RU2208063C2 - Method for obtaining semi-finished products from metals and alloys by pseudopowder metallurgy process - Google Patents

Abstract

FIELD: pseudopowder metallurgy. SUBSTANCE: method involves non-detachable joining of blanks with preliminarily set microstructure and/or properties over their aligned surfaces and solid phase mixing by deforming in several stages under temperature and speed conditions selected on the basis of predetermined microstructure and/or properties of semi-finished products and initial microstructure of blanks; in the process of deformation, changing direction of applying deforming load, and/or type of loading, and/or using loading including twisting with deformation extent at each stage providing changing of shape and/or spatial orientation of surfaces to be joined, and/or increasing joining area as compared to initial state or area obtained at previous stage. According to method, deformation is effected in three stages: first stage involves compressing blanks, second stage provides drawing for producing bar and third stage provides twisting deformation. EFFECT: uniform structure and properties of resultant semi-finished products. 22 cl, 25 dwg, 1 tbl, 11 ex

Description

 The invention relates to the field of metallurgy, and in particular to methods for producing semi-finished products with a given microstructure and properties, including regulated by volume distributed from separate homogeneous or heterogeneous workpieces using intense plastic deformation.

 The resulting semi-finished products can be used in the manufacture of parts and assemblies in the engineering, aviation and space industries.

 The intensive development of scientific and technological progress today poses the task of creating materials with new properties and at the same time further improving the technological and operational characteristics of the known and widely used in the production of metals and alloys. Ensuring the reliability of specified properties in materials is another task that is becoming quite relevant today.

 In recent years, interest has arisen in the methods of ultrasonic testing (ultrasonic testing) of the condition of products that have worked out a certain resource. An analysis of the results of ultrasonic testing shows that the finer the microstructure in the semi-finished product, the more transparent it becomes for the sound signal. Therefore, defects that are formed in the parts both at the manufacturing stage and during operation can be detected by ultrasonic testing long before the destruction of parts begins.

 Thus, increasing the technological and operational characteristics of structural materials, as well as the possibility of using reliable non-destructive methods for monitoring the condition of parts, is achieved by creating a certain microstructural state in the material.

 Intensive plastic deformation in combination with heat treatment is the most effective means of forming the required microstructure, and therefore the whole range of properties in semi-finished products from various materials.

The most famous methods of preparing the structure in metals and their alloys, which are based on intense plastic deformation, include:
a) a method for producing semi-finished products with a nanocrystalline (NC) structure, based on intense cold plastic deformation, implemented under conditions of quasi-hydrostatic shear on the Bridgman anvil;
b) a method for producing semi-finished products with a submicrocrystalline (SMC) structure, based on intense plastic deformation of the workpieces, implemented under conditions of comprehensive shear under equal-channel angular pressing;
c) a method for producing semi-finished products with a submicrocrystalline (SMC) structure, based on a comprehensive, with the change of the axes of loading, hot deformation by compression of the workpieces subjected to hydrogen plasticization;
d) a method for producing semi-finished products with a microcrystalline (MK) structure, based on hot deformation and heat treatment;
e) a method for producing semi-finished products, and especially large ones, with a microcrystalline structure, based on hot deformation under complex loading conditions.

 As a rule, semi-finished products subjected to intense plastic deformation have limited dimensions. The increase in size is associated with the solution of physical, technical and economic problems.

 Physical problems are determined by the physical properties of materials and are often difficult to solve. One of the important physical characteristics of the material is thermal conductivity and linear expansion coefficient. The heating and cooling rates of the workpiece depend on the thermal conductivity and linear expansion coefficient. The larger its transverse dimensions, the greater the dependence of the heating rate of the workpiece on its heating rate. To increase the efficiency of the processing process, it is usually customary to lower the temperature exit time in the workpiece to a predetermined value, which is achieved by overheating the workpiece by increasing the temperature difference in the volume of the workpiece during heating, for example, in the center of the workpiece and on its periphery. An increase in the degree of overheating leads to the formation of thermal cracks in the workpiece or to the appearance of heterogeneity.

 An example of a technical problem that arises in the case of obtaining a microcrystalline structure by deformation-heat treatment is the problem of ensuring the uniformity of the temperature field in the working zone of the deforming device and the accuracy of its maintenance. Failure to meet these conditions during hot deformation leads to an inhomogeneous development of plastic deformation, the appearance of zones of intense material flow, as well as stagnant zones. The result - the formation of subsequently incorrigible heterogeneity in the entire volume of the processed semi-finished product.

 Economic problems that arise when preparing a microcrystalline structure in large-sized semi-finished products are associated with additional costs for increasing the power of the equipment used, for heating the working tool, as well as for the use of special auxiliary devices, such as manipulators, etc. The low resistance of the deforming tool is another cost item that appears during the preparation of the microstructure in large-sized semi-finished products.

 Reducing the size of the processed workpieces simplifies the process of obtaining a microstructure of a given type, increases the uniformity of its distribution throughout the volume, and allows one to achieve average grain sizes of less than 0.1 μm, opening up the possibility of obtaining semi-finished products with SMC and even NK structures.

 Materials with a similar type of microstructure have high structural and technological properties. However, the specific costs spent on obtaining this type of microstructure in a material increase significantly with increasing size.

 It should be noted that the achieved average grain size in the workpiece being processed is proportional to its dimensions. In other words, the finer the required grain size, the smaller should be the size of the workpiece.

 For example, on the Bridgman anvil, it is possible to obtain an NK structure in washers with dimensions of 20.0–25.0 mm in diameter and 2.0–5.0 mm high. Using the method of equal channel angular pressing, it is possible to obtain a QMS structure in bars with a diameter of 20.0-30.0 mm and a length of 100.0-200.0 mm. Comprehensive forging of hydrogen-plasticized rods makes it possible to obtain a QMS structure in them. Moreover, the cross-sectional dimensions of the rods affect the uniform distribution of hydrogen throughout the volume, and therefore the uniform distribution of the transformed microstructure. Typical bar sizes: 20.0-30.0 mm - diameter and 60.0-90.0 mm - length.

 Thus, the analysis showed the existence of the problem of obtaining large-sized semi-finished products with a given microstructure and properties from the known and most often used in industry metals and alloys.

 A known method of producing semi-finished products, including large-sized from various metallic and non-metallic materials with specified microcrystalline structure and properties, based on the technology of powder metallurgy. The method involves obtaining individual elements — powders with a given microstructure and properties. At the same time, the possibility of significant subcooling of powders and obtaining a high degree of homogeneity in chemical composition at the stage of powder production is realized. Either an alloy with a given chemical composition or pure metal can serve as a starting material for the production of powders. At the stage of prolonged and intensive mixing of the powders, a homogeneous mass is obtained, which is then subjected to compacting. The compacting process can be accompanied by mechanical fixing of particles with each other, as well as partial or complete formation of a solid-phase connection between the particles along the contact surface. After compacting, diffusion sintering is carried out by high-temperature gas-static pressing, achieving an increase in the density of processed semi-finished products due to healing of pores and discontinuities as a result of the development of diffusion creep processes.

 To increase the economic efficiency of the powder metallurgy method, the compacting stage is usually combined with the shaping process by compacting into a matrix that has a shape close to the shape of the finished product.

 One of the obvious advantages of the powder metallurgy method when producing massive semi-finished products from various materials, including pure metals and their alloys, is the solution to one of the main metallurgical problems - the elimination of zonal and dendritic segregation in the ingot during its smelting.

 When obtaining powders from an ingot, another equally important material science problem is solved - the formation of a metastable microstructure in powders. The high degree of non-equilibrium of the microstructural state in the powders, as well as the dispersion of the powder determine the dispersion of the microcrystalline structure in the resulting semi-finished products.

 Along with the listed advantages of powder metallurgy as a method of obtaining materials with a given microstructure and properties, there are serious disadvantages.

 One of them is the need to comply with high requirements for production culture, similar to those presented for the production of microchips and microcircuits in the electronics industry.

 Deviation from these norms inevitably leads to contamination of the material with various uncontrolled impurities that are absorbed by the surface of the powders at numerous stages of their production. Moreover, the higher the dispersion of the powder, the higher the total surface of the powders and the higher the percentage of contamination with uncontrolled impurities in the finished semi-finished product.

 Indeed, the powder production process is based on the atomization of a liquid metal either in a stream of inert gas (argon, helium, etc.) or in vacuum. Depending on the required dispersion of the obtained microstructure, for example, in the production of SMC microstructure, an operation is also introduced to grind the powder in ball mills. As you can see, at all the main stages of the production of the starting material - powder, the powders are in contact either with an inert gas, or with residual pressure gases during evacuation, or with the surface of the deforming tool of ball mills. Only by increasing the purity of the neutral gas used, as well as the degree of rarefaction when creating a vacuum, it is impossible to completely get rid of impurities such as oxygen, hydrogen, nitrogen, carbon monoxide and carbon dioxide, etc.

где P_b - остаточное давление газа; М - относительная молекулярная масса; Т - температура. Нетрудно заметить, что при атмосферном давлении при комнатной температуре об 1 см² поверхности каждую секунду ударяется 5•10²² молекул кислорода, что примерно в 10⁸ раз больше, чем необходимо для мономолекулярного покрытия поверхности. Следовательно, даже если ювенильно чистую поверхность металлического материала, свободную от окисной пленки, поместить в вакуумную среду с остаточным парциальным давлением 1,3•10^-3 Па, то на поверхности уже через 0,18 секунд образуется моноатомный слой окисла данного металла. Понижение остаточного парциально давления на один порядок увеличивает время образования моноатомного слоя также на порядок.It is known that the highest degree of purification of a neutral gas such as argon, in terms of the amount of impurities, including oxygen, corresponds to a vacuum with a depth of 10 ^-1 Pa. From the kinetic theory of gases it is known that the number of molecules n, striking about 1 cm ² surface in one second, is determined by the expression

where P _b is the residual gas pressure; M is the relative molecular weight; T is the temperature. It is easy to see that at atmospheric pressure at room temperature about 1 cm ^{2 of the} surface, 5 • 10 ²² oxygen molecules are hit every second, which is about 10 ⁸ times more than is necessary for a monomolecular surface coating. Therefore, even if a juvenile clean surface of a metal material free of an oxide film is placed in a vacuum medium with a residual partial pressure of 1.3 • 10 ^-3 Pa, then in 0.18 seconds a monatomic oxide layer of this metal is formed on the surface. A decrease in the residual partial pressure by one order increases the formation time of the monoatomic layer also by an order of magnitude.

 As you can see, under real conditions of powder production, at least a monoatomic oxide film is inevitably formed on the surface of the powders, which becomes an alloying element in the resulting bulk semi-finished product. And the higher the dispersion of the powder, the higher the degree of uncontrolled alloying.

 In addition, the possibilities of using the powder metallurgy method in the production of semi-finished products intended for the manufacture of critical parts are limited for those materials in which the decomposition of oxides on the surface occurs by the mechanism of oxygen dissolution in the bulk of the material, for example, for materials such as titanium and its alloys.

 Another quite serious drawback of the powder metallurgy method is the residual porosity. This problem stems from the characteristics of the powder metallurgy method. It is no coincidence that the operation of high-temperature gas-static pressing is built into the technological chain of material production. This operation is primarily aimed at healing pores and discontinuities through the development of diffusion creep processes under the influence of a comprehensive compressive load on the semi-finished product at a high (> 0.4 Tm) processing temperature. The physical essence of the high-temperature gas-static pressing process is based on diffusion mass transfer processes. Moreover, the higher the temperature, the more diffusion processes are activated. It follows that in the case of using a powder with SMC and NK structure as the starting material at the stage of high-temperature gas-static pressing, the practical possibility of maintaining the microstructure in the semi-finished product at the microstructure level of the initial powder is lost. In other words, it is quite difficult to avoid a sharp grain growth at the stage of high-temperature gas-static pressing, without resorting to suppressing their growth process by lowering the operating temperature and increasing the pressure of comprehensive compression (hydrostatic component of the stress tensor).

 On the other hand, an increase in hydrostatic pressure suppresses the activity of diffusion processes, lowering the equilibrium concentration of vacancies, slows down the creep rate, and increases the duration of the sintering process as a whole.

 Thus, the preparation of semi-finished products with a QMS and NK structure by powder metallurgy comes up against two very serious problems - uncontrolled contamination of the material with various impurities, primarily oxygen, and residual porosity. These two problems are a serious obstacle to the widespread adoption of powder metallurgy in the production of critical parts in the engineering and aviation industries.

