CN103628114B - The surface treatment method of magnadure - Google Patents

Abstract

The surface that the present invention relates to alloy material processes, the surface treatment method of a kind of magnadure.Experimental technique: polishing → degreasing → alkaline etching → chemical polishing → anodic oxidation → electrolytic coloring → sealing of hole.The present invention is reasonable in design, uses anodised method to form the oxidation film layer of thickness and densification at surface of magnesium aluminium alloy, to significantly change the corrosion resistance of magnadure, improves hardness, wearability and decoration performance.But, magnadure anode oxide film has very high porosity and adsorption capacity, and the most contaminated and corrosive medium corrodes, it is necessary to carry out sealing pores, to improve corrosion resistance, contamination resistance and fixed pigment body.

Description

Surface treatment method of magnesium aluminum alloy

technical field

The invention relates to the surface treatment of alloy materials, in particular to a surface treatment method of magnesium and aluminum alloys.

Background technique

Due to its high strength/weight ratio, easy forming and processing, and excellent physical and chemical properties, magnesium-aluminum alloy materials have become more metal materials than aluminum alloys in industry. However, magnesium-aluminum alloy materials have low hardness and poor wear resistance, and frequent abrasion and damage. Therefore, before use, magnesium-aluminum alloys often need to undergo corresponding surface treatment to meet their environmental adaptability and safety, reduce abrasion, and prolong their durability. service life.

Since the surface of magnesium-aluminum alloy is easy to form an oxide film, it is very stable in the atmosphere, but the wear resistance and corrosion resistance of the naturally formed oxide film are not strong enough, so artificial methods are used for anodic oxidation treatment. .

The anodic oxidation treatment of magnesium-aluminum alloy is based on the principle of electrolysis to form a layer of wear-resistant porous aluminum oxide film on the surface of magnesium-aluminum alloy vessels or parts, so as to improve the hardness, wear resistance and corrosion resistance of the magnesium-aluminum alloy surface. and insulation, and can be used as a primer for staining and painting on the surface of aluminum parts.

The growth of oxide film on the surface of magnesium alloy during anodic oxidation involves two processes: electrochemical formation of oxide film and chemical dissolution process. Only when the growth rate of the oxide film is greater than the dissolution rate, the oxide film can grow and thicken. Common anodizing mainly includes sulfuric acid anodizing, chromic acid anodizing, oxalic acid anodizing and phosphoric acid anodizing.

Contents of the invention

The purpose of the present invention is to provide a new magnesium-aluminum alloy surface treatment method.

The present invention is realized by adopting the following technical solutions:

A surface treatment method for magnesium-aluminum alloys, comprising the steps of:

(1) Use mechanical grinding to remove the oxide film naturally formed on the surface of the magnesium-aluminum alloy sheet;

(2) Put the polished magnesium-aluminum alloy sheet into a degreasing solution at a temperature of 70-75°C for 3-5 minutes. The degreasing solution consists of Na ₂ CO ₃ solution, Na ₃ PO ₄ solution and Na ₄ SiO ₄ The solution is configured at a volume ratio of 1:1:1, the concentration of the Na ₂ CO ₃ solution is 40g/L, the concentration of the Na ₃ PO ₄ solution is 40g/L, and the concentration of the Na ₄ SiO ₄ solution The concentration is 20g/L;

(3) Put the degreased magnesium-aluminum alloy sheet into an alkali etching solution at a temperature of 50-70° C. for 3-5 minutes, and the alkali etching solution is a NaOH solution with a concentration of 20 g/L;

(4) Put the alkali-etched magnesium-aluminum alloy sheet into a polishing solution at a temperature of 90-110°C for 3-5 minutes. The polishing solution consists of a H ₃ PO ₄ solution with a relative density of 1.70 and a relative density of 1.84 The H ₂ SO ₄ solution is configured at a volume ratio of 1:1;

(5) Perform sulfuric acid anodic oxidation on the polished magnesium-aluminum alloy sheet, the conditions for anodic oxidation are: the concentration of sulfuric acid is 1.5g/l, the temperature is 15-25°C, the voltage is 10-20V, and the time is 20-30min ;

(6) Perform electrolytic coloring on the anodized magnesium-aluminum alloy sheet;

(7) Sealing: use the boiling water method, keep in deionized water at 90-100°C for 10-15 minutes; or use hydrolysis salt solution for sealing, the content of NiSO ₄ •7H ₂ O in the hydrolysis salt solution is 4 ～5g/L, the content of CoSO ₄ •7H ₂ O is 0.5～0.8g/L, the content of H ₃ BO ₃ is 4～5g/L, the content of NaAc•3H ₂ O is 4～6g/L, hydrolyzed salt The pH value of the solution is 4-6, the temperature is 80-85° C., and the holding time is 15-20 minutes.

