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Research ArticleFabrication of Friction Stir Processed Al-Ni ParticulateComposite and Its Impression Creep Behaviour

Prakrathi Sampath Vineeth Krishna ParangodathKota Rajendra Udupa and Udaya Bhat Kuruveri

Department of Metallurgical and Materials Engineering NITK Surathkal 575025 India

Correspondence should be addressed to Udaya Bhat Kuruveri udayabhatkgmailcom

Received 6 September 2014 Revised 10 January 2015 Accepted 11 January 2015

Academic Editor Hui Shen Shen

Copyright copy 2015 Prakrathi Sampath et al This is an open access article distributed under the Creative Commons AttributionLicense which permits unrestricted use distribution and reproduction in any medium provided the original work is properlycited

Nickel powders were troweled on roughened Al base plate using a friction tool made from tool steel Friction stir processing (FSP)was carried out using a load of 8 kN and with a tool rotation speed of 800 rpm and thus a surface composite was processedProcessed samples were characterized for revealing the microstructural features SEM and XRD analysis revealed the presenceof fine Ni particles in the stir zone which lead to a significant increase in hardness Using the ldquorefined energy modelrdquo the maximumtemperature developed within the processed zone was estimated and found to be around 275∘C Impression creep behaviour wasassessed on both the base metal and processed zone at the temperature of 30 100 and 200∘C Creep curves were generated andsteady state creep rate (SSCR) values were found out to determine the activation energy It is observed that friction stirred regionsrecord higher creep rate values compared to the base metal Estimated activation energy is in the range of 6 to 16 kJmol Activationenergy is marginally lower in the base metal compared to friction stir processed region

1 Introduction

Aluminium is the second most plentiful metallic elementon earth and it is well suited for many of the engineeringapplications due to its light weight appearance mechanicalproperties and ease of fabrication However pure Al isextremely poor in strength and hardness and it is one of themajor limitations as far as the end application is concernedThere are many established ways to improve the strengthand hardness of Al A few of them are precipitation hard-ening dispersion hardening and composite hardening [1]These hardening processes also limit some other desiredproperties like formability and weldability Further they mayalso involve additional expenditure in the form of use ofcostly alloying elements and additional processing stepsAn alternative approach is to convert only the surface ofthe component as a particle dispersed composite withoutaltering the bulk Friction stir processing is a method suitablefor converting surface of a component in to a composite

Friction stir processing (FSP) is a thermomechanicalworking process developed on the concept of friction stir

welding (FSW) [2 3] In this process the local compositionand properties of a material can be modified without chang-ing the bulk property of the same For this reason FSP isconsidered as one of the techniques of surface engineering inwhich the surface property can be modified according to theneed of the designer This process consists of a nonconsum-able rotating tool with specially designed pin and shoulderinserted onto the surface of the material and then moved andsimultaneously rotated with choice of the speed under thepredetermined load [4] The primary functions of noncon-sumable rotating tool are (i) to heat the specimen in the local-ized zone and (ii) to move and transport the materials withinthe processing zone (iii) to facilitate mixing up of externallyadded material to produce a composite material within theprocessed zoneThematerial flow associatedwith stirring andplastic deformation facilitates distribution of second phaseparticles As a result the stirred zone becomes a metal matrixcomposite with improved hardness and wear resistance [5]The movement of softened material along and around themoving rotating pin can promote nonequilibrium metal-lurgical events at the localized subsurface volume of the

Hindawi Publishing CorporationJournal of CompositesVolume 2015 Article ID 428630 9 pageshttpdxdoiorg1011552015428630

2 Journal of Composites

(a) (b)

Figure 1 Microstructure of the base metal Al (a) initial morphology of nickel powders used for friction stir processing (b)

material Because of this sometimes friction stir processingis considered as a nonequilibrium materials processing

Composite fabrication using friction stir processing routeis reviewed by Arora et al [6] Surface engineering by FSP ofAl with Ni powder is an interesting area [7ndash9] because it cangive rise to many important phases which are stable at hightemperature [5 10ndash12]

There are a few investigations focusing on producingmetal (matrix) metal (reinforcement) composite using fric-tion stir processing route Yadav and Bauri [13] reportedthe dispersion of nickel in Al alloy using FSP route andthey observed no detectable aluminides in the friction stirprocessed zone Ke et al [14] reported in situ formation ofAl3Ni intermetallics during friction stirring of Al substrate

with nickel powder They also reported formation of Al3Ni

and Al3Ni2after heat treatment Composite also consisted of

some amount of unreacted nickel powders Using FSP routeQian et al [15 16] produced Al-Al

3Ni in situ composites

and this composite had better hardness and tensile propertiescompared to Al substrate alone

Impression creep experiment is an important method ofmechanical characterization of surface composites [17] It canbe used to estimatemechanical properties of a small restrictedvolume of the material (like surface composite) at varioustemperature levels The method takes smaller time durationfor the test The temperature and stress dependency of creeprate could be obtained with minimum number of samplesThis method is applicable to assessing the creep behavior ofthe parent metal and processed zone independently [17 18]

An attempt is being made in the present investigation toassess the creep behavior of friction stirred Al with nickelpowder processed with 8 kN load at different tip rotationspeed of 800 rpm The processing parameters are entirelydifferent compared to those reported earlier in reference[19] Microstructural features and mechanical properties ofFSP Al-Ni composite with 10 kN normal force and 1200 rpmare reported in [19] Reduction in normal load and toolrotation speed is expected to alter the severity of the stirringmicrostructural features and mechanical properties

2 Experimental Details

Friction stir processing is carried out on the commercial pureAl plate of 5mm thickness Base metal has relatively largegrains (average grain size sim130 120583m) without the presence ofany second phase particles Initially the substrate surfaceis made rough by a friction stir pass without any powderaddition Electrolytic nickel powder is mixed with methanolto get a paste consistency and is applied to rough substrateCoverage of the powder is approximately 1 gcm2 of thesampleThemicrostructure of Al basemetal andmorphologyof the nickel powder used are given in Figures 1(a) and1(b) respectively The substrate along with the powder isdried and used for friction stir processing For friction stirprocessing a friction tool made from heat treated tool steelis used Dimensions of the tool are shoulder diameter 10mmpin diameter 6mm and pin depth 3mm The FSP processparameters used are following tool rotation speedmdash800 rpmtool travel speedmdash03mms and axial forcemdash8 kN

Using a precision sample cutting machine the specimenis cut across the plate in the direction perpendicular to thatof the run The cut samples are polished using standardmetallographic techniques and etched to reveal the metal-lurgical structure of the processed material Macrostructureand microstructures are studied using scanning electronmicroscope (SEM JEOL make Model 6480 LA) with theattachment of EDS For imaging and EDS analysis an accel-erating voltage of 20 kV is used X-ray diffractometer (JEOLmake Cu K120572 radiation) is used to analyze the phases presentin the materials

