Consequences of intra-cascade clustering on defect accumulation and materials performance

Abstract

Considerations of intracascade clustering of self-interstitial atoms (SIAs) and vacancies during the cooling-down phase of a cascade and of the difference between thermal stabilities of SIA and vacancy clusters give rise to the concept of production bias. In recent years, various aspects of this concept including the effects of cluster annihilation by one-dimensional glide have been investigated. The salient features of these investigations and their results are summarized. The most important conclusion emerging from these investigations is that a realistic modelling of accumulation of surviving defects under cascade damage conditions must explicitly consider the role of formation, thermal stability and mobility (glide and climb) of clusters produced in the cascades. Examples are shown where appropriate considerations of these features have led to predictions regarding dose, temperature and recoil energy dependence of void swelling which are consistent with experimental results. The special feature such as enhanced damage accumulation near grain boundaries has been successfully explained in terms of production bias and one-dimensional glide of small loops produced in the cascades. Finally, it is shown that the decoration of grown-in dislocations by gliding SIA loops produced in the cascades may also explain the irradiation-induced increase in the upper yield stress.

Key Words:

• Cascade
• Production bias
• Intra-cascade clustering
• SIAs
• Vacancies
• One-dimensional glide