RU2244135C2 - Valve of internal combustion engine, method of its manufacture, and heat resistant titanium alloy used for its manufacture - Google Patents

Abstract

FIELD: mechanical engineering; piston internal combustion engines.

SUBSTANCE: invention relates to valve of internal combustion engine, method of its manufacture and heat-resistant titanium alloy used for manufacture of valve consisting of following components, mass %: aluminum 7.5-12.5; molybdenum 1.6-2.6; zirconium 1.4-2.4; silicon 0.1-0.2' yttrium 0.005-0.1; titanium - the rest. It has α+α₂+β phase composition with intermetallide α₂ phase on Ti₃Al base dispersed in α phase. Proposed method includes forming of valve from cylindrical blank by deformation machining with preliminary heating and subsequent heat treatment. Preliminary heating of part of blank related to rod done to temperature 5-20^oC lower than temperature of complete polymorphic transformation of alloy, and its deformation machining is carrying out by wedge cross rolling. Deformation machining of part of blank related to head is done by forging with preliminary heating to temperature 5-50^oC higher than temperature of complete polymorphic transformation of alloy corresponding to beginning of forging, and forging is finished at temperature lower than complete polymorphic transformation of alloy to form plate head of valve and transition section provided smooth changing of head into rod. Invention provides designing of valve, method of its manufacture and heat-resistant alloy used in manufacture of valve making it possible to operate valve within operating temperature range owing to increased long-term strength and creep resistant of valve head material and increased strength, modulus of elasticity and hardness of valve rod material.

EFFECT: improved quality of valve and increased reliability in operation.

16 cl, 3 tbl, 1 ex, 15 dwg

Description

The field of technology. The invention relates to mechanical engineering, more specifically to engine building, and can be used in reciprocating internal combustion engines (ICE).

The prior art. Over the long period of development of internal combustion engines for various purposes and taking into account the experience of their operation, designs, materials and methods of thermal hardening for intake and exhaust valves have been worked out, which mainly ensure the reliability and durability of engine operation. As materials for the manufacture of ICE valves, special steel grades are usually used. However, in the manufacture of valves from steels having a high density (ρ = 7.63 ... 8.0 g / cm ³ ), the mass of valves is significant, which is a negative factor for valve mechanisms of modern high-speed engines operating at high speeds and accelerations . High inertial loads due to the mass of the valves lead to the appearance of increased loads in the links of the valve drive mechanisms, significant shock loads when the valves are planted in the seats. This, in turn, causes a decrease in the reliability and reliability of the gas distribution mechanism and the engine as a whole. Of the total number of failures of gasoline engines, the gas distribution mechanism accounts for up to 45% of failures, and their main share is associated with defects in exhaust valves. The mass of valves is one of the limiting factors when creating high-speed engines of special design and engines of sports cars. Piston ICE valves (especially exhaust valves) work under conditions of increased thermal loads. So, taking into account the variety of piston ICEs produced: stationary, transport (ship, diesel, tractor, aviation, automobile, motorcycle) and special designs, the steady-state temperatures in the center of the valve heads are 500 ... 650 ° C for inlet valves, for exhaust valves 650 ... 900 ° C (see Fig. 14 and 15). Moreover, in the transition zone from the valve head to the stem, large temperature differences occur, reaching 200-300 ° C in the axial direction. In the valve head itself, temperature differences reach 150-200 ° C in the radial direction. This leads to a high level of temperature stresses in the valve head and in the transition zone and accelerated destruction of the valves (see Internal Combustion Engines: Design and Strength Analysis of Piston and Combined Engines. Edited by A.S. Orlin, M.G. Kruglova. - 4th ed., Revised and enlarged - M .: Mechanical Engineering, 1984, pp. 247-250, 258. / Raikov I.Ya., Rytvinsky G.N. Design of Automobile and Tractor Engines.M .: Higher School 1986, pp. 115-119).

In order to reduce the weight of the valves, increase their long-term heat resistance and create the prerequisites for improving the design of ICE with significantly improved indicators of fuel economy and exhaust emissions, new materials with a lower density and increased heat resistance are being searched for, as well as methods for manufacturing gas distribution valves from them. Of the new materials, these conditions are largely met by alloys based on titanium and titanium intermetallic compounds of the titanium-aluminum (Ti-Al) system, which have high heat resistance at low density (ρ = 3.9-4.2 g / cm ³ ). The most actively studied and prepared for use are alloys based on intermetallic compounds containing an α ₂ phase based on the Ti ₃ Al compound, or a γ phase based on the TiAl compound. These compounds and alloys based on them have advantages in heat resistance and modulus of elasticity over traditional titanium alloys; the level of operating temperatures for them is 750-900 ° C. Alloys based on the TiAl intermetallic compound containing the γ phase have very low ductility at room temperature (δ = 0.5-1.5%) and are mainly manufactured by casting technology. Alloys based on the γ phase with a level of operating temperatures up to 850 ° C are known, including for creating exhaust valves (see Table 1, items 1, 2). However, valves made by foundry technology are characterized by porosity due to the distributed shrink shell and a characteristic cast structure with crystallization segregation. “Healing” of foundry porosity is possible only with high-temperature gas isolation. As a result, internal combustion engine valves made of γ-phase-based alloys have an increased manufacturing cost (see Structure and properties of semi-finished products from Ti-48Al-2Nb-2Cr alloy based on TiAl intermetallic obtained by shaped casting (Lukyanichev S.Yu. et al. - Light Alloy Technology, 1996, No. 3, p. 16 / A. Choudhury, M. Blum, P. Busse, D. Lupton, M. Gorywoda. Herstellung von TiAl-Ventilen Durch Schlendergub in Metallische Dauerformen. Symposium 2: Werkstoffe fur die Verkehrstechnik, 12997 by DGM Informationsgesellshaft mbh, p. 49-54).

Alloys from the group based on the α ₂ phase, with an aluminum content of 8-14 wt.%, Are alloys of the deformation type with reduced technological ductility. These alloys have increased heat resistance, slightly inferior in it to alloys based on the γ-phase, and have undeniable advantages in terms of manufacturability and cost of production compared with these alloys.

A number of heat-resistant titanium alloys was developed for aerospace engineering, among which, as the most heat-resistant, alloys of the grades VT18U and VT25U (Russia), IMI 829 and IMI 834 (England), Ti 6242 Si and Timetal 1100 (USA) should be distinguished (see table 1, items 3-8). These are complex alloyed deformation type alloys. Subject to very strict temperature-time multi-stage modes of deformation processing and heat treatment in these alloys, the formation of the necessary macro- and microstructures and the formation of a set of useful properties are ensured: strength, heat resistance, fatigue resistance, etc. At the same time, long-term operation at elevated temperatures is limited for these alloys in the range of 500-600 ° C (see O.P.Solonina, S.G. Glazunov. Heat-resistant titanium alloys. M: Metallurgy, 1976, pp. 61-128. \ Titanium 95: Science and Technology. Igor V. Gorynin "Research and Fabrication and Devel opment of Titanium in the CIS ", p.32). The low level of operating temperatures (not more than 600 ° C) does not allow using them for exhaust valves of internal combustion engines.

