Numerical and experimental study of molten pool formation during continuous laser welding of AZ91 magnesium alloy

Heat transfer from the laser keyhole to the weld pool and details of the fluid flow play an important role in determining weld shape and size. In this work, both the experiment and the finite volume method (FVM) are utilized to investigate the thermal phenomena during continuous laser keyhole welding. Firstly, the experiments are carried out to examine the effects of laser welding parameters on the pool dimensions. Secondly, 3D FVM model is developed using the hydrodynamic software FLUENT to simulate the keyhole and pool formation during the interaction between continuous laser and AZ91 magnesium alloy sheet. In this simulation, based on a control volume method, a volumetric heat source is used to model the laser beam. Then, the equations of species, mass, momentum and energy are solved. Laser power and welding speed have a strong effect. Using the developed model, it has been found that the shape and size of the molten pool in the workpiece are affected by welding parameters such as welding speed and the incident laser power. Furthermore, it has been observed that the surface tension temperature coefficient, Marangoni convection, is sensitive to the active elements in the magnesium alloy composition. These coefficients also affect the pattern of the fluid flow in the molten pool. Finally, the simulation results were compared with the experimental data. The effectiveness of the developed computational procedure has been confirmed.