An aluminum-silicon alloy, its preparation method and application

Abstract

This invention discloses an aluminum-silicon alloy, its preparation method, and its applications, belonging to the field of alloy technology. The aluminum-silicon alloy of this invention has a divorced eutectic structure, with no eutectic silicon phase, an average primary silicon grain size ≤ 5.2 μm, a shape factor ≥ 0.6, and primary silicon uniformly distributed in an ultrafine equiaxed α-Al grain matrix with an average α-Al grain size ≤ 5 μm. The alloy porosity is ≤ 0.15%, thermal conductivity ≥ 180 W / (m·K), tensile strength ≥ 265 MPa, and elongation ≥ 5.5%. The preparation method utilizes a combined technical route of "glass tube suction casting + multi-gradient solid solution + single-pass ECAP + semi-solid treatment + aging treatment" to prepare a hypereutectic aluminum-silicon alloy with an ultrafine spheroidized silicon phase, high thermal conductivity, high strength, and high toughness, while also possessing low porosity, high thermal conductivity, high strength, and high plasticity. It can be widely used in aerospace, automotive industry, thermal management systems, and other fields.

Description

Technical Field

[0001] This invention relates to an aluminum-silicon alloy, its preparation method, and its applications. Specifically, it relates to a hypereutectic aluminum-silicon alloy with ultrafine spheroidized silicon phase and high thermal conductivity and high strength and toughness, prepared through a combined technical route of "glass tube suction casting + multi-gradient solid solution + single-pass ECAP + semi-solid treatment + aging treatment," and its preparation method and applications. Its microstructure is a unique microstructure of "ultrafine equiaxed matrix + ultrafine spheroidized silicon phase + ultra-low defect," and it also possesses low porosity, high thermal conductivity, high strength, and high plasticity. This invention belongs to the field of alloy technology. Background Technology

[0002] Hypereutectic aluminum-silicon alloys are widely used in automotive engine pistons and electronic device heat dissipation components due to their excellent wear resistance and low coefficient of thermal expansion resulting from high silicon content, as well as the low density characteristics imparted by the aluminum matrix. However, under traditional casting processes (such as metal mold casting and sand casting), hypereutectic aluminum-silicon alloys tend to form coarse, plate-like primary silicon phases (particle size 20-50 μm) that are interconnected and interwoven with eutectic grains, forming coarse eutectic silicon wafers. These coarse and irregularly shaped silicon phases severely disrupt the aluminum matrix, resulting not only in extremely poor alloy strength and ductility (tensile strength typically <120 MPa, elongation typically <2%), but also in blocking heat conduction paths, causing thermal conductivity to generally fall below 100 W / (m·K), making it difficult to meet the integrated requirements of high-end equipment for materials with "high thermal conductivity + high strength + high toughness".

[0003] Existing technologies for improving the properties of hypereutectic aluminum-silicon alloys face significant bottlenecks: First, while modification treatments (such as P and Sr modification) can refine the eutectic silicon phase, they cannot alter the morphology of the primary silicon phase and easily introduce impurities, leading to performance fluctuations. Second, rapid solidification techniques (such as spray deposition) can achieve fine-grained structures, but subsequent forming is difficult and costly, hindering industrial-scale application. Third, when directly performing ECAP processing on traditional ingots, the primary silicon is coarse and contains numerous lamellar eutectic silicon layers, resulting in stress concentration within the ingot, making it prone to cracking during extrusion. Furthermore, the high deformation resistance necessitates multiple passes to break the silicon phase, leading to high energy consumption, the introduction of lattice defects, and poor thermal conductivity. In addition, existing technologies have not addressed the crucial role of the "divergent eutectic structure of hypereutectic aluminum-silicon alloys" in subsequent single-pass ECAP processing.

[0004] Therefore, for hypereutectic aluminum-silicon alloys, developing a preparation method that can obtain a divorced eutectic structure through glass tube suction casting, and then combine multi-gradient solid solution treatment, single-pass ECAP processing, semi-solid isothermal treatment, and aging treatment to achieve silicon phase ultrafine spheroidization and synergistic performance improvement has become the key to breaking through the performance bottleneck of this material. Summary of the Invention

[0005] The core objective of this invention is to overcome the shortcomings of traditional hypereutectic aluminum-silicon alloys, such as continuous eutectic structure, coarse silicon phase, numerous casting defects, and difficulty in achieving a balance between performance and properties. It provides a method for preparing hypereutectic aluminum-silicon alloys with ultrafine spheroidized silicon phase and high thermal conductivity and high strength and toughness, without requiring alloy composition optimization, solely through process innovation. The core lies in achieving a leapfrog improvement in alloy structure and performance through a synergistic process of "glass tube suction casting + multi-gradient solid solution + single-pass ECAP + semi-solid treatment + aging treatment".

[0006] Meanwhile, this invention provides an ultrafine spheroidized silicon phase and a hypereutectic aluminum-silicon alloy with high thermal conductivity and high strength and toughness, achieving a synergistic improvement in thermal conductivity and plasticity. It aims to meet the urgent need for improved efficiency of current thermal management systems, meet the urgent need for integrated development of battery packs and liquid cooling plates in the new energy field, improve resource recycling rate, reduce primary mineral consumption, and reduce carbon emissions by simplifying the recycling process, thereby achieving synergistic optimization of economic and ecological benefits.

[0007] Meanwhile, this invention provides an application of an ultrafine spheroidized silicon phase and a hypereutectic aluminum-silicon alloy with high thermal conductivity and high strength and toughness in materials that combine lightweight, high-performance heat dissipation, and long service life.

[0008] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows:

[0009] Castings with a heterogeneous eutectic structure were prepared using glass tube suction casting, which completely eliminated the brittle eutectic silicon phase and initially refined the primary silicon phase, creating ideal conditions for subsequent single-pass ECAP processing. The castings with the heterogeneous structure underwent multi-gradient solution treatment to eliminate macroscopic elemental segregation in the as-cast structure and achieve high solid solution treatment of alloying elements. Single-pass ECAP achieved porosity closure, ultrafine silicon phase fragmentation, and ultrafine α-Al matrix. This is something that conventional ECAP processes cannot achieve with conventional as-cast structures. Simultaneously, subsequent semi-solid treatment and aging treatment further promoted the spheroidization and uniform distribution of the silicon phase and further improved the alloy strength. Ultimately, a novel material with a unique microstructure of "ultrafine equiaxed crystal matrix + ultrafine spheroidized silicon phase + ultra-low defect" was obtained, thus achieving a synergistic leap in the three key properties of hypereutectic aluminum-silicon alloys: strength, plasticity, and thermal conductivity.

[0010] The aluminum alloy is a hypereutectic aluminum-silicon alloy, in which the silicon content is 14-16 wt.%, the copper content is 4-6 wt.%, the iron content is <0.1 wt.%, the magnesium content is <0.01 wt.%, the manganese content is <0.01 wt.%, the zinc content is <0.01 wt.%, and the remainder is aluminum.

