Super-corrosion-resistant magnesium alloy and preparation method thereof

Abstract

The application relates to a super-corrosion-resistant magnesium alloy, which is composed of 6-11wt% of Al, 0.01-1.5wt% of Y, 0.01-0.5wt% of Mn, the balance of Mg and inevitable impurities, and the percentage is based on mass. The application also relates to a preparation method of the super-corrosion-resistant magnesium alloy. The super-corrosion-resistant magnesium alloy has a dense beta-Mg 17 Al 12 second phase structure, can effectively block the invasion of corrosion, and has ideal uniform corrosion behavior. In addition, the Al and Y elements added in the application can promote the formation of a dense oxide film on the surface of the magnesium alloy, the corrosion product film formed contains a large amount of Al elements, the film layer is a dense Al-rich passivation film, and therefore excellent corrosion resistance is shown. The weight loss corrosion rate after immersion in a 3.5wt% NaCl solution for 9 days is only 0.046mg / cm 2 / day, and the hydrogen evolution rate is only 0.028mL / cm 2 / day. The super-corrosion-resistant extruded magnesium alloy has excellent mechanical properties, the tensile strength can reach 310MPa, and the yield strength can reach 220MPa.

Description

Technical Field

[0001] This application relates to the field of magnesium alloy technology, specifically to an ultra-corrosion-resistant magnesium alloy and its preparation method. Background Technology

[0002] Magnesium alloys are currently the lightest structural metallic materials. Due to their advantages such as low density, high specific strength and specific stiffness, excellent thermal conductivity and damping properties, good electromagnetic shielding performance, and biocompatibility, magnesium alloys have broad application prospects in automotive lightweighting, electronic product lightweighting, and aerospace lightweighting. Simultaneously, as a new generation of biodegradable biomedical materials, magnesium alloys also have wide applications in the biomedical field. However, due to the chemically active nature of magnesium, it has the lowest standard electrode potential (-2.37V / SHE) among structural metals, exhibiting a high thermodynamic susceptibility to corrosion. From a kinetic perspective, since the corrosion product film of magnesium is mainly composed of Mg(OH)₂ and MgO, and its PBR (Pilling-Bedworth ratio) is less than 1, exhibiting loose and porous characteristics, it cannot effectively prevent the spread of corrosion. Therefore, magnesium alloys exhibit poor corrosion resistance in practical applications, and corrosion has become the main bottleneck restricting the further widespread application of magnesium alloys.

[0003] The applicant disclosed a high-strength, high-corrosion-resistant ternary magnesium alloy in Chinese invention patent CN111304510B, entitled "A High-Strength, High-Corrosion-Resistant Ternary Magnesium Alloy and Its Preparation Method." This ternary magnesium alloy comprises the following elemental composition by mass percentage: Y 8-12wt%, Al 0.6-3wt%, with the balance being Mg. After immersion in a 3.5wt% NaCl solution for 336 hours, the weight loss rate of this ternary magnesium alloy was 0.14 mg / cm³. 2 / day, hydrogen evolution rate is 0.1mL / cm 2 / day.

[0004] Therefore, designing and preparing magnesium alloys with high corrosion resistance or even super corrosion resistance has become an urgent task in the field of magnesium alloy research. Summary of the Invention

[0005] The purpose of this application is to provide a super corrosion-resistant magnesium alloy, thereby solving the problem of poor corrosion resistance of magnesium alloys in the prior art. The super corrosion-resistant magnesium alloy described herein incorporates Al and Y elements with high PBR (Polyacrylonitrile Biomass Ratio). The Al2O3 and Y2O3 formed by oxidation give the magnesium alloy oxide film high density and strong passivation ability, thereby improving the corrosion resistance of the resulting magnesium alloy.

[0006] The purpose of this application is also to provide a low-cost and large-scale application method for preparing ultra-high corrosion-resistant magnesium alloys.

[0007] To address the aforementioned technical problems, this application provides the following technical solution.

[0008] In a first aspect, this application provides an ultra-corrosion-resistant magnesium alloy, wherein the composition of the ultra-corrosion-resistant magnesium alloy, based on mass percentage, is: Al 6-11wt%, Y 0.01-1.5wt%, Mn 0.01-0.5wt%, with the balance being Mg and unavoidable impurities.

[0009] In a second aspect, this application provides a method for preparing a super corrosion-resistant magnesium alloy as described in the first aspect, the method comprising the following steps:

[0010] S1: Based on the proportion of magnesium alloy, calculate the required amounts of pure magnesium ingots, pure aluminum ingots, Mg-Y master alloy, and Mn source, and prepare and preheat the materials. The Mn source includes Mg-Mn master alloy or divalent manganese salt.

