Preparation method of cold spraying gradient porous micro-channel liquid cooling plate

Abstract

The invention discloses a preparation method of a cold spraying gradient porous micro-channel liquid cooling plate, and relates to the technical field of thermal management devices. The invention can provide a low-cost and high-efficiency liquid cooling plate preparation technology which is adaptive to an aluminum alloy micro-channel, has no impurity residue and can accurately regulate and control a porous structure. The method comprises the steps that after the surface of a cold plate aluminum alloy matrix is pretreated, a target surface is obtained, and the pretreatment process sequentially comprises alkali washing treatment, acid pickling treatment and activating treatment; a cold spraying technology is adopted, metal powder of various particle size grades is sprayed to the target surface, so that side walls of various porous structures are formed on the target surface, runners are formed between the side walls, the hole diameter of the metal powder closer to the side wall of a heat source is smaller, and the porosity is larger; and connecting the cover body with the target surface and the upper part of each side wall in a sealing manner to form a closed flow channel, thereby obtaining the target liquid cooling plate.

Description

Technical Field

[0001] This application relates to the field of thermal management device technology, and in particular to a method for preparing a cold-sprayed gradient porous microchannel liquid cooling plate. Background Technology

[0002] As modern electronic devices rapidly evolve towards higher power density and miniaturization, their heat generation per unit volume is increasing dramatically, making traditional heat dissipation methods increasingly inadequate for meeting the demands for efficient and uniform temperature control. Against this backdrop, aluminum alloy microchannel cold plates, with their advantages of lightweight structure, high thermal conductivity, and compact and efficient design, have become the mainstream high-performance heat dissipation solution.

[0003] However, existing aluminum alloy microchannel cold plates suffer from two major bottlenecks: First, the smooth inner walls of the microchannels result in insufficient vaporization nuclei for boiling heat transfer, leading to low heat exchange efficiency and limited critical heat flux density. Second, the current aluminum alloy cold plate manufacturing process involves first machining the microchannels and then using sintering or ablation processes to create a porous layer within the flow channel. This results in poor pore uniformity and low bonding strength with the substrate, hindering the improvement of the heat transfer coefficient and complicating the process, requiring multiple processing steps. Third, traditional microchannels have uniform pore size and cross-section. As the working fluid flows from the heat source region (inflow end) to the outlet (outflow end), the uniform structure easily leads to "blockage" of the vapor-liquid two-phase flow as the working fluid temperature rises and bubbles are generated, increasing flow resistance and reducing heat dissipation stability. Furthermore, existing technologies cannot differentiate the microchannel structure (such as pore size and porosity) according to the heat dissipation requirements of the heat source location, and can only adopt a uniform structure, which cannot match the dynamic process requirements of the working fluid's "heat absorption-phase change-out". In addition, existing porous coating preparation technologies have obvious drawbacks: a dense oxide layer (Al2O3) is easily formed on the surface of aluminum alloys, requiring the addition of additional sintering aids (such as Mg and Li compounds) or sintering under vacuum / inert atmosphere, which not only increases the complexity of the process but also leads to a 30% to 50% increase in cost. Furthermore, residual sintering aids can easily clog microchannels and affect heat dissipation stability. Thermal spraying methods can easily lead to oxidation and burn-off of the aluminum alloy substrate, and the coating pores have poor connectivity. Traditional sintering porous layer preparation requires the use of pore-forming agents such as magnesium and aluminum, which can easily leave impurities after subsequent sintering. At the same time, it is difficult to adapt to the uniform coating requirements of narrow microchannel spaces (usually 50 to 500 μm wide). Summary of the Invention

[0004] This application provides a method for preparing a cold-sprayed gradient porous microchannel liquid cooling plate, which can provide a low-cost and high-efficiency liquid cooling plate preparation technology that is adapted to aluminum alloy microchannels, has no impurity residue, and can precisely control the porous structure.

