A heat treatment free high corrosion resistance high heat resistance flame retardant die casting magnesium alloy and a preparation method thereof

Abstract

The application relates to a heat-treatment-free high-corrosion-resistance high-heat-resistance flame-retardant die-casting magnesium alloy and a preparation method thereof, the weight percentage of each component in the alloy is as follows: Al: 4-7%; RE: 3-7%; Mn: 0.2-0.5%; Be: 0.001-0.02%; X: 0.002-2%; Z: 0.002-2%, X is at least one of Ca and Sr, Z is at least one of Zn and In; the total amount of other impurities is less than or equal to 0.3%, and the balance is Mg. The alloy can significantly improve the corrosion resistance, heat resistance and flame retardance of the alloy by adding X and Z elements. The creep performance, corrosion resistance and flame retardance of the alloy are far superior to those of traditional die-casting magnesium alloys, and can be basically equivalent to those of traditional die-casting aluminum alloy ADC12. In addition, the alloy also has good die-casting performance, can be used for forming heat-resistant shells, cylinder bodies and cylinder covers or other parts, and greatly expands the application scenarios of the die-casting magnesium alloy.

Description

Technical Field

[0001] This invention relates to the field of metallic materials technology, specifically to a heat-treatable, high corrosion-resistant, high heat-resistant, and flame-retardant die-cast magnesium alloy and its preparation method. Background Technology

[0002] Current automotive R&D is moving towards high efficiency, low energy consumption, and low emissions. Given the significant challenge of increasing the energy density of electric vehicle batteries, reducing the structural weight of electric vehicles significantly improves their driving range. Furthermore, reducing vehicle weight simultaneously improves vehicle efficiency, reduces braking distance for enhanced safety, and lowers energy consumption and emissions; lightweighting has become a crucial direction for automotive development. Among various forming methods for automotive parts, high-pressure casting is the most widely used and economical method due to its high production efficiency and high level of automation. With the rapid development of the electric vehicle and die-casting industries, leading electric vehicle companies like Tesla are gradually consolidating parts, shifting from multi-part assembly to integrated die-casting. Integrated die-casting significantly reduces total production time, the number of molds, and factory construction time and costs. It also reduces the number of operators and managers, significantly lowering manufacturing costs. Moreover, the reduced manufacturing steps make part quality easier to control.

[0003] The development of heat-treatment-free alloys is a key solution to the production of large, integrated die-cast parts. For traditional alloy materials, heat treatment is essential to ensure the mechanical properties of die-cast parts. However, heat treatment can cause deformation, leading to deviations in dimensional accuracy. Deformation is inevitable in large, integrated parts during heat treatment. While straightening processes can provide some repair, most deformed parts are irreparable and must be scrapped. Furthermore, heat treatment can cause bulging, cracking, and other problems, ultimately resulting in a sharp increase in costs. Therefore, compared to traditional heat-treated alloys, heat-treatment-free alloys can reduce production steps, save energy, reduce carbon emissions, and lower production costs, making the production of large, integrated die-cast parts possible.

[0004] Currently, many domestic enterprises and universities have developed several high-performance heat-treatable die-cast aluminum alloys and applied them to the actual production of electric vehicles. my country's heat-treatable die-cast aluminum alloys are at an internationally leading level. Magnesium alloys have high specific strength, excellent shock absorption performance, and electromagnetic shielding capabilities, making them the most promising structural metal materials. However, their poor high-temperature performance, poor corrosion resistance, and flammability limit their application as heat-resistant shell parts. The development of heat-treatable, high corrosion-resistant, high heat-resistant, and flame-retardant die-cast magnesium alloys is still relatively lagging. As the country with the richest magnesium resources, my country's development of heat-treatable, high corrosion-resistant, high heat-resistant, and flame-retardant die-cast magnesium alloys and their application in integrated heat-resistant shell parts for electric vehicles, such as three-in-one motor housings, two-in-one motor housings, transmission housings, and end caps, can further reduce the weight of electric vehicles, improve their range, driving performance, and safety, and significantly enhance my country's level of lightweight alloy materials and automotive lightweighting technology. This has significant scientific research and practical application value.

[0005] Die-cast magnesium alloys are mainly Mg-Al based alloys. Currently, the most widely used are AZ91D (Mg-Al-Zn) based die-cast magnesium alloys and AM60 (Mg-Al-Mn) based die-cast magnesium alloys. The main eutectic phase in both AZ91D and AM60 alloys is low-melting-point Mg. 17 Al 12 The presence of this phase results in poor heat resistance in the alloy, therefore AZ91D and AM60 alloys are mainly used in exterior parts such as steering wheels and dashboard frames. Among Mg-Al die-casting magnesium alloys, the AX (Mg-Al-Ca) series die-casting magnesium alloys have better heat resistance, but due to the large amount of Ca added, the alloy has a high tendency to hot cracking, poor casting performance, and is difficult to form complex and large integrated parts.

[0006] AE (Mg-Al-RE) die-cast magnesium alloys are produced by adding RE elements (mixed rare earth elements) to combine with Al elements to form Al. 11 The RE3 eutectic phase has a high melting point and strong heat resistance, resulting in superior heat resistance for the alloy. However, the heat resistance of AE-based die-cast magnesium alloys still lags behind that of currently used die-cast aluminum alloys, making it difficult to directly replace existing die-cast aluminum alloys. Furthermore, Al... 11 The RE3 eutectic phase has a high potential difference, resulting in a large potential difference between it and the Mg matrix. This leads to poor corrosion resistance of the alloy, limiting its application.

[0007] The inventors' team previously filed a Chinese patent, 202310638270.4, which disclosed "a high-strength, high-toughness, and high-heat-resistant Mg-Al-RE die-cast magnesium alloy and its preparation method." This method improves the alloy's strength, heat resistance, and toughness by controlling the Al content to 4.5-6%, the La content to 4.5-6%, the Mn content to 0.2-0.5%, and adding a small amount of Sn. However, it does not mention corrosion resistance, and since Sn has a high potential, it is foreseeable that the alloy will have poor corrosion resistance.

[0008] Chinese patent 201611082654.9 discloses "a high thermal conductivity, corrosion resistance, and heat resistance die-cast magnesium alloy and its manufacturing method." This magnesium alloy contains 1-6 wt% La, 2-4.5 wt% Al, 0.05-0.5 wt% Mn, 0.16-1.5 wt% Ca, and 0.02-1.5 wt% Sr, giving it high thermal conductivity, corrosion resistance, and heat resistance. To ensure the alloy's thermal conductivity, a relatively small amount of Al is added; however, insufficient Al content leads to poor casting performance. Furthermore, the addition of only Ca and Sr is insufficient to significantly improve the alloy's corrosion resistance. The minimum corrosion rate of the magnesium alloy in this patent is 4.11 g·m⁻¹. -2 ·d -1 After unit conversion, it is approximately 0.83 mm / year, which is about four times the corrosion rate of traditional die-cast aluminum alloy ADC12. Therefore, it is still difficult to replace existing die-cast aluminum alloy heat-resistant shell parts.

[0009] Therefore, existing die-cast magnesium alloy materials face the technical challenge of simultaneously achieving heat resistance, corrosion resistance, flame retardancy, and casting performance. This makes it impossible for current die-cast magnesium alloys to meet the demand for heat-resistant, corrosion-resistant, heat-resistant, and flame-retardant die-cast magnesium alloys that require no heat treatment for large, integrated heat-resistant components. There is an urgent need to develop new heat-resistant, corrosion-resistant, heat-resistant, and flame-retardant die-cast magnesium alloys to meet the requirements for magnesium alloys in large, integrated heat-resistant components. Summary of the Invention

[0010] The purpose of this invention is to provide a heat-treatable, high-corrosion-resistant, high-heat-resistant, and flame-retardant die-cast magnesium alloy and its preparation method. While ensuring good casting performance, this invention solves the problem that existing magnesium alloys cannot simultaneously achieve high corrosion resistance, high heat resistance, and flame retardancy without heat treatment. This expands the application scenarios of die-cast magnesium alloys, allowing them to be used in heat-resistant shells, cylinder blocks, or cylinder heads, replacing traditional die-cast aluminum alloys or steel. This can significantly reduce the weight of parts and improve my country's lightweight technology level.

