Die-casting magnesium alloy, preparation method thereof and automobile structural part

Abstract

The invention relates to a die-casting magnesium alloy, a preparation method thereof and an automobile structural part. Based on the total weight of the die-casting magnesium alloy, the die-casting magnesium alloy comprises the following components in percentage by weight: 5-7% of Al, 7-12% of La, 0.2-0.4% of Mn, less than 0.3% of impurities and the balance of Mg, wherein the ratio of the content of Al to the content of La is 0.50-0.75. The magnesium alloy which is low in cost, high in strength, heat-resistant and creep-resistant can be provided, and the application of the die-casting magnesium alloy to high-strength heat-resistant parts is expanded.

Description

Technical Field

[0001] The present disclosure relates to the technical field of die-cast magnesium alloys, and in particular to a die-cast magnesium alloy and a preparation method thereof, and an automobile structural part. Background Art

[0002] Magnesium alloy has the advantages of low density, high specific strength and specific stiffness, good damping performance, etc. With the widespread adoption of lightweight automotive parts, magnesium alloy is used to replace aluminum alloy, steel and other metal materials in many fields of the automotive industry, and is one of the lightweight materials with application prospects. When casting magnesium alloy, due to the slow filling of gravity casting, low production efficiency, low density of casting products, many internal pore defects, and poor strength of castings, most magnesium alloys are currently die-cast.

[0003] The most widely used traditional die-cast magnesium alloys are AZ series (such as AZ91D) and AM series (such as AM50, AM60) alloys, but the Mg17Al12 eutectic phase in AZ and AM series alloys has a low melting point and is easy to soften at high temperatures, resulting in poor high-temperature mechanical properties and creep resistance of AZ and AM series alloys. The AX series alloys (such as AX53, AXJ530) with better heat resistance in traditional die-cast magnesium alloys have a strong tendency to hot cracking and poor part formability.

[0004] Existing die-cast magnesium alloy materials cannot simultaneously take into account the technical difficulties of cost, high strength, and heat resistance and creep resistance, making die-cast magnesium alloys unable to meet the needs of new energy vehicle motor housing components with high requirements for strength and heat resistance. Summary of the invention

[0005] The purpose of the present disclosure is to provide a die-cast magnesium alloy and a preparation method thereof, and an automobile structural part, so as to provide a magnesium alloy that takes into account cost, high strength, heat resistance and creep resistance, and expand the application of die-cast magnesium alloys in high-strength and heat-resistant parts.

[0006] In order to achieve the above-mentioned purpose, the first aspect of the present disclosure provides a die-cast magnesium alloy. Based on the total weight of the die-cast magnesium alloy, the die-cast magnesium alloy includes: 5-7 weight % Al, 7-12 weight % La, 0.2-0.4 weight % Mn, less than 0.3 weight % impurities and the remainder Mg; wherein the content ratio of Al to La is 0.50-0.75.

[0007] Preferably, based on the total weight of the die-cast magnesium alloy, the die-cast magnesium alloy comprises: 5-6 wt % Al, 8-11 wt % La, 0.3-0.4 wt % Mn, less than 0.2 wt % impurities and the balance Mg.

[0008] Preferably, in the die-cast magnesium alloy, the contents of Al and La satisfy: 80≤11Al+3La≤100.

[0009] Preferably, the yield strength of the die-cast magnesium alloy is 190-200 MPa, and the tensile strength is 240-260 MPa; under creep conditions of 120° C., 100 MPa, and 100 h, the creep strain generated by the die-cast magnesium alloy is 0.009-0.02%.

[0010] A second aspect of the present disclosure provides a method for preparing a die-cast magnesium alloy, comprising the following steps: S1. In a protective atmosphere, a Mg raw material is subjected to a first melting treatment; then an Al raw material, a La raw material and a Mn raw material are added to perform a second melting treatment to obtain a first alloy melt; based on the total weight of the first alloy melt, the first alloy melt comprises 5-7 weight % of Al, 7-12 weight % of La, 0.2-0.4 weight % of Mn, less than 0.3 weight % of impurities and the remainder of Mg; wherein the content ratio of Al to La is 0.50-0.75; S2, refining and deslagging the first alloy melt to obtain a second alloy melt; S3, subjecting the second alloy melt to die casting.

