Last number

 
№7  2018

1.
dx.doi.org/ 10.18577/2307-6046-2018-0-7-3-9
УДК 669.715
Kuznetsov A.O., Oglodkov M.S., Klimkina A.A.
THE INFLUENCE OF CHEMICAL COMPOSITION ON STRUCTURE AND PROPERTIES OF Al–Mg–Si ALLOY

The analysis of Russian and foreign literature in aluminum high-end corrosion resistant alloys area was made. Main tendencies of development of high-end Al alloys are:

– enhancement of mechanical protrerties by means of Cu, Mg, Zn, transition and rare earth metals addition.

– enhancement of plasticity properties by means of microalloying and intermetallic phases control and by improvement of technological process.

– enhancement of corrosion resistance by means of Zn addition.

– enhancement of machinability by means of addition of Mg and Si in estimated ratio.

Four experimental compositions of Al-Mg-Si alloy were chosen for investigations.

The investigations of phases chemical composition by means of electron probe analysis were made. All of the samples have a typical Al2Si phase of their structure. Inhomogenized samples have a AlCu-type phase in structure which is dissolving in homogenization process. A structure of homogenized ingot has a nonequilibrium AlFeMn-type phase in its structure.

A microstructure analysis shown that Ti and Zr are good grain refiners. Ti creates an additional crystallization centers and as a result a quantity of nucleation centers and grain size decreases. A Zr addition leads to a Al3Zr dispersoids formation in alloy, which decreases a speed of grain boundary migration, as they are a barrier for dislocation movement.

A Cr and Ti addition as a Zr and V addition allows to enhance a crack resistance properties. A formation of finely divided phases in heat treatment could be the reason of it.

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2.
dx.doi.org/ 10.18577/2307-6046-2018-0-7-10-24
УДК 66.017
Antipov V.V., Petrova A.P., Kozlov I.A., Fomina M.A., Volkov I.A.
INFLUENCE OF TECHNOLOGICAL HEATINGS AND WAYS OF SURFACE PREPARATION UNDER PASTING ON MECHANICAL PROPERTIES OF ALUMINUM FOIL FROM ALLOY AMg2N

The influence of methods and technological modes of preparation of the surface of the AMg2N alloy foil on the corrosion resistance of the foil in the salt fog chamber, including after its exposure at a temperature of minus 60°C and plus 185°C. It was found that the samples of aluminum foil with the studied coatings and chemical treatment have low corrosion resistance: corrosion damage occurs after 168 hours of exposure in the salt fog chamber. The most significant corrosion damage is observed on foil samples preheated at 185°C for 24 hours. The use of an additional polymer coating with a thickness of up to 3 microns can significantly increase the corrosion resistance of aluminum foil with the studied coatings and chemical treatment: 336 hours of exposure in the salt fog chamber no corrosion. It was found that all the methods and technological modes of preparation of the surface of aluminum foil for bonding provide satisfactory corrosion resistance of the foil in the fuel and oil, including after its exposure at temperatures of minus 60°C and plus 185°C (weight loss is 0.1 g/m2).

It was found that in some cases the thermal effect on the foil at temperatures of minus 60° and plus 185°C leads to a change in the morphology and structure of its surface. Exceptions are uncoated foil samples and with Pickling treatment. The use of microarc oxidation and chemical oxidation leads to a significant increase in the specific surface area in contact with the glue, which should have a positive impact on the adhesive strength of the adhesive compound. When using "Pickling" treatment and ion-plasma deposition of Al2O3, the specific surface area of aluminum foil varies slightly (not more than 10%).

The study of the influence of methods of preparing the surface of aluminum foil on the strength characteristics of the adhe

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3.
dx.doi.org/ 10.18577/2307-6046-2018-0-7-25-32
УДК 621.74.045
Pentuykhin S.I., Trapeznikov A.V., Vlasova K.A., Klyukvina T.D.
DETERMINATION OF OPTIMAL MANUFACTURING TECHNOLOGY OF CASTING ALLOY АК7ч. WITH USING OF CERAMIC MOLDS

Investment casting is the process of making castings by pouring molten metal into a mold that is obtained using a wax model. This technology is a complex and time-consuming process that provides castings of complex configurations ranging in weight from a few grams to tens of kilograms, with a wall thickness of 0.5 mm, with a surface corresponding to the 4–6 grade of purity, and with high dimensional accuracy in comparison with other methods of casting. The dimensions of the castings obtained by the investment casting method are as close as possible to the dimensions of the finished part. By reducing the machining process, the cost of the finished product is reduced. In other words, the use of this technology allows you to get an accurate casting. So nowadays this technology is the most common for accurate casting.

