Achieving high strength-ductility synergy in a hierarchical structured metastable β-titanium alloy using through-transus forging

High-strength titanium (Ti) alloys are progressively demanded for structural applications in weight-critical aerospace industry. Improving mechanical properties of the alloys are thus exploited in response to the requirement. In this study, a strategy of through-transus thermomechanical forging was applied to the Ti–10 V–2Fe–3Al metastable β-Ti alloy, and the resulting microstructures and mechanical properties were systematically investigated in comparison to the conventional (α+β) dual-phase field forging. It is found that the through-transus thermomechanical forging significantly enhances strength, ductility and strain hardening capacity, while it is the inferior combinations of mechanical properties in the alloys subjected to the (α+β) dual-phase field forging. Microstructural characterization reveals that the former renders the hierarchical microstructure composed of intergranular α_p-necklaces, and intragranular α_p-rods as well as α_s-lamellae in the β-matrix. The superior combinations of mechanical properties are conferred by good strain compatibility of these microstructural constituents. By contrast, the latter renders the network microstructure comprised of intergranular globular α_p-phase and continuous grain boundary (GB) α_GB-films as well as the intragranular α_s-lamellae. Local deformation-damage is more preferred to initiate in the intergranular network structure. These findings provide fundamental understanding on the correlation between mechanical properties and microstructures, facilitating manufacturing high-performance β-Ti alloys at an industry scale using commercially available thermomechanical processing.