Aluminum alloy material for grain refinement, grain refinement method and casting mold of aluminum alloy material

Abstract

The invention provides a grain-refined aluminum alloy material, a grain refining method and a casting mold of the grain-refined aluminum alloy material, and aims to solve the technical problems that the current aluminum alloy grain refining technology depends on an additional nucleating agent or conventional external field treatment, the effect is easy to attenuate, the aluminum alloy is poisoned by alloy elements, the refining limit exists, and an ultra-fine grain structure is difficult to realize. According to the method, alloy components containing copper and rare earth elements in a specific proportion are designed, a refrigerant unit array embedded in a casting mold is utilized in the initial stage of solidification, an instantaneous and super-strong cooling field is locally applied to melt, and therefore liquid phase separation in the melt is induced, and dispersed copper-rich / rare earth nano liquid drops are generated. The nano liquid drops preferentially separate out a high-melting-point intermetallic compound in subsequent solidification, and the high-melting-point intermetallic compound serves as an endogenous high-density nucleation core, so that ultra-fining of crystal grains is achieved. According to the special mold, dry ice packaged by a porous shell with uniform micropores is used as a refrigerant, so that safe and controllable transient strong cooling is realized. The aluminum alloy prepared through the method is excellent in cast-state comprehensive mechanical property.

Description

Technical Field

[0001] This invention relates to the field of aluminum alloy technology, and more specifically to an aluminum alloy material with refined grains, a grain refinement method, and a casting mold thereof. Background Technology

[0002] As an important lightweight structural material, the comprehensive mechanical properties of aluminum alloys largely depend on the size and morphology of the as-cast grains. Therefore, grain refinement is one of the core metallurgical methods to improve the strength, plasticity, and processing performance of aluminum alloys.

[0003] Currently, the most widely used grain refinement technology in industrial production is the addition of intermediate alloy refiners such as Al-Ti-B or Al-Ti-C. This technology relies on introducing high-melting-point particles such as TiB2 and TiC as heterogeneous nucleation cores to promote the nucleation and refinement of α-Al grains. However, this method has several inherent limitations: First, the introduced foreign nucleation particles are prone to agglomeration and sedimentation in the melt, resulting in uneven refinement and a decrease in refinement effect with prolonged residence time; second, elements commonly found in alloys, such as Zr and Cr, can "poison" these particles, causing them to lose their nucleation activity; finally, this method typically has a refinement limit of approximately 50-100 μm, making it difficult to meet the growing demand for ultrafine grain structures (grain size <20 μm).

[0004] To overcome these shortcomings, researchers have explored various technical approaches. For example, external field treatments such as ultrasonic vibration and electromagnetic stirring are used to improve melt convection, break dendrites, and promote the dispersion of nucleation particles. However, these methods are energy-intensive, have limited scope and effectiveness, and struggle to achieve orders-of-magnitude improvements in grain refinement. On the other hand, alloying design, adding elements such as Sc and Zr to form coherent precipitates like Al3(Sc,Zr) as nucleation nuclei, can yield fine-grained structures, but faces challenges such as high cost, narrow process windows, and the tendency for element segregation. Furthermore, while rapid solidification techniques can significantly refine the microstructure, they typically focus on increasing the overall cooling rate, neglecting the active and precise control of the local microstructure of the melt in the initial solidification stage, and failing to fully utilize extreme non-equilibrium conditions to induce endogenous, large-scale nucleation behavior.

[0005] In summary, existing aluminum alloy grain refinement technologies mainly face the following bottlenecks: 1. They rely on external nucleating agents, and their effectiveness is limited by agglomeration, attenuation, and "poisoning" effects, resulting in insufficient stability; 2. Conventional external field treatment methods have an upper limit on grain refinement improvement and are not economically viable; 3. High-end alloying routes are extremely expensive and difficult to apply on a large scale; 4. There is a lack of innovative methods that can actively and instantaneously control the thermal / mass conditions at the solidification front to induce instability in the melt's own structure and generate a large number of effective nucleation cores. Summary of the Invention

[0006] To address the technical problems of current aluminum alloy grain refinement technologies that rely on external nucleating agents or conventional external field treatments, which suffer from easy attenuation of effects, poisoning by alloying elements, refinement limits, and difficulty in achieving ultrafine grain structures, this invention provides an aluminum alloy material for grain refinement, a grain refinement method, and a casting mold. Through the synergy of composition design and transient strong cooling process, high-density nano-nucleation cores are generated in situ within the melt without relying on external refiners. This solves the problems of attenuation of refinement effects, element poisoning, and refinement limits in traditional methods, achieving a step-wise refinement of grain size (≤20μm) and stable improvement of microstructure and properties.

