Mechanical properties and strengthening mechanisms of titanium matrix nanocomposites reinforced with onion-like carbons

Nanodiamonds were annealed in a spark plasma sintering (SPS) furnace to synthesize onion-like carbon (OLC) powder, and thereafter, OLC-reinforced titanium (Ti) matrix composites with 0.1-1.0 wt% OLCs were fabricated through SPS. Experimental results showed that OLCs were partially in-situ reacted with the Ti matrix forming nano- to submicron TiC particles and some OLCs were retained after the SPS processing. The content and morphology of TiC in sintered samples was determined by the amount of OLCs, which also affected the mechanical properties of the resultant composites. The Ti-0.35 wt% OLCs composite possessed excellent compressive and tensile properties with acceptable ductility, which are 54% and 40% higher than those of pure Ti, respectively. The strengthening of the composites reinforced with the hybrid reinforcements of TiC/OLCs can be attributed to a group of mechanisms: solution strengthening, grain refinement, load transferring effect, and dispersion strengthening.