Laminated foil roll internal pressure forming-high-temperature in-situ reaction composite preparation method of intermetallic compound thin-wall pipe fitting

Abstract

The invention belongs to the technical field of pipe fitting forming preparation, and particularly relates to a laminated foil roll internal pressure forming-high-temperature in-situ reaction composite preparation method of an intermetallic compound thin-wall pipe fitting, which comprises the following preparation steps: S1, preparing a laminated foil roll preform; s2, room-temperature internal pressure forming is conducted, specifically, the laminated foil coil prefabricated body is placed in a forming die with a target pipe fitting cavity, axial pressure is applied to solid particle media through a hydraulic horizontal cylinder on a press machine platform and acts on the inner wall of a laminated foil coil, and a laminated pipe fitting with a target shape is formed; s3, high-temperature in-situ reaction is conducted, specifically, in-situ heating is conducted after room-temperature internal pressure forming, and a target alloy is generated; and S4, post-treatment, wherein after the reaction is finished, a formed part is taken out. According to the method, the open type laminated foil roll serves as an initial blank, part of material plastic deformation is replaced with material movement, forming preparation is achieved through the excellent plastic deformation capacity of the metal elementary substance at the room temperature, the alloy material is generated through in-situ reaction after forming, and the working progress is improved.

Description

Technical Field

[0001] This invention belongs to the field of pipe forming and preparation technology, and particularly relates to a composite preparation method of intermetallic compound thin-walled pipes by stacked foil roll internal pressure forming-high temperature in-situ reaction. Background Technology

[0002] With the development of next-generation aerospace vehicles towards lightweight and high-speed designs, there is an urgent need for lightweight, heat-resistant, complex thin-walled tubing. Commonly used titanium alloys cannot meet the high-temperature requirements, while high-temperature alloys have high density, which does not align with the trend towards lightweight equipment. Intermetallic compounds, such as NiAl-based alloys and TiAl-based alloys, are ideal materials for manufacturing lightweight, heat-resistant, thin-walled components such as air intakes and exhaust nozzles for high-speed aircraft due to their high specific strength, excellent high-temperature performance, and low density. However, the poor room-temperature plasticity and narrow hot working window of these materials pose significant challenges to the fabrication of their thin-walled tubing.

[0003] Traditional methods for manufacturing thin-walled metal tubes typically use rolled slabs or tube blanks as initial raw materials, followed by forming processes such as superplastic forming, hot stamping, and welding. This approach follows a technical route of first forming the alloy blank and then shaping the component. However, intermetallic compounds such as NiAl-based alloys and TiAl-based alloys have poor plastic deformation capabilities, and there are currently no commercially available sheet or tube materials. Furthermore, their hot forming conditions are demanding, requiring sophisticated equipment (forming temperature >1200℃).

[0004] Therefore, in the prior art, such as the invention patent published by the State Intellectual Property Office of a NiAl alloy curved plate component synthesis, preparation and forming integrated method (authorization announcement number: CN107081345B), it is disclosed that the component shape is first formed using metal element foil as the initial blank, and then the alloy material is generated through foil reaction, which innovatively proposes a technical route of first forming the component and then reacting to generate the alloy. Regarding the invention patent published by the State Intellectual Property Office for NiAl alloy thin-walled tubing, a method for the integrated forming and control of NiAl alloy thin-walled tubing (authorization announcement number: CN110142332B), it proposes to prepare Ni / Al laminated foil tubes by tube rolling and welding. However, the thickness of the foil is usually less than 0.1 mm, making the welding of multi-layered foil tubes difficult to achieve. Furthermore, it requires maintaining high pressure (>10 MPa) at high temperatures (>1000℃) for extended periods (>1 h), posing a serious sealing challenge. The State Intellectual Property Office also published an invention patent for a forming method for complex thin-walled hollow NiAl alloy components (authorization announcement number: CN111804810B), which proposes a method for forming a rigid core... Complex thin-walled hollow components are fabricated using a staggered overlapping method supported by a shaft. However, this method is only suitable for forming thin-walled cylindrical parts, and seamless joining of metal foils in the staggered areas is difficult and complex. Furthermore, the State Intellectual Property Office has published an invention patent for a method of forming dissimilar metal laminated thin-walled cylindrical parts (authorization announcement number: CN113020423B), but the support method of a separate rigid mandrel cannot form complex thin-walled tubes. The State Intellectual Property Office has also published an invention patent for an integrated manufacturing method of high-temperature resistant thin-walled components using metal foil strip laying (authorization announcement number: CN111168407B). This method introduces numerous interfaces, making local composition and defect control extremely difficult, and still faces the challenge of long-term high-temperature and high-pressure sealing. Currently, the manufacturing of complex thin-walled tubes made of intermetallic compounds remains a bottleneck problem in my country's aerospace and other fields, urgently requiring the development of a new preparation method. Summary of the Invention

[0005] This invention addresses the technical problems existing in the manufacturing process of complex thin-walled intermetallic compound tubes mentioned above. It proposes a composite preparation method for intermetallic compound thin-walled tubes, which is rationally designed, simple in structure, and easy to process. The method uses open-type stacked foil rolls as initial blanks, replaces part of the material's plastic deformation by material movement, and makes full use of the excellent plastic deformation capacity of elemental metals at room temperature, thus avoiding the hot forming process. At the same time, solid particles are used as the supporting medium for room temperature internal pressure loading and high-temperature reaction, which can realize the in-situ reaction to generate alloy materials after forming and avoid the problem of long-term high temperature and high pressure sealing.

