Effect of baking on mechanical properties of 5182 aluminum/DP 780 steel spot welding joints

Using traditional resistance spot welding with a novel bulged double-helix electrode, 5182 aluminum alloy and DP780 galvanized steel were welded under two different current parameters. After baking, both samples exhibited a similar average peak load of 3.30 kN, while defect locations showed significant differences. In the low-current sample, defects remained near the nugget center (11.64 μm), whereas in the high-current sample, defects shifted farther away (1490.3 μm). Crack initiation in both cases started along interfacial compounds at the weld edge. In the low-current sample, the crack propagated along interfacial defects on the aluminum side until complete fracture. In contrast, the high-current sample exhibited crack deflection into the aluminum, leading to a pullout fracture. The findings highlight the influence of post-welding baking on the durability and performance of welded joints. This study provides valuable insights for optimizing aluminum-steel resistance spot welding in industrial applications, particularly for reliability after baking.