A method for forming a conversion film on the surface of an aluminum alloy

Abstract

This invention belongs to the field of surface modification technology for metallic materials, specifically relating to a method for generating a conversion film on the surface of aluminum alloys. The method includes the following steps: Sodium hypophosphite and boric acid are added to deionized water and heated and stirred to obtain solution A; copper salt and sodium citrate are first added to deionized water and heated and stirred to obtain a complexed copper solution; solution A and the complexed copper solution are mixed, then nickel salt is added, followed by deionized water, and the mixture is adjusted to alkalinity to obtain a conversion solution; a pretreated aluminum alloy sample is placed in the conversion solution and magnetically stirred to generate a uniform conversion film on the surface of the aluminum alloy sample. Under alkaline conditions, copper ions are not promptly reduced to elemental copper, but instead form monovalent copper ions, which then rapidly react with aluminate ions to generate a ceramic film Cu2Al4O7 under suitable temperature and alkaline conditions. This ceramic film, due to its high hardness and high melting point, significantly enhances the wear resistance of the aluminum alloy surface.

Description

Technical Field

[0001] This invention belongs to the field of surface modification technology of metal materials, and specifically relates to a method for generating a conversion film on the surface of aluminum alloy. Background Technology

[0002] Given concerns about resource scarcity, achieving green and sustainable development has become an inevitable trend. Aluminum alloys, as a key lightweight material, possess numerous advantages, such as low density, high specific strength, good plasticity and ductility, excellent electrical and thermal conductivity, and good low-temperature performance. Therefore, they have wide applications in machinery manufacturing, aerospace, and transportation. In automobile manufacturing, aluminum alloys can be used to manufacture body panels, suspension systems, engine components, etc., to reduce vehicle weight and improve fuel economy. However, aluminum alloys have poor surface wear resistance and are prone to wear when in contact with other materials, affecting not only the material's appearance but also potentially impacting vehicle performance and lifespan, leading to resource waste. Currently, the hardness and strength of aluminum alloys can be improved by modifying heat treatment processes and alloy composition. Adjusting the alloy composition can alter the material's hardness and toughness, thereby improving wear resistance. Appropriate heat treatment processes can refine alloy grains, improving the material's mechanical properties and wear resistance. Nanotechnology is also being applied to aluminum alloy research to obtain nano-aluminum alloys with higher strength and hardness. However, these methods are costly.

[0003] Since most wear damage to aluminum alloys occurs at the surface layer, surface treatment techniques can form a protective film on the aluminum alloy surface. This protective film makes the aluminum alloy surface harder, thus resisting friction and wear, and effectively improving the wear resistance of the aluminum alloy. Currently, research on aluminum alloy surface modification mainly focuses on processes such as anodizing, micro-arc oxidation, and thermal spraying. These processes are affected by various factors, such as the properties of the electrolyte, current density, and voltage, making it difficult to maintain uniform film thickness. Furthermore, the micro-arc oxidation process may generate waste gas and wastewater, causing significant environmental impact. While these methods improve the wear resistance of aluminum alloy surfaces to some extent, they are prone to surface damage and uneven treatment layers during the process. Therefore, developing a novel aluminum alloy surface modification method to improve its wear resistance while avoiding surface damage is of significant application value and practical importance. Summary of the Invention

[0004] The purpose of this invention is to provide a method for generating a conversion film on the surface of aluminum alloy, thereby solving the problem of poor wear resistance of aluminum alloy surfaces.

[0005] This invention is achieved through the following technical solution: A method for generating a conversion film on an aluminum alloy surface includes the following steps: The aluminum alloy sample was pretreated and set aside for later use. Sodium hypophosphite and boric acid were added to deionized water and heated and stirred until completely dissolved to obtain solution A; copper salt and sodium citrate were added to deionized water and heated and stirred until completely dissolved to obtain a complexed copper solution. After mixing solution A with the complexed copper solution, nickel salt is added, followed by deionized water. The mixture is then adjusted to alkalinity to obtain the conversion solution. The pretreated aluminum alloy sample was placed in the conversion solution and magnetically stirred to generate a uniform conversion film on the surface of the aluminum alloy sample.

