Hot deformation behavior and processing map of a new type Al-Zn-Mg-Er-Zr alloy

Abstract

Isothermal compression tests of a new type Al-Zn-Mg-Er-Zr alloy are carried out on a Gleeble-3800 thermal simulator at temperatures varying from 573 to 733 K and strain rates ranging from 0.001 to 10 s−1. Processing maps have been constructed to study on hot workability characteristics of the alloy. The results show that the stable and unstable regions in the processing maps of Al-Kn-Mg-Er-Zr alloy should be identified based on the comprehensive consideration of the strain rate sensitivity m, power dissipation efficiency η and instability criterionξ(ε˙). The processing maps exhibit two regions with high efficiency of power dissipation: one is at temperature of 620–680 K and strain rate of 0.001–0.003 s−1; another is at temperature of 680–733 K and strain rate of 0.001–0.1 s−1. The highest η value occurs at about 653 K/0.001 s−1 and the peak η values are all above 37%. According to the microstructure observation, the flow instability is manifested as adiabatic shear bands and flow localization, while the microstructures characteristics in the “safe” domains mainly exhibit dynamic recovery. The presence of coherent L12-structured Al3(Er,Zr) particles effectively pin the dislocation movement and the subgrain boundary slide so as to restrain the occurrence of dynamic recrystallization behavior, and the dominant softening mechanism is dynamic recovery during isothermal compression.