Low-cost high-strength corrosion-resistant magnesium alloy and preparation method thereof

Abstract

The invention relates to a low-cost high-strength corrosion-resistant magnesium alloy and a preparation method thereof. The magnesium alloy comprises the following components in percentage by mass: 6-11% of Al, 0.4-0.6% of Zn, 0.2-0.6% of Mn, 0.2-0.4% of Y, 0.2-0.6% of Ca and the balance of Mg and inevitable impurities. A small amount of Ca and Y elements are added, on one hand, an alpha-Mg matrix structure can be refined, beta phase distribution is more uniform, and the mechanical property is improved; and on the other hand, the solid solubility of the alloy element Y in an alpha-Mg matrix can be improved by adding the Ca element, the compactness of a surface oxidation film and a corrosion product film is promoted, compared with other rare earth elements, the potential difference between Al-Ca and Al-Y phases formed by Ca, Y and Al and the magnesium matrix is smaller, micro galvanic corrosion is smaller, and the corrosion resistance of the alloy is remarkably improved.

Description

Technical Field

[0001] This invention relates to a magnesium alloy and its preparation method, and particularly to a low-cost, high-strength, corrosion-resistant magnesium alloy and its preparation method, belonging to the field of metal materials technology. Background Technology

[0002] Magnesium alloys, as the lightest metallic structural materials, possess characteristics such as low density, high specific strength, and excellent electromagnetic shielding performance, demonstrating enormous potential for lightweight applications in aerospace, new energy vehicles, and 3C electronics. However, traditional magnesium alloys generally suffer from two major technical bottlenecks: insufficient mechanical properties and poor corrosion resistance, which severely restrict their large-scale industrial application.

[0003] Currently widely used commercial magnesium alloys (such as AZ91 and AM60 series) are mainly strengthened by adding Al, but their room temperature strength (tensile strength is usually below 280 MPa) is insufficient to meet the requirements of high-end equipment. Furthermore, Al readily forms galvanic corrosion microcells with the magnesium alloy matrix, leading to a significantly increased corrosion rate (>2 mm / y) in humid environments or Cl-containing media. In addition, while rare earth-strengthened magnesium alloys (such as WE43 and Mg-Gd-Y series) can balance strength and corrosion resistance to some extent, the high cost of rare earth elements (accounting for more than 30% of the total material cost) limits their large-scale application.

[0004] The main methods for improving the corrosion resistance of magnesium alloys currently include: 1) using high-purity raw materials to reduce the content of impurity elements such as Fe, Ni, and Cu; 2) adding a large amount of noble metal elements (such as Ag and Au) or rare earth elements (Nd and As) to inhibit cathodic hydrogen evolution or anodic dissolution; and 3) surface modification techniques (such as micro-arc oxidation and chemical plating). However, the above methods have obvious drawbacks. The addition of high-purity raw materials and high rare earth elements will significantly increase costs, and surface treatment requires additional processes and suffers from problems such as insufficient coating adhesion and easy peeling.

[0005] In terms of manufacturing processes, existing high-strength magnesium alloys mostly rely on complex processes such as rapid solidification, constant diameter angular extrusion, or powder metallurgy. Although these processes can refine grains to below the micrometer level, they suffer from problems such as large equipment investment, high energy consumption, and poor process stability, making it difficult to meet the demand for low-cost mass production. Currently disclosed technologies (such as CN 102534330 B, CN 114395667 B, CN 115637363 B) generally suffer from a triangular contradiction of "strength-corrosion resistance-cost". That is, while using rare earth elements or complex processes can improve performance, they also significantly increase costs. However, simplifying the process or reducing alloy quality makes it difficult to meet the synergistic requirements of high strength and high corrosion resistance.

[0006] In summary, the goal is to develop a method that combines low cost, high strength (tensile strength ≥ 280 MPa) with excellent corrosion resistance (salt spray corrosion rate ≤ 0.05 mg / cm²). 2 The development of novel magnesium alloys ( / d) and their efficient preparation methods has become a key technological direction for overcoming the bottlenecks in the application of magnesium alloys. Summary of the Invention

[0007] The purpose of this invention is to address the shortcomings of existing technologies by providing a low-cost, high-strength, corrosion-resistant magnesium alloy and its preparation method. The alloy provided by this invention exhibits significantly improved corrosion resistance due to the synergistic effect of various alloying elements, possessing excellent corrosion resistance. Furthermore, the alloy has a relatively uniform microstructure and good mechanical properties. This invention achieves room temperature tensile strength ≥280 MPa, yield strength ≥130 MPa, and elongation ≥6% for magnesium alloy castings; and room temperature tensile strength ≥350 MPa, yield strength ≥220 MPa, and elongation ≥12% for hot-deformed parts. The corrosion rate measured under immersion in 3.5 wt.% NaCl solution or under salt spray conditions according to GB / T 10125-2012 standard is ≤0.05 mg / cm². 2 Furthermore, the preparation method provided by this invention has the advantages of simple process, high efficiency, and suitability for large-scale production, and has broad application prospects in the aerospace and 3C fields.