Also known is a titanium alloy containing an intermetallic (α ₂ phase based on the Ti ₃ Al compound (RU No. 2081929) (see Table 1, item 9). The phase composition of the α + α ₂ alloy. Hydrogen is proposed to increase its technological plasticity technology based on the use of reversible alloying of the alloy with hydrogen and thermal exposure.The technology allows to improve the structure of titanium alloys of systems (α + α ₂ ) and α ₂ and increase their mechanical properties (see Mamonov AM, Kusakina Yu.N., Ilyin AA Patterns of the formation of phase composition and structure in heat treatment a titanium alloy with intermetallic hardening when alloyed with hydrogen // Metals, 1999, No. 3, pp. 84-87) However, this operation is technologically complex, expensive and not applicable for the mass production of ICE valves.

Analogs of the present invention “Valve of an internal combustion engine” are known valve designs of combined designs made of industrial titanium alloys, in which, in order to reduce the cost of the valve, the core is made of low alloy titanium alloys, and the head with the transition to the core is made of heat-resistant high alloy titanium alloys ( US No. 5169460, JP No. 03009008, JP No. 62-197610) (see Table 1, paragraphs 10-12). Separately manufactured head and rod are then joined by welding or pressed. However, valves manufactured in this way do not have the required strength and reliability.

Another analog is a valve (JP No. 06184683), which is made from a 2-phase (α + β) titanium alloy rod. Two different microstructures with grain sizes in one part of the valve 1-4 microns and in the second - more than 300 microns are created in different parts of the valve, in the stem and head, by deformation processing. A disadvantage of the known valve is that it does not have the required heat resistance that meets the conditions of its long-term mechanical and thermal loading.

The closest in technical essence analogue to the proposed “Valve of an internal combustion engine” is a titanium valve having various microstructures in its parts, rod and head (US No. 4729546). The known valve is made of heat-resistant titanium alloy (α + β) of phase composition and consists of a cylindrical rod, a disk-shaped head and a transition section that provides smooth connection of the rod and the head, and has various microstructures in its parts. The microstructure of the rod and the section connecting the rod to the valve head mainly contains a mixture of zones of thin equiaxed grains of the α phase and zones with a microstructure of the type of colonies, with a grain size of 5-50 μm, with high tensile strength and high fatigue resistance. A valve head with a substantially uniform zone with a microstructure of the type of colony, with a colony size of 50-300 μm, has a reduced creep resistance - at a temperature of 760 ° C, equal to 1% deformation, at a voltage of 27.5 MPa per 100 hours.

A disadvantage of the known valve is that the two-phase (α + β) titanium alloys and their microstructure used for its manufacture do not provide the necessary strength properties for ICE valves operating under conditions of long-term thermal and short-term high-temperature (up to 900 ° C) loading. In particular, for the valve head, the chemical composition of the alloys (see Table 1, paragraphs 13-16) and the microstructure do not provide long-term heat resistance properties at temperatures above 600 ° C. The heat resistance of a titanium alloy is determined by the α phase. The heat resistance of the α phase can be increased only by additional alloying. Any structural transformations of two-phase titanium alloys, as is done in the known valve, do not lead to a significant increase in heat resistance. In addition, a uniform microstructure in the valve head, such as colonies, does not provide an increase in creep resistance of the valve material. The microstructure in the valve stem and in the portion of the transition of the stem into the plate-shaped head in the known patent is a mixture of zones of thin equiaxed α-phase grains and zones with a microstructure of the type of colonies with a grain size of 5-50 μm. Such a microstructure does not provide increased long-term strength for the transition section, especially the exhaust valve, operating under creep conditions at high temperatures (600-700 ° C, see Fig. 15), and the reliable operation of the valve as a whole. The valve stem operating under cyclic tensile and bending loads also does not provide the required properties due to the low modulus of elasticity, hardness and strength at elevated temperatures. This leads to the occurrence of permanent deformation and lengthening of the valve stem during operation. This is especially evident in the operation of forced engines.

The closest in technical essence to the analogue of the invention “Method of manufacturing a valve of an internal combustion engine” is a method of manufacturing a valve with various regulated microstructure (US No. 4675964). According to this method, the engine valve, including the exhaust valve, is made of industrial heat-resistant 2-phase (α + β) titanium alloys (see Table 1, paragraphs 13-16). The technical result of the known method is to obtain a valve with a double microstructure. In the manufacturing process, various microstructures are created in the valve stem and head by deformation methods and subsequent heat treatments with properties close to the conditions of mechanical and thermal loading of the valve during its operation in the internal combustion engine.

A known method of manufacturing a valve of an internal combustion engine from a heat-resistant titanium alloy is that a valve with a different microstructure is formed in its rod and head as a result of deformation processing and subsequent heat treatment. Deformation processing and subsequent heat treatment are carried out in two stages, with the formation of the microstructure of the rod in the first stage, and the microstructure of the head in the second. At the same time, at the first stage, by means of extrusion processing, a part of the workpiece related to the rod is subjected to deformation treatment. Before deformation, the preform is heated to a temperature that is lower than the temperature of the complete polymorphic transformation for this alloy (T _PP ). In the second stage, the part of the preform related to the valve head is deformed by stamping, preheating it to a temperature that is higher than the temperature of the complete polymorphic transformation for this alloy (T _PP ). As a result of deformation and heat treatment, various microstructures are obtained in the shaft and head providing properties close to the conditions of mechanical and thermal loading of valve parts in the engine. The microstructure of the first zone of the valve (the rod and the section connecting the rod to the head) contains mainly a mixture of zones of thin equiaxed grains of the α phase and zones of the type of colonies with a size of 5-50 μm and has high strength and fatigue strength at room temperature. The microstructure of the second zone of the valve (head) contains a homogeneous microstructure, mainly of the type of colonies with a colony size of 50-300 microns.

The disadvantages of this method include:

- Using the extrusion process, it is impossible to form a valve stem when using heat-resistant alloys with reduced technological ductility for its manufacture.

- The process of extrusion of the valve stem is accompanied by rapid wear of a pressing tool made of expensive heat-resistant steels, especially when extruding titanium alloys in a two-phase α + β region.

- Heating the entire workpiece for hot pressing of the valve stem leads to an undesirable grain growth in the part of the workpiece related to the valve head, which reduces its quality during the stamping process.

