Hybrid resistance-laser spot welding of aluminum to steel dissimilar materials: Microstructure and mechanical properties

In this work, an innovative hybrid resistance spot-laser welding process, which first conducts resistance spot welding of aluminum and steel dissimilar materials, followed by laser spot welding, is proposed to join aluminum to steel. Through innovative designing of the electrode structure, the welding current distribution and the weld structure were optimized to produce a thin and uniform intermetallic layer with its thickness below 1.2 lm. Furthermore, the faying interface morphology of aluminum and steel dissimilar materials was changed from a traditional flat surface to an interface with a deep bulge into the aluminum weld. It was found that resistance spot weld had a considerable tensile-shear load but poor ductility and energy absorption due to the presence of a weak bonding area around the periphery of the joint, where facilitated the crack initiation and rapid propagation. The following laser spot welding process was conducted in the weak bonding area of the resistance spot welding joint, which inhibited rapid propagation of the cracks along the faying interface avoiding the interface fracture. Compared with resistance spot welding joints, the tensile-shear peak load and energy absorption were increased by 18.2 % and 424.8 % for hybrid welding joints, respectively. CO 2022 Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license (http:// creativecommons.org/licenses/by-nc-nd/4.0/).