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<p>To optimize the mechanical properties of Al-Mg-Si-Cu alloy welded joints fabricated by metal inert gas welding process, a modified V-groove configuration was implemented to precisely control the welding dilution ratio and thermal input. This strategic groove design effectively increased the welding dilution rate to 22.4%, doubling the solid-solution Mg content in the weld seam to 1.41 wt.% compared to that in the conventional I-groove configurations. The elevated Mg concentration directly promoted the precipitation of Mg<sub>2</sub>Si phases, increasing their number density from 2.2 × 10<sup>3</sup>/mm<sup>2</sup> to 3.4 × 10<sup>3</sup>/mm<sup>2</sup>. This microstructural evolution improved the weld seam’s microhardness by 20%, from 63.5 to 76.2 HV. Additionally, the reduced thermal input modified the heat-affected zone thermal profile, lowering the peak temperature by 18% and shortening the high-temperature residence time by 32%. These changes refined the Q particles in the critical softening region of the heat-affected zone, reducing their average size from 126.1 ± 53.2 to 27.5 ± 16.9 nm<sup>2</sup> and increasing number density from 1.3 × 10<sup>14</sup>/m<sup>2</sup> to 9.0 × 10<sup>14</sup>/m<sup>2</sup>. Consequently, the HAZ softening degree decreased from 47 to38%, enhancing the welded joint’s tensile strength (281.2&#xa0;MPa) and yield strength (150.1&#xa0;MPa). Furthermore, the nanoscale Q particles distribution effectively mitigated stress concentrations at phase boundaries, improving resistance to crack initiation and propagation. This increased elongation from 6.7 ± 0.1 % to 7.4 ± 0.1%. Overall, this groove design strategy effectively balances strength and ductility in high-performance aluminum alloy welded structures.</p>

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Study on the Softening Regulation of Al-Mg-Si-Cu Alloy Metal Inert Gas Welded Joints

  • 期刊论文

  • 发表日期：

    2025年8月13日

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  • Pengfei Pei,
  • Xiaming Chen,
  • Jiajie Zhang,
  • Jia Song,
  • Xiaonan Wang,
  • Nagaumi Hiromi

摘要

To optimize the mechanical properties of Al-Mg-Si-Cu alloy welded joints fabricated by metal inert gas welding process, a modified V-groove configuration was implemented to precisely control the welding dilution ratio and thermal input. This strategic groove design effectively increased the welding dilution rate to 22.4%, doubling the solid-solution Mg content in the weld seam to 1.41 wt.% compared to that in the conventional I-groove configurations. The elevated Mg concentration directly promoted the precipitation of Mg2Si phases, increasing their number density from 2.2 × 103/mm2 to 3.4 × 103/mm2. This microstructural evolution improved the weld seam’s microhardness by 20%, from 63.5 to 76.2 HV. Additionally, the reduced thermal input modified the heat-affected zone thermal profile, lowering the peak temperature by 18% and shortening the high-temperature residence time by 32%. These changes refined the Q particles in the critical softening region of the heat-affected zone, reducing their average size from 126.1 ± 53.2 to 27.5 ± 16.9 nm2 and increasing number density from 1.3 × 1014/m2 to 9.0 × 1014/m2. Consequently, the HAZ softening degree decreased from 47 to38%, enhancing the welded joint’s tensile strength (281.2 MPa) and yield strength (150.1 MPa). Furthermore, the nanoscale Q particles distribution effectively mitigated stress concentrations at phase boundaries, improving resistance to crack initiation and propagation. This increased elongation from 6.7 ± 0.1 % to 7.4 ± 0.1%. Overall, this groove design strategy effectively balances strength and ductility in high-performance aluminum alloy welded structures.