Workability and dynamic restoration mechanisms of Al-6.2Zn-2.1Mg-0.15Zr alloy during medium temperature compression

Medium temperature compressions were implemented in the range of 433–593 K and 0.001–5 s−1 to reveal the workability and dynamic restoration mechanisms of quenched Al-6.2Zn-2.1Mg-0.15Zr alloy. The activation energy evolution with processing parameters was inspected through the modified kinetic equation that derived by integrally considering the strain and deformation parameters, and the results suggested activation energies decreased with the increasing strain rate and deformation temperature while less affected by the increase of strain at a specific strain rate condition. The 3D processing map was constructed to optimize the processing regions, in which two unstable domains yielded by distinct microscopic instabilities were marked whilst the safe working regions could be identified at 533–593 K, 0.001–0.1 s−1 with dissipation efficiency >20%. The microstructural evolution of the compressed specimens was examined, and the results confirmed different types of dynamic recovery (DRV) involving dislocation migration and rearrangement were dominate restoration process during the compression. Also, the microstructures of the specimens deformed at unstable domains were characterized, the results revealed fluctuating flow localization, micro cracking and particles debonding as well as dynamic strain aging were responsible for compression failure.