RU2509817C1 - Powder composite - Google Patents

Abstract

FIELD: metallurgy.

SUBSTANCE: invention can be used as a structural material for parts operated at high mechanical and thermal loads, for example, pistons of augmented ICEs operated at 350°C and higher. Proposed composition contains the following substances, in wt %: silicon - 12.05…14.65, nickel - 2.80…3.40, iron - 1.50…1.70, aluminium oxide - 1.05…1.30, carbon - 1.35…1.65, aluminium making the rest.

EFFECT: lower thermal expansion factor, higher heat and wear resistance.

4 dwg, 3 tbl

Description

The invention relates to the field of powder metallurgy, in particular, to heat-resistant and wear-resistant composite materials based on aluminum with a reduced coefficient of thermal linear expansion and can be used for parts operating under conditions of high mechanical (gas pressure, inertial forces) and thermal loads, in particular , for the manufacture of pistons of forced internal combustion engines (ICE).

The lateral surface of such a piston due to expansion due to heating is subject to wear when moving along the surface of the cylinder. As a result of the friction of the piston rings and the side surface against the cylinder walls, the piston heats up additionally. Due to the high temperature of the piston bottom surface, the strength of the material from which it is made is reduced, which can lead to the formation of cracks and even burnouts in it.

For ramped engines with a limited service life, the pistons of which during operation can heat up to 150 ... 200 ° C, solid pistons (cast or hot-stamped) made of special piston heat-resistant aluminum alloys are used. In particular, for the manufacture of pistons by chill casting, eutectically alloyed aluminum cast alloys based on the Al-Si system (silumins) of the AL25 and AL30 grades are used, having a tensile strength at normal temperature of 200 ... 240 MPa and a relative elongation of 0.2 ... 0.6% . At a temperature of 300 ° C, the tensile strength of these alloys decreases to 100 ... 10 MPa. The coefficient of thermal linear expansion (KTLR) of these alloys in the temperature range (20 ... 300) ° C is not less than 21 · 10 ^-6 1 / ° C (see Application of aluminum alloys: reference, ed. / M.B. Altman, Yu. .P. Arbuzov et al. - M.: Metallurgy, 1985, p.163-167).

Pistons obtained by hot stamping from wrought aluminum alloys based on the Al-Si system (for example, grades AK4, AK4-1), as a rule, have higher strength characteristics than cast alloys, but they have a higher KTLR value - (22.0 ... 24.3) -10 ^-6 1 / ° C (see Vyrubov D.N., Efimov S.I., Ivashchenko N.A. Internal combustion engines: design and strength analysis of piston and combined engines. - M. : Engineering, 1984, p.134).

After reaching such a level of ICE forcing, when the average effective pressure is 1.5 ... 1.8 MPa or more, the temperature of the piston head can reach 350 ° C and higher. In this case, the heat resistance level of the above and other standard aluminum alloys becomes insufficient so that they can be used for the manufacture of ICE pistons.At such heating temperatures, aluminum materials should also have significantly lower CTLR values than standard aluminum alloys (see Cutouts D .N., Efimov S.I., Ivashchenko N.A. Internal combustion engines: design and strength analysis of piston and combined engines. - M: Mechanical Engineering, 1984, p.129). This necessitated the manufacture of forced-piston engines as composite: the piston skirt, which is much less heated than the bottom, is made from standard heat-resistant aluminum alloys, and the bottom is made from heat-resistant materials with low KTLR capable of operating at temperatures of 350 ° C and above. In particular, to increase the heat resistance of the bottom of the piston, where the temperature of highly accelerated diesels can reach 350 ... 450 ° C, this part is reinforced with an insert made of heat-resistant material, for example, of heat-resistant steel 20Kh3MVF, which significantly increases the mass of the piston (see. Cutouts D. N., Efimov S.I., Ivashchenko N.A. Internal Combustion Engines: Design and Strength Analysis of Piston and Combined Engines. - M.: Mechanical Engineering, 1984, p.133).

