Heat-treatment-free die-casting aluminum alloy as well as preparation process and use method thereof

Abstract

The heat-treatment-free die-casting aluminum alloy comprises the following components in percentage by weight: 6 to 11 weight percent of Si, 0.3 to 2.1 weight percent of Mn, 1.2 to 1.8 weight percent of Mg, 1.2 to 1.8 weight percent of Cu, 0.1 to 0.2 weight percent of Ti, 0.01 to 0.05 weight percent of Sr, 0.01 to 0.2 weight percent of Zn, 0.04 to 0.2 weight percent of Cr, 0 to 0.3 weight percent of Zr, 0.1 to 0.3 weight percent of Ce, 0.06 to 0.2 weight percent of Mo, less than 0.75 weight percent of Fe, less than 0.2 weight percent of other inevitable impurity elements, and the balance of Al, wherein the content of any single impurity element is less than 0.1 weight percent; according to the invention, the alloy composition proportion is accurately optimized, and a dual strengthening mechanism of nano-particle strengthening and eutectic silicon refining is constructed, so that the comprehensive mechanical property of the die-cast aluminum alloy is remarkably improved, and the bearing requirement of a large-scale structural member can be met without heat treatment; the technical bottlenecks that an existing heat-treatment-free aluminum alloy is low in mechanical property and the strength and plasticity are difficult to consider are solved, and the aluminum alloy can directly meet the use requirements of key structural parts such as an integrated rear bottom plate of a new energy automobile.

Description

Technical Field

[0001] This invention relates to the field of metal materials technology, specifically to heat-free die-cast aluminum alloys and their preparation process and usage methods. Background Technology

[0002] Driven by global strategies for lightweighting and low-carbon development, aluminum alloys, with their low density, high specific strength, good die-casting formability, and recyclability, are widely used in key fields such as new energy vehicles, aerospace, and high-end equipment. Among these, die casting has become the mainstream manufacturing method for aluminum alloy components due to its ability to achieve near-net-shape forming of complex structural components and its high production efficiency. However, traditional die-cast aluminum alloys (such as A380 and ADC12) suffer from relatively low mechanical properties, typically requiring heat treatment processes such as solution treatment and aging to improve strength and meet the load-bearing requirements of structural components.

[0003] With the rise of integrated die-casting technology for new energy vehicles, the demand for large and complex components (such as integrated rear floor plates, battery casings, and subframes) has surged, highlighting the drawbacks of the traditional "die-casting + heat treatment" model. On the one hand, large components are prone to defects such as thermal deformation and cracking during heat treatment, making it difficult to guarantee dimensional accuracy. Moreover, the heat treatment process consumes a large amount of energy, increasing production costs and carbon emissions, which contradicts the concept of low-carbon production. On the other hand, traditional die-cast aluminum alloys have strict restrictions on the use of recycled aluminum, while primary aluminum production is energy-intensive and has high carbon emissions, hindering the green and sustainable development of the aluminum alloy industry. Therefore, developing die-cast aluminum alloys that can meet the mechanical performance requirements of structural components without heat treatment and are compatible with a high proportion of recycled aluminum has become a core demand for industry development.

[0004] Existing heat-free die-cast aluminum alloys still face several technical bottlenecks: First, unreasonable composition design and a single or unevenly distributed strengthening phase result in limited improvement in mechanical properties, making it difficult to balance high strength and high plasticity, and thus failing to meet the complex load-bearing requirements of large structural components. Second, immature preparation processes, with raw material pretreatment relying solely on hot air drying, easily leaving residual moisture and oil, leading to a high porosity defect rate in castings. Uneven dissolution of alloying elements and coarse grains during smelting, coupled with a lack of effective nano-strengthening mechanisms, result in poor melt purification, high hydrogen and inclusion content, severely affecting the density and mechanical property stability of castings. Third, poor compatibility with recycled aluminum, with heavy metal impurities and harmful elements such as Fe easily accumulating in recycled aluminum, causing fluctuations in alloy properties and limiting the high-proportion application of recycled aluminum. Fourth, the modification effect of existing alloys is unsatisfactory, with coarse eutectic silicon structures, limited plasticity improvement, and a lack of synergistic control technology for newly added rare earth elements (such as Ce) and traditional modification elements (such as Sr). Summary of the Invention

[0005] The purpose of this invention is to provide heat-free die-cast aluminum alloys, their preparation process, and their usage methods to solve the problems mentioned in the background art.

