Atmosphere protection-vacuum infiltration composite integrated aluminum-based porous sandwich panel preparation method

Abstract

The application relates to a preparation method of an atmosphere-protection-vacuum infiltration composite integrated aluminum-based porous sandwich plate, and belongs to the technical field of layered porous composite material preparation. The application provides a preparation method of an atmosphere-protection-vacuum infiltration composite integrated aluminum-based porous sandwich plate, which comprises plate type mold assembly, filler, vacuum infiltration casting and material cooling and forming processing, and an aluminum-based porous sandwich plate with excellent surface performance and metallurgical combination between foamed aluminum and a metal plate surface is prepared. The infiltration process is completed in an integrated furnace, and the problem of high-temperature oxidation is effectively avoided, so that the quality of the interface metallurgical combination is obviously improved. Meanwhile, effective infiltration can be realized under the condition of lower heat input, the surface flatness and integrity of the sandwich plate are obviously improved, heat input is more easily controlled, and batch stable production is facilitated.

Description

Technical Field

[0001] This invention belongs to the field of layered porous composite material preparation technology, and relates to a method for preparing an integrated aluminum-based porous sandwich panel with atmosphere protection and vacuum infiltration. Background Technology

[0002] Aluminum-based porous composite sandwich panels are a new type of composite material that integrates structure and function. They possess characteristics such as high strength, excellent impact resistance, high specific stiffness and strength, excellent thermal and sound insulation properties, and good electromagnetic shielding performance. Unlike aluminum foam sandwich panels, their structure typically consists of two face panels sandwiching a core layer of aluminum-based porous composite material. Based on these properties, aluminum-based porous composite sandwich panels have broad application prospects in aerospace, automotive, construction, and defense industries.

[0003] Besides the materials of the face and core layers, the bonding method between the face and core layers is also a factor affecting the performance of aluminum-based porous composite sandwich panels. Existing main preparation methods typically include: adhesive bonding, welding, powder metallurgy, and pressure percolation. Adhesive bonding is relatively simple but suffers from insufficient bond strength and susceptibility to aging at high temperatures, while welding requires high sample flatness and is more complex. Metallurgical bonding offers high bond strength, while powder metallurgy has stringent process requirements and the interface between the core layer and the metal plate is not smooth.

[0004] Invention patent CN114030262A discloses a method for preparing a foam metal sandwich panel with interfacial metal bonding. This method involves introducing a low-melting-point interlayer between the core layer and the panel, applying pressure after melting the interlayer, and enhancing the interfacial bonding by opening and grooving the foam metal. However, this method has the following shortcomings: First, it is suitable for foam metals with surface pore structures to achieve mechanical interlocking, while aluminum-based porous composite materials have smaller pore sizes and denser structures, making it difficult to form effective mechanical interlocking. Second, this method essentially relies on the interlayer for bonding; a direct metallurgical bond is not formed between the panel and the core layer, and the bonding strength is still limited by the performance of the interlayer.

[0005] Invention patent CN120735459A discloses an integrated molding method for aluminum-based porous composite sandwich panels. The method involves combining the panel and core material (ceramic hollow spheres) in a mold to form a preform. The mold and aluminum alloy are preheated separately under a protective atmosphere. Then, molten aluminum is poured into the mold and forced into the gaps between the hollow spheres under pressure. After cooling, the aluminum-based porous composite sandwich panel is obtained. This method solves the problems of uneven interface and difficulty in controlling layer thickness to some extent, but it still has the following drawbacks: First, the pressure infiltration method requires pressurizing the preheated mold using a press. Since this method lacks a protective atmosphere during preparation, the metal panel will rapidly oxidize at high temperatures without such protection, affecting the interface bonding. Furthermore, the pressurized infiltration process is difficult to implement due to the large size of the press and the multiple steps required from removing the preheated mold to pressurized infiltration, while also needing to meet high-temperature resistance requirements. Therefore, it is difficult to install a protective atmosphere device to eliminate the high-temperature oxidation problem of the metal panel during the preheating to pressurized infiltration stage. In addition, when the metal panel is made of low-melting-point metals such as aluminum alloy, preheating the mold can cause the metal panel to melt, resulting in poor surface quality. This problem arises because existing technologies use pressure casting methods that require pressing on a press table, and it's difficult to heat the mold during the process. Therefore, to prevent the aluminum liquid from seeping out, the process heats the aluminum liquid to 300°C above its melting point. Excessively high aluminum liquid temperature causes the panel to melt during cooling, leading to poor surface quality and uneven interfaces.

[0006] Meanwhile, existing technologies generally only produce one sandwich panel at a time, resulting in low production efficiency. Previous inventions using powder metallurgy-bonded sandwich panels primarily employed horizontal placement during fabrication, making it difficult to produce multiple panels at once. Patents using vertically placed sandwich panels with pressurized percolation set the temperature of the cast aluminum molten metal at 300°C above its melting point to ensure smooth percolation. However, this method is prone to heat accumulation during cooling, leading to sandwich panel fabrication failures, making mass production difficult.

[0007] In summary, existing technologies for preparing aluminum-based porous sandwich panels suffer from several drawbacks. These include the bulky size of the press equipment, poor thermal conductivity of the molds, and limitations in the process flow. The molds need to be transferred to the press table for percolation, leading to defects in the aluminum-based porous composite sandwich panels: increasing the aluminum melt temperature to ensure fluidity causes the metal panels to soften or even partially melt, resulting in surface deformation and collapse; the inability to achieve full-process atmosphere protection during preheating and percolation introduces oxidation risks, affecting the bonding quality between the panel and the core layer; and the long preparation cycle and low production efficiency are due to limitations in the thermal conductivity of the molds and equipment. Therefore, there is an urgent need for a method to prepare aluminum-based porous composite sandwich panels that achieves flat panels, high bonding strength, and mass production capabilities. Summary of the Invention

[0008] This invention aims to provide a method for preparing aluminum-based porous composite sandwich panels using atmosphere protection and percolation technology. This method can produce multiple aluminum-based porous composite sandwich panels with metallurgically bonded core layers in one process, and can ensure that the panels are not oxidized throughout the entire preparation process, while also ensuring that the flatness of the panel surface is within a controllable range.

[0009] To achieve the above objectives, the present invention adopts the following technical solution:

[0010] A method for preparing an integrated aluminum-based porous sandwich panel with atmosphere protection and vacuum infiltration is specifically carried out according to the following steps:

[0011] S1. Plate mold assembly:

[0012] Select a metal panel based on the target sandwich panel, and after cleaning, grinding and smoothing the metal panel, fix and assemble it in the frame structure to obtain the panel mold.

[0013] The plate mold is a through structure, including a rectangular outer shell made of metal plates and partitions distributed in the outer shell at the same height as the outer shell. The partitions divide the frame-shaped outer shell into through cuboid units. The specifications of the cuboid units match the specifications of the target sandwich panel, and the quantity is set according to the requirements.

[0014] During the metal panel assembly process, the metal panels after assembly are fixed in relative positions of each cuboid unit, and the distance between the metal panels is the core layer thickness of the target sandwich panel.

