Enhanced Hall-Petch strengthening in graphene/Cu nanocomposites

Grain size dependent strength, known as Hall-Petch relation, has been approved to be valid in crystalline metals and alloys. However, softening would eventually occur as grain size reduced into nanoscale that below a critical value. Hence, it is essential to find a way to break the strength limitation by avoiding the deformation mechanism transition from dislocation-mediated to grain-boundary-mediated processes. By replacing grain boundary (GB) of nanocrystalline Cu with graphene, in the present study, molecular dynamics simulations show that graphene-boundary (GrB) embedded GrB/Cu nanocomposites exhibit enhanced enlarged Hall-Petch slope with decreasing grain size. The absence of inverse-Hall-Petch relation and the extremely high strength derived at the GrB/Cu nanocomposites were interpreted by the high back stress and abundant dislocation activity that attributed from the high-degree of heterogeneous structure of the nanocomposites.