Aluminum alloy brazing connection method based on surface activation and presetting of Ni layer

Abstract

This invention proposes a brazing method for aluminum alloys based on surface activation and a pre-placed Ni layer. The method includes: Step 1, pre-treating the aluminum alloy surface to be brazed to ensure it is dust-free and oil-free; Step 2, subjecting the aluminum alloy surface to ion bombardment to remove the oxide film and activate the surface; Step 3, depositing a Ni thin film on the aluminum alloy surface to form a pre-placed Ni layer; Step 4, assembling the aluminum alloys to be brazed and placing them in a vacuum brazing furnace, with the Ni layers of the two aluminum alloys in contact. Pressure is applied to ensure the upper and lower aluminum alloys are tightly bonded and to prevent relative sliding. The furnace is then vacuum-heated to 540℃~585℃ and held for a preset time before cooling to room temperature to obtain an aluminum alloy / Ni / aluminum alloy brazed joint. The joint obtained by this surface-activated, pre-placed Ni layer-based aluminum alloy brazing method has the characteristics of no oxide film at the interface, high tensile strength, and low deformation rate.

Description

Technical Field

[0001] This invention relates to the field of brazing technology, and in particular to a brazing method for aluminum alloys based on surface activation and a pre-formed Ni layer. Background Technology

[0002] As is well known, with the rapid development of artificial intelligence computing clusters, new energy vehicle power systems, and aerospace electronic equipment, the heat flux density per unit area is increasing exponentially, making traditional air cooling and simple liquid cooling technologies insufficient to meet their high-efficiency heat dissipation requirements. Microchannel liquid-cooled radiators, due to their large specific surface area and high heat exchange efficiency, have become a core solution to the "thermal barrier" problem in these fields. Regarding radiator materials, while copper has excellent thermal conductivity, its high density, poor corrosion resistance, and susceptibility to galvanic corrosion from prolonged contact with coolant make it difficult to meet the requirements of lightweight design and long-life reliability. Aluminum alloys, due to their high specific strength, good thermal and electrical conductivity, and excellent corrosion resistance, have become an ideal material to replace copper in the manufacture of microchannel radiators. Therefore, achieving high-quality connections for aluminum alloy microchannel plates is crucial for upgrading the heat dissipation of these high-power devices.

[0003] In current aluminum alloy brazing processes, a dense oxide film easily forms on the aluminum surface. This oxide film not only severely hinders the wetting and spreading of the brazing filler metal on the aluminum alloy surface but also impedes atomic diffusion between the base metal and the brazing filler metal. Residual oxide film can also cause defects such as cracks and voids in the joint. Microchannel plates typically have a thin-walled, complex mesh structure with extremely high dimensional accuracy requirements. Under high-temperature thermal cycling, traditional brazing processes, due to the high thermal expansion coefficient and uneven thickness of aluminum alloys, are prone to generating significant residual stress and deformation, leading to microchannel blockage, which drastically reduces heat dissipation efficiency and can even render the product unusable. Summary of the Invention

[0004] To address the problems existing in the prior art, this application proposes a brazing connection method for aluminum alloys based on surface activation and pre-placed Ni layer, which can effectively remove the oxide film on the surface of aluminum alloys and prevent the surface of aluminum alloys from being re-oxidized, and can realize brazing of aluminum alloys at low temperature, resulting in a joint with a low deformation rate.

[0005] To achieve the above objectives, this application proposes a brazing connection method for aluminum alloys based on surface activation and a pre-formed Ni layer, comprising the following steps: Step 1: Pre-treat the aluminum alloy surface to be welded to ensure it is free of dust and oil. Step 2: Ion bombard the aluminum alloy surface to be welded to remove the oxide film and activate the surface. Step 3: Deposit a Ni thin film on the aluminum alloy surface to be welded to form a pre-placed Ni layer; Step 4: Assemble the aluminum alloys to be welded and place them in a vacuum brazing furnace, with the Ni layers of the two aluminum alloys to be welded in contact. Apply pressure to make the upper and lower aluminum alloys to be welded stick together and prevent relative sliding. Vacuum heat to 540℃~585℃ and hold for a preset time, then cool down to room temperature to obtain an aluminum alloy / Ni / aluminum alloy brazed joint.

[0006] In some embodiments, in step 1, the pretreatment includes: a grinding process, an ultrasonic cleaning process, and a drying process performed sequentially.

