A surface micro-arc oxidation dense ceramic film aluminum alloy and a preparation method thereof

Abstract

The application discloses a kind of surface micro-arc oxidation dense ceramic film aluminum alloy and its preparation method.After annealing treatment of aluminum alloy base material, it is in turn treated by oil and grease removal, micro-arc oxidation and drying, and obtained;The conditions of the annealing treatment are as follows: temperature is 200-300 DEG C, time is 50-80 min;The conditions of the micro-arc oxidation are as follows: current density is 8-10 A / dm 2 , time is 15-20 min;The method forms dense ceramic film on the surface of alloy base material through the synergistic effect of annealing and maintenance oxidation, which can effectively improve the comprehensive performance of the material;The aluminum alloy obtained by the technical scheme of the application has excellent corrosion resistance and wear resistance, and solves the corrosion problem of aluminum alloy welding structure in high temperature, high humidity and high salt mist environment.

Description

Technical Field

[0001] This invention relates to a dense ceramic film aluminum alloy material, and more particularly to a surface micro-arc oxidation dense ceramic film aluminum alloy and its preparation method, belonging to the field of metal surface treatment technology. Background Technology

[0002] Low Earth orbit development and deep space exploration activities require the use of lightweight materials in spacecraft to reduce fuel consumption and carbon emissions. Aluminum-magnesium-scandium alloys (AMCO) have been widely used in the aerospace and shipbuilding industries due to their lightweight, high strength, and good weldability, with products primarily targeting welded heavy-duty structural components for manned spacecraft. However, in the harsh marine environments of transport, storage, and launch, AMCO is susceptible to pitting and intergranular corrosion, which significantly limits its application, especially in corrosive environments characterized by high temperature, high humidity, and high salt spray.

[0003] Currently, many efforts have been made to improve the corrosion resistance of aluminum-magnesium-scandium alloys through annealing. However, relying on the inherent properties of the base metal to operate in harsh environments, the reliable service life of aluminum-magnesium-scandium alloy structural components is severely reduced during their service life. Surface treatment technology is an effective way to improve the surface properties of aluminum alloys. Protective coatings have been prepared on aluminum alloys using techniques such as anodizing, physical vapor deposition (PVD), electrolytic deposition, sol-gel deposition, laser treatment, and plasma spraying. However, these methods have various drawbacks, such as high cost, complex processes, poor controllability, and difficulties in pretreatment.

[0004] Micro-arc oxidation, also known as plasma electrolytic oxidation, is an electrolytic surface modification technique that can produce thick, hard, and adherent ceramic films on aluminum and its alloys, protecting them from severe corrosion, especially exfoliation and stress corrosion. Current research on the microstructure of micro-arc oxidation ceramic films on aluminum alloy surfaces mainly focuses on electrolyte composition, electrical parameters, and oxidation time. However, micro-arc oxidation ceramic films have high surface porosity, and the ceramic / substrate interface region contains numerous defects such as cracks, voids, and pores, which seriously affect the service safety of spacecraft structural materials. Therefore, to further increase the density of the oxide film, it is essential and urgent to research and develop new methods suitable for improving the densification of micro-arc oxidation ceramic films on aluminum alloys, enhancing their tight bonding with the substrate, corrosion resistance, and wear resistance. Summary of the Invention

[0005] To address the problems existing in the prior art, the present invention provides an aluminum alloy with a dense ceramic film formed by surface micro-arc oxidation. This aluminum alloy uses an Al-Mg-Sc alloy as the substrate and constructs a dense ceramic oxide film on the surface of the substrate, which effectively improves the corrosion resistance and wear resistance of the material and significantly enhances the overall service performance of the alloy material.

[0006] The second objective of this invention is to provide a method for preparing a dense ceramic film aluminum alloy by surface micro-arc oxidation. Based on the synergistic effect between each step, this invention changes the surface conductivity of the substrate through annealing, and then forms a tightly bonded ceramic film on the substrate surface through micro-arc oxidation. This ceramic film is not only firmly bonded to the substrate, but also has uniform thickness and low surface roughness, which can effectively improve the overall performance of the material.