[0006] Furthermore, the pretreatment of the aluminum alloy sample specifically involves grinding, cleaning, and drying the aluminum alloy sample.

[0007] Furthermore, the polishing process specifically involves using various types of wet sandpaper with different grits to polish the aluminum alloy sample step by step.

[0008] Furthermore, the cleaning and drying processes specifically include: After polishing, the aluminum alloy sample is placed in acetone to remove oil, washed with water, and finally dried with hot air.

[0009] Furthermore, during the preparation of the conversion solution, the molar concentration ratio of sodium hypophosphite, boric acid, nickel salt, copper salt, and sodium citrate added is (0.06-0.3):(0.2-1):(0.002-0.008):(0.02-0.08):(0.05-0.3).

[0010] Furthermore, the pH of the mixed solution was adjusted to 8-10 using an alkaline reagent.

[0011] Furthermore, the reaction conditions for magnetic stirring are heating to 60-70℃, rotating at 100-300 r / min, and reacting for 1-4 hours.

[0012] Furthermore, after obtaining the conversion membrane, the conversion membrane is cleaned and dried, specifically as follows: The aluminum alloy sample was removed from the conversion solution and rinsed in deionized water to remove any residual solution from the surface. Then, ultrasonic cleaning is performed. After cleaning, the water is rinsed again with deionized water and then dried.

[0013] Furthermore, the generated conversion film is a ceramic film, with Cu2Al4O7 as its main component.

[0014] Furthermore, the coefficient of friction of the conversion film is 0.14-0.3, and the wear rate is (2-10)*10. -11 m 3 / N·m.

[0015] Compared with the prior art, the present invention has the following beneficial technical effects: This invention discloses a method for generating a conversion film on the surface of aluminum alloys. The method employs chemical conversion treatment technology to prepare a uniform and dense chemical conversion film on the aluminum alloy surface, thereby improving its wear resistance. Before pre-coating, aluminum alloy surfaces, being amphoteric metals, rapidly react with hydroxide ions in alkaline solutions to form aluminates. To improve the catalytic efficiency of copper ions on sodium hypophosphite, a small amount of nickel ions is added to the conversion solution. Under alkaline conditions, copper ions fail to be promptly reduced to elemental copper, instead forming monovalent copper ions, which then rapidly react with aluminates to generate a ceramic film, Cu2Al4O7, under suitable temperature and alkaline conditions. This ceramic film, due to its high hardness and high melting point, significantly enhances the wear resistance of the aluminum alloy surface. This method is simple to operate, uses mild processing conditions, and produces aluminum alloy surfaces with excellent wear resistance. Compared to technologies such as micro-arc oxidation, this method is simple to operate, requires no complex equipment, and reduces production costs. It has minimal environmental impact, aligns with green environmental protection trends, and contributes to resource utilization and environmental protection. Therefore, the application of this method can not only reduce maintenance costs, but also improve the efficiency of material use, which is of great significance for promoting industrial development and saving resources.

[0016] The chemical conversion film prepared by this invention has a main phase composition of Cu2Al4O7. Besides improving the wear resistance of aluminum alloy surfaces, it also possesses other properties such as electrical conductivity, without affecting the overall application of the aluminum alloy. The film has uniform thickness and a consistent coating distribution on the part surface, thus significantly improving the consistency of product performance.