[0011] S2: In the presence of a protective gas, pure magnesium ingots, pure aluminum ingots, Mg-Y master alloy and Mn source are melted to obtain magnesium alloy melt;

[0012] S3: In the presence of a protective gas, the magnesium alloy melt is stirred, refined, kept still and slag removed in sequence to obtain a purified magnesium alloy melt.

[0013] S4: In the presence of a protective gas, the purified magnesium alloy melt is poured into a preheated mold to obtain a magnesium alloy ingot.

[0014] S5: The magnesium alloy ingot is homogenized, then extruded and cooled to obtain the ultra-corrosion resistant magnesium alloy.

[0015] Compared with the prior art, the positive effects of this application are as follows:

[0016] (1) This application incorporates Al and Y elements with high PBR (Problem-to-Body Ratio). The Al2O3 and Y2O3 formed by oxidation give the magnesium alloy oxide film high density and strong passivation ability. The corrosion product film formed by ordinary magnesium alloys after corrosion is mainly composed of Mg(OH)2 and MgO. Due to its loose and porous nature, it cannot effectively prevent the spread of corrosion, thus exhibiting poor corrosion resistance. The corrosion product film of the ultra-corrosion-resistant magnesium alloy in this application contains a large amount of Al elements (Al2O3 and Al(OH)3), giving the corrosion product film high density and thus exhibiting ultra-high corrosion resistance. The ultra-corrosion-resistant magnesium alloy of this application has a weight loss rate of only 0.04 mg / cm³ in a 7-day neutral salt spray test (5 wt% NaCl solution). 2The weight loss rate was only 0.06 mg / cm³ / day during a 6-day acidic salt spray test (5 wt% NaCl solution, pH = 3.2). 2 / day. The rate of weight loss corrosion after immersion in 3.5wt% NaCl solution for 9 days was only 0.046 mg / cm³. 2 / day, the hydrogen evolution rate is only 0.028 mL / cm². 2 / day. The corrosion rate of the super corrosion-resistant magnesium alloy in this application is much lower than that of the corrosion-resistant magnesium alloy in the existing authorized patent CN111304510B.

[0017] (2) The magnesium alloy of this application has dense β-Mg 17 Al 12 The second-phase structure effectively prevents further corrosion propagation. Simultaneously, the dense and fine second phase effectively reduces the micro-galvanic corrosion effect between the magnesium matrix and the second phase. Therefore, compared to ordinary commercial magnesium alloys (such as AZ91D), its corrosion failure mode changes from the severe pitting corrosion behavior in AZ91D to a slight uniform corrosion behavior. It is well known that pitting corrosion in magnesium alloys significantly reduces their mechanical properties and leads to unpredictable failure. The ultra-corrosion-resistant extruded magnesium alloy of this application exhibits uniform corrosion behavior, with corrosion damage having a relatively small impact on its mechanical degradation.

[0018] (3) The ultra-corrosion-resistant extruded magnesium alloy of this application not only has excellent corrosion resistance but also excellent mechanical properties. Its tensile strength can reach 310 MPa and its yield strength can reach 220 MPa. Its mechanical properties are superior to those of the currently used commercial AZ91D and AZ31B magnesium alloys, and can meet the needs of most industrial applications. More importantly, the ultra-corrosion-resistant extruded magnesium alloy of this application has low cost, simple preparation, and is easy to mass-produce, and has great industrial application value. Attached Figure Description

[0019] Figure 1 This is a SEM microstructure of the ultra-corrosion-resistant magnesium alloy in Example 2 of this application;

[0020] Figure 2 The images show the cross-sectional SEM and surface scan distribution of the ultra-corrosion-resistant magnesium alloy after salt spray corrosion in Example 2 of this application.

[0021] Figure 3 This is a cross-sectional SEM image of the corrosion products of a commercial AZ91D magnesium alloy after salt spray corrosion in Comparative Example 1 of this application;

[0022] Figure 4 The polarization curves of the ultra-corrosion-resistant magnesium alloy in Example 2 of this application are shown at 0.5 hours and 24 hours.

[0023] Figure 5 The weight loss and hydrogen evolution rate of the ultra-corrosion-resistant magnesium alloy in Example 2 of this application after immersion in a corrosive medium for 9 days;

[0024] Figure 6 This is a surface morphology image of the ultra-corrosion-resistant magnesium alloy after 3 days of salt spray corrosion in Example 2 of this application;

[0025] Figure 7 This is a surface morphology image of the ultra-corrosion resistant magnesium alloy after cleaning the salt spray corrosion products after 3 days in Example 2 of this application. Detailed Implementation

[0026] Unless otherwise stated, implied from the context, or as is customary in the art, all parts and percentages in this application are based on weight, and all testing and characterization methods used are concurrent with the filing date of this application. Where applicable, any patent, patent application, or disclosure relating to this application is incorporated herein by reference in its entirety, and its equivalent patent families are also incorporated herein by reference. If any definition of a specific term disclosed in the prior art is inconsistent with any definition provided in this application, the definition provided in this application shall prevail.

