Numerical Investigation on Thermal Transport Phenomena during Laser Welding of Aluminium and Magnesium Alloys in Lap Configuration using Enthalpy Update Scheme

Abstract A laser welding process of dissimilar materials (Al-5754 and Mg-AZ31) in a lap configuration is investigated numerically in this study. A set of volume-averaged mass, momentum, and energy conservation equations is used to simulate the process, along with appropriate boundary conditions. The discretized set of governing equations based on the finite volume method (FVM) is then solved numerically using the SIMPLER algorithm, pressure-velocity coupling, and TDMA. It is observed that a laser welding process involves simultaneous melting, solidification, and remelting. The novelty of this study lies, therefore, in identifying these simultaneous phenomena during laser welding using the enthalpy update scheme. The predicted thermal investigation is validated initially with the existing experimental and numerical investigations. The progression of the associated transport phenomena is then presented elaborately through the observation of the weld pool and heat-affected zone (HAZ) at various laser powers. It has been found that a minimum of about 2500 W laser power is needed to weld a 2 mm thick Al-alloy sheet onto a Mg-alloy sheet in a lap configuration. It is also found that there is a limit to the laser application time when the laser beam is applied statically. The depth of the weld pool increases within this time limit, and further laser application does not increase the depth of the weld pool due to periodic remelting and solidification. Such a limit disappears at higher values of laser power, i.e., greater than 3000 W.