EFFECT OF ANNEALING ON SHAPE MEMORY CHARACTERISTICS OF Ti-50.85at.%Ni ALLOY

Abstract

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 Ti3Ni4 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 Ti3Ni4. The critical stress for slip decreases rapidly with increasing annealing temperature, influenced by interaction between the distribution of Ti3Ni4 precipitates and recovery of cold-worked structure.