PROPERTIES OF Ni-Ti-X SHAPE MEMORY ALLOYS PRODUCED BY ARC RE-MELTING

Abstract

This paper deals with Ni-Ti46 and Ni-Ti-X wt. % alloys prepared by arc re-melting under argon protective atmosphere. The melting was repeated three times to obtain a homogenous chemical composition of samples. Niobium, vanadium and silicon were chosen as alloying elements and they were added into the alloy in an amount of 5 wt. %. Microstructure, phase composition, hardness and transformation behaviour were investigated parameters. Properties of cast alloys are compared with alloys of the same chemical composition prepared by powder metallurgy method – self-propagating high-temperature synthesis (SHS). Arc re-melting produced a more homogeneous microstructure with a lower content of the Ti2Ni phase than powder metallurgy methods in case of Ni-Ti-X alloys. Quite a high amount of the secondary phase (a mixture of the Ni2Ti, NiTi and Ti2Ni phases) was created in the microstructure of Ni-Ti46 wt. % alloy. The addition of silicon caused an increase of transformation temperatures and hardness.