A microstructure-resolved crystal plasticity finite element model for strain-rate-dependent deformation of CMSX-4 nickel-based single crystal

Microstructure-resolved crystal plasticity modelling provides an effective approach for analysing local plastic deformation in nickel-based single-crystal superalloys, where the macroscopic response is strongly affected by γ/γ′ phase interactions. In this study, a dislocation-density-based crystal plasticity finite element model was implemented in the open-source MOOSE framework to investigate the deformation behaviour of CMSX-4 under [001] monotonic tensile loading at room temperature. Idealized two-phase representative volume elements were constructed, and phase-dependent resistance contributions were introduced to describe dislocation evolution, forest hardening, precipitate shearing resistance associated with anti-phase boundary and superlattice stacking fault mechanisms, and Orowan-type strengthening. The material parameters were calibrated using a genetic-algorithm-based inverse procedure based on experimental tensile stress-strain curves. The calibrated model captures the tensile responses at the investigated strain rates and provides spatially resolved effective plastic strain and mobile/immobile dislocation-density fields. The simulations show that the higher strain-rate condition promotes stronger local deformation gradients and dislocation accumulation near γ/γ′ interfaces, leading to increased flow resistance. A numerical study with different characteristic γ′ spacings further indicates that smaller precipitate spacing enhances the predicted stress response through Orowan-type resistance and intensified dislocation accumulation in γ channels. These results provide a computational basis for interpreting phase-resolved plastic deformation in γ/γ′ single-crystal superalloys.