[0005] To achieve the above objectives, this application adopts the following technical solution: In a first aspect, this application provides a method for preparing a cold-sprayed gradient porous microchannel liquid-cooled plate, characterized in that the method includes: After pretreatment of the surface of the cold-rolled aluminum alloy substrate, the target surface is obtained. The pretreatment process includes, in sequence, alkaline washing, acid washing and activation treatment. Using cold spraying technology, metal powders of various particle sizes are sprayed onto the target surface to form sidewalls with multiple porous structures on the target surface. Flow channels are formed between the sidewalls. The metal powder with larger pore size and greater porosity is located on the sidewalls closer to the heat source. The cover is sealed to the top of the target surface and each sidewall to form a closed flow channel, thus obtaining the target liquid cooling plate.

[0006] As one possible approach, alkaline washing treatment is applied to the surface of the cold-rolled aluminum alloy substrate, including: The surface of the cold-rolled aluminum alloy substrate is placed in a 10-15wt% NaOH solution and immersed at 50-60℃ for 10-15 minutes to obtain an alkaline-washed surface.

[0007] As one possible approach, pickling is performed on the surface of the cold-rolled aluminum alloy substrate, including: The alkaline-washed surface is placed in a 12-15wt% HNO3 solution and soaked for 5-10 minutes at room temperature to obtain an acid-washed surface.

[0008] As one possible approach, the surface of the cold-rolled aluminum alloy substrate is activated, including: The pickled surface is placed in a 2-5 wt% KH550 silane solution and immersed for 10-15 minutes at room temperature. Then, the cold-rolled aluminum alloy substrate is placed in an oven and baked at 100-120°C for 10-20 minutes to obtain the target surface.

[0009] As one possible implementation, the step of spraying metal powders of various particle sizes onto the target surface to form multiple sidewalls on the target surface includes: Using a CNC cold spraying equipment, under the first spraying parameters, metal powder of the first particle size is sprayed onto the target surface along a preset trajectory to form at least one porous first sidewall. Using a CNC cold spraying equipment, under the second spraying parameters, metal powder with a secondary particle size is sprayed onto the target surface to form at least one porous second sidewall. The primary particle size is 5-30 μm, the secondary powder particle size is 31-50 μm, and the first sidewall is close to the heat source.

[0010] As one possible implementation, the first spraying parameters include: spraying gas pressure of 2.5-3.5 MPa, spraying gas temperature of 350-450℃, spraying distance of 70-120 mm, and scanning speed of 4-10 mm / s.

[0011] As one possible implementation, the second spraying parameters include: spraying gas pressure of 2.5-3.5 MPa, spraying gas temperature of 350-450℃, spraying distance of 50-100 mm, and scanning speed of 4-10 mm / s.

[0012] As one possible implementation, the average pore size of the first sidewall is 5-20 μm, and the porosity is 40-60%. The average pore size of the second sidewall is 21-30 μm, and the porosity is 20-39%.

[0013] As one possible implementation, the height of the sidewall is 0.5-1.5 mm.

[0014] In a second aspect of this application, a liquid cooling plate is provided, which is prepared by the method for preparing a cold-sprayed gradient porous microchannel liquid cooling plate described in the first aspect of this application.

[0015] The beneficial effects of the technical solutions provided in this application include at least the following: The method for preparing a cold-sprayed gradient porous microchannel liquid cooling plate provided in this application embodiment involves pre-treating the surface of the aluminum alloy substrate of the cooling plate to obtain a target surface. The pre-treatment process includes, in sequence, alkaline washing, acid washing, and activation treatment. Using cold spraying technology, metal powders of various particle sizes are sprayed onto the target surface to form sidewalls with multiple porous structures. Flow channels are formed between the sidewalls, wherein the metal powders closer to the heat source have smaller pore sizes and higher porosity. A cover is then sealed to the target surface and the top of each sidewall to form a closed flow channel, thus obtaining the target liquid cooling plate.