[0011] Optionally, in step S1, the conditions of the first melting treatment include: a melting temperature of 680-720°C; the conditions of the second melting treatment include: a melting temperature of 740-760°C, and a melting time of 1-2h; The protective atmosphere is selected from one or more of N2, CO2 and SF6 gases; Optionally, the Mg raw material includes pure magnesium, the Al raw material includes pure aluminum, the La raw material includes pure lanthanum, and the Mn raw material includes one or more of pure manganese, manganese-magnesium master alloy or manganese-aluminum master alloy.

[0012] Optionally, in step S2, the refining treatment conditions include: adding a refining agent for refining at 720-740° C., stirring at the same time, and standing for 10-15 minutes; The deslagging process includes removing scum using a deslagging tool.

[0013] Optionally, in step S3, the conditions of the die-casting process include: The die casting pressure is 50~100MPa, the vacuum degree is 50~100mbar, and the temperature of the second alloy melt is 700~730℃.

[0014] A third aspect of the present disclosure provides a die-cast magnesium alloy prepared by the method described in the second aspect of the present disclosure.

[0015] A fourth aspect of the present disclosure provides an automobile structural part, comprising the die-cast magnesium alloy described in the first aspect or the third aspect of the present disclosure.

[0016] Through the above technical solution, the present invention provides a die-cast magnesium alloy and a preparation method thereof, and an automobile structural part. The die-cast magnesium alloy provided by the present invention accurately controls the content of Al and La elements and the content ratio of the two elements, so as to form an Al content of appropriate 11 The La3 eutectic phase ensures the strength, heat resistance and formability of the magnesium alloy; the die-cast magnesium alloy provided by the present disclosure has the comprehensive performance of high strength and high heat resistance. The die-cast aluminum alloy provided by the present disclosure can be applied to parts with high strength and high heat resistance requirements, and can meet the performance requirements of high-performance and high-torque motor housing parts of current new energy vehicles.

[0017] Other features and advantages of the present disclosure will be described in detail in the following detailed description. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] The accompanying drawings are used to provide a further understanding of the present disclosure and constitute 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 of the present disclosure. In the accompanying drawings: Figure 1 A process flow chart of a method for preparing a die-cast magnesium alloy provided by the present disclosure is shown; Figure 2 This is a SEM microstructure photograph of the die-cast magnesium alloy obtained in Example 1 of the present disclosure; Figure 3 This is a SEM microstructure photograph of the die-cast magnesium alloy obtained in Comparative Example 2 of the present disclosure; Figure 4 This is a SEM microstructure photograph of the die-cast magnesium alloy obtained in Comparative Example 3 of the present disclosure. DETAILED DESCRIPTION

[0019] The specific implementation of the present disclosure is described in detail below in conjunction with the accompanying drawings. It should be understood that the specific implementation described herein is only used to illustrate and explain the present disclosure, and is not used to limit the present disclosure.

[0020] A first aspect of the present disclosure provides a die-cast magnesium alloy. Based on the total weight of the die-cast magnesium alloy, the die-cast magnesium alloy includes: 5-7 weight % of Al (aluminum), 7-12 weight % of La (lanthanum), 0.2-0.4 weight % of Mn (manganese), less than 0.3 weight % of impurities and the remainder of Mg (magnesium); wherein the content ratio of Al to La is 0.50-0.75.

[0021] The present invention discloses a die-cast magnesium alloy, wherein the content of Al and La elements is precisely controlled to form an Al2O3 alloy having a suitable content. 11The La3 eutectic phase ensures the strength, heat resistance and formability of the magnesium alloy; the die-cast magnesium alloy provided by the present disclosure has the comprehensive performance of high strength and high heat resistance. The die-cast aluminum alloy provided by the present disclosure can be applied to parts with high strength and high heat resistance requirements, and can meet the performance requirements of high-performance and high-torque motor housing parts of current new energy vehicles. The inventors of the present disclosure also found that the ratio of Al to La in the magnesium alloy will have an important influence on the performance of the alloy. When the ratio of Al to La is within the range provided in the present embodiment, the magnesium alloy has better performance; and when the La content exceeds this ratio, the Al element is not enough to combine all the La elements, and the excess La elements will combine with the Mg element to form a MgLa phase that will increase the thermal cracking tendency of the alloy, which is not conducive to the forming of the alloy; if the Al content exceeds this ratio, the La element is not enough to combine all the Al elements, and the excess Al elements will combine with the Mg element to form a low-melting-point Mg 17 Al 12 phase, which reduces the heat resistance of the alloy.

