Method for in-situ growth of different blue ceramic film layers on surface of magnesium-zinc magnesium alloy

Abstract

The invention belongs to the technical field of magnesium-zinc magnesium alloy surface treatment, and particularly relates to a method for in-situ growth of different blue ceramic film layers on the surface of a magnesium-zinc magnesium alloy. Comprising the following steps that the surface of a magnesium-zinc magnesium alloy sample is polished and cleaned, and then the surface of the sample is sequentially subjected to primary alkali washing, primary water washing, primary acid pickling, secondary water washing, secondary acid pickling, tertiary water washing and secondary alkali washing, so that the pretreated magnesium alloy is obtained; the pretreated magnesium alloy is placed in electrolyte for micro-arc oxidation treatment, and a blue ceramic film layer is generated on the surface of the magnesium alloy in situ; the electrolyte is formed by adding potassium fluotitanate and cobaltous sulfate into a silicate and phosphate composite electrolyte system; or the electrolyte is obtained by adding potassium fluotitanate into a phosphate electrolyte system. Different blue ceramic film layers are prepared, the ornamental value of the magnesium-zinc magnesium alloy component can be improved, and the visual effect is improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of surface treatment of magnesium-zinc series magnesium alloys, and particularly relates to a method for in-situ growth of different blue ceramic film layers on the surface of magnesium-zinc series magnesium alloys. Background Art

[0002] Magnesium-zinc series magnesium alloys are an important branch of magnesium-based alloys. Magnesium-zinc series magnesium alloys mainly use magnesium as the matrix, add zinc as the main alloying element in the matrix, and other auxiliary alloying elements can also be added, such as zirconium element. Due to the low specific gravity of magnesium, magnesium-zinc series magnesium alloys have good lightweight characteristics and are suitable for applications in products that require weight reduction, such as aerospace, automotive parts, and electronic device casings. Adding an appropriate amount of zinc element can improve the strength and hardness of the alloy while keeping the alloy with a certain plasticity and toughness.

[0003] Magnesium-zinc series magnesium alloys are one of the indispensable materials in the electronic product manufacturing industry, and are widely used in products such as laptops, mobile phones, tablet computers, and wearable devices. The reasons are as follows: (1) For electronic products pursuing a thin and light design, high specific strength is required for the material. Magnesium-zinc series magnesium alloys have a very high specific strength, so they are ideal materials for manufacturing thin and light electronic products. (2) Electronic devices generate heat during operation. Good heat dissipation performance can effectively prevent overheating, extend the device life, and improve the user experience. Magnesium-zinc series magnesium alloys have excellent heat conduction performance and can quickly dissipate the heat generated inside. (3) In the design of electronic products, good signal shielding function is necessary to prevent external electromagnetic interference and radio frequency interference. Magnesium-zinc series magnesium alloys can provide effective electromagnetic shielding, protect the internal circuit from external signal interference, and at the same time reduce the electromagnetic radiation of the device itself to the outside.

[0004] For electronic products, in addition to the above requirements, color diversification is also very necessary. Colorful designs often give people a modern, vibrant, and personalized feeling, meeting consumers' pursuit of aesthetics. In addition, unique colors can enhance consumers' impressions and make products stand out in the highly competitive market. Therefore, color design in electronic products is not only an aesthetic choice but also a functional and practical requirement, which is of great significance for improving user experience, information expression efficiency, and product market competitiveness. Therefore, it is very necessary to in-situ grow different blue ceramic film layers on the surface of magnesium-zinc series magnesium alloys.

[0005] At present, there are many methods for surface treatment of magnesium alloys, including the micro-arc oxidation process. The micro-arc oxidation process has the following advantages: low production cost, simple process, good film-substrate bonding, and is also applicable to the surface treatment of magnesium alloy specimens of various shapes. Therefore, it has gradually become the main method for magnesium alloy surface treatment. The preparation technology of colored micro-arc oxidation film is an advanced surface treatment method, which can improve the surface properties of metal materials and endow them with excellent wear resistance, corrosion resistance, insulation and decoration. This technology is based on the principle of micro-arc oxidation. By applying a high voltage on the surface of the workpiece, local micro-arc discharge phenomena occur, and the resulting high temperature and high pressure conditions will cause the surface of the workpiece to undergo an oxidation reaction, forming a dense ceramic oxide film that is tightly combined with the substrate.

[0006] However, at present, most of the colored micro-arc oxidation film layers are prepared on the surface of magnesium-aluminum series magnesium alloys, and it is difficult to prepare different blue ceramic film layers on the surface of magnesium-zinc series magnesium alloys because the compositions of the two magnesium alloys are different. For magnesium-aluminum series magnesium alloys, they contain aluminum element, and aluminum is an effective alloying element that can improve the corrosion resistance of magnesium alloys. Adding aluminum to magnesium alloys can, on the one hand, enhance the passivation ability of the alloy matrix α-Mg phase and form a more stable surface oxide film, which can effectively prevent the further occurrence of corrosion reactions. On the other hand, aluminum is also beneficial to the formation of β phases with stronger corrosion resistance. These phases are distributed at grain boundaries and within grains, providing additional corrosion protection. The aluminum oxide formed by aluminum is very dense and stable, providing a good protective barrier for the surface of magnesium-aluminum alloys to prevent the further penetration of corrosive media. In contrast, although the zinc element in magnesium-zinc series magnesium alloys can also form a protective oxide layer, the stability and protection of this oxide layer are usually not as good as that of aluminum oxide. And for magnesium-aluminum series magnesium alloys, they also contain other trace elements. The trace elements act synergistically with aluminum to further optimize the corrosion resistance of the alloy. Therefore, compared with magnesium-aluminum series magnesium alloys, the magnesium-zinc series magnesium alloys have poor corrosion resistance. Therefore, during the micro-arc oxidation process, it is not easy to control parameters such as the applied current, resulting in poor quality of the finally prepared film layer. The quality of the film layer will affect the final displayed color effect, leading to problems such as uneven film layer color or concentrated color distribution. Therefore, how to prepare a high-quality blue film layer with adjustable blue color on the surface of magnesium-zinc series magnesium alloys is the problem to be solved by the present invention. Summary of the Invention

[0007] In order to solve the above technical problems, the present invention provides a method for in-situ growth of different blue ceramic film layers on the surface of magnesium-zinc series magnesium alloys. By improving the electrolyte formula and micro-arc oxidation parameters, different blue ceramic film layers, namely cloisonné blue, sky blue, lupin blue, star blue, lake blue and distant mountain blue, are successfully grown in-situ on the surface of magnesium-zinc series magnesium alloys, solving the problem that it is difficult to prepare different blue ceramic film layers on the surface of magnesium-zinc series magnesium alloys at present.