[0007] The technical solution of this invention is:

[0008] A method for refining the grain size of aluminum alloys includes the following steps:

[0009] S10. Prepare an aluminum alloy master melt, wherein the master melt comprises an aluminum matrix, silicon copper and rare earth elements;

[0010] S20. The master melt is introduced into the mold, and in the initial stage of the contact between the melt and the mold, a transient high-intensity cooling field lasting no more than 5 seconds is applied to a local area of ​​the melt to form a second phase droplet rich in copper and rare earth elements that is dispersed in the aluminum matrix melt.

[0011] S30. Stop the transient high-intensity cooling field so that the melt in the entire mold can solidify according to the set cooling program.

[0012] Optionally, in step S10, the rare earth element is selected from at least one of yttrium, gadolinium, and erbium;

[0013] The mother melt contains 5.0%-12.0% silicon, 2.0%-5.0% copper, and 0.5%-2.0% rare earth elements.

[0014] Optionally, the master melt also contains 0.3%-1.0% magnesium.

[0015] Optionally, in step S20, the transient high-intensity cooling field is applied by one or more micro heat sink units embedded in the cooling surface of the mold;

[0016] When activated, the surface temperature of the micro heat sink unit in contact with the melt is reduced to below 250°C.

[0017] Optionally, in step S20, under the action of the transient high-intensity cooling field, the molten thin layer in contact with it experiences an instantaneous cooling rate of more than 1000°C / s, and the duration of application of the transient high-intensity cooling field is 0.5-3.0s.

[0018] Optionally, in step S30, the set cooling procedure is to solidify the melt as a whole at an average cooling rate of 20°C / s-200°C / s.

[0019] The present invention also provides a technical solution:

[0020] A mold for casting the aluminum alloy material, comprising:

[0021] A casting body having a cavity at its top for filling the master melt, the casting body having a cooling surface with multiple embedded holes on the cooling surface;

[0022] Multiple refrigerant units are disposed one-to-one within the embedded holes.

[0023] Optionally, the refrigerant unit includes:

[0024] The housing is detachably disposed within the embedded hole. The housing is a porous structure with uniform micropores, the pore diameter of which is 1-10 μm.

[0025] Refrigerant pellets are filled inside the casing.

[0026] Optionally, the interior of the casting body is further provided with an air chamber, which communicates with all the embedded holes and with the housing, and the air chamber is connected to an inert gas micro-pressure supply system.

[0027] The present invention also provides a technical solution:

[0028] A grain-refining aluminum alloy material, the composition of which, by mass percentage, is:

[0029] Silicon: 5.0%-12.0%;

[0030] Copper: 2.5%-4.5%;

[0031] Rare earth elements: 0.8%-1.8%, wherein the rare earth element is at least one of Y, Gd, and Er;

[0032] Magnesium: 0-1.0%;

[0033] Unavoidable impurity elements: individual ≤0.05%, total ≤0.15%;

[0034] The balance is aluminum (Al);

[0035] The mass ratio of copper to rare earth elements is 1.5-4.0.

[0036] Compared with the prior art, the beneficial effects of the present invention are:

[0037] Through precise alloy composition design (specific ratios of copper, rare earth elements, and silicon), the melt itself possesses a thermodynamic tendency to undergo liquid-phase separation under extreme non-equilibrium conditions. Utilizing a transient high-intensity cooling field, diffusely distributed copper- and rare earth-rich second-phase nanodroplets are induced in situ within the melt during the initial solidification stage. These second-phase nanodroplets then act as endogenous, high-density, and thermally stable nucleation nuclei during subsequent overall solidification, inducing large-scale uniform nucleation of α-Al. This solves the inherent problems of agglomeration, sedimentation, attenuation, and elemental "poisoning" inherent in traditional refining agents, achieving a self-generating, stable, and efficient nucleation mechanism. Attached Figure Description

[0038] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0039] Figure 1 A schematic diagram of the process steps for refining aluminum alloy grains;

[0040] Figure 2 A schematic diagram of the structure of the mold for casting the aluminum alloy material.

[0041] Figure label:

[0042] 10. Casting mold body; 11. Mold cavity; 12. Embedding hole; 13. Air chamber;

[0043] 20. Refrigerant unit; 21. Housing; 22. Refrigerant pellets. Detailed Implementation

[0044] In the following description, only certain exemplary embodiments are briefly described. As those skilled in the art will recognize, the described embodiments can be modified in various ways without departing from the spirit or scope of the invention. Therefore, the drawings and description are considered to be exemplary in nature and not restrictive.