[0017] Furthermore, an alkaline reagent is used to adjust the pH of the mixed solution to 8-10, primarily to regulate the membrane quality and reaction rate. If the pH is too high, the temperature during magnetic stirring will be too high, the stirring speed too fast, and the reaction too vigorous, resulting in a loose and poorly bonded conversion membrane. If the pH is too low, the temperature too low, and the stirring speed too slow, the reaction will be too inefficient. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the basic process of the present invention; Figure 2 SEM images of the conversion membranes prepared in Examples 1-3; Figure 3 The images show the three-dimensional surface morphology of the conversion films prepared in Examples 1-5. Figure 4 XRD patterns of the conversion films prepared in Examples 1-5; Figure 5 The graph shows the coefficient of friction between the conversion films prepared in Examples 1-5 and pure aluminum alloy (sample 4); Figure 6The images show the surface wear marks of the conversion films prepared in Examples 1-5 and those on pure aluminum alloy (sample 4). Figure 7 The wear rate diagrams are for the conversion films prepared in Examples 1-5 and for pure aluminum alloy (sample 4). Detailed Implementation

[0019] To make the objectives, technical solutions, and advantages of the present invention clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention; that is, the described embodiments are only a part of the embodiments of the present invention, and not all of them.

[0020] The components described and illustrated in the accompanying drawings and embodiments of this invention can be arranged and designed in various different configurations. Therefore, the detailed description of the embodiments of the invention provided in the following drawings is not intended to limit the scope of the claimed invention, but merely to illustrate one selected embodiment of the invention. All other embodiments obtained by those skilled in the art based on the accompanying drawings and embodiments of this invention without inventive effort are within the scope of protection of this invention.

[0021] It should be noted that the terms “comprising,” “including,” or any other variations are intended to cover non-exclusive inclusion, such that a process, element, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to the process, element, method, article, or apparatus.

[0022] like Figure 1 As shown, this invention discloses a method for generating a conversion film on the surface of an aluminum alloy, comprising the following steps: The aluminum alloy sample was pretreated and set aside for later use. Sodium hypophosphite and boric acid were added to deionized water and heated and stirred until completely dissolved to obtain solution A; copper salt and sodium citrate were added to deionized water and heated and stirred until completely dissolved to obtain a complexed copper solution. After mixing solution A with the complexed copper solution, nickel salt is added, followed by deionized water. The mixture is then adjusted to alkalinity to obtain the conversion solution. The pretreated aluminum alloy sample was placed in the conversion solution and magnetically stirred to generate a uniform conversion film on the surface of the aluminum alloy sample.

[0023] Taking copper sulfate as the salt and nickel sulfate as the nickel salt as an example, the conversion solution preparation process is as follows: 1. Weigh out 3-10g of copper sulfate pentahydrate, 8-30g of boric acid, 4-15g of sodium hypophosphite, 8-30g of sodium citrate, and 0.2-1g of nickel sulfate; 2. First, dissolve 3-10g of copper sulfate pentahydrate and 8-30g of sodium citrate in 100ml of heated deionized water by stirring thoroughly to obtain a complexed copper sulfate solution; 3. Then, dissolve 4-15g of sodium hypophosphite and 8-30g of boric acid in 100ml of heated deionized water by stirring thoroughly to obtain a reduced mixed solution; 4. Then mix the two together, add 0.2-1g of nickel sulfate, and finally add deionized water to 500ml; 5. Adjust the pH to 8-10 using sodium hydroxide solution.

[0024] The specific components of the conversion solution and their functions are as follows: Main salt: Copper sulfate 0.02-0.08M; Complexing agent: Sodium citrate 0.06-0.3M; Reducing agent: Sodium hypophosphite 0.06-0.3M; Stabilizer: Boric acid 0.2-1M; Additive: Nickel sulfate 0.002-0.008M; Sodium hydroxide: Provides an alkaline environment.

[0025]

[0026]

[0027] AlO2 - + Cu + A complex reaction occurs under conditions of pH 8-10 and 60-70℃ to produce Cu2Al4O7.

[0028] The features and performance of the present invention will be further described in detail below with reference to embodiments.

[0029] Example 1 This embodiment describes a method for preparing a conversion film on an aluminum alloy surface. The specific preparation method includes the following steps: Step 1: Pre-treat the aluminum alloy sample by grinding it step by step with 400#, 800#, 1000#, 1500#, and 2000# wet sandpaper to remove surface dirt, oxide film, and defects, and to make the surface smooth and uniform in thickness. After completion, immerse the sample in acetone for 3 minutes to remove oil, rinse with water, and finally dry with hot air.

