0
Interface-related micromechanics in TWIP steels
I. Gutierrez-Urrutia, S. Zaefferer, D. Raabe
28. October 2009, MS&T, Pitts...
Overview
Dierk Raabe, MS&T, Pittsburgh, 28. Oct. 2009, MPIE
2
200 300 400 500 600 700 800 900 1000 1100 1200 1300 1400 1500 1600
0
10
20
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60
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80
totalelongationtofracture[%...
3
200 300 400 500 600 700 800 900 1000 1100 1200 1300 1400 1500 1600
0
10
20
30
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60
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80
totalelongationtofracture[%...
Characterization
Dierk Raabe, MS&T, Pittsburgh, 27. Oct. 2009, MPIE
5
Scaling issue in microscopy
?
TEM EBSD
EBSD orientation contrast
is not lattice defect contrast
Large scale mapping of l...
6
EBSD
High spatial and
angular resolution
ECCI
1 nm
10 nm
100 nm
1000 nm
0.001º 0.01º 0.1º 1º
Spatial
resolution
Angular
...
Electron channeling contrast mechanism
Dislocation imaging
[A.J. Wilkinson, P.B. Hirsch, Micron 28 (1997) 279]
Requirement...
8
Fe-22Mn-0.6C (wt%) TWIP steel
High resolution EBSD ECCI
twins
Dislocation cells
Comparison EBSD-ECCI
Electron Channeling...
9
SEM
10
SEM
TEM
11
ECCI / SEM
(-220)
Dislocation cells are clearly seen by ECCI
TEM-Bright Field
Fe-22Mn-0.6C (wt%) TWIP steel
Electron Ch...
12
0
500
1000
1500
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3000
3500
4000
0 0.1 0.2 0.3 0.4 0.5
True stress
Hardening (MPa)
Hardening/Stress(MPa)
True s...
0
500
1000
1500
2000
2500
3000
3500
4000
0 0.1 0.2 0.3 0.4 0.5
True stress
Hardening (MPa)
Hardening/Stress(MPa)
True stra...
2nd hardening stage:
2%<e< 10%
ECCI: Work hardening of TWIP steels, Fe-22Mn-0.6C (wt%)
I. Gutierrez-Urrutia, et al. Mater....
0
500
1000
1500
2000
2500
3000
3500
4000
0 0.1 0.2 0.3 0.4 0.5
True stress
Hardening (MPa)
Hardening/Stress(MPa)
True stra...
3rd hardening stage:
10%<e< 25%
ECCI: Work hardening of TWIP steels, Fe-22Mn-0.6C (wt%)
I. Gutierrez-Urrutia, et al. Mater...
0
500
1000
1500
2000
2500
3000
3500
4000
0 0.1 0.2 0.3 0.4 0.5
True stress
Hardening (MPa)
Hardening/Stress(MPa)
True stra...
5th hardening stage:
35%<e< 50%
ECCI: Work hardening of TWIP steels, Fe-22Mn-0.6C (wt%)
I. Gutierrez-Urrutia, et al. Mater...
Type I
5th hardening stage:
35%<e< 50%
ECCI: Work hardening of TWIP steels, Fe-22Mn-0.6C (wt%)
I. Gutierrez-Urrutia, et al...
Type II
5th hardening stage:
35%<e< 50%
ECCI: Work hardening of TWIP steels, Fe-22Mn-0.6C (wt%)
I. Gutierrez-Urrutia, et a...
Type III
5th hardening stage:
35%<e< 50%
ECCI: Work hardening of TWIP steels, Fe-22Mn-0.6C (wt%)
I. Gutierrez-Urrutia, et ...
0
20
40
60
80
100
0.05 0.1 0.2 0.4
DDW+Cells
DDW+Cells+Twins
Type I
Type II
Type III
%
True strain
Type of grain
Interface...
Most of the grains follow
the Schmid’s Law (3/4)
True strain: 40%
EBSD: Growth of deformation twins in TWIP steels
I. Guti...
True strain: 40%
Some of the grains follow
the Schmid’s Law
EBSD: Growth of deformation twins in TWIP steels
I. Gutierrez-...
True strain: 40%
1-2activated twinning
systems nucleated at
grain boundaries
No twins inside the grain (few degrees from [...
