Design of TRIP-Assisted Steels for Automobiles

Microstructure has been extensively studied Microstructure understood: most aspects can be calculated Mechanical properties cannot be calculated Mechanical properties badly related to microstructure

Bhadeshia & Edmonds, (1980) Typical composition: Fe-0.15C-1.5Si- 1.5Mn wt%

Bhadeshia & Edmonds, (1980)   b

Swallow & Bhadeshia, 1996

engineering strain engineering stress / MPa Mizui et al. (1997)

Jacques et al. (2001)

Ro et al. (1994)

transformation-induced plasticity 50  m

 s 1 s 1  1 uniaxial dilatation simple shear general invariant-plane strain s=0.26  =0.03

c r  s 1 Transformation is a deformation on habit plane Can be induced by stress

Bhadeshia, 1982

 50  m polycrystalline austenite Bhadeshia, 1982

 s z3z3 z1z1

u v

Sakuma et al. (1991)

absorbed energy / kJ Yoshitake et al. (1996)

Bhadeshia & Edmonds, (1980) Composite of soft and hard phase

Bhadeshia & Edmonds, (1980) strain in soft phase Strain in hard phase

Tomota (1976)

Bhadeshia & Edmonds, (1980)

Chester and Bhadeshia, 1997

low silicon high silicon Jacques et al. (2001) silicon causes scale

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)