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<p>Conventionally, improving the wear resistance and thermal conductivity of hypereutectic Al-Si alloys primary relies on refining primary Si particles (PSPs) and modifying eutectic Si morphology. In this work, a novel glass tube suction casting (GTSC) technique was applied to the A390 hypereutectic Al-Si alloy, achieving simultaneous refinement of PSPs and complete elimination of eutectic Si. At 570&#xa0;°C, the alloy exhibits coupled growth, resulting in coarse PSPs (average equivalent diameter (D) ≈ 29.4&#xa0;μm, average shape factor (F) ≈ 0.42). When the temperature is increased to 650&#xa0;°C, solidification undergoes a transition to fully divorced growth, yielding fine and spherical PSPs (D ≈ 7.4&#xa0;μm, F ≈ 0.79). This transition mechanism is attributed to the GTSC-induced initial undercooling, which facilitates independent nucleation of PSPs and suppresses eutectic reactions. Consequently, the wear rate decreases from 76.4 to 40.6 (mm<sup>3</sup>/(N·m) × 10<sup>−5</sup>), and thermal conductivity improves from 134.6 to 142.2 W/(m·K). These enhancements result from reduced Si spalling and diminished electron scattering. This study proposes a microstructure-controlled route to optimize multifunctional performance in hypereutectic Al-Si alloys.</p>

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Silicon Morphology Control and Performance of Hypereutectic Al-Si Alloys: A Study on Divorced Versus Coupled Growth

  • 期刊论文

  • 发表日期：

    2025年9月25日

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  • Chengcheng Han,
  • Yitong Hu,
  • Hao Huang,
  • Ting Yuan,
  • Huan Liu,
  • Jinghua Jiang,
  • Hengcheng Liao,
  • Feng Fang,
  • Yuna Wu

摘要

Conventionally, improving the wear resistance and thermal conductivity of hypereutectic Al-Si alloys primary relies on refining primary Si particles (PSPs) and modifying eutectic Si morphology. In this work, a novel glass tube suction casting (GTSC) technique was applied to the A390 hypereutectic Al-Si alloy, achieving simultaneous refinement of PSPs and complete elimination of eutectic Si. At 570 °C, the alloy exhibits coupled growth, resulting in coarse PSPs (average equivalent diameter (D) ≈ 29.4 μm, average shape factor (F) ≈ 0.42). When the temperature is increased to 650 °C, solidification undergoes a transition to fully divorced growth, yielding fine and spherical PSPs (D ≈ 7.4 μm, F ≈ 0.79). This transition mechanism is attributed to the GTSC-induced initial undercooling, which facilitates independent nucleation of PSPs and suppresses eutectic reactions. Consequently, the wear rate decreases from 76.4 to 40.6 (mm3/(N·m) × 10−5), and thermal conductivity improves from 134.6 to 142.2 W/(m·K). These enhancements result from reduced Si spalling and diminished electron scattering. This study proposes a microstructure-controlled route to optimize multifunctional performance in hypereutectic Al-Si alloys.