Anodizing method for aluminum alloy 3d printed parts

Abstract

The application provides an anodizing method for an aluminum alloy 3D printed part, and belongs to the technical field of anodizing. The method comprises the following steps: after the aluminum alloy 3D printed part is sequentially subjected to pretreatment and anodizing, an anodized aluminum alloy 3D printed part is obtained; the pretreatment comprises the following steps of once alkali washing, once acid washing, twice alkali washing and twice acid washing; the once alkali washing solution has a hydroxide concentration greater than a silicate concentration; the once acid washing solution has a nitric acid concentration greater than a phosphoric acid concentration; the twice alkali washing solution has a silicate concentration greater than a hydroxide concentration; the twice acid washing solution has a phosphoric acid concentration greater than a nitric acid concentration; and the electrolyte for anodizing comprises the following components with the following concentrations: 100-200 g / L of sulfuric acid and 5-20 g / L of oxalic acid. The anodizing method can improve the hardness of the anodized aluminum alloy 3D printed part.

Description

Technical Field

[0001] This application belongs to the field of anodizing technology, and more specifically, relates to anodizing methods for 3D printed aluminum alloy parts. Background Technology

[0002] Aluminum alloy 3D printing technology can directly manufacture complex geometric structures that are difficult to achieve using traditional subtractive manufacturing processes, and it has wide applications in aerospace, medical implants, and automotive lightweighting. However, the surfaces of 3D-printed parts often have defects such as steps, sintered powder, and pores, which affect the surface properties of aluminum alloy 3D-printed parts. Anodizing, which grows an alumina ceramic film on the surface of an Al substrate through electrochemical methods, is a common method to improve the surface quality of aluminum alloy 3D-printed parts.

[0003] However, during the 3D printing process, the high cooling rate causes aluminum alloy 3D printed parts to form a non-equilibrium microstructure. Unlike the cast or forged state, 3D printed aluminum alloys, especially high-silicon aluminum alloys with Si content ≥7wt%, have supersaturated Si elements dissolved in the Al matrix and distributed as Si-rich phases on the matrix surface. This is not conducive to subsequent anodizing treatment because the Si-rich phases will hinder the growth of alumina ceramic films.

[0004] Currently, the industry typically uses traditional aluminum alloy pretreatment processes for anodizing 3D printed aluminum alloy parts, namely, surface activation and oxide removal through acid pickling. However, traditional acid pickling methods present the following problems when processing 3D printed aluminum alloy parts: while the acid corrodes the Al matrix, exposing and removing the Si-rich phase, it repeatedly exposes new Al matrix. These newly exposed Al matrix are prone to localized electrochemical corrosion, causing supersaturated Si atoms dissolved in the Al lattice to agglomerate and precipitate at the corrosion interface due to aging, forming a poorly adhered, discontinuous Si-rich layer. This hinders the uniform distribution of current and the nucleation of the oxide film in the initial stage of anodizing, resulting in defects such as poor surface hardness of the anodized aluminum alloy 3D printed parts. Summary of the Invention

[0005] In view of the above problems, this application provides an anodizing method for aluminum alloy 3D printed parts, thereby solving or at least alleviating one or more of the above-mentioned problems and other problems existing in the prior art.

[0006] A first aspect of this application provides a method for anodizing aluminum alloy 3D printed parts, comprising:

[0007] After undergoing pretreatment and anodizing, the aluminum alloy 3D printed parts are obtained as anodized aluminum alloy 3D printed parts.

[0008] The pretreatment includes a first alkaline wash, a first acid wash, a second alkaline wash, and a second acid wash performed sequentially.

[0009] In the first alkaline wash, the hydroxide concentration in the alkaline wash solution is greater than the silicate concentration.

[0010] In the first pickling process, the concentration of nitric acid in the pickling solution is greater than the concentration of phosphoric acid.

[0011] In the secondary alkaline washing, the silicate concentration in the secondary alkaline washing solution is greater than the hydroxide concentration.

[0012] In the secondary pickling process, the concentration of phosphoric acid in the pickling solution is greater than that of nitric acid.

[0013] The electrolyte for anodic oxidation comprises the following components at the following concentrations: sulfuric acid 100-200 g / L and oxalic acid 5-20 g / L.

[0014] In one embodiment, the primary alkaline washing solution comprises components at the following concentrations: hydroxide 80-120 g / L, silicate 10-20 g / L; and / or

[0015] The primary pickling solution comprises the following components at the following concentrations: nitric acid 80-120 g / L, phosphoric acid 10-20 g / L; and / or

[0016] The secondary alkaline washing solution comprises the following components at the following concentrations: silicate 30-40 g / L, hydroxide 10-20 g / L; and / or

[0017] The secondary pickling solution comprises the following components at the following concentrations: phosphoric acid 60-80 g / L and nitric acid 20-30 g / L.

[0018] In one embodiment, the primary alkaline washing solution further includes components at the following concentrations: persulfate 4-8 g / L; and / or

[0019] The primary pickling solution also includes the following components at concentrations: fluoride 2-4 g / L; and / or

[0020] The secondary alkaline washing solution also includes the following components at concentrations: persulfate 1~2 g / L; and / or

[0021] The secondary pickling solution also includes the following components at the following concentrations: fluoride 0.5~1g / L.