[0007] To achieve the above technical objectives, this invention provides a method for preparing a dense ceramic film aluminum alloy with surface micro-arc oxidation. The method involves annealing the aluminum alloy substrate, followed by degreasing, micro-arc oxidation, and drying. The annealing conditions are: temperature 200–300℃, time 50–80 min; the micro-arc oxidation conditions are: current density 8–10 A / dm³. 2 The time is 15 to 20 minutes.

[0008] In the preparation method provided by the present invention, the surface conductivity of the alloy material is controlled by annealing, and a controllable ceramic film is formed on the surface of the alloy substrate by micro-arc oxidation. The process parameters are executed as described above. The annealing temperature is directly controlled to the surface conductivity of the alloy substrate, while the current density of micro-arc oxidation directly controls the bonding force between the film and the substrate. The oxidation time controls the thickness and roughness of the film. Therefore, a dense ceramic film aluminum alloy material can only be obtained under the above requirements.

[0009] As a preferred embodiment, the annealing conditions are: temperature 225–300°C, time 60–80 min. More preferably, the annealing conditions are: temperature 300°C, time 60 min. The annealing temperature is directly related to the surface conductivity of the alloy substrate. As the annealing temperature increases, the surface conductivity of the alloy substrate first increases significantly and then decreases slightly. The density of the oxide film formed during the subsequent micro-arc oxidation process first increases significantly and then fluctuates slightly. Excessively high annealing temperatures can lead to thermal fatigue of the aluminum alloy substrate, and in severe cases, can cause cracks and spalling, directly affecting the mechanical properties of the substrate. Therefore, the annealing temperature should be strictly controlled within the range required by this invention.

[0010] As a preferred embodiment, the micro-arc oxidation conditions are: a current density of 10 A / dm². 2 The time is 15 minutes. The current density is directly proportional to the density of the oxide film. The higher the current density, the denser the oxide film and the stronger the adhesion to the substrate. However, if the current density is too high, it will lead to excessive exposure of defects on the alloy surface, which may cause the oxide film to break down at the surface defects and destroy the uniformity of the oxide film. Therefore, the current density should be strictly controlled within the range required by this invention.

[0011] As a preferred embodiment, the aluminum alloy substrate is an Al-Mg-Sc alloy, comprising the following elements by mass percentage: Mg 5.20–6.22%, Sc 0.20–0.30%, Mn 0.3–0.4%, with the balance being Al. More preferably, the aluminum alloy substrate comprises the following elements by mass percentage: Mg 6.02%, Sc 0.25%, Mn 0.32%, with the balance being Al.

[0012] As a preferred embodiment, the degreasing treatment is performed as follows: the surface of the aluminum alloy substrate is polished with metallographic sandpaper of 800 to 2000#, followed by ultrasonic degreasing in acetone, and then washed and dried with deionized water.

[0013] As a preferred embodiment, the micro-arc oxidation process is as follows: using an aluminum alloy substrate that has undergone degreasing as the anode and a stainless steel plate as the cathode, a composite electrolyte is added until the anode is completely immersed, and constant current DC oxidation is performed.

[0014] As a preferred embodiment, the composite electrolyte comprises sodium silicate and sodium hydroxide.

[0015] As a preferred embodiment, the sodium silicate content is 7–13 g / L, and the sodium hydroxide content is 1–2 g / L.

[0016] As a preferred embodiment, after the micro-arc oxidation treatment is completed, the aluminum alloy is removed, ultrasonically cleaned with ethanol and pure water in sequence, and then dried by cold airflow.

[0017] This invention also provides a detailed preparation process for a surface micro-arc oxidation dense ceramic film aluminum alloy, including:

[0018] Step 1: Anneal the Al-Mg-Sc alloy cold-rolled sheet;

[0019] Step 2: Perform degreasing pretreatment, and polish the sample surface with 800#, 1200#, 1500# and 2000# metallographic sandpaper. After polishing, the sample is ultrasonically degreased in acetone. Then, the sample is washed with sufficient deionized water and dried in a cool air stream.