[0008] To achieve the above-mentioned objectives, the technical solution of this invention is as follows: This invention provides a low-cost, high-strength, corrosion-resistant magnesium alloy with the following chemical element mass percentages: 6~11% Al, 0.4~0.6% Zn, 0.2~0.6% Mn, 0.2~0.4% Y, 0.2~0.6% Ca, 0.1~0.3% Ti, and the remainder being Mg.

[0009] Furthermore, the mass percentage of Ca is preferably 0.2 to 0.4%, more preferably 0.2 to 0.3%.

[0010] Furthermore, the preferred Al mass percentage is 8-11%.

[0011] Furthermore, the mass percentage of Y+Ca is ≥0.5%.

[0012] Furthermore, low-cost, high-strength, corrosion-resistant magnesium alloys contain unavoidable impurities.

[0013] This invention also provides a method for preparing the low-cost, high-strength, corrosion-resistant magnesium alloy as described above, comprising the following steps: S1. Based on the proportion of magnesium alloy materials, calculate the required amounts of pure Mg ingots, pure Al ingots, pure Zn ingots, Al-Mn master alloy, Al-Ti master alloy, Mg-Y master alloy, and Mg-Ca master alloy, and prepare and preheat the materials. S2. Place pure Mg ingots in a crucible and heat them until they are completely melted. When the temperature of the melt rises to 720~730℃, add pure Al ingots, pure Zn ingots and Al-Mn master alloy in sequence. After melting, stir evenly. S3. Control the temperature of the melt obtained in S2 to 720 ~ 730℃, and add Al-Ti master alloy, Mg-Y master alloy and Mg-Ca master alloy in sequence. After melting, stir evenly. S4. The melt obtained after step S3 is refined, slag removed, and allowed to stand to obtain a purified magnesium alloy melt. S5. The melt obtained in step S4 is poured to obtain an alloy ingot or alloy casting. S6. The alloy ingot obtained in step S5 is homogenized to obtain a homogenized ingot. The homogenized ingot is then hot-deformed to obtain the hot-deformed product. Alternatively, the alloy casting obtained in step S5 can be homogenized to obtain a homogenized casting. S7. Perform aging heat treatment on the hot-deformed product or homogenized casting obtained in step S6 to obtain a low-cost, high-strength, corrosion-resistant magnesium alloy component with uniform microstructure.

[0014] Furthermore, in step S2, the heating temperature is 660~680℃.

[0015] Furthermore, in step S2, the obtained melt undergoes a metamorphic treatment, followed by slag removal. The metamorphic treatment temperature is 730℃, and the metamorphic agent is magnesite; the slag removal involves removing slag from the bottom and surface of the melt 2-3 times respectively, followed by manual stirring for 2-3 minutes.

[0016] Furthermore, in step S3, the temperature is continuously increased during the melting process. The initial temperature in S2 is 720~730℃, but when it reaches S3, the temperature will exceed 730℃. Therefore, the temperature is controlled at 720~730℃.

[0017] Furthermore, in step S4, the refining temperature is 750~760℃, and the time is 10~30 minutes. The refining agent is RJ6, and the refining is carried out under argon atmosphere.

[0018] Furthermore, in step S4, the slag removal involves removing slag from the bottom and surface of the melt 2-3 times, followed by manual stirring for 2-3 minutes.

[0019] Furthermore, in step S4, the initial temperature for settling is 750~760℃, and the settling time is 20~30 minutes.

[0020] Furthermore, in step S5, the pouring temperature is 680~710℃. The pouring method is gravity pouring.

[0021] Furthermore, steps S2 to S5 are all performed under flux protection. Furthermore, in step S6, the homogenization treatment is performed under two-stage solution treatment conditions, wherein the two-stage solution treatment conditions are: the first-stage heat treatment temperature is 350~370℃, and the time is 2~3 h; the second-stage heat treatment temperature is 400~420℃, and the time is 10~20 h. The cooling method is air cooling.

[0022] Furthermore, in step S6, the homogenized ingot obtained from the homogenization process is subjected to hot deformation treatment to obtain the hot-deformed product. The temperature of the hot deformation treatment is 320~380 ℃, and the total amount of hot deformation is 70~90%.

[0023] The hot deformation treatment is one of forging, extrusion, or rolling.

[0024] When hot deformation is forging, the resulting hot-deformed product is a forging; When heat deformation is performed by extrusion, the resulting heat-deformed product is a profile. When hot deformation is achieved through rolling, the resulting hot-deformed product is a sheet material.

[0025] Furthermore, in step S7, the aging heat treatment temperature is 160~210℃, and the time is 10~30 h. The cooling method is air cooling.

[0026] Furthermore, in step S7, the microstructure of the obtained low-cost, high-strength, corrosion-resistant magnesium alloy includes a continuous network β phase, Al2Ca phase, Al2Y phase, and Al-Mn-Y phase, wherein the Al2Ca phase is distributed on the β phase and inside the grains, and the Al2Y phase and Al-Mn-Y phase are uniformly distributed inside the grains, with a grain size of 2~60 μm.

