Dual multi-scale heterogeneous microstructure via shear bands for strength-plasticity synergy in Ti-7333 alloy

Metastable β titanium alloys are essential for aerospace and high-performance applications but are constrained by the longstanding strength-plasticity trade-off. In this work, a shear band assisted dual multi-scale heterogeneous (DMH) microstructure is developed in a Ti-7333 alloy through a simple route of cold rolling induced shear bands followed by direct aging. This microstructure integrates (i) a heterogeneous β matrix composed of residual β and nanoscale equiaxed β grains, and (ii) multiscale α precipitates including micron-sized spherical α, submicron rod-like α, nanoscale acicular α, and nanoscale equiaxed α. Nanoscale equiaxed (α+β) dual phases preferentially form inside shear bands, while nanoscale acicular α precipitates dominate outside, constructing a dense α/β interface. The optimized DMH alloy (CRA-540) exhibits a yield strength of 1309 MPa, an ultimate tensile strength of 1375 MPa, and a total elongation of 6.0%, achieving a favorable strength-plasticity synergy compared with typical solution treatment + aging process. Quantitative analysis indicates that hetero-deformation induced (HDI) strengthening from abundant α/β interfaces is the dominant contributor, supplemented by precipitation and grain refinement strengthening. The plasticity is primarily attributed to the activation of <c+a> slip systems in the α phase, additional hetero-deformation induced hardening effect. The present deformation-band-assisted DMH strategy provides an effective and scalable pathway for tailoring strength-plasticity synergy in metastable β titanium alloys containing deformation shear bands.