[0030] Here, the sample is made of 6061 aluminum alloy and is cylindrical with dimensions of Φ20×6 mm.

[0031] Step 2: Weigh the required reagents, including 5g of copper sulfate pentahydrate, 15g of boric acid, 14g of sodium hypophosphite, 7g of sodium citrate, and 0.5g of nickel sulfate.

[0032] Step 3: Prepare the conversion solution. First, add 5g of copper sulfate pentahydrate and 7g of sodium citrate to a beaker, then add 100mL of deionized water and stir until completely dissolved to form a copper sulfate solution. Then, in another beaker, add 100 mL of deionized water to 14 g of sodium hypophosphite and 15 g of boric acid, and stir until completely dissolved. Mix the two solutions, add 0.5g of nickel sulfate, add deionized water to 500mL, and adjust the pH of the mixed solution to 8 with sodium hydroxide.

[0033] Step 4: Prepare the conversion film. Place the solution on a magnetic stirrer, fix the pretreated aluminum alloy in the solution with copper wires, and adjust the temperature and speed of the magnetic stirrer to form a uniform conversion film on the surface of the aluminum alloy. The mass of the conversion film is 0.053g.

[0034] The reaction conditions were: heating to 65°C, rotation speed of 300 r / min, and reaction time of 2 hours.

[0035] Step 5: Cleaning and drying the conversion coating. Remove the aluminum alloy sample coated with the conversion coating from the conversion solution and rinse it in deionized water to remove any residual solution from the surface. Next, place the sample in an ultrasonic cleaner, add an appropriate amount of deionized water, and perform ultrasonic cleaning for approximately 10 minutes. After cleaning, rinse again with deionized water and then dry it in hot air. This sample is designated as Sample A and is ready for use.

[0036] The conversion film prepared in this embodiment has a friction coefficient of 0.16 and a wear rate of 2.1*10. -11 m 3 / N·m.

[0037] Example 2 This embodiment describes a method for improving the surface wear resistance of 6061 aluminum alloy. The specific preparation method includes the following steps: Step 1: Pre-treat the aluminum alloy sample by grinding it step by step with 400#, 800#, 1000#, 1500#, and 2000# wet sandpaper to remove surface dirt, oxide film, and defects, and to make the surface smooth and uniform in thickness. After completion, immerse the sample in acetone for 3 minutes to remove oil, rinse with water, and finally dry with hot air.

[0038] Here, the sample is made of 6061 aluminum alloy and is cylindrical with dimensions of Φ20×6 mm.

[0039] Step 2: Weigh the required reagents, including 5g of copper sulfate pentahydrate, 15g of boric acid, 14g of sodium hypophosphite, 7g of sodium citrate, and 0.5g of nickel sulfate.

[0040] Step 3: Prepare the conversion solution. First, add 5g of copper sulfate pentahydrate and 7g of sodium citrate to a beaker, then add 100mL of deionized water and stir until completely dissolved to form a copper sulfate solution. Then, in another beaker, add 100 mL of deionized water to 14 g of sodium hypophosphite and 15 g of boric acid, and stir until completely dissolved. Mix the two solutions, add 0.5g of nickel sulfate, add deionized water to 500mL, and adjust the pH of the mixed solution to 9 with sodium hydroxide.

[0041] Step 4: Prepare the conversion film. Place the solution on a magnetic stirrer and fix the pretreated aluminum alloy in the solution with copper wires. Adjust the temperature and speed of the magnetic stirrer to generate a uniform conversion film on the surface of the aluminum alloy. The mass of the conversion film is 0.094g.

[0042] The reaction conditions were: heating to 65°C, rotation speed of 300 r / min, and reaction time of 2 hours.

[0043] Step 5: Cleaning and drying the conversion coating. Remove the aluminum alloy sample from the conversion solution and rinse it in deionized water to remove any residual solution from the surface. Next, place the sample in an ultrasonic cleaner, add an appropriate amount of deionized water, and perform ultrasonic cleaning for approximately 10 minutes. After cleaning, rinse again with deionized water and then dry it in hot air. This sample is designated as Sample B and will be used later.