[0015] The metal panel is cleaned with anhydrous ethanol until the surface is free of oil and dust; the thickness of the metal panel does not exceed 60mm.

[0016] The metal panel material mentioned in S1 is one of aluminum alloy, magnesium alloy, steel and titanium alloy;

[0017] S2. Packing material:

[0018] A refractory fiber felt is laid at the bottom of the vacuum infiltration mold. The plate mold opening is placed vertically upwards into the cavity of the infiltration mold. The gap between the outer wall of the plate mold and the inner wall of the infiltration mold is filled with graphite powder and compacted to ensure stable positioning of the plate mold within the infiltration mold. Hollow spheres used to prepare the porous core material are filled into the inner cavity of the plate mold. The hollow spheres are filled and vibrated until they are flush with the upper edge of the plate mold, ensuring that the core material forming area is flat and free of graphite powder contamination.

[0019] The vacuum permeation mold described in S2 consists of three parts: a vacuum permeation mold cover, a graphite sealing ring, and a vacuum permeation mold body. The cover includes an aluminum inlet, a pressure gauge, and a protective gas inlet, and both the aluminum inlet and the protective gas inlet are equipped with sealing valves. The vacuum permeation mold body consists of a cylindrical structure and a vacuum pipe. The vacuum pipe opening is located at the bottom of the cylinder, and the pipe is equipped with a sealing valve.

[0020] The graphite powder in S2 has a particle size of 200-500 mesh, which serves to support, fix, fill, and ensure uniform temperature.

[0021] The hollow spheres in S2 are one or a combination of several of the following: alumina hollow spheres, glass microspheres, fly ash hollow spheres, silicon carbide hollow spheres, and expanded perlite; the average particle size of the hollow spheres is 50μm to 2000μm.

[0022] S3. Vacuum infiltration casting:

[0023] Secure the top cover of the percolation mold to the graphite sealing ring using the flange to ensure a reliable overall seal of the mold, and close the aluminum inlet valve. Connect the vacuum pump and inert gas cylinder to the mold vacuum interface to complete the assembly of the gas path and vacuum system.

[0024] 1. Vacuuming in one step:

[0025] Open the vacuum valve and vacuum pump to evacuate the cavity of the percolation mold, and fully extract the air inside the cavity and the gas trapped in the gaps between the hollow sphere particles.

[0026] 2. Primary protective gas filling:

[0027] Turn off the vacuum pump and vacuum valve, and introduce inert protective gas into the percolation mold to achieve a slight positive pressure inside the mold, allowing the protective gas to fully penetrate the gaps between the hollow sphere particles.

[0028] 3. Secondary vacuuming:

[0029] The vacuum pump and vacuum valve are turned on again to perform a second vacuuming, further extracting the residual gas in the gaps between the hollow spheres and graphite powder to ensure that the percolation mold cavity is clean and oxygen-free.

[0030] 4. Secondary protective gas pressure maintenance:

[0031] Turn off the vacuum pump and vacuum valve, and reintroduce inert protective gas to maintain a stable slight positive pressure inside the mold, ensuring that the entire cavity of the seepage mold and the gap between the hollow spheres are under a protective atmosphere.

[0032] After atmosphere replacement is completed, the entire infiltration mold is placed in a heating furnace for preheating. The preheating temperature is lower than the melting point of the metal panel, and the temperature is maintained for 2-4 hours to ensure uniform temperature inside and outside the infiltration mold. During the preheating of the infiltration mold, aluminum raw materials are weighed, heated and melted, kept at a constant temperature to remove gas, and then allowed to stand. After both the preheating of the infiltration mold and the melting of the aluminum alloy are completed, the infiltration mold is kept in a preheated state, the aluminum inlet valve is opened, and molten aluminum is injected to completely cover the mold filling area. After the molten aluminum covers the area, the protective atmosphere is immediately turned off, and the vacuum system is simultaneously turned on. The system vacuum degree is controlled at -0.03MPa to -0.09MPa (gauge pressure). Under negative pressure, the molten aluminum infiltrates and fills the gaps between the hollow spherical particles, completing the vacuum infiltration casting.

[0033] The inert protective gas in S3 is argon or nitrogen, and the micro-positive pressure is 0.01MPa-0.05MPa.

[0034] The preheating temperature mentioned in S3 is determined by the material of the metal panel, and the preheating temperature is usually 10℃-50℃ lower than the melting point temperature of the panel.

[0035] S3 was evacuated twice until the vacuum level inside the seepage mold cavity was less than -0.08 MPa;

[0036] The aluminum raw material mentioned in S3 is one or a combination of several of the following: pure Al, Al-Si alloy, Al-Si-Mg alloy, Al-Mg alloy, Al-Si-Cu alloy, Al-Cu-Mg alloy, Al-Zn-Cu alloy, Al-Zn-Mg-Cu alloy, and Al-Si-Cu-Mg alloy.

[0037] S4. Material cooling and forming process:

[0038] After vacuum infiltration is complete, the vacuum system is shut off, the top cover is removed, and once the surface of the molten aluminum has completely solidified, gas is introduced into the mold through the vacuum valve interface for backflushing, thereby accelerating sample cooling and assisting in demolding. After cooling to room temperature, the plate mold is removed, and the upper and lower end faces of the sample are cut flat using a wire cutter to obtain an aluminum-based porous composite sandwich panel.

[0039] The thickness of the aluminum-based porous sandwich panel is 1mm to 140mm.

[0040] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0041] 1. Improved metallurgical bonding quality at the interface between the panel and the core layer:

[0042] This invention employs a vacuum infiltration process under a protective atmosphere, ensuring that the metal panel and core layer remain in a controlled atmosphere throughout the entire process from room temperature to high temperature until infiltration is complete. This effectively avoids high-temperature oxidation and significantly improves the interfacial metallurgical bonding quality. Furthermore, this invention completes the infiltration process within an integrated furnace, eliminating this limitation from the process path perspective and representing a fundamental difference.

[0043] 2. Sandwich panels have better surface quality:

[0044] This invention effectively improves surface quality through the following measures: First, a plate-type mold structure provides stable support for the metal panel, suppressing its deformation at high temperatures; second, the entire percolation process is completed inside the furnace, eliminating the need to transfer the mold, thereby reducing the preheating temperature of the mold and aluminum raw materials, and minimizing the thermal shock of the aluminum raw materials to the panel while ensuring percolation; finally, graphite powder is used as a filling medium to improve the system's thermal conductivity, accelerate the heating and cooling rates, and allow the material to quickly complete the solidification process before the panel melts. The synergistic effect of these measures enables this invention to achieve effective percolation under relatively low heat input conditions, significantly improving the surface flatness and integrity of the sandwich panel.

[0045] 3. Improved efficiency in sandwich panel manufacturing:

[0046] This invention employs a plate-type mold design, enabling the simultaneous fabrication of multiple sandwich panels by adjusting the spacing and arrangement of the plates, significantly increasing output per unit time. Simultaneously, the use of highly thermally conductive carbon graphite powder to fill the mold gaps improves heat transfer efficiency and shortens heating and cooling times, further enhancing overall fabrication efficiency. Furthermore, this invention completes the fabrication process at a lower percolation temperature, making heat input easier to control compared to existing high-temperature casting processes, which is beneficial for achieving stable mass production.

