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No 1 (2025)
Articles
Influence of complex modification on crystallization of complex-alloyed hypereutectic silumin
Abstract
The work is devoted to the study of the influence of complex modification on the crystallization of complex-alloyed hypereutectic silumin of the Al-Si-Cu-Mg-Ni-Mn system. Based on the study and analysis of literary sources and experimental studies, the phase composition of the alloy under study was determined. The crystallization process of complex-alloyed hypereutectic silumin was studied and the stages of the crystallization process were determined. The influence of complex modification on the crystallization process of the experimental alloy was studied. The influence of the components of complex modifying compositions on the liquidus and solidus temperatures of the alloy and the crystallization temperatures of the main structural components of the alloy was studied. The influence of complex modification on the crystallization process of complex-alloyed hypereutectic silumin is shown.
5—19
Structure and tribological characteristics of TiAlZrN-InSn system based coatings
Abstract
Thin composite solid lubricating coatings (SLC) TiAlZrN and TiAlZrN-InSn were obtained by sputtering (Ti, Al, Zr, InSn) of cathodes of different magnetrons. The structure, elemental and phase composition were studied by electron microscopy, X-ray spectral and X-ray diffraction analysis. The surface globularity of the coatings significantly increased with increasing indium content and decreasing Al/Zr concentration ratio. Different phase compositions were obtained in the coatings depending on the ratio of the main components: single-phase TiAlZrN with the lattice period a close to 4.24 Å, two-phase with InSn, two-phase, including nitride TiAlZrN with the lattice period ~4.24 Å, and ZrTiAlN, where a = 4.29–4.58 Å, and three-phase with InSn. The microhardness of the coatings reached 1056 HV0,05 with the highest values for a two-phase nitride structure. Tribological tests were carried out in the reciprocating wear mode. The friction coefficients of the coatings varied from 0.20 to 0.33. The lowest wear was obtained for coatings containing two nitride phases and indium in an amount of less than 3.7 at.%.
20—29
Study of volume and surface properties of the iron melts containing phosphorus impurity
Abstract
The structure-sensitive properties (density and surface tension) of iron melts were studied depending on the phosphorus impurity content at different temperatures. In the region of low phosphorus contents (hundredths of a percent), a compression effect and the appearance of negative deviations from Raoult’s law were detected. In the region of the higher compositions (tenths of a percent of phosphorus), a shift towards positive deviations is observed. The adsorption factor has a significant influence on the properties of the melt due to the formation of oxide film from the residual oxygen amount, its complete or partial disintegration at heating temperature. With increasing phosphorus content, the amount of adsorbed substance increased.
30—40
The influence of low-alloy pipe steel hydrogen saturation conditions on the sorption process
Abstract
The kinetics of hydrogen sorption and desorption during electrolytic hydrogen saturation of steel grade 09G2C has been studied. A method for determining the effective hydrogen diffusion coefficient and a method for calculating the concentration profile over the section of a cylindrical sample are proposed. It is shown that the equilibrium concentration of hydrogen at a pressure of 25 MPa in the test material without applied stresses does not exceed 1 ppm. The influence of the stress-strain state on the sorption process during hydrogen saturation from the gas phase has been studied. A method is proposed for quantifying the equilibrium hydrogen concentration depending on pressure and the level of tensile stresses, taking into account influence of plastic deformation.
