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1.
dx.doi.org/ 10.18577/2307-6046-2019-0-10-3-13
УДК 537.621
Morgunov R.B., Valeev R.A., Skvortsov A.A., Korolev D.V., Piskorsky V.P., Kunitsyna E.I., Kucheryaev V.V., Koplak O.V.
MAGNETOPLASTIC AND MAGNETOMECHANIC EFFECTS IN ALUMINUM ALLOYS WITH MAGNETOSTRICTIVE MICRO INCLUSIONS

The influence of the magnetic field on the plasticity of Al–Fe–Si–Mn aluminum alloy is reported. Measurements of the magnetic moment of the alloy revealed the presence of magnetic hysteresis inherent in microinclusions detected by electron microscopy. According to the mössbauer spectra and chemical shift, the inclusions are FeAl alloy with increased magnetostriction. Micro-inclusions formed by aggregation of iron impurities or instrumental treatment of samples before measurement. The apparent «randomness» of the formation of micro-inclusions in the matrix of non-magnetic metal is offset by the systematic detection of magnetic hysteresis in all technical alloys of aluminum, copper, etc. in our experiments. The results show that the controlled introduction of microparticles having magnetostrictive properties, can be the basis of new technologies plasticizing aluminum and reduce energy consumption during processing of aluminum and other soft «non-magnetic» metals. The opposite effect is also reported, which manifests itself as the occurrence of a non-zero coercive force of microinclusions under the action of plastic deformation of aluminum, despite the fact that prior to plastic deformation, the coercive force was zero. The reverse effect of plastic deformation on the coercive force of FeAl microinclusions is observed. Plastic deformation increases the coercive force of inclusions, which can be caused by an increase in their size and a corresponding increase in magnetic anisotropy.

The detected phenomena can be used to control the mechanical properties of aluminum products in the process of their machining, especially in conditions of controlled controlled introduction of microinclusions of a predetermined concentration and with an increased value of the magnetostriction coefficient.

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2.
dx.doi.org/ 10.18577/2307-6046-2019-0-10-14-24
УДК 669.295:669.017
Ospennikova O.G., Naprienko S.A., Medvedev P.N., Krupnina O.A., Rogalev A.M.
FEATURES OF THE STRUCTURE OF Ti–6Al–4V ALLOY OBTAINED BY SELECTIVE LASER MELTING

On the example of titanium alloy Ti-6Al-4V structural features were determined and defects characteristic of α+β titanium alloys obtained by selective laser melting were identified.

Studies of the structure have shown that in the process of synthesis formed elongated in the direction of cultivation of the former β-grain. In the synthesis plane, the structure is represented by square structural components with a cell size corresponding to the distance between the tracks. The material has a plate microstructure identical to two-phase titanium alloys in the cast state.

As a result of the synthesis, a phase transition texture from the high-temperature beta phase is formed similar to the texture formed in the classical precipitation technologies in the β-region. Annealing at 840°C for 2 hours has no significant effect on the microstructure and texture.

In SLS defects are formed in the form of pores and non-fusion, which form a grid with a cell size of 1 mm in the synthesis plane. This is due to the shift of Islands on each subsequent synthesis layer by 1 mm, and the pores themselves are formed along the boundaries of the Islands.

Also, a characteristic defect is discontinuity in the form of bowls along the boundaries of the granules, oriented convex surface in the direction of the substrate.  This leads to the formation of sharp concentrators in the synthesis plane.

A specific defect for titanium alloys obtained by SLS method are separate granules or fragments of powder granules, which retained their shape as a result of synthesis. These defects are distributed chaotically in the volume and have on their surface a rim of the alphanumeric layer. The formation of an alpha layer is due to the formation of a thin layer of scale on i

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3.
dx.doi.org/ 10.18577/2307-6046-2019-0-10-25-33
УДК 669.295
Shiryaev A.A., Nochovnaya N.A., Pomelnikova A.S.
EFFECT OF ISOTHERMAL EXPOSURES ON HARDNESS EVOLUTION OF HIGH-STRENGTH METASTABLE-β-TITANIUM ALLOY VT47

Rockwell hardness (HRC) and microstructure studies have been accomplished on samples cut from sheets of metastable b-titanium alloy VT47 after isothermal exposures (ageing) in the temperature range from 350 to 650°С and exposure durations from 10 minutes to 128 hours. A diagram and «C-shaped» hardness curves for the VT47 alloy have been plotted on the basis of experimental results, and a comparative assessment of the plotted curves with a «time-temperature-phase transformations» diagram for a metastable b-titanium alloy Beta-C, being one of the closest analogues, has been carried out.