- The entire billet under the extrusion method is usually heated in furnaces with an external heat source. In this case, the heating time of the workpiece for deformation will be at least 10 minutes. Such prolonged heating leads to the formation of a solid oxide layer with a thickness of 0.1-0.3 mm, causing wear of the press tool and additional difficulties during subsequent machining or requires additional measures to protect the workpiece from oxidation.

- Complicated and difficult heat treatment with a large temperature difference between the head and valve stem. Since the valve head is heated above T _pp during heat treatment, and the rod is heated to a temperature below T _pp , the temperature gradient between the valve head and valve stem is 10–205 ° C with exposure at these temperatures from 0.5 to 8 hours. It is quite difficult to implement such a heating scheme in the process of mass production.

- Formed by a known method, the structure in the valve stem does not provide the required properties of the valve due to the low modulus of elasticity, hardness and strength at elevated temperatures.

- A homogeneous microstructure formed in the valve head according to the known method, such as colonies, with a colony size of 50-300 μm, while the size of the primary β-grain in the microstructure can exceed the size of the colonies by 3 times or more, does not provide the necessary valve health at high temperatures, since it does not have increased creep resistance and long-term strength (see Table I Relationships between critical microstructural features and mechanical properties of titanium alloys. ASM Handbook, vol. 2, 1990, p. 1052. Reviewed by Gerhard Welsch, Case Western Reserve University, and Rodney Boyer, Boeing Commercial Airplane Company).

The closest analogue of the invention, “Heat-resistant titanium alloy” is an alloy used for the manufacture of gas distribution valves of internal combustion engines by the method of hot deformation, Ti-6Al-2Sn-4Zr-2Mo-0,1Si (US No. 4675964). This is a titanium alloy with a (α + β) phase composition. ICE valves made from such alloys are capable of long-term operation only at temperatures of 550-600 ° C. Known from US patent No. 4675964 2-phase (α + β) titanium alloys (see Table 1, claims 13-16) provide long-term heat resistance properties (long-term strength, creep resistance) only up to temperatures of 600 ° C. This fact is confirmed by the author of US patent No. 4675964, 4729546 in his article containing the test results of valves made of 2-phase titanium alloys (Allison JE, Sherman AM, Bapna MR Titanium in engine valve system. "J. Metals", 1987, 39, No. 3. P. 15-18).

Disclosure of inventions.

The objective of the invention is to increase the reliability and reliability of the engine valves and increase the durability of the engine. At the same time, a technical result is achieved, which consists in improving the properties of the valve material, ensuring the efficiency of the internal combustion engine valve in the operating temperature range, by increasing the long-term heat resistance of the valve head (long-term strength, creep resistance) and increasing the mechanical properties of the valve stem (strength at elevated temperatures, normal module elasticity, hardness). This makes it possible: a) to increase the operating temperature of the valve head to 850 ° C during prolonged operation of the engine, and to 900 ° C when operating in forced engines with a limited period of operation; b) reduce the structural dimensions of the valve stem and the transition from the rod to the head.

The proposed invention allows:

- to provide increased durability of the engines by improving the reliability and reliability of the engine;

- reduce the mass of the valve by 10-20% by reducing the structural dimensions of the valve stem and the transition section of the rod into the head, as well as reduce dynamic loads on the links of the valve mechanism;

- reduce the efforts of the valve springs, which will provide an additional reduction in the loads in the valve mechanism, reducing friction losses and improving engine performance;

- force the engine in rotation speed, thereby increasing its efficiency;

- manage the properties of the internal combustion engine valves, making them with the necessary and sufficient heat resistance for engines for various purposes and the level of forcing;

- use in the manufacture of ICE valves deformation processes in the field of limited technological plasticity of titanium alloys, achieving high performance and low cost in mass production.

The specified technical result and the elimination of shortcomings in the proposed valve of an internal combustion engine made of heat-resistant titanium alloy containing a cylindrical rod, a disk-shaped head and a transition section that provides smooth coupling of the rod and the head is achieved by the fact that the titanium alloy has α + α ₂ + β- phase intermetallic compound with α ₂ -phase based compound Ti ₃ Al, a dispersedly distributed α-phase, the microstructure of the rod is a combination of microstructures of three types, smooth passing from one type to another in the radial direction, from the surface to the center: equiaxial, bimodal and lamellar, respectively, the head microstructure is a mixture of two types of microstructures: basket weaving and lamellar, and the transition section has a mixed microstructure consisting of microstructures characteristic of the rod and heads.

In particular cases of the invention, the core has a microstructure with a grain size of 3-40 microns, and the head has a microstructure with a grain size of 50-200 microns.

The mass fraction of the intermetallic α ₂ phase based on the Ti ₃ Al compound is from 7 to 80 wt.% When the aluminum content in the alloy is from 7.5 to 12.5 wt.%.

In the present invention, the aforementioned disadvantages are eliminated by creating a valve with a different microstructure for the rod and for the head and additional content in the alloy from which the valve is made of an intermetallic α ₂ phase based on the Ti ₃ Al compound, which is dispersed in the α phase . Moreover, the content of the α ₂ phase dispersed in the α phase in the valve material, as well as the combination of these microstructures in the valve stem, provide it with increased tensile strength at elevated temperatures, normal elastic modulus and hardness, and resistance to nucleation and propagation of fatigue cracks fracture toughness and impact strength. This increases the strength and heat resistance properties of the valve. The content of the α ₂ phase dispersed in the α phase in the material of the valve head and the mixture of microstructures in the valve head give it long-term heat resistance properties by increasing the long-term strength and creep resistance.

Additional alloying of the heat-resistant titanium alloy with aluminum transfers the alloy from two-phase (α + β) to three-phase (α + β + α ₂ ), while the α ₂ phase based on the Ti ₃ Al compound is dispersedly distributed in the α phase and mainly precipitates in the heat treatment process. The release of the α ₂ phase in the alloy occurs during the ordering of the α phase containing supercon equilibrium dissolved aluminum. For example, the solubility limit of aluminum in the α phase at 550 ° C is 7.0-7.5% (see Titanium. Sources, compositions, properties, metal chemistry and application. Kornilov I.I. M .: Nauka, 1975 p. 187). At high aluminum concentrations at this temperature, the α ₂ phase is dispersed, which is a solid solution based on Ti ₃ Al. This allows you to increase the heat resistance of the alloy up to 750-900 ° C depending on the amount of α ₂ phase. The necessary combination of mechanical properties and heat resistance (depending on the operating temperature of the valve) is achieved when the content of the α ₂ phase in the alloy is from 7 to 80 wt.%. For a more detailed confirmation and justification of the materiality of the features of the invention “Valve of an internal combustion engine”, see the section “Example of carrying out the inventions”.

