the deformation behavior of rare-earth containing mg alloys · 2014. 5. 14. · the deformation...

The Deformation Behavior of Rare-earth

Containing Mg Alloys

Ajith Chakkedath1, C.J. Boehlert1,2, Z. Chen1, M.T. Perez-Prado2,

J. Llorca2, J. Bohlen3, S. Yi3, and D. Letzig3.

1 Michigan State University, East Lansing, Michigan. 2 IMDEA Materials Institute, Madrid, Spain.

3 Magnesium Innovation Centre MagIC, Helmholtz Centre, Geesthacht, Germany.

CHEMS Annual Research Forum, East Lansing, MI, May 14 2014.

This work was supported by the NSF Division of Material Research “Materials World Network”

(Grant No. DMR1107117).

Our Lab and Equipment

2

Scanning Electron

Microscope

• Backscatter

Electron detector.

• EDS detector.

• EBSD detector.

Metallography lab

In-situ stage

• Screw driven.

• Tension/compression.

• Heater (~800C).

• Cooling system.

20 mm

Website:

http://www.egr.msu.edu/~boehlert/GROUP/

Magnesium

https://www.wikipedia.org/

http://www.cvmminerals.com/images/table.jpg

King, J. F. "Magnesium: commodity or exotic?." Materials science and technology 23.1 (2007): 1-14.

Plastic

Fe

Mg

Al

*The size of the circle corresponds

to the density of the material

3

Advantages

• Mg is the lightest structural metal (1.7 g/cc).

35% lighter than Al (2.7 g/cc).

Over four times lighter than steel (7.9 g/cc).

• High specific strength and stiffness

compared to other engineering materials.

• Mg is plentiful.

Eight most common element on earth; third most abundant metal.

(each cubic meter of sea water contains ~1.3 kg Mg).

The ores are found in most countries.

R. J. L. Stanner: Am. Sci., 1976, 64, 258. Shigley, C. M. "Minerals from the sea." J. Metals 3 (1951): 25-29.

King, J. F. "Magnesium: commodity or exotic?." Materials science and technology 23.1 (2007): 1-14.

Kulekci, M K. "Mg and its alloys applications in auto industry." The International Journal of Advanced Manufacturing Technology39.9-10 (2008): 851-865.

Plastics Mg

Al

Ti

Steel

Specific strength

Specific stiffness

4

History

1960s: Titan I rocket

(~1100 lbs Mg sheet)

1940s: Northrop XP-56

(First airplane nearly

completely designed with Mg)

1950s:

B-36 Bomber

(Contained ~19000 lbs of Mg)

Friedrich, Horst E., and Barry L. Mordike. Magnesium technology. Berlin [etc.]: Springer, 2006. 5

http://auto.howstuffworks.com/

1930s: VW Beetle

(~20 kg of Mg; Mg crankcase

and transmission housing)

Applications

• Automotive industry (powertrain, body parts,

chassis, etc.)

• Electronic devices (laptop cases, etc.)

• Sporting goods (bicycle frame, etc.)

• Aerospace (transmission, etc.)

• Hand-held working tools

• Biomedical applications

Gupta, Manoj, and Nai Mui Ling Sharon. Magnesium, magnesium alloys, and magnesium composites. John Wiley & Sons, 2011. 6

Porsche 911 Targa:

Mg roof shell and panel

bow.

Ford F-150 front structure bolster/radiator

support component is die-cast Mg.

IMA Mg showcase, Jan 2009, 1-4.

Why Light-weighting?

7 http://www.whitehouse.gov/

http://www.washingtonpost.com/

Why Light-weighting?

S. Sugimoto, 53rd Annual Mg Congress (Ube City, Japan, 1996), p. 38.

Friedrich, H E., and B L. Mordike. Mag Tech. Berlin [etc.]: Springer, 2006.

Ghassemieh, E. "Mater’s in auto appl, state of the art & prospects." Ch 20 (2011).

Kulekci, M K. The International Journal of Advanced Manufacturing Technology39.9-10 (2008): 851-865.

Committee on the Effectiveness and Impact of CAFE Standards, National Research Council, Washington D.C.: National Academies Press, 2002.

8

• For every 10% of weight reduction, the fuel

economy improves by 6.6-8%.

– Weight reduction of 100 kg represents a fuel

saving of about 0.5 l / 100 km for a vehicle.

• Every kg of

weight reduced

in a vehicle,

results in ~20 kg

of CO2 reduction.