[0022] In one embodiment, the temperature of the first alkaline wash is 40~70°C and the time is 5~30 minutes.

[0023] In one embodiment, the temperature of the first pickling is 10~40°C and the time is 1~5 minutes.

[0024] In one embodiment, the temperature of the secondary alkaline washing is 40~70℃ and the time is 5~30min.

[0025] In one embodiment, the secondary pickling temperature is 10~40℃ and the time is 1~3min.

[0026] In one embodiment, the electrolyte further includes components at the following concentrations: 5-10 g / L of triethanolamine borate and 1-5 g / L of vanadium oxalate.

[0027] In one embodiment, the anodizing voltage is 8~15V, the time is 20~30min, and the temperature is 10~25℃.

[0028] In one embodiment, the Si content of the aluminum alloy 3D printed part is ≥7wt%.

[0029] The beneficial effects of the embodiments of this application are as follows:

[0030] This application adopts a synergistic treatment method of "one-time alkaline washing, one-time acid washing, two-time alkaline washing, and two-time acid washing", which effectively avoids the problem of surface Si-rich layer regeneration caused by local electrochemical corrosion in the traditional one-time acid washing process of aluminum alloy 3D printed parts. This prepares a good surface for subsequent anodizing treatment, thereby enhancing the forming quality of the anodized film and improving the hardness of the anodized aluminum alloy 3D printed parts.

[0031] Specifically, in the first alkaline wash, an alkaline solution with a hydroxide concentration greater than that of silicate is used. This allows the high concentration of hydroxide to effectively dissolve the internal support and residual sintered powder of the aluminum alloy 3D printed part, while the small amount of silicate prevents the hydroxide from over-corroding the substrate. In the first acid wash, a mixed acid solution with a nitric acid concentration greater than that of phosphoric acid is used. This effectively dissolves and removes the Si phase exposed after the first alkaline wash. Furthermore, the small amount of phosphoric acid can form phosphorus-containing compounds on the new Al substrate surface. These phosphorus-containing compounds can synergistically interact with the silicate in the second alkaline wash. In the second alkaline wash, an alkaline solution with a silicate concentration greater than that of hydroxide is used. The high concentration of silicate can combine with the phosphorus-containing compounds formed in the first acid wash to form a silicon-phosphorus composite film on the surface of the aluminum alloy 3D printed part. This silicon-phosphorus composite film effectively inhibits the segregation and precipitation of Si atoms, thereby preventing the formation of a new Si-rich layer. In the secondary pickling process, a mixed acid solution with a phosphoric acid concentration greater than that of nitric acid is used. This can effectively dissolve and remove the silicon-phosphorus composite film formed in the secondary alkaline pickling process, while avoiding the occurrence of Si segregation. This lays a good surface foundation for subsequent anodizing, enhances the forming quality of the anodized film, and improves the hardness of the anodized aluminum alloy 3D printed parts. Attached Figure Description

[0032] To more clearly illustrate the technical solutions in the embodiments of this application, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0033] Figure 1 This is a microscopic image of the aluminum alloy 3D printed part after pretreatment in Example 1;

[0034] Figure 2 This is a microscopic image of the aluminum alloy 3D printed part after pretreatment, as shown in Comparative Example 1. Detailed Implementation

[0035] To enable those skilled in the art to better understand the technical solutions in the embodiments of this application, the technical solutions in the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments in the specific implementation of this application should fall within the protection scope of the embodiments of this application.

[0036] It should be understood that, unless the context clearly states otherwise, the terms "comprising," "including," or "having" as used herein refer to the presence of an element, but do not exclude the presence or addition of one or more other elements. Furthermore, "comprising" and / or "including" as used herein specify the presence of shapes, numbers, steps, operations, members, elements, and / or combinations thereof, and do not exclude the presence or addition of one or more other shapes, numbers, operations, elements, and / or combinations thereof. Some embodiments of this application are described in detail below with reference to the accompanying drawings. Where there is no conflict between the embodiments, the following embodiments and features can be combined with each other. The steps in the following method embodiments are for illustrative purposes only and are not intended to limit this application.

[0037] In this application, the numerical range indicated by "~" refers to the range of values ​​specified as the lower and upper limits, respectively, before or after the term. When multiple values ​​for the upper or lower limit of any numerical range are mentioned, the range disclosed herein can be understood as a range with any one of the mentioned upper limits as its upper limit and any one of the mentioned lower limits as its lower limit.

[0038] To make the objectives, technical solutions, and advantages of this application clearer, the anodizing method for aluminum alloy 3D printed parts will be described below through specific embodiments.

[0039] In one embodiment of this application, an anodizing method for aluminum alloy 3D printed parts is provided, comprising:

[0040] After undergoing pretreatment and anodizing, the aluminum alloy 3D printed parts are obtained as anodized aluminum alloy 3D printed parts.