[0047] In summary, the present invention has achieved significant improvements in interface bonding quality, surface quality and preparation efficiency. Moreover, the related technical effects all depend on the synergistic effect of specific process paths and structural designs, which are difficult to obtain by simply improving existing technologies. Attached Figure Description

[0048] Figure 1 This is a cross-sectional schematic diagram of the implementation device of the present invention;

[0049] In the diagram, 1-pressure gauge, 2-aluminum inlet, 3-aluminum inlet valve, 4-protective gas inlet, 5-percolation mold cover, 6-graphite sealing ring, 7-plate mold, 8-percolation mold body, 9-graphite powder, 10-refractory fiber felt, 11-vacuum pipe, 12-hollow sphere particles, 13-metal panel.

[0050] Figure 2 This is a schematic diagram of the plate mold of the present invention;

[0051] In the diagram, 13 is the metal panel, 14 is the partition, and 15 is the outer casing.

[0052] Figure 3 The results of the three-point bending test on the sandwich panel sample obtained in Example 1 are shown in different states of the end face; where (a) is the first stage state, (b) is the second stage state, (c) is the third stage state of the sample, and (d) is the macrostructure at the crack of the sample.

[0053] Figure 4 The results are as follows: (a) Macroscopic results of the sandwich panel of Example 2, (b) Mesoscopic results of the interface of the sandwich panel of Example 2, (c) Microscopic results of the interface of the sandwich panel of Example 2, (d)-(f) Microscopic EDS surface scan characterization results of the interface of the sandwich panel of Example 2, (g) Macroscopic results of the sandwich panel of Comparative Example 2, (h) Mesoscopic results of the interface of the sandwich panel of Comparative Example 2, (i) Microscopic results of the interface of the sandwich panel of Comparative Example 2, (j)-(l) Microscopic EDS surface scan characterization results of the interface of the sandwich panel of Comparative Example 2 (within the white box).

[0054] Figure 5 The images show macroscopic views of the sandwich panels obtained in Example 2 and Comparative Example 1 at different locations; where (a) is the front panel of the sandwich panel in Comparative Example 1, (b) is the cross-section of the sandwich panel in Comparative Example 1, (c) is the front panel of the sandwich panel in Example 2, and (d) is the cross-section of the sandwich panel in Example 2. Detailed Implementation

[0055] In the method provided by this invention, the plate mold 7 has a through structure, such as... Figure 2 As shown, the structure includes a rectangular outer shell 15 constructed from metal plates, partitions 14 distributed within the outer shell 15 and flush with its height, and fixedly assembled metal panels 13. The partitions 14 divide the frame-like outer shell 15 into through-type cuboid units; the specifications of these cuboid units match the specifications of the target sandwich panel, and the quantity is set according to requirements; during the assembly of the metal panels 13, the metal panels 13 are fixedly assembled in relative positions to each cuboid unit, and the distance between the metal panels 13 is the core layer thickness of the target sandwich panel.

[0056] This invention provides a method for preparing an integrated aluminum-based porous sandwich panel using an atmosphere-protected, vacuum-permeation composite, wherein the vacuum permeation mold used is as follows: Figure 1As shown, the percolation mold consists of three parts: a top cover 5, a graphite sealing ring 6, and a main body 8. The graphite sealing ring 6 is located between the top cover 5 and the main body 8. A vacuum pipe 11 is installed at the bottom of the main body 8, and refractory fiber felt 10 is laid at the bottom of the percolation mold cavity. An aluminum inlet 2 is located in the middle of the top cover 5, and a pressure gauge 1 and a protective gas inlet 4 are respectively installed on both sides of the aluminum inlet 2. An aluminum inlet valve 3 is installed at the aluminum inlet 2. Sealing valves are installed on the protective gas inlet 4 and the vacuum pipe 11, respectively. Hollow spherical particles 12 are distributed between the metal panels 13.

[0057] This invention provides a method for preparing an integrated aluminum-based porous sandwich panel with atmosphere protection and vacuum permeation, comprising the following steps:

[0058] S1. Assembly of plate mold 7:

[0059] Select a metal panel 13 according to the target sandwich panel, and after cleaning, grinding and smoothing the metal panel 13, fix and assemble it in the frame structure to obtain the panel mold 7.

[0060] The plate mold 7 is a through structure, including a rectangular outer shell 15 built of metal plates, partitions 14 distributed in the outer shell 15 and flush with the height of the outer shell, and a fixedly assembled metal panel 13. The partitions 14 divide the frame structure into through cuboid units. The specifications of the cuboid units match the specifications of the target sandwich panel, and the quantity is set according to the requirements.

[0061] During the assembly of the metal panel 13, the metal panel 13 after the assembly process is fixed in the relative position of each cuboid unit. The distance between the metal panels 13 is the core layer thickness of the target sandwich panel.

[0062] Among them, the metal panel 13 is cleaned with anhydrous ethanol until the surface is free of oil and dust; the thickness of the metal panel 13 does not exceed 60mm;

[0063] S2. Packing material:

[0064] A refractory fiber felt 10 is laid at the bottom of the vacuum infiltration mold. The plate mold 7 is placed vertically upwards into the body of the infiltration mold 8. The gap between the outer wall of the plate mold 7 and the inner wall of the infiltration mold is filled with graphite powder 9 and compacted to ensure that the plate mold 7 is stably positioned in the infiltration mold. Hollow sphere particles 12 used to prepare the porous core material are filled into the inner cavity of the plate mold 7. The hollow sphere particles 12 are filled and vibrated until they are flush with the upper edge of the plate mold 7, ensuring that the core material forming area is flat and free of graphite powder 9.

[0065] S3. Vacuum infiltration casting:

[0066] Secure the top cover 5 of the percolation mold to the graphite sealing ring 6 using a flange to ensure a reliable overall seal of the mold, and close the aluminum inlet valve 3. Connect the vacuum pump and the inert gas cylinder to the mold vacuum pipeline 11 and the protective gas port 4, respectively, to complete the assembly of the gas path and vacuum system.

[0067] 1. Vacuuming in one step:

[0068] Open the vacuum sealing valve and vacuum pump to evacuate the percolation mold cavity, and fully extract the air inside the cavity and the gas trapped in the gaps between the hollow sphere particles 12.

[0069] 2. Primary protective gas filling:

[0070] Turn off the vacuum pump and vacuum sealing valve, and introduce inert protective gas into the percolation mold to achieve a slight positive pressure inside the percolation mold, allowing the protective gas to fully permeate into the gaps between the hollow sphere particles 12.

[0071] 3. Secondary vacuuming:

[0072] The vacuum pump and vacuum sealing valve are turned on again to perform a second vacuuming, further extracting the residual gas in the gaps between the hollow sphere particles 12 and the graphite powder 9, ensuring that the percolation mold cavity is clean and oxygen-free.

[0073] 4. Secondary protective gas pressure maintenance:

[0074] Turn off the vacuum pump and vacuum sealing valve, and reintroduce inert protective gas to maintain a stable micro-positive pressure inside the mold, ensuring that the entire cavity of the seepage mold and the gaps between the hollow sphere particles 12 are under a protective atmosphere.

