Effects of boron addition on microstructure and mechanical properties of Ti–Td–Ni high-temperature shape memory alloys

Abstract The application of Ti–Pd–Ni high-temperature shape memory alloys to practical use is restricted due to their low critical stress for slip at high temperatures. About 0.2 at.% boron was added to a Ti 50 Pd 30 Ni 20 alloy to improve its high-temperature mechanical properties including high-temperature shape memory characteristics. The influence of boron on martensitic transformation temperatures, microstructure and high-temperature mechanical properties was studied. The results show that TiB 2 precipitates with an average size larger than 1 μ m are produced in Ti 50 Pd 30 Ni 19.8 B 0.2 alloy due to proper heat treatments described in the text. These TiB 2 precipitates seem to be distributed within grains, rather than to segregate to grain boundaries. The addition of boron is beneficial to high-temperature ductility of Ti–Pd–Ni alloy. The addition of boron has no noticeable influence on high-temperature shape memory characteristics of Ti 50 Pd 30 Ni 20 alloy, and the reason for this is discussed.