Manufacturing method of high-thermal-conductivity die-casting radiator

Abstract

The invention relates to a radiator manufacturing technology, in particular to a manufacturing method of a high-thermal-conductivity die-casting radiator, and aims to solve the problems that in the prior art, internal air holes and shrinkage porosity defects are easily generated in the manufacturing process of a traditional die-casting aluminum radiator, so that the thermal conductivity of the traditional die-casting aluminum radiator is generally at a low level of 160-180 W / m.K, and the manufacturing cost is low. And the heat dissipation requirement of the high-heat-flux chip is difficult to effectively meet. According to the invention, the embedded integrated structure is formed by preparing the microstructure metal prefabricated member and die-casting, and the graphene nano composite coating is combined, so that the heat conductivity and mechanical strength of the radiator are effectively improved, and the radiator has the advantages of improving the heat dissipation efficiency and prolonging the service life.

Description

Technical Field

[0001] This application relates to radiator manufacturing technology, and more specifically, to a method for manufacturing a high thermal conductivity die-cast radiator. Background Technology

[0002] With the rapid development of 5G mobile communication technology and the Industrial Internet, the power density of communication and industrial equipment continues to increase, placing more stringent demands on the heat dissipation efficiency and mechanical strength of heat sinks. Traditional die-cast aluminum heat sinks are prone to internal porosity and shrinkage defects during the manufacturing process, resulting in a thermal conductivity that is typically at a low level of 160 to 180 W / m·K, making it difficult to effectively meet the heat dissipation requirements of high heat flux density chips.

[0003] The fins and the base are joined only by metallurgical bonding, and the bonding strength is generally lower than 12 MPa. Under long-term thermal cycling and high vibration working environment, delamination and cracking are prone to occur, which seriously affects the structural integrity and service life of the radiator.

[0004] In addition, although the surface anodized layer can provide basic corrosion protection, its thermal conductivity is only 20 to 30 W / m·K, which creates a significant barrier to heat transfer.

[0005] In the existing technology, microstructure interlocking technology is mainly used in the field of plastic molding, while graphene coating technology is mostly used in planar heat dissipation scenarios. There is no public solution that combines microstructure interlocking and graphene coating technology and applies it to die-cast aluminum heat sinks, which leads to obvious limitations of existing heat sinks in high power density application scenarios.

[0006] To address the aforementioned issues, existing technologies urgently need improvement. Summary of the Invention

[0007] (a) Technical problems to be solved The purpose of this application is to provide a method for manufacturing a high thermal conductivity die-cast radiator, which has the advantages of improving the thermal conductivity and mechanical strength of the radiator, enhancing heat dissipation efficiency and service life.

[0008] (II) Technical Solution This application provides a method for manufacturing a high thermal conductivity die-cast heat sink, the technical solution of which is as follows: Includes the following steps: S100, Prepare microstructured metal preforms with porous layers on the surface; S200. Position and place the microstructured metal preform into the preheated die-casting mold cavity. S300: Molten aluminum alloy liquid is injected into a mold and allowed to penetrate into the porous layer and gaps of the preform under pressure. After cooling, it forms an integrated heat sink casting. S400, Perform surface treatment and degassing on radiator castings; S500: Prepare a graphene nanocomposite coating on the surface of the radiator casting, and then perform curing and edge sealing treatment.

[0009] Furthermore, this application also proposes that the molten aluminum alloy liquid is composed of the following components by mass percentage: Si 10.5-12.5%, Cu 0.6-0.9%, Mg 0.3-0.5%, Ti 0.05-0.15%, Fe ≤0.3%, with the balance being Al and unavoidable impurities.

[0010] Furthermore, this application also proposes that the purity of aluminum in the raw materials for preparing aluminum alloy liquid is not less than 99.7%.

[0011] Furthermore, this application also proposes that step S100 specifically includes: using an aluminum alloy foil with a thickness of 0.08-0.12 mm to fabricate a preform with a micro-tooth structure, wherein the height of the micro-tooth is 1.8-2.2 mm and the tooth spacing is 1.2-1.8 mm; subsequently, the preform is subjected to micro-arc oxidation treatment with a treatment voltage of 400-450 V and a treatment time of 10-15 min, so as to form a porous alumina layer with a thickness of 5-8 μm on its surface.

[0012] Furthermore, this application also proposes that, in step S300, the die-casting process parameters for injecting the molten aluminum alloy into the mold are as follows: Mold preheating temperature: 220-250℃; aluminum alloy liquid temperature: 720-740℃; injection speed: 3-4m / s; pressurization pressure: 80-90MPa; holding time: 15-20s.

[0013] Furthermore, this application also proposes that, in step S500, the graphene nanocomposite coating is prepared on the surface of the radiator casting using an electrostatic rotary cup spraying process, with the following parameters: Spraying voltage 60-80kV, atomization pressure 0.3-0.5MPa, and coating wet film thickness controlled at 30-40μm.

[0014] Furthermore, this application also proposes that the curing and edge-sealing steps in step S500 include: The coated radiator was baked at 180℃ for 60 minutes to cure the coating; then the edges of the coating were scanned and sealed with a laser with a power of 1200-1800W and a scanning speed of 10-15mm / s.

[0015] Furthermore, this application also proposes that the slurry used for the graphene nanocomposite coating is composed of the following components by mass percentage: 6-10% graphene nanosheets, 40-50% organosilicon resin, 20-25% nano-aluminum powder, 2-4% coupling agent KH-550, 18-24% butyl acetate, and 0.5-1% defoamer.

[0016] Furthermore, this application also proposes that the graphene nanosheets in the slurry have a 5-10 layer structure and the particle size of the nano-aluminum powder is 50-150 nm.

[0017] Furthermore, this application also proposes that the S400 step further includes: first, mechanically grinding to achieve a surface roughness Ra ≤ 1.6 μm, and then maintaining the surface at a vacuum level not exceeding 1 × 10⁻³ Pa and a temperature of 450℃ for 2 hours. (III) Beneficial Effects Compared with the prior art, the beneficial effects of the present invention are as follows: In this invention, a microstructured metal preform is prepared and die-cast to form an integrated structure. Combined with a graphene nanocomposite coating, the thermal conductivity and mechanical strength of the radiator are effectively improved, which has the advantages of improving heat dissipation efficiency and extending service life. Attached Figure Description

[0018] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0019] Figure 1 This is a flowchart illustrating the manufacturing process of a die-cast radiator. Detailed Implementation

[0020] The technical solutions of this application will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are merely some embodiments of this application, and not all embodiments. The components of this application described and shown in the accompanying drawings can generally be arranged and designed in various different configurations. Therefore, the following detailed description of the embodiments of this application provided in the accompanying drawings is not intended to limit the scope of the claimed application, but merely to illustrate selected embodiments of this application. All other embodiments obtained by those skilled in the art based on the embodiments of this application without inventive effort are within the scope of protection of this application.

[0021] It should be noted that similar reference numerals and letters in the following figures indicate similar items; therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures. Furthermore, in the description of this application, terms such as "first," "second," etc., are used only to distinguish descriptions and should not be construed as indicating or implying relative importance.

[0022] In the manufacturing and application of traditional die-cast aluminum heat sinks, insufficient thermal conductivity leads to reduced heat transfer efficiency. Internal porosity and shrinkage defects interrupt heat conduction paths. Insufficient bonding strength between the fins and the base easily causes interfacial delamination and cracking under vibration and thermal cycling conditions. The thermal conductivity characteristics of the surface anodized layer create interfacial thermal resistance, hindering effective heat dissipation to the environment. In particular, internal defects weaken the continuity of heat conduction, insufficient interfacial bonding strength reduces structural stability under dynamic loads, and surface thermal resistance further limits the final heat dissipation efficiency. Therefore, these heat sinks cannot meet the thermal management performance requirements of high-power-density electronic devices.

[0023] For example, in the RF power amplifier heat dissipation system of a 5G communication base station, the heat sink operates under a combined condition of continuous vibration caused by fan operation and high chip load heat generation. In practical applications, microcracks were detected at the junction of the heat sink fins and the base, and the surface oxide layer caused heat to accumulate at the interface, resulting in an abnormal rise in chip temperature. The system was forced to enter a protective frequency reduction state to avoid overheating damage, which in turn affected the stable transmission of communication signals and the continuous operation capability of the equipment.

[0024] If the above problems are not solved, the structural integrity of the heat sink will be difficult to maintain under high vibration and high load scenarios, resulting in decreased reliability of electronic devices, increased risk of system operation interruption, and inability to meet the long-term stable operation requirements of heat dissipation components in harsh application environments such as industrial internet and rail transportation, thereby limiting the deployment and application of high power density equipment in key areas.

[0025] In this regard, such as Figure 1 As shown, this application proposes a method for manufacturing a high thermal conductivity die-cast heat sink, which specifically includes the following steps: In step S100, a microstructured metal preform with a porous layer on its surface is prepared.

[0026] This step aims to provide the heat sink with a basic structure featuring an enhanced bonding interface. For example, micron-sized grooves or protrusions can be etched into the surface of a metal substrate using machining methods, followed by chemical etching or electrochemical treatment to form a porous oxide layer on the surface of these microstructures. Another approach is to prepare a preform with a certain porosity from metal powder using a sintering process; the surface pore structure can directly serve as a porous layer. In these ways, the surface of the preform is endowed with properties that allow for mechanical interlocking and permeation bonding with the subsequently injected molten metal.

[0027] In step S200, the microstructured metal preform is positioned and placed inside the preheated die-casting mold cavity.

[0028] This step aims to ensure the accurate positioning of the preform during die casting and to create favorable temperature conditions for the full penetration of the molten metal. For example, the preform can be secured by mechanical limiting structures within the mold cavity or by using high-temperature resistant locating pins to prevent displacement during high-speed injection. Simultaneously, the mold cavity is heated to a certain temperature before the preform is placed to reduce premature solidification of the molten metal due to excessive temperature difference upon contact with the mold and the preform, thus ensuring good fluidity and penetration.

[0029] In step S300, molten aluminum alloy is injected into a mold and, under pressure, it penetrates the porous layer and gaps of the preform. After cooling, it forms an integrated radiator casting.

[0030] This step is crucial for achieving a seamless integration between the preform and the casting. For example, pre-melted molten aluminum alloy can be rapidly injected into a preheated mold cavity containing the preform via an injection system. During injection, high pressure is applied, causing the molten aluminum alloy not only to fill the macroscopic space of the mold cavity but also to forcefully penetrate the microporous structure and micro-tooth gaps on the surface of the preform. Subsequently, cooling and solidification occur within the mold, forming a tight mechanical interlock and metallurgical bond between the molten aluminum alloy and the preform, resulting in a dense composite casting with high bonding strength.

[0031] In step S400, the radiator casting undergoes surface treatment and degassing.

[0032] This step aims to optimize the surface condition and internal quality of the casting, laying the foundation for subsequent coating preparation and improved overall performance. For example, mechanical methods such as sandblasting, polishing, or grinding can be used to treat the casting surface to remove burrs, oxide layers, or uneven areas, resulting in a smoother and cleaner surface. Simultaneously, to eliminate any micropores or residual stress that may exist within the casting, heat treatment can be applied, such as holding it at a specific temperature to allow internal gases to escape and homogenize the microstructure, thereby improving the casting's density and mechanical properties.

[0033] In step S500, a graphene nanocomposite coating is prepared on the surface of the radiator casting, and then cured and sealed.