[0022] According to the present disclosure, the Al content in the die-cast magnesium alloy is controlled within 5-7% by weight and the La content is controlled within 7-12% by weight, so that the synergistic effect of the two elements can be exerted, and an Al content of appropriate content can be formed. 11 The La3 eutectic phase avoids the undesirable phenomenon that too much hard eutectic phase significantly reduces the plasticity and formability of the alloy, while too little hard eutectic phase cannot guarantee the strength and heat resistance of the alloy.

[0023] According to the present disclosure, a small amount of Mn element is added to the die-cast magnesium alloy, and the Mn element content is controlled in the range of 0.2~0.4 weight%. The Mn element can reduce the harm of impurity elements such as Fe and Ni, improve the corrosion resistance of the alloy and reduce the burning loss of the alloy during the smelting process.

[0024] In a preferred embodiment, based on the total weight of the die-cast magnesium alloy, the die-cast magnesium alloy includes: 5-6 weight % Al, 8-11 weight % La, 0.3-0.4 weight % Mn, 0.2 weight % or less impurities and the balance Mg. The die-cast magnesium alloy having the component contents provided in this embodiment can have better comprehensive properties such as strength and heat resistance.

[0025] In a preferred embodiment, in the die-cast magnesium alloy, the content ratio of Al to La is 0.5 to 0.6. When the content ratio of Al to La in the die-cast magnesium alloy is within the preferred range provided in this embodiment, the magnesium alloy can have a higher yield strength and better heat resistance.

[0026] In a more preferred embodiment, in the die-cast magnesium alloy, the contents of Al and La satisfy: 80≤11Al+3La≤100, preferably, 82≤11Al+3La≤95. When the content relationship of Al and La in the die-cast magnesium alloy is within the range provided in this embodiment, especially within the preferred range, the magnesium alloy can have a higher tensile strength.

[0027] In a specific embodiment, the yield strength of the die-cast magnesium alloy is 190-200 MPa, preferably 195-200 MPa; the tensile strength is 240-260 MPa, preferably 250-260 MPa; under the creep conditions of 120°C, 100 MPa, and 100 h, the creep strain generated is 0.009-0.02%, preferably 0.009-0.015%. The die-cast magnesium alloy provided by the present disclosure has the comprehensive properties of ultra-high strength and ultra-high heat resistance, and has a lower creep strain, which is one order of magnitude lower than the creep strain of the conventional die-cast aluminum alloy ADC12 under the same test conditions (ADC12 of ADC12 is about 0.125%).

[0028] A second aspect of the present disclosure provides a method for preparing a die-cast magnesium alloy, comprising the following steps: S1. In a protective atmosphere, a Mg raw material is subjected to a first melting treatment; then an Al raw material, a La raw material and a Mn raw material are added to perform a second melting treatment to obtain a first alloy melt; based on the total weight of the first alloy melt, the first alloy melt comprises 5-7 weight % of Al, 7-12 weight % of La, 0.2-0.4 weight % of Mn, less than 0.3 weight % of impurities and the remainder of Mg, wherein the content ratio of Al to La is 0.50-0.75; S2, refining and deslagging the first alloy melt to obtain a second alloy melt; S3, subjecting the second alloy melt to die casting.

[0029] The method for preparing a die-cast magnesium alloy provided by the present disclosure has a simple process and high production efficiency, and the prepared magnesium alloy has the comprehensive properties of ultra-high strength and ultra-high heat resistance.

[0030] In one embodiment, in step S1, the conditions of the first melting treatment include: a melting temperature of 680-720°C; the conditions of the second melting treatment include: a melting temperature of 740-760°C, and a melting time of 1-2h; The protective atmosphere is selected from one or more of N2, CO2 and SF6 gases. According to the conditions provided in this embodiment, the alloy solution can have uniform composition, less element burnout, and less oxidized slag inclusions. In the present disclosure, the first melting process and the second melting process can be carried out using a common magnesium alloy melting furnace.

[0031] In a specific embodiment, the Mg raw material includes pure magnesium, the Al raw material includes pure aluminum, the La raw material includes pure lanthanum, and the Mn raw material includes one or more of pure manganese, manganese-magnesium master alloy or manganese-aluminum master alloy.

