Fabrication and mechanical properties of MWCNTs and graphene synergetically reinforced Cu–graphite matrix composites

Multi-walled carbon nanotubes (MWCNTs) and graphene synergetically reinforced Cu–graphite matrix composites with alloying elements and the rare earth element lanthanum were fabricated by powder metallurgy, and their mechanical properties were evaluated. An innovative solution for dispersing the solution into the MWCNTs and graphene was adopted by surface modification with gallic acid solution or rutin solution, instead of strong acid and base solutions, respectively. The interfacial bonding between MWCNTs or graphene and the copper matrix, and the particle distribution uniformity, were enhanced by mechanical alloying and freeze-drying. Nearly complete densification of the MWCNTs and graphene synergetically reinforced Cu–graphite matrix composites was achieved by hot-pressing and hot isostatic pressing sintering. The microstructure and mechanical properties of the composites indicated that the interfaces between the reinforcing phases and matrix were tightly bonded, confirming that the interface bonding between the MWCNTs, graphene, and copper matrix was mainly established as mechanical locks. The dominant strengthening mechanisms in the composites were the fine grain strengthening, load transferring, and solution strengthening, followed by dislocation strengthening.