[0034] This step aims to impart excellent surface heat dissipation performance and long-term reliability to the radiator. For example, a pre-prepared slurry containing graphene nanosheets, binders, and other functional additives can be uniformly coated onto the treated casting surface using methods such as spraying, dipping, or brushing. After coating, the binder in the coating is cured by heating or ultraviolet irradiation, forming a stable composite coating adhered to the casting surface. To prevent the coating edges from peeling off due to wear or impact during use, additional protective treatment can be applied to the coating edges, such as applying a sealant or performing localized sintering.

[0035] For ease of understanding, the following explains some key terms in this embodiment: High thermal conductivity die-cast heat sinks are devices manufactured through die-casting and subjected to special structural design and surface treatment to achieve excellent thermal conductivity and mechanical strength, suitable for heat dissipation requirements with high heat flux density.

[0036] Microstructured metal preforms are metal components that are pre-fabricated before die casting and have a specific microscopic geometry and / or porous layer on their surface. Their function is to provide mechanical anchoring and a metallurgical bonding interface for the subsequently injected molten metal.

[0037] A porous layer refers to a structural layer with micron-sized pores formed on the surface of a microstructured metal preform. This layer increases the contact area between the preform and the molten metal and provides penetration channels, thereby promoting a tighter bond between the two.

[0038] A die-casting mold cavity refers to the space inside the die-casting mold used to form the shape of the casting. During the die-casting process, molten metal is poured into it and cooled to solidify.

[0039] Molten aluminum alloy refers to aluminum-based alloy material in a liquid state. During the die casting process, it is injected into the mold cavity and combined with preforms to form a radiator casting.

[0040] Integrated radiator castings refer to microstructured metal preforms that are tightly bonded to molten aluminum alloy under pressure, forming a monolithic casting with interpenetrating internal structures that is macroscopically inseparable. This structure aims to improve the overall thermal conductivity and mechanical strength of the casting.

[0041] Graphene nanocomposite coating refers to a composite coating containing graphene nanosheets and other functional nanomaterials, prepared on the surface of radiator castings. This coating aims to significantly reduce the surface thermal resistance of the radiator and improve its heat dissipation capacity through radiation and convection.

[0042] Curing and edge sealing refer to the heat treatment of the prepared graphene nanocomposite coating to stabilize its shape, and the special treatment of the coating edges to prevent peeling or damage, ensuring the long-term adhesion and performance of the coating.

[0043] The following example will provide a more detailed explanation of the above technical solution: First, in step S100, a microstructured metal preform is prepared. Specifically, an aluminum alloy sheet is selected, and a series of micron-sized tooth-like structures are formed on its surface through precision milling. The sheet is then chemically oxidized to form an oxide layer with nanoscale pores on its surface. The micro-tooth structure and porous oxide layer of this preform together constitute the interface for subsequent bonding with the molten aluminum alloy.

[0044] Next, in step S200, the prepared microstructured metal preform is precisely placed into the die-casting mold cavity, which is preheated to approximately 200°C. The preform is firmly fixed by a positioning mechanism inside the mold, ensuring that it will not shift during subsequent high-pressure injection. The preheating of the mold ensures a moderate temperature on the cavity wall, preventing premature solidification of the molten aluminum alloy.

[0045] Subsequently, in step S300, molten aluminum alloy at approximately 730°C is injected at high speed into the mold cavity via an injection system. Under a pressure of approximately 85 MPa, the molten aluminum alloy not only rapidly fills the macroscopic space of the mold but is also forcibly penetrates into the micro-gap and porous oxide layer on the surface of the preform. After a holding time of approximately 18 seconds, the molten aluminum alloy cools and solidifies within the mold, forming a monolithic radiator casting with the preform, characterized by internal structural interpenetration, mechanical interlocking, and metallurgical bonding. This integrated structure significantly improves the continuity of the heat conduction path within the radiator and enhances the bonding strength between the fins and the base.

[0046] After casting, the radiator casting undergoes surface treatment and degassing in step S400. First, mechanical grinding removes burrs and rough areas from the casting surface, ensuring a smooth surface suitable for subsequent coating. Then, the casting is placed in a vacuum furnace and held at approximately 400°C and a vacuum of 1×10⁻⁴ Pa for 2 hours. This process aims to thoroughly eliminate any micropores that may exist within the casting and release residual stress generated during casting, further improving the casting's density and long-term reliability.

[0047] Finally, in step S500, a graphene nanocomposite coating is prepared on the surface of the radiator casting, followed by curing and edge sealing. Specifically, an electrostatic spraying device is used to uniformly spray a composite slurry containing graphene nanosheets, silicone resin, and nano-aluminum powder onto the casting surface, forming a wet film. After spraying, the radiator is placed in an oven at 180°C for 60 minutes to fully cure the coating. To prevent peeling of the coating edges during use, laser scanning is used to locally remelt and seal the coating edges, forming a dense protective layer. Thus, a highly thermally conductive and highly adhesive graphene nanocomposite coating is formed on the radiator surface, significantly reducing surface thermal resistance and improving overall heat dissipation efficiency.

[0048] The high thermal conductivity die-cast heat sink obtained through the above manufacturing method has a dense internal structure, a firm bond between the fins and the base, and a highly efficient thermally conductive coating on the surface. It can effectively cope with the heat generated by high-power communication equipment and ensure stable operation under long-term vibration and thermal cycling conditions.

[0049] Based on the above examples, the overall technical concept of this application demonstrates a significant technical contribution.

[0050] Traditional die-cast heat sinks rely primarily on simple metallurgical bonding to bond the fins to the base. In the example above, using only traditional die-casting processes easily leads to porosity and shrinkage within the heat sink, and the bond strength between the fins and base is typically low, making delamination and cracking likely after prolonged thermal cycling. To address this, this application employs an integrated design in steps S100 and S300, where a microstructured metal preform is embedded within the molten aluminum alloy. In the example, the micro-tooth structure and porous oxide layer of the preform, combined with the high-pressure-infiltrated molten aluminum alloy, form a dual connection of mechanical interlocking and metallurgical bonding, significantly improving internal bonding strength and heat transfer efficiency, and effectively suppressing the generation of internal defects.

[0051] Furthermore, traditional radiator surfaces are typically anodized, resulting in a low thermal conductivity oxide layer that becomes a bottleneck for heat transfer. In the example above, if only anodizing is used, the radiator surface thermal resistance would be high, limiting overall heat dissipation performance. This application prepares a graphene nanocomposite coating in step S500. In this example, the coating utilizes a three-dimensional thermally conductive network formed by graphene nanosheets, significantly reducing the radiator surface thermal resistance and improving heat radiation and convection heat dissipation capabilities. Simultaneously, the surface treatment and degassing in step S400, in this example, through mechanical grinding and vacuum degassing, provides a smoother and denser substrate for the coating and eliminates internal stress, further improving coating adhesion and the long-term reliability of the casting.

[0052] Therefore, the manufacturing method of this application is not a simple superposition of single technical means, but rather an organic combination of internal structural optimization and external surface performance enhancement achieved through the synergistic effect of microstructure interlocking die casting and graphene nanocomposite coating. In the example, this integrated design fundamentally solves the multiple technical problems of low thermal conductivity, insufficient bonding strength, and high surface thermal resistance in traditional die-cast heat sinks, demonstrating innovation and progress that surpasses existing technologies.

[0053] In some of the embodiments described above in this application, molten aluminum alloy liquid is used for die casting to form radiator castings. However, if the composition of the aluminum alloy liquid is not optimized during this process, it may result in insufficient thermal conductivity, low mechanical strength, and excessive impurity content in the castings, which may affect heat dissipation performance and structural stability.

[0054] In this regard, this application further proposes that the molten aluminum alloy liquid is composed of the following components by mass percentage: Si 10.5-12.5%, Cu 0.6-0.9%, Mg 0.3-0.5%, Ti 0.05-0.15%, Fe ≤ 0.3%, with the balance being Al and unavoidable impurities.

[0055] Specifically, silicon is a common alloying element in aluminum alloys, significantly affecting their fluidity, casting properties, and thermal conductivity. In aluminum alloys, silicon is primarily used to improve fluidity and lower the melting point, thereby enhancing casting performance. Simultaneously, the presence of silicon also affects the alloy's mechanical properties and thermal conductivity. This can be achieved by adding high-purity industrial silicon ingots or ferrosilicon alloys as alloying elements, or by using recycled aluminum or pre-alloyed aluminum containing a specific silicon content as raw materials. Copper is an important strengthening element in aluminum alloys, improving their strength and hardness through solid solution strengthening and age precipitation strengthening.

[0056] The addition of copper can significantly improve the tensile strength, yield strength, and hardness of aluminum alloys, but excessive amounts can also reduce the alloy's corrosion resistance and thermal conductivity. Copper can be added through alloying with pure copper or copper-aluminum master alloys (such as Al-Cu master alloys), or by using scrap aluminum or pre-alloys containing a specific copper content as raw materials. Magnesium is a commonly used lightweight alloying element in aluminum alloys. It can form the Mg₂Si phase with silicon, strengthening the alloy. The addition of magnesium can improve the strength, hardness, and corrosion resistance of aluminum alloys, especially when acting synergistically with silicon to form a strengthening phase. Magnesium can be added through alloying with pure magnesium ingots or magnesium-aluminum master alloys (such as Al-Mg master alloys), or by using recycled aluminum or pre-alloys containing a specific magnesium content as raw materials. Titanium is a commonly used grain refiner in aluminum alloys. It can refine the as-cast microstructure by forming compounds such as TiAl₃ as heterogeneous nucleation sites. The addition of titanium can refine the grains of aluminum alloys, thereby improving the mechanical properties of the alloy, such as strength and toughness, and improving casting performance. It can be alloyed by adding titanium-aluminum master alloys (such as Al-Ti master alloys), or by adding composite grain refiners containing titanium elements during the smelting process.

[0057] Iron is a common impurity element in aluminum alloys, but its content needs to be strictly controlled. Iron readily forms brittle intermetallic compounds (such as the Al-Fe-Si phase) in aluminum alloys, which reduce the alloy's plasticity, toughness, and thermal conductivity. Therefore, controlling the iron content is crucial for ensuring the alloy's performance. This can be achieved by selecting high-purity aluminum raw materials and alloying elements to control iron introduction at the source, or by employing specific refining techniques during the smelting process to reduce the iron content. Aluminum is the matrix element of this alloy system, and its purity directly affects the overall performance of the alloy. Unavoidable impurities refer to other elements that will still exist in small amounts during industrial production, even with strict control measures. As the matrix element, aluminum bears the performance contribution of all alloying elements. Its high purity is the foundation for ensuring the alloy's high thermal conductivity and high strength. Controlling unavoidable impurities aims to minimize their negative impact on alloy performance. This can be achieved by selecting electrolytic aluminum or high-purity aluminum ingots as the main raw material, or by strictly controlling the furnace lining materials, tools, and atmosphere during the smelting process to reduce the introduction of impurities.

[0058] This application addresses the deficiencies in thermal conductivity and mechanical strength of radiator castings by limiting the specific components of the molten aluminum alloy. Specifically, the silicon content is controlled within the range of 10.5-12.5%, optimizing the balance between the aluminum alloy's fluidity and thermal conductivity. This avoids a decrease in thermal conductivity due to excessive silicon content, while ensuring excellent fluidity of the molten aluminum alloy at the die-casting temperature. This allows it to fully penetrate the porous layer and micro-tooth gaps of the microstructured metal preform, preventing insufficient integration due to inadequate fluidity. The copper content is set at 0.6-0.9%, working synergistically with magnesium (0.3-0.5%) to form the Mg2Si strengthening phase. Copper promotes the dispersed precipitation of this phase, significantly improving the high-temperature mechanical strength of the casting. Simultaneously, the addition of magnesium can partially offset the negative impact of copper on corrosion resistance.

