Superplastic forming diffusion bonding method for titanium alloy multi-layer structure with large height-width ratio

Abstract

The invention discloses a titanium alloy large-aspect-ratio multilayer structure superplastic forming diffusion bonding method, and relates to the field of high-temperature titanium alloy superplastic forming, the titanium alloy large-aspect-ratio multilayer structure superplastic forming diffusion bonding method is used for forming a grid structure, the grid structure comprises two panels, and a vertical rib structure is formed between the two panels through a core veneer, and the titanium alloy large-aspect-ratio multilayer structure superplastic forming diffusion bonding method comprises the steps that simulation calculation is conducted on the superplastic forming process of the grid structure, analyzing the thickness distribution of the core plate after superplastic forming, and determining an easy-to-crack area of the core plate; the panel is pre-formed, and a formed panel is obtained; performing strain pre-dispersion on the core plate according to the easy-to-crack area of the core plate, and finally performing superplastic forming between the core plate and the formed panel. The core plate is pre-formed, and the strain distribution of the core plate is changed, so that the original easy-to-crack area is thickened in the superplastic forming process, and the crack is avoided.

Description

Technical Field

[0001] The present application belongs to the technical field of superplastic forming of high-temperature titanium alloys, and in particular relates to a superplastic forming diffusion bonding method for a titanium alloy multilayer structure with a large aspect ratio. Background Art

[0002] Aerospace-related equipment has stringent requirements for lightweight structures. At the same time, its surface faces severe aerodynamic heating. High-temperature titanium alloys with the characteristics of light weight, high strength and high temperature resistance are widely used in the load-bearing structures of aerospace-related equipment.

[0003] At present, the load-bearing structures of aerospace-related equipment mostly adopt complex hollow structures to reduce weight. The hollow multi-layer structure requires sufficient grid density to ensure structural strength. For thick structures, the grid aspect ratio is large. However, high-temperature titanium alloys have insufficient superplastic deformation capacity, and cracking and failure often occur during the forming process of large aspect ratio grids. This limits the application of high-temperature titanium alloys and hinders the further development of aerospace-related equipment. Summary of the invention

[0004] The technical problem solved by the present application is: to overcome the shortcomings of the prior art and provide a method for strain pre-dispersed superplastic forming diffusion bonding of a titanium alloy multi-layer structure with a large aspect ratio. In view of the problem of cracking and failure that is prone to occur during the superplastic forming of a four-layer structure with a large aspect ratio, it is proposed to pre-form the core plate and change the strain distribution of the core plate so that the original crack-prone area during the superplastic forming process is thickened to avoid cracking.

[0005] The technical solutions provided by this application are as follows:

[0006] A superplastic forming diffusion bonding method for a titanium alloy high aspect ratio multilayer structure is used to form a grid structure, wherein the grid structure includes two panels, and a rib structure is formed between the two panels through a core plate, including:

[0007] The superplastic forming process of the grid structure is simulated and calculated, the thickness distribution of the core plate after superplastic forming is analyzed, and the core plate's prone-to-breakage area is determined;

[0008] Preforming the panel to obtain a formed panel;

[0009] According to the core plate's prone-to-break area, the core plate is strain pre-dispersed, and finally superplastic forming is performed between the core plate and the formed rear panel.

[0010] The method of pre-dispersing the strain of the core plate according to the easily ruptured area of ​​the core plate, and finally performing superplastic forming between the core plate and the formed rear panel, comprises:

[0011] The core plate preforming mold is determined according to the core plate prone to rupture area. The core plate preforming mold includes a preforming upper mold and a preforming lower mold. The side of the preforming upper mold facing the preforming lower mold is a non-planar surface, and the side of the preforming lower mold facing the preforming upper mold cooperates with the non-planar surface of the preforming lower mold; and the core plate preforming and superplastic forming processes are jointly simulated. If the core plate still has the risk of rupture, the non-planar surface of the preforming upper mold is iteratively optimized until the core plate has no risk of rupture during the forming process;

[0012] After the blank is cut, the face plate and core plate are obtained;

