Numerical and experimental analysis on the effect of ring beam-driven flow in coaxial dual-beam laser welding of aluminum alloy

Abstract

This study investigates the effect of the ring beam-driven flow and the temperature gradient on the solidification pattern in coaxial dual-beam laser welding of aluminum alloy. The microstructure of the weld metal is significantly influenced by the heat transfer and fluid flow in the molten pool, and the thermal and fluid flow characteristics of the molten pool in coaxial dual-beam laser welding differ from those in the conventional single-beam laser welding process. Therefore, a numerical model simulating the coaxial dual-beam laser welding of aluminum alloy was developed to investigate the solidification pattern and reveal the influence of the temperature gradient and circulation flow in the molten pool induced by the ring beam on keyhole behavior, mechanical properties, and behavior of the molten pool surface. Accordingly, the solidification pattern induced by the temperature gradient and ring beam-driven flow was quantitatively characterized. Additionally, the microstructure morphology according to the power of the ring beam was elucidated by comparing the columnar-to-equiaxed-transition (CET) position from the EBSD results of the weld metal and the numerical model.