Defect and Diffusion Forum Vols. 237-240

Abstract: The initial stages of reactive diffusion have been studied by Monte-Carlo simulations. New MC-scheme describing the competition of two ordered intermediate phases is proposed. Main peculiarity of presented MC-model is a strong dependence of interatomic interaction energies on the local atomic surrounding, enabling us to distinguish new phases more distinctly.

Abstract: The paper presents the application of multitracer method of diffusion measurement in Cr-Mn steels. Two austenitic steels were investigated: Cr13Mn18SiCa and Cr17Mn17 as well as austenitic-ferritic one: Cr15Mn19. The serial sectioning technique was used for simultaneous evaluation of diffusion coefficients of radioisotopes of chromium 51Cr, manganese 54Mn and iron 59Fe at 1073K and 1173 K. Diffusion coefficients of radiotracers at 1173 K were calculated on the basis of both: activity of removed layer (differential method) and residual activity of the sample (integral method). The evaluated diffusion coefficients of metals in austenitic steels are higher than those in austenitic-ferritic one; their values are about 10-12 ÷ 10-11 cm2s-1. Moreover it was found that at 1173 K the diffusion rate of manganese is higher than that for iron and chromium while at 1073 K diffusion rates of chromium and manganese are comparable and higher than that for iron. Furthermore the experimental results point out that at 1173 K the volume diffusion is the dominant mechanism of metals’ transport while at 1073 K the high diffusivity paths diffusion prevails.

Abstract: Phase transformations during the heating of amorphous Fe-Si-B alloys were investigated. The differential thermomagnetic analysis and X-ray method are used for the studies. The intervals of phase transformations are revealed, and the magnetic properties of phases are determined. The method of calculation of magnetic effects during the phase transformations, registered by differential technique is suggested.

Abstract: Enhanced intermixing, induced by a laser beam, has been recently observed in amorphous Se/As2S3 and similar multilayers. We report a model, based on the concept of thermal spikes, which can consistently describe experimental observations. The concentration dependence of the light absorption properties causes the photo-stimulated diffusion to be non-linear even when a concentration independent coefficient of thermo-stimulated diffusion is assumed.

Abstract: Nuclear resonant scattering (NRS) methods allow to determine diffusion coefficients and jump directions. The capability to measure the diffusion mechanism in ordered intermetallics on atomic scale by mean of NRS was shown in various experiments and in different geometries (transmission [1,2], Bragg [3], grazing incidence [4]). A combination of NRS and grazing incidence geometry can be used as a very sensitive tool to investigate thin films or near-surface-regions [4]. Fe3Si with a D03 structure stable at high temperature and with a well known diffusion mechanism was chosen for this investigation.

Abstract: The growth of non-stoichiometric particles of an intermediate ternary phase during the decomposition of a weakly supersaturated solution is considered. A mathematical model which describes a non-parabolic growth of precipitates and concentrations tending to asymptotic value at long times is suggested. Shape instability during the growth of the stoichiometric ternary phase based on one of the components in the supersaturated solution is investigated.