[0059] The titanium content is 0.05-0.15%, which refines the grains by forming a TiAl3 heterogeneous nucleation core, improving not only mechanical strength but also the filling ability of the aluminum alloy liquid and reducing uneven bonding at the interfacial interface caused by coarse grains. The iron content is limited to no more than 0.3%, which effectively inhibits the formation of brittle Al-Fe-Si phases, preventing them from reducing thermal conductivity and mechanical toughness and hindering the metallurgical bonding between the aluminum alloy liquid and the preform. The balance is aluminum and unavoidable impurities, ensuring the purity of the main components and the consistency of overall performance. The synergistic control of these components ensures that the aluminum alloy liquid can effectively penetrate into the preform during the die casting process, forming a highly thermally conductive and high-strength interfacial structure. In addition, the melting point and fluidity of this component system are precisely matched with the die casting parameters, ensuring that the aluminum alloy liquid can quickly penetrate into the porous layer of the preform under high pressure, forming a dense interfacial structure. At the same time, its solidification shrinkage characteristics complement the micro-tooth structure of the preform, reducing shrinkage porosity and further strengthening internal heat conduction and mechanical connection. The optimized alloy formulation, combined with the subsequent vacuum degassing process, can significantly reduce the porosity inside the casting, providing a dense matrix for the subsequent preparation of graphene nanocomposite coatings.

[0060] In one specific implementation, the molten aluminum alloy liquid can be composed of the following components by mass percentage: silicon 11.5%, copper 0.75%, magnesium 0.4%, titanium 0.1%, iron 0.2%, with the balance being aluminum and unavoidable impurities. The alloy liquid can be prepared using aluminum ingots with a purity of not less than 99.7% as the main raw material, and industrial silicon blocks, copper-aluminum master alloys, magnesium-aluminum master alloys, and titanium-aluminum master alloys are added sequentially according to the target proportions for smelting and alloying. During the smelting process, the iron content is ensured to be controlled below 0.2% by strictly controlling the purity of the raw materials and the smelting process.

[0061] Through the above technical solution, the radiator casting prepared in this application has excellent thermal conductivity and mechanical strength, which can effectively solve the problems of insufficient thermal conductivity, low mechanical strength, and excessive impurity content affecting heat dissipation performance and structural stability of traditional die-cast aluminum radiators due to unoptimized composition. This alloy formulation gives the molten aluminum alloy good fluidity and permeability during the die-casting process, enabling it to fully fill the fine structure of the microstructure preform, forming a dense and firmly bonded integrated radiator casting.

[0062] Meanwhile, the synergistic effect of the various elements in the alloy effectively inhibits the formation of harmful phases, refines the grains, and significantly improves the overall thermal conductivity, fatigue resistance, and vibration resistance of the casting, providing reliable heat dissipation for high power density equipment.

[0063] In some of the solutions described above in this application, aluminum alloy liquid is proposed for die casting to form radiator castings. However, in this process, if the purity of aluminum is insufficient and the impurity content is high, it may lead to reduced fluidity and decreased thermal conductivity of the aluminum alloy liquid, as well as porosity or shrinkage defects in the casting, thereby affecting heat dissipation efficiency and mechanical strength.

[0064] In this regard, this application further proposes that the purity of aluminum in the raw materials for preparing the aluminum alloy liquid is not less than 99.7%.

[0065] The purity of aluminum refers to the content of aluminum element in aluminum metal, usually expressed as a percentage by mass. High-purity aluminum means that the content of impurity elements is extremely low. To ensure that the purity of aluminum is not less than 99.7%, several methods can be adopted. One method is to obtain aluminum ingots or rods with a purity of not less than 99.7% through high-purity aluminum production processes such as electrolytic refining or zone melting as raw materials.

[0066] Another approach is to strictly adhere to supplier quality standards when procuring aluminum raw materials, requiring them to provide aluminum with corresponding purity test reports and conducting incoming inspections to ensure the aluminum purity meets the requirement of not less than 99.7%. Furthermore, recycled aluminum can be subjected to deep purification treatment, such as using a three-layer liquid electrolysis method or vacuum distillation, to remove impurities and achieve a purity of 99.7% or higher.

[0067] This method ensures the purity of the molten aluminum alloy by strictly controlling the purity of the aluminum in the raw materials used to prepare the molten aluminum alloy, thereby optimizing the entire die-casting process and the performance of the final radiator casting. When the purity of aluminum is not less than 99.7%, the content of low-melting-point harmful impurities such as sodium, calcium, and phosphorus, as well as elements such as iron, can be effectively limited. These impurities tend to form low-melting-point eutectic phases in the molten state, or precipitate and accumulate at grain boundaries during solidification, thereby reducing the fluidity of the alloy liquid, disrupting the heat conduction network, and weakening intergranular bonding.

[0068] The use of high-purity aluminum raw materials ensures excellent fluidity of the molten aluminum alloy when injected into the mold, allowing it to fully penetrate the porous layers and gaps of the microstructured metal preform, forming a dense and defect-free interlocking structure. Simultaneously, the low impurity content helps suppress the formation of porosity and shrinkage defects within the casting, guaranteeing the overall density and uniformity of the radiator casting. Furthermore, the use of high-purity aluminum raw materials provides a cleaner and more uniform substrate surface for subsequent surface treatment and graphene nanocomposite coating preparation, which is beneficial for good coating adhesion and performance.

[0069] As a specific implementation method, the raw material for preparing the aluminum alloy liquid can be electrolytic aluminum, whose purity is tested to ensure that the aluminum content reaches more than 99.7%. For example, A00 grade electrolytic aluminum ingots can be used as the main raw material.

[0070] The above technical solution effectively solves problems such as poor fluidity, decreased thermal conductivity, and casting defects caused by insufficient aluminum purity in molten aluminum alloys. This ensures that the molten aluminum alloy can fully penetrate and fill the fine structure of the microstructure preform, forming a highly dense radiator casting with high bonding strength. Simultaneously, the significant reduction in internal defects ensures that the radiator casting possesses excellent thermal conductivity and mechanical strength, thereby improving the overall heat dissipation efficiency and service life of the radiator. Furthermore, the cleaner surface of the high-purity casting facilitates the uniform adhesion and stable performance of the subsequent graphene nanocomposite coating, further enhancing the radiator's thermal conductivity and corrosion resistance.

[0071] In the traditional high thermal conductivity die-cast heat sink manufacturing process, if the microstructure size and oxide layer parameters are not appropriate, the porous layer may be uneven or insufficient in thickness, which may affect the penetration efficiency of the aluminum alloy liquid and the thermal performance stability of the final heat sink.

[0072] In this regard, this application further proposes a specific method for preparing a microstructured metal preform with a porous layer on its surface, including using an aluminum alloy foil with a thickness of 0.08-0.12 mm to prepare a preform with a microtooth structure, wherein the height of the microtooth is 1.8-2.2 mm and the tooth spacing is 1.2-1.8 mm; subsequently, the preform is subjected to micro-arc oxidation treatment with a treatment voltage of 400-450 V and a treatment time of 10-15 min to form a porous alumina layer with a thickness of 5-8 μm on its surface.

[0073] In this process, a preform with a micro-tooth structure is fabricated using aluminum alloy foil with a thickness of 0.08-0.12 mm. The aluminum alloy foil serves as the substrate for the preform, and its thickness range is designed to ensure structural stability and appropriate flexibility during subsequent processing and die casting. Various grades of aluminum alloy foil can be used, such as 1-series pure aluminum, 3-series aluminum-manganese alloys, or 5-series aluminum-magnesium alloys, which exhibit good thermal conductivity or formability in specific applications; alternatively, 6-series aluminum-magnesium-silicon alloys can be used, which possess excellent strength and corrosion resistance. The micro-tooth structure is designed to significantly increase the surface area of ​​the preform, thereby promoting mechanical interlocking with the molten aluminum alloy.

[0074] The micro-tooth structure can be formed on aluminum alloy foil through precision stamping, laser etching, or chemical etching; alternatively, it can be achieved through roll forming or molding. The height of the micro-tooth is 1.8-2.2 mm, which affects the contact area and interlocking depth between the micro-tooth and the molten aluminum alloy. The height of the micro-tooth can be precisely controlled through mold design or laser etching depth; alternatively, a micro-tooth structure with a specific height can be formed through multi-layer lamination and sintering. The tooth spacing is 1.2-1.8 mm, which affects the fluidity and filling efficiency of the molten aluminum alloy, as well as the strength of the final interlocking structure. The tooth spacing is controlled similarly to the micro-tooth height, mainly through mold design or processing parameters; alternatively, a fusible or volatile spacer can be placed between the micro-tooths and removed in subsequent processing to form a precise spacing. Subsequently, the preform undergoes micro-arc oxidation treatment, which aims to form a porous oxide layer on the surface of the preform to enhance the bonding force with the molten aluminum alloy.

[0075] Micro-arc oxidation is typically performed in solutions containing electrolytes such as silicates, phosphates, or borates; alternatively, it can be carried out in solutions containing electrolytes such as oxalates or sulfates. The processing voltage is 400-450V, a key parameter in the micro-arc oxidation process that affects the growth rate, pore structure, and density of the oxide layer. Voltage application can be achieved using a constant voltage mode, pulsed voltage control at specific stages, or a constant current mode, indirectly controlling the voltage by controlling the current density to achieve a similar oxidation effect. The processing time is 10-15 minutes, which determines the thickness of the oxide layer and the full formation of the pore structure. Time control can be achieved through precise timing using automated equipment; alternatively, the processing time can be dynamically adjusted by real-time monitoring of oxide layer thickness or electrolyte parameter changes. This results in the formation of a porous alumina layer with a thickness of 5-8 μm on the surface. This porous alumina layer provides mechanical anchoring points for the molten aluminum alloy and may promote interfacial reactions and enhance bonding strength. The porosity and pore size of the porous alumina layer can be further optimized by adjusting the electrolyte composition, temperature and current density; or, its surface properties can be changed by post-treatment after the formation of the oxide layer, such as impregnation or filling.

[0076] The solution proposed in this application ensures the optimization of the microstructure and porous layer through precise control of the preform fabrication process. Specifically, the aluminum alloy foil thickness of 0.08-0.12 mm, the micro-tooth height of 1.8-2.2 mm, and the tooth spacing of 1.2-1.8 mm are designed synergistically to achieve a precise match. The thickness of the aluminum alloy foil determines the structural rigidity of the micro-tooth, preventing bending deformation of the micro-tooth during die casting high-pressure jetting, and avoiding excessive thickness that would result in insufficient tooth spacing and hinder the flow of molten aluminum alloy.

[0077] The specific ratio of micro-tooth height to tooth spacing maximizes the contact area with the molten aluminum alloy, thereby improving the interlocking strength and thermal conductivity. Simultaneously, sufficient flow channels are reserved to ensure that the molten aluminum alloy can quickly and evenly penetrate all gaps and porous layers under high pressure, avoiding localized accumulation or dead zones. These dimensional parameters are compatible with the die-casting mold cavity dimensions, allowing for precise batch placement directly through mold positioning. Subsequently, a porous alumina layer with a thickness of 5-8 μm is formed on the surface of the preform using a micro-arc oxidation voltage of 400-450V and a processing time of 10-15 minutes. This micro-arc oxidation process not only ensures the full progress of the oxidation reaction but also creates a dual-layer structure of "porous surface + dense inner layer." The porous surface structure provides abundant anchoring points for the molten aluminum alloy, while the dense inner layer enhances the strength of the micro-tooth itself.

