High-toughness and high-heat-resistance Mg-Al-RE series die-casting magnesium alloy and preparation method thereof

Abstract

The application relates to a high-strength high-toughness high-heat-resistance Mg-Al-RE series die-casting magnesium alloy and a preparation method thereof, the weight percentage of each component in the alloy is as follows: Al: 4.5-6%; La: 4.5-6%; Mn: 0.2-0.5%; Sn: 0.02-0.1%; Be: 0.002-0.02%; the total amount of other impurities is less than or equal to 0.3%, and the balance is Mg; and the above elements also need to simultaneously satisfy: 0 < Al-(0.7La+2Mn) < 1.2. Compared with traditional die-casting magnesium alloys (such as AZ91D, AM60, AE44 and the like), the alloy has the characteristics of high strength, high toughness and high heat resistance, and the yield strength, elongation and creep performance can exceed those of A380 die-casting aluminum alloy; in addition, the alloy also has good die-casting performance, and greatly expands the application scenarios of the die-casting magnesium alloy.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of metal materials, in particular to a high-strength and high-ductility high-heat-resistant Mg-Al-RE series die-casting magnesium alloy and a preparation method thereof. BACKGROUND

[0002] Magnesium alloy has high specific strength and is the lightest metal structural material. Its main forming methods include gravity casting, high-pressure casting, extrusion and forging. Among them, high-pressure casting has the advantages of high production efficiency and relatively low cost, and is the most economical forming method. However, the absolute strength and plasticity of magnesium alloy are poor, and the heat resistance is insufficient, which limits its application as a structural component or heat-resistant component. Therefore, the development of high-strength and high-ductility high-heat-resistant die-casting magnesium alloy can expand the application scenarios of magnesium alloy, such as its application in various brackets, vehicle bodies, chassis and other structural components of electric vehicles, or its application in transmission housings, cylinder blocks, battery packs and other components that have certain requirements for heat resistance (A380 die-casting aluminum alloy is commonly used at present). This can significantly reduce the weight of electric vehicles, improve the range and performance of electric vehicles, and significantly improve the light weight technology level of China's automobiles, which has important scientific research and practical application value.

[0003] Die-casting magnesium alloy is mainly Mg-Al series alloy. AZ (Mg-Al-Zn) series die-casting magnesium alloy AZ91 alloy and AM (Mg-Al-Mn) series die-casting magnesium alloy AM60 alloy are the most widely used die-casting magnesium alloys at present due to their low cost, moderate mechanical properties, excellent fluidity and good casting performance. However, AZ91 alloy has a high Al content, which leads to the formation of a large number of network-distributed Mg 17 Al 12 Second phase; at the same time, the addition of strengthening element Zn improves the yield strength of the alloy, but seriously deteriorates the plasticity of the alloy. AM60 alloy has low strength due to the lack of strengthening elements. In addition, the main second phase Mg 17 Al 12 In AZ91 and AM60 alloys, the main second phase Mg

[0004] The heat resistance of the alloy as a whole is poor due to the low melting point and poor thermal stability of the second phase.

[0005] AE (Mg-Al-RE) series die-casting magnesium alloy generates high-melting-point Al 11 RE3 or Al2RE phase by adding RE element (commonly mixed lanthanum and cerium rare earth), thereby avoiding the formation of low-melting-point Mg17 Al 12 The phase formation not only improves the plasticity of the alloy but also improves the heat resistance of the alloy, and the plasticity of the AE44 alloy can reach more than 16%, which is the alloy with the best comprehensive mechanical properties in the current die-casting magnesium alloy. However, the yield strength (about 160 MPa) of the AE44 die-casting magnesium alloy is still low, and it is difficult to replace the currently commonly used A380 and ADC12 die-casting aluminum alloys, thereby limiting its application.

[0006] Chinese patent 201810158747.8 discloses "a die-casting magnesium alloy with high-temperature heat resistance and a manufacturing method thereof". The magnesium alloy mainly contains Al, RE, Ca, Sr, and Mn, wherein the RE element includes at least one of La, Gd, and Y. Compared with the traditional AZ91D alloy, the magnesium alloy has good creep performance at 200℃ and 70MPa. However, in order to improve the heat resistance of the alloy, a large amount of Ca and Sr elements are added to the alloy, which can significantly increase the hot cracking tendency of the alloy and make the elongation of the alloy at room temperature insufficient, only 4.5-7.6%. The commonly used heat-resistant die-casting magnesium alloys on the market, such as AXJ530 and AJ62, have this problem, which limits the application range of heat-resistant die-casting magnesium alloys. At the same time, the Gd or Y element contained in the alloy has a high cost, which is not conducive to its commercial application.

[0007] Chinese patent 201210294073.7 discloses "a rare earth-containing heat-resistant magnesium alloy". The magnesium alloy mainly contains Al, RE, and Mn, wherein the rare earth elements are cerium, lanthanum, and neodymium. Compared with the traditional AE44 alloy, the magnesium alloy has good creep performance, but its yield strength at room temperature is insufficient, only 133-142 MPa, which does not exceed the yield strength of the traditional AE44 alloy or the A380 die-casting aluminum alloy. At the same time, the neodymium element contained in the alloy has a high cost, which is not conducive to its commercial application.

[0008] Therefore, the existing die-casting magnesium alloy material has the technical problem of being unable to simultaneously consider the cost, strength, toughness, and heat resistance, so that the existing die-casting magnesium alloy cannot meet the demand of high-performance structural parts for high-strength, high-toughness, and high-heat-resistant die-casting magnesium alloy. It is urgent to develop a new type of high-strength, high-toughness, and high-heat-resistant die-casting magnesium alloy to meet the use demand of magnesium alloy in structural parts and heat-resistant parts. SUMMARY

[0009] The purpose of the present application is to provide a high-strength, high-toughness, and high-heat-resistant die-casting magnesium alloy and a preparation method thereof. Under the premise of ensuring good casting performance, the problem that the existing magnesium alloy cannot simultaneously consider high strength, high toughness, and high heat resistance is solved, thereby widening the application scenarios of die-casting magnesium alloy, using die-casting magnesium alloy for structural parts or heat-resistant parts, replacing traditional steel or die-casting aluminum alloy (such as A380), and improving the light weight technology level of China.

[0010] To achieve this purpose, the present application in the study of Mg-Al-RE series die casting magnesium alloy, by adjusting the AE series die casting magnesium alloy commonly used in the mixed rare earth of pure lanthanum, can change the second phase morphology of Mg-Al-RE series die casting magnesium alloy, using mixed rare earth of Mg-Al-RE alloy in the second phase in addition to Al 11 RE3 phase, there is also granular Al2RE phase, and using pure lanthanum rare earth of Mg-Al-La alloy in the second phase almost all for dendritic Al 11 RE3 phase, Al 11 RE3 phase is better than Al2RE phase, so the heat resistance of Mg-Al-La alloy is better than Mg-Al-RE alloy. In addition, dendritic Al 11 RE3 phase is far higher than the number density of granular Al2RE phase, so its blocking ability for dislocation is stronger, so the strength of Mg-Al-La alloy is also better than Mg-Al-RE alloy.