Tański, T., L. A. Dobrzański, and K. Labisz. ISSUES 1 (2010): 2. Kulekci, M K. The Intl J. of Adv Manu. Tech 39.9-10 (2008): 851-865. 9

22% to 70% weight

reduction is possible

for automotive

components by using

Mg alloys instead of

alternative materials.

Life cycle inventory study on Mg alloy

substitution suggests decrease in total

energy consumption and CO2 emissions.

Why Mg is Attractive to Auto Industry?

Physical Properties of Mg

10

• Mg has hexagonal close-packed

(HCP) structure at RT and

atmospheric pressure.

• Typical lattice parameters:

a = 0.32 nm & c = 0.52 nm

c/a ratio = 1.624

Unit cell of Mg

• The non-symmetric HCP structure partly complicates the

mechanical and physical properties of Mg and its alloys

(unlike steel or Al which has highly symmetric cubic structure).

Yoo, M. H. "Slip, twinning, and fracture in hexagonal close-packed metals."Metallurgical Transactions A 12.3 (1981): 409-418.

Common Deformation Modes

11

Slip Twin

Basal <a> slip {0001}<1-210>

1st order prismatic <a> slip

{-1100}<11-20>

2nd order pyramidal <c+a> slip

{-12-12}<1-213>

Extension twin {01-12}<0-111>

86 @ <11-20>

Contraction twin {01-11}<01-1-2>

56 @ <11-20>

Schmid Factor & Critical Resolved Shear Stress (CRSS)

12

Shear stress is required to move dislocations.

F = Applied force

A = cross sectional area

Applied stress, σ = F/A

Component of force in slip direction:

Area of slip surface:

Resolves shear stress

on the slip plane in the slip direction:

Schmid law: slip happens when resolved shear stress is greater than a critical

value. So, systems with high Schmid factor are more likely to be active.

E. Schmid and W. Boas, Kristalplas (Plasticity of Crystals) (Berlin and London: Springer and Hughes, 1950)

Challenges for Mg Use

• Anisotropic material properties.

• Low elevated temperature strength.

• Limited cold formability:

– Extension twinning and basal slip (provides only 2 independent

deformation modes) are easily activated at RT.

– According to Von Mises criterion at least 5 independent modes are

required for homogeneous deformation of polycrystals.

– Normally processed at 300-450C to activate more deformation modes.

R. von Mises: Z. Angew. Math. Mech., 1928, vol. 6, p. 85. Yoo, M. H. Metallurgical Transactions A 12.3 (1981): 409-418.

Bettles, C, and M Gibson. Jom 57.5 (2005): 46-49. Barnett, M. R. Metallurgical and materials transactions A 34.9 (2003): 1799-1806. 13

CRSS Vs. Temperature for

different deformation modes.

Challenges – Texture Formation

• Conventional alloys: strong texture formation during wrought

processing (Eg: Mg-9Al-1Zn (wt%)).

Zhe Chen’s dissertation, 2012, MSU. Watanabe, H., et al. Materials Science and Engineering: A 527.23 (2010): 6350-6358.

Bohlen, Jan, et al. Materials Science and Engineering: A 527.26 (2010): 7092-7098. 14

Schematic

representation

of texture

formation in

conventional

alloys.

0001

RD

TD

max=20.385

32.000

16.000

8.000

4.000

2.000

1.000

0.500

• The strong texture formation can be inhibited by dilute RE additions

(Eg: Ce, Y, Gd, Nd).

0001 pole figure showing strong basal

texture in rolled Mg-3Al-1Zn (wt%).

0001 pole figure showing weak

random texture in extruded

Mg-1Mn-1Nd (wt%).

Nd was shown to be a stronger

texture modifier compared

to other RE elements (Ce, Y) in

Mg-Mn alloys.

Ram

Extrusion

direction

Goals

• To understand why Nd additions inhibit Texture Formation in Mg alloys.

• Understand the effect of Nd on the deformation behavior, mechanical

properties and microstructural evolution.

• Optimize the Nd content and microstructure for Structural Applications.

