Pre-embedded brazing flux aluminum alloy composite material and preparation method thereof

Abstract

The present application relates to the technical fields of aluminum alloy brazing, and particularly relates to a pre-embedded brazing flux aluminum alloy composite material and a preparation method thereof; comprising: adding first metal powder into a package to form a first powder layer, and placing a first aluminum foil on the first powder layer; adding second metal powder and brazing flux powder into the package to form a second powder layer on the surface of the first aluminum foil away from the first powder layer, and placing a second aluminum foil on the second powder layer; adding third metal powder into the package to form a third powder layer on the surface of the second aluminum foil away from the second powder layer, and obtaining a composite layer in the package; the third metal powder comprises aluminum-silicon alloy; cold isostatic pressing the composite layer to form a green compact in the package; sintering the green compact to obtain a sintered compact; stacking at least one side of an alloy ingot in the thickness direction with the side of the sintered compact close to the first powder layer, heating to form a composite compact, and performing hot rolling, cold rolling and annealing to obtain the pre-embedded brazing flux aluminum alloy composite material.

Description

Technical Field

[0001] This invention relates to the field of aluminum alloy brazing technology, and in particular to an aluminum alloy composite material with pre-embedded brazing flux and its preparation method. Background Technology

[0002] In recent years, during the preparation of aluminum alloy composite materials, such as automotive heat exchangers and other components requiring brazing connections, there has been a demand for simplified brazing processes and improved connection reliability. To eliminate the cumbersome step of additionally spraying or coating flux on the component surface during brazing, a "pre-embedded flux" solution has been proposed. This involves pre-compacting the flux into the aluminum alloy sheet, enabling the material itself to autonomously break down the oxide film and fill the weld seam during brazing heating. Specifically, a mixed metal powder containing flux is pre-formed into a brazing-functional block blank using powder metallurgy methods, such as hot isostatic pressing. This powder metallurgy blank is then laminated with a cast aluminum alloy core material, which serves as the structural main body, and the composite is achieved through a hot rolling process. However, this method has the following drawbacks: Because the powder metallurgy billet layer contains non-metallic flux phases, its intrinsic ductility and machinability differ significantly from the dense, homogeneous cast core layer. During hot rolling composite processes with large deformations, the interfaces of these two materials with vastly different properties struggle to achieve coordinated plastic flow, generally resulting in poor interfacial bonding. This interfacial fragility leads to technical problems such as composite layer cracking, peeling, and even overall sheet shape failure during subsequent rolling thinning, especially in the manufacture of thin-gauge products.

[0003] Therefore, how to effectively overcome the problem of the difficulty in forming a high-strength metallurgical bond at the interface when hot-rolling the powder metallurgy functional layer and the cast core material layer has become an important research topic. Summary of the Invention

[0004] In view of this, the present invention aims to at least partially solve one of the technical problems in the related art. To this end, the present invention provides a pre-embedded flux aluminum alloy composite material and a method for preparing the same.

[0005] To solve the above-mentioned technical problems, the present invention is implemented as follows: According to one aspect of the present invention, a method for preparing a pre-embedded flux aluminum alloy composite material is provided, comprising the following steps: A first metal powder is added to a sleeve with an opening on at least one side to form a first powder layer, and a first aluminum foil is placed on the first powder layer; wherein, the first metal powder includes an aluminum alloy; A second metal powder and flux powder are added to the sheath, and a second powder layer is formed on the surface of the first aluminum foil away from the first powder layer. A second aluminum foil is placed on the second powder layer. The second metal powder comprises an aluminum-silicon alloy. A third metal powder is added to the casing, and a third powder layer is formed on the surface of the second aluminum foil away from the second powder layer, thus obtaining a composite layer in the casing; the third metal powder comprises an aluminum-silicon alloy. The composite layer is subjected to cold isostatic pressing to form a green blank in the cladding; the green blank is then sintered to obtain a sintered blank. At least one side of the alloy ingot in the thickness direction is stacked with the side of the sintered billet closest to the first powder layer, and heated to form a composite billet. The composite billet is then hot-rolled, cold-rolled, and annealed to obtain a pre-embedded flux aluminum alloy composite material.

[0006] In some embodiments, the aluminum alloy comprises 3003 aluminum alloy powder.

[0007] In some embodiments, the aluminum-silicon alloy comprises Al-Si alloy powder.

[0008] In some embodiments, the flux powder comprises a KAlF4-K2AlF5 mixed powder, wherein the weight ratio of KAlF4 to K2AlF5 is (70-80):(20-30).

[0009] In some embodiments, the weight ratio of the second metal powder to the flux powder is (82~91):(9~18).

[0010] In some of these embodiments, the median particle size D of the Al-Si alloy powder 50 The range is 20μm to 60μm.

[0011] In some embodiments, the oxygen content of the Al-Si alloy powder is less than or equal to 300 ppm.

[0012] In some of these embodiments, the median particle size D of the flux powder 50 The range is 10μm to 50μm.

[0013] In some of these embodiments, the median particle size D of the 3003 aluminum alloy powder 50 The range is 30μm to 70μm.

[0014] In some embodiments, the oxygen content of the 3003 aluminum alloy powder is less than or equal to 300 ppm.

[0015] In some of these embodiments, the thickness of the first powder layer accounts for 10% to 20% of the thickness of the composite layer.

[0016] In some embodiments, the thickness of the second powder layer accounts for 30% to 45% of the thickness of the composite layer.

[0017] In some embodiments, the thickness of the third powder layer accounts for 40% to 55% of the thickness of the composite layer.

[0018] In some embodiments, the thickness of the first aluminum foil is 0.004 mm to 0.006 mm.

[0019] In some embodiments, the thickness of the second aluminum foil is 0.004 mm to 0.006 mm.

[0020] In some embodiments, the second metal powder and the flux powder are mixed using a V-type mixer; wherein the mixing speed is 4 r / min to 6 r / min and the mixing time is 2 h to 5 h.

[0021] In some of these embodiments, the temperature during the cold isostatic pressing process is 20°C to 30°C; the pressure is 150MPa to 300MPa; and the time is 5 min to 15 min.

[0022] In some of these embodiments, the sintering includes: The green blank is placed in a vacuum sintering furnace, and the vacuum level in the furnace is lower than 1×10⁻⁶. -2 Pa, heat to the sintering temperature and sinter to obtain the sintered blank; Furthermore, the sintering process also satisfies at least one of features (1) to (3): (1) The heating rate is 5℃ / min to 10℃ / min; (2) The sintering temperature is 480℃ to 540℃; (3) The sintering time is 2h to 5h.

[0023] In some of these embodiments, the alloy ingot comprises 3003 aluminum alloy.

[0024] In some embodiments, the thickness of the alloy ingot is 30 mm to 80 mm.

[0025] In some of these embodiments, the heating temperature is 450°C to 500°C, and the heating time is 4 hours to 6 hours.

[0026] In some embodiments, the hot rolling includes performing multiple hot rolling operations on the composite billet on a hot rolling mill, with the final hot rolling temperature being greater than 300°C.

[0027] In some of these embodiments, the single-pass reduction of the cold rolling is 20% to 30%.

[0028] In some embodiments, the thickness of the blank obtained after cold rolling is 0.3 mm to 2.0 mm.

