ROLE OF GRAIN-BOUNDARY PHASE IN FORMATION OF STRUCTURE AND PROPERTIES OF MECHANOCOMPOSITES BASED ON COPPER AND IRON

KOVALIOVA Svetlana A., Senior Researcher, Joint Institute of Mechanical Engineering of the NAS of Belarus, Minsk, Republic of Belarus

ZHORNIK Viktor I., D. Sc. in Eng, Assoc. Prof., Head of the Laboratory of Nanostructured and Superhard Materials, Joint Institute of Mechanical Engineering of the NAS of Belarus, Minsk, Republic of Belarus, This email address is being protected from spambots. You need JavaScript enabled to view it.">This email address is being protected from spambots. You need JavaScript enabled to view it.

SHKURKO Vladimir V., Ph. D. in Phys. and Math., Assoc. Prof., Vice-Rector for Academic Work, Graduate School of the NAS of Belarus, Minsk, Republic of Belarus

The phenomenological description of the formation of mechanocomposites is proposed, which can be taken as model representations for obtaining the mechanocomposites from a wide range of metals with FCC and BCC lattice, as well as for forecasting of the structural state and properties of sintered composites based on them. The  main stages of the formation of the mechanocomposite include: 1) dispersion of the material and increase of its reactivity due to  defect formation; 2) fragmentation of the submicrostructure and formation of a “liquid-like” grain-boundary phase; 3)   deformation and diffusion saturation of the boundary phase by the segregations and followed crystallization of new phases according to the mechanism of the emergence and growth of nuclei with the formation of nanostructural composites. The mechanocomposites formed at the last stage are characterized by the increased strength properties and structural stability due to dispersion hardening by intermetallic compounds. The results of studying of the structural-phase evolution of the composites formed in the Cu-Sn and Fe-Ga systems during the mechanochemical synthesis are presented. The interrelation of the phase separation process during the synthesis of mechanocomposites with the features of the grain-boundary phase structure is considered. It is shown that the volume fraction of the grain boundary phase is formed at the level of 20–50 vol.% in the process of mechanocomposite synthesis. The materials obtained by the thermobaric sintering on their basis retain the nanosized structure and are characterized by high microhardness values (for Cu–Sn ~ 3 GPa, and for Fe–Ga ~ 7  GPa). The formation of dispersed inclusions in the alloy at the increased temperature of the annealing makes it possible to reduce the rate of microhardness decrease during heating and to provide its values at the level 2.5 GPa after annealing at 700 °С.

mechanochemical synthesis, mechanocomposite, grain boundary phase, dispersed hardening

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EFFECT OF MECHANICAL ACTIVATION AND HIGH PRESSURE HIGH TEMPERATURE TREATMENT ON SYNTHESIS OF MATERIAL BASED ON NANOSTRUCTURED BORON NITRIDE

SENYUT Vladimir T., Ph. D. in Eng., Leading Researcher of the Laboratory of Nanostructured and Superhard Materials, Joint Institute of Mechanical Engineering of the NAS of Belarus, Minsk, Republic of Belarus, This email address is being protected from spambots. You need JavaScript enabled to view it.">This email address is being protected from spambots. You need JavaScript enabled to view it.

KOVALIOVA Svetlana A., Senior Researcher of the Laboratory of Nanostructured and Superhard Materials, Joint Institute of Mechanical Engineering of the NAS of Belarus, Minsk, Republic of Belarus, This email address is being protected from spambots. You need JavaScript enabled to view it.">This email address is being protected from spambots. You need JavaScript enabled to view it.

VAL`KOVICH Igor V., Researcher of the Laboratory of Nanostructured and Superhard Materials, Joint Institute of Mechanical Engineering of the NAS of Belarus, Minsk, Republic of Belarus, This email address is being protected from spambots. You need JavaScript enabled to view it.">This email address is being protected from spambots. You need JavaScript enabled to view it.

ZHORNIK Viktor I., D. Sc. in Eng., Assoc. Prof., Deputy Head of the Department of Technologies of Mechanical Engineering and Metallurgy — Head of the Laboratory of Nanostructured and Superhard Materials, Joint Institute of Mechanical Engineering of the NAS of Belarus, Minsk, Republic of Belarus, This email address is being protected from spambots. You need JavaScript enabled to view it.">This email address is being protected from spambots. You need JavaScript enabled to view it.

