Change of Cr atoms distribution in Fe85Cr15 alloy caused by 250 keV He+ ion irradiation to different doses

摘要

Redistribution of Cr atoms in a Fe85Cr15 alloy caused by its irradiation with250 keV He ions to different doses viz. 5, 10 and 30 dpa was investigated bymeans of conversion electrons Mossbauer spectroscopy. The redistribution wasexpressed in terms of the Warren-Cowley short-range order parameters alpha1,alpha2 and alpha12 pertaining to the first, second and both neighbor shells,respectively. Clear evidence was found, both for non-irradiated and irradiatedsamples that the actual distribution of Cr atoms is characteristic of theshell, and for a given shell it depends on the irradiation dose. In particular,alpha1 is positive, hence indicates an under population of Cr atoms in 1NN withrespect to the random case, alpha2 is negative, giving evidence thereby that2NN is overpopulated by Cr atoms, and alpha12 is weakly positive. Under theapplied irradiation the number of Cr atoms in both neighbor shells decreasedsignifying thereby a clustering of Cr atoms. The underlying decrease of Crconcentration within the two-shells volume around the probe Fe atoms wasestimated at 1.5 at% ranging between 2.1 for the lowest and 0.8 at% for thehighest dose.