[0078] Precise control of the oxide layer thickness avoids problems such as insufficient anchor points and weak interlocking due to excessive thickness, while preventing the oxide layer from becoming brittle and cracking under die-casting pressure due to excessive thickness. Simultaneously, this thickness does not sever the metallurgical bonding path between the micro-teeth and the molten aluminum alloy. This optimized preform can fully bond with high-purity, high-fluidity molten aluminum alloy (as described in claims 2 and 3) during die-casting. Under a pressure of 80-90 MPa, the molten aluminum alloy can effectively fill the 1.2-1.8 mm tooth spacing and porous layer pores. Furthermore, the 5-8 μm porous alumina layer can undergo a slight interfacial reaction with the molten aluminum alloy at 720-740°C, forming a metallurgical bonding transition layer, thus making the dual connection of "mechanical interlocking + metallurgical bonding" even stronger. The regular micro-tooth structure also reduces the difficulty of subsequent surface treatments (such as mechanical polishing in step S400), ensuring that the surface roughness meets the requirements and providing a uniform adhesion substrate for the subsequent graphene nanocomposite coating (step S500). At the same time, the preferred aluminum alloy foil material (such as 6061) has good compatibility with the molten aluminum-silicon alloy formulation, avoiding the problem of mismatch in the coefficient of thermal expansion at the interlocking interface due to material differences, and reducing interfacial stress during thermal cycling.

[0079] In one specific implementation, a preform with a micro-tooth structure can be fabricated using a 0.1 mm thick 6061 aluminum alloy foil through a precision stamping process. The height of the micro-tooth is controlled at 2.0 mm, and the tooth spacing is 1.5 mm. Subsequently, the preform is immersed in an electrolyte containing silicates and phosphates for micro-arc oxidation treatment. During the treatment, a voltage of 420 V is applied and maintained for 12 minutes. In this way, a porous alumina layer with a thickness of approximately 6 μm can be formed on the surface of the preform. This porous alumina layer has a uniform pore structure, providing an ideal interface for the subsequent infiltration of molten aluminum alloy.

[0080] The above technical solution effectively solves the problem of uneven porous layer and insufficient thickness caused by improper microstructure size and oxide layer parameters during the preparation of traditional prefabricated components, which in turn affects the penetration efficiency of aluminum alloy liquid and the final thermal performance stability of the heat sink. This solution significantly improves the reliability and structural stability of the interlocking interface through precise and coordinated control of aluminum alloy foil thickness, micro-tooth structure size, and micro-arc oxidation treatment parameters. This greatly enhances the bonding strength between the fins and the base, effectively resists interfacial stress during thermal cycling, and avoids cracking and peeling.

[0081] Meanwhile, the well-defined micro-tooth structure and uniform porous layer ensure the formation of a continuous and efficient heat-conducting network after the aluminum alloy liquid is filled, reducing interfacial thermal resistance and thus optimizing the heat conduction path inside the radiator. Furthermore, the parameter range of this solution is compatible with industrial production equipment, enabling standardized mass production of prefabricated components, improving production yield, and balancing high performance with mass production feasibility. This comprehensive performance improvement resulting from multi-parameter synergy allows the radiator to provide more stable and efficient heat dissipation performance when facing high power density and high heat flux density applications.

[0082] Traditional high thermal conductivity die-cast radiators are manufactured by injecting molten aluminum alloy into a mold to penetrate the porous layer of a preform to form an integrated radiator casting. However, inaccurate die-casting process parameters can lead to insufficient penetration, porosity, insufficient bonding strength, and low heat dissipation efficiency.

[0083] In this regard, this application further proposes that, in step S300, the die-casting process parameters for injecting molten aluminum alloy into the mold are as follows: mold preheating temperature 220-250℃, aluminum alloy liquid temperature 720-740℃, injection speed 3-4m / s, pressurization pressure 80-90MPa, and holding time 15-20s.

[0084] Mold preheating temperature refers to heating the mold to a specific temperature before die casting. Setting this temperature is crucial for controlling the fluidity of the molten metal, preventing premature solidification, and reducing casting defects. Mold preheating can be achieved in various ways, such as internal heating using electric heating rods or external heating using circulating heat transfer oil or gas.

[0085] The temperature of molten aluminum alloy refers to the temperature of the molten aluminum alloy when it is injected into the mold. This temperature directly affects the viscosity, fluidity, and solidification behavior of the molten aluminum alloy. A suitable temperature ensures that the molten aluminum alloy fully fills the mold cavity and penetrates the preform. The temperature of the molten aluminum alloy is typically precisely regulated using equipment such as induction furnaces, resistance furnaces, or crucible furnaces. Injection speed refers to the speed at which the die-casting machine propels the molten aluminum alloy into the mold cavity. Controlling this speed is crucial for preventing molten metal splashing, reducing air entrapment, and ensuring smooth filling. Injection speed can be adjusted through the hydraulic system of the die-casting machine, for example, by controlling the flow rate of the hydraulic cylinders or using a servo drive system for precise control. Boost pressure refers to the additional pressure applied to the molten metal within the mold after filling is complete.

[0086] This pressure is designed to compensate for metal solidification shrinkage, improve casting density, and enhance the bond strength between the metal and the preform. The pressure boosting is typically provided by the die-casting machine's booster mechanism, such as through a hydraulic booster cylinder or a separate pressure control unit. Holding time refers to the duration for which the molten metal is held under pressure within the mold. During this time, the molten metal solidifies under pressure to minimize defects such as shrinkage porosity and blowholes. The holding time is set and timed by the die-casting machine's control system to ensure continuous pressure is applied until the metal has completely solidified.

[0087] The proposed solution establishes a synergistic closed-loop control system by precisely controlling the mold preheating temperature, aluminum alloy molten temperature, injection speed, pressurization pressure, and holding time in the die-casting process. This optimizes the penetration process of the molten aluminum alloy into the microstructured metal preform and ensures the quality and performance of the final radiator casting. Specifically, the mold preheating temperature is controlled at 220-250℃, creating a precise temperature difference with the aluminum alloy molten temperature of 720-740℃. This temperature difference prevents the aluminum alloy molten material from solidifying prematurely upon contact with the mold surface due to excessive temperature difference, forming a "cold barrier" that hinders its penetration into the porous layers and gaps of the preform. Conversely, it also prevents shrinkage defects caused by excessively small temperature differences leading to slow solidification.

[0088] Meanwhile, mold preheating helps reduce water vapor condensation on the mold cavity surface, thereby reducing the risk of water vapor reacting with the molten aluminum alloy to form hydrogen pores. The injection speed is controlled at 3-4 m / s to ensure that the molten aluminum alloy is smoothly injected into the mold cavity, avoiding turbulence and bubble entrainment caused by high-speed injection. This is crucial for protecting the integrity of the preform with a micro-tooth structure made of aluminum alloy foil with a thickness of 0.08-0.12 mm, preventing deformation of the micro-tooths or the detachment of the 5-8 μm thick porous alumina layer formed on its surface. Based on this, the pressurization pressure is set at 80-90 MPa and applied immediately after filling. This high pressure forces the molten aluminum alloy to penetrate deeply into the 5-8 μm thick porous alumina layer on the preform surface and into the micro-tooth gaps with a spacing of 1.2-1.8 mm, achieving deep and uniform penetration, thus forming a strong mechanical and metallurgical bond.

[0089] The holding time is set to 15-20 seconds to precisely cover the solidification cycle of the aluminum alloy liquid. Continuous pressure is applied during the later stages of solidification to effectively compensate for solidification shrinkage, "compact" any potential pores, and continuously replenish the micro-tooth gaps with the aluminum alloy liquid, preventing localized unfilled areas and significantly suppressing porosity and shrinkage defects within the casting. Furthermore, for aluminum alloy liquids composed of Si 10.5-12.5%, Cu 0.6-0.9%, Mg 0.3-0.5%, Ti 0.05-0.15%, Fe ≤ 0.3%, with the balance being Al and unavoidable impurities, a liquid temperature of 720-740℃ can balance its fluidity and silicon phase precipitation behavior. Combined with mold preheating at 220-250℃, silicon phase segregation can be reduced, ensuring a uniform internal structure within the casting.

[0090] For molten aluminum alloys with an aluminum purity of not less than 99.7% in the raw materials, this parameter combination further reduces the risk of oxidation and gas absorption, ensuring the tightness of the interlocking. Through the synergistic effect of the above parameters, this scheme achieves full penetration and tight bonding of the molten aluminum alloy into the microstructure preform, effectively suppressing the generation of internal defects in the casting, thus laying the foundation for manufacturing high thermal conductivity and high strength die-cast radiators.

[0091] The following is a specific example. In practice, a horizontal cold chamber die-casting machine can be used to produce radiator castings. First, the die-casting mold is preheated using an electric heating rod to stabilize its preheating temperature at 230℃. Then, molten aluminum alloy is precisely heated in an induction furnace to maintain its temperature at 735℃. After the prepared microstructured metal preform is positioned within the preheated die-casting mold cavity, the die-casting machine injects the molten aluminum alloy into the mold at an injection speed of 3.2 m / s. Immediately after mold filling, a pressure of 88 MPa is applied and maintained for 17 seconds to ensure that the molten aluminum alloy fully penetrates the porous layers and gaps of the preform under pressure and solidifies. After cooling, a fully integrated radiator casting is obtained.

[0092] Through the above technical solution, this application can significantly improve the manufacturing quality and performance of high thermal conductivity die-cast heat sinks. Precise control of the mold preheating temperature, aluminum alloy liquid temperature, injection speed, pressurization pressure, and holding time allows the molten aluminum alloy liquid to deeply and uniformly penetrate the porous layer and gaps of the microstructured metal preform, thereby forming a stronger mechanical and metallurgical bond. This effectively solves the problems of insufficient penetration and inadequate bonding strength in traditional die casting.

[0093] Simultaneously, this parameter combination can maximally suppress defects such as porosity and shrinkage within the casting, preventing these defects from disrupting the heat conduction network and ensuring a dense internal structure, thereby optimizing the heat conduction path. Furthermore, this approach promotes uniform internal microstructure within the casting, further enhancing the overall thermal conductivity and mechanical stability of the radiator. These optimizations not only improve the reliability of the radiator but also provide a high-quality substrate for subsequent surface treatment and coating preparation, ensuring the excellent heat dissipation performance of the final product.

[0094] In some of the embodiments described above in this application, a graphene nanocomposite coating is prepared on the surface of a radiator casting to improve heat dissipation performance and bonding strength. However, in the process of its implementation, the lack of specific definition of the coating preparation process may lead to uneven coating distribution and large thickness fluctuations, which may affect the heat conduction efficiency and coating durability.

[0095] In this regard, this application further proposes that in step S500, the graphene nanocomposite coating is prepared on the surface of the radiator casting using an electrostatic rotary cup spraying process with the following parameters: spraying voltage 60-80kV, atomization pressure 0.3-0.5MPa, and coating wet film thickness controlled at 30-40μm.

