Microstructure Evolution and Mechanical Properties of Laser Oscillation Welded 2219 Aluminum Alloy

During the laser welding process of 2xxx series aluminum alloys, the strength of the welded joint is significantly reduced by severe grain boundary segregation in the weld seam, thereby greatly impairing the service performance of the welded structure. The laser beam oscillation can be used to improve the solidification behavior of the molten pool, and effectively suppress grain boundary segregation in the weld seam. In this work, laser beam oscillation welding was applied on the joining of 2219 aluminum alloy plates, and the influence of oscillating patterns on grain boundary segregation in the weld seam was investigated. The experimental results indicated that the circular oscillating pattern shows the best suppression effect on grain boundary segregation in the weld seam. This is attributed to a more uniform temperature distribution in the molten pool promoted by laser beam oscillation. The non-equilibrium solidification phenomena can be significantly reduced, and the distribution of Cu elements in the joint is more uniform. The suppression of grain boundary segregation in the weld seam significantly enhances the joint strength, which increases from 217 to 273 MPa, corresponding to 85% of the base metal, and elongation after break is improved from 1.5 to 4.9%. A foundation for achieving high-quality connections of 2 series aluminum alloys is provided by the findings of this study, thereby the application range of 2 series aluminum alloy welding structure is expanded.