Multilayer composite aluminum alloy for water-cooled plate and preparation method thereof

Abstract

This application discloses a method for preparing a multilayer composite aluminum alloy for water-cooled plates, comprising: casting a core layer, a first intermediate layer, a second intermediate layer, and a brazing layer respectively; sawing and milling the core layer, the first intermediate layer, the second intermediate layer, and the brazing layer respectively; hot rolling the first intermediate layer, the second intermediate layer, and the brazing layer respectively; performing composite hot rolling, cold rolling, and annealing in the order of brazing layer, first intermediate layer, core layer, and second intermediate layer; brazing the annealed composite material at a temperature of 600-615℃ for a holding time of 6-10 minutes; and artificially aging the material after cooling at an aging temperature of 180-220℃ for a holding time of 60-120 minutes. By optimizing the content and ratio of Mg and Si elements in the core material, the solidus temperature is maximized to ensure that overheating does not occur during brazing.

Description

Technical Field

[0001] This application relates to the field of aluminum alloy manufacturing technology, specifically to a multilayer composite aluminum alloy for water-cooled plates and its preparation method. Background Technology

[0002] To develop new energy vehicles, various countries have launched national development plans. For example, my country aims to have over one million electric vehicles by 2025, and to largely eliminate fossil fuels from urban transportation by 2035. The China Passenger Car Association (CPCA) predicts that in 2023, sales of new energy passenger vehicles in China will reach 8.5 million units, while sales of conventional passenger vehicles will reach 23.5 million units, with an annual penetration rate of 36%. In the first half of 2023, production and sales of new energy vehicles reached 3.786 million and 3.747 million units respectively, representing year-on-year increases of 42.4% and 44.1%.

[0003] One of the key technologies for battery-powered new energy vehicles is battery cooling, which mainly falls into three categories: air cooling, liquid cooling, and direct cooling. Air cooling is widely used in electric buses, liquid cooling is more common in passenger cars, while direct cooling has the highest requirements and represents the future development direction of electric vehicles. With the rapid development of electric vehicles, the demand for aluminum alloys used in power battery water-cooling plates will continue to increase, typically 10-20 kg per battery.

[0004] There are two main types of brazed water-cooled structures commonly used in batteries: water-cooled plate structures and direct-cooled plate structures. For the water-cooled plate materials of these two types of components, the primary considerations are material strength and the product's corrosion resistance. High-strength composite materials combined with water-cooled plate structural designs can achieve the goals of thinning and cost reduction; therefore, the continuous development of new materials is a crucial foundation for the development of water-cooled plates. The yield strength of traditional Al-Mn aluminum alloys after brazing is generally between 40-80 MPa, and there is no significant room for improvement through conventional alloy element optimization and process optimization, which cannot meet the future demands for high-strength materials. Summary of the Invention

[0005] To address the aforementioned deficiencies in this field, this application aims to provide a multilayer composite aluminum alloy for water-cooled plates and its preparation method.

[0006] According to one aspect of this application, a method for preparing a multilayer composite aluminum alloy for water-cooled plates is provided, comprising:

[0007] The core material layer, the first intermediate layer, the second intermediate layer, and the brazing layer are cast separately;

[0008] The core layer, the first intermediate layer, the second intermediate layer, and the brazing layer are sequentially sawed and milled.

[0009] The first intermediate layer, the second intermediate layer, and the brazing layer are hot-rolled respectively;

[0010] The composite hot rolling, cold rolling, and annealing are carried out in the order of brazing layer, first intermediate layer, core material layer, and second intermediate layer;

[0011] The annealed composite material is brazed: the brazing temperature is 600-615℃, the brazing holding time is 6-10 minutes, and there is no overheating during the brazing process.

[0012] After cooling, artificial aging process is carried out: aging temperature 180-220℃, aging process holding time 60-120min.

[0013] According to some embodiments of this application, the aging temperature is 200°C and the aging process holding time is 120 min.

[0014] According to some embodiments of this application, the initial rolling temperature of the composite hot rolling is 460-480℃, and the hot-rolled coil has a thickness of 6-8mm.

