Method for preparing aluminum alloy capillary structure based on selective laser melting technology

Abstract

The invention discloses a method for preparing an aluminum alloy capillary structure based on a selective laser melting technology, which comprises the following steps of: comprehensively regulating and controlling technological parameters of selective laser melting according to laser energy density by utilizing the forming principle of'incomplete melting pores' and'keyhole pores' in a selective laser melting forming process; and the porosity-adjustable aluminum alloy capillary structure is prepared. The method mainly comprises the following steps that firstly, aluminum alloy spherical powder with the particle size range suitable for the selective laser melting process is selected; secondly, a laser energy density reference value is selected according to the optimal technological parameters of selective laser melting forming of the aluminum alloy solid structure; then, according to the laser energy density, the laser power, the scanning rate, the scanning interval and other technological parameters are comprehensively regulated and controlled, the powder laying layer thickness is set, and the aluminum alloy capillary structure is prepared; and finally, the porosity of the capillary structure is measured, the correlation between the technological parameters and the porosity is established, a technological window is determined, and the aluminum alloy capillary structure with the adjustable porosity is prepared.

Description

Technical Field

[0001] The present invention belongs to the technical field of additive manufacturing, and specifically relates to a method for preparing an aluminum alloy capillary structure based on selective laser melting technology. Background Art

[0002] With the rapid development of aerospace, electronic information, transportation and other fields, their key components have higher requirements for various properties such as lightweight, thermal management, and energy absorption of materials. Aluminum alloy, as a lightweight alloy material, has good comprehensive properties such as mechanics, thermals, and forming processability, and is widely used in aviation, aerospace, automobile, electronics and other industrial fields. Capillary structure materials, as a special type of porous material, have good heat transfer performance, mass transfer performance, shock absorption performance, and energy absorption performance. Therefore, the preparation of aluminum alloy capillary structures is expected to provide an effective solution for the manufacture of key components in aviation, aerospace, automobile, electronics and other industrial fields, especially thermal management components.

[0003] The fabrication of capillary-structured metal materials using traditional powder metallurgy methods is limited by numerous factors, including the complexity of the pore-forming process, pore size accuracy, minimum pore size, and the need to clean residual powder after forming. Selective laser melting, as an additive manufacturing technique, offers precision and flexibility that are difficult to achieve with traditional capillary structure fabrication processes. In selective laser melting, variations in factors such as laser power, scanning speed, scanning pitch, and powder layer thickness can lead to the formation of numerous pores. While pores are generally considered a defect in additive manufacturing processes, negatively impacting material performance, they are a core structural characteristic of capillary-structured materials, and porosity is closely linked to their mechanical, thermal, and other physical properties. Leveraging the pore formation patterns of selective laser melting allows for the controllable fabrication of aluminum alloy capillary structures, providing a new approach for capillary structure fabrication. Currently, a systematic, selective laser melting-based process for fabricating capillary structures with controllable porosity is lacking. Summary of the Invention

[0004] The primary purpose of this invention is to overcome the shortcomings and deficiencies of existing capillary structure fabrication techniques and to provide a method and structure for fabricating aluminum alloy capillary structures using selective laser melting. This method utilizes the formation patterns of "unfused pores" and "keyhole pores" during selective laser melting. By adjusting laser process parameters and powder layer thickness, the relationship between the selective laser melting process and the porosity of the aluminum alloy capillary structure is explored, enabling the efficient fabrication of aluminum alloy capillary structures with controllable porosity.

