The phase transformation and superelasticity of cold rolled and annealed Ti-50.8Ni-0.4Valloys were studied by metallographic microscope,differential calorimetric analysis and tensile test.The results show that annealing treatment has a significant effect on the phase transformation and superelastic(SE)properties of cold rolled alloys.The cold rolled alloy with a large number of dislocation plug product is linear SE,and the annealed alloy is nonlinear SE.The annealed alloy at 350 ℃ shows two-step phase transformation(A→R→M/M →R→ A).The shape recovery rate Rr is 96％,which has excellent SE characteristics.The annealed alloys at 600 ℃ and 650 ℃ are completely recrystallized and the R phase disappears with the increase of temperature.The phase transition is(A→R→M)/(M→A)and(A→M)/(M→ A),respectively.The shape recovery rate Rr is less than 29％,and the SE characteristics become worse obviously.
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