[0029] In some of these embodiments, the annealing temperature is 380°C to 400°C, and the time is 2 hours to 4 hours.

[0030] According to another aspect of the present invention, the present invention provides a pre-embedded flux aluminum alloy composite material, comprising: a pre-embedded flux aluminum alloy composite material prepared by the preparation method described in any of the above embodiments.

[0031] In some embodiments, the aluminum alloy composite material includes an alloy layer and a brazing functional layer on at least one side of the alloy layer in the thickness direction; the brazing functional layer includes a composite layer close to the alloy layer and an aluminum-silicon alloy layer away from the alloy layer, the alloy layer includes 3003 aluminum alloy, the composite layer includes an aluminum-silicon alloy and flux, and the aluminum-silicon alloy layer includes an aluminum-silicon alloy. Furthermore, the aluminum alloy composite material satisfies the following conditions: based on the total thickness of the aluminum alloy composite material, the thickness ratio of the alloy layer is 70%~88%; and / or, based on the total thickness of the aluminum alloy composite material, the thickness ratio of the brazing functional layer is 6%~15%.

[0032] Implementing the technical solution of the present invention has at least the following beneficial effects: In this invention, by sequentially constructing a first powder layer containing aluminum alloy, a second powder layer containing aluminum-silicon alloy and flux, and a third powder layer containing aluminum-silicon alloy within a casing, and placing aluminum foil between each powder layer to isolate different powders, powder cross-displacement and interlayer interference are effectively prevented, ensuring clear functional layering. Subsequent cold isostatic pressing allows for sufficient rearrangement of powder particles and the formation of a green compact with a certain strength. The sintering process then achieves diffusion metallurgical bonding between the powder particles, resulting in a dense sintered compact. The alloy ingot and the side of the sintered compact closest to the first powder layer are stacked, heated, and hot-rolled together. This allows each layer to undergo sufficient plastic deformation and extrusion of fresh metal at the interface under high temperature and pressure. The aluminum foil breaks during processing and is absorbed by the matrix, thereby achieving reliable metallurgical bonding between the sintered compact and the ingot, as well as between each powder layer. Furthermore, this invention overcomes the problems of insufficient bonding strength and processing cracking caused by interface barriers, significantly improving the interfacial bonding reliability, production yield, and overall performance of the composite material.

[0033] Additional aspects and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Attached Figure Description

[0034] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with the invention and, together with the description, serve to explain the principles of the invention.

[0035] Figure 1 The diagram shows the process flow chart of the preparation method of the pre-embedded flux aluminum alloy composite material provided by the present invention.

[0036] Figure 2 The image shown is a metallographic diagram of the pre-embedded flux aluminum alloy composite material provided by the present invention.

[0037] Figure 3 The diagram shown is a schematic diagram of the encapsulation and composite layer structure provided in an embodiment of the present invention.

[0038] Figure 4 The diagram shown is a process flow chart for preparing pre-embedded flux aluminum alloy composite materials according to an embodiment of the present invention.

[0039] Explanation of reference numerals in the attached figures: 1—Third powder layer; 2—Aluminum foil; 3—Second powder layer; 4—First powder layer; 5—Sheath.

[0040] The accompanying drawings have illustrated specific embodiments of the invention, which will be described in more detail below. These drawings and descriptions are not intended to limit the scope of the invention in any way, but rather to illustrate the concept of the invention to those skilled in the art through reference to particular embodiments. Detailed Implementation

[0041] The present invention will be further illustrated below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention.

[0042] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges or individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0043] Unless otherwise specified, all embodiments and optional embodiments of the present invention can be combined with each other to form new technical solutions.

[0044] Unless otherwise specified, all technical features and optional technical features of this invention can be combined to form new technical solutions.

[0045] Unless otherwise specified, all steps of the present invention may be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), indicating that the method may include steps (a) and (b) performed sequentially, or it may include steps (b) and (a) performed sequentially. For example, the mention that the method may also include step (c) indicates that step (c) may be added to the method in any order. For example, the method may include steps (a), (b), and (c), or it may include steps (a), (c), and (b), or it may include steps (c), (a), and (b), etc.

[0046] Unless otherwise specified, the terms "comprising" and "including" as used in this invention can be open-ended or closed-ended. For example, "comprising" and "including" can mean that other components not listed may also be included, or that only the listed components may be included.

[0047] Currently, in the preparation of aluminum alloy composites with embedded flux, the relevant technology employs a method of hot rolling composite material where a powder metallurgy billet containing flux is directly hot-rolled with a cast aluminum alloy core ingot. The drawback of this method is that, because the flux, as a non-metallic phase, is dispersed between the metal powder particles, it hinders atomic diffusion and metallurgical bonding between the metal matrix under the high temperature and pressure conditions of hot rolling composite. This results in insufficient bonding strength at the composite interface and easily leads to cracking or even peeling of the composite layer during rolling with large deformations. This is particularly pronounced when the flux content is high or the target product thickness is thin, limiting its applicability and resulting in a low yield.

[0048] During the research process of this invention, the researchers found that the main mechanisms leading to interfacial bonding failure are as follows: First, from the perspective of material compatibility at the composite interface, the high-temperature plastic rheological behavior of the flux-containing powder metallurgy layer differs significantly from that of a fully dense cast aluminum alloy due to the presence of a large number of non-metallic phases within it. The two cannot achieve coordinated flow during rolling deformation, resulting in continuous shear stress accumulation at the interface. When this stress exceeds the interfacial bonding strength, cracks initiate. Second, from the perspective of the physical process of interfacial bonding, flux particles directly occupy the effective contact area of ​​the surface to be composited, physically blocking direct contact between the core material ingot and the metal particles in the powder metallurgy layer. This significantly reduces the clean interface required for atomic diffusion, making it impossible to form a continuous metallurgical bond. Third, from the perspective of billet preparation methods, related technologies often use a single-component flux-containing powder layer directly composited with the core material, lacking design for the composition and structure of the transition region, which exacerbates the adverse effects of the above two factors. Existing technologies attempt to alleviate the aforementioned problems by altering the forming method of flux-containing blanks or designing specific filling structures. For example, hot isostatic pressing is used to increase the blank density, or a metal sheath of a specific shape is used to contain the flux powder. However, this does not eliminate the inherent deformation incompatibility and interfacial barrier between the flux layer and the core layer. Therefore, further research is still needed to achieve high interfacial bonding strength, high flux content, and compatibility with thin-gauge products.

[0049] In view of the technical problems existing in the prior art, the present invention provides a pre-embedded flux aluminum alloy composite material and its preparation method. By reconstructing the internal layers of the powder preform used to form the final brazing functional layer, a transition metal powder layer made of the same material as the ingot is introduced between the flux-containing powder layer and the alloy ingot to be composited. A breakable insulating aluminum foil is placed between each functional powder layer. Subsequently, a dense sintered blank with a layered transition structure is formed by cold isostatic pressing and vacuum sintering. During hot rolling composite processing, the sintered blank is stacked with the homogeneous alloy ingot on the side containing the transition metal powder layer. Since the transition layer and the composite blank ingot are made of the same material, they undergo synergistic plastic deformation as the same material during hot rolling, achieving atomic-level metallurgical bonding at the interface. Simultaneously, the flux-containing functional layer is completely preserved on the outside of the transition layer, and the flux inside does not intervene in the bonding interface between the transition layer and the composite blank. By designing the layered structure of the powder preform, the advantages of metallurgical bonding of homogeneous materials are combined with the functional requirements of flux pre-embedding, thereby avoiding the problems of interface weakening and processing cracking caused by flux obstruction.