[0008] The present invention is specifically implemented through the following technical solutions.

[0009] A method for in-situ growth of different blue ceramic film layers on the surface of a magnesium-zinc-based magnesium alloy, comprising the following steps: Grind and clean the surface of the magnesium-zinc-based magnesium alloy sample, and then successively perform one-time alkali washing, one-time water washing, one-time acid washing, two-time water washing, two-time acid washing, three-time water washing, and two-time alkali washing on the sample surface to obtain the pretreated magnesium alloy.

[0010] Place the pretreated magnesium alloy in an electrolyte and perform micro-arc oxidation treatment to in-situ grow different blue ceramic film layers on the surface of the magnesium alloy.

[0011] The electrolyte is to add potassium fluotitanate and cobalt sulfate to a composite electrolyte system of silicate and phosphate. The corresponding micro-arc oxidation treatment is as follows: Use a bipolar pulse power supply, in the positive constant current and negative constant voltage mode, the positive current density is 1.5 A / dm 2 ~2 A / dm 2 , the negative voltage is 20 V, the positive power supply frequency is 1000 Hz, the positive duty cycle is 10%, the negative power supply frequency is 800 Hz, and the negative duty cycle is 35%.

[0012] Or: The electrolyte is to add potassium fluotitanate to a phosphate electrolyte system. The corresponding micro-arc oxidation treatment is as follows: Use a bipolar pulse power supply, in the positive constant current and negative constant voltage mode, the positive current density is 1.5 A / dm 2 ~2 A / dm 2 , the negative voltage is 20 V, the positive power supply frequency is 1000 Hz, the positive duty cycle is 10%, the negative power supply frequency is 800 Hz, and the negative duty cycle is 35%.

[0013] When the electrolyte is to add potassium fluotitanate and cobalt sulfate to a composite electrolyte system of silicate and phosphate, the color of the prepared ceramic film layer is cloisonné blue or sky blue. In order to ensure the preparation of high-quality cloisonné blue or sky blue, the following parameter optimizations are also carried out:

[0014] In a preferred embodiment of the present invention, when the electrolyte is to add potassium fluotitanate and cobalt sulfate to a composite electrolyte system of silicate and phosphate, in this electrolyte, the content of potassium fluotitanate is 10 g / L, the content of cobalt sulfate is 2 g / L, and the pH of the electrolyte is 11.

[0015] In a preferred embodiment of the present invention, the time of micro-arc oxidation treatment is 15 min.

[0016] In a preferred embodiment of the present invention, the silicate and phosphate composite electrolyte system is composed of sodium silicate, sodium phosphate, potassium fluoride, a complexing agent, and water. Among them, the content of sodium silicate is 60 g / L, the content of sodium phosphate is 15 g / L, the content of potassium fluoride is 10 g / L, and the content of the complexing agent is 5 g / L.

[0017] In a preferred embodiment of the present invention, the complexing agent is disodium ethylenediaminetetraacetate.

[0018] When the electrolyte is prepared by adding potassium fluotitanate and cobalt sulfate to the silicate and phosphate composite electrolyte system, in this electrolyte, sodium silicate, sodium phosphate, and potassium fluoride are the main film-forming substances in the ceramic film layer, and cobalt sulfate and potassium fluotitanate are the main substances for realizing the blue ceramic film layer. The role of the complexing agent is to enable cobalt ions and fluotitanate ions to stably exist in the alkaline solution. The addition of cobalt sulfate and potassium fluotitanate to the electrolyte provides cobalt ions and fluotitanate ions. When the two act together, fluotitanate ions can participate in the nucleation and growth process of the oxide film, and by regulating the film layer structure and composition, improve the quality of the oxide film. Cobalt ions can enter the oxide lattice by doping or exist at the defect positions of the film layer, thereby affecting the reflection and absorption characteristics of light to achieve the purpose of coloring.

[0019] When the electrolyte is prepared by adding potassium fluotitanate to the phosphate electrolyte system, the color of the prepared ceramic film layer is lupin blue, star blue, lake blue, or distant mountain blue. In order to ensure the preparation of high-quality lupin blue, star blue, lake blue, or distant mountain blue, the present invention also performs the following parameter optimizations: In a preferred embodiment of the present invention, when the electrolyte is prepared by adding potassium fluotitanate to the phosphate electrolyte system, the content of potassium fluotitanate in this electrolyte is 6 g / L to 10 g / L.

[0020] In a preferred embodiment of the present invention, the time of micro-arc oxidation treatment is 15 min.

[0021] In a preferred embodiment of the present invention, when the electrolyte is prepared by adding potassium fluotitanate to the phosphate electrolyte system, the phosphate electrolyte system is composed of sodium phosphate, potassium fluoride, sodium hydroxide, and water. Among them, the content of sodium phosphate is 10 g / L to 15 g / L, the content of potassium fluoride is 5 g / L to 6 g / L, and the content of sodium hydroxide is 2 g / L.

[0022] When the electrolyte is potassium fluotitanate added to a phosphate electrolyte system, in this electrolyte, sodium phosphate is used as the main salt, potassium fluotitanate is used as the colorant, and potassium fluoride and sodium hydroxide are added. Among them, sodium hydroxide can regulate the pH of the electrolyte to make the alkaline condition reach the required pH value of 11, increasing the conductivity. Potassium fluoride can improve the density and hardness of the film layer. Fluoride ions have a small radius and can effectively penetrate into the micropores and defects of the oxide film and react with the oxide to form a denser fluoride layer. This can not only block the pores of the film layer, reduce the penetration of corrosive media, but also significantly improve the hardness and wear resistance of the film layer. The addition of potassium fluoride can change the phase structure and composition of the oxide film, introduce fluorine elements, and form fluorine-containing composite oxides or fluorides. These new phases often have better corrosion resistance and anti-wear performance. The presence of fluoride ions can reduce the initial voltage of the oxidation reaction, making micro-arc discharge easier to occur, which helps to form a high-quality ceramic film layer with lower energy consumption. Fluoride ions can accelerate the growth rate of the oxide film. By changing the chemical properties and electric field distribution of the electrolyte, the film layer can reach the required thickness and performance in a shorter time. An appropriate amount of potassium fluoride can promote the bonding force between the film layer and the substrate material, reducing the risk of film layer peeling.