[0027] The choice of a higher Al content in this invention is based on the following three considerations: (1) In Mg-Al alloys, Mg and Al can form an intermetallic compound β phase. During the subsequent solid solution and aging process, this phase can hinder dislocation movement through the mechanisms of "dispersion strengthening" and "precipitation strengthening", thereby significantly improving the tensile strength and yield strength of the alloy.

[0028] (2) Due to the addition of trace amounts of Ca and Y elements, the higher Al content can promote the combination of Al and Y / Ca during the casting process, form nucleation particles, refine the grain structure, reduce the formation of coarse dendrites, thereby reducing the internal stress of the casting and reducing the risk of cracking.

[0029] (3) A higher Al content is beneficial to promoting the formation of a denser and more stable oxide film (Al2O3, Y2O3, CaO) on the alloy surface by elements such as Y and Ca, which is beneficial to improving the corrosion resistance of the alloy.

[0030] Excessive Al content leads to an overabundance of the β phase, preventing subsequent solid solution infiltration and consequently affecting the alloy's strength and ductility. Conversely, insufficient Al content results in substandard strength and corrosion resistance.

[0031] This invention, by employing a composite addition of Y, Ca, and Ti, can significantly refine the grain structure, avoiding the magnesite metamorphic steps required in traditional Mg-Al systems.

[0032] Compared with the prior art, the present invention has the following substantial features and significant progress: (1) The composite addition of Ti, Ca and Y elements in this invention can effectively serve as the core of heterogeneous nucleation of Al-Ca, Al-Y and Al-Ti phases formed during the melting process, and improve the undercooling of the solid-liquid front, thereby greatly refining the α-Mg matrix structure. In addition, the addition of Ti can reduce the degree of Al segregation at the grain boundary, inhibit the generation of lamellar β phase and columnar crystal growth, refine the eutectic β phase, and expand the equiaxed crystal region. The combined effect of the two promotes the improvement of the mechanical properties of the alloy.

[0033] (2) In this invention, a small amount of Ca and Y elements are added. The addition of Ca can improve the solid solubility of alloy element Y in the α-Mg matrix, which can effectively promote the formation of dense Y2O3 / CaO composite film and overcome the defects of loose and porous traditional MgO film. In addition, the trace amount of Ti mainly exists in the matrix in solid solution form and will not generate new phases. Compared with other rare earth elements, the Al-Ca and Al-Y phases formed by Ca, Y and Al have a smaller potential difference with the magnesium matrix and less microgalvanic corrosion, which significantly improves the corrosion resistance of the alloy.

[0034] (3) Compared with the addition of Mn alone, the composite addition of trace amounts of Ti, Ca, Y and Mn in this invention can greatly improve the self-purification effect of the melt during the smelting process, reduce harmful impurity elements (such as Fe, Ni, Cu, etc.) in the melt, significantly reduce the purity requirements of raw materials, and reduce production costs; at the same time, the reduction of impurity content can greatly reduce the cathode hydrogen evolution reaction and improve the corrosion resistance of the alloy.

[0035] (4) The alloy element content of the present invention is low. Al, Zn, Ca and Mn are all low-cost alloy elements. The amount of rare earth element Y added is less than 0.4 wt.%, which breaks through the traditional path of high-strength corrosion-resistant magnesium alloys relying on high content of rare earth (such as Gd and Nd), and significantly reduces the cost of alloy raw materials. In addition, the preparation method provided by the present invention has the advantages of simple process, high efficiency and suitability for large-scale production, which can effectively meet the needs of lightweight development in the aerospace and 3C fields.

[0036] (5) The low-cost, high-strength, corrosion-resistant magnesium alloy of the present invention, after casting, homogenization treatment, and aging heat treatment, has a room temperature tensile strength ≥280 MPa, yield strength ≥130 MPa, and elongation ≥6% for castings; and a room temperature tensile strength ≥350 MPa, yield strength ≥220 MPa, and elongation ≥12% for hot-deformed parts; the corrosion rate measured under immersion in 3.5 wt.% NaCl solution or under standard salt spray conditions (GB / T10125-2012) is ≤0.05 mg / cm². 2 Compared to traditional AZ-based magnesium alloys, this alloy exhibits 100 times better corrosion resistance. Furthermore, all main elements are low-cost, resulting in low raw material costs and a simple manufacturing process, making it suitable for large-scale production and possessing significant industrial application value. Attached Figure Description

[0037] Other features, objects, and advantages of the present invention will become more apparent from the following detailed description of non-limiting embodiments with reference to the accompanying drawings: Figure 1 Image showing the metallographic structure of the magnesium alloy casting of Example 1; Figure 2 The image shows the corrosion morphology of the magnesium alloy casting in Example 1 after 10 days of salt spray testing. Figure 3 Here are metallographic images of the magnesium alloy profile component from Example 4; Figure 4 The image shows the metallographic structure of the magnesium alloy casting in Comparative Example 1. Figure 5 The image shows the microstructure of the magnesium alloy profile component in Comparative Example 4 using SEM. Detailed Implementation

[0038] The embodiments of the present invention are described in detail below: These embodiments are implemented based on the technical solution of the present invention, and detailed implementation methods and processes are given. However, the scope of protection of the present invention is not limited to the following embodiments.