[0044] The conversion film prepared in this embodiment has a friction coefficient of 0.18 and a wear rate of 3.38*10. -11 m 3 / N·m.

[0045] Example 3 This embodiment describes a method for improving the surface wear resistance of 6061 aluminum alloy. The specific preparation method includes the following steps: Step 1: Pre-treat the aluminum alloy sample by grinding it step by step with 400#, 800#, 1000#, 1500#, and 2000# wet sandpaper to remove surface dirt, oxide film, and defects, and to make the surface smooth and uniform in thickness. After completion, immerse the sample in acetone for 3 minutes to remove oil, rinse with water, and finally dry with hot air.

[0046] Here, the sample is made of 6061 aluminum alloy and is cylindrical with dimensions of Φ20×6 mm.

[0047] Step 2: Weigh the required reagents, including 5g of copper sulfate pentahydrate, 15g of boric acid, 14g of sodium hypophosphite, 7g of sodium citrate, and 0.5g of nickel sulfate.

[0048] Step 3: Prepare the conversion solution. First, add 5g of copper sulfate pentahydrate and 7g of sodium citrate to a beaker, then add 100mL of deionized water and stir until completely dissolved to form a copper sulfate solution. Then, in another beaker, add 100 mL of deionized water to 14 g of sodium hypophosphite and 15 g of boric acid, and stir until completely dissolved. Mix the two solutions, add 0.5g of nickel sulfate, add deionized water to 500mL, and adjust the pH of the mixed solution to 10 with sodium hydroxide.

[0049] Step 4: Prepare the conversion film. Place the solution on a magnetic stirrer and fix the pretreated aluminum alloy in the solution with copper wires. Adjust the temperature and speed of the magnetic stirrer to generate a uniform conversion film on the surface of the aluminum alloy. The mass of the conversion film is 0.19g.

[0050] The reaction conditions were: heating to 65°C, rotation speed of 300 r / min, and reaction time of 2 hours.

[0051] Step 5: Cleaning and drying the conversion coating. Remove the aluminum alloy sample from the conversion solution and rinse it in deionized water to remove any residual solution from the surface. Next, place the sample in an ultrasonic cleaner, add an appropriate amount of deionized water, and perform ultrasonic cleaning for approximately 10 minutes. After cleaning, rinse again with deionized water and then dry it in hot air. This sample is designated as Sample C and will be used later.

[0052] The conversion film prepared in this embodiment has a friction coefficient of 0.21 and a wear rate of 9.71*10. -11 m 3 / N·m.

[0053] Figure 2 The images show SEM images of the conversion films prepared in Examples 1, 2, and 3. The surfaces of the conversion films prepared in all examples are uniform and dense. Different pH values ​​affect grain growth; the lower the pH, the finer the grains. However, at pH=8, the coating process is relatively slow, so pH=9 was used in the other examples.

[0054] Example 4 This embodiment describes a method for improving the surface wear resistance of 6061 aluminum alloy. The specific preparation method includes the following steps: Step 1: Pre-treat the aluminum alloy sample by grinding it step by step with 400#, 800#, 1000#, 1500#, and 2000# wet sandpaper to remove surface dirt, oxide film, and defects, and to make the surface smooth and uniform in thickness. After completion, immerse the sample in acetone for 3 minutes to remove oil, rinse with water, and finally dry with hot air.

[0055] Here, the sample is made of 6061 aluminum alloy and is cylindrical with dimensions of Φ20×6 mm.

[0056] Step 2: Weigh the required reagents, including 3g of copper sulfate pentahydrate, 15g of boric acid, 9g of sodium hypophosphite, 7g of sodium citrate, and 0.5g of nickel sulfate.

[0057] Step 3: Prepare the conversion solution. First, add 3g of copper sulfate pentahydrate and 7g of sodium citrate to a beaker, then add 100mL of deionized water and stir until completely dissolved to form a copper sulfate solution. Then, in another beaker, add 100 mL of deionized water to 9 g of sodium hypophosphite and 15 g of boric acid, and stir until completely dissolved; Mix the two solutions, add 0.5g of nickel sulfate, add deionized water to 500mL, and adjust the pH of the mixed solution to 9 with sodium hydroxide.

