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<p>This study investigates the AlSi7Mg0.3 alloy using a novel dual-wave-shaped protrusion semi-solid slurry preparation device combined with rheological squeeze casting. The effects of heat treatment conditions (510&#xa0;°C solution treatment for 3/6/8/10 hours, followed by 155&#xa0;°C artificial aging for 6 hours) on the microstructure, mechanical properties, and fracture behavior of the alloy are investigated. The study specifically explores the synergistic enhancement mechanism of high plasticity and the strengthening–toughening mechanism of the alloy. The results reveal that the solution treatment duration significantly influences the morphological characteristics and distribution of the eutectic Si phase. As the solution time is extended from 3 to 10&#xa0;h, the eutectic Si phase morphologies transition from sharp, elongated forms to necked, fractured, and rounded shapes, ultimately becoming rod-like, elliptical, and granular. Furthermore, the phase distribution transitions from aggregation at the grain boundaries to a more uniform dispersion, which effectively hinders crack propagation by the dispersed Si phase particles and the <i>α</i>-Al matrix, shifting the fracture mechanism from brittle to ductile. Moreover, when the solution time exceeds 6&#xa0;h, the Mg-rich π-Al<sub>8</sub>Mg<sub>3</sub>FeSi<sub>6</sub> phase is almost completely dissolved, while the amount of Fe-rich <i>β</i>-Al<sub>5</sub>FeSi phase decreases significantly with increased solution duration, transitioning from elongated to elliptical or granular shapes. The adequate solubility of Mg enhances the solid solution strengthening effect, increasing the matrix's strength. Mechanical properties exhibit a pronounced synergistic enhancement trend with increased solution time. Compared to unheat-treated rheological extrusion cast samples, the yield strength and tensile strength of the RSC-10-6 sample increase to 240.92&#xa0;MPa and 293.42&#xa0;MPa, respectively, while elongation rises from 4.82 to 11.01%. This study demonstrates that optimizing the semi-solid rheological extrusion casting process combined with solution treatment can effectively address the limitations of traditional aluminum–silicon alloys regarding high plasticity, offering a new solution for performance enhancement in high-end applications.</p>

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Microstructure Evolution and Strengthening Mechanisms of AlSi7Mg0.3 Alloy Processed by Semi-Solid Rheological Squeeze Casting and Heat Treatment

  • 期刊论文

  • 发表日期：

    2026年4月19日

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  • Wentao Xiong,
  • Runguang Zhang,
  • Yichao Ding,
  • Fanggong Cai,
  • Jianfei Cao,
  • Minhong He

摘要

This study investigates the AlSi7Mg0.3 alloy using a novel dual-wave-shaped protrusion semi-solid slurry preparation device combined with rheological squeeze casting. The effects of heat treatment conditions (510 °C solution treatment for 3/6/8/10 hours, followed by 155 °C artificial aging for 6 hours) on the microstructure, mechanical properties, and fracture behavior of the alloy are investigated. The study specifically explores the synergistic enhancement mechanism of high plasticity and the strengthening–toughening mechanism of the alloy. The results reveal that the solution treatment duration significantly influences the morphological characteristics and distribution of the eutectic Si phase. As the solution time is extended from 3 to 10 h, the eutectic Si phase morphologies transition from sharp, elongated forms to necked, fractured, and rounded shapes, ultimately becoming rod-like, elliptical, and granular. Furthermore, the phase distribution transitions from aggregation at the grain boundaries to a more uniform dispersion, which effectively hinders crack propagation by the dispersed Si phase particles and the α-Al matrix, shifting the fracture mechanism from brittle to ductile. Moreover, when the solution time exceeds 6 h, the Mg-rich π-Al8Mg3FeSi6 phase is almost completely dissolved, while the amount of Fe-rich β-Al5FeSi phase decreases significantly with increased solution duration, transitioning from elongated to elliptical or granular shapes. The adequate solubility of Mg enhances the solid solution strengthening effect, increasing the matrix's strength. Mechanical properties exhibit a pronounced synergistic enhancement trend with increased solution time. Compared to unheat-treated rheological extrusion cast samples, the yield strength and tensile strength of the RSC-10-6 sample increase to 240.92 MPa and 293.42 MPa, respectively, while elongation rises from 4.82 to 11.01%. This study demonstrates that optimizing the semi-solid rheological extrusion casting process combined with solution treatment can effectively address the limitations of traditional aluminum–silicon alloys regarding high plasticity, offering a new solution for performance enhancement in high-end applications.