[0096] This electrostatic rotary cup spraying process is a highly efficient coating application technology. Its core principle lies in using a high-speed rotating cup to fling out and atomize the coating into fine droplets, while simultaneously applying high-voltage electrostatics to charge these droplets. Under the influence of the electric field, the charged droplets are attracted and uniformly deposited onto the grounded or oppositely charged workpiece surface.

[0097] This method significantly improves coating utilization and coating uniformity, especially suitable for workpieces with complex geometries. As a specific implementation, rotary cups with different diameters or edge designs can be used to accommodate coatings with varying viscosities or rheological properties and optimize atomization. Furthermore, the degree of atomization and droplet size can be precisely controlled by adjusting the rotary cup's rotation speed. The 60-80kV spraying voltage refers to the high-voltage potential applied to the electrodes of the rotary cup or spray gun during electrostatic spraying. This voltage setting is crucial for the charge on the coating particles, the electric field strength, and ultimately, the deposition efficiency and coating quality. Within the 60-80kV range, sufficient charge is ensured for the graphene nanocomposite slurry particles, enabling efficient and uniform directional migration and deposition onto the radiator casting surface under the influence of the electric field. For example, a stable DC high-voltage power supply can be used to provide the voltage output, or a pulsed high-voltage power supply can be used, with the electric field distribution and the charge on the coating particles optimized by adjusting the pulse frequency and duty cycle.

[0098] Atomization pressure of 0.3-0.5 MPa refers to the gas pressure used to assist in paint atomization or control the spray pattern during electrostatic rotary cup spraying. This pressure, in conjunction with the mechanical atomization effect of the rotary cup, jointly determines the droplet size distribution, spray fan width, and paint transport efficiency. Controlling the atomization pressure within the range of 0.3-0.5 MPa helps to atomize the graphene nanocomposite slurry into suitable fine droplets, ensuring a smooth and even coating while avoiding excessive atomization and paint loss due to excessive pressure, or insufficient atomization and a rough coating due to insufficient pressure. Specifically, the atomization pressure can be precisely controlled by adjusting the air pressure regulating valve on the spray gun, or by using an intelligent spraying system with a built-in pressure sensor for real-time monitoring and adjustment.

[0099] The wet film thickness control of 30-40 μm refers to the thickness of the liquid film layer after the coating is applied to the surface of the radiator casting, before it dries or cures. Precise control of the wet film thickness is crucial to ensuring the final dry film performance and avoiding coating defects. Maintaining the wet film thickness within the 30-40 μm range aims to provide an ideal starting point for the subsequent curing process, ensuring that a dry film with a continuous thermally conductive network and good adhesion to the substrate is formed after curing. Methods for achieving wet film thickness control can include: comprehensive adjustment of parameters such as coating flow rate, spraying speed, spraying distance, and number of sprays using the spraying equipment; or real-time monitoring using an online wet film thickness gauge and automatic adjustment of spraying parameters based on feedback signals.

[0100] This application utilizes an electrostatic rotary cup spraying process to prepare a graphene nanocomposite coating on the surface of a radiator casting, achieving uniform and efficient coating deposition. Specifically, in step S500, a high-speed rotating cup ejects and initially atomizes the graphene nanocomposite slurry, forming tiny droplets with a certain kinetic energy. Simultaneously, a 60-80kV spraying voltage applied to the rotary cup imparts an electrostatic charge to these droplets. Under the influence of an electric field, these charged droplets are efficiently adsorbed onto the grounded or oppositely charged surface of the radiator casting. During this process, the atomization pressure of 0.3-0.5MPa synergistically works with the mechanical atomization of the rotary cup to further refine the droplet size, ensuring uniform dispersion of graphene nanosheets and nano-aluminum powder in the slurry and preventing agglomeration, thereby forming a continuous and dense three-dimensional thermally conductive network in the coating.

[0101] The wet film thickness of the coating is precisely controlled within 30-40 μm. This not only provides a suitable film thickness for the subsequent curing process, avoiding curing defects caused by excessive thickness, but also ensures that the dry film thickness after curing provides sufficient heat conduction path without affecting the structural integrity and assembly accuracy of the radiator. It is worth noting that the electrostatic rotary cup spraying process and its parameter settings work well with the surface treatment and degassing of the radiator casting in the preceding S400 step. The casting, after being polished to a surface roughness Ra≤1.6 μm and degassed in the S400 step, has a smooth and dense surface, which is conducive to the uniform adsorption of charged coating particles and avoids coating blistering or reduced adhesion caused by surface unevenness.

[0102] Furthermore, this parameter system fully considers the characteristics of graphene nanocomposite slurry. By optimizing the spraying voltage and atomization pressure, it effectively prevents graphene nanosheets from being damaged or agglomerated due to excessive shear force during spraying, thus ensuring their thermal conductivity in the coating. This synergistic effect ensures that the graphene nanocomposite coating can adhere to the complex microstructure surface of the radiator casting in its optimal state, thereby maximizing its high thermal conductivity.

[0103] As a specific implementation method, in step S500, an electrostatic rotary cup spraying device equipped with a high-voltage electrostatic generator and an adjustable-speed rotary cup can be used. During the spraying operation, the spraying voltage is set to 70kV to ensure that the graphene nanocomposite slurry particles are fully charged. Simultaneously, the atomization pressure is adjusted to 0.4MPa, allowing the slurry to be atomized into fine droplets with uniform particle size distribution, thereby forming a smooth and defect-free coating on the surface of the radiator casting. During the spraying process, by precisely controlling the moving speed of the spraying equipment and the paint flow rate, the wet film thickness of the coating on the surface of the radiator casting is kept stable at 35μm. For example, a robotic spraying system can be used, employing a preset spraying path and speed curve to achieve comprehensive coverage and precise thickness control of the complex geometry of the radiator casting. During the spraying process, an online wet film thickness sensor can be used to monitor the coating thickness in real time, and the spraying parameters can be fine-tuned based on the feedback data to ensure that the wet film thickness remains within the target range.

[0104] Through the above technical solution, this application effectively solves the problems of uneven coating distribution and large thickness fluctuations caused by the lack of specific limitations in the coating preparation process in the prior art, which in turn affect the heat conduction efficiency and coating durability. This solution, through electrostatic rotary cup spraying technology and its precise parameter control, ensures that the graphene nanocomposite coating achieves highly uniform and seamless coverage on the surface of heat sink castings, especially on complex structures such as micro-toothed and finned surfaces. This allows the graphene nanosheets to form a continuous and efficient three-dimensional thermally conductive network in the coating, significantly reducing the thermal resistance of the heat sink surface and thus greatly improving the overall heat dissipation efficiency.

[0105] Meanwhile, precise control of spraying voltage and atomization pressure, combined with appropriate wet film thickness, not only strengthens the adhesion between the coating and the casting substrate, effectively preventing coating peeling or cracking under long-term thermal cycling and vibration conditions, but also ensures the structural integrity of the cured coating, improving the durability and reliability of the radiator. Furthermore, this solution enables automated and mass production of the coating preparation process, improving production efficiency and product consistency, and providing a stable and reliable solution for the heat dissipation needs of high-power-density equipment.

[0106] In some of the solutions described above in this application, a graphene nanocomposite coating is prepared on the surface of a heat sink and then cured and sealed to improve the adhesion and sealing of the coating, thereby enhancing heat dissipation efficiency and durability. However, in this process, the edge area of ​​the coating may peel off due to uneven curing or insufficient sealing, resulting in obstructed heat transfer and reduced coating life.

[0107] In this regard, this application further proposes that the curing and edge sealing process in step S500 includes: baking the sprayed heat sink at 180°C for 60 minutes to cure the coating; and then using a laser to scan and seal the edge of the coating, with a laser power of 1200-1800W and a scanning speed of 10-15mm / s.

[0108] The process involves baking the sprayed radiator at 180°C for 60 minutes to cure the coating. This step aims to induce a cross-linking reaction in the organic components of the graphene nanocomposite coating through heat treatment, forming a stable three-dimensional network structure. This transforms the coating from a liquid or semi-solid state to a solid state, resulting in sufficient mechanical strength, adhesion, and chemical resistance. Precisely controlled temperature and time parameters ensure sufficient evaporation of the solvent and complete curing of the resin within the coating, while avoiding thermal damage to functional components such as graphene nanosheets and nano-aluminum powder. One method is to use an industrial oven or tunnel furnace for batch curing. The sprayed radiator is placed in an oven with a preset temperature of 180°C and maintained for 60 minutes, ensuring temperature uniformity within the oven. Alternatively, infrared heating or convection heating can be used for curing. By adjusting the infrared radiation intensity or hot air circulation speed, the radiator surface temperature can be reached at 180°C and maintained for 60 minutes.

[0109] Laser scanning and sealing of the coating edges utilizes the high energy density and precise controllability of lasers to locally heat-treat the edge areas of the cured coating. This creates a denser bonding layer between the coating and the substrate, or induces micro-fusion of the coating edge material, effectively sealing the coating edge, preventing environmental intrusion, and enhancing its resistance to peeling. One approach is to use fiber lasers or CO2 lasers, with a galvanometer scanning system or robotic arm driving the laser head to scan along a preset path along the heat sink coating edge. The laser beam's focus can be precisely controlled at the interface between the coating edge and the substrate. Alternatively, a pulsed laser can be used. By setting appropriate pulse frequencies and energy, the coating edge can be processed point-by-point or line-by-line, allowing for more precise control of heat input.

[0110] The laser power is 1200-1800W, a key parameter affecting the laser edge sealing effect, determining the amount of heat energy transferred to the coating edge per unit time. Selecting an appropriate power within this range aims to provide sufficient energy for localized melting of the coating edge material or interfacial reaction with the substrate, forming a strong bond, while avoiding excessive power that could lead to coating ablation, substrate deformation, or an excessively large heat-affected zone. One approach is to use the power adjustment module built into the laser equipment; for example, 1500W can be set for coatings of specific thickness and composition. Another approach is to determine the optimal power value through experimentation based on the thermal conductivity of the heat sink substrate material and the coating thickness. For example, for aluminum alloy substrates with good thermal conductivity, higher power may be required to achieve the desired edge sealing effect.

[0111] The scanning speed is 10-15 mm / s. This parameter determines the speed at which the laser beam moves along the coating edge, thus affecting the interaction time between the laser and the material. Selecting an appropriate scanning speed within this range aims to ensure that the laser energy has sufficient dwell time at the coating edge to complete effective heat treatment and fusion, while maintaining high production efficiency and avoiding localized overheating due to excessively slow speeds or insufficient energy and incomplete edge sealing due to excessively fast speeds. One approach is to precisely set the scanning speed through the laser equipment's control software; for example, when the laser power is set to 1500W, the scanning speed can be set to 12 mm / s. Another approach is to adjust the speed according to the geometry and complexity of the coating edge. For curved or sharp-angled edges, the scanning speed can be appropriately reduced to ensure uniformity and integrity of the edge sealing.

[0112] This application's solution effectively solves the problem of potential peeling of graphene nanocomposite coating edges due to uneven curing or insufficient sealing by baking the sprayed radiator at 180°C for 60 minutes to cure the coating, followed by laser scanning and sealing of the coating edges using a laser power of 1200-1800W and a scanning speed of 10-15mm / s. Specifically, a microstructured metal preform with a porous surface is prepared and positioned in a preheated die-casting mold cavity. Molten aluminum alloy is then injected into the mold, penetrating the porous layers and gaps of the preform under pressure. After cooling, an integrated radiator casting is formed. Following surface treatment and degassing of the radiator casting, a graphene nanocomposite coating is prepared on its surface. Subsequently, a coating curing process is performed. The sprayed radiator is baked at 180°C for 60 minutes; this precisely controlled curing parameter is customized to the characteristics of the graphene nanocomposite coating slurry used in this application.

