Investigation on the mechanical properties of stir-cast Al7075-T6-based nanocomposites with microstructural and fractographic surface analysis

Introduction. Aluminum-based metal matrix composites (MMCs) have garnered considerable attention recently due to their enhanced mechanical properties, making them suitable for a wide range of industrial applications. While other methods exist for incorporating reinforcements into the base metal, stir casting is a particularly efficient process as it promotes a more uniform distribution of reinforcement particles throughout the matrix. The purpose of this work. It has been demonstrated that adding silicon carbide (SiC) reinforcements to alloys from the 7XXX series enhances their fatigue strength. The impact of SiC reinforcements on the mechanical properties of A356 composites, such as elongation, compressive strength, tensile strength, and hardness, has also been investigated. However, there is a need for more research on how hybrid reinforcement particles affect the mechanical properties of Al7075-T6 alloy. Methods. Considering the broad application spectrum of aluminum matrix composites (AMCs) in the automotive and aerospace sectors, this study examines the influence of varying ratios of nano-sized SiC and graphene reinforcements on the hardness and tensile strength of stir-cast Al7075-T6 aluminum alloy. The scanning electron microscopy — energy-dispersive X-ray spectroscopy (SEM-EDS) analysis of the composites' microstructural and fractographic surfaces is also included. The objectives of this work are to develop lightweight, high-performance hybrid metal matrix nanocomposite materials and to explore the feasibility of integrating graphene and SiC nanoparticles into Al7075 alloy. Particular emphasis is placed on the discussion of the mechanical characteristics of these hybrid materials. Results and discussion. This study found that mechanical stirring improved the bonding, wetting, and cohesion between the reinforcements and matrix while reducing porosity. Compared to composites produced without stirring, stirred composites exhibited improved strength and toughness due to microstructural changes. The study suggests that appropriate mixing strategies can significantly impact the mechanical properties and surface morphology of Al7075 nanocomposites. The results indicated that the hybrid reinforcement nanoparticles significantly improved both the hardness and tensile strength of the Al7075-T6 alloy. Moreover, a distinct correlation between the ratio of silicon carbide to graphene nanoparticles and the mechanical properties of the specimens was observed. Specifically, an Al7075 specimen reinforced with 0.5 wt.% graphene and 3 wt.% silicon carbide nanoparticles demonstrated superior hardness and tensile strength compared to unreinforced Al7075 and other combinations of silicon carbide and graphene nanoparticles considered in this study. With a 0.5 wt.% graphene content and 1–3 wt.% SiC content, the Al7075-based nanocomposites consistently exhibited a well-defined grain structure with distinct, continuous grain boundaries. The resulting finely dispersed nanoparticles, ranging in size from 62.57 to 91.54 nm, facilitated effective load transfer, grain refinement, and impeded dislocation motion, leading to enhanced mechanical properties. An Al7075-based nanocomposite exhibited superior mechanical performance characterized by a dense, dimpled surface featuring uniform microvoids and minimal particle pull-out. This behavior was attributed to ductile fracture resulting from strong matrix-reinforcement bonding and efficient load transfer. Consistent with these observations, the study indicates that the mechanical behavior of hybrid Al7075-based nanocomposites is significantly influenced by the reinforcement ratio, particle size, and dispersion quality. This information is valuable for advanced industrial applications. The study further demonstrates that a balanced combination of graphene and silicon carbide nanoparticle reinforcements can enhance the mechanical properties of Al7075, emphasizing the need for further investigation into these synergistic effects.