[0005] In order to achieve the above object, the present invention adopts the following technical solutions:

[0006] The first aspect of the present invention discloses a method for preparing an aluminum alloy capillary structure based on selective laser melting technology. The method is carried out in an inert gas protection chamber. Aluminum alloy powder is evenly spread layer by layer on a substrate. Laser is used as a heat source. The laser melts the powder according to a preset scanning path to freely form an aluminum alloy capillary structure component with controllable porosity. The method includes the following steps:

[0007] S1. Select aluminum alloy spherical powder with a suitable particle size range and dry the aluminum alloy powder; the dried powder is evenly spread on a preheated substrate;

[0008] S2. Refer to the laser energy density value under the 99.9% density forming process conditions of aluminum alloy, and design the selective laser melting process parameters according to different energy density percentages, including laser power, laser beam spot shape, scanning rate, and scanning spacing; according to the powder particle size distribution, set different powder layer thicknesses for forming;

[0009] S3. According to the selected laser melting process parameters set above, the alloy powder is laser melted and formed under the protection of an inert gas to prepare an aluminum alloy capillary structure;

[0010] S4. Measure the porosity of the aluminum alloy capillary structure during forming with different selective laser melting process parameters and powder coating thicknesses, and correlate the mapping relationship between the porosity of the aluminum alloy capillary structure and the laser process parameters;

[0011] S5. According to the porosity requirements of the formed part, appropriate laser selective melting process parameters and powder thickness are selected according to the above mapping relationship to complete the preparation of the capillary structure formed part.

[0012] This method first designs the selective laser melting process parameters, including laser power, laser beam spot shape, scanning rate, scanning spacing, and powder layer thickness, to achieve the preparation of aluminum alloy capillary structures; then measures its porosity and correlates the porosity with the selective laser melting process parameters to confirm the process window for preparing capillary structures with different porosities using laser process parameters; finally, refers to the process window to repeatedly prepare aluminum alloy capillary structures for process verification.

[0013] Furthermore, the method for preparing the aluminum alloy capillary structure is achieved by utilizing the "unfused pores" and "keyhole pores" in the selective laser melting process, and the porosity of the prepared aluminum alloy capillary structure can be adjusted between 5% and 65%.

[0014] Furthermore, the beam spot shape of the laser is one or more of circular, rectangular and elliptical.

[0015] Furthermore, the aluminum alloy powder has a particle size range of 15 to 150 μm and a near-spherical morphology. This suitable particle size distribution and near-spherical powder shape ensure good powder flowability, which is key to achieving uniform distribution of "unfused porosity" and "keyhole porosity," ensuring a uniform capillary structure.

[0016] Furthermore, the aluminum alloy powder is dried at 80°C for 180 to 540 minutes. The purpose of the drying process is to improve the fluidity of the powder and obtain a uniform capillary structure.

[0017] Furthermore, in step S1, the substrate is preheated to 80-120° C. The purpose of the preheating treatment is to reduce thermal stress during the forming process and obtain a complete capillary structure.

[0018] Furthermore, the energy density corresponding to the selective laser melting process parameters ranges from 5% to 90% of the energy density for a part density of 99.9%. Laser energy density is a key parameter for controlling the formation of "unfused porosity" and "keyhole porosity." Furthermore, laser energy density controls the surface quality of the melted powder layer, which in turn influences the coating quality of the next powder layer and the number and distribution of porosity after forming. When the energy density is below 5%, the powder cannot be melted, and thus forming is impossible. When the energy density is above 90%, the part is nearly dense, and no pores can be formed. Therefore, selecting the appropriate laser energy density is a key step in achieving a controllable number of "unfused porosity" and "keyhole porosity."

[0019] Furthermore, the powder layer thickness range is set to [5μm, 75μm]. The powder layer thickness controls the pore distribution characteristics of the powder before melting and forming. When the powder layer thickness is less than 33% of the minimum powder particle size, the amount of powder applied is too small, and a complete capillary structure cannot be formed. When the powder layer thickness is greater than 50% of the maximum powder particle size, the amount of powder applied is too large, the porosity of the formed part is low, and it is difficult to control. Therefore, precise control of the layer thickness is also a key step in obtaining a controllable amount of "unfused pores" and "keyhole pores."

[0020] Furthermore, the selective laser melting process parameters for preparing the aluminum alloy capillary structure in step S5 are set as follows: laser power: 100 to 400 W, scanning rate: 100 to 6000 mm / s, and scanning spacing: 100 to 600 μm. Appropriate selective laser melting process parameters ensure the integrity and stability of the aluminum alloy capillary structure.