[0113] At this temperature and time, the silicone resin can fully cross-link and cure, forming a stable physical structure that ensures the overall mechanical strength and adhesion of the coating, while preventing functional components such as graphene nanosheets and nano-aluminum powder from failing due to excessively high temperatures. Furthermore, this curing process allows for the full evaporation of solvents within the coating, forming a dense coating substrate that is compatible with the thermal expansion characteristics of the degassed casting substrate, reducing potential interfacial stress during curing. Based on the stable structure formed by the overall curing of the coating, laser scanning is further used to seal the coating edges. The laser power is set between 1200-1800W, and the scanning speed is controlled at 10-15mm / s. These parameters work synergistically to produce a "low-temperature rapid fusion" effect at the interface between the coating edge and the substrate. The laser energy is highly focused on the edge region, causing slight remelting of the silicone resin on the coating surface and activating the interfacial reaction between the nano-aluminum powder and the aluminum substrate, thereby forming an extremely thin metallurgical bonding transition layer, achieving a strong connection between the coating, transition layer, and substrate.

[0114] This localized fusion not only enhances the adhesion at the coating edges, but more importantly, it precisely reinforces the sharp corners of the microstructured heat sink—a weak point prone to stress concentration and corrosion. Laser edge sealing eliminates stress concentration at the corners and seals edge pores, effectively preventing moisture, dust, and other media from penetrating the coating-substrate interface and fundamentally avoiding edge peeling. Through this closed-loop process of "overall curing and shaping + precise edge sealing," the proposed solution ensures the overall stability and edge durability of the graphene nanocomposite coating on the heat sink surface, thereby maximizing heat dissipation efficiency and service life.

[0115] In one specific implementation, after electrostatic rotary cup spraying of the graphene nanocomposite coating, the heat sink can be placed in an industrial oven with precise temperature control. The internal temperature of this oven can be set to 180°C and maintained constant. The heat sink remains in the oven for 60 minutes to ensure that the silicone resin in the coating is fully cross-linked and cured, forming a uniform and dense coating structure. After curing, the heat sink is transferred to a laser edge-sealing workstation. This workstation is equipped with a fiber laser, whose laser head is controlled by a high-precision galvanometer scanning system. The operator pre-sets the laser path in the control software, allowing it to precisely scan along the edge of the graphene nanocomposite coating on the surface of the heat sink casting. The laser output power can be set to 1500W, and the galvanometer scanning speed can be set to 12mm / s. The laser beam moves rapidly along the coating edge, locally heating the interface between the coating and the substrate, forming a strong sealing layer. The entire process can be automated, ensuring the consistency and efficiency of the edge sealing.

[0116] Through the above technical solution, this application effectively solves the technical problem of easy peeling of graphene nanocomposite coatings at the edge area of ​​heat sinks. First, the precise curing process of baking at 180℃ for 60 minutes ensures full cross-linking of the silicone resin in the coating, forming a highly stable three-dimensional network structure. This ensures the overall mechanical strength of the coating and its adhesion to the substrate, avoids internal defects caused by uneven curing, and maintains the continuous and complete three-dimensional thermally conductive network formed by the graphene nanosheets, thus ensuring stable maintenance of the coating's thermal conductivity. Second, laser scanning and sealing of the coating edges utilizes the high energy density and precise control of the laser to form a strong metallurgical bonding transition layer between the coating edge and the substrate, significantly improving edge adhesion.

[0117] This precise reinforcement of the complex edges of microstructured heat sinks effectively eliminates stress concentration, seals edge pores, and fundamentally prevents the intrusion of environmental media. This significantly improves the coating's durability in harsh environments such as thermal cycling, humidity, and dust, preventing heat dissipation performance degradation and shortened lifespan caused by edge peeling. This solution, through a closed-loop process of "overall curing and shaping + precise edge sealing," not only ensures the stability and reliability of the entire coating area but also significantly extends the heat sink's lifespan without affecting its thermal conductivity, guaranteeing long-term stable operation in high-power-density applications. Furthermore, the process parameters are compatible with existing industrial equipment, facilitating mass production and ensuring batch-to-batch performance stability and consistency.

[0118] In some embodiments described above in this application, graphene nanocomposite coatings are proposed to improve the thermal conductivity and bonding strength of heat sinks. However, during the coating preparation process, if the slurry composition is unreasonable, it may lead to low thermal conductivity, weak adhesion, and easy generation of bubbles or defects, affecting the overall heat dissipation effect and reliability. To address this, this application proposes a slurry for graphene nanocomposite coatings, which, by mass percentage, consists of the following components: 6-10% graphene nanosheets, 40-50% silicone resin, 20-25% nano-aluminum powder, 2-4% coupling agent KH-550, 18-24% butyl acetate, and 0.5-1% defoamer.

[0119] Graphene nanosheets are two-dimensional carbon nanomaterials with extremely high in-plane thermal conductivity and excellent mechanical strength. In this application, they serve as the main thermally conductive filler, constructing a highly efficient thermally conductive network in the slurry and significantly improving the thermal conductivity of the coating. Graphene nanosheets can be single-layer, few-layer, or multi-layer structures, and their lateral dimensions and thickness can be adjusted according to specific needs to optimize their dispersion in the slurry and the continuity of the thermal conduction path.

[0120] Organosilicon resin is a polymer with silicon-oxygen bonds as its main chain, possessing excellent heat resistance, weather resistance, electrical insulation, and good adhesion properties. In this application, it serves as the matrix material for the coating slurry, not only firmly bonding thermally conductive fillers (such as graphene nanosheets and nano-aluminum powder) together to form a continuous and stable coating, but also ensuring reliable adhesion between the coating and the heat sink substrate. The organosilicon resin can be modified with different functional groups, such as epoxy-modified or acrylic-modified organosilicon resin, to adapt to different curing conditions and final performance requirements. Nano-aluminum powder refers to aluminum metal powder with a particle size at the nanoscale. In this application, nano-aluminum powder serves as an auxiliary thermally conductive filler, synergistically working with graphene nanosheets to further enhance the overall thermal conductivity of the coating. Nano-aluminum powder exhibits good electrical and thermal conductivity and good compatibility with the aluminum matrix. Its particle size can be controlled within a small range, such as 10-50 nm or 150-300 nm, to achieve better filling effect and the construction of thermal conductive pathways. Furthermore, nano-aluminum powder can enhance the mechanical strength and wear resistance of the coating. Coupling agent KH-550 is a substance that can improve the interfacial bonding performance between inorganic fillers and organic polymers. In this application, coupling agent KH-550 is used to enhance the interfacial adhesion between inorganic fillers such as graphene nanosheets and nano-aluminum powder and the organosilicon resin matrix, reducing interfacial thermal resistance, thereby improving the overall thermal conductivity and adhesion of the coating.

[0121] Coupling agents typically possess an amphoteric structure, with one end reacting with inorganic surfaces and the other with organic polymers. Besides KH-550, other types of silane coupling agents, such as KH-560 or KH-570, or titanate coupling agents, zirconate aluminate coupling agents, etc., can be selected to suit different material systems. Butyl acetate is a commonly used organic solvent with a moderate evaporation rate and good solubility. In this application, butyl acetate is used as a solvent for the slurry to adjust its viscosity, ensuring good flowability and atomization during spraying, guaranteeing uniform coating distribution without sagging. Furthermore, it helps disperse the solid components in the slurry, preventing agglomeration.

[0122] Besides butyl acetate, other alcohols, ketones, or aromatic solvents, such as methyl ethyl ketone, toluene, or xylene, can be used to meet different process requirements and environmental standards. Defoamers are additives that can eliminate or inhibit the generation of bubbles in coatings, inks, and other systems. In this application, the defoamer is used to eliminate bubbles that may be generated during the preparation, storage, and spraying of the slurry, ensuring a smooth surface and dense interior after coating curing, avoiding defects such as pinholes and shrinkage cavities caused by bubbles, thereby ensuring that the thermal conductivity and adhesion of the coating are not affected. Defoamers can be of various types, such as silicone-based, polyether-based, or mineral oil-based, and their selection depends on the characteristics of the slurry system and the required defoaming effect.

[0123] This slurry utilizes 6-10% graphene nanosheets to construct a highly efficient thermally conductive main network, leveraging their superior two-dimensional thermal conductivity to provide a rapid channel for heat transfer. Simultaneously, 20-25% nano-aluminum powder serves as an auxiliary thermally conductive filler, filling the gaps between the graphene nanosheets to form a secondary thermally conductive network. Working synergistically with the graphene nanosheets, this not only further enhances the overall thermal conductivity of the coating but also, through its good compatibility with the aluminum substrate, undergoes a slight metallurgical reaction with the substrate during subsequent laser edge sealing, strengthening the adhesion between the coating and the substrate. 40-50% silicone resin acts as the bonding matrix for the coating, firmly encapsulating and adhering the thermally conductive filler to the surface of the radiator casting. Its excellent heat resistance and elastic structure buffer the difference in thermal expansion coefficients between the coating and the substrate during thermal cycling, effectively preventing coating cracking or peeling.

[0124] The coupling agent KH-550 2-4% establishes a chemical bridge between the thermally conductive filler and the silicone resin, significantly improving interfacial compatibility, reducing interfacial thermal resistance, and enhancing the coating's adhesion and water resistance. Butyl acetate 18-24% acts as a solvent, precisely adjusting the slurry viscosity to suit the electrostatic rotary cup spraying process, ensuring uniform atomization and a consistent coating thickness. The defoamer 0.5-1% effectively eliminates air bubbles generated during slurry preparation and spraying, ensuring a dense internal structure and smooth surface after coating curing, preventing pinholes and other defects from disrupting the thermally conductive network. This slurry formulation is closely integrated with the S500 step in the manufacturing method of high thermal conductivity die-cast radiators, particularly synergistically with the electrostatic rotary cup spraying process and the curing and edge-sealing steps. The precise ratio of butyl acetate ensures the slurry viscosity forms fine atomized particles during electrostatic rotary cup spraying, preventing graphene nanosheet agglomeration and ensuring uniform dispersion of the thermally conductive filler in the coating.

[0125] The crosslinking properties of the silicone resin match the curing temperature of 180℃, ensuring that the coating forms a stable structure after baking. The presence of nano-aluminum powder provides the material basis for subsequent laser edge sealing, and the interfacial reaction induced by laser energy further enhances the bonding strength between the coating and the radiator casting. This multi-component, multi-functional synergistic slurry design allows for seamless integration with the overall manufacturing process, jointly improving the comprehensive performance of the high thermal conductivity die-cast radiator.

[0126] As a specific implementation method, the slurry used for the graphene nanocomposite coating can be composed of the following mass percentages: 8% graphene nanosheets, 45% silicone resin, 22% nano-aluminum powder, 3% coupling agent KH-550, 21% butyl acetate, and 1% defoamer. The graphene nanosheets can be multilayer graphene with an average of 7 layers and a lateral dimension of approximately 5-10 micrometers. The silicone resin can be a high-temperature resistant methylphenyl silicone resin. The nano-aluminum powder can be spherical or flake-shaped nano-sized aluminum powder. The coupling agent KH-550 can be commercially available aminopropyltriethoxysilane. The butyl acetate can be an industrial-grade product. The defoamer can be a polyether-modified silicone defoamer. In preparing the slurry, the silicone resin, butyl acetate, and defoamer are first mixed evenly. Then, the graphene nanosheets, nano-aluminum powder, and coupling agent KH-550 are gradually added. High-speed stirring and grinding processes are used to ensure that all solid components are fully dispersed, forming a uniform and stable slurry.

