Deformation mechanisms of Gr covering on Cu under nanoindentation: A molecular dynamics simulation

Abstract Many research studies have shown that graphene can enhance the mechanical properties of copper (Cu). However, the deformation behaviors and defects evolution of Gr/Cu during indentation and the recovery ratio, surface morphology, and residual defects during retraction are rarely reported. In this research, the indentation responses and deformation mechanisms of Gr/Cu are studied during whole indentation and retraction by employing molecular dynamics simulation (MD). It comes to light that the elastic phase agrees perfectly with the Hertzian theoretical model. With the nucleation of dislocation generating, the curve deviates from the Hertzian theoretical model, which indicates that the material indentation enters the plastic stage. The loading force of the Gr/Cu system fluctuates greatly during the indentation process due to the generation and emission of dislocation loops and the interaction of stacking faults. Due to the extension of the contact area and inherent properties of graphene, the elastic recovery ratio of Gr/Cu is 18.3%, which is greatly improved. The surface pile-up effect is reduced effectively by covering graphene. The types of residual defects in the Gr/Cu system include stacking fault tetrahedral (SFT), Wing-like-dislocations, prismatic loops, stacking faults, and atomic clusters.