Hot Deformation Behavior of Homogenized Al-7.8Zn-1.65Mg-2.0Cu (wt.%) Alloy.

The flow curves of Al-7.8Zn-1.65Mg-2.0Cu (wt.%) alloy in the temperature range of 300-450 °C and strain rate range of 0.01-10 s⁻¹ were obtained by hot compression tests on a Gleeble-3500 isothermal simulator. The effects of deformation heat-induced temperature rising and friction on the flow curves were discussed and the flow curves were corrected to exclude these influences. The constitutive model was constructed and its accuracy was evaluated by the correlation coefficient (R) and average absolute relative error. The values of the corresponding evaluators were determined to be 0.9841 and 6.2346%, respectively. The processing maps were developed and through which the optimal hot working window for this alloy was determined in the range of 380-450 °C and 0.01-0.368 s⁻¹. The microstructure evolution observations revealed that micro-crack and flow localization occurred at 300 °C and 10 s⁻¹ and 400 °C and 10 s⁻¹, which located in the instability region of processing map. With the increasing strain rate, the deformation activation energy decreased, simultaneously, the dislocation multiplication rate accelerated, which resulted in pronounced increasing of LAGBs and HAGBs. [ABSTRACT FROM AUTHOR]