[0011] A method for preparing an aluminum-silicon alloy includes the following steps:

[0012] Step 1, Raw Material Preparation and Melting: Based on the composition of the hypereutectic aluminum-silicon alloy, prepare Al-20Si alloy, Al-20Cu alloy, and pure Al ingot raw materials. Place the graphite crucible in a resistance furnace and heat it to 490-510℃. Add the polished, cleaned, and dried raw materials in an orderly manner. Set the furnace temperature to 750-780℃. After complete melting, perform multiple stirrings and slag skimming. Then, set the furnace temperature to 720-750℃ and hold for 30-60 minutes.

[0013] Step 2, refining and degassing: Add hexachloroethane refining agent to the alloy melt at a rate of 0.5-0.8 wt.% of the total mass of the alloy melt. Use a graphite bell jar to press the refining agent into the alloy melt and swing it up and down to allow it to fully react with the H element. After the process is complete, skim off the residue and set the temperature to 650-680℃ and hold for 1-1.5 hours. This process is a commonly used degassing and slag removal process in the foundry industry.

[0014] Step 3: Preparation of a heterogeneous eutectic structure by glass tube suction casting: The suction casting mold is inserted into the refined alloy melt at 650-680℃ to a depth of 50-80mm. The liquid alloy is drawn into a room temperature glass tube with an inner diameter of 30-35mm, a length of 500-550mm, and a wall thickness of 1-2mm. The tube is then cooled with air. Throughout this process, the negative pressure suction device and the tube are kept sealed to ensure that the external air pressure continuously pushes the alloy melt upwards. The glass tube ruptures during cooling, exposing the alloy and yielding a hypereutectic aluminum-silicon alloy casting with a heterogeneous eutectic structure.

[0015] Step 4, Multi-gradient Solution Treatment: Take a 45mm long sample from the upper end (near the suction device) of the casting obtained in Step 3, remove glass slag and cutting marks from the surface with sandpaper, and polish the surface smooth. First, raise the polished casting to 250-300℃ at room temperature at 5-10℃ / min and hold for 30-60min to eliminate residual stress. Then, raise the temperature to 400-450℃ at 3-6℃ / min and hold for 1-1.5h (pre-solution of low-melting-point phases). Finally, raise the temperature to 470-490℃ at 2-4℃ / min and hold for 1.5-2h, using Ar + 0.5-0.8%H2 (i.e., 99.2-99.5% Ar and 0.5-0.8% H2) as a protective gas to eliminate macroscopic element segregation in the as-cast microstructure and achieve high solid solution of alloying elements. After the heat preservation is completed, the alloy is immediately water quenched to 150-200℃ at a cooling rate of 200-250℃ / s, and then air-cooled to room temperature to reduce residual stress.

[0016] Step 5, single-pass ECAP processing: Graphite is evenly applied to the specimen and the inside of the ECAP mold after the solution treatment in Step 4 to act as a lubricant. At the same time, the specimen and mold are placed in a box-type resistance furnace and preheated at 320-400℃ for 1-2 hours before a single extrusion process is carried out at an extrusion speed of 3-5 mm / s.

[0017] Step 6, semi-solid isothermal treatment: Heat the billet after ECAP extrusion in Step 5 to 580-600℃, hold for 10-20 minutes, and then cool to room temperature at a rate of 10-15℃ / s.

[0018] Step 7, Aging treatment: After the semi-solid treatment in step 6, the alloy is held at 160-180℃ for 4-8 hours and then cooled to room temperature in the furnace to obtain the finished product of the hypereutectic aluminum-silicon alloy with ultrafine spheroidized silicon phase and high thermal conductivity and high strength and toughness.

[0019] In step one, before melting, the alloy ingot raw material is first ground to remove the surface oxide layer. Then, the surface debris of the ground alloy ingot is cleaned and placed in a degreasing solution for ultrasonic cleaning for 5-10 minutes to further remove impurities and oil stains. The graphite crucible and all tools in contact with the melt are evenly sprayed with a 1-2 mm thick coating to avoid the introduction of impurity elements during the casting process. The coating consists of analytical grade zinc oxide, analytical grade sodium silicate nonahydrate, and deionized water in a ratio of 2:1:5. The mold used for suction casting is cleaned with anhydrous ethanol to ensure that there are no other impurities on the inner wall and to avoid interference from heterogeneous nucleation substrates. All prepared raw materials, molds, and casting tools are placed in a forced-air drying oven for preheating and drying, and the heat preservation time is controlled at more than 4 hours to ensure absolute dryness.

[0020] In step two, the refining agent used in refining is wrapped in aluminum foil to ensure a leak-proof seal. Before refining, it is placed in a forced-air drying oven for 1 hour to ensure absolute dryness.

[0021] After step three, the eutectic silicon phase in the alloy disappears, forming a divorced eutectic structure.

[0022] After step four, the composition and microstructure of the alloy are more uniform, the α-Al matrix softens, the plasticity is improved, the deformation resistance is reduced, making the ECAP extrusion process easier; the residual stress in the alloy is reduced, reducing the risk of cracking during subsequent ECAP extrusion.

[0023] After step five, the porosity in the alloy is greatly reduced and maintained at a low level; the primary silicon particles are largely broken down and refined, and are uniformly distributed in the α-Al matrix; the α-Al matrix is ​​transformed from coarse dendrites into ultrafine equiaxed crystals.

[0024] In step five, the channel angle of the ECAP mold is 90°.

[0025] After step six, the silicon phase distribution becomes more uniform, the shape factor coefficient increases, and further spheroidization occurs.

[0026] After step seven, fine reinforcing phases precipitate, further improving the alloy strength.

[0027] The high thermal conductivity, high strength and toughness hypereutectic aluminum-silicon alloy has a porosity ≤0.15%, thermal conductivity ≥180W / (m·K), tensile strength ≥265MPa, and elongation ≥5.5%.

[0028] Application of an aluminum-silicon alloy in materials that combine lightweight, high-performance heat dissipation, and long service life.

[0029] The aforementioned hypereutectic aluminum-silicon alloy, which combines lightweight advantages with high thermal conductivity and high strength and toughness, is mainly used in integrated structures of new energy vehicle battery packs and dynamic joint modules of industrial robots, as well as other medium-to-high load heat dissipation components. It is important to balance the material's strength and toughness with its thermal conductivity. In addition, it also focuses on precision components such as chip substrates, power module heat dissipation shells, and IGBT components in the field of electronic packaging, as well as aerospace materials such as core components of hydraulic systems, wear-resistant components of landing gear, satellite payload supports, and valve shells of propulsion systems.

[0030] It places greater emphasis on the simultaneous optimization of the material's low expansion characteristics and thermal / mechanical properties. At the material design level, this invention utilizes a common technical approach, including advanced solidification technology, advanced solution treatment technology, advanced ECAP deformation technology, advanced semi-solid isothermal treatment technology, and aging treatment technology, to achieve the unified goal of refining the microstructure and improving macroscopic properties.

