Heat-treatment-free high strength and toughness die-cast magnesium alloy and preparation method therefor

Abstract

The present invention relates to a heat-treatment-free high strength and toughness die-cast magnesium alloy and a preparation method therefor. The alloy comprises the following components in percentage by weight: 3%-6% of Al; 2.5%-6% of RE; 0.2%-0.5% of Mn; 0.002%-0.02% of Be; 0.003%-1% of X; less than or equal to 0.3% of other impurities; and the balance being Mg, wherein X is at least one of Bi, Ti, V, Zr, Cr, Ni and Cu. The strength and ductility of the alloy can be significantly improved by using the element X. The typical properties of the alloy are: a yield strength of 150-180 MPa, a tensile strength of 260-290 MPa, and an elongation rate of 15-24%. The elongation rate of the alloy is far superior to that of conventional die-cast magnesium alloys (such as AZ91D and AM60), and the strength and elongation rate of the alloy in as-cast condition can also exceed those of some heat-treatment-free die-cast magnesium alloys already in use on the market. In addition, the alloy also has good die-casting properties, and can be used for forming large integrated body structural members or other parts, greatly expanding the application scenarios of the die-cast magnesium alloy.

Description

A heat-treasure-free high-strength and high-toughness die-cast magnesium alloy and its preparation method Technical Field

[0001] This invention relates to the field of metallic materials technology, specifically to a heat-free high-strength and high-toughness 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 battery energy density, 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 body parts, shifting from multi-part assembly to integrated die-casting. Integrated die-casting significantly reduces total production time, the number of molds, 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-treatable high-strength and high-toughness alloys is a key solution to the production of large, integrated die-cast structural components. For traditional alloy materials, heat treatment is essential to ensure the mechanical properties of die-cast parts. However, heat treatment inevitably causes deformation, leading to dimensional inaccuracies. Deformation is even more pronounced in large, integrated parts during heat treatment. While straightening processes can provide some repair, most deformed parts are beyond repair 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-treatable alloys, heat-treatable alloys can reduce production steps, save energy, reduce carbon emissions, and lower production costs, making the production of large, integrated die-cast structural components 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 are currently the lightest structural metal materials, one-third lighter than aluminum, and have high specific strength and high specific stiffness. However, the poor absolute strength and plasticity of magnesium alloys limit their application as structural components. At present, the development of heat-treatable high-strength and high-toughness die-cast magnesium alloys and large integrated die-cast magnesium alloy structural components is still at a relatively backward level. As the country with the richest magnesium resources, my country's development of heat-treatable high-strength and high-toughness die-cast magnesium alloys and their application in large integrated body structural components of electric vehicles, such as the front compartment, rear compartment, and chassis, can further reduce the weight of electric vehicles, improve their range, driving performance, and safety, and significantly enhance my country's level of light 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, with the most widely used being AZ91D alloy from the AZ (Mg-Al-Zn) system and AM60 alloy from the AM (Mg-Al-Mn) system. However, due to its high Al content, the AZ91D alloy exhibits a higher proportion of brittle Mg atoms distributed along grain boundaries in a network structure. 17 Al 12 The second phase severely deteriorates the alloy's plasticity. Furthermore, the AM60 alloy, due to its lower strength and insufficient plasticity caused by fewer strengthening elements, is primarily used in exterior components such as steering wheels and dashboard frames.

[0006] AE (Mg-Al-RE) die-cast magnesium alloys, through the addition of RE elements (mixed rare earth elements), combine with Al elements to form dendritic Al. 11 RE3 eutectic phase, compared to brittle Mg distributed in a network along grain boundaries 17 Al 12 In comparison, it has less impact on the plasticity of the alloy, thus the alloy has better plasticity. For example, the plasticity of AE44 alloy can reach about 16%, making it the alloy with the best comprehensive mechanical properties among die-cast magnesium alloys currently available. However, the dendritic Al in AE44 die-cast magnesium alloy... 11 The morphology of the RE3 eutectic phase is not good enough. When die-casting actual parts, the alloy properties are significantly reduced, and its strength and plasticity cannot be guaranteed, which limits its application in large integrated die-cast structural parts.

[0007] Chinese Patent 201810812693.2 discloses "a method for preparing a die-cast magnesium alloy material". This magnesium alloy contains one or more of Al, Mn, La, Ce, and Pr, and one or more of Gd, Y, Sm, Nd, Er, Eu, Ho, Tm, Lu, Dy, and Yb. Although the alloy has good strength and plasticity, the elements such as Gd, Y, Sm, Nd, Er, Eu, Ho, Tm, Lu, Dy, and Yb contained in the alloy are relatively expensive and highly reactive. They are easily oxidized and burned off during the production process, producing obvious oxide scale. The oxide scale is rolled into the casting, which significantly reduces the strength and plasticity of the alloy, as well as the stability of the mechanical properties of the casting. In addition, compared with Mg, Pr, Gd, Sm, Nd, Er, Eu, Ho, Tm, Lu, Dy, and Yb have a larger atomic mass and are prone to sedimentation during the production process, causing compositional deviations. Therefore, in actual production, the casting process of this alloy is poor, the quality of castings is unstable, and there are serious safety hazards.

[0008] The inventors' team previously filed 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, the magnesium alloy obtained by this method has a microstructure mainly composed of an α-Mg matrix and dendritic Al11RE3 second phase, with an elongation of only 9–15%.

[0009] Therefore, existing die-cast magnesium alloy materials face the technical challenge of simultaneously achieving cost, strength, toughness, and processability, making them unable to meet the demand for heat-treatment-free, high-strength, and high-toughness die-cast magnesium alloys in large, integrated structural components. There is an urgent need to develop new heat-treatment-free, high-strength, and high-toughness die-cast magnesium alloys to meet the application requirements of magnesium alloys in large, integrated structural components. Summary of the Invention

[0010] The purpose of this invention is to provide a heat-treasure-free high-strength and high-toughness 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 strength and high toughness without heat treatment. This expands the application scenarios of die-cast magnesium alloys, allowing them to be used in large integrated structural components, replacing traditional multi-part connection and assembly processes or heat-treasure-free die-cast aluminum alloys. This can significantly reduce the weight of parts and improve my country's lightweight technology level.

[0011] To achieve this objective, the present invention, in its research on Mg-Al-RE die-cast magnesium alloys, discovered that: 1) by adding a small amount of the modifying element Bi, the dendritic Al in Mg-Al-RE die-cast magnesium alloys can be reduced. 11 RE3 eutectic phase transformation results in a granular structure, compared to the dendritic Al. 11 In the case of RE3 eutectic phase, dislocations are more likely to cut through or bypass granular Al. 11 RE3 eutectic phase, and granular Al 11 The number density of the RE3 eutectic phase is lower than that of the dendritic Al phase. 11 The presence of the RE3 phase weakens its ability to block dislocations, significantly increasing the alloy's plasticity. Furthermore, Bi has a high solid solubility in magnesium, allowing excess Bi in magnesium alloys to dissolve in the Mg matrix, increasing the alloy's strength. However, excessive Bi will form a large amount of brittle Mg3Bi2 second phase, significantly reducing the alloy's plasticity, while insufficient Bi will not play a role in modifying Al. 11 Due to the effect of the RE3 eutectic phase, the Bi element content is controlled at 0.003-1% in this invention. 2) By adding a small amount of refining elements such as at least one of Ti, V, and Zr, Al3Ti, Al3V, and Al are formed in the melt. 21 Heterogeneous nucleation sites such as V2 and Al3Zr can significantly refine the dendritic Al in Mg-Al-RE die-cast magnesium alloys. 11 RE3 eutectic phase; compared to coarse dendritic Al 11 Regarding the RE3 eutectic phase, fine Al... 11 RE3 eutectic significantly reduces the cutting effect on the matrix, resulting in a significant increase in the alloy's plasticity. Furthermore, the heterogeneous nucleation particles formed by refining elements themselves possess high strength and hardness, enabling dispersion strengthening and increasing the alloy's strength. However, excessive refining elements can lead to the aggregation of heterogeneous nucleation particles, which not only loses the refining effect on Al... 11 The RE3 eutectic phase can actually impair the alloy's plasticity, while too few refining elements will not refine the Al content. 11 The effect of the RE3 eutectic phase is considered, therefore the content of refining elements is controlled at 0.003-1% in this invention. 3) By adding a small amount of strengthening elements, such as at least one of Cr, Ni, and Cu, strengthening phases such as Al7Cr, Al4Cr, Al3Ni, Al2Cu, and Al2CuMg are formed in the melt, which can significantly improve the strength of Mg-Al-RE system die-cast magnesium alloys; and these elements, as high-temperature elements, form strengthening phases that will form in the early stage of solidification, which can serve as Al 11 The nucleation particles of the RE3 eutectic phase can refine Al to a certain extent. 11RE3 eutectic phase improves the plasticity of die-cast magnesium alloys. However, these elements and the strengthening phases they form have high electrode potentials, resulting in a large potential difference with the magnesium matrix. Excessive addition of strengthening elements will severely damage the corrosion resistance and plasticity of the alloy, while insufficient addition will not improve the strength of the alloy. Therefore, this invention controls the content of strengthening elements to 0.003-1%.