[0013] Placing two core plates between a preforming upper die and a preforming lower die, and performing hot pressing to obtain a preformed core plate;

[0014] The preformed core plate forms a plurality of protrusions in sequence starting from one end thereof, the plane portion between two adjacent protrusions is a diffusion connection area between the two preformed core plates, the other portions between the two preformed core plates are non-diffusion connection areas, and the preformed core plate and the formed rear panel are diffusion connection areas; the non-diffusion connection areas of the formed rear panel and the preformed core plate are coated with solder resist; the rear periphery is sealed and welded after assembling in the order of the formed rear panel, the preformed core plate, the preformed core plate, and the formed rear panel, and the opposite sides of the two preformed core plates are bonded to obtain a sealed welded part;

[0015] The seal is placed in the final forming mold for superplastic forming between the preformed core plate and the formed rear panel.

[0016] The surface of the preformed upper die has a plurality of protrusions, and a plane portion is provided between two adjacent protrusions. The position of the plane portion corresponds to the position of the vertical ribs of the grid structure, and the protrusion surface and the plane portion form a non-planar surface.

[0017] The step of placing the sealing weld part into the final forming mold to perform superplastic forming between the preformed core plate and the formed rear panel comprises:

[0018] After the sealing weld is loaded into the final forming mold and heated up, the first chamber is formed between the two preformed core plates and one formed rear panel, the second chamber is formed between the two preformed core plates and the other formed rear panel, and the third chamber is formed between the two preformed core plates. High-pressure gas is filled into the first chamber and the second chamber to achieve diffusion connection between the two preformed core plates, and then high-pressure gas is filled into the third chamber to achieve superplastic forming diffusion connection between the preformed core plate and the formed rear panel to obtain a formed part.

[0019] The panel is preformed to obtain a formed rear panel, including: coating a solder resist between two panels and performing sealing, placing the two panels in a final forming mold, filling high-pressure gas between the two panels for superplastic forming, and cutting and separating the two panels after the forming is completed to obtain the formed rear panel.

[0020] The method of pre-dispersing the strain of the core plate according to the easily ruptured area of ​​the core plate, and finally performing superplastic forming between the core plate and the formed rear panel, comprises:

[0021] The pads are determined according to the core plate's prone-to-fracture area, and the core plate preforming and superplastic forming processes are jointly simulated. If the core plate still has the risk of rupture, the shape, size, and position of the pads are iteratively optimized until the core plate has no risk of rupture during the forming process.

[0022] After blanking, pads, panels and core plates are obtained;

[0023] The pad is located between the two core plates, the two ends of the pad and the two core plates are diffusion connection areas, the other positions between the two core plates are non-diffusion connection areas, and the core plate and the formed rear panel are diffusion connection areas; the non-diffusion connection areas of the formed rear panel, the core plate and the pad are coated with solder resist, and the formed rear panel, the core plate, the pad, the core plate, and the formed rear panel are assembled in the order and the edges are sealed and welded to obtain a sealed welded part;

[0024] The seal is placed in the final forming mold for superplastic forming between the preformed core plate and the formed rear panel.

[0025] Before the forming rear panel, core plate, cushion block, core plate and formed rear panel are assembled in order and the edges are sealed and welded, the process includes: spot welding the cushion block and the core plate to position them.

[0026] In summary, this application at least includes the following beneficial technical effects:

[0027] The present invention provides a method for superplastic forming diffusion bonding of a titanium alloy multilayer structure with a large aspect ratio. The core plate is preformed before superplastic forming to change the thickness distribution of the core plate, thereby avoiding the risk of cracking during the superplastic forming of the core plate, realizing the forming of a four-layer structure with a large aspect ratio, and expanding the application range of the titanium alloy multilayer hollow structure. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 It is a four-layer reinforced structure;

[0029] Figure 2 for Figure 1 The forming process;

[0030] Figure 3 Optimize the design process for preforming tools;

[0031] Figure 4 This is a schematic diagram of core plate preforming;

[0032] Figure 5 It is a schematic diagram of panel preforming;

[0033] Figure 6It is a schematic diagram of the final forming of the multi-layer structure;

[0034] Figure 7 Optimize the design process for pads;

[0035] Figure 8 Provide schematic diagrams for assembling panels, core boards and spacers;

[0036] Fig. 9 Schematic diagram of superplastic final forming of a multi-layer structure using a spacer;

[0037] Fig.10 Schematic diagram of the forming mold.

