High-toughness die-casting aluminum alloy for vehicle, preparation method of high-toughness die-casting aluminum alloy and aluminum alloy die casting

Abstract

The invention discloses a high-strength and high-toughness die-casting aluminum alloy for a vehicle, and relates to the technical field of aluminum alloys, the high-strength and high-toughness die-casting aluminum alloy for the vehicle comprises 7.0-9.5% of Si, less than or equal to 0.3% of Fe, 0.2-0.8% of Cu, 0.3-0.8% of Mn, 0.1-0.6% of Mg, 0.04-0.15% of Cr, 0.05-0.20% of Zn, less than or equal to 0.1% of Ti, 0.015-0.045% of Sr, 0.01-0.06% of Mo, 0.01-0.08% of RE and the balance Al and impurities, and the total content of the impurities is less than or equal to 0.25%. According to the preparation method, the defects caused by a die-casting process can be effectively reduced, a subsequent alloy heat treatment process is avoided, the prepared die-casting aluminum alloy has relatively high obdurability and relatively good hot crack resistance in an as-cast state, and further the comprehensive mechanical property of the die-casting aluminum alloy is improved.

Description

Technical Field

[0001] This invention relates to the field of aluminum alloy materials technology, specifically to a high-strength and high-toughness die-cast aluminum alloy for automobiles, its preparation method, and aluminum alloy die-cast parts. Background Technology

[0002] With the increasing demand for lightweight vehicles and the rapid development of the new energy vehicle industry, the demand and requirements for automotive profiles are also constantly increasing. Unlike traditional vehicles, new energy vehicles use batteries as a power source. Due to factors such as battery weight and driving range limitations, lightweight materials are the most favored in the design and material selection of new energy vehicles. Among them, aluminum alloy profiles have become a key focus of research and development in the automotive industry and new materials companies because of their short development cycle, low mold costs, and flexible structure. This makes aluminum alloy materials the preferred material for automotive lightweighting.

[0003] However, existing die-cast aluminum alloy materials (such as ADC12, A380, etc.) have the following technical drawbacks:

[0004] (1) Insufficient strength and toughness: The yield strength of traditional Al-Si alloys is generally below 200MPa and the elongation is less than 8%, which makes it difficult to meet the impact resistance requirements of high load-bearing components.

[0005] (2) Grain coarsening defects: During rapid die casting, coarse primary α-Al phase and brittle eutectic silicon are easily formed, leading to stress concentration inside the material;

[0006] (3) High process sensitivity: It relies on complex post-processing (such as T6) heat treatment to improve performance, which increases energy consumption and deformation risk.

[0007] Based on this, the applicant proposed a high-strength and high-toughness die-cast aluminum alloy for automobiles and its preparation method by optimizing composition, controlling microstructure and improving process, in order to solve the problems existing in the prior art. Summary of the Invention

[0008] This invention aims to at least partially solve one of the technical problems in the prior art. To this end, embodiments of this invention propose a high-strength, high-toughness die-cast aluminum alloy for automotive applications, its preparation method, and die-cast parts. This aluminum alloy exhibits good fluidity, high iron tolerance, achieves high strength and toughness in the as-cast state, and possesses good mechanical properties without the need for heat treatment.

[0009] To achieve the above objectives, the high-strength and high-toughness die-cast aluminum alloy for automobiles described in this application, based on the total weight of the die-cast aluminum alloy, comprises: Si 7.0-9.5%, Fe≤0.3%, Cu 0.2-0.8%, Mn 0.3-0.8%, Mg 0.1-0.6%, Cr 0.04-0.15%, Zn 0.05-0.20%, Ti≤0.1%, Sr 0.015-0.045%, Mo 0.01-0.06%, RE 0.01-0.08%, with the balance being Al and impurities, wherein the total impurity content is ≤0.25%.

[0010] As a further improvement of the present invention, based on the total weight of the die-cast aluminum alloy, the high-strength and high-toughness die-cast aluminum alloy for automobiles comprises: Si 8.0-9.5%, Fe 0.1-0.2%, Cu 0.4-0.6%, Mn 0.5-0.7%, Mg 0.3-0.5%, Cr 0.09-0.18%, Zn 0.09-0.12%, Ti 0.05-0.08%, Sr 0.02-0.04%, Mo 0.04-0.06%, and RE 0.05-0.08%.