• The following alloys are part of my study (*All compositions are in wt%):

Extruded Mg-1Mn-1Nd (two extrusions)

Extruded Mg-1Mn-0.3Nd

Extruded Mg-1Mn

Cast Mg-1Mn-1Nd

Cast Mg-1Mn-0.3Nd 15

Indirect extrusion

www.kayealu.co.uk

In-Situ Characterization Technique

16

In-situ uniaxial testing using

a screw driven stage

inside a SEM

+

EBSD analysis

EBSD detector SE detector

Tensile stage

Specimen

BSE detector

Heater

Cooling water

Thermocouple

A specially-designed specimen was used

along with an Ernest Fullam Tensile Stage

to perform in-situ tensile and compression

experiments. SE SEM images were

acquired during the deformation. EBSD

orientation maps were acquired before

and after the tensile tests.

-1 -0.5 0 0.5 1

-1

-0.8

-0.6

-0.4

-0.2

0

0.2

0.4

0.6

0.8

1

123

45

6

7

8

9

10

11

12

Slip Trace Analysis

17

Secondary electron (SE) SEM images

Undeformed 6.8% strain 16.8% strain 27.4% strain

Schmid

factor

Slip

system

Plane/

direction

0.44 3 (0001)[-1-120]

0.41 7 (11-2-2)[-1-123]

0.40 8 (-12-12)[1-213]

0.40 12 (2-1-12)[-2113]

0.22 2 (0001)[-12-10]

0.21 1 (0001)[-2110]

0.21 9 (-2112)[2-1-13]

0.20 11 (1-212)[-12-13]

0.11 5 (10-10)[1-210]

0.11 4 (01-10)[2-1-10]

0.02 10 (-1-122)[11-23]

0.00 6 (-1100)[11-20]

3 – Basal slip (0001)[-1-120]

Schmid factor 0.44

Generated

slip traces

Loading direction

Euler angle:

199.271 66.071 168.56

Twin Trace Analysis

18

Undeformed 6% strain 2.7% strain Undeformed - Unit cell rotation

Euler angle: 59.207 59.304 287.98

Loading direction Schmid

factor

Twin

system

Plane/

direction

0.33 5 (0-112)[01-11]

0.28 2 (01-12)[0-111]

0.11 12 (1-101)[1-10-2]

0.10 10 (-1011)[-101-2]

0.02 4 (-1012)[10-11]

0.01 6 (1-102)[-1101]

0.00 1 (10-12)[-1011]

-0.02 3 (-1102)[1-101]

-0.03 11 (0-111)[0-112]

-0.10 9 (-1101)[-110-2]

-0.12 7 (10-11)[10-1-2]

-0.47 8 (01-11)[01-1-2]

5 – extension twin

(0 -1 1 2)<0 1 -1 1>

Schmid factor 0.33

Euler angle:

59.207 59.304 287.98

Secondary electron (SE) SEM images

Rotation across

twin boundary:

83.1o about [-2 1 1 0]

EBSD map

6% strain

-1 -0.5 0 0.5 1

-1

-0.5

0

0.5

1

1

2

3

4

5

6

7

8

9

10

11

12

Generated

twin traces

Tensile Properties

19

0

20

40

60

80

100

120

140

160

0 0.5 1 1.5 2

MN10 Tension

50C150C

250C

Str

ess, M

Pa

Displacement, mm

0

20

40

60

80

100

120

140

160

0 0.5 1 1.5 2

MN11 Tension

50C150C250C

Str

ess,

MP

a

Displacement, mm

Mg-1Mn-1Nd (wt%) Mg-1Mn-0.3Nd (wt%)

The load drops indicate the stress relaxation that occurred when the experiment was paused

and SE SEM photomicrographs were acquired.

The strength values decreased with increasing temperature.

Mg-1Mn-0.3Nd (wt%) exhibited greater strength than Mg-1Mn-1Nd (wt%) at RT.

0

2

4

6

8

10

12

Nu

mb

er o

f Sl

ip T

race

s o

r Tw

ins

Ob

serv

ed in

all

of

the

Gra

ins

An

alyz

ed

Schmid Factor distribution

extension twin

pyramidal <c+a>

prismatic <a>

basal <a>

31 %

14 %

5 %

50 %

Number of observations: 9

Extension twin 8 nos

Contraction twin 1 nos

0

2

4

6

Nu

mb

er o

f Sl

ip T

race

s o

r Tw

ins

Ob

serv

ed in

all

of

the

Gra

ins

An

alyz

ed

Schmid factor distribution

extension twin

contraction twin

89 %

11 %

Mg-1Mn-1Nd (wt%)



Pyramidal <c+a> 6 nos

Prismatic <a> 2 nos

Basal <a> 21 nos

Deformation Mode Distribution @ 50C

20

Mg-1Mn-0.3Nd (wt%)

