Research on Quality and Corrosion Behavior of 6082-T6 Aluminum Alloy Laser MIG Composite Welding Joint

Abstract

In this study, the effects of internal grain structure on microhardness, tensile properties, and corrosion behavior of 6082-T6 laser MIG hybrid welded joints were investigated. The welding current of 102A and the welding speed of 50 mm/s will lead to more porosity defects. The tensile fracture surface of the welded joint exhibits a quasi-cleavage fracture mechanism. There are many spatter or inclusions in the matrix that affect the expansion of the quasi-cleavage surface, and there are many vacancies, impurities, and other defects at the grain boundary. Due to the inhomogeneity of the microstructure at the weld and the presence of precipitated phases, the electrode potential of each part of the joint is not uniform, causing electrochemical corrosion in corrosive media, resulting in more serious corrosion at the weld than at the base metal. The AlFeSi compound is easy to aggregate at the grain boundary, and there is a local potential difference with the Al matrix, which aggravates the corrosion phenomenon. The Mg element at the grain boundary is relatively higher than the Mg element inside the grain. Due to the low corrosion potential of Mg element, corrosion is more likely to occur in the Mg-rich region. The corrosion phenomenon of columnar crystal structure is more serious than that of equiaxed crystal structure.