[0011] To achieve this objective, this invention, in its research on Mg-Al-RE die-cast magnesium alloys, discovered that the composite addition of elements such as Ca, Sr, Zn, and In can significantly improve the alloy's corrosion resistance, heat resistance, and flame retardancy. Ca, Sr, Zn, and In elements can all dissolve in the Mg matrix, increasing the Mg matrix's potential, reducing the potential difference between the Mg matrix and the second phase, improving the alloy's corrosion resistance, and also acting as solid solution strengthening, increasing the strength of the Mg matrix, and further improving the alloy's heat resistance. Furthermore, the radii of Ca and Sr atoms are larger than those of Mg atoms. The radii of Zn and In atoms are smaller than those of Mg atoms, resulting in optimal solid solution performance when added in combination. The combined addition of Ca, Sr, Zn, and In elements can also form second phases such as Al2XZ and Al4XZ (X = Ca, Sr, Z = Zn, In). These second phases have lower potentials than the AlRE eutectic phase, which can isolate the low-potential Mg matrix from the high-potential AlRE eutectic phase, weakening the micro-area galvanic corrosion effect and significantly improving the alloy's corrosion resistance. Furthermore, these second phases themselves possess extremely high melting points and thermal strengths, significantly improving the alloy's heat resistance and ignition point. In addition, the poor corrosion resistance of magnesium alloys is also due to the inability to form a dense oxide film during oxidation, which fails to prevent corrosion from penetrating and eventually leading to perforation. The combined addition of Ca, Sr, Zn, and In elements can fill the gaps in the loose oxide film formed during oxidation, increasing the density of the oxide film and protecting the internal magnesium alloy from damage, thus improving the alloy's corrosion resistance and ignition point. However, excessive amounts of Ca, Sr, Zn, and In elements significantly increase the hot cracking susceptibility of the alloy, severely impairing its plasticity and castability. Furthermore, the resulting AlXZ phase agglomerates, which in turn reduces the alloy's corrosion resistance, heat resistance, and flame retardancy. Conversely, insufficient amounts of Ca, Sr, Zn, and In elements fail to improve these properties. Therefore, this invention controls the Ca and Sr content to 0.002–2% and the Zn and In content to 0.002–2%. In our previous experiments, we also attempted a scheme involving the combined addition of Z elements such as Bi, Ti, V, Zr, and Cr with X elements (Ca and / or Sr), but this did not achieve a synergistic effect in improving creep resistance, corrosion resistance, or flame retardancy.

[0012] This invention further reveals that when the weight percentages of elements X and Z in the alloy satisfy X + Z / 2 ≥ 0.5, the alloy exhibits higher solid solubility of elements X and Z and a higher content of the high-melting-point, high-thermal-strength Al2XZ and Al4XZ second phases, resulting in better heat resistance. The creep strain at 150℃, 100MPa, and 100h can be below 0.070%. When the weight percentages of elements X and Z in the alloy satisfy 1 ≤ X / Z ≤ 5, the oxide film formed during oxidation is the densest, leading to higher corrosion resistance and ignition point. The corrosion rate under 5% NaCl neutral salt spray for 168h can be below 0.2mm / year, and the ignition point can be above 980℃.

[0013] To balance the strength and toughness of the alloy, the Al content is controlled at 4-7%, and the RE content at 3-7%. At these levels, Al and RE can form a suitable Al alloy. 11 The RE3 eutectic phase, if present in excess, reduces the alloy's plasticity and increases its hot cracking resistance, while insufficient eutectic phase fails to guarantee the alloy's strength and heat resistance. The rare earth element used in this invention is at least one of La and Ce, both highly abundant and inexpensive rare earth elements, resulting in a lower alloy cost that meets the needs of industrial applications. This invention also finds that, since RE is a high-melting-point metal, as the RE content increases, the alloy's liquidus temperature also increases. An excessively high liquidus temperature causes premature solidification during die casting, leading to micro-cold shuts on the surface of the die-cast parts and internal defects such as pre-crystallization, shrinkage cavities, and porosity. Al, on the other hand, can lower the alloy's liquidus temperature. Therefore, to ensure the surface and internal quality of the die-cast parts, this invention preferably uses an Al / RE content of ≥0.6. However, when the Al content is too high, the solid solution of RE and Al in magnesium is insufficient to completely consume the Al, and the excess Al will form low-melting-point Mg. 17 Al 12 The second phase significantly reduces the heat resistance of the alloy. Therefore, the present invention also preferably requires that the Al and RE contents simultaneously satisfy the condition Al / RE ≤ 1.7.

[0014] Furthermore, this invention also adds small amounts of Mn and Be elements to the aforementioned alloy. The Mn content is controlled at 0.2-0.5%. Mn can combine with and remove impurity elements such as Fe and Ni from the magnesium melt, ensuring the purity of the magnesium melt and reducing galvanic corrosion between impurity elements and the magnesium matrix, thus enhancing the alloy's corrosion resistance. Excess Mn is dissolved in the magnesium matrix, ensuring the alloy's strength. Be helps form a dense protective film on the magnesium alloy surface, significantly reducing oxidation and combustion during the smelting process. This reduces oxide inclusions or alloy element loss due to combustion, improving the purity and compositional stability of the magnesium alloy during smelting, thereby further enhancing the stability of the magnesium alloy product.

[0015] Accordingly, the technical solution adopted by the present invention is as follows:

[0016] In a first aspect, the present invention relates to a heat-treatable, high corrosion-resistant, high heat-resistant, and flame-retardant die-cast magnesium alloy, wherein the weight percentages of each component in the die-cast magnesium alloy are as follows: Al: 4-7%; RE: 3-7%; Mn: 0.2-0.5%; Be: 0.001-0.02%; X: 0.002-2%; Z: 0.002-2%, where X is at least one of Ca and Sr, and Z is at least one of Zn and In; the total amount of other impurities is ≤0.3%, and the balance is Mg.

[0017] Preferably, when X is a combination of Ca and Sr, the mixing ratio is not particularly limited and can be any ratio.

[0018] Preferably, when Z is a combination of Zn and In, the mixing ratio is not particularly limited and can be any ratio.

[0019] Preferably, the RE in the die-cast magnesium alloy is at least one of La and Ce. When the RE is a combination of La and Ce, the mixing ratio is not particularly limited and can be any ratio.

[0020] Preferably, in the die-cast magnesium alloy, the weight percentage of Al and RE elements must meet the following condition: 0.6≤Al / RE≤1.7.

[0021] Preferably, the weight percentages of X and Z elements in the die-cast magnesium alloy satisfy the following condition: X + Z / 2 ≥ 0.5, and the creep strain of the die-cast magnesium alloy prepared therefrom can be below 0.070% at 150℃, 100MPa and 100h.

[0022] Preferably, the weight percentages of X and Z elements in the die-cast magnesium alloy satisfy the following condition: 1≤X / Z≤5. The die-cast magnesium alloy prepared thereby can have a corrosion rate of less than 0.2 mm / year under 5% NaCl neutral salt spray for 168 h, and an ignition point of more than 980℃.

[0023] More preferably, in the die-cast magnesium alloy, the weight percentages of Al and RE elements must meet the following conditions: 0.6≤Al / RE≤1.7; and the weight percentages of X and Z elements in the die-cast magnesium alloy must simultaneously meet the following conditions: 0.5≤X+Z / 2≤2.7, 1.05≤X / Z≤4.3;

[0024] The die-cast magnesium alloy prepared in this way simultaneously meets the following requirements: creep strain below 0.070% at 150℃, 100MPa, and 100h; corrosion rate below 0.2mm / year under 5% NaCl neutral salt spray for 168h; and ignition point above 985℃.

[0025] Secondly, the present invention also relates to a method for preparing the aforementioned heat-treatable, high corrosion-resistant, high heat-resistant, and flame-retardant die-cast magnesium alloy, the method comprising the following steps:

[0026] S1. Material preparation: Prepare materials according to the aforementioned magnesium alloy composition; wherein, Mg, Al, and Zn are prepared in the form of pure magnesium, pure aluminum, and pure zinc, RE is prepared in the form of pure rare earth or Mg-RE or Al-RE master alloy, X and In are prepared in the form of pure X, pure In or magnesium-containing master alloy or aluminum-containing master alloy, and Mn and Be are prepared in the form of magnesium-containing or aluminum-containing master alloy.

[0027] S2. Melting: First, preheat the crucible to 300-500℃, put the pure Mg ingot into the crucible, and melt it under a protective gas or in a vacuum environment. Alternatively, first cover the crucible with a layer of covering agent, add the pure Mg ingot, and after it melts, cover the surface of the melt with another layer of covering agent. Then, raise the temperature to 750-780℃ and add Al-Be or Mg-Be master alloy. After the master alloy melts, maintain this temperature and add pure rare earth or Mg-RE or Al-RE master alloy. After it melts, lower the temperature to 720-750℃, and then add pure aluminum, pure zinc, Al-Mn or Mg-Mn master alloy, pure X or Al-X or Mg-X master alloy, or pure In or Al-In or Mg-In master alloy for melting.

[0028] S3. Refining: The melt from step S2 is heated to 720-750°C, and a gas containing refining agent powder is introduced into the melt for powder spraying refining and slag removal treatment.