[0038] Explanation of the reference numerals: 1. core board; 11. protrusion; 12. plane part; 2. panel; 3. rib structure;

[0039] 31. preforming upper die; 32. preforming lower die;

[0040] 41. Final forming upper die; 411. Air pipe groove; 42. Final forming lower die;

[0041] 51, first chamber; 52, second chamber; 53, third chamber;

[0042] 6. Pad. DETAILED DESCRIPTION

[0043] In order to make the objectives, technical solutions and advantages of the present invention more clear, the embodiments disclosed in the present invention will be further described in detail below with reference to the accompanying drawings.

[0044] for Figure 1 and Figure 2 The four-layer vertical rib structure shown is currently formed by superplastic forming / diffusion bonding method. During the forming process, the core plate 1 is blown from a flat plate into a grid by high-pressure inert gas. When the height-to-width ratio of the grid is large, the core plate 1 deforms greatly and is easily broken due to local excessive thinning.

[0045] The embodiment of the present application discloses a method for superplastic forming diffusion bonding of a titanium alloy multilayer structure with a large aspect ratio, which is used to form a grid structure, wherein the grid structure includes two panels 2, and a rib structure is formed between the two panels 2 through a core plate 1. The method of the present patent pre-disperses the strain of the core plate 1, changes its strain distribution, thickens the area with a risk of rupture, avoids the risk of rupture, and realizes the formation of a multilayer structure with a large aspect ratio. There are two methods to realize the strain pre-dispersion process of the core plate 1.

[0046] Method 1 is to use a pre-forming mold to achieve core plate strain pre-dispersion

[0047] 1. Optimize the pre-forming mold surface. Figure 3 shown.

[0048] The superplastic forming process of the grid structure with a large aspect ratio is simulated and calculated, and the thickness distribution of the core plate 1 after superplastic forming is analyzed to determine the area of ​​the core plate that is prone to rupture. A core plate preforming mold is designed based on the area of ​​the core plate that is prone to rupture. Specifically, the thinnest area of ​​the core plate is obtained according to the finite element simulation calculation, and this area is used as the center of the raised area of ​​the preforming mold, and a smooth transition is made to the non-raised area of ​​the preforming mold, that is, the diffusion connection area of ​​the core plate. The core plate preforming and superplastic forming processes are jointly simulated. If the core plate still has the risk of rupture, the preforming mold is iteratively optimized to ensure that there is no risk of rupture of the core plate 1 during the forming process, and to obtain the simulation optimization result.

[0049] The preforming mold includes a preforming upper mold 31 and a preforming lower mold 32. The side of the preforming upper mold 31 facing the preforming lower mold 32 is a non-planar surface, and the side of the preforming lower mold 32 facing the preforming upper mold 31 cooperates with the non-planar surface of the preforming lower mold 32. Among them, the non-planar surface can be formed by: a plurality of trapezoidal protrusions 11 on the surface of the preforming upper mold 31, or a plurality of arc-shaped protrusions 11 on the surface. In this embodiment, there are a plurality of trapezoidal protrusions 11 on the surface of the preforming upper mold 31, and there is a plane part 12 between two adjacent trapezoidal protrusions 11. The position of the plane part 12 corresponds to the position of the vertical rib structure 3 of the grid structure, and the surface of the protrusion 11 and the plane part 12 form a non-planar surface.

[0050] 2. Mould design and manufacturing: Manufacture pre-forming moulds and final forming moulds according to the simulation optimization results.

[0051] like Fig.10 As shown, the final forming mold includes a final forming upper mold 41 and a final forming lower mold 42. The forming cavities on the opposite sides of the final forming upper mold 41 and the final forming lower mold 42 collide with the shape of the four-layer vertical rib structure. A plurality of air pipe grooves 411 are provided on the opposite sides of the final forming upper mold 41 and the final forming lower mold 42 to allow air pipes to pass into the final forming mold. Different air pipes are connected to the first cavity 51, the second cavity 52 and the third cavity 53 respectively.

