Comparative Study of Shape Memory Effects in Ni-Rich Ti–Ni Alloy After Training in Various Phase States

Abstract

Six various training modes were used for a systematic study of the effect of the initial phase state when training procedure on shape memory effect (SME) and two-way SME (TWSME) in nanostructured Ti–50.7 at% Ni alloy. Two types of the B2 austenite structure were chosen: (1) the mixed structure consisting of nanosubgrained and nanograined structures (cold drawing with a true strain of e = 0.6 followed by aging 430 °C, 10 h,) and (2) recrystallized structure (annealing at 700 °C, 20 min followed by the same aging) with the average grain size of 10 μm. The SME and TWSME training procedure was performed in bending under load. Nanostructured material manifests the maximum recovery strain 14–14.7% as a result of using training modes involving R → B19′ transformation under load. The maximum TWSME value of 3.2–3.5% was realized in the material with both structure types.