[0015] According to some embodiments of this application, the proportion of the intermediate layer ingot in the composite hot rolling is 8-20%, and the proportion of the brazing layer ingot is 5-10%.

[0016] According to some embodiments of this application, the cold rolling is the process of rolling the hot-rolled coil into a cold-rolled coil of 1.0-3.0 mm through 3-4 passes.

[0017] According to some embodiments of this application, the annealing temperature is 350-370°C, and the holding time is 2-4 hours.

[0018] According to another aspect of this application, a multilayer composite aluminum alloy for water-cooled plates is provided, wherein the composition and weight percentage of the core layer are as follows: Si: 0.38-0.65%, Fe: 0.40-0.65%, Cu: 0.10-0.25%, Mn: ≤0.05%, Mg: 0.60-1.0%, Zn: ≤0.05%, Ti: ≤0.05%, Cr: ≤0.01%, Zr: ≤0.03%, other elements with individual content <0.03%, total content <0.15%, and the balance being aluminum;

[0019] The composition and weight percentage of the first and second intermediate layers are as follows: Si: 0.05-0.25%, Fe: 0.10-0.20%, Cu: ≤0.05%, Mn: 0.40-1.0%, Mg: ≤0.05%, Zn: ≤0.05%, Ti: ≤0.03%, other elements with individual content <0.03% and total content <0.15%, with the balance being aluminum;

[0020] The brazing layer is made of 4045 or 4343 aluminum alloy.

[0021] According to some embodiments of this application, the composition and weight percentage of the core material layer are as follows: Si: 0.45-0.60%, Fe: 0.45-0.60%, Cu: 0.10-0.20%, Mn: ≤0.03%, Mg: 0.70-0.90%, Zn: ≤0.03%, Ti: ≤0.03%, Cr: ≤0.01%, Zr: ≤0.03%, other elements with individual content <0.02%, total content <0.10%, and the balance being aluminum;

[0022] The composition and weight percentage of the first and second intermediate layers are as follows: Si: 0.05-0.15%, Fe: 0.10-0.20%, Cu: ≤0.03%, Mn: 0.55-0.75%, Mg: ≤0.03%, Zn: ≤0.03%, Ti: ≤0.03%, other elements with individual content <0.02%, total content <0.10%, and the balance being aluminum.

[0023] According to some embodiments of this application, the potential of the first intermediate layer and the second intermediate layer is -750 to -770 mV, and the potential of the core layer is -720 to -735 mV.

[0024] According to some embodiments of this application, the average grain length of the intermediate layer is >150 μm.

[0025] According to some embodiments of this application, the tensile strength is >220MPa, the yield strength is >160MPa, and the elongation is >10%.

[0026] Compared with the prior art, this application has at least the following beneficial effects:

[0027] This application provides a multilayer composite aluminum alloy for water-cooled plates. By optimizing the content and ratio of Mg and Si elements in the core material, the solidus temperature is made as high as possible to ensure that overheating does not occur during the brazing process.

[0028] The potential of the intermediate layer in this application is increased to -750 to -770 mV by adding a certain amount of Mn. The potential of the core alloy is increased to -720 to -735 mV by adding Fe and Cu elements with positive potential. This makes the potential of the intermediate layer more than 30 mV lower than that of the core material, which can play a sacrificial anode protection role for the core material. If the content of the above alloy components in the intermediate layer or the core material is further increased, the potential difference will be reduced, which is not conducive to the sacrificial anode protection role of the intermediate layer. Attached Figure Description

[0029] Figure 1 This is a schematic diagram of the structure of the multilayer composite aluminum alloy used for the water-cooled plate in this application.

[0030] Figure 2 This is a schematic diagram of the sample structure for the experimental example of this application.

[0031] Figure 3 This diagram illustrates the overheating phenomenon that occurs during the brazing of aluminum alloy materials, serving as a comparative example of this application.

[0032] Figure 4 This diagram illustrates the overheating phenomenon that occurs during the brazing of aluminum alloy materials, serving as a comparative example of this application. Detailed Implementation

[0033] The technical solution of this application will be clearly and completely described below with reference to the embodiments of this application. Obviously, the described embodiments are only some embodiments of this application, 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.

