Kochergin Prot Met 1996 32 134ndash

136

266 G V Kharina M V Kuznetsov and V P Kochergin Russ J

Electrochem 1998 34 482ndash485

267 V S Sinyavskii V D Valrsquokov and E V Titkova Prot Met

1998 34 549ndash555

268 Y L Wu F H Froes C G Li and J Liu Proc lsquoSynthesis

processing of lightweight metallic materials IIrsquo Orlando FL

USA February 1997 73ndash81

269 Z Ahmad and B J Abdul-Aleem Proc EuroCorr 2000

270 Z Ahmad A Ul-Hamid and B J Abdul-Aleem Corros Sci

2001 43 1227ndash1243

271 R Braun B Lenczowski and G Tempus Mater Sci Forum

2000 331ndash337 1647ndash1652

272 T Torma E Kovacs-Csetenyi L Vitalis I Vitanyi

J Stepanov and M Butova Mater Sci Forum 1987 1314

497ndash503

273 Z Wang P Wang K S Kumar and C L Briant in lsquoChemistry

and electrochemistry of corrosion and stress corrosion crackingrsquo

(ed R H Jones) 573ndash582 2001 TMS

274 V I Elagin V V Zakharov A A Petrova and E V

Vyshegorodtseva Russ Metall 1983 (4) 143ndash146

Roslashyset and Ryum Scandium in aluminium alloys

44 International Materials Reviews 2005 VOL 50 NO 1

Page 18: Scandium in aluminium alloys - Atom probe · A considerable part of the available literature on scandium in aluminium alloys is reviewed. ... behaviour in Al Cu, Al Mg Si,

coherent dispersoids were observed to dissolve at therecrystallisation front and re-precipitate as smallercoherent Al3Sc cuboids

Superplastic forming

It seems that the first publication on superplasticproperties of Sc-containing Al-alloys was a study of anAlndash35Cundash14Mgndash045Mnndash04(SczZr) alloy188

It was recognised that the superplastic properties are aresult of the stabilisation of the fine grain structure byAl3Sc dispersoids The Sc-containing Al alloys that havereceived most attention for their superplastic propertieshowever are those of the AlndashMgndashSc system which wasfirst published in a patent189 Here it was noted that anAlndash4 wt-Mgndash05 wt-Sc alloy had superior superplasticproperties compared to fine-grained 7475 (AlndashZnndashMgndashCu alloy) Binary Alndash05 wt-Sc and Alndash4 wt-Mgalloys did not behave superplastically The flow stress atthe hot forming temperature was found to be much (30ndash40) lower in the ternary alloy than that of the twobinary alloys

The superplastic properties of AlndashMgndashSc alloys havebeen explored by several research groups over the lastdecade190ndash196 It has frequently been found that thedeformation mechanism is dominated by grain bound-ary sliding190 However it has also been reported thatAlndashMgndashSc alloy may deform superplastically withoutnoticeable grain boundary sliding23 It is generallyrecognised that the grain boundary sliding mechanismis facilitated when the average grain size is very smalland grain boundaries are predominantly high-angleSuch a microstructure may be achieved by carefulthermomechanical processing of the starting mate-rial193194197198 It has however been shown that a finegrained structure with high angle boundaries maydevelop during superplastic forming of AlndashMgndashSc alloyseven if the starting microstructure is an entirely differentone for instance that of a cold rolled sheet192 It has alsobeen suggested that superplastic forming of as castmaterial may be possible189

One of the more efficient thermomechanical processesfor achieving an ultrafine grain structure with high anglegrain boundaries in Al-alloys is equal channel angularpressing (ECAP) A JapanesendashAmerican group ofscientists has published an impressive body of researchon improvements in superplastic properties in Al-alloys processed by ECAP over the last few years andseveral of the publications are from investigations onAlndashMgndashSc alloys170199ndash224 Maximum strains in excessof 2000 at a strain rate of 0033 s21 have beenachieved170201202217 which is an extraordinarily goodcombination of high strain and high strain rate for analuminium alloy

Superplastic properties of AlndashCundashMg(ndashMn)ndashSc(ndashZr)and AlndashMgndashSc(ndashZr) alloys have been mentionedNoticeable superplasticity in other Sc-containing Al-alloys has also been reported such as AlndashZnndashMg(ndashCu)ndashScndashZr169225ndash228 AlndashLindashSc229 AlndashMgndashLindashScndashZr229ndash234

AlndashLindashMgndashCundashScndashZr235236 and AlndashCundashLindashScndashZr233

Precipitation hardeningHardening by Al3Sc precipitates

It has been noted that when Al3Sc particles precipitate inthe temperature range 250ndash350uC they give a significanthardness increase in the alloy Some authors point out

that Sc is a more effective precipitation hardening elementper atomic fraction added than the elements that arecommonly used for precipitation hardening121130 (In onepaper29 it is claimed that only Au has a strongerstrengthening effect than Sc) However the amount ofSc that can be precipitated from supersaturated solidsolution is rather limited and thus the absolute values ofthe hardness increase from the precipitation hardening ismuch lower than what is normally associated withprecipitation hardened alloys Also the temperatureregime for age hardening by precipitation of Al3Sc issomewhere in between the temperature regimes for agehardening and solution heat treatments of commonprecipitation hardened alloys This makes a combinedprecipitation of Al3Sc and other strengthening precipi-tates unfeasible Thus precipitation strengthening byAl3Sc is most feasible in alloy systems that are non-heat-treatable The non-heat-treatable aluminium alloy sys-tems are according to the Aluminum Associationdesignations the 1xxx series (99 pure Al) the 3xxxseries (AlndashMn) and the 5xxx series (AlndashMg) The purposeof adding Sc to these alloys may be either to stabilise themicrostructure of wrought semiproducts (extrusionsrolled plates forgings etc) as discussed in the sectionon lsquoRecrystallisation resistancersquo above or to provideextra strength to the alloy through precipitation hard-ening In the latter case it is appropriate to considerwhether the Sc-containing alloy still should be classifiedas non-heat-treatable A heat treatment is applied thatbrings about a significant precipitation hardening On theother hand the hardness increase that is achieved throughthe heat treatment is lower than what is normallyassociated with heat-treatable alloy systems Hence eventhough it seems like a contradiction one chooses to keepusing the term lsquonon-heat-treatablersquo about these alloys

Table 7 gives an overview of some mechanicalproperties of Sc-containing non-heat-treatable alloysthat are reported in the literature Most of theexperimental work on Sc in 1xxx-types of alloys hasbeen done on binary AlndashSc alloys with much higherpurity than industrial alloys

Strengthening mechanisms

When the precipitates are larger than a critical size thestrengthening effect is due to the Orowan-mechanism iedislocations can only pass the precipitates by looping Inthis case the strengthening effect of the particles isapproximately inversely proportional to the mean parti-cle spacing When the precipitates can be sheared bydislocations there are a number of strengthening mechan-isms that apply It is proposed by Parker et al108 that thetwo major contributing mechanisms are coherency strainand anti-phase-boundary energy In a recent detailedstudy of strengthening mechanisms in binary AlndashSc alloysby Marquis and colleagues117118 the strengthening fromshear modulus mismatch between the matrix and theprecipitates is also accounted for A qualitatively goodmatch between theoretical strengthening and measuredvalues is achieved in this work both for deformation atroom temperature and at 300uC

Effect of Sc on precipitation strengthening in heat-treatablealloys

Following the AA designation system the traditionalheat-treatable Al-alloys are those that belong to the 2xxx

Roslashyset and Ryum Scandium in aluminium alloys

36 International Materials Reviews 2005 VOL 50 NO 1

series (AlndashCu) 6xxx series (AlndashMgndashSi) and 7xxx series(AlndashZnndashMg) AlndashLi alloys should also be mentionedSeveral investigations have been carried out in order toclarify the effects of Sc on the precipitation behaviour inthese alloy systems

AlndashCu alloys

The precipitation sequence in AlndashCu alloys is oftendescribed as follows

Supersaturated solid solutionRGP-zonesRh0Rh9Rh(Al2Cu)

The highest strength is normally achieved when the h0or h9 precipitates are predominant Typical precipitationheat treatment temperatures for AlndashCu alloys are in therange 160ndash190uC238 which is considerably lower thanthe typical precipitation temperature for Al3ScComparisons of the aging responses of AlndashCu and AlndashCundashSc alloys at 150 and 200uC indicate that there is nonoticeable effect of Sc on the precipitation kinetics ofh9153 It is observed that the h9 precipitates may nucleateon Al3Sc particles153 At 300uC it is observed that h9particles are somewhat smaller in AlndashCundashSc alloys thanin AlndashCu alloys156

AlndashMgndashSi alloys

The following precipitation sequence is commonlyreported for AlndashMgndashSi alloys

Supersaturated solid solutionRGP-zonesRb0Rb9Rb(Mg2Si)

For peak aged alloys the predominant precipitatetype is b0 for which the stoichiometric composition hasrecently been resolved to be Mg5Si6239 Temperatures inthe range 160ndash205uC are typically used for precipitationhardening of these alloys238 Adding both 03 wt-Scand 01 wt-Zr to an Alndash06 wt-Mgndash065 wt-Sialloy does not seem to alter the precipitation kineticsof b0 at 165uC However the hardness increase becauseof precipitation hardening appears to be smaller in theSczZr-containing alloy240 In another investigationadditions of 01 wt-Sc 015 wt-Sc 02 wt-Sc04 wt-Sc and 02 wt-Scz01 wt-Zr were made toan Alndash08 wt-Mgndash07 wt-Si alloy241 Here it wasalso observed that the precipitation kinetics of b0 wasseemingly independent of the Sc additions (Fig 28)TEM observations indicated that the b0 precipitateswere of comparable sizes in the investigated alloys andno interactions between Al3Sc and b0 were observed(Fig 29) In a third study242 where the effect of Sc onthe precipitation in an AlMgSindashSiC metal matrixcomposite was investigated there also does not seemto be any effect on the precipitation kinetics Howevercontrary to the findings of Ref 240 it is reported thatthe Sc addition leads to a higher hardness increase thanin the corresponding Sc free alloy

AlndashMgndashZn alloys

For these alloys the following precipitation sequence isoften ascribed

Table 7 Mechanical properties in non-heat-treatable Al-alloys with Sc

Reference Alloy wt- YS MPa UTS MPa Note

1xxx alloys171 000Sc 15 48 Cast material aged 288uC8 h

023Sc 159 185 Cast material aged 288uC8 h038Sc 199 220 Cast material aged 288uC8 h000Sc 14 49 Cold rolled material (89) aged 288uC8 h023Sc 198 208 Cold rolled material (89) aged 288uC8 h038Sc 240 264 Cold rolled material (89) aged 288uC8 h000Sc 8 34 Cold rolled material quenched from 649uC aged 288uC8 h023Sc 147 157 Cold rolled material quenched from 649uC aged 288uC8 h038Sc 193 199 Cold rolled material quenched from 649uC aged 288uC8 h

121 05Sc 160 ndash Forged material quenched from 635uC aged 250uC50 h23 05Sc 298 319 Hot rolled 288uC cold rolled 69ndash81 aged 288uC4 h112 01Sc 132 166 Hot z cold rolled material quenched from 630uC

aged 320uC133 h148 02Sc 138 ndash Cast material aged 300uC10 h compression test159 04Sc 196 ndash Cast material aged 300uC10 h compression test117 118 03Sc 209 ndash Cast material quenched from 648uC aged 300uC5 h

compression test3xxx alloys171 1Mn 015Sc 216 221 Cold rolled material (89) aged 288uC8 h

1Mn 05Sc 309 323 Cold rolled material (89) aged 288uC8 h186 05Mn 02Mg

026Sc 015Zr162 201 Extruded material solutionised 600uC aged 250uC

5xxx alloys171 1Mg 43 111 Cold rolled material (89) aged 288uC8 h

1Mg 03Sc 288 303 Cold rolled material (89) aged 288uC8 h53Mg 147 259 Cold rolled material (50) wintermediate anneals

at 343uC aged 288uC8 h53Mg 03Sc 368 401 Cold rolled material (50) wintermediate anneals

at 343uC aged 288uC8 h23 2Mg 05Sc 376 401 Hot rolled 288uC cold rolled 69ndash81 aged 288uC4 h

4Mg 05Sc 414 4606Mg 05Sc 433 503

237 4Mg 1Sc 420 525 Cold rolled material (83) aged 320uC1 h148 4Mg 02Sc 194 ndash Cast material aged 300uC10 h compression test

Tensile test data except where noted YS yield strength UTS ultimate tensile strength

Roslashyset and Ryum Scandium in aluminium alloys

International Materials Reviews 2005 VOL 50 NO 1 37

Supersaturated solid solutionRGP-zonesRg9Rg(Zn2Mg)

The maximum hardness is normally achieved whenthe g9 precipitates are predominant Common precipita-tion hardening temperatures are in the range 95ndash180uCand a two-step precipitation heat treatment within thistemperature regime is often used238 It has beenobserved in some investigations that Sc and SczZradditions to AlndashMgndashZn alloys slow down the precipita-tion of g9 somewhat243 Other investigations find thatthere is no effect of Sc on the precipitation behaviour ofg9244245 and yet others report that Sc additionssignificantly speed up the precipitation of g9246 In Ref247 it is found that an Sc addition leads to coarser g9precipitates and it is claimed that this gives an improvedductility of the alloy The strength-loss associated withlarger particle size is reported to be counterbalanced bystrengthening from Al3Sc precipitates

AlndashLi alloys

The precipitation sequence in binary AlndashLi alloys isapparently simple

Supersaturated solid solutionRd9Rd (AlLi)

where d9 is the metastable Al3Li phase which just likeAl3Sc has the L12 type of atomic arrangement Thetypical temperature regime for precipitation of d9 whichis the strengthening phase in this system is approx 150ndash200uC A comparison of the age hardening response ofan Alndash26 wt-Li and an Alndash24 wt-Lindash019 wt-Scalloy at 180uC248 and 200uC161 indicates that the onsetof d9 precipitation is not altered by the presence of ScThe hardness curves for the two alloys are practicallyidentical at 200uC whereas at 180uC the peak hardnesslevel is slightly higher in the AlndashLi than the AlndashLindashScalloy DSC measurements at constant heating ratesindicate that the addition of Sc to an AlndashLi alloysincreases the activation energy for d9 precipitation andmoves the exothermic peak associated with d9 precipita-tion to a higher temperature248 For specimens aged at

either 180uC or 200uC TEM observations reveal that thed9 precipitates are much smaller in the Sc containingalloy than in binary AlndashLi both in the peak agedcondition and in the overaged condition161248 Additionof Sc has also been observed to reduce the size of d9precipitates in other AlndashLi based alloys249ndash251 In an AlndashLindashCundashZr alloy an addition of Sc has been reported toslow down the homogeneous precipitation of d9252253 Ithas been claimed that Sc reduces the quench sensitivityand delays room temperature aging of AlndashLi basedalloys254ndash256

When present in the microstructure before the pre-cipitation of d9 the Al3Sc precipitates may act as effec-tive nucleation sites for d9 The resulting precipitates arespheres of d9 with a core of Al3Sc161249252ndash255257ndash261

Corrosion resistanceAn appreciable amount of data is available on the effectsof Sc on the corrosion behaviour of wrought Al-alloysSome of these effects are apparently derived from theeffects of Sc on the microstructure of the alloys It hasbeen reported that an addition of Sc increases thecorrosion potential (makes it less negative) in pureAl262ndash264 in AlndashZn alloys265266 AlndashMg alloys267 AlndashZnndashMgndashCu alloys264268 AlndashCundashMgndashMn alloys264 andin AlndashCundashLindashMgndashAg alloys264 Even though Sc alsohas been reported to decrease the corrosion potential in

28 Age hardening response at 175uC for Alndash08 wt-Mgndash

07 wt-Si alloy (Base) with additions of 02 wt-Sc

04 wt-Sc and 02 wt-Scz01 wt-Zr from Ref 241

29 TEM images of a b0 precipitates in Alndash08 wt-Mgndash

07 wt-Si alloy and b b0 and Al3(Sc1ndashxZrx) in a similar

alloy with addition of 02 wt-Scz01 wt-Zr from

Ref 241

Roslashyset and Ryum Scandium in aluminium alloys

38 International Materials Reviews 2005 VOL 50 NO 1

AlndashMg alloys269270 it seems that the general trend isthat adding Sc to an alloy makes it slightly more nobleThe change in corrosion potential is much morepronounced when Sc is added in amounts larger thanthe eutectic composition263 ie there is a considerablecontribution from primary or eutectic Al3Sc to theoverall potential It has also been demonstrated that thechange in corrosion potential caused by Sc can dependon the heat treatment applied to the alloy267268

Even though the corrosion potential is an essentialparameter in establishing the corrosion behaviour of analloy an increase in the corrosion potential does notnecessarily imply an improved self-corrosion resistanceHowever measurements of corrosion rates and passiva-tion current densities strongly suggest that the self-corrosion resistance in general is considerably improvedwhen Sc is added to wrought Al-alloys263264267 Someobserved variations in corrosion potential and passiva-tion current densities with Sc content in binary AlndashScalloys are plotted in Fig 30

Material failure in corrosive environments is often dueto localised corrosion attacks which may propagaterapidly even though the bulk material has a goodresistance against general corrosion It has been pointedout that hypereutectic additions of Sc may lead tomicrogalvanic corrosion beside primary Al3Sc parti-cles264 In AlndashMg alloys grain boundary precipitation ofAl8Mg5 can lead to localised corrosion attacks such asintergranular corrosion (IGC) exfoliation corrosion(EC) and stress corrosion cracking (SCC) In wroughtmaterial such precipitation may occur in the 60ndash180uCtemperature regime and heating in this temperaturerange is referred to as lsquosensitationrsquo An AlndashMgndashSc alloywas found to be immune against intergranular corrosionand have moderate susceptibility to exfoliation corro-sion after annealing at 350uC271 After sensitation heattreatments severe IGC and EC was observed but notquite as severe as in a corresponding alloy without ScAs for SCC the AlndashMgndashSc alloy was found to be highlyresistant271 In another study it was found that additionof 056 wt-Sc reduces the SCC susceptibility of an Alndash68 wt-Mg alloy in the as-rolled state and afterannealing at 250uC whereas in a sensitised specimenthe SCC susceptibility is somewhat increased by the Scaddition272 A third investigation found that Sc has nomeasurable detrimental effect on the SCC susceptibilityof sensitised Alndash5Mgndash015Zr alloy273 SCC is also a

severe problem in high strength AlndashZnndashMgndashCu alloys Ithas been shown that small Sc additions are effective inreducing the SCC sensitivity of these alloys244246268274

Use of Sc-containing Al alloysA systematic development of Sc-containing aluminiumalloys took place in the former USSR in the 1980s andthe interest for Sc as an alloying element in aluminiumalloys hit the western world approximately 10 yearslater Even though a number of improvements in Alalloys achieved by Sc addition have been demonstratedthe current uses of such alloys are very limited This isrelated to the very high price of scandium

In Russia some parts of military aircraft are made ofSc-containing AlndashLi alloys In the western world themain usage of Sc-containing alloys is for sportsequipment Ashurst Technology and Kaiser Aluminumdeveloped a Sc-containing 7xxx alloy for baseball andsoftball bats which was introduced to the Americanmarket in 1997 by Easton Alcoa soon followed with aSc-containing alloy for a competing brand of batsLouisville Slugger Since then several new and improvedSc-containing alloys for bats have been introduced tothe market The purpose of adding Sc is to increase theyield strength of the alloy allowing for a down-gaugingof the wall thickness which in turn gives a strongerlsquospring-rsquo or lsquotrampoline-rsquo effect when the ball hits thebat

Shortly after the introduction of the Sc containingbats Easton also launched Sc-containing 7xxx tubingfor bicycle frames Just as in the bats Sc increases theyield strength of the alloy allowing for down-gauging oftube wall thickness and a corresponding weight reduc-tion of the bicycle frame An Italian manufacturer ofbicycle tubing Dedacciai also delivers tubes in a Sc-containing 7xxx alloy

Other sports equipment made from Sc-containingaluminium alloys includes lacrosse sticks and tent polesSmith and Wesson has also introduced a series ofhandguns where the frame is made from a Sc-containingAl alloy

A common factor for the items mentioned above isthat the material cost is only a minor part of the totalmanufacturing cost of the end product and also thatthese products are aimed at a group of customers thathave a certain awareness of new materials Both baseballbats and bicycle frames have been marketed aslsquoscandium alloyrsquo even though the Sc content is muchlower than 1

Currently AlndashSc master alloys for the production ofSc-containing Al alloys are available at a price thatcorresponds to US$ 2000 per kg of Sc This means that ifone wants to add 02 wt-Sc to an alloy which is afairly common content one also increases the price ofthe alloy by US$ 4 per kg alloy Depending on the alloytype Sc is added to this represents a tripling orquadrupling of the price of the alloy There are notmany existing products where such an increase inmaterial cost can be justified In order to see awidespread use of Sc in high-volume products the Scprice has to come down considerably Actually the priceof adding Sc to Al alloys has gone down by a factor 3ndash10over the last 10ndash15 years and substantial price reduc-tions are also expected in the future

30 Observed variations in corrosion potential and passi-

vation current densities with Sc content in binary Alndash

Sc alloys based on data from Ref 263

Roslashyset and Ryum Scandium in aluminium alloys

International Materials Reviews 2005 VOL 50 NO 1 39

The current production of AlndashSc master alloys isbased upon and will continue to be based upon for theforeseeable future the reduction of Sc2O3 or other Sccompounds directly in molten aluminium It is notnecessary as many tend to believe to take the route viametallic Sc Thus the price of AlndashSc master alloy isgoverned by the price of Sc2O3 or other Sc compoundsin question and not by the price of metallic scandiumThe Sc2O3 which is the main source for todayrsquos AlndashScmaster alloy production comes from stockpiles in theformer USSR These stockpiles will be exhausted withina few years and new reliable sources of Sc2O3 or otherSc compound production are sought It turns out thatthe most economically viable option that has beendisclosed so far is the processing of Red Mud from theBayer process of extracting alumina from bauxiteScandium is enriched in the Red Mud and is extractedfrom a Red Mud aqueous slurry by selective leachingsubsequent ion-exchange procedure and finally a liquidndashliquid extraction procedure It is not required to build aseparate lsquoSc factoryrsquo to do this but rather build an lsquoadd-onrsquo to existing Bayer process plants Such a processroute is expected to bring down the price of Sc2O3

considerably which in turn means that AlndashSc masteralloy price should drop accordingly Preliminary ana-lyses suggest a price of approx US$ 400 per kg Sc in themaster alloy which translates to an added cost of 80cent per kilo when 02 wt-Sc is added to an aluminiumalloy This is also a considerable increase in the materialcost but with such prices one should expect to see Sccontaining alloys in many more applications than whatis the case at the present time

Concluding remarksThe body of published investigations on Al-based alloyswith Sc addition provides a sound basis of knowledgefor metallurgists that want to look into the possibility ofenhancing the performance of a wrought Al-alloy byadding Sc to it Ternary AlndashScndashX phase diagrams areavailable for practically every technologically importantalloying element in Al The effect of a wide range ofternary alloying elements on the precipitation behaviourof Al3Sc is accounted for It has been shown that theAl3Sc phase can be effective as a grain refiner adispersoid former and a precipitate hardening agentand some of the underlying conditions for achieving thedesired Al3Sc formation have been outlined Addingsome Zr together with Sc has proven to be beneficial Itmay lead to effective grain refinement at a lower Sc levelbut the most prominent effect is the refinement indispersoid distribution that can be achieved An addi-tion of Sc has little if any effect on precipitation in the2xxx 6xxx and 7xxx alloy systems and some effects onthe precipitation in AlndashLi based alloys With respect tocorrosion behaviour adding Sc to an Al-alloy does ingeneral seem to make the alloy slightly more noble andto increase its self-corrosion resistance Scandium-containing Al alloys have very few uses at the presenttime as a result of the high price of scandium The priceof Sc is expected to decrease significantly in the futureand this should lead to the disclosure of moreapplications where it is economically feasible to takeadvantage of the improved properties of some Sc-containing aluminium alloys