[0050] refer to Figure 1 In some embodiments of the present invention, a method for preparing a pre-embedded flux aluminum alloy composite material is provided, comprising the following steps: S101. First metal powder is added to a sleeve with an opening on at least one side to form a first powder layer, and a first aluminum foil is placed on the first powder layer; wherein the first metal powder includes an aluminum alloy.

[0051] As an example, the material of the sleeve 5 can be made of polymers such as neoprene rubber and polytetrafluoroethylene, and one end of the sleeve has an opening, such as... Figure 3 As shown; the first metal powder is added into the casing, and can be filled, compacted and leveled by means of vibration or other methods. The first aluminum foil is placed on the formed first powder layer. The material of the first aluminum foil can be pure aluminum foil.

[0052] S102. The second metal powder and flux powder are added to the sheath, and a second powder layer is formed on the surface of the first aluminum foil away from the first powder layer. The second aluminum foil is placed on the second powder layer. The second metal powder includes an aluminum-silicon alloy.

[0053] As an example, the second metal powder and flux powder are mixed evenly and added to the sheath, i.e., the surface of the first aluminum foil, to form a second powder layer, and the second aluminum foil is placed on the second powder layer. It can be understood that the material of the second aluminum foil can also be pure aluminum foil.

[0054] S103. A third metal powder is added to the casing, and a third powder layer is formed on the surface of the second aluminum foil away from the second powder layer, thus obtaining a composite layer in the casing; the third metal powder includes an aluminum-silicon alloy.

[0055] As an example, a third metal powder is added to the second aluminum foil to form a third powder layer. After the three powder layers are filled in the casing, a composite layer is formed. The first and second aluminum foils primarily serve as insulating elements. During the powder spreading stage, the powders from different layers are physically separated by the aluminum foil, preventing powder cross-contamination and unintended interlayer mixing, thus ensuring precise control of the thickness of each functional layer and the purity of its components. The aluminum foil is extremely thin and will easily break during subsequent cold isostatic pressing and high-temperature hot working. The broken aluminum foil fragments are extremely small and made of pure aluminum. Under high temperature, high pressure, and intense plastic deformation, they can completely dissolve or diffuse into the surrounding aluminum matrix, without remaining as inclusions at the interface as defect sources. This ensures a smooth transition to defect-free interlayer metallurgical bonding after achieving interlayer isolation.

[0056] S104. The composite layer is subjected to cold isostatic pressing to form a green blank in the cladding; the green blank is sintered to obtain a sintered blank.

[0057] For example, the composite layer obtained in the above steps is subjected to cold isostatic pressing. During the cold isostatic pressing process, each powder particle or gas pressure medium within the composite layer acts uniformly on the powder body in all directions through the flexible sheath, causing the powder particles to displace and rearrange, and undergo preliminary plastic deformation and mechanical interlocking, significantly reducing the porosity between particles. Subsequently, the volume of the powder body within the enclosed space of the sheath shrinks, forming a green body with uniform density, no delamination defects, and sufficient handling strength, improving the interfacial bonding strength between the interfaces of the green body. Furthermore, the flexible sheath can be easily removed after isostatic pressing.

[0058] S105. Stack the alloy ingot on at least one side of its thickness direction with the side of the sintered billet closest to the first powder layer, heat to form a composite billet, and then hot-roll, cold-roll, and anneal the composite billet to obtain a pre-embedded flux aluminum alloy composite material.

[0059] For example, on one or both sides of the alloy ingot along its thickness direction, there are stacked sintered blanks, and one side of the first powder layer of the sintered blank is stacked with the alloy ingot for subsequent processing; thus, the alloy ingot and the first powder layer are made of the same material. Through the above process steps, the pre-embedded flux aluminum alloy composite material achieves reliable metallurgical bonding between the sintered blank and the ingot, as well as between each powder layer, effectively improving the interfacial bonding strength of each interface of the composite material, overcoming the problems of insufficient bonding strength and processing cracking caused by interfacial barriers, and significantly improving the interfacial bonding reliability, production yield, and overall performance of the composite material; it also greatly improves the brazing performance of the aluminum alloy composite material.

[0060] In some embodiments, the aluminum alloy includes, but is not limited to, 3003 aluminum alloy powder.

[0061] In some embodiments, the aluminum-silicon alloy includes, but is not limited to, Al-Si alloy powder.

[0062] In some embodiments, the flux powder comprises a KAlF4-K2AlF5 mixed powder, wherein the weight ratio of KAlF4 to K2AlF5 is (70-80):(20-30). Exemplarily, the weight ratio of KAlF4 to K2AlF5 in the KAlF4-K2AlF5 mixed powder can be any one of 70:30, 72:28, 76:24, or 80:20, or any value between any two.

[0063] In some embodiments, the weight ratio of the second metal powder to the flux powder is (82~91):(9~18). Exemplarily, the weight ratio of the second metal powder to the flux powder can be any one of 9:91, 10:90, 12:88, 15:85, or 18:82, or any ratio between any two. The mass percentage of flux in the mixed powder is in the range of 9% to 18%. This balances the brazing film breaking requirements with the formability of the powder metallurgy billet. If the ratio is less than the above range, the effective film-breaking dose released during brazing is insufficient, making it difficult to completely and quickly break the dense oxide film on the surface to be brazed, potentially leading to insufficient solder wetting and poor bonding. For example, for heat exchanger components with complex structures and narrow gaps, flux accessibility is inherently limited, and a lower flux pre-embedding amount will amplify this defect. If the density exceeds the above range, a large number of dispersed brittle non-metallic flux particles will severely rupture the aluminum matrix during sintering, hindering atomic diffusion between aluminum powder particles and the growth of sintering necks, resulting in a sharp decrease in the density of the sintered billet, an increase in internal porosity, and a severe deterioration in the ductility of the material.

[0064] In some embodiments, the median particle size D of the Al-Si alloy powder 50 The particle size ranges from 20 μm to 60 μm. For example, the median particle size D of Al-Si alloy powder... 50 The particle size can be any value from 20μm, 25μm, 30μm, 35μm, 40μm, 45μm, 50μm, 55μm, 58μm, or 60μm, or any point value between any two. It is understood that the above particle size can be determined using a laser particle size analyzer based on wet dispersion. This approach balances the flowability and filling properties of the Al-Si alloy powder. If the particle size is smaller than the above range, the specific surface area between particles increases dramatically, leading to severe powder agglomeration due to van der Waals forces, resulting in poor flowability. This makes it difficult to evenly spread within the enclosure and achieve high bulk density and uniform density, easily introducing low-density regions into the green body. Simultaneously, the oxygen content of excessively fine powder is usually more difficult to control, and the increased oxide film on the surface hinders atomic diffusion during sintering, reducing the density and bonding strength of the sintered green body. If the particle size is larger than the above range, the particles are too coarse. Although the flowability improves, larger pores remain between the particles, making it difficult to completely fill even under the high pressure of cold isostatic pressing, resulting in excessively large initial pore sizes in the green body. In the subsequent sintering process, large pores require a longer diffusion distance and higher energy to close, which increases the difficulty of achieving high density, or requires higher sintering temperature and longer holding time. However, excessively high temperatures may have an adverse effect on flux stability.