[0011] As a further improvement of the present invention, the high-strength and high-toughness die-cast aluminum alloy for automobiles further includes Be; based on the total weight of the die-cast aluminum alloy, the high-strength and high-toughness die-cast aluminum alloy for automobiles includes: Be 0.01-0.1%.

[0012] As a further improvement of the present invention, the Zn / Be mass ratio is not less than 2, based on the total weight of the die-cast aluminum alloy.

[0013] As a further improvement of the present invention, the RE component is Y and Er, and the mass ratio of Y to Er is 1:1.

[0014] As a further improvement of the present invention, the aluminum alloy material has a tensile strength ≥270MPa, a yield strength ≥140MPa, and an elongation after fracture ≥13%.

[0015] This invention also discloses a method for preparing high-strength and high-toughness die-cast aluminum alloy for automobiles, comprising the following steps:

[0016] (1) Prepare each raw material according to the ratio. First, place the aluminum raw material in the melting furnace to obtain an aluminum solution. Then, heat it to 760-780℃ and add Si raw material, Cu raw material, Mn raw material, Cr raw material, Fe raw material, RE raw material and Zn raw material to the aluminum solution while stirring at this temperature to obtain the first alloy liquid.

[0017] (2) Let the first alloy liquid stand for 10-20 minutes, and then use argon as a carrier to uniformly spray the sodium-free refining agent into the first alloy liquid for refining, degassing and removing slag to obtain the second alloy liquid.

[0018] (3) The temperature of the second alloy liquid is controlled at 720-740℃. The second alloy liquid is protected with inert gas. Then, Mg raw material is pressed into the second alloy liquid through a bell jar. The reaction is carried out for 3-5 minutes. Then, Sr raw material and Mo raw material are added for smelting to obtain the third alloy liquid.

[0019] (5) Drain the third alloy liquid in the melting furnace into the settling furnace, let it stand for 20-30 minutes, then add Al-5Ti-1B alloy wire and press it into the bottom for online grain refinement treatment to obtain the fourth aluminum alloy liquid.

[0020] (6) Take a sample of the fourth aluminum alloy liquid and analyze its composition. If it meets the requirements, proceed to step (7). If it does not meet the requirements, add additional elements to make the content of the elements meet the requirements.

[0021] (7) A mixture of argon and chlorine gas is introduced into the fourth alloy liquid for refining. After refining, the slag is removed to obtain the fifth alloy liquid.

[0022] (8) The refined fifth alloy liquid is subjected to online degassing and online filtration in sequence;

[0023] (9) The fifth alloy liquid after degassing and filtration is die-cast to obtain a high-strength and high-toughness aluminum alloy for automobiles.

[0024] As a further improvement of the present invention, the temperature of aluminum raw material smelting in step (1) is 720-740℃.

[0025] As a further improvement of the present invention, the online degassing step (8) specifically involves injecting argon gas into the bottom of the fifth alloy liquid while stirring, wherein the flow rate of the argon gas is 0.10-0.14 m³ / s. 3 The stirring speed is 260-280 r / min, and the online filtration is performed using a bipolar filter plate composed of 30ppi+40ppi foam ceramic filter plates.

[0026] As a further improvement of the present invention, the die-casting conditions in step (9) include: the die-casting temperature is controlled at 700-710℃; the die-casting mold temperature is controlled at 200-230℃; the first-stage injection speed is 0.08-0.15m / s, the second-stage injection speed is 3-5m / s; the die-casting pressure is 70-90MPa, and the holding pressure is 20-30s.

