A pre-embedded brazing flux aluminum alloy composite material and a preparation method thereof

Abstract

The present application relates to the technical field of aluminum brazing, in particular to a pre-embedded flux aluminum alloy composite material and a preparation method thereof, the aluminum alloy composite material comprises a main body material and a pre-embedded flux arranged on at least one side surface of the main body material along the thickness direction; the main body material is an aluminum alloy; the pre-embedded flux comprises a first aluminum-silicon layer arranged on the surface of the main body material, a composite flux layer arranged on the side surface of the first aluminum-silicon layer away from the main body material, and a second aluminum-silicon layer arranged on the side surface of the composite flux layer away from the main body material; wherein the composite flux layer comprises a Cs / K composite flux; the Cs / K composite flux comprises a Cs salt flux and a K salt flux. The pre-embedded flux aluminum alloy composite material of the present application can delay the diffusion of Mg from the core material to the flux layer, and the Cs in the Cs / K composite flux reacts with Mg preferentially to generate a low-melting-point eutectic, thereby maintaining the fluidity and activity of the flux. + ​

Description

Technical Field

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

[0002] Aluminum alloys, due to their lightweight, high specific strength, good thermal conductivity, and corrosion resistance, have become the core material for manufacturing automotive heat exchangers (such as condensers, evaporators, oil coolers, and water-cooled plates). With the increasing demands for lightweight vehicles, higher strength requirements are being placed on aluminum alloys used in heat exchangers. Adding magnesium (Mg) to 3000 series aluminum alloys (such as 3005 aluminum alloy) can effectively improve the strength of brazed aluminum alloys; without Mg, the brazed yield strength can be increased from 40-60 MPa to over 80 MPa. Using high-strength 3000 series aluminum alloys containing Mg in the production of heat exchangers is of great significance for the lightweighting of heat exchangers.

[0003] Currently, the mainstream manufacturing process for aluminum heat exchangers is controlled atmosphere brazing. This involves coating or spraying flux (such as Nocolok flux) onto the surface of the aluminum alloy components to be welded, followed by heating under an inert gas atmosphere to melt the filler metal and fill the weld seam. However, when the Mg content in the aluminum alloy exceeds 0.3 wt%, the brazing performance of traditional potassium fluoroaluminate-based fluxes (the eutectic reaction product of KF-AlF3, known as K-series fluxes) deteriorates drastically. The mechanism lies in the interaction between Mg and the flux. On the one hand, it produces high-melting-point products such as KMgF3 and MgF2; on the other hand, it reduces the effective components of the flux. As a result, the flux's melting point increases, its fluidity decreases, and its activity decreases, leading to partial or even complete flux failure.

[0004] To address the brazing challenges of Mg-containing aluminum alloys, three main technical approaches exist. The first involves placing a Mg diffusion-inhibiting layer (intermediate layer) between the core material and the filler metal to suppress Mg diffusion and improve brazing performance. However, when the Mg content in the core material is high, this structure cannot completely prevent the reduction in brazing performance, making it difficult to balance strength and brazing performance. Furthermore, it increases the number of layers and processes in the composite plate, significantly raising costs and increasing process complexity. The second approach uses Cs salt flux (a CsF-AlF3 eutectic reaction product), but Cs-containing fluxes are expensive, prone to flux residue, and have poor accessibility. The third approach generates a Mg barrier layer in situ, but this may require annealing to form the barrier layer. The flux system is singular, with limited adaptability to Mg content. For aluminum alloys with high Mg content, the barrier layer cannot completely prevent Mg diffusion and flux failure. Therefore, there is an urgent need in this field for a new aluminum alloy material that can reduce the problems of flux failure, residue, and poor accessibility while also being cost-effective and suitable for large-scale mass production. Summary of the Invention

[0005] In view of this, the present invention aims to provide a pre-embedded flux aluminum alloy composite material and its preparation method, so as to solve the problems of flux failure, residue, and poor accessibility in the prior art.

[0006] To solve the above-mentioned technical problems, the present invention is implemented as follows: A first aspect of the present invention provides a pre-embedded flux aluminum alloy composite material, the pre-embedded flux aluminum alloy composite material comprising a main material and a pre-embedded flux disposed on at least one surface of the main material along the thickness direction; The main material is aluminum alloy; The pre-embedded flux includes a first aluminum-silicon layer disposed on the surface of the main body material, a composite flux layer disposed on the surface of the first aluminum-silicon layer away from the main body material, and a second aluminum-silicon layer disposed on the surface of the composite flux layer away from the main body material. The composite flux layer includes a Cs / K composite flux; the Cs / K composite flux includes Cs salt flux and K salt flux.