[0039] This invention provides a low-cost, high-strength, corrosion-resistant magnesium alloy with the following chemical element mass percentages: 6~11% Al, 0.4~0.6% Zn, 0.2~0.6% Mn, 0.2~0.4% Y, 0.2~0.6% Ca, 0.1~0.3% Ti, and the remainder being Mg.

[0040] Furthermore, the mass percentage of Ca is preferably 0.2 to 0.4%, more preferably 0.2 to 0.3%.

[0041] Furthermore, the preferred Al mass percentage is 8-11%.

[0042] Furthermore, the mass percentage of Y+Ca is ≥0.5%.

[0043] Example 1 The low-cost, high-strength, corrosion-resistant magnesium alloy described in this embodiment has the following chemical element mass percentages: 8% Al, 0.5% Zn, 0.6% Mn, 0.3% Y, 0.3% Ca, 0.3% Ti, with the remainder being Mg and unavoidable impurities.

[0044] The low-cost, high-strength, corrosion-resistant magnesium alloy described in this embodiment is prepared using the following steps: S1. Based on the proportion of magnesium alloy ingredients, calculate the required quantities of pure Mg ingots (purity of 99.9%), pure Al ingots, pure Zn ingots, Al-10Mn master alloy, Mg-20Y master alloy, and Mg-20Ca master alloy, and prepare and preheat the materials. The preheating temperature is 200℃ and the preheating time is 12h. S2. Place the pure Mg ingot in a crucible, set the temperature to 670℃, heat it until it is completely melted, and when the melt temperature rises to 720℃, add the pure Al ingot, pure Zn ingot and Al-Mn master alloy in sequence, and stir evenly after melting. S3. The melt obtained after step S2 is subjected to a metamorphic treatment, followed by slag removal. The metamorphic treatment temperature is 730℃, the metamorphic agent is magnesite, and the slag removal is performed twice, once at the bottom and once at the surface of the melt. After slag removal, the melt is manually stirred for 2 minutes. S4. When the temperature of the S3 melt drops to 720℃, add the Mg-Y master alloy and Mg-Ca master alloy in sequence, and stir until melted and homogeneous. S5. The melt obtained after step S4 is refined, slag removed, and allowed to stand in sequence to obtain a purified magnesium alloy melt. The refining temperature is 750℃, the refining agent is RJ6, and the argon refining is carried out for 30 minutes. The slag removal is carried out twice, once at the bottom and once at the surface of the melt. After slag removal, the melt is stirred manually for 2 minutes. The settling temperature is 770℃ and the settling time is 30 minutes. S6. The melt obtained in step S5 is poured to obtain an alloy casting, wherein the pouring temperature is 690℃ and the pouring method is gravity pouring. Steps S2 to S6 are all performed under the protection of flux (RJ2); S7. The alloy casting obtained in step S6 is subjected to homogenization treatment to obtain a homogenized component, wherein the homogenization treatment is a two-stage solution treatment: the first stage heat treatment temperature is 350 ℃, the time is 2 h; the second stage heat treatment temperature is 400 ℃, the time is 16 h, and air cooling is performed. S8. The homogenized casting obtained in step S7 is subjected to aging heat treatment to obtain a low-cost, high-strength, corrosion-resistant magnesium alloy component with uniform microstructure. The aging heat treatment temperature is 160℃, the time is 24 h, and the component is air-cooled.

[0045] The mechanical properties and salt spray test results of the prepared alloy are as follows: tensile strength 295 MPa, yield strength 135 MPa, elongation 8%, corrosion rate 0.05 mg / cm². 2 / d.

[0046] Example 2 The low-cost, high-strength, corrosion-resistant magnesium alloy described in this embodiment has the following chemical element mass percentages: 11% Al, 0.6% Zn, 0.4% Mn, 0.4% Y, 0.2% Ca, 0.2% Ti, with the remainder being Mg and unavoidable impurities.

