The microstructure and martensitic transformation of Ti–V–Al–B elevated temperature shape memory alloy tailored by thermo-mechanical treatment

In the present work, the mechanical and strain recovery characteristics of Ti–V–Al–B shape memory alloy were tailored by changing annealing temperatures. Moreover, effect of annealing temperatures on microstructure and martensitic transformation behavior were investigated systematically. At the annealing temperatures of 650 °C and 700 °C, both α" martensite phase and hard α phase coexisted in the annealed Ti–V–Al–B alloys. With the annealing temperatures increasing, amount of α phase gradually decreased and α" martensite phase was dominated. The reduction of α phase resulted in the compositional variation, which further triggered the rising of transformation temperatures. The elongation of annealed Ti–V–Al–B alloys continuously increased with the annealing temperatures increasing; whereas the yield strength gradually decreased. The mechanical properties were closely related to the amount of α precipitates and dislocations. Under optimum annealing condition of 700 °C, the maximum yield strength of 489 MPa can be achieved in Ti–V–Al–B alloy. Meanwhile, it showed a largest recoverable strain of 4.6% in correspondence to 6% applied pre-strain.