The specified technical result and the elimination of shortcomings in the proposed method of manufacturing a valve of an internal combustion engine from a heat-resistant titanium alloy, comprising forming a valve from a cylindrical billet by deformation processing with preliminary heating and subsequent heat treatment, is achieved by the fact that the titanium alloy has α + α ₂ + β-phase intermetallic compound with α ₂ -phase based compound Ti ₃ Al, a dispersed distributed α-phase, preheating of the preform relating to the terminal, etc. lead to a temperature of 5-20 ° C below the temperature of the complete polymorphic transformation of the alloy, and its deformation processing is carried out by wedge rolling to obtain a radially smooth transition from one type to another in the rod, from the surface to the center of the combination of three types of microstructures: equiaxial , bimodal and lamellar, respectively, the deformation processing of the part of the preform related to the head is carried out by stamping with its preliminary heating to a temperature of 5-50 ° C above full temperature about the polymorphic transformation of the alloy corresponding to the beginning of stamping, and the end of stamping is carried out at a temperature below the temperature of the complete polymorphic transformation of the alloy, forming the valve head of a plate-shaped valve with a mixed microstructure of two types: basket-like weaving and plate-like and a transition section that provides smooth coupling of the head with the rod and having mixed microstructure consisting of microstructures characteristic of the rod and head.

In particular cases of carrying out the invention after the manufacture of the valve, the rod has a microstructure with a grain size of 3-40 microns, and the head is 50-200 microns.

Pre-heating of the part of the billet related to the rod is carried out by the electric contact method.

Pre-heating of the part of the preform related to the rod is carried out at a speed of 10-50 ° C / s.

Wedge cross rolling is carried out with a degree of deformation of 30-55%.

Preheating a portion of the workpiece related to the head

carried out by induction method.

Pre-heating of the part of the preform related to the head is carried out at a speed of 20-50 ° C / s.

Stamping of the workpiece related to the head is carried out with a degree of deformation of 40-60%.

Preheating of the part of the preform related to the head and part of the preform related to the rod is carried out under temperature control.

Heat treatment is carried out by annealing.

Annealing is carried out by heating parts of the preform obtained after deformation processing of its parts related to the rod and the head to a temperature of 650-950 ° C, holding at this temperature for 0.1-5.0 hours, cooling to a temperature of 500-650 ° C, subsequent exposure at this temperature for 5-50 hours and cooling.

Thus, the inventive method of manufacturing the valve is based on the use of deformation technologies, alternating with heat treatment. This allows you to get the valve of an internal combustion engine with a microstructure that meets the conditions of its mechanical and long-term thermal loading in the internal combustion engine, including for forced engines. For more details on the confirmation and substantiation of the materiality of the features for the invention, “Method for manufacturing a valve of an internal combustion engine”, see “Example of carrying out the inventions”.

The specified technical result and elimination of shortcomings in the proposed heat-resistant titanium alloy containing aluminum, molybdenum, zirconium and silicon is achieved by the fact that it additionally contains yttrium in the following ratio of components, wt.%: Aluminum 7.5-12.5, molybdenum 1, 6-2.6, zirconium 1.4-2.4, silicon 0.1-0.2, yttrium 0.05-0.1, titanium - the rest and has α + α ₂ + β - phase composition with intermetallic α ₂ phase based on a Ti ₃ Al compound dispersed in the α phase.

Application for manufacturing valves of both inlet and outlet, titanium alloys, additionally hardened with intermetallic α ₂ phase based on Ti ₃ Al compound dispersed in the α phase, provides enhanced mechanical properties of the internal combustion engine valve, primarily heat-resistant, and their long-term work with a limited period of operation at temperatures in the head up to 900 ° C for exhaust valves of forced internal combustion engines.

A brief description of the figures of the drawings.

The invention is illustrated by drawings, where:

figure 1 shows a General view of the internal combustion engine valve;

figure 2 shows the original cylindrical billet;

figure 4 shows the billet of the valve of the internal combustion engine after stamping;

figure 5 shows the equiaxed microstructure located on the surface of the valve stem;

figure 6 shows a bimodal microstructure located in the intermediate part of the valve stem;

figure 7 shows a plate microstructure located in the Central zone of the valve stem;

on Fig-10 depicts the microstructure of the valve stem for the case of heating it under wedge rolling to a temperature above the claimed (permissible) temperature range (T _PP -5 ° C), when it is impossible to obtain the necessary combination of microstructures in the valve stem;

figure 11 shows the microstructure of the valve head, which is a mixture of two microstructures: basket weaving and plate;

on Fig shows a fragment of a plate microstructure in the valve head, on an enlarged scale;

on Fig shows a fragment of the microstructure of basket weaving in the valve head, on an enlarged scale;

on Fig presents the calculated distribution of operating temperatures in the intake valve for example, the engine is an average level of forcing;

on Fig presents the calculated distribution of operating temperatures in the exhaust valve by the example of an engine of medium level boost.

An example embodiment of the invention.

The valve (figure 1) contains a rod 1 of constant diameter and a plate-shaped head 2, including a transition section 3, providing a smooth pairing of the rod and the head.

Intake and exhaust valves are made of a titanium alloy with different aluminum contents in the range of 7.5-12.5 wt.% (See Table 1 p. 17 and Table 3). These alloys are additionally hardened with an intermetallic α ₂ phase dispersed in the α phase, which increases the heat resistance of the alloy to 900 ° C. Used in the manufacture of the valve by deformation treatments and heat treatments, according to the claimed method, various microstructures are created in the rod 1, head 2 and transition section 3.

The microstructure in the rod 1 is a combination of three types of microstructures: equiaxial, bimodal and lamellar. The indicated structures smoothly pass from one type to another in the radial direction, from the surface to the center, in the indicated direction.

To achieve maximum strength characteristics, a heterogeneous microstructure consisting of three microstructures is created in the valve stem.

An equiaxed microstructure is created on the surface of the valve stem (FIG. 5). An equiaxed microstructure enhances the strength, ductility, and fatigue limit, as well as increasing the resistance to nucleation of fatigue cracks and resistance to low-cycle fatigue (see Kolachev B.A., Polkin I.S., Talalaev V.D. Titanium alloys from different countries., Ed. VILS, 2000, p. 297). Thus, the increased resistance to the initiation of fatigue cracks in combination with other positive properties of this microstructure (strength, ductility, endurance) does not require additional surface treatment of the valve stem (shot peening, polishing, etc.) to increase its fatigue strength.

Between the surface of the valve stem and its central part is a bimodal microstructure (Fig.6). Bimodal microstructure allows you to achieve the optimal combination of the mechanical properties of the alloy and the advantages of equiaxial and plate microstructures. In addition, the formation of a bimodal microstructure in the transition layer between equiaxial and lamellar microstructures contributes to a smooth transition from one type of microstructure to another and favorably affects the increase in the mechanical properties of the valve stem material.