The mechanical characterization of the processed zoneand base metal is carried out using hardness and impressioncreep tests Hardness test is conducted at different locationsusing microhardness tester (Make Shimadzu model HMVG20ST Load 50 g) Impression creep tests are carried outboth at friction stir zone (FSZ) and base metal zone (BMZ)using a tungsten carbide indentor Figure 2 shows a sketch oftungsten carbide indentor used for impression creep experi-mentsDuring experiments the indentor ismade to penetrate

Journal of Composites 3

ΦD

H

h

Φd

D = 60 d = 20

H = 15 h = 35 R = 25

(all dimensions are in mm)

Figure 2 Dimensions of the tungsten carbide indentor used forimpression creep experiments

Al-Ni 800rpm 8kN

Figure 3 Top view of friction stir processed Al-Ni at load of 8 kNwith rotation speed of 800 rpm

the sample at either FSZorBMZAnormal load of 5 kg is usedduring the impression test On a two-millimeter diametercontact area this generates a stress of about 156MPa Thisstress value is smaller compared to yield strength of thealuminum [20] During impression creep tests the depthof the penetration of the indentor into the specimen ismeasured continuously using a linear variable differentialtransducer (LVDT) Impression creep tests are carried outfor the duration of 180 minutes and it is believed that thistime is sufficient to attain steady state creep conditionsUsing this data a creep curve (ie plot of impression depthversus time) is drawn The creep experiments are conductedat various temperatures namely 30∘C 100∘C and 200∘CThey are used for estimating the activation energy for creepand understanding the creep mechanismThemaximum testtemperature is slightly less than half of the absolute meltingtemperature of pure Al (193∘C)

3 Results and Discussion

31 Characterization of Friction Stir Zone Figure 3 showstop view of the friction stir processed sample and it showscharacteristic marks of the friction stir processing Morpho-logical features are uniform throughout the length indicatingthat steady state conditions are attained during friction stirprocessing Figure 4 shows amacroveiwof the processed zone

Friction stir zone

Base metal zone

I

BA

II

1mm

Figure 4 The macroview along perpendicular direction to thefriction stir processing direction It reveals two distinct regions (A)base metal zone and (B) stir processed zone

obtained after cutting the sample perpendicular to processedzone polishing the cut section using standardmetallographictechniques and etching to reveal the macrostructure (etchantused Poultonrsquos reagent composition 12mL concentratedhydrochloric acid + 6mL concentrated nitric acid + 1mL48 hydrofluoric acid + 1mL distilled water) Figure 4clearly distinguishes FSZ and BMZ FSZ is wider at the topand became narrower in the depth direction The depth ismuch greater than the pin length used (ie 3mm) Similarmorphology during friction stir processing is reported in theliterature by Kwon et al [21] Oh-Ishi and McNelley [22]Leitao et al [23] and Cui et al [24]

In the present investigation it is found that the quality ofnugget is good there are no defects like porosity inclusionsblow holes or lack of bonding The depth of the nugget isaround 45mm width at the top is about 20mm and areaof cross section of nugget is 48mm2 The friction stir zone(FSZ) has two clearly visible regions onewith onion-ring-likemorphology (referred to as region I) and remaining portionin FSZ is region II The FSZ can be thought of as the result ofoverlapping of material flow due to shoulder and pin In thecase of friction stir welding the tool driven material flow isclassified into shoulder driven material flow and pin drivenmaterial flow [25 26] Since tool features are kept similareven in FSP two types of friction driven material flow areexpected to take place and theymerge to form a FSZThe toolgeometry axial force tool rotation speed traverse speed andtool tilt angle are important process parameters which decidethe heat input and material flow and in turn the quality ofFSZ [2 27 28]The temperature will be maximum at the toolpin-substrate interface and it drops being moved away fromthe interface Depending on the temperature and plastic flowbehaviour of the material a section of the material close totool flowsThe volume of thematerial in this section is ldquoactionvolumerdquo Material flow is an important reason for promotingmixing of powder Material enters from the retreading sidein to the action volume and rotates at the back of the toolFratini et al [29] reported that the tool rotation drives thematerial from the retreating side to advancing side and theflux is intense at the back of the tool near the shoulder Themacrostructure shows that more material flows towards theadvancing side near the shoulder This is due to confinementof the transferred material with the processing cavity Whenthe tool is traversed the material in the leading edge flowsvia retreating side to the trailing edge This is continuous


(a) (b)

Figure 5 Microstructural features in region I (a) Flow bands are visible (b) distribution of second phase particles is presented

and helps in filling the space created in the trailing edgeDuring this transfer process the plasticized material flowsbetween the tool and the relatively colder base material Thematerial flow at the top occurs by the sliding action of toolshoulder over the pin driven material [27 28] When axialforce exceeds a critical value the flow becomes intense It isresponsible for shoulder driven flow

The macrostructure shown in Figure 4 exhibits onion-ring-like structure with in FSZ Formation of onion ringis a geometric effect Semicylindrical sheets of material areextruded between friction tool and substrate material duringeach rotation of the tool During tool rotation with axialforce the pin-driven material interacts with the shoulderat the retreating side Material which is flowing carriesminute microstructural and flow details Depending on themagnitudes of the pin driven and shoulder driven flowcomplex lamellar or vortex-like patterns are formedThey arereferred to as onion-ring pattern The material within thisregion is highly intercalated consisting of layers of materialswhich can be easily macroetched [27 30] Presence of secondelement particles increases the tendency for differential flowbehavior which in turn increases the contrast

32 Mixing of Particles during Friction Stirring In this par-ticular composite Ni is acting as particulate reinforcementand Al is the ductile matrix From performance angle itis desired that the nickel particles are uniformly and finelydistributed in the Al matrix SEM photomicrographs aretaken at appropriate magnifications to investigate the parti-clesrsquo size and their distribution Figure 5(a) shows a lowmag-nification micrograph from region I Figure 5(b) is a magni-fied microstructure from Figure 5(a) Similarly Figures 6(a)and 6(b) show a low and high magnification micrographfrom the region marked as II in the macroview presented inFigure 4 Comparing Figures 5(b) and 6(b) we see a cleardifference in the size of particles and their distribution Theparticles shown in Figure 5(b) (region I in FSZ) are finer andclosely spaced compared to particles in Figure 6(b) RegionI is towards retreading side in the FSZ This also indicatesthat stirring action is more severe in region I compared tothat in region II Several researchers have suggested that thereis a difference in the metal flow behaviour between the tool

retreating sides (RS) and advancing side (AS) [25 31] Henceit is likely that thesemicrostructural differences resulted fromthe different flow behaviour on both sides

