A die-cast magnesium alloy material, its preparation method, and an automotive structural component

Abstract

The present disclosure relates to a die-cast magnesium alloy material, a preparation method thereof, and an automotive structural member. The die-cast magnesium alloy comprises: 5-10% by weight of Al, 0.4-1.0% by weight of Zn, 0.15-0.6% by weight of Mn, 0.01-1.0% by weight of Ca, 5-30 ppm of Be, Si below 0.08% by weight, Fe below 0.004% by weight, Cu below 0.02% by weight, Ni below 0.001% by weight, 0.001-0.1% by weight of Hf, impurities below 0.01% by weight, and the balance of Mg. The die-cast magnesium alloy material provided by the present disclosure can take into account cost, high strength, and corrosion resistance at the same time; and can meet the requirements for the body performance of automotive structural members.

Description

Technical Field

[0001] The present disclosure relates to the technical field of die-cast magnesium alloys, and specifically, to a die-cast magnesium alloy material, a preparation method thereof, and an automotive structural component. Background Art

[0002] With the wide adoption of lightweight automotive components, magnesium alloys are applied in many fields of the automotive industry. Currently, most magnesium alloys are die-cast. The most widely used traditional die-cast magnesium alloys are AZ series (such as AZ91D) and AM series (such as AM50, AM60) alloys. However, the eutectic phase of Mg 17 Al 12 in the AZ series and AM series alloys has a relatively low melting point and is prone to softening at high temperatures, resulting in poor high-temperature mechanical properties and creep resistance of the AZ series and AM series alloys. And the AX series alloys (such as AX53, AXJ530) with better heat resistance in traditional die-cast magnesium alloys have a large hot cracking tendency and poor part formability. Therefore, it is difficult for traditional die-cast magnesium alloys to balance high strength, heat resistance, and good formability, resulting in poor application of magnesium alloys in high-strength and heat-resistant components. Therefore, the existing die-cast magnesium alloy materials cannot simultaneously solve the technical problems of cost, high strength, and corrosion resistance, making die-cast magnesium alloys unable to meet the requirements of components such as new energy vehicle motor housings with high strength and heat resistance requirements. There is an urgent need to develop new high-strength and high-heat-resistant die-cast magnesium alloys to expand the application of die-cast magnesium alloys in high-strength and heat-resistant components.

[0003] In addition, more attention should be paid to the bulk properties that magnesium alloy materials can achieve in structural components. However, the performance requirements currently met by die-cast magnesium alloy materials are not based on bulk sampling. Summary of the Invention

[0004] The purpose of the present disclosure is to provide a die-cast magnesium alloy material, a preparation method thereof, and an automotive structural component, which can simultaneously balance cost, high strength, and corrosion resistance; and can meet the bulk property requirements of automotive structural components.

[0005] To achieve the above purpose, in the first aspect of the present disclosure, a die-cast magnesium alloy material is provided. Based on the total weight of the die-cast magnesium alloy material, the die-cast magnesium alloy includes: 5-10% by weight of Al, 0.4-1.0% by weight of Zn, 0.15-0.6% by weight of Mn, 0.01-1.0% by weight of Ca, 5-30 ppm of Be, Si below 0.08% by weight, Fe below 0.004% by weight, Cu below 0.02% by weight, Ni below 0.001% by weight, 0.001-0.1% by weight of Hf, impurities below 0.01% by weight, and the balance of Mg.

[0006] Optionally, the die-cast magnesium alloy comprises: 8.5-9.5 wt% of Al, 0.5-0.8 wt% of Zn, 0.15-0.6 wt% of Mn, 0.3-0.7 wt% of Ca, 5-30 ppm of Be, Si below 0.08 wt%, Fe below 0.004 wt%, Cu below 0.02 wt%, Ni below 0.001 wt%, 0.04-0.08 wt% of Hf, impurities below 0.01 wt% and the balance of Mg.

[0007] Optionally, in the die-cast magnesium alloy material, the content ratio of Hf / Al ≥ 45 / 10000.

[0008] Optionally, the bulk properties of the die-cast magnesium alloy material include: yield strength above 140 MPa, tensile strength above 230 MPa, and elongation above 1.5%.

