CN117965968A - Die-casting aluminum alloy and preparation method thereof - Google Patents

Abstract

The invention belongs to the technical field of metal materials, and relates to a cast aluminum alloy and a preparation method thereof. The cast aluminum alloy and the preparation method thereof are characterized in that the heat-treatment-free cast aluminum alloy comprises the following components by taking the total weight of the cast aluminum alloy as a reference: 7.5 to 9.0wt.% Si,0.08 to 0.4wt.% Mg,0.4 to 0.8wt.% Mn,0.08 to 0.4wt.% Fe,0.01 to 0.25wt.% V,0.01 to 0.15wt.% Re,0.05 to 0.15wt.% Ti,0.01 to 0.4wt.% Cu,0.01 to 0.4wt.% Zn,0.01 to 0.06wt.% Sr,0.01 to 0.5wt.% mixed refiners, unavoidable impurity elements less than or equal to 0.1wt.%, and the balance Al; wherein the mixed refiner is Al-Ti-B-C; the mass ratio Mn/(V+Re) is greater than 4; and R is at least one selected from Ce, la and Y. The die-casting aluminum alloy provided by the invention has the performances of remarkably better yield strength (133-170 MPa), tensile strength (283-295 MPa) and elongation (12% -17%), and better casting performance.

Description

A kind of die-casting aluminum alloy and preparation method thereof

Technical Field

The invention belongs to the technical field of metal materials and relates to a die-casting aluminum alloy and a preparation method thereof.

Background technique

With the rapid development of new energy vehicles, the proportion of aluminum alloy as the main lightweight material in new energy vehicles has increased rapidly, among which aluminum alloy die-castings are developing towards large, thin-walled, complex, high-precision, and high-strength and toughness. Taking Tesla as an example, Tesla uses aluminum alloy integrated die-casting technology in large structural parts such as the rear floor and front cabin of Model Y, reducing the traditional stamping + welding parts from more than one or two hundred to 1-2 large castings, greatly improving production efficiency.

At present, the connection method between one-piece die-cast aluminum castings and car bodies is mainly based on SPR riveting and other technologies. The riveting process generally requires the material elongation to be more than 8%, otherwise riveting cracks will occur. The requirements of mainstream car companies for the mechanical properties of one-piece die-cast heat-treatment-free aluminum alloy materials are: tensile strength greater than 220MPa, yield strength greater than 105MPa, and elongation greater than 8%. At the same time, large die-castings have high requirements for material fluidity. When the silicon content is in the range of 7-12%, the die-casting fluidity increases with the increase of silicon content, but silicon is a hard and brittle phase in aluminum, resulting in a decrease in elongation. The ADC12 aluminum alloy, which is the most widely used in the die-casting industry, has a silicon content of about 11%, close to the eutectic point, and has the best fluidity, but the room temperature elongation is usually not higher than 2%, and it cannot be used for automotive structural parts. In the 1990s, German Rhein Aluminum developed Silafont-36 (AlSi10MnMg) (patent publication number: US6364970B1), a die-cast aluminum alloy. It was the most important die-cast aluminum alloy used in automotive structural parts before 2020. However, the elongation of this material in the die-cast state is only 5-7%, and subsequent heat treatment (T6 or T7 heat treatment) is required to meet the strength and toughness requirements. The entire process is relatively long, and the deformation of the parts caused by the heat treatment limits the size of the parts.

To solve the above problems, related enterprises adopt the method of reducing silicon content and strictly controlling iron content to improve the as-cast elongation. For example, Alcoa C611 material is currently a widely used one-piece die-casting heat-treatment-free material (patent publication number: WO2005071127A1). In actual application, this material improves elongation by reducing silicon content to about 6.5%, but the low silicon content leads to poor die-casting processability, large solidification shrinkage of the material, and easy casting defects. At the same time, some enterprises also adopt the method of reducing magnesium content to improve as-cast elongation. For example, Rhein Aluminum Ci37 material (patent number: CN1537961A) maintains a silicon content of about 9.5% to ensure die-casting processability, but in order to offset the elongation loss caused by high silicon content, the content of strengthening element magnesium is reduced, and the magnesium content is less than 0.06%, resulting in low strength. The strength of the as-cast and painted baked state is less than 120MPa, and the wall thickness attenuation is obvious. For test pieces with a thickness of 5mm or more, its yield strength is often only 95MPa. At the same time, the above-mentioned C611 and Ci37 materials both require extremely low iron content (iron less than 0.15%) to reduce the impact of iron impurities on the elongation of the material. In order to meet the corresponding iron content requirements, all virgin electrolytic aluminum must be used. The carbon emission factors of the materials are large, which is not conducive to the achievement of the company's dual carbon goals.

Based on this, the present invention aims to provide a die-cast aluminum alloy with good fluidity, high iron tolerance and high strength and toughness in the cast state.

Summary of the invention

The purpose of the present invention is to provide a die-cast aluminum alloy with good fluidity, high iron tolerance and high strength and toughness in the cast state. The die-cast aluminum alloy can achieve high strength and toughness in the cast state while maintaining a high silicon content. At the same time, the die-cast aluminum alloy can use a higher iron content, which can solve the problem that recycled aluminum cannot be added to the current one-piece die-cast material and reduce carbon emissions.

According to a first aspect of the present invention, the present invention provides a die-casting aluminum alloy, based on the total weight of the die-casting aluminum alloy, the heat-treatment-free die-casting aluminum alloy comprises: 7.5-9.0wt.% Si, 0.08-0.4wt.% Mg, 0.4-0.8wt.% Mn, 0.08-0.4wt.% Fe, 0.01-0.25wt.% V, 0.01-0.15wt.% Re, 0.05-0.15wt.% % Ti, 0.01-0.4wt.% Cu, 0.01-0.4wt.% Zn, 0.01-0.06wt.% Sr, 0.01-0.5wt.% mixed refiner, less than or equal to 0.1wt.% inevitable impurity elements, and the balance Al; wherein the mixed refiner is Al-Ti-B-C; the mass ratio of Mn/(V+Re) is greater than 4; and the Re is selected from at least one of Ce, La, and Y.

In the above solution provided by the present invention, the main function of Si is to increase the fluidity of the alloy while reducing the volume shrinkage during solidification. Silicon can also improve the strength of the alloy within a certain range, but excessive silicon content will significantly reduce the plasticity of the material. For die-casting materials, the inventor has verified based on a large number of experiments that in the technical solution provided by the present invention, when the silicon content is between 7.5% and 9%, sufficient eutectic structure can be generated, that is, the eutectic reaction during the solidification process is sufficient to ensure the fluidity of the material.

