Analysis of droplet transfer, weld formation and microstructure in Al-Cu alloy bead welding joint with pulsed ultrasonic-GMAW method

The ultrasonic intensity was changed in different ultrasonic radiator heights (URH). Compared with conventional GMAW, the pulsed ultrasonic assisted gas metal arc welding (PU-GMAW) was an effective and newly-developed aluminum alloy welding method, because of its rapid droplet transfer and deep weld penetration. In PU-GMAW, the penetration and width of weld was increased due to the increase of the arc energy. When the URH was 20 mm and 22 mm, the droplet transfer mode of projected transfer changed to the mixed transition, which included projected transfer and short-circuiting transfer. The hardness of welded joint increased with the effect of pulsed ultrasonic, and the columnar crystal zone width of weld seam decreased. Ultrasonic radiation force was a determinant factor in arc compression and droplet transfer acceleration. The microstructure improvement in the PU-GMAW was caused by ultrasonic vibration and ultrasonic cavitation.