[0031] Traditional ECAP processes typically yield alloys with coarse, conventional as-cast microstructures containing lamellar eutectic silicon. These alloys exhibit high deformation resistance, requiring high temperatures and numerous passes to fully refine the silicon phase, resulting in high energy consumption and a tendency to introduce lattice defects, which negatively impacts thermal conductivity. This invention utilizes glass tube suction casting to prepare a preform with a unique "non-equilibrium segregated eutectic microstructure." This microstructure is an "ideal precursor" for achieving "super-solid plastic rheological processing" in a single-pass ECAP, making it possible to perform single-pass ECAP on hypereutectic aluminum-silicon alloys at lower temperatures. The fine primary silicon, acting as a dispersed phase, is more prone to rotation, slip, and further refinement and spheroidization under shear forces. The α-Al matrix also exhibits more uniform plastic flow and dynamic recrystallization. The "in-situ spheroidization of the silicon phase and ultra-refinement of the matrix" occurring during ECAP is a unique evolutionary result of this special microstructure under shear forces, exhibiting a profound coupling mechanism rather than a simple superposition.

[0032] The beneficial effects of adopting the above technical solution are as follows: This invention provides a high thermal conductivity, high strength and toughness hypereutectic aluminum-silicon alloy that can be prepared on a large scale, with simple process and controllable cost, and its preparation method. It can optimize the comprehensive performance of the material without relying on complex alloying elements or extreme processing conditions, and mainly has the following advantages:

[0033] (1) The hypereutectic aluminum-silicon alloy of the present invention does not contain any other expensive alloying elements. The alloy contains 14-16 wt.% silicon, 4-6 wt.% copper, <0.1 wt.% iron, <0.01 wt.% magnesium, <0.01 wt.% manganese, <0.01 wt.% zinc, and the remainder is aluminum. Therefore, the material cost is lower and recycling is simpler, perfectly meeting the core demand of the cost-effective industrial profile field for low-cost and environmentally friendly materials.

[0034] (2) The glass tube suction casting process used in this invention does not require the addition of modifiers and refiners, thus avoiding the pollution caused by the addition of modifiers to the environment and will not introduce new impurities into the melt. It has low operating costs, does not require vacuum conditions, and is simple to operate. Compared with other processes that require complex equipment and high energy consumption, it has more environmental advantages.

[0035] (3) This invention adopts single-pass ECAP technology, which can achieve ultrafine crushing of silicon phase and ultrafine α-Al matrix in just one pass, and can refine primary silicon phase and α-Al phase to the submicron level. Compared with conventional multi-pass ECAP or other complex processing technology, the synergistic process of "glass tube suction casting + multi-gradient solid solution + single-pass ECAP + semi-solid treatment + aging treatment" can obtain excellent microstructure and performance. Its process is highly controllable, simple to operate, and suitable for industrial production.

[0036] (4) This invention is not only a process, but also provides a new theory of tissue regulation:

[0037] Genetic effects—The microstructure characteristics (fineness, spheroidization, and aberration) created by GTSC are "inherited" and "amplified" by the ECAP process, rather than being completely reversed. Strain-induced spheroidization mechanism—In the pure shear stress field of ECAP, the primary silicon phase undergoes further strain-induced spheroidization through a "dissolution-diffusion-reprecipitation" mechanism (Ostwald ripening is suppressed by shear rheology), further enhancing the shape factor (F).

[0038] In summary, this invention proposes a method for preparing a high thermal conductivity, high strength, and high toughness hypereutectic aluminum-silicon alloy with a unique microstructure consisting of an ultrafine equiaxed crystal matrix, an ultrafine spheroidized silicon phase, and ultra-low defects. This alloy exhibits excellent thermal conductivity and mechanical properties, and the experimental design is simple and easy to implement, significantly reducing production costs. It perfectly meets the core demand of the cost-effective industrial profile sector for low-cost and environmentally friendly materials, possessing significant industrial application value and suitable for industrial applications in aerospace, automotive, and thermal management systems.

[0039] This invention relates to hypereutectic aluminum-silicon alloy material processing technology, specifically to a method for obtaining a unique microstructure with "ultra-fine equiaxed crystal matrix + ultra-fine spheroidized silicon phase + ultra-low defects" through a synergistic process of "glass tube suction casting + multi-gradient solid solution + single-pass ECAP + semi-solid treatment + aging treatment", thereby realizing the preparation of high thermal conductivity and high strength and toughness hypereutectic aluminum-silicon alloys and their application in lightweight, high-performance heat dissipation, and long service life materials. This invention, through the deep integration of eutectic solidification separation growth technology, heat treatment technology, and large plastic deformation technology, successfully constructs a ternary synergistic integrated structure of "ultra-fine equiaxed crystal matrix + ultra-fine spheroidized silicon phase + ultra-low defect" in hypereutectic aluminum-silicon alloy. Its internal primary silicon has an average particle size ≤5.2μm and a shape factor ≥0.6, an average particle size of matrix α-Al ≤5μm, a porosity ≤0.15%, a thermal conductivity ≥180W / (m·K), a tensile strength ≥265MPa, and an elongation ≥5.5%. It has excellent thermal conductivity, high strength, and high toughness, and can simultaneously improve thermal conductivity and mechanical properties. Attached Figure Description

[0040] Figure 1 This is a flow chart of the aluminum-silicon alloy preparation process in this invention;

[0041] Figure 2 This is a porosity distribution diagram of the aluminum-silicon alloy in the as-cast and ECAP states in this invention;

[0042] Figure 3 The images show a comparison of the silicon phase morphology in the ECAP state of aluminum-silicon alloys in Example 1 and Comparative Example 1 of this invention. Detailed Implementation

[0043] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments. The following embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Example 1

[0044] High thermal conductivity, high strength and toughness hypereutectic aluminum-silicon alloy block specimens with dimensions of 45 mm × 20 mm × 20 mm were prepared.

[0045] A hypereutectic aluminum-silicon alloy with ultrafine spheroidized silicon phase and high thermal conductivity and high strength and toughness is disclosed. The process involves preparing a casting with a segregated eutectic structure using eutectic solidification separation growth technology (GTSC), which completely eliminates the brittle eutectic silicon phase and initially refines the primary silicon phase. Multi-gradient solid solution treatment is then used to eliminate macroscopic elemental segregation in the as-cast structure and achieve high solid solution of alloying elements. Simultaneously, single-pass ECAP is used to achieve porosity closure, ultrafine silicon phase fragmentation, and ultrafine α-Al matrix. Subsequent semi-solid treatment and aging treatment further promote the spheroidization and uniform distribution of the silicon phase and further enhance the alloy strength. The final product possesses a unique microstructure of "ultrafine equiaxed matrix + ultrafine spheroidized silicon phase + ultra-low defects," thereby achieving a synergistic leap in the three key properties of the hypereutectic aluminum-silicon alloy: strength, plasticity, and thermal conductivity.

