Crystal Plasticity Modeling of Strain Hardening Induced by Coherent Precipitates in Inconel 718 Superalloy

In this work, a crystal plasticity (CP)-based continuum modeling approach is employed to investigate the interaction between dislocations and coherent γ″ precipitates in the Inconel 718 (IN718) superalloy. A finite element (FE) model is developed to accurately represent realistic microstructures in IN718, specifically incorporating a disk-shaped precipitate embedded within a matrix phase. A length-scale-dependent CP modeling simulation informed by molecular dynamics (MD) findings is conducted. The results indicate that the three γ″ variants behave differently under uniaxial loading conditions, altering the deformation process in the γ phase and leading to significant strain and stress heterogeneities. The presence of dislocation shearing in the γ″ variants reduces the localization of strain and dislocation densities in the adjacent γ phase. The strain gradient-governed geometrically necessary dislocation (GND) density plays a dominant role in influencing strain hardening behavior. The length scale effect is further quantified by considering four different precipitate sizes, with the major axis ranging from 12.5 nm to 100 nm. The findings show that smaller precipitate sizes result in stronger strain hardening, and the size of γ″ precipitates significantly alters GND density evolution.