[0045] The following disclosure provides many different embodiments or examples for implementing various structures of the invention. To simplify the disclosure, specific examples of components and arrangements are described below. These are merely examples and are not intended to limit the invention. Furthermore, reference numerals and / or letters may be repeated in different examples; such repetition is for simplification and clarity and does not in itself indicate a relationship between the various embodiments and / or arrangements discussed. In addition, examples of various specific processes and materials are provided in this invention, but those skilled in the art will recognize the application of other processes and / or the use of other materials.

[0046] The embodiments of the present invention will now be described in detail with reference to the accompanying drawings.

[0047] Example 1:

[0048] See Figure 1 This embodiment discloses a method for refining the grain size of aluminum alloys. By combining precise design of the alloy composition with active control of extreme solidification conditions, in-situ induction and utilization of liquid phase separation within the aluminum melt achieves ultra-refined grain size. The method includes the following steps:

[0049] S10. Prepare aluminum alloy master melt with specific composition.

[0050] The mother melt not only contains an aluminum matrix and silicon, but more importantly, it contains a specific proportion of copper and at least one rare earth element selected from yttrium, gadolinium, and erbium. The synergistic effect of all elements forms the thermodynamic basis for subsequent liquid-phase separation.

[0051] In a preferred specific formulation, the components, by mass percentage, range as follows: Silicon content is 5.0%-12.0%, used to ensure the casting fluidity of the aluminum alloy and form the necessary eutectic structure. Copper content is 2.0%-5.0%, serving as the main driving element for liquid phase separation, exhibiting a strong solute redistribution tendency with the aluminum matrix under rapid cooling. Rare earth element content is 0.5%-2.0%, possessing both interfacial activity and the ability to form high-melting-point compounds, stabilizing the separated second-phase droplets and optimizing the nucleation interface.

[0052] To further enhance the material's strength, the master melt may also contain 0.3%-1.0% magnesium. This composition is intended to cause the alloy's melt structure to destabilize under extremely rapid cooling, spontaneously entering a metastable, immiscible liquid state.

[0053] S20. Apply a transient high-intensity cooling field to induce liquid phase separation.

[0054] After the mother melt is introduced into a specially designed mold, during the initial solidification stage when it comes into contact with the mold wall, a transient cooling field with a very short duration (no more than 5 seconds, preferably 0.5-3.0 seconds) and extremely high intensity is applied to a local area of ​​the melt.

[0055] This transient cooling field is applied by one or more refrigerant units 20 embedded in the cooling surface of the mold. Upon activation, the surface temperature of the refrigerant unit 20 in contact with the melt can be rapidly reduced to below 250°C, thereby generating extreme non-equilibrium conditions with an instantaneous cooling rate exceeding 1000°C / s within the extremely thin layer of melt in contact with it (micrometer to millimeter scale). Under this intense supercooling, the thermodynamic instability of the aluminum alloy melt designed in step S10 is triggered, resulting in microscale liquid phase separation. The originally homogeneous melt decomposes into two coexisting liquid phases in a localized region: a matrix liquid phase enriched with aluminum and silicon, and a second-phase droplet enriched with copper and rare earth elements, dispersed within the matrix liquid phase. The small size and uniform distribution of the second-phase droplets provide a vast number of potential nucleation sites for subsequent solidification.

[0056] S30, conventional cooling and solidification, to complete the formation of ultrafine crystalline structure.

[0057] After completing the aforementioned transient intensive cooling steps and stabilizing the microstructure formed by liquid phase separation, the high-intensity cooling field is stopped. Subsequently, the melt within the entire mold is allowed to solidify according to the set conventional cooling program, with the average cooling rate during this stage typically controlled between 20℃ / s and 200℃ / s.

[0058] During the overall solidification process in step S30, due to compositional differences, the copper- and rare-earth-rich second-phase droplets formed in step S20 will solidify preferentially before the aluminum matrix. Near their own solidification points, the second-phase droplets precipitate high-melting-point intermetallic compound nanoparticles such as Al2Cu and Al3RE. These in-situ precipitated nanoparticles, with a clean interface to the melt, can induce heterogeneous nucleation in the aluminum matrix (α-Al). Due to the large number and uniform distribution of nuclei, α-Al can undergo explosive nucleation growth almost simultaneously and throughout the melt. The intergranular competition and constraint among grains ultimately result in an aluminum alloy ingot with significantly refined grain size and uniform microstructure.

