▎ 摘　　要

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 dy-namics (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.