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<p>This study investigates the trade-off in welding high-strength Al–Mg–Si alloys, where high heat input suppresses porosity but may exacerbate heat-affected zone (HAZ) softening. Increasing the heat input to 150&#xa0;J/mm raised the weld formation factor (<i>φ</i>) to 2.9, compared to 2.1 at 107&#xa0;J/mm. This increase extended the molten pool solidification time from 0.7&#xa0;s to 1.3&#xa0;s, thereby promoting bubble escape and completely eliminating dense porosity. The resultant porosity was reduced to 0.1%. The absence of dense pores suppresses the initiation and propagation of microcracks, delaying fracture in the weld seam (WS). Although the higher heat input (150&#xa0;J/mm) widened the HAZ, the degree of softening remained marginal, stabilizing between 48.4% (at 125&#xa0;J/mm) and 50.0% (at 150&#xa0;J/mm). Consequently, the increased heat input did not weaken the HAZ but enhanced the mechanical properties of the WS. Specifically, the strength–ductility product of the WS reached 1636.8&#xa0;MPa%, representing a 4.5-fold increase over that achieved with a low heat input of 125&#xa0;J/mm.</p>

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Synergistic regulation of porosity and softening behavior in the Al–Mg–Si alloys CMT mix synchro-pulse welded joints

  • 期刊论文

  • 发表日期：

    2026年4月1日

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  • Xiaming Chen,
  • Guang Ji,
  • Jinhua Long,
  • Na Li

摘要

This study investigates the trade-off in welding high-strength Al–Mg–Si alloys, where high heat input suppresses porosity but may exacerbate heat-affected zone (HAZ) softening. Increasing the heat input to 150 J/mm raised the weld formation factor (φ) to 2.9, compared to 2.1 at 107 J/mm. This increase extended the molten pool solidification time from 0.7 s to 1.3 s, thereby promoting bubble escape and completely eliminating dense porosity. The resultant porosity was reduced to 0.1%. The absence of dense pores suppresses the initiation and propagation of microcracks, delaying fracture in the weld seam (WS). Although the higher heat input (150 J/mm) widened the HAZ, the degree of softening remained marginal, stabilizing between 48.4% (at 125 J/mm) and 50.0% (at 150 J/mm). Consequently, the increased heat input did not weaken the HAZ but enhanced the mechanical properties of the WS. Specifically, the strength–ductility product of the WS reached 1636.8 MPa%, representing a 4.5-fold increase over that achieved with a low heat input of 125 J/mm.