[0027] The numerical ranges in this application are approximate values ​​and therefore may include values ​​outside the range unless otherwise stated. A numerical range includes all values ​​from the lower limit to the upper limit, increasing by one unit, provided there is an interval of at least two units between any lower and any higher value. For example, if a component, physical, or other property (such as molecular weight, melt index, etc.) is described as 100 to 1000, this means that all individual values, such as 100, 101, 102, etc., are explicitly listed, as well as all subranges, such as 100 to 166, 155 to 170, 198 to 200, etc. For ranges containing values ​​less than 1 or fractions greater than 1 (e.g., 1.1, 1.5, etc.), one unit is appropriately considered as 0.0001, 0.001, 0.01, or 0.1. For ranges containing single digits less than 10 (e.g., 1 to 5), one unit is generally considered as 0.1. These are merely specific examples of what is intended to be expressed, and all possible combinations of values ​​between the listed minimum and maximum values ​​are considered to be clearly stated in this application. It should also be noted that the terms "first," "second," etc., used herein are not intended to specify a particular order, but are merely used to distinguish substances with different structures.

[0028] When referring to chemical compounds, unless explicitly stated otherwise, the singular includes all isomers, and vice versa. Additionally, unless explicitly stated otherwise, nouns described with "an," "a," or "the" also include their plural forms.

[0029] The terms “comprising,” “including,” “having,” and their derivatives do not exclude the presence of any other components, steps, or processes, regardless of whether such other components, steps, or processes are disclosed in this application. To eliminate any doubt, unless expressly stated otherwise, all compositions using the terms “comprising,” “including,” or “having” in this application may contain any additional additives, excipients, or compounds. Conversely, except for those necessary for operational performance, the term “substantially constitutes…” excludes any other components, steps, or processes described below with respect to that term. The term “consisting of…” does not include any components, steps, or processes not specifically described or listed. Unless expressly stated otherwise, the term “or” refers to the individual members listed or any combination thereof.

[0030] Super corrosion-resistant magnesium alloy

[0031] As mentioned above, one of the bottlenecks restricting the widespread application of magnesium alloys is their susceptibility to corrosion. Therefore, in a first aspect, this application provides an ultra-corrosion-resistant magnesium alloy.

[0032] In one embodiment, the composition of the ultra-corrosion-resistant magnesium alloy, based on mass percentage, is: Al 6-11 wt%, Y 0.01-1.5 wt%, Mn 0.01-0.5 wt%, with the balance being Mg and unavoidable impurities. Unavoidable impurities may include Fe not exceeding 0.01 wt%, Ni not exceeding 0.005 wt%, Cu not exceeding 0.005 wt%, and Si not exceeding 0.3 wt%.

[0033] In one specific embodiment, the composition of the ultra-corrosion-resistant magnesium alloy, based on mass percentage, is: Al 6-10 wt%, Y 0.01-1.0 wt%, Mn 0.01-0.3 wt%, with the balance being Mg and unavoidable impurities. Unavoidable impurities may include Fe not exceeding 0.005 wt%, Ni not exceeding 0.001 wt%, Cu not exceeding 0.001 wt%, and Si not exceeding 0.1 wt%.

[0034] In one specific embodiment, the super corrosion-resistant magnesium alloy may contain 6 wt%, 6.5 wt%, 7 wt%, 7.5 wt%, 8 wt%, 8.5 wt%, 9 wt%, 9.5 wt%, 10 wt%, or any two of these values ​​or a subrange thereof, of Al.

[0035] In one specific embodiment, the super corrosion-resistant magnesium alloy may contain Y in the range or subrange of any two of the following values: 0.01wt%, 0.05wt%, 0.1wt%, 0.15wt%, 0.2wt%, 0.25wt%, 0.3wt%, 0.35wt%, 0.4wt%, 0.45wt%, 0.5wt%, 0.55wt%, 0.6wt%, 0.65wt%, 0.7wt%, 0.75wt%, 0.8wt%, 0.85wt%, 0.9wt%, 0.95wt%, 1.0wt%, or Y in the range or subrange of any two of these values.

[0036] In one specific embodiment, the super corrosion-resistant magnesium alloy may contain 0.01wt%, 0.05wt%, 0.1wt%, 0.15wt%, 0.2wt%, 0.25wt%, 0.3wt%, or any two of these values ​​or a subrange of Mn.