[0065] In some embodiments, the oxygen content of the Al-Si alloy powder is less than or equal to 300 ppm. Exemplarily, the oxygen content of the Al-Si alloy powder can be any value of 300 ppm, 200 ppm, or 150 ppm and below. It is understood that the oxygen content can be determined using a LECOONH-3000 oxygen-nitrogen-hydrogen analyzer or an inert gas melting-infrared absorption method, and there is no specific limitation thereto.

[0066] In some embodiments, the median particle size D of the flux powder 50 The particle size ranges from 10 μm to 50 μm. For example, the median particle size D of the flux powder... 50 The flux thickness can be any value within or between 10μm, 15μm, 18μm, 20μm, 25μm, 30μm, 40μm, or 50μm. If the thickness is less than this range, the flux has a large specific surface area and high surface energy. Although it does not melt during sintering, it is prone to agglomeration or prematurely consuming some of its activity through slight reactions. Furthermore, it is more likely to become airborne during powder mixing and transport, causing compositional deviations and contamination. If the thickness is greater than this range, the time required for the flux to completely melt and distribute evenly in the Al-Si solder melt becomes longer, potentially leading to delayed localized film breakage during brazing and affecting the uniform spreading of the solder.

[0067] In some embodiments, the median particle size D of the 3003 aluminum alloy powder 50 The particle size is 30μm to 70μm. For example, the median particle size D of 3003 aluminum alloy powder is... 50 It can be any point value between any one of 30μm, 35μm, 40μm, 45μm, 50μm, 55μm, 60μm, 65μm, 68μm or 70μm.

[0068] In some embodiments, the oxygen content of the 3003 aluminum alloy powder is less than or equal to 300 ppm. Exemplarily, the oxygen content of the 3003 aluminum alloy powder can be any value of 300 ppm, 200 ppm, or 150 ppm and below.

[0069] In some embodiments, the thickness of the first powder layer accounts for 10% to 20% of the thickness of the composite layer. For example, the thickness percentage of the first powder layer can be any one of 10%, 12%, 15%, 18%, or 20%, or any value between any two.

[0070] In some embodiments, the thickness of the second powder layer accounts for 30% to 45% of the total thickness of the composite layer. For example, the thickness percentage of the second powder layer can be any one of 30%, 32%, 35%, 38%, 40%, 42%, or 45%, or any value between any two of these.

[0071] In some embodiments, the thickness of the third powder layer accounts for 40% to 55% of the composite layer thickness. For example, the thickness percentage of the third powder layer can be any one of 40%, 42%, 45%, 48%, 50%, 52%, or 55%, or any value between any two.

[0072] By limiting the thickness proportions of the aforementioned powder layers, after cold isostatic pressing and vacuum sintering, the volume shrinkage, but with a generally consistent linear shrinkage rate for each layer, allows the material to be retained in the sintered billet, resulting in excellent synergy between functionality and processability. The thicker surface Al-Si layer is designed to serve as the main body of the brazing fillet, ensuring a sufficiently wide and full weld radius during brazing, and physically covering and protecting the first powder layer containing flux. The first powder layer, while providing a sufficient amount of homogeneous material to achieve a perfect metallurgical interface with the ingot, occupies as little of the effective thickness of the composite billet as possible, allowing the main thickness of the final product to be contributed by the high-strength 3003 alloy ingot, thereby maximizing the specific strength of the composite material.

[0073] In some embodiments, the thickness of the first aluminum foil can be any one of 0.004 mm, 0.005 mm, or 0.006 mm, or any value between any two.

[0074] In some embodiments, the thickness of the second aluminum foil can be any one of 0.004 mm, 0.005 mm, or 0.006 mm, or any value between any two.

[0075] In some embodiments, the second metal powder and flux powder are mixed using a V-type mixer; wherein, during the mixing process, the rotation speed is 4 r / min to 6 r / min, and the time is 2 h to 5 h. Exemplarily, when using the V-type mixer, the mixing time can be any one of 2 h, 4 h, or 5 h, or any value between any two; the rotation speed can be any one of 2 r / min, 4 r / min, or 6 r / min, or any value between any two. Using a V-type mixer and its low-speed mixing parameters is to avoid significant stratification of the second metal powder and flux powder with large density differences during the mixing process, ensuring uniform flux distribution in the final dense powder layer, thereby guaranteeing the consistency of the overall composite material surface performance.

[0076] In some embodiments, during the cold isostatic pressing process, the temperature is 20°C to 30°C; the pressure is 150MPa to 300MPa; and the time is 5min to 15min. Exemplarily, during the cold isostatic pressing process, the temperature can be any value among 20°C, 25°C, or 30°C, and the pressure can be any value among 150MPa, 200MPa, or 300MPa.

[0077] In some embodiments, sintering includes: The green blanks are placed in a vacuum sintering furnace, and the vacuum level in the furnace is lower than 1×10⁻⁶. -2 Pa, heat to the sintering temperature and sinter to obtain a sintered blank; Furthermore, the sintering process also satisfies at least one of the characteristics (1) to (3): (1) The heating rate is 5℃ / min~10℃ / min; (2) The sintering temperature is 480℃~540℃; (3) The sintering time is 2h~5h.

[0078] For example, a completely sealed enclosure is placed in a graphite mold inside a vacuum hot-pressing sintering furnace. After closing the furnace cavity, the furnace cavity is evacuated again to achieve a vacuum level below 1×10⁻⁶. -2 The Pa level is adjusted to further eliminate interference from ambient gases. Then, the heating program is started to rapidly raise the furnace temperature from room temperature to the set sintering temperature for sintering.

[0079] Optionally, the sintering temperature can be any one of 450℃, 500℃, or 540℃, or any value between any two; the heating rate can be any one of 5℃ / min, 8℃ / min, or 10℃ / min, or any value between any two. By limiting the heating rate, the temperature difference between the inside and outside of the green compact can be effectively controlled. An excessively rapid heating rate may cause a large temperature gradient between the powder particles inside the green compact, resulting in uneven thermal expansion, which in turn causes irregular deformation of the green compact and affects the geometric accuracy of the final sintered compact. At the same time, under the combined action of high temperature and high pressure, the mixed powder inside the green compact undergoes a violent compaction and densification process. The Al-Si alloy powder is in a high-temperature softened or even partially semi-solid state within this temperature range. Driven by triaxial compressive stress, it undergoes plastic flow, gradually filling the voids between particles, and causing the remaining gas to be squeezed out or pressed into the aluminum matrix to form micro-dispersed closed pores.

[0080] In some embodiments, the alloy ingot includes, but is not limited to, 3003 aluminum alloy.

[0081] In some embodiments, the thickness of the alloy ingot is 30 mm to 80 mm. Exemplarily, the thickness of the alloy ingot is any value among 30 mm, 50 mm, or 80 mm.

[0082] In some embodiments, the heating temperature is 450°C to 500°C, and the heating time is 4 hours to 6 hours. Exemplarily, the heating temperature can be any value among 420°C, 450°C, or 500°C, and the holding time can be any value among 4 hours to 6 hours.