Grains with “low” twinning activity:
-Short twins (less than 5 microns length)
-Few twins
EBSD: Growth of deformation twin...
Grains with “high” twinning activity:
-Long twins
-Thick bundles of twins
-High population of twins
These results suggest ...
Type I
3rd hardening stage:
10%<e< 25%
ECCI: Work hardening of TWIP steels, Fe-22Mn-0.6C (wt%)
I. Gutierrez-Urrutia, et al...
Type II
3rd hardening stage:
10%<e< 25%
ECCI: Work hardening of TWIP steels, Fe-22Mn-0.6C (wt%)
I. Gutierrez-Urrutia, et a...
Type III
3rd hardening stage:
10%<e< 25%
ECCI: Work hardening of TWIP steels, Fe-22Mn-0.6C (wt%)
I. Gutierrez-Urrutia, et ...
31
Fe22Mn0.6C TWIP steel
Mechanical twins
Dislocation cells
Electron Channeling Contrast Imaging
I. Gutierrez-Urrutia, et ...
EBSD: Growth of deformation twins in TWIP steels
I. Gutierrez-Urrutia, et al. Mater. Sc. Engin. A 527 (2010) 3552
Dierk Raabe, MS&T, Pittsburgh, 27. Oct. 2009, MPIE
Summary
34
I. Gutierrez-Urrutia, S. Zaefferer, D. Raabe: Scripta Mater. 61 (2009) 737-740
Electron channeling contrast imaging of ...
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  1. 1. Interface-related micromechanics in TWIP steels I. Gutierrez-Urrutia, S. Zaefferer, D. Raabe 28. October 2009, MS&T, Pittsburgh Acknowledgements: SFB 761 “Steel ab initio”; discussions with Marty Crimp and Tom Bieler (Michigan State University) see also: talk at 2 pm Thursday room 328, EBSD session
  2. 2. Overview Dierk Raabe, MS&T, Pittsburgh, 28. Oct. 2009, MPIE
  3. 3. 2 200 300 400 500 600 700 800 900 1000 1100 1200 1300 1400 1500 1600 0 10 20 30 40 50 60 70 80 totalelongationtofracture[%] ultimate tensile strength [MPa] TRIP and complex phase martensitic maraging TRIP dual phase ferritic Ductility-strength profile for sheet steels austenitic stainless advanced TWIP and TRIP www.mpie.de www.mpie.de www.mpie.de
  4. 4. 3 200 300 400 500 600 700 800 900 1000 1100 1200 1300 1400 1500 1600 0 10 20 30 40 50 60 70 80 totalelongationtofracture[%] ultimate tensile strength [MPa] TRIP and complex phase martensitic maraging TRIP dual phase ferritic Ductility-strength profile for sheet steels austenitic stainless advanced TWIP and TRIP
  5. 5. Characterization Dierk Raabe, MS&T, Pittsburgh, 27. Oct. 2009, MPIE
  6. 6. 5 Scaling issue in microscopy ? TEM EBSD EBSD orientation contrast is not lattice defect contrast Large scale mapping of lattice defects TEM information in SEM Electron Channeling Contrast Imaging Example: Fe-22Mn-0.6C (wt%), TWIP
  7. 7. 6 EBSD High spatial and angular resolution ECCI 1 nm 10 nm 100 nm 1000 nm 0.001º 0.01º 0.1º 1º Spatial resolution Angular resolution Limited spatial and angular resolution Good spatial and angular resolution TEM Overview characterization
  8. 8. Electron channeling contrast mechanism Dislocation imaging [A.J. Wilkinson, P.B. Hirsch, Micron 28 (1997) 279] Requirement: Crystal at Bragg condition Imaging under controlled diffraction conditions
