Modeling of flow behavior for 7050-T7451 aluminum alloy considering microstructural evolution over a wide range of strain rates

• Compression tests of 7050-T7451 alloy over wide loading ranges were presented.
• Microstructure evolution over a wide range of strain rates was studied.
• The loading strain rate affects the microstructure and work hardening rate.
• Thermal softening rate decreases with the increasing logarithmic strain rate.
• A modified JC model for 7050-T7451 alloy was proposed and validated.

The compression mechanical behaviors of 7050-T7451 alloy over a wide range of strain rates were studied. The quasi-static and dynamic uniaxial compression tests were presented over a wide range of strain rates (0.0001 s−1, 0.01 s−1, 2500 s−1, 4000 s−1, 7500 s−1 and 10,000 s−1) and temperatures (20 °C, 100 °C, 200 °C and 270 °C). The work hardening behavior changes from work hardening to flow softening with the increase of plastic strain at dynamic conditions. In addition, the dynamic recrystallization (DRX), grain refining and phase transition were observed from the microstructures of the cross-section of the compressed specimens. The microstructure evolution at dynamic condition leads to a smaller work hardening rate than that at most of the quasi-static conditions, indicating a coupling effect of the work hardening and strain rate for 7050-T7451 alloy. Besides, the calculated average thermal softening rate decreases with the increase of logarithmic strain rate, which indicates a coupled effect of thermal softening and strain rate. Based on the calculated work hardening and thermal softening behaviors, a modified Johnson Cook (JC) model was developed to incorporate the coupled effects into the items of work hardening and thermal softening. Most of the average absolute relative errors (AARE) between the predicted and measured flow stresses were less than 5%. In addition, the prediction accuracy of the proposed constitutive model was further evaluated by a loading condition jump test.