Generally speaking, Fe is a harmful impurity element in aluminum alloys, but iron is inevitably present in industrial alloys and recycled scrap aluminum. Processing processes such as smelting will also cause the material to increase iron due to contact with iron tools. For the adverse effects of Fe on aluminum alloy materials, the existing technology often uses Mn to modify the iron-rich phase, and transforms the needle-like β-Al ₅ FeSi into the Chinese character-shaped α-Al ₁₅ (Fe, Mn) ₃ Si ₂ phase to reduce the splitting of the iron-rich phase to the matrix and thus improve the elongation. However, this method is often only effective for lithium alloy materials with an Fe content of less than 0.2%. When the Fe content in the aluminum alloy material exceeds 0.2%, needle-like β-Al ₅ FeSi can often still be formed. Aluminum alloy materials such as C611 and Ci37 require extremely low iron content (iron is less than 0.15%) to reduce the influence of iron-containing impurities on the relative elongation. Based on this, the present invention has found through a large number of experiments that when Mn, V, and Re are added simultaneously and the mass ratio of Mn/(V+Re) is controlled within a range greater than 4, the iron-rich phase can be transformed from a needle-like shape to an irregular polygonal shape that is more favorable to toughness during die casting solidification, thereby achieving the modification of the iron-rich phase and further improving the toughness of the material. Preferably, when the Re is Ce, the contents of Mn, V, and Ce are within the above range and when Mn/(V+Ce)>4, since the Mn content is much higher than the V and Ce contents, the Chinese character-shaped Al-(Mn,Fe,V,Ce)-Si complex phase formed is similar to the α-Al ₁₅ (Fe,Mn) ₃ Si ₂ phase structure formed when Mn is used alone for modification. The main difference is that V and Ce partially replace the position of Mn atoms in the lattice to form a new complex phase Al-(Mn,Fe,V,Ce)-Si, and the melting point of the new complex phase is higher than that of aluminum and also higher than that of the α-Al ₁₅ (Fe,Mn) ₃ Si formed when Mn is used alone for modification. ₂ phases, plus the complex phase has a greater mass density than the aluminum melt, so that the cast aluminum alloy melt of the present invention is more inclined to crystallize in advance and settle to the bottom of the aluminum melt under the action of gravity in the static stage after refining, thereby reducing the content of harmful iron impurity phases in the die casting, and further enabling the cast aluminum alloy of the present invention to tolerate the presence of more than 0.2% of iron. For example, when the above-mentioned Mn, V, Re composite modification scheme of the present invention is adopted, even if the iron content in the aluminum melt is as high as 0.4%, an elongation of more than 10% can still be obtained. It can be seen that the above-mentioned technical scheme of the present invention has a significant effect on reducing the damage of Fe to the die-cast aluminum alloy material.

When recycled aluminum is used as aluminum raw material, in addition to Fe, there is often a small amount of Zn and Cu in the recycled aluminum. The inventor has found through research that when the total content of Cu+Zn is limited within the above range, the presence of Cu and Zn does not damage the elongation of the material, but improves the strength to a certain extent. At the same time, when the Zn content is within the above content range, it has no obvious effect on the anti-corrosion performance of the aluminum alloy material, and when the Cu content is within the above range, it mainly exists in the form of solid solution and CuAl _2. Because the potential of CuAl ₂ and the copper-saturated matrix differs by only a few hundred volts, it does not affect the corrosion performance of the material.

In the above scheme provided by the present invention, Sr is crucial to the modification of eutectic silicon. The present invention has found through research that under die-casting conditions, the material solidifies quickly, and controlling the Sr content between 0.01% and 0.06% has the most obvious modification effect on the aluminum alloy material of the present invention. When the Sr content exceeds 0.08%, the surface of the material after solidification has a surface state of obvious fine cracks. This is because the excessive Sr content destroys the oxide film on the surface of the aluminum alloy. When Sr is further increased to 1%, a second phase containing Sr will be formed and the material will obviously absorb air, resulting in an increase in internal defects. Therefore, the present invention controls the Sr content between 0.01% and 0.06%.

Therefore, the present invention further controls the contents of silicon, magnesium, manganese, iron, vanadium, titanium, copper, zinc, strontium, rare earth elements, mixed refiners, aluminum and other elements in the die-cast aluminum silicon alloy within the above-mentioned range, which can effectively reduce the defects caused by the die-casting process, avoid subsequent alloy heat treatment processes, and make the prepared die-cast aluminum alloy have higher toughness and better thermal cracking resistance in the cast state, thereby improving its comprehensive mechanical properties.

In some embodiments of the present invention, based on the total weight of the die-casting aluminum alloy, the heat treatment-free die-casting aluminum alloy includes: 7.5-9.0wt% Si, 0.08-0.4wt.% Mg, 0.5-0.8wt.% Mn, 0.12-0.35wt.% Fe, 0.01-0.15wt.% V, 0.01-0.15wt.% Re, 0.08-0.12wt.% Ti, 0.01-0.25wt.% Cu, 0.01-0.15wt.% Zn, 0.015-0.04wt.% Sr, 0.02-0.5wt.% mixed refiner, less than or equal to 0.1wt.% unavoidable impurity elements, and the balance Al.

In some embodiments of the present invention, the heat treatment-free die-casting aluminum alloy further contains Li element; based on the total weight of the die-casting aluminum alloy, the heat treatment-free die-casting aluminum alloy includes 0.01 to 0.2 wt.% Li; preferably, based on the total weight of the die-casting aluminum alloy, the mass ratio of Mg/Li is greater than 1.5.

