Effect of weld conditions on microstructures and mechanical properties of friction stir welded joints on AZ31B magnesium alloys

rotational direction of the friction stir welding (FSW) tool plays a role as important as the weld parameters in FSW processes for magnesium alloys. The formation quality of the weld joints strongly relies on the rotational direction of the stir tool. Based on the present results the better tensile properties of the weld joints are achieved by welding at a higher rotational speed no matter what direction the stir tool rotates. The face bend properties are superior to the root bend properties of the joints. The optimal weld parameters are 1500 rev min(-1)/90 mm min(-1) and 1200 rev min(-1)/60 mm min(-1) for the clockwise and counterclockwise directions of the stir tool respectively. Regardless of the direction which the tool rotates in, fractures of the tensile specimens are mostly located at the boundary between the thermal mechanical affect zone and the nugget zone.