A New Prototype Two‐Phase (TiNi)–(β‐W) SMA System with Tailorable Thermal Hysteresis

Abstract

Abstract The Ti–Ni–W two‐phase shape memory alloy (SMA) thin film system is presented as a prototype for new SMAs with tailorable thermal transformation hysteresis (Δ T ). The concept is to combine the SMA TiNi with almost insoluble W to create the two‐phase system (TiNi)–( β ‐W). This system behaves like a pseudobinary TiNi system. Phase transformation behavior for compositions above the solubility limit of W in TiNi exhibit a B2–R phase transformation with characteristically small Δ T . Moreover, Δ T is dependent on the amount of W and it can be tailored to zero and even negative. This phenomenon is rationalized as being due to the mechanical interaction between the phases B2‐TiNi and β ‐W. The presented results are very promising for the development of high‐speed Ti–Ni‐based SMA actuators.