[0047] The low-cost, high-strength, corrosion-resistant magnesium alloy described in this embodiment is prepared using the following steps: S1. Based on the proportion of magnesium alloy ingredients, calculate the required quantities of pure Mg ingots (purity of 99.9%), pure Al ingots, pure Zn ingots, Al-10Mn master alloy, Mg-20Y master alloy, and Mg-20Ca master alloy, and prepare and preheat the materials. The preheating temperature is 200℃ and the preheating time is 12h. S2. Place the pure Mg ingot in a crucible, set the temperature to 670℃, heat it until it is completely melted, and when the melt temperature rises to 720℃, add the pure Al ingot, pure Zn ingot and Al-Mn master alloy in sequence, and stir evenly after melting. S3. The melt obtained after step S2 is subjected to a metamorphic treatment, followed by slag removal. The metamorphic treatment temperature is 750℃, the metamorphic agent is magnesite, and the slag removal is performed twice, once at the bottom and once at the surface of the melt. After slag removal, the melt is manually stirred for 2 minutes. S4. When the temperature of the S3 melt drops to 730℃, add the Mg-Y master alloy and Mg-Ca master alloy in sequence, and stir until melted and homogeneous. S5. The melt obtained after step S4 is refined, slag removed, and allowed to stand in sequence to obtain a purified magnesium alloy melt. The refining temperature is 760℃, the refining agent is RJ6, and argon refining is carried out for 20 minutes. The slag removal is carried out twice, once at the bottom and once at the surface of the melt. After slag removal, the melt is stirred manually for 3 minutes. The settling temperature is 770℃ and the settling time is 30 minutes. S6. The melt obtained in step S5 is poured to obtain an alloy casting, wherein the pouring temperature is 700℃ and the pouring method is gravity pouring. All steps S2 to S6 are performed under flux protection; S7. The alloy casting obtained in step S6 is subjected to homogenization treatment to obtain homogenized components, wherein the homogenization treatment is a two-stage solution treatment: the first stage heat treatment temperature is 360 ℃, the time is 3 h; the second stage heat treatment temperature is 420 ℃, the time is 10 h, and air cooling is performed. S8. The homogenized casting obtained in step S7 is subjected to aging heat treatment to obtain a low-cost, high-strength, corrosion-resistant magnesium alloy component with uniform microstructure. The aging heat treatment temperature is 210℃, the time is 18 h, and the component is air-cooled.

[0048] The mechanical properties and salt spray test results of the prepared alloy are as follows: tensile strength 310 MPa, yield strength 140 MPa, elongation 10%, corrosion rate 0.03 mg / cm². 2 / d.

[0049] Example 3 The low-cost, high-strength, corrosion-resistant magnesium alloy described in this embodiment has the following chemical element mass percentages: 6% Al, 0.4% Zn, 0.2% Mn, 0.2% Y, 0.6% Ca, 0.1% Ti, with the remainder being Mg and unavoidable impurities.

[0050] The low-cost, high-strength, corrosion-resistant magnesium alloy described in this embodiment is prepared using the following steps: S1. Based on the proportion of magnesium alloy ingredients, calculate the required quantities of pure Mg ingots (purity of 99.9%), pure Al ingots, pure Zn ingots, Al-10Mn master alloy, Mg-20Y master alloy, and Mg-20Ca master alloy, and prepare and preheat the materials. The preheating temperature is 200℃ and the preheating time is 12h. S2. Place the pure Mg ingot in a crucible, set the temperature to 670℃, heat it until it is completely melted, and when the melt temperature rises to 720℃, add the pure Al ingot, pure Zn ingot and Al-Mn master alloy in sequence, and stir evenly after melting. S3. The melt obtained after step S2 is subjected to a metamorphic treatment, followed by slag removal. The metamorphic treatment temperature is 740℃, the metamorphic agent is magnesite, and the slag removal is performed by removing slag from the bottom and surface of the melt three times respectively. After slag removal, the melt is manually stirred for 2 minutes. S4. When the temperature of the S3 melt drops to 720℃, add the Mg-Y master alloy and Mg-Ca master alloy in sequence, and stir until melted and homogeneous. S5. The melt obtained after step S4 is refined, slag removed, and allowed to stand in sequence to obtain a purified magnesium alloy melt. The refining temperature is 750℃, the refining agent is RJ6, and the argon refining is carried out for 25 minutes. The slag removal is carried out twice, once at the bottom and once at the surface of the melt. After slag removal, the melt is stirred manually for 3 minutes. The settling temperature is 770℃ and the settling time is 25 minutes. S6. The melt obtained in step S5 is poured to obtain an alloy casting, wherein the pouring temperature is 690℃ and the pouring method is gravity pouring. All steps S2 to S6 are performed under flux protection; S7. The alloy casting obtained in step S6 is subjected to homogenization treatment to obtain homogenized components, wherein the homogenization treatment is a two-stage solution treatment: the first stage heat treatment temperature is 370 ℃, the time is 2 h; the second stage heat treatment temperature is 400 ℃, the time is 15 h, and air cooling is performed. S8. The homogenized casting obtained in step S7 is subjected to aging heat treatment to obtain a low-cost, high-strength, corrosion-resistant magnesium alloy component with uniform microstructure. The aging heat treatment temperature is 210℃, the time is 18 h, and the component is air-cooled.

[0051] The mechanical properties and salt spray test results of the prepared alloy are as follows: tensile strength 280 MPa, yield strength 132 MPa, elongation 7%, corrosion rate 0.04 mg / cm². 2 / d.

