Effect of thermo-mechanical treatment on Ti-Ta-Hf high temperature shape memory alloy

The microstructure, martensitic transformation and mechanical/functional properties of Ti-Ta-Hf alloys with various thermo-mechanical treatments were investigated. The results reveal that the hot-rolling could refine the grain size and introduce a certain number of defects, resulting in the disappearance of martensitic transformation. The as-casted and solution treated Ti-Ta-Hf alloys were composed of alpha"martensite phase and smaller volume of beta phase. In contrast, the grain size of solution treated Ti-Ta-Hf alloy was slightly less than that of as-casted Ti-Ta-Hf alloy. This should be responsible to the higher yield stress and superior strain recovery characteristics for solution treated Ti-Ta-Hf alloy. The yield stress for the dislocation slip and the maximum recoverable strain of solution treated Ti-Ta-Hf alloy were 723 MPa and 5.06%, respectively.