High-corrosion-resistance die-casting magnesium alloy

Abstract

The invention relates to the technical field of alloys, and discloses a high-corrosion-resistance die-casting magnesium alloy which comprises the following components in percentage by weight: 8.0-10.0% of aluminum, 0.4-0.9% of zinc, 0.15-0.4% of manganese, 0.002-0.2% of beryllium, 1.0-3.0% of calcium, 2.0-5.0% of rare-earth metal elements, less than or equal to 0.004% of iron, less than or equal to 0.2% of impurity elements and the balance of Mg. According to the alloy, Ca and RE elements are added on the basis of an AZ91D magnesium alloy, on the premise that it is guaranteed that the alloy has the good pressure casting performance, deformation and heat treatment are not needed to regulate and control the structure, good corrosion resistance and mechanical performance can be obtained, and the alloy can be used for manufacturing light-weight parts.

Description

TECHNICAL FIELD

[0001] The application relates to the alloy technical field, in particular to a high-corrosion-resistance die-casting magnesium alloy. BACKGROUND

[0002] Under the background of advocating automobile light weight, energy saving and emission reduction, using light weight materials to replace iron materials to manufacture automobile parts is a feasible way to reduce energy consumption and promote environmental protection in the automobile industry. Magnesium and magnesium alloy are considered to be one of the most promising light weight materials due to their small density, high specific strength and specific stiffness. However, the application of magnesium alloy is greatly limited due to its poor corrosion resistance, which is because: (1) Magnesium has a high electronegativity potential (-2.37V vs. NHE standard hydrogen electrode), which leads to magnesium matrix as the anode of most second phases, causing galvanic corrosion; (2) The oxidation film of magnesium is mainly composed of MgO, and its PBR (Pilling-Bedworth ratio, the volume ratio of oxide to the metal consumed to form the oxide) is less than 1, which cannot form a dense and complete protection on the surface of magnesium matrix; secondly, the corrosion product Mg(OH)2 generated by magnesium alloy in the corrosion medium also has the characteristics of loose and porous, which is easy to be penetrated by chloride ions, further losing the protection effect.

[0003] In view of the poor corrosion resistance of magnesium alloy, the patent with publication number CN113981286B discloses a kind of corrosion-resistant high strength plastic magnesium alloy and its preparation method, by adding Al, Sn, Ca, Mn, RE and other elements, and adopting sub-quick inner solidification, pre-rolling, gradient solid solution, cross rolling, stress relief annealing and other steps, the size and distribution of second phase in magnesium alloy are controlled, so as to prepare a stable and dense corrosion product film of high strength plastic corrosion-resistant magnesium alloy. The patent with publication number CN116926391A discloses a kind of high-brightness high-corrosion-resistance magnesium alloy and its preparation method, by adding Al, Y and other elements, and adopting extrusion heating treatment method to control the magnesium alloy organization, a large number of fine nano precipitated phase is obtained, and the oxidation corrosion of magnesium matrix is promoted to form a dense corrosion product film. It is not difficult to see that the above-mentioned patent needs to prepare ingot first, and adopts deformation + heat treatment method to obtain magnesium alloy with good corrosion resistance, the process is relatively complicated, and subsequent CNC machining method is still needed to obtain the final part, which will increase the production cost.

[0004] Die casting has the advantages of one-time forming, high dimensional accuracy, etc. If die casting is used, the processing cost can be greatly reduced and the production cycle can be shortened. However, the wall thickness of the die casting is generally thin, and it is easy to bulge and deform during heat treatment, resulting in scrap of the parts, so the above heat treatment process cannot be used to regulate the magnesium alloy organization to enhance its corrosion resistance. AZ91D belongs to a representative die-casting magnesium alloy, and the alloy has low cost, medium mechanical properties, good fluidity and small tendency of hot cracking, and is the most common die-casting magnesium alloy. However, the corrosion resistance of AZ91D magnesium alloy is insufficient, and its application is limited to a certain extent.

