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<p>AZ91 magnesium alloy is valuable for lightweight structures, but its use in sand casting is hindered by Al<sub>8</sub>Mn<sub>5</sub> macrosegregation. This defect undermines integrity and quality. While previous research emphasized microscale phenomena, the macroscale mechanism lacked clarity. We introduce a stepwise model: "Seeds" form during high-temperature solidification and evolve during low-temperature eutectic reaction, aided by slow cooling. Oxide films speed this up by promoting particle agglomeration. Experiments validate this model. Building on this, we developed a mitigation system using local cooling, reducing oxides, and optimized casting. Industrial trials show scrap rates drop from over 18% to below 5% with little added cost. This offers a framework for addressing defects and improving sand-cast Mg component quality.</p>

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Analysis and Solution of Macroscopic Segregation of Mn-containing Phase in Sand Casting of AZ91 Magnesium Alloy

  • 期刊论文

  • 发表日期：

    2026年1月20日

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  • Shiwei Xin,
  • Yufei Li,
  • Zehua Li,
  • Zhijun Feng,
  • Ming Ruan,
  • Zhizhong Liu,
  • Licheng Zhou,
  • Xiao Li,
  • Shengwei Bai,
  • Jiayi Liu,
  • Bowen Chang

摘要

AZ91 magnesium alloy is valuable for lightweight structures, but its use in sand casting is hindered by Al8Mn5 macrosegregation. This defect undermines integrity and quality. While previous research emphasized microscale phenomena, the macroscale mechanism lacked clarity. We introduce a stepwise model: "Seeds" form during high-temperature solidification and evolve during low-temperature eutectic reaction, aided by slow cooling. Oxide films speed this up by promoting particle agglomeration. Experiments validate this model. Building on this, we developed a mitigation system using local cooling, reducing oxides, and optimized casting. Industrial trials show scrap rates drop from over 18% to below 5% with little added cost. This offers a framework for addressing defects and improving sand-cast Mg component quality.