[0020] Step 3: Weigh the film-forming agent according to the ratio, add it to deionized water, and stir with a magnetic stirrer for 10-20 minutes to obtain the electrolyte for later use;

[0021] Step 4: Using the Al-Mg-Sc alloy matrix obtained in Step 2 as the anode and the stainless steel plate as the cathode, pour the electrolyte obtained in Step 3 into the electrolytic cell and immerse the anode. The micro-arc oxidation power supply is controlled in constant current mode, with a current density range of 8–10 A / dm³. 2 Micro-arc oxidation treatment for 15–20 min;

[0022] Step 5: After the micro-arc oxidation treatment is completed, the Al-Mg-Sc alloy substrate is removed, and then ultrasonically cleaned with ethanol and pure water in sequence, and dried in a flowing cold airflow, which is the micro-arc oxidation ceramic film that is tightly bonded to the substrate on the surface of the Al-Mg-Sc alloy.

[0023] The present invention also provides a surface micro-arc oxidation dense ceramic film aluminum alloy, which is prepared by any one of the preparation methods described above.

[0024] As a preferred embodiment, the thickness of the ceramic film is 8–12 μm.

[0025] Compared with the prior art, the beneficial technical effects of the technical solution of the present invention are as follows:

[0026] 1) The surface micro-arc oxidation dense ceramic film aluminum alloy provided by the present invention uses Al-Mg-Sc alloy as the substrate and constructs a dense oxidation ceramic film on the surface of the substrate, which effectively improves the corrosion resistance and wear resistance of the material and greatly improves the overall service performance of the alloy material.

[0027] 2) The preparation method provided by the present invention is based on the synergistic effect between each step. The surface conductivity of the substrate is changed by annealing, and then a tightly bonded ceramic film is formed on the substrate surface by micro-arc oxidation. The ceramic film is not only firmly bonded to the substrate, but also has uniform thickness and low surface roughness, which can effectively improve the comprehensive performance of the material. The preparation method has the advantages of simple process flow, convenient operation, low cost and environmental friendliness. The obtained micro-arc oxidized ceramic film is complete, dense and uniform in thickness, and tightly bonded to the substrate. Attached Figure Description

[0028] Figure 1 The images show the surface microstructure of the micro-arc oxidation ceramic films obtained in Comparative Example 1, Example 1, and Example 2; wherein:

[0029] Figure 1 (a) is a microscopic morphology diagram of the surface of the micro-arc oxidation ceramic film obtained in Comparative Example 1; Figure 1 (b) is a microscopic morphology diagram of the surface of the micro-arc oxidation ceramic film obtained in Example 1; Figure 1 (c) is a microscopic morphology diagram of the surface of the micro-arc oxidation ceramic film obtained in Example 2;

[0030] Figure 2 The surface roughness of the micro-arc oxidation ceramic film obtained in Comparative Example 1, Example 1, and Example 2 is shown below; wherein:

[0031] Figure 2 (a) is the surface roughness of the micro-arc oxidation ceramic film obtained in Comparative Example 1; Figure 2 (b) is the surface roughness of the micro-arc oxidation ceramic film obtained in Example 1; Figure 2 (c) is the surface roughness of the micro-arc oxidation ceramic film obtained in Example 2;

[0032] Figure 3 The images show the cross-sectional microstructures of the micro-arc oxidation ceramic films obtained in Comparative Example 1, Example 1, and Example 2; wherein:

[0033] Figure 3 (a) is a cross-sectional microstructure of the micro-arc oxidation ceramic film obtained in Comparative Example 1. Figure 3 (b) is a cross-sectional microstructure of the micro-arc oxidation ceramic film obtained in Example 1; Figure 3 (c) is a cross-sectional microstructure of the micro-arc oxidation ceramic film obtained in Example 2;

[0034] Figure 4 The image shows the potentiodynamic polarization curves of the micro-arc oxidation ceramic films obtained in Comparative Example 1, Example 1, and Example 2. Detailed Implementation

[0035] To facilitate understanding of the present invention, a more comprehensive description will be given below with reference to specific embodiments. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a thorough and complete understanding of the disclosure of the present invention.