[0009] The second aspect of the present disclosure provides a method for preparing a die-cast magnesium alloy material, comprising the following steps:

[0010] S1. Under a protective atmosphere, melting the alloy raw material mixture in a melting furnace to obtain a first alloy melt; based on the total weight of the alloy raw material mixture, the alloy raw material mixture comprises: 5-10 wt% of Al, 0.4-1.0 wt% of Zn, 0.15-0.6 wt% of Mn, 0.01-1.0 wt% of Ca, 5-30 ppm of Be, Si below 0.08 wt%, Fe below 0.004 wt%, Cu below 0.02 wt%, Ni below 0.001 wt%, 0.001-0.1 wt% of Hf, impurities below 0.01 wt% and the balance of Mg;

[0011] S2. Refining and slag skimming the first alloy melt to obtain a second alloy melt;

[0012] S3. Die-casting the second alloy melt.

[0013] Optionally, in step S1, Mg, Al, and Zn in the alloy raw material mixture are prepared in the form of pure magnesium, pure aluminum, and pure zinc; Mn and Ca are prepared in the form of Mg-containing Mn master alloy and Mg-containing Ca master alloy, and Hf is prepared in the form of Al-10.45Hf master alloy;

[0014] Step S1 includes:

[0015] Under a protective atmosphere, melting the pure magnesium in the alloy raw material mixture in a melting furnace to obtain a magnesium melt; adding other alloy raw materials except pure magnesium to the magnesium melt and carrying out heat preservation melting to obtain the first alloy melt.

[0016] Optionally, the conditions for melting the pure magnesium include: a temperature of 680 - 745 °C and a time of 1 - 2 h;

[0017] The conditions for holding and melting include: a temperature above 740 °C and a time above 30 min;

[0018] The protective atmosphere includes one or more of N 2 , CO 2 and SF 6 in it.

[0019] Optionally, in step S2, the conditions for the refining treatment include: a temperature of 720 - 740 °C and a standing time of 10 - 15 min;

[0020] In step S3, the conditions for the die - casting treatment include: a die - casting temperature of 700 - 730 °C, an injection speed of 2 - 5 m / s, and a casting pressure of 80 - 160 MPa.

[0021] The third aspect of the present disclosure provides a die - cast magnesium alloy material prepared by the method according to the second aspect of the present disclosure.

[0022] The fourth aspect of the present disclosure provides an automotive structural component including the die - cast magnesium alloy material described in the first aspect or the third aspect of the present disclosure.

[0023] Through the above - mentioned technical solutions, the present disclosure provides a die - cast magnesium alloy material, its preparation method, and an automotive structural component. The die - cast magnesium alloy realizes the effects of modification and fine - grain strengthening by alloying control and AI model iteration, by exploring the content ranges of Al, Zn, Mn, as well as the addition of Hf and Ca, and the ratio content of Hf and Al elements, to obtain a material with the best comprehensive strength and elongation rate suitable for motor housings; and the performance of the die - cast magnesium alloy of the present disclosure has been fully verified on the motor housing mold. At the position of the motor cylinder wall, which is the place where the motor requires the highest strength, in - situ sampling can be achieved and the in - situ performance requirements can be met; this die - cast magnesium alloy can also achieve the performance after heat treatment of other conventional alloys without heat treatment, which can save costs and reduce carbon emissions, and also has great benefits for the dimensional accuracy of parts; the corrosion resistance of the die - cast magnesium alloy material has also been improved to a certain extent (the corrosion performance can reach the level equivalent to ADC12), and it is more suitable for the application environment where the electric drive is located on the chassis.

[0024] Other features and advantages of the present disclosure will be described in detail in the subsequent specific implementation section. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] The accompanying drawings are used to provide a further understanding of the present disclosure and form a part of the specification. Together with the following specific embodiments, they are used to explain the present disclosure, but do not constitute a limitation to the present disclosure. In the accompanying drawings:

[0026] Figure 1 It shows a process flow chart of the method for preparing a die-cast magnesium alloy material provided by the present disclosure;

[0027] Figure 2 It shows an electron microscope photograph of the cast magnesium alloy material obtained in Example 1 of the present disclosure;

[0028] Figure 3 It shows a motor housing and a sampling position for in-situ sampling of the die-cast magnesium alloy material provided by the present disclosure.