In the Central zone of the rod is a plate microstructure (Fig.7). Lamellar microstructure allows to increase the fracture toughness, resistance to the growth of fatigue cracks, impact strength, as well as creep and long-term strength. The formation of a fine-grained lamellar microstructure in the central zone of the valve stem (grain size not exceeding 40 μm) allows one to obtain increased fracture toughness, toughness and resistance to fatigue crack growth, consistent with the nature of the cyclic tensile stress loads acting on the valve stem, with a high frequency. The formation of such a microstructure is also positive for the part of the stem of the exhaust valve adjacent to the hot head and operating in the temperature range of 500-650 ° C (see Fig. 15), i.e. in conditions of creep and increased resistance to long-term strength. It also helps to increase the strength properties of the valve stem.

This combination of microstructures will create a valve stem with high rates of reliability and durability.

The best technical result in terms of reliability and durability of the valve stem is achieved when the grain size for the microstructure of the valve stem 3-40 microns. Grain less than 3 microns leads to the occurrence of internal stresses during the deformation processing and the formation of microcracks. Grain more than 40 microns reduces the strength and fatigue properties of the valve.

The microstructure of the valve head 2 is a mixture of two types of microstructures (Fig. 11): basket weaving and plate and, as a result, has all the advantages of such microstructures. The plate microstructure in the valve head (FIG. 12) provides increased fracture toughness, impact strength, resistance to growth of fatigue cracks, creep resistance, and long-term strength. The microstructure of basket weaving (Fig) provides an increase in long-term strength, as well as creep resistance. The mixture of basket-like and plate-like microstructures formed in the valve head has a chaotic character, without distinct zones, which helps to combine the positive properties inherent in each of these microstructures. The microstructure of basket weaving to a greater extent provides increased resistance to long-term strength with a sufficiently high creep resistance. The coarse-grained lamellar microstructure (grain size 50-200 μm) to a greater extent provides increased creep resistance, as well as other positive properties characteristic of the lamellar microstructure. Such a mixture of microstructures is quite consistent with the nature of the loading of the valve head (cyclic alternating shock loads with a high frequency in the temperature range of 600-850 ° C, and in some cases up to 900 ° C). This leads to increased reliability and reliability of the engine valves and increases the durability of the engine.

The best technical result is achieved with grain sizes for the microstructure in the valve head in the range of 50-200 microns. An increase in grain of more than 200 μm leads to a decrease in strength due to weakening of grain boundaries. A decrease in grain of less than 50 microns reduces creep resistance at high temperatures.

In the zone of transition section 3, there is a smooth transition from one type of microstructures related to the valve stem to another type of microstructures related to the valve head, which ensures reliable operation of the transition section of the valve under a temperature gradient, from a high operating temperature in the valve head to the operating temperature in the valve stem (see Fig.14 and 15).

The use of titanium alloys for valves (both inlet and outlet), additionally hardened with an intermetallic α ₂ phase based on Ti ₃ Al dispersed in the α phase, with increased heat resistance, ensures long-term operation of ICE valves for various purposes and the level of forcing at temperatures in the valve head from 600 to 900 ° C, while in the known titanium alloys the level of heat resistance does not exceed 600 ° C. In the valve stem and in the transition section, an increase in hardness and normal elastic modulus is provided due to the content of the α ₂ phase dispersed in the α phase. This allows you to reduce the structural dimensions of the rod and the transition section of the valve, which leads to a decrease in the mass of the valve by 10-20% in comparison with the alloy of the prototype. According to the data given in Table 3, paragraphs 8 and 9, the superiority of the properties of the claimed alloy over the properties of the alloy according to the patent US 4729546 is seen. So the values of specific indicators of strength (σв / ρ) and rigidity (E / ρ) for the developed alloy exceed the values of these indicators for the prototype alloy: for σв / ρ (at 800 ° С) from 2 to 4 times, and for Е / ρ (at room temperature) by 11-27%.

The solubility limit of aluminum in the α phase ranges from 6 to 7.5 wt.%. With its greater content in the alloy, a dispersively distributed α ₂ phase is released, which is a solid solution based on the Ti ₃ Al intermetallic compound, which additionally increases the heat resistance of the alloy and the normal elastic modulus. At the same time, this leads to a decrease in technological plasticity. The required level of technological plasticity is achieved by the ratio of α- and β-phases in the alloy. This ratio can be controlled by the amount of α- and β-stabilizing elements in the alloy. The most effective α-phase stabilizer is aluminum. Molybdenum is one of the most effective β-phase stabilizers. With this in mind, the developed titanium (α + β) alloy dispersively hardened by the α ₂ phase has in its composition:

- aluminum, increasing the heat resistance of the alloy and determining the content of α ₂ phase;

- molybdenum, which stabilizes the β phase and affects the ductility of the alloy (a relative decrease in the molybdenum content in the alloy with an increase in aluminum content further reduces ductility and manufacturability);

- zirconium, expanding the region of homogeneity of the α phase and affecting the release of the α ₂ phase and its amount, especially at low aluminum contents.

It is known that the content of dissolved oxygen in the alloy significantly reduces its ductility. The introduction of yttrium into the alloy allows you to organize the process of internal deoxidation in the alloy. Yttrium, dissolving in the alloy during melting, interacts with dissolved oxygen to form Y ₂ O ₃ oxide, which reduces the oxygen content dissolved in the α and β phases and increases the process plasticity.

In the proposed heat-resistant titanium alloy, the aluminum content is 7.5-12.5 wt.%. Thus, an increase in the aluminum content of more than 6-7.5% without changing the content of other elements leads to an additional decrease in the technological ductility of the alloy. Varying the content of aluminum, molybdenum and zirconium, as well as yttrium in the alloy, it is possible to change the heat-resistant properties of the alloy while maintaining technological plasticity at a level that allows deformation processing of the alloy.

Heat-resistant titanium alloy was smelted by double vacuum arc remelting. An alloy ingot with a diameter of 350 mm was extruded into a rod with a diameter of 50 mm and rolled into rods with a diameter of 16-22 mm. After rolling, the rods were annealed.

The rods were cut into cylindrical billets of 4 measured lengths, depending on the dimensions of the manufactured valves (FIG. 2).

To obtain the proposed microstructure, different for the valve stem and head, two stages of deformation processing were carried out, with preliminary heating before deformation and subsequent heat treatment.

Heated workpieces for wedge cross rolling were carried out by the electric contact method. The current was supplied through water-cooled copper contacts. The workpiece in the contact zone remained cold, and the central part of the workpiece was heated to a predetermined temperature by alternating or direct current. Monitoring the heating temperature was carried out using an infrared pyrometer. When the set temperature is reached, the pyrometer sent a signal to the microprocessor controller, which transmitted the control signal to the actuators with pneumatic actuators, and the heated billet was delivered to the rolling zone with minimal time delays.

