Microstructure Evolution and Constitutive Modeling Based on Flow Behavior of 2297 Al-Cu-Li Alloy

Flow behavior and microstructure evolution of 2297 Al-Cu-Li alloy were investigated by isothermal compression tests conducted at the deformation temperature of 300-500°C and strain rates of 0.001-10s-1. The results demonstrate that the characteristics of stress-strain curves depended on the interaction of work hardening and dynamic softening. The true stress increased with the decreasing of temperature and the increasing of the strain rate. At a given deformation condition, the flow curve consisted of three stages: stage I (work hardening stage), stage II (softening stage) and stage III (steady stage). Deformation temperature and strain rate had a great influence on microstructure evolution. 2297 alloy deformed at low temperature (300°C) and high strain rate (10s-1) showed a DRV characteristic. As deformed at high temperature (500°C) and low strain rate (0.001s-1), DRX gradually become the main softening mechanism. The measured flow stress was friction corrected and then employed to develop constitutive equations on the basis of the Arrhenius-type equation by considering the effect of the strain on material constants by a sixth orders polynomials. Flow stress value of 2297 alloy predicted by the proposed constitutive equations shows a good agreement with experimental results, thereby confirming the validity of the developed constitutive relation.