[0046] The aluminum alloy is a hypereutectic aluminum-silicon alloy, with a silicon content of 14 wt.%, a copper content of 4 wt.%, an iron content of <0.1 wt.%, a magnesium content of <0.01 wt.%, a manganese content of <0.01 wt.%, a zinc content of <0.01 wt.%, and the remainder being aluminum.

[0047] like Figure 1 As shown, a method for preparing a hypereutectic aluminum-silicon alloy with ultrafine spheroidized silicon phase and high thermal conductivity and high strength and toughness is as follows:

[0048] (1) Raw material preparation and smelting: Based on the composition of the hypereutectic aluminum-silicon alloy, prepare Al-20Si alloy, Al-20Cu alloy and pure Al ingot raw materials. Place the graphite crucible in the resistance furnace and heat it to 500℃. Add the polished, cleaned and dried raw materials in an orderly manner. Set the furnace temperature to 750℃. After all the raw materials have melted, stir and skim off the slag multiple times. Then set the furnace temperature to 720℃ and hold for 30 minutes.

[0049] (2) Refining and degassing: Add hexachloroethane refining agent to the alloy melt obtained in step (1), the amount of which is 0.5 wt.% of the total mass of the alloy melt, and use a graphite bell jar to press the refining agent into the interior of the alloy melt, swinging it up and down to allow it to fully react with H element. After the process is completed, remove the residue, set the temperature to 650℃ and keep it at that temperature for 1 hour. This process is a commonly used degassing and slag removal process in the casting industry.

[0050] (3) Preparation of a heterogeneous eutectic structure by glass tube suction casting: The suction casting mold is inserted into the alloy melt at 650°C after refining in step (2) to a depth of 50 mm. The liquid alloy is drawn into a room temperature glass tube with an inner diameter of 30 mm, a length of 500 mm, and a wall thickness of 1 mm. The tube is cooled with air. During this process, the negative pressure suction device and the tube are kept sealed at all times to ensure that the external air pressure always pushes the alloy melt at the lower end upward. The glass tube breaks during the cooling process, exposing the alloy and obtaining a hypereutectic aluminum-silicon alloy casting with a heterogeneous eutectic structure.

[0051] (4) Multi-gradient solution treatment: Take a 45mm long specimen from the upper end (the end near the suction device) of the casting obtained in step (3), remove the glass slag and cutting marks on the surface with sandpaper, and polish the surface smooth. First, raise the polished casting to 250℃ at room temperature at 5℃ / min and hold for 30min to eliminate residual stress. Then raise it to 400℃ at 3℃ / min and hold for 1h (pre-solution of low melting point phase). Finally, raise it to 470℃ at 2℃ / min and hold for 1.5h, and use Ar+0.5%H2 (i.e., 99.5% Ar and 0.5% H2) as protective gas to eliminate macroscopic segregation of elements in the as-cast structure and achieve high solid solution of alloying elements. After the heat treatment, immediately quench the alloy with water at a cooling rate of 200℃ / s to 150℃, and then air cool to room temperature to reduce residual stress;

[0052] (5) Single-pass ECAP processing: Graphite is evenly coated onto the specimen and ECAP mold after solution treatment in step (4) to act as a lubricant. At the same time, the specimen and mold are placed in a box-type resistance furnace and preheated at 320°C for 1 hour before a single-pass extrusion process is carried out at an extrusion speed of 4 mm / s.

[0053] (6) Semi-solid isothermal treatment: Heat the billet after ECAP extrusion in step (5) to 580°C, hold for 15 min, and then cool to room temperature at a rate of 15°C / s.

[0054] (7) Aging treatment: After the alloy after the semi-solid treatment in step (6) is kept at 180°C for 6 hours, it is cooled to room temperature in the furnace to obtain the finished product of the superfine spheroidized silicon phase and high thermal conductivity and high strength and toughness hypereutectic aluminum-silicon alloy.

[0055] like Figure 2 The image shows Nano CT 3D images and porosity distribution diagrams of eutectic aluminum-silicon alloy in the as-cast and ECAP states after glass tube suction casting. Figure 2 (a1) Figure 2 (a2) shows the three-dimensional diagram and porosity distribution diagram of the eutectic aluminum-silicon alloy in the as-cast state after being vacuum-cast in a glass tube; Figure 2 (b1) Figure 2 (b2) shows the 3D diagram and porosity distribution diagram of the ECAP state of the eutectic aluminum-silicon alloy after glass tube suction casting. As can be seen from the figure, compared with the as-cast state, the orange pore area in the alloy is significantly reduced and more dispersed after one ECAP processing, indicating that ECAP processing can effectively break up and disperse the pores accumulated in the as-cast state.

[0056] like Figure 3 The image shown is a comparison of the silicon phase morphology in the ECAP state of the hypereutectic aluminum-silicon alloy obtained in this embodiment. Figure 3(a1) shows the OM microstructure of the primary silicon phase in the alloy after the glass tube suction casting and one ECAP processing step involved in the process. Figure 3 (a2) shows the SEM three-dimensional morphology of the primary silicon phase in the alloy after the glass tube suction casting and one ECAP processing step involved in the process. Figure 3 (b1) shows the OM microstructure of the silicon phase in the alloy after conventional metal mold casting and one ECAP process (Comparative Example 1). Figure 3 (b2) is the SEM three-dimensional morphology of the silicon phase in the alloy after conventional metal mold casting and one ECAP process (Comparative Example 1).

[0057] from Figure 3 As can be seen, compared to conventional metal mold casting, glass tube casting can significantly refine the primary silicon phase and make its morphology closer to roundness. Even after one ECAP process, the coarse and sharp silicon phase at the beginning of conventional metal mold casting is not sufficiently improved (unfavorable morphologies such as plate / needle shapes are still retained); while the fine spheroidized silicon phase at the beginning of glass tube casting further maintains the advantages of "fine, round, and uniform" after ECAP. In hypereutectic aluminum-silicon alloys, coarse and sharp silicon phases are prone to stress concentration, reducing the alloy's toughness and strength; while fine and round silicon phases are more conducive to improving the alloy's overall mechanical properties. Therefore, the glass tube casting process combined with ECAP is more conducive to obtaining high-performance hypereutectic aluminum-silicon alloys.

[0058] This embodiment describes the application of an ultrafine spheroidized silicon phase and a hypereutectic aluminum-silicon alloy with high thermal conductivity and high strength and toughness in materials that combine lightweight, high-performance heat dissipation, and long service life.

[0059] Materials that combine lightweight design, high-performance heat dissipation, and long service life include materials used in aerospace, automotive, and thermal management systems.

