Mechanical, Tribological and Thermal Characterisation of Aluminium 6061 Matrix Composites Reinforced with Graphene Nanoplatelets Fabricated by Powder Metallurgy

lightweight structural and functional materials for aerospace, automotive, and electronic packaging applications, offering the possibility of simultaneously tailoring mechanical, tribological, and thermal properties within a single material system. This study investigates the processing-structure-property relationships in AA6061 aluminium alloy matrix composites reinforced with graphene nanoplatelets (GNPs) at weight fractions of 0.1, 0.3, 0.5, 0.75, and 1.0 wt%, fabricated by a powder metallurgy route involving ball milling and uniaxial hot-pressing at 550°C. The effects of GNP content on microstructure (SEM, XRD, EDS), density, tensile strength, Vickers hardness, dry sliding wear behaviour (pin-on-disc at 10– 50 N loads), coefficient of friction, thermal conductivity, and coefficient of thermal expansion (27–400°C) are systematically characterised and discussed in terms of GNP–matrix interfacial bonding, dispersion homogeneity, and load-transfer efficiency. The AA6061 + 0.5 wt% GNP composite achieves the optimal balance across all property domains: ultimate tensile strength of 281 MPa (34% improvement over unreinforced AA6061), Vickers hardness of 117 HV (33% improvement), wear rate of 0.97 × 10⁻³ mm³/m at 30 N (50% reduction), coefficient of friction of 0.37 (34% reduction), thermal conductivity of 178 W/m·K (15% improvement), and CTE of 21.7 × 10⁻⁶ /°C (6% reduction). Beyond 0.5 wt%, GNP agglomeration—confirmed by SEM and evidenced by declining density and mechanical properties—reduces reinforcement efficiency, establishing 0.5 wt% as the percolation-limited optimum for this processing route