In casting for investment models, accuracy is mainly determined by the parameters of their initial melting model (IM). In turn, the accuracy of any IM, the configuration features of the IM and rigging. The casting aluminum alloy АК7ч (AЛ9) was used as a material for the casting. This alloy refers to hermetic alloys of the Al–Si system (silumin).

The article contains data on the main requirements for the ceramic shell, as well as the method and materials used in its manufacture. An experiment was conducted to determine the required number of layers of ceramic coating for aluminum castings of various configurations.

It has also been revealed that the use of quartz sand as a supporting filler for castings made from aluminum alloys is unacceptable, due to a decrease in the heat transfer of the castings and, as a consequence, a deterioration in their mechanical properties, such as tensile strength and elongation.

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4.
dx.doi.org/ 10.18577/2307-6046-2018-0-7-33-40
УДК 669.14.018.8:669.715
Levchuk V.V., Trapeznikov A.V., Pentuykhin S.I.
CORROSION-RESISTANT FOUNDRY ALUMINUM ALLOYS (review)

In the article are presented an overview of aluminum alloys with different contents of magnesium and other alloying elements, such as titanium, beryllium, silicon, zinc and others. Aluminum casting alloys can be conditionally divided into three groups: corrosion-resistant, heat-resistant and high-strength. Aluminum corrosion-resistant alloys can be divided into various alloy systems, such as Al–Mg, Al–Mg-Si, Al-Zn-Mg. Aluminum corrosion-resistant alloys are divided into two subgroups: with magnesium content up to 6% – deformed alloys and more than 6% magnesium – cast alloys. The advantages and disadvantages of these alloys are described in the article, their mechanical characteristics and corrosion properties are presented.

The processes of interaction of metal of various aqueous media are related to the type of electrochemical corrosion. Local corrosion is formed by separate areas on the surface of the metal. Distinguish corrosion by stains, ulcers, point, and also intergranular.

All corrosion-resistant alloys of the Al–Mg system have a disadvantage – a relatively low operating temperature (usually up to 150°C). Preservation of mechanical properties and increase in operating temperature are the main directions in the development of aluminum cast corrosion-resistant alloys.

The work is executed within the implementation of the complex scientific direction 10.10. «Energy-efficient, resource-saving and additive technologies for manufacturing deformed semi-finished products and shaped castings from magnesium and aluminum alloys» («Strategic Directions for the Development of Materials and Technologies for Their Processing until 2030»).

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5.
dx.doi.org/ 10.18577/2307-6046-2018-0-7-41-48
УДК 669.721.5
Mostyaev I.V., Akinina M.V.
FEATURES AND DEVELOPMENT TRENDS IN THE FIELD OF HEAT TREATMENT OF MAGNESIUM ALLOYS (review)

Magnesium alloys with increased strength and heat resistance characteristics are promising the lightest structural material, which has a number of advantages over other metal structural materials: low density, high specific strength and specific rigidity, good damping, fatigue characteristics and manufacturability. Abroad and in Russia - these alloys find application in various modern branches of technology: electronics, automotive industry, aviation industry, medicine, etc. This explains the growing interest of developers to magnesium alloys.

The purpose of thermal processing of products from magnesium alloys is to increase the strength properties, increase plasticity, relieve internal stresses and stabilize properties.

The technology of heat treatment of deformable magnesium alloys, used at present, mainly uses the achievements of the past years. Nevertheless, in this area, research is being conducted, and there are achievements.

At present, several main directions in the field of heat treatment of deformable magnesium alloys can be noted: increasing the characteristics of deformable magnesium alloys according to the scheme: theoretical premises–alloy composition–technology of its production (including application of certain heat treatment regimes); selection and optimization of alloying alloy elements; use of combined schemes of TMP (thermomechanical treatment). However, the prevailing tendency is the dependence of the selection of the optimum mode of heat treatment on the content of alloying elements, mainly the REE, in the alloy.

