Constitutive modeling for the dynamic recrystallization kinetics of as-extruded 3Cr20Ni10W2 heat-resistant alloy based on stress-strain data

In order to improve the understanding of the dynamic recrystallization (DRX) behaviors of as-extruded 3Cr20Ni10W2 heat-resistant alloy, a series of isothermal upsetting experiments with a fixed height reduction of 60% were performed at the temperatures of 1203 K, 1253 K, 1303 K, 1353 K and 1403 K, and the strain rates of 0.01 s(-1), 0.1 s(-1), 1 s(-1) and 10 s(-1) on a Gleeble1500 thermo-mechanical simulator. By the regression analysis for conventional hyperbolic sine equation, the activation energy of DRX was determined as Q = 892.3511 kJ mol(-1). According to the conventional strain hardening rate curves (d sigma/d epsilon versus sigma) and their derived results, three characteristic points including the critical strain for DRX initiation (epsilon(c)), the strain for peak stress (epsilon(p)), and the strain for maximum softening rate (epsilon*) were identified. In order to characterize the evolution of DRX volume fraction, the modified Avrami type equation including epsilon(c) and epsilon* as a function of the dimensionless parameter controlling the stored energy, Z/A, was evaluated, and the influence of deformation conditions was described in details. Finally, the theoretical prediction results of DRX volume fraction were shown to be in agreement with experimental observations. (C) 2013 Elsevier Ltd. All rights reserved.