Research on the Al/Cu dissimilar metals laser welding process with alternating magnetic field assisted

Superior Al/Cu dissimilar metal joints is crucial for the development of the new energy electric vehicle industry. This study aims to enhance the mechanical properties of Al/Cu joints while minimizing their electrical contact resistance. Laser lap welding of 5A06 Al and T2 Cu was conducted applying an Alternating magnetic field (AMF) assisted method at various frequencies. Surface fluctuations, joint strength, and electrical contact resistance were compared with those of joints welded without the application of magnetic fields. The application of an AMF reduced the surface fluctuation of Al/Cu joints by 34.67 %, significantly improving the surface quality of the joints. Microscopic analysis of the welded joints reveals that, under the influence of the AMF, the α-Al and Al-Cu eutectic phase transform to Al₂Cu and a mixture of α-Al and Al-Cu eutectic phase in the middle of the molten pool. Simultaneously, the Cu-rich Al₄Cu₉ phase is no longer observed at the bottom of the molten pool. Additionally, Al-Cu intermetallic compounds (IMCs), particularly Al₂Cu, which accumulate at the junction of the bottom of the molten pool, are effectively dispersed under the action of the AMF. The growth of small Al₂Cu is inhibited by the alternating Lorentz force, leading to simultaneous enhancements in both the mechanical properties and electrical conductivity of the Al/Cu joint. Tensile properties and electrical contact resistance measurements show that the shear resistance of the Al/Cu joints is improved by up to 19.03 %, and the electrical contact resistance is reduced by 1.2 % under the AMF-assisted condition at 150 Hz. In this study, AMF-assisted laser welding of Al/Cu significantly enhances the mechanical properties of the joints while reducing their electrical contact resistance. These findings provide valuable reference for producing superior Al/Cu joints for batteries in new energy electric vehicles.