[0021] Furthermore, during the forming process, the printing of each layer is first completed by the laser beam according to a preset scanning path, scanning and melting the entire area in the form of short straight lines to complete single-layer printing; the steps of single-layer printing are repeated layer by layer until the manufacturing and forming of the aluminum alloy capillary structure is completed.

[0022] A second aspect of the present invention discloses an aluminum alloy capillary structure prepared based on the selective laser melting technology. The aluminum alloy capillary structure is prepared using the above-mentioned method for preparing an aluminum alloy capillary structure based on the selective laser melting technology.

[0023] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0024] (1) The present invention realizes the rapid preparation of aluminum alloy capillary structures by regulating the process parameters of selective laser melting, and constructs a process window for preparing aluminum alloy capillary structures by selective laser melting, so that the porosity can be adjusted between 5 and 65%, and the minimum pore size is almost not limited by the forming process.

[0025] (2) The present invention is a method for directly forming a capillary structure, such as steps S1-S3. Compared with the traditional sintering foaming process, this method avoids the use of foaming agent, foaming treatment and related cleaning processes, and realizes single-step forming, thereby achieving fast and low-cost manufacturing.

[0026] (3) The present invention is a method for directly forming a capillary structure, such as steps S1-S3. Compared with the additive manufacturing process of a three-dimensional array porous structure, this method eliminates the model design of the three-dimensional array structure, eliminates the limitation of the additive manufacturing process accuracy on the pore size accuracy and minimum pore size in the three-dimensional array structure, and avoids the problem of cleaning the residual powder inside the pores after additive manufacturing; thus achieving fast and low-cost manufacturing.

[0027] (4) The present invention prepares aluminum alloy capillary structures by regulating the process parameters of selective laser melting, such as steps S1-S3. Based on the characteristics of selective laser melting technology, the personalized and customized free forming of capillary structural parts can be achieved, so that the application scenarios of capillary structural parts are expanded, such as the rapid manufacturing of lightweight complex parts, structural and functional integration, and multifunctionality. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0029] Figure 1 This is a process flow chart of a method for preparing an aluminum alloy capillary structure based on selective laser melting technology disclosed in the present invention;

[0030] Figure 2 The AlSi10Mg capillary structure prepared in Example 1 (size: 8×8×8 mm 3)’s macroscopic morphology;

[0031] Figure 3 is a surface micromorphology image of the AlSi10Mg capillary structure with a porosity of ~33% in Example 1;

[0032] Figure 4 Metallographic images of the top and side surfaces of an AlSi10Mg capillary structure with a porosity of ~33%;

[0033] Figure 5 is a porosity diagram of the AlSi110Mg capillary structure prepared in Example 1;

[0034] Figure 6 This is a nearly dense solid image of a capillary structure with a low porosity and a failed formation in Comparative Example 1;

[0035] Figure 7 The AlSi7Mg capillary structure prepared in Example 2 (size: 8×8×8 mm 3 )’s macroscopic morphology;

[0036] Figure 8 is a microscopic surface morphology of the AlSi7Mg capillary structure with a porosity of ~62% in Example 2;

[0037] Figure 9 The top and side macromorphology of the AlSi7Mg capillary structure with a porosity of ~62%;

[0038] Figure 10 This is the porosity diagram of the AlSi7Mg capillary structure prepared in Example 2. DETAILED DESCRIPTION

[0039] In order to enable those skilled in the art to better understand the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments in the present invention, all other embodiments obtained by those skilled in the art without creative work are within the scope of protection of the present invention.

[0040] References to "embodiments" in this application mean that a particular feature, structure, or characteristic described in connection with the embodiment may be included in at least one embodiment of the application. The appearance of this phrase in various places in the specification does not necessarily refer to the same embodiment, nor does it constitute an independent or alternative embodiment that is mutually exclusive of other embodiments. It is understood, both explicitly and implicitly, by those skilled in the art that the embodiments described in this application may be combined with other embodiments.

