Recent Developments in High-Temperature Shape Memory Thin Films

Abstract

High-temperature shape memory alloy (HTSMA) thin films are candidates for development of microactuators with operating temperatures exceeding 100 °C. This article reviews recent advances and developments in the field of HTSMA thin films during the past decade, with focus on the systems Ti–Ni–X (X = Hf, Zr, Pd, Pt and Au), Ti–Ta, and Au–Cu–Al. These actuator films offer a wide range of transformation temperatures, thermal hysteresis, and recoverable strains suitable for high-temperature applications. Promising alloy compositions in the systems Ti–Ni–Hf, Ti–Ni–Pd, Ti–Ni–Au, and Au–Cu–Al are highlighted for further upscaling and development. The remaining challenges as well as prospects for development of HTSMA thin films are also discussed.