With the development of heat-resistant composite materials based on aluminum, it became possible to reinforce the bottom of the pistons with inserts of such materials. For example, a heat-resistant dispersion-hardened composite material of the Al-CO system with a content of 4.0% by weight in its initial composition is known. carbon (see Belyavsky GI, Shalunov EP Obtaining bimetallic castings with inserts from dispersion-hardened composites // Foundry. - 1991. - No. 3, p.15-16), used for the manufacture of inserts for bottom parts of the composite piston. This material was obtained using the method of reactive mechanical alloying in an attritor and powder and granular metallurgy technologies. Its subgrain structure with mechanochemically synthesized from powder aluminum and carbon (in the form of soot) and aluminum and oxygen hardening phases, respectively, Al ₄ C ₃ and Al ₂ O ₃ with an average particle size of 40 nm provide the material with high tensile strength in conditions of normal temperature (500 ... 520 MPa), but, most importantly, at a temperature of 350 ° C - 200 ... 210 MPa. The connection of the reinforcing insert stamped from the rod of this material with the bottom of the piston from the cast aluminum alloy AL25 was carried out by the diffusion mechanism during the preparation of the piston by injection molding with crystallization under pressure (LCD). But at the same time, the CTLR of this aluminum material is slightly higher than the CTLR of the AL25 alloy, i.e. is equal to more than 21 · 10 ^-6 1 / ° C, and therefore during operation of the piston in the zone of diffusion connection of the insert with its bottom part there were additional stresses that adversely affect the strength of this connection.

Calculations made according to the methodology and formulas given in the source - Vyrubov D.N., Efimov S.I., Ivashchenko N.A. Internal combustion engines: design and strength analysis of piston and combined engines. - M .: Mashinostroenie, 1984, p.134-152 - showed that the aluminum material of the inserts for the bottom of composite pistons with a diameter of 72 ... 156 mm, heated during operation to a temperature of 350 ° C, must have a coefficient of linear thermal expansion in the temperature range testing (20 ... 150) ° C, equal to 17.5 · 10 ^-6 1 / ° C or less, with values of tensile strength at normal temperature not less than 600 MPa. Moreover, it must possess, in comparison with casting piston alloys, a certain reserve of plastic properties, in particular, the relative elongation of such an aluminum material should be at least 1.5%. At a test temperature of 350 ° C, its tensile strength shall not decrease below 180 MPa, and the coefficient of temperature linear expansion in the range of test temperatures (20 ... 350) ° C should increase more than 19.5 · 10 ^-6 1 / ° C.

Aluminum material with the above characteristics can be effectively used in forced-combustion engines in the form of solid pistons obtained by hot forging, or in the form of inserts for their bottom. In particular, the manufacture of the insert 2 of the bottom part of the composite piston shown in Fig. 1 from an aluminum composite material having a KTLR is significantly less than that of an aluminum cast alloy (for example, AL25), from which the piston skirt 1 is made by the method of LCD, firstly, to increase the strength of the connection of the heat-resistant insert with the bottom and skirt by creating a preload that increases as the piston heats up in zone A of this connection and, secondly, to reduce the volume change of the piston during operation by correctly calculating the height H annular collar insert. Therefore, you can create a smaller gap between the piston and the cylinder, which will reduce engine power loss, reduce oil and fuel consumption.

Due to the fact that in heterogeneous alloys the coefficient of temperature linear expansion is additive to the values of the thermal expansion coefficient of the phases that form the material (see Aluminum alloys. Industrial deformable, sintered and cast aluminum alloys: reference, manual. - M .: Metallurgy, 1972, p.326 ), the production of aluminum materials with low KTLR values is carried out by alloying aluminum with elements (primarily silicon) that reduce the KTLR of aluminum. But when the silicon content in cast aluminum alloys exceeds 15 mass%, even in the case of applying various modification methods, silicon forms coarse primary crystals, embrittlement of the alloy and reducing its strength and technological properties. At the same time, the minimum KTLR value in the test temperature range (20 ... 300) ° C of cast binary alloys of the Al-Si system is at least 21 · 10 ^-6 1 / ° C (see Application of aluminum alloys: reference, ed. / M.B Altman, Yu.P. Arbuzov et al. - M.: Metallurgy, 1985, p.163-167).