In the present invention, the magnesium aluminum alloy is electrolyzed in sulfuric acid aqueous solution for anodic oxidation, so that an oxide film layer is formed on the surface. Under the conditions of temperature, voltage, time, electrolyte concentration, etc., the sulfuric acid anodic oxidation film layer of magnesium aluminum alloy has high adsorption capacity, and it is easy to carry out sealing or coloring treatment.

The sulfuric acid anodizing process of magnesium aluminum alloy is simple to operate, the electrolyte is stable, and the cost is not high, which further improves its corrosion resistance and appearance. The advantages of this sulfuric acid anodizing are as follows:

1. The operation process is simple, at a temperature of 15-20 ° C, 5-10 minutes, easy to operate;

2. Very safe, will not cause environmental pollution and be harmful to operators;

3. Craft medicines are cheap.

In addition, the influence of different conditions on the coloring effect is as follows

1. Yellow

1.1. Under the conditions of time change, see Table 1:

Table 1

It can be seen from Table 1 that the coloring time is prolonged and the color tone is deepened. Under the voltage of 15V, coloring for 5 minutes can get the golden yellow with the best tone. If the color is too light, it can be colored for a period of time.

1.2. Under the condition that the temperature of the coloring liquid changes, the electrical conductivity increases with the increase of the temperature during coloring. Under the conditions of the same voltage, same time, and same concentration, the higher the temperature, the faster the color will be. However, due to the increase of the reaction temperature, the reaction speed will be accelerated, the color will be uneven, and striped or blocky patterns will appear.

1.3. The conditions for changing the concentration of the coloring solution are shown in Table 2:

Table 2

It can be seen from Table 2 that, under the condition that other conditions remain unchanged, the concentration of the coloring liquid increases and the coloring increases.

1.4. Under the conditions of voltage change, see Table 3:

table 3

It can be seen from Table 2 that the voltage is too low, the current is all used for charging the barrier layer, and there is no metal deposition, so there is no coloring. 10-15V is the voltage range of golden yellow coloring, and the amount of metal deposition is relatively large; the coloring current above 15V increases, the amount of metal deposition increases, and the color tone deepens with the increase of voltage; the coloring is uneven when the current is too high above 20V, and streaks appear.

Therefore, for yellow electrolysis, use a KMnO ₄ solution with a concentration of 20g/l, and the conditions are: temperature 18-20°C, voltage 15V, time 5min.

2. Red

2.1. Under the conditions of time change, see Table 4:

Table 4

It can be seen from Table 4 that the longer the coloring time, the deeper the color will be. When the coloring time is more than 10 minutes, the color is red and black. If the coloring is too light, you can continue to color in the coloring solution.

2.2. Under the condition of changing the temperature of the coloring liquid, under the same voltage, same time, and same concentration, the higher the temperature, the faster the coloring will be. Shaped or block pattern.

2.3. The conditions for changing the concentration of the coloring solution are shown in Table 5:

table 5

It can be seen from Table 5 that, under the condition that all conditions remain unchanged, the greater the concentration, the darker the color.

2.4. Under the conditions of voltage change, see Table 6:

Table 6

It can be seen from Table 6 that if the voltage is low, the current in the coloring solution is insufficient, the metal deposition is less, and the coloring is too light; if the voltage is too high, the current in the coloring solution is too large, causing Cu to precipitate in CuSO ₄ and adhere to the colored magnesium-aluminum alloy. On the sheet, the edges are thickened and not colored. When the temperature is constant and the concentration is constant, the time is prolonged and the voltage is strengthened. After the voltage is strengthened, Cu precipitates in CuSO ₄ ; when the time is prolonged, CuSO ₄ precipitates more Cu, and Cu ions will appear on the surface of the magnesium-aluminum alloy sheet without coloring.