Figure 7 shows XRD plot of the FSP nugget The plotshows that nugget has the presence of Al and Ni There areno detectable intermetallics of Al and NiThemicrostructurefeatures and XRD plot confirm the fact that the weld nuggetconsists of Al and Ni Ni is dispersed as fine particles in Almatrix It is clear that the stirring conditions are not severeenough to facilitate the formation of Al-Ni intermetallicsIt is reported that nature of interface between the matrixand reinforcement is important in deciding mechanicalproperties [26] From Figures 5(b) and 6(b) we see thatAl matrix-Ni particle interface is good without any visibleseparation Similar features are observed by Yadav and Bauri[13] A good interface is very essential to strengthen theAl and to reduce the dislocation movement There are fewinvestigations reporting formation of Al-Ni intermetallicsduring FSP Prakrathi et al [19] and Qian et al [15] reportedformation of Al

3Ni by in situ reaction during FSP of Al with

Ni particles under different stirring conditionsDuring FSP Ni particles disintegrate due to severe defor-

mation and high temperature Severe plastic flow with toolrotation causes fragmentation of the original Ni particlesYadav and Bauri [13] and Fujii et al [32] discussed howrotation speed influences the plastic flow and the heat inputAs rotation speed increases particles are reduced due tostirring effect Material rotation in the weldment and stirringeffect ensures a contamination-free surface and facilitatesatom to atom contact and this promotes a good particle-matrix interface

33 Estimation of Nugget Temperature In friction stir pro-cessing the heat is generated by the friction between thetool and the work piece as well as a result of the plasticdeformation of the work piece [33] An attempt is made inthe present work to determine the energy generated andmaximum temperature obtainedwithin the processed zone ofthe nugget during FSP using a ldquorefined energy based modelrdquoThough the model is generated for friction stir welding[34 35] the same can be used for friction stir processingwithout any modification The values of parameters used for


(a) (b)

Figure 6Microstructural features in region II in Figure 4 (a) Lowmagnificationmicrograph showing shape and distribution of the particles(b) High magnification micrograph showing microporosities

Inte

nsity

(au

)

30 35 40 45 50 55 60 65 70 75 80 85 90 95 100 105

Al (111

)

Al (200

) N

i (111

)

Al (220

)

Al (311

)A

l (222

)

Ni (222

) Al (400

)

Al-Ni-800-8 kN

2120579 (deg)

Figure 7 XRD plot of the FSZ showing Al and Ni particles Novisible indication of Al-Ni intermetallic compounds

calculation of total power effective energy and maximumtemperature generated within the processed zone of frictionstirred samples are recorded in Table 1 It is found that themaximum temperature attained is around 548∘K (275∘C) forthe conditions under which stirring is carried out in thepresent work

Kwon et al [21]measured temperature during friction stirprocessing of Al and found that the peak temperature is astrong function of tool rotation speed As reported by themat 560 rpm the maximum temperature measured is 200∘CUse of a higher tool rotation speed will lead to higher peaktemperature and the temperature is sufficient to promoterecrystallisation [21] Mishra and Ma [2] have reported atemperature of 550∘C during FSW of 5083 Al alloy withhigh tool rotation speed Mishra et al [36] reported a peaktemperature of 480∘C in the case of friction stir welding of6061 Al alloy and 500∘C in the case of friction stir welding of2024 Al alloy They have used a triflute tool

Table 1 Material and processing parameters used for calculation oftotal power effective energy and maximum temperature generatedwithin the processed zone of friction stirred sample

Sl number Parameter Value1 Shoulder radius 119903

119900

(m) 500E minus 032 Pin radius 119903

119894

(m) 150E minus 033 Pin height ℎ (m) 300E minus 034 Co-efficient of friction 120583 0455 Tool translational velocity 119881

119900

(ms) 300E minus 046 Scale factor 119904 17 Effective strain 120576

119890

68 Strength coefficient 119870 6909 Strain hardening exponent 119899 01610 Effective stress 120590

119890

9190811 Thickness of the work piece 119905 (m) 600E minus 0312 Solidus temperature 119879

119904

(K) 93313 Compressive force 119865 (kN) 814 Tool rotational speed 120596 (rpm) 800

15 Energy generated due to plasticdeformation 119864

119875

(N) 496E minus 02

16 Torque due to friction 119879119891

(Nm) 1394

17 Energy generated per unit length ofthe weld 119864

119891

(kN) 61973

18 Power generated due to friction119875

119891

(Nms) 18592

19 Total energy 119864 (kN) 6197320 Total power 119875 (Nms) 186119864 + 0221 Effective energy 119864eff (kN) 3098622 Maximum temperature 119879max (K) 54800

34 Hardness Profile Figure 8 shows hardness profiles alongtwo lines over the FSZ Line 1 shows variation of hardnessat a depth of 05mm from the top surface measured overan equidistance of 05mm Similarly line 2 shows hardnessvariation at a depth of 15mm from the top surface Thehardness profiles reveal two regions in the nugget zone


20

30

40

50

0 2 4 6 8 10 12 14 16 18 20

Hv

Distance (mm)

Distance (mm)

20

30

40

50

60

0 2 4 6 8 10 12 14 16 18 20

Hv

I

2

III

II

Al-Ni-800-8 kN

1

Figure 8 Hardness profile along two depths in the FSZ Line1 05mm depth from the top and line 2 15mm depth from the top

region I in which hardness values fluctuate highly and regionII in which hardness values fluctuate mildly around anaverage value In line 1 peak hardness is about 58Hv againsta minimum hardness of 40Hv In line 2 the peak valueis 49Hv against a minimum value of 40Hv In region IIof FSZ the increase in hardness is marginal (sim10) Thevalues are consistent with the extent of reinforcement asseen in Figures 5(b) and 6(b) In region I the extent ofparticle reinforcement is higher and the spacing betweenthe particles is smaller Both features promote strengtheningby particles The material flow and particle entrapment arenot homogeneous as revealed in flow lines This may be thecause of fluctuations in hardness In region II the extentof particle reinforcement is smaller and also the amount ofdefect (pores) is larger Because of these features observedhardness improvement is smaller compared to region I

The literature has recorded a mixed trend as far asvariation of hardness during friction processing is concernedMany researchers have reported a drop in the hardness afterfriction stirring [37 38] In contrast to that Kwon et al [21]reported 37 increase in the hardness compared to the basemetal and attributed that to very small recrystallised grains inthe FSZ Ke et al [14] producedAl-Ni intermetallic compositeby friction stir processing and they reported a hardnessvalue of 53Hv in the composite against 37Hv in the friction

