RU2203975C2 - Method of treatment of blanks made from metals or alloys - Google Patents

Abstract

FIELD: metallurgy; heat treatment and machining of blanks having cast coarse-grained laminated microstructure and made from titanium or its alloys. SUBSTANCE: proposed method includes obtaining of microstructure at required sizes of grains by means of plastic deformation performed at one or several stages depending on size of grains in starting blank and required size of blank, temperature and rate of procedure selected for transformation of structure in the course of dynamic recrystallization; stage is performed at several passes for complete transformation of structure; during treatment of axisymmetric blank, layers specified in volume are treated in passes making use of complex loading which includes torsion at least at first pass of first stage as single or primary component and compression and tension at subsequent passes or combination of compression or tension with torsion; treatment is performed under isothermal or quasi-isothermal conditions. Proposed method ensures grinding of microstructure to size of grains of 5.0 to 10.0 mkm and lesser in large-sized blanks exceeding 200 kg in mass. EFFECT: enhanced efficiency of grinding microstructure. 50 cl, 31 dwg

Description

 The invention relates to the field of metallurgy, namely to thermomechanical processing of workpieces with cast coarse-grained, coarse-grained lamellar microstructure, in particular from titanium and its alloys, in order to obtain a given microstructure in them.

 The invention can be used to obtain forgings and pre-preparations for the manufacture of products intended for use in various fields of industry, including aerospace.

 Obtaining high technological and operational characteristics in most alloys, as a rule, is associated with obtaining a certain type of microcrystalline structure on the one hand and its uniformity on the other. In this case, the microcrystalline structure of the micro-duplex type with an average grain size d = 1.0-10.0 μm is optimal from the point of view of low values of flow stress and maximum ductility. At the same time, a combination of satisfactory ductility, high toughness and long-term strength can be obtained by having a microstructure such as basket weaving. It is known that the main method of obtaining such a microstructure is the heat treatment of a material which, in its initial state, has a microcrystalline structure of the micro duplex type. Thus, the relevance of the problem of obtaining the maximum strength characteristics of the material in the products is directly related to the problem of obtaining high technological characteristics of the material in the workpieces.

 Currently, a number of technological methods are known that make it possible to obtain a microcrystalline structure both in small samples [1,2] and in large-sized blanks [3]. The analysis shows that all these methods are basically of a single physical nature: an increase in the internal energy of deformable samples due to hardening as a result of intense plastic deformation and its transition to a stable state due to the development of softening processes, such as recovery, recrystallization, etc.

 A known method of processing metal materials [1] in which, using intense plastic deformation, which is realized by deformation by sediment with torsion of thin plates between two flat strikers, it is possible to obtain a microstructure with an average grain size of 50 nm. This method of processing workpieces is called "deformation on the anvil of Bridgman." Intensive shear deformation of workpieces from difficult-to-deform materials, possible as a result of increasing their plasticity resource during torsion, is achieved by creating a stress state in the workpiece close to quasi-hydrostatic compression.

 The disadvantages of this method include the limited ability to obtain blanks of large sizes. With the increase in the size of the workpiece, the heterogeneity of the distribution of accumulated strain over the cross section increases, which leads to an increase in the heterogeneity of the distribution of the microstructure in the workpiece. In connection with these shortcomings, this method is used, as a rule, in laboratory conditions.

A known method of processing materials [2], which, like the previous one, is based on shear deformation under conditions of quasi-hydrostatic pressure, called "Equal channel angular pressing". In contrast to the previously considered method, intense shear deformation is gained here as a result of repeated pressing, as a rule, axisymmetric and lengthy workpieces in a channel of constant cross section with a fracture. The angle of fracture is chosen equal to or less than 90 ^o . Depending on the magnitude of the friction forces between the workpiece and the tool, the method allows the use of backpressure pressing.

 The main advantage of the "Equal-channel pressing" method compared to the "deformation on the anvil of Bridgman" is the possibility of its use for preparing the microstructure in larger workpieces.

 This method is used in the processing of billets of metals and alloys in order to obtain the desired microstructure in them at low temperatures. When processing workpieces from difficult-to-deform materials, in particular from titanium and its alloys, at high temperatures, the problem of protective-lubricating coatings arises, which has not yet been solved.

 Thus, the known methods [1,2] are intended to obtain a given microstructure in small samples in laboratory conditions.

 In addition, the known methods [1,2] do not allow to obtain a regulated inhomogeneous structure over the cross section of the workpiece.

 A known method of processing workpieces from difficult to deform materials, which consists in obtaining a workpiece microcrystalline structure [3], which is selected as a prototype.

The method includes the initial hot deformation of the workpieces by upsetting with a degree leading to a change in the cross-sectional area to a value of 1: 4 at temperatures not higher than 450 F (232.2 ^o C), but not lower than the recrystallization temperature, and subsequent hot die forging at a temperature 350 F (176.7 ^o C), but not lower than the temperature of recrystallization of the processed alloy.

 The formation of a microcrystalline structure in preforms during such processing is achieved due to the development of recrystallization processes after hot work hardening during hot processing of preforms by pressure.

 One of the main advantages of this method is the ability to effectively process semi-finished products of medium size, as well as products of complex shape.

 However, the method has inherent disadvantages.

 As is known, the selected scheme for processing workpieces by compression is characterized by heterogeneity of the flow of deformation of the material over the cross section, which is expressed in the formation of a forging cross, as well as stagnant zones, directly in the area of contact between the stamping tool and the workpiece. With an increase in the dimensions of the workpieces being processed, the uneven distribution of deformation over the volume of the workpieces is aggravated, which leads to the appearance of an uncontrolled gradient in grain size in the volume of the workpieces. In this regard, there is practically no possibility of obtaining a given microstructure over the cross section of the workpiece.

 Fundamentally, there is no possibility of the controlled production of a regulated microstructure characterized by different grain sizes over the billet cross section.

 Hardly deformed materials, especially titanium alloys, have a rather low value of the coefficient of thermal conductivity, which mainly affects the rate of heating and cooling. This effect is especially noticeable with an increase in the transverse dimensions of the workpieces. The presence of the compression operation at the first stage of processing the workpieces introduces restrictions on the ratio of the size of the workpiece in height to the transverse size, due to the loss of stability of the workpieces during upsetting. Therefore, with an increase in mass, the transverse size of the workpieces and the duration of their heating under deformation increase. By increasing the heating rate, it is possible to reduce the time required for heating the workpieces, however, in this case, the gradient of the temperature field over the cross section increases, which leads to a violation of the uniformity of the distribution of grain sizes over the volume of the workpiece.

 It is known from experiments that the higher the deformation temperature and the longer the heating time of the workpiece under hot deformation, the larger the grain, which, along with the uneven structure, significantly limits the use of this method in the processing of large workpieces.

 The method under consideration involves the use of compression in isothermal conditions and, as a consequence, the use of a heated die tool. Experience shows that the mass of a stamping tool is tens of times greater than the mass of a workpiece. Therefore, with an increase in the dimensions of the workpiece being processed, along with an increase in the cost of material and the manufacture of a stamped tool, the costs of heating it also increase, which are many times more than the costs of heating the workpiece.

 An increase in the size of the workpiece to be processed entails an increase in the required efforts of the press equipment. It is known that a change in the transverse dimensions of the workpiece by two times leads to a change in the power of the required equipment by four times.

 Thus, the considered method of processing workpieces can be attributed to the category of highly energy-intensive processes. Moreover, the degree of energy intensity increases proportionally with increasing mass of the workpiece.

 Thus, the analysis of the data published in the technical and patent literature showed that the processing of large-sized workpieces from metals and alloys with the aim of obtaining a uniform or regulated microcrystalline structure over the cross section is an urgent technological problem.

 The objective of the invention is to increase the grinding efficiency of the microstructure, namely the achievement of grain size of 5.0-10.0 microns or less in large-sized, including more than 200 kg, workpieces. The objective of the invention is to provide the possibility of obtaining in the workpieces homogeneous, or regulation of heterogeneous in the cross section of the microstructure. The objective of the invention is to reduce specific energy consumption with increasing dimensions of the workpiece. An additional object of the invention is to reduce the complexity of the process as a whole.

 The problem is solved by the method of processing billets of metals and alloys by means of plastic deformation with a degree and in temperature and speed conditions, providing grinding of the microstructure, characterized in that they process the entire billet or its regulated part in one or several stages using one, and if there are several stages, mainly in the first stage, as the predominant or sole component of torsion loading, and in subsequent ones, as mainly of the first or only component of tensile or compression loading, in addition, at least the stage, including torsion loading, is performed in several transitions, and the loading conditions are selected to ensure the transformation of the microstructure during deformation and / or during the heat treatment between transitions and / or stages.

где V₀ - объем всей заготовки;
V₁ - объем трансформированной части заготовки;
σ₁ - напряжения течения материала с микрокристаллической структурой;
σ₂ - напряжения течения материала в исходной заготовке,
кроме того, температуру второго этапа выбирают не выше температуры первого этапа деформирования;
- деформацию осуществляют за три этапа, причем на третьем этапе при использовании осевой компоненты нагружения осуществляют формообразование заготовки;
- в качестве исходной берут осесимметричную заготовку в виде прутка, размер которой в поперечном сечении выбирают тем меньшим, чем меньше заданный размер зерен, при этом в качестве осевой компоненты нагружения используют одноосное растяжение;
- в качестве исходной берут осесимметричную заготовку в виде шайбы, высоту которой выбирают тем меньше, чем меньше заданный размер зерен, при этом на втором этапе, в качестве осевой компоненты нагружения используют одноосное сжатие.The task is also solved if:
- the processing is carried out in several stages, while the first stage provides the transformation of the microstructure until the conditions for the occurrence of deformation in the worked layer at the next stages under conditions of superplasticity;
- the number of stages and type of loading is selected taking into account the configuration of the initial and final workpiece and the grain size in the original workpiece;
- the number of stages and type of loading is selected taking into account a given distribution of grain size in the cross section of the workpiece;
- when processing billets of titanium and its alloys, the degree and temperature-speed conditions of deformation at the transition are chosen to ensure the occurrence of dynamic recrystallization in the β-phase, and heat treatment is provided between the transitions to ensure the occurrence of phase transformations;
- when processing billets of titanium and its alloys, the degree and temperature-speed conditions of deformation at the transition are chosen to ensure the occurrence of static recrystallization in the β-phase, and recrystallization annealing is performed between the transitions, followed by heat treatment, which ensures the occurrence of phase transformations;
- when processing workpieces from (α + β) titanium alloys, the workpiece is deformed at least at one of the transitions at a constant temperature, not higher than [T _Ac3 - (20 ÷ 30)] ^o С;
- when processing workpieces of pseudo α- and α-titanium alloys, preform, at least at one of the transitions is deformed at a constant temperature in the temperature range of _Ac3 T ÷ T _Ar3 alloy to be treated;
- heat treatment is carried out by cooling the workpiece with a regulated speed, ensuring the flow of direct phase transformation by the diffusion mechanism;
- the cooling rate is chosen not more than the speed corresponding to the martensitic transformation in the β phase and not less than the speed corresponding to the highest intensity of the formation of annealing twins in the α phase;
- cooling is carried out to a temperature of the subsequent transition;
- the temperature of the subsequent transition is chosen below the temperature of the previous transition;
- the temperature of the subsequent transition is chosen equal to the temperature of the previous transition;
- cooling is carried out to a temperature below the temperature of the subsequent transition, with further heating to the temperature of the subsequent transition;
- cooling is carried out to room temperature, followed by heating to a temperature of a subsequent transition;
- at least after one of the transitions, it is heated to a temperature higher than the processing temperature at the previous transition, followed by cooling to the temperature of the subsequent transition;
- at least at one of the transitions, the workpiece is processed at a variable temperature;
- when processing billets of titanium and its alloys with the initial cast structure, before the first stage, additional processing is carried out, which ensures the occurrence of dynamic recrystallization in the β-phase and heat treatment, which ensures the occurrence of reverse phase transformations;
- when processing billets of titanium and its alloys with the initial cast structure, before the first stage, additional processing is carried out, which ensures the occurrence of dynamic recrystallization in the β-phase and heat treatment, which ensures the occurrence of direct phase transformations;
- the strain temperature in the subsequent stages is chosen below the strain temperature in the first stage;
- deformation is carried out in one step, while the number of transitions and the amount of accumulated deformation are selected depending on the depth of the layer being worked out and the plasticity resource of the processed material;
- the deformation is carried out in two stages, while the amount of accumulated deformation in the first stage is selected from the conditions for ensuring the grinding of the microstructure in the volume, which is determined from the ratio

where V ₀ - the volume of the entire workpiece;
V ₁ - the volume of the transformed part of the workpiece;
σ ₁ - stress flow of a material with a microcrystalline structure;
σ ₂ - stress flow of the material in the original workpiece,
in addition, the temperature of the second stage is chosen not higher than the temperature of the first stage of deformation;
- the deformation is carried out in three stages, and in the third stage, when using the axial components of the load, the workpiece is shaped;
- the axisymmetric billet in the form of a rod is taken as the initial one, the size of which in the cross section is chosen the smaller, the smaller the given grain size, while uniaxial tension is used as the axial component of the load;
- the axisymmetric blank in the form of a washer is taken as the initial one, the height of which is selected the smaller, the smaller the given grain size, while in the second stage, uniaxial compression is used as the axial component of the load.

- at the first stage, the workpiece is deformed by a combination of torsion and compression;
- at the first stage, the workpiece is deformed by a combination of torsion and tension;
- at the first stage, the workpiece is deformed alternately by torsion, tension and compression;
- at the first stage, torsion is combined with the action of alternating axial loading;
- at the first stage, the workpiece is deformed, combining axial loading with alternating torsion;
- at the first stage, with monotonous two-component loading, the ratio of the axial component of the deforming force to the torque is selected no more than 0.2;
- at the second stage, the workpiece is deformed by a combination of compression with torsion;
- at the second stage, the workpiece is deformed by a combination of compression with tension;
- the workpiece is deformed in a shell made of a material capable of superplastic deformation, while the shell is pre-deformed by uniaxial tension to ensure contact between the workpiece and the shell along the side surface of the workpiece, which prevents them from being displaced relative to each other during processing;
- when processing a hollow workpiece, a core is installed inside the workpiece, and the workpiece is subjected to deformation;
- when processing a hollow billet with a multicomponent loaded inside the billet, a core made of a material is installed, which is deformed under conditions of super-plasticity under conditions of temperature and speed of processing the billet, and the core and the billet are subjected to deformation, mainly in the second stage;
- the workpiece assembly with the core is deformed in a shell made of a material capable of superplastic deformation, while the shell is preliminarily deformed by uniaxial tension to ensure contact between the workpiece and the shell along the side surface of the workpiece, which prevents them from being displaced relative to each other during processing;
- the core is hollow;
- the core is solid;
- the workpiece and the core are deformed together;
- the workpiece and the core are deformed separately;
- processing the workpiece is performed in the conditions of distribution of the core by feeding into the inner cavity of the core under the pressure of the working medium.

