Effect of heat treatment on microstructure and mechanical properties of Ti-Ni alloy

Effect of heat treatment on microstructure and mechanical properties of Ti-Ni alloy cold-deformed with 48% and annealed at different temperature(350~600 ℃)was investigated.The results show that there appears some amorphous nanometer structure after cold deformation.Cold deformed Ti-Ni alloy begins to recrystallize at 400 ℃.Recrystallization is finished at 500 ℃ and grains start to grow at the same time.When the alloy is annealed at 600 ℃,the grains coarsen completely and only the coarsening self-accommodated martensite phase exists at ambient temperature.The tensile strength of the alloy decreases drastically with the annealing temperature increasing.When the annealing temperature is over 500 ℃,the elongation of the alloy increases distinctly,even above 50%.The critical stress(σs)of stress-induced martensitic transformation is affected by the annealing and transformation temperature.