1520

1525

1530

1535

1540

1545

1550

1555

1560

0 20 40 60 80 100 120 140 160 180 200

Disp

lace

men

t (m

m)

Time (min)

Al-30∘C

Figure 9 A typical impression depth versus time profile in Al basemetal at 30∘C

stir processed Al alloy (without reinforcement) Yadav andBauri [13] reported a hardness value of 50Hv in the Al-Nicomposite produced by friction stir processing of Al whichhad a hardness value of 29Hv In the present study increase inhardness is attributed to combined effect of fine particles andrefinement of grains in the matrix Value of the hardness isnot found to be constant and it is attributed to presence of dif-ferent microstructures at different locations in the stir zoneComplex material flow pattern in the processing zone gener-ates a gradient in temperature strain and strain rate acrossthe stir zone and it leads to different microstructures at dif-ferent locations in the stir zone Qian et al [15] reported thatfor commercial pure Al friction stirring without Ni additionhas no effect on the microhardness Significant improvementinmicrohardness is possible with the addition of Ni particles

35 Impression Creep Behaviour In impression creep exper-iments a predetermined load is applied on the indentorpositioned at either friction stir zone or base metal zone inthe sample The penetration depth is measured continuouslyas a function of time and using this data a plot of penetrationdepth versus time is drawn A typical impression depth versustime curve generated for base metal at room temperature(30∘C) with a constant load of 5 kg is presented in Figure 9Such depth versus time curves is generated for base metaland friction stir zones at room temperature of (30∘C) 100∘C150∘C and 200∘C and is used in analysis These curves areshown in Figures 10(a) and 10(b) for base metal and frictionstir zone respectively For each curve impression creep strain(120576) is estimated at different instant of time following theapproach presented by Sastry [17] These data are used fordrawing creep strain versus time plots (ie creep curves)Using these creep profiles steady state creep rates (1205761015840) aredetermined as follows

120576 =

Δ119897

119863

120576

1015840

=

Δ120576

Δ119905

(1)

where Δ119897 is penetration depth 119863 is diameter of the indenterand Δ120576 represents incremental creep strain in the secondary


Disp

lace

men

t (m

m)

Time (min)

14

16

18

2

0 20 40 60 80 100 120 140 160 180 200

Al at 200∘C

Al at 100∘C

Al at 30∘C

(a)

Disp

lace

men

t (m

m)

Time (min)

1

11

12

13

14

15

16

17

18

0 50 100 150 200

Al-Fe at 200∘C

Al-Fe at 100∘C

Al-Fe at 30∘C

(b)

Figure 10 Displacement versus time plots for impression tests at 30∘C 100∘C and 200∘C (a) for Al base metal (b) FSP nugget

Table 2 Steady state creep rate values at various temperatures forFSZ and BMZ

Steady state creep rate (10minus5minminus1)Temperature (∘C) Base metal zone Friction stirred zone30 39 46100 83 152200 122 238

Table 3 Activation energy (119876) values for FSZ and BMZ

Activation energy (119876) values in kJmolTemperature (∘C) Base metal zone Friction stirred zone30ndash100 10 159100ndash200 58 66

stage of the creep curve profile over the incremental time[17] The values of steady state creep rates are estimated atdifferent temperatures at both FSZ and BMZ These valuesare presented in Table 2 and it shows that creep resistanceof base metal zone is better than that of friction stir zoneFurther the creep resistance decreases or steady state creeprate increases as temperature is increased for both BMZ andFSZ Following observations could be made from the datapresented in Table 2

(i) At all test temperatures the steady state creep rate islower in friction stir zone compared to that in basemetal zone

(ii) For both FSZ and BMZ the steady state creep rateincreases exponentially with increase in temperature

Using test temperature and corresponding steady statecreep rate (1205761015840) activation energy (119876) is estimated

119876 =

119877 ln (12057610158401

120576

1015840

2

)

(1119879

2) minus (1119879

1)

(2)

where 12057610158401

and 12057610158402

are steady state creep rates at temperatures 1198791

and1198792 respectively Table 3 shows values of activation energy

for the impression creep of the friction stirred zone and basemetal The value of activation energy is very small comparedto the activation energy for movement of dislocations inAl as reported by Luthy et al [39] For high purity Al atlower temperatures (lt400∘K) an activation energy in therange of 20 kJmol is reported by Ishikawa et al [40] andUeda et al [41] For commercial purity Al an activationenergy value (119876) = 25 kJmol is reported by Shen et al[42] Also a low activation energy 119876 = 20ndash35 kJmol undervery low strain rate conditions (lt6 lowast 10minus5min) is reported[42] They pointed that in the case of pure metals withhigh stacking fault energy (HSFE) dislocation cross slip is apossible creep mechanism It is pointed that creep behaviorat low temperatures and very low strain rates depends on thegrain size and impurity concentration [42]The reported119876 =25 kJmol is for average grain size of 25 120583m for a commercialpure Al Also it is pointed that dislocations are gettinggenerated at the grain boundary by ldquoFrank Reed sourcerdquo andthey interact with the intragranular dislocations Continuousgeneration of dislocations and their interactions with theinner dislocations promote dislocation cross slip and the factthat a large number of slip systems promote jog formationand help in strain accommodation [41] This leads to plasticstrain at low temperatures and low stress values Ueda et al[41] reported that at a temperature of 473∘K a normalizedstress is 10minus4 (approximately sim7MPa) which could produce asteady state creep rate of 10minus6minutes This value is slightlyless than that in our results The difference is attributed touse of higher level of stress Also in the friction stir zonethe SSCR is still higher and it is attributed to nonequilibriumnature in the FSP zone Sherby and Taleff [43] reported thatat low stresses dislocation glide and climb are the mode ofplastic deformation and generally climb controls the rateFineness in the grain size promotes dislocation generationand the solute atoms or the second phase particle decidesresistance for movement of dislocation Carreno and Ruano[44] reported that addition of transition elements increasesactivation energy for creep deformation

