Constitutive Model and Microstructure Evolution of a Novel TG6 High-Temperature Titanium Alloy during Hot Deformation

The thermal deformation behavior of a novel TG6 titanium alloy from 850 to 1050 °C with a strain rate of 0.001-10 s−1 was studied using a Gleeble-3500 thermal simulation compressor. The constitutive model was established, then metallography was used to observe the evolution of microstructure under the influence of temperature or deformation rate, the evolution of α/β phase, and the angular distribution of grain boundaries during thermal deformation were described with the help of EBSD. The results after comprehensive analysis are as follows: TG6 titanium alloy is a strain rate and temperature-sensitive material, the flow stress increases with an increase in strain rate when the temperature is stable, and the flow stress decreases with increasing temperature at a stable strain rate. Furthermore, the flow stress increases rapidly with increase in strain in the initial stage of deformation; after reaching the maximum, it begins to decrease slowly until a relatively stable state. The morphology, size, and content of the phase can be affected by the deformation temperature and strain rate to a certain extent. The elongation and distortion of the α phase occur as the temperature falls below 950 °C and the strain rate increases above 0.01 s−1; besides, as the temperature rises near the phase transition point, the primary α phase begins to dissolve, the acicular α phase gradually precipitates from the coarse β phase and tends to continue coarsening. Finally, the combination of EBSD analysis and 3D hot processing map reveals that the dynamic recrystallization behavior is more evident at low temperatures and strain rates.