Manufacturing method of micro porous structure additive added with thermal expansion graphite

Abstract

The invention discloses a micro-porous structure additive manufacturing method with thermal expansion graphite added, and belongs to the technical field of micro-porous structure additive manufacturing. According to the method, thermal expansion graphite powder is added into additive manufacturing powder as a high-efficiency pore-forming agent, and thermal expansion graphite with certain initial expansion temperature, particle size, complete expansion temperature and expansion multiplying power is selected according to the difference of the particle size of matrix powder, the additive manufacturing temperature and the internal pore size and porosity of a part; the method comprises the following steps: preparing thermal expansion graphite, uniformly mixing the thermal expansion graphite with matrix powder according to a certain proportion for additive manufacturing, melting the matrix powder by using an external high-energy beam under a certain temperature condition, expanding the volume of the thermal expansion graphite, and directly processing a target part with a micro porous structure. According to the method provided by the invention, the design and control of the pore size and porosity of the final workpiece are realized, the technical vacancy of the additive manufacturing technology in the field of micro porous structure part preparation is made up, and the method has remarkable technical advantages and wide application prospects.

Description

Technical Field

[0001] This invention belongs to the field of additive manufacturing technology of microporous structures, and relates to a method for additive manufacturing of microporous structures by incorporating thermally expanded graphite. Specifically, it relates to a method in which thermally expanded graphite is added as a pore-forming agent to metal or non-metal powders for additive manufacturing, and the external temperature field is used to cause the thermally expanded graphite to expand rapidly during the additive manufacturing process, thereby forming a microporous or loose structure around it. Background Technology

[0002] Additive manufacturing uses metal or non-metal powders as raw materials, melting, depositing, and growing them with high-energy beams such as lasers and electron beams to manufacture parts. Compared with traditional manufacturing methods, additive manufacturing has advantages such as strong customization, flexible design, fast response speed, and short production cycle, and has been widely used in aerospace, weaponry, biomedicine, and other fields. Currently, due to the need for lightweight or functional parts, the demand for porous or loose structures is increasing. For such parts, the additive manufacturing process is generally based on CAD digital model design of specific honeycomb or lattice structures to achieve macroscopic porous morphologies. For example, Chinese patent "A Three-Dimensional Lattice Superstructure Based on Additive Manufacturing and Its Application" (application number 202310145709.X, publication number: CN115870516A, publication date 2023.03.31) discloses a three-dimensional lattice superstructure based on additive manufacturing, which uses small-section discontinuous scanning characteristics of selective laser melting to additively manufacture the three-dimensional lattice superstructure. In addition, in the construction industry, porous concrete can also be prepared by reacting magnesium oxide, calcium oxide, calcium sulfoaluminate and other substances with water. For example, Chinese patent "A method for preparing a self-stressed high-strength sound-insulating floor slab" (application number 202411031147.7, publication number: CN118952407A, publication date 2024.11.15) discloses a method for preparing high-strength porous concrete floor slabs by hydration reaction of magnesium oxide, calcium sulfoaluminate and other substances in an alkaline humid environment of 30℃-180℃.

[0003] Thermally expandable graphite is a novel carbon material formed by artificially inserting other molecules, atoms, or ions into the interlayer of natural flake graphite. When heated to a certain temperature (called the initial expansion temperature), the interlayer compounds in thermally expandable graphite begin to decompose and generate a significant thrust, causing its volume to increase. The volume reaches its maximum at the full expansion temperature. Currently, thermally expandable graphite is mainly used in aerospace, military electronics, environmental protection, and chemical industries for sealing, flame retardancy, adsorption, and electromagnetic interference control, playing an irreplaceable role.

[0004] In the additive manufacturing process, thermally expanded graphite is used as a functional pore-forming agent and mixed with metal and non-metal powders. While the metal and non-metal powders are melted by heating with high-energy beams such as lasers and electron beams, the thermally expanded graphite is heated and expands to form a uniformly distributed microporous or loose structure around it. This is a brand-new technical approach and can also open up new avenues for the preparation of high-performance lightweight functional components. Summary of the Invention

[0005] The purpose of this invention is to overcome the limitations of existing additive manufacturing technologies in the preparation of microporous structures with porosity (10%-30%) and pore size (30µm-100µm). It innovatively proposes adding thermally expanded graphite powder as a highly efficient pore-forming agent to the additive manufacturing powder. Based on the particle size of the matrix powder, the additive manufacturing temperature, and the internal pore size and porosity of the part, a specific initial expansion temperature, particle size, complete expansion temperature, and expansion ratio of the thermally expanded graphite are selected and uniformly mixed with the matrix powder in a certain proportion. During the additive manufacturing process, an external high-energy beam melts the matrix powder under certain temperature conditions, while simultaneously causing the thermally expanded graphite to expand in volume, directly processing the microporous structure required for the part.

