A study of the dynamic recrystallization kinetics of V-microalloyed medium carbon steel

Abstract

The Avrami kinetics of the dynamic recrystallization (DRX) of V-microalloyed medium carbon steel is studied by measuring the flow curves and evolution of grain size distribution (GSD) due to DRX and by modeling the flow softening kinetics and flow curves under various deformation conditions. The epsilon(1/2) method is proposed as a new method of modeling the Avrami kinetics and is shown to be, unlike the conventional t (1/2) method, capable of modeling the flow softening kinetics and flow curves with a single variable Z (= exp(Q (def)/RT)). The time exponent "n" of the Avrami kinetics decreases from 2.3 to 1.4 with increasing Z, which results from a shift in the mode of necklace recrystallization from boundary migration dominant mode to nucleation dominant mode. The GSD method is proposed as a new method for estimating the DRX fraction in deformation conditions where it is difficult to distinguish recrystallized grains from un-recrystallized grains. The softening fractions estimated from the flow curves tend to overestimate the DRX fractions at a later stage of deformation, where DRX kinetics appear to be retarded by dynamic precipitation.