Numerical Investigation on Molten Pool Dynamics and Defect Formation in Electron Beam Welding of Aluminum Alloy
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JMEPEG https://doi.org/10.1007/s11665-020-05111-2
Numerical Investigation on Molten Pool Dynamics and Defect Formation in Electron Beam Welding of Aluminum Alloy Ziyou Yang, Yuchao Fang, and Jingshan He (Submitted May 27, 2020; in revised form August 9, 2020) 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. Keywords
aluminum alloy, defects formation, electron beam welding, modeling and simulation, molten pool dynamic
1. Introduction Electron beam welding (EBW) is an advanced technology that can improve the quality of welding joints. This material processing method has high energy density, high welding speed and a narrow heat-affected zone characteristic (Ref 1, 2). Because of the advantages of the technology, this method is particularly suitable for welding dissimilar metals and materials with high thermal conductivity, such as aluminum alloys (Ref 3). Spiking defects and penetration depth fluctuations are the most common and undesirable defects during EBW of aluminum alloy, which heavily degrade the mechanical properties of welded joints (Ref 4-6). To suppress these defects, extensive experimental and theoretical studies have been conducted. According to the results of studies, the welding quality usually depends on the oscillation of the molten pool (Ref 7-10). Therefore, the study of the molten pool dynamics not only has theoretical and engineering significance but also deepens our understanding of the welding process. Lately, research on the thermal field and velocity field is currently major topics in EBW. Many experimental investigations have been conducted on the dynamic molten pool to study the physical phenomena in welding. Experimental methods, Ziyou Yang, Yuchao Fang, and Jingshan He, State Key Laboratory of Advanced Welding and Joining, Harbin Institute of Technology, Harbin 150001, China. Contact e-mails: [email protected] and [email protected].
Journal of Materials Engineering and Performance
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