[0012] To balance the strength and toughness of the alloy, the Al content is controlled at 3-6%, and the RE content at 2.5-6%. At these levels, Al and RE can form a suitable Al content. 11 RE3 eutectic phase: Excessive hard eutectic phase reduces the alloy's plasticity, while insufficient hard eutectic phase fails to guarantee the alloy's strength. 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 found that, since RE is a high-melting-point metal, the liquidus temperature of the alloy increases with increasing RE content. Excessively high liquidus temperatures cause 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 can lower the liquidus temperature of the alloy. Therefore, to ensure the surface and internal quality of the die-cast parts, this invention preferably uses an Al / RE content of ≥0.8. However, when the Al content is too high, the solid solution of RE and Al in magnesium is insufficient to consume all the Al, resulting in excess Al forming brittle Mg. 17 Al 12 The second phase significantly reduces the plasticity of the alloy, therefore, the present invention also preferably requires that the Al and RE contents simultaneously satisfy the condition Al / RE≤2.

[0013] Furthermore, this invention also adds small amounts of Mn and Be elements to the above alloy. The Mn content is controlled at 0.2-0.5%. Mn can combine with and remove Fe impurities in the magnesium melt, ensuring the purity of the magnesium melt and reducing galvanic corrosion between impurities and the magnesium matrix, thus enhancing the alloy's corrosion resistance. Excess Mn dissolves 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 and alloy element loss due to combustion, improving the purity and compositional stability of the magnesium alloy during smelting.

[0014] Accordingly, the technical solution adopted by the present invention is as follows:

[0015] In a first aspect, the present invention relates to a heat-treasure-free high-strength and high-toughness die-cast magnesium alloy, wherein the weight percentages of each component in the die-cast magnesium alloy are: Al: 3-6%; RE: 2.5-6%; Mn: 0.2-0.5%; Be: 0.002-0.02%; X: 0.003-1%; the total amount of other impurities is ≤0.3%, and the balance is Mg;

[0016] Wherein, X is at least one of Bi, Ti, V, Zr, Cr, Ni, and Cu.

[0017] 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.

[0018] Preferably, in the die-cast magnesium alloy, the weight percentage of Al and RE elements must meet the following condition: 0.8 ≤ Al / RE ≤ 2.

[0019] Preferably, the weight percentages of Al, RE, and X elements in the die-cast magnesium alloy satisfy the following condition: Al + RE + X ≤ 8.5, and the elongation of the die-cast magnesium alloy prepared thereby can be above 18%.

[0020] Preferably, the weight percentages of Al, RE, and X elements in the die-cast magnesium alloy satisfy the following condition: Al + RE + X > 8.5, thereby the yield strength of the die-cast magnesium alloy prepared therefrom can be above 160 MPa.

[0021] Preferably, X is Bi.

[0022] Preferably, X is at least one of Ti, V, and Zr; when X is a combination of two or more of Ti, V, and Zr, the mixing ratio is not particularly limited and can be any ratio.

[0023] Preferably, X is at least one of Cu, Cr, and Ni; when X is a combination of two or more of Cu, Cr, and Ni, the mixing ratio is not particularly limited and can be any ratio.

[0024] Secondly, the present invention also relates to a method for preparing the aforementioned heat-free high-strength and high-toughness die-cast magnesium alloy, the method comprising the following steps:

[0025] S1. Material preparation: Prepare the magnesium alloy according to the composition of claim 1; wherein, Mg and Al are prepared in the form of pure magnesium and pure aluminum, RE is prepared in the form of pure rare earth or Mg-RE or Al-RE master alloy, X is prepared in the form of pure X 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.

[0026] S2. Melting: First, preheat the crucible to 400-500℃, 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, Al-Mn or Mg-Mn master alloy, pure X or Mg-X or Al-X master alloy for melting.

[0027] S3. Refining: The melt from step S2 is heated to 730-750°C, and a gas containing refining agent powder is introduced into the melt for powder spraying refining and slag removal treatment.

[0028] S4. Casting or die casting: After the melt from step S3 refining and slag removal 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.

[0029] Preferably, step S1 further includes a step of preheating the prepared raw materials to 180-240°C for preheating and drying.

[0030] 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 a mixture of N2+SF6 or CO2+SF6 or pure SF6 protective gas introduced into the furnace.

[0031] 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.

[0032] 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.

[0033] Preferably, in step S3, the amount of the refining agent added is 0.3% to 2.0% of the total weight of the melt. The gas includes argon.

[0034] Preferably, in step S3, after refining and degassing, the process further includes a step of settling and then performing pre-furnace component analysis testing.

[0035] More preferably, the settling time is 5 to 10 minutes.

[0036] Preferably, in step S4, the casting temperature is 690–730°C.

[0037] 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.

[0038] 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.

[0039] This invention further enhances strength and toughness by employing specific casting temperatures of 690–730°C, high-speed injection speeds of 2–8 m / s, and casting pressures of 40–150 MPa.

[0040] Preferably, when X is at least one of Ti, V, and Zr, in step S4, when using the die-casting magnesium alloy to produce die-cast parts, the production time of the die-cast parts shall not exceed 12 hours.

[0041] Compared with the prior art, the present invention has the following beneficial effects:

[0042] 1. The heat-free high-strength and high-toughness die-cast magnesium alloy of the present invention is based on conventional Mg-Al-RE die-cast magnesium alloys, by adding Bi element (X) to the alloy to reduce the dendritic Al... 11 RE3 eutectic phase transformation into granular Al 11 RE3 significantly improves the alloy's plasticity, giving it a good balance of strength and ductility. By adding Ti, V, and Zr as X, the heterogeneous nucleation sites they form significantly refine the dendritic Al deposits in the alloy. 11 The RE3 eutectic phase enhances the alloy's plasticity, resulting in a good balance of strength and ductility. By adding X (Cr, Ni, or Cu), the Al-X strengthening phase formed significantly improves the alloy's strength and, to some extent, refines the Al content. 11 The RE3 eutectic phase gives the alloy good strength and ductility.

[0043] 2. The die-cast magnesium alloy obtained by this invention possesses comprehensive properties of high strength and high toughness. Its yield strength in the die-cast state can reach 150–180 MPa, tensile strength can reach 260–290 MPa, and elongation can reach 15–24%. Furthermore, based on improvements in strength or plasticity, this invention achieves an elongation of over 18% by specifically selecting the weight percentage content of Al, RE, and X to satisfy Al+RE+X≤8.5; and achieves a yield strength of over 160 MPa by specifically selecting the weight percentage content of Al, RE, and Bi to satisfy Al+RE+X>8.5. Attached Figure Description

[0044] 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:

[0045] Figure 1 is a microstructure photograph of the die-cast magnesium alloy part obtained in Example 1-1 of the present invention.

[0046] Figure 2 is a microstructure photograph of the die-cast magnesium alloy part obtained in Comparative Example 1-1 of the present invention.

[0047] Figure 3 shows the room temperature tensile curves of the die-cast alloy parts obtained in Embodiment 1-1 and Comparative Examples 1-1 and 1-2 of the present invention.

[0048] Figure 4 is a microstructure photograph of the die-cast magnesium alloy part obtained in Example 2-1 of the present invention.

[0049] Figure 5 is a microstructure photograph of the die-cast magnesium alloy part obtained in Comparative Example 2-1 of the present invention.

[0050] Figure 6 shows the room temperature tensile curves of the die-cast alloy parts obtained in Embodiment 2-1 and Comparative Examples 2-1 and 2-2 of the present invention.

[0051] Figure 7 is a microstructure photograph of the die-cast magnesium alloy part obtained in Example 3-1 of the present invention.

[0052] Figure 8 is a photograph of the microstructure of the die-cast magnesium alloy part obtained in Comparative Example 3-1 of the present invention.

[0053] Figure 9 shows the room temperature tensile curves of the die-cast alloy parts obtained in Example 3-1 and Comparative Examples 3-1 and 3-2 of the present invention.

[0054] Figure 10 shows photographs of the salt spray corrosion results of the die-cast alloy parts obtained in Examples 3-1, 3-6 and Comparative Example 3-2 of the present invention. Detailed Implementation

[0055] 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.

[0056] The measured compositions of the magnesium alloys in the various embodiments and comparative examples of this invention are summarized in Tables 1, 3, and 5, with the remainder being Mg and other unavoidable impurities. The performance test results of the magnesium alloys in the various embodiments and comparative examples are summarized in Tables 2, 4, and 6. The room temperature tensile properties were tested according to the method in GB / T 228.1-2021 "Metallic materials – Tensile testing – Part 1: Room temperature test method", and 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.

[0057] Example 1-1

[0058] 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:

[0059] 1) Based on the theoretical weight percentage of each component being Mg-4Al-0.5La-2.5Ce-0.35Mn-0.01Be-0.2Bi, pure Mg ingot, pure Al ingot, pure Bi, Mg-30La, Mg-30Ce, Al-10Mn, and Al-3Be master alloys were selected as raw materials, and the raw materials were preheated to 200℃ and dried.

