A magnesium alloy material and a method for manufacturing the same, and a driving system

Abstract

The embodiment of the present application provides a magnesium alloy material, a preparation method thereof and a driving system. The preparation method of the magnesium alloy material comprises the following steps: obtaining a chemical conversion treatment solution comprising sodium vanadate 10-20 g / L, sodium fluoride 10-20 g / L and ammonium fluoroborate 15-20 g / L; and placing a magnesium alloy base into the chemical conversion treatment solution to form a passivation film on the surface of the magnesium alloy base, thereby obtaining a first magnesium alloy material. The embodiment of the present application forms a composite passivation film containing magnesium hydroxide, magnesium oxide, vanadium oxide, magnesium vanadate and magnesium fluoride on the surface of the magnesium alloy base, the composite passivation film uniformly and tightly wraps the surface of the magnesium alloy base, has a compact and stable structure, and the surface is similar to a non-porous or microporous structure, thereby effectively improving the corrosion resistance of the magnesium alloy material and prolonging the service life of the magnesium alloy material. The magnesium alloy material is suitable for the operating environment of a vehicle driving system, is environmentally friendly, and is suitable for industrial application.

Description

Technical Field

[0001] This invention relates to the field of materials technology, and in particular to a magnesium alloy material, a method for preparing a magnesium alloy material, and a drive system. Background Technology

[0002] Magnesium alloys have broad application prospects in vehicle lightweighting due to their advantages such as low density, high specific strength, and good shock absorption, especially in vehicle drive systems where their use is gradually increasing. However, magnesium alloys are chemically reactive and are prone to corrosion during vehicle service, affecting the vehicle's lifespan. Summary of the Invention

[0003] One objective of this invention is to provide a magnesium alloy material to improve its corrosion resistance and extend its service life; another objective is to provide a method for preparing the magnesium alloy material; and a third objective is to provide a drive system.

[0004] To achieve the above objectives, the technical solution adopted by the present invention is as follows: The first aspect of this invention provides a method for preparing a magnesium alloy material, the method comprising: Obtain a chemical conversion treatment solution; the chemical conversion treatment solution includes sodium vanadate 10g / L~20g / L, sodium fluoride 10g / L-20g / L, and ammonium fluoroborate 15g / L~20g / L; The magnesium alloy substrate is placed in the chemical conversion treatment solution for treatment, and a passivation film is formed on the surface of the magnesium alloy substrate to obtain the first magnesium alloy material.

[0005] Optionally, the chemical conversion treatment liquid further includes an oxidant of 10 g / L to 15 g / L and a complexing agent of 5 g / L to 8 g / L.

[0006] Optionally, the oxidant is at least one of sodium nitrate, sodium molybdate, sodium persulfate, and potassium permanganate, and the complexing agent is at least one of sodium citrate, tartaric acid, phytic acid, and oxalic acid.

[0007] Optionally, the step of immersing the magnesium alloy substrate in the chemical conversion treatment solution to form a passivation film on the surface of the magnesium alloy substrate to obtain the first magnesium alloy material includes: The magnesium alloy matrix is ​​placed in the chemical conversion treatment solution and treated at 55℃~65℃ for 12~15 minutes to obtain the first magnesium alloy material.

[0008] Optionally, prior to the step of obtaining the chemical conversion treatment solution, the method further includes: The magnesium alloy substrate is cleaned; The cleaned magnesium alloy substrate is then surface-adjusted to obtain a surface-adjusted magnesium alloy substrate.

[0009] Optionally, the step of cleaning the magnesium alloy substrate includes at least one of the following steps: The magnesium alloy substrate is pre-degreased using at least one of alkaline solution cleaning, electrolysis, and ultrasonic methods. The magnesium alloy matrix was degreased using a magnesium alloy degreasing agent; The magnesium alloy matrix was washed once with deionized water. The magnesium alloy substrate was pickled using a pickling solution; The magnesium alloy matrix was subjected to a second water wash using deionized water.

[0010] Optionally, the step of performing surface conditioning on the cleaned magnesium alloy substrate to obtain a surface-conditioned magnesium alloy substrate includes: Obtain a surface conditioning solution; the surface conditioning solution comprises a 68% nitric acid solution with a concentration of 200 ml / L to 400 ml / L, a 40% hydrofluoric acid solution with a concentration of 100 ml / L to 200 ml / L, and the remainder is deionized water; The cleaned magnesium alloy substrate is immersed in the surface conditioning solution at room temperature for 1 to 3 minutes to obtain a surface-conditioned magnesium alloy substrate.

[0011] Optionally, the method further includes: The first magnesium alloy material was washed with deionized water; The first magnesium alloy material after washing is dried.

[0012] Optionally, the method further includes: Obtain the micro-arc oxidation treatment solution; The first magnesium alloy material is placed in the micro-arc oxidation treatment solution to perform micro-arc oxidation treatment on the first magnesium alloy material, forming a ceramic layer on the surface of the first magnesium alloy material to obtain the second magnesium alloy material.

[0013] Optionally, the micro-arc oxidation treatment solution comprises sodium silicate 80g / L~120g / L, sodium hydroxide 5g / L~10g / L, and sodium fluorosilicate 3g / L~5g / L.

[0014] Optionally, the pH value of the micro-arc oxidation treatment solution is 10-11, and the temperature is less than or equal to 35°C.

[0015] Optionally, the step of placing the first magnesium alloy material in the micro-arc oxidation treatment solution to perform micro-arc oxidation treatment on the first magnesium alloy material, forming a ceramic layer on the surface of the first magnesium alloy material to obtain the second magnesium alloy material includes: The first magnesium alloy material is placed in a tank containing the micro-arc oxidation treatment liquid; wherein the first magnesium alloy material and the tank are respectively connected to a preset DC pulse power supply, the first magnesium alloy material is connected as the anode to the positive terminal of the DC pulse power supply, and the tank is connected as the cathode to the negative terminal of the DC pulse power supply. Using a forward voltage of 300V~400V and a forward current density of 10A / dm² 2 ~15A / dm 2 The first magnesium alloy material is subjected to micro-arc oxidation treatment for 20 to 30 minutes with electrical parameters of pulse frequency of 500 Hz to 800 Hz and duty cycle of 30% to 50%, forming a ceramic layer on the surface of the first magnesium alloy material to obtain the second magnesium alloy material.

[0016] Optionally, the method further includes: The ceramic layer on the surface of the second magnesium alloy material is sealed.

[0017] Optionally, the step of sealing the ceramic layer on the surface of the second magnesium alloy material includes: The second magnesium alloy material is immersed in deionized water at 100°C to seal the pores of the ceramic layer on the surface of the second magnesium alloy material; and / or, The second magnesium alloy material is immersed in an organic solution, and the organic solution seals the pores of the ceramic layer on the surface of the second magnesium alloy material.

[0018] Optionally, prior to the step of obtaining the micro-arc oxidation treatment solution, the method further includes: The first magnesium alloy material is subjected to a decontamination treatment; The first magnesium alloy material, after being decontaminated, is cleaned.

[0019] A second aspect of the present invention provides a magnesium alloy material, which is prepared by the preparation method of magnesium alloy material as described in any one of the embodiments of the present invention.

[0020] A third aspect of the present invention provides a drive system comprising an outer housing and / or an internal water channel, the outer housing comprising a first magnesium alloy material as described in any one embodiment of the present invention, and the internal water channel comprising a second magnesium alloy material as described in any one embodiment of the present invention.

[0021] The embodiments of the present invention have the following advantages: The method for preparing magnesium alloy materials according to embodiments of the present invention includes: obtaining a chemical conversion treatment solution; the chemical conversion treatment solution comprising 10-20 g / L sodium vanadate, 10-20 g / L sodium fluoride, and 15-20 g / L ammonium fluoroborate; immersing a magnesium alloy substrate in the chemical conversion treatment solution for treatment, forming a passivation film on the surface of the magnesium alloy substrate, thereby obtaining a first magnesium alloy material. The magnesium alloy material prepared according to embodiments of the present invention forms a composite passivation film on the surface of the magnesium alloy substrate containing magnesium hydroxide, magnesium oxide, vanadium oxide, magnesium vanadate, and magnesium fluoride. The composite passivation film uniformly and tightly coats the surface of the magnesium alloy substrate, possessing a dense and stable structure, with a surface approximately non-porous or microporous, effectively improving the corrosion resistance of the magnesium alloy material and extending its service life. It is suitable for the operating environment of vehicle drive systems, and the process is environmentally friendly, making it suitable for industrial applications. Attached Figure Description

[0022] Figure 1 This is an external view of the magnesium alloy matrix; Figure 2 This is an appearance diagram of the first magnesium alloy material prepared in Example 1 of the present invention; Figure 3 This is an appearance diagram of the second magnesium alloy material prepared according to Example 1 of the present invention; Figure 4 This is a scanning electron microscope image of the first magnesium alloy material prepared in Example 1 of the present invention; Figure 5 This is a scanning electron microscope image of the second magnesium alloy material prepared in Example 1 of the present invention; Figure 6 The image shows the appearance of the magnesium alloy substrate after a 336-hour coolant corrosion test. Figure 7 This is an image of the appearance of the first magnesium alloy material prepared in Example 1 of the present invention after a 336-hour coolant corrosion test; Figure 8 This is an image of the appearance of the second magnesium alloy material prepared in Example 1 of the present invention after a 336-hour coolant corrosion test; Figure 9 Metallographic image of a magnesium alloy matrix after a 336-hour coolant corrosion test; Figure 10 The image shows the metallographic structure of the first magnesium alloy material prepared in Example 1 of this invention after a 336-hour cooling liquid corrosion test. Figure 11 The image shows the metallographic structure of the second magnesium alloy material prepared in Example 1 of this invention after a 336-hour cooling liquid corrosion test. Detailed Implementation

[0023] The embodiments of the present invention will be described below with reference to the accompanying drawings and preferred embodiments. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention. It should be understood that the preferred embodiments are only for illustrating the present invention and not for limiting the scope of protection of the present invention.

[0024] Generally, to improve the corrosion resistance of magnesium alloys, chemical conversion treatments are typically used to treat the surface of the magnesium alloy material. These chemical conversion treatments usually include chromate conversion treatments and phosphate conversion treatments.

