A 3D-printed high-strength aluminum alloy with no cracks suitable for anodic oxidation and a preparation method thereof

Abstract

The application discloses a 3D printing high-strength aluminum alloy without cracks suitable for anodic oxidation and a preparation method thereof, which comprises the following components in percentage by mass: Cu: 1.5-4 wt%; Fe: 0.5-3 wt%; Mg: 0-1 wt%; Ti: 0-1 wt%; Sc: 0-0.7 wt%; Zr: 0-0.7 wt%; Si: 0-0.08 wt%; and the rest is Al. The application converts the traditional harmful elements Cu and Fe into functional components by utilizing the rapid solidification characteristics of 3D printing, Cu forms CuO-Al2O3 composite oxide film to enhance coloring property, Fe and Cu cooperatively form Al 23 CuFe4 conductive phase optimizes anode current distribution. Meanwhile, Ti, Sc, Zr and other elements are introduced to refine grains and improve strength.

Description

Technical Field

[0001] This invention belongs to the field of additive manufacturing materials technology, specifically relating to a crack-free high-strength aluminum alloy suitable for anodizing and its preparation method for 3D printing. Background Technology

[0002] In the consumer 3C (computer, communication, and consumer electronics) sector, 3D-printed aluminum alloys are gradually becoming an important material choice for manufacturing exterior components such as phone cases and watch cases due to their unique properties and advantages. Aluminum alloys possess advantages such as light weight, high strength, good heat dissipation, recyclability, and a unique metallic texture, allowing them to meet the demands for thinner and more portable 3C products while providing a good user experience. However, the low surface hardness and poor wear resistance of aluminum alloys limit their direct application in some high-requirement exterior components. Anodizing, as an effective surface treatment technology, can significantly improve the corrosion resistance, hardness, and wear resistance of aluminum alloys. Furthermore, through dyeing, it can impart rich colors to aluminum alloy exterior components, achieving aesthetic and decorative effects and meeting consumers' demands for personalized and beautiful product appearances.

[0003] However, current 3D printing aluminum alloy anodizing faces bottlenecks. Most crack-free aluminum alloys suitable for 3D printing produce uneven oxide films after anodizing, leading to color differences and film peeling during the oxidation process. On one hand, internal defects in 3D-printed aluminum alloys make it difficult to control the uniformity and density of the anodized film, affecting the appearance and performance consistency of the final product. On the other hand, different compositions of 3D-printed aluminum alloys result in inconsistent conductivity, leading to varying anodic current densities during anodizing and inconsistent uniformity of the generated anodized film. Therefore, designing 3D-printed aluminum alloy compositions suitable for anodizing is crucial, requiring a balance between 3D printing formability and anodizing capability. Summary of the Invention

[0004] The purpose of this section is to outline some aspects of embodiments of the present invention and to briefly describe some preferred embodiments. Simplifications or omissions may be made in this section, as well as in the abstract and title of this application, to avoid obscuring the purpose of these documents; however, such simplifications or omissions should not be construed as limiting the scope of the invention.

[0005] In view of the problems existing in the above and / or prior art, the present invention is proposed.

[0006] Therefore, the purpose of this invention is to overcome the shortcomings of the prior art and provide a crack-free high-strength aluminum alloy suitable for anodizing and its preparation method.

[0007] To solve the above-mentioned technical problems, the present invention provides the following technical solution: a high-strength, crack-free aluminum alloy suitable for anodizing in 3D printing, characterized in that: by mass fraction, it is composed of the following components: Cu: 1.5~4wt%; Fe: 0.5~3wt%; Mg: 0~1wt%; Ti: 0~1wt%; Sc: 0~0.7wt%; Zr: 0~0.7wt%; Si: 0~0.08wt%; the remainder is Al.

[0008] Furthermore, in this technical solution:

[0009] The role of Cu (Cu) in anodizing: Cu effectively enhances the mechanical properties of alloys. Although Cu is currently considered a detrimental element in the anodizing of cast alloys, believed to accelerate the chemical dissolution of the anodic oxide film (electric field-induced dissolution effect), leading to uneven film texture, poor continuity, and even difficulty in forming a dense oxide film, the rapid solidification of 3D printing provides higher solid solubility and forms fine, dispersed precipitates, showcasing the benefits of Cu in the anodizing process. On one hand, Cu dissolved atoms form Cu oxide (CuO) during anodizing, which, together with aluminum oxide (Al2O3), constitutes the oxide film. This composite oxide film can improve the corrosion resistance of the material to some extent. It also affects the microstructure of the oxide film, making it denser and contributing to improved surface smoothness and gloss. On the other hand, Cu-containing oxide films more readily adsorb certain colorants, thereby improving the coloring effect. It is important to note that the Cu content must be controlled within a suitable range; excessively high levels may lead to uneven or localized corrosion of the oxide film, requiring optimization of process parameters such as current density and electrolyte composition.

