NUMERICAL MODELING OF THERMO-FLUID FLOW AND METAL MIXING IN LASER KEYHOLE WELDING OF DISSIMILAR METALS

In laser keyhole welding of dissimilar metals, the thermo-fluid flow in the molten pool has decisive effects on the compositional mixing of different chemical elements and hence the formation of detrimental intermetallic compounds. A numerical model is developed in this work to investigate the composition mixing in laser keyhole welding of dissimilar metals. The model takes into account multiple important physics in the process, including dynamic keyhole evolution, laser matter-interaction, phase change, thermo-fluid flow, and composition diffusion/advection. The preliminary simulation results demonstrate that the keyhole behavior is strongly affected by the properties of the dissimilar metals, and the keyhole fluctuation causes an unstable flow in the molten pool that facilitates the compositional mixing through advection.