[0005] It can be seen that the existing magnesium alloy material has contradictions in corrosion resistance, processing cycle and cost. It is necessary to develop a die-casting magnesium alloy material that can meet the die-casting forming and has good corrosion resistance. SUMMARY

[0006] In order to solve the problems mentioned in the background art, the purpose of the present application is to provide a high corrosion-resistant die-casting magnesium alloy, which solves the problem that the existing magnesium alloy cannot simultaneously meet the die-casting forming and has good corrosion resistance, under the premise of not adding expensive rare earth elements, by using a low-cost alloy formula.

[0007] The purpose of the present application can be achieved by the following technical solutions: A high corrosion-resistant die-casting magnesium alloy, comprising the following components measured by mass percentage: Aluminum 8.0-10.0%, zinc 0.4-0.9%, manganese 0.15-0.4%, beryllium 0.002-0.2%, calcium 1.0-3.0%, rare earth metal elements 2.0-5.0%, iron ≤0.004%, total amount of impurity elements ≤0.2%, and the balance being magnesium.

[0008] As a further scheme of the present application, the rare earth metal elements are at least one of lanthanum or cerium.

[0009] As a further scheme of the present application, the preparation method of the high corrosion-resistant die-casting magnesium alloy comprises the following steps: Step S1, using pure aluminum ingot, pure magnesium ingot, pure zinc ingot, Mn, Ca, Be intermediate alloy containing Mg or Al, and rare earth metal as raw materials, and the raw materials are weighed and mixed according to the weight percentage of each raw material; Step S2, the raw material roasted in step S1 is preheated, the preheating temperature is 180-240℃, then the crucible is heated to 400-500℃, the pure magnesium ingot is put into the crucible, the melting is carried out under the protection of the protective gas or in a vacuum environment, or a layer of covering agent is first covered in the crucible, the pure magnesium ingot is added and melted, then a layer of covering agent is covered on the surface of the melt; then the temperature is increased to 750-780℃, the aluminum-boron intermediate alloy is added, after the intermediate alloy is melted, the rare earth metal is added, after the alloy is completely melted, the temperature is decreased to 720-750℃, then the magnesium-calcium intermediate alloy, pure Al and pure Zn are added to melt to obtain a melt; Step S3: the melt obtained in step S2 is heated to 740-760℃, and a refining agent powder is added to the melt for refining and slag removal treatment; Step S4: the melt after refining and slag removal in step S3 is die cast into a die casting.

[0010] As a further scheme of the application, in step S1, the rare earth metal is any one of pure lanthanum, pure cerium, magnesium-lanthanum intermediate alloy, magnesium-cerium intermediate alloy, aluminum-lanthanum intermediate alloy or aluminum-cerium intermediate alloy.

[0011] In the above technical scheme, the added Ca element can be solid-soluted in Mg 17 Al 12 In the eutectic phase and the Mg matrix, the Ca solid-soluted in the Mg 17 Al 12 Eutectic phase can improve the strength of the Mg 17 Al 12 Eutectic phase, thereby improving the strength of the alloy; the Ca solid-soluted in the Mg matrix can improve the potential of the Mg matrix, thereby reducing the potential difference between the Mg matrix and the Mg 17 Al 12 Eutectic phase, thereby improving the corrosion resistance of the alloy. In addition, the Ca element has strong activity and can combine with carbon dioxide in the atmosphere to generate calcium compounds and enrich in the corrosion products of the magnesium alloy, thereby filling the gaps of the oxide film generated in the corrosion environment of Mg, and further improving the protective property of the film layer and the corrosion resistance of the alloy. However, research shows that a large amount of Ca element will seriously reduce the plasticity of the alloy, so the addition amount of Ca element is 1.0-3.0%.