[0025] Chromate conversion treatment involves immersing magnesium alloy materials in a chromic acid or chromate solution containing hexavalent chromium, forming a passivation film containing both trivalent and hexavalent chromium on the surface of the magnesium alloy, protecting it from water or other corrosive media. However, the passivation film formed by chromate conversion treatment is usually thin, with a thickness of 0.5~3μm. It is fragile and porous, and contains water of crystallization. Under certain temperatures, it may develop microcracks due to dehydration, resulting in poor wear resistance and corrosion resistance. It can only slow down the corrosion rate and is difficult to achieve long-term corrosion protection.

[0026] Phosphate conversion treatment is an environmentally friendly, chromium-free conversion process that immerses magnesium alloy materials in a phosphate-containing solution for chemical conversion, forming a phosphate-containing passivation film on the surface of the magnesium alloy. The phosphate passivation film is primarily crystalline in structure and exhibits good adhesion to the magnesium alloy, thus possessing a certain degree of corrosion resistance. However, compared to chromate passivation films, the crystalline structure of the phosphate passivation film results in lower corrosion resistance. Furthermore, the crystallization nucleation rate during phosphate passivation film formation is lower, leading to a coarser microstructure and making it difficult to obtain a uniformly distributed, crack-free passivation film, thus affecting its performance.

[0027] For vehicle drive systems, different parts typically face different corrosive environments. The outer casing of the vehicle drive system mainly faces corrosion caused by external environments such as humid environments or salt spray environments, such as coastal environments or post-snow removal road environments, or galvanic corrosion caused by potential differences when the outer casing is in contact with dissimilar metals.

[0028] The internal cooling channels of a vehicle's drive system face a more complex corrosive environment than the external casing. Prolonged contact between the inner walls of the channels and the coolant, a mixture of ethylene glycol, water, and corrosion inhibitors, can cause corrosion. The circulating coolant washes away the inner walls, causing surface wear and accelerating corrosion. The coolant may also degrade to produce organic acids, subjecting the channels to acidic corrosion. Furthermore, the complex structure of the cooling channels allows coolant to stagnate in bends, blind holes, and welded areas, creating oxygen-deficient zones in these areas and oxygen-rich zones in the main channels. These oxygen-deficient zones can act as anodes, and the oxygen-rich zones as cathodes, forming localized micro-cells in these dead zones, further accelerating corrosion and exacerbating the overall corrosion problem within the cooling channels. Furthermore, during vehicle operation, the temperature of the coolant may fluctuate drastically within the range of -40℃ (low temperature start-up) to 105℃ (high temperature operating conditions), causing thermal stress to be generated in the magnesium alloy matrix and the chromate passivation film or phosphate passivation film on its surface due to the difference in the coefficient of thermal expansion, which leads to cracking of the passivation film and accelerates waterway corrosion.

[0029] To address the corrosive environment of the internal cooling channels in vehicle drive systems, organic coatings such as epoxy resin and polytetrafluoroethylene (PTFE) can be applied to the inner walls of the channels to improve corrosion resistance. However, organic coatings have poor high-temperature resistance and are prone to softening at high temperatures, increasing coolant flow resistance and making them unsuitable for the high-temperature operating conditions of vehicle drive systems. Electrochemical methods can also be used to form an oxide film on the inner walls of the channels. However, traditional anodizing methods are highly corrosive to magnesium alloys, potentially leading to over-corrosion and a rough surface, which may also increase coolant flow resistance when used on the inner walls of the channels. Furthermore, the oxide film itself has high porosity, limiting its corrosion resistance. Alternatively, a nickel-phosphorus alloy with better corrosion resistance can be deposited on the inner walls of the channels, but this method is costly, and nickel is a heavy metal, making wastewater treatment difficult and hindering industrial application.

[0030] This invention discloses a method for preparing magnesium alloy materials, the method comprising: Step 101: Obtain the chemical conversion treatment solution; the chemical conversion treatment solution includes sodium vanadate 10g / L~20g / L, sodium fluoride 10g / L-20g / L, and ammonium fluoroborate 15g / L~20g / L; Step 102: The magnesium alloy substrate is placed in a chemical conversion treatment solution to form a passivation film on the surface of the magnesium alloy substrate, thereby obtaining the first magnesium alloy material.

[0031] In this embodiment of the invention, a passivation film can be formed on the surface of the magnesium alloy substrate through chemical conversion treatment to improve the corrosion resistance of the magnesium alloy substrate. Specifically, the magnesium alloy substrate may mainly include magnesium, and may also contain at least one of other metallic elements such as aluminum, zinc, and manganese. It may also contain rare earth elements such as cerium, lanthanum, neodymium, and yttrium, and may also contain other functional elements such as zirconium, calcium, and lithium, which are not limited by this invention.

[0032] The chemical conversion treatment solution may include sodium vanadate, sodium fluoride, and ammonium fluoroborate. Sodium vanadate (Na3VO4) can provide pentavalent vanadium ions (V... 5+ Vanadium ions have strong oxidizing properties. When in contact with a magnesium alloy matrix, they can undergo a redox reaction with the magnesium in the matrix to generate magnesium ions (Mg). 2+ ) and trivalent vanadium ions (V 3+ Magnesium ions and trivalent vanadium ions can further react with hydroxide ions (OH-) in the solution. - ) Incompletely restored VO4 3- Further deposition reactions occur, forming a continuous and uniform passivation film on the magnesium alloy substrate surface. The passivation film mainly consists of magnesium hydroxide (Mg(OH)2), magnesium oxide (MgO), and vanadium oxide (V2O3, with a small amount of V2O4), as well as trace amounts of magnesium vanadate (Mg3(VO4)2), forming a composite system of "metal oxide-vanadium oxide." The vanadium oxide particles are fine, belonging to the nanoscale, and can effectively fill the tiny pores in the magnesium hydroxide, resulting in a passivation film with good density and a surface that is nearly non-porous or microporous. This effectively resists external corrosion of the magnesium alloy material and improves its corrosion resistance.

[0033] Furthermore, compared to other vanadates, sodium vanadate can provide vanadate ions without introducing interfering ions or disrupting the film-forming environment, enabling a stable and dense passivation film to form on the magnesium alloy substrate surface. Specifically, other vanadates can include calcium vanadate, magnesium vanadate, barium vanadate, potassium vanadate, and lithium vanadate. However, calcium vanadate, magnesium vanadate, and barium vanadate have extremely low solubility in water, making it difficult to dissociate into a sufficient concentration of vanadate ions, and their cations (Ca... 2+ Mg 2+ Ba 2+ ) will react with fluoride ions (F) in the chemical conversion treatment solution - These compounds combine to form insoluble fluoride precipitates, consuming fluoride ions in the system, disrupting the stability of the chemical conversion solution, and affecting the quality of the passivation film. For potassium vanadate and lithium vanadate, potassium ions (K... + The radius is larger than that of sodium ions (Na). +It easily adsorbs onto the surface of the activated magnesium alloy matrix, hindering the reaction of vanadate and magnesium ions (Mg). 2+ ( ) combines to form a film, and the industrial cost of potassium vanadate is much higher than that of sodium vanadate. Lithium ions (Li + If the radius is too small, it will form a stable complex with complexing agents such as citric acid, consuming the complexing agent components in the chemical conversion treatment solution, leading to an excessive amount of dissolved magnesium ions (Mg²⁺) in the solution. 2+ It cannot be effectively controlled and is prone to over-corrosion, which also affects the film quality of the passivation film.

[0034] Sodium fluoride and ammonium fluoroborate in the chemical conversion treatment solution can further provide fluoride ions (F). - ), and magnesium ions generated by redox reactions (Mg) 2+ The reaction produces magnesium fluoride (MgF2). Magnesium fluoride is a dense and stable compound that can further improve the density and stability of the passivation film. Simultaneously, fluoride ions (F...) react to form magnesium fluoride (MgF2). - It can slightly etch the surface of the magnesium alloy substrate to form a micro-rough structure, further enhancing the bonding force between the passivation film and the magnesium alloy substrate.

[0035] Furthermore, in this embodiment of the invention, by simultaneously using sodium fluoride and ammonium fluoroborate, sodium fluoride can rapidly activate the substrate and provide nucleation sites for film formation, while ammonium fluoroborate can gently complex, inhibit excessive corrosion, and regulate film growth. The two can produce a synergistic effect, resulting in a better formation of a continuous, dense, and strongly bonded passivation film. Specifically, sodium fluoride is a simple inorganic fluoride salt with a rapid dissociation rate and high degree of ionization under intermediate temperature conditions, enabling it to quickly release free fluoride ions (F₂F₃) into the solution. - ); Free fluoride ions (F - It can rapidly participate in the reaction and simultaneously micro-etch the magnesium alloy substrate, forming uniform micro-etching points on the substrate surface. These micro-etching points are the core nucleation sites for the combination of vanadate and magnesium ions to form a film, achieving rapid activation of the magnesium alloy surface and laying the foundation for subsequent film growth. Ammonium fluoroborate is a complex fluoride salt that dissociates mildly and stepwise under medium-temperature conditions, releasing fluoride ions. The dissociated fluoroborate ions (BF)... 4 The fluoride ion is a complexed fluoride ion, not a free fluoride ion (F). - It cannot perform strong etching on magnesium alloy substrates. However, it can work synergistically with sodium fluoride to form fluoroborate (BF). 4 Magnesium ions (Mg) dissolved during the micro-etching process and redox process of magnesium alloy substrates can interact with magnesium ions. 2+ This forms a stable Mg(BF4)2 complex, reducing the amount of free magnesium ions (Mg) in the solution. 2+ Concentration, to avoid free fluoride ions (F) of sodium fluoride. -This process causes excessive etching of the magnesium alloy substrate, preventing pitting and pinholes. Simultaneously, ammonium fluoroborate can dissociate stepwise to release small amounts of free fluoride ions (F...). - Sodium fluoride replenishes the fluoride ions consumed by sodium fluoride in the early stages, maintaining a stable fluoride ion concentration in the solution and ensuring a uniform film growth rate. If only sodium fluoride is used, excessive etching may lead to corrosion of the magnesium alloy substrate and a porous film. If only ammonium fluoroborate is used, the slow activation rate and insufficient nucleation sites may result in discontinuous films and poor adhesion. The combination of sodium fluoride and ammonium fluoroborate ensures sufficient activation of the magnesium alloy surface and achieves precise control of the film formation process, ultimately forming a continuous, dense, and strongly bonded film.

