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<p>This study investigates the microstructural evolution, mechanical properties, and fracture behaviour of LM25 aluminium alloy and LM25–10 wt% SiC composite in both as-cast and T6 heat-treated conditions. Optical microscopy revealed that T6 treatment significantly refined the eutectic Si morphology and improved matrix homogeneity. The Vickers hardness and tensile tests revealed significant improvements following heat treatment, with the LM25–SiC composite exhibiting the highest values 96 ± 6 HV for hardness, 229 MPa for yield strength, and 248 MPa for ultimate tensile strength. However, the ductility of the composite remained limited due to the presence of hard SiC particles. SEM fracture analysis indicated a transition from brittle to more ductile fracture modes after heat treatment, evidenced by microvoid coalescence and improved matrix–reinforcement bonding. Impact testing also supported these findings, showing that heat-treated samples absorbed more energy because of their improved microstructure and stress distribution. Although the composite had lower impact strength than the base alloy, heat treatment helped reduce its brittle behaviour. Fractography revealed features such as oxide bifilms, particle pull-out, and cleavage fractures in the as-cast state, which transformed into ductile dimples and shear lips post-treatment. These findings highlight the beneficial role of T6 treatment in enhancing the mechanical performance and fracture resistance of LM25-based composites.</p>

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Fracture behaviour and failure mechanisms of LM25 alloy and LM25–10% SiC composite under impact loading

  • 期刊论文

  • 发表日期：

    2026年7月25日

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  • Jayashree Baral

摘要

This study investigates the microstructural evolution, mechanical properties, and fracture behaviour of LM25 aluminium alloy and LM25–10 wt% SiC composite in both as-cast and T6 heat-treated conditions. Optical microscopy revealed that T6 treatment significantly refined the eutectic Si morphology and improved matrix homogeneity. The Vickers hardness and tensile tests revealed significant improvements following heat treatment, with the LM25–SiC composite exhibiting the highest values 96 ± 6 HV for hardness, 229 MPa for yield strength, and 248 MPa for ultimate tensile strength. However, the ductility of the composite remained limited due to the presence of hard SiC particles. SEM fracture analysis indicated a transition from brittle to more ductile fracture modes after heat treatment, evidenced by microvoid coalescence and improved matrix–reinforcement bonding. Impact testing also supported these findings, showing that heat-treated samples absorbed more energy because of their improved microstructure and stress distribution. Although the composite had lower impact strength than the base alloy, heat treatment helped reduce its brittle behaviour. Fractography revealed features such as oxide bifilms, particle pull-out, and cleavage fractures in the as-cast state, which transformed into ductile dimples and shear lips post-treatment. These findings highlight the beneficial role of T6 treatment in enhancing the mechanical performance and fracture resistance of LM25-based composites.