Excellent strength-ductility synergy in a novel metastable Ti alloy via architecting an unusual hierarchical structure

For metastable beta Ti alloys, it still remains a key challenge to enhance their limited yield strength (YS) while retaining good strain hardenability and ductility. Here we report a new strategy to evade this trade-off dilemma via introducing an uncommon hierarchical structure with the assistance of spinodal structures. The new Ti-11Mo-2V alloy exhibits high YS (693 MPa), high ultimate tensile strength (857 MPa) and large total elongation (31.8 %). Such excellent strength-ductility synergy originates from successive activation of multiple deformation mechanisms, including primary {332}<113> twins, secondary martensite and secondary {112}<111> twins. Importantly, the stress-induced secondary martensite is the desirable alpha ' martensite rather than the common alpha'' martensite. Spinodal decomposition in parent beta grains is expected to facilitate the unusual hierarchical structure where primary {332}<113> twins ensure high YS while secondary alpha ' martensite and {112}<111> twins result in excellent strain hardening ability.