[0016] The method for preparing a gradient porous microchannel liquid-cooled plate by cold spraying provided in this application utilizes cold spraying technology to prepare gradient porous microchannels on an aluminum alloy liquid-cooled plate. This method avoids the technical difficulties encountered in existing preparation processes, such as the difficulty in sintering aluminum powder, burn-through, deformation, and poor pore connectivity. It eliminates the need for pore-forming agents, avoiding the risk of corrosion caused by residual impurities. Furthermore, it eliminates the need for machining, achieving one-piece molding, reducing process costs, and improving production efficiency. Furthermore, by designing pores during the sidewall preparation process, heat transfer efficiency is improved. High-density nucleation sites in the heat source region are achieved using small-pore porous materials to reduce boiling initiation superheat, enhance liquid supply, prevent localized drying, provide efficient heat conduction, and ensure rapid heat transfer to the liquid. In the non-heat source region, efficient bubble escape channels are achieved using large-pore porous materials to reduce steam escape resistance, prevent bubble accumulation, optimize the liquid return path, maintain continuous heat exchange, reduce overall flow resistance, reduce pumping power consumption, and resolve the contradiction between "bubble accumulation and liquid return," thus achieving synergistic optimization of heat transfer and flow performance. Furthermore, the porosity and pore size of the sidewalls of this application can be flexibly adjusted according to the working fluid characteristics of different scenarios (such as water for new energy battery cold plates and acetone for chip heat spreaders), and the components are lightweight and corrosion resistant, and can be widely used in new energy, electronics, data centers and other fields, with broad market application prospects. Attached Figure Description

[0017] Figure 1 A flowchart illustrating a method for preparing a cold-sprayed gradient porous microchannel liquid-cooled plate according to an embodiment of this application; Figure 2 A schematic diagram of a sidewall in a target liquid cooling plate provided in an embodiment of this application; Figure 3 A scanning electron microscope image of a first sidewall provided in an embodiment of this application; Figure 4 A scanning electron microscope image of a second sidewall provided in an embodiment of this application. Detailed Implementation

[0018] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0019] Hereinafter, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of embodiments of this disclosure, unless otherwise stated, "a plurality of" means two or more.

[0020] In addition, the use of “based on” or “according to” implies openness and inclusivity, because processes, steps, calculations or other actions “based on” or “according to” one or more conditions or values ​​can in practice be based on additional conditions or values ​​beyond those conditions.

[0021] This application belongs to the field of thermal management device technology, specifically relating to a method for preparing a gradient porous microchannel liquid cooling plate using cold spraying. This application integrates porous microchannel flow channels on the surface of an aluminum alloy substrate using cold spraying, improving traditional single-phase liquid cooling heat transfer to two-phase boiling heat transfer, significantly increasing the heat transfer coefficient of the liquid cooling plate. It is particularly suitable for high-power-density heat dissipation scenarios such as new energy battery packs, high-power chips (CPU / GPU), and data center servers, addressing the core pain points of insufficient heat transfer performance and high process costs in existing heat dissipation solutions.

[0022] This application provides a method for preparing a cold-sprayed gradient porous microchannel liquid-cooled plate, such as... Figure 1 As shown, the method includes the following steps: Step 101: After pre-treating the surface of the cold-rolled aluminum alloy substrate, the target surface is obtained. The pre-treatment process includes, in sequence, alkaline washing, acid washing and activation treatment.

[0023] Optionally, the surface of the cold-rolled aluminum alloy substrate is subjected to alkaline washing treatment, including: placing the surface of the cold-rolled aluminum alloy substrate in a 10-15wt% NaOH solution and immersing it at 50-60℃ for 10-15 minutes to obtain an alkaline-washed surface.

[0024] Pickling the surface of the cold-rolled aluminum alloy substrate includes: placing the alkaline-washed surface in a 12-15wt% HNO3 solution and immersing it at room temperature for 5-10 minutes to obtain the pickled surface.

