The heterogeneous globularization related to crystal and geometrical orientation of two-phase titanium alloys with a colony microstructure

Abstract

Understanding the heterogeneous globularization phenomena and the underlying mechanisms is important to process design for primary hot working of titanium alloys. To this end, hot compression of a TA15 titanium alloy with initially colony structure was carried out at 900 °C and strain rate of 0.1 s−1 on a Gleeble thermal simulator. Comprehensive electron back scatter diffraction (EBSD) examination was conducted to check how the heterogeneous microstructural developments were affected by the geometrical and crystal orientations of the colony. A crystal plasticity model was employed to quantify the heterogeneous deformation and orientation evolution during compression. The heterogeneous globularization behavior is interpreted from the orientation perspective by relating the orientation spread within alpha lamellae to the slip activation, strain partitioning in the constituent phases as well as microstructural phenomena such as deformation banding and dynamic recrystallization. The activation of the prism and basal slips in alpha phase and strain partitioning between the alpha and beta phases would enhance the orientation spread, which accounts for the relatively high globularization efficiency in inclined colonies.