Self–ion irradiation of high purity iron: Unveiling plasticity mechanisms through nanoindentation experiments and large-scale atomistic simulations

Ion irradiation may enhance material hardness through crystal defect nucleation and reorganization. In this study, we examine the nanomechanical behavior of high-purity iron samples, comparing the response of pristine specimen to those that have been self–irradiated with 5 MeV ions at 300^∘C. We utilize spherical nanoindentation to investigate the nanomechanical response, and we focus on the comprehensive modeling of the self–irradiation effects in high-purity iron through large-scale molecular simulations. Transmission electron microscopy is used in the irradiated regions, at various depths below the nanoindentation imprint, to analyze the nucleation of dislocation networks and the plastic deformation mechanisms at room temperature. Large scale novel molecular dynamics simulations are conducted to simulate overlapping collision cascades reaching an irradiation dose with defect density similar to experiments, followed by nanoindentation simulations that display qualitative agreement to experiments. We find that irradiated sample requires higher critical load for the transition from elastic to plastic deformation due to interaction of dislocation lines with the dislocation loops and point defects formed during the irradiation, leading to hardening.