Therefore, if the electrolysis is red, use a CuSO ₄ solution with a concentration of 20g/L, and the conditions are: temperature 18-20°C, voltage 25V, time 5min.

3. Purple

3.1. Under the conditions of time change, see Table 7:

Table 7

3.2. The conditions for changing the concentration of the coloring solution are shown in Table 8:

Table 8

3.3. Change the concentration of H ₂ SO ₄ and keep the concentration of CuSO ₄ unchanged, as shown in Table 9:

Table 9

It can be seen from Table 9 that changing the concentrations of CuSO ₄ and H ₂ SO ₄ mutually causes the change of the colored color. When CuSO ₄ occupies more, the color is reddish; when H ₂ SO ₄ occupies more, the color is dark green.

3.4. Under the conditions of voltage change, see Table 10:

Table 10

It can be seen from Table 10 that when the voltage is gradually increased, Cu is precipitated in the coloring solution and adheres to the edge of the aluminum sheet, so that the aluminum sheet cannot be colored normally.

Therefore, if the electrolysis is purple, use a mixed solution of CuSO ₄ with a concentration of 30g/L and H ₂ SO ₄ with a concentration of 20g/L at a volume ratio of 1:1. The parameters are: temperature 18-20 ℃, voltage 25V, time 3min.

The roughness and brightness of the magnesium-aluminum alloy sheet substrate have a great influence on the color of the colored film. The colored magnesium-aluminum alloy material must have a high brightness and can be chemically polished. If the surface treatment is not good, only a yellow film or no Uniform oxide film. If an uneven oxide film is produced, the colored color will appear as a strip or block product. In the above process, the change of the coloring time of all colors has a certain influence on the experimental product. If the voltage, electrolyte concentration, and coloring temperature are not changed, the coloring of the product will be darker if the coloring time is prolonged, and the coloring time will be shortened. The resulting product is lighter in color. When the voltage, coloring time, and coloring temperature are not changed, the color of the product will be darker if the concentration of the coloring electrolyte is increased, and the color of the product will be lighter if the concentration of the coloring electrolyte is reduced. .

The invention is suitable for industrial production, and can better save medicine and have better coloring effect when applied in mass production.

The invention has a reasonable design, adopts an anodic oxidation method to form a thick and dense oxide film layer on the surface of the magnesium-aluminum alloy, so as to significantly change the corrosion resistance of the magnesium-aluminum alloy and improve the hardness, wear resistance and decorative performance. However, the magnesium-aluminum alloy anodized film has high porosity and adsorption capacity, and is easily corroded by pollution and corrosive media. It must be sealed to improve corrosion resistance, anti-pollution ability and fix pigment bodies.

Our country has many personalities, rapid economic development, and continuous expansion of cities. The construction magnesium aluminum alloy profile industry must be a sustainable development industry. The surface treatment of architectural magnesium-aluminum alloy materials can not only improve the performance and service life, but also improve the appearance quality and decoration grade, so it will still be in the first priority for development.

detailed description

Specific embodiments of the present invention will be described in detail below.

Example 1

A surface treatment method for magnesium-aluminum alloys, comprising the steps of:

(1) Use sandpaper to remove the naturally formed oxide film on the surface of the magnesium-aluminum alloy sheet (thickness 1.5mm) and make it smooth;

(2) Put the polished magnesium-aluminum alloy sheet into a degreasing solution at a temperature of 70°C for 5 minutes. The degreasing solution is composed of Na ₂ CO ₃ solution, Na ₃ PO ₄ solution and Na ₄ SiO ₄ solution in volume ratio The concentration of the Na ₂ CO ₃ solution is 40g/L, the concentration of the Na ₃ PO ₄ solution is 40g/L, and the concentration of the Na ₄ SiO ₄ solution is 20g/L. L;

(3) Put the degreased magnesium-aluminum alloy sheet into an alkaline etching solution at a temperature of 60° C. for 4 minutes, and the alkaline etching solution is a NaOH solution with a concentration of 20 g/L;

(4) Put the alkali-etched magnesium-aluminum alloy sheet into a polishing solution at a temperature of 90°C for 3 minutes. The polishing solution consists of a H ₃ PO ₄ solution with a relative density of 1.70 and H ₂ SO with a relative density of 1.84. ₄ The solution is prepared with a volume ratio of 1:1;

(5) Perform sulfuric acid anodization on the polished magnesium-aluminum alloy sheet, the conditions of anodization are: the concentration of sulfuric acid is 1.5g/L, the temperature is 20°C, the voltage is 10V, and the time is 30min;

(6) Perform electrolytic coloring on the anodized magnesium-aluminum alloy sheet; for yellowing, use KMnO ₄ solution with a concentration of 20g/l, the conditions are: temperature 18-20°C, voltage 15V, time 5min;

(7) Sealing: use the boiling water method, keep in deionized water at 100°C for 10-15 minutes.