  9. 9. 8 Fe-22Mn-0.6C (wt%) TWIP steel High resolution EBSD ECCI twins Dislocation cells Comparison EBSD-ECCI Electron Channeling Contrast Imaging
  10. 10. 9 SEM
  11. 11. 10 SEM TEM
  12. 12. 11 ECCI / SEM (-220) Dislocation cells are clearly seen by ECCI TEM-Bright Field Fe-22Mn-0.6C (wt%) TWIP steel Electron Channeling Contrast Imaging I. Gutierrez-Urrutia et al. Scripta Mater. 61 (2009) 737-740
  13. 13. 12 0 500 1000 1500 2000 2500 3000 3500 4000 0 0.1 0.2 0.3 0.4 0.5 True stress Hardening (MPa) Hardening/Stress(MPa) True strain YS: 210 MPa UTS: 1200 MPa Ductility: 51% strain rate: 2.5x10-4 s-1 tensile test, room temperature 10% 20% 40% TA twins TA step size: 50 nm twins do not provide much strain but the 2nd hardening plateau EBSD: Work hardening of TWIP steels, Fe-22Mn-0.6C (wt%) I. Gutierrez-Urrutia et al. Scripta Mater. 61 (2009) 737-740
  14. 14. 0 500 1000 1500 2000 2500 3000 3500 4000 0 0.1 0.2 0.3 0.4 0.5 True stress Hardening (MPa) Hardening/Stress(MPa) True strain YS: 210 MPa UTS: 1200 MPa Ductility: 51% strain rate: 2.5x10-4 s-1 2% 10% 25% 35% 2nd hardening stage: 2%<e< 10% -Planar slip structures + wavy structures -Few mechanical twins* ECCI: Work hardening of TWIP steels, Fe-22Mn-0.6C (wt%) I. Gutierrez-Urrutia et al. Scripta Mater. 61 (2009) 737-740
  15. 15. 2nd hardening stage: 2%<e< 10% ECCI: Work hardening of TWIP steels, Fe-22Mn-0.6C (wt%) I. Gutierrez-Urrutia, et al. Mater. Sc. Engin. A 527 (2010) 3552
  16. 16. 0 500 1000 1500 2000 2500 3000 3500 4000 0 0.1 0.2 0.3 0.4 0.5 True stress Hardening (MPa) Hardening/Stress(MPa) True strain YS: 210 MPa UTS: 1200 MPa Ductility: 51% strain rate: 2.5x10-4 s-1 2% 10% 25% 35% 3rd hardening stage: 10%<e< 25% -Wavy structures: dislocation cells -Mechanical twins -3 Types of grains ECCI: Work hardening of TWIP steels, Fe-22Mn-0.6C (wt%) I. Gutierrez-Urrutia, et al. Mater. Sc. Engin. A 527 (2010) 3552
  17. 17. 3rd hardening stage: 10%<e< 25% ECCI: Work hardening of TWIP steels, Fe-22Mn-0.6C (wt%) I. Gutierrez-Urrutia, et al. Mater. Sc. Engin. A 527 (2010) 3552
  18. 18. 0 500 1000 1500 2000 2500 3000 3500 4000 0 0.1 0.2 0.3 0.4 0.5 True stress Hardening (MPa) Hardening/Stress(MPa) True strain YS: 210 MPa UTS: 1200 MPa Ductility: 51% strain rate: 2.5x10-4 s-1 2% 10% 25% 35% 5th hardening stage: 35%<e< 50% -Wavy structures: dislocation cells -Mechanical twins -3 Types of grains ECCI: Work hardening of TWIP steels, Fe-22Mn-0.6C (wt%) I. Gutierrez-Urrutia, et al. Mater. Sc. Engin. A 527 (2010) 3552
  19. 19. 5th hardening stage: 35%<e< 50% ECCI: Work hardening of TWIP steels, Fe-22Mn-0.6C (wt%) I. Gutierrez-Urrutia, et al. Mater. Sc. Engin. A 527 (2010) 3552
  20. 20. Type I 5th hardening stage: 35%<e< 50% ECCI: Work hardening of TWIP steels, Fe-22Mn-0.6C (wt%) I. Gutierrez-Urrutia, et al. Mater. Sc. Engin. A 527 (2010) 3552
  21. 21. Type II 5th hardening stage: 35%<e< 50% ECCI: Work hardening of TWIP steels, Fe-22Mn-0.6C (wt%) I. Gutierrez-Urrutia, et al. Mater. Sc. Engin. A 527 (2010) 3552