In this project the «incubation period» has been determined for the VT47 alloy hardness increase (up to ≈28–30 HRC) during ageing, which occurred to be ≈32 hours at 350°С, ≈16 hours at 400°С, ≈2 hours at 450°С, ≈2–4 hours at 500°С, ≈4 hours at 550°С, and was not observed at 650°С.

It was revealed that isothermal ageing at a temperature of 650°С did not result in noticeable changes in hardness throughout the studied ageing durations, which was due to the predominant grain-boundary morphology and a small amount of secondary α-phase precipitates. Exposures at lower temperatures lead to a significant hardness increase owing to both the secondary α-phase volume fraction increase and its precipitation change towards the intragranular fine lamellar morphology as well as a more homogeneous distribution of α-phase precipitates over the initial β-grains volume. The lowering of the isothermal ageing temperature to 350°С results in both “incubation period” expansion and a significant slowdown in the process of alloy hardening together with lower maximum hardness values even after long-time exposures.

It h

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4.
dx.doi.org/ 10.18577/2307-6046-2019-0-10-34-49
УДК 678.8
Kondrashov S.V., Pykhtin A.A., Larionov S.A., Sorokin A.E.
INFLUENCE OF THE TECHNOLOGICAL FDM-MODES OF THE PRESS AND STRUCTURE OF USED MATERIALS ON PHYSIC-MECHANICAL CHARACTERISTICS OF FDM-MODELS (review)

On the basis of the analysis of literary data it is established that strength characteristics of the samples received by the way FDM of printing depend on a number of parameters of technological process: orientations of thread of fusion, distances between threads, the choice of the mode of its laying, temperatures of a nozzle and the platform of creation. These parameters define diagrams of internal thermoelastic stresses, quality of a surface, adhesive communication between threads of fusion and, eventually, the strength and relative deformation of the printed models. Strength characteristics of the details made with use of optimum printing options come very close to properties of the products received by way of casting under pressure.

Use as initial materials of a poliefirimid, polifenilensulfid, polifenilensulfon, poliefirefirketon, liquid crystal aromatic polyair allows to receive in the way FDM of printing of a detail of irregular geometrical shape with strength more than 100 MPas and with the glass transition temperature more than 200 °C.

The technology of FDM printing gives a unique opportunity to receive details of irregular shape from the polymeric matrixes reinforced by continuous fiber. The developed modern industrial printers for printing of products on this technology allow to make samples with strength characteristics close to aluminum alloys, at the same time their weight characteristics are twice less.

The conducted researches allow to pass from prototyping which was a main objective of development of FDM printers, to production of real details, specific devices and constructions. However for achievement of this purpose it is necessary to solve a number of research problems, in particular:

– a research of influence of structure of a polymeric matrix and the techno

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5.
dx.doi.org/ 10.18577/2307-6046-2019-0-10-50-60
УДК 629.7.023.224
Movenko D.A., Medvedev P.N.
MICROSTRUCTURE CHANGES DURING MCrAlY BOND COATS OXIDATION (review)

The evolution of microstructure and oxidation in TBC’s bond coats, occurring at long-term high-temperature exposure, significantly affect the thermomechanical properties of TBC and, therefore, may affect their service life. MCrAlY coatings (where M–Ni or/and Co) provide excellent protection against high temperature oxidation and corrosion. Such coatings are considered two-phase and consist of a matrix based on γ-Ni (Co, Cr) and the second phase β-NiAl – «aluminum reservoir». In addition, other phases such as σ-phase enriched with cobalt and chromium, α-Cr phase and γ' (Ni3Al) phase may be present in the coating structure. The evolution of the microstructure depends on the composition of materials and temperature.

