Heat-treatment-free high-toughness die-casting magnesium alloy and preparation method thereof

Abstract

The invention relates to a heat-treatment-free high-toughness die-casting magnesium alloy and a preparation method thereof. The alloy comprises the following components in percentage by weight: 3-6% of Al; 2.5%-6% of RE; 0.2 to 0.5 percent of Mn; 0.002% to 0.02% of Be; 0.003% to 1% of X; the sum of the total amount of other impurities is less than or equal to 0.3%; wherein X is at least one of Bi, Ti, V, Zr, Cr, Ni and Cu. The strength and plasticity of the alloy can be remarkably improved through the X element. The typical performance of the alloy is that the yield strength ranges from 150 MPa to 180 MPa, the tensile strength ranges from 260 MPa to 290 MPa, the elongation rate ranges from 15% to 24%, the elongation rate of the alloy is far better than that of traditional die-casting magnesium alloy (such as AZ91D and AM60), the strength and the elongation rate of the alloy in the casting state can further exceed that of some heat-treatment-free die-casting aluminum alloy applied in the market, and in addition, the alloy has the good die-casting performance and can be widely applied to the field of die casting. The die-casting magnesium alloy can be used for forming large-scale integrated car body structural parts or other parts, and the application scene of the die-casting magnesium alloy is greatly expanded.

Description

Technical Field

[0001] The present invention relates to the technical field of metal materials, and in particular to a high-strength and toughness die-cast magnesium alloy free of heat treatment and a preparation method thereof. Background Art

[0002] At present, automobile research and development is developing in the direction of high efficiency, low energy consumption and low emissions. When it is difficult to improve the energy density of automobile batteries, reducing the structural quality of electric vehicles has a significant effect on improving the range of electric vehicles. In addition, reducing the dead weight of the car can also improve the efficiency of the car, reduce the braking distance, improve the safety of the car, and reduce the energy consumption and emissions of the car. Lightweighting has become an important direction for the development of automobiles. Among the various forming methods of automobile parts, high-pressure casting has the advantages of high production efficiency and high degree of intelligence. It is the most widely used and economical forming method. With the rapid development of the electric vehicle industry and the die-casting industry, advanced electric vehicle companies represented by Tesla are gradually merging the parts of the car body, changing the process of connecting and assembling multiple parts to the process of integrated die-casting. The integrated die-casting process can significantly reduce the total production time of parts, the number of molds, the construction time and cost of the plant. In addition, it can also reduce the number of operators and managers, which can significantly reduce the manufacturing cost. And because the manufacturing links are reduced, the quality of the parts is easier to control.

[0003] The development of high-strength and tough alloys that do not require heat treatment is a key issue in solving the production of large-scale integrated die-casting structural parts. For traditional alloy materials, heat treatment is a necessary means to ensure the mechanical properties of die-casting parts, but the parts will deform during the heat treatment process, resulting in deviations in dimensional accuracy. The deformation of large-scale integrated parts during heat treatment is even more inevitable. Although some repairs can be made through orthopedic processes, most deformed parts cannot be repaired and are scrapped. In addition, parts may also be scrapped due to bulging, cracking, and other problems during the heat treatment process, which ultimately leads to a sharp increase in costs. Therefore, compared with traditional heat-treated alloys, heat-treated alloys can reduce production processes, save energy, reduce carbon emissions, and reduce production costs, making the production of large-scale integrated die-casting structural parts possible.

[0004] At present, many domestic enterprises and universities have developed a number of high-performance heat-treatment-free die-cast aluminum alloys and applied them to the actual production of electric vehicles. my country's heat-treatment-free die-cast aluminum alloys are already at the international leading level. Magnesium alloy is currently the lightest structural metal material, 1 / 3 lighter than aluminum, with high specific strength and high specific stiffness. However, the absolute strength and plasticity of magnesium alloy are poor, which limits its application as a structural part. At present, the development of heat-treatment-free high-strength and toughness die-cast magnesium alloys and large-scale integrated die-cast magnesium alloy structural parts is still at a relatively backward level. As the country with the richest magnesium resources, my country has developed heat-treatment-free high-strength and toughness die-cast magnesium alloys and applied them to large-scale integrated body structural parts of electric vehicles, such as the front cabin, rear cabin, chassis, etc., which can further reduce the weight of electric vehicles, improve the endurance, driving performance and safety of electric vehicles, and significantly improve the level of light alloy materials and automobile lightweight technology in my country, which has important scientific research and practical application value.

[0005] Die-cast magnesium alloys are mainly Mg-Al alloys. Currently, the most widely used are AZ91D alloy in AZ (Mg-Al-Zn) die-cast magnesium alloys and AM60 alloy in AM (Mg-Al-Mn) die-cast magnesium alloys. However, due to its high Al content, AZ91D alloy forms a large number of brittle Mg alloys distributed in a network along the grain boundaries. 17 Al 12 The second phase seriously deteriorates the plasticity of the alloy. AM60 alloy has less strengthening elements, lower strength and insufficient plasticity. Therefore, AZ91D and AM60 alloys are mainly used in steering wheels, instrument panel frames and other exterior parts.

[0006] AE (Mg-Al-RE) die-cast magnesium alloys are formed by adding RE elements (mixed rare earth) to combine with Al elements to form dendritic Al 11 Compared with the brittle Mg ions distributed in a network along the grain boundaries, the RE3 eutectic phase 17 Al 12 Relatively speaking, the harm to the alloy plasticity is relatively small, so the alloy plasticity is better, such as the plasticity of AE44 alloy can reach about 16%, which is the alloy with the best comprehensive mechanical properties among the current die-casting magnesium alloys. 11 The morphology of the RE3 eutectic phase is not good enough. When die-casting actual parts, the alloy performance is greatly attenuated, and its strength and plasticity cannot be guaranteed, which limits its application in large-scale integrated die-casting structural parts.

[0007] Chinese Patent No. 201810812693.2 discloses "a die-cast magnesium alloy material and its preparation method". 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 are added to the magnesium alloy. Although the alloy has good strength and plasticity, the elements Gd, Y, Sm, Nd, Er, Eu, Ho, Tm, Lu, Dy, and Yb contained in the alloy are relatively expensive and highly active. They are easily oxidized and burned during the production process, producing obvious oxide scale. The oxide scale is involved in the casting, which significantly reduces the strength and plasticity of the alloy and the stability of the mechanical properties of the casting. In addition, compared with Mg, the atomic mass of elements such as Pr, Gd, Sm, Nd, Er, Eu, Ho, Tm, Lu, Dy, and Yb is too large, and they are prone to sedimentation during the production process, resulting in composition deviation. Therefore, in actual production, the casting processability of this alloy is poor, the quality of castings is unstable, and there are serious safety hazards.

[0008] The Chinese patent 202310638270.4 previously applied by the inventor team discloses "a high-strength, high-toughness, high-heat-resistant Mg-Al-RE die-cast magnesium alloy and its preparation method". This method achieves the requirements of improving the strength, heat resistance and toughness of the alloy 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 alloy structure of the magnesium alloy obtained by this method is mainly composed of α-Mg matrix and dendritic Al 11 RE3 is composed of the second phase, and its elongation is only 9-15%.

[0009] Therefore, the existing die-cast magnesium alloy materials have the technical difficulty of not being able to take into account the cost, toughness and processability at the same time, making the existing die-cast magnesium alloys unable to meet the demand of large integrated structural parts for high-strength and tough die-cast magnesium alloys without heat treatment. It is urgent to develop new high-strength and tough die-cast magnesium alloys without heat treatment to meet the use demand of magnesium alloys in large integrated structural parts. Summary of the invention

[0010] The purpose of the present invention is to provide a high-strength and toughness die-cast magnesium alloy without heat treatment and a preparation method thereof. Under the premise of ensuring good casting performance, the problem that the existing magnesium alloy cannot have both high strength and high toughness without heat treatment is solved, thereby broadening the application scenarios of die-cast magnesium alloys, using the die-cast magnesium alloy on large integrated structural parts, replacing the traditional multi-part connection assembly process or heat-treatment-free die-cast aluminum alloy, which can significantly reduce the weight of parts and improve my country's lightweight technology level.

[0011] In order to achieve this goal, the present invention has found in the research on Mg-Al-RE series die-casting magnesium alloy that: 1) by adding a small amount of modified element Bi, the dendritic Al in Mg-Al-RE series die-casting magnesium alloy can be 11 The RE3 eutectic phase is transformed into a granular state, which is different from the dendritic Al 11 For RE3 eutectic phase, dislocations are more likely to cut through or bypass the granular Al 11 RE3 eutectic phase, and granular Al 11 The number density of RE3 eutectic phase is lower than that of dendritic Al 11 RE3 phase, so its blocking ability for dislocations is weakened, and the plasticity of the alloy is significantly increased. In addition, the solid solubility of Bi in magnesium is relatively large, and the excess Bi in the magnesium alloy can be dissolved in the Mg matrix to increase the strength of the alloy. However, too much Bi will form a large amount of brittle Mg3Bi2 second phase, which significantly reduces the plasticity of the alloy, while too little Bi will not play a role in modifying Al 11 RE3 eutectic phase, so the present invention controls the Bi content to 0.003-1%. 2) By adding a small amount of refining elements such as at least one of Ti, V, and Zr, Al3Ti, Al3V, Al 21 Heterogeneous nucleation particles 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 the coarse dendritic Al 11 For RE3 eutectic phase, fine Al 11 The splitting effect of RE3 eutectic on the matrix is ​​significantly reduced, and the plasticity of the alloy is significantly increased. In addition, the heterogeneous nucleation particles formed by the refinement elements have high strength and hardness, which can form dispersion strengthening and increase the strength of the alloy. However, the heterogeneous nucleation particles formed by too many refinement elements will agglomerate, which will not only lose the refinement of Al 11 The effect of RE3 eutectic phase will damage the plasticity of the alloy, while too little refining element will not play the role of refining Al 11 RE3 eutectic phase, so the present invention controls the content of the refining elements to 0.003-1%. 3) By adding a small amount of strengthening elements, such as at least one of Cr, Ni, and Cu, Al7Cr, Al4Cr, Al3Ni, Al2Cu, Al2CuMg, and other strengthening phases are formed in the melt, which can significantly improve the strength of the Mg-Al-RE series die-casting magnesium alloy; and these elements, as high-temperature elements, form strengthening phases that will form in the early stage of solidification and can serve as Al 11 The nucleation points of RE3 eutectic phase can refine Al 11RE3 eutectic phase improves the plasticity of die-cast magnesium alloy. However, the electrode potential of these elements and the strengthening phase formed is relatively high, and the electrode potential difference with the magnesium matrix is ​​too large. Too much strengthening element addition will seriously damage the corrosion resistance and plasticity of the alloy, while too little strengthening element will not improve the strength of the alloy. Therefore, the present invention controls the content of strengthening elements to 0.003-1%.

