Complete-joint-penetration vacuum laser beam welding of 20 mm thick aluminum alloy with beam oscillation

Laser beam oscillation can improve the tolerance of weld seam gaps, eliminate porosity, maintain a uniform structure, and refine grain size, while a vacuum environment can greatly improve the weld penetration depth and welding quality. In this study, a complete-joint-penetration butt welding experiment was conducted on a thick aluminum alloy using oscillating laser beam welding in a vacuum environment. The impact of beam oscillation on forming quality, mechanical properties, microstructure distribution, porosity, and pore distribution in fully penetrated butt joints was examined. The results show that, with identical welding parameters, the incorporation of a laser featuring reduced oscillating facilitates complete penetration of 20 mm aluminum alloy butt joints. This approach also enlarges the weld fusion width, resulting in improved weld formation quality. In addition, even in a vacuum environment, there will still be a number of pores in laser-welded, complete-joint-penetration butt joints. The addition of laser beam oscillation can significantly reduce the porosity and shape the weld sidewall. Therefore, under the action of an oscillating laser, the overall mechanical properties of thick aluminum alloy butt joints are greatly improved, and the uniformity of their mechanical properties in the thickness direction is also guaranteed. At different positions on 20 mm thick aluminum alloy butt joints, the tensile properties can reach more than 85 % of the base metal, which will provide guidance for the application of vacuum oscillating laser welding in engineering.