Interstitial migration in irradiated iron and iron-based dilute alloys. I. Interstitial trapping and detrapping in FeMo, FeV and FeTi dilute alloys

Abstract

Three series of dilute iron alloys, with oversized solutes, FeTi, FeV and FeMo, in the concentration range 50 at.ppm to 3 at.%, have been electron-irradiated at low temperature together with the metal. A strong dependence of the solute and defect resistivities on the solute concentration is observed, which is analysed in terms of the two-current model. The specimens have then been annealed throughout stage I (self-interstitial migration) and stage II up to stage III (vacancy migration), with their resistivity measured. In these alloys, the mobile Fe self-interstitials, which are not annihilated at vacancies, are observed to get trapped at solute atoms in stage I and released from traps in stage II. Detrapping occurs in stage I at a temperature, TII, depending on the solute. Trapping is the weakest for V (TII approximately=140 K) and the strongest for Ti (TII approximately=180 K). At very low concentration (50 and 100 at.ppm), the solute trapping efficiency is lost at the beginning of stage III (200 K) for all these solutes. In the most concentrated FeMo alloys, an important fraction of the radiation-induced resistivity is retained at 200 K, due to multiple trapping (trapping of iron interstitials by more than one Mo atom).