Recent progress on Ti-Ta-based high temperature shape memory alloys

Ti-Ta-based alloys have received increasing scientific attention during the last years as they combine specific properties which make them attractive as high temperature shape memory alloys (HTSMAs). Most importantly, they do not contain expensive noble metals, and they exhibit excellent ductility and cold workability. However, they are characterized by a limited microstructural and functional stability. During exposure to elevated temperatures different types of phases form which affect elemental processes of the martensitic transformation and thus shape memory behavior. In the present paper we provide an overview on metallurgical aspects of Ti-Ta-based HTSMAs. We show how phase transformation temperatures, hysteresis width, shape memory strain and microstructural/functional stability depend on alloy composition and microstructure. We show how Ti-Ta-based SMAs can be applied as actuators, and we present strategies to improve fatigue life. The presented results were obtained in frame of recent 6-year research program where these HTSMA were in focus.