Hot deformation behavior and processing map of Zr-4 alloy

The hot deformation behavior of Zr-4 alloy at the deformation temperature range of 750-1000 degrees C and the strain rate range of 0.001-10 s(-1) was studied on a Gleeble-3500 thermal simulator. The results show that the flow stress increases with the increasing strain rates or the decreasing deformation temperature. Based on the experimental data, the strain-compensated constitutive equation was established to predict flow stress during different strains, strain rates and temperatures. Meanwhile, the hot deformation activation energy of Zr-4 alloy was respectively calculated to be 224.31 kJ/mol, 593.50 kJ/mol and 345.71 kJ/mol in alpha single-phase region, alpha+beta two-phase region and beta single-phase region, which are obviously much higher than the activation energy of pure zirconium (113 kJ/mol). It indicates that the main deformation mechanism is not the dynamic recovery but other deformation mechanisms. According to the dynamic material model and Murty instability criterion, Murty processing maps have been constructed at the true strain of 0.6 and 1.2. Moreover, by combining microstructural observations, the areas of 750-880 degrees C/0.01-0.32 s(-1) and 900-1000 degrees C/0.03-1 s(-1) are identified to be the optimum hot working parameters. (C) 2020 Elsevier B.V. All rights reserved.