Novel hierarchical α structure enhanced strength-ductility synergy in metastable (3 titanium alloy

Heterogeneous structures and hierarchical structures are effective methods for overcoming strength-ductility trade-off in metals. In current study, a heterogeneous (3 structure, containing heterogeneity of grain size and defects (including dislocations and low-angle grain boundaries), was obtained through hot rolling and partial recrystallization processes in metastable (3 titanium alloy Ti-7Mo-3Nb-3Cr-3Al. On this basis, a novel hierarchical alpha structure was constructed through a simple aging process. The hierarchical structure couples the heterogeneous (3 lamella structure with a combination of small and large alpha phase, including alternately distributed micron-sized phases (alpha WGBs, alpha l) and submicron-sized alpha s phases in equiaxed grain regions, and submicron-sized phases (alpha l, alpha p) and nanosized alpha s phases in deformed grain regions. An excellent strength-ductility synergy was achieved in the designed hierarchical alpha structure, with a yield strength of 1360 MPa, tensile strength of 1430 MPa, and an elongation of 8.1 % at room temperature. The hierarchical alpha structure facilitates strain distribution and transfer during deformation, and could deform compatibly with the (3 matrix. Simultaneously, the grain boundary Widmansta<spacing diaeresis>tten alpha WGBs phase reinforces grain boundary regions prone to failure, ensuring the alloy retains plasticity while enhancing strength. Back stress strengthening has been proven to be the most significant factor that enhance strength. This study provides a new simple approach for constructing hierarchical structure in metastable (3 titanium alloys, offering meaningful insights into achieving strength-ductility synergy.