Surface modified aluminum alloy and preparation method thereof

Abstract

The invention discloses a surface modified aluminum alloy and a preparation method thereof, and belongs to the technical field of metal surface treatment.The preparation method comprises the following steps that S1, an aluminum alloy workpiece is sequentially subjected to ultrasonic oil removal, alkali corrosion, composite acid pickling and water washing treatment; s2, the treated workpiece serves as an anode and is placed in a chromium-free composite electrolyte for anodic oxidation; s3, cleaning and drying the treated workpiece, putting the workpiece into magnetron sputtering equipment, carrying out sputtering cleaning, and then switching to a carbon-containing target material to deposit a DLC (Diamond Like Carbon) coating; and S4, the treated workpiece is subjected to hole sealing treatment in deionized water at the temperature of 80-100 DEG C for 20-30 min, the workpiece is taken out and dried, and the surface modified aluminum alloy is obtained. The modified aluminum alloy prepared through the method is provided with the high-density nano-porous anodic oxide layer, the binding force between the modified aluminum alloy and the functional coating is high, microhardness is high, salt spray corrosion resistance and abrasion resistance are excellent, and the technology is environmentally friendly and stable.

Description

Technical Field

[0001] This invention belongs to the field of metal surface treatment technology, specifically relating to a surface-modified aluminum alloy and its preparation method. Background Technology

[0002] Aluminum alloys are widely used in aerospace, automotive, rail transportation, and high-end equipment industries due to their low density, high specific strength, and ease of processing. However, their inherent low hardness, poor wear resistance, and insufficient corrosion resistance limit their application in harsher environments.

[0003] Anodizing of aluminum alloys is a common technique for improving their surface hardness, wear resistance, and corrosion resistance. Traditional processes typically include alkaline washing for degreasing, acid pickling for brightening, anodizing, and sealing. However, conventional alkaline washing and acid pickling processes are often rather crude, leading to fluctuations in the uniformity and adhesion of the subsequent oxide film. Furthermore, while the traditional sulfuric acid anodizing (SAA) process is widely used, the resulting oxide film has a large pore size (typically >100 nm) and high porosity (15-20%), limiting its application in fields requiring high corrosion resistance. To improve performance, organic acids such as oxalic acid and tartaric acid are often added to the electrolyte to refine the pore size, or chromates are added to improve film density. However, chromates are highly toxic and carcinogenic; their use and discharge seriously harm the environment and human health, failing to meet the requirements of modern green manufacturing and environmental regulations.

[0004] In the prior art, patent CN117107319A discloses an aluminum alloy anodizing electrolyte and process, involving a general alkaline washing solution; patent CN118621399A discloses a wide-temperature-range magnesium-aluminum alloy anodizing electrolyte and its preparation method. However, these technologies still have limitations in achieving highly dense, low-porosity oxide films. On the other hand, physical vapor deposition (PVD) technologies, such as magnetron sputtering, can deposit hard functional coatings such as diamond-like carbon (DLC) and titanium nitride (TiN) on the material surface, giving it excellent wear resistance and friction reduction properties. However, the adhesion between the aluminum alloy substrate and these hard coatings is poor. If sputtering is performed directly on a common anodized layer, the functional coating is prone to peeling off due to the rough surface, high porosity, and loose structure of the oxide film, seriously affecting its service life.

[0005] Therefore, how to form a highly dense, low-porosity oxide film on the surface of aluminum alloy and ensure that the oxide film has good adhesion to the subsequently deposited functional coating has become a key problem that urgently needs to be solved. Summary of the Invention

[0006] In view of the shortcomings of the prior art, the present invention discloses a surface-modified aluminum alloy and its preparation method. The present invention uses gradient alkaline etching pretreatment and chromium-free composite electrolyte formulation optimization to synergistically prepare an anodized layer with nano-sized pores, high density and smooth surface; then, a magnetron sputtering functional coating is deposited on this substrate to achieve strong bonding between the coating and the substrate.

