Plastic deformation of ferritic grains in presence of ODS particles and irradiation-induced defect clusters: A 3D dislocation dynamics simulation study

Ferritic steels strengthened by oxide particle dispersions (ODS) are prime candidate for future nuclear applications. So far, the beneficial mechanical characteristics of ODS steels are not fully understood, in terms of dislocation-based mechanisms. In this work, three-dimensional discrete dislocation dynamics simulations were carried out to analyze pre and post-irradiation plastic deformation in ferritic grains, with and without ODS particles. In the absence of irradiation induced defect loops, ODS-grains are stronger and plastic strain is more localized than in the corresponding, particle-free grain. After irradiation however, ODS-grain become more resistant to loop-induced hardening, while plastic strain spreading is broader, with respect to particle-free grain. This effect is due to dislocations accumulating next to the precipitates, generating internal stress allowing cross-slipped dislocations to go past the irradiation induced defect loops. Cross-slip is therefore a key feature of our model, for explaining the beneficial role of ODS particles on post-irradiation plastic deformation.