Sustainable processing of recycled aluminium alloy hybrid composites with Si3N4 and MoS2 reinforcements for lightweight applications

The growing need for lightweight, high-performance materials has intensified the focus on recycling aluminium alloys from industrial scrap. Nevertheless, obtaining sufficient mechanical and corrosion characteristics from recycled alloys continues to pose a significant challenge. This study involved the synthesis of an Al–Zn–Mg–Cu alloy utilising elements sourced from scrap, which was then reinforced with different proportions of silicon nitride (Si3N4) and molybdenum disulfide (MoS2) to improve its structural, corrosion, and tribological performance. The composites were fabricated using squeeze casting, exerting an instantaneous pressure of 150 MPa on the molten metal to ensure homogeneous dispersion and enhanced adhesion between the blends. Microstructural examination revealed that Si3N4 particles were inclined to occupy grain boundaries and served as effective nucleation sites during solidification, thereby facilitating the formation of a finer microstructure. The refinement of the grain structure, coupled with enhanced interfacial bonding within the mixture, played a crucial role in improving the mechanical properties. Moreover, the incorporation of MoS2 particles into the interstitial voids of Si3N4 effectively decreased porosity and promoted densification. As a consequence, the synthesised hybrid blend found a substantial increase in hardness (32 ± 0.1 %), tensile (35 ± 0.1 %), compressive (41 ± 0.1 %), and flexural strength (35 ± 0.2 %) when compared to as-cast recycled Al–Zn–Mg–Cu alloys. The enhancement in corrosion resistance is noteworthy, as evidenced by a reduction in the corrosion rate to 0.0002902 mm/year, alongside a significant minimization of wear loss by 40 ± 0.2 %. The results found that hybrid reinforcement, combined with intricate processing, enhances the properties of recycled aluminum alloys for use in structural and automotive applications.