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Severe Plastic Deformation

Laszlo S. TothLaboratoire d’Etude des Microstructure et de Mécanique des MatériauxLaboratoire d’Etude des Microstructure et de Mécanique des Matériaux

Université de Metz, France

Laboratoire d’Excellence Design des Alliages Métalliques pour Allègement des Structures, DAMAS

Action Nationale de Formation métallurgie fondamentale.Aussois 22-25 octobre 2012

Content

• For Introduction: Keywords and objectives• Strain modes in SPD• Strain hardening • Microstructure features• Texture evolution • Texture evolution • A model of grain refinement• Effect of strain path on grain refinement and

texture• Strong points and future key issues

Action Nationale de Formation métallurgie fondamentale. Aussois

22-25 octobre 2012

Keywords and objectives

Keywords:

SPD: Severe Plastic Deformation, Hyperdéformation

UFG: Ultra Fine Grain

BNM: Bulk Nanostructured Materials

NanoSPD: Nanostructured Materials by SPD

NanoSPD6: Metz, 2014, June 30-July 4


22-25 octobre 2012

Objectives:

To apply SPD for reducing the grain size.

Modern SPD techniques: obtain large strains without changing the shape!

SPD transforms the microstructure, introduces very large amount of new GB.

Grain boundary engineering

Explore the properties between nano and conventional grain structures, in the UFG regime.

Publication activity in SPD

Number of publications Number of citations


22-25 octobre 2012

Paradox of strength vs ductility

The paradox of strength vs ductility; the nano-Ti and nano-Cu

has superior propertiesRZ Valiev, IV Alexandrov, TC Lowe, et al., J Mater Res 17 (2002) 5


22-25 octobre 2012

NANO

Palladium, HREM


22-25 octobre 2012

Static Model (steel balls)

For microstructure teaching

5 nm


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Model for plastic deformation of nanocrystals

For microstructure teaching-dislocation

b


22-25 octobre 2012

SPD processes

ECAP (ECAE), NECAP, ARB, HPT, HPTT

fixed anvil

twisting anvil

before after

1 2

3

4

Next pass

before HPTT

after HPTT

Equal Channel Angular Extrusion Non-Equal Channel Angular Extrusion High pressure torsion High Pressure Tube Twisting

Accumulated roll-bonding


22-25 octobre 2012

SPD in LEM3, Metz

ECAE

Twisting Mandrel

Fixe Mandrel

Sample

Compression

HPTTAction Nationale de Formation

métallurgie fondamentale. Aussois 22-25 octobre 2012

Experimental evidence for grain fragmentation in SPD

100 mµ 100 mµ

5 mµ Shear, γ = 4

Al, CP, defomed by HPTT – Arzaghi, thesisAction Nationale de Formation


Acta Materialia 60 (2012), pp. 4393-4408

The strain mode in SPD

Strain field in ECAE(simple shear model)

yx’

:velocity gradient

:

1 1 01

1 1 02

0 0 0

velocity gradient

− −

x

y’0 1 0

0 0 0

0 0 0

−

0 0 0

Deformation state:compression, tension+ rigid body rotation


22-25 octobre 2012

Experiment, Segal, 1999

Gholinia, Bate, Prangnell, 2002 Beyerlein, Tome, 2004

0

2

4

6

0 2 4 6

Toth, 2003

Gholinia, Bate, Prangnell, 2002

αα

Φ

β α

Φ

Central fanLow deformation

Rotating region

Beyerlein, Tome, 2004


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Strain mode in HPTT et HPT

HPTHPTT


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Strain heterogeneity in HPTT

4

6

8

10 Tube wall

γ

Experimental Simulated

Local strain

r = ar = b IF steel


22-25 octobre 2012

6.4 6.6 6.8 7.0 7.2 7.4 7.60

2

4

Transition zone

Radius [mm]

Pougis et al. Scripta Materialia, 66 (2012) 773-776

Average strain:( )b

a

rdr

r

γθ = ∫ ln( / )b a

θγ =

Strain hardening in SPD

HPTT

During HPTTECAE ( )

( )2 2

lnT b a

b a hτ

π=

−

model

Arzaghi et al. Acta Materialia 60 (2012), pp. 4393-4408L. Toth, Computational Materials Science 32 (2005) 568–576


22-25 octobre 2012

0

50

100

150

200

250

300

350

0 2 4 6 8 10 12 14 16 18

Yσ [MPa]

Compression Test

Ring Hoop Tension Test

( )HPTTγ

After HPTT

(a) (b)

Compression disks

Tube θ

8 mm

1

5 mm

3 mm

Tube with Rout = 8mm

Reduced section

D-blocks

Pin

60°

Al 1050Ring-hoop tensile test

compression

Microstructure features

Toth et al., Acta Materialia, 58 (2010) 6706-67163-pass ECAECu

0 5 10 15 20 25 30 35 40 45 50 55 60 650.00

0.01

0.02

0.03

0.04

0.05

In grain interior

At grain boundary


22-25 octobre 2012

int int( ) ( ) ( )total OBG OBGf fυ θ υ θ υ θ= +new grain in interior of old grain

Microstructure in ARB

B. Beausir, T.U. DresdenAction Nationale de Formation


Al pure + Al 1050

Texture evolution

measured simulated

pass 1

pass 2

ECAE, Route A, Copper


22-25 octobre 2012

A new quantitative grain fragmentation model

A new model is proposed for grain fragmentation that is based on lattice curvature. The lattice curvature is produced by the grain boundaries where lattice rotation is slowed down.

