Porosity inhibition of aluminum alloy by power-modulated laser welding and mechanism analysis

Porosity is a significant issue when conducting laser welding (LW) of aluminum (Al) alloys. Laser oscillating welding appears a good choice for suppressing porosity, but it is accompanied by energy losses. To address the above issues, this paper proposes an innovative power-modulated LW system that simultaneously achieved porosity suppression, power modulation, and energy loss reduction. To demonstrate the effectiveness of the system, comparative experiments were performed using three welding modes: conventional LW, constant power (CP) laser oscillating welding, and gradient power (GP) laser oscillating welding. The results of the experiments indicated that the GP mode was more effective at reducing porosity and the weld depth was greater than that of the CP mode. Numerical simulations were conducted to describe this process. The results showed that changes in the molten pool (MP) flow behavior of the GP mode determined the welding effect. The physical mechanism by which the GP mode suppressed porosity and reduced energy losses was revealed.