[0060] 2) Preheat the crucible to 150℃, coat the inner wall of the crucible with a coating evenly, dry it, and then heat it to 460℃. Introduce a CO2+SF6 mixed gas, put the pure Mg ingot into the crucible, and melt it completely under the protection of the mixed protective gas of CO2 and SF6. Then raise the temperature to 770℃, add Al-3Be master alloy, and after the alloy is completely melted, add Mg-30La and Mg-30Ce master alloys until they are completely melted. Cool down to 740℃, add pure Al, pure Bi, and Al-10Mn 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.

[0061] 3) Heat the melt to 750°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;

[0062] 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 4.0 m / s and a casting pressure (boost) of 90 MPa. The mold used in the production process is a die-casting test rod mold.

[0063] The properties of the resulting die-cast magnesium alloy parts are shown in Table 2.

[0064] Examples 1-2

[0065] 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:

[0066] 1) Based on the theoretical weight percentage of each component being Mg-3.5Al-3.3La-0.4Mn-0.008Be-0.06Bi, pure Mg ingot, pure Al ingot, Mg-10Bi, Al-60La, Mg-10Mn, and Mg-3Be master alloy were selected as raw materials, and the raw materials were preheated to 210℃ and dried.

[0067] 2) Preheat the crucible to 150℃, coat the inner wall of the crucible with a coating evenly, dry it, and then heat it to 450℃. Introduce a CO2+SF6 mixed gas, put the pure Mg ingot into the crucible, and melt it completely under the protection of the mixed protective gas of CO2 and SF6. Then raise the temperature to 760℃, add the Mg-3Be master alloy, and after the alloy is completely melted, add the Al-60La master alloy until it is completely melted. Cool down to 730℃, add the pure Al, Mg-10Bi, and Mg-10Mn 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.

[0068] 3) Heat the melt to 750°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 introduce gas for 10 minutes to remove slag and gas;

[0069] 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 715-725℃, with an injection speed of 5m / s and a casting pressure of 80MPa. The mold used in the production process is a die-casting test rod mold.

[0070] The properties of the resulting die-cast magnesium alloy parts are shown in Table 2.

[0071] Examples 1-3

[0072] 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:

[0073] 1) Based on the theoretical weight percentage of each component as Mg-5.2Al-0.5La-5.5Ce-0.28Mn-0.012Be-0.003Bi, pure Mg ingot, pure Al ingot, pure Ce, Al-30La, Al-10Bi, Al-10Mn, and Mg-3Be master alloys were selected as raw materials, and the raw materials were preheated to 180℃ and dried.

[0074] 2) Preheat the crucible to 150℃, coat the inner wall of the crucible with a coating evenly, dry it, and then heat it to 400℃. Introduce a CO2+SF6 mixed gas, put the pure Mg ingot into the crucible, and melt it completely under the protection of the mixed protective gas of CO2 and SF6. Then raise the temperature to 750℃, add the Mg-3Be master alloy, and after the alloy is completely melted, add the pure Ce and Al-30La master alloys until they are completely melted. Cool down to 720℃, add the pure Al, Al-10Bi, and Al-10Mn 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.

[0075] 3) Heat the melt to 740°C, introduce argon gas at a pressure of 0.2 MPa into the melt, and introduce 1.0% of the total weight of the melt refining agent (specifically, Torch brand magnesium alloy refining agent, purchased from Zhangjiagang Haohua Light Alloy Materials Co., Ltd.) powder, and then continue to purge for 10 minutes to remove slag and gas;

[0076] 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 3.0m / s and a casting pressure of 110MPa. The mold used in the production process is a die-casting test rod mold.

[0077] The properties of the resulting die-cast magnesium alloy parts are shown in Table 2.

[0078] Examples 1-4

[0079] 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:

[0080] 1) Based on the theoretical weight percentage of each component being Mg-3.8Al-1.8La-1.8Ce-0.2Mn-0.005Be-0.02Bi, pure Mg ingot, pure Al ingot, pure Bi, Mg-90La, Al-90Ce, Al-10Mn, and Al-3Be master alloys were selected as raw materials, and the raw materials were preheated to 190℃ and dried.

[0081] 2) Preheat the crucible to 150℃, coat the inner wall of the crucible with a coating evenly, dry it, and then heat it to 420℃. Introduce a mixture of N2 and SF6 gas, and place the pure Mg ingot into the crucible. Under the protection of the mixed protective gas of N2 and SF6, melt it completely. Then raise the temperature to 760℃, add Al-3Be master alloy, and after the alloy is completely melted, add Mg-90La and Al-90Ce master alloys until they are completely melted. Cool down to 730℃, add pure Al, pure Bi, and Al-10Mn 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.

[0082] 3) Heat the melt to 740°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.

[0083] 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 720-730℃, with an injection speed of 6.2m / s and a casting pressure of 120MPa. The mold used in the production process is a die-casting test rod mold.

[0084] The properties of the resulting die-cast magnesium alloy parts are shown in Table 2.

[0085] Examples 1-5

[0086] 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:

[0087] 1) Based on the theoretical weight percentage of each component being Mg-4.3Al-4.1Ce-0.5Mn-0.014Be-0.1Bi, pure Mg ingot, pure Al ingot, Mg-10Bi, pure Ce, Al-20Mn, and Al-3Be master alloys were selected as raw materials, and the raw materials were preheated to 220℃ and dried.

[0088] 2) Preheat the crucible to 150℃, coat the inner wall of the crucible with a coating evenly, dry it, and then heat it to 410℃. Introduce a mixture of N2 and SF6 gas, put the pure Mg ingot into the crucible, and melt it completely under the protection of the N2 and SF6 mixture. Then raise the temperature to 760℃, add Al-3Be master alloy, and after the alloy is completely melted, add pure Ce until it is completely melted. Cool down to 730℃, add pure Al, Mg-10Bi, and Al-20Mn master alloy, 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.

[0089] 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.

[0090] 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 705-715℃, with an injection speed of 2.5m / s and a casting pressure of 65MPa. The mold used in the production process is a die-casting test rod mold.

[0091] The properties of the resulting die-cast magnesium alloy parts are shown in Table 2.

[0092] Examples 1-6

[0093] 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:

[0094] 1) Based on the theoretical weight percentage of each component being Mg-3Al-2La-0.5Ce-0.44Mn-0.002Be-1Bi, pure Mg ingot, pure Al ingot, pure Bi, pure La, Mg-90Ce, Mg-5Mn, and Mg-3Be master alloys were selected as raw materials, and the raw materials were preheated to 240℃ and dried.

[0095] 2) Preheat the crucible to 150°C, coat the inner wall of the crucible with a coating evenly, dry it, and then heat it to 490°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 the pure Mg ingot into the crucible and wait for it to melt completely. Cover the surface of the melt with another layer of covering agent, raise the temperature to 780°C, add Mg-3Be master alloy, and after the alloy is completely melted, add pure La and Mg-90Ce master alloy until it is completely melted. Cool down to 750°C and add pure Al, pure Bi, and Mg-5Mn 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.

[0096] 3) Heat the melt to 760°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.

[0097] 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 690-700℃, with an injection speed of 2.0m / s and a casting pressure of 40MPa. The mold used in the production process is a die-casting test rod mold.

[0098] The properties of the resulting die-cast magnesium alloy parts are shown in Table 2.

[0099] Examples 1-7

[0100] 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:

[0101] 1) Based on the theoretical weight percentage of each component being Mg-4.7Al-1.9La-2.8Ce-0.25Mn-0.02Be-0.3Bi, pure Mg ingot, pure Al ingot, Mg-10Bi, Al-90La, Al-90Ce, Al-3Be, and Mg-5Mn master alloy were selected as raw materials, and the raw materials were preheated to 220℃ and dried.

[0102] 2) Preheat the crucible to 150℃, coat the inner wall of the crucible with a coating evenly, dry it, heat it to 430℃, introduce SF6 gas, put pure Mg ingots into the crucible, and melt them completely under the protection of SF6 protective gas. Then raise the temperature to 770℃, 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 740℃, add pure Al, Mg-10Bi and Mg-5Mn 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.

[0103] 3) Heat the melt to 760°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;

[0104] 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 690-700℃, with an injection speed of 8.0 m / s and a casting pressure of 150 MPa. The mold used in the production process is a die-casting test rod mold.

[0105] The properties of the resulting die-cast magnesium alloy parts are shown in Table 2.

[0106] Examples 1-8

[0107] 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:

[0108] 1) Based on the theoretical weight percentage of each component being Mg-6Al-2.3La-1.4Ce-0.39Mn-0.016Be-0.8Bi, pure Mg ingot, pure Al ingot, pure Bi, Al-60La, Mg-30Ce, Al-10Mn, and Al-5Be master alloys were selected as raw materials, and the raw materials were preheated to 200℃ and dried.

[0109] 2) Preheat the crucible to 150℃, coat the inner wall of the crucible with a coating evenly, dry it, and then heat it to 480℃. Introduce a CO2+SF6 mixed gas, put the pure Mg ingot into the crucible, and melt it completely under the protection of the mixed protective gas of CO2 and SF6. Then raise the temperature to 770℃, add Al-5Be master alloy, and after the alloy is completely melted, add Al-60La and Mg-30Ce master alloys until they are completely melted. Cool down to 740℃, add pure Al, pure Bi, and Al-10Mn 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.

