Enhanced strength-ductility synergy in fiber-like structural titanium matrix composites by controlling TiB content

Abstract

A new titanium matrix composites (TMCs) with distinctive architecture consisting of isolated fiber-like structural composites region (FLSCR) within continuously Ti region were designed and fabricated by powder metallurgy, hot extrusion, and subsequent hot rolling. This work systematically investigated the important role of TiB contents on microstructural evolution and mechanical response of the as-rolled fiber-like structural TMCs. The designed FLSCR-5% and FLSCR-10% with fiber-like structure obtain high ductility of 24.4% and 19%, respectively, which shows a better combination of strength and ductility. The strengthening is attributed to the refinement of the equiaxed α grains and the load-bearing effect of TiB whiskers. Meanwhile, continuously Ti region significantly reflects and blunts the crack propagation which is supposed to improve the static toughness of the fiber-like structural TMCs, but the ductility would be decreased by increasing TiB content in the FLSCR, which is attributed to the decreasing volume fraction of titanium matrix and the increasing crack initiation rate. Additionally, due to the fiber-like composites region, the strain hardening rate of the FLSCR-10% (from ~0.05 to ~0.135 strain) is significantly strengthened by the hetero-deformation induced back stress, which is beneficial to the ductility. • Novel fiber-like structure obtained high matching of high strength and ductility in TMCs. • Continuously Ti region significantly reflected and blunted the crack propagation. • Hetero-deformation induced back stress which improved the work hardening rate and ductility of the FLSCR-10% composites.