Mg is a commonly used strengthening element in aluminum-silicon cast aluminum alloys. Increasing the magnesium content can improve the material strength, but the material toughness (elongation) is very sensitive to the magnesium content. For example, the Ci37 material (patent number: CN1537961A) needs to strictly limit the magnesium content to less than 0.06% to ensure that the cast elongation of the material reaches 10%. Too low magnesium content leads to poor strength of the material and high wall thickness sensitivity. For example, when the die-cast 3mm thick test piece has a yield strength of 110MPa, but when the thickness is increased to 5mm test piece, the yield strength of the material is only 95MPa. The inventors found in their research that adding the strengthening element Li to the Al-Si-Mn-Mg alloy while maintaining a certain Mg/Li weight ratio can further significantly enhance the strength of the alloy. In addition, the addition of Li is also conducive to the granulation and homogenization of the Si phase, weakening the splitting effect of the silicon phase on the matrix, thereby improving the material's fracture elongation. That is, in a more preferred embodiment of the present invention, Mg and Li are mixed and added, and the Mg+Li content is within the range of 0.1-0.5% and the Mg/Li mass ratio is greater than 1.5, which can not only significantly improve the strength of the material, but also ensure that the toughness of the material is not significantly affected. The microscopic principle is that Li and Na are both group IV elements, with the same extranuclear electronic structure and similar physical and chemical properties. Li can be selectively adsorbed in the valley of Si twins, affecting the growth mechanism of silicon, thereby causing a metamorphic effect on eutectic silicon, which is beneficial to the improvement of material plasticity. In addition, since the primary _Mg2Si phase is a hard and brittle phase, it is very unfavorable to the plasticity of the material, and Li is active in nature and has a high binding energy with vacancies, which indirectly inhibits the diffusion of Mg atoms, reduces the binding rate of Mg and Si, and reduces the formation of coarse _Mg2Si phases, thereby improving strength while avoiding the reduction of plasticity.

In some embodiments of the present invention, the preparation method of Al-Ti-B-C comprises: using 40-50wt.% Al-B-C master alloy, 10-15wt.% titanium additive and the remainder industrial pure aluminum as raw materials, melting at 1000-1200°C and then casting.

In some embodiments of the present invention, the titanium additive is selected from at least one of Ti75 and Ti50.

In some embodiments of the present invention, the preparation method of Al-Ti-B-C comprises the following steps:

(1) preparing 40% to 50% Al-B-C master alloy, 10% to 15% titanium additive, and the balance being industrial pure aluminum;

(2) Melting the Al-B-C master alloy and the industrial pure aluminum at 760-790° C. and heating to 1000-1200° C., keeping the temperature for 20 minutes, adding the titanium additive, stirring evenly after all are melted, and keeping the temperature for 30-40 minutes to obtain an Al-Ti-B-C mixed refiner melt; casting the melt to obtain the Al-Ti-B-C mixed refiner.

In the die-casting process, the coarse die-casting chamber pre-crystallization structure ESCs is inevitable. The coarse structure will reduce the mechanical properties of the material. Traditional grain refiners such as Al-5Ti-B cannot be used because they will react with important modifiers such as Sr to cause poisoning. In the present invention, the inventors found through a large number of experiments that by adding Al-Ti-B-C as a mixed refiner, the influence of Sr on the weaving effect of eutectic silicon can be avoided, and at the same time, the pre-crystallization structure ESCs is refined, further improving the toughness of the material.

According to a second aspect of the present invention, the present invention further provides a method for preparing a heat treatment-free die-casting aluminum alloy as described in any one of the first aspects of the present invention, comprising the following steps:

1) Material preparation: weigh each raw material according to the set chemical composition and the metering ratio;

2) Melting aluminum: Place the preheated aluminum raw material in a smelting furnace for melting, and keep it warm after it is completely melted;

3) Melting: After heating once, add crystalline silicon, add Al-Fe master alloy after all are melted, cool down once after all Al-Fe master alloy is melted, and keep warm; after keeping warm, add Al-Cu master alloy, Al-Mn master alloy, Al-V master alloy, Al-Re master alloy, and cool down twice after melting; after protecting the melt with inert gas, add Al-Li master alloy, pure zinc, pure magnesium, Al-Ti-B-C mixed refiner, and press it into the bottom to melt to obtain a melt, after all are melted, add Al-Sr master alloy, and melt to obtain a melt;

4) Refining: heating the melt in step (3) for a second time and refining;

5) Die casting: die casting the refined melt to obtain the heat treatment-free die casting aluminum alloy;

Wherein, the aluminum raw material includes recycled scrap aluminum and industrial pure aluminum/or industrial pure aluminum; the Al-Re master alloy is selected from at least one of Al-Ce, Al-La, and Al-Y.

Regarding the preparation method of the heat-treatment-free die-cast aluminum alloy, the prior art discloses that after melting the aluminum raw material, the silicon raw material is melted together with other element raw materials. However, the present invention has found through research that since the temperature required for melting silicon is higher, while the temperature required for other elements is lower, if they are melted together, it may cause the precipitation of primary silicon due to insufficient temperature. Primary silicon is a brittle phase and is not conducive to the plasticity of the material. The present invention melts the aluminum raw material, keeps the temperature, raises the temperature, melts the silicon raw material first, and then adds other element raw materials for melting and other subsequent operations. Such operations can further improve the relevant properties of the material.

In some embodiments of the present invention, in step 1), the preheating temperature is 160-180°C; the melting temperature is 750-780°C; and the insulation time is 30-50 min.

In some embodiments of the present invention, in step 2), the temperature of the first heating is 760-790°C; the temperature of the first cooling is 730-740°C; the insulation time after the first cooling is 10-20min; the temperature of the second cooling is 680-700°C.

In some embodiments of the present invention, in step 3), the secondary heating temperature is 730-740°C; the refining comprises: using a rotary degassing device to introduce nitrogen or argon into the melt for refining for 7-10 minutes, skimming and cooling to 680-690°C, and standing for 30-50 minutes.

In some embodiments of the present invention, in step 4), the die-casting conditions include: the temperature of the aluminum liquid in the insulation furnace is controlled at 680-710°C; the mold temperature controller is set at 160-190°C; the low-speed injection speed of the die-casting machine is 0.05-0.2m/s, and the high-speed injection speed of the die-casting machine is 3-5m/s; the die-casting pressure is 60-100MPa; the vacuum degree in the mold cavity is not greater than 8KPa.

In some embodiments of the present invention, the preparation method further comprises: performing surface cleaning and drying treatments on the prepared raw materials before performing subsequent melting or smelting steps.

In some embodiments of the present invention, the preparation method further includes: after performing the refining step, sampling the inside of the obtained liquid melt, cooling to room temperature, and performing a composition test on the melt, and performing a subsequent die-casting step after the composition test in the melt is qualified; if the composition test of the melt is unqualified, the mass of raw materials to be added is calculated based on the alloy element composition, and the raw materials are added according to the calculated results so that the composition of the melt reaches a qualified range, and then the subsequent die-casting step is performed.

