Dierk Raabe D P Steel R X& G G 2010 Sheffield
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Transcript of Dierk Raabe D P Steel R X& G G 2010 Sheffield
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, [email protected]
RX&GG iV 5, July 2010 Sheffield, UK
* Inst. f. Physik, Universität Tübingen, Germany** Salzgitter Mannesmann Forschung, Salzgitter, Germany*** Daimler AG, Sindelfingen, Germany
Motivation
Experiments
Microstructure and texture evolution
3D tomographic analysis of interface regions and correlation to mechanical properties
Ultra-fine grained DP
Simulations
Conclusions
Overview
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High-strength ductile C-Mn DP steels for weight reduction
Microstructure evolution in hot rolled, cold rolled, and annealed DP
Intercritical annealing: recovery, recrystallization, phase transformation
Parameters: heating&cooling rates, temperature, time
Through-thickness inhomogeneity (texture, phases, grain size,….)
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Motivation, outline and strategy
Overview
Calcagnotto et al. Mater. Sc. Engin. A 527 (2010) 2738 4
Motivation
Experiments
Microstructure and texture evolution
3D tomographic analysis of interface regions and correlation to mechanical properties
Ultra-fine grained DP
Simulations
Conclusions
5
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
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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
6Peranio et al: Mater Sc Engin A 527 (2010) 4161
Overview
Peranio et al: Mater Sc Engin A 527 (2010) 4161 7
Motivation
Experiments
Microstructure and texture evolution
3D tomographic analysis of interface regions and correlation to mechanical properties
Ultra-fine grained DP
Simulations
Conclusions
8
Texture and microstructure–rolled, annealed, through thickness
Peranio et al: Mater Sc Engin A 527 (2010) 4161
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Texture and microstructure–rolled, annealed, through thickness
Peranio et al: Mater Sc Engin A 527 (2010) 4161
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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
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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
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Microstructure and texture evolution – hot band through thickness
Recrystallization dual phase steels
phase changes in dual phase steels
intercritical annealing
deformed ferrite pearlite
strain freeaustenite
recrystallizedferrite
recoveredferrite
room temperature
recrystallized/strain free
ferrite
recovered/strainedferrite
martensite
cold rolled
13Peranio et al: Mater Sc Engin A 527 (2010) 4161
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Texture evolution –rolled, annealed, through thickness
Peranio et al: Mater Sc Engin A 527 (2010) 4161
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Texture: recrystallization-transformation, through thickness
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Competition: recrystallization -transformation, through thickness
Calcagnotto et al. Mater. Sc. Engin. A 527 (2010) 2738
annealing time
Effect of annealing time on martensite contentEffect of annealing process / rates on martensite contentEffect of through-thickness inhomogeneity
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Competition: recrystallization -transformation, through thickness
Peranio et al: Mater Sc Engin A 527 (2010) 4161
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Microstructure evolution
Calcagnotto, Ponge, Raabe: ISIJ 48 (2008) 1096
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Competition: recrystallization -transformation, through thickness
Peranio et al: Mater Sc Engin A 527 (2010) 4161
Overview
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Motivation
Experiments
Microstructure and texture evolution
3D tomographic analysis of interface regions and correlation to mechanical properties
Ultra-fine grained DP
Simulations
Conclusions
21
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
sample in cutting position
(36° tilt)
e-
x-ra
ys
e-
sample in EBSD position
(70° tilt)
ion milling
to EBSD detector
electron beam
tilt 34 °
alignment marker
FIB column
EBSD camera
EDX
detector
SEM objective lens
Ga+
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Principle of serial sectioning & orientation microscopy
Konrad et al. Acta Mater. 54 (2006) 1369
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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)
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From local misorientations to GNDs
misorientation
orientation gradient(spacing d from EBSD scan)
Demir, Raabe, Zaafarani, Zaefferer: Acta Mater. 57 (2009) 559
orientation difference
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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
T TT
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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
T TT
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martensiteferrite
111
001 101
3D EBSD analysis of DP microstructure and texture
Calcagnotto et al. Mater. Sc. Engin. A 527 (2010) 2738
3D EBSD experiment
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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
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GND analysis of DP microstructure and texture
Calcagnotto, Ponge, Raabe: ISIJ 48 (2008) 1096
Zaefferer, Wright, Raabe: Metal. Mater. Trans. A 39A (2008) 374 Demir, Raabe, Zaafarani, Zaefferer: Acta Mater. 57 (2009) 559
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ferrite-ferrite interfaces
ferrite-martensite interfaces
3D GND analysis of DP microstructure
Calcagnotto et al. Mater. Sc. Engin. A 527 (2010) 2738
Overview
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Motivation
Experiments
Microstructure and texture evolution
3D tomographic analysis of interface regions and correlation to mechanical properties
Ultra-fine grained DP
Simulations
Conclusions
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Ultrafine grained DP steels
Calcagnotto et al. Mater. Sc. Engin. A 527 (2010) 2738
all with ca. 30% martensite
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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
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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 %
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Coarse grained DP (12.4 µm)
Berkovich 50 nmConstant load 500 µN
3D GND analysis of DP microstructure
Calcagnotto et al. Mater. Sc. Engin. A 527 (2010) 2738
Overview
Calcagnotto et al. Mater. Sc. Engin. A 527 (2010) 2738 38
Motivation
Experiments
Microstructure and texture evolution
3D tomographic analysis of interface regions and correlation to mechanical properties
Ultra-fine grained DP
Simulations
Conclusions
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Simulation of recrystallization (CA & Calphad & DICTRA)
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Simulation of recrystallization (CA & Calphad & DICTRA)
Java based
Windows Linux Apple OS X
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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)
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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
Overview
Calcagnotto et al. Mater. Sc. Engin. A 527 (2010) 2738 43
Motivation
Experiments
Microstructure and texture evolution
3D tomographic analysis of interface regions and correlation to mechanical properties
Ultra-fine grained DP
Simulations
Conclusions
Conclusions
Strong through-thickness gradients inherited from hot rolling
Competition between RX and PT depends strongly on heat treatment conditions
3D tomographic analysis of texture and micromechanics
Correlation of microstructure, texture, orientation gradients and interface strenght
Enabling CA/Thermocalc and CPFEM / YS simulations for industrial applications
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