[0012] At the same time, in order to take into account the strength and toughness of the alloy, the Al content is controlled at 3-6%, and the RE content is controlled at 2.5-6%. At this content, Al and RE elements can form an appropriate content of Al 11 RE3 eutectic phase, too much hard eutectic phase will reduce the plasticity of the alloy, while too little hard eutectic phase cannot guarantee the strength of the alloy. The rare earth used in the present invention is at least one of La and Ce, both of which are high-abundance cheap rare earth elements, which makes the cost of the alloy low and can meet the needs of industrial applications. The present invention also found that since the RE element is a high-melting-point metal, as the RE element content increases, the liquidus temperature of the alloy will also increase. Too high a liquidus temperature will cause the alloy to solidify prematurely during the die-casting process. The surface of the die-cast parts is prone to micro-cold shuts, and the interior is also prone to defects such as pre-crystallization, shrinkage cavities and shrinkage. The Al element can reduce the liquidus temperature of the alloy. Therefore, in order to ensure the surface and internal quality of the die-cast parts, the present invention preferably satisfies the following conditions for the Al and RE content: Al / RE≥0.8. However, when the Al content is too high, the solid solution of the RE element and Al in magnesium is not enough to consume all the Al elements, and the excess Al element will form brittle Mg 17 Al 12 The second phase significantly reduces the plasticity of the alloy, so the present invention also preferably requires that the Al and RE contents simultaneously satisfy the condition of Al / RE≤2.

[0013] In addition, the present invention also adds a small amount of Mn and Be elements to the above alloy. The Mn element content is controlled at 0.2-0.5%. The Mn element can combine with and remove the Fe impurity element in the magnesium melt, which ensures the purity of the magnesium melt on the one hand, and reduces the galvanic corrosion between the impurity elements and the magnesium matrix on the other hand, thereby enhancing the corrosion resistance of the alloy; the excess Mn element is dissolved in the magnesium matrix to ensure the strength of the alloy. The Be element helps to form a dense protective film on the surface of the magnesium alloy, which can significantly reduce the oxidation and combustion of the magnesium alloy during the smelting process, thereby reducing the oxidation slag in the magnesium alloy or the burning of the alloy elements caused by combustion, and improves the purity of the magnesium alloy during the smelting process and the stability of the composition.

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

[0015] In a first aspect, the present invention relates to a high-strength and toughness die-cast magnesium alloy without heat treatment, wherein 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%; the total amount of other impurities is ≤0.3%, and the balance is Mg;

[0016] Among them, 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 percentages of Al and RE elements must satisfy 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 meet 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, and the yield strength of the die-cast magnesium alloy prepared thereby may be above 160 MPa.

[0021] Preferably, X is Bi.

[0022] Preferably, the X is at least one of Ti, V and Zr; when the 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] In a second aspect, the present invention also relates to a method for preparing the aforementioned heat-treatment-free high-strength and toughness die-cast magnesium alloy, the method comprising the following steps:

[0025] S1. Material preparation: The magnesium alloy composition according to claim 1 is prepared; 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, smelting: first preheat the crucible to 400-500°C, put the pure Mg ingot into the crucible, melt it under protective gas or vacuum, or first cover the crucible with a layer of covering agent, add the pure Mg ingot and cover the melt surface with another layer of covering agent after it is melted; then heat it to 750-780°C and add Al-Be or Mg-Be master alloy, after the master alloy is melted, keep this temperature and add pure rare earth or Mg-RE or Al-RE master alloy, after it is melted, cool it to 720-750°C, then add pure aluminum, Al-Mn or Mg-Mn master alloy, pure X or Mg-X or Al-X master alloy to melt;

[0027] S3, refining: heating the melt of step S2 to 730-750°C, introducing gas with refining agent powder into the melt for powder spraying, refining and slag removal;

[0028] S4, casting or die-casting: After the melt after refining and slag removal in step S3 reaches the casting temperature, an alloy ingot casting operation or a die-casting process operation is performed to finally complete the production of alloy ingots or die-casting parts.

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

[0030] Preferably, in step S2, the covering agent is a solvent with a density of <1.58 g / cm 3 The covering agent can be of the type conventionally selected in the art and can be obtained through ordinary commercial channels; the protective gas is a mixed gas of N2+SF6 or CO2+SF6 or a pure SF6 protective gas introduced into the furnace.

[0031] Preferably, step S2 further includes the steps of allowing the melt to stand and perform a pre-furnace composition analysis after the melt is evenly stirred, detecting the component content of the alloy solution, supplementing or diluting the melt with a deviation in content to bring its composition within an acceptable range.

[0032] Preferably, in step S3, the refining agent is a salt flux capable of absorbing impurities in the magnesium alloy melt, and the refining agent may be a salt flux conventionally selected in the art and may be obtained through common commercial channels.

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

[0034] Preferably, in step S3, after refining and degassing, the process further includes standing the product and performing a pre-furnace component analysis test.

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

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

[0037] Preferably, in step S4, when the die-cast magnesium alloy is used to produce die-cast parts, the high-speed injection speed ranges from 2 to 8 m / s.

[0038] Preferably, in step S4, when the die-cast magnesium alloy is used to produce die-cast parts, the casting pressure ranges from 40 to 150 MPa.

[0039] The present invention can further achieve the effect of improving strength and toughness by specifically adopting a pouring temperature of 690-730°C, a high-speed injection speed of 2-8m / s, and a casting pressure of 40-150MPa.

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

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

[0042] 1. The heat treatment-free high-strength and toughness die-cast magnesium alloy of the present invention is based on the conventional Mg-Al-RE series die-cast magnesium alloy, by adding X as Bi element to the dendritic Al in the alloy. 11 RE3 eutectic phase transforms into granular Al 11 RE3 significantly improves the plasticity of the alloy, making the alloy have a better combination of strength and plasticity; by adding X as Ti, V, and Zr, the heterogeneous nucleation particles formed by them are used to significantly refine the dendritic Al in the alloy. 11 RE3 eutectic phase improves the plasticity of the alloy, making the alloy have a better combination of strength and plasticity; by adding X as Cr, Ni, Cu, using the Al-X strengthening phase formed by them, the strength of the alloy is significantly improved, and the Al 11 RE3 eutectic phase gives the alloy a better combination of strength and plasticity.

[0043] 2. The die-cast magnesium alloy obtained by the present invention has the comprehensive properties of high strength and high toughness, and its yield strength in the die-cast state can reach 150-180MPa, the tensile strength can reach 260-290MPa, and the elongation can reach 15-24%. The present invention is further based on the improvement of strength or plasticity, by specifically selecting the weight percentage content of Al, RE and X to meet Al+RE+X≤8.5, so that the elongation of the die-cast magnesium alloy reaches more than 18%; by specifically selecting the weight percentage content of Al, RE and Bi to meet Al+RE+X>8.5, so that the yield strength of the die-cast magnesium alloy reaches more than 160MPa. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] Other features, objects and advantages of the present invention will become more apparent from the detailed description of non-limiting embodiments made with reference to the following drawings:

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

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

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

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

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

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

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

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

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

[0054] Fig.10 The following are photos of the salt spray corrosion results of the die-cast alloy parts obtained in Examples 3-1 and 3-6 of the present invention and Comparative Example 3-2. DETAILED DESCRIPTION

[0055] The present invention is described in detail below in conjunction with specific embodiments. The following embodiments will help those skilled in the art to further understand the present invention, but are not intended to limit the present invention in any form. It should be noted that, for those of ordinary skill in the art, several variations and improvements may be made without departing from the concept of the present invention. These all belong to the protection scope of the present invention.

[0056] The measured components of the magnesium alloys of the embodiments and comparative examples of the present invention are summarized in Tables 1, 3 and 5, and the rest are Mg and other unavoidable impurities. The performance test results of the magnesium alloys of the embodiments and comparative examples are summarized in Tables 2, 4 and 6. Among them, the room temperature tensile performance test is carried out according to the method in the standard GB / T 228.1-2021 "Metallic Material Tensile Test Part 1: Room Temperature Test Method", and the salt spray corrosion test is carried out according to the method in the standard GB / T10125-2021 "Artificial Atmosphere Corrosion Test Salt Spray Test", using 5% neutral NaCl solution, and the experiment is carried out for 168 hours.

[0057] Example 1-1

[0058] This embodiment provides a method for preparing a heat-treatment-free high-strength and toughness die-cast magnesium alloy, and the specific steps are as follows:

[0059] 1) According to 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 alloy are selected as raw materials, and the raw materials are preheated to 200° C. for drying;

[0060] 2) Preheat the crucible to 150°C, evenly apply the coating on the inner wall of the crucible, dry and heat to 460°C, introduce a CO2+SF6 mixed gas, put the pure Mg ingot into the crucible, completely melt it under the protection of the mixed protective gas of CO2 and SF6, then heat it to 770°C, add Al-3Be master alloy, add Mg-30La and Mg-30Ce master alloys until the alloy is completely melted, cool it to 740°C, add pure Al, pure Bi and Al-10Mn master alloys, stir them fully after they are completely melted, let them stand and perform pre-furnace composition analysis, detect the composition content of the alloy solution, supplement or dilute the solution with deviation in content, so that its composition reaches the designed magnesium alloy composition range;

[0061] 3) The melt is heated to 750° C., argon gas at a pressure of 0.2 MPa is introduced into the melt, and 0.8% of the total weight of the melt is introduced into the refining agent (specifically Torch brand magnesium alloy refining agent in this embodiment, purchased from Zhangjiagang Haohua Light Alloy Material Co., Ltd.) powder, and then the slag and gas removal is continued for 10 minutes;

[0062] 4) The refined melt is left to stand for 10 minutes, and then the composition analysis test is carried out before the furnace. After the composition is qualified, high-pressure casting production is carried out at 710-720°C, the injection speed is 4.0m / s, and the casting pressure (boost) is 90MPa. The mold used in the production process is a die-casting test bar mold.

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

[0064] Example 1-2

[0065] This embodiment provides a method for preparing a heat-treatment-free high-strength and toughness die-cast magnesium alloy, and the specific steps are as follows:

[0066] 1) According to 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 are selected as raw materials, and the raw materials are preheated to 210° C. for drying;

[0067] 2) Preheat the crucible to 150°C, evenly apply the coating on the inner wall of the crucible, dry and heat to 450°C, introduce a CO2+SF6 mixed gas, put the pure Mg ingot into the crucible, completely melt it under the protection of the mixed protective gas of CO2 and SF6, then heat it to 760°C, add the Mg-3Be master alloy, add the Al-60La master alloy until the alloy is completely melted, cool it to 730°C, add pure Al, Mg-10Bi, and Mg-10Mn master alloys, stir them fully after they are completely melted, let them stand and perform a furnace composition analysis, detect the composition content of the alloy solution, supplement or dilute the solution with deviation in content, so that its composition reaches the designed magnesium alloy composition range;

[0068] 3) The melt is heated to 750° C., argon gas at a pressure of 0.2 MPa is introduced into the melt, and 0.6% of the total weight of the melt is introduced into the refining agent (specifically Torch brand magnesium alloy refining agent in this embodiment, purchased from Zhangjiagang Haohua Light Alloy Material Co., Ltd.) powder, and then the slag and gas removal are continued for 10 minutes;

[0069] 4) The refined melt is left to stand for 10 minutes, and then the composition analysis test is carried out before the furnace. After the composition is qualified, high-pressure casting production is carried out at 715-725℃, the injection speed is 5m / s, and the casting pressure is 80MPa. The mold used in the production process is a die-casting test bar mold.

