A composite modifier for use in conductive and thermally conductive aluminum alloy profiles and its preparation method

Abstract

This invention relates to the field of aluminum alloy smelting technology, and provides a composite modifier for use in conductive and thermally conductive aluminum alloy profiles and its preparation method, solving the technical problems of existing aluminum alloy modifiers, such as difficulty in synergistic purification and grain refinement, easy oxidation and uneven distribution of active elements, and large amounts of smoke and dust and inaccurate quantitative analysis during the feeding process. The modifier includes a carrier skeleton and a surface modification layer covering the outer surface of the carrier skeleton. The carrier skeleton is composed of porous alumina ceramic spheres and includes the following raw materials: Al2O3, SiO2, and MgO. The surface modification layer is composed of KAlF4. The pores of the carrier skeleton are filled with a pore adsorbed phase, which includes the following raw materials by weight percentage: Cu-P alloy, rare earth fluorides, and K2TiF6; the rare earth fluorides are CeF3 and / or LaF3.

Description

Technical Field

[0001] This invention relates to the field of aluminum alloy smelting technology, and in particular to a composite modifier for use in conductive and thermally conductive aluminum alloy profiles and its preparation method. Background Technology

[0002] With the rapid development of new energy vehicles, 5G base stations, and ultra-high voltage power transmission and transformation, stringent requirements have been placed on the comprehensive performance of aluminum alloy profiles, demanding both high electrical and thermal conductivity and high strength and toughness. However, the strengthening mechanism of aluminum alloys often exhibits an inverse relationship with their electrical and thermal conductivity. While traditional grain refiners such as Al-Ti-B and Al-Ti-C can refine the microstructure, the ceramic phase particles they introduce, such as TiB2 and TiC, become strong scattering centers for electrons and phonons, leading to a significant decrease in the material's electrical conductivity.

[0003] To address these issues, the industry has attempted to use rare earth elements (such as Ce and La) and phosphorus (P) for composite modification treatment. Rare earth elements possess extremely high chemical reactivity, reacting with hydrogen and impurity elements in molten aluminum to form high-melting-point compounds, thus achieving degassing and purification. Cu-P alloys are commonly used to refine the eutectic silicon phase in aluminum-silicon alloys. However, existing technologies still suffer from the following insurmountable drawbacks in practical applications: (1) Burn-off and uncontrolled reaction of active elements. When active components such as rare earth fluorides are directly added to molten aluminum, they are prone to oxidation and burn-off or reaction with flux, resulting in low and uncontrollable actual yield. At the same time, due to the lack of protection, active elements often react violently on the surface of the melt and are difficult to penetrate into the interior, resulting in uneven microstructure and even the formation of coarse, hard and brittle intermetallic compound inclusions, which in turn deteriorates the mechanical properties.

[0004] (2) The contradiction between purification and degradation. Existing degradation treatments often focus on nucleation refinement, lacking the simultaneous improvement of melt purity. If the introduced degradation agent carrier or reaction byproducts (such as fluoride residues) cannot be effectively removed, they will inhibit conductivity.

[0005] (3) Poor feeding process. Traditional powdered degrading agents are prone to generating dust during feeding, which not only pollutes the environment but also poses a safety hazard of dust explosion. In addition, it is difficult to accurately measure the amount added, resulting in poor batch stability.

[0006] Chinese Patent Publication No. CN117987678A discloses an aluminum alloy modifier and a method for modifying aluminum alloys. The aluminum alloy modifier comprises NaCl, KCl, NF, KBF4, pure aluminum, aluminum-cerium master alloy, and aluminum-phosphorus master alloy. In the aluminum alloy modifier, by weight percentage, the content of NaCl is 10-20%, the content of KCl is 10-20%, the content of NF is 5-10%, the content of KBF4 is 10-20%, the content of cerium is 8-10%, and the content of phosphorus is 0.2-0.4%. This method directly adds Al-Ce master alloy and Al-P master alloy in powder form to molten aluminum at 900℃. Rare earth elements and phosphorus are easily oxidized and burned off, and due to density differences, they tend to segregate in the melt, leading to uneven modification. Furthermore, the purification function relies on salt fluxes such as NaCl / KCl, which easily remain in the aluminum matrix, forming flux inclusions.