[0029] S4. Casting or die casting: After the melt undergoes powder spraying, refining and slag removal in step S3 reaches the casting temperature, the alloy ingot casting operation or die casting operation is carried out to finally complete the production of alloy ingots or die castings.

[0030] Preferably, step S1 further includes a step of preheating the prepared raw materials to 150-250°C for preheating and drying.

[0031] Preferably, in step S2, the covering agent has a solvent density <1.58 g / cm³. 3 The covering agent can be of a type conventionally selected in the art and can be obtained through ordinary commercial channels; the protective gas is any one of the following: a mixture of N2+SF6, a mixture of CO2+SF6, a mixture of Ar+SF6, or a pure SF6 protective gas introduced into the furnace.

[0032] Preferably, step S2 further includes the following steps: after the melt is stirred evenly, it is allowed to stand and a pre-furnace composition analysis is performed to detect the composition content of the alloy melt, and the melt with a deviation in content is replenished or diluted to bring its composition to the qualified range.

[0033] Preferably, in step S3, the refining agent is a salt flux that can adsorb impurities in the magnesium alloy melt. It can be a type conventionally selected in the art and can be obtained through ordinary commercial channels.

[0034] Preferably, in step S3, the amount of the refining agent added is 0.3% to 2.0% of the total weight of the melt.

[0035] Preferably, in step S3, the gas includes argon.

[0036] Preferably, in step S3, after the powder spraying refining and slag removal treatment, the process further includes a settling period followed by a pre-furnace composition analysis test.

[0037] More preferably, the settling time is 5 to 15 minutes.

[0038] Preferably, in step S4, the casting temperature is 690–740°C.

[0039] Preferably, in step S4, when using the die-casting magnesium alloy to produce die-cast parts, the high-speed injection speed range is 2 to 8 m / s.

[0040] Preferably, in step S4, when using the die-casting magnesium alloy to produce die-cast parts, the casting pressure range is 40 to 150 MPa.

[0041] This invention further enhances corrosion resistance, heat resistance, and flame retardancy by specifically employing a pouring temperature of 690–740°C, a high-speed injection velocity of 2–8 m / s, and a casting pressure of 40–150 MPa.

[0042] Compared with the prior art, the present invention has the following beneficial effects:

[0043] 1. The heat-treatable, high-corrosion-resistant, high-heat-resistant, and flame-retardant die-cast magnesium alloy of this invention is based on conventional Mg-Al-RE die-cast magnesium alloys, with the addition of X and Z elements, which can significantly improve the alloy's corrosion resistance, heat resistance, and flame-retardant properties. Specifically, by adding Ca, Sr, Zn, and In elements, the potential difference between the Mg matrix and the AlRE eutectic phase is effectively reduced, and a dense oxide film can be formed on the surface of the magnesium alloy, significantly improving the alloy's corrosion resistance and ignition point; it can also form high-melting-point and high-thermal-strength Al2XZ and Al4XZ (X = Ca, Sr, Z = Zn, In) second phases, improving the alloy's heat resistance and ignition point; thus, the alloy possesses a good balance of corrosion resistance, heat resistance, and flame retardancy.

[0044] 2. The die-cast magnesium alloy obtained by this invention has comprehensive properties of high corrosion resistance, high heat resistance, and flame retardancy. Its creep strain at 150℃, 100MPa, and 100h is 0.056-0.088%, its corrosion rate at 5% NaCl neutral salt spray for 168h is 0.1-0.3mm / year, and its ignition point is 950-1000℃. The creep performance, corrosion resistance, and flame retardancy of this alloy are far superior to those of traditional die-cast magnesium alloys (such as AZ91D and AM60), and are basically equivalent to those of traditional die-cast aluminum alloy ADC12. In addition, this alloy also has good die-casting properties and can be used to form heat-resistant shells, cylinder blocks, cylinder heads, or other parts, greatly expanding the application scenarios of die-cast magnesium alloys.

[0045] 3. Furthermore, based on the improvement of heat resistance, by specifically selecting the weight percentages of Al and RE elements to meet the requirement of 0.6≤Al / RE≤1.7, and the weight percentage content of X and Z to meet the requirement of X+Z / 2≥0.5, the creep strain of the die-cast magnesium alloy at 150℃, 100MPa, and 100h can be kept below 0.070%. Furthermore, based on the improvement of corrosion resistance and ignition point, by specifically selecting the weight percentages of Al and RE elements to meet the requirement of 0.6≤Al / RE≤1.7, and the weight percentage content of X and Z to meet the requirement of 1≤X / Z≤5, the corrosion rate of the die-cast magnesium alloy under 5% NaCl neutral salt spray for 168h can be kept below 0.2mm / year, and the ignition point can be kept above 980℃. Attached Figure Description

[0046] 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:

[0047] Figure 1 The images show the microstructure of the die-cast magnesium alloy part and the potentials of each phase obtained in Comparative Example 1 of this invention; wherein, Figure 1 A is a microscopic tissue photograph; Figure 1 B is Figure 1 The potentials of each phase are measured at the dashed arrows in A.

[0048] Figure 2 The images show the microstructure of the die-cast magnesium alloy part and the potentials of each phase obtained in Example 1 of this invention; wherein, Figure 2 A is a microscopic tissue photograph; Figure 2 B is Figure 1 The potentials of each phase are measured at the dashed arrows in A.

[0049] Figure 3 This is a microstructure photograph of the die-cast magnesium alloy part obtained in Example 2 of the present invention.

[0050] Figure 4 This is a photograph of the microstructure of the die-cast magnesium alloy part obtained in Comparative Example 2 of the present invention.

[0051] Figure 5 This is a photograph showing the microstructure of the surface of the die-cast magnesium alloy part obtained in Comparative Example 1 of the present invention after a salt spray corrosion test.

[0052] Figure 6 This is a microscopic morphology photograph of the surface of the die-cast magnesium alloy part obtained in Example 1 of the present invention after a salt spray corrosion test.

[0053] Figure 7 The creep curves are those of the die-cast alloy parts obtained in Example 1 and Comparative Examples 1-4 of this invention. Detailed Implementation

[0054] The present invention will now be described in detail with reference to specific embodiments. These embodiments will help those skilled in the art to further understand the present invention, but do not limit the invention in any way. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention. These all fall within the scope of protection of the present invention.

[0055] The measured composition of the magnesium alloys in each embodiment and comparative example of this invention is summarized in Table 1, with the remainder being Mg and other unavoidable impurities. The creep performance test results of the magnesium alloys in each embodiment and comparative example are summarized in Table 2; the corrosion resistance and ignition point test results of the magnesium alloys in each embodiment and comparative example are summarized in Table 3; and the room temperature tensile performance test results of the magnesium alloys in each embodiment and comparative example are summarized in Table 4. The creep performance test was conducted according to the method in GB / T 2039-2024 "Metallic Materials - Uniaxial Tensile Creep Test Method"; the salt spray corrosion test was conducted according to the method in GB / T 10125-2021 "Artificial Atmosphere Corrosion Test - Salt Spray Test" using a 5% neutral NaCl solution for 168 hours; and the room temperature tensile performance test was conducted according to the method in GB / T 228.1-2021 "Metallic Materials - Tensile Testing - Part 1: Room Temperature Test Method".

[0056] Example 1

[0057] This embodiment provides a method for preparing a heat-tight high-strength and high-toughness die-cast magnesium alloy without heat treatment. The specific steps are as follows:

[0058] 1) Based on the theoretical weight percentage of each component being Mg-5.5Al-5La-1Ce-0.36Mn-0.008Be-0.9Ca-0.3In, pure Mg ingots, pure Al ingots, pure In ingots, Mg-30La, Mg-30Ce, Al-20Mn, Al-3Be, and Mg-30Ca master alloys were selected as raw materials, and the raw materials were preheated to 200℃ and dried.

[0059] 2) Preheat the crucible to 150°C, and evenly coat the inner wall of the crucible with crucible coating (mainly used to prevent magnesium liquid from sticking to the crucible; conventionally selected types in this field can be used, which can be obtained through ordinary commercial channels, the same below). After drying, heat to 400°C and introduce a CO2+SF6 mixed gas (mixed volume ratio of CO2:SF6 is 99:1). Place pure Mg ingots into the crucible and melt them completely under the protection of the mixed protective gas of CO2 and SF6. Then raise the temperature to 760°C and add Al-3Be master alloy. After the alloy is completely melted, add Mg-30La and Mg-30Ce master alloys until they are completely melted. Cool down to 730°C and add pure Al ingots, pure In ingots, Al-20Mn, and Mg-30Ca master alloys. After complete melting, stir thoroughly, let stand, and perform pre-furnace composition analysis to detect the composition content of the alloy melt. For melts with deviations in content, add material or dilute to make the composition reach the designed magnesium alloy composition range.