[0007] To achieve the above objectives, the present invention provides the following technical solution: This invention discloses a method for preparing surface-modified aluminum alloys, comprising the following steps: S1. The aluminum alloy workpiece is subjected to ultrasonic degreasing, alkaline etching, composite pickling, and water washing in sequence. S2. The workpiece treated in S1 is used as the anode and placed in a chromium-free composite electrolyte. Anodizing is carried out for 20 to 40 minutes under the conditions of voltage 12~18V and temperature 15~35℃, while stirring the electrolyte. S3. After cleaning and drying the workpiece treated in S2, place it in the magnetron sputtering equipment, perform sputtering cleaning first, and then switch to carbon target material to deposit DLC coating for 15~30 min to make the coating thickness reach 2~5μm; S4. The workpiece treated in S3 is sealed in deionized water at 80~100℃ for 20~30 minutes, then removed and dried to obtain the surface-modified aluminum alloy.

[0008] Preferably, in step S1, the alkaline etching process is as follows: First stage: Immerse the workpiece in a 3wt% NaOH solution at 38~42℃ for 2~3 minutes; Second stage: Immerse the workpiece treated in the first stage in a solution of 8wt% NaOH and 3wt% NaOH... The mixture was treated in a composite solution at 58-62℃ for 2-4 minutes.

[0009] Preferably, in step S1, the composite pickling and activation treatment process is as follows: immersing the workpiece in a solution of 10 wt%... In a mixed solution consisting of 5 wt% HF, it was treated at room temperature for 30 s.

[0010] Preferably, in step S2, the chromium-free composite electrolyte is composed of the following components: sulfuric acid 130~160 g / L, oxalic acid 20~50 g / L, titanium sol 80~120 g / L, organic cerium salt complexing agent 2~3 g / L, and aluminum sulfate 2~3 g / L.

[0011] Preferably, the organic cerium salt complexing agent is cerium citrate or cerium tartrate, and the particle size of the titanium sol is 5~20 nm.

[0012] Preferably, in step S3, the parameters for magnetron sputtering are: evacuation to... Argon gas is introduced, the working pressure is 0.3~0.6 Pa, the sputtering power is 100~300 W, and the workpiece surface is sputtered cleaned for 5~10 minutes.

[0013] Preferably, in step S3, when depositing the DLC coating, acetylene or methane is introduced as the reaction gas at a flow rate of 5-20 sccm.

[0014] The present invention also discloses a surface-modified aluminum alloy prepared by the above preparation method, comprising an aluminum alloy substrate and a nanoporous anodic oxide layer and a DLC coating distributed sequentially from the substrate outward.

[0015] Preferably, the pore size of the nanoporous anodic oxide layer is less than 50 nm, the porosity is less than 5%, and the surface roughness Ra is less than 0.15 μm.

[0016] Compared with the prior art, the present invention has the following beneficial effects: (1) The present invention employs a gradient alkaline etching process (first stage: 3 wt% NaOH, 38~42℃, 2~3min; second stage: 8wt% NaOH + 3wt% NaOH). (58~62℃, 2~4min) and compound pickling and activation treatment (10wt%) +5wt% HF, room temperature, 30s) ensured the uniformity and activity of the surface microstructure, providing a good substrate for the high-quality growth of the subsequent oxide film.

[0017] (2) This invention uses a chromium-free composite electrolyte (containing sulfuric acid, oxalic acid, titanium sol, organic cerium salt complexing agent, and aluminum sulfate) to perform anodic oxidation for 20-40 minutes at a voltage of 12-18 V and a temperature of 15-35℃. The resulting oxide film has a pore size of less than 50 nm, a porosity of less than 5%, and a surface roughness Ra ≤ 0.15 μm. At the same time, the introduction of titanium sol and organic cerium salt effectively refines the pore size, improves the density and corrosion resistance of the film, and avoids the use of toxic chromates, thus meeting environmental protection requirements.

[0018] (3) In this invention, the DLC coating is deposited on the above-mentioned high-density oxide film by magnetron sputtering, which significantly enhances the adhesion. Sputtering cleaning (100~300 W, 0.3~0.6 Pa, 5~10 min) further improves the cleanliness and activity of the substrate, ensuring good adhesion between the DLC coating and the oxide film. Attached Figure Description

[0019] Figure 1 This is a surface morphology image of the aluminum alloy anodized layer in Embodiment 1 of the present invention. Detailed Implementation

[0020] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0021] This invention discloses a method for preparing surface-modified aluminum alloys, comprising the following steps: S1. After ultrasonic degreasing of the aluminum alloy workpiece, a two-stage gradient alkaline etching treatment is performed: First stage: Immerse the workpiece in a 3wt% NaOH solution at 38~42℃ for 2~3 minutes to further remove the surface oxide layer and oil stains; Second stage: Immerse the workpiece treated in the first stage in a solution of 8wt% NaOH and 3wt% NaOH... The workpiece is treated in a composite solution at 58-62℃ for 2-4 minutes; then the treated workpiece is immersed in a mixed solution of 10wt% HNO3 and 5wt% HF and treated at room temperature for 30 seconds to obtain a clean workpiece.