In some embodiments of the present invention, the added raw material is at least one of industrial pure aluminum, crystalline silicon, Al-Mn master alloy, Al-V master alloy, pure magnesium, pure zinc, Al-Cu master alloy, Al-Fe master alloy, Al-Ti-B-C mixed refiner, Al-Sr master alloy, and Al-Re master alloy. The Al-Re master alloy is selected from at least one of Al-Ce, Al-La, and Al-Y.

According to the third aspect of the present invention, the present invention also provides an automobile body structural part, which includes a die-cast aluminum alloy, and the die-cast aluminum alloy is the heat-free die-cast aluminum alloy described in any embodiment of the first aspect of the present invention or the heat-free die-cast aluminum alloy prepared by the preparation method described in any embodiment of the second aspect of the present invention.

Compared with the prior art, the present invention has the following beneficial effects:

The present invention provides a heat-treatment-free die-cast aluminum alloy. By controlling the contents of silicon, magnesium, manganese, iron, vanadium, rare earth elements, titanium, copper, zinc, strontium, Al-Ti-B-C mixed refiner, aluminum and other elements in the die-cast aluminum alloy, the defects caused by the die-casting process are effectively reduced, the subsequent alloy heat treatment process is avoided, and the prepared die-cast aluminum alloy has high toughness and good thermal cracking resistance in the cast state, thereby improving its comprehensive mechanical properties. Compared with the existing die-cast aluminum alloy materials, the die-cast aluminum alloy provided by the present invention has significantly better yield strength (133-170MPa), tensile strength (276-295MPa) and elongation (12%-17%) performance and better casting performance.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG1 is a metallographic structure diagram of a die-cast aluminum alloy material prepared in Example 1 of the present invention;

FIG2 is a flat plate sample of an embodiment of the present invention and a comparative example; the thickness of the flat plate sample is 3 mm, and samples of all mechanical properties are randomly sampled from test pieces at various positions of the flat plate mold, and standard mechanical tensile specimens are obtained by machining according to the requirements of GB/T 228.1 and the relevant mechanical properties are tested.

Detailed ways

The technical solution of the present invention is further described below by specific embodiments, which do not limit the protection scope of the present invention. Some non-essential modifications and adjustments made by others based on the concept of the present invention still fall within the protection scope of the present invention.

As used in the present invention, including as used in the examples and unless otherwise expressly provided, all numbers may be considered to be preceded by the words "substantially", "approximately" or "about", even if the term does not explicitly appear. The phrases "approximately" or "about" may be used when describing an amplitude and/or position to indicate that the described numerical value and/or position is within a reasonable expected value and/or position range. For example, a numerical value may be ±0.1% of the numerical value (or numerical range), ±1% of the numerical value (or numerical range), ±2% of the numerical value (or numerical range), ±5% of the numerical value (or numerical range), ±10% of the numerical value (or numerical range), ±15% of the numerical value (or numerical range), ±20% of the numerical value (or numerical range), etc. Any numerical range described in the present invention is intended to include all subranges or intermediate values contained therein.

The disclosure of the numerical value and numerical range of specific parameters (such as temperature, weight percentage, weight fraction, etc.) does not exclude other numerical values and numerical ranges useful to the present invention. It is conceivable that two or more specific example numerical values of a given parameter can determine the endpoints of the numerical range that the parameter can require. For example, if parameter X is exemplified herein as having numerical value A and also exemplified as having numerical value Z, it is expected that parameter X can have a numerical range from about A to about Z. Similarly, it is expected that two or more numerical ranges of disclosed parameters (whether these ranges are nested, overlapped or distinct) have just included all possible combinations of numerical ranges that can be required using the endpoints of the disclosed ranges. For example, if parameter X is exemplified herein as having a value in the range of 1-10, it also describes the sub-range of parameter X, including only as an example, such as: 1-9, 1-8, 1-7, 2-9, 2-8, 2-7, 3-9, 3-8, 3-7, 2-8, 3-7, 4-6 or 7-10, 8-10 or 9-10. Ranges include their endpoints and values within the endpoints, for example, the range 0-5 includes 0, >0, 1, 2, 3, 4, <5, and 5.

Hereinafter, the present invention will be described in more detail through specific examples and comparative examples.

Example 1

This embodiment provides a cast aluminum-silicon alloy, which includes the following components by mass percentage:

Si 8.5wt.％; Mg 0.2wt.％％; Li 0.1wt.％; Mn 0.75wt.％; Fe 0.35wt.％; V0.12wt.％; Ce0.05wt.％; Ti 0.1wt.％; Cu 0.1wt.％; Zn 0.1wt.％; Sr 0.03wt.％; Al-Ti-B-C mixed refiner 0.4wt.％; other unavoidable impurities less than 0.1wt.％; the balance is Al.

The preparation method of cast aluminum silicon alloy is as follows:

(1) Preparation of Al-Ti-B-C mixed refiner:

Prepare 40wt.% Al-B-C master alloy, 15wt.% titanium additive Ti75, and 45wt.% industrial pure aluminum;

The Al-B-C master alloy and industrial pure aluminum are melted at 780°C and heated to 1200°C. After keeping the temperature for 20 minutes, titanium additive Ti75 is added. After all are melted, they are stirred evenly and kept warm for 40 minutes to obtain Al-Ti-B-C mixed refiner melt. The melt is scooped out and cast into 2-5 kg block Al-Ti-B-C mixed refiner for standby use.

(2) Material preparation: according to the chemical composition set above, recycled scrap aluminum, industrial pure aluminum ingots, crystalline silicon, Al-Mn master alloy, pure magnesium, Al-Li master alloy, Al-V master alloy, pure zinc, Al-Cu master alloy, Al-Fe master alloy, Al-Ti master alloy, Al-Ti-B-C mixed refiner, Al-Sr master alloy, Al-Ce master alloy are weighed and set aside;

(3) Melting aluminum ingots: The recycled aluminum scrap and industrial pure aluminum ingots preheated to 160°C are placed in a melting furnace for melting at a melting temperature of 780°C and kept warm for 30 minutes after melting;

(4) Melting: After the melt after heat preservation in step (3) is adjusted to a temperature of 760°C, crystalline silicon is added, and after all the melt is melted, Al-Fe master alloy is added. After the Al-Fe master alloy is completely melted, the furnace temperature is lowered to 740°C, and Al-Cu master alloy, Al-Mn master alloy, Al-V master alloy, Al-Ti master alloy, and Al-Ce master alloy are added. After melting, the temperature is lowered to 680°C, and Al-Li master alloy, pure zinc, pure magnesium, and Al-Ti-B-C mixed refiner are added. The mixture is pressed into the bottom of the melting furnace for melting. After all the melt is complete, Al-Sr master alloy is added and melted to obtain a melt.