[0012] The added rare earth element (RE) can form an AlRE phase with the Al element in the alloy. On the one hand, the existence of the AlRE phase can consume the Al element in the alloy, thereby reducing the proportion of the Mg 17 Al 12 Eutectic phase, on the other hand, the AlRE phase can hinder the growth of the Mg 17 Al 12 Eutectic phase, thereby refining the Mg 17 Al 12Eutectic phase. In this way, the mechanical properties of the alloy are improved. At the same time, due to the micro-electric corrosion effect of the magnesium alloy being affected by the area of the cathode phase, when Mg 17 Al 12 When the proportion of eutectic phase is reduced and refined, Mg 17 Al 12 The micro-electric corrosion effect between the eutectic phase and the magnesium matrix is weakened, which can effectively reduce the electric corrosion damage of the alloy. In addition, due to the strong activity of RE elements, the gaps in the oxide film generated in the corrosion environment of Mg can be filled, so that the oxide film becomes dense, and the corrosion resistance of the alloy is improved. However, excessive addition of RE will increase the cost and new large RE-containing phases will appear, which will increase the micro-electric corrosion effect and reduce the mechanical properties, so the addition amount of RE elements is 2.0-5.0%.

[0013] The currently used commercial magnesium alloy such as AZ91D has a strong micro-electric corrosion effect between the coarse network second phase organization and the magnesium matrix, which is easy to cause local corrosion, and cannot form an effective corrosion product film to protect the matrix. By refining Mg 17 Al 12 Phase and AlRE phase, thereby forming a large number of fine second phases, which can form a weak micro-electric corrosion pair with the surrounding magnesium matrix, produce a corrosion oxide film product, and under the assistance of the gap filling effect of Ca elements and RE elements, a dense corrosion product film layer is quickly formed on the surface of the magnesium matrix, thereby realizing the protection of the magnesium matrix and improving the corrosion resistance of the alloy.

[0014] As a further scheme of the present application, in step S2, the protective gas is a mixed gas of N2+SF6 or a mixed gas of CO2+SF6 or pure SF6 gas.

[0015] As a further scheme of the present application, in step S2, the covering agent is a salt flux without sodium ions and with a density value less than 1.58g / cm 3 , which can avoid the oxidation of the alloy melt during the smelting process and ensure the quality of the melt.

[0016] As a further scheme of the present application, in step S4, during the die casting process, the pouring temperature is 680-720℃, the injection speed is 2-5m / s, and the casting pressure is 80-160MPa.

[0017] The beneficial effects of the present application are: (1) The high corrosion-resistant die-casting magnesium alloy of the present application is based on the conventional AZ91D magnesium alloy, using conventional alloying elements Al, Zn and Mn as basic elements, and adding Ca and RE elements to ensure that the alloy has excellent casting performance, and has better corrosion resistance than the traditional AD91D.

[0018] (2) Through the combination of alloy composition design and die casting process, the high cooling rate of die casting is used to make the elements solid solution into the matrix and limit the growth of the second phase, so that good mechanical properties are obtained without special deformation processing and heat treatment.

[0019] (3) The high corrosion-resistant die-casting magnesium alloy described in the application is obtained by adding Ca, RE and other elements to the conventional commercial AZ91D magnesium alloy. The raw alloy is convenient to obtain, and the rare earth used is a cheap rare earth element, so the alloy cost is low.

[0020] Of course, implementing any product of the present application does not necessarily require achieving all the advantages described above at the same time. BRIEF DESCRIPTION OF DRAWINGS

[0021] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following will briefly introduce the drawings needed for the description of the embodiments. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor.

[0022] Figure 1 SEM images of the microstructure of the castings obtained in Examples 1, 2 and Comparative Examples 1, 2 and 3; Figure 2 Macroscopic morphology of the magnesium alloy prepared in Example 1, Example 2, commercial AZ91D magnesium alloy and ADC12 aluminum alloy after salt spray test. DETAILED DESCRIPTION

[0023] The technical solutions in the embodiments of the present application will be described clearly and completely in the following with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only some embodiments of the present application, not all. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor are within the scope of protection of the present application.