[0037] In one specific embodiment, the composition of the ultra-corrosion-resistant magnesium alloy, based on mass percentage, is: Al 7.28wt%, Y 0.13wt%, Mn 0.11wt%, unavoidable impurities include: Fe 0.0024wt%, Ni 0.0001wt%, Cu 0.0003wt%, Si 0.04wt%, with the balance being Mg. Al has a high solid solubility in magnesium, and the Al₂O₃ formed by the oxidation of Al has a high PBR, which can promote the densification of the oxide film on the magnesium alloy and also has passivation properties. Appropriate addition of Al can enhance the corrosion resistance of the magnesium matrix; however, excessive addition of Al can lead to brittleness of the alloy, making it difficult to extrude and compromising corrosion resistance. The addition of rare earth element Y can synergistically work with Al, and the resulting Al₂O₃ and Y₂O₃ can further promote the densification of the oxide film and corrosion product film on the magnesium alloy surface. Simultaneously, the addition of a small amount of Y can purify the melt and remove the influence of harmful impurities on corrosion resistance. The addition of a small amount of Mn can increase the allowable limit of Fe impurity in magnesium, while reducing the impurity elements in the magnesium matrix and improving corrosion resistance.

[0038] Preparation method of super corrosion resistant magnesium alloy

[0039] In another embodiment, this application also provides a method for preparing the super corrosion-resistant magnesium alloy as described above.

[0040] In one specific embodiment, the preparation method includes the following steps:

[0041] S1: Based on the proportion of magnesium alloy, calculate the required amounts of pure magnesium ingots, pure aluminum ingots, Mg-Y master alloy, and Mn source, and prepare and preheat the materials. The Mn source includes Mg-Mn master alloy or divalent manganese salt.

[0042] S2: In the presence of a protective gas, pure magnesium ingots, pure aluminum ingots, Mg-Y master alloy and Mn source are melted to obtain magnesium alloy melt;

[0043] S3: In the presence of a protective gas, the magnesium alloy melt is stirred, refined, kept still and slag removed in sequence to obtain a purified magnesium alloy melt.

[0044] S4: In the presence of a protective gas, the purified magnesium alloy melt is poured into a preheated mold to obtain a magnesium alloy ingot.

[0045] S5: The magnesium alloy ingot is homogenized, then extruded and cooled to obtain the ultra-corrosion resistant magnesium alloy.

[0046] In one specific embodiment, the preparation method further includes the following steps:

[0047] S6: The super corrosion-resistant magnesium alloy is subjected to heat treatment to obtain a heat-treated super corrosion-resistant magnesium alloy, wherein the heat treatment includes aging treatment and / or solution treatment of the super corrosion-resistant magnesium alloy.

[0048] In one specific embodiment, step S2 includes: S21: melting magnesium ingots at 700°C under the protection of a mixed gas of SF6 and CO2, then adding Mg-Mn master alloy or MnCl2 powder at 720-750°C and holding for 20-30 minutes; S22: removing slag from the surface of the melt obtained in step S21, adding aluminum ingots at 750°C, and sprinkling a covering agent on the liquid surface; S23: after holding for 20-30 minutes, removing the surface slag, adding Mg-Y master alloy, and stirring for 3-5 minutes; then holding at 750°C for 20-30 minutes to obtain the magnesium alloy melt. In this embodiment, the covering agent is preferably RJ6.

[0049] In one specific embodiment, in step S3, the refining temperature is 720-740℃, and the stirring is vigorous for 3-5 minutes; the settling temperature is 740-750℃, and the settling time is 40-50 minutes.

[0050] In one specific embodiment, in step S4, the casting temperature is 690-720℃.

[0051] In one specific embodiment, in step S5, the homogenization treatment temperature is 350-420℃, and the treatment time is 5-24 hours. Preferably, the extrusion molding process is as follows: extrusion temperature 320-390℃, extrusion speed 0.9-1.5m / min, and extrusion ratio 6:1-25:1.

[0052] In one specific embodiment, when the super corrosion-resistant magnesium alloy is heat-treated, the heat treatment may include any one of the following heat treatment processes: heat treatment process 1: direct aging treatment, with an aging temperature of 100-250°C and an aging time of 5-72 hours; heat treatment process 2: solution treatment, with a solution temperature of 380-445°C and a solution time of 1-24 hours; and heat treatment process 3: the super corrosion-resistant magnesium alloy is subjected to heat treatment process 2 first, and then subjected to heat treatment process 1.

[0053] Example

[0054] The technical solution of this application will be clearly and completely described below with reference to the embodiments of this application. Unless otherwise specified, the reagents and raw materials used can be purchased commercially. Experimental methods in the following embodiments that do not specify specific conditions are performed according to conventional methods and conditions, or according to the product instructions.

[0055] Example 1

[0056] This embodiment relates to the preparation of a super corrosion-resistant extruded magnesium alloy, and the specific implementation steps are as follows:

[0057] (1) Taking 20kg alloy as an example, calculate the amount of each raw material required according to the proportion of magnesium alloy, and carry out material preparation and preheating treatment.