[0060] 3) Heat the melt to 730°C, introduce argon gas at a pressure of 0.2 MPa into the melt, and introduce 1% of the total weight of the refining agent (specifically, Torch brand magnesium alloy refining agent, purchased from Zhangjiagang Haohua Light Alloy Materials Co., Ltd.) powder into the melt, and then continue to purge for 10 minutes to remove slag and gas.

[0061] 4) After refining, the melt is allowed to stand for 10 minutes, and then a pre-furnace composition analysis test is performed. If the composition is qualified, high-pressure casting is carried out at 710-720℃, with an injection speed of 3.8m / s and a casting pressure (boost) of 90MPa. The mold used in the production process is a die-casting test rod mold.

[0062] The properties of the resulting die-cast magnesium alloy parts are shown in Tables 2, 3, and 4.

[0063] Example 2

[0064] This embodiment provides a method for preparing a heat-tight high-strength and high-toughness die-cast magnesium alloy without heat treatment. The specific steps are as follows:

[0065] 1) Based on the theoretical weight percentage of each component as Mg-6Al-2.4La-2.4Ce-0.25Mn-0.01Be-0.4Ca-0.8Sr-0.1Zn-0.1In, pure Mg ingot, pure Al ingot, pure Zn ingot, pure In ingot, Al-60La, Mg-30Ce, Mg-10Mn, Mg-3Be, Al-10Ca, and Mg-30Sr master alloys were selected as raw materials, and the raw materials were preheated to 170℃ and dried.

[0066] 2) Preheat the crucible to 150℃, evenly coat the inner wall of the crucible with crucible coating, dry it and then heat it to 440℃. Introduce a mixture of N2 and SF6 gas (mixing volume ratio of N2:SF6 is 99:1). Place pure Mg ingots into the crucible and melt them completely under the protection of the mixed protective gas of N2 and SF6. Then raise the temperature to 750℃ and add Mg-3Be master alloy. After the alloy is completely melted, add Al-60La and Mg-30Ce master alloys until they are completely melted. Cool down to 725℃ and add pure Al ingots, pure Zn ingots, pure In ingots, Mg-10Mn, Al-10Ca, and Mg-30Sr master alloys. After they are completely melted, stir them thoroughly, let them stand and perform pre-furnace composition analysis to detect the composition content of the alloy melt. For melts with deviations in content, add materials or dilute them to make the composition reach the designed magnesium alloy composition range.

[0067] 3) Heat the melt to 725°C, introduce argon gas at a pressure of 0.2 MPa into the melt, and introduce 1.5% of the total weight of the refining agent (specifically, Torch brand magnesium alloy refining agent, purchased from Zhangjiagang Haohua Light Alloy Materials Co., Ltd.) powder into the melt, and then continue to purge for 10 minutes to remove slag and gas.

[0068] 4) After refining, the melt is allowed to stand for 12 minutes, and then a pre-furnace composition analysis test is performed. If the composition is qualified, high-pressure casting is carried out at 720-730℃, with an injection speed of 3.5m / s and a casting pressure of 110MPa. The mold used in the production process is a die-casting test rod mold.

[0069] The properties of the resulting die-cast magnesium alloy parts are shown in Tables 2, 3, and 4.

[0070] Example 3

[0071] This embodiment provides a method for preparing a heat-tight high-strength and high-toughness die-cast magnesium alloy without heat treatment. The specific steps are as follows:

[0072] 1) Based on the theoretical weight percentage of each component as Mg-4Al-1.6La-2.7Ce-0.31Mn-0.004Be-0.06Ca-0.01Sr-0.008Zn, pure Mg ingot, pure Al ingot, pure Zn ingot, pure Ce, Al-90La, Al-10Mn, Mg-3Be, pure Ca, and pure Sr master alloys were selected as raw materials. The raw materials were preheated to 210℃ and dried.

[0073] 2) Preheat the crucible to 150℃, evenly coat the inner wall of the crucible with crucible coating, dry it and then heat it to 370℃. Introduce pure SF6 gas, put pure Mg ingot into the crucible, and melt it completely under the protection of pure SF6 protective gas. Then raise the temperature to 770℃, add Mg-3Be master alloy, and after the alloy is completely melted, add pure Ce ingot and Al-90La master alloy until they are completely melted. Cool down to 750℃, add pure Al ingot, pure Ca ingot, pure Sr ingot, pure Zn ingot, and Al-10Mn master alloy. After it is completely melted, stir it thoroughly, let it stand and perform pre-furnace composition analysis to detect the composition content of the alloy melt. For melts with deviations in content, add material or dilute it to make its composition reach the designed magnesium alloy composition range.

[0074] 3) Heat the melt to 745°C, introduce argon gas at a pressure of 0.2 MPa into the melt, and introduce 0.8% of the total weight of the refining agent (specifically, Torch brand magnesium alloy refining agent, purchased from Zhangjiagang Haohua Light Alloy Materials Co., Ltd.) powder into the melt, and then continue to purge for 10 minutes to remove slag and gas;

[0075] 4) After refining, the melt is allowed to stand for 7 minutes, and then a pre-furnace composition analysis test is performed. If the composition is qualified, high-pressure casting is carried out at 705-715℃, with an injection speed of 2m / s and a casting pressure of 50MPa. The mold used in the production process is a die-casting test rod mold.

[0076] The properties of the resulting die-cast magnesium alloy parts are shown in Tables 2, 3, and 4.

[0077] Example 4

[0078] This embodiment provides a method for preparing a heat-tight high-strength and high-toughness die-cast magnesium alloy without heat treatment. The specific steps are as follows:

[0079] 1) Based on the theoretical weight percentage of each component being Mg-5.1Al-3Ce-0.4Mn-0.012Be-0.8Ca-0.8Sr-2In, pure Mg ingots, pure Al ingots, Al-90Ce, Al-10Mn, Al-3Be, Mg-60Ca, Mg-60Sr, and Mg-30In master alloys were selected as raw materials, and the raw materials were preheated to 150℃ and dried.

[0080] 2) Preheat the crucible to 150℃, evenly coat the inner wall of the crucible with crucible coating, dry it and then heat it to 300℃. Introduce a mixture of N2 and SF6 gas (mixing volume ratio of N2:SF6 is 99:1). Place the pure Mg ingot into the crucible and melt it completely under the protection of the mixed protective gas of N2 and SF6. Then raise the temperature to 765℃ and add Al-3Be master alloy. After the alloy is completely melted, add Al-90Ce master alloy until it is completely melted. Cool down to 740℃ and add pure Al ingot, Al-10Mn, Mg-60Ca, Mg-60Sr and Mg-30In master alloy. After it is completely melted, stir it thoroughly, let it stand and perform pre-furnace composition analysis to detect the composition content of the alloy melt. For melts with deviations in content, add material or dilute it to make its composition reach the designed magnesium alloy composition range.

[0081] 3) Heat the melt to 720°C, introduce argon gas at a pressure of 0.2 MPa into the melt, and introduce 1.2% of the total weight of the refining agent (specifically, Torch brand magnesium alloy refining agent, purchased from Zhangjiagang Haohua Light Alloy Materials Co., Ltd.) powder into the melt, and then continue to purge for 10 minutes to remove slag and gas;

[0082] 4) After refining, the melt is allowed to stand for 11 minutes, and then a pre-furnace composition analysis test is performed. If the composition is qualified, high-pressure casting is carried out at 725-735℃, with an injection speed of 2.7m / s and a casting pressure of 70MPa. The mold used in the production process is a die-casting test rod mold.

[0083] The properties of the resulting die-cast magnesium alloy parts are shown in Tables 2, 3, and 4.

[0084] Example 5

[0085] This embodiment provides a method for preparing a heat-tight high-strength and high-toughness die-cast magnesium alloy without heat treatment. The specific steps are as follows:

[0086] 1) Based on the theoretical weight percentage of each component as Mg-5.7Al-0.6La-3.4Ce-0.5Mn-0.014Be-0.1Sr-0.1Zn, pure Mg ingot, pure Al ingot, pure Zn ingot, pure Ce, pure La, Al-20Mn, Al-3Be, and Mg-10Sr master alloy were selected as raw materials. The raw materials were preheated to 220℃ and dried.

[0087] 2) Preheat the crucible to 150℃, evenly coat the inner wall of the crucible with crucible coating, dry it and then heat it to 450℃. Introduce a CO2+SF6 mixed gas (mixed volume ratio of CO2:SF6 is 99:1). Place pure Mg ingots into the crucible and melt them completely under the protection of the mixed protective gas of CO2 and SF6. Then raise the temperature to 780℃ and add Al-3Be master alloy. After the alloy is completely melted, add pure Ce and pure La until they are completely melted. Cool down to 735℃ and add pure Al ingots, pure Zn ingots, Al-20Mn, and Mg-10Sr master alloy. After complete melting, stir thoroughly, let it stand and perform pre-furnace composition analysis to detect the composition content of the alloy melt. For melts with deviations in content, add material or dilute to make the composition reach the designed magnesium alloy composition range.

