Abstract
The effects of He+ irradiation on a distribution of Cr atoms in Fe100−xCrx (x = 5.8, 10.75, 15.15) alloys were studied by 57Fe Conversion Electron Mössbauer Spectroscopy (CEMS). The alloys were irradiated with doses up to 12 × 1016 ions/cm2 with 0.25 and 2.0 MeV He+ ions. The distribution of Cr atoms within the first two coordination shells around Fe atoms was expressed with short-range order parameters α1 (first-neighbor shell, 1NN), α2 (second-neighbor shell, 2NN), and α12 (1NN + 2NN). In non-irradiated alloys, α1 >0 and α2 <0 was revealed for all three samples. The value of α12 ≈0, i.e., the distribution of Cr atoms averaged over 1NN and 2NN, was random. The effect of the irradiation of the Fe94.2Cr5.8 alloy was similar for the two energies of He+, viz., increase of number of Cr atoms in 1NN and decrease in 2NN. Consequently, the degree of ordering increased. For the other two samples, the effect of the irradiation depends on the composition, and is stronger for the less energetic ions where, for Fe89.25Cr10.75 alloy, the disordering disappeared and some traces of Cr clustering appeared. In Fe84.85Cr15.15 alloy, the clustering was clear. In the samples irradiated with 2. 0 MeV He+ ions, the ordering also survived in the samples with x = 10.75 and 15.15, yet its degree became smaller than in the Fe94.2Cr5.8 alloy.
Highlights
FE-CR-BASED ferritic steels (FS) such as ODS and ferritic–martensitic (F-Mossbauer spectroscopy (MS)) steels such as EUROFER constitute an important class of structural materials
The results reported in this paper are, to our best knowledge, the first that give evidence on clustering of Cr atoms in an Fe84.85Cr15.15 alloy irradiated with He+ ions
The following conclusions can be drawn based on the results obtained in this study: 1. The population of Cr atoms in the first-neighbor shell (1NN) around the probe Fe atoms in the non-irradiated alloys is lower (a1 > 0) and in the second-neighbor shell (2NN) it is higher (a2 < 0) than expected from the binomial distribution
Summary
FE-CR-BASED ferritic steels (FS) such as ODS and ferritic–martensitic (F-MS) steels such as EUROFER constitute an important class of structural materials. The irradiation of Fe-Cr alloys with He+ ions is of interest, as the production of helium occurs during exposure of the various devices produced therefrom to proton and/ or neutron irradiation.[1] Its presence deteriorates mechanical properties of steels It lowers the critical stress for intergranular structure and it may bring about a severe decrease of the fracture toughness.[30] understanding the effects of radiation damage and the effects of helium on the mechanical properties of FS/F-MS are important topics to be studied in the context of gaining a better understanding of irradiation-induced degradation processes in engineering materials used in various important branches of industry, including nuclear power
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