Aim of the work

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Compensation of residual stress in welds using
phase transformation
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How to reduce residual stress
ve
Stress
0
-ve
Temperature
Reduce transformation temperature
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Why martensite?
To achieve minimum transformation
temperature. Martensite transformation causes
deformation. Under stress plates are aligned in
favoured direction.
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Alloy Design
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Neural net analysis
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Final chemistry
Residual stress measurements using neutron
diffraction Real time phase transformations
using synchrotron X-rays Scanning electron
microscopy Electron backscattered diffraction
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Synchrotron Study
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Synchrotron study
Effect of external stress on transformation
temperature and kinetics. Variant selection
during martensite transformation. Nature of
stress in various phases.
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Synchrotron results
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Crystallography Model
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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
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001
(F B F)
b
b'
100
o
a'
a
b
(a)
o
b'
(F J F)
(b)
a,a'
(F S F)(F B F) (F J F)
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(F S F)(F P F)(F J F)
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24 variants of martensite
(g J a) Coordinate transformation matrix
u v w (g J a) 1 0 0
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Single crystal of austenite, lt0 0 1gt poles of
martensite
010 g
100 g
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Poly crystal
Relationship between two grains (g1 J g2)
u v w (g1 J g2)1 0 0
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Future work
Construction of pole figure in polycrystalline
material Effect of stress on the pole figures
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Thank you