[0007] Chinese Patent Publication No. CN109868396A discloses a molten salt material, its preparation method, and its application. The molten salt material is made from the following raw materials in parts by weight: sodium phosphate 13-18%, aluminum chloride 5-9%, manganese fluoride 0.6-1.2%, manganese acetate 5-8%, manganese nitrate 3-6%, sodium fluoride 11-15%, sodium fluorosilicate 3-7%, lithium fluoride 0.2-0.6%, ceramic powder 2-7%, with the balance being potassium chloride. The synergistic effect of various modifying elements such as rare earth elements ytterbium, thulium, sodium, and lithium results in excellent modification effects. Chlorite powder in the raw materials can act as a carrier for the modifier, removing gas and slag, simplifying the smelting steps, and improving smelting efficiency. The abundant alumina and silicon oxide in chlorite significantly enhance the hardness of the alloy. Combining molten salt electrolytic deposition with modification smelting fully utilizes the excellent modification effects of the molten salt material, significantly improving the strength, plasticity, and hardness of aluminum alloy castings. However, the hypoeutectic aluminum-silicon alloy prepared by this method aims for high strength and high hardness, but its electrical and thermal conductivity is relatively poor. The chlorite used for degassing also introduces a large amount of sodium salt, potassium salt, and lithium salt. These alkali metals remain in the aluminum matrix, which will seriously affect the conductivity. Summary of the Invention

[0008] Therefore, in view of the above problems, the present invention provides a composite modifier for use in conductive and thermally conductive aluminum alloy profiles and its preparation method, which solves the technical problems of existing aluminum alloy modifiers, such as difficulty in synergistic purification and grain refinement, easy oxidation and burn-off of active elements and uneven distribution, and large amount of smoke and dust and inaccurate quantitative analysis during the feeding process.

[0009] To achieve the above objectives, the present invention adopts the following technical solution: A composite modifier for use in conductive and thermally conductive aluminum alloy profiles includes a carrier skeleton and a surface modification layer covering the outer surface of the carrier skeleton; the carrier skeleton is composed of porous alumina ceramic spheres and includes the following raw materials by weight percentage: 85-92wt% Al2O3, 5-10wt% SiO2, and 1-3wt% MgO; the surface modification layer is composed of KAlF4. The pores of the carrier skeleton are filled with a pore adsorption phase, which includes the following raw materials by weight percentage: 85-90wt% Cu-P alloy, 3-8wt% rare earth fluoride, and 2-5wt% K2TiF6. The rare earth fluoride is CeF3 and / or LaF3.

[0010] Furthermore, based on the total weight of the composite modifier, the mass percentage of each component is as follows: the carrier skeleton 70%-85wt; the porous adsorption phase 10%-25wt; and the surface modification layer 3%-8wt.

[0011] Furthermore, the rare earth fluoride undergoes surface alloying pretreatment before use to form an Al-Ni alloy coating layer.

[0012] Rare earth fluorides have high surface energy and metal-repellent properties, making them prone to agglomeration when directly introduced into molten metal. The Al-Ni coating layer, acting as a transition interface, effectively reduces the interfacial energy of the system and improves the wettability between rare earth particles and Cu-P alloy liquid, thereby ensuring uniform dispersion of active elements in the melt.