[0032] In one embodiment, in step S2, the refining treatment conditions include: adding a refining agent for refining at 720-740° C., stirring at the same time, and standing for 10-15 minutes; wherein the refining agent is a conventionally selected type in the art and can be obtained through common commercial channels; The deslagging process includes removing scum using a deslagging tool.

[0033] In one embodiment, in step S3, the conditions of the die-casting process include: The die casting pressure is 50-100 MPa, the vacuum degree is 50-100 mbar, and the temperature of the second alloy melt is 700-730°C; preferably, the die casting pressure is 80-100 MPa, and the vacuum degree is 50-70 mbar. According to the die casting conditions in this embodiment, especially according to the preferred die casting conditions, the magnesium alloy obtained by die casting has the effects of high density, good mechanical properties and good surface quality.

[0034] A third aspect of the present disclosure provides a die-cast magnesium alloy prepared by the method described in the second aspect of the present disclosure.

[0035] A fourth aspect of the present disclosure provides an automobile structural part, comprising the die-cast magnesium alloy described in the first aspect or the third aspect of the present disclosure.

[0036] Furthermore, the automotive structural parts include parts that are formed by die casting and have high strength, high yield and high heat resistance requirements for the parts themselves, including but not limited to motor housings, motor end covers, reducer housings and other electric drive parts.

[0037] The present disclosure is further described in detail by way of examples. The raw materials used in the examples can all be obtained through commercial sources.

[0038] The SEM test of die-casting alloy samples was carried out using a PHENOM XL scanning electron microscope.

[0039] Example 1 This embodiment provides an ultra-high strength heat-resistant die-casting magnesium alloy, and the weight percentage of each component is: Al: 6% by weight; La: 8.8% by weight; Mn: 0.3% by weight; the total amount of other impurities is ≤0.2% by weight, and the balance is Mg.

[0040] The preparation method of the ultra-high strength heat-resistant die-casting magnesium alloy comprises the following steps: (1) preparing materials according to the formula ingredients; wherein Mg, Al, and La are prepared in the form of pure magnesium, pure aluminum, and pure lanthanum, and Mn is prepared in the form of Al-10Mn master alloy (i.e., the Mn content is 10 wt %); (2) First, pure magnesium is placed in a melting furnace, and CO2+SF6 protective gas (wherein the volume fraction of CO2 is 99 volume %) is introduced for the first melting treatment, and the melting temperature is 700°C; then, pure aluminum, pure lanthanum, and Al-10Mn master alloy are added, and the temperature is kept at 750°C for 2 hours (second melting treatment). After melting, the molten metal is stirred evenly to obtain a first alloy melt; (3) adding refining agent powder to the melt (first alloy melt) at 730°C for refining, standing for 15 minutes, and slagging to obtain a second alloy melt; (4) After the melt (second alloy melt) reaches 720°C, die casting is performed to obtain die-cast parts, wherein the die casting pressure is 90 MPa and the vacuum degree is 60 mbar.

[0041] The SEM microstructure photograph of the die-cast magnesium alloy part prepared in this embodiment is as follows: Figure 2 As shown, it can be seen that the alloy structure obtained in this embodiment is basically Al 11 La3 eutectic phase, containing only a small amount of α-Mg.

[0042] Example 2 This embodiment provides an ultra-high strength heat-resistant die-cast magnesium alloy, wherein the weight percentages of the components are: Al: 5.5% by weight; La: 11% by weight; Mn: 0.35% by weight; the total amount of other impurities is ≤0.2% by weight, and the balance is Mg.

[0043] The preparation method of the ultra-high strength heat-resistant die-casting magnesium alloy comprises the following steps: (1) preparing materials according to the formula ingredients; wherein Mg, Al, and La are prepared in the form of pure magnesium, pure aluminum, and pure lanthanum, and Mn is prepared in the form of Mg-5Mn master alloy (i.e., the Mn content is 5 wt%); (2) First, pure magnesium is placed in a melting furnace, and N2+SF6 protective gas (wherein the volume fraction of N2 is 99 volume %) is introduced for the first melting, and the melting temperature is 710°C; then, pure aluminum, pure lanthanum, and Mg-5Mn master alloy are added, and the temperature is kept at 745°C for 1 hour (second melting treatment). After melting, the molten metal is stirred evenly to obtain a first alloy melt; (3) adding refining agent powder to the melt (first alloy melt) at 725°C for refining, standing for 10 minutes, and slagging to obtain a second alloy melt; (4) After the melt (second alloy melt) reaches 710°C, die casting is performed to obtain die-cast parts, wherein the die casting pressure is 70 MPa and the vacuum degree is 70 mbar.

