Dynamic recrystallization mechanisms and microstructure evolution of a novel Al-Zn-Mg-Cu-Zr alloy by isothermal compression

The dynamic recrystallization (DRX) behavior and microstructure evolution of a novel Al-Zn-Mg-Cu-Zr alloy was investigated by isothermal compression tests at temperature of 350-470 degrees C and strain rate of 0.0001(-1) s(-1). The results showed that the flow behavior revealed typical dynamic recovery (DRV) characteristics at a high strain rate (1 s(-1)), while exhibited a DRX shape when the strain rate decreased. The critical strains (epsilon(c)) of the DRX decreased with the decrease of strain rate or the increase of deformation temperature. A low temperature was conductive to precipitation behavior, the coarse precipitates and dispersed Al3Zr particles would pin the dislocations and substructures, which inhibit the DRX process. The DRX mechanism of the Al-Zn-Mg-Cu-Zr alloy was dominated by continuous dynamic recrystallization (CDRX) and discontinuous dynamic recrystallization (DDRX) during the hot deformation process, upon increasing the temperature and decreasing the strain rate, there was a transition point of DRX mechanism from DDRX to CDRX. Moreover, the linear relationship between the ZenerHollomon (Z) parameter and DRX grain size was established for the further exploration of the transition of the dominant DRX mechanism.