Influence of Cu Coating on the Microstructure and Mechanical Properties of Laser Welded Joints in Dissimilar Metals

The microstructure and tensile properties of a 316L stainless steel and 6061 Al laser welded joint in an overlap configuration were studied, and the effects of Cu coating on the quality of the 316L stainless steel/6061 Al dissimilar joints were investigated. The results indicated that the shear strength of the joints increased, while the formation of intermetallic compounds (IMCs) and microcracks at the bottom or near the interface decreased with the increasing thickness of Cu coating. The addition of the Cu coating effectively decreased the rate at which liquid Al penetrated into the molten pool, and then resulted in an increase in the joint toughness. The fracture locations of the joints changed from inside of the molten pool to the 6061 Al substrate, and the fracture mode changed from cleavage fracture to mixed fracture consisting of quasi-cleavage and ductile fracture modes.