[0088] 3) Heat the melt to 735°C, introduce argon gas at a pressure of 0.2 MPa into the melt, and introduce 0.3% of the total weight of the refining agent (specifically, Torch brand magnesium alloy refining agent, purchased from Zhangjiagang Haohua Light Alloy Materials Co., Ltd.) powder into the melt, and then continue to purge for 10 minutes to remove slag and gas;

[0089] 4) After refining, the melt is allowed to stand for 8 minutes, and then a pre-furnace composition analysis test is performed. If the composition is qualified, high-pressure casting is carried out at 690-700℃, with an injection speed of 4.5m / s and a casting pressure of 40MPa. The mold used in the production process is a die-casting test rod mold.

[0090] The properties of the resulting die-cast magnesium alloy parts are shown in Tables 2, 3, and 4.

[0091] Example 6

[0092] This embodiment provides a method for preparing a heat-tight high-strength and high-toughness die-cast magnesium alloy without heat treatment. The specific steps are as follows:

[0093] 1) Based on the theoretical weight percentage of each component as Mg-4.6Al-6.5La-0.23Mn-0.017Be-0.002Sr-0.5Zn-0.1In, pure Mg ingot, pure Al ingot, pure Zn ingot, Mg-90La, Mg-5Mn, Mg-3Be, Al-20Sr, and Al-20In master alloys were selected as raw materials, and the raw materials were preheated to 180℃ and dried.

[0094] 2) Preheat the crucible to 150°C, evenly coat the inner wall of the crucible with crucible coating, dry it and then heat it to 500°C. Cover the crucible with a layer of covering agent (in this embodiment, the specific covering agent used is Torch brand flux, purchased from Zhangjiagang Haohua Light Alloy Materials Co., Ltd.). Place pure Mg ingots into the crucible and wait for them to melt completely. Cover the surface of the melt with another layer of covering agent, raise the temperature to 755°C, add Mg-3Be master alloy, and after the alloy is completely melted, add Mg-90La master alloy until it is completely melted. Cool down to 720°C and add pure Al ingots, pure Zn ingots, Mg-5Mn, Al-20Sr, and Al-20In master alloys. After complete melting, stir thoroughly, let stand and perform pre-furnace composition analysis to detect the composition content of the alloy melt. For melts with deviations in content, add materials or dilute to make the composition reach the designed magnesium alloy composition range.

[0095] 3) Heat the melt to 750°C, introduce argon gas at a pressure of 0.2 MPa into the melt, and introduce 0.5% of the total weight of the refining agent (specifically, Torch brand magnesium alloy refining agent, purchased from Zhangjiagang Haohua Light Alloy Materials Co., Ltd.) powder into the melt, and then continue to purge for 10 minutes to remove slag and gas;

[0096] 4) After refining, the melt is allowed to stand for 5 minutes, and then a pre-furnace composition analysis test is performed. If the composition is qualified, high-pressure casting is carried out at 700-710℃, with an injection speed of 6m / s and a casting pressure of 150MPa. The mold used in the production process is a die-casting test rod mold.

[0097] The properties of the resulting die-cast magnesium alloy parts are shown in Tables 2, 3, and 4.

[0098] Example 7

[0099] This embodiment provides a method for preparing a heat-tight high-strength and high-toughness die-cast magnesium alloy without heat treatment. The specific steps are as follows:

[0100] 1) Based on the theoretical weight percentage of each component as Mg-5.3Al-2La-1.5Ce-0.47Mn-0.001Be-2Ca-0.5Zn-0.9In, pure Mg ingot, pure Al ingot, pure Zn ingot, Al-90La, Al-90Ce, Al-3Be, Mg-5Mn, Mg-20Ca, and Mg-50In master alloys were selected as raw materials, and the raw materials were preheated to 160℃ and dried.

[0101] 2) Preheat the crucible to 150℃, evenly coat the inner wall of the crucible with crucible coating, dry it and then heat it to 480℃. Introduce pure SF6 gas, put pure Mg ingot into the crucible, and melt it completely under the protection of SF6 protective gas. Then raise the temperature to 760℃, add Al-3Be master alloy, and after the alloy is completely melted, add Al-90La and Al-90Ce master alloys until they are completely melted. Cool down to 745℃, add pure Al ingot, pure Zn ingot, Mg-5Mn, Mg-20Ca, and Mg-50In master alloys, and stir thoroughly after complete melting. Let it stand and perform pre-furnace composition analysis to detect the composition content of the alloy melt. For melts with deviations in content, add material or dilute it to make its composition reach the designed magnesium alloy composition range.

[0102] 3) Heat the melt to 740°C, introduce argon gas at a pressure of 0.2 MPa into the melt, and introduce 2% of the total weight of the refining agent (specifically, Torch brand magnesium alloy refining agent, purchased from Zhangjiagang Haohua Light Alloy Materials Co., Ltd.) powder into the melt, and then continue to purge for 10 minutes to remove slag and gas.

[0103] 4) After refining, the melt is allowed to stand for 13 minutes, and then a pre-furnace composition analysis test is performed. If the composition is qualified, high-pressure casting is carried out at 715-725℃, with an injection speed of 8.0 m / s and a casting pressure of 120 MPa. The mold used in the production process is a die-casting test rod mold.

[0104] The properties of the resulting die-cast magnesium alloy parts are shown in Tables 2, 3, and 4.

[0105] Example 8

[0106] This embodiment provides a method for preparing a heat-tight high-strength and high-toughness die-cast magnesium alloy without heat treatment. The specific steps are as follows:

[0107] 1) Based on the theoretical weight percentage of each component as Mg-6.6Al-4.5La-2.1Ce-0.2Mn-0.02Be-0.02Ca-0.8Zn-0.16In, pure Mg ingot, pure Al ingot, pure Zn ingot, Al-60La, Mg-30Ce, Al-10Mn, Al-5Be, Mg-40Ca, and Al-50In master alloys were selected as raw materials, and the raw materials were preheated to 250℃ and dried.

[0108] 2) Preheat the crucible to 150℃, evenly coat the inner wall of the crucible with crucible coating, dry it and then heat it to 350℃. Introduce Ar+SF6 mixed gas (mixed volume ratio of Ar:SF6 is 99:1). Place pure Mg ingots into the crucible and melt them completely under the protection of the mixed protective gas of Ar and SF6. Then raise the temperature to 775℃ and add Al-5Be master alloy. After the alloy is completely melted, add Al-60La and Mg-30Ce master alloys until they are completely melted. Cool down to 730℃ and add pure Al ingots, pure Zn ingots, Al-10Mn, Mg-40Ca, and Al-50In master alloys. After they are completely melted, stir them thoroughly, let them stand and perform pre-furnace composition analysis to detect the composition content of the alloy melt. For melts with deviations in content, add materials or dilute them to make the composition reach the designed magnesium alloy composition range.

[0109] 3) Heat the melt to 730°C, introduce argon gas at a pressure of 0.2 MPa into the melt, and introduce 1.7% of the total weight of the refining agent (specifically, Torch brand magnesium alloy refining agent, purchased from Zhangjiagang Haohua Light Alloy Materials Co., Ltd.) powder into the melt, and then continue to purge for 10 minutes to remove slag and gas;

[0110] 4) After refining, the melt is allowed to stand for 6 minutes, and then a pre-furnace composition analysis test is performed. If the composition is qualified, high-pressure casting is carried out at 695-705℃, with an injection speed of 5.6m / s and a casting pressure of 80MPa. The mold used in the production process is a die-casting test rod mold.

[0111] The properties of the resulting die-cast magnesium alloy parts are shown in Tables 2, 3, and 4.

[0112] Example 9

[0113] This embodiment provides a method for preparing a heat-tight high-strength and high-toughness die-cast magnesium alloy without heat treatment. The specific steps are as follows:

[0114] 1) Based on the theoretical weight percentage of each component as Mg-7Al-0.2La-5Ce-0.34Mn-0.018Be-0.002Ca-0.003Sr-0.002In, pure Mg ingot, pure Al ingot, pure La, Al-60Ce, Mg-5Mn, Mg-5Be, Al-10Ca, Al-10Sr, and Mg-10In master alloys were selected as raw materials, and the raw materials were preheated to 240℃ and dried.