[0058] (2) Under a protective gas atmosphere (a mixture of SF6 and CO2), pure magnesium is first melted at 700℃, then the temperature is raised to 750℃ and a prepared Mg-Mn master alloy is added. After holding at this temperature for 20–30 minutes, the slag on the surface of the melt is removed, pure aluminum ingots are added, and a layer of covering agent is applied. After holding at this temperature for another 20–30 minutes, the surface slag is removed, Mg-Y master alloy is added, and the mixture is stirred for 3–5 minutes. Then, the temperature is held at 750℃ for 20–30 minutes to obtain a magnesium alloy melt.

[0059] (3) Under a protective gas atmosphere, the mixture is refined at 730°C and stirred vigorously for 3-5 minutes. Then the furnace temperature is raised to 750°C and held for 40-50 minutes to obtain a magnesium alloy melt.

[0060] (4) Under a protective gas, the furnace temperature is reduced to 710°C, the slag on the surface of the molten liquid is removed, and the alloy molten liquid is poured into a preheated mold to obtain a magnesium alloy ingot.

[0061] (5) The obtained magnesium alloy ingot is placed in an air furnace and homogenized at 350°C for 10 hours. Then, the magnesium alloy ingot is hot extruded at 350°C with an extrusion ratio of 15:1 and flows out of the profile at an extrusion rate of 1m / min to obtain extruded magnesium alloy.

[0062] (6) The obtained extruded magnesium alloy is subjected to heat treatment. The heat treatment process is heat treatment 1, the aging temperature is 225℃, and the aging time is 24 hours. Finally, an ultra-corrosion resistant extruded magnesium alloy is obtained.

[0063] The chemical composition of the magnesium alloy obtained in this embodiment was determined by testing as follows: Al 7.28wt%, Y 0.13wt%, Mn 0.11wt%; impurity element content: Fe 0.0024wt%, Ni 0.0001wt%, Cu 0.0003wt%, Si 0.04wt%, with the remainder being Mg.

[0064] Example 2

[0065] This embodiment prepares a super corrosion-resistant extruded magnesium alloy, and the specific implementation steps are as follows:

[0066] (1) Taking 20kg alloy as an example, calculate the amount of each raw material required according to the proportion of magnesium alloy, and carry out material preparation and preheating treatment.

[0067] (2) Under a protective gas atmosphere (a mixture of SF6 and CO2), pure magnesium is first melted at 700℃, then the temperature is raised to 750℃ and prepared MnCl2 powder is added. After holding at this temperature for 20–30 minutes, the slag on the surface of the melt is removed, pure aluminum ingots are added, and a layer of covering agent is sprinkled on top. After holding at this temperature for another 20–30 minutes, the surface slag is removed, Mg-Y master alloy is added, and the mixture is stirred for 3–5 minutes. Then, the temperature is held at 750℃ for 20–30 minutes to obtain a magnesium alloy melt.

[0068] (3) Under a protective gas atmosphere, the mixture is refined at 730°C and stirred vigorously for 3-5 minutes. Then the furnace temperature is raised to 750°C and held for 40-50 minutes to obtain a magnesium alloy melt.

[0069] (4) Under a protective gas, the furnace temperature is reduced to 710°C, the slag on the surface of the molten liquid is removed, and the alloy molten liquid is poured into a preheated mold to obtain a magnesium alloy ingot.

[0070] (5) The obtained magnesium alloy ingot is placed in an air furnace and homogenized at 350°C for 10 hours. Then, the magnesium alloy ingot is hot extruded at 350°C with an extrusion ratio of 15:1 and flows out of the profile at an extrusion rate of 1m / min to obtain extruded magnesium alloy.

[0071] (6) The obtained extruded magnesium alloy is subjected to heat treatment, and the heat treatment process is heat treatment process 3. The solution treatment temperature is 390℃ and the solution treatment time is 5 hours; the aging treatment temperature is 225℃ and the time is 24 hours, and finally an ultra-corrosion resistant extruded magnesium alloy is obtained.

[0072] The chemical composition of the magnesium alloy obtained in this embodiment was determined by testing as follows: Al 8.33wt%, Y 0.15wt%, Mn 0.10wt%, unavoidable impurities include: Fe 0.0004wt%, Ni 0.0011wt%, Cu 0.0002wt%, Si 0.15wt%, with the balance being Mg.

[0073] Example 3

[0074] This embodiment prepares a super corrosion-resistant extruded magnesium alloy, and the specific implementation steps are as follows:

[0075] (1) Taking 20kg alloy as an example, calculate the amount of each raw material required according to the proportion of magnesium alloy, and carry out material preparation and preheating treatment.

