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 Ti50Pd30Ni20 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 TiB2 precipitates with an average size larger than 1 μm are produced in Ti50Pd30Ni19.8B0.2 alloy due to proper heat treatments described in the text. These TiB2 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 Ti50Pd30Ni20 alloy, and the reason for this is discussed.