In the case of spraying a molten silicon-containing aluminum alloy with a high cooling rate of (10 ³ ... 10 ⁶ ) ° C / s -, it is possible to obtain a powder in which the silicon content reaches up to 30% of the mass. and more, and the structure of the material itself is quite fine-grained. In this way, for example, a sintered aluminum alloy CAC-1 is obtained with a silicon content of 25 ... 30% by mass. and nickel - 5 ... 7% of the mass., also reducing the CTRL of the alloy (see Kolachev B.A., Livanov V.A., Elagin V.I. Metallurgy and heat treatment of non-ferrous metals and alloys: a textbook for universities. - M.: Metallurgy, 1981, p.145). This alloy has a CTLR at a test temperature of (20 ... 100) ° C equal to (14.5 ... 15.5) 10 ^-6 1 / ° C, but has a low tensile strength even at normal temperature (no more than 240 MPa), and also brittle (elongation does not exceed 0.5%).

Even lower KTLR values - (14 ... 15) 10 ^-6 1 / ° C - at a test temperature of (20 ... 100) ° C have an aluminum composite material obtained by powder metallurgy from rapidly crystallized alloy powder containing 36% by weight. silicon and 1% of the mass. magnesium, to which graphite was mixed in an amount of 1% of the mass. (see Volochko A.T., Rumyantseva I.N. Composite high-alloyed aluminum materials: thesis. report of the 3rd All-Union Conference on Pellet Metallurgy. - M.: VILS, 1981, p. 32-33). Here, graphite, having a coefficient of linear thermal expansion almost equal to the thermal expansion coefficient of silicon, is used as an additive that simultaneously reduces the thermal expansion coefficient of the material and increases its antifriction properties. But this material cannot be used at a temperature of 350 ° C, because even at normal temperature it has low strength characteristics - for example, hardness is only 80 ... 95 HB.

It is known (see. Portnoy K.I., Babich B.N. Dispersion-hardened materials. - M .: Metallurgy, 1974, p. 45-45) that for providing aluminum materials with high strength characteristics at temperatures equal to 0.85 ... 0.90 of the melting temperature of aluminum, and, in particular, at 350 ° C, it is necessary to inhibit grain growth during heating due to the presence of thermodynamically stable particles of the second phase in the matrix of the material, which impede the slip of dislocations. Such a second phase can be oxides, carbides, nitrides, borides of aluminum and other metals, which not only provide dispersed hardening of aluminum, but, having a low CTRL, equal for most of them (6 ... 8) 10 ^-6 1 / ° C also reduce its coefficient of temperature linear expansion. Moreover, the smaller the particles of the second phase, the higher, with an equal volume in the material, its heat resistance.

It is most simple, productive, and inexpensive to carry out disperse hardening of aluminum with particles of its oxide, carbide, boride, and nitride of a nanoscale level (less than 100 nm) by treating aluminum powder with appropriate additives and in a suitable medium in high-energy ball mills, for example, in attritors providing mechanochemical synthesis of these particles. When processing aluminum powder in an environment of oxygen or heated nitrogen, aluminum oxide or nitride can be synthesized, respectively, and when carbon (in the form of soot or graphite) or boron powder is added to aluminum powder, aluminum carbide or boride are formed, respectively.

The closest in technical essence and the achieved effect to the claimed invention is taken as a prototype (see RF patent No. 2353689 dated 11/15/2006, published 04/27/2009) powder composite material containing aluminum, silicon, nickel, beryllium, oxide aluminum and carbon in the following ratio of components (% wt.):

silicon 35.0 ... 46.0; nickel 2.0 ... 5.0; beryllium 0.0001 ... 0.049; aluminium oxide 0.1 ... 3.0; carbon 0.5 ... 2.0; aluminum rest.

In the preparation of this material, we used both fast crystallization of a melt containing aluminum, silicon, nickel, and beryllium to obtain a sprayed alloy powder, and subsequent mechanical alloying of this powder with dispersed carbon and silicon in a nitrogen – oxygen mixture in the aggreter. Due to such a high content in the material of components that reduce the thermal expansion coefficient of aluminum, it has a low coefficient of linear thermal expansion equal to (9.94 ... 14.40) 10 ^-6 1 / ° C in the test temperature range (20 ... 150) ° C. However, the extremely high supersaturation of aluminum solid solution does not allow it to effectively interact with carbon when processing atomized alloy powder in an attritor and, thus, to form finely dispersed aluminum carbide, which could provide dispersed hardening of the material and give it heat-resistant properties. As follows from the description of the prototype, the main functions of carbon in the production of this material are to provide a lubricating effect during mechanical alloying, preventing clumping of powder particles, and reducing, when in free form, the coefficient of linear thermal expansion of aluminum material.

