A Comparison of Mechanical Properties and Microstructure in Friction Stir Welded and MIG Welded Light Alloys

Joining technologies are in a very interesting phase today due to some relevant innovations concerning new techniques. Friction Stir Welding (FSW) is a relatively new process, patented by TWI in 1991, able to weld through a solid state bonding materials considered difficult to be welded or unweldable by more traditional fusion welding techniques. By using this process welded joints are obtained with no external heat supplier, generating the required temperature increase by means of a revolving pin that follows a proper trajectory partially sunk in the workpiece surface. As for today, although first examples of industrial application can be found in the aeronautical and aerospace fields, the process is hardly applied for other sectors of the transportation industry, as the naval and the automotive ones, in which traditional fusion processes as MIG or TIG are still used. In the paper a comparison between the mechanical and metallurgical properties of FSWed and MIG welded sheets is carried out. In particular, two different thicknesses of AA5083 H321 aluminum alloy sheets, usually utilized for naval and marine applications, were utilized for the welds utilizing both the processes. The obtained results clearly highlight the supremacy of FSW in both mechanical resistance and joint integrity.