 From an economic point of view, the method of high-temperature gas-static pressing has considerable complexity, energy intensity and is based on the use of high pressures at high temperatures. In addition, during its implementation there is a need to comply with additional safety requirements that apply to the performance of work using high pressures.

 A known method of producing semi-finished products from individual preforms with a prepared microstructure [2] by connecting the preforms to each other by means of a solid-phase connection (TFS) [3] under temperature and speed conditions corresponding to the conditions of superplastic deformation of the preform material.

 A distinctive feature of this method in comparison with the powder metallurgy method is that relatively massive preforms are used as initial billets, which combine over the surfaces to be joined and carry out their solid-phase connection. The connected surfaces are generally flat. Immediately before joining, the surface is subjected to special, mechanical, chemical or electrochemical treatment. The blanks are assembled, the assembly is placed in a vacuum oven, where it is heated to the welding temperature (~ 0.4 from Tm.). Instead of a vacuum medium, protective or reducing media can be used. The workpieces are deformed by compression, applying a compressive force perpendicular to the joined surface. Depending on the tasks in the compression process, macroplastic deformation of the workpieces is allowed under conditions corresponding to the optimal conditions for the manifestation of superplasticity in the material of the workpieces being joined. The maximum degree of compression of the workpieces in height, as a rule, does not exceed the value of 50-70%.

 The main advantage of the solid-phase compound method in the preparation of semi-finished products with a given microstructure and properties compared to the powder metallurgy method is that when preparing semi-finished products from massive preforms, the conditions for contamination of the semi-finished product with impurities are significantly reduced due to a decrease in the total surface area of the compound.

 Other advantages of the method include less energy-intensive equipment in comparison with powder metallurgy, less stringent requirements for the production culture and safety precautions due to lower values of required efforts, processing temperature and reduction in the length of free surfaces.

 However, the solid-phase compound method also has disadvantages.

 The main one is the instability of the mechanical properties of the compound and the need for this to apply tough and reliable methods of non-destructive testing of the quality of the formed solid-phase compound.

 It is known that the main defects in the formation of a solid-phase compound are micropores, as well as the zones of the compound that have not passed the final, third stage of its formation. The appearance of micropores is due to the fact that the result of the formation of TPS is the disappearance of two contact surfaces. Obviously, the disappearance of contact surfaces must be accompanied by the release of free energy. Therefore, pores, according to one of the hypotheses that exist today, are a form of scattering of free energy released when two surfaces disappear. The morphology of defects of a solid-phase compound at the initial stages of its formation, as well as the density of their distribution, depends on the nature of the relief of the combined surfaces, on the bonding modes, as well as on the initial microstructure of the workpieces. At the same time, at the final stages of the formation of the compound, an arbitrary form of defects as a result of the development of surface diffusion processes is transformed into the equilibrium, i.e. stable, spherical shape. As an analysis of the results of studying the process of formation of a solid-phase compound shows, most of the time and of the time required for the formation of a compound with equal strength to the basic material is spent on healing microdefects of the compound, primarily such as micropores.

 As in the case of the powder metallurgy method, in case of solid-phase bonding, the most effective conditions for eliminating pores are the conditions of comprehensive compression. Plastic deformation in the general case does not lead to healing of pores, if it is not accompanied by the development of grain-boundary slippage and grain rotation. As studies show, in the TFS process, the joined surface is in these conditions.

 It was noted above that the surfaces to be joined are subjected to special chemical, electrochemical and other types of treatment before welding in order to remove all kinds of contamination. Another method for obtaining a clean surface is high temperature vacuum annealing. In the process of vacuum annealing, immediately before welding, the joined surface, in contact with gas molecules, in quality and quantity corresponding to the residual partial pressure determined by air pumping means, is freed from all kinds of impurities, dirt and oxides by various mechanisms, for example, dissolution, sublimation and evaporation . Of course, the chemical composition of the surface layers changes. Therefore, during the subsequent solid-phase joining of the preforms, another structural defect is formed - a chemical heterogeneity in the joint zone. The restoration of chemical homogeneity is possible and even partially occurs as a result of the development of the diffusion mass transfer process. Therefore, for its complete completion requires the use of high temperatures, as well as considerable time.

 The implementation of the process of formation of a solid-phase compound under conditions corresponding to optimal superplasticity conditions partially solves the problem of micropore removal and chemical heterogeneity by increasing the uniformity of deformation in the joint zone. However, for a complete and guaranteed elimination of defects, intense plastic deformation is required in the zone of connection of the workpieces. This is possible only if the degree of deformation exceeds the level of deformation that is actually achievable during the formation of a solid-phase compound (as, for example, in the considered example) by an order of magnitude.

 Another disadvantage of the TFS method is the orientation of the set of joint defects, which is determined by the shape of the joined surface. In reality, preparing a flat surface for welding is easier. Therefore, after joining micropores, micro-discontinuities, chemical heterogeneity is also located in the plane in the welded semi-finished product, thus violating the condition of isotropy of the material properties in the entire volume of the obtained semi-finished product. The latter circumstance limits the application of this method in the production of critical products.

 The experimentally proven fact is known of the positive effect on the healing of defects of a solid-phase compound of intense plastic deformation of samples under optimal conditions of superplasticity of a deformable material [4]. By the example of a VT14 titanium alloy (Ti - 3.5-6.3Al - 2.5-3.8Mo - 0.9-1.9V) with a microcrystalline structure (average grain size d = 2.0-3.0 μm) A special experiment was conducted, during which the change in size and shape of the selected defect of the solid-phase compound — pores of an arbitrary size during uniaxial hot deformation of the sample along the surface of the compound — was monitored. The sample was a package of pre-welded to each other by solid-phase connection of the workpieces.

 When performing targeted observation, it was found that the disappearance of the original pore (figure 1) occurs by slamming it (figure 2). A decrease in the pore size occurs as a result of the rotation of the surrounding grain pores after the deformation of the sample to a degree of deformation of e ~ 18-20%. The main mechanism for grain rotation is grain boundary slippage, activated as a result of deformation of the sample under conditions corresponding to optimal conditions for the development of superplastic deformation for VT 14 alloy with a microcrystalline structure.

 This experiment is direct evidence that in order to form a defect-free solid-phase compound, it is necessary to ensure the development of intensive grain mixing processes in the joint zone. At the same time, neither the powder metallurgy method, nor the solid-phase compound method allows to fully realize the condition of intensive mixing of grains in the joint zone, since it does not provide the necessary level of degree of deformation directly in the joint zone.

 An analysis of the above methods for producing semi-finished products with a given microstructural state and other special properties allows us to conclude that none of them can be used to produce high-quality semi-finished products that would have sufficient dimensions, the necessary microstructure and properties, for making them critical parts, such as shafts, discs, gas turbine engine blades in the aviation industry, etc.

 The closest analogue to the proposed method is a method for producing semi-finished products from metals and alloys, including one-piece connection on compatible surfaces of the workpieces with prepared microstructure and / or properties and solid-phase mixing by deformation in several stages under temperature and speed conditions, selected taking into account a given microstructure and / or properties of semi-finished products, as well as the initial microstructure of the workpieces, and during deformation, the direction of application of the deforming loads and / or type of loading and / or use loading, including torsion, with a degree of deformation at each stage, providing a change in the shape and / or orientation in space of the surface of the connection and / or an increase in the area of the connection compared to the initial state or obtained at the previous stage [ 2].

 The objective of the invention is the creation of a new method of producing semi-finished products from separate homogeneous or heterogeneous preforms with a given microstructure and properties, in which an equal-strength basic material compound, the required chemical and structural uniformity in semi-finished products are achieved due to the possibility of intensive mixing of pre-connected with the formation of contact, preventing mutual slipping blanks (i.e. preventing the blanks from shifting from each other relative to a friend with a violation of the continuity of the obtained compound) under intense plastic deformation under complex loading as a result of a multiple increase in the area and transformation of the shape of the joined surface compared to the original.

 Including the objective of the invention is to obtain large-sized blanks from a material with a given microstructure and properties.

 Including the objective of the invention is to obtain composite materials.

 Including the objective of the invention is the synthesis of complex materials from elementary in the volume of semi-finished products.

 The technical result is achieved by the fact that in the method for producing semi-finished products from metals and alloys, including one-piece connection on compatible surfaces of the workpieces with the prepared microstructure and / or properties and solid-phase mixing by deformation in several stages under temperature and speed conditions, selected taking into account the given microstructure and / or the properties of semi-finished products, as well as the initial microstructure of the workpieces, and during deformation, the direction of application of the deforming load is changed and / or type of loading and / or using loading, including torsion, with a degree of deformation at each stage, providing a change in the shape and / or orientation in space of the surface of the connection and / or increase the area of the connection compared with the initial state or obtained in the previous stage, according to According to the invention, the deformation is carried out in three stages, while in the first stage the preforms are compressed, in the second they are drawn to obtain a bar, and in the third bar they are deformed by torsion.

In addition, the task is solved due to the fact that:
- choose workpieces with a prepared microstructure that provides solid-phase mixing under temperature and speed conditions corresponding to the optimal interval of manifestation of superplasticity in the material of the workpieces;
- choose blanks with prepared microcrystalline structure with an average grain size of 1.0-50.0 microns;
- choose blanks with a prepared submicrocrystalline structure with an average grain size of 0.5-1.0 microns;
- preforms are selected from dissimilar materials forming intermetallic compounds, solid-phase mixing is carried out at all stages except the last under temperature and speed conditions that prevent the formation of brittle layers, and at the last stage, the temperature is raised until the formation of an intermetallic compound in the entire volume of the semi-finished product;
- a workpiece made of a material having a higher melting point is selected with a smaller grain size;
- in the manufacture of composite semi-finished products, preforms are selected from materials with various properties, and when connected, they are alternated;
- alternating preforms are selected from materials with different values of the coefficient of linear expansion so that the coefficient of linear expansion of the preform from a material with high strength properties is greater than the coefficient of linear expansion of the preform from a material with lower strength properties;
- alternating preforms are selected from materials with different ductility characteristics;
- at least two preforms in the form of a bar are selected, which are combined along the end surfaces, the manufacture of the semi-finished product is carried out in three stages, while at the first stage the preforms are compressed by applying force along the symmetry axis of the preforms until the washer is obtained, at the second stage, the washer is pulled along the axis perpendicular to the axis of symmetry of the washer until the rod is obtained, on the third, the workpieces are deformed by torsion, applying torque to the opposite end sections of the rod in a plane perpendicular to the axis and bar symmetry;
- at the first stage, the compression is combined with torsion,
- perform reverse torsion;
- choose at least two tubular billets, which are installed axially, the manufacture of the semi-finished product is carried out in three stages: at the first stage, the billets are deformed by compression to obtain a strip, applying a compressive force perpendicular to the axis of symmetry of the initial billets, at the second stage, the strip is drawn until a bar is obtained, on the third stage, torsional deformation is performed by applying a torque to the opposite end sections of the bar in a plane perpendicular to the axis of symmetry of the bar;
- choose a tubular billet and a billet in the form of a rod, the billets are installed one into the other, the semi-finished product is manufactured in three stages, while at the first stage the billets are deformed by compression until a strip is obtained, applying a deforming force perpendicular to the axis of symmetry of the billets, at the second stage, the strip is stretched to of obtaining the rod, in the third stage, torsional deformation is performed by applying torque to the opposite end sections of the rod in a plane perpendicular to the axis of symmetry of TKA;
- choose a tubular billet and a billet in the form of a rod, the billets are installed one into the other, the semi-finished product is manufactured in three stages, while at the first stage the billets are deformed by compression to obtain a washer, applying a deforming force to the ends of the billets, along the axis of symmetry of the billets, at the second stage pulling the resulting washer along a direction perpendicular to the axis of symmetry of the washer to obtain a bar;
- choose blanks in the form of rods having a cross-section of an equilateral polygon with a flat face, which are combined along the lateral surfaces along their generatrix, are connected, and the manufacture of the semi-finished product is carried out in two stages, while at the first stage the blank is deformed by compression to obtain a bar, applying force compression perpendicular to the axis of symmetry of the initial workpieces, at the second stage, torsional deformation is performed, applying torque to the opposite end sections of the rod in the plane, perpend the ocular axis of symmetry of the bar;
- choose blanks in the form of plates that connect, and the manufacture of the semi-finished product is carried out in three stages, while at the first stage the blank is deformed by compression to obtain a strip, applying a compressive force to the opposite joined surfaces of the blanks, along the normal to these surfaces, at the second stage the strip is stretched before the formation of the rod, and at the third stage, the rod is deformed by torsion, applying torque to its opposite ends in a plane perpendicular to the rod;
- at the third stage, torsion is combined with tension;
- at the third stage, torsion is combined with compression;
- introduce an additional operation - obtaining a solid-phase connection of the workpieces to be processed on compatible surfaces, which is performed before the first step of processing the workpieces;
- introduce an additional operation - obtaining a solid-phase connection of the workpieces on compatible surfaces, which is combined with at least part of the first stage;
- the preparation of semi-finished products is carried out in N cycles, each of which includes the indicated steps.

