Formation and microstructure of aluminum alloy CMT joint assisted by mechanical vibration

Based on the high-frequency micro-vibration platform, the mechanical vibration-assisted cold metal transfer welding (CMT) test of 6082 aluminum alloy was carried out to explore the influence of high-frequency micro-vibration CMT process on the microstructure and properties of joints. The results show that after applying vibration, the weld reinforcement increased slightly, the weld width decreased, and the penetration depth increased. When the vibration frequency was 1 119 Hz, the weld reinforcement and penetration depth increased by 4.5% and 23% respectively. The vibration narrowed the width of the heat-affected zone, and the grain size near the fusion line had reduced from the original 20 µm to 15 µm. After vibration was applied, the bubble escape speed was accelerated, the growth trend of columnar crystals was suppressed, the crystal grains were refined, the hardness of the joint softening zone was improved, and the hardness distribution of the welded joint was more uniform. When the vibration frequency was 1 119 Hz, the Vickers hardness of the weld softening zone reached the highest value of 77. Vibration can effectively reduce the residual stress of the welded joint and the heat-affected zone. When the vibration frequency was 1119 Hz, the average value of the maximum residual stress of the welded joint and the heat-affected zone had reduced by 9.6% and 6.3% respectively, and the mechanical properties of the welded joint were improved.