[0006] To achieve the above objectives, the following technical solution is adopted:

[0007] The present invention discloses an additive manufacturing method for microporous structures incorporating thermally expanded graphite, comprising the following steps:

[0008] Step 1: Selection of thermally expanded graphite:

[0009] Based on the particle size of the metal or non-metal matrix powder, the additive manufacturing temperature, and the internal pore size of the target workpiece, select a certain initial expansion temperature, particle size, full expansion temperature, and expansion ratio of thermally expanded graphite.

[0010] Step 2: Determine the ratio of the mixed powders:

[0011] According to the porosity requirements of the workpiece, the matrix powder and thermally expanded graphite powder are mixed in a certain proportion to obtain a composite powder with uniform composition.

[0012] Step 3: Powder application:

[0013] The composite powder is laid on the molding substrate to form a uniform powder layer;

[0014] Step 4: Melting and Hole Forming

[0015] (1) Control the movement of the high-energy beam to scan the composite powder layer and melt the matrix powder;

[0016] (2) Thermally expanding graphite powder expands in volume and forms tiny pores;

[0017] Step 5: Stacking and Shaping

[0018] The molding substrate is lowered by one layer thickness, and steps three and four are repeated to make the microporous structure continuously distributed in three-dimensional space, and finally stacked to form a three-dimensional workpiece with a microporous structure inside.

[0019] Step Six: Obtain the workpiece:

[0020] After printing is complete, remove the three-dimensional workpiece.

[0021] In step one, the particle size of thermally expanded graphite is smaller than that of the matrix powder, the initial expansion temperature is more than 100°C lower than the melting temperature of the matrix powder, the full expansion temperature is more than 100°C higher than the heating temperature of additive manufacturing, and the particle size after free expansion at the heating temperature is 5-15 times the pore size of the part.

[0022] In step two, according to the porosity requirements of the workpiece, the matrix powder and thermally expanded graphite powder are mixed in a specific ratio, which is: the thermally expanded graphite powder accounts for 0.5%-3% of the total powder volume fraction.

[0023] In step three, the thickness of the powder layer is set to be more than twice the particle size of the matrix powder, and the heat from the high-energy beam can penetrate the matrix powder layer to melt all the matrix powder.

[0024] In step four, the thermally expanded graphite powder expands in the molten matrix powder and forms a microporous structure with a porosity of 10%-30% and a pore size of 30µm-100µm.

[0025] In step five, after the current layer scan is completed, a new composite powder is laid, and steps three and four are repeated.

[0026] In step six, after all layers have been scanned, the scanning is stopped, and the workpiece is removed after it has cooled down.

[0027] The present invention discloses an additive manufacturing method for microporous structures incorporating thermally expanded graphite, the advantages of which are as follows:

[0028] In additive manufacturing, the high-temperature expansion effect of thermally expanded graphite is utilized. By precisely controlling the expansion ratio, initial expansion temperature, complete expansion temperature, addition ratio, and particle size of thermally expanded graphite, and combining this with additive manufacturing processes, the final workpiece's pore size and porosity can be designed and controlled. This fills the technological gap in additive manufacturing technology for the preparation of micro-porous structural parts, possessing significant technological advantages and broad application prospects. This technical solution is highly versatile, has high production efficiency, and can be combined with various metal and non-metal powders to prepare micro-porous structural parts in various material systems. Attached Figure Description

[0029] Figure 1 This is a schematic diagram of the high-energy beam additive manufacturing scanning and thermal expansion graphite expansion pore creation of the present invention. Detailed Implementation

[0030] This invention provides an additive manufacturing method for microporous structures incorporating thermally expanded graphite, such as... Figure 1 As shown, it includes the following steps:

[0031] Step 1: Selection of thermally expanded graphite:

[0032] Based on the particle size of the matrix powder, the additive manufacturing temperature, and the internal pore size of the target workpiece, thermally expandable graphite with a specific initial expansion temperature, particle size, full expansion temperature, and expansion ratio is selected. Specifically, the particle size of the thermally expandable graphite is smaller than that of the matrix powder, the initial expansion temperature is more than 100°C lower than the melting temperature of the matrix powder, the full expansion temperature is more than 100°C higher than the additive manufacturing heating temperature, and the particle size after free expansion at the heating temperature is 5-15 times the pore size of the workpiece. The matrix powder can be either metallic or non-metallic.

