The decomposition of low temperature electron irradiated Cu-Ni alloys upon isochronal annealing

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Abstract
The residual resistivity of Cu-Ni alloys with Ni contents between 42 and 71 at % has been investigated upon isochronal annealing after 3 MeV electron irradiation at 4 K and 200 K. The clustering of vacancies was studied by positron annihilation measurements on a 50 at. % Ni alloy after 3 MeV electron irradiation at 80 K. Above 100 K negative resistivity changes due to decomposition occur. The decomposition is due to an interstitialcy mass transport in the temperature range 100K-250K and due to the vacancy mechanism above this range. Vacancy clustering starts to occur above 200 K. The dissolution of the vancancy clusters occurs between 350 K and 510 K. From the resistivity kinetics upon annealing a vacancy migration energy of 1.06 ± 0.05 CV was determined. The degree of de-decomposition decreases above 600 K, i.e. above the critical temperature range of the miscibility gap as deduced from neutron scattering experiments.