[0127] Through the above technical solution, the graphene nanocomposite coating slurry proposed in this application provides a high-performance coating solution for the manufacture of high thermal conductivity die-cast heat sinks. This slurry formulation, by optimizing the synergistic effect of thermally conductive fillers (graphene nanosheets and nano-aluminum powder), constructs a highly efficient and uniform thermally conductive network, significantly improving the thermal conductivity of the coating and thus effectively improving the overall heat dissipation performance of the heat sink. Using silicone resin as the matrix, combined with the interface modification effect of coupling agent KH-550, greatly enhances the adhesion between the coating and the heat sink casting, solving the problems of easy peeling and cracking of traditional coatings, and ensuring the reliability and durability of the heat sink under long-term thermal cycling and high-load conditions.

[0128] Furthermore, the precise formulation of butyl acetate ensures a suitable slurry viscosity. Combined with the use of defoamers, this effectively prevents the formation of bubbles and defects during spraying, guaranteeing the surface quality and internal density of the coating. This allows the coating to adhere evenly and stably to the radiator surface, perfectly complementing subsequent curing and laser sealing processes, further enhancing the overall performance and manufacturing yield of the radiator. This customized slurry formulation not only solves the performance bottlenecks of the coating itself but also forms an organic whole with the overall manufacturing process, jointly achieving a comprehensive improvement in the radiator's thermal conductivity, mechanical strength, and service life.

[0129] In some of the above-mentioned schemes of this application, a slurry composition was proposed for preparing a high thermal conductivity coating. However, in this process, the number of graphene nanosheets and the particle size of the nano-aluminum powder were not optimized, which may lead to insufficient thermal conductivity and uneven dispersion of the coating, affecting the overall heat dissipation efficiency and mechanical stability of the coating.

[0130] In this regard, this application further proposes that the graphene nanosheets in the slurry have a 5-10 layer structure and the particle size of the nano-aluminum powder is 50-150nm.

[0131] Graphene nanosheets have a 5-10 layer structure, meaning the thickness of the graphene material consists of 5 to 10 stacked single-atom layers. This range of layer counts retains the excellent thermal conductivity of single-layer graphene while increasing structural stability through appropriate interlayer stacking. This facilitates good dispersibility in slurries and avoids the drawbacks of single-layer graphene, such as easy agglomeration and difficulty in processing. Graphene nanosheets with this layer count structure can be prepared using various techniques, including mechanical exfoliation, chemical vapor deposition, or a combination of redox and ultrasonic exfoliation. For example, by controlling the degree of reduction of graphene oxide and the ultrasonic treatment time, graphene nanosheets with a specific layer count distribution can be obtained; alternatively, liquid-phase exfoliation technology can be used to precisely control the exfoliation parameters to obtain graphene nanosheets with the target layer count.

[0132] The particle size of nano-aluminum powder is 50-150 nm, meaning the average size of the aluminum powder particles is between 50 nm and 150 nm. Nano-aluminum powder within this particle size range possesses a high specific surface area and excellent filling performance, effectively filling the tiny gaps between graphene nanosheets to construct a dense three-dimensional thermally conductive network. Furthermore, nano-aluminum powder within this particle size range can form a good interfacial bond with the matrix during subsequent laser processing. Nano-aluminum powder with a particle size of 50-150 nm can be prepared using methods such as vapor deposition, plasma methods, chemical reduction methods, or mechanical ball milling. For example, by controlling the reaction temperature and pressure during vapor deposition, the particle size of the aluminum powder can be precisely controlled; alternatively, a wet chemical method can be used to prepare nano-aluminum powder with a uniform particle size distribution under the action of specific reducing agents and surfactants.

[0133] This application optimizes the structure and size of key thermally conductive fillers in the slurry, specifically limiting the graphene nanosheets to a 5-10 layer structure and the aluminum nanoparticles to a particle size of 50-150 nm, to construct a highly efficient and stable thermally conductive network. Specifically, the 5-10 layer graphene nanosheets, while maintaining high thermal conductivity, exhibit good dispersion stability in the silicone resin matrix due to their appropriate layer count, enabling the formation of a continuous two-dimensional thermally conductive main network. This effectively avoids the problems of easy agglomeration of single-layer graphene and the decreased thermal conductivity of multi-layer graphene. Simultaneously, the 50-150 nm aluminum nanoparticles, with their size forming a good size gradient with the graphene sheet thickness, can precisely fill the micron-level gaps between graphene sheets, constructing a three-dimensional thermally conductive secondary network, thereby compensating for potential thermally conductive blind spots in the two-dimensional graphene structure.

[0134] This combination of graphene nanosheets and nano-aluminum powder not only allows the graphene sheets to act as the primary heat conductor, while the nano-aluminum powder serves as a filler and bridging material, forming a dense and defect-free composite heat conduction path, but also enables the nano-aluminum powder to act as a "spacer" for the graphene sheets, further suppressing graphene aggregation. Furthermore, the nano-aluminum powder with this specific particle size can fully interact with laser energy in the subsequent laser sealing process, undergoing slight melting to form a metallurgical bonding transition layer with the aluminum substrate, thereby enhancing the bonding strength and sealing performance between the coating and the substrate. This refined filler structure and size control ensures that the slurry has an appropriate viscosity during preparation, adapting to the atomization requirements of the electrostatic rotary cup spraying process, avoiding nozzle clogging, and guaranteeing coating uniformity.

[0135] As a specific implementation method, the graphene nanosheets in the slurry can be graphene oxide prepared by a modified Hummers method, followed by a gentle reduction and ultrasonic exfoliation process to precisely control the layer distribution between 5 and 10 layers, ensuring good dispersibility and thermal conductivity in the silicone resin. For example, graphene nanosheets with an average of 7 layers can be selected. Simultaneously, the nano-aluminum powder can be spherical nano-aluminum powder prepared by vapor-phase condensation, with a particle size distribution concentrated in the range of 50-150 nm, for example, nano-aluminum powder with an average particle size of 100 nm. This particle size of nano-aluminum powder can effectively fill the gaps between the graphene sheets and form a stable composite structure with the silicone resin matrix. During slurry preparation, these fillers with specific structures and particle sizes are added to a mixture of silicone resin, coupling agent, butyl acetate, and defoamer in a predetermined ratio. High-speed stirring and grinding processes ensure uniform dispersion of the fillers, forming a stable slurry.

[0136] Through the above technical solution, the structure and size of graphene nanosheets and nano-aluminum powder in the slurry are optimized, effectively solving the problems of insufficient thermal conductivity and uneven dispersion of the coating. Specifically, the 5-10 layer graphene nanosheets and 50-150nm nano-aluminum powder work synergistically to construct a highly efficient and dense two-dimensional-three-dimensional composite thermally conductive network, significantly improving the overall thermal conductivity of the coating, allowing heat to be conducted away from the surface of the radiator casting more quickly and evenly. At the same time, this optimized filler combination greatly improves the dispersion stability of the slurry, avoids graphene agglomeration and nano-aluminum powder sedimentation, and ensures the uniformity and consistency of the coating after spraying. In addition, the nano-aluminum powder of a specific particle size forms a good interfacial bond with the substrate during laser edge sealing, further enhancing the mechanical strength and weather resistance of the coating, effectively preventing cracking or peeling of the coating under long-term thermal cycling and vibration conditions, thereby comprehensively improving the heat dissipation efficiency and service life of the high thermal conductivity die-cast radiator.

[0137] In some embodiments described above in this application, surface treatment and degassing steps are proposed to prepare the radiator surface for subsequent coating treatment. However, in this process, high surface roughness or residual gas may lead to insufficient coating adhesion and increased thermal resistance.

[0138] In this regard, this application further proposes that, in the above manufacturing method, step S400 further includes: first, mechanically grinding to achieve a surface roughness Ra of no more than 1.6 μm, and then, under a vacuum degree of no more than 1 × 10⁻⁶. -3 Keep warm for 2 hours at 450℃ and Pa.

[0139] Specifically, the surface roughness Ra of the radiator casting is reduced to no more than 1.6 μm through mechanical grinding. Mechanical grinding is a processing method that removes uneven parts of the material surface using mechanical force to achieve the desired surface finish. Its purpose is to reduce surface micro-undulations, providing a smooth and uniform substrate for subsequent coatings, ensuring good contact and adhesion between the coating and the substrate, and effectively reducing interfacial thermal resistance. Methods for achieving mechanical grinding include, but are not limited to: using a precision grinding machine to gradually reduce surface roughness by controlling grinding parameters and selecting appropriate abrasives; or using polishing equipment with polishing agents of different grit sizes for multi-stage polishing until the target roughness requirement is met. Based on this, a vacuum degree of no more than 1×10⁻⁶ is applied. -3 The radiator casting is held at 450°C for 2 hours under high temperature and vacuum conditions. This step aims to thoroughly remove any adsorbed or residual gas molecules and volatile impurities from the surface and interior of the radiator casting through a high-temperature and high-vacuum environment. If these gases and impurities are not removed, they may escape during the subsequent coating curing process, causing bubbles, voids, or delamination in the coating, thus affecting the coating's adhesion and thermal conductivity. Methods for achieving high-temperature vacuum holding include, but are not limited to: placing the radiator casting in a high-vacuum heat treatment furnace and heating it to a specified temperature using resistance heating or induction heating, while maintaining a high vacuum; or using a vacuum oven, precisely controlling the pumping rate of the vacuum pump and the power of the heating elements to ensure that the required vacuum level and temperature are reached and maintained within a specified time.

[0140] This application's solution combines mechanical grinding with vacuum high-temperature insulation to form a synergistic surface pretreatment process. First, the mechanical grinding step physically removes macroscopic and microscopic defects from the casting surface, such as burrs, oxide layers, and uneven areas, achieving extremely low surface roughness. This lays the physical foundation for the uniform spreading and tight bonding of the subsequent graphene nanocomposite coating. A smooth surface maximizes the effective contact area between the coating and the substrate, thereby optimizing coating adhesion and reducing interfacial thermal resistance. Following this, the subsequent vacuum high-temperature insulation step thoroughly removes adsorbed gases, moisture, and other volatile organic compounds that may have been introduced during grinding or are inherent to the casting itself, through both chemical and physical adsorption. Under high temperature, these adsorbate molecules gain sufficient energy to detach from the substrate surface; simultaneously, the high vacuum environment ensures that these desorbed gases are rapidly extracted, preventing re-adsorption or the formation of defects during coating curing. This process of first physically leveling and then chemically purifying ensures that the surface of the radiator casting is not only smooth on a macroscopic level, but also clean and flawless on a microscopic level. This provides an ideal adhesion interface for the graphene nanocomposite coating, greatly improving the coating's bonding strength and thermal conductivity.