The supersaturation of the aluminum solid solution together with the use of an oxygen-nitrogen medium during processing in the attritor provides the final material with a low aluminum oxide content of 0.1 ... 3.0 mass%, at which the material cannot have the required level of heat resistance. So, when the content of aluminum oxide in the standard aluminum alloy SAP-1 obtained from processed in a ball mill in an oxygen atmosphere of aluminum powder, in an amount of even 6 ... 9% of the mass. this alloy has a tensile strength at normal temperature of 300 MPa, and at a temperature of 350 ° C it is only 140 MPa (see Kolachev B.A., Livanov V.A., Elagin V.I. Metallurgy and heat treatment of non-ferrous metals and alloys: textbook for universities. - M .: Metallurgy, 1981, p.142-143).

The above allows us to conclude that the powder composite material, which is the prototype of the claimed invention, has a low level of dispersion hardening by particles of carbide and aluminum oxide, and therefore, it does not have the required heat resistance and cannot be operated at temperatures of 350 ° C,

In addition, this material has a very low ductility: elongation does not exceed 0.5%. So, the relative elongation of a standard sintered aluminum alloy САС-1, containing a total significantly less silicon and nickel (silicon - 25 ... 30% mass. And nickel - 5 ... 7% mass.) Than the powder composite material, which is the prototype of the claimed invention, is only 0.5% (see Kolachev B.A., Livanov V.A., Elagin V.I. Metallurgy and heat treatment of non-ferrous metals and alloys: textbook for universities. - M .: Metallurgy, 1981, p. 145). In addition, the mechanical alloying used in the preparation of a powder composite material in the attritor always leads to a decrease in the plastic properties of materials made in this way (see Shalunov E.P. Strength and ductility of bulk nanostructured materials obtained by reactive mechanical alloying // Actual problems of strength: Sat Tr. 53rd international scientific conference, Vitebsk, October 2-5, 2012 - Vitebsk: UO "VSTU", 2012. - P.120-1221.

The deficient and expensive beryllium contained in the powder composite material, although it is an element that effectively reduces the thermal expansion coefficient of aluminum, also leads to embrittlement of the material and increases its cost (see Aluminum alloys. Industrial wrought, sintered and cast aluminum alloys: reference, manual. - M .: Metallurgy, 1972, p.326).

The task to which the claimed invention is directed is to create a powder composite material based on aluminum with a set of interconnected physical, mechanical, technological and operational properties and low cost, capable of being used in pistons of forced internal combustion engines at a temperature of 350 ° C and above.

The expected technical result is to provide the claimed material with a tensile strength at normal temperature of at least 600 MPa with a relative elongation of at least 1.5% and a tensile strength at a temperature of 350 ° C of at least 180 MPa with a coefficient of linear thermal expansion in the test temperature range (20 ... 150) ° C, equal to not more than 17.5 · 10 ^-6 1 / ° C, and equal to not more than 19.5 · 10 ^-6 1 / ° C in the temperature range (20 ... 350) ° C, due to, before total selection of a balanced chemical composition of the material, as well as use to obtain it echnology providing simultaneous intensive plastic deformation, precipitation hardening and dispersion hardening additively influencing the formation of the desired structure and properties of the resultant material.

The expected technical result is achieved in that the aluminum-based powder composite material containing silicon, nickel, aluminum oxide and carbon additionally contains iron in the following ratio of components,% mass:

silicon 12.05 ... 14.65; nickel 2.80 ... 3.40; aluminium oxide 1.05 ... 1.30; carbon 1.35 ... 1.65; iron 1.50 ... 1.70; aluminum rest.

The above chemical composition is obtained by mixing the pre-obtained rapidly crystallized atomized powder of an aluminum alloy of the Al-Si-Ni-Fe system and a pre-prepared powder mixture consisting of technical aluminum powder and carbon black.

Obtaining powder compositions of the above chemical composition and their further processing into the final powder composite material is as follows.

1. Preparation of a melt of an aluminum alloy of the Al-Si-Ni-Fe system of the compositions given in Table 1 based on pig aluminum A7 grade (GOST 11070-74) by introducing AlSi50 grade silicon alloys (EN AM-91402) and nickel pelletized alloys into it TPF-12 grade and TPF-13 grade iron.