[0059] In this embodiment, instead of relying on external nucleating agents that are prone to agglomeration and poisoning, the melt itself generates a high-density nucleation core in the early stage of solidification through composition and process design, thus solving the problems of attenuation and interference in traditional methods.

[0060] By triggering the non-equilibrium process of liquid phase separation, it is possible to achieve a level of ultrafine grains that is difficult to achieve by traditional methods (the average grain size can be stably reduced to below 20 micrometers), and the microstructure is extremely uniform.

[0061] By precisely controlling the intensity, time, and spatial distribution of the transient cooling field, the degree of liquid phase separation and the characteristics of the second-phase droplets can be actively regulated, thereby achieving precise control over the final grain size and high process repeatability and stability.

[0062] Example 2:

[0063] See Figure 2 This embodiment discloses a casting mold specifically designed to implement the method in Embodiment 1. This mold is a key piece of equipment for implementing the "transient high-intensity cooling field" process, ensuring the reliable, accurate, and repeatable implementation of extreme cooling conditions.

[0064] The mold mainly consists of a casting body 10 and a refrigerant unit 20.

[0065] Specifically, the top of the mold body 10 is provided with a cavity 11 for pouring the master melt. Multiple regularly arranged insert holes 12 are machined on its critical cooling surface (typically the bottom surface or a specific sidewall). The mold body 10 also contains a gas chamber 13, which communicates with the bottom of all the insert holes 12 via internal channels. The gas chamber 13 is connected to a micro-pressure inert gas supply system (such as a nitrogen source and a precision pressure valve).

[0066] The number of refrigerant units 20 corresponds one-to-one with the embedding holes 12. Each refrigerant unit 20 is detachably installed in one embedding hole 12, so that the cooling surface inside the cavity 11 remains flat. Each refrigerant unit 20 is the core component that performs the cooling function. The refrigerant unit 20 specifically includes a housing 21 and a refrigerant projectile 22.

[0067] The shell 21 is made of a material with high thermal conductivity and resistance to molten aluminum corrosion (such as high thermal conductivity ceramics). Crucially, the shell 21 is a porous structure with uniformly interconnected micropores. The pore size of all micropores is precisely controlled within the range of 1-10 micrometers. The pore size must simultaneously meet the following requirements: 1. Sufficiently small pore size to utilize the significant resistance of the molten aluminum alloy under capillary action in the micropores, preventing molten aluminum from back-permeating into the shell 21 under hydrostatic pressure, ensuring safety; 2. Sufficiently high porosity (e.g., 40%-60%) and uniform pore size distribution to ensure rapid gas passage and achieve the jetting effect.

[0068] The refrigerant pellets 22 are solid phase-change cooling media filled within the porous shell 21. Preferably, they are small cylinders (e.g., 3-8 mm in diameter, 5-15 mm in length) pressed from solid carbon dioxide (dry ice) powder. Dry ice has advantages such as low sublimation temperature, high latent heat of sublimation, and inert gas as the sublimation product with no residue. When the high-temperature molten aluminum comes into contact with the shell 21, heat is rapidly transferred, causing the dry ice to sublimate violently, instantly generating high-pressure, low-temperature gas.

[0069] When using this mold, firstly, during the preparation stage, refrigerant pellets 22 made of dry ice are loaded into the housing 21 to assemble a refrigerant unit 20, which is then inserted into the embedding hole 12 of the casting body 10. A slightly positive pressure nitrogen gas is introduced into the gas chamber 13 and the back cavity of the housing 21 through an inert gas system to expel air and prevent premature sublimation of the dry ice.

[0070] During the transient intensive cooling stage, when the high-temperature aluminum alloy molten masterbatch is poured into the mold cavity 11 and contacts the cooling surface, heat is rapidly conducted through the wall of the porous shell 21 to the internal dry ice. The dry ice undergoes explosive sublimation, causing a sudden increase in pressure inside the shell 21. High-pressure, low-temperature carbon dioxide gas rapidly penetrates the micropores on the shell 21 and is sprayed onto the thin layer of molten masterbatch tightly adhering to the shell 21. This process is completed within 0.5-3.0 seconds, achieving transient ultra-intensive cooling of over 1000°C / s in the corresponding region of the molten masterbatch, perfectly meeting the process requirements of step S20 in Example 1.

