OBRABOTKAMETALLOV MATERIAL SCIENCE Vol. 27 No. 3 2025 distributed reinforcing phase in Fig. 8, a. Due to their higher surface area-to-volume ratio, these nanoscale particles exhibit strong bonding with the matrix, thereby improving mechanical properties. Effective load transfer, grain refinement, and impediment of dislocation motion contribute to increased hardness, tensile strength, and wear resistance. These microstructural observations corroborate the superior hardness (155.52 BHN) and tensile strength (156.62 MPa) observed for Specimen 7. Conversely, Fig. 8, b depicts a coarser particle distribution ranging from 90.49 to 116.9 nm for Specimen 8. Coarser and irregular grains with less distinct grain boundaries are apparent. The clustered structure and larger particle size suggest agglomeration, often resulting from inadequate mixing or thermodynamic instability during processing.Agglomerated particles concentrate stress and degrade matrixreinforcement interaction, limiting load transfer. The reduced grain boundary density and uniformity lead to decreased dislocation impediment, which correlates with the diminished mechanical properties observed for Specimen 8. This comparative microstructure analysis demonstrates that reinforcement percentage, particle size, and dispersion quality are key determinants of the mechanical behavior of hybrid Al7075-based nanocomposites. The study provides valuable insights for the development of advanced materials with enhanced performance for various industrial applications. Conclusions This research investigated the effects of varying ratios of nanosized SiC and graphene reinforcements on the hardness and tensile strength of Al7075-T6 aluminum alloy produced via stir casting, considering the widespread use of aluminum matrix composites (AMCs) in aerospace and automotive applications. The microstructural and fracture surface analysis of the composites was also performed using SEM-EDX. This study aimed to develop lightweight, high-performance hybrid metal matrix nanocomposite materials and explore the potential of combining graphene and SiC nanoparticles with Al7075 alloy, with particular attention given to characterizing the mechanical properties of these hybrid materials. The following conclusions can be drawn from this work: – An Al7075-based nanocomposite with a 0.5 wt.% graphene and 3 wt.% SiC composition exhibited a tensile strength of 156.62 MPa and a hardness of 155.52 BHN. SiC nanoparticles were found to be most effective in hardening metal matrix composites, while graphene contributed to enhancing the tensile strength of the nanocomposites. – Mechanical stirring effectively reduced porosity and improved bonding, wetting, and cohesion between the matrix and reinforcements. The resulting microstructural changes led to superior strength and toughness in stirred composites compared to unstirred composites. The use of appropriate mixing techniques significantly influenced the surface morphology and mechanical properties of Al7075 nanocomposites. – Al7075-based nanocomposites with 1 wt.% graphene and 2 wt.% SiC content exhibited decreased mechanical properties, which correlated with reduced dislocation obstruction due to decreased grain boundary density and uniformity. – Al7075-based nanocomposites with 0.5 wt.% graphene and 1‑3 wt.% SiC content displayed a uniformly polished grain structure with distinct and continuous grain boundaries. The fine-polished nanoparticles produced, ranging in size from 62.57 to 91.54 nm, demonstrated superior mechanical characteristics through efficient load transfer, grain refinement, and dislocation motion impediment. – Al7075-based nanocomposites with a dense, dimpled surface, homogeneous microvoids, and minimal particle pull-out exhibited superior mechanical properties. This was attributed to ductile fracture with strong matrix-reinforcement bonding and effective load transfer. – Reinforcement percentage, particle size, and dispersion quality significantly influence the mechanical behavior of hybrid Al7075-based nanocomposites, providing valuable insights for advanced industrial applications.
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