[0110] 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.

[0111] 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 5.6m / s and a casting pressure of 140MPa. The mold used in the production process is a die-casting test rod mold.

[0112] The properties of the resulting die-cast magnesium alloy parts are shown in Table 2.

[0113] Examples 1-9

[0114] 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:

[0115] 1) Based on the theoretical weight percentage of each component as Mg-5.6Al-1.5La-1.3Ce-0.31Mn-0.007Be-0.6Bi, pure Mg ingot, pure Al ingot, pure La, Al-60Ce, Al-20Bi, Mg-5Mn, and Mg-5Be master alloys were selected as raw materials, and the raw materials were preheated to 230℃ and dried.

[0116] 2) Preheat the crucible to 150℃, coat the inner wall of the crucible with a coating evenly, dry it, and then heat it to 500℃. Introduce a mixture of N2 and SF6 gas, put the pure Mg ingot into the crucible, and melt it completely under the protection of the N2 and SF6 mixture. Then raise the temperature to 760℃, add the Mg-5Be master alloy, and after the alloy is completely melted, add the pure La and Al-60Ce master alloys until they are completely melted. Cool down to 730℃, add the pure Al, Al-20Bi, and Mg-5Mn 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. Add or dilute the melt with a deviation in content to make its composition reach the designed magnesium alloy composition range.

[0117] 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.

[0118] 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 720-730℃, with an injection speed of 7m / s and a casting pressure of 50MPa. The mold used in the production process is a die-casting test rod mold.

[0119] The properties of the resulting die-cast magnesium alloy parts are shown in Table 2.

[0120] Examples 1-10

[0121] 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 1-1, except that the Mg-30La master alloy used in this embodiment is added at a theoretical weight percentage of 2.5% of La.

[0122] The properties of the resulting die-cast magnesium alloy parts are shown in Table 2.

[0123] Examples 1-11

[0124] 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 Examples 1-5, except that the amount of Mg-10Bi master alloy added in this embodiment is 0.5% of the theoretical weight percentage of Bi.

[0125] The properties of the resulting die-cast magnesium alloy parts are shown in Table 2.

[0126] Examples 1-12

[0127] 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 Embodiments 1-1, except that: in this embodiment, the Al added is 3% of the total theoretical weight percentage of Al; the Mg-30La master alloy added is 0.7% of the theoretical weight percentage of La; and the Mg-30Ce master alloy added is 3.3% of the theoretical weight percentage of Ce.

[0128] The properties of the resulting die-cast magnesium alloy parts are shown in Table 2.

[0129] Examples 1-13

[0130] 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 Examples 1-5, except that: in this embodiment, the amount of Al added is 5.7% of the theoretical weight percentage of Al; and the amount of pure Ce added is 2.7% of the theoretical weight percentage of Ce.

[0131] The properties of the resulting die-cast magnesium alloy parts are shown in Table 2.

[0132] Comparative Example 1-1

[0133] 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 1-1, except that Bi element is not added in this comparative example.

[0134] The properties of the resulting die-cast magnesium alloy parts are shown in Table 2.

[0135] Comparative Examples 1-2

[0136] 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 1-1, except that the amount of pure Bi added in this comparative example is 1.1% by theoretical weight of Bi.

[0137] The properties of the resulting die-cast magnesium alloy parts are shown in Table 2.

[0138] Figure 1 is a microstructure photograph of the die-cast magnesium alloy part obtained in Example 1-1 of the present invention. As can be seen from Figure 1, the alloy structure mainly consists of an α-Mg matrix and granular Al. 11 Composed of RE3 eutectic phase, dendritic Al 11 The content of RE3 eutectic phase was low. No obvious Bi-rich phase was found in the microstructure. EDS point scanning revealed Bi enrichment in the α-Mg matrix, with Bi mainly dissolved in the α-Mg matrix.

[0139] Figure 2 shows the microstructure of the die-cast magnesium alloy parts obtained in Comparative Example 1-1 of this invention. As can be seen from Figure 2, the high-strength and high-toughness die-cast magnesium alloy without Bi element addition, due to the absence of Bi element to modify its eutectic phase, has a eutectic phase in the alloy microstructure that is basically dendritic Al. 11 RE3 eutectic phase, granular Al 11 The content of the RE3 eutectic phase is very low.

[0140] Figure 3 shows the room temperature tensile curves of the die-cast alloy parts of Example 1-1 and Comparative Examples 1-1 and 1-2 of the present invention. By comparing the tensile curves of Example 1-1 with those of Comparative Examples 1-1 and 1-2 in Figure 3, it can be found that the elongation and tensile strength of Example 1-1 are significantly better than those of Comparative Examples 1-1 and 1-2.

[0141] 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, and Table 2 shows the performance test results. 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 comprehensive mechanical properties. In the die-cast magnesium alloys prepared in Examples 1-1, 1-2, 1-4, 1-5, and 1-6, the sum of the weight percentages of Al, RE, and Bi elements is ≤8.5%, and the elongation of their die-cast magnesium alloy parts is all above 20%, with yield strengths exceeding 150 MPa and tensile strengths exceeding 260 MPa. In the die-cast magnesium alloys prepared in Examples 1-3, 1-7, 1-8, 1-9, 1-10, and 1-11, the sum of the weight percentages of Al, RE, and Bi elements is all >8.5%, and the yield strength of their die-cast magnesium alloy parts is all above 160 MPa, with tensile strengths exceeding 270 MPa, and elongation exceeding 17%.

[0142] The weight percentage of Al in the heat-free high-strength and high-toughness die-cast magnesium alloys prepared in Examples 1-12 does not meet the requirement of Al / RE ≥ 0.8. Compared with Examples 1-1, the elongation and tensile strength in their room temperature tensile properties are significantly reduced.

[0143] The Al element weight percentage in the heat-free high-strength and high-toughness die-cast magnesium alloys prepared in Examples 1-13 is greater than 2 times the RE element weight percentage, which does not meet the requirement of Al / RE≤2. Compared with Examples 1-5, the elongation and tensile strength in their room temperature tensile properties are also significantly reduced.

[0144] Comparative Example 1-1 is a heat-free high-strength and high-toughness die-cast magnesium alloy without Bi element. Since there is no Bi element to modify its eutectic phase, its room temperature tensile properties, especially elongation, are significantly lower than those of the heat-free high-strength and high-toughness die-cast magnesium alloy with Bi element added in Example 1-1.

[0145] The Bi element added in Comparative Examples 1-2 was too much, which did not meet the requirement that the weight percentage of Bi be in the range of 0.003 to 1%, and the elongation in their room temperature tensile properties was also significantly reduced compared with that of Examples 1-1.

[0146] Table 1 Unit: Weight Percentage

[0147] Table 2

[0148] Example 2-1

[0149] 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:

[0150] 1) Based on the theoretical weight percentage of each component being Mg-4Al-0.5La-2.5Ce-0.35Mn-0.01Be-0.1Ti-0.1Zr, pure Mg ingot, pure Al ingot, Mg-30La, Mg-30Ce, Al-20Mn, Al-3Be, Al-10Ti, and Mg-10Zr master alloys were selected as raw materials, and the raw materials were preheated to 200℃ and dried.

[0151] 2) Preheat the crucible to 150℃, coat the inner wall of the crucible with a coating evenly, dry it, and then heat it to 460℃. Introduce a CO2+SF6 mixed gas, put the pure Mg ingot into the crucible, and melt it completely under the protection of the mixed protective gas of CO2 and SF6. Then raise the temperature to 770℃, add Al-3Be master alloy, and after the alloy is completely melted, add Mg-30La and Mg-30Ce master alloys until they are completely melted. Cool down to 740℃, add pure Al, Al-20Mn, Al-10Ti, and Mg-10Zr 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.

[0152] 3) Heat the melt to 750°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;

[0153] 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 4.0 m / s and a casting pressure (boost) of 90 MPa. The mold used in the production process is a die-casting test rod mold.

[0154] The properties of the resulting die-cast magnesium alloy parts are shown in Table 4.

[0155] Example 2-2

[0156] 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:

[0157] 1) Based on the theoretical weight percentage of each component being Mg-3.5Al-3.3La-0.4Mn-0.008Be-0.07Ti, pure Mg ingots, pure Al ingots, Al-60La, Mg-10Mn, Mg-3Be, and Al-5Ti master alloys were selected as raw materials, and the raw materials were preheated to 210℃ and dried.

[0158] 2) Preheat the crucible to 150℃, coat the inner wall of the crucible with a coating evenly, dry it, and then heat it to 450℃. Introduce a mixture of CO2 and SF6 gas, and place pure Mg ingots into the crucible. Under the protection of the mixed protective gas of CO2 and SF6, melt it completely. Then raise the temperature to 760℃, add Mg-3Be master alloy, and after the alloy is completely melted, add Al-60La master alloy until it is completely melted. Cool down to 730℃, and add pure Al, Al-5Ti, and Mg-10Mn master alloys. 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.

