Shape memory effect and superelastic behavior of TiNi shape memory alloy processed by vacuum plasma spray method

Machining of TiNi shape memory alloy into a complicated three-dimensional (3D) shape is quite difficult, thus a near-net shape forming of 3D shaped TiNi alloy is attractive and cost-effective. Vacuum plasma spray (VPS) process is one of such near-net shape forming processes. In this paper, two kinds of thick TiNi layer, Ni-rich and Ti-rich compositions, were fabricated by VPS process and their shape memory effect (SME) and superelastic (SE) behaviors were characterized. As-VPS processed Ni-rich TiNi which was subjected to homogenization at 1163 K for 7.2 ks and subsequent aging at 773 K for 18 ks exhibited good martensitic transformation behavior. The recoverable strain of the TiNi alloys due to SME and SE behavior were measured to be 2.4% and 5.0%, respectively. The Ti-rich TiNi alloy also exhibited good martensitic transformation behavior and SME in the as-homogenized state.