Abstract
A physical-based constitutive model was developed to model the viscoplastic flow behavior and microstructure evolution of AZ80 magnesium alloy during the hot working process. The competing deformation mechanisms, including work hardening, dynamic recovery, and dynamic recrystallization, in an isothermal compression environment were considered in the model. The internal state variables, including the normalized dislocation density and recrystallized volume fraction, were incorporated into the model to articulate the microstructure evolution during hot deformation. The kinetic condition critical for dynamic recrystallization, considering the effects of the deformation temperature and strain rate, was obtained by employing both the Poliak-Jonas criterion and Zener-Hollomon parameter. Microstructure observations indicate that the recrystallized volume fraction increases with decreasing Z parameter at constant strain, which is consistent with the predicted kinetics model. Based on the developed model, a good correlation was also obtained between the predicted and experimental flow stress. The results indicate a good predictability of the model in describing the hot deformation behavior and microstructure evolution of AZ80 magnesium alloy.
Highlights
Magnesium alloy is one of the most promising lightweight metallic materials for structural applications in the automotive and aerospace industries owing to its low density, high specific strength, and good recyclability [1, 2]
The results indicate a good predictability of the model in describing the hot deformation behavior and microstructure evolution of AZ80 magnesium alloy
Numerous constitutive models have been established such as phenomenological models, e.g., Arrhenius-type model and Physical-based constitutive model considering the microstructure evolution during hot working
Summary
Magnesium alloy is one of the most promising lightweight metallic materials for structural applications in the automotive and aerospace industries owing to its low density, high specific strength, and good recyclability [1, 2]. The aforementioned study is a good reference and basis for establishing the physical-based constitutive model for AZ80 magnesium alloy to describe the flow behavior and microstructure evolution during the hot working process. Many constitutive models, which are available for magnesium alloys, are generally phenomenologically constructed by introducing a few macroscopic variables to the model and formulated as functions of the temperature, strain rate and strain They are basically experimental and based on classical viscoplastic theory to describe work hardening and thermal softening phenomena during the hot working process. In view of the important role of DRX in the grain refinement and improvement of mechanical properties during the hot working of magnesium alloy, the establishment of a constitutive model that can reflect the evolution of the recrystallized microstructure is urgently needed. The proposed constitutive model can be used to analyze the hot deformation behavior and microstructure evolution of AZ80 magnesium alloy
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