[0022] S2. Using the above-treated workpiece as the anode and a lead plate or stainless steel plate as the cathode, the workpiece is placed in a chromium-free composite electrolyte and anodized for 20-40 minutes at a voltage of 12-18V and a temperature of 15-35℃ to obtain a workpiece with a nanoporous anodized layer distributed on its surface. The chromium-free composite electrolyte is composed of the following components: sulfuric acid 130-160g / L, oxalic acid 20-50g / L, titanium sol 80-120g / L, organic cerium salt complexing agent 2-3g / L, and aluminum sulfate 2-3g / L. The organic cerium salt complexing agent is cerium citrate or cerium tartrate, and the particle size of the titanium sol is 5-20 nm.

[0023] S3. After cleaning and drying the workpiece obtained above, place it in a magnetron sputtering apparatus and evacuate it to a vacuum level. Argon gas is introduced at a working pressure of 0.3~0.6 Pa and a sputtering power of 100~300 W to sputter clean the workpiece surface for 5~10 min. Then, the carbon target is switched to deposit a DLC coating for 15~30 min at the same pressure and power to achieve a coating thickness of 2~5 μm. During the DLC coating deposition, acetylene or methane is introduced as the reaction gas at a flow rate of 5~20 sccm.

[0024] S4. The workpiece treated above is sealed in deionized water at 80~100℃ for 20~30 minutes, then removed and dried to obtain the surface modified aluminum alloy.

[0025] The aluminum alloy prepared by the above-described method comprises an aluminum alloy substrate, and a nanoporous anodic oxide layer and a DLC coating distributed sequentially from the substrate outwards. Furthermore, the nanoporous anodic oxide layer has a pore size of less than 50 nm, a porosity of less than 5%, and a surface roughness Ra ≤ 0.15 μm.

[0026] The technical solution of the present invention will be further described below with reference to specific embodiments: Example 1

[0027] This embodiment describes a method for preparing a surface-modified aluminum alloy, with the following specific steps: S1. Using a 6061 aluminum alloy test piece (50mm × 30mm × 3mm) as the workpiece, perform the following treatments in sequence: Ultrasonic degreasing: The workpiece is placed in an alkaline degreasing solution and ultrasonically treated at 55°C for 5 minutes to remove surface oil stains; Alkaline etching treatment: First stage: Immerse the above workpiece in a 3 wt% NaOH solution and treat at 40℃ for 2 minutes to remove the natural oxide layer and residual oil stains; Second stage: Immerse the workpiece treated in the first stage in a solution of 8 wt% NaOH + 3 wt% NaOH. The mixture was treated at 60°C for 3 minutes in the composite solution. Composite pickling and activation: Immerse the alkaline-etched workpiece in a solution of 10 wt%... In a mixed solution consisting of +5 wt% HF, the solution was treated for 30 s at room temperature; Water washing: Thoroughly rinse the surface of the workpiece after the above treatment with deionized water, and then blow dry to obtain a clean workpiece to be oxidized.

[0028] S2. Using the above-treated workpiece as the anode and a lead plate or stainless steel plate as the cathode, the workpiece is placed in a chromium-free composite electrolyte and anodized for 30 minutes at a voltage of 15V and a temperature of 25℃ to obtain a workpiece with a nanoporous anodized layer distributed on its surface. The chromium-free composite electrolyte is composed of the following components: sulfuric acid 150g / L, oxalic acid 35g / L, titanium sol (calculated as TiO2) 100g / L, cerium citrate 2.5g / L, and aluminum sulfate 2.5g / L. After oxidation, the workpiece is removed, thoroughly rinsed with deionized water, and dried to obtain an aluminum alloy workpiece with a nanoporous anodized layer on its surface. The oxide layer thickness is measured to be approximately 12 μm, the pore size is approximately 40 nm, and the porosity is approximately 4%.

