4.1. INTRODUCTION

In the previous chapter, special attention was given to the effect of impurity and alloying elements in pure metals and solid solutions on the processes of buildup of radiation defects in the formation of defect-impurity complexes, clusters of defects, dislocation loops and voids. The problems of phase changes and their effect on the structure of radiation damage have been studied only partially. In the present chapter, this problem will be given special attention, taking into account the fact that the phase changes, caused by the intensification of the processes of ordering, phase clustering and breakdown of solid solutions, coalescence and the dissolution of the phases may prevail over the purely imperfect effect of irradiation, controlling the degradation of the properties of irradiated metallic materials. In addition, the processes of formation of clusters of defects, dislocation loops and voids are usually inter-related with the variation of the chemical composition of the matrix solid solutions and even with the phase instability of single-phase and more complex alloys. The detailed analysis of these mechanisms makes it possible to interpret more efficiently and predict the radiation damage in alloys and develop methods of preventing it.

The current interest in the radiation-stimulated phase changes is associated mainly with the tendency for increasing the service parameters of materials in nuclear power engineering: temperature, intensity, fluence and service life of steels and alloys, and also the problem of development of fusion reactors in which the conditions of operation of structural metallic materials under the effect...