High-strength graphene network reinforced copper matrix composites achieved by architecture design and grain structure regulation

Developing metallic materials with heterogenous nanostructures is one of the most promising strategies for obtaining excellent integrated mechanical properties towards structural applications. To explore the possibility of realizing intentional structural heterogeneities in graphene/metal composites, herein, we demonstrate a novel copper composite reinforced by three-dimensional network-like graphene powders, achieved by hot-pressing, cryo-rolling and low-temperature annealing. It was found that the structure of three-dimensional graphene could be well remained during the processing and thereby resulted in an alternated distribution of lath-like graphene-rich zones and graphene-free zones in the composites. The yield strength (380 +/- 5 MPa) and tensile strength (412 +/- 7 MPa) of 1.5 vol % graphene/copper composite were 74% and 30% higher than that of pure Cu, respectively. Moreover, the ultimate tensile strength and fracture elongation of graphene/copper composite with heterogenous graphene distribution both exceeded those of a composite reinforced by homogeneously-distributed two-dimensional reduced graphene oxide nanosheets. The dominant strengthening mechanisms were verified as the Hall-Patch strengthening thanks to the highly refined matrix grain size of sub-micron level and the load transfer strengthening originated from the formation of 'graphene-rich zones' in the copper matrix. This study highlights the importance of architecture design in graphene reinforced metal matrix composites for actualizing their strengthening potential while retaining a balanced ductility.