[0007] In some embodiments, during the grinding process, the aluminum alloy surface to be welded is ground to a surface roughness Ra≤2.0μm by mechanical grinding; the ultrasonic cleaning process includes ultrasonic cleaning of the aluminum alloy surface to be welded with acetone, anhydrous ethanol, and deionized water for 10min~15min each; the drying process can be carried out by vacuum drying oven.

[0008] In some embodiments, in step 2, the aluminum alloy to be welded is placed in a combined ion bombardment and magnetron sputtering system, and the background vacuum is evacuated to 1.0 × 10⁻⁶. -4 Pa ~ 1.0 × 10 -5 Pa, then inert gas is introduced to adjust the vacuum to 9Pa~1Pa and ionize the inert gas, and ion bombard the aluminum alloy surface to be welded under the action of the electric field.

[0009] In some embodiments, in step 2, the inert gas is helium or argon, the ion bombardment power is 50W~100W, and the bombardment time is 20min~60min.

[0010] In some embodiments, in step 3, the aluminum alloy to be welded is transferred to the magnetron sputtering cavity of the ion bombardment and magnetron sputtering combined system, and the background vacuum is evacuated to 1.0 × 10⁻⁶. -4 Pa ~ 1.0 × 10 -5 Pa, then an inert gas was introduced to adjust the vacuum to 5.0 × 10⁻⁶. -1 Pa ~ 1.0 × 10 -1 Pa generates glow discharge, and under the action of the electric field, Ni thin film is deposited on the surface of the aluminum alloy to be welded to form a pre-placed Ni layer. The Ni layer serves as a solder layer and undergoes a eutectic reaction with Al at the brazing temperature to achieve brazing.

[0011] In some embodiments, in step 3, the inert gas is argon, the magnetron sputtering power is 150W~200W, the bias voltage is 50V~100V, the sputtering time is 120min~250min, and the thickness of the formed Ni layer is 2μm~5μm.

[0012] In some embodiments, the applied pressure in step 4 ranges from 0.1 MPa to 0.2 MPa.

[0013] In some embodiments, in step 4, the process of vacuum heating to 540℃~585℃ and holding at that temperature for a preset time followed by cooling to room temperature specifically involves: [the process is described in the original text, but the provided excerpt ends here.] -3 Heating is performed under vacuum conditions below Pa, with the temperature increased to 540℃~585℃ at a rate of 10℃ / min and brazed and held at that temperature for 20min~90min. After brazing, the temperature is reduced to 200℃ at a rate of 10℃ / min, and finally cooled to room temperature with the furnace.

[0014] The beneficial effects of this solution are as follows: the above-mentioned aluminum alloy brazing connection method based on surface activation and pre-placed Ni layer has the following advantages: 1) Surface activation by ion bombardment can effectively remove the oxide film on the surface of aluminum alloy to be welded. At the same time, under the action of ion bombardment, the grain boundary density, surface energy and compressive stress of the surface of aluminum alloy to be welded can be increased, thereby achieving the surface activation effect and promoting atomic diffusion in the subsequent brazing process.

[0015] 2) In-situ sputtering of Ni film after ion bombardment using magnetron sputtering can protect the surface to be soldered from oxidation and reduce the brazing temperature by utilizing the Al-Ni eutectic reaction.

[0016] 3) It can achieve reliable connection of aluminum alloys at lower temperatures, which can largely preserve the strength of the aluminum alloy base material and reduce softening and deformation caused by high temperatures.

[0017] 4) The resulting joint has the characteristics of no oxide film at the interface, high tensile strength, and low deformation rate. Attached Figure Description

[0018] Figure 1 A flowchart is shown for a brazing connection method for aluminum alloys based on surface activation and a pre-applied Ni layer.

[0019] Figure 2 The cross-sectional microstructure of the aluminum alloy surface to be welded after ion bombardment and magnetron sputtering of Ni is shown, wherein the magnetron sputtering time is 120 min.

[0020] Figure 3 shows the microstructure of the aluminum alloy brazed joints obtained in Examples 1-4, where (a) is Example 1 with a brazing temperature of 560°C, (b) is Example 2 with a brazing temperature of 565°C, (c) is Example 3 with a brazing temperature of 575°C, and (d) is Example 4 with a brazing temperature of 585°C.

[0021] Figure 4 shows the tensile strength of the aluminum alloy brazed joints obtained in Examples 1-4.

