Dynamic recrystallization and precipitation behavior of a novel Sc, Zr alloyed Al-Zn-Mg-Cu alloy during hot deformation

Abstract

The hot deformation behavior of a novel Sc, Zr alloyed Al-Zn-Mg-Cu alloy was explored in the isothermal hot compression test with a temperature range of 300–500 °C and a strain rate of 0.001–10 s −1 . The stress-strain curve, constitutive equation, and processing map were integrated to evaluate the flow behavior and hot workability of the studied alloy. Besides, the relationship between dynamic recrystallization and precipitation behavior and the Zener-Hollomon (Z) parameter during hot deformation was deeply explored. As lnZ decreased, the dislocation density decreased, while the misorientation angle increased. Meanwhile, with the decrease of lnZ, the amount of low-angle grain boundaries and medium-low-angle grain boundaries decreased. Moreover, dynamic recovery is the dominant dynamic softening mechanism, while three different dynamic recrystallization (DRX) mechanisms were the main DRX mechanisms at different lnZ values. Discontinuous DRX dominated at high lnZ value (lnZ ≥33.33); Continuous DRX (CDRX) dominated at middle lnZ value (23.4 < lnZ < 33.33); Geometric DRX dominated at low lnZ value (lnZ ≤23.44). Meanwhile, increasing lnZ value is conducive to precipitation behavior. The intragranular precipitates and grain boundary precipitates are identified as the phase containing Al, Fe, Mn, and Si, the equilibrium η phase containing Cu and Al 3 (Sc, Zr) particles. • The following constitutive equation of the experimental alloy is constructed: ɛ ̇ =1.110 × 10 13 [sinh (0.0160σ)] 5.170 exp(16981/RT). • The microstructure relied on the lnZ value during hot compression. • DDRX, CDRX, and GDRX were the dominant DRX processes at high, medium and low lnZ values respectively. • Increasing lnZ value is conducive to precipitation behavior.