Achieving High Strength in Metastable β‐Ti Alloys via ω‐Reinforced Heterostructures With Ultrafine Hierarchical Nano‐Martensites

ABSTRACT

Precipitation of isothermal ω phase is an effective way to strengthen the metastable β‐Ti alloys but generally severely embrittles the materials by suppressing stress‐induced martensitic transformation and deformation twinning. Here, we architect heterogeneous structures with tailored ω phase in a metastable β‐Ti‐20Zr‐12Nb‐2Sn alloy via combination of severe cold rolling, flash treatment and controlled aging. It is demonstrated that through short‐term aging, a high yield strength at 1.09 GPa is achieved with marginal loss of uniform elongation, outperforming the unprecipitated condition. This improvement stems from the fine and diffusive ω precipitates that provide moderate strengthening while steering martensitic transformation toward massive ultrafine hierarchical nano‐martensites, featuring secondary plates as thin as 25 nm and tertiary variants only a few nanometers in scale. In contrast, long‐term aging promotes detrimental heterogeneous structure composited by the acicular‐ω and α″ phases, which severely suppresses martensitic transformation and leads to rapid embrittlement. This work not only provides a strategy to achieve strength‐ductility trade‐off but also elucidates how ω‐mediated deformation mechanisms can be tailored to trigger unique ultrafine nano‐martensitic architectures.