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Plastic localization in irradiated ferritic systems: new insights from modeling and simulation

Low temperature irradiation of crystalline materials is known to result in hardening and loss of ductility, which limits the usefulness of candidate materials in harsh nuclear environments. In bcc metals, this mechanical property degradation is caused by the interaction of in-grown dislocations with irradiation defects, particularly small dislocation loops resulting from the microstructural evolution of displacement cascades. In this work, we present a multi scale model encompassing dislocation dynamics (DD) simulations, crystal plasticity, and finite element (FE) simulations of bcc Fe containing various concentrations of dislocation loops produced by irradiation in an attempt to gain insight into the processes that lead to hardening and embrittlement.  The DD simulations reveal a transition from homogenous to highly localized deformation at a critical loop density. Above it, plastic flow proceeds heterogeneously, creating defect-free channels in its wake. These simulations are then used to calibrate a tensorial crystal plasticity model capable of reaching strains in excess of 10%. The calibrated crystal plasticity model is used as the constitutive relation in FE simulations of polycrystalline irradiated Fe systems.