[0076] (2) Under a protective gas atmosphere (a mixture of SF6 and CO2), pure magnesium is first melted at 700℃, then the temperature is raised to 750℃ and prepared MnCl2 powder is added. After holding at this temperature for 20–30 minutes, the slag on the surface of the melt is removed, pure aluminum ingots are added, and a layer of covering agent is sprinkled on top. After holding at this temperature for another 20–30 minutes, the surface slag is removed, Mg-Y master alloy is added, and the mixture is stirred for 3–5 minutes. Then, the temperature is held at 750℃ for 20–30 minutes to obtain a magnesium alloy melt.

[0077] (3) Under a protective gas atmosphere, the mixture is refined at 730°C and stirred vigorously for 3-5 minutes. Then the furnace temperature is raised to 750°C and held for 40-50 minutes to obtain a magnesium alloy melt.

[0078] (4) Under a protective gas, the furnace temperature is reduced to 710°C, the slag on the surface of the molten liquid is removed, and the alloy molten liquid is poured into a preheated mold to obtain a magnesium alloy ingot.

[0079] (5) The obtained magnesium alloy ingot is placed in an air furnace and homogenized at 350°C for 10 hours. Then, the magnesium alloy ingot is hot extruded at 350°C with an extrusion ratio of 15:1 and flows out of the profile at an extrusion rate of 1m / min to obtain extruded magnesium alloy.

[0080] (6) The obtained extruded magnesium alloy is subjected to heat treatment. The heat treatment process is heat treatment 1. The aging temperature is 200℃ and the aging time is 48 hours, and finally, an ultra-corrosion resistant extruded magnesium alloy is obtained.

[0081] The chemical composition of the magnesium alloy obtained in this embodiment was determined by testing as follows: Al 8.33wt%, Y 0.15wt%, Mn 0.10wt%, unavoidable impurities include: Fe 0.0004wt%, Ni 0.0011wt%, Cu 0.0002wt%, Si 0.15wt%, with the balance being Mg.

[0082] Example 4

[0083] This embodiment uses the extruded corrosion-resistant magnesium alloy that was not heat-treated in Example 1. The chemical composition of the magnesium alloy is: Al 7.28wt%, Y 0.13wt%, Mn 0.11wt%; impurity element content: Fe 0.0024wt%, Ni 0.0001wt%, Cu 0.0003wt%, Si 0.04wt%, with the remainder being Mg.

[0084] Comparative Example 1

[0085] This comparative example uses commercial AZ91D magnesium alloy for comparison. The chemical composition of the magnesium alloy is: Al 8.9wt%, Zn 0.65wt%, Mn 0.23wt%, Fe 0.052wt%, Ni 0.0010wt%, Cu 0.0008wt%, Si 0.08wt%.

[0086] Comparative Example 2

[0087] In this comparative example, commercially available AZ31B extruded magnesium alloy was selected for comparison. The chemical composition of AZ31B magnesium alloy is: Al 0.25wt%, Zn 0.66wt%, Mn 0.14wt%, Fe 0.0048wt%, Ni 0.0007wt%, Cu 0.0008wt%, Si 0.016wt%.

[0088] Corrosion performance and mechanical property testing:

[0089] The testing standard was ASTM 117 - Continuous Spray, the test solution was a neutral 5wt% NaCl solution, the test temperature was 35℃, three parallel samples were tested, each measuring 20×20×5mm, and the testing period was 3 days. Mechanical testing was conducted according to the national standard GB / T228.1-2010. Table 1 shows the salt spray corrosion weight loss rate and mechanical test results for four examples and two comparative examples.

[0090] Table 1. Performance data of magnesium alloys in Examples 1-4 and comparative examples.

[0091]

[0092] As shown in Table 1, the ultra-corrosion-resistant extruded magnesium alloy of this application exhibits a weight loss rate as low as 0.052 mg / cm³ after 3 days of neutral salt spray testing. 2 / day, and the weight loss rate of Examples 1-3 is all less than 0.07 mg / cm³. 2 / day. It can be seen that even the extruded magnesium alloy in Example 4 has a weight loss rate of only 0.17 mg / cm³. 2The rate of weight loss per day is significantly lower than that of commercially available AZ91D and AZ31B magnesium alloys. Furthermore, it can be seen that the ultra-corrosion-resistant extruded magnesium alloy of this application possesses excellent mechanical properties, with a tensile strength reaching 310 MPa and a yield strength reaching 225 MPa, which are far superior to the mechanical properties of currently commercially available AZ91D and AZ31B extruded magnesium alloys.

[0093] Figure 1 This is a SEM image of the ultra-corrosion-resistant extruded magnesium alloy from Example 2. It can be seen that finely dispersed β-Mg... 17 Al 12 The second phase is uniformly distributed throughout the magnesium matrix. This uniform and fine second phase effectively reduces the area ratio between the cathode β phase and the anode α-Mg phase, thereby significantly reducing the micro-galvanic corrosion effect between the second phase and the magnesium matrix. Ordinary magnesium alloys, such as AZ91D magnesium alloy, are prone to pitting corrosion due to the strong micro-galvanic effect between their coarse second phase and the magnesium matrix, thus exhibiting poor corrosion resistance.