[0034] It should be particularly noted that similar substitutions and modifications made to this application are obvious to those skilled in the art, and they are all considered to be included in this application. Those skilled in the art can obviously make modifications or appropriate alterations and combinations to the methods and applications described herein without departing from the content, spirit, and scope of this application to implement and apply the technology of this application. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments.

[0035] Unless otherwise specified, this application is conducted under standard conditions or conditions recommended by the manufacturer. The raw materials or excipients used, as well as the reagents or instruments used, whose manufacturers are not specified, are all conventional products that can be obtained commercially.

[0036] The following is a detailed description of this application.

[0037] The yield strength of existing Al-Mn alloys after brazing is generally between 40-80 MPa. Al-Mg-Si aluminum alloys can be strengthened by heat treatment; brazing at temperatures above 600℃ followed by artificial aging can improve their strength, making them stronger than Al-Mn alloys. However, the solidus temperature of Al-Mg-Si aluminum alloys is generally lower than that of Al-Mn alloys, making them prone to overheating during brazing at temperatures above 600℃, which negatively impacts their performance. Therefore, it is necessary to control the alloy composition.

[0038] Furthermore, Al-Mg-Si aluminum alloys have a high Mg content, which easily diffuses to the surface during brazing and reacts with the flux. The resulting compounds hinder the flow of the core material and affect the weld quality. Therefore, the proportion of the interlayer needs to be appropriate, and the larger the interlayer grains, the fewer grain boundaries there are, and the fewer channels for rapid diffusion of Mg atoms. In this application, the interlayer has a reasonable proportion and coarse grains, which can more effectively hinder the diffusion of Mg in the core material.

[0039] The Fe and Mn elements in the core alloy of this application absorb Si elements to form compounds such as AlFeSi or AlFeMnSi, thereby reducing the amount of Mg2Si formed in the alloy. To ensure the strength of the alloy, the alloy design must have excess Si elements to compensate for the loss caused by Fe, Mn, and other elements. However, if there is too much excess Si, Si is more likely to segregate at the grain boundaries, causing the alloy to become embrittled, reducing plasticity, and also reducing corrosion resistance. Therefore, the Mg / Si ratio of the core alloy in this application is 1.20-1.58.

[0040] Trace amounts of Cr have a significant impact on the recrystallization process, inhibiting it and refining the grains, thereby increasing the quenching sensitivity of the alloy. To minimize the quenching sensitivity of the alloy, the Cr content must be strictly controlled.

[0041] The water-cooled plate of this application uses a multi-layer composite aluminum alloy, wherein...

[0042] The core material composition and weight percentage are as follows: Si: 0.38-0.65%, Fe: 0.40-0.65%, Cu: 0.10-0.25%, Mn: ≤0.05%, Mg: 0.60-1.0%, Zn: ≤0.05%, Ti: ≤0.05%, Cr: ≤0.01%, Zr: ≤0.03%, other elements with individual content <0.03%, total content <0.15%, and the balance being aluminum;

[0043] The composition and weight percentage of the first and second intermediate layers are as follows: Si: 0.05-0.25%, Fe: 0.10-0.20%, Cu: ≤0.05%, Mn: 0.40-1.0%, Mg: ≤0.05%, Zn: ≤0.05%, Ti: ≤0.03%, other elements with individual content <0.03% and total content <0.15%, with the balance being aluminum;

[0044] The brazing layer is made of 4045 or 4343 aluminum alloy.

[0045] The processing method of the multilayer composite aluminum alloy for water-cooled plates in this application includes:

[0046] The core material, first intermediate layer, second intermediate layer and brazing layer alloy are batched according to element composition, melted, refined, settled, degassed and filtered, cast into ingots, and the head and tail are sawed and the surface is milled.

[0047] The first intermediate layer and the second intermediate layer brazing layer are hot rolled. The ingot after milling the first intermediate layer, the second intermediate layer and the brazing layer is heated and then hot rolled to a certain thickness.