[0115] 2) Preheat the crucible to 150℃, evenly coat the inner wall of the crucible with crucible coating, dry it and then heat it to 420℃. Introduce a mixture of N2 and SF6 gas (mixing volume ratio of N2:SF6 is 99:1). Place pure Mg ingots into the crucible and melt them completely under the protection of the mixed protective gas of N2 and SF6. Then raise the temperature to 765℃ and add Mg-5Be master alloy. After the alloy is completely melted, add pure La ingots and Al-60Ce master alloy until they are completely melted. Cool down to 750℃ and add pure Al ingots, pure Zn ingots, Mg-5Mn, Al-10Ca, Al-10Sr, and Mg-10In master alloy. After they are completely melted, stir them thoroughly, let them stand and perform pre-furnace composition analysis to detect the composition content of the alloy melt. For melts with deviations in content, add materials or dilute them to make the composition reach the designed magnesium alloy composition range.

[0116] 3) Heat the melt to 745°C, introduce argon gas at a pressure of 0.2 MPa into the melt, and introduce 0.6% of the total weight of the refining agent (specifically, Torch brand magnesium alloy refining agent, purchased from Zhangjiagang Haohua Light Alloy Materials Co., Ltd.) powder into the melt, and then continue to purge for 10 minutes to remove slag and gas;

[0117] 4) After refining, the melt is allowed to stand for 15 minutes, and then a pre-furnace composition analysis test is performed. If the composition is qualified, high-pressure casting is carried out at 730-740℃, with an injection speed of 7.2m / s and a casting pressure of 100MPa. The mold used in the production process is a die-casting test rod mold.

[0118] The properties of the resulting die-cast magnesium alloy parts are shown in Tables 2, 3, and 4.

[0119] Example 10

[0120] This embodiment provides a method for preparing a heat-tight high-strength and high-toughness die-cast magnesium alloy without heat treatment. The specific steps are as follows:

[0121] 1) Based on the theoretical weight percentage of each component as Mg-4.2Al-7Ce-0.28Mn-0.005Be-0.09Ca-0.28Sr-0.03Zn, pure Mg ingot, pure Al ingot, pure Zn ingot, pure Ce, Al-10Mn, Al-3Be, Al-60Ca, and Mg-60Sr master alloys were selected as raw materials. The raw materials were preheated to 230℃ and dried.

[0122] 2) Preheat the crucible to 150℃, evenly coat the inner wall of the crucible with crucible coating, dry it, and then heat it to 320℃. Introduce a CO2+SF6 mixed gas (mixed volume ratio of CO2:SF6 is 99:1). Place pure Mg ingots into the crucible and melt them completely under the protection of the mixed protective gas of CO2 and SF6. Then raise the temperature to 770℃ and add Al-3Be master alloy. After the alloy is completely melted, add pure Ce ingots until they are completely melted. Cool down to 735℃ and add pure Al ingots, pure Zn ingots, Al-10Mn, Al-60Ca, and Mg-60Sr master alloys. After they are completely melted, stir them thoroughly, let them stand, and perform pre-furnace composition analysis to detect the composition content of the alloy melt. For melts with deviations in content, add materials or dilute them to make their composition reach the designed magnesium alloy composition range.

[0123] 3) Heat the melt to 735°C, introduce argon gas at a pressure of 0.2 MPa into the melt, and introduce 1.8% of the total weight of the refining agent (specifically, Torch brand magnesium alloy refining agent, purchased from Zhangjiagang Haohua Light Alloy Materials Co., Ltd.) powder into the melt, and then continue to purge for 10 minutes to remove slag and gas.

[0124] 4) After refining, the melt is allowed to stand for 9 minutes, and then a pre-furnace composition analysis test is performed. If the composition is qualified, high-pressure casting is carried out at 710-720℃, with an injection speed of 4m / s and a casting pressure of 140MPa. The mold used in the production process is a die-casting test rod mold.

[0125] The properties of the resulting die-cast magnesium alloy parts are shown in Tables 2, 3, and 4.

[0126] Example 11

[0127] This embodiment provides a method for preparing a heat-tight high-strength and high-toughness die-cast magnesium alloy without heat treatment. The specific steps are as follows:

[0128] 1) Based on the theoretical weight percentage of each component as Mg-4.4Al-3.7La-1.8Ce-0.42Mn-0.007Be-0.2Sr-0.01Zn-0.03In, pure Mg ingot, pure Al ingot, pure Zn ingot, pure La, Mg-90Ce, Mg-10Mn, Al-3Be, pure Sr, and Al-10In master alloys were selected as raw materials, and the raw materials were preheated to 190℃ and dried.

[0129] 2) Preheat the crucible to 150℃, evenly coat the inner wall of the crucible with crucible coating, dry it and then heat it to 360℃. Introduce Ar+SF6 mixed gas (mixed volume ratio Ar:SF6 is 99:1). Place pure Mg ingots into the crucible and melt them completely under the protection of the mixed protective gas of Ar and SF6. Then raise the temperature to 760℃ and add Al-3Be master alloy. After the alloy is completely melted, add pure La ingots and Mg-90Ce master alloy until they are completely melted. Cool down to 740℃ and add pure Al ingots, pure Zn ingots, Mg-10Mn, pure Sr ingots, and Al-10In master alloy. After they are completely melted, stir them thoroughly, let them stand and perform pre-furnace composition analysis to detect the composition content of the alloy melt. For melts with deviations in content, add materials or dilute them to make the composition reach the designed magnesium alloy composition range.

[0130] 3) Heat the melt to 720°C, introduce argon gas at a pressure of 0.2 MPa into the melt, and introduce 1.4% of the total weight of the refining agent (specifically, Torch brand magnesium alloy refining agent, purchased from Zhangjiagang Haohua Light Alloy Materials Co., Ltd.) powder into the melt, and then continue to purge for 10 minutes to remove slag and gas;

[0131] 4) After refining, the melt is allowed to stand for 14 minutes, and then a pre-furnace composition analysis test is performed. If the composition is qualified, high-pressure casting is carried out at 725-735℃, with an injection speed of 5m / s and a casting pressure of 60MPa. The mold used in the production process is a die-casting test rod mold.

[0132] The properties of the resulting die-cast magnesium alloy parts are shown in Tables 2, 3, and 4.

[0133] Example 12

[0134] This embodiment provides a method for preparing a heat-free high-strength and high-toughness die-cast magnesium alloy, which is basically the same as the method in Example 10, except that the amount of pure zinc added in this embodiment is 0.3% of the theoretical weight percentage of Zn.

[0135] The properties of the resulting die-cast magnesium alloy parts are shown in Tables 2, 3, and 4.

[0136] Example 13

[0137] This embodiment provides a method for preparing a heat-free high-strength and high-toughness die-cast magnesium alloy, which is basically the same as the method in Example 4, except that the Mg-30In master alloy used in this embodiment is added at a theoretical weight percentage of 1.5% of In.

[0138] The properties of the resulting die-cast magnesium alloy parts are shown in Tables 2, 3, and 4.

[0139] Example 14

[0140] This embodiment provides a method for preparing a heat-free high-strength and high-toughness die-cast magnesium alloy, which is basically the same as the method in Example 5, except that the amount of Mg-10Sr master alloy added in this embodiment is 0.48% of the theoretical weight percentage of Sr.

[0141] The properties of the resulting die-cast magnesium alloy parts are shown in Tables 2, 3, and 4.

[0142] Example 15

[0143] This embodiment provides a method for preparing a heat-free high-strength and high-toughness die-cast magnesium alloy, which is basically the same as the method in Embodiment 7, except that: the Al-90La master alloy used in this embodiment is added at a theoretical weight percentage of 1.8% for La, and the Al-90Ce master alloy used in this embodiment is added at a theoretical weight percentage of 1.3% for Ce.

[0144] The properties of the resulting die-cast magnesium alloy parts are shown in Tables 2, 3, and 4.

[0145] Example 16

[0146] This embodiment provides a method for preparing a heat-free high-strength and high-toughness die-cast magnesium alloy, which is basically the same as the method in Example 10, except that the Al added in this embodiment is 4.1% of the theoretical total weight of Al.

[0147] The properties of the resulting die-cast magnesium alloy parts are shown in Tables 2, 3, and 4.

[0148] Comparative Example 1

[0149] This comparative example provides a method for preparing a high-strength and high-toughness die-cast magnesium alloy without heat treatment, which is basically the same as the method in Example 1, except that Ca and In elements are not added in this comparative example.

[0150] The properties of the resulting die-cast magnesium alloy parts are shown in Tables 2, 3, and 4.

[0151] Comparative Example 2

[0152] This comparative example provides a method for preparing a heat-free high-strength and high-toughness die-cast magnesium alloy, which is basically the same as the method in Example 1, except that the Mg-30Ca master alloy used in this example is added at a theoretical weight percentage of 2.1% of Ca.

[0153] The properties of the resulting die-cast magnesium alloy parts are shown in Tables 2, 3, and 4.

