Constructing processing maps for hot deformation and microstructural evolution of Al-Zn-Mg-Cu alloys

The hot deformation behaviour of a high-alloy Al-Zn-Mg-Cu alloy was evaluated via hot compression tests over a temperature range of 300 degrees C-460 degrees C and a strain rate range of 0.001-10 s(-1). Hot processing maps were established based on a dynamic materials model, the deformed microstructural characteristics were analysed. The processing map reveals that the safe regions for deforming are located at the high temperature and the low strain rate. Unstable regions appear on the map at high strain rates (1-10 s(-1)), wherein numerous adiabatic bands and micro/macrocracks form in the corresponding microstructures. The power dissipation efficiency (eta) increases with increasing temperature and decreasing strain rate. Dynamic recovery was determined to be the main dynamic softening behaviour, while continuous dynamic recrystallization (CDRX) and discontinuous dynamic recrystallization (DDRX) also occurred. The dynamic recrystallization mechanism correlated well with the power dissipation efficiency; specifically, it was CDRX at eta > 0.35 and DDRX at eta < 0.27.