[0044] Example 3 This embodiment provides an ultra-high strength heat-resistant die-casting magnesium alloy, the weight percentage of each component is: Al: 5 wt.%; La: 9.2 wt.%; Mn: 0.38 wt.%; the total amount of other impurities is ≤0.2 wt.%, and the balance is Mg.

[0045] The preparation method of the ultra-high strength heat-resistant die-casting magnesium alloy comprises the following steps: (1) Prepare materials according to the formula ingredients; Mg, Al, and La are prepared in the form of pure magnesium, pure aluminum, and pure lanthanum, and Mn is prepared in the form of pure manganese master alloy; (2) First, pure magnesium is placed in a melting furnace and CO2 protective gas is introduced for the first melting at a melting temperature of 690°C; then, pure aluminum, pure lanthanum, and pure manganese are added and kept at 760°C for 1.5 hours. After melting, the molten metal is stirred evenly to obtain a first alloy melt; (3) adding refining agent powder to the melt (first alloy melt) at 735°C for refining, standing for 12 minutes, and slagging to obtain a second alloy melt; (4) After the melt (second alloy melt) reaches 730°C, die casting is performed to obtain die-cast parts, wherein the die casting pressure is 50 MPa and the vacuum degree is 50 mbar.

[0046] Example 4 This embodiment provides an ultra-high strength heat-resistant die-cast magnesium alloy, and the weight percentage of each component is: Al: 7% by weight; La: 10% by weight; Mn: 0.24% by weight; the total amount of other impurities is ≤0.3% by weight, and the balance is Mg.

[0047] The preparation method of the ultra-high strength heat-resistant die-casting magnesium alloy is the same as that of Example 1.

[0048] Example 5 This embodiment provides an ultra-high strength heat-resistant die-cast magnesium alloy, wherein the weight percentages of the components are: Al: 5.2 weight %; La: 7 weight %; Mn: 0.4 weight %; the total amount of other impurities is ≤0.3 weight %, and the balance is Mg.

[0049] The preparation method of the ultra-high strength heat-resistant die-casting magnesium alloy is the same as that of Example 1.

[0050] Example 6 This embodiment provides an ultra-high strength heat-resistant die-cast magnesium alloy, and the weight percentage of each component is: Al: 6.8% by weight; La: 11.1% by weight; Mn: 0.2% by weight; the total amount of other impurities is ≤0.3% by weight, and the balance is Mg.

[0051] The preparation method of the ultra-high strength heat-resistant die-casting magnesium alloy is the same as that of Example 1.

[0052] Example 7 This embodiment provides an ultra-high strength heat-resistant die-casting magnesium alloy, and the weight percentage of each component is: Al: 6.5% by weight; La: 12% by weight; Mn: 0.28% by weight; the total amount of other impurities is ≤0.3% by weight, and the balance is Mg.

[0053] The preparation method of the ultra-high strength heat-resistant die-casting magnesium alloy is the same as that of Example 1.

[0054] Comparative Example 1 This comparative example provides a traditional ADC12 die-casting aluminum alloy, and the weight percentage of each component is: Si: 10.8% by weight; Fe: 0.9% by weight; Cu: 1.6% by weight; Mn: 0.21% by weight; Mg: 0.13% by weight; Zn: 0.65% by weight; Ni: 0.24% by weight; the total amount of other impurities is ≤0.3% by weight, and the balance is Al.

[0055] The ADC12 die-casting aluminum alloy of this comparative example directly adopts commercial ADC12 die-casting aluminum alloy ingots for melting, refining, and slag removal. After the melt reaches 660° C., die-casting production is carried out to obtain die-cast parts.

[0056] Comparative Example 2 This comparative example provides a die-cast magnesium alloy in which the weight percentages of the components are as follows: Al: 4.9 weight %; La: 8.8 weight %; Mn: 0.3 weight %; the total amount of other impurities is ≤0.2 weight %, and the balance is Mg.

[0057] The preparation of the die-cast magnesium alloy and its die-casting process provided in this comparative example are the same as those in Example 1.

