Athermally enhanced recrystallization kinetics of ultra-low carbon steel via electric current treatment

Abstract

The direct application of electric current as well as heat treatment can be used to recrystallize metallic materials. Electric current enhances the recrystallization kinetics, making the process time- and energy- saving. The enhanced recrystallization kinetics observed during electric current treatment cannot be ex- plained by Joule heating alone, and its quantitative analysis is yet to be conducted. This study system- atically investigates the athermal effect of electric current on the recrystallization kinetics of ultra-low carbon steel. Specimens were subjected to electric current at various current densities to reach the target temperatures, and the resulting recrystallization kinetics were analyzed. A comparison with the speci- mens heat-treated at comparable target temperatures clearly shows that electric current treatment en- hances the degree of recrystallization, and the recrystallization kinetics have a unique tendency to de- crease and then increase as the electric current density increases. From the recrystallization fraction dif- ference between the electric current-treated and heat-treated specimens, we deduce the athermal effect of the electric current on recrystallization and describe the athermally enhanced recrystallization kinet- ics using the Johnson-Mehl-Avrami-Kolmogorov equation considering the effective activation energy and temperature. The calculated recrystallization fraction implies that the athermal effect of the electric cur- rent becomes more pronounced with increasing electric current density. This study suggests that the athermal effect of electric current in the material fabrication process can be evaluated and predicted.