[0010] The role of Fe: Fe forms the intermetallic compound Al with Cu in aluminum alloys. 23 The CuFe4 phase, with its high conductivity and electrode potential similar to that of the aluminum matrix, is not easily dissolved and is dispersed throughout the matrix. This facilitates uniform current distribution during anodizing, preventing uneven oxide film thickness and localized dissolution. Before anodizing, Fe, as a solid solution strengthening element, already enhances the strength and toughness of the aluminum alloy, providing a more stable supporting matrix for the subsequent oxide film. Similar to Cu, Fe is considered a harmful element in the anodizing process of traditional cast alloys, as it is believed that Fe impurities can disrupt the compactness of the oxide film, forming micro-cell corrosion points and reducing the corrosion resistance of the aluminum alloy. However, during the rapid solidification process of 3D printing, the easily soluble Al3Fe phase no longer forms; instead, the metastable Al6Fe phase is formed, along with Al2Fe formed together with Cu. 23 The CuFe4 phase consists of intermetallic compounds that are not easily dissolved. It is important to note that the Fe content must be controlled within a suitable range; excessively high levels may lead to uneven oxide film formation or localized corrosion. The effect needs to be optimized by adjusting process parameters such as current density and electrolyte composition.

[0011] The role of magnesium (Mg): In aluminum alloys, Mg works synergistically with other elements (such as Si and Cu) to refine the grain structure of alumina (Al₂O₃) formed during anodizing, resulting in a denser and more uniform oxide film. This dense structure effectively blocks the penetration of external corrosive media, thereby enhancing the corrosion resistance of the aluminum alloy. Simultaneously, Mg optimizes the interfacial bonding between the substrate and the oxide film. During anodizing, Mg partially dissolves and participates in the oxidation reaction, forming magnesium oxides (such as MgO). These oxides, combined with the alumina film, enhance the adhesion between the oxide film and the substrate, reducing the risk of peeling. Furthermore, the presence of Mg can moderately neutralize the acidity of the electrolyte (such as sulfuric acid), slowing down the chemical dissolution rate of the oxide film and facilitating the formation of a thicker oxide film.

[0012] The role of titanium (Ti): As a grain refiner, titanium significantly refines the microstructure of aluminum alloys. After grain refinement, the alumina film formed during anodizing is more uniform and dense, reducing defects such as micropores and cracks, thereby improving the overall quality of the oxide film. Furthermore, titanium's grain-refining effect reduces the difference in electrochemical activity between the aluminum alloy matrix and the precipitated particles, resulting in higher chemical stability of the anodized film. A more uniform film can more effectively block corrosive media, thus improving corrosion resistance.

[0013] The role of Sc and Zr elements is primarily to form L12-Al3(Sc,Zr) nanoparticles in the Al matrix. These nanoparticles, typically located in the laser remelting region at the molten pool boundary, act as nucleation sources, significantly refining the grains and increasing liquid supply to reduce cracking. The room-temperature strengthening effect of L12 coherent particles is significant, giving the alloy excellent room-temperature mechanical properties. Simultaneously, Sc forms dipoles with Cu and Fe in the matrix, remaining stable within it. These dipoles can act as "microelectrodes" during the anodic oxidation process, promoting uniform current distribution, resulting in a denser and more uniform film, further enhancing corrosion resistance.

[0014] The role of silicon (Si): Although added only as a trace element, it has a certain impact on the alloy properties. In the sealing treatment after anodizing (such as hot water or nickel salt sealing), silicon oxide (SiO2) may fill the micropores of the alumina film, reduce porosity, form a more complete protective barrier, and effectively block the penetration of corrosive media.

[0015] As a preferred embodiment of the 3D-printed crack-free high-strength aluminum alloy suitable for anodizing according to the present invention, the 3D-printed crack-free high-strength aluminum alloy has the following characteristics:

[0016] (i) Density exceeding 99.95%, average hardness 135~160 HV 0.2 ;

[0017] (ii) Room temperature yield strength 410~470 MPa, tensile strength 458~513 MPa, elongation exceeding 6%;

[0018] (iii) The average hardness increases to 320~375 HV after anodizing. 0.2 The average single-point withstand voltage is 1.55~1.78kV.

[0019] As a preferred embodiment of the 3D-printed crack-free high-strength aluminum alloy suitable for anodizing as described in this invention, the alloy comprises, by mass fraction, the following components: Cu: 2.5 wt%; Fe: 2 wt%; Mg: 0.5 wt%; Ti: 0.5 wt%; Sc: 0.5 wt%; Zr: 0.5 wt%; Si: 0.05 wt%; with the remainder being Al.

[0020] Another objective of this invention is to overcome the shortcomings of the prior art and provide a method for preparing a crack-free high-strength aluminum alloy for 3D printing, wherein the components are weighed, raw materials are prepared, and alloy powder is obtained by vacuum melting and gas atomization treatment.

[0021] The alloy powder is sieved and dried.

[0022] After drying, the material is 3D printed and stress-relief annealed.

[0023] The surface is sandblasted and then anodized.

[0024] As a preferred embodiment of the preparation method described in this invention, the vacuum melting temperature is 700~800℃, the melting chamber pressure is 3~7 MPa; the atomization powdering pressure is 2~5 MPa; and the powder is dried at 50~90℃ for 2~6 hours.

[0025] In a preferred embodiment of the preparation method described in this invention, the stress-relief annealing temperature is 150~175℃.

[0026] As a preferred embodiment of the preparation method described in this invention, the 3D printing parameters are: laser power: 100~400 W; scanning speed: 800~1500 mm / s; scanning spacing: 0.06~0.10 mm; scanning layer thickness: 0.03~0.06 mm; the scanning strategy is that the rotation angle between adjacent layers is 0~67°; the oxygen content is controlled below 0.25% during 3D printing; and the substrate heating temperature is 80~100℃.