[0041] The pretreatment process includes a first alkaline wash, a first acid wash, a second alkaline wash, and a second acid wash performed sequentially.

[0042] In the first alkaline wash, the concentration of hydroxide in the alkaline wash solution is greater than the concentration of silicate.

[0043] In a single pickling process, the concentration of nitric acid in the pickling solution is greater than that of phosphoric acid.

[0044] Secondary alkaline washing, in which the silicate concentration in the secondary alkaline washing solution is greater than the hydroxide concentration;

[0045] Secondary pickling, in which the concentration of phosphoric acid in the secondary pickling solution is greater than that of nitric acid;

[0046] The electrolyte for anodizing includes the following components at the following concentrations: sulfuric acid 100~200g / L and oxalic acid 5~20g / L.

[0047] The surface treatment method of this application is applicable to 3D printed aluminum alloys of any grade, such as 2-series, 3-series, 4-series, 5-series, 6-series, and 7-series aluminum alloys, and is particularly suitable for high-silicon aluminum alloys with a Si content ≥7wt%, such as A360 aluminum alloy, A380 aluminum alloy, AlSi10Mg aluminum alloy, and AlSi12 aluminum alloy. The anodized aluminum alloy 3D printed parts of this application exhibit good hardness, which can be measured according to GB / T 4340.1-2024 "Metallic Materials - Vickers Hardness Test - Part 1: Test Method". Taking an AlSi12 aluminum alloy 3D printed part as an example, its hardness exceeds 500HV0.025 after anodizing treatment using the method of this application.

[0048] Both the primary alkaline washing solution and the secondary alkaline solution in this application are aqueous solutions. The hydroxide can be any strongly alkaline hydroxide or a combination thereof, for example, including but not limited to sodium hydroxide, potassium hydroxide, and a combination of sodium hydroxide and potassium hydroxide, preferably sodium hydroxide. The silicate can be any water-soluble silicate or a combination thereof, for example, including but not limited to sodium silicate, potassium silicate, and a combination of sodium silicate and potassium silicate, preferably sodium silicate. The temperature of the primary alkaline washing can be 40~70℃, for example, including but not limited to 40℃, 50℃, 60℃, and 70℃; the time of the primary alkaline washing can be 5~30min, for example, including but not limited to 5min, 10min, 15min, 20min, 25min, and 30min. Within this temperature and time range, excessive corrosion of the aluminum alloy 3D printed parts due to excessively high temperature and time is avoided, as is ineffective removal of the internal supports and residual sintering powder from the aluminum alloy 3D printed parts due to excessively low temperature and time. The temperature of the secondary alkaline washing can be 40~70℃, for example, including but not limited to 40℃, 50℃, 60℃, and 70℃; the time of the secondary alkaline washing can be 5~30min, for example, including but not limited to 5min, 10min, 15min, 20min, 25min, and 30min. Within this temperature and time range, it avoids the excessive growth of the silicon-phosphorus composite film due to excessively high temperature and time, which would affect the removal effect of the subsequent secondary acid washing, and also avoids the inability to effectively form a dense silicon-phosphorus composite film to suppress the segregation of Si atoms due to excessively low temperature and time.

[0049] Both the primary and secondary pickling solutions in this application are aqueous solutions. The temperature of the primary pickling can be 10~40℃, for example, including but not limited to 10℃, 20℃, 30℃, and 40℃; the time of the primary pickling can be 1~5min, for example, including but not limited to 1min, 2min, 3min, 4min, and 5min. Within this temperature and time range, excessive corrosion of the aluminum alloy 3D printed parts due to excessively high temperature and time is avoided, as is ineffective removal of the Si phase and insufficient formation of phosphorus-containing compounds due to excessively low temperature and time, which would affect the formation of the silicon-phosphorus composite film during the subsequent secondary alkaline pickling. The temperature for the secondary pickling can be 10~40℃, for example, including but not limited to 10℃, 20℃, 30℃, and 40℃; the time for the secondary pickling can be 1~3min, for example, including but not limited to 1min, 2min, and 3min; within this temperature and time range, it avoids both excessive dissolution of the aluminum alloy 3D printed parts due to excessively high temperature and time, and ineffective removal of the silicon-phosphorus composite film due to excessively low temperature and time, which would affect the ion exchange during subsequent anodizing.

[0050] In this application, a mixed acid solution of sulfuric acid and oxalic acid is used during anodizing. The synergistic effect of these two acids ensures the alumina film has good density, effectively avoiding the problem of loose alumina film when using a single acid. Furthermore, when the concentration of sulfuric acid is 100-200 g / L and the concentration of oxalic acid is 5-20 g / L, a moderate oxidation reaction rate is ensured, guaranteeing the high-quality formation of the alumina film. In some specific embodiments of this application, the concentration of sulfuric acid (based on H2SO4) can be 100 g / L, 120 g / L, 140 g / L, 160 g / L, 180 g / L, or 200 g / L; and the concentration of oxalic acid (based on C2H2O4) can be 5 g / L, 10 g / L, 15 g / L, or 20 g / L.

