Constructing micro-network of Ti₂Cu and in-situ formed TiC phases in titanium composites as new strategy for significantly enhancing strength

Titanium matrix composites (TMCs) with homogeneous microstructures often exhibit inferior mechanical properties including low strength and poor ductility, thus severely restricting their wide-range applications as engineering structural parts. Herein, we designed a hybrid structured (TiC + Ti₂Cu)/TC4 composites consisting of TiC particles and micro-network structures of Ti₂Cu, using reduced graphene oxides (rGO) and copper nano-powders as precursors via a two-step low energy ball milling and spark plasma sintering. These in-situ formed TiC particles were uniformly distributed within the TC4 matrix, whereas Ti₂Cu nanoparticles were generated by the eutectoid reaction and distributed at the α/β phase interfaces, forming a micro-network structure within the titanium alloy matrix. Sizes, morphologies, distributions and fractions of Ti₂Cu structures were adjusted by controlling the Cu contents, and these play dominant roles in determining tensile properties of the composites. The fabricated (TiC + Ti₂Cu)/TC4 composites exhibit significantly higher tensile strengths than that of the monolithic TC4 (increased by 32.2 %), which is mainly attributed to the refinement strengthening from TiC + Ti₂Cu hybrid reinforcements and precipitation strengthening from Ti₂Cu with micro-network structures. This study develops a new methodology to significantly improve the tensile strength of carbonaceous nanomaterial reinforced titanium matrix composites.