Thermal and mechanical properties of high-temperature shape memory alloys in non-equal molar CuNiTiHfZr HEA(Invited Speaker)

The non-equal molar CuNiTiHfZr HEAs were developed for high-temperature shape memory effect. The alloying elements are divided into two groups, (CuNi)50 and (TiHfZr)50. The content of Cu in (CuNi)50 is modulated to investigate the influences of Cu on martensitic transformation of the HEAs by studying structural evolution and transformation behavior at elevated temperature. The as-cast of Cu₁₅Ni₃₅Ti₂₅Hf_12.5Zr_12.5 has shown exhibited a shape recovery ratio of 88.7% under an immense stress of 1400 MPa. By an in-situ high-temperature X-ray diffractometer, the alloy was established to undergo phase transformation from B19’ to B2 phase from ambient temperature to 400 ^oC. The thermal stability and compressive property are discussed. After homogenization. The cast of dendrites and inter-dendrites is eliminated, resulting in a reduction in the phase transformation temperatures by XRD and DSC curves indicated the presence of B2 peaks in the as-homogenized states, demonstrating a decrease in phase transformation temperatures. Mechanical properties, such as elongation and hardness, were improved due to the uniform microstructures achieved after homogenization.