[0027] Compared with the prior art, the embodiments of this application have at least the following beneficial effects:

[0028] This invention provides a high-strength and high-toughness die-cast aluminum alloy for automotive applications. By controlling the content of elements such as Si, Fe, Cu, Mn, Mg, Cr, Zn, Ti, Sr, Mo, and Al in the die-cast aluminum alloy, defects caused by the die-casting process are effectively reduced, subsequent alloy heat treatment processes are avoided, and the prepared die-cast aluminum alloy exhibits high strength and toughness and good resistance to hot cracking in the as-cast state, thereby improving its comprehensive mechanical properties. Compared with existing die-cast aluminum alloy materials, the die-cast aluminum alloy provided by this invention has significantly better yield strength ≥140MPa, tensile strength ≥270MPa, elongation ≥13%, and superior casting performance. Detailed Implementation

[0029] The specific embodiments of the present invention will be further described below with reference to the examples. The following examples are only used to illustrate the technical solutions of the present invention more clearly, and should not be used to limit the scope of protection of the present invention.

[0030] This application was filed by the inventor based on the following questions:

[0031] Existing die-cast aluminum alloy materials (such as ADC12, A380, etc.) have the following technical challenges:

[0032] (1) Insufficient strength and toughness: The yield strength of traditional Al-Si alloys is generally below 200MPa and the elongation is less than 8%, which makes it difficult to meet the impact resistance requirements of high load-bearing components.

[0033] (2) Grain coarsening defects: During rapid die casting, coarse primary α-Al phase and brittle eutectic silicon are easily formed, leading to stress concentration inside the material;

[0034] (3) High process sensitivity: It relies on complex post-processing (such as T6) heat treatment to improve performance, which increases energy consumption and deformation risk;

[0035] (4) In the prior art, in order to improve the mechanical properties of aluminum alloys, more Mn, Zn and other elements are added. Although the mechanical properties of aluminum alloys can be improved, the crack resistance of aluminum alloys will also be reduced.

[0036] Based on this, this application proposes a high-strength and high-toughness die-cast aluminum alloy for automobiles and its preparation method.

[0037] According to an embodiment of this application, based on the total weight of the die-cast aluminum alloy, the high-strength and high-toughness die-cast aluminum alloy for automobiles comprises: Si 7.0-9.5%, Fe≤0.3%, Cu 0.2-0.8%, Mn 0.3-0.8%, Mg 0.1-0.6%, Cr0.04-0.15%, Zn 0.05-0.20%, Ti≤0.1%, Sr 0.015-0.045%, Mo 0.01-0.06%, RE 0.01-0.08%, with the balance being Al and impurities, wherein the total impurity content is ≤0.25%.

[0038] Therefore, this application effectively reduces defects caused by the die-casting process by controlling the content of elements such as Si, Fe, Cu, Mn, Mg, Cr, Zn, Ti, Sr, Mo, and Al in the die-cast aluminum alloy, avoiding subsequent alloy heat treatment processes, and enabling the prepared die-cast aluminum alloy to have high strength and toughness and good resistance to hot cracking in the as-cast state, thereby improving its comprehensive mechanical properties. Compared with existing die-cast aluminum alloy materials, the die-cast aluminum alloy provided by this invention has significantly better yield strength ≥140MPa, tensile strength ≥270MPa, and elongation ≥13%, as well as superior casting performance.

[0039] The principle behind the high-strength and high-toughness die-cast aluminum alloy for automobiles proposed in this application, which enables the above-mentioned beneficial effects, will be explained in detail below:

[0040] In this embodiment, the addition of Si can improve the fluidity of the alloy in the molten state, but excessive Si will reduce the plasticity of the aluminum material. In this embodiment, the silicon content is controlled within the above range, the fluidity of the aluminum alloy meets the requirements of die casting, and it can form a Mg2Si strengthening phase with Mg, which helps to improve the mechanical properties of the aluminum alloy.

[0041] In this application, the addition of Fe can strengthen the alloy by forming high-density, fine-grained Al-Fe and Al-Fe-Mn structures with Al and Mn, thereby improving the welding performance of the aluminum alloy and facilitating welding operations during the manufacturing and assembly process of new energy vehicles. However, due to the extremely low solubility of Fe in Al, Fe crystallizes before the primary α-(Al) phase during the solidification process, typically precipitating as brittle, lamellar, or needle-like β-phase compounds, thus reducing the mechanical properties of the alloy. This application utilizes the combination of added Mn, Cr, and Mo to suppress the formation of needle-like or lamellar β-rich iron phases, promote the formation of Chinese character-like or skeletal α-rich iron phases, and increase the recrystallization temperature of the alloy, thereby neutralizing the harmful effects of Fe.