[0024] Example 1 A preparation method of a high corrosion-resistant die-casting magnesium alloy comprises the following steps: Step S1, taking pure Al ingot, pure Mg ingot, pure Zn ingot, Al-10Mn, Al-5Be, Mg-30Ce, Mg-30Ca intermediate alloy as raw materials, the raw materials are weighed according to the weight percentage, and each raw material is preheated to 200℃ for drying treatment; Step S2, preheat the crucible to 150℃, then heat the crucible to 500℃, put the pure Mg ingot into the crucible, pass in the CO2+SF6 mixed gas, completely melt under the protection of the mixed protective gas of CO2 and SF6, then heat up to 760℃, add Al-5Be and Mg-30Ce intermediate alloy to completely melt, cool down to 740℃, add pure Al ingot, pure Zn ingot, Al-10Mn, Mg-30Ca intermediate alloy, fully stir after complete melting, stand still and conduct pre-furnace component analysis, detect the component content of the alloy melt, supplement or dilute the melt with content deviation to make the component reach the designed magnesium alloy component range, and form the melt; Step S3: heat the melt to 750℃, add 0.8% of the total weight of the melt of the refining agent powder to the melt for refining and slag removal treatment; Step S4: after refining, the melt stands still for 5min, and pre-furnace component analysis test is conducted again, and after the component is qualified, high-pressure casting production is conducted at 700℃, the injection speed is 4.0m / s, and the casting pressure is 100MPa.

[0025] Example 2 A preparation method of a high-corrosion-resistant die-casting magnesium alloy includes the following steps: Step S1, take pure Al ingot, pure Mg ingot, pure Zn ingot, Al-10Mn, Al-5Be, Mg-30La, and Mg-30Ca intermediate alloy as raw materials, and dry the raw materials by preheating to 200℃; Step S2, preheat the crucible to 150℃, then heat the crucible to 500℃, put the pure Mg ingot into the crucible, pass in the CO2+SF6 mixed gas, completely melt under the protection of the mixed protective gas of CO2 and SF6, then heat up to 760℃, add Al-5Be and Mg-30La intermediate alloy to completely melt, cool down to 740℃, add pure Al, pure Zn, Al-10Mn, and Mg-30Ca intermediate alloy, fully stir after complete melting, stand still and conduct pre-furnace component analysis, detect the component content of the alloy melt, and supplement or dilute the melt with content deviation to make the component reach the designed magnesium alloy component range; Step S3, heat the melt to 730℃, add 0.8% of the total weight of the melt of the refining agent powder to the melt, and then conduct slag removal treatment; After refining, the melt stands still for 5min, and pre-furnace component analysis test is conducted again, and after the component is qualified, high-pressure casting production is conducted at 700℃, the injection speed is 3.8m / s, and the casting pressure is 102MPa.

[0026] Example 3 A preparation method of a high-corrosion-resistant die-casting magnesium alloy includes the following steps: Step S1, select pure Al ingot, pure Mg ingot, pure Zn ingot, Al-10Mn, Al-5Be, Mg-30Ce, Mg-30Ca intermediate alloy as raw material, preheat the raw material to 200℃ drying treatment; Step S2, preheat the crucible to 150℃, then heat the crucible to 500℃, put the pure Mg ingot into the crucible, and blow in the mixed gas of CO2+SF6, completely melt under the protection of the mixed protective gas of CO2 and SF6, then heat to 760℃, add Al-5Be and Mg-30Ce intermediate alloy to completely melt, cool to 730℃, add pure aluminum, pure zinc, Al-10Mn, Mg-30Ca intermediate alloy, fully stir after completely melting, stand and carry out pre-furnace component analysis, detect the component content of the alloy melt, supplement or dilute the melt with content deviation to make the component reach the designed magnesium alloy component range; Step S3, heat the melt to 740℃, add 0.8% of the total weight of the melt refining agent powder to the melt, and then perform slag removal treatment; Step S4, after refining, the melt is placed for 5min, and the pre-furnace component analysis test is carried out again, and after the component is qualified, high pressure casting production is carried out at 700℃, the injection speed is 3.9m / s, and the casting pressure is 101MPa.

