Hot deformation behavior and microstructure evolution of Al-6.4Zn-2.2Cu–2Mg alloy

To achieve the cross-rolling composite forming of aluminum alloy hollow shafts, hot compression tests were conducted on extruded Al-6.4Zn-2.2Cu-2Mg alloys using a Gleeble-3500 thermal-mechanical simulator. The deformation temperatures ranged from 320 to 440 °C, with strain rates spanning 0.01 to 10 s -1 . Based on the experimental data, a 3D predictive model for constitutive parameters was established, incorporating both temperature and strain rate. Analysis of conventional strain-compensated models revealed inherent limitations; in contrast, the proposed modified Arrhenius constitutive model demonstrated superior predictive accuracy. Furthermore, hot processing maps were constructed to identify instability domains, which were primarily concentrated in high strain rate regions. The optimal hot deformation window was determined to be 660-710 K with a strain rate of 0.01-0.1 s -1 . Electron backscatter diffraction (EBSD) analysis indicated that the alloy’s hot deformation follows an evolutionary path of dislocation accumulation, subgrain rotation, and recrystallization. Continuous dynamic recrystallization (CDRX) was identified as the dominant mechanism, accompanied by localized discontinuous dynamic recrystallization (DDRX). High temperatures and low strain rates were found to facilitate CDRX. These findings provide a theoretical foundation for the cross-piercing rolling of Al-6.4Zn-2.2Cu-2Mg alloy hollow shafts.