References1 D R Lide lsquoCRC handbook of chemistry and physicsrsquo 71st edn

4ndash29 1990 Boston USA CRC Press

2 E M Savitsky V F Terehova I V Burov and O P Naumkin

Proc Fourth Conf on lsquoRare earth researchrsquo Phoenix Arizona

USA April 1964 409ndash420

3 E M Savitskii V F Terekhova I V Burov O P Naumkin and

I A Markova Inorg Mater 1965 1 1503ndash1512

4 O P Naumkin V T Terekhova and E M Savitskiy Russ

Metall 1965 (4) 128ndash136

5 W G Moffatt lsquoThe handbook of binary phase diagramsrsquo 1981

Schenectady NY USA General Electric Co

6 E A Brandes (ed) lsquoSmithells metals reference bookrsquo 6th edn

1983 London UK Butterworths

7 R P Elliott and F A Shunk Bull Alloy Phase Diagrams 1981

2 (2) 222ndash223

8 K A Gschneider Jr and F W Calderwood Bull Alloy Phase

Diagrams 1989 10 34ndash36

9 H Okamoto J Phase Equil 1991 12 612ndash613

10 J L Murray J Phase Equil 1998 19 380ndash384

11 M E Drits E S Kadaner T V Dobatkina and N I Turkina

Russ Metall 1973 (4) 152ndash154

12 S-I Fujikawa M Sugaya H Takei and K-I Hirano J Less-

Common Met 1979 63 87ndash97

13 N Blake and M A Hopkins J Mater Sci 1985 20 2861ndash2867

14 V I Kononenko and S V Golubev Russ Metall 1990 (2) 193ndash

195

15 T B Massalski J L Murray L H Bennett and H Baker (eds)

lsquoBinary alloy phase diagramsrsquo 1986 Metals Park OH USA

ASM

16 G Cacciamani P Riani G Borzone N Parodi A Saccone

R Ferro A Pisch and R Schmid-Fetzer Intermetallics 1999 7

101ndash108

17 H Okamoto J Phase Equil 2000 21 310

18 A F Norman P B Pragnell and R S McEwen Acta Mater

1998 46 5715ndash5732

19 I N Pyagai and A V Vakhobov Russ Metall 1990 (5) 50ndash52

20 C L Fu J Mater Res 1990 5 971ndash979

21 X Lu and Y Wang Calphad 2002 26 555ndash561

22 R R Sawtell and J W Morris Jr Proc lsquoDispersion strengthened

aluminium alloysrsquo Phoenix Arizona USA January 1988 409ndash

420

23 R R Sawtell and C L Jensen Metall Trans A 1990 21A 421ndash

430

24 L A Willey Unpublished research Alcoa 1970 Data points are

extracted from Ref 10

25 N I Turkina and V I Kuzmina Russ Metall 1976 (4) 179ndash

183

26 T Torma E Kovacs-Csetenyi I Vitanyi M Butova and

J Stepanov Proc 6th Int Symp on lsquoHigh purity materials in

science and technologyrsquo Akademie der Wissenschaften der DDR

Dresden Germany May 1985 388ndash389

27 A L Berezina V A Volkov B P Domashnikov and K V

Chuistov Metallofizika 1987 9 (5) 43ndash47

28 H-H Jo J Korean Inst Metals 1990 28 499ndash504

29 H-H Jo and S-I Fujikawa Mater Sci Eng 1993 A 171 151ndash

161

30 S Celotto and T J Bastow Philos Mag A 2000 80 1111ndash1125

31 J Roslashyset and N Ryum submitted to Mater Sci Eng

32 M E Drits L S Toropova Yu G Bykov F L Gushchina V I

Elagin and Yu A Filatov Russ Metall 1983 (1) 150ndash153

33 L S Toropova D G Eskin M L Kharakterova and T V

Dobatkina lsquoAdvanced aluminum alloys containing scandium

structure and propertiesrsquo 1998 Amsterdam The Netherlands

Gordon and Breach Science Publishers

34 V V Cherkasov P P Pobezhimov L P Nefedova E V Belov

and G M Kuznetsov Met Sci Heat Treat 1996 (6) 268ndash270

35 Kh O Odinaev I N Ganiev V V Kinzhibalo and B Ya

Kotur Dokl Akad Nauk Tadzh SSR 1989 32 37ndash38

36 Kh O Odinaev I N Ganiev and A V Vakhobov Russ Metall

1991 (4) 200ndash203

37 J Grobner R Schmid-Fetzer A Pisch G Cacciamani P Riani

N Parodi G Borzone A Saccone and R Ferro Z Metallkd

1999 90 872ndash880

38 E A Marquis and D N Seidman Microsc Microanal 2002 8

(Suppl 2) 1100CDndash1101CD

39 A Pisch J Grobner and R Schmid-Fetzer Mater Sci Eng A

2000 A 289 123ndash129

Roslashyset and Ryum Scandium in aluminium alloys

40 International Materials Reviews 2005 VOL 50 NO 1

40 C Xia F Zeng and Y Gu Trans Nonferrous Met Soc China

2003 13 1124ndash1127

41 M Yu Teslyuk and V S Protasov Sov Phys Crystallogr 1966

10 470ndash471

42 M L Kharakterova and T V Dobatkina Russ Metall 1988

(6) 175ndash178

43 M L Kharakterova Russ Metall 1991 (4) 195ndash199

44 L S Toropova M L Kharakterova and D G Eskin Russ

Metall 1992 (3) 194ndash199

45 P Riani L Arrighi R Marazza D Mazzone G Zanicchi and

R Ferro J Phase Equil Diff 2004 25 22ndash52

46 A T Tyvanchuk T I Yanson B Ya Kotur O S Zarechnyuk

and M L Kharakterova Russ Metall 1988 (4) 190ndash192

47 L L Rokhlin T V Dobatkina and M L Kharakterova Powder

Metall Met Ceram 1997 36

48 A Z Ikromov I N Ganiev and V V Kinzhibalo Dokl Akad

Nauk Tadzh SSR 1990 (6) 391ndash392

49 I N Ganiev A Z Ikromov and V G Khudoiberdiev Russ

Metall 1995 (3) 125ndash127

50 I N Fridlyander L L Rokhlin T V Dobatkina and N I

Nikitina Met Sci Heat Treat 1993 (10) 567ndash571

51 I N Fridlyander L L Rokhlin T V Dobatkina V V

Kinzhibalo and A T Tyvanchuk Russ Metall 1998 (1) 161ndash

166

52 R A Emigh E L Bradley and J W Morris Jr in lsquoLight-weight

alloys for aerospace applications IIrsquo (ed E W Lee and N J

Kim) 27ndash43 1991 TMS

53 L S Toropova A N Kamardinkin V V Kindzhibalo and A T

Tyvanchuk Phys Met Metall 1990 70 (6) 106ndash110

54 A N Kamardinkin T V Dobatkina and T D Rostova Russ

Metall 1991 (4) 216ndash218

55 L S Torodskaya T V Dobatkina and A N Kamardinkin

Russ Metall 1992 (5) 128ndash131

56 E M Sokolovskaya E F Kazakova E I Poddyakova and A

A Ezhov Met Sci Heat Treat 1997 (5) 211ndash213

57 Y Harada and D C Dunand Mater Sci Eng 2002 A 329ndash331

686ndash695

58 N E Drits L S Toropova and F L Gushchina Russ Metall

1984 (4) 229ndash232

59 E M Sokolovskaya E F Kazakova V A Alikhanov and E V

Zhuravleva Moscow Univ Chem Bull 1997 52 (5) 70ndash72

60 E M Sokolovskaya E F Kazakova and E I Poddyakova Met

Sci Heat Treat 1989 (11) 837ndash839

61 G M Cheldieva E F Kazakova E M Sokolovskaya and N I

Kaloev Russ Metall 1990 (6) 87ndash90

62 E M Sokolovskaya E F Kazakova and O D-S Kendivan

Russ Metall 1998 (4) 135ndash137

63 N G Bukhanko E F Kazakova and E M Sokolovskaya Russ

Metall 2001 (4) 425ndash431

64 E D Trubnyakova O I Bodak I N Ganiev and A V

Vakhobov Russ Metall 1987 (3) 219ndash222

65 I N Fridlyander and L V Molchanova Russ Metall 2003 (5)

476ndash480

66 R A Altynbaev S Kh Khairidinov and A V Vakhobov Russ

Metall 1987 (4) 194ndash196

67 J C Schuster and J Bauer J Less-Common Met 1985 109

345ndash350

68 L L Rokhlin A S Fridman T V Dobatkina and D G Eskin

Russ Metall 1991 (6) 146ndash148

69 A S Fridman T V Dobatkina and E V Muratova Russ

Metall 1992 (1) 207ndash209

70 C Xia F Zeng and Y Gu Trans Nonferrous Met Soc China

2003 13 546ndash552

71 F Zeng C Xia and Y Gu J Alloys Comp 2004 363 175ndash181

72 L L Rokhlin T V Dobatkina N R Bochvar and E V Lysova

J Alloys Comp 2004 367 10ndash16

73 T V Dobatkina A S Fridman and E V Muratova Russ

Metall 1992 (5) 125ndash127

74 I N Fridlyander L L Rokhlin N R Bochvar E V Lysova

and O V Boteva Russ Metall 2001 (6) 661ndash666

75 V N Rechkin L K Lamikhov and T I Samsonova Sov Phys

Crystallogr 1964 9 325ndash327

76 I I Zalutskii and P I Kripyakevich Sov Phys Crystallogr

1967 12 341ndash343

77 T J Bastow C T Forwood M A Gibson and M E Smith

Phys Rev B 1998 58 2988ndash2997

78 K Fukunaga M Kolbe K Yamada and Y Miura Mater Sci

Eng 1997 A 234ndash236 594ndash597

79 E P George J A Horton W D Porter and J H Schneibel

J Mater Res 1990 5 1639ndash1648

80 E P George D P Pope C L Fu and J H Schneibel ISIJ Int

1991 31 1063ndash1075

81 Y Harada and D C Dunand Acta Mater 2000 48 3477ndash3487

82 J H Schneibel and E P George Scripta Metall Mater 1990 24

1069ndash1074

83 J H Schneibel and P M Hazzledine Mater Res Soc Symp

Proc 1991 213 323ndash328

84 J H Schneibel and P M Hazzledine J Mater Res 1992 7

868ndash875

85 C J Sparks E D Specht G E Ice P Zschack and J Schneibel

Mater Res Soc Symp Proc 1991 213 363ndash368

86 J Tarnacki and Y-W Kim Scripta Metall Mater 1989 23

1063ndash1068

87 M Asta V Ozolins and C Woodward JOM 2001 53 (9) 16ndash

19

88 M E Drits L S Toropova F L Gushchina and S G Fedotov

Sov Non-Ferrous Met Res 1984 12 83ndash85

89 Y Harada and D C Dunand Scripta Mater 2003 48 219ndash222

90 C Woodward M Asta G Kresse and J Hafner Phys Rev B

2001 63 094103-1-6

91 J-H Xu and A J Freeman Phys Rev B 1990 41 12553ndash12561

92 M F Bartholomeusz and J A Wert Acta Metall Mater 1992

40 673ndash682

93 G Bester and M Fahnle J Phys Condens Matter 2001 13

11551ndash11565

94 C L Fu and M H Yoo Proc lsquoOrdered intermetallics ndash physical

metallurgy and mechanical behaviorrsquo Irsee Germany June 1991

155ndash164

95 K Fukunaga T Shouji and Y Miura Mater Sci Eng 1997 A

239ndash240 202ndash205

96 D P Pope Proc lsquoOrdered intermetallics ndash physical metallurgy

and mechanical behaviorrsquo Irsee Germany June 1991 143ndash153

97 J-S Wang Acta Mater 1998 46 2663ndash2674

98 M H Yoo and C L Fu Mater Sci Eng 1992 A 153 470ndash478

99 R W Hyland Jr and R C Stiffler Scripta Metall Mater 1991

25 473ndash477

100 I G Brodova I V Polents O A Korzhavina P S Popelrsquo I P

Korshunov and V O Esin Melts 1992 4 392ndash397

101 I G Brodova O A Chikova I V Polents P S Popelrsquo and V O

Esin Casting Processes 1992 1 (2) 158ndash160

102 I G Brodova D V Bashlikov and I V Polents Mater Sci

Forum 1998 269ndash272 589ndash594

103 K B Hyde A F Norman and P B Pragnell Mater Sci Forum

2000 331ndash337 1013ndash1018

104 K B Hyde A F Norman and P B Pragnell Acta Mater 2001

49 1327ndash1337

105 J Roslashyset and N Ryum Proc 6th Int Conf on lsquoAluminum

alloysrsquo Toyohashi Japan July 1998 793ndash798

106 V I Elagin V V Zakharov and T D Rostova Met Sci Heat

Treat 1993 (6) 317ndash319

107 R W Hyland Jr Metall Trans A 1992 23A 1947ndash1955

108 B A Parker Z F Zhou and P Nolle J Mater Sci 1995 30

452ndash458

109 C L Rohrer M D Asta S M Foiles and R W Hyland Jr

Mater Res Soc Symp Proc 1996 398 477ndash482

110 G M Novotny and A J Ardell Mater Sci Eng 2001 A 318

144ndash154

111 J D Robson M J Jones and P B Pragnell Acta Mater 2003

51 1453ndash1468

112 C Tan Z Zheng and B Wang Proc 3rd Int Conf on

lsquoAluminium alloysrsquo Vol I NTH Trondheim Norway June

1992 290ndash294

113 M Nakayama A Furuta and Y Miura Mater Trans JIM

1997 38 852ndash857

114 E A Marquis and D N Seidman Acta Mater 2001 49 1909ndash

1919

115 M J Jones and F J Humphreys Acta Mater 2003 51 2149ndash

2159

116 E A Marquis D N Seidman and D C Dunand in lsquoCreep

deformation fundamentals and applicationsrsquo (ed R S Mishra

J C Earthman and S V Raj) 299ndash308 2002 TMS

117 D N Seidman E A Marquis and D C Dunand Acta Mater

2002 50 4021ndash4035

118 E A Marquis D N Seidman and D C Dunand Acta Mater

2003 51 285ndash287

119 M E Drits L S Toropova U G Bikov and G K Anastaseva

Proc lsquoDiffusion in metals and alloysrsquo Tihany Hungary Augustndash

September 1982 616ndash623

120 V I Elagin V V Zakharov and T D Rostova Met Sci Heat

Treat 1983 (7) 546ndash549

Roslashyset and Ryum Scandium in aluminium alloys

International Materials Reviews 2005 VOL 50 NO 1 41

121 M Ye Drits L B Ber Yu G Bykov L S Toropova and G K

Anastaseva Phys Met Metall 1984 57 (6) 118ndash126

122 M E Drits L S Toropova and Yu G Bykov Sov Non-Ferrous

Met Res 1985 13 309ndash314

123 V I Yelagin V V Zakharov S G Pavlenko and T D Rostova

Phys Met Metall 1985 60 (1) 88ndash92

124 N Sano Y Hasegawa K Hono H Jo K Hirano H W

Pickering and T Sakurai Journal de Physique 1987 48 C6 337ndash

342

125 N Sano H-H Jo K-I Hirano and T Sakurai J Jpn Inst

Metals 1989 39 444ndash450

126 N Sano H Jo K Hirano and T Sakurai Proc Second Int

Conf on lsquoAluminium alloysrsquo Beijing China October 1990 549ndash

554

127 Y Miura M Nakayama and A Furuta Proc lsquoAspects of high

temperature deformation and fracture in crystalline materialsrsquo

Nagoya Japan July 1993 255ndash262

128 Y W Riddle and T H Sanders Jr Mater Sci Forum 2000

331ndash337 939ndash944

129 Y W Riddle M McIntosh and T H Sanders Jr in lsquoLightweight

alloys for aerospace application VIrsquo (ed K Jata E W Lee

W Frazier and N J Kim) 25ndash39 2001 TMS

130 M E Drits J Dutkiewicz L S Toropova and J Salawa Crystal

Res Technol 1984 19 1325ndash1330

131 Y W Riddle MSc thesis Georgia Tech GA USA 1998

132 T J Bastow and S Celotto Mater Sci Eng 2003 C 23 757ndash

762

133 M C Carroll M J Mills G S Daehn P I Gouma M F

Savage and B R Dunbar in lsquoAutomotive Alloys 1999rsquo (ed

S Das) 239ndash246 2000 TMS

134 E Clouet M Nastar and C Sigli Phys Rev B 2004 69 064109-

1-14

135 V V Zakharov Met Sci Heat Treat 1997 (2) 61ndash66

136 J W Christian lsquoThe theory of transformation in metals and

alloysrsquo 2nd edn 1975 Pergamon Press Ltd

137 A L Berezina V A Volkov B P Domashnikov S V Ivanov

and K V Chuistov Phys Metals 1990 10 296ndash304

138 S-I Fujikawa and S Sakauchi Proc 6th Int Conf on

lsquoAluminum alloysrsquo Toyohashi Japan July 1998 805ndash810

139 Y S Touloukian R K Kirby R E Taylor and P D Desai

(eds) lsquoThermal expansion metallic elements and alloysrsquo 1975

New York Plenum

140 J Roslashyset and N Ryum submitted to Scripta Mater

141 R O Simmons and R W Balluffi Phys Rev 1960 117 52ndash61

142 M Ocko E Babic R Krsmik E Girt and B Leontic J Phys F

Metals Phys 1976 6 703ndash707

143 M J Jones and F J Humphreys Proc First Joint Int Conf on

lsquoRecrystallization and grain growthrsquo Aachen Germany August

2001 Springer Verlag 1287ndash1292

144 S Iwamura M Nakayama and Y Miura Mater Sci Forum

2002 396ndash402 1151ndash1156

145 S Iwamura and Y Miura Acta Mater 2004 52 591ndash600

146 M Asta S M Foiles and A A Quong Phys Rev B 1998 57

11265ndash11275

147 R W Hyland Jr M Asta S M Foiles and C L Rohrer Acta

Mater 1998 46 3667ndash3678

148 J Roslashyset and N Ryum Proc 4th Int Conf on lsquoAluminium

alloysrsquo Vol I Atlanta GA USA September 1994 194ndash201

149 M E Drits L S Toropova G K Anastaseva and G L

Nagornichnykh Russ Metall 1984 (3) 192ndash195

150 E A Marquis D N Seidman and D C Dunand Acta Mater

2003 51 4751ndash4760

151 M E Drits L S Toropova and Yu G Bykov Met Sci Heat

Treat 1983 (7) 550ndash554

152 V V Zakharov and T D Rostova Met Sci Heat Treat 1995

(2) 65ndash69

153 M Nakayama and Y Miura Proc 4th Int Conf on lsquoAluminium

alloysrsquo Vol I Atlanta GA USA September 1994 538ndash545

154 M Nakayama and Y Miura J Jpn Inst Light Metals 1996 46

275ndash279

155 M Nakayama T Okuyama and Y Miura Mater Sci Forum

2000 331ndash337 927ndash932

156 M Nakayama T Okuyama and Y Miura Proc 6th Int Conf

on lsquoAluminum alloysrsquo Toyohashi Japan July 1998 517ndash522

157 M L Kharakterova D G Eskin and L S Toropova Acta

Metall Mater 1994 42 2285ndash2290

158 V I Elagin V V Zakharov and T D Rostova Met Sci Heat

Treat 1992 (1) 37ndash45

159 H Wiik Siv Ing thesis NTH Institute of Metallurgy

Trondheim Norway 1995

160 J Roslashyset H Hovland and N Ryum Mater Sci Forum 2002

396ndash402 619ndash624

161 Y Miura K Horikawa K Yamada and M Nakayama Proc

4th Int Conf on lsquoAluminium alloysrsquo Vol II Atlanta GA USA

September 1994 161ndash168

162 Y W Riddle PhD thesis Georgia Tech GA USA 2000

163 B Forbord W Lefebvre F Danoix H Hallem and

K Marthinsen Scripta Mater 2004 51 333ndash337

164 J D Robson Acta Mater 2004 52 1409ndash1421

165 C B Fuller J L Murray and D N Seidman submitted to Acta

Mater 2004

166 M G Mousavi C E Cross and Oslash Grong Sci Technol Weld

Joining 1999 4 381ndash388

167 J S Vetrano S M Bruemmer L M Pawlowski and I M

Robertson Mater Sci Eng 1997 A 238 101ndash107

168 Y W Riddle and T H Sanders Jr Mater Sci Forum 2000

331ndash337 799ndash803

169 G M Khan A O Nikiforov V V Zakharov and I I Novikov

Tsvetnye Metally 1993 34 (11) 43ndash45

170 Z Horita M Furukawa M Nemoto A J Barnes and T G

Langdon Acta Mater 2000 48 3633ndash3640

171 L A Willey US Patent 3 619 181 9 November 1971

172 L K Lamikhov and G V Samsonov Tsvetnye Metally 1964 5

(8) 77ndash80

173 A L Berezina K V Chuistov N I Kolobnev L B

Khokhlatova and T A Monastyrskaya Mater Sci Forum

2002 396ndash402 741ndash746

174 F A Fasoyinu J Thomson D Cousineau T Castles and M

Sahoo Proc 6th Int AFS Conf on lsquoMolten aluminum

processingrsquo Orlando FL USA November 2001

175 Z Yin Q Pan Y Zhang and F Jiang Mater Sci Eng 2000

A 280 151ndash155

176 I I Novikov and O E Grushko Mater Sci Technol 1995 11

926ndash932

177 D Cousineau M Sahoo P D Newcombe T Castles and F A

Fasoyinu Proc lsquoAFS 105th casting congressrsquo Dallas TX USA

AprilndashMay 2001 157ndash184

178 C E Cross and Oslash Grong Proc 6th Int Conf on lsquoAluminum

alloysrsquo Toyohashi Japan July 1998 1441ndash1446

179 F A Costello J D Robson and P B Prangnell Mater Sci

Forum 2002 396ndash402 757ndash762

180 K B Hyde A F Norman and P B Prangnell Mater Sci

Forum 2002 396ndash402 39ndash44

181 M E Drits S G Pavlenko L S Toropova Yu G Bukov and

L B Ber Sov Phys Dokl 1981 26 (3) 344ndash346

182 A M Drits and B A Kopeliovich Russ Metall 1985 (4) 147ndash

151

183 V G Davydov V I Elagin V V Zakharov and T D Rostova

Met Sci Heat Treat 1996 (8) 347ndash352

184 M E Drits L S Toropova Yu G Bykov L B Ber and S G

Pavlenko Russ Metall 1982 (1) 148ndash152

185 T D Rostova V G Davydov V I Yelagin and V V Zakharov

Mater Sci Forum 2000 331ndash337 793ndash798

186 Y W Riddle H Hallem and N Ryum Mater Sci Forum 2002

396ndash402 563ndash568

187 J Roslashyset and Y W Riddle Proc 9th Int Conf on lsquoAluminium

alloysrsquo Brisbane Australia August 2004 1210ndash1215

188 A M Diskin V K Portnoi A M Drits and A A Alalykin Sov

Non-Ferrous Met Res 1986 14 499ndash500

189 R R Sawtell P E Bretz and C L Jensen US Patent 4 689 090

25 August 1987

190 G A Salishchev Yu B Timoshenko and R A Saitova Proc

Second Int Conf on lsquoAluminium alloysrsquo Beijing China October

1990 413ndash415

191 T G Nieh R Kaibyshev L M Hsiung N Nguyen and

J Wadsworth Scripta Mater 1997 36 1011ndash1016

192 T G Nieh L M Hsiung J Wadsworth and R Kaibyshev Acta

Mater 1998 46 2789ndash2800

193 J S Vetrano C H Henager Jr M T Smith and S M

Bruemmer in lsquoHot deformation of aluminum alloys IIrsquo (ed T R

Bieler L A Lalli and S R MacEwen) 407ndash418 1998 TMS

194 J S Vetrano C H Henager Jr S M Bruemmer Y Ge and

C H Hamilton in lsquoSuperplasticity and Superplastic Forming

1998rsquo (ed A K Gosh and T R Bieler) 89ndash97 1998 TMS

195 V Y Gertsman J S Vetrano C H Henager Jr and S M

Bruemmer Proc First Joint Int Conf on lsquoRecrystallization and

grain growthrsquo Aachen Germany August 2001 Springer Verlag

2001 837ndash842

196 Y Xiao C Gao H Ma and S Tian Trans Nonferrous Met Soc

China 2001 11 235ndash238

Roslashyset and Ryum Scandium in aluminium alloys

42 International Materials Reviews 2005 VOL 50 NO 1

197 A Gholinia F J Humphreys and P B Prangnell Acta Mater

2002 50 4461ndash4476

198 A Gholinia F J Humphreys and P B Prangnell Mater Sci

Forum 2002 408ndash412 1519ndash1524

199 S Komura P B Berbon M Furukawa Z Horita M Nemoto

and T G Langdon Scripta Mater 1998 38 1851ndash1856

200 S Komura P B Berbon A Utsunomiya M Furukawa

Z Horita M Nemoto and T G Langdon in lsquoHot deformation

of aluminum alloys IIrsquo (ed T R Bieler L A Lalli and S R

MacEwen) 125ndash138 1998 TMS

201 S Komura Z Horita M Furukawa M Nemoto and T G

Langdon J Mater Res 2000 15 2571ndash2576

202 S Komura M Furukawa Z Horita M Nemoto and T G

Langdon Mater Sci Eng 2001 A 297 111ndash118

203 S Komura Z Horita M Furukawa M Nemoto and T G

Langdon Metall Mater Trans A 2001 32A 707ndash716

204 Z Horita M Furukawa K Oh-ishi M Nemoto and T G

Langdon Proc Fourth Int Conf on lsquoRecrystallization and

related phenomenarsquo (ed T Sakai and H G Suzuki) 1999 The

Japan Institute of Metals 301ndash308

205 Z Horita S Komura P B Berbon A Utsunomiya

M Furukawa M Nemoto and T G Langdon Mater Sci

Forum 1999 304ndash306 91ndash96

206 Z Horita S Lee S Ota K Neishi and T G Langdon Mater

Sci Forum 2001 357ndash359 471ndash476

207 Z Horita T Fujinami K Sato S B Kang H W Kim and T G

Langdon in Proc James T Staley Honorary Symposium on

Aluminum Alloys lsquoAdvances in the metallurgy of aluminum

alloysrsquo (ed M Tiryakioglu) 271ndash275 2001 ASM

208 P B Berbon S Komura A Utsunomiya Z Horita

M Furukawa M Nemoto and T G Langdon Mater Trans

JIM 1999 40 772ndash778

209 M Nemoto Z Horita M Furukawa and T G Langdon Mater

Sci Forum 1999 304ndash306 59ndash66

210 M Furukawa Z Horita M Nemeto and T G Langdon Proc

lsquoLight Metals 1999rsquo Quebec City PQ Canada August 1999 583ndash

592

211 M Furukawa K Oh-ishi S Komura A Yamashita Z Horita

M Nemeto and T G Langdon Mater Sci Forum 1999 304ndash

306 97ndash102

212 M Furukawa A Utsunomiya K Matsubara Z Horita and

T G Langdon Acta Mater 2001 49 3829ndash3838

213 M Furukawa A Utsunomiya S Komura Z Horita M Nemoto

and T G Langdon Mater Sci Forum 2001 357ndash359 431ndash436

214 M Furukawa Z Horita and T G Langdon in Proc James T

Staley Honorary Symposium on Aluminum Alloys lsquoAdvances in

the metallurgy of aluminum alloysrsquo (ed M Tiryakioglu) 47ndash56

2001 ASM

215 M Furukawa Z Horita M Nemoto and T G Langdon Mater

Sci Eng 2002 A 324 82ndash89

216 M Furukawa Z Horita and T G Langdon in lsquoUltrafine grained

materials IIrsquo (ed Y T Zhu T G Langdon R S Mishra S L

Semiatin M J Saran and T C Lowe) 459ndash468 2002 TMS

217 T G Langdon M Furukawa Z Horita and M Nemoto Proc

NATO Advanced Research Workshop on lsquoInvestigations and

applications of severe plastic deformationrsquo Moscow August

1999 NATO Science Series Series 3 High Technology vol 80

Kluwer Academic Publishers The Netherlands 2000 149ndash154

218 S Lee H Akamatsu A Utsunomiya K Neishi M Furukawa

Z Horita and T G Langdon Proc Thermec 2000 Las Vegas

USA December 2000

219 S Lee A Utsunomiya H Akamatsu K Neishi M Furukawa

Z Horita and T G Langdon Acta Mater 2002 50 553ndash564

220 A Yamashita D Yamaguchi Z Horita and T G Langdon

Mater Sci Eng 2000 A 287 100ndash106

221 K Oh-ishi Z Horita D J Smith and T G Langdon J Mater

Res 2001 16 583ndash589

222 H Akamatsu T Fujinami Z Horita and T G Langdon Scripta

Mater 2001 44 759ndash764

223 S Ota H Akamatsu K Neishi M Furukawa Z Horita and

T G Langdon Mater Trans 2002 43 2364ndash2369

224 K Furuno H Akamatsu K Oh-ishi M Furukawa Z Horita

and T G Langdon Acta Mater 2004 52 2497ndash2507

225 I N Fridlyander O G Senatorova N A Ryazanova and A O

Nikiforov Mater Sci Forum 1994 170ndash172 345ndash349

226 J N Fridlyander and O G Senatorova Mater Sci Forum 1996

217ndash222 1813ndash1818

227 J Liu and D J Chakrabarti Acta Mater 1996 44 4647ndash4661

228 O G Senatorova A N Uksusnikov J N Fridlyander

J Koshorst R R Romanova N A Ryazanova A Galliot

and V V Cherkassov Proc 6th Int Conf on lsquoAluminum alloysrsquo

July 1998 Toyohashi Japan 589ndash593

229 R A Emigh E L Bradley and J W Morris Jr in

lsquoSuperplasticity in aerospace IIrsquo (ed T R McNelley and H C

Heikkenen) 303ndash315 1990 TMS

230 E L Bradley III R A Emigh and J W Morris Jr Scripta

Metall Mater 1991 25 717ndash721

231 N I Kolobnev L B Khokhlatova V D Makarov E Yu

Semenova and V V Redchits Proc Sixth Int Aluminiumndash

Lithium Conference Garmisch-Partenkirchen Germany October

1991 1053ndash1056

232 N K Tsenev R Z Valiev O V Obraztsov and I N Fridlander

Proc Sixth Int AluminiumndashLithium Conference Garmisch-

Partenkirchen Germany October 1991 1125ndash1132

233 A M Shammazov N K Tsenev R Z Valiev M M

Myshlyaev M M Bikbulatov and S P Lebedich Phys Met

Metall 2000 89 (3) 314ndash318

234 F Musin R Kaibyshev Y Motohashi T Sakuma and G Itoh

Mater Trans A 2002 43A 2370ndash2377

235 M Shagiev Y Motohashi F Musin R Kaibyshev and G Itoh

Mater Trans A 2003 44A 1694ndash1697

236 M Shagiev Y Motohashi F Musin R Kaibyshev and G Itoh

Mater Trans A 2003 44A 1698ndash1701

237 B A Parker and Z F Zhou Proc 3rd Int Conf on lsquoAluminium

alloysrsquo Vol I NTH Trondheim Norway June 1992 363ndash367

238 J R Davies lsquoASM specialty handbook aluminum and aluminum

alloysrsquo 1993 Materials Park OH USA ASM

239 S J Andersen H W Zandbergen J Jansen C Traeholt

U Tundal and O Reiso Acta Mater 1998 46 3283ndash3298

240 M L Kharakterova D G Eskin and L L Rokhlin Russ

Metall 1997 (1) 104ndash109

241 J Roslashyset Dr Ing thesis NTNU Trondheim Norway 2002

242 P P Chattopadhyay S Datta and M K Banerjee Mater Sci

Eng 2002 A 333 67ndash71

243 L I Kaigorodova E I Selnikhina E A Tkachenko and O G

Senatorova Phys Met Metall 1996 81 513ndash519

244 Y-L Wu F H Froes C Li and A Alvarez Metall Mater

Trans A 1999 30A 1017ndash1024

245 Z Yin L Yang Q Pan and F Jiang Trans Nonferrous Met

Soc China 2001 11 822ndash825

246 V I Elagin V V Zakharov and T D Rostova Met Sci Heat

Treat 1994 36 (7) 375ndash380

247 Y V Milman A I Sirko D V Lotsko O N Senkov and D B

Miracle Mater Sci Forum 2002 396ndash402 1217ndash1222

248 C-H Joh K Yamada and Y Miura Mater Trans JIM 1999

40 439ndash442

249 X J Jiang Q H Gui Y Y Li L M Ma G J Liang and C X

Shi Scr Metall Mater 1993 29 211ndash216

250 X J Jiang Y Y Li W Deng L Y Xiong W M Wu Y J Gao

and C X Shi Adv Cryogenic Eng (Mater) 1994 40 1369ndash

1376

251 C-H Joh T Katsube K Yamada and Y Miura Proc 6th Int

Conf on lsquoAluminum alloysrsquo Toyohashi Japan July 1998 799ndash

804

252 L I Kaygorodova A M Dritz T V Krymova and I N

Fridlyander Proc Sixth Int AluminiumndashLithium Conference

Garmisch-Partenkirchen Germany October 1991 363ndash367

253 L I Kaigorodova A M Drits Ya V Zhingel T V Krymova

and I N Fridlyander Phys Met Metall 1992 73 286ndash290

254 A L Berezina V A Volkov S V Ivanov N I Kolobnev and

K V Chuistov Phys Met Metall 1991 71 (2) 167ndash175

255 I N Fridlyander N I Kolobnev A L Berezina and K V

Chuistov Proc Sixth Int AluminiumndashLithium Conference

Garmisch-Partenkirchen Germany October 1991 107ndash112

256 L I Kaigorodova A M Drits Ya V Zhingel T V Krymova

and V A Rassokhin Phys Met Metall 1992 73 281ndash285

257 I N Fridlyander S F Danilov E N Malysheva T A

Gorokhova and N N Kirkina Proc Sixth Int Aluminiumndash

Lithium Conference Garmisch-Partenkirchen Germany October

1991 381ndash386

258 G Dlubek S Krause H Krause A L Beresina V S

Mikhalenkov and K V Chuistov J Phys Condens Matter

1992 4 6317ndash6328

259 S Krause H Krause G Dlubek A L Beresina and K S

Chuistov Mater Sci Forum 1992 105ndash110 1109ndash1112

260 C Y Tan Z Q Zheng and S Q Liang Proc 4th Int Conf on

lsquoAluminium alloysrsquo Vol II Atlanta GA USA September 1994

329ndash333

261 A L Beresina N I Kolobnev K V Chuistov A V Kotko and

O A Molebny Mater Sci Forum 2002 396ndash402 977ndash981

Roslashyset and Ryum Scandium in aluminium alloys

International Materials Reviews 2005 VOL 50 NO 1 43

262 I N Ganiev I Yunusov and V V Krasnoyarskii J Appl Chem

USSR 1986 60 1961ndash1965

263 I N Ganiev Prot Met 1995 31 543ndash546

264 N V Vyazovikina Prot Met 1999 35 448ndash453

265 G V Kharina and V P Kochergin Prot Met 1996 32 134ndash

136

266 G V Kharina M V Kuznetsov and V P Kochergin Russ J

Electrochem 1998 34 482ndash485

267 V S Sinyavskii V D Valrsquokov and E V Titkova Prot Met

1998 34 549ndash555

268 Y L Wu F H Froes C G Li and J Liu Proc lsquoSynthesis

processing of lightweight metallic materials IIrsquo Orlando FL

USA February 1997 73ndash81

269 Z Ahmad and B J Abdul-Aleem Proc EuroCorr 2000

270 Z Ahmad A Ul-Hamid and B J Abdul-Aleem Corros Sci

2001 43 1227ndash1243

271 R Braun B Lenczowski and G Tempus Mater Sci Forum

2000 331ndash337 1647ndash1652

272 T Torma E Kovacs-Csetenyi L Vitalis I Vitanyi

J Stepanov and M Butova Mater Sci Forum 1987 1314

497ndash503

273 Z Wang P Wang K S Kumar and C L Briant in lsquoChemistry

and electrochemistry of corrosion and stress corrosion crackingrsquo

(ed R H Jones) 573ndash582 2001 TMS

274 V I Elagin V V Zakharov A A Petrova and E V

Vyshegorodtseva Russ Metall 1983 (4) 143ndash146

Roslashyset and Ryum Scandium in aluminium alloys

44 International Materials Reviews 2005 VOL 50 NO 1

Page 19: Scandium in aluminium alloys - Atom probe · A considerable part of the available literature on scandium in aluminium alloys is reviewed. ... behaviour in Al Cu, Al Mg Si,

series (AlndashCu) 6xxx series (AlndashMgndashSi) and 7xxx series(AlndashZnndashMg) AlndashLi alloys should also be mentionedSeveral investigations have been carried out in order toclarify the effects of Sc on the precipitation behaviour inthese alloy systems

AlndashCu alloys

The precipitation sequence in AlndashCu alloys is oftendescribed as follows

Supersaturated solid solutionRGP-zonesRh0Rh9Rh(Al2Cu)

The highest strength is normally achieved when the h0or h9 precipitates are predominant Typical precipitationheat treatment temperatures for AlndashCu alloys are in therange 160ndash190uC238 which is considerably lower thanthe typical precipitation temperature for Al3ScComparisons of the aging responses of AlndashCu and AlndashCundashSc alloys at 150 and 200uC indicate that there is nonoticeable effect of Sc on the precipitation kinetics ofh9153 It is observed that the h9 precipitates may nucleateon Al3Sc particles153 At 300uC it is observed that h9particles are somewhat smaller in AlndashCundashSc alloys thanin AlndashCu alloys156

AlndashMgndashSi alloys

The following precipitation sequence is commonlyreported for AlndashMgndashSi alloys

Supersaturated solid solutionRGP-zonesRb0Rb9Rb(Mg2Si)

For peak aged alloys the predominant precipitatetype is b0 for which the stoichiometric composition hasrecently been resolved to be Mg5Si6239 Temperatures inthe range 160ndash205uC are typically used for precipitationhardening of these alloys238 Adding both 03 wt-Scand 01 wt-Zr to an Alndash06 wt-Mgndash065 wt-Sialloy does not seem to alter the precipitation kineticsof b0 at 165uC However the hardness increase becauseof precipitation hardening appears to be smaller in theSczZr-containing alloy240 In another investigationadditions of 01 wt-Sc 015 wt-Sc 02 wt-Sc04 wt-Sc and 02 wt-Scz01 wt-Zr were made toan Alndash08 wt-Mgndash07 wt-Si alloy241 Here it wasalso observed that the precipitation kinetics of b0 wasseemingly independent of the Sc additions (Fig 28)TEM observations indicated that the b0 precipitateswere of comparable sizes in the investigated alloys andno interactions between Al3Sc and b0 were observed(Fig 29) In a third study242 where the effect of Sc onthe precipitation in an AlMgSindashSiC metal matrixcomposite was investigated there also does not seemto be any effect on the precipitation kinetics Howevercontrary to the findings of Ref 240 it is reported thatthe Sc addition leads to a higher hardness increase thanin the corresponding Sc free alloy

AlndashMgndashZn alloys

For these alloys the following precipitation sequence isoften ascribed

Table 7 Mechanical properties in non-heat-treatable Al-alloys with Sc

Reference Alloy wt- YS MPa UTS MPa Note

1xxx alloys171 000Sc 15 48 Cast material aged 288uC8 h

023Sc 159 185 Cast material aged 288uC8 h038Sc 199 220 Cast material aged 288uC8 h000Sc 14 49 Cold rolled material (89) aged 288uC8 h023Sc 198 208 Cold rolled material (89) aged 288uC8 h038Sc 240 264 Cold rolled material (89) aged 288uC8 h000Sc 8 34 Cold rolled material quenched from 649uC aged 288uC8 h023Sc 147 157 Cold rolled material quenched from 649uC aged 288uC8 h038Sc 193 199 Cold rolled material quenched from 649uC aged 288uC8 h

121 05Sc 160 ndash Forged material quenched from 635uC aged 250uC50 h23 05Sc 298 319 Hot rolled 288uC cold rolled 69ndash81 aged 288uC4 h112 01Sc 132 166 Hot z cold rolled material quenched from 630uC

aged 320uC133 h148 02Sc 138 ndash Cast material aged 300uC10 h compression test159 04Sc 196 ndash Cast material aged 300uC10 h compression test117 118 03Sc 209 ndash Cast material quenched from 648uC aged 300uC5 h

compression test3xxx alloys171 1Mn 015Sc 216 221 Cold rolled material (89) aged 288uC8 h

1Mn 05Sc 309 323 Cold rolled material (89) aged 288uC8 h186 05Mn 02Mg

026Sc 015Zr162 201 Extruded material solutionised 600uC aged 250uC

5xxx alloys171 1Mg 43 111 Cold rolled material (89) aged 288uC8 h

1Mg 03Sc 288 303 Cold rolled material (89) aged 288uC8 h53Mg 147 259 Cold rolled material (50) wintermediate anneals

at 343uC aged 288uC8 h53Mg 03Sc 368 401 Cold rolled material (50) wintermediate anneals

at 343uC aged 288uC8 h23 2Mg 05Sc 376 401 Hot rolled 288uC cold rolled 69ndash81 aged 288uC4 h

4Mg 05Sc 414 4606Mg 05Sc 433 503

237 4Mg 1Sc 420 525 Cold rolled material (83) aged 320uC1 h148 4Mg 02Sc 194 ndash Cast material aged 300uC10 h compression test

Tensile test data except where noted YS yield strength UTS ultimate tensile strength

Roslashyset and Ryum Scandium in aluminium alloys

International Materials Reviews 2005 VOL 50 NO 1 37

Supersaturated solid solutionRGP-zonesRg9Rg(Zn2Mg)

The maximum hardness is normally achieved whenthe g9 precipitates are predominant Common precipita-tion hardening temperatures are in the range 95ndash180uCand a two-step precipitation heat treatment within thistemperature regime is often used238 It has beenobserved in some investigations that Sc and SczZradditions to AlndashMgndashZn alloys slow down the precipita-tion of g9 somewhat243 Other investigations find thatthere is no effect of Sc on the precipitation behaviour ofg9244245 and yet others report that Sc additionssignificantly speed up the precipitation of g9246 In Ref247 it is found that an Sc addition leads to coarser g9precipitates and it is claimed that this gives an improvedductility of the alloy The strength-loss associated withlarger particle size is reported to be counterbalanced bystrengthening from Al3Sc precipitates

AlndashLi alloys

The precipitation sequence in binary AlndashLi alloys isapparently simple

Supersaturated solid solutionRd9Rd (AlLi)

where d9 is the metastable Al3Li phase which just likeAl3Sc has the L12 type of atomic arrangement Thetypical temperature regime for precipitation of d9 whichis the strengthening phase in this system is approx 150ndash200uC A comparison of the age hardening response ofan Alndash26 wt-Li and an Alndash24 wt-Lindash019 wt-Scalloy at 180uC248 and 200uC161 indicates that the onsetof d9 precipitation is not altered by the presence of ScThe hardness curves for the two alloys are practicallyidentical at 200uC whereas at 180uC the peak hardnesslevel is slightly higher in the AlndashLi than the AlndashLindashScalloy DSC measurements at constant heating ratesindicate that the addition of Sc to an AlndashLi alloysincreases the activation energy for d9 precipitation andmoves the exothermic peak associated with d9 precipita-tion to a higher temperature248 For specimens aged at

either 180uC or 200uC TEM observations reveal that thed9 precipitates are much smaller in the Sc containingalloy than in binary AlndashLi both in the peak agedcondition and in the overaged condition161248 Additionof Sc has also been observed to reduce the size of d9precipitates in other AlndashLi based alloys249ndash251 In an AlndashLindashCundashZr alloy an addition of Sc has been reported toslow down the homogeneous precipitation of d9252253 Ithas been claimed that Sc reduces the quench sensitivityand delays room temperature aging of AlndashLi basedalloys254ndash256

When present in the microstructure before the pre-cipitation of d9 the Al3Sc precipitates may act as effec-tive nucleation sites for d9 The resulting precipitates arespheres of d9 with a core of Al3Sc161249252ndash255257ndash261

Corrosion resistanceAn appreciable amount of data is available on the effectsof Sc on the corrosion behaviour of wrought Al-alloysSome of these effects are apparently derived from theeffects of Sc on the microstructure of the alloys It hasbeen reported that an addition of Sc increases thecorrosion potential (makes it less negative) in pureAl262ndash264 in AlndashZn alloys265266 AlndashMg alloys267 AlndashZnndashMgndashCu alloys264268 AlndashCundashMgndashMn alloys264 andin AlndashCundashLindashMgndashAg alloys264 Even though Sc alsohas been reported to decrease the corrosion potential in

28 Age hardening response at 175uC for Alndash08 wt-Mgndash

07 wt-Si alloy (Base) with additions of 02 wt-Sc

04 wt-Sc and 02 wt-Scz01 wt-Zr from Ref 241

29 TEM images of a b0 precipitates in Alndash08 wt-Mgndash

07 wt-Si alloy and b b0 and Al3(Sc1ndashxZrx) in a similar

alloy with addition of 02 wt-Scz01 wt-Zr from

Ref 241

Roslashyset and Ryum Scandium in aluminium alloys

38 International Materials Reviews 2005 VOL 50 NO 1

AlndashMg alloys269270 it seems that the general trend isthat adding Sc to an alloy makes it slightly more nobleThe change in corrosion potential is much morepronounced when Sc is added in amounts larger thanthe eutectic composition263 ie there is a considerablecontribution from primary or eutectic Al3Sc to theoverall potential It has also been demonstrated that thechange in corrosion potential caused by Sc can dependon the heat treatment applied to the alloy267268

Even though the corrosion potential is an essentialparameter in establishing the corrosion behaviour of analloy an increase in the corrosion potential does notnecessarily imply an improved self-corrosion resistanceHowever measurements of corrosion rates and passiva-tion current densities strongly suggest that the self-corrosion resistance in general is considerably improvedwhen Sc is added to wrought Al-alloys263264267 Someobserved variations in corrosion potential and passiva-tion current densities with Sc content in binary AlndashScalloys are plotted in Fig 30

Material failure in corrosive environments is often dueto localised corrosion attacks which may propagaterapidly even though the bulk material has a goodresistance against general corrosion It has been pointedout that hypereutectic additions of Sc may lead tomicrogalvanic corrosion beside primary Al3Sc parti-cles264 In AlndashMg alloys grain boundary precipitation ofAl8Mg5 can lead to localised corrosion attacks such asintergranular corrosion (IGC) exfoliation corrosion(EC) and stress corrosion cracking (SCC) In wroughtmaterial such precipitation may occur in the 60ndash180uCtemperature regime and heating in this temperaturerange is referred to as lsquosensitationrsquo An AlndashMgndashSc alloywas found to be immune against intergranular corrosionand have moderate susceptibility to exfoliation corro-sion after annealing at 350uC271 After sensitation heattreatments severe IGC and EC was observed but notquite as severe as in a corresponding alloy without ScAs for SCC the AlndashMgndashSc alloy was found to be highlyresistant271 In another study it was found that additionof 056 wt-Sc reduces the SCC susceptibility of an Alndash68 wt-Mg alloy in the as-rolled state and afterannealing at 250uC whereas in a sensitised specimenthe SCC susceptibility is somewhat increased by the Scaddition272 A third investigation found that Sc has nomeasurable detrimental effect on the SCC susceptibilityof sensitised Alndash5Mgndash015Zr alloy273 SCC is also a

severe problem in high strength AlndashZnndashMgndashCu alloys Ithas been shown that small Sc additions are effective inreducing the SCC sensitivity of these alloys244246268274

Use of Sc-containing Al alloysA systematic development of Sc-containing aluminiumalloys took place in the former USSR in the 1980s andthe interest for Sc as an alloying element in aluminiumalloys hit the western world approximately 10 yearslater Even though a number of improvements in Alalloys achieved by Sc addition have been demonstratedthe current uses of such alloys are very limited This isrelated to the very high price of scandium

In Russia some parts of military aircraft are made ofSc-containing AlndashLi alloys In the western world themain usage of Sc-containing alloys is for sportsequipment Ashurst Technology and Kaiser Aluminumdeveloped a Sc-containing 7xxx alloy for baseball andsoftball bats which was introduced to the Americanmarket in 1997 by Easton Alcoa soon followed with aSc-containing alloy for a competing brand of batsLouisville Slugger Since then several new and improvedSc-containing alloys for bats have been introduced tothe market The purpose of adding Sc is to increase theyield strength of the alloy allowing for a down-gaugingof the wall thickness which in turn gives a strongerlsquospring-rsquo or lsquotrampoline-rsquo effect when the ball hits thebat

Shortly after the introduction of the Sc containingbats Easton also launched Sc-containing 7xxx tubingfor bicycle frames Just as in the bats Sc increases theyield strength of the alloy allowing for down-gauging oftube wall thickness and a corresponding weight reduc-tion of the bicycle frame An Italian manufacturer ofbicycle tubing Dedacciai also delivers tubes in a Sc-containing 7xxx alloy

Other sports equipment made from Sc-containingaluminium alloys includes lacrosse sticks and tent polesSmith and Wesson has also introduced a series ofhandguns where the frame is made from a Sc-containingAl alloy

A common factor for the items mentioned above isthat the material cost is only a minor part of the totalmanufacturing cost of the end product and also thatthese products are aimed at a group of customers thathave a certain awareness of new materials Both baseballbats and bicycle frames have been marketed aslsquoscandium alloyrsquo even though the Sc content is muchlower than 1

Currently AlndashSc master alloys for the production ofSc-containing Al alloys are available at a price thatcorresponds to US$ 2000 per kg of Sc This means that ifone wants to add 02 wt-Sc to an alloy which is afairly common content one also increases the price ofthe alloy by US$ 4 per kg alloy Depending on the alloytype Sc is added to this represents a tripling orquadrupling of the price of the alloy There are notmany existing products where such an increase inmaterial cost can be justified In order to see awidespread use of Sc in high-volume products the Scprice has to come down considerably Actually the priceof adding Sc to Al alloys has gone down by a factor 3ndash10over the last 10ndash15 years and substantial price reduc-tions are also expected in the future

30 Observed variations in corrosion potential and passi-

vation current densities with Sc content in binary Alndash

Sc alloys based on data from Ref 263

Roslashyset and Ryum Scandium in aluminium alloys

International Materials Reviews 2005 VOL 50 NO 1 39

The current production of AlndashSc master alloys isbased upon and will continue to be based upon for theforeseeable future the reduction of Sc2O3 or other Sccompounds directly in molten aluminium It is notnecessary as many tend to believe to take the route viametallic Sc Thus the price of AlndashSc master alloy isgoverned by the price of Sc2O3 or other Sc compoundsin question and not by the price of metallic scandiumThe Sc2O3 which is the main source for todayrsquos AlndashScmaster alloy production comes from stockpiles in theformer USSR These stockpiles will be exhausted withina few years and new reliable sources of Sc2O3 or otherSc compound production are sought It turns out thatthe most economically viable option that has beendisclosed so far is the processing of Red Mud from theBayer process of extracting alumina from bauxiteScandium is enriched in the Red Mud and is extractedfrom a Red Mud aqueous slurry by selective leachingsubsequent ion-exchange procedure and finally a liquidndashliquid extraction procedure It is not required to build aseparate lsquoSc factoryrsquo to do this but rather build an lsquoadd-onrsquo to existing Bayer process plants Such a processroute is expected to bring down the price of Sc2O3

considerably which in turn means that AlndashSc masteralloy price should drop accordingly Preliminary ana-lyses suggest a price of approx US$ 400 per kg Sc in themaster alloy which translates to an added cost of 80cent per kilo when 02 wt-Sc is added to an aluminiumalloy This is also a considerable increase in the materialcost but with such prices one should expect to see Sccontaining alloys in many more applications than whatis the case at the present time

Concluding remarksThe body of published investigations on Al-based alloyswith Sc addition provides a sound basis of knowledgefor metallurgists that want to look into the possibility ofenhancing the performance of a wrought Al-alloy byadding Sc to it Ternary AlndashScndashX phase diagrams areavailable for practically every technologically importantalloying element in Al The effect of a wide range ofternary alloying elements on the precipitation behaviourof Al3Sc is accounted for It has been shown that theAl3Sc phase can be effective as a grain refiner adispersoid former and a precipitate hardening agentand some of the underlying conditions for achieving thedesired Al3Sc formation have been outlined Addingsome Zr together with Sc has proven to be beneficial Itmay lead to effective grain refinement at a lower Sc levelbut the most prominent effect is the refinement indispersoid distribution that can be achieved An addi-tion of Sc has little if any effect on precipitation in the2xxx 6xxx and 7xxx alloy systems and some effects onthe precipitation in AlndashLi based alloys With respect tocorrosion behaviour adding Sc to an Al-alloy does ingeneral seem to make the alloy slightly more noble andto increase its self-corrosion resistance Scandium-containing Al alloys have very few uses at the presenttime as a result of the high price of scandium The priceof Sc is expected to decrease significantly in the futureand this should lead to the disclosure of moreapplications where it is economically feasible to takeadvantage of the improved properties of some Sc-containing aluminium alloys