 - a material is placed between the workpiece and the core, which at least during the processing of the workpiece acquires viscous flow properties.

 - after processing the workpiece, the workpiece is distributed by feeding into the cavity between the workpiece and the core under the pressure of the working medium.

- the processing of hollow thin-walled preforms is carried out in the shell, while pre-dispensing of the preforms is carried out until contact between the preform and the shell is made along the side surface of the preform, which prevents them from moving relative to each other during processing;
- the shell is made of a material that, at the selected temperature and speed modes of processing the workpiece, is deformed under conditions of superplasticity;
- a hollow workpiece is installed between the shell and the core, made of a material that does not undergo a change during processing of the workpiece, provide uniform contact across the entire contact surface of the workpiece and the core, preventing mutual displacement of the workpiece, shell and core during processing, and the deformation of the workpiece is performed by displacing the shell and core relative to each other;
- the workpiece and the contact surfaces of the shell and core are made conical in shape;
- the contact between the hollow billet, the shell and the solid core is ensured by the formation of thermal interference;
- the contact between the hollow billet, the shell and the solid core is provided by a solder joint, while the initial thickness of the layer Δ is chosen from the condition of 50.0 μm <Δ <200.0 μm;
- when processing plates, they are placed between the shell and the rod with contact across the entire surface by preliminary deformation of the plates, and deformation during processing is carried out by displacing the shell and the rod relative to each other;
- the shell and the rod are conical in shape, while the preliminary deformation of the plates is carried out during assembly;
- when processing workpieces in the form of rods, torsion is carried out by applying a deforming force to the end surface, uniformly over an area having a radius r equal to 0.7 <r <R, where R is the radius of the workpiece;
- the deforming force on the workpiece is transmitted due to its integral connection with the tool;
- one-piece connection is performed by fusion welding;
- one-piece connection is performed by welding in the solid phase;
- one-piece connection is performed by soldering, while the solder material is selected from the condition that its melting temperature is higher than the workpiece processing temperature, and the interlayer thickness is selected from the ratio of 50.0 μm <Δ <200.0 μm;
- the deforming force on the workpiece is transmitted due to its detachable connection with the tool.

 The efficiency of grinding the microstructure in the proposed technical solution is achieved through the use of soft loading schemes or their combination with medium and hard loading schemes, which ensure the achievement of more significant degrees of accumulated deformation, and thereby lowering the temperature of recrystallization, or at a given temperature, increasing the recrystallized volume and speed of the process recrystallization. Moreover, shear deformation during the processing of large-sized workpieces is effectively used due to the fact that not all of the workpiece is subjected to shear immediately, but surface layers.

The degree of deformation achieved with this treatment provides grain refinement:
- or in the process of deformation only due to dynamic recrystallization;
- or as a result of deformation and development of the process of static recrystallization during heat treatment after deformation;
- or as a result of deformation, the development of dynamic recrystallization in one phase and heat treatment, ensuring the occurrence of direct phase transformations;
- or as a result of deformation, the development of static recrystallization during heat treatment after deformation and the second heat treatment cycle, which ensures the occurrence of reverse phase transformations.

 The choice of one or another alternative depends on the physical properties of the material being processed, on the structure in the initial workpiece, the temperature and speed conditions of deformation, as well as the specified or maximum permissible degree of deformation.

 All of the above conditions are taken into account when determining the number of transitions during processing in stages. For example, when a material with low plastic properties is subjected to processing, the required layer development is achieved through the use of multi-transition processing and recrystallization annealing between transitions.

 The development of the process of plastic deformation under the conditions of the development of intense shear deformation during torsion stimulates the formation of stable dislocation clusters in the material, which alone or in combination with the subsequent heat treatment ensures the controlled development of either dynamic or static recrystallization, or in combination with phase transformations, accelerates the development the processes of transformation of a coarse-grained, or coarse lamellar microstructure into a globular, including micro-duplex in host layers.

 At the second stage, axial loading by tension or compression creates a uniform stress and strain state in the cross section of the workpiece. The increased sensitivity of flow stresses to the strain rate, typical for materials with superplastic properties, of the transformed volume in the surface layers, allows the central part of the workpiece to be processed into fine grain during subsequent deformation, ensuring the flow of the deformation process uniformly over the cross section, without neck formation under tension or without formation forging cross during compression and premature destruction of the workpiece as a whole.

 The use of torsion at the first stage and the implementation of processing in one stage allows you to get a regulated microstructure non-uniform in cross section due to the transformation of the microstructure in the surface layers of the workpiece. Processing in two or more stages allows to obtain a microstructure that is uniform throughout the volume.

 When processing workpieces in two or more stages, the recommended condition is to obtain a microstructure at the first stage, which ensures subsequent flow in the worked-out deformation layer under superplasticity conditions.

 The proposed mechanical loading scheme makes it possible to increase the dimensions of the workpieces being processed, due to the predominant increase in long dimensions, since in the second stage it is possible to use tension or tension with torsion. The possibility of increasing the mass of the workpieces by increasing the long size without changing the transverse ensures uniform heating of the workpieces in less time, which allows to obtain in the workpieces weighing 200 kg or more a microcrystalline structure with an average grain size of 10.0-15.0 microns.

 With a decrease in the transverse dimensions of the workpiece, it is possible to obtain an average grain size significantly less than 10.0-15.0 microns.

 The decrease in specific energy consumption with an increase in the mass of workpieces is achieved due to the fact that the loading scheme by torsion requires less energy. In particular, they are reduced due to the absence of a deforming tool in the working area. Moreover, the larger the dimensions of the processed workpieces, the higher the effectiveness of the proposed method according to this criterion.

The use of torsion as the main component of loading during processing of billets allows to a large extent (an order of magnitude) compared, for example, with compression, to increase the speed of the process while maintaining the strain rate of the material in the entire volume of controlled, constant and optimal. For example, when preparing the structure in billets with a diameter of 100.0 mm and a length of 250.0 mm, made of VT6 titanium alloy, in the initial state having a cast structure, while ensuring a strain rate on the side surface of 10 ^-3 s ^-1 , the strain value is e = 3 6 was scored in 12.0-15.0 minutes. At the same time, 80% of the workpiece volume underwent transformation into a micro-duplex type structure. A similar value of the accumulated deformation, when compressing the same size ingot, which is necessary for the complete transformation to take place, is gained in 4-7 working shifts and is associated with the need for intermediate heating.

 The effectiveness of the method is also confirmed by such a criterion as the absence of a deforming tool in the working area, which excludes the appearance of friction forces and the costs associated with overcoming them, the value of which in known solutions also grows with increasing dimensions of the processed workpieces.

 In addition, preserving the transverse dimensions and increasing the long dimensions of the workpiece reduces its warming up time to operating temperatures, and makes the heating time almost independent of the dimensions of the workpiece being processed.

 The number of stages and type of loading is chosen taking into account the configuration of the initial and final workpiece and the grain size in the original workpiece. The shape, geometric dimensions of the workpieces, as well as the initial microstructure, determine the modes of deformation-heat treatment of the workpieces in order to obtain a microcrystalline structure in them, as well as the types of loading used. For example, it is advisable to process hollow billets by torsion. When processing long workpieces, torsion or torsion with tension is used in the first stage, and only tension in the subsequent ones. When processing workpieces with a short length, torsion or torsion with compression is used in the first stage, and only compression in the subsequent ones. In those cases when it is required to process a workpiece with a low-plastic structure, it is advisable to deform the workpieces in shells.

 The number of stages and type of loading is selected taking into account a given distribution of grain size in the cross section of the workpiece. In cases where it is necessary to perform only surface treatment of the workpieces, it is advisable to use only torsion. The predetermined grain size in the cross section of the workpieces being processed is achieved due to the predetermined level of the strain accumulated during the torsion process, which is determined by the twist angle, speed and the possibility of reverse twisting.

When processing billets of titanium and its alloys, it is sufficient to choose the degree and temperature-speed conditions of deformation at the transition that ensure the occurrence of dynamic recrystallization only in the β phase. The presence of many equivalent slip systems in the body-centered cubic lattice of the high-temperature allotropic modification of the β phase determines the development of the plastic flow of the material due to multiple slip. The relatively low value of the stacking fault energy for the β phase, E ~ 20 erg / mm ² [4], causes the appearance of stable, both flat and spatial dislocation clusters, which are transformed upon further deformation into a cellular microstructure with a mesh size of 1-2 μm, with a wall thickness of 0.6-0.7 μm and consisting of bulk coils with a high dislocation density at the boundary and a low dislocation density inside the cells. Further deformation leads to a decrease in the thickness of the cell boundaries and an increase in their curvature. Against this background, an increase in crystallographic misorientation between neighboring cells also occurs. Such an evolution of the dislocation structure, as is known, precedes the onset of dynamic recrystallization, the result of which is the formation of high-angle grain boundaries. It is obvious that recrystallization in the β-phase occurs at lower degrees of deformation, which as a result reduces the overall level of deformation required to grind the structure. The implementation between the transitions of heat treatment aimed at ensuring the occurrence of direct phase transformation by the diffusion mechanism, for example, when the workpiece is cooled at a controlled speed, will lead to the release of the α phase in the triple joints of the newly formed intergranular boundaries of the β phase. The predominant separation of the α phase at triple junctions is due to the increased value of the diffusion coefficient at the intergranular (β-β) - boundary of the general type compared to the special coherent interphase (β-α) - boundary, as well as their greater length per unit volume due to the small size grains. On the other hand, a high energy level of the intergranular boundary as compared with the interphase one is the cause of the appearance of a chemical potential gradient, which determines the directional diffusion mass transfer. Thus, from both the thermodynamic and kinetic points of view, it becomes more advantageous to isolate the α phase at triple junctions than at interphase boundaries. As a result, microduplex structure is formed.

 When treating billets of titanium and its alloys with the same degree of deformation that is necessary for the development of dynamic recrystallization, the temperature and speed conditions of deformation at the transition are chosen to ensure the occurrence of static recrystallization in the β phase during subsequent heat treatment, which allows us to include a larger structure in the process of transformation layer in the workpiece processed by torsion or torsion with tension. Recrystallization annealing between transitions ensures the occurrence of static and metadynamic recrystallization in these layers, which, in combination with the dynamic recrystallization preceding the plastic strain transition, increases the uniformity and completeness of the formation of grain boundaries in the β phase. Subsequent heat treatment aimed at direct phase transformation, which develops according to the diffusion mechanism, as in the previous case, provides a micro-duplex type structure.

When processing workpieces from (α + β) titanium alloys, the workpiece is deformed at least at one of the transitions at a constant temperature, not more than [T _Ac3 - (20 ÷ 30)] ^o C. When heated to the indicated temperature, the microstructure, as a rule, represents a colony of thin plates of the α-phase in the matrix β-phase. In this case, the achieved minimum amount of the α phase does not change their lamellar morphology, while retaining the ability to limit the grain growth of the recrystallized matrix β phase. The deformation-heat treatment performed in this case provides the development of the transformation of the rough plate structure according to one of the three schemes described above. These modes are recommended for workpieces with the initial structure with a sufficiently large β-grain size, of the order of 1 mm or more.

When processing workpieces of α-titanium alloys, preform, at least at one of the transitions is deformed at a constant temperature in the temperature range T T _Ac3 and _Ar3 alloy to be treated. The processing of alloys of this group in the two-phase α + β temperature range makes it possible to most advantageously realize the benefits of processing the β-phase under conditions of moderate grain growth in the two phase region.

 Heat treatment in preforms subjected to deformation, at transitions or at stages is carried out by cooling at a regulated speed, which ensures the direct phase transformation through the diffusion mechanism, which ensures β → α transformation mainly in triple joints and at intergranular boundaries of the β phase.

 The cooling rate is chosen not more than the speed, the speed corresponding to the martensitic transformation in the β phase and not less than the speed corresponding to the highest intensity of the formation of annealing twins in the α phase. For many alloys, this speed is optimal from the point of view of the simultaneous occurrence of the following processes: phase transformations by the diffusion mechanism, recrystallization, including metadynamic, as well as the formation of annealing twins, which contribute to the development of fragmentation of α-plates during subsequent heating.

 Cooling is carried out to a temperature of the subsequent transition in order to combine the completion of the heat treatment process with the deformation processing. Reducing the time for cooling and heating in this case has a positive effect on reducing the final grain size of the transformed microstructure.

 The temperature of the subsequent transition is chosen below the temperature of the previous transition. In the case when it is required to obtain the smallest possible grain size, the processing process must be carried out with decreasing temperature at each of the subsequent transitions. In this case, the processing of billets at the transition can be considered as a method of increasing the plasticity resource of the billet during its processing at subsequent transitions at a lower temperature due to the gradual grinding of grains. A decrease in temperature and an increase in the plasticity margin due to the fine grain of the transformed microstructure obtained by processing the workpieces at previous transitions makes it possible to increase the degree or rate of deformation, which, combined with a decrease in temperature, allows not only to activate the development of dynamic recrystallization at subsequent transitions, but also to obtain a transformed microstructure with a smaller grain size.

 The temperature of the subsequent transition is chosen equal to the temperature of the previous transition. In cases where it is necessary to increase the completeness of the transformation, the uniformity of the distribution of grains in the volume due to the combination of deformation processing with heat treatment, for example, in the case of processing single-phase materials, it is advisable to perform processing at the transitions at the same temperature.

 Cooling is carried out to a temperature below the temperature of the subsequent transition, with further heating to the temperature of the subsequent transition. Such thermocyclic treatment is aimed at realizing a more complete course of direct phase transformations and intensification of the structure transformation process.

 Cooling to room temperature, followed by heating to the temperature of the next transition, especially with a regulated speed, provides the appearance of phase hardening necessary to ensure the passage of the α-phase return, or polygonization, or twinning in the plates. The superposition of phase hardening processes on the return processes accelerates the formation of small-angle boundaries and twinning. Subsequent heating leads to fragmentation of the α-phase plates by structural defects, namely, by small-angle boundaries and twins, in the process of reverse phase transformation.

 At least after one of the transitions, heating is carried out to a temperature above the processing temperature at the previous transition and cooling to the temperature of the subsequent transition. The expediency of such an operation is due to the possibility in some cases, for example, when processing materials in which phase transformations occur during heating, to influence the process of structure transformation at the stage of development of reverse phase transformations.

 At least at one of the transitions, the workpiece is processed at a variable temperature. The relevance of this operation becomes apparent on the example of processing α-titanium alloys, when the temperature range for the simultaneous existence of α and β phases is extremely narrow, therefore processing the workpieces with a change in temperature, i.e. in the oscillation mode inside or with a short-term exit beyond the two-phase region, one of the methods for obtaining microcrystalline structure in these materials. In addition, the combination of deformation processing with thermal cycling activates the processes of fragmentation of α-plates both due to the formation of fragments during deformation and due to the development of direct and reverse phase transformations.

