铝合金激光焊气孔数值模拟

Numerical Simulation on Porosity Formation in Aluminum Alloy Laser Welding

采用透明玻璃观察激光焊过程的匙孔行为。基于菲涅耳吸收和多重反射方法,引入气泡模型,建立三维数值模型,研究铝合金激光焊中匙孔行为和匙孔型气孔的形成机理。结果表明:匙孔的形成与坍塌机理在数值模拟与试验中是相似的;匙孔前壁处的熔融金属沿前沿方向向下流动,而在匙孔后壁的熔池形成顺时针涡流;匙孔坍塌的主要步骤是匙孔后壁处形成凸起,匙孔后壁上的凸起继续向匙孔前壁处流动并与匙孔前壁接触形成液桥;气孔形成的主要因素是匙孔坍塌形成气泡和气泡被凝固界面捕获。

With the addition of transparent glass,the keyhole behavior is directly observed in laser welding of aluminum alloy.Based on the Fresnel absorption model,multiple reflections of the laser beam and the adiabatic bubble model,a three-dimensional model is built to research the keyhole behavior and the keyhole-induced porosity formation.The numerical and experimental results show that the process of keyhole formation and keyhole collapse are similar.Downward flow is observed in the front of the keyhole wall,and a clockwise vortex is found in the rear part of the weld pool.The formation of bulges at the rear keyhole wall,molten metal flows toward the front keyhole wall and the liquid bridge formed by the connection between the rear keyhole wall and front keyhole wall are the main effective compositions for the formation of keyhole collapse.The keyhole-induced porosity formation mechanism can be sketched that the bubble is formed due to the keyhole collapse and then captured by solidication interface.