[0052] 3. Blanking. Blanks are prepared according to the structure to be prepared. After blanking, the face plate 2 and the core plate 1 are obtained. The face plate 2 and the core plate 1 are surface treated to ensure that the surface is clean and free of oxidation.

[0053] 4. Preform the core plate 1. Figure 4 As shown, the two core plates 1 are hot-pressed by using a preforming die, that is, the two core plates 1 are placed between a preforming upper die 31 and a preforming lower die 32 for hot-pressing, which increases the sheet length of the core plates 1, and more sheets participate in deformation in the final superplastic forming process. After the forming is completed, the surface is treated to ensure that the surface is clean and free of oxidation, and a preformed core plate is obtained.

[0054] 5. Preform the panel 2. Figure 5 As shown, the two panels 2 are coated with solder resist and sealed, and the panels 2 are superplastic formed using a final forming mold. High-pressure gas is filled between the two panels 2 for superplastic forming. After forming, the two panels 2 are cut and separated, and surface treatment is performed to ensure that the surface is clean and free of oxidation, so as to obtain the formed panel.

[0055] 6. The multi-layer structure is finally formed. Figure 6 As shown, the preformed core plate forms a plurality of complete trapezoidal protrusions in sequence starting from one end thereof, the plane portion between two adjacent trapezoidal protrusions is the diffusion connection area between the two preformed core plates, the other portions between the two preformed core plates are the non-diffusion connection areas, and the preformed core plate and the formed rear panel are all diffusion connection areas; in order to form a multi-layer grid structure, it is necessary to coat the non-diffusion connection areas of the formed rear panel and the preformed core plate with solder resist; the periphery is sealed and welded after assembling in the order of the formed rear panel, the preformed core plate, the preformed core plate, and the formed rear panel, and the opposite sides of the two preformed core plates are fitted together to obtain a sealed welded part;

[0056] The sealing welded parts are placed in the final forming mold. The first cavity 51 is between the two pre-formed core plates and one formed rear panel, the second cavity 52 is between the two pre-formed core plates and the other formed rear panel, and the third cavity 53 is between the two pre-formed core plates. Figure 6 The first chamber 51 and the second chamber 52 shown are filled with high-pressure gas to achieve diffusion connection between the two preformed core plates, and then the third chamber 53 is filled with high-pressure gas to achieve superplastic forming diffusion connection between the preformed core plate and the formed rear panel to obtain a formed part.

[0057] 7. Residue removal: Mechanical processing removes the peripheral margin of the formed part.

[0058] Method 2 is to use spacer 6 to achieve core plate strain pre-dispersion

[0059] 1. Optimize the shape, size and position of the pad 6. Figure 7 As shown, the superplastic forming process of the structure with a large aspect ratio is simulated and calculated, the thickness distribution of the core plate after superplastic forming is analyzed, and the core plate is easily broken. The cushion block 6 is designed according to the core plate easily broken area. Specifically, according to the finite element simulation calculation, the core plate thickness is the thinnest area, and the cushion block is set near this area. The shape, height and position of each cushion block can be different. Fig. 9During the inward deformation of the core plate, due to the supporting effect of the pad, the stress state of the core plate changes, and the thinning area of ​​the core plate changes, thereby avoiding the risk of core plate rupture; determine the pad 6, the position of the pad 6 is opposite to the position of the vertical rib structure, and simulate the positive and negative bulging superplastic forming process of the core plate. If the core plate still has the risk of rupture, iteratively optimize the shape, size, and position of the pad 6 to ensure that there is no risk of rupture of the core plate during the forming process.

[0060] 2. Manufacturing of the cushion block 6 and the mold The cushion block 6 is manufactured according to the results of the simulation optimization.

[0061] 3. Blank cutting. Blanks are prepared according to the structure to be prepared. After blank cutting, face plates and core plates are obtained. The face plates and core plates are surface treated to ensure that the surface is clean and free of oxidation.