[0042] In this embodiment, the addition of Cu can form a solid solution phase with aluminum, and the precipitated Al2Cu phase is dispersed on the grain boundaries of the aluminum alloy. This precipitated phase is a strengthening phase, which can improve the strength and toughness of the aluminum alloy. However, when the Cu content is too high, it will affect the fracture elongation of the aluminum alloy. Therefore, in this embodiment, the copper content is not higher than 0.8%; and the CuZn bond phase formed by Cu and Zn can effectively improve the mechanical strength of the alloy.

[0043] In this embodiment, the addition of Mn can dissolve into the aluminum alloy matrix to strengthen it. Simultaneously, it can inhibit the growth of primary Si and α-Al grains, allowing the primary silicon content to be dispersed between the grains, thus achieving dispersion strengthening and improving the strength and toughness of the aluminum alloy. Most of the Mn will segregate to the grain boundaries of the aluminum alloy, combining with Fe to form needle-like AlFeMnSi phases, thereby increasing the overall strength of the aluminum alloy. However, the Mn content should not be too high or too low; in this embodiment, it is appropriately controlled at 0.1-0.6%. If Mn is excessive, the resulting large number of needle-like structures will cause cracking of the aluminum alloy matrix, leading to a decrease in the toughness of the aluminum alloy.

[0044] In this embodiment, Mg is the main component of the aluminum alloy (content controlled at 0.1-0.6%), forming a eutectic Mg2Si phase with Si. The Si and Mg compounds are quite small in size and exist as dispersed phases in the material, further strengthening it. Mg exists in a solid solution state in the @-Al matrix; after heat treatment, the Mg2Si phase precipitates and disperses, thereby improving the material's strength.

[0045] The addition of Cr in the embodiments of this application can improve the alloy strength and resistance to stress corrosion cracking. However, excessive Cr will form coarse intermediate compounds with other elements in the alloy, such as Mn, Fe and Ti, which will reduce the alloy's formability. In the embodiments of this application, the Cr content is controlled at 0.04-0.15%. Among them, Cr forms intermetallic compounds such as (CrFe)Al7 and (CrMn)Al12 in aluminum, which hinder the nucleation and growth process of recrystallization, thus having a certain strengthening effect on the alloy and improving the alloy's toughness and reducing its sensitivity to stress corrosion cracking.

[0046] In this embodiment, the addition of Zn effectively dissolves in α-Al to form a solid solution, thereby strengthening the mechanical properties of the aluminum alloy. It also improves the machinability and flowability of the aluminum alloy. However, adding zinc alone to aluminum has limited effect on increasing the strength of the alloy under deformation conditions and also tends towards stress corrosion cracking, thus limiting its application. Therefore, in the prior art, Zn is often added synergistically with Mg and Cu to form a strengthening phase, which has a significant strengthening effect on the alloy. However, the strengthening effect varies depending on the chemical composition and ratio. Furthermore, during solidification, Zn can accumulate on the surface of the Al-Si-Cu-Mg and Fe phases, inhibiting their growth and reducing their size, thereby significantly improving the as-cast properties of the aluminum alloy.

[0047] In this embodiment, Sr can be used as a modifier. During the solidification process of the alloy, Sr can inhibit the irregular morphology of eutectic Si caused by the anisotropic growth of eutectic Si, and it is always adsorbed on the surface of eutectic Si during the solidification and crystallization process, and causes the needle-like silicon phase to spheroidize, thereby improving the mechanical properties of the alloy.

[0048] In the embodiments of this application, Ti can effectively refine and control the microstructure, thereby effectively improving the strength and elongation of aluminum alloys.

[0049] In this embodiment, the added Mo element can inhibit the formation of needle-like or plate-like β-iron-rich phases and promote the formation of Chinese character-like or skeletal α-iron-rich phases, thereby effectively improving the elongation of the aluminum alloy.