After each step, the magnesium-aluminum alloy sheet was cleaned with deionized water.

Example 2

A surface treatment method for magnesium-aluminum alloys, comprising the steps of:

(1) Use sandpaper to remove the naturally formed oxide film on the surface of the magnesium-aluminum alloy sheet (thickness 1.5mm) and make it smooth;

(2) Put the polished magnesium-aluminum alloy sheet into a degreasing solution at a temperature of 75°C for 4 minutes. The degreasing solution is composed of Na ₂ CO ₃ solution, Na ₃ PO ₄ solution and Na ₄ SiO ₄ solution in volume ratio The concentration of the Na ₂ CO ₃ solution is 40g/L, the concentration of the Na ₃ PO ₄ solution is 40g/L, and the concentration of the Na ₄ SiO ₄ solution is 20g/L. L;

(3) Put the degreased magnesium-aluminum alloy sheet into an alkaline etching solution at a temperature of 70° C. for 3 minutes, and the alkaline etching solution is a NaOH solution with a concentration of 20 g/L;

(4) Put the alkali-etched magnesium-aluminum alloy sheet into a polishing solution at a temperature of 100°C for 5 minutes. The polishing solution consists of a H ₃ PO ₄ solution with a relative density of 1.70 and H ₂ SO with a relative density of 1.84. ₄ The solution is prepared with a volume ratio of 1:1;

(5) Perform sulfuric acid anodization on the polished magnesium-aluminum alloy sheet, the conditions of anodization are: the concentration of sulfuric acid is 1.5g/L, the temperature is 25°C, the voltage is 15V, and the time is 25min;

(6) Perform electrolytic coloring on the anodized magnesium-aluminum alloy sheet; for red coloring, use a CuSO ₄ solution with a concentration of 20g/l, the conditions are: temperature 18-20°C, voltage 25V, time 5min;

(7) Sealing: use hydrolysis salt solution for sealing, the content of NiSO ₄ •7H ₂ O in the hydrolysis salt solution is 4g/L, the content of CoSO ₄ •7H ₂ O is 0.8g/L, H ₃ BO The content of ₃ is 4g/L, the content of NaAc•3H ₂ O is 6g/L, the pH value of the hydrolysis salt solution is 4, the temperature is 80°C, and the holding time is 20min.

After each step, the magnesium-aluminum alloy sheet was cleaned with deionized water.

Example 3

A surface treatment method for magnesium-aluminum alloys, comprising the steps of:

(1) Use sandpaper to remove the naturally formed oxide film on the surface of the magnesium-aluminum alloy sheet and make it smooth;

(2) Put the polished magnesium-aluminum alloy sheet into a degreasing solution at a temperature of 72°C for 3 minutes. The degreasing solution is composed of Na ₂ CO ₃ solution, Na ₃ PO ₄ solution and Na ₄ SiO ₄ solution in volume ratio The concentration of the Na ₂ CO ₃ solution is 40g/L, the concentration of the Na ₃ PO ₄ solution is 40g/L, and the concentration of the Na ₄ SiO ₄ solution is 20g/L. L;

(3) Put the degreased magnesium-aluminum alloy sheet into an alkaline etching solution at a temperature of 50° C. for 5 minutes, and the alkaline etching solution is a NaOH solution with a concentration of 20 g/L;

(4) Put the alkali-etched magnesium-aluminum alloy sheet into a polishing solution at a temperature of 110°C for 4 minutes. The polishing solution consists of a H ₃ PO ₄ solution with a relative density of 1.70 and H ₂ SO with a relative density of 1.84. ₄ The solution is prepared with a volume ratio of 1:1;

(5) Perform sulfuric acid anodization on the polished magnesium-aluminum alloy sheet. The conditions for anodization are: the concentration of sulfuric acid is 1.5g/L, the temperature is 15°C, the voltage is 20V, and the time is 20min;