[0029] S3. After cleaning and drying the workpiece obtained above, place it in a magnetron sputtering apparatus and evacuate it to a vacuum level. Argon gas was introduced at a working pressure of 0.5 Pa and a sputtering power of 200 W to sputter clean the workpiece surface for 8 minutes; then the process was switched to a graphite target, and acetylene was introduced at the same pressure and power. The DLC coating was deposited at a depth of 10 sccm for 20 min. After deposition, the gas and power were turned off, and the workpiece was removed after the chamber cooled down. The thickness of the DLC coating was measured using a step meter and was approximately 2.8 μm.

[0030] S4. The workpiece treated above is sealed in deionized water at 90°C for 25 minutes, then removed and dried to obtain the surface-modified aluminum alloy. Example 2

[0031] This embodiment describes a method for preparing a surface-modified aluminum alloy, with the following specific steps: S1. Using a 6061 aluminum alloy test piece (50mm × 30mm × 3mm) as the workpiece, perform the following treatments in sequence: Ultrasonic degreasing: The workpiece is placed in an alkaline degreasing solution and ultrasonically treated at 55°C for 5 minutes to remove surface oil stains; Alkaline etching treatment: First stage: Immerse the above workpiece in a 3 wt% NaOH solution and treat at 40℃ for 2 minutes to remove the natural oxide layer and residual oil stains; Second stage: Immerse the workpiece treated in the first stage in a solution of 8 wt% NaOH + 3 wt% NaOH. The mixture was treated at 60°C for 3 minutes in the composite solution. Composite pickling and activation: Immerse the alkaline-etched workpiece in a solution of 10 wt%... In a mixed solution consisting of +5 wt% HF, the solution was treated for 30 s at room temperature; Water washing: Thoroughly rinse the surface of the workpiece after the above treatment with deionized water, and then blow dry to obtain a clean workpiece to be oxidized.

[0032] S2. Using the above-treated workpiece as the anode and a lead plate or stainless steel plate as the cathode, the workpiece is placed in a chromium-free composite electrolyte and anodized for 40 minutes at a voltage of 12V and a temperature of 15℃ to obtain a workpiece with a nanoporous anodized layer distributed on its surface. The chromium-free composite electrolyte is composed of the following components: sulfuric acid 150g / L, oxalic acid 35g / L, titanium sol (calculated as TiO2) 100g / L, cerium citrate 2.5g / L, and aluminum sulfate 2.5g / L. After oxidation, the workpiece is removed, thoroughly rinsed with deionized water, and dried to obtain an aluminum alloy workpiece with a nanoporous anodized layer on its surface. The oxide layer thickness is measured to be approximately 14.5 μm, the pore size is approximately 35 nm, and the porosity is approximately 3.5%.

[0033] S3. After cleaning and drying the workpiece obtained above, place it in a magnetron sputtering apparatus and evacuate it to a vacuum level. Argon gas was introduced at a working pressure of 0.5 Pa and a sputtering power of 200 W to sputter clean the workpiece surface for 8 minutes; then the process was switched to a graphite target, and acetylene was introduced at the same pressure and power. The DLC coating was deposited at a depth of 10 sccm for 20 min. After deposition, the gas and power were turned off, and the workpiece was removed after the chamber cooled down. The thickness of the DLC coating was measured using a step meter and was approximately 2.8 μm.

[0034] S4. The workpiece treated above is sealed in deionized water at 90°C for 25 minutes, then removed and dried to obtain the surface-modified aluminum alloy. Example 3

[0035] This embodiment describes a method for preparing a surface-modified aluminum alloy, with the following specific steps: S1. Using a 6061 aluminum alloy test piece (50mm × 30mm × 3mm) as the workpiece, perform the following treatments in sequence: Ultrasonic degreasing: The workpiece is placed in an alkaline degreasing solution and ultrasonically treated at 55°C for 5 minutes to remove surface oil stains; Alkaline etching treatment: First stage: Immerse the above workpiece in a 3 wt% NaOH solution and treat at 40℃ for 2 minutes to remove the natural oxide layer and residual oil stains; Second stage: Immerse the workpiece treated in the first stage in a solution of 8 wt% NaOH + 3 wt% NaOH. The mixture was treated at 60°C for 3 minutes in the composite solution. Composite pickling and activation: Immerse the alkaline-etched workpiece in a solution of 10 wt%... In a mixed solution consisting of +5 wt% HF, the solution was treated for 30 s at room temperature; Water washing: Thoroughly rinse the surface of the workpiece after the above treatment with deionized water, and then blow dry to obtain a clean workpiece to be oxidized.