[0006] To achieve the above objectives, the present invention provides the following technical solution:

[0007] The heat-free die-cast aluminum alloy comprises, by weight percentage: Si: 6-11wt%, Mn: 0.3-2.1wt%, Mg: 1.2-1.8wt%, Cu: 1.2-1.8wt%, Ti: 0.1-0.2wt%, Sr: 0.01-0.05wt%, Zn: 0.01-0.2wt%, Cr: 0.04-0.2wt%, Zr: 0-0.3wt%, Ce: 0.1-0.3wt%, Mo: 0.06-0.2wt%, Fe: <0.75wt%, and the total amount of other unavoidable impurity elements is <0.2wt%, with the content of any single impurity element being <0.1wt%, and the balance being Al.

[0008] Preferably, its die-cast mechanical properties meet the following requirements: tensile strength ≥ 270 MPa, yield strength ≥ 130 MPa, and elongation ≥ 10%.

[0009] The preparation process of heat-free die-cast aluminum alloy includes the following steps:

[0010] (1) Raw material pretreatment and batching

[0011] The raw materials are selected and pretreated, including composite aluminum raw materials, Al-20Si master alloy, Al-10Mn master alloy, pure Mg ingot, pure Cu ingot, Al-10Cr master alloy, Al-10Zr master alloy, Al-10Mo master alloy, Al-10Ti master alloy, Al-10Ce master alloy, pure Zn particles, Al-10Sr master alloy, and Al-K2TiF6-K2ZrF6-KBF4 reaction system; wherein the composite aluminum raw materials are composed of primary aluminum and recycled aluminum, with recycled aluminum accounting for 30-50%;

[0012] The raw material is subjected to a gradient preheating and vacuum drying composite process, the composite process including first preheating at 120-150℃ for 1-2 hours, then raising the temperature to 180-200℃ and holding it at 100mbar for 2 hours;

[0013] Based on thermodynamic calculation software, precise batching is optimized and executed, with batching error controlled within ±0.05wt%.

[0014] (2) Segmented smelting and alloying

[0015] Basic smelting: The pretreated composite aluminum raw material is smelted and heated to 760-810℃ in a stepped heating mode to make it completely melted. Then Al-20Si and Al-10Mn master alloys are added and the mixture is kept at a constant temperature using a combination of electromagnetic stirring and mechanical stirring.

[0016] Alloy element addition and in-situ generation of strengthening phase: The melt temperature was lowered to 720-740℃, and pure Mg ingot, pure Cu ingot, Al-10Cr, Al-10Zr, Al-10Mo, Al-10Ti, Al-10Ce master alloy and pure Zn particles were added under a high-purity argon atmosphere. Then, a pretreated Al-K2TiF6-K2ZrF6-KBF4 reaction system was added, and TiB2 and ZrB2 nanoparticles were generated and uniformly distributed in the melt through the synergistic effect of mechanical stirring and short-term ultrasonic vibration.

[0017] Modification treatment: Keep the melt temperature at 720-730℃, add Al-10Sr master alloy and stir and perform short-term ultrasonic vibration, then keep it at the temperature and let it stand, and use the synergistic effect of Sr and Ce to refine the eutectic silicon structure.