[0029] Description of reference numerals

[0030] a - eutectic phase, b - Hf strengthening phase, c - α-Mg phase, 1 - in-situ sampling position. Specific embodiments

[0031] The following provides a detailed description of the specific embodiments of the present disclosure in conjunction with the accompanying drawings. It should be understood that the specific embodiments described herein are only used to illustrate and explain the present disclosure, and are not used to limit the present disclosure.

[0032] The inventors of the present disclosure found that the currently developed magnesium alloy materials are developed based on the properties of tensile test bars, which have no reference significance for the actual product development process. They do not represent the performance requirements of the actual application conditions, and the performance of the test bars / plate die specimens will further decay in the actual product in-situ sampling performance. Moreover, the degree of decay will also vary depending on the sampling position of the housing and the process parameters. Therefore, this performance cannot be used as the input for product development. Therefore, aiming at the problem that the current die-cast magnesium alloys cannot meet the requirements of parts with high strength and heat resistance such as automotive motor housings, and there is no corresponding in-situ performance data, the present disclosure developed a high-strength die-cast magnesium alloy by controlling the content of each element in the alloy, which can achieve high strength and elongation in the performance of the electric drive housing body under the condition of heat treatment-free, so as to expand the application of die-cast magnesium alloys in high-strength and heat-resistant parts.

[0033] In the first aspect of the present disclosure, a die-cast magnesium alloy material is provided. Based on the total weight of the die-cast magnesium alloy material, the die-cast magnesium alloy comprises: 5-10 wt% of Al (aluminum), 0.4-1.0 wt% of Zn (zinc), 0.15-0.6 wt% of Mn (manganese), 0.01-1.0 wt% of Ca (calcium), 5-30 ppm of Be (beryllium), Si (silicon) of 0.08 wt% or less, Fe (iron) of 0.004 wt% or less, Cu (copper) of 0.02 wt% or less, Ni (nickel) of 0.001 wt% or less, 0.001-0.1 wt% of Hf (hafnium), impurities of 0.01 wt% or less, and the balance of Mg (magnesium).

[0034] The present disclosure provides a die-cast magnesium alloy material. Through alloying control and AI model iteration, by exploring the content ranges of Al, Zn, and Mn, as well as the addition of Hf and Ca, and the ratio content of Hf and Al elements, the effects of modification and fine grain strengthening are achieved, which have a significant impact on the microstructure and mechanical properties of the alloy, and a material with the best comprehensive strength and elongation rate suitable for the motor housing is obtained; moreover, the performance of the die-cast magnesium alloy of the present disclosure has been fully verified on the motor housing mold. At the position of the motor barrel wall, where the motor requires the highest strength, in-situ sampling can be achieved and the in-situ performance requirements can be met; the corrosion resistance of the die-cast magnesium alloy material has also been improved to a certain extent (the corrosion performance can reach the level equivalent to ADC12), making it more suitable for the application environment where the electric drive is located on the chassis.

[0035] According to the present disclosure, the Ca element in the die-cast magnesium alloy is dissolved in Mg 17 Al 12 phase, which improves the strength, hardness, melting point, and thermal stability of the Mg 17 Al 12 phase, can improve the strength and heat resistance of the magnesium alloy, thereby improving the high-temperature heat resistance of the alloy.

[0036] According to the present disclosure, Hf in the die-cast magnesium alloy mainly exists in the form of undissolved particles and dissolved Hf solute. The strong compositional supercooling caused by the Hf solute will prevent the continuous growth of α-Mg dendrites, realizing grain refinement. At the same time, the undissolved Hf particles can serve as heterogeneous nucleation sites to promote nucleation and further limit grain growth.

[0037] In a preferred embodiment, based on the total weight of the die-cast magnesium alloy material, the die-cast magnesium alloy comprises: 8.5-9.5% by weight of Al, 0.5-0.8% by weight of Zn, 0.15-0.6% by weight of Mn, 0.3-0.7% by weight of Ca, 5-30 ppm of Be, Si below 0.08% by weight, Fe below 0.004% by weight, Cu below 0.02% by weight, Ni below 0.001% by weight, 0.04-0.08% by weight of Hf, impurities below 0.01% by weight and the balance of Mg. The die-cast magnesium alloy with the component contents provided by this embodiment can have more excellent strength and elongation.