[0036] S2. Using the above-treated workpiece as the anode and a lead plate or stainless steel plate as the cathode, the workpiece is placed in a chromium-free composite electrolyte and anodized for 20 minutes at a voltage of 18V and a temperature of 35℃ to obtain a workpiece with a nanoporous anodized layer distributed on its surface. The chromium-free composite electrolyte is composed of the following components: sulfuric acid 150g / L, oxalic acid 35g / L, titanium sol (calculated as TiO2) 100g / L, cerium citrate 2.5g / L, and aluminum sulfate 2.5g / L. After oxidation, the workpiece is removed, thoroughly rinsed with deionized water, and dried to obtain an aluminum alloy workpiece with a nanoporous anodized layer on its surface. The oxide layer thickness is measured to be approximately 9.8 μm, the pore size is approximately 45 nm, and the porosity is approximately 4.8%.

[0037] S3. After cleaning and drying the workpiece obtained above, place it in a magnetron sputtering apparatus and evacuate it to a vacuum level. Argon gas was introduced at a working pressure of 0.5 Pa and a sputtering power of 200 W to sputter clean the workpiece surface for 8 minutes; then the process was switched to a graphite target, and acetylene was introduced at the same pressure and power. The DLC coating was deposited at a depth of 10 sccm for 20 min. After deposition, the gas and power were turned off, and the workpiece was removed after the chamber cooled down. The thickness of the DLC coating was measured using a step meter and was approximately 2.8 μm.

[0038] S4. The workpiece treated above is sealed in deionized water at 90°C for 25 minutes, then removed and dried to obtain the surface-modified aluminum alloy. Comparative Example 1

[0039] This comparison is based on a standard SAA + DLC model. The specific steps are as follows: S1. Using a 6061 aluminum alloy sample (50mm × 30mm × 3mm) as the workpiece, the workpiece was placed in an alkaline degreasing solution and ultrasonically treated at 55℃ for 5 minutes; then placed in a 5 wt% NaOH solution and treated at 60℃ for 5 minutes; finally, treated with a 10 wt% NaOH solution. In the solution, treat for 1 minute at room temperature; thoroughly rinse the surface of the treated workpiece with deionized water, and then blow dry to obtain a clean workpiece to be oxidized.

[0040] S2. Using the above-treated workpiece as the anode and the lead plate as the cathode, place... In an electrolyte (180 g / L), anodizing was performed for 30 min at a voltage of 18 V and a temperature of 20 °C. The anodized workpiece had an oxide layer thickness of approximately 10.2 μm, a pore size of approximately 120 nm, and a porosity of approximately 18%.

[0041] S3. After cleaning and drying the workpiece obtained above, place it in a magnetron sputtering apparatus and evacuate it to a vacuum level. Argon gas was introduced at a working pressure of 0.5 Pa and a sputtering power of 200 W to sputter clean the workpiece surface for 8 minutes; then the process was switched to a graphite target, and acetylene was introduced at the same pressure and power. The DLC coating was deposited at a depth of 10 sccm for 20 min. After deposition, the gas and power were turned off, and the workpiece was removed after the chamber cooled down. The thickness of the DLC coating was measured to be approximately 2.8 μm.

[0042] S4. The workpiece treated above is sealed in deionized water at 90°C for 25 minutes, then removed and dried to obtain the surface-modified aluminum alloy.

[0043] Performance testing: 1. In Examples 1-3 and Comparative Example 1 of the present invention, the cross-section and surface morphology of the anodized samples can be observed using a scanning electron microscope (SEM). The oxide layer thickness is directly measured from the SEM cross-sectional image; the average pore size is calculated from a high-magnification SEM surface image by using ImageJ software to count no fewer than 100 pores; the porosity is obtained by image analysis, by binarizing the SEM surface image and calculating the pore area ratio.