[0094] Figure 2 The images show the cross-sectional SEM morphology and elemental distribution of the ultra-corrosion-resistant extruded magnesium alloy from Example 2 after 3 days of neutral salt spray testing. It can be seen that the corrosion product film of the ultra-corrosion-resistant magnesium alloy is very uniform and thin, indicating uniform corrosion and a very low corrosion rate. The elemental distribution images show that the corrosion product film of the ultra-corrosion-resistant magnesium alloy is mainly composed of Mg, Al, and O elements, indicating that in addition to the basic Mg(OH)2 and MgO, the corrosion product film also contains a large amount of Al elements (Al(OH)3 and Al2O3). Therefore, this ultra-corrosion-resistant magnesium alloy has a denser corrosion product film than ordinary magnesium alloys, thus exhibiting excellent corrosion resistance.

[0095] Figure 3 The image shows a cross-sectional SEM image of the corrosion products of the commercial AZ91D magnesium alloy in Comparative Example 1 after 3 days of testing in neutral salt spray. It can be seen that the AZ91D magnesium alloy exhibited severe pitting corrosion, with pit depths exceeding 500 μm. Furthermore, the formed corrosion products are porous and cracked, indicating poor corrosion protection. This is because the AZ91D magnesium alloy contains coarse β-Mg... 17 Al 12 There is a strong microcouple effect between the β phase and the magnesium matrix. The β phase has a high potential and acts as the cathode, while the surrounding magnesium matrix acts as the anode and undergoes severe corrosion and dissolution.

[0096] Figure 4The image shows the potentiodynamic polarization curves of the ultra-corrosion-resistant extruded magnesium alloy from Example 2 after immersion in a 3.5 wt% NaCl solution for 0.5 hours and 24 hours. The electrochemical workstation used was a Gamry 1010E, and the scan rate was 1 mV / s. It can be seen that after immersion in the solution for 0.5 hours, the ultra-corrosion-resistant magnesium alloy did not exhibit significant passivation behavior, i.e., there was no significant film breakdown potential E. b It can be seen that after immersion for 24 hours, the polarization curve of the alloy shows obvious passivation behavior, and its film breakdown potential E b Gundam -1.12V SCE This indicates that the ultra-corrosion-resistant magnesium alloy can rapidly form a passivation film in corrosive media with increasing immersion time, thereby significantly reducing the corrosion rate of the alloy. Simultaneously, its corrosion current density I... corr From 13.2 μA / cm in 0.5 hours 2 It decreased to 1.65 μA / cm after 24 hours. 2 .

[0097] Figure 5 The figures show the weight loss and hydrogen evolution rate of the ultra-corrosion-resistant extruded magnesium alloy in Example 2 of this application after immersion in a 3.5 wt% NaCl solution for 9 days. It can be seen that the weight loss rate of the ultra-corrosion-resistant extruded magnesium alloy after immersion for 9 days is only 0.046 mg / cm³. 2 / day, the hydrogen evolution rate is only 0.028 mL / cm². 2 / day. According to the authorized patent CN111304510B, the corrosion-resistant magnesium alloy exhibits a weight loss rate of 0.14 mg / cm³ after immersion in a 3.5 wt% NaCl solution for 336 hours. 2 / day, hydrogen evolution rate is 0.1mL / cm 2 / day. The corrosion rate of the ultra-corrosion-resistant extruded magnesium alloy of this application is much lower than that of the corrosion-resistant magnesium alloy in the authorized invention patent CN111304510B.

[0098] Figure 6 The image shows the surface corrosion morphology of the ultra-corrosion-resistant extruded magnesium alloy in Example 2 after 3 days of neutral salt spray testing. It can be seen that the corrosion product film is very uniform and dense. Scratches on the substrate surface are also observed, indicating that the corrosion is very shallow.

[0099] Figure 7 The image shows the magnesium substrate surface after cleaning with the neutral salt spray corrosion product film from the ultra-corrosion-resistant extruded magnesium alloy in Example 2 after 3 days. It can be seen that the magnesium substrate surface is very smooth, without pitting, and exhibits a uniform corrosion morphology. In summary, the ultra-corrosion-resistant extruded magnesium alloy of this application possesses excellent corrosion resistance, far exceeding that of currently used commercial magnesium alloy grades.

[0100] The above description of the embodiments is intended to enable those skilled in the art to understand and apply this application. It will be apparent to those skilled in the art that various modifications can be easily made to these embodiments, and the general principles described herein can be applied to other embodiments without creative effort. Therefore, this application is not limited to the embodiments described herein, and any improvements and modifications made by those skilled in the art based on the disclosure of this application without departing from the scope and spirit of this application are within the scope of this application.

