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

AbstractThe 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 (ΔT). 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 ΔT. Moreover, ΔT 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.