Numerical simulation study on heat and mass transfer processes in laser deep penetration welding of thin-plate copper-aluminum dissimilar metals

In the field of new energy vehicles, copper and aluminum materials are extensively employed for power battery tabs and busbars. Nevertheless, due to significant discrepancies in their melting points, densities, and other physical properties, challenges such as poor molten pool stability and high crack sensitivity often arise during laser deep-penetration welding. In this work, a nonlinear transient finite element model coupled with a double-ellipsoid heat source model is developed to investigate the effects of laser power (P=900−1400W) and welding speed (v=25−65mm/s) on heat and mass transfer as well as weld quality. The results revealed that the temperature field exhibits symmetry along the welding direction. Laser power predominantly influences the dimensions of the molten pool and the diffusion degree of “aluminum invading copper,” while welding speed affects the flow behavior of the molten pool through energy density. When the laser power is P=1100W and the welding speed is v=55mm/s, the molten pool receives sufficient heat input, with surface tension and recoil pressure reaching equilibrium. This condition leads to favorable weld formation, uniform copper-aluminum mixing, minimal formation of brittle phases, and a heat-affected zone primarily composed of blocky and columnar crystals. The prediction errors of weld width and depth are 2.594% and 5.369%, respectively, both within ±10%, thereby fully validating the model’s reliability. This study provides a crucial theoretical basis for optimizing process parameters in the efficient welding of power battery tabs and busbars.