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

[0071] Examples 1-3

[0072] This embodiment provides a method for preparing a heat-treatment-free high-strength and toughness die-cast magnesium alloy, and the specific steps are as follows:

[0073] 1) According to the theoretical weight percentage of each component being 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 alloy are selected as raw materials, and the raw materials are preheated to 180° C. for drying;

[0074] 2) Preheat the crucible to 150°C, evenly apply the coating on the inner wall of the crucible, dry and heat to 400°C, introduce a CO2+SF6 mixed gas, put the pure Mg ingot into the crucible, completely melt it under the protection of the mixed protective gas of CO2 and SF6, then heat it to 750°C, add the Mg-3Be master alloy, after the alloy is completely melted, add pure Ce and Al-30La master alloy until it is completely melted, cool it to 720°C, add pure Al, Al-10Bi, Al-10Mn master alloy, stir it fully after it is completely melted, let it stand and perform a furnace composition analysis, detect the composition content of the alloy solution, supplement or dilute the solution with deviation in content, so that its composition reaches the designed magnesium alloy composition range;

[0075] 3) The melt is heated to 740° C., argon gas at a pressure of 0.2 MPa is introduced into the melt, and 1.0% of the total weight of the melt is introduced into the refining agent (specifically Torch brand magnesium alloy refining agent in this embodiment, purchased from Zhangjiagang Haohua Light Alloy Material Co., Ltd.) powder, and then the slag and gas removal are continued for 10 minutes;

[0076] 4) The refined melt is left to stand for 5 minutes, and then the composition analysis test is carried out before the furnace. After the composition is qualified, high-pressure casting production is carried out at 700-710°C, the injection speed is 3.0m / s, and the casting pressure is 110MPa. The mold used in the production process is a die-casting test bar mold.

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

[0078] Examples 1-4

[0079] This embodiment provides a method for preparing a heat-treatment-free high-strength and toughness die-cast magnesium alloy, and the specific steps are as follows:

[0080] 1) According to 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 alloy are selected as raw materials, and the raw materials are preheated to 190° C. for drying;

[0081] 2) Preheat the crucible to 150°C, evenly apply the coating on the inner wall of the crucible, dry and heat to 420°C, introduce N2+SF6 mixed gas, put the pure Mg ingot into the crucible, completely melt it under the protection of the mixed protective gas of N2 and SF6, then heat it to 760°C, add Al-3Be master alloy, add Mg-90La and Al-90Ce master alloy until the alloy is completely melted, cool it to 730°C, add pure Al, pure Bi and Al-10Mn master alloy, stir it fully after it is completely melted, let it stand and perform pre-furnace composition analysis, detect the composition content of the alloy solution, supplement or dilute the solution with deviation in content, so that its composition reaches the designed magnesium alloy composition range;

[0082] 3) The melt is heated to 740° C., argon gas at a pressure of 0.2 MPa is introduced into the melt, and 1.5% of the total weight of the melt is introduced into the refining agent (specifically Torch brand magnesium alloy refining agent in this embodiment, purchased from Zhangjiagang Haohua Light Alloy Material Co., Ltd.) powder, and then the slag and gas removal is continued for 10 minutes;

[0083] 4) The refined melt is left to stand for 8 minutes, and then the composition analysis test is carried out before the furnace. After the composition is qualified, high-pressure casting production is carried out at 720-730°C, the injection speed is 6.2m / s, and the casting pressure is 120MPa. The mold used in the production process is a die-casting test bar mold.

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

[0085] Examples 1-5

[0086] This embodiment provides a method for preparing a heat-treatment-free high-strength and toughness die-cast magnesium alloy, and the specific steps are as follows:

[0087] 1) According to 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 alloy are selected as raw materials, and the raw materials are preheated to 220° C. for drying;

[0088] 2) Preheat the crucible to 150°C, evenly apply the coating on the inner wall of the crucible, dry and heat to 410°C, introduce N2+SF6 mixed gas, put the pure Mg ingot into the crucible, completely melt it under the protection of the mixed protective gas of N2 and SF6, then heat it to 760°C, add Al-3Be master alloy, add pure Ce until the alloy is completely melted, cool it to 730°C, add pure Al, Mg-10Bi, Al-20Mn master alloy, stir it fully after it is completely melted, let it stand and perform pre-furnace composition analysis, detect the composition content of the alloy solution, supplement or dilute the solution with deviation in content, so that its composition reaches the designed magnesium alloy composition range;

[0089] 3) The melt is heated to 740° C., argon gas at a pressure of 0.2 MPa is introduced into the melt, and a refining agent (specifically Torch brand magnesium alloy refining agent in this embodiment, purchased from Zhangjiagang Haohua Light Alloy Material Co., Ltd.) powder of 2% of the total weight of the melt is introduced, and then the slag and gas removal is continued for 10 minutes;

[0090] 4) The refined melt is left to stand for 9 minutes, and then the composition analysis test is carried out before the furnace. After the composition is qualified, high-pressure casting production is carried out at 705-715°C, the injection speed is 2.5m / s, and the casting pressure is 65MPa. The mold used in the production process is a die-casting test bar mold.

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

[0092] Examples 1-6

[0093] This embodiment provides a method for preparing a heat-treatment-free high-strength and toughness die-cast magnesium alloy, and the specific steps are as follows:

[0094] 1) According to 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 alloy are selected as raw materials, and the raw materials are preheated to 240° C. for drying;

[0095] 2) Preheat the crucible to 150°C, evenly apply the coating on the inner wall of the crucible, dry and heat to 490°C, cover the crucible with a layer of covering agent (the specific covering agent used in this embodiment is Torch brand flux purchased from Zhangjiagang Haohua Light Alloy Material Co., Ltd.), put the pure Mg ingot into the crucible and wait for it to melt, cover the surface of the melt with another layer of covering agent, heat 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 to 750°C, add pure Al, pure Bi, and Mg-5Mn master alloy, stir thoroughly after complete melting, let stand and perform furnace composition analysis, detect the composition content of the alloy solution, supplement or dilute the solution with deviation in content, so that its composition reaches the designed magnesium alloy composition range;

[0096] 3) The melt is heated to 760° C., argon gas at a pressure of 0.2 MPa is introduced into the melt, and 1.8% of the total weight of the melt is introduced into the refining agent (specifically Torch brand magnesium alloy refining agent in this embodiment, purchased from Zhangjiagang Haohua Light Alloy Material Co., Ltd.) powder, and then the slag and gas removal is continued for 10 minutes;

[0097] 4) The refined melt is left to stand for 6 minutes, and then the composition analysis test is carried out before the furnace. After the composition is qualified, high-pressure casting production is carried out at 690-700°C, the injection speed is 2.0m / s, and the casting pressure is 40MPa. The mold used in the production process is a die-casting test bar mold.

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

[0099] Examples 1-7

[0100] This embodiment provides a method for preparing a heat-treatment-free high-strength and toughness die-cast magnesium alloy, and the specific steps are as follows:

[0101] 1) According to 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 are selected as raw materials, and the raw materials are preheated to 220° C. for drying;

[0102] 2) Preheat the crucible to 150°C, evenly apply the coating on the inner wall of the crucible, dry and heat to 430°C, introduce SF6 gas, put the pure Mg ingot into the crucible, completely melt it under the protection of SF6 protective gas, then heat it to 770°C, add Al-3Be master alloy, add Al-90La and Al-90Ce master alloys until the alloy is completely melted, cool it to 740°C, add pure Al, Mg-10Bi and Mg-5Mn master alloys, stir them fully after they are completely melted, let them stand and perform pre-furnace composition analysis, detect the composition content of the alloy solution, supplement or dilute the solution with deviation in content, so that its composition reaches the designed magnesium alloy composition range;

[0103] 3) The melt is heated to 760° C., argon gas at a pressure of 0.2 MPa is introduced into the melt, and 0.3% of the total weight of the melt is introduced into the refining agent (specifically Torch brand magnesium alloy refining agent in this embodiment, purchased from Zhangjiagang Haohua Light Alloy Material Co., Ltd.) powder, and then the slag and gas removal is continued for 10 minutes;

[0104] 4) The refined melt is left to stand for 7 minutes, and then the composition analysis test is carried out before the furnace. After the composition is qualified, high-pressure casting production is carried out at 690-700°C, the injection speed is 8.0m / s, and the casting pressure is 150MPa. The mold used in the production process is a die-casting test bar mold.

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

[0106] Examples 1-8

[0107] This embodiment provides a method for preparing a heat-treatment-free high-strength and toughness die-cast magnesium alloy, and the specific steps are as follows:

[0108] 1) According to 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 alloy are selected as raw materials, and the raw materials are preheated to 200° C. for drying;

[0109] 2) Preheat the crucible to 150°C, evenly apply the coating on the inner wall of the crucible, dry and heat to 480°C, introduce a CO2+SF6 mixed gas, put the pure Mg ingot into the crucible, completely melt it under the protection of the mixed protective gas of CO2 and SF6, then heat it to 770°C, add Al-5Be master alloy, add Al-60La and Mg-30Ce master alloy until the alloy is completely melted, cool it to 740°C, add pure Al, pure Bi and Al-10Mn master alloy, stir it fully after it is completely melted, let it stand and perform pre-furnace composition analysis, detect the composition content of the alloy solution, supplement or dilute the solution with deviation in content, so that its composition reaches the designed magnesium alloy composition range;

[0110] 3) The melt is heated to 750° C., argon gas at a pressure of 0.2 MPa is introduced into the melt, and 0.5% of the total weight of the melt is introduced into the refining agent (specifically Torch brand magnesium alloy refining agent in this embodiment, purchased from Zhangjiagang Haohua Light Alloy Material Co., Ltd.) powder, and then the slag and gas removal are continued for 10 minutes;

[0111] 4) The refined melt is left to stand for 10 minutes, and then the composition analysis test is carried out before the furnace. After the composition is qualified, high-pressure casting production is carried out at 710-720°C, the injection speed is 5.6m / s, and the casting pressure is 140MPa. The mold used in the production process is a die-casting test bar mold.

