The atomic structure evolution and strengthening mechanism in three-dimensional network graphene enhanced Cu: A molecular dynamics simulation

Three-dimensional network graphene (3DN-Gr) is a promising reinforcement for Cu matrix composites. Herein, molecular dynamics (MD) simulations are performed to investigate the structural evolution of three-dimensional network graphene/copper (3DN-Gr/Cu) composites, as well as the influences on mechanical properties. Generally, "Y"-shaped junctions could be formed between single-layer graphene sheets (S-Gr) upon hot sintering, which could promote the bonding between graphene and copper, and effectively hinder the gliding of dislocations. Whereas, hollow double "Y"-shaped junctions could be formed between double-layer graphene (D-Gr), and weak Van der Waals force exists between them so that it is easy for them to debond from each other during the stretching process. As a result, the interfacial bonding in the S-Gr enhanced copper is stronger than that in D-Gr enhanced one. 3D network structure might be formed at the graphene content of 3.03 wt% or higher, and the strengthening effect is significantly improved. Moreover, the copper grains in the composites are refined. and the sliding and rotation of refined grains are suppressed by the 3DN-Gr, which even breaks the inverse Hall-Petch relationship in conventional nanocrystalline copper.