A simple approach to obtaining enhanced mechanical properties of graphene/copper composites with heterogeneous grain structures

Abstract Strengthening metal matrix composites by grain refinement and high content of reinforcement usually compromises a dramatic sacrifice of ductility. Here multimodal powder metallurgy is developed to construct heterogeneous grain structures in reduced graphene oxide (RGO) reinforced Cu matrix composites through high temperature oxidation and high energy ball milling for the electrolytic Cu powder followed by spark plasma sintering (SPS) and hot rolling. This process involves the formation of the combined structure of RGO covered with Cu nanoparticles through thermal reduction, which is critical to ensuring the nano-level dispersion of RGO in metal matrix and strong interfacial bonding. Those composites exhibit both high normalized yield stress of up to 3.4 and high uniform tensile strain of 21.8%. The results indicate that the improved strength-ductility synergy may be attributed to the synergistic effects of the RGO and heterogeneous grain structures. This approach could realize macroscopic mixing of powders and nano-level dispersion of reinforcement to manufacture metal matrix composites with heterogeneous grain structures in large-scale productivity, and will help in developing new microstructures for high overall performance.