[0023] In a preferred embodiment of the present invention, during the micro-arc oxidation treatment process, the electrolyte is in a stirred state and the temperature is 20°C to 25°C.

[0024] The depth of the blue color can be regulated by changing the electrolyte formula. For the same electrolyte, as long as the magnitude of the electrical parameters is adjusted within a reasonable range, the depth of the blue color can be regulated.

[0025] The formation mechanism of cloisonné blue or sky blue of the present invention: During the color micro-arc oxidation process of potassium fluotitanate and cobalt sulfate on the surface of a magnesium-zinc series magnesium alloy, they act synergistically to generate an oxide film layer with a specific color.

[0026] During the micro-arc oxidation process, potassium fluotitanate can chemically react with magnesium in the electrolyte and form a titanium-containing ceramic oxide film at the high temperature generated by the discharge. This oxide film has high hardness, good wear resistance, and certain corrosion resistance. Fluotitanate ions can participate in the nucleation and growth process of the oxide film, and improve the quality of the oxide film by regulating the film layer structure and composition.

[0027] Cobalt sulfate can be adsorbed and incorporated into the film layer when the oxide film is formed. Cobalt ions can change the color of the oxide film because when different metal ions are contained in the film layer, different colors will be presented due to the selective absorption or interference effect of light. Cobalt ions affect the reflection and absorption characteristics of light by doping into the oxide lattice or existing at the defect positions of the film layer.

[0028] Generally speaking, when potassium fluotitanate and cobalt sulfate act together in the micro-arc oxidation system of magnesium alloy, the former optimizes the basic properties of the oxide film, and the latter endows the film layer with unique colors. The whole process involves complex physical and chemical reactions, including high-temperature oxidation caused by micro-arc discharge, ion doping and diffusion, film layer growth and structural evolution, etc. It should be further noted that different from the electrolyte with cobalt ions added alone, the cobalt ions in the present invention do not act alone. The electrolyte is a composite electrolyte system of silicate and phosphate in which cobalt ions and potassium fluotitanate act synergistically as two colorants, and it is an alkaline solution. When potassium fluotitanate and cobalt sulfate coexist in the electrolyte, they produce a synergistic effect, which not only promotes the formation of a composite ceramic layer containing various oxides and fluorides, but also improves the corrosion resistance and anti-wear performance of the coating through the doping of cobalt elements. The introduction of cobalt can change the defect structure inside the coating and reduce the formation of cracks. At the same time, the presence of fluorides helps to seal these defects, making the coating more complete and improving its comprehensive performance. When potassium fluotitanate and cobalt sulfate act simultaneously, their complex modification of the coating structure and composition will produce new compounds or phase changes, thereby affecting the optical properties of the coating. Different proportions of oxides and fluorides, as well as the doping amount of cobalt, can change the characteristics of the coating reflecting and absorbing light, thus regulating the depth of color.

[0029] The formation mechanism of lupine blue, star blue, lake blue or distant mountain blue in the present invention: During micro-arc oxidation discharge, the high-temperature plasma generated under high voltage rapidly oxidizes magnesium and zinc elements, and chemically reacts with the titanate anions of titanate in the electrolyte.

[0030] During the micro-arc oxidation process, potassium fluotitanate decomposes and participates in the oxidation reaction, forming titanium-containing oxides on the surface of the magnesium alloy substrate. These oxides such as TiO 2 , MgTiO 3 or ZnTiO 3 and other mixed oxides constitute the basic structure of the film layer. During the micro-arc oxidation process, titanium ions enter the lattice of the generated oxide film as dopants, changing the energy band structure of the oxide film and affecting its optical properties. When light with a specific wavelength irradiates the oxide film containing doped titanium ions, due to electron transition and energy level filling, the oxide film will selectively absorb certain wavelengths of light, and the unabsorbed blue light is reflected, thus achieving the coloring effect.

[0031] Therefore, potassium fluotitanate indirectly participates in the regulation of the film layer color by changing the physical and chemical properties and microstructure of the micro-arc oxidation film layer.

[0032] The present invention has the following beneficial effects compared with the prior art: In the present invention, different degrees of blue ceramic film layers are in-situ grown on the matrix of a magnesium-zinc-based magnesium alloy by regulating the electrolyte formula and controlling the micro-arc oxidation parameters, overcoming the problems of poor corrosion resistance, poor film-forming property, and difficulty in preparing blue film layers in magnesium-zinc-based magnesium alloys.

[0033] The micro-arc oxidation electrolyte used in the present invention has simple composition, stable solution and can be reused, the reaction process is safe and stable, there is no limitation on the shape and size of the magnesium alloy specimen, and the production cost is greatly saved. During the preparation process, the electrolyte is stable and uniform, and the prepared ceramic film layer has uniform blue color, smooth and dense. In addition, by strictly controlling the parameters in the micro-arc oxidation process, the quality of the micro-arc oxidation film layer is improved, so that the finally prepared film layer shows different degrees of blue color and the color is uniform.

[0034] In summary, the film layer prepared by the present invention has a blue color, uniform color, smooth and dense, which is beneficial to expanding the application fields of magnesium-zinc-based magnesium alloys. Brief Description of the Drawings

[0035] Figure 1 Pictures of different blue ceramic film layers prepared in Examples 1 to 6, where (a) is the cloisonné blue prepared in Example 1, (b) is the sky blue prepared in Example 2, (c) is the lupin blue prepared in Example 3, (d) is the star blue prepared in Example 4, (e) is the lake blue prepared in Example 5, and (f) is the distant mountain blue prepared in Example 6.