[0048] After hot rolling, the layers are composite hot rolled: the four alloy layers, namely the first intermediate layer, the second intermediate layer and the brazing layer on one side of the core material, are combined in ingots in proportion and then hot rolled; the initial rolling temperature is 460-480℃, the hot rolled coil has a thickness of 6-8mm, the proportion of the first intermediate layer ingot is 8-20%, the proportion of the second intermediate layer ingot is 8-15%, and the proportion of the brazing layer ingot is 5-10%.

[0049] Hot-rolled coils are rolled into cold-rolled coils of 1.0-3.0 mm through 3-4 passes;

[0050] The cold-rolled coil is placed in an annealing furnace for annealing at a temperature of 350-370℃ and held for 2-4 hours before being removed from the furnace.

[0051] The annealed composite material is brazed at a temperature of 600-615℃ for 6-10 minutes. After brazing, the furnace door is opened to cool the material.

[0052] After brazing, artificial aging is performed at a temperature of 180-220℃ for 60-120 minutes, preferably at 200℃ for 120 minutes.

[0053] Example 1

[0054] The multilayer composite aluminum alloy used to prepare the water-cooled plate of this application.

[0055] The core material composition and weight percentage are as follows: Si: 0.38-0.65%, Fe: 0.40-0.65%, Cu: 0.10-0.25%, Mn: ≤0.05%, Mg: 0.60-1.0%, Zn: ≤0.05%, Ti: ≤0.05%, Cr: ≤0.01%, Zr: ≤0.03%, other elements with individual content <0.03%, total content <0.15%, and the balance being aluminum;

[0056] The composition and weight percentage of the first and second intermediate layers are as follows: Si: 0.05-0.25%, Fe: 0.10-0.20%, Cu: ≤0.05%, Mn: 0.40-1.0%, Mg: ≤0.05%, Zn: ≤0.05%, Ti: ≤0.03%, other elements with individual content <0.03% and total content <0.15%, with the balance being aluminum;

[0057] The brazing layer is made of 4045 or 4343 aluminum alloy.

[0058] (1) Alloy ingot: The core material, the first intermediate layer, the second intermediate layer, and the brazing layer alloy are respectively batched, smelted, refined, settled, degassed, and filtered according to the above-mentioned element composition, and then cast into ingots;

[0059] (2) Sawing and milling: The above-mentioned ingots are sawed at the head and tail and milled.

[0060] (3) Hot rolling: After milling the first intermediate layer, the second intermediate layer and the brazing layer, the ingot is heated and then hot rolled to 51mm, 93mm and 32mm respectively, with an initial rolling temperature of 490℃.

[0061] (4) Composite hot rolling: Composite hot rolling is carried out in the order of brazing layer, first intermediate layer, core material layer and second intermediate layer. The initial rolling temperature is 460℃. The ingot ratio of the first intermediate layer is 8%, the ingot ratio of the second intermediate layer is 15%, the ingot ratio of the brazing layer is 5%, and the hot rolled coil has a thickness of 8mm.

[0062] (5) Cold rolling: The hot-rolled coil is rolled into a cold-rolled coil of 3.0 mm through 3 passes;

[0063] (6) Finished product annealing: The cold-rolled coil is placed in an annealing furnace for annealing at a temperature of 350℃ and held for 2 hours before being taken out of the furnace.

[0064] (7) Brazing process: Brazing is performed at 600℃ after the furnace is removed from the furnace, and the temperature is maintained for 10 minutes before cooling.

[0065] (8) Artificial aging: After brazing, artificial aging process is carried out at 200℃ for 120 minutes.

[0066] Example 2

[0067] The multilayer composite aluminum alloy used to prepare the water-cooled plate of this application.

[0068] The core material composition and weight percentage are as follows: Si: 0.38-0.65%, Fe: 0.40-0.65%, Cu: 0.10-0.25%, Mn: ≤0.05%, Mg: 0.60-1.0%, Zn: ≤0.05%, Ti: ≤0.05%, Cr: ≤0.01%, Zr: ≤0.03%, other elements with individual content <0.03%, total content <0.15%, and the balance being aluminum;

[0069] The composition and weight percentage of the first and second intermediate layers are as follows: Si: 0.05-0.25%, Fe: 0.10-0.20%, Cu: ≤0.05%, Mn: 0.40-1.0%, Mg: ≤0.05%, Zn: ≤0.05%, Ti: ≤0.03%, other elements with individual content <0.03% and total content <0.15%, with the balance being aluminum;

[0070] The brazing layer is made of 4045 or 4343 aluminum alloy.