[0060] Materials used in thermal management systems include precision components such as chip substrates, power module heat dissipation housings, and IGBT components in the field of electronic packaging; medium- and high-load heat dissipation components such as integrated structures for new energy vehicle battery packs and dynamic joint modules for industrial robots; and materials used in aerospace, including hydraulic system components, wear-resistant landing gear components, satellite payload supports, and valve housings for propulsion systems.

[0061] like Figures 2-3 As shown, the sample microstructure contains no eutectic silicon phase, the primary silicon has an average grain size of 4.3 μm and a shape factor of 0.71, and is uniformly distributed in the ultrafine equiaxed α-Al grain matrix; the alloy has a porosity of 0.12%, a thermal conductivity of 195 W / (m·K), a tensile strength of 318 MPa, and an elongation of 6.9%, exhibiting excellent thermal conductivity, high strength, and high toughness. Example 2

[0062] High thermal conductivity, high strength and toughness hypereutectic aluminum-silicon alloy block specimens with dimensions of 45 mm × 20 mm × 20 mm were prepared.

[0063] A hypereutectic aluminum-silicon alloy with ultrafine spheroidized silicon phase and high thermal conductivity and high strength and toughness is disclosed. The process involves preparing a casting with a segregated eutectic structure using eutectic solidification separation growth technology (GTSC), which completely eliminates the brittle eutectic silicon phase and initially refines the primary silicon phase. Multi-gradient solid solution treatment is then used to eliminate macroscopic elemental segregation in the as-cast structure and achieve high solid solution of alloying elements. Simultaneously, single-pass ECAP is used to achieve porosity closure, ultrafine silicon phase fragmentation, and ultrafine α-Al matrix. Subsequent semi-solid treatment and aging treatment further promote the spheroidization and uniform distribution of the silicon phase and further enhance the alloy strength. The final product possesses a unique microstructure of "ultrafine equiaxed matrix + ultrafine spheroidized silicon phase + ultra-low defects," thereby achieving a synergistic leap in the three key properties of the hypereutectic aluminum-silicon alloy: strength, plasticity, and thermal conductivity.

[0064] The aluminum alloy is a hypereutectic aluminum-silicon alloy, with a silicon content of 16 wt.%, a copper content of 5 wt.%, an iron content of <0.1 wt.%, a magnesium content of <0.01 wt.%, a manganese content of <0.01 wt.%, a zinc content of <0.01 wt.%, and the remainder being aluminum.

[0065] A method for preparing a hypereutectic aluminum-silicon alloy with ultrafine spheroidized silicon phase and high thermal conductivity and high strength and toughness is as follows:

[0066] (1) Raw material preparation and smelting: Based on the composition of the hypereutectic aluminum-silicon alloy, prepare Al-20Si alloy, Al-20Cu alloy and pure Al ingot raw materials. Place the graphite crucible in the resistance furnace and heat it to 490℃. Add the polished, cleaned and dried raw materials in an orderly manner. Set the furnace temperature to 780℃. After all the raw materials have melted, stir and skim off the slag multiple times. Then set the furnace temperature to 750℃ and hold for 60 minutes.

[0067] (2) Refining and degassing: Add hexachloroethane refining agent to the alloy melt obtained in step (1), the amount of which is 0.8 wt.% of the total mass of the alloy melt, and use a graphite bell jar to press the refining agent into the alloy melt, swinging it up and down to allow it to fully react with H element. After the process is completed, remove the residue, set the temperature to 680℃ and keep it at that temperature for 1.5 hours. This process is a commonly used degassing and slag removal process in the casting industry.

[0068] (3) Preparation of a heterogeneous eutectic structure by glass tube suction casting: The suction casting mold is inserted into the alloy melt at 680°C after refining in step (2) to a depth of 80 mm. The liquid alloy is drawn into a room temperature glass tube with an inner diameter of 35 mm, a length of 550 mm, and a wall thickness of 2 mm. The tube is cooled with air. During this process, the negative pressure suction device and the tube are kept sealed at all times to ensure that the external air pressure always pushes the alloy melt at the lower end upward. The glass tube breaks during the cooling process, exposing the alloy and obtaining a hypereutectic aluminum-silicon alloy casting with a heterogeneous eutectic structure.

[0069] (4) Multi-gradient solution treatment: Take a 45mm long specimen from the upper end (the end near the suction device) of the casting obtained in step (3), remove the glass slag and cutting marks on the surface with sandpaper, and polish the surface smooth. First, raise the polished casting to 300℃ at room temperature at 10℃ / min and hold for 60min to eliminate residual stress. Then raise it to 450℃ at 6℃ / min and hold for 1.5h (pre-solution of low melting point phase). Finally, raise it to 490℃ at 4℃ / min and hold for 2h, and use Ar+0.8%H2 (i.e., 99.2% Ar and 0.8% H2) as protective gas to eliminate macroscopic segregation of elements in the as-cast structure and achieve high solid solution of alloying elements. After the heat treatment, immediately quench the alloy to 200℃ with water at a cooling rate of 250℃ / s, and then air cool to room temperature to reduce residual stress;

[0070] (5) Single-pass ECAP processing: Graphite is evenly coated onto the specimen and ECAP mold after solution treatment in step (4) to act as a lubricant. At the same time, the specimen and mold are placed in a box-type resistance furnace and preheated at 400°C for 2 hours before a single extrusion process is carried out at an extrusion speed of 5 mm / s.

[0071] (6) Semi-solid isothermal treatment: Heat the billet after ECAP extrusion in step (5) to 600°C, hold for 10 min, and then cool to room temperature at a rate of 10°C / s.

[0072] (7) Aging treatment: After the alloy after the semi-solid treatment in step (6) is kept at 160°C for 4 hours, it is cooled to room temperature in the furnace to obtain the finished product of the superfine spheroidized silicon phase and high thermal conductivity and high strength and toughness hypereutectic aluminum-silicon alloy.

[0073] This embodiment describes the application of an ultrafine spheroidized silicon phase and a hypereutectic aluminum-silicon alloy with high thermal conductivity and high strength and toughness in materials that combine lightweight, high-performance heat dissipation, and long service life.

[0074] Materials that combine lightweight design, high-performance heat dissipation, and long service life include materials used in aerospace, automotive, and thermal management systems.

[0075] Materials used in thermal management systems include precision components such as chip substrates, power module heat dissipation housings, and IGBT components in the field of electronic packaging; medium- and high-load heat dissipation components such as integrated battery pack structures for new energy vehicles and dynamic joint modules for industrial robots; and materials used in aerospace, including hydraulic system components, wear-resistant landing gear components, satellite payload supports, and valve housings for propulsion systems.

