The surface of Cu cathode was alloyed by several elements, including pure Ni , Fe , Ag and pyrolytic graphite, during electric spark processing technology (ESP). The energy, gap between the electrode and matrix, and the total fabricating time of ESP are 0.9 J, 0.5 mm, and 30 s, respectively. The ESP was performed under a constant magnetic field (CMF) of 630 kA/m. The atom distribution profiles along the depth were measured by a serial sectioning and autoradiography. The lattice constants were studied by an X-ray diffractometer. The results show that there is one or several concentration peaks in the subsurface of Cu . When the depth is beyond the location corresponding to the concentration peaks, the concentration distribution in the matrix can be described by an exponential function. Fe and C atoms can homogeneously diffuse into the Cu lattice, accompanied by mechanical mixtures, and no traces of diffusion along the grain boundaries can be found. Comparing with the condition without a CMF, the diffusion coefficient decreases when the magnetic field is parallel to the surface, whereas the diffusion coefficient is the smallest when the magnetic field is perpendicular to the surface. The lattice constant of Cu becomes smaller after the ESP.

За допомогою методу радіоактивних індикаторів вивчений вплив попереднього введення інертних газів у метали у плазмі жевріючого розряду на дифузію (масоперенесення) при різних зовнішніх впливах. Показано, що наявність попередньо введеного інертного газу в залізо та сплави на його основі призводить до зменшення рухливості атомів при ізотермічних відпалах, низькотемпературному імпульсному навантаженні в широкому інтервалі швидкостей деформації та подальшому іонному бомбардуванні у жевріючому розряді. Бар'єрна дія введеного газу пов'язується із структурно-фазовими змінами у приповерхневих шарах. Ключові слова: дифузія, рухливість атомів, інертні гази, жевріючий розряд, імпульсні навантаження.

No abstract

Since 1975 a so-called anomalous mass-transfer in metals and alloys under pulse loading is being investigated in the Institute of Metal Physics. This phenomenon remains to be a challenge to theoreticians. Besides, one more phenomenon (observed at the same systems) was discovered – formation of metastable alloys (solutions, and, sometimes, ordered phases), with solubility limits far exceeding the equilibrium values and depending on the deformation rate. Since formation of nonequilibrium phases is also typical for alloys under irradiation, it seemed natural for us to use some of concepts and models invented in the “materials under irradiation” community. We propose 3 types of models for description of metastable solid solution formation in diffusion couple under pulse loading: 1) flux balance for both components at the interface with account of non-equilibrium defects generated during pulse loading; 2) “ballistic jump” concept, which had been invented by George Martin et al. for materials under irradiation or ball-milling, combined with another Martin’s kinetic model (1994) of diffusion; 3) modification of such a concept for the case of non-equilibrium interstitial defects. Non-equilibrium phase diagrams obtained by all 3 models are built and compared with experimental data which reflect a qualitative correspondence to one another.

Regularities of interaction of iron, steels, nickel, copper, titanium with light elements and inert gases in the plasma of the glow discharge studied by methods based on the use of radioactive indicators 55Fe, 44Ti, 14C, 13N, 85Kr, 41Ar (layer-by-layer radiometric analysis of residual integrated activity, macro- and microautoradiography, activation autoradiography), as well as metallography, X-ray analysis and spectral analysis. Processing was carried out according to the diode circuit with parameters of 1 - 55 hours, 0.2 - 2 kV, ~ 500 K. Neutral (argon, krypton) and saturating (nitrogen, ammonia, methane) media were used for processing in the discharge, and further processing of metals previously saturated with nitrogen or carbon was carried out in a neutral medium. It is established that in the process of introduction into metals (Fe, Ti) under the action of a glow discharge burning in a saturating medium, atoms soluble under equilibrium conditions of elements (N, C), there are interstitial solutions and phases that differ from those formed in isothermal annealing, only the presence of supersaturated solid solutions and some violation of the stoichiometry of carbides and nitrides, as well as a steeper decrease in the concentration of the alloying impurity with increasing distance from the surface. The shape of the concentration profiles outside the layer of the interstitial phase is described by an exponential dependence on the square of the penetration depth. As for the penetration into copper of nitrogen, carbon, argon or krypton atoms, insoluble under equilibrium conditions, in ion bombardment in appropriate media from the treated surface to the end of the diffusion zone there is only a solid solution with a concentration that decreases by the exponent. It turned out that further treatment of nickel, iron and steel saturated with light elements by argon and krypton ion bombardment leads to redistribution of alloying impurities, separation of interstitial phases mainly at grain boundaries, surface or at some distance from the surface, which contributes to some disturbance of concentration profile. When processing pre-saturated copper interstitial phases do not occur, but the type of profile changes dramatically, but from the maximum to the end of the diffusion zone is described by the exponent. It is shown that the use of saturating and neutral media, as well as their sequential application for processing in the glow discharge makes it possible to create predetermined doping profiles and enter the required amount of doping impurity. Keywords: glow discharge, radioactive isotopes, light elements, inert gases, diffusion, formation of phases and solid solutions.