Response of austenite finish temperature and phase transformation characteristics of thin medical-grade Ni–Ti wire to short-time annealing

Short-time annealing is commonly applied as shape setting or passivation treatment on Ni–Ti wire. Its influence on the austenite finish (Af) temperature and the martensite–austenite transformation characteristics has been investigated in detail using a newly constructed device implementing a bend and free recovery test with high resolution. Short-time annealing at 450–600 °C can shift the Af temperature from ΔAf = +25 to −15 K and can render the phase transformation either one-stage or two-stage.