Thermoplastic behavior and microstructure evolution of Al-Zn-Mg-Cu-Zr-Sc-Er alloy

Hot compression tests were performed to investigate the hot deformation behavior of the Al-8.2Zn-2.5Mg-1.4Cu-0.08Zr-0.09Sc-0.08Er alloy over a temperature range of 350∼470 °C and strain rates of 0.001∼10 s -1 . The results indicate that the flow stress increases with increasing strain rate and decreases with increasing deformation temperature, demonstrating a positive strain-rate sensitivity. A constitutive equation describing the flow behavior of the alloy was developed based on the Zener–Hollomon parameter, and the apparent activation energy for hot deformation was determined to be 165.398 kJ·mol -1 . Based on power-dissipation efficiency and flow-instability criteria, hot-processing maps were constructed at multiple strain levels. These maps indicate that the optimal processing window for the alloy lies within 420∼460 °C and 0.001∼0.01 s -1 . Microstructural characterization under different deformation conditions reveals that at high strain rates and low temperatures, the alloy retains a pronounced fibrous structure. Deformation-related shear textures such as Brass and S dominate, reflecting a deformation mechanism governed primarily by dislocation slip with limited recovery. Reducing the strain rate and increasing the deformation temperature significantly enhance dynamic recovery, leading to a pronounced reduction in dislocation density. Under these conditions, some grains undergo dynamic recrystallization through subgrain growth. Consequently, the volume fractions of recrystallization-related textures increase, indicating that orientation selection gradually evolves from being dominated by deformation textures toward recrystallization textures. With increasing strain, deformation textures continue to accumulate because of their inherent orientation stability under large plastic deformation. In contrast, the development of recrystallization textures becomes relatively constrained, largely due to the pinning effect of the dispersed precipitates, which restrict grain boundary migration and local nucleation, thereby limiting the extent of dynamic recrystallization.