Phase stability of Cu-Ni-Fe alloys under ion irradiation

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Abstract
Ion irradiation of Cu-Ni-Fe alloys has been carried out in order to investigate the counteraction of cascade mixing and radiation-enhanced diffusion in a periodic two-phase structure. It was found that heavy-ion irradiation (Cu, Ne and N) causes dissolution of the precipitates. Proton irradiation, however, accelerates the process of decomposition and coarsening. The microstructural evolution is determined by displacement rate and temperature. The size of the precipitates influences its stability–a coarser structure dissolves only under higher displacement rates. A model is proposed which interprets these effects as a competition between cascade mixing and the recovery of the two-phase structure by radiation-enhanced interdiffusion. From the equalization of both mechanisms, the size of the volume dissolved by a cascade is deduced. This volume decreases with increasing precipitate size due to the low efficiency of mixing for equal sizes of precipitates and cascades. The similarity of results for the heavy ions is explained on the basis of calculated damage spectra.