At the first stage of deformation processing, a preform of intermediate shape was obtained from the cylindrical billet by the wedge-shaped rolling method for the subsequent stamping of the valve head (Fig. 3). During wedge rolling, a valve stem structure was formed. A distinctive feature of wedge cross rolling is the heating of the workpiece only in zone 5, which is rolling. Heating only the deformable part of the workpiece allows you to avoid unwanted grain growth in its non-deformable part 6 and facilitate the formation of the valve head during stamping, which is essential for difficult to deform alloys.

Wedge cross rolling was carried out with a degree of deformation of 30-70%.

It was experimentally established that in this range of degrees of deformation in the valve stem, a combination of three types of microstructures is obtained: equiaxial, bimodal and lamellar, ensuring the achievement of the necessary technical result. When the degree of deformation is less than 30%, it was not possible to accumulate a sufficient amount of metal in the stamped part of the workpiece for the subsequent formation of the valve head. With a degree of deformation of more than 70%, the billet broke during rolling.

Wedge rolling was carried out at a temperature of 5-20 ° C below the temperature of the complete polymorphic transformation (T _PP ) for this alloy, that is, in the α + β-region of the alloy. It was experimentally established that in this temperature range, wedge rolling provides a combination of three types of microstructures in the rod: fine-grained equiaxial, bimodal and plate, necessary to obtain the achieved technical result. When the rolling temperature is less than the lower limit (T _PP -20 ° C), the workpiece breaks. When the rolling temperature above the upper limit (T _PP -5 ° C) do not get the necessary combination of microstructures (Fig-10).

In the wedge rolling process for microstructure in the valve stem, a grain size of 3-40 μm was obtained. Since the deformation effect of wedge rolling is reduced from the surface to the center, in the surface layers the initial structure of the bar stock is transformed to equiaxial, and in the central zone, where the deformation effect is minimal, a plate microstructure typical of an undeformed alloy subjected to heating was obtained.

Electric contact heating of the deformable part of the preform for wedge cross rolling was carried out at a speed of 10-50 ° C / s. Direct electric heating makes it possible to realize such rather high heating rates and to ensure uniform temperature over the cross section and length of the workpiece. At a heating rate of more than 50 ° C / s, the central part of the rod blank is heated to lower temperatures than on the surface, which leads to a deterioration in the quality of rolling. At speeds of less than 10 ° C, the surface of the workpiece is oxidized and an undesirable oxide layer appears.

Wedge cross rolling allows you to get a blank for stamping with high productivity, about 4-5 blanks per minute, with minimal cost for the deformation tool (rolls). The resistance of wedge rolling rolls is 10-20 times higher than the resistance of extrusion dies.

Hot stamping of the valve head was carried out on a mechanical crank press.

Heating for stamping was carried out by the induction method of only that part of the workpiece that was subjected to deformation during the formation of the valve head. The heating rate was 20-50 ° C / s. After heating to a predetermined temperature, the valve head was stamped (Fig. 4).

Stamping was started at deformation temperatures 5–50 ° C above the point of complete polymorphic transformation (T _pp ) for this alloy. The final stage of valve head formation occurred at temperatures below T _pp . In this case, by stamping, a valve-shaped valve head 7 was formed with a smooth section 8 of transition to the rod 9. It was experimentally established that such a stamping temperature regime provides a mixture of two types of microstructures: basket-like weaving and plate-like with a grain size of 50-200 μm, necessary to ensure heat resistance valve heads. For the transition section, a mixed microstructure was obtained, consisting of microstructures characteristic of the rod and head, which ensured a smooth transition of the microstructures and valve properties from one part (rod) to another (head).

When the preform is overheated for stamping, that is, heating it above temperature T _pp + 50 ° C, an undesirable grain growth occurs above 200 μm, which leads to a decrease in the strength properties of the valve head due to the weakening of grain boundaries.

With insufficient heating of the workpiece, below a temperature of Tβ + 5 ° C, cracking of the valve head occurs during the stamping process.

Fast and one-time heating of the deformable part of the preform does not allow the formation of scale and an oxide layer on its surface, which contributes to a more favorable course of deformation processes during stamping, a decrease in the resistance to deformation, and obtaining a high-quality stamping surface without cracking, wrinkles and wrinkles.

Heating at a rate of more than 50 ° C / s led to a high inhomogeneity in the heating of the workpiece, due to which its central part did not have time to warm up to the set temperatures, while the surface overheated. This led to poor stamping quality. Heating at a rate of less than 20 ° C / s reduced the performance of stamping.

After the deformation processing was completed, the valve blank was heat treated. Heat treatment was carried out using quenching and annealing or - using only annealing.

In the first variant of heat treatment, quenching was carried out immediately after the end of each of the stages of deformation processing. After the wedge cross rolling was completed, the billet was quenched, for example, in water. In this case, the structure was fixed in the valve stem in the two-phase (α + β) region and the α ₂ phase separation process ceased. During quenching after stamping, the microstructure was fixed in the valve head. According to the state diagram of titanium - aluminum, the release of the α ₂ phase begins at temperatures of 500-650 ° (see Titanium. Sources, compositions, properties, metal chemistry and application. Kornilov II M.: Nauka, 1975, pp. 185-197 ) The higher the process temperature, the larger the release of the α ₂ phase. The best results on the dispersion separation of the α ₂ phase are obtained as a result of diffusion processes at temperatures of 500-650 ° C. In this case, an α ₂ phase with a precipitate size of 20–50 nm is released. At temperatures below 500 ° C, diffuse processes are very slow. At temperatures above 650 ° C, the size of the α ₂ phase is large. Annealing in the claimed temperature range leads to an increase in heat resistance. Heating the workpiece to a temperature of 650-950 ° C is aimed at relieving internal stresses.

In the second variant of heat treatment, annealing was performed at the end of valve formation, i.e., after the second stage of deformation processing. Annealing was performed to prepare the valve as a whole.

Annealing in the first and second heat treatment options was carried out in two stages. In the first stage of annealing, the billet was heated to a temperature of 650–950 ° C, held at this temperature for 0.1–5.0 hours, and cooled to a temperature of 500–650 ° C.

At the second stage of annealing, the workpiece was held at a temperature of 500-650 ° C for 5-50 hours, followed by cooling.

According to the first variant of heat treatment, the best result was achieved when the content of the α ₂ phase in the alloy was in the amount of 7-25 wt.%. In this case, the increase in mechanical characteristics occurs by the hardening mechanism of 2-phase (α + β) alloys and due to the dispersed precipitation of the α ₂ phase. The achieved effect of hardening, as a result of quenching and annealing, exceeds the effect of hardening due to the separation of the α ₂ phase in the amount of 7-25 wt.%. Carrying out the heat treatment according to the first embodiment is preferable for an alloy with an aluminum content in the range of 7.5-9.5 wt.%. As a result of such heat treatment, the internal combustion engine valves (mainly inlet) were obtained, providing long-term operation in the temperature range of 600-650 ° C (see Table 2).

