Abstract
In order to determine the kinetics of recrystallization in plain carbon steels, double-hit compression tests have been performed using a computerized Gleeble machine. Based on the nucleation mechanism of subgrain coalescence and the measured softening data, a kinetic model was developed to predict the start times for the static recrystallization occuring after hot deformation. Both the model calculations and experimental observations indicate that the onset of recrystallization is decelerated with increasing reheating temperatue but speeded up as the deformation temperature is increased. The former case can be attributed to the larger initial austenite grain size produced at higher reheating temperatures, which in turn results in larger subgrains and reduces the rate of coalescence. The latter case is due to the higher boundary diffusivity and mobility attained at higher deformation temperatures, which accelerates the process of subgrain coalescence. The accelerating effects of strain and strain rate can also be similarly explained by means of the higher dislocation density and finer subgrains generated during the higher strain and strain rate deformation. The good agreement obtained between model predictions and experimental results finally supports the view point that the coalescence of subgrains could be the rate controlling mechanism for the nucleation process of static recrystallization in austenite.