[0051] The anodizing process described in this application can employ DC constant voltage, DC constant current, and pulse methods. Taking the DC constant voltage method as an example, the anodizing voltage can be 8~15V, for example, including but not limited to 8V, 10V, 12V, and 15V; the time can be 20~30min, for example, including but not limited to 20min, 25min, and 30min; and the temperature can be 10~25℃, for example, including but not limited to 10℃, 15℃, 20℃, and 25℃. Anodizing within the above range provides sufficient motive force for the anodizing reaction, maintains the stability of the oxidation reaction, and ensures the formation of an excellent alumina film.

[0052] In this embodiment, the primary alkaline washing solution comprises the following components at the following concentrations: hydroxide 80~120g / L and silicate 10~20g / L.

[0053] In this application, the primary purpose of the alkaline cleaning solution is to remove the internal support and residual sintered powder from the aluminum alloy 3D printed parts, and to prevent over-corrosion. Hydroxide, as the cleaning agent, requires a relatively high concentration to ensure effective cleaning, but excessive concentration must be avoided to prevent over-corrosion. Therefore, the hydroxide concentration can be 80~120 g / L, for example, including but not limited to 80 g / L, 90 g / L, 100 g / L, 110 g / L, and 120 g / L. Silicate's role is to inhibit over-corrosion. On the one hand, excessive silicate concentration must be avoided to prevent it from affecting the cleaning effect of hydroxide; on the other hand, the inhibitory effect of silicate must be ensured. Therefore, the silicate concentration can be 10~20 g / L, for example, including but not limited to 10 g / L, 12 g / L, 14 g / L, 16 g / L, 18 g / L, and 20 g / L.

[0054] In this embodiment, the pickling solution includes the following components at the following concentrations: nitric acid 80~120g / L and phosphoric acid 10~20g / L.

[0055] In this application, the primary purpose of acid washing is to remove the Si phase and form a small amount of phosphorus-containing compounds. Nitric acid has strong oxidizing and corrosive properties and can effectively dissolve the Si phase. To quickly remove the Si phase while avoiding excessive corrosion, the concentration of nitric acid (based on HNO3) can be 80-120 g / L, for example, including but not limited to 80 g / L, 90 g / L, 100 g / L, 110 g / L, and 120 g / L. Phosphoric acid, in addition to assisting nitric acid washing, also participates in the formation of phosphorus-containing compounds. If the concentration is too low, sufficient phosphorus-containing compounds cannot be formed; if the concentration is too high, it may affect the washing effect of nitric acid. Therefore, the concentration of phosphoric acid (based on H3PO4) can be 10-20 g / L, for example, including but not limited to 10 g / L, 12 g / L, 14 g / L, 16 g / L, 18 g / L, and 20 g / L.

[0056] In this embodiment, the secondary alkaline washing solution includes the following components at the following concentrations: silicate 30~40g / L and hydroxide 10~20g / L.

[0057] In this application, the secondary alkaline washing primarily utilizes the silicate and phosphorus-containing compounds from the primary acid washing to form a silicon-phosphorus composite film, inhibiting Si atom segregation. If the silicate concentration is too low, a sufficiently dense silicon-phosphorus composite film may not be formed to effectively suppress Si atom segregation; if the silicate concentration is too high, the silicon-phosphorus composite film may grow too thick, affecting the removal of the silicon-phosphorus composite film by the secondary acid washing. Therefore, the silicate concentration can be 30~40 g / L, for example, including but not limited to 30 g / L, 32 g / L, 34 g / L, 36 g / L, 38 g / L, and 40 g / L. Hydroxide plays an auxiliary role in the reaction; on the one hand, its concentration must not be too low, and on the other hand, it must be prevented from damaging the silicon-phosphorus composite film due to excessive concentration. Therefore, the hydroxide concentration can be 10~20 g / L, for example, including but not limited to 10 g / L, 12 g / L, 14 g / L, 16 g / L, 18 g / L, and 20 g / L.

[0058] In this embodiment, the secondary pickling solution includes the following components at the following concentrations: phosphoric acid 60~80g / L and nitric acid 20~30g / L.

[0059] The secondary acid pickling is primarily for removing the silicon-phosphorus composite film formed after the secondary alkaline pickling. Phosphoric acid, as the main agent for removing the silicon-phosphorus composite film, requires a high concentration to ensure effective removal while preventing excessive corrosion due to excessive concentration. Therefore, the phosphoric acid concentration, calculated as H3PO4, can be 60-80 g / L, for example, including but not limited to 60 g / L, 65 g / L, 70 g / L, 75 g / L, and 80 g / L. Nitric acid can assist phosphoric acid in cleaning and adjust the acidic environment of the pickling solution. If the nitric acid concentration is too low, it may not effectively assist in cleaning; if the nitric acid concentration is too high, it will cause excessive corrosion. Therefore, the nitric acid concentration, calculated as HNO3, can be 20-30 g / L, for example, including but not limited to 20 g / L, 22 g / L, 24 g / L, 26 g / L, 28 g / L, and 30 g / L.

[0060] In this embodiment, the primary alkaline washing solution also includes the following components at the following concentrations: persulfate 4~8 g / L.