The heat treatment according to the second embodiment, it is advisable to carry out at a content of α ₂ phase in an amount of 25-80 wt.%. In this case, an increase in mechanical properties is ensured mainly due to the dispersed isolation of the α ₂ phase. The heat treatment according to the second embodiment is preferable for an alloy with an aluminum content of from 9.5 to 12.5 wt.%. Valves (both exhaust and inlet) from an alloy with an aluminum content of wt.%: 9.5-10.5, 10.5-11.5 and 11.5-12.5 provide continuous operation in the temperature range: 650- 700 ° C, 700-800 ° C and 800-850 ° C, respectively, for engines with a long period of operation (see Table 2). Valves with an aluminum content of 11.5-12.5 wt.% Provide a limited period of operation in the temperature range up to 900 ° C for forced engines (see Table 2).

Performing deformation and heat treatments according to the declared modes in the manufacture of an internal combustion engine valve from an alloy with an aluminum content of 7.5 to 12.5 wt.% Provides the necessary mechanical properties in the internal combustion engine valves shown in Table 3.

From Table 3 it is seen that the developed alloy with an aluminum content of 7.5-12.5 wt.%, Hardened by intermetallic α ₂ phase, has the following higher mechanical properties in the temperature range up to 900 ° C (in comparison with the properties of the prototype alloys ):

- strength is 3.5 times higher for an alloy with an aluminum content of 7.5-9.5 wt.% at temperatures of 700-760 ° C and 4 or more times higher - for an alloy with an aluminum content of 9.5-10.5 wt.%;

- the strength of the alloy with an increase in its aluminum content from 7.5-9.0 wt.% to 12.0-12.5 wt.% increases by 2 times in the case of the valve head at a temperature of 800 ° C and voltages in the range from 260 to 520 MPa;

- with increasing aluminum content from 7.5 to 12.5 wt% specific strength (σ _in / ρ) is 2-4 times higher in the temperature range from 760 to 800 ° C and the specific stiffness (E / ρ) higher. 11-27% at room temperature (this allows you to make a valve with a smaller design dimensions for the valve and the transition of the rod into the plate and thereby reduce the mass of the valve by 10-20%);

- the creep resistance of the alloy at temperatures of 600-800 ° C significantly exceeds this figure for the prototype.

The valve blank prepared by the method described above was machined by known methods, such as turning and grinding. After machining, the outer surface of the valve was strengthened, for example, by nitriding to a depth of 50-100 μm.

The proposed method of manufacturing the valve allows you to get the internal combustion engine valves, which are consistent with the level of thermal loading in engines for various purposes and the degree of forcing. Moreover, during the manufacturing process, it is possible to control the properties of the valves, varying the properties of the material, primarily heat resistance. The proposed method is based on the use of high-performance deformation technologies and can be used in the mass production of ICE valves.

Table 1.
The chemical composition and properties of analog titanium alloys used for ICE valves. No. p / p Brand fusion Chemical composition,% wt. Basic properties 1 Ti-48Ai + 2Cr-2Nb Alloy based on TiAl (γ). Low ductility (δ = 0.5-1.5%). They undergo forming mainly by foundry technologies. T _max = 750-900 ° C 2 Ti-46Al-1Cr-0.2Si In accordance with paragraph 1. 3 VT18U Ti-6.5Al-2.5Sn-4Zr-1Nb-0.7Mo-0.15Si σ _in = 1075 MPa *, δ = 12.5% *. long-term strength up to 600 ° C. 4 VT25U Ti-65Al-18Sn-4Zr-4Mo-1W-0.2Si σ _in = 1230 MPa *, δ = 43.5% *, long-term strength up to 550 ° C. 5 IMI829 Ti-55Al-3,5Sn-3Zr-1Nb-0,25Mo-0,3Si σ _in , = 950 MPa *, δ = 11% *, combination of properties: creep resistance up to 540 ° С and oxidation resistance. 6 M834 Ti-5.8Al-4Sn-3.5Zr-0.7Nb-0.5Mo-0.35Si σ _in = 1050 MPa *, δ = 42% *, increased tensile strength and creep resistance up to 600 ° C 7 Ti-6242S Ti-6Al-2Sn-4Zr-2Mo-0.08Si σ _in = 1030-1176 MPa *, δ = 8-10% *, good creep resistance under tension and fatigue up to 540 ° C. 8 Timetal1100 Ti-6Al-2,8Sn-4Zr-0,4Mo-0,5Si σ _in = 1000 MPa *, δ = 8-11% *, resistance to high-temperature creep, long-term operation at temperatures up to 600 ° C nine Patent RU No. 2081929 Ti- (13-15) Al- (34) Nb- (2-4) V- (0.5-1) Zr Heat resistance up to 850 ° C, low ductility. To increase technological plasticity, a reversible doping with hydrogen is proposed. 10 US patent No. 5169460 Ti- (2-4) Al- (1,5-3,5) V-rod of the valve
Ti- (2-7) Al- (3-20) V-head Foundry technology of the valve head with its inherent disadvantages eleven JP Patent No. 03009006 Ti- (7-12) Al- (0.5-5) Sn- (0.5-5) Zr- (0.5-5) Mo Foundry technology with its inherent disadvantages 12 JP patent No. 62-197610 Ti-6Al-4V-valve stem
Ti-6Al-2Sn-4Zr-2Mo-0.08Si-valve head σ _in = 1030-1176 MPa *, δ = 8-10% *. good tensile and fatigue creep resistance up to 540 ° С thirteen US patent No. 4679964 Ti-6Al-4V σ _in = 950-1050 MPa *, δ≥10% *, the alloy does not belong to the class of heat-resistant, it is recommended to use up to 400 ° C 14 - "- Ti-6Al-2Sn-4Zr-2Mo-0.08Si σ _in = 1030-1176 MPa *, δ = 8-10% *, good creep resistance under tension and fatigue up to 540 ° C fifteen - "- Ti-5Al-5Sn-2Zr-4Mo-0.3Si Long-term heat resistance up to 600 ° C 16 - "- Ti-5Al-6Sn-2Zr-1Mo-0.3Si Long-term heat resistance up to 600 ° C 17 According to the invention Ti- (7.5-12.5) Al- (1.6-2.6) Mo- (1.4-2.4) Zr- (0.1-0.2) Si- (0.05 -0.1) Y See Table 3, long-term heat resistance in the temperature range 600-850 ° С and short-term up to 900 ° С Notes:
*) - properties are given at room temperature
- properties of foreign alloys are taken from Kolachev B.A., Polkin I.O., Talalaev V.D. Titanium alloys from different countries. Reference-M.: VILS, 2000. Table 2.
Coordination of the developed alloy with the purpose of the internal combustion engine valves according to their level of thermal loading and depending on the aluminum content in the alloy. The aluminum content in the alloy, wt.%: Valve type Range of maximum valve temperatures, ° С 7.5-9.5 inlet up to 650 9.5-10.5 inlet, outlet 650-700 10.5-11.5 graduation 700-800 11.5-12.5 graduation 800-850 11.5-12.5 Exhaust for forced combustion engines with a limited period of operation up to 900 Table 3.
The properties of heat-resistant alloys based on titanium, hardened by intermetallic a ₂ -phase (Ti ₃ A1) in accordance with the invention and the patent prototype. No. p / p Properties of titanium-based alloys In accordance with the invention, depending on the aluminum content in the alloy, wt.% According to patent No. 4.729.546 (USA) - 7.5-9.5 9.5-10.5 10.5-11.5 11.5-12.5 prototype 1. Density (ρ), g / cm ³ 4.38 4.35 4.33 4.3 4.54 (for alloy Ti-6Al-2Sn-4Zr-2Mo-0,1Si) 2. Hardness (after annealing), HB 340-380 380-420 318 (for alloy Ti-6Al-2Sn-4Zr-2Mo-0,1Si) 3. Tensile strength (σ _in ), MPa: at 20 ° C 1175-1250 1140-1165 1100-1150 1000-1040 965-1240 at 600 ° C 670-760 730-770 780-800 800-820 620-725 (510 ° C) at 800 ° C 180-210 280-330 380-430 500-520 ≥138 (760 ° C) at 900 ° C - - 110-140 190-220 - 4. Modulus of normal elasticity (E), tensile, GPa 122-127 129-131 133-135 139-142 115-118 (for alloy Ti-6AI-2Sn-4Zr-2Mo-0,1Si) 5. Ultimate Strength (σ ₁₀₀ ), MPa: In patent at 600 ° C - 260 - - no data at 800 ° C - 46 - - are given 6. Creep limit, MPa: - deformation of 0.1% at 600 ° C for 100 hours. - 155.0 - - - - 1% deformation at 760 ° C for 100 hours. - - - - 27.5 - deformation of 0.1% at 800 ° C for 100 hours. - 21.0 - 62.0 - 7. Specific strength (σ _in / ρ), m · 10 ^-3 : at 20 ° C 26.8-28.5 26.2-26.8 25.4-26.5 23.25-24.2 21.25-27.3 at 800 ° C 4.1-4.8 6.3-7.6 8.8-9.9 11.6-12.1 ≥3.04 (760 ° C) 8. Specific rigidity (E / ρ), m · 10 ⁶ 278.5-290 297-301 307-312 323-330 253-260

