Effect of annealing on shape memory characteristics of Ti-50.85at.%Ni alloy

In order to clarify the effect of annealing on the shape memory behavior of Ti-50.85at.%Ni alloy, the deformation and transformation behavior were investigated using tensile tests and differential scanning calorimeter (DSC). The martensitic transformation temperature increases with increasing annealing temperature until it reach as a maximum, and then decreases with further increasing annealing temperature. This can be rationalized by interaction between the distribution of Ti ₃Ni ₄ precipitates and recovery of cold-worked structure. The R-phase transformation temperature increases with increasing annealing temperature until reaching a maximum, and then decreases with a further increase of annealing temperature. This is attributed to the change of Ni content in the matrix caused by precipitation of Ti ₃Ni ₄. The critical stress for slip decreases rapidly with increasing annealing temperature, influenced by interaction between the distribution of Ti ₃Ni ₄ precipitates and recovery of cold-worked structure.