Effect of adjustable ring mode laser on the microstructure and mechanical properties of Cu-on-Al foil lap joints

Adjustable Ring Mode (ARM) laser welding has become an advanced technique to stabilize the welding process and improve joint quality. However, its application in Cu-on-Al welding remains underexplored, despite the challenges associated with conventional welding methods in achieving high-quality joints. In this study, ARM laser welding was employed to fabricate Cu-on-Al lap joints using T2 Cu and 1050 Al foils (400 μm thick). By optimizing the independent power distribution of the core and ring lasers, a hybrid bonding mechanism was achieved, consisting of fusion welding at the weld center and weld-brazing at the periphery, where molten Al infiltrated the Cu base metal. This process effectively expanded the bonding area and suppressed the formation of continuous brittle intermetallic compounds (IMCs), thereby improving joint mechanical performance. The resulting hybrid joint exhibited enhanced stability, with predominantly ductile fracture occurring in the Al base metal. At optimal process parameters, the joint demonstrated a load-bearing capacity of 30.4 ± 2.0 N/mm. These findings highlight ARM laser welding as an effective strategy for Cu-on-Al welding, offering a scalable solution for critical applications, such as lithium-ion battery component welding in electric vehicles.