Abstract: Aiming at the critical technical issues such as porosity and joint softening in the pulsed MIG welding process of 6082 aluminum alloy, a mechanical vibration-assisted welding method was proposed. The high-speed camera, scanning electron microscopy (SEM), transmission electron microscopy (TEM), and testing of mechanical properties are used to study the effect of mechanical vibration on the arc morphology, droplet transfer behaviour, porosity distribution, precipitate evolution, and mechanical properties. The results show that when mechanical vibration is applied during welding, the arc is less likely to drift, the droplet transfer is stable, and the number of weld pores is reduced. Mechanical vibration can effectively refine the grains and promote the formation of GP zones in the weld, reduce the size of coarse Mg₂Si particles but increase the number of fine α-AlFeMnSi particles in the heat affected zone, and make the distribution of precipitates more dispersed, resulting in obvious precipitation-hardening effect and thus improving the strength and hardness of the joint. At a vibration frequency of 100 Hz, the joint has the maximum tensile strength of 246 MPa, an increase of approximately 12% compared to the joint obtained without mechanical vibration. Excessive vibrational frequency can lead to a poor appearance of weld, thus deteriorating the mechanical properties of the joint. The results are of important significance in increasing the service safety and life of the bodies of electric cars.

Key words: 6082-T6 aluminum alloy, mechanical vibration, pulsed MIG welding, precipitate