Microstructure evolution mechanisms and a physically-based constitutive model for an Al-Zn-Mg-Cu-Zr aluminum alloy during hot deformation

High-temperature flow features of the Al Zn Mg Cu Zr aluminum alloy was revealed by hot compression tests. The evolution mechanisms of dislocation clusters, subgrain, and dynamic recrystallization (DRX) grains, are thoroughly explored by EBSD and TEM analysis. Experimental results suggest that the high strain rate can exacerbate dislocation clusters formation, as well as subgrain nucleation/accumulation, inducing the increasing of flow stress. Nevertheless, the noticeable annihilation of substructures, as well as the growth of DRX grains, emerge at the higher temperature, causing the descending of flow stress. Three types of DRX nucleating mechanisms, i.e., discontinuous DRX (DDRX), geometric DRX (GDRX) and continuous DRX (CDRX) are activated in the Al Zn Mg Cu Zr aluminum alloy during hot compression. Simultaneously, the GDRX often appears at a high compressed temperature or a low strain rate. A physically based (PB) model is proposed to collaboratively reconstruct true stresses and microstructure evolution features. The estimated values of true stress, DRX fractions and average grain size preferably fit the experimental data, indicating the proposed PB model can precisely catch the thermal compression behaviors and microstructure evolution characteristics of the Al Zn Mg Cu Zr aluminum alloy.(c) 2023 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).

Automated summary

The high-temperature flow features of the Al Zn Mg Cu Zr aluminum alloy were investigated through hot compression tests. The evolution mechanisms of dislocation clusters, subgrain, and dynamic recrystallization (DRX) grains were thoroughly explored. It was found that high strain rate promotes the formation of dislocation clusters and subgrain nucleation/accumulation, leading to an increase in flow stress; however, at higher temperatures, the noticeable annihilation of substructures and the growth of DRX grains result in a decrease in flow stress. Three types of DRX nucleating mechanisms are activated during hot compression. The physically based (PB) model accurately predicts the true stresses and microstructure evolution features of the alloy.