 When processing billets of titanium and its alloys with the initial cast structure, before the first stage, additional processing is carried out, which ensures the occurrence of dynamic recrystallization in the β-phase and heat treatment, which ensures the occurrence of reverse phase transformations. A fairly mild processing method, to which the proposed operation relates, allows, using the mechanical features of torsion processing, to begin processing a material having a cast structure and to ensure the massive development of dynamic recrystallization in the β phase. An additional effect is homogenization, i.e. alignment of the chemical composition of the ingots in volume over time, by orders of magnitude less than with conventional heat treatment.

 When processing billets of titanium and its alloys with the initial cast structure, before the first stage, additional processing is carried out, which ensures the occurrence of dynamic recrystallization in the β-phase and heat treatment, which ensures the occurrence of direct phase transformations. When processing some workpieces, for example, subjected to pre-homogenizing annealing, but still having a cast microstructure, it is possible to perform their deformation processing in a two-phase region near the Ac3 point. In this case, the occurrence of dynamic recrystallization in interlayers of the β-phase located between the plates of the α-phase will not be accompanied by accelerated growth of β-grains, and subsequent heating of the preform into the single-phase β-region will allow the use of recrystallized grains, like nuclei during reverse phase transformations, increasing the uniformity of distribution β-grains in the volume of the workpiece.

 The deformation temperature in subsequent stages is chosen below the deformation temperature in the first stage. The feasibility of this restriction is determined by the fact that at the subsequent stages of processing the workpiece, it is possible to use intense deformation, which is also aimed at shaping the final product. Intensive processing, as is known, is accompanied by intense heat generation, which may ultimately lead to coarsening of the microstructure already transformed at the previous stages.

 Plastic deformation of the workpieces is carried out in one step, while the number of transitions and the amount of accumulated deformation are selected depending on the depth of the layer being worked out and the plasticity resource of the processed material. The necessity of this condition is due to the limited plasticity resource in each case, determined by the initial microstructure of the material being processed and the correspondence to the available plasticity resource of the ultimate strain in the surface layers of the processed workpiece.

где V₀ - объем всей заготовки;
V₁ - объем трансформированной части заготовки;
σ₁ - напряжения течения материала с микрокристаллической структурой;
σ₂ - напряжения течения материала в исходной заготовке,
а температуру второго этапа при этом выбирать не выше температуры первого этапа деформирования. Данное выражение получено расчетным путем, при анализе ситуации, когда деформации подвергают композит. При этом полагают, что механическое поведение отдельных элементов композита и поведение композита в целом связано принципом аддетивности.In cases where the deformation is carried out in two stages, the value of the accumulated deformation in the first stage, it is advisable to choose from the conditions for ensuring the grinding of the microstructure in the volume of the workpiece, which is determined from the ratio:

where V ₀ - the volume of the entire workpiece;
V ₁ - the volume of the transformed part of the workpiece;
σ ₁ - stress flow of a material with a microcrystalline structure;
σ ₂ - stress flow of the material in the original workpiece,
and the temperature of the second stage in this case should be chosen no higher than the temperature of the first stage of deformation. This expression is obtained by calculation, when analyzing the situation when the composite is subjected to deformation. It is believed that the mechanical behavior of the individual elements of the composite and the behavior of the composite as a whole are related by the principle of additivity.

 If the deformation is carried out in three stages, in the third stage, the axial component of the load is used to shape the workpiece. In those cases when the manufacture of a particular part is associated with significant shaping, accompanied by intense shear deformation, it is advisable to prepare the microstructure in the sections of the workpiece at the first stages, and to combine the preparation of the structure with intensive shaping at others.

An axisymmetric billet in the form of a bar is taken as the initial one, the size of which in the cross section is chosen the smaller, the smaller the given grain size, while uniaxial tension is used as the axial component of the load. One of the parameters that determine the process of preparing the structure is the initial geometry of the processed workpieces. Reducing the transverse dimensions of the workpieces expands the possibility of using the heating and cooling rates to solve the problem of obtaining a microstructure with a given grain size and the necessary uniformity of their distribution over the volume of the workpiece. In addition, when processing large axisymmetric blanks, their mass can be increased without changing their diameter, but only by changing the length. In this case, it becomes possible not only to expand the spectrum of the resulting structures, but also to increase the productivity of the process. Since it is possible to process one long workpiece by torsion with tension during one technological cycle, with its subsequent division into several workpieces, instead of processing individual short workpieces in compliance with the critical compression ratio of the workpiece height to diameter,
An axisymmetric billet in the form of a washer is taken as the initial one, the size of which is chosen in height the smaller, the smaller the given grain size, while in the second stage, uniaxial compression is used as the axial component of loading. When processing blanks of the washer type, the need to reduce the height size is caused by the desire to change the heating or cooling rate in large intervals, which ultimately expands the range of achievable grain sizes of the transformed microstructure, including the minimum possible.

 At the first stage, the workpiece is deformed by a combination of torsion and compression. Torsion with compression allows you to deform the workpiece to a greater degree of deformation. Thereby, an additional decrease in the temperature of recrystallization is achieved, and as a result, the average grain size in the transformed structure decreases. This operation is recommended to be used in cases where a workpiece such as a washer is subjected to processing.

 At the first stage, the workpiece is deformed by a combination of torsion and tension. The main component of loading is torsion. However, to intensify the transformation process on the one hand and increase the stability of the bar deformation as a whole, on the other hand, torsion must be combined with axial loading. When processing long workpieces for these purposes, it is advisable to use tension.

At the first stage, the workpiece is deformed, combining alternating torsion with alternating axial loading. The broken deformation trajectory (with a bend angle on the deformation trajectory in the torsion - axial deformation space equal to 90 ^o ), implemented at the first stage of preparation of the structure, is aimed at creating conditions for the development of massive multiple slip of various types of dislocations that flow uniformly throughout the workpiece . At the same time, the processes of formation of a cellular or polygonized structure are facilitated, depending on the temperature and strain rate, the processes of recrystallization and phase transformations are accelerated, and, as a result, the processes of transformation of the lamellar structure and the formation of a microcrystalline microduplex type are intensified.

 At the first stage, monotonous torsion is combined with alternating axial loading. When machining axisymmetric workpieces with a long size that is not much larger than the critical size according to the criterion of stability during upsetting, it is advisable to use torsion as the main component of loading, and uniaxial tension alternately combine with uniaxial compression as an additional component. This technique, along with the intensification of the process of transformation of the structure, can reduce the magnitude of the axial component of loading by about 25-50%.

 At the first stage, the workpiece is deformed, combining alternating torsion with monotonous axial loading. The use of reverse torsion as a loading component, along with the intensification of the structure transformation process, due to an increase in the allowable accumulated deformation, promotes blurring of crystallographic and metallographic textures, and the formation of a microcrystalline structure with a textureless state.

 At the first stage, with monotonous two-component loading, the ratio of the axial component of the deforming force to the torque is selected no more than 0.2. A similar ratio of torsion and tensile components under monotonic two-component loading allows the most efficient use of complex loading when processing preforms in order to intensify the process of transformation of the coarse structure and obtain a microcrystalline structure in the surface layers in the preforms.

 At the second stage, the workpiece is deformed by a combination of compression with torsion. The use at the second stage as the predominant component of loading - compression, it is advisable to apply in cases where workpieces with a length not exceeding the triple minimum size in the cross section are subjected to processing. Otherwise, during deformation by compression, the workpieces lose their stability. In addition, the combination of torsion and compression can significantly reduce the required efforts to overcome the harmful effects of friction forces. This is due to the reversal of the resulting deformation vector and ultimately leads to a decrease in axial force by 25-50% and to increase tool life.

 At the second stage, the workpiece is deformed by a combination of torsion and tension. The use of preforms at the second stage of processing as the predominant tensile component is advisable in those cases when preforms are processed with a working part length three times greater than their minimum cross-sectional size.

 When processing materials having a coarse microstructure and characterized by a limited plasticity resource, such as, for example, intermetallic compounds, it is advisable to process them in a shell to increase the plasticity resource of preforms. Moreover, the formation of cracks on the side surface of the workpiece will largely depend on how tightly the shell will be in contact with the side surface of the workpiece. By deforming the shell by uniaxial tension under conditions of superplasticity, it is possible to achieve the formation of close contact of the shell with the surface of the workpiece and, as a result, successfully solve the problem of increasing the plasticity resource of the material. By increasing the shell thickness, in combination with the choice of material, it is also possible to ensure the deformation of the workpieces under conditions close to the conditions of comprehensive compression, which also increases the plasticity resource of the processed material. In other cases, the use of shells can be used to prevent oxidation of the workpieces during deformation in the air.

 The process of deformation of hollow billets using torsion loading as the predominant component is limited by deformation, after which there is a loss of stability of the hollow billet. Therefore, in order to increase the degree of stable deformation, it is advisable to deform the hollow workpieces with the core installed inward. In addition, if torsion with tension is used at the workpiece processing stage, the core will prevent the development of deformation by reducing the transverse dimensions of the hollow workpiece, i.e. it will make it possible to create in the hollow billet the most optimal scheme of stress-strain state from the point of view of grinding the structure on the one hand and to keep the internal size of the hollow billet unchanged on the other.

 When processing a hollow billet with multicomponent loading, a core made of a material is installed inside the billet, which deforms under superplasticity under temperature and speed conditions of processing the billet, and the core and the billet are subjected to deformation, mainly in the second stage. The use of a core for processing hollow preforms, the material of which is capable of deforming in the superplasticity mode, in addition to the advantages listed in the previous section, makes it quite easy to remove the preform from the core after processing the preform by deforming the core by stretching with a uniform decrease in its transverse dimensions along the length and creating a guaranteed gap between blank and core.

 The workpiece assembly with the core is deformed in a shell made of a material capable of superplastic deformation, while the shell is preliminarily deformed by uniaxial tension to ensure contact between the workpiece and the shell along the side surface of the workpiece, which prevents them from being displaced relative to each other during processing. The feasibility of deforming a hollow billet in a shell is already described in the previous sections. The main objective of this operation is to increase the plasticity resource during the deformation of thin-walled shells from brittle materials with a limited plasticity resource, as well as to increase the resistance to plastic deformation, both by torsion and by tension or compression. Additionally, the problem of leveling the temperature field in the volume of a thin-walled billet during deformation is not solved not due to the uniformity of the temperature field of the furnace, but due to the redistribution of temperature by heat transfer through the shell and core.

 The core is hollow when hollow billets with a large diameter and a small thickness are subjected to processing. In this case, with a decrease in the total mass of the assembly, the concomitant problems of heat treatment of workpieces with a large mass, which have already been mentioned, are eliminated.

 The core is made continuous in cases where it is important to ensure uniform distribution of the temperature field over the volume of the hollow thin-walled billet due to the massive core, using its mass as a kind of energy accumulator to increase the thermal inertia of the system. This is advisable in cases where materials with a rather narrow temperature range of their existence are subjected to simultaneous treatment in two allotropic modifications, for example, α-titanium alloys.

 The preform and core are deformed together in those cases when the plasticity resource to achieve the degrees necessary for the development of dynamic recrystallization is insufficient, for example, in materials such as intermetallic compounds.

 The workpiece and the core are deformed separately when it is important that the assembly is easy to assemble before processing and disassemble after appropriate processing. This also applies to cases where subsequent processing steps are used to give the workpiece the required geometric dimensions using the core as a gauge.

 The processing of the workpiece is carried out under the conditions of distribution of the hollow core by feeding a working medium into its internal cavity under pressure. Adding to the main components of loading: torsion, tension, compression - additional distribution of the workpiece helps to intensify the process of transformation of the structure in the hollow workpiece, and can also be used to give the workpiece the desired shape.

 A material is placed between the workpiece and the core, which at least during the processing of the workpiece acquires viscous flow properties. It is proposed to use this operation to prevent the preform and core from setting, to increase the uniformity of deformation in this connection and to simplify the operation of removing the core from the preform.

 After processing the workpiece, the workpiece is distributed by feeding into the cavity between the workpiece and the core under the pressure of the working medium. The use of the distribution of the hollow billet provides a uniform development of deformation along the length, reducing friction between the billet and the core in the case when the core is not subjected to deformation during processing.

 The processing of hollow thin-walled preforms is carried out in the shell, while the pre-distribution of the preform is carried out until contact is made between the preform and the shell along the side surface of the preform, which prevents them from being displaced relative to each other during processing. Preliminary distribution of the workpiece allows you to increase the uniformity of the development of deformation during the main cycle of processing hollow workpieces due to the deformation of the workpiece under conditions close to the conditions of comprehensive compression. The creation of a tight contact between the workpiece and the shell can also increase the uniformity of the temperature field during processing.

 The shell is made of a material that, at the selected temperature and speed modes of processing the workpiece, is deformed under conditions of superplasticity. This makes it possible to increase the uniformity of the distribution of compressive stresses over the cross section of the workpiece being processed on the one hand, and on the other hand, it increases the uniformity of the development of deformation of the hollow workpiece during processing. In addition, the shell acts as a protective shield that prevents the oxidation of a thin-walled hollow billet during its deformation at high temperatures in the air.

A hollow billet is installed between the shell and the core, made of a material that does not undergo a change during processing of the workpiece, provide uniform contact over the entire contact surface of the workpiece and the core, preventing mutual displacement of the workpiece, shell and core during processing, and the deformation of the workpiece is performed by displacing the shell and core relative to each other. The use of this loading scheme when deforming a hollow billet is inherently a technological technique in which shear deformation is carried out by displacing the inner and outer layers in the workpiece relative to each other, by rotating in the opposite directions of the shell and core, rigidly connected with the workpiece. Obviously, in this case, minor displacements cause significant shear deformation in the volume of the workpiece. The main feature of the development of such a deformation is its high uniformity in the volume of the workpiece
when the condition of tight contact between the workpiece, the shell and the core. Moreover, the denser the contact, the greater the magnitude of the accumulated deformation. When processing workpieces of medium and large sizes, it is possible to achieve a strain value close to that which can be achieved when processing micro samples on the Bridgman anvil. The preferable type of loading in this example, as in previous cases, is torsion. This is primarily due to the peculiarity inherent in this type of loading, namely, that torsional deformation is not accompanied by a significant change in the shape of the workpiece, as, for example, under tension or compression.

 The blank and contact surfaces of the shell and core are made conical in shape. In the manufacture of a conical shape of the shell and core surface mating with the workpiece, combining torsion with compression of the workpiece having a conical shape, while maintaining the predominant component of torsion loading, it is possible not only to increase the axial strain component compared to the previous case, but also use the possibility of processing the workpieces in quasi-hydrostatic conditions, i.e. under conditions of comprehensive compression. From the point of view of the stress state scheme for large-sized preforms, this technique is similar to the known deformation methods [1,2] used to obtain micro-, submicro-, and nanocrystalline structures in laboratory workpieces in small sizes. At the same time, the proposed technique is unique, since it approaches the Bridgman anvil method to the maximum possible hydrostatic pressure and, in terms of uniformity of the stress and strain state in the whole volume, to the method of equal channel pressing. Therefore, this technique is a way to obtain homogeneous micro-, submicro- and nanocrystalline structures in large-sized blanks.