[0062] 4. Panel preforming. Apply solder resist between the two panels and perform sealing. Use the final forming mold to perform superplastic forming on the panels, such as Figure 5 As shown, after the forming is completed, the two panels are cut and separated, and surface treatment is performed to ensure that the surface is clean and free of oxidation to obtain the formed panel.

[0063] 5. Assemble and seal. The spacer 6 is located between the two core plates. The two ends of the spacer 6 and the two core plates are diffusion connection areas. The other positions between the two core plates are non-diffusion connection areas. The core plate and the formed rear panel are diffusion connection areas. First, the non-diffusion connection areas of the formed rear panel, the core plate and the spacer 6 are coated with solder resist, and the spacer 6 and the core plate are spot welded in advance. Then, they are assembled and sealed in the order of the formed rear panel, the core plate, the spacer 6, the core plate, and the formed rear panel to obtain a sealed component. Figure 8 shown.

[0064] 6. Final formation of multi-layer structure. After the sealing welding parts are loaded into the final forming mold and heated in the furnace, first Fig. 9 The first chamber 51 and the second chamber 52 shown are filled with high-pressure gas to realize the positive expansion process of the core plate, increase the deformation area of ​​the core plate, and complete the diffusion forming of the core plate and the end of the pad 6, and then the third chamber 53 is filled with high-pressure gas to realize the reverse expansion superplastic forming and diffusion connection process of the core plate.

[0065] 7. Removal of excess. Mechanical processing removes the peripheral excess.

[0066] Specific implementation plan

[0067] This example provides a design and forming method for a titanium alloy multilayer structure with a large aspect ratio. The material is TC4 titanium alloy, the diffusion bonding and superplastic forming temperature is 920°C, and the formed part is a box-shaped part with a length of 600mm, a width of 400mm, and a thickness of 70mm. The specific method steps are as follows:

[0068] First, design the process parts. Design the process allowance area on the part model to obtain the process part model, simulate the superplastic forming process of the process parts with large aspect ratio, analyze the superplastic forming thickness distribution of the core plate, and determine the core plate prone to rupture area.

[0069] Second, the core plate preforming mold is designed according to the core plate superplastic forming simulation results, and the core plate preforming process is simulated and calculated to analyze the core plate preforming thickness distribution. According to the core plate preforming thickness distribution results, the superplastic forming simulation calculation of the preformed core plate is performed to analyze the core plate thickness distribution. If there are still easy-to-break areas in the core plate, the thickness distribution of the preformed core plate is changed by iteratively optimizing the core plate preforming mold to ensure that there are no easy-to-break areas in the preformed core plate during the superplastic forming process. The pressure-time curves of the panel superplastic forming and the core plate superplastic forming can be obtained from the simulation calculation.

[0070] Third, mold design and manufacturing. Design and manufacture the forming mold according to the designed process parts, such as Fig.10 shown.

[0071] Fourth, blank cutting. The blank is designed and prepared according to the structure to be prepared. After the blank is cut, it needs to be surface treated to ensure that the surface is clean and free of oxidation.

[0072] Fifth, core plate preforming. Use preforming mold to hot press the core plate. The forming temperature is 700℃, and the preforming mold is closed and the pressure is maintained for 10 minutes. After the core plate is preformed, the surface is treated to ensure that the surface is clean and free of oxidation.

[0073] Sixth, pre-forming the panel. Coat the two panels with solder resist and seal them. Figure 3 As shown in the figure, the mold is loaded into the furnace, and the mold is closed when the temperature reaches 700℃, and the pressure is 10t. After the temperature continues to rise to the diffusion bonding temperature of 920℃, high-pressure inert gas is filled into the cavity between the two panels, and the pressure loading is performed according to the panel superplastic forming pressure-time loading curve obtained by simulation, so as to realize the superplastic forming of the panel. After the panel is pre-formed, it is cut open, the two panels are separated, and the surface is treated to ensure that the surface is clean and free of oxidation.

