Magnesium alloy plating layer preparation method and magnesium alloy plating layer

Abstract

The invention discloses a preparation method of a magnesium alloy plating layer and the magnesium alloy plating layer. The preparation method of the magnesium alloy plating layer comprises a material preparation step, an assembly step, a preparation step, a film plating step and a sampling step. Preparing materials: providing a magnesium alloy sample, an aluminum-magnesium alloy target, a yttrium metal target and a plating device; assembling: a plating device is provided with a tray, a plating cavity and two target material seats, the magnesium alloy is arranged on the tray, and the aluminum magnesium alloy target and the yttrium metal target are respectively mounted on different target material seats; preparing: sealing the plating cavity, vacuumizing the plating cavity, and injecting ionization gas into the plating cavity; coating: heating the coating cavity, and applying power to the two target material seats, so that the aluminum-magnesium alloy target and the yttrium metal target are sputtered to the magnesium alloy sample; and sampling: cooling the plating cavity to room temperature. According to the preparation method of the magnesium alloy plating layer, the blunt magnesium alloy plating layer relative to the anode is obtained on the surface of the magnesium alloy sample, barrier protection and cathode protection are carried out on the magnesium alloy sample, and the corrosion resistance of the magnesium alloy sample is improved.

Description

Technical Field

[0001] This invention relates to the technical field of metal material coating, and particularly to a method for preparing a magnesium alloy coating and a magnesium alloy coating. Background Technology

[0002] Magnesium alloys exhibit poor corrosion resistance due to their high chemical reactivity, particularly in humid or saline environments. Therefore, it is necessary to coat magnesium alloys with an anti-corrosion layer to improve their corrosion resistance. However, in related technologies, during the coating process, a porous structure is formed in the coating layer. This leads to a galvanic effect between the magnesium alloy and the coating layer, resulting in corrosion of the magnesium alloy and damage to the coating layer. Summary of the Invention

[0003] The present invention aims to at least solve one of the technical problems existing in the prior art. To this end, the present invention proposes a method for preparing a magnesium alloy coating, which can obtain a passive magnesium alloy coating with a relative anodic effect on the surface of a magnesium alloy sample, improve the integrity and corrosion resistance of the coating, enable the coated magnesium alloy sample to provide barrier protection and cathodic protection, and improve the corrosion resistance of the magnesium alloy sample.

[0004] The present invention also proposes a magnesium alloy coating having the above-mentioned method for preparing magnesium alloy coating.

[0005] According to a first aspect of the present invention, the method for preparing a magnesium alloy coating includes a material preparation step, an assembly step, a preparatory step, a coating step, and a sampling step.

[0006] Materials preparation: Provide magnesium alloy samples, aluminum-magnesium alloy targets, yttrium metal targets, and plating equipment, wherein the magnesium alloy samples are plating substrates; Assembly: The plating device has a tray, a plating cavity and two target holders. The tray and the two target holders are disposed in the plating cavity. The magnesium alloy sample is placed on the tray, and the aluminum-magnesium alloy target and the yttrium metal target are respectively installed in the different target holders. Preparation: Seal the plating chamber, evacuate the plating chamber, and inject ionized gas into the plating chamber; Coating: The coating chamber is heated, and power is applied to the two target holders to sputter the aluminum-magnesium alloy target and the yttrium metal target onto the magnesium alloy sample to form a coating layer combining magnesium, yttrium and aluminum on the surface of the magnesium alloy sample; Sampling: After cooling the plating chamber to room temperature, take out the magnesium alloy sample with the plating layer.

[0007] The method for preparing a magnesium alloy coating according to embodiments of the present invention has at least the following beneficial effects: A magnesium-yttrium-aluminum (Mg-Y-Al) coating is formed on the surface of a magnesium alloy by co-sputtering with an aluminum-magnesium alloy target and a yttrium metal target. Because the Mg-Y-Al coating possesses passivation and repair capabilities, it can self-repair when it cracks, thereby improving the integrity of the coating and its barrier protection for the magnesium alloy substrate. Furthermore, since the corrosion potential of the coating is lower than that of the magnesium alloy, when the magnesium alloy sample is exposed and a galvanic effect occurs, the coating provides cathodic protection to the magnesium alloy substrate, further protecting the magnesium alloy.

[0008] According to some embodiments of the present invention, the method for preparing the magnesium alloy coating further includes a pretreatment step, which is located between the assembly step and the material preparation step. In the pretreatment step, the magnesium alloy sample is sequentially ground, polished, rinsed and dried.

