Microstructure evolution during recrystallization
of dual-phase steels
N. Perannio*, M. Calcagnotto, B. Springub**, M. Feu...
Overview
1
2
Motivation, outline and strategy
Overview
Calcagnotto et al. Mater. Sc. Engin. A 527 (2010) 2738 3
4
 hot band: 70% ferrite, 30% pearlite; 0.147 wt% C, 1.9 wt. % Mn, 0.4 wt.% Al
 cold band: 43%, 50%, 63%
 Annealing: sa...
5
Intercritical deformation and isothermal holding
PF
Ar3
Hot Deformation
T
t
Large Strain
Warm Deformation
e=1.6
Annealin...
Overview
Peranio et al: Mater Sc Engin A 527 (2010) 4161 6
7
Texture and microstructure–rolled, annealed, through thickness
Peranio et al: Mater Sc Engin A 527 (2010) 4161
8
Texture and microstructure–rolled, annealed, through thickness
Peranio et al: Mater Sc Engin A 527 (2010) 4161
9
Results - EBSD – cold rolled
cold rolled, center of sample
pearlite
ferrite
unfiltered
 image quality signal allows sep...
10
inverse pole figures and ODF, cold rolled, center
 <110> parallel RD (a-fiber), {111} parallel ND (g-fiber)
 typical ...
11
Microstructure and texture evolution – hot band through thickness
Recrystallization dual phase steels
phase changes in dual phase steels
intercritical
annealing
deformed ferrite pearlite
s...
13
Texture evolution –rolled, annealed, through thickness
Peranio et al: Mater Sc Engin A 527 (2010) 4161
14
Texture: recrystallization-transformation, through thickness
15
Competition: recrystallization -transformation, through thickness
Calcagnotto et al. Mater. Sc. Engin. A 527 (2010) 273...
16
Competition: recrystallization -transformation, through thickness
Peranio et al: Mater Sc Engin A 527 (2010) 4161
17
Microstructure evolution
Calcagnotto, Ponge, Raabe: ISIJ 48 (2008) 1096
18
Competition: recrystallization -transformation, through thickness
Peranio et al: Mater Sc Engin A 527 (2010) 4161
Overview
19
20
Instrument overview
• Scanning electron microscope (SEM)
– observation of microstructure
SEM & FIB:
Zeiss
Crossbeam 154...
sample in
cutting position
(36° tilt)
e-
e-
sample in
EBSD position
(70° tilt)
ion milling
to EBSD detector
electron
beam
...
22
3D EBSD: joint FIB-EBSD tomography (Zeiss; FEI)
• Increase phase space of microstructure analysis
6D (j1,f,j2,x,y,z): C...
23
From local misorientations to GNDs
misorientation
orientation gradient
(spacing d from EBSD scan)
Demir, Raabe, Zaafara...
24
From local misorientations to GNDs
distortion
(sym, a-sym)
dislocation tensor (GND)
J. F. Nye. Some geometrical relatio...
25
From local misorientations to GNDs
Frank loop through area r
18 b,t combinations
9 b,t combinations
Demir, Raabe, Zaafa...
26
martensite
ferrite
111
001 101
3D EBSD analysis of DP microstructure and texture
Calcagnotto et al. Mater. Sc. Engin. A...
27
Image Quality Kernel Average Misorientation
(martensite highlighted in black)
3D EBSD analysis of DP microstructure and...
28
GND analysis of DP microstructure and texture
Calcagnotto, Ponge, Raabe: ISIJ 48 (2008) 1096
Zaefferer, Wright, Raabe: ...
29
ferrite-ferrite interfaces
ferrite-martensite interfaces
3D GND analysis of DP microstructure
Calcagnotto et al. Mater....
Overview
30
31
Ultrafine grained DP steels
Calcagnotto et al. Mater. Sc. Engin. A 527 (2010) 2738
all with ca. 30% martensite
32
Effect on microstructure
effect of deformation
effect of holding time
a) ε = 0, t = 1 min
b) ε = 0.5, t = 1 min
c) ε = ...
33
Effect on retained austenite fraction
effect of deformation
effect of holding time
RD
ND
b) ε = 0.3, t = 1 min
γ = 3.4 ...
34
35
36
Coarse grained DP (12.4 µm)
Berkovich 50 nm
Constant load 500 µN
3D GND analysis of DP microstructure
Calcagnotto et al...
Overview
Calcagnotto et al. Mater. Sc. Engin. A 527 (2010) 2738 37
38
Simulation of recrystallization (CA & Calphad & DICTRA)
39
Simulation of recrystallization (CA & Calphad & DICTRA)
Java based
 Windows
 Linux
 Apple OS X
40
Simulation of forming (CPFEM, virtual lab, yield surface)
Kraska, Doig, Tikhomirov, Raabe, Roters, Comp. Mater. Sc. 46 ...
41
Simulation of forming (CPFEM, virtual lab, yield surface)
Kraska, Doig, Tikhomirov, Raabe, Roters, Comp. Mater. Sc. 46 ...