[0036] Figure 2 Pictures of ceramic film layers prepared in each comparative example group, where (g) is Comparative Example 1, (h) is Comparative Example 2, (i) is Comparative Example 3, and (j) is Comparative Example 4. Detailed Embodiments

[0037] In order to enable those skilled in the art to better understand and implement the technical solutions of the present invention, the present invention will be further described below in conjunction with specific embodiments and drawings, but the specific embodiments cited are not intended to limit the present invention. In the following embodiments, the experimental methods and detection methods are all conventional methods unless otherwise specified; the reagents and materials are all commercially available unless otherwise specified.

[0038] The present invention provides a blue film-forming electrolyte formula for magnesium-zinc-based magnesium alloys. Based on the electrolyte formula, the micro-arc oxidation electrical parameters are adjusted and optimized to achieve precise control of the film layer color, and a stable and brightly colored blue film layer is obtained. In the magnesium-zinc-based magnesium alloy of the present invention, the content of zinc element is 4wt.% to 7wt.%, the content of rare earth element RE is 0.5wt.% to 2wt.%, the content of Zr is 0.4wt.% to 0.9wt.%, and the balance is Mg, totaling 100%.

[0039] Specifically, the method for preparing the cloisonné or sky-blue ceramic film layer provided by the present invention includes the following steps: Step 1: Use water sandpaper to remove the oxides and impurities on the surface of the above-mentioned magnesium-zinc series magnesium alloy sample by polishing, and then ultrasonically clean the polished sample with deionized water and anhydrous ethanol respectively.

[0040] Step 2: The ultrasonically cleaned magnesium alloy sample is successively subjected to one alkali wash, one water wash, one acid wash, two water washes, two acid washes, three water washes and two alkali washes. The first alkali wash is to remove the grease on the sample surface, the first water wash is to remove the alkali wash solution on the sample surface, the first acid wash is to remove the oxides and corrosion products on the sample surface, and the second water wash is to remove the acid solution of the first acid wash on the sample surface. The second acid wash is because although the magnesium oxides and magnesium corrosion products on the sample surface will be removed during the first acid wash, a light yellow product will be generated on the sample surface. Therefore, it is removed by the second acid wash. The third water wash is to remove the acid solution of the second acid wash on the sample surface. The second alkali wash is to neutralize acidic substances and prevent re-oxidation corrosion.

[0041] Step 3: Put the pretreated magnesium alloy sample into the micro-arc oxidation electrolyte. The electrolyte is prepared by adding potassium fluotitanate and cobalt sulfate to a composite electrolyte system of silicate and phosphate. The composite electrolyte system of silicate and phosphate consists of sodium silicate, sodium phosphate, potassium fluoride, complexing agent and water. In this electrolyte, the content of sodium silicate is 60 g / L, the content of sodium phosphate is 15 g / L, the content of complexing agent is 5 g / L, the content of potassium fluotitanate is 10 g / L, the content of cobalt sulfate is 2 g / L, the content of potassium fluoride is 10 g / L, and the pH value is 11.

[0042] Step 4: Use a bipolar pulse power supply to adjust the electrical parameters for micro-arc oxidation treatment, and in-situ generate a cloisonné or sky-blue ceramic film layer on the surface of the magnesium alloy sample.

[0043] During the micro-arc oxidation treatment, a bipolar pulse power supply is used in the positive constant current and negative constant voltage mode. The positive current density is 1.5 A / dm 2 ~2 A / dm 2 , the negative voltage is 20 V, the positive power supply frequency is 1000 Hz, the positive duty cycle is 10%, the negative power supply frequency is 800 Hz, the negative duty cycle is 35%, and the micro-arc oxidation treatment time is 15 min.

[0044] The electrolyte is in a stirred state, and the reaction temperature is 20 °C to 25 °C.

[0045] Step 5: Ultrasonically clean the sample after micro-arc oxidation treatment with deionized water and anhydrous ethanol successively and blow it dry with a hair dryer.

[0046] Specifically, the preparation method of lupin blue, star blue, lake blue or distant mountain blue ceramic film layer provided by the present invention includes the following steps: Step 1: Use water sandpaper to polish and remove the oxides and impurities on the surface of the magnesium-zinc series magnesium alloy sample, and then ultrasonically clean the polished sample with deionized water and anhydrous ethanol respectively.

[0047] Step 2: The ultrasonically cleaned magnesium alloy sample is successively subjected to one alkali wash, one water wash, one acid wash, two water washes, two acid washes, three water washes and two alkali washes. The first alkali wash is to remove the grease on the surface of the sample, the first water wash is to remove the alkali wash solution on the surface of the sample, the first acid wash is to remove the oxides and corrosion products on the surface of the sample, and the second water wash is to remove the acid solution of the first acid wash on the surface of the sample. The second acid wash is because although the magnesium oxide and magnesium corrosion products on the surface of the sample will be removed during the first acid wash, a light yellow product will be generated on the surface of the sample, so it is removed by the second acid wash. The third water wash is to remove the acid solution of the second acid wash on the surface of the sample. The second alkali wash is to neutralize acidic substances and prevent re-oxidation corrosion.

[0048] Step 3: Put the pretreated magnesium alloy sample into the micro-arc oxidation electrolyte. This electrolyte is obtained by adding potassium fluotitanate to the phosphate electrolyte system. The phosphate electrolyte system is composed of sodium phosphate, potassium fluoride, sodium hydroxide and water. In this electrolyte, the content of potassium fluotitanate is 6 g / L to 10 g / L, the content of sodium phosphate is 10 g / L to 15 g / L, the content of potassium fluoride is 5 g / L to 6 g / L, and the content of sodium hydroxide is 2 g / L.

[0049] Step 4: Use a bipolar pulse power supply to adjust the electrical parameters for micro-arc oxidation treatment, and in-situ generate a lupin blue, star blue, lake blue or distant mountain blue ceramic film layer on the surface of the magnesium alloy sample.

[0050] During the micro-arc oxidation treatment, a bipolar pulse power supply is used, in the positive constant current and negative constant voltage mode, the positive current density is 1.5 A / dm 2 ~2 A / dm 2 , the negative voltage is 20 V, the positive power supply frequency is 1000 Hz, the positive duty cycle is 10%, the negative power supply frequency is 800 Hz, the negative duty cycle is 35%, and the micro-arc oxidation treatment time is 15 min.

