Hot deformation constitutive model and processing maps of homogenized Al–5Mg–3Zn–1Cu alloy

Abstract

Isothermal uniaxial compression experiments were performed in the range of 300–450 °C and 0.001 to 10 s −1 to clarify the hot deformation behavior of homogenized Al–5Mg–3Zn–1Cu alloy. The results revealed that the flow curves exhibited typical characteristics of DRV/DRX accompanied by the work-hardening, and the existence of three distinct stages of work-hardening, transition, and steady-state in each flow curve. A strain-compensated constitutive model for determining flow stress in this alloy was established with highly acceptable predictability. The dominant deformation mechanism of the alloy is dislocation climbing. Also, dynamic-material-model-based processing maps at various strains were constructed, and the unstable and workable domains were distinguished. Instability generally occurred in high strain rates and low temperatures zone with prevalent instability forms such as cracking and flow localization. The workable domain was 375–450 °C and 0.001–0.1 s −1 , in which the microstructure of the deformed alloy was characterized by dynamic recovery and multiple types of dynamic recrystallization. The dynamic precipitates were labeled as T-Mg 32 (AlZnCu) 49 phase. These intermittently distributed precipitates along the grain boundaries were stable in all temperature ranges, while the intragranular precipitates were inhibited at 300 °C. Temperature increment to 400 °C led to a large number of dispersed intragranular precipitates which redissolved into the matrix as temperature exceeded 450 °C.