[0013] Furthermore, the preparation process of the porous alumina ceramic spheres is as follows: a. Raw material compounding and pore formation: Al2O3, SiO2 and MgO powders are mixed according to weight percentage to obtain a first mixture. Spherical polymethyl methacrylate microspheres accounting for 15%-25% of the total mass of the first mixture are added as pore-forming agents, and 2%-5% methylcellulose and 1%-3% glycerol are added as auxiliary agents to obtain a second mixture. b. Pulverizing and aging: Deionized water is sprayed onto the second mixture obtained in step a to form wet granules. After repeated extrusion and degassing in a vacuum pulverizer, the mixture is sealed and aged for 24-48 hours to obtain pulverized material. c. Shaping: The clay material aged in step b is extruded and granulated into spherical green bodies of 1-3mm. d. Drying and sintering: The spherical green body is dried to a moisture content of <1%, and then sintered in two stages. First, the temperature is raised to 600℃ at 2℃ / min and held for 2h for degreasing, and then the temperature is raised to 1300℃-1450℃ at 5℃ / min and held for 3-5h for sintering to obtain porous alumina ceramic spheres.

[0014] By introducing spherical polymethyl methacrylate (PMMA) and sintering at 600℃, PMMA undergoes thermal decomposition and is completely discharged, constructing spherical cavities in situ within the carrier skeleton, thus forming a three-dimensional porous network. In the high-temperature sintering range of 1300℃-1450℃, SiO2 and MgO components reach a eutectic temperature, forming a transient liquid phase (glass phase). This liquid phase wets and fills the regions between Al2O3 particles, promoting metallurgical bonding between Al2O3 particles.

[0015] The preparation method of the composite modifier used in conductive and thermally conductive aluminum alloy profiles described above includes the following steps: S1. Place the porous alumina ceramic balls in a 5wt% HCl solution and ultrasonically clean for 30 min, then heat treat at 500℃ for 2 h. S2. Mix rare earth fluorides with Al powder and Ni powder, and perform high-energy ball milling under high-purity argon protection. The ball milling speed is 300-400 rpm and the time is 2 hours. An Al-Ni alloy coating layer is formed on the surface of the rare earth fluorides to obtain surface alloyed rare earth fluorides. S3. The surface-alloyed rare earth fluoride obtained in step S2 is dry mechanically mixed with K2TiF6 particles for 10-20 minutes to allow the K2TiF6 particles to adhere to the surface of the surface-alloyed rare earth fluoride, thus obtaining a third mixture. The third mixture is preheated to 300-400°C and then added to molten Cu-P alloy liquid at 750°C. Under inert gas protection, it is mechanically stirred for 5-10 minutes to form a solid-liquid mixed impregnation slurry. S4. Preheat the porous alumina ceramic balls treated in step S1 to 400-500℃, then immerse them in a solid-liquid mixing impregnation slurry, apply a vacuum negative pressure of -0.08MPa to -0.1MPa and maintain it for 10-15 minutes, then take them out and air cool them to room temperature to obtain loaded ceramic balls. S5. The loaded ceramic spheres obtained in step S4 are mixed with KAlF4 powder, so that KAlF4 adheres to the surface of the carrier. The composite modifier particles are collected, wrapped with aluminum foil, and placed in a mold for cold pressing. The mixture is pressed into a cylindrical preform with a diameter of 30-50 mm and a height of 20-40 mm. The cold pressing pressure is 200-400 MPa to obtain the composite modifier.

[0016] In step S3, through dry mechanical mixing, micron-sized K2TiF6 particles are tightly adhered to the surface of the surface-alloyed rare earth fluoride, forming composite particles. This gradation structure can effectively increase the effective density of the solid particle group and reduce the density gradient between it and the Cu-P alloy liquid, thereby weakening the Stokes sedimentation driving force.

[0017] In step S5, KAlF4 rapidly spreads under the surface tension of the molten aluminum, forming a low-melting-point flux coating layer. Based on the principle of "like dissolves like," the flux has a strong ability to capture Al2O3 inclusions and adsorbed [H] atoms in the molten aluminum. Through the dual action of physical adsorption and chemical dissolution, it encapsulates and carries them into the slag phase, achieving efficient impurity removal. This effectively removes heterogeneous phases that may become electron scattering centers and solves the problem of impurity introduction that the modifier itself may bring.