[0051] During the micro-arc oxidation treatment, the electrolyte is in a stirred state, and the temperature is 20 °C to 25 °C.

[0052] Step 5: Ultrasonically clean the sample after micro-arc oxidation treatment with deionized water and anhydrous ethanol in sequence and dry it with a hair dryer.

[0053] The content of the present invention will be specifically described below through the following examples and comparative examples. In the following examples and comparative examples, during the alkali washing, the reagent used is a mixed aqueous solution of potassium hydroxide and sodium gluconate, wherein the content of potassium hydroxide is 50 g / L and the content of sodium gluconate is 10 g / L, and the alkali washing temperature is 65 °C. The solutions for the first alkali washing and the second alkali washing are the same. During the first acid washing, the reagent used is a mixed solution of concentrated nitric acid and phosphoric acid, wherein the content of concentrated nitric acid is 100 mL / L and the content of phosphoric acid is 100 mL / L, and the first acid washing temperature is 65 °C. During the second acid washing, the reagent used is a mixed solution of concentrated nitric acid and citric acid, wherein the content of concentrated nitric acid is 100 mL / L and the content of citric acid is 20 g / L, and the second acid washing temperature is 65 °C.

[0054] Example 1 A method for in-situ growth of cloisonné ceramic film on the surface of a magnesium-zinc series magnesium alloy, comprising the following steps: Step 1: Use water sandpaper to remove oxides and impurities on the surface of the magnesium alloy sample by polishing, and then ultrasonically clean the polished sample with deionized water and absolute ethanol respectively.

[0055] Step 2: The ultrasonically cleaned magnesium alloy sample is successively subjected to the first alkali washing, the first water washing, the first acid washing, the second water washing, the second acid washing, the third water washing and the second alkali washing.

[0056] Step 3: Put the pretreated magnesium alloy sample into a micro-arc oxidation electrolyte, which is composed of sodium silicate, sodium phosphate, potassium fluoride, potassium fluotitanate, cobalt sulfate, disodium ethylenediaminetetraacetate and water. Among them, the content of sodium silicate is 60 g / L, the content of sodium phosphate is 15 g / L, the content of potassium fluoride is 10 g / L, the content of potassium fluotitanate is 10 g / L, the content of cobalt sulfate is 2 g / L, the content of disodium ethylenediaminetetraacetate is 5 g / L, and the pH value of the electrolyte is 11.

[0057] Step 4: Use a bipolar pulse power supply, in the positive constant current and negative constant voltage mode, adjust the process parameters for micro-arc oxidation treatment to in-situ generate a blue ceramic film of cloisonné on the surface of the magnesium alloy sample; specifically, the positive current density is 2 A / dm 2 , the positive power supply frequency is 1000 Hz, the positive duty cycle is 10%, the negative voltage is 20 V, the negative power supply frequency is 800 Hz, the negative duty cycle is 35%, and the working time is 15 min. The electrolyte is in a stirred state, and the reaction temperature is 20 °C to 25 °C.

[0058] Step 5: Ultrasonically clean the sample after micro-arc oxidation treatment with deionized water and absolute ethanol in sequence, and dry it with a hair dryer.

[0059] Comparative Example 1 Potassium fluotitanate is not added to the electrolyte: Step 1: Use water sandpaper to remove oxides and impurities on the surface of the magnesium alloy sample by polishing, and then ultrasonically clean the polished sample with deionized water and anhydrous ethanol respectively.

[0060] Step 2: Perform alkali washing once, water washing once, acid washing once, water washing twice, acid washing twice, water washing three times and alkali washing twice on the ultrasonically cleaned magnesium alloy sample in sequence.

[0061] Step 3: Put the pretreated magnesium alloy sample into a micro-arc oxidation electrolyte, which is composed of sodium silicate, sodium phosphate, potassium fluoride, cobalt sulfate, disodium ethylenediaminetetraacetate and water. Among them, the content of sodium silicate is 60 g / L, the content of sodium phosphate is 15 g / L, the content of potassium fluoride is 10 g / L, the content of cobalt sulfate is 2 g / L, the content of disodium ethylenediaminetetraacetate is 5 g / L, and the pH value of the electrolyte is 11.

[0062] Step 4: Adopt a bipolar pulse power supply, in the positive constant current and negative constant voltage mode, adjust the process parameters to carry out micro-arc oxidation treatment to in-situ generate a ceramic film layer on the surface of the magnesium alloy sample; specifically, the positive current density is 2 A / dm 2 , the positive power supply frequency is 1000 Hz, the positive duty cycle is 10%, the negative voltage is 20 V, the negative power supply frequency is 800 Hz, the negative duty cycle is 35%, and the working time is 15 min. The electrolyte is in a stirring state, and the reaction temperature is 20 °C - 25 °C.

[0063] Step 5: Ultrasonically clean the sample after micro-arc oxidation treatment with deionized water and anhydrous ethanol in sequence, and then dry it with a hair dryer.

[0064] Comparative Example 2 Cobalt sulfate is not added to the electrolyte: Step 1: Use water sandpaper to remove oxides and impurities on the surface of the magnesium alloy sample by polishing, and then ultrasonically clean the polished sample with deionized water and anhydrous ethanol respectively.

[0065] Step 2: Perform alkali washing once, water washing once, acid washing once, water washing twice, acid washing twice, water washing three times and alkali washing twice on the ultrasonically cleaned magnesium alloy sample in sequence.

[0066] Step 3: Put the pretreated magnesium alloy sample into a micro-arc oxidation electrolyte, which is composed of sodium silicate, sodium phosphate, potassium fluoride, potassium fluotitanate, disodium ethylenediaminetetraacetate and water. Among them, the content of sodium silicate is 60 g / L, the content of sodium phosphate is 15 g / L, the content of potassium fluoride is 10 g / L, the content of potassium fluotitanate is 10 g / L, the content of disodium ethylenediaminetetraacetate is 5 g / L, and the pH value of the electrolyte is 11.