[0061] In this application, the addition of persulfate to the primary alkaline cleaning solution enhances its cleaning ability and accelerates the dissolution of internal supports and residual sintered powder in the aluminum alloy 3D printed parts. The concentration of persulfate can be 4-8 g / L, for example, including but not limited to 4 g / L, 6 g / L, and 8 g / L. Within this range, on the one hand, it avoids insufficient oxidation due to excessively low concentration, thus preventing the enhanced cleaning effect; on the other hand, it avoids unnecessary corrosion of the aluminum alloy 3D printed parts surface due to excessively high concentration. The persulfate can be any water-soluble persulfate or a combination of water-soluble persulfates, for example, at least one of sodium persulfate, potassium persulfate, and ammonium persulfate, preferably ammonium persulfate.

[0062] In this embodiment, the pickling solution also includes the following components at the following concentrations: fluoride 2~4 g / L.

[0063] In this application, adding fluoride to the pickling solution enhances the removal of the Si phase by utilizing the complexing ability of fluoride ions. The concentration of fluoride can be 2-4 g / L, for example, including but not limited to 2 g / L, 3 g / L, and 4 g / L. Within this range, on the one hand, the enhancement effect can be insignificant due to too low a concentration, and on the other hand, excessive etching of the aluminum alloy 3D printed part surface can be avoided due to too high a concentration. The fluoride can be any water-soluble fluoride or a combination of water-soluble fluorides, for example, at least one of sodium fluoride and potassium fluoride, preferably sodium fluoride.

[0064] In this embodiment, the secondary alkaline washing solution also includes the following components at the following concentrations: persulfate 1~2 g / L.

[0065] In this application, the addition of persulfate to the secondary alkaline washing solution can maintain the surface cleanliness during the formation of the silicon-phosphorus composite film, ensuring that the formation of the silicon-phosphorus composite film is not interfered with by impurities. The concentration of persulfate can be 1~2 g / L, for example, including but not limited to 1 g / L, 1.5 g / L, and 2 g / L. Within this range, on the one hand, it can avoid the impurity inhibition effect being insignificant due to too low a concentration, and on the other hand, it can avoid damage to the silicon-phosphorus composite film due to too high a concentration and excessively strong oxidizing effect. The persulfate can be any water-soluble persulfate and a combination of water-soluble persulfates, for example, it can be at least one of sodium persulfate, potassium persulfate, and ammonium persulfate, preferably ammonium persulfate.

[0066] In this embodiment, the secondary pickling solution also includes the following components at the following concentrations: fluoride 0.5~1g / L.

[0067] In this application, the addition of fluoride to the secondary alkaline washing solution can accelerate the removal of the silicon-phosphorus composite film. The concentration of fluoride can be 0.5~1 g / L, for example, including but not limited to 0.5 g / L, 0.8 g / L, and 1 g / L. Within this range, on the one hand, the removal effect of the silicon-phosphorus composite film can be accelerated, and on the other hand, excessive concentration can be avoided, which may cause excessive corrosion to the aluminum alloy 3D printed parts. The fluoride can be any water-soluble fluoride and a combination of water-soluble fluorides, for example, at least one of sodium fluoride and potassium fluoride, preferably sodium fluoride.

[0068] In this embodiment, the electrolyte also includes the following components at concentrations: 5-10 g / L triethanolamine borate and 1-5 g / L vanadium oxalate.

[0069] In this application, triethanolamine borate and vanadium oxalate in the electrolyte can synergistically improve the hardness of anodized aluminum alloy 3D printed parts through optimized crystal structure and enhanced alumina film density. Specifically, during the anodizing process, triethanolamine borate can adsorb onto the surface of the aluminum alloy 3D printed parts, causing the alumina film to grow in a denser direction. Furthermore, the borate ions generated from its decomposition can participate in the formation of the alumina film, enhancing its mesh structure. Vanadium oxalate, on the other hand, can hydrolyze and oxidize at the anode interface, forming a composite oxide with the alumina film, further enhancing its mesh structure. It can also act as a second phase within the alumina film, thereby further improving the hardness of the anodized aluminum alloy 3D printed parts. If triethanolamine borate is used alone, although the hardness of the alumina film is slightly improved, the enhancement effect on the alumina film's mesh structure is not significant; if vanadium oxalate is used alone, although the hardness of the alumina film is slightly improved, the film density is poor. When both work together, they can compensate for each other's shortcomings, resulting in a more significant hardness improvement. The concentration of triethanolamine borate ester can be 5~10 g / L, for example, including but not limited to 5 g / L, 8 g / L, and 10 g / L. The concentration of vanadium oxalate can be 1~5 g / L, for example, including but not limited to 1 g / L, 3 g / L, and 5 g / L.

[0070] The present application will be described in detail below with reference to examples. The embodiments described below according to the present application can be modified in various forms, therefore the scope of the present application should not be construed as limited to the embodiments described in detail below. Examples are provided to help those skilled in the art to more easily understand the present application.