[0018] (3) Melt purification treatment

[0019] Refining and impurity removal: Heat the melt to 740-760℃, add a composite refining agent, and stir with argon bubbles, then let it stand to allow the inclusions to float to the surface;

[0020] Degassing treatment: The melt temperature is reduced to 720-730℃, and degassing is carried out using an online argon rotary blowing process to ensure that the hydrogen content of the melt is ≤0.12ml / 100gAl;

[0021] Slag removal and testing: Thoroughly remove slag from the liquid surface and perform online testing and adjustment of the melt composition and cleanliness to ensure that the melt cleanliness level is ≥95%;

[0022] (4) Die casting

[0023] The purified melt is cooled to 690-720℃ and held at that temperature; the mold, preheated to 180-250℃, is used for die casting. The die casting process adopts a high vacuum die casting process with a vacuum degree ≤50mbar, and the injection speed and holding pressure parameters are controlled in stages; after die casting is completed, the mold is opened, the part is removed, and cleaned.

[0024] Preferably, the electromagnetic stirring power is 5-8kW, the mechanical stirring rate is 300-500r / min, and the stirring time is 3-5 minutes.

[0025] Preferably, the atomic ratio of Ti to B in the Al-K2TiF6-K2ZrF6-KBF4 reaction system is 1:2, and the Ti is dried at 200°C to remove water before being added; the short-time ultrasonic vibration power is 1000-1500W, and the duration is 2-3 minutes.

[0026] Preferably, the slow injection speed is 0.3-0.5 m / s, the fast injection speed is 3-5 m / s, the injection specific pressure is 80-120 MPa, the holding pressure is 60-80 MPa, and the holding time is 5-10 seconds.

[0027] The usage methods of heat-free die-cast aluminum alloys include:

[0028] The heat-free die-cast aluminum alloy is used to manufacture die-cast structural parts that do not require subsequent heat treatment.

[0029] The die-cast structural parts are prohibited from undergoing any form of solution treatment or aging heat treatment during subsequent processing;

[0030] When machining the die-cast structural parts, the cutting speed is controlled at 150-300 m / min, the feed rate is 0.1-0.3 mm / r, and cooling lubricant is added.

[0031] Preferably, the die-cast structural component is an integrated die-cast rear bottom plate, battery housing, motor housing, or subframe for new energy vehicles.

[0032] Preferably, when welding the die-cast structural parts, argon arc welding is used, and the welding temperature is controlled at 650-700℃, while inert gas protection is applied.

[0033] Preferably, the method also includes recycling the waste die-cast structural parts, controlling the Fe content to be below 0.75wt% during the remelting and regeneration process, and adjusting the performance by adding refining agents and microalloying elements.

[0034] Compared with the prior art, the beneficial effects of the present invention are:

[0035] 1. By precisely optimizing the alloy composition ratio and constructing a dual strengthening mechanism of "nanoparticle reinforcement + eutectic silicon refinement," the comprehensive mechanical properties of die-cast aluminum alloys are significantly improved, meeting the load-bearing requirements of large structural components without heat treatment. This invention specifically introduces Ce element to form a synergistic modification effect with Sr, effectively refining the eutectic silicon structure; simultaneously, uniformly distributed TiB2 and ZrB2 nanoparticles are generated in situ through the Al-K2TiF6-K2ZrF6-KBF4 reaction system, combined with strengthening phases formed by elements such as Mg and Cu, resulting in a tensile strength ≥270MPa, yield strength ≥130MPa, and elongation ≥10% for the die-cast alloy. This solves the technical bottleneck of existing heat-free aluminum alloys having low mechanical properties and difficulty in balancing strength and plasticity, and can be directly adapted to the usage requirements of key structural components such as integrated rear floor plates in new energy vehicles.

[0036] 2. By adopting a composite raw material system of "primary aluminum + 30-50% recycled aluminum," combined with a gradient preheating + vacuum drying pretreatment process and a precise batching scheme, the limitations of existing technologies on the proportion of recycled aluminum used are overcome, achieving low-carbon and green production. The high proportion of recycled aluminum significantly reduces dependence on primary aluminum, reducing production energy consumption and carbon emissions. The gradient preheating + vacuum drying process can thoroughly remove oil, moisture, and oxide scale from the surface of the raw materials, reducing porosity defects by more than 80% compared to traditional hot air drying. At the same time, by optimizing the batching and establishing an impurity prediction model through thermodynamic calculation software, the Fe content is effectively controlled to be <0.75wt% and the total impurities to be <0.2wt%, solving the problem of alloy performance fluctuations caused by the accumulation of impurities in recycled aluminum, thus balancing economy and performance stability.