[0075] After atmosphere replacement is completed, the entire infiltration mold is placed in a heating furnace for preheating. The preheating temperature is lower than the melting point of the metal panel (13), and the temperature is maintained for 2-4 hours to ensure uniform temperature inside and outside the infiltration mold. During the preheating of the infiltration mold, aluminum raw materials are weighed, heated and melted, kept at a constant temperature to remove gas, and then allowed to stand. After both the preheating of the infiltration mold and the melting of the aluminum alloy are completed, the infiltration mold is kept in a preheated state, and the aluminum inlet valve 3 is opened to inject molten aluminum, so that the molten aluminum completely covers the mold filling area. After the molten aluminum covers the area, the protective atmosphere is immediately closed, and the vacuum system is simultaneously turned on. The system vacuum degree is controlled at -0.03MPa to -0.09MPa (gauge pressure). Under negative pressure, the molten aluminum infiltrates and fills the gaps between the hollow spherical particles 12, completing the vacuum infiltration casting.

[0076] S4. Material cooling and forming process:

[0077] After vacuum infiltration is completed, the vacuum system is shut off, and the top cover 5 of the infiltration mold is removed. After the surface of the molten aluminum has completely solidified, gas is introduced into the mold through the vacuum valve interface to backflush, thereby accelerating sample cooling and assisting in demolding. After cooling to room temperature, the plate mold 7 is removed, and the upper and lower end faces of the sample are cut flat using a wire cutter to obtain an aluminum-based porous composite sandwich panel.

[0078] According to a preferred embodiment of the present invention, the thickness of the aluminum-based porous sandwich panel is 1mm to 140mm.

[0079] According to a preferred embodiment of the present invention, the metal panel 13 is made of one of aluminum alloy, magnesium alloy, steel and titanium alloy, and its thickness does not exceed 60 mm.

[0080] According to a preferred embodiment of the present invention, the graphite powder 9 has a particle size of 200-500 mesh, which serves to support, fix, fill and ensure uniform temperature.

[0081] According to a preferred embodiment of the present invention, the hollow sphere particles 12 are one or a combination of several of the following: alumina hollow spheres, glass microspheres, fly ash hollow spheres, silicon carbide hollow spheres, and expanded perlite.

[0082] According to a preferred embodiment of the present invention, the average particle size of the hollow spherical particles 12 is 50 μm to 2000 μm.

[0083] According to a preferred embodiment of the present invention, the preheating temperature of the percolation mold is determined according to the material of the metal panel 13, and the preheating temperature is 10°C to 50°C lower than the melting point of the metal panel 13.

[0084] According to a preferred embodiment of the present invention, the aluminum raw material is one or a combination of several of the following: pure Al, Al-Si alloy, Al-Si-Mg alloy, Al-Mg alloy, Al-Si-Cu alloy, Al-Cu-Mg alloy, Al-Zn-Cu alloy, Al-Zn-Mg-Cu alloy, and Al-Si-Cu-Mg alloy.

[0085] In the method provided by this invention, the process of evacuating the inner cavity of the seepage mold and filling it with protective gas is specifically carried out according to the following steps:

[0086] First vacuuming: Open the vacuum valve and vacuum pump to evacuate the cavity of the percolation mold, and fully extract the air inside the cavity and the gas trapped in the gaps between the hollow sphere particles 12;

[0087] First protective gas filling: Close the vacuum pump and vacuum valve, and introduce inert protective gas into the percolation mold to make the inside of the percolation mold reach a slight positive pressure, so that the protective gas can fully percolate into the gaps of the hollow sphere particles 12.

[0088] Secondary vacuuming: The vacuum pump and vacuum valve are turned on again to perform secondary vacuuming, further extracting the residual gas in the gaps between the hollow sphere particles 12 and the graphite powder 9, ensuring that the permeation mold cavity is clean and oxygen-free.

[0089] Secondary protective gas pressure maintenance: Close the vacuum pump and vacuum valve, and introduce inert protective gas again to maintain a stable slight positive pressure inside the mold, ensuring that the entire cavity of the seepage mold and the gaps between the 12 hollow spheres are under a protective atmosphere.

[0090] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0091] Example 1:

[0092] This embodiment provides a method for preparing an integrated aluminum-based porous sandwich panel with atmosphere protection and permeation properties, including the following steps:

[0093] S1. Assembly of plate mold 7:

[0094] Metal panel 13 was selected based on the target sandwich panel. A 2mm thick 6063 aluminum alloy panel was cleaned with anhydrous ethanol until the surface was free of oil and dust, then polished to smooth the surface and remove the oxide layer. Four metal plates were used as frame panels to construct a rectangular through-frame structure. Two matching metal plates were placed parallel to the frame panels within the frame structure, dividing it into three identical through-type cuboid units. Metal panels 13 were vertically fixed onto these metal plates to obtain panel mold 7. The distance between the two metal plates in each cuboid unit was 20mm. The processed 6063 aluminum alloy panels were then fixed in relative positions within each cuboid unit.

[0095] S2. Packing material:

[0096] A refractory fiber felt 10 is laid at the bottom of the vacuum infiltration mold. The plate mold 7 is then placed vertically upwards into the cavity of the infiltration mold. The gap between the outer wall of the plate mold 7 and the inner wall of the infiltration mold is filled and compacted with graphite powder 9 with a particle size of 200-500 mesh to ensure stable positioning of the plate mold 7 within the infiltration mold. Hollow fly ash spheres with a particle size of 1mm-2mm are filled into the inner cavity of the plate mold 7. The fly ash spheres are then compacted until they are flush with the upper edge of the plate mold 7, ensuring a flat core material forming area without any graphite powder 9 mixed in.

[0097] S3. Vacuum infiltration casting:

[0098] Secure the top cover 5 of the percolation mold to the graphite sealing ring 6 using a flange to ensure a reliable overall seal of the mold. Close the aluminum inlet valve 3. Connect the vacuum pump and argon cylinder to the mold's vacuum interface to complete the gas path and vacuum system assembly. Then, evacuate the percolation mold cavity to a vacuum level less than -0.08 MPa, and then fill the cavity with argon gas until the internal pressure reaches 0.03 MPa. Repeat the evacuation and inert gas filling process to maintain a stable, slightly positive pressure inside the percolation mold, ensuring that the entire cavity of the percolation mold and the gaps between the fly ash hollow spheres are under a protective atmosphere, thus completing the atmosphere replacement.

[0099] After atmosphere replacement, the entire infiltration mold is placed in a heating furnace for preheating to 600℃ both inside and outside the mold, and held at this temperature for 2 hours to ensure uniform temperature distribution. During mold preheating, ZL102 aluminum alloy is heated to 680℃ for melting, held to remove gas, and then allowed to stand. Once mold preheating and aluminum alloy melting are complete, the mold temperature is maintained at 600℃, and inlet valve 3 is opened to inject molten aluminum, ensuring complete coverage of the mold filling area. Immediately after coverage, the protective atmosphere is shut off, and the vacuum system is simultaneously activated, maintaining the system vacuum at -0.03MPa to -0.09MPa (gauge pressure). Under negative pressure, the molten aluminum rapidly infiltrates and fills the gaps between the fly ash hollow spheres, completing vacuum infiltration casting.