WENSHENG Li, D. Sc. in Eng., Prof., Director of Science & Technology Department, Lanzhou University of Technology, Lanzhou, China, This email address is being protected from spambots. You need JavaScript enabled to view it.">This email address is being protected from spambots. You need JavaScript enabled to view it.

CHENG Bo, Ph. D. in Eng., Assoc. Prof., Researcher of the State Key Laboratory of Advanced Processing and Recycling of Non-Ferrous Metals, Lanzhou University of Technology, Lanzhou, China, This email address is being protected from spambots. You need JavaScript enabled to view it.">This email address is being protected from spambots. You need JavaScript enabled to view it.

DONGQING He, Ph. D. in Eng., Assoc. Prof., Researcher of the State Key Laboratory of Advanced Processing and Recycling of Non-Ferrous Metals, Lanzhou University of Technology, Lanzhou, China, This email address is being protected from spambots. You need JavaScript enabled to view it.">This email address is being protected from spambots. You need JavaScript enabled to view it.

ZHAI Haimin, Ph. D. in Eng., Assoc. Prof., Researcher of the State Key Laboratory of Advanced Processing and Recycling of Non-Ferrous Metals, Lanzhou University of Technology, Lanzhou, China, This email address is being protected from spambots. You need JavaScript enabled to view it.">This email address is being protected from spambots. You need JavaScript enabled to view it.

In the paper, the study of the influence of mechanical activation (MA) and subsequent high pressure high temperature (HPHT) treatment of the powder of hexagonal boron nitride (hBN) on its structure and phase composition is given. X-ray diffraction and electron microscope studies show that MA leads to the transformation of the BN substructure from crystalline to nanocrystalline and amorphous. At the same time, along with the formation of amorphous nanocrystalline cubic boron nitride (cBN) in BN powders after MA, another high-pressure phase  — wurtzite boron nitride wBN is formed. As a result of sintering of the hBN powders after MA under pressure of  2.5  GPa and under temperature in the range of 1000–1300 °C, in addition to the hBN, wBN and cBN phases, the BN phases of rhombic, hexagonal and tetragonal crystallographic systems are formed in the resulting material. The HPHT treatment of the hBN powders after MA under pressure of 7 GPa allows to obtain a material containing a cBN phase with cBN crystallites about 50 nm in size. The addition of aluminum decreases the sintering pressure, but at the same time, due to recrystallization, the grain size of cBN in the obtained material increases by an order of  magnitude compared with the original powder.

nanocrystalline BN, mechanical activation, chemical purification, high pressure high temperature

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INFLUENCE OF TIN IN UNDERLAYER MATERIAL ON AL-Si ALLOY STRUCTURE DEPOSITED USING CENTRIFUGAL INDUCTION METHOD

KOMAROV Alexander I., Ph. D. in Eng., Head of the Laboratory of Modification Technologies of Engineering Materials, Joint Institute of Mechanical Engineering of the NAS of Belarus, Minsk, Republic of Belarus, This email address is being protected from spambots. You need JavaScript enabled to view it.">This email address is being protected from spambots. You need JavaScript enabled to view it.

SOSNOVSKIY Igor A., Senior Researcher, Joint Institute of Mechanical Engineering of the NAS of Belarus, Minsk, Republic of Belarus, This email address is being protected from spambots. You need JavaScript enabled to view it.">This email address is being protected from spambots. You need JavaScript enabled to view it.

ORDA Dmitriy V., Junior Researcher, Joint Institute of Mechanical Engineering of the NAS of Belarus, Minsk, Republic of Belarus, This email address is being protected from spambots. You need JavaScript enabled to view it.">This email address is being protected from spambots. You need JavaScript enabled to view it.

KURILYONOK Artem A., Ph. D. in Eng., Senior Researcher, Joint Institute of Mechanical Engineering of the NAS of Belarus, Minsk, Republic of Belarus, This email address is being protected from spambots. You need JavaScript enabled to view it.">This email address is being protected from spambots. You need JavaScript enabled to view it.

ISKANDAROVA Donata O., Junior Researcher, Joint Institute of Mechanical Engineering of the NAS of Belarus, Minsk, Republic of Belarus, This email address is being protected from spambots. You need JavaScript enabled to view it.">donatаThis email address is being protected from spambots. You need JavaScript enabled to view it.