[0037] 3. By controlling the entire process of segmented melting, composite stirring, synergistic dispersion, and efficient melt purification, the stability of alloy preparation and casting quality are improved. In the basic melting stage, stepped heating and electromagnetic-mechanical composite stirring are used to ensure the full dissolution of alloying elements. In the alloying stage, mechanical stirring and ultrasonic vibration are used to promote the uniform distribution of nanoparticles. Melt purification employs a composite refining agent + argon rotary blowing process, achieving a hydrogen content ≤0.12ml / 100gAl and a cleanliness level ≥95%. This effectively solves problems such as alloying element segregation, coarse grains, and low melt cleanliness in existing processes, significantly reducing the casting defect rate and improving the consistency of batch production.

[0038] 4. A comprehensive recycling system has been established to further improve resource utilization. Subsequent heat treatment is strictly prohibited in the usage methods to avoid Q-phase decomposition leading to performance degradation. Specific mechanical processing parameters, welding processes, and environmental adaptability thresholds have been defined to reduce issues such as work hardening and weld oxidation. The recycling rate of waste components can reach over 80%. Composition control during remelting ensures performance meets standards, solving the problems of vague usage specifications and high recycling difficulty in existing heat-treated aluminum alloys, thus extending the product's entire life cycle value. Attached Figure Description

[0039] Figure 1 This is a process flow diagram of the present invention. Detailed Implementation

[0040] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0041] Example 1

[0042] This invention provides a technical solution:

[0043] The heat-free die-cast aluminum alloy comprises, by weight percentage: Si: 6-11wt%, Mn: 0.3-2.1wt%, Mg: 1.2-1.8wt%, Cu: 1.2-1.8wt%, Ti: 0.1-0.2wt%, Sr: 0.01-0.05wt%, Zn: 0.01-0.2wt%, Cr: 0.04-0.2wt%, Zr: 0-0.3wt%, Ce: 0.1-0.3wt%, Mo: 0.06-0.2wt%, Fe: <0.75wt%, and other unavoidable impurity elements totaling <0.2wt%, with any single impurity element content <0.1wt%, and the balance being Al. Its die-cast mechanical properties meet the following requirements: tensile strength ≥270MPa, yield strength ≥130MPa, and elongation ≥10%.

[0044] Firstly, Si and Mg form the Mg2Si strengthening phase, and Mg and Cu form the Q phase (Al5Cu2Mg8Si6). Both types of strengthening phases precipitate uniformly during the rapid solidification process of die casting, thereby enhancing the alloy strength through precipitation strengthening.

[0045] Secondly, the Mn, Cr, Zr, and Mo elements form fine intermetallic compounds that can pin grain boundaries, inhibit grain growth, and hinder dislocation movement, thereby achieving fine grain strengthening and dispersion strengthening.

[0046] Third, the innovative introduction of Ce element to form a synergistic modification effect with Sr. Ce has a large atomic radius and can be adsorbed at the front end of eutectic silicon growth to hinder its growth. Together with Sr, it refines the traditional coarse needle-like eutectic silicon into fine fibrous structure, significantly reducing stress concentration and improving alloy plasticity.

[0047] Fourth, the Fe content is strictly controlled to be <0.75wt% and the total impurities to be <0.2wt%, to avoid the formation of coarse Fe-Al-Si harmful phases, reduce the risk of phase interface cracking, and ensure performance stability. In addition, Ti provides part of the Ti source required for the nucleation of TiB2 particles in situ through the reaction system, further refining the grain size.

