Characteristic constitution model and microstructure of an Al-3.5Cu-1.5Li alloy subjected to thermal deformation

Abstract

The constitution model and microstructure of 2A97 Al-Li alloy during thermal deformation were investigated. The thermal deformation behavior was dominated by the interaction between work hardening and dynamic softening. The constitution model was constructed to predict the rheology behavior, in which Zener-Holloman equation with a fifth-order polynomial was set to describe the effect of various strains on the material parameters. Processing maps displayed to exist two unstable domains in microstructure (one domain with the temperature range from 300 °C to 370 °C and the strain rate range from 100.5 s−1 to 10s−1, and the other with the temperature range from 380 °C to 500 °C and the strain rate range from 0 s−1 to 10 s−1). Microstructural characteristics of dynamic recovery (DRV) and dynamic recrystallization (DRX) in the stable domain and local rheology in the unstable domain were observed, respectively. The dynamic precipitation (DPN) of T1 phases and the interaction between dislocations and Al20Cu2Mn3 and Al3Zr phases were concluded by high resolution transmission electron microscopy (HRTEM), which was the first experimental evidence for the DPN in 2A97 Al-Li alloy. All these confirmed the occurrence of the continuous dynamic recrystallization during thermal deformation.