High-temperature mechanical and shape memory properties of TiPt–Zr and TiPt–Ru alloys

Ti–50Pt (all compositions in atomic %) alloy exhibits phase transformation from B2 phase having bcc crystal structure to orthorhombic martensitic (B19) phase above 1200 K. However, it exhibits a partial shape memory effect due to its low critical stress for slip deformation compared with the stress required for martensitic transformation. In order to improve the shape memory properties and strength of Ti–50Pt alloys at high temperature, this study examined the effects of partial substitution (e.g. 5 at%) of Ti with group IV (e.g. Zr) transition metals and the effects of partial substitution of Pt with platinum group (e.g. Ru) transition metals. The compressive strength and shape memory properties at high temperature were improved by partial substitution of Ti with Zr as well as by partial substitution of Pt with Ru in Ti–50Pt alloys: e.g., 1468 MPa for TiPt–Zr, 712 MPa for TiPt–Ru and 485 MPa for TiPt alloys. Furthermore, Ti–50Pt–5Zr alloy exhibited much higher strength and better shape memory effect than Ti–45Pt–5Ru alloy.