Fabrication, characterization and potential application of larger bulk Ti-Ni-Hf high temperature shape memory alloy composite reinforced by hybrid particles

The microstructure, martensitic transformation behaviour, mechanical and strain recovery characteristics of the sintered Ti-Ni-Hf alloy composites reinforced by hybrid particles were investigated systematically, which had an instructive significance on the production of larger and complex high temperature shape memory alloy composite parts with the high mechanical and functional performance. The results showed that multiple particles including the in-situ TiB whisker, residual TiB2 phase and the (Ti,Hf)(2) Ni phase were observed in all samples. The gradually increased TiB2 content resulted in the continuous decrease of the transformation temperature as a result of mechanical and compositional effect. Nevertheless, the transformation temperature (Ms) of the Ti-Ni-Hf alloy composite containing 1.5 wt% TiB2 was still above 100 degrees C, which can meet the requirement of high temperature applications. The hybrid reinforcements enhanced the matrix strength, and without sacrificing severely the compressive strain. In addition, the maximum completely recoverable strain of 6% can be obtained in the present composite. (C) 2018 Elsevier B.V. All rights reserved.