Microstructure and mechanical properties of GNPs and in-situ TiB hybrid reinforced Ti–6Al–4V matrix composites with 3D network architecture

Graphene nanoplatelets (GNPs) and TiB whiskers (TiBw) hybrid reinforced Ti–6Al–4V (TC4) matrix composites ((GNPs + TiBw)/TC4) were fabricated by Fast Hot-Press Sintering (FHPS) and hot rolling (HR) method. The microstructure, mechanical properties and strengthening mechanisms were systematically studied with various TiBw contents. Microstructure observation results indicate that GNPs can be mostly preserved and TiBw are rarely obtained during the sintering process. HR process was applied to further densify the composites and obtain the in-situ TiBw. The high ductility of composites was achieved via designing network structure with reinforcements of GNPs and in-situ TiBw, which reduce the interface reaction of the GNPs/Ti and improved the interface bonding. The tensile ductility of the GNPs/TC4 composites were improved with the addition of TiB₂ powders. As a result, 0.1 wt% GNPs/TC4 composites with the addition of 0.05 wt% TiB₂ powders showed the best combination of ultimate tensile strength of 1158 MPa and a fracture elongation of 15.8%. Compared to the fracture elongation of pure TC4 alloy (15.2%), there was no sacrifice of ductility.