The shape memory effect in a Ti50Pd50 alloy

Shape memory alloys (SMA) have in the past few decades attracted considerable attention as new functional materials, with commercial applications in pipe couplings, electrical connectors, various actuators, medical use etc. Among many shape memory alloys, Ti-Ni alloys are used mostly because of excellent mechanical properties. However, the maximum temperatures they can be used at is about 373K, due to the limitations of available transformation temperatures. Thus, a strong need exists to develop high temperature shape memory alloys, to widen the applications of SMA. As such candidates, Ti-Pd and Ni-Al alloys systems and a Ti-Ni-Zr alloy look most hopeful. The martensitic transformation in the Ti-Pd alloy was first found by Donkersloot and Van Vucht. Khachin et al. systematically studied the pseudo-binary TiPd-TiNi alloy system, and determined the transformation temperatures and the structures of the martensites as a function of composition.