Based on the literature review, three criteria of TBC durability were estimated: β-depletion, Al-depletion and critical thickness of TGO, which can be used for different compositions of TBC’s bond coats. Corundum (α-Al2O3) is characterized by low growth rate and low diffusion capacity. Therefore, TGO, consisting of corundum, is considered preferable. For the MeCrAlY bond coat, the main source of aluminum for the formation of Al2O3 is the β-NiAl (β'-CoAl) phase. Other oxides, including Cr2O3, NiO, or various spinels, may form as aluminum concentrations decrease or temperatures rise.

Depending on the coating methods, the microstructure features, mechanical properties and bonding mechanisms of the coating layers may vary. The use of thermal methods of applying TBC’s bond coats leads to an increased initial content of oxides and, as a consequence, to a more intensive growth rate of TGO. The use of nanocrystallization coatings can reduce the grain size of the TBC’s bond coats, which con

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6.
dx.doi.org/ 10.18577/2307-6046-2019-0-10-61-75
УДК 620.193
Kurs M.G., Kutyrev A.E., Kirichok P.F., Fomina M.A.
ACCELERATED AND CYCLIC CORROSION TESTS OF AVIATION MATERIALS

The existing variety of methods for accelerated testing in climatic chambers often does not allow obtaining comparable results of material durability; However, the question of the possibility of predicting corrosion resistance according to the results of accelerated tests remains open and is the subject of research by many scientists around the world.

This paper presents the results of a study of the corrosion resistance of samples made of aluminum alloy 1163 and carbon steel 30HGSA when tested in a salt fog chamber and under accelerated cyclic testing according to the VDA 621-415 method compared with the results of full-scale exposure for 2 years in a moderately warm seaside climate zone.

The test results show the difference in the dynamics of local corrosion damage (depth of intergranular and pitting corrosion) of an aluminum alloy during accelerated tests compared to full-scale

ones, which makes it impossible to predict corrosion losses in atmospheric conditions according to the results of accelerated tests. The predominant tendency to pitting during accelerated testing compared with the prevailing tendency to MKC during full-scale exposure is due to some difference in the corrosion mechanism of aluminum alloys due to the presence of moisture films of different thicknesses on the surface of the samples. This demonstrates the need to develop accelerated testing methods that require greater compliance with full-scale tests, as well as the development of modes taking into account the corrosive aggressiveness of the atmosphere where the tested materials will be operated.

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7.
dx.doi.org/ 10.18577/2307-6046-2019-0-10-76-83
УДК 620.1:669.14
Gulina I.V., Sedov O.V., Yakovlev N.O., Grinevich A.V.
FEATURES OF THE TESTED BEARING STEEL

The article considers the problem of evaluating the performance of bearing steels based on standard methods of mechanical testing. To ensure high performance of the rolling bearing, it is necessary to implement a minimum contact area of the ball or roller with the rings. Therefore, the material must have high resistance to collapse. Slipping of balls and rollers along the rings leads to their abrasion. To ensure high abrasion resistance of the mating surfaces of the bearing, it is necessary to achieve maximum hardness of the material. Strength characteristics determined during standard tensile tests can serve as indicative indicators of the performance of the bearing material. The tensile strength correlates with hardness and, therefore, determines abrasion. Evaluation of the tensile strength is also an assessment of the crushing strength. The ultimate strength indirectly characterizes contact fatigue. Tensile testing of standard samples are the basic tests for testing the alloy composition and heat treatment modes. The first series of tests established the impossibility of assessing strength indicators using standard samples. The exceptional brittleness of bearing steel led to failure in fillets, which are stress concentrators. The fabricated samples were finalized with the formation of corset thinning in the working part of the sample. Tests of the modified samples allowed us to correctly assess the tensile strength of bearing steel. When testing bearing steel samples, the destruction mostly occurred along two planes, one of which is a plane of static destruction, and the second is caused by a tensile wave, which leads to the separation nature of the destruction.

