The effect of laser off-axis angle on the formation of porosities, fluid flow and keyhole formation of an aluminum alloy (AA1050) in the laser welding process

Laser welding of busbars to battery tabs in electric vehicles (EVs) is crucial due to the rapid advancements in electric mobility technology. Ensuring weld quality is paramount, as it depends on factors such as porosity generation, fluid flow in the molten pool during welding, applied laser power, and welding speed. However, conventional laser welding techniques, which primarily focus on adjusting laser parameters along the weld direction, struggle to effectively mitigate porosity formation. While the effect of laser angles along the weld direction has been extensively studied, the effects of off-axis laser angles, i.e., angled in the plane perpendicular to the weld direction, have not yet been explored. This study introduces an innovative approach to laser welding by varying the laser off-axis angle at different laser energy densities to optimize the process specifically for porosity reduction. By implementing a three-dimensional computational fluid dynamics (CFD) model of laser welding of aluminum AA1050, we provide a detailed analysis of the fluid flow and melt pool dimensions while employing different off-axis angles. Our model incorporates multiple reflections, upward vapor pressure, and recoil pressure to explain porosity formation at different laser off-axis angles. The results show that increasing the laser off-axis angle at optimized laser power and welding speed significantly reduces porosity. The numerical analysis indicates a maximum deviation from the experimental melt pool width of 11% at a laser off-axis angle of 4.92 degrees and a minimum error of 2.6% at an off-axis angle of 2.74 degrees. For melt pool depth, the maximum deviation is 7.2% at an off-axis angle of 4.92 degrees, and the minimum difference is 0.5% at an off-axis angle of 7.42 degrees. This study presents a novel methodology for improving laser welding processes by addressing the specific challenge of porosity formation.