Research on the hot-temperature rheological behavior and microstructural evolution of TA18 titanium alloy

The thermal deformation behavior and microstructure evolution of TA18 (Ti-3Al-2.5 V) titanium alloy were investigated by hot compression tests in the temperature range of 1073–1323 K and strain rate range of 0.001–10 s⁻¹. The strain-compensated Arrhenius constitutive model was established based on the stress-strain curve. The hot processing map of the alloy was established according to the dynamic materials model. The results show that the correlation coefficient R and average relative error (AARE) are 0.9864 and 6.48 %, and the experimental values are in good agreement with the predicted values. The change trend of activation energy confirms that the softening mechanism of TA18 titanium alloy during deformation in the two-phase region is mainly dynamic recrystallization, and the single-phase region is mainly dynamic recovery. Continuous dynamic recrystallization (CDRX) caused by sub-grain progressive rotation and discontinuous dynamic recrystallization (DDRX) caused by grain boundary expansion are identified during hot deformation. The optimal high-temperature deformation processing window is 1098–1148 K for the deformation temperature and 0.001–0.01 s⁻¹ for the strain rate, when the proportion of dynamic recrystallization is larger. The instability area is mainly concentrated in the low-temperature high strain rate region and is dominated by flow localization and cracks.