(6) Perform electrolytic coloring on the anodized magnesium-aluminum alloy sheet; for purple, use CuSO ₄ with a concentration of 30g/L and H ₂ SO ₄ with a concentration of 20g/L at a volume ratio of 1:1 The parameters of the mixed solution are as follows: temperature 18-20°C, voltage 25V, time 3min;

(7) Sealing: use hydrolysis salt solution for sealing, the content of NiSO ₄ •7H ₂ O in the hydrolysis salt solution is 5g/L, the content of CoSO ₄ •7H ₂ O is 0.5g/L, H ₃ BO The content of ₃ is 5g/L, the content of NaAc·3H ₂ O is 4g/L, the pH value of the hydrolysis salt solution is 6, the temperature is 85°C, and the holding time is 15min.

After each step, the magnesium-aluminum alloy sheet was cleaned with deionized water.

Common faults and analysis are as follows in the embodiment:

(1) Pitting corrosion After sulfuric acid anodization of magnesium-aluminum alloys, the oxide film is dull and dull, sometimes pitting corrosion occurs, and black spotting corrosion is prominent in severe cases, resulting in the scrapping of magnesium-aluminum alloy parts and great losses. There are generally two reasons for this kind of phenomenon: one is that during the production and turnover process of the parts, the anti-rust work between the processes is not done well, the parts are polluted by the active medium, the surface is electrochemically corroded, and there are local small spots on the surface. Pores, or "pockets", are especially noticeable after caustic corrosion. Another reason is accidental. For example, during the anodizing process of magnesium and aluminum alloys, the power is cut off and then re-powered on. During the power failure, the parts stay in the cleaning tank for too long, the cleaning tank is too acidic, the water quality is not clean, or contains suspended solids, There are many mud and sand, etc., which often cause electrochemical corrosion of magnesium-aluminum alloy parts, making the oxide film dull, or pitting corrosion and black spots. At this time, if tap water is added to the electrolyte, the Cl content of the water will exceed the standard after the bleaching powder treatment, resulting in pitting corrosion of the parts.

(2) The color is dull or grayish. After sulfuric acid anodization of magnesium aluminum alloy, the local surface color of the oxide film is dull or even black, and there are large black spots or dark gray spots. This phenomenon generally occurs in larger and thicker magnesium-aluminum alloy parts. The reason is that the local cooling of the material is slow during quenching (such as insufficient cooling rate, local water temperature is too high) or the transfer time is too long, and the main strengthening phase in the local structure is precipitated in large quantities, which reduces the solid solution strengthening effect of the alloy elements in the aluminum alloy matrix, and at the same time Due to the large amount of completely incoherent precipitation of the second phase from the crystal grains, this will reduce the corrosion resistance of the material and increase the anodic corrosion rate. The degree of corrosion will eventually show different surface colors due to reflective properties.

(3) Black spots or stripes After the parts are anodized with sulfuric acid, a local non-oxidized film layer occurs, showing black spots or stripes visible to the naked eye. This situation is generally related to the inhomogeneity of the surface metal phase, structure segregation, micro impurity segregation or uneven structure of various parts caused by improper heat treatment, which will lead to selective oxidation or selective dissolution. For example, the segregation of the silicon content in the local area of the material often results in a local non-oxidized film or black spots and stripes, or local selective dissolution to generate holes. Of course, if the content of suspended impurities, dust, copper and iron and other metal impurity ions in the sulfuric acid electrolyte is too high, this phenomenon will also be caused, thereby affecting the corrosion resistance of the oxide film.

(4) The anodized magnesium-aluminum alloy parts treated with the same tank have no oxide film or the film layer is thin or incomplete, or there is burning and erosion at the contact between the fixture and the part. This is because the insulating property of the aluminum oxide film is good. Aluminum alloy parts must be firmly mounted on general or special fixtures before anodizing to ensure good electrical conductivity. The conductive rod should be made of copper or copper alloy and ensure sufficient contact area.

