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[en] The results are shown of Moessbauer spectra measurement during annealing at 570 to 700 degC of a vacuum quenched Ni₃Co-1 at.% ⁵⁷Fe sample. Physical parameters calculated from the spectra (internal magnetic field, isomer shift) show that during annealing at the given temperatures local redistribution of atoms takes place. Activation energy of the process was determined. (author)

[en] The instance is considered when austenitic steel of the Fe-C-Cr-Ni type comes in contact with flowing liquid sodium at temperatures of 500 - 600 degC. The self-diffusion coefficients of components were measured for this ternary system. The self-diffusion coefficients increase with iron content increasina from 0 to 15% and decline at an iron content of more than 35%. The ratio of self-diffusion coefficients of the individual components is constant for the entire studied temperature and concentration interval. Using determinations of thermodynamic activities in the binary systems Fe-Ni, Fe-Cr and Ni-Cr it is possible to assess the regrouping of elements in austenitic steels and thereby to estimate the possible long-term changes in the mechanical properties of these materials. (M.D.)

[en] Moessbauer spectroscopy was used in studying short-range ordering in the Ni₃Co alloy. Moessbauer spectra were taken during annealing of a ⁵⁷Fe-doped Ni₃Co sample at various temperatures between 600 and 700 degC. A non-monotonous variation of isomer shift and other Moessbauer parameters with the time of annealing was found, similar to that obtained previously at 700 degC. The non-monotonous dependence is explained by a short-range ordering in the first stage of annealing which is compensated during further annealing by the influence of more distant co-ordination spheres. A linear dependence was found of log tsub(o) on 1/T, tsub(o) being the annealing time corresponding to the extremal values of isomer shift and other hyperfine parameters at temperature T. It is shown that the supposed short-range ordering in Ni₃Co is controlled by a thermally activated mechanism with an effective activation enthalpy given mainly by vacancy volume diffusion. (A.K.)

[en] Atomization of europium, praseodymium and yttrium was investigated from surfaces of electrographite, pyrolytic graphite, Mo, W and Ta carbides and W and Ta metals. The determination of praseodymium and yttrium using electrographite tubes or tubes coated with carbides appeared unsuitable. Also, in a tube with a pyrolytic graphite layer the sensitivity of determination was low for these elements as compared with europium. Interactions of analyte with the graphite tube is observable by scanning electron microscopic examination of the internal tube surface. Spherical crystallite aggregations are typical of the pyrolytic coating. No appreciable surface changes were found after 300 determinations of europium, whereas after the analysis of praseodymium and yttrium, changes were observable. In addition to the specific effects of the various metals, the different quantities applied, viz. 75 μg Pr, 3 μg Y and 0.6 μg Eu, also played a part in this. Pr and Y are likely to cause graphite corrosion, which depends on the atomization temperature, properties of the carbide or another compound of the element with graphite, and the amount of the element. For tubes with pyrolytic graphite coated with metal carbides the sensitivity of determination of the three analytes virtually did not change, which is in contrast with published data. The memory effect was never observed. The effect of acids was evaluated. The life of Ta foils 0.1 mm thick did not exceed 45 cycles at 2600 degC (t_R = 1 s), for foils 0.05 mm thick the life was 25 cycles. W sheets could be used for no more than 15 cycles. At t_R = 0 the Ta foil cracked in 5 cycles; t_R = 1 was optimal. The low life of the foils is a consequence of the formation of carbides. (P.A.). 4 figs., 2 tabs., 15 refs

[en] In the presence of organic compounds such as EDTA, citric acid or triethanolamine, the absorbance signal of Cd during atomization in a tube of electrographite or covered with pyrolytic graphite appears at a lower temperature than the signal from CdCl₂. Some of these compounds, e.g. EDTA, eliminate the interfering effect of NaCl and MgCl₂. With urine, however, addition of these compounds often causes splitting of the single absorbance pulse of Cd or an increase of one of the components of a split pulse. Addition of a simple modifier HNO₃ is therefore recommended for analyses of urine using atomization in a tube of electrographite. Cadmium concentration was evaluated from integrated absorbances by the method of standard additions. (author) 5 tabs., 7 figs., 17 refs

[en] Phase equilibria in selected phase regions of the Fe-Cr-Ni and Fe-Cr-C systems were investigated at the temperatures 795 C, 900 C and 1000 C. The fcc/bcc, fcc/(σ phase) phase equilibria in Fe-Cr-Ni system and fcc/bcc/M₂₃C₆, fcc/M₇C₃/M₂₃C₆, bcc/M₂₃C₆ phase equilibria in Fe-Cr-C system were investigated. The wavelength dispersive microanalysis for bulk specimens, carbon layer extraction technique for carbide composition analysis, and electron diffraction phase identification on foils were applied. The new information concerning fcc/(σ phase) phase region of the Fe-Cr-Ni system at 900 C is presented and the precision to M₂₃C₆ carbide equilibria in the Fe-Cr-C system at 1000 C is given. (orig.)

[en] Phase relationships in the Fe-Cr-Ni-C system have been studied at temperatures of 1000, 900, and 795 C, for nickel concentrations equal to 8 wt.%, 18 wt.% and 30 wt.% level, for chromium concentrations from 15 wt.% to 30 wt.% and carbon ones from 0.1 wt.% to 0.8 wt.%. Carbon extraction replicas were used for analysis of the carbide composition. The component concentrations in individual phases were determined by means of microprobe technique. The experimental results obtained are compared with calculated sections of the phase diagram. (orig.)

[en] Phase equilibria between the fcc matrix and the hcp nitride phase were installed by long-time heat treatment at 1273 and 1073 K, respectively, in different Fe-Cr-Mn-N alloys. The composition of the phases was determined applying wavelength-dispersive X-ray microanalysis. The results are compared with thermodynamic calculations using published data describing the fcc and the hcp phases in the system Fe-Cr-Mn-N. The agreement is satisfactory at medium concentrations at 1273 K but there are considerable differences at 1073 K. (orig.)

[en] The existing assessment of thermodynamic and phase equilibrium data in the Ag-Pd system was revised on the basis of calorimetric data for liquid Ag-Pd alloys published recently in the literature and on new determination of liquidus and solidus temperatures and activity data for Ag in liquid phase, using differential scanning calorimetry (DSC) coupled with Knudsen cell mass spectrometry (KC/MS). A substantially narrower liquid/fcc two-phase field in phase diagram as well as new non-ideal activity data were revealed.