R. Konieczny

A study of defects in iron-based binary alloys by the Mössbauer and positron annihilation spectroscopies

The room temperature positron annihilation lifetime spectra and 57Fe Mossbauer spectra were measured for pure Fe as well as for iron-based Fe1−xRex, Fe1−xOsx, Fe1−xMox, and Fe1−xCrx solid solutions, where x is in the range between 0.01 and 0.05. The measurements were performed in order to check if the known from the literature, theoretical calculations on the interactions between vacancies and solute atoms in iron can be supported by the experimental data. The vacancies were created during formation and further mechanical processing of the iron systems under consideration so the spectra mentioned above were collected at least twice for each studied sample synthesized in an arc furnace— after cold rolling to the thickness of about 40 μm as well as after subsequent annealing at 1270 K for 2 h. It was found that only in Fe and the Fe-Cr system the isolated vacancies thermally generated at high temperatures are not observed at the room temperature and cold rolling of the materials leads to creation of another...

Interactions between osmium atoms dissolved in iron observed by the 57Fe Mössbauer spectroscopy

Abstract The room temperature 57Fe Mössbauer spectra for binary iron-based solid solutions Fe1−xOsx, with x in the range 0.01 ≤ x ≤ 0.05, were analyzed in terms of binding energy Eb between two Os atoms in the Fe-Os system. The extrapolated values of Eb for x = 0 were used for computation of enthalpy of solution of osmium in iron. The result was compared with that resulting from the cellular atomic model of alloys by Miedema. The comparison shows that our findings are in qualitative agreement with the Miedemas model predictions.

Atomic short-range order in mechanically synthesized iron based Fe-Zn alloys studied by 57Fe Mössbauer spectroscopy

Abstract Mechanical alloying method was applied to prepare nanocrystalline iron-based Fe1−xZnx solid solutions with x in the range 0.01 ≤ x ≤ 0.05. The structural properties of the materials were investigated with the Mössbauer spectroscopy by measuring the room temperature spectra of 57Fe for as-obtained and annealed samples. The spectra were analyzed in terms of parameters of their components related to unlike surroundings of the iron probes, determined by different numbers of zinc atoms existing in the neighborhood of iron atoms. The obtained results gave clear evidence that after annealing process, the distribution of impurity atoms in the first coordination spheres of 57Fe nuclei is not random and it cannot be described by binomial distribution. The estimated, positive values of the short-range order parameters suggest clustering tendencies of Zn atoms in the Fe-Zn alloys with low zinc concentration. The results were compared with corresponding data derived from Calphad calculation and resulting from the cellular atomic model of alloys by Miedema.

Thermodynamic properties of dilute Co-Fe solid solutions studied by 57Fe Mössbauer spectroscopy

Abstract The Co1-xFex alloys where x ranges from 0.01 to 0.06 were measured at room temperature using transmission Mössbauer spectroscopy (TMS). The analysis of the obtained data allowed the determination of the short-range order (SRO), the binding energy Eb between two iron atoms in the studied materials using the extended Hrynkiewicz-Królas idea and the enthalpy of solution HCo-Fe of Fe in Co. The results showed that the Fe atoms dissolved in a Co matrix interact repulsively and the estimated value of HCo-Fe = -0.166(33) eV/atom. Finally, values of the enthalpy of solution were used to predict the enthalpy of mixing for the Co-Fe system. These findings were compared with corresponding data given in the literature, which were derived from calorimetric experiments and from the cellular atomic model of alloys described by Miedema.

Corrosion of Polycrystalline Fe-Si Alloys Studied by TMS, CEMS, and XPS

The high-temperature corrosion behavior of three polycrystalline Fe-Si alloys containing approximately 4, 5, and 10 at% Si was studied using transmission Mossbauer spectroscopy (TMS), conversion el...

Hyperfine fields at 57Fe in dilute iron-based alloys determined by Mössbauer spectroscopy

The room temperature Mossbauer spectra of 57Fe were measured for several dilute iron-based alloys, Fe1−xDx (D = Co, Cr, Mn, Mo, Pt, Re, Ta, V, W), annealed at 1270 K for 2 h before the measurements. The analysis of the spectra shows that the effective hyperfine field B at 57Fe nuclei depends on the concentration x of the minority component of the alloys under consideration and the dependence is different for iron nuclei having unlike numbers of impurities in their neighbourhood. The latter is at variance with previously published data, which suggest that the general B(x) dependence is common for all impurity configurations present in the vicinity of iron nuclei.

Mean hyperfine fields at 57Fe in dilute iron-based alloys studied by Mössbauer spectroscopy

Abstract The room temperature Mössbauer spectra of 57Fe were measured for numerous dilute iron-based alloys Fe1−xDx (D = Al, Co, Cr, Mn, Mo, Ni, Os, Pt, Re, Ru, Ta, Ti, V, W, Zn), annealed at 1270 K for 2 h before the measurements. The spectra were analyzed using the Hesse–Rübartsch method in order to determine the mean hyperfine magnetic field at the 57Fe nuclei as a function of concentration x of the minority component of the alloy. As the binary alloys are one-faze solid solutions of an element D in iron, a linear relationship between and x is observed. The result supports the suggestion that Mössbauer spectroscopy is a useful tool for the study of dissolution of different elements in iron.

Temperature dependence of the short-range order parameter for Fe0.90Cr0.10 and Fe0.88Cr0.12 alloys

Abstract The 57Fe Mössbauer spectra for the iron-based solid solutions Fe0.90Cr0.10 and Fe0.88Cr0.12 were measured at different temperatures ranging from 300 K to 900 K. Analysis of the obtained spectra shows that the distribution of impurity atoms in the two first coordination shells of 57Fe nuclei is not random and it cannot be described by the binomial distribution. Quantitatively, the effects were described in terms of the atomic short-range order (SRO) parameters and the pair-wise interaction energy with the help of a quasi-chemical type formulation introduced by Cohen and Fine. The obtained results reveal strong clustering-type correlations in the studied samples (a predominance of Fe-Fe and Cr-Cr bonds). Moreover, the changes in SRO values observed during thermal processing suggest that the distribution of Cr atoms in an α-iron matrix is strongly temperature dependent.