László S. Toth, Yuri Estrin, Rimma Lapovok, Chengfan GuActa Materialia 58 (2010) 1782-1794

The new model predicts:

Grain size evolution and distribution

Misorientation distribution of grains

Misorientation of cell walls

Texture development

Strain hardening


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Lattice curvature in a grain

Uniformlattice rotation

Grain

Initial lattice plane

Distorded lattice plane

zone affected by GB

zone not affected by GB

Al-Si alloy, Skjervold, 1995


22-25 octobre 2012

Experimental evidence

Ti rolled to 2% -Fundenberger-Beausir


22-25 octobre 2012

Lattice curvature in experiments

EBSD map of GND density, Cu ECAP 1 passC.F. Gu, L.S. Tóth, B. Beausir, Scripta Materialia, 2012.

1GND ij ijb

ρ α α=

(2 ) 2 2 2 2 212 13 21 23 33

1Dρ α α α α α= + + + +

:ijα Nye’s dislocation density tensor

12 13 21 23 33GND bρ α α α α α= + + + +

(3 ) (2 )3 5GND GND

D Dρ ρ=

Assuming isotropy:

) 14 2(3 4.38 10 mGND

Dρ −= ×

x1015m-2

0.33 0.7 1.3 2.0 2.7 3.35

BC

0

Lattice curvature in a grain

OR

µ

A

B

C

d

Initial

Rotated-curved1

Curvature-induced dislocation density:

D/2

Lattice rotation

Rotated-curved1CIDb

Rκ ρ= =

( )( ) ( )2

12sin, 1, 2, or 3.

cos cos 8CID k k

bD

µρ

µ µ

Ω= =

− Ω + Ω +


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Grain fragmentation procedure


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Grain fragmentation

GBSG G SGΩ = Ω + Ω& & &

Sugbrain rotations:


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Application to ECAP of copper

Measured:Simulated with grain refinement:

Passs-1

Simulated without grain refinement:

Taylor model, µµµµ=0.5, 500 initial grains 6 million grains

Passs-2, Route Bc


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Grain size

10

20

30

gra

in s

ize

[mik

ro m

]

Measured

Simulated 0 1 2 3 4 5D (micron)

0.0

0.5

1.0

1.5

2.0

2.5

Freq

uenc

y de

nsity

0.0 0.5 1.0 1.5 2.0 2.5von Mises strain

0

10

Ave

rage

Simulated

D (micron)

0 1 2 3 4 5D (micron)

0.0

0.5

1.0

1.5

2.0

2.5

Freq

uenc

y de

nsity


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Misorientation distribution (NNMD)

0.025

0.03

0.035

0.04

experiment

M. Arzaghi, Ph.D. thesis, Metz, France, 2010

Al 1050 HPTTArzaghi et al. Acta Materialia 60 (2012), pp. 4393-4408


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0

0.005

0.01

0.015

0.02

0 10 20 30 40 50 60

Next-grain misorientation distribution Al 1050 HPTT, shear = 4

experiment

simulation

The dislocation-cell based hardening model

Cell wall:

12 /3

1 2 00

3 * (1 )6 * (1 )(1 ) (1 )

n

r ws wg wrws r ws

ffk

bdf fb

β γ ρ ρ γβ γρ ξ ξ γ ργ

−− + −= − + − −

& &&& &

&

2/3

1 2

3 * (1 )6 * (1 ) r ws wgrwg

ff

bdf fb

β γ ρ ρβ γρ ξ ξ− +−= +

&&&

Y. Estrin, L.S. Toth, A. Molinari, Y. Bréchet, Acta materialia, 46, 5509-5522, 1998, cited 182 timesL.S. Toth, A. Molinari, Y. Estrin, J. Eng. Mat. Techn. 124, 71-77, 2002, cited 70 times.


