Strain Energy Criterion of Martensitic Transformation.
CALIFORNIA UNIV LOS ANGELES DEPT OF MATERIALS
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A new theory of martensitic transformation based on the minimization of total strain energy has been developed, where the plastic relaxation strain PRS concept is introduced in order to relieve the high internal stress due to martensitic transformation in Ti, Ti-Mn, -Cr, -Ta, and -Zr alloys. For the analysis of Ti martensite, a total of 84 glide and twin systems were evaluated as PRS. For oblate spheroids with aspect ratio less than 0.01, 1,0,-1,1 -1,0,1,2 twin, 1,0,-1,1 -1,-1,2,3 glide and 1,1,-2,2 -1,-1,2,3 glide or twin systems produced strain energy minima at shear strain less than 2, although crystal plasticity data of Paton and Backofen rules out the latter twin system. Theoretical predictions on habit plane in Ti, Ti-Ta and -Zr alloys turned out to be close to 334 sub B. In Ti-Mn and -Cr alloys, both 334 sub B and 344 sub B habit planes were predicted depending on the variant of 1,0,-1,1 -1,0,1,2 twin. These and other predictions are in excellent agreement with experimental observations.
- Properties of Metals and Alloys