Graphene Nanoplatelet-Reinforced Hybrid Aluminum Matrix Composites: Recent Advances and Future Perspectives

Hybrid aluminum matrix composites (HAMCs) reinforced with graphene nanoplatelets (GNPs) and secondary reinforcements have emerged as promising lightweight structural materials due to their superior strength, wear resistance, and multifunctional performance. This review critically evaluates recent developments in GNPs-reinforced HAMCs, categorizing them into carbide-assisted, oxide-assisted, carbonaceous, and emerging sustainable hybrid systems. The influence of processing routes including semi-solid stir casting (compocasting), ultrasonic-assisted stir casting (UASC), powder metallurgy (PM), friction stir processing (FSP), accumulative roll bonding (ARB), and laser powder bed fusion (L-PBF) on reinforcement dispersion, interfacial bonding, and resultant properties (grain refinement, load-transfer mechanisms, etc.) is systematically discussed. Further, particular emphasis is placed on the role of the hybrid reinforcements in improving the mechanical and tribological performances of the HAMCs in reference to their processing techniques. Comparative analysis reveals that carbide-assisted systems provide the highest strengthening response, where Al/(GNPs+SiC) composites achieve tensile strengths up to 589 MPa through severe grain refinement, while GNPs+WC systems exhibit nearly 350% relative strength enhancement. Among oxide-assisted systems, L-PBF fabricated AA2024/(0.2GNPs+1ZrO2) (wt.%) composites attain a peak tensile strength of 624 MPa after T6 treatment due to the formation of a crack-free bimodal microstructure. Carbonaceous hybrids such as reduced graphene oxide (rGO)+CNTs systems demonstrate an excellent balance between strength (460 MPa) and ductility (31.6%) through interconnected carbon networks that suppress crack propagation. Tribologically, graphene-based tribo-films significantly reduce friction and wear, with GO+CNTs hybrids achieving a minimum coefficient of friction of 0.295, whereas GNPs+B4C and GNPs+waste-derived Al hybrid systems exhibit excellent wear resistance with wear rates as low as 1.9x10-3 mm3 m-1. The review further highlights key challenges including reinforcement agglomeration, porosity, and interfacial instability at higher GNPs loadings (>1–2 wt.%). Overall, the study provides a comparative and data-driven framework for designing next-generation HAMCs for aerospace, automotive, defense, and thermal-management applications.