[0027] As a preferred embodiment of the preparation method described in this invention, the anodizing process includes: first, rinsing with clean water and chemical degreasing: using HO-730 aluminum cleaning agent at room temperature for 3 min; then, alkali etching: using 60 g / L NaOH at room temperature for 3 min; followed by brightening: using 60 g / L HNO3 and 12 g / L HF, immersing at room temperature for 3 min before anodizing; finally, potassium dichromate sealing and nickel salt sealing treatment, and surface cleaning.

[0028] As a preferred embodiment of the preparation method described in this invention, the current density for anodic oxidation is 1.5 A / dm2; the solution is 150 g / L sulfuric acid + 15 g / L oxalic acid + 5 g / L aluminum sulfate; the solution temperature is maintained at 20±2℃ during anodic oxidation; and the oxidation time is 60 min.

[0029] In a preferred embodiment of the preparation method described in this invention, the thickness of the anodic oxide film is 20~28 μm.

[0030] Beneficial effects of this invention:

[0031] (1) This invention is applicable to the laser printing of 3D printed aluminum alloy powder after anodization. The resulting sample has low metallurgical defects, high density, and excellent formability. It achieves a synergistic improvement in high strength and crack resistance. The L12-Al3(Sc,Zr) nanoparticles formed by Sc / Zr achieve grain boundary strengthening and crack suppression. Combined with the dispersion strengthening of Cu / Fe intermetallic compounds (AlFeCu phase), the room temperature tensile strength of the alloy exceeds 450MPa and the elongation is ≥6%, which is significantly better than that of traditional cast aluminum alloys (such as the 200MPa strength of 6061 aluminum alloy). At the same time, it overcomes the hot cracking tendency of the 3D printing process.

[0032] (2) This invention overcomes the limitations of existing 3D aluminum alloys, which are not suitable for anodizing and are prone to defects such as uneven oxide film and irregular spots. The oxide film is made denser and more corrosion-resistant. Ti / Mg synergistically refines the grains to <5μm, making the oxide film thickness uniformity deviation ≤10%, and reducing the porosity of the CuO-Al2O3 composite film layer to <5%. The Fe / Cu conductive phase optimizes the current density distribution, avoids local dissolution defects, and has a uniform surface with no obvious color difference, making it suitable for various colors.

[0033] (3) The present invention uses a selective laser melting device for printing and sets specific process parameters for the special powder proposed in the present invention. Specifically, the laser scanning strategy is set according to the needs of the printed parts, appropriate process parameters are selected, and 3D printing aluminum alloy powder suitable for anodizing is selected. The printed zero sample has uniform strength, and the printing process is carried out in an inert gas environment.

[0034] (4) The anodizing of the present invention is mixed acid anodizing, and specific anodizing process parameters are set for the anodizing-specific sample proposed in the present invention, namely, the current density is set to 1.5 A / dm based on the anodizing process. 2 The solution was a sulfuric acid-oxalic acid system. During anodizing, the solution temperature was maintained at 20±2 ℃, and the oxidation time was 60 min.

[0035] (5) The present invention is applicable to intermetallic compounds formed in anodized alloys that are not easily dissolved during the anodizing process and have an electrode potential comparable to that of the aluminum matrix, thus preventing voids from being left in the oxide film. The elements have a coupling effect, resulting in low crack sensitivity of the alloy and the ability to form crack-free samples. On the one hand, the second phase provides sufficient room temperature strength; at the same time, its electrode potential in sulfuric acid is similar to that of the aluminum matrix, so it will not preferentially oxidize or dissolve. On the other hand, the second phase has a higher formation temperature and can act as a nucleating agent to promote grain refinement and ensure uniform reaction during the anodizing process. Attached Figure Description

[0036] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort. Wherein:

[0037] Figure 1 The surface morphology of the crack-free high-strength aluminum alloy prepared for anodizing in Example 1 after anodizing is compared with the surface morphology of other 3D printed aluminum alloys after anodizing.

[0038] Figure 2 The image shows a cross-sectional scan of the oxide film after anodizing of a 3D-printed crack-free high-strength aluminum alloy suitable for anodizing prepared in Example 1. The scale bar is 20 micrometers.

[0039] Figure 3 The image shows the morphology scan of crack-free high-strength aluminum alloy powder suitable for anodizing in Example 1, with a scale bar of 100 micrometers.

[0040] Figure 4 Metallographic image of a crack-free, high-strength aluminum alloy suitable for anodizing prepared in Example 1, with a scale bar of 200 micrometers;

[0041] Figure 5 Backscattered electron image of a crack-free, high-strength aluminum alloy suitable for anodizing prepared for 3D printing in Example 1, with a scale bar of 10 micrometers. Detailed Implementation

[0042] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the specific embodiments of the present invention will be described in detail below with reference to the examples in the specification.

[0043] Many specific details are set forth in the following description in order to provide a full understanding of the invention. However, the invention may also be practiced in other ways different from those described herein, and those skilled in the art can make similar extensions without departing from the spirit of the invention. Therefore, the invention is not limited to the specific embodiments disclosed below.