 The essence of the invention is to obtain semi-finished products with a given microstructure and properties by the method of pseudopowder metallurgy by solid-phase mixing, which has fundamental differences compared with known methods.

 Solid-phase mixing is the uniform redistribution of connected preforms with a pre-prepared microstructure and having the desired properties with increasing contact surface area and changing its configuration. It should be noted that the combined workpieces are subjected to stirring, in which there is contact over the entire surface of the joint, which ensures their joint deformation, as well as the deformation of the joint zone during solid-phase mixing. Solid-phase mixing is realized in the process of intense plastic deformation, under the conditions of simple and complex loading, which is carried out at high (> 0.4 Tm) deformation temperatures with a strain rate lying in the range of superplastic deformation rates of the workpiece material to significant (several hundred and even thousands of percent) of the degree of deformation. The possibility of implementing these loading conditions is due to the use of preforms with a prepared microstructure.

Such loading guarantees:
- the flow of grain-boundary slippage in the connection zone evenly over the entire contact surface of the workpieces;
- redistribution of structural defects, such as heterogeneity of the chemical and phase composition in the zone of formation of the compound;
- the disappearance of micropores and discontinuities due to the development of shear deformations, determined by the complex, shear nature of loading.

 Consider and compare the basic operations that are inherent in powder metallurgy and the claimed method.

 Unlike powder metallurgy, where powders play the role of blanks, the proposed method uses relatively massive blanks that have finite dimensions. The preforms are mixed during intense plastic deformation under temperature and speed conditions, which are determined by the microstructure of the preforms, which makes it possible to obtain a semi-finished product with a given microstructure and chemical composition uniformly distributed in the bulk of the semi-finished product. In addition, a significant decrease in the initial surface of the connection of the workpieces leads to a significant reduction in the degree of contamination of the material of the semi-finished product with various undesirable impurities.

 Similarity with powder metallurgy to the claimed method gives the operation of mixing the material. In the first case, this is the mechanical mixing of individual "preforms" - powders, and in the second - this is the mixing of pre-connected preforms, in which there is an increase in the initial contact surface and its uniform redistribution in the entire volume of the semi-finished product.

 In view of the foregoing, the authors propose to name the inventive method for producing semi-finished products from connected preforms by means of their solid-phase mixing by the method of pseudopowder metallurgy.

 Unlike powder metallurgy, the inventive pseudopowder metallurgy method allows monolithic workpieces with the maximum allowable geometric dimensions having nano- and submicrocrystalline structure, while ensuring the production of large-sized semi-finished products with a microcrystalline structure of a given type.

 Let us also consider and compare the basic operations that are inherent in the solid-phase compound and the claimed methods.

 The method of solid-phase connection involves the development of plastic deformation, and, consequently, an increase in the area of initial contact in the zone of connection of the workpieces. However, with solid-phase mixing, the strain rate is at least two to three times higher than the maximum strain rate, which is usually achieved in the solid-phase compound method.

 In the formation of a solid-phase compound, along with the deformation, an important role in the formation of the compound is played by diffusion processes, however, in the case of solid-phase mixing, the deformation processes play a decisive role at all stages of the formation of the compound, and diffusion processes are usually suppressed.

 During the entire process of formation of a solid-phase compound, the surface of the initial contact of the monolithic preforms remains unchanged in shape. In this case, the position of the joint defects, such as residual porosity, chemical and phase inhomogeneities, remains unchanged in volume. The presence of defects in the plane of the initial contact leads to the appearance of anisotropic mechanical properties.

 When semi-finished products are obtained by the pseudo-powder metallurgy method during solid-phase mixing of pre-connected preforms, not only the redistribution of the preform material in the semi-finished product takes place, but also the redistribution in the volume of defects that are present on the original joint surface.

 Intensive plastic deformation under the conditions of a complex process, including torsion and loading, provides not only an increase in the uniformity of mechanical properties, but also almost completely eliminates porosity and increases chemical uniformity in the semi-finished product due to the development of stimulated grain boundary slippage, grain rotation, and mutual displacement grains, which is provided by the nonmonotonic development of shear deformation in the joint zone.

 After solid-phase mixing of the workpieces, the concept of the joint surface, i.e. the surface, which divides the semi-finished product into clearly distinguishable parts with well-defined and characterizing these parts properties, completely disappears, since the interface disappears.

 In the physical sense of the processes, especially at the initial stage, solid-phase mixing resembles the process of solid-phase compound.

 However, with a solid-phase compound, the process ends with a volumetric interaction step. The stage of volumetric interaction is based on the healing of microdefects of a solid-phase compound as a result of diffusion creep of the material under conditions of comprehensive compression of the material volumes adjacent to the defect.

 Solid-phase mixing under complex loading occurs as a result of the development of intense shear plastic deformation, which increases the plasticity resource of the material. And nonmonotonic shear deformation caused by complex loading contributes to the formation of stable dislocation complexes, which inhibits grain growth in the entire volume of the semi-finished product during its processing.

 These factors can increase the degree of deformation during deformation, as well as further reduce the processing temperature. All this extends the technical capabilities of the proposed method, since it makes it possible to obtain large-sized semi-finished products with micro-, submicro- and nanocrystalline structures.

 By large-sized semi-finished products here we mean semi-finished products of such geometric dimensions that are at least twice the size of the workpieces, in which it is technically possible to obtain a microstructure evenly distributed throughout the volume with the smallest possible grain size.

 So, for example, by the method of quasi-hydrostatic torsion (torsion on the Bridgman anvil), it is now possible to obtain NK microstructure in workpieces with dimensions of the order of 20.0–25.0 mm in diameter and 0.5–1.0 mm in thickness. Therefore, by definition, the semi-finished product obtained by solid-phase mixing of two, three or more preforms with dimensions of 20.0-25.0 mm in diameter and 0.5 mm thick allows one to obtain a large-sized semi-finished product with an NK microstructure.

 Another example is based on the application of the hydrogen doping method in the preparation of the SMC microstructure in biphasic titanium alloys. It is known that the addition of hydrogen to the alloy lowers the temperature of the direct β_ → α + β phase transition, which contributes to an increase in the dispersion of the hardened microstructure after rapid cooling. An increase in the dispersion of the microstructure allows one to lower the temperature of deformation processing and simultaneously increase the rate of deformation while maintaining a sufficient resource of plasticity of the material for the development of processes of transformation of the plate microstructure in it and the formation of a globular SMC structure. However, for guaranteed removal of hydrogen from the workpiece material after its deformation processing, the workpieces should be sheet-like and have a thickness of not more than 2.0-3.0 mm.

 The possibility of obtaining massive, large-sized semi-finished products from several workpieces with a QMS structure obtained by the hydrogen doping method, according to the inventors, can be most effectively realized using solid-phase mixing of sheet blanks.

 The essence of the additional claims is as follows.

 In the case when preforms with a microstructure prepared in them are selected, it is advisable to perform solid-phase mixing under conditions corresponding to the optimal range of superplasticity in the material of the processed preforms. The effect is to reduce the required deformation efforts, to increase the plasticity resource of the material, workpieces, and to intensify the healing of defects in the solid-phase compound.

 In the case when preforms with a prepared microcrystalline structure with an average grain size of 1.0-50.0 μm are selected, it is advisable to carry out solid-phase mixing of the preforms under temperature and speed conditions corresponding to the highest value of the speed sensitivity coefficient of the processed material in order to fully realize the advantages superplastic deformation in terms of reducing deforming forces and increasing its ductility resource.

The choice of preforms with a submicrocrystalline structure prepared in them with an average grain size of 0.1-1.0 μm allows, firstly, to lower the processing temperature, thereby suppressing the activation of diffusion processes as a result of plastic deformation, thereby contributing to the formation of stable dislocation complexes in the material activating the course of the dynamic recrystallization process, which leads to additional refinement of the microstructure or prevents grain growth in
conditions of intense plastic deformation. Secondly, it increases the limit values of the degree of deformation by increasing the resource of plasticity of the material at low temperatures, preventing the premature destruction of the processed semi-finished products.

 In the case when the synthesis of intermetallic compounds is carried out in the process of solid-phase mixing, heterogeneous materials forming intermetallic compounds are selected as blanks, and solid-phase mixing is carried out at all stages except the final stage in temperature-speed conditions that prevent the formation of brittle layers, and at the final stage the temperature raise to the beginning of the formation of intermetallic compounds in the entire volume of the semi-finished product. In this case, a preform of a material having a higher melting point is selected with a smaller grain size in order to lower the optimum temperature of its deformation and bring it closer to the deformation temperature of a material having a lower melting point, in order to approximate the deformation characteristics of preforms of various materials to each other.

 In the manufacture of composite semi-finished products, such as magnetic rotors, preforms are selected from materials with different properties, and when connected, they are alternated. These conditions are aimed at increasing the complex of properties in the semi-finished product. For example, its operational characteristics and, above all, ductility, while maintaining a sufficiently high level of magnetic properties.

 An additional condition for choosing the workpiece material in the manufacture of composite semi-finished products is that the conditions for alternating workpieces from materials with different values of the coefficient of linear expansion are observed, and the coefficient of linear expansion of workpieces from a material with high strength properties should be less than the coefficient of linear expansion of workpieces from a material with low strength properties.

 It is known that most of the materials from which permanent magnets are made belong to the group of precision alloys, that is, to alloys in which the chemical composition must be strictly observed for the optimum composition providing maximum magnetic properties. It is known that with increasing dimensions of the ingots, it becomes difficult or even almost impossible to ensure that the chemical composition in the entire volume of the ingot corresponds to the required composition. Another feature of these materials is the almost zero plasticity of the material after its thermomagnetic treatment.

 Obtaining a composite large-sized semi-finished product by pseudopowder metallurgy from alternating preforms of the optimal size from magnetic material with preforms from a more durable material and having a larger coefficient of linear expansion compared to magnetic material allows the semi-finished product and then the product to provide the desired high magnetic properties, combined with high structural properties. High magnetic properties are achieved by increasing the accuracy of the chemical composition in the workpieces by choosing the optimal shape and size of the castings. High strength characteristics are achieved due to the fact that the solid-phase mixing process provides for uniform mixing of alternating workpieces in the semi-finished product under conditions of torsion-intensive loading. After such processing, the initially planar blanks are transformed into a multilayer screw structure. Considering the fact that solid-phase mixing occurs at high temperatures, after cooling it is brittle, the magnetic material is surrounded by a stronger material, which ensures the creation of comprehensive compression conditions in it. The composite rotor in operation experiences tensile radial loads from the action of centrifugal forces during its rotation. Tensile loads are partially compensated by compressive stresses previously created in it, and this significantly increases the reliability and service life of the composite rotor.

 Another additional condition for choosing the material of the workpieces for the manufacture of composite semi-finished products is the observance of the conditions for the alternation of workpieces from materials with different values of ductility characteristics. This condition allows to increase the ductility of the semi-finished product obtained by solid-phase mixing of billets from brittle materials through the use of more ductile intermediate layers.

 The most effective method of solid-phase mixing from the point of view of minimal contamination of the volume of the semi-finished product with uncontrolled impurities is possible in the case when at least two preforms in the form of a rod are selected that are combined along the end surfaces. The manufacture of the semi-finished product in this case is carried out in three stages.

 At the first stage, the preforms are compressed by applying a force along the axis of symmetry of the preforms. The workpieces are plastically deformed, and the semi-finished product takes the form of a washer.

 At the second stage, the washer is pulled along an axis that is perpendicular to the axis of symmetry of the washer until a rod is obtained. After such processing, the axis of the bar coincides with the axis of the broach.

 At the third stage, the bar is deformed by torsion, applying a torque to the opposite end sections of the bar in a plane perpendicular to the axis of symmetry of the bar.

