Numerical Investigation on Molten Pool Dynamics and Defect Formation in Electron Beam Welding of Aluminum Alloy

Abstract

Penetration depth fluctuations and spiking defects, which appear almost simultaneously during partial penetration electron beam welding (EBW) of aluminum alloy, lead to weakened joint strength. In this study, a novel dynamic heat source model, which can be used to understand the coupling behavior between the electron beam and keyhole wall, is proposed to simulate the EBW process. While studying molten pool patterns, the formation mechanism of weld defects is also discussed in detail. In addition, a corresponding experimental test is carried out as verification. The weld bead profile and dimensions predicted by simulations agree well with the experimental data. The periodic oscillation of the molten pool is the root cause of the penetration depth fluctuations. The simulation results show that spiking defect formation has four crucial steps: keyhole collapse, liquid metal backfilling, cutting by the molten pool boundary and liquid metal backfilling. The findings from this work provide a fundamental understanding of the formation mechanism of the penetration depth fluctuations and spiking defects during EBW of aluminum alloy to improve the weld bead quality.