Configuration of new fiber-like structure driven high matching of strength-ductility in TiB reinforced titanium matrix composites

Abstract

To fulfill the combination of high strength and ductility, configuration of novel fiber-like structural TiB reinforced titanium matrix composites was designed and successfully fabricated through series of powder metallurgy and hot working process. The influence of the fiber-like structure and microstructures on the mechanical response is investigated to clarify their strengthening and plasticizing mechanisms. Smaller equiaxed α-Ti grains generated in both the composites region and Ti region of the TiB/Ti composites. The new configuration improved the tensile strength from 573.5 MPa to 659.1 MPa while the ductility (24.4%) was comparable with that of pure Ti (23.5%). Besides, prismatic <a> slips with Schmid factors above 0.4 had higher distribution in both the composites region and Ti region of the TiB/Ti composites than pure Ti along the loading direction, suggesting the higher deformation ability of the TiB/Ti composites. Moreover, the loading-unloading-reloading (LUR) true stress-strain curves showed much higher back stress in fiber-like structural TiB/Ti composites compared with unreinforced Ti during deformation. The existence of the back stress increased the strain hardening rate when the true strain was above 0.05 and strengthened the Ti region, which was caused by deformation incompatible between the composites region and Ti region during tensile loading in the TiB/Ti composites. The higher mechanical response of the TiB/Ti composites is attributed to the introduction of TiB reinforcements with the new fiber-like structure, and the coupling effect of consequent grain refinement, load transferring effect, dislocation pinning effect of the fine TiB particles, back stress strengthening and the higher Schmid factors of prismatic<a> slips. • Novel fiber-like structure was designed to match the high strength and ductility in TMCs. • Configuration design of high strength composites without losing ductility by tailoring the spatial distribution of reinforcements. • The ductility of the composites was maintained for the higher Schmid factor values of prismatic<a> system and back stress. • Grain refinement, load transferring effect and back stress strengthening result to the strength improvement.