[0006] To achieve the above objectives, the technical solution adopted in this invention is a composite preparation method for intermetallic compound thin-walled tubular components, which involves internal pressure forming of laminated foil rolls followed by high-temperature in-situ reaction, comprising the following preparation steps:

[0007] S1: Preparation of the laminated foil roll preform: Calculate the required thickness ratio of the elemental metal foils based on the atomic ratio of the chemical composition of the target intermetallic compound, and determine the thickness of each elemental metal foil; calculate and cut the elemental metal foils of the corresponding size according to the dimensions of the target intermetallic compound fittings; after the elemental metal foils are made into suitable specifications, they are stacked alternately to form a laminated foil, and then the laminated foil roll is rolled into a cylindrical shape under the support of a rigid mandrel. The mandrel is removed to obtain a laminated foil roll preform with a certain overlap.

[0008] S2: Room temperature internal pressure forming: The laminated foil roll preform is placed in a forming mold with the target tube cavity, and then solid granular medium is filled into the inner cavity of the laminated foil roll preform. The axial sides of the preform are limited by the left and right punches. The hydraulic horizontal cylinder on the press platform applies axial pressure to the solid granular medium and acts on the inner wall of the laminated foil roll, causing material movement and plastic deformation at room temperature until the laminated foil roll adheres tightly to the mold cavity, forming a laminated tube with the target shape.

[0009] S3: High-temperature in-situ reaction: After room temperature internal pressure forming, without opening the mold, the forming mold, stacked tubes and filling solid particle medium are heated in-situ according to the preset heating regime, so that the metal element foils undergo a high-temperature diffusion reaction and the target alloy is generated in-situ.

[0010] S4: Post-processing: After the reaction is completed, the furnace is cooled or controlled to room temperature. While maintaining the clamping force, the left and right horizontal cylinders are removed, and the upper and lower molds of the forming mold are opened to remove the formed part. At the same time, the solid particulate medium is separated and recovered to obtain the target alloy thin-walled pipe.

[0011] Preferably, step S1 further includes the following step:

[0012] S1.1: Annealing heat treatment is performed on the metal elemental foil used to prepare the target alloy to improve the room temperature forming performance of the foil. Then, surface treatment processes such as pickling / alkali washing, ultrasonic cleaning, and drying are performed to remove dirt and oxide layer from the foil surface.

[0013] S1.2: The method for calculating the length and width dimensions of a metallic foil is as follows:

[0014] Let the length of the intermetallic compound tube be L1, then the length of the laminated foil roll preform is L2 = (1+n)L1, where n is the proportion of the axial length of the process section, taken as 20%; the width of the foil is W = (1+n)L1.

[0015] Let the minimum diameter of the intermetallic compound pipe be R1 and the wall thickness be T1. Then the diameter of the laminated foil roll preform should be R2=R1 / (1+m), where m is the minimum expansion rate, taken as 3~5%; the wall thickness of the laminated foil roll preform is T2=T1(1+o), where o is the thinning rate due to high temperature reaction; considering the overlap amount α, the length of each type of foil needs to be increased to l=2πR2T2 / (TA+TB+TC+…)+2πR2α / 360°, where TA, TB, and TC are the thicknesses of each type of foil.

[0016] Preferably, in step S1, the overlap amount refers to the overlap angle α between the outermost and innermost edges of the foil roll. It is determined by theoretical analysis and finite element simulation based on the shape requirements of the target tube, and ensures that the overlap angle α after the stacked tube is formed is less than 30°.

[0017] Preferably, the solid particulate medium in step S2 is selected from high-temperature resistant ceramic or metal particles / powders with a particle size of 0.01mm-0.5mm.

[0018] Preferably, the forming mold in step S2 includes an upper mold and a lower mold, which are respectively connected to the upper platform and the lower platform of the press.

[0019] Preferably, when a horizontal forming device is used in step S2, the lateral pressure inside the cylinder is... The distribution along the axial direction of the foil roll preform satisfies: ;

[0020] in, This is the distance from the axial end of the foil roll to the axial center of the foil roll. This indicates the position where the lateral pressure inside the cylinder is 0; This represents the axial pressure applied by the platform's horizontal cylinder; a and c are constants, related to the particle material, particle diameter, and cylinder diameter.

[0021] Lateral pressure inside the cylinder required for forming laminated foil roll preforms ;

[0022] in, Let be the yield stress of a certain metallic foil; The thickness of a roll of a certain metal foil; The radius of a roll of a certain elemental metal foil; This is the foil roll load-bearing capacity factor, the value of which is related to the number of layers in the foil roll, and the value ranges from 0 to 1; This represents the number of types of metallic foil rolls;

[0023] Lateral pressure inside the cylinder required for shaping laminated foil roll preforms ;

[0024] in, This represents the minimum radius of the formed tube; at this point, the preform is basically attached to the mold. Due to the frictional force of the mold on the outside of the preform, the shaping process of the preform is simplified to an integral tube blank, i.e., the foil roll bearing capacity. =1;

[0025] When using a vertical forming device, i.e., the pipe's axial direction is parallel to the press platform's movement direction, a die sleeve needs to be applied to the outside of the original upper and lower dies to constrain the horizontal displacement of the dies; the thickness of the die sleeve... ,in, This represents the maximum value of the lateral pressure inside the cylinder. The yield strength of the mold sleeve, This represents the maximum radius of the formed tube.

