The presented contribution referred to basic effects of 150 key proton irradiation on ready prepared FIM tips of Cu-Be and Cu-Ni-Fe alloys. Dilute solid solutions of Be in Cu are known to form incoherent precipitates of the 3 phase (B2 structure) upon heavy ion irradiation /l/. Electron irradiation, however, induces G.P. zone formation 121. While the radiation-induced X precipitation has been 'studied in great detail and seems to be understood quantitatively 131, important parameters are still

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... nknown for the electron irradiation case. Aim of the reported work was to check whether proton irradiation would cause G.P. zone formation as well, and to determine the radiation-induced enhancement of Be precipitation. Knowledge of the latter would help to understand the format ion process. Advantage has been derived from the ability of FIM to image G.P. zones. They appear as dark lines of one atomic layer thickness 141 the length of which should measure the volume fraction of the zones. For a Cu-12.4at.%Be alloy segregatdon of nearly the entire Be content in G.P. zones was observed after fluences of only bO-displacements per atom (dpa) for proton irradiation at a displacement rate of 6 X 10-dpals at room temperature 151. For the sink strength of the tip surface one obtains I O -~ 161. Further, with the vacancy migration enthalpy of 0.72 eV 171, the steady state vacancy concentration is controlled predominantly by recombination after 250 sec irradiation time. Evaluation of the G.P. zone formation rate and comparison with thermally activated formation rates leads to the conclusion that the usual vacancy migration mechanism would be sufficient for the observed Be transport. Interstitial transport or radiation-induced phase instabilities need not to be invoked. For supersaturated Cu-47at.%Ni-8at.%Fe samples it was observed by small angle neutron scattering (SANS) that proton irradiation at temperatures within the miscibility gap changes the decomposition morphology and the gap size (length of tie line) /8/. The latter observation suggested an irradiation-induced alteration of the Fe dispysion during the unmixing process. By atom probing of samples irradiated with protons (10-dpa/s) at 673 K to 0.1 dpa, Fe-rich clusters were observed 151 which are not present in thermally aged samples 191. These clusters have diameters between 2 and 3 nm, and an Fe content of about 25at.%, i.e. twice as high as the equilibrium value of the Fe/Ni-rich phase. The corresponding depletion of the two unmixed phases gives rise to the effective shortening of the tie-lines as quoted from earlier SANS observations 181. Article published online by EDP Sciences and available at http://dx.