[0050] In the embodiments of this application, rare earth elements (REs) provide heterogeneous nuclei during solidification, mainly distributed in the α(Al) phase, phase boundaries, grain boundaries, and interdendritic segregation sites of the aluminum alloy, refining the dendritic structure and grains, especially strengthening the aluminum alloy of this invention. They are dispersed in the matrix, producing dispersion strengthening. Furthermore, rare earth elements can react with hydrogen in the melt to produce REmHn, thereby reducing pinhole defects in the casting after solidification and improving the mechanical properties of the alloy.

[0051] Be can adsorb onto the surface of Al, hindering grain growth and thus refining the grains, thereby further enhancing the strength of the aluminum alloy. Furthermore, by ensuring that the Zn / Be mass ratio is not less than 2, this application not only significantly improves the material strength but also ensures that the toughness of the aluminum alloy is not significantly affected.

[0052] Example 1

[0053] This embodiment provides a high-strength and high-toughness die-cast aluminum alloy for automotive applications, comprising, by weight percentage: Si 8.50%, Fe 0.15%, Cu 0.40%, Mn 0.77%, Mg 0.40%, Cr 0.12%, Zn 0.15%, Ti 0.05%, Sr 0.015%, Mo 0.04%, RE 0.04%, with the balance being Al and impurities, wherein the total impurity content is ≤0.25%, and the specific contents are shown in Table 1.

[0054] Its preparation method includes the following steps:

[0055] (1) Prepare each raw material according to the ratio. First, place the aluminum raw material in the melting furnace to obtain an aluminum solution. Then, heat it to 760-780℃ and add Si raw material, Cu raw material, Mn raw material, Cr raw material, Fe raw material, RE raw material and Zn raw material to the aluminum solution while stirring at this temperature to obtain the first alloy liquid.

[0056] (2) Let the first alloy liquid stand for 15 minutes, and then use argon as a carrier to uniformly spray the sodium-free refining agent into the first alloy liquid for refining, degassing and removing slag to obtain the second alloy liquid.

[0057] (3) The temperature of the second alloy liquid is controlled at 730℃. The second alloy liquid is protected with inert gas. Then, Mg raw material is pressed into the second alloy liquid through a bell jar. After reacting for 4 minutes, Sr raw material and Mo raw material are added for smelting to obtain the third alloy liquid.

[0058] (5) The third alloy liquid in the melting furnace is discharged into the settling furnace and settling for 25 minutes. Then Al-5Ti-1B alloy wire is added and pressed into the bottom for online grain refinement treatment to obtain the fourth aluminum alloy liquid.

[0059] (6) Take a sample of the fourth aluminum alloy liquid and analyze its composition. If it meets the requirements, proceed to step (7). If it does not meet the requirements, add additional elements to make the content of the elements meet the requirements.

[0060] (7) A mixture of argon and chlorine gas is introduced into the fourth alloy liquid for refining. After refining, the slag is removed to obtain the fifth alloy liquid.

[0061] (8) The refined fifth alloy liquid is subjected to online degassing and online filtration in sequence;

[0062] (9) The fifth alloy liquid after degassing and filtration is die-cast to obtain a high-strength and high-toughness aluminum alloy for automobiles.

[0063] In step (1), the temperature during aluminum raw material smelting is 720-740℃.

[0064] Specifically, in step (8), the online degassing process involves injecting argon gas into the bottom of the fifth alloy liquid while stirring, with an argon gas flow rate of 0.12 m³ / s. 3 The stirring speed is 270 r / min, and the online filtration is performed using a bipolar filter plate composed of 30ppi + 40ppi foam ceramic filter plates.

[0065] The die-casting conditions in step (9) include: the die-casting temperature is controlled at 705℃; the die-casting mold temperature is controlled at 215℃; the first-stage injection speed is 0.11m / s, the second-stage injection speed is 4m / s; the die-casting pressure is 80MPa, and the holding pressure is 25.

[0066] Examples 2-11

[0067] The preparation methods of Examples 2-11 are basically the same as those of Example 1, except that the content of each component of the high-strength and high-toughness die-cast aluminum alloy for automobiles is as shown in Table 1.

