A review of the magnetic relaxation and its application to the study of atomic defects in alpha-iron and its diluted alloys

This review presents a comprehensive survey on intensive studies performed during the last decades on point defect reactions on alpha -iron (alpha -fe ) and its diluted alloys. Our intention is to give an actual account of the knowledge accumulated on this subject, as it has been obtained predominant ly by means of the magnetic after-effect (MAE) spectroscopy. After a concis e introduction into the theoretical and experimental fundamentals of this t echnique, the main concern is focused on the presentation and detailed disc ussion of the MAE spectra arising - after low-temperature electron (e(-))- or neutron(n)-irradiation and subsequent annealing - in: (i) high-purity al pha -Fe and alpha -Fe doped with (ii) substitutional solutes (like Ni, V, A l, Cu, Ti, Be, Si, Mn,...) or (iii) interstitial solutes (like O, H, C, N). During the course of systematic annealing treatments, these respective spe ctra undergo dramatic variations at specific temperatures thereby revealing in great detail the underlying intrinsic reactions of the radiation-induce d defects, i.e., reorientation, migration, clustering, dissolution and fina lly annihilation. In alloyed Fe systems the corresponding reaction sequence s are even multiplied due to additional interactions between defects and so lute atoms. Most valuable information concerning formation-, dissociation- and binding enthalpies of small, mixed clusters (of the type CiVk, NiVk; k greater than or equal to 1) has been obtained in high-purity alpha -Fe base material which, after charging with C or N, had been e(-)-irradiated. Conc erning the basic recovery mechnnisms in alpha -Fe, two complementary result s are obtained from the analysis of the various systems: (i) in high-purity and substitutionally alloyed alpha -Fe the recovery in Stage-III (200 K) i s governed by a three-dimensionally migrating (H-I(M) = 0.56 eV) stable int erstitial (dumb bell); (ii) following the formation and dissociation kineti cs of small clusters (C1Vk, N1Vk) in interstitially alloyed alpha -Fe the m igration enthalpy of the monovacancy must hold the following relation H-N(M ) (0.76 eV) < H-C(M) (0.84 eV) < H-V1(M). These results are in dear agreeme nt with the so-called two-interstitial model (21M) in alpha -Fe - a conclus ion being further substantiated by a systematic comparison with the results obtained from nonrelaxational techniques, like i.e. position annihilation (PA), which by their authors are preferentially interpreted in terms of the one-interstitial model (1IM).