[0025] The activation treatment of the surface of the cold-rolled aluminum alloy substrate includes: placing the pickled surface in a 2-5wt% KH550 silane solution and immersing it at room temperature for 10-15 minutes; then placing the cold-rolled aluminum alloy substrate in an oven and baking it at 100-120℃ for 10-20 minutes to obtain the target surface.

[0026] In the actual processing, the surface of the cold-rolled aluminum alloy substrate is sequentially subjected to alkaline washing, acid washing, and activation treatment to remove oil and oxide layers, forming a rough surface. Specifically, the process can be as follows: The surface of the cold-rolled aluminum alloy substrate is immersed in a 10-15 wt% NaOH solution at 50-60°C for 10-15 minutes to remove oil, resulting in an alkaline-washed surface. Then, the alkaline-washed surface is immersed in a 12-15 wt% HNO3 solution at room temperature for 5-10 minutes to remove the oxide layer, resulting in an acid-washed surface. Finally, the acid-washed surface is immersed in a 2-5 wt% KH550 silane solution at room temperature for 10-15 minutes. Afterward, the cold-rolled aluminum alloy substrate is placed in an oven and baked at 100-120°C for 10-20 minutes to obtain the target surface.

[0027] Understandably, alkaline washing and acid washing can remove oil stains, impurities, and oxide layers from the aluminum alloy surface, improving adhesion for the subsequent spraying process. Activation treatment allows for the formation of a corrosion-resistant transition layer on the acid-washed surface, followed by drying to obtain the target surface. The specific principle behind the formation of the corrosion-resistant transition layer is as follows: Silane molecules (such as KH550) contain an amino group (-NH2) at one end, which can chemically react with the hydroxyl groups (-OH) on the aluminum alloy oxide film surface to form a strong chemical bond; the other end contains an alkoxy group (-OCH3), which, after hydrolysis, forms silanol groups (-SiOH), which can cross-link with the hydroxyl groups on the surface of the cold-sprayed powder particles (aluminum powder), generating the corrosion-resistant transition layer. This "bridging effect" of the corrosion-resistant transition layer breaks down the barrier of the oxide film, allowing the sidewalls of the porous structure generated by subsequent spraying to achieve a tighter bond with the surface of the cold-rolled aluminum alloy substrate through the silane transition layer. This can increase the bonding strength by 15-25%, while reducing particle rebound loss during cold spraying and improving deposition efficiency.

[0028] Step 102: Using cold spraying technology, metal powders of various particle sizes are sprayed onto the target surface to form sidewalls with various porous structures on the target surface. Flow channels are formed between the sidewalls. The metal powder particles with smaller particle sizes are closer to the heat source on the sidewalls. Optionally, the step of spraying metal powders of various particle sizes onto the target surface to form sidewalls with various porous structures on the target surface includes: Using a CNC cold spraying equipment, under the first spraying parameters, metal powder of the first particle size is sprayed onto the target surface along a preset trajectory to form at least one porous first sidewall. Using a CNC cold spraying equipment, under the second spraying parameters, metal powder with a secondary particle size is sprayed onto the target surface to form at least one porous second sidewall. The primary particle size is 5-30 μm, the secondary powder particle size is 31-50 μm, and the first sidewall is close to the heat source.

[0029] Optionally, the first spraying parameters include: spraying gas pressure of 2.5-3.5MPa, spraying gas temperature of 350-450℃, spraying distance of 70-120mm, and scanning speed of 4-10mm / s.

[0030] Optionally, the second spraying parameters include: spraying gas pressure of 2.5-3.5MPa, spraying gas temperature of 350-450℃, spraying distance of 50-100mm, and scanning speed of 4-10mm / s.

[0031] Optionally, the average pore size of the first sidewall is 5-20 μm, and the porosity is 40-60%. The average pore size of the second sidewall is 21-30 μm, and the porosity is 20-39%.

[0032] Optionally, the height of the sidewall is 0.5-1.5 mm.

