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<p>This study investigates the feasibility of using red mud, an industrial byproduct of the Bayer process, as a sustainable partial replacement for commercial grade silica sand in green and dry sand molds for A-356 aluminum alloy casting. The motivation for this work arises from the increasing scarcity and environmental concerns associated with silica sand mining, while red mud disposal poses significant environmental challenges. The experimental investigation involved replacing silica sand with 0–15 wt% red mud, while bentonite content (8–12 wt%) and moisture (2–6%) were varied to optimize mold properties. The materials were characterized using X-ray fluorescence (XRF), scanning electron microscopy (SEM), sieve analysis, and pH–density measurements. Mold properties were evaluated according to AFS Standards. While casting quality was assessed through fluidity, surface roughness, porosity, hardness, and microstructural analysis. The results showed that permeability decreased with increasing red mud content due to finer particle size, but remained within acceptable foundry limits. At the optimal composition of 8–10 wt% red mud, 10 wt% bentonite, and 3–4% moisture, the green mold exhibited permeability within the acceptable range with mold hardness of 85–90, and compressive strength of approximately 1.1–1.2&#xa0;kg/cm<sup>2</sup>. Dry molds demonstrated significantly higher strength, reaching compressive strength values of about 6&#xa0;kg/cm<sup>2</sup>. Casting trials revealed improved fluidity and surface quality for red mud molds. The average surface roughness of castings produced using red mud molds was 4.8&#xa0;µm, compared with 6.7&#xa0;µm for conventional silica sand molds. However, slightly higher porosity (4.33%) was observed compared with silica sand molds (2.25%). The hardness of the A-356 alloy casting produced in red mud molds was 82 ± 2 HV, which is comparable to the 86 ± 2 HV obtained from silica sand molds. Microstructural analysis confirmed similar α-Al dendritic matrix and eutectic (α-Al + Si) structures for both mold systems. The results demonstrate that up to 15 wt% red mud can effectively replace silica sand without compromising mold properties or casting performance.</p> Graphical Abstract <p></p>

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Feasibility Assessment of Red Mud as a Partial Substitute for Commercial Silica Sand in Green Sand Casting of A356 Alloy

  • 期刊论文

  • 发表日期：

    2026年5月13日

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  • Dheerendra Singh Patel,
  • Ramesh Kumar Nayak,
  • Sanjana Ahuja,
  • Harsh Jain,
  • Animesh Mishra,
  • Prem Kumar

摘要

This study investigates the feasibility of using red mud, an industrial byproduct of the Bayer process, as a sustainable partial replacement for commercial grade silica sand in green and dry sand molds for A-356 aluminum alloy casting. The motivation for this work arises from the increasing scarcity and environmental concerns associated with silica sand mining, while red mud disposal poses significant environmental challenges. The experimental investigation involved replacing silica sand with 0–15 wt% red mud, while bentonite content (8–12 wt%) and moisture (2–6%) were varied to optimize mold properties. The materials were characterized using X-ray fluorescence (XRF), scanning electron microscopy (SEM), sieve analysis, and pH–density measurements. Mold properties were evaluated according to AFS Standards. While casting quality was assessed through fluidity, surface roughness, porosity, hardness, and microstructural analysis. The results showed that permeability decreased with increasing red mud content due to finer particle size, but remained within acceptable foundry limits. At the optimal composition of 8–10 wt% red mud, 10 wt% bentonite, and 3–4% moisture, the green mold exhibited permeability within the acceptable range with mold hardness of 85–90, and compressive strength of approximately 1.1–1.2 kg/cm2. Dry molds demonstrated significantly higher strength, reaching compressive strength values of about 6 kg/cm2. Casting trials revealed improved fluidity and surface quality for red mud molds. The average surface roughness of castings produced using red mud molds was 4.8 µm, compared with 6.7 µm for conventional silica sand molds. However, slightly higher porosity (4.33%) was observed compared with silica sand molds (2.25%). The hardness of the A-356 alloy casting produced in red mud molds was 82 ± 2 HV, which is comparable to the 86 ± 2 HV obtained from silica sand molds. Microstructural analysis confirmed similar α-Al dendritic matrix and eutectic (α-Al + Si) structures for both mold systems. The results demonstrate that up to 15 wt% red mud can effectively replace silica sand without compromising mold properties or casting performance.

Graphical Abstract