In-situ synthesis of graphene decorated with nickel nanoparticles for fabricating reinforced 6061Al matrix composites

Graphene has attracted a lot of interest to be used as reinforcement in Aluminum matrix composites (AMCs) on account of its superior mechanical properties. However, the most serious and challenging issues in graphene-reinforced AMCs are that reinforcements are quite difficult to disperse uniformly in metal matrix and ensure intimate interfacial bonding simultaneously. In this work, an ultrafine Ni nanoparticles (NPs)-decorated graphene hybrid (indicated with Ni-NPs@GNP) was firstly synthesized by an in-situ chemical vapor deposition method to improve the wettability between metal and carbon nanophase, then the Ni-NPs@GNP/6061Al composite powders were obtained by dispersing the Ni-NPs@GNP into 6061Al alloy particles via a short time intermittent ball milling process. Finally, the Ni-NPs@GNP/6061Al bulk composites were fabricated through hot-pressing sintering of the composite powders. It was demonstrated that good dispersion of reinforcements was achieved in the Ni-NPs@GNP/6061Al composite coupled with remarkably enhanced interfacial bonding by introducing Ni NPs on the graphene, which resulted in the formation of Al3Ni intermetallic at the interface and thus improved the interfacial adhesion between 6061Al and graphene. As a result, the Ni-NPs@GNP/6061Al composite with 0.7 wt% reinforcement exhibited much enhanced mechanical properties, namely, a high yield strength of 140 MPa together with a tensile strength of 213 MPa can be achieved, which were 75% and 30% higher than that of the monolithic 6061Al, respectively. This work provides an inspiring strategy for fabricating 6061Al composites with adjustable mechanical properties as well as controllable interfacial bonding.