Vol 9, No 1 (2018)

Low-cycle fatigue of the superalloy VZh175 heat-resistant alloy was studied under controlled deformation at room and high temperatures. The parameters of cyclic elastoplastic deformation and characteristics of fatigue strength were considered. The peculiarities of nucleation and development of low-cycle fatigue cracks were studied.

This paper is devoted to structure formation and phase transformations in the metastable Ti–15Mo β alloy during high-pressure torsion at room temperature. Transmission electron microscopy and X-ray diffraction analysis show that grain refinement takes place together with a β ↔ ω phase transformation and a nonmonotonic change in the volume fraction of the ω phase when the true strain is increased. The effect of the ω phase on the strength and the elastic properties of the alloy is considered. It is shown that nanostructure formation with a minimum amount of the ω phase is responsible for the marked hardening of the Ti–15Mo alloy while retaining its relatively low elastic modulus.

Using the methods of transmission electron diffraction microscopy and measurement of microhardness, the regularities of the change in the structural-phase states and defective substructure of the surface layers of rails up to 10 mm by fillet after long-term operation (the passed tonnage of 1000 million tons gross) are established. The possible causes of the observed regularities are discussed. A quantitative analysis of the mechanisms of strengthening of rails at different distance from the rolling surface by fillet after long-term operation is carried out. It is shown that strengthening is multifactorial in nature and is due to substructural strengthening caused by the formation of nanoscale fragments; dispersion strengthening by carbide phase particles; strengthening caused by the formation of Cottrell and Suzuki atmospheres on dislocations; internal stress fields, formed inside; and interphase boundaries.

Bibliometric and thematic analyses of the relevant array of publications by the CAPlus global database and the results of the questionnaire survey of experts by the Delphi method have made it possible to reveal the main problems of domestic Arctic materials science (AMS) and propose the ways to overcome them as well as areas of focus and goals of the further development of this field.

Metal-ceramic materials based on NiFe₂O₄ and Fe₂O₃ with additions of copper oxide and transition metals Cu, Ni, Co, and Fe were obtained. Changes in the phase content of materials based on iron oxide were shown, and the electrical conductivity of the obtained composites was studied. Samples of inert anodes were tested in an electrolytic cell; high resistance of cermets NiFe₂O₄ + Cu, Ni against alumina-cryolite melts and stability of aluminum electrolysis were established.

Vertical zone melting under argon pressure is used to grow crystals of GaSe and GaS binary compounds, as well as solid solutions in the GaSe–GaS system. The crystals of these compounds are applied in laser optics owing to a high transmission coefficient in the IR region, but they are also of a special interest in nonlinear optics, where they are used as frequency converters in the terahertz range. In this context, interest grows in alloying with isovalent and non-isovalent dopants as in a method aimed at increasing efficiency of optical frequency converters. In this work, it is shown that crystals of solid solutions are characterized by unit cell parameters which decrease linearly as the sulfur content increases. It is shown that doping of GaSe with sulfur leads to a regular shift of the edge of the transmission spectrum to the short wavelength region and to a shift of low temperature photoluminescence peaks to higher energies. Measurements of microhardness show high magnitudes depending on composition of the crystals.

New test results for samples of the titanium alloy VT3-1 in the region of very high cycle fatigue at the loading frequency of 20 kHz are obtained. Using the metallographic analysis on the sections of the compressor disk from which samples were made to study the stamped material, significant heterogeneity in the distribution of two-phase plate structure is revealed. At the asymmetry of the cycle R =–1, the behavior of the extruded and stamped material differs little from each other, and at the asymmetry of the cycle R = 0.1, the extruded material has better fatigue characteristics. The compressing part of the cycle balances the effect of structural heterogeneity on the accumulation of defects in VT3-1 alloy.

A method for obtaining apatite crystallization precursors via chemical transformation of plasma coatings based on α-tricalcium phosphate (α-TCP) into dicalcium phosphate dihydrate (DCPDH) with subsequent hydrolysis into octacalcium phosphate (OCP) is studied. X-ray diffraction (XRD) phase analysis, IR spectroscopy, and scanning electron microscopy (SEM) techniques are used for studying the phase composition and microstructure of the experimentally obtained samples depending on the process conditions. The approach described in this paper makes it possible to obtain two-phase calcium phosphates with different ratios between DCPDH-OCP and hydroxyapatite (HA).

An effect of small concentrations of nanosized titanium dioxide and silicon particles exerted on the formation of the supramolecular structure of poly-3-hydroxybutyrate fibers is studied. The fibers were obtained by means of electrospinning from a poly-3-hydroxybutyrate solution in chloroform. The structure of fibrous materials is studied by means of DSC, ESR, SEM, and physicomechanical testing. It is established that the fibers have intercrystalline areas with different ordering level. Using a small concentration of nanosized titanium dioxide and silicon particles leads to a slowing down of crystallization processes and to a decrease in the activation energy of the phase transition of PHB fiber melting. At the same time, the average fiber diameter decreases and the packing density increases. The obtained bioresorbable matrices can be successfully used in biomedicine for growing various connective and integumentary tissues of an organism.

Preparation of polymer composition materials with glacial matrix (GPCMs) from distilled water and aqueous solutions with high-molecular modifiers reinforced with Rusar-S aramid filaments is described. The physicomechanical properties of the composites are studied and the possibility of the control of their strength properties by varying the amount and topology of the reinforcing component is given. An improvement of strength properties of composites as compared to the glacial specimens prepared from distilled water is discovered.

A study on the character of influence of organic derivatives of quinquevalent phosphorus (cyclohexyl phosphonic acid and its nickel salts) on photodegradation of high-density polyethylene is performed. It is established that organophosphorus compounds demonstrate both photostabilizing and photocatalytic degradation effects toward polyethylene.

The four mostly frequently used gold nanoparticle species—nanospheres, nanorods, nanoshells, and nanocells—whose surface plasmonic resonance peaks lie in the visible to near-infrared range are considered. Their synthesis, optical properties, and some fields of practical application of the relevant materials are analyzed.

Electrically conductive layers prepared by the inkjet printing method with the use of an ink on the basis of the electrically conductive poly(3,4-ethylenedioxythiophene) and carbon nanoparticles were studied. The physicochemical properties of the ink components were considered. The dependence of the electrical conductivity was measured as a function of temperature and time of formation of a dry layer.