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

[0113] Examples 1-9

[0114] This embodiment provides a method for preparing a heat-treatment-free high-strength and toughness die-cast magnesium alloy, and the specific steps are as follows:

[0115] 1) According to the theoretical weight percentage of each component being 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 alloy are selected as raw materials, and the raw materials are preheated to 230° C. for drying;

[0116] 2) Preheat the crucible to 150°C, evenly apply the coating on the inner wall of the crucible, dry and heat to 500°C, introduce N2+SF6 mixed gas, put the pure Mg ingot into the crucible, completely melt it under the protection of the mixed protective gas of N2 and SF6, then heat it to 760°C, add Mg-5Be master alloy, after the alloy is completely melted, add pure La and Al-60Ce master alloy until it is completely melted, cool it to 730°C, add pure Al, Al-20Bi, Mg-5Mn master alloy, stir it fully after it is completely melted, let it stand and perform pre-furnace composition analysis, detect the composition content of the alloy solution, supplement or dilute the solution with deviation in content, so that its composition reaches the designed magnesium alloy composition range;

[0117] 3) The melt is heated to 750° C., argon gas at a pressure of 0.2 MPa is introduced into the melt, and 0.5% of the total weight of the melt is introduced into the refining agent (specifically Torch brand magnesium alloy refining agent in this embodiment, purchased from Zhangjiagang Haohua Light Alloy Material Co., Ltd.) powder, and then the slag and gas removal are continued for 10 minutes;

[0118] 4) The refined melt is left to stand for 8 minutes, and then the composition analysis test is carried out before the furnace. After the composition is qualified, high-pressure casting production is carried out at 720-730℃, the injection speed is 7m / s, and the casting pressure is 50MPa. The mold used in the production process is a die-casting test bar mold.

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

[0120] Examples 1-10

[0121] This embodiment provides a method for preparing a high-strength and tough die-cast magnesium alloy without heat treatment, which is basically the same as the method in Example 1-1, except that the addition amount of Mg-30La intermediate alloy used in this embodiment is 2.5% of La theoretical weight percentage.

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

[0123] Embodiment 1-11

[0124] This embodiment provides a method for preparing a high-strength and tough die-cast magnesium alloy without heat treatment, which is basically the same as the method of embodiments 1-5, except that the addition amount of the Mg-10Bi intermediate alloy used in this embodiment is 0.5% of the theoretical weight percentage of Bi.

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

[0126] Examples 1-12

[0127] The present embodiment provides a method for preparing a high-strength and tough die-cast magnesium alloy that does not require heat treatment, which is basically the same as the method in Example 1-1, with the only difference being that: the amount of Al added in the present embodiment is 3% of the total theoretical weight percentage of Al; the amount of Mg-30La intermediate alloy added in the present embodiment is 0.7% of the theoretical weight percentage of La; the amount of Mg-30Ce intermediate alloy added in the present embodiment is 3.3% of the theoretical weight percentage of Ce.

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

[0129] Examples 1-13

[0130] The present embodiment provides a method for preparing a high-strength and tough die-cast magnesium alloy that does not require heat treatment, which is basically the same as the method of Examples 1-5, with the only difference being that: the amount of Al added in the present embodiment is 5.7% of the total theoretical weight percentage of Al; the amount of pure Ce added in the present embodiment is 2.7% of the theoretical weight percentage of Ce.

[0131] The properties of the obtained 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 tough die-cast magnesium alloy without heat treatment, which is basically the same as the method in Example 1-1, except that the Bi element is not added in this comparative example.

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

[0135] Comparative Example 1-2

[0136] This comparative example provides a method for preparing a high-strength and tough die-cast magnesium alloy without heat treatment, which is basically the same as the method in Example 1-1, except that the addition amount of pure Bi used in this comparative example is 1.1% of the theoretical weight percentage of Bi.

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

[0138] Figure 1 The microstructure photograph of the die-cast magnesium alloy part obtained in Example 1-1 of the present invention is shown in FIG. Figure 1 It can be seen that the alloy structure is mainly composed of α-Mg matrix and granular Al 11 RE3 eutectic phase, dendritic Al 11 The content of RE3 eutectic phase is low. No obvious Bi-rich phase is found in the structure. Through EDS point scanning, it is found that Bi element is enriched in the α-Mg matrix, and Bi element is mainly dissolved in the α-Mg matrix.

[0139] Figure 2 The microstructure photo of the die-cast magnesium alloy part obtained in Comparative Example 1-1 of the present invention is shown in FIG. Figure 2 It can be seen that the heat-treatment-free high-strength and toughness die-cast magnesium alloy without Bi element addition has a dendritic Al structure because there is no Bi element to modify its eutectic phase. 11 RE3 eutectic phase, granular Al 11 The content of RE3 eutectic phase is very low.

[0140] Figure 3 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 are shown in FIG. Figure 3 By comparing the tensile curves of Example 1-1 with those of Comparative Examples 1-1 and 1-2, 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 of 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 Table 1 and Table 2, it can be seen that the die-cast magnesium alloys obtained by the present invention all have excellent comprehensive mechanical properties; the sum of the weight percentages of Al, RE, and Bi elements in the die-cast magnesium alloys prepared in Examples 1-1, 1-2, 1-4, 1-5, and 1-6 is ≤8.5, and the elongation of the die-cast magnesium alloy parts is above 20%, and the yield strength is also above 150MPa, and the tensile strength is above 260MPa; the sum of the weight percentages of Al, RE, and Bi elements in the die-cast magnesium alloys prepared in Examples 1-3, 1-7, 1-8, 1-9, 1-10, and 1-11 is all >8.5, and the yield strength of the die-cast magnesium alloy parts is above 160MPa, the tensile strength is above 270MPa, and the elongation is also above 17%.

[0142] The ratio of the weight percentage of Al element to the weight percentage of RE element in the heat treatment-free high-strength and toughness die-cast magnesium alloy prepared in Example 1-12 does not meet the condition requirement of Al / RE≥0.8. Compared with Example 1-1, the elongation and tensile strength in its room temperature tensile properties are significantly reduced.

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

[0144] Comparative Example 1-1 is a high-strength and toughness die-cast magnesium alloy that does not require heat treatment but to which no Bi element is added. Since there is no Bi element to modify its eutectic phase, its room temperature tensile properties, especially the elongation, are significantly lower than those of the high-strength and toughness die-cast magnesium alloy that does not require heat treatment but to which Bi element is added in Example 1-1.

[0145] In Comparative Example 1-2, too much Bi element is added, which does not meet the Bi weight percentage requirement of 0.003 to 1%, and the elongation in the room temperature tensile performance is also significantly lower than that of Example 1-1.

[0146] Table 1 Unit: Weight percentage

[0147]

[0148]

[0149] Table 2

[0150]

[0151]

[0152] Example 2-1

[0153] This embodiment provides a method for preparing a heat-treatment-free high-strength and toughness die-cast magnesium alloy, and the specific steps are as follows:

[0154] 1) According to 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, Mg-10Zr master alloy are selected as raw materials, and the raw materials are preheated to 200° C. for drying;

[0155] 2) Preheat the crucible to 150°C, evenly apply the coating on the inner wall of the crucible, dry and heat to 460°C, introduce a CO2+SF6 mixed gas, put the pure Mg ingot into the crucible, completely melt it under the protection of the mixed protective gas of CO2 and SF6, then heat it to 770°C, add Al-3Be master alloy, add Mg-30La and Mg-30Ce master alloys until the alloy is completely melted, cool it to 740°C, add pure Al, Al-20Mn, Al-10Ti, Mg-10Zr master alloys, stir them fully after they are completely melted, let them stand and perform pre-furnace composition analysis, detect the composition content of the alloy solution, supplement or dilute the solution with deviation in content, so that its composition reaches the designed magnesium alloy composition range;

[0156] 3) The melt is heated to 750° C., argon gas at a pressure of 0.2 MPa is introduced into the melt, and 0.8% of the total weight of the melt is introduced into the refining agent (specifically Torch brand magnesium alloy refining agent in this embodiment, purchased from Zhangjiagang Haohua Light Alloy Material Co., Ltd.) powder, and then the slag and gas removal is continued for 10 minutes;

[0157] 4) The refined melt is left to stand for 10 minutes, and then the composition analysis test is carried out before the furnace. After the composition is qualified, high-pressure casting production is carried out at 710-720°C, the injection speed is 4.0m / s, and the casting pressure (boost) is 90MPa. The mold used in the production process is a die-casting test bar mold.

[0158] The properties of the obtained die-cast magnesium alloy parts are shown in Table 4.

[0159] Example 2-2

[0160] This embodiment provides a method for preparing a heat-treatment-free high-strength and toughness die-cast magnesium alloy, and the specific steps are as follows:

[0161] 1) According to the theoretical weight percentage of each component being Mg-3.5Al-3.3La-0.4Mn-0.008Be-0.07Ti, pure Mg ingot, pure Al ingot, Al-60La, Mg-10Mn, Mg-3Be, Al-5Ti master alloy are selected as raw materials, and the raw materials are preheated to 210° C. for drying;

[0162] 2) Preheat the crucible to 150°C, evenly apply the coating on the inner wall of the crucible, dry and heat to 450°C, introduce a CO2+SF6 mixed gas, put the pure Mg ingot into the crucible, completely melt it under the protection of the mixed protective gas of CO2 and SF6, then heat it to 760°C, add the Mg-3Be master alloy, add the Al-60La master alloy until the alloy is completely melted, cool it to 730°C, add pure Al, Al-5Ti, and Mg-10Mn master alloys, stir them fully after they are completely melted, let them stand and perform a pre-furnace composition analysis, detect the composition content of the alloy solution, supplement or dilute the solution with deviation in content, so that its composition reaches the designed magnesium alloy composition range;

[0163] 3) The melt is heated to 750° C., argon gas at a pressure of 0.2 MPa is introduced into the melt, and 0.6% of the total weight of the melt is introduced into the refining agent (specifically Torch brand magnesium alloy refining agent in this embodiment, purchased from Zhangjiagang Haohua Light Alloy Material Co., Ltd.) powder, and then the slag and gas removal are continued for 10 minutes;

[0164] 4) The refined melt is left to stand for 10 minutes, and then the composition analysis test is carried out before the furnace. After the composition is qualified, high-pressure casting production is carried out at 715-725℃, the injection speed is 5m / s, and the casting pressure is 80MPa. The mold used in the production process is a die-casting test bar mold.

[0165] The properties of the obtained die-cast magnesium alloy parts are shown in Table 4.

[0166] Example 2-3

[0167] This embodiment provides a method for preparing a heat-treatment-free high-strength and toughness die-cast magnesium alloy, and the specific steps are as follows:

[0168] 1) According to the theoretical weight percentage of each component being 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 alloy are selected as raw materials, and the raw materials are preheated to 180° C. for drying;

[0169] 2) Preheat the crucible to 150°C, evenly apply the coating on the inner wall of the crucible, dry and heat to 400°C, introduce a CO2+SF6 mixed gas, put the pure Mg ingot into the crucible, completely melt it under the protection of the mixed protective gas of CO2 and SF6, then heat it to 750°C, add the Mg-3Be master alloy, after the alloy is completely melted, add pure Ce and Al-30La master alloy until it is completely melted, cool it to 720°C, add pure Al, Al-10V, Al-10Mn master alloy, stir it fully after it is completely melted, let it stand and perform a furnace composition analysis, detect the composition content of the alloy solution, supplement or dilute the solution with deviation in content, so that its composition reaches the designed magnesium alloy composition range;

[0170] 3) The melt is heated to 740° C., argon gas at a pressure of 0.2 MPa is introduced into the melt, and 1.0% of the total weight of the melt is introduced into the refining agent (specifically Torch brand magnesium alloy refining agent in this embodiment, purchased from Zhangjiagang Haohua Light Alloy Material Co., Ltd.) powder, and then the slag and gas removal are continued for 10 minutes;

[0171] 4) The refined melt is left to stand for 5 minutes, and then the composition analysis test is carried out before the furnace. After the composition is qualified, high-pressure casting production is carried out at 700-710°C, the injection speed is 3.0m / s, and the casting pressure is 110MPa. The mold used in the production process is a die-casting test bar mold.