[0009] According to some embodiments of the present invention, in the coating step, when sputtering the aluminum-magnesium alloy target and the yttrium metal target onto the magnesium alloy sample, the tray used to hold the magnesium alloy sample is rotated, so that the magnesium alloy sample rotates relative to the target holder.

[0010] According to some embodiments of the present invention, in the aluminum-magnesium alloy target, the atomic percentage of aluminum is between 1% and 99%, the atomic percentage of iron is less than 0.2%, the atomic percentage of copper is less than 0.2%, and the sum of the atomic percentages of zinc, manganese and silicon is not greater than 10%.

[0011] According to some embodiments of the present invention, in the coating layer, the atomic percentage of magnesium is between 30% and 90%, the atomic percentage of yttrium is between 1% and 70%, the atomic percentage of aluminum is between 1% and 20%, and the sum of the atomic percentages of iron, copper, zinc, manganese and silicon is not greater than 10%.

[0012] According to some embodiments of the present invention, in the preparatory step, the injected ionized gas is argon.

[0013] According to some embodiments of the present invention, the argon gas injection flow rate is from 10 standard cubic centimeters per minute to 90 standard cubic centimeters per minute; The air pressure value of the plating chamber is 10. -4 Pa to 10 -3 Pa.

[0014] According to some embodiments of the present invention, in the coating step, the power applied to the target holder on which the aluminum-magnesium alloy target is mounted is 10 watts to 300 watts, and the power applied to the target holder on which the yttrium metal target is mounted is 10 watts to 300 watts.

[0015] According to some embodiments of the present invention, in the coating step, the temperature of the coating chamber is heated to 20 degrees Celsius to 300 degrees Celsius.

[0016] According to a second aspect of the present invention, the magnesium alloy plating layer is prepared by the magnesium alloy plating layer preparation method described in any of the above embodiments, and the magnesium alloy plating layer includes magnesium, yttrium and aluminum.

[0017] The magnesium alloy coating according to embodiments of the present invention has at least the following beneficial effects: the magnesium alloy coating protects the surface of the magnesium alloy. Since the corrosion potential of the coating is lower than that of the magnesium alloy, the coating will corrode first when a galvanic effect occurs, thereby improving the corrosion resistance of the magnesium alloy.

[0018] Additional aspects and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Attached Figure Description

[0019] The present invention will be further described below with reference to the accompanying drawings and embodiments, wherein: Figure 1 This is a schematic flowchart of the magnesium alloy coating preparation method in an embodiment of the present invention; Figure 2 This is a schematic diagram showing the power supply used in the coating step and the elemental composition of the coating obtained by scanning the coating layer with an energy dispersive spectroscopy (EDS) instrument in an embodiment of the present invention. Figure 3 This is a surface morphology image of an AZ91 magnesium alloy with a coating layer on its surface after being immersed in artificial seawater (ASTM D1141-98 standard) for 7 days in an embodiment of the present invention. Figure 4 The following is a diagram showing the potentiodynamic polarization curves of AZ91 magnesium alloy, pure magnesium, pure yttrium, and AZ91 magnesium alloy with surface coating in artificial seawater in an embodiment of the present invention. Figure 5 In this embodiment of the invention, after the coating layer is prepared on the surface of AZ91 magnesium alloy, the coating layer is scratched. The impedance spectrum of the exposed coating substrate at the scratched area (left image) and the surface image after immersion for 5 days (right image) are shown. Figure 6The figures show the volume diagram (left side) and the change diagram (right side) of hydrogen evolution in artificial seawater for AZ91 magnesium alloy with a coating layer on its surface in an embodiment of the present invention. Detailed Implementation

[0020] Embodiments of the present invention are described in detail below. Examples of these embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and should not be construed as limiting the present invention.

[0021] In the description of this invention, it should be understood that the orientation descriptions, such as up, down, front, back, left, right, etc., are based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limiting this invention.

[0022] In the description of this invention, "several" means one or more, "multiple" means two or more, "greater than," "less than," and "exceeding" are understood to exclude the stated number, while "above," "below," and "within" are understood to include the stated number. The use of "first" and "second" in the description is merely for distinguishing technical features and should not be construed as indicating or implying relative importance, or implicitly indicating the number of indicated technical features, or implicitly indicating the order of the indicated technical features.

[0023] In the description of this invention, unless otherwise explicitly defined, terms such as "set up," "install," and "connect" should be interpreted broadly, and those skilled in the art can reasonably determine the specific meaning of the above terms in this invention in conjunction with the specific content of the technical solution.

