The higher compressive strength (TiB+La2O3)/Ti–Ni shape memory alloy composite with the larger recoverable strain

Abstract In the present study, in-situ TiB whiskers and La2O3 particles showing a network structure were designed and introduced into Ti–Ni composites. With LaB6 content increasing, the amount of in-situ TiB whiskers and La2O3 particles also increases. In addition to the in-situ reinforcements, Ti2Ni second phase also precipitates. The B19´⇌B2 martensitic transformation can be detected in all Ti–Ni composites, irrespective of LaB6 contents. It should be noted that R-phase transformation also appears for Ti–Ni composite added 0.5wt.%LaB6. The martensitic transformation temperatures firstly decrease and then increase with the increased LaB6 content, which can be attributed to the changing of matrix composition. As LaB6 content increases from 0wt.% to 0.97wt.%, the evolution of network structure is as follows: quasi-continuous network structure → continuous network structure → quasi-continuous network structure. In proportion, the mechanical properties of Ti–Ni composites firstly decrease and then increase. The superior mechanical properties with the highest fracture strain of 35.9% and the largest fracture stress of 2476 MPa can be obtained in Ti–Ni composite with adding 0.97wt.%LaB6, which is due to the larger capacity of bearing the loading for reinforcements showing a quasi-continuous network structure. Meanwhile, at the pre-strain of 7%, the maximum strain recovery ratio of Ti–Ni composite is 88.34%.