[0100] S4. Cooling and forming process:

[0101] After shutting down the vacuum system and removing the top cover 5 of the percolation mold, and after the surface of the molten aluminum has completely solidified and the sample has reached the preset solidification time, gas is introduced into the percolation mold through the vacuum valve interface for backflushing to accelerate sample cooling and assist in demolding. After the sample has cooled to room temperature, the plate mold 7 is removed, and the upper and lower end faces of the sample are cut flat using a wire cutter to obtain an aluminum-based porous composite sandwich panel.

[0102] Figure 3 The image shows the macroscopic microstructure of the end face of the sandwich panel sample obtained in Example 1 during a three-point bending test. It can be seen that the sample interface is flat without a clear boundary line, and the face panel and core layer maintain a metallurgical bond throughout the three-point bending test. The bending strength of the sample, characterized by a three-point bending test, reaches 118.8 MPa. The bond strength between the face panel and core layer of the prepared sandwich panel is tested and found to be 35.4 MPa.

[0103] Example 2:

[0104] This embodiment provides a method for preparing an integrated aluminum-based porous sandwich panel with atmosphere protection and permeation properties, including the following steps:

[0105] S1. Assembly of plate mold 7:

[0106] Metal panel 13 was selected based on the target sandwich panel. A 2.5mm thick 6061 aluminum alloy panel was cleaned with anhydrous ethanol until the surface was free of oil and dust, then polished to smooth the surface and remove the oxide layer. Four metal plates were used as frame panels to construct a rectangular through-frame structure. Five matching metal plates were placed parallel to the frame panels within the frame structure, dividing it into six identical through-type cuboid units. Metal panels 13 were vertically fixed onto these metal plates to obtain the panel mold 7. The distance between two metal plates in each cuboid unit was 15mm. The processed 6061 aluminum alloy panels were then fixed in relative positions within each cuboid unit.

[0107] S2. Packing material:

[0108] A refractory fiber felt 10 is laid at the bottom of the vacuum percolation mold. The plate mold 7 is then placed vertically upwards into the cavity of the percolation mold. The gap between the outer wall of the plate mold 7 and the inner wall of the percolation mold is filled and compacted with graphite powder 9 with a particle size of 200-500 mesh to ensure stable positioning of the plate mold 7 within the percolation mold. Hollow alumina spheres with a particle size of 150μm-200μm are filled into the inner cavity of the plate mold 7. The alumina hollow spheres are then compacted until they are flush with the upper edge of the plate mold 7, ensuring that the core material forming area is flat and free of graphite powder 9.

[0109] S3. Vacuum infiltration casting:

[0110] Secure the top cover 5 of the percolation mold to the graphite sealing ring 6 using a flange to ensure a reliable overall seal of the mold. Close the aluminum inlet valve 3. Connect the vacuum pump and nitrogen cylinder to the mold's vacuum interface to complete the gas path and vacuum system assembly. Then, evacuate the percolation mold cavity to a vacuum level less than -0.08 MPa, and then fill the cavity with nitrogen until the internal pressure reaches 0.04 MPa. Repeat the evacuation and inert gas filling process to maintain a stable, slightly positive pressure inside the percolation mold, ensuring that the entire cavity of the percolation mold and the gaps between the alumina hollow spheres are under a protective atmosphere, thus completing the atmosphere replacement.

[0111] After atmosphere replacement, the entire infiltration mold is placed in a heating furnace for preheating to 600℃ both inside and outside the mold, and held at this temperature for 2 hours to ensure uniform temperature distribution. During mold preheating, ZL201 aluminum alloy is heated to 700℃ for melting, held to remove gas, and then allowed to stand. Once mold preheating and aluminum alloy melting are complete, the mold temperature is maintained at 600℃, and inlet valve 3 is opened to inject molten aluminum, ensuring complete coverage of the mold filling area. Immediately after coverage, the protective atmosphere is shut off, and the vacuum system is simultaneously activated, maintaining the system vacuum at -0.03MPa to -0.09MPa (gauge pressure). Under negative pressure, the molten aluminum rapidly infiltrates and fills the gaps between the fly ash hollow spheres, completing the vacuum infiltration casting process.

[0112] S4. Cooling and forming process:

[0113] After shutting down the vacuum system and removing the top cover 5 of the percolation mold, and after the surface of the molten aluminum has completely solidified and the sample has reached the preset solidification time, gas is introduced into the percolation mold through the vacuum valve interface for backflushing to accelerate sample cooling and assist in demolding. After the sample has cooled to room temperature, the plate mold 7 is removed, and the upper and lower end faces of the sample are cut flat using a wire cutter to obtain an aluminum-based porous composite sandwich panel.

[0114] Figure 4 Characterizing the interface bonding of the prepared samples reveals that the interface between the core layer and the panel is flat and distinct on a macroscopic scale, and areas of insufficient welding are not visible to the naked eye. Using EDS surface scanning to characterize the interface bonding, it is found that the interface bonding achieves metallurgical bonding, with no obvious oxidation boundary line.

[0115] Example 3:

[0116] This embodiment provides a method for preparing an integrated aluminum-based porous sandwich panel with atmosphere protection and permeation properties, including the following steps:

[0117] S1. Assembly of plate mold 7:

[0118] Metal panel 13 was selected based on the target sandwich panel. A 1mm thick 45# steel panel was cleaned with anhydrous ethanol until the surface was free of oil and dust, then ground smooth to remove the oxide layer from the 6061 aluminum alloy panel. Four metal plates were used as frame panels to construct a rectangular through-frame structure. Four matching metal plates were placed parallel to the frame panels within the frame structure, dividing it into five identical through-type cuboid units. Metal panels 13 were vertically fixed onto these metal plates to obtain panel mold 7. The distance between two metal plates in each cuboid unit was 10mm. The processed 45# steel panels were then fixed in relative positions within each cuboid unit.

[0119] S2. Packing material:

[0120] A refractory fiber felt 10 is laid at the bottom of the vacuum percolation mold. The plate mold 7 is then placed vertically upwards into the cavity of the percolation mold. The gap between the outer wall of the plate mold 7 and the inner wall of the percolation mold is filled and compacted with graphite powder 9 with a particle size of 200-500 mesh to ensure stable positioning of the plate mold 7 within the percolation mold. Hollow alumina spheres with a particle size of 200μm-500μm are filled into the inner cavity of the plate mold 7. The alumina hollow spheres are then compacted until they are flush with the upper edge of the plate mold 7, ensuring that the core material forming area is flat and free of graphite powder 9.

[0121] S3. Vacuum infiltration casting:

[0122] Secure the top cover 5 of the percolation mold to the graphite sealing ring 6 using a flange to ensure a reliable overall seal of the mold. Close the aluminum inlet valve 3. Connect the vacuum pump and nitrogen cylinder to the mold's vacuum interface to complete the gas path and vacuum system assembly. Then, evacuate the percolation mold cavity to a vacuum level less than -0.08 MPa, and then fill the cavity with nitrogen until the internal pressure reaches 0.03 MPa. Repeat the evacuation and inert gas filling process to maintain a stable, slightly positive pressure inside the percolation mold, ensuring that the entire cavity of the percolation mold and the gaps between the alumina hollow spheres are under a protective atmosphere, thus completing the atmosphere replacement.

