| Summary: | This research work aims at investigating the influence of a fixed content of silicon nitride (Si<sub>3</sub>N<sub>4</sub>) and varied contents of graphene nanoplatelets (GNPs) on the physical (density, structural, morphological) and mechanical properties (microhardness, nanoindentation) of Al-Si<sub>3</sub>N<sub>4</sub>-GNPs composites. The composites were fabricated by a microwave-assisted powder metallurgy route. The Si<sub>3</sub>N<sub>4</sub> concentration was fixed at (5 wt.%) in Al-Si<sub>3</sub>N<sub>4</sub>-GNPs composites while the GNPs concentration was varied between (0 wt.%) to (1.5 wt.%) with an increment of (0.5 wt.%). The structural analysis indicates the formation of phase pure materials with high crystallinity. The microstructural analysis confirmed the presence of the Si<sub>3</sub>N<sub>4</sub> and GNPs showing enhanced agglomeration with the increasing amount of GNPs. Moreover, the surface roughness of the synthesized composites increases with an increasing amount of GNPs reaching its maximum value (RMS = 65.32 nm) at 1.5 wt.% of GNPs. The Al-Si<sub>3</sub>N<sub>4</sub>-GNPs composites exhibit improved microhardness and promising load-indentation behavior during nanoindentation when compared to pure aluminum (Al). Moreover, Al-Si<sub>3</sub>N<sub>4</sub>-GNPs composites demonstrate higher values of compressive yield strength (CYS) and ultimate compressive strength (UCS) when compared to pure Al despite showing a declining trend with an increasing amount of GNPs in the matrix. Finally, a shear mode of fracture is prevalent in Al-Si<sub>3</sub>N<sub>4</sub>-GNPs composites under compression loading.
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