Microstructural Optimization Achieving Strength–Ductility Synergy in Ti-6Al-4V Alloy via Multi-Pass Hot Rolling and Annealing

In this study, the microstructural evolution and mechanical behavior of Ti-6Al-4 V alloy were systematically investigated through multi-pass hot rolling followed by annealing at varied temperatures. Optical microscopy, EBSD, SEM, and XRD analyses revealed that increasing rolling deformation promotes microstructural homogenization and grain refinement, resulting in significantly enhanced yield strength and ultimate tensile strength. However, this strengthening effect is typically accompanied by a decline in ductility. Interestingly, post-deformation annealing at 750 °C facilitated dislocation recovery and partial recrystallization without causing excessive grain growth, thereby preserving strength while enhancing ductility. Local misorientation and kernel average misorientation (KAM) analysis indicated reduced dislocation densities in annealed specimens, especially in highly deformed states. The specimens annealed at 750 °C demonstrated a noticeable mitigation of the classical strength–ductility trade-off with a yield strength of 1042 MPa, an ultimate tensile strength of 1135 MPa, and an elongation of 16.2%, suggesting a synergistic enhancement governed by grain boundary evolution and dislocation dynamics. These findings provide insights into tailoring microstructures in α + β titanium alloys for optimized mechanical performance.