Numerical study of heat transfer and solute distribution in hybrid laser-MIG welding

In the quest for the transport mechanism in the molten pool during hybrid laser-MIG welding of aluminum alloy, an improved three-dimensional numerical model is developed. A modified model for laser heat source is utilized to investigate the energy absorption mechanism in keyhole. Some driving forces are considered to simulate the fluid flow, such as electromagnetic force, surface tension and buoyancy. The effects of arc pressure and droplet impact are taken into account to track the free surface. Several dimensionless numbers are utilized to analyze the relative importance of driving forces. The temperature field, liquid velocity field and magnesium and zinc distribution are numerically and experimentally studied. Results shows that the laser beam create a great impression on the heat transfer, fluid flow, solute distribution and weld bead geometry. In MIG welding, there is an insufficient mixing zone at the front of the pool, while the solute distribution in hybrid laser-MIG welding is observed more uniform. Magnesium and zinc are found concentrated in lower and upper part of the molten pool, respectively. The mathematical model is well validated by the experimental observations, and the calculated element distribution agrees well with the experimental measurements. Furthermore, the improved model provides an effective method for parametric optimization to improve the properties of hybrid laser-MIG welding joints