[0036] In specific implementations, the chemical conversion treatment solution may include sodium vanadate at 10 g / L to 20 g / L, sodium fluoride at 10 g / L to 20 g / L, and ammonium fluoroborate at 15 g / L to 20 g / L. Specifically, sodium vanadate may be at concentrations of 10 g / L, 12 g / L, 14 g / L, 16 g / L, 18 g / L, 20 g / L, etc.; sodium fluoride may be at concentrations of 10 g / L, 12 g / L, 14 g / L, 16 g / L, 18 g / L, 20 g / L, etc.; and ammonium fluoroborate may be at concentrations of 15 g / L, 16 g / L, 17 g / L, 18 g / L, 19 g / L, 20 g / L, etc. This invention does not impose any limitations on these concentrations. Sodium vanadate, sodium fluoride, and ammonium fluoroborate can react well with the magnesium alloy substrate within this concentration range to form a passivation film, and the synergistic effect of sodium fluoride and ammonium fluoroborate improves the adhesion between the passivation film and the magnesium alloy substrate.

[0037] A magnesium alloy substrate is treated in a chemical conversion solution to form a passivation film on its surface, yielding a first magnesium alloy material, which is primarily white or gray in appearance. The film thickness ranges from 1 μm to 5 μm. Its resistance to neutral salt spray remains unchanged for over 72 hours, and its resistance to the double 85 test (85℃, 85% RH) remains unchanged for over 240 hours. Compared to existing magnesium alloy materials, it exhibits superior corrosion resistance, making it particularly suitable for vehicle drive systems. Furthermore, the chemical conversion solution is environmentally friendly, free of heavy metals, and the process is simple, making it suitable for industrial applications.

[0038] In some embodiments of the present invention, the chemical conversion treatment liquid further includes an oxidant of 10 g / L to 15 g / L and a complexing agent of 5 g / L to 8 g / L.

[0039] The oxidant can be 10 g / L, 11 g / L, 12 g / L, 13 g / L, 14 g / L, 15 g / L, etc., and this invention does not limit this. Within the concentration range of 10 g / L to 15 g / L, the oxidant can be used during the passivation film formation process to promote a uniform oxidation reaction on the surface of the magnesium alloy substrate, causing slight corrosion, thereby changing the microenvironment on the surface of the magnesium alloy substrate, forming micro-batteries on the surface of the magnesium alloy substrate, promoting the rapid crystallization and nucleation of core film-forming substances such as magnesium ions, vanadium ions, and fluoride ions on the surface of the magnesium alloy substrate, increasing the film formation rate of the passivation film, further reducing the porosity of the passivation film, and further improving the corrosion resistance of the passivation film.

[0040] The complexing agent can be 5 g / L, 6 g / L, 7 g / L, 8 g / L, etc., and this invention does not limit this. Within the concentration range of 5 g / L to 8 g / L, the complexing agent can be used during the passivation film formation process to complex with excess dissolved metal ions such as magnesium ions and zinc ions in the magnesium alloy matrix, avoiding the formation of free precipitates such as magnesium hydroxide (Mg(OH)2) and zinc hydroxide (Zn(OH)2) in the system, thus ensuring the quality of the passivation film. Simultaneously, it can stabilize the pH value of the system in a weakly acidic environment (5.5~6.5), controlling the stability of the system environment during film formation.

[0041] In some embodiments of the present invention, the oxidant is at least one of sodium nitrate, sodium molybdate, sodium persulfate, and potassium permanganate, and the complexing agent is at least one of sodium citrate, tartaric acid, phytic acid, and oxalic acid.

[0042] Specifically, sodium nitrate, sodium molybdate, sodium persulfate, and potassium permanganate all possess good oxidizing properties, promoting uniform corrosion of the magnesium alloy substrate surface, forming micro-cells, accelerating the nucleation of film-forming substances on the magnesium alloy substrate surface, and reducing film porosity. Among these, sodium nitrate (NaNO3) exhibits strong oxidizing properties under acidic to neutral conditions, rapidly oxidizing the magnesium alloy substrate and inducing rapid nucleation of film-forming substances on the substrate surface. Sodium molybdate (Na2MoO4) tends to oxidize the magnesium alloy substrate surface more stably, promoting passivation film formation. Sodium persulfate (Na2S2O8) contains persulfate (S2O8) ions. 2- The oxidizing properties of potassium permanganate (KMnO4) are higher than those of nitrate, which can promote the crystallization and nucleation of film-forming substances on the surface of magnesium alloy substrates more quickly. KMnO4 also has strong oxidizing properties and can help form a denser passivation film.

[0043] The complexing agent can be a substance suitable for weakly acidic environments and capable of complexing metal ions, such as at least one of sodium citrate, tartaric acid, phytic acid, and oxalic acid. Sodium citrate, tartaric acid, phytic acid, and oxalic acid have similar complexing abilities, similar pH ranges, and good biodegradability, making them suitable for use in the chemical conversion treatment solution of this invention to improve the film quality of the passivation film.

[0044] In some embodiments of the present invention, the step of immersing a magnesium alloy substrate in a chemical conversion treatment solution to form a passivation film on the surface of the magnesium alloy substrate to obtain a first magnesium alloy material includes: Step 1021: Place the magnesium alloy matrix into a chemical conversion treatment solution and treat it at 55℃~65℃ for 12~15 minutes to obtain the first magnesium alloy material.

[0045] In practice, the magnesium alloy substrate can be immersed in a chemical conversion treatment solution and treated at a medium temperature of 55℃~65℃ for 12~15 minutes to form a passivation film on the surface of the magnesium alloy substrate, thus obtaining the first magnesium alloy material. The reaction environment between the magnesium alloy substrate and the chemical conversion treatment solution is relatively mild, making this treatment process easy to apply industrially.

[0046] The reaction temperature can be 55℃, 57℃, 59℃, 61℃, 63℃, 65℃, etc., and the processing time can be 12 minutes, 13 minutes, 14 minutes, 15 minutes, etc. The present invention does not limit these.

[0047] In some embodiments of the present invention, prior to the step of obtaining the chemical conversion treatment liquid, the method further includes: Step 201: Clean the magnesium alloy substrate; Step 202: Perform surface adjustment on the cleaned magnesium alloy substrate to obtain a surface-adjusted magnesium alloy substrate.

[0048] Specifically, before chemical conversion treatment of the magnesium alloy substrate, the substrate can be cleaned to remove any oxide film, grease, dust, iron filings, and other impurities that may be attached to the surface. This ensures that the subsequent chemical conversion treatment steps are not affected by impurities, and the passivation film can be tightly bonded to the magnesium alloy substrate, thereby improving the film formation effect of the passivation film.

[0049] After cleaning the magnesium alloy substrate, the surface of the magnesium alloy substrate can be further adjusted to form a rough surface, which can further improve the adhesion between the subsequently formed passivation film and the magnesium alloy substrate, and further improve the corrosion resistance of the passivation film.

[0050] In some embodiments of the present invention, the step of cleaning the magnesium alloy substrate includes at least one of the following steps: Step 2011: The magnesium alloy substrate is pre-degreased using at least one of the following methods: alkaline solution cleaning, electrolysis, and ultrasonic cleaning. Specifically, in order to remove grease and impurities such as dust and iron filings that may adhere to the surface of the magnesium alloy substrate, at least one of the following methods can be used to pre-degrease the magnesium alloy substrate: alkaline solution cleaning, electrolysis, and ultrasonic cleaning.

[0051] When using an alkaline solution cleaning method, an alkaline solution with a concentration of 45g~70g / L can be used to treat the magnesium alloy substrate for 8~12 minutes at a temperature range of 50℃~60℃. The alkaline solution may include 20g / L~30g / L sodium hydroxide, 15~25g / L sodium carbonate, and 10~15g / L sodium silicate. Using this raw material ratio, the saponification and emulsification effects of the alkaline substances on grease can be utilized to effectively remove grease and impurities from the magnesium alloy substrate, ensuring that subsequent chemical conversion treatment steps are not affected by impurities.

[0052] As an example of the present invention, sodium hydroxide can be 20 g / L, 22 g / L, 24 g / L, 26 g / L, 28 g / L, 30 g / L, etc., sodium carbonate can be 15 g / L, 17 g / L, 19 g / L, 21 g / L, 23 g / L, 25 g / L, etc., and sodium silicate can be 10 g / L, 11 g / L, 12 g / L, 13 g / L, 14 g / L, 15 g / L, etc., and the present invention does not limit these.

[0053] In the electrolysis method, the magnesium alloy substrate can be immersed in water. The gas generated by the electrolysis of water acts on the surface of the magnesium alloy substrate, mechanically removing grease and impurities. In a specific implementation, a current density of 5 A / dm³ can be used. 2 ~8A / dm 2 Pre-degreasing of the magnesium alloy matrix was performed under electrical parameters of 10V~15V. The current density could be 5A / dm³. 2 6A / dm 2 7A / dm 2 8A / dm 2 The voltage can be 10V, 11V, 12V, 13V, 14V, 15V, etc., and this invention does not limit it.

[0054] When using the ultrasonic method, the magnesium alloy substrate can be immersed in water. The ultrasonic waves generate cavitation in the water, forming microbubbles that burst on the surface of the magnesium alloy substrate, producing a localized high-pressure jet that mechanically removes grease and impurities from the substrate surface. In practice, an ultrasonic transducer with a frequency of 25kHz to 40kHz and a power of 300W to 500W can be used to generate ultrasonic waves for pre-degreasing the magnesium alloy substrate. The frequencies can be 25kHz, 30kHz, 35kHz, 40kHz, etc., and the powers can be 300W, 350W, 400W, 450W, 500W, etc.; this invention does not impose any limitations on these settings.

[0055] Alternatively, during the electrolytic and ultrasonic treatment of the magnesium alloy substrate, the substrate can be immersed in the same alkaline solution as in the alkaline cleaning method to further improve the pre-degreasing effect of the electrolytic and ultrasonic methods. Step 2012: Degrease the magnesium alloy matrix using a magnesium alloy degreasing agent; Specifically, in order to remove oxide films, release agents and other impurities that may exist on the surface of magnesium alloy substrates, magnesium alloy degreasing agents can be used to soak the magnesium alloy substrates, so that the surface of the magnesium alloy substrates is uniform and clean, so that the subsequent chemical conversion treatment steps are not affected by impurities, and the passivation film can be tightly bonded to the magnesium alloy substrate, thereby improving the film formation effect of the passivation film.

