The Avrami kinetics of dynamic recrystallization

Twenty-six flow curves determined under dynamic recrystallization (DRX) conditions on 11 different steels were analyzed. The double-differentiation method was used to define the critical strain ec for initiation of DRX. The “athermal” hardening parameter h and the dynamic recovery parameter r were evaluated from the work-hardening behavior prior to ec. The saturation stresses σsat pertaining to the unrecrystallized regions as well as the associated work-hardening curves, σrecov, were derived in this way. The net softening attributable to DRX was then defined as the difference between the σrecov and experimental curves. Avrami plots were prepared from all 26 sets of data. The time exponents were all in the neighborhood of 3.0; however, the strain rate and temperature dependences differed considerably from their static values. The dependence of the time of half-softening, t50, on strain rate and temperature is used to predict the DRX curves expected under industrial conditions.