Effect of Electric Pulse Treatment on Properties of Friction Stir Welded Joint of 2024-T4 Aluminum Alloy
XU Aijun1 , TANG Zejun2 , ZHANG Jintao2 , WAN Haifeng2 , WANG Zihan2
(1. Beijing Spacecrafts Co., Ltd., Beijing 100090, China; 2. College of Mechanical and Electrical Engineering, Nanjing University of Aeronautics and Astronautics, Nanjing 210016, China)
Abstract：Electrical pulse treatment was carried out on 2024–T4 aluminum alloy friction stir welding (FSW) samples. The results show that the strength of the sample decreases obviously and the elongation increases obviously after the treatment. When the effective current density is 135A/mm2 , the tensile strength decreases by 25% and the elongation increases by 50%. The engineering stress-strain curve of the welding sample shows the zigzag fluctuation of PLC effect. After the aging treatment following by the electrical pulse treatment, the serrated fluctuation of tensile curve disappears. The elongation decreases slightly, while the strength increases. The material’s mechanical properties return to the FSW samples’ level. The tensile strength of the sample is 8% higher than that of the original joint after artificial reaging treatment, while the tensile strength is 4% higher than that of the original joint after natural reaging treatment. The microstructure shows that the grains are refined to different degrees in different areas of the joint after solution-treatment. The strengthening phase dissolves in the process of solution treatment, but re-precipitates in the process of reaging treatment. In addition, the volume and quantity of strengthening phase precipitated in nugget zone after artificial reaging treatment are larger in comparison to that after natural reaging treatment. The dissolution and precipitation of strengthening phase are the reasons for the change of mechanical properties and PLC effect of FSW samples after the reaging treatment following by solution treatment.
2021, 