[0011] At the same time, in order to take into account the strength, heat resistance and toughness of the alloy, the content of Al element is controlled at 4.5-6%, the content of La element is controlled at 4.5-6%, the content of Mn element is controlled at 0.2-0.5%, especially at the same time also meet: 0 < Al-(0.7La+2Mn) < 1.2; Al-(0.7La+2Mn) > 0 is to ensure that Al element and La element in addition to the combination of Al 11 RE3 phase, a small amount of Al element remains, solid solution in magnesium matrix, to ensure the strength of the alloy, and the Al and Mn elements solid solution in magnesium matrix can be combined into AlMn phase precipitation, blocking dislocation movement, improving the creep properties of the alloy; Al-(0.7La+2Mn) < 1.2 is to ensure that the Al element remains not too much, otherwise the excess Al will be combined with Mg to generate low melting point Mg 17 Al 12 phase, seriously damaging the plasticity of the alloy and reducing the heat resistance of the alloy.

[0012] In addition, by adding a small amount of Sn element in the above alloy, the aging precipitation ability of the alloy can be enhanced, a small amount of Sn element can be solid solution in Mg matrix, improving the strength of the alloy, and can be combined with Al element into AlSn phase precipitation during the creep process, blocking dislocation movement, improving the creep properties of the alloy. But the content of Sn element should not be too high, otherwise Sn element is easy to combine with Al element to form a large number of AlSn phase around Al 11 RE3 phase, significantly reducing the plasticity of the alloy.

[0013] The present application further adds trace Be element in the alloy, and the Be element helps the magnesium alloy to form a dense protective film on the surface, can significantly reduce the oxidation and burning of the magnesium alloy in the smelting process, thereby reducing the oxidation inclusions or the alloy element burning loss caused by burning in the magnesium alloy, and improving the purity and the stability of the composition of the magnesium alloy in the smelting process.

[0014] Accordingly, the technical scheme of the present application is as follows:

[0015] In a first aspect, the present application relates to a high-strength and high-heat-resistance Mg-Al-RE series die-casting magnesium alloy, wherein the weight percentage of each component in the die-casting magnesium alloy is as follows: Al: 4.5-6%; La: 4.5-6%; Mn: 0.2-0.5%; Sn: 0.02-0.1%; Be: 0.002-0.02%; the total amount of other impurities is less than or equal to 0.3%, and the rest is Mg.

[0016] Preferably, in the weight percentage of each component of the die-casting magnesium alloy, the Al, La and Mn elements satisfy the following conditions:

[0017] 0 < Al-(0.7La+2Mn) < 1.2.

[0018] In a second aspect, the present application further relates to a preparation method of the aforementioned high-strength and high-heat-resistance Mg-Al-RE series, and the method comprises the following steps:

[0019] S1, material preparation: the magnesium alloy components according to claim 1 are prepared; wherein the Mg, Al and Sn are prepared in the form of pure magnesium, pure aluminum and pure tin, the La is prepared in the form of pure lanthanum or Mg-La or Al-La intermediate alloy, and the Mn and Be are prepared in the form of intermediate alloy containing magnesium or aluminum;

[0020] S2, smelting: the crucible is preheated to 400-500 DEG C, the pure Mg ingot is put into the crucible, and the melting is carried out under the protection of gas or in a vacuum environment, or a layer of covering agent is first covered in the crucible, the pure Mg ingot is added and melted, and then a layer of covering agent is covered on the surface of the melt; then the temperature is raised to 750-780 DEG C, the Al-Be or Mg-Be intermediate alloy is added, after the intermediate alloy is melted, the temperature is kept, the pure lanthanum or Mg-La or Al-La intermediate alloy is added, after the intermediate alloy is melted, the temperature is lowered to 720-750 DEG C, and then the Al-Mn or Mg-Mn intermediate alloy, pure aluminum and pure tin are added for melting;

[0021] S3, refining: the melt of step S2 is heated to 740-760 DEG C, and the gas with the refining agent powder is sprayed to refine and remove the slag in the melt;

[0022] S4, casting or die casting: after the molten metal after refining and slagging in step S3 reaches the casting temperature, the casting ingot operation or die casting process operation is carried out, and finally the alloy ingot production or die casting production is completed.

[0023] Preferably, in step S1, the prepared raw materials are preheated to 180-240°C, and the preheating and drying steps are carried out.

[0024] Preferably, in step S2, the covering agent is a covering agent without Na ions, and the solvent density is <1.58 g / cm 3 The protective gas is a mixed gas of N2+SF6 or CO2+SF6 or pure SF6 protective gas.

[0025] Preferably, in step S2, after melting and stirring uniformly, the step of standing and carrying out pre-furnace component analysis to detect the component content of the alloy melt is carried out, and the melt with content deviation is supplemented or diluted to make the component reach the qualified range.

[0026] Preferably, in step S3, the refining agent is a salt flux without Na ions.

[0027] Preferably, in step S3, the amount of the refining agent added is 0.3-1.2% of the total weight of the melt.

[0028] Preferably, in step S3, the gas includes argon or chlorine or hexachloroethane gas.

[0029] Preferably, in step S3, after refining and degassing treatment, the step of standing and carrying out pre-furnace component analysis test is further included.

[0030] More preferably, the standing time is 5-10 min.

[0031] Preferably, in step S4, the temperature of the casting is 700-730°C.

[0032] Preferably, in step S4, when the die casting magnesium alloy is used for die casting production, the injection speed range is 2.5-5 m / s.

[0033] Preferably, in step S4, when the die casting magnesium alloy is used for die casting production, the casting pressure (boosting) range is 60-150 MPa.

[0034] The application can further improve the strength, toughness and heat resistance by using pouring temperature of 700-730 DEG C, injection speed of 2.5-5 m / s and casting pressure of 60-150 MPa. In the early experiments of the inventor, it is found that if the pouring temperature is too low, a large number of pre-crystallization appears in the die casting, the strength of the alloy is reduced, and cold shut defects are prone to occur, which results in poor formability of the die casting; if the pouring temperature is too high, a large number of shrinkage holes and shrinkage porosities appear in the die casting, and the hot cracking tendency of the alloy is increased, which significantly reduces the plasticity and creep performance of the alloy; if the injection speed is too low, the flow marks and cold lines on the surface of the die casting are more serious, and cold shut defects are prone to occur, the surface quality and formability of the die casting are poor; if the injection speed is too high, air entrapment in the die casting process is increased, a large number of pores appear in the die casting, and the performance of the alloy is significantly reduced; if the casting pressure is too low, the die casting cannot be well compensated, the shrinkage holes and shrinkage porosities in the die casting are increased, and the plasticity and creep performance of the alloy are reduced; if the casting pressure is too high, it approaches or even exceeds the upper limit of the pressure relief of some die casting machines, which causes the instability of various die casting parameters in the die casting process, and finally leads to the instability of the performance of the die casting.

[0035] Compared with the prior art, the application has the following beneficial effects:

[0036] 1. The high-strength and high-toughness Mg-Al-RE series die casting magnesium alloy of the application is based on the conventional Mg-Al-RE series die casting magnesium alloy, and the RE element is adjusted to pure La to improve the strength and heat resistance of the alloy. By adjusting the content of Al and La elements, the plasticity of the alloy is ensured. The addition of Sn element further improves the strength and heat resistance of the alloy.

