Influence of chemical composition on the amount of second phases precipitates and transformation temperatures of TiNiPdCu shape memory alloys prepared through novel powder metallurgy route.

Abstract

The chemical composition of TiNiPdCu high temperature shape memory alloys (HTSMAs) affects their microstructure and martensitic transformations. In TiNiPdC HTSMAs, second phase precipitates were found. Extremely high densities of nanoscale precipitates of TiPdCu and Ti2Pd of particle size 0.8-4.4 μm were found to be produced by the TiNiPdCu alloys. It was found that the TiPdCu-type precipitates were favoured by the preferential migration of Cu atoms towards the heterogeneous nucleation sites, which in turn favoured the fine Ti2Pd-type precipitates. Due primarily to their high-temperature stability, these precipitates significantly strengthened the resistance against transformation-induced plasticity and creep deformation, especially at high loads and high temperatures. High concentrations of these nanoscaled precipitates led to a significant rise in transformation temperatures by 12% and a small decrease in thermal hysteresis by 30%. It was anticipated that the current research findings will have a significant positive impact on the creation of HTSMAs that maintain their benefits of simplicity of manufacture. The HTSMAs developed in current research are beneficial for high temperature sensors and actuators at optimum cost.