[0044] Secondly, the term "one embodiment" or "embodiment" as used herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the present invention. The phrase "in one embodiment" appearing in different places in this specification does not necessarily refer to the same embodiment, nor is it a single or selective embodiment that is mutually exclusive with other embodiments. Example 1

[0045] This embodiment provides a method for preparing crack-free, high-strength aluminum alloys suitable for anodizing in 3D printing. Specifically:

[0046] 1) Prepare raw aluminum alloy ingots according to the following mass percentages:

[0047] Cu: 2.5 wt%; Fe: 2 wt%; Mg: 0.5 wt%; Ti: 0.5 wt%; Sc: 0.5 wt%; Zr: 0.5 wt%; Si: 0.05 wt%; the remainder is Al.

[0048] 2) The weighed aluminum alloy ingot was vacuum melted at 750℃ and 4.6MPa in the melting chamber. Then, nitrogen was used as the medium to atomize the molten metal droplets at an atomization pressure of 3MPa to prepare spherical powder.

[0049] 3) Sieve out the powder of 15~53μm and dry it in a vacuum drying oven at 90℃ for 4 hours to obtain aluminum alloy powder that can be used for PBF-LB printing;

[0050] 4) The substrate is heated to 100°C and laser powder bed melting (PBF-LB) printing is performed. The printing process is as follows: laser power: 350W; scanning speed: 1200mm / s; scanning spacing: 0.08mm; scanning layer thickness: 0.03mm; scanning strategy is that the rotation angle between adjacent layers is 67° to obtain the 3D printed sample.

[0051] 5) The printed sample was subjected to stress-relief annealing at 175℃ for 2 hours, and the surface was sandblasted before anodizing.

[0052] 6) The 3D printed sample was anodized according to the following steps: ① After rinsing with water, chemical degreasing was performed using HO-730 aluminum cleaner at room temperature for 3 minutes; ② Then, alkaline etching was performed using 60 g / L NaOH at room temperature for 3 minutes; ③ After that, brightening was performed using 60 g / L HNO3 and 12 g / L HF, immersing at room temperature for 3 minutes, followed by anodizing with a current density of 1.5 A / dm³. 2 The solution is a sulfuric acid-oxalic acid system. During anodizing, the solution temperature is maintained at 20±2 ℃ and the oxidation time is 60 min. Finally, a sealing treatment is performed and the surface is cleaned to obtain the anodized 3D printed aluminum alloy of this embodiment.

[0053] The performance of the crack-free high-strength aluminum alloy suitable for anodizing prepared in this embodiment was tested. The results showed that the alloy was dense under a light microscope. In the density test, the sample density reached 99.98%, and the average hardness reached 160 HV. 0.2 The room temperature yield strength is 449 MPa, the tensile strength is 503 MPa, and the elongation exceeds 9%. After anodizing, the oxide film thickness is 28 μm, and the average hardness increases to 360 HV. 0.2 The average single-point withstand voltage is 1.78 kV, and the oxide film is dense and brightly colored.

[0054] The surface morphology of crack-free high-strength aluminum alloys suitable for anodizing after anodizing is compared with the surface morphology of other 3D printed aluminum alloys after anodizing. Figure 1 As shown; cross-sectional scan image of oxide film as shown Figure 2 As shown, the powder morphology scanning image is as follows: Figure 3 As shown, the metallographic diagram of the alloy is as follows: Figure 4 As shown, the backscattered electron pattern of the sample side is as follows: Figure 5 As shown. Example 2

[0055] This embodiment provides a method for preparing crack-free, high-strength aluminum alloys suitable for anodizing in 3D printing. Specifically:

[0056] 1) The raw material aluminum alloy ingots are prepared according to the following mass percentages: Cu: 1.5wt%; Fe: 3wt%; Mg: 0.5wt%; Ti: 0.5wt%; Sc: 0.5wt%; Zr: 0.5wt%; Si: 0.05wt%; and the remainder is Al.

[0057] 2) The weighed aluminum alloy ingot was vacuum melted at 750℃ and 4.6MPa in the melting chamber. Then, nitrogen was used as the medium to atomize the molten metal droplets at an atomization pressure of 3MPa to prepare spherical powder.

[0058] 3) Sieve out the powder of 15~53μm and dry it in a vacuum drying oven at 90℃ for 8 hours to obtain aluminum alloy powder that can be used for PBF-LB printing;

[0059] 4) The substrate is heated to 100°C and laser powder melting forming (PBF-LB) printing is performed. The printing process is as follows: laser power: 350W; scanning speed: 1200mm / s; scanning spacing: 0.08mm; scanning layer thickness: 0.03mm; scanning strategy is that the rotation angle between adjacent layers is 67° to obtain the 3D printed sample.

[0060] 5) The printed sample was subjected to stress-relief annealing at 175℃ for 2 hours, and the surface was sandblasted before anodizing.

[0061] 6) The 3D printed sample was anodized according to the following steps: ① After rinsing with water, chemical degreasing was performed using HO-730 aluminum cleaner at room temperature for 3 minutes; ② Then, alkaline etching was performed using 60 g / L NaOH at room temperature for 3 minutes; ③ After that, brightening was performed using 60 g / L HNO3 and 12 g / L HF, immersing at room temperature for 3 minutes, followed by anodizing with a current density of 1.5 A / dm³. 2 The solution is a sulfuric acid-oxalic acid system. During anodizing, the solution temperature is maintained at 20±2 ℃ and the oxidation time is 60 min. Finally, a sealing treatment is performed and the surface is cleaned to obtain the anodized 3D printed aluminum alloy of this embodiment.

