Untersuchung von Frenkeldefekten in Nickel und Nickellegierungen mit Hilfe der diffusen Röntgenstreuung

Bender, O.

Book/Report

FZJ-2018-01851

Untersuchung von Frenkeldefekten in Nickel und Nickellegierungen mit Hilfe der diffusen Röntgenstreuung

Bender, O. (Corresponding author)FZJ*

1982
Kernforschungsanlage Jülich, Verlag Jülich

Jülich : Kernforschungsanlage Jülich, Verlag, Berichte der Kernforschungsanlage Jülich 1769, 117 p. (1982)

Please use a persistent id in citations: http://hdl.handle.net/2128/17665

Report No.: Juel-1769

Abstract: Single crystals of pure Ni and of the alloys Ni$_{62}$Cu$_{38}$ and Ni$_{3}$Fe (as quenched (S=0) or ordered (S=0.7-0.9) ) were irradiated at 4.5 K with 3 MeV electrons. The irradiation induced defects were investigated by measurements of the Huang diffuse scattering of X-rays and the change of the lattice parameter and the electrical resistivity. At 6 K we observed statistically distributed Frenkel defects in all metals. The configuration of the single interstitial atoms (SIA) in Ni agrees with the (100)-split configuration and there are no indications for different configurations of the SIA in the alloys. The relaxation volume of the SIA is 1.7($\pm$0.3) atomic volumes in Ni and 1.5($\pm$0.3) atomic volumes in Ni$_{3}$Fe, independently of the degree of order. For the Frenkel defect resistivity $\rho_{F}$ we found $\rho_{F}$ = 6.1($\pm$1.1)$\mu \Omega$cm in Ni, $\rho_{F}$ = 7.2($\pm$2.0)$\mu \Omega$cm in Ni$_{3}$Fe (no difference for quenched and ordered samples), and $\rho_{F}$ = 13.2($\pm$4.0)$\mu \Omega$cm for Ni$_{62}$Cu$_{38}$. In order to investigate the defect reactions at higher temperatures the measurements were repeated after several steps of an isochronal annealing program. The annealing behaviour of pure Ni is characterized by interstitial motion during stage I and growth of the agglomerates during stage II that eventually form dislocation loops on {III}-planes. Vacancy agglomeration has been directly observed after stage III; there is a simultaneous decrease of $\rho_{F}$ with the formation of the agglomerates. All of these reactions are very similar to Cu although the growth of the interstitial clusters is slower for Ni. The SIA is more mobile than the vacancy for the alloys investigated here as it is in the pure metals. Whereas the mobility of the agglomerates is only little suppressed for NiCu, even the di-interstitial seems to be immobile up to stage III for Ni$_{3}$Fe. As the vacancy mobility in the alloys is not suppressed relative to Ni the range of annealing stage II is reduced in the alloys. In Ni$_{62}$Cu$_{38}$ a decomposition of the alloy has been observed not onlyduring motion of the SIA but also during the agglomeration processes in stage II. In contrast to this, interstitial motion does not contribute to the ordering of Ni$_{3}$Fe. Vacancy mobility during stage III causes a further decomposition of NiCu and an increase of the order in preordered Ni$_{3}$Fe but not for the quenched Ni$_{3}$Fe. This difference can be tentatively explained by a lower efficacy for ordering of the vacancy jumps in a disordered alloy relative to a preordered one, where the sublattices are already weIl defined. In contrast to pure Ni no large vacancy agglomerates were observed in the alloys; this may be explained by the smaller interstitial agglomerates at the end of stage II and the consequently shorter distances of the vacancies to their sinks. Thus recombination dominates in the alloys and prevents the formation of agglomerates which are stable up to high temperatures.

Contributing Institute(s):