Dierk Raabe D P Steel R X& G G 2010 Sheffield
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The document summarizes research on the microstructure evolution during recrystallization of dual-phase steels. Key points include: - Experiments were conducted on hot-rolled and cold-rolled dual-phase steel compositions with varying annealing temperatures, times, and cooling/heating rates. - Microstructure and texture were characterized through electron backscatter diffraction and scanning electron microscopy. Recrystallization and phase transformations were studied through thickness. - Numerical simulations were also used to model recrystallization, forming processes, and yield surfaces to complement experimental findings. - The competition between recrystallization and phase transformations, and their effect on microstructure, texture, and retained austenite fraction were
Dierk Raabe D P Steel R X& G G 2010 Sheffield
- 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. Overview 1
- 3. 2 Motivation, outline and strategy
- 4. Overview Calcagnotto et al. Mater. Sc. Engin. A 527 (2010) 2738 3
- 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. 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. Overview Peranio et al: Mater Sc Engin A 527 (2010) 4161 6
- 8. 7 Texture and microstructure–rolled, annealed, through thickness Peranio et al: Mater Sc Engin A 527 (2010) 4161
- 9. 8 Texture and microstructure–rolled, annealed, through thickness Peranio et al: Mater Sc Engin A 527 (2010) 4161
- 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. 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. 11 Microstructure and texture evolution – hot band through thickness
- 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. 13 Texture evolution –rolled, annealed, through thickness Peranio et al: Mater Sc Engin A 527 (2010) 4161
- 15. 14 Texture: recrystallization-transformation, through thickness
- 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. 16 Competition: recrystallization -transformation, through thickness Peranio et al: Mater Sc Engin A 527 (2010) 4161
- 18. 17 Microstructure evolution Calcagnotto, Ponge, Raabe: ISIJ 48 (2008) 1096
- 19. 18 Competition: recrystallization -transformation, through thickness Peranio et al: Mater Sc Engin A 527 (2010) 4161
- 20. Overview 19
- 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. 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. 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. 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. 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. 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. 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. 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. 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. 29 ferrite-ferrite interfaces ferrite-martensite interfaces 3D GND analysis of DP microstructure Calcagnotto et al. Mater. Sc. Engin. A 527 (2010) 2738
- 31. Overview 30
- 32. 31 Ultrafine grained DP steels Calcagnotto et al. Mater. Sc. Engin. A 527 (2010) 2738 all with ca. 30% martensite
- 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. 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. 34
- 36. 35
- 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. Overview Calcagnotto et al. Mater. Sc. Engin. A 527 (2010) 2738 37
- 39. 38 Simulation of recrystallization (CA & Calphad & DICTRA)
- 40. 39 Simulation of recrystallization (CA & Calphad & DICTRA) Java based Windows Linux Apple OS X
- 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. 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. Overview Calcagnotto et al. Mater. Sc. Engin. A 527 (2010) 2738 42
- 44. Conclusions 43