[0071] After casting is completed, the final cleaning and maintenance stage begins. A high pressure is applied to the gas chamber 13 via an inert gas system to back-purge the porous shell 21, removing any trace residue and ensuring smooth operation for future use. The refrigerant unit 20 features a detachable design for easy refrigerant replacement and replenishment.

[0072] In this embodiment, extreme pulsed cooling of the melt is achieved. Through the instantaneous phase change expansion of the solid refrigerant pellet 22, millisecond-level ultra-strong cooling capacity and extremely high cooling intensity that cannot be achieved by traditional circulating liquid cooling or gas cooling are realized.

[0073] The micropores in the porous shell 21, through their physical barrier effect, allow for high-speed gas ejection while effectively preventing the penetration of molten aluminum, ensuring the safety of the process. Furthermore, by altering the array arrangement, density, and position of the embedded holes 12 and the refrigerant units 20, cooling fields of varying intensities can be flexibly applied to different parts of the casting, achieving customized temperature field control to adapt to the production of complex castings.

[0074] In one specific embodiment:

[0075] The pore size of the aforementioned micropores should meet three criteria:

[0076] First principle: The maximum characteristic size of the micropores must be smaller than the capillary penetration critical size of the molten aluminum alloy on the shell material 21 at the operating temperature. This ensures that molten aluminum cannot spontaneously seep into the pores when the refrigerant gas pressure is completely released and the molten metal is under static pressure.

[0077] The second criterion is that the total flow area and structure of the micropores must allow the high-pressure gas generated by the refrigerant explosion to pass through rapidly within milliseconds to seconds, in order to create a powerful jetting effect.

[0078] The third criterion is that porous structures must have sufficient mechanical strength and thermal shock resistance to withstand the instantaneous thermal shock from contact with high-temperature melts and the internal pressure shock.

[0079] Based on the above criteria, the outer shell should be designed as a porous structure with uniform micropores, rather than a few large pores.

[0080] Specifically, the maximum diameter of the pore (first criterion) and the penetration of molten aluminum alloy into refractory materials are mainly controlled by capillary force, therefore the following must be satisfied: capillary pressure >Melt static pressure And we also need to consider the possible gas pressure difference. Therefore, the condition for preventing leakage is: capillary pressure. >Melt static pressure +Gas pressure difference .

[0081] Among them, capillary pressure , The surface tension of molten aluminum, The contact angle of the molten aluminum on the shell material 21. This refers to the radius of the capillary pore. Generally speaking... >90°, A negative value indicates rejection; for simplification, the absolute value is used to calculate a conservative value.

[0082] melt static pressure , The density of molten aluminum, This refers to the height of the melt pressure head.

[0083] To ensure safety, the design At least for More than 5 to 10 times.

[0084] Taking A356 as an example, at 720℃, , Assuming ,design for 10 times. Then .

[0085] Substitute the values ​​into the formula to calculate the critical radius of the micropore: .

[0086] In addition, sufficient gas flux is required to meet the requirement of rapid release. The gas flow through the multi-porous shell 21 may be turbulent under high pressure differential, but it can be estimated as Darcy flow.

[0087] Darcy's Law is: ,in, Where is the volumetric flow rate, k is the permeability of the porous material (related to pore size and porosity), and A is the surface area of ​​the unit shell (gas outflow area). The pressure difference between the inside and outside of the casing 21 The viscosity of CO2 gas at high temperatures. The thickness is the porous shell wall thickness.

[0088] Assuming a refrigerant unit 20 contains 1 gram of dry ice, complete sublimation will produce approximately 0.5 liters of gas (under standard conditions). Under high temperature and pressure, the volume will expand, and the release time is targeted to be less than 0.5 seconds.

[0089] To achieve a high permeability k, the porosity is 40%-60% to provide numerous gas channels. The pore size is distributed in the range of 1-10 μm, and the wall thickness L of the shell 21 is as thin as possible while ensuring strength, preferably 0.5 mm-1.0 mm.

[0090] Example 3:

[0091] This embodiment discloses an aluminum alloy material with refined grains produced by the method of Embodiment 1, and optionally using the mold of Embodiment 2. The chemical composition of the material, in mass percentage, ranges as follows:

[0092] Silicon: 5.0%-12.0%, providing good casting properties.

[0093] Copper: 2.5%-4.5%, is the core element that induces liquid phase separation and forms a copper-rich second phase.

[0094] Rare earth elements: 0.8%-1.8%, at least one of Y, Gd, and Er, used to stabilize the second phase, refine the precipitated phase, and purify the melt.

[0095] Magnesium: 0-1.0%, used for subsequent aging strengthening.