[0172] The properties of the obtained die-cast magnesium alloy parts are shown in Table 4.

[0173] Embodiment 2-4

[0174] This embodiment provides a method for preparing a heat-treatment-free high-strength and toughness die-cast magnesium alloy, and the specific steps are as follows:

[0175] 1) According to the theoretical weight percentage of each component being 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, Mg-5Zr master alloy are selected as raw materials, and the raw materials are preheated to 190° C. for drying;

[0176] 2) Preheat the crucible to 150°C, evenly apply the coating on the inner wall of the crucible, dry and heat to 420°C, introduce N2+SF6 mixed gas, put the pure Mg ingot into the crucible, completely melt it under the protection of the mixed protective gas of N2 and SF6, then heat it to 760°C, add Al-3Be master alloy, add Mg-90La and Al-90Ce master alloy until the alloy is completely melted, cool it to 730°C, add pure Al, Al-10Mn, Al-5V, Mg-5Zr master alloy, stir it fully after it is completely melted, let it stand and perform pre-furnace composition analysis, detect the composition content of the alloy solution, supplement or dilute the solution with deviation in content, so that its composition reaches the designed magnesium alloy composition range;

[0177] 3) The melt is heated to 740° C., argon gas at a pressure of 0.2 MPa is introduced into the melt, and 1.5% of the total weight of the melt is introduced into the refining agent (specifically Torch brand magnesium alloy refining agent in this embodiment, purchased from Zhangjiagang Haohua Light Alloy Material Co., Ltd.) powder, and then the slag and gas removal is continued for 10 minutes;

[0178] 4) The refined melt is left to stand for 8 minutes, and then the composition analysis test is carried out before the furnace. After the composition is qualified, high-pressure casting production is carried out at 720-730°C, the injection speed is 6.2m / s, and the casting pressure is 120MPa. The mold used in the production process is a die-casting test bar mold.

[0179] The properties of the obtained die-cast magnesium alloy parts are shown in Table 4.

[0180] Embodiment 2-5

[0181] This embodiment provides a method for preparing a heat-treatment-free high-strength and toughness die-cast magnesium alloy, and the specific steps are as follows:

[0182] 1) According to 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 alloy are selected as raw materials, and the raw materials are preheated to 220° C. for drying;

[0183] 2) Preheat the crucible to 150°C, evenly apply the coating on the inner wall of the crucible, dry and heat to 410°C, introduce N2+SF6 mixed gas, put the pure Mg ingot into the crucible, completely melt it under the protection of the mixed protective gas of N2 and SF6, then heat it to 760°C, add Al-3Be master alloy, add pure Ce until the alloy is completely melted, cool it to 730°C, add pure Al, Al-20Mn, Mg-10Ti, Mg-10V master alloy, stir it fully after it is completely melted, let it stand and perform pre-furnace composition analysis, detect the composition content of the alloy solution, supplement or dilute the solution with deviation in content, so that its composition reaches the designed magnesium alloy composition range;

[0184] 3) The melt is heated to 740° C., argon gas at a pressure of 0.2 MPa is introduced into the melt, and a refining agent (specifically Torch brand magnesium alloy refining agent in this embodiment, purchased from Zhangjiagang Haohua Light Alloy Material Co., Ltd.) powder of 2% of the total weight of the melt is introduced, and then the slag and gas removal is continued for 10 minutes;

[0185] 4) The refined melt is left to stand for 9 minutes, and then the composition analysis test is carried out before the furnace. After the composition is qualified, high-pressure casting production is carried out at 705-715°C, the injection speed is 2.5m / s, and the casting pressure is 65MPa. The mold used in the production process is a die-casting test bar mold.

[0186] The properties of the obtained die-cast magnesium alloy parts are shown in Table 4.

[0187] Embodiment 2-6

[0188] This embodiment provides a method for preparing a heat-treatment-free high-strength and toughness die-cast magnesium alloy, and the specific steps are as follows:

[0189] 1) According to 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 alloy are selected as raw materials, and the raw materials are preheated to 240° C. for drying;

[0190] 2) Preheat the crucible to 150°C, evenly apply the coating on the inner wall of the crucible, dry and heat to 490°C, cover the crucible with a layer of covering agent (the specific covering agent used in this embodiment is Torch brand flux purchased from Zhangjiagang Haohua Light Alloy Material Co., Ltd.), put the pure Mg ingot into the crucible and wait for it to melt, cover the surface of the melt with another layer of covering agent, heat 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 to 750°C, add pure Al, Mg-5Mn, and Mg-30Zr master alloy, stir fully after complete melting, let stand and perform furnace composition analysis, detect the composition content of the alloy solution, supplement or dilute the solution with deviation in content, so that its composition reaches the designed magnesium alloy composition range;

[0191] 3) The melt is heated to 760° C., argon gas at a pressure of 0.2 MPa is introduced into the melt, and 1.8% of the total weight of the melt is introduced into the refining agent (specifically Torch brand magnesium alloy refining agent in this embodiment, purchased from Zhangjiagang Haohua Light Alloy Material Co., Ltd.) powder, and then the slag and gas removal is continued for 10 minutes;

[0192] 4) The refined melt is left to stand for 6 minutes, and then the composition analysis test is carried out before the furnace. After the composition is qualified, high-pressure casting production is carried out at 690-700°C, the injection speed is 2.0m / s, and the casting pressure is 40MPa. The mold used in the production process is a die-casting test bar mold.

[0193] The properties of the obtained die-cast magnesium alloy parts are shown in Table 4.

[0194] Embodiment 2-7

[0195] This embodiment provides a method for preparing a heat-treatment-free high-strength and toughness die-cast magnesium alloy, and the specific steps are as follows:

[0196] 1) According to the theoretical weight percentage of each component being Mg-4.7Al-1.9La-2.8Ce-0.25Mn-0.02Be-0.4V, pure Mg ingot, pure Al ingot, Al-90La, Al-90Ce, Al-3Be, Mg-5Mn, Mg-5V master alloy are selected as raw materials, and the raw materials are preheated to 220° C. for drying;

[0197] 2) Preheat the crucible to 150°C, evenly apply the coating on the inner wall of the crucible, dry and heat to 430°C, introduce SF6 gas, put the pure Mg ingot into the crucible, completely melt it under the protection of SF6 protective gas, then heat it to 770°C, add Al-3Be master alloy, add Al-90La and Al-90Ce master alloys until the alloy is completely melted, cool it to 740°C, add pure Al, Mg-5Mn and Mg-5V master alloys, stir them fully after they are completely melted, let them stand and perform pre-furnace composition analysis, detect the composition content of the alloy solution, supplement or dilute the solution with deviation in content, so that its composition reaches the designed magnesium alloy composition range;

[0198] 3) The melt is heated to 760° C., argon gas at a pressure of 0.2 MPa is introduced into the melt, and 0.3% of the total weight of the melt is introduced into the refining agent (specifically Torch brand magnesium alloy refining agent in this embodiment, purchased from Zhangjiagang Haohua Light Alloy Material Co., Ltd.) powder, and then the slag and gas removal is continued for 10 minutes;

[0199] 4) The refined melt is left to stand for 7 minutes, and then the composition analysis test is carried out before the furnace. After the composition is qualified, high-pressure casting production is carried out at 690-700°C, the injection speed is 8.0m / s, and the casting pressure is 150MPa. The mold used in the production process is a die-casting test bar mold.

[0200] The properties of the obtained die-cast magnesium alloy parts are shown in Table 4.

[0201] Embodiment 2-8

[0202] This embodiment provides a method for preparing a heat-treatment-free high-strength and toughness die-cast magnesium alloy, and the specific steps are as follows:

[0203] 1) According to the theoretical weight percentage of each component being 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, Mg-10Zr master alloy are selected as raw materials, and the raw materials are preheated to 200° C. for drying;

[0204] 2) Preheat the crucible to 150°C, evenly apply the coating on the inner wall of the crucible, dry and heat to 480°C, introduce a CO2+SF6 mixed gas, put the pure Mg ingot into the crucible, completely melt it under the protection of the mixed protective gas of CO2 and SF6, then heat it to 770°C, add Al-5Be master alloy, add Al-60La and Mg-30Ce master alloy until the alloy is completely melted, cool it to 740°C, add pure Al, Al-10Mn, Mg-5V, Mg-10Zr master alloy, stir it fully after it is completely melted, let it stand and perform pre-furnace composition analysis, detect the composition content of the alloy solution, supplement or dilute the solution with deviation in content, so that its composition reaches the designed magnesium alloy composition range;

[0205] 3) The melt is heated to 750° C., argon gas at a pressure of 0.2 MPa is introduced into the melt, and 0.5% of the total weight of the melt is introduced into the refining agent (specifically Torch brand magnesium alloy refining agent in this embodiment, purchased from Zhangjiagang Haohua Light Alloy Material Co., Ltd.) powder, and then the slag and gas removal are continued for 10 minutes;

[0206] 4) The refined melt is left to stand for 10 minutes, and then the composition analysis test is carried out before the furnace. After the composition is qualified, high-pressure casting production is carried out at 710-720°C, the injection speed is 5.6m / s, and the casting pressure is 140MPa. The mold used in the production process is a die-casting test bar mold.

[0207] The properties of the obtained die-cast magnesium alloy parts are shown in Table 4.

[0208] Embodiment 2-9

[0209] This embodiment provides a method for preparing a heat-treatment-free high-strength and toughness die-cast magnesium alloy, and the specific steps are as follows:

[0210] 1) According to the theoretical weight percentage of each component, 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, Al-10Zr master alloy are selected as raw materials, and the raw materials are preheated to 230° C. for drying;

[0211] 2) Preheat the crucible to 150°C, evenly apply the coating on the inner wall of the crucible, dry and heat to 500°C, introduce N2+SF6 mixed gas, put the pure Mg ingot into the crucible, completely melt it under the protection of the mixed protective gas of N2 and SF6, then heat it to 760°C, add Mg-5Be master alloy, after the alloy is completely melted, add pure La and Al-60Ce master alloy until it is completely melted, cool it to 730°C, add pure Al, Mg-5Mn, Mg-10Ti, Al-10V, Al-10Zr master alloy, stir it fully after it is completely melted, let it stand and perform pre-furnace composition analysis, detect the composition content of the alloy solution, supplement or dilute the solution with deviation in content, so that its composition reaches the designed magnesium alloy composition range;

[0212] 3) The melt is heated to 750° C., argon gas at a pressure of 0.2 MPa is introduced into the melt, and 0.5% of the total weight of the melt is introduced into the refining agent (specifically Torch brand magnesium alloy refining agent in this embodiment, purchased from Zhangjiagang Haohua Light Alloy Material Co., Ltd.) powder, and then the slag and gas removal are continued for 10 minutes;

[0213] 4) The refined melt is left to stand for 8 minutes, and then the composition analysis test is carried out before the furnace. After the composition is qualified, high-pressure casting production is carried out at 720-730℃, the injection speed is 7m / s, and the casting pressure is 50MPa. The mold used in the production process is a die-casting test bar mold.