[0018] Furthermore, in step S2, the mixture of Al powder and Ni powder is a fourth mixture, and the mass ratio of the rare earth fluoride to the fourth mixture is 1:(0.2-0.5).

[0019] Furthermore, in step S2, the molar ratio of Al powder to Ni powder is (1-3):1.

[0020] Furthermore, in step S2, the grinding balls used in the high-energy ball mill are zirconia balls, and the ball-to-material ratio is (5-10):1.

[0021] Furthermore, in step S5, the particle size of the KAlF4 is 80-150 mesh, and the amount of KAlF4 added is 3%-8% of the loaded ceramic balls.

[0022] Furthermore, in step S5, the cold pressing adopts unidirectional molding, and the holding time is 10-30s.

[0023] By adopting the aforementioned technical solution, the beneficial effects of the present invention are as follows: 1. By utilizing the KAlF4 flux layer on the surface of the carrier skeleton, Al2O3 inclusions and [H] atoms are efficiently removed through the dual effects of physical adsorption and chemical slagging, significantly reducing electron scattering and improving the electrical and thermal conductivity of aluminum alloys; 2. Using Al-Ni alloy to coat rare earth fluorides, the melting point characteristics of intermetallic compounds are utilized to prevent the oxidation and burn-off of rare earth at high temperatures, and to achieve the controlled release of active elements in the melt, thus avoiding the formation of coarse, hard and brittle phases. 3. By dry mixing, K2TiF6 is attached to the rare earth surface to form composite particles, which effectively reduces the density difference with Cu-P alloy liquid, overcomes the Stokes sedimentation effect, and ensures that the active components inside the pores of the carrier skeleton are evenly distributed without segregation. 4. By utilizing the pore-forming mechanism of PMMA and the liquid-phase sintering mechanism of SiO2 and MgO, a connected three-dimensional pore network is constructed while ensuring the strength of the carrier skeleton, providing a high capillary force channel for subsequent vacuum impregnation. 5. By cold-pressing composite balls into prefabricated blocks wrapped in aluminum foil, the problems of smoke and dust pollution and inaccurate metering during powder feeding are solved. The prefabricated blocks disintegrate rapidly after entering the furnace, and have excellent deterioration and purification capabilities. Attached Figure Description

[0024] Figure 1 This is a schematic diagram illustrating the preparation of the composite modifier in an embodiment of the present invention. Detailed Implementation Example 1

[0025] A composite modifier for use in conductive and thermally conductive aluminum alloy profiles includes a carrier skeleton and a surface modification layer covering the outer surface of the carrier skeleton; the carrier skeleton is composed of porous alumina ceramic spheres and includes the following raw materials by weight percentage: 88wt% Al2O3, 9wt% SiO2, and 3wt% MgO; the surface modification layer is composed of KAlF4. The pores of the carrier skeleton are filled with a pore adsorption phase, which comprises the following raw materials by weight percentage: 87wt% Cu-P alloy, 8wt% rare earth fluoride, and 5wt% K2TiF6. The rare earth fluoride is CeF3.

[0026] Based on the total weight of the composite modifier, the mass percentage of each component is as follows: the carrier skeleton 78wt%; the porous adsorbent phase 17wt%; and the surface modification layer 5wt%.

[0027] The rare earth fluoride undergoes surface alloying pretreatment before use to form an Al-Ni alloy coating layer.

