Modification of radiation damage microstructure by helium

Abstract

Abstract Current experimental findings on the effects of helium on the evolution of radiation damage microstructure in metals at temperatures where vacancies are mobile are reviewed. It is shown that helium concentrations as low as a few parts per million promote the formation of cavities and dislocations, may increase or decrease swelling, and can alter the development of precipitate phases. Mechanisms underlying these processes are discussed in terms of the theory of radiation effects. Helium-vacancy trapping and the stabilization of cavities is seen as the unifying, underlying feature. Promotion of cavities is explained by reduction of critical cavity size by helium. This promotion, and the attendant increase in dislocations, changes the point-defect sink strengths and thereby modifies swelling. Correspondingly, solute segregation at sinks is changed, resulting in alteration of precipitate phases.