Flow Behavior and Microstructure Characterization of an Ultrahigh-Alloyed Al–Zn–Mg–Cu Alloy

Abstract

Hot compression tests were conducted on an ultrahigh-alloyed Al–Zn–Mg–Cu alloy within a temperature range of 250 to 450°C and a strain rate range of 0.001 to 1 s^–1. The effects of strain rate and temperature on the flow curves were analyzed, along with the relationship between flow stress and microstructural evolution. The results indicate that, except for a strain rate of 1 s^–1 across all temperatures, the flow curves following the peak stress do not exhibit monotonic work hardening or dynamic softening. In contrast, continuous work hardening is observed at this strain rate. The diverse shapes of the flow curves are attributed to the various precipitates formed due to the high alloying element content. Dynamic recovery (DRV) is identified as the main flow softening mechanism for the ultrahigh-alloyed Al–Zn–Mg–Cu alloy. While dynamic recrystallization (DRX) contributes to flow softening at a strain rate of 0.001 s^–1, the deformed microstructure becomes the predominant softening mechanism at lower temperatures and higher strain rates. Additionally, the low intensity of isotropic texture at higher temperatures and strain rates facilitates DRX, resulting in a decrease in peak stress.