[0123] After atmosphere replacement, the entire infiltration mold is placed in a heating furnace for preheating to 650℃ both inside and outside the mold, and held at this temperature for 4 hours to ensure uniform temperature distribution. During mold preheating, ZL101 aluminum alloy is heated to 680℃ for melting, held to remove gas, and then allowed to stand. Once mold preheating and aluminum alloy melting are complete, the mold temperature is maintained at 650℃. Inlet valve 3 is opened to inject molten aluminum, ensuring complete coverage of the mold filling area. Immediately after coverage, the protective atmosphere is shut off, and the vacuum system is simultaneously activated, maintaining the system vacuum between -0.03MPa and -0.09MPa (gauge pressure). Under negative pressure, the molten aluminum rapidly infiltrates and fills the gaps between the fly ash hollow spheres, completing the vacuum infiltration casting process.

[0124] S4. Cooling and forming process:

[0125] After shutting down the vacuum system and removing the top cover 5 of the percolation mold, and after the surface of the molten aluminum has completely solidified and the sample has reached the preset solidification time, gas is introduced into the percolation mold through the vacuum valve interface for backflushing to accelerate sample cooling and assist in demolding. After the sample has cooled to room temperature, the plate mold 7 is removed, and the upper and lower end faces of the sample are cut flat using a wire cutter to obtain an aluminum-based porous composite sandwich panel.

[0126] The sample was subjected to a three-point bending test to characterize its bending strength, which reached 274.1 MPa. The bonding strength between the face panel and the core layer of the prepared sandwich panel was tested and found to be 31.82 MPa.

[0127] Example 4:

[0128] This embodiment provides a method for preparing an integrated aluminum-based porous sandwich panel with atmosphere protection and permeation properties, including the following steps:

[0129] S1. Assembly of plate mold 7:

[0130] Metal panel 13 was selected based on the target sandwich panel. A 0.5mm thick TC4 titanium alloy panel was cleaned with anhydrous ethanol until the surface was free of oil and dust, then polished to smooth the surface and remove the oxide layer. Four metal plates were used as frame panels to construct a rectangular through-frame structure. Six matching metal plates were placed parallel to the frame panels within the frame structure, dividing it into seven identical through-frame rectangular units. Metal panels 13 were vertically fixed onto these metal plates to obtain panel mold 7. The distance between two metal plates in each rectangular unit was 8mm. The TC4 titanium alloy panels were then assembled and fixed in relative positions within each rectangular unit.

[0131] S2. Packing material:

[0132] A refractory fiber felt 10 is laid at the bottom of the vacuum percolation mold. The plate mold 7 is then placed vertically upwards into the cavity of the percolation mold. The gap between the outer wall of the plate mold 7 and the inner wall of the percolation mold is filled and compacted with graphite powder 9 with a particle size of 200-500 mesh to ensure stable positioning of the plate mold 7 within the percolation mold. Hollow fly ash spheres with a particle size of 250μm-600μm are filled into the inner cavity of the plate mold 7. The fly ash hollow spheres are then packed and compacted until they are flush with the upper edge of the plate mold 7, ensuring that the core material forming area is flat and free of graphite powder 9.

[0133] S3. Vacuum infiltration casting:

[0134] Secure the top cover 5 of the percolation mold to the graphite sealing ring 6 using a flange to ensure a reliable overall seal of the mold. Close the aluminum inlet valve 3. Connect the vacuum pump and argon cylinder to the mold's vacuum interface to complete the gas path and vacuum system assembly. Then, evacuate the percolation mold cavity to a vacuum level less than -0.08 MPa, and then fill the cavity with argon gas until the internal pressure reaches 0.03 MPa. Repeat the evacuation and inert gas filling process to maintain a stable, slightly positive pressure inside the percolation mold, ensuring that the entire cavity of the percolation mold and the gaps between the fly ash hollow spheres are under a protective atmosphere, thus completing the atmosphere replacement.

[0135] After atmosphere replacement, the entire infiltration mold is placed in a heating furnace for preheating to 600℃ both inside and outside the mold, and held at this temperature for 4 hours to ensure uniform temperature distribution. During mold preheating, ZL201 aluminum alloy is heated to 710℃ for melting, held to remove gas, and then allowed to stand. Once mold preheating and aluminum alloy melting are complete, the mold temperature is maintained at 600℃, and aluminum inlet valve 3 is opened to inject molten aluminum, ensuring complete coverage of the mold filling area. Immediately after coverage, the protective atmosphere is shut off, and the vacuum system is simultaneously activated, maintaining the system vacuum at -0.03MPa to -0.09MPa (gauge pressure). Under negative pressure, the molten aluminum rapidly infiltrates and fills the gaps between the fly ash hollow spheres, completing vacuum infiltration casting.

[0136] S4. Cooling and forming process:

[0137] After shutting down the vacuum system and removing the top cover 5 of the percolation mold, and after the surface of the molten aluminum has completely solidified and the sample has reached the preset solidification time, gas is introduced into the percolation mold through the vacuum valve interface for backflushing to accelerate sample cooling and assist in demolding. After the sample has cooled to room temperature, the plate mold 7 is removed, and the upper and lower end faces of the sample are cut flat using a wire cutter to obtain an aluminum-based porous composite sandwich panel.

[0138] The sample was subjected to a three-point bending test to characterize its bending strength, which reached 125.2 MPa. The bonding strength between the face panel and the core layer of the prepared sandwich panel was tested and found to be 28.4 MPa.

[0139] Comparative Example 1:

[0140] This comparative example provides a method for preparing an aluminum-based porous sandwich panel, including the following steps:

[0141] S1. Packing material:

[0142] Select metal panel 13 according to the target sandwich panel. Clean the 2.5mm thick 6061 aluminum alloy panel with anhydrous ethanol until the surface is free of oil and dust. Then grind and smooth the surface to remove the oxide layer. Lay refractory fiber felt 10 at the bottom of the vacuum percolation mold. Fix the treated metal panel 13 vertically in the vacuum percolation mold. Fix two metal panels 13 parallel to each other according to the sandwich panel design dimensions. Fill the space between the two metal panels 13 with hollow alumina spheres with a particle size of 150μm-200μm and vibrate to compact them. Fill the gap between the outer wall of the metal panel 13 and the inner wall of the percolation mold with graphite powder 9 with a particle size of 200~500 mesh and compact it to keep the sandwich panel preform stably positioned in the percolation mold.

[0143] S2. Vacuum infiltration casting:

[0144] Secure the top cover 5 of the percolation mold to the graphite sealing ring 6 using a flange to ensure a reliable overall seal of the mold. Close the aluminum inlet valve 3. Connect the vacuum pump and nitrogen cylinder to the mold's vacuum interface to complete the gas path and vacuum system assembly. Then, evacuate the percolation mold cavity to a vacuum level less than -0.08 MPa, and then fill the cavity with nitrogen until the internal pressure reaches 0.04 MPa. Repeat the evacuation and inert gas filling process to maintain a stable, slightly positive pressure inside the percolation mold, ensuring that the entire cavity of the percolation mold and the gaps between the alumina hollow spheres are under a protective atmosphere, thus completing the atmosphere replacement.