[0027] Example 4 A preparation method of a high corrosion-resistant die-casting magnesium alloy comprises the following steps: Step S1, select pure Al ingot, pure Mg ingot, pure Zn ingot, Al-10Mn, Al-5Be, Mg-30Ce, Mg-30Ca intermediate alloy as raw material, preheat the raw material to 200℃ drying treatment; Step S2, preheat the crucible to 150℃, then heat the crucible to 500℃, put the pure Mg ingot into the crucible, and blow in the mixed gas of CO2+SF6, completely melt under the protection of the mixed protective gas of CO2 and SF6, then heat to 760℃, add Al-5Be and Mg-30Ce intermediate alloy to completely melt, cool to 730℃, add pure aluminum, pure zinc, Al-10Mn, Mg-30Ca intermediate alloy, fully stir after completely melting, stand and carry out pre-furnace component analysis, detect the component content of the alloy melt, supplement or dilute the melt with content deviation to make the component reach the designed magnesium alloy component range; Step S3, heat the melt to 750℃, add 0.8% of the total weight of the melt refining agent powder to the melt, and then perform slag removal treatment; Step S4, after refining, the melt is placed for 5min, and the pre-furnace component analysis test is carried out again, and after the component is qualified, high pressure casting production is carried out at 700℃, the injection speed is 4.1m / s, and the casting pressure is 106MPa.

[0028] Comparative Example 1 A preparation method of a high corrosion-resistant die-casting magnesium alloy comprises the following steps: Step S1, selecting pure Al ingot, pure Mg ingot, pure Zn ingot, Al-10Mn, Al-5Be intermediate alloy as raw materials, and preheating the raw materials to 200 DEG C for drying treatment; Step S2, preheating the crucible to 150 DEG C, then heating the crucible to 500 DEG C, putting the pure Mg ingot into the crucible, and introducing CO2+SF6 mixed gas, completely melting under the protection of the mixed protective gas of CO2 and SF6, then heating to 740 DEG C, adding Al-5Be intermediate alloy, pure aluminum, pure zinc and Al-10Mn intermediate alloy, fully melting, fully stirring, standing and carrying out pre-furnace component analysis, detecting the component content of the alloy melt, and supplementing or diluting the melt with content deviation to make the component reach the designed magnesium alloy component range; Step S3, heating the melt to 750 DEG C, adding 0.8% of the total weight of the melt of refining agent powder into the melt, and then carrying out slag removal treatment; Step S4, standing the refined melt for 5 min, and then carrying out pre-furnace component analysis test, and after the component is qualified, carrying out high-pressure casting production at 700-710 DEG C, the injection speed is 4.0 m / s, and the casting pressure is 100 MPa.

[0029] Comparative Example 2 A preparation method of a high corrosion-resistant die-casting magnesium alloy comprises the following steps: Step S1, selecting pure Al ingot, pure Mg ingot, pure Zn ingot, Al-10Mn, Al-5Be, Mg-30La, Mg-30Ca intermediate alloy as raw materials, and preheating the raw materials to 200 DEG C for drying treatment; Step S2, preheating the crucible to 150 DEG C, then heating the crucible to 500 DEG C, putting the pure Mg ingot into the crucible, and introducing CO2+SF6 mixed gas, completely melting under the protection of the mixed protective gas of CO2 and SF6, then heating to 760 DEG C, adding Al-5Be and Mg-30La intermediate alloy to completely melt, cooling to 740 DEG C, adding pure aluminum, pure zinc, Al-10Mn, Mg-30Ca intermediate alloy, fully melting, fully stirring, standing and carrying out pre-furnace component analysis, detecting the component content of the alloy melt, and supplementing or diluting the melt with content deviation to make the component reach the designed magnesium alloy component range; Step S3, heating the melt to 750 DEG C, adding 0.8% of the total weight of the melt of refining agent powder into the melt, and then carrying out slag removal treatment; Step S4, the refined melt is left for 5 min, and the pre-furnace component analysis test is performed again. After the components are qualified, high-pressure casting is performed at 700℃, the injection speed is 4.0 m / s, and the casting pressure is 101 MPa.

