Constitutive modeling of dynamic recrystallization kinetics and processing maps of Mg-2.0Zn-0.3Zr alloy based on true stress-strain curves

To investigate the effects on the dynamic recrystallization (DRX) behaviors, Mg-2.0Zn-0.3Zr alloy compression experiments with height reduction 60% were performed at the temperatures of 300 C, 350 degrees C, 400 degrees C, 450 degrees C and 500 degrees C, and the strain rates of 0.001 s(-1), 0.01 s(-1), 0.1 s(-1) and 1 s(-1) on a Gleeble 1500 thermo-mechanical simulator. By means of regression analysis for the Arrhenius type equation of flow behavior, the apparent average activation energy of deformation was determined as Q=169.8 KJ/mol. From the Avrami type equation, the DRX kinetic model of Mg-2.0Zn-0.3Zr alloy is described X-DRx = 1-exp [-1.3250 (epsilon-epsilon(c)/epsilon*)(2.0405)]. Through the flow stress behavior, the processing maps are calculated and analyzed according to the dynamic material model (DMM). In the processing map the variation of the efficiency of the power dissipation is fitted to a function of temperature and strain rate. The processing maps exhibit two domains of complete DRX occurring (350-500 degrees C at 0.001 s(-1), 400-500 degrees C at 0.01-1 s(-1)) which are the optimum parameters for hot working of the alloy. (C) 2012 Elsevier B.V. All rights reserved.