Effect of heat treatment on transformation behavior of Ti–Ni–V shape memory alloy

Effects of annealing and aging processes on the transformation behaviors of Ti–50.8Ni–0.5V (atomic fraction, %) shape memory alloy were investigated by means of differential scanning calorimetry (DSC). The A → R/R → A (A – parent phase, R – R phase) type one-stage reversible transformation occurs in 350–400 °C annealed alloy, the A → R → M/M → R → A (M – martensite) type two-stage transformation occurs in 450–500 °C annealed alloy, the A → R → M/M → A type transformation occurs in 550 °C annealed alloy, and A → M/M → A type transformation occurs in the alloy annealed at above 600 °C upon cooling/heating. The transformation type of 300 °C aged alloy is A → R/R → A, and that of 500 °C aged alloy is A → R → M/M → A, while that of 400 °C aged alloy changes from A → R/R → A to A → R → M/M → R → A with increasing aging time. The effects of annealing and aging processes on R and M transformation temperatures and temperature hysteresis are given. The influence of annealing and aging temperature on transformation behaviors is stronger than that of annealing and aging time.

► New shape memory alloy (SMA) – Ti–50.8Ni–0.5V SMA.
► The evolution laws of transformation types of annealed Ti–50.8Ni–0.5V SMA.
► The evolution laws of transformation types of aged Ti–50.8Ni–0.5V SMA.
► The effect laws of annealing on transformation temperature and hysteresis of the alloy.
► The effect laws of aging on transformation temperature and hysterises of the alloy.