 Moreover, unlike the mentioned methods, the described technique is characterized by the absence or minimization of slippage on the contact surface of the workpiece with the shell and core. This circumstance allows us to use this technique, also as a method of implementing intense shear deformation at high temperatures of large-sized workpieces made of materials such as, for example, Ti-Al or Ni-Al intermetallic compounds, etc.

The contact between the hollow billet, the shell and the solid core is ensured by the formation of thermal interference. In the case where the preform, shell and rod have a cylindrical or conical surface with low taper, for example less than 7 ^o , it is advisable to ensure close contact due to the formation of thermal interference. In this case, it is necessary to adhere to the following rule: the workpiece, when installed in a deforming tool, should not experience tensile forces. For this, for example, first of all, a contact is formed between the workpiece and the shell, then between the assembly consisting of the shell and the workpiece and the core.

 The contact between the hollow billet of thickness t, the shell and the solid core is ensured by a solder joint, while the initial thickness of the solder layer Δ is selected from the condition Δ≤0.005 t. This thickness of the interlayer is chosen in order to increase the strength of the joint compared with the strength of the solder material, based on the specificity of the boundary conditions on the contact surface of the workpiece with the shell and / or core. The goal, as in the first case, is to ensure tight contact and prevent slippage. An additional goal of this operation is to facilitate the removal of the workpiece from the assembly by heating above the melting temperature of the solder material.

 When processing plates in order to obtain a micro-, submicro-, and nanocrystalline structure in them, they are placed between the shell and the rod to ensure contact over the entire surface by preliminary deformation of the plates, and during processing, shear deformation is carried out by twisting the shell and the rod relative to each other. So you can process not only hollow or annular blanks, but also flat plates, which are bent in the form of rings before processing and place them between the shell and the rod.

 The shell and the rod are conical in shape, with the preliminary deformation of the plates being carried out during assembly. Tight contact is formed directly during the processing of the plates.

 When processing workpieces in the form of rods, torsion is carried out by applying a deforming force to the end surface uniformly over an area having a radius r equal to 0.7 <r <R, where R is the radius of the workpiece. The application of a deforming force to the workpiece thus reduces the unevenness of deformation along the cross section of the bar, which is especially important when preparing a microcrystalline structure uniformly throughout the volume of the workpiece.

 The deforming force on the workpiece is transmitted due to its integral connection with the tool. This type of connection in a single production is the simplest and cheapest.

 If the rod is subjected to processing, then fusion welding, for example, by an electron beam, using the dagger mode, allows reliable connection of the workpiece with a deforming tool.

 If a material is subjected to processing, which, when melted, forms a eutectic, and then brittle intermetalide, as a joint, it is more expedient to use solid-state welding directly by connecting the workpiece and the tool, or by connecting through the interlayer. The peculiarity of this type of connection is that it is able to withstand high static loads, to a level exceeding the level of the main material, but at the same time collapse from the action of a small applied force of a dynamic or cyclic nature. The latter circumstance can be successfully used when separating the workpiece and tool after processing.

 One-piece connection can be made by soldering, while the material of the solder is selected so that its melting temperature is higher than the temperature of the workpiece, and the thickness of the layer of solder is selected from the ratio (0.005 ÷ 0.01) D, where D is the transverse dimension of the connection between the workpiece and the tool. As in the previous case, after processing the workpieces, heating the workpiece and tool to the melting point of the solder makes it quite simple to solve the problem of separating the workpiece and tool. The thickness of the solder joint is selected based on the optimal ratio of the thickness of the interlayer to the transverse size of the contact area, taking into account contact hardening, which allows to increase the strength of the joint by 20-50% of the value of the flow stresses of the solder material.

 The deforming force on the workpiece is transmitted due to a detachable, as a rule, spline connection of it with the tool. This type of connection is advisable to use when processing workpieces in conditions of mass production, when the cost of manufacturing a tool easily pays off. A splined connection can be made in the form of a set of longitudinal and transverse splines located relative to each other at an angle of ninety degrees, which during processing can transmit both torque and axial load. When processing thin-walled hollow billets, it is advisable to produce slots on the contact surfaces of the shell and the rod.

 When analyzing sources of information regarding methods of processing metals and alloys, a method was not found that is characterized by features identical to all the essential features of the claimed invention. Therefore, the claimed invention meets the condition of "novelty."

 When analyzing the hallmarks, it was revealed that the claimed invention does not follow explicitly from the prior art. For the first time, a method for processing metals and alloys under the conditions of simple and complex loading, including the deformation of workpieces by torsion, in one or several stages is proposed. The method allows to obtain a significant regulated accumulated deformation, which in combination with a complex of heat treatments aimed at the development of dynamic and / or static recrystallization, and when processing materials in which phase transformations occur, aimed at the development of phase transformations, in turn, allows to obtain micro- , submicro- and nanocrystalline structure with a given size and uniform or regulated uneven grain distribution in the volume of the workpiece , including bulky workpieces.

 The listed fundamental features of the invention are new and non-obvious. Therefore, the claimed invention meets the condition of "inventive step".

 The invention is illustrated by the following graphic materials.

 Figure 1 - installation diagram for implementing the method.

 Figure 2 - appearance of the installation.

 Figure 3 - appearance of the workpiece.

 Figure 4 - the initial microstructure of the workpiece from alloy VT9.

 FIG. 5a is a diagram of a two-stage processing of a long workpiece made of VT9 alloy.

 Fig.5b is a diagram of the corresponding loading path.

 FIG. 6 is an external view of a machined lengthy VT9 alloy billet after the first step.

 FIG. 7 - microstructure in the processed long billet of alloy VT9 after the second stage.

 Fig. 8a is a diagram of a two-stage processing of a short blank of VT9 alloy.

 Fig. 8b is a diagram of a corresponding loading path.

 Fig.9 - the initial microstructure of the workpiece from alloy VT6.

 FIG. 10a is a diagram of a one-stage processing of a long workpiece made of VT6 alloy.

 Fig. 10b is a diagram of a corresponding loading path.

 11 is an external view of the machined workpiece of alloy VT6.

 Fig - microstructure of the processed billet of alloy VT6.

 FIG. 13a is a diagram of a two-stage processing of a long workpiece with three transitions in the first stage and an intermediate heat treatment between them aimed at the development of phase transformations.

 Fig.13b is a diagram of the corresponding loading path.

 Fig. 14a is a diagram of a two-stage processing of a lengthy workpiece by stirrups at the first stage and intermediate heat treatment between them aimed at the development of static recrystallization and heat treatment aimed at the development of phase transformations.

 Fig.14b is a diagram of the corresponding loading path.

 FIG. 15a is a diagram of a one-stage processing of a long workpiece with three transitions in the first stage and an intermediate heat treatment between them, aimed at the development of phase transformations.

 Figb is a diagram of the corresponding loading path.

 Figa is a diagram of a two-stage processing of a long workpiece with three transitions in the first stage and an intermediate heat treatment between them aimed at the development of phase transformations.

 Fig.16b is a diagram of the corresponding loading path.

 Fig - the original microstructure of the workpiece from alloy VT8.

 FIG. 18a is a diagram of a two-stage processing of a long workpiece made of VT8 alloy with two transitions in the first stage and an intermediate between the stages of heat treatment aimed at the development of phase transformations.

 Fig. 18b is a diagram of a corresponding loading path.

 Fig. 19 shows the microstructure of a VT8 alloy billet after processing.

 Figure 20 shows the macrostructure of a large-sized blank of VT6 alloy in its initial state.

 Figure 21 shows the microstructure of a large-sized blank of VT6 alloy in its initial state.

 FIG. 22a is a diagram of the processing of a large-sized workpiece made of VT6 alloy, including preliminary and main two-stage processing of a long workpiece with one transition in the first stage.

 Figb is a diagram of the corresponding loading path.

 FIG. 23 is an external view of a large-sized blank of VT6 alloy after processing.

 FIG. 24 - macrostructure of a bulky VT6 alloy billet after processing.

 FIG. 25 - microstructure of a large-sized billet of alloy VT6 after processing.

 Fig is a diagram of the joint processing of a cylindrical workpiece.

 FIG. 27 is a diagram of a separate treatment of a tubular billet with an undeformable core installed inward.

 FIG. 28 is a diagram of the processing of a tubular billet with an undeformable core installed inward using a billet distribution.

 FIG. 29 is a diagram of the joint processing of a tubular billet in a shell with a hollow deformable rod installed inward using a workpiece shell and rod distribution.

 Fig - scheme of processing the workpiece between the shell and the rod with a cylindrical contact surface.

 Fig - scheme of processing the workpiece between the shell and the rod with a tapered contact surface.

 The installation, a diagram of which is shown in FIG. 1 and the appearance in FIG. 2, consists of a power casing 1, including lower 2 and upper 3 power plates, fastened together by four columns 4. In the lower part of the casing there is a kinematic loading system 5. In the upper part there is a system for recording power and kinematic parameters of the loading process 6.

 Sample 7 is installed in interchangeable grippers 8, 9 connected to a fixed upper 10 and movable lower 11 traverses.

 The installation has an electronic control system 12, which is designed to ensure mechanical testing of samples with a constant strain rate or constant strain rate. The kinematic scheme of the installation allows deformation by uniaxial tension and compression, as well as monotonous or reverse torsion. In the case of using tubular samples, the installation provides for the possibility of loading samples with the internal pressure of the working medium (the structural implementation of this feature is not shown in Fig. 1).

 The registration system of the force and kinematic parameters of the loading process 6 allows you to independently record the force and kinematic parameters of the loading: the angle of twisting and torque; axial displacement and axial force; pressure of the gaseous working medium, in numerical format, directly to a personal computer or to a chart tape.

The high-temperature furnace 13 with the electronic control system of the furnace 14 allows experiments at high, up to 1000 ^o C, temperatures with an accuracy of ± 5 ^o C. The design of the furnace allows for various kinds of heat treatment, including thermal cycling.

 As already noted above, the installation has the ability to use interchangeable grippers 8, 9 to deform samples 7 of various shapes and sizes: from 10.0 mm in diameter and a length of the working part of 40.0 mm to 100.0 mm in diameter and a length of the working part of 200 , 0 mm.

 The installation allows you to develop a maximum tensile-compression force of up to 150.0 kN and a torque of up to 300.0 N • m.

 The method is implemented in the device as follows.

The workpiece 7 is installed in the grippers 8 of the clamping device, which ensures the fixation of the workpiece. In this case, the grippers are connected to the workpiece using a detachable, for example, splined connection, or one-piece connection, for example, by soldering or welding. The workpiece installed in the grippers is heated to a predetermined temperature in the furnace 13 with an average heating rate of about 50 ^o C / min. After the temperature reaches the operating mode, additional exposure is carried out for about 15 minutes. After which the sample is deformed according to the claimed modes.

 Schemes for transitional and phased processing and the corresponding loading paths for various materials, shapes and sizes of the workpieces are given in examples of specific loading.

 By transition is meant the operation of deforming a workpiece with one, two, or multicomponent, continuous loading, including continuous loading along a deformation path with an orthogonal fracture. Transitions can separate the heat treatment operations.

 By a stage is meant a combination of loading and heat treatment operations, or only loading, aimed at obtaining a given microstructure in certain parts of the workpiece.

 During processing, in a continuous mode, the loading parameters are recorded on the chart tape and in a file on the computer. Also, during the test, information about the accumulated deformation, which is necessary to control the processing of workpieces, is displayed on the computer monitor.

 At the end of processing, the workpiece is removed from the jaws of a releasable clamping device. In the case where the preform and grips are joined before processing by forming a solder joint, after processing the preform and removable grips are heated to a temperature above the temperature of the solder joint, and the blank is released. In the case where the workpiece and grippers are connected by welding, for example, by an electron beam, the workpiece and gripper are separated by either turning or EDM. In those cases where the workpiece and grips are connected by means of a solid-phase connection, after processing, along with turning and EDM, it is possible to use bending dynamic action.

Case Studies
Example 1
A billet (α + β) titanium alloy of martensitic class VT9 is subjected to processing (Ti - base; 5.8-7.0 Al; 2.8-3.8 Mo; 0.8-2.0 Zr; 0.2 -0.3 Si) with a diameter of 10.0 mm and a length of the working part of 60.0 mm, using a specialized installation for complex loading (Fig.1, 2).

Figure 3 presents the microstructure, and figure 4 is the appearance of the workpiece in the initial state. The workpiece has a coarse lamellar microstructure with a grain size of the transformed β-phase, D = 0.5-1.0 mm This type of microstructure is typical for hot-rolled billets that have undergone additional heat treatment - annealing at a temperature of 1100 ^o C for 30 minutes and subsequent cooling in air. The temperature Ac3, (α + β → β) of the transformation was determined by trial hardening and for this material was equal to T = 1000 ^o C.

 It is necessary to obtain a fine-grained microcrystalline structure with an average grain size d = 3.0-7.0 μm, distributed uniformly throughout the volume of the workpiece.

 With this in mind, two-stage processing is selected. At the first stage, the microstructure is preliminarily prepared in the surface layer, and at the second stage, the structure is prepared to the specified grain size in the entire volume of the preform, including the central part. Moreover, it is taken into account that at the first stage, to ensure the occurrence of deformation of the material at subsequent stages under conditions of superplasticity, a microstructure with an average grain size d = 4.0-10.0 μm should be formed in the surface layer.

The value of the worked-out layer of the workpiece material in the first stage V ₁ is determined based on the expression (1), where
V ₀ = 3141.59 mm ³ - the volume of the entire workpiece;
σ ₁ = 15.0 MPa — stresses of the flow of a material with a microcrystalline structure during its deformation in the optimal range of temperature-speed conditions of superplastic deformation;
σ ₂ = 40.0 MPa — stresses of the flow of a material with a rough structure during its deformation in the optimal range of temperature-speed conditions of superplastic deformation.

The values of σ ₁ and σ _{2 are} found from the results of preliminary experiments or from literature data.

According to the found values of V ₁ find the degree of equivalent deformation e _i on the side surface. In this case, this deformation amounted to a value of e _i = 1.1-1.3.

т.е. менее 0,2.At the first stage of processing the workpiece, two-component proportional loading is selected. The predominant component is simple torsion, the additional component is uniaxial tension. The ratio of the components of the torsion strain and tensile strain rates is chosen equal to:

those. less than 0.2.

As a result of the analysis of literature data, it was found that the optimal range of strain rates for this material lies in the range 10 ^-4 -10 ^-3 s ^-1 .

с^-1, а скорость деформации заготовки компонентой растяжения также выбирают постоянной и равной е=1,0•10^-4 с^-1.Both in the first and in the second stages of deformation, the degree of deformation and temperature-speed loading modes are chosen to ensure the occurrence of the transformation of the structure during loading, i.e. due to the development of dynamic recrystallization. In this example, as in the following examples, the rate of deformation of the workpiece by the torsion component is chosen constant throughout the deformation at the stages and equal

s ^-1 , and the strain rate of the workpiece by the tensile component is also chosen constant and equal to e = 1.0 • 10 ^-4 s ^-1 .

The deformation temperature in the first and second stage is chosen equal and equal to T = 950 ^o C.

