Role of dislocation loops in the development of vacancy voids

Abstract

This paper presents the results of a transmission electron microscopy (TEM)-investigation of the effect of post-irradiation innealing on the structure of molybdenum and nickel doped with helium atoms that was irradiated with high-energy a-particles and fission neutrons. It is shown that: • The number of interstitial atoms in dislocation loops and the number of vacancies in helium bubbles increase as annealing temperature and time increase. • The growth of helium bubbles on the grain boundary is mainly observed on the side of the grain body where there are dislocation loops. • Post-irradiation annealing of dislocation loops fonmed by SO-MeV a-particles and fission neutrons at 60°C results in the growth of vacancy voids. Thus, high temperature post-irradiation annealing or irradiation at high temperature (more than 0.3Tme«) constitutes the conditions under which dislocation loops are powerful sources of vacancies. Consequently, if in the crystal structure of the irradiated material there are HemVn groups, vacancy oversaturation caused by the thermal emission of vacancies by radiationinduced dislocation loops may be the main driving force for the nucleation and growth of vacancy voids.