[0033] like Figure 2 The diagram shown is a schematic of a sidewall in a target liquid-cooled plate provided in this application. It includes a first sidewall and a second sidewall, with a flow channel between the sidewalls through which the working fluid (cooling liquid) flows. The sidewalls are formed on the surface of the aluminum alloy substrate of the cold plate. The heat source is located in the middle of the target liquid-cooled plate, specifically near the heat source on the first sidewall.

[0034] It should be noted that this application can use powders of multiple particle sizes to spray and form sidewalls with various pore sizes and porosities. This application is not limited to using only two particle sizes of powder to spray and form two sidewalls, as long as the particle size of the sprayed powder used on the sidewalls from the heat source to the sidewalls away from the heat source changes in a gradient.

[0035] Understandably, this application designs the first sidewall near the heat source region as a porous structure with small pores. This provides a high density of nucleation sites in the heat source region, reduces the initial superheat of boiling, enhances liquid supply, prevents localized drying, provides efficient heat conduction, and ensures rapid heat transfer to the liquid. The second sidewall away from the heat source region is designed as a porous structure with large pores. This reduces steam escape resistance, prevents bubble accumulation, optimizes the liquid return path, maintains heat exchange, reduces overall flow resistance, and lowers pumping power consumption. The design of the first and second sidewalls in this application resolves the contradiction between "bubble accumulation and liquid return," achieving synergistic optimization of heat transfer and flow performance.

[0036] Step 103: Seal the cover to the target surface and the top of each sidewall to form a closed flow channel, thus obtaining the target liquid cooling plate.

[0037] This application allows for a sealed connection between the cover, the cold plate substrate, and the porous flow channel via welding, forming a closed flow channel that only allows the inlet and outlet of the cooling liquid. Diffusion welding can be used, resulting in a target liquid-cooled plate with a leakage rate ≤1×10⁻⁶. -8 Pa·m³ / s.

[0038] The method for preparing a cold-sprayed gradient porous microchannel liquid-cooled plate is based on the above embodiments. This application also provides some specific embodiments. The following embodiments describe the technical solutions of this application in more detail. These embodiments are for illustrative purposes only, as various modifications and variations within the scope of the disclosure of this application will be apparent to those skilled in the art. The reagents and raw materials used in the embodiments are commercially available or synthesized using conventional methods and can be used directly without further processing. The instruments and apparatus used in the embodiments are also commercially available.

[0039] This application takes the heat source area in the middle of the liquid cooling plate as an example. The aluminum alloy substrate of the cooling plate is made of 5052 aluminum alloy, the flow channel design width is 1mm, and the area of ​​the liquid cooling plate is 100×100mm for specific embodiments.

[0040] 1. Pretreatment of cold-rolled aluminum alloy substrate: The surface of the cold-rolled aluminum alloy substrate is subjected to alkaline washing, acid washing, and activation treatment in sequence to remove oil and oxide layer and form the target surface. The specific process includes: ① Alkaline washing treatment: immersion in 10wt% NaOH solution at 60℃ for 10min to remove oil; ② Acid washing treatment: immersion in 12wt% HNO3 solution at room temperature for 5min to remove oxide layer; ③ Activation treatment: immersion in 2wt% KH550 silane solution at room temperature for 10min to form a corrosion-resistant transition layer; ④ Drying: drying in an oven at 100℃ for 10min, ready for use.

[0041] 2. Cold spraying parameter design: Select metal powder with at least two particle sizes, with the first-stage powder having a particle size of 5μm and the second-stage powder having a particle size of 35μm; set the cold spraying gas pressure to 2.5MPa and the gas temperature to 350℃; the metal powder is spherical powder with a purity of 99.9%.

