PRECIPITATION AND DEFECT CLUSTERING IN ELECTRON-IRRADIATED AL-CU ALLOYS

Radiation-induced defect clustering and radiation-induced precipitation in Al-0.06 at% Cu and -0.29 at% Cu alloys were studied by in-situ observations in a high voltage electron microscope. During irradiation at room temperature, interstitial dislocation loops were observed only near surfaces, while small and diffuse-contrast clusters were observed in the bulk. Dislocation loops were seldom observed during irradiation at 473 K. On the other hand, disk-shaped precipitates (which were believed to be multi-layer G.P.(II) zones) were observed homogeneously in the bulk at that temperature. They shrank and disappeared on interruption of the irradiation. Analysis of the characteristic spatial distribution of clusters helps understand the formation of defect clusters under strong solute-point defect interaction. This interpretation can be extended to explain the precipitation under irradiation.