[0067] Step 4: Use a bipolar pulse power supply in the positive constant current and negative constant voltage mode, adjust the process parameters for micro-arc oxidation treatment, and in-situ generate a ceramic film layer on the surface of the magnesium alloy sample; specifically: the positive current density is 2 A / dm 2 , the positive power supply frequency is 1000 Hz, the positive duty cycle is 10%, the negative voltage is 20 V, the negative power supply frequency is 800 Hz, the negative duty cycle is 35%, and the working time is 15 min. The electrolyte is in a stirred state, and the reaction temperature is 20 °C to 25 °C.

[0068] Step 5: Ultrasonically clean the sample after micro-arc oxidation treatment with deionized water and anhydrous ethanol in sequence, and then dry it with a hair dryer.

[0069] Comparative Example 3 Change the content: Step 1: Use water sandpaper to remove the oxides and impurities on the surface of the magnesium alloy sample by polishing, and then ultrasonically clean the polished sample with deionized water and anhydrous ethanol respectively.

[0070] Step 2: Perform one alkali wash, one water wash, one acid wash, two water washes, two acid washes, three water washes and two alkali washes on the ultrasonically cleaned magnesium alloy sample in sequence.

[0071] Step 3: Put the pretreated magnesium alloy sample into the micro-arc oxidation electrolyte, which is composed of sodium silicate, sodium phosphate, potassium fluoride, potassium fluotitanate, cobalt sulfate, disodium ethylenediaminetetraacetate and water. Among them, the content of sodium silicate is 40 g / L, the content of sodium phosphate is 20 g / L, the content of potassium fluoride is 10 g / L, the content of cobalt sulfate is 3 g / L, the content of potassium fluotitanate is 20 g / L, the content of disodium ethylenediaminetetraacetate is 5 g / L, and the pH value of the electrolyte is 11.

[0072] Step 4: Use a bipolar pulse power supply in the positive constant current and negative constant voltage mode, adjust the process parameters for micro-arc oxidation treatment, and in-situ generate a ceramic film layer on the surface of the magnesium alloy sample; specifically, the positive current density is 2 A / dm 2 , the positive power supply frequency is 1000 Hz, the positive duty cycle is 10%, the negative voltage is 20 V, the negative power supply frequency is 800 Hz, the negative duty cycle is 35%, and the working time is 15 min. The electrolyte is in a stirred state, and the reaction temperature is 20 °C to 25 °C.

[0073] Step 5: Ultrasonically clean the sample after micro-arc oxidation treatment with deionized water and anhydrous ethanol in sequence, and then dry it with a hair dryer.

[0074] Example 2 A method for in-situ growth of a cyan blue ceramic film layer on the surface of a magnesium-zinc series magnesium alloy, comprising the following steps: Step 1: Use water sandpaper to remove oxides and impurities on the surface of the magnesium alloy sample by polishing, and then ultrasonically clean the polished sample with deionized water and anhydrous ethanol respectively.

[0075] Step 2: Perform one alkali cleaning, one water washing, one acid pickling, two water washings, two acid picklings, three water washings and two alkali washings on the ultrasonically cleaned magnesium alloy sample in sequence.

[0076] Step 3: Put the pretreated magnesium alloy sample into a micro-arc oxidation electrolyte, which is composed of sodium silicate, sodium phosphate, potassium fluoride, potassium fluotitanate, cobalt sulfate, disodium ethylenediaminetetraacetate and water. Among them, the content of sodium silicate is 60 g / L, the content of sodium phosphate is 15 g / L, the content of potassium fluoride is 10 g / L, the content of potassium fluotitanate is 10 g / L, the content of cobalt sulfate is 2 g / L, the content of disodium ethylenediaminetetraacetate is 5 g / L, and the pH value of the electrolyte is 11.

[0077] Step 4: Adopt a bipolar pulse power supply, in the positive constant current and negative constant voltage mode, adjust the process parameters to carry out micro-arc oxidation treatment, and in-situ generate a cyan blue ceramic film layer on the surface of the magnesium alloy sample; specifically, the positive current density is 1.5 A / dm 2 , the positive power frequency is 1000 Hz, the positive duty cycle is 10%, the negative voltage is 20 V, the negative power frequency is 800 Hz, the negative duty cycle is 35%, the working time is 15 min, the electrolyte is in a stirring state, and the reaction temperature is 20 °C - 25 °C.

[0078] Step 5: Ultrasonically clean the sample after micro-arc oxidation treatment with deionized water and anhydrous ethanol in sequence, and then dry it with a hair dryer.

[0079] Example 3 A method for in-situ growth of lupetidin blue ceramic film layer on the surface of a magnesium-zinc series magnesium alloy, comprising the following steps: Step 1: Use water sandpaper to remove oxides and impurities on the surface of the magnesium alloy sample by polishing, and then ultrasonically clean the polished sample with deionized water and anhydrous ethanol respectively.

[0080] Step 2: Perform one alkali cleaning, one water washing, one acid pickling, two water washings, two acid picklings, three water washings and two alkali washings on the ultrasonically cleaned magnesium alloy sample in sequence.

[0081] Step 3: Put the pretreated magnesium alloy sample into a micro-arc oxidation electrolyte, which is composed of sodium phosphate, sodium hydroxide, potassium fluoride, potassium fluotitanate and water. Among them, the content of sodium phosphate is 10 g / L, the content of potassium fluotitanate is 6 g / L, the content of sodium hydroxide is 2 g / L, and the content of potassium fluoride is 5 g / L.

[0082] Step 4: Adopt a bipolar pulse power supply in the positive constant current and negative constant voltage mode, adjust the process parameters for micro-arc oxidation treatment, and in-situ generate a lupetidin blue ceramic film layer on the surface of the magnesium alloy sample; specifically, the positive current density is 2 A / dm 2 , the positive power supply frequency is 1000 Hz, the positive duty cycle is 10%, the negative voltage is 20 V, the negative power supply frequency is 800 Hz, the negative duty cycle is 35%, the working time is 15 min, the electrolyte is in a stirred state, and the reaction temperature is 20 °C to 25 °C.

[0083] Step 5: Ultrasonically clean the sample after micro-arc oxidation treatment successively with deionized water and absolute ethanol, and then dry it with a hair dryer.

[0084] Comparative Example 4 Potassium fluotitanate is not added to the electrolyte: Step 1: Use water sandpaper to polish and remove the oxides and impurities on the surface of the magnesium alloy sample, and then ultrasonically clean the polished sample successively with deionized water and absolute ethanol.

