Numerical simulation of keyhole morphology and molten pool flow behavior in aluminum alloy electron-beam welding

A three-dimensional transient model for solid-liquid-gas transition of 2A12 electron beam welding (EBW) was established to reveal the mechanism of pores formation. The keyhole stability and fluid flow were analyzed in the model. The simulation results showed that it was beneficial for metal vapor to escape by increasing welding speed properly and maintaining keyhole penetration. With the increasing welding speed, the slope of the molten pool wall was increased, the metal vapor cavity was reduced, which indicated a more stable keyhole. The liquid metal at molten pool edge flows to the keyhole and converges with the liquid metal near keyhole under high-speed welding. The liquid metal flows from the bottom of the molten pool to the surface by metal vapor, which is propitious to the escape of metal vapor. In addition, during penetrating welding, the escape exit of metal vapor is increased. Meanwhile, the escape path is shortened, which is beneficial to the escape of metal vapor. It is proved that both higher welding speed and the penetrating welding are conducive to the metal vapor escape and pore defects controlling through the analysis of the cross section under different welding parameters. (C) 2019 Elsevier Ltd. All rights reserved.