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Compensation of residual stress in welds using phase transformation

Compensation of residual stress in welds using phase transformation. How to reduce residual stress. +ve. Stress. 0. -ve. Temperature. Reduce transformation temperature. Why martensite?. To achieve minimum transformation temperature. Martensite transformation causes deformation.

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Compensation of residual stress in welds using phase transformation

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  1. Compensation of residual stress in welds using phase transformation

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

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

  4. Alloy Design

  5. Neural net analysis

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

  7. Synchrotron Study

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

  9. Synchrotron results

  10. Crystallography Model

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

  12. [001] (F B F) b b' [100] o a' a b (a) (F J F) o b' (b) a,a' (F S F)=(F B F) (F J F)

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

  14. 24 variants of martensite (g J a) Coordinate transformation matrix [u v w] = (g J a) [1 0 0]

  15. Single crystal of austenite, <0 0 1> poles of martensite 010 g 100 g

  16. g1 g2 Poly crystal Relationship between two grains: (g1 J g2) [u v w]= (g1 J g2)[1 0 0]

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

  18. Thank you …

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