Hot deformation mechanism and microstructure evolution of a new near β titanium alloy

Transmission Electron Microscope (TEM) and Electron Backscattered Diffraction (EBSD) are employed to explore the influence of deformation conditions on microstructure and the deformation mechanism of a new near β titanium alloy Ti-7333 after hot compression tests which at temperatures ranging from 770 to 970°C and strain rates ranging from 0.001 to 10s^-1. The results showed that the effect of deformation parameters on microstructure evolution is significantly. Both increasing the temperature and decreasing the strain rate seem to promote the dynamic recrystallization process. The mechanism is dominated by dynamic recovery, globularization and dynamic recrystallization. The globularization trend of α phase is more remarkable deformed at higher temperature and lower strain rate. And reverse, the lower temperature and higher strain rate are more favorable to α phase refinement. The fraction of low-angle grain boundaries in the deformation microstructure decreases with the increasing of temperature and decreasing of strain rate. It illustrates the low-angle grain boundaries would turn to high-angle grain boundaries during deformation. The expression of the size of recrystallized grains _Dr and parameter Z is obtained by regression analysis as lnD_r=8.79964-0.33663lnZ. All the deformed samples present strong 〈001〉 and weak 〈111〉 fiber texture. With the increasing of temperature and decreasing of strain rate, the 〈001〉 texture strengthens gradually and 〈111〉 texture weakens gradually until extinction.