Numerical Modeling of Welding Porosity Formation and Dendrite Growth of 6xxx Aluminum Alloys

A cellular automaton-finite difference-lattice Boltzmann (CA-FD-LB) model, coupled with the calculation of ternary alloy thermodynamics, has been applied for the simulations of welding porosity formation and dendritic solidification during welding of 6xxx aluminum alloys (Al-Mg-Si). It is revealed that the nucleation and growth of the welding pores occur in the interdendritic space, and that the pores are squeezed into irregular shapes by the growing dendrites. During the solidification of the weld pool, the porosity percentage and welding pore number continuously increase. The effects of the heat input on the welding pore formation and dendrite growth have been investigated. The results indicate that, with the heat input decreasing, the dendrite arms become finer, while the percentage of porosity decreases and the gas pore numbers increase. This work not only reproduces the welding porosity formation of 6xxx aluminum alloys but also guides the prediction of the microstructure of the welded joints.