Abstract:The hot deformation response and dynamic recrystallization behavior of two representative initial microstructures (a fully lamellar microstructure and an equiaxed-lamellar bi-modal microstructure) were systematically investigated in a wide-width hot-rolled bloom TC4 alloy using a Gleeble thermal simulation testing system at deformation temperature of 1173 K and strain rates of 10 and 0.01 s?1. Meanwhile, a coupled phase-field and crystal plasticity model was developed to simulate the stress-strain distribution and dislocation density evolution in the α/β phases under different initial microstructural conditions. This model was used to examine how initial microstructure configurations influence the dynamic recrystallization behavior of the α phase. The results indicate that under a high strain rate of 10 s?1 and the deformation of 60%, the fully lamellar microstructure undergoes significant dynamic recrystallization in the α phase, resulting in a uniform fine-grained structure with an average grain size of 0.58 μm. In contrast, in the bi-modal structure, only part of the lamellar α phase exhibits localized recrystallization, while the equiaxed α phase primarily undergoes dynamic recovery. Compared with the fully lamellar structure, the bi-modal microstructure requires greater deformation to activate dynamic recrystallization in both the equiaxed and lamellar α phases. This discontinuous recrystallization behavior is attributed to differences in stress-strain distribution between the equiaxed and lamellar α phases during concurrent deformation. These differences influence dislocation accumulation and subgrain formation, ultimately altering the driving force conditions for dynamic recrystallization.