Effect of Hot Rolling on the Microstructure and Shape Memory Effect of a NiTiHf High Temperature Shape Memory Alloy

Among NiTi-based high temperature shape memory alloys, NTiHf has received much attention due to high phase transformation temperatures, good thermal stability and low cost. But the ductility and the strength of the matrix is low which results in only about 3% shape memory effect. In this paper, the effect of hot rolling on the microstructure and shape memory effect of Ni50Ti35Hf15 is investigated. Vacuum induction melting process was utilized to prepare the ingot. After homogenizing at 1000 °C for 2 h,the sample was 45% deformed via hot rolling at 850 °C. icrostructure observation was carried out by optical microscopy and bending test was used to measure the shape memory effect (recovery strain). Results demonstrate that hot rolling improves the microstructure and shape memory effect .