The effect of Pd content on microstructure and shape-memory properties of Ti–Ni–Pd–Cu alloys

The effect of Pd content on the microstructure and high-temperature shape memory properties of Ti–Ni–Pd–Cu alloys was investigated. The increase in Pd content led to the increase of transformation temperatures. The volume fraction of two types of precipitates (i.e. TiPdCu and Ti2Pd) also increased with increasing Pd content. Although the formation of these precipitates resulted in an increased resistance against the plastic deformation, the amount of recovery strain decreased during thermal cycling tests at various stress levels. By adjusting the heat treatment time, a high transformation temperature and large amount of recovery strain could be achieved while keeping the enough resistance against the plastic deformation.