Melt flow and thermal transfer during magnetically supported laser beam welding of thick aluminum alloy plates

A multi-field coupled numerical model was proposed to calculate the weld pool dynamics during the full-penetration laser beam welding of 12 mm thick aluminum alloy plates under the function of a longitudinal magnetic field. The model dealt with the melt flow, heat transfer, solid-liquid transition and magnetic diffusion phenomena in welding process. The Lorentz force directing from the keyhole to the liquid-solid interface was induced in magnetic field supported cases. The Marangoni convection near the weld pool surfaces was obviously weakened due to the electromagnetic braking effect, which was featured with decreased velocity and compressed vortex. The heat transfer condition was largely changed, resulting in declined weld pool dimensions. When the magnetic flux density applied was larger than 0.5 T, the convective heat exchange at the middle height of weld pool became notable again due to the reversed melt flow direction. The liquid-solid lines with lower curvature were achieved. The reinforcement of Hartmann effect became limited. The model and the simulated weld pool morphologies were verified in experiment.