[0024] In the description of this invention, the terms "one embodiment," "some embodiments," "illustrative embodiment," "example," "specific example," or "some examples," etc., refer to specific features, structures, materials, or characteristics described in connection with that embodiment or example, which are included in at least one embodiment or example of the invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0025] The preparation method of the magnesium alloy coating according to the first aspect of the present invention and the magnesium alloy coating according to the second aspect of the present invention will be described below with reference to the accompanying drawings.

[0026] The first aspect of this invention provides a method for preparing a magnesium alloy coating, which is used to prepare a magnesium alloy plating layer. (See attached document.) Figure 1 As shown, the method for preparing a magnesium alloy coating includes a material preparation step S100, an assembly step S300, a preparatory step S400, a coating step S500, and a sampling step S600. The specific steps are as follows: S100. Material Preparation: Prepare the magnesium alloy sample to be used as the coating substrate, and also prepare the aluminum-magnesium alloy target, yttrium metal target, and coating apparatus. The coating apparatus includes a tray, a coating chamber, and a target holder. The tray is used to mount the magnesium alloy sample. The coating chamber is where the anti-corrosion layer is coated onto the magnesium alloy sample.

[0027] S300, Assembly: Place the magnesium alloy sample on the tray of the coating apparatus, and install the aluminum-magnesium alloy target and the yttrium metal target on two different target holders within the coating chamber. The aluminum-magnesium alloy target and the yttrium metal target are positioned facing the magnesium alloy sample so that they can be sputtered together onto the sample, thereby forming an anti-corrosion coating layer on the surface of the magnesium alloy sample. The aluminum-magnesium alloy target can also be divided into one magnesium target and one aluminum target, each installed on a different target position within the coating chamber. That is, the target holder for the aluminum-magnesium alloy target can be further divided into a first target position and a second target position. The first target position is for the magnesium target, and the second target position is for the aluminum target. During sputtering, the magnesium target and the aluminum target are sputtered together to form the aluminum-magnesium alloy.

[0028] S400, Preparation: After the components are assembled, the plating chamber is sealed to fix the magnesium alloy sample inside. Then, the inside of the plating chamber is evacuated to remove air and impurity gases. Subsequently, ionized gas (usually an inert gas) is introduced into the plating chamber to provide a plasma plating environment for the magnesium alloy sample.

[0029] S500, Coating: The coating chamber is heated, and power is applied to the two target holders to co-sputter the aluminum-magnesium alloy target and the yttrium metal target onto the magnesium alloy sample, forming a coating layer composed of magnesium, yttrium, and aluminum on the surface of the magnesium alloy sample. Specifically, the coating chamber is heated while maintaining an ionized gas atmosphere. Heating the coating chamber improves the density of the coating layer, thus promoting its corrosion resistance. After the coating chamber is heated to a specified temperature, power is applied to the two target holders, causing the aluminum-magnesium alloy target and the yttrium metal target to co-sputter and form a coating film on the surface of the magnesium alloy sample. During the coating process, magnesium and aluminum atoms from the aluminum-magnesium alloy target and yttrium atoms from the yttrium metal target are co-deposited on the surface of the magnesium alloy substrate, thereby forming a coating layer containing magnesium, yttrium, and aluminum on the surface of the magnesium alloy sample. When the aluminum-magnesium alloy target is divided into a magnesium target and an aluminum target and installed on two different target positions in the coating cavity, the different power applied to them can be adjusted to adjust the sputtering deposition rate of magnesium and aluminum, thereby adjusting the magnesium and aluminum content of the coating layer.

[0030] S600, Sampling: After the plating chamber has cooled to room temperature, open the plating chamber and take out the magnesium alloy sample with the plating layer formed on the surface.

[0031] Specifically, in one embodiment, when coating a magnesium alloy sample, the magnesium alloy sample is first selected as the coating substrate, and an aluminum-magnesium alloy target, a yttrium metal target, and a coating apparatus are prepared. The coating substrate is then mounted on a tray, and the target is mounted in a target holder. The relative positions of the target holder and the coating substrate are adjusted so that the surface of the magnesium alloy sample to be coated faces the aluminum-magnesium alloy target and the yttrium metal target. Next, the coating chamber is sealed, and a vacuum device is activated to evacuate the chamber, creating a vacuum state to remove air, moisture, and other impurities. Then, an inert gas (such as argon) is introduced into the coating chamber as the working gas to place the magnesium alloy sample in a plasma atmosphere. After maintaining the inert gas atmosphere, the coating chamber is heated to improve the adhesion and density of the coating layer during the coating process. After heating, power is applied to the two targets; the power can be DC, radio frequency, or pulsed. In this embodiment, the power is in DC mode. This allows for simultaneous sputtering of the aluminum-magnesium alloy target and the yttrium metal target, forming a coating on the surface of the magnesium alloy sample. Finally, after the coating process is complete, the coating chamber is cooled to room temperature. The coated magnesium alloy substrate is then removed from the coating chamber. The magnesium alloy sample is now ready for subsequent applications or testing.