[0056] The magnesium alloy degreasing agent may include 8%~12% nonionic surfactant, 5%~8% chelating agent, 3%~5% corrosion inhibitor, and the balance being deionized water. The nonionic surfactant can be 8%, 9%, 10%, 11%, 12%, etc., the chelating agent can be 5%, 6%, 7%, 8%, etc., and the corrosion inhibitor can be 3%, 4%, 5%, etc., and this invention does not impose any limitations on these proportions. With this raw material ratio, the magnesium alloy degreasing agent exhibits good degreasing performance, good anti-fouling ability, and is not easily depleted even after long-term use. Compared to conventional phosphate processes, the service life of the degreasing agent is significantly extended.

[0057] Nonionic surfactants such as fatty alcohol polyoxyethylene ether, dodecylphenol polyoxyethylene ether, and octylphenol polyoxyethylene ether serve as core cleaning components. Through emulsification, wetting, and dispersion, they can peel off and encapsulate oxide films and release agents such as paraffin or silicone oil on the magnesium alloy substrate surface within micelles, preventing secondary deposition. Chelating agents such as trisodium citrate, disodium EDTA, and sodium gluconate can complex with free metal ions such as magnesium, calcium, and iron ions released during degreasing, preventing their deposition on the magnesium alloy substrate surface and the formation of new contaminants. Corrosion inhibitors such as benzotriazole, phytic acid, or silicates can remove oil stains with the degreasing agent and form a protective film on the clean magnesium alloy substrate surface, preventing corrosion during degreasing and protecting the integrity of the magnesium alloy substrate.

[0058] In a specific implementation, the magnesium alloy substrate can be immersed in a magnesium alloy degreasing agent for 10 to 15 minutes within a temperature range of 40℃ to 50℃ to complete the degreasing treatment of the magnesium alloy substrate. To further enhance the degreasing effect, stirring can be performed at a speed of 30 to 50 rpm during the degreasing process to improve the degreasing effect. The reaction temperature can be 40℃, 42℃, 44℃, 46℃, 48℃, 50℃, etc., the treatment time can be 10 minutes, 11 minutes, 12 minutes, 13 minutes, 14 minutes, 15 minutes, etc., and the rotation speed can be 30 rpm, 35 rpm, 40 rpm, 45 rpm, 50 rpm, etc., and this invention does not impose any limitations on these settings.

[0059] Step 2013: The magnesium alloy substrate is washed once with deionized water; After pre-degreasing and / or degreasing treatment of the magnesium alloy substrate, the magnesium alloy substrate can be washed once with deionized water to remove any impurities that may remain on the surface of the magnesium alloy substrate and to remove unnecessary components from the surface of the magnesium alloy substrate.

[0060] In practice, deionized water with a conductivity of less than 50 μS / cm can be used to rinse the magnesium alloy substrate for 2 to 3 minutes at a flow rate of 1 to 1.5 m / s at room temperature. Once there is no visible oil or degreasing agent residue on the surface of the magnesium alloy substrate, the water rinse is complete.

[0061] Step 2014: The magnesium alloy substrate is pickled using a pickling solution; In this embodiment of the invention, in order to more thoroughly clean the surface of the magnesium alloy substrate and remove any residual oxide film and other possible impurities, an acid pickling solution can be used to pickle the magnesium alloy substrate.

[0062] The pickling solution may include 10 ml / L to 30 ml / L of nitric acid with a mass concentration of 68%, with the remainder being water. The 68% nitric acid concentration may be 10 ml / L, 15 ml / L, 20 ml / L, 25 ml / L, 30 ml / L, etc., and this invention does not limit this.

[0063] In practice, the magnesium alloy substrate can be immersed in an acid pickling solution at room temperature for 20 to 40 seconds. The immersion time can be 20, 25, 30, 35, or 40 seconds, etc., and this invention does not limit this. At this immersion time, any residual oxide film and other impurities on the surface of the magnesium alloy substrate can be thoroughly cleaned, while maintaining a uniform and clean surface and preventing unnecessary corrosion.

[0064] Step 2015: The magnesium alloy substrate is washed a second time with deionized water.

[0065] In this embodiment of the invention, after the pickling process is completed, the magnesium alloy substrate can be washed a second time with deionized water to remove any impurities and pickling solution that may remain on the surface of the magnesium alloy substrate, so as to keep the magnesium alloy substrate in a uniform and clean state.

[0066] In practice, deionized water with a conductivity of less than 50 μS / cm can be used to clean the magnesium alloy substrate at room temperature for 3 to 4 minutes. Specifically, the magnesium alloy substrate can be sprayed with deionized water at a flow rate of 1 to 1.5 m / s for 1 minute, and then immersed in deionized water for 2 to 3 minutes until the pH value of the magnesium alloy substrate surface recovers to approximately 6 to 7, completing the second water wash.

[0067] In some embodiments of the present invention, the step of performing surface conditioning on the cleaned magnesium alloy substrate to obtain a surface-conditioned magnesium alloy substrate includes: Step 2021: Obtain the surface conditioning solution; the surface conditioning solution includes 200 ml / L to 400 ml / L of 68% nitric acid solution, 100 ml / L to 200 ml / L of 40% hydrofluoric acid solution, and the remainder is deionized water; Step 2022: Immerse the cleaned magnesium alloy substrate in a surface conditioning solution at room temperature for 1-3 minutes to obtain a surface-conditioned magnesium alloy substrate.

[0068] In this embodiment of the invention, a surface conditioning solution can be used to condition the surface of the magnesium alloy substrate, creating a rough surface that further enhances the adhesion between the subsequently formed passivation film and the magnesium alloy substrate, thereby improving the corrosion resistance of the passivation film. The surface conditioning solution comprises a 68% nitric acid solution at a concentration of 200 ml / L to 400 ml / L, a 40% hydrofluoric acid solution at a concentration of 100 ml / L to 200 ml / L, and the remainder being deionized water. The concentration of the 68% nitric acid solution can be 200 ml / L, 250 ml / L, 300 ml / L, 350 ml / L, 400 ml / L, etc., and the concentration of the 40% hydrofluoric acid solution can be 100 ml / L, 120 ml / L, 140 ml / L, 160 ml / L, 180 ml / L, 200 ml / L, etc., and this invention does not impose any limitations on these concentrations.

[0069] The surface conditioning solution is highly acidic, which can remove the stubborn oxide layer on the surface of the magnesium alloy substrate. At the same time, it can cause micro-etching, forming a tiny uneven structure on the surface of the magnesium alloy substrate. During the subsequent passivation film formation process, it can increase the contact area between the magnesium alloy substrate and the passivation film, improve the adhesion of the passivation film on the surface of the magnesium alloy substrate, and enable the passivation film with good corrosion resistance to be tightly bonded to the surface of the magnesium alloy substrate, thereby further improving the corrosion resistance of the magnesium alloy material.

[0070] In a specific implementation, a cleaned magnesium alloy substrate with a uniform and clean surface can be immersed in a surface conditioning solution at room temperature for 1 to 3 minutes. The immersion time can be 1 minute, 1.5 minutes, 2 minutes, 2.5 minutes, or 3 minutes; this invention does not limit the duration. At this immersion time, a micro-roughened surface can be formed on the magnesium alloy substrate, while the substrate as a whole is not excessively etched by the surface conditioning solution, thus better preserving its original morphology.

[0071] In some embodiments of the present invention, the method further includes: Step 301: Wash the first magnesium alloy material with deionized water; Step 302: Dry the first magnesium alloy material after water washing.

[0072] In this embodiment of the invention, after forming a passivation film on the surface of the magnesium alloy substrate to obtain the first magnesium alloy material, the first magnesium alloy material can be washed with deionized water to remove any residual chemical conversion treatment liquid and other impurities from its surface, thus protecting the corrosion resistance of the passivation film from being affected. Subsequently, the washed first magnesium alloy material can be dried to ensure it is in a dry state, facilitating its subsequent use in an electric drive system or further for the preparation of a second magnesium alloy material.

[0073] In practice, deionized water with a conductivity of less than 30 μS / cm can be used to immerse the first magnesium alloy material at room temperature for 4 to 5 minutes, during which time it can be stirred at a speed of 20 to 30 r / min. Afterward, high-pressure spraying at a pressure of 0.2 MPa to 0.3 MPa can be used to rinse the first magnesium alloy material, including any edges, corners, and blind holes.

[0074] After washing the first magnesium alloy material, it can be baked in an environment of 30℃~60℃ for 10 to 30 minutes. After drying, it can be naturally cooled to room temperature before further preparing the second magnesium alloy material, avoiding the passivation film cracking caused by temperature difference.

[0075] Specifically, a hot air circulating oven can be used for drying. If the wall thickness of the first magnesium alloy material is greater than 5 mm, drying should be carried out at a temperature range of 50℃ to 60℃. If the wall thickness of the first magnesium alloy material is less than 5 mm, drying should be carried out at a temperature range of 30℃ to 40℃. After baking for 10 to 30 minutes, the moisture content of the first magnesium alloy material should be measured using a Karl Fischer moisture meter. If the moisture content is ≤0.5%, the drying of the first magnesium alloy material is considered complete.

[0076] In some embodiments of the present invention, the method further includes: Step 401: Obtain the micro-arc oxidation treatment solution; Step 402: The first magnesium alloy material is placed in a micro-arc oxidation solution to perform micro-arc oxidation treatment on the first magnesium alloy material, forming a ceramic layer on the surface of the first magnesium alloy material to obtain the second magnesium alloy material.

[0077] In this embodiment of the invention, for the internal water channels of the vehicle drive system, since the corrosive environment they face is more complex than that of the external shell, a micro-arc oxidation treatment liquid can be further used to perform micro-arc oxidation treatment on the first magnesium alloy material. A high-voltage electric field is applied to the first magnesium alloy material, and a plasma reaction is generated through high-voltage discharge. Multiple breakdown points are generated on the surface of the first magnesium alloy material, and tiny electric arcs are generated at the breakdown points. The instantaneous temperature can reach 2000K-10000K. At high temperature, the first magnesium alloy material and the film-forming substances in the micro-arc oxidation treatment liquid undergo electrochemical and thermochemical reactions, and a ceramic layer is formed in situ on the surface of the first magnesium alloy material to obtain the second magnesium alloy material.

