Effect of Dislocation Density in an Unrecrystallized Part of Austenite on Growth Rate of Recrystallizing Grain

Abstract

The growth rate of recrystallizing austenite grains of Si-Mn steels and Nb added steels after hot deformation was investigated by measurement of the fraction of recrystallized austenite and recrystallized austenite grain size. The fraction of recrystallized austenite(Xcr) at which the mechanism of recrystallization changed from nucleation and growth (NG) to site saturation (SS) was formulated as a function of Nb concentration and deformation conditions.According to the increase in deformation temperature and strain, Xcr increases while the increase in Nb in solution decreases Xcr.
The growth rate of recrystallizing austenite was also formulated as a function of strain energy (Fv) and Nb concentration. Strain energy, Fv is calculated with the dislocation density decreasing due to static recovery during holding time after deformation by the method shown in the previous reports. The growth rate decreases rapidly after deformation due to the decrease in Fv and is obviously restrained by Nb addition.