Enhancing mechanical and tribological behaviour of Al7075 hybrid composites reinforced with boron carbide and molybdenum disulphide

Al7075 hybrid metal matrix composites reinforced with boron carbide (B₄C) and molybdenum disulphide (MoS₂) were fabricated using a double stir casting technique to evaluate the combined effect of hard ceramic and solid-lubricant reinforcements. Three compositions Al7075, Al7075–5 wt% B₄C, and Al7075–5 wt% B₄C–5 wt% MoS₂ were developed and characterised. Microstructural analysis using Optical Microscopy, FESEM, and EDAX confirmed uniform reinforcement distribution, clear phase identification, and good interfacial bonding. Mechanical testing showed that B₄C significantly enhanced hardness and tensile strength through grain refinement and load transfer mechanisms. Tribological studies under dry sliding conditions revealed that MoS₂ reduced friction and wear by forming a lubricating tribo-film at the contact interface. SEM analysis of worn surfaces at different magnifications identified wear grooves, delamination cracks, adhesive smearing, and compacted debris, indicating a transition from severe abrasive wear in the base alloy to a mild lubricative wear regime in the hybrid composite. The synergistic interaction between B₄C and MoS₂ provided an optimal balance between strength and wear resistance. The developed hybrid composite demonstrates improved tribological performance and is suitable for aerospace and automotive applications.