[0078] The second magnesium alloy material prepared in this embodiment of the invention is white or gray in appearance, with a film thickness of 15-25 μm on the surface of the magnesium alloy substrate. Its resistance to neutral salt spray remains unchanged for over 1000 hours, its resistance to acidic salt spray remains unchanged for over 336 hours, its resistance to filamentous corrosion remains unchanged for over 240 hours, its resistance to damp heat remains unchanged for over 1000 hours, its resistance to mold remains unchanged for over 28 days, its hardness is not less than 350 HV, its wear resistance is such that the wear loss does not exceed 20 mg, its water resistance is non-corrosive and does not peel off, its resistance to anhydrous ethanol immersion is non-corrosive and does not peel off, its resistance to coolant corrosion shows no significant change for over 336 hours, and its resistance to lubricating oil corrosion shows no change for over 500 hours. It is evident that, compared to the first magnesium alloy material, the second magnesium alloy material possesses higher hardness and better corrosion resistance, better able to withstand the corrosive environment of drastic temperature fluctuations in internal water channels and prolonged contact with coolant, maintaining a longer service life for the magnesium alloy material. Furthermore, the process is environmentally friendly and suitable for industrial applications.

[0079] In some embodiments of the present invention, the micro-arc oxidation treatment solution comprises 80 g / L to 120 g / L sodium silicate, 5 g / L to 10 g / L sodium hydroxide, and 3 g / L to 5 g / L sodium fluorosilicate. This micro-arc oxidation treatment solution is free of heavy metals, has good environmental performance, and is easy to use in industrial applications.

[0080] The concentration of sodium silicate can be 80 g / L, 90 g / L, 100 g / L, 110 g / L, 120 g / L, etc., and this invention does not impose any limitation on this. Sodium silicate (Na2SiO3) 9H2O can be the main film-forming material in the micro-arc oxidation process. Under the action of an electric field, silicate ions can migrate towards the anode and react with magnesium ions (Mg ions) released from the magnesium alloy matrix. 2+ The magnesium alloy matrix is ​​sintered under plasma reaction to form a magnesium olivine (Mg2SiO4) ceramic phase, which serves as the main material of the ceramic layer. Simultaneously, during the micro-arc oxidation process, under the action of a high-voltage electric field, magnesium atoms in the magnesium alloy matrix can migrate outward and undergo an oxidation reaction to form magnesium oxide, a ceramic phase, which also serves as the main material of the ceramic layer.

[0081] The concentration of sodium hydroxide can be 5 g / L, 6 g / L, 7 g / L, 8 g / L, 9 g / L, 10 g / L, etc., and this invention does not limit this. Sodium hydroxide can mainly control the pH value during the micro-arc oxidation process to maintain it between 10 and 11, thereby maintaining the micro-arc oxidation solution with suitable conductivity and ensuring the stable presence of silicate ions in the solution, thus improving the film-forming effect of the ceramic layer.

[0082] Alternatively, if the pH value changes during the micro-arc oxidation process, it can be adjusted using a 10% sodium hydroxide solution or a 5% sulfuric acid solution to keep the pH value stable between 10 and 11.

[0083] The concentration of sodium fluorosilicate (Na2SiF6) can be 3 g / L, 3.5 g / L, 4 g / L, 4.5 g / L, 5 g / L, etc., and this invention does not limit this. Sodium fluorosilicate is mainly used to assist in film formation. Fluoride ions can inhibit the reaction of the first magnesium alloy material with water during micro-arc oxidation, thus preventing excessive hydrogen evolution corrosion. Furthermore, it can form magnesium fluoride (MgF2) on the surface of the first magnesium alloy material, and the surface of the first magnesium alloy material itself also contains magnesium fluoride. Magnesium fluoride has good insulation properties and is uniformly distributed on the surface of the first magnesium alloy material. During the micro-arc oxidation reaction, it can induce smaller, denser, and more uniform arcs, resulting in smaller and denser ceramic grains, thereby further improving the uniformity and density of the ceramic layer distribution and enhancing the corrosion resistance of the second magnesium alloy material.

[0084] In some embodiments of the present invention, the pH value of the micro-arc oxidation treatment solution is 10-11, and the temperature is less than or equal to 35°C.

[0085] In this embodiment of the invention, in order to ensure that the micro-arc oxidation treatment solution has good electrical conductivity and to keep the silicate ions stable in the solution, the pH value of the micro-arc oxidation treatment solution can be controlled to be 10~11. Within this pH range, the micro-arc oxidation treatment solution can react well with the first magnesium alloy material to form a uniform ceramic layer.

[0086] Meanwhile, since the micro-arc oxidation process involves high-voltage discharge, the temperature of the reaction system may rise rapidly. A cooling system can be added to control the temperature of the micro-arc oxidation solution to be less than or equal to 35°C, ensuring that the reaction process is temperature-controlled and reaction is controllable, thereby improving the film quality of the ceramic layer. Furthermore, the lower temperature maintains suitable electrical conductivity, resulting in a finer and more uniform electric arc, which can lead to the formation of smaller ceramic grains, further improving the density of the ceramic layer and enhancing its corrosion resistance.

[0087] In practical implementation, if the micro-arc oxidation treatment solution is placed in a tank to react with the first magnesium alloy material, a cooling water jacket can be installed on the outside of the tank, and cold water at a temperature of 15℃~20℃ can be introduced to control the electrolyte temperature to be stably maintained within a range of less than or equal to 35℃. In industrial mass production scenarios, the consistency of the ceramic layer can be well maintained, and good corrosion resistance can be preserved.

[0088] Furthermore, during the micro-arc oxidation process, the micro-arc oxidation process can be stirred at a speed of 60 r / min to 80 r / min to ensure the electrolyte is uniform and to maintain the good uniformity of the formed ceramic layer.

[0089] In some embodiments of the present invention, the step of placing a first magnesium alloy material in a micro-arc oxidation treatment solution to perform micro-arc oxidation treatment on the first magnesium alloy material, forming a ceramic layer on the surface of the first magnesium alloy material, and obtaining a second magnesium alloy material includes: Step 4021: Place the first magnesium alloy material into a tank containing a micro-arc oxidation treatment solution; wherein the first magnesium alloy material and the tank are respectively connected to a preset DC pulse power supply, the first magnesium alloy material is connected as the anode to the positive terminal of the DC pulse power supply, and the tank is connected as the cathode to the negative terminal of the DC pulse power supply. Step 4022: Use a forward voltage of 300V~400V and a forward current density of 10A / dm². 2 ~15A / dm 2 With electrical parameters of pulse frequency 500Hz~800Hz and duty cycle 30%~50%, the first magnesium alloy material is subjected to micro-arc oxidation treatment for 20 minutes~30 minutes to form a ceramic layer on the surface of the first magnesium alloy material, thus obtaining the second magnesium alloy material.

[0090] In practice, the first magnesium alloy material can be placed in a tank containing a micro-arc oxidation treatment solution. The first magnesium alloy material and the tank are then connected to a pre-set DC pulse power supply. The first magnesium alloy material serves as the anode, connected to the positive terminal of the DC pulse power supply, while the tank serves as the cathode, connected to the negative terminal. Compared to traditional AC power supplies, DC pulse power supplies can significantly reduce energy consumption.

[0091] During the subsequent micro-arc oxidation process, the first magnesium alloy material, acting as the anode, loses electrons, causing magnesium in the first magnesium alloy material to lose electrons and form magnesium ions. The stainless steel tank, acting as the cathode, can provide a large cathode area, which helps to ensure a uniform distribution of electric field lines. Even when the first magnesium alloy material is a workpiece with a complex shape, it can also maintain a consistent current density throughout the first magnesium alloy material, making it easier to maintain a consistent thickness throughout the formed ceramic layer.

[0092] Subsequently, a forward voltage of 300V~400V and a forward current density of 10A / dm were used. 2 ~15A / dm 2 A second magnesium alloy material is obtained by micro-arc oxidation treatment of a first magnesium alloy material for 20 to 30 minutes, using electrical parameters with a pulse frequency of 500Hz to 800Hz and a duty cycle of 30% to 50%. The forward voltage can be 300V, 320V, 340V, 360V, 380V, 400V, etc., and the forward current density can be 10A / dm³. 2 11A / dm 2 12A / dm 2 13A / dm 2 14A / dm 2 15A / dm2 The pulse frequency can be 500Hz, 600Hz, 700Hz, 800Hz, etc., the duty cycle can be 30%, 35%, 40%, 45%, 50%, etc., and the micro-arc oxidation treatment time can be 20 minutes, 22 minutes, 24 minutes, 26 minutes, 28 minutes, 30 minutes, etc., and the present invention does not limit these.

[0093] With a forward voltage of 300V~400V, which is higher than the breakdown voltage of the passivation film on the surface of the first magnesium alloy material, a relatively stable micro-arc discharge can be achieved. Simultaneously, the voltage is not excessively high, maintaining a relatively smooth ceramic layer surface with small pores. At a forward current density of 10A / dm²... 2 ~15A / dm 2 Under controlled conditions, the ceramic layer can be generated at a relatively fast rate during the micro-arc oxidation process, achieving ceramic layer growth within 20 to 30 minutes with a suitable thickness of 15-25 μm. This thickness effectively improves the corrosion resistance of magnesium alloy materials. With a pulse frequency of 500 Hz to 800 Hz and a duty cycle of 30% to 50%, the heat generated during the reaction can be effectively dissipated, preventing excessive accumulation and maintaining a relatively stable temperature in the reaction system. This allows for the formation of finer ceramic grains, resulting in a final ceramic layer with better density and corrosion resistance.

[0094] In some embodiments of the present invention, the method further includes: Step 501: Perform a pore-sealing treatment on the ceramic layer on the surface of the second magnesium alloy material.

[0095] Specifically, since the ceramic layer formed by micro-arc oxidation has numerous micropores on its surface, to further improve the corrosion resistance of the second magnesium alloy material, the ceramic layer on the surface of the second magnesium alloy material can be sealed. This prevents corrosive media from penetrating into the second magnesium alloy material through the micropores, thereby improving its corrosion resistance. Simultaneously, the sealing treatment can enhance the color of the ceramic layer on the surface of the second magnesium alloy material, improving its aesthetic appeal.

[0096] In some embodiments of the present invention, the step of sealing the ceramic layer on the surface of the second magnesium alloy material includes: Step 5011: Immerse the second magnesium alloy material in deionized water at 100°C to seal the pores of the ceramic layer on the surface of the second magnesium alloy material; and / or, Step 5012: Immerse the second magnesium alloy material in an organic solution to seal the pores of the ceramic layer on the surface of the second magnesium alloy material.

