Plastic deformation behavior and microstructure of friction stir welded joint of 2024 aluminum alloy

To explore the mechanical properties and the plastic deformation behavior of the friction stir welding brazed tube, the microstructures and mechanical properties of the 5 mm thick 2024-O aluminum alloy friction stir welded (FSW) joints were investigated. Emphasis was placed on the effect of the microstructure heterogeneity on the global and local tensile properties of FSW joints. The relationship between microstructures and mechanical properties of FSW joints were studied. The results show that the tensile properties of the joint are very heterogeneous leading to lower ductility. The middle zone of the BM is the weakest region where the strain localizes early and reaches 23% during the tensile test. However, the local strain of the weld nugget zone and the base material are 3% and 11% respectively. The highly inhomogeneous deformation throughout the joint caused by heterogeneous microstructure is the reason for the 44% decrease in elongation of the as-welded joint compared with that of the BM.