[0058] The SEM microstructure of the die-cast magnesium alloy part prepared in this comparative example is as follows: Figure 3 As shown, from Figure 3 It can be seen that the alloy structure obtained in this comparative example is composed of α-Mg and Al 11 The La3 eutectic phase is formed, and the content of α-Mg is much higher than that in Example 1. This shows that the die-cast magnesium alloy with the alloy composition disclosed in Example 1 has a higher content of Al 11 La3 eutectic phase.

[0059] Comparative Example 3 This comparative example provides a die-cast magnesium alloy in which the weight percentages of the components are as follows: Al: 5.4 weight %; La: 11 weight %; Mn: 0.35 weight %; the total amount of other impurities is ≤0.2 weight %, and the balance is Mg.

[0060] The preparation of the die-cast magnesium alloy and its die-casting process provided in this comparative example are the same as those in Example 2.

[0061] The SEM microstructure of the die-cast magnesium alloy part prepared in this comparative example is as follows: Figure 4 As shown, from Figure 4 It can be seen that the alloy structure obtained in this comparative example has 11 In addition to the La3 eutectic phase, a MgLa second phase is also produced.

[0062] Comparative Example 4 This comparative example provides a die-cast magnesium alloy in which the weight percentages of the components are as follows: Al: 7.6 weight %; La: 10 weight %; Mn: 0.24 weight %; the total amount of other impurities is ≤0.3 weight %, and the balance is Mg.

[0063] The preparation of the die-cast magnesium alloy and its die-casting process provided in this comparative example are the same as those in Example 1.

[0064] The compositions of the die-cast magnesium alloys obtained in the above examples and comparative examples are listed in Table 1 below.

[0065] Table 1

[0066] Test Case The die-cast alloy products prepared in the above embodiments and comparative examples were subjected to room temperature tensile mechanical property tests and creep property tests. The creep test conditions were as follows: creep temperature 120°C, creep stress 100 MPa, creep time 100 h. The creep property of the alloy was judged by creep strain. Under the same conditions, the smaller the creep strain, the better the creep property. The alloy property test results are listed in Table 2 below.

[0067] The room temperature tensile mechanical properties test refers to the GB / T 228.1-2021 standard; the creep properties test refers to the GB / T2039-2012 standard.

[0068] Table 2

[0069] According to the data in Table 2, we can see that: Comparative Example 1 provides an ADC12 aluminum alloy. Compared with the aluminum alloy of Comparative Example 1, the die-cast magnesium alloys provided in Examples 1 to 7 have higher yield strength and elongation, and the creep strain of the die-cast magnesium alloys in Examples 1 to 7 is significantly lower than that of the aluminum alloy of Comparative Example 1. In Comparative Example 2, the Al element is too little and is not within the composition range of the die-cast magnesium alloy provided in the present disclosure. The tensile properties and creep properties of the die-cast magnesium alloy obtained in Comparative Example 2 are relatively low. The strength properties and creep properties of the die-cast magnesium alloys having the alloy composition provided in Examples 1 to 7 are significantly improved. The Al / La content ratio in Comparative Example 3 is not within the range provided by the present disclosure, and a MgLa phase with a greater tendency to hot cracking is generated in the alloy structure, the alloy has poor formability, and its various properties are significantly reduced. This shows that the strength and creep properties of the die-cast magnesium alloys with the alloy composition provided by the present disclosure in Examples 1 to 7 are significantly improved; In Comparative Example 4, too much Al element is added, which is not within the composition range of the die-cast magnesium alloy provided in the present disclosure, and its Al / La content ratio is not within the range of the present disclosure. The alloy structure of the magnesium alloy obtained in Comparative Example 4 produces a low-melting-point Mg 17 Al 12 The creep performance of the alloy is significantly reduced. This shows that the die-cast magnesium alloys with the alloy composition provided by the present disclosure in Examples 1 to 7 have better strength and creep performance.

