Tailoring strength-ductility of titanium matrix composites reinforced with graphene nanoplatelets

In this study, graphene nanoplatelets reinforced titanium matrix (GNPs/CT20) composites with adjustable performance were fabricated via 3D vibration milling and spark plasma sintering. With the progressive increase of GNPs, a quasi-continuous 3D reinforcement (TiC-GNPs-TiC) network was established and a peculiar phenomenon is observed that the ductility of GNPs/CT20 composites trends in hump type while the strength increases monotonically. The first crest of the humping ductility for GNPs/CT20 composites was attributed to the fine-grained CT20 matrix contributed by GNPs and in-situ generated TiC. Subsequently, the increasing TiC with discrete distribution dominated the tensile ductility behaviour which showed as the valley of humping ductility. Further additions of GNPs led to the network distribution of TiC-GNPs-TiC, which contributed to a relatively uniform deformation and the near equiaxed fine-grained microstructure gradually replacing the original Widmanstätten microstructure, thus promoting the second crest of the humping ductility. Finally, lots of TiC-GNPs-TiC further improved strength but inevitably reduced ductility for their serious agglomeration. This study focuses on the strengthening and toughening mechanisms of the quasi-continuous 3D TiC-GNPs-TiC network in titanium matrix reinforced by GNPs (TMCGs) and provides new insights into the design and fabrication of TMCGs with excellent strength-ductility.