[0032] Compared to related technologies, the plating layer often exhibits a porous structure, exposing the magnesium alloy substrate and leading to a galvanic effect between the magnesium alloy and the plating layer, thus corroding the magnesium alloy. The magnesium alloy plating layer preparation method of this invention involves co-sputtering an aluminum-magnesium alloy target with a yttrium metal target to form a magnesium-yttrium-aluminum (Mg-Y-Al) plating layer on the surface of a magnesium alloy sample. Because the Mg-Y-Al plating layer possesses repair capabilities, it can self-repair when it cracks, protecting the magnesium alloy sample and improving both the corrosion resistance of the magnesium alloy sample and the integrity of the plating layer. Furthermore, since the corrosion potential of the plating layer is lower than that of the magnesium alloy sample, when the magnesium alloy sample is exposed and a galvanic effect occurs, the plating layer will corrode before the magnesium alloy substrate, thereby reducing the galvanic effect between the magnesium alloy sample and the plating layer and further protecting the magnesium alloy sample.

[0033] In some embodiments, see Figure 1 As shown, the preparation of the anti-corrosion magnesium alloy coating also includes a pretreatment step. The pretreatment step S200 is located between the material preparation step S100 and the assembly step S300. In the pretreatment step S200, the magnesium alloy sample, which serves as the coating substrate, undergoes surface cleaning and activation, specifically including sequential grinding, polishing, rinsing, and drying operations.

[0034] Specifically, in pretreatment step S200, the surface of the magnesium alloy sample is first polished to remove oxide films, oil stains, or defects. Then, the magnesium alloy sample is polished to further reduce surface roughness and minimize marks left from polishing. Next, the polished magnesium alloy sample is rinsed to remove residual abrasive particles, polishing fluid, and other impurities. Rinsing can be done using solutions such as alcohol or ether. Finally, the rinsed magnesium alloy sample is placed in an oven or drying environment to remove liquid from its surface, preventing evaporation that could affect the vacuum level of the plating chamber or cause defects such as porosity in the plating layer.

[0035] In some embodiments, during the coating step S500, while sputtering the aluminum-magnesium alloy target and the yttrium metal target, a tray used to support the magnesium alloy substrate is rotated about the central axis of the coating chamber, so that the magnesium alloy sample rotates continuously relative to the two target seats, thereby allowing multiple surfaces of the magnesium alloy sample to be coated to improve the coating efficiency of the magnesium alloy sample.

[0036] Specifically, the tray is connected to a drive mechanism (such as a stepper motor or servo motor), which can rotate the tray. If the magnesium alloy sample needs to be coated on multiple surfaces, rotating the tray allows the magnesium alloy sample surface to periodically pass through the sputtering coverage areas of each target material during sputtering of aluminum-magnesium alloy and yttrium metal targets, thereby achieving deposition on multiple surfaces of the magnesium alloy sample. In this embodiment, the tray rotates at a constant speed, which avoids problems such as uneven coating thickness or elemental segregation caused by changes in the tray speed, thus improving the coating quality of the magnesium alloy sample.

[0037] In some embodiments, the atomic percentage of aluminum in the aluminum-magnesium alloy target is between 1% and 99%, the atomic percentage of iron is less than 0.2%, the atomic percentage of copper is less than 0.2%, and the combined atomic percentages of zinc, manganese, and silicon do not exceed 10%. In this embodiment, the aluminum-magnesium alloy target can actually use commercially available aluminum-containing magnesium alloys, such as AZ31, AZ61, AM60, AM80, and AZ91. The atomic percentage of aluminum can be 1%, 2%, 20%, 50%, or 99%, the atomic percentage of copper can be 0.1%, 0.15%, or 0.2%, and the sum of the atomic percentages of zinc, manganese, and silicon can be 0%, 1%, 5%, or 10%. Specifically, since the aluminum-magnesium alloy target is mainly based on magnesium, aluminum can improve the reactivity of sputtered particles and promote the density of the coating. Simultaneously, aluminum can improve the thermal stability and passivation ability of the coating, thereby improving its corrosion resistance. Specifically, if the aluminum content is below 1 at.%, the passivation ability of the coating will decrease, leading to a reduction in its corrosion resistance. If the aluminum content exceeds 99 at.%, the magnesium content in the coating will decrease, potentially causing the corrosion potential of the coating to be higher than that of the magnesium alloy sample, resulting in galvanic corrosion of the magnesium alloy sample. If the atomic percentage content of other elements (zinc, manganese, and silicon) is higher than 10%, the corrosion resistance of the coating will also decrease.