From the values for activation energy it could be inferredthat dislocation creep is the major mechanism of creep So


activation energy for creep is decided by energy required togenerate the dislocation and resistance offered by the matrixto the movement of dislocation Friction stir processinghas created largely a metastable condition in the zone Thethermodynamic instability increases as the speed of theprocessing is increased This leads to a situation where hugenumber of dislocation can be readily moved by a smallamount of thermal activation For a similar reason processzone records higher rate of creep compared to Al basemetal Kwon et al [21] reported that the FSZ has very finerecrystallised grains with very low dislocation density Asrotational speed increases the temperature increases leadingto growth of the recrystallised grains FSP is an effective toolto reduce grain size in Al alloys via dynamic recrystallisationA fine grain size in the range of 05 to 5 120583m in the recrys-tallisated zone by many investigators [2 3 6]The submicrongrain structure gets stabilized in presence of submicronsized particles The fine particles in the matrix aid in theevolution of finer grain structure during thermomechanicalprocessing through particle pinning It also aids in materialstrengthening through grain boundary strengthening [6]Yadav and Bauri [5] reported a final grain size of 7 120583mduringFSP with a relatively less normal force and slightly higherRPM Also FSP reduces both nickel particle and matrixgrain size Yazdipour et al [45] reported the formation ofnanograins due to dynamic recrystallisation The size of therecrystallised grain is closely related to interaction of grainboundaries with second phase particles

4 Conclusions

Following conclusions are drawn from this investigation(i) A surface composite on commercial pure Al is proc-

essed using friction stir processing route The surfaceconsists of fine nickel particles embedded in Almatrix

(ii) Formation of friction stir zone can be explained usingthe concept of pin driven flow and shoulder drivenflow

(iii) During friction stir processing both particle size andmatrix grain are reduced Dynamic recrystallisationof the matrix is possible due to high plastic deforma-tion and heat generated during processing

(iv) Microstructure and particle distribution are nonho-mogeneous and it is attributed to less severe pro-cessing conditions used (lower load and smaller toolrotation speed) This is reflected in the scatteredmicrohardness values in the FSZ

(v) Compared to base metal friction stir zone recordedhigher creep rate and for both basemetal and frictionstirred region creep rate increases with increase oftemperature

(vi) A low value of activation energy is observed and itis attributed to fine grain size and large amount ofdislocation density in the processed zone The valueof activation energy is compared with the reportedvalues

Conflict of Interests

The authors declare that there is no conflict of interestsregarding publication of this paper

Acknowledgments

The authors gratefully acknowledge The Director NITKSurathkal for his continuous support for carrying out thiswork They also acknowledge the help of Dr G Phanikumarand Dr Raffi IIT Madras in carrying out friction stirprocessing work

References

[1] M F Ashby and D R H Zones Engineering Materials vol 2Butterworth-Heinemann 2nd edition 1998

[2] R S Mishra and Z Y Ma ldquoFriction stir welding and process-ingrdquo Materials Science and Engineering R Reports vol 50 no1-2 pp 1ndash78 2005

[3] R S Mishra MWMahoney S X McFadden N A Mara andA K Mukherjee ldquoHigh strain rate superplasticity in a frictionstir processed 7075 Al alloyrdquo Scripta Materialia vol 42 no 2pp 163ndash168 1999

[4] R S Mishra Z Y Ma and I Charit ldquoFriction stir processing anovel technique for fabrication of surface compositerdquoMaterialsScience and Engineering A vol 341 no 1-2 pp 307ndash310 2003

[5] D Yadav and R Bauri ldquoNickel particle embedded aluminiummatrix composite with high ductilityrdquoMaterials Letters vol 64no 6 pp 664ndash667 2010

[6] H S Arora H Singh and B K Dhindaw ldquoComposite fabri-cation using friction stir processingmdasha reviewrdquo InternationalJournal of Advanced Manufacturing Technology vol 61 no 9ndash12 pp 1043ndash1055 2012

[7] Z Zhang E Akiyama Y Watanabe Y Katada and KTsuzaki ldquoEffect of 120572-AlAl

3

Ni microstructure on the corrosionbehaviour of Al-54 wt Ni alloy fabricated by equal-channelangular pressingrdquo Corrosion Science vol 49 no 7 pp 2962ndash2972 2007

[8] C-J Song Z-M Xu and J-G Li ldquoIn-situ AlAl3

Ni function-ally graded materials by electromagnetic separation methodrdquoMaterials Science and Engineering A vol 445-446 pp 148ndash1542007

[9] G Gonzalez A Sagarzazu D Bonyuet L DrsquoAngelo and RVillalba ldquoSolid state amorphisation in binary systems preparedby mechanical alloyingrdquo Journal of Alloys and Compounds vol483 no 1-2 pp 289ndash297 2009

[10] T P D Rajan R M Pillai and B C Pai ldquoFunctionallygraded AlndashAl

3

Ni in situ intermetallic composites fabricationand microstructural characterizationrdquo Journal of Alloys andCompounds vol 453 no 1-2 pp L4ndashL7 2008

[11] B S B Reddy K Rajasekhar M Venu J J S Dilip S Das andK Das ldquoMechanical activation-assisted solid-state combustionsynthesis of in situ aluminum matrix hybrid (Al

3

NiAl2

O3

)nanocompositesrdquo Journal of Alloys and Compounds vol 465no 1-2 pp 97ndash105 2008

[12] J B Fogagnolo E M J A Pallone D R Martin C S Kim-inami C Bolfarini and W J Botta ldquoProcessing of Al matrixcomposites reinforced with Al-Ni compounds and Al

2

O3

byreactive milling and reactive sinteringrdquo Journal of Alloys andCompounds vol 471 no 1-2 pp 448ndash452 2009


[13] D Yadav and R Bauri ldquoProcessing microstructure andmechanical properties of nickel particles embedded aluminiummatrix compositerdquo Materials Science and Engineering A vol528 no 3 pp 1326ndash1333 2011

[14] L Ke C Huang L Xing and K Huang ldquoAl-Ni intermetalliccomposites produced in situ by friction stir processingrdquo Journalof Alloys and Compounds vol 503 no 2 pp 494ndash499 2010

[15] J Qian J Li J Xiong F Zhang and X Lin ldquoIn situ synthesizingAl3

Ni for fabrication of intermetallic-reinforced aluminumalloy composites by friction stir processingrdquo Materials Scienceand Engineering A vol 550 pp 279ndash285 2012

[16] C J Hsu P W Kao and N J Ho ldquoIntermetallic-reinforcedaluminum matrix composites produced in situ by friction stirprocessingrdquoMaterials Letters vol 61 no 6 pp 1315ndash1318 2007

[17] D H Sastry ldquoImpression creep techniquemdashan overviewrdquoMate-rials Science and EngineeringA vol 409 no 1-2 pp 67ndash75 2005

[18] G Sharma R V Ramanujan T R G Kutty and N PrabhuldquoIndentation creep studies of iron aluminide intermetallicalloyrdquo Intermetallics vol 13 no 1 pp 47ndash53 2005

[19] S Prakrathi M Ravikumar K R Udupa and K U BhatldquoFabrication of hybrid surface composite through friction stirprocessing and its impression creep behaviourrdquo ISRNMaterialsScience vol 2013 Article ID 541762 6 pages 2013

