Characteristics of Ti50Pd30Ni20 high-temperature shape memory alloy

The decrease in critical stress for slip with increasing temperature leads to the introduction of permanent strain and thus deteriorates shape memory (SM) characteristics of high-temperature SM alloys. Thermomechanical treatment consisting of cold-rolling and subsequent annealing at various temperatures, was applied for the first time to improve the high-temperature SM characteristics of the Ti50Pd30Ni20 alloy. Then, a systematic study of transformation temperatures, microstructure and associated mechanical behaviour at 443-548K was carried out. The remarkable improvement in SM characteristics was found for the alloy cold-rolled to 24-25% reduction in thickness and annealed at 673K for 3.6 ks. In addition, superelasticity was observed for the first time in this alloy. Finally, the key factor for improvement of high-temperature SM characteristics in the alloy is pointed out.