Radiation Damage Studies in Model Ferritic Alloys Using Micromagnetic Techniques

The related micromagnetic techniques of Barkhausen emission (BE) and magneto-acoustic emission (MAE) are used to study neutron damage effects in α-iron and iron—copper alloys following irradiation to 2.4 to 2.9 × 1019 n cm−2 (> 1 MeV) at 60 and 290 °C, respectively. The role of initial heat treatment and thermal ageing are also examined. 60 °C-nentron irradiation suppresses strong BE and MAE activity in annealed α-iron, and the behaviour is attributed to irradiation-induced dissolution of nitride precipitates and formation of interstitial solute-point defect complexes. The techniques exhibit sensitivity to thermally-induced copper precipitation in an Fe—0.7% Cu alloy and to 290 °C-irradiation and post-irradiation recovery in an Fe—0.2% Cu alloy. The BE and MAE response for the irradiated Fe—0.2% Cu alloy is interpreted in terms of a dislocation loop and an irradiated-indviced copper precipitate component to the damage structure. The potential of the techniques for monitoring irradiation effects in ferromagnetic systems is briefly considered. Die miteinander verknupften mikromagnetischen Methoden der Barkhausen-Emission (BE) und magneto-akustischen Emission (MAE) werden zur Untersuchung von Neutronendamage effekten in α-Eisen und Eisen—Kupferlegierungen nach einer Bestrahlung bis zu 2,4 bis 2,9 × × 1019 n cm−2 (>l MeV) bei 60 bzw. 290 °C benutzt. Die Rolle einer anfanglichen Warmebehandlung und thermischer Alterung wird ebenfalls untersucht. 60 °C-Neutronenbestrahlung unterdruckt in getempertem α-Eisen die starke BE- und MAE-Aktivitat und dieses Verhalten wird der strahlungsinduzierten Bildung von Nitridprazipitaten und der Bildung von Zwischengitterverun- reinigungen-Punktdefekt-Komplexen zugeordnet. Die Techniken zeigen eine Empfindlichkeit gegenuber thermisch-induzierter Kupferausfallung in einer Fe-0,7% Cu-Legierung und gegenuber 290 °C-Bestrahlung und Erholung in einer Fe-0,2% Cu-Legierung. Die BE- und MAE-response fur die bestrahlte Fe-0,2 % Cu-Legierung wird mit Versetzungsschleifen und bestrahlungsin- duzierten Kupferprazipitatkomponenten aus der Damagestruktur interpretiert. Die Moglichkeiten der Technik zur Verfolgung von Bestrahlungseffekten in ferromagnetischen Systemen wird kurz betrachtet.

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