[0036] Comparative Example 1

[0037] 1. Pretreatment: The sample is made of Al-Mg-Sc alloy and cut into a rectangle of 20mm×20mm×2mm. Then, the sample surface is sanded with sandpaper to 2000#, then polished to mirror finish, and finally rinsed with deionized water and dried for later use.

[0038] 2. Preparation of electrolyte: The electrolyte adopts a sodium silicate-sodium hydroxide system. Add 10g / L sodium silicate nonahydrate and 1g / L sodium hydroxide, and stir with a magnetic stirrer for 10min for later use.

[0039] 3. Preparation of micro-arc oxidation ceramic film: A stainless steel plate was used as the cathode, and a pretreated Al-Mg-Sc alloy sample was used as the anode. Constant current output mode was used with a current density of 10 A / dm³. 2 The processing time is 15 minutes. During the processing, the cooling water circulation system is turned on to keep the electrolyte temperature below 40°C. Then the substrate is taken out, washed with deionized water, and dried with cold air to obtain a micro-arc oxidation ceramic film that is tightly bonded to the substrate metal.

[0040] Example 1

[0041] 1. Pretreatment: The sample is made of Al-Mg-Sc alloy and cut into a rectangle of 20mm×20mm×2mm; anneal at 200℃ for 1h, then sand the sample surface with sandpaper to 2000#, then polish to mirror finish, and finally rinse with deionized water and blow dry for later use.

[0042] 2. Preparation of electrolyte: The electrolyte adopts a sodium silicate-sodium hydroxide system. Add 10g / L sodium silicate nonahydrate and 1g / L sodium hydroxide, and stir with a magnetic stirrer for 10min for later use.

[0043] 3. Preparation of micro-arc oxidation ceramic film: A stainless steel plate was used as the cathode, and a pretreated Al-Mg-Sc alloy sample was used as the anode. Constant current output mode was used with a current density of 10 A / dm³. 2 The processing time is 15 minutes. During the processing, the cooling water circulation system is turned on to keep the electrolyte temperature below 40°C. Then the substrate is taken out, washed with deionized water, and dried with cold air to obtain a micro-arc oxidation ceramic film that is tightly bonded to the substrate metal.

[0044] Example 2

[0045] 1. Pretreatment: The sample is made of Al-Mg-Sc alloy and cut into a rectangle of 20mm×20mm×2mm; anneal at 300℃ for 1h, then sand the sample surface with sandpaper to 2000#, then polish to mirror finish, and finally rinse with deionized water and blow dry for later use.

[0046] 2. Preparation of electrolyte: The electrolyte adopts a sodium silicate-sodium hydroxide system. Add 10g / L sodium silicate nonahydrate and 1g / L sodium hydroxide, and stir with a magnetic stirrer for 10min for later use.

[0047] 3. Preparation of micro-arc oxidation ceramic film: A stainless steel plate was used as the cathode, and a pretreated Al-Mg-Sc alloy sample was used as the anode. Constant current output mode was used with a current density of 10 A / dm³. 2 The processing time is 15 minutes. During the processing, the cooling water circulation system is turned on to keep the electrolyte temperature below 40°C. Then the substrate is taken out, washed with deionized water, and dried with cold air to obtain a micro-arc oxidation ceramic film that is tightly bonded to the substrate metal.