[0097] In practice, the second magnesium alloy material can be sealed with boiling water or organic materials. If boiling water is used, the second magnesium alloy material can be immersed in deionized water at 100°C. At this time, the magnesium oxide and other oxides contained in the ceramic layer can react with the deionized water at 100°C to form magnesium hydroxide and other hydroxides with larger volume, thereby reducing or sealing the pores of the ceramic layer on the surface of the second magnesium alloy material.

[0098] After the second magnesium alloy material is cooled to room temperature, it can be immersed in an organic solution such as Teflon, silicone, or stearic acid. The organic material can penetrate into the micropores of the ceramic layer through capillary action. After the organic material dries or solidifies, it can effectively seal the pores of the ceramic layer on the surface of the second magnesium alloy material.

[0099] As a specific example of the present invention, the second magnesium alloy material can be immersed in deionized water at 100°C for 10 to 15 minutes to complete the initial sealing of the pores in the ceramic layer. Subsequently, the second magnesium alloy material can be cooled to room temperature and immersed in a diluted epoxy resin solution (10% to 15% epoxy resin, 85% to 90% acetone) for 5 to 8 minutes. After removal, it can be cured in an oven at 60°C to 80°C for 30 to 40 minutes to form a secondary sealing layer, thus completing the pore sealing.

[0100] In some embodiments of the present invention, prior to the step of obtaining the micro-arc oxidation treatment solution, the method further includes: Step 601: Decontamination treatment is performed on the first magnesium alloy material; Step 602: Clean the first magnesium alloy material that has undergone decontamination treatment.

[0101] Specifically, in order to improve the quality of the ceramic layer formed by micro-arc oxidation, the first magnesium alloy material can be decontaminated before micro-arc oxidation, and the decontaminated first magnesium alloy material can be cleaned to remove grease and impurities from the surface of the first magnesium alloy material.

[0102] In a specific implementation, ultrasonic cleaning can be used to clean the first magnesium alloy material at a temperature of 50℃~60℃ for 15 to 20 minutes. The ultrasonic parameters are a frequency of 40~50kHz and a power of 500~800W. Specifically, the frequency can be 40kHz, 42kHz, 44kHz, 46kHz, 48kHz, 50kHz, etc., the power can be 500W, 600W, 700W, 800W, etc., the temperature can be 50℃, 52℃, 54℃, 56℃, 58℃, 60℃, etc., and the cleaning time can be 15 minutes, 16 minutes, 17 minutes, 18 minutes, 19 minutes, 20 minutes, etc., and this invention does not impose any limitations on these parameters.

[0103] During the ultrasonic cleaning process, the first magnesium alloy material can also be soaked in an alkaline degreasing agent. The alkaline degreasing agent may include 15g / L~20g / L sodium hydroxide, 5g / L~8g / L sodium dodecylbenzenesulfonate, and the remainder being water. The concentration of sodium hydroxide can be 15g / L, 16g / L, 17g / L, 18g / L, 19g / L, 20g / L, etc., and the concentration of sodium dodecylbenzenesulfonate can be 5g / L, 6g / L, 7g / L, 8g / L, etc., and this invention does not impose any limitations on these concentrations.

[0104] When using the ultrasonic method, the magnesium alloy substrate can be immersed in water. The ultrasonic waves generate cavitation in the water, forming microbubbles that burst on the surface of the magnesium alloy substrate, producing a localized high-pressure jet that mechanically removes grease and impurities from the substrate surface. In practice, an ultrasonic transducer with a frequency of 25kHz to 40kHz and a power of 300W to 500W can be used to generate ultrasonic waves for pre-degreasing the magnesium alloy substrate. The frequencies can be 25kHz, 30kHz, 35kHz, 40kHz, etc., and the powers can be 300W, 350W, 400W, 450W, 500W, etc.; this invention does not impose any limitations on these settings.

[0105] Furthermore, if the structure of the first magnesium alloy material is relatively complex, such as having blind hole areas, high-pressure spraying with a pressure of 0.5MPa~0.8MPa and an alkaline degreasing agent flow rate of 5L / min~8L / min can be used for decontamination.

[0106] Subsequently, the first magnesium alloy material can be rinsed at room temperature with deionized water with a conductivity ≤50μS / cm for 5 to 8 minutes until the pH of the outflowing water is 6 to 7 and the conductivity is consistent with that of the inflow water, which is ≤50μS / cm.

[0107] This invention also provides a magnesium alloy material, which is prepared using any of the magnesium alloy material preparation methods described in this invention.

[0108] The magnesium alloy material prepared by the embodiments of the present invention forms a composite passivation film on the surface of the magnesium alloy substrate, which includes magnesium hydroxide, magnesium oxide, vanadium oxide, magnesium vanadate, and magnesium fluoride. The composite passivation film uniformly and tightly wraps the surface of the magnesium alloy substrate, has a dense and stable structure, and the surface is approximately non-porous or microporous, which effectively improves the corrosion resistance of the magnesium alloy material, extends the service life of the magnesium alloy material, and is suitable for the operating environment of vehicle drive systems.

[0109] This invention also provides a drive system, the drive system including an outer housing and / or an internal water channel, the outer housing including a first magnesium alloy material as described in any one of the embodiments of this invention, and the internal water channel including a second magnesium alloy material as described in any one of the embodiments of this invention.

[0110] The drive system provided by this invention uses a first magnesium alloy material for its outer casing. This first magnesium alloy material has a composite passivation film containing magnesium hydroxide, magnesium oxide, vanadium oxide, magnesium vanadate, and magnesium fluoride. The composite passivation film uniformly and tightly coats the surface of the magnesium alloy substrate, exhibiting a dense and stable structure with a surface that is nearly pore-free or microporous. This effectively improves the corrosion resistance of the magnesium alloy material and extends its service life, making it suitable for the operating environment of vehicle drive systems. The second magnesium alloy material undergoes further micro-arc oxidation treatment on top of the first magnesium alloy material to form a ceramic layer. This results in higher hardness and better corrosion resistance, allowing it to better cope with the corrosive environment of drastic temperature fluctuations in the internal water channels and prolonged contact with coolant, thus maintaining a longer service life for the magnesium alloy material.

[0111] To enable those skilled in the art to better understand the present invention, the following specific embodiments illustrate the preparation method of the magnesium alloy material of the present invention.

[0112] Example 1 (1) Pre-degreasing: The magnesium alloy substrate was treated with an alkaline solution (sodium hydroxide 25g / L, sodium carbonate 20g / L, sodium silicate 12g / L) at 55℃ for 8 minutes using ultrasonic treatment (frequency 30kHz, power 400W). (2) Degreasing: Magnesium alloy special degreasing agent (10% fatty alcohol polyoxyethylene ether, 6% trisodium citrate, 4% benzotriazole) was used to soak the magnesium alloy substrate for 12 minutes at a temperature of 45℃ and a stirring speed of 40r / min. (3) First water wash: Use deionized water with a conductivity of 40 μS / cm to rinse the magnesium alloy substrate for 3 min at room temperature with a water flow rate of 1.2 m / s; (4) Pickling: Use a pickling solution containing 20 ml / L of 68% nitric acid and immerse the magnesium alloy substrate at room temperature for 30 seconds; (5) Secondary water washing: spray the magnesium alloy substrate with deionized water for 1 minute, and then soak the magnesium alloy substrate for 3 minutes. The pH of the surface is measured to be 6.5, confirming that the secondary water washing is completed. (6) Surface conditioning: The magnesium alloy substrate was immersed in a surface conditioning solution containing 300 ml / L of 68% nitric acid and 150 ml / L of 40% hydrofluoric acid for 2 min at room temperature; (7) Chemical conversion: The magnesium alloy matrix was treated with a chemical conversion treatment solution at 60°C for 13 min to obtain the first magnesium alloy material; wherein the chemical conversion treatment solution included sodium vanadate 15 g / L, sodium fluoride 15 g / L, ammonium fluoroborate 18 g / L, sodium nitrate 12 g / L, and citric acid 6 g / L. (8) Three water washes: The first magnesium alloy material was soaked in deionized water with a conductivity of 25 μS / cm for 5 min at a stirring speed of 25 r / min, and then the edges and corners of the first magnesium alloy material were rinsed with a high pressure spray of 0.25 MPa. (9) Drying: Use a hot air oven to dry the first magnesium alloy material at 45℃ for 20 minutes. The moisture content is measured to be 0.3%, and the drying is confirmed to be complete. (10) Pretreatment: The first magnesium alloy material was cleaned for 18 min by ultrasonic cleaning (frequency 45 kHz, power 600 W) at 55 ℃ using an alkaline degreasing agent (sodium hydroxide 18 g / L, sodium dodecylbenzene sulfonate 6 g / L); then it was rinsed with deionized water for 7 min, and the conductivity of the outflowing water was detected to be 45 μS / cm, confirming that the cleaning was completed. (11) Micro-arc oxidation: The first magnesium alloy material is placed in a tank containing micro-arc oxidation treatment solution; wherein the first magnesium alloy material and the tank are respectively connected to a preset DC pulse power supply, the first magnesium alloy material is connected to the positive electrode of the DC pulse power supply as the anode, and the tank is connected to the negative electrode of the DC pulse power supply as the cathode; the micro-arc oxidation treatment solution includes sodium silicate 100g / L, sodium hydroxide 8g / L, sodium fluorosilicate 4g / L, and the pH value is controlled at 10.5; Using a forward voltage of 350V and a current density of 12A / dm² 2 With electrical parameters of 600Hz frequency and 40% duty cycle, the first magnesium alloy material was subjected to micro-arc oxidation treatment for 25 minutes, and the cooling water jacket temperature was controlled at 30℃. A ceramic layer was formed on the surface of the first magnesium alloy material to obtain the second magnesium alloy material. (12) Post-treatment: The second magnesium alloy material was sealed with boiling water for 12 min, and then the second magnesium alloy material was soaked in epoxy resin solution (12% epoxy resin and 88% acetone) for 6 min and cured at 80℃ for 35 min to obtain the second magnesium alloy material with the sealing treatment completed.

