Mesoscale Modeling of Microstructural Effects on Inelastic Behavior of High Entropy Alloys

Abstract High Entropy Alloys (HEAs) are promising for next-generation structural materials due to their exceptional mechanical properties. The compositional variations in these alloys result in microstructural heterogeneities, such as grains, grain boundaries, second-phase particles, and voids, which significantly affect properties like yielding and hardening. In this work, we study the influence of grain-size distribution on the yielding and hardening behavior of HEAs. Our approach is a mesoscale formulation wherein we model the inelastic deformation using a distribution of the nucleation sites for local inelastic deformation. We consider the grains to be nucleation sites for the local inelastic deformation, and grain size distributions, calculated via phase-field modeling, are used to get nucleation stress using a Hall-Petch-like relation. To model the effects of grain yielding on the surrounding material, we use the analytical Eshelby inclusion solution and an image field that enforces the prescribed boundary conditions of the boundary value problem. The image field boundary value problem is solved by the finite element method using ABAQUS software. Combining the Eshelby and image field solutions allows us to calculate the change in stress state due to individual grain-yielding events while accounting for boundary effects. This framework can be applied to computationally or experimentally observed microstructures to provide an inelastic response that accounts for both the boundary conditions and internal microstructure. We will discuss the yielding and hardening of the stress-strain response of several HEAs with different microstructures by considering the distributions of nucleation sites and biases in the nucleation pattern.