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 x 1019 n cm-2 (> 1 MeV) at 60 and 290 0C, respectively. The role of initial heat treatment and thermal ageing are also examined. 60 0C-neutron 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 0C-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-induced copper precipitate component to the damage structure. The potential of the techniques for monitoring irradiation effects in ferromagnetic systems is briefly considered. (author)