Weld formation mechanism during fiber laser welding of aluminum alloys with focus rotation and vertical oscillation

Laser non-penetrating welding of aluminum alloy has such problems as poor weld morphology and relatively high porosity. In this paper, the effects of focus movement parameters on the weld formation, weld depth and pore formation were investigated during fiber laser welding of aluminum alloy with focus rotation and vertical oscillation. Experimental results show that focus rotation and vertical oscillation can effectively improve the weld surface morphology, reduce the porosity in weld, increase weld depth, and enhance weld quality during laser welding of aluminum alloy. Further analysis shows that laser focus rotation and vertical oscillation can actively regulate the flow and solidification behaviors of the weld pool, which can improve the weld formation with scaly morphology. Laser focus rotation can improve the interaction way between the laser beam and keyhole wall, and enlarge the keyhole mouth to make it less liable to collapse or close, thus significantly reducing the size and number of the keyhole-induced pores. Vertical oscillation of laser beam focus with appropriate amplitudes can increase weld depth, improve welding efficiency, and reduce the negative influence of focus rotation on weld depth.