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8.
dx.doi.org/ 10.18577/2307-6046-2019-0-10-84-94
УДК 669.017
Morozova L.V., Grigorenko V.B., Konyshev D.V., Vlasov A.I.
REASONS FOR THE DESTRUCTION OF SEPARATORS SINGLE-ROW RADIAL ROLLING BEARING STUDY

The paper presents the results of studies of operational fracture of single-row radial rolling bearings, in which cages of textolite and bronze alloy were used. The study of operational damage cases allows us to establish the cause of their occurrence and develop a set of recommendations and measures to eliminate adverse factors. To establish the causes of destruction, a comprehensive study was carried out using the methods of scanning electron and optical microscopy and X-ray spectral microanalysis. Studies of the chemical composition, microstructure and nature of the destruction of bearing parts have been carried out. It was established that the chemical composition of the material of the parts meets the requirements of regulatory documentation, there are no defects of metallurgical origin. In the steel parts of bearings, the content of non-metallic inclusions does not exceed 1 point, defects in the microstructure in the form of streakiness, carbide mesh and carbide segregation are not observed.

In bearings with PCB cages, as a result of cyclic loads, fatigue cracks formed in the rivets of the cage, which develop from surface damage. Under the influence of tensile stresses, the cross section was thinned and the rivets increased in length, which led to an increase in the gaps between the separator parts and the balls falling out of the separator cells. The displacement of the balls relative to the seats in the cage led to jamming of the bearing, heating of the parts and the final destruction of both rivets and textolite parts of the composite cage.

The destruction of the bearing with a bronze cage occurred as a result of uneven abrasive wear during operation. Uneven abrasion on the surface of the separator indicates a lack of lubricant and the effect of axial load resulting from slight misalignment during installation.

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9.
dx.doi.org/ 10.18577/2307-6046-2019-0-10-95-102
УДК 669.017.165
Alekseev A.V., Rastegayeva G.Yu., Pahomkina T.N.
DETERMINATION SULFUR, CARBON, NITROGEN AND OXYGEN IN ALLOYS OF SYSTEM Pr–Dy–Fe–Co–B AND Nd–Dy–Fe–Co–B

Modern navigation devices require the use of magnetic materials with both magnetic and thermostable properties. The most promising such materials are alloys of REM–Fe–Co–B (REM – rare earth metals). These alloys are increasingly used for the manufacture of magnets used in the production of dynamically adjustable gyroscopes (DNG) and accelerometers and are characterized by wider temperature ranges than previously used materials.

The main properties of alloys of REM–Fe–Co–B systems directly depend on their chemical composition, both on the content of the main components of the system, and on the content of various impurities – nitrogen, oxygen, carbon and sulfur. Production of high-quality materials is not possible without precise control of the content of these impurities in the alloys.

Classical methods for the determination of sulfur, oxygen, nitrogen and carbon are extremely time-consuming, time-consuming and require the use of a large number of different reagents and equipment. Modern methods for the determination of sulfur and carbon in various objects is the method of burning the sample sample in an induction furnace of the gas analyzer, followed by detection in the infrared cell of the spectrometer, and for the determination of nitrogen and oxygen, reducing melting in a vacuum or in an inert carrier gas stream is used.

In this paper, the alloys of Pr–Dy–Fe–Co–B and Nd–Dy–Fe–Co–B systems were analyzed for the content of gas-forming impurities. The sulfur and carbon content was determined by combustion in the induction furnace of the LECO CS-444 gas analyzer with subsequent detection in the infrared cell of the spectrometer, and for the determination of oxygen and nitrogen, the method of reducing melting in the inert carrier ga

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10.
dx.doi.org/ 10.18577/2307-6046-2019-0-10-103-110
УДК 699.81:678.747.2
Barbotko S.L., Volnyj O.S., Marachovskiy P.C.
INVESTIGATION OF THE INFLUENCE OF THE REINFORCEMENT SCHEME ON THE COMBUSTIBILITY CHARACTERISTICS OF CARBON FIBER REINFORCED POLYMER MATERIAL

Currently, the use of polymer structural composite materials (PCM) for the manufacture of aircraft components is constantly increasing. PCM have a number of advantages over traditionally used metal materials in terms of specific mechanical properties. However, unlike metal materials, PCM, due to the presence of a polymer matrix, are capable of combustion reactions and flame propagation on the surface.