[0038] The inventors of the present disclosure also found that the content ratio of Hf / Al in the die-cast magnesium alloy material also has an impact on the performance of the die-cast magnesium alloy.

[0039] In a preferred embodiment, in the die-cast magnesium alloy material, the content ratio of Hf / Al ≥ 45 / 10000, preferably the content ratio of Hf / Al ≥ 50 / 10000. When the content ratio of Hf / Al is within the range of this embodiment, especially within the preferred range, the bulk properties of the die-cast magnesium alloy material can be further improved.

[0040] In a specific embodiment, the bulk properties of the die-cast magnesium alloy material include: the yield strength is above 140 MPa, the tensile strength is above 230 MPa, and the elongation is above 1.5%; preferably, the yield strength is above 150 MPa, the tensile strength is above 250 MPa, and the elongation is above 1.5%. In the present disclosure, the bulk properties of the die-cast magnesium alloy material refer to: taking a qualified tensile specimen from the actual application part and performing a tensile test to obtain the strength properties on the part body. The bulk sampling can be carried out by the following method: First, obtain the part body through the die-casting process, mark the area that meets the tensile specimen, then cut to obtain the marked sample block, and obtain the standard tensile specimen from the above sample block by using the slow wire cutting method.

[0041] The second aspect of the present disclosure provides a method for preparing a die-cast magnesium alloy material, comprising the following steps:

[0042] S1. Under a protective atmosphere, the alloy raw material mixture is melted in a melting furnace to obtain a first alloy melt. Based on the total weight of the alloy raw material mixture, the alloy raw material mixture includes: 5 - 10 wt% of Al, 0.4 - 1.0 wt% of Zn, 0.15 - 0.6 wt% of Mn, 0.01 - 1.0 wt% of Ca, 5 - 30 ppm of Be, Si below 0.08 wt%, Fe below 0.004 wt%, Cu below 0.02 wt%, Ni below 0.001 wt%, 0.001 - 0.1 wt% of Hf, impurities below 0.01 wt% and the balance of Mg;

[0043] S2. The first alloy melt is subjected to refining treatment and slag skimming treatment to obtain a second alloy melt;

[0044] S3. The second alloy melt is subjected to die - casting treatment.

[0045] The present disclosure provides a method for preparing a die - cast magnesium alloy material, which can achieve the performance after heat treatment of other conventional alloys without heat treatment. Without heat treatment, it can not only save costs and reduce carbon emissions, but also bring greater benefits to the dimensional accuracy of parts.

[0046] In a preferred embodiment, based on the total weight of the alloy raw material mixture, the alloy raw material mixture includes: 8.5 - 9.5 wt% of Al, 0.5 - 0.8 wt% of Zn, 0.15 - 0.6 wt% of Mn, 0.3 - 0.7 wt% of Ca, 5 - 30 ppm of Be, Si below 0.08 wt%, Fe below 0.004 wt%, Cu below 0.02 wt%, Ni below 0.001 wt%, 0.04 - 0.08 wt% of Hf, impurities below 0.01 wt% and the balance of Mg. By using the alloy raw material mixture with the component contents provided in this embodiment, a die - cast magnesium alloy material with better strength and elongation can be prepared.

[0047] In a preferred embodiment, in the alloy raw material mixture, the content ratio of Hf / Al ≥ 45 / 10000, preferably the content ratio of Hf / Al ≥ 50 / 10000. Controlling the content ratio of Hf / Al in the alloy raw material mixture within the range of this embodiment, especially within the preferred range, can further improve the bulk properties of the obtained die - cast magnesium alloy material.

[0048] In a specific embodiment, in step S1, Mg, Al, and Zn in the alloy raw material mixture are prepared in the form of pure magnesium, pure aluminum, and pure zinc; Mn and Ca are prepared in the form of Mg - containing Mn master alloy and Mg - containing Ca master alloy, and Hf is prepared in the form of Al - 10.45Hf master alloy;

[0049] Step S1 includes:

[0050] Under a protective atmosphere, pure magnesium in the alloy raw material mixture is placed in a melting furnace for melting to obtain a magnesium melt; other alloy raw materials except pure magnesium are added to the magnesium melt, and heat preservation melting is carried out to obtain the first alloy melt.