(5) The film falls off, the oxide film is loose and pulverized, and even falls off when touched by hand, especially after filling and sealing, a powder layer appears on the surface of the part, which means that the corrosion resistance is poor. This type of phenomenon mostly occurs in sulfuric acid anodizing tanks without cooling devices in summer. After processing parts in 1-2 tanks, loose powdering will appear. Due to the high resistance of the magnesium-aluminum alloy anodized film, a large amount of Joule heat will be generated during the anodic oxidation process. The higher the cell voltage is, the greater the heat will be generated, which will cause the temperature of the electrolyte to rise continuously. Therefore, during the anodic oxidation process, a stirring or cooling device must be used to control the temperature of the electrolyte between 10 and 25°C to ensure the quality of the oxide film. If the liquid temperature exceeds 30°C, the oxide film will be loose and pulverized, and in severe cases, there will be "burning". In addition, when the electrolyte temperature is constant, the anode current density must also be limited, because the anode current density is too high and the temperature rises sharply, and the same problem will occur.

The quality of magnesium-aluminum-aluminum sulfuric acid anodic oxidation film is good or bad, and the performance of anti-corrosion protection mainly depends on the composition of magnesium-aluminum alloy, film thickness and anodic oxidation treatment process conditions, such as temperature, current density, water quality and after anodic oxidation. The filling and sealing process, etc. To reduce or avoid anodic oxidation faults and improve product quality, we must start from the subtleties and take effective measures.

Claims (3)

1. a surface treatment method of magnesium-aluminum alloy, is characterized in that: comprise the steps: (1) Use mechanical grinding to remove the oxide film naturally formed on the surface of the magnesium-aluminum alloy sheet; (2) Put the polished magnesium-aluminum alloy sheet into a degreasing solution at a temperature of 70-75°C for 3-5 minutes. The degreasing solution consists of Na ₂ CO ₃ solution, Na ₃ PO ₄ solution and Na ₄ SiO ₄ The solution is configured with a volume ratio of 1:1:1, the concentration of the Na ₂ CO ₃ solution is 40g/L, the concentration of the Na ₃ PO ₄ solution is 40g/L, and the Na ₄ SiO ₄ solution The concentration is 20g/L; (3) Put the degreased magnesium-aluminum alloy sheet into an alkali etching solution at a temperature of 50-70° C. for 3-5 minutes, and the alkali etching solution is a NaOH solution with a concentration of 20 g/L; (4) Put the alkali-etched magnesium-aluminum alloy sheet into a polishing solution at a temperature of 90-110°C for 3-5 minutes. The polishing solution consists of a H ₃ PO ₄ solution with a relative density of 1.70 and a relative density of 1.84 The H ₂ SO ₄ solution is configured at a volume ratio of 1:1; (5) Perform sulfuric acid anodic oxidation on the polished magnesium-aluminum alloy sheet, the conditions of anodic oxidation are: the concentration of sulfuric acid is 1.5g/L, the temperature is 15-20°C, the voltage is 10-20V, and the time is 20-30min ; (6) Perform electrolytic coloring on the anodized magnesium-aluminum alloy sheet; the details are as follows: if the electrolytic color is yellow, use a KMnO ₄ solution with a concentration of 20g/L, and the conditions are: temperature 18-20°C, voltage 15V, The time is 5 minutes; if the electrolysis is red, use a CuSO ₄ solution with a concentration of 20g/L, and the conditions are: temperature 18-20°C, voltage 25V, time 5min; if the electrolysis is purple, use a CuSO solution with a concentration of 30g/L. ₄ and H ₂ SO ₄ with a concentration of 20g/L at a volume ratio of 1:1, the parameters are: temperature 18-20°C, voltage 25V, time 3min; (7) Sealing: use the boiling water method, keep in deionized water at 90-100°C for 10-15 minutes; or use hydrolysis salt solution for sealing, the content of NiSO ₄ •7H ₂ O in the hydrolysis salt solution is 4 ～5g/L, the content of CoSO ₄ •7H ₂ O is 0.5～0.8g/L, the content of H ₃ BO ₃ is 4～5g/L, the content of NaAc•3H ₂ O is 4～6g/L, hydrolyzed salt The pH value of the solution is 4-6, the temperature is 80-85° C., and the holding time is 15-20 minutes. 2. The surface treatment method of magnesium-aluminum alloy according to claim 1, characterized in that: the magnesium-aluminum alloy sheet is cleaned with deionized water after each step. 3. The surface treatment method of magnesium-aluminum alloy according to claim 2, characterized in that: the thickness of the magnesium-aluminum alloy sheet is 1.5mm.