Secondary defects in quenched aluminium studied by Mossbauer spectroscopy

Abstract

The authors measured the Debye-Waller factor, the isomer shift and the second-order Doppler effect in a quenched aluminium-based alloy containing 200 PPM of ⁵⁷Fe, after an annealing treatment up to temperatures ranging from 78 to 623K. A discontinuity in the smooth variations of the Mossbauer parameters appeared for samples annealed at temperatures around 260K, which depends on the quenching rate and the thermal history of the specimen. This discontinuity was interpreted both in terms of vacancies trapped at ⁵⁷Fe impurities and the subsequent agglomeration process and of annealing of the dislocation loops up to the initial stage of the precipitation of iron. Supplementary investigations of the overall variations of the Mossbauer parameters led to information on the 3d to s electron transfer process related to the isomer shift temperature dependence.