 Suppose two cylindrical blanks are selected. Workpieces are connected along the end surface. The connection surface is a plane. After performing the three loading steps, a semi-finished product is obtained in which the flat surface of the joint or contact is transformed into a helical surface uniformly twisted in the entire volume of the semi-finished product. The workpieces are also redistributed and mixed evenly throughout the semi-finished product. The initially flat and perpendicular axis of the workpieces transforms the joint surface during drawing, first to a flat surface parallel to the axis of the semi-finished product, and then to a helical surface, most of which tends to again take a position perpendicular to the axis of the semi-finished product. Thus, solid-phase mixing of the processed workpieces is realized, which occurs with minimal contamination of the entire volume of the obtained semi-finished product with oxides, and carbon (fat molecules) and hydrogen-containing (water molecules) chemical compounds.

 To increase the efficiency of the first stage of processing by activating the process of healing defects in the solid-phase connection of the workpieces by combining the deformation of the workpieces with compression and torsion. The joint, intensive shear deformation of the workpieces under compressive loads accelerates the healing of defects in the solid-phase compound, which improves the quality of the semi-finished product.

 If at the first stage the compression is supplemented with reverse torsion, then this will lead to a decrease in the required deformation forces due to the fact that activation of relaxation processes in the deformable material will occur. The development of relaxation processes will ensure the development of dynamic recrystallization due to the fact that during deformation by cyclic loading, dislocations of various slip systems are intensively formed, which, entering into dislocation reactions, form dislocation clusters, which are the centers of nucleation of new grains.

 It is possible to obtain semi-finished products with a given microstructure and properties by the method of pseudopowder metallurgy from workpieces of any shape and size.

 For example, in the case when technical capabilities do not allow casting to obtain a massive cylindrical workpiece without defects, which are concentrated in the center of the workpiece, two or more tubular workpieces are selected. Tubular billets from the point of view of high-quality microstructural state can be obtained by centrifugal casting.

 The blanks are set axially. When installing blanks, it is possible to use thermal interference for sealing the surface of the joint and subsequent auto-vacuum heating.

 The manufacture of the semi-finished product in this case is carried out in three stages.

 At the first stage, the workpieces are placed in the working space of the deforming installation, the required medium is created, heated to the working temperature and deformed by compression to obtain a strip, applying a compressive force perpendicular to the axis of symmetry of the initial workpieces. Compression is carried out until a contact is formed on the inner surface of the inner cylindrical workpiece and a strip is formed.

 At the second stage, the strip is pulled to obtain a bar.

 At the third stage, the bar is deformed by torsion, applying a torque to the opposite end sections in a plane perpendicular to the axis of symmetry of the bar.

 The considered method for producing semi-finished products allows to improve their quality by improving the quality of cast billets, for example when casting thin-walled pipes, through the use of centrifugal casting.

 In some cases, it is advisable to use a tubular blank and a blank in the form of a bar. For example, when one of the preforms is very fragile, it is axially mounted in a plastic tubular shell.

 In this case, the workpieces are set one into the other. The manufacture of a semi-finished product is carried out in three stages.

 At the first stage, the workpieces are deformed by compression to obtain a strip, applying a deforming force perpendicular to the axis of symmetry of the workpieces.

 At the second stage, the obtained strip is pulled to obtain a bar.

 At the third stage, the bar is deformed by torsion, applying a torque to the opposite end sections in a plane perpendicular to the axis of symmetry of the bar. This is advisable if the length of the tubular billet and bar exceeds a value equal to two external diameters of the tubular billet.

 At the first stage of solid-phase mixing, the deformation of axially mounted workpieces can be carried out along the axis of symmetry of the workpieces until the washer is formed, and at the second stage, the washer is drawn along the axis perpendicular to the axis of symmetry of the washer until a bar is obtained. It is advisable to perform such a sequence of operations if the length of the tubular workpiece and the bar does not exceed the value necessary to maintain the stability of the assembly.

 In some cases, it is easier to prepare a microstructure of a given type in preforms by direct or reverse extrusion, by extrusion, or by drawing. After such processing, the workpieces usually have a large length and a small cross section compared to the length, that is, they take the form of rods.

 In this case, the workpieces are aligned on the side surfaces along their generatrix. The manufacture of a semi-finished product is carried out in two stages.

 At the first stage, the pack of blanks is deformed by compression to obtain a rod of a larger diameter, applying a compressive force perpendicular to the axis of symmetry of the initial blanks.

 At the second stage, the resulting rod is deformed by torsion, applying torque to the opposite end sections of the rod in a plane perpendicular to its axis of symmetry.

 In order to simplify the process of obtaining the connection and increase the efficiency of the operation of broaching the workpiece, a polygon with a flat side surface, for example a triangle, a quadrangle, a hexagon, etc., is selected in cross section.

 Using the method of solid-phase mixing, it is possible to process preforms in the form of plates or strips when the microstructure in the preforms is prepared by rolling. Workpieces are joined along large lateral surfaces. The manufacture of a semi-finished product is carried out in three stages.

 At the first stage, the pack of blanks is deformed by compression to obtain a strip, applying a compressive force perpendicular to the axis of symmetry of the initial blanks.

 In the second stage, the strip is stretched to form a bar.

 At the third stage, the obtained rod is deformed by torsion, applying a torque to the opposite end sections in a plane perpendicular to its axis of symmetry. This method can be most effectively applied in cases where hydrogen plasticization is used at the stages of microstructure preparation and when subsequent removal of hydrogen from the workpieces during degassing is required. Sheet blanks due to their small thickness are excellent objects for obtaining massive semi-finished products in the process of their solid-phase mixing.

 Upon receipt of the semi-finished product using a three-stage processing after the second stage, the workpieces usually have a cylindrical or close to cylindrical shape. If the ratio of the length of the workpiece to its transverse size is large enough, for example, more than 2.5-3.0, then it becomes advisable at the third stage to combine the torsion of the workpieces with tension. An additional tensile component to torsion allows to increase the plasticity resource of mixed billets, activates the dynamic recrystallization processes, as well as the development of grain-boundary slipping processes, increasing the uniformity of the distribution of the microstructure and chemical composition in the entire volume of the obtained semi-finished product, and therefore their quality.

 To increase the efficiency of the solid-phase mixing process and, above all, the quality of the obtained semi-finished product when processing short workpieces, it is possible to combine torsional deformation with compression at the third stage.

 Various methods can be used to obtain an integral connection of workpieces subjected to solid-phase mixing: conventional soldering, reactive soldering, known methods of fusion welding, solid-phase bonding.

 It is advisable to use a solid-phase connection, which can be performed both before the first stage and at the beginning of the first stage, using the modes known, for example, from the source [3] as an integral connection of preforms on compatible surfaces. If solid-phase bonding is used as a method for joining preforms, then it becomes possible to achieve the maximum level of quality of the semi-finished product in terms of the absence of contamination products in the volume of semi-finished products due to the automatic fulfillment of strict requirements for a high degree of production culture.

 In some cases, it is advisable to combine the operation of joining the workpieces with the first stage and thus increase the productivity of the process for producing semi-finished products.

 In the event that, according to the conditions of the tasks, it is required to obtain finely mixed workpieces in the semi-finished product, then the semi-finished products are obtained in N cycles, each of which includes the steps discussed above.

 Obtaining semi-finished products with the specified microstructure and properties by the method of pseudopowder metallurgy additionally reduces the complexity and cost of producing large-sized semi-finished products through the use of less energy-intensive equipment and minimizing manual labor.

 The list of figures of graphic images.

1. The microstructure of the plot of the solid-phase compound of the VT14 titanium alloy subjected to hot deformation under conditions of superplasticity:
a - The initial state.

 b - After deformation by uniaxial tension.

1,6•10^-4 с^-1.Deformation degree ε = 19.0%, deformation temperature Т = 860 ^o С, strain rate

1.6 • 10 ^-4 s ^-1 .

2. Scheme of the process of solid-phase mixing of two massive billets:
a - The first stage is compression.

 b - The second stage - broach.

 c - The third stage is torsion.

3. Microstructure of VT9 alloy:
a - Section of the semi-finished product after solid-phase mixing.

 b - The destruction surface of the semi-finished product.

4. Microstructure of VT6 alloy:
a - Section of the semi-finished product after solid-phase mixing.

 b - The destruction surface of the semi-finished product.

5. Microstructure of alloy 25X15K:
a - Section of the semi-finished product after solid-phase mixing.

 b - The destruction surface of the semi-finished product.

6. Scheme of the process of solid-phase mixing of sheet blanks:
a - The first stage is compression.

 b - The second stage - broach.

 c - The third stage is torsion.

7. Scheme of the process of solid-phase mixing of billets in the form of rods:
a - Assembly of blanks.

 b - The first stage is direct extrusion.

 c - The second stage is torsion.

8. Scheme of the process of solid-phase mixing of two tubular blanks:
a - The first stage - compression along the axis of symmetry of the workpieces.

 b - The second stage - broach.

 c - The third stage is torsion.

9. Scheme of the process of solid-phase mixing of the tubular billet and the bar installed inside the tubular billet:
a - Assembly of blanks.

 b - The first stage is the compression of the blanks along an axis perpendicular to the axis of symmetry of the blanks.

 c - The second stage is torsion.

10. Scheme of the process of solid-phase mixing of the tubular billet and the bar installed inside the tubular billet:
a - Assembly of blanks.

 b - The first stage is compression along the axis of symmetry of the workpieces.

 c - The second stage is a broach.

 d - The third stage is torsion.

11. Scheme of the second cycle of the process of obtaining a composite semi-finished product in three stages and two cycles:
a - The first stage is compression.

 b - The second stage - broach.

 c - The third stage is torsion.

 In the figures illustrating the process diagrams, the images of individual blanks differ in different hatching.

 Examples of specific performance.

 The following examples do not exhaust the scope of the proposed method. By way of illustration, examples are presented in which semi-finished products, including large-sized ones, are obtained from materials that are most widely known and used in technology. In particular, examples 3 and 7, concerning the preparation of a large-sized semi-finished product from a 25X15K magnetic alloy and a composite semi-finished product using blanks from a 25X15K magnetic alloy and the heat-resistant alloy EI435, confirm the possibility of obtaining semi-finished products from heat-resistant, difficult to deform materials.

 In all examples, the temperature and speed conditions are selected taking into account the given microstructure in the semi-finished product, as well as the initial microstructure in the workpieces.

 In addition, in some examples, temperature and speed conditions are also selected taking into account the properties of the semi-finished products.

 In all examples of processing two-phase titanium alloys, hot deformation modes corresponding to optimal superplasticity modes were used.

 Example 1

 Two cylindrical billets of two-phase VT9 titanium alloy (Ti - base; 5.8-7.0 Al; 2.8-3.8 Mo; 0.8-2.0 Zr; 0.2-0.35) are subjected to solid-phase mixing Si). The microcrystalline structure in the workpieces is prepared in the process of hot deformation under complex loading conditions using a complex loading apparatus according to the regimes providing a microstructure with an average grain size of ~ 5.0 μm. After thermomechanical processing, the preforms have a globular microstructure with an average grain size dcp = 4.0-5.0 μm, uniformly distributed over the entire volume of the preforms. Two blanks are selected. The diameter of the blanks is 130.0 mm, the length of each is 100.0 mm.

Processing blanks is performed using the following processing equipment:
1. Vacuum furnace with gas distribution panel.

 2. Rolling mill.

 3. 630 tons hydraulic press with a rotary table mounted on the lower die plate.

 The process is carried out in three stages. A diagram of the process is presented in figa, b, c.

Before the first, main stage of workpiece processing, an additional operation is performed - solid-phase connection of the workpieces. Why the connected end surfaces of the workpieces are cleaned of dirt and degreased by rinsing in acetone. Next, the workpieces are combined on the treated surfaces. Then they are installed in a device that allows to transmit uniform compression force over the entire end surface of the workpieces, transmitting the force to the workpieces with gaseous argon through a flexible metal membrane. The device with the blanks installed in them is placed in a vacuum oven. In the working chamber of the furnace, a vacuum is created with a residual pressure of 5.0 • 10 ^-3 Pa and the workpieces are heated to a temperature of 920 ^o C. The welding temperature is selected 30 ^o C below the temperature of the subsequent deformation processing in order to prevent grain growth in the workpieces during their high-temperature exposure to the stage of formation of the compound. After the temperature reaches the working level, the workpieces are compressed by applying a pressure of 2.0 MPa to the end surfaces. The workpieces are kept at a given pressure for one hour. After that, the pressure is removed, the temperature is lowered, bringing it to room temperature, air is let into the working chamber of the vacuum furnace, the device is removed from the furnace, the welded workpieces are dismantled and removed from it.