At the second stage of preparation of the structure, uniaxial tension is chosen as the loading scheme. The strain rate in the second stage, as well as in the first stage, is kept constant and equal to e = 1.0 • 10 ^-4 s ^-1 , and the deformation is completed when the strain intensity value is equal to e _i = 0.8.

 The described modes and loading program at both stages are presented in figa, b.

After the first processing step, the sample is cooled in air to room temperature. Then reheated to a temperature of 950 ^o With an average heating rate of 50 ^o C / min, carry out exposure for 15 minutes and deformed by uniaxial tension according to the mode and program of the second stage figa, b.

 Upon completion of the second stage, the sample is cooled in air and removed from the grips.

 The appearance of the preform after processing in the first step is shown in FIG. 6. The results of metallographic studies conducted after processing the workpiece in the first and second stages are presented in Fig.7. Quantitative metallographic studies showed that the values of the α-plate shape coefficient Kα for the central part of the processed workpiece was 3.1, and for the peripheral part 2.0. The thickness of the α-plates in the central part was 2.2, in the peripheral part 2.4.

 Thus, we can conclude that the microstructure in the processed workpiece was transformed uniformly throughout the volume and has a microcrystalline structure with an average grain size d = 3.5-5.0 μm.

Example 2
A cylindrical billet with a diameter of 20.0 mm and a length of the working part of 40.0 mm from a two-phase (α + β) titanium alloy of martensitic class VT9 (Ti - base; 5.8-7.0 Al; 2.8-3.8 Mo; 0.8-2.0 Zr; 0.2-0.35 Si).

Figure 3 presents the original microstructure of the workpiece. The workpiece has a coarse lamellar microstructure with a grain size of the transformed β-phase, D = 0.5-1.0 mm The temperature of the polymorphic (α + β → β) transformation, the Ac3 point, was determined by trial hardening and for the material used is T = 1000 ^o C.

 In this example, it is necessary to obtain a microcrystalline structure with an average grain size d = 3.0-5.0 μm, distributed uniformly throughout the volume of the workpiece. However, after processing, the workpiece should be in the form of a flat disk with a thickness of 10.0 mm

 Both at the first and at the second stages of deformation, the degree of deformation and the temperature-speed loading modes are selected based on the conditions of the structure transformation during loading, i.e. due to dynamic recrystallization.

 To solve the problem, choose two-stage processing.

 At the first stage, the microstructure in the surface layer is preliminarily prepared, deforming the sample by proportional two-component loading. The torsion component is specified as the predominant component, and compression is the additional component. The use of this loading scheme is aimed at preparing the microstructure primarily in the surface layers, including the layers directly lying under the strikers.

 At the second stage, the structure is prepared in the central part of the preform to a predetermined grain size in the process of deformation of the preform by compression. In this case, compression is also used to form the final configuration of the product.

с^-1, а скорость деформации компоненты сжатия выбирают также постоянной и равной е=1,0•10^-4 с^-1.The value of the accumulated deformation on the side surface of the workpiece e _i at the first stage is selected based on calculations performed by analogy with example 1, equal to 0.9-1.1, and after the second stage, equal to e _i = 1.0-1.25, based on the final shape and size of the workpiece. At the first stage, the strain rate of the torsion components is chosen constant throughout the deformation and equal to

s ^-1 , and the strain rate of the compression components is also chosen constant and equal to e = 1.0 • 10 ^-4 s ^-1 .

The deformation temperature in the first and second stage is chosen equal to the temperature T = 950 ^o C.

The strain rate by compression in the second stage, as well as in the first stage, is kept constant and equal to e = 1.0 • 10 ^-4 s ^-1 , and the deformation is completed when the strain intensity value is equal to e _i = 1.25.

 The program described in this example, and the corresponding loading modes are presented in Fig. 8.a, b.

After the first processing step, the sample is cooled in air to room temperature. Then reheated to a temperature of 950 ^o With an average heating rate of 50 ^o C / min, hold for 15 minutes and deform by uniaxial stretching according to the mode and program of the second stage Fig.8.a, b.

 Upon completion of the second stage, the sample is removed from the furnace and cooled in air.

 The results of metallographic studies carried out after processing the blanks are similar to the results of example 1. The values of the shape coefficient α-plates Kα for the central part of the processed blank is 2.9, and for the peripheral part 2.1. The thickness of the α-plates in the central part is 2.1 μm in the peripheral part of 2.3 μm.

 Thus, we can conclude that the microstructure in the working part of the processed workpiece was transformed uniformly throughout the volume and has a microcrystalline structure with an average grain size d = 3.5-4.0 μm.

Example 3
The treatment is subjected to a cylindrical billet of biphasic (α + β) titanium alloy martensitic class VT6 (Ti - base; 5.3-6.8 Al; 3.5-5.3 V).

 A cylindrical billet with a diameter and length of the working part equal to 20.0 mm and 100.0 mm, respectively, in the initial state has a rough plate microstructure. Figure 9 presents the microstructure of the workpiece in its original state. The average grain size of the transformed β-phase is D = 10.0-15.0 mm.

 It is necessary to obtain a fine-grained microcrystalline structure with an average grain size d = 4.0-8.0 μm in the peripheral part of the workpiece. In the central part of the workpiece, the presence of a plate microstructure is allowed.

 In this example, as in examples 1 and 2, the degree of deformation and temperature-speed loading conditions are selected based on the conditions of transformation of the structure during loading.

с^-1.To solve this problem, choose one-stage processing (Fig. 10A). The sample is deformed by single-component loading (Fig. 10b). The only component of loading is torsion. The deformation temperature is chosen equal to 930 ^o C. the Workpiece is deformed with a constant strain rate corresponding to its value on the side surface

s ^-1 .

In accordance with the expression (1), the degree of e _i accumulated deformation on the side surface is chosen equal to 2.0. The specified degree of deformation is sufficient to work out the microstructure in the workpiece for 1/2 of its volume. The heating rate is chosen equal to 50 deg / min, and after processing the workpiece is cooled in air.

 In FIG. 11 is a macro view, and in FIG. 12, a microstructure of a deformed sample. The results of metallographic studies showed that the values of the shape factor α-plates Kα for the central part of the processed workpiece is equal to 7.6, and for the peripheral part of 2.5. The thickness of the α-plates in the central part is 2.9 in the peripheral part 3.3.

 Thus, we can conclude that the structure in the working part of the processed workpiece was transformed non-uniformly in cross section. The morphology of the structure in the central part has a lamellar structure, and on the periphery it is equiaxed microcrystalline, with an average grain size d = 4.0-6.0 μm.

Example 4
The workpiece is subjected to treatment from a two-phase (α + β) VT9 titanium alloy (Ti - base; 5.8-7.0 Al; 2.8-3.8 Mo; 0.8-2.0 Zr; 0.2-0 , 35 Si).

 The appearance and geometric dimensions of the workpiece in the initial state were similar to example 1 (figure 4).

The workpiece has a rough plate microstructure with a grain size of the transformed β-phase equal to D = 1.0-2.0 mm (figure 3). The temperature of the polymorphic (α + β → β) transformation, the Ac3 point, was determined by trial hardening and for this material is equal to T = 1000 ^o C.

 It is necessary to obtain a fine-grained microcrystalline structure with an average grain size d = 3.0-7.0 μm, distributed uniformly throughout the volume of the workpiece. Therefore, taking into account the fact that in the initial state the preform has a rough lamellar structure and its plasticity margin is limited for the development of dynamic recrystallization processes in the α phase, two-stage processing with three transitions at the first stage is chosen. At all three transitions of the first processing stage, as well as at the second stage, the degree of deformation and temperature-speed loading modes are chosen to ensure the transformation of the structure during loading due to dynamic recrystallization in the β phase.

 Transitions are separated by heat treatment operations aimed at the development of phase transformations in the process of temperature change and the absence of a deforming effect on the workpiece.

с^-1, до значения интенсивности деформации е_i1=0,5.The deformation temperature at all three transitions of the first stage, as well as at the second stage, is chosen equal to T = 960 ^o C. At the first transition of the first stage, the workpiece is deformed by torsion with a constant strain rate equal to

s ^-1 , to the value of the strain intensity e _i1 = 0.5.

After the first transition, the workpiece is heated for 15 minutes to a temperature of 1010 ^{° C.} above the Ac ₃ point. After the oven reaches the set temperature, the heating is turned off, bringing the temperature to the previous value, choosing a cooling rate equal to 2.0 deg / min.

с^-1. Скорость деформации компоненты растяжения также поддерживают постоянной и равной е=10^-4 с^-1. Соотношение компонент скоростей деформации кручения и растяжения на втором переходе выбирают из соотношения:

Деформацию осуществляют до величины е_i2=0,6. После второго перехода заготовку охлаждают на 40-60^oС ниже температуры обработки со скоростью 2,0 град/мин, уменьшая мощность нагрева печи. По достижению заданной температуры, мощность нагрева печи увеличивают, доводя до температуры обработки следующего перехода.Processing the workpiece at the second transition is performed by proportional (torsion with simultaneous stretching) loading. The strain rate of the torsion components is kept constant and equal.

s ^-1 . The strain rate of the tensile components is also kept constant and equal to e = 10 ⁻⁴ s ⁻¹ . The ratio of the components of the torsional and tensile strain rates at the second transition is selected from the ratio:

The deformation is carried out to a value of e _i2 = 0.6. After the second transition, the workpiece is cooled to 40-60 ^o C below the processing temperature at a speed of 2.0 deg / min, reducing the heating power of the furnace. Upon reaching the set temperature, the heating power of the furnace is increased, bringing to the processing temperature of the next transition.

The processing of the workpiece at the final, third transition of the first stage is performed by uniaxial tension, deforming the workpiece with a strain rate of e = 1.0 • 10 ^-4 s ^-1 to a strain intensity value of e _i3 = 0.2.

 The processing scheme and the corresponding loading scheme at the transitions and stages are presented in figa, b.

 The choice of a three-transition processing scheme at the first stage with intermediate processing aimed at the development of phase transformations made it possible not only to increase the plasticity margin and increase the accumulated degree of deformation at the stage, due to the refinement of the structure as a result of additional division of the α-phase plates during reverse and direct phase transformations , and also increased the degree and uniformity of transformation of α-phase plates in the surface layers of the workpiece.

 After the first stage, the preform is cooled to room temperature in air, and after heating to the processing temperature of the second stage, it is subjected to uniaxial tension deformation, similarly to Example 1, according to the mode of the second stage.

 After completion of the processing process, the workpiece is removed from the furnace and cooled in air.

 Note that the workpiece that underwent processing at the first stage in this mode, compared to example 1, at the second stage was deformed more uniformly, with a less pronounced deformation relief on the side surface.

 The results of qualitative and quantitative metallographic studies carried out after processing the workpieces showed that the values of the shape coefficient α-plates Kα for the central part of the processed workpiece is 3.0, and for the peripheral part 2.1. The thickness of the α-plates in the central part is 2.3, in the peripheral part 2.4.

 Thus, we can conclude that the microstructure in the processed workpiece was transformed uniformly throughout the volume and has a microcrystalline structure with an average grain size d = 3.0-4.0 μm.

Example 5
The treatment is subjected to a cylindrical billet of two-phase (α + β) VT9 titanium alloy (Ti - base; 5.8-7.0 Al; 2.8-3.8 Mo; 0.8-2.0 Zr; 0.2- 0.35 Si) with a diameter of 40.0 mm and a length of the working part of 80 mm.

The workpiece has a rough plate microstructure with a grain size of the transformed β-phase equal to D = 1.0-2.0 mm (figure 3). The temperature of the polymorphic (α + β → β) transformation, the Ac3 point, is determined by trial hardening. For the processed material, it is equal to T = 1000 ^o C.

 It is required to prepare a homogeneous microcrystalline structure in the entire volume of the workpiece with an average grain size of 2.0-4.0 μm, therefore, given the fact that in the initial state the workpiece has a rough plate structure and the plasticity margin is insufficient for using temperature-speed processing conditions, providing the development of dynamic recrystallization in the α and β phases, two-stage processing is chosen. The first stage is performed in two transitions. The transitions are separated by heat treatment operations aimed at the course of static recrystallization, supplementing the effect of slight dynamic recrystallization in one way or another proceeding in the process of deformation, aimed at forming grain boundaries in the β phase, which in combination with additional heat treatment, causing direct phase transformations in the process changes in temperature and the absence of a deforming effect on the workpiece leads to an acceleration of the division of α-phase plates and the formation of microcr and structure.

 The loading of the workpiece at the first stage is carried out by a combination of alternating torsion with alternating axial action, i.e. at the first transition, the workpiece is deformed by torsion clockwise with subsequent compression, at the second transition, the workpiece is deformed by torsion counterclockwise with subsequent stretching. The deformation path under such loading is a closed loop. The choice of such a processing loading scheme is aimed at intensifying the transformation of the lamellar structure and at the formation of a microcrystalline structure close to a textureless state. At the second stage, the workpiece is deformed by stretching.

The deformation temperature in the first and second stage is chosen equal and equal to T = 960 ^o C.

с^-1, до значения интенсивности деформации е_i1=0,9. Одновременно с завершением кручения начинают сжатие. Скорость деформации поддерживают постоянной и равной е=1,0•10^-4 с^-1. Деформацию осуществляют до значения е_i2=0,2.At the first transition of the first stage, the workpiece is deformed by torsion clockwise with a constant strain rate equal to

s ^-1 , to the value of the strain intensity e _i1 = 0.9. Simultaneously with the completion of torsion, compression begins. The strain rate is kept constant and equal to e = 1.0 • 10 ^-4 s ^-1 . The deformation is carried out to a value of e _i2 = 0.2.

After the first transition, the workpiece is held at processing temperature for 15 minutes. Then the workpiece is cooled to a temperature of 900 ^o With a cooling rate equal to a speed of 1.5 deg / min. After cooling the workpiece to a predetermined temperature, it is again heated to the processing temperature at the second transition.

с^-1, до значения интенсивности деформации e_i3=0,9. Одновременно с завершением кручения начинают растяжение. Скорость деформации поддерживают постоянной и равной е= 1,0•10^-4 с^-1. Деформацию осуществляют до значения е_i4=0,2.At the second transition of the first stage, the workpiece is deformed by torsion counterclockwise with a constant strain rate equal to

s ^-1 , to the value of the strain intensity e _i3 = 0.9. Simultaneously with the completion of torsion, tension begins. The strain rate is kept constant and equal to e = 1.0 • 10 ^-4 s ^-1 . The deformation is carried out to a value of e _i4 = 0.2.

 After the second transition, the workpiece is kept at a processing temperature for 15 minutes, then cooled to room temperature in air.

The workpiece at the second stage is deformed by tension, with a strain rate corresponding to the manifestation of the superplasticity effect e = 1.0 • 10 ^-4 s ^-1 in the processed material to a strain intensity value e _i3 = 1.0. Upon completion of the processing process, the workpiece is removed from the furnace and cooled in air.

 The processing and loading diagram at the transitions and stages is shown in FIG. 14a, b.

