Research on Microstructure and Property Control and Forming Quality Simulation of 5A06 Aluminum Alloy in Deep-penetration Vacuum Laser Welding

Aiming at the problems such as insufficient penetration depth, porosity defects and difficult deformation control in the welding of thick plates of 5A06 aluminum alloy, the optimization of process parameters, the regulation of microstructure and properties, and the simulation of forming quality of vacuum laser welding with deep-penetration were carried out. The 35 mm thick 5A06 aluminum alloy sheet was adopted. Through experiments, the influence laws of laser power, welding speed, defocus amount and swing parameters on the weld formation were explored. Combined with the ANSYS thermo-structural coupling finite element model, the mechanism of swing parameters on the motion and stress field of the molten pool was analyzed. The results show that when the laser power is 4 kW, the welding speed is 0.9 m/min, the defocus amount is -5 mm, the swing mode is 8-shaped, the swing frequency is 200 Hz, and the swing amplitude is 0.6 mm, the weld formation quality is best, the penetration depth and penetration width match well, and there are no defects such as collapse and undercut. In a vacuum environment, the uniformity of the microstructure of the welded joint is significantly improved. The average hardness and tensile strength are increased by 9.7% and 12.9% respectively compared with non-vacuum welding, and the fracture surface shows typical ductile fracture characteristics. The simulation model reveals the mechanism by which swing welding reduces stress peak and minimizes the welding deformation through energy redistribution, providing "experiment+simulation" technical support for high-quality welding of complex aluminum alloy components.