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

Abstract

For metastable β 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 α′ martensite rather than the common α'' martensite. Spinodal decomposition in parent β grains is expected to facilitate the unusual hierarchical structure where primary {332}<113> twins ensure high YS while secondary α′ martensite and {112}<111> twins result in excellent strain hardening ability.