41—50
Phase composition, texture and residual stresses in steels with 1.6 and 2.9% Mn after hardening and cold rolling
Abstract
The influence of composition and cold rolling on the structure and properties of steels with 1.6 and 2.9 Mn was evaluated using X-ray diffraction analysis of phase composition, texture, and residual stresses, as well as tensile testing. It was shown that after quenching from 1100°C, in addition to the α-phase, the steel with 1.6 Mn contains 4.7% and 2.5% of γ- and ε-phases, respectively. These phases transform into α-phase after cold rolling with a reduction of 20%. In the steel with 2.9 Mn, the amount of γ-phase after quenching was 49%, which decreases to 20% after a reduction of 20%, 12% after 40%, and 10% after 60 and 80%. In both steels, with increasing reduction, the reflections corresponding to the components of the rolling texture of BCC metals (200) and (222) intensify. In the steel with 2.9 Mn, a single-component texture of γ-phase of the «brass» type {110}<112> is formed. In the steel with 2.9 Mn at reductions of 20 and 40%, compressive stresses are formed due to the increase in volume during the γ→α transformation. Increasing the reduction during cold rolling leads to an increase in the yield strength of both steels, while the strength level of the steel with 1.6 Mn is significantly higher than that of the steel with 2.9 Mn. The relative elongation at reductions less than 40% correlates with the amount of deformation-unstable γ-phase.
51—58
Analysis of the mechanisms of hardening of high-carbon steels during surface treatment with a highly concentrated plasma jet
Abstract
The microstructure, phase composition and parameters of the crystalline structure of high-carbon steels (65G, U8 and U10) after plasma surface hardening were studied. It has been established that the strengthening of martensite is caused by its solid-solution strengthening, an increase in the dislocation density, the presence of a large number of subboundaries, and the release of nanodispersed carbides during self-tempering. This leads to a 3.5–4.5 times increase in hardness compared to the initial state and by 120–170 HV compared to volumetric hardening. As a result of the re-search, a methodological approach to controlling structure formation was developed for the process of plasma surface hardening (nanostructuring) of high-carbon steels.
59—66
Study of the protective properties of thin metal coatings obtained by magnetron sputtering on low-alloy molybdenum alloys
Abstract
The influence of chromium and titanium coatings on the gas corrosion of low-alloyed molybdenum alloys has been investigated. The samples after the gas corrosion test were analyzed using scanning electron microscopy and X-ray phase analysis. It is shown that the phase composition of corrosion products varies for different temperature ranges. The dependence of the depth of corrosion damage on the thickness of the coatings was determined. It is established that magnetron coatings of a certain thickness can peel off due to a defective structure.
67—77
Electrochemical production of microdispersed tungsten oxide powder from technogenic waste of metallic tungsten under the influence of alternating current in ammonia carbonate solutions
Abstract
A comparative analysis of the processes of electrochemical oxidation of metallic tungsten in ammonium carbonate solutions under the action of direct and sinusoidal alternating current of industrial frequency (50 Hz) was carried out with a change in current density (0.3 – 2.0 A/cm2), temperature (20 – 50 °C) and concentration of ammonium carbonate (0.5 – 1.0 M) in the electrolyte. It was revealed that the maximum oxidation rate of metallic tungsten under the action of alternating current, corresponding to its complete transition into solution, is ~960 mg/cm2•h, but is two times lower than that when using direct current. It was found that the use of alternating current allows for the electrochemical oxidation of tungsten with the formation of a microdispersed powder based on tungsten (IV) oxide. A basic technological scheme of the process of electrochemical processing of metallic tungsten waste under the action of alternating current has been proposed and tested, allowing the production of tungsten oxide powder (with a tungsten extraction rate of ~42%) along with ammonium paratungstate.
78—90
Research of processes stimulating plastic deformation of metal materials arising under the action of electric current pulses
Abstract
The electrodynamic effect of an electric current pulse, which causes fast–flowing shock wave processes in metallic materials, has been experimentally established. The fronts of the electric pulse are formed in metal by mechanical shocks and vibroacoustic waves propagating in the form of bending shapes, and along the axis of the forms of stretching-compression. These processes are nonpolar in nature and dominate the electroplastic effect (EPE), stimulating plastic deformation and structural changes in the metal. Their action is similar to ultrasound. The thermal deformation of the sample and the pinch effect are polar in nature. They are insignificant and do not prevail at EPI current densities and durations. The results obtained will contribute to the creation of a consistent theory of EPE and the development of new technologies.
91—98