Bimodal α precipitation mediates deformation coordination and strength-ductility synergy in a Zr-rich metastable β Ti alloy

A Zr-rich Ti-Zr-Nb-V-Mo-Al metastable β titanium alloy was developed via high-to-low two-step aging to achieve a superior strength-ductility synergy. Two-step aging produced a bimodal α microstructure composed of coarse primary α laths and high-density fine secondary α precipitates with coherent α/β interfaces. The Aged-2 alloy exhibited a yield strength of ∼1.48 GPa, an ultimate tensile strength of ∼1.56 GPa, and a total elongation of ∼11%. Post-deformation STEM/TEM analyses revealed that coarse α laths accommodated dislocations, whereas fine α precipitates promoted dislocation interactions and strain hardening. This bimodal α architecture provides an effective strategy for strengthening Zr-rich β titanium alloys.