[0037] 2. The die casting magnesium alloy obtained by the application has high strength, high toughness and high heat resistance, and the yield strength of the die casting state can reach 170-180 MPa, the tensile strength can reach 270-280 MPa, the elongation can reach 9-15%, and the anti-creep ability (the creep strain under the condition of 175 DEG C, 100 h and 90 MPa can reach 0.125-0.215%) is much higher than that of A380 die casting aluminum alloy. BRIEF DESCRIPTION OF DRAWINGS

[0038] Other features, objects and advantages of the application will become more apparent after reading the detailed description of the non-limiting embodiments with reference to the following drawings:

[0039] Figure 1 The microstructure photo of the die casting magnesium alloy part of Example 1 of the application.

[0040] Figure 2 The microstructure photo of the die casting magnesium alloy part of Comparative Example 1 of the application.

[0041] Figure 3 Microstructure of the magnesium alloy part of the present application comparative example 3.

[0042] Figure 4 Creep strain-time curves of the magnesium alloy parts of the present application example 1 and comparative examples 1, 2 and 4 under a creep stress of 175℃ and 90MPa. DETAILED DESCRIPTION

[0043] The present application will be described in detail below with specific examples. The following examples will help those skilled in the art to further understand the present application, but do not limit the present application in any form. It should be noted that those skilled in the art can make several modifications and improvements without departing from the concept of the present application. These are within the scope of the present application.

[0044] The measured composition of the magnesium alloy of each embodiment and comparative example of the present application is summarized in Table 1, and the rest is Mg and other unavoidable impurities. The performance test results of the magnesium alloy of each embodiment and comparative example are summarized in Table 2. Among them, the room temperature tensile property test is carried out according to the method in the standard of GB / T 228.1-2021 “Metallic Materials Tensile Test Part 1: Room Temperature Test Method”, and the creep property test is carried out according to the method in the standard of GB / T 2039-2012 “Metallic Materials Uniaxial Tensile Creep Test Method”.

[0045] Example 1

[0046] The present embodiment provides a preparation method of a high-strength and high-ductility high-heat-resistant Mg-Al-RE series die-casting magnesium alloy, and the specific steps are as follows:

[0047] 1) According to the theoretical weight percentage of each component Mg-5.1Al-5.1La-0.35Mn-0.01Be-0.05Sn, pure Mg ingot, pure Al ingot, pure Sn ingot, Mg-30La, Al-10Mn, and Al-3Be intermediate alloy are selected as raw materials, and the raw materials are preheated to 200℃ for drying treatment;

[0048] 2) Preheat the crucible to 150℃, evenly coat the coating on the inner wall of the crucible, and after drying, heat to 460℃, and introduce CO2+SF6 mixed gas, put the pure Mg ingot into the crucible, completely melt under the protection of the mixed protective gas of CO2 and SF6, then heat to 770℃, add Al-3Be intermediate alloy, and after the alloy is completely melted, add Mg-30La intermediate alloy until it is completely melted, cool to 740℃, add pure Al, pure Sn, and Al-10Mn intermediate alloy, completely melt, and then fully stir, stand still and carry out pre-furnace composition analysis, detect the composition content of the alloy melt, and supplement or dilute the melt with composition deviation to make the composition reach the designed magnesium alloy composition range;

[0049] 3) The melt is heated to 750°C, argon gas with a pressure of 0.2 MPa is introduced into the melt, and 0.8% of a refining agent (salt flux without Na ions, specifically HuoTeng brand magnesium alloy refining agent, purchased from Zhangjiagang HaoHua Light Alloy Material Co., Ltd.) powder is introduced into the melt, and then the gas is continued to be introduced for 10 min to remove slag and gas;

[0050] 4) The refined melt is left for 10 min, and then the pre-furnace component analysis test is performed again. After the components are qualified, high-pressure casting is performed at 710-720°C, the injection speed is 4.0 m / s, and the casting pressure (boosting) is 90 MPa. The mold used in the production process is a die casting test bar mold.

[0051] The properties of the die-cast magnesium alloy part obtained are shown in Table 2.

[0052] Example 2

[0053] The embodiment provides a preparation method of a high-strength and high-toughness high-heat-resistant Mg-Al-RE series die-cast magnesium alloy, and the specific steps are as follows:

[0054] 1) The raw materials are designed and selected according to the theoretical weight percentage of each component as Mg-4.5Al-4.5La-0.2Mn-0.002Be-0.02Sn, pure Mg ingot, pure Al ingot, pure Sn ingot, Al-30La, Al-10Mn and Al-3Be intermediate alloy, and the raw materials are preheated to 210°C for drying treatment;

[0055] 2) The crucible is preheated to 150°C, the inner wall of the crucible is uniformly coated with paint, and after drying, the temperature is raised to 450°C, CO2+SF6 mixed gas is introduced, the pure Mg ingot is put into the crucible, and the pure Mg ingot is completely melted under the protection of the mixed protective gas of CO2 and SF6, then the temperature is raised to 760°C, the Al-3Be intermediate alloy is added, and after the alloy is completely melted, the Al-30La intermediate alloy is added until it is completely melted, the temperature is lowered to 730°C, the pure Al, the pure Sn and the Al-10Mn intermediate alloy are added, and after complete melting, the mixture is stirred thoroughly, left to stand and subjected to pre-furnace component analysis, the component content of the alloy melt is detected, and the melt with content deviation is supplemented or diluted to make the components reach the designed magnesium alloy component range;

[0056] 3) The melt is heated to 750°C, argon gas with a pressure of 0.2 MPa is introduced into the melt, and 0.7% of a refining agent (salt flux without Na ions, specifically HuoTeng brand magnesium alloy refining agent, purchased from Zhangjiagang HaoHua Light Alloy Material Co., Ltd.) powder is introduced into the melt, and then the gas is continued to be introduced for 10 min to remove slag and gas;

[0057] 4) The refined melt is left to stand for 10 min, and the pre-furnace component analysis test is performed again. After the components are qualified, high-pressure casting is performed at 710-720 °C, with a injection speed of 3.5 m / s and a casting pressure of 100 MPa. The mold used in the production process is a die casting test bar mold.

[0058] The properties of the obtained die-cast magnesium alloy parts are shown in Table 2.