[0048] This composition design achieves a synergistic improvement in both high strength and high plasticity in the die-cast state, meeting the load-bearing requirements of structural components in key fields such as new energy vehicles without heat treatment. It solves the technical pain point of traditional heat-free aluminum alloys, which struggle to balance strength and plasticity. Specifically, it exhibits a die-cast tensile strength ≥270MPa, yield strength ≥130MPa, and elongation ≥10%, representing a comprehensive performance improvement over existing conventional heat-free die-cast aluminum alloys (tensile strength 220-250MPa, elongation 6-8%).

[0049] Example 2

[0050] The preparation process of heat-free die-cast aluminum alloy includes the following steps:

[0051] (1) Raw material pretreatment and batching

[0052] The raw materials are selected and pretreated, including composite aluminum raw materials, Al-20Si master alloy, Al-10Mn master alloy, pure Mg ingot, pure Cu ingot, Al-10Cr master alloy, Al-10Zr master alloy, Al-10Mo master alloy, Al-10Ti master alloy, Al-10Ce master alloy, pure Zn particles, Al-10Sr master alloy, and Al-K2TiF6-K2ZrF6-KBF4 reaction system; wherein the composite aluminum raw materials are composed of primary aluminum and recycled aluminum, with recycled aluminum accounting for 30-50%;

[0053] The raw material is subjected to a gradient preheating and vacuum drying composite process, the composite process including first preheating at 120-150℃ for 1-2 hours, then raising the temperature to 180-200℃ and holding it at 100mbar for 2 hours;

[0054] Based on thermodynamic calculation software, precise batching is optimized and executed, with batching error controlled within ±0.05wt%.

[0055] (2) Segmented smelting and alloying

[0056] Basic smelting: The pretreated composite aluminum raw material is smelted and heated to 760-810℃ in a stepped heating mode to make it completely melted. Then Al-20Si and Al-10Mn master alloys are added and the mixture is kept at a constant temperature using a combination of electromagnetic stirring and mechanical stirring.

[0057] Alloy element addition and in-situ generation of strengthening phase: The melt temperature was lowered to 720-740℃, and pure Mg ingot, pure Cu ingot, Al-10Cr, Al-10Zr, Al-10Mo, Al-10Ti, Al-10Ce master alloy and pure Zn particles were added under a high-purity argon atmosphere. Then, a pretreated Al-K2TiF6-K2ZrF6-KBF4 reaction system was added, and TiB2 and ZrB2 nanoparticles were generated and uniformly distributed in the melt through the synergistic effect of mechanical stirring and short-term ultrasonic vibration.

[0058] Modification treatment: Keep the melt temperature at 720-730℃, add Al-10Sr master alloy and stir and perform short-term ultrasonic vibration, then keep it at the temperature and let it stand, and use the synergistic effect of Sr and Ce to refine the eutectic silicon structure.

[0059] (3) Melt purification treatment

[0060] Refining and impurity removal: Heat the melt to 740-760℃, add a composite refining agent, and stir with argon bubbles, then let it stand to allow the inclusions to float to the surface;

[0061] Degassing treatment: The melt temperature is reduced to 720-730℃, and degassing is carried out using an online argon rotary blowing process to ensure that the hydrogen content of the melt is ≤0.12ml / 100gAl;

[0062] Slag removal and testing: Thoroughly remove slag from the liquid surface and perform online testing and adjustment of the melt composition and cleanliness to ensure that the melt cleanliness level is ≥95%;

[0063] (4) Die casting

[0064] The purified melt is cooled to 690-720℃ and held at that temperature; the mold, preheated to 180-250℃, is used for die casting. The die casting process adopts a high vacuum die casting process with a vacuum degree ≤50mbar, and the injection speed and holding pressure parameters are controlled in stages; after die casting is completed, the mold is opened, the part is removed, and cleaned.

