Combination of multiple strengthening mechanisms facilitates excellent strength-ductility balance in metastable β titanium alloy

Abstract

A remarkable balance between the strength (844 MPa) and ductility (35.6%) of the Ti-4V-2Mo-2Fe alloy was achieved by hot rolling. Notably, alloy specimens rolled at 700°C exhibited a yield strength exceeding 1 GPa. This outstanding yield strength from several factors: fine-grain strengthening, dislocations strengthening in the non-recrystallized region, and precipitation strengthening of α phase and isothermal ω phase. Within the 750 to 900°C temperature range, a notable enhancement in yield strength, uniform elongation, total elongation, and work hardening rate was observed as rolling temperature decreased. This enhancement can be attributed to the “dynamic Hall-Petch effect” caused by the stress-induced twins. Additionally, grain refinement and stress-induced ω phase further enhanced ductility and work hardening capacity. These findings show that reasonable adjustment of microstructure and deformation mechanism is an effective strategy to achieve excellent strength-ductility balance of metastable β titanium alloys.