Laser deposition of Ti65 titanium alloy microstructure and fatigue properties

The effects of laser power and temperature on the high-cycle fatigue properties of Ti65 titanium alloy fabricated by laser deposition are studied by single variable method, and the microstructure, internal defects and fracture morphology of the samples are analyzed by optical microscope, ultrasonic detector and scanning electron microscope (SEM). The results show that the microstructure of the samples with different power is the basket structure, and the content of the α phase is significantly higher than that of the β phase, and the α phase in the basket structure is coarsenized at high temperature, and some massive α phases appear inside the grain, and the uniformity of the structure decreases. The fatigue limits of high-power and low-power samples at room temperature and high temperature are 454, 398.5, 371.5 MPa and 336.25 MPa, respectively, and the fatigue limits of high-power samples are more than 10% higher than those of low-power samples at the same temperature. At the same power, the fatigue limit of the room temperature sample is more than 18% higher than that of the high temperature sample, and the temperature has a greater influence on the high cycle fatigue. There are porosity defects in Ti65 titanium alloy specimens made by laser deposition, and the number of pores in low-power specimens is large and the diameter is large, and the fatigue source is homogeneously nucleated at the porosity defects. The larger the diameter of the pores, the closer the distance from the surface, the faster the crack initiation, the lower the fatigue life, the number of pores in the high-power sample is small and the diameter is small, the fatigue source is germinated in the surface crack, and the existence of defects has a great impact on the germination of cracks.