[0038] Furthermore, in some embodiments, in the coating layer, the atomic percentage of magnesium is between 30% and 90%, the atomic percentage of yttrium is between 1% and 70%, the atomic percentage of aluminum is between 1% and 20%, and the atomic percentage of other elements (iron, copper, zinc, manganese, and silicon) is between 0% and 10%. Specifically, the atomic percentage of magnesium can be 30%, 40%, 60%, or 90%; the atomic percentage of yttrium can be 1%, 2%, 20%, 50%, or 70%; the atomic percentage of aluminum can be 1%, 10%, 15%, or 20%; and the atomic percentage of other elements (iron, copper, zinc, manganese, and silicon) can be 0%, 0.5%, 1%, 5%, or 20%.

[0039] Specifically, controlling the magnesium content between 30% and 90% allows for the formation of uniform nanocrystals with yttrium (Y), improving the compatibility between the coating and the magnesium alloy substrate. Since magnesium alloys are active metals, they can participate in the passivation reaction during corrosion, thereby enhancing the self-healing ability of yttrium and aluminum atoms. If the magnesium content is below 30%, the coating cannot form uniform fine grains, potentially leading to poor compatibility between the coating and the magnesium alloy substrate. If the magnesium content exceeds 90%, the coating becomes too active, reducing its protective and corrosion-resistant capabilities. Secondly, setting the yttrium content between 1% and 70% allows yttrium atoms to react with moisture or oxygen to form the primary passivation layer (such as Y₂O₃ or Y(OH)₃), enabling repair when the coating cracks. If the yttrium content is below 1%, the corrosion resistance of the coating will decrease. If the yttrium content exceeds 70%, the uniform nanocrystals on the surface will grow into larger grains, leading to microgalvanic corrosion between the grains. Finally, limiting the aluminum content to 1%–20% can improve the deposition of yttrium (Y) on the magnesium alloy sample surface and allow aluminum to react and form oxides such as Al₂O₃, thereby improving the density and self-healing properties of the coating. If the content of other elements (iron, copper, zinc, manganese, and silicon) exceeds 10%, it will affect the formation of the passivation film and reduce its corrosion resistance.

[0040] In some embodiments, in the preparatory step S400, the ionized gas introduced into the plating chamber is argon (Ar). Specifically, during the plating process, since the magnesium alloy sample is placed in an argon atmosphere, after applying power to the aluminum-magnesium alloy target and the yttrium metal target, the argon gas can be ionized to form argon ions (Ar). +Argon is used to transfer momentum to aluminum-magnesium alloy and yttrium metal targets, thereby improving the sputtering efficiency of these targets. Furthermore, since argon does not chemically react with the target material or the substrate, it avoids argon adhering to the surface of the magnesium alloy sample, thus improving the purity of the coating (Mg-Y-Al) and enhancing its corrosion resistance.

[0041] In one illustrative embodiment, the injection gas flow rate of argon (Ar) is between 10 standard cubic centimeters per minute (sccm) and 90 standard cubic centimeters per minute (sccm). The gas flow rate can be values ​​such as 10 sccm, 20 sccm, 50 sccm, or 90 sccm.

[0042] Specifically, maintaining an argon flow rate between 10 and 90 standard cubic centimeters per minute (sccm) improves plasma density balance and enhances gas scattering. If the argon flow rate is below 10 sccm, the argon needs to be ionized during the coating process; therefore, a low flow rate leads to lower ionization stability or less energy acting on the target atoms, affecting the coating's forming efficiency and continuity. If the argon flow rate is above 90 sccm, the pressure in the coating chamber becomes too high, resulting in more ionized argon molecules. During sputtering, magnesium, yttrium, and aluminum atoms are sputtered onto the surface of the magnesium alloy sample. An excessively high flow rate increases the probability of collisions between ionized gas molecules and sputtered particles, leading to uneven sputtered coatings and defects such as looseness or porosity.