[0083] In some embodiments, hot rolling includes performing multiple hot rolling operations on a hot rolling mill on the composite billet, with the final hot rolling temperature being greater than 300°C.

[0084] For example, multiple hot rolling can be performed in 7 passes, achieving a total reduction rate of 92.5%, reducing the composite from its initial thickness to an intermediate thickness of 6 mm, with a final rolling temperature of 350°C. Alternatively, it can be performed in 9 passes, ultimately obtaining an 8 mm thick hot-rolled plate, with a final rolling temperature of 330°C. During the multi-pass hot rolling process, the rolling force acts on the entire composite through the rolls. An intermediate layer containing flux is provided between the third powder layer and the first powder layer, and the shear stress it bears during this process is relatively limited. The inventors of this invention discovered that the intense shear deformation during hot rolling is mainly borne by the outer aluminum-silicon alloy layer, the bottom 3003 aluminum alloy layer, and the 3003 ingot composite billet. The brittle, dense powder layer (second powder layer) with poor plasticity in the middle does not directly bear the strong in-plane shear force; its deformation is mainly due to compressive stress-driven thinning in the thickness direction and planar extension under the constraint of the upper and lower rigid layers. This stress shielding effect enables the stable rolling of composite billets with high flux content. Meanwhile, the bottom surface of the composite billet and the two sides of the interface of the 3003 ingot are made of the same material. Under high temperature and high pressure, atoms can fully diffuse across the interface, achieving atomic-level metallurgical bonding. The bonding strength far exceeds the level of mechanical interlocking of dissimilar materials.

[0085] In some embodiments, the single-pass reduction in cold rolling is 20% to 30%.

[0086] In some embodiments, the thickness of the billet obtained after cold rolling is 0.3 mm to 2.0 mm. Exemplarily, to avoid interlaminar shear failure or edge cracking induced by excessive single-pass deformation during cold rolling, the reduction per rolling pass is limited. The reduction per pass is controlled within the range of 20% to 30%. For example, using 5 passes of cold rolling with a reduction of 20% to 25% per pass, the composite billet is rolled from a thickness of 6 mm to a finished thickness of 0.8 mm; or using 7 passes of cold rolling, the sheet is rolled from a thickness of 8 mm to a finished thickness of 1.2 mm. By limiting the reduction per pass to no more than 30%, it can be ensured that the layers do not separate due to excessive stress concentration during continuous synergistic deformation, enabling the stable production of ultra-thin pre-embedded flux aluminum alloy composite materials with a thickness as low as 0.3 mm.

[0087] In some embodiments, the annealing temperature is 380℃~400℃, and the time is 2h~4h. The annealing temperature can be any one of 380℃, 390℃, 400℃, or any value in between, and the holding time can be any one of 2h, 3h, or 4h, or any value in between. Annealing eliminates processing stress and restores the plasticity of the sheet, thereby obtaining a pre-embedded flux aluminum alloy composite material that possesses both mechanical and brazing properties.

[0088] In some embodiments, reference is made to Figure 4A method for preparing a pre-embedded flux aluminum alloy composite material is provided, comprising the following steps: Step 1: Powder Preparation Third powder layer: Al-(7~12.5%)Si alloy powder, D 50 =20~60μm, oxygen content <300ppm.

[0089] Second powder layer: Al-(7~12.5%)Si alloy powder and potassium fluoroaluminate flux powder are mixed uniformly at a weight ratio of (82~91):(9~18). Al-Si powder D 50 =20~60μm, flux powder D 50 =10~50μm, KAlF4 and K2AlF5 weight ratio is (70-80):(20~30). Mixing method: V-type mixer, speed 4~6r / min, mixing time 2-5h.

[0090] First powder layer: 3003 aluminum alloy powder, D 50 =30~70μm, oxygen content <300ppm.

[0091] Step 2: Layering and Separating the Powder Prepare a flexible square rubber sheath. Spread powder (3003) at the bottom of the sheath, with a thickness of 10-20%, and smooth it. Place a layer of 0.004-0.006mm thick double-zero aluminum foil on top of the metal powder. Spread metal powder (Al-Si + flux mixture) on the aluminum foil, with a thickness of 30-45%, and smooth it. Place another layer of double-zero aluminum foil on top of the metal powder. Spread the first layer of metal powder (Al-Si) on the top layer of aluminum foil, with a thickness of 40-55%, and smooth it. Seal the sheath opening and prepare for cold isostatic pressing.

[0092] Step 3: Cold Isostatic Pressing The package containing the powder is placed in a cold isostatic press at a pressure of 150-300 MPa for 5-15 minutes at room temperature. After cold isostatic pressing, the powder is pressed into a green body with a certain strength. The volume shrinkage is significant, and the layers are separated by aluminum foil but have already achieved initial densification.

[0093] Step 4: Vacuum sintering The cold isostatically pressed green blank is removed from the packaging and placed into a vacuum sintering furnace. The furnace is then evacuated until the vacuum level is below 1×10⁻⁶. -2 The powder is heated to 480-540℃ at a heating rate of 5-10℃ / min and held for sintering for 2-5 hours to allow sufficient atomic diffusion and metallurgical bonding between the powder particles. The powder is then cooled to room temperature in the furnace and the sintered blank is removed.

[0094] Calculations show that the volume shrinkage rate of the sintered billet is approximately 44-50%, meaning the thickness of the sintered billet is approximately 50-56% of the original loosely packed thickness. The thickness ratio of each layer remains basically unchanged.

[0095] Step 5: Hot rolling composite Prepare 3003 aluminum alloy ingots as the core material, with a thickness of 30-80mm and a smooth, milled surface. Depending on product requirements, choose single-sided or double-sided composite material. Single-sided composite: The bottom surface of the sintered billet is superimposed on the 3003 ingot (the first layer of the sintered billet faces outward).

[0096] Double-sided composite: Two sintered billets are stacked on the top and bottom surfaces of a 3003 ingot, with the bottom surface of the 3003 sintered billet in contact with the ingot.

[0097] The composite billet is heated to 450-500℃ and held for 4-6 hours. It is then hot-rolled multiple times on a hot rolling mill, with a final rolling temperature greater than 300℃, to a thickness of 5-8mm. Because the bottom surface of the sintered billet and the core material are both made of 3003 homogeneous material, the synergistic deformation capability during hot rolling is excellent, resulting in a high-strength metallurgical bonding interface.

[0098] Step Six: Cold Rolling and Finished Product Annealing Cool the hot-rolled sheet to room temperature. Perform multiple cold rolling passes to achieve a final finished thickness of 0.3~2.0 mm. The reduction per cold rolling pass is controlled at 20~30%.

[0099] According to the product requirements, the finished product is annealed at 380~400℃ for 2~4 hours to obtain the pre-embedded flux aluminum alloy composite material. In some embodiments of the present invention, a pre-embedded flux aluminum alloy composite material is also provided, comprising: the pre-embedded flux aluminum alloy composite material prepared by the preparation method in any of the above embodiments.