It is shown that simultaneous application of two or more REEs belonging to different subgroups is effective. As a result of the joint doping of the magnesium alloy of rare earth elements from different subgroups, the time to achieve the greatest e

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6.
dx.doi.org/ 10.18577/2307-6046-2018-0-7-49-57
УДК 669.295
Panin P.V., Lukinа E.A., Alexeev E.B.
EFFECT OF HYDROGEN DOPING ON STRUCTURE AND PHASE COMPOSITION OF SHEET SEMI-PRODUCTS OF VT23 TITANIUM ALLOY

The influence of extra hydrogen doping on phase and structural transformations in high-strength VT23 alloy has been studied.

The samples of commercial sheet semi-products with 1.8 mm thickness have been chosen as research objects (chemical composition of the samples, % (wt.): Ti–4.5Al–4.0V–1.8Mo–0.86Cr–0.44Fe). Hydrogen doping has been accomplished in solid state by thermo-diffusion procedure with high-purity molecular hydrogen medium. A laboratory Siverts apparatus has been used for hydrogenation, the annealing process having been provided at temperatures of 650, 700, 750, and 800°С up to hydrogen concentrations 0.1–1.0% (wt.). After complete absorption of the desired amount of hydrogen the samples were cooled down to a room temperature with the rate ~1 K/s.

The volume ratios of a and b phases have been defined for room temperature state in dependence on hydrogen amount and hydrogenating annealing temperature. It has been shown that the alloy contains approximately 30 % (vol.) of b phase in annealed condition with initial hydrogen concentration of 0.006% (wt.). The increase of hydrogen content in the samples causes continuous increase of b phase volume fraction and decrease of primary aI phase content and particles size due to the a®b transformation initiated by hydrogen. It has been shown that doping with 0.1% (wt.) of hydrogen results in b phase volume fraction increase from 50 % after hydrogenation at 650°C to 80% after hydrogenation at 800°C. The dimensions of a particles within the mentioned conditions change from 0.6–1.2 to 1.8–2.2 mm.

It has been experimentally revealed that extra doping of the VT23 samples with hydrogen up to concentrations higher than 0.2% (wt.) at a temperature of 800°С, 0.3% (wt.) at 750°С, and 0.4% (wt.)&

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7.
dx.doi.org/ 10.18577/2307-6046-2018-0-7-58-68
УДК 669.295
Panin P.V., Dzunovich D.А., Lukinа E.A.
EFFECT OF HYDROGEN DOPING ON PROCESSING DUCTILITY AND TEXTURE OF SHEET SEMI-PRODUCTS OF VT23 TITANIUM ALLOY

The influence of extra hydrogen doping on processing ductility and crystallographic texture formation in high-strength VT23 alloy has been studied.

The plate-like samples of commercial sheet semi-products with the dimensions 1.8´10´70 mm have been chosen as research objects (chemical composition of the samples, % (wt.): Ti–4.5Al–4.0V–1.8Mo–0.86Cr–0.44Fe). Processing ductility evaluation has been accomplished by three-point bending tests of the samples being in contact with two carriers whereon localized loading (through the punches with diameters of 2 and 5 mm) is applied in the point of half-distance between the carriers.

It has been shown that doping of the samples with 0.1 % H (wt.) at a temperature of 750°C results in room temperature processing ductility increase in comparison to that in the initial state. These optimal hydrogenation parameters give the opportunity to provide after low-temperature (600°C) vacuum annealing the following ultimate tensile strength values: 1050 MPa for the rolling direction, and 1110 MPa for the transverse direction. It has been revealed that the higher strength values in the transverse direction are accounted for the preferred basal planes {00.2} location wherein sliding is activated at higher shear stresses, while increased elongation in comparison to that in the rolling direction is due to a phase grains repositioning upon deformation processes with prismatic {10.0}-type orientations formation which are favorable for plastic flow.

The research results have given the opportunity to develop recommendations on how to cut the sheets of 1,8–2,2 mm thickness: when bending is being accomplished by the punch with diameter less than 5 mm one should cut the sheet in such a way when a bending edge will be across the rolling direction.