[0062] The performance of the crack-free, high-strength aluminum alloy suitable for anodizing prepared in this embodiment was tested. The results showed that the alloy had few defects under a light microscope. In the density test, the sample density reached 99.85%, the room temperature yield strength was 470 MPa, the tensile strength was 513 MPa, and the elongation exceeded 6%. After anodizing, the oxide film thickness was 25 μm, and the average hardness increased to 375 HV. 0.2 The average single-point withstand voltage is 1.75 kV, and the oxide film shows localized unevenness.

[0063] Example 3

[0064] This embodiment provides a method for preparing crack-free, high-strength aluminum alloys suitable for anodizing in 3D printing. Specifically:

[0065] 1) Prepare raw aluminum alloy ingots according to the following mass percentages:

[0066] Cu: 3.5 wt%; Fe: 1 wt%; Mg: 0.5 wt%; Ti: 0.5 wt%; Sc: 0.5 wt%; Zr: 0.5 wt%; Si: 0.05 wt%; the remainder is Al.

[0067] 2) The weighed aluminum alloy ingot was vacuum melted at 750℃ and 4.6MPa in the melting chamber. Then, nitrogen was used as the medium to atomize the molten metal droplets at an atomization pressure of 3MPa to prepare spherical powder.

[0068] 3) Sieve out the powder of 15~53μm and dry it in a vacuum drying oven at 90℃ for 8 hours to obtain aluminum alloy powder that can be used for PBF-LB printing;

[0069] 4) The substrate is heated to 100°C and laser powder melting forming (PBF-LB) printing is performed. The printing process is as follows: laser power: 350W; scanning speed: 1200mm / s; scanning spacing: 0.08mm; scanning layer thickness: 0.03mm; scanning strategy is that the rotation angle between adjacent layers is 67° to obtain the 3D printed sample.

[0070] 5) The printed sample was subjected to stress-relief annealing at 175℃ for 2 hours, and the surface was sandblasted before anodizing.

[0071] 6) The 3D printed sample was anodized according to the following steps: ① After rinsing with water, chemical degreasing was performed using HO-730 aluminum cleaner at room temperature for 3 minutes; ② Then, alkaline etching was performed using 60 g / L NaOH at room temperature for 3 minutes; ③ After that, brightening was performed using 60 g / L HNO3 and 12 g / L HF, immersing at room temperature for 3 minutes, followed by anodizing with a current density of 1.5 A / dm³. 2 The solution is a sulfuric acid-oxalic acid system. During anodizing, the solution temperature is maintained at 20±2 ℃ and the oxidation time is 60 min. Finally, a sealing treatment is performed and the surface is cleaned to obtain the anodized 3D printed aluminum alloy of this embodiment.

[0072] The performance of the crack-free, high-strength aluminum alloy suitable for anodizing prepared in this embodiment was tested. The results showed that the sample achieved a density of 99.7%, a room temperature yield strength of 430 MPa, a tensile strength of 475 MPa, and an elongation exceeding 7%. After anodizing, the oxide film thickness was 20 μm, and the average hardness increased to 340 HV. 0.2 The average single-point withstand voltage is 1.55 kV, and the oxide film is basically uniform, but has a slightly brown and slightly gray appearance.

[0073] Example 4

[0074] This embodiment provides a method for preparing crack-free, high-strength aluminum alloys suitable for anodizing in 3D printing. Specifically:

[0075] 1) Prepare raw aluminum alloy ingots according to the following mass percentages:

[0076] Cu: 4wt%; Fe: 0.5wt%; Mg: 0.5wt%; Ti: 0.5wt%; Sc: 0.5wt%; Zr: 0.5wt%; Si: 0.05wt%; the remainder is Al.

[0077] 2) The weighed aluminum alloy ingot was vacuum melted at 750℃ and 4.6MPa in the melting chamber. Then, nitrogen was used as the medium to atomize the molten metal droplets at an atomization pressure of 3MPa to prepare spherical powder.

[0078] 3) Sieve out the powder of 15~53μm and dry it in a vacuum drying oven at 90℃ for 8 hours to obtain aluminum alloy powder that can be used for PBF-LB printing;

[0079] 4) The substrate is heated to 100°C and laser powder melting forming (PBF-LB) printing is performed. The printing process is as follows: laser power: 350W; scanning speed: 1200mm / s; scanning spacing: 0.08mm; scanning layer thickness: 0.03mm; scanning strategy is that the rotation angle between adjacent layers is 67° to obtain the 3D printed sample.

[0080] 5) The printed sample was subjected to stress-relief annealing at 175℃ for 2 hours, and the surface was sandblasted before anodizing.

[0081] 6) The 3D printed sample was anodized according to the following steps: ① After rinsing with water, chemical degreasing was performed using HO-730 aluminum cleaner at room temperature for 3 minutes; ② Then, alkaline etching was performed using 60 g / L NaOH at room temperature for 3 minutes; ③ After that, brightening was performed using 60 g / L HNO3 and 12 g / L HF, immersing at room temperature for 3 minutes, followed by anodizing with a current density of 1.5 A / dm³. 2 The solution is a sulfuric acid-oxalic acid system. During anodizing, the solution temperature is maintained at 20±2 ℃ and the oxidation time is 60 min. Finally, a sealing treatment is performed and the surface is cleaned to obtain the anodized 3D printed aluminum alloy of this embodiment.