[0058] Step 4: Prepare the conversion film. Place the solution on a magnetic stirrer and fix the pretreated aluminum alloy in the solution with copper wires. Adjust the temperature and speed of the magnetic stirrer to generate a uniform conversion film on the surface of the aluminum alloy. The mass of the conversion film is 0.143.

[0059] The reaction conditions were: heating to 70°C, rotation speed of 200 r / min, and reaction time of 2 hours.

[0060] Step 5: Cleaning and drying the conversion coating. Remove the aluminum alloy sample from the conversion solution and rinse it in deionized water to remove any residual solution from the surface. Next, place the sample in an ultrasonic cleaner, add an appropriate amount of deionized water, and perform ultrasonic cleaning for approximately 10 minutes. After cleaning, rinse again with deionized water and then dry it in hot air. This sample is designated as sample D and is ready for use.

[0061] The conversion film prepared in this embodiment has a friction coefficient of 0.2 and a wear rate of 6.7*10. -11 m 3 / N·m.

[0062] Example 5 This embodiment describes a method for improving the surface wear resistance of 6061 aluminum alloy. The specific preparation method includes the following steps: Step 1: Pre-treat the aluminum alloy sample by grinding it step by step with 400#, 800#, 1000#, 1500#, and 2000# wet sandpaper to remove surface dirt, oxide film, and defects, and to make the surface smooth and uniform in thickness. After completion, immerse the sample in acetone for 3 minutes to remove oil, rinse with water, and finally dry with hot air.

[0063] Here, the sample is made of 6061 aluminum alloy and is cylindrical with dimensions of Φ20×6 mm.

[0064] Step 2: Weigh the required reagents, including 10g of copper sulfate pentahydrate, 30g of boric acid, 15g of sodium hypophosphite, 14g of sodium citrate, and 1g of nickel sulfate.

[0065] Step 3: Prepare the conversion solution. First, add 10g of copper sulfate pentahydrate and 14g of sodium citrate to a beaker, then add 100mL of deionized water and stir until completely dissolved to form a copper sulfate solution. Then, in another beaker, add 200 mL of deionized water to 15 g of sodium hypophosphite and 30 g of boric acid, and stir until completely dissolved. Mix the two solutions, add 1g of nickel sulfate, add deionized water to 500mL, and adjust the pH of the mixed solution to 9 with sodium hydroxide.

[0066] Step 4: Prepare the conversion film. Place the solution on a magnetic stirrer and fix the pretreated aluminum alloy in the solution with copper wires. Adjust the temperature and speed of the magnetic stirrer to generate a uniform conversion film on the surface of the aluminum alloy. The mass of the conversion film is 0.152.

[0067] The reaction conditions were: heating to 60°C, rotation speed of 200 r / min, and reaction time of 2 hours.

[0068] Step 5: Cleaning and drying the conversion coating. Remove the aluminum alloy sample from the conversion solution and rinse it in deionized water to remove any residual solution from the surface. Next, place the sample in an ultrasonic cleaner, add an appropriate amount of deionized water, and perform ultrasonic cleaning for approximately 10 minutes. After cleaning, rinse again with deionized water and then dry it in hot air. This sample is designated as Sample E and is ready for use.

[0069] The conversion film prepared in this embodiment has a friction coefficient of 0.15 and a wear rate of 2.2*10⁻⁶. -11 m 3 / N·m.

[0070] Figure 3 The images show the three-dimensional surface morphology of the conversion films prepared in Examples 1, 2, 3, 4, and 5. The surfaces of the conversion films prepared in different examples are all uniform and dense, and the surface roughness is all below 2.

[0071] Figure 4 The X-ray diffraction patterns of the conversion films prepared in Examples 1, 2, 3, 4, and 5 are shown. Phase analysis shows that the final conversion film layer in all examples is Cu2Al4O7.