[0100] In some embodiments, the aluminum alloy composite material includes an alloy layer and a brazing functional layer on at least one side of the alloy layer thickness direction; the brazing functional layer includes a composite layer close to the alloy layer and an aluminum-silicon alloy layer away from the alloy layer, the alloy layer includes 3003 aluminum alloy, the composite layer includes an aluminum-silicon alloy and flux, and the aluminum-silicon alloy layer includes an aluminum-silicon alloy; and the aluminum alloy composite material satisfies the following: based on the total thickness of the aluminum alloy composite material, the thickness ratio of the alloy layer is 70% to 88%.

[0101] In some embodiments, the thickness of the brazed functional layer in the aluminum alloy composite material accounts for 6% to 15% based on the total thickness of the aluminum alloy composite material.

[0102] For example, the proportion of alloy layer thickness is limited to 70% to 88%. Correspondingly, the total thickness of the single-sided brazing functional layer accounts for 12% to 30%, and for double-sided composites, the sum of the thicknesses of the brazing functional layers on both sides accounts for 12% to 30%, while the core alloy layer still accounts for 70% to 88%. This is mainly based on the balance between brazing process requirements and structural integrity. The inventors found that when the alloy layer thickness is less than 70%, it means that the brazing functional layer is too thick, which not only consumes too much brazing filler metal and flux, increasing material costs, but more importantly, it weakens the load-bearing and pressure-bearing capacity of the 3003 alloy layer, which is the main structural component. In the subsequent heat exchanger operating environment, a thinner alloy layer may deform or fail under the medium pressure. When the alloy layer thickness is greater than 88%, that is, when the brazing functional layer thickness is less than 12%, the amount of molten brazing filler metal and flux provided may not be sufficient to fully fill the joint gap, effectively break the oxide film on the surface of the components to be brazed, and achieve large-area spreading connection during the brazing process, resulting in a decrease in the welding rate or discontinuous weld. This ensures that the composite material has both high-strength structural support and sufficient and efficient self-brazing capability.

[0103] Since the pre-embedded flux aluminum alloy composite material provided in this embodiment adopts all the technical solutions of the above embodiments, it has at least all the beneficial effects brought about by the technical solutions of the above embodiments, and will not be described in detail here.

[0104] The present invention will be described in detail below with reference to the accompanying drawings and examples. However, the implementation and protection of the present invention are not limited thereto. The following embodiments are only some embodiments of the present invention and are not intended to limit the present invention.

[0105] Example 1 (1) Powder preparation The third powder layer: uses Al-Si alloy powder (Si content is 10.0%), D 50 =40μm, oxygen content 250ppm.

[0106] Second powder layer: Al-Si alloy powder (Si content 10.0%, D...) 50 =40μm) mixed with flux KAlF4-K5AlF5 powder (weight ratio 70:30), D 50 =25μm, mix evenly.

[0107] First powder layer: Utilizes gas-atomized 3003 aluminum alloy powder, D 50 =45μm, oxygen content is 260ppm.

[0108] (2) Layered powder application and interlayer setting A flexible rubber sheath is used, with internal dimensions (length × width × height) of 220mm × 170mm × 22mm. Lay the sheath in the following order: First, lay a layer of 3003 powder, 15% thickness, and level it. Then place a layer of double-zero aluminum foil (0.005mm thick). Next, lay a layer of Al-Si alloy powder and flux mixture (88%:12% by mass), 35% thickness, and level it. Then place another layer of double-zero aluminum foil. Finally, lay a layer of Al-Si alloy powder, 50% thickness, and level it. After filling with powder, seal the sleeve opening.

[0109] (3) Cold isostatic pressing The powder-filled sleeve is placed in a cold isostatic press and held at 200 MPa for 10 minutes at room temperature to obtain a green compact. The density of the green compact is approximately 88% of the theoretical density.

[0110] (4) Vacuum sintering Remove the green billet from the packaging and place it into the vacuum sintering furnace. Evacuate the furnace until the vacuum level is below 3 × 10⁻⁶. -3 Pa was heated to 520℃ at a heating rate of 3℃ / min and held for 3 hours for solid-state diffusion sintering. After holding, the furnace was cooled to room temperature to obtain a three-layer composite sintered blank. Measurements showed that the thickness shrinkage of the sintered blank was approximately 45% of the powder thickness, the density reached 96%, the thickness ratio of each layer remained basically unchanged, the interlayer bonding was good, and there was no flux melting or loss.

[0111] (5) Hot-rolled composite (double-sided) The sintered billets were flattened on a hydraulic press (approximately 200mm × 150mm × 12mm in size), and after surface cleaning, they were combined with a 3003 aluminum alloy ingot core material (approximately 200mm × 150mm × 80mm in size, with a milled surface). The two sintered billets were stacked on the top and bottom surfaces of the 3003 ingot, respectively, with the 3003 bottom surface of the sintered billet in contact with the ingot and the Al-Si top surface of the sintered billet facing outward. The stacked billets were heated to 480℃ and held for 5 hours. They were then hot-rolled in 7 passes on a hot rolling mill with a total reduction of 92.5%, a final rolling thickness of 6mm, and a final rolling temperature of 350℃.

[0112] (6) Cold rolling and annealing The hot-rolled plate was cooled to room temperature and then cold-rolled in 5 passes, with a reduction of 20-25% per pass, resulting in a final rolled thickness of 0.8 mm. The finished product was then annealed: held at 390℃ for 3 hours and air-cooled.

[0113] Example 2 (1) Powder preparation The third powder layer: uses Al-Si alloy powder (Si content is 12.0%), D 50 =50μm, oxygen content 280ppm.

[0114] Second powder layer: Al-Si alloy powder (Si content 12.0%, D...) 50 =50μm) and flux powder (KAlF4-K5AlF5 mixed powder, weight ratio 76:24, D 50 =35μm) were mixed at a weight ratio of 85:15. A V-type mixer was used at a speed of 4 r / min for 5 hours.

[0115] First powder layer: Utilizes gas-atomized 3003 aluminum alloy powder, D 50 =55μm, oxygen content is 270ppm.

[0116] (2) Layered powder application and interlayer setting A flexible rubber sheath is used, with internal dimensions (length × width × height) of 420mm × 320mm × 32mm. Lay the material in the following order: First, lay a layer of 3003 powder, 15% thickness, and level it. Then place a layer of double-zero aluminum foil (0.005mm thick). Next, lay a layer of Al-Si alloy powder and flux mixture (85%:15% by mass), 30% thickness, and level it. Then place another layer of double-zero aluminum foil. Finally, lay a layer of Al-Si alloy powder, 55% thickness, and level it. After filling with powder, seal the sleeve opening.

[0117] (3) Cold isostatic pressing The powder-filled sleeve is placed in a cold isostatic press and held at 250 MPa for 8 minutes at room temperature to obtain a green compact. The density of the green compact is approximately 89% of the theoretical density.

[0118] (4) Vacuum sintering Remove the green billet from the packaging and place it into the vacuum sintering furnace. Evacuate the furnace until the vacuum level is below 5 × 10⁻⁶. -3 Pa was heated to 530℃ at a heating rate of 3℃ / min and held at that temperature for 5 hours for solid-state diffusion sintering. After holding, the furnace was cooled to room temperature to obtain a three-layer composite sintered blank. The thickness shrinkage rate of the sintered blank was approximately 44%, the density reached over 95%, and the interlayer bonding was good.