[0071] In the following examples and comparative examples, the aluminum alloy 3D printed parts were AlSi12 samples, which were made by selective laser melting of AlSi12 powder with a particle size range of 15~53μm. The sample size was 10mm×10mm×10mm. The concentration of sulfuric acid was expressed as H2SO4, the concentration of oxalic acid as C2H2O4, the concentration of nitric acid as HNO3, and the concentration of phosphoric acid as H3PO4.

[0072] Example 1

[0073] An anodizing method for 3D printed aluminum alloy parts includes the following steps:

[0074] The aluminum alloy 3D printed part is subjected to a series of processes: one alkaline wash, one acid wash, a second alkaline wash, and a second acid wash, to obtain a pre-treated aluminum alloy 3D printed part. This pre-treated part is then subjected to DC constant voltage anodizing to obtain an anodized aluminum alloy 3D printed part.

[0075] During a single alkaline wash, the alkaline wash solution contains the following components at the following concentrations: 80 g / L potassium hydroxide and 10 g / L potassium silicate. The temperature for the single alkaline wash is 40°C and the time is 30 min.

[0076] During a single pickling process, the pickling solution contains the following components at the following concentrations: nitric acid 80 g / L and phosphoric acid 10 g / L. The pickling temperature is 10°C and the pickling time is 5 min.

[0077] During the secondary alkaline washing, the secondary alkaline washing solution includes the following components at the following concentrations: potassium silicate 30g / L and potassium hydroxide 10g / L. The temperature of the secondary alkaline washing is 40℃ and the time is 30min.

[0078] During the secondary pickling process, the secondary pickling solution contains the following components at the following concentrations: 60 g / L phosphoric acid and 20 g / L nitric acid. The temperature of the secondary pickling is 10°C and the time is 3 min.

[0079] During anodizing, the electrolyte contains the following components at the following concentrations: sulfuric acid 100 g / L, oxalic acid 5 g / L, and the anodizing voltage is 8 V, the time is 30 min, and the temperature is 10 °C.

[0080] Example 2

[0081] An anodizing method for 3D printed aluminum alloy parts includes the following steps:

[0082] The aluminum alloy 3D printed part is subjected to a series of processes: one alkaline wash, one acid wash, a second alkaline wash, and a second acid wash, to obtain a pre-treated aluminum alloy 3D printed part. This pre-treated part is then subjected to DC constant voltage anodizing to obtain an anodized aluminum alloy 3D printed part.

[0083] During a single alkaline wash, the alkaline wash solution contains the following components at the following concentrations: sodium hydroxide 120 g / L, sodium silicate 20 g / L, and sodium persulfate 4 g / L. The temperature of the single alkaline wash is 70°C and the time is 5 min.

[0084] During a single pickling process, the pickling solution contains the following components at the following concentrations: nitric acid 120 g / L, phosphoric acid 20 g / L, and sodium fluoride 2 g / L. The temperature for a single pickling is 40°C and the time is 1 min.

[0085] During the secondary alkaline washing, the secondary alkaline washing solution includes the following components at the following concentrations: sodium silicate 40 g / L, sodium hydroxide 20 g / L, and sodium persulfate 1 g / L. The temperature of the secondary alkaline washing is 70℃ and the time is 5 min.

[0086] During the secondary pickling process, the secondary pickling solution contains the following components at the following concentrations: 80 g / L phosphoric acid, 30 g / L nitric acid, and 0.5 g / L sodium fluoride. The temperature of the secondary pickling is 40°C and the time is 1 min.

[0087] During anodizing, the electrolyte contains the following components at the following concentrations: sulfuric acid 200 g / L and oxalic acid 20 g / L. The anodizing voltage is 15 V, the time is 20 min, and the temperature is 25 °C.

[0088] Example 3

[0089] The only difference between this embodiment and Embodiment 2 is that in this embodiment:

[0090] The primary alkaline washing solution comprises the following components at the following concentrations: sodium hydroxide 120 g / L, sodium silicate 20 g / L, and ammonium persulfate 8 g / L;

[0091] The pickling solution contains the following components at the following concentrations: nitric acid 120 g / L, phosphoric acid 20 g / L, and potassium fluoride 4 g / L;

[0092] The secondary alkaline washing solution contains the following components at the following concentrations: sodium silicate 40 g / L, sodium hydroxide 20 g / L, and ammonium persulfate 2 g / L;

[0093] The secondary pickling solution contains the following components at the following concentrations: 80 g / L phosphoric acid, 30 g / L nitric acid, and 1 g / L potassium fluoride.

[0094] Example 4

[0095] The only difference between this embodiment and Embodiment 3 is that, in this embodiment, the electrolyte for anodic oxidation includes the following components at the following concentrations: sulfuric acid 200 g / L, oxalic acid 20 g / L, and triethanolamine borate 6 g / L.

[0096] Example 5

[0097] The only difference between this embodiment and Embodiment 3 is that, in this embodiment, the electrolyte for anodic oxidation includes the following components at the following concentrations: sulfuric acid 200 g / L, oxalic acid 20 g / L, and vanadium oxalate 6 g / L.

