Improved mechanical properties in titanium matrix composites reinforced with quasi-continuously networked graphene nanosheets and in-situ formed carbides

Abstract

In order to construct quasi-continuously networked reinforcement in titanium (Ti) matrix composites, in this study, Ti-6Al-4V spherical powders were uniformly coated with a graphene nanosheet (GNS) layer by high energy ball milling and then consolidated by spark plasma sintering. Results showed that the GNS layer on the powder surface inhibited continuous metallurgy bonding between powders during sintering, which led to the formation of quasi-networked hybrid reinforcement structure consisting of in-situ TiC and remained GNSs. The networked GNSs/Ti64 composite possessed noticeably higher tensile strength but similar ductility to the Ti64 alloy, leading to both better tensile strength and ductility than the GNSs/Ti composite with randomly dispersed GNSs and TiC. The formation mechanism and the fracture mechanism of the networked hybrid reinforcement were discussed. The results provided a method to fabricate Ti matrix composites with high strength and good ductility. • Networked GNSs/Ti composite was fabricated by combination of two-step mixing and SPS. • Increment defects of GNSs would cause GNSs chemically reacting and forming TiC wall. • GNSs or TiC inhibited the powder metallurgy bond and kept a powder size of networks. • Different phase interfaces of networked GNSs/Ti64 were observed by HRTEM and STEM. • Formation mechanisms and strengthening effects of networked structure were discussed.