Numerical simulation of transport phenomena and its effect on the weld profile and solute distribution during laser welding of dissimilar aluminium alloys with and without beam oscillation

Remote Laser Welding (RLW) of Aluminium alloys has significant importance in lightweight manufacturing to decrease the weight of the body in white. It is critical to understand the physical process of transport phenomena during welding which is highly related to the mechanical performance of the joints. To investigate the underlying physics during welding and to understand the influence of beam oscillation on heat transfer, fluid flow and material mixing a transient three-dimensional Finite Element (FE) based Multiphysics model has been developed and validated from the experiments. The effect of welding speed, oscillation amplitude and oscillation frequency on the fusion zone dimensions, flow profile, vorticity profile, cooling rate and thermal gradient during the butt welding of Al-5754 to Al-6005, with sinusoidal beam oscillation, is analysed. It was found that one additional vortex is formed during beam oscillation welding due to the churning action of the oscillating beam. With the increase in oscillation amplitude, welds become wider and the depth of penetration decreases. An increase in oscillation frequency leads to an increase in the flow rate of the molten metal suggesting that the beam oscillation introduces a churning action that leads to an increase in mixing. It was highlighted that the material mixing depends on both diffusion and convection.

Automated summary

Remote Laser Welding (RLW) of Aluminium alloys is important for lightweight manufacturing and understanding the physical processes during welding is critical for the mechanical performance of joints. A transient three-dimensional Finite Element (FE) based Multiphysics model was developed and validated to investigate the influence of beam oscillation on heat transfer, fluid flow, and material mixing. The study found that beam oscillation during welding creates an additional vortex, and increasing oscillation amplitude widens the welds but decreases penetration depth. Higher oscillation frequency increases the flow rate of molten metal, indicating increased mixing due to the churning action of the oscillating beam. Material mixing depends on diffusion and convection.