 The first stage of solid-phase mixing - compression of the workpieces with torsion to obtain the washer is performed on a hydraulic press equipped with a rotary table (figa).

 The compression process aims to increase the initial surface area of the joint by about 60%. The combination of compression with torsion is aimed at intensifying the processes of intragranular slip along various slip systems and the formation of annihilation-resistant dislocation clusters that contribute to dynamic recrystallization, which leads to additional grinding of the initial grain by an average of 10-15%. The use of reverse torsion reduces the required effort, as practice shows on average by 20%.

The workpiece processing mode in the first stage is as follows:
- deformation temperature - 950 ^o C;
- strain rate ~ 10 ^-3 s ^-1 ;
- the degree of compression of the workpieces in height - 60%,
- rotational speed of the turntable - 1.0 revolution / min.

 - the direction of rotation during processing is changed four times.

 In a second step, the resulting washer is pulled along a direction perpendicular to the axis of the washer until a rod is formed. The broach is performed with a degree of deformation, providing changes in both the orientation of the surface of the connection relative to the initial position (figb), as well as the area of the initial connection.

Washer pull mode is as follows:
- deformation temperature - 950 ^o C;
- strain rate ~ 10 ^-3 s ^-1 .

 The broach is carried out on a hydraulic press.

 After broaching get a bar, which is subjected to machining on a lathe to remove defects from the surface. The dimensions of the bar are as follows: length - 200.0 mm, diameter - 100.0 mm. The surface of the joint after drawing becomes parallel to the generatrix of the bar.

The third stage is the torsion of the bar (pigv). Additionally, with torsion, a compressive load is applied to the bar. Torsion is performed on a rolling mill. The processing mode of the torsion bar in combination with tension is as follows:
deformation temperature - 950 ^o C;
- rotation speed of the movable gripper - 0.5 revolution / min;
- number of revolutions - 10;
- the degree of compression of the workpieces in height - 20%.

 Upon completion of the third stage, the initial flat surface of the connection, dividing the workpiece into two parts, is transformed into a helical surface, which seems to divide the workpiece into several parts (pigv). An increase in the number of revolutions leads to an increase in the parts into which the workpiece is divided, and, accordingly, the area of the initial joint. Moreover, an increase in the number of revolutions leads to the fact that most of the helical surface tend to occupy a position perpendicular to the axis of the workpiece.

 In FIG. 3a shows the microstructure of the semi-finished product after the final third stage of the solid-phase mixing process in the area, including the zone of connection of the blanks with each other, indicating the absence of joint defects. On figb presents the destruction surface of the semi-finished product in this area. A viscous, cellular fracture indicates that fracture does not occur along the surface of the joint, but along the base material.

The performed ultrasonic testing showed a high degree of uniformity in the distribution of the microstructure in the volume of the entire semi-finished product. The results of metallogaphic analysis indicate that the grain size in the semi-finished product is d = 5.0-6.0 μm. No micropore defects were found in the contact zone of the workpieces. After the third stage of processing, the tensile strength of the semi-finished material is equal to the tensile strength of the workpiece material in the initial state and corresponds to the value of σ _in = 900 MPa.

 Example 2

 Two cylindrical billets of two-phase VT6 titanium alloy (Ti - base; 5.3-6.5 Al; 3.5-4.5 V) are subjected to solid-phase mixing.

 The blanks have a globular microstructure with an average grain size dcp = 4.0-6.0 μm, uniformly distributed throughout the volume. Two blanks are selected. The dimensions of the blanks are the same as in the previous example. The workpieces are processed in three stages as in example 1.

Apply the following processing equipment:
1. A hydraulic press with a force of 630 tons with a rotary table mounted on the lower die plate.

Considering the fact that the compression operation is the basis of the first stage of solid-phase mixing, the process of solid-phase joining of workpieces is combined with the first stage. Why surfaces of the workpieces are cleaned of contamination and degreased in acetone. Next, the workpieces are combined on prepared surfaces, set between plane-parallel plates of the stamp and compressed. Then the workpieces are heated, constantly maintaining the compression force on the workpieces at a level of ~ 0.5-0.7 from the level of the current value of the flow stress. This operation is aimed at preventing oxidation of the joining surfaces of the workpieces and the implementation of the auto-vacuum effect. After the temperature reaches the level of 910-915 ^o With carry out the exposure of the workpieces under the action of compressive forces for 30 minutes After that, the process is continued, compressing the workpieces with simultaneous reverse twisting to obtain the washer.

The workpiece processing mode in the first stage is as follows:
- deformation temperature - 930 ^o C;
- the velocity of the axial component of the strain ~ 10 ⁻³ s ⁻¹ ;
- the degree of compression of the workpieces in height - 60%;
- rotary table rotation speed - 1.0 rpm;
- the direction of rotation during processing is changed four times.

 At the second stage, the obtained washer is pulled along the direction perpendicular to the axis of the washer until a rod is formed.

Washer pull mode is as follows:
- deformation temperature - 930 ^o C;
- strain rate ~ 10 ^-3 s ^-1 .

 After broaching get a bar, which is subjected to machining on a lathe. After removing defects from the surface of the bar during turning, the dimensions of the bar become the following: length - 200.0 mm, diameter - 100.0 mm.

 The third stage is the torsion of the bar. Additionally, with torsion, a compressive load is applied to the bar.

The bar processing mode is as follows:
- deformation temperature - 930 ^o C;
- rotation speed of the movable gripper - 0.5 revolution / min;
- the number of revolutions of the rotary table - 10;
- the degree of compression of the workpieces in height - 15%.

 Since in this example we used a workpiece processing scheme similar to Example 1. Therefore, the change in the area of the original surface, its shape and orientation in space also occurs similarly to example 1.

 On figa presents the microstructure of the semi-finished product in the zone of contact of the preforms with each other after the final third stage of the solid-phase mixing process, and on figb - the fracture surface in the semi-finished product in the connection zone.

The results of metallogaphic and ultrasonic analyzes showed a high uniformity of the distribution of the microstructure over the entire volume of the semi-finished product. The average grain size in the semi-finished product was d = 5.0-6.0 μm. No micropore defects were found in the contact zone of the workpieces. After the third stage of processing, the tensile strength of the semi-finished material was equal to the tensile strength of the workpiece material in the initial state and corresponded to the value of σ _in = 910 MPa.

 Example 3

 A semifinished product of iron-chromium-cobalt alloy 25X15K is obtained. Ten blanks with a height of 25.0 mm and a diameter of 90.0 mm are used as blanks.

 This example illustrates the possibility of obtaining a large-sized semi-finished product from individual billets of a precision alloy, which are subject to increased requirements for uniform distribution of the chemical composition in the entire volume.

 Given the fact that the alloy 25X15K belongs to the class of difficultly deformed and difficult to weld materials compared to the two-phase titanium alloys used in examples 1 and 2, the possibility of using the inventive method to obtain semi-finished products, including large ones, from difficultly deformed and difficult to confirm, is further confirmed welded materials.

 The table shows the chemical composition of the used alloy according to GOST, as well as the actual composition, which is obtained in the workpieces. The material is obtained in the form of castings with a diameter of 40.0 mm and a length of 300.0 mm. The resulting rods are cut into measured billets, and then washers are made using hot plastic deformation. Casting is allowed as washers. As a rule, such castings have a fine-grained structure with a fairly uniform distribution of alloying elements throughout the volume.

 After hot working, the washers have a globular microstructure with an average grain size dcp = 10.0–20.0 μm, which is evenly distributed over their entire volume.

 Use three-stage processing with preliminary solid-phase connection of the workpieces with each other. The processing scheme is similar to example 1.

In this example, the following process equipment is used:
1. Vacuum furnace with gas distribution panel.

 2. Slope mill.

 3. 630 tons hydraulic press with a rotary table mounted on the lower die plate.

Preliminary solid-phase connection of the workpieces is as follows. The end surfaces of the washers are ground and then degreased, washing successively in acetone and then in ethanol. After that, the workpieces are combined on the treated surfaces. Then installed in the device, allowing to transmit uniform compression force over the entire end surface of the workpieces. For these purposes, the method of solid-phase bonding with gaseous argon is used, transferring force to the workpieces through a flexible metal membrane. The device with the blanks installed in them is placed in a vacuum oven. In the working chamber of the furnace, a vacuum is created with a residual pressure of 5.0 • 10 ^-3 Pa and the preforms are heated to a temperature of 1300 ^o C. The temperature is selected based on the fact that the oxides of the main and alloying alloy elements on the connection surface are sublimated, i.e. self-cleaning takes place.

 After the temperature reaches the working level, the workpieces are compressed by applying a pressure of 2.0 MPa to the end surfaces. The workpieces are kept at a given pressure for one hour. After that, the pressure is removed, the temperature is lowered, bringing to room temperature, air is let into the working chamber of the vacuum furnace, the device is removed from the furnace and disassembled, removing the welded workpieces from it.

The first stage is to obtain the puck in the compression process with simultaneous reverse torsion performed in air. Billets are processed using the following mode:
- deformation temperature - 960 ^o C;
- strain rate ~ 10 ^-3 s ^-1 ;
- the degree of compression of the workpieces in height - 60%;
- rotational speed of the turntable - 1.0 revolution / min;
- the direction of rotation during processing was changed four times.

 At the second stage, the obtained washer is pulled along the direction perpendicular to the axis of the washer until a rod is formed.

Washer pull mode is as follows:
- deformation temperature - 960 ^o C;
- strain rate - ~ 10 ^-3 s ^-1 .

 After broaching get a bar, which is subjected to machining on a lathe. After removing defects from the surface, the dimensions of the bar are as follows: length - 230.0 mm, diameter - 90.0 mm.

 The third stage is the torsion of the bar. Additionally, with torsion, a compressive load is applied to the bar.

The bar processing mode is as follows:
- deformation temperature - 960 ^o C;
- rotation speed of the movable gripper - 0.5 revolution / min;
- the number of revolutions of the rotary table - 10;
- the degree of compression of the workpieces in height - 15%.

 In this example, as in the previous one, the workpiece processing scheme is used similarly to example 1. Therefore, the change in the area of the initial surface, its shape and orientation in space occurs in the same way as in example 1.

 In FIG. 5a shows the microstructure of the semi-finished product in the contact zone of the preforms with each other after the final third stage of the solid-phase mixing process, and Fig. 5b shows the fracture surface.

The results of metallogaphic and ultrasonic analyzes showed a high uniformity of the distribution of the microstructure over the entire volume of the semi-finished product. The average grain size in the semi-finished product was dcp = 15.0-25.0 μm. No micropore defects were found in the contact zone of the workpieces. After the third treatment step the tensile strength was equal semifinished material strength limit of the material blanks in the initial state and corresponds to _a value of σ = 680 MPa.

 After deformation processing, standard thermomagnetic processing of the semi-finished product was carried out, and the direction of the external field was perpendicular to the axis of the semi-finished product.

Measurements of the magnetic properties of the semi-finished product showed that the coercive force is equal to N _s = 38.0 kA / m, and the residual induction is equal to Br = 1.0 T, which corresponds to the values determined by GOST for this material.

 Example 4

 Ten sheet blanks of VT9 titanium alloy are subjected to solid-phase mixing (Ti - base; 5.8-7.0 Al; 2.8-3.8 Mo; 0.8-2.0 Zr; 0.2-0.35 Si )

 The submicrocrystalline structure is obtained by deformation-heat treatment of billets previously subjected to hydrogen plasticization and subsequent hot rolling of the material into strips on an isothermal rolling mill.

The dimensions of the sheet blanks are as follows:
- width - 20.0 mm;
- thickness - 3.0 mm;
- length - 200.0 mm.

 In the initial state, the preforms have a submicrocrystalline structure with an average grain size d = 0.4-0.6 μm.

 Solid-phase mixing is carried out in three stages: the first stage is the compression of the workpieces along the direction perpendicular to the surface of the connection (Fig. 6a); the second stage is the broaching of the blanks (Fig.6b) and the third stage is the twisting of the blanks with simultaneous stretching (Fig.6b).

In this example, the following process equipment is used:
1. Vacuum furnace with gas distribution panel.

