Evolution of Precipitates in a Mechanical Vibration-Assisted Metal Inert Gas Welded Joint of 6082-T6 Aluminum Alloy Made with an ER5356 Filler Wire

Advanced welding techniques of aluminum alloy are of great practical interest for applications in the electric vehicle industry. However, heat-affected zone (HAZ) softening is one of the most daunting technical challenges facing the welding of aluminum alloy. In this work, a mechanical vibration-assisted MIG welding process with a ER5356 filler wire was used to strength the welded joint of 6082-T6 aluminum alloy. During welding, a continuous, hammering-like force was applied to the workbench by a vibrator and transferred to the weldment, causing mechanical vibration of the weldment in a direction perpendicular to the aluminum plate. The microstructures of the welded joints were characterized by optical microscopy (OM), scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy-dispersive spectroscopy (EDS), and electron backscatter diffraction (EBSD). To evaluate the mechanical properties of the welded joints, tensile test and Vickers microhardness test were performed. The joint strength was significantly enhanced by the mechanical vibration-assisted MIG welding process. The alpha (AlFeMnSi) precipitate formed during welding leads to precipitation hardening in the heat-affected zone (HAZ) and therefore strengthens the HAZ. Degassing of the weld pool and grain refinement in the weld, which also contributed to the strength of the welded joint, can be achieved by means of mechanical vibration to stir the weld pool.