[0068] Comparative Examples 1-8

[0069] The preparation methods of Comparative Examples 1-8 are basically the same as those of Example 1, except that the content of each component of the high-strength and high-toughness die-cast aluminum alloy for automobiles is as shown in Table 1.

[0070] Table 1

[0071]

[0072]

[0073]

[0074] To verify the progressiveness of the embodiments of this application, the high-strength and high-toughness die-cast aluminum alloys for automobiles prepared in Examples 1-11 and Comparative Examples 1-8 were subjected to the following performance tests:

[0075] 1. Yield strength test: GB / T 228.1-2010 "Metallic materials, tensile testing - Part 1: Test at room temperature";

[0076] 2. Tensile strength test: GB / T 228.1-2010 "Metallic materials, tensile testing - Part 1: Test at room temperature";

[0077] 3. Elongation at break test: GB / T 228.1 Metallic materials - Tensile testing method.

[0078] The results are shown in Table 2.

[0079] Table 2

[0080]

[0081]

[0082] As can be seen from Table 2, the elongation of Example 1 is significantly improved compared with Comparative Example 1. This shows that adding a specific amount of Mo to the aluminum alloy can effectively improve the elongation of the aluminum alloy.

[0083] As can be seen from Table 2, compared with Comparative Example 2, the tensile strength, yield strength and elongation of Example 1 are significantly improved. It can be seen that by adding a specific amount of Cr to the aluminum alloy, the tensile strength, yield strength and elongation of the aluminum alloy can be effectively improved.

[0084] As can be seen from Table 2, compared with Example 1, the tensile strength, yield strength and elongation of Comparative Example 3 are significantly reduced. It can be seen that if the content of Si in the aluminum alloy is too low, it will be impossible to effectively improve the strength of the aluminum alloy and effectively ensure the castability of the aluminum alloy.

[0085] As can be seen from Table 2, compared with Example 1, the tensile strength, yield strength and elongation of Comparative Example 4 are significantly reduced. It can be seen that by adding a specific amount of RE to the aluminum alloy, the tensile strength, yield strength and elongation of the aluminum alloy can be effectively improved.

[0086] As can be seen from Table 2, compared with Example 1, the tensile strength, yield strength and elongation of Comparative Example 5 are reduced. It can be seen that by adding a specific amount of Ti to the aluminum alloy, the tensile strength, yield strength and elongation of the aluminum alloy can be effectively improved.

[0087] As can be seen from Table 2, compared with Example 1, the tensile strength, yield strength and elongation of Comparative Example 6 are reduced. It can be seen that adding a certain excessive amount of RE to the aluminum alloy will result in the inability to effectively improve the strength and elongation of the aluminum alloy.

[0088] As can be seen from Table 2, compared with Example 1, the tensile strength, yield strength and elongation of Comparative Example 7 are reduced. It can be seen that when the Zn / Be mass ratio is less than 2, it will be impossible to effectively improve the strength and elongation of the aluminum alloy.

[0089] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A high-strength, high-toughness die-cast aluminum alloy for automotive applications, characterized in that, Based on the total weight of the die-cast aluminum alloy, the automotive high-strength and high-toughness die-cast aluminum alloy comprises: Si 7.0-9.5%, Fe≤0.3%, Cu 0.2-0.8%, Mn 0.3-0.8%, Mg0.1-0.6%, Cr 0.04-0.15%, Zn 0.05-0.20%, Ti≤0.1%, Sr 0.015-0.045%, Mo0.01-0.06%, RE 0.01-0.08%, with the balance being Al and impurities, wherein the total impurity content is ≤0.25%.

2. The high-strength and high-toughness die-cast aluminum alloy for automobiles according to claim 1, characterized in that, Based on the total weight of the die-cast aluminum alloy, the high-strength and high-toughness die-cast aluminum alloy for automobiles comprises: Si 8.0-9.5%, Fe 0.1-0.2%, Cu 0.4-0.6%, Mn 0.5-0.7%, Mg 0.3-0.5%, Cr 0.09-0.12%, Zn 0.09-0.18%, Ti 0.05-0.08%, Sr 0.02-0.04%, Mo 0.04-0.06%, and RE 0.05-0.08%.

