Microstructures of Ti_50-0.5xNi_50-0.5xCu_x Alloys

By observation and analysis of the microstructures of Ti_50-0.5xNi_50-0.5xCu_x alloys, the effect of the Cu content on microstructures was investigated. When x = 2, the alloy mainly consists of NiTi (B2) phase and there is no CuNiTi phase. When x = 5, there is a little of CuNiTi phase in the microstructure before heat treatment. When x ≥ 10, network-like CuNiTi phase with big size forms. Heat treatment influences the microstructure. When x ≥ 5, a lot of needle-like CuNiTi phase precipitates and distributes dispersedly in NiTi phase after proper heat treatment. The precipitation of CuNiTi phase lowers the transformation temperature.