[0145] After atmosphere replacement, the entire infiltration mold is placed in a heating furnace for preheating to 600℃ both inside and outside the mold, and held at this temperature for 2 hours to ensure uniform temperature distribution. During mold preheating, ZL201 aluminum alloy is heated to 700℃ for melting, held to remove gas, and then allowed to stand. Once mold preheating and aluminum alloy melting are complete, the mold temperature is maintained at 600℃, and inlet valve 3 is opened to inject molten aluminum, ensuring complete coverage of the mold filling area. Immediately after coverage, the protective atmosphere is shut off, and the vacuum system is simultaneously activated, maintaining the system vacuum at -0.03MPa to -0.09MPa (gauge pressure). Under negative pressure, the molten aluminum rapidly infiltrates and fills the gaps between the fly ash hollow spheres, completing the vacuum infiltration casting process.

[0146] S3. Cooling and forming process:

[0147] After shutting down the vacuum system and removing the top cover 5 of the percolation mold, and after the surface of the molten aluminum has completely solidified and the sample has reached the preset solidification time, gas is introduced into the percolation mold through the vacuum valve interface for backflushing, thereby accelerating sample cooling and assisting in demolding. After the sample has cooled to room temperature, the upper and lower end faces of the sample are cut flat using a wire cutter to obtain an aluminum-based porous composite sandwich panel.

[0148] The sandwich panels prepared in Example 2 and Comparative Example 1 were observed at different locations, and the results are as follows: Figure 5 As shown in the figure, the samples (a) and (b) prepared without using the plate mold 7 to constrain the panel have poor panel surface flatness with many pits formed by alloy melting, and the interface between the panel and the core layer is not straight but wavy. The samples (c) and (d) prepared by using the plate mold 7 to constrain the panel have a flat panel surface and a relatively straight interface between the core layer and the panel. In addition, the bending strength and the bonding strength between the panel and the core layer of the two sandwich panels were characterized by a three-point bending test. The bending strength of the sandwich panel prepared in Example 2 reached 179.2 MPa, which is 43.1% higher than the bending strength (125.2 MPa) of Comparative Example 1, and the bonding strength was 44.7 MPa, which is 1.57 times the bonding strength (28.4 MPa) of Comparative Example 1.

[0149] Comparative Example 2:

[0150] This comparative example provides a method for preparing an aluminum-based porous sandwich panel, including the following steps:

[0151] S1. Assembly of plate mold 7:

[0152] Metal panel 13 was selected based on the target sandwich panel. A 2.5mm thick 6061 aluminum alloy panel was cleaned with anhydrous ethanol until the surface was free of oil and dust, then polished to smooth the surface and remove the oxide layer. Four metal plates were used as frame panels to construct a rectangular through-frame structure. Five matching metal plates were placed parallel to the frame panels within the frame structure, dividing it into six identical through-type cuboid units. Metal panels 13 were vertically fixed onto these metal plates to obtain the panel mold 7. The distance between two metal plates in each cuboid unit was 15mm. The processed 6061 aluminum alloy panels were then fixed in relative positions within each cuboid unit.

[0153] S2. Packing material:

[0154] A refractory fiber felt 10 is laid at the bottom of the vacuum percolation mold. The plate mold 7 is then placed vertically upwards into the cavity of the percolation mold. The gap between the outer wall of the plate mold 7 and the inner wall of the percolation mold is filled and compacted with graphite powder 9 with a particle size of 200-500 mesh to ensure stable positioning of the plate mold 7 within the percolation mold. Hollow alumina spheres with a particle size of 200μm-1000μm are filled into the inner cavity of the plate mold 7. The alumina hollow spheres are then compacted until they are flush with the upper edge of the plate mold 7, ensuring that the core material forming area is flat and free of graphite powder 9.

[0155] S3. Vacuum infiltration casting:

[0156] Secure the top cover 5 of the percolation mold to the graphite sealing ring 6 using a flange to ensure a reliable overall seal of the mold. Close the aluminum inlet valve 3. Connect the vacuum pump and nitrogen cylinder to the mold's vacuum interface to complete the gas path and vacuum system assembly. Then, evacuate the percolation mold cavity to a vacuum level less than -0.08 MPa, and then fill the cavity with nitrogen until the internal pressure reaches 0.04 MPa. Repeat the evacuation and inert gas filling process to maintain a stable, slightly positive pressure inside the percolation mold, ensuring that the entire cavity of the percolation mold and the gaps between the alumina hollow spheres are under a protective atmosphere, thus completing the atmosphere replacement.

[0157] After atmosphere replacement, the entire infiltration mold is placed in a heating furnace for preheating to 600℃ both inside and outside the mold, and held at this temperature for 2 hours to ensure uniform temperature distribution. During mold preheating, ZL201 aluminum alloy is heated to 700℃ to melt, held to remove gas, and then allowed to stand. Once both mold preheating and aluminum alloy melting are complete, the mold temperature is maintained at 600℃, the protective gas is turned off, and the mold cover 5 is removed and left to stand for 1 minute to simulate the absence of a protective atmosphere during the preparation process. Then, molten aluminum is poured into the vacuum mold, ensuring complete coverage of the mold filling area. The vacuum system is then activated, and the vacuum level is controlled between -0.03MPa and -0.09MPa (gauge pressure). Under negative pressure, the molten aluminum rapidly infiltrates and fills the gaps between the fly ash hollow spheres, completing the vacuum infiltration casting process.

[0158] S4. Cooling and forming process:

[0159] After shutting down the vacuum system and removing the top cover 5 of the percolation mold, and after the surface of the molten aluminum has completely solidified and the sample has reached the preset solidification time, gas is introduced into the percolation mold through the vacuum valve interface for backflushing to accelerate sample cooling and assist in demolding. After the sample has cooled to room temperature, the plate mold 7 is removed, and the upper and lower end faces of the sample are cut flat using a wire cutter to obtain an aluminum-based porous composite sandwich panel.

[0160] The sandwich panels prepared in Example 2 and Comparative Example 2 were characterized at different scales, and the results are as follows: Figure 4 As shown in the figure. Characterization of the interface bonding of the sample prepared in Example 2 (a)-(f) reveals that the interface between the core layer and the panel is macroscopically straight and distinct, with no areas of insufficient bonding visible to the naked eye. EDS surface scanning characterizes the interface, showing metallurgical bonding without obvious oxide boundaries. Characterization of the interface bonding of the sandwich panel prepared in Comparative Example 2 (g)-(l) reveals that the interface between the core layer and the panel is macroscopically straight and distinct, with no areas of insufficient bonding visible to the naked eye. EDS surface scanning characterizes the interface, revealing unbonded areas at the interface, indicating a lack of metallurgical bonding and obvious oxygen element boundaries. Meanwhile, the bending strength and the bonding strength between the two sandwich panels were characterized. The bending strength was characterized by a three-point bending test. The bending strength of the sandwich panel prepared in Example 2 reached 179.2 MPa, which was 46.8% higher than that of Comparative Example 2 (122.1 MPa). The bonding strength was 44.7 MPa, which was 1.7 times that of Comparative Example 2 (25.82 MPa).