[0085] Step 2: Perform one alkali cleaning, one water washing, one acid cleaning, two water washings, two acid washings, three water washings, and two alkali washings on the magnesium alloy sample after ultrasonic cleaning in sequence.

[0086] Step 3: Put the pretreated magnesium alloy sample into the micro-arc oxidation electrolyte, which is composed of sodium phosphate, sodium hydroxide, potassium fluoride, and water. Among them, the content of sodium phosphate is 10 g / L, the content of sodium hydroxide is 2 g / L, and the content of potassium fluoride is 5 g / L.

[0087] Step 4: Adopt a bipolar pulse power supply in the positive constant current and negative constant voltage mode, adjust the process parameters for micro-arc oxidation treatment, and in-situ generate a ceramic film layer on the surface of the magnesium alloy sample. Specifically: the positive current density is 2 A / dm 2 , the positive power supply frequency is 1000 Hz, the positive duty cycle is 10%, the negative voltage is 20 V, the negative power supply frequency is 800 Hz, the negative duty cycle is 35%, the working time is 15 min, the electrolyte is in a stirred state, and the reaction temperature is 20 °C to 25 °C.

[0088] Step 5: Ultrasonically clean the sample after micro-arc oxidation treatment successively with deionized water and absolute ethanol, and then dry it with a hair dryer.

[0089] Example 4 A method for in-situ growth of a star blue ceramic film layer on the surface of a magnesium-zinc series magnesium alloy, comprising the following steps: Step 1: Use water sandpaper to polish and remove the oxides and impurities on the surface of the magnesium alloy sample, and then ultrasonically clean the polished sample successively with deionized water and absolute ethanol.

[0090] Step 2: The magnesium alloy sample after ultrasonic cleaning is successively subjected to one alkali cleaning, one water washing, one acid pickling, two water washings, two acid picklings, three water washings and two alkali washings.

[0091] Step 3: The pretreated magnesium alloy sample is put into a micro-arc oxidation electrolyte, which is composed of sodium phosphate, sodium hydroxide, potassium fluoride, potassium fluotitanate and water. Among them, the content of sodium phosphate is 15 g / L, the content of potassium fluotitanate is 10 g / L, the content of sodium hydroxide is 2 g / L, and the content of potassium fluoride is 6 g / L.

[0092] Step 4: A bipolar pulse power supply is adopted, with a positive constant current and negative constant voltage mode. The process parameters are adjusted for micro-arc oxidation treatment to in-situ generate a star blue ceramic film layer on the surface of the magnesium alloy sample. Specifically, the positive current density is 2 A / dm 2 , the positive power supply frequency is 1000 Hz, the positive duty cycle is 10%, the negative voltage is 20 V, the negative power supply frequency is 800 Hz, the negative duty cycle is 35%, the working time is 15 min, the electrolyte is in a stirred state, and the reaction temperature is 20 °C to 25 °C.

[0093] Step 5: The sample after micro-arc oxidation treatment is successively ultrasonically cleaned with deionized water and absolute ethanol, and then dried with a hair dryer.

[0094] Example 5 A method for in-situ growing a lake blue ceramic film layer on the surface of a magnesium-zinc series magnesium alloy, comprising the following steps: Step 1: The oxides and impurities on the surface of the magnesium alloy sample are removed by polishing with water sandpaper, and then the polished sample is ultrasonically cleaned with deionized water and absolute ethanol respectively.

[0095] Step 2: The magnesium alloy sample after ultrasonic cleaning is successively subjected to one alkali cleaning, one water washing, one acid pickling, two water washings, two acid picklings, three water washings and two alkali washings.

[0096] Step 3: The pretreated magnesium alloy sample is put into a micro-arc oxidation electrolyte, which is composed of sodium phosphate, sodium hydroxide, potassium fluoride, potassium fluotitanate and water. Among them, the content of sodium phosphate is 15 g / L, the content of potassium fluotitanate is 10 g / L, the content of sodium hydroxide is 2 g / L, and the content of potassium fluoride is 6 g / L.

[0097] Step 4: A bipolar pulse power supply is adopted, with a positive constant current and negative constant voltage mode. The process parameters are adjusted for micro-arc oxidation treatment to in-situ generate a lake blue ceramic film layer on the surface of the magnesium alloy sample. Specifically, the positive current density is 1.5 A / dm 2, the positive power supply frequency is 1000 Hz, the positive duty cycle is 10%, the negative voltage is 20 V, the negative power supply frequency is 800 Hz, the negative duty cycle is 35%, the working time is 15 min, the electrolyte is in a stirred state, and the reaction temperature is 20 °C to 25 °C.

[0098] Step Five: Ultrasonically clean the samples after micro-arc oxidation treatment successively with deionized water and absolute ethanol, and then dry them with a hair dryer.

[0099] Example 6 A method for in-situ growth of a distant mountain blue ceramic film layer on the surface of a magnesium-zinc series magnesium alloy, comprising the following steps: Step One: Use water sandpaper to remove the oxides and impurities on the surface of the magnesium alloy sample by polishing, and then ultrasonically clean the polished sample successively with deionized water and absolute ethanol.

[0100] Step Two: Perform one alkali wash, one water wash, one acid wash, two water washes, two acid washes, three water washes and two alkali washes on the magnesium alloy sample after ultrasonic cleaning in sequence.

[0101] Step Three: Put the pretreated magnesium alloy sample into the micro-arc oxidation electrolyte used in Example 5.

[0102] Step Four: Adopt a bipolar pulse power supply, a positive constant current and negative constant voltage mode, and adjust the process parameters to carry out micro-arc oxidation treatment to in-situ generate a distant mountain blue ceramic film layer on the surface of the magnesium alloy sample. Specifically, the positive current density is 1.5 A / dm 2 , the positive power supply frequency is 1000 Hz, the positive duty cycle is 10%, the negative voltage is 20 V, the negative power supply frequency is 800 Hz, the negative duty cycle is 35%, the working time is 15 min, the electrolyte is in a stirred state, and the reaction temperature is 20 °C to 25 °C.

[0103] Step Five: Ultrasonically clean the samples after micro-arc oxidation treatment successively with deionized water and absolute ethanol, and then dry them with a hair dryer.