[0022] Figure 5 shows the deformation rate of the aluminum alloy brazed joints obtained in Examples 1-4.

[0023] Figure 6 The cross-sectional microstructure of the aluminum alloy surface to be welded after ion bombardment and magnetron sputtering of Ni is shown, wherein the magnetron sputtering time is 250 min.

[0024] Figure 7 shows the microstructure of the aluminum alloy brazed joints obtained in Examples 5-7, where (a) is Example 5 with a brazing temperature of 560°C, (b) is Example 6 with a brazing temperature of 565°C, and (c) is Example 7 with a brazing temperature of 570°C.

[0025] Figure 8 shows the tensile strength of the aluminum alloy brazed joints obtained in Examples 5-7.

[0026] Figure 9 shows the deformation rate of the aluminum alloy brazed joints obtained in Examples 5-7. Detailed Implementation

[0027] The specific embodiments of this application will be further described below with reference to the accompanying drawings.

[0028] In the description of this application, it should be understood that the terms "upper", "lower", "front", "rear", "left", "right", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this application.

[0029] like Figure 1 As shown, the aluminum alloy brazing connection method based on surface activation and pre-formed Ni layer involved in this application includes the following steps: Step 1: Pre-treat the aluminum alloy surface to be welded to ensure it is free of dust and oil.

[0030] Specifically, in step 1, the pretreatment includes: sequential grinding, ultrasonic cleaning, and drying. During grinding, mechanical grinding is used to grind the aluminum alloy surface to be welded until the surface roughness Ra ≤ 2.0 μm. Ultrasonic cleaning involves sequentially ultrasonically cleaning the aluminum alloy surface to be welded with acetone, anhydrous ethanol, and deionized water for 10-15 minutes each. Drying is performed using a vacuum drying oven. After these pretreatments, the surface to be welded will be free of dust and oil.

[0031] Step 2: Ion bombard the aluminum alloy surface to be welded to remove the oxide film and activate the surface.

[0032] In step 2, the aluminum alloy to be welded is placed in a combined ion bombardment and magnetron sputtering system, and the base vacuum is evacuated to 1.0 × 10⁻⁶. -4 Pa ~ 1.0 × 10 -5 The vacuum level is adjusted to 9 Pa to 1 Pa by introducing an inert gas, which is then ionized. Under the influence of the electric field, the aluminum alloy surface to be welded is bombarded with ions. The inert gas is either helium (He) or argon (Ar), the ion bombardment power is 50 W to 100 W, and the bombardment time is 20 min to 60 min.

[0033] In this step, surface activation is achieved by ion bombardment, which can effectively remove the oxide film on the aluminum alloy surface to be welded. At the same time, under the action of ion bombardment, the grain boundary density, surface energy and compressive stress of the aluminum alloy surface to be welded can be increased, thereby achieving the surface activation effect and promoting atomic diffusion in the subsequent brazing process.

[0034] Step 3: Deposit a Ni thin film on the aluminum alloy surface to be welded to form a pre-placed Ni layer.

[0035] In step 3, the aluminum alloy to be welded is transferred to the magnetron sputtering cavity of the combined ion bombardment and magnetron sputtering system, and the background vacuum is evacuated to 1.0 × 10⁻⁶. -4 Pa ~ 1.0 × 10 -5 Pa, then an inert gas was introduced to adjust the vacuum to 5.0 × 10⁻⁶. -1 Pa ~ 1.0 × 10 -1 Pa generates glow discharge, and under the action of an electric field, a Ni thin film is deposited on the aluminum alloy surface to be soldered, forming a pre-placed Ni layer. This Ni layer serves as the solder layer and undergoes a eutectic reaction with Al at the soldering temperature to achieve brazing. The inert gas is argon (Ar), the magnetron sputtering power is 150W~200W, the bias voltage is 50V~100V, the sputtering time is 120min~250min, and the thickness of the formed Ni layer is 2μm~5μm. These settings ensure sufficient reaction between the base material and the solder, reducing porosity and incomplete soldering defects.

[0036] In this step, a Ni thin film is sputtered in situ after ion bombardment using magnetron sputtering. This protects the surface to be soldered from oxidation and reduces the soldering temperature by utilizing the Al-Ni eutectic reaction.