[0059] Example 3

[0060] The present example provides a preparation method of a high-strength and high-ductility high-heat-resistant Mg-Al-RE series die-cast magnesium alloy, and the specific steps are as follows:

[0061] 1) The raw materials are designed and selected according to the theoretical weight percentage of each component as Mg-6Al-6La-0.5Mn-0.02Be-0.1Sn, and pure Mg ingot, pure Al ingot, pure Sn ingot, Al-60La, Mg-5Mn, and Mg-3Be intermediate alloy are used as the raw materials, which are preheated to 180 °C for drying treatment;

[0062] 2) The crucible is preheated to 150 °C, the inner wall of the crucible is uniformly coated with paint, and after drying, it is heated to 400 °C, CO2+SF6 mixed gas is introduced, the pure Mg ingot is put into the crucible, and it is completely melted under the protection of the mixed protective gas of CO2 and SF6, then the temperature is raised to 750 °C, the Mg-3Be intermediate alloy is added, and after the alloy is completely melted, the Al-60La intermediate alloy is added until it is completely melted, the temperature is lowered to 720 °C, the pure Al, pure Sn, and Mg-5Mn intermediate alloy are added, and after complete melting, it is fully stirred, left to stand, and the pre-furnace component analysis is performed, the component content of the alloy melt is detected, and the melt with content deviation is supplemented or diluted to make the components reach the designed magnesium alloy component range;

[0063] 3) The melt is heated to 740 °C, argon gas with a pressure of 0.2 MPa is introduced into the melt, and 1.0% of the total weight of the melt is added into the melt as a refining agent (a salt flux without Na ions, in the present example, it is specifically a torch brand magnesium alloy refining agent, which is purchased from Zhangjiagang Haohua Light Alloy Material Co., Ltd.), and then the gas is continued to be introduced for 10 min to remove slag and gas;

[0064] 4) The refined melt is left to stand for 10 min, and the pre-furnace component analysis test is performed again. After the components are qualified, high-pressure casting is performed at 710-720 °C, with a injection speed of 3.5 m / s and a casting pressure of 100 MPa. The mold used in the production process is a die casting test bar mold.

[0065] The properties of the obtained die-cast magnesium alloy parts are shown in Table 2.

[0066] Example 4

[0067] The embodiment provides a preparation method of a high-toughness high-heat-resistance Mg-Al-RE series die-casting magnesium alloy, and the specific steps are as follows.

[0068] 1) according to the theoretical weight percentage of each component Mg-5.4Al-5.5La-0.25Mn-0.004Be-0.09Sn, pure Mg ingot, pure Al ingot, pure Sn ingot, Mg-90La, Al-10Mn and Al-3Be intermediate alloy are selected as raw materials, and the raw materials are preheated to 190 DEG C and dried;

[0069] 2) the crucible is preheated to 150 DEG C, the inner wall of the crucible is uniformly coated with paint, and after drying, the temperature is heated to 420 DEG C, N2+SF6 mixed gas is introduced, the pure Mg ingot is put into the crucible, and the pure Mg ingot is completely melted under the protection of the mixed protective gas of N2 and SF6, then the temperature is increased to 760 DEG C, the Al-3Be intermediate alloy is added, after the alloy is completely melted, the Mg-90La intermediate alloy is added until it is completely melted, the temperature is decreased to 730 DEG C, the pure Al, the pure Sn and the Al-10Mn intermediate alloy are added, after complete melting, the mixture is fully stirred, and then the composition analysis is carried out, the composition content of the alloy melt is detected, and the melt with content deviation is supplemented or diluted to make the composition reach the designed magnesium alloy composition range;

[0070] 3) the melt is heated to 740 DEG C, the hexachloroethane gas with a pressure of 0.2 MPa is introduced into the melt, 1.1% of the refining agent (salt molten agent without Na ion, in the embodiment, it is specifically torch magnesium alloy refining agent, which is purchased from Zhangjiagang Haohua Light Alloy Material Co., Ltd.) powder is introduced into the melt, and then the gas is continuously introduced for 10 min to remove slag and gas;

[0071] 4) the refined melt is placed for 10 min, and then the composition analysis is carried out again, after the composition is qualified, high-pressure casting is carried out at 720-730 DEG C, the injection speed is 5.0 m / s, and the casting pressure is 110 MPa. The mold used in the production process is a die-casting test bar mold.

[0072] The performance of the obtained die-casting magnesium alloy part is shown in Table 2.

[0073] Embodiment 5

[0074] The embodiment provides a preparation method of a high-toughness high-heat-resistance Mg-Al-RE series die-casting magnesium alloy, and the specific steps are as follows:

[0075] 1) according to the theoretical weight percentage of each component Mg-5.2Al-4.8La-0.43Mn-0.017Be-0.06Sn, pure Mg ingot, pure Al ingot, pure Sn ingot, Al-30La, Mg-5Mn and Al-3Be intermediate alloy are selected as raw materials, and the raw materials are preheated to 220 DEG C and dried;

[0076] 2) Preheat the crucible to 150°C, evenly coat the coating on the inner wall of the crucible, and after drying, heat to 410°C, introduce N2+SF6 mixed gas, put the pure Mg ingot into the crucible, completely melt under the protection of the mixed protective gas of N2 and SF6, then heat to 760°C, add Al-3Be intermediate alloy, after the alloy is completely melted, add Al-30La intermediate alloy until it is completely melted, cool to 730°C, add pure Al, pure Sn, and Mg-5Mn intermediate alloy, completely melt, and then stir thoroughly, stand still, and perform pre-furnace component analysis, detect the component content of the alloy melt, and supplement or dilute the melt with deviations in content to make the components reach the designed magnesium alloy component range;

[0077] 3) Heat the melt to 740°C, introduce hexachloroethane gas with a pressure of 0.2 MPa into the melt, and bring in 0.9% of the refining agent (salt flux without Na ions, in this embodiment, it is specifically a torch magnesium alloy refining agent, purchased from Zhangjiagang Haohua Light Alloy Material Co., Ltd.) powder into the melt, and then continue to ventilate for 10 min to remove slag and gas;

[0078] 4) After refining, the melt is stood still for 10 min, and pre-furnace component analysis is performed again. After the components are qualified, high-pressure casting is performed at 680-690°C, the injection speed is 2.5 m / s, and the casting pressure is 90 MPa. The mold used in the production process is a die casting test bar mold.

[0079] The performance of the obtained die-cast magnesium alloy part is shown in Table 2.

[0080] Example 6

[0081] The embodiment provides a preparation method of a high-strength and high-toughness high-heat-resistant Mg-Al-RE series die-cast magnesium alloy, and the specific steps are as follows:

[0082] 1) According to the theoretical weight percentage of each component being Mg-4.7Al-5.3La-0.31Mn-0.012Be-0.03Sn, pure Mg ingot, pure Al ingot, pure Sn ingot, pure La ingot, Mg-5Mn, and Mg-3Be intermediate alloy are designed and selected as raw materials, and the raw materials are preheated to 240°C for drying treatment;

[0083] 2) Preheat the crucible to 150°C, evenly coat the coating on the inner wall of the crucible, and after drying, heat to 490°C, cover a layer of covering agent (a salt without Na ions, and the solvent density is <1.58 g / cm 3The covering agent used in this embodiment is Torch brand flux (purchased from Zhangjiagang Haohua Light Alloy Materials Co., Ltd.). Pure Mg ingots are placed in a crucible and melted. Then, a layer of covering agent is applied to the surface of the melt. The temperature is raised to 780°C, and Mg-3Be master alloy is added. After the alloy is completely melted, pure La ingots are added until they are completely melted. The temperature is lowered to 750°C, and pure Al, pure Sn, and Mg-5Mn master alloys are added. After complete melting, the mixture is stirred thoroughly, allowed to stand, and pre-furnace composition analysis is performed to detect the composition content of the alloy melt. For melts with deviations in content, additional material is added or diluted to bring the composition to the designed range of magnesium alloy composition.