[0026] Preferably, in step S3, the high-temperature in-situ reaction process maintains the clamping force and axial force loading, and ensures that the minimum internal lateral pressure on the pipe is greater than the critical reaction pressure.

[0027] Compared with the prior art, the advantages and positive effects of the present invention are as follows:

[0028] This invention provides a composite preparation method for thin-walled intermetallic compound tubes using a laminated foil roll internal pressure forming-high-temperature in-situ reaction. This method features a short process flow, low energy consumption, and eliminates the need for high-temperature pressure sealing. Specifically, it uses open-type laminated foil rolls as the initial blank, replacing some of the material's plastic deformation through material movement, and fully utilizing the excellent plastic deformation capacity of elemental metals at room temperature, thus avoiding the hot forming process. Simultaneously, using solid particles as the supporting medium for room-temperature internal pressure loading and high-temperature reaction enables in-situ reaction generation of alloy materials after forming, avoiding the challenges of long-term high-temperature and high-pressure sealing. This method can be widely applied to the preparation of thin-walled intermetallic compound tubes that are difficult to deform, such as those based on TiAl, NiAl, and NbAl. Attached Figure Description

[0029] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the following description of the embodiments will be briefly introduced. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0030] Figure 1 This is a schematic diagram of the preparation method in the existing technology;

[0031] Figure 2 A schematic diagram illustrating the process principle of the preparation method provided by this invention;

[0032] Figure 3 A schematic diagram illustrating the fabrication of the laminated foil roll preform provided by this invention;

[0033] Figure 4 This is a schematic diagram of room temperature internal pressure forming of the laminated foil roll preform provided by the present invention.

[0034] Figure 5 This is a schematic diagram of the high-temperature in-situ reaction of the laminated pipe fitting provided by the present invention;

[0035] Figure 6 The results of the room temperature internal pressure forming of the laminated variable diameter pipe fitting provided by this invention are as follows:

[0036] Figure 7 The results of the room temperature internal pressure forming finite element simulation of the laminated square cross-section component provided by this invention;

[0037] Figure 8 This is a schematic diagram of the processing of the horizontal forming device provided by the present invention;

[0038] Figure 9 This is a schematic diagram of the processing of the vertical forming device provided by the present invention;

[0039] Figure 10 This is a schematic diagram of the pipe fitting specifications provided in Embodiment 1 of the present invention;

[0040] Figure 11 This is a schematic diagram of the pipe fitting specifications provided in Example 2 of the present invention;

[0041] Figure 12 This is a schematic diagram of the pipe fitting specifications provided in Example 3 of the present invention. Detailed Implementation

[0042] To better understand the above-mentioned objectives, features, and advantages of the present invention, the present invention will be further described below in conjunction with the accompanying drawings and embodiments. It should be noted that, unless otherwise specified, the embodiments and features described in these embodiments can be combined with each other.

[0043] Numerous specific details are set forth in the following description in order to provide a full understanding of the invention. However, the invention may also be practiced in other ways than those described herein, and therefore the invention is not limited to the specific embodiments disclosed in the following specification.

[0044] Example 1, such as Figures 1-12 As shown, a composite preparation method for intermetallic compound thin-walled tubular components using laminated foil roll internal pressure forming and high-temperature in-situ reaction is disclosed. The target intermetallic compound tubular component is a NiAl alloy variable diameter tubular component with a wall thickness of 2 mm. The preparation method includes the following steps:

[0045] S1: The target alloy is a NiAl alloy. Based on the atomic ratio of Ni to Al of 1:1, the calculated thickness ratio of Ni foil to Al foil is 1:1.5. Initially, the Al foil thickness can be selected as 100μm. This specification of Al foil is readily available for purchase, therefore the Ni foil thickness should be 67μm. The Ni foil needs to be sourced from relatively thicker materials, and its thickness can be controlled by immersion in an HF solution. Alternatively, based on available products, a Ni foil thickness of 60μm can be initially selected, in which case the Al foil thickness should be 90μm. The Al foil thickness can be adjusted by immersion in a NaOH solution.

[0046] Calculate and cut the corresponding size of the metal element foil based on the dimensions of the target intermetallic compound tube. The length of the NiAl tube is L1=230mm, then the length of the laminated foil roll preform is L2=(1+20%)230=276mm, that is, the width of the foil is W=276mm.

[0047] The minimum diameter of the NiAl alloy pipe fitting is R1=38mm and the wall thickness is T1=2mm. Therefore, the diameter of the laminated foil roll preform should be R2=38 / (1+5%)=36mm, with a minimum expansion rate of 5%; the wall thickness of the laminated foil roll preform is T2=2(1+10%)=2.2mm, with a high-temperature reaction thinning rate of 10%; the length of each type of foil is l=2π×36×2.2 / (0.1+0.067)=2978mm. Setting the overlap α (the overlap angle between the outermost and innermost edges of the foil roll) to 90°, the foil length needs to be increased by 2π×36×90° / 360°=57mm. The total length of each type of foil is then l=2978+57=3035mm.