[0048] Surface microscopic scanning was performed on the samples obtained in Example 1, Example 1, and Example 2, and the results are as follows: Figure 1 As shown in the figure, the sample prepared by the method provided in this invention has higher surface smoothness and higher density. This is evident from the fact that... Figure 2 It can also be seen that the surface roughness of the samples obtained in Example 1 and Example 2 are 3.12 μm and 2.65 μm, respectively, while the surface roughness of the sample obtained in Comparative Example 1 is as high as 4.31 μm; through Figure 3It can be seen that the sample obtained in Comparative Example 1 has relatively dense fine pores at the interface between the ceramic film and the substrate. The number of pores in the samples obtained in Example 1 and Example 2 is significantly reduced, and the density of the interface is improved. Compared with the sample obtained in Example 1, the substrate in Example 2 has a higher annealing temperature, and the conductivity of the substrate is between that of Comparative Example 1 and Example 1. The film formation rate of the oxide film is moderate. Therefore, the porosity at the interface between the ceramic film and the substrate is further reduced, and the obtained sample is the most dense. However, it should be noted that if the annealing temperature is further increased, it will lead to heat loss of the substrate, a decrease in the mechanical properties of the substrate, and the pores between the oxide film and the substrate will rapidly increase over time, and may even fall off over a large area.

[0049] The present invention also conducted potential polarization tests on the samples obtained in Comparative Example 1, Example 1, and Example 2, and the test results are as follows: Figure 4 As shown, potential polarization testing can directly reflect the corrosion resistance of a sample, through... Figure 4 It can be seen that the corrosion resistance of the samples obtained in Example 1 and Example 2 is significantly better than that of Comparative Example 1, proving that the ceramic films obtained in Example 1 and Example 2 have stronger density and can effectively improve the overall corrosion resistance of the material.

Claims

1. A method for preparing a dense ceramic film aluminum alloy with surface micro-arc oxidation, characterized in that: The aluminum alloy substrate is annealed, then sequentially subjected to degreasing, micro-arc oxidation, and drying to obtain the final product. The annealing conditions are: temperature 200~300℃, time 50~80min; the micro-arc oxidation conditions are: current density 8~10A / dm³. 2 Time: 15-20 minutes; The aluminum alloy substrate is an Al-Mg-Sc alloy, containing the following elements by mass percentage: Mg 5.20~6.22%, Sc 0.20~0.30%, Mn 0.3~0.4%, with the balance being Al.

2. The method for preparing a dense ceramic film aluminum alloy with surface micro-arc oxidation according to claim 1, characterized in that: The aluminum alloy substrate contains the following elements by mass percentage: Mg 6.02%, Sc 0.25%, Mn 0.32%, with the balance being Al.

3. The method for preparing a dense ceramic film aluminum alloy with surface micro-arc oxidation according to claim 1, characterized in that: The degreasing treatment method is as follows: the surface of the aluminum alloy substrate is polished with metallographic sandpaper of 800~2000# in sequence, followed by ultrasonic degreasing treatment in acetone, and then washed and dried with deionized water in sequence.

4. The method for preparing a dense ceramic film aluminum alloy with surface micro-arc oxidation according to claim 1, characterized in that: The micro-arc oxidation process is as follows: using an aluminum alloy substrate that has been degreased as an anode and a stainless steel plate as a cathode, a composite electrolyte is added until the anode is completely immersed, and constant current DC oxidation is performed.

5. The method for preparing a dense ceramic film aluminum alloy with surface micro-arc oxidation according to claim 4, characterized in that: The composite electrolyte contains sodium silicate and sodium hydroxide.

6. The method for preparing a dense ceramic film aluminum alloy with surface micro-arc oxidation according to claim 4, characterized in that: The composite electrolyte contains 7-13 g / L sodium silicate and 1-2 g / L sodium hydroxide.

7. The method for preparing a dense ceramic film aluminum alloy with surface micro-arc oxidation according to claim 1, characterized in that: After the micro-arc oxidation treatment is completed, the aluminum alloy is removed and ultrasonically cleaned with ethanol and pure water in sequence, and then dried by cold airflow.

8. An aluminum alloy with a dense ceramic film formed by surface micro-arc oxidation, characterized in that: It is prepared by the preparation method according to any one of claims 1 to 7.

9. The aluminum alloy with a dense ceramic film formed by surface micro-arc oxidation according to claim 8, characterized in that: The thickness of the ceramic film is 8~12μm.

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