[0084] 3) Heat the melt to 760°C, introduce hexachloroethane gas at a pressure of 0.2 MPa into the melt, and introduce 1.2% of the total weight of the melt refining agent (a salt flux without Na ions, specifically Torch brand magnesium alloy refining agent in this embodiment, purchased from Zhangjiagang Haohua Light Alloy Materials Co., Ltd.) powder, and then continue to purge for 10 minutes to remove slag and gas;

[0085] 4) After refining, the melt is allowed to stand for 10 minutes, and then a pre-furnace composition analysis test is performed. If the composition is qualified, high-pressure casting is carried out at 700-710℃, with an injection speed of 3.5m / s and a casting pressure of 130MPa. The mold used in the production process is a die-casting test rod mold.

[0086] The properties of the resulting die-cast magnesium alloy parts are shown in Table 2.

[0087] Example 7

[0088] This embodiment provides a method for preparing a high-strength, high-toughness, and high-heat-resistant Mg-Al-RE die-cast magnesium alloy. The specific steps are as follows:

[0089] 1) Based on the theoretical weight percentage of each component being Mg-5.5Al-5.4La-0.28Mn-0.008Be-0.07Sn, pure Mg ingot, pure Al ingot, pure Zn ingot, pure La ingot, Mg-5Mn, and Al-3Be master alloy were selected as raw materials, and the raw materials were preheated to 220℃ and dried.

[0090] 2) Preheat the crucible to 150℃, coat the inner wall of the crucible with a coating evenly, dry it, heat it to 430℃, introduce SF6 gas, put pure Mg ingot into the crucible, and melt it completely under the protection of SF6 protective gas. Then raise the temperature to 770℃, add Al-3Be master alloy, and after the alloy is completely melted, add pure La ingot until it is completely melted. Cool down to 740℃, add pure Al, pure Sn, and Mg-5Mn master alloy, and stir thoroughly after complete melting. Let it stand and perform pre-furnace composition analysis to detect the composition content of the alloy melt. For melts with deviations in content, add material or dilute it to make its composition reach the designed magnesium alloy composition range.

[0091] 3) The melt is heated to 760℃, and chlorine gas with a pressure of 0.2 MPa is introduced into the melt, and 0.3% of a refining agent (a salt flux without Na ions, and in this embodiment, it is specifically a torch brand magnesium alloy refining agent, which is purchased from Zhangjiagang Haohua Light Alloy Material Co., Ltd.) powder is introduced into the melt, and then the gas is continued to be introduced for 10 min to remove slag and gas;

[0092] 4) The refined melt is left for 10 min, and then a pre-furnace component analysis test is performed again, and after the components are qualified, high-pressure casting is performed at 690-700℃, the injection speed is 3.0 m / s, and the casting pressure is 80 MPa. The mold used in the production process is a die casting test bar mold.

[0093] The properties of the obtained die-cast magnesium alloy part are shown in Table 2.

[0094] Example 8

[0095] The embodiment provides a preparation method of a high-strength and high-ductility high-heat-resistant Mg-Al-RE series die-cast magnesium alloy, and the specific steps are as follows:

[0096] 1) The raw materials are designed and selected according to the theoretical weight percentage of each component as Mg-5.7Al-5.8La-0.37Mn-0.016Be-0.04Sn, pure Mg ingot, pure Al ingot, pure Sn ingot, Mg-60La, Al-10Mn and Al-3Be intermediate alloy, and the raw materials are preheated to 200℃ for drying treatment;

[0097] 2) The crucible is preheated to 150℃, the inner wall of the crucible is uniformly coated with paint, and after drying, it is heated to 480℃, CO2+SF6 mixed gas is introduced, the pure Mg ingot is put into the crucible, and it is completely melted under the protection of the mixed protective gas of CO2 and SF6, then it is heated to 770℃, the Al-3Be intermediate alloy is added, and after the alloy is completely melted, the Mg-60La intermediate alloy is added until it is completely melted, and then it is cooled to 740℃, the pure Al, the pure Sn and the Al-10Mn intermediate alloy are added, and after complete melting, it is fully stirred, and then it is left and subjected to a pre-furnace component analysis, the component content of the alloy melt is detected, and the melt with content deviation is supplemented or diluted to make the components reach the designed magnesium alloy component range;

[0098] 3) The melt is heated to 750℃, and argon gas with a pressure of 0.2 MPa is introduced into the melt, and 0.6% of a refining agent (a salt flux without Na ions, and in this embodiment, it is specifically a torch brand magnesium alloy refining agent, which is purchased from Zhangjiagang Haohua Light Alloy Material Co., Ltd.) powder is introduced into the melt, and then the gas is continued to be introduced for 10 min to remove slag and gas;

[0099] 4) The refined melt is left to stand for 10 min, and the pre-furnace component analysis test is performed again. After the components are qualified, high-pressure casting is performed at 710-720 °C, the injection speed is 4.0 m / s, and the casting pressure is 140 MPa. The mold used in the production process is a die casting test bar mold.

[0100] The properties of the obtained die-cast magnesium alloy parts are shown in Table 2.

[0101] Example 9

[0102] The embodiment provides a preparation method of a high-strength and high-ductility high-heat-resistant Mg-Al-RE series die-cast magnesium alloy, and the specific steps are as follows:

[0103] 1) The raw materials are designed and selected according to the theoretical weight percentage of Mg-5.9Al-5.7La-0.46Mn-0.005Be-0.08Sn, and pure Mg ingot, pure Al ingot, pure Sn ingot, Al-90La, Mg-5Mn and Al-3Be intermediate alloy are used, and the raw materials are preheated to 230 °C and dried.

[0104] 2) The crucible is preheated to 150 °C, the inner wall of the crucible is uniformly coated with paint, and after drying, it is heated to 500 °C, N2+SF6 mixed gas is introduced, the pure Mg ingot is put into the crucible, and it is completely melted under the protection of the mixed protective gas of N2 and SF6, then the temperature is raised to 760 °C, the Al-3Be intermediate alloy is added, and after the alloy is completely melted, the Al-90La intermediate alloy is added until it is completely melted, the temperature is lowered to 730 °C, the pure Al, the pure Sn and the Mg-5Mn intermediate alloy are added, and after complete melting, the melt is stirred thoroughly, and then left to stand and the pre-furnace component analysis is performed. The component content of the alloy melt is detected, and the melt with content deviation is supplemented or diluted to make the components reach the designed magnesium alloy component range.

[0105] 3) The melt is heated to 750 °C, argon gas with a pressure of 0.2 MPa is introduced into the melt, 0.5% of a refining agent (a salt flux without Na ions, in this embodiment, it is specifically a torch magnesium alloy refining agent, which is purchased from Zhangjiagang Haohua Light Alloy Material Co., Ltd.) powder is introduced into the melt, and then the gas is continued to be introduced for 10 min to remove slag and gas;

[0106] 4) The refined melt is left to stand for 10 min, and the pre-furnace component analysis test is performed again. After the components are qualified, high-pressure casting is performed at 710-720 °C, the injection speed is 4.0 m / s, and the casting pressure is 140 MPa. The mold used in the production process is a die casting test bar mold.