Claims

1. A method for preparing an integrated aluminum-based porous sandwich panel using an atmosphere-protected, vacuum-flow composite structure, characterized in that, Includes the following steps: S1. Panel mold assembly: Select a metal panel according to the target sandwich panel, clean and grind the metal panel to make it flat, and then fix it in the frame structure to obtain the panel mold. S2. Filler: Refractory fiber felt is laid at the bottom of the vacuum percolation mold. The plate mold opening is placed vertically upward into the cavity of the vacuum percolation mold. The gap between the outer wall of the plate mold and the inner wall of the vacuum percolation mold is filled with graphite powder and compacted to keep the plate mold stably positioned in the vacuum percolation mold. Hollow spheres used to prepare porous core materials are filled into the inner cavity of the plate mold. The hollow spheres are filled and vibrated until they are flush with the upper edge of the plate mold to ensure that the core material forming area is flat and free of graphite powder. S3. Vacuum Infiltration Casting: Ensure the overall sealing of the vacuum infiltration mold is reliable. After replacing the atmosphere inside the vacuum infiltration mold, preheat and maintain the temperature of the entire vacuum infiltration mold. After heating and melting the aluminum raw material, maintain the temperature, degas, and let it stand to obtain molten aluminum. Keep the vacuum infiltration mold in a preheated state and inject the molten aluminum into the vacuum infiltration mold until the molten aluminum completely covers the core material forming area. Immediately after the molten aluminum covers the core material, turn off the protective atmosphere and simultaneously turn on the vacuum system. Control the system vacuum degree at -0.03MPa to -0.09MPa to perform vacuum infiltration casting. S4. Material cooling and forming process: shut down the vacuum system, remove the top cover of the percolation mold, and after the surface of the aluminum liquid has completely solidified, introduce gas into the vacuum percolation mold to backflush, thereby accelerating the cooling of the sample and assisting in demolding; after the sample has cooled to room temperature, remove the plate mold, and use a wire cutter to cut the upper and lower end faces of the sample flat to obtain an aluminum-based porous composite sandwich panel.

2. The method for preparing an integrated aluminum-based porous sandwich panel with atmosphere protection and vacuum permeation as described in claim 1, characterized in that, In S3, the atmosphere replacement process inside the vacuum percolation mold includes a first vacuuming, a first protective gas filling, a second vacuuming, and a second protective gas pressure holding, specifically as follows: First vacuuming: Open the vacuum sealing valve and vacuum pump to evacuate the vacuum permeation mold cavity until the vacuum degree is less than -0.08MPa; First protective gas filling: Close the vacuum pump and vacuum sealing valve, and introduce inert protective gas into the vacuum permeation mold to make the inside of the vacuum permeation mold reach a slight positive pressure; Secondary vacuuming: Re-open the vacuum pump and vacuum sealing valve, and perform a second vacuuming until the vacuum level is less than -0.08MPa to ensure that the vacuum permeation mold cavity is clean and oxygen-free; Secondary protective gas pressure maintenance: Close the vacuum pump and vacuum sealing valve, and introduce inert protective gas again to maintain a stable micro-positive pressure inside the vacuum percolation mold, ensuring that the entire cavity of the vacuum percolation mold and the gaps between the hollow sphere particles are under a protective atmosphere.

3. The method for preparing an integrated aluminum-based porous sandwich panel with atmosphere protection and vacuum permeation as described in claim 2, characterized in that, In S3, the micro-positive pressure is 0.01MPa-0.05MPa; the inert protective gas is argon or nitrogen.

4. The method for preparing an integrated aluminum-based porous sandwich panel with atmosphere protection and vacuum permeation as described in claim 2, characterized in that, In S1, the plate mold is a through structure, including a rectangular outer shell built of metal plates, and partitions distributed in the outer shell and level with the height of the outer shell. The partitions divide the frame-shaped outer shell into through cuboid units. The specifications of the cuboid units match the specifications of the target sandwich panel, and the quantity is set according to the requirements. During the metal panel assembly process, the metal panels are fixed in relative positions to each cuboid unit after assembly. The distance between the metal panels is the core layer thickness of the target sandwich panel.

5. The method for preparing an integrated aluminum-based porous sandwich panel with atmosphere protection and vacuum permeation as described in claim 2 or 4, characterized in that, In S1, the metal panel is cleaned with anhydrous ethanol until the surface is free of oil and dust. The thickness of the metal panel shall not exceed 60mm; The metal panel is made of one of the following materials: aluminum alloy, magnesium alloy, steel, and titanium alloy.

6. The method for preparing an integrated aluminum-based porous sandwich panel with atmosphere protection and vacuum permeation as described in claim 2 or 4, characterized in that, The vacuum percolation mold consists of three parts: a percolation mold cover, a graphite sealing ring, and a percolation mold body. The graphite sealing ring is located between the percolation mold cover and the percolation mold body. A vacuum pipe is located at the bottom of the percolation mold body, and refractory fiber felt is laid at the bottom of the vacuum percolation mold cavity. An aluminum inlet is located in the middle of the percolation mold cover, and a pressure gauge and a protective gas port are located on both sides of the aluminum inlet. An aluminum inlet valve is also provided at the aluminum inlet. Sealing valves are installed on the protective gas port and the vacuum pipe, and hollow spherical particles are distributed between the metal panels.

7. The method for preparing an integrated aluminum-based porous sandwich panel with atmosphere protection and vacuum permeation as described in claim 2 or 4, characterized in that, In S2, the graphite powder has a particle size of 200-500 mesh; The hollow spheres are one or a combination of several of the following: alumina hollow spheres, glass microspheres, fly ash hollow spheres, silicon carbide hollow spheres, and expanded perlite; the average particle size of the hollow spheres is 50μm to 2000μm.

8. The method for preparing an integrated aluminum-based porous sandwich panel with atmosphere protection and vacuum permeation according to claim 2 or 4, characterized in that, In S3, the preheating temperature of the vacuum permeation mold is determined according to the material of the metal panel, and the preheating temperature is 10℃~50℃ lower than the melting point of the metal panel; The preheating and heat preservation time is 2h~4h.

9. A method for preparing an integrated aluminum-based porous sandwich panel with atmosphere protection and vacuum permeation as described in claim 2 or 4, characterized in that, The thickness of the aluminum-based porous sandwich panel is 1mm to 140mm.

10. A method for preparing an integrated aluminum-based porous sandwich panel with atmosphere protection and vacuum permeation according to claim 2 or 4, characterized in that, The aluminum raw material is one or a combination of several of the following: pure Al, Al-Si alloy, Al-Si-Mg alloy, Al-Mg alloy, Al-Si-Cu alloy, Al-Cu-Mg alloy, Al-Zn-Cu alloy, Al-Zn-Mg-Cu alloy, and Al-Si-Cu-Mg alloy.

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