Experimental investigation via torsion testing and simulation of static recrystallization of ferrite in ultra-low carbon steel

• Torsion tests provide high strain grades and wide strain variation within each specimen. • The annealing temperature after cold deformation strongly influences the resulting grain size and saturation level. • A cubic root function is used for describing the evolution of the subgrain boundary misorientation, especially important during stage IV hardening. • By using the developed approach, recrystallization kinetics and grain size evolution during static recrystallization can be predicted. High-strain cold deformation introduces high driving forces for recrystallization, i.e., high dislocation densities, which in turn remarkably alters the microstructure. The static recrystallization behavior of ultra-low carbon steel during annealing, following cold torsion tests with engineering strain greater than 2, is experimentally investigated. Metallographic and EBSD analysis are used to evaluate the resulting microstructure after deformation and annealing. The recrystallized grain size decreases with increasing strain until reaching a saturation point. The study reveals that torsion tests are well suited to investigate the recrystallization behavior for a wide range of strain in ferritic steel. The experimental results are compared to computer simulations using a mean-field recrystallization model implemented in MatCalc. By using an extended Kocks-Mecking model approach and considering the subgrain boundary misorientation, the simulations consistently reproduce the experimental results, validating the accuracy of the model.