The effect of heat treatment on the structural stability of TiNi alloys

Abstract

The influence of work hardening and subsequent isothermal annealing on the stability of the individual phases formed in TiNi shape memory alloys is investigated. Work hardening promotes the formation of the rhombohedral R phase. The matrix work hardening suppresses the phase transformation B2 --> B19'. It is assumed that the increase in dislocation density in the matrix reduces the mobility of phase boundaries during the phase transformations and reorientation processes, respectively. The stresses needed for the stress induced martensitic transformation and/or the reorientation processes are higher in the work-hardened matrix.