[0048] Therefore, the Ni foil is 3035mm long, 276mm wide, and 67μm thick; the Al foil is 3035mm long, 276mm wide, and 100μm thick.

[0049] The required Ni and Al foils need to undergo annealing heat treatment to improve their room temperature forming properties. The annealing temperature for Ni foil is 700℃~900℃, holding for 1-4 hours, followed by air cooling / furnace cooling. The annealing temperature for Al foil is 300℃~400℃, holding for 0.5-3 hours, followed by air cooling / furnace cooling.

[0050] Afterwards, the foils undergo surface treatment processes such as acid / alkali washing, ultrasonic cleaning, and drying to remove surface contaminants and oxide layers. Ni foils are cleaned with a 5%–15% (v / v) HF solution, followed by ultrasonic cleaning, rinsing with distilled water, and then dried with a hairdryer on a cool setting. Al foils are cleaned with a 5%–15% (v / v) NaOH solution, followed by ultrasonic cleaning, rinsing with distilled water, and then dried with a hairdryer on a cool setting.

[0051] After being made into suitable specifications and subjected to heat treatment and surface treatment, the metal elemental foils are stacked alternately to form a multilayer metal elemental foil. The multilayer foil is then rolled into a cylindrical shape under the support of a mandrel. The mandrel is cylindrical or tubular, with a length of 300mm and a diameter of 34mm. The material can be an elastic material such as polyurethane or a rigid material such as low-carbon steel. After rolling, the mandrel is removed, resulting in a prefabricated multilayer foil roll with a certain overlap.

[0052] The thickness of each elemental metal foil needs to be determined based on the calculated elemental metal foil thickness ratio, taking into account market supply and the difficulty of subsequent forming / reaction. Foil that is too thick will affect the reaction process, while foil that is too thin will increase the difficulty of forming.

[0053] S2: Design and process the upper and lower molds according to the shape of the target pipe fitting, and then install them on the upper and lower platforms of the press, respectively. The length of the mold is the length of the preform + two process sections L2 + 2 × 30mm = 336mm. The purpose of the process sections is to facilitate the installation of the left and right punches. Place the laminated foil roll preform into the forming mold with the cavity of the target pipe fitting, and then fill the inner cavity of the laminated foil roll preform with solid granular medium. The axial sides of the preform are limited and pre-tightened by the left and right punches. The solid granular medium is selected from high-temperature resistant ceramic or metal particles / powders with a particle size of 0.01mm-0.5mm.

[0054] During the room temperature internal pressure forming process, the hydraulic horizontal cylinder on the press platform applies axial pressure to the solid particulate medium and acts on the inner wall of the laminated foil roll, causing it to move and plastically deform at room temperature until the laminated foil roll adheres tightly to the mold cavity, forming a laminated tube with the target shape.

[0055] Lateral pressure inside the cylinder required for forming laminated foil roll preforms ;in, The yield stress of a certain metal foil is given by (the yield strength of annealed Al foil is taken as 20 MPa, and the yield strength of annealed Ni foil is taken as 70 MPa). The thickness of a certain metal foil roll is (the thickness of Al foil is 0.1mm × 13 = 1.3mm, and the thickness of Ni foil is 0.067 × 13 = 0.9mm). Let 38mm be the radius of a certain metal foil roll; The foil roll bearing capacity factor is set to 1. The value is 2, representing the number of types of single-element metal foil rolls. Therefore, the internal lateral pressure required for forming the laminated foil roll preform is calculated to be 2.5 MPa.

[0056] Lateral pressure inside the cylinder required for shaping laminated foil roll preforms ;in, The minimum radius for forming the pipe fitting is set to 15mm. At this point, the preform is basically attached to the mold. Due to the frictional force of the mold on the outside of the preform, the shaping process of the preform is simplified to an integral pipe blank, i.e., the foil roll bearing capacity. The value is 1. Therefore, the internal lateral pressure required for shaping the laminated foil roll preform is calculated to be 6.0 MPa.

[0057] When axial pressure is applied to the solid particles inside the preform via a horizontal cylinder, the lateral pressure inside the cylinder... The distribution along the axial direction of the foil roll preform satisfies: ;in, This is the distance from the axial end of the foil roll to the axial center of the foil roll. This indicates the position where the lateral pressure inside the cylinder is 0; This represents the axial pressure applied by the platform's horizontal cylinder; a and c are constants related to the particle material, particle diameter, and cylinder diameter. Based on the above pipe dimensions and simulation results, a is taken as 0.005, b as 170, and c as 0.82. It is necessary to ensure that the minimum lateral pressure inside the cylinder is greater than the lateral pressure required for shaping the laminated foil roll preform; therefore, the calculated axial pressure applied by the horizontal cylinder should be greater than 75 MPa. Based on the axial projected area of ​​the pipe, the axial force applied by the horizontal cylinder is greater than 50 tons.

[0058] Based on the maximum lateral pressure inside the cylinder and the projected area of ​​the component in the horizontal direction, the clamping force of the upper and lower platforms of the press should be greater than 160 tons.

[0059] The above processing procedure uses "metallic elemental laminated foil rolls" as the initial blank, taking advantage of the good plasticity of metallic elements at room temperature and using material movement to replace part of the plastic deformation, thereby improving the forming limit of the material. "Solid particulate medium" is used as the only internal pressure application and support medium, which connects the two stages of room temperature forming and high temperature reaction, completely avoiding the problem of high temperature gas sealing. The final tube shape is obtained directly through "room temperature internal pressure forming", eliminating the energy-consuming hot forming process, shortening the process flow to a certain extent, reducing energy consumption, and meeting the usage requirements.

