Achieving better strength-toughness synergy in heterogeneous Cu/Ni/graphene composites: A molecular dynamics simulation

The non-wetting nature of copper (Cu) and graphene, coupled with the brittle behavior of graphene, impedes the strength-toughness synergy in graphene-reinforced Cu matrix (Cu/graphene) composites, limiting their practical applications. Benefiting from interface modification engineering and heterogeneous structure strengthening effects, here a novel strengthening and toughening strategy for Cu/graphene composites by introducing a variable-thickness nickel (Ni) modification layer sandwiched between Cu and graphene (Cu/Ni/graphene) was proposed, and the influence of layer thickness-related structural heterogeneity on mechanical properties and underlying deformation mechanisms were investigated via molecular dynamics simulations. The results revealed that an optimal Ni thickness of 2.44 nm within increased Ni layer thickness enhanced the strength-toughness synergy in the Cu/Ni/graphene composites. This was attributed to altered interface structure, stress distribution, and graphene fracture behaviors due to layer thickness-related deformation behavior. In addition to common strengthening mechanisms like graphene load-bearing effect, interface dislocation nucleation, and interface dislocation blockage strengthening, the layer thickness-dependent semi-coherent Cu/Ni and Ni/graphene heterogeneous interface stress strengthening contributed to extra strength enhancement. Furthermore, cooperative deformation behavior among heterogeneous components improved toughness. The interfacial engineering strategy, achieved by tailoring the modification layer thickness, may pave the way for producing nanostructured metallic composites with extraordinary mechanical properties. [Display omitted] •The thickness of modification layer dependent strengthening strategy is proposed in Cu/graphene composite.•Cu/Ni/graphene composite with 2.44 nm Ni layer owns optimal strength-toughness synergy.•Multiple strengthening mechanisms lead to strong and tough Cu/Ni/graphene composite.•Layer thickness-related heterogeneous interface stress contributes to extra strength.