Influence of Heat Treatment on Phase Transformation of Ni-rich TiNi Foils Produced via Ultrafine Laminates

Abstract

Using the ultrafine laminate method, thin foils (50 μm) of Ni-rich TiNi shape memory alloys were produced. Overall composition of the Ti/Ni laminate is Ti-50.7%Ni. TiNi (B2) phase was obtained after different diffusion treatments at 1073 K for 259.2 ks and 1173 K for 36 ks and 259.2 ks. Aging treatments at 773 K for 3.6, 18, 36, 72 and 144 ks were also performed. Multiple step martensitic transformation was observed for aged samples. The shape memory strain was 3.69 × 10-2 in the sample aged at 773 K for 18 ks.