Investigation of interstitial clustering in Al following electron irradiation at low temperature

The clustering of interstitials in Al has been investigated by x-ray diffuse scattering during an isochronal annealing program following electron irradiation at approx. 5 K. Measurements of the specific resistivity, volume relaxation, and lattice-parameter change before annealing are in satisfactory agreement with previous results for Frenkel defects in Al. The annealing data indicate that single interstitials migrate at the end of Stage I (approx. 36 K) and a statistical distribution of di-, tri-, and tetra-interstitials is produced, which remains somewhat stable from 38 to 44 K. There is evidence that the di-interstitial migrates in Stage II1 (approx.45 K) and a new cluster size distribution consisting mostly of 3--6 interstitials results. This distribution is stable from 50 to 55 K. Above 55 K, the clusters resume growth attaining a maximum size of 12--25 interstitials per cluster at 100--160 K. The observed cluster sizes following single and di-interstitial migration are consistent with the predictions of a simple kinetic model for diffusion annealing