Interfacial Feature and Mechanical Property of Friction Stir Lap Repair Welded 7B04 Aluminum Alloy

Friction stir repair welding of the lap structure of 2-mm-thick 7B04-T74 aluminum alloy is investigated in this study. A groove on the bottom plate surface was used to simulate the defect formed by the lap structure failure, by which an attempt was made to investigate the friction stir lap repair welding technology. The results show that the lap structure turns to butt–lap coexistent structure for the repair welding, leading to the variations of material flow patterns and weld formation features. Compared with the initial lap joint, both effective sheet thickness and effective lap width are improved in the repaired joints, and the hook tips of repaired joints are better metallurgically bonded. The nugget zone of repaired joint possesses significantly higher hardness than the initial joint. In addition, the fracture strength of the repaired joints is largely improved for advancing side loading configuration.