Calculation of radiation-induced instability in concentrated alloys

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Abstract
Long-range concentration fluctuation (spinodal-type decomposition) with a wavelength of 45 AA has been reported by Wagner, Poerschke and Wollenberger in a concentrated Cu-Ni alloy during electron irradiation. The differences from thermodynamic models in the kinetics of this decomposition have prompted the present investigation of an irradiation-induced process. The system is treated as a dissipative structure in which a small bias in the vacancy-interstitial recombination reaction and irradiation mixing effect in enriched zones of the alloy produces fluxes of interstitials leading to growth and shrinkage of such zones. The system is modelled in a mean-field treatment as a homogeneous lossy medium with a non-linear coupling of the defect concentrations and an averaged parameter characterising these zones. A linear stability analysis shows that an instability can develop in such a solid solution leading to concentration fluctuations. The model yields a temperature- and dose-independent wavelength which is not inconsistent with experimental observations.