[0159] 3) Heat the melt to 750°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 introduce gas for 10 minutes to remove slag and gas;

[0160] 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 715-725℃, with an injection speed of 5m / s and a casting pressure of 80MPa. The mold used in the production process is a die-casting test rod mold.

[0161] The properties of the resulting die-cast magnesium alloy parts are shown in Table 4.

[0162] Example 2-3

[0163] 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:

[0164] 1) Based on the theoretical weight percentage of each component as Mg-5.2Al-0.5La-5.5Ce-0.28Mn-0.012Be-0.003V, pure Mg ingot, pure Al ingot, pure Ce, Al-30La, Al-10V, Al-10Mn, and Mg-3Be master alloys were selected as raw materials, and the raw materials were preheated to 180℃ and dried.

[0165] 2) Preheat the crucible to 150℃, coat the inner wall of the crucible with a coating evenly, dry it, and then heat it to 400℃. Introduce a CO2+SF6 mixed gas, put the pure Mg ingot into the crucible, and melt it completely under the protection of the mixed protective gas of CO2 and SF6. Then raise the temperature to 750℃, add the Mg-3Be master alloy, and after the alloy is completely melted, add the pure Ce and Al-30La master alloys until they are completely melted. Cool down to 720℃, add the pure Al, Al-10V, and Al-10Mn 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.

[0166] 3) Heat the melt to 740°C, introduce argon gas at a pressure of 0.2 MPa into the melt, and introduce 1.0% of the total weight of the melt refining agent (specifically, Torch brand magnesium alloy refining agent, purchased from Zhangjiagang Haohua Light Alloy Materials Co., Ltd.) powder, and then continue to purge for 10 minutes to remove slag and gas;

[0167] 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 3.0m / s and a casting pressure of 110MPa. The mold used in the production process is a die-casting test rod mold.

[0168] The properties of the resulting die-cast magnesium alloy parts are shown in Table 4.

[0169] Examples 2-4

[0170] 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:

[0171] 1) Based on the theoretical weight percentage of each component as Mg-3.8Al-1.8La-1.8Ce-0.2Mn-0.005Be-0.01V-0.01Zr, pure Mg ingot, pure Al ingot, Mg-90La, Al-90Ce, Al-10Mn, Al-3Be, Al-5V, and Mg-5Zr master alloys were selected as raw materials, and the raw materials were preheated to 190℃ and dried.

[0172] 2) Preheat the crucible to 150℃, coat the inner wall of the crucible with a coating evenly, dry it, and then heat it to 420℃. Introduce a mixture of N2 and SF6 gas, and place the pure Mg ingot into the crucible. Under the protection of the mixed protective gas of N2 and SF6, melt it completely. Then raise the temperature to 760℃, add Al-3Be master alloy, and after the alloy is completely melted, add Mg-90La and Al-90Ce master alloys until they are completely melted. Cool down to 730℃, and add pure Al, Al-10Mn, Al-5V, and Mg-5Zr 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.

[0173] 3) Heat the melt to 740°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.

[0174] 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 720-730℃, with an injection speed of 6.2m / s and a casting pressure of 120MPa. The mold used in the production process is a die-casting test rod mold.

[0175] The properties of the resulting die-cast magnesium alloy parts are shown in Table 4.

[0176] Examples 2-5

[0177] 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:

[0178] 1) Based on the theoretical weight percentage of each component being Mg-4.3Al-4.1Ce-0.5Mn-0.014Be-0.02Ti-0.08V, pure Mg ingot, pure Al ingot, pure Ce, Al-20Mn, Al-3Be, Mg-10Ti, and Mg-10V master alloys were selected as raw materials, and the raw materials were preheated to 220℃ and dried.

[0179] 2) Preheat the crucible to 150℃, coat the inner wall of the crucible with a coating evenly, dry it, and then heat it to 410℃. Introduce a mixture of N2 and SF6 gas, and place pure Mg ingots into the crucible. Under the protection of the mixed protective gas of N2 and SF6, melt it completely. Then raise the temperature to 760℃, add Al-3Be master alloy, and after the alloy is completely melted, add pure Ce until it is completely melted. Cool down to 730℃, and add pure Al, Al-20Mn, Mg-10Ti, and Mg-10V master alloys. 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.

[0180] 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.

[0181] 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 705-715℃, with an injection speed of 2.5m / s and a casting pressure of 65MPa. The mold used in the production process is a die-casting test rod mold.

[0182] The properties of the resulting die-cast magnesium alloy parts are shown in Table 4.

[0183] Examples 2-6

[0184] 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:

[0185] 1) Based on the theoretical weight percentage of each component being Mg-3Al-2La-0.5Ce-0.44Mn-0.002Be-1Zr, pure Mg ingot, pure Al ingot, pure La, Mg-90Ce, Mg-5Mn, Mg-3Be, and Mg-30Zr master alloys were selected as raw materials, and the raw materials were preheated to 240℃ and dried.

[0186] 2) Preheat the crucible to 150°C, coat the inner wall of the crucible with a coating evenly, dry it, and then heat it to 490°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 the pure Mg ingot into the crucible and wait for it to melt completely. Cover the surface of the melt with another layer of covering agent, raise the temperature to 780°C, add Mg-3Be master alloy, and after the alloy is completely melted, add pure La and Mg-90Ce master alloy until it is completely melted. Cool down to 750°C and add pure Al, Mg-5Mn, and Mg-30Zr 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.

[0187] 3) Heat the melt to 760°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.

[0188] 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 690-700℃, with an injection speed of 2.0m / s and a casting pressure of 40MPa. The mold used in the production process is a die-casting test rod mold.

[0189] The properties of the resulting die-cast magnesium alloy parts are shown in Table 4.

[0190] Examples 2-7

[0191] 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:

[0192] 1) Based on the theoretical weight percentage of each component being Mg-4.7Al-1.9La-2.8Ce-0.25Mn-0.02Be-0.4V, pure Mg ingots, pure Al ingots, Al-90La, Al-90Ce, Al-3Be, Mg-5Mn, and Mg-5V master alloys were selected as raw materials, and the raw materials were preheated to 220℃ and dried.

[0193] 2) Preheat the crucible to 150℃, coat the inner wall of the crucible with a coating evenly, dry it, heat it to 430℃, introduce SF6 gas, put pure Mg ingots into the crucible, and melt them completely under the protection of SF6 protective gas. Then raise the temperature to 770℃, 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 740℃, add pure Al, Mg-5Mn and Mg-5V 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.

[0194] 3) Heat the melt to 760°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;

[0195] 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 690-700℃, with an injection speed of 8.0 m / s and a casting pressure of 150 MPa. The mold used in the production process is a die-casting test rod mold.

[0196] The properties of the resulting die-cast magnesium alloy parts are shown in Table 4.

[0197] Examples 2-8

[0198] 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:

[0199] 1) Based on the theoretical weight percentage of each component as Mg-6Al-2.3La-1.4Ce-0.39Mn-0.016Be-0.3V-0.6Zr, pure Mg ingot, pure Al ingot, Al-60La, Mg-30Ce, Al-10Mn, Al-5Be, Mg-5V, and Mg-10Zr master alloys were selected as raw materials, and the raw materials were preheated to 200℃ and dried.

[0200] 2) Preheat the crucible to 150℃, coat the inner wall of the crucible with a coating evenly, dry it, and then heat it to 480℃. Introduce a CO2+SF6 mixed gas, put the pure Mg ingot into the crucible, and melt it completely under the protection of the mixed protective gas of CO2 and SF6. Then raise the temperature to 770℃, add Al-5Be master alloy, and after the alloy is completely melted, add Al-60La and Mg-30Ce master alloys until they are completely melted. Cool down to 740℃, add pure Al, Al-10Mn, Mg-5V, and Mg-10Zr 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.

[0201] 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.

[0202] 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 5.6m / s and a casting pressure of 140MPa. The mold used in the production process is a die-casting test rod mold.

[0203] The properties of the resulting die-cast magnesium alloy parts are shown in Table 4.

[0204] Examples 2-9

[0205] 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:

[0206] 1) Based on the theoretical weight percentage of each component as Mg-5.6Al-1.5La-1.3Ce-0.31Mn-0.007Be-0.4Ti-0.1V-0.1Zr, pure Mg ingot, pure Al ingot, pure La, Al-60Ce, Mg-5Mn, Mg-5Be, Mg-10Ti, Al-10V, and Al-10Zr master alloys were selected as raw materials, and the raw materials were preheated to 230℃ and dried.

[0207] 2) Preheat the crucible to 150℃, coat the inner wall of the crucible with a coating evenly, dry it, and then heat it to 500℃. Introduce a mixture of N2 and SF6 gas, place the pure Mg ingot into the crucible, and melt it completely under the protection of the N2 and SF6 mixture. Then raise the temperature to 760℃, add the Mg-5Be master alloy, and after the alloy has completely melted, add the pure La and Al-60Ce master alloys until they are completely melted. Cool down to 730℃, and add the pure Al, Mg-5Mn, Mg-10Ti, Al-10V, and Al-10Zr 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.

[0208] 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.