[0060] S3: High-temperature in-situ reaction: After room temperature internal pressure forming, without opening the mold, the forming mold, stacked tubes and filling solid particle medium are heated in-situ according to the preset heating regime, so that the metal element foils undergo a high-temperature diffusion reaction and the target alloy is generated in-situ.

[0061] During the high-temperature in-situ reaction process, the clamping force and axial force are maintained continuously, ensuring that the minimum lateral pressure inside the cylinder on the pipe is greater than the critical reaction pressure. Furthermore, the high-temperature diffusion reaction process must be carried out in a vacuum environment to prevent air from being trapped between the laminated foils and to prevent oxidation. Therefore, the press platform needs to be equipped with a vacuum heating furnace, and a vacuum of less than 0.1 Pa must be drawn before heating.

[0062] The high-temperature diffusion reaction of Ni foil and Al foil is divided into two steps: (1) below the melting point of Al, 550~630℃, 5~10MPa, 1~4h; (2) 1100-1200℃, 3~5MPa, 1~2h. During the high-temperature diffusion reaction, the lateral pressure inside the stacked tube needs to be maintained at 5MPa. Therefore, the axial force applied by the horizontal cylinder should be greater than 40 tons, and the clamping force of the upper and lower platforms of the press should be greater than 130 tons. During the high-temperature diffusion reaction, the axial force and clamping force need to be maintained continuously.

[0063] In the above process, the microstructure is precisely controlled under the support of solid particulate media through an optimized "multi-step high-temperature in-situ reaction" system to obtain high-performance intermetallic compounds.

[0064] S4: Post-processing: After the reaction is completed, the furnace is cooled or controlled to room temperature. While maintaining the clamping force, the left and right horizontal cylinders are removed, and the upper and lower molds of the forming mold are opened to remove the formed part. At the same time, the solid particulate medium is separated and recovered to obtain the target alloy thin-walled pipe.

[0065] To further improve the rationality of the preparation process, step S1 also includes the following steps:

[0066] S1.1: Annealing heat treatment is performed on the metal elemental foil used to prepare the target alloy to improve the room temperature forming performance of the foil. Then, surface treatment processes such as pickling / alkali washing, ultrasonic cleaning, and drying are performed to remove dirt and oxide layer from the foil surface.

[0067] S1.2: The method for calculating the length and width dimensions of a metallic foil is as follows:

[0068] Let the length of the intermetallic compound tube be L1, then the length of the laminated foil roll preform is L2 = (1+n)L1, where n is the proportion of the axial length of the process section, taken as 20%; the width of the foil is W = (1+n)L1.

[0069] Let the minimum diameter of the intermetallic compound pipe be R1 and the wall thickness be T1. Then the diameter of the laminated foil roll preform should be R2 = R1 / (1+m), where m is the minimum expansion rate, taken as 3~5%; the wall thickness of the laminated foil roll preform is T2 = T1(1+o), where o is the thinning rate due to high temperature reaction; considering the overlap amount α, the length of each type of foil needs to be increased to l = 2πR2T2 / (TA+TB+TC+…)+2πR2α / 360°, where TA, TB, and TC are the thicknesses of each type of foil;

[0070] The above calculation method can obtain more accurate dimensions of the metal foil, ensuring the accuracy of pipe fitting manufacturing.

[0071] To ensure the ease of fabrication of the laminated foil roll preform, the solid particulate medium in step S2 is selected from high-temperature resistant ceramic or metal particles / powders with a particle size of 0.01mm-0.5mm. The solid particulate medium can be selected from materials such as zirconium oxide, quartz sand, or steel balls. Axial force is applied to the solid particulate medium and then to the laminated foil roll preform, which facilitates its formation and completes the corresponding fabrication work.

[0072] To ensure convenient force application during the preparation of the laminated foil roll preform, the forming mold in step S2 includes an upper mold and a lower mold, which are respectively connected to the upper platform and lower platform of the press. For the press structure, i.e. the forming device, provided in this embodiment, existing technologies such as horizontal or vertical mechanisms are used. For a horizontal forming device, it generally includes a lower platform and an upper platform, a left horizontal cylinder and a right horizontal cylinder located outside the upper and lower platforms, and connected to punches to act on the solid particulate medium to form the workpiece. The upper and lower platforms are connected to the upper mold and the lower mold respectively to define the forming shape of the workpiece. For a vertical forming device, it includes an upper platform, a lower platform, and a mold sleeve placed between the two. A forming mold is set in the mold sleeve, and upper punches and lower punches are respectively connected to the upper and lower platforms to act on the solid particulate medium to complete the forming preparation of the workpiece. Of course, the specific composition of the horizontal forming device and the vertical forming device are also existing mature technologies that can be known to those skilled in the art.

[0073] To ensure the forming quality of the workpiece, when using a vertical forming device in step S2 (i.e., the pipe axis is parallel to the direction of movement of the press platform), a die sleeve needs to be applied to the outside of the original upper and lower dies to constrain the horizontal displacement of the dies; the thickness of the die sleeve... ,in, This represents the maximum value of the lateral pressure inside the cylinder. The yield strength of the mold sleeve, This represents the maximum radius of the formed tube.

