The role of various Zr additions in static softening behavior of Al-Zn-Mg-Cu alloys during interval holding of double-stage hot deformation

Double-stage interrupted uniaxial hot compression tests were conducted to investigate the static softening behavior in Al-Zn-Mg-Cu alloys with various Zr additions at temperature of 300 degrees C and 400 degrees C and strain rates of 0.01 s(-1) and 0.1 s(-1). The microstructural evolution was also characterized by utilizing electron backscatter diffraction and transmission electron microscopy. The results revealed that static softening fraction of the studied alloys increases with increased Zr additions. Different static softening kinetics and plateaus were indicated to be the functions of deformation temperature, strain rate and Zr addition. At 300 degrees C, the observed short static softening plateaus were attributed to static recovery, static precipitation and its coarsening during post-deformation holding. High static softening fractions and long plateaus were presented when deformed at 400 degrees C and 0.1 s(-1), which were resulted from rapid static recovery and recrystallization within very short time. (C) 2019 Elsevier B.V. All rights reserved.