[20] R A Higgins Engineering Metallurgy Arnold Publisher NewYork NY USA 6th edition 1993

[21] Y-J Kwon I Shigematsu andN Saito ldquoProduction of ultra-finegrained aluminum alloy using friction stir processrdquo MaterialsTransactions vol 44 no 7 pp 1343ndash1350 2003

[22] K Oh-Ishi and T R McNelley ldquoMicrostructural modificationof as-cast NiAl bronze by friction stir processingrdquoMetallurgicalandMaterials Transactions A PhysicalMetallurgy andMaterialsScience vol 35 no 9 pp 2951ndash2961 2004

[23] C Leitao A Loureiro D M Rodrigues P Vilaca and R MLeal ldquoMaterial flow in heterogeneous friction stir welding ofthin aluminium sheets effect of shoulder geometryrdquo MaterialsScience and Engineering A vol 498 no 1-2 pp 384ndash391 2008

[24] G R Cui Z Y Ma and S X Li ldquoThe origin of non-uniformmicrostructure and its effects on the mechanical properties of afriction stir processed Al-Mg alloyrdquo Acta Materialia vol 57 no19 pp 5718ndash5729 2009

[25] A P Reynolds ldquoVisualisation of material flow in autogenousfriction stir weldsrdquo Science and Technology of Welding andJoining vol 5 no 2 pp 120ndash124 2000

[26] S C Tjong and Z Y Ma ldquoMicrostructural and mechanicalcharacteristics of in situ metal matrix compositesrdquo MaterialsScience and Engineering R Reports vol 29 no 3 pp 49ndash1132000

[27] K Kumar and S V Kailas ldquoThe role of friction stir weldingtool onmaterial flow andweld formationrdquoMaterials Science andEngineering A vol 485 no 1-2 pp 367ndash374 2008

[28] Z W Chen T Pasang and Y Qi ldquoShear flow and formationof Nugget zone during friction stir welding of aluminium alloy5083-Ordquo Materials Science and Engineering A vol 474 no 1-2pp 312ndash316 2008

[29] L Fratini G Buffa D Palmeri J Hua and R ShivpurildquoMaterial flow in FSW of AA7075-T6 butt joints continuousdynamic recrystallization phenomenardquo Journal of EngineeringMaterials Technology vol 128 no 3 pp 428ndash435 2006

[30] L E Murr ldquoA review of FSW research on dissimilar metaland alloy systemsrdquo Journal of Materials Engineering and Perfor-mance vol 19 no 8 pp 1071ndash1089 2010

[31] K Colligan ldquoMaterial flow behavior during friction stir weldingof aluminumrdquo Welding Journal vol 78 no 7 pp 229sndash237s1999

[32] H Fujii Y G Kim T Tsumura T Komazaki and K NakataldquoEstimation of material flow in stir zone during friction stirwelding by distribution measurement of Si particlesrdquoMaterialsTransactions vol 47 no 1 pp 224ndash232 2006

[33] R Nandan T DebRoy and H K D H Bhadeshia ldquoRecentadvances in friction-stir welding-process weldment structureand propertiesrdquo Progress in Materials Science vol 53 no 6 pp980ndash1023 2008

[34] S A Emam and A E Domiaty ldquoA refined energy based modelfor friction stir weldingrdquoWorld Academy of Science Engineeringand Technology vol 29 pp 1010ndash1016 2009

[35] C Hamilton S Dymek and A Sommers ldquoA thermal model offriction stir welding in aluminum alloysrdquo International Journalof Machine Tools andManufacture vol 48 no 10 pp 1120ndash11302008

[36] R S Mishra W Murray and T Mahoney Friction Stir weldingand Processing ASM International 2007

[37] L EMurr G Liu and J CMcCure ldquoDynamic recrystallisationin friction stir welding of 1100 Aluminumrdquo Journal of MaterialsScience Letters vol 16 pp 1801ndash1803 1997

[38] S Benavides Y Li L E Murr D Brown and J C McClureldquoLow-temperature friction-stir welding of 2024 aluminumrdquoScripta Materialia vol 41 no 8 pp 809ndash815 1999

[39] H Luthy A K Miller and O D Sherby ldquoThe stress andtemperature dependence of steady state flow at intermediatetemperatures for pure polycrystalline Alrdquo Acta Metallurgicavol 28 no 2 pp 169ndash178 1980

[40] K Ishikawa M Maehara and Y Kobayashi ldquoMechanicalmodeling and microstructural observation of pure aluminumcrept under constant stressrdquo Materials Science and EngineeringA vol 322 no 1-2 pp 153ndash158 2002

[41] S Ueda T Kameyama T Matsunaga K Kitazono and E SatoldquoRe-examination of creep behaviour of high purity aluminiumat low temperaturerdquo Journal of Physics vol 240 Article ID012073 2010

[42] J Shen S Yamasaki K-I Ikeda S Hata and H NakashimaldquoLow-temperature creep at ultra-low strain rates in pure alu-minum studied by a helicoid spring specimen techniquerdquoMaterials Transactions vol 52 no 7 pp 1381ndash1387 2011

[43] O D Sherby and E M Taleff ldquoInfluence of grain size soluteatoms and second-phase particles on creep behavior of poly-crystalline solidsrdquoMaterials Science and Engineering A vol 322no 1-2 pp 89ndash99 2002

[44] F Carreno and O A Ruano ldquoInfluence of dispersoids on thecreep behavior of dispersion strengthened aluminum materi-alsrdquo Revista de Metalurgia vol 33 no 5 pp 324ndash332 1997

[45] A Yazdipour M A Shafiei and K Dehghani ldquoModelingthe microstructural evolution and effect of cooling rate onthe nanograins formed during the friction stir processing ofAl5083rdquo Materials Science and Engineering A vol 527 no 1-2pp 192ndash197 2009

Submit your manuscripts athttpwwwhindawicom

ScientificaHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CorrosionInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Polymer ScienceInternational Journal of



CeramicsJournal of


CompositesJournal of

NanoparticlesJournal of



International Journal of

Biomaterials


NanoscienceJournal of

TextilesHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Journal of

NanotechnologyHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

CrystallographyJournal of


The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014


CoatingsJournal of

Advances in

Materials Science and EngineeringHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Smart Materials Research



MetallurgyJournal of


BioMed Research International

MaterialsJournal of


Nano

materials


Journal ofNanomaterials


(a) (b)

Figure 1 Microstructure of the base metal Al (a) initial morphology of nickel powders used for friction stir processing (b)

material Because of this sometimes friction stir processingis considered as a nonequilibrium materials processing