[0074] In addition, if a vertical forming device is used, a strong compression spring needs to be placed between the upper and lower punches and the mold to improve the uniformity of the lateral pressure inside the preform.

[0075] To suppress wrinkling and localized necking in the overlapping areas of the laminated foil roll preform, normal constraints can be applied to the outside of the foil roll. For example, a highly ductile aluminum tube or low-carbon steel tube can be used to cover the outside of the foil roll. Alternatively, a non-closed covering tube or a covering plate that only acts locally can be used. If a closed covering tube is selected, it needs to be removed by machining after forming.

[0076] When using a cover plate or a cover tube, the cover tube / cover plate must be removed after forming, and then an internal pressure forming process must be performed to ensure the dimensional accuracy of the formed pipe fitting.

[0077] Example 2: NiAl alloy square section pipe fitting with a corner radius of 6mm and a wall thickness of 2mm.

[0078] Unlike Example 1, the pipe has a small rounded corner feature, which increases the lateral pressure inside the cylinder required for shaping the laminated foil roll preform. Correspondingly, the axial force applied by the horizontal cylinder and the clamping force of the press also need to be increased during the room temperature internal pressure forming process.

[0079] Lateral pressure inside the cylinder required for shaping laminated foil roll preforms ;in, The minimum radius of the formed tube is taken as 6 mm. Therefore, the internal lateral pressure required for shaping the laminated foil roll preform is calculated to be 15.0 MPa.

[0080] When axial pressure is applied to the solid particles inside the preform via a horizontal cylinder, the lateral pressure inside the cylinder... The distribution along the axial direction of the foil roll preform satisfies: ;in, This is the distance from the axial end of the foil roll to the axial center of the foil roll. This indicates the position where the lateral pressure inside the cylinder is 0; This represents the axial pressure applied by the platform's horizontal cylinder; a and c are constants related to the particle material, particle diameter, and cylinder diameter. Based on the above pipe dimensions and simulation results, a is set to 0.005, b to 170, and c to 0.82. It is necessary to ensure that the minimum lateral pressure inside the cylinder is greater than the lateral pressure required for shaping the laminated foil roll preform; therefore, the calculated axial force applied by the horizontal cylinder is greater than 125 tons.

[0081] Based on the maximum lateral pressure inside the cylinder and the projected area of ​​the component in the horizontal direction, the clamping force of the upper and lower platforms of the press should be greater than 400 tons.

[0082] Example 3: Target intermetallic compound pipe fitting: Ti2AlNb alloy (Ti-22Al-25Nb) reducing pipe fitting, wall thickness 2mm.

[0083] The preparation steps include the following:

[0084] S1: Preparation of the laminated foil roll preform: Calculate the required thickness ratio of the elemental foils based on the atomic ratio of the target intermetallic compound, and determine the thickness of each elemental foil. The target alloy is Ti2AlNb alloy (Ti-22Al-25Nb alloy). Based on the atomic percentages of Ti, Al, and Nb in the alloy, the selected thicknesses are 106 μm for Ti foil, 42 μm for Al foil, and 52 μm for Nb foil. The thicknesses of the Ti and Nb foils can be controlled by acid washing (HF solution), and the thickness of the Al foil can be controlled by alkaline washing (NaOH solution).

[0085] Calculate and cut the corresponding size of the metal element foil based on the dimensions of the target intermetallic compound tube. The length of the NiAl tube is L1=230mm, then the length of the laminated foil roll preform is L2=(1+20%)230=276mm, that is, the width of the foil is W=276mm.

[0086] The minimum diameter of the Ti2AlNb alloy pipe fitting is R1=38mm, and the wall thickness is T1=2mm. Therefore, the diameter of the laminated foil roll preform should be R2=38 / (1+5%)=36mm, with a minimum expansion rate of 5%; the wall thickness of the laminated foil roll preform is T2=2(1+10%)=2.2mm, with a high-temperature reaction thinning rate of 10%; the length of each type of foil is l=2π×36×2.2 / (0.106+0.042+0.052)=2261mm. Setting the overlap α (the overlap angle between the outermost and innermost edges of the foil roll) to 90°, the foil length needs to be increased by 2π×36×90° / 360°=57mm. The total length of each type of foil is then l=2261+57=2318mm. Therefore, the Ti foil is 2318 mm long, 276 mm wide, and 106 μm thick; the Al foil is 2318 mm long, 276 mm wide, and 42 μm thick; and the Nb foil is 2318 mm long, 276 mm wide, and 52 μm thick.

[0087] The required Ti, Al, and Nb foils require annealing heat treatment to improve their room temperature forming properties. The annealing temperature for Ti foil is 700℃~850℃, holding for 1-4 hours, followed by air cooling / furnace cooling. The annealing temperature for Al foil is 300℃~400℃, holding for 0.5-3 hours, followed by air cooling / furnace cooling. The annealing temperature for Nb foil is 1000℃~1150℃, holding for 0.5-3 hours, followed by air cooling / furnace cooling.

[0088] Afterwards, the foils undergo surface treatment processes such as acid / alkali washing, ultrasonic cleaning, and drying to remove surface contaminants and oxide layers. Ti and Nb foils are cleaned with a 5%–15% (v / v) HF solution, followed by ultrasonic cleaning, rinsing with distilled water, and then dried with a hairdryer on a cool setting. Al foils are cleaned with a 5%–15% (v / v) NaOH solution, followed by ultrasonic cleaning, rinsing with distilled water, and then dried with a hairdryer on a cool setting.