[0076] The sample microstructure contained no eutectic silicon phase, and the primary silicon had an average grain size of 4.5 μm, a shape factor of 0.68, and was uniformly distributed in an ultrafine equiaxed α-Al grain matrix. The alloy had a porosity of 0.13%, a thermal conductivity of 188 W / (m·K), a tensile strength of 292 MPa, and an elongation of 6.3%, exhibiting excellent thermal conductivity, high strength, and high toughness. Example 3

[0077] High thermal conductivity, high strength and toughness hypereutectic aluminum-silicon alloy block specimens with dimensions of 45 mm × 20 mm × 20 mm were prepared.

[0078] A hypereutectic aluminum-silicon alloy with ultrafine spheroidized silicon phase and high thermal conductivity and high strength and toughness is disclosed. The process involves preparing a casting with a segregated eutectic structure using eutectic solidification separation growth technology (GTSC), which completely eliminates the brittle eutectic silicon phase and initially refines the primary silicon phase. Multi-gradient solution treatment is then used to eliminate macroscopic elemental segregation in the as-cast microstructure and achieve high solid solution concentration of alloying elements. Simultaneously, single-pass ECAP is used to achieve porosity closure, ultrafine silicon phase fragmentation, and ultrafine α-Al matrix. Subsequent semi-solid treatment and aging treatment further promote the spheroidization and uniform distribution of the silicon phase and further enhance the alloy strength. The final product possesses a unique microstructure of "ultrafine equiaxed matrix + ultrafine spheroidized silicon phase + ultra-low defect," thereby achieving a synergistic leap in the three key properties of the hypereutectic aluminum-silicon alloy: strength, plasticity, and thermal conductivity.

[0079] The aluminum alloy is a hypereutectic aluminum-silicon alloy, with a silicon content of 15 wt.%, a copper content of 6 wt.%, an iron content of <0.1 wt.%, a magnesium content of <0.01 wt.%, a manganese content of <0.01 wt.%, a zinc content of <0.01 wt.%, and the remainder being aluminum.

[0080] A method for preparing a hypereutectic aluminum-silicon alloy with ultrafine spheroidized silicon phase and high thermal conductivity and high strength and toughness is as follows:

[0081] (1) Raw material preparation and smelting: Based on the composition of the hypereutectic aluminum-silicon alloy, prepare Al-20Si alloy, Al-20Cu alloy and pure Al ingot raw materials. Place the graphite crucible in the resistance furnace and heat it to 510℃. Add the polished, cleaned and dried raw materials in an orderly manner. Set the furnace temperature to 760℃. After all the raw materials have melted, stir and skim off the slag multiple times. Then set the furnace temperature to 735℃ and hold for 45 minutes.

[0082] (2) Refining and degassing: Add hexachloroethane refining agent to the alloy melt obtained in step (1), the amount of which is 0.6 wt.% of the total mass of the alloy melt, and use a graphite bell jar to press the refining agent into the interior of the alloy melt, swinging it up and down to allow it to fully react with H element. After the process is completed, remove the residue, set the temperature to 670℃ and keep it at that temperature for 1 hour. This process is a commonly used degassing and slag removal process in the casting industry.

[0083] (3) Preparation of a heterogeneous eutectic structure by glass tube suction casting: The suction casting mold is inserted into the alloy melt at 650°C after refining in step (2) to a depth of 60 mm. The liquid alloy is drawn into a room temperature glass tube with an inner diameter of 30 mm, a length of 500 mm, and a wall thickness of 1 mm. The tube is cooled with air. During this process, the negative pressure suction device and the tube are kept sealed at all times to ensure that the external air pressure always pushes the alloy melt at the lower end upward. The glass tube breaks during the cooling process, exposing the alloy and obtaining a hypereutectic aluminum-silicon alloy casting with a heterogeneous eutectic structure.

[0084] (4) Multi-gradient solution treatment: Take a 45mm long specimen from the upper end (the end near the suction device) of the casting obtained in step (3), remove the glass slag and cutting marks on the surface with sandpaper, and polish the surface smooth. First, raise the polished casting to 280℃ at room temperature at 7℃ / min and hold for 45min to eliminate residual stress. Then raise it to 420℃ at 5℃ / min and hold for 1h (pre-solution of low melting point phase). Finally, raise it to 480℃ at 3℃ / min and hold for 1.5h, and use Ar+0.5%H2 (i.e., 99.5% Ar and 0.5% H2) as protective gas to eliminate macroscopic segregation of elements in the as-cast structure and achieve high solid solution of alloying elements. After the heat treatment, immediately quench the alloy to 150℃ at a cooling rate of 200℃ / s, and then air cool to room temperature to reduce residual stress;

[0085] (5) Single-pass ECAP processing: Graphite is evenly coated onto the specimen and ECAP mold after solution treatment in step (4) to act as a lubricant. At the same time, the specimen and mold are placed in a box-type resistance furnace and preheated at 350°C for 1.5 hours before a single extrusion process is carried out at an extrusion speed of 3 mm / s.

[0086] (6) Semi-solid isothermal treatment: Heat the billet after ECAP extrusion in step (5) to 590°C, hold for 20 min, and then cool to room temperature at a rate of 12°C / s.

[0087] (7) Aging treatment: After the alloy after the semi-solid treatment in step (6) is kept at 170°C for 8 hours, it is cooled to room temperature in the furnace to obtain the finished product of the superfine spheroidized silicon phase and high thermal conductivity and high strength and toughness hypereutectic aluminum-silicon alloy.

[0088] This embodiment describes the application of an ultrafine spheroidized silicon phase and a hypereutectic aluminum-silicon alloy with high thermal conductivity and high strength and toughness in materials that combine lightweight, high-performance heat dissipation, and long service life.

[0089] Materials that combine lightweight design, high-performance heat dissipation, and long service life include materials used in aerospace, automotive, and thermal management systems.

[0090] Materials used in thermal management systems include precision components such as chip substrates, power module heat dissipation housings, and IGBT components in the field of electronic packaging; medium- and high-load heat dissipation components such as integrated battery pack structures for new energy vehicles and dynamic joint modules for industrial robots; and materials used in aerospace, including hydraulic system components, wear-resistant landing gear components, satellite payload supports, and valve housings for propulsion systems.

[0091] The sample microstructure contained no eutectic silicon phase, and the primary silicon had an average grain size of 5.2 μm, a shape factor of 0.6, and was uniformly distributed in an ultrafine equiaxed α-Al grain matrix. The alloy had a porosity of 0.15%, a thermal conductivity of 180 W / (m·K), a tensile strength of 265 MPa, and an elongation of 5.5%, exhibiting excellent thermal conductivity, high strength, and high toughness.

[0092] Comparative Example 1

[0093] The only difference between this comparative example and Example 1 is that step (3) was performed using conventional metal mold casting (the specific process is: the melt refined in step (2) was slightly stirred, the slag was skimmed off, the crucible containing the melt was taken out using cast iron clamps, and poured smoothly into a dry metal mold with a mold size of 25×40×10mm. After cooling with air, the mold was finally demolded to complete the casting), that is, no divorced eutectic structure was obtained; the sample structure obtained in this comparative example has an average primary silicon particle size of 27.5μm and a shape factor of 0.32; the porosity of the alloy is 0.2%, the thermal conductivity is 110W / (m·K), the tensile strength is 220MPa, and the elongation is 3.3%.

