Microstructural Evolution of Ti-55511 Titanium Alloy During Quasi-Beta Forging

The quasi-beta forging behavior of Ti-55511 alloy is systematically studied by hot compressive deformation experiments and electron back-scattered diffraction (EBSD) tests. The results show that the strain rates have obvious effects on the hot deformation behaviors of the studied alloy. With the increase of strain rate, the flow stress increases. At low strain rates, the work hardening rates hardly change until a critical strain, and then the work hardening rates slightly increase. At a medium strain rate (0.1 s−1), the work hardening rate gradually decreases until a critical strain, and then the work hardening rate shows little variation with strain. However, at high strain rates (1 s−1), the positive work hardening rate indicates the obvious work hardening at the initial deformation stage, and the work hardening rates change to negative and then to positive with strain when the strain rate is further increased to 10 s−1. The main soften mechanism of β grain is DRV. With the increase of strain rate, the fraction of DRX grains and the sub-grains decrease. Too high strain rate leads to the formation of flow localization.