[0119] (5) Hot-rolled composite (single-sided) The sintered billet was flattened on a hydraulic press (approximately 400mm × 300mm × 18mm in size), and after surface cleaning, it was combined with a 3003 aluminum alloy ingot core material (approximately 400mm × 300mm × 135mm in size, with a milled surface). The 3003 bottom surface of the sintered billet was stacked with the 3003 ingot, with the Al-Si top surface of the sintered billet facing outwards. The stacked billet was heated to 470℃ and held for 6 hours. It was then hot-rolled in 9 passes on a hot rolling mill to a final thickness of 8mm at a final rolling temperature of 330℃.

[0120] (6) Cold rolling and annealing The hot-rolled plate was cooled to room temperature and then cold-rolled in 7 passes, with a reduction of 20-25% per pass, resulting in a final rolled thickness of 1.2 mm. The finished product was then annealed: held at 380℃ for 4 hours and air-cooled.

[0121] Example 3 (Double-sided composite, thin profile, with the brazed functional layer accounting for approximately 10% of the total thickness) (1) Powder preparation The third powder layer: uses Al-Si alloy powder (Si content is 7.5%), D 50 =30μm, oxygen content 220ppm.

[0122] Second powder layer: Al-Si alloy powder (Si content 7.5%, D...) 50 =30μm) and flux powder (KAlF4-K5AlF5 mixed powder, weight ratio 80:20, D 50 =15μm) were mixed at a weight ratio of 91:9. A V-type mixer was used at a speed of 6 r / min for 3 hours.

[0123] First powder layer: Utilizes gas-atomized 3003 aluminum alloy powder, D 50 =35μm, oxygen content 230ppm.

[0124] (2) Layered powder application and interlayer setting A flexible rubber sheath is used, with internal dimensions (length × width × height) of 520mm × 420mm × 52mm. Lay the material in the following order: First, lay a layer of 3003 powder, 20% thickness, and smooth it. Then place a layer of double-zero aluminum foil (0.006mm thick). Next, lay a layer of Al-Si alloy powder and flux mixture (91%:9% by mass), 40% thickness, and smooth it. Then place another layer of double-zero aluminum foil. Finally, lay a layer of Al-Si alloy powder, 40% thickness, and smooth it. Seal the sleeve opening.

[0125] (3) Cold isostatic pressing The powder-filled sleeve is placed in a cold isostatic press and held at 180 MPa for 12 minutes at room temperature to obtain a green compact. The density of the green compact is approximately 87% of the theoretical density.

[0126] (4) Vacuum sintering Remove the green billet from the packaging and place it into the vacuum sintering furnace. Evacuate the furnace until the vacuum level is below 5 × 10⁻⁶. -3The material was heated to 510℃ at a heating rate of 2℃ / min and held at that temperature for 8 hours for solid-state diffusion sintering. After holding, the material was cooled to room temperature in the furnace to obtain a three-layer composite sintered blank. The sintered blank had a thickness shrinkage rate of approximately 44%, a density of over 95%, and good interlayer bonding.

[0127] (5) Hot-rolled composite (double-sided) The two sintered billets were flattened on a hydraulic press (approximately 500mm × 400mm × 29mm in size). Two more sintered billets and one 3003 aluminum alloy ingot core (approximately 500mm × 400mm × 170mm in size, with a milled surface) were prepared. The two sintered billets were stacked on the top and bottom surfaces of the 3003 ingot, respectively, with the 3003 bottom surface of the sintered billet in contact with the ingot and the Al-Si top surface of the sintered billet facing outward. The stacked billets were heated to 500℃ and held for 4 hours. Six passes of hot rolling were performed on a hot rolling mill to a final thickness of 5mm at a final rolling temperature of 380℃.

[0128] (6) Cold rolling and annealing The hot-rolled plate is cooled to room temperature and then cold-rolled in four passes, with a reduction of 20-25% per pass, resulting in a final rolled thickness of 0.5 mm. The finished product is then annealed: held at 400℃ for 2 hours, followed by air cooling.

[0129] Comparative Example 1 The difference between Comparative Example 1 and Example 1 is that Comparative Example 1 does not contain a third powder layer. Specifically: (1) Powder preparation Second powder layer: Al-Si alloy powder (Si content 10.0%, D...) 50 =40μm) mixed with flux KAlF4-K5AlF5 powder (weight ratio 70:30), D 50 =25μm, mix evenly.

[0130] First powder layer: Utilizes gas-atomized 3003 aluminum alloy powder, D 50 =45μm, oxygen content is 260ppm.

[0131] (2) Layered powder application and interlayer setting A flexible rubber sheath is used, with internal dimensions (length × width × height) of 220mm × 170mm × 22mm. Lay the sheath in the following order: First, lay a layer of 3003 aluminum alloy powder, 30% thickness, and level it. Then place a layer of double-zero aluminum foil (0.005mm thick). Next, lay a layer of Al-Si alloy powder and flux mixture (88%:12% by mass), 70% thickness, and level it. After filling with powder, seal the sleeve opening. The rest is the same as in the example.

[0132] Comparative Example 2 The difference between Comparative Example 2 and Example 1 is that the green billet was removed from the packaging and placed in a sintering furnace, heated to 530°C at a heating rate of 3°C / min, and held at that temperature for 5 hours for solid-state diffusion sintering. After the holding period, the billet was cooled to room temperature with the furnace to obtain a three-layer composite sintered billet.

[0133] Comparative Example 3 The difference between Comparative Example 3 and Example 1 is as follows: (1) Powder preparation The third powder layer: uses Al-Si alloy powder (Si content is 10.0%), D 50 =40μm, oxygen content 250ppm.

[0134] Second powder layer: Al-Si alloy powder (Si content 10.0%, D...) 50 =40μm) mixed with flux KAlF4-K5AlF5 powder (weight ratio 70:30), D 50 =25μm, mix evenly.

[0135] First powder layer: Utilizes gas-atomized 3003 aluminum alloy powder, D 50 =45μm, oxygen content is 260ppm.

[0136] (2) Layered powder application and interlayer setting A flexible rubber sheath is used, with internal dimensions (length × width × height) of 220mm × 170mm × 22mm. Lay the sheath in the following order: First, lay a layer of 3003 powder, 15% thickness, and level it. Then place a layer of double-zero aluminum foil (0.005mm thickness). Next, lay a layer of Al-Si alloy powder, 50% thickness, and level it. Then place another layer of double-zero aluminum foil. Afterward, lay a layer of a mixture of Al-Si alloy powder and flux (88%:12% by mass), 35% thickness, and level it. Once the powder filling is complete, seal the sleeve opening. The rest is the same as in the example.

[0137] Test example: 1. Thickness: Measured using a micrometer.

[0138] 2. Interface bonding strength: The interface bonding strength was tested using an electronic universal testing machine at a tensile speed of 5 mm / min.

[0139] 3. Brazing performance: Tested according to GB / T 11364-2008 "Test Method for Wetting Properties of Brazing Alloy". A Φ6mm×2mm cylindrical sample was cut from the composite material and placed in the center of a 40mm×40mm×2mm 3003 aluminum test plate. Under a nitrogen protective atmosphere, the sample was heated from room temperature to 598~605℃ for 24 minutes and held for 4~6 minutes. The spread area was measured using image analysis software, and the average value was calculated from three tests. Metallographic examination of the brazed joint cross-section was performed to check for fullness of the brazed joint. Visual inspection and scanning electron microscopy (SEM) energy dispersive spectroscopy analysis were conducted to determine the presence and quantity of flux residue.

