Strength-ductility synergy in 3D-printed (TiB + TiC)/Ti6Al4V composites with unique dual-heterogeneous structure

Abstract

The 3D-printed (TiB + TiC)/Ti6Al4V composite with tailored network reinforcement architecture and heterogeneous α lamellae structure (i.e., a dual-heterogeneous structure) possesses simultaneously improved tensile strength and uniform ductility. To reveal the fundamentals behind the strengthening and deformation mechanisms, the microstructural evolution and tensile deformation behavior of as-printed (TiB + TiC)/Ti6Al4V composite were carefully examined under in-situ tensile testing together with as-printed Ti6Al4V. The heterogeneous structure in the composites induced significant constraint effect, affording deformation compatibility via strain partitioning throughout the composite. Importantly, owing to the heterogeneous α lamellae structure and the pinning effect of reinforcements, the hetero-deformation induced additional strengthening effect and strain-hardening potential, leading to much enhanced plastic deformation capacity and improved strengthening efficiency. Furthermore, the microcracks arresting stabilized the plastic deformation at the later deformation stage and offered extra ductility. Based on these investigations, the intrinsic strengthening and deformation mechanisms behind the synergetic strength-ductility over the whole deformation process were elucidated. This work highlights the importance of heterogeneous structure design strategy in the development of discontinuous metal matrix composites.