Interstitial-solute complexes in an irradiated Al-Fe alloy

Abstract

The internal friction spectra of preferentially orientated polycrystalline and single-crystal samples of a dilute Al-Fe alloy have been measured after electron irradiation at 4.7K and after annealing at various temperatures. Several low-temperature internal friction peaks were found that are attributed to the stress-induced reorientation of self-interstitial-Fe complexes. At least three different defect configurations with large binding and migration energies co-exist in the sample after annealing at 80K. All four major peaks anneal simultaneously, providing strong evidence of vacancy migration in stage III. Defects with tetragonal or (100)-orthorhombic symmetry are not consistent with the observed orientation dependence of the major peaks; trigonal defects ((111) symmetry axis) possess the highest symmetry in agreement with the three largest peaks. Previous interpretations of channelling and Mossbauer measurements based on the formation of isolated, (100)-tetragonal, mixed-dumbbell interstitials in Al-Fe alloys are not consistent with the present internal friction results.