[0043] Furthermore, when the plating chamber is evacuated, the air pressure value of the plating chamber is between 10... -4 Pa to 10 -3 Between 10 and 10 Pa. The air pressure value can be 10. -4 Pa, 2*10 -4 Pa or 10 -3 The values ​​are Pa, etc. Specifically, the plating cavity is kept at 10. -4 Pa to 10 -3 Within a pressure range of Pa, air, water vapor, and other reactive impurities can be removed from the coating chamber, thus preventing impurities from reacting on the target material or deposited atoms during the sputtering process and affecting the purity and composition of the coating layer. However, if the vacuum level in the coating chamber is too low (e.g., pressure higher than 10 Pa),... - If the vacuum level in the plating chamber is too high (e.g., the pressure is below 10 Pa), impurities will remain in the plating chamber, affecting the quality of the plating layer. -4 If the pressure is below a certain level (e.g., 10 Pa), it will prolong the evacuation time of the plating chamber, thereby reducing the plating efficiency. Furthermore, a lower pressure will reduce the stability of the subsequently introduced ionized gas.

[0044] In one example, in the coating step S500, the power applied to the target holder on which the aluminum-magnesium alloy target and the yttrium metal target are mounted is between 10 watts and 300 watts. The power can be 10 watts, 20 watts, 50 watts, 200 watts, or 300 watts, etc. Specifically, because aluminum-magnesium alloy has better conductivity than yttrium metal, the power applied to the aluminum-magnesium alloy target is less than that applied to the yttrium metal target. Maintaining the power between 10 watts and 300 watts improves the discharge efficiency of the target and the uniformity of sputtering. If the target power is less than 10 watts, the sputtering yield will be too low, resulting in a low content of the target element in the coating layer, leading to component deficiencies and reduced protective effect of the coating layer. If the power of the target exceeds 300 watts, it will cause the local temperature of the target holder to be too high, which will increase the melting of the target sputtering and pose a risk of the coating peeling off after the metal element is plated on the magnesium alloy sample.

[0045] It is understood that in some embodiments, during the coating step S500, when heating the coating chamber, the temperature of the coating chamber is controlled between 20 degrees Celsius and 300 degrees Celsius. The temperature of the coating chamber can be 20 degrees Celsius, 50 degrees Celsius, 200 degrees Celsius, or 300 degrees Celsius, etc.

[0046] Specifically, since magnesium alloys are heat-sensitive metals, maintaining a temperature between 20°C and 300°C helps preserve the integrity of the magnesium alloy sample and prevents thermal deformation. This temperature range also enhances atomic migration on the magnesium alloy sample surface, thereby improving the adhesion between the coating and the sample. If the coating chamber temperature is below 20°C, the bonding and migration rates between magnesium, yttrium, and aluminum atoms during sputtering may decrease, affecting the density of the coating and its adhesion to the magnesium alloy sample. If the coating chamber temperature is above 300°C, it can lead to thermal deformation of the magnesium alloy substrate and segregation of the target material, affecting the formation of the coating.

[0047] Specifically, in one example, AZ91 magnesium alloy is used as the plating substrate. In practice, AZ91 magnesium alloy, an aluminum-magnesium alloy target, a yttrium metal target, and a plating apparatus are prepared in advance. The AZ91 magnesium alloy is then ground and polished, rinsed with alcohol, dried, and placed on the tray of the plating apparatus. Next, the aluminum-magnesium alloy target is installed on one of the target holders of the plating apparatus, and the yttrium metal target is installed on the other. In this embodiment, the aluminum-magnesium alloy target is specifically an AZ61 magnesium alloy target, and the yttrium metal target is a target material with a purity greater than 99.9%.

[0048] When preparing for coating, the coating chamber should be closed first, then the cooling water circulation system should be turned on and a mechanical pump should be used to pre-evacuate the chamber. When the vacuum level in the coating chamber is lower than 1 Pa, a molecular pump should be switched to continue evacuating the chamber until the air pressure in the coating chamber reaches 5.0 × 10⁻⁶. -4 Pa. Then the argon valve is opened. In this embodiment, the argon flow rate is adjusted to 35 standard cubic centimeters per minute, the rotation speed of the tray supporting the AZ91 magnesium alloy is set to 10 revolutions per minute, and the heating temperature of the plating chamber is set to 175 degrees Celsius.

[0049] See Figure 2 As shown in the table, this embodiment conducted six sets of experiments. One set used only an aluminum-magnesium alloy target to coat the AZ91 magnesium alloy, four sets used both aluminum-magnesium alloy and yttrium metal targets to coat the AZ91 magnesium alloy, and the power input to the yttrium metal target increased progressively in the four sets. The coating time was uniformly 4200 s. The final coating thickness on the AZ91 surface was approximately 3 μm. After the AZ91 magnesium alloy cooled to room temperature, it was removed from the coating chamber for testing. The materials in Table 1 are the elemental composition of the magnesium alloy coating obtained by energy dispersive spectroscopy (EDS). The percentage of elements contained in the coating varied under different power inputs.