[0030] Comparative Example 3 A preparation method of a high-corrosion-resistant die-casting magnesium alloy includes the following steps: Step S1, pure Al ingot, pure Mg ingot, pure Zn ingot, Al-10Mn, Al-5Be, Mg-30Ce, and Mg-30Ca intermediate alloys are selected as raw materials, and the raw materials are preheated to 200℃ for drying treatment; Step S2, the crucible is preheated to 150℃, then the crucible is heated to 500℃, the pure Mg ingot is put into the crucible, CO2+SF6 mixed gas is introduced, 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 760℃, the Al-5Be and Mg-30Ce intermediate alloys are added until they are completely melted. The temperature is decreased to 740℃, the pure Al, pure Zn, Al-10Mn, and Mg-30Ca intermediate alloys are added, and after complete melting, the melt is fully stirred. The melt is 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. Step S3, the melt is heated to 750℃, and then 0.8% of the total weight of the melt is added as a refining agent powder, and then the slag is removed; Step S4, the refined melt is left for 5 min, and the pre-furnace component analysis test is performed again. After the components are qualified, high-pressure casting is performed at 700℃, the injection speed is 4.0 m / s, and the casting pressure is 101 MPa.

[0031] The refining agent powder in the above examples and comparative examples is purchased from Zhangjiagang Haohua Light Alloy Material Co., Ltd., and the brand is JDMJ.

[0032] The alloy components of each example and comparative example are summarized in Table 1.

[0033] Table 1 Summary of alloy components of each example and comparative example (mass percentage)

[0034] Figure 1 SEM observation results of the microstructure of the castings obtained in Examples 1, 2 and Comparative Examples 1, 2, and 3 are shown. The SEM results show that no obvious Ca-rich phase is found in the microstructure of the castings with added Ca element, and the Ca element is dissolved in the Mg17Al12 eutectic phase and the α-Mg matrix. The RE added in the castings mainly exists in the form of Al11RE3 phase. The microstructure is as follows: Figure 1The microstructure of the magnesium alloy of the present application is shown in (1) and (2) of the figure, and the microstructure of the magnesium alloy of the comparative example is shown in (3) and (4) of the figure. The microstructure comparison results show that the Ca and RE elements have important influence on the microstructure.

[0035] Test Example a. The magnesium alloys in the examples and the comparative examples were subjected to mechanical property test, and the results are shown in Table 2: Table 2 - Mechanical property test results

[0036] It can be seen from the test results that changing the type of rare earth element without changing its content has little influence on the mechanical property, as shown in Example 1 and Example 2. It can be seen from the comparison between Example 1-4 and Comparative Example 1 and Comparative Example 3 that changing the content of Ca and RE elements has important influence on the mechanical property of the alloy.

[0037] b. The magnesium alloys in the examples and the comparative examples were subjected to salt spray test, and the salt spray test conditions were 5% NaCl, neutral salt spray test, 7x24h, die-cast bare plate (without any surface treatment), and the specific test results are shown in Table 3: Table 3 - Salt spray test results

[0038] Figure 2 The macroscopic morphology of the high corrosion-resistant die-cast magnesium alloy (Example 1 and Example 2), the commercial AZ91D magnesium alloy and the ADC12 aluminum alloy castings after salt spray test is shown. It can be seen that the ADC12 aluminum alloy has more corrosion products on the surface; the patent alloy has a small amount of corrosion products on the surface, and can still retain a large area of bright surface, but the commercial AZ91D has more corrosion products on the surface.

[0039] It can be seen from the test results that the corrosion rate of the magnesium alloy prepared in the examples of the present application is slightly worse than that of the ADC12 aluminum alloy, but better than that of the conventional commercial AZ91D magnesium alloy. At the same time, it can be shown that when the Ca element and the RE element are insufficient, the corrosion rate of the alloy increases.

[0040] In summary, the alloy of the present application adds Ca and RE elements on the basis of the AZ91D magnesium alloy, and under the premise of ensuring that the alloy has good die-casting performance, the corrosion resistance of the alloy can be improved without deformation and heat treatment, and the alloy can be used for the manufacture of lightweight parts.

