Recovery of Electron-Irradiated Aluminum and Aluminum Alloys. III. Stage III

Abstract

The recovery of the residual electrical resistivities of pure Al and the Al alloys (nominally 0.1 at.%) Al-Mg, Al-Ga, and Al-Ag have been investigated following 1-MeV electron irradiation near 4°K. Analysis of the data for nominally pure Al in stage III (170-300°K) discloses substructure. (A very small substage occurs at lower temperatures and appears to be influenced by the residual impurities.) The main portion of the stage shows a variation in the observed activation energy with purity: The higher the purity of the "asreceived" material, the lower the observed activation energy. A range of 0.46 to 0.59 eV was found for the materials investigated. The effective frequency factor for these materials showed a concurrent systematic variation. These effects are believed to be due to the interaction of migrating defects with residual impurities in the material. The recovery of the alloys in the stage-III region is more complex than in the pure material. There is more substructure in the recovery spectrum of the alloys, and the observed activation energies in stage III are higher. Al-Ag showed a resistivity decrease followed by an increase which is attributed to the clustering of Ag atoms. The observations are interpreted in terms of interstitial migration, restricted by impurities, in the earlier portion of stage III; vacancy migration becomes important in the latter portion of stage III. Stated differently, interstitials migrate in stage III and vacancies migrate in stage IV, but in Al these stages overlap appreciably.