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 ε_c for initiation of DRX. The “athermal” hardening parameter h and the dynamic recovery parameter r were evaluated from the work-hardening behavior prior to ε_c. The saturation stresses σ_sat pertaining to the unrecrystallized regions as well as the associated work-hardening curves, σ_recov, were derived in this way. The net softening attributable to DRX was then defined as the difference between the σ_recov 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.