[0141] The following example illustrates the surface treatment and degassing process for radiator castings. First, a CNC precision grinding machine can be used to perform multi-pass grinding on the surface of the radiator casting. For example, rough grinding can be performed first using a P220 grit wheel, followed by fine grinding using a P400 grit wheel, and finally ultra-fine polishing using a P800 grit polishing pad to ensure that the final surface roughness Ra meets the requirement of not exceeding 1.6 μm. After mechanical grinding, the ground radiator casting is immediately transferred to a resistance heating heat treatment furnace with high vacuum capability. The vacuum pump is started to evacuate the vacuum level in the furnace chamber to no higher than 1 × 10⁻⁶. -3 Pa, then the casting temperature is slowly increased to 450°C using furnace heating elements and maintained at this temperature for 2 hours. During this process, the vacuum system inside the furnace operates continuously to ensure that the desorbed gases are effectively discharged. After the holding period, the casting is either protected by an inert gas or naturally cooled to room temperature to obtain a radiator casting with a smooth, clean surface free of gas residue, preparing it for subsequent preparation of the graphene nanocomposite coating.

[0142] The above technical solution firstly controls the surface roughness of the radiator casting to an extremely low level through mechanical grinding, significantly improving surface smoothness. This provides an ideal physical basis for the uniform coating and tight bonding of the subsequent graphene nanocomposite coating, effectively reducing the interfacial thermal resistance between the coating and the substrate. Secondly, heat preservation treatment under strictly controlled vacuum and high temperature conditions thoroughly removes adsorbed gases and volatile impurities from the surface and interior of the casting, fundamentally avoiding coating defects such as bubbles and delamination caused by gas escape during coating curing, greatly enhancing the bonding strength between the coating and the substrate. This pretreatment method, combining precision mechanical grinding and vacuum high-temperature degassing, ensures that the graphene nanocomposite coating adheres to the surface of the radiator casting in optimal condition. This not only significantly improves the adhesion and stability of the coating but, more importantly, maximizes the high thermal conductivity of the graphene nanocomposite coating, thereby greatly improving the overall heat dissipation efficiency and long-term operational reliability of the high thermal conductivity die-cast radiator. Example

[0143] Formula proportions (by weight, total 100%) Aluminum alloy liquid formulation: Si 11.5%, Cu 0.75%, Mg 0.4%, Ti 0.1%, Fe 0.2%, balance Al (87.05%) and unavoidable impurities (≤0.05%).

[0144] Graphene nanocomposite coating slurry formulation: 8% graphene nanosheets (5-10 layers), 45% organosilicon resin, 22% nano aluminum powder (50-150nm), 3% coupling agent KH-550, 21% butyl acetate, and 1% defoamer (BYK-066N).

[0145] Raw materials for aluminum alloy liquid preparation: aluminum purity ≥ 99.7% (A00 grade electrolytic aluminum ingot).

[0146] Process steps and parameters S100, Preparation of microstructured metal preforms with porous surfaces 0.1mm thick 6061 aluminum alloy foil was selected and laser-cut to create a micro-tooth structure with a tooth height of 2.0mm and a tooth spacing of 1.5mm.

[0147] Micro-arc oxidation treatment: The electrolyte is a silicate-phosphate composite system, the treatment voltage is 420V and the treatment time is 12min, forming a porous alumina layer with a thickness of 6μm on the surface of the preform.

[0148] S200, Precast component positioning and mold preheating The microstructure preform is fixed to the fin forming area of ​​the die-casting mold using high-temperature resistant ceramic positioning pins, with a positioning gap of ≤0.05mm.

[0149] The mold is preheated to 230℃ and kept at that temperature for 30 minutes before the precast part is placed.

[0150] S300, interlocking die casting Aluminum alloy melt smelting: Add raw materials according to the formula ratio, smelt at 730℃, hold for 20 minutes to remove gas.

[0151] Die casting parameters: aluminum alloy liquid temperature 730℃, injection speed 3.5m / s, pressurization pressure 85MPa, holding time 18s, mold opening time 35s, after cooling, an integrated heat sink casting is formed.

[0152] S400, Surface Treatment and Degassing Mechanical grinding: Robotic grinding is used to remove gates and flash, resulting in a surface roughness Ra=1.2μm.

[0153] Vacuum degassing: Vacuum furnace vacuum degree 5×10 -4 Pa, temperature 450℃, heat preservation for 2 hours to eliminate internal pores and stress.

[0154] S500, Graphene Coating Preparation and Curing Edge Sealing Electrostatic rotary cup spraying: spraying voltage 70kV, atomization pressure 0.4MPa, coating wet film thickness 35μm, ensuring full coverage of micro-tooth and fin roots.

[0155] Curing treatment: Bake in an oven at 180℃ for 60 minutes to allow the coating to fully cross-link and cure.

[0156] Laser edge sealing: Fiber laser power 1500W, scanning speed 12mm / s, scanning along the edge of the coating for edge sealing, heat-affected zone width ≤0.5mm. Example

[0157] Formula ratio Completely consistent with Example 1.

[0158] Differences in process steps Step S100 is omitted, and molten aluminum alloy is directly injected into a conventional die-casting mold. The remaining process steps and parameters are the same as in Example 1. Example

[0159] Formula ratio differences The aluminum alloy liquid formulation is as follows: Si 9.0%, Cu 1.2%, Mg 0.2%, Ti 0.03%, Fe 0.4%, with the balance being Al and unavoidable impurities. The remaining slurry formulation is the same as in Example 1.

[0160] Process steps Completely consistent with Example 1. Example

[0161] Formula ratio differences Raw materials for preparing aluminum alloy liquid: The purity of aluminum is 99.5% (ordinary industrial pure aluminum), and the rest of the formula is the same as in Example 1.

[0162] Process steps Completely consistent with Example 1. Example

[0163] Formula ratio Completely consistent with Example 1.

[0164] Differences in process steps S100 step: Select 0.15mm thick aluminum alloy foil, micro-tooth height 2.5mm, tooth spacing 1.0mm; micro-arc oxidation treatment voltage 380V, time 8min, to form a 3μm thick porous alumina layer, the remaining process steps and parameters are the same as in Example 1. Example

[0165] Formula ratio Completely consistent with Example 1.

[0166] Differences in process steps S300 steps: mold preheating temperature 200℃, aluminum alloy liquid temperature 700℃, injection speed 2.8m / s, pressurization pressure 70MPa, holding time 12s, the remaining process steps and parameters are the same as in Example 1. Example

[0167] Formula ratio differences Slurry formulation: 12% graphene nanosheets, 38% organosilicon resin, 18% nano-aluminum powder, 2% coupling agent KH-550, 28% butyl acetate, 0.3% defoamer, and the remaining formulation is the same as in Example 1.

[0168] Differences in process steps S500 Step: Air spraying process is used, with a spraying pressure of 0.6MPa and a wet film thickness of 45μm; curing temperature of 160℃ and time of 40min; no laser sealing is performed, and the remaining process steps and parameters are the same as in Example 1. In summary, Example 1 exhibits the best overall performance, with a fin-base bonding strength of 19.2 MPa, an overall thermal conductivity of 225 W / (m·K), and a 23.5% improvement in heat dissipation efficiency compared to the traditional solution. After 1000 thermal cycles, it showed no cracking or coating peeling, and its internal porosity was only 0.3%. In contrast, Example 2, lacking microstructure prefabrication, had a bonding strength reduced to 10.5 MPa, a heat dissipation efficiency improvement of only 8.2%, and fin delamination. Example 3, due to deviations in the aluminum alloy liquid formulation, had a bonding strength of 14.8 MPa and a thermal conductivity of 188 W / (m·K), with localized porosity expansion. Example 4 suffered from insufficient aluminum raw material purity (99.5%). Example 1 showed a bonding strength of 15.3 MPa and a thermal conductivity of 195 W / (m·K), with slight surface oxidation. Example 5, due to improper microstructure and micro-arc oxidation parameters, had a bonding strength of 13.6 MPa and a thermal conductivity of 183 W / (m·K), with the coating edge lifting. Example 6, due to deviations in die-casting process parameters, had a bonding strength of 12.8 MPa and a thermal conductivity of 178 W / (m·K), with significant internal shrinkage. Example 7, due to deviations in coating process and slurry parameters, had a bonding strength of 11.7 MPa and a thermal conductivity of 190 W / (m·K), with coating blistering and peeling. The porosity of each control example was between 0.7% and 1.8%, significantly higher than that of Example 1.

[0169] The above description is merely an embodiment of this application and is not intended to limit the scope of protection of this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the scope of protection of this application.

Claims

1. A method for manufacturing a high thermal conductivity die-cast radiator, characterized in that, Includes the following steps: S100, Prepare microstructured metal preforms with porous layers on the surface; S200. Position the microstructured metal preform into the preheated die-casting mold cavity. S300. Molten aluminum alloy liquid is injected into a mold and allowed to penetrate into the porous layer and gaps of the preform under pressure. After cooling, an integrated heat sink casting is formed. S400. Perform surface treatment and degassing on the radiator casting; S500. Prepare a graphene nanocomposite coating on the surface of the radiator casting, and then cure and seal it.

2. The manufacturing method according to claim 1, characterized in that, The molten aluminum alloy liquid is composed of the following components by mass percentage: Si 10.5-12.5%, Cu 0.6-0.9%, Mg 0.3-0.5%, Ti 0.05-0.15%, Fe ≤0.3%, with the balance being Al and unavoidable impurities.

3. The manufacturing method according to claim 2, characterized in that, The purity of aluminum in the raw materials for preparing the aluminum alloy liquid is not less than 99.7%.

4. The manufacturing method according to claim 1, characterized in that, The S100 step specifically includes: using an aluminum alloy foil with a thickness of 0.08-0.12 mm to fabricate a preform with a micro-tooth structure, wherein the height of the micro-tooth is 1.8-2.2 mm and the tooth spacing is 1.2-1.8 mm; subsequently, the preform is subjected to micro-arc oxidation treatment with a treatment voltage of 400-450V and a treatment time of 10-15 min to form a porous alumina layer with a thickness of 5-8 μm on its surface.

5. The manufacturing method according to claim 1, characterized in that, In step S300, the die-casting process parameters for injecting the molten aluminum alloy into the mold are as follows: Mold preheating temperature: 220-250℃; aluminum alloy liquid temperature: 720-740℃; injection speed: 3-4m / s; pressurization pressure: 80-90MPa; holding time: 15-20s.

6. The manufacturing method according to claim 1, characterized in that, In step S500, the graphene nanocomposite coating is prepared on the surface of the radiator casting using an electrostatic rotary cup spraying process, with the following parameters: Spraying voltage 60-80kV, atomization pressure 0.3-0.5MPa, and coating wet film thickness controlled at 30-40μm.

7. The manufacturing method according to claim 1, characterized in that, In step S500, the curing and edge sealing process includes: The coated radiator was baked at 180℃ for 60 minutes to cure the coating; then the edges of the coating were scanned and sealed with a laser with a power of 1200-1800W and a scanning speed of 10-15mm / s.

8. The manufacturing method according to claim 1, characterized in that, The slurry used in the graphene nanocomposite coating is composed of the following components by mass percentage: 6-10% graphene nanosheets, 40-50% organosilicon resin, 20-25% nano-aluminum powder, 2-4% coupling agent KH-550, 18-24% butyl acetate, and 0.5-1% defoamer.

9. The manufacturing method according to claim 8, characterized in that, The graphene nanosheets in the slurry have a 5-10 layer structure, and the nano-aluminum powder has a particle size of 50-150 nm.

10. The manufacturing method according to any one of claims 1, 4, 5, 6 or 7, characterized in that, The S400 step further includes: First, mechanical grinding is used to achieve a surface roughness Ra ≤ 1.6 μm, then the surface is further ground under a vacuum degree not exceeding 1 × 10⁻⁶. -3 Keep warm for 2 hours at 450℃ and Pa.

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