Effect of annealing temperature on microstructure, texture and tensile properties of TC4 titanium alloy wire

In this paper, TC4 titanium alloy wire was taken as the research object, and four groups of different temperatures of 920 °C, 940 °C, 960 °C and 980 °C were set to annealing the alloy. The effects of different annealing temperatures on the microstructure, phase, texture and tensile properties of TC4 titanium alloy wire were studied. The results show that with the increase of annealing temperature, the volume fraction of primary α phase decreases and the morphology tends to be equiaxed, while the content of secondary α phase increases. After annealing at different temperatures, the microstructure is composed of α phase and β phase. The diffraction peak intensity of α phase as the main phase is higher, while the content of β phase is less and the diffraction peak is weaker. The texture analysis shows that the orientation concentration of the alloy changes from <10-10> and <11-20> directions to <11-20> single direction with the increase of annealing temperature, and the texture strength decreases from 7.48 to 5.27. In terms of tensile properties, the strength of the alloy remains stable when the annealing temperature is 920–940 °C. When the temperature rises to 960 °C, the strength increases significantly and the plasticity decreases. At 980 °C, the strength reaches the peak (tensile strength is 1,210 MPa, yield strength is 1,110 MPa), but the elongation is only 5%. The fracture analysis shows that the fracture presents uniformly distributed equiaxed dimples in the range of 920–940 °C, while the number and size of dimples decrease in the range of 960–980 °C, and tear ridges appear. It is found that secondary crack morphology appears in all tensile fractures.