[0107] The properties of the obtained die-cast magnesium alloy parts are shown in Table 2.

[0108] Example 10

[0109] The embodiment provides a preparation method of a high-toughness high-heat-resistance Mg-Al-RE series die-casting magnesium alloy. Compared with the method of the embodiment 1, only the weight percentages of Al, La and Mn are different. The specific steps are as follows:

[0110] 1) According to the theoretical weight percentage of each component, the pure Mg ingot, the pure Al ingot, the pure Sn ingot, the Mg-30La, the Al-10Mn and the Al-3Be intermediate alloy are designed and selected as raw materials, and the raw materials are preheated to 200 DEG C and dried;

[0111] 2) The crucible is preheated to 150 DEG C, the inner wall of the crucible is uniformly coated with paint, and after drying, the temperature is heated to 460 DEG C, the CO2+SF6 mixed gas is introduced, the pure Mg ingot is put into the crucible, and the pure Mg ingot is completely melted under the protection of the mixed protective gas of CO2 and SF6, then the temperature is increased to 770 DEG C, the Al-3Be intermediate alloy is added, and after the alloy is completely melted, the Mg-30La intermediate alloy is added until it is completely melted, the temperature is decreased to 740 DEG C, the pure Al, the pure Sn and the Al-10Mn intermediate alloy are added, and after complete melting, the alloy is fully stirred, and the composition of the alloy is analyzed, the composition of the alloy is analyzed, and the composition of the alloy is analyzed.

[0112] 3) The melt is heated to 750 DEG C, the argon gas with a pressure of 0.2 MPa is introduced into the melt, and the refining agent (the salt refining agent without Na ion, in the embodiment, the torch magnesium alloy refining agent is purchased from Zhangjiagang Haohua Light Alloy Material Co., Ltd.) powder with a total weight of 0.8% is introduced into the melt, and then the gas is continued for 10 min to remove slag and gas;

[0113] 4) The refined melt is placed for 10 min, and the composition is analyzed again, and after the composition is qualified, the high-pressure casting is carried out at 710-720 DEG C, the injection speed is 4.0 m / s, and the casting pressure is 90 MPa. The mold used in the production process is a die-casting test bar mold.

[0114] The performance of the obtained die-casting magnesium alloy part is shown in Table 2.

[0115] Embodiment 11

[0116] The embodiment provides a preparation method of a high-toughness high-heat-resistance Mg-Al-RE series die-casting magnesium alloy. Compared with the method of the embodiment 1, only the weight percentages of Al, La and Mn are different. The specific steps are as follows:

[0117] 1) According to the theoretical weight percentage of each component Mg-5.6Al-5.1RE-0.35Mn-0.01Be-0.05Sn, pure Mg ingot, pure Al ingot, pure Sn ingot, Mg-30La, Al-10Mn, Al-3Be intermediate alloy are selected as raw materials, and the raw materials are preheated to 200℃ for drying treatment;

[0118] 2) The crucible is preheated to 150℃, the inner wall of the crucible is evenly coated with paint, and after drying, it is heated to 460℃, and CO2+SF6 mixed gas is introduced, pure Mg ingot is put into the crucible, and it is completely melted under the protection of CO2 and SF6 mixed protective gas, then the temperature is raised to 770℃, Al-3Be intermediate alloy is added, after the alloy is completely melted, Mg-30La intermediate alloy is added until it is completely melted, the temperature is lowered to 740℃, pure Al, pure Sn, Al-10Mn intermediate alloy is added, after completely melting, it is fully stirred, and the composition analysis is carried out before the furnace, the composition content of the alloy melt is detected, and the melt with content deviation is supplemented or diluted to make the composition reach the designed magnesium alloy composition range;

[0119] 3) The melt is heated to 750℃, argon gas with a pressure of 0.2MPa is introduced into the melt, and 0.8% of the refining agent (salt flux without Na ion, in this embodiment, it is specifically torch magnesium alloy refining agent, purchased from Zhangjiagang Haohua Light Alloy Material Co., Ltd.) powder is introduced into the melt, then the gas is continued for 10min to remove slag and gas;

[0120] 4) The refined melt is placed for 10min, and the composition analysis test is carried out before the furnace, and after the composition is qualified, high pressure casting is carried out at 710-720℃, the injection speed is 4.0m / s, and the casting pressure is 90MPa. The mold used in the production process is a die casting test bar mold.

[0121] The performance of the obtained die casting magnesium alloy part is shown in Table 2.

[0122] Comparative Example 1

[0123] This comparative example provides a preparation method of AE44, and the specific steps are as follows:

[0124] 1) According to the theoretical weight percentage of each component Mg-5.6Al-5.1RE-0.35Mn-0.01Be-0.05Sn, pure Mg ingot, pure Al ingot, pure Sn ingot, Mg-30La, Al-10Mn, Al-3Be intermediate alloy are selected as raw materials, and the raw materials are preheated to 200℃ for drying treatment;

[0125] 2) Preheat the crucible to 150°C, evenly coat the coating on the inner wall of the crucible, and after drying, heat to 460°C, and then introduce CO2+SF6 mixed gas, put the pure Mg ingot into the crucible, and completely melt under the protection of the mixed protective gas of CO2 and SF6, then heat to 770°C, add Al-3Be intermediate alloy, and after the alloy is completely melted, add Mg-30La intermediate alloy until it is completely melted, cool to 740°C, add pure Al, pure Sn and Al-10Mn intermediate alloy, completely melt, and then fully stir, stand and analyze the composition of the alloy melt, and supplement or dilute the melt with content deviation to make the composition reach the designed magnesium alloy composition range;

[0126] 3) Heat the melt to 750°C, introduce argon gas with a pressure of 0.2 MPa into the melt, and introduce 0.8% of the refining agent (salt flux without Na ion, in this embodiment, it is specifically torch magnesium alloy refining agent, purchased from Zhangjiagang Haohua Light Alloy Material Co., Ltd.) powder into the melt, and then continue to ventilate for 10 min to remove slag and gas;

[0127] 4) After refining, the melt is placed for 10 min, and the composition is analyzed and tested again, and after the composition is qualified, high-pressure casting is carried out at 710-720°C, the injection speed is 4.0 m / s, and the casting pressure is 90 MPa. The mold used in the production process is a die casting test bar mold.

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

[0129] Comparative Example 2

[0130] The present comparative example provides a preparation method of a high-strength and high-ductility high-heat-resistant Mg-Al-RE series die-cast magnesium alloy, which is basically the same as the method of Example 1, and the only difference is that Sn element is not added in the present comparative example.

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

[0132] Comparative Example 3

[0133] The present comparative example provides a preparation method of a high-strength and high-ductility high-heat-resistant Mg-Al-RE series die-cast magnesium alloy, which is basically the same as the method of Example 1, and the only difference is that the addition amount of pure Sn ingot used in the present comparative example is 0.15% of the theoretical weight percentage of Sn.