Composite fabrication using friction stir processing routeis reviewed by Arora et al [6] Surface engineering by FSP ofAl with Ni powder is an interesting area [7ndash9] because it cangive rise to many important phases which are stable at hightemperature [5 10ndash12]

There are a few investigations focusing on producingmetal (matrix) metal (reinforcement) composite using fric-tion stir processing route Yadav and Bauri [13] reportedthe dispersion of nickel in Al alloy using FSP route andthey observed no detectable aluminides in the friction stirprocessed zone Ke et al [14] reported in situ formation ofAl3Ni intermetallics during friction stirring of Al substrate

with nickel powder They also reported formation of Al3Ni

and Al3Ni2after heat treatment Composite also consisted of

some amount of unreacted nickel powders Using FSP routeQian et al [15 16] produced Al-Al

3Ni in situ composites

and this composite had better hardness and tensile propertiescompared to Al substrate alone

Impression creep experiment is an important method ofmechanical characterization of surface composites [17] It canbe used to estimatemechanical properties of a small restrictedvolume of the material (like surface composite) at varioustemperature levels The method takes smaller time durationfor the test The temperature and stress dependency of creeprate could be obtained with minimum number of samplesThis method is applicable to assessing the creep behavior ofthe parent metal and processed zone independently [17 18]

An attempt is being made in the present investigation toassess the creep behavior of friction stirred Al with nickelpowder processed with 8 kN load at different tip rotationspeed of 800 rpm The processing parameters are entirelydifferent compared to those reported earlier in reference[19] Microstructural features and mechanical properties ofFSP Al-Ni composite with 10 kN normal force and 1200 rpmare reported in [19] Reduction in normal load and toolrotation speed is expected to alter the severity of the stirringmicrostructural features and mechanical properties

2 Experimental Details

Friction stir processing is carried out on the commercial pureAl plate of 5mm thickness Base metal has relatively largegrains (average grain size sim130 120583m) without the presence ofany second phase particles Initially the substrate surfaceis made rough by a friction stir pass without any powderaddition Electrolytic nickel powder is mixed with methanolto get a paste consistency and is applied to rough substrateCoverage of the powder is approximately 1 gcm2 of thesampleThemicrostructure of Al basemetal andmorphologyof the nickel powder used are given in Figures 1(a) and1(b) respectively The substrate along with the powder isdried and used for friction stir processing For friction stirprocessing a friction tool made from heat treated tool steelis used Dimensions of the tool are shoulder diameter 10mmpin diameter 6mm and pin depth 3mm The FSP processparameters used are following tool rotation speedmdash800 rpmtool travel speedmdash03mms and axial forcemdash8 kN

Using a precision sample cutting machine the specimenis cut across the plate in the direction perpendicular to thatof the run The cut samples are polished using standardmetallographic techniques and etched to reveal the metal-lurgical structure of the processed material Macrostructureand microstructures are studied using scanning electronmicroscope (SEM JEOL make Model 6480 LA) with theattachment of EDS For imaging and EDS analysis an accel-erating voltage of 20 kV is used X-ray diffractometer (JEOLmake Cu K120572 radiation) is used to analyze the phases presentin the materials

The mechanical characterization of the processed zoneand base metal is carried out using hardness and impressioncreep tests Hardness test is conducted at different locationsusing microhardness tester (Make Shimadzu model HMVG20ST Load 50 g) Impression creep tests are carried outboth at friction stir zone (FSZ) and base metal zone (BMZ)using a tungsten carbide indentor Figure 2 shows a sketch oftungsten carbide indentor used for impression creep experi-mentsDuring experiments the indentor ismade to penetrate


ΦD

H

h

Φd

D = 60 d = 20

H = 15 h = 35 R = 25



Al-Ni 800rpm 8kN





Friction stir zone

Base metal zone

I

BA

II

1mm





(a) (b)












(a) (b)


Inte

nsity

(au

)

30 35 40 45 50 55 60 65 70 75 80 85 90 95 100 105

Al (111

)

Al (200

) N

i (111

)

Al (220

)

Al (311

)A

l (222

)

Ni (222

) Al (400

)

Al-Ni-800-8 kN

2120579 (deg)






119900


119894


119900


119890


119890


119904



119875

(N) 496E minus 02


(Nm) 1394


119891

(kN) 61973


119891

(Nms) 18592




20

30

40

50

0 2 4 6 8 10 12 14 16 18 20

Hv

Distance (mm)

Distance (mm)

20

30

40

50

60

0 2 4 6 8 10 12 14 16 18 20

Hv

I

2

III

II

Al-Ni-800-8 kN

1




1520

1525

1530

1535

1540

1545

1550

1555

1560

0 20 40 60 80 100 120 140 160 180 200

Disp

lace

men

t (m

m)

Time (min)

Al-30∘C




120576 =

Δ119897

119863

120576

1015840

=

Δ120576

Δ119905

(1)



Disp

lace

men

t (m

m)

Time (min)

14

16

18

2

0 20 40 60 80 100 120 140 160 180 200

Al at 200∘C

Al at 100∘C

Al at 30∘C

(a)

Disp

lace

men

t (m

m)

Time (min)

1

11

12

13

14

15

16

17

18

0 50 100 150 200

Al-Fe at 200∘C

Al-Fe at 100∘C

Al-Fe at 30∘C

(b)










119876 =

119877 ln (12057610158401

120576

1015840

2

)

(1119879

2) minus (1119879

1)

(2)

where 12057610158401

and 12057610158402







4 Conclusions










Acknowledgments


References








3






3



3

NiAl2

O3



2

O3












































CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials




ΦD

H

h

Φd

D = 60 d = 20

H = 15 h = 35 R = 25



Al-Ni 800rpm 8kN





Friction stir zone

Base metal zone

I

BA

II

1mm





(a) (b)












(a) (b)


Inte

nsity

(au

)

30 35 40 45 50 55 60 65 70 75 80 85 90 95 100 105

Al (111

)

Al (200

) N

i (111

)

Al (220

)

Al (311

)A

l (222

)

Ni (222

) Al (400

)

Al-Ni-800-8 kN

2120579 (deg)






119900


119894


119900


119890


119890


119904



119875

(N) 496E minus 02


(Nm) 1394


119891

(kN) 61973


119891

(Nms) 18592




20

30

40

50

0 2 4 6 8 10 12 14 16 18 20

Hv

Distance (mm)

Distance (mm)

20

30

40

50

60

0 2 4 6 8 10 12 14 16 18 20

Hv

I

2

III

II

Al-Ni-800-8 kN

1




1520

1525

1530

1535

1540

1545

1550

1555

1560

0 20 40 60 80 100 120 140 160 180 200

Disp

lace

men

t (m

m)

