Atom transport and phase separation in irradiated Cu-Ni-Fe alloys

Radiation-induced atom transport controls phase stability under irradiation. Quantitative understanding of the latter phenomenon requires measurement of all relevant components of atom transport as well as of all quantities which characterize the concurrent phases. These requirements can be met for sufficiently simple systems. The paper gives an overview on studies by means of electron microscopy, field ion microscopy with atom probe, small angle neutron scattering, and diffusion coefficient measurements by depth profiling with dynamical secondary ion mass spectroscopy, all for samples irradiated with electrons, protons or heavy ions of Cu-Ni-Fe. Evaluation of the data revealed detailed insights into the counteraction of precipitate dissolution by atomic mixing and re-precipitation by radiation-enhanced interdiffusion as well as into the evolution path of phase changes. In Cu-Ni-Fe the interstitial transport mechanism changes the tie-line for the alloy decomposition substantially when compared with the unirradiated case. Proton irradiation to fluences above 0.1 dpa indicate evolution of long-range composition fluctuations superimposed on the periodically decomposed two-phase structure. The obtained information show the importance of a combined application of microscopic, diffraction, and direct methods for atomic transport measurements