0

2

4

6

8

Nu

mb

er o

f Sl

ip T

race

s o

r Tw

ins

Ob

serv

ed in

all

of

the

Gra

ins

An

alyz

ed


extension twin

contraction twin

basal <a>

14 %

14 %

72 %

Mg-1Mn-1Nd (wt%)


Mg-1Mn-0.3Nd (wt%)

0

2

4

6

8

10

12

14

16

Nu

mb

er o

f Sl

ip T

race

s o

r Tw

ins

Ob

serv

ed in

all

of

the

Gra

ins

An

alyz

ed


extension twin

pyramidal <c+a>

prismatic <a>

basal <a>

6 %

6 %

29 %

59 %




Prismatic <a> 14 nos

Basal <a> 29 nos



Contraction twin 1 nos

Basal <a> 5 nos

21

Mg-1Mn-1Nd (wt%)


Mg-1Mn-0.3Nd (wt%)



Prismatic <a> 4 nos

Basal <a> 105 nos

0

5

10

15

20

25

Nu

mb

er o

f Sl

ip T

race

s o

r Tw

ins

Ob

serv

ed in

all

of

the

Gra

ins

An

alyz

ed


pyramidal <c+a>

prismatic <a>

basal <a>

3 %

12 %

85 %



Prismatic <a> 4 nos

Basal <a> 28 nos

0

5

10

15

20

25

30

35

40

45

50

Nu

mb

er o

f Sl

ip T

race

s o

r Tw

ins

Ob

serv

ed in

all

of

the

Gra

ins

An

alyz

ed


pyramidal <c+a>

prismatic <a>

basal <a>

9 %

3 %

88 %

CRSS Ratio Estimation Methodology

23

Initial microstructure

Schmid factor dist Basal Prism Py c+a Ext twin

0-0.05 0 0 0 0

0.05-0.10 0 0 1 0

0.10-0.15 0 0 0 2

0.15-0.20 0 0 0 0

0.20-0.25 1 0 1 0

0.25-0.30 0 0 0 1

0.30-0.35 0 0 0 0

0.35-0.40 1 1 0 0

0.40-0.45 13 4 1 0

0.45-0.50 14 9 0 0

Experimentally observed distribution

Schmid factor dist Basal Prism Py c+a Ext twin

0-0.05 544 484 1611 814

0.05-0.10 446 425 1269 667

0.10-0.15 478 485 1036 500

0.15-0.20 483 424 883 420

0.20-0.25 452 404 715 342

0.25-0.30 393 402 664 284

0.30-0.35 376 455 629 213

0.35-0.40 316 386 477 152

0.40-0.45 306 374 475 93

0.45-0.50 313 268 455 78

Potential

deformation

system

distribution

NO

RM

ALIZ

E

Li, H., et al. "Methodology for estimating the CRSS

ratios of α-phase Ti using EBSD-based trace

analysis." Acta Materialia 61.20 (2013): 7555-7567.

Estimated CRSS Ratios

24

The mean CRSS ratios and the corresponding 90% confidence intervals (listed in

parenthesis) for prismatic <a> slip, pyramidal <c+a> slip and extension twinning

estimated using the deformation results at 50C.

For Mg-1Mn-1Nd (wt%) extrusions at 50C:

Material/

Testing condition

Prismatic <a>

Basal <a>

Pyramidal <c+a>

Basal <a>

Extension

twinning

Basal <a>

Extrusion 1* 12.6

(3.1, 30.4)

12.2

(0.6, 40.0)

0.6

(0.2, 1.4)

Extrusion 2* 11.0

(3.4, 18.7)

875.9

(29.8, 4033.5)

0.8

(0.3, 1.5)

*Extrusion 1 was extruded at 300C and extrusion 2 at 275C.

What we have learned thus far…

• Higher Nd content results in better high temperature

strength retention in Mg-1Mn (wt%).

• More than 0.3 wt% Nd is needed to inhibit the conventional

extrusion texture which causes anisotropic behavior.

• The estimated CRSS ratios suggest that Nd addition to Mg-

1Mn (wt%) results in an increase of the CRSS for basal slip.

• Overall, Nd-containing Mg alloys show promise for

automobile applications.

• Mg alloys have a bright future and are here to stay!

25

Thank you for your attention!

the deformation behavior of rare-earth containing mg alloys · 2014. 5. 14. · the deformation...

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