A Comparison of Classical Constitutive Models for High‐Entropy Alloy Behavior: Effects of Medium Strain Rates and Temperature on Plastic Flow

ABSTRACT Four different constitutive models (Johnson–Cook, Zerilli–Armstrong, Rusinek–Klepaczko, and Voyiadjis–Abed models) are systematically evaluated and compared to characterize the dynamic material behaviors of FeCoNiCr and Al 0.6 FeCoNiCr high‐entropy alloys over a wide range of temperatures and high strain rates. Key features of the experimentally observed dynamic behavior of these alloys are first analyzed to guide model selection and formulation. To capture the experimentally observed nonlinear strain rate sensitivity, the classical logarithmic strain rate term is replaced by a nonlogarithmic formulation. Material constants for each model are then identified for each material using the experimental data in the existing literature. The predictive capabilities and limitations of each model are then critically assessed, with particular emphasis on strain rate sensitivity, temperature dependence, and physically unrealistic responses at extreme loading conditions.