[0113] Example 2 (1) Pre-degreasing: Use an alkaline solution (sodium hydroxide 20g / L, sodium carbonate 15g / L, sodium silicate 10g / L) at 50℃ to soak the magnesium alloy substrate for 12min; (2) Degreasing: Magnesium alloy special degreasing agent (8% fatty alcohol polyoxyethylene ether, 5% trisodium citrate, 3% benzotriazole) was used to soak the magnesium alloy substrate for 15 minutes at a temperature of 40℃ and a stirring speed of 50r / min. (3) First water wash: Use deionized water with a conductivity of 40 μS / cm to rinse the magnesium alloy substrate for 2 min at room temperature with a water flow rate of 1.5 m / s; (4) Pickling: Use a pickling solution containing 10 ml / L of 68% nitric acid and immerse the magnesium alloy substrate at room temperature for 40 seconds; (5) Secondary water washing: spray the magnesium alloy substrate with deionized water for 1 minute, and then soak the magnesium alloy substrate for 2 minutes. The pH of the surface is detected to be 6.5, confirming that the secondary water washing is completed. (6) Surface conditioning: The magnesium alloy substrate was immersed in a surface conditioning solution containing 200 ml / L of 68% nitric acid and 100 ml / L of 40% hydrofluoric acid at room temperature for 3 min. (7) Chemical conversion: The magnesium alloy matrix was treated with a chemical conversion treatment solution at 55°C for 15 min to obtain the first magnesium alloy material; wherein the chemical conversion treatment solution included sodium vanadate 10 g / L, sodium fluoride 10 g / L, ammonium fluoroborate 15 g / L, sodium nitrate 10 g / L, and citric acid 5 g / L. (8) Three water washes: The first magnesium alloy material was soaked in deionized water with a conductivity of 25 μS / cm for 4 min at a stirring speed of 30 r / min, and then the edges and corners of the first magnesium alloy material were rinsed with a high pressure spray of 0.3 MPa. (9) Drying: Use a hot air drying oven at 30°C to dry the first magnesium alloy material for 30 minutes. The moisture content is measured to be 0.4%, and the drying is confirmed to be complete. (10) Pretreatment: The first magnesium alloy material was cleaned for 20 min by ultrasonic cleaning (frequency 40 kHz, power 800 W) at 50 °C using an alkaline degreasing agent (sodium hydroxide 15 g / L, sodium dodecylbenzene sulfonate 5 g / L); then it was rinsed with deionized water for 8 min, and the conductivity of the outflowing water was tested to be 47 μS / cm, confirming that the cleaning was completed. (11) Micro-arc oxidation: The first magnesium alloy material is placed in a tank containing micro-arc oxidation treatment solution; wherein, the first magnesium alloy material and the tank are respectively connected to a preset DC pulse power supply, the first magnesium alloy material is connected to the positive electrode of the DC pulse power supply as the anode, and the tank is connected to the negative electrode of the DC pulse power supply as the cathode; the micro-arc oxidation treatment solution includes sodium silicate 80g / L, sodium hydroxide 5g / L, sodium fluorosilicate 3g / L, and the pH value is controlled at 10.5; Using electrical parameters of 300V forward voltage, 15A / dm² current density, 800Hz frequency, and 50% duty cycle, the first magnesium alloy material was subjected to micro-arc oxidation treatment for 30 minutes, and the cooling water jacket temperature was controlled at 30℃. A ceramic layer was formed on the surface of the first magnesium alloy material to obtain the second magnesium alloy material. (12) Post-treatment: The second magnesium alloy material was sealed with boiling water for 10 min, and then the second magnesium alloy material was soaked in epoxy resin solution (10% epoxy resin and 90% acetone) for 8 min and cured at 60℃ for 40 min to obtain the second magnesium alloy material with the sealing treatment completed.

[0114] Example 3 (1) Pre-degreasing: using an alkaline solution (sodium hydroxide 30g / L, sodium carbonate 25g / L, sodium silicate 15g / L), at a temperature of 60℃, electrolytic treatment (current density 6A / dm³). 2 (12V voltage) Magnesium alloy substrate for 5 minutes; (2) Degreasing: Magnesium alloy special degreasing agent (12% fatty alcohol polyoxyethylene ether, 8% trisodium citrate, 5% benzotriazole) was used to soak the magnesium alloy substrate for 10 minutes at a temperature of 50℃ and a stirring speed of 30r / min. (3) First water wash: Use deionized water with a conductivity of 40 μS / cm to rinse the magnesium alloy substrate for 3 min at room temperature with a water flow rate of 1 m / s; (4) Pickling: Use a pickling solution containing 30 ml / L of 68% nitric acid and immerse the magnesium alloy substrate at room temperature for 20 seconds; (5) Secondary water washing: spray the magnesium alloy substrate with deionized water for 1 minute, and then soak the magnesium alloy substrate for 3 minutes. The pH of the surface is measured to be 6.5, confirming that the secondary water washing is completed. (6) Surface conditioning: The magnesium alloy substrate was immersed in a surface conditioning solution containing 400 ml / L of 68% nitric acid and 200 ml / L of 40% hydrofluoric acid for 1 min at room temperature; (7) Chemical conversion: The magnesium alloy matrix was treated with a chemical conversion treatment solution at 60°C for 12 min to obtain the first magnesium alloy material; wherein the chemical conversion treatment solution included sodium vanadate 20 g / L, sodium fluoride 20 g / L, ammonium fluoroborate 20 g / L, sodium nitrate 15 g / L, and citric acid 5 g / L. (8) Three water washes: The first magnesium alloy material was soaked in deionized water with a conductivity of 25 μS / cm for 5 min at a stirring speed of 20 r / min, and then the edges and corners of the first magnesium alloy material were rinsed with a high pressure spray of 0.2 MPa. (9) Drying: Use a hot air oven to dry the first magnesium alloy material at 60℃ for 10 minutes, and check the moisture content to be 0.2% to confirm that the drying is complete; (10) Pretreatment: The first magnesium alloy material was cleaned for 10 min by ultrasonic cleaning (frequency 50kHz, power 500W) at 60℃ using an alkaline degreasing agent (sodium hydroxide 20g / L, sodium dodecylbenzene sulfonate 8g / L); then rinsed with deionized water for 5 min, and the conductivity of the outflowing water was measured to be 42μS / cm, confirming that the cleaning was completed. (11) Micro-arc oxidation: The first magnesium alloy material is placed in a tank containing micro-arc oxidation treatment solution; wherein the first magnesium alloy material and the tank are respectively connected to a preset DC pulse power supply, the first magnesium alloy material is connected to the positive electrode of the DC pulse power supply as the anode, and the tank is connected to the negative electrode of the DC pulse power supply as the cathode; the micro-arc oxidation treatment solution includes sodium silicate 120g / L, sodium hydroxide 10g / L, sodium fluorosilicate 5g / L, and the pH value is controlled at 10.5; Using electrical parameters of 400V forward voltage, 10A / dm² current density, 500Hz frequency, and 30% duty cycle, the first magnesium alloy material was subjected to micro-arc oxidation treatment for 20 minutes, and the cooling water jacket temperature was controlled at 30℃. A ceramic layer was formed on the surface of the first magnesium alloy material to obtain the second magnesium alloy material. (12) Post-treatment: The second magnesium alloy material was sealed with boiling water for 15 minutes, and then the second magnesium alloy material was soaked in epoxy resin solution (15% epoxy resin and 85% acetone) for 5 minutes and cured at 80°C for 30 minutes to obtain the second magnesium alloy material with the sealing treatment completed.

[0115] Comparative Example 1 The magnesium alloy matrix was treated using an existing chromate conversion process. The process involved immersing the magnesium alloy matrix in a 5% chromic acid solution, treating it at 60°C for 10 minutes, and then drying it at 80°C to obtain the magnesium alloy material.

[0116] Appearance test Direct observation was conducted on the first and second magnesium alloy materials prepared in Examples 1-3. It was observed that the first magnesium alloy material prepared in Examples 1-3 was uniformly white, while the second magnesium alloy material was uniformly gray. Neither the first nor the second magnesium alloy material exhibited cracks or peeling. This demonstrates that the passivation film and ceramic layer in the first and second magnesium alloy materials prepared using the embodiments of this invention can tightly and uniformly coat the magnesium alloy substrate surface without cracking or peeling, effectively protecting the magnesium alloy and improving its corrosion resistance.

[0117] Furthermore, such as Figures 1-3 As shown, Figure 1 This is an external view of the magnesium alloy matrix. Figure 2 This is an appearance diagram of the first magnesium alloy material prepared in Example 1 of the present invention. Figure 3This is an appearance image of the second magnesium alloy material prepared according to Example 1 of the present invention. As can be seen from the appearance image, the magnesium alloy substrate itself is white with uneven gray patches on the surface. The first magnesium alloy material is whiter than the magnesium alloy substrate, and its surface color distribution is more uniform. This indicates that the passivation film formed by the first magnesium alloy material can uniformly coat the surface of the magnesium alloy substrate, exhibiting a stable structure and improving the corrosion resistance of the magnesium alloy material. The second magnesium alloy material is grayish, with a uniform surface color and no gray patches. This shows that, compared to the magnesium alloy substrate, the second magnesium alloy material can uniformly coat the surface of the first magnesium alloy material, further improving the corrosion resistance of the magnesium alloy material.

[0118] Furthermore, such as Figures 4-5 As shown, Figure 4 This is a scanning electron microscope image of the first magnesium alloy material prepared in Example 1 of the present invention. Figure 5 This is a scanning electron microscope (SEM) image of the second magnesium alloy material prepared in Example 1 of this invention. It can be seen that a continuous, uniform, and dense passivation film has formed on the surface of the first magnesium alloy material. The film layer completely covers the entire surface without any obvious exposed substrate area, exhibiting a dense appearance. Similarly, a continuous, uniform, and dense micro-arc oxide film has formed on the surface of the second magnesium alloy material. The film layer completely covers the entire surface without any obvious exposed substrate area, exhibiting a dense appearance.

[0119] Coolant corrosion test The magnesium alloy matrix, the first magnesium alloy material prepared in Example 1, and the second magnesium alloy material were respectively immersed in 750 mL of coolant, with an air flow rate of 100 ± 10 mL / min and a temperature of 88 ± 2 °C. They were then bonded to SWPCH35K steel and subjected to a galvanic corrosion test for 336 h. The results are as follows: Figures 6-11 As shown. The coolant consists of 45% ethylene glycol and 55% water, with the remainder being additives such as triethanolamine and phosphoric acid.

