Strengthening mechanism of Al matrix composites reinforced by nickel-coated graphene: Insights from molecular dynamics simulation

The inadequate bonding strength of graphene and metal matrix is a major challenge to improve the mechanical properties of graphene metal-matrix composites. Here, molecular dynamics simulation is performed to investigate the effect of layer thickness on the mechanical properties of the nickel-coated graphene-reinforced aluminum (NGR-Al) matrix nano-multilayers (NMs) under uniaxial tension and compression load. The results show that the Ni coating on the surface of graphene is an effective method to ameliorate the load transfer ability between graphene and metal matrix. There is a critical layer thickness above which the tensile yield strength and the layer thickness obey the Hall-Petch (HP) relation, and under which the inverse HP relation is followed. The results indicate that compared with pure Al, the introduction of Ni-coated graphene makes the sample have a significant plastic strain strengthening effect under compression load, and the smaller the layer thickness is, the better the strengthening effect is.