Table 1 Aluminum alloy melt composition number (aluminum alloy powder composition number) The content of components in the molten aluminum alloy,% mass .: Si Ni Fe Al one 2 3 four 5 one 26.3 7.6 3.2 rest 2 26.3 6.2 2.7 rest 3 26.3 5.1 2,3 rest

2. Spraying with compressed nitrogen the prepared melt of the compositions indicated in Table 1 with a cooling rate of 10 ⁴ ° C / s with trapping the resulting atomized powder of aluminum alloy in a neutral nitrogen atmosphere.

3. Preparation of a powder mixture consisting of 97% of the mass. powder of industrial aluminum brand PP-1 (GOST 5591-71), which contains surface films of aluminum oxide in an amount of 2.4% wt., silicon - 0.4% of the mass. and 0.5% of the mass. iron), and 3% of the mass. carbon black in the form of carbon black brand DG-100 (GOST 7885-77, with the following components in the powder mixture (% wt.):

carbon 3.00; aluminium oxide 2.33; silicon 0.39; iron 0.49; aluminum rest.

4. Preparation of powder compositions consisting of rapidly crystallized atomized powder of an aluminum alloy and a powder mixture, are given in table 2 of the compositions.

table 2 The composition number of the powder composition (composition number of the composite material) The composition of the powder composition,% mass. The content of components in the powder composition,% mass .: atomized aluminum alloy powder powder mix Si Ni Fe Al ₂ O ₃ C Al composition number content one 2 3 four 5 6 7 8 9 10 one one 45 55 12.05 3.40 1.70 1.30 1.65 rest 2 3 55 45 14.65 2.80 1,50 1.05 1.35 rest 3 2 45 55 12.05 2.80 1,50 1.30 1.65 rest four 2 fifty fifty 13.50 3.10 1,60 1.15 1,50 rest 5 2 55 45 14.65 3.40 1.70 1.05 1.35 rest

5. Processing of powder compositions in the attritor with a working chamber capacity of 15 l for 120 min with a rotor speed of 600 rpm, with a ratio of the mass of grinding balls to the mass of the processed powder composition as 24: 1, in the air of the working chamber of the attritor.

6. Sieving of powder compositions obtained in the attritor by reactive mechanical alloying on sieve 016 (GOST 6613-86).

7. Cold two-sided compacting of the powder compositions obtained by reactive mechanical alloying in a rigid container of a hydraulic press with a pressure of 600 MPa into briquettes with a diameter of 25 mm.

8. Hot vacuum degassing of briquettes in a vacuum furnace at a temperature of 500 ° C with holding at this temperature for 60 minutes and a residual pressure in the furnace of 5 · 10 ^-4 mm. Hg (1.33 · 10 ^-8 bar).

9. Heating degassed briquettes in an electric furnace to a temperature of 450 ° C, holding at this temperature for 60 minutes and subsequent hot extrusion into rods with a diameter of 6.5 mm from a hydraulic press container heated to 415 ° C with a pressing speed of 4.20 mm / s and the degree of drawing equal to 17.

Samples were made from the obtained rods, which were subjected to various types of research and testing by standard methods.

Based on the metallographic studies, it was found that during processing in the attritor, the rapidly crystallized powder, which had the correct (spherical) shape in the initial state (Fig. 2), after processing in the attritor began to have a comminuted shape (Fig. 3), which indicates grinding powder during processing in the attritor.

Studies of the fine structure of rapidly crystallized atomized powder, carried out using X-ray analysis methods, before and after its processing in the attritor showed that if the average size of coherent scattering blocks characterizing the approximate size of subgrains for the powder before processing in the attritor is 140 nm, then after processing it is 42 nm . This indicates a strong grinding of the initial powder structure during intense plastic deformation (SPD) occurring during processing in the attritor, due to which the measured microhardness of the powder treated in the attritor increased by 2 times. Due to the high degree of SPD, the obtained powder composite material possesses not only a highly ground fine structure, but also a highly ground macrostructure shown in Fig. 4.

The inventive powder composite material does not contain scarce and expensive beryllium, which positively affects the cost of the material. But this material, in addition to silicon, nickel, aluminum oxide and carbon, additionally contains iron, which is many times cheaper than beryllium, but has the same coefficient of thermal linear expansion - approximately 12 · 10 ^-6 1 / ° C at a test temperature range of 20 ... 100 ° C.