References1 D R Lide lsquoCRC handbook of chemistry and physicsrsquo 71st edn

4ndash29 1990 Boston USA CRC Press

2 E M Savitsky V F Terehova I V Burov and O P Naumkin

Proc Fourth Conf on lsquoRare earth researchrsquo Phoenix Arizona

USA April 1964 409ndash420

3 E M Savitskii V F Terekhova I V Burov O P Naumkin and

I A Markova Inorg Mater 1965 1 1503ndash1512

4 O P Naumkin V T Terekhova and E M Savitskiy Russ

Metall 1965 (4) 128ndash136

5 W G Moffatt lsquoThe handbook of binary phase diagramsrsquo 1981

Schenectady NY USA General Electric Co

6 E A Brandes (ed) lsquoSmithells metals reference bookrsquo 6th edn

1983 London UK Butterworths

7 R P Elliott and F A Shunk Bull Alloy Phase Diagrams 1981

2 (2) 222ndash223

8 K A Gschneider Jr and F W Calderwood Bull Alloy Phase

Diagrams 1989 10 34ndash36

9 H Okamoto J Phase Equil 1991 12 612ndash613

10 J L Murray J Phase Equil 1998 19 380ndash384

11 M E Drits E S Kadaner T V Dobatkina and N I Turkina

Russ Metall 1973 (4) 152ndash154

12 S-I Fujikawa M Sugaya H Takei and K-I Hirano J Less-

Common Met 1979 63 87ndash97

13 N Blake and M A Hopkins J Mater Sci 1985 20 2861ndash2867

14 V I Kononenko and S V Golubev Russ Metall 1990 (2) 193ndash

195

15 T B Massalski J L Murray L H Bennett and H Baker (eds)

lsquoBinary alloy phase diagramsrsquo 1986 Metals Park OH USA

ASM

16 G Cacciamani P Riani G Borzone N Parodi A Saccone

R Ferro A Pisch and R Schmid-Fetzer Intermetallics 1999 7

101ndash108

17 H Okamoto J Phase Equil 2000 21 310

18 A F Norman P B Pragnell and R S McEwen Acta Mater

1998 46 5715ndash5732

19 I N Pyagai and A V Vakhobov Russ Metall 1990 (5) 50ndash52

20 C L Fu J Mater Res 1990 5 971ndash979

21 X Lu and Y Wang Calphad 2002 26 555ndash561

22 R R Sawtell and J W Morris Jr Proc lsquoDispersion strengthened

aluminium alloysrsquo Phoenix Arizona USA January 1988 409ndash

420

23 R R Sawtell and C L Jensen Metall Trans A 1990 21A 421ndash

430

24 L A Willey Unpublished research Alcoa 1970 Data points are

extracted from Ref 10

25 N I Turkina and V I Kuzmina Russ Metall 1976 (4) 179ndash

183

26 T Torma E Kovacs-Csetenyi I Vitanyi M Butova and

J Stepanov Proc 6th Int Symp on lsquoHigh purity materials in

science and technologyrsquo Akademie der Wissenschaften der DDR

Dresden Germany May 1985 388ndash389

27 A L Berezina V A Volkov B P Domashnikov and K V

Chuistov Metallofizika 1987 9 (5) 43ndash47

28 H-H Jo J Korean Inst Metals 1990 28 499ndash504

29 H-H Jo and S-I Fujikawa Mater Sci Eng 1993 A 171 151ndash

161

30 S Celotto and T J Bastow Philos Mag A 2000 80 1111ndash1125

31 J Roslashyset and N Ryum submitted to Mater Sci Eng

32 M E Drits L S Toropova Yu G Bykov F L Gushchina V I

Elagin and Yu A Filatov Russ Metall 1983 (1) 150ndash153

33 L S Toropova D G Eskin M L Kharakterova and T V

Dobatkina lsquoAdvanced aluminum alloys containing scandium

structure and propertiesrsquo 1998 Amsterdam The Netherlands

Gordon and Breach Science Publishers

34 V V Cherkasov P P Pobezhimov L P Nefedova E V Belov

and G M Kuznetsov Met Sci Heat Treat 1996 (6) 268ndash270

35 Kh O Odinaev I N Ganiev V V Kinzhibalo and B Ya

Kotur Dokl Akad Nauk Tadzh SSR 1989 32 37ndash38

36 Kh O Odinaev I N Ganiev and A V Vakhobov Russ Metall

1991 (4) 200ndash203

37 J Grobner R Schmid-Fetzer A Pisch G Cacciamani P Riani

N Parodi G Borzone A Saccone and R Ferro Z Metallkd

1999 90 872ndash880

38 E A Marquis and D N Seidman Microsc Microanal 2002 8

(Suppl 2) 1100CDndash1101CD

39 A Pisch J Grobner and R Schmid-Fetzer Mater Sci Eng A

2000 A 289 123ndash129

Roslashyset and Ryum Scandium in aluminium alloys

40 International Materials Reviews 2005 VOL 50 NO 1

40 C Xia F Zeng and Y Gu Trans Nonferrous Met Soc China

2003 13 1124ndash1127

41 M Yu Teslyuk and V S Protasov Sov Phys Crystallogr 1966

10 470ndash471

42 M L Kharakterova and T V Dobatkina Russ Metall 1988

(6) 175ndash178

43 M L Kharakterova Russ Metall 1991 (4) 195ndash199

44 L S Toropova M L Kharakterova and D G Eskin Russ

Metall 1992 (3) 194ndash199

45 P Riani L Arrighi R Marazza D Mazzone G Zanicchi and

R Ferro J Phase Equil Diff 2004 25 22ndash52

46 A T Tyvanchuk T I Yanson B Ya Kotur O S Zarechnyuk

and M L Kharakterova Russ Metall 1988 (4) 190ndash192

47 L L Rokhlin T V Dobatkina and M L Kharakterova Powder

Metall Met Ceram 1997 36

48 A Z Ikromov I N Ganiev and V V Kinzhibalo Dokl Akad

Nauk Tadzh SSR 1990 (6) 391ndash392

49 I N Ganiev A Z Ikromov and V G Khudoiberdiev Russ

Metall 1995 (3) 125ndash127

50 I N Fridlyander L L Rokhlin T V Dobatkina and N I

Nikitina Met Sci Heat Treat 1993 (10) 567ndash571

51 I N Fridlyander L L Rokhlin T V Dobatkina V V

Kinzhibalo and A T Tyvanchuk Russ Metall 1998 (1) 161ndash

166

52 R A Emigh E L Bradley and J W Morris Jr in lsquoLight-weight

alloys for aerospace applications IIrsquo (ed E W Lee and N J

Kim) 27ndash43 1991 TMS

53 L S Toropova A N Kamardinkin V V Kindzhibalo and A T

Tyvanchuk Phys Met Metall 1990 70 (6) 106ndash110

54 A N Kamardinkin T V Dobatkina and T D Rostova Russ

Metall 1991 (4) 216ndash218

55 L S Torodskaya T V Dobatkina and A N Kamardinkin

Russ Metall 1992 (5) 128ndash131

56 E M Sokolovskaya E F Kazakova E I Poddyakova and A

A Ezhov Met Sci Heat Treat 1997 (5) 211ndash213

57 Y Harada and D C Dunand Mater Sci Eng 2002 A 329ndash331

686ndash695

58 N E Drits L S Toropova and F L Gushchina Russ Metall

1984 (4) 229ndash232

59 E M Sokolovskaya E F Kazakova V A Alikhanov and E V

Zhuravleva Moscow Univ Chem Bull 1997 52 (5) 70ndash72

60 E M Sokolovskaya E F Kazakova and E I Poddyakova Met

Sci Heat Treat 1989 (11) 837ndash839

61 G M Cheldieva E F Kazakova E M Sokolovskaya and N I

Kaloev Russ Metall 1990 (6) 87ndash90

62 E M Sokolovskaya E F Kazakova and O D-S Kendivan

Russ Metall 1998 (4) 135ndash137

63 N G Bukhanko E F Kazakova and E M Sokolovskaya Russ

Metall 2001 (4) 425ndash431

64 E D Trubnyakova O I Bodak I N Ganiev and A V

Vakhobov Russ Metall 1987 (3) 219ndash222

65 I N Fridlyander and L V Molchanova Russ Metall 2003 (5)

476ndash480

66 R A Altynbaev S Kh Khairidinov and A V Vakhobov Russ

Metall 1987 (4) 194ndash196

67 J C Schuster and J Bauer J Less-Common Met 1985 109

345ndash350

68 L L Rokhlin A S Fridman T V Dobatkina and D G Eskin

Russ Metall 1991 (6) 146ndash148

69 A S Fridman T V Dobatkina and E V Muratova Russ

Metall 1992 (1) 207ndash209

70 C Xia F Zeng and Y Gu Trans Nonferrous Met Soc China

2003 13 546ndash552

71 F Zeng C Xia and Y Gu J Alloys Comp 2004 363 175ndash181

72 L L Rokhlin T V Dobatkina N R Bochvar and E V Lysova

J Alloys Comp 2004 367 10ndash16

73 T V Dobatkina A S Fridman and E V Muratova Russ

Metall 1992 (5) 125ndash127

74 I N Fridlyander L L Rokhlin N R Bochvar E V Lysova

and O V Boteva Russ Metall 2001 (6) 661ndash666

75 V N Rechkin L K Lamikhov and T I Samsonova Sov Phys

Crystallogr 1964 9 325ndash327

76 I I Zalutskii and P I Kripyakevich Sov Phys Crystallogr

1967 12 341ndash343

77 T J Bastow C T Forwood M A Gibson and M E Smith

Phys Rev B 1998 58 2988ndash2997

78 K Fukunaga M Kolbe K Yamada and Y Miura Mater Sci

Eng 1997 A 234ndash236 594ndash597

79 E P George J A Horton W D Porter and J H Schneibel

J Mater Res 1990 5 1639ndash1648

80 E P George D P Pope C L Fu and J H Schneibel ISIJ Int

1991 31 1063ndash1075

81 Y Harada and D C Dunand Acta Mater 2000 48 3477ndash3487

82 J H Schneibel and E P George Scripta Metall Mater 1990 24

1069ndash1074

83 J H Schneibel and P M Hazzledine Mater Res Soc Symp

Proc 1991 213 323ndash328

84 J H Schneibel and P M Hazzledine J Mater Res 1992 7

868ndash875

85 C J Sparks E D Specht G E Ice P Zschack and J Schneibel

Mater Res Soc Symp Proc 1991 213 363ndash368

86 J Tarnacki and Y-W Kim Scripta Metall Mater 1989 23

1063ndash1068

87 M Asta V Ozolins and C Woodward JOM 2001 53 (9) 16ndash

19

88 M E Drits L S Toropova F L Gushchina and S G Fedotov

Sov Non-Ferrous Met Res 1984 12 83ndash85

89 Y Harada and D C Dunand Scripta Mater 2003 48 219ndash222

90 C Woodward M Asta G Kresse and J Hafner Phys Rev B

2001 63 094103-1-6

91 J-H Xu and A J Freeman Phys Rev B 1990 41 12553ndash12561

92 M F Bartholomeusz and J A Wert Acta Metall Mater 1992

40 673ndash682

93 G Bester and M Fahnle J Phys Condens Matter 2001 13

11551ndash11565

94 C L Fu and M H Yoo Proc lsquoOrdered intermetallics ndash physical

metallurgy and mechanical behaviorrsquo Irsee Germany June 1991

155ndash164

95 K Fukunaga T Shouji and Y Miura Mater Sci Eng 1997 A

239ndash240 202ndash205

96 D P Pope Proc lsquoOrdered intermetallics ndash physical metallurgy

and mechanical behaviorrsquo Irsee Germany June 1991 143ndash153

97 J-S Wang Acta Mater 1998 46 2663ndash2674

98 M H Yoo and C L Fu Mater Sci Eng 1992 A 153 470ndash478

99 R W Hyland Jr and R C Stiffler Scripta Metall Mater 1991

25 473ndash477

100 I G Brodova I V Polents O A Korzhavina P S Popelrsquo I P

Korshunov and V O Esin Melts 1992 4 392ndash397

101 I G Brodova O A Chikova I V Polents P S Popelrsquo and V O

Esin Casting Processes 1992 1 (2) 158ndash160

102 I G Brodova D V Bashlikov and I V Polents Mater Sci

Forum 1998 269ndash272 589ndash594

103 K B Hyde A F Norman and P B Pragnell Mater Sci Forum

2000 331ndash337 1013ndash1018

104 K B Hyde A F Norman and P B Pragnell Acta Mater 2001

49 1327ndash1337

105 J Roslashyset and N Ryum Proc 6th Int Conf on lsquoAluminum

alloysrsquo Toyohashi Japan July 1998 793ndash798

106 V I Elagin V V Zakharov and T D Rostova Met Sci Heat

Treat 1993 (6) 317ndash319

107 R W Hyland Jr Metall Trans A 1992 23A 1947ndash1955

108 B A Parker Z F Zhou and P Nolle J Mater Sci 1995 30

452ndash458

109 C L Rohrer M D Asta S M Foiles and R W Hyland Jr

Mater Res Soc Symp Proc 1996 398 477ndash482

110 G M Novotny and A J Ardell Mater Sci Eng 2001 A 318

144ndash154

111 J D Robson M J Jones and P B Pragnell Acta Mater 2003

51 1453ndash1468

112 C Tan Z Zheng and B Wang Proc 3rd Int Conf on

lsquoAluminium alloysrsquo Vol I NTH Trondheim Norway June

1992 290ndash294

113 M Nakayama A Furuta and Y Miura Mater Trans JIM

1997 38 852ndash857

114 E A Marquis and D N Seidman Acta Mater 2001 49 1909ndash

1919

115 M J Jones and F J Humphreys Acta Mater 2003 51 2149ndash

2159

116 E A Marquis D N Seidman and D C Dunand in lsquoCreep

deformation fundamentals and applicationsrsquo (ed R S Mishra

J C Earthman and S V Raj) 299ndash308 2002 TMS

117 D N Seidman E A Marquis and D C Dunand Acta Mater

2002 50 4021ndash4035

118 E A Marquis D N Seidman and D C Dunand Acta Mater

2003 51 285ndash287

119 M E Drits L S Toropova U G Bikov and G K Anastaseva

Proc lsquoDiffusion in metals and alloysrsquo Tihany Hungary Augustndash

September 1982 616ndash623

120 V I Elagin V V Zakharov and T D Rostova Met Sci Heat

Treat 1983 (7) 546ndash549

Roslashyset and Ryum Scandium in aluminium alloys

International Materials Reviews 2005 VOL 50 NO 1 41

121 M Ye Drits L B Ber Yu G Bykov L S Toropova and G K

Anastaseva Phys Met Metall 1984 57 (6) 118ndash126

122 M E Drits L S Toropova and Yu G Bykov Sov Non-Ferrous

Met Res 1985 13 309ndash314

123 V I Yelagin V V Zakharov S G Pavlenko and T D Rostova

Phys Met Metall 1985 60 (1) 88ndash92

124 N Sano Y Hasegawa K Hono H Jo K Hirano H W

Pickering and T Sakurai Journal de Physique 1987 48 C6 337ndash

342

125 N Sano H-H Jo K-I Hirano and T Sakurai J Jpn Inst

Metals 1989 39 444ndash450

126 N Sano H Jo K Hirano and T Sakurai Proc Second Int

Conf on lsquoAluminium alloysrsquo Beijing China October 1990 549ndash

554

127 Y Miura M Nakayama and A Furuta Proc lsquoAspects of high

temperature deformation and fracture in crystalline materialsrsquo

Nagoya Japan July 1993 255ndash262

128 Y W Riddle and T H Sanders Jr Mater Sci Forum 2000

331ndash337 939ndash944

129 Y W Riddle M McIntosh and T H Sanders Jr in lsquoLightweight

alloys for aerospace application VIrsquo (ed K Jata E W Lee

W Frazier and N J Kim) 25ndash39 2001 TMS

130 M E Drits J Dutkiewicz L S Toropova and J Salawa Crystal

Res Technol 1984 19 1325ndash1330

131 Y W Riddle MSc thesis Georgia Tech GA USA 1998

132 T J Bastow and S Celotto Mater Sci Eng 2003 C 23 757ndash

762

133 M C Carroll M J Mills G S Daehn P I Gouma M F

Savage and B R Dunbar in lsquoAutomotive Alloys 1999rsquo (ed

S Das) 239ndash246 2000 TMS

134 E Clouet M Nastar and C Sigli Phys Rev B 2004 69 064109-

1-14

135 V V Zakharov Met Sci Heat Treat 1997 (2) 61ndash66

136 J W Christian lsquoThe theory of transformation in metals and

alloysrsquo 2nd edn 1975 Pergamon Press Ltd

137 A L Berezina V A Volkov B P Domashnikov S V Ivanov

and K V Chuistov Phys Metals 1990 10 296ndash304

138 S-I Fujikawa and S Sakauchi Proc 6th Int Conf on

lsquoAluminum alloysrsquo Toyohashi Japan July 1998 805ndash810

139 Y S Touloukian R K Kirby R E Taylor and P D Desai

(eds) lsquoThermal expansion metallic elements and alloysrsquo 1975

New York Plenum

140 J Roslashyset and N Ryum submitted to Scripta Mater

141 R O Simmons and R W Balluffi Phys Rev 1960 117 52ndash61

142 M Ocko E Babic R Krsmik E Girt and B Leontic J Phys F

Metals Phys 1976 6 703ndash707

143 M J Jones and F J Humphreys Proc First Joint Int Conf on

lsquoRecrystallization and grain growthrsquo Aachen Germany August

2001 Springer Verlag 1287ndash1292

144 S Iwamura M Nakayama and Y Miura Mater Sci Forum

2002 396ndash402 1151ndash1156

145 S Iwamura and Y Miura Acta Mater 2004 52 591ndash600

146 M Asta S M Foiles and A A Quong Phys Rev B 1998 57

11265ndash11275

147 R W Hyland Jr M Asta S M Foiles and C L Rohrer Acta

Mater 1998 46 3667ndash3678

148 J Roslashyset and N Ryum Proc 4th Int Conf on lsquoAluminium

alloysrsquo Vol I Atlanta GA USA September 1994 194ndash201

149 M E Drits L S Toropova G K Anastaseva and G L

Nagornichnykh Russ Metall 1984 (3) 192ndash195

150 E A Marquis D N Seidman and D C Dunand Acta Mater

2003 51 4751ndash4760

151 M E Drits L S Toropova and Yu G Bykov Met Sci Heat

Treat 1983 (7) 550ndash554

152 V V Zakharov and T D Rostova Met Sci Heat Treat 1995

(2) 65ndash69

153 M Nakayama and Y Miura Proc 4th Int Conf on lsquoAluminium

alloysrsquo Vol I Atlanta GA USA September 1994 538ndash545

154 M Nakayama and Y Miura J Jpn Inst Light Metals 1996 46

275ndash279

155 M Nakayama T Okuyama and Y Miura Mater Sci Forum

2000 331ndash337 927ndash932

156 M Nakayama T Okuyama and Y Miura Proc 6th Int Conf

on lsquoAluminum alloysrsquo Toyohashi Japan July 1998 517ndash522

157 M L Kharakterova D G Eskin and L S Toropova Acta

Metall Mater 1994 42 2285ndash2290

158 V I Elagin V V Zakharov and T D Rostova Met Sci Heat

Treat 1992 (1) 37ndash45

159 H Wiik Siv Ing thesis NTH Institute of Metallurgy

Trondheim Norway 1995

160 J Roslashyset H Hovland and N Ryum Mater Sci Forum 2002

396ndash402 619ndash624

161 Y Miura K Horikawa K Yamada and M Nakayama Proc

4th Int Conf on lsquoAluminium alloysrsquo Vol II Atlanta GA USA

September 1994 161ndash168

162 Y W Riddle PhD thesis Georgia Tech GA USA 2000

163 B Forbord W Lefebvre F Danoix H Hallem and

K Marthinsen Scripta Mater 2004 51 333ndash337

164 J D Robson Acta Mater 2004 52 1409ndash1421

165 C B Fuller J L Murray and D N Seidman submitted to Acta

Mater 2004

166 M G Mousavi C E Cross and Oslash Grong Sci Technol Weld

Joining 1999 4 381ndash388

167 J S Vetrano S M Bruemmer L M Pawlowski and I M

Robertson Mater Sci Eng 1997 A 238 101ndash107

168 Y W Riddle and T H Sanders Jr Mater Sci Forum 2000

331ndash337 799ndash803

169 G M Khan A O Nikiforov V V Zakharov and I I Novikov

Tsvetnye Metally 1993 34 (11) 43ndash45

170 Z Horita M Furukawa M Nemoto A J Barnes and T G

Langdon Acta Mater 2000 48 3633ndash3640

171 L A Willey US Patent 3 619 181 9 November 1971

172 L K Lamikhov and G V Samsonov Tsvetnye Metally 1964 5

(8) 77ndash80

173 A L Berezina K V Chuistov N I Kolobnev L B

Khokhlatova and T A Monastyrskaya Mater Sci Forum

2002 396ndash402 741ndash746

174 F A Fasoyinu J Thomson D Cousineau T Castles and M

Sahoo Proc 6th Int AFS Conf on lsquoMolten aluminum

processingrsquo Orlando FL USA November 2001

175 Z Yin Q Pan Y Zhang and F Jiang Mater Sci Eng 2000

A 280 151ndash155

176 I I Novikov and O E Grushko Mater Sci Technol 1995 11

926ndash932

177 D Cousineau M Sahoo P D Newcombe T Castles and F A

Fasoyinu Proc lsquoAFS 105th casting congressrsquo Dallas TX USA

AprilndashMay 2001 157ndash184

178 C E Cross and Oslash Grong Proc 6th Int Conf on lsquoAluminum

alloysrsquo Toyohashi Japan July 1998 1441ndash1446

179 F A Costello J D Robson and P B Prangnell Mater Sci

Forum 2002 396ndash402 757ndash762

180 K B Hyde A F Norman and P B Prangnell Mater Sci

Forum 2002 396ndash402 39ndash44

181 M E Drits S G Pavlenko L S Toropova Yu G Bukov and

L B Ber Sov Phys Dokl 1981 26 (3) 344ndash346

182 A M Drits and B A Kopeliovich Russ Metall 1985 (4) 147ndash

151

183 V G Davydov V I Elagin V V Zakharov and T D Rostova

Met Sci Heat Treat 1996 (8) 347ndash352

184 M E Drits L S Toropova Yu G Bykov L B Ber and S G

Pavlenko Russ Metall 1982 (1) 148ndash152

185 T D Rostova V G Davydov V I Yelagin and V V Zakharov

Mater Sci Forum 2000 331ndash337 793ndash798

186 Y W Riddle H Hallem and N Ryum Mater Sci Forum 2002

396ndash402 563ndash568

187 J Roslashyset and Y W Riddle Proc 9th Int Conf on lsquoAluminium

alloysrsquo Brisbane Australia August 2004 1210ndash1215

188 A M Diskin V K Portnoi A M Drits and A A Alalykin Sov

Non-Ferrous Met Res 1986 14 499ndash500

189 R R Sawtell P E Bretz and C L Jensen US Patent 4 689 090

25 August 1987

190 G A Salishchev Yu B Timoshenko and R A Saitova Proc

Second Int Conf on lsquoAluminium alloysrsquo Beijing China October

1990 413ndash415

191 T G Nieh R Kaibyshev L M Hsiung N Nguyen and

J Wadsworth Scripta Mater 1997 36 1011ndash1016

192 T G Nieh L M Hsiung J Wadsworth and R Kaibyshev Acta

Mater 1998 46 2789ndash2800

193 J S Vetrano C H Henager Jr M T Smith and S M

Bruemmer in lsquoHot deformation of aluminum alloys IIrsquo (ed T R

Bieler L A Lalli and S R MacEwen) 407ndash418 1998 TMS

194 J S Vetrano C H Henager Jr S M Bruemmer Y Ge and

C H Hamilton in lsquoSuperplasticity and Superplastic Forming

1998rsquo (ed A K Gosh and T R Bieler) 89ndash97 1998 TMS

195 V Y Gertsman J S Vetrano C H Henager Jr and S M

Bruemmer Proc First Joint Int Conf on lsquoRecrystallization and

grain growthrsquo Aachen Germany August 2001 Springer Verlag

2001 837ndash842

196 Y Xiao C Gao H Ma and S Tian Trans Nonferrous Met Soc

China 2001 11 235ndash238

Roslashyset and Ryum Scandium in aluminium alloys

42 International Materials Reviews 2005 VOL 50 NO 1

197 A Gholinia F J Humphreys and P B Prangnell Acta Mater

2002 50 4461ndash4476

198 A Gholinia F J Humphreys and P B Prangnell Mater Sci

Forum 2002 408ndash412 1519ndash1524

199 S Komura P B Berbon M Furukawa Z Horita M Nemoto

and T G Langdon Scripta Mater 1998 38 1851ndash1856

200 S Komura P B Berbon A Utsunomiya M Furukawa

Z Horita M Nemoto and T G Langdon in lsquoHot deformation

of aluminum alloys IIrsquo (ed T R Bieler L A Lalli and S R

MacEwen) 125ndash138 1998 TMS

201 S Komura Z Horita M Furukawa M Nemoto and T G

Langdon J Mater Res 2000 15 2571ndash2576

202 S Komura M Furukawa Z Horita M Nemoto and T G

Langdon Mater Sci Eng 2001 A 297 111ndash118

203 S Komura Z Horita M Furukawa M Nemoto and T G

Langdon Metall Mater Trans A 2001 32A 707ndash716

204 Z Horita M Furukawa K Oh-ishi M Nemoto and T G

Langdon Proc Fourth Int Conf on lsquoRecrystallization and

related phenomenarsquo (ed T Sakai and H G Suzuki) 1999 The

Japan Institute of Metals 301ndash308

205 Z Horita S Komura P B Berbon A Utsunomiya

M Furukawa M Nemoto and T G Langdon Mater Sci

Forum 1999 304ndash306 91ndash96

206 Z Horita S Lee S Ota K Neishi and T G Langdon Mater

Sci Forum 2001 357ndash359 471ndash476

207 Z Horita T Fujinami K Sato S B Kang H W Kim and T G

Langdon in Proc James T Staley Honorary Symposium on

Aluminum Alloys lsquoAdvances in the metallurgy of aluminum

alloysrsquo (ed M Tiryakioglu) 271ndash275 2001 ASM

208 P B Berbon S Komura A Utsunomiya Z Horita

M Furukawa M Nemoto and T G Langdon Mater Trans

JIM 1999 40 772ndash778

209 M Nemoto Z Horita M Furukawa and T G Langdon Mater

Sci Forum 1999 304ndash306 59ndash66

210 M Furukawa Z Horita M Nemeto and T G Langdon Proc

lsquoLight Metals 1999rsquo Quebec City PQ Canada August 1999 583ndash

592

211 M Furukawa K Oh-ishi S Komura A Yamashita Z Horita

M Nemeto and T G Langdon Mater Sci Forum 1999 304ndash

306 97ndash102

212 M Furukawa A Utsunomiya K Matsubara Z Horita and

T G Langdon Acta Mater 2001 49 3829ndash3838

213 M Furukawa A Utsunomiya S Komura Z Horita M Nemoto

and T G Langdon Mater Sci Forum 2001 357ndash359 431ndash436

214 M Furukawa Z Horita and T G Langdon in Proc James T

Staley Honorary Symposium on Aluminum Alloys lsquoAdvances in

the metallurgy of aluminum alloysrsquo (ed M Tiryakioglu) 47ndash56

2001 ASM

215 M Furukawa Z Horita M Nemoto and T G Langdon Mater

Sci Eng 2002 A 324 82ndash89

216 M Furukawa Z Horita and T G Langdon in lsquoUltrafine grained

materials IIrsquo (ed Y T Zhu T G Langdon R S Mishra S L

Semiatin M J Saran and T C Lowe) 459ndash468 2002 TMS

217 T G Langdon M Furukawa Z Horita and M Nemoto Proc

NATO Advanced Research Workshop on lsquoInvestigations and

applications of severe plastic deformationrsquo Moscow August

1999 NATO Science Series Series 3 High Technology vol 80

Kluwer Academic Publishers The Netherlands 2000 149ndash154

218 S Lee H Akamatsu A Utsunomiya K Neishi M Furukawa

Z Horita and T G Langdon Proc Thermec 2000 Las Vegas

USA December 2000

219 S Lee A Utsunomiya H Akamatsu K Neishi M Furukawa

Z Horita and T G Langdon Acta Mater 2002 50 553ndash564

220 A Yamashita D Yamaguchi Z Horita and T G Langdon

Mater Sci Eng 2000 A 287 100ndash106

221 K Oh-ishi Z Horita D J Smith and T G Langdon J Mater

Res 2001 16 583ndash589

222 H Akamatsu T Fujinami Z Horita and T G Langdon Scripta

Mater 2001 44 759ndash764

223 S Ota H Akamatsu K Neishi M Furukawa Z Horita and

T G Langdon Mater Trans 2002 43 2364ndash2369

224 K Furuno H Akamatsu K Oh-ishi M Furukawa Z Horita

and T G Langdon Acta Mater 2004 52 2497ndash2507

225 I N Fridlyander O G Senatorova N A Ryazanova and A O

Nikiforov Mater Sci Forum 1994 170ndash172 345ndash349

226 J N Fridlyander and O G Senatorova Mater Sci Forum 1996

217ndash222 1813ndash1818

227 J Liu and D J Chakrabarti Acta Mater 1996 44 4647ndash4661

228 O G Senatorova A N Uksusnikov J N Fridlyander

J Koshorst R R Romanova N A Ryazanova A Galliot

and V V Cherkassov Proc 6th Int Conf on lsquoAluminum alloysrsquo

July 1998 Toyohashi Japan 589ndash593

229 R A Emigh E L Bradley and J W Morris Jr in

lsquoSuperplasticity in aerospace IIrsquo (ed T R McNelley and H C

Heikkenen) 303ndash315 1990 TMS

230 E L Bradley III R A Emigh and J W Morris Jr Scripta

Metall Mater 1991 25 717ndash721

231 N I Kolobnev L B Khokhlatova V D Makarov E Yu

Semenova and V V Redchits Proc Sixth Int Aluminiumndash

Lithium Conference Garmisch-Partenkirchen Germany October

1991 1053ndash1056

232 N K Tsenev R Z Valiev O V Obraztsov and I N Fridlander

Proc Sixth Int AluminiumndashLithium Conference Garmisch-

Partenkirchen Germany October 1991 1125ndash1132

233 A M Shammazov N K Tsenev R Z Valiev M M

Myshlyaev M M Bikbulatov and S P Lebedich Phys Met

Metall 2000 89 (3) 314ndash318

234 F Musin R Kaibyshev Y Motohashi T Sakuma and G Itoh

Mater Trans A 2002 43A 2370ndash2377

235 M Shagiev Y Motohashi F Musin R Kaibyshev and G Itoh

Mater Trans A 2003 44A 1694ndash1697

236 M Shagiev Y Motohashi F Musin R Kaibyshev and G Itoh

Mater Trans A 2003 44A 1698ndash1701

237 B A Parker and Z F Zhou Proc 3rd Int Conf on lsquoAluminium

alloysrsquo Vol I NTH Trondheim Norway June 1992 363ndash367

238 J R Davies lsquoASM specialty handbook aluminum and aluminum

alloysrsquo 1993 Materials Park OH USA ASM

239 S J Andersen H W Zandbergen J Jansen C Traeholt

U Tundal and O Reiso Acta Mater 1998 46 3283ndash3298

240 M L Kharakterova D G Eskin and L L Rokhlin Russ

Metall 1997 (1) 104ndash109

241 J Roslashyset Dr Ing thesis NTNU Trondheim Norway 2002

242 P P Chattopadhyay S Datta and M K Banerjee Mater Sci

Eng 2002 A 333 67ndash71

243 L I Kaigorodova E I Selnikhina E A Tkachenko and O G

Senatorova Phys Met Metall 1996 81 513ndash519

244 Y-L Wu F H Froes C Li and A Alvarez Metall Mater

Trans A 1999 30A 1017ndash1024

245 Z Yin L Yang Q Pan and F Jiang Trans Nonferrous Met

Soc China 2001 11 822ndash825

246 V I Elagin V V Zakharov and T D Rostova Met Sci Heat

Treat 1994 36 (7) 375ndash380

247 Y V Milman A I Sirko D V Lotsko O N Senkov and D B

Miracle Mater Sci Forum 2002 396ndash402 1217ndash1222

248 C-H Joh K Yamada and Y Miura Mater Trans JIM 1999

40 439ndash442

249 X J Jiang Q H Gui Y Y Li L M Ma G J Liang and C X

Shi Scr Metall Mater 1993 29 211ndash216

250 X J Jiang Y Y Li W Deng L Y Xiong W M Wu Y J Gao

and C X Shi Adv Cryogenic Eng (Mater) 1994 40 1369ndash

1376

251 C-H Joh T Katsube K Yamada and Y Miura Proc 6th Int

Conf on lsquoAluminum alloysrsquo Toyohashi Japan July 1998 799ndash

804

252 L I Kaygorodova A M Dritz T V Krymova and I N

Fridlyander Proc Sixth Int AluminiumndashLithium Conference

Garmisch-Partenkirchen Germany October 1991 363ndash367

253 L I Kaigorodova A M Drits Ya V Zhingel T V Krymova

and I N Fridlyander Phys Met Metall 1992 73 286ndash290

254 A L Berezina V A Volkov S V Ivanov N I Kolobnev and

K V Chuistov Phys Met Metall 1991 71 (2) 167ndash175

255 I N Fridlyander N I Kolobnev A L Berezina and K V

Chuistov Proc Sixth Int AluminiumndashLithium Conference

Garmisch-Partenkirchen Germany October 1991 107ndash112

256 L I Kaigorodova A M Drits Ya V Zhingel T V Krymova

and V A Rassokhin Phys Met Metall 1992 73 281ndash285

257 I N Fridlyander S F Danilov E N Malysheva T A

Gorokhova and N N Kirkina Proc Sixth Int Aluminiumndash

Lithium Conference Garmisch-Partenkirchen Germany October

1991 381ndash386

258 G Dlubek S Krause H Krause A L Beresina V S

Mikhalenkov and K V Chuistov J Phys Condens Matter

1992 4 6317ndash6328

259 S Krause H Krause G Dlubek A L Beresina and K S

Chuistov Mater Sci Forum 1992 105ndash110 1109ndash1112

260 C Y Tan Z Q Zheng and S Q Liang Proc 4th Int Conf on

lsquoAluminium alloysrsquo Vol II Atlanta GA USA September 1994

329ndash333

261 A L Beresina N I Kolobnev K V Chuistov A V Kotko and

O A Molebny Mater Sci Forum 2002 396ndash402 977ndash981

Roslashyset and Ryum Scandium in aluminium alloys

International Materials Reviews 2005 VOL 50 NO 1 43

262 I N Ganiev I Yunusov and V V Krasnoyarskii J Appl Chem

USSR 1986 60 1961ndash1965

263 I N Ganiev Prot Met 1995 31 543ndash546

264 N V Vyazovikina Prot Met 1999 35 448ndash453

265 G V Kharina and V P Kochergin Prot Met 1996 32 134ndash

136

266 G V Kharina M V Kuznetsov and V P Kochergin Russ J

Electrochem 1998 34 482ndash485

267 V S Sinyavskii V D Valrsquokov and E V Titkova Prot Met

1998 34 549ndash555

268 Y L Wu F H Froes C G Li and J Liu Proc lsquoSynthesis

processing of lightweight metallic materials IIrsquo Orlando FL

USA February 1997 73ndash81

269 Z Ahmad and B J Abdul-Aleem Proc EuroCorr 2000

270 Z Ahmad A Ul-Hamid and B J Abdul-Aleem Corros Sci

2001 43 1227ndash1243

271 R Braun B Lenczowski and G Tempus Mater Sci Forum

2000 331ndash337 1647ndash1652

272 T Torma E Kovacs-Csetenyi L Vitalis I Vitanyi

J Stepanov and M Butova Mater Sci Forum 1987 1314

497ndash503

273 Z Wang P Wang K S Kumar and C L Briant in lsquoChemistry

and electrochemistry of corrosion and stress corrosion crackingrsquo

(ed R H Jones) 573ndash582 2001 TMS

274 V I Elagin V V Zakharov A A Petrova and E V

Vyshegorodtseva Russ Metall 1983 (4) 143ndash146

Roslashyset and Ryum Scandium in aluminium alloys

44 International Materials Reviews 2005 VOL 50 NO 1

Page 20: Scandium in aluminium alloys - Atom probe · A considerable part of the available literature on scandium in aluminium alloys is reviewed. ... behaviour in Al Cu, Al Mg Si,

Supersaturated solid solutionRGP-zonesRg9Rg(Zn2Mg)

The maximum hardness is normally achieved whenthe g9 precipitates are predominant Common precipita-tion hardening temperatures are in the range 95ndash180uCand a two-step precipitation heat treatment within thistemperature regime is often used238 It has beenobserved in some investigations that Sc and SczZradditions to AlndashMgndashZn alloys slow down the precipita-tion of g9 somewhat243 Other investigations find thatthere is no effect of Sc on the precipitation behaviour ofg9244245 and yet others report that Sc additionssignificantly speed up the precipitation of g9246 In Ref247 it is found that an Sc addition leads to coarser g9precipitates and it is claimed that this gives an improvedductility of the alloy The strength-loss associated withlarger particle size is reported to be counterbalanced bystrengthening from Al3Sc precipitates

AlndashLi alloys

The precipitation sequence in binary AlndashLi alloys isapparently simple

Supersaturated solid solutionRd9Rd (AlLi)

where d9 is the metastable Al3Li phase which just likeAl3Sc has the L12 type of atomic arrangement Thetypical temperature regime for precipitation of d9 whichis the strengthening phase in this system is approx 150ndash200uC A comparison of the age hardening response ofan Alndash26 wt-Li and an Alndash24 wt-Lindash019 wt-Scalloy at 180uC248 and 200uC161 indicates that the onsetof d9 precipitation is not altered by the presence of ScThe hardness curves for the two alloys are practicallyidentical at 200uC whereas at 180uC the peak hardnesslevel is slightly higher in the AlndashLi than the AlndashLindashScalloy DSC measurements at constant heating ratesindicate that the addition of Sc to an AlndashLi alloysincreases the activation energy for d9 precipitation andmoves the exothermic peak associated with d9 precipita-tion to a higher temperature248 For specimens aged at

either 180uC or 200uC TEM observations reveal that thed9 precipitates are much smaller in the Sc containingalloy than in binary AlndashLi both in the peak agedcondition and in the overaged condition161248 Additionof Sc has also been observed to reduce the size of d9precipitates in other AlndashLi based alloys249ndash251 In an AlndashLindashCundashZr alloy an addition of Sc has been reported toslow down the homogeneous precipitation of d9252253 Ithas been claimed that Sc reduces the quench sensitivityand delays room temperature aging of AlndashLi basedalloys254ndash256

When present in the microstructure before the pre-cipitation of d9 the Al3Sc precipitates may act as effec-tive nucleation sites for d9 The resulting precipitates arespheres of d9 with a core of Al3Sc161249252ndash255257ndash261

Corrosion resistanceAn appreciable amount of data is available on the effectsof Sc on the corrosion behaviour of wrought Al-alloysSome of these effects are apparently derived from theeffects of Sc on the microstructure of the alloys It hasbeen reported that an addition of Sc increases thecorrosion potential (makes it less negative) in pureAl262ndash264 in AlndashZn alloys265266 AlndashMg alloys267 AlndashZnndashMgndashCu alloys264268 AlndashCundashMgndashMn alloys264 andin AlndashCundashLindashMgndashAg alloys264 Even though Sc alsohas been reported to decrease the corrosion potential in

28 Age hardening response at 175uC for Alndash08 wt-Mgndash

07 wt-Si alloy (Base) with additions of 02 wt-Sc

04 wt-Sc and 02 wt-Scz01 wt-Zr from Ref 241

29 TEM images of a b0 precipitates in Alndash08 wt-Mgndash

07 wt-Si alloy and b b0 and Al3(Sc1ndashxZrx) in a similar

alloy with addition of 02 wt-Scz01 wt-Zr from

Ref 241

Roslashyset and Ryum Scandium in aluminium alloys

38 International Materials Reviews 2005 VOL 50 NO 1

AlndashMg alloys269270 it seems that the general trend isthat adding Sc to an alloy makes it slightly more nobleThe change in corrosion potential is much morepronounced when Sc is added in amounts larger thanthe eutectic composition263 ie there is a considerablecontribution from primary or eutectic Al3Sc to theoverall potential It has also been demonstrated that thechange in corrosion potential caused by Sc can dependon the heat treatment applied to the alloy267268

Even though the corrosion potential is an essentialparameter in establishing the corrosion behaviour of analloy an increase in the corrosion potential does notnecessarily imply an improved self-corrosion resistanceHowever measurements of corrosion rates and passiva-tion current densities strongly suggest that the self-corrosion resistance in general is considerably improvedwhen Sc is added to wrought Al-alloys263264267 Someobserved variations in corrosion potential and passiva-tion current densities with Sc content in binary AlndashScalloys are plotted in Fig 30

Material failure in corrosive environments is often dueto localised corrosion attacks which may propagaterapidly even though the bulk material has a goodresistance against general corrosion It has been pointedout that hypereutectic additions of Sc may lead tomicrogalvanic corrosion beside primary Al3Sc parti-cles264 In AlndashMg alloys grain boundary precipitation ofAl8Mg5 can lead to localised corrosion attacks such asintergranular corrosion (IGC) exfoliation corrosion(EC) and stress corrosion cracking (SCC) In wroughtmaterial such precipitation may occur in the 60ndash180uCtemperature regime and heating in this temperaturerange is referred to as lsquosensitationrsquo An AlndashMgndashSc alloywas found to be immune against intergranular corrosionand have moderate susceptibility to exfoliation corro-sion after annealing at 350uC271 After sensitation heattreatments severe IGC and EC was observed but notquite as severe as in a corresponding alloy without ScAs for SCC the AlndashMgndashSc alloy was found to be highlyresistant271 In another study it was found that additionof 056 wt-Sc reduces the SCC susceptibility of an Alndash68 wt-Mg alloy in the as-rolled state and afterannealing at 250uC whereas in a sensitised specimenthe SCC susceptibility is somewhat increased by the Scaddition272 A third investigation found that Sc has nomeasurable detrimental effect on the SCC susceptibilityof sensitised Alndash5Mgndash015Zr alloy273 SCC is also a

severe problem in high strength AlndashZnndashMgndashCu alloys Ithas been shown that small Sc additions are effective inreducing the SCC sensitivity of these alloys244246268274