[0041] Example 1

[0042] This embodiment specifically discloses a method for preparing an AlSi10Mg capillary structure (size: 8×8×8 mm) based on selective laser melting technology. 3 ) method, the implementation steps are as follows:

[0043] S1. Select an appropriate AlSi10Mg alloy powder with the following composition: 9 ≤ Si ≤ 11 wt.%, 0.2 ≤ Mg ≤ 0.45 wt.%, Al ≥ 88.55 wt.%. The powder particle size should be 20 to 63 μm, and the powder morphology should be nearly spherical. Before preparation, the AlSi10Mg alloy powder should be dried at 80°C for 360 minutes. The dried powder should be evenly spread on the baseplate of the forming chamber, which should be preheated to 100°C.

[0044] S2. Design the selective laser melting process parameters, as shown in Table 1. The specific parameter ranges are: laser power: 50–200 W; scanning rate: 200–5600 mm / s; scanning spacing: 100–300 μm; and powder layer thickness: 20–40 μm.

[0045] Table 1. Process parameters for forming AlSi10Mg alloy capillary structures

[0046]

[0047] S3. During the forming process, the laser beam first scans and melts the entire area in a short straight line according to a preset scanning path to complete single-layer printing. The steps of single-layer printing are repeated layer by layer until the additive manufacturing of the AlSi10Mg capillary structure is completed. Figure 2 As shown in Figure 2, the AlSi10Mg capillary structure has a complete macroscopic morphology. Figure 3 and Figure 4 As shown in Figure 3, the pores of the capillary structure are mainly composed of “unfused pores” and “keyhole pores” of uniformly distributed, spherical powders.

[0048] S4. Measure the porosity of the prepared AlSi10Mg capillary structure, such as Figure 5 As shown in the figure, it can be seen that according to the designed process parameters, capillary structures with different porosities can be prepared, and the porosity of the capillary structure can be accurately controlled within a certain range.

[0049] Comparative Example 1

[0050] The process parameters for selective laser melting were designed as shown in Tables 1 and 2. The specific parameter ranges are: laser power: 100-200 W; scanning rate: 400-5600 mm / s; scanning spacing: 100-300 μm; and powder layer thickness: 20-40 μm. Compared with Example 1, when the energy density is 4.5% and 95%, the capillary structure either fails to form or a nearly dense solid structure is obtained, such as Figure 6 shown.

[0051] Example 2

[0052] This embodiment specifically discloses a method for preparing an AlSi7Mg capillary structure (size: 8×8×8 mm) based on selective laser melting technology. 3 ) method, the implementation steps are as follows:

[0053] S1. Select an appropriate AlSi7Mg alloy powder with an aluminum alloy composition of 6.5 ≤ Si ≤ 7.5 wt.%, 0.2 ≤ Mg ≤ 0.6 wt.%, and Al ≥ 90 wt.%. The powder particle size should range from 15 to 63 μm, and the powder morphology should be nearly spherical. Before preparation, the AlSi7Mg alloy powder should be dried at 80°C for 360 minutes. The dried powder should be evenly spread on the baseplate of the forming chamber, which should be preheated to 100°C.

[0054] S2. Design the selective laser melting process parameters, as shown in Table 2. The specific parameter ranges are: laser power: 150 W; scanning rate: 100 to 4500 mm / s; scanning spacing: 200 to 500 μm; and powder layer thickness: 20 to 40 μm.

[0055] Table 2. Process parameters for forming capillary structures of AlSi7Mg alloy

[0056]

[0057] S3. During the forming process, the laser beam first scans and melts the entire area in a short straight line according to a preset scanning path to complete single-layer printing. The single-layer printing steps are repeated layer by layer until the AlSi7Mg capillary structure is formed. Figure 7 As shown in Figure 2, the AlSi10Mg capillary structure has a complete macroscopic morphology. Figure 8 and Figure 9 As shown in Figure 3, the pores of the capillary structure are mainly composed of “unfused pores” and “keyhole pores” of uniformly distributed, spherical powders.

