Phase Transformation and Shape Memory Effect of Ti(Pt, Ir).

The martensitic transformation and shape memory effect of Ti(Pt, Ir) with 5-37.5 at. pct Ir were investigated using differential thermal analysis (DTA), high-temperature X-ray diffraction (HT-XRD), and compression tests. The austenite finish temperature, A, increased with increasing Ir content from 1331 K (1058 °C) in Ti-50 at. pct Pt to 1491 K (1218 °C) in Ti-12.5Pt-37.5Ir. The structure of the parent and martensite phases was identified as B2 and B19 in all tested alloys. A large strain recovery rate was obtained in Ti(Pt, Ir) with 10 to 30 at. pct Ir. The highest shape recovery ratio was 57 pct in Ti-25Pt-25Ir after deformation at 1123 K (850 °C), followed by heating to above A. Using HT-XRD, the dependence of lattice parameter change on Ir content and temperature was investigated. The volume change during phase transformation from B2 to B19 was estimated using the lattice parameter of the B2 and B19 phases. Strain recovery is discussed along with volume change and lattice parameter change. [ABSTRACT FROM AUTHOR]