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Friction stir welding (FSW) shows advantages for joining lightweight alloys for automotive applications. In this research, the feasibility of friction stir welding aluminum for an automotive component application was studied. The objective of this research was to improve the Friction Stir Spot Welding (FSSW) technique used to weld an aluminum closure panel (CP). The spot welds were made using the newly designed swing-FSSW technique. In a previous study (unpublished), the panel was welded from the thin to thick side using both an 8 mm and a 10 mm diameter tool. The 10 mm tool passed various fatigue tests; however, the target was to improve performance of the 8 mm tool, especially to increase the number of cycle before the first crack appearance during fatigue testing. In this study fatigue tests and static strength was recorded for weld specimens that were welded from thick-to-thin with an 8 mm diameter tool.

In this research, the feasibility of FSW dissimilar magnesium alloys was investigated. Specifically, die cast MRI-153M and wrought AZ31 were butt-welded. The effects of weld parameters such as tool rotation and weld speed on the weld quality have been characterized in terms of macrostructure, microstructure, hardness profile as well as tensile strength. A relatively wide FSW process window exists to achieve void-free welds. In the stir zone MRI-153M transforms from cast structure to fine grain structure during FSW, while AZ31 transforms from originally twinned grains to equi-axed grains without twins. MRI-153M in the stir zone becomes stronger than the base metal and the stir zone on the AZ31 side becomes weaker than the base metal. Tensile coupons failed in the base metal of MRI-153M, and the tensile strength was found to depend on the quality of the base metal of MRI-153M.

A design of experiments (DOE) on the effects of weld parameters on friction stir stitch welding has been carried out. Lap shear specimens of automotive aluminum alloy A6022-T4 were welded using a C-frame welder. Welds were made with numerous weld parameters such as; tool pin length, tool rotating speed, tool plunging speed and depth, hold time, welding speed and weld length. The results of this study show that transverse welds have higher lap shear strength than longitudinal welds and lap shear strength increases linearly with weld length. Increasing hold time-1 and hold time-2 also increased shear strength. The effects of pin length and rpm need more investigation and will be studied further.

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.

Friction stir welding has been successfully applied to stitch weld aluminum sheet metal for automotive closure panel assemblies. The weldment was applied to a lap joint on A6000 series aluminum sheet. The effects of weld parameters, such as tool rotating speed and hold time, on mechanical and metallurgical properties of the joint were studied and then optimized. Resultant stitch weld shows higher lap shear and cross tension strength than those of friction stir spot welding and resistance spot welding. Furthermore, a C-frame gun for stitch welding was developed to demonstrate the capabilities for this technology for automotive closure panel applications. Stitch welding showed increased joint strength compared to spot welding