[0214] The properties of the obtained die-cast magnesium alloy parts are shown in Table 4.

[0215] Embodiment 2-10

[0216] This embodiment provides a method for preparing a high-strength and tough die-cast magnesium alloy without heat treatment, which is basically the same as the method in Example 2-1, except that the addition amount of Mg-30La intermediate alloy used in this embodiment is 2.5% of the theoretical weight percentage of La.

[0217] The properties of the obtained die-cast magnesium alloy parts are shown in Table 4.

[0218] Example 2-11

[0219] The present embodiment provides a method for preparing a high-strength and tough die-cast magnesium alloy that does not require heat treatment, which is basically the same as the method of Examples 2-5, with the only difference being that the Mg-10Ti intermediate alloy used in the present embodiment is added in an amount of 0.1% of the theoretical weight percentage of Ti, and the Mg-10V intermediate alloy is added in an amount of 0.4% of the theoretical weight percentage of V.

[0220] The properties of the obtained die-cast magnesium alloy parts are shown in Table 4.

[0221] Example 2-12

[0222] The present embodiment provides a method for preparing a high-strength and tough die-cast magnesium alloy that does not require heat treatment, which is basically the same as the method in Example 2-1, with the only difference being that: the amount of Al added in the present embodiment is 3% of the total theoretical weight percentage of Al; the amount of Mg-30La intermediate alloy added in the present embodiment is 0.7% of the theoretical weight percentage of La; the amount of Mg-30Ce intermediate alloy added in the present embodiment is 3.3% of the theoretical weight percentage of Ce.

[0223] The properties of the obtained die-cast magnesium alloy parts are shown in Table 4.

[0224] Example 2-13

[0225] The present embodiment provides a method for preparing a high-strength and tough die-cast magnesium alloy that does not require heat treatment, which is basically the same as the method of Examples 2-5, with the only difference being that: the amount of Al added in the present embodiment is 5.7% of the total theoretical weight percentage of Al; the amount of pure Ce added in the present embodiment is 2.7% of the theoretical weight percentage of Ce.

[0226] The properties of the obtained die-cast magnesium alloy parts are shown in Table 4.

[0227] Comparative Example 2-1

[0228] This comparative example provides a method for preparing a high-strength and tough 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.

[0229] The properties of the obtained die-cast magnesium alloy parts are shown in Table 4.

[0230] Comparative Example 2-2

[0231] This comparative example provides a method for preparing a high-strength and tough die-cast magnesium alloy that does not require heat treatment, which is basically the same as the method in Example 2-1, with the only difference being that: the Al-10Ti intermediate alloy used in this example is added in an amount of 0.2% of the theoretical weight percentage of Ti; the Mg-10Zr intermediate alloy used in this example is added in an amount of 0.9% of the theoretical weight percentage of Zr.

[0232] The properties of the obtained die-cast magnesium alloy parts are shown in Table 4.

[0233] Figure 4 The microstructure photograph of the die-cast magnesium alloy part obtained in Example 2-1 of the present invention is shown in FIG. Figure 4 It can be seen that the alloy structure is mainly composed of α-Mg matrix and dendritic Al 11 RE3 eutectic phase, and the dendritic Al11 The RE3 eutectic phase is very fine and dense. A small amount of Al3Ti and Al3Zr particles can also be found in the structure.

[0234] Figure 5 The microstructure photograph of the die-cast magnesium alloy part obtained in Comparative Example 2-1 of the present invention is shown in FIG. Figure 5 It can be seen that the heat-treatment-free high-strength and toughness die-cast magnesium alloy without the addition of Ti, V, Zr and other elements has no Ti, V, Zr and other elements to refine its eutectic phase, and the eutectic phase in the alloy structure is basically coarse dendritic Al 11 RE3 eutectic phase.

[0235] Figure 6 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 are shown in FIG. Figure 6 By comparing the tensile curves of Example 2-1 with those of Comparative Examples 2-1 and 2-2, 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.

[0236] The following Table 3 shows the actual measured weight percentages of the components of the die-cast magnesium alloy parts prepared in the embodiments and comparative examples, and Table 4 shows the performance test results. Combining the data in Table 3 and Table 4, it can be seen that the die-cast magnesium alloys obtained in the present invention have excellent comprehensive mechanical properties; the sum of the weight percentages of Al, RE, and X elements (Ti, V, Zr) in the die-cast magnesium alloys prepared in Examples 2-1, 2-2, 2-4, 2-5, and 2-6 is ≤8.5, and the elongation of the die-cast magnesium alloy parts is above 20%, and the yield strength is also above 150 MPa, and the tensile strength is above 260 MPa; the sum of the weight percentages of Al, RE, and X elements (Ti, V, Zr) in the die-cast magnesium alloys prepared in Examples 2-3, 2-7, 2-8, 2-9, 2-10, and 2-11 is all >8.5, and the yield strength of the die-cast magnesium alloy parts is above 162 MPa, the tensile strength is above 274 MPa, and the elongation is also above 17%.

[0237] The ratio of the weight percentage of Al element to the weight percentage of RE element in the heat treatment-free high-strength and toughness die-cast magnesium alloy prepared in Example 2-12 does not meet the condition requirement of Al / RE≥0.8. Compared with Example 2-1, the elongation and tensile strength in its room temperature tensile properties are significantly reduced.

[0238] The weight percentage of Al element in the heat treatment-free high-strength and toughness die-cast magnesium alloy prepared in Example 2-13 is greater than 2 times the weight percentage of RE element, which does not meet the condition requirement of Al / RE≤2. Compared with Example 2-5, its elongation and tensile strength in room temperature tensile properties are also significantly reduced.

[0239] Comparative Example 2-1 is a high-strength and toughness die-cast magnesium alloy that does not require heat treatment but to which elements such as Ti, V, and Zr are not added. Since there are no elements such as Ti, V, and Zr to refine its eutectic phase, its room temperature tensile properties, especially the elongation, are significantly lower than those of Example 2-1, which is a high-strength and toughness die-cast magnesium alloy that does not require heat treatment but to which Ti and Zr elements are added.

[0240] Too much Ti, V, Zr and other elements are added in Comparative Example 2-2, which does not meet the requirement that the total weight percentage of Ti, V, Zr and other elements should be within the range of 0.003 to 1%. The elongation in its room temperature tensile performance is also significantly lower than that in Example 2-1.

[0241] Table 3 Unit: Weight percentage

[0242]

[0243] Table 4

[0244]

[0245]

[0246] Example 3-1

[0247] This embodiment provides a method for preparing a heat-treatment-free high-strength and toughness die-cast magnesium alloy, and the specific steps are as follows:

[0248] 1) According to the theoretical weight percentage of each component being 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, Mg-10Ni master alloy are selected as raw materials, and the raw materials are preheated to 200°C for drying;

[0249] 2) Preheat the crucible to 150°C, evenly apply the coating on the inner wall of the crucible, dry and heat to 460°C, introduce a CO2+SF6 mixed gas, put the pure Mg ingot into the crucible, completely melt it under the protection of the mixed protective gas of CO2 and SF6, then heat it to 770°C, add Al-3Be master alloy, add Mg-30La and Mg-30Ce master alloys until the alloy is completely melted, cool it to 740°C, add pure Al, Al-20Mn, Al-50Cu and Mg-10Ni master alloys, stir them fully after they are completely melted, let them stand and perform a furnace composition analysis, detect the composition content of the alloy solution, supplement or dilute the solution with deviation in content, so that its composition reaches the designed magnesium alloy composition range;

[0250] 3) The melt is heated to 750° C., argon gas at a pressure of 0.2 MPa is introduced into the melt, and 0.8% of the total weight of the melt is introduced into the refining agent (specifically Torch brand magnesium alloy refining agent in this embodiment, purchased from Zhangjiagang Haohua Light Alloy Material Co., Ltd.) powder, and then the slag and gas removal is continued for 10 minutes;

[0251] 4) The refined melt is left to stand for 10 minutes, and then the composition analysis test is carried out before the furnace. After the composition is qualified, high-pressure casting production is carried out at 710-720°C, the injection speed is 4.0m / s, and the casting pressure (boost) is 90MPa. The mold used in the production process is a die-casting test bar mold.

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

[0253] Example 3-2

[0254] This embodiment provides a method for preparing a heat-treatment-free high-strength and toughness die-cast magnesium alloy, and the specific steps are as follows:

[0255] 1) According to 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, Al-10Ni master alloy are selected as raw materials, and the raw materials are preheated to 210°C for drying;

[0256] 2) Preheat the crucible to 150°C, evenly apply the coating on the inner wall of the crucible, dry and heat to 450°C, introduce a CO2+SF6 mixed gas, put the pure Mg ingot into the crucible, completely melt it under the protection of the mixed protective gas of CO2 and SF6, then heat it to 760°C, add the Mg-3Be master alloy, add the Al-60La master alloy until the alloy is completely melted, cool it to 730°C, add pure Al, Al-10Ni, and Mg-10Mn master alloys, stir them fully after they are completely melted, let them stand and perform a furnace composition analysis, detect the composition content of the alloy solution, supplement or dilute the solution with deviation in content, so that its composition reaches the designed magnesium alloy composition range;

[0257] 3) The melt is heated to 750° C., argon gas at a pressure of 0.2 MPa is introduced into the melt, and 0.6% of the total weight of the melt is introduced into the refining agent (specifically Torch brand magnesium alloy refining agent in this embodiment, purchased from Zhangjiagang Haohua Light Alloy Material Co., Ltd.) powder, and then the slag and gas removal are continued for 10 minutes;

[0258] 4) The refined melt is left to stand for 10 minutes, and then the composition analysis test is carried out before the furnace. After the composition is qualified, high-pressure casting production is carried out at 715-725℃, the injection speed is 5m / s, and the casting pressure is 80MPa. The mold used in the production process is a die-casting test bar mold.