[0037] Step 4: Assemble the aluminum alloys to be welded and place them in a vacuum brazing furnace, with the Ni layers of the two aluminum alloys to be welded in contact. Apply pressure to make the upper and lower aluminum alloys to be welded stick together and prevent relative sliding. Vacuum heat to 540℃~585℃ and hold for a preset time, then cool down to room temperature to obtain an aluminum alloy / Ni / aluminum alloy brazed joint.

[0038] In step 4, the applied pressure ranges from 0.1 MPa to 0.2 MPa to ensure that the two aluminum alloy pieces to be welded are tightly adhered and to prevent relative slippage. The vacuum heating to 540℃~585℃ followed by a preset holding time and then cooling to room temperature specifically involves: 5×10... -3 Heating is performed under vacuum conditions below Pa, with the temperature increased at a rate of 10℃ / min to ensure furnace temperature uniformity. The temperature is raised to 540℃~585℃ and brazed for 20min~90min. After brazing, the temperature is reduced to 200℃ at a rate of 10℃ / min, and finally cooled to room temperature with the furnace.

[0039] The aluminum alloy brazing connection method based on surface activation and pre-formed Ni layer involved in this application has the following advantages: 1) Surface activation by ion bombardment can effectively remove the oxide film on the surface of aluminum alloy to be welded. At the same time, under the action of ion bombardment, the grain boundary density, surface energy and compressive stress of the surface of aluminum alloy to be welded can be increased, thereby achieving the surface activation effect and promoting atomic diffusion in the subsequent brazing process.

[0040] 2) In-situ sputtering of Ni film after ion bombardment using magnetron sputtering can protect the surface to be soldered from oxidation and reduce the brazing temperature by utilizing the Al-Ni eutectic reaction.

[0041] 3) It can achieve reliable connection of aluminum alloys at lower temperatures, which can largely preserve the strength of the aluminum alloy base material and reduce softening and deformation caused by high temperatures.

[0042] 4) The resulting joint has the characteristics of no oxide film at the interface, high tensile strength, and low deformation rate.

[0043] The aluminum alloy brazing connection method based on surface activation and pre-placed Ni layer involved in this application is suitable for connecting precision aluminum alloy components with strict requirements for strength and dimensional orientation.

[0044] Example 1 In this embodiment, the aluminum alloy brazing connection method based on surface activation and a pre-placed Ni layer includes: Step 1: Grind the 3A21 aluminum alloy sequentially on 800#, 1200#, and 2000# silicon carbide sandpaper, and then polish the surface to be welded using a metallographic polishing machine and diamond polishing compound to achieve a surface roughness Ra≤2.0μm. Subsequently, perform ultrasonic cleaning for 15 minutes each with acetone, anhydrous ethanol, and deionized water, and finally dry in a vacuum drying oven to ensure the aluminum alloy surface to be welded is free of dust and oil.

[0045] Step 2: Place the pretreated aluminum alloy into the combined ion bombardment and magnetron sputtering system, and wait for the vacuum level to reach 1.0 × 10⁻⁶. -4 Pa ~ 1.0 × 10-5 High-purity argon gas (Ar) was introduced at a flow rate of 100 sccm. The vacuum was then adjusted to 3 Pa and the argon gas was ionized. Under the acceleration of the electric field, high-energy Ar ions bombarded the aluminum alloy surface to be welded. The ion bombardment power was 80 W and the bombardment time was 40 min.

[0046] Step 3: Transfer the aluminum alloy to be welded to the magnetron sputtering chamber of the combined ion bombardment and magnetron sputtering system, and evacuate the base vacuum to 5.8 × 10⁻⁶. -5 At Pa, the gas valve was opened to introduce Ar gas at a flow rate of 13 sccm. The vacuum level was adjusted to 0.3 Pa, and glow discharge was generated. The bias voltage was 80 V, the magnetron sputtering power was 200 W, and the magnetron sputtering duration was 120 min to deposit a Ni thin film on the aluminum alloy surface to be welded. The resulting Ni layer thickness was 2 μm. Figure 2 As shown. After ion bombardment, in-situ Ni thin film deposition is performed on the aluminum alloy surface to be soldered by magnetron sputtering to prevent re-oxidation of the aluminum alloy surface and to serve as a brazing filler layer.