[0209] 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 720-730℃, with an injection speed of 7m / s and a casting pressure of 50MPa. The mold used in the production process is a die-casting test rod mold.

[0210] The properties of the resulting die-cast magnesium alloy parts are shown in Table 4.

[0211] Example 2-10

[0212] 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 2-1, except that the Mg-30La master alloy used in this embodiment is added at a theoretical weight percentage of 2.5% of La.

[0213] The properties of the resulting die-cast magnesium alloy parts are shown in Table 4.

[0214] Example 2-11

[0215] 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 Examples 2-5, except that: in this embodiment, the amount of Mg-10Ti master alloy added is 0.1% of the theoretical weight percentage of Ti, and the amount of Mg-10V master alloy added is 0.4% of the theoretical weight percentage of V.

[0216] The properties of the resulting die-cast magnesium alloy parts are shown in Table 4.

[0217] Example 2-12

[0218] 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 2-1, except that: in this embodiment, the Al added is 3% of the total theoretical weight percentage of Al; the Mg-30La master alloy added is 0.7% of the theoretical weight percentage of La; and the Mg-30Ce master alloy added is 3.3% of the theoretical weight percentage of Ce.

[0219] The properties of the resulting die-cast magnesium alloy parts are shown in Table 4.

[0220] Example 2-13

[0221] 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 Examples 2-5, except that: in this embodiment, the amount of Al added is 5.7% of the theoretical weight percentage of Al; and the amount of pure Ce added is 2.7% of the theoretical weight percentage of Ce.

[0222] The properties of the resulting die-cast magnesium alloy parts are shown in Table 4.

[0223] Comparative Example 2-1

[0224] 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 2-1, except that Ti and Zr elements are not added in this comparative example.

[0225] The properties of the resulting die-cast magnesium alloy parts are shown in Table 4.

[0226] Comparative Example 2-2

[0227] 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 2-1, except that: the Al-10Ti master alloy used in this example is added at a theoretical weight percentage of 0.2% for Ti; and the Mg-10Zr master alloy used in this example is added at a theoretical weight percentage of 0.9% for Zr.

[0228] The properties of the resulting die-cast magnesium alloy parts are shown in Table 4.

[0229] Figure 4 is a microstructure photograph of the die-cast magnesium alloy part obtained in Example 2-1 of the present invention. As can be seen from Figure 4, the alloy structure mainly consists of α-Mg matrix and dendritic Al. 11 It is composed of RE3 eutectic phase and dendritic Al 11The RE3 eutectic phase is very fine. Small amounts of Al3Ti and Al3Zr particles can also be found in the microstructure.

[0230] Figure 5 shows the microstructure of the die-cast magnesium alloy parts obtained in Comparative Example 2-1 of this invention. As can be seen from Figure 5, the high-strength and tough die-cast magnesium alloy without heat treatment, which does not contain elements such as Ti, V, and Zr, has relatively coarse dendritic Al phases in its microstructure because these elements are not used to refine the eutectic phases. 11 RE3 eutectic phase.

[0231] Figure 6 shows the room temperature tensile curves of the die-cast alloy parts of Example 2-1 and Comparative Examples 2-1 and 2-2 of the present invention. By comparing the tensile curves of Example 2-1 with those of Comparative Examples 2-1 and 2-2 in Figure 6, it can be found that the elongation and tensile strength of Example 2-1 are significantly better than those of Comparative Examples 2-1 and 2-2.

[0232] Table 3 below shows the actual measured weight percentage of each component in the die-cast magnesium alloy parts prepared in each embodiment and comparative example, and Table 4 shows the performance test results. Combining the data in Tables 3 and 4, it can be seen that the die-cast magnesium alloys obtained by this invention all possess excellent comprehensive mechanical properties. In the die-cast magnesium alloys prepared in Examples 2-1, 2-2, 2-4, 2-5, and 2-6, the sum of the weight percentages of Al, RE, and X elements (Ti, V, Zr) is ≤8.5, and the elongation of their die-cast magnesium alloy parts is all above 20%, with yield strength reaching above 150 MPa and tensile strength reaching above 260 MPa. In the die-cast magnesium alloys prepared in Examples 2-3, 2-7, 2-8, 2-9, 2-10, and 2-11, the sum of the weight percentages of Al, RE, and X elements (Ti, V, Zr) is all >8.5, and the yield strength of their die-cast magnesium alloy parts is all above 162 MPa, tensile strength is above 274 MPa, and elongation is also above 17%.

[0233] The weight percentage of Al in the heat-free high-strength and high-toughness die-cast magnesium alloy prepared in Examples 2-12 does not meet the requirement of Al / RE ≥ 0.8. Compared with Example 2-1, its room temperature tensile properties show a significant decrease in elongation and tensile strength.

[0234] The Al element weight percentage in the heat-free high-strength and high-toughness die-cast magnesium alloys prepared in Examples 2-13 is greater than 2 times the RE element weight percentage, which does not meet the requirement of Al / RE≤2. Compared with Examples 2-5, the elongation and tensile strength in their room temperature tensile properties are also significantly reduced.

[0235] Comparative Example 2-1 is a heat-free high-strength and high-toughness die-cast magnesium alloy without the addition of elements such as Ti, V, and Zr. Since there are no elements such as Ti, V, and Zr to refine its eutectic phase, its room temperature tensile properties, especially its elongation, are significantly lower than those of the heat-free high-strength and high-toughness die-cast magnesium alloy with added elements such as Ti and Zr in Example 2-1.

[0236] The addition of too many elements such as Ti, V, and Zr in Comparative Example 2-2 does not meet the requirement that the total weight percentage of elements such as Ti, V, and Zr should be between 0.003% and 1%, and its elongation in room temperature tensile properties is also significantly lower than that in Example 2-1.

[0237] Table 3 Unit: Weight Percentage

[0238] Table 4

[0239] Example 3-1

[0240] 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:

[0241] 1) Based on the theoretical weight percentage of each component as Mg-4Al-0.5La-2.5Ce-0.35Mn-0.01Be-0.2Cu-0.1Ni, pure Mg ingot, pure Al ingot, Mg-30La, Mg-30Ce, Al-20Mn, Al-3Be, Al-50Cu, and Mg-10Ni master alloys were selected as raw materials. The raw materials were preheated to 200℃ and dried.

[0242] 2) Preheat the crucible to 150℃, coat the inner wall of the crucible with a coating evenly, dry it, and then heat it to 460℃. Introduce a CO2+SF6 mixed gas, put the pure Mg ingot into the crucible, and melt it completely under the protection of the mixed protective gas of CO2 and SF6. Then raise the temperature to 770℃, add Al-3Be master alloy, and after the alloy is completely melted, add Mg-30La and Mg-30Ce master alloys until they are completely melted. Cool down to 740℃, add pure Al, Al-20Mn, Al-50Cu, and Mg-10Ni 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.

[0243] 3) Heat the melt to 750°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;

[0244] 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 4.0 m / s and a casting pressure (boost) of 90 MPa. The mold used in the production process is a die-casting test rod mold.

[0245] The properties of the resulting die-cast magnesium alloy parts are shown in Table 6.

[0246] Example 3-2

[0247] 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:

[0248] 1) Based on the theoretical weight percentage of each component being Mg-3.5Al-3.3La-0.4Mn-0.008Be-0.06Ni, pure Mg ingot, pure Al ingot, Al-60La, Mg-10Mn, Mg-3Be, and Al-10Ni master alloys were selected as raw materials, and the raw materials were preheated to 210℃ and dried.

[0249] 2) Preheat the crucible to 150℃, coat the inner wall of the crucible with a coating evenly, dry it, and then heat it to 450℃. Introduce a CO2+SF6 mixed gas, put the pure Mg ingot into the crucible, and melt it completely under the protection of the mixed protective gas of CO2 and SF6. Then raise the temperature to 760℃, add the Mg-3Be master alloy, and after the alloy is completely melted, add the Al-60La master alloy until it is completely melted. Cool down to 730℃, add the pure Al, Al-10Ni, and Mg-10Mn 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.

[0250] 3) Heat the melt to 750°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 introduce gas for 10 minutes to remove slag and gas;

[0251] 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 715-725℃, with an injection speed of 5m / s and a casting pressure of 80MPa. The mold used in the production process is a die-casting test rod mold.

[0252] The properties of the resulting die-cast magnesium alloy parts are shown in Table 6.

[0253] Example 3-3

[0254] 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:

[0255] 1) Based on the theoretical weight percentage of each component as Mg-5.2Al-0.5La-5.5Ce-0.28Mn-0.012Be-0.003Cr, pure Mg ingot, pure Al ingot, pure Ce, Al-30La, Al-5Cr, Al-10Mn, and Mg-3Be master alloys were selected as raw materials. The raw materials were preheated to 180℃ and dried.

[0256] 2) Preheat the crucible to 150℃, coat the inner wall of the crucible with a coating evenly, dry it, and then heat it to 400℃. Introduce a CO2+SF6 mixed gas, put the pure Mg ingot into the crucible, and melt it completely under the protection of the mixed protective gas of CO2 and SF6. Then raise the temperature to 750℃, add the Mg-3Be master alloy, and after the alloy is completely melted, add the pure Ce and Al-30La master alloys until they are completely melted. Cool down to 720℃, add the pure Al, Al-5Cr, and Al-10Mn 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.

