Thermomechanical cyclic stability of porous NiTi shape memory alloy

Abstract

It is known that shape memory and phase transition response of NiTi shape memory alloy (SMA) is dependent on mechanical or thermal background, and the presence of phases such as B2(NiTi), B19'(NiTi), Ni4Ti3, Ni3Ti2 and NiTi2. The volume fraction of metastable Ni4Ti3 phase in NiTi matrix can be easily changed by heat treatments. Both Ni4Ti3 phases and Ni ingredient affect the phase transition kinetics and the shape memory response. This work deals with the effect of thermomechanical cycling on the shape memory response of a porous Ni50.8Ti49.2 SMA, which is homogenized at 1050 degrees C and aged at 800 degrees C, afterwards slow cooled. Full recoverable shape memory response and cyclic stability were achieved during thermomechanical cycling under a compressive stress of 5 MPa