The results of metallographic studies, durometric and tribotechnical tests of coatings made of silumin AlSi12, deposited on a steel base by centrifugal induction surfacing are presented. To ensure the adhesion of the coating with the base during surfacing, babbit B83S and tin–lead solder POS61 were introduced to form a transition layer. It is established that when using B83S, tin is distributed throughout the coating with a certain degree of segregation to the steel base, and iron-containing inclusions are also present in the coating structure. The use of POS61 leads to increase in the homogeneity of the structure, while there are no inclusions of tin alloy. The obtained coatings are characterized by high tribotechnical properties. The average value of the coefficient of friction for the surfaced coatings using babbit is 0.031–0.037, and in the case of POS61, a decrease in the coefficient of friction to 0.010–0.013 with an increase in the load to 30 MPa is recorded. It is established that changes in the structure of the coating are mainly determined by the content of tin in the added alloy, and the presence of lead increases the rate of dissolution of iron in aluminum. It is assumed that the presence of iron-containing inclusions contributes to the tribotechnical properties improvement by increasing the proportion of solid particles in the soft matrix.

AlSi12, babbit B83S, POS61 tin-lead solder, induction surfacing, structure, transition layer, adhesive properties, X-ray spectral analysis, friction coefficient, wear resistance

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10. Sosnovskiy I.A., Belyavin K.E., Belotserkovsky M.A. K voprosu formirovaniya kontakta mezhdu poroshkovymi pokrytiyami i osnovoy [To the problem of formation of contact between powder coatings and the base]. Promyshlennost regiona: problemy i perspektivy innovatsionnogo razvitiya [Industry of the region: problems and prospects of innovative development], 2013, pp. 189–193.
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14. Luzhnikov L.P. Materialy v mashinostroenii. Vybor i primenenie. T. 1. Tsvetnye metally i splavy [Materials in mechanical engineering. Selection and application Vol.1. Non-ferrous metals and alloys]. Moscow, Mashinostroenie Publ., 1967. 304 p.

MATHEMATICAL MODELING AND MECHANISM OF COARSENING OF AUSTENITIC GRAIN AT HIGH-TEMPERATURE HEATING OF ALLOYED STRUCTURAL STEELS

KUKAREKO Vladimir A., D. Sc. in Phys. and Math., Prof., Head of the Center of Structural Research and Tribo-Mechanical Testing of Materials and Mechanical Engineering Products of Collective Use, Joint Institute of Mechanical Engineering of the NAS of Belarus, Minsk, Republic of Belarus, This email address is being protected from spambots. You need JavaScript enabled to view it.">This email address is being protected from spambots. You need JavaScript enabled to view it.

GACURO Vladimir M., Deputy Technical Director for Preparation of Metallurgical Production – Chief Metallurgist, OJSC “Minsk Tractor Works”, Minsk, Republic of Belarus

GRIGORCHIK Aleksandr N., Ph. D. in Eng., Senior Researcher, Joint Institute of Mechanical Engineering of the NAS of Belarus, Minsk, Republic of Belarus

CHICHIN Aleksey N., First Category Process Engineer, OJSC “Minsk Tractor Works”, Minsk, Republic of Belarus

The influence of the heating rate of typical cemented steels 15KhGN2TA and 25KhGT on the growth of austenitic grain at long isothermal exposures in the process of high-temperature chemical-thermal treatment is studied. It is shown that the change in the heating rate of cemented steels in the temperature range α → γ of transformation at chemical and thermal treatment has a significant impact on the growth process of austenitic grain in them. The equations of regression are obtained that describe the dependence of the average size of austenitic grain on the heating rate, pre-ignition temperature and cementation temperature, which allow to select the modes of cementation of different steels. The phenomenological model is developed which describes the mechanism of formation and growth of austenitic grains in the steels at heating with different speeds. The conclusion is made that the slow heating of the steels in the interval of phase α → γ transformation contributes to the formation of a complex of small austenitic grains separated by high angular boundaries with impurity atoms adsorbed on them, which provides the increased stability of the grain structure to coalescence and reduces the rate of boundary migration at long term high-temperature austenization.

high-temperature cementation, 15KhGN2TA and 25KhGT steels, austenitic grain size, heating rate

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