[0033] Step 2: Determine the ratio of the mixed powders:

[0034] According to the porosity requirements of the workpiece, thermally expanded graphite powder is mixed with matrix powder at a ratio of 0.5%-3% of the total powder volume fraction to obtain a composite powder with uniform composition.

[0035] Step 3: Powder application:

[0036] The composite powder is laid on a molding substrate to form a uniform powder layer with a layer thickness of more than twice the particle size of the matrix powder and the high-energy beam heat can penetrate the powder layer to melt all the matrix powder.

[0037] Step 4: Melting and Hole Forming

[0038] (1) Control the movement of the high-energy beam to scan the composite powder layer and melt the matrix powder;

[0039] (2) Thermally expanded graphite powder expands in the molten matrix powder and forms a microporous structure with a porosity of 10%-30% and a pore size of 30µm-100µm;

[0040] Step 5: Stacking and Shaping

[0041] The molding substrate is lowered by one layer thickness, and steps three and four are repeated to make the microporous structure continuously distributed in three-dimensional space, and finally stacked to form a three-dimensional workpiece with a microporous structure inside.

[0042] Step Six: Obtain the workpiece:

[0043] After all layers have been scanned, stop scanning and remove the workpiece after it has cooled down.

[0044] In the method provided by this invention, for workpieces requiring smaller apertures, low-magnification thermal expansion graphite, such as 10-20 times, is typically used. For workpieces requiring larger apertures, medium-to-high-magnification thermal expansion graphite, such as 20-40 times, is typically used.

[0045] In additive manufacturing, the expansion process of thermally expandable graphite is precisely matched with the melting process of the matrix powder. If thermal expansion starts too early, the matrix has not melted and pores cannot be formed; if thermal expansion starts too late, the matrix has solidified and the expansion force cannot break through the solidified matrix, making it difficult to form effective pores. Therefore, by setting the initial expansion temperature of thermally expandable graphite to be more than 100°C lower than the matrix melting temperature and the complete expansion temperature to be more than 100°C higher than the additive manufacturing heating temperature, the thermally expandable graphite starts to expand when the matrix powder begins to melt and completes the main expansion process after the matrix is ​​completely melted. The fluidity of the molten matrix is ​​used to wrap the expanded graphite to form pores, avoiding pore collapse and preventing over-expansion. At the same time, by adjusting the expansion ratio, initial expansion temperature, complete expansion temperature, volume fraction of thermally expandable graphite, and matrix powder particle size and layer thickness, precise control of pore size and porosity can be achieved.

[0046] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. The following embodiments are used to illustrate the present invention, but are not intended to limit the scope of the present invention.

[0047] Example 1:

[0048] This embodiment provides a method for preparing a microporous aluminum alloy part, including the following steps:

[0049] Step 1: Selection of thermally expanded graphite:

[0050] The additive manufacturing matrix is ​​pure aluminum powder with a particle size of 30μm-50μm and a melting temperature of approximately 660℃. The required pore size is 35µm-65µm, and the porosity is 10%-20%. Therefore, based on these requirements, thermally expandable graphite with an initial expansion temperature of 200℃, a complete expansion temperature of 950℃, a particle size of 12μm-16μm, and an expansion ratio of 28 times is selected as the pore-forming agent.

[0051] Step 2: Determine the ratio of the mixed powders:

[0052] According to the porosity requirements, the two powders are uniformly mixed at a volume fraction of 0.6% to obtain a composite powder with uniform composition.

[0053] Step 3: Powder application:

[0054] Pure aluminum powder and thermally expanded graphite composite powder are laid on a molded substrate with a layer thickness of 100μm-120μm.

[0055] Step 4: Melting and Hole Forming

[0056] (1) Set the laser power of the laser SLM printer to 220W, the scanning speed to 500mm / s, the scanning spacing to 0.10mm, the scanning layer thickness to 0.12mm, the energy density to 440J / m, and the temperature to 750℃-800℃. Control the laser movement to scan pure aluminum powder and thermally expanded graphite composite powder, and melt the pure aluminum powder;

[0057] (2) The thermally expanded graphite powder expands freely to a particle size of 336μm-448μm. After expansion, the particle size of the thermally expanded graphite powder is 5.2-12.8 times the pore size of the part, and forms micropores with a pore size of 35µm-65µm.

