Effect of welding parameters on mechanical properties of friction stir welded T-lap dissimilar metal joints between 7075 and 5083 aluminum alloys

Dissimilar T-lap joint between aluminum alloy 7075-T651 and 5083-H116 was fabricated by friction stir welding. Special focus was paid to the defect formation and mechanical properties which were significantly affected by the welding parameters. The results showed that four typical types of defects were detected in the T-lap joint; tunnel, kissing bond, hook, and bonding line defects. The tunnel and bonding line defects could be avoidable by decreasing the welding rate. At low welding rate, however, the hook defect was formed and reduced the skin effective thickness. The kissing bond defect was too hard to be eliminated by using one welding pass only by changing the welding parameters. Among these defects, the hook defect played the important role in the mechanical properties of T-lap joint. It is a special finding that there was the optimum welding rate by which the maximum joint efficiency was attained. These findings were summarized into the table and map which can optimize the joint properties.