Process-dependent microstructural evolution of a hot-deformed damage tolerance titanium alloy

Microstructural evolution of titanium alloy is highly hot process-dependent, especially for the damage-tolerant titanium alloy. In this work, the microstructural evolution in a hot-deformed Ti-Al-Sn-Zr-Mo-Cr-Nb alloy was studied, and the relevant results indicate that the dynamic recrystallization (DRX) is the primary microstructural evolution mechanism for the α phase. The hot deformation processing parameters significantly affect the DRX behaviors of the α phase. High deformation temperatures, low strain rates, and large strains are in favor of the DRX process. With the increased strain, the fraction of HAGBs is increased, the main softening mechanism of the α phase mainly transforms from dynamic recovery (DRV) to continuous dynamic recrystallization (CDRX), and DRX is the main deformation mechanism of the α phase at large strain. The dynamic spheroidization mechanism of the lamellar α phase includes the formation of sub-structures, the fragmentation of sub-boundaries, the penetration of the β phase, and the formation of new α phases. CDRX occurs through the gradual rotation of sub-grains, whereas discontinuous dynamic recrystallization (DDRX) is mainly triggered by grain boundary bulging and deformation-induced. DDRX primarily occurs under high-temperature conditions, while CDRX is the primary mechanism under other deformation conditions.