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8.
dx.doi.org/ 10.18577/2307-6046-2018-0-7-69-77
УДК 669.018.95
Bolsunovskaya T.A., Efimochkin I.Yu., Sevostyanov N.V., Burkovskaya N.P.
THE GRAPHITE GRADES LUBRICATION EFFECT ON TRIBOTECHNICAL PROPERTIES OF THE METALLIC COMPOSITE MATERIAL

The article is devoted to the influence of graphite structure and its origin on tribotechnical properties in the composition of a copper-based composite material.

The research purpose is to establish tribotechnical properties of different graphite grades as solid lubricants in the composition of a copper-based metallic composite material.

Tribotechnical tests were carried out according to the finger-disk scheme with varying slip velocity and contact loading. For the tests, different crystalline structure graphite grades, dispersion and production method were chosen, such as colloid (C-1), fine-grained dense (PGM-7), coarse-grained (KK) and synthetic special purity State Standart 23463-79 (Especially Pure). Testing Specimens were produced by powder technology technics. The starting copper and graphite powders were spark plasma sintered.

Colloidal highly dispersed Graphite Grade possesses a fine-grained structure which allows it to be eventually highly distributed in the composite material matrix. The coarse-grained graphite and MPG-7 grade manufactured by sintering distinguish by the crystal structure. Synthetic graphite possesses a coarse-crystalline structure, high strength properties and chemical purity.

Tribotechnical tests have revealed the graphite grades effect on the friction coefficient and wear resistance of the composite material. The best antifriction properties showed by colloidal graphite.

The lowest resistance to antifriction (high friction coefficient and low anti-wear properties) was demonstrated by synthetic graphite.

Also tribotechnical tests have shown the increasing wear of the composite material in dependence of grain fineness of the graphite structure.

The tribotechnical properties of the sintered graphite depend on

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9.
dx.doi.org/ 10.18577/2307-6046-2018-0-7-78-87
УДК 678.067.5
Kondrashov S.V., Solovyanchik L.V., Melnikov A.A., Dyachkova T.P., Bouznik V.M.
HYBRID COMPOSITE FIBERGLASS FOR SHIELDING OF ELECTROMAGNETIC RADIATION OF ULTRAHIGH FREQUENCIES

Giving to polymeric composites of constructional purpose of padding functional properties, such as electrical conductivity and screening of electromagnetic waves of a radio-frequency range, is one of priority problems of the modern materials science. One of optional versions of the solution of this task is development of the hybrid polymeric composites (HPC) in which along with traditional reinforcing fillers (glass – or carbon fiber) various functional excipients use: carbon nanotubes, including functionalize, carboniferous and metal-containing nanoparticles, metal fiber nanocomposites.

In work hybrid fibreglasses on the basis of epoxy binding, modified by carbon nanotubes with covalently attachment carboxyl groups are synthesized, the maintenance of nanotubes made from 1 to 8%. The structure of the synthesized materials and also their electrophysical properties, reflectivities, passings and absorption of an electromagnetic radiation in the centimetric range of lengths of waves are investigated.

It is established that various technological modes of receiving modified POUND allow to receive GPKM which in one case can be characterized as «the poor metal», and in another – as «the poor dielectric». Both options of the received HPC are demanded and perspective for application as constructional and functional radio engineering materials.

In work it is shown that hybrid polymeric materials of the functional purpose with a high degree of admission can be made by receiving the coverings containing carbon nanotubes functionalize carboxyl groups and epoxy composition, on layers of the reinforcing excipient with its subsequent molding. The specific conductivity of HPC received in such a way reaches the size 1,6∙10-2 Sm∙sm-1.

Use as a part of a matrix of mix of oli

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10.
dx.doi.org/ 10.18577/2307-6046-2018-0-7-88-95
УДК 620.1:678.026
Alifanov E.V., Chaykun A.М., Gorlov D.S., Venediktova M.A.
FRICTION COEFFICIENT OF THE ALKYD COVERINGS WITH ABRASIVE FILLERS IN DRY CONDITION AND IN WATER

In article results of research of tribologal properties of model systems of nonskid coatings where, as polymeric basis it is taken one-component alkyd binding are provided, and as abrasive filler sand and electrocorundum of different fractional structure was applied.

Definition of friction coefficient were carried out on the tribometer CETR UMT-3MT with use of drive of R33HE350 for reciprocating motion at temperature 20°С. As counterbody the cylinder from polyurethane has been taken.

