Design of TRIP-Assisted Steels for Automobiles

1. Design of TRIP-Assisted Steels for Automobiles

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

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

4. a b a Bhadeshia & Edmonds, (1980)

5. Swallow & Bhadeshia, 1996

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

9. Jacques et al. (2001)

10. Ro et al. (1994)

12. 50 mm transformation-induced plasticity

14. general invariant-plane strain simple shear uniaxial dilatation s s d d 1 1 1 s=0.26 d=0.03

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

16. Bhadeshia, 1982

19. polycrystalline austenite s 50 mm Bhadeshia, 1982

20. s d z3 z1

21. v u

22. Sakuma et al. (1991)

23. absorbed energy / kJ Yoshitake et al. (1996)

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

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

26. Tomota (1976)

27. Bhadeshia & Edmonds, (1980)

28. Chester and Bhadeshia, 1997

30. Chester and Bhadeshia, 1997

31. Chester and Bhadeshia, 1997

32. Chester and Bhadeshia, 1997

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

34. 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)