[0047] Step 4: Assemble the aluminum alloys to be welded and place them in a vacuum brazing furnace, ensuring the Ni layers of the two aluminum alloys to be welded are in contact. Apply a pressure of 0.1 MPa to ensure the upper and lower aluminum alloys are tightly pressed together and to prevent relative slippage. When the vacuum level inside the furnace reaches 5 × 10⁻⁶, continue brazing until the furnace reaches a pressure of 5 × 10⁻⁶. -3 The heating program was started at Pa for brazing. First, the temperature was increased to 560℃ at a rate of 10℃ / min and held at that temperature for 20 minutes. After brazing, the temperature was decreased to 200℃ at a rate of 10℃ / min, and finally cooled to room temperature with the furnace, resulting in an aluminum alloy / Ni / aluminum alloy brazed joint. The microstructure of the resulting joint is as follows: Figure 3 As shown in (a), Figure 4 As shown, the average tensile strength of the obtained joint is 68.25 MPa. Figure 5 As shown, the deformation rate of the obtained joint is 0.658%.

[0048] Example 2 The difference between this embodiment and Embodiment 1 is that the brazing temperature in step 4 is 565℃, while the other steps are the same as in Embodiment 1. The microstructure of the resulting joint is shown in the figure below. Figure 3 As shown in (b), the performance of the obtained joint, compared with Example 1, shows an increase in average tensile strength and an increase in deformation rate, as... Figures 4-5 As shown, in this embodiment, the average tensile strength of the obtained joint is 80.65 MPa, and the deformation rate of the obtained joint is 1.65%.

[0049] Example 3 The difference between this embodiment and Embodiment 2 is that the brazing temperature in step 4 is 575℃, while the other steps are the same as in Embodiment 2. The microstructure of the resulting joint is shown in the figure below. Figure 3 As shown in (c), the performance of the obtained joint, compared with Example 2, shows an increase in average tensile strength and a greater deformation rate, as... Figures 4-5 As shown, in this embodiment, the average tensile strength of the obtained joint is 83.10 MPa, and the deformation rate of the obtained joint is 2.64%.

[0050] Example 4 The difference between this embodiment and Embodiment 3 is that the brazing temperature in step 4 is 585℃, while the other steps are the same as in Embodiment 3. The microstructure of the resulting joint is shown in the figure below. Figure 3 As shown in (d), the performance of the obtained joint, compared with Example 3, shows an increase in average tensile strength and a greater deformation rate, as... Figures 4-5 As shown, in this embodiment, the average tensile strength of the obtained joint is 90.62 MPa, and the deformation rate of the obtained joint is 4.13%.

[0051] Through Examples 1-4, it can be concluded that, under the same conditions, as the brazing temperature increases, the average tensile strength of the joint continuously increases, but the deformation rate of the joint also gradually increases.

[0052] Example 5 The difference between this embodiment and Embodiment 1 is that the magnetron sputtering duration in step 3 is 250 min to deposit a Ni thin film on the aluminum alloy surface to be welded, forming a Ni layer with a thickness of 5 μm. Figure 6 As shown, the other steps are the same as in Example 1, and the microstructure of the resulting joint is shown in the figure. Figure 7 As shown in (a), Figure 8 As shown, the average tensile strength of the obtained joint is 66.67 MPa. Figure 9 As shown, the deformation rate of the obtained joint is 0.94%.

[0053] Example 6 The difference between this embodiment and Embodiment 5 is that the brazing temperature in step 4 is 565℃, while the other steps are the same as in Embodiment 5. The microstructure of the resulting joint is shown in the figure below. Figure 7 As shown in (b), the performance of the obtained joint, compared with Example 5, shows an increase in average tensile strength and an increase in deformation rate, as... Figures 8-9 As shown, in this embodiment, the average tensile strength of the obtained joint is 81.61 MPa, and the deformation rate of the obtained joint is 1.79%.

[0054] Example 7 The difference between this embodiment and Embodiment 6 is that the brazing temperature in step 4 is 570℃, while the other steps are the same as in Embodiment 6. The microstructure of the resulting joint is shown in the figure below. Figure 7 As shown in (c), the performance of the obtained joint, compared with Example 6, shows an increase in average tensile strength and a greater deformation rate, as... Figures 8-9 As shown, in this embodiment, the average tensile strength of the obtained joint is 91.35 MPa, and the deformation rate of the obtained joint is 2.21%.

[0055] Examples 5-7 also show that, under the same conditions, as the brazing temperature increases, the average tensile strength of the joint increases continuously, but the deformation rate of the joint also gradually increases.

