Analysis of mechanical properties and fracture mechanism in LM30 Al alloy composites with single and dual size reinforcements

This study examines the effect of reinforcement particle size and distribution, both single and dual, on the mechanical properties of aluminium composites. Using the stir-casting method, the composites were fabricated with ilmenite particles in single-range and dual-range forms. Experimental analysis, including tensile, impact, and fracture behaviour, revealed that the composite strength and toughness are significantly affected by particle size, content, and fine-to-coarse reinforcement ratio. The LM30 base alloy has a tensile strength of 188 MPa, which increases to 327 MPa with 15 wt.% 32–50 μm particles and 526 MPa with 15 wt.% fine to coarse (4:1) particles. However, elongation drops from 5.08 % to 1.82 % and 1.57 %, respectively, indicating increased brittleness. Impact strength also decreases from 22.33 J to 14.42 J and 15.92 J. While dual particles composite shows the highest tensile strength, they also slightly mitigate impact strength loss compared to single reinforced composite. Scanning electron microscopy and energy-dispersive spectroscopy provided insights into fracture mechanisms, showing a transition from brittle to ductile failure with optimized reinforcement distribution. The novelty of this research lies in its systematic investigation of single and dual-range reinforcement, which offers a balance between strength, ductility, and impact resistance, providing valuable design considerations for next-generation aluminium metal matrix composites.