Overview
Calcagnotto et al. Mater. Sc. Engin. A 527 (2010) 2738 42
Conclusions
43
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Dierk Raabe D P Steel R X&amp; G G 2010 Sheffield

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Dierk Raabe D P Steel R X&amp; G G 2010 Sheffield

  1. 1. Microstructure evolution during recrystallization of dual-phase steels N. Perannio*, M. Calcagnotto, B. Springub**, M. Feucht***, D. Raabe, F. Roters, D. Ponge, S. Zaefferer Düsseldorf, Germany WWW.MPIE.DE d.raabe@mpie.de RX&GG iV 5, July 2010 Sheffield, UK * Inst. f. Physik, Universität Tübingen, Germany ** Salzgitter Mannesmann Forschung, Salzgitter, Germany *** Daimler AG, Sindelfingen, Germany
  2. 2. Overview 1
  3. 3. 2 Motivation, outline and strategy
  4. 4. Overview Calcagnotto et al. Mater. Sc. Engin. A 527 (2010) 2738 3
  5. 5. 4  hot band: 70% ferrite, 30% pearlite; 0.147 wt% C, 1.9 wt. % Mn, 0.4 wt.% Al  cold band: 43%, 50%, 63%  Annealing: salt bath, conductive, hot dip galvanizing  temperature 740°C≈Ac1, 860°C≈Ac3, 920°C  time 100 s, 200 s, 300 s  cooling rate 7 K/s, 15 K/s, 22 K/s  heating rate 10 K/s, 20 K/s, 30 K/s Experiments Peranio et al: Mater Sc Engin A 527 (2010) 4161 Fe C Si Mn P N N bal. 0.147 0.403 1.868 0.01 0.0056 0.0056 Cr Ni V Ti Nb Al Al 0.028 0.044 0.098 0.005 0.047 0.037 0.037
  6. 6. 5 Intercritical deformation and isothermal holding PF Ar3 Hot Deformation T t Large Strain Warm Deformation e=1.6 Annealing (2h) air cooling Intercritical Annealing  UFG F/M DP Ac1 e = 0.1, 0.3, 0.5 Intercritical Annealing  UFG F/M DP Ac1 t = 1 min, 10 min, 30 min 5Peranio et al: Mater Sc Engin A 527 (2010) 4161
  7. 7. Overview Peranio et al: Mater Sc Engin A 527 (2010) 4161 6
  8. 8. 7 Texture and microstructure–rolled, annealed, through thickness Peranio et al: Mater Sc Engin A 527 (2010) 4161
  9. 9. 8 Texture and microstructure–rolled, annealed, through thickness Peranio et al: Mater Sc Engin A 527 (2010) 4161
  10. 10. 9 Results - EBSD – cold rolled cold rolled, center of sample pearlite ferrite unfiltered  image quality signal allows separate analysis of the constituents  ferrite volume fraction 74%  grain size 4.8 mm, aspect ratio 0.26  large grains are deformed TD ND TD ND TD ND Peranio et al: Mater Sc Engin A 527 (2010) 4161
  11. 11. 10 inverse pole figures and ODF, cold rolled, center  <110> parallel RD (a-fiber), {111} parallel ND (g-fiber)  typical texture for bcc-materials TD ND TD ND ND RD large grains are closer to the a-fiber EBSD – cold rolled Peranio et al: Mater Sc Engin A 527 (2010) 4161
  12. 12. 11 Microstructure and texture evolution – hot band through thickness
  13. 13. Recrystallization dual phase steels phase changes in dual phase steels intercritical annealing deformed ferrite pearlite strain free austenite recrystallized ferrite recovered ferrite room temperature recrystallized/ strain free ferrite recovered/strained ferrite martensite cold rolled 12Peranio et al: Mater Sc Engin A 527 (2010) 4161
  14. 14. 13 Texture evolution –rolled, annealed, through thickness Peranio et al: Mater Sc Engin A 527 (2010) 4161
  15. 15. 14 Texture: recrystallization-transformation, through thickness
  16. 16. 15 Competition: recrystallization -transformation, through thickness Calcagnotto et al. Mater. Sc. Engin. A 527 (2010) 2738 annealing time Effect of annealing time on martensite content Effect of annealing process / rates on martensite content Effect of through-thickness inhomogeneity
  17. 17. 16 Competition: recrystallization -transformation, through thickness Peranio et al: Mater Sc Engin A 527 (2010) 4161
  18. 18. 17 Microstructure evolution Calcagnotto, Ponge, Raabe: ISIJ 48 (2008) 1096
  19. 19. 18 Competition: recrystallization -transformation, through thickness Peranio et al: Mater Sc Engin A 527 (2010) 4161
  20. 20. Overview 19
  21. 21. 20 Instrument overview • Scanning electron microscope (SEM) – observation of microstructure SEM & FIB: Zeiss Crossbeam 1540 EBSD system: TSL with Hikari camera • Quantitative images with EBSD and EDX – quantitative characterisation of microstructure • Scanning Ga+-ion microscope (FIB = focused ion beam) – sputtering of material for serial sectioning Zaefferer et al., Met. Mater. Trans. 39A (2008) 374
