The role of softening in elastic constant c₄₄ in martensitic transformation

To summarize the above, the simple picture of martensitic transformation only by basal plane shear and shuffle cannot explain all of MTs (e.g., TiNi), although it explains the most cases. Martensitic transformation with non-basal plane strain may occur, if non-basal plane distortions have strong enough correlation with the basal plane shear. The effect of alloying on the martensite structure is ascribed to its influence on the relavant correlation strength as well as on the harmonic energies through changing elastic constants and phonon energy. Based on this study, we conclude that the monoclinic martensite structure B19′ in TiNi alloy stems from a coupling between c′ shear and c₄₄ shear, in which the c₄₄ shear {001} <11̄0> creates the monoclinic distortion to the otherwise orthorhombic structure B19.