A 3D arc-droplet-molten pool integrated model of Al alloy GMAW process: Heat transfer, fluid flow and the effect of external magnetic field

GMAW is one of the principal processes for the fabrication of aluminum alloy components, and the external magnetic field (EMF) is innovatively introduced to assist in improving forming quality and mechanical properties. To deeply understand the action mechanism of the EMF and provide a sufficient basis for process parameters optimization, we have developed an arc-droplet-molten pool integrated model to investigate the effect of EMF on the behaviors of heat transfer and fluid flow. The integrated model is firstly validated by comparing the droplet shapes between simulated results and experimental observations, which present great agreements. Regardless of whether there is an EMF, the temperature distribution of the arc plasma, as well as the arc shape, is no longer rotationally symmetric. A moderate magnetic flux density of EMF will not only compress the arc plasma and decrease the average temperature of droplet metal, but enhance the peak velocity of plasma and expand the high-velocity plasma zone. In addition, an EMF will reduce the dimensions of the molten pool in the early stages of welding because of the enhancement of metal spread and heat dissipation, and also significantly change the flow pattern of liquid metal in the molten pool.