Effect of deformation by stress-induced martensitic transformation on the transformation behaviour of NiTi

Abstract It has been reported that martensite in near-equiatomic NiTi is thermally stabilised after a moderate deformation via martensite reorientation. This work continues the study by investigating the effect of deformation via stress-induced martensitic transformation on the transformation behaviour of the alloy. It was observed that the stress-induced martensite was also stabilised relative to the thermal martensite formed on cooling, as indicated by an increase in the critical temperature for the reverse transformation. Associated with the stabilisation, the heat effect, as determined by differential scanning calorimetry, and the temperature interval of the reverse transformation, were measured and found to decrease with increasing level of deformation. The experimental results also demonstrated that the stress-induced martensitic transformation was microscopically localised, as expected for a first-order phase transformation.