Use of Sc-containing Al alloysA systematic development of Sc-containing aluminiumalloys took place in the former USSR in the 1980s andthe interest for Sc as an alloying element in aluminiumalloys hit the western world approximately 10 yearslater Even though a number of improvements in Alalloys achieved by Sc addition have been demonstratedthe current uses of such alloys are very limited This isrelated to the very high price of scandium

In Russia some parts of military aircraft are made ofSc-containing AlndashLi alloys In the western world themain usage of Sc-containing alloys is for sportsequipment Ashurst Technology and Kaiser Aluminumdeveloped a Sc-containing 7xxx alloy for baseball andsoftball bats which was introduced to the Americanmarket in 1997 by Easton Alcoa soon followed with aSc-containing alloy for a competing brand of batsLouisville Slugger Since then several new and improvedSc-containing alloys for bats have been introduced tothe market The purpose of adding Sc is to increase theyield strength of the alloy allowing for a down-gaugingof the wall thickness which in turn gives a strongerlsquospring-rsquo or lsquotrampoline-rsquo effect when the ball hits thebat

Shortly after the introduction of the Sc containingbats Easton also launched Sc-containing 7xxx tubingfor bicycle frames Just as in the bats Sc increases theyield strength of the alloy allowing for down-gauging oftube wall thickness and a corresponding weight reduc-tion of the bicycle frame An Italian manufacturer ofbicycle tubing Dedacciai also delivers tubes in a Sc-containing 7xxx alloy

Other sports equipment made from Sc-containingaluminium alloys includes lacrosse sticks and tent polesSmith and Wesson has also introduced a series ofhandguns where the frame is made from a Sc-containingAl alloy

A common factor for the items mentioned above isthat the material cost is only a minor part of the totalmanufacturing cost of the end product and also thatthese products are aimed at a group of customers thathave a certain awareness of new materials Both baseballbats and bicycle frames have been marketed aslsquoscandium alloyrsquo even though the Sc content is muchlower than 1

Currently AlndashSc master alloys for the production ofSc-containing Al alloys are available at a price thatcorresponds to US$ 2000 per kg of Sc This means that ifone wants to add 02 wt-Sc to an alloy which is afairly common content one also increases the price ofthe alloy by US$ 4 per kg alloy Depending on the alloytype Sc is added to this represents a tripling orquadrupling of the price of the alloy There are notmany existing products where such an increase inmaterial cost can be justified In order to see awidespread use of Sc in high-volume products the Scprice has to come down considerably Actually the priceof adding Sc to Al alloys has gone down by a factor 3ndash10over the last 10ndash15 years and substantial price reduc-tions are also expected in the future

30 Observed variations in corrosion potential and passi-

vation current densities with Sc content in binary Alndash

Sc alloys based on data from Ref 263

Roslashyset and Ryum Scandium in aluminium alloys

International Materials Reviews 2005 VOL 50 NO 1 39

The current production of AlndashSc master alloys isbased upon and will continue to be based upon for theforeseeable future the reduction of Sc2O3 or other Sccompounds directly in molten aluminium It is notnecessary as many tend to believe to take the route viametallic Sc Thus the price of AlndashSc master alloy isgoverned by the price of Sc2O3 or other Sc compoundsin question and not by the price of metallic scandiumThe Sc2O3 which is the main source for todayrsquos AlndashScmaster alloy production comes from stockpiles in theformer USSR These stockpiles will be exhausted withina few years and new reliable sources of Sc2O3 or otherSc compound production are sought It turns out thatthe most economically viable option that has beendisclosed so far is the processing of Red Mud from theBayer process of extracting alumina from bauxiteScandium is enriched in the Red Mud and is extractedfrom a Red Mud aqueous slurry by selective leachingsubsequent ion-exchange procedure and finally a liquidndashliquid extraction procedure It is not required to build aseparate lsquoSc factoryrsquo to do this but rather build an lsquoadd-onrsquo to existing Bayer process plants Such a processroute is expected to bring down the price of Sc2O3

considerably which in turn means that AlndashSc masteralloy price should drop accordingly Preliminary ana-lyses suggest a price of approx US$ 400 per kg Sc in themaster alloy which translates to an added cost of 80cent per kilo when 02 wt-Sc is added to an aluminiumalloy This is also a considerable increase in the materialcost but with such prices one should expect to see Sccontaining alloys in many more applications than whatis the case at the present time

Concluding remarksThe body of published investigations on Al-based alloyswith Sc addition provides a sound basis of knowledgefor metallurgists that want to look into the possibility ofenhancing the performance of a wrought Al-alloy byadding Sc to it Ternary AlndashScndashX phase diagrams areavailable for practically every technologically importantalloying element in Al The effect of a wide range ofternary alloying elements on the precipitation behaviourof Al3Sc is accounted for It has been shown that theAl3Sc phase can be effective as a grain refiner adispersoid former and a precipitate hardening agentand some of the underlying conditions for achieving thedesired Al3Sc formation have been outlined Addingsome Zr together with Sc has proven to be beneficial Itmay lead to effective grain refinement at a lower Sc levelbut the most prominent effect is the refinement indispersoid distribution that can be achieved An addi-tion of Sc has little if any effect on precipitation in the2xxx 6xxx and 7xxx alloy systems and some effects onthe precipitation in AlndashLi based alloys With respect tocorrosion behaviour adding Sc to an Al-alloy does ingeneral seem to make the alloy slightly more noble andto increase its self-corrosion resistance Scandium-containing Al alloys have very few uses at the presenttime as a result of the high price of scandium The priceof Sc is expected to decrease significantly in the futureand this should lead to the disclosure of moreapplications where it is economically feasible to takeadvantage of the improved properties of some Sc-containing aluminium alloys

References1 D R Lide lsquoCRC handbook of chemistry and physicsrsquo 71st edn

4ndash29 1990 Boston USA CRC Press

2 E M Savitsky V F Terehova I V Burov and O P Naumkin

Proc Fourth Conf on lsquoRare earth researchrsquo Phoenix Arizona

USA April 1964 409ndash420

3 E M Savitskii V F Terekhova I V Burov O P Naumkin and

I A Markova Inorg Mater 1965 1 1503ndash1512

4 O P Naumkin V T Terekhova and E M Savitskiy Russ

Metall 1965 (4) 128ndash136

5 W G Moffatt lsquoThe handbook of binary phase diagramsrsquo 1981

Schenectady NY USA General Electric Co

6 E A Brandes (ed) lsquoSmithells metals reference bookrsquo 6th edn

1983 London UK Butterworths

7 R P Elliott and F A Shunk Bull Alloy Phase Diagrams 1981

2 (2) 222ndash223

8 K A Gschneider Jr and F W Calderwood Bull Alloy Phase

Diagrams 1989 10 34ndash36

9 H Okamoto J Phase Equil 1991 12 612ndash613

10 J L Murray J Phase Equil 1998 19 380ndash384

11 M E Drits E S Kadaner T V Dobatkina and N I Turkina

Russ Metall 1973 (4) 152ndash154

12 S-I Fujikawa M Sugaya H Takei and K-I Hirano J Less-

Common Met 1979 63 87ndash97

13 N Blake and M A Hopkins J Mater Sci 1985 20 2861ndash2867

14 V I Kononenko and S V Golubev Russ Metall 1990 (2) 193ndash

195

15 T B Massalski J L Murray L H Bennett and H Baker (eds)

lsquoBinary alloy phase diagramsrsquo 1986 Metals Park OH USA

ASM

16 G Cacciamani P Riani G Borzone N Parodi A Saccone

R Ferro A Pisch and R Schmid-Fetzer Intermetallics 1999 7

101ndash108

17 H Okamoto J Phase Equil 2000 21 310

18 A F Norman P B Pragnell and R S McEwen Acta Mater

1998 46 5715ndash5732

19 I N Pyagai and A V Vakhobov Russ Metall 1990 (5) 50ndash52

20 C L Fu J Mater Res 1990 5 971ndash979

21 X Lu and Y Wang Calphad 2002 26 555ndash561

22 R R Sawtell and J W Morris Jr Proc lsquoDispersion strengthened

aluminium alloysrsquo Phoenix Arizona USA January 1988 409ndash

420

23 R R Sawtell and C L Jensen Metall Trans A 1990 21A 421ndash

430

24 L A Willey Unpublished research Alcoa 1970 Data points are

extracted from Ref 10

25 N I Turkina and V I Kuzmina Russ Metall 1976 (4) 179ndash

183

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J Stepanov Proc 6th Int Symp on lsquoHigh purity materials in

science and technologyrsquo Akademie der Wissenschaften der DDR

Dresden Germany May 1985 388ndash389

27 A L Berezina V A Volkov B P Domashnikov and K V

Chuistov Metallofizika 1987 9 (5) 43ndash47

28 H-H Jo J Korean Inst Metals 1990 28 499ndash504

29 H-H Jo and S-I Fujikawa Mater Sci Eng 1993 A 171 151ndash

161

30 S Celotto and T J Bastow Philos Mag A 2000 80 1111ndash1125

31 J Roslashyset and N Ryum submitted to Mater Sci Eng

32 M E Drits L S Toropova Yu G Bykov F L Gushchina V I

Elagin and Yu A Filatov Russ Metall 1983 (1) 150ndash153

33 L S Toropova D G Eskin M L Kharakterova and T V

Dobatkina lsquoAdvanced aluminum alloys containing scandium

structure and propertiesrsquo 1998 Amsterdam The Netherlands

Gordon and Breach Science Publishers

34 V V Cherkasov P P Pobezhimov L P Nefedova E V Belov

and G M Kuznetsov Met Sci Heat Treat 1996 (6) 268ndash270

35 Kh O Odinaev I N Ganiev V V Kinzhibalo and B Ya

Kotur Dokl Akad Nauk Tadzh SSR 1989 32 37ndash38

36 Kh O Odinaev I N Ganiev and A V Vakhobov Russ Metall

1991 (4) 200ndash203

37 J Grobner R Schmid-Fetzer A Pisch G Cacciamani P Riani

N Parodi G Borzone A Saccone and R Ferro Z Metallkd

1999 90 872ndash880

38 E A Marquis and D N Seidman Microsc Microanal 2002 8

(Suppl 2) 1100CDndash1101CD

39 A Pisch J Grobner and R Schmid-Fetzer Mater Sci Eng A

2000 A 289 123ndash129

Roslashyset and Ryum Scandium in aluminium alloys

40 International Materials Reviews 2005 VOL 50 NO 1

40 C Xia F Zeng and Y Gu Trans Nonferrous Met Soc China

2003 13 1124ndash1127

41 M Yu Teslyuk and V S Protasov Sov Phys Crystallogr 1966

10 470ndash471

42 M L Kharakterova and T V Dobatkina Russ Metall 1988

(6) 175ndash178

43 M L Kharakterova Russ Metall 1991 (4) 195ndash199

44 L S Toropova M L Kharakterova and D G Eskin Russ

Metall 1992 (3) 194ndash199

45 P Riani L Arrighi R Marazza D Mazzone G Zanicchi and

R Ferro J Phase Equil Diff 2004 25 22ndash52

46 A T Tyvanchuk T I Yanson B Ya Kotur O S Zarechnyuk

and M L Kharakterova Russ Metall 1988 (4) 190ndash192

47 L L Rokhlin T V Dobatkina and M L Kharakterova Powder

Metall Met Ceram 1997 36

48 A Z Ikromov I N Ganiev and V V Kinzhibalo Dokl Akad

Nauk Tadzh SSR 1990 (6) 391ndash392

49 I N Ganiev A Z Ikromov and V G Khudoiberdiev Russ

Metall 1995 (3) 125ndash127

50 I N Fridlyander L L Rokhlin T V Dobatkina and N I

Nikitina Met Sci Heat Treat 1993 (10) 567ndash571

51 I N Fridlyander L L Rokhlin T V Dobatkina V V

Kinzhibalo and A T Tyvanchuk Russ Metall 1998 (1) 161ndash

166

52 R A Emigh E L Bradley and J W Morris Jr in lsquoLight-weight

alloys for aerospace applications IIrsquo (ed E W Lee and N J

Kim) 27ndash43 1991 TMS

53 L S Toropova A N Kamardinkin V V Kindzhibalo and A T

Tyvanchuk Phys Met Metall 1990 70 (6) 106ndash110

54 A N Kamardinkin T V Dobatkina and T D Rostova Russ

Metall 1991 (4) 216ndash218

55 L S Torodskaya T V Dobatkina and A N Kamardinkin

Russ Metall 1992 (5) 128ndash131

56 E M Sokolovskaya E F Kazakova E I Poddyakova and A

A Ezhov Met Sci Heat Treat 1997 (5) 211ndash213

57 Y Harada and D C Dunand Mater Sci Eng 2002 A 329ndash331

686ndash695

58 N E Drits L S Toropova and F L Gushchina Russ Metall

1984 (4) 229ndash232

59 E M Sokolovskaya E F Kazakova V A Alikhanov and E V

Zhuravleva Moscow Univ Chem Bull 1997 52 (5) 70ndash72

60 E M Sokolovskaya E F Kazakova and E I Poddyakova Met

Sci Heat Treat 1989 (11) 837ndash839

61 G M Cheldieva E F Kazakova E M Sokolovskaya and N I

Kaloev Russ Metall 1990 (6) 87ndash90

62 E M Sokolovskaya E F Kazakova and O D-S Kendivan

Russ Metall 1998 (4) 135ndash137

63 N G Bukhanko E F Kazakova and E M Sokolovskaya Russ

Metall 2001 (4) 425ndash431

64 E D Trubnyakova O I Bodak I N Ganiev and A V

Vakhobov Russ Metall 1987 (3) 219ndash222

65 I N Fridlyander and L V Molchanova Russ Metall 2003 (5)

476ndash480

66 R A Altynbaev S Kh Khairidinov and A V Vakhobov Russ

Metall 1987 (4) 194ndash196

67 J C Schuster and J Bauer J Less-Common Met 1985 109

345ndash350

68 L L Rokhlin A S Fridman T V Dobatkina and D G Eskin

Russ Metall 1991 (6) 146ndash148

69 A S Fridman T V Dobatkina and E V Muratova Russ

Metall 1992 (1) 207ndash209

70 C Xia F Zeng and Y Gu Trans Nonferrous Met Soc China

2003 13 546ndash552

71 F Zeng C Xia and Y Gu J Alloys Comp 2004 363 175ndash181

72 L L Rokhlin T V Dobatkina N R Bochvar and E V Lysova

J Alloys Comp 2004 367 10ndash16

73 T V Dobatkina A S Fridman and E V Muratova Russ

Metall 1992 (5) 125ndash127

74 I N Fridlyander L L Rokhlin N R Bochvar E V Lysova

and O V Boteva Russ Metall 2001 (6) 661ndash666

75 V N Rechkin L K Lamikhov and T I Samsonova Sov Phys

Crystallogr 1964 9 325ndash327

76 I I Zalutskii and P I Kripyakevich Sov Phys Crystallogr

1967 12 341ndash343

77 T J Bastow C T Forwood M A Gibson and M E Smith

Phys Rev B 1998 58 2988ndash2997

78 K Fukunaga M Kolbe K Yamada and Y Miura Mater Sci

Eng 1997 A 234ndash236 594ndash597

79 E P George J A Horton W D Porter and J H Schneibel

J Mater Res 1990 5 1639ndash1648

80 E P George D P Pope C L Fu and J H Schneibel ISIJ Int

1991 31 1063ndash1075

81 Y Harada and D C Dunand Acta Mater 2000 48 3477ndash3487

82 J H Schneibel and E P George Scripta Metall Mater 1990 24

1069ndash1074

83 J H Schneibel and P M Hazzledine Mater Res Soc Symp

Proc 1991 213 323ndash328

84 J H Schneibel and P M Hazzledine J Mater Res 1992 7

868ndash875

85 C J Sparks E D Specht G E Ice P Zschack and J Schneibel

Mater Res Soc Symp Proc 1991 213 363ndash368

86 J Tarnacki and Y-W Kim Scripta Metall Mater 1989 23

1063ndash1068

87 M Asta V Ozolins and C Woodward JOM 2001 53 (9) 16ndash

19

88 M E Drits L S Toropova F L Gushchina and S G Fedotov

Sov Non-Ferrous Met Res 1984 12 83ndash85

89 Y Harada and D C Dunand Scripta Mater 2003 48 219ndash222

90 C Woodward M Asta G Kresse and J Hafner Phys Rev B

2001 63 094103-1-6

91 J-H Xu and A J Freeman Phys Rev B 1990 41 12553ndash12561

92 M F Bartholomeusz and J A Wert Acta Metall Mater 1992

40 673ndash682

93 G Bester and M Fahnle J Phys Condens Matter 2001 13

11551ndash11565

94 C L Fu and M H Yoo Proc lsquoOrdered intermetallics ndash physical

metallurgy and mechanical behaviorrsquo Irsee Germany June 1991

155ndash164

95 K Fukunaga T Shouji and Y Miura Mater Sci Eng 1997 A

239ndash240 202ndash205

96 D P Pope Proc lsquoOrdered intermetallics ndash physical metallurgy

and mechanical behaviorrsquo Irsee Germany June 1991 143ndash153

97 J-S Wang Acta Mater 1998 46 2663ndash2674

98 M H Yoo and C L Fu Mater Sci Eng 1992 A 153 470ndash478

99 R W Hyland Jr and R C Stiffler Scripta Metall Mater 1991

25 473ndash477

100 I G Brodova I V Polents O A Korzhavina P S Popelrsquo I P

Korshunov and V O Esin Melts 1992 4 392ndash397

101 I G Brodova O A Chikova I V Polents P S Popelrsquo and V O

Esin Casting Processes 1992 1 (2) 158ndash160

102 I G Brodova D V Bashlikov and I V Polents Mater Sci

Forum 1998 269ndash272 589ndash594

103 K B Hyde A F Norman and P B Pragnell Mater Sci Forum

2000 331ndash337 1013ndash1018

104 K B Hyde A F Norman and P B Pragnell Acta Mater 2001

49 1327ndash1337

105 J Roslashyset and N Ryum Proc 6th Int Conf on lsquoAluminum

alloysrsquo Toyohashi Japan July 1998 793ndash798

106 V I Elagin V V Zakharov and T D Rostova Met Sci Heat

Treat 1993 (6) 317ndash319

107 R W Hyland Jr Metall Trans A 1992 23A 1947ndash1955

108 B A Parker Z F Zhou and P Nolle J Mater Sci 1995 30

452ndash458

109 C L Rohrer M D Asta S M Foiles and R W Hyland Jr

Mater Res Soc Symp Proc 1996 398 477ndash482

110 G M Novotny and A J Ardell Mater Sci Eng 2001 A 318

144ndash154

111 J D Robson M J Jones and P B Pragnell Acta Mater 2003

51 1453ndash1468

112 C Tan Z Zheng and B Wang Proc 3rd Int Conf on

lsquoAluminium alloysrsquo Vol I NTH Trondheim Norway June

1992 290ndash294

113 M Nakayama A Furuta and Y Miura Mater Trans JIM

1997 38 852ndash857

114 E A Marquis and D N Seidman Acta Mater 2001 49 1909ndash

1919

115 M J Jones and F J Humphreys Acta Mater 2003 51 2149ndash

2159

116 E A Marquis D N Seidman and D C Dunand in lsquoCreep

deformation fundamentals and applicationsrsquo (ed R S Mishra

J C Earthman and S V Raj) 299ndash308 2002 TMS

117 D N Seidman E A Marquis and D C Dunand Acta Mater

2002 50 4021ndash4035

118 E A Marquis D N Seidman and D C Dunand Acta Mater

2003 51 285ndash287

119 M E Drits L S Toropova U G Bikov and G K Anastaseva

Proc lsquoDiffusion in metals and alloysrsquo Tihany Hungary Augustndash

September 1982 616ndash623

120 V I Elagin V V Zakharov and T D Rostova Met Sci Heat

Treat 1983 (7) 546ndash549

Roslashyset and Ryum Scandium in aluminium alloys

International Materials Reviews 2005 VOL 50 NO 1 41

121 M Ye Drits L B Ber Yu G Bykov L S Toropova and G K

Anastaseva Phys Met Metall 1984 57 (6) 118ndash126

122 M E Drits L S Toropova and Yu G Bykov Sov Non-Ferrous

Met Res 1985 13 309ndash314

123 V I Yelagin V V Zakharov S G Pavlenko and T D Rostova

Phys Met Metall 1985 60 (1) 88ndash92

124 N Sano Y Hasegawa K Hono H Jo K Hirano H W

Pickering and T Sakurai Journal de Physique 1987 48 C6 337ndash

342

125 N Sano H-H Jo K-I Hirano and T Sakurai J Jpn Inst

Metals 1989 39 444ndash450

126 N Sano H Jo K Hirano and T Sakurai Proc Second Int

Conf on lsquoAluminium alloysrsquo Beijing China October 1990 549ndash

554

127 Y Miura M Nakayama and A Furuta Proc lsquoAspects of high

temperature deformation and fracture in crystalline materialsrsquo

Nagoya Japan July 1993 255ndash262

128 Y W Riddle and T H Sanders Jr Mater Sci Forum 2000

331ndash337 939ndash944

129 Y W Riddle M McIntosh and T H Sanders Jr in lsquoLightweight

alloys for aerospace application VIrsquo (ed K Jata E W Lee

W Frazier and N J Kim) 25ndash39 2001 TMS

130 M E Drits J Dutkiewicz L S Toropova and J Salawa Crystal

Res Technol 1984 19 1325ndash1330

131 Y W Riddle MSc thesis Georgia Tech GA USA 1998

132 T J Bastow and S Celotto Mater Sci Eng 2003 C 23 757ndash

762

133 M C Carroll M J Mills G S Daehn P I Gouma M F

Savage and B R Dunbar in lsquoAutomotive Alloys 1999rsquo (ed

S Das) 239ndash246 2000 TMS

134 E Clouet M Nastar and C Sigli Phys Rev B 2004 69 064109-

1-14

135 V V Zakharov Met Sci Heat Treat 1997 (2) 61ndash66

136 J W Christian lsquoThe theory of transformation in metals and

alloysrsquo 2nd edn 1975 Pergamon Press Ltd

137 A L Berezina V A Volkov B P Domashnikov S V Ivanov

and K V Chuistov Phys Metals 1990 10 296ndash304

138 S-I Fujikawa and S Sakauchi Proc 6th Int Conf on

lsquoAluminum alloysrsquo Toyohashi Japan July 1998 805ndash810

139 Y S Touloukian R K Kirby R E Taylor and P D Desai

(eds) lsquoThermal expansion metallic elements and alloysrsquo 1975

New York Plenum

140 J Roslashyset and N Ryum submitted to Scripta Mater

141 R O Simmons and R W Balluffi Phys Rev 1960 117 52ndash61

142 M Ocko E Babic R Krsmik E Girt and B Leontic J Phys F

Metals Phys 1976 6 703ndash707

143 M J Jones and F J Humphreys Proc First Joint Int Conf on

lsquoRecrystallization and grain growthrsquo Aachen Germany August

2001 Springer Verlag 1287ndash1292

144 S Iwamura M Nakayama and Y Miura Mater Sci Forum

2002 396ndash402 1151ndash1156

145 S Iwamura and Y Miura Acta Mater 2004 52 591ndash600

146 M Asta S M Foiles and A A Quong Phys Rev B 1998 57

11265ndash11275

147 R W Hyland Jr M Asta S M Foiles and C L Rohrer Acta

Mater 1998 46 3667ndash3678

148 J Roslashyset and N Ryum Proc 4th Int Conf on lsquoAluminium

alloysrsquo Vol I Atlanta GA USA September 1994 194ndash201

149 M E Drits L S Toropova G K Anastaseva and G L

Nagornichnykh Russ Metall 1984 (3) 192ndash195

150 E A Marquis D N Seidman and D C Dunand Acta Mater

2003 51 4751ndash4760

151 M E Drits L S Toropova and Yu G Bykov Met Sci Heat

Treat 1983 (7) 550ndash554

152 V V Zakharov and T D Rostova Met Sci Heat Treat 1995

(2) 65ndash69

153 M Nakayama and Y Miura Proc 4th Int Conf on lsquoAluminium

alloysrsquo Vol I Atlanta GA USA September 1994 538ndash545

154 M Nakayama and Y Miura J Jpn Inst Light Metals 1996 46

275ndash279

155 M Nakayama T Okuyama and Y Miura Mater Sci Forum

2000 331ndash337 927ndash932

156 M Nakayama T Okuyama and Y Miura Proc 6th Int Conf

on lsquoAluminum alloysrsquo Toyohashi Japan July 1998 517ndash522

157 M L Kharakterova D G Eskin and L S Toropova Acta

Metall Mater 1994 42 2285ndash2290

158 V I Elagin V V Zakharov and T D Rostova Met Sci Heat

Treat 1992 (1) 37ndash45

159 H Wiik Siv Ing thesis NTH Institute of Metallurgy

Trondheim Norway 1995

160 J Roslashyset H Hovland and N Ryum Mater Sci Forum 2002

396ndash402 619ndash624

161 Y Miura K Horikawa K Yamada and M Nakayama Proc

4th Int Conf on lsquoAluminium alloysrsquo Vol II Atlanta GA USA

September 1994 161ndash168

162 Y W Riddle PhD thesis Georgia Tech GA USA 2000

163 B Forbord W Lefebvre F Danoix H Hallem and

K Marthinsen Scripta Mater 2004 51 333ndash337

164 J D Robson Acta Mater 2004 52 1409ndash1421

165 C B Fuller J L Murray and D N Seidman submitted to Acta

Mater 2004

166 M G Mousavi C E Cross and Oslash Grong Sci Technol Weld

Joining 1999 4 381ndash388

167 J S Vetrano S M Bruemmer L M Pawlowski and I M

Robertson Mater Sci Eng 1997 A 238 101ndash107

168 Y W Riddle and T H Sanders Jr Mater Sci Forum 2000

331ndash337 799ndash803

169 G M Khan A O Nikiforov V V Zakharov and I I Novikov

Tsvetnye Metally 1993 34 (11) 43ndash45

170 Z Horita M Furukawa M Nemoto A J Barnes and T G

Langdon Acta Mater 2000 48 3633ndash3640

171 L A Willey US Patent 3 619 181 9 November 1971

172 L K Lamikhov and G V Samsonov Tsvetnye Metally 1964 5

(8) 77ndash80

173 A L Berezina K V Chuistov N I Kolobnev L B

Khokhlatova and T A Monastyrskaya Mater Sci Forum

2002 396ndash402 741ndash746

174 F A Fasoyinu J Thomson D Cousineau T Castles and M

Sahoo Proc 6th Int AFS Conf on lsquoMolten aluminum

processingrsquo Orlando FL USA November 2001

175 Z Yin Q Pan Y Zhang and F Jiang Mater Sci Eng 2000

A 280 151ndash155

176 I I Novikov and O E Grushko Mater Sci Technol 1995 11

926ndash932

177 D Cousineau M Sahoo P D Newcombe T Castles and F A

Fasoyinu Proc lsquoAFS 105th casting congressrsquo Dallas TX USA

AprilndashMay 2001 157ndash184

178 C E Cross and Oslash Grong Proc 6th Int Conf on lsquoAluminum

alloysrsquo Toyohashi Japan July 1998 1441ndash1446

179 F A Costello J D Robson and P B Prangnell Mater Sci

Forum 2002 396ndash402 757ndash762

180 K B Hyde A F Norman and P B Prangnell Mater Sci

Forum 2002 396ndash402 39ndash44

181 M E Drits S G Pavlenko L S Toropova Yu G Bukov and

L B Ber Sov Phys Dokl 1981 26 (3) 344ndash346

182 A M Drits and B A Kopeliovich Russ Metall 1985 (4) 147ndash

151

183 V G Davydov V I Elagin V V Zakharov and T D Rostova

Met Sci Heat Treat 1996 (8) 347ndash352

184 M E Drits L S Toropova Yu G Bykov L B Ber and S G

Pavlenko Russ Metall 1982 (1) 148ndash152

185 T D Rostova V G Davydov V I Yelagin and V V Zakharov

Mater Sci Forum 2000 331ndash337 793ndash798

186 Y W Riddle H Hallem and N Ryum Mater Sci Forum 2002

396ndash402 563ndash568

187 J Roslashyset and Y W Riddle Proc 9th Int Conf on lsquoAluminium

alloysrsquo Brisbane Australia August 2004 1210ndash1215

188 A M Diskin V K Portnoi A M Drits and A A Alalykin Sov

Non-Ferrous Met Res 1986 14 499ndash500

189 R R Sawtell P E Bretz and C L Jensen US Patent 4 689 090

25 August 1987

190 G A Salishchev Yu B Timoshenko and R A Saitova Proc

Second Int Conf on lsquoAluminium alloysrsquo Beijing China October

1990 413ndash415

191 T G Nieh R Kaibyshev L M Hsiung N Nguyen and

J Wadsworth Scripta Mater 1997 36 1011ndash1016

192 T G Nieh L M Hsiung J Wadsworth and R Kaibyshev Acta

Mater 1998 46 2789ndash2800

193 J S Vetrano C H Henager Jr M T Smith and S M

Bruemmer in lsquoHot deformation of aluminum alloys IIrsquo (ed T R

Bieler L A Lalli and S R MacEwen) 407ndash418 1998 TMS

194 J S Vetrano C H Henager Jr S M Bruemmer Y Ge and

C H Hamilton in lsquoSuperplasticity and Superplastic Forming

1998rsquo (ed A K Gosh and T R Bieler) 89ndash97 1998 TMS

195 V Y Gertsman J S Vetrano C H Henager Jr and S M

Bruemmer Proc First Joint Int Conf on lsquoRecrystallization and

grain growthrsquo Aachen Germany August 2001 Springer Verlag

2001 837ndash842

196 Y Xiao C Gao H Ma and S Tian Trans Nonferrous Met Soc

China 2001 11 235ndash238

Roslashyset and Ryum Scandium in aluminium alloys

42 International Materials Reviews 2005 VOL 50 NO 1

197 A Gholinia F J Humphreys and P B Prangnell Acta Mater

2002 50 4461ndash4476

198 A Gholinia F J Humphreys and P B Prangnell Mater Sci

Forum 2002 408ndash412 1519ndash1524

199 S Komura P B Berbon M Furukawa Z Horita M Nemoto

and T G Langdon Scripta Mater 1998 38 1851ndash1856

200 S Komura P B Berbon A Utsunomiya M Furukawa

Z Horita M Nemoto and T G Langdon in lsquoHot deformation

of aluminum alloys IIrsquo (ed T R Bieler L A Lalli and S R

MacEwen) 125ndash138 1998 TMS

201 S Komura Z Horita M Furukawa M Nemoto and T G

Langdon J Mater Res 2000 15 2571ndash2576

202 S Komura M Furukawa Z Horita M Nemoto and T G

Langdon Mater Sci Eng 2001 A 297 111ndash118

203 S Komura Z Horita M Furukawa M Nemoto and T G

Langdon Metall Mater Trans A 2001 32A 707ndash716

204 Z Horita M Furukawa K Oh-ishi M Nemoto and T G

Langdon Proc Fourth Int Conf on lsquoRecrystallization and

related phenomenarsquo (ed T Sakai and H G Suzuki) 1999 The

Japan Institute of Metals 301ndash308

205 Z Horita S Komura P B Berbon A Utsunomiya

M Furukawa M Nemoto and T G Langdon Mater Sci

Forum 1999 304ndash306 91ndash96

206 Z Horita S Lee S Ota K Neishi and T G Langdon Mater

Sci Forum 2001 357ndash359 471ndash476

207 Z Horita T Fujinami K Sato S B Kang H W Kim and T G

Langdon in Proc James T Staley Honorary Symposium on

Aluminum Alloys lsquoAdvances in the metallurgy of aluminum

alloysrsquo (ed M Tiryakioglu) 271ndash275 2001 ASM

208 P B Berbon S Komura A Utsunomiya Z Horita

M Furukawa M Nemoto and T G Langdon Mater Trans

JIM 1999 40 772ndash778

209 M Nemoto Z Horita M Furukawa and T G Langdon Mater

Sci Forum 1999 304ndash306 59ndash66

210 M Furukawa Z Horita M Nemeto and T G Langdon Proc

lsquoLight Metals 1999rsquo Quebec City PQ Canada August 1999 583ndash

592

211 M Furukawa K Oh-ishi S Komura A Yamashita Z Horita

M Nemeto and T G Langdon Mater Sci Forum 1999 304ndash

306 97ndash102

212 M Furukawa A Utsunomiya K Matsubara Z Horita and

T G Langdon Acta Mater 2001 49 3829ndash3838

213 M Furukawa A Utsunomiya S Komura Z Horita M Nemoto

and T G Langdon Mater Sci Forum 2001 357ndash359 431ndash436

214 M Furukawa Z Horita and T G Langdon in Proc James T

Staley Honorary Symposium on Aluminum Alloys lsquoAdvances in

the metallurgy of aluminum alloysrsquo (ed M Tiryakioglu) 47ndash56

2001 ASM

215 M Furukawa Z Horita M Nemoto and T G Langdon Mater

Sci Eng 2002 A 324 82ndash89

216 M Furukawa Z Horita and T G Langdon in lsquoUltrafine grained

materials IIrsquo (ed Y T Zhu T G Langdon R S Mishra S L

Semiatin M J Saran and T C Lowe) 459ndash468 2002 TMS

217 T G Langdon M Furukawa Z Horita and M Nemoto Proc

NATO Advanced Research Workshop on lsquoInvestigations and

applications of severe plastic deformationrsquo Moscow August

1999 NATO Science Series Series 3 High Technology vol 80

Kluwer Academic Publishers The Netherlands 2000 149ndash154

218 S Lee H Akamatsu A Utsunomiya K Neishi M Furukawa

Z Horita and T G Langdon Proc Thermec 2000 Las Vegas

USA December 2000

219 S Lee A Utsunomiya H Akamatsu K Neishi M Furukawa

Z Horita and T G Langdon Acta Mater 2002 50 553ndash564

220 A Yamashita D Yamaguchi Z Horita and T G Langdon

Mater Sci Eng 2000 A 287 100ndash106

221 K Oh-ishi Z Horita D J Smith and T G Langdon J Mater

Res 2001 16 583ndash589

222 H Akamatsu T Fujinami Z Horita and T G Langdon Scripta

Mater 2001 44 759ndash764

223 S Ota H Akamatsu K Neishi M Furukawa Z Horita and

T G Langdon Mater Trans 2002 43 2364ndash2369

224 K Furuno H Akamatsu K Oh-ishi M Furukawa Z Horita

and T G Langdon Acta Mater 2004 52 2497ndash2507

225 I N Fridlyander O G Senatorova N A Ryazanova and A O

Nikiforov Mater Sci Forum 1994 170ndash172 345ndash349

226 J N Fridlyander and O G Senatorova Mater Sci Forum 1996

217ndash222 1813ndash1818

227 J Liu and D J Chakrabarti Acta Mater 1996 44 4647ndash4661

228 O G Senatorova A N Uksusnikov J N Fridlyander

J Koshorst R R Romanova N A Ryazanova A Galliot

and V V Cherkassov Proc 6th Int Conf on lsquoAluminum alloysrsquo

July 1998 Toyohashi Japan 589ndash593

229 R A Emigh E L Bradley and J W Morris Jr in

lsquoSuperplasticity in aerospace IIrsquo (ed T R McNelley and H C

Heikkenen) 303ndash315 1990 TMS

230 E L Bradley III R A Emigh and J W Morris Jr Scripta

Metall Mater 1991 25 717ndash721

231 N I Kolobnev L B Khokhlatova V D Makarov E Yu

Semenova and V V Redchits Proc Sixth Int Aluminiumndash

Lithium Conference Garmisch-Partenkirchen Germany October

1991 1053ndash1056

232 N K Tsenev R Z Valiev O V Obraztsov and I N Fridlander

Proc Sixth Int AluminiumndashLithium Conference Garmisch-

Partenkirchen Germany October 1991 1125ndash1132

233 A M Shammazov N K Tsenev R Z Valiev M M

Myshlyaev M M Bikbulatov and S P Lebedich Phys Met

Metall 2000 89 (3) 314ndash318

234 F Musin R Kaibyshev Y Motohashi T Sakuma and G Itoh

Mater Trans A 2002 43A 2370ndash2377

235 M Shagiev Y Motohashi F Musin R Kaibyshev and G Itoh

Mater Trans A 2003 44A 1694ndash1697

236 M Shagiev Y Motohashi F Musin R Kaibyshev and G Itoh

Mater Trans A 2003 44A 1698ndash1701

237 B A Parker and Z F Zhou Proc 3rd Int Conf on lsquoAluminium

alloysrsquo Vol I NTH Trondheim Norway June 1992 363ndash367

238 J R Davies lsquoASM specialty handbook aluminum and aluminum

alloysrsquo 1993 Materials Park OH USA ASM

239 S J Andersen H W Zandbergen J Jansen C Traeholt

U Tundal and O Reiso Acta Mater 1998 46 3283ndash3298

240 M L Kharakterova D G Eskin and L L Rokhlin Russ

Metall 1997 (1) 104ndash109

241 J Roslashyset Dr Ing thesis NTNU Trondheim Norway 2002

242 P P Chattopadhyay S Datta and M K Banerjee Mater Sci

Eng 2002 A 333 67ndash71

243 L I Kaigorodova E I Selnikhina E A Tkachenko and O G

Senatorova Phys Met Metall 1996 81 513ndash519

244 Y-L Wu F H Froes C Li and A Alvarez Metall Mater

Trans A 1999 30A 1017ndash1024

245 Z Yin L Yang Q Pan and F Jiang Trans Nonferrous Met

Soc China 2001 11 822ndash825

246 V I Elagin V V Zakharov and T D Rostova Met Sci Heat

Treat 1994 36 (7) 375ndash380

247 Y V Milman A I Sirko D V Lotsko O N Senkov and D B

Miracle Mater Sci Forum 2002 396ndash402 1217ndash1222

248 C-H Joh K Yamada and Y Miura Mater Trans JIM 1999

40 439ndash442

249 X J Jiang Q H Gui Y Y Li L M Ma G J Liang and C X

Shi Scr Metall Mater 1993 29 211ndash216

250 X J Jiang Y Y Li W Deng L Y Xiong W M Wu Y J Gao

and C X Shi Adv Cryogenic Eng (Mater) 1994 40 1369ndash

1376

251 C-H Joh T Katsube K Yamada and Y Miura Proc 6th Int

Conf on lsquoAluminum alloysrsquo Toyohashi Japan July 1998 799ndash

804

252 L I Kaygorodova A M Dritz T V Krymova and I N

Fridlyander Proc Sixth Int AluminiumndashLithium Conference

Garmisch-Partenkirchen Germany October 1991 363ndash367

253 L I Kaigorodova A M Drits Ya V Zhingel T V Krymova

and I N Fridlyander Phys Met Metall 1992 73 286ndash290

254 A L Berezina V A Volkov S V Ivanov N I Kolobnev and

K V Chuistov Phys Met Metall 1991 71 (2) 167ndash175

255 I N Fridlyander N I Kolobnev A L Berezina and K V

Chuistov Proc Sixth Int AluminiumndashLithium Conference

Garmisch-Partenkirchen Germany October 1991 107ndash112

256 L I Kaigorodova A M Drits Ya V Zhingel T V Krymova

and V A Rassokhin Phys Met Metall 1992 73 281ndash285

257 I N Fridlyander S F Danilov E N Malysheva T A

Gorokhova and N N Kirkina Proc Sixth Int Aluminiumndash

Lithium Conference Garmisch-Partenkirchen Germany October

1991 381ndash386

258 G Dlubek S Krause H Krause A L Beresina V S

Mikhalenkov and K V Chuistov J Phys Condens Matter

1992 4 6317ndash6328

259 S Krause H Krause G Dlubek A L Beresina and K S

Chuistov Mater Sci Forum 1992 105ndash110 1109ndash1112

260 C Y Tan Z Q Zheng and S Q Liang Proc 4th Int Conf on

lsquoAluminium alloysrsquo Vol II Atlanta GA USA September 1994

329ndash333

261 A L Beresina N I Kolobnev K V Chuistov A V Kotko and

O A Molebny Mater Sci Forum 2002 396ndash402 977ndash981

Roslashyset and Ryum Scandium in aluminium alloys

International Materials Reviews 2005 VOL 50 NO 1 43

262 I N Ganiev I Yunusov and V V Krasnoyarskii J Appl Chem

USSR 1986 60 1961ndash1965

263 I N Ganiev Prot Met 1995 31 543ndash546

264 N V Vyazovikina Prot Met 1999 35 448ndash453

265 G V Kharina and V P Kochergin Prot Met 1996 32 134ndash

136

266 G V Kharina M V Kuznetsov and V P Kochergin Russ J

Electrochem 1998 34 482ndash485

267 V S Sinyavskii V D Valrsquokov and E V Titkova Prot Met

1998 34 549ndash555

268 Y L Wu F H Froes C G Li and J Liu Proc lsquoSynthesis

processing of lightweight metallic materials IIrsquo Orlando FL

USA February 1997 73ndash81

269 Z Ahmad and B J Abdul-Aleem Proc EuroCorr 2000

270 Z Ahmad A Ul-Hamid and B J Abdul-Aleem Corros Sci

2001 43 1227ndash1243

271 R Braun B Lenczowski and G Tempus Mater Sci Forum

2000 331ndash337 1647ndash1652

272 T Torma E Kovacs-Csetenyi L Vitalis I Vitanyi

J Stepanov and M Butova Mater Sci Forum 1987 1314

497ndash503

273 Z Wang P Wang K S Kumar and C L Briant in lsquoChemistry

and electrochemistry of corrosion and stress corrosion crackingrsquo

(ed R H Jones) 573ndash582 2001 TMS

274 V I Elagin V V Zakharov A A Petrova and E V

Vyshegorodtseva Russ Metall 1983 (4) 143ndash146

Roslashyset and Ryum Scandium in aluminium alloys

44 International Materials Reviews 2005 VOL 50 NO 1

Page 21: Scandium in aluminium alloys - Atom probe · A considerable part of the available literature on scandium in aluminium alloys is reviewed. ... behaviour in Al Cu, Al Mg Si,

