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<p>Aluminium metal matrix composites (AMMCs) are extensively used in lightweight engineering applications; however, their conventional machining is difficult because of tool wear, surface damage, and non-uniform material removal caused by reinforcement phases. Biomachining offers a low-energy and non-thermal alternative for controlled material removal. In this study, aluminium–magnesium–molybdenum disulphide composites were fabricated through powder metallurgy and biomachined using two chemolithotrophic bacteria, <i>Acidithiobacillus ferrooxidans</i> (<i>A.ferrooxidans</i>) and <i>Acidithiobacillus thiooxidans</i> (<i>A.thiooxidans</i>). Six compositions, namely pure Al, Al–4%Mg, Al–6%Mg, Al–Mg– MoS₂ (91–6–3), Al–Mg– MoS₂ (90–6–4), and Al–Mg–MoS₂ (89–6–5), were evaluated under controlled biomachining conditions at 30&#xa0;°C and 180&#xa0;rpm for 24, 48, and 72&#xa0;h. Material removal rate, specific material removal rate, surface roughness, and normalized performance index were used to assess machining efficiency and surface quality. The results revealed that <i>A.thiooxidans</i> produced approximately 1.4 − 1.8 times higher material removal rate than <i>A.ferrooxidans</i>, which may be assigned to sustained sulfuric acid generation and lower ferric-precipitation-related surface coverage. The maximum material removal was noticed during the first 24&#xa0;h, followed by a gradual reduction at longer machining durations due to changes in acidity and accumulation of reaction products. Magnesium-rich compositions exhibited increased surface roughness, whereas molybdenum disulphide-containing composites showed more stable material removal and better surface integrity. Among the investigated materials, Al–Mg– MoS₂ (91–6–3) showed the best-balanced biomachining performance by combining high material removal with comparatively lower surface roughness. The study confirms that both microbial species and alloy chemistry strongly influence the biomachining performance of aluminium-based composites.</p>

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Effect of Acidithiobacillus species on biomachining of aluminium matrix composites

  • 期刊论文

  • 发表日期：

    2026年7月31日

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  • Ch Narmada,
  • S Rajesh

摘要

Aluminium metal matrix composites (AMMCs) are extensively used in lightweight engineering applications; however, their conventional machining is difficult because of tool wear, surface damage, and non-uniform material removal caused by reinforcement phases. Biomachining offers a low-energy and non-thermal alternative for controlled material removal. In this study, aluminium–magnesium–molybdenum disulphide composites were fabricated through powder metallurgy and biomachined using two chemolithotrophic bacteria, Acidithiobacillus ferrooxidans (A.ferrooxidans) and Acidithiobacillus thiooxidans (A.thiooxidans). Six compositions, namely pure Al, Al–4%Mg, Al–6%Mg, Al–Mg– MoS₂ (91–6–3), Al–Mg– MoS₂ (90–6–4), and Al–Mg–MoS₂ (89–6–5), were evaluated under controlled biomachining conditions at 30 °C and 180 rpm for 24, 48, and 72 h. Material removal rate, specific material removal rate, surface roughness, and normalized performance index were used to assess machining efficiency and surface quality. The results revealed that A.thiooxidans produced approximately 1.4 − 1.8 times higher material removal rate than A.ferrooxidans, which may be assigned to sustained sulfuric acid generation and lower ferric-precipitation-related surface coverage. The maximum material removal was noticed during the first 24 h, followed by a gradual reduction at longer machining durations due to changes in acidity and accumulation of reaction products. Magnesium-rich compositions exhibited increased surface roughness, whereas molybdenum disulphide-containing composites showed more stable material removal and better surface integrity. Among the investigated materials, Al–Mg– MoS₂ (91–6–3) showed the best-balanced biomachining performance by combining high material removal with comparatively lower surface roughness. The study confirms that both microbial species and alloy chemistry strongly influence the biomachining performance of aluminium-based composites.