[0065] Raw material pretreatment and batching: A combined process of "gradient preheating + vacuum drying" is adopted. First, low-temperature preheating (120-150℃) removes adsorbed water, followed by high-temperature (180-200℃) vacuum insulation to remove oil, crystal water, and oxide scale, reducing the source of gas in the melt. Based on thermodynamic calculation software, precise batching and an impurity prediction model are established, allowing for dynamic adjustment of raw material dosage to compensate for impurity fluctuations in recycled aluminum, controlling the batching error within ±0.05wt%, and preventing excessive impurity accumulation. The "primary aluminum + recycled aluminum" composite raw material system removes heavy metal impurities through recycled aluminum pretreatment, reducing its adverse effects on alloy performance, while simultaneously reducing the amount of primary aluminum used and lowering carbon emissions.

[0066] In the segmented melting and alloying stages: a "stepped heating" mode avoids localized overheating and oxidation of the raw materials; composite stirring (electromagnetic + mechanical) utilizes the macroscopic homogenization effect of electromagnetic stirring and the localized strong shearing effect of mechanical stirring to improve the dissolution efficiency of alloying elements and reduce segregation; during the alloying element replenishment stage, the temperature is controlled at 720-740℃, and under the protection of high-purity argon, easily oxidized elements such as Mg and Cu are prevented from burning off. At the same time, TiB2 and ZrB2 nanoparticles are generated in situ in the Al-K2TiF6-K2ZrF6-KBF4 reaction system. The Al-K2TiF6-K2ZrF6-KBF4 reaction system (particle size 50-200nm) is made by mixing aluminum powder, K2TiF6, K2ZrF6 and KBF4 in a certain proportion. The atomic ratio of Ti to B is 1:2 to ensure sufficient reaction to generate TiB2 and ZrB2. The particles are dispersed by ultrasonic vibration and mechanical stirring to form a large number of nucleation cores and achieve fine grain strengthening. Sr and Ce are synergistically modified and the uniformity is further improved by ultrasonic vibration, which refines the eutectic silicon structure.

[0067] Melt purification and die casting process: Composite refining agent + argon bubble stirring can efficiently adsorb and remove oxides and sulfide inclusions in the melt. Online argon rotating spray increases the gas-liquid contact area through micro bubbles (50-100μm in diameter) and efficiently adsorbs hydrogen, making the hydrogen content ≤0.12ml / 100gAl. High vacuum die casting (vacuum degree ≤50mbar) reduces air entrainment during the filling process. The injection speed and holding pressure parameters are controlled in stages to ensure complete melt filling and dense solidification, thereby improving the density of the casting.

[0068] This method improves the uniformity of alloy composition and the density of castings, reduces the defect rate, and achieves efficient utilization of a high proportion of recycled aluminum, balancing production stability with low-carbon and environmentally friendly requirements. Specifically, it reduces the defect rate of porosity and inclusions in castings by more than 80% compared to traditional processes, achieves melt cleanliness ≥95%, and allows recycled aluminum to account for 30-50%, a significant improvement over existing technologies (recycled aluminum ≤20%), while reducing production energy consumption by 30%.

[0069] Example 3

[0070] The usage methods of heat-free die-cast aluminum alloys include:

[0071] The heat-free die-cast aluminum alloy is used to manufacture die-cast structural parts that do not require subsequent heat treatment.

[0072] The die-cast structural parts are prohibited from undergoing any form of solution treatment or aging heat treatment in subsequent processing. The die-cast structural parts are integrated die-cast rear bottom plates, battery housings, motor housings, or subframes for new energy vehicles.

[0073] When machining the die-cast structural parts, the cutting speed is controlled at 150-300 m / min, the feed rate is 0.1-0.3 mm / r, and cooling lubricant is added. When welding the die-cast structural parts, argon arc welding is used, and the welding temperature is controlled at 650-700℃. Inert gas protection is applied. The process also includes recycling the waste die-cast structural parts. During the remelting and regeneration process, the Fe content is controlled to be below 0.75 wt%, and the properties are adjusted by adding refining agents and microalloying elements.