[0052] Example 4 The low-cost, high-strength, corrosion-resistant magnesium alloy described in this embodiment has the following chemical element mass percentages: 6% Al, 0.4% Zn, 0.2% Mn, 0.2% Y, 0.6% Ca, 0.1% Ti, with the remainder being Mg and unavoidable impurities.

[0053] The high-strength, corrosion-resistant magnesium alloy described in this embodiment is prepared using the following steps: S1. Based on the proportion of magnesium alloy ingredients, calculate the required quantities of pure Mg ingots (purity of 99.9%), pure Al ingots, pure Zn ingots, Al-10Mn master alloy, Mg-20Y master alloy, and Mg-20Ca master alloy, and prepare and preheat the materials. The preheating temperature is 200℃ and the preheating time is 12h. S2. Place the pure Mg ingot in a crucible, set the temperature to 670℃, heat it until it is completely melted, and when the melt temperature rises to 720℃, add the pure Al ingot, pure Zn ingot and Al-Mn master alloy in sequence, and stir evenly after melting. S3. The melt obtained after step S2 is subjected to a metamorphic treatment, followed by slag removal. The metamorphic treatment temperature is 740℃, the metamorphic agent is magnesite, and the slag removal is performed by removing slag from the bottom and surface of the melt three times respectively. After slag removal, the melt is manually stirred for 2 minutes. S4. When the temperature of the S3 melt drops to 720℃, add the Mg-Y master alloy and Mg-Ca master alloy in sequence, and stir until melted and homogeneous. S5. The melt obtained after step S4 is refined, slag removed, and allowed to stand in sequence to obtain a purified magnesium alloy melt. The refining temperature is 750℃, the refining agent is RJ6, and the argon refining is carried out for 25 minutes. The slag removal is carried out twice, once at the bottom and once at the surface of the melt. After slag removal, the melt is stirred manually for 3 minutes. The settling temperature is 770℃ and the settling time is 25 minutes. S6. The melt obtained in step S5 is poured to obtain an alloy ingot, wherein the pouring temperature is 690℃ and the pouring method is gravity pouring. All steps S2 to S6 are performed under flux protection; S7. The alloy ingot obtained in step S6 is homogenized to obtain a homogenized ingot. The homogenized ingot is then extruded to obtain a hot-deformed profile product. The homogenization treatment is a two-stage solution treatment: the first stage heat treatment temperature is 370 ℃ for 2 h; the second stage heat treatment temperature is 400 ℃ for 15 h, followed by air cooling; the extrusion temperature is 350 ℃, and the extrusion amount is 80%. S8. The homogenized casting obtained in step S7 is subjected to aging heat treatment to obtain a low-cost, high-strength, corrosion-resistant magnesium alloy component with uniform microstructure. The aging heat treatment temperature is 210℃, the time is 18 h, and the component is air-cooled.

[0054] The mechanical properties and salt spray test results of the obtained alloy are as follows: tensile strength 360 MPa, yield strength 230 MPa, elongation 14%, corrosion rate 0.02 mg / cm². 2 / d.

[0055] Examples 5-7 The low-cost, high-strength, corrosion-resistant magnesium alloy described in this embodiment is prepared using the same method as in Example 2, and its chemical element mass percentage composition is shown in Table 1 below: Table 1

[0056] Comparative Example 1 This comparative example provides a magnesium alloy with the following chemical element mass percentages: 8% Al, 0.5% Zn, 0.6% Mn, with the remainder being Mg and unavoidable impurities. Compared to Example 1, this comparative example does not include the addition of Y and Ca to the alloy composition. The preparation process and conditions are the same. The mechanical properties and salt spray test results of the obtained alloy are as follows: tensile strength 240 MPa, yield strength 95 MPa, elongation 8%, and corrosion rate 1.5 mg / cm² / d.

[0057] Compared with Example 1, this comparative example has a coarser β phase due to the lack of Y and Ca elements, and the presence of Al-Mn phase with high potential in the microstructure, which significantly deteriorates the mechanical and corrosion properties of the alloy.

[0058] Comparative Example 2 The magnesium alloy described in this comparative example has the following chemical element mass percentages: 11% Al, 0.6% Zn, 0.4% Mn, 0.1% Y, 0.1% Ca, with the remainder being Mg and unavoidable impurities. Compared to Example 2, this comparative example differs in that the contents of Y and Ca in the alloy composition are both below the lower limit of the protected composition. The preparation process and conditions are the same. The mechanical properties and salt spray test results of the obtained alloy are as follows: tensile strength 260 MPa, yield strength 100 MPa, elongation 8%, corrosion rate 0.4 mg / cm². 2 / d.

[0059] Compared with Example 2, this comparative example has fewer Al-Ca and Al-Y phases formed because the contents of Y and Ca in the alloy composition are both lower than the lower limit of the protective composition, resulting in poor grain refinement. In addition, the lower Ca and Y contents lead to a lower amount of Y2O3 / CaO generated during corrosion, and the density of the corrosion product film is worse. The combined effect of these two factors results in poor strength and corrosion resistance of the alloy.