[0028] The preparation process of the porous alumina ceramic spheres is as follows: a. Raw material compounding and pore formation: Al2O3, SiO2 and MgO powders are mixed according to weight percentage to obtain a first mixture. Spherical polymethyl methacrylate microspheres accounting for 20% of the total mass of the first mixture are added as pore-forming agents, and 3% methylcellulose and 2% glycerol are added as auxiliary agents to obtain a second mixture. b. Pulverizing and aging: Deionized water is sprayed onto the second mixture obtained in step a to form wet granules. After repeated extrusion and degassing in a vacuum pulverizer, the mixture is sealed and aged for 24 hours to obtain pulverized material. c. Shaping: The clay material aged in step b is extruded and granulated into 3mm spherical green bodies; d. Drying and sintering: The spherical green body is dried to a moisture content of <1%, and then sintered in two stages. First, the temperature is raised to 600℃ at 2℃ / min and held for 2h for degreasing, and then the temperature is raised to 1380℃ at 5℃ / min and held for 4h for sintering to obtain porous alumina ceramic spheres.

[0029] refer to Figure 1 The preparation method of the composite modifier used in conductive and thermally conductive aluminum alloy profiles described above includes the following steps: S1. Place the porous alumina ceramic balls in a 5wt% HCl solution and ultrasonically clean for 30 min, then heat treat at 500℃ for 2 h. S2. Rare earth fluoride is mixed with Al powder and Ni powder, and then subjected to high-energy ball milling under high-purity argon protection at a speed of 300 rpm for 2 hours to form an Al-Ni alloy coating layer on the surface of the rare earth fluoride, thus obtaining surface-alloyed rare earth fluoride; the mixture of Al powder and Ni powder is a fourth mixture, and the mass ratio of the rare earth fluoride to the fourth mixture is 1:0.3; the molar ratio of Al powder to Ni powder is 2:1; the grinding balls used in the high-energy ball mill are zirconia balls, and the ball-to-material ratio is 8:1; S3. The surface-alloyed rare earth fluoride obtained in step S2 is dry mechanically mixed with K2TiF6 particles for 10 min, so that the K2TiF6 particles are attached to the surface of the surface-alloyed rare earth fluoride to obtain a third mixture. The third mixture is preheated to 300°C and then added to molten Cu-P alloy liquid at 750°C. Under inert gas protection, it is mechanically stirred for 10 min to form a solid-liquid mixed impregnation slurry. S4. The porous alumina ceramic balls treated in step S1 are preheated to 400°C, then immersed in a solid-liquid mixing impregnation slurry, a vacuum negative pressure of -0.08MPa is applied and maintained for 10 minutes, and then taken out and air-cooled to room temperature to obtain loaded ceramic balls. S5. The loaded ceramic balls obtained in step S4 are mixed with KAlF4 powder, so that KAlF4 adheres to the surface of the carrier. The composite modifier particles are collected, wrapped with aluminum foil, and placed in a mold for cold pressing to form a cylindrical preform with a diameter of 40 mm and a height of 30 mm. The cold pressing pressure is 300 MPa to obtain the composite modifier. The particle size of KAlF4 is 100 mesh, and the amount of KAlF4 added is 5% of the loaded ceramic balls. The cold pressing adopts unidirectional molding and the holding time is 20 s. Example 2

[0030] The difference from Example 1 is as follows: The pores of the carrier skeleton are filled with a pore adsorption phase, which comprises the following raw materials by weight percentage: 90wt% Cu-P alloy, 8wt% rare earth fluoride, and 2wt% K2TiF6. The rare earth fluoride is LaF3; In step S5, the amount of KAlF4 added is 8% of the amount of the loaded ceramic balls.

[0031] Other technical solutions are the same as in Example 1. Example 3

[0032] The difference from Example 1 is as follows: The carrier skeleton is composed of porous alumina ceramic spheres, comprising the following raw materials by weight percentage: 92wt% Al2O3, 5wt% SiO2, and 3wt% MgO; Other technical solutions are the same as in Example 1.

[0033] Comparative Example 1 The difference from Example 1 is as follows: Step S5 is not performed, i.e., KAlF4 is not coated on the surface of the loaded ceramic balls.

[0034] Other technical solutions are the same as in Example 1.

[0035] Comparative Example 2 The difference from Example 1 is as follows: Step S2 is not performed, i.e., no Al-Ni alloy coating is formed on the surface of rare earth fluorides.

