The four-step multiple stage transformation in deformed and annealed Ti49Ni51 shape memory alloy Original Research Article

A four-step multiple stage transformation is observed in 20% deformed and 500 °C annealed Ti49Ni51 shape memory alloy. Two extra B2 → B19′ transformation peaks appear before the previously described B2 → R and R → B19′ peaks while cooling, and these correspond to one new peak, which appears after the original B19′ → B2 peak during heating. These two extra peaks are caused by the combined effect of severe cold-working and long-time annealing on Ti49Ni51 alloy, and they come separately from the B2 → B19′ transformation occurring in regions with low and high dislocation densities, which are originally suppressed by cold-working.