[0104] The chromaticity of the film layer is evaluated according to the CIELAB chromaticity evaluation standard, and the average values of the parameters of Examples 1 to 6 measured by a color difference meter are shown in Table 1: Table 1 Average values of the parameters of Examples 1 to 6 measured by a color difference meter The smaller the value, the bluer the color of the film layer.

[0105] The sample morphology prepared in Example 1 is shown in Figure 1 in (a). The sample morphology prepared in Example 2 is shown in Figure 1In (b). Compared with Example 1, Example 2 only changes the current density, that is, the color is changed to sunny blue. It can be seen that the color can be regulated by controlling the current density. The morphology of the sample prepared in Example 3 is shown in Figure 1 In (c). The morphology of the sample prepared in Example 4 is shown in Figure 1 In (d). The morphology of the sample prepared in Example 5 is shown in Figure 1 In (e). Compared with Example 4, Example 5 only changes the current density, and the color can be changed. It can be seen that the color can be regulated by changing the current density. The morphology of the sample prepared in Example 6 is shown in Figure 1 In (f). The electrolyte used in Example 6 is the secondary utilization of the electrolyte in Example 5, and the electrical parameters are the same. The colors are different because the coloring ions are consumed. It can be seen that the color can also be regulated by recycling the electrolyte.

[0106] In Comparative Example 1, potassium fluotitanate is not added to the electrolyte. The morphology of the sample prepared in Comparative Example 1 is as shown in Figure 2 In (g). It can be seen that the film layer is rough and the film-forming quality is poor. In Comparative Example 2, cobalt sulfate is not added to the electrolyte. The morphology of the sample prepared in Comparative Example 2 is shown in Figure 2 In (h). It can be seen that there is no blue color in the film layer. When potassium fluotitanate and cobalt sulfate act synergistically, cobalt sulfate plays a leading role in the color. The morphology of the sample prepared in Comparative Example 3 is shown in Figure 2 In (i). The blue color of the film layer is uneven and concentrated small blue dots are formed. It can be seen that when the dosage of raw materials in the electrolyte exceeds a certain range, the quality of the prepared film layer is not good. In Comparative Example 4, potassium fluotitanate is not added to the electrolyte. The morphology of the sample prepared in Comparative Example 4 is shown in Figure 2 In (j). There is no blue color in the film layer.

[0107] Obviously, those skilled in the art can make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalent technologies, these changes and variations are also intended to be included.

Claims

1. A method for in-situ growth of different blue ceramic film layers on the surface of a magnesium-zinc alloy, characterized in that: The following steps are involved: The surface of the magnesium-zinc magnesium alloy sample is polished and cleaned, and then the surface of the sample is sequentially subjected to one alkali wash, one water wash, one acid wash, two water washes, two acid washes, three water washes and two alkali washes to obtain a pretreated magnesium alloy; The pretreated magnesium alloy is placed in an electrolyte for micro-arc oxidation treatment to in-situ grow different blue ceramic film layers on the surface of the magnesium alloy; The electrolyte is a composite electrolyte system of silicate and phosphate with potassium fluorotitanate and cobalt sulfate added; or: The electrolyte is a phosphate electrolyte system with potassium fluorotitanate added; The micro-arc oxidation treatment is: using a bipolar pulse power supply, positive constant current and negative constant voltage mode, and the forward current density is 1.5A / dm 2 ~2A / dm 2 , the negative voltage is 20V, the positive power supply frequency is 1000Hz, the positive duty cycle is 10%, the negative power supply frequency is 800Hz, and the negative duty cycle is 35%.

2. The method for in-situ growth of different blue ceramic film layers on the surface of a Mg-Zn alloy according to claim 1, characterized in that: When the electrolyte is a silicate and phosphate composite electrolyte system in which potassium fluorotitanate and cobalt sulfate are added, the content of potassium fluorotitanate in the electrolyte is 10 g / L, the content of cobalt sulfate is 2 g / L, and the pH of the electrolyte is 11.

3. The method for in-situ growth of different blue ceramic film layers on the surface of a Mg-Zn alloy according to claim 1, characterized in that: The silicate and phosphate composite electrolyte system consists of sodium silicate, sodium phosphate, potassium fluoride, a complexing agent and water, wherein the content of sodium silicate is 60 g / L, the content of sodium phosphate is 15 g / L, the content of potassium fluoride is 10 g / L, and the content of the complexing agent is 5 g / L.

4. The method for in-situ growth of different blue ceramic film layers on the surface of a Mg-Zn alloy according to claim 3, characterized in that: The complexing agent is disodium ethylenediaminetetraacetate.

5. The method for in-situ growth of different blue ceramic film layers on the surface of Mg-Zn alloy according to claim 1, characterized in that: When the electrolyte is a phosphate electrolyte system in which potassium fluorotitanate is added, the content of potassium fluorotitanate in the electrolyte is 6 g / L to 10 g / L.

6. The method for in-situ growth of different blue ceramic film layers on the surface of Mg-Zn alloy according to claim 1, characterized in that: The phosphate electrolyte system consists of sodium phosphate, potassium fluoride, sodium hydroxide and water, wherein the content of sodium phosphate is 10g / L-15g / L, the content of potassium fluoride is 5g / L-6g / L, and the content of sodium hydroxide is 2g / L.

7. The method for in-situ growth of different blue ceramic film layers on the surface of Mg-Zn alloy according to claim 1, characterized in that: The micro-arc oxidation treatment time is 15 min.

8. The method for in-situ growth of different blue ceramic film layers on the surface of Mg-Zn alloy according to claim 1, characterized in that: During the micro-arc oxidation process, the electrolyte is in a stirring state and the temperature is 20°C to 25°C.

9. The method for in-situ growth of different blue ceramic film layers on the surface of Mg-Zn alloy according to claim 1, characterized in that: When the electrolyte is a composite electrolyte system of silicate and phosphate with potassium fluorotitanate and cobalt sulfate added, the color of the ceramic film layer is cloisonné or clear blue; When the electrolyte is a phosphate electrolyte system in which potassium fluorotitanate is added, the color of the ceramic film layer is lupine blue, star blue, lake blue or distant mountain blue.

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