[0036] Other technical solutions are the same as in Example 1.

[0037] Comparative Example 3 The difference from Example 1 is as follows: The porous alumina ceramic spheres prepared without using this technical solution are made by directly mechanically mixing raw materials Cu-P alloy, rare earth fluoride, K2TiF6, and KAlF4 and then cold pressing them into blocks.

[0038] The composite modifiers prepared in Examples 1 to 3 and Comparative Examples 1 to 3 were added to 6063 aluminum alloy melt at a ratio of 0.2 wt%. After melting at 720°C, they were cast into tensile test bars and conductivity test specimens. The performance was then tested, and the test results are shown in Table 1.

[0039] Table 1 Comparative Example 1 58.2 205 215 120 Poor (lots of junk) Comparative Example 2 56.5 198 230 80 (mixed) generally Comparative Example 3 55.0 190 210 150 Difference Example 1 61.5 228 245 45 excellent Example 2 62.0 225 238 50 good Example 3 60.5 230 260 35 excellent As can be seen from Table 1, compared with the existing technology, this technical solution solves the long-standing problem of mutual exclusion between purification and modification in conductive aluminum alloys, and significantly improves mechanical properties without sacrificing conductivity, demonstrating outstanding substantive features and significant progress.

[0040] Electrical conductivity: Refer to GB / T 12966-2022 "Eddy current test method for electrical conductivity of aluminum alloys".

[0041] Thermal conductivity: Refer to GB / T 22588-2008 "Measurement of thermal diffusivity or thermal conductivity by flash method".

[0042] Tensile strength: Refer to GB / T 228.1-2021 "Metallic materials - Tensile testing - Part 1: Test method at room temperature".

[0043] Grain size: Refer to GB / T 6394-2017 "Method for determination of average grain size of metals".

[0044] Purification effect evaluation: Refer to GB / T 3246.1-2024 "Test methods for microstructure of wrought aluminum and aluminum alloy products - Part 1: Test methods for microstructure".

[0045] Although the invention has been specifically shown and described in conjunction with preferred embodiments, those skilled in the art should understand that various changes in form and detail may be made to the invention without departing from the spirit and scope of the invention as defined in the appended claims, all of which shall be within the scope of protection of the invention.

Claims

1. A composite modifier for use in conductive and thermally conductive aluminum alloy profiles, characterized in that, It includes a carrier skeleton and a surface modification layer covering the outer surface of the carrier skeleton; the carrier skeleton is composed of porous alumina ceramic spheres, comprising the following raw materials by weight percentage: 85-92wt% Al2O3, 5-10wt% SiO2, and 1-3wt% MgO; the surface modification layer is composed of KAlF4. The pores of the carrier skeleton are filled with a pore adsorption phase, which includes the following raw materials by weight percentage: 85-90wt% Cu-P alloy, 3-8wt% rare earth fluoride, and 2-5wt% K2TiF6. The rare earth fluoride is CeF3 and / or LaF3.

2. The composite modifier for use in conductive and thermally conductive aluminum alloy profiles according to claim 1, characterized in that, Based on the total weight of the composite modifier, the mass percentage of each component is as follows: the carrier skeleton 70%-85wt; the porous adsorption phase 10%-25wt; and the surface modification layer 3%-8wt.

3. The composite modifier for use in conductive and thermally conductive aluminum alloy profiles according to claim 1, characterized in that, The rare earth fluoride undergoes surface alloying pretreatment before use to form an Al-Ni alloy coating layer.

