Non-isothermal recrystallization kinetics in low−carbon Mn−Si steels during continuous annealing

Abstract The non−isothermal recrystallization kinetics of two cold−rolled low−carbon Mn−Si steels were analyzed. The degree of recrystallization was determined as a function of microhardness at different annealing temperatures, maintaining a constant heating rate. Metallographic analysis and Electron Backscatter Diffraction (EBSD) analysis were performed to validate the recrystallized volume fraction. A modular kinetic model was utilized to ascertain the kinetic parameters and adjust the degree of recrystallization under non−isothermal conditions. The steel with the highest silicon and manganese content (1.2Mn−0.7Si steel) showed a delay in the degree of recrystallization compared to the steel with lower silicon and manganese content (0.4Mn−0.1Si steel). This delay can be attributed to the solute drag effect. The activation energy values were measured at 363 kJ mol⁻¹ for the 1.2Mn−0.7Si steel and 356 kJ mol⁻¹ for the 0.4Mn−0.1Si steel. The growth exponent for both steels was found to be less than one, indicating a diffusion−controlled growth rate. Subsequently, the kinetic parameters were applied to evaluate the degree of recrystallization behavior at a faster heating rate. The model predictions suggest that both the starting and ending recrystallization temperatures shift to higher values as the heating rate increases under continuous and isochronous conditions. However, caution is advised when applying this model at elevated heating rates, as it does not consider the effects of austenite formation on recrystallization kinetics, which may lead to an overlap between recrystallization and austenite formation.