[0074] Seventh, the core board and the core board are diffused and connected. The non-diffusion connection area of ​​the panel and the preformed core board is coated with solder resist, and the periphery is sealed after the panel and the core board are assembled. Figure 5 As shown in the figure, the mold is loaded into the furnace, and the mold is closed when the temperature reaches 700℃, and the pressure is 10t. After the temperature continues to rise to the diffusion bonding temperature of 920℃, high-pressure inert gas is filled into the cavity between the two layers of the panel, and the gas pressure is raised to 2MPa, and the pressure is maintained for 2h. At the same time, the cavity between the two layers of the core board is evacuated, so that the core boards are diffused and bonded.

[0075] Eighth, superplastic forming of the core plate. The air pressure in the cavity between the two layers of the panel is reduced to 0.1 MPa, and then high-pressure inert gas is filled into the cavity between the two layers of the core plate. According to the simulated core plate superplastic forming air pressure-time loading curve, air pressure loading is performed to achieve superplastic forming of the core plate.

[0076] Ninth, diffusion bonding between the core plate and the face plate. The air pressure in the cavity between the two core plates is raised to 2 MPa and maintained for 2 hours to complete the diffusion bonding between the core plate and the face plate.

[0077] Tenth, cool down the furnace, take out the parts, and perform mechanical processing to remove the excess.

[0078] The contents not described in detail in this application specification belong to the common knowledge of those skilled in the art.

[0079] The present application is described in detail above in conjunction with specific implementation methods and exemplary examples, but these descriptions cannot be understood as limiting the present application. Those skilled in the art understand that, without departing from the spirit and scope of the present application, a variety of equivalent replacements, modifications or improvements can be made to the technical solution of the present application and its implementation methods, all of which fall within the scope of the present application. The scope of protection of the present application shall be subject to the attached claims.

Claims

1. A method for superplastic forming and diffusion bonding of a titanium alloy high aspect ratio multilayer structure, used for forming a grid structure, the grid structure comprising two face plates (2), a rib structure (3) formed between the two face plates (2) through a core plate (1), characterized in that: include: Simulating the superplastic forming process of the grid structure, analyzing the thickness distribution of the core plate (1) after superplastic forming, and determining the easily ruptured area of ​​the core plate (1); Preforming the panel (2) to obtain a formed panel (2); According to the easily ruptured area of ​​the core plate (1), the strain of the core plate (1) is pre-dispersed, and finally superplastic forming is performed between the core plate (1) and the formed rear panel (2).

2. The method for superplastic forming and diffusion bonding of a titanium alloy high aspect ratio multilayer structure according to claim 1, characterized in that: The method comprises: pre-dispersing the strain of the core plate (1) according to the easily ruptured area of ​​the core plate (1), and finally performing superplastic forming between the core plate (1) and the formed rear panel (2), comprising: A preforming mold of the core plate (1) is determined according to the easily fractured area of ​​the core plate (1), wherein the preforming mold of the core plate (1) comprises a preforming upper mold (31) and a preforming lower mold (32), wherein the side of the preforming upper mold (31) facing the preforming lower mold (32) is a non-planar surface, and the side of the preforming lower mold (32) facing the preforming upper mold (31) cooperates with the non-planar surface of the preforming lower mold (32); and a joint simulation is performed on the preforming and superplastic forming processes of the core plate (1); if the core plate (1) still has a risk of fracture, the non-planar surface of the preforming upper mold (31) is iteratively optimized until the core plate (1) is free of the risk of fracture during the forming process; After the blank is cut, a face plate (2) and a core plate (1) are obtained; Placing two core plates (1) between a preforming upper die (31) and a preforming lower die (32) and performing hot pressing to obtain a preformed core plate (1); A plurality of protrusions (11) are sequentially formed on a preformed core plate (1) starting from one end thereof, a flat portion (12) between two adjacent protrusions (11) is a diffusion connection area between the two preformed core plates (1), the other portions between the two preformed core plates (1) are non-diffusion connection areas, and the preformed core plate (1) and the formed rear panel (2) are all diffusion connection areas; a solder resist is coated on the non-diffusion connection areas of the formed rear panel (2) and the preformed core plate (1); the peripheries are sealed and welded after being assembled in the order of the formed rear panel (2), the preformed core plate (1), the preformed core plate (1), and the formed rear panel (2), and the opposite sides of the two preformed core plates (1) are bonded to obtain a sealed welded part; The sealing member is placed in a final forming mold to perform superplastic forming between the preformed core plate (1) and the formed rear panel (2).

