Migration of carbon atoms in irradiated and non-irradiated alpha-iron studied by magnetic after-effect

Magnetic After-Effect (MAE) and magnetic AC susceptibility studies have been performed on high-purity non-irradiated and Fe-ion irradiated, α-Fe foil samples in the high-temperature range, which became experimentally accessible recently. The pronounced difference in the temperature profile of MAE between non-irradiated and irradiated samples has been identified and ascribed to the trapping of carbon in the irradiated sample into structures that are reluctant to decompose by standard temperature cycling. The accurate background of MAE relaxations at 430 and 610 K in non-irradiated α-Fe samples has been scrutinized by the annealing-type studies in temperature and time domains to conclude that it relies on the formation, decomposition, and mutual transformations of carbide nanoprecipitates nucleated in dislocations, grain boundaries, and in the bcc matrix. Long-term trapping of migrating carbon into carbides and in the 100 nm thick surface layer has also been shown to take place.