Mössbauer Spectrometry of Model Binary Fe_100−xCr_x (1 ≤ x ≤ 50) Alloys

Abstract

Herein, several ways to evaluate Mössbauer spectra of model binary Fe100−xCrx alloys with chromium content varying in the range from 1 to 50 at% (x = 0.94, 2.2, 4.9, 10.4, 15.4, 22.1, and 52.9) are discussed. For low chromium concentrations (up to 15 at%), the method of binomial distribution of individual sextets is suitable. Depending upon the Cr content, the number of sextets used can be, however, as high as 20. The specific number of sextets is determined according to probabilities of individual atomic sites calculated from binomial distribution. Mössbauer spectra of samples with Cr concentrations higher than 20 at% are evaluated by distributions of hyperfine magnetic fields. The composition of model alloys is verified using X‐ray fluorescence. Their surface is analyzed by two different surface‐sensitive methods: scanning electron microscopy and atomic force microscopy. The main technique used to analyze the materials’ subsurface layers is conversion electron Mössbauer spectroscopy. The applied fitting models and results are useful in studies of the microstructure of real types of construction and stainless steels.

Microstructure of High‐Chromium Ferritic–Martensitic Steels for Next‐Generation Reactors

“…where β coefficient determines the change (decrease) with increasing chromium concentration in 1NN-2NN assuming the random distribution of atoms. Based on the results from the articles by Košovský et al [44] and Dubiel et al [45,46,51] (see Figure 8), the chromium concentration was calculated, which reaches 13.9(0)-14.3(7) at% Cr and is similar to the value determined by chemical analysis.…”

“…The estimation of chromium solubility limit in NS219 steel was determined using the saturation value of the hyperfine magnetic field (29.4 T). On the basis of previous studies, [44][45][46] it can be concluded that the dependence of the magnetic hyperfine field as a function of the impurity atom has a linear character (Equation ( 6)):…”

“…Based on the chemical composition (Table 1), the relations and calculation procedures presented in the previous article were used. [44] There are two different models of atomic short-range order (SRO) in crystalline solid solutions, which can be divided into two types: homogeneous (statistical) SRO model and heterogeneous SRO. The statistical SRO is continuous over the entire volume and can be characterized by Warren-Cowley parameter for the nearest neighborhood (NN) or by a set of such parameters for several NN of the resonant atom.…”

“…The other alloying elements in the material have a minor presence in the first and second coordination shells and thus their influence on the change of the spectral parameters (hyperfine magnetic field and the isomer shift) is negligible. [44][45][46][47][48][49][50][51][52][53][54][55][56][57][58][59][60] Based on these assumptions, we can proceed to the calculation according to the probability equations of the BDM (Equation ( 2)). To calculate the contribution from impurity element to the average hyperfine magnetic field, we also follow the article Košovský et al [44] and Dubiel et al, [45,46] which describes the change in spectral parameters experienced by chromium atoms in binary Fe-Cr alloys as a function of composition (Cr concentration) of 1NN-2NN, known as additive multielement BDM.…”

“…Based on the chemical composition (Table 1), the relations and calculation procedures presented in the previous article were used. [ 44 ]…”