[0094] like Figure 3 The image shown is a comparison diagram of the silicon phase morphology of this comparative example and Example 1. Figure 3 (b1) shows the OM microstructure of the silicon phase in the alloy after conventional metal mold casting and one ECAP process (Comparative Example 1). Figure 3 (b2) shows the SEM three-dimensional morphology of the silicon phase in the alloy after conventional metal mold casting and one ECAP process (Comparative Example 1). Figure 3As can be seen, compared to conventional metal mold casting, glass tube casting can significantly refine the primary silicon phase and make its morphology closer to roundness. Even after one ECAP process, the coarse and sharp silicon phase at the beginning of conventional metal mold casting is not sufficiently improved (unfavorable morphologies such as plate / needle shapes are still retained); while the fine spheroidized silicon phase at the beginning of glass tube casting further maintains the advantages of "fine, round, and uniform" after ECAP. In hypereutectic aluminum-silicon alloys, coarse and sharp silicon phases are prone to stress concentration, reducing the alloy's toughness and strength; while fine and round silicon phases are more conducive to improving the alloy's overall mechanical properties. Therefore, the glass tube casting process combined with ECAP is more conducive to obtaining high-performance hypereutectic aluminum-silicon alloys.

[0095] The alloy prepared in this comparative example does not have a divorced eutectic structure. The primary silicon in the sample is coarse, irregular in shape, and contains a lot of eutectic silicon, which affects the thermal conductivity and mechanical properties of the alloy.

[0096] Comparative Example 2

[0097] The only difference between this comparative example and Example 1 is that step (4) involved conventional solution treatment, i.e., the sample was kept at 480°C for 4 hours. The sample obtained in this comparative example had an average primary silicon grain size of 6.8 μm and a shape factor of 0.54. The alloy had a porosity of 0.15%, a thermal conductivity of 169 W / (m·K), a tensile strength of 253 MPa, and an elongation of 5.1%. Because this comparative example did not undergo multi-gradient solution treatment, the primary silicon phase inside was excessively coarsened. After ECAP treatment, although the silicon phase was broken, the primary silicon phase was relatively coarse and cracked, so the improvement on the alloy performance was very limited.

[0098] Comparative Example 3

[0099] The only difference between this comparative example and Example 1 is that: step (6) was not subjected to semi-solid isothermal treatment, that is, only steps (1), (2), (3), (4), (5), and (7) were performed; the average particle size of primary silicon in the microstructure of the sample obtained in this comparative example is 5.4 μm, the shape factor is 0.54; the porosity of the alloy is 0.16%, the thermal conductivity is 175 W / (m·K), the tensile strength is 259 MPa, and the elongation is 5.3%.

[0100] Comparative Example 4

[0101] The only difference between this comparative example and Example 1 is that step (7) was not aged, i.e., only steps (1), (2), (3), (4), (5), and (6) were performed; the average particle size of primary silicon in the microstructure of the sample obtained in this comparative example is 5.2 μm, the shape factor is 0.59; the porosity of the alloy is 0.15%, the thermal conductivity is 168 W / (m·K), the tensile strength is 251 MPa, and the elongation is 5.0%.

[0102] Detailed data of the hypereutectic aluminum-silicon alloys obtained in Examples 1-3 and Comparative Examples 1-4 of the present invention are shown in Table 1 below.

[0103] Table 1 Properties of Hypereutectic Aluminum-Silicon Alloys

[0104]

[0105] Main testing methods:

[0106] Scanning electron microscopy (SEM) observation:

[0107] The three-dimensional morphology of the silicon phase was observed using a Hitachi S-3400N scanning electron microscope (SEM). The silicon phase three-dimensional morphology sample was prepared by deep etching in 10% NaOH aqueous solution for 2 hours. Every half hour of etching, the sample was taken out and ultrasonically vibrated in anhydrous ethanol to wash away the etching products, finally forming a surface with only silicon phase.

[0108] Electron backscatter diffraction (EBSD) analysis:

[0109] The samples were characterized by electron backscatter diffraction (EBSD) using a Hitachi S-3400N scanning electron microscope equipped with an electron backscatter diffractometer (SEM / EBSD), and comprehensive statistical results were obtained using HKL-CHANNEL5 software. Samples used for EBSD testing required good conductivity and a clean, smooth, and stress-free surface. During sample preparation, the samples were first mechanically polished until the surface was bright and scratch-free, followed by electropolishing. The electropolishing solution consisted of 10% HClO4 + 90% C2H5OH, with the temperature set at -20℃, the voltage constant at 32 V, and the electropolishing time at 60 s. After electropolishing, the sample was immersed face down in a beaker containing anhydrous ethanol for ultrasonic cleaning, then dried with a warm air blower, placed in a sample box, packaged, and vacuum-sealed, awaiting testing.

[0110] Thermal conductivity test:

[0111] In this study, the thermal conductivity (TC) of all samples was measured using a NETZSCH LFA467 Micro Flash laser thermal conductivity meter (NETZSCH AG, Germany). The test samples were thin sheets ranging from 1.5 to 2.5 mm thick. The sample surfaces were smoothed with 2000 CW sandpaper, mechanically polished, then cleaned with anhydrous ethanol and dried. Thermal conductivity is defined as the energy transferred per unit area of ​​thermally conductive material per unit time over a unit temperature gradient (a temperature decrease of 1 K over a length of 1 m), expressed in W / (m·K). To ensure the authenticity and reliability of the test results, three points were selected from the sample surface for each test, and the average value was taken.

[0112] Mechanical property testing:

[0113] Tensile tests were conducted at room temperature on a universal testing machine to obtain the tensile strength and elongation of the samples. The tensile rate was 0.36 mm / min. Tensile specimens of the relevant ECAP extrusion samples were all sampled along the extrusion direction (ED direction), with a gauge length of 6 mm and a thickness of 2 mm.

[0114] Porosity test:

[0115] The porosity of the sample was characterized using a nanoVoxel-5000 high-resolution nano-CT scanner. The sample dimensions were 2 mm in diameter and 4 mm in height.

[0116] The average grain size of the α-Al matrix is ​​≤5μm, achieved according to the standardized test method T / CFA 0106024-2021, using electron backscatter diffraction (EBSD) technology combined with grain size statistics. The matrix grain size was then statistically analyzed using EBSD analysis software (HKL Channel 5).

[0117] The average grain size of primary silicon was measured according to T / CFA 0106024-2021 "Method for Determination of Average Grain Size of Cast Aluminum-Silicon Alloys," using the area method to statistically analyze the primary silicon size. At least five representative fields of view were captured using a metallographic microscope (magnification 200-500×) to ensure coverage of the uneven distribution of primary silicon. The primary silicon regions were identified using image analysis software (Image-Pro Plus), and the equivalent circle diameter (D=2(A / π)) was calculated. 1 / 2 The average value of ).