(5) Refining: the melt obtained in step (4) is heated to 740° C. and subjected to rotary degassing and blowing refining, specifically comprising: introducing nitrogen or argon into the melt by a rotary degassing device for 10 min, skimming the slag and cooling the temperature to 680° C., and standing for 30 min to obtain a refined melt; sampling the refined melt and conducting melt composition detection, and performing subsequent die-casting steps after the melt composition detection is qualified; if the melt composition detection is unqualified, the mass of raw materials to be added is calculated based on the alloy element composition, and the raw materials are added according to the calculated results to make the melt composition reach a qualified range, and then the subsequent die-casting steps are performed;

(6) Die casting: The refined melt that has passed the component test is die-casted. During die casting, the temperature of the aluminum liquid in the insulation furnace is controlled at 690°C, the mold temperature controller is set at 160°C, the low-speed injection speed of the die-casting machine is 0.15m/s, the high-speed injection speed is 4.6m/s, the casting pressure is 75MPa, and the vacuum degree in the mold cavity is 5KPa. After the above die casting, the above-mentioned cast aluminum silicon alloy is obtained.

Figure 1 is a metallographic structure diagram of the cast aluminum alloy of Example 1 of the present invention. As can be seen from Figure 1, its metallographic structure is composed of matrix α-Al, Al-Si structure and irregular polygonal Al-Si-Mn-V(Ce)-Fe complex phase. The matrix α-Al structure is fine and uniform, without obvious coarse pre-crystallized ESCs structure. The eutectic silicon is fine and fibrous, showing excellent metamorphic effect. The iron-rich phase generates Al-Si-Mn-V(Ce)-Fe complex phase under the joint action of Mn, V and Ce. The morphology is a relatively small polygon and is evenly distributed. This morphology is significantly lower than the stress concentration caused by the conventional needle-shaped iron-rich phase on the matrix, which is extremely beneficial to the improvement of material plasticity.

Example 2

This embodiment provides a cast aluminum-silicon alloy, which includes the following components, measured by mass percentage: Si 8.6wt.%, Mg 0.2wt.%, Li 0.1wt.%, Mn 0.8wt.%, Fe 0.32wt.%, V 0.15wt.%, Ce 0.04wt.%, Ti 0.1wt.%, Cu 0.15wt.%, Zn 0.15wt.%, Sr 0.03wt.%, Al-Ti-B-C mixed refiner 0.4wt.%, other unavoidable impurities less than 0.1wt.%, and the balance is Al.

The preparation method is the same as that of Example 1.

Example 3

This embodiment provides a cast aluminum-silicon alloy, which includes the following components, measured by mass percentage: Si 9.0wt.%, Mg 0.08wt.%, Li 0.04wt.%, Mn 0.6wt.%, Fe 0.2wt.%, V 0.01wt.%, Ce 0.01wt.%, Ti0.1wt.%, Cu 0.05wt.%, Zn 0.05wt.%, Sr 0.04wt.%, Al-Ti-B-C mixed refiner 0.02wt.%, other unavoidable impurities less than 0.1wt.%, and the balance is Al.

The preparation method is the same as that of Example 1.

Example 4

This embodiment provides a cast aluminum-silicon alloy, which includes the following components, measured by mass percentage: Si 7.5wt.%, Mg 0.26wt.%, Li 0.15wt.%, Mn 0.55wt.%, Fe 0.15wt.%, V 0.01wt.%, Ce 0.1wt.%, Ti 0.12wt.%, Cu 0.25wt.%, Zn 0.15wt.%, Sr 0.03wt.%, Al-Ti-B-C mixed refiner 0.5wt.%, other unavoidable impurities less than 0.1wt.%, and the balance is Al.

The preparation method is the same as that of Example 1.

Example 5

This embodiment provides a cast aluminum-silicon alloy, which includes the following components, measured by mass percentage: Si 8.1wt.%, Mg 0.2wt.%, Li 0.05wt.%, Mn 0.6wt.%, Fe 0.25wt.%, V 0.05wt.%, Ce 0.05wt.%, Ti0.08wt.%, Cu 0.2wt.%, Zn 0.01wt.%, Sr 0.02wt.%, Al-Ti-B-C mixed refiner 0.3wt.%, other unavoidable impurities less than 0.1wt.%, and the balance is Al.

The preparation method is the same as that of Example 1.

Example 6

This embodiment provides a cast aluminum-silicon alloy, which includes the following components, measured by mass percentage: Si 8.2wt.%, Mg 0.18wt.%, Li 0.01wt.%, Mn 0.5wt.%, Fe 0.12wt.%, V 0.01wt.%, Ce 0.01wt.%, Ti0.08wt.%, Cu 0.01wt.%, Zn 0.01wt.%, Sr 0.02wt.%, Al-Ti-B-C mixed refiner 0.3wt.%, other unavoidable impurities less than 0.1wt.%, and the balance is Al.

The preparation method is the same as that of Example 1.

Example 7

This embodiment provides a cast aluminum-silicon alloy, which includes the following components, measured by mass percentage: Si 7.5wt.%, Mg 0.26wt.%, Li 0.04wt.%, Mn 0.66wt.%, Fe 0.15wt.%, V 0.01wt.%, Ce 0.15wt.%, Ti0.12wt.%, Cu 0.25wt.%, Zn 0.15wt.%, Sr 0.015wt.%, Al-Ti-B-C mixed refiner 0.5wt.%, other unavoidable impurities less than 0.1wt.%, and the balance is Al.

The preparation method is the same as that of Example 1.

Example 8

This embodiment provides a cast aluminum-silicon alloy, which includes the following components, measured by mass percentage: Si 7.5wt.%, Mg 0.26wt.%, Li 0.04wt.%, Mn 0.75wt.%, Fe 0.3wt.%, V 0.01wt.%, Ce 0.01wt.%, Ti0.12wt.%, Cu 0.25wt.%, Zn 0.15wt.%, Sr 0.015wt.%, Al-Ti-B-C mixed refiner 0.5wt.%, other unavoidable impurities less than 0.1wt.%, and the balance is Al.

The preparation method is the same as that of Example 1.