 2. A hydraulic press with an effort of 630 tons.

 3. The machine is complex loading.

 Before the first stage, solid-phase connection of the workpieces in a vacuum furnace is carried out, combining this process with the removal of residual hydrogen from the workpieces.

 The blanks are laid one on top of the other, combining along most of the sides. A pack is formed. The section of the pack is 20.0 x 30.0 x 200.0 mm. The pack is installed in the device, heated and connected.

The mode of preparation of the solid phase compound is as follows:
The residual pressure in the chamber is 5 • 10 ^-3 Pa.

Welding temperature - 700 ^o C.

 Welding pressure - 3.0 MPa.

 Welding time - 1.0 hour.

The first stage is the compression of the workpieces to obtain the strip is performed on a hydraulic press. The workpiece processing mode in the first stage is selected as follows:
- deformation temperature - 700 ^o C;
- strain rate - 10 ^-3 s ^-1 ;
- the degree of compression of the workpieces in height - 30%.

 The second stage is the broaching of blanks, which is performed according to the modes similar to the first stage of compression. After broaching and subsequent machining on a lathe, the bar has a diameter of 25.0 mm and a length of 200.0 mm.

The third stage is the torsion of the bar. Torsion is combined with stretching. Hot deformation of the bar is performed on the installation for complex loading in the following mode:
- deformation temperature - 700 ^o C;
- rotation speed of the movable gripper - 0.5 rpm;
- number of revolutions -10;
- the speed of the axial component of the deformation is 10 ^-3 s ^-1 ;
- the degree of deformation of the axial component is 80%.

 In this example, we used a processing scheme in which the third stage intensively twists the workpieces, therefore, the initial surface area, its shape and spatial orientation change in the same way as in example 1 after the third stage.

 The results of metallogaphic and ultrasonic analyzes showed a high uniformity in the distribution of the microstructure over the entire volume of the workpiece. The average grain size in the semi-finished product did not exceed the value d = 0.3-0.5 microns. No micropore defects were detected in the contact zone.

 Example 5

 Six long billets of technically pure titanium VT 1-0 are subjected to solid-phase mixing. The submicrocrystalline structure in the workpieces was obtained by equal channel angular pressing. The cross section of the intersecting channels was made in the form of an equilateral triangle. Therefore, the blanks in cross section had the shape of an equilateral triangle with a side of 20.0 mm. The length of each workpiece is 100.0 mm.

In this example, the following process equipment is used:
1. 630 tons hydraulic press.

 2. Complex loading machine.

 In the initial state, the preforms have a microstructure with an average grain size d = 0.3-0.5 microns.

 The workpieces are combined on the side surfaces, forming a package with a hexagonal section. An interference fit package is installed in a shell made of technically pure titanium VT1-0 (Fig. 7a), sealed at the ends, welded by argon-arc welding, and connected to a vacuum system via a pipeline.

The shell with the blanks installed in it is heated to a temperature of 200 ^o C, the air is pumped out of the inner cavity of the shell to the value of the residual pressure equal to B = 5 • 10 ^-2 Pa, and the first stage of loading is carried out.

 The process of obtaining the semi-finished product by solid-phase mixing is carried out in two stages. The process flow chart is presented in figb, c.

The first stage is combined with a solid-phase compound (Fig.7b). The blanks are compressed in a direction perpendicular to the axis of symmetry by direct extrusion of the container with blanks on a hydraulic press with an effort of 630 tons. The amount of compression during extrusion is 2.0. The extrusion operation is performed at a temperature of 200 ^o C. The direct extrusion operation involves the deformation of the workpieces in conditions of complex two-component loading. In this case, the radial compression strain is combined with the axial tensile strain. The speed of the movable punch during extrusion is 10.0 mm / min.

 At the second stage, the blanks are deformed directly in the container, combining torsion with tension (Fig. 7c). This is done in order to exclude the formation of cracks on the side surface of the workpieces, as well as in order to save time and money. Torsional deformation with tension is performed on a complex loading machine.

The workpiece processing mode on the complex loading machine is as follows:
- deformation temperature - 200 ^o C;
- rotation speed of the movable gripper - 0.5 rpm;
- number of revolutions - 10;
- tensile deformation rate - 5.0 mm / min.

 - the magnitude of the deformation of the axial component of the tension is 20.0%.

 After processing, the semi-finished product is ground, removing the material of the container from the surface.

 The results of ultrasonic and metallogaphic analyzes showed a high uniformity of the distribution of the microstructure over the entire volume of the semi-finished product. The average grain size in the semi-finished product did not exceed the value d = 0.2-0.4 μm.

 Example 6

 A semifinished product is obtained from an iron-chromium-cobalt alloy 25X15K having an initial microstructure, as in Example 3, Ten washers with a height of 25.0 mm and a diameter of 90.0 mm are used as blanks. The blanks are coated with 0.5 mm Ni, galvanically depositing it on the joined surfaces of the washers. Coatings in this example play the role of alternating layers of ductile Ni and brittle 25X15K material. The processing scheme for workpieces is similar to Example 3. Only the solid-phase compound mode is changed.

 This example, as well as example 3, illustrates the possibility of obtaining a large-sized composite semi-finished product from individual billets of a precision alloy, which are subject to increased requirements for the uniformity of the distribution of the chemical composition in the volume of the magnetic material. The alternating interlayer of technically pure nickel has a higher ductility compared to the matrix alloy (25X15K) and solves the problem of preventing brittle fracture of the material both at the stage of manufacturing the workpieces and at the stage of operation of the products. Galvanic coating prevents oxidation of the surface of 25X15K alloy billets upon heating, additionally solving the problem of lowering the temperature of the solid-phase bonding of billets, which leads to a decrease in the coarsening of the microstructure.

 The table shows the chemical composition of the alloy used according to GOST, as well as the actual composition in the workpieces. Billets are obtained in the form of castings with a diameter of 40.0 mm and a length of 300.0 mm. The resulting rods are cut into measured billets, and then washers are made using hot plastic deformation.

 After hot working, the washers have a globular microstructure with an average grain size dcp = 10.0–20.0 μm, which is uniformly distributed throughout the volume.

 After manufacturing, Ni is deposited onto the surface of the washers during electrochemical processing. Coating thickness 0.5 mm.

 In this example, three-stage processing of preforms with preliminary solid-phase connection of them with each other is used. The processing scheme is similar to example 3.

In the example, the following process equipment is used:
1. Vacuum furnace with gas distribution panel.

 2. Slope mill.

 3. 630 tons hydraulic press with a rotary table mounted on the lower die plate.

Solid-phase connection of the workpieces is as follows. Before welding, the end surfaces of the Ni-coated washers are degreased by washing successively in acetone and then in ethanol. After that, the workpieces are combined on the treated surfaces. Then install a device that allows you to transfer uniform compression force over the entire end surface of the workpieces. For these purposes, gas diffusion welding technology is used, transferring force to the workpieces through a flexible metal membrane. The device with the blanks installed in them is placed in a vacuum oven. In the working chamber of the furnace, a vacuum is created with a residual pressure of 5.0 • 10 ^-3 Pa and the workpieces are heated to a temperature of 1100 ^o C. The welding temperature is selected based on the fact that the Ni surface is self-cleaning, starting at a temperature of 1000 ^o С, and at 1100 ^o C its chemical activity is already sufficient for additional cleaning of the surface of the matrix magnetic alloy located beneath it. After the temperature reaches the working level, the workpieces are compressed by applying a pressure of 2.0 MPa to the end surfaces. The workpieces are kept under the specified pressure for one and a half hours. After that, the pressure is removed, the temperature is lowered, bringing to room temperature, air is let into the working chamber of the vacuum furnace, the device is removed from the furnace and disassembled, removing the welded workpieces from it.

The first stage is to obtain the puck in the compression process with simultaneous reverse torsion performed in air. Billets are processed using the following mode:
- deformation temperature - 960 ^o C;
- strain rate ~ 10 ^-3 s ^-1 ;
- the degree of compression of the workpieces in height - 60%;
- rotational speed of the turntable - 1.0 revolution / min.

 - the direction of rotation during processing is changed four times.

 In a second step, the resulting washer is pulled along a direction perpendicular to the axis of the washer until a rod is formed.

Washer pull mode is as follows:
- deformation temperature - 960 ^o C;
- strain rate - ~ 10 ^-3 s ^-1 .

 After broaching get a bar, which is subjected to machining on a lathe. After removing defects from the surface, the dimensions of the bar are as follows: length - 230.0 mm, diameter - 90.0 mm.

 The third stage is the torsion of the bar. Additionally, with torsion, a compressive load is applied to the bar.

The bar processing mode is as follows:
- deformation temperature - 960 ^o C;
- rotation speed of the movable gripper - 0.5 revolution / min;
- the number of revolutions of the rotary table - 10;
- the degree of compression of the workpieces in height - 15%.

 In this example, we used a workpiece processing scheme similar to Example 3. Therefore, the change in the area of the initial surface, its shape and orientation in space occurs in the same way as in example 3.

 The results of metallogaphic and ultrasonic analyzes showed a high uniformity of the distribution of the microstructure over the entire volume of the semi-finished product. The average grain size in the semi-finished product was dcp = 15.0-25.0 μm. No micropore defects were found in the contact zone of the workpieces. After the third stage of processing, the tensile strength of the semi-finished material was equal to the tensile strength of the workpiece material in the initial state, and the ductility exceeded the ductility of the base material by three times.

After deformation processing, standard thermomagnetic processing of the semi-finished product was carried out. Measurements of the magnetic properties of the semi-finished product showed that the coercive force in it is equal to N _s = 39.0 kA / m, and the residual induction is equal to Br = 1.0 T, which corresponds to the values determined by GOST for this alloy.

 Example 7

 A composite semi-finished product is obtained from alternating billets of an iron-chromium-cobalt alloy 25X15K and a nickel-based alloy XH76T (EI435). The initial microstructure in the 25X15K alloy is the same as in Example 3. In the EI 435 alloy, the average grain size is 20.0 μm.

 The chemical composition of the alloy 25X15K is presented in the table. The chemical composition of the alloy EI435 is as follows (% by weight): 19.5-22.5 Cr; 0.15-0.35 Ti; ≤ 6.0 Fe; ≤0.8 Si; ≤0.7 Mn; ≤0.12 C; ≤0.0012 S; ≤0.015 P; the rest is Ni.

Alloy EI435 at room temperature has a _strength σ == 800 MPa, the ductility δ = 40% and a coefficient of linear expansion in the temperature range 20-1000 ^o C - α = 17,0 • June ^10, K ^-1.

Alloy 25H15K at room temperature has a _strength σ == 700 MPa, the ductility of the alloy after the magnetic annealing is δ <1,0%, a linear expansion coefficient - α == 12,0 • June ^10, K ^-1.

 To obtain a semi-finished product, five washers 10.0 mm thick from EI435 alloy and four washers 25.0 mm thick from 25X15K alloy are used. The diameter of all washers is 90.0 mm.

 The blanks are coated with 0.1 mm thick Ni, galvanically depositing it on the joined surfaces of the washers. In this example, the use of the coating, as in the previous one, is associated with the need to reduce the welding temperature, as well as with the need to prevent the interaction of alloying elements of alloys EI435 and 25X15K with each other with the formation of brittle joints during deformation.

 The blank processing scheme is similar to the previous example.

 This example, as well as examples 3.6, illustrates the possibility of obtaining a large-sized composite semi-finished product from individual blanks of a precision alloy, which are subject to increased requirements for the uniformity of the chemical composition in the volume of the magnetic material. Alternating with magnetic layers of heat-resistant alloy EI435 has greater strength, ductility, as well as the coefficient of linear expansion. This combination of properties solves the problem of preventing brittle fracture of the magnetic material in the composite rotor both at the stage of manufacturing the blanks and at the stage of operation of the product.

 As in the previous examples, the 25X15K alloy material is obtained in the form of castings with a diameter of 40.0 mm and a length of 300.0 mm. The resulting rods are cut into measured billets, and then washers are made using hot plastic deformation.

 After hot working, the washers have a globular microstructure with an average grain size dcp = 10.0–20.0 μm, which is uniformly distributed throughout the volume.

 Washers from alloy EI435 are made from deformed rods with a diameter of 40.0 mm.

 After manufacturing, Ni is deposited onto the surface of the washers during electrochemical processing. Coating thickness 0.1 mm.