[0082] The performance of the crack-free, high-strength aluminum alloy suitable for anodizing prepared in this embodiment was tested. The results showed that the sample achieved a density of 99.7%, a room temperature yield strength of 415 MPa, a tensile strength of 455 MPa, and an elongation exceeding 8%. After anodizing, the oxide film thickness was 18 μm, and the average hardness increased to 320 HV. 0.2 The average single-point withstand voltage is 1.35 kV, the oxide film is basically uniform, but the dyed film has a dull luster.

[0083] Table 1. Room temperature mechanical properties of the alloys prepared in Examples 1-4

[0084] Table 2. Surface hardness, oxide film thickness, and color of the alloys obtained in Examples 1-4 after anodizing treatment.

[0085] Oxide film thickness (μm) <![CDATA[Hardness (HV 0.2 )]]> Oxide film color Example 1 28 360 No color difference, vibrant colors Example 2 25 375 Localized unevenness in oxide film Example 3 20 340 The oxide film is basically uniform, but has a slightly brown and slightly gray appearance. Example 4 18 320 The oxide film is generally uniform, but the dyed film has a dull luster.

[0086] As can be seen from Tables 1 and 2, the alloy system of this invention exhibits significant advantages in overall mechanical properties (yield strength, tensile strength, elongation) as well as in the thickness and surface hardness of the oxide film after anodizing. The alloy system of this invention also possesses the technical advantages of high performance and low cost.

[0087] Comparative Example 1

[0088] This comparative example provides a method for preparing crack-free, high-strength aluminum alloys suitable for anodizing in 3D printing. Specifically:

[0089] 1) Prepare raw aluminum alloy ingots according to the following mass percentages:

[0090] Cu: 4wt%; Fe: 4wt%; Mg: 0.5wt%; Ti: 0.5wt%; Sc: 0.5wt%; Zr: 0.5wt%; Si: 0.05wt%; the remainder is Al.

[0091] 2) The weighed aluminum alloy ingot was vacuum melted at 800℃ and 4MPa in the melting chamber. Then, nitrogen was used as the medium to atomize the molten metal droplets at an atomization pressure of 3.5MPa to prepare spherical powder.

[0092] 3) Sieve out the powder of 15~53μm and dry it in a vacuum drying oven at 90℃ for 8 hours to obtain aluminum alloy powder that can be used for PBF-LB printing;

[0093] 4) The substrate is heated to 100°C and laser powder melting forming (PBF-LB) printing is performed. The printing process is as follows: laser power: 350W; scanning speed: 1200mm / s; scanning spacing: 0.08mm; scanning layer thickness: 0.03mm; scanning strategy is that the rotation angle between adjacent layers is 67° to obtain the 3D printed sample.

[0094] 5) The printed sample was subjected to stress-relief annealing at 175℃ for 2 hours, and the surface was sandblasted before anodizing.

[0095] 6) The 3D printed sample was anodized according to the following steps: ① After rinsing with water, chemical degreasing was performed using HO-730 aluminum cleaner at room temperature for 3 minutes; ② Then, alkaline etching was performed using 60 g / L NaOH at room temperature for 3 minutes; ③ After that, brightening was performed using 60 g / L HNO3 and 12 g / L HF, immersing at room temperature for 3 minutes, followed by anodizing with a current density of 1.5 A / dm³. 2 The solution is a sulfuric acid-oxalic acid system. During anodizing, the solution temperature is maintained at 20±2 ℃ and the oxidation time is 60 min. Finally, a sealing treatment is performed and the surface is cleaned to obtain the anodized 3D printed aluminum alloy of this embodiment.

[0096] The performance of the crack-free high-strength aluminum alloy suitable for anodizing and prepared in this comparative example was tested. The results showed that the sample density reached 99.4% in the density test, but the sample had a large number of cracks, making it difficult to form large-sized samples. Although the strength was improved, the average hardness reached 170 HV. 0.2 The yield strength at room temperature is 482 MPa, and the tensile strength is 530 MPa, but the elongation is less than 2%. After anodizing, the oxide film thickness is 15 μm, and the average hardness increases to 320 HV. 0.2 The average single-point withstand voltage is 1.15 kV, the oxide film thickness is uneven, the oxide film peels off, and the coloring is uneven.

[0097] Comparative Example 2

[0098] This comparative example provides a method for preparing crack-free, high-strength aluminum alloys suitable for anodizing in 3D printing. Specifically:

[0099] 1) Prepare raw aluminum alloy ingots according to the following mass percentages:

[0100] Cu: 2.5 wt%; Fe: 2 wt%; Ti: 0.5 wt%; Sc: 0.5 wt%; Zr: 0.5 wt%; the remainder is Al.

[0101] The weighed aluminum alloy ingot was vacuum melted at 800℃ and a melting chamber pressure of 4MPa. Then, nitrogen was used as the medium to atomize the molten metal droplets at an atomization pressure of 3.5MPa to prepare spherical powder.

[0102] 3) Sieve out the powder of 15~53μm and dry it in a vacuum drying oven at 90℃ for 8 hours to obtain aluminum alloy powder that can be used for PBF-LB printing;

[0103] 4) The substrate is heated to 100°C and laser powder melting forming (PBF-LB) printing is performed. The printing process is as follows: laser power: 350W; scanning speed: 1200mm / s; scanning spacing: 0.08mm; scanning layer thickness: 0.03mm; scanning strategy is that the rotation angle between adjacent layers is 67° to obtain the 3D printed sample.