  22. 22. Type III 5th hardening stage: 35%<e< 50% ECCI: Work hardening of TWIP steels, Fe-22Mn-0.6C (wt%) I. Gutierrez-Urrutia, et al. Mater. Sc. Engin. A 527 (2010) 3552
  23. 23. 0 20 40 60 80 100 0.05 0.1 0.2 0.4 DDW+Cells DDW+Cells+Twins Type I Type II Type III % True strain Type of grain Interface statistics I. Gutierrez-Urrutia, et al. Mater. Sc. Engin. A 527 (2010) 3552
  24. 24. Most of the grains follow the Schmid’s Law (3/4) True strain: 40% EBSD: Growth of deformation twins in TWIP steels I. Gutierrez-Urrutia, et al. Mater. Sc. Engin. A 527 (2010) 3552
  25. 25. True strain: 40% Some of the grains follow the Schmid’s Law EBSD: Growth of deformation twins in TWIP steels I. Gutierrez-Urrutia, et al. Mater. Sc. Engin. A 527 (2010) 3552
  26. 26. True strain: 40% 1-2activated twinning systems nucleated at grain boundaries No twins inside the grain (few degrees from [001]) EBSD: Growth of deformation twins in TWIP steels I. Gutierrez-Urrutia, et al. Mater. Sc. Engin. A 527 (2010) 3552
  27. 27. Grains with “low” twinning activity: -Short twins (less than 5 microns length) -Few twins EBSD: Growth of deformation twins in TWIP steels I. Gutierrez-Urrutia, et al. Mater. Sc. Engin. A 527 (2010) 3552
  28. 28. Grains with “high” twinning activity: -Long twins -Thick bundles of twins -High population of twins These results suggest a Sslip/Stwinning relationship on twin growth EBSD: Growth of deformation twins in TWIP steels I. Gutierrez-Urrutia, et al. Mater. Sc. Engin. A 527 (2010) 3552
  29. 29. Type I 3rd hardening stage: 10%<e< 25% ECCI: Work hardening of TWIP steels, Fe-22Mn-0.6C (wt%) I. Gutierrez-Urrutia, et al. Mater. Sc. Engin. A 527 (2010) 3552
  30. 30. Type II 3rd hardening stage: 10%<e< 25% ECCI: Work hardening of TWIP steels, Fe-22Mn-0.6C (wt%) I. Gutierrez-Urrutia, et al. Mater. Sc. Engin. A 527 (2010) 3552
  31. 31. Type III 3rd hardening stage: 10%<e< 25% ECCI: Work hardening of TWIP steels, Fe-22Mn-0.6C (wt%) I. Gutierrez-Urrutia, et al. Mater. Sc. Engin. A 527 (2010) 3552
  32. 32. 31 Fe22Mn0.6C TWIP steel Mechanical twins Dislocation cells Electron Channeling Contrast Imaging I. Gutierrez-Urrutia, et al. Mater. Sc. Engin. A 527 (2010) 3552
  33. 33. EBSD: Growth of deformation twins in TWIP steels I. Gutierrez-Urrutia, et al. Mater. Sc. Engin. A 527 (2010) 3552
  34. 34. Dierk Raabe, MS&T, Pittsburgh, 27. Oct. 2009, MPIE Summary
  35. 35. 34 I. Gutierrez-Urrutia, S. Zaefferer, D. Raabe: Scripta Mater. 61 (2009) 737-740 Electron channeling contrast imaging of twins and dislocations in twinning- induced plasticity steels under controlled diffraction conditions in a scanning electron microscope I. Gutierrez-Urrutia, S. Zaefferer, D. Raabe: Mater. Sc. Engin. A 527 (2010) 3552-3560 The effect of grain size and grain orientation on deformation twinning in a Fe–22 wt.% Mn–0.6 wt.% C TWIP steel References
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