  22. 22. sample in cutting position (36° tilt) e- e- sample in EBSD position (70° tilt) ion milling to EBSD detector electron beam tilt 34 ° alignment marker EBSD camera SEM objective lens Ga+ 21 Principle of serial sectioning & orientation microscopy Konrad et al. Acta Mater. 54 (2006) 1369
  23. 23. 22 3D EBSD: joint FIB-EBSD tomography (Zeiss; FEI) • Increase phase space of microstructure analysis 6D (j1,f,j2,x,y,z): Crystallography and texture with morphology 8D (j1,f,j2,h,k,x,y,z): Interface crystallography (interface texture) • Spatial texture and phases (connectivity, percolation, correlations) • FIB, EBSD, EDX Review: Zaefferer et al., Met. Mater. Trans. 39A, (2008) 374 Konrad et al. Acta Mater. 54 (2006) 1369 GND (Kröner-Nye)
  24. 24. 23 From local misorientations to GNDs misorientation orientation gradient (spacing d from EBSD scan) Demir, Raabe, Zaafarani, Zaefferer: Acta Mater. 57 (2009) 559 orientation difference
  25. 25. 24 From local misorientations to GNDs distortion (sym, a-sym) dislocation tensor (GND) J. F. Nye. Some geometrical relations in dislocated crystals. Acta Metall. 1:153, 1953. E. Kröner. Kontinuumstheorie der Versetzungen und Eigenspannungen (in German). Springer, Berlin, 1958. E. Kröner. Physics of defects, chapter Continuum theory of defects, p.217. North-Holland Publishing, Amsterdam, Netherlands, 1981. Demir, Raabe, Zaafarani, Zaefferer: Acta Mater. 57 (2009) 559
  26. 26. 25 From local misorientations to GNDs Frank loop through area r 18 b,t combinations 9 b,t combinations Demir, Raabe, Zaafarani, Zaefferer: Acta Mater. 57 (2009) 559
  27. 27. 26 martensite ferrite 111 001 101 3D EBSD analysis of DP microstructure and texture Calcagnotto et al. Mater. Sc. Engin. A 527 (2010) 2738 3D EBSD experiment
  28. 28. 27 Image Quality Kernel Average Misorientation (martensite highlighted in black) 3D EBSD analysis of DP microstructure and texture Calcagnotto et al. Mater. Sc. Engin. A 527 (2010) 2738 3D EBSD experiment
  29. 29. 28 GND analysis of DP microstructure and texture Calcagnotto, Ponge, Raabe: ISIJ 48 (2008) 1096 Zaefferer, Wright, Raabe: Metal. Mater. Trans. A 39A (2008) 374Demir, Raabe, Zaafarani, Zaefferer: Acta Mater. 57 (2009) 559
  30. 30. 29 ferrite-ferrite interfaces ferrite-martensite interfaces 3D GND analysis of DP microstructure Calcagnotto et al. Mater. Sc. Engin. A 527 (2010) 2738
  31. 31. Overview 30
  32. 32. 31 Ultrafine grained DP steels Calcagnotto et al. Mater. Sc. Engin. A 527 (2010) 2738 all with ca. 30% martensite
  33. 33. 32 Effect on microstructure effect of deformation effect of holding time a) ε = 0, t = 1 min b) ε = 0.5, t = 1 min c) ε = 0, t = 30 min RD ND 1 µm 1 µm 1 µm
  34. 34. 33 Effect on retained austenite fraction effect of deformation effect of holding time RD ND b) ε = 0.3, t = 1 min γ = 3.4 % γ = 0.2 % c) ε = 0, t = 10 min a) ε = 0, t = 1 min γ = 2.6 %
  35. 35. 34
  36. 36. 35
  37. 37. 36 Coarse grained DP (12.4 µm) Berkovich 50 nm Constant load 500 µN 3D GND analysis of DP microstructure Calcagnotto et al. Mater. Sc. Engin. A 527 (2010) 2738
  38. 38. Overview Calcagnotto et al. Mater. Sc. Engin. A 527 (2010) 2738 37
  39. 39. 38 Simulation of recrystallization (CA & Calphad & DICTRA)
  40. 40. 39 Simulation of recrystallization (CA & Calphad & DICTRA) Java based  Windows  Linux  Apple OS X
  41. 41. 40 Simulation of forming (CPFEM, virtual lab, yield surface) Kraska, Doig, Tikhomirov, Raabe, Roters, Comp. Mater. Sc. 46 (2009) 383 Together with Mercedes, FhG, Volkswagen, Audi, Inpro Roters et al. Acta Mater.58 (2010)
  42. 42. 41 Simulation of forming (CPFEM, virtual lab, yield surface) Kraska, Doig, Tikhomirov, Raabe, Roters, Comp. Mater. Sc. 46 (2009) 383 Together with Inpro, Berlin Tension 0° (RD) Tension 90° (Querrichtung) Tension biaxial Tension 45° RVE from annealed DP
  43. 43. Overview Calcagnotto et al. Mater. Sc. Engin. A 527 (2010) 2738 42
  44. 44. Conclusions 43

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