AlndashMg alloys269270 it seems that the general trend isthat adding Sc to an alloy makes it slightly more nobleThe change in corrosion potential is much morepronounced when Sc is added in amounts larger thanthe eutectic composition263 ie there is a considerablecontribution from primary or eutectic Al3Sc to theoverall potential It has also been demonstrated that thechange in corrosion potential caused by Sc can dependon the heat treatment applied to the alloy267268

Even though the corrosion potential is an essentialparameter in establishing the corrosion behaviour of analloy an increase in the corrosion potential does notnecessarily imply an improved self-corrosion resistanceHowever measurements of corrosion rates and passiva-tion current densities strongly suggest that the self-corrosion resistance in general is considerably improvedwhen Sc is added to wrought Al-alloys263264267 Someobserved variations in corrosion potential and passiva-tion current densities with Sc content in binary AlndashScalloys are plotted in Fig 30

Material failure in corrosive environments is often dueto localised corrosion attacks which may propagaterapidly even though the bulk material has a goodresistance against general corrosion It has been pointedout that hypereutectic additions of Sc may lead tomicrogalvanic corrosion beside primary Al3Sc parti-cles264 In AlndashMg alloys grain boundary precipitation ofAl8Mg5 can lead to localised corrosion attacks such asintergranular corrosion (IGC) exfoliation corrosion(EC) and stress corrosion cracking (SCC) In wroughtmaterial such precipitation may occur in the 60ndash180uCtemperature regime and heating in this temperaturerange is referred to as lsquosensitationrsquo An AlndashMgndashSc alloywas found to be immune against intergranular corrosionand have moderate susceptibility to exfoliation corro-sion after annealing at 350uC271 After sensitation heattreatments severe IGC and EC was observed but notquite as severe as in a corresponding alloy without ScAs for SCC the AlndashMgndashSc alloy was found to be highlyresistant271 In another study it was found that additionof 056 wt-Sc reduces the SCC susceptibility of an Alndash68 wt-Mg alloy in the as-rolled state and afterannealing at 250uC whereas in a sensitised specimenthe SCC susceptibility is somewhat increased by the Scaddition272 A third investigation found that Sc has nomeasurable detrimental effect on the SCC susceptibilityof sensitised Alndash5Mgndash015Zr alloy273 SCC is also a

severe problem in high strength AlndashZnndashMgndashCu alloys Ithas been shown that small Sc additions are effective inreducing the SCC sensitivity of these alloys244246268274

Use of Sc-containing Al alloysA systematic development of Sc-containing aluminiumalloys took place in the former USSR in the 1980s andthe interest for Sc as an alloying element in aluminiumalloys hit the western world approximately 10 yearslater Even though a number of improvements in Alalloys achieved by Sc addition have been demonstratedthe current uses of such alloys are very limited This isrelated to the very high price of scandium

In Russia some parts of military aircraft are made ofSc-containing AlndashLi alloys In the western world themain usage of Sc-containing alloys is for sportsequipment Ashurst Technology and Kaiser Aluminumdeveloped a Sc-containing 7xxx alloy for baseball andsoftball bats which was introduced to the Americanmarket in 1997 by Easton Alcoa soon followed with aSc-containing alloy for a competing brand of batsLouisville Slugger Since then several new and improvedSc-containing alloys for bats have been introduced tothe market The purpose of adding Sc is to increase theyield strength of the alloy allowing for a down-gaugingof the wall thickness which in turn gives a strongerlsquospring-rsquo or lsquotrampoline-rsquo effect when the ball hits thebat

Shortly after the introduction of the Sc containingbats Easton also launched Sc-containing 7xxx tubingfor bicycle frames Just as in the bats Sc increases theyield strength of the alloy allowing for down-gauging oftube wall thickness and a corresponding weight reduc-tion of the bicycle frame An Italian manufacturer ofbicycle tubing Dedacciai also delivers tubes in a Sc-containing 7xxx alloy

Other sports equipment made from Sc-containingaluminium alloys includes lacrosse sticks and tent polesSmith and Wesson has also introduced a series ofhandguns where the frame is made from a Sc-containingAl alloy

A common factor for the items mentioned above isthat the material cost is only a minor part of the totalmanufacturing cost of the end product and also thatthese products are aimed at a group of customers thathave a certain awareness of new materials Both baseballbats and bicycle frames have been marketed aslsquoscandium alloyrsquo even though the Sc content is muchlower than 1

Currently AlndashSc master alloys for the production ofSc-containing Al alloys are available at a price thatcorresponds to US$ 2000 per kg of Sc This means that ifone wants to add 02 wt-Sc to an alloy which is afairly common content one also increases the price ofthe alloy by US$ 4 per kg alloy Depending on the alloytype Sc is added to this represents a tripling orquadrupling of the price of the alloy There are notmany existing products where such an increase inmaterial cost can be justified In order to see awidespread use of Sc in high-volume products the Scprice has to come down considerably Actually the priceof adding Sc to Al alloys has gone down by a factor 3ndash10over the last 10ndash15 years and substantial price reduc-tions are also expected in the future

30 Observed variations in corrosion potential and passi-

vation current densities with Sc content in binary Alndash

Sc alloys based on data from Ref 263

Roslashyset and Ryum Scandium in aluminium alloys

International Materials Reviews 2005 VOL 50 NO 1 39

The current production of AlndashSc master alloys isbased upon and will continue to be based upon for theforeseeable future the reduction of Sc2O3 or other Sccompounds directly in molten aluminium It is notnecessary as many tend to believe to take the route viametallic Sc Thus the price of AlndashSc master alloy isgoverned by the price of Sc2O3 or other Sc compoundsin question and not by the price of metallic scandiumThe Sc2O3 which is the main source for todayrsquos AlndashScmaster alloy production comes from stockpiles in theformer USSR These stockpiles will be exhausted withina few years and new reliable sources of Sc2O3 or otherSc compound production are sought It turns out thatthe most economically viable option that has beendisclosed so far is the processing of Red Mud from theBayer process of extracting alumina from bauxiteScandium is enriched in the Red Mud and is extractedfrom a Red Mud aqueous slurry by selective leachingsubsequent ion-exchange procedure and finally a liquidndashliquid extraction procedure It is not required to build aseparate lsquoSc factoryrsquo to do this but rather build an lsquoadd-onrsquo to existing Bayer process plants Such a processroute is expected to bring down the price of Sc2O3

considerably which in turn means that AlndashSc masteralloy price should drop accordingly Preliminary ana-lyses suggest a price of approx US$ 400 per kg Sc in themaster alloy which translates to an added cost of 80cent per kilo when 02 wt-Sc is added to an aluminiumalloy This is also a considerable increase in the materialcost but with such prices one should expect to see Sccontaining alloys in many more applications than whatis the case at the present time

Concluding remarksThe body of published investigations on Al-based alloyswith Sc addition provides a sound basis of knowledgefor metallurgists that want to look into the possibility ofenhancing the performance of a wrought Al-alloy byadding Sc to it Ternary AlndashScndashX phase diagrams areavailable for practically every technologically importantalloying element in Al The effect of a wide range ofternary alloying elements on the precipitation behaviourof Al3Sc is accounted for It has been shown that theAl3Sc phase can be effective as a grain refiner adispersoid former and a precipitate hardening agentand some of the underlying conditions for achieving thedesired Al3Sc formation have been outlined Addingsome Zr together with Sc has proven to be beneficial Itmay lead to effective grain refinement at a lower Sc levelbut the most prominent effect is the refinement indispersoid distribution that can be achieved An addi-tion of Sc has little if any effect on precipitation in the2xxx 6xxx and 7xxx alloy systems and some effects onthe precipitation in AlndashLi based alloys With respect tocorrosion behaviour adding Sc to an Al-alloy does ingeneral seem to make the alloy slightly more noble andto increase its self-corrosion resistance Scandium-containing Al alloys have very few uses at the presenttime as a result of the high price of scandium The priceof Sc is expected to decrease significantly in the futureand this should lead to the disclosure of moreapplications where it is economically feasible to takeadvantage of the improved properties of some Sc-containing aluminium alloys