In this paper, we continued research on the evaluation of carbon fibre reinforcement composite. The influence of the VKU-25 / SYT49S carbon-fibre reinforcement composite based on the VSE ‑ 1212 binder and SYT49S high-strength carbon rope on the combustibility characteristics determined in accordance with the requirements of aviation standards FAR‑25 Appendix F Part I has been studied. Fire tests were carried out according to the procedure set out in State Standard R 57924 (method 2).

To calculate the thermal conductivity of the material, an experimental determination of thermal conductivity (according to State Standard 57943), heat capacity (according to State Standard R 56754) and density (according to State Standard 20018) was carried out.

The significant effect of the reinforcement scheme on the value of the residual duration of combustion and the length of the burn-out is shown. It has been established that in the entire range of the studied material thicknesses (from 1 to 4 mm) the samples of unidirectional material with the orientation of the carbon filler [0] have significantly worse fire safety values compared to the samples with the orientation [90] or with an equally strong material (quasi-isotropic laying). The obtained results on the effect of the PCM reinforcement structure on the fire safety values can be explained by a significant difference in the thermal conductivity&

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11.
dx.doi.org/ 10.18577/2307-6046-2019-0-10-111-124
УДК 620.1
Podzhivotov N.Y.
EXPRESS METHOD OF A COMPARATIVE ASSESSMENT PROPERTIES LEVELS OF MATERIALS

The express method of a comparative assessment of levels properties of two and more materials, provided in article, is directed on a choice of the material possessing preferential level of properties in the conditions of empirical uncertainty.

This method allows to build consistently if necessary compared materials in an objective order of increase (reduction) of values of levels of their characteristics, for example for priority of their possible application or modernization within the considered constructive decision.

Important feature of an offered method is that this method allows to carry out comparison of values of estimates of levels properties of  the materials characteristics received experimentally both on small, and on big samples, i.e. regardless of the volume of experimental data. The main condition of correct comparison characteristics of materials is the equal quantity of experimental data according to each characteristic of each material. Thus this method does not extend on an order of receiving probabilistic estimates of levels of properties of materials. Compared characteristics thus have to be equivalent from the point of view of a preferential choice of a material. If separate characteristics of compared materials are not equivalent at a material choice on the importance for this or that design (conditions of operational loading etc., experience and the purposes of the researcher), this method allows introduction for such characteristics weight factors. The order of a choice and value of weight factors are an independent task and in this article are not considered.

At observance of a condition of equality of volume of the experimental data, the offered method allows to carry out comparison of unlimited number of materials on unlimited number of their characteristics. Thus, the more characteristics, an

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12.
dx.doi.org/ 10.18577/2307-6046-2019-0-10-125-132
УДК 620.1
Gorbovets M.A., Slavin A.V.
THE CODED MARKING OF SPECIMENS FOR HIGH-TEMPERATURE TESTS

In modern aviaengine building the great attention is given to indicators of durability, reliability and non-failure operation of nodes and design elements that, in turn, imposes high requirements of the materials applied in design. Assessment of physicomechanical properties of materials for determination of reliable values carry out in the accredited test laboratories. Requirements to test laboratories contain in ISO 17025–2009. In particular, one of requirements is ensuring identification of object of testing. The most reliable way for identification of sample is drawing marking (and other identification information) is direct on it even if it will be separated from packaging and is mixed with other samples. The analysis of existing ways of shaped coding is carried out and opportunity and expediency of their use with reference to test pieces is evaluated. Drawing alphanumeric marking on sample allows to identify visually unambiguously it without use of additional devices. 2D barcodes allow to cipher the bigger volume of information on the smaller area. For identification of metal samples for high-temperature tests by the optimum decision drawing complete (expanded) marking on packaging and the reduced marking on sample end face on which it is possible to identify unambiguously sample within sample party is. Thus it is necessary to take measures for exception of possibility of hashing of samples from different parties. For drawing expanded information on sample it is reasonable to use Data matrix code and to put it on sample packaging. Thus it is desirable to have at the enterprise database with the complete information about sample stories. Drawing Data matrix of code on end face of sample is the ambiguous decision. In spite of the fact that it provides unambiguous identification of sample, code damage is very probable during testing, additional expenditure for equipment acquisition for drawing code on sample thus are required.

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