[0071] (1) Alloy ingot: The core material, the first intermediate layer, the second intermediate layer, and the brazing layer alloy are respectively batched, smelted, refined, settled, degassed, and filtered according to the above-mentioned element composition, and then cast into ingots;

[0072] (2) Sawing and milling: The above-mentioned ingots are sawed at the head and tail and milled.

[0073] (3) Hot rolling: After the ingots with milled surfaces of the first intermediate layer, the second intermediate layer and the brazing layer are heated, they are hot rolled to 104mm, 70mm and 72mm respectively, with an initial rolling temperature of 495℃.

[0074] (4) Composite hot rolling: Composite hot rolling is carried out in the order of brazing layer, intermediate layer, core material layer, and intermediate layer. The initial rolling temperature is 480℃. The ingot ratio of the first intermediate layer is 15%, the ingot ratio of the second intermediate layer is 10%, the ingot ratio of the brazing layer is 10%, and the hot-rolled coil has a thickness of 6mm.

[0075] (5) Cold rolling: The hot-rolled coil is rolled into a cold-rolled coil of 2.0 mm through 3 passes;

[0076] (6) Finished product annealing: The cold-rolled coil is placed in an annealing furnace for annealing at a temperature of 360°C and held for 4 hours before being taken out of the furnace.

[0077] (7) Brazing process: Brazing is performed at 615℃ after the furnace is removed from the furnace, and the temperature is maintained for 8 minutes before cooling.

[0078] (8) Artificial aging: After brazing, artificial aging process is carried out at 220℃ for 60 minutes.

[0079] Example 3

[0080] The multilayer composite aluminum alloy used to prepare the water-cooled plate of this application.

[0081] The core material composition and weight percentage are as follows: Si: 0.38-0.65%, Fe: 0.40-0.65%, Cu: 0.10-0.25%, Mn: ≤0.05%, Mg: 0.60-1.0%, Zn: ≤0.05%, Ti: ≤0.05%, Cr: ≤0.01%, Zr: ≤0.03%, other elements with individual content <0.03%, total content <0.15%, and the balance being aluminum;

[0082] The composition and weight percentage of the first and second intermediate layers are as follows: Si: 0.05-0.25%, Fe: 0.10-0.20%, Cu: ≤0.05%, Mn: 0.40-1.0%, Mg: ≤0.05%, Zn: ≤0.05%, Ti: ≤0.03%, other elements with individual content <0.03% and total content <0.15%, with the balance being aluminum;

[0083] The brazing layer is made of 4045 or 4343 aluminum alloy.

[0084] (1) Alloy ingot: The core material, the first intermediate layer, the second intermediate layer, and the brazing layer alloy are respectively batched, smelted, refined, settled, degassed, and filtered according to the above-mentioned element composition, and then cast into ingots;

[0085] (2) Sawing and milling: The above-mentioned ingots are sawed at the head and tail and milled.

[0086] (3) Hot rolling: After the ingots with milled surfaces of the first intermediate layer, the second intermediate layer and the brazing layer are heated, they are hot rolled to 138mm, 58mm and 56mm respectively, with an initial rolling temperature of 500℃.

[0087] (4) Composite hot rolling: Composite hot rolling is carried out in the order of brazing layer, intermediate layer, core material layer, and intermediate layer. The initial rolling temperature is 470℃. The ingot ratio of the first intermediate layer is 20%, the ingot ratio of the second intermediate layer is 8%, the ingot ratio of the brazing layer is 8%, and the hot-rolled coil has a thickness of 7mm.

[0088] (5) Cold rolling: The hot-rolled coil is rolled into a cold-rolled coil of 1.0 mm through 4 passes;

[0089] (6) Finished product annealing: The cold-rolled coil is placed in an annealing furnace for annealing at a temperature of 370℃ and held for 3 hours before being taken out of the furnace.

[0090] (7) Brazing process: Brazing is performed at 610℃ after the furnace is removed from the furnace, and the temperature is maintained for 6 minutes before cooling.