[0098] Example 6

[0099] The only difference between this embodiment and Embodiment 3 is that, in this embodiment, the electrolyte for anodic oxidation includes the following components at the following concentrations: sulfuric acid 200 g / L, oxalic acid 20 g / L, triethanolamine borate 5 g / L, and vanadium oxalate 1 g / L.

[0100] Example 7

[0101] The only difference between this embodiment and Embodiment 3 is that, in this embodiment, the electrolyte for anodic oxidation includes the following components at the following concentrations: sulfuric acid 200 g / L, oxalic acid 20 g / L, triethanolamine borate 10 g / L, and vanadium oxalate 5 g / L.

[0102] Comparative Example 1

[0103] The only difference between this comparative example and Example 1 is that in this comparative example, the aluminum alloy 3D printed part is subjected to one alkaline wash and one acid wash in sequence to obtain a pretreated aluminum alloy 3D printed part, wherein:

[0104] During a single alkaline wash, the alkaline wash solution contains the following components at the following concentrations: 80 g / L potassium hydroxide and 10 g / L potassium silicate. The temperature for the single alkaline wash is 40°C and the time is 30 min.

[0105] During a single pickling process, the pickling solution contains the following components at the following concentrations: 80 g / L nitric acid and 10 g / L phosphoric acid. The pickling temperature is 10°C and the pickling time is 5 min.

[0106] Comparative Example 2

[0107] The only difference between this comparative example and Example 1 is that in this comparative example, the aluminum alloy 3D printed part is subjected to one alkaline wash, one acid wash, a second alkaline wash, and a second acid wash in sequence to obtain the pretreated aluminum alloy 3D printed part, wherein:

[0108] During a single alkaline wash, the alkaline wash solution contains the following components at the following concentrations: 80 g / L potassium hydroxide and 10 g / L potassium silicate. The temperature for the single alkaline wash is 40°C and the time is 30 min.

[0109] During a single pickling process, the pickling solution contains the following components at the following concentrations: nitric acid 80 g / L and phosphoric acid 10 g / L. The pickling temperature is 10°C and the pickling time is 5 min.

[0110] During the secondary alkaline washing, the secondary alkaline washing solution includes the following components at the following concentrations: potassium hydroxide 30g / L and potassium silicate 10g / L. The temperature of the secondary alkaline washing is 40℃ and the time is 30min.

[0111] During the secondary pickling process, the secondary pickling solution contains the following components at the following concentrations: 60 g / L nitric acid and 20 g / L phosphoric acid. The secondary pickling temperature is 10°C and the time is 3 min.

[0112] Comparative Example 3

[0113] The only difference between this comparative example and Example 1 is that in this comparative example, the aluminum alloy 3D printed part is subjected to one alkaline wash, one acid wash, a second alkaline wash, and a second acid wash in sequence to obtain the pretreated aluminum alloy 3D printed part, wherein:

[0114] During a single alkaline wash, the alkaline wash solution contains the following components at the following concentrations: 80 g / L potassium hydroxide and 10 g / L potassium silicate. The temperature for the single alkaline wash is 40°C and the time is 30 min.

[0115] During a single pickling process, the pickling solution contains the following components at the following concentrations: 80 g / L nitric acid, and the pickling temperature is 10°C for 5 minutes.

[0116] During the secondary alkaline washing, the secondary alkaline washing solution includes the following components at the following concentrations: potassium silicate 30g / L and potassium hydroxide 10g / L. The temperature of the secondary alkaline washing is 40℃ and the time is 30min.

[0117] During the secondary pickling process, the secondary pickling solution contains the following components at the following concentrations: 60 g / L phosphoric acid and 20 g / L nitric acid. The secondary pickling temperature is 10°C and the time is 3 min.

[0118] Comparative Example 4

[0119] The only difference between this comparative example and Example 1 is that in this comparative example, the aluminum alloy 3D printed part is subjected to one alkaline wash, one acid wash, a second alkaline wash, and a second acid wash in sequence to obtain the pretreated aluminum alloy 3D printed part, wherein:

[0120] During a single alkaline wash, the alkaline wash solution contains the following components at the following concentrations: 80 g / L potassium hydroxide and 10 g / L potassium silicate. The temperature for the single alkaline wash is 40°C and the time is 30 min.

[0121] During a single pickling process, the pickling solution contains the following components at the following concentrations: nitric acid 80 g / L and phosphoric acid 10 g / L. The pickling temperature is 10°C and the pickling time is 5 min.

[0122] During the secondary alkaline washing, the secondary alkaline washing solution includes the following components at the following concentrations: potassium hydroxide 30g / L, the temperature of the secondary alkaline washing is 40℃, and the time is 30min;

[0123] During the secondary pickling process, the secondary pickling solution contains the following components at the following concentrations: 60 g / L phosphoric acid and 20 g / L nitric acid. The secondary pickling temperature is 10°C and the time is 3 min.

[0124] The following performance tests were conducted on the pretreated and anodized aluminum alloy 3D printed parts from Examples 1-7 and Comparative Examples 1-4:

[0125] (1) Microscopic morphology test: The presence of a Si-rich layer in the pre-treated aluminum alloy 3D printed parts was observed using a scanning electron microscope;

[0126] (2) The hardness of the anodized aluminum alloy 3D printed parts was tested in accordance with GB / T 4340.1-2024 "Metallic materials Vickers hardness test - Part 1: Test method", where the test force was 0.2452N.