[0140] The test results are shown in Table 1.

[0141] Table 1 As can be seen from Table 1, the pre-embedded flux aluminum alloy composite material prepared by the preparation method of the present invention has good interfacial bonding strength and brazing performance, and no visible flux residue is visible on the surface after brazing.

[0142] The parts of this invention not described in detail are techniques known to those skilled in the art.

[0143] The basic principles of the present invention have been described above with reference to specific embodiments. However, it should be noted that the advantages, benefits, and effects mentioned in the present invention are merely examples and not limitations, and should not be considered as essential features of each embodiment of the present invention. Furthermore, the specific details disclosed above are for illustrative and facilitative purposes only, and are not limitations. These details do not limit the present invention to the necessity of employing the aforementioned specific details.

[0144] It should be noted that the terms "and / or" or " / " used herein are merely descriptions of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, or B existing alone. The singular forms "a," "described," and "the" used in the embodiments of the invention and the appended claims are also intended to include the plural forms, unless the context clearly indicates otherwise.

[0145] In the detailed description and claims, a list of items connected by the terms "at least one of," "at least one of," "at least one of," or other similar terms may mean any combination of the listed items. For example, if items A and B are listed, then the phrase "at least one of A and B" means only A; only B; or A and B. In another example, if items A, B, and C are listed, then the phrase "at least one of A, B, and C" means only A; or only B; only C; A and B (excluding C); A and C (excluding B); B and C (excluding A); or all of A, B, and C. Item A may contain a single element or multiple elements. Item B may contain a single element or multiple elements. Item C may contain a single element or multiple elements.

[0146] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing a pre-embedded flux aluminum alloy composite material, characterized in that, Includes the following steps: A first metal powder is added to a sleeve with an opening on at least one side to form a first powder layer, and a first aluminum foil is placed on the first powder layer; wherein, the first metal powder includes an aluminum alloy; A second metal powder and flux powder are added to the sheath, and a second powder layer is formed on the surface of the first aluminum foil away from the first powder layer. A second aluminum foil is placed on the second powder layer. The second metal powder comprises an aluminum-silicon alloy. A third metal powder is added to the casing, and a third powder layer is formed on the surface of the second aluminum foil away from the second powder layer, thus obtaining a composite layer in the casing; the third metal powder comprises an aluminum-silicon alloy. The composite layer is subjected to cold isostatic pressing to form a green blank in the cladding; the green blank is then sintered to obtain a sintered blank. At least one side of the alloy ingot in the thickness direction is stacked with the side of the sintered billet closest to the first powder layer, and heated to form a composite billet. The composite billet is then hot-rolled, cold-rolled, and annealed to obtain a pre-embedded flux aluminum alloy composite material.

2. The method for preparing the pre-embedded flux aluminum alloy composite material according to claim 1, characterized in that, The aluminum alloy includes 3003 aluminum alloy powder; And / or, the aluminum-silicon alloy comprises Al-Si alloy powder; And / or, the flux powder comprises a KAlF4-K2AlF5 mixed powder, wherein the weight ratio of KAlF4 to K2AlF5 is (70-80):(20-30); And / or, the weight ratio of the second metal powder to the flux powder is (82~91):(9~18).

3. The method for preparing the pre-embedded flux aluminum alloy composite material according to claim 2, characterized in that, Satisfying at least one of features (1) to (5): (1) The median particle size D of the Al-Si alloy powder 50 The thickness ranges from 20μm to 60μm. (2) The oxygen content of the Al-Si alloy powder is less than or equal to 300 ppm; (3) The median particle size D of the flux powder 50 The range is 10μm to 50μm; (4) The median particle size D of the 3003 aluminum alloy powder 50 The thickness ranges from 30μm to 70μm. (5) The oxygen content of the 3003 aluminum alloy powder is less than or equal to 300 ppm.

4. The method for preparing the pre-embedded flux aluminum alloy composite material according to claim 1, characterized in that, Satisfying at least one of features (1) to (5): (1) Based on the thickness of the composite layer, the thickness of the first powder layer accounts for 10% to 20%; (2) Based on the thickness of the composite layer, the thickness of the second powder layer accounts for 30% to 45%; (3) Based on the thickness of the composite layer, the thickness of the third powder layer accounts for 40% to 55%; (4) The thickness of the first aluminum foil is 0.004 mm to 0.006 mm; (5) The thickness of the second aluminum foil is 0.004mm~0.006mm.

5. The method for preparing the pre-embedded flux aluminum alloy composite material according to claim 1, characterized in that, The second metal powder and the flux powder are mixed using a V-type mixer; wherein, during the mixing process, the rotation speed is 4 r / min to 6 r / min, and the time is 2 h to 5 h; And / or, during the cold isostatic pressing process, the temperature is 20℃~30℃; the pressure is 150MPa~300MPa; and the time is 5min~15min.

6. The method for preparing the pre-embedded flux aluminum alloy composite material according to claim 1, characterized in that, The sintering includes: The green blank is placed in a vacuum sintering furnace, and the vacuum level in the furnace is lower than 1×10⁻⁶. -2 Pa, heat to the sintering temperature and sinter to obtain the sintered blank; Furthermore, the sintering process also satisfies at least one of features (1) to (3): (1) The heating rate is 5℃ / min to 10℃ / min; (2) The sintering temperature is 480℃ to 540℃; (3) The sintering time is 2h to 5h.

7. The method for preparing the pre-embedded flux aluminum alloy composite material according to claim 1, characterized in that, The alloy ingot comprises 3003 aluminum alloy; And / or, the thickness of the alloy ingot is 30mm~80mm; And / or, the heating temperature is 450℃~500℃, and the time is 4h~6h; And / or, the hot rolling includes: performing multiple hot rolling operations on the composite billet on a hot rolling mill, wherein the temperature of the final hot rolling operation is greater than 300°C.

8. The method for preparing the pre-embedded flux aluminum alloy composite material according to claim 1, characterized in that, The single-pass reduction in the cold rolling process is 20% to 30%. And / or, the thickness of the blank obtained after cold rolling is 0.3 mm to 2.0 mm; And / or, the annealing temperature is 380℃~400℃, and the time is 2h~4h.

9. A pre-embedded flux aluminum alloy composite material, characterized in that, include: The pre-embedded flux aluminum alloy composite material prepared by the preparation method according to any one of claims 1 to 8.

10. The pre-embedded flux aluminum alloy composite material according to claim 9, characterized in that, The aluminum alloy composite material includes an alloy layer and a brazing functional layer on at least one side of the alloy layer in the thickness direction; the brazing functional layer includes a composite layer close to the alloy layer and an aluminum-silicon alloy layer away from the alloy layer, the alloy layer includes 3003 aluminum alloy, the composite layer includes an aluminum-silicon alloy and flux, and the aluminum-silicon alloy layer includes an aluminum-silicon alloy. Furthermore, the aluminum alloy composite material satisfies the following conditions: based on the total thickness of the aluminum alloy composite material, the thickness ratio of the alloy layer is 70%~88%; and / or, based on the total thickness of the aluminum alloy composite material, the thickness ratio of the brazing functional layer is 6%~15%.

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