Experimental and numerical study on the effect of increasing frequency on the morphology and microstructure of aluminum alloy in laser wobbling welding

Laser wobbling welding is effective in reducing porosity and improving microstructure of aluminum welds. This work adopts the research form of experiment combined with numerical simulation to establish the relationship between different parameters and morphology and microstructure of the welds. The dynamic behavior of the molten pool and the keyhole, the thermal cycle process and the solidification parameters can be obtained through the numerical simulation considering the fluid flow and heat transfer. The research reveals that laser wobbling welding improves the weld formation by significantly weakening the molten pool eruption and stabilizing the welding process and also confirms that there is a special cross-regional flow field in the molten pool and the mushy zone which is different from ordinary laser welding. In addition, it is proved that the grain refinement at the weld boundary is the result of the combined effects of solidification parameters, dendrite remelting and flow field stirring, but the grain refinement at the center of the weld is mainly caused by the flow field stirring. These results explain the influence of the laser wobbling welding on the flow, heat transfer and solidification parameters of the welds and reveal the reasons for improving the weld formation and refining the microstructure.