Example 9

This embodiment provides a cast aluminum-silicon alloy, which includes the following components, measured by mass percentage: Si 9.0wt.%, Mg 0.26wt.%, Li 0.04wt.%, Mn 0.75wt.%, Fe 0.3wt.%, V 0.01wt.%, Ce 0.01wt.%, Ti0.12wt.%, Cu 0.1wt.%, Zn 0.1wt.%, Sr 0.03wt.%, Al-Ti-B-C mixed refiner 0.5wt.%, other unavoidable impurities less than 0.1wt.%, and the balance is Al.

The preparation method is the same as that of Example 1.

Example 10

This embodiment provides a cast aluminum-silicon alloy, which includes the following components by mass percentage:

Si 8.5wt.％; Mg 0.2wt.％％; Li 0.0wt.％; Mn 0.75wt.％; Fe 0.35wt.％; V0.12wt.％; Ce0.05wt.％; Ti 0.1wt.％; Cu 0.1wt.％; Zn 0.1wt.％; Sr 0.03wt.％; Al-Ti-B-C mixed refiner 0.4wt.％; other unavoidable impurities less than 0.1wt.％; the balance is Al.

Embodiment 11

This embodiment provides a cast aluminum-silicon alloy, which includes the following components, measured by mass percentage: Si 7.5wt.%, Mg 0.26wt.%, Mn 0.55wt.%, Fe 0.15wt.%, V 0.01wt.%, Ce 0.1wt.%, Ti 0.12wt.%, Cu 0.25wt.%, Zn 0.15wt.%, Sr 0.03wt.%, Al-Ti-B-C mixed refiner 0.5wt.%, other unavoidable impurities less than 0.1wt.%, and the balance is Al.

The preparation method is the same as that of Example 1.

Example 12

This embodiment provides a cast aluminum-silicon alloy, which includes the following components, measured by mass percentage: Si 7.5wt.%, Mg 0.26wt.%, Mn 0.75wt.%, Fe 0.3wt.%, V 0.01wt.%, Ce 0.01wt.%, Ti 0.12wt.%, Cu 0.25wt.%, Zn 0.15wt.%, Sr 0.015wt.%, Al-Ti-B-C mixed refiner 0.5wt.%, other unavoidable impurities less than 0.1wt.%, and the balance is Al.

The preparation method is the same as that of Example 1.

Example 13

This embodiment provides a cast aluminum-silicon alloy, which includes the following components, measured by mass percentage: Si 9.0wt.%, Mg 0.26wt.%, Mn 0.75wt.%, Fe 0.3wt.%, V 0.01wt.%, Ce 0.01wt.%, Ti 0.12wt.%, Cu 0.1wt.%, Zn 0.1wt.%, Sr 0.03wt.%, Al-Ti-B-C mixed refiner 0.5wt.%, other unavoidable impurities less than 0.1wt.%, and the balance is Al.

The preparation method is the same as that of Example 1.

Embodiment 14

This embodiment provides a cast aluminum-silicon alloy, which includes the following components, measured by mass percentage: Si 7.5wt.%, Mg 0.4wt.%, Li 0.1wt.%, Mn 0.6wt.%, Fe 0.15wt.%, V 0.01wt.%, Ce 0.01wt.%, Ti0.08wt.%, Cu 0.01wt.%, Zn 0.01wt.%, Sr 0.02wt.%, Al-Ti-B-C mixed refiner 0.5wt.%, other unavoidable impurities less than 0.1wt.%, and the balance is Al.

The preparation method is the same as that of Example 1.

Embodiment 15

This embodiment provides a cast aluminum-silicon alloy, which includes the following components, measured by mass percentage: Si 7.5wt.%, Mg 0.4wt.%, Mn 0.6wt.%, Fe 0.15wt.%, V 0.01wt.%, Ce 0.01wt.%, Ti 0.08wt.%, Cu 0.01wt.%, Zn 0.01wt.%, Sr 0.02wt.%, Al-Ti-B-C mixed refiner 0.5wt.%, other unavoidable impurities less than 0.1wt.%, and the balance is Al.

The preparation method is the same as that of Example 1.

Comparative Example 1

The comparative example provides a cast aluminum-silicon alloy, which comprises the following components by mass percentage:

Si 8.5wt.％; Mg 0.15wt.％％; Li 0.15wt.％; Mn 0.75wt.％; Fe 0.35wt.％; V0.12wt.％; Ce 0.05wt.％; Ti 0.1wt.％; Cu 0.1wt.％; Zn 0.1wt.％; Sr 0.03wt.％; Al-Ti-B-C mixed refiner 0.4wt.％; other unavoidable impurities less than 0.1wt.％; the balance is Al.

The preparation method is the same as that of Example 1.

Comparative Example 2

The comparative example provides a cast aluminum-silicon alloy, which comprises the following components by mass percentage:

Si 8.5wt.％; Mg 0.1wt.％％; Li 0.15wt.％; Mn 0.75wt.％; Fe 0.35wt.％; V0.12wt.％; Ce0.05wt.％; Ti 0.1wt.％; Cu 0.1wt.％; Zn 0.1wt.％; Sr 0.03wt.％; Al-Ti-B-C mixed refiner 0.4wt.％; other unavoidable impurities less than 0.1wt.％; the balance is Al.

The preparation method is the same as that of Example 1.

Comparative Example 3

The comparative example provides a cast aluminum-silicon alloy, which comprises the following components by mass percentage:

Si 8.5wt.%, Mg 0.2wt.%, Mn 0.75wt.%, Fe 0.35wt.%, V 0.12wt.%, Ce0.05wt.%, Ti0.1wt.%, Cu 0.1wt.%, Sr 0.03wt.%, other unavoidable impurities less than 0.1wt.%, and the balance is Al.

The preparation method is the same as that of Example 1.

Comparative Example 4

The comparative example provides a cast aluminum-silicon alloy, which comprises the following components by mass percentage:

Si 8.5wt.％; Mg 0.2wt.％％; Li 0.1wt.％; Mn 0.75wt.％; Fe 0.35wt.％; V0.12wt.％; Ce0.05wt.％; Ti 0.1wt.％; Cu 0.1wt.％; Zn 0.1wt.％; Sr 0.03wt.％; other unavoidable impurities less than 0.1wt.％; the balance is Al.

The preparation method is the same as that of Example 1.

Comparative Example 5

The comparative example provides a cast aluminum-silicon alloy, which comprises the following components by mass percentage:

Si 8.5wt.％; Mg 0.2wt.％％; Li 0.1wt.％; Mn 0.75wt.％; Fe 0.35wt.％; Ti0.1wt.％; Cu0.1wt.％; Zn 0.1wt.％; Sr 0.03wt.％; Al-Ti-B-C mixed refiner 0.4wt.％; other unavoidable impurities less than 0.1wt.％; the balance is Al.