[0051] In a preferred embodiment, the conditions for melting the pure magnesium include: the temperature is 680 - 745 °C, and the time is 1 - 2 h; preferably, the temperature is 690 - 745 °C, and the time is 1 - 1.5 h;

[0052] The conditions for heat preservation melting include: the temperature is above 740 °C, and the time is above 30 min; preferably, the temperature is 740 - 750 °C, and the time is 40 - 60 min;

[0053] The protective atmosphere includes N 2 , CO 2 and SF 6 or several of them.

[0054] In one embodiment, the conditions for the refining treatment include: the temperature is 720 - 740 °C, and the standing time is 10 - 15 min; preferably, the temperature is 730 - 740 °C, and the standing time is 12 - 15 min; specifically, the refining treatment includes: adding a refining agent to the first alloy melt under stirring, and then standing; the refining agent can be of the types conventionally selected in the art and can be obtained through ordinary commercial channels. According to the conditions in this embodiment, especially according to the preferred process conditions, the refining treatment has a better purification effect;

[0055] The slag skimming treatment includes removing the floating slag by using a slag skimming tool.

[0056] In one embodiment, in step S3, the conditions for the die-casting treatment include: the die-casting temperature is 700 - 730 °C, the injection speed is 2 - 5 m / s, and the casting pressure is 80 - 160 MPa. According to the process conditions in this embodiment, especially according to the preferred process conditions, a die-cast magnesium alloy material with better body performance can be obtained.

[0057] The third aspect of the present disclosure provides a die-cast magnesium alloy material prepared by the method according to the second aspect of the present disclosure.

[0058] The fourth aspect of the present disclosure provides an automotive structural component, including the die-cast magnesium alloy material according to the first aspect or the third aspect of the present disclosure.

[0059] Further, the automotive structural components include parts formed by die-casting and having high strength and high yield requirements for the parts themselves, including but not limited to electric drive parts such as motor housings, motor end covers, intermediate housings, balance disks, and reducer housings. As Figure 3 shown, Figure 3 the motor housing of the structure shown in

[0060] where the body sampling position 1 is on the motor housing.

[0061] The SEM photos of the die-cast magnesium alloys obtained in the following examples were obtained by testing with a PHENOM XL scanning electron microscope.

[0062] Example 1

[0063] This example prepared a die-cast magnesium alloy according to the alloy raw material composition listed in Table 1, including the following steps:

[0064] (1) Prepare materials according to the formula composition; among them, Mg, Al, and Zn are prepared in the form of pure magnesium, pure aluminum, and pure zinc, Mn and Ca are prepared in the form of Mn and Ca master alloys containing Mg, and Hf is prepared in the form of an Al-10.45Hf master alloy;

[0065] (2) First, place pure magnesium in a melting furnace, introduce a protective gas (CO 2 +SF 6 protective gas. In the mixed gas, the volume content of CO 2 is in the range of 5-8% by volume) for melting at a temperature of 745 °C for 1 h; then add the prepared materials of other components except pure magnesium, and carry out heat preservation melting at a temperature of 750 °C for 50 min. After melting, stir the molten metal evenly to obtain a first alloy melt;

[0066] (3) Add a refining agent powder to the first alloy melt for refining treatment, and skim the slag to obtain a second alloy melt; the conditions for the refining treatment include: adding a refining agent for refining at 730 °C while stirring; after adding the refining agent, let it stand for 15 minutes;

[0067] (4) Carry out die-casting treatment on the second alloy melt. The conditions for the die-casting treatment include: die-casting temperature of 720 °C, injection speed of 4 m / s, and casting pressure of 90 MPa.

[0068] The SEM photo of the die-cast magnesium alloy material prepared in this example is as shown in Figure 2 shown, and it can be seen from Figure 2 that the structure of this die-cast magnesium alloy material is mainly composed of α-Mg, eutectic phase, and trace Hf strengthening precipitates, and α-Mg and eutectic phase are fine and evenly distributed;Figure 1 In it, a represents the eutectic phase (white), b represents the Hf strengthening phase (white granular), and c represents α-Mg (black).

