Abstract

Currently, the growing importance of sustainable manufacturing and efficient resource utilization has increased interest in recycling industrial metal waste, particularly copper, which is essential for electrical and electronic applications due to its excellent electrical and thermal conductivity properties. However, recycled copper, similar to commercial copper, exhibits low hardness, poor wear resistance, and limited mechanical strength, which restricts its use under demanding service conditions. To overcome these limitations, reinforcing copper with hard ceramic particles such as SiC is an effective approach to improve mechanical performance. However, in conventional metal matrix composites (MMCs), enhancements in properties are typically accompanied by a reduction in electrical conductivity, thereby limiting their applicability in electrical systems. Functionally graded composites (FGCs) offer a promising approach to addressing this challenge. By gradually varying the reinforcement content across the bulk material, FGCs achieve a graded structure in which the outer layers provide enhanced hardness and wear resistance, while the copper-rich core preserves high conductivity. This graded architecture enables a property combination that is unattainable in uniformly reinforced MMCs. In this study, Cu/SiC composite powders were produced from recycled industrial copper scrap refined via electrolytic processing and reinforced with varying SiC contents (5-20 vol%) using high-energy ball milling (HEBM) for 6 h. The composite powders were subsequently consolidated into graded structures using the field-assisted sintering technique (FAST/SPS). The designed FGC architecture consisted of a pure copper core surrounded by symmetric layers containing 5, 10, 15, and 20 vol% SiC, each with a thickness of 0.5 mm, resulting in a sintered disc with a diameter of 40 mm and a total thickness of 5 mm. For comparison, uniformly reinforced MMC samples with corresponding SiC contents were also fabricated. The microstructural evolution and phase composition of the composite powders and consolidated samples were examined using light microscopy (LM), scanning electron microscopy (SEM), and X-ray diffraction (XRD). Particle size distribution was determined by laser diffraction, while microhardness measurements were performed to assess the effects of milling time and reinforcement content. After 6 h of milling, a homogeneous distribution of SiC particles and a near-spherical powder morphology were achieved. Increasing SiC content and milling time resulted in particle refinement and a pronounced increase in hardness, with microhardness values rising from approximately 85 HV for unreinforced copper to about 300 HV at 20 vol% SiC. The Functional properties of the consolidated MMC and FGC samples were evaluated through microhardness, density, and electrical conductivity measurements. The FGC samples retained high conductivity (90-100% IACS) in the copper-rich core, while the outer layers achieved enhanced surface hardness of 200 HV. In contrast, the MMCs exhibited increased hardness accompanied by a reduction in electrical conductivity with increasing SiC content. Overall, the developed FGCs produced from recycled copper powder can successfully combine sustainability with high functional performance, demonstrating strong potential for industrial applications in electrical contacts that require both high wear resistance and high conductivity.