  The effect of He-ion irradiation on a short-range ordering in model
Fe100-xCrx (x=5.8, 10.75, 15.15) was studied by means of conversion electrons
Mossbauer spectroscopy. The alloys were irradiated to the dose of 7.5 dpa with
ions of 0.25 and 2.0 MeV. The short-range order was expressed in terms of the
Warren-Cowley parameters: alpha1 (for the first nearest-neighbor shell), alpha2
(for the second nearest-neighbor shell) and alpha12 (for both shells). For all
alloys and both energies a clustering of Cr atoms was revealed, as far as
alpha1 and alpha2 are considered, yet its degree was found to be both
concentration and energy dependent. The average short-range order parameter,
alpha12, exhibits, however, a cross-over transition at x=10 from ordering into
clustering. The strongest effect of energy occurs at x=5.8 and the weakest one
at x=10.75.