[0069] Examples 2 to 7

[0070] Referring to the preparation method in Example 1, the difference from Example 1 is that: the magnesium alloy material is prepared according to the composition of the magnesium alloy raw materials listed in Table 1, and the remaining processes are the same as those in Example 1.

[0071] Comparative Examples 1 to 3

[0072] Referring to the preparation method in Example 1, the difference from Example 1 is that: the magnesium alloy material is prepared according to the composition of the magnesium alloy raw materials listed in Table 1, and the remaining processes are the same as those in Example 1.

[0073] Table 1

[0074]

[0075] In Table 1, the content units of Al, Zn, Mn, Ca, Si, Fe, Cu, Ni, and Hf are "wt%"; the content unit of Be is ppm.

[0076] Test Example 1

[0077] This test example is used to take bulk samples of the products prepared in the above examples and comparative examples and conduct mechanical property tests.

[0078] The method for taking bulk samples is as follows: First, obtain the part body through the die-casting process, mark the area that meets the tensile specimen, then obtain the marked sample block by cutting, and obtain the standard tensile specimen from the above sample block by using the slow wire cutting method; the sample specification is the small-size test according to ASTM E8, the thickness is the actual thickness of the body, about 4 - 6 mm, and tensile specimens are taken.

[0079] The test methods for the yield strength, tensile strength, and elongation of the bulk specimens refer to Standard GB / T228.1. The test results are listed in Table 2 below.

[0080] Table 2

[0081]

[0082] It can be seen from the data in Table 2 above that:

[0083] In Comparative Example 1, metal Y (yttrium) was used to replace Hf in the die-cast magnesium alloy material, and the content of Ca was not within the range provided by the present disclosure; in Comparative Example 2, Hf was not added to the die-cast magnesium alloy, and the component contents were not within the range provided by the present disclosure; in Comparative Example 3, metal Ce (cerium) was used to replace Hf, and the contents of the remaining components were the same as those in Example 1; the die-cast magnesium alloy materials obtained in Comparative Examples 1 to 3 could not simultaneously achieve high yield strength, high tensile strength, and high elongation; compared with the die-cast magnesium alloys obtained in Comparative Examples 1 to 3, the die-cast magnesium alloys with the component contents provided by the present disclosure in Examples 1 to 7 could simultaneously have high yield strength, tensile strength, and elongation, and had better comprehensive performance;

[0084] Comparing Example 1 with Examples 2 to 7, it can be seen that the composition of the die-cast magnesium alloy material obtained in Example 1 was within the preferred range provided by the present disclosure. The die-cast magnesium alloy material of Example 1 had higher yield strength and tensile strength, and also had high elongation, with better comprehensive performance;

[0085] Among them, comparing Example 1 with Examples 2 to 3 and 7, it can be seen that the ratio of Hf / Al content in the die-cast magnesium alloy material in Example 1 was within the optimized range provided by the present disclosure (Hf / Al≥45 / 10000). The die-cast magnesium alloy material obtained in Example 1 had higher yield strength and tensile strength, and also had high elongation, with better comprehensive performance.

[0086] Test Example 2

[0087] This test example was used to test the corrosion resistance of the die-cast magnesium alloys obtained in some examples and comparative examples.

[0088] The test method referred to GB / T10125. The test results were listed in Table 3 below.

[0089] Table 3

[0090]

[0091] It can be seen from the data in Table 3 above that:

[0092] The corrosion rate of the die-cast magnesium alloy obtained in Example 1 was lower than that of the die-cast magnesium alloy obtained in Comparative Example 1, and the corrosion resistance was better; and the die-cast magnesium alloy obtained in Example 1 could achieve corrosion resistance equivalent to that of ADC12.

[0093] The preferred embodiments of the present disclosure have been described in detail above with reference to the accompanying drawings. However, the present disclosure is not limited to the specific details in the above embodiments. Within the scope of the technical concept of the present disclosure, various simple modifications can be made to the technical solutions of the present disclosure, and these simple modifications all fall within the protection scope of the present disclosure.

