Abstract: The influence of the annealing temperature on the microstructures,phase transitions and super-elasticity of Ti-51 Ni shape-memory alloy,an advanced material for electronic devices,was investigated.The results show that the annealing temperature had a major impact.For instance,after annealing,the Ti-51 Ni alloy comprised r-phase and martensite phase.Textured fiber and equiaxed crystalline grains formed at low and high annealing temperatures,respectively.When it comes to transformation and inverse transformation,the peak temperature for martensite phase changed in an increase-decrease way,whereas the peak temperature for R-phase decreased monotonically.Annealing in 300~400℃ range increased the mechanical strength,and annealing in 500~600℃ range increased the plasticity.As the annealing temperature approached to the transformation temperature,the magnetoresistance decreased sharply,accompanied by the transformation.As the annealing temperature increased,the residual strain changed in a decrease-increase.