Friction Stir Welding of Magnesium for Automotive Applications

Friction stir welding (FSW) shows significant advantages in the joining of magnesium alloys. In this paper, the feasibility of FSW for several kinds of the automotive magnesium alloys and the dissimilar material joint of magnesium to aluminum alloys were studied. Butt welded magnesium alloys of wrought and die-cast show advantages expected of the FSW process, i.e. good appearance and joint integrity. The 0.2% proof stress and ultimate tensile strength of friction stir welds in AZ31 are almost the same as the annealed parent metal. In any die-cast AZ91D, AM50A and AM60B alloys, the hardness in the stir zone is higher than the base metal. The proof stress and the tensile strength of the AM50A and AM60B joints are almost at the same level as the base metal. In the case of dissimilar material joint, the material mixing is limited and a more mechanical interlocking joint forms. Furthermore, intermetallic phases about 2μm thick are formed so that the ductility of the dissimilar material joint is inferior to those of the parent metal.