3. The high-strength and high-toughness die-cast aluminum alloy for automobiles according to claim 1 or 2, characterized in that, The high-strength and high-toughness die-cast aluminum alloy for automobiles also includes Be; based on the total weight of the die-cast aluminum alloy, the high-strength and high-toughness die-cast aluminum alloy for automobiles includes: Be 0.01-0.1%.

4. The high-strength and high-toughness die-cast aluminum alloy for automobiles according to claim 3, characterized in that, Based on the total weight of the die-cast aluminum alloy, the Zn / Be mass ratio is not less than 2.

5. The high-strength and high-toughness die-cast aluminum alloy for automobiles according to claim 1, characterized in that, The RE component consists of Y and Er, with a mass ratio of Y to Er of 1:

1.

6. The high-strength and high-toughness die-cast aluminum alloy for automobiles according to claim 1, characterized in that, The aluminum alloy material has a tensile strength ≥270MPa, a yield strength ≥140MPa, and an elongation after fracture ≥13%.

7. The method for preparing high-strength and high-toughness die-cast aluminum alloy for automobiles according to any one of claims 1-6, characterized in that, Includes the following steps: (1) Prepare each raw material according to the ratio. First, place the aluminum raw material in the melting furnace to obtain an aluminum solution. Then, heat it to 760-780℃ and add Si raw material, Cu raw material, Mn raw material, Cr raw material, Fe raw material, RE raw material and Zn raw material to the aluminum solution while stirring at this temperature to obtain the first alloy liquid. (2) Let the first alloy liquid stand for 10-20 minutes, and then use argon as a carrier to uniformly spray the sodium-free refining agent into the first alloy liquid for refining, degassing and removing slag to obtain the second alloy liquid. (3) The temperature of the second alloy liquid is controlled at 720-740℃. The second alloy liquid is protected with inert gas. Then, Mg raw material is pressed into the second alloy liquid through a bell jar. The reaction is carried out for 3-5 minutes. Then, Sr raw material and Mo raw material are added for smelting to obtain the third alloy liquid. (5) Drain the third alloy liquid in the melting furnace into the settling furnace, let it stand for 20-30 minutes, then add Al-5Ti-1B alloy wire and press it into the bottom for online grain refinement treatment to obtain the fourth aluminum alloy liquid. (6) Take a sample of the fourth aluminum alloy liquid and analyze its composition. If it meets the requirements, proceed to step (7). If it does not meet the requirements, add additional elements to make the content of the elements meet the requirements. (7) A mixture of argon and chlorine gas is introduced into the fourth alloy liquid for refining. After refining, the slag is removed to obtain the fifth alloy liquid. (8) The refined fifth alloy liquid is subjected to online degassing and online filtration in sequence; (9) The fifth alloy liquid after degassing and filtration is die-cast to obtain a high-strength and high-toughness aluminum alloy for automobiles.

8. The method for preparing high-strength and high-toughness die-cast aluminum alloy for automobiles according to claim 7, characterized in that, In step (1), the temperature during aluminum raw material smelting is 720-740℃.

9. The method for preparing high-strength and high-toughness die-cast aluminum alloy for automobiles according to claim 7, characterized in that, The specific steps of online degassing in step (8) involve injecting argon gas into the bottom of the fifth alloy liquid while stirring, with an argon gas flow rate of 0.10-0.14 m³ / s. 3 The stirring speed is 260-280 r / min, and the online filtration is performed using a bipolar filter plate composed of 30ppi+40ppi foam ceramic filter plates.

10. The method for preparing high-strength and high-toughness die-cast aluminum alloy for automobiles according to claim 7, characterized in that, The die-casting conditions in step (9) include: the die-casting temperature is controlled at 700-710℃; the die-casting mold temperature is controlled at 200-230℃; the first-stage injection speed is 0.08-0.15m / s, the second-stage injection speed is 3-5m / s; the die-casting pressure is 70-90MPa, and the holding pressure is 20-30s.

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