Study on Phase Transformation and Superelasticity of Cold Rolled Ti-50.8Ni-0.4V Shape Memory Alloy

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 R_r 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 R_r is less than 29%, and the SE characteristics become worse obviously.