Stress Localization Resulting from Grain Boundary Dislocation Interactions in Relaxed and Defective Grain Boundaries

Large-scale molecular dynamics simulations are used to study strain and stress localization in atomistic polycrystalline FCC digital samples in a thin-film configuration, deformed in tension. Special focus is placed on the effects of additional grain boundary disorder on the dislocation-grain boundary interaction. The development of the localized stress and strain regions is studied as dislocations are emitted from and arrive at grain boundaries. Digital samples with two different degrees of disorder in the grain boundaries but otherwise identical microstructures are compared in order to understand the effects of additional defects on the stress concentration that develops at the grain boundaries. Localization phenomena are found to depend on the details of the grain boundary defect structure and relaxation state. The results clearly show that the samples with more disordered grain boundaries are more prone to strain and stress localization, with a higher fraction of atoms experiencing extreme deformation. The simulation results are validated by comparison with the predictions of continuum theories and experimental measurements of localized stress performed in austenitic stainless steel.