Interstitial migration in iron at 220 K

Abstract

A synopsis is given of recent at.tempts to clarify the nature of the prominent resist.ivity recovery stage a t 220 I< (Stage 111) in irradiated high-purity cr-iron and of the related magnetic and mechanical relaxation processes. With increasing irradiation dose the height of this stage increases linearly, and its position shifts to lower temperatures according to a second-order reaction. I n accord with other experimental results this is taken as evidence for free migration of a n elementary point defect in iron at about 220 K. Since vacancy migration can be excluded on t,he basis of thermal-equilibrium measurements, Stage I11 is attributed to interstitial migration. Suggestions for the interpretation of the Stage-111 relaxation phenomena are presented.Es wird iiber neueste Untersuchungen a n bestrahltem hochreinem a-Eisen berichtet, die durchgefiihrt wurden, um die Vorgange in der ausgepragten Erholungsstufe des elektrischen Widerstandes bei 220 K (Stufe 111) und die in diesem Temperaturbereich auftretenden magnetischen iind meehanischen Relaxationsprozesse aufzuklaren. Mit wachsender Bestrahlungsdosis wachst Stufe I11 linear an und verschiebt sich zu tieferen Temperaturen gemaD einer Reaktion zweiter Ordnung. Daraus wird geschlossen, daB in Eisen bei ungefahr 220 K eine elementare at.omare Fehlstelle frei wandert. Da Leerstellenwanderung aufgrund von Messungen im thermischen Gleichgewicht ausgeschlossen werden kann, wird Stufe I11 der freien Wanderung von Zwischengitteratomen zugeschrieben. Deutungsmoglichkeiten der Relaxationserscheinungen im Bereich der Stufe I11 werden vorgeschlagen.

Interaction of carbon with vacancy and self-interstitial atom clusters in α-iron studied using metallic–covalent interatomic potential

“…As established from the DFT calculations, a vacancy-carbon pair has the dissociation energy of 1.12 eV, which is close to the vacancy migration energy, 1.28 eV, estimated in Fe containing limited concentration of carbon from high temperature measurements [38]. The results obtained with the J and H potentials are consistent with both DFT and experimental suggestions.…”

Radiation Damage in Metals

“…Such stages were observed in fcc metals copper, silver, nickel and lead [111], where the activation energies for Stage IV agree with the activation enthalpies for vacancy migration as obtained from thermal-equilibrium measurements. A similar result was found for α-iron, where Stage III annealing is attributed to three-dimensional interstitial migration with enthalpy H M I = 0.5 eV, while Stage IV at 500 -580 K is again assigned to vacancy migration with a H M V = 1.28 eV in agreement with thermal equilibrium measurements [112]. These results support the two-interstitial model, which assumes free migration of the stable dumbbell interstitial in Stage III and vacancy migration in Stage IV.…”

A Review of the Magnetic Relaxation and Its Application to the Study of Atomic Defects in ?-Iron and Its Diluted Alloys

“…Its development is found to be governed by an activation enthalpy of 1.26 eV, which agrees fairly well with the migration enthalpy of monovacancies as predicted by the 2IM [116,132]. Moreover, the observed reaction order, g 2, is in agreement with comparable concentrations of both reaction partners, i.e.…”

“…An additional, serious argument against vacancy migration in Stage III has been developed by Decker et al [116] by considering the migration enthalpy of monovacancies as the difference between their respective enthalpies of self-diffusion and formation,…”

“…Inserting these values into (5.1) leads to a monovacancy migration enthalpy of [116,131,132] H M 1V 1:24 AE 0:13 eV : 5:4…”