Investigation of High-Temperature Constitutive Behavior of Ti555211 Titanium Alloy Subjected to Plastic Deformation in the Different Phase Regions

Ti555211 titanium alloy is subjected to plastic deformation in the dual-phase (α + β phase) zone and single-phase (β phase) zone at various deformation temperatures and strain rates. High-temperature constitutive equations of the alloy in the dual-phase zone and single-phase zone are established in order to describe deformation behavior of the alloy in the different phase zones. By comparing the constitutive equation of the alloy in the dual-phase zone with that of the alloy in the single-phase zone, the deformation activation energy of the former was found to be higher than that of the latter. It is obvious that the deformation activation energy of α phase is obviously greater than that of β phase. Furthermore, the microstructural evolution of the alloy is different in the dual-phase zone and single-phase zone. When the alloy was subjected to plastic deformation in the dual-phase zone, the size of the grains in the β phase increased with the decreasing strain rate. When the alloy was subjected to plastic deformation in the single-phase zone, the size of the grains in the β phase considerably increased with the increasing deformation temperature. In particular, in the microstructures of the alloy subjected to plastic deformation in the single-phase region, the elongated grains can be observed at higher strain rates. Furthermore, it is more difficult for the alloy to induce plastic deformation in the dual-phase region than in the single-phase region.