 The choice of the loading scheme at the first stage with intermediate heat treatment aimed at the development of phase transformations made it possible not only to increase the plasticity margin and increase the accumulated degree of deformation at the stage, due to the refinement of the structure as a result of additional fission of α-phase plates during reverse and direct phase transformations , and also increased the degree and uniformity of transformation of α-phase plates in the surface layers of the workpiece.

 The results of qualitative and quantitative metallographic studies carried out after processing the workpieces showed that the values of the shape factor α-plates Kα for the central part of the processed workpiece is 2.8, and for the peripheral part 2.5. The thickness of the α-plates in the central part is 2.4, in the peripheral part 2.5.

 Thus, we can conclude that the microstructure in the processed workpiece was transformed uniformly throughout the volume and has a microcrystalline structure with an average grain size d = 3.0-4.0 μm.

Example 6
A billet made of α-titanium alloy VT5-1 (Ti - base; 4.3-6.0 Al; 2.0-3.0 Sn) with a diameter of 40.0 mm and a length of the working part of 80.0 mm was subjected to processing.

The preform has a coarse lamellar microstructure with a grain size of the transformed β-phase equal to D = 0.5 mm. The temperature of the reverse polymorphic (α + β → β) transformation, the Ac3 point, and the direct (α + β → α), the Ar3 point, are determined by trial hardening. For the processed material, the point Ac3 is equal to T = 1020 ^o C, and Ar3 is equal to 980 ^o C.

 It is required to obtain a homogeneous microcrystalline structure in the entire volume of the workpiece with an average grain size of 4.0-8.0 microns.

In this example, the workpiece is processed in one step, consisting of three transitions. Given the narrow interval of the two-phase region, as well as the initial coarse microstructure, the preform at the first transition is processed at a temperature of 950 ^o C, at the second at 1050 ^o C, at the third at 980 ^o C.

 Transitions are separated by heat treatment operations aimed at the occurrence of reverse and direct phase transformations. Additional heat treatment in combination with hot deformation under complex loading is aimed at accelerating the process of grinding the structure.

 At each of the three transitions, the workpiece is deformed by proportional two-component loading (reverse torsion with simultaneous tension).

Скорость деформации компоненты кручения выбирают постоянной и равной

с^-1, а скорость деформации компоненты растяжения выбирают также постоянной и равной е=2,0•10^-4 с^-1. Интенсивность деформации на этапе выбирают равной e_i=1,2.At the first transition, torsion clockwise is used as the predominant component, and uniaxial tension is used as an additional component. The ratio of the components of the torsion strain and tensile strain rates is chosen equal to:

The strain rate of the torsion components is chosen constant and equal

s ^-1 , and the strain rate of the tensile components is also chosen constant and equal to e = 2.0 • 10 ^-4 s ^-1 . The strain rate at the stage is chosen equal to e _i = 1.2.

 After the first transition, the workpiece is heated at a speed of 5.0 deg / min to the temperature of the second transition and is deformed according to the second transition mode.

Скорость деформации компоненты кручения выбирают постоянной и равной

с^-1, а скорость деформации компоненты растяжения выбирают также постоянной и равной е=2,0•10^-4 с^-1. Интенсивность деформации на этапе выбирают равной e_i=1,2.At the second transition, torsion counterclockwise is used as the predominant component, and uniaxial tension is used as an additional component. The ratio of the components of the torsion strain and tensile strain rates is chosen equal to:

The strain rate of the torsion components is chosen constant and equal

s ^-1 , and the strain rate of the tensile components is also chosen constant and equal to e = 2.0 • 10 ^-4 s ^-1 . The strain rate at the stage is chosen equal to e _i = 1.2.

After the second transition, the preform is cooled to the temperature of the third transition at a speed of 1.0 ^o C / min and deformed according to the regime of the third transition.

Скорость деформации компоненты кручения выбирают постоянной и равной

c^-1, а скорость деформации компоненты растяжения выбирают также постоянной и равной е=2,0•10^-4 с^-1. Интенсивность деформации на этапе выбирают равной е_i=1,2.At the third transition, torsion clockwise is used as the predominant component, and uniaxial tension is used as an additional component. The ratio of the components of the torsion strain and tensile strain rates is chosen equal to:

The strain rate of the torsion components is chosen constant and equal

c ^-1 , and the strain rate of the tensile components is also chosen constant and equal to e = 2.0 • 10 ^-4 s ^-1 . The strain rate at the stage is chosen equal to e _i = 1,2.

 Processing the workpiece was carried out according to the mode shown in figa, b. After processing, the workpiece is cooled to room temperature in air.

 The results of qualitative and quantitative metallographic studies carried out after processing the workpieces showed that the average grain size in the center and at the periphery lies in the range d = 5.0-7.0 μm.

Example 7
The treatment is subjected to a cylindrical billet of two-phase (α + β) VT9 titanium alloy (Ti - base; 5.8-7.0 Al; 2.8-3.8 Mo; 0.8-2.0 Zr; 0.2- 0.35 Si) with a diameter of 40.0 mm and a length of the working part of 80.0 mm.

The workpiece has a coarse lamellar microstructure with a grain size of the transformed β-phase D = 1.0-2.0 mm (figure 3). The temperature of the polymorphic (α + β → β) transformation, the Ac3 point, is determined by trial hardening. For the processed material, it is equal to T = 1000 ^o C.

 Since in the initial state the preform has a rough lamellar structure, with a limited margin of ductility, and it is required to obtain a sufficiently small grain size, of the order of d = 1.0-2.0 μm, a two-stage processing with lowering the temperature at the transitions is chosen. The first stage is performed in three transitions. The degree of deformation and temperature-speed processing regimes at the transition are chosen to ensure dynamic recrystallization in the β phase. The transitions are separated by heat treatment operations aimed at the development of direct phase transformations that enhance the refinement of the microstructure due to the formation of α-grains along the boundaries of the recrystallized β-phase.

The processing temperature of the first transition is chosen equal to 960 ^o С, the second 930 ^o С, the third 900 ^o С. At each of the three transitions, the workpiece is deformed by proportional two-component loading (torsion with simultaneous axial reversal, compression-tension). Using this scheme allows you to more fully work out the structure at the first stage.

Скорость деформации компоненты кручения выбирают постоянной и равной

с^-1. Скорость деформации компоненты растяжения выбирают также постоянной и равной е=2,0•10^-4 с^-1. Интенсивность деформации на переходе выбирают равной e_i=0,6. По завершении первого перехода заготовку охлаждают до температуры следующего перехода со скоростью 1,0^oС/мин и деформируют по режиму второго перехода.At the first transition, the workpiece is deformed by torsion with simultaneous stretching. Torsion is used as the predominant component of loading, and uniaxial tension is used as an additional component. The ratio of the components of the torsion strain and tensile strain rates is chosen equal to:

The strain rate of the torsion components is chosen constant and equal

s ^-1 . The strain rate of the tensile components is also chosen constant and equal to e = 2.0 • 10 ^-4 s ^-1 . The strain rate at the transition is chosen equal to e _i = 0.6. Upon completion of the first transition, the workpiece is cooled to the temperature of the next transition at a speed of 1.0 ^o C / min and deformed according to the second transition.

Скорость деформации компоненты кручения выбирают постоянной и равной

с^-1. Скорость деформации компоненты растяжения выбирают также постоянной и равной е=4,0•10^-4 с^-1. Интенсивность деформации на этапе выбирают равной е_i= 1,2. По завершению второго перехода заготовку охлаждают до температуры следующего перехода со скоростью 1,0^oС/мин и деформируют по режиму третьего перехода.At the second transition, the workpiece is deformed by torsion with simultaneous compression. Torsion is used as the predominant component of loading, and uniaxial compression is used as an additional component. The ratio of the components of the torsion and compression strain rates is chosen equal to:

The strain rate of the torsion components is chosen constant and equal

s ^-1 . The strain rate of the tensile component is also chosen constant and equal to e = 4.0 • 10 ^-4 s ^-1 . The strain rate at the stage is chosen equal to e _i = 1,2. Upon completion of the second transition, the workpiece is cooled to the temperature of the next transition with a speed of 1.0 ^o C / min and deformed according to the regime of the third transition.

 At the third transition, the workpiece is deformed similarly to the first transition by torsion with simultaneous extension. The degree and speed of deformation at the third transition is chosen to be the same as at the first transition.

 After the first step, the preform is cooled in air to room temperature.

In the second stage, the preform is heated to a temperature of 900 ^o C, placed in a furnace, kept for 15-20 minutes and deformed by uniaxial tension at a speed of 5.5 • 10 ^-3 s ^-1 to a degree of deformation equal to e _i = 1,0.

 The processing and loading schemes are presented in figa, b.

 After processing, the preform is removed from the furnace and cooled to room temperature in air.

 The results of qualitative and quantitative metallographic studies carried out after processing the workpieces showed that the average grain size in the center and on the periphery lies in the range d = 1.5-2.0 μm.

Example 8
The treatment is subjected to a cylindrical billet of VT8 titanium alloy (Ti - base; 5.8-7.0 Al; 2.8-3.8 Mo; 0.2-0.35 Si) with a diameter of 30.0 mm and a length of the working part of 100 , 0 mm. The appearance of the workpiece due to the simplicity of the form is not shown in the drawing.

 In FIG. 17 shows the microstructure of the material; in the initial state, the grain size of the transformed β-phase is D = 1.0–2.0 mm.

The temperature Ac3, (α + β → β) of the transformation was determined by the method of trial hardening and for this material was equal to T = 1010 ^o C.

 It is necessary to obtain a fine-grained microcrystalline structure with an average grain size d = 5.0-7.0 μm, distributed uniformly throughout the volume of the workpiece.

 With this in mind, choose two-stage processing (figa, b) with two transitions in the first stage. At the first stage, the microstructure is preliminarily prepared in the surface layer, and at the second stage, the structure is prepared to the specified grain size, including the central part of the workpiece.

 The value of the worked-out layer of the workpiece material at the first stage and the corresponding degree of accumulated deformation are determined in the same way as in example 1.

The first stage is performed in two transitions. Deformation at the first and second transition is carried out at a variable temperature. The temperature of the start of processing at the first transition is chosen equal to T = 900 ^o C. In the process of deformation of the workpiece, the temperature is gradually increased to 960 ^o C, and then, at the second transition, lower again to the original level. The processing at the second stage is performed by uniaxial tension, with an optimal strain rate of the corresponding superplasticity of the workpiece material.

т.е менее 0,2. Скорость деформации компоненты кручения выбирают постоянной и равной

с^-1. Скорость деформации компоненты растяжения выбирают также постоянной и равной е=8,0• 10^-4 с^-1. Интенсивность деформации на каждом из этапов выбирают равной е_i1=е_i2=0,8.The loading scheme, the degree and speed of deformation at the first and second transitions are chosen the same: two-component proportional loading (Fig. 18a, b). The predominant component is simple torsion, the additional component is uniaxial tension. The ratio of the components of the torsion strain and tensile strain rates is chosen equal to:

i.e. less than 0.2. The strain rate of the torsion components is chosen constant and equal

s ^-1 . The strain rate of the tensile components is also chosen constant and equal to e = 8.0 • 10 ^-4 s ^-1 . The strain rate at each stage is chosen equal to e _i1 = e _i2 = 0.8.

 After the first step, the preform is cooled to room temperature.

At the second stage of processing, the workpiece is heated to a temperature of 900 ^o C, placed in a furnace, kept for 10-15 minutes and deformed by uniaxial tension at a speed of 5.5 • 10 ^-3 s ^-1 to the degree of e _i = 0,8.

 The results of high-quality metallographic studies are presented in FIG. 19. Quantitative metallographic studies of the blanks, carried out after the final processing of the second stage, showed that the values of the shape coefficient of α-plates Kα for the central part is 2.0, and for the peripheral part 2.1. The thickness of the α-plates in the central part is 2.3 in the peripheral part of 2.4.

 Thus, we can conclude that the microstructure in the processed workpiece was transformed uniformly throughout the volume and has a microcrystalline structure with an average grain size d = 4.0-5.0 μm.

Example 9
A large cylindrical billet of VT6 titanium alloy is subjected to processing (Ti - base; 5.3-6.8 Al; 3.5-5.3 V).

 The dimensions of the workpiece are as follows: the diameter of the workpiece is 140.0 mm, the length of the workpiece is 300.0 mm.

 In the initial state, the preform has a molded microstructure with an average grain size of the transformed β-phase equal to 10.0-15.0 mm.

The transformation temperature Ac3, (α + β → β) for the VT6 alloy was determined by trial hardening and for this material was T = 990 ^o C.

 It is necessary to obtain a microcrystalline structure evenly distributed over the entire volume of the workpiece with an average grain size of d = 6.0-9.0 μm.

Since the material, VT6 alloy, was delivered in the form of a washer cut from an ingot with a diameter of 500.0 mm and a length of 200.0 mm, which has a shape and dimensions that are unacceptable for processing with the equipment available, the washer is pre-cut into four parts. One part is subjected to high-temperature deformation processing by compression with the change of the loading axes and subsequent broaching on a hydraulic press with a maximum force of 1600, i.e., on flat strippers of the isothermal stamp block UISHB-510. The temperature of the beginning of processing is chosen equal to Tn = 1100 ^o C, and the temperature of the end of Tk = 930 ^o C. After processing, the forging is cooled in air. The dimensions of the forgings are as follows: circle diameter 180.0 mm; length 320.0 mm. Next, the forging is subjected to turning to the size of the workpiece.

 The macrostructure of the cross section of the workpiece before the main processing is presented in Fig.20. The preform has a coarse lamellar microstructure with a grain size of the transformed β-phase equal to D = 1.5-2.5 mm (Fig. 21), fairly evenly distributed over the cross section of the preform.

The pre-workpiece was welded to a deforming tool, which was made of heat-resistant titanium alloy by diffusion welding. Diffusion welding is performed using local sealing and evacuation in the joint zone. The diffusion welding mode was as follows: temperature T = 950 ^o C; welding force P = 2.0 MPa; welding time τ = 15 min; vacuum depth B = 1.0 • 10 ^-3 Pa.

The main processing consists of two stages (figa, b). The processing temperature in the first stage is chosen equal to T = 950 ^o C, and in the second T = 930 ^o C.

Скорость деформации компоненты кручения выбирают постоянной и равной

с^-1, а скорость деформации компоненты растяжения выбирают также постоянной и равной е=5,0•10^-5 с^-1. Деформацию осуществляют до значения интенсивности деформации на первом этапе, равной е_i=4,0.At the first stage, the workpiece is deformed by proportional two-component loading. Torsion is used as the predominant component, and tension is used as an additional component. The ratio of the components of the torsion strain and tensile strain rates is chosen equal to:

The strain rate of the torsion components is chosen constant and equal

s ^-1 , and the strain rate of the tensile components is also chosen constant and equal to e = 5.0 • 10 ^-5 s ^-1 . The deformation is carried out to the value of the strain intensity in the first stage, equal to e _i = 4.0.

