Static recrystallization kinetics of ferrite in cold-deformed medium carbon steel

Abstract

Static recrystallization (SRX) kinetics of a cold rolled commercial medium carbon steel (AISI 4130) at subcritical temperatures was studied for proposing a comprehensive Johnson-Mehl-Avrami-Kolmogorov (JMAK) equation. The value of the recrystallization activation energy (Q SRX) was near the activation energy for lattice diffusion in α-iron (251 kJ mol-1). Therefore, the atomic mechanism for SRX of ferrite in this material was considered to be the self-diffusion in α-iron. It was revealed for the first time that the pre-exponential constant (K 0) in the equation of the overall rate constant (K) depend exponentially on the reduction in thickness (r). The Avrami exponent (n) of ∼1 was determined, which was interpreted in terms of the nucleation of recrystallization on grain boundaries. Accordingly, a JMAK equation with incorporation of the effects of annealing temperature and reduction in thickness was proposed, which can be used for grain refinement of this material for industrial applications.