[0056] The above description is merely a preferred embodiment of this application, but the scope of protection of this application is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in this application, based on the technical solution and concept of this application, should be included within the scope of protection of this application.

Claims

1. A brazing connection method for aluminum alloys based on surface activation and a pre-formed Ni layer, characterized in that: Includes the following steps: Step 1: Pre-treat the aluminum alloy surface to be welded to ensure it is free of dust and oil. Step 2: Ion bombard the aluminum alloy surface to be welded to remove the oxide film and activate the surface. Step 3: Deposit a Ni thin film on the aluminum alloy surface to be welded to form a pre-placed Ni layer; Step 4: Assemble the aluminum alloys to be welded and place them in a vacuum brazing furnace, with the Ni layers of the two aluminum alloys to be welded in contact. Apply pressure to make the upper and lower aluminum alloys to be welded stick together and prevent relative sliding. Vacuum heat to 540℃~585℃ and hold for a preset time, then cool down to room temperature to obtain an aluminum alloy / Ni / aluminum alloy brazed joint.

2. The aluminum alloy brazing connection method based on surface activation and pre-placed Ni layer according to claim 1, characterized in that: In step 1, the pretreatment includes: grinding, ultrasonic cleaning and drying processes performed sequentially.

3. The aluminum alloy brazing connection method based on surface activation and pre-placed Ni layer according to claim 2, characterized in that: During the grinding process, the aluminum alloy surface to be welded is ground to a surface roughness Ra≤2.0μm by mechanical grinding; the ultrasonic cleaning process includes ultrasonic cleaning of the aluminum alloy surface to be welded with acetone, anhydrous ethanol and deionized water for 10min~15min each; the drying process is carried out by vacuum drying oven.

4. The aluminum alloy brazing connection method based on surface activation and pre-placed Ni layer according to claim 1, characterized in that: In step 2, the aluminum alloy to be welded is placed in a combined ion bombardment and magnetron sputtering system, and the base vacuum is evacuated to 1.0 × 10⁻⁶. -4 Pa ~ 1.0 × 10 -5 Pa, then inert gas is introduced to adjust the vacuum to 9Pa~1Pa and ionize the inert gas, and ion bombard the aluminum alloy surface to be welded under the action of the electric field.

5. The aluminum alloy brazing connection method based on surface activation and pre-placed Ni layer according to claim 4, characterized in that: In step 2, the inert gas is helium or argon, the ion bombardment power is 50W~100W, and the bombardment time is 20min~60min.

6. The aluminum alloy brazing connection method based on surface activation and pre-placed Ni layer according to claim 1, characterized in that: In step 3, the aluminum alloy to be welded is transferred to the magnetron sputtering cavity of the combined ion bombardment and magnetron sputtering system, and the background vacuum is evacuated to 1.0 × 10⁻⁶. -4 Pa ~ 1.0 × 10 -5 Pa, then an inert gas was introduced to adjust the vacuum to 5.0 × 10⁻⁶. -1 Pa ~ 1.0 × 10 -1 Pa generates glow discharge, and under the action of the electric field, Ni thin film is deposited on the surface of the aluminum alloy to be welded to form a pre-placed Ni layer. The Ni layer serves as a solder layer and undergoes a eutectic reaction with Al at the brazing temperature to achieve brazing.

7. The aluminum alloy brazing connection method based on surface activation and pre-placed Ni layer according to claim 6, characterized in that: In step 3, the inert gas is argon, the magnetron sputtering power is 150W~200W, the bias voltage is 50V~100V, the sputtering time is 120min~250min, and the thickness of the formed Ni layer is 2μm~5μm.

8. The aluminum alloy brazing connection method based on surface activation and pre-placed Ni layer according to claim 1, characterized in that: In step 4, the applied pressure ranges from 0.1 MPa to 0.2 MPa.

9. The aluminum alloy brazing connection method based on surface activation and pre-placed Ni layer according to claim 1, characterized in that: In step 4, the process of vacuum heating to 540℃~585℃ and holding at that temperature for a preset time before cooling to room temperature specifically involves: [the process is described in the original text, which is incomplete and requires further context to translate accurately.] - 3 Heating is performed under vacuum conditions below Pa, with the temperature increased to 540℃~585℃ at a rate of 10℃ / min and brazed and held at that temperature for 20min~90min. After brazing, the temperature is reduced to 200℃ at a rate of 10℃ / min, and finally cooled to room temperature with the furnace.

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