[0050] See Figure 3 As shown, after immersing AZ91 magnesium alloy with a coating (Mg-Y-Al coating) for 7 days, the surface morphology of the AZ91 magnesium alloy shows that after 7 days of corrosion, the first group of Mg... 95 Al5 exhibits severe surface corrosion, with obvious cracks in the surface coating. Under high magnification, a network oxide film appears on the surface, which does not meet corrosion protection requirements; Mg 82 Y 14 Al4 has fewer corrosion products on its surface, and its surface appears uneven under high magnification; Mg 63 Y 34 Al3 exhibits fewer corrosion products on its surface, and at high magnification, it shows a dense, void-free surface with extremely fine and uniform grains; Mg 46 Y 51 Al3 surface shows almost no corrosion product accumulation; however, high magnification reveals surface porosity and the presence of both large and fine grains; Mg 36 Y 62 Al2 exhibits fewer surface corrosion products, but numerous pinholes are visible under high magnification; only sputtered Y shows surface cracks, exposing the substrate. This indicates that combining magnesium, yttrium, and aluminum can reduce surface corrosion products in magnesium alloys, resulting in a coating with good corrosion resistance and thus improving the corrosion resistance of magnesium alloys.

[0051] See Figure 4 As shown, AZ91 magnesium alloy with a coating (Mg-Y-Al coating), pure metallic magnesium, and AZ91 magnesium alloy were placed in artificial seawater, and the potentiodynamic polarization curves of each material were analyzed. The potentiodynamic polarization curves show that, in artificial seawater, the corrosion current density of AZ91 magnesium alloy with the coating (Mg-Y-Al coating) is Mg... 95 Al5 (2.240×10 -6 A / cm2), Mg 82 Y 14 Al4 (1.772×10) -6 A / cm 2 ), Mg 63 Y 34 Al3 (5.709×10) -7 A / cm 2 ), Mg 46 Y 51 Al3 (4.000×10 - 7 A / cm 2 ), Mg 36 Y 62 Al2 (4.653×10 -7 A / cm 2 Sputtered Y (2.299×10) -7 A / cm 2 The corrosion current density of pure metallic magnesium is 8.720 × 10⁻⁶. -5 A / cm 2 The corrosion current density of AZ91 magnesium alloy is 2.187 × 10⁻⁶. -5 A / cm 2 Therefore, compared to AZ91 magnesium alloy, the current density of the magnesium alloy sample with the coating is reduced, and further reduced with the addition of yttrium. Furthermore, the polarization curve of the coating shows significant passivation, indicating that yttrium can form a dense oxide film to protect the substrate. Simultaneously, the corrosion potential of the magnesium alloy sample with the coating is lower than that of AZ91 magnesium alloy, suggesting that when the coating cracks and exposes the substrate, the galvanic effect preferentially corrodes the coating.

[0052] See Figure 5 As shown, an AZ91 magnesium alloy with a coating (Mg-Y-Al coating) was scratched, and the impedance spectrum and potentiodynamic polarization diagram were tested when the substrate was exposed at the scratch location. The impedance spectrum is shown below. Figure 5 The attached diagram on the left shows the potentiodynamic polarization diagram. Figure 5The attached diagram on the right shows the impedance spectrum and potentiodynamic polarization diagram. The impedance spectrum shows a higher low-frequency resistance for the magnesium alloy sample with the coating, while the potentiodynamic polarization diagram shows a lower corrosion current density. This indicates that the coating still provides good protection for the AZ91 magnesium alloy and effectively inhibits galvanic corrosion. The low-frequency resistance increases over time, and the corrosion current density on the fifth day of the potentiodynamic polarization diagram further decreases, indicating a more significant passivation effect. Because the corrosion potential of the coating is lower than that of the substrate (AZ91 magnesium alloy), galvanic corrosion preferentially corrodes the coating. The coating is corroded and forms an oxide film covering the scratches and defects, and the repair is further improved over time.

[0053] See Figure 6 As shown, AZ91 magnesium alloy and AZ91 magnesium alloy with a coating (Mg-Y-Al coating) were placed in artificial seawater, and the changes in hydrogen evolution volume and open circuit potential were recorded. The hydrogen evolution volume diagram is shown below. Figure 6 The attached diagram on the left shows the open-circuit potential variation. Figure 6 The attached diagram on the right shows that the coating effectively inhibited hydrogen evolution, as evidenced by the volume change graph of hydrogen gas collected from the sample. Furthermore, the open-circuit potential graph shows that, compared to ordinary AZ91 magnesium alloy, the open-circuit potential of the AZ91 magnesium alloy with the coating (Mg-Y-Al coating) remains relatively stable, reflecting that the corrosion process is suppressed and delayed.