[0118] The shape factor of primary silica was measured according to ASTM D3398-00, "Standard Test Method for the Shape and Texture Index of Aggregates," using a metallographic microscope (magnification 200-500×) to capture at least five representative fields of view, ensuring coverage of areas with uneven primary silica distribution. Primary silica regions were identified using image analysis software (Image-Pro Plus) and measured using the formula 4πA / L. 2 Calculate, where A is the particle area and L is the perimeter (the closer the value is to 1, the closer it is to a circle).

[0119] Finally, it should be noted that the above embodiments are only for illustrating the technical concept and features of the present invention and are not intended to limit it. Different preparation methods can still be modified according to this technical solution, and the modified technical solution cannot deviate from the spirit of the technical solution of the present invention.

[0120] It should be understood that, in order to simplify this disclosure and aid in understanding one or more of the various aspects of the invention, features of the invention are sometimes grouped together in a single embodiment, figure, or description thereof in the above description of exemplary embodiments of the invention. However, this method of disclosure should not be interpreted as reflecting an intention that the claimed invention requires more features than expressly recited in each claim. Rather, as reflected in the claims, inventive aspects lie in fewer than all the features of the foregoingly disclosed embodiments. Therefore, the claims, following the detailed description, are hereby expressly incorporated into that detailed description, wherein each claim itself is a separate embodiment of the invention.

[0121] Although the invention has been described with reference to a limited number of embodiments, those skilled in the art will understand from the foregoing description that other embodiments are conceivable within the scope of the invention described herein. Furthermore, it should be noted that the language used in this specification has been chosen primarily for readability and instructional purposes, and not for the purpose of interpreting or limiting the subject matter of the invention. Therefore, many modifications and variations will be apparent to those skilled in the art without departing from the scope and spirit of the appended claims. The disclosure of the invention is illustrative and not restrictive, and the scope of the invention is defined by the appended claims.

[0122] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing an aluminum-silicon alloy, characterized in that, The aluminum-silicon alloy exhibits a divorced eutectic structure, with no eutectic silicon phase present. The primary silicon has an average grain size ≤ 5.2 μm, a shape factor ≥ 0.6, and is uniformly distributed within an ultrafine equiaxed α-Al grain matrix. The matrix α-Al has an average grain size ≤ 5 μm, the alloy porosity ≤ 0.15%, thermal conductivity ≥ 180 W / (m·K), tensile strength ≥ 265 MPa, and elongation ≥ 5.5%. The preparation method includes the following steps: Step 1: Raw material preparation and smelting to obtain alloy melt; Step two, refining and degassing, to obtain a refined alloy melt; Step 3, glass tube suction casting to prepare a heterogeneous eutectic structure: The suction casting mold is inserted into the refined alloy melt at 650-680℃, and the liquid refined alloy melt is drawn into a glass tube at room temperature and cooled with air. The glass tube breaks during the cooling process to obtain a hypereutectic aluminum-silicon alloy casting with a heterogeneous eutectic structure. Step 4, multi-gradient solution treatment: Take a sample from the top of the casting obtained in Step 3, grind it, first raise the temperature of the ground sample to 250-300℃ at room temperature at 5-10℃ / min and hold it for 30-60min; then raise it to 400-450℃ at 3-6℃ / min and hold it for 1-1.5h; finally raise it to 470-490℃ at 2-4℃ / min and hold it for 1.5-2h, with Ar+0.5-0.8%H2 as the protective gas; after the holding period, immediately water quench the alloy to 150-200℃ at a cooling rate of 200-250℃ / s, and then air cool it to room temperature; Step 5, single-pass ECAP processing: Apply lubricant evenly to the specimen and the inside of the ECAP mold after solution treatment in Step 4. At the same time, place the specimen and the ECAP mold into a box-type resistance furnace, preheat at 320-400℃ for 1-2 hours, and then perform a single-pass extrusion process at an extrusion speed of 3-5 mm / s. Step 6, semi-solid isothermal treatment: Heat the blank after ECAP processing in step 5 to 580-600℃, hold for 10-20 minutes, and then cool to room temperature at a rate of 10-15℃ / s. Step 7, Aging treatment: After the semi-solid treatment in step 6, the alloy is held at 160-180℃ for 4-8 hours and then cooled to room temperature in the furnace to obtain the final product.

2. The method for preparing an aluminum-silicon alloy according to claim 1, characterized in that, It includes the following components by weight percentage: silicon 14-16 wt.%, copper 4-6 wt.%, iron <0.1 wt.%, magnesium <0.01 wt.%, manganese <0.01 wt.%, zinc <0.01 wt.%, and the remainder is aluminum.

3. The preparation method according to claim 1, characterized in that, Step one includes the following steps: Based on the composition of the aluminum-silicon alloy, prepare Al-20Si alloy, Al-20Cu alloy, and pure Al ingot raw materials; place the graphite crucible in a resistance furnace and heat it to 490-510℃, add the polished, cleaned, and dried raw materials, set the furnace temperature to 750-780℃, and after it is completely melted, stir and skim off the slag. Then set the furnace temperature to 720-750℃ and hold for 30-60 minutes to obtain the alloy melt.

4. The preparation method according to claim 3, characterized in that, Step two includes the following steps: add hexachloroethane refining agent to the alloy melt, the amount of which is 0.5-0.8 wt.% of the total mass of the alloy melt, and use a graphite bell jar to press the refining agent into the alloy melt, swinging it up and down to allow it to fully react with the H element. After the reaction is complete, remove the residue, set the temperature to 650-680℃ and hold for 1-1.5 hours to obtain the refined alloy melt.

5. The preparation method according to claim 3, characterized in that, In step three, the depth to which the suction casting mold is inserted into the refined alloy melt is 50-80mm.

6. The preparation method according to claim 3, characterized in that, In step four, the upper end of the casting is the end closest to the suction device; the test piece is polished by using sandpaper to remove glass shards and cutting marks from the surface of the test piece and polishing the surface smooth.

7. The preparation method according to claim 3, characterized in that, In step five, the lubricant is graphite.

8. The application of an aluminum-silicon alloy obtained by the preparation method according to any one of claims 1 to 7 in materials possessing lightweight, high-performance heat dissipation, and long service life, characterized in that, Materials that combine lightweight, high-performance heat dissipation, and long service life include materials for aerospace, automotive, and thermal management systems.

9. The application according to claim 8, characterized in that, Materials used in thermal management systems include chip substrates, power module heat dissipation housings, and IGBT components in the electronic packaging field; materials used in the automotive industry include integrated structures for new energy vehicle battery packs and dynamic joint modules for industrial robots; and materials used in aerospace include hydraulic system components, wear-resistant landing gear components, satellite payload supports, and valve housings for propulsion systems.

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