High-Temperature Shape Memory Effect in Ti-Ta Thin Films Sputter Deposited at Room Temperature

Ti-Ta based alloys are potential high-temperature shape memory materials with operation temperatures above 100 °C. In this study, the room temperature fabrication of Ti-Ta thin films showing a reversible martensitic transformation and a high temperature shape memory effect above 200 °C is reported. In contrast to other shape memory thin films, no further heat treatment is necessary to obtain the functional properties. A disordered α″ martensite (orthorhombic) phase is formed in the as-deposited co-sputtered Ti70Ta30, Ti68Ta32 and Ti67Ta33 films, independent of the substrate. A Ti70Ta30 free-standing film shows a reversible martensitic transformation, as confirmed by temperature–dependent XRD measurements during thermal cycling between 125 °C to 275 °C. Furthermore, a one-way shape memory effect is qualitatively confirmed in this film. The observed properties of the Ti-Ta thin films make them promising for applications on polymer substrates and especially in microsystem technologies.