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

[0260] Example 3-3

[0261] This embodiment provides a method for preparing a heat-treatment-free high-strength and toughness die-cast magnesium alloy, and the specific steps are as follows:

[0262] 1) According to the theoretical weight percentage of each component being 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 alloy are selected as raw materials, and the raw materials are preheated to 180° C. for drying;

[0263] 2) Preheat the crucible to 150°C, evenly apply the coating on the inner wall of the crucible, dry and heat to 400°C, introduce a CO2+SF6 mixed gas, put the pure Mg ingot into the crucible, completely melt it under the protection of the mixed protective gas of CO2 and SF6, then heat it to 750°C, add the Mg-3Be master alloy, after the alloy is completely melted, add pure Ce and Al-30La master alloy until it is completely melted, cool it to 720°C, add pure Al, Al-5Cr, Al-10Mn master alloy, stir it fully after it is completely melted, let it stand and perform a furnace composition analysis, detect the composition content of the alloy solution, supplement or dilute the solution with deviation in content, so that its composition reaches the designed magnesium alloy composition range;

[0264] 3) The melt is heated to 740° C., argon gas at a pressure of 0.2 MPa is introduced into the melt, and 1.0% of the total weight of the melt is introduced into the refining agent (specifically Torch brand magnesium alloy refining agent in this embodiment, purchased from Zhangjiagang Haohua Light Alloy Material Co., Ltd.) powder, and then the slag and gas removal are continued for 10 minutes;

[0265] 4) The refined melt is left to stand for 5 minutes, and then the composition analysis test is carried out before the furnace. After the composition is qualified, high-pressure casting production is carried out at 700-710°C, the injection speed is 3.0m / s, and the casting pressure is 110MPa. The mold used in the production process is a die-casting test bar mold.

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

[0267] Embodiment 3-4

[0268] This embodiment provides a method for preparing a heat-treatment-free high-strength and toughness die-cast magnesium alloy, and the specific steps are as follows:

[0269] 1) According to the theoretical weight percentage of each component, Mg-3.8Al-1.8La-1.8Ce-0.2Mn-0.005Be-0.01Cr-0.01Ni, pure Mg ingot, pure Al ingot, Mg-90La, Al-90Ce, Al-10Mn, Al-3Be, Mg-5Cr, Al-20Ni master alloy are selected as raw materials, and the raw materials are preheated to 190°C for drying;

[0270] 2) Preheat the crucible to 150°C, evenly apply the coating on the inner wall of the crucible, dry and heat to 420°C, introduce N2+SF6 mixed gas, put the pure Mg ingot into the crucible, completely melt it under the protection of the mixed protective gas of N2 and SF6, then heat it to 760°C, add Al-3Be master alloy, add Mg-90La and Al-90Ce master alloy until the alloy is completely melted, cool it to 730°C, add pure Al, Al-10Mn, Mg-5Cr and Al-20Ni master alloy, stir it fully after it is completely melted, let it stand and perform pre-furnace composition analysis, detect the composition content of the alloy solution, supplement or dilute the solution with deviation in content, so that its composition reaches the designed magnesium alloy composition range;

[0271] 3) The melt is heated to 740° C., argon gas at a pressure of 0.2 MPa is introduced into the melt, and 1.5% of the total weight of the melt is introduced into the refining agent (specifically Torch brand magnesium alloy refining agent in this embodiment, purchased from Zhangjiagang Haohua Light Alloy Material Co., Ltd.) powder, and then the slag and gas removal is continued for 10 minutes;

[0272] 4) The refined melt is left to stand for 8 minutes, and then the composition analysis test is carried out before the furnace. After the composition is qualified, high-pressure casting production is carried out at 720-730°C, the injection speed is 6.2m / s, and the casting pressure is 120MPa. The mold used in the production process is a die-casting test bar mold.

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

[0274] Embodiment 3-5

[0275] This embodiment provides a method for preparing a heat-treatment-free high-strength and toughness die-cast magnesium alloy, and the specific steps are as follows:

[0276] 1) According to the theoretical weight percentage of each component being 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 alloy are selected as raw materials, and the raw materials are preheated to 220° C. for drying;

[0277] 2) Preheat the crucible to 150°C, evenly apply the coating on the inner wall of the crucible, dry and heat to 410°C, introduce N2+SF6 mixed gas, put the pure Mg ingot into the crucible, completely melt it under the protection of the mixed protective gas of N2 and SF6, then heat it to 760°C, add Al-3Be master alloy, add pure Ce until the alloy is completely melted, cool it to 730°C, add pure Al, Al-20Mn, Mg-10Cu, Mg-10Cr master alloy, stir it fully after it is completely melted, let it stand and perform pre-furnace composition analysis, detect the composition content of the alloy solution, supplement or dilute the solution with deviation in content, so that its composition reaches the designed magnesium alloy composition range;

[0278] 3) The melt is heated to 740° C., argon gas at a pressure of 0.2 MPa is introduced into the melt, and a refining agent (specifically Torch brand magnesium alloy refining agent in this embodiment, purchased from Zhangjiagang Haohua Light Alloy Material Co., Ltd.) powder of 2% of the total weight of the melt is introduced, and then the slag and gas removal is continued for 10 minutes;

[0279] 4) The refined melt is left to stand for 9 minutes, and then the composition analysis test is carried out before the furnace. After the composition is qualified, high-pressure casting production is carried out at 705-715°C, the injection speed is 2.5m / s, and the casting pressure is 65MPa. The mold used in the production process is a die-casting test bar mold.

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

[0281] Embodiment 3-6

[0282] This embodiment provides a method for preparing a heat-treatment-free high-strength and toughness die-cast magnesium alloy, and the specific steps are as follows:

[0283] 1) According to 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 alloy are selected as raw materials, and the raw materials are preheated to 240° C. for drying;

[0284] 2) Preheat the crucible to 150°C, evenly apply the coating on the inner wall of the crucible, dry and heat to 490°C, cover the crucible with a layer of covering agent (the specific covering agent used in this embodiment is Torch brand flux purchased from Zhangjiagang Haohua Light Alloy Material Co., Ltd.), put the pure Mg ingot into the crucible and wait for it to melt, cover the surface of the melt with another layer of covering agent, heat 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 to 750°C, add pure Al, pure Cu, and Mg-5Mn master alloy, stir fully after complete melting, let stand and perform furnace composition analysis, detect the composition content of the alloy solution, supplement or dilute the solution with deviation in content, so that its composition reaches the designed magnesium alloy composition range;

[0285] 3) The melt is heated to 760° C., argon gas at a pressure of 0.2 MPa is introduced into the melt, and 1.8% of the total weight of the melt is introduced into the refining agent (specifically Torch brand magnesium alloy refining agent in this embodiment, purchased from Zhangjiagang Haohua Light Alloy Material Co., Ltd.) powder, and then the slag and gas removal is continued for 10 minutes;

[0286] 4) The refined melt is left to stand for 6 minutes, and then the composition analysis test is carried out before the furnace. After the composition is qualified, high-pressure casting production is carried out at 690-700°C, the injection speed is 2.0m / s, and the casting pressure is 40MPa. The mold used in the production process is a die-casting test bar mold.

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

[0288] Embodiment 3-7

[0289] This embodiment provides a method for preparing a heat-treatment-free high-strength and toughness die-cast magnesium alloy, and the specific steps are as follows:

[0290] 1) According to the theoretical weight percentage of each component being 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, Al-10Cr master alloy are selected as raw materials, and the raw materials are preheated to 220° C. for drying;

[0291] 2) Preheat the crucible to 150°C, evenly apply the coating on the inner wall of the crucible, dry and heat to 430°C, introduce SF6 gas, put the pure Mg ingot into the crucible, completely melt it under the protection of SF6 protective gas, then heat it to 770°C, add Al-3Be master alloy, add Al-90La and Al-90Ce master alloy until the alloy is completely melted, cool it to 740°C, add pure Al, Mg-5Mn, Al-20Cu and Al-10Cr master alloy, stir it fully after it is completely melted, let it stand and perform pre-furnace composition analysis, detect the composition content of the alloy solution, supplement or dilute the solution with deviation in content, so that its composition reaches the designed magnesium alloy composition range;

[0292] 3) The melt is heated to 760° C., argon gas at a pressure of 0.2 MPa is introduced into the melt, and 0.3% of the total weight of the melt is introduced into the refining agent (specifically Torch brand magnesium alloy refining agent in this embodiment, purchased from Zhangjiagang Haohua Light Alloy Material Co., Ltd.) powder, and then the slag and gas removal is continued for 10 minutes;

[0293] 4) The refined melt is left to stand for 7 minutes, and then the composition analysis test is carried out before the furnace. After the composition is qualified, high-pressure casting production is carried out at 690-700°C, the injection speed is 8.0m / s, and the casting pressure is 150MPa. The mold used in the production process is a die-casting test bar mold.

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

[0295] Embodiment 3-8

[0296] This embodiment provides a method for preparing a heat-treatment-free high-strength and toughness die-cast magnesium alloy, and the specific steps are as follows:

[0297] 1) According to the theoretical weight percentage of each component being 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, Al-20Cr master alloy are selected as raw materials, and the raw materials are preheated to 200° C. for drying;

[0298] 2) Preheat the crucible to 150°C, evenly apply the coating on the inner wall of the crucible, dry and heat to 480°C, introduce a CO2+SF6 mixed gas, put the pure Mg ingot into the crucible, completely melt it under the protection of the mixed protective gas of CO2 and SF6, then heat it to 770°C, add Al-5Be master alloy, after the alloy is completely melted, add Al-60La and Mg-30Ce master alloy until it is completely melted, cool it to 740°C, add pure Al, Al-10Mn, Mg-20Cu, Mg-5Ni, Al-20Cr master alloy, stir it fully after it is completely melted, let it stand and perform pre-furnace composition analysis, detect the composition content of the alloy solution, supplement or dilute the solution with deviation in content, so that its composition reaches the designed magnesium alloy composition range;

[0299] 3) The melt is heated to 750° C., argon gas at a pressure of 0.2 MPa is introduced into the melt, and 0.5% of the total weight of the melt is introduced into the refining agent (specifically Torch brand magnesium alloy refining agent in this embodiment, purchased from Zhangjiagang Haohua Light Alloy Material Co., Ltd.) powder, and then the slag and gas removal are continued for 10 minutes;

[0300] 4) The refined melt is left to stand for 10 minutes, and then the composition analysis test is carried out before the furnace. After the composition is qualified, high-pressure casting production is carried out at 710-720°C, the injection speed is 5.6m / s, and the casting pressure is 140MPa. The mold used in the production process is a die-casting test bar mold.

