Deformation temperature, strain rate, and irradiation microstructure effects on localized plasticity in 304L SS

The present study examines the deformation behavior of ion-irradiated, low-carbon 304L stainless steel to investigate the influence of irradiation microstructure, deformation temperature and strain rate on localized plasticity. Dislocation loop character, size and density are linked to changes in deformation character. Lower doses produce small faulted loops and stacking fault tetrahedra that impede dislocation mobility. Dislocations are pinned at defects and require higher stress to break free from the defects. Larger defects take the form of faulted Frank loops that can interact with glide dislocations to form microtwins at lower temperatures and faster strain rates. Deformation at higher temperatures and slower strain rates promotes interactions between glide dislocations and loops leading to loop annihilation. Dislocation free zones or ''channels'' form where further plastic deformation is highly localized. Results are compared to limited observations for neutron-irradiated materials. These irradiation-induced changes can be an important concern for light-water reactor (LWR) stainless steel (SS) structural components due to a reduced damage tolerance, and potential susceptibility to environmental cracking such as irradiation-assisted stress corrosion cracking (IASCC)