[0060] Comparative Example 3 The magnesium alloy described in this comparative example has the following chemical element mass percentages: 6% Al, 0.4% Zn, 0.2% Mn, 0.6% Ca, with the remainder being Mg and unavoidable impurities. This comparative example differs from Example 3 in that it does not contain Y, but the preparation process and conditions are the same. The mechanical properties and salt spray test results of the obtained alloy are as follows: tensile strength 230 MPa, yield strength 85 MPa, elongation 6%, and corrosion rate 0.12 mg / cm². 2 / d.

[0061] Compared with Example 3, this comparative example lacks Y element, resulting in no dispersed Al-Y phase precipitation during aging, which deteriorates the mechanical properties of the alloy. At the same time, the lack of Y element reduces the self-purification effect of the melt, thereby worsening the corrosion resistance of the alloy.

[0062] Comparative Example 4 The magnesium alloy described in this comparative example has the following chemical element mass percentages: 6% Al, 0.4% Zn, 0.2% Mn, 0.2% Y, with the remainder being Mg and unavoidable impurities. This comparative example differs from Example 4 in that it does not contain Ca, but the preparation process and conditions are the same. The mechanical properties and salt spray test results of the obtained alloy are as follows: tensile strength 310 MPa, yield strength 180 MPa, elongation 10%, and corrosion rate 0.09 mg / cm². 2 / d.

[0063] Compared with Example 4, this comparative example has a coarse initial grain size in the ingot due to the lack of Ca element. Therefore, even with the hot extrusion process, the grain size is still relatively large, resulting in a decrease in strength.

[0064] Comparative Examples 5-9 The low-cost, high-strength, corrosion-resistant magnesium alloy described in this comparative example is prepared using the same method as in Example 2, and its chemical element mass percentage composition is shown in Table 1.

[0065] Figure 1 The image shows the metallographic structure of the magnesium alloy casting in Example 1. It can be seen that the grain size is about 45 μm, the size is uniform, and the second phase is dispersed in the grain interior and on the grain boundaries.

[0066] Figure 2 The image shows the corrosion morphology of the magnesium alloy casting in Example 1 after 10 days of salt spray testing. It can be seen that after 10 days of salt spray testing, no obvious corrosion pits or white corrosion products were produced on the sample surface, indicating that the magnesium alloy in Example 1 can form a complete oxide film on the magnesium alloy surface under the test conditions, which plays a good protective role for the magnesium alloy body.

[0067] Figure 3 The image shows the metallographic structure of the magnesium alloy profile component in Example 4. It can be seen that the grain size is about 5 μm, and the structure is significantly refined after extrusion.

[0068] Figure 4 The image shows the metallographic structure of the magnesium alloy casting in Comparative Example 1. The grain size is approximately 185 μm, and there are no obvious precipitates at the grain boundaries. Furthermore, the grain size of the alloy in Comparative Example 1 is significantly higher than that of the alloy in Example 1, indicating that the addition of Ca and Y elements is beneficial for grain refinement.

[0069] Figure 5 The image shows a SEM image of the microstructure of the magnesium alloy profile component in Comparative Example 4. The extruded grain size is approximately 13 μm.

[0070] The test methods for the mechanical and corrosion properties of the magnesium alloys in Examples 1-4 and Comparative Examples 1-4 are as follows: Mechanical property testing: The yield strength, tensile strength and elongation of the magnesium alloys in Examples 1-4 and Comparative Examples 1-4 were tested according to GB / T 228.1-2010 "Metallic materials - Tensile testing - Part 1: Test method at room temperature", with the pull bar size being M8×φ5 mm. Corrosion performance testing: The corrosion resistance of the magnesium alloys in Examples 1-4 and Comparative Examples 1-4 was tested according to GB / T10125-2012 "Artificial Atmosphere Corrosion Test - Salt Spray Test". The test solution was a neutral 5wt.% NaCl solution, the test temperature was 35 ℃, and three parallel samples were tested, each with a size of 50×50×5 mm. 3 The test lasted for 20 days, and the rate of weightlessness was calculated. Vw=(W1-W2) / (ST) Where W1 is the initial weight of the sample (unit: mg); W2 is the weight after etching and removal of surface corrosion products (unit: mg); S is the surface area of ​​the sample (unit: cm²). 2 T represents the test time (in days). Table 2 shows the grain size and performance data of the magnesium alloys in Examples 1-4 and Comparative Examples 1-4.

[0071] Table 2 Grain size and performance data of different magnesium alloys

[0072] As shown in Table 1, the magnesium alloys of Examples 1-4 of this invention exhibit good mechanical properties. The room temperature tensile strength of the castings is ≥280 MPa, the yield strength is ≥130 MPa, and the elongation is ≥6%. The room temperature tensile strength of the hot-deformed parts is ≥350 MPa, the yield strength is ≥220 MPa, and the elongation is ≥12%. The corrosion rate of the low-cost, high-strength, corrosion-resistant magnesium alloy measured under the salt spray conditions of GB / T 10125-2012 standard is ≤0.05 mg / cm². 2 / d can effectively meet the needs of industries such as aerospace, military, and automotive for lightweight equipment.