[0041] The principles and implementations of the present application are described herein with specific examples, and the above examples are only used to help understand the method of the present application and its core idea, including the best mode, and also enable any person skilled in the art to practice the present application, including manufacturing and using any device or system, and implementing any combined method. It should be noted that, for those skilled in the art, some improvements and modifications can be made to the present application without departing from the principles of the present application, and these improvements and modifications also fall within the protection scope of the claims of the present application. The scope of patent protection of the present application is defined by the claims, and can include other embodiments that can be conceived by those skilled in the art. If these other embodiments have structural elements similar to the literal expression of the claims, or if they include equivalent structural elements that are not substantially different from the literal expression of the claims, then these other embodiments should also be included within the scope of the claims.

[0042] The above examples are only used to illustrate the technical solutions of the present application, and not to limit it; although the present application has been described in detail with reference to the foregoing examples, those skilled in the art should understand that they can still modify the technical solutions recorded in the foregoing examples, or make equivalent substitutions for part of the technical features; and these modifications or substitutions will not cause the essence of the corresponding technical solution to deviate from the spirit and scope of the technical solutions of the embodiments of the present application.

Claims

1. A high corrosion resistant die-cast magnesium alloy, characterized in that: Includes the following ingredients measured in percentage by mass: Aluminum 8.0~10.0%, zinc 0.4~0.9%, manganese 0.15~0.4%, beryllium 0.002~0.2%, calcium 1.0~3.0%, rare earth metal elements 2.0~5.0%, iron ≤0.004%, total impurity elements ≤0.2%, balance magnesium.

2. The high corrosion-resistant die-cast magnesium alloy according to claim 1, characterized in that: The rare earth metal element is at least one of lanthanum and cerium.

3. The high corrosion resistant die-cast magnesium alloy according to claim 1, characterized in that: The preparation method of the high corrosion-resistant die-cast magnesium alloy comprises the following steps: Step S1: using pure aluminum ingots, pure magnesium ingots, pure zinc ingots, master alloys of Mn, Ca, Be containing Mg or Al, and rare earth metals as raw materials, and preparing the ingredients according to the mass percentage of each raw material; Step S2: preheating the raw materials in step S1 to a temperature of 180-240° C., then heating the crucible to 400-500° C., placing a pure magnesium ingot in the crucible, and melting it under a protective gas or in a vacuum environment, or first covering the crucible with a layer of covering agent, adding the pure magnesium ingot, and then covering the melt surface with another layer of covering agent after it melts; then heating the crucible to 750-780° C., adding an aluminum-beryllium master alloy, and after the master alloy melts, adding a rare earth metal. After the alloy is completely melted, cooling the crucible to 720-750° C., then adding a magnesium-calcium master alloy, pure Al, and pure Zn to melt to obtain a melt; Step S3: heating the melt obtained in step S2 to 740-760°C, adding refining agent powder to the melt for refining and slag removal; Step S4: die-casting the melt after refining and deslagging in step S3 into a die-casting part.

4. The high corrosion resistant die-cast magnesium alloy according to claim 3, characterized in that: In step S1, the rare earth metal is any one of pure lanthanum, pure cerium, magnesium-lanthanum master alloy, magnesium-cerium master alloy, aluminum-lanthanum master alloy or aluminum-cerium master alloy.

5. The high corrosion resistant die-cast magnesium alloy according to claim 3, characterized in that: In step S2, the protective gas is a mixed gas of N2+SF6 or a mixed gas of CO2+SF6 or pure SF6 gas.

6. The high corrosion resistant die-cast magnesium alloy according to claim 3, characterized in that: In step S2, the covering agent does not contain sodium ions and has a density value less than 1.58 g / cm 3 salt flux.

7. The high corrosion resistant die-cast magnesium alloy according to claim 3, characterized in that: In step S4, during the die-casting process, the pouring temperature is 680-720°C, the injection speed is 2-5 m / s, and the casting pressure is 80-160 MPa.

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