The preparation method is the same as that of Example 1.

Comparative Example 6

The comparative example provides a cast aluminum-silicon alloy, which comprises the following components by mass percentage:

Si 8.5wt.％; Mg 0.2wt.％％; Li 0.1wt.％; Mn 0.75wt.％; Fe 0.35wt.％; V0.12wt.％; Ti0.1wt.％; Cu 0.1wt.％; Zn 0.1wt.％; Sr 0.03wt.％; Al-Ti-B-C mixed refiner 0.4wt.％; other unavoidable impurities less than 0.1wt.％; the balance is Al.

The preparation method is the same as that of Example 1.

Comparative Example 7

The comparative example provides a cast aluminum-silicon alloy, which comprises the following components by mass percentage:

Si 8.5wt.％; Mg 0.2wt.％％; Li 0.1wt.％; Mn 0.75wt.％; Fe 0.35wt.％; Ce0.05wt.％; Ti0.1wt.％; Cu 0.1wt.％; Zn 0.1wt.％; Sr 0.03wt.％; Al-Ti-B-C mixed refiner 0.4wt.％; other unavoidable impurities less than 0.1wt.％; the balance is Al.

The preparation method is the same as that of Example 1.

Comparative Example 8

The comparative example provides a cast aluminum-silicon alloy, which comprises the following components by mass percentage:

Si 8.5wt.％; Mg 0.2wt.％％; Li 0.1wt.％; Mn 0.75wt.％; Fe 0.35wt.％; V0.12wt.％; Ce0.15wt.％; Ti 0.1wt.％; Cu 0.1wt.％; Zn 0.1wt.％; Sr 0.03wt.％; Al-Ti-B-C mixed refiner 0.4wt.％; other unavoidable impurities less than 0.1wt.％; the balance is Al.

The preparation method is the same as that of Example 1.

Comparative Example 9

The comparative example provides a cast aluminum-silicon alloy, which comprises the following components by mass percentage:

Si 8.5wt.％; Mg 0.2wt.％％; Li 0.1wt.％; Mn 0.75wt.％; Fe 0.35wt.％; V0.12wt.％; Ce0.1wt.％; Ti 0.1wt.％; Cu 0.1wt.％; Zn 0.1wt.％; Sr 0.03wt.％; Al-Ti-B-C mixed refiner 0.4wt.％; other unavoidable impurities less than 0.1wt.％; the balance is Al.

The preparation method is the same as that of Example 1.

The composition and content of the cast aluminum-silicon alloy in Examples 1-15 and Comparative Examples 1-9 are shown in Table 1:

Table 1 Composition and content of cast aluminum-silicon alloy in Examples 1-15 and Comparative Examples 1-9 (mass fraction/wt%)

The composition and content of conventional aluminum alloy materials ADC12, SF36, Ci37, and C611 in the automotive industry are shown in Table 2.

Table 2 Composition and content of conventional aluminum alloy materials in the automotive industry (mass fraction/wt%)

Effect example

The cast properties of the cast aluminum alloys prepared by the above Examples 1-15 and Comparative Examples 1-13 were tested, and the results are shown in Table 3:

Table 3 Comparison of cast properties of cast aluminum alloys prepared in Examples 1-15 and Comparative Examples 1-13

From the results in Table 3, it can be seen that the strength and elongation of the die-cast aluminum alloy provided by the present invention in the cast state are significantly higher than the cast state performance of the traditional die-cast aluminum alloy. As shown in Table 3, the ADC12 aluminum alloy, which is the most widely used in the die-casting industry, has a silicon content of about 11%, close to the eutectic point, and has the best fluidity. Although its yield strength and tensile strength basically meet the requirements of mainstream car companies for one-piece die-casting heat-treatment-free aluminum alloy materials (i.e., yield strength greater than 105MPa, tensile strength greater than 220MPa), its elongation is only 1%; similarly, the SF36 of Rhein Aluminum Company has a silicon content of up to 10.2, and in the cast state, its yield strength and tensile strength performance basically meet the standards, but the elongation is only 6%, which is lower than 8%, and does not meet the application requirements. It needs to be heat treated at T6 to meet the standards; for the Ci37 aluminum alloy material, although its yield strength, tensile strength and elongation basically meet the requirements of mainstream car companies, However, in order to offset the loss of elongation caused by its high silicon content, it is necessary to strictly control the Mg and Fe contents, that is, the magnesium content is 0.06% or less and the Fe content is less than 0.15%. The lower Mg content requirement leads to lower material strength, and the lower Fe content requirement requires the use of a higher purity aluminum source. Similarly, for C611 material, although its yield strength, tensile strength and elongation basically meet the requirements of mainstream car companies for one-piece die-casting heat-treatment-free aluminum alloy materials, its low silicon content leads to poor die-casting processability, large material solidification shrinkage, easy to produce casting defects, and cause difficulties in die-casting. At the same time, it requires an extremely low iron content (less than 0.12%), which makes it impossible to use recycled aluminum. The die-cast aluminum alloy provided by the present invention has high yield strength (133-170MPa), tensile strength (276-295MPa) and good elongation (12%-17%), while maintaining a high silicon content (7.5-9.0). The high silicon content enables the aluminum alloy material to have better casting performance. At the same time, while maintaining a high silicon content, the present invention further increases the Mg and Fe contents (up to 0.4%). The increase in Mg content further improves the strength of the material. The increase in Fe content reduces the purity requirements for Al source materials, and recycled waste aluminum can be used, which is more conducive to reducing costs and carbon emissions.

It is to be understood that the present invention is described by some embodiments, and it is known to those skilled in the art that various changes or equivalent substitutions may be made to these features and embodiments without departing from the spirit and scope of the present invention. In addition, under the teachings of the present invention, these features and embodiments may be modified to adapt to specific circumstances and materials without departing from the spirit and scope of the present invention. Therefore, the present invention is not limited by the specific embodiments disclosed herein, and all embodiments falling within the scope of the claims of the present invention are within the scope of protection of the present invention.