After the first step, the preform is cooled in air to room temperature. In the second stage, the workpiece is heated to a temperature of 930 ^o C, maintained for 30 minutes and deformed by stretching to a degree of deformation equal to e _i = 0.4. After processing, the workpiece is cooled with the oven to room temperature. Then the workpiece is separated from the tool using EDM.

 The appearance of the workpiece with welded removable grippers (tool) after processing at the final stage is presented in Fig.23. It also shows half of the machined workpiece cut along the axis.

 On Fig presents the macrostructure of the workpiece after processing. From the ends, at a distance of about 30 mm, the unprocessed part of the structure is visible, since the workpiece was chosen to be obviously larger in length for comparative analysis and subsequent metallographic studies.

 The microstructure in the workpiece after processing is presented in Fig.25. Quantitative metallographic studies of the blanks, carried out at the end of the second stage of final processing, showed that the shape coefficient of α-plates Kα for the central part is 2.0, and for the peripheral part 2.1. The thickness of the α-plates in the central part is 5.0, in the peripheral part 4.9.

 Thus, we can conclude that the microstructure in the processed workpiece was transformed uniformly throughout the volume and has a microcrystalline structure with an average grain size d = 8.0-9.0 μm.

Example 10
The treatment is subjected to a cylindrical billet of biphasic (α + β) titanium alloy martensitic class VT9 (Ti - base; 5.8-7.0 Al; 2.8-3.8 Mo; 0.8-2.0 Zr; 0, 2-0.35 Si) with a diameter of 50.0 mm and a length of the working part of 200.0 mm.

 The material and the initial microstructure are similar to example 1. The microstructure has a rough plate morphology with a grain size of the transformed β-phase equal to D = 1.0-2.0 mm (figure 3).

The temperature Ac3, (α + β → β) of the transformation is equal to T = 1000 ^o C.

 It is necessary to obtain a microcrystalline structure with an average grain size d = 2.0-3.0 μm, distributed uniformly throughout the volume of the workpiece.

The workpiece processing (Fig. 26) is performed in a shell with a thickness of 4.0 mm, with an inner diameter of 52.0 mm and a length of 200.0 mm, made of titanium alloy VT14 with a microcrystalline structure with an average grain size of d = 1.0-2, 0 microns in two stages. The first stage is performed at a reduced temperature T = 880 ^o C, the second at a temperature of 920 ^o C.

 It is taken into account that processing the workpiece in the shell increases not only the uniformity of deformation along the length of the workpiece during its torsion with slight stretching, but also the plasticity resource, by eliminating the formation of deformation folds on the surface of the workpiece that are similar to those observed when processing cylindrical workpieces after the first stage , in example 1 (Fig.6) and in example 9 (Fig.23). The exclusion of the formation of a deformation relief suppresses the process of crack development.

 Choose a two-stage processing similar to example 1 (figa, b). At the first stage, the microstructure is preliminarily prepared in the surface layer, and at the second stage, the structure is prepared to the specified grain size in the entire volume, including the central part of the workpiece.

The preform is pre-installed in the shell, a vacuum is created in the cavity between the shell and the workpiece, the assembly is heated to a temperature of 860 ^° C, then the shell is deformed by uniaxial tension to form tight contact with the workpiece. The strain rate of the shell is chosen equal to 1.0 • 10 ^-4 s ^-1 . Upon completion of the deformation, the temperature is brought to the processing temperature of the workpiece in the first stage. The workpiece and the shell are deformed together using two-component loading - torsion with simultaneous stretching. The loading scheme, the degree of deformation, as well as high-speed modes of processing the workpiece at the first stage are chosen similar to example 1.

 Upon completion of the processing in the first stage, the preform in the shell is heated to the temperature of the second stage and deformed by uniaxial tension. The loading scheme, the degree of deformation, as well as high-speed modes of processing the workpiece in the second stage are chosen similar to example 1.

 After processing, the preform is removed from the furnace and cooled to room temperature in air. Then the shell is removed by turning.

 Metallographic analysis showed that after this treatment, the preform has a microcrystalline structure homogeneous throughout the volume with an average grain size of d = 1.5-3.0 μm.

Example 11
The treatment is subjected to a tubular billet of two-phase (α + β) titanium alloy of the martensitic class VT9 (Ti - base; 5.8-7.0 Al; 2.8-3.8 Mo; 0.8-2.0 Zr; 0, 2-0.35 Si).

 The dimensions of the workpiece are as follows: outer diameter 50.0 mm, inner diameter 40.0 mm; the length of the working part is 200.0 mm.

In this example, a material is used with an initial microstructure similar to that of Example 1 (FIG. 3), having a rough plate morphology with a transformed β-phase grain size of D = 1.0-2.0 mm. The temperature Ac3, (α + β → β) of the transformation is equal to T = 1000 ^o C.

 It is necessary to obtain a microcrystalline structure with an average grain size d = 2.0-3.0 μm, uniform in the volume of the workpiece.

 With this in mind, choose two-stage processing, similar to example 1 (figa, b). At the first stage, the microstructure is preliminarily prepared in a larger volume of the workpiece, in the outer layer, and at the second stage, the structure is prepared to a predetermined grain size, including the inner layers of the tubular workpiece.

 At the first stage, the workpiece, as in the first example, is deformed by proportional two-component loading. Torsion is used as the predominant component, and tension is used as an additional component. The ratio of the loading components at the stages, processing temperature, degree and strain rate are chosen the same as in example 1.

 In order to eliminate the loss of stability of the tubular billet during its deformation in the first stage and to increase the efficiency of the structure transformation in the second stage, due to the complication of the deformation scheme, while maintaining a fairly simple loading scheme, a solid core made of heat-resistant Ni- is installed inside the billet before processing alloy ZhS6 with an inner diameter of 38.0 mm and a length of 200.0 mm (Fig.27). A layer of glass grease is applied to the outer surface of the core. Next, the preform and core are heated to the temperature of the first stage and deformed according to the scheme and loading mode of the first stage.

 Note that throughout the processing, only the workpiece is subjected to deformation.

 After processing in the first stage, the preform is cooled in air to room temperature. Then the preform is again heated to the temperature of the second stage and deformed by uniaxial tension. Upon completion of the deformation in the second stage, the preform is distributed by feeding argon gas under pressure into the inner cavity of the preform, the value of which is changed in the range 2.0-3.0 MPa.

 Distribution can be combined with stretching. This increases the efficiency of transformation of the structure by stimulating the development of grain boundary slippage.

 Next, the core preform is cooled to room temperature and disassembled, removing the core.

 Metallographic analysis showed that after this treatment, the preform has a uniform microcrystalline structure throughout the volume with an average grain size of d = 2.0-0.3 μm.

Example 12
The treatment is subjected to a tubular billet of two-phase (α + β) titanium alloy of the martensitic class VT9 (Ti - base; 5.8-7.0 Al; 2.8-3.8 Mo; 0.8-2.0 Zr; 0, 2-0.35 Si).

 The dimensions of the workpiece are as follows: outer diameter 50.0 mm, inner diameter 40.0 mm; the length of the working part is 200.0 mm.

In this case, as in the previous one, a material with an initial microstructure similar to that of Example 1 (FIG. 3) is used, which has a rough plate morphology with a transformed β-phase grain size of D = 1.0-2.0 mm. The temperature Ac3, (α + β → β) of the transformation is equal to T = 1000 ^o C.

 It is necessary to obtain a microcrystalline structure with an average grain size d = 2.0-3.0 μm, uniform in volume.

 With this in mind, choose a two-stage processing similar to example 1 (Fig. 5A, b). At the first stage, preliminary preparation of the microstructure is carried out. At the second stage, the structure is prepared to a predetermined grain size.

 At the first stage, the workpiece, as in example 1, is deformed by proportional two-component loading. Torsion is used as the predominant component, and tension is used as an additional component. The ratio of the loading components at the stages, the degree and rate of deformation are chosen the same as in example 1.

The processing of the tubular billet is carried out together with a hollow core made of VT14 titanium alloy with a microcrystalline structure with an average grain size of d = 1.0-2.0 μm, in two stages. The first stage is performed at a reduced temperature T = 880 ^o C, the second at a temperature of 930 ^o C.

 The use of a hollow core is necessary in order to eliminate the loss of stability of the tubular billet during its deformation, especially at the first stage, as well as to increase the transformation efficiency of the structure, due to the complexity of the deformation scheme, while maintaining a fairly simple loading scheme. Therefore, before processing, a hollow core made of VT14 titanium alloy with an external diameter of 38.0 mm, a wall thickness of 5.0 mm, and a length of 200.0 mm is installed inside the workpiece inside (Fig. 28).

 In cases where the processing process is not associated with a significant change in the workpiece and core, it is advisable to apply separating materials, for example, a layer of glass grease, on the outer surface of the core in order to facilitate the separation of the workpiece and core after processing.

 Next, the preform and core are heated to the temperature of the first stage and deformed according to the scheme and loading mode of the first stage.

 Before the main processing, the core is distributed, providing the formation of uniform contact over the entire surface of the workpiece and core, feeding argon gas under pressure into the core cavity. The pressure value is varied within P = 2.0-3.0 MPa.

 Note that throughout the treatment, the workpiece and core are subjected to deformation.

 Upon completion of the first stage, the workpiece is cooled in air to room temperature. Then it is again heated to the temperature of the second stage and deformed by uniaxial tension.

 The adjustable supply of gaseous argon during the distribution of the workpiece with the core allows not only to increase the efficiency of the process of transformation of the structure, but also to change the final shape of the workpiece.

 Next, the core preform is cooled to room temperature and disassembled. The core is removed by turning.

 Metallographic analysis showed that after this treatment, the preform has a uniform microcrystalline structure throughout the volume with an average grain size of d = 2.0-0.3 μm.

Example 13
A thin-walled preform having an external diameter of 50.0 mm, an internal diameter of 46.0 mm and a length of a working part of 200.0 mm of titanium gamma aluminide (TiAl) is subjected to processing. In the initial state, the workpiece has a rough microstructure with an average grain size of d = 0.3-0.5 mm.

 It is necessary to obtain a microcrystalline structure in the preform with an average grain size d = 5.0-10.0 μm, distributed uniformly throughout the entire preform volume.

 An analysis of the literature data allowed us to conclude that the processing modes of the VT9 titanium alloy in a first approximation can be used to process gamma titanium aluminum aluminide.

 With this in mind, two-stage processing is chosen, similar to example 1 (Fig. 5A, b). At the first stage, preliminary preparation of the microstructure is carried out. At the second stage, the structure is prepared to a predetermined grain size.

 Since the plasticity resource of the material being processed is insufficient to complete the entire loading cycle, the workpiece is processed between the shell and the core with the necessary plasticity resource (Fig. 29).

Before processing, a hollow core is installed inside the workpiece. Core dimensions are as follows: outer diameter 44.0 mm; inner diameter 34.0 mm; core length 250.0 mm. The blank and core are placed in a shell. Shell dimensions are as follows: outer diameter 62.0 mm; inner diameter 52.0 mm; sheath length 250.0 mm. The shell and core are made of VT9 titanium alloy having a microcrystalline structure with an average size of d = 5.0-10.0 μm. Next, the assembly is heated to a temperature of 900 ^o C and carry out the deformation of the shell by uniaxial tension at a speed of 5.0 • 10 ^-4 s ^-1 . At the same time, argon gas is supplied into the core under a pressure of 2.0-3.0 MPa.

 After the assembly temperature reaches the operating level, they begin processing the workpiece according to the program, loading scheme, and also in the temperature-speed mode of example 1.

 It should be noted that throughout the processing, the entire assembly is simultaneously deformed. After processing, the assembly is removed from the furnace and cooled in air to room temperature. The shell and core are removed by turning.

 Metallographic analysis showed that after this treatment, the workpiece has a uniform microcrystalline structure throughout the volume with an average grain size of d = 5.0-10.0 μm.

Example 14
Thin-walled tubular billet from biphasic (α + β) titanium alloy of martensitic class VT9 (Ti - base; 5.8-7.0 Al; 2.8-3.8 Mo; 0.8-2.0 Zr; 0) is subjected to treatment , 2-0.35 Si).

 The dimensions of the workpiece are as follows: outer diameter 50.0 mm; inner diameter 46.0 mm; the length of the working part is 200.0 mm. The workpiece was obtained from a sheet by preliminary bending into a pipe followed by argon-arc welding along the generatrix.

In order to obtain the initial homogeneous microstructure in the preform similar to the structure of Example 1, the preform is preliminarily annealed in a vacuum oven at a temperature of 1100 ^o C for 2 hours. After heat treatment, the structure has a rough lamellar morphology with a grain size of the transformed β-phase equal to D = 0.5-1.0 mm.

 It is required to obtain a microcrystalline structure with an average grain size d = 2.0-3.0 μm, uniform in the volume of the workpiece.

 With this in mind, choose a two-stage processing, similar to example 1 (Fig. 5A, b). At the first stage, preliminary preparation of the microstructure is carried out. At the second stage, the structure is prepared to a predetermined grain size.

 At the first stage, the workpiece, as in the first example, is deformed by proportional two-component loading. Torsion is used as the predominant component, and tension is used as an additional component. The ratio of the loading components at the stages, the degree and rate of deformation are chosen the same as in example 1.

The processing of a thin-walled tubular billet is carried out together with a hollow shell and a hollow core (Fig. 29) made of titanium alloy VT14 with a microcrystalline structure, with an average grain size d = 1.0-2.0 μm, in two stages. The first stage is performed at a reduced temperature T = 880 ^o C, the second at a temperature of 930 ^o C.

 The use of a hollow shell and a hollow core is necessary in order to exclude the loss of stability of the tubular billet during its deformation, especially at the first stage, as well as to increase the transformation efficiency of the structure, due to the complexity of the deformation scheme, while maintaining a fairly simple loading scheme. In addition, the use of the shell makes the stress state scheme more favorable, i.e. conditions close to the conditions of comprehensive compression are realized. At the same time, an increase in the plasticity resource is also achieved by eliminating the formation of a deformation relief on the surface of the workpiece itself.

 The shell and core have the following dimensions.

 Shell: inner diameter 52.0 mm, wall thickness 5.0 mm, length 200.0 mm. Core dimensions: outer diameter 44.0 mm, wall thickness 5.0 mm, length 200.0 mm.

 In cases where the processing process is associated with a slight change in the shell, preform and core, it is advisable to apply separation materials, for example, yttrium oxide, alumina, boron nitride, etc., to the outer and inner surfaces of the preform, in order to facilitate the process separation of the workpiece and the core after processing.

 Before processing, the workpiece is installed between the shell and the core. Next, the preform and core are heated to the temperature of the first stage and deformed according to the scheme and loading mode of the first stage.

 Immediately before loading according to the scheme of the first stage, the billet and core are distributed, providing uniform contact over the entire surface of the shell, billet and core, feeding argon gas under pressure into the core cavity. The pressure value is varied within P = 2.0-3.0 MPa.

 Note that throughout the treatment, the entire assembly is subjected to deformation, i.e. shell, blank and core.

 Upon completion of the first stage, the assembly is cooled in air to room temperature. Then it is again heated to the temperature of the second stage and deformed by uniaxial tension.