[0058] Step 5: Stacking and Shaping

[0059] The molding substrate is lowered by one layer thickness, and steps three and four are repeated to make the microporous structure continuously distributed in three-dimensional space, and finally stacked to form a three-dimensional workpiece with a microporous structure inside.

[0060] Step Six: Obtain the workpiece:

[0061] After all layers have been scanned, stop scanning and remove the workpiece after it has cooled down.

[0062] Example 2:

[0063] This embodiment provides a method for fabricating a PEEK microporous structure part, including the following steps:

[0064] Step 1: Selection of thermally expanded graphite:

[0065] PEEK powder was selected as the matrix material, with a preferred particle size of 50 μm. The melting temperature of this PEEK powder is approximately 343℃. The required pore size is 65 μm-95 μm, and the porosity is 20%-30%. Therefore, based on these requirements, thermally expandable graphite with an initial expansion temperature of 180℃, a complete expansion temperature of 700℃, a particle size of 18 μm-24 μm, and an expansion ratio of 35 times was selected as the pore-forming agent.

[0066] Step 2: Determine the ratio of the mixed powders:

[0067] According to the porosity requirements, the two powders are uniformly mixed at a volume fraction of 0.8% to obtain a composite powder with uniform composition.

[0068] Step 3: Powder application:

[0069] PEEK powder and thermally expanded graphite composite powder were laid on a molded substrate with a layer thickness of 100 μm.

[0070] Step 4: Melting and Hole Forming

[0071] (1) Set the laser power of the laser SLM printer to 25W, the scanning speed to 600mm / s, the scanning spacing to 0.13mm, the scanning layer thickness to 0.1mm, the energy density to 41.7J / m, and the temperature to 400℃. Control the laser movement to scan PEEK powder and thermally expanded graphite composite powder, and melt the PEEK powder;

[0072] (2) The thermally expanded graphite powder expands freely to a particle size of 630μm-840μm. After expansion, the particle size of the thermally expanded graphite powder is 6.6-12.9 times the pore size of the part, and forms micropores with a pore size of 65µm-95µm.

[0073] Step 5: Stacking and Shaping

[0074] The molding substrate is lowered by one layer thickness, and steps three and four are repeated to make the microporous structure continuously distributed in three-dimensional space, and finally stacked to form a three-dimensional workpiece with a microporous structure inside.

[0075] Step Six: Obtain the workpiece:

[0076] After all layers have been scanned, stop scanning and remove the workpiece after it has cooled down.

[0077] Comparative Example 1:

[0078] This comparative example provides a method for additive manufacturing of aluminum alloy parts, specifically additive manufacturing without the addition of thermally expanded graphite, including the following steps:

[0079] Step 1: Prepare the powder:

[0080] Pure aluminum spherical powder, identical to that used in Example 1, was selected as the matrix powder.

[0081] Step 2: Powder application:

[0082] Pure aluminum powder is laid on a molded substrate with a layer thickness of 100μm-120μm.

[0083] Step 3: Melting

[0084] The laser power of the SLM printer is set to 220W, scanning speed to 500mm / s, scanning spacing to 0.10mm, layer thickness to 0.12mm, energy density to 440J / m, and temperature to 750℃-800℃. The laser is controlled to move and scan pure aluminum powder, melting it.

[0085] Step 4: Stacking and Shaping

[0086] Lower the molding substrate by one layer thickness, repeat steps three and four, and finally stack and mold a three-dimensional workpiece.

[0087] Step 5: Obtain the workpiece:

[0088] After all layers have been scanned, stop scanning and remove the workpiece after it has cooled down.

[0089] The difference between this comparative example and Example 1 is that no thermally expanded graphite powder was added in this comparative example; additive manufacturing was performed directly. The resulting workpiece had a dense structure and failed to achieve an internal microporous structure. In contrast, additive manufacturing was performed using a composite powder with added thermally expanded graphite powder. The thermally expanded graphite powder formed pores in the molten aluminum alloy pool, resulting in a part with a microporous structure. This demonstrates that the key process for preparing microporous structure parts in this invention is mixing thermally expanded graphite powder into the matrix powder.

[0090] Comparative Example 2:

[0091] This comparative example provides a method for additive manufacturing of aluminum alloy parts, specifically using high expansion ratio thermally expandable graphite, including the following steps:

[0092] Step 1: Selection of thermally expanded graphite:

[0093] The additive manufacturing matrix is ​​pure aluminum powder with a particle size of 30μm-50μm and a melting temperature of approximately 660℃. The required pore size is 35µm-65µm, and the porosity is 10%-20%. Therefore, based on these requirements, thermally expandable graphite with an initial expansion temperature of 200℃, a complete expansion temperature of 950℃, a particle size of 12μm-16μm, and an expansion ratio of 85 times is selected as the pore-forming agent.