[0154] Comparative Example 3

[0155] This comparative example provides a method for preparing a heat-free high-strength and high-toughness die-cast magnesium alloy, which is basically the same as the method in Example 1, except that the amount of pure In added in this example is 2.1% by theoretical weight of In.

[0156] The properties of the resulting die-cast magnesium alloy parts are shown in Tables 2, 3, and 4.

[0157] Comparative Example 4

[0158] This comparative example provides a method for preparing a high-strength and high-toughness die-cast magnesium alloy without heat treatment, which is basically the same as the method in Example 1, except that: no In element is added in this comparative example, and the Mg-30Ca master alloy used in this example is added at a theoretical weight percentage of 1.05% of Ca.

[0159] The properties of the resulting die-cast magnesium alloy parts are shown in Tables 2, 3, and 4.

[0160] Figure 1 The microstructure photographs and potentials of each phase of the die-cast magnesium alloy part obtained in Comparative Example 1 of this invention are shown below. Figure 1 As can be seen from A, the microstructure of the alloy without the addition of X and Z elements mainly consists of an α-Mg matrix and Al. 11 The structure consists of a RE3 eutectic phase. The potentials of each phase were measured using an atomic force scanning electron microscope (Gemini 360 / Semilab) at the dashed arrows in the left-hand figure, and the results are as follows. Figure 1 As shown in B, Al 11 The potential difference between the RE3 phase and the α-Mg matrix is ​​approximately 0.9 V.

[0161] Figure 2 The microstructure photographs and potentials of each phase of the die-cast magnesium alloy part obtained in Example 1 of this invention are shown below. Figure 2 As can be seen from A, the alloy microstructure mainly consists of an α-Mg matrix and Al. 11 It consists of RE3 eutectic phase and Al2CaIn phase. The Al2CaIn phase is mainly distributed in Al 11 The RE3 eutectic phase is surrounded by [a region of interest]. At the points indicated by the dashed arrows in the left-hand image, the potentials of each phase were measured using an atomic force scanning electron microscope (Gemini360 / Semilab), and the results are as follows: Figure 2 As shown in Figure B, the potential difference between the Al2CaIn phase and the α-Mg matrix is ​​approximately 0.6 V. Figure 1 Comparing the results, it can be concluded that the potential difference between the Al2CaIn phase and the α-Mg matrix is ​​smaller than that between Al2CaIn and Al2CaIn. 11 Potential difference between RE3 phase and α-Mg matrix; Al 11 The Al2CaIn phase surrounding the RE3 eutectic phase will have a high potential difference in Al 11The RE3 phase is isolated from the α-Mg matrix, reducing micro-galvanic corrosion in the alloy and significantly improving its corrosion resistance. Furthermore, the Al2CaIn phase possesses a high melting point and thermal strength, which can significantly enhance the alloy's heat resistance and ignition point.

[0162] Figure 3 The image shows the microstructure of the die-cast magnesium alloy part obtained in Example 2 of this invention. Figure 3 It can be seen that the alloy microstructure mainly consists of an α-Mg matrix and Al. 11 It consists of the RE3 eutectic phase, Al2(CaSr)(ZnIn) phase, and Al4(SrCa)(ZnIn) phase. The Al2(CaSr)(ZnIn) and Al4(SrCa)(ZnIn) phases are mainly distributed in Al 11 Surrounding the RE3 eutectic phase, the Al2(CaSr)(ZnIn) and Al4(SrCa)(ZnIn) phases will have a high potential difference in Al. 11 The RE3 phase is isolated from the α-Mg matrix, reducing micro-galvanic corrosion in the alloy and significantly improving its corrosion resistance. Furthermore, the Al2(CaSr)(ZnIn) and Al4(SrCa)(ZnIn) phases possess high melting points and thermal strength, which can significantly improve the alloy's heat resistance and ignition point.

[0163] Figure 4 The image shows the microstructure of the die-cast magnesium alloy part obtained in Comparative Example 2 of this invention. Figure 4 It can be seen that when too much Ca is added, an agglomerated Al2CaIn phase will form in the alloy, which will reduce the various properties of the alloy.

[0164] Figure 5 These are microscopic images of the surface morphology of the die-cast magnesium alloy part obtained in Comparative Example 1 of this invention after a salt spray corrosion test. Figure 4 As can be seen, after the salt spray corrosion test, the oxide products on the surface of the alloy without added Ca and In elements exhibit a loose, blocky morphology. The loose oxide products cannot effectively isolate the corrosive environment from the alloy and cannot play a protective role.

[0165] Figure 6 These are microscopic images of the surface morphology of the die-cast magnesium alloy part obtained in Example 1 of this invention after a salt spray corrosion test. Figure 5 As can be seen, after salt spray corrosion tests, the oxide products on the surface of alloys with added Ca and In elements exhibit a dense spherical morphology. The dense oxide products can effectively isolate the corrosive environment from the alloy, significantly reduce the corrosion rate of the alloy, and improve the corrosion resistance and ignition point of the alloy.

[0166] Figure 7 The creep curves are shown for the die-cast alloy parts of Embodiment 1 and Comparative Examples 1-4 of the present invention. (The text is incomplete and requires further context.) Figure 7 A comparison of the creep curves of Example 1 and Comparative Examples 1-4 reveals that, under the same conditions of temperature, creep stress, and time, the creep strain of Example 1 is significantly lower than that of Comparative Examples 1-4. Therefore, the creep performance of Example 1 is significantly better than that of Comparative Examples 1-4.

[0167] Table 1 below shows the actual measured weight percentage of each component in the die-cast magnesium alloy parts prepared in each embodiment and comparative example; Table 2 shows the creep performance test results; Table 3 shows the corrosion resistance and flame retardant performance test results; and Table 4 shows the room temperature tensile performance test results.

[0168] Combining the data in Tables 1 and 2, it can be seen that the die-cast magnesium alloys obtained by this invention all possess excellent heat resistance properties. In the die-cast magnesium alloys prepared in Examples 1, 2, 4, 7, 8, 12, 13, and 14, the element weight percentage of 0.6 ≤ Al / RE ≤ 1.7 and the sum of the weight percentages of X+Z / 2 elements are all ≥ 0.5. The creep strain of the die-cast magnesium alloy parts at 150℃, 100MPa, and 100h is below 0.070%. In the die-cast magnesium alloys prepared in Examples 3, 5, 6, 9, 10, and 11, the element weight percentage of 0.6 ≤ Al / RE ≤ 1.7 and the sum of the weight percentages of X+Z / 2 elements are all < 0.5. The creep strain of the die-cast magnesium alloy parts at 150℃, 100MPa, and 100h is also below 0.088%.

[0169] Combining the data in Tables 1 and 3, it can be seen that the die-cast magnesium alloys obtained by this invention all possess excellent corrosion resistance and flame retardant properties. In Examples 1, 5, 7, 9, 11, 12, 13, and 14, the die-cast magnesium alloys have a content of 0.6 ≤ Al / RE ≤ 1.7, and the weight percentages of X and Z elements satisfy 1 ≤ X / Z ≤ 5. The corrosion rate of their die-cast magnesium alloy parts is below 0.2 mm / year, and the ignition point is above 980℃. In Examples 2, 3, 4, 6, 8, and 10, the die-cast magnesium alloys have a content of 0.6 ≤ Al / RE ≤ 1.7, and the weight percentages of X and Z elements do not satisfy 1 ≤ X / Z ≤ 5. The corrosion rate of their die-cast magnesium alloy parts is also below 0.3 mm / year, and the ignition point is above 950℃.

[0170] Combining the data in Tables 1, 2, and 3, it can be seen that the die-cast magnesium alloys obtained by this invention all possess excellent heat resistance, corrosion resistance, and flame retardant properties. In the die-cast magnesium alloys prepared in Examples 1, 7, 12, 13, and 14, 0.6≤Al / RE≤1.7, and the weight percentages of X and Z elements satisfy 0.5≤X+Z / 2≤2.7 and 1.05≤X / Z≤4.3. The creep strain of the die-cast magnesium alloy parts at 150℃, 100MPa, and 100h is below 0.070%, the corrosion rate is below 0.2mm / year, and the ignition point is above 985℃.

[0171] The Al element weight percentage in the heat-free high-strength and high-toughness die-cast magnesium alloy prepared in Example 15 is greater than 1.7 times the RE element weight percentage, which does not meet the requirement of Al / RE≤1.7. Compared with Example 7, its creep properties and room temperature tensile properties are significantly reduced (results in Tables 2 and 4).

[0172] The Al element weight percentage in the heat-free high-strength and high-toughness die-cast magnesium alloy prepared in Example 16 is less than 0.6 times the RE element weight percentage, which does not meet the requirement of Al / RE ≥ 0.6. Compared with Example 10, its creep properties and room temperature tensile properties are also significantly reduced (results in Tables 2 and 4).