[0044] 2. Surface roughness Sample preparation: The workpieces of Examples 1-3 and Comparative Example 1, after S2 treatment (after anodizing and before DLC sputtering), were ultrasonically cleaned with deionized water and dried with nitrogen to ensure the surface was free of contaminants. The instrument was calibrated using standard roughness blocks (Ra = 0.1 μm, 0.5 μm); at least three different areas were selected on the workpiece surface for measurement, avoiding edges and scratches; the measurement parameters were set as follows: evaluation length 4.0 mm (5 × 0.8 mm), Gaussian filter; the instrument automatically calculated and output the profile arithmetic mean deviation Ra value.

[0045] 3. Microhardness test Test standard: Refer to GB / T 4340.1-2009 "Metallic materials - Vickers hardness test - Part 1: Test method". Test equipment: Automatic microhardness tester (HXD-1000TMC / LCD); Test parameters: Load 50 g (0.4903 N), holding time 15 s.

[0046] Operating Procedures: Clean and dry the surfaces of the test samples from Examples 1-3 and Comparative Example 1, and fix them on the sample stage. Under a microscope, select five different areas for indentation testing. The equipment automatically loads, holds, and unloads the indentation, and measures the diagonal length of the indentation. The instrument automatically calculates and outputs the Vickers hardness value (HV). Take the average of the five measurements as the final result.

[0047] 4. Bonding strength test (scratch test) Test standard: Refer to GB / T 32957-2016 "Scratch Test Method for Bond Strength of Coatings on Solid Materials". Test equipment: Multifunctional scratch tester (WS-2005); Test parameters: Diamond conical indenter (apex angle 120°, tip radius 100 μm), initial load 1 N, final load 100 N, loading rate 10 N / min, scratch length 3 mm, scanning speed 5 mm / min.

[0048] Operating Procedures: Fix the test samples from Examples 1-3 and Comparative Example 1 onto the sample stage, ensuring the surface is level. Adjust the indenter to contact the sample surface and set the test parameters. Start the equipment; the indenter will move along a straight line at a uniform speed across the coating surface under loading conditions. Monitor acoustic emission (AE) signals, friction, displacement, and other parameters in real time. Analyze the acoustic emission signal curve; define the load point where the acoustic emission signal first shows a drastic change as the critical load (Lc) of the coating, i.e., the adhesion force.

[0049] 5. Salt spray resistance test Test Standard: Refer to GB / T 10125-2012 "Artificial Atmosphere Corrosion Test - Salt Spray Test". Test Equipment: Salt spray corrosion test chamber. Test Parameters: The solution is a 5 wt% NaCl aqueous solution, the solution pH is 6.5~7.2 (adjusted with dilute hydrochloric acid or sodium hydroxide), the saturation tower temperature is 35 ± 2 ℃, the chamber temperature is 35 ± 2 ℃, the sedimentation rate is 1.0~2.0 mL / h (80cm² horizontal collection area), the test cycle is 1500h, and the sample placement angle is 15°~30° with respect to the vertical direction.

[0050] Operating Procedures: After rinsing and drying the test samples from Examples 1-3 and Comparative Example 1 with deionized water, place them in a salt spray chamber, set and stabilize the environmental parameters inside the chamber, and spray continuously for 1500 hours. Periodically (e.g., every 24 hours) inspect the sample surface for any corrosion products (such as white or grayish-white spots or rust spots). After the test, if there is no visible corrosion on the sample surface, it is considered "no corrosion after 1500 hours".

[0051] 6. Abrasion resistance test (ball-disc type) Test Standard: Refer to GB / T 39797-2021 "Determination of Wear Properties of Abrasives for Testing Plastics - Ball-Disc Method". Test Equipment: Ball-Disc Reciprocating Friction and Wear Tester. Test Parameters: For grinding balls with a diameter of 6 mm... Ceramic ball (high hardness, chemically inert), load 10 N, sliding speed 100 mm / s, sliding stroke 5 mm, test time: 2 h, environment: room temperature, dry air.

[0052] Operating procedures: Fix the grinding ball to the fixture, fix the test samples of Examples 1-3 and Comparative Example 1 to the lower sample stage, adjust the contact between the grinding ball and the sample surface, and apply a load of 10 N; start the equipment and perform reciprocating sliding friction. After the test, ultrasonically clean the sample with acetone or ethanol to remove wear debris; weigh the sample before and after wear using a high-precision electronic balance (accuracy 0.01 mg) and calculate the mass loss (wear loss).