[0074] (1) Prohibition of subsequent heat treatment: The strengthening mechanism of the alloy of the present invention depends on the metastable strengthening phase (Mg2Si, Q phase) and fine grain structure in the die-cast state. Subsequent solution / aging heat treatment will lead to the decomposition of metastable phase and grain growth, which will destroy the strengthening effect. Therefore, it is clearly prohibited to avoid component deformation and mechanical property decline (experimental verification: tensile strength decreased by ≥20% after heat treatment).

[0075] (2) Adaptive processing and welding: Taking into account the moderate hardness and good plasticity of the alloy, the machining parameters (cutting speed 150-300m / min, feed rate 0.1-0.3mm / r) are optimized to reduce work hardening and surface damage. The use of cooling lubricant avoids high-temperature oxidation. The control of argon arc welding (TIG welding) and welding temperature of 650-700℃ can reduce oxidation and grain coarsening in the weld area. Inert gas protection avoids the formation of pores and cracks in the weld, ensuring welding reliability.

[0076] (3) Recycling guarantee: During the remelting of waste components, the Fe content is controlled to be <0.75wt%, which can avoid the precipitation of harmful phases. Impurities generated during the remelting process are removed by refining agent, and microalloying elements (Ce, Ti) are added to compensate for the loss of components, restore the ability to precipitate strengthening phases and the effect of fine grains, and realize the recycling of resources.

[0077] This ensures the reliability and service life of components, reduces processing and assembly costs, and simultaneously achieves efficient recycling of waste components, improving resource utilization. Specifically, this manifests as no significant performance degradation of components over long-term use, a machining qualification rate ≥98%, good matching between welded joint strength and the substrate, a waste component recycling rate ≥80%, and the recycled components still meeting usage requirements.

Claims

1. Heat-treatable die-cast aluminum alloy, the composition of which, by weight percentage, includes: Si: 6-11 wt%, Mn: 0.3-2.1 wt%, Mg: 1.2-1.8 wt%, Cu: 1.2-1.8 wt%, Ti: 0.1-0.2 wt%, Sr: 0.01-0.05 wt%, Zn: 0.01-0.2 wt%, Cr: 0.04-0.2 wt%, Zr: 0-0.3 wt%, Ce: 0.1-0.3 wt%, Mo: 0.06-0.2 wt%, Fe: <0.75 wt%, other unavoidable impurity elements total <0.2 wt%, and the content of any single impurity element is <0.1 wt%, with the balance being Al.

2. The heat-free die-cast aluminum alloy according to claim 1, characterized in that, Its die-cast mechanical properties meet the following requirements: tensile strength ≥270MPa, yield strength ≥130MPa, and elongation ≥10%.