[0089] After being made into suitable specifications and subjected to heat treatment and surface treatment, the metal elemental foils are stacked alternately to form a multilayer metal elemental foil. The multilayer foil is then rolled into a cylindrical shape under the support of a mandrel. The mandrel is cylindrical or tubular, with a length of 300mm and a diameter of 34mm. The material can be an elastic material such as polyurethane or a rigid material such as low-carbon steel. After rolling, the mandrel is removed, resulting in a prefabricated multilayer foil roll with a certain overlap.

[0090] S2: Design and process the upper and lower molds according to the shape of the target pipe fitting, and then install them on the upper and lower platforms of the press, respectively. The length of the mold is the length of the preform + two process sections L2 + 2 × 30mm = 336mm. The purpose of the process sections is to facilitate the installation of the left and right punches. Place the laminated foil roll preform into the forming mold with the cavity of the target pipe fitting, and then fill the inner cavity of the laminated foil roll preform with solid granular medium. The axial sides of the preform are limited and pre-tightened by the left and right punches. The solid granular medium is selected from high-temperature resistant ceramic or metal particles / powders with a particle size of 0.01mm-0.5mm.

[0091] During the room temperature internal pressure forming process, the hydraulic horizontal cylinder on the press platform applies axial pressure to the solid particulate medium and acts on the inner wall of the laminated foil roll, causing it to move and plastically deform at room temperature until the laminated foil roll adheres tightly to the mold cavity, forming a laminated tube with the target shape.

[0092] Lateral pressure inside the cylinder required for forming laminated foil roll preforms ;in, The yield stress of a certain metal foil is given by (the yield strength of annealed Ti foil is taken as 200 MPa, the yield strength of annealed Al foil is taken as 20 MPa, and the yield strength of annealed Nb foil is taken as 150 MPa). The thickness of a certain metal foil roll is (Ti foil thickness is 0.106mm×11=1.17mm, Al foil thickness is 0.042×11=0.46mm, Nb foil thickness is 0.052×11=0.57mm). Let 38mm be the radius of a certain metal foil roll; The foil roll bearing capacity factor is set to 1. The value is 3, representing the number of types of single-element metal foil rolls. Therefore, the internal lateral pressure required for forming the laminated foil roll preform is calculated to be 9.0 MPa.

[0093] Lateral pressure inside the cylinder required for shaping laminated foil roll preforms ;in, The minimum radius for forming the pipe fitting is set to 15mm. At this point, the preform is basically attached to the mold. Due to the frictional force of the mold on the outside of the preform, the shaping process of the preform is simplified to an integral pipe blank, i.e., the foil roll bearing capacity. The value is 1. Therefore, the internal lateral pressure required for shaping the laminated foil roll preform is calculated to be 22.8 MPa.

[0094] When axial pressure is applied to the solid particles inside the preform via a horizontal cylinder, the lateral pressure inside the cylinder... The distribution along the axial direction of the foil roll preform satisfies: ;in, This is the distance from the axial end of the foil roll to the axial center of the foil roll. This indicates the position where the lateral pressure inside the cylinder is 0; This represents the axial pressure applied by the platform's horizontal cylinder; a and c are constants related to the particle material, particle diameter, and cylinder diameter. Based on the above pipe dimensions and simulation results, a is taken as 0.005, b as 170, and c as 0.82. It is necessary to ensure that the minimum lateral pressure inside the cylinder is greater than the lateral pressure required for shaping the laminated foil roll preform; therefore, the calculated axial pressure applied by the horizontal cylinder should be greater than 262 MPa. Based on the axial projected area of ​​the pipe, the axial force applied by the horizontal cylinder is greater than 175 tons.

[0095] Based on the maximum lateral pressure inside the cylinder and the projected area of ​​the component in the horizontal direction, the clamping force of the upper and lower platforms of the press should be greater than 560 tons.

[0096] S3: High-temperature in-situ reaction: After room temperature internal pressure forming, without opening the mold, the forming mold, stacked tubes and filling solid particle medium are heated in-situ according to the preset heating regime, so that a high-temperature diffusion reaction occurs between Ti foil, Al foil and Nb foil, and Ti2AlNb alloy is generated in-situ.

[0097] The high-temperature diffusion reaction process must be carried out in a vacuum environment to prevent air from getting trapped between the stacked foils and to prevent oxidation. Therefore, the press platform needs to be equipped with a vacuum heating furnace, and a vacuum of less than 0.1 Pa must be drawn before heating.

[0098] The high-temperature diffusion reaction of Ti foil, Al foil and Nb foil is divided into three steps: a: below the melting point temperature of Al (660℃), 550-630℃ / 0.5-2h / 5-20MPa; b: below the melting point temperature of TiAl2 (1200℃), 1000-1150℃ / 0.5-2h / 5-20MPa; c: below the melting point temperature of NbAl3 (1600℃), 1300-1400℃ / 0.5-4h / 5-20MPa.

