1.16 - Dislocation Dynamics

Abstract

Neutron irradiation of structural materials results in the production of a variety of atomic-size defects, which generally increases the strength but can severely reduce ductility. Defect-induced strengthening, or radiation hardening, is also associated in many cases with inhomogeneous plastic deformation, manifesting as dislocation channels, where shear strains of a few hundred percent can accumulate while most of the volume in between such channels is virtually undeformed. Because of these unique features of plasticity in irradiated materials, the method of dislocation dynamics has been developed for the description of microscale plastic deformation. We first review the mathematical and computational methods employed in understanding dislocation interactions with irradiation-induced defects and the collective behavior of dislocation ensembles. We present results for dislocation interaction with self-interstitial atom (SIA) clusters and with stacking fault tetrahedra (SFTs), followed by quantitative modeling of radiation hardening and dislocation channel formation as a result of these defects. We then describe a model for analyzing the ductile-to-brittle transition temperature (DBTT) in ferritic steels under neutron irradiation, and show quantitative comparisons with experiments.