Design of TRIP-Assisted Steels for Automobiles

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Design of TRIP-Assisted Steels for Automobiles
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• Microstructure has been extensively studied
• Microstructure understood most aspects can be
  calculated
• Mechanical properties cannot be calculated
• Mechanical properties badly related to
  microstructure

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Typical composition Fe-0.15C-1.5Si-1.5Mn wt
Bhadeshia Edmonds, (1980)
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a
b
a
Bhadeshia Edmonds, (1980)
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Swallow Bhadeshia, 1996
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engineering stress / MPa
engineering strain
Mizui et al. (1997)
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Jacques et al. (2001)
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Ro et al. (1994)
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transformation-induced plasticity
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general invariant-plane strain
simple shear
uniaxial dilatation
s
s
d
d
1
1
1
s0.26 d0.03
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s
d
c
r
1
Transformation is a deformation on habit
plane Can be induced by stress
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Bhadeshia, 1982
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polycrystalline austenite
s
50 mm
Bhadeshia, 1982
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z3
z1
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v
u
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Sakuma et al. (1991)
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absorbed energy / kJ
Yoshitake et al. (1996)
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Composite of soft and hard phase
Bhadeshia Edmonds, (1980)
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Strain in hard phase
strain in soft phase
Bhadeshia Edmonds, (1980)
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Tomota (1976)
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Bhadeshia Edmonds, (1980)
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Chester and Bhadeshia, 1997
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Chester and Bhadeshia, 1997
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Chester and Bhadeshia, 1997
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Chester and Bhadeshia, 1997
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high silicon
low silicon
silicon causes scale
Jacques et al. (2001)
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Summary

• Assistance from TRIP is less than 1.4 of total
  strain
• Emphasis could be shifted from retained austenite
  to studies of composite deformation
• Low silicon steels can perform well (Jacques)