[0104] 5) The printed sample was subjected to stress-relief annealing at 175℃ for 2 hours, and the surface was sandblasted before anodizing.

[0105] 6) The 3D printed sample was anodized according to the following steps: ① After rinsing with water, chemical degreasing was performed using HO-730 aluminum cleaner at room temperature for 3 minutes; ② Then, alkaline etching was performed using 60 g / L NaOH at room temperature for 3 minutes; ③ After that, brightening was performed using 60 g / L HNO3 and 12 g / L HF, immersing at room temperature for 3 minutes, followed by anodizing with a current density of 1.5 A / dm³. 2 The solution is a sulfuric acid-oxalic acid system. During anodizing, the solution temperature is maintained at 20±2 ℃ and the oxidation time is 60 min. Finally, a sealing treatment is performed and the surface is cleaned to obtain the anodized 3D printed aluminum alloy of this embodiment.

[0106] The performance of the crack-free high-strength aluminum alloy suitable for anodizing prepared in this embodiment was tested. The results showed that metallurgical defects increased under a light microscope, with obvious pores appearing. The sample density was 98.5%, and the strength was similar to that of Experimental Example 1, with an average hardness of 158 HV. 0.2 The room temperature yield strength is 440 MPa, the tensile strength is 498 MPa, and the elongation is 7%. After anodizing, the oxide film thickness is 25 μm, and the average hardness increases to 340 HV. 0.2 The average single-point withstand voltage is 1.68 kV, and the oxide film is dense and dark in color.

[0107] Comparative Example 3

[0108] This comparative example provides a method for preparing crack-free, high-strength aluminum alloys suitable for anodizing in 3D printing. Specifically:

[0109] 1) Prepare raw aluminum alloy ingots according to the following mass percentages:

[0110] Cu: 2.5 wt%; Fe: 2 wt%; Mg: 1 wt%; Si: 0.08 wt%; the remainder is Al.

[0111] 2) The weighed aluminum alloy ingot was vacuum melted at 750℃ and 4MPa in the melting chamber. Then, nitrogen was used as the medium to atomize the molten metal droplets at an atomization pressure of 3.5MPa to prepare spherical powder.

[0112] 3) Sieve out the powder of 15~53μm and dry it in a vacuum drying oven at 90℃ for 8 hours to obtain aluminum alloy powder that can be used for PBF-LB printing;

[0113] 4) The substrate is heated to 100°C and laser powder melting forming (PBF-LB) printing is performed. The printing process is as follows: laser power: 350W; scanning speed: 1200mm / s; scanning spacing: 0.08mm; scanning layer thickness: 0.03mm; scanning strategy is that the rotation angle between adjacent layers is 67° to obtain the 3D printed sample.

[0114] 5) The printed sample was subjected to stress-relief annealing at 175℃ for 2 hours, and the surface was sandblasted before anodizing.

[0115] 6) The 3D printed sample was anodized according to the following steps: ① After rinsing with water, chemical degreasing was performed using HO-730 aluminum cleaner at room temperature for 3 minutes; ② Then, alkaline etching was performed using 60 g / L NaOH at room temperature for 3 minutes; ③ After that, brightening was performed using 60 g / L HNO3 and 12 g / L HF, immersing at room temperature for 3 minutes, followed by anodizing with a current density of 1.5 A / dm³. 2 The solution is a sulfuric acid-oxalic acid system. During anodizing, the solution temperature is maintained at 20±2 ℃ and the oxidation time is 60 min. Finally, a sealing treatment is performed and the surface is cleaned to obtain the anodized 3D printed aluminum alloy of this embodiment.

[0116] The performance of the crack-free high-strength aluminum alloy suitable for anodizing and prepared in this comparative example was tested. The results showed that the sample achieved a density of 99.3% and an average hardness of 150 HV in the density test. 0.2 The yield strength at room temperature is 425 MPa, the tensile strength is 475 MPa, and the elongation is 6%. After anodizing, the oxide film thickness is 21 μm, and the average hardness increases to 335 HV. 0.2 The average single-point withstand voltage is 1.35 kV, the oxide film thickness is uneven, and the coloring is uneven.

[0117] Table 3. Room temperature mechanical properties of the alloys prepared in Comparative Examples 1-3

[0118] Table 4 shows the surface hardness, oxide film thickness, and color of the alloys prepared in Comparative Examples 1-3 after anodizing treatment.