22-25 octobre 2012

slip from the cells

FR sources for dislocations coming from the cell

annihilation (cross slip)

Cell interior:( )

1

013 0

61* *

3 1

n

w c cc w c ck

b bd f

ρ γ γρ α γ β γ ργ

−

= − − −

& && & &

&

by FR sources from the walls

flux to the walls

Hardening

400

600

ress

[MP

a]

Predicted strain hardening curve

pass 1 pass 2

0.0 0.5 1.0 1.5 2.0 2.5von Mises strain

0

200

Equ

ival

ent s

tr


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Dislocation densities

2E+16

3E+16

4E+16

ion

dens

ity [1

/m]

rtotal

rwall

pass 1

pass 2

0.0 0.5 1.0 1.5 2.0 2.5von Mises strain

0E+0

1E+16

disl

ocat

i

rGND

rcell


22-25 octobre 2012

Cell-wall misorientation

2

3

4

rient

atio

n [°] pass 2pass 1

wgbdθ ρ=

0.0 0.5 1.0 1.5 2.0 2.5von Mises strain

0

1

2

Cel

l-wal

l dis

or

pass 1


22-25 octobre 2012

Strain path effect on grain refinement

Simulated (continuous lines) and experimental (symbols) development of average grain size obtained in ECAE and rolling


22-25 octobre 2012

C.F. Gu, L.S. Toth, M. Arzaghi, C.H.J. Davies,Scripta Materialia, 64 (2011) 284–287

Strain reversal effect on texture and grain refinement

Route C two-pass measured texture

Route C ECAEC.F. Gu and L.S. Tóth,Acta Materialia, 59 (2011) 5749-5757

Route C two-pass measured texture

Simulated texture by traditionalVPSC model

Simulated texture by the new grain refinement model


22-25 octobre 2012

0 1 2 3 4 5Grain size (micron)

0.0

0.5

1.0

1.5

Fre

quen

cy

0 1 2 3 4 5Grain size (micron)

0.0

0.5

1.0

1.5

Freq

uenc

y

Pass 1 Pass 2

Grain size

C.F. Gu, L.S. Toth, C.H.J. Davies,Scripta Materialia, 65 (2011), 167-170

Strong points and future key issues

Strong points:

- SPD deformation techniques can produce ultra fine grain microstructures with enhanced mechanical properties in bulk form.

- Grain sizes are in the range of sub-micron, in between the minimum grain sizes by DRX et nano-structures, readily feasible

- BNM materials are excellent candidates for biomechanics applications and micro-parts.

Future keys issues:

- Up-scaling from laboratory to industrial processes.

- Mastering of microstructure variations grand potential in metallurgy

- Understanding the grain subdivision process


22-25 octobre 2012

Fundamental publications in SPD

Bulk nanostructured materials from severe plastic deformation, Valiev, RZ; Islamgaliev, RK; Alexandrov, IV, PROGRESS IN MATERIALS SCIENCE 45, 2000, 103-189, 2622citations

Principles of equal-channel angular pressing as a processing tool for grain refinement, Valiev, Ruslan Z.; Langdon, Terence G. PROGRESS IN MATERIALS SCIENCE 51 2006 881-981, 972citations

STRUCTURE AND PROPERTIES OF ULTRAFINE-GRAINED MATERIALS PRODUCED BY SEVERE PLASTIC-DEFORMATION, VALIEV, RZ; KORZNIKOV, AV; MULYUKOV, RR, MATERIALS SCIENCE AND ENGINEERING 168 1993141-148, 779citations

Ultra-fine grained bulk aluminum produced by accumulative roll-bonding (ARB) process, Saito, Y; Tsuji, N; Utsunomiya, H; et


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Ultra-fine grained bulk aluminum produced by accumulative roll-bonding (ARB) process, Saito, Y; Tsuji, N; Utsunomiya, H; et al. SCRIPTA MATERIALIA 39 19981221-1227,462citations

Producing bulk ultrafine-grained materials by severe plastic deformation, Valiev, RZ; Estrin, Y; Horita, Z; et al., JOM 58 200633-39, 407citations

Nanostructuring of metals by severe plastic deformation for advanced properties, Valiev, R, NATURE MATERIALS 3 2004511-516, 355citations

Analysis of texture evolution in equal channel angular extrusion of copper using a new flow field, Toth, LS; Massion, RA; Germain, L; et al., ACTA MATERIALIA 52 20041885-1898, 109citations

Texture evolution in equal-channel angular extrusion, Beyerlein, Irene J.; Toth, Laszlo S., PROGRESS IN MATERIALS SCIENCE 54 2009, 427-510, 60citations

Acknowledgements

S. Suwas (Bangalore), W. Skrotzki (Dresden), M. Zehetbauer (Vienna),

I. Beyerlein (Los Alamos), C. Tomé (Los Alamos), C.F. Gu (Melbourne),

Y. Estrin(Melbourne), R. Lapovok(Melbourne), O. Bouaziz (ArcelorMittal), Y. Estrin(Melbourne), R. Lapovok(Melbourne), O. Bouaziz (ArcelorMittal), A. Hasani (Iran), A. Eberhardt (ENIM-LEM3), J.J. Fundenberger (LEM3),

L. Germain (LEM3), M. Arzaghi (LEM3), R. Arruffat (LEM3), B. Beausir (LEM3), A. Molinari (LEM3) , A. Pougis (LEM3)

ANR HYPERTUBE


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