[0091] (8) Artificial aging: After brazing, artificial aging process is carried out at 180℃ for 100 minutes.

[0092] Comparative Example 1

[0093] The ingredients and weight percentages for each layer are as follows:

[0094] Core material layer: Si: 0.80-0.90%, Fe: 0.30-0.40%, Cu: 0.30-0.40%, Mn: 0.10-0.30%, Mg: 0.80-1.0%, Zn: ≤0.05%, Ti: ≤0.05%, other elements, individual content <0.03%, total content <0.15%, balance is aluminum;

[0095] The first intermediate layer, the second intermediate layer, and the brazing layer are the same as in Example 1.

[0096] The preparation method is the same as in Example 1, but overheating occurs during brazing (e.g. Figure 3 It cannot be used anymore.

[0097] Comparative Example 2

[0098] The ingredients and weight percentages for each layer are as follows:

[0099] Core material layer: Si: 0.2-0.3%, Fe: 0.30-0.40%, Cu: 0.20-0.30%, Mn: 0.10-0.30%, Mg: 1.0-1.2%, Zn: ≤0.05%, Ti: ≤0.05%, Cr: ≤0.05%, Zr: ≤0.03%, other elements individually <0.03%, total <0.15%, balance is aluminum;

[0100] The first intermediate layer, the second intermediate layer, and the brazing layer are the same as in Example 1.

[0101] The preparation method is the same as in Example 1, but overheating occurs during brazing (e.g. Figure 4 It cannot be used anymore.

[0102] Comparative Example 3

[0103] The preparation process is the same as in Example 1, except that the aging process is carried out at 150°C for 120 min.

[0104] Comparative Example 4

[0105] The preparation process is the same as in Example 2, except that the aging process is carried out at 230°C for 100 min.

[0106] Comparative Example 5

[0107] The preparation process is the same as in Example 1, except that no aging process is performed.

[0108] Experimental Example

[0109] The properties of the aluminum alloys in Examples 1-3 and Comparative Examples 1-7 were tested respectively, including tensile strength, yield strength, elongation, and cupping value.

[0110] The testing method is as follows:

[0111] according to Figure 2 Prepare samples and conduct tensile tests on mechanical properties according to GB / T228.1-2010.

[0112] Figure 2 In the diagram: Lt is the total length of the specimen; Lc is the parallel length; Lo is the original gauge length; bo is the original width of the parallel length of the rectangular cross section; bt is the width of the clamping head of the fixture; and r is the radius of the arc.

[0113] The test results are as follows:

[0114]

[0115]

[0116] According to the table above, in Examples 1-3, after brazing and artificial aging, the tensile strength is greater than 220 MPa, the yield strength is greater than 160 MPa, and the elongation is greater than 10%. In Comparative Example 5, no artificial aging was performed after brazing, and the yield strength was slightly improved. In Comparative Examples 3 and 4, the aging processes of holding at 150℃ for 120 min and 230℃ for 100 min, respectively, also showed obvious aging strengthening effects, but failed to meet the preferred requirements of tensile strength greater than 220 MPa and yield strength greater than 160 MPa. In Comparative Examples 1 and 2, due to the low solidus temperature, overheating occurred after brazing, which will affect the mechanical properties and corrosion resistance of the materials, and they cannot be used.

[0117] The above description of the embodiments is only for the purpose of helping to understand the method and core ideas of this application. It should be noted that, for those skilled in the art, several improvements and modifications can be made to this application without departing from the principles of this application, and these improvements and modifications also fall within the protection scope of the claims of this application.

