A Discrete Dislocation Dynamics Study of Prior Particle Boundary Effects in Ni-based Superalloys

Ni-based superalloys produced via powder metallurgy (PM) undergo hot isostatic pressing (HIP) and subsequent forming operations, during which prior particle boundaries (PPBs) are formed and only partially eliminated. The residual PPB clusters strongly influence the mechanical and thermomechanical performance of these alloys. In this study, a polycrystalline discrete dislocation dynamics (DDD) framework is employed to investigate the role of PPBs in governing dislocation behavior, residual stress evolution, and macroscopic hardening in Ni-based superalloys. Realistic grain morphologies are incorporated, and PPBs are modeled as non-transmissive interfaces that restrict dislocation motion across boundaries. The simulations reveal that PPBs induce localized dislocation pile-ups and back stresses, thereby enhancing strain hardening and yield strength. Larger and more densely distributed PPB clusters intensify these effects due to increased dislocation pinning. Residual stress analysis further shows that regions adjacent to PPBs retain higher compressive stresses after unloading, with relaxation strongly dependent on PPB density. These results highlight the critical role of PPB size, number, and spatial configuration in shaping the deformation and stress evolution behavior of PM-processed Ni-based superalloys. The study underscores the need to control PPB characteristics during HIP and post-HIP processing to achieve an optimal balance between strengthening and stress recovery.