[0042] 3. Cold spraying to form porous microchannels: A CNC cold spraying device is used to spray the microchannels in sections along a preset trajectory on the surface of the cold-rolled plate substrate. The positioning accuracy of the CNC cold spraying device is ≤±0.01mm, and it is equipped with a rectangular focusing nozzle with an outlet size of 0.5-2mm. The spraying gas is selected from nitrogen. The spraying parameters for the second sidewall are: spraying distance (100 mm), scanning speed (4 mm / s), spraying secondary powder to form a porous layer with an average pore size of 20 μm and a porosity of 20%. The spraying parameters for the first sidewall are: spraying distance (120 mm), scanning speed (4 mm / s), and primary powder spraying to form a porous layer with an average pore size of 5 μm and a porosity of 40%. Figure 3 The image shown is a scanning electron microscope image of the first sidewall obtained during preparation. The above method uses multi-layer superposition spraying to make the height of the sidewall, that is, the depth of the flow channel, reach 1mm, thus obtaining a porous microchannel structure on the sidewall. 4. Encapsulation and Working Fluid Filling: The cover, cold plate substrate, and upper part of the porous flow channel can be sealed by welding to form a closed flow channel, leaving only the inlet and outlet of the coolant. Diffusion welding can be used to form the target liquid cooling plate, and the leakage rate of the target liquid cooling plate is ≤1×10⁻⁶. -8 Pa·m³ / s.

[0043] Example 2: 1. Pretreatment of cold-rolled aluminum alloy substrate: The surface of the cold-rolled aluminum alloy substrate is subjected to alkaline washing, acid washing, and activation treatment in sequence to remove oil and oxide layer and form the target surface. The specific process includes: ① Alkaline washing treatment: immersion in 10wt% NaOH solution at 60℃ for 10min to remove oil; ② Acid washing treatment: immersion in 12wt% HNO3 solution at room temperature for 5min to remove oxide layer; ③ Activation treatment: immersion in 2wt% KH550 silane solution at room temperature for 10min to form a corrosion-resistant transition layer; ④ Drying: drying in an oven at 100℃ for 10min, ready for use.

[0044] 2. Cold spraying parameter design: Select metal powder with at least two particle sizes, with the first-stage powder having a particle size of 30μm and the second-stage powder having a particle size of 50μm; set the cold spraying gas pressure to 3.5MPa and the gas temperature to 450℃; the metal powder is spherical powder with a purity of 99.9%.

[0045] 3. Cold spraying to form porous microchannels: A CNC cold spraying device is used to spray the microchannels in sections along a preset trajectory on the surface of the cold-rolled plate substrate. The positioning accuracy of the CNC cold spraying device is ≤±0.01mm, and it is equipped with a rectangular focusing nozzle with an outlet size of 0.5-2mm. The spraying gas is selected from nitrogen. The spraying parameters for the second sidewall are: spraying distance (50 mm), scanning speed (10 mm / s), and spraying of secondary powder to form a porous layer with an average pore size of 20 μm and a porosity of 40%. Figure 4 The image shown is a scanning electron microscope image of the prepared second sidewall; The spraying parameters for the first sidewall are: spraying distance (70 mm), scanning speed (10 mm / s), spraying primary powder to form a porous layer with an average pore size of 5 μm and a porosity of 60%. The above method uses multi-layer superposition spraying to make the height of the sidewall, that is, the depth of the flow channel, reach 1mm, thus obtaining a porous microchannel structure on the sidewall. 4. Encapsulation and Working Fluid Filling: The cover, cold plate substrate, and upper part of the porous flow channel can be sealed by welding to form a closed flow channel, leaving only the inlet and outlet of the coolant. Diffusion welding can be used to form the target liquid cooling plate, and the leakage rate of the target liquid cooling plate is ≤1×10⁻⁶. -8 Pa·m³ / s.

[0046] Comparative Example 1 Unlike Example 2, the first sidewall in Comparative Example 1 was prepared using the same spraying parameters as the second sidewall in Example 2, with the remaining processes being the same as in Example 2. Essentially, the first and second sidewalls in Comparative Example 1 are identical.

[0047] Comparative Example 2 Unlike Example 2, the second sidewall in Comparative Example 2 was prepared according to the spraying parameters of the first sidewall in Example 2, and the rest of the process was the same as in Example 2.