Metallographic studies, including using a scanning electron microscope with a local X-ray microanalyzer, revealed that iron, being in the inventive composition in a rapidly crystallized aluminum alloy powder, forms a dispersed intermetallic phase Al ₃ Fe with aluminum. In the rapidly crystallized atomized aluminum alloy powder, the primary Al ₃ Fe crystals had the form of branched dendrites, but after the powder was processed in the attritor, they were ground to a submicrocrystalline state. By transmission electron microscopy using thin fouls from a bar of the obtained powder composite material and carbon replicas from its thin sections, it was found that the average Al ₃ Fe particle size is 130 nm. As is known (see Lebedeva T.I., Konkevich V.Yu., Skotnikov I.A. Features of the hardening mechanism of ultrafast crystallized alloys based on an aluminum-iron system: abstract of the 3rd All-Union conference on pellet metallurgy. - M .: VILS, 1981. p.5), the Al ₃ Fe phase is stable when heated to 350 ° C and, in such a ground state, is an effective obstacle to slip dislocations and, accordingly, inhibits the grain growth of the material upon heating, providing it with high stability to softening and heat resistance.

The presence of iron in the obtained powder composite material also ensured the bonding of part of free silicon, which negatively affects the plastic properties of aluminum alloys and develops a tendency to heat resistance in them (see Kolachev B.A., Livanov V.A., Elagin V.I. heat treatment of non-ferrous metals and alloys: a textbook for universities. - M .: Metallurgy, 1981, p. 58-61), in the α phase (AlFeSi), which reduced the risk of formation of cracks in the material during heating and ensured an increase in its plastic properties .

In the claimed material, due to a significant decrease in the content of silicon compared to the prototype material, the degree of oversized aluminum solid solution is reduced and, thereby, its reactivity to form, in addition to the Al ₃ Fe phase, mechanochemically synthesized strengthening thermodynamically stable particles of the second phase (aluminum oxide) and aluminum carbide), which are also an obstacle to the slip of dislocations and, accordingly, inhibit the grain growth of the material upon heating, providing it with high stability resistance to softening and heat resistance.

Using transmission electron microscopy using thin foils from a bar of the obtained powder composite material and carbon replicas from its thin sections, it was also found that it also contains inclusions with an average size of 43 nm. Calculation of electron diffraction patterns obtained in the mode of macrodiffraction on thin foils with a diameter of 3 mm, as well as X-ray diffraction and x-ray phase analysis on a diffractometer, including anode precipitates of dissolved material, made it possible to establish that these inclusions are particles of Al ₂ O ₃ and Al ₄ C ₃ aluminum carbide . The content of alumina in the rod of the obtained powder composite material is 6.6 ... 6.9% by mass, which is more than 5 times its content in the original powder composition and 2.3 ... 66 times its content in the material selected as a prototype of the claimed invention. This is explained by the fact that to ensure a high content of aluminum oxide in the claimed material, technical aluminum powder is additionally introduced into the initial powder composition, which, when processed in an attritor, mechanochemically synthesizes additional aluminum oxide particles with an oxygen atmosphere in the working chamber of the attritor, moreover, at a nanoscale level. Moreover, their number is much larger than the number of larger (100 ... 200 nm) alumina particles, which are crushed films of this compound, with which particles of aluminum powder were originally coated.

Due to the reduction in the degree of supersaturation of the aluminum solid solution and the presence of technical aluminum powder additionally introduced into the initial powder mixture, free aluminum becomes enough to mechanically chemically synthesize with carbon the necessary volume of particles of aluminum carbide of a nanoscale level and not leave free (residual) material in the matrix ) carbon, which adversely affects the strength and plastic properties of the material. The content of Al ₄ C ₃ in the obtained powder composite material is, depending on the specific chemical composition of the initial powder composition, from 4% by weight. up to 5% of the mass.

Studies of the structure of the powder composite material found that it also contains silicon particles with sizes of 8 ... 12 microns and Al ₃ Ni compounds with a size of 15 ... 22 microns. Individual inclusions reach sizes of 25 ... 30 microns.

The fine structure and macrostructure of the inventive powder composite material described above is formed as a result of the implementation of three simultaneously proceeding processes upon receipt thereof:

- intense plastic deformation, providing a finer structure and strong hardening of the material;

- dispersion hardening, providing the formation of fine phases Al ₃ Fe, α (AlFeSi) and Al ₃ Ni;

- dispersed hardening, ensuring the formation of particles of thermodynamically stable phases Al ₂ O ₃ and Al ₄ C ₃ nanoscale level.

