Achieving ultrahigh strength in dual-phase titanium alloys via severe cold drawing

Ultra-strong titanium alloys have gained extensive attention in advanced engineering applications due to their significance of weight reduction. In this study, ultrahigh strength is achieved in dual-phase Ti-6Al-4 V alloy through a severe cold drawing method. Severely-drawn Ti-6Al-4 V (ε = 1.12) showcases a remarkable YS (1230 MPa) and an ultrahigh UTS (1382 MPa) owing to the synergetic effects of pronounced dislocation strengthening and fine-grain strengthening. Distinct deformation and strengthening mechanisms are active at different levels of strain during the cold drawing process. Plastic deformation is governed by < a > dislocation slip in α phases at lower strain levels (ε = 0 and 0.53), while dislocation slip in both α and β phases, along with enhanced activities of < c + a > dislocations, becomes the dominant deformation mechanism at higher strain levels (ε = 0.91 and 1.12). Subsequent moderate-temperature annealing (400 ~ 500 °C) can effectively restore the ductility of severely-drawn Ti-6Al-4 V without compromising its exceptional YS due to the retention of significant strengthening contributions from the prior severe drawing process, resulting in an excellent strength-ductility synergy.