[0048] Comparative Example 3 Unlike Example 2, in Comparative Example 3, the first and second sidewalls are machined to form smooth flow channels, which are not porous structures. The rest of the process is the same as in Example 2.

[0049] The performance of the liquid-cooled plates prepared in Examples 1-2 and Comparative Examples 1-3 is shown in Table 1. The working fluid used in the tests was 3MNovec 7200 (purity ≥99.5%), with a flow rate of 1 L / min, an inlet temperature of 40°C, and a heating source of 300 W.

[0050] As shown in Table 1, the liquid cooling plates prepared in Examples 1 and 2 have high strength, high efficiency in heat exchange, and good pressure performance, and all properties are stable. Compared with Example 2: In Comparative Example 1, the first and second sidewalls were not prepared with a gradient, and were both porous channels with large pore size and small porosity (consistent with the pore size of the inlet and outlet channels). This resulted in insufficient vaporization nuclei in the heat source area, which significantly affected the boiling heat transfer performance of the liquid cooling plate channel and significantly reduced the heat exchange performance. In Comparative Example 2, the first and second sidewalls were not prepared with a gradient, and were both porous sidewalls with small pore size and large porosity (consistent with the pore size of the heat source channel). Although the heat exchange capacity still maintained good performance, "bubble blockage" (small pores trapping boiling bubbles) easily occurred in the non-heat source area, resulting in a sharp increase in flow resistance, which increased the pressure drop of the entire liquid cooling plate, requiring higher pump power and consuming more energy. In Comparative Example 3, the first and second sidewalls were not designed with porous structures and were both smooth channels. Their strength was reduced, and the heat exchange capacity was greatly reduced. In summary, the preferred two-phase porous microchannel design of this application can greatly improve the heat exchange performance of the liquid cooling plate, with low cost and excellent porous bonding strength.

[0051] Table 1 Test results of the examples and comparative examples

[0052] The method for preparing a cold-sprayed gradient porous microchannel liquid cooling plate provided in this application embodiment involves pre-treating the surface of the aluminum alloy substrate of the cooling plate to obtain a target surface. The pre-treatment process includes, in sequence, alkaline washing, acid washing, and activation treatment. Using cold spraying technology, metal powders of various particle sizes are sprayed onto the target surface to form sidewalls with multiple porous structures. Flow channels are formed between the sidewalls. The metal powder particles closer to the heat source have smaller particle sizes, smaller pore sizes, and higher porosity. A cover is then sealed to the target surface and the top of each sidewall to form a closed flow channel, thus obtaining the target liquid cooling plate.

[0053] The method for preparing a gradient porous microchannel liquid-cooled plate by cold spraying provided in this application utilizes cold spraying technology to prepare gradient porous microchannels on an aluminum alloy liquid-cooled plate. This method avoids the technical difficulties encountered in existing preparation processes, such as the difficulty in sintering aluminum powder, burn-through, deformation, and poor pore connectivity. It eliminates the need for pore-forming agents, avoiding the risk of corrosion caused by residual impurities. Furthermore, it eliminates the need for machining, achieving one-piece molding, reducing process costs, and improving production efficiency. Furthermore, by designing pores during the sidewall preparation process, heat transfer efficiency is improved. High-density nucleation sites in the heat source region are achieved using small-pore porous materials to reduce boiling initiation superheat, enhance liquid supply, prevent localized drying, provide efficient heat conduction, and ensure rapid heat transfer to the liquid. In the non-heat source region, efficient bubble escape channels are achieved using large-pore porous materials to reduce steam escape resistance, prevent bubble accumulation, optimize the liquid return path, maintain continuous heat exchange, reduce overall flow resistance, reduce pumping power consumption, and resolve the contradiction between "bubble accumulation and liquid return," thus achieving synergistic optimization of heat transfer and flow performance. Furthermore, the porosity and pore size of the sidewalls of this application can be flexibly adjusted according to the working fluid characteristics of different scenarios (such as water for new energy battery cold plates and acetone for chip heat spreaders), and the components are lightweight and corrosion resistant, and can be widely used in new energy, electronics, data centers and other fields, with broad market application prospects.