 Next, the core preform is cooled to room temperature and disassembled. The shell and core are removed by turning.

 Metallographic analysis showed that after this treatment, the workpiece has a uniform microcrystalline structure throughout the volume with an average grain size of d = 2.0-3.0 μm.

Example 15
Processing is subjected to a sheet blank 2.0 mm thick of technically pure titanium grade VT1-0.

 In a sheet preform, it is necessary to obtain a microcrystalline structure with an average grain size d = 0.3-0.5 μm, uniform in the volume of the preform.

 As the loading scheme, an intensive shear is used, which is realized by torsion of the workpiece between the non-deformable shell and the core (Fig. 30).

To do this, the workpiece is pre-deformed by bending on a three-roll plate bending machine, giving a shape close to the shape of the pipe with dimensions: the outer diameter of the pipe is 50.0 mm, the height of the pipe is 25.0 mm. Pb-Sn based solder is applied to the external and internal surface of the pipe by vacuum spraying. The core, made of stainless steel, with a pre-installed blank on it, is cooled in liquid nitrogen and installed in an assembled split shell, also made of stainless steel, heated to a temperature of 250 ^o C.

After soldering, the assembly is cooled to room temperature and the workpiece is deformed at a temperature of T = 25 ^° C by rotating the rod and shell relative to each other clockwise and counterclockwise at a rotation speed of 0.1-0.5 revolutions per minute.

The degree of deformation at the transition (one-way rotation) is chosen equal to 1.0, and the number of transitions, chosen equal to 10. After processing, the assembly is heated to a temperature of T = 300 ^o C, kept in order to complete the recrystallization processes and disassembled in a hot state.

 Metallographic analysis showed that after this treatment, the workpiece has a uniform microcrystalline structure throughout the volume with an average grain size of d = 0.3-0.6 μm.

Example 16
Three thin-walled blanks of gamma titanium aluminum aluminide (TiAl) are processed using specialized press equipment (FIG. 31). The size of the blanks is as follows: blank thickness 2.0 mm, height 25.0 mm, width 50.0 mm.

 In preforms, it is necessary to obtain a microcrystalline structure with an average grain size of d = 5.0-10.0 μm, uniform in the volume of preforms.

Billets are installed between the shell and the rod. Heated to a temperature of T = 930 ^o With and deform, applying axial load to the shell. In this case, the rod is stationary. This operation is aimed at giving the workpieces a cone shape that is close in size to the working surface of the shell and the rod.

The inner surface of the shell and the outer surface of the rod are conical with a cone angle of 30 ^o . The contact surfaces of the shell and the rod have notches along the radius and along the generatrix of the cone in order to increase the adhesion of the workpiece to the shell and the rod. After the preliminary forming operation, the preforms are cooled to room temperature and the preforms are turned so that they form a cone without gaps if possible.

It is known that during the deformation of Ti-Al system intermetallic compounds at high temperatures, starting, for example, from 900-950 ^o С and higher under conditions of intensive workpiece slippage along the tool contact surface, Ti begins to interact with Ni, which is an obligatory component in those heat-resistant alloys that are widely used for tooling. During the interaction of Ti with Ni, the formation of a low-melting eutectic occurs, which leads to the melting of the workpiece and tooling, the development of so-called reactive soldering processes and the formation of a connection between the workpiece and tooling. The use of various lubricants does not prevent the formation of these scoring. In this example, there is no such drawback due to the fact that it is not allowed to slip on the contact surface of the workpiece with the tool under high normal contact pressures, due to their conical. Therefore, in this case, various interlayers can be effectively used not only as a material that prevents the development of diffusion processes on the contact surface, but also as a means of increasing the friction coefficient.

 In this example, before assembly, the contacting surfaces of the shell and the shaft are coated with an emulsion of sodium oxide in ethanol.

The workpieces are again installed between the shell and the core, heated to a temperature of the beginning of processing T = 950 ^o C and subjected to deformation. Immediately before processing, the workpiece is tightly clamped between the conical shell and the conical rod and deformed by shear due to the rotation of the shell around the fixed rod, while simultaneously combining with axial deformation by compression, applying a constant axial force to the rod in the range of 0.2-0.5 MPa. The deformation of the workpiece in the first stage is carried out in isothermal conditions at T = 950 ^o C. In the second stage with a decrease in temperature at the end of processing to T = 750 ^o . At the first stage, the shear strain rate is chosen equal to 5.0 • 10 ^-4 s ^-1 , and the cumulative strain value is equal to e = 2.5. The shift in the first and second stages is performed by alternating rotation of the shell and the rod relative to each other by the amount of strain intensity per rotation e _i = 0.5. At the second stage, the workpiece is deformed according to the scheme of the first stage. The total value of the accumulated strain is set equal to 5.0.

 After final processing, the assembly is removed from the furnace and cooled in air to room temperature.

 Metallographic analysis showed that after this treatment, the preform has a microcrystalline structure homogeneous throughout the volume with an average grain size of d = 5.0-10.0 μm.

Sources of information
1. Segal V.M., Reznikov V.I., Kopylov V.I. The processes of plastic structure formation of metals. Minsk: Navuka i tehnika, 1994, 230 p.

 2. Segal V.M., Reznikov V.I., Kopylov V.I. The processes of plastic structure formation of metals. Minsk: Navuka i tehnika, 1994, 230 p.

 3. US patent 3519503, CL C 22 F 1/10, 1970.

 4. Physical metallurgy of titanium. Kolachev B.A. Series "Successes in modern metal science". M .: Metallurgy, 1976, 184 p.

Claims (50)

 1. The method of processing billets of metals and alloys, which consists in obtaining a microstructure with the required grain size by plastic deformation, carried out in one or several stages, and the number of steps is set based on the grain size in the initial billet and the required temperature and speed conditions at the stage they are chosen to ensure the transformation of the structure in the process of dynamic recrystallization, in addition, the stage is performed in several transitions for the most complete transformation of the structure in the volume of the work ki, characterized in that when processing an axisymmetric workpiece at the transitions, workpiece-regulated layers of the workpiece are worked out using complex loading, including at least at the first transition of the first stage, torsion as the sole or predominant component, and compression or tension at subsequent transitions , or a combination of compression or tension with torsion, in addition, the processing is carried out in isothermal or quasi-isothermal conditions.  2. The method according to p. 1, characterized in that at the first transition, the microstructure is transformed until the deformation in the developed layer is satisfied at subsequent transitions under conditions of superplasticity. 3. The method according to p. 2, characterized in that the amount of accumulated deformation in the first stage is selected from the conditions for ensuring the grinding of the microstructure in the volume, which is determined from the ratio

where V _about - the volume of the entire workpiece;
V ₁ - the volume of the transformed part of the workpiece;
σ ₁ - stress flow of a material with a microcrystalline structure;
σ ₂ - stress flow of the material in the original workpiece,
in addition, the temperature of the second stage is chosen not higher than the temperature of the first stage of deformation.  4. The method according to p. 1, characterized in that the number of stages and type of loading is selected taking into account a given distribution of grain size in the cross section of the workpiece.  5. The method according to p. 1, characterized in that when processing billets of alloys having phase transformations, between the transitions carry out heat treatment, ensuring the occurrence of phase transformations.  6. The method according to p. 1, characterized in that when processing billets of titanium and its alloys, the degree and temperature-speed conditions of deformation at the transition are chosen to ensure the occurrence of dynamic recrystallization in the β-phase.  7. The method according to p. 1, characterized in that when processing billets of titanium and its alloys, the degree and temperature-speed conditions of deformation at the transition are chosen to ensure the occurrence of static recrystallization in the β-phase during subsequent recrystallization annealing between transitions and subsequent heat treatment, providing the course of phase transformations. 8. The method according to p. 1, characterized in that when processing billets of (α + β) titanium alloys, the billet, at least at one of the transitions, is deformed at a constant temperature of not more than [T _Ac3 - (20-30)] ^o C. . 9. A process according to claim 1, characterized in that when processing workpieces of pseudo α- and α-titanium alloys, preform, at least at one of the transitions is deformed at a constant temperature in the temperature range of _Ac3 T - T _Ar3 alloy to be treated .  10. The method according to p. 7, characterized in that the heat treatment between the transitions is carried out by cooling the workpiece with a regulated speed, ensuring the flow of direct phase transformation by the diffusion mechanism.  11. The method according to p. 10, characterized in that the cooling rate is chosen not more than the speed corresponding to the martensitic transformation in the β-phase and not less than the speed corresponding to the highest intensity of the formation of annealing twins in the α-phase.  12. The method according to p. 10, characterized in that the cooling is carried out to a temperature of the subsequent transition.  13. The method according to p. 10, characterized in that the cooling is carried out to a temperature below the temperature of the subsequent transition, with further heating to the temperature of the subsequent transition.  14. The method according to p. 10, characterized in that the temperature of the subsequent transition is selected below the temperature of the previous transition.  15. The method according to p. 10, characterized in that the temperature of the subsequent transition is chosen equal to the temperature of the previous transition.  16. The method according to p. 10, characterized in that the cooling is carried out to room temperature, followed by heating to a temperature of the subsequent transition.  17. The method according to p. 5, characterized in that, at least after one of the transitions, it is heated to a temperature higher than the processing temperature at the previous transition, followed by cooling to the temperature of the subsequent transition.  18. The method according to p. 1, characterized in that when processing billets of titanium and its alloys with the original cast structure, before the first stage, additional processing is carried out, which ensures the occurrence of dynamic recrystallization in the β-phase, and heat treatment, which ensures the occurrence of reverse phase transformations .  19. The method according to p. 1, characterized in that when processing billets of titanium and its alloys with the initial cast structure, before the first stage, additional processing is carried out, which ensures the occurrence of dynamic recrystallization in the β-phase, and heat treatment, which ensures the occurrence of direct phase transformations .  20. The method according to p. 1, characterized in that if the deformation is carried out in more than two stages, in subsequent stages the axial component of the load is used to shape the workpiece.  21. The method according to p. 1, characterized in that when the axisymmetric billet in the form of a rod is taken as the initial one, its cross-sectional size is selected the smaller, the smaller the given grain size, while uniaxial tension is used as the axial component of the load.  22. The method according to p. 1, characterized in that when the preform is taken in the form of a washer, its height size is chosen the smaller, the smaller the specified grain size, while in the second stage, uniaxial compression is used as the axial component of the load.  23. The method according to p. 1, characterized in that when processing the workpieces in the form of a washer, at one stage the workpiece is deformed, combining torsion with compression.  24. The method according to p. 1, characterized in that when processing the workpieces in the form of rods at one of the stages, the workpiece is deformed, combining torsion with tension.  25. The method according to any one of paragraphs. 23 and 24, characterized in that they combine alternating torsion with alternating axial loading.  26. The method according to any one of paragraphs. 23 and 24, characterized in that they combine monotonous torsion with alternating axial loading.  27. The method according to any one of paragraphs. 23 and 24, characterized in that they combine alternating torsion with monotonous axial loading.  28. The method according to any one of paragraphs. 23-27, characterized in that the ratio of the axial component of the deforming force to the torque is selected no more than 0.2.  29. The method according to p. 1, characterized in that the preform is deformed in a shell made of a material capable of superplastic deformation, while pre-deforming the shell by uniaxial tension to ensure contact between the workpiece and the shell on the side surface of the workpiece, preventing their displacement relative to each other friend during processing.  30. The method according to p. 1, characterized in that when processing a hollow workpiece, a core is installed inside the workpiece, and the workpiece is subjected to deformation.  31. The method according to p. 1, characterized in that when processing a hollow billet, by multi-component loading inside the billet, a core is made of a material that deforms under superplasticity under temperature and speed conditions of processing the billet, and the core is subjected to deformation mainly in the second stage , and blank.  32. The method according to any one of paragraphs. 30 and 31, characterized in that the workpiece assembly with the core is deformed in a shell made of a material capable of superplastic deformation, while the shell is pre-deformed by uniaxial tension to ensure contact between the workpiece and the shell along the side surface of the workpiece, preventing them from displacing relative to each other friend during processing.  33. The method according to any one of paragraphs. 31 and 32, characterized in that the core is made hollow.  34. The method according to p. 33, characterized in that the processing of the workpiece is performed in the conditions of distribution of the core by feeding into the inner cavity of the core under pressure of the working medium.  35. The method according to any one of paragraphs. 31 and 32, characterized in that a material is placed between the preform and the core, which, at least during the processing of the preform, acquires viscous flow properties.  36. The method according to any one of paragraphs. 31 and 32, characterized in that after processing the workpiece, the workpiece is distributed by supplying a working medium under pressure into the cavity between the workpiece and the core.  37. The method according to p. 1, characterized in that during the processing of tubular thin-walled blanks, the deformation is carried out in the shell, while the workpieces are preliminarily distributed until contact is made between the workpiece and the shell along the side surface of the workpiece, which prevents them from being displaced relative to each other during processing.  38. The method according to p. 37, characterized in that the shell is made of a material that, at the selected temperature and speed modes of processing the workpiece, is deformed under conditions of superplasticity.  39. The method according to p. 1, characterized in that when processing tubular billets it is installed between the shell and the core, made of material that does not undergo a change during processing of the workpiece, while ensuring uniform contact over the entire contact surface of the workpiece and the core, preventing mutual displacement the workpiece, shell and core during processing, and the deformation of the workpiece is performed by displacing the shell and core relative to each other.  40. The method according to p. 39, characterized in that the workpiece and the contacting surfaces of the shell and core are made in a conical shape.  41. The method according to p. 37, characterized in that the contact between the hollow billet, the shell and the solid core is provided by the formation of thermal interference.  42. The method according to p. 37, characterized in that the contact between the hollow billet with a thickness of t, the shell and the solid core is provided by a solder joint, while the initial thickness of the solder interlayer Δ is selected from the condition Δ <0,005t.  43. The method according to p. 1, characterized in that when processing the plates, they are placed between the shell and the rod with contact across the entire surface by pre-deformation of the plates, and during processing by shifting the shell and the rod relative to each other.  44. The method according to p. 43, characterized in that the shell and the rod are conical in shape, with the preliminary deformation of the plates being carried out during assembly.  45. The method according to p. 1, characterized in that in the processing of billets in the form of rods, torsion is carried out by applying a deforming force to the end surface, uniformly over an area having a radius r equal to 0.7 <r <R, where R is the radius of the machined blanks.  46. The method according to p. 1, characterized in that the deforming force on the workpiece is transmitted due to its permanent connection with the tool.  47. The method according to p. 46, characterized in that the one-piece connection is performed by fusion welding.  48. The method according to p. 46, characterized in that the one-piece connection is performed by welding in the solid phase.  49. The method according to p. 46, characterized in that the one-piece connection is performed by soldering, while the solder material is selected from the condition that its melting temperature is higher than the processing temperature of the workpiece, and the thickness of the interlayer is selected from the ratio (0.005-0.01) τ \, where τ is the transverse dimension of the connection between the workpiece and the tool.  50. The method according to p. 1, characterized in that the deforming force on the workpiece is transmitted due to its detachable connection with the tool.

Images