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

[0135] Comparative Example 4

[0136] The present comparative example provides a preparation method of A380, and the specific steps are as follows:

[0137] 1) The raw materials are selected from pure Al, pure Zn, Al-20Si, Al-50Cu, Al-20Fe, Al-10Mn, Al-10Ni intermediate alloy, and the raw materials are preheated to 200°C for drying treatment;

[0138] 2) The crucible is preheated to 150°C, and the inner wall of the crucible is evenly coated with paint. After drying, heat to 460°C. Put the pure Al ingot and Al-20Si intermediate alloy into the crucible and completely melt. Then heat to 770°C, add Al-50Cu, Al-20Fe, Al-10Mn, Al-10Ni intermediate alloy, and after the alloy is completely melted, cool to 720°C, add pure Zn, completely melt, and fully stir. After standing and analyzing the composition of the alloy melt, detect the composition content of the alloy melt, and supplement or dilute the melt with a deviation in content to make the composition reach the designed aluminum alloy composition range;

[0139] 3) The melt is heated to 730°C, argon gas with a pressure of 0.2 MPa is introduced into the melt, and 0.8% of the refining agent (salt flux without Na ion, in this embodiment, it is a refining, modification, and slag cleaning three-in-one flux from Huo Torch, purchased from Zhangjiagang Haohua Light Alloy Material Co., Ltd.) powder is introduced into the melt, and then the gas is continued for 10 min to remove slag and gas; After skimming, 0.002% of Al-10Sr modifier is added to the melt for modification treatment;

[0140] 4) The refined melt is allowed to stand for 10 min, and the composition is analyzed again. After the composition is qualified, high-pressure casting is carried out at 680-690°C, the injection speed is 3.0 m / s, and the casting pressure is 90 MPa. The mold used in the production process is a die casting test bar mold.

[0141] The properties of the obtained die-cast magnesium alloy parts are shown in Table 2.

[0142] Comparative Example 5

[0143] This comparative example provides a method for preparing a high-strength and high-ductility high-heat-resistant Mg-Al-RE series die-cast magnesium alloy. The method is basically the same as that of Example 2, except that the addition amount of pure Al ingot in this comparative example is 4.2% based on the theoretical weight percentage of Al.

[0144] The properties of the obtained die-cast magnesium alloy parts are shown in Table 2.

[0145] Comparative Example 6

[0146] This comparative example provides a method for preparing a high-strength, high-toughness, and high-heat-resistant Mg-Al-RE die-cast magnesium alloy, which is basically the same as the method in Example 2, except that the amount of Mg-30La master alloy added in this comparative example is 4.3% of the theoretical weight percentage of La.

[0147] The properties of the resulting die-cast magnesium alloy parts are shown in Table 2.

[0148] Comparative Example 7

[0149] This comparative example provides a method for preparing a high-strength, high-toughness, and high-heat-resistant Mg-Al-RE die-cast magnesium alloy, which is basically the same as the method in Example 3, except that the amount of pure Al ingots added in this comparative example is 6.1% by theoretical weight of Al.

[0150] The properties of the resulting die-cast magnesium alloy parts are shown in Table 2.

[0151] Comparative Example 8

[0152] This comparative example provides a method for preparing a high-strength, high-toughness, and high-heat-resistant Mg-Al-RE die-cast magnesium alloy, which is basically the same as the method in Example 3, except that the amount of Mg-60La master alloy added in this comparative example is 6.2% of the theoretical weight percentage of La.

[0153] The properties of the resulting die-cast magnesium alloy parts are shown in Table 2.

[0154] Figure 1 The image shows the microstructure of the die-cast magnesium alloy part obtained in Example 1 of this invention. Figure 1 As can be seen, the alloy microstructure mainly consists of an α-Mg matrix and dendritic Al atoms. 11 The structure consists of a second phase (RE3), and no obvious grain boundary network of Mg was found in the microstructure. 17 Al 12 The phase or granular Al2RE phase or AlSn phase.

[0155] Figure 2 The image shows the microstructure of the die-cast magnesium alloy part obtained in Comparative Example 1 of this invention. Figure 2 As can be seen from the data, the alloy microstructure consists of an α-Mg matrix and dendritic Al atoms. 11 In addition to the RE3 second phase, it also contains a large amount of granular Al2RE phase. From the morphology of the two AlRE phases, it can be seen that the dendritic Al... 11 The number density of the RE3 phase is much higher than that of the granular Al2RE phase, therefore Al 11 RE3 has a stronger blocking ability compared to dislocations.

[0156] Figure 3The microstructure photograph of the die-casting magnesium alloy part obtained for the present application comparative example 3 can be seen from Figure 3 The alloy microstructure contains a large amount of AlSn phase gathered around the Al 11 RE3 second phase, which significantly reduces the plasticity of the alloy. 11 RE3 phase, which significantly reduces the plasticity of the alloy.

[0157] Figure 4 The creep strain-time curves of the die-casting alloy parts of the present application example 1 and comparative examples 1, 2 and 4 under a creep stress of 175℃ and 90MPa. By Figure 4 The comparison of the creep properties of example 1 and comparative examples 1, 2 and 4 can find that the creep properties of example 1 are significantly better than those of comparative examples 1, 2 and 4.

[0158] The following table 1 is the weight percentage of each component of the die-casting magnesium alloy parts prepared in each example and comparative example, and table 2 is the performance test results. It can be known from the data of table 1 and table 2 that the room temperature tensile properties and creep properties of the die-casting magnesium alloy obtained by the present application are significantly improved compared with the conventional AE44 magnesium alloy (comparative example 1), and the elongation in the room temperature tensile properties and the creep properties are significantly improved compared with the conventional A380 aluminum alloy (comparative example 4).

[0159] Comparative example 2 is a Mg-Al-La alloy without adding Sn element, and its room temperature tensile properties and creep properties are lower than those of the Mg-Al-La alloy with Sn element.

[0160] In comparative example 3, the added Sn element is too much, which does not meet the requirement of Sn: 0.02-0.1% specified by the present application, and the elongation in the room temperature tensile properties is significantly reduced, and the creep properties are also reduced.

[0161] In comparative examples 5 and 6, the Al or La element is lower than the requirement of Al: 4.5-6% and La: 4.5-6% specified by the present application, and the room temperature tensile strength and creep properties of the obtained alloy are not as good as those of the high strength and toughness high heat-resistant Mg-Al-RE series die-casting magnesium alloy described in the present application.

[0162] In comparative examples 7 and 8, the Al or La element is higher than the requirement of Al: 4.5-6% and La: 4.5-6% specified by the present application, and although the room temperature tensile strength and creep properties of the obtained alloy are higher, the elongation of the alloy is significantly reduced.

[0163] In addition, although the content of each element in Example 10 is within the component range specified in the present application, Al=4.60 and 0.7La+2Mn=4.76, which do not satisfy the requirement of Al-(0.7La+2Mn)>0 specified in the present application, the content of Al element in solid solution in the alloy is insufficient, and the room temperature tensile strength and creep performance of the obtained alloy are both inferior to those of the high-strength and high-ductility high-heat-resistant Mg-Al-RE series die-casting magnesium alloy described in Example 1 of the present application. This shows that when Al-(0.7La+2Mn)>0 is further preferred in the composition of each element, the room temperature tensile strength and creep performance can be further improved.

