Thermodynamic coupling numerical simulation and mechanical properties analysis of TC4 laser welding

To accurately predict the temperature changes during the laser welding process of TC4 titanium alloy and the mechanical properties after welding, a laser welding temperature field model was established using ABAQUS subroutines. The temperature field during laser welding was simulated and analyzed, and the changes in temperature and residual stress during and after welding were studied. The hardness and surface residual stress of the welded joints were tested, and the microstructure was analyzed. The results showed that when the peak temperature of the thermal cycle reached 2601 ℃, the molten pool temperature was significantly higher than the liquidus line, there are no solid phase grains in the molten pool, but rather a small amount of columnar crystals formed after solidification. Additionally, the heat-affected zone near the weld had coarser grains, with higher quantity and density of martensite within the grains. After laser welding, the microhardness in the weld zone was consistent, with slightly higher surface microhardness, averaging 385 HV. The longitudinal residual stress along the welding direction showed a uniform peak in the middle of the weld, with slightly lower transverse stress. The average stress errors for the longitudinal and transverse central regions were 1.4% and 2.9%, respectively, and the residual stress distribution perpendicular to the weld direction was consistent. Subsequently, the mechanical properties of the welded joints were studied through tensile simulations. The temperature field and residual stress distribution obtained from numerical simulations matched the microstructure and surface residual stress distribution of the welded samples. The displacement-load data from tensile tests and numerical simulations also matched, proving the feasibility and accuracy of the laser welding temperature field model and the tensile fracture model.