Том 8, № 1 (2017)

The microstructure evolution and mechanical behavior of the two-phase titanium VT8M-1 alloy with initial globular-lamellar structure are investigated during compression in the temperature range of 650–800°C at a strain rate of 1.4 × 10^–3 s^–1. It is established that the microstructure evolution of the alloy during compression is associated with the development of globularization and dynamic recrystallization of α-phase lamellae with subsequent formation of globular-shaped particles. The extent of the steady-state flow stress and the average size of recrystallized α-phase particles in the alloy increase as the temperature of plastic deformation is increased from 650 to 800°C. The possible formation of ultrafine-grained structure in the VT8M-1 alloy in the studied temperature–rate conditions of plastic deformation is shown.

The influence of rare earth metals, such as praseodymium, neodymium, and erbium, and the technology of smelting a nickel aluminide alloy based on “clean” raw materials and using 25, 50, and 75 wt % of waste is investigated. It is found that doping with neodymium and/or erbium in the smelting of structural intermetallic nickel-based alloy increases the heat strength at a temperature of 1200°C and heat resistance at the temperatures of 1100 and 1200°C for 100 h at a weight gain from 1 m². Introducing a different percentage of waste during the smelting the intermetallic alloy results in a slight decrease in the heat resistance but preserves the same level of values when 25, 50, or 75 wt % of waste is included.

Defects of heat-resistant alloys synthesized by the method of selective laser melting are studied. It is shown that the main defects were pores and cracks in the metal, and the main reasons for the formation of those defects are given.

Wetting of Ag, Au, and BeO by B₂O₃ and B₂O₃ + PbO melts depending on temperature is investigated. It is shown that the strongest interaction of such melts occurs with BeO.

Composite hydrogels in the system of sodium alginate–tricalcium phosphate (TCP) are studied. The gelation time, mechanical properties, and solubility of composite hydrogels are investigated in relation to the content of a reinforcing component such as TCP granules introduced in an amount of 10, 20, and 30 wt %.

One- and two-step syntheses of composite coatings with an A–OOO polyimide matrix filled with 40-nm tungsten disulfide nanoparticles produced using gas-phase synthesis, which are intended for operation under dry friction conditions, are described. Results of studying the tribological behavior of these coatings are presented.

By example of determination of the fractal dimension on a photo of the profile of Palmqvist microcrack obtained as a result of indentation of a Vickers indenter to the surface of a section of metal-ceramic solid alloy (MSA) based on titanium carbonitride, the relationship of microstructure parameters to the characteristic features of the destruction caused by the development of microcrack is studied. An attempt to find the numerical values of the fractal dimension of microcracks is made. As a solid alloy based on titanium carbonitride, alloys of KNT3, KNT7, and KNT12 grades are selected, where the number indicates volumetric content of the binder phase of Ni–Mo in the alloy, respectively.

The dependence of the sintering of zirconium dioxide on the aluminum oxide content and the use of additives forming the liquid phase during sintering is studied. Dense nanostructured ceramic materials based on zirconium dioxide containing aluminum oxide are synthesized. It is shown that the use of additives based on sodium silicate contributes to the sintering and the formation of a nonporous structure at 1330°C. It is revealed that aluminum oxide in the amount of 1 and 5 wt % increases the density of materials, while at the content of 16 wt % the sintering until the dense state does not occur even at temperatures up to 1550°C.

The results of investigation of the influence of variable sulfur content on the thermal stability of single crystals of heat-resistant nickel Ni–Al–Co–Re–Ta–Mo–W–Ru–Cr alloy with coating and without it were presented. The negative influence of the increased sulfur content of 0.00030 wt % on the heat resistance of single crystals of this alloy at temperature Т = 1150°С for 500 h on the samples with coating and without it was established.

The phase composition and grain structure of Pb–13 wt % Sb produced by the method of rapid solidification are studied. In the foils of alloys, formation of dispersed rounded antimony segregations takes place, distributed macroscopically homogeneously in the alloy foil; the foils have microcrystalline structure and texture (111) + (100) of lead and (101̄2) + (101̄1) of antimony.

Some research directions of formulations and technology of development for polymeric antifrictional composites (solid lubrican Fts) with increased physicomechanical tribological properties are considered. These composites are based on polytetrafluoroethylene and semi-interpenetrating polymer network (SIPN) matrices and mixed organic–inorganic fillers. Comparative analysis of qualification of materials when tested in field conditions and express testing using laboratory equipment provide a reliable screening of the service life of the materials to evaluate the performance of machines and mechanisms operating under the climatic conditions of the Russian North and the Arctic.

Hydrated amorphous calcium pyrophosphate powder was synthesized from an aqueous solution containing pyrophosphoric acid and calcium acetate with the addition of an aqueous solution of ammonia. A distinctive feature of the proposed synthesis consisted in the use of pyrophosphoric acid synthesized by treatment of a sodium pyrophosphate solution with ion exchange resin (H⁺ form). The phase composition of ceramic fabricated from the powder after the calcination at 600–1000°C was represented by β-Ca₂P₂O₇. The synthesized powder can be recommended for the fabrication of porous biocompatible resorbable ceramic.

By transmission diffraction electron microscopy, study of the changes in the phase composition arising in 0.3C-1Mn-1Si-Fe steel upon plasma electrolytic nitrocarburizing with increasing distance from the modified surface is performed. It is found that, with increasing distance from the surface, the list of carbonitride phases and their volume fraction are reduced. The morphology of the steel matrix is changed.

The properties of nitrile-butadiene rubber reinforced with basalt and carbon short fibers are studied. The physicomechanical properties, hardness, and stability under abrasive wear and in a corrosive environment are established depending on the amount of introduced fibers. The structural properties of reinforced elastomeric composites are studied using electron and atomic force microscopy.

A calculation is performed for the temperature distribution and studies are conducted for the structure of the heat-affected (HAZ) zone in sheet steel St3 with a thickness of 6 and 10 mm after laser cutting (LC). It is shown that, with increasing LC speed, the temperature in any section of the HAZ is reduced. Increasing laser power in the studied range has almost no effect on the temperature distribution in the HAZ. The temperature fields appearing in the course of LC are compared with the location of the HAZ regions differing in structure. The area with ferrite structure under heating stays in a state of pre-transformation before a eutectoid transformation; the cause of its formation could be an enhanced diffusion mobility of interstitial atoms near the critical point A_c1.

A determining factor for application of new materials for structural elements exposed to processing and operational heating is their thermal stability and operability at increased temperatures. This article presents the results of investigation into the influence of a minor addition of cobalt on modification of the microstructure of cold rolled sheets after thermal strengthening treatment. Furthermore, improvement of long term strength at increased temperature is demonstrated, which makes it possible to use the addition of cobalt in development of heat-resistant aluminum alloys.

Novel compounds—substituted indolo[3,2-b]carbazoles (SIC)—which demonstrate semiconducting properties are synthesized. Electroluminescence (EL) is studied in multilayer diode structures based on SIC. The values of hole (6.38 × 10^–5 cm²/(V s)) and electron mobilities (1.31 × 10^–5 cm²/(V s)) of these electroactive materials are measured. It is estimated that heteroaromatic nuclei are the electron transport centers of SIC molecules.

A method of modification of mineral shungite (shungite-III) material was proposed that made possible a nanodispersive porous sorbent with the carbon content exceeding 75% and the pore size of 19 nm. The effect of the physicochemical modification of shungite on its composition and sorption properties was studied.