Surface oxide films and the lifetime of vacancies in thin crystals

Abstract

During annealing experiments in the electron microscope, prismatic dislocation loops and helices have been observed to grow in thin foils prepared from quenched and aged samples of supersaturated aluminium—magnesium alloys. Growth in pure aluminium or dilute aluminium-magnesium alloys has not been reported. It has been suggested recently that the excess vacancies required for growth are residual quenched-in vacancies which were not able to sink at external surfaces due to the presence of an impervious oxide film. The oxide mechanism fails to account for the fact that growth has not been observed in pure aluminium and dilute aluminium alloys. This point and others concerning the lifetime of vacancies in thin crystals are discussed.