References1 D R Lide lsquoCRC handbook of chemistry and physicsrsquo 71st edn

4ndash29 1990 Boston USA CRC Press

2 E M Savitsky V F Terehova I V Burov and O P Naumkin

Proc Fourth Conf on lsquoRare earth researchrsquo Phoenix Arizona

USA April 1964 409ndash420

3 E M Savitskii V F Terekhova I V Burov O P Naumkin and

I A Markova Inorg Mater 1965 1 1503ndash1512

4 O P Naumkin V T Terekhova and E M Savitskiy Russ

Metall 1965 (4) 128ndash136

5 W G Moffatt lsquoThe handbook of binary phase diagramsrsquo 1981

Schenectady NY USA General Electric Co

6 E A Brandes (ed) lsquoSmithells metals reference bookrsquo 6th edn

1983 London UK Butterworths

7 R P Elliott and F A Shunk Bull Alloy Phase Diagrams 1981

2 (2) 222ndash223

8 K A Gschneider Jr and F W Calderwood Bull Alloy Phase

Diagrams 1989 10 34ndash36

9 H Okamoto J Phase Equil 1991 12 612ndash613

10 J L Murray J Phase Equil 1998 19 380ndash384

11 M E Drits E S Kadaner T V Dobatkina and N I Turkina

Russ Metall 1973 (4) 152ndash154

12 S-I Fujikawa M Sugaya H Takei and K-I Hirano J Less-

Common Met 1979 63 87ndash97

13 N Blake and M A Hopkins J Mater Sci 1985 20 2861ndash2867

14 V I Kononenko and S V Golubev Russ Metall 1990 (2) 193ndash

195

15 T B Massalski J L Murray L H Bennett and H Baker (eds)

lsquoBinary alloy phase diagramsrsquo 1986 Metals Park OH USA

ASM

16 G Cacciamani P Riani G Borzone N Parodi A Saccone

R Ferro A Pisch and R Schmid-Fetzer Intermetallics 1999 7

101ndash108

17 H Okamoto J Phase Equil 2000 21 310

18 A F Norman P B Pragnell and R S McEwen Acta Mater

1998 46 5715ndash5732

19 I N Pyagai and A V Vakhobov Russ Metall 1990 (5) 50ndash52

20 C L Fu J Mater Res 1990 5 971ndash979

21 X Lu and Y Wang Calphad 2002 26 555ndash561

22 R R Sawtell and J W Morris Jr Proc lsquoDispersion strengthened

aluminium alloysrsquo Phoenix Arizona USA January 1988 409ndash

420

23 R R Sawtell and C L Jensen Metall Trans A 1990 21A 421ndash

430

24 L A Willey Unpublished research Alcoa 1970 Data points are

extracted from Ref 10

25 N I Turkina and V I Kuzmina Russ Metall 1976 (4) 179ndash

183

26 T Torma E Kovacs-Csetenyi I Vitanyi M Butova and

J Stepanov Proc 6th Int Symp on lsquoHigh purity materials in

science and technologyrsquo Akademie der Wissenschaften der DDR

Dresden Germany May 1985 388ndash389

27 A L Berezina V A Volkov B P Domashnikov and K V

Chuistov Metallofizika 1987 9 (5) 43ndash47

28 H-H Jo J Korean Inst Metals 1990 28 499ndash504

29 H-H Jo and S-I Fujikawa Mater Sci Eng 1993 A 171 151ndash

161

30 S Celotto and T J Bastow Philos Mag A 2000 80 1111ndash1125

31 J Roslashyset and N Ryum submitted to Mater Sci Eng

32 M E Drits L S Toropova Yu G Bykov F L Gushchina V I

Elagin and Yu A Filatov Russ Metall 1983 (1) 150ndash153

33 L S Toropova D G Eskin M L Kharakterova and T V

Dobatkina lsquoAdvanced aluminum alloys containing scandium

structure and propertiesrsquo 1998 Amsterdam The Netherlands

Gordon and Breach Science Publishers

34 V V Cherkasov P P Pobezhimov L P Nefedova E V Belov

and G M Kuznetsov Met Sci Heat Treat 1996 (6) 268ndash270

35 Kh O Odinaev I N Ganiev V V Kinzhibalo and B Ya

Kotur Dokl Akad Nauk Tadzh SSR 1989 32 37ndash38

36 Kh O Odinaev I N Ganiev and A V Vakhobov Russ Metall

1991 (4) 200ndash203

37 J Grobner R Schmid-Fetzer A Pisch G Cacciamani P Riani

N Parodi G Borzone A Saccone and R Ferro Z Metallkd

1999 90 872ndash880

38 E A Marquis and D N Seidman Microsc Microanal 2002 8

(Suppl 2) 1100CDndash1101CD

39 A Pisch J Grobner and R Schmid-Fetzer Mater Sci Eng A

2000 A 289 123ndash129

Roslashyset and Ryum Scandium in aluminium alloys

40 International Materials Reviews 2005 VOL 50 NO 1

40 C Xia F Zeng and Y Gu Trans Nonferrous Met Soc China

2003 13 1124ndash1127

41 M Yu Teslyuk and V S Protasov Sov Phys Crystallogr 1966

10 470ndash471

42 M L Kharakterova and T V Dobatkina Russ Metall 1988

(6) 175ndash178

43 M L Kharakterova Russ Metall 1991 (4) 195ndash199

44 L S Toropova M L Kharakterova and D G Eskin Russ

Metall 1992 (3) 194ndash199

45 P Riani L Arrighi R Marazza D Mazzone G Zanicchi and

R Ferro J Phase Equil Diff 2004 25 22ndash52

46 A T Tyvanchuk T I Yanson B Ya Kotur O S Zarechnyuk

and M L Kharakterova Russ Metall 1988 (4) 190ndash192

47 L L Rokhlin T V Dobatkina and M L Kharakterova Powder

Metall Met Ceram 1997 36

48 A Z Ikromov I N Ganiev and V V Kinzhibalo Dokl Akad

Nauk Tadzh SSR 1990 (6) 391ndash392

49 I N Ganiev A Z Ikromov and V G Khudoiberdiev Russ

Metall 1995 (3) 125ndash127

50 I N Fridlyander L L Rokhlin T V Dobatkina and N I

Nikitina Met Sci Heat Treat 1993 (10) 567ndash571

51 I N Fridlyander L L Rokhlin T V Dobatkina V V

Kinzhibalo and A T Tyvanchuk Russ Metall 1998 (1) 161ndash

166

52 R A Emigh E L Bradley and J W Morris Jr in lsquoLight-weight

alloys for aerospace applications IIrsquo (ed E W Lee and N J

Kim) 27ndash43 1991 TMS

53 L S Toropova A N Kamardinkin V V Kindzhibalo and A T

Tyvanchuk Phys Met Metall 1990 70 (6) 106ndash110

54 A N Kamardinkin T V Dobatkina and T D Rostova Russ

Metall 1991 (4) 216ndash218

55 L S Torodskaya T V Dobatkina and A N Kamardinkin

Russ Metall 1992 (5) 128ndash131

56 E M Sokolovskaya E F Kazakova E I Poddyakova and A

A Ezhov Met Sci Heat Treat 1997 (5) 211ndash213

57 Y Harada and D C Dunand Mater Sci Eng 2002 A 329ndash331

686ndash695

58 N E Drits L S Toropova and F L Gushchina Russ Metall

1984 (4) 229ndash232

59 E M Sokolovskaya E F Kazakova V A Alikhanov and E V

Zhuravleva Moscow Univ Chem Bull 1997 52 (5) 70ndash72

60 E M Sokolovskaya E F Kazakova and E I Poddyakova Met

Sci Heat Treat 1989 (11) 837ndash839

61 G M Cheldieva E F Kazakova E M Sokolovskaya and N I

Kaloev Russ Metall 1990 (6) 87ndash90

62 E M Sokolovskaya E F Kazakova and O D-S Kendivan

Russ Metall 1998 (4) 135ndash137

63 N G Bukhanko E F Kazakova and E M Sokolovskaya Russ

Metall 2001 (4) 425ndash431

64 E D Trubnyakova O I Bodak I N Ganiev and A V

Vakhobov Russ Metall 1987 (3) 219ndash222

65 I N Fridlyander and L V Molchanova Russ Metall 2003 (5)

476ndash480

66 R A Altynbaev S Kh Khairidinov and A V Vakhobov Russ

Metall 1987 (4) 194ndash196

67 J C Schuster and J Bauer J Less-Common Met 1985 109

345ndash350

68 L L Rokhlin A S Fridman T V Dobatkina and D G Eskin

Russ Metall 1991 (6) 146ndash148

69 A S Fridman T V Dobatkina and E V Muratova Russ

Metall 1992 (1) 207ndash209

70 C Xia F Zeng and Y Gu Trans Nonferrous Met Soc China

2003 13 546ndash552

71 F Zeng C Xia and Y Gu J Alloys Comp 2004 363 175ndash181

72 L L Rokhlin T V Dobatkina N R Bochvar and E V Lysova

J Alloys Comp 2004 367 10ndash16

73 T V Dobatkina A S Fridman and E V Muratova Russ

Metall 1992 (5) 125ndash127

74 I N Fridlyander L L Rokhlin N R Bochvar E V Lysova

and O V Boteva Russ Metall 2001 (6) 661ndash666

75 V N Rechkin L K Lamikhov and T I Samsonova Sov Phys

Crystallogr 1964 9 325ndash327

76 I I Zalutskii and P I Kripyakevich Sov Phys Crystallogr

1967 12 341ndash343

77 T J Bastow C T Forwood M A Gibson and M E Smith

Phys Rev B 1998 58 2988ndash2997

78 K Fukunaga M Kolbe K Yamada and Y Miura Mater Sci

Eng 1997 A 234ndash236 594ndash597

79 E P George J A Horton W D Porter and J H Schneibel

J Mater Res 1990 5 1639ndash1648

80 E P George D P Pope C L Fu and J H Schneibel ISIJ Int

1991 31 1063ndash1075

81 Y Harada and D C Dunand Acta Mater 2000 48 3477ndash3487

82 J H Schneibel and E P George Scripta Metall Mater 1990 24

1069ndash1074

83 J H Schneibel and P M Hazzledine Mater Res Soc Symp

Proc 1991 213 323ndash328

84 J H Schneibel and P M Hazzledine J Mater Res 1992 7

868ndash875

85 C J Sparks E D Specht G E Ice P Zschack and J Schneibel

Mater Res Soc Symp Proc 1991 213 363ndash368

86 J Tarnacki and Y-W Kim Scripta Metall Mater 1989 23

1063ndash1068

87 M Asta V Ozolins and C Woodward JOM 2001 53 (9) 16ndash

19

88 M E Drits L S Toropova F L Gushchina and S G Fedotov

Sov Non-Ferrous Met Res 1984 12 83ndash85

89 Y Harada and D C Dunand Scripta Mater 2003 48 219ndash222

90 C Woodward M Asta G Kresse and J Hafner Phys Rev B

2001 63 094103-1-6

91 J-H Xu and A J Freeman Phys Rev B 1990 41 12553ndash12561

92 M F Bartholomeusz and J A Wert Acta Metall Mater 1992

40 673ndash682

93 G Bester and M Fahnle J Phys Condens Matter 2001 13

11551ndash11565

94 C L Fu and M H Yoo Proc lsquoOrdered intermetallics ndash physical

metallurgy and mechanical behaviorrsquo Irsee Germany June 1991

155ndash164

95 K Fukunaga T Shouji and Y Miura Mater Sci Eng 1997 A

239ndash240 202ndash205

96 D P Pope Proc lsquoOrdered intermetallics ndash physical metallurgy

and mechanical behaviorrsquo Irsee Germany June 1991 143ndash153

97 J-S Wang Acta Mater 1998 46 2663ndash2674

98 M H Yoo and C L Fu Mater Sci Eng 1992 A 153 470ndash478

99 R W Hyland Jr and R C Stiffler Scripta Metall Mater 1991

25 473ndash477

100 I G Brodova I V Polents O A Korzhavina P S Popelrsquo I P

Korshunov and V O Esin Melts 1992 4 392ndash397

101 I G Brodova O A Chikova I V Polents P S Popelrsquo and V O

Esin Casting Processes 1992 1 (2) 158ndash160

102 I G Brodova D V Bashlikov and I V Polents Mater Sci

Forum 1998 269ndash272 589ndash594

103 K B Hyde A F Norman and P B Pragnell Mater Sci Forum

2000 331ndash337 1013ndash1018

104 K B Hyde A F Norman and P B Pragnell Acta Mater 2001

49 1327ndash1337

105 J Roslashyset and N Ryum Proc 6th Int Conf on lsquoAluminum

alloysrsquo Toyohashi Japan July 1998 793ndash798

106 V I Elagin V V Zakharov and T D Rostova Met Sci Heat

Treat 1993 (6) 317ndash319

107 R W Hyland Jr Metall Trans A 1992 23A 1947ndash1955

108 B A Parker Z F Zhou and P Nolle J Mater Sci 1995 30

452ndash458

109 C L Rohrer M D Asta S M Foiles and R W Hyland Jr

Mater Res Soc Symp Proc 1996 398 477ndash482

110 G M Novotny and A J Ardell Mater Sci Eng 2001 A 318

144ndash154

111 J D Robson M J Jones and P B Pragnell Acta Mater 2003

51 1453ndash1468

112 C Tan Z Zheng and B Wang Proc 3rd Int Conf on

lsquoAluminium alloysrsquo Vol I NTH Trondheim Norway June

1992 290ndash294

113 M Nakayama A Furuta and Y Miura Mater Trans JIM

1997 38 852ndash857

114 E A Marquis and D N Seidman Acta Mater 2001 49 1909ndash

1919

115 M J Jones and F J Humphreys Acta Mater 2003 51 2149ndash

2159

116 E A Marquis D N Seidman and D C Dunand in lsquoCreep

deformation fundamentals and applicationsrsquo (ed R S Mishra

J C Earthman and S V Raj) 299ndash308 2002 TMS

117 D N Seidman E A Marquis and D C Dunand Acta Mater

2002 50 4021ndash4035

118 E A Marquis D N Seidman and D C Dunand Acta Mater

2003 51 285ndash287

119 M E Drits L S Toropova U G Bikov and G K Anastaseva

Proc lsquoDiffusion in metals and alloysrsquo Tihany Hungary Augustndash

September 1982 616ndash623

120 V I Elagin V V Zakharov and T D Rostova Met Sci Heat

Treat 1983 (7) 546ndash549

Roslashyset and Ryum Scandium in aluminium alloys

International Materials Reviews 2005 VOL 50 NO 1 41

121 M Ye Drits L B Ber Yu G Bykov L S Toropova and G K

Anastaseva Phys Met Metall 1984 57 (6) 118ndash126

122 M E Drits L S Toropova and Yu G Bykov Sov Non-Ferrous

Met Res 1985 13 309ndash314

123 V I Yelagin V V Zakharov S G Pavlenko and T D Rostova

Phys Met Metall 1985 60 (1) 88ndash92

124 N Sano Y Hasegawa K Hono H Jo K Hirano H W

Pickering and T Sakurai Journal de Physique 1987 48 C6 337ndash

342

125 N Sano H-H Jo K-I Hirano and T Sakurai J Jpn Inst

Metals 1989 39 444ndash450

126 N Sano H Jo K Hirano and T Sakurai Proc Second Int

Conf on lsquoAluminium alloysrsquo Beijing China October 1990 549ndash

554

127 Y Miura M Nakayama and A Furuta Proc lsquoAspects of high

temperature deformation and fracture in crystalline materialsrsquo

Nagoya Japan July 1993 255ndash262

128 Y W Riddle and T H Sanders Jr Mater Sci Forum 2000

331ndash337 939ndash944

129 Y W Riddle M McIntosh and T H Sanders Jr in lsquoLightweight

alloys for aerospace application VIrsquo (ed K Jata E W Lee

W Frazier and N J Kim) 25ndash39 2001 TMS

130 M E Drits J Dutkiewicz L S Toropova and J Salawa Crystal

Res Technol 1984 19 1325ndash1330

131 Y W Riddle MSc thesis Georgia Tech GA USA 1998

132 T J Bastow and S Celotto Mater Sci Eng 2003 C 23 757ndash

762

133 M C Carroll M J Mills G S Daehn P I Gouma M F

Savage and B R Dunbar in lsquoAutomotive Alloys 1999rsquo (ed

S Das) 239ndash246 2000 TMS

134 E Clouet M Nastar and C Sigli Phys Rev B 2004 69 064109-

1-14

135 V V Zakharov Met Sci Heat Treat 1997 (2) 61ndash66

136 J W Christian lsquoThe theory of transformation in metals and

alloysrsquo 2nd edn 1975 Pergamon Press Ltd

137 A L Berezina V A Volkov B P Domashnikov S V Ivanov

and K V Chuistov Phys Metals 1990 10 296ndash304

138 S-I Fujikawa and S Sakauchi Proc 6th Int Conf on

lsquoAluminum alloysrsquo Toyohashi Japan July 1998 805ndash810

139 Y S Touloukian R K Kirby R E Taylor and P D Desai

(eds) lsquoThermal expansion metallic elements and alloysrsquo 1975

New York Plenum

140 J Roslashyset and N Ryum submitted to Scripta Mater

141 R O Simmons and R W Balluffi Phys Rev 1960 117 52ndash61

142 M Ocko E Babic R Krsmik E Girt and B Leontic J Phys F

Metals Phys 1976 6 703ndash707

143 M J Jones and F J Humphreys Proc First Joint Int Conf on

lsquoRecrystallization and grain growthrsquo Aachen Germany August

2001 Springer Verlag 1287ndash1292

144 S Iwamura M Nakayama and Y Miura Mater Sci Forum

2002 396ndash402 1151ndash1156

145 S Iwamura and Y Miura Acta Mater 2004 52 591ndash600

146 M Asta S M Foiles and A A Quong Phys Rev B 1998 57

11265ndash11275

147 R W Hyland Jr M Asta S M Foiles and C L Rohrer Acta

Mater 1998 46 3667ndash3678

148 J Roslashyset and N Ryum Proc 4th Int Conf on lsquoAluminium

alloysrsquo Vol I Atlanta GA USA September 1994 194ndash201

149 M E Drits L S Toropova G K Anastaseva and G L

Nagornichnykh Russ Metall 1984 (3) 192ndash195

150 E A Marquis D N Seidman and D C Dunand Acta Mater

2003 51 4751ndash4760

151 M E Drits L S Toropova and Yu G Bykov Met Sci Heat

Treat 1983 (7) 550ndash554

152 V V Zakharov and T D Rostova Met Sci Heat Treat 1995

(2) 65ndash69

153 M Nakayama and Y Miura Proc 4th Int Conf on lsquoAluminium

alloysrsquo Vol I Atlanta GA USA September 1994 538ndash545

154 M Nakayama and Y Miura J Jpn Inst Light Metals 1996 46

275ndash279

155 M Nakayama T Okuyama and Y Miura Mater Sci Forum

2000 331ndash337 927ndash932

156 M Nakayama T Okuyama and Y Miura Proc 6th Int Conf

on lsquoAluminum alloysrsquo Toyohashi Japan July 1998 517ndash522

157 M L Kharakterova D G Eskin and L S Toropova Acta

Metall Mater 1994 42 2285ndash2290

158 V I Elagin V V Zakharov and T D Rostova Met Sci Heat

Treat 1992 (1) 37ndash45

159 H Wiik Siv Ing thesis NTH Institute of Metallurgy

Trondheim Norway 1995

160 J Roslashyset H Hovland and N Ryum Mater Sci Forum 2002

396ndash402 619ndash624

161 Y Miura K Horikawa K Yamada and M Nakayama Proc

4th Int Conf on lsquoAluminium alloysrsquo Vol II Atlanta GA USA

September 1994 161ndash168

162 Y W Riddle PhD thesis Georgia Tech GA USA 2000

163 B Forbord W Lefebvre F Danoix H Hallem and

K Marthinsen Scripta Mater 2004 51 333ndash337

164 J D Robson Acta Mater 2004 52 1409ndash1421

165 C B Fuller J L Murray and D N Seidman submitted to Acta

Mater 2004

166 M G Mousavi C E Cross and Oslash Grong Sci Technol Weld

Joining 1999 4 381ndash388

167 J S Vetrano S M Bruemmer L M Pawlowski and I M

Robertson Mater Sci Eng 1997 A 238 101ndash107

168 Y W Riddle and T H Sanders Jr Mater Sci Forum 2000

331ndash337 799ndash803

169 G M Khan A O Nikiforov V V Zakharov and I I Novikov

Tsvetnye Metally 1993 34 (11) 43ndash45

170 Z Horita M Furukawa M Nemoto A J Barnes and T G

Langdon Acta Mater 2000 48 3633ndash3640

171 L A Willey US Patent 3 619 181 9 November 1971

172 L K Lamikhov and G V Samsonov Tsvetnye Metally 1964 5

(8) 77ndash80

173 A L Berezina K V Chuistov N I Kolobnev L B

Khokhlatova and T A Monastyrskaya Mater Sci Forum

2002 396ndash402 741ndash746

174 F A Fasoyinu J Thomson D Cousineau T Castles and M

Sahoo Proc 6th Int AFS Conf on lsquoMolten aluminum

processingrsquo Orlando FL USA November 2001

175 Z Yin Q Pan Y Zhang and F Jiang Mater Sci Eng 2000

A 280 151ndash155

176 I I Novikov and O E Grushko Mater Sci Technol 1995 11

926ndash932

177 D Cousineau M Sahoo P D Newcombe T Castles and F A

Fasoyinu Proc lsquoAFS 105th casting congressrsquo Dallas TX USA

AprilndashMay 2001 157ndash184

178 C E Cross and Oslash Grong Proc 6th Int Conf on lsquoAluminum

alloysrsquo Toyohashi Japan July 1998 1441ndash1446

179 F A Costello J D Robson and P B Prangnell Mater Sci

Forum 2002 396ndash402 757ndash762

180 K B Hyde A F Norman and P B Prangnell Mater Sci

Forum 2002 396ndash402 39ndash44

181 M E Drits S G Pavlenko L S Toropova Yu G Bukov and

L B Ber Sov Phys Dokl 1981 26 (3) 344ndash346

182 A M Drits and B A Kopeliovich Russ Metall 1985 (4) 147ndash

151

183 V G Davydov V I Elagin V V Zakharov and T D Rostova

Met Sci Heat Treat 1996 (8) 347ndash352

184 M E Drits L S Toropova Yu G Bykov L B Ber and S G

Pavlenko Russ Metall 1982 (1) 148ndash152

185 T D Rostova V G Davydov V I Yelagin and V V Zakharov

Mater Sci Forum 2000 331ndash337 793ndash798

186 Y W Riddle H Hallem and N Ryum Mater Sci Forum 2002

396ndash402 563ndash568

187 J Roslashyset and Y W Riddle Proc 9th Int Conf on lsquoAluminium

alloysrsquo Brisbane Australia August 2004 1210ndash1215

188 A M Diskin V K Portnoi A M Drits and A A Alalykin Sov

Non-Ferrous Met Res 1986 14 499ndash500

189 R R Sawtell P E Bretz and C L Jensen US Patent 4 689 090

25 August 1987

190 G A Salishchev Yu B Timoshenko and R A Saitova Proc

Second Int Conf on lsquoAluminium alloysrsquo Beijing China October

1990 413ndash415

191 T G Nieh R Kaibyshev L M Hsiung N Nguyen and

J Wadsworth Scripta Mater 1997 36 1011ndash1016

192 T G Nieh L M Hsiung J Wadsworth and R Kaibyshev Acta

Mater 1998 46 2789ndash2800

193 J S Vetrano C H Henager Jr M T Smith and S M

Bruemmer in lsquoHot deformation of aluminum alloys IIrsquo (ed T R

Bieler L A Lalli and S R MacEwen) 407ndash418 1998 TMS

194 J S Vetrano C H Henager Jr S M Bruemmer Y Ge and

C H Hamilton in lsquoSuperplasticity and Superplastic Forming

1998rsquo (ed A K Gosh and T R Bieler) 89ndash97 1998 TMS

195 V Y Gertsman J S Vetrano C H Henager Jr and S M

Bruemmer Proc First Joint Int Conf on lsquoRecrystallization and

grain growthrsquo Aachen Germany August 2001 Springer Verlag

2001 837ndash842

196 Y Xiao C Gao H Ma and S Tian Trans Nonferrous Met Soc

China 2001 11 235ndash238

Roslashyset and Ryum Scandium in aluminium alloys

42 International Materials Reviews 2005 VOL 50 NO 1

197 A Gholinia F J Humphreys and P B Prangnell Acta Mater

2002 50 4461ndash4476

198 A Gholinia F J Humphreys and P B Prangnell Mater Sci

Forum 2002 408ndash412 1519ndash1524

199 S Komura P B Berbon M Furukawa Z Horita M Nemoto

and T G Langdon Scripta Mater 1998 38 1851ndash1856

200 S Komura P B Berbon A Utsunomiya M Furukawa

Z Horita M Nemoto and T G Langdon in lsquoHot deformation

of aluminum alloys IIrsquo (ed T R Bieler L A Lalli and S R

MacEwen) 125ndash138 1998 TMS

201 S Komura Z Horita M Furukawa M Nemoto and T G

Langdon J Mater Res 2000 15 2571ndash2576

202 S Komura M Furukawa Z Horita M Nemoto and T G

Langdon Mater Sci Eng 2001 A 297 111ndash118

203 S Komura Z Horita M Furukawa M Nemoto and T G

Langdon Metall Mater Trans A 2001 32A 707ndash716

204 Z Horita M Furukawa K Oh-ishi M Nemoto and T G

Langdon Proc Fourth Int Conf on lsquoRecrystallization and

related phenomenarsquo (ed T Sakai and H G Suzuki) 1999 The

Japan Institute of Metals 301ndash308

205 Z Horita S Komura P B Berbon A Utsunomiya

M Furukawa M Nemoto and T G Langdon Mater Sci

Forum 1999 304ndash306 91ndash96

206 Z Horita S Lee S Ota K Neishi and T G Langdon Mater

Sci Forum 2001 357ndash359 471ndash476

207 Z Horita T Fujinami K Sato S B Kang H W Kim and T G

Langdon in Proc James T Staley Honorary Symposium on

Aluminum Alloys lsquoAdvances in the metallurgy of aluminum

alloysrsquo (ed M Tiryakioglu) 271ndash275 2001 ASM

208 P B Berbon S Komura A Utsunomiya Z Horita

M Furukawa M Nemoto and T G Langdon Mater Trans

JIM 1999 40 772ndash778

209 M Nemoto Z Horita M Furukawa and T G Langdon Mater

Sci Forum 1999 304ndash306 59ndash66

210 M Furukawa Z Horita M Nemeto and T G Langdon Proc

lsquoLight Metals 1999rsquo Quebec City PQ Canada August 1999 583ndash

592

211 M Furukawa K Oh-ishi S Komura A Yamashita Z Horita

M Nemeto and T G Langdon Mater Sci Forum 1999 304ndash

306 97ndash102

212 M Furukawa A Utsunomiya K Matsubara Z Horita and

T G Langdon Acta Mater 2001 49 3829ndash3838

213 M Furukawa A Utsunomiya S Komura Z Horita M Nemoto

and T G Langdon Mater Sci Forum 2001 357ndash359 431ndash436

214 M Furukawa Z Horita and T G Langdon in Proc James T

Staley Honorary Symposium on Aluminum Alloys lsquoAdvances in

the metallurgy of aluminum alloysrsquo (ed M Tiryakioglu) 47ndash56

2001 ASM

215 M Furukawa Z Horita M Nemoto and T G Langdon Mater

Sci Eng 2002 A 324 82ndash89

216 M Furukawa Z Horita and T G Langdon in lsquoUltrafine grained

materials IIrsquo (ed Y T Zhu T G Langdon R S Mishra S L

Semiatin M J Saran and T C Lowe) 459ndash468 2002 TMS

217 T G Langdon M Furukawa Z Horita and M Nemoto Proc

NATO Advanced Research Workshop on lsquoInvestigations and

applications of severe plastic deformationrsquo Moscow August

1999 NATO Science Series Series 3 High Technology vol 80

Kluwer Academic Publishers The Netherlands 2000 149ndash154

218 S Lee H Akamatsu A Utsunomiya K Neishi M Furukawa

Z Horita and T G Langdon Proc Thermec 2000 Las Vegas

USA December 2000

219 S Lee A Utsunomiya H Akamatsu K Neishi M Furukawa

Z Horita and T G Langdon Acta Mater 2002 50 553ndash564

220 A Yamashita D Yamaguchi Z Horita and T G Langdon

Mater Sci Eng 2000 A 287 100ndash106

221 K Oh-ishi Z Horita D J Smith and T G Langdon J Mater

Res 2001 16 583ndash589

222 H Akamatsu T Fujinami Z Horita and T G Langdon Scripta

Mater 2001 44 759ndash764

223 S Ota H Akamatsu K Neishi M Furukawa Z Horita and

T G Langdon Mater Trans 2002 43 2364ndash2369

224 K Furuno H Akamatsu K Oh-ishi M Furukawa Z Horita

and T G Langdon Acta Mater 2004 52 2497ndash2507

225 I N Fridlyander O G Senatorova N A Ryazanova and A O

Nikiforov Mater Sci Forum 1994 170ndash172 345ndash349

226 J N Fridlyander and O G Senatorova Mater Sci Forum 1996

217ndash222 1813ndash1818

227 J Liu and D J Chakrabarti Acta Mater 1996 44 4647ndash4661

228 O G Senatorova A N Uksusnikov J N Fridlyander

J Koshorst R R Romanova N A Ryazanova A Galliot

and V V Cherkassov Proc 6th Int Conf on lsquoAluminum alloysrsquo

July 1998 Toyohashi Japan 589ndash593

229 R A Emigh E L Bradley and J W Morris Jr in

lsquoSuperplasticity in aerospace IIrsquo (ed T R McNelley and H C

Heikkenen) 303ndash315 1990 TMS

230 E L Bradley III R A Emigh and J W Morris Jr Scripta

Metall Mater 1991 25 717ndash721

231 N I Kolobnev L B Khokhlatova V D Makarov E Yu

Semenova and V V Redchits Proc Sixth Int Aluminiumndash

Lithium Conference Garmisch-Partenkirchen Germany October

1991 1053ndash1056

232 N K Tsenev R Z Valiev O V Obraztsov and I N Fridlander

Proc Sixth Int AluminiumndashLithium Conference Garmisch-

Partenkirchen Germany October 1991 1125ndash1132

233 A M Shammazov N K Tsenev R Z Valiev M M

Myshlyaev M M Bikbulatov and S P Lebedich Phys Met

Metall 2000 89 (3) 314ndash318

234 F Musin R Kaibyshev Y Motohashi T Sakuma and G Itoh

Mater Trans A 2002 43A 2370ndash2377

235 M Shagiev Y Motohashi F Musin R Kaibyshev and G Itoh

Mater Trans A 2003 44A 1694ndash1697

236 M Shagiev Y Motohashi F Musin R Kaibyshev and G Itoh

Mater Trans A 2003 44A 1698ndash1701

237 B A Parker and Z F Zhou Proc 3rd Int Conf on lsquoAluminium

alloysrsquo Vol I NTH Trondheim Norway June 1992 363ndash367

238 J R Davies lsquoASM specialty handbook aluminum and aluminum

alloysrsquo 1993 Materials Park OH USA ASM

239 S J Andersen H W Zandbergen J Jansen C Traeholt

U Tundal and O Reiso Acta Mater 1998 46 3283ndash3298

240 M L Kharakterova D G Eskin and L L Rokhlin Russ

Metall 1997 (1) 104ndash109

241 J Roslashyset Dr Ing thesis NTNU Trondheim Norway 2002

242 P P Chattopadhyay S Datta and M K Banerjee Mater Sci

Eng 2002 A 333 67ndash71

243 L I Kaigorodova E I Selnikhina E A Tkachenko and O G

Senatorova Phys Met Metall 1996 81 513ndash519

244 Y-L Wu F H Froes C Li and A Alvarez Metall Mater

Trans A 1999 30A 1017ndash1024

245 Z Yin L Yang Q Pan and F Jiang Trans Nonferrous Met

Soc China 2001 11 822ndash825

246 V I Elagin V V Zakharov and T D Rostova Met Sci Heat

Treat 1994 36 (7) 375ndash380

247 Y V Milman A I Sirko D V Lotsko O N Senkov and D B

Miracle Mater Sci Forum 2002 396ndash402 1217ndash1222

248 C-H Joh K Yamada and Y Miura Mater Trans JIM 1999

40 439ndash442

249 X J Jiang Q H Gui Y Y Li L M Ma G J Liang and C X

Shi Scr Metall Mater 1993 29 211ndash216

250 X J Jiang Y Y Li W Deng L Y Xiong W M Wu Y J Gao

and C X Shi Adv Cryogenic Eng (Mater) 1994 40 1369ndash

1376

251 C-H Joh T Katsube K Yamada and Y Miura Proc 6th Int

Conf on lsquoAluminum alloysrsquo Toyohashi Japan July 1998 799ndash

804

252 L I Kaygorodova A M Dritz T V Krymova and I N

Fridlyander Proc Sixth Int AluminiumndashLithium Conference

Garmisch-Partenkirchen Germany October 1991 363ndash367

253 L I Kaigorodova A M Drits Ya V Zhingel T V Krymova

and I N Fridlyander Phys Met Metall 1992 73 286ndash290

254 A L Berezina V A Volkov S V Ivanov N I Kolobnev and

K V Chuistov Phys Met Metall 1991 71 (2) 167ndash175

255 I N Fridlyander N I Kolobnev A L Berezina and K V

Chuistov Proc Sixth Int AluminiumndashLithium Conference

Garmisch-Partenkirchen Germany October 1991 107ndash112

256 L I Kaigorodova A M Drits Ya V Zhingel T V Krymova

and V A Rassokhin Phys Met Metall 1992 73 281ndash285

257 I N Fridlyander S F Danilov E N Malysheva T A

Gorokhova and N N Kirkina Proc Sixth Int Aluminiumndash

Lithium Conference Garmisch-Partenkirchen Germany October

1991 381ndash386

258 G Dlubek S Krause H Krause A L Beresina V S

Mikhalenkov and K V Chuistov J Phys Condens Matter

1992 4 6317ndash6328

259 S Krause H Krause G Dlubek A L Beresina and K S

Chuistov Mater Sci Forum 1992 105ndash110 1109ndash1112

260 C Y Tan Z Q Zheng and S Q Liang Proc 4th Int Conf on

lsquoAluminium alloysrsquo Vol II Atlanta GA USA September 1994

329ndash333

261 A L Beresina N I Kolobnev K V Chuistov A V Kotko and

O A Molebny Mater Sci Forum 2002 396ndash402 977ndash981

Roslashyset and Ryum Scandium in aluminium alloys

International Materials Reviews 2005 VOL 50 NO 1 43

262 I N Ganiev I Yunusov and V V Krasnoyarskii J Appl Chem

USSR 1986 60 1961ndash1965

263 I N Ganiev Prot Met 1995 31 543ndash546

264 N V Vyazovikina Prot Met 1999 35 448ndash453

265 G V Kharina and V P Kochergin Prot Met 1996 32 134ndash

136

266 G V Kharina M V Kuznetsov and V P Kochergin Russ J

Electrochem 1998 34 482ndash485

267 V S Sinyavskii V D Valrsquokov and E V Titkova Prot Met

1998 34 549ndash555

268 Y L Wu F H Froes C G Li and J Liu Proc lsquoSynthesis

processing of lightweight metallic materials IIrsquo Orlando FL

USA February 1997 73ndash81

269 Z Ahmad and B J Abdul-Aleem Proc EuroCorr 2000

270 Z Ahmad A Ul-Hamid and B J Abdul-Aleem Corros Sci

2001 43 1227ndash1243

271 R Braun B Lenczowski and G Tempus Mater Sci Forum

2000 331ndash337 1647ndash1652

272 T Torma E Kovacs-Csetenyi L Vitalis I Vitanyi

J Stepanov and M Butova Mater Sci Forum 1987 1314

497ndash503

273 Z Wang P Wang K S Kumar and C L Briant in lsquoChemistry

and electrochemistry of corrosion and stress corrosion crackingrsquo

(ed R H Jones) 573ndash582 2001 TMS

274 V I Elagin V V Zakharov A A Petrova and E V

Vyshegorodtseva Russ Metall 1983 (4) 143ndash146

Roslashyset and Ryum Scandium in aluminium alloys

44 International Materials Reviews 2005 VOL 50 NO 1

Page 22: Scandium in aluminium alloys - Atom probe · A considerable part of the available literature on scandium in aluminium alloys is reviewed. ... behaviour in Al Cu, Al Mg Si,

The current production of AlndashSc master alloys isbased upon and will continue to be based upon for theforeseeable future the reduction of Sc2O3 or other Sccompounds directly in molten aluminium It is notnecessary as many tend to believe to take the route viametallic Sc Thus the price of AlndashSc master alloy isgoverned by the price of Sc2O3 or other Sc compoundsin question and not by the price of metallic scandiumThe Sc2O3 which is the main source for todayrsquos AlndashScmaster alloy production comes from stockpiles in theformer USSR These stockpiles will be exhausted withina few years and new reliable sources of Sc2O3 or otherSc compound production are sought It turns out thatthe most economically viable option that has beendisclosed so far is the processing of Red Mud from theBayer process of extracting alumina from bauxiteScandium is enriched in the Red Mud and is extractedfrom a Red Mud aqueous slurry by selective leachingsubsequent ion-exchange procedure and finally a liquidndashliquid extraction procedure It is not required to build aseparate lsquoSc factoryrsquo to do this but rather build an lsquoadd-onrsquo to existing Bayer process plants Such a processroute is expected to bring down the price of Sc2O3

considerably which in turn means that AlndashSc masteralloy price should drop accordingly Preliminary ana-lyses suggest a price of approx US$ 400 per kg Sc in themaster alloy which translates to an added cost of 80cent per kilo when 02 wt-Sc is added to an aluminiumalloy This is also a considerable increase in the materialcost but with such prices one should expect to see Sccontaining alloys in many more applications than whatis the case at the present time

Concluding remarksThe body of published investigations on Al-based alloyswith Sc addition provides a sound basis of knowledgefor metallurgists that want to look into the possibility ofenhancing the performance of a wrought Al-alloy byadding Sc to it Ternary AlndashScndashX phase diagrams areavailable for practically every technologically importantalloying element in Al The effect of a wide range ofternary alloying elements on the precipitation behaviourof Al3Sc is accounted for It has been shown that theAl3Sc phase can be effective as a grain refiner adispersoid former and a precipitate hardening agentand some of the underlying conditions for achieving thedesired Al3Sc formation have been outlined Addingsome Zr together with Sc has proven to be beneficial Itmay lead to effective grain refinement at a lower Sc levelbut the most prominent effect is the refinement indispersoid distribution that can be achieved An addi-tion of Sc has little if any effect on precipitation in the2xxx 6xxx and 7xxx alloy systems and some effects onthe precipitation in AlndashLi based alloys With respect tocorrosion behaviour adding Sc to an Al-alloy does ingeneral seem to make the alloy slightly more noble andto increase its self-corrosion resistance Scandium-containing Al alloys have very few uses at the presenttime as a result of the high price of scandium The priceof Sc is expected to decrease significantly in the futureand this should lead to the disclosure of moreapplications where it is economically feasible to takeadvantage of the improved properties of some Sc-containing aluminium alloys

