Flowing Behaviors And Microstructural Evolutions Under High Temperature Thermal Deformation Of Titanium Alloy

In the present study, TC4, TC11and TC17titanium alloy are target metals. Weanalyze the effect of deformation temperature and strain rate on thermal flow behaviorsystematically. The microstructure evolution and dynamic recrystallization mechanism arethoroughly investigated. Moreover, we comparatively investigate the quenchedmicrostructural evolution under conditions both with and without hot deformation.The true stress-strain curves show that the true stress of TC4, TC11and TC17titanium alloys is sensitive to the deformation parameters. The true stress decreases withthe increasing temperature and decreasing strain rate. More detailed, for TC4and TC11titanium alloy, the influence of strain rate is more obvious when the temperature is lowerthan Tβ.The microstructure evolution of TC4and TC11alloys is different from that of TC17alloy. In the case of TC4and TC11titanium alloy, when deformed in α+β phase region,there are residual primary α phases and the fraction of primary α phase decreases evidentlywith increasing temperature. In addition, the fraction of primary α phase is significantlyaffected by the strain rate in near-β phase region. The β grains are compressed elongatedand there are obvious recrystallized grains in the single β-phase region. Besides the abovementioned feastures, acicular α phase generates in the β transformation organization ofTC4and TC11titanium alloys.For TC17titanium alloy, there are residual primary α phases at900oC and950oC.Obvious recrystallization grains are observed as the temperature is above950oC. Therecrystallization mechanism is mainly CDRX at1000oC. While both CDRX and DDRXoccur at1050oC and1100oC.The effect of hot deformation on quenched microstructure of titanium alloy is evident.On one hand, deformation accelerates the transformation of primary α phase. On the otherhand, deformation destroys the interfaces between the phases and grains. As a result, themorphology of acicular microstructure represents the diversity. More detailed, by fitting ofthe split α-Ti peaks of TC11titanium alloy, martensitic transformation products of α″phases are distinguished in the quenched microstructures of hot deformed specimens.