4. The composite modifier for use in conductive and thermally conductive aluminum alloy profiles according to claim 1, characterized in that, The preparation process of the porous alumina ceramic spheres is as follows: a. Raw material compounding and pore formation: Al2O3, SiO2 and MgO powders are mixed according to weight percentage to obtain a first mixture. Spherical polymethyl methacrylate microspheres accounting for 15%-25% of the total mass of the first mixture are added as pore-forming agents, and 2%-5% methylcellulose and 1%-3% glycerol are added as auxiliary agents to obtain a second mixture. b. Pulverizing and aging: Deionized water is sprayed onto the second mixture obtained in step a to form wet granules. After repeated extrusion and degassing in a vacuum pulverizer, the mixture is sealed and aged for 24-48 hours to obtain pulverized material. c. Shaping: The clay material aged in step b is extruded and granulated into spherical green bodies of 1-3mm. d. Drying and sintering: The spherical green body is dried to a moisture content of <1%, and then sintered in two stages. First, the temperature is raised to 600℃ at 2℃ / min and held for 2h for degreasing, and then the temperature is raised to 1300℃-1450℃ at 5℃ / min and held for 3-5h for sintering to obtain porous alumina ceramic spheres.

5. The method for preparing a composite modifier for use in conductive and thermally conductive aluminum alloy profiles according to claim 1, characterized in that, Includes the following steps: S1. Place the porous alumina ceramic balls in a 5wt% HCl solution and ultrasonically clean for 30 min, then heat treat at 500℃ for 2 h. S2. Mix rare earth fluorides with Al powder and Ni powder, and perform high-energy ball milling under high-purity argon protection. The ball milling speed is 300-400 rpm and the time is 2 hours. An Al-Ni alloy coating layer is formed on the surface of the rare earth fluorides to obtain surface alloyed rare earth fluorides. S3. The surface-alloyed rare earth fluoride obtained in step S2 is dry mechanically mixed with K2TiF6 particles for 10-20 minutes to allow the K2TiF6 particles to adhere to the surface of the surface-alloyed rare earth fluoride, thus obtaining a third mixture. The third mixture is preheated to 300-400°C and then added to molten Cu-P alloy liquid at 750°C. Under inert gas protection, it is mechanically stirred for 5-10 minutes to form a solid-liquid mixed impregnation slurry. S4. Preheat the porous alumina ceramic balls treated in step S1 to 400-500℃, then immerse them in a solid-liquid mixing impregnation slurry, apply a vacuum negative pressure of -0.08MPa to -0.1MPa and maintain it for 10-15 minutes, then take them out and air cool them to room temperature to obtain loaded ceramic balls. S5. The loaded ceramic spheres obtained in step S4 are mixed with KAlF4 powder, so that KAlF4 adheres to the surface of the carrier. The composite modifier particles are collected, wrapped with aluminum foil, and placed in a mold for cold pressing. The mixture is pressed into a cylindrical preform with a diameter of 30-50 mm and a height of 20-40 mm. The cold pressing pressure is 200-400 MPa to obtain the composite modifier.

6. The method for preparing a composite modifier for use in conductive and thermally conductive aluminum alloy profiles according to claim 5, characterized in that, In step S2, the mixture of Al powder and Ni powder is a fourth mixture, and the mass ratio of the rare earth fluoride to the fourth mixture is 1:(0.2-0.5).

7. The method for preparing a composite modifier for use in conductive and thermally conductive aluminum alloy profiles according to claim 5, characterized in that, In step S2, the molar ratio of Al powder to Ni powder is (1-3):

1.

8. The method for preparing a composite modifier for use in conductive and thermally conductive aluminum alloy profiles according to claim 5, characterized in that, In step S2, the grinding balls used in the high-energy ball mill are zirconia balls, and the ball-to-material ratio is (5-10):

1.

9. The method for preparing a composite modifier for use in conductive and thermally conductive aluminum alloy profiles according to claim 5, characterized in that, In step S5, the particle size of KAlF4 is 80-150 mesh, and the amount of KAlF4 added is 3%-8% of the loaded ceramic balls.

10. The method for preparing a composite modifier for use in conductive and thermally conductive aluminum alloy profiles according to claim 5, characterized in that, In step S5, the cold pressing is performed using unidirectional molding, and the holding time is 10-30 seconds.

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