Due to the balanced chemical composition claimed as an invention and the described structure, the obtained powder composite material has a high degree of hardening that persists when it is heated, which leads to high heat resistance of this material.

Table 3 shows the main physical and mechanical properties of the obtained powder composite material and, for comparison, the prototype material.

From table 3 it follows that the inventive powder composite material has a tensile strength at normal temperature of 600 ... 650 MPa with a relative elongation of 1.7 ... 2.5% and 180 ... 195 MPa at a test temperature of 350 ° C, while the coefficient of thermal linear expansion in the test temperature range (20 ... 150) ° C is (16.8 ... 17.4) · 10 ^-6 l / ° C and in the test temperature range (20 ... 350) ° C - (18.9 ... 19.5 ) · 10 ^-6 1 / ° C.

Table 3 Powder Composition Number
material Absolute density at a temperature (° C) of tests, g / cm ³ Tensile strength at temperature (° C) of tests, MPa Elongation at temperature
re (° C) tests,% Precision limit of proportionality at temperature (° C) of tests, MPa Vickers hardness at temperature
re (° C) tests, MPa The coefficient of temperature linear expansion in the temperature range (° C) of the test, 10 ^-6 1 / ° C twenty twenty 350 twenty twenty 350 twenty 20 ... 150 20 ... 350 one 2 3 four 5 6 7 8 9 10 one 2.68 645 195 1.9 215 65 1760 17.4 19,4 2 2.69 600 180 2,5 180 55 1620 17.1 19,2 3 2.62 650 195 1.7 195 60 1775 17.5 19.5 four 2.68 625 190 2.2 190 60 1705 17.3 19,4 5 2.70 605 185 2,3 180 55 1640 16.8 18.9 Prototype 2,52-2,66 38-57 9.94-14.40

Such material characteristics make it possible to obtain the expected technical result and on its basis provide a solution to the problem posed in the invention aimed at creating a powder composite material based on aluminum with a set of interconnected physical, mechanical, technological and operational properties and low cost, capable of being used in forced pistons internal combustion engines at a temperature of 350 ° C and above.

Compared with the powder composite material adopted as a prototype of a technical solution, the claimed material really has significantly higher strength characteristics. In particular, the precision proportionality limit characterizing the ability of a material to resist microplastic deformations under short-term loading of the prototype material at normal temperature is 38 ... 57 MPa, while this characteristic of the claimed material is 55 ... 65 MPa, and at a test temperature of 350 ° C. At normal temperature, it reaches 180 ... 215 MPa.

The coefficient of thermal linear expansion of the claimed material, as expected, has higher values than the material of the prototype, but these values are balanced with the strength characteristics of the material, especially at high temperatures and are quite sufficient to achieve the goals of the invention.

Additionally, comparative bench tests of ring samples with a diameter of 50 mm and a wall thickness of 10 mm made from the inventive powder composite material and used for the manufacture of ICE pistons of standard aluminum alloys AL25 (Al - 12% Si - 1.2% Mg - 2% Cu - 1% Ni -% 1 Fe - 0.5% Mn) and AK12M2MgN (Al - 12% Si - 1.2% Mg - 2% Cu - 1% Ni -% 1 Fe - 0.4% Mn), paired with pins with a diameter of 10 mm from gray cast iron SCH20, pressed by a force of 200 N to the lateral surface of the rings rotating at a speed of 7 m / s, it was found that the wear of the rings of the claimed composite of the material is 3.5 times lower than the wear of the rings from cast aluminum AL25 alloy and 2.8 times lower than the wear of the rings from wrought aluminum alloy AK12M2MgN. This allows us to consider the claimed material more wear-resistant compared to modern aluminum alloys used for the manufacture of cast and hot-stamped pistons of internal combustion engines, including forced ones.

Due to a significant reduction in the content of the claimed material alloying elements and the rejection of its alloying with scarce and expensive beryllium, it is cheaper than the prototype material.

Claims (1)

An aluminum-based powder composite material containing silicon, nickel, aluminum oxide and carbon, characterized in that it additionally contains iron in the following ratio, wt.%:
silicon 12.05 ... 14.65 nickel 2.80 ... 3.40 aluminium oxide 1.05 ... 1.30 carbon 1.35 ... 1.65 iron 1.50 ... 1.70 aluminum rest

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