1.12 - Atomic-Level Dislocation Dynamics in Irradiated Metals

Primary damage and microstructure evolution in structural nuclear materials operating under conditions of a high flux of energetic atomic particles and high temperature and stress lead to the formation of a high concentration, nonhomogeneous distribution of defect clusters in the form of dislocation loops, voids, gas-filled bubbles, and radiation-induced precipitates of nanometer scale. They cause changes in many material properties. Being obstacles to dislocation glide, they strongly affect mechanical properties in particular. This gives rise to an increase in yield and flow stress and a reduction in ductility. Atomic-scale computer simulation can provide details of how these effects are influenced by obstacle structure, applied stress, strain rate, and temperature. Processes such as obstacle cutting, transformation, absorption, and drag are observed. Some recent results for body-centered and face-centered cubic metals are described in this chapter and, where appropriate, comparisons are drawn with predictions based on the elasticity theory of crystal defects.