[0096] Unavoidable impurity elements: strictly controlled, individual ≤0.05%, total ≤0.15%.

[0097] The balance is aluminum.

[0098] The preferred mass ratio of copper to rare earth elements is controlled within the range of 1.5-4.0. This ratio range can most effectively synergistically promote liquid-phase separation under transient quenching conditions and ensure that the second-phase droplets can precipitate high-melting-point nucleation particles of appropriate size and quantity.

[0099] Thanks to the aforementioned principles and processes, the obtained aluminum alloy ingot exhibits an ultrafine equiaxed grain structure, with the average grain size stably controlled below 20 micrometers, even reaching the submicrometer level, representing a breakthrough of orders of magnitude compared to traditional methods. Simultaneously, nanoscale intermetallic compounds precipitated from second-phase droplets are uniformly dispersed within the grains, forming a unique composite strengthening structure of an ultrafine-grained matrix and a nanoscale second phase. This structure not only enhances the material's strength, hardness, and wear resistance at room temperature, but also simultaneously improves its plasticity, toughness, and fatigue properties due to a significant increase in grain boundary ratio and a reduction in stress concentration. Furthermore, the refined equiaxed grain structure greatly improves the material's isotropy, hot workability, and surface quality.

[0100] The embodiments described above are merely illustrative of specific implementations of the present invention, and while the descriptions are detailed, they should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements all fall within the scope of protection of the present invention.

Claims

1. A method for refining the grain size of aluminum alloys, characterized in that, Includes the following steps: S10. Prepare an aluminum alloy master melt, wherein the master melt comprises an aluminum matrix, silicon copper and rare earth elements; S20. The master melt is introduced into the mold, and in the initial stage of the contact between the melt and the mold, a transient high-intensity cooling field lasting no more than 5 seconds is applied to a local area of ​​the melt to form a second phase droplet rich in copper and rare earth elements that is dispersed in the aluminum matrix melt. S30. Stop the transient high-intensity cooling field so that the melt in the entire mold can solidify according to the set cooling program.

2. The method for refining aluminum alloy grains according to claim 1, characterized in that: In step S10, the rare earth element is selected from at least one of yttrium, gadolinium, and erbium; The mother melt contains 5.0%-12.0% silicon, 2.0%-5.0% copper, and 0.5%-2.0% rare earth elements.

3. The method for refining aluminum alloy grains according to claim 2, characterized in that, The mother melt also contains 0.3%-1.0% magnesium.

4. The method for refining aluminum alloy grains according to claim 1, characterized in that: In step S20, the transient high-intensity cooling field is applied by one or more micro heat sink units embedded in the cooling surface of the mold; When activated, the surface temperature of the micro heat sink unit in contact with the melt is reduced to below 250°C.

5. The method for refining aluminum alloy grains according to claim 1, characterized in that, In step S20, under the action of the transient high-intensity cooling field, the molten thin layer in contact with it experiences an instantaneous cooling rate of more than 1000℃ / s, and the duration of application of the transient high-intensity cooling field is 0.5-3.0s.

6. The method for refining aluminum alloy grains according to claim 1, characterized in that, In step S30, the set cooling program is to solidify the melt as a whole at an average cooling rate of 20°C / s-200°C / s.

7. A mold for casting any of the aluminum alloy materials described in claims 1-6, characterized in that, include: A casting body having a cavity at its top for filling the master melt, the casting body having a cooling surface with multiple embedded holes on the cooling surface; Multiple refrigerant units are disposed one-to-one within the embedded holes.

8. The mold according to claim 7, characterized in that, The refrigerant unit includes: The housing is detachably disposed within the embedded hole. The housing is a porous structure with uniform micropores, the pore diameter of which is 1-10 μm. Refrigerant pellets are filled inside the casing.

9. The mold according to claim 8, characterized in that, The interior of the casting body is also provided with an air chamber, which is connected to all the embedded holes and to the shell. The air chamber is connected to an inert gas micro-pressure supply system.

10. An aluminum alloy material with refined grains, characterized in that, Its composition, expressed as a percentage by mass, is as follows: Silicon: 5.0%-12.0%; Copper: 2.5%-4.5%; Rare earth elements: 0.8%-1.8%, wherein the rare earth element is at least one of Y, Gd, and Er; Magnesium: 0-1.0%; Unavoidable impurity elements: individual ≤0.05%, total ≤0.15%; The balance is aluminum (Al); The mass ratio of copper to rare earth elements is 1.5-4.0.

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