Strain dependence of the Clausius-Clapeyron relation for thermoelastic martensitic transformations in NiTi

The temperature-stress dependence of thermoelastic martensitic transformations in shape memory alloys is a critical design tool for applications of these alloys in smart structures. This dependence has been most fundamentally expressed in a Clausius-Clapeyron linear relationship. This paper presents a theoretical analysis of this relationship, with particular attention given to the effect of the strain parameter in the equation for the case of equiatomic NiTi alloys. The theory is refined in two different forms describing two distinctive conditions corresponding to complete and incomplete stress-induced martensitic transformations. The conclusions of the analysis are used to clarify the mechanisms of post-plateau deformation of NiTi.