Microstructure and mechanical properties of 1 mm thin plate TC4 titanium alloy joint by ring laser welding

Abstract Ring laser welding was used to weld 1 mm thin plates TC4 titanium alloy, and the effects of different ring laser powers on the microstructure and mechanical properties of the weld were studied. The results indicate that the microstructure in the weld zone under different powers all contain basket structures, although the morphology of the martensite within the baskets differs. The microstructure in the weld zone is mainly composed of acicular α ′ martensite, secondary α phase, and residual β phase. The microstructure in the heat-affected zone of the weld is mainly composed of acicular α ′ martensite, initial α phase, secondary α phase, and residual β phase. The hardness of the weld is higher than that of the base metal, showing an overall trend of first increasing, then decreasing, and then increasing again before decreasing. The tensile specimens under different powers all fractured in the heat-affected zone of the weld, and the type of fracture is quasi-cleavage. At a laser power of 900 W, the weld has good formation, with minimal spatter on the surface, and good weld penetration. The microstructure of the weld is mainly composed of acicular α ′ martensite, initial α phase, secondary α phase, and residual β phase. The hardness of the weld is 387.76 HV. The tensile strength and elongation are 1098.3 MPa and 12%, respectively.