Time (min)

Al-30∘C




120576 =

Δ119897

119863

120576

1015840

=

Δ120576

Δ119905

(1)



Disp

lace

men

t (m

m)

Time (min)

14

16

18

2

0 20 40 60 80 100 120 140 160 180 200

Al at 200∘C

Al at 100∘C

Al at 30∘C

(a)

Disp

lace

men

t (m

m)

Time (min)

1

11

12

13

14

15

16

17

18

0 50 100 150 200

Al-Fe at 200∘C

Al-Fe at 100∘C

Al-Fe at 30∘C

(b)










119876 =

119877 ln (12057610158401

120576

1015840

2

)

(1119879

2) minus (1119879

1)

(2)

where 12057610158401

and 12057610158402







4 Conclusions










Acknowledgments


References








3






3



3

NiAl2

O3



2

O3












































CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials




(a) (b)












(a) (b)


Inte

nsity

(au

)

30 35 40 45 50 55 60 65 70 75 80 85 90 95 100 105

Al (111

)

Al (200

) N

i (111

)

Al (220

)

Al (311

)A

l (222

)

Ni (222

) Al (400

)

Al-Ni-800-8 kN

2120579 (deg)






119900


119894


119900


119890


119890


119904



119875

(N) 496E minus 02


(Nm) 1394


119891

(kN) 61973


119891

(Nms) 18592




20

30

40

50

0 2 4 6 8 10 12 14 16 18 20

Hv

Distance (mm)

Distance (mm)

20

30

40

50

60

0 2 4 6 8 10 12 14 16 18 20

Hv

I

2

III

II

Al-Ni-800-8 kN

1




1520

1525

1530

1535

1540

1545

1550

1555

1560

0 20 40 60 80 100 120 140 160 180 200

Disp

lace

men

t (m

m)

Time (min)

Al-30∘C




120576 =

Δ119897

119863

120576

1015840

=

Δ120576

Δ119905

(1)



Disp

lace

men

t (m

m)

Time (min)

14

16

18

2

0 20 40 60 80 100 120 140 160 180 200

Al at 200∘C

Al at 100∘C

Al at 30∘C

(a)

Disp

lace

men

t (m

m)

Time (min)

1

11

12

13

14

15

16

17

18

0 50 100 150 200

Al-Fe at 200∘C

Al-Fe at 100∘C

Al-Fe at 30∘C

(b)










119876 =

119877 ln (12057610158401

120576

1015840

2

)

(1119879

2) minus (1119879

1)

(2)

where 12057610158401

and 12057610158402







4 Conclusions










Acknowledgments


References








3






3



3

NiAl2

O3



2

O3












































CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials




(a) (b)


Inte

nsity

(au

)

30 35 40 45 50 55 60 65 70 75 80 85 90 95 100 105

Al (111

)

Al (200

) N

i (111

)

Al (220

)

Al (311

)A

l (222

)

Ni (222

) Al (400

)

Al-Ni-800-8 kN

2120579 (deg)






119900


119894


119900


119890


119890


119904



119875

(N) 496E minus 02


(Nm) 1394


119891

(kN) 61973


119891

(Nms) 18592




20

30

40

50

0 2 4 6 8 10 12 14 16 18 20

Hv

Distance (mm)

Distance (mm)

20

30

40

50

60

0 2 4 6 8 10 12 14 16 18 20

Hv

I

2

III

II

Al-Ni-800-8 kN

1




1520

1525

1530

1535

1540

1545

1550

1555

1560

0 20 40 60 80 100 120 140 160 180 200

Disp

lace

men

t (m

m)

Time (min)

Al-30∘C




120576 =

Δ119897

119863

120576

1015840

=

Δ120576

Δ119905

(1)



Disp

lace

men

t (m

m)

Time (min)

14

16

18

2

0 20 40 60 80 100 120 140 160 180 200

Al at 200∘C

Al at 100∘C

Al at 30∘C

(a)

Disp

lace

men

t (m

m)

Time (min)

1

11

12

13

14

15

16

17

18

0 50 100 150 200

Al-Fe at 200∘C

Al-Fe at 100∘C

Al-Fe at 30∘C

(b)










119876 =

119877 ln (12057610158401

120576

1015840

2

)

(1119879

2) minus (1119879

1)

(2)

where 12057610158401

and 12057610158402







4 Conclusions










Acknowledgments


References








3






3



3

NiAl2

O3



2

O3












































CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials




20

30

40

50

0 2 4 6 8 10 12 14 16 18 20

Hv

Distance (mm)

Distance (mm)

20

30

40

50

60

0 2 4 6 8 10 12 14 16 18 20

Hv

I

2

III

II

Al-Ni-800-8 kN

1




1520

1525

1530

1535

1540

1545

1550

1555

1560

0 20 40 60 80 100 120 140 160 180 200

Disp

lace

men

t (m

m)

Time (min)

Al-30∘C




120576 =

Δ119897

119863

120576

1015840

=

Δ120576

Δ119905

(1)



Disp

lace

men

t (m

m)

Time (min)

14

16

18

2

0 20 40 60 80 100 120 140 160 180 200

Al at 200∘C

Al at 100∘C

Al at 30∘C

(a)

Disp

lace

men

t (m

m)

Time (min)

1

11

12

13

14

15

16

17

18

0 50 100 150 200

Al-Fe at 200∘C

Al-Fe at 100∘C

Al-Fe at 30∘C

(b)










119876 =

119877 ln (12057610158401

120576

1015840

2

)

(1119879

2) minus (1119879

1)

(2)

where 12057610158401

and 12057610158402







4 Conclusions










Acknowledgments


References








3






3



3

NiAl2

O3



2

O3












































CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials




Disp

lace

men

t (m

m)

Time (min)

14

16

18

2

0 20 40 60 80 100 120 140 160 180 200

Al at 200∘C

Al at 100∘C

Al at 30∘C

(a)

Disp

lace

men

t (m

m)

Time (min)

1

11

12

13

14

15

16

17

18

0 50 100 150 200

Al-Fe at 200∘C

Al-Fe at 100∘C

Al-Fe at 30∘C

(b)










119876 =

119877 ln (12057610158401

120576

1015840

2

)

(1119879

2) minus (1119879

1)

(2)

where 12057610158401

and 12057610158402







4 Conclusions










Acknowledgments


References








3






3



3

NiAl2

O3



2

O3












































CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials





4 Conclusions










Acknowledgments


References








3






3



3

NiAl2

O3



2

O3












































CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials













































CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials



research article fabrication of friction stir …downloads.hindawi.com/archive/2015/428630.pdfmetal...

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