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

The mechanism in the beta phase evolution during hot deformation of a near beta 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 beta phase exhibits significant variation in orientation, local texture and grain boundary during hot deformation, which is highly related to the globularization of alpha platelets. Kinking of the alpha platelets promotes the continuous dynamic recrystallization (CDRX) of beta phase by increasing the misorientation, and formation of the globular a grains assists in the recrystallization of beta phase via grain boundary sliding. The strain rate plays an important role in the beta phase evolution as well which is greatly affected by the a phase evolution. The recrystallization of beta phase is more evident during kinking at a higher strain rate where a structure with more and finer beta recrystallized grains occurs, while dynamic recovery (DRC) is the main mechanism in the beta phase where the globularization of a phase is relatively low at a larger strain. (C) 2015 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.