[0099] During the high-temperature diffusion reaction, a lateral pressure of 5 MPa must be maintained inside the laminated pipe fittings. Therefore, the axial force applied by the horizontal cylinder should be greater than 40 tons, and the clamping force of the upper and lower platforms of the press should be greater than 130 tons. The axial force and clamping force must be maintained continuously during the high-temperature diffusion reaction.

[0100] S4: Post-processing: After the reaction is complete, the furnace is cooled to room temperature under controlled cooling. While maintaining the clamping force, the left and right horizontal cylinders are removed, and then the upper and lower molds of the forming die are opened to remove the formed part. At the same time, the solid particulate medium is separated and recovered to obtain the target alloy thin-walled pipe.

[0101] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any other way. Any person skilled in the art may make changes or modifications to the above-disclosed technical content to create equivalent embodiments for application in other fields. However, any simple modifications, equivalent changes, and modifications made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the protection scope of the present invention.

Claims

1. A method for preparing intermetallic compound thin-walled tubular components by lamination of foil rolls under internal pressure forming and high-temperature in-situ reaction, characterized in that, The preparation steps include the following: S1: Preparation of the laminated foil roll preform: Calculate the required thickness ratio of the elemental metal foils based on the atomic ratio of the chemical composition of the target intermetallic compound, and determine the thickness of each elemental metal foil; Based on the dimensions of the target intermetallic compound pipe fitting, calculate and cut the corresponding size of the metal element foil; after the metal element foil is made into the appropriate specifications, it is stacked in an alternating manner to form a metal element laminated foil, and then the laminated foil is rolled into a cylindrical shape under the support of a rigid mandrel. The mandrel is removed to obtain a laminated foil roll preform with a certain overlap. S2: Room temperature internal pressure forming: The laminated foil roll preform is placed in a forming mold with the target tube cavity, and then solid granular medium is filled into the inner cavity of the laminated foil roll preform. The axial sides of the preform are limited by the left and right punches. The hydraulic horizontal cylinder on the press platform applies axial pressure to the solid granular medium and acts on the inner wall of the laminated foil roll, causing material movement and plastic deformation at room temperature until the laminated foil roll adheres tightly to the mold cavity, forming a laminated tube with the target shape. S3: High-temperature in-situ reaction: After room temperature internal pressure forming, without opening the mold, the forming mold, stacked tubes and filling solid particle medium are heated in-situ according to the preset heating regime, so that the metal element foils undergo a high-temperature diffusion reaction and the target alloy is generated in-situ. S4: Post-processing: After the reaction is completed, the furnace is cooled or controlled to room temperature. While maintaining the clamping force, the left and right horizontal cylinders are removed, and the upper and lower molds of the forming mold are opened to remove the formed part. At the same time, the solid particulate medium is separated and recovered to obtain the target alloy thin-walled pipe.

2. The method for preparing intermetallic compound thin-walled tubular components by lamination foil roll internal compression forming-high temperature in-situ reaction composite according to claim 1, characterized in that, Step S1 also includes the following steps: S1.1: Annealing heat treatment is performed on the metal elemental foil used to prepare the target alloy to improve the room temperature forming performance of the foil. Then, surface treatment processes such as pickling / alkali washing, ultrasonic cleaning, and drying are performed to remove dirt and oxide layer from the foil surface. S1.2: The method for calculating the length and width dimensions of a metallic foil is as follows: Let the length of the intermetallic compound tube be L1, then the length of the laminated foil roll preform is L2 = (1 + n)L1, where n is the proportion of the axial length of the process section, taken as 20%; the width of the foil is W = (1 + n)L 1； Let the minimum diameter of the intermetallic compound pipe be R1 and the wall thickness be T1. Then the diameter of the laminated foil roll preform should be R2=R1 / (1+m), where m is the minimum expansion rate, taken as 3~5%; the wall thickness of the laminated foil roll preform is T2=T1(1+o), where o is the thinning rate due to high temperature reaction; considering the overlap amount α, the length of each type of foil needs to be increased to l=2πR2T2 / (TA+TB+TC+…)+2πR2α / 360°, where TA, TB, and TC are the thicknesses of each type of foil.

3. The method for preparing intermetallic compound thin-walled tubular components by lamination of foil rolls under internal pressure forming and high-temperature in-situ reaction according to claim 2, characterized in that, In step S1, the overlap amount refers to the overlap angle α between the outermost and innermost edges of the foil roll. It is determined by theoretical analysis and finite element simulation based on the shape requirements of the target tube, and ensures that the overlap angle α after the stacked tube is formed is less than 30°.

4. The method for preparing intermetallic compound thin-walled tubular components by lamination foil roll internal compression forming-high-temperature in-situ reaction composite according to claim 3, characterized in that, The solid particulate medium in step S2 is selected from high-temperature resistant ceramic or metal particles / powders with a particle size of 0.01mm-0.5mm.

5. The method for preparing intermetallic compound thin-walled tubular components by lamination of foil rolls under internal pressure forming and high-temperature in-situ reaction according to claim 4, characterized in that, The forming mold in step S2 includes an upper mold and a lower mold, which are respectively connected to the upper platform and the lower platform of the press.

6. The method for preparing intermetallic compound thin-walled tubular components by lamination foil roll internal compression forming-high temperature in-situ reaction composite according to claim 6, characterized in that, In step S3, the high-temperature in-situ reaction process maintains the clamping force and axial force loading, and ensures that the minimum internal lateral pressure on the pipe is greater than the critical reaction pressure.

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