Formation of submicroscopic vacancy clusters and radiation-induced refining in metals by electron-irradiation at high temperatures

Abstract

Abstract Experimental results are reported which demonstrate that submicroscopic changes occur in metal specimens electron-irradiated in a high-voltage electron microscope at high temperatures where no visible damage is produced. These changes give rise to drastic effects on the visible radiation damage created during a later re-irradiation of the specimen at lower temperatures. The observations made on copper are explained by the formation of small vacancy aggregates. The results obtained for aluminium are explained in terms of specimen purification by radiation-induced segregation of impurity atoms to the specimen surfaces. In the two other metals investigated, molybdenum and nickel, high-temperature irradiation leads to submicroscopic changes which can also be attributed to impurity effects.