Claims

1. A super corrosion resistant magnesium alloy, characterized by, The composition of the super-corrosion-resistant magnesium alloy is: Al 6-11 wt%, Y 0.01-0.2 wt%, Mn 0.01-0.5 wt%, the balance being Mg and inevitable impurities, based on mass percentage; the fine and dispersed β-Mg 17 Al 12 The second phase is uniformly distributed in the entire magnesium matrix; The preparation method of the super-corrosion-resistant magnesium alloy comprises the following steps: S1: according to the proportion of the magnesium alloy, the amount of pure magnesium ingot, pure aluminum ingot, Mg-Y intermediate alloy and Mn source is calculated, and the materials are prepared and preheated, and the Mn source comprises Mg-Mn intermediate alloy or divalent manganese salt; S2: the pure magnesium ingot, the pure aluminum ingot, the Mg-Y intermediate alloy and the Mn source are melted in the presence of protective gas to obtain a magnesium alloy melt; wherein the step S2 comprises: S21: the magnesium ingot is melted at 700 DEG C under the protection of mixed gas of SF6 and CO2, then the Mg-Mn intermediate alloy or MnCl2 powder is added at 720-750 DEG C, and the temperature is kept for 20-30 minutes; S22: the slag on the surface of the melt obtained in step S21 is removed, the aluminum ingot is added at 750 DEG C, and a layer of covering agent is sprinkled on the liquid surface; S23: after keeping the temperature for 20-30 minutes, the surface slag is removed, the Mg-Y intermediate alloy is added, and stirring is carried out for 3-5 minutes; then the temperature is kept for 20-30 minutes at 750 DEG C to obtain the magnesium alloy melt; S3: the magnesium alloy melt is subjected to stirring, refining, standing and slagging in sequence in the presence of protective gas to obtain a purified magnesium alloy melt; the refining temperature is 720-740 DEG C, and the stirring is carried out for 3-5 minutes; the standing temperature is 740-750 DEG C, and the standing time is 40-50 minutes; S4: the purified magnesium alloy melt is cast into a preheated mold in the presence of protective gas to obtain a magnesium alloy ingot; the casting temperature is 690-720 DEG C; S5: the magnesium alloy ingot is subjected to homogenization treatment, then is extruded to form a magnesium alloy, and the magnesium alloy is cooled to obtain the super-corrosion-resistant magnesium alloy; the homogenization treatment temperature is 350-420 DEG C, and the treatment time is 5-24 hours; the extrusion forming process is as follows: the extrusion temperature is 320-390 DEG C, the extrusion speed is 0.9-1.5 m / min, and the extrusion ratio is 6:1-25:1; S6: the super-corrosion-resistant magnesium alloy is subjected to heat treatment to obtain a heat-treated super-corrosion-resistant magnesium alloy, and the heat treatment comprises aging treatment and / or solid solution treatment.

2. The ultra corrosion resistant magnesium alloy according to claim 1, wherein The super-corrosion-resistant magnesium alloy comprises, by mass percentage: Al 6-10 wt%, Y 0.01-0.2 wt%, Mn 0.01-0.3 wt%, and the balance of Mg and inevitable impurities.

3. The ultra corrosion resistant magnesium alloy according to claim 1, wherein The super-corrosion-resistant magnesium alloy comprises, by mass percentage: Al 7.28 wt%, Y 0.13 wt%, Mn 0.11 wt%, inevitable impurities including Fe 0.0024 wt%, Ni 0.0001 wt%, Cu 0.0003 wt%, Si 0.04 wt%, and the balance of Mg.

4. The ultra corrosion resistant magnesium alloy according to claim 1, wherein The super corrosion resistant magnesium alloy has the following components in percentage of mass: Al 8.33 wt%, Y 0.15 wt%, Mn 0.10 wt%, inevitable impurities including Fe 0.0004 wt%, Ni 0.0011 wt%, Cu 0.0002 wt%, Si 0.15 wt%, and the rest is Mg.

5. A method of manufacture, characterized by, The preparation method of the super corrosion resistant magnesium alloy according to claim 1.

6. The production method according to claim 5, wherein The covering agent is RJ6.

7. The production method according to claim 5, wherein The heat treatment includes any one of the following heat treatment processes: Heat treatment process 1: direct aging treatment, aging temperature is 100-250℃, aging time is 5-72 hours; Heat treatment process 2: solid solution treatment, solid solution temperature is 380-445℃, solid solution time is 1-24 hours; and, Heat treatment process 3: the super corrosion resistant magnesium alloy is first subjected to the heat treatment process 2, and then subjected to the heat treatment process 1.

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