Microstructure evolution and superior tensile properties of low content graphene nanoplatelets reinforced pure Ti matrix composites

Titanium matrix composites with the discontinuous reinforcement of graphene nanoplatelets (GNPs) were produced by powder metallurgy and subsequent hot-rolling. In the process of spark plasma sintering (SPS), the GNPs were well preserved at low temperature and high compressive pressure. Hot-rolling process was applied to improve the microstructure and properties of the GNPs-Ti matrix composites. The GNPs were uniformly distributed and arranged along with the rolling direction (RD). Also, the GNPs blocked slipping so that the matrix generated {101̅1} <101̅2̅> compressive twining to be compatible with deformation in the rolling process with the increase of GNPs content. Tensile strength test demonstrated an excellent ultimate tensile strength that was 54.2% higher than pure titanium with merely 0.1 wt% GNPs addition. The strengthening mechanism of composites was discussed by three main strengthening factors combined with a modified load transfer model and it was thought that the composites were strengthen by grain refinement, load transfer from Ti matrix to GNPs and texture strengthening.