[0070] Comparing Examples 1, 4 to 6 with Examples 2 to 3 and 7, the Al / La content ratio in the die-cast magnesium alloys obtained in Examples 2 to 3 and 7 is within the preferred range provided in the present disclosure, and the die-cast magnesium alloys obtained in Examples 2 to 3 and 7 have higher yield strength, lower creep strain, and better creep performance; Comparing Examples 1 to 3 with Examples 4 to 7, it can be seen that the component contents of the die-cast magnesium alloys in Examples 1 to 3 and the values ​​of 11Al+3La are within the preferred ranges provided in the present disclosure, and the die-cast magnesium alloys obtained in Examples 1 to 3 have higher tensile strength; Comparing Examples 2 to 3 with Examples 1 and 4 to 7, it can be seen that the component content, Al / La content ratio and 11Al+3La value of the die-cast magnesium alloy in Examples 2 to 3 are all within the preferred range provided in the present disclosure, and the yield strength and tensile strength of the die-cast magnesium alloy in Examples 2 to 3 are higher and the creep strain is lower.

[0071] The preferred embodiments of the present disclosure are described in detail above in conjunction with the accompanying drawings; however, the present disclosure is not limited to the specific details in the above embodiments. Within the technical concept of the present disclosure, a variety of simple modifications can be made to the technical solution of the present disclosure, and these simple modifications all fall within the protection scope of the present disclosure.

[0072] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. In order to avoid unnecessary repetition, the present disclosure will not further describe various possible combinations.

[0073] In addition, various embodiments of the present disclosure may be arbitrarily combined, and as long as they do not violate the concept of the present disclosure, they should also be regarded as the contents disclosed by the present disclosure.

Claims

1. A die-cast magnesium alloy, characterized in that: Based on the total weight of the die-cast magnesium alloy, the die-cast magnesium alloy includes: 5-7 weight % of Al, 7-12 weight % of La, 0.2-0.4 weight % of Mn, less than 0.3 weight % of impurities and the balance of Mg; wherein the content ratio of Al to La is 0.50-0.

75.

2. The die-cast magnesium alloy according to claim 1, characterized in that: Based on the total weight of the die-cast magnesium alloy, the die-cast magnesium alloy includes: 5-6 weight % of Al, 8-11 weight % of La, 0.3-0.4 weight % of Mn, less than 0.2 weight % of impurities and the balance of Mg.

3. The die-cast magnesium alloy according to claim 1, characterized in that: In the die-cast magnesium alloy, the contents of Al and La satisfy: 80≤11Al+3La≤100.

4. The die-cast magnesium alloy according to claim 1, characterized in that: The yield strength of the die-cast magnesium alloy is 190-200 MPa, and the tensile strength is 240-260 MPa; under creep conditions of 120° C., 100 MPa, and 100 h, the creep strain generated by the die-cast magnesium alloy is 0.009-0.02%.

5. A method for preparing a die-cast magnesium alloy, characterized in that: The following steps are involved: S1. In a protective atmosphere, a Mg raw material is subjected to a first melting treatment; then an Al raw material, a La raw material and a Mn raw material are added to perform a second melting treatment to obtain a first alloy melt; based on the total weight of the first alloy melt, the first alloy melt comprises 5-7 weight % of Al, 7-12 weight % of La, 0.2-0.4 weight % of Mn, less than 0.3 weight % of impurities and the remainder of Mg, wherein the content ratio of Al to La is 0.50-0.75; S2, refining and deslagging the first alloy melt to obtain a second alloy melt; S3, subjecting the second alloy melt to die casting.

6. The method according to claim 5, characterized in that In step S1, the conditions of the first melting treatment include: the melting temperature is 680-720°C; the conditions of the second melting treatment include: the melting temperature is 740-760°C, and the melting time is 1-2h; The protective atmosphere is selected from one or more of N2, CO2 and SF6 gases; Optionally, the Mg raw material includes pure magnesium, the Al raw material includes pure aluminum, the La raw material includes pure lanthanum, and the Mn raw material includes one or more of pure manganese, manganese-magnesium master alloy or manganese-aluminum master alloy.

7. The method according to claim 5, characterized in that In step S2, the refining treatment conditions include: adding a refining agent for refining at 720-740° C., stirring at the same time, and standing for 10-15 minutes; The deslagging process includes removing scum using a deslagging tool.

8. The method according to claim 5, characterized in that In step S3, the conditions of the die casting process include: The die casting pressure is 50~100MPa, the vacuum degree is 50~100mbar, and the temperature of the second alloy melt is 700~730℃.

9. The die-cast magnesium alloy prepared according to the method according to any one of claims 5 to 8.

10. An automobile structural part, characterized in that: Including the die-cast magnesium alloy as described in any one of claims 1 to 4 and 9.

Images