Study on Fracture of Aluminum Alloy Joints Welded by Friction Stir Welding

The precisely controlled heat treatment was studied in order to meet the special requirements of aerospace industry for materials of aluminum alloy. 2219 aluminum alloy welded plate was prepared by friction stir welding, its microstructure and mechanical properties were studied, and the reasons for strength reduction of welded joints were analyzed and summarized correspondingly. The results shows that the plasticity of joints of 2219 aluminium alloy is poor after FSW, the elongation is reduced about 50% to that of base material. With the process of general post-weld heat treatment technology, the plasticity is further reduced, the elongation is reduced about 50% to that of welded joints. But after high temperature solution treatment, the average elongation of the joints increase to corresponding level of as-welded joints, which is about 12.6%. In this precisely controlled heat treatment, the fine grains can be maintained, the plasticity of aluminum alloy can be restored, which means that the softening problem can be eliminated and the mechanical strength can be improved.