[0257] 3) Heat the melt to 740°C, introduce argon gas at a pressure of 0.2 MPa into the melt, and introduce 1.0% of the total weight of the melt refining agent (specifically, Torch brand magnesium alloy refining agent, purchased from Zhangjiagang Haohua Light Alloy Materials Co., Ltd.) powder, and then continue to purge for 10 minutes to remove slag and gas;

[0258] 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 3.0m / s and a casting pressure of 110MPa. The mold used in the production process is a die-casting test rod mold.

[0259] The properties of the resulting die-cast magnesium alloy parts are shown in Table 6.

[0260] Examples 3-4

[0261] 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:

[0262] 1) Based on the theoretical weight percentage of each component being Mg-3.8Al-1.8La-1.8Ce-0.2Mn-0.005Be-0.01Cr-0.01Ni, pure Mg ingots, pure Al ingots, Mg-90La, Al-90Ce, Al-10Mn, Al-3Be, Mg-5Cr, and Al-20Ni master alloys were selected as raw materials, and the raw materials were preheated to 190℃ and dried.

[0263] 2) Preheat the crucible to 150℃, coat the inner wall of the crucible with a coating evenly, dry it, and then heat it to 420℃. Introduce a mixture of N2 and SF6 gas, and place the pure Mg ingot into the crucible. Under the protection of the mixed protective gas of N2 and SF6, melt it completely. Then raise the temperature to 760℃, add Al-3Be master alloy, and after the alloy is completely melted, add Mg-90La and Al-90Ce master alloys until they are completely melted. Cool down to 730℃, and add pure Al, Al-10Mn, Mg-5Cr, and Al-20Ni 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.

[0264] 3) Heat the melt to 740°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.

[0265] 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 720-730℃, with an injection speed of 6.2m / s and a casting pressure of 120MPa. The mold used in the production process is a die-casting test rod mold.

[0266] The properties of the resulting die-cast magnesium alloy parts are shown in Table 6.

[0267] Examples 3-5

[0268] 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:

[0269] 1) Based on the theoretical weight percentage of each component as Mg-4.3Al-4.1Ce-0.5Mn-0.014Be-0.02Cu-0.08Cr, pure Mg ingot, pure Al ingot, pure Ce, Al-20Mn, Al-3Be, Mg-10Cu, and Mg-10Cr master alloys were selected as raw materials. The raw materials were preheated to 220℃ and dried.

[0270] 2) Preheat the crucible to 150℃, coat the inner wall of the crucible with a coating evenly, dry it, and then heat it to 410℃. Introduce a mixture of N2 and SF6 gas, put the pure Mg ingot into the crucible, and melt it completely under the protection of the N2 and SF6 mixture. Then raise the temperature to 760℃, add Al-3Be master alloy, and after the alloy is completely melted, add pure Ce until it is completely melted. Cool down to 730℃, add pure Al, Al-20Mn, Mg-10Cu, and Mg-10Cr 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. Add or dilute the melt with deviations in content to make its composition reach the designed magnesium alloy composition range.

[0271] 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.

[0272] 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 705-715℃, with an injection speed of 2.5m / s and a casting pressure of 65MPa. The mold used in the production process is a die-casting test rod mold.

[0273] The properties of the resulting die-cast magnesium alloy parts are shown in Table 6.

[0274] Examples 3-6

[0275] 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:

[0276] 1) Based on the theoretical weight percentage of each component being Mg-3Al-2La-0.5Ce-0.44Mn-0.002Be-1Cu, pure Mg ingot, pure Al ingot, pure La, pure Cu, Mg-90Ce, Mg-5Mn, and Mg-3Be master alloys were selected as raw materials, and the raw materials were preheated to 240℃ and dried.

[0277] 2) Preheat the crucible to 150°C, coat the inner wall of the crucible with a coating evenly, dry it, and then heat it to 490°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 780°C, add Mg-3Be master alloy, and after the alloy is completely melted, add pure La and Mg-90Ce master alloy until they are completely melted. Cool down to 750°C and add pure Al, pure Cu, and Mg-5Mn master alloy. After they are completely melted, 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.

[0278] 3) Heat the melt to 760°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.

[0279] 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 690-700℃, with an injection speed of 2.0m / s and a casting pressure of 40MPa. The mold used in the production process is a die-casting test rod mold.

[0280] The properties of the resulting die-cast magnesium alloy parts are shown in Table 6.

[0281] Examples 3-7

[0282] 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:

[0283] 1) Based on the theoretical weight percentage of each component as Mg-4.7Al-1.9La-2.8Ce-0.25Mn-0.02Be-0.4Cu-0.1Cr, pure Mg ingot, pure Al ingot, Al-90La, Al-90Ce, Al-3Be, Mg-5Mn, Al-20Cu, and Al-10Cr master alloys were selected as raw materials. The raw materials were preheated to 220℃ and dried.

[0284] 2) Preheat the crucible to 150℃, coat the inner wall of the crucible with a coating evenly, dry it, heat it to 430℃, introduce SF6 gas, put pure Mg ingots into the crucible, and melt them completely under the protection of SF6 protective gas. Then raise the temperature to 770℃, 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 740℃, add pure Al, Mg-5Mn, Al-20Cu and Al-10Cr 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.

[0285] 3) Heat the melt to 760°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;

[0286] 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 690-700℃, with an injection speed of 8.0 m / s and a casting pressure of 150 MPa. The mold used in the production process is a die-casting test rod mold.

[0287] The properties of the resulting die-cast magnesium alloy parts are shown in Table 6.

[0288] Examples 3-8

[0289] 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:

[0290] 1) Based on the theoretical weight percentage of each component as Mg-6Al-2.3La-1.4Ce-0.39Mn-0.016Be-0.1Cu-0.5Ni-0.2Cr, pure Mg ingot, pure Al ingot, Al-60La, Mg-30Ce, Al-10Mn, Al-5Be, Mg-20Cu, Mg-5Ni, and Al-20Cr master alloys were selected as raw materials. The raw materials were preheated to 200℃ and dried.

[0291] 2) Preheat the crucible to 150℃, coat the inner wall of the crucible with a coating evenly, dry it, and then heat it to 480℃. Introduce a CO2+SF6 mixed gas, put the pure Mg ingot into the crucible, and melt it completely under the protection of the mixed protective gas of CO2 and SF6. Then raise the temperature to 770℃, add Al-5Be master alloy, and after the alloy is completely melted, add Al-60La and Mg-30Ce master alloys until they are completely melted. Cool down to 740℃, add pure Al, Al-10Mn, Mg-20Cu, Mg-5Ni, and Al-20Cr 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.

[0292] 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.

[0293] 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 5.6m / s and a casting pressure of 140MPa. The mold used in the production process is a die-casting test rod mold.

[0294] The properties of the resulting die-cast magnesium alloy parts are shown in Table 6.

[0295] Examples 3-9

[0296] 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:

[0297] 1) Based on the theoretical weight percentage of each component as Mg-5.6Al-1.5La-1.3Ce-0.31Mn-0.007Be-0.2Ni-0.4Cr, pure Mg ingot, pure Al ingot, pure La, pure Ni, Al-60Ce, Mg-5Mn, Mg-5Be, and Al-10Cr master alloy were selected as raw materials. The raw materials were preheated to 230℃ and dried.

[0298] 2) Preheat the crucible to 150℃, coat the inner wall of the crucible with a coating evenly, dry it, and then heat it to 500℃. Introduce a mixture of N2 and SF6 gas, put the pure Mg ingot into the crucible, and melt it completely under the protection of the N2 and SF6 mixture. Then raise the temperature to 760℃, add the Mg-5Be master alloy, and after the alloy is completely melted, add the pure La and Al-60Ce master alloys until they are completely melted. Cool down to 730℃, add the pure Al, pure Ni, Mg-5Mn, and Al-10Cr 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.

[0299] 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.

[0300] 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 720-730℃, with an injection speed of 7m / s and a casting pressure of 50MPa. The mold used in the production process is a die-casting test rod mold.

[0301] The properties of the resulting die-cast magnesium alloy parts are shown in Table 6.

[0302] Examples 3-10

[0303] 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 3-1, except that the Mg-30La master alloy used in this embodiment is added at a theoretical weight percentage of 2.5% of La.

[0304] The properties of the resulting die-cast magnesium alloy parts are shown in Table 6.

[0305] Example 3-11

[0306] 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 Examples 3-5, except that: in this embodiment, the amount of Mg-10Cu master alloy added is 0.1% of the theoretical weight percentage of Cu, and the amount of Mg-10Cr master alloy added is 0.4% of the theoretical weight percentage of Cr.

[0307] The properties of the resulting die-cast magnesium alloy parts are shown in Table 6.

[0308] Example 3-12

[0309] 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 3-1, except that: in this embodiment, the amount of Al added is 3% of the total theoretical weight percentage of Al; the amount of Mg-30La master alloy added is 0.7% of the theoretical weight percentage of La; and the amount of Mg-30Ce master alloy added is 3.3% of the theoretical weight percentage of Ce.

