Improved Mechanical Properties of SUS304/AA5083 Dissimilar Joint by Laser Ablation Pretreatment in Vortex- Friction Stir Lap Welding

Abstract

To obtain a high-quality Al/steel dissimilar joint, a micro-groove-assisted vortex-friction stir lap welding (MG-VFSLW) process was developed. Through prefabricating micro-grooves on the steel plate surface by laser ablation, high-quality mechanical interlock and metallurgical bonding were obtained simultaneously in the MG-VFSLW process. The weld formation, interface microstructure, mechanical properties, and failure mode in MG-VFSLW were studied by comparing them with those in VFSLW. The results showed that a line load of the AA5083/SUS304 dissimilar joint up to 485.9 N/mm was obtained by MG-VFSLW, which is 40.1% higher than that in VFSLW. Remarkable intermetallic compound layers and cracks were found in VFSLW. The cracks were closely related to the oxides on the interface. However, in MG-VFSLW, cross-riveting aluminum rivets and steel rivets were formed on the interface due to the micro-grooves and flashes made by the laser ablation. Good metallurgical bonding was also formed between AA5083 and SUS304. No remarkable intermetallic compound layers and cracks occurred. During the tensile shear tests, the aluminum rivets were cut off and some dimples and tear ridges existed on the fracture surface. In short, the high strength of the Al/steel lap joint in MG-VFSLW was attributed to the high-quality mechanical interlock and metallurgical bonding.