[0058] S4. Measure the porosity of the prepared AlSi7Mg capillary structure, such as Figure 10As shown in the figure, it can be seen that according to the designed process parameters, capillary structures with different porosities can be prepared, and the porosity of the capillary structure can be accurately controlled within a certain range.

[0059] It should be noted that, for the sake of convenience, the aforementioned method embodiments are all expressed as a series of action combinations, but those skilled in the art should know that the present invention is not limited to the described order of actions, because according to the present invention, certain steps can be performed in other orders or simultaneously.

[0060] The technical features of the above embodiments can be combined arbitrarily. To make the description concise, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0061] The above embodiments are preferred implementation modes of the present invention, but the implementation modes of the present invention are not limited to the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications that do not deviate from the spirit and principles of the present invention should be considered as equivalent replacement methods and are included in the scope of protection of the present invention.

Claims

1. A method for fabricating an aluminum alloy capillary structure using selective laser melting technology. This method is carried out in an inert gas chamber. Aluminum alloy powder is evenly spread layer by layer on a substrate. Laser heat is used as a heat source. The laser melts the powder along a preset scanning path, freely forming an aluminum alloy capillary structure component with controllable porosity. The method is characterized by: The method comprises the following steps: S1. Select aluminum alloy spherical powder with a suitable particle size range and dry the aluminum alloy powder; the dried powder is evenly spread on a preheated substrate; S2. Refer to the laser energy density value under the 99.9% density forming process conditions of aluminum alloy, and design the selective laser melting process parameters according to different energy density percentages, including laser power, laser beam spot shape, scanning rate, and scanning spacing; according to the powder particle size distribution, set different powder layer thicknesses for forming; S3. According to the selected laser melting process parameters set above, the alloy powder is laser melted and formed under the protection of an inert gas to prepare an aluminum alloy capillary structure; S4. Measure the porosity of the aluminum alloy capillary structure during forming with different selective laser melting process parameters and powder coating thicknesses, and correlate the mapping relationship between the porosity of the aluminum alloy capillary structure and the laser process parameters; S5. According to the porosity requirements of the formed part, appropriate laser selective melting process parameters and powder thickness are selected according to the above mapping relationship to complete the preparation of the capillary structure formed part.

2. The method according to claim 1, characterized in that The method for preparing an aluminum alloy capillary structure is achieved by utilizing "unfused pores" and "keyhole pores" in the selective laser melting process. The porosity of the prepared aluminum alloy capillary structure can be adjusted between 5% and 65%.

3. The method according to claim 1, characterized in that The beam spot shape of the laser is one or more of circular, rectangular and elliptical.

4. The method according to claim 1, wherein The particle size of the aluminum alloy powder ranges from 15 to 150 μm, and the powder morphology is nearly spherical.

5. The method according to claim 1, characterized in that The aluminum alloy powder drying process is to keep the temperature at 80 ℃ for 180~540 minutes, and preheat the substrate to 80~120 ℃.

6. The method according to claim 1, wherein The energy density value corresponding to the selective laser melting process parameters is 5% to 90% of the energy density value when the density of the formed part is 99.9%.

7. The method according to claim 1, characterized in that The thickness of the powder layer is set to [5 μm, 75 μm].

8. The method according to claim 1, characterized in that The laser selective melting process parameters for preparing the aluminum alloy capillary structure in step S5 are set as follows: laser power: 100 ~ 400 W, scanning rate: 100 ~ 6000 mm / s, and scanning spacing: 100 ~ 600 μm.

9. The method according to claim 1, characterized in that During the forming process, the printing of each layer is first completed by the laser beam according to a preset scanning path, scanning and melting the entire area in the form of short straight lines to complete single-layer printing; the single-layer printing steps are repeated layer by layer until the manufacturing and forming of the aluminum alloy capillary structure is completed.

10. An aluminum alloy capillary structure prepared based on selective laser melting technology, characterized in that: The aluminum alloy capillary structure is prepared by the method described in any one of claims 1 to 9 above.

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