[0072] Figure 5 The graph shows the friction coefficients of the conversion films prepared in Examples 1, 2, 3, 4, and 5 and pure aluminum alloy (sample 4). Compared with pure aluminum alloy, the average friction coefficients of each example treated under different conditions show certain differences, but they are all much lower than the friction coefficient of pure aluminum alloy.

[0073] Figure 6 The images show the wear morphology of the conversion films prepared in Examples 1, 2, 3, 4, and 5 and the pure aluminum alloy (sample 4). As can be seen from the images, the pure aluminum alloy (sample 4) has a large and deep wear area and severe wear, while the wear on the surfaces of the examples treated under different conditions is relatively light.

[0074] Figure 7 The graph shows the volumetric wear rate of the conversion films prepared in Examples 1, 2, 3, 4, and 5, compared to that of pure aluminum alloy (Sample 4). The wear rates differ slightly among the examples, but are reduced by two orders of magnitude compared to pure aluminum alloy (Sample 4). This is consistent with... Figure 5 and Figure 6 The results correspond.

[0075] Testing revealed that the method of this invention, by preparing a chemical conversion film on the surface of 6061 aluminum alloy, gives the aluminum alloy excellent friction reduction properties and improves its wear resistance.

[0076] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the specific implementation of the present invention. Any modifications or equivalent substitutions that do not depart from the spirit and scope of the present invention should be covered within the scope of protection of the claims of the present invention.

Claims

1. A method for generating a conversion film on the surface of an aluminum alloy, characterized in that, The process includes the following: The aluminum alloy sample was pretreated and set aside for later use. Sodium hypophosphite and boric acid were added to deionized water and heated and stirred until completely dissolved to obtain solution A; copper salt and sodium citrate were added to deionized water and heated and stirred until completely dissolved to obtain a complexed copper solution. After mixing solution A with the complexed copper solution, nickel salt is added, followed by deionized water. The mixture is then adjusted to alkalinity to obtain the conversion solution. The pretreated aluminum alloy sample was placed in the conversion solution and magnetically stirred to generate a uniform conversion film on the surface of the aluminum alloy sample. The generated conversion film was a ceramic film with Cu2Al4O7 as its main component. During the preparation of the conversion solution, the molar ratio of sodium hypophosphite, boric acid, nickel salt, copper salt, and sodium citrate added was (0.06-0.3):(0.2-1):(0.002-0.008):(0.02-0.08):(0.05-0.3). The reaction conditions for magnetic stirring are heating to 60-70℃, rotating at 100-300 r / min, and reacting for 1-4 hours.

2. The method for generating a conversion film on an aluminum alloy surface according to claim 1, characterized in that, The pretreatment of aluminum alloy samples specifically involves grinding, cleaning, and drying the aluminum alloy samples.

3. The method for generating a conversion film on an aluminum alloy surface according to claim 2, characterized in that, The polishing process involves using various grit sandpapers to polish the aluminum alloy sample step by step.

4. The method for generating a conversion film on an aluminum alloy surface according to claim 2, characterized in that, The cleaning and drying processes are as follows: After polishing, the aluminum alloy sample is placed in acetone to remove oil, washed with water, and finally dried with hot air.

5. The method for generating a conversion film on an aluminum alloy surface according to claim 1, characterized in that, The pH of the mixed solution was adjusted to 8-10 using an alkaline reagent.

6. The method for generating a conversion film on an aluminum alloy surface according to claim 1, characterized in that, After obtaining the conversion membrane, the conversion membrane is cleaned and dried, specifically as follows: The aluminum alloy sample was removed from the conversion solution and rinsed in deionized water to remove any residual solution from the surface. Then, ultrasonic cleaning is performed. After cleaning, the water is rinsed again with deionized water and then dried.

7. The method for generating a conversion film on an aluminum alloy surface according to claim 1, characterized in that, The coefficient of friction of the conversion film is 0.14-0.3, and the wear rate is (2-10). 10 -11 m 3 / N·m.

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