In work values of friction coefficient of model systems of nonskid coating, as are given in dry condition, and «drowned» in water. The main patterns of the theory of friction of polymers are also given and attempt to explain the obtained experimental data is made.

The provided data show that model systems with coarse abrasive fillers are characterized by high heterogeneity. In the course of definition of friction coefficient chipping of particles of filler is observed, and, first of all the biggest ones. Reduction of dispersion of filler leads to improvement of uniformity of received coverings, and, application of such thickeners as glass microspheres make additional positive impact. Thus the friction coefficient remains at rather high level.

Values of friction coefficients in the presence of water above, than in dry condition have shown significant amount of the studied model systems. That confirms efficiency of application of abrasive fillers for creation of nonskid coatings. In their absence (for pure aluminum and polymeric binding without filler) considerable falling of friction coefficient in water presence is observed, that is the typical effect of lubricant takes place.

Submitted data can be used when developing nonskid coatings which are actively app

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11.
dx.doi.org/ 10.18577/2307-6046-2018-0-7-96-105
УДК 620.193.21
Varchenko E.A., Kurs M.G.
CREVICE CORROSION OF ALUMINUM ALLOYS AND STAINLESS STEEL IN MARINE WATER

Crevice corrosion, as one of the most significant types of local corrosion of metals and alloys, plays a significant role in the destruction of structures, pipelines, instruments, machines. Since local corrosion causes the entire material effect of the process to concentrate on a very limited area, its danger is exceptionally high. In addition, local corrosion often appears suddenly and it can not be recognized in time. In connection with this, local corrosion studies are of great practical interest. Equally important is the scientific side of the issue, since the mechanism of these processes is very poorly understood.

Particularly sensitive to crevice corrosion are certain metals, the passive state of which is due to the access of oxidants, which ensure their preservation in the passive state. These include, first of all, stainless steels and aluminum alloys. Crevice corrosion of these materials is most actively developed in an atmosphere with a high content of chloride ions. However, most of the work on the investigation of crevice corrosion of metallic materials is based on the results of laboratory studies in chloride-containing solutions and in salt fog. In addition, fouling of structures in the sea also creates a condition for the appearance of gaps in which intense corrosion develops. In the present work, the results of studies of the resistance of metallic materials to crevice corrosion in natural sea water with qualitative assessment of biofouling are presented.

The estimation of the external appearance of the samples, the metallographic analysis, the estimation of the degree of biofouling of aluminum alloys AMg6, D16T and stainless steel 08X17 during testing for 3, 6 and 12 months in the natural sea water of the Black Sea (Gelendzhik Bay water area)

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12.
dx.doi.org/ 10.18577/2307-6046-2018-0-7-106-116
УДК 620.193:669.175
Kirichok P.F.
CORROSION CRACKING OF ALUMINUM ALLOYS AND STAINLESS STEELS: KEY FEATURES AND TEST METHODS (review)

Despite the abundance of works related to the study of the term "corrosion cracking", to counteract the occurrence of corrosion lesions and ways to increase the corrosion resistance of metallic materials, the search for answers to these questions still remains in demand. This is due primarily to the fact that most of the structural elements in operation face a prolonged joint impact of loads and aggressive working environments. The use of metal products and structures in such conditions is associated with the appearance of corrosion lesions and, accordingly, adversely affects their short-term and long-term physico-mechanical characteristics, is the cause of the change in the stress-strain state and, as a result, greatly reduces their bearing capacity of durability. As a result, emergency situations can occur and mechanisms fail before the technical deadlines stated in the technical and technical specifications.

Before proceeding to the methods aimed at studying the resistance of metals to corrosion attack during testing for stress-corrosion cracking, it is worthwhile to understand the essence of the term "corrosion cracking". According to information published in the Journal of Combustion, stress corrosion cracking is the destruction of various metals and alloys during the prolonged simultaneous exposure to it of corrosion damage and static tensile stresses. The effect of cyclic stresses on the occurrence of fatigue state of the material, and compression does not cause destruction.

Corrosion cracking occurs only with the simultaneous continuous action of a number of external and internal factors: the composition of the corrosive medium, the chemical and phase composition of the alloy, the nature and magnitude of internal stresses, the uneven distribution of tensile stresses, and the like. At the same time, changing these factors can lead to an increase or decrea

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