Claims (10)

1. A heat-treatment-free die-casting aluminum alloy, characterized in that, based on the total weight of the die-casting aluminum alloy, the heat-treatment-free die-casting aluminum alloy comprises: 7.5-9.0wt.% Si, 0.08-0.4wt.% Mg, 0.4-0.8wt.% Mn, 0.08-0.4wt.% Fe, 0.01-0.25wt.% V, 0.01-0.15wt.% Re, 0.05-0.15wt.% Ti, 0.01-0.4wt.% Cu, 0.01-0.4wt.% Zn, 0.01-0.06wt.% Sr, 0.01-0.5wt.% mixed refiner, less than or equal to 0.1wt.% inevitable impurity elements, and the balance Al; Wherein, the mixed refiner is Al-Ti-B-C; The mass ratio of Mn/(V+Re) is greater than 4; The Re is selected from at least one of Ce, La, and Y. 2. The heat-treatment-free die-casting aluminum alloy according to claim 1, characterized in that, based on the total weight of the die-casting aluminum alloy, the heat-treatment-free die-casting aluminum alloy comprises: 7.5-9.0wt% Si, 0.08-0.4wt.% Mg, 0.5-0.8wt.% Mn, 0.12-0.35wt.% Fe, 0.01-0.15wt.% V, 0.01-0.15wt.% Re, 0.08-0.12wt.% Ti, 0.01-0.25wt.% Cu, 0.01-0.15wt.% Zn, 0.015-0.04wt.% Sr, 0.02-0.5wt.% mixed refiner, less than or equal to 0.1wt.% inevitable impurity elements, and balance Al. 3. The heat-treatment-free die-casting aluminum alloy according to claim 1 or 2, characterized in that the heat-treatment-free die-casting aluminum alloy further contains Li element; based on the total weight of the die-casting aluminum alloy, the heat-treatment-free die-casting aluminum alloy includes 0.01 to 0.2 wt.% of Li; Preferably, based on the total weight of the die-cast aluminum alloy, the mass ratio of Mg/Li is greater than 1.5. 4. The heat-treatment-free die-casting aluminum alloy according to claim 1 or 2, characterized in that the preparation method of the Al-Ti-B-C comprises: using 40-50wt.% of Al-B-C master alloy, 10-15wt.% of titanium additive and the balance of industrial pure aluminum as raw materials, melting at 1000-1200°C and then casting; Preferably, the titanium additive is selected from at least one of Ti75 and Ti50. 5. The heat treatment-free die-casting aluminum alloy according to claim 4, characterized in that the preparation method of the Al-Ti-B-C comprises the following steps: (1) preparing 40% to 50% Al-B-C master alloy, 10% to 15% titanium additive, and the balance being industrial pure aluminum; (2) Melting the Al-B-C master alloy and the industrial pure aluminum at 760-790° C. and heating to 1000-1200° C., keeping the temperature for 20 minutes, adding the titanium additive, stirring evenly after all are melted, and keeping the temperature for 30-40 minutes to obtain an Al-Ti-B-C mixed refiner melt; casting the melt to obtain the Al-Ti-B-C. 6. A method for preparing a heat treatment-free die-casting aluminum alloy according to any one of claims 1 to 5, characterized in that it comprises the following steps: 1) Material preparation: weigh each raw material according to the set chemical composition and the metering ratio; 2) Melting aluminum: Place the preheated aluminum raw material in a smelting furnace for melting, and keep it warm after it is completely melted; 3) Melting: After heating once, add crystalline silicon, add Al-Fe master alloy after all are melted, cool down once after all Al-Fe master alloy is melted, and keep warm; after keeping warm, add Al-Cu master alloy, Al-Mn master alloy, Al-V master alloy, Al-Re master alloy, and cool down twice after melting; after protecting the melt with inert gas, add Al-Li master alloy, pure zinc, pure magnesium, Al-Ti-B-C mixed refiner, and press it into the bottom for melting, after all are melted, add Al-Sr master alloy, and obtain melt after melting; 4) Refining: heating the melt in step (3) for a second time and refining; 5) Die casting: die casting the refined melt to obtain the heat treatment-free die casting aluminum alloy; Wherein, the aluminum raw material includes recycled scrap aluminum and industrial pure aluminum/or industrial pure aluminum; The Al-Re master alloy is selected from at least one of Al-Ce, Al-La and Al-Y. 7. The preparation method according to claim 6, characterized in that in the step 1), the preheating temperature is: 160-180°C; the melting temperature is 750-780°C; the holding time is 30-50min; Preferably, in step 2), the temperature of the first heating is 760-790°C; the temperature of the first cooling is 730-740°C; the insulation time after the first cooling is 10-20min; the temperature of the second cooling is 680-700°C; Preferably, in step 3), the secondary heating temperature is 730-740°C; the refining comprises: using a rotary degassing device to introduce nitrogen or argon into the melt for refining for 7-10 minutes, skimming and cooling to 680-690°C, and standing for 30-50 minutes; Preferably, in step 4), the die-casting conditions include: the temperature of the aluminum liquid in the insulation furnace is controlled at 680-710°C; the mold temperature controller is set at 160-190°C; the low-speed injection speed of the die-casting machine is 0.05-0.2m/s, and the high-speed injection speed of the die-casting machine is 3-5m/s; the die-casting pressure is 60-100MPa; the vacuum degree in the mold cavity is not greater than 8KPa. 8. The preparation method according to claim 6, characterized in that the preparation method further comprises: surface cleaning and drying of the prepared raw materials before subsequent melting or smelting steps. 9. The preparation method according to claim 6, characterized in that the preparation method further comprises: after the smelting step, sampling is performed inside the obtained liquid melt, and after cooling to room temperature, the composition of the melt is detected, and the subsequent die-casting step is performed after the composition detection is qualified; if the composition detection of the melt is unqualified, the mass of the raw material to be added is calculated with the alloy element composition as the target, and the raw material is added according to the calculated result, so that the composition of the melt reaches the qualified range; Preferably, the added raw material is at least one of industrial pure aluminum, crystalline silicon, Al-Mn master alloy, Al-V master alloy, pure magnesium, pure zinc, Al-Cu master alloy, Al-Fe master alloy, Al-Ti-B-C mixed refiner, Al-Sr master alloy, and Al-Re master alloy; the Al-Re master alloy is selected from at least one of Al-Ce, Al-La, and Al-Y. 10. An automobile body structural part, characterized in that it comprises a die-cast aluminum alloy, wherein the die-cast aluminum alloy is the heat-treatment-free die-cast aluminum alloy according to any one of claims 1 to 5 or the heat-treatment-free die-cast aluminum alloy prepared by the preparation method according to any one of claims 6 to 9.