 In this example, three-stage processing of preforms with preliminary solid-phase connection of them with each other is used. The processing scheme is similar to example 3.

In the example, the following process equipment is used:
1. Vacuum furnace with gas distribution panel.

 2. Rolling mill.

 3. 630 tons hydraulic press with a rotary table mounted on the lower die plate.

 Solid-phase connection of the workpieces is as follows.

Before welding, the end surfaces of the coated washers are degreased by washing successively in acetone and then in ethanol. After that, the workpieces are combined on the treated surfaces, alternating between them. Then installed in the device, allowing to transmit uniform compression force over the entire end surface of the workpieces. For these purposes, the method of solid-phase bonding with gaseous argon is used, transferring force to the workpieces through a flexible metal membrane. The device with the blanks installed in them is placed in a vacuum oven. In the working chamber of the furnace, a vacuum is created with a residual pressure of 5.0 • 10 ^-3 Pa and the workpieces are heated to a temperature of 1100 ^o C. The welding temperature is selected based on the fact that the Ni surface is self-cleaning, starting at a temperature of 1000 ^o С, and at 1100 ^o Since its chemical activity is already sufficient for additional cleaning of the surface of matrix alloys located beneath it.

 After the temperature reaches the working level, the workpieces are compressed by applying a pressure of 2.5 MPa to the end surfaces. The workpieces are kept at a given pressure for two hours. After that, the pressure is removed, the temperature is lowered, bringing to room temperature, air is let into the working chamber of the vacuum furnace, the device is removed from the furnace and disassembled, removing the welded workpieces from it.

The first stage is to obtain the puck in the compression process with simultaneous torsion performed in air. Billets are processed using the following mode:
- deformation temperature - 960 ^o C;
- strain rate ~ 10 ^-3 s ^-1 ;
- the degree of compression of the workpieces in height - 60%;
- rotational speed of the turntable - 1.0 revolution / min.

 At the second stage, the obtained washer is pulled along the direction perpendicular to the axis of the washer until a rod is formed.

Washer pull mode is as follows:
- deformation temperature - 960 ^o C;
- strain rate - ~ 10 ^-3 s ^-1 .

 After broaching get a bar, which is subjected to machining on a lathe. After removing defects from the surface, the dimensions of the bar are as follows: length - 230.0 mm, diameter - 90.0 mm.

 The third stage is the torsion of the bar. Additionally, with torsion, a compressive load is applied to the bar.

The bar processing mode is as follows:
- deformation temperature - 960 ^o C,
- rotation speed of the movable gripper - 0.5 revolution / min;
- the number of revolutions of the rotary table - 10;
- the degree of compression of the workpieces in height - 15%.

 In this example, we used a workpiece processing scheme similar to Example 3. Therefore, the change in the area of the initial surface, its shape and orientation in space occurs in the same way as in example 1.

The results of metallographic and ultrasonic analyzes showed a high uniformity of the distribution of the microstructure throughout the volume of the semi-finished product. The average grain size in the semi-finished product was dcp = 15.0-25.0 μm. No defects in the form of micropores were found in the junction of the workpieces. After the third treatment step the tensile strength was equal semifinished material strength limit of the material blanks in the initial state and corresponds to _a value of σ = 780 MPa and ductility corresponded to the value δ = 10,0%.

After deformation processing, standard thermomagnetic processing of the semi-finished product was carried out. Measurements of the magnetic properties of the semi-finished product showed that the coercive force is equal to Н _c = 39.0 kA / m, and the residual induction is equal to Br = 1.0 T, which corresponds to the values determined by GOST for the selected magnetic material.

 Example 8

 Solid-phase mixing is subjected to two tubular preforms of alloy 25X15K pre-installed in each other. The average grain size in the tubular billet is 50.0-100.0 μm. In order to improve the microstructure of the workpieces and minimize the formation of dendritic segregation, the workpieces are obtained by centrifugal casting.

 One workpiece has an external diameter of 120.0 mm and a thickness of 15.0 mm. The second workpiece has an external diameter of 90.0 mm and a thickness of 15.0 mm. The length of the workpieces is 250.0 mm. The surface of the workpieces is subjected to fine turning. Then they are degreased and installed tightly one into the other. Plugs are hermetically welded to the ends, connecting the internal cavity of the assembly with the vacuum system through a metal pipe.

 Processing blanks is carried out in three stages. The process flow chart is presented in figa, b, c.

Thermomechanical processing is performed on the following process equipment:
1. Gas distribution panel with a system for creating a vacuum.

 2. Rolling mill.

 3. A hydraulic press with a force of 630 tons with a rotary table integrated on the lower die plate.

 The first stage is the compression of the workpieces along the direction perpendicular to the axis of symmetry of the workpiece (figa).

Before heating the workpieces, the air is pumped out of the internal cavity of the assembly, bringing the residual pressure to the level B = 5.0 • 10 ^-2 Pa. Then the workpiece is heated to a temperature of T = 1300 ^o C, constantly maintaining a residual pressure of B = 5.0 • 10 ^-2 Pa in the internal cavity. After the temperature reaches the preset level, the workpieces are compressed using the following modes:
- deformation temperature - 1300 ^o C;
- strain rate ~ 10 ^-3 s ^-1 .

 Compression of the workpieces until the inner surface is closed and the solid-phase compound is formed is carried out in a stamp of a special configuration, Fig. 8a. The design of the stamp provides localization of deformation in the area of inflection of the inner surface of the workpieces, removing the defective areas in the bulk. The first stage is performed on a hydraulic press with an effort of 630 tons. After closing the halves of the stamp carry out exposure in a compressed state for 0.5 hours.

At the second stage, the prefabricated mill is removed by milling and is pulled on the press, giving it the shape of a cylinder (Fig. 8b). The processing mode of the semi-finished product in the second stage is as follows:
- deformation temperature - 960 ^o C;
- strain rate - ~ 10 ^-3 s ^-1 .

 After the second stage is completed, the semi-finished product is machined on a lathe to a diameter of 100.0 mm and a length of 200.0 mm.

 The third stage is the torsion of the semi-finished product (pigv) is carried out on a rolling mill. Why the workpiece is installed in the working space of the rolling mill, fixing in the grips of the rotating device.

Before deformation, the workpiece is heated to a temperature of 950 ^o C, maintained for 0.5 hours and deformed by torsion at a speed of 0.5 revolutions per minute for six full revolutions. In the process of torsion deformation, the maximum deformation is concentrated near the surface of the joint, in the zone where defects of the solid-phase compound are most likely to occur. Therefore, intense deformation in this case solves the problem of healing defects of a solid-phase compound, as well as their mixing in the bulk of the semi-finished product. In the third stage of processing the semi-finished product, as in the previous examples, there is an increase in the surface area of the solid-phase compound and a change in its shape.

 Ultrasonic testing and metallogaphic analysis showed a high uniformity of the distribution of the microstructure throughout the volume of the semi-finished product. The average grain size in the semi-finished product was d = 15.0-20.0 microns. No micropore defects were detected in the solid-phase compound zone.

After deformation processing, standard thermomagnetic processing of the semi-finished product was carried out. Measurements of the magnetic properties of the semi-finished product showed that the coercive force is equal to N _s = 37.0 kA / m, and the residual induction is equal to Br = 1.10 T, which corresponds to the values determined by GOST for this material.

 Example 9

 The tubular billet and the billet in the form of a cylindrical rod from 25X15K alloy are subjected to solid-phase mixing. The microstructure in the workpieces was the same as in example 8. The chemical composition of the alloy is presented in the table.

 Compared to the previous one, this example illustrates the possibility of completely eliminating the formation of defects in a solid-phase compound, starting from the first stage, while maintaining a high level of material properties by reducing the dimensions of the ingots.

 The tubular billet has an external diameter of 90.0 mm and a wall thickness of 25.0 mm. The bar has an external diameter of 40.0 mm. The length of the workpieces is 250.0 mm. The surface of the workpieces is subjected to fine turning. Then they are degreased and installed tightly one into the other (figa). Processing blanks is carried out in two stages. The process flow chart is presented in figb, c.

Thermomechanical processing is performed on the following process equipment:
1. Rolling mill.

 2. A hydraulic press with a force of 630 tons with a rotary table integrated on the lower die plate.

The first stage is the compression of the workpieces along the direction perpendicular to the axis of symmetry (figb), carried out in the process of drawing. Workpieces are heated to a predetermined temperature. After the temperature reaches the working level, the workpieces are compressed using the following modes:
- deformation temperature - 1300 ^o C;
- strain rate ~ 10 ^-3 s ^-1 ;
- the degree of compression of the workpieces - 30%.

 At the first stage, the semi-finished product is stretched along the axis of symmetry, giving it the shape of a cylinder. The stress-strain state in this case corresponds to complex loading.

 The first stage is performed on a hydraulic press with an effort of 630 tons. After completion of the first stage, the semi-finished product is machined on a lathe to a diameter of 100.0 mm and a length of 200.0 mm.

 The second stage is the torsion of the semi-finished product (pigv) carried out on a rolling mill. Why the workpiece is installed in the working space of the rolling mill, fixing in the grips of the rotating device.

Before deformation, the workpiece is heated to a temperature of 950 ^o C, maintained for 0.5 hours and deformed by torsion at a speed of 0.5 rpm for eight full revolutions.

 At the first stage of processing the semi-finished product, as in the previous examples, there is an increase in the surface area of the solid-phase compound. The change in the shape of the surface of the compound in the second stage does not occur. However, the quality of the joint is growing, which is due to uniform, intense shear deformation during torsion in the joint zone.

 Ultrasonic testing and metallogaphic analysis showed a high uniformity of the distribution of the microstructure throughout the volume of the semi-finished product. The average grain size in the semi-finished product was d = 15.0-20.0 microns. No micropore defects were detected in the solid-phase compound zone.

After deformation processing, standard thermomagnetic processing of the semi-finished product was carried out. Measurements of the magnetic properties of the semi-finished product showed that the coercive force is equal to N _s = 37.0 kA / m, and the residual induction is equal to Br = 1.10 T, which corresponds to the values determined by GOST for this material.

 Example 10

 Similarly to the previous example, tubular and cylindrical workpieces from 25X15K alloy are subjected to solid-phase mixing. The blanks have the same microstructure as in example 8. The chemical composition of the alloy is presented in the table. The cylindrical billet after casting and subsequent machining had an external diameter of 40.0 mm and a length of 200.0 mm. After machining, the tubular billet had an internal diameter of 40.0 mm, an external diameter of 100.0 mm, and a length of 200.0 mm. Workpieces after mechanical treatment are washed and degreased in acetone and ethyl alcohol.

 Inside the tubular workpiece with interference fit a cylindrical workpiece (figa).

 The process of obtaining a semi-finished product by solid-phase mixing of the workpieces is carried out in three stages. The process flow chart is presented in FIG. 10b, c, d.

Thermomechanical processing is performed on the following process equipment:
1. A hydraulic press with a force of 630 tons with a rotary table mounted on the lower die plate.

 2. Rolling mill.

 The first stage is the compression of the workpieces along the axis of symmetry of the workpieces combined with torsion and performed on a hydraulic press, ensuring that the work of compressing the workpieces with their twisting is combined (Fig. 10b).

 The compression stage with simultaneous twisting is combined with the process of forming a solid-phase connection between the workpieces. To do this, apply a stamp with special strikers. The strikers have a slight bulge in the central part. The design of the stamp provides localization of deformation in the center of the workpieces and the formation of contact on the connection surface of the cylindrical workpiece and the rod due to the distribution of the workpieces.

 Compression of the workpieces is combined with twisting in order to intensify the process of formation of a solid-phase compound and to activate the healing of defects in the compound at the first stage.

The workpiece processing mode in the first stage is as follows:
deformation temperature - 1200 ^o C;
- the rotation speed of the movable striker is 0.5 rpm;
- number of revolutions - 5;
- the degree of compression in height - 60%.

At the second stage, the washer is pulled along a direction perpendicular to the axis of symmetry of the washer until a rod is formed (Fig. 10c). The broach is carried out on a hydraulic press. Washer pull mode is as follows:
- deformation temperature - 960 ^o C;
- strain rate - 10 ^-3 s ^-1 .

 After the broaching operation, the bar is grinded to the following sizes: length - 200 mm, diameter 90.0 mm.

The third stage is the torsion of the bar (Fig.10g). The torsion of the bar is performed on a rolling mill. The torsion bar processing mode is as follows:
- deformation temperature - 960 ^o C;
- rotation speed of the movable gripper - 0.5 rpm;
- number of revolutions - 10.