[0054] In addition, this application embodiment also provides a liquid cooling plate, which is prepared by the preparation method of the cold spray gradient porous microchannel liquid cooling plate described in this application embodiment.

[0055] For the limitations on the liquid cooling plate, please refer to the limitations on the preparation method of the cold spray gradient porous microchannel liquid cooling plate in this application, which will not be elaborated further here.

[0056] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0057] The above embodiments merely illustrate several implementation methods of this application, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this patent application should be determined by the appended claims.

Claims

1. A method for preparing a cold-sprayed gradient porous microchannel liquid-cooled plate, characterized in that, The method includes: After pretreatment of the surface of the cold-rolled aluminum alloy substrate, the target surface is obtained. The pretreatment process includes, in sequence, alkaline washing, acid washing and activation treatment. Using cold spraying technology, metal powders of various particle sizes are sprayed onto the target surface to form sidewalls with multiple porous structures on the target surface. Flow channels are formed between the sidewalls. The metal powders closer to the heat source have smaller pore sizes and higher porosity. The cover is sealed to the top of the target surface and each sidewall to form a closed flow channel, thus obtaining the target liquid cooling plate.

2. The method according to claim 1, characterized in that, Alkali washing treatment is performed on the surface of the cold-rolled aluminum alloy substrate, including: The surface of the cold-rolled aluminum alloy substrate is placed in a 10-15wt% NaOH solution and immersed at 50-60℃ for 10-15 minutes to obtain an alkaline-washed surface.

3. The method according to claim 2, characterized in that, Pickling treatment is performed on the surface of the cold-rolled aluminum alloy substrate, including: The alkaline-washed surface is placed in a 12-15wt% HNO3 solution and soaked for 5-10 minutes at room temperature to obtain an acid-washed surface.

4. The method according to claim 3, characterized in that, Activation treatment of the surface of the cold-rolled aluminum alloy substrate includes: The pickled surface is placed in a 2-5 wt% KH550 silane solution and immersed for 10-15 minutes at room temperature. Then, the cold-rolled aluminum alloy substrate is placed in an oven and baked at 100-120°C for 10-20 minutes to obtain the target surface.

5. The method according to claim 1, characterized in that, The process of spraying metal powders of various particle sizes onto the target surface to form sidewalls with various porous structures on the target surface includes: Using a CNC cold spraying equipment, under the first spraying parameters, metal powder of the first particle size is sprayed onto the target surface along a preset trajectory to form at least one porous first sidewall. Using a CNC cold spraying equipment, under the second spraying parameters, metal powder with a secondary particle size is sprayed onto the target surface to form at least one porous second sidewall. The primary particle size is 5-30 μm, the secondary powder particle size is 31-50 μm, the first sidewall is close to the heat source, and the second sidewall is far from the heat source.

6. The method according to claim 5, characterized in that, The first spraying parameters include: spraying gas pressure of 2.5-3.5MPa, spraying gas temperature of 350-450℃, spraying distance of 70-120mm, and scanning speed of 4-10mm / s.

7. The method according to claim 5, characterized in that, The second spraying parameters include: spraying gas pressure of 2.5-3.5MPa, spraying gas temperature of 350-450℃, spraying distance of 50-100mm, and scanning speed of 4-10mm / s.

8. The method according to claim 5, characterized in that, The average pore size of the first sidewall is 5-20 μm, and the porosity is 40-60%. The average pore size of the second sidewall is 21-30 μm, and the porosity is 20-39%.

9. The method according to claim 1, characterized in that, The height of the sidewall is 0.5-1.5mm.

10. A liquid-cooled plate, characterized in that, The plate was prepared using the method described in any one of claims 1-9 for preparing a cold-sprayed gradient porous microchannel liquid-cooled plate.

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