Effects of ageing on microstructure, martensitic transformation and shape memory performance of a Ni-rich Ti49.5Ni34.5Cu11.5Pd4.5 alloy

The ageing effects on the microstructure, martensitic transformation and shape memory performance of a Ni-rich Ti49.5Ni34.5Cu11.5Pd4.5 alloy as a function of temperature were investigated. The formation of (Ni,Cu)(2) Ti-type precipitated phases arises from the ageing treatment. When ageing at 500 degrees C, the fine precipitated phases are diffusely distributed, which improves the shape memory performance efficiently. With the tensile deformation of 5%, the 500 degrees C aged specimen shows a 25% larger strain recovery rate (a maximum value of 96.8%) than that of the specimen under solution treatment. And after 100 thermal cycles, the transformation temperature variation is lesser than 0.2 degrees C in the specimen aged at 500 degrees C. There presents excellent thermal cycling stability while keeping near-zero thermal hysteresis. (C) 2020 Elsevier B.V. All rights reserved.