Stress-induced martensite reorientation and its related performances in trained β-Ti based shape memory alloy

Abstract

In the present study, the influence of training on the microstructural evolution, martensitic transformation behavior and mechanical/functional properties of Ti–V–Al–Zr shape memory alloy was investigated systematically. With the increasing of training cycling number, the degree of martensite reorientation became larger and larger. Moreover, higher density of dislocations appeared in the interior of martensite variants, upon the excessive training cycling number was applied. The international stress can be brought into the matrix, which not only promoted to the ω→αˊˊ transition, but also made the martensite phase stabilizer and even suppressed the αˊˊ→β martensitic transformation during training process. The superior mechanical properties including maximum fracture stress of 906 MPa and the higher fracture strain of 33.6% can be obtained in Ti–V–Al–Zr shape memory alloy subjected with the training cycles number of 5th, which can be attributed to the matrix strengthening stemmed from work hardening and suppression of ω precipitation. Meanwhile, the lower critical stress for the martensite variant reorientation and enhanced matrix strength synergistically contributed to the superior strain recovery characteristics with total completely recoverable strain of 6% in Ti–V–Al–Zr shape memory alloy by controlling training cycles number of 5th. Meanwhile, the higher micro-hardness can be obtained by training.

Keywords

• β-Ti based shape memory alloy
• Training
• Martensitic transformation
• Microstructural evolution
• Functional properties