3. The preparation process of the heat-free die-cast aluminum alloy according to claim 1, characterized in that, Includes the following steps: (1) Raw material pretreatment and batching The raw materials are selected and pretreated, including composite aluminum raw materials, Al-20Si master alloy, Al-10Mn master alloy, pure Mg ingot, pure Cu ingot, Al-10Cr master alloy, Al-10Zr master alloy, Al-10Mo master alloy, Al-10Ti master alloy, Al-10Ce master alloy, pure Zn particles, Al-10Sr master alloy, and Al-K2TiF6-K2ZrF6-KBF4 reaction system; wherein the composite aluminum raw materials are composed of primary aluminum and recycled aluminum, with recycled aluminum accounting for 30-50%; The raw material is subjected to a gradient preheating and vacuum drying composite process, the composite process including first preheating at 120-150℃ for 1-2 hours, then raising the temperature to 180-200℃ and holding it at 100mbar for 2 hours; Based on thermodynamic calculation software, precise batching is optimized and executed, with batching error controlled within ±0.05wt%. (2) Segmented smelting and alloying Basic smelting: The pretreated composite aluminum raw material is smelted and heated to 760-810℃ in a stepped heating mode to make it completely melted. Then Al-20Si and Al-10Mn master alloys are added and the mixture is kept at a constant temperature using a combination of electromagnetic stirring and mechanical stirring. Alloy element addition and in-situ generation of strengthening phase: The melt temperature was lowered to 720-740℃, and pure Mg ingot, pure Cu ingot, Al-10Cr, Al-10Zr, Al-10Mo, Al-10Ti, Al-10Ce master alloy and pure Zn particles were added under a high-purity argon atmosphere. Then, a pretreated Al-K2TiF6-K2ZrF6-KBF4 reaction system was added, and TiB2 and ZrB2 nanoparticles were generated and uniformly distributed in the melt through the synergistic effect of mechanical stirring and short-term ultrasonic vibration. Modification treatment: Keep the melt temperature at 720-730℃, add Al-10Sr master alloy and stir and perform short-term ultrasonic vibration, then keep it at the temperature and let it stand, and use the synergistic effect of Sr and Ce to refine the eutectic silicon structure. (3) Melt purification treatment Refining and impurity removal: Heat the melt to 740-760℃, add a composite refining agent, and stir with argon bubbles, then let it stand to allow the inclusions to float to the surface; Degassing treatment: The melt temperature is reduced to 720-730℃, and degassing is carried out using an online argon rotary blowing process to ensure that the hydrogen content of the melt is ≤0.12ml / 100gAl; Slag removal and testing: Thoroughly remove slag from the liquid surface and perform online testing and adjustment of the melt composition and cleanliness to ensure that the melt cleanliness level is ≥95%; (4) Die casting The purified melt is cooled to 690-720℃ and held at that temperature; the mold, preheated to 180-250℃, is used for die casting. The die casting process adopts a high vacuum die casting process with a vacuum degree ≤50mbar, and the injection speed and holding pressure parameters are controlled in stages; after die casting is completed, the mold is opened, the part is removed, and cleaned.

4. The preparation process of the heat-free die-cast aluminum alloy according to claim 3, characterized in that, In the basic smelting step, the electromagnetic stirring power is 5-8kW, the mechanical stirring speed is 300-500r / min, and the stirring time is 3-5 minutes.

5. The preparation process of the heat-free die-cast aluminum alloy according to claim 3, characterized in that, In the steps of adding alloying elements and generating the strengthening phase in situ, the atomic ratio of Ti to B in the Al-K2TiF6-K2ZrF6-KBF4 reaction system is 1:2, and the Ti is dried at 200°C to remove water before being added; the short-time ultrasonic vibration power is 1000-1500W, and the time is 2-3 minutes.

6. The preparation process of the heat-free die-cast aluminum alloy according to claim 3, characterized in that, In the die casting process, the slow injection speed is 0.3-0.5 m / s, the fast injection speed is 3-5 m / s, the injection specific pressure is 80-120 MPa, the holding pressure is 60-80 MPa, and the holding time is 5-10 seconds.

7. The method of using the heat-free die-cast aluminum alloy according to claim 1 or 2, characterized in that, include: The heat-free die-cast aluminum alloy is used to manufacture die-cast structural parts that do not require subsequent heat treatment. The die-cast structural parts are prohibited from undergoing any form of solution treatment or aging heat treatment during subsequent processing; When machining the die-cast structural parts, the cutting speed is controlled at 150-300 m / min, the feed rate is 0.1-0.3 mm / r, and cooling lubricant is added.

8. The method of using the heat-free die-cast aluminum alloy according to claim 7, characterized in that, The die-cast structural components are integrated die-cast rear floor plates, battery housings, motor housings, or subframes for new energy vehicles.

9. The method of using the heat-free die-cast aluminum alloy according to claim 7, characterized in that, When welding the die-cast structural parts, argon arc welding is used, and the welding temperature is controlled at 650-700℃, while inert gas protection is applied.

10. The method of using the heat-free die-cast aluminum alloy according to claim 7, characterized in that, It also includes recycling the waste die-cast structural parts, controlling the Fe content to be below 0.75wt% during the remelting and regeneration process, and adjusting the performance by adding refining agents and microalloying elements.

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