[0094] Step 2: Determine the ratio of the mixed powders:

[0095] According to the porosity requirements, the two powders are uniformly mixed at a volume fraction of 0.6% to obtain a composite powder with uniform composition.

[0096] Step 3: Powder application:

[0097] Pure aluminum powder and thermally expanded graphite composite powder are laid on a molded substrate with a layer thickness of 100μm-120μm.

[0098] Step 4: Melting and Hole Forming

[0099] (1) Set the laser power of the laser SLM printer to 220W, the scanning speed to 500mm / s, the scanning spacing to 0.10mm, the scanning layer thickness to 0.12mm, the energy density to 440J / m, and the temperature to 750℃-800℃. Control the laser movement to scan pure aluminum powder and thermally expanded graphite composite powder, and melt the pure aluminum powder;

[0100] (2) The thermally expanded graphite powder expands freely to a particle size of 1020μm-1360μm. After expansion, the particle size of the thermally expanded graphite powder is 15.7-38.9 times the pore size of the part, and forms pores with a pore size of 68μm-272μm.

[0101] Step 5: Stacking and Shaping

[0102] The molding substrate is lowered by one layer thickness, and steps three and four are repeated to make the porous structure continuously distributed in three-dimensional space, and finally stacked to form a three-dimensional workpiece with a porous structure inside.

[0103] Step Six: Obtain the workpiece:

[0104] After all layers have been scanned, stop scanning and remove the workpiece after it has cooled down.

[0105] The comparative example, prepared using thermally expanded graphite with a high expansion ratio, differs from Example 1 in that the resulting workpiece exhibits larger and more irregular internal pore sizes, severely disrupting workpiece continuity and failing to meet design requirements. This comparative example powerfully demonstrates that, in the technical solution of this invention, the expansion ratio of thermally expanded graphite is a key process for achieving precise porosity manufacturing, highlighting the inventiveness and technical depth of this invention. When the expansion ratio of thermally expanded graphite is too high, the force and volume generated by its expansion are excessive, resulting in larger and more irregular pore sizes formed during additive manufacturing, thus failing to meet design requirements.

[0106] Comparative Example 3:

[0107] This comparative example provides a method for additive manufacturing of aluminum alloy workpieces, specifically the preparation of microporous structures under conditions where thermally expanding graphite does not effectively expand, including the following steps:

[0108] Step 1: Selection of thermally expanded graphite:

[0109] The additive manufacturing matrix is ​​pure aluminum powder with a particle size of 30μm-50μm and a melting temperature of approximately 660℃. The required pore size is 35µm-65µm, and the porosity is 10%-20%. Therefore, based on these requirements, thermally expandable graphite with an initial expansion temperature of 200℃, a complete expansion temperature of 950℃, a particle size of 12μm-16μm, and an expansion ratio of 5 times is selected as the pore-forming agent.

[0110] Step 2: Determine the ratio of the mixed powders:

[0111] According to the porosity requirements, the two powders are uniformly mixed at a volume fraction of 0.6% to obtain a composite powder with uniform composition.

[0112] Step 3: Powder application:

[0113] Pure aluminum powder and thermally expanded graphite composite powder are laid on a molded substrate with a layer thickness of 100μm-120μm.

[0114] Step 4: Melting and Hole Forming

[0115] (1) Set the laser power of the laser SLM printer to 220W, the scanning speed to 500mm / s, the scanning spacing to 0.10mm, the scanning layer thickness to 0.12mm, the energy density to 440J / m, and the temperature to 750℃-800℃. Control the laser movement to scan pure aluminum powder and thermally expanded graphite composite powder, and melt the pure aluminum powder;

[0116] (2) The thermally expanded graphite powder expands freely to a particle size of 60μm-80μm. After expansion, the particle size of the thermally expanded graphite powder is 0.9-2.3 times the pore size of the part, and forms micropores with a pore size of 4μm-16μm.

[0117] Step 5: Stacking and Shaping

[0118] The molding substrate is lowered by one layer thickness, and steps three and four are repeated to make the microporous structure continuously distributed in three-dimensional space, and finally stacked to form a three-dimensional workpiece with a microporous structure inside.

