Thermal Deformation Behavior and Microstructural Evolution Mechanism of TC4 Titanium Alloy Based on Hot Processing Map

In this paper, thermal compression tests of TC4 titanium alloy were carried out at 800–950°C and strain rates of 0.01–10 s⁻¹. Based on the hot processing map, the microstructure evolution characteristics and deformation mechanisms were analyzed. The results demonstrate that the power dissipation efficiency (η) generally exhibits an initial increase followed by a decrease as the temperature rises. With temperature range of 840–890°C and strain rate range of 0.01–10 s⁻¹, η value is > 0.5, which is conducive to dynamic recrystallization (DRX), and DRX volume fraction is > 38.74%. Furthermore, as the strain rate decreases and the deformation temperature increases, the DRX mechanism transforms from discontinuous dynamic recrystallization (DDRX) to continuous dynamic recrystallization (CDRX). At higher temperatures (920–950°C), the deformation mechanism shifts to dynamic recovery (DRV), accompanied by α phase dynamic spheroidization mechanism. Consequently, the primary α phase tends to have an equiaxed shape, and a significant amount of secondary α phase in the form of lamellar precipitates can be observed. The unstable region mainly concentrates at low temperatures and high strain rates (800–820°C, 0.5–10 s⁻¹), with flow localization being the instability phenomenon. Additionally, a small portion of the unstable region also appears at 920°C–0.1 s⁻¹ because of the generation of deformation bands.