The results of metallographic analysis and ultrasonic testing showed a high uniformity in the distribution of the microstructure over the entire volume of the semi-finished product. The average grain size in the semi-finished product was dcp = 15.0-25.0 μm. No micropore defects were found in the contact zone of the workpieces. After the third treatment step the material tensile strength was equal semifinished material strength limit of blanks in the initial state and corresponds to _a value of σ = 780 MPa.

After deformation processing, standard thermomagnetic processing of the semi-finished product was carried out. Measurements of the magnetic properties of the semi-finished product showed that the coercive force is equal to N _s = 39.0 kA / m, and the residual induction is equal to Br = 1.0 T, which corresponds to the values determined by GOST for the material being processed.

 In this example, the tubular and cylindrical billets were made from the same 25X15K alloy. However, the method used in this case can also be used to obtain a composite semi-finished product in which a cylindrical billet is made of brittle magnetic material, for example 25X15K, and tubular from high-strength material EI435. The processing scheme of the composite semi-finished product is chosen to be the same as in example 10, and the temperature-speed processing modes are the same as in example 7.

 Example 11

 Workpieces made of technically pure titanium and aluminum are subjected to solid-phase mixing in order to obtain a composite semi-finished product for the subsequent manufacture of sheets of it from the Ti-Al system intermetallic. After receiving the composite semi-finished product, it is rolled and subjected to additional heat treatment.

The blanks are in the form of washers with the following dimensions:
- diameter - 50.0 mm;
- thickness - 10.0 mm.

 The number of blanks from Al is five, the number of blanks from Ti is six.

 In Ti blanks, a QMS structure is preliminarily prepared. The method of preparing the structure is similar to example 5.

Processing blanks is performed on the following process equipment:
1. A hydraulic press with a force of 630 tons with a rotary table mounted on the lower die plate.

 2. Rolling mill.

 3. Isothermal rolling mill.

 The process of obtaining a composite semi-finished product is carried out in three main stages, repeating the steps three times, that is, for three identical cycles and the fourth cycle of isothermal rolling in four passes. At the final passage, the synthesis of intermetallic is performed. If at the stages of the first three cycles an intensive change occurs in the joint area and its surface, then during rolling there is a slight change in the shape and spatial position of the joint surface against the background of a significant change in the area of the initial joint.

 All three main processing cycles of the semi-finished product are similar to example 1. Therefore, in Fig. 11a, b, as an example, only the processing scheme of the semi-finished product in the second cycle is presented.

 Before assembly, the surface of the workpieces is cleaned with a wire brush, removing dirt and oxide film from the surface.

The blanks are laid one on top of the other, alternating between a titanium blank and an aluminum blank, forming an assembly. The assembly is installed in a container of technically pure titanium. The container is sealed by connecting the pipeline to a gas distribution panel, ensuring the maintenance of vacuum inside the container at the level of 5.0 • 10 ^-2 Pa.

 The first stage of solid-phase mixing - compression of the workpieces to obtain the washer is performed on a hydraulic press equipped with a rotary table in isothermal conditions. The deformation temperature is chosen so as to minimize the formation of brittle intermetallic compounds (figa).

At the first stage, compression is combined with torsion. The workpiece processing mode in the first stage is as follows:
- deformation temperature - 450 ^o C,
- strain rate - 10 ^-3 s ^-1 ;
- the degree of compression of the workpieces in height - 60%;
- the rotation speed of the movable striker is 0.5 revolutions / min.

At the second stage, the washer is pulled along a direction perpendicular to the axis of the washer until a rod is formed (Fig. 11b). The broaching is carried out in isothermal conditions on a hydraulic press using the following mode:
- deformation temperature - 450 ^o C;
- strain rate - 10 ^-3 s ^-1 .

 After the second step, the container is removed using turning.

The third stage is the torsion of the bar with simultaneous compression (Fig.11c) is performed on a rolling mill. The processing mode of the bar in the third stage is as follows:
- deformation temperature - 450 ^o C;
- rotation speed of the movable gripper - 0.5 rpm;
- number of revolutions - 10;
- the degree of axial component of the deformation is 30%.

 The use of the container is due to a significant difference in the deformation behavior of technically pure titanium and aluminum at a selected deformation temperature and is aimed, like the pretreatment of titanium billets, to partially equalize the deformation characteristics of the processed billets, especially at the first and second stages of processing the first cycle.

 After completion of each treatment cycle, the semi-finished product is grinded, removing surface defects.

 The second (figa, b, c) and the third cycles (not shown in the figure) are performed according to a similar scheme and modes as the first.

 After the final third cycle of deformation-heat treatment, taking into account mechanical processing, the dimensions of the semi-finished product were as follows: diameter - 45.0 mm, length - 90.0 mm. The semi-finished product is a laminar composite. Layers of titanium and aluminum in it alternate and form a complex helical surface. Moreover, if in the initial state the number of layers was eleven, then after three processing cycles their number increased and became equal to ~ 1000.

 Sheets of 0.5 mm thickness are made from the obtained semifinished product by synthesizing the Ti-Al system intermetallic compound during isothermal rolling (not shown in the figure). Before rolling, the semifinished product is deformed by compression to form a washer 5.0 mm thick. Compression is combined with torsion (not shown in the figure). The deformation is performed on a hydraulic press according to the mode of the first stage. A strip of 100.0 mm wide is cut out of the obtained washer, which is then rolled on an isothermal mill.

Strip rolling is performed in three passes to a thickness of ~ 2.0 mm at a constant temperature T = 450 ^o C. The final fourth pass is carried out at a temperature of T = 850 ^o C, obtaining a sheet with a thickness of 0.7 mm The resulting sheet billet is placed in a furnace, where it is annealed at a temperature of 1000 ^o C for five hours in argon medium in order to guarantee equalization of the chemical composition in the entire volume of the sheet.

 After annealing, the sheet blank is subjected to dimensional etching operations, bringing the sheet thickness to the desired value of 0.5 mm.

 Metallographic analysis showed a high uniformity in the distribution of the microstructure throughout the sheet. The average grain size was dcp = 10.0-15.0 μm. No micropores were found in the volume of the obtained sheet. X-ray microanalysis confirmed that the resulting sheets are TiAl intermetallic.

Sources of information
1. Powder metallurgy in the USSR: History. The current state. Perspectives), Moscow: Nauka, 1986. Edited by I.N. Frantsevich, V.I. Trefilova, 294s.

 2. RF patent 2134308, C 22 F 1/18, 1999

 3. E.S. Karakozov, L.M. Orlova, V.V. Peshkov, V.I. Gregorievsky. Diffusion welding of titanium - M .: - "Metallurgy", 1977, 272 p.

 4. O.A. Kaybyshev, R.Ya. Lutfullin, V.K. Berdin. The nature of the formation of a solid-phase compound under superplasticity conditions - Dokl. USSR Academy of Sciences, 1991, v. 319, 6, pp. 615-618.

 5. V.K. Berdin "Formation of a solid-phase compound of industrial titanium alloys under superplastic deformation." The dissertation for the degree of candidate of technical sciences, Ufa, 1992, 157 p.

Claims (22)

 1. A method of producing semi-finished products from metals and alloys, comprising an integral connection on the compatible surfaces of the workpieces with a prepared microstructure and / or properties and solid-phase mixing by deformation in several stages under temperature and speed conditions, selected taking into account the given microstructure and / or properties of the semi-finished products, and also the initial microstructure of the workpieces, and during deformation, they change the direction of application of the deforming load and / or the type of loading and / or use the load a phenomenon including torsion, with a degree of deformation at each stage, providing a change in the shape and / or orientation in the space of the surface of the connection and / or an increase in the area of the connection compared to the initial state or obtained at the previous stage, characterized in that the deformation is carried out in three stages, at the same time, at the first stage, the workpieces are compressed, at the second, a broaching is carried out until a bar is obtained, and at the third, the bar is deformed by torsion.  2. The method according to claim 1, characterized in that the preform is selected with a prepared microstructure that provides solid-phase mixing at temperature and speed conditions corresponding to the optimal interval of manifestation of superplasticity of the material of the workpieces.  3. The method according to claim 2, characterized in that the preform is selected with a prepared microcrystalline structure with an average grain size of 1.0-50.0 microns.  4. The method according to claim 2, characterized in that the preform is selected with a prepared submicrocrystalline structure with an average grain size of 0.5-1.0 μm.  5. The method according to claim 1, characterized in that preforms are selected from materials with a heterogeneous melting point forming intermetallic compounds, and solid-phase mixing is carried out at all stages except the last under temperature-speed conditions to prevent the formation of brittle layers, and the last stage is at the temperature at which the formation of the intermetallic compound begins in the entire volume of the semi-finished product.  6. The method according to claim 5, characterized in that the preform of a material with a high melting point has a smaller grain size.  7. The method according to claim 1, characterized in that upon joining, preforms are selected from materials with various properties and alternated to obtain composite semi-finished products.  8. The method according to claim 7, characterized in that the preform is selected from materials with different values of the coefficient of linear expansion, and the coefficient of linear expansion of the preform from a material with high strength properties is greater than the coefficient of linear expansion of the preform from a material with low strength properties.  9. The method according to claim 7, characterized in that use blanks from materials with different plasticity characteristics.  10. The method according to p. 1, characterized in that at the connection, at least two preforms in the form of a rod are selected, which are connected along the end surfaces, and compression deformation is carried out by applying a force along the symmetry axis of the preforms to obtain the washer, it is stretched along axis perpendicular to the axis of symmetry of the washer until a rod is obtained, and when torsionally deformed, torque is applied to opposite end portions of the rod in a plane perpendicular to the axis of symmetry of the rod.  11. The method according to claim 10, characterized in that in the first stage the compression is combined with torsion.  12. The method according to claim 10 or 11, characterized in that the reverse torsion is carried out.  13. The method according to p. 1, characterized in that at the connection, at least two tubular billets are selected, which are installed axially, and deformation by compression is carried out until a strip is obtained, applying a compression force perpendicular to the axis of symmetry of the initial billets, the strip is stretched until a rod is obtained and during torsional deformation, torque is applied to opposite end sections of the rod in a plane perpendicular to the axis of symmetry of the rod.  14. The method according to claim 1, characterized in that when connecting, choose a tubular billet and a billet in the form of a rod, they are installed one into the other, and deformation by compression is carried out to obtain a strip, applying a deforming force perpendicular to the axis of symmetry of the workpieces, the strip is stretched until a rod is obtained and during torsional deformation, a torque is applied to the opposite end sections of the rod in a plane perpendicular to the axis of symmetry of the rod.  15. The method according to claim 1, characterized in that when connecting, choose a tubular billet and a billet in the form of a rod, the billets are installed one into the other, and deformation by compression is carried out to obtain the washer, applying a deforming force to the ends of the billets, along the axis of symmetry of the billets, the washer stretched along a direction perpendicular to the axis of its symmetry until a rod is obtained.  16. The method according to claim 1, characterized in that when connecting, preforms are selected in the form of rods having a cross-section of an equilateral polygon with a flat face that are aligned along the side surfaces along their generatrix, and compression deformation is combined with tension to obtain a bar, applying a compressive force perpendicular to the axis of symmetry of the initial workpieces, and during torsional deformation, apply torque to the opposite end sections of the bar in a plane perpendicular to the axis of symmetry of the bar.  17. The method according to claim 1, characterized in that upon joining, preforms are selected in the form of plates, and compression deformation is carried out to obtain a strip, applying a compressive force to the opposite joined surfaces of the preforms, along the normal to these surfaces, the strip is stretched to form a rod, and during torsional deformation, a torque is applied to opposite end portions of the rod in a plane perpendicular to the generatrix of the rod.  18. The method according to any one of paragraphs.10 and 13-17, characterized in that the torsion is combined with stretching.  19. The method according to any one of paragraphs.10 and 13-17, characterized in that the torsion is combined with compression.  20. The method according to claim 1, characterized in that the one-piece connection of the workpieces on compatible surfaces is carried out by solid-phase connection of the workpieces to be processed, which is performed before the first step of processing the workpieces.  21. The method according to claim 1, characterized in that the one-piece connection of the workpieces on compatible surfaces is carried out by solid-phase connection of the workpieces to be processed and combined, at least with part of the first stage.  22. The method according to claim 1, characterized in that the semi-finished products are obtained by repeating cycles, each of which includes these steps.

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