CHARACTERISTICS OF TI50PD30NI20 HIGH-TEMPERATURE SHAPE-MEMORY ALLOY

The decrease in critical stress for slip with increasing temperature l eads to the introduction of permanent strain and thus deteriorates sha pe memory (SM) characteristics of high-temperature SM alloys. Thermome chanical treatment consisting of cold-rolling and subsequent annealing at various temperatures, was applied for the first time to improve th e 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 rema rkable improvement in SM characteristics was found-for the alloy cold- rolled to 24-25% reduction in thickness and annealed at 673K for 3.6 k s. In addition, superelasticity was observed for the first time in thi s alloy. Finally, the key factor for improvement of high-temperature S M characteristics in the alloy is pointed out.