Theory of radiation-induced segregation

In this paper we review the basic knowledge of the mechanisms involved in radiation-induced segregation and discuss models and model calculations that describe the process. The next section presents a short, qualitative description of the segregation process which requires the existence of persistent defect fluxes and their preferential coupling to the fluxes of alloying components. The causes of the preferential coupling are attractive interactions between defects and some alloying elements, and/or preferential migration of defects via atoms of some alloy components. In dilute alloys, the interactions can be described by vacancy-solute and interstitial-solute binding, i.e. the formation of defect-solute complexes; the preferential migration can include complex migration as well as preferential defect migration via solute or solvent atoms. Section 3 gives an overview of point-defect solute interactions in dilute alloys and their effects on solute fluxes. The coupling of defect and atom fluxes to composition and defect concentration gradients in concentrated alloys is discussed in Section 4. The phenomenological equations describing the segregation process are formulated, and the computational formalism to obtain time-dependent solutions to the phenomenological equations is outlined in Section 5. Some model calculation results are discussed in Section 6. (author)