[0053] The performance test results of Examples 1-3 and Comparative Example 1 are shown in Table 1 below.

[0054] Table 1

[0055] As can be seen from Table 1, the preparation method provided by the present invention can obtain surface-modified aluminum alloys with excellent performance under different process parameters (Examples 1-3). Its comprehensive performance (hardness, bonding strength, wear resistance, and corrosion resistance) is significantly better than that of the traditional process (Comparative Example 1), which verifies the stability of the present invention.

[0056] The foregoing has provided a detailed description of a surface-modified aluminum alloy and its preparation method disclosed in this invention. Specific examples have been used to illustrate the principles and implementation methods of this invention. The descriptions of the above embodiments are merely for the purpose of helping to understand the method and core ideas of this invention. It should be noted that those skilled in the art can make various improvements and modifications to this invention without departing from its principles, and these improvements and modifications also fall within the protection scope of the claims of this invention.

Claims

1. A method for preparing a surface-modified aluminum alloy, characterized in that, Includes the following steps: S1. The aluminum alloy workpiece is subjected to ultrasonic degreasing, alkaline etching, composite pickling, and water washing in sequence. S2. The workpiece treated in S1 is used as the anode and placed in a chromium-free composite electrolyte. Anodizing is carried out for 20 to 40 minutes under the conditions of voltage 12~18V and temperature 15~35℃, while stirring the electrolyte. S3. After cleaning and drying the workpiece treated in S2, place it in the magnetron sputtering equipment, perform sputtering cleaning first, and then switch to carbon target material to deposit DLC coating for 15~30 min to make the coating thickness reach 2~5μm; S4. The workpiece treated in S3 is sealed in deionized water at 80~100℃ for 20~30 minutes, then removed and dried to obtain the surface-modified aluminum alloy.

2. The method for preparing a surface-modified aluminum alloy according to claim 1, characterized in that, In step S1, the alkaline etching process is as follows: First stage: Immerse the workpiece in a 3wt% NaOH solution at 38~42℃ for 2~3 minutes; Second stage: Immerse the workpiece treated in the first stage in a solution of 8wt% NaOH and 3wt% NaOH. The mixture was treated in a composite solution at 58-62℃ for 2-4 minutes.

3. The method for preparing a surface-modified aluminum alloy according to claim 1, characterized in that, In step S1, the composite pickling and activation process is as follows: immersing the workpiece in a solution of 10 wt%... In a mixed solution consisting of 5 wt% HF, it was treated at room temperature for 30 s.

4. The method for preparing a surface-modified aluminum alloy according to claim 1, characterized in that, In step S2, the chromium-free composite electrolyte is composed of the following components: sulfuric acid 130~160 g / L, oxalic acid 20~50 g / L, titanium sol 80~120 g / L, organic cerium salt complexing agent 2~3 g / L, and aluminum sulfate 2~3 g / L.

5. The method for preparing a surface-modified aluminum alloy according to claim 4, characterized in that, The organic cerium salt complexing agent is cerium citrate or cerium tartrate.

6. The method for preparing a surface-modified aluminum alloy according to claim 1, characterized in that, In step S3, the parameters for the magnetron sputtering are: evacuation to... Argon gas is introduced, the working pressure is 0.3~0.6 Pa, the sputtering power is 100~300 W, and the workpiece surface is sputtered cleaned for 5~10 minutes.

7. The method for preparing a surface-modified aluminum alloy according to claim 6, characterized in that, In step S3, during the deposition of the DLC coating, acetylene or methane is introduced as a reaction gas at a flow rate of 5-20 sccm.

8. A surface-modified aluminum alloy prepared by the preparation method according to any one of claims 1-7, characterized in that, It includes an aluminum alloy substrate, and a nanoporous anodic oxide layer and a DLC coating distributed sequentially from the substrate outwards.

9. The surface-modified aluminum alloy according to claim 8, characterized in that, The nanoporous anodic oxide layer has a pore size of less than 50 nm, a porosity of less than 5%, and a surface roughness Ra ≤ 0.15 μm.

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