Claims

1. A method for preparing a multilayer composite aluminum alloy for water-cooled plates, characterized in that, include: The brazing layer, the first intermediate layer, the core material layer, and the second intermediate layer are cast separately. The core layer, the first intermediate layer, the second intermediate layer, and the brazing layer are respectively sawed and milled. After milling, the first intermediate layer, the second intermediate layer, and the brazing layer are hot rolled respectively; The milled core layer, the hot-rolled first intermediate layer, the second intermediate layer, and the brazing layer are arranged in the order of brazing layer, first intermediate layer, core layer, and second intermediate layer, and then composite hot rolling, cold rolling, and annealing are performed to obtain a composite material. The composite material is brazed at a temperature of 600-615℃ for 6-10 minutes. After brazing and cooling, artificial aging is performed at a temperature of 180-220℃ for 60-120 minutes. The initial rolling temperature of the composite hot rolling is 460-480℃, and the hot-rolled coil after composite hot rolling has a thickness of 6-8mm; the thickness ratio of the first intermediate layer in the composite material is 8-20%, the thickness ratio of the second intermediate layer is 8-15%, and the thickness ratio of the brazing layer is 5-10%. The core material layer consists of the following components and weight percentages: Si: 0.38-0.65%, Fe: 0.40-0.65%, Cu: 0.10-0.25%, Mn: ≤0.05%, Mg: 0.60-1.0%, Zn: ≤0.05%, Ti: ≤0.05%, Cr: ≤0.01%, Zr: ≤0.03%, with individual content of other elements <0.03% and total content <0.15%, and the balance being aluminum. The composition and weight percentage of the first and second intermediate layers are as follows: Si: 0.05-0.25%, Fe: 0.10-0.20%, Cu: ≤0.05%, Mn: 0.40-1.0%, Mg: ≤0.05%, Zn: ≤0.05%, Ti: ≤0.03%, other elements with individual content <0.03% and total content <0.15%, with the balance being aluminum; The brazing layer is made of 4045 or 4343 aluminum alloy.

2. The preparation method according to claim 1, characterized in that, The artificial aging temperature is 200℃, and the artificial aging holding time is 120min.

3. The preparation method according to claim 1, characterized in that, The cold rolling process involves rolling the hot-rolled coil into a cold-rolled coil of 1.0-3.0 mm through 3-4 passes.

4. The preparation method according to claim 1, characterized in that, The annealing temperature is 350-370℃, and the holding time is 2-4 hours.

5. A multilayer composite aluminum alloy for water-cooled plates prepared by the preparation method according to any one of claims 1-4, characterized in that, The core material layer composition and weight percentage are as follows: Si: 0.38-0.65%, Fe: 0.40-0.65%, Cu: 0.10-0.25%, Mn: ≤0.05%, Mg: 0.60-1.0%, Zn: ≤0.05%, Ti: ≤0.05%, Cr: ≤0.01%, Zr: ≤0.03%, other elements with individual content <0.03%, total content <0.15%, and the balance being aluminum; The composition and weight percentage of the first and second intermediate layers are as follows: Si: 0.05-0.25%, Fe: 0.10-0.20%, Cu: ≤0.05%, Mn: 0.40-1.0%, Mg: ≤0.05%, Zn: ≤0.05%, Ti: ≤0.03%, other elements with individual content <0.03% and total content <0.15%, with the balance being aluminum; The brazing layer is made of 4045 or 4343 aluminum alloy.

6. The multilayer composite aluminum alloy for water-cooled plates according to claim 5, characterized in that, The composition and weight percentage of the core material layer are as follows: Si: 0.45-0.60%, Fe: 0.45-0.60%, Cu: 0.10-0.20%, Mn: ≤0.03%, Mg: 0.70-0.90%, Zn: ≤0.03%, Ti: ≤0.03%, Cr: ≤0.01%, Zr: ≤0.03%, other elements with individual content <0.02%, total content <0.10%, and the balance being aluminum; The composition and weight percentage of the first and second intermediate layers are as follows: Si: 0.05-0.15%, Fe: 0.10-0.20%, Cu: ≤0.03%, Mn: 0.55-0.75%, Mg: ≤0.03%, Zn: ≤0.03%, Ti: ≤0.03%, other elements with individual content <0.02% and total content <0.10%, with the balance being aluminum.

7. The multilayer composite aluminum alloy for water-cooled plates according to claim 6, characterized in that, The potential of the first intermediate layer and the second intermediate layer is -750 to -770 mV, and the potential of the core layer is -720 to -735 mV.

8. The multilayer composite aluminum alloy for water-cooled plates according to claim 7, characterized in that, The average grain length of the first intermediate layer and the second intermediate layer is >150μm.

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