[0094] In addition, it should be noted that, in the above specific embodiments, the various specific technical features described can be combined in any suitable manner without contradiction. To avoid unnecessary repetition, the present disclosure will not separately describe various possible combination manners.

[0095] In addition, any combinations can be made among the various different embodiments of the present disclosure, as long as they do not violate the idea of the present disclosure, and they should also be regarded as the content disclosed by the present disclosure.

Claims

1. A die-cast magnesium alloy material, characterized in that: Based on the total weight of the die-cast magnesium alloy material, the die-cast magnesium alloy includes: 5-10 weight % of Al, 0.4-1.0 weight % of Zn, 0.15-0.6 weight % of Mn, 0.01-1.0 weight % of Ca, 5-30 ppm of Be, less than 0.08 weight % of Si, less than 0.004 weight % of Fe, less than 0.02 weight % of Cu, less than 0.001 weight % of Ni, 0.001-0.1 weight % of Hf, less than 0.01 weight % of impurities and the remainder of Mg; the bulk properties of the die-cast magnesium alloy material include: a yield strength of more than 140 MPa, a tensile strength of more than 230 MPa, and an elongation of more than 1.5%.

2. The die-cast magnesium alloy material according to claim 1, characterized in that: The die-casting magnesium alloy includes: 8.5-9.5 weight % of Al, 0.5-0.8 weight % of Zn, 0.15-0.6 weight % of Mn, 0.3-0.7 weight % of Ca, 5-30 ppm of Be, less than 0.08 weight % of Si, less than 0.004 weight % of Fe, less than 0.02 weight % of Cu, less than 0.001 weight % of Ni, 0.04-0.08 weight % of Hf, less than 0.01 weight % of impurities and the balance of Mg.

3. The die-cast magnesium alloy material according to claim 1, characterized in that: In the die-cast magnesium alloy material, the content ratio of Hf / Al is ≥45 / 10000.

4. A method for preparing the die-cast magnesium alloy material according to claim 1, characterized in that: The following steps are involved: S1. Under a protective atmosphere, melting an alloy raw material mixture in a melting furnace to obtain a first alloy melt; based on the total weight of the alloy raw material mixture, the alloy raw material mixture comprises: 5-10 wt % Al, 0.4-1.0 wt % Zn, 0.15-0.6 wt % Mn, 0.01-1.0 wt % Ca, 5-30 ppm Be, 0.08 wt % or less Si, 0.004 wt % or less Fe, 0.02 wt % or less Cu, 0.001 wt % or less Ni, 0.001-0.1 wt % Hf, 0.01 wt % or less impurities and the remainder Mg; S2, refining and deslagging the first alloy melt to obtain a second alloy melt; S3, subjecting the second alloy melt to die casting.

5. The method according to claim 4, characterized in that In step S1, Mg, Al, and Zn in the alloy raw material mixture are prepared in the form of pure magnesium, pure aluminum, and pure zinc; Mn and Ca are prepared in the form of Mg-containing Mn master alloy and Mg-containing Ca master alloy; and Hf is prepared in the form of Al-10.45Hf master alloy; Step S1 includes: Under a protective atmosphere, pure magnesium in the alloy raw material mixture is placed in a melting furnace for melting to obtain a magnesium melt; other alloy raw materials except pure magnesium are added to the magnesium melt, and the mixture is kept warm and melted to obtain the first alloy melt.

6. The method according to claim 5, characterized in that The conditions for melting the pure magnesium include: a temperature of 680-745° C. and a time of 1-2 hours; The heat preservation and melting conditions include: a temperature of 740°C or higher and a time of 30 minutes or higher; The protective atmosphere includes one or more of N2, CO2 and SF6.

7. The method according to claim 4, characterized in that In step S2, the refining treatment conditions include: temperature of 720-740°C and standing time of 10-15 minutes; In step S3, the die-casting treatment conditions include: a die-casting temperature of 700-730° C., an injection speed of 2-5 m / s, and a casting pressure of 80-160 MPa.

8. An automobile structural part, characterized in that: The invention comprises the die-casting magnesium alloy material as described in any one of claims 1 to 3.

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