1. Compensation of residual stress in welds using phase transformation

3. How to reduce residual stress Temperature Stress +ve -ve 0 Reduce transformation temperature

4. Why martensite? To achieve minimum transformation temperature. Martensite transformation causes deformation. Under stress plates are aligned in favoured direction.

5. Alloy Design

7. Neural net analysis

8. Residual stress measurements using neutron diffraction Real time phase transformations using synchrotron X-rays Scanning electron microscopy Electron backscattered diffraction Final chemistry

9. Synchrotron Study

10. Synchrotron study Effect of external stress on transformation temperature and kinetics. Variant selection during martensite transformation. Nature of stress in various phases.

11. Synchrotron results

13. Crystallography Model

14. (a) BAIN STRAIN (c) Body-centered tetragonal austenite (d) Body-centered cubic martensite a a a 1 2 3 b 3 b 1 b 2 (b)

15. [100] [001] o a a' b b' o b a,a' (a) (b) (F B F) (F J F) (F S F)=(F B F) (F J F)

16. Austenite (a) w x y z Twinned Martensite Twin Boundary Correct macroscopic shape, correct structure x w z y z Slipped Martensite LATTICE -INVARIANT DEFORMATION x w y Observed shape, wrong structure P (b) w x z y 1 (F P F) RB (c) x wz y P 2 Martensite (wrong shape) (F J F) (F S F)=(F P F)(F J F)

17. [u v w] = (  J  ) [1 0 0] 24 variants of martensite (  J  ) Coordinate transformation matrix

18. Single crystal of austenite, poles of martensite 100  010 

19. Poly crystal 11 22 Relationship between two grains: (  1 J  2 ) [u v w]= (  1 J  2 )[1 0 0]

20. Future work Construction of pole figure in polycrystalline material Effect of stress on the pole figures

21. Thank you …