[0007] Optionally, based on the Mg content in the main material, when the Mg content is <0.5wt%, the Cs salt flux accounts for 10%~20% of the mass of the Cs / K composite flux, and the K salt flux accounts for 80%~90% of the mass of the Cs / K composite flux; and / or, based on the Mg content in the main material, when 0.5wt% ≤ the Mg content <1.0wt%, the Cs salt flux accounts for 10%~20% of the mass of the Cs / K composite flux; and / or, based on the Mg content in the main material, when 0.5wt% ≤ the Mg content <1.0wt%, the Cs salt flux accounts for 80%~90% of the mass of the Cs / K composite flux. The Cs / K composite flux comprises 30% to 40% by mass, and the K salt flux comprises 60% to 70% by mass; and / or, based on the Mg content in the main material, when 1.0 wt% ≤ the Mg content ≤ 1.5 wt%, the Cs salt flux comprises 50% to 70% by mass, and the K salt flux comprises 30% to 50% by mass.

[0008] Optionally, the content of the Cs / K composite flux is 8wt to 16wt, based on the total mass of the composite flux layer.

[0009] Optionally, the Cs salt flux is a eutectic reaction product of CsF and AlF3, wherein the mass ratio of CsF to AlF3 is (70~75):(25~30); and / or, the K salt flux is a eutectic reaction product of KF and AlF3, wherein the mass ratio of KF to AlF3 is (42~48):(52~58).

[0010] Optionally, the first aluminum-silicon layer comprises a first aluminum-silicon alloy, wherein the content of Si element in the first aluminum-silicon alloy is 7~12.5wt% based on the total mass of the first aluminum-silicon alloy; and / or, the second aluminum-silicon layer comprises a second aluminum-silicon alloy, wherein the content of Si element in the second aluminum-silicon alloy is 7~12.5wt% based on the total mass of the second aluminum-silicon alloy.

[0011] Optionally, based on the total thickness of the pre-embedded flux, the thickness of the first aluminum-silicon layer accounts for 30% to 50%, the thickness of the composite flux layer accounts for 20% to 40%, and the thickness of the second aluminum-silicon layer accounts for 20% to 50%.

[0012] A second aspect of the present invention provides a method for preparing a pre-embedded flux aluminum alloy composite material, the method comprising the following steps: S1. The first aluminum-silicon alloy powder, the first aluminum foil, the composite flux layer powder, the second aluminum foil, the second aluminum-silicon alloy powder, and the third aluminum foil are sequentially laid into the flexible sleeve and subjected to cold isostatic pressing to obtain a green blank. S2. Vacuum sintering is performed on the green blank to obtain a composite sintered blank; S3. The composite sintered billet is stacked with the main material to obtain a composite billet; the composite billet is subjected to heat treatment and hot rolling to obtain a hot-rolled plate; S4. After the hot-rolled plate is cooled, it undergoes cold rolling and annealing. The main material is aluminum alloy; The composite flux layer powder includes Cs / K composite flux; the Cs / K composite flux includes Cs salt flux and K salt flux.

[0013] Optionally, the first aluminum-silicon alloy powder has a D50 of 20μm to 60μm and an oxygen content of <300ppm; and / or, the second aluminum-silicon alloy powder has a D50 of 20μm to 60μm and an oxygen content of <300ppm; and / or, the composite flux layer powder further includes a third aluminum-silicon alloy powder, wherein, based on the total mass of the composite flux layer powder, the content of the third aluminum-silicon alloy powder is 84wt% to 92wt% and the content of the Cs / K composite flux is 8wt% to 16wt%; and / or, the composite flux layer powder has a D50 of 20μm to 60μm.

[0014] Optionally, in step S1, the conditions for the cold isostatic pressing treatment include: pressure of 150 MPa to 300 MPa, holding time of 5 min to 15 min, and temperature of 10℃ to 40℃; and / or, in step S2, the conditions for the vacuum sintering treatment include: vacuum degree below 1×10⁻⁶. -2Pa, heating rate of 2℃ / min~5℃ / min, sintering temperature of 440℃~460℃, sintering time of 4h~10h; and / or, in step S3, the heat treatment conditions include: temperature of 440℃~460℃, time of 2h~4h; and / or, the final rolling temperature of the hot rolling treatment is >300℃, and the intermediate thickness of the hot-rolled plate is 5 mm~8mm; and / or, in step S4, the single-pass reduction of the cold rolling treatment is 20%~30%, and the thickness of the composite material after the cold rolling treatment is 0.3 mm~2.0 mm; and / or, the annealing conditions include: temperature of 380℃~400℃, time of 2h~4h.

[0015] Optionally, in step S3, the overlapping is a single-sided overlapping or a double-sided overlapping.

[0016] The beneficial technical effects of the present invention through the above technical solution are as follows: (1) The pre-embedded flux of the present invention includes a first aluminum-silicon layer disposed on the surface of the main material, a composite flux layer disposed on the surface of the first aluminum-silicon layer away from the main material, and a second aluminum-silicon layer disposed on the surface of the composite flux layer away from the main material. The first aluminum-silicon layer serves as a physical transition layer, which to some extent delays the diffusion of Mg from the core material to the flux layer. If the first aluminum-silicon layer is missing, it may not be able to inhibit the poisoning of Mg on the flux or remove surface Al2O3. During the soldering process, Cs in the Cs / K composite flux... + It preferentially reacts with Mg to form a low-melting-point eutectic, thus maintaining the fluidity and activity of the flux.

[0017] (2) The present invention designs a gradient formulation of Cs / K composite