In-situ grown few-layer graphene reinforced Ni matrix composites with simultaneously enhanced strength and ductility

Highlights: • Graphene reinforced Ni matrix composites have been fabricated by a novel in-situ approach. • PMMA molecules transform into few-layer graphene under the high-temperature sintering process. • The composites can simultaneously achieve an improved strength and ductility. • Grain refinement, effective load transfer, crack bridging, and graphene pull-out raise the excellent mechanical properties. Few-layer graphene reinforced nickel matrix (GNs/Ni) composites were fabricated by a facile in-situ processing strategy involving the transformation from solid carbon precursors to graphene reinforcements under the vacuum hot-press sintering. It enabled the homogeneous distribution of reinforcements, the effective interfacial bonding between graphene nanosheets and Ni matrix, as well as the resisted grain growth during the high-temperature consolidation process. The GNs/Ni composites exhibited exceptionally enhancement of the strength and ductility simultaneously. The composite with 0.3 wt% graphene achieved the optimal yield strength, tensile strength, and fracture elongation of 285 MPa, 611 MPa, and 56%, respectively, which were enhanced by 1.16, 1.34 and 1.37 folds compared to those of pure Ni bulk. The microstructures before and after tensile deformation demonstrated that the strengthening effect of in-situ grown graphene in the Ni matrix was attributed to the grain refinement and effective load transfer, while the toughening effect was related to the crack bridging and graphene pull-out mechanisms.