Precipitation of gamma ' phase and helium bubbles during proton and alpha-particle irradiation of nickel-silicon

摘要

Segregation of silicon was induced by light-ion irradiation at elevated temperatures in Ni-8Si specimens. Its occurrence at external surfaces, helium-induced cavities, dislocation loops, coherent twin boundaries, grain boundaries, and precipitate-matrix interfaces has been investigated by transmission electron microscopy. Layers of ordered gamma'(Ni3Si) phase were formed at most of these point defect sinks. The behaviour of grain boundary precipitation was found to be exceptional in various respects. In particular, a high rate of precipitation distinguishes grain boundaries from all other kinds of point defect sinks investigated here. This phenomenon of rapid precipitation was found to be adjoined to precipitation-driven grain boundary migration and is attributed to a radiation-induced "discontinuous" precipitate reaction. Observations of helium bubble distributions created during alpha-particle irradiations at growing dislocation loops and at migrating grain boundaries are also briefly discussed.