[0173] Comparative Example 1 is a heat-free, corrosion-resistant, heat-resistant, and flame-retardant die-cast magnesium alloy without the addition of Ca and In elements. Since there are no Ca and In elements to form a heat-resistant and low-potential second phase, and no Ca and In elements to increase the density of the oxide film on the surface of the magnesium alloy, its creep performance, corrosion resistance, and flame-retardant performance are significantly lower than those of the heat-free, corrosion-resistant, heat-resistant, and flame-retardant die-cast magnesium alloy with the addition of Ca and In elements in Example 1.

[0174] The addition of too much Ca in Comparative Example 2 does not meet the requirement that the total weight percentage of Ca and Sr should be between 0.002% and 2%, and its creep performance, corrosion resistance, and flame retardant performance are all significantly reduced compared to Example 1.

[0175] The addition of too much In element in Comparative Example 3 does not meet the requirement that the total weight percentage of In and Zn elements should be between 0.002% and 2%, and its creep performance, corrosion resistance, and flame retardant performance are also significantly reduced compared to Example 1.

[0176] In Comparative Example 4, Ca was added alone to make X+Z / 2 = 1.05, which is the same as X+Z / 2 in Example 1. However, its creep performance, corrosion resistance, and flame retardant performance were significantly lower than those of the heat-free, high corrosion-resistant, high heat-resistant, and flame-retardant die-cast magnesium alloy in Example 1, which was combined with Ca and In elements.

[0177] As can be seen from the results in Table 4, the die-cast magnesium alloys prepared in Examples 1-14 of this invention exhibit excellent room-temperature tensile properties, with yield strength exceeding 180 MPa, tensile strength exceeding 280 MPa, and elongation exceeding 6%. In contrast, the die-cast magnesium alloys prepared in Comparative Examples 1-4 do not meet these requirements for room-temperature tensile properties.

[0178] Table 1 Unit: Weight Percentage

[0179] Serial Number Al La Ce Mn Be Ca Sr Zn In Mg Example 1 5.51 5.01 0.99 0.35 0.008 0.90 / / 0.30 margin Example 2 6.02 2.40 2.41 0.26 0.011 0.41 0.81 0.101 0.101 margin Example 3 4.00 1.59 2.71 0.31 0.004 0.059 0.011 0.008 / margin Example 4 5.10 / 3.00 0.41 0.011 0.81 0.82 / 2.00 margin Example 5 5.71 0.62 3.41 0.50 0.013 / 0.11 0.11 / margin Example 6 4.61 6.49 / 0.24 0.017 / 0.002 0.51 0.1 margin Example 7 5.28 2.00 1.52 0.46 0.001 2.00 / 0.49 0.89 margin Example 8 6.59 4.52 2.07 0.20 0.020 0.02 / 0.79 0.17 margin Example 9 7.00 0.21 5.01 0.34 0.018 0.002 0.003 / 0.002 margin Example 10 4.20 / 7.00 0.28 0.005 0.09 0.28 0.031 / margin Example 11 4.41 3.69 1.78 0.41 0.007 / 0.20 0.011 0.029 margin Example 12 4.20 / 7.00 0.27 0.005 0.09 0.28 0.28 / margin Example 13 5.10 / 3.00 0.41 0.011 0.81 0.82 / 1.50 margin Example 14 5.71 0.62 3.41 0.50 0.013 / 0.47 0.11 / margin Example 15 5.28 1.79 1.30 0.46 0.001 2.00 / 0.49 0.89 margin Example 16 4.10 / 7.00 0.28 0.005 0.09 0.28 0.031 / margin Comparative Example 1 5.50 5.00 0.99 0.36 0.009 / / / / margin Comparative Example 2 5.51 5.01 1.00 0.35 0.008 2.11 / / 0.30 margin Comparative Example 3 5.50 4.99 1.02 0.36 0.009 0.90 / / 2.10 margin Comparative Example 4 5.51 5.00 1.00 0.35 0.008 1.05 / / / margin

[0180] Table 2

[0181]

[0182] Table 3

[0183]

[0184]

[0185] Table 4

[0186]

[0187]

[0188] The above description is merely an embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent structural or procedural transformations made using the present invention specification, or direct or indirect applications in other related technical fields, are similarly included within the patent protection scope of the present invention.

Claims

1. A heat-treatment-free high corrosion resistance high heat resistance flame retardant die-cast magnesium alloy, characterized by, The weight percentage of each component in the die-casting magnesium alloy is: Al: 4~7%; RE: 3~7%; Mn: 0.2~0.5%; Be: 0.001~0.02%; X: 0.002~2%; Z: 0.002~2%, X is at least one of Ca and Sr, and Z is at least one of Zn and In; the total amount of other impurities is ≤0.3%, and the balance is Mg; The RE in the die-casting magnesium alloy is at least one of La and Ce; In the die-casting magnesium alloy, the weight percentage of Al and RE elements satisfies the following condition: 0.6≤Al / RE≤1.7; In the die-casting magnesium alloy, the weight percentage of X and Z elements satisfies the following condition: X+Z / 2≥0.5, and the creep strain of the die-casting magnesium alloy under 150 ℃, 100 MPa and 100 h is below 0.070%; or In the die-casting magnesium alloy, the weight percentage of X and Z elements satisfies the following condition: 1≤X / Z≤5, the corrosion rate of the die-casting magnesium alloy under 5% NaCl neutral salt spray for 168 h is below 0.2 mm / year, and the ignition point is above 980 ℃.

2. A process for the production of a heat-treatment free, high corrosion resistant, high heat resistant, fire retardant die casting magnesium alloy as claimed in claim 1, characterized in that, The method comprises the following steps: S1, material preparation: the magnesium alloy components according to claim 1 are prepared; wherein, Mg, Al and Zn are prepared in the form of pure magnesium, pure aluminum and pure zinc, RE is prepared in the form of pure rare earth or Mg-RE or Al-RE intermediate alloy, X and In are prepared in the form of pure X, pure In or magnesium-containing intermediate alloy or aluminum-containing intermediate alloy, and Mn and Be are prepared in the form of magnesium-containing or aluminum-containing intermediate alloy; S2, melting: first preheat the crucible to 300~500 ℃, put the pure Mg ingot into the crucible, melt under protective gas or in a vacuum environment, or first cover a layer of covering agent in the crucible, add the pure Mg ingot and cover another layer of covering agent on the surface of the melt after it is melted; then heat to 750~780 ℃ and add Al-Be or Mg-Be intermediate alloy, after the intermediate alloy is melted, maintain this temperature and add pure rare earth or Mg-RE or Al-RE intermediate alloy, after it is melted, cool to 720~750 ℃, then add pure aluminum, pure zinc, Al-Mn or Mg-Mn intermediate alloy, pure X or Mg-X or Al-X intermediate alloy, and pure In or Mg-In or Al-In intermediate alloy for melting; S3, refining: heat the melt of step S2 to 720~750 ℃, and spray powder refining slag removal treatment by blowing gas with refining agent powder into the melt; S4, casting or die-casting: after the melt after the spray powder refining slag removal treatment of step S3 reaches the casting temperature, perform the casting ingot operation or the die-casting process operation, and finally complete the alloy ingot production or the die-casting production.

3. The process for preparing a heat treatment free high corrosion resistant high heat resistant flame retardant die casting magnesium alloy according to claim 2, characterized in that, In step S1, the prepared raw materials are also preheated to 150~250 ℃ for preheating and drying.

4. The process for preparing heat treatment free high corrosion resistant high heat resistant flame retardant die casting magnesium alloy according to claim 2, characterized in that, In step S2, the covering agent is a solvent with a density < 1.58 g / cm 3 The covering agent is a solvent with a density < 1.58 g / cm The protective gas is any one of N2+SF6, CO2+SF6, Ar+SF6 or pure SF6 In step S2, after melting and stirring uniformly, the composition of the alloy melt is analyzed, the content of the alloy melt is detected, and the melt with content deviation is supplemented or diluted to make the composition reach the qualified range.

5. The process for preparing a heat treatment free high corrosion resistant high heat resistant flame retardant die casting magnesium alloy according to claim 2, wherein, In step S3, the refining agent is a salt flux capable of adsorbing impurities in the magnesium alloy melt; the amount of the refining agent added is 0.3-2.0% of the total weight of the melt; and the gas includes argon.

6. The method of producing a heat treatment free high corrosion resistant high heat resistant flame retardant die casting magnesium alloy according to claim 2, wherein, In step S4, the temperature for the casting is 690-740 ℃. In step S4, when the die-casting magnesium alloy is used for die-casting production, the injection speed range is 2-8 m / s. In step S4, when the die-casting magnesium alloy is used for die-casting production, the casting pressure range is 40-150 MPa.

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