[0119] Step Six: Obtain the workpiece:

[0120] After all layers have been scanned, stop scanning and remove the workpiece after it has cooled down.

[0121] The comparative example uses thermally expanded graphite with a low expansion ratio. The difference between this example and Example 1 is that the thermally expanded graphite powder failed to reach the required expansion volume during preparation, resulting in a workpiece that did not meet the requirements for pore size and porosity. This comparative example demonstrates that when the expansion ratio of the thermally expanded graphite is too low, the force generated by its expansion is insufficient to form stable and obvious pores in the matrix, thus failing to achieve effective pore formation. This further confirms that selecting an appropriate expansion ratio is crucial for successfully preparing microporous structure parts. Comparative Examples 2 and 3 together demonstrate that the parameter coupling design of selecting graphite with the corresponding expansion ratio based on the target pore size in this invention is key to achieving a qualified microporous structure, and cannot be achieved simply by adjusting the type of graphite.

[0122] It should be noted that the specific embodiments and examples described above are only used to clearly illustrate the technical solutions of the present invention, and are not intended to limit them. The high-energy beam types used to implement the method of the present invention, such as lasers and electron beams, and the powder supply methods, such as powder spreading and powder feeding, can all be equivalently replaced or combined. These obvious modifications or equivalent substitutions are all within the protection scope of the present invention.

Claims

1. A method for additive manufacturing of microporous structures incorporating thermally expanded graphite, characterized in that, Includes the following steps: Step 1: Selection of thermally expanded graphite: Based on the particle size of the matrix powder, the additive manufacturing temperature, and the internal pore size of the target workpiece, a certain initial expansion temperature, particle size, full expansion temperature, and expansion ratio of thermally expanded graphite are selected; wherein, the matrix powder can be metal powder or non-metal powder. Step 2: Determine the ratio of the mixed powders: According to the porosity requirements of the workpiece, the matrix powder and thermally expanded graphite powder are mixed in a certain proportion to obtain a composite powder with uniform composition. Step 3: Powder application: The composite powder is laid on the molding substrate to form a uniform powder layer; Step 4: Melting and Hole Forming (1) Control the movement of the high-energy beam to scan the composite powder layer and melt the matrix powder; (2) Thermally expanding graphite powder expands in volume and forms tiny pores; Step 5: Stacking and Shaping The molding substrate is lowered by one layer thickness, and steps three and four are repeated to make the microporous structure continuously distributed in three-dimensional space, and finally stacked to form a three-dimensional workpiece with a microporous structure inside. Step Six: Obtain the workpiece: After printing is complete, remove the three-dimensional workpiece.

2. The additive manufacturing method for microporous structures with added thermally expanded graphite according to claim 1, characterized in that, In step one, the particle size of thermally expanded graphite is smaller than that of the matrix powder, the initial expansion temperature is more than 100°C lower than the melting temperature of the matrix powder, and the full expansion temperature is more than 100°C higher than the heating temperature of additive manufacturing.

3. The additive manufacturing method for microporous structures with added thermally expanded graphite according to claim 2, characterized in that, In step one, after the thermally expanded graphite expands freely at the heating temperature, its particle size is 5-15 times the pore size of the part.

4. The additive manufacturing method for microporous structures incorporating thermally expanded graphite according to claim 2 or 3, characterized in that, In step two, according to the porosity requirements of the workpiece, the matrix powder and thermally expanded graphite powder are mixed in a specific ratio, which is: the thermally expanded graphite powder accounts for 0.5%-3% of the total powder volume fraction.

5. A method for additive manufacturing of microporous structures with added thermally expanded graphite according to claim 2 or 3, characterized in that, In step three, the thickness of the powder layer is set to be more than twice the particle size of the matrix powder, and the heat from the high-energy beam can penetrate the matrix powder layer to melt all the matrix powder.

6. The additive manufacturing method for microporous structures incorporating thermally expanded graphite according to claim 2 or 3, characterized in that, In step four, the thermally expanded graphite powder expands in the molten matrix powder and forms a microporous structure with a porosity of 10%-30% and a pore size of 30µm-100µm.

7. The additive manufacturing method for microporous structures incorporating thermally expanded graphite according to claim 2 or 3, characterized in that, In step five, after the current layer is scanned, a new composite powder is laid, and steps three and four are repeated.

8. A method for additive manufacturing of microporous structures with added thermally expanded graphite according to claim 2 or 3, characterized in that, In step six, after all layers have been scanned, the scanning is stopped, and the workpiece is removed after cooling.

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