3. The method for superplastic forming and diffusion bonding of a titanium alloy high aspect ratio multilayer structure according to claim 2, characterized in that: The surface of the preforming upper mold (31) has a plurality of protrusions (11), a plane portion (12) is provided between two adjacent protrusions (11), the position of the plane portion (12) corresponds to the position of the vertical ribs of the grid structure, and the surface of the protrusion (11) and the plane portion (12) form a non-planar surface.

4. The method for superplastic forming and diffusion bonding of a titanium alloy high aspect ratio multilayer structure according to claim 2, characterized in that: The step of placing the sealing weld part into a final forming mold to perform superplastic forming between the preformed core plate (1) and the formed rear panel (2) comprises: After the sealing parts are loaded into the final forming mold and heated, a first chamber (51) is formed between the two preformed core plates (1) and one formed rear panel (2), a second chamber (52) is formed between the two preformed core plates (1) and the other formed rear panel (2), and a third chamber (53) is formed between the two preformed core plates (1). High-pressure gas is filled into the first chamber (51) and the second chamber (52) to achieve diffusion connection between the two preformed core plates (1), and then high-pressure gas is filled into the third chamber (53) to achieve superplastic forming diffusion connection between the preformed core plate (1) and the formed rear panel (2), thereby obtaining a formed part.

5. The method for superplastic forming and diffusion bonding of a titanium alloy high aspect ratio multilayer structure according to claim 1, characterized in that: The panel (2) is preformed to obtain a formed panel (2), comprising: coating a solder resist between two panels (2) and performing sealing welding, placing the two panels (2) in a final forming mold, injecting high-pressure gas between the two panels (2) to perform superplastic forming, and cutting and separating the two panels (2) after the forming is completed to obtain the formed panel (2).

6. The method for superplastic forming and diffusion bonding of a titanium alloy multilayer structure with a large aspect ratio according to claim 1, characterized in that: The method comprises: pre-dispersing the strain of the core plate (1) according to the easily ruptured area of ​​the core plate (1), and finally performing superplastic forming between the core plate (1) and the formed rear panel (2), comprising: The cushion block (6) is determined according to the easily broken area of ​​the core plate (1), and the preforming and superplastic forming processes of the core plate (1) are jointly simulated. If the core plate (1) still has the risk of breaking, the shape, size and position of the cushion block (6) are iteratively optimized until the core plate (1) has no risk of breaking during the forming process; After blanking, a spacer block (6), a face plate (2) and a core plate (1) are obtained; The pad (6) is located between the two core plates (1); the two ends of the pad (6) and the two core plates (1) are diffusion connection areas; the other positions between the two core plates (1) are non-diffusion connection areas; and the core plate (1) and the formed rear panel (2) are diffusion connection areas; the non-diffusion connection areas of the formed rear panel (2), the core plate (1) and the pad (6) are coated with solder resist; the formed rear panel (2), the core plate (1), the pad (6), the core plate (1), and the formed rear panel (2) are assembled in the order of the formed rear panel (2), the core plate (1), the pad (6), the core plate (1), and the formed rear panel (2), and the edges are sealed and welded to obtain a sealed welded part; The sealing member is placed in a final forming mold to perform superplastic forming between the preformed core plate (1) and the formed rear panel (2).

7. The method for superplastic forming and diffusion bonding of a titanium alloy multilayer structure with a large aspect ratio according to claim 6, characterized in that: Before assembling and sealing the edges of the formed rear panel (2), the core panel (1), the cushion block (6), the core panel (1), and the formed rear panel (2) in this order, the process includes: spot welding the cushion block (6) and the core panel (1) to position them.

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