Influence of magnetic field orientation on molten pool dynamics during magnet-assisted laser butt welding of thick aluminum alloy plates

An externally applied magnetic field has been proved effective in controlling the molten flow behavior during the laser beam welding. This paper reveals how a magnetic field applied in different orientations influences the weld pool dynamics during the full-penetration laser butt welding of thick aluminum alloy plates. A multi-physics coupling model was developed and numerically solved by considering the electromagnetic interaction between static magnetic field and magnetofluid. The dynamic and electromagnetic information within the weld pool were predicted and comparatively analyzed. The results show that Lorentz force and Hartmann effect induced in magnet-assisted weld pool are quite sensitive to magnetic field direction. The horizontally directed magnetic field leads to limited Hartmann effect by inducing additional molten vortexes, while the field aligned vertically to aluminum surface can obviously reduce the molten flow velocity and weaken the Marangoni convection. The work can provide a reference in optimizing the operating parameters when an electromagnetic system is employed to improve the welding quality.