[0127] The test results are shown in Table 1 below.

[0128] Table 1 Performance Test Results

[0129]

[0130] The pretreatment method of this application avoids the formation of a Si-rich layer on the surface of aluminum alloy 3D printed parts. Figure 1 The image shows the microstructure of the aluminum alloy 3D printed part after pretreatment in Example 1. No Si-rich layer is visible in the image. Figure 2 The image shows the microstructure of the aluminum alloy 3D printed part after pretreatment in Comparative Example 1. The diffusely distributed black dot-like areas in the image indicate the presence of a Si-rich layer.

[0131] The hardness of the anodized aluminum alloy 3D printed parts in Example 1 was significantly higher than that in Comparative Examples 1-4, indicating that the anodizing method of this application can significantly improve the hardness of the anodized film on aluminum alloy 3D printed parts. The hardness of the anodized aluminum alloy 3D printed parts in Examples 6-7 was significantly higher than that in Examples 3-5, indicating that triethanolamine borate and vanadium oxalate in the anodizing electrolyte can have a synergistic effect, further improving the hardness of the anodized film on the aluminum alloy 3D printed parts.

[0132] The above are merely specific embodiments of this application, but the scope of protection of this application is not limited thereto. Any person skilled in the art can easily conceive of various equivalent modifications or substitutions within the technical scope disclosed in this application, and these modifications or substitutions should all be covered within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. An anodizing method for aluminum alloy 3D printed parts, characterized in that, include: After undergoing pretreatment and anodizing, the aluminum alloy 3D printed parts are obtained as anodized aluminum alloy 3D printed parts. The pretreatment includes a first alkaline wash, a first acid wash, a second alkaline wash, and a second acid wash performed sequentially. In the first alkaline wash, the concentration of strongly alkaline hydroxide in the wash solution is greater than the concentration of silicate. In the first pickling process, the concentration of nitric acid in the pickling solution is greater than the concentration of phosphoric acid. The secondary alkaline washing solution contains a silicate concentration greater than the concentration of a strongly alkaline hydroxide. In the secondary pickling process, the concentration of phosphoric acid in the pickling solution is greater than that of nitric acid. The electrolyte for anodic oxidation comprises the following components at the following concentrations: sulfuric acid 100-200 g / L and oxalic acid 5-20 g / L.

2. The anodizing method for aluminum alloy 3D printed parts as described in claim 1, characterized in that, The primary alkaline washing solution comprises the following components at the following concentrations: 80-120 g / L of strong alkaline hydroxide, 10-20 g / L of silicate; and / or The primary pickling solution comprises the following components at the following concentrations: nitric acid 80-120 g / L, phosphoric acid 10-20 g / L; and / or The secondary alkaline washing solution comprises the following components at the following concentrations: silicate 30-40 g / L, strong alkaline hydroxide 10-20 g / L; and / or The secondary pickling solution comprises the following components at the following concentrations: phosphoric acid 60-80 g / L and nitric acid 20-30 g / L.

3. The anodizing method for aluminum alloy 3D printed parts as described in claim 2, characterized in that, The primary alkaline washing solution also includes the following components at concentrations: persulfate 4-8 g / L; and / or The primary pickling solution also includes the following components at concentrations: fluoride 2-4 g / L; and / or The secondary alkaline washing solution also includes the following components at concentrations: persulfate 1~2 g / L; and / or The secondary pickling solution also includes the following components at the following concentrations: fluoride 0.5~1g / L.

4. The anodizing method for aluminum alloy 3D printed parts as described in any one of claims 1 to 3, characterized in that, The temperature of the first alkaline wash is 40~70℃ and the time is 5~30min.

5. The anodizing method for aluminum alloy 3D printed parts as described in any one of claims 1 to 3, characterized in that, The temperature of the first pickling is 10~40℃ and the time is 1~5min.

6. The anodizing method for aluminum alloy 3D printed parts as described in any one of claims 1 to 3, characterized in that, The temperature of the secondary alkaline washing is 40~70℃ and the time is 5~30min.

7. The anodizing method for aluminum alloy 3D printed parts as described in any one of claims 1 to 3, characterized in that, The temperature of the secondary pickling is 10~40℃ and the time is 1~3min.

8. The anodizing method for aluminum alloy 3D printed parts as described in any one of claims 1 to 3, characterized in that, The electrolyte also includes the following components at the following concentrations: triethanolamine borate 5~10 g / L and vanadium oxalate 1~5 g / L.

9. The anodizing method for aluminum alloy 3D printed parts as described in any one of claims 1 to 3, characterized in that, The anodizing voltage is 8~15V, the time is 20~30min, and the temperature is 10~25℃.

10. The anodizing method for aluminum alloy 3D printed parts as described in any one of claims 1 to 3, characterized in that, The Si content of the aluminum alloy 3D printed part is ≥7wt%.

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