[0073] While the present invention has been described with reference to certain preferred embodiments, those skilled in the art should understand that the above description is a further detailed explanation of the invention in conjunction with specific embodiments, and should not be construed as limiting the specific implementation of the invention to these descriptions. Various changes in form and detail can be made by those skilled in the art, including several simple deductions or substitutions, without departing from the spirit and scope of the invention.

Claims

1. A low-cost, high-strength, corrosion-resistant magnesium alloy, wherein the chemical element mass percentage is: 6~11% Al, 0.4~0.6% Zn, 0.2~0.6% Mn, 0.2~0.4% Y, 0.2~0.6% Ca, 0.1~0.3% Ti, with the remainder being Mg.

2. The low-cost, high-strength, corrosion-resistant magnesium alloy according to claim 1, characterized in that, The mass percentage of Ca is 0.2%~0.4%.

3. The low-cost, high-strength, corrosion-resistant magnesium alloy according to claim 1, characterized in that, The mass percentage of Al is 8-11%.

4. A method for preparing a low-cost, high-strength, corrosion-resistant magnesium alloy as described in claim 1, characterized in that, Includes the following steps: S1. Based on the proportion of magnesium alloy materials, calculate the required amounts of pure Mg ingots, pure Al ingots, pure Zn ingots, Al-Mn master alloy, Al-Ti master alloy, Mg-Y master alloy, and Mg-Ca master alloy, and prepare and preheat the materials. S2. Place pure Mg ingots in a crucible and heat them until they are completely melted. When the temperature of the melt rises to 720~730℃, add pure Al ingots, pure Zn ingots and Al-Mn master alloy in sequence. After melting, stir evenly. S3. Control the temperature of the melt obtained in S2 to 720 ~ 730℃, and add Al-Ti master alloy, Mg-Y master alloy and Mg-Ca master alloy in sequence. After melting, stir evenly. S4. The melt obtained after step S3 is refined, slag removed, and allowed to stand to obtain a purified magnesium alloy melt. S5. The melt obtained in step S4 is poured to obtain an alloy ingot or alloy casting. S6. The alloy ingot obtained in step S5 is homogenized to obtain a homogenized ingot. The homogenized ingot is then hot-deformed to obtain the hot-deformed product. Alternatively, the alloy casting obtained in step S5 can be homogenized to obtain a homogenized casting. S7. Perform aging heat treatment on the hot-deformed product or homogenized casting obtained in step S6 to obtain a low-cost, high-strength, corrosion-resistant magnesium alloy component with uniform microstructure.

5. The method for preparing low-cost, high-strength, corrosion-resistant magnesium alloy according to claim 4, characterized in that, In step S4, the refining temperature is 750~760℃ and the time is 10~30min; And / or, in step S4, the slag removal is to remove slag from the bottom and surface of the melt 2 to 3 times respectively, and then manually stir for 2 to 3 minutes after removing the slag; And / or, in step S4, the initial temperature for settling is 750~760℃, and the settling time is 20~30min.

6. The method for preparing low-cost, high-strength, corrosion-resistant magnesium alloy according to claim 4, characterized in that, In step S5, the pouring temperature is 680~710℃.

7. The method for preparing low-cost, high-strength, corrosion-resistant magnesium alloy according to claim 4, characterized in that, In step S6, the homogenization treatment is performed under two-stage solution treatment conditions, wherein the two-stage solution treatment conditions are: the first stage heat treatment temperature is 350~370℃, and the time is 2~3 h; the second stage heat treatment temperature is 400~420℃, and the time is 10~20 h.

8. The method for preparing low-cost, high-strength, corrosion-resistant magnesium alloy according to claim 4, characterized in that, In step S6, the temperature for heat deformation treatment is 320~380 ℃, and the total amount of heat deformation is 70~90%. And / or, the hot deformation treatment is one of forging, extrusion, or rolling; When hot deformation is forging, the resulting hot-deformed product is a forging; When heat deformation is performed by extrusion, the resulting heat-deformed product is a profile. When hot deformation is achieved through rolling, the resulting hot-deformed product is a sheet material.

9. The method for preparing low-cost, high-strength, corrosion-resistant magnesium alloy according to claim 4, characterized in that, In step S7, the aging heat treatment temperature is 160~210℃ and the time is 10~30 h.

10. The method for preparing low-cost, high-strength, corrosion-resistant magnesium alloy according to claim 4, characterized in that, In step S7, the microstructure of the obtained low-cost, high-strength, corrosion-resistant magnesium alloy includes a continuous network β phase, Al2Ca phase, Al2Y phase, and Al-Mn-Y phase. The Al2Ca phase is distributed on the β phase and inside the grains, while the Al2Y phase and Al-Mn-Y phase are uniformly distributed inside the grains. The grain size is 2~60μm.

Images