References1 D R Lide lsquoCRC handbook of chemistry and physicsrsquo 71st edn

4ndash29 1990 Boston USA CRC Press

2 E M Savitsky V F Terehova I V Burov and O P Naumkin

Proc Fourth Conf on lsquoRare earth researchrsquo Phoenix Arizona

USA April 1964 409ndash420

3 E M Savitskii V F Terekhova I V Burov O P Naumkin and

I A Markova Inorg Mater 1965 1 1503ndash1512

4 O P Naumkin V T Terekhova and E M Savitskiy Russ

Metall 1965 (4) 128ndash136

5 W G Moffatt lsquoThe handbook of binary phase diagramsrsquo 1981

Schenectady NY USA General Electric Co

6 E A Brandes (ed) lsquoSmithells metals reference bookrsquo 6th edn

1983 London UK Butterworths

7 R P Elliott and F A Shunk Bull Alloy Phase Diagrams 1981

2 (2) 222ndash223

8 K A Gschneider Jr and F W Calderwood Bull Alloy Phase

Diagrams 1989 10 34ndash36

9 H Okamoto J Phase Equil 1991 12 612ndash613

10 J L Murray J Phase Equil 1998 19 380ndash384

11 M E Drits E S Kadaner T V Dobatkina and N I Turkina

Russ Metall 1973 (4) 152ndash154

12 S-I Fujikawa M Sugaya H Takei and K-I Hirano J Less-

Common Met 1979 63 87ndash97

13 N Blake and M A Hopkins J Mater Sci 1985 20 2861ndash2867

14 V I Kononenko and S V Golubev Russ Metall 1990 (2) 193ndash

195

15 T B Massalski J L Murray L H Bennett and H Baker (eds)

lsquoBinary alloy phase diagramsrsquo 1986 Metals Park OH USA

ASM

16 G Cacciamani P Riani G Borzone N Parodi A Saccone

R Ferro A Pisch and R Schmid-Fetzer Intermetallics 1999 7

101ndash108

17 H Okamoto J Phase Equil 2000 21 310

18 A F Norman P B Pragnell and R S McEwen Acta Mater

1998 46 5715ndash5732

19 I N Pyagai and A V Vakhobov Russ Metall 1990 (5) 50ndash52

20 C L Fu J Mater Res 1990 5 971ndash979

21 X Lu and Y Wang Calphad 2002 26 555ndash561

22 R R Sawtell and J W Morris Jr Proc lsquoDispersion strengthened

aluminium alloysrsquo Phoenix Arizona USA January 1988 409ndash

420

23 R R Sawtell and C L Jensen Metall Trans A 1990 21A 421ndash

430

24 L A Willey Unpublished research Alcoa 1970 Data points are

extracted from Ref 10

25 N I Turkina and V I Kuzmina Russ Metall 1976 (4) 179ndash

183

26 T Torma E Kovacs-Csetenyi I Vitanyi M Butova and

J Stepanov Proc 6th Int Symp on lsquoHigh purity materials in

science and technologyrsquo Akademie der Wissenschaften der DDR

Dresden Germany May 1985 388ndash389

27 A L Berezina V A Volkov B P Domashnikov and K V

Chuistov Metallofizika 1987 9 (5) 43ndash47

28 H-H Jo J Korean Inst Metals 1990 28 499ndash504

29 H-H Jo and S-I Fujikawa Mater Sci Eng 1993 A 171 151ndash

161

30 S Celotto and T J Bastow Philos Mag A 2000 80 1111ndash1125

31 J Roslashyset and N Ryum submitted to Mater Sci Eng

32 M E Drits L S Toropova Yu G Bykov F L Gushchina V I

Elagin and Yu A Filatov Russ Metall 1983 (1) 150ndash153

33 L S Toropova D G Eskin M L Kharakterova and T V

Dobatkina lsquoAdvanced aluminum alloys containing scandium

structure and propertiesrsquo 1998 Amsterdam The Netherlands

Gordon and Breach Science Publishers

34 V V Cherkasov P P Pobezhimov L P Nefedova E V Belov

and G M Kuznetsov Met Sci Heat Treat 1996 (6) 268ndash270

35 Kh O Odinaev I N Ganiev V V Kinzhibalo and B Ya

Kotur Dokl Akad Nauk Tadzh SSR 1989 32 37ndash38

36 Kh O Odinaev I N Ganiev and A V Vakhobov Russ Metall

1991 (4) 200ndash203

37 J Grobner R Schmid-Fetzer A Pisch G Cacciamani P Riani

N Parodi G Borzone A Saccone and R Ferro Z Metallkd

1999 90 872ndash880

38 E A Marquis and D N Seidman Microsc Microanal 2002 8

(Suppl 2) 1100CDndash1101CD

39 A Pisch J Grobner and R Schmid-Fetzer Mater Sci Eng A

2000 A 289 123ndash129

Roslashyset and Ryum Scandium in aluminium alloys

40 International Materials Reviews 2005 VOL 50 NO 1

40 C Xia F Zeng and Y Gu Trans Nonferrous Met Soc China

2003 13 1124ndash1127

41 M Yu Teslyuk and V S Protasov Sov Phys Crystallogr 1966

10 470ndash471

42 M L Kharakterova and T V Dobatkina Russ Metall 1988

(6) 175ndash178

43 M L Kharakterova Russ Metall 1991 (4) 195ndash199

44 L S Toropova M L Kharakterova and D G Eskin Russ

Metall 1992 (3) 194ndash199

45 P Riani L Arrighi R Marazza D Mazzone G Zanicchi and

R Ferro J Phase Equil Diff 2004 25 22ndash52

46 A T Tyvanchuk T I Yanson B Ya Kotur O S Zarechnyuk

and M L Kharakterova Russ Metall 1988 (4) 190ndash192

47 L L Rokhlin T V Dobatkina and M L Kharakterova Powder

Metall Met Ceram 1997 36

48 A Z Ikromov I N Ganiev and V V Kinzhibalo Dokl Akad

Nauk Tadzh SSR 1990 (6) 391ndash392

49 I N Ganiev A Z Ikromov and V G Khudoiberdiev Russ

Metall 1995 (3) 125ndash127

50 I N Fridlyander L L Rokhlin T V Dobatkina and N I

Nikitina Met Sci Heat Treat 1993 (10) 567ndash571

51 I N Fridlyander L L Rokhlin T V Dobatkina V V

Kinzhibalo and A T Tyvanchuk Russ Metall 1998 (1) 161ndash

166

52 R A Emigh E L Bradley and J W Morris Jr in lsquoLight-weight

alloys for aerospace applications IIrsquo (ed E W Lee and N J

Kim) 27ndash43 1991 TMS

53 L S Toropova A N Kamardinkin V V Kindzhibalo and A T

Tyvanchuk Phys Met Metall 1990 70 (6) 106ndash110

54 A N Kamardinkin T V Dobatkina and T D Rostova Russ

Metall 1991 (4) 216ndash218

55 L S Torodskaya T V Dobatkina and A N Kamardinkin

Russ Metall 1992 (5) 128ndash131

56 E M Sokolovskaya E F Kazakova E I Poddyakova and A

A Ezhov Met Sci Heat Treat 1997 (5) 211ndash213

57 Y Harada and D C Dunand Mater Sci Eng 2002 A 329ndash331

686ndash695

58 N E Drits L S Toropova and F L Gushchina Russ Metall

1984 (4) 229ndash232

59 E M Sokolovskaya E F Kazakova V A Alikhanov and E V

Zhuravleva Moscow Univ Chem Bull 1997 52 (5) 70ndash72

60 E M Sokolovskaya E F Kazakova and E I Poddyakova Met

Sci Heat Treat 1989 (11) 837ndash839

61 G M Cheldieva E F Kazakova E M Sokolovskaya and N I

Kaloev Russ Metall 1990 (6) 87ndash90

62 E M Sokolovskaya E F Kazakova and O D-S Kendivan

Russ Metall 1998 (4) 135ndash137

63 N G Bukhanko E F Kazakova and E M Sokolovskaya Russ

Metall 2001 (4) 425ndash431

64 E D Trubnyakova O I Bodak I N Ganiev and A V

Vakhobov Russ Metall 1987 (3) 219ndash222

65 I N Fridlyander and L V Molchanova Russ Metall 2003 (5)

476ndash480

66 R A Altynbaev S Kh Khairidinov and A V Vakhobov Russ

Metall 1987 (4) 194ndash196

67 J C Schuster and J Bauer J Less-Common Met 1985 109

345ndash350

68 L L Rokhlin A S Fridman T V Dobatkina and D G Eskin

Russ Metall 1991 (6) 146ndash148

69 A S Fridman T V Dobatkina and E V Muratova Russ

Metall 1992 (1) 207ndash209

70 C Xia F Zeng and Y Gu Trans Nonferrous Met Soc China

2003 13 546ndash552

71 F Zeng C Xia and Y Gu J Alloys Comp 2004 363 175ndash181

72 L L Rokhlin T V Dobatkina N R Bochvar and E V Lysova

J Alloys Comp 2004 367 10ndash16

73 T V Dobatkina A S Fridman and E V Muratova Russ

Metall 1992 (5) 125ndash127

74 I N Fridlyander L L Rokhlin N R Bochvar E V Lysova

and O V Boteva Russ Metall 2001 (6) 661ndash666

75 V N Rechkin L K Lamikhov and T I Samsonova Sov Phys

Crystallogr 1964 9 325ndash327

76 I I Zalutskii and P I Kripyakevich Sov Phys Crystallogr

1967 12 341ndash343

77 T J Bastow C T Forwood M A Gibson and M E Smith

Phys Rev B 1998 58 2988ndash2997

78 K Fukunaga M Kolbe K Yamada and Y Miura Mater Sci

Eng 1997 A 234ndash236 594ndash597

79 E P George J A Horton W D Porter and J H Schneibel

J Mater Res 1990 5 1639ndash1648

80 E P George D P Pope C L Fu and J H Schneibel ISIJ Int

1991 31 1063ndash1075

81 Y Harada and D C Dunand Acta Mater 2000 48 3477ndash3487

82 J H Schneibel and E P George Scripta Metall Mater 1990 24

1069ndash1074

83 J H Schneibel and P M Hazzledine Mater Res Soc Symp

Proc 1991 213 323ndash328

84 J H Schneibel and P M Hazzledine J Mater Res 1992 7

868ndash875

85 C J Sparks E D Specht G E Ice P Zschack and J Schneibel

Mater Res Soc Symp Proc 1991 213 363ndash368

86 J Tarnacki and Y-W Kim Scripta Metall Mater 1989 23

1063ndash1068

87 M Asta V Ozolins and C Woodward JOM 2001 53 (9) 16ndash

19

88 M E Drits L S Toropova F L Gushchina and S G Fedotov

Sov Non-Ferrous Met Res 1984 12 83ndash85

89 Y Harada and D C Dunand Scripta Mater 2003 48 219ndash222

90 C Woodward M Asta G Kresse and J Hafner Phys Rev B

2001 63 094103-1-6

91 J-H Xu and A J Freeman Phys Rev B 1990 41 12553ndash12561

92 M F Bartholomeusz and J A Wert Acta Metall Mater 1992

40 673ndash682

93 G Bester and M Fahnle J Phys Condens Matter 2001 13

11551ndash11565

94 C L Fu and M H Yoo Proc lsquoOrdered intermetallics ndash physical

metallurgy and mechanical behaviorrsquo Irsee Germany June 1991

155ndash164

95 K Fukunaga T Shouji and Y Miura Mater Sci Eng 1997 A

239ndash240 202ndash205

96 D P Pope Proc lsquoOrdered intermetallics ndash physical metallurgy

and mechanical behaviorrsquo Irsee Germany June 1991 143ndash153

97 J-S Wang Acta Mater 1998 46 2663ndash2674

98 M H Yoo and C L Fu Mater Sci Eng 1992 A 153 470ndash478

99 R W Hyland Jr and R C Stiffler Scripta Metall Mater 1991

25 473ndash477

100 I G Brodova I V Polents O A Korzhavina P S Popelrsquo I P

Korshunov and V O Esin Melts 1992 4 392ndash397

101 I G Brodova O A Chikova I V Polents P S Popelrsquo and V O

Esin Casting Processes 1992 1 (2) 158ndash160

102 I G Brodova D V Bashlikov and I V Polents Mater Sci

Forum 1998 269ndash272 589ndash594

103 K B Hyde A F Norman and P B Pragnell Mater Sci Forum

2000 331ndash337 1013ndash1018

104 K B Hyde A F Norman and P B Pragnell Acta Mater 2001

49 1327ndash1337

105 J Roslashyset and N Ryum Proc 6th Int Conf on lsquoAluminum

alloysrsquo Toyohashi Japan July 1998 793ndash798

106 V I Elagin V V Zakharov and T D Rostova Met Sci Heat

Treat 1993 (6) 317ndash319

107 R W Hyland Jr Metall Trans A 1992 23A 1947ndash1955

108 B A Parker Z F Zhou and P Nolle J Mater Sci 1995 30

452ndash458

109 C L Rohrer M D Asta S M Foiles and R W Hyland Jr

Mater Res Soc Symp Proc 1996 398 477ndash482

110 G M Novotny and A J Ardell Mater Sci Eng 2001 A 318

144ndash154

111 J D Robson M J Jones and P B Pragnell Acta Mater 2003

51 1453ndash1468

112 C Tan Z Zheng and B Wang Proc 3rd Int Conf on

lsquoAluminium alloysrsquo Vol I NTH Trondheim Norway June

1992 290ndash294

113 M Nakayama A Furuta and Y Miura Mater Trans JIM

1997 38 852ndash857

114 E A Marquis and D N Seidman Acta Mater 2001 49 1909ndash

1919

115 M J Jones and F J Humphreys Acta Mater 2003 51 2149ndash

2159

116 E A Marquis D N Seidman and D C Dunand in lsquoCreep

deformation fundamentals and applicationsrsquo (ed R S Mishra

J C Earthman and S V Raj) 299ndash308 2002 TMS

117 D N Seidman E A Marquis and D C Dunand Acta Mater

2002 50 4021ndash4035

118 E A Marquis D N Seidman and D C Dunand Acta Mater

2003 51 285ndash287

119 M E Drits L S Toropova U G Bikov and G K Anastaseva

Proc lsquoDiffusion in metals and alloysrsquo Tihany Hungary Augustndash

September 1982 616ndash623

120 V I Elagin V V Zakharov and T D Rostova Met Sci Heat

Treat 1983 (7) 546ndash549

Roslashyset and Ryum Scandium in aluminium alloys

International Materials Reviews 2005 VOL 50 NO 1 41

121 M Ye Drits L B Ber Yu G Bykov L S Toropova and G K

Anastaseva Phys Met Metall 1984 57 (6) 118ndash126

122 M E Drits L S Toropova and Yu G Bykov Sov Non-Ferrous

Met Res 1985 13 309ndash314

123 V I Yelagin V V Zakharov S G Pavlenko and T D Rostova

Phys Met Metall 1985 60 (1) 88ndash92

124 N Sano Y Hasegawa K Hono H Jo K Hirano H W

Pickering and T Sakurai Journal de Physique 1987 48 C6 337ndash

342

125 N Sano H-H Jo K-I Hirano and T Sakurai J Jpn Inst

Metals 1989 39 444ndash450

126 N Sano H Jo K Hirano and T Sakurai Proc Second Int

Conf on lsquoAluminium alloysrsquo Beijing China October 1990 549ndash

554

127 Y Miura M Nakayama and A Furuta Proc lsquoAspects of high

temperature deformation and fracture in crystalline materialsrsquo

Nagoya Japan July 1993 255ndash262

128 Y W Riddle and T H Sanders Jr Mater Sci Forum 2000

331ndash337 939ndash944

129 Y W Riddle M McIntosh and T H Sanders Jr in lsquoLightweight

alloys for aerospace application VIrsquo (ed K Jata E W Lee

W Frazier and N J Kim) 25ndash39 2001 TMS

130 M E Drits J Dutkiewicz L S Toropova and J Salawa Crystal

Res Technol 1984 19 1325ndash1330

131 Y W Riddle MSc thesis Georgia Tech GA USA 1998

132 T J Bastow and S Celotto Mater Sci Eng 2003 C 23 757ndash

762

133 M C Carroll M J Mills G S Daehn P I Gouma M F

Savage and B R Dunbar in lsquoAutomotive Alloys 1999rsquo (ed

S Das) 239ndash246 2000 TMS

134 E Clouet M Nastar and C Sigli Phys Rev B 2004 69 064109-

1-14

135 V V Zakharov Met Sci Heat Treat 1997 (2) 61ndash66

136 J W Christian lsquoThe theory of transformation in metals and

alloysrsquo 2nd edn 1975 Pergamon Press Ltd

137 A L Berezina V A Volkov B P Domashnikov S V Ivanov

and K V Chuistov Phys Metals 1990 10 296ndash304

138 S-I Fujikawa and S Sakauchi Proc 6th Int Conf on

lsquoAluminum alloysrsquo Toyohashi Japan July 1998 805ndash810

139 Y S Touloukian R K Kirby R E Taylor and P D Desai

(eds) lsquoThermal expansion metallic elements and alloysrsquo 1975

New York Plenum

140 J Roslashyset and N Ryum submitted to Scripta Mater

141 R O Simmons and R W Balluffi Phys Rev 1960 117 52ndash61

142 M Ocko E Babic R Krsmik E Girt and B Leontic J Phys F

Metals Phys 1976 6 703ndash707

143 M J Jones and F J Humphreys Proc First Joint Int Conf on

lsquoRecrystallization and grain growthrsquo Aachen Germany August

2001 Springer Verlag 1287ndash1292

144 S Iwamura M Nakayama and Y Miura Mater Sci Forum

2002 396ndash402 1151ndash1156

145 S Iwamura and Y Miura Acta Mater 2004 52 591ndash600

146 M Asta S M Foiles and A A Quong Phys Rev B 1998 57

11265ndash11275

147 R W Hyland Jr M Asta S M Foiles and C L Rohrer Acta

Mater 1998 46 3667ndash3678

148 J Roslashyset and N Ryum Proc 4th Int Conf on lsquoAluminium

alloysrsquo Vol I Atlanta GA USA September 1994 194ndash201

149 M E Drits L S Toropova G K Anastaseva and G L

Nagornichnykh Russ Metall 1984 (3) 192ndash195

150 E A Marquis D N Seidman and D C Dunand Acta Mater

2003 51 4751ndash4760

151 M E Drits L S Toropova and Yu G Bykov Met Sci Heat

Treat 1983 (7) 550ndash554

152 V V Zakharov and T D Rostova Met Sci Heat Treat 1995

(2) 65ndash69

153 M Nakayama and Y Miura Proc 4th Int Conf on lsquoAluminium

alloysrsquo Vol I Atlanta GA USA September 1994 538ndash545

154 M Nakayama and Y Miura J Jpn Inst Light Metals 1996 46

275ndash279

155 M Nakayama T Okuyama and Y Miura Mater Sci Forum

2000 331ndash337 927ndash932

156 M Nakayama T Okuyama and Y Miura Proc 6th Int Conf

on lsquoAluminum alloysrsquo Toyohashi Japan July 1998 517ndash522

157 M L Kharakterova D G Eskin and L S Toropova Acta

Metall Mater 1994 42 2285ndash2290

158 V I Elagin V V Zakharov and T D Rostova Met Sci Heat

Treat 1992 (1) 37ndash45

159 H Wiik Siv Ing thesis NTH Institute of Metallurgy

Trondheim Norway 1995

160 J Roslashyset H Hovland and N Ryum Mater Sci Forum 2002

396ndash402 619ndash624

161 Y Miura K Horikawa K Yamada and M Nakayama Proc

4th Int Conf on lsquoAluminium alloysrsquo Vol II Atlanta GA USA

September 1994 161ndash168

162 Y W Riddle PhD thesis Georgia Tech GA USA 2000

163 B Forbord W Lefebvre F Danoix H Hallem and

K Marthinsen Scripta Mater 2004 51 333ndash337

164 J D Robson Acta Mater 2004 52 1409ndash1421

165 C B Fuller J L Murray and D N Seidman submitted to Acta

Mater 2004

166 M G Mousavi C E Cross and Oslash Grong Sci Technol Weld

Joining 1999 4 381ndash388

167 J S Vetrano S M Bruemmer L M Pawlowski and I M

Robertson Mater Sci Eng 1997 A 238 101ndash107

168 Y W Riddle and T H Sanders Jr Mater Sci Forum 2000

331ndash337 799ndash803

169 G M Khan A O Nikiforov V V Zakharov and I I Novikov

Tsvetnye Metally 1993 34 (11) 43ndash45

170 Z Horita M Furukawa M Nemoto A J Barnes and T G

Langdon Acta Mater 2000 48 3633ndash3640

171 L A Willey US Patent 3 619 181 9 November 1971

172 L K Lamikhov and G V Samsonov Tsvetnye Metally 1964 5

(8) 77ndash80

173 A L Berezina K V Chuistov N I Kolobnev L B

Khokhlatova and T A Monastyrskaya Mater Sci Forum

2002 396ndash402 741ndash746

174 F A Fasoyinu J Thomson D Cousineau T Castles and M

Sahoo Proc 6th Int AFS Conf on lsquoMolten aluminum

processingrsquo Orlando FL USA November 2001

175 Z Yin Q Pan Y Zhang and F Jiang Mater Sci Eng 2000

A 280 151ndash155

176 I I Novikov and O E Grushko Mater Sci Technol 1995 11

926ndash932

177 D Cousineau M Sahoo P D Newcombe T Castles and F A

Fasoyinu Proc lsquoAFS 105th casting congressrsquo Dallas TX USA

AprilndashMay 2001 157ndash184

178 C E Cross and Oslash Grong Proc 6th Int Conf on lsquoAluminum

alloysrsquo Toyohashi Japan July 1998 1441ndash1446

179 F A Costello J D Robson and P B Prangnell Mater Sci

Forum 2002 396ndash402 757ndash762

180 K B Hyde A F Norman and P B Prangnell Mater Sci

Forum 2002 396ndash402 39ndash44

181 M E Drits S G Pavlenko L S Toropova Yu G Bukov and

L B Ber Sov Phys Dokl 1981 26 (3) 344ndash346

182 A M Drits and B A Kopeliovich Russ Metall 1985 (4) 147ndash

151

183 V G Davydov V I Elagin V V Zakharov and T D Rostova

Met Sci Heat Treat 1996 (8) 347ndash352

184 M E Drits L S Toropova Yu G Bykov L B Ber and S G

Pavlenko Russ Metall 1982 (1) 148ndash152

185 T D Rostova V G Davydov V I Yelagin and V V Zakharov

Mater Sci Forum 2000 331ndash337 793ndash798

186 Y W Riddle H Hallem and N Ryum Mater Sci Forum 2002

396ndash402 563ndash568

187 J Roslashyset and Y W Riddle Proc 9th Int Conf on lsquoAluminium

alloysrsquo Brisbane Australia August 2004 1210ndash1215

188 A M Diskin V K Portnoi A M Drits and A A Alalykin Sov

Non-Ferrous Met Res 1986 14 499ndash500

189 R R Sawtell P E Bretz and C L Jensen US Patent 4 689 090

25 August 1987

190 G A Salishchev Yu B Timoshenko and R A Saitova Proc

Second Int Conf on lsquoAluminium alloysrsquo Beijing China October

1990 413ndash415

191 T G Nieh R Kaibyshev L M Hsiung N Nguyen and

J Wadsworth Scripta Mater 1997 36 1011ndash1016

192 T G Nieh L M Hsiung J Wadsworth and R Kaibyshev Acta

Mater 1998 46 2789ndash2800

193 J S Vetrano C H Henager Jr M T Smith and S M

Bruemmer in lsquoHot deformation of aluminum alloys IIrsquo (ed T R

Bieler L A Lalli and S R MacEwen) 407ndash418 1998 TMS

194 J S Vetrano C H Henager Jr S M Bruemmer Y Ge and

C H Hamilton in lsquoSuperplasticity and Superplastic Forming

1998rsquo (ed A K Gosh and T R Bieler) 89ndash97 1998 TMS

195 V Y Gertsman J S Vetrano C H Henager Jr and S M

Bruemmer Proc First Joint Int Conf on lsquoRecrystallization and

grain growthrsquo Aachen Germany August 2001 Springer Verlag

2001 837ndash842

196 Y Xiao C Gao H Ma and S Tian Trans Nonferrous Met Soc

China 2001 11 235ndash238

Roslashyset and Ryum Scandium in aluminium alloys

42 International Materials Reviews 2005 VOL 50 NO 1

197 A Gholinia F J Humphreys and P B Prangnell Acta Mater

2002 50 4461ndash4476

198 A Gholinia F J Humphreys and P B Prangnell Mater Sci

Forum 2002 408ndash412 1519ndash1524

199 S Komura P B Berbon M Furukawa Z Horita M Nemoto

and T G Langdon Scripta Mater 1998 38 1851ndash1856

200 S Komura P B Berbon A Utsunomiya M Furukawa

Z Horita M Nemoto and T G Langdon in lsquoHot deformation

of aluminum alloys IIrsquo (ed T R Bieler L A Lalli and S R

MacEwen) 125ndash138 1998 TMS

201 S Komura Z Horita M Furukawa M Nemoto and T G

Langdon J Mater Res 2000 15 2571ndash2576

202 S Komura M Furukawa Z Horita M Nemoto and T G

Langdon Mater Sci Eng 2001 A 297 111ndash118

203 S Komura Z Horita M Furukawa M Nemoto and T G

Langdon Metall Mater Trans A 2001 32A 707ndash716

204 Z Horita M Furukawa K Oh-ishi M Nemoto and T G

Langdon Proc Fourth Int Conf on lsquoRecrystallization and

related phenomenarsquo (ed T Sakai and H G Suzuki) 1999 The

Japan Institute of Metals 301ndash308

205 Z Horita S Komura P B Berbon A Utsunomiya

M Furukawa M Nemoto and T G Langdon Mater Sci

Forum 1999 304ndash306 91ndash96

206 Z Horita S Lee S Ota K Neishi and T G Langdon Mater

Sci Forum 2001 357ndash359 471ndash476

207 Z Horita T Fujinami K Sato S B Kang H W Kim and T G

Langdon in Proc James T Staley Honorary Symposium on

Aluminum Alloys lsquoAdvances in the metallurgy of aluminum

alloysrsquo (ed M Tiryakioglu) 271ndash275 2001 ASM

208 P B Berbon S Komura A Utsunomiya Z Horita

M Furukawa M Nemoto and T G Langdon Mater Trans

JIM 1999 40 772ndash778

209 M Nemoto Z Horita M Furukawa and T G Langdon Mater

Sci Forum 1999 304ndash306 59ndash66

210 M Furukawa Z Horita M Nemeto and T G Langdon Proc

lsquoLight Metals 1999rsquo Quebec City PQ Canada August 1999 583ndash

592

211 M Furukawa K Oh-ishi S Komura A Yamashita Z Horita

M Nemeto and T G Langdon Mater Sci Forum 1999 304ndash

306 97ndash102

212 M Furukawa A Utsunomiya K Matsubara Z Horita and

T G Langdon Acta Mater 2001 49 3829ndash3838

213 M Furukawa A Utsunomiya S Komura Z Horita M Nemoto

and T G Langdon Mater Sci Forum 2001 357ndash359 431ndash436

214 M Furukawa Z Horita and T G Langdon in Proc James T

Staley Honorary Symposium on Aluminum Alloys lsquoAdvances in

the metallurgy of aluminum alloysrsquo (ed M Tiryakioglu) 47ndash56

2001 ASM

215 M Furukawa Z Horita M Nemoto and T G Langdon Mater

Sci Eng 2002 A 324 82ndash89

216 M Furukawa Z Horita and T G Langdon in lsquoUltrafine grained

materials IIrsquo (ed Y T Zhu T G Langdon R S Mishra S L

Semiatin M J Saran and T C Lowe) 459ndash468 2002 TMS

217 T G Langdon M Furukawa Z Horita and M Nemoto Proc

NATO Advanced Research Workshop on lsquoInvestigations and

applications of severe plastic deformationrsquo Moscow August

1999 NATO Science Series Series 3 High Technology vol 80

Kluwer Academic Publishers The Netherlands 2000 149ndash154

218 S Lee H Akamatsu A Utsunomiya K Neishi M Furukawa

Z Horita and T G Langdon Proc Thermec 2000 Las Vegas

USA December 2000

219 S Lee A Utsunomiya H Akamatsu K Neishi M Furukawa

Z Horita and T G Langdon Acta Mater 2002 50 553ndash564

220 A Yamashita D Yamaguchi Z Horita and T G Langdon

Mater Sci Eng 2000 A 287 100ndash106

221 K Oh-ishi Z Horita D J Smith and T G Langdon J Mater

Res 2001 16 583ndash589

222 H Akamatsu T Fujinami Z Horita and T G Langdon Scripta

Mater 2001 44 759ndash764

223 S Ota H Akamatsu K Neishi M Furukawa Z Horita and

T G Langdon Mater Trans 2002 43 2364ndash2369

224 K Furuno H Akamatsu K Oh-ishi M Furukawa Z Horita

and T G Langdon Acta Mater 2004 52 2497ndash2507

225 I N Fridlyander O G Senatorova N A Ryazanova and A O

Nikiforov Mater Sci Forum 1994 170ndash172 345ndash349

226 J N Fridlyander and O G Senatorova Mater Sci Forum 1996

217ndash222 1813ndash1818

227 J Liu and D J Chakrabarti Acta Mater 1996 44 4647ndash4661

228 O G Senatorova A N Uksusnikov J N Fridlyander

J Koshorst R R Romanova N A Ryazanova A Galliot

and V V Cherkassov Proc 6th Int Conf on lsquoAluminum alloysrsquo

July 1998 Toyohashi Japan 589ndash593

229 R A Emigh E L Bradley and J W Morris Jr in

lsquoSuperplasticity in aerospace IIrsquo (ed T R McNelley and H C

Heikkenen) 303ndash315 1990 TMS

230 E L Bradley III R A Emigh and J W Morris Jr Scripta

Metall Mater 1991 25 717ndash721

231 N I Kolobnev L B Khokhlatova V D Makarov E Yu

Semenova and V V Redchits Proc Sixth Int Aluminiumndash

Lithium Conference Garmisch-Partenkirchen Germany October

1991 1053ndash1056

232 N K Tsenev R Z Valiev O V Obraztsov and I N Fridlander

Proc Sixth Int AluminiumndashLithium Conference Garmisch-

Partenkirchen Germany October 1991 1125ndash1132

233 A M Shammazov N K Tsenev R Z Valiev M M

Myshlyaev M M Bikbulatov and S P Lebedich Phys Met

Metall 2000 89 (3) 314ndash318

234 F Musin R Kaibyshev Y Motohashi T Sakuma and G Itoh

Mater Trans A 2002 43A 2370ndash2377

235 M Shagiev Y Motohashi F Musin R Kaibyshev and G Itoh

Mater Trans A 2003 44A 1694ndash1697

236 M Shagiev Y Motohashi F Musin R Kaibyshev and G Itoh

Mater Trans A 2003 44A 1698ndash1701

237 B A Parker and Z F Zhou Proc 3rd Int Conf on lsquoAluminium

alloysrsquo Vol I NTH Trondheim Norway June 1992 363ndash367

238 J R Davies lsquoASM specialty handbook aluminum and aluminum

alloysrsquo 1993 Materials Park OH USA ASM

239 S J Andersen H W Zandbergen J Jansen C Traeholt

U Tundal and O Reiso Acta Mater 1998 46 3283ndash3298

240 M L Kharakterova D G Eskin and L L Rokhlin Russ

Metall 1997 (1) 104ndash109

241 J Roslashyset Dr Ing thesis NTNU Trondheim Norway 2002

242 P P Chattopadhyay S Datta and M K Banerjee Mater Sci

Eng 2002 A 333 67ndash71

243 L I Kaigorodova E I Selnikhina E A Tkachenko and O G

Senatorova Phys Met Metall 1996 81 513ndash519

244 Y-L Wu F H Froes C Li and A Alvarez Metall Mater

Trans A 1999 30A 1017ndash1024

245 Z Yin L Yang Q Pan and F Jiang Trans Nonferrous Met

Soc China 2001 11 822ndash825

246 V I Elagin V V Zakharov and T D Rostova Met Sci Heat

Treat 1994 36 (7) 375ndash380

247 Y V Milman A I Sirko D V Lotsko O N Senkov and D B

Miracle Mater Sci Forum 2002 396ndash402 1217ndash1222

248 C-H Joh K Yamada and Y Miura Mater Trans JIM 1999

40 439ndash442

249 X J Jiang Q H Gui Y Y Li L M Ma G J Liang and C X

Shi Scr Metall Mater 1993 29 211ndash216

250 X J Jiang Y Y Li W Deng L Y Xiong W M Wu Y J Gao

and C X Shi Adv Cryogenic Eng (Mater) 1994 40 1369ndash

1376

251 C-H Joh T Katsube K Yamada and Y Miura Proc 6th Int

Conf on lsquoAluminum alloysrsquo Toyohashi Japan July 1998 799ndash

804

252 L I Kaygorodova A M Dritz T V Krymova and I N

Fridlyander Proc Sixth Int AluminiumndashLithium Conference

Garmisch-Partenkirchen Germany October 1991 363ndash367

253 L I Kaigorodova A M Drits Ya V Zhingel T V Krymova

and I N Fridlyander Phys Met Metall 1992 73 286ndash290

254 A L Berezina V A Volkov S V Ivanov N I Kolobnev and

K V Chuistov Phys Met Metall 1991 71 (2) 167ndash175

255 I N Fridlyander N I Kolobnev A L Berezina and K V

Chuistov Proc Sixth Int AluminiumndashLithium Conference

Garmisch-Partenkirchen Germany October 1991 107ndash112

256 L I Kaigorodova A M Drits Ya V Zhingel T V Krymova

and V A Rassokhin Phys Met Metall 1992 73 281ndash285

257 I N Fridlyander S F Danilov E N Malysheva T A

Gorokhova and N N Kirkina Proc Sixth Int Aluminiumndash

Lithium Conference Garmisch-Partenkirchen Germany October

1991 381ndash386

258 G Dlubek S Krause H Krause A L Beresina V S

Mikhalenkov and K V Chuistov J Phys Condens Matter

1992 4 6317ndash6328

259 S Krause H Krause G Dlubek A L Beresina and K S

Chuistov Mater Sci Forum 1992 105ndash110 1109ndash1112

260 C Y Tan Z Q Zheng and S Q Liang Proc 4th Int Conf on

lsquoAluminium alloysrsquo Vol II Atlanta GA USA September 1994

329ndash333

261 A L Beresina N I Kolobnev K V Chuistov A V Kotko and

O A Molebny Mater Sci Forum 2002 396ndash402 977ndash981

Roslashyset and Ryum Scandium in aluminium alloys

International Materials Reviews 2005 VOL 50 NO 1 43

262 I N Ganiev I Yunusov and V V Krasnoyarskii J Appl Chem

USSR 1986 60 1961ndash1965

263 I N Ganiev Prot Met 1995 31 543ndash546

264 N V Vyazovikina Prot Met 1999 35 448ndash453

265 G V Kharina and V P Kochergin Prot Met 1996 32 134ndash

136

266 G V Kharina M V Kuznetsov and V P Kochergin Russ J

Electrochem 1998 34 482ndash485

267 V S Sinyavskii V D Valrsquokov and E V Titkova Prot Met

1998 34 549ndash555

268 Y L Wu F H Froes C G Li and J Liu Proc lsquoSynthesis

processing of lightweight metallic materials IIrsquo Orlando FL

USA February 1997 73ndash81

269 Z Ahmad and B J Abdul-Aleem Proc EuroCorr 2000

270 Z Ahmad A Ul-Hamid and B J Abdul-Aleem Corros Sci

2001 43 1227ndash1243

271 R Braun B Lenczowski and G Tempus Mater Sci Forum

2000 331ndash337 1647ndash1652

272 T Torma E Kovacs-Csetenyi L Vitalis I Vitanyi

J Stepanov and M Butova Mater Sci Forum 1987 1314

497ndash503

273 Z Wang P Wang K S Kumar and C L Briant in lsquoChemistry

and electrochemistry of corrosion and stress corrosion crackingrsquo

(ed R H Jones) 573ndash582 2001 TMS

274 V I Elagin V V Zakharov A A Petrova and E V

Vyshegorodtseva Russ Metall 1983 (4) 143ndash146

Roslashyset and Ryum Scandium in aluminium alloys

44 International Materials Reviews 2005 VOL 50 NO 1

Page 23: Scandium in aluminium alloys - Atom probe · A considerable part of the available literature on scandium in aluminium alloys is reviewed. ... behaviour in Al Cu, Al Mg Si,

40 C Xia F Zeng and Y Gu Trans Nonferrous Met Soc China

2003 13 1124ndash1127

41 M Yu Teslyuk and V S Protasov Sov Phys Crystallogr 1966

10 470ndash471

42 M L Kharakterova and T V Dobatkina Russ Metall 1988

(6) 175ndash178

43 M L Kharakterova Russ Metall 1991 (4) 195ndash199

44 L S Toropova M L Kharakterova and D G Eskin Russ

Metall 1992 (3) 194ndash199

45 P Riani L Arrighi R Marazza D Mazzone G Zanicchi and

R Ferro J Phase Equil Diff 2004 25 22ndash52

46 A T Tyvanchuk T I Yanson B Ya Kotur O S Zarechnyuk

and M L Kharakterova Russ Metall 1988 (4) 190ndash192

47 L L Rokhlin T V Dobatkina and M L Kharakterova Powder

Metall Met Ceram 1997 36

48 A Z Ikromov I N Ganiev and V V Kinzhibalo Dokl Akad

Nauk Tadzh SSR 1990 (6) 391ndash392

49 I N Ganiev A Z Ikromov and V G Khudoiberdiev Russ

Metall 1995 (3) 125ndash127

50 I N Fridlyander L L Rokhlin T V Dobatkina and N I

Nikitina Met Sci Heat Treat 1993 (10) 567ndash571

51 I N Fridlyander L L Rokhlin T V Dobatkina V V

Kinzhibalo and A T Tyvanchuk Russ Metall 1998 (1) 161ndash

166

52 R A Emigh E L Bradley and J W Morris Jr in lsquoLight-weight

alloys for aerospace applications IIrsquo (ed E W Lee and N J

Kim) 27ndash43 1991 TMS

53 L S Toropova A N Kamardinkin V V Kindzhibalo and A T

Tyvanchuk Phys Met Metall 1990 70 (6) 106ndash110

54 A N Kamardinkin T V Dobatkina and T D Rostova Russ

Metall 1991 (4) 216ndash218

55 L S Torodskaya T V Dobatkina and A N Kamardinkin

Russ Metall 1992 (5) 128ndash131

56 E M Sokolovskaya E F Kazakova E I Poddyakova and A

A Ezhov Met Sci Heat Treat 1997 (5) 211ndash213

57 Y Harada and D C Dunand Mater Sci Eng 2002 A 329ndash331

686ndash695

58 N E Drits L S Toropova and F L Gushchina Russ Metall

1984 (4) 229ndash232

59 E M Sokolovskaya E F Kazakova V A Alikhanov and E V

Zhuravleva Moscow Univ Chem Bull 1997 52 (5) 70ndash72

60 E M Sokolovskaya E F Kazakova and E I Poddyakova Met

Sci Heat Treat 1989 (11) 837ndash839

61 G M Cheldieva E F Kazakova E M Sokolovskaya and N I

Kaloev Russ Metall 1990 (6) 87ndash90

62 E M Sokolovskaya E F Kazakova and O D-S Kendivan

Russ Metall 1998 (4) 135ndash137

63 N G Bukhanko E F Kazakova and E M Sokolovskaya Russ

Metall 2001 (4) 425ndash431

64 E D Trubnyakova O I Bodak I N Ganiev and A V

Vakhobov Russ Metall 1987 (3) 219ndash222

65 I N Fridlyander and L V Molchanova Russ Metall 2003 (5)

476ndash480

66 R A Altynbaev S Kh Khairidinov and A V Vakhobov Russ

Metall 1987 (4) 194ndash196

67 J C Schuster and J Bauer J Less-Common Met 1985 109

345ndash350

68 L L Rokhlin A S Fridman T V Dobatkina and D G Eskin

Russ Metall 1991 (6) 146ndash148

69 A S Fridman T V Dobatkina and E V Muratova Russ

Metall 1992 (1) 207ndash209

70 C Xia F Zeng and Y Gu Trans Nonferrous Met Soc China

2003 13 546ndash552

71 F Zeng C Xia and Y Gu J Alloys Comp 2004 363 175ndash181

72 L L Rokhlin T V Dobatkina N R Bochvar and E V Lysova

J Alloys Comp 2004 367 10ndash16

73 T V Dobatkina A S Fridman and E V Muratova Russ

Metall 1992 (5) 125ndash127

74 I N Fridlyander L L Rokhlin N R Bochvar E V Lysova

and O V Boteva Russ Metall 2001 (6) 661ndash666

75 V N Rechkin L K Lamikhov and T I Samsonova Sov Phys

Crystallogr 1964 9 325ndash327

76 I I Zalutskii and P I Kripyakevich Sov Phys Crystallogr

1967 12 341ndash343

77 T J Bastow C T Forwood M A Gibson and M E Smith

Phys Rev B 1998 58 2988ndash2997

78 K Fukunaga M Kolbe K Yamada and Y Miura Mater Sci

Eng 1997 A 234ndash236 594ndash597

79 E P George J A Horton W D Porter and J H Schneibel

J Mater Res 1990 5 1639ndash1648

80 E P George D P Pope C L Fu and J H Schneibel ISIJ Int

1991 31 1063ndash1075

81 Y Harada and D C Dunand Acta Mater 2000 48 3477ndash3487

82 J H Schneibel and E P George Scripta Metall Mater 1990 24

1069ndash1074

83 J H Schneibel and P M Hazzledine Mater Res Soc Symp

Proc 1991 213 323ndash328

84 J H Schneibel and P M Hazzledine J Mater Res 1992 7

868ndash875

85 C J Sparks E D Specht G E Ice P Zschack and J Schneibel

Mater Res Soc Symp Proc 1991 213 363ndash368

86 J Tarnacki and Y-W Kim Scripta Metall Mater 1989 23

1063ndash1068

87 M Asta V Ozolins and C Woodward JOM 2001 53 (9) 16ndash

19

88 M E Drits L S Toropova F L Gushchina and S G Fedotov

Sov Non-Ferrous Met Res 1984 12 83ndash85

89 Y Harada and D C Dunand Scripta Mater 2003 48 219ndash222

90 C Woodward M Asta G Kresse and J Hafner Phys Rev B

2001 63 094103-1-6

91 J-H Xu and A J Freeman Phys Rev B 1990 41 12553ndash12561

92 M F Bartholomeusz and J A Wert Acta Metall Mater 1992

40 673ndash682

93 G Bester and M Fahnle J Phys Condens Matter 2001 13

11551ndash11565

94 C L Fu and M H Yoo Proc lsquoOrdered intermetallics ndash physical

metallurgy and mechanical behaviorrsquo Irsee Germany June 1991

155ndash164

95 K Fukunaga T Shouji and Y Miura Mater Sci Eng 1997 A

239ndash240 202ndash205

96 D P Pope Proc lsquoOrdered intermetallics ndash physical metallurgy

and mechanical behaviorrsquo Irsee Germany June 1991 143ndash153

97 J-S Wang Acta Mater 1998 46 2663ndash2674

98 M H Yoo and C L Fu Mater Sci Eng 1992 A 153 470ndash478

99 R W Hyland Jr and R C Stiffler Scripta Metall Mater 1991

25 473ndash477

100 I G Brodova I V Polents O A Korzhavina P S Popelrsquo I P

Korshunov and V O Esin Melts 1992 4 392ndash397

101 I G Brodova O A Chikova I V Polents P S Popelrsquo and V O

Esin Casting Processes 1992 1 (2) 158ndash160

102 I G Brodova D V Bashlikov and I V Polents Mater Sci

Forum 1998 269ndash272 589ndash594

103 K B Hyde A F Norman and P B Pragnell Mater Sci Forum

2000 331ndash337 1013ndash1018

104 K B Hyde A F Norman and P B Pragnell Acta Mater 2001

49 1327ndash1337

105 J Roslashyset and N Ryum Proc 6th Int Conf on lsquoAluminum

alloysrsquo Toyohashi Japan July 1998 793ndash798

106 V I Elagin V V Zakharov and T D Rostova Met Sci Heat

Treat 1993 (6) 317ndash319

107 R W Hyland Jr Metall Trans A 1992 23A 1947ndash1955

108 B A Parker Z F Zhou and P Nolle J Mater Sci 1995 30

452ndash458

109 C L Rohrer M D Asta S M Foiles and R W Hyland Jr

Mater Res Soc Symp Proc 1996 398 477ndash482

110 G M Novotny and A J Ardell Mater Sci Eng 2001 A 318

144ndash154

111 J D Robson M J Jones and P B Pragnell Acta Mater 2003

51 1453ndash1468

112 C Tan Z Zheng and B Wang Proc 3rd Int Conf on

lsquoAluminium alloysrsquo Vol I NTH Trondheim Norway June

1992 290ndash294

113 M Nakayama A Furuta and Y Miura Mater Trans JIM

1997 38 852ndash857

114 E A Marquis and D N Seidman Acta Mater 2001 49 1909ndash

1919

115 M J Jones and F J Humphreys Acta Mater 2003 51 2149ndash

2159

116 E A Marquis D N Seidman and D C Dunand in lsquoCreep

deformation fundamentals and applicationsrsquo (ed R S Mishra

J C Earthman and S V Raj) 299ndash308 2002 TMS

117 D N Seidman E A Marquis and D C Dunand Acta Mater

2002 50 4021ndash4035

118 E A Marquis D N Seidman and D C Dunand Acta Mater

2003 51 285ndash287

119 M E Drits L S Toropova U G Bikov and G K Anastaseva

Proc lsquoDiffusion in metals and alloysrsquo Tihany Hungary Augustndash

September 1982 616ndash623

120 V I Elagin V V Zakharov and T D Rostova Met Sci Heat

Treat 1983 (7) 546ndash549

Roslashyset and Ryum Scandium in aluminium alloys

International Materials Reviews 2005 VOL 50 NO 1 41

121 M Ye Drits L B Ber Yu G Bykov L S Toropova and G K

Anastaseva Phys Met Metall 1984 57 (6) 118ndash126

122 M E Drits L S Toropova and Yu G Bykov Sov Non-Ferrous

Met Res 1985 13 309ndash314

123 V I Yelagin V V Zakharov S G Pavlenko and T D Rostova

Phys Met Metall 1985 60 (1) 88ndash92

124 N Sano Y Hasegawa K Hono H Jo K Hirano H W

Pickering and T Sakurai Journal de Physique 1987 48 C6 337ndash

342

125 N Sano H-H Jo K-I Hirano and T Sakurai J Jpn Inst

Metals 1989 39 444ndash450

126 N Sano H Jo K Hirano and T Sakurai Proc Second Int

Conf on lsquoAluminium alloysrsquo Beijing China October 1990 549ndash

554

127 Y Miura M Nakayama and A Furuta Proc lsquoAspects of high

temperature deformation and fracture in crystalline materialsrsquo

Nagoya Japan July 1993 255ndash262

128 Y W Riddle and T H Sanders Jr Mater Sci Forum 2000

331ndash337 939ndash944

129 Y W Riddle M McIntosh and T H Sanders Jr in lsquoLightweight

alloys for aerospace application VIrsquo (ed K Jata E W Lee

W Frazier and N J Kim) 25ndash39 2001 TMS

130 M E Drits J Dutkiewicz L S Toropova and J Salawa Crystal

Res Technol 1984 19 1325ndash1330

131 Y W Riddle MSc thesis Georgia Tech GA USA 1998

132 T J Bastow and S Celotto Mater Sci Eng 2003 C 23 757ndash

762

133 M C Carroll M J Mills G S Daehn P I Gouma M F

Savage and B R Dunbar in lsquoAutomotive Alloys 1999rsquo (ed

S Das) 239ndash246 2000 TMS

134 E Clouet M Nastar and C Sigli Phys Rev B 2004 69 064109-

1-14

135 V V Zakharov Met Sci Heat Treat 1997 (2) 61ndash66

136 J W Christian lsquoThe theory of transformation in metals and

alloysrsquo 2nd edn 1975 Pergamon Press Ltd

137 A L Berezina V A Volkov B P Domashnikov S V Ivanov

and K V Chuistov Phys Metals 1990 10 296ndash304

138 S-I Fujikawa and S Sakauchi Proc 6th Int Conf on

lsquoAluminum alloysrsquo Toyohashi Japan July 1998 805ndash810

139 Y S Touloukian R K Kirby R E Taylor and P D Desai

(eds) lsquoThermal expansion metallic elements and alloysrsquo 1975

New York Plenum

140 J Roslashyset and N Ryum submitted to Scripta Mater

141 R O Simmons and R W Balluffi Phys Rev 1960 117 52ndash61

142 M Ocko E Babic R Krsmik E Girt and B Leontic J Phys F

Metals Phys 1976 6 703ndash707

143 M J Jones and F J Humphreys Proc First Joint Int Conf on

lsquoRecrystallization and grain growthrsquo Aachen Germany August

2001 Springer Verlag 1287ndash1292

144 S Iwamura M Nakayama and Y Miura Mater Sci Forum

2002 396ndash402 1151ndash1156

145 S Iwamura and Y Miura Acta Mater 2004 52 591ndash600

146 M Asta S M Foiles and A A Quong Phys Rev B 1998 57

11265ndash11275

147 R W Hyland Jr M Asta S M Foiles and C L Rohrer Acta

Mater 1998 46 3667ndash3678

148 J Roslashyset and N Ryum Proc 4th Int Conf on lsquoAluminium

alloysrsquo Vol I Atlanta GA USA September 1994 194ndash201

149 M E Drits L S Toropova G K Anastaseva and G L

Nagornichnykh Russ Metall 1984 (3) 192ndash195

150 E A Marquis D N Seidman and D C Dunand Acta Mater

2003 51 4751ndash4760

151 M E Drits L S Toropova and Yu G Bykov Met Sci Heat

Treat 1983 (7) 550ndash554

152 V V Zakharov and T D Rostova Met Sci Heat Treat 1995

(2) 65ndash69

153 M Nakayama and Y Miura Proc 4th Int Conf on lsquoAluminium

alloysrsquo Vol I Atlanta GA USA September 1994 538ndash545

154 M Nakayama and Y Miura J Jpn Inst Light Metals 1996 46

275ndash279

155 M Nakayama T Okuyama and Y Miura Mater Sci Forum

2000 331ndash337 927ndash932

156 M Nakayama T Okuyama and Y Miura Proc 6th Int Conf

on lsquoAluminum alloysrsquo Toyohashi Japan July 1998 517ndash522

157 M L Kharakterova D G Eskin and L S Toropova Acta

Metall Mater 1994 42 2285ndash2290

158 V I Elagin V V Zakharov and T D Rostova Met Sci Heat

Treat 1992 (1) 37ndash45

159 H Wiik Siv Ing thesis NTH Institute of Metallurgy

Trondheim Norway 1995

160 J Roslashyset H Hovland and N Ryum Mater Sci Forum 2002

396ndash402 619ndash624

161 Y Miura K Horikawa K Yamada and M Nakayama Proc

4th Int Conf on lsquoAluminium alloysrsquo Vol II Atlanta GA USA

September 1994 161ndash168

162 Y W Riddle PhD thesis Georgia Tech GA USA 2000

163 B Forbord W Lefebvre F Danoix H Hallem and

K Marthinsen Scripta Mater 2004 51 333ndash337

164 J D Robson Acta Mater 2004 52 1409ndash1421

165 C B Fuller J L Murray and D N Seidman submitted to Acta

Mater 2004

166 M G Mousavi C E Cross and Oslash Grong Sci Technol Weld

Joining 1999 4 381ndash388

167 J S Vetrano S M Bruemmer L M Pawlowski and I M

Robertson Mater Sci Eng 1997 A 238 101ndash107

168 Y W Riddle and T H Sanders Jr Mater Sci Forum 2000

331ndash337 799ndash803

169 G M Khan A O Nikiforov V V Zakharov and I I Novikov

Tsvetnye Metally 1993 34 (11) 43ndash45

170 Z Horita M Furukawa M Nemoto A J Barnes and T G

Langdon Acta Mater 2000 48 3633ndash3640

171 L A Willey US Patent 3 619 181 9 November 1971

172 L K Lamikhov and G V Samsonov Tsvetnye Metally 1964 5

(8) 77ndash80

173 A L Berezina K V Chuistov N I Kolobnev L B

Khokhlatova and T A Monastyrskaya Mater Sci Forum

2002 396ndash402 741ndash746

174 F A Fasoyinu J Thomson D Cousineau T Castles and M

Sahoo Proc 6th Int AFS Conf on lsquoMolten aluminum

processingrsquo Orlando FL USA November 2001

175 Z Yin Q Pan Y Zhang and F Jiang Mater Sci Eng 2000

A 280 151ndash155

176 I I Novikov and O E Grushko Mater Sci Technol 1995 11

926ndash932

177 D Cousineau M Sahoo P D Newcombe T Castles and F A

Fasoyinu Proc lsquoAFS 105th casting congressrsquo Dallas TX USA

AprilndashMay 2001 157ndash184

178 C E Cross and Oslash Grong Proc 6th Int Conf on lsquoAluminum

alloysrsquo Toyohashi Japan July 1998 1441ndash1446

179 F A Costello J D Robson and P B Prangnell Mater Sci

Forum 2002 396ndash402 757ndash762

180 K B Hyde A F Norman and P B Prangnell Mater Sci

Forum 2002 396ndash402 39ndash44

181 M E Drits S G Pavlenko L S Toropova Yu G Bukov and

L B Ber Sov Phys Dokl 1981 26 (3) 344ndash346

182 A M Drits and B A Kopeliovich Russ Metall 1985 (4) 147ndash

151

183 V G Davydov V I Elagin V V Zakharov and T D Rostova

Met Sci Heat Treat 1996 (8) 347ndash352

184 M E Drits L S Toropova Yu G Bykov L B Ber and S G

Pavlenko Russ Metall 1982 (1) 148ndash152

185 T D Rostova V G Davydov V I Yelagin and V V Zakharov

Mater Sci Forum 2000 331ndash337 793ndash798

186 Y W Riddle H Hallem and N Ryum Mater Sci Forum 2002

396ndash402 563ndash568

187 J Roslashyset and Y W Riddle Proc 9th Int Conf on lsquoAluminium

alloysrsquo Brisbane Australia August 2004 1210ndash1215

188 A M Diskin V K Portnoi A M Drits and A A Alalykin Sov

Non-Ferrous Met Res 1986 14 499ndash500

189 R R Sawtell P E Bretz and C L Jensen US Patent 4 689 090

25 August 1987

190 G A Salishchev Yu B Timoshenko and R A Saitova Proc

Second Int Conf on lsquoAluminium alloysrsquo Beijing China October

1990 413ndash415

191 T G Nieh R Kaibyshev L M Hsiung N Nguyen and

J Wadsworth Scripta Mater 1997 36 1011ndash1016

192 T G Nieh L M Hsiung J Wadsworth and R Kaibyshev Acta

Mater 1998 46 2789ndash2800

193 J S Vetrano C H Henager Jr M T Smith and S M

Bruemmer in lsquoHot deformation of aluminum alloys IIrsquo (ed T R

Bieler L A Lalli and S R MacEwen) 407ndash418 1998 TMS

194 J S Vetrano C H Henager Jr S M Bruemmer Y Ge and

C H Hamilton in lsquoSuperplasticity and Superplastic Forming

1998rsquo (ed A K Gosh and T R Bieler) 89ndash97 1998 TMS

195 V Y Gertsman J S Vetrano C H Henager Jr and S M

Bruemmer Proc First Joint Int Conf on lsquoRecrystallization and

grain growthrsquo Aachen Germany August 2001 Springer Verlag

2001 837ndash842

196 Y Xiao C Gao H Ma and S Tian Trans Nonferrous Met Soc

China 2001 11 235ndash238

Roslashyset and Ryum Scandium in aluminium alloys

42 International Materials Reviews 2005 VOL 50 NO 1

197 A Gholinia F J Humphreys and P B Prangnell Acta Mater

2002 50 4461ndash4476

198 A Gholinia F J Humphreys and P B Prangnell Mater Sci

Forum 2002 408ndash412 1519ndash1524

199 S Komura P B Berbon M Furukawa Z Horita M Nemoto

and T G Langdon Scripta Mater 1998 38 1851ndash1856

200 S Komura P B Berbon A Utsunomiya M Furukawa

Z Horita M Nemoto and T G Langdon in lsquoHot deformation

of aluminum alloys IIrsquo (ed T R Bieler L A Lalli and S R

MacEwen) 125ndash138 1998 TMS

201 S Komura Z Horita M Furukawa M Nemoto and T G

Langdon J Mater Res 2000 15 2571ndash2576

202 S Komura M Furukawa Z Horita M Nemoto and T G

Langdon Mater Sci Eng 2001 A 297 111ndash118

203 S Komura Z Horita M Furukawa M Nemoto and T G

Langdon Metall Mater Trans A 2001 32A 707ndash716

204 Z Horita M Furukawa K Oh-ishi M Nemoto and T G

Langdon Proc Fourth Int Conf on lsquoRecrystallization and

related phenomenarsquo (ed T Sakai and H G Suzuki) 1999 The

Japan Institute of Metals 301ndash308

205 Z Horita S Komura P B Berbon A Utsunomiya

M Furukawa M Nemoto and T G Langdon Mater Sci

Forum 1999 304ndash306 91ndash96

206 Z Horita S Lee S Ota K Neishi and T G Langdon Mater

Sci Forum 2001 357ndash359 471ndash476

207 Z Horita T Fujinami K Sato S B Kang H W Kim and T G

Langdon in Proc James T Staley Honorary Symposium on

Aluminum Alloys lsquoAdvances in the metallurgy of aluminum

alloysrsquo (ed M Tiryakioglu) 271ndash275 2001 ASM

208 P B Berbon S Komura A Utsunomiya Z Horita

M Furukawa M Nemoto and T G Langdon Mater Trans

JIM 1999 40 772ndash778

209 M Nemoto Z Horita M Furukawa and T G Langdon Mater

Sci Forum 1999 304ndash306 59ndash66

210 M Furukawa Z Horita M Nemeto and T G Langdon Proc

lsquoLight Metals 1999rsquo Quebec City PQ Canada August 1999 583ndash

592

211 M Furukawa K Oh-ishi S Komura A Yamashita Z Horita

M Nemeto and T G Langdon Mater Sci Forum 1999 304ndash

306 97ndash102

212 M Furukawa A Utsunomiya K Matsubara Z Horita and

T G Langdon Acta Mater 2001 49 3829ndash3838

213 M Furukawa A Utsunomiya S Komura Z Horita M Nemoto

and T G Langdon Mater Sci Forum 2001 357ndash359 431ndash436

214 M Furukawa Z Horita and T G Langdon in Proc James T

Staley Honorary Symposium on Aluminum Alloys lsquoAdvances in

the metallurgy of aluminum alloysrsquo (ed M Tiryakioglu) 47ndash56

2001 ASM

215 M Furukawa Z Horita M Nemoto and T G Langdon Mater

Sci Eng 2002 A 324 82ndash89

216 M Furukawa Z Horita and T G Langdon in lsquoUltrafine grained

materials IIrsquo (ed Y T Zhu T G Langdon R S Mishra S L

Semiatin M J Saran and T C Lowe) 459ndash468 2002 TMS

217 T G Langdon M Furukawa Z Horita and M Nemoto Proc

NATO Advanced Research Workshop on lsquoInvestigations and

applications of severe plastic deformationrsquo Moscow August

1999 NATO Science Series Series 3 High Technology vol 80

Kluwer Academic Publishers The Netherlands 2000 149ndash154

218 S Lee H Akamatsu A Utsunomiya K Neishi M Furukawa

Z Horita and T G Langdon Proc Thermec 2000 Las Vegas

USA December 2000

219 S Lee A Utsunomiya H Akamatsu K Neishi M Furukawa

Z Horita and T G Langdon Acta Mater 2002 50 553ndash564

220 A Yamashita D Yamaguchi Z Horita and T G Langdon

Mater Sci Eng 2000 A 287 100ndash106

221 K Oh-ishi Z Horita D J Smith and T G Langdon J Mater

Res 2001 16 583ndash589

222 H Akamatsu T Fujinami Z Horita and T G Langdon Scripta

Mater 2001 44 759ndash764

223 S Ota H Akamatsu K Neishi M Furukawa Z Horita and

T G Langdon Mater Trans 2002 43 2364ndash2369

224 K Furuno H Akamatsu K Oh-ishi M Furukawa Z Horita

and T G Langdon Acta Mater 2004 52 2497ndash2507

225 I N Fridlyander O G Senatorova N A Ryazanova and A O

Nikiforov Mater Sci Forum 1994 170ndash172 345ndash349

226 J N Fridlyander and O G Senatorova Mater Sci Forum 1996

217ndash222 1813ndash1818

227 J Liu and D J Chakrabarti Acta Mater 1996 44 4647ndash4661

228 O G Senatorova A N Uksusnikov J N Fridlyander

J Koshorst R R Romanova N A Ryazanova A Galliot

and V V Cherkassov Proc 6th Int Conf on lsquoAluminum alloysrsquo

July 1998 Toyohashi Japan 589ndash593

229 R A Emigh E L Bradley and J W Morris Jr in

lsquoSuperplasticity in aerospace IIrsquo (ed T R McNelley and H C

Heikkenen) 303ndash315 1990 TMS

230 E L Bradley III R A Emigh and J W Morris Jr Scripta

Metall Mater 1991 25 717ndash721

231 N I Kolobnev L B Khokhlatova V D Makarov E Yu

Semenova and V V Redchits Proc Sixth Int Aluminiumndash

Lithium Conference Garmisch-Partenkirchen Germany October

1991 1053ndash1056

232 N K Tsenev R Z Valiev O V Obraztsov and I N Fridlander

Proc Sixth Int AluminiumndashLithium Conference Garmisch-

Partenkirchen Germany October 1991 1125ndash1132

233 A M Shammazov N K Tsenev R Z Valiev M M

Myshlyaev M M Bikbulatov and S P Lebedich Phys Met

Metall 2000 89 (3) 314ndash318

234 F Musin R Kaibyshev Y Motohashi T Sakuma and G Itoh

Mater Trans A 2002 43A 2370ndash2377

235 M Shagiev Y Motohashi F Musin R Kaibyshev and G Itoh

Mater Trans A 2003 44A 1694ndash1697

236 M Shagiev Y Motohashi F Musin R Kaibyshev and G Itoh

Mater Trans A 2003 44A 1698ndash1701

237 B A Parker and Z F Zhou Proc 3rd Int Conf on lsquoAluminium

alloysrsquo Vol I NTH Trondheim Norway June 1992 363ndash367

238 J R Davies lsquoASM specialty handbook aluminum and aluminum

alloysrsquo 1993 Materials Park OH USA ASM

239 S J Andersen H W Zandbergen J Jansen C Traeholt

U Tundal and O Reiso Acta Mater 1998 46 3283ndash3298

240 M L Kharakterova D G Eskin and L L Rokhlin Russ

Metall 1997 (1) 104ndash109

241 J Roslashyset Dr Ing thesis NTNU Trondheim Norway 2002

242 P P Chattopadhyay S Datta and M K Banerjee Mater Sci

Eng 2002 A 333 67ndash71

243 L I Kaigorodova E I Selnikhina E A Tkachenko and O G

Senatorova Phys Met Metall 1996 81 513ndash519

244 Y-L Wu F H Froes C Li and A Alvarez Metall Mater

Trans A 1999 30A 1017ndash1024

245 Z Yin L Yang Q Pan and F Jiang Trans Nonferrous Met

Soc China 2001 11 822ndash825

246 V I Elagin V V Zakharov and T D Rostova Met Sci Heat

Treat 1994 36 (7) 375ndash380

247 Y V Milman A I Sirko D V Lotsko O N Senkov and D B

Miracle Mater Sci Forum 2002 396ndash402 1217ndash1222

248 C-H Joh K Yamada and Y Miura Mater Trans JIM 1999

40 439ndash442

249 X J Jiang Q H Gui Y Y Li L M Ma G J Liang and C X

Shi Scr Metall Mater 1993 29 211ndash216

250 X J Jiang Y Y Li W Deng L Y Xiong W M Wu Y J Gao

and C X Shi Adv Cryogenic Eng (Mater) 1994 40 1369ndash

1376

251 C-H Joh T Katsube K Yamada and Y Miura Proc 6th Int

Conf on lsquoAluminum alloysrsquo Toyohashi Japan July 1998 799ndash

804

252 L I Kaygorodova A M Dritz T V Krymova and I N

Fridlyander Proc Sixth Int AluminiumndashLithium Conference

Garmisch-Partenkirchen Germany October 1991 363ndash367

253 L I Kaigorodova A M Drits Ya V Zhingel T V Krymova

and I N Fridlyander Phys Met Metall 1992 73 286ndash290

254 A L Berezina V A Volkov S V Ivanov N I Kolobnev and

K V Chuistov Phys Met Metall 1991 71 (2) 167ndash175

255 I N Fridlyander N I Kolobnev A L Berezina and K V

Chuistov Proc Sixth Int AluminiumndashLithium Conference

Garmisch-Partenkirchen Germany October 1991 107ndash112

256 L I Kaigorodova A M Drits Ya V Zhingel T V Krymova

and V A Rassokhin Phys Met Metall 1992 73 281ndash285

257 I N Fridlyander S F Danilov E N Malysheva T A

Gorokhova and N N Kirkina Proc Sixth Int Aluminiumndash

Lithium Conference Garmisch-Partenkirchen Germany October

1991 381ndash386

258 G Dlubek S Krause H Krause A L Beresina V S

Mikhalenkov and K V Chuistov J Phys Condens Matter

1992 4 6317ndash6328

259 S Krause H Krause G Dlubek A L Beresina and K S

Chuistov Mater Sci Forum 1992 105ndash110 1109ndash1112

260 C Y Tan Z Q Zheng and S Q Liang Proc 4th Int Conf on

lsquoAluminium alloysrsquo Vol II Atlanta GA USA September 1994

329ndash333

261 A L Beresina N I Kolobnev K V Chuistov A V Kotko and

O A Molebny Mater Sci Forum 2002 396ndash402 977ndash981

Roslashyset and Ryum Scandium in aluminium alloys

International Materials Reviews 2005 VOL 50 NO 1 43

262 I N Ganiev I Yunusov and V V Krasnoyarskii J Appl Chem

USSR 1986 60 1961ndash1965

263 I N Ganiev Prot Met 1995 31 543ndash546

264 N V Vyazovikina Prot Met 1999 35 448ndash453

265 G V Kharina and V P Kochergin Prot Met 1996 32 134ndash

136

266 G V Kharina M V Kuznetsov and V P Kochergin Russ J

Electrochem 1998 34 482ndash485

267 V S Sinyavskii V D Valrsquokov and E V Titkova Prot Met

1998 34 549ndash555

268 Y L Wu F H Froes C G Li and J Liu Proc lsquoSynthesis

processing of lightweight metallic materials IIrsquo Orlando FL

USA February 1997 73ndash81

269 Z Ahmad and B J Abdul-Aleem Proc EuroCorr 2000

270 Z Ahmad A Ul-Hamid and B J Abdul-Aleem Corros Sci

2001 43 1227ndash1243

271 R Braun B Lenczowski and G Tempus Mater Sci Forum

2000 331ndash337 1647ndash1652

272 T Torma E Kovacs-Csetenyi L Vitalis I Vitanyi

J Stepanov and M Butova Mater Sci Forum 1987 1314

497ndash503

273 Z Wang P Wang K S Kumar and C L Briant in lsquoChemistry

and electrochemistry of corrosion and stress corrosion crackingrsquo

(ed R H Jones) 573ndash582 2001 TMS

274 V I Elagin V V Zakharov A A Petrova and E V

Vyshegorodtseva Russ Metall 1983 (4) 143ndash146

Roslashyset and Ryum Scandium in aluminium alloys

44 International Materials Reviews 2005 VOL 50 NO 1

Page 24: Scandium in aluminium alloys - Atom probe · A considerable part of the available literature on scandium in aluminium alloys is reviewed. ... behaviour in Al Cu, Al Mg Si,