[0164] Although the content of each element in Example 11 is within the component range specified in the present application, Al=5.60 and 0.7La+2Mn=4.27, which do not satisfy the requirement of Al-(0.7La+2Mn)<1.2 specified in the present application, the content of Al element is excessive, and the excessive Al combines with Mg to generate low-melting-point Mg 17 Al 12 phase in a network distribution at the grain boundary, and the room temperature elongation and creep performance of the obtained alloy are both inferior to those of the high-strength and high-ductility high-heat-resistant Mg-Al-RE series die-casting magnesium alloy described in Example 1 of the present application. This shows that when Al-(0.7La+2Mn)<1.2 is further preferred in the composition of each element, the room temperature tensile elongation and creep performance can be further improved.

[0165] Table 1 Unit: weight percentage

[0166]

[0167]

[0168] Table 2

[0169]

[0170] The above description is only an embodiment of the present application, and does not limit the patent scope of the present application. Any equivalent structure or equivalent process transformation made by using the specification of the present application, or direct or indirect application in other related technical fields, is also included in the patent protection scope of the present application.

Claims

1. A high-toughness high-heat-resistant Mg-Al-RE series die-casting magnesium alloy, characterized in that, The weight percentage of each component in the die-casting magnesium alloy is: Al: 4.5-6%; La: 4.5-6%; Mn: 0.2-0.5%; Sn: 0.02-0.1%; Be: 0.002-0.02%; the total amount of other impurities is ≤0.3%, and the balance is Mg; In the weight percentage of each component of the die-casting magnesium alloy, the Al, La and Mn elements satisfy the following conditions: 0 < Al-(0.7La+2Mn) < 1.2; The yield strength of the die-casting magnesium alloy in the die-casting state is 170-180 MPa, the tensile strength is 270-280 MPa, the elongation is 9-15%, and the creep strain under 175℃, 100h and 90MPa is 0.125-0.215%; The preparation method of the high-strength and high-toughness Mg-Al-RE series die-casting magnesium alloy comprises the following steps: S1, material preparation: material preparation according to magnesium alloy composition; wherein, Mg, Al and Sn are prepared in the form of pure magnesium, pure aluminum and pure tin, La is prepared in the form of pure lanthanum or Mg-La or Al-La intermediate alloy, and Mn and Be are prepared in the form of intermediate alloy containing magnesium or aluminum; S2, melting: first preheat the crucible to 400-500℃, put the pure Mg ingot into the crucible, melt under protection gas or in vacuum environment, or first cover a layer of covering agent in the crucible, add pure Mg ingot until it is melted, then cover another layer of covering agent on the surface of the melt; then heat to 750-780℃ and add Al-Be or Mg-Be intermediate alloy, after the intermediate alloy is melted, keep the temperature and add pure lanthanum or Mg-La or Al-La intermediate alloy, after it is melted, cool to 720-750℃, then add Al-Mn or Mg-Mn intermediate alloy, pure aluminum and pure tin for melting; S3, refining: heat the melt of step S2 to 740-760℃, and spray powder refining deslagging treatment by blowing gas with refining agent powder into the melt; S4, casting or die-casting: after the melt after refining and slagging of step S3 reaches the casting temperature, perform the casting ingot operation or die-casting process operation, finally complete the alloy ingot production or die-casting production.

2. The method for preparing the high-ductility and high-heat-resistance Mg-Al-RE series die-casting magnesium alloy according to claim 1, characterized in that, The method comprises the following steps: S1, material preparation: material preparation according to magnesium alloy composition; wherein, Mg, Al and Sn are prepared in the form of pure magnesium, pure aluminum and pure tin, La is prepared in the form of pure lanthanum or Mg-La or Al-La intermediate alloy, and Mn and Be are prepared in the form of intermediate alloy containing magnesium or aluminum; S2, melting: first preheat the crucible to 400-500℃, put the pure Mg ingot into the crucible, melt under protection gas or in vacuum environment, or first cover a layer of covering agent in the crucible, add pure Mg ingot until it is melted, then cover another layer of covering agent on the surface of the melt; then heat to 750-780℃ and add Al-Be or Mg-Be intermediate alloy, after the intermediate alloy is melted, keep the temperature and add pure lanthanum or Mg-La or Al-La intermediate alloy, after it is melted, cool to 720-750℃, then add Al-Mn or Mg-Mn intermediate alloy, pure aluminum and pure tin for melting; S3, refining: the melt of step S2 is heated to 740-760℃, and a gas with a refining agent powder is blown into the melt to perform powder refining and slag removal treatment; S4, casting or die casting: after the melt after refining and slag removal of step S3 reaches the casting temperature, casting ingot operation or die casting process operation is performed, and finally the production of alloy ingot or die casting is completed.

3. The method of producing a high-toughness high-heat-resistant Mg-Al-RE series die-casting magnesium alloy according to claim 2, characterized by, In step S1, the prepared raw materials are preheated to 180-240℃, and the preheating and drying steps are performed.

4. The method of producing a high-toughness and high-heat-resistance Mg-Al-RE series die-casting magnesium alloy according to claim 2, characterized in that, The covering agent in step S2 is a covering agent without Na ion and solvent density <1.58 g / cm 3 The covering agent in step S2 is a covering agent without Na ion and solvent density <1.58 g / cm 3 The covering agent in step S2 is a covering agent without Na ion and solvent density <1.58 g / cm 3 The covering agent in step S2 is a covering agent without Na ion and solvent density <1.58 g / cm 3 The covering agent in step S2 is a covering agent without Na ion and solvent density <1.58 g / cm 3 The covering agent in step S2 is a covering agent without Na ion and solvent density <1.58 g / cm 3 The covering agent in step S2 is a covering agent without Na ion and solvent density <1.58 g / cm 3 The covering agent in step S2 is a covering agent without Na ion and solvent density <1.58 g / cm 3 The covering agent in step S2 is a covering agent without Na ion and solvent density <1.58 g / cm 3 The covering agent in step S2 is a covering agent without Na ion and solvent density <1.58 g / cm 3 The covering agent in step S2 is a covering agent without 5. The method of producing a high-toughness high-heat-resistance Mg-Al-RE series die-casting magnesium alloy according to claim 2, characterized by, In step S3, the refining agent is a salt flux without Na ions; The gas includes argon or chlorine or hexachloroethane gas.

6. The method of producing a high-toughness and high-heat-resistance Mg-Al-RE series die-casting magnesium alloy according to claim 2, characterized in that, In step S4, the temperature of the casting is 700-730℃.

7. The method of producing a high-toughness and high-heat-resistance Mg-Al-RE series die-casting magnesium alloy according to claim 2, characterized by, In step S4, when the die casting magnesium alloy is used for die casting production, the injection speed range is 2.5-5 m / s.

8. The method of producing a high-toughness and high-heat-resistance Mg-Al-RE series die-casting magnesium alloy according to claim 2, characterized by, In step S4, when the die casting magnesium alloy is used for die casting production, the casting pressure range is 60-150 MPa.

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