Mechanism in the β phase evolution during hot deformation of Ti-5Al-2Sn-2Zr-4Mo-4Cr with a transformed microstructure

The mechanism in the β phase evolution during hot deformation of a near β titanium alloy Ti-5Al-2Sn-2Zr-4Mo-4Cr with a transformed microstructure was investigated in the present work by the high-resolution electron backscatter diffraction (EBSD) and transmission electron microscope (TEM) techniques. The β phase exhibits significant variation in orientation, local texture and grain boundary during hot deformation, which is highly related to the globularization of α platelets. Kinking of the α platelets promotes the continuous dynamic recrystallization (CDRX) of β phase by increasing the misorientation, and formation of the globular α grains assists in the recrystallization of β phase via grain boundary sliding. The strain rate plays an important role in the β phase evolution as well which is greatly affected by the α phase evolution. The recrystallization of β phase is more evident during kinking at a higher strain rate where a structure with more and finer β recrystallized grains occurs, while dynamic recovery (DRC) is the main mechanism in the β phase where the globularization of α phase is relatively low at a larger strain.