121 M Ye Drits L B Ber Yu G Bykov L S Toropova and G K

Anastaseva Phys Met Metall 1984 57 (6) 118ndash126

122 M E Drits L S Toropova and Yu G Bykov Sov Non-Ferrous

Met Res 1985 13 309ndash314

123 V I Yelagin V V Zakharov S G Pavlenko and T D Rostova

Phys Met Metall 1985 60 (1) 88ndash92

124 N Sano Y Hasegawa K Hono H Jo K Hirano H W

Pickering and T Sakurai Journal de Physique 1987 48 C6 337ndash

342

125 N Sano H-H Jo K-I Hirano and T Sakurai J Jpn Inst

Metals 1989 39 444ndash450

126 N Sano H Jo K Hirano and T Sakurai Proc Second Int

Conf on lsquoAluminium alloysrsquo Beijing China October 1990 549ndash

554

127 Y Miura M Nakayama and A Furuta Proc lsquoAspects of high

temperature deformation and fracture in crystalline materialsrsquo

Nagoya Japan July 1993 255ndash262

128 Y W Riddle and T H Sanders Jr Mater Sci Forum 2000

331ndash337 939ndash944

129 Y W Riddle M McIntosh and T H Sanders Jr in lsquoLightweight

alloys for aerospace application VIrsquo (ed K Jata E W Lee

W Frazier and N J Kim) 25ndash39 2001 TMS

130 M E Drits J Dutkiewicz L S Toropova and J Salawa Crystal

Res Technol 1984 19 1325ndash1330

131 Y W Riddle MSc thesis Georgia Tech GA USA 1998

132 T J Bastow and S Celotto Mater Sci Eng 2003 C 23 757ndash

762

133 M C Carroll M J Mills G S Daehn P I Gouma M F

Savage and B R Dunbar in lsquoAutomotive Alloys 1999rsquo (ed

S Das) 239ndash246 2000 TMS

134 E Clouet M Nastar and C Sigli Phys Rev B 2004 69 064109-

1-14

135 V V Zakharov Met Sci Heat Treat 1997 (2) 61ndash66

136 J W Christian lsquoThe theory of transformation in metals and

alloysrsquo 2nd edn 1975 Pergamon Press Ltd

137 A L Berezina V A Volkov B P Domashnikov S V Ivanov

and K V Chuistov Phys Metals 1990 10 296ndash304

138 S-I Fujikawa and S Sakauchi Proc 6th Int Conf on

lsquoAluminum alloysrsquo Toyohashi Japan July 1998 805ndash810

139 Y S Touloukian R K Kirby R E Taylor and P D Desai

(eds) lsquoThermal expansion metallic elements and alloysrsquo 1975

New York Plenum

140 J Roslashyset and N Ryum submitted to Scripta Mater

141 R O Simmons and R W Balluffi Phys Rev 1960 117 52ndash61

142 M Ocko E Babic R Krsmik E Girt and B Leontic J Phys F

Metals Phys 1976 6 703ndash707

143 M J Jones and F J Humphreys Proc First Joint Int Conf on

lsquoRecrystallization and grain growthrsquo Aachen Germany August

2001 Springer Verlag 1287ndash1292

144 S Iwamura M Nakayama and Y Miura Mater Sci Forum

2002 396ndash402 1151ndash1156

145 S Iwamura and Y Miura Acta Mater 2004 52 591ndash600

146 M Asta S M Foiles and A A Quong Phys Rev B 1998 57

11265ndash11275

147 R W Hyland Jr M Asta S M Foiles and C L Rohrer Acta

Mater 1998 46 3667ndash3678

148 J Roslashyset and N Ryum Proc 4th Int Conf on lsquoAluminium

alloysrsquo Vol I Atlanta GA USA September 1994 194ndash201

149 M E Drits L S Toropova G K Anastaseva and G L

Nagornichnykh Russ Metall 1984 (3) 192ndash195

150 E A Marquis D N Seidman and D C Dunand Acta Mater

2003 51 4751ndash4760

151 M E Drits L S Toropova and Yu G Bykov Met Sci Heat

Treat 1983 (7) 550ndash554

152 V V Zakharov and T D Rostova Met Sci Heat Treat 1995

(2) 65ndash69

153 M Nakayama and Y Miura Proc 4th Int Conf on lsquoAluminium

alloysrsquo Vol I Atlanta GA USA September 1994 538ndash545

154 M Nakayama and Y Miura J Jpn Inst Light Metals 1996 46

275ndash279

155 M Nakayama T Okuyama and Y Miura Mater Sci Forum

2000 331ndash337 927ndash932

156 M Nakayama T Okuyama and Y Miura Proc 6th Int Conf

on lsquoAluminum alloysrsquo Toyohashi Japan July 1998 517ndash522

157 M L Kharakterova D G Eskin and L S Toropova Acta

Metall Mater 1994 42 2285ndash2290

158 V I Elagin V V Zakharov and T D Rostova Met Sci Heat

Treat 1992 (1) 37ndash45

159 H Wiik Siv Ing thesis NTH Institute of Metallurgy

Trondheim Norway 1995

160 J Roslashyset H Hovland and N Ryum Mater Sci Forum 2002

396ndash402 619ndash624

161 Y Miura K Horikawa K Yamada and M Nakayama Proc

4th Int Conf on lsquoAluminium alloysrsquo Vol II Atlanta GA USA

September 1994 161ndash168

162 Y W Riddle PhD thesis Georgia Tech GA USA 2000

163 B Forbord W Lefebvre F Danoix H Hallem and

K Marthinsen Scripta Mater 2004 51 333ndash337

164 J D Robson Acta Mater 2004 52 1409ndash1421

165 C B Fuller J L Murray and D N Seidman submitted to Acta

Mater 2004

166 M G Mousavi C E Cross and Oslash Grong Sci Technol Weld

Joining 1999 4 381ndash388

167 J S Vetrano S M Bruemmer L M Pawlowski and I M

Robertson Mater Sci Eng 1997 A 238 101ndash107

168 Y W Riddle and T H Sanders Jr Mater Sci Forum 2000

331ndash337 799ndash803

169 G M Khan A O Nikiforov V V Zakharov and I I Novikov

Tsvetnye Metally 1993 34 (11) 43ndash45

170 Z Horita M Furukawa M Nemoto A J Barnes and T G

Langdon Acta Mater 2000 48 3633ndash3640

171 L A Willey US Patent 3 619 181 9 November 1971

172 L K Lamikhov and G V Samsonov Tsvetnye Metally 1964 5

(8) 77ndash80

173 A L Berezina K V Chuistov N I Kolobnev L B

Khokhlatova and T A Monastyrskaya Mater Sci Forum

2002 396ndash402 741ndash746

174 F A Fasoyinu J Thomson D Cousineau T Castles and M

Sahoo Proc 6th Int AFS Conf on lsquoMolten aluminum

processingrsquo Orlando FL USA November 2001

175 Z Yin Q Pan Y Zhang and F Jiang Mater Sci Eng 2000

A 280 151ndash155

176 I I Novikov and O E Grushko Mater Sci Technol 1995 11

926ndash932

177 D Cousineau M Sahoo P D Newcombe T Castles and F A

Fasoyinu Proc lsquoAFS 105th casting congressrsquo Dallas TX USA

AprilndashMay 2001 157ndash184

178 C E Cross and Oslash Grong Proc 6th Int Conf on lsquoAluminum

alloysrsquo Toyohashi Japan July 1998 1441ndash1446

179 F A Costello J D Robson and P B Prangnell Mater Sci

Forum 2002 396ndash402 757ndash762

180 K B Hyde A F Norman and P B Prangnell Mater Sci

Forum 2002 396ndash402 39ndash44

181 M E Drits S G Pavlenko L S Toropova Yu G Bukov and

L B Ber Sov Phys Dokl 1981 26 (3) 344ndash346

182 A M Drits and B A Kopeliovich Russ Metall 1985 (4) 147ndash

151

183 V G Davydov V I Elagin V V Zakharov and T D Rostova

Met Sci Heat Treat 1996 (8) 347ndash352

184 M E Drits L S Toropova Yu G Bykov L B Ber and S G

Pavlenko Russ Metall 1982 (1) 148ndash152

185 T D Rostova V G Davydov V I Yelagin and V V Zakharov

Mater Sci Forum 2000 331ndash337 793ndash798

186 Y W Riddle H Hallem and N Ryum Mater Sci Forum 2002

396ndash402 563ndash568

187 J Roslashyset and Y W Riddle Proc 9th Int Conf on lsquoAluminium

alloysrsquo Brisbane Australia August 2004 1210ndash1215

188 A M Diskin V K Portnoi A M Drits and A A Alalykin Sov

Non-Ferrous Met Res 1986 14 499ndash500

189 R R Sawtell P E Bretz and C L Jensen US Patent 4 689 090

25 August 1987

190 G A Salishchev Yu B Timoshenko and R A Saitova Proc

Second Int Conf on lsquoAluminium alloysrsquo Beijing China October

1990 413ndash415

191 T G Nieh R Kaibyshev L M Hsiung N Nguyen and

J Wadsworth Scripta Mater 1997 36 1011ndash1016

192 T G Nieh L M Hsiung J Wadsworth and R Kaibyshev Acta

Mater 1998 46 2789ndash2800

193 J S Vetrano C H Henager Jr M T Smith and S M

Bruemmer in lsquoHot deformation of aluminum alloys IIrsquo (ed T R

Bieler L A Lalli and S R MacEwen) 407ndash418 1998 TMS

194 J S Vetrano C H Henager Jr S M Bruemmer Y Ge and

C H Hamilton in lsquoSuperplasticity and Superplastic Forming

1998rsquo (ed A K Gosh and T R Bieler) 89ndash97 1998 TMS

195 V Y Gertsman J S Vetrano C H Henager Jr and S M

Bruemmer Proc First Joint Int Conf on lsquoRecrystallization and

grain growthrsquo Aachen Germany August 2001 Springer Verlag

2001 837ndash842

196 Y Xiao C Gao H Ma and S Tian Trans Nonferrous Met Soc

China 2001 11 235ndash238

Roslashyset and Ryum Scandium in aluminium alloys

42 International Materials Reviews 2005 VOL 50 NO 1

197 A Gholinia F J Humphreys and P B Prangnell Acta Mater

2002 50 4461ndash4476

198 A Gholinia F J Humphreys and P B Prangnell Mater Sci

Forum 2002 408ndash412 1519ndash1524

199 S Komura P B Berbon M Furukawa Z Horita M Nemoto

and T G Langdon Scripta Mater 1998 38 1851ndash1856

200 S Komura P B Berbon A Utsunomiya M Furukawa

Z Horita M Nemoto and T G Langdon in lsquoHot deformation

of aluminum alloys IIrsquo (ed T R Bieler L A Lalli and S R

MacEwen) 125ndash138 1998 TMS

201 S Komura Z Horita M Furukawa M Nemoto and T G

Langdon J Mater Res 2000 15 2571ndash2576

202 S Komura M Furukawa Z Horita M Nemoto and T G

Langdon Mater Sci Eng 2001 A 297 111ndash118

203 S Komura Z Horita M Furukawa M Nemoto and T G

Langdon Metall Mater Trans A 2001 32A 707ndash716

204 Z Horita M Furukawa K Oh-ishi M Nemoto and T G

Langdon Proc Fourth Int Conf on lsquoRecrystallization and

related phenomenarsquo (ed T Sakai and H G Suzuki) 1999 The

Japan Institute of Metals 301ndash308

205 Z Horita S Komura P B Berbon A Utsunomiya

M Furukawa M Nemoto and T G Langdon Mater Sci

Forum 1999 304ndash306 91ndash96

206 Z Horita S Lee S Ota K Neishi and T G Langdon Mater

Sci Forum 2001 357ndash359 471ndash476

207 Z Horita T Fujinami K Sato S B Kang H W Kim and T G

Langdon in Proc James T Staley Honorary Symposium on

Aluminum Alloys lsquoAdvances in the metallurgy of aluminum

alloysrsquo (ed M Tiryakioglu) 271ndash275 2001 ASM

208 P B Berbon S Komura A Utsunomiya Z Horita

M Furukawa M Nemoto and T G Langdon Mater Trans

JIM 1999 40 772ndash778

209 M Nemoto Z Horita M Furukawa and T G Langdon Mater

Sci Forum 1999 304ndash306 59ndash66

210 M Furukawa Z Horita M Nemeto and T G Langdon Proc

lsquoLight Metals 1999rsquo Quebec City PQ Canada August 1999 583ndash

592

211 M Furukawa K Oh-ishi S Komura A Yamashita Z Horita

M Nemeto and T G Langdon Mater Sci Forum 1999 304ndash

306 97ndash102

212 M Furukawa A Utsunomiya K Matsubara Z Horita and

T G Langdon Acta Mater 2001 49 3829ndash3838

213 M Furukawa A Utsunomiya S Komura Z Horita M Nemoto

and T G Langdon Mater Sci Forum 2001 357ndash359 431ndash436

214 M Furukawa Z Horita and T G Langdon in Proc James T

Staley Honorary Symposium on Aluminum Alloys lsquoAdvances in

the metallurgy of aluminum alloysrsquo (ed M Tiryakioglu) 47ndash56

2001 ASM

215 M Furukawa Z Horita M Nemoto and T G Langdon Mater

Sci Eng 2002 A 324 82ndash89

216 M Furukawa Z Horita and T G Langdon in lsquoUltrafine grained

materials IIrsquo (ed Y T Zhu T G Langdon R S Mishra S L

Semiatin M J Saran and T C Lowe) 459ndash468 2002 TMS

217 T G Langdon M Furukawa Z Horita and M Nemoto Proc

NATO Advanced Research Workshop on lsquoInvestigations and

applications of severe plastic deformationrsquo Moscow August

1999 NATO Science Series Series 3 High Technology vol 80

Kluwer Academic Publishers The Netherlands 2000 149ndash154

218 S Lee H Akamatsu A Utsunomiya K Neishi M Furukawa

Z Horita and T G Langdon Proc Thermec 2000 Las Vegas

USA December 2000

219 S Lee A Utsunomiya H Akamatsu K Neishi M Furukawa

Z Horita and T G Langdon Acta Mater 2002 50 553ndash564

220 A Yamashita D Yamaguchi Z Horita and T G Langdon

Mater Sci Eng 2000 A 287 100ndash106

221 K Oh-ishi Z Horita D J Smith and T G Langdon J Mater

Res 2001 16 583ndash589

222 H Akamatsu T Fujinami Z Horita and T G Langdon Scripta

Mater 2001 44 759ndash764

223 S Ota H Akamatsu K Neishi M Furukawa Z Horita and

T G Langdon Mater Trans 2002 43 2364ndash2369

224 K Furuno H Akamatsu K Oh-ishi M Furukawa Z Horita

and T G Langdon Acta Mater 2004 52 2497ndash2507

225 I N Fridlyander O G Senatorova N A Ryazanova and A O

Nikiforov Mater Sci Forum 1994 170ndash172 345ndash349

226 J N Fridlyander and O G Senatorova Mater Sci Forum 1996

217ndash222 1813ndash1818

227 J Liu and D J Chakrabarti Acta Mater 1996 44 4647ndash4661

228 O G Senatorova A N Uksusnikov J N Fridlyander

J Koshorst R R Romanova N A Ryazanova A Galliot

and V V Cherkassov Proc 6th Int Conf on lsquoAluminum alloysrsquo

July 1998 Toyohashi Japan 589ndash593

229 R A Emigh E L Bradley and J W Morris Jr in

lsquoSuperplasticity in aerospace IIrsquo (ed T R McNelley and H C

Heikkenen) 303ndash315 1990 TMS

230 E L Bradley III R A Emigh and J W Morris Jr Scripta

Metall Mater 1991 25 717ndash721

231 N I Kolobnev L B Khokhlatova V D Makarov E Yu

Semenova and V V Redchits Proc Sixth Int Aluminiumndash

Lithium Conference Garmisch-Partenkirchen Germany October

1991 1053ndash1056

232 N K Tsenev R Z Valiev O V Obraztsov and I N Fridlander

Proc Sixth Int AluminiumndashLithium Conference Garmisch-

Partenkirchen Germany October 1991 1125ndash1132

233 A M Shammazov N K Tsenev R Z Valiev M M

Myshlyaev M M Bikbulatov and S P Lebedich Phys Met

Metall 2000 89 (3) 314ndash318

234 F Musin R Kaibyshev Y Motohashi T Sakuma and G Itoh

Mater Trans A 2002 43A 2370ndash2377

235 M Shagiev Y Motohashi F Musin R Kaibyshev and G Itoh

Mater Trans A 2003 44A 1694ndash1697

236 M Shagiev Y Motohashi F Musin R Kaibyshev and G Itoh

Mater Trans A 2003 44A 1698ndash1701

237 B A Parker and Z F Zhou Proc 3rd Int Conf on lsquoAluminium

alloysrsquo Vol I NTH Trondheim Norway June 1992 363ndash367

238 J R Davies lsquoASM specialty handbook aluminum and aluminum

alloysrsquo 1993 Materials Park OH USA ASM

239 S J Andersen H W Zandbergen J Jansen C Traeholt

U Tundal and O Reiso Acta Mater 1998 46 3283ndash3298

240 M L Kharakterova D G Eskin and L L Rokhlin Russ

Metall 1997 (1) 104ndash109

241 J Roslashyset Dr Ing thesis NTNU Trondheim Norway 2002

242 P P Chattopadhyay S Datta and M K Banerjee Mater Sci

Eng 2002 A 333 67ndash71

243 L I Kaigorodova E I Selnikhina E A Tkachenko and O G

Senatorova Phys Met Metall 1996 81 513ndash519

244 Y-L Wu F H Froes C Li and A Alvarez Metall Mater

Trans A 1999 30A 1017ndash1024

245 Z Yin L Yang Q Pan and F Jiang Trans Nonferrous Met

Soc China 2001 11 822ndash825

246 V I Elagin V V Zakharov and T D Rostova Met Sci Heat

Treat 1994 36 (7) 375ndash380

247 Y V Milman A I Sirko D V Lotsko O N Senkov and D B

Miracle Mater Sci Forum 2002 396ndash402 1217ndash1222

248 C-H Joh K Yamada and Y Miura Mater Trans JIM 1999

40 439ndash442

249 X J Jiang Q H Gui Y Y Li L M Ma G J Liang and C X

Shi Scr Metall Mater 1993 29 211ndash216

250 X J Jiang Y Y Li W Deng L Y Xiong W M Wu Y J Gao

and C X Shi Adv Cryogenic Eng (Mater) 1994 40 1369ndash

1376

251 C-H Joh T Katsube K Yamada and Y Miura Proc 6th Int

Conf on lsquoAluminum alloysrsquo Toyohashi Japan July 1998 799ndash

804

252 L I Kaygorodova A M Dritz T V Krymova and I N

Fridlyander Proc Sixth Int AluminiumndashLithium Conference

Garmisch-Partenkirchen Germany October 1991 363ndash367

253 L I Kaigorodova A M Drits Ya V Zhingel T V Krymova

and I N Fridlyander Phys Met Metall 1992 73 286ndash290

254 A L Berezina V A Volkov S V Ivanov N I Kolobnev and

K V Chuistov Phys Met Metall 1991 71 (2) 167ndash175

255 I N Fridlyander N I Kolobnev A L Berezina and K V

Chuistov Proc Sixth Int AluminiumndashLithium Conference

Garmisch-Partenkirchen Germany October 1991 107ndash112

256 L I Kaigorodova A M Drits Ya V Zhingel T V Krymova

and V A Rassokhin Phys Met Metall 1992 73 281ndash285

257 I N Fridlyander S F Danilov E N Malysheva T A

Gorokhova and N N Kirkina Proc Sixth Int Aluminiumndash

Lithium Conference Garmisch-Partenkirchen Germany October

1991 381ndash386

258 G Dlubek S Krause H Krause A L Beresina V S

Mikhalenkov and K V Chuistov J Phys Condens Matter

1992 4 6317ndash6328

259 S Krause H Krause G Dlubek A L Beresina and K S

Chuistov Mater Sci Forum 1992 105ndash110 1109ndash1112

260 C Y Tan Z Q Zheng and S Q Liang Proc 4th Int Conf on

lsquoAluminium alloysrsquo Vol II Atlanta GA USA September 1994

329ndash333

261 A L Beresina N I Kolobnev K V Chuistov A V Kotko and

O A Molebny Mater Sci Forum 2002 396ndash402 977ndash981

Roslashyset and Ryum Scandium in aluminium alloys

International Materials Reviews 2005 VOL 50 NO 1 43

262 I N Ganiev I Yunusov and V V Krasnoyarskii J Appl Chem

USSR 1986 60 1961ndash1965

263 I N Ganiev Prot Met 1995 31 543ndash546

264 N V Vyazovikina Prot Met 1999 35 448ndash453

265 G V Kharina and V P Kochergin Prot Met 1996 32 134ndash

136

266 G V Kharina M V Kuznetsov and V P Kochergin Russ J

Electrochem 1998 34 482ndash485

267 V S Sinyavskii V D Valrsquokov and E V Titkova Prot Met

1998 34 549ndash555

268 Y L Wu F H Froes C G Li and J Liu Proc lsquoSynthesis

processing of lightweight metallic materials IIrsquo Orlando FL

USA February 1997 73ndash81

269 Z Ahmad and B J Abdul-Aleem Proc EuroCorr 2000

270 Z Ahmad A Ul-Hamid and B J Abdul-Aleem Corros Sci

2001 43 1227ndash1243

271 R Braun B Lenczowski and G Tempus Mater Sci Forum

2000 331ndash337 1647ndash1652

272 T Torma E Kovacs-Csetenyi L Vitalis I Vitanyi

J Stepanov and M Butova Mater Sci Forum 1987 1314

497ndash503

273 Z Wang P Wang K S Kumar and C L Briant in lsquoChemistry

and electrochemistry of corrosion and stress corrosion crackingrsquo

(ed R H Jones) 573ndash582 2001 TMS

274 V I Elagin V V Zakharov A A Petrova and E V

Vyshegorodtseva Russ Metall 1983 (4) 143ndash146

Roslashyset and Ryum Scandium in aluminium alloys

44 International Materials Reviews 2005 VOL 50 NO 1

Page 25: Scandium in aluminium alloys - Atom probe · A considerable part of the available literature on scandium in aluminium alloys is reviewed. ... behaviour in Al Cu, Al Mg Si,

197 A Gholinia F J Humphreys and P B Prangnell Acta Mater

2002 50 4461ndash4476

198 A Gholinia F J Humphreys and P B Prangnell Mater Sci

Forum 2002 408ndash412 1519ndash1524

199 S Komura P B Berbon M Furukawa Z Horita M Nemoto

and T G Langdon Scripta Mater 1998 38 1851ndash1856

200 S Komura P B Berbon A Utsunomiya M Furukawa

Z Horita M Nemoto and T G Langdon in lsquoHot deformation

of aluminum alloys IIrsquo (ed T R Bieler L A Lalli and S R

MacEwen) 125ndash138 1998 TMS

201 S Komura Z Horita M Furukawa M Nemoto and T G

Langdon J Mater Res 2000 15 2571ndash2576

202 S Komura M Furukawa Z Horita M Nemoto and T G

Langdon Mater Sci Eng 2001 A 297 111ndash118

203 S Komura Z Horita M Furukawa M Nemoto and T G

Langdon Metall Mater Trans A 2001 32A 707ndash716

204 Z Horita M Furukawa K Oh-ishi M Nemoto and T G

Langdon Proc Fourth Int Conf on lsquoRecrystallization and

related phenomenarsquo (ed T Sakai and H G Suzuki) 1999 The

Japan Institute of Metals 301ndash308

205 Z Horita S Komura P B Berbon A Utsunomiya

M Furukawa M Nemoto and T G Langdon Mater Sci

Forum 1999 304ndash306 91ndash96

206 Z Horita S Lee S Ota K Neishi and T G Langdon Mater

Sci Forum 2001 357ndash359 471ndash476

207 Z Horita T Fujinami K Sato S B Kang H W Kim and T G

Langdon in Proc James T Staley Honorary Symposium on

Aluminum Alloys lsquoAdvances in the metallurgy of aluminum

alloysrsquo (ed M Tiryakioglu) 271ndash275 2001 ASM

208 P B Berbon S Komura A Utsunomiya Z Horita

M Furukawa M Nemoto and T G Langdon Mater Trans

JIM 1999 40 772ndash778

209 M Nemoto Z Horita M Furukawa and T G Langdon Mater

Sci Forum 1999 304ndash306 59ndash66

210 M Furukawa Z Horita M Nemeto and T G Langdon Proc

lsquoLight Metals 1999rsquo Quebec City PQ Canada August 1999 583ndash

592

211 M Furukawa K Oh-ishi S Komura A Yamashita Z Horita

M Nemeto and T G Langdon Mater Sci Forum 1999 304ndash

306 97ndash102

212 M Furukawa A Utsunomiya K Matsubara Z Horita and

T G Langdon Acta Mater 2001 49 3829ndash3838

213 M Furukawa A Utsunomiya S Komura Z Horita M Nemoto

and T G Langdon Mater Sci Forum 2001 357ndash359 431ndash436

214 M Furukawa Z Horita and T G Langdon in Proc James T

Staley Honorary Symposium on Aluminum Alloys lsquoAdvances in

the metallurgy of aluminum alloysrsquo (ed M Tiryakioglu) 47ndash56

2001 ASM

215 M Furukawa Z Horita M Nemoto and T G Langdon Mater

Sci Eng 2002 A 324 82ndash89

216 M Furukawa Z Horita and T G Langdon in lsquoUltrafine grained

materials IIrsquo (ed Y T Zhu T G Langdon R S Mishra S L

Semiatin M J Saran and T C Lowe) 459ndash468 2002 TMS

217 T G Langdon M Furukawa Z Horita and M Nemoto Proc

NATO Advanced Research Workshop on lsquoInvestigations and

applications of severe plastic deformationrsquo Moscow August

1999 NATO Science Series Series 3 High Technology vol 80

Kluwer Academic Publishers The Netherlands 2000 149ndash154

218 S Lee H Akamatsu A Utsunomiya K Neishi M Furukawa

Z Horita and T G Langdon Proc Thermec 2000 Las Vegas

USA December 2000

219 S Lee A Utsunomiya H Akamatsu K Neishi M Furukawa

Z Horita and T G Langdon Acta Mater 2002 50 553ndash564

220 A Yamashita D Yamaguchi Z Horita and T G Langdon

Mater Sci Eng 2000 A 287 100ndash106

221 K Oh-ishi Z Horita D J Smith and T G Langdon J Mater

Res 2001 16 583ndash589

222 H Akamatsu T Fujinami Z Horita and T G Langdon Scripta

Mater 2001 44 759ndash764

223 S Ota H Akamatsu K Neishi M Furukawa Z Horita and

T G Langdon Mater Trans 2002 43 2364ndash2369

224 K Furuno H Akamatsu K Oh-ishi M Furukawa Z Horita

and T G Langdon Acta Mater 2004 52 2497ndash2507

225 I N Fridlyander O G Senatorova N A Ryazanova and A O

Nikiforov Mater Sci Forum 1994 170ndash172 345ndash349

226 J N Fridlyander and O G Senatorova Mater Sci Forum 1996

217ndash222 1813ndash1818

227 J Liu and D J Chakrabarti Acta Mater 1996 44 4647ndash4661

228 O G Senatorova A N Uksusnikov J N Fridlyander

J Koshorst R R Romanova N A Ryazanova A Galliot

and V V Cherkassov Proc 6th Int Conf on lsquoAluminum alloysrsquo

July 1998 Toyohashi Japan 589ndash593

229 R A Emigh E L Bradley and J W Morris Jr in

lsquoSuperplasticity in aerospace IIrsquo (ed T R McNelley and H C

Heikkenen) 303ndash315 1990 TMS

230 E L Bradley III R A Emigh and J W Morris Jr Scripta

Metall Mater 1991 25 717ndash721

231 N I Kolobnev L B Khokhlatova V D Makarov E Yu

Semenova and V V Redchits Proc Sixth Int Aluminiumndash

Lithium Conference Garmisch-Partenkirchen Germany October

1991 1053ndash1056

232 N K Tsenev R Z Valiev O V Obraztsov and I N Fridlander

Proc Sixth Int AluminiumndashLithium Conference Garmisch-

Partenkirchen Germany October 1991 1125ndash1132

233 A M Shammazov N K Tsenev R Z Valiev M M

Myshlyaev M M Bikbulatov and S P Lebedich Phys Met

Metall 2000 89 (3) 314ndash318

234 F Musin R Kaibyshev Y Motohashi T Sakuma and G Itoh

Mater Trans A 2002 43A 2370ndash2377

235 M Shagiev Y Motohashi F Musin R Kaibyshev and G Itoh

Mater Trans A 2003 44A 1694ndash1697

236 M Shagiev Y Motohashi F Musin R Kaibyshev and G Itoh

Mater Trans A 2003 44A 1698ndash1701

237 B A Parker and Z F Zhou Proc 3rd Int Conf on lsquoAluminium

alloysrsquo Vol I NTH Trondheim Norway June 1992 363ndash367

238 J R Davies lsquoASM specialty handbook aluminum and aluminum

alloysrsquo 1993 Materials Park OH USA ASM

239 S J Andersen H W Zandbergen J Jansen C Traeholt

U Tundal and O Reiso Acta Mater 1998 46 3283ndash3298

240 M L Kharakterova D G Eskin and L L Rokhlin Russ

Metall 1997 (1) 104ndash109

241 J Roslashyset Dr Ing thesis NTNU Trondheim Norway 2002

242 P P Chattopadhyay S Datta and M K Banerjee Mater Sci

Eng 2002 A 333 67ndash71

243 L I Kaigorodova E I Selnikhina E A Tkachenko and O G

Senatorova Phys Met Metall 1996 81 513ndash519

244 Y-L Wu F H Froes C Li and A Alvarez Metall Mater

Trans A 1999 30A 1017ndash1024

245 Z Yin L Yang Q Pan and F Jiang Trans Nonferrous Met

Soc China 2001 11 822ndash825

246 V I Elagin V V Zakharov and T D Rostova Met Sci Heat

Treat 1994 36 (7) 375ndash380

247 Y V Milman A I Sirko D V Lotsko O N Senkov and D B

Miracle Mater Sci Forum 2002 396ndash402 1217ndash1222

248 C-H Joh K Yamada and Y Miura Mater Trans JIM 1999

40 439ndash442

249 X J Jiang Q H Gui Y Y Li L M Ma G J Liang and C X

Shi Scr Metall Mater 1993 29 211ndash216

250 X J Jiang Y Y Li W Deng L Y Xiong W M Wu Y J Gao

and C X Shi Adv Cryogenic Eng (Mater) 1994 40 1369ndash

1376

251 C-H Joh T Katsube K Yamada and Y Miura Proc 6th Int

Conf on lsquoAluminum alloysrsquo Toyohashi Japan July 1998 799ndash

804

252 L I Kaygorodova A M Dritz T V Krymova and I N

Fridlyander Proc Sixth Int AluminiumndashLithium Conference

Garmisch-Partenkirchen Germany October 1991 363ndash367

253 L I Kaigorodova A M Drits Ya V Zhingel T V Krymova

and I N Fridlyander Phys Met Metall 1992 73 286ndash290

254 A L Berezina V A Volkov S V Ivanov N I Kolobnev and

K V Chuistov Phys Met Metall 1991 71 (2) 167ndash175

255 I N Fridlyander N I Kolobnev A L Berezina and K V

Chuistov Proc Sixth Int AluminiumndashLithium Conference

Garmisch-Partenkirchen Germany October 1991 107ndash112

256 L I Kaigorodova A M Drits Ya V Zhingel T V Krymova

and V A Rassokhin Phys Met Metall 1992 73 281ndash285

257 I N Fridlyander S F Danilov E N Malysheva T A

Gorokhova and N N Kirkina Proc Sixth Int Aluminiumndash

Lithium Conference Garmisch-Partenkirchen Germany October

1991 381ndash386

258 G Dlubek S Krause H Krause A L Beresina V S

Mikhalenkov and K V Chuistov J Phys Condens Matter

1992 4 6317ndash6328

259 S Krause H Krause G Dlubek A L Beresina and K S

Chuistov Mater Sci Forum 1992 105ndash110 1109ndash1112

260 C Y Tan Z Q Zheng and S Q Liang Proc 4th Int Conf on

lsquoAluminium alloysrsquo Vol II Atlanta GA USA September 1994

329ndash333

261 A L Beresina N I Kolobnev K V Chuistov A V Kotko and

O A Molebny Mater Sci Forum 2002 396ndash402 977ndash981

Roslashyset and Ryum Scandium in aluminium alloys

International Materials Reviews 2005 VOL 50 NO 1 43

262 I N Ganiev I Yunusov and V V Krasnoyarskii J Appl Chem

USSR 1986 60 1961ndash1965

263 I N Ganiev Prot Met 1995 31 543ndash546

264 N V Vyazovikina Prot Met 1999 35 448ndash453

265 G V Kharina and V P Kochergin Prot Met 1996 32 134ndash

136

266 G V Kharina M V Kuznetsov and V P Kochergin Russ J

Electrochem 1998 34 482ndash485

267 V S Sinyavskii V D Valrsquokov and E V Titkova Prot Met

1998 34 549ndash555

268 Y L Wu F H Froes C G Li and J Liu Proc lsquoSynthesis

processing of lightweight metallic materials IIrsquo Orlando FL

USA February 1997 73ndash81

269 Z Ahmad and B J Abdul-Aleem Proc EuroCorr 2000

270 Z Ahmad A Ul-Hamid and B J Abdul-Aleem Corros Sci

2001 43 1227ndash1243

271 R Braun B Lenczowski and G Tempus Mater Sci Forum

2000 331ndash337 1647ndash1652

272 T Torma E Kovacs-Csetenyi L Vitalis I Vitanyi

J Stepanov and M Butova Mater Sci Forum 1987 1314

497ndash503

273 Z Wang P Wang K S Kumar and C L Briant in lsquoChemistry

and electrochemistry of corrosion and stress corrosion crackingrsquo

(ed R H Jones) 573ndash582 2001 TMS

274 V I Elagin V V Zakharov A A Petrova and E V

Vyshegorodtseva Russ Metall 1983 (4) 143ndash146

Roslashyset and Ryum Scandium in aluminium alloys

44 International Materials Reviews 2005 VOL 50 NO 1

Page 26: Scandium in aluminium alloys - Atom probe · A considerable part of the available literature on scandium in aluminium alloys is reviewed. ... behaviour in Al Cu, Al Mg Si,

262 I N Ganiev I Yunusov and V V Krasnoyarskii J Appl Chem

USSR 1986 60 1961ndash1965

263 I N Ganiev Prot Met 1995 31 543ndash546

264 N V Vyazovikina Prot Met 1999 35 448ndash453

265 G V Kharina and V P Kochergin Prot Met 1996 32 134ndash

136

266 G V Kharina M V Kuznetsov and V P Kochergin Russ J

Electrochem 1998 34 482ndash485

267 V S Sinyavskii V D Valrsquokov and E V Titkova Prot Met

1998 34 549ndash555

268 Y L Wu F H Froes C G Li and J Liu Proc lsquoSynthesis

processing of lightweight metallic materials IIrsquo Orlando FL

USA February 1997 73ndash81

269 Z Ahmad and B J Abdul-Aleem Proc EuroCorr 2000

270 Z Ahmad A Ul-Hamid and B J Abdul-Aleem Corros Sci

2001 43 1227ndash1243

271 R Braun B Lenczowski and G Tempus Mater Sci Forum

2000 331ndash337 1647ndash1652

272 T Torma E Kovacs-Csetenyi L Vitalis I Vitanyi

J Stepanov and M Butova Mater Sci Forum 1987 1314

497ndash503

273 Z Wang P Wang K S Kumar and C L Briant in lsquoChemistry

and electrochemistry of corrosion and stress corrosion crackingrsquo

(ed R H Jones) 573ndash582 2001 TMS

274 V I Elagin V V Zakharov A A Petrova and E V

Vyshegorodtseva Russ Metall 1983 (4) 143ndash146

Roslashyset and Ryum Scandium in aluminium alloys

44 International Materials Reviews 2005 VOL 50 NO 1


Selected Aluminium Alloys

ALUMINIUM ALLOYS Composition Details Ok

Aluminum-Scandium Alloys: Material Characterization ... · PDF filei NASA/TM—2004–213604 Aluminum-Scandium Alloys: Material Characterization, Friction Stir Welding, and Compatibility

Atmospheric Corrosion of Aluminium Alloys

Aluminium and aluminium alloys — Extruded rod/bar, tube

ADVANCED LIGHTWEIGHT ALLOYS · market. However, this has the potential to change rapidly as scandium from primary mine production is brought on stream and expanded. Aluminium-Scandium

OF ALUMINIUM AND ALUMINIUM ALLOYS - Vsquare

EFFECTS OF SCANDIUM ON HYPO-EUTECTIC ALUMINUM … · Key words: Atomization, Al-alloys, Scandium, Microstructures, Heat treatment Abstract This work addresses the microstructures

Aluminium Casting Alloys

Aluminium and its alloys - University of Cincinnatibeaucag/Classes/Properties of Materials/Slides/Yaw... · Wrought Aluminium alloys Composition of aluminium alloys are regulated

Machinability of aluminium alloys

Resistance welding of aluminium and aluminium alloys (Group 16)

ULTRASONIC TREATMENT OF ALUMINIUM ALLOYS

Aluminum alloys containing scandium with zirconium additions

High Efficiency Machining for Aluminium Alloys …...TOOLS NEWS 2009.1 Update B118G Expand High Efficiency Machining for Aluminium Alloys High efficiency machining for aluminium alloys

ALUMINIUM AND ITS ALLOYS - library.sciencemadness.orglibrary.sciencemadness.org/library/books/aluminium_and_its_alloys.pdf · aluminium and its alloys their properties, thermal treatment

Creep Resistant Aluminium Alloys

IS 734 (1975): Wrought aluminium and aluminium alloys ... · 1972 ‘ Wrought aluminium and aluminium alloys, forging stock and for- ’ gings ’ issued by the British Standards

Scandium for Lightweight Alloys - Clean TeQcleanteq.com/wp-content/uploads/2016/12/lightweight...Scandium for Lightweight Alloys Scandium is a metallic element with atomic number 21

5- Aluminium Alloys 2010-2011

Aluminium alloys applications

Aluminium and aluminium alloys Foil

Metallica Minerals Ltd · Metallica Minerals Ltd ... Sc is a key ingredient in high performance aluminium alloys ... scandium alloys for select aerospace industry components

Zinc - Aluminium alloys ( Zamak) … · Zinc - Aluminium alloys ( Zamak) Zinc - Aluminium alloys ( Zamak) Bars & Rods Profiles Tubes Wires Billets Ingots Bushings Forged Parts Machining

Aluminium alloys study

Aluminium Alloys

Aluminium Casting Alloys EnglishVersion

The Aluminum-Scandium Alloy Advantage · 2017-03-08 · manufactured aluminum alloys, ... The Aluminum-Scandium Alloy Advantage. stress. Copper adds density to alloys, ... • Corrosion

Primary aluminium Casting alloys - RHEINFELDEN ALLOYS...ALLOYS can be found wherever steel designs or iron castings can be replaced by light aluminium castings. RHEINFELDEN ALLOYS

Alcoa Specialty Alloys - European Aluminium

Aluminium Casting Alloys EnglishVersion 2011

aluminium and its alloys

Investigation of Microstructure And Mechanical Properties ...Scandium (Sc) used for grain refinement agent in cast aluminium alloys [1]-[3]. The main functions of these ... Impurity

ALUMINIUM & ALUMINIUM ALLOYS - Welding … · ALUMINIUM & ALUMINIUM ALLOYS . 8 ALUMINIUM & ALUMINIUM ALLOYS A 5 4 3 2 1 4½ 4 4 4 A- Mechanical strength B- Versatility ... between

ALUMINIUM ALLOYS ALLUMINIUM … ALLOYSALLUMINIUM ALLOYS Aluminium alloys are alloys in which aluminium is the predominant metal. The typical alloying elements are copper, magnesium,