Forging-induced orientation evolution of intragranular α-phase and its effect on the mechanical properties of Ti-652 titanium alloy

The intragranular α phase in dual-phase titanium alloys are predominantly composed of primary α (αₚ) and secondary α (αₛ). To date, the evolution of orientation relationships (ORs) between these α phases and their correlation with mechanical properties remain poorly understood. To address this, the current study investigates the evolution of ORs between αₚ and β, as well as that between αₚ and αₛ during the dynamic spheroidization of αₚ by employing M1-M9 forgings with varying deformation levels. It was found that as deformation accumulates, the OR between αₚ and the β phase initially deviates from the Burgers orientation relationship (BOR) before eventually reverting to it. Concurrently, the misorientation angle between αₛ and αₚ gradually diminishes, resulting in a basal // basal alignment at the final forging stage. These changes in ORs indicate that accumulated deformation facilitates the deformation accommodation between αₚ and β, as well as that between αₛ and αₚ. Quasi-static tensile strength, elongation, and impact toughness tests conducted on the M1-M9 forgings revealed that the M9 sample, which represents the final forging stage, achieves the optimal combination of mechanical properties. These results suggest that the reduction in misorientation between intragranular α phases contributes to improved deformation compatibility and mechanical performance, together with concurrent microstructural refinement and spheroidization, providing new insights into the crystallographic mechanisms governing the mechanical behavior of dual phase titanium alloys.