Interstitials in Copper-Zinc Alloys

In Cu-30 Zn alloys during irradiation with 2-MeV electrons from a Van de Graaff generator, the electrical resistivity first decreases due to radiation-enhanced ordering and then increases due to the formation of very small interstitial clusters. The activation energy during irradiation for both processes is approximately Q_irr = 0.3₇ eV and is interpreted as half of the migration energy of freely migrating interstitials. For irradiation temperatures below 75°C, a second resistivity increase is found that is attributed to the formation of stable interstitial clusters. The observed radiation-enhanced diffusion rates below ambient temperature are many orders of magnitude smaller and larger than those predicted by the one- and the two-interstitial models, respectively, and these rates are in agreement with the predictions of the modified two-interstitial model.