Achieving excellent thermal stability in continuous three-dimensional graphene network reinforced copper matrix composites

The stabilization of ultrafine crystalline grains is a tough issue for developing high-performance copper (Cu) matrix composites towards the application in the electronic industries. In order to solve this problem, here we introduced the construction of a three-dimensional graphene network (3DGN) in the Cu matrix to boost the stabilization of both the bi-crystal grain boundaries and the triple junctions. Mechanical properties tests demonstrated that 3DGN/Cu possessed an excellent thermal stability up to 0.9Tm and high-temperature Vickers hardness, which are much higher than those of pure Cu and composites reinforced by two-dimensional (2D) reduced graphene oxides nanosheets. Microstructure characterization revealed that during the hot-rolling (HR) deformation, 3DGN had a strong pinning effect on the recrystallized Cu grains with high-angle grain boundaries and improved the intragranular dislocation density as well as the fractions of the low-angle grain boundaries thus resulting in retaining the equiaxed grain shape and ultrafine grain size. The experimental and molecular dynamics (MD) simulation results both indicated that the key point of attaining the high stability of the graphene/Cu composites lied in the effective restriction of the grain boundary triple junctions migration. These findings may provide guidance for promoting the thermomechanical properties of 2D nanomaterials/Cu composites.