Study on keyhole coupling and melt flow dynamic behaviors simulation of 2219 aluminum alloy T-joint during the dual laser beam bilateral synchronous welding

In this research, the keyhole coupling and melt flow behaviors of 2219 aluminum alloy T-joint during dual laser beam bilateral synchronous welding (DLBSW) process are investigated by simulation, which involves fluid heat transfer and fluid flow. The calculated mesh model of the T-joint is established by simplifying the equal boss of the skin. The combined Gaussian laser heat source is adopted to simulate the laser energy loaded on the base metal during the welding process. The obtained simulation results are reliably matched with the experimental results. Subsequently, not only the coupling process of two keyholes and the evolution characteristics of the coupled keyhole are analyzed, but also the characteristics of molten pool and the flow behaviors of the liquid metal are studied in detail. The results demonstrate that the keyhole profile's oscillations continuously exist, whether before or after the keyhole coupling. The flow direction of the liquid metal near the coupled keyhole wall includes the flow parallel to the keyhole wall and that around the keyhole wall. Besides, the maximum depth of the molten pool slightly lags behind the rear wall of the keyhole. On the coupled keyhole wall and molten pool surface, the melt flow velocities are significantly greater than that inside the molten pool. The vortexes are produced near the upper and lower regions of the coupled keyhole wall.