OBRABOTKAMETALLOV MATERIAL SCIENCE Vol. 27 No. 3 2025 Results and Discussion This section presents 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, conducted using SEM-EDX analysis, is also presented. This research aims to develop lightweight, high-performance hybrid metal matrix nanocomposite materials and explore the potential of combining SiC and graphene nanoparticles with Al7075 alloy, focusing on characterizing the mechanical properties of these hybrid materials. The following aspects will be addressed: – The influence of varying proportions of nanosized SiC and graphene on the hardness and tensile strength of Al7075-T6 alloy; – The microstructure and fracture surface morphology of Al7075-T6 nanocomposites, investigated using SEM-EDX analysis; – Key findings of the study and directions for further research. Mechanical properties of Al7075-T6 nanocomposites This subsection discusses the mechanical properties ‑ hardness and tensile strength – of both unreinforced and reinforced Al7075-T6 nanocomposite specimens prepared using stir casting. As shown in Table 2, a total of eight different Al7075-T6 nanocomposite specimens were fabricated via stir casting, with varying silicon carbide (SiC) and graphene nanoparticle reinforcements. The mechanical properties – hardness and tensile strength – were measured and compared between the unreinforced and differently reinforced Al7075-T6 nanocomposites. Fig. 2 illustrates the hardness and tensile strength of both unreinforced and reinforced Al7075-T6 nanocomposites. As illustrated in Fig. 2, the addition of graphene and SiC reinforcements to Al7075 significantly increases the material’s tensile strength and hardness, resulting in a considerable improvement in overall strength. Specimen 1, representing the unreinforced Al7075 material, exhibits a tensile strength of 89.47 MPa and a Brinell hardness number (BHN) of 84.3. Increasing the graphene percentage from 0.1% to 0.3% in Specimens 2 through 4, while maintaining a constant 0.5% SiC reinforcement, results in a gradual increase in hardness (101.40‑107.5 BHN) and tensile strength (117.68‑141.82 MPa). Furthermore, increasing the SiC percentage from 1% to 3% in Specimens 5 through 7, while maintaining a constant 0.5% graphene reinforcement, leads to a significant improvement in tensile strength (151.55‑156.62 MPa) and hardness (132.60‑163.40 BHN). Fig. 2 demonstrates that reinforced Al7075-T6 nanocomposites exhibit greater hardness and tensile strength compared to the unreinforced Al7075 specimen. Furthermore, these properties increase with higher concentrations of SiC and graphene nanoparticle reinforcements. However, the increase in these properties, particularly hardness, appears more pronounced with SiC reinforcement compared to graphene reinforcement in the Al7075-T6 alloy. With a constant 1% graphene reinforcement, tensile strength decreases when SiC reinforcement exceeds 2%. Increasing the SiC percentage from 2% to 4% in Al7075-based nanocomposites, while maintaining a constant 1% graphene reinforcement (Specimens 8 and 9), results in a significant decrease in tensile strength (120.24‑126.16 MPa) compared to the increase in hardness (145.16‑163.40 BHN). The decrease Fig. 2. Hardness and tensile strength of Al7075-T6 nanocomposites
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