Effects of annealing and deforming temperature on microstructure and deformation characteristics of Ti–Ni–V shape memory alloy

Effects of annealing temperature Tan and deforming temperature Td on microstructure and deformation characteristics of Ti–50.8Ni–0.5V (atomic fraction, %) shape memory alloy were investigated by means of optical microscopy and tensile test. With increasing Tan, the microstructure of Ti–50.8Ni–0.5V alloy wire changes from fiber style to equiaxed grain, and the recrystallization temperature of the alloy is about 580 °C; the critical stress for stress-induced martensite σM of the alloy decreases first and then increases, and the minimum value 382 MPa is got at Tan = 450 °C; the residual strain ɛR first increases, then decreases, and then increases, and its maximum value 2.5% is reached at Tan = 450 °C. With increasing Td, a transformation from shape memory effect (SME) to superelasticity (SE) occurs in the alloy annealed at different temperatures, and the SME → SE transformation temperature was affected by Tan; the σM of the alloy increases linearly; the ɛR of the alloy annealed at 350–600 °C decreases first and then tends to constant, while that of the alloy annealed at 650 °C and 700 °C decreases first and then increases. To get an excellent SE at room temperature for Ti–50.8Ni–0.5V alloy, Tan should be 500–600 °C.