[0054] A second aspect of this invention provides a magnesium alloy coating, which is prepared by the method described in any of the above embodiments. The magnesium alloy coating includes magnesium, yttrium, and aluminum. Specifically, the magnesium alloy coating is attached to the surface of a magnesium alloy substrate to protect the surface of the magnesium alloy sample. Because the magnesium alloy coating includes magnesium, yttrium, and aluminum, it possesses repair capabilities. Furthermore, since the corrosion potential of the coating is lower than that of the magnesium alloy sample, the coating will corrode first when a galvanic effect occurs, thereby improving the corrosion resistance of the magnesium alloy sample.

[0055] The embodiments of the present invention have been described in detail above with reference to the accompanying drawings. However, the present invention is not limited to the above embodiments. Within the scope of knowledge possessed by those skilled in the art, various changes can be made without departing from the spirit of the present invention. Furthermore, unless otherwise specified, the embodiments of the present invention and the features thereof can be combined with each other.

Claims

1. A method for preparing a magnesium alloy coating, characterized in that, Includes the following steps: Materials preparation: Provide magnesium alloy samples, aluminum-magnesium alloy targets, yttrium metal targets, and plating apparatus, wherein the magnesium alloy samples are plating substrates; Assembly: The plating device has a tray, a plating cavity and two target holders. The tray and the two target holders are disposed in the plating cavity. The magnesium alloy sample is placed on the tray, and the aluminum-magnesium alloy target and the yttrium metal target are respectively installed in the different target holders. Preparation: Seal the plating chamber, evacuate the plating chamber, and inject ionized gas into the plating chamber; Coating: The coating chamber is heated, and power is applied to the two target holders to sputter the aluminum-magnesium alloy target and the yttrium metal target onto the magnesium alloy sample to form a coating layer combining magnesium, yttrium and aluminum on the surface of the magnesium alloy sample; Sampling: After cooling the plating chamber to room temperature, take out the magnesium alloy sample with the plating layer.

2. The method for preparing a magnesium alloy coating according to claim 1, characterized in that, The method for preparing the magnesium alloy coating also includes a pretreatment step, which is located between the assembly step and the material preparation step. In the pretreatment step, the magnesium alloy sample is sequentially ground, polished, rinsed and dried.

3. The method for preparing a magnesium alloy coating according to claim 1, characterized in that, During the coating step, when the aluminum-magnesium alloy target and the yttrium metal target are sputtered onto the magnesium alloy sample, the tray used to hold the magnesium alloy sample is rotated, causing the magnesium alloy sample to rotate relative to the target holder.

4. The method for preparing a magnesium alloy coating according to claim 1, characterized in that, In the aluminum-magnesium alloy target, the atomic percentage of aluminum is between 1% and 99%, the atomic percentage of iron is less than 0.2%, the atomic percentage of copper is less than 0.2%, and the sum of the atomic percentages of zinc, manganese and silicon is no more than 10%.

5. The method for preparing a magnesium alloy coating according to claim 4, characterized in that, In the coating, the atomic percentage of magnesium is between 30% and 90%, the atomic percentage of yttrium is between 1% and 70%, the atomic percentage of aluminum is between 1% and 20%, and the sum of the atomic percentages of iron, copper, zinc, manganese and silicon is no more than 10%.

6. The method for preparing a magnesium alloy coating according to claim 1, characterized in that, In the preparatory step, the injected ionized gas is argon.

7. The method for preparing a magnesium alloy coating according to claim 6, characterized in that, The argon gas injection flow rate is from 10 standard cubic centimeters per minute to 90 standard cubic centimeters per minute; The air pressure value of the plating chamber is 10. -4 Pa to 10 -3 Pa.

8. The method for preparing a magnesium alloy coating according to claim 1, characterized in that, In the coating step, the power applied to the target holder on which the aluminum-magnesium alloy target is mounted is 10 watts to 300 watts, and the power applied to the target holder on which the yttrium metal target is mounted is 10 watts to 300 watts.

9. The method for preparing a magnesium alloy coating according to claim 1, characterized in that, In the coating step, the temperature of the coating chamber is heated to 20 degrees Celsius to 300 degrees Celsius.

10. A magnesium alloy coating, characterized in that, The magnesium alloy coating is prepared by the method for preparing magnesium alloy coating according to any one of claims 1 to 9, and the magnesium alloy coating includes magnesium, yttrium and aluminum.

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