[0119] In summary, poor dyeing is a common problem in the entire oxidation dyeing process due to oxidation process issues. Uniform oxide film thickness and porosity are prerequisites and foundations for obtaining uniform color during dyeing. Ensuring good conductivity is crucial for achieving a uniform oxide film. The alloy composition significantly affects conductivity; the content of Cu and Fe in the alloy needs strict control, and the total content should not exceed 5%. Otherwise, it is more prone to galvanic corrosion (pitting corrosion) during the dyeing process compared to other alloys, as proven by experimental results. Mg and Si elements are beneficial for increasing liquid fluidity and can significantly improve density. Although small amounts do not contribute much to strength, they are beneficial to formability and elongation. Adding appropriate percentages of Ti, Sc, and Zr elements can not only reduce crack sensitivity but also prepare alloys with excellent mechanical properties, low metallurgical defects, and high density. Grain size has a certain influence on the structure and properties of the oxide film. Coarse grains react unevenly during oxidation, often resulting in an orange peel appearance. Refining the grains has a beneficial effect on improving the surface quality of the anodic oxide alloy. The second phase is not easily dissolved during anodizing and has an electrode potential similar to that of the aluminum matrix, thus preventing voids from being left in the oxide film. The elements exhibit a coupling effect, resulting in low crack sensitivity in the alloy and the ability to form crack-free specimens. On one hand, the second phase provides sufficient room-temperature strength; simultaneously, its electrode potential in sulfuric acid is similar to that of the aluminum matrix, preventing preferential oxidation or dissolution. On the other hand, the second phase forms at a relatively high temperature, acting as a nucleating agent to promote grain refinement and ensure a uniform reaction during anodizing.

[0120] This invention addresses the challenges of poor anodizing results, uneven oxide films, and poor coloring in existing 3D-printed aluminum alloys. It innovatively proposes a crack-free, high-strength aluminum alloy suitable for anodizing. A revolutionary elemental reconstruction: leveraging the rapid solidification characteristics of 3D printing, the "harmful elements" Cu and Fe in traditional anodizing are transformed into functional components. Cu forms a CuO-Al2O3 composite oxide film in a super-solid solution state, improving corrosion resistance while enhancing coloring; Fe synergistically forms Al with Cu. 23 CuFe4 intermetallic compound, with its high conductivity, promotes uniform distribution of anodic oxidation current. Combined with the "microelectrode" effect of L12-Al3(Sc,Zr) nanoparticles formed by Sc / Zr, the density of the oxide film is increased by more than 30%.

[0121] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the present invention.

Claims

1. A crack-free, high-strength aluminum alloy suitable for anodizing in 3D printing, characterized in that: Based on the mass fraction of the raw materials, it consists of the following components: Cu: 1.5~4wt%, Fe: 0.5~3wt%, Mg: 0.5~1wt%, Ti: 0.5~1wt%, Sc: 0.5~0.7wt%, Zr: 0.5~0.7wt%, Si: 0.05~0.08wt%, with the remainder being Al; The 3D-printed crack-free high-strength aluminum alloy has the following characteristics: (i) Density exceeding 99.95%, average hardness 135~160 HV 0.2 ; (ii) Room temperature yield strength 410~470 MPa, tensile strength 458~513 MPa, elongation exceeding 6%; (iii) The average hardness increases to 320~375 HV after anodizing. 0.2 The average single-point withstand voltage is 1.55~1.78kV; The method for preparing crack-free high-strength aluminum alloy by 3D printing includes, Weigh each component, prepare the raw materials, and obtain alloy powder through vacuum melting and gas atomization treatment; The alloy powder is sieved and dried to obtain aluminum alloy powder for PBF-LB printing; Aluminum alloy powder is 3D printed and stress-relief annealed to obtain 3D printed crack-free high-strength aluminum alloy. After surface sandblasting, it is anodized. The stress-relief annealing temperature is 150~175℃, and the time is 1~2 hours; The parameters for 3D printing are as follows: laser power: 100~400 W; scanning speed: 800~1500 mm / s; scanning spacing: 0.06~0.10 mm; scanning layer thickness: 0.03~0.06 mm; scanning strategy: rotation angle between adjacent layers is 0~67°; oxygen content is controlled below 0.25% during 3D printing; substrate heating temperature is 80~100℃.

2. The 3D-printed crack-free high-strength aluminum alloy as described in claim 1, characterized in that: By mass fraction, it consists of the following components: Cu: 2.5 wt%; Fe: 2 wt%; Mg: 0.5 wt%; Ti: 0.5 wt%; Sc: 0.5 wt%; Zr: 0.5 wt%; Si: 0.05 wt%; and the remainder is Al.

3. The 3D-printed crack-free high-strength aluminum alloy as described in claim 1, characterized in that: The vacuum melting temperature is 700~800℃, the melting chamber pressure is 3~7 MPa; the gas atomization powder production pressure is 2~5 MPa; the powder is collected and dried at 50~90℃ for 2~6 hours.

4. The 3D-printed crack-free high-strength aluminum alloy as described in claim 1, characterized in that: The anodizing process includes first rinsing with clean water and then chemically degreasing: using HO-730 aluminum cleaning agent at room temperature for 3 minutes; followed by alkaline etching: using 60g / L NaOH at room temperature for 3 minutes. Next, brightening is performed: the surface is immersed in 60 g / L HNO3 and 12 g / L HF at room temperature for 3 minutes, followed by anodizing, and finally sealed with potassium dichromate and nickel salt, and the surface is cleaned.

5. The 3D-printed crack-free high-strength aluminum alloy as described in claim 4, characterized in that: The current density for anodizing is 1.5 A / dm³. 2 The solution consisted of 150 g / L sulfuric acid + 15 g / L oxalic acid + 5 g / L aluminum sulfate. During anodizing, the solution temperature was maintained at 20±2 ℃, and the oxidation time was 60 min.

6. The 3D-printed crack-free high-strength aluminum alloy as described in claim 4, characterized in that: The thickness of the anodic oxide film is 20~28 μm.

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