Claims (15)

1. Valve of an internal combustion engine made of heat-resistant titanium alloy, containing a cylindrical rod, a disk-shaped head and a transition section providing smooth conjugation of the rod and head, characterized in that the titanium alloy has an α + α ₂ + β phase composition with intermetallic α ₂ - phase based on Ti ₃ Al compound dispersion distributed in α-phase, wherein the rod has a microstructure representing a mix of microstructures of three types of smoothly transitioning from one type to another in radial direction, t surface to center: equiaxial, bimodal and lamellar respectively, the head has a microstructure representing a mix of microstructures of two types: basket-weave and lamellar, and the transition portion has a mixed microstructure consisting of microstructures characteristic of rod and head. 2. The valve according to claim 1, characterized in that the rod has a microstructure with a grain size of 3-40 microns, the head is 50-200 microns. 3. The valve according to claim 1, characterized in that the mass fraction of the intermetallic α ₂ phase based on the Ti ₃ Al compound is from 7 to 80 wt.% When the aluminum content in the alloy is from 7.5 to 12.5 wt.%. 4. A method of manufacturing a valve of an internal combustion engine from a heat-resistant titanium alloy, comprising forming a valve from a cylindrical billet by deformation processing with preheating and subsequent heat treatment, characterized in that the titanium alloy has an α + α ₂ + β phase composition with an intermetallic α ₂ phase based on the compound Ti ₃ Al, a dispersedly distributed α-phase, the preheating of the preform relating to the terminal, is performed to a temperature 5-20 ° C below the temperature of complete polymerase complete transformation of the alloy, and its deformation processing is carried out by wedge rolling to obtain in the rod smoothly passing from one type to another in the radial direction from the surface to the center of the combination of microstructures of three types: equiaxial, bimodal and plate, respectively, deformation processing of the part of the workpiece related to the head, is carried out by stamping with its preliminary heating to a temperature of 5-50 ° C above the temperature of the complete polymorphic transformation of the alloy, corresponding to the beginning Mpovka, and the end of stamping is carried out at a temperature below the temperature of the complete polymorphic transformation of the alloy, forming a valve head of a plate-shaped valve with a mixed microstructure of two types: basket-like weaving and plate-like and a transition section that provides smooth coupling of the head with the rod and having a mixed microstructure consisting of microstructures characteristic for rod and head. 5. The method according to claim 4, characterized in that after manufacturing the valve, the rod has a microstructure with a grain size of 3-40 microns, and the head is 50-200 microns. 6. The method according to claim 4, characterized in that the preliminary heating of the part of the workpiece related to the rod is carried out by an electric contact method. 7. The method according to claim 4 or 6, characterized in that the preliminary heating of the part of the preform related to the rod is carried out at a speed of 10-50 ° C / s. 8. The method according to claim 4, characterized in that the wedge transverse rolling of the part of the workpiece related to the rod is carried out with a degree of deformation of 30-55%. 9. The method according to claim 4, characterized in that the preliminary heating of the part of the preform related to the head is carried out by the induction method. 10. The method according to claim 4 or 9, characterized in that the preliminary heating of the part of the preform related to the head is carried out at a speed of 20-50 ° C / s. 11. The method according to claim 4, characterized in that the stamping of the workpiece related to the head is carried out with a degree of deformation of 40-60%. 12. The method according to any one of claims 4, 6, 7, 9, and 10, characterized in that the preheating of the part of the workpiece related to the rod and the part of the workpiece related to the head is carried out under temperature control. 13. The method according to claim 4, characterized in that the heat treatment is carried out by annealing. 14. The method of claim 13, wherein the annealing is carried out by heating the preform obtained after deformation processing of its parts related to the rod and the head to a temperature of 650-950 ° C, holding at this temperature for 0.1-5 , 0 h, cooling to a temperature of 500-650 ° C, subsequent exposure at this temperature for 5-50 h and cooling. 15. Heat-resistant titanium alloy containing aluminum, molybdenum, zirconium and silicon, characterized in that it additionally contains yttrium in the following ratio of components, wt.%: Aluminum 7.5-12.5 Molybdenum 1.6-2.6 Zirconium 1.4-2.4 Silicon 0.1-0.2 Yttrium 0.05-0.1 Titanium rest and has an α + α ₂ + β phase composition with an intermetallic α ₂ phase based on a Ti ₃ Al compound dispersed in the α phase.

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