[0310] The properties of the resulting die-cast magnesium alloy parts are shown in Table 6.

[0311] Example 3-13

[0312] 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 Examples 3-5, except that: in this embodiment, the amount of Al added is 5.7% of the theoretical weight percentage of Al; and the amount of pure Ce added is 2.7% of the theoretical weight percentage of Ce.

[0313] The properties of the resulting die-cast magnesium alloy parts are shown in Table 6.

[0314] Comparative Example 3-1

[0315] 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 3-1, except that Cu and Ni elements are not added in this comparative example.

[0316] The properties of the resulting die-cast magnesium alloy parts are shown in Table 6.

[0317] Comparative Example 3-2

[0318] 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 3-1, except that: the Al-50Cu master alloy used in this example is added at a theoretical weight percentage of 0.6% of Cu; the Mg-10Ni master alloy used in this example is added at a theoretical weight percentage of 0.5% of Ni.

[0319] The properties of the resulting die-cast magnesium alloy parts are shown in Table 6.

[0320] Figure 7 is a microstructure photograph of the die-cast magnesium alloy part obtained in Example 3-1 of the present invention. As can be seen from Figure 7, the alloy structure mainly consists of an α-Mg matrix and small dendritic Al flakes. 11 The structure consists of a RE3 eutectic phase, and also includes Al2CuMg and Al3Ni reinforcing phases. 11The RE3 eutectic phase grows attached to the Al2CuMg and Al3Ni strengthening phases.

[0321] Figure 8 shows the microstructure of the die-cast magnesium alloy parts obtained in Comparative Example 3-1 of this invention. As can be seen from Figure 8, the heat-free high-strength and high-toughness die-cast magnesium alloy without added Cr, Ni, Cu, etc., lacks the reinforcing phases formed by Cr, Ni, Cu, etc., and exhibits dendritic Al... 11 The RE3 eutectic phase exhibits a large-scale growth morphology.

[0322] Figure 9 shows the room temperature tensile curves of the die-cast alloy parts of Example 3-1 and Comparative Examples 3-1 and 3-2 of the present invention. By comparing the tensile curves of Example 3-1 with those of Comparative Examples 3-1 and 3-2 in Figure 9, it can be found that the elongation and tensile strength of Example 3-1 are significantly better than those of Comparative Examples 3-1 and 3-2.

[0323] Figure 10 shows photographs of the salt spray corrosion results of die-cast alloy parts of Examples 3-1, 3-6 and Comparative Example 3-2 of the present invention. As can be observed from Figure 10, after salt spray corrosion, there are a small amount of corrosion products on the surface of Example 3-1, and more corrosion products on the surface of Example 3-6. The corrosion conditions of Examples 3-1 and 3-6 are within acceptable ranges. However, the die-cast alloy part of Comparative Example 3-2 cannot maintain its original shape after salt spray corrosion. The corrosion condition is very serious and it is difficult to meet the requirements of body structure parts or other parts.

[0324] Table 5 below shows the actual measured weight percentage of each component in the die-cast magnesium alloy parts prepared in each embodiment and comparative example, and Table 6 shows the performance test results. As can be seen from the data in Tables 5 and 6, the die-cast magnesium alloys obtained by this invention all possess excellent comprehensive mechanical properties. In the die-cast magnesium alloys prepared in Examples 3-1, 3-2, 3-4, 3-5, and 3-6, the sum of the weight percentages of Al, RE, and X elements (Cr, Ni, Cu) is ≤8.5, and the elongation of their die-cast magnesium alloy parts is above 18%, with yield strengths above 160 MPa and tensile strengths above 270 MPa. In the die-cast magnesium alloys prepared in Examples 3-3, 3-7, 3-8, 3-9, 3-10, and 3-11, the sum of the weight percentages of Al, RE, and X elements (Cr, Ni, Cu) is >8.5, and the yield strength of their die-cast magnesium alloy parts is above 171 MPa, tensile strength is above 284 MPa, and elongation is above 15%.

[0325] The weight percentage of Al in the heat-free high-strength and high-toughness die-cast magnesium alloy prepared in Examples 3-12 does not meet the requirement of Al / RE≥0.8 compared with Example 3-1. As a result, the elongation and tensile strength in its room temperature tensile properties are significantly reduced.

[0326] The Al element weight percentage in the heat-free high-strength and high-toughness die-cast magnesium alloys prepared in Examples 3-13 is greater than 2 times the La element weight percentage, which does not meet the requirement of Al / RE≤2. Compared with Examples 3-5, the elongation and tensile strength in their room temperature tensile properties are also significantly reduced.

[0327] Comparative Example 3-1 is a heat-free high-strength and high-toughness die-cast magnesium alloy without the addition of elements such as Cr, Ni, and Cu. Since there are no elements such as Cr, Ni, and Cu to form a reinforcing phase, its room temperature tensile properties, especially the yield strength and tensile strength, are significantly lower than those of the heat-free high-strength and high-toughness die-cast magnesium alloy with the addition of elements such as Cu and Ni in Example 3-1.

[0328] The addition of excessive Cr, Ni, Cu, and other elements in Comparative Example 3-2 does not meet the requirement that the total weight percentage of Cr, Ni, Cu, and other elements should be between 0.003% and 1%. As a result, the elongation in its room temperature tensile properties is significantly lower than that in Example 3-1, and its corrosion resistance is also significantly reduced.

[0329] Table 5 Unit: Weight Percentage

[0330] Table 6

[0331] 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 strength and toughness die-cast magnesium alloy, characterized in that, The weight percentage of each component in the die-cast magnesium alloy is: Al: 3-6%; RE: 2.5~6%; Mn: 0.2~0.5%; Be: 0.002~0.02%; X: 0.003–1%; total other impurities ≤0.3%, balance Mg; Wherein, X is at least one of Bi, Ti, V, Zr, Cr, Ni, and Cu.

2. The heat treatment free high strength to toughness permanent mold magnesium alloy according to claim 1, characterized in that, RE in the die-cast magnesium alloy is at least one of La and Ce.

3. The heat treatment free high strength to toughness permanent mold magnesium alloy according to claim 1, characterized in that, In the die-cast magnesium alloy, the weight percentage of Al and RE elements must meet the following condition: 0.8≤Al / RE≤2.

4. The heat-toughness-free die-cast magnesium alloy according to claim 1, 2, or 3, characterized in that, The weight percentages of Al, RE, and X elements in the die-cast magnesium alloy meet the following condition: Al + RE + X ≤ 8.5, and the elongation of the die-cast magnesium alloy prepared thereby can be above 18%.

5. The heat-toughness-free die-cast magnesium alloy according to claim 1, 2, or 3, characterized in that, The weight percentages of Al, RE, and X elements in the die-cast magnesium alloy meet the following condition: Al + RE + X > 8.5, and the yield strength of the die-cast magnesium alloy prepared thereby can be above 160 MPa.

6. A method for preparing a heat-tough, high-strength, die-cast magnesium alloy as described in any one of claims 1 to 5, characterized in that, The method includes the following steps: S1. Material preparation: Prepare the magnesium alloy according to the composition of claim 1; wherein, Mg and Al are prepared in the form of pure magnesium and pure aluminum, RE is prepared in the form of pure rare earth or Mg-RE or Al-RE master alloy, X is prepared in the form of pure X 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. S2. Melting: First, preheat the crucible to 400-500℃, 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, Al-Mn or Mg-Mn master alloy, pure X or Mg-X or Al-X master alloy for melting. S3. Refining: The melt from step S2 is heated to 730-750°C, and a gas containing refining agent powder is introduced into the melt for powder spraying refining and slag removal treatment. S4. Casting or die casting: After the melt from step S3 refining and slag removal 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.

7. The method for preparing a heat-tough, high-strength, die-cast magnesium alloy without heat treatment as described in claim 6, characterized in that, Step S1 also includes the step of preheating the prepared raw materials to 180-240°C for preheating and drying.

8. The method for preparing a heat-toughened high-strength and high-toughness die-cast magnesium alloy as described in claim 6, characterized in that, In step S2, the covering agent has a solvent density <1.58 g / cm³. 3 The covering agent; the protective gas is a mixture of N2+SF6, CO2+SF6, or pure SF6 that is introduced into the furnace. Step S2 also 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. For melts with deviations in content, the melt is replenished or diluted to bring its composition to the qualified range.

9. The method for preparing a heat-toughened high-strength and high-toughness die-cast magnesium alloy as described in claim 6, characterized in that, In step S3, the refining agent is a salt flux that can adsorb impurities in the magnesium alloy melt; the amount of the refining agent added is 0.3 to 2.0% of the total weight of the melt; the gas includes argon.

10. The method for preparing a heat-toughened high-strength and high-toughness die-cast magnesium alloy as described in claim 6, characterized in that, In step S4, the casting temperature is 690–730°C; In step S4, when using the aforementioned die-casting magnesium alloy to produce die-cast parts, the injection speed range is 2 to 8 m / s; In step S4, when using the die-casting magnesium alloy to produce die-cast parts, the casting pressure range is 40 to 150 MPa.

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