Dynamic recrystallization mechanisms and thermomechanical processing optimization in Q1300 ultrahigh-strength steel

To optimize thermomechanical processing and achieve the desired mechanical performance in ultrahigh-strength steels, a thorough understanding of hot deformation behavior and dynamic recrystallization mechanisms is essential. In this study, the hot deformation behavior and dynamic recrystallization characteristics of Q1300 steel were systematically investigated through isothermal compression tests over a broad range of temperatures (850–1100 °C) and strain rates (0.01–10 s−1). A strain-compensated Arrhenius-type constitutive model was developed, achieving high prediction accuracy across varying deformation conditions. The critical strains for DRX initiation were determined from inflection points on strain hardening rate curves, while DRX volume fractions were quantified based on Avrami-type kinetics. Processing maps constructed via the Dynamic Materials Model identified optimal processing windows within 995–1060 °C and 4.40–10 s−1, while EBSD analysis revealed distinct DRX mechanisms, including both discontinuous and continuous recrystallization. Under optimal conditions, fine equiaxed grains with homogeneous orientation distributions were achieved, whereas low-temperature/low-strain–rate conditions led to partial recrystallization or abnormal grain coarsening. The combined analysis clarifies the interplay between deformation parameters, microstructure evolution, and softening mechanisms, offering practical guidance for thermomechanical process design and industrial application of ultrahigh-strength steels.