[0120] from Figures 6-8 As can be seen from the appearance images, the unprotected magnesium alloy substrate is severely corroded, with a darkened surface color and black spots. The first magnesium alloy material prepared in Example 1 shows slight corrosion, with black spots appearing in a few areas. The second magnesium alloy material prepared in Example 1 shows no obvious corrosion, and its surface remains smooth and clean.

[0121] from Figures 9-11 As can be seen from the metallographic diagram, Figure 9 The upper black area is the magnesium alloy substrate, and the lower half is the area where the magnesium alloy substrate has been corroded. It can be seen that the magnesium alloy substrate has been severely corroded and the surface has been severely damaged. Figure 10 The lower black area is the magnesium alloy substrate, and the upper gray area is the passivation film. Figure 11The upper black area is the magnesium alloy substrate, and the lower gray area is the passivation film and ceramic layer. It can be seen that the interiors of the first and second magnesium alloy materials are basically uncorroded.

[0122] It can be seen that the magnesium alloy material prepared by the magnesium alloy material preparation method provided in the embodiments of the present invention can effectively improve the corrosion resistance of magnesium alloy, and is particularly suitable for vehicle drive systems. The second magnesium alloy material can remain corrosion-free in the environment of the internal water channels of the drive system and has excellent corrosion resistance.

[0123] Film thickness detection Metallographic images of Examples 1-3 and Comparative Example 1 were taken using a metallographic microscope, and the thickness of the film layer on the surface of the magnesium alloy substrate was measured based on the metallographic images. The results are shown in Table 1.

[0124] Table 1. Film thickness on magnesium alloy substrate surface

[0125] As can be seen, the first magnesium alloy material and the second magnesium alloy material prepared in Examples 1 to 3 have a film thickness on the surface of the magnesium alloy substrate that is significantly thicker than that of the comparative example. Compared with the comparative example, they can provide better protection for the magnesium alloy and improve the corrosion resistance of the magnesium alloy material.

[0126] Neutral salt spray test The corrosion was tested according to GB / T 10125-2012 "Artificial Atmosphere Corrosion Test - Salt Spray Test". A sodium chloride solution with a concentration of 50 g / L ± 5 g / L was sprayed in a neutral salt spray chamber, and the temperature was maintained at 35℃ ± 2℃. The corrosion of Examples 1-3 and Comparative Example 1 was evaluated. The results are shown in Table 2.

[0127] Table 2 Results of neutral salt spray test

[0128] As can be seen, the first magnesium alloy material and the second magnesium alloy material prepared in Examples 1 to 3 respectively, the first magnesium alloy material can remain corrosion-free for 72 hours and the second magnesium alloy material can remain corrosion-free for 1000 hours. Compared with the comparative example, the corrosion resistance of both is significantly improved and they are suitable for vehicle drive systems. The corrosion resistance of the second magnesium alloy material is even better than that of the first magnesium alloy material, and it is even more suitable for the internal water channels of vehicle drive systems.

[0129] Double 85 test The aging degree of Examples 1-3 and Comparative Example 1 was evaluated under the environmental conditions of 85°C and 85% humidity. The results are shown in Table 3.

[0130] Table 3. Results of the Double 85 Test

[0131] As can be seen, the first magnesium alloy material and the second magnesium alloy material prepared in Examples 1-3 respectively, the first magnesium alloy material can remain unchanged for 240 hours and the second magnesium alloy material can remain unchanged for 1000 hours. Compared with the comparative example, the corrosion resistance of both is significantly improved and they are suitable for vehicle drive systems. The corrosion resistance of the second magnesium alloy material is even better than that of the first magnesium alloy material, and it is even more suitable for use in the internal water channels of vehicle drive systems.

[0132] Hardness test The Vickers hardness test was conducted according to GB / T4340.1 "Metallic materials - Vickers hardness test - Part 1: Test method". A diamond square pyramid indenter with a vertex angle of 136° was used to press into the surface of the second magnesium alloy materials prepared in Examples 1-3, respectively. The hardness was calculated by measuring the diagonal length of the indentation. The results are shown in Table 4.

[0133] Table 4 Hardness Test Results

[0134] As can be seen, the second magnesium alloy materials prepared in Examples 1-3 have a hardness greater than 375 HV. This hardness can effectively protect the second magnesium alloy material from damage in the internal water channel environment of the vehicle drive system, improve the corrosion resistance of the second magnesium alloy material, and make the second magnesium alloy material suitable for the internal water channel of the vehicle drive system.

[0135] The above embodiments are merely preferred embodiments provided to fully illustrate the present invention, and the scope of protection of the present invention is not limited thereto. Equivalent substitutions or modifications made by those skilled in the art based on the present invention are all within the scope of protection of the present invention.

Claims

1. A method for preparing a magnesium alloy material, characterized in that, The method includes: Obtain a chemical conversion treatment solution; the chemical conversion treatment solution includes sodium vanadate 10g / L~20g / L, sodium fluoride 10g / L-20g / L, and ammonium fluoroborate 15g / L~20g / L; The magnesium alloy substrate is placed in the chemical conversion treatment solution for treatment, and a passivation film is formed on the surface of the magnesium alloy substrate to obtain the first magnesium alloy material.

2. The method according to claim 1, characterized in that, The chemical conversion treatment solution also includes an oxidant of 10 g / L to 15 g / L and a complexing agent of 5 g / L to 8 g / L.

3. The method according to claim 2, characterized in that, The oxidant is at least one of sodium nitrate, sodium molybdate, sodium persulfate, and potassium permanganate, and the complexing agent is at least one of sodium citrate, tartaric acid, phytic acid, and oxalic acid.

4. The method according to claim 1, characterized in that, The step of immersing the magnesium alloy substrate in the chemical conversion treatment solution to form a passivation film on the surface of the magnesium alloy substrate to obtain the first magnesium alloy material includes: The magnesium alloy matrix is ​​placed in the chemical conversion treatment solution and treated at 55℃~65℃ for 12~15 minutes to obtain the first magnesium alloy material.

5. The method according to claim 1, characterized in that, Prior to the step of obtaining the chemical conversion treatment solution, the method further includes: The magnesium alloy substrate is cleaned; The cleaned magnesium alloy substrate is then surface-adjusted to obtain a surface-adjusted magnesium alloy substrate.

6. The method according to claim 5, characterized in that, The step of cleaning the magnesium alloy substrate includes at least one of the following steps: The magnesium alloy substrate is pre-degreased using at least one of alkaline solution cleaning, electrolysis, and ultrasonic methods. The magnesium alloy matrix was degreased using a magnesium alloy degreasing agent; The magnesium alloy matrix was washed once with deionized water. The magnesium alloy substrate was pickled using a pickling solution; The magnesium alloy matrix was subjected to a second water wash using deionized water.

7. The method according to claim 5, characterized in that, The step of performing surface conditioning on the cleaned magnesium alloy substrate to obtain a surface-conditioned magnesium alloy substrate includes: Obtain a surface conditioning solution; the surface conditioning solution comprises a 68% nitric acid solution with a concentration of 200 ml / L to 400 ml / L, a 40% hydrofluoric acid solution with a concentration of 100 ml / L to 200 ml / L, and the remainder is deionized water; The cleaned magnesium alloy substrate is immersed in the surface conditioning solution at room temperature for 1 to 3 minutes to obtain a surface-conditioned magnesium alloy substrate.

8. The method according to claim 1, characterized in that, The method further includes: The first magnesium alloy material was washed with deionized water; The first magnesium alloy material after washing is dried.

9. The method according to any one of claims 1 to 8, characterized in that, The method further includes: Obtain the micro-arc oxidation treatment solution; The first magnesium alloy material is placed in the micro-arc oxidation treatment solution to perform micro-arc oxidation treatment on the first magnesium alloy material, forming a ceramic layer on the surface of the first magnesium alloy material to obtain the second magnesium alloy material.

10. The method according to claim 9, characterized in that, The micro-arc oxidation treatment solution comprises sodium silicate 80g / L~120g / L, sodium hydroxide 5g / L~10g / L, and sodium fluorosilicate 3g / L~5g / L.

11. The method according to claim 9, characterized in that, The pH value of the micro-arc oxidation treatment solution is 10~11, and the temperature is less than or equal to 35℃.

12. The method according to claim 9, characterized in that, The step of placing the first magnesium alloy material in the micro-arc oxidation treatment solution to perform micro-arc oxidation treatment on the first magnesium alloy material, forming a ceramic layer on the surface of the first magnesium alloy material, and obtaining the second magnesium alloy material includes: The first magnesium alloy material is placed in a tank containing the micro-arc oxidation treatment liquid; wherein the first magnesium alloy material and the tank are respectively connected to a preset DC pulse power supply, the first magnesium alloy material is connected as the anode to the positive terminal of the DC pulse power supply, and the tank is connected as the cathode to the negative terminal of the DC pulse power supply. Using a forward voltage of 300V~400V and a forward current density of 10A / dm² 2 ~15A / dm 2 The first magnesium alloy material is subjected to micro-arc oxidation treatment for 20 to 30 minutes with electrical parameters of pulse frequency of 500 Hz to 800 Hz and duty cycle of 30% to 50%, forming a ceramic layer on the surface of the first magnesium alloy material to obtain the second magnesium alloy material.

13. The method according to claim 9, characterized in that, The method further includes: The ceramic layer on the surface of the second magnesium alloy material is sealed.

14. The method according to claim 13, characterized in that, The step of sealing the ceramic layer on the surface of the second magnesium alloy material includes: The second magnesium alloy material is immersed in deionized water at 100°C to seal the pores of the ceramic layer on the surface of the second magnesium alloy material; and / or, The second magnesium alloy material is immersed in an organic solution, and the organic solution seals the pores of the ceramic layer on the surface of the second magnesium alloy material.

15. The method according to claim 5, characterized in that, Prior to the step of obtaining the micro-arc oxidation treatment solution, the method further includes: The first magnesium alloy material is subjected to a decontamination treatment; The first magnesium alloy material, after being decontaminated, is cleaned.

16. A magnesium alloy material, characterized in that, The magnesium alloy material is prepared by the preparation method of magnesium alloy material as described in any one of claims 1 to 15.

17. A drive system, characterized in that, The drive system includes an outer housing and / or an internal water channel, the outer housing comprising a first magnesium alloy material as described in any one of claims 1 to 8, and the internal water channel comprising a second magnesium alloy material as described in any one of claims 9 to 15.

Images