Enhancing strength-ductility synergy via hierarchical microstructure in fine-grained Ti-10Mo-8V-1Fe-3.5Al alloy

[Display omitted] •Partially-recrystallized β structure with abundant substructures and defects was characterized.•Microstructural hierarchies were obtained in β + α microstructure.•Excellent strength-ductility synergy could be achieved no matter in β or α + β phased condition.•Enhanced strain-hardening rate postponed the occurrence of plastic instability. Microstructural hierarchies of a fine-grained (∼6μm) Ti-10Mo-8 V-1Fe-3.5Al alloy fabricated by hot working process were investigated in β-phased and (α + β)-phased condition respectively. The β-phased microstructure was characterized by a fraction (∼24%) of recrystallized β-grains distributed randomly in the matrix, including subgrains with abundant substructures and defects. After aging, the consequent precipitation behavior of α featured by heterogeneous and insular areas with coarse α(∼0.9 μm) embedded in the ultrafine α(∼0.13 μm). It was clarified that excellent strength-ductility synergy can be achieved by hierarchical microstructure no matter in β or α + β phased condition, in sharp contrast to their coarse-grained counterparts. The microstructural dependence of mechanical properties was discussed in terms of the strain-hardening rate arising from the formation of dislocation pile-up influenced by a dispersion of precipitates, and by grain size (GS).