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

[0302] Embodiment 3-9

[0303] This embodiment provides a method for preparing a heat-treatment-free high-strength and toughness die-cast magnesium alloy, and the specific steps are as follows:

[0304] 1) According to the theoretical weight percentage of each component being 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, Al-10Cr master alloy are selected as raw materials, and the raw materials are preheated to 230° C. for drying;

[0305] 2) Preheat the crucible to 150°C, evenly apply the coating on the inner wall of the crucible, dry and heat to 500°C, introduce N2+SF6 mixed gas, put the pure Mg ingot into the crucible, completely melt it under the protection of the mixed protective gas of N2 and SF6, then heat it to 760°C, add Mg-5Be master alloy, after the alloy is completely melted, add pure La and Al-60Ce master alloy until it is completely melted, cool it to 730°C, add pure Al, pure Ni, Mg-5Mn and Al-10Cr master alloy, stir it fully after it is completely melted, let it stand and perform pre-furnace composition analysis, detect the composition content of the alloy solution, supplement or dilute the solution with deviation in content, so that its composition reaches the designed magnesium alloy composition range;

[0306] 3) The melt is heated to 750° C., argon gas at a pressure of 0.2 MPa is introduced into the melt, and 0.5% of the total weight of the melt is introduced into the refining agent (specifically Torch brand magnesium alloy refining agent in this embodiment, purchased from Zhangjiagang Haohua Light Alloy Material Co., Ltd.) powder, and then the slag and gas removal are continued for 10 minutes;

[0307] 4) The refined melt is left to stand for 8 minutes, and then the composition analysis test is carried out before the furnace. After the composition is qualified, high-pressure casting production is carried out at 720-730℃, the injection speed is 7m / s, and the casting pressure is 50MPa. The mold used in the production process is a die-casting test bar mold.

[0308] The properties of the obtained die-cast magnesium alloy parts are shown in Table 6.

[0309] Embodiment 3-10

[0310] This embodiment provides a method for preparing a high-strength and tough die-cast magnesium alloy without heat treatment, which is basically the same as the method in Example 3-1, except that the addition amount of Mg-30La intermediate alloy used in this embodiment is 2.5% of the theoretical weight percentage of La.

[0311] The properties of the obtained die-cast magnesium alloy parts are shown in Table 6.

[0312] Example 3-11

[0313] The present embodiment provides a method for preparing a high-strength and tough die-cast magnesium alloy that does not require heat treatment, which is basically the same as the method of Examples 3-5, with the only difference being that the Mg-10Cu intermediate alloy used in the present embodiment is added in an amount of 0.1% Cu theoretical weight percentage, and the Mg-10Cr intermediate alloy is added in an amount of 0.4% Cr theoretical weight percentage.

[0314] The properties of the obtained die-cast magnesium alloy parts are shown in Table 6.

[0315] Example 3-12

[0316] The present embodiment provides a method for preparing a high-strength and tough die-cast magnesium alloy that does not require heat treatment, which is basically the same as the method in Example 3-1, with the only difference being that: the amount of Al added in the present embodiment is 3% of the total theoretical weight percentage of Al; the amount of Mg-30La intermediate alloy added in the present embodiment is 0.7% of the theoretical weight percentage of La; the amount of Mg-30Ce intermediate alloy added in the present embodiment is 3.3% of the theoretical weight percentage of Ce.

[0317] The properties of the obtained die-cast magnesium alloy parts are shown in Table 6.

[0318] Example 3-13

[0319] The present embodiment provides a method for preparing a high-strength and tough die-cast magnesium alloy that does not require heat treatment, which is basically the same as the method of Examples 3-5, with the only difference being that: the amount of Al added in the present embodiment is 5.7% of the total theoretical weight percentage of Al; the amount of pure Ce added in the present embodiment is 2.7% of the theoretical weight percentage of Ce.

[0320] The properties of the obtained die-cast magnesium alloy parts are shown in Table 6.

[0321] Comparative Example 3-1

[0322] This comparative example provides a method for preparing a high-strength and tough 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.

[0323] The properties of the obtained die-cast magnesium alloy parts are shown in Table 6.

[0324] Comparative Example 3-2

[0325] This comparative example provides a method for preparing a high-strength and tough die-cast magnesium alloy that does not require heat treatment, which is basically the same as the method in Example 3-1, with the only difference being that: the Al-50Cu intermediate alloy used in this example is added in an amount of 0.6% of Cu theoretical weight percentage; the Mg-10Ni intermediate alloy used in this example is added in an amount of 0.5% of Ni theoretical weight percentage;.

[0326] The properties of the obtained die-cast magnesium alloy parts are shown in Table 6.

[0327] Figure 7 The microstructure photograph of the die-cast magnesium alloy part obtained in Example 3-1 of the present invention is shown in FIG. Figure 7 It can be seen that the alloy structure is mainly composed of α-Mg matrix and small pieces of dendritic Al 11RE3 eutectic phase, in addition, there are Al2CuMg and Al3Ni strengthening phases, Al 11 The RE3 eutectic phase grows on the Al2CuMg and Al3Ni strengthening phases.

[0328] Figure 8 The microstructure photograph of the die-cast magnesium alloy part obtained in Comparative Example 3-1 of the present invention is shown in FIG. Figure 8 It can be seen that the heat-treatment-free high-strength and toughness die-cast magnesium alloy without adding Cr, Ni, Cu and other elements has no strengthening phase formed by Cr, Ni, Cu and other elements, and the dendritic Al 11 The RE3 eutectic phase presents a large-scale growth morphology.

[0329] Fig. 9 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 are shown in FIG. Fig. 9 By comparing the tensile curves of Example 3-1 with those of Comparative Examples 3-1 and 3-2, 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.

[0330] Fig.10 The salt spray corrosion results of the die-cast alloy parts of Examples 3-1, 3-6 and Comparative Example 3-2 of the present invention are shown in Figure 1. Fig.10 It can be observed that 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 both within an acceptable range; while the die-cast alloy parts of Comparative Example 3-2 cannot maintain their original appearance after salt spray corrosion, and the corrosion is very serious, making it difficult to meet the requirements of vehicle body structural parts or other parts.

[0331] The following Table 5 shows the actual measured weight percentages of the components of the die-cast magnesium alloy parts prepared in the embodiments and comparative examples, and Table 6 shows the performance test results. Combining the data in Table 5 and Table 6, it can be seen that the die-cast magnesium alloys obtained in the present invention have excellent comprehensive mechanical properties; the sum of the weight percentages of Al, RE, and X elements (Cr, Ni, Cu) in the die-cast magnesium alloys prepared in Examples 3-1, 3-2, 3-4, 3-5, and 3-6 is ≤8.5, and the elongation of the die-cast magnesium alloy parts is above 18%, and the yield strength is also above 160 MPa, and the tensile strength is above 270 MPa; the sum of the weight percentages of Al, RE, and X elements (Cr, Ni, Cu) in the die-cast magnesium alloys prepared in Examples 3-3, 3-7, 3-8, 3-9, 3-10, and 3-11 is all >8.5, and the yield strength of the die-cast magnesium alloy parts is above 171 MPa, the tensile strength is above 284 MPa, and the elongation is also above 15%.

[0332] The ratio of the weight percentage of Al element to the weight percentage of La element in the heat treatment-free high-strength and toughness die-cast magnesium alloy prepared in Example 3-12 does not meet the condition requirement of Al / RE≥0.8. Compared with Example 3-1, the elongation and tensile strength in its room temperature tensile properties are significantly reduced.

[0333] The weight percentage of Al element in the heat treatment-free high-strength and toughness die-cast magnesium alloy prepared in Example 3-13 is greater than 2 times the weight percentage of La element, which does not meet the condition requirement of Al / RE≤2. Compared with Example 3-5, the elongation and tensile strength in its room temperature tensile properties are also significantly reduced.

[0334] Comparative Example 3-1 is a high-strength and toughness die-cast magnesium alloy that does not require heat treatment but to which elements such as Cr, Ni, and Cu are not added. Since there is no strengthening phase formed by elements such as Cr, Ni, and Cu, its room temperature tensile properties, especially the yield strength and tensile strength, are significantly lower than those of the high-strength and toughness die-cast magnesium alloy that does not require heat treatment but to which Cu and Ni elements are added in Example 3-1.

[0335] In comparative example 3-2, too much Cr, Ni, Cu and other elements are added, which does not meet the requirement that the total weight percentage of Cr, Ni, Cu and other elements is within the range of 0.003 to 1%. The elongation in its room temperature tensile performance is significantly lower than that of example 3-1, and its corrosion resistance is significantly reduced.

[0336] Table 5 Unit: Weight percentage

[0337]

[0338]

[0339] Table 6

[0340]

[0341] The above descriptions are only embodiments of the present invention and are not intended to limit the patent scope of the present invention. Any equivalent structure or equivalent process transformation made using the specification of the present invention, or directly or indirectly applied in other related technical fields, are also included in the patent protection scope of the present invention.

Claims

1. A high-strength and tough die-cast magnesium alloy without heat treatment, characterized in that: The weight percentages of the components 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%, the balance is Mg; Among them, X is at least one of Bi, Ti, V, Zr, Cr, Ni, and Cu.

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

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

4. The heat-treatment-free high-strength and toughness 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 treatment-free high-strength and toughness 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-treatment-free high-strength and toughness die-cast magnesium alloy as claimed in any one of claims 1 to 5, characterized in that: The method comprises the following steps: S1. Material preparation: The magnesium alloy composition according to claim 1 is prepared; 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, smelting: first preheat the crucible to 400-500°C, put the pure Mg ingot into the crucible, melt it under protective gas or vacuum, or first cover the crucible with a layer of covering agent, add the pure Mg ingot and cover the melt surface with another layer of covering agent after it is melted; then heat it to 750-780°C and add Al-Be or Mg-Be master alloy, after the master alloy is melted, keep this temperature and add pure rare earth or Mg-RE or Al-RE master alloy, after it is melted, cool it to 720-750°C, then add pure aluminum, Al-Mn or Mg-Mn master alloy, pure X or Mg-X or Al-X master alloy to melt; S3, refining: heating the melt of step S2 to 730-750°C, introducing gas with refining agent powder into the melt for powder spraying, refining and slag removal; S4, casting or die-casting: After the melt after refining and slag removal in step S3 reaches the casting temperature, an alloy ingot casting operation or a die-casting process operation is performed to finally complete the production of alloy ingots or die-casting parts.

7. The method for preparing a heat-treatment-free high-strength and toughness die-cast magnesium alloy according to claim 6, characterized in that: Step S1 also includes the steps of preheating the prepared raw materials to 180-240° C., and performing preheating and drying treatments.

8. The method for preparing a heat-treatment-free high-strength and toughness die-cast magnesium alloy according to claim 6, characterized in that: In step S2, the covering agent is a solvent with a density of <1.58 g / cm 3 The protective gas is a mixed gas of N2+SF6 or a mixed gas of CO2+SF6 or a pure SF6 protective gas introduced into the furnace; Step S2 also includes the steps of allowing the melt to stand and perform a pre-furnace composition analysis after the melt is evenly melted and stirred, detecting the composition content of the alloy melt, supplementing or diluting the melt with a deviation in content to bring its composition within an acceptable range.

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

10. The method for preparing a heat treatment-free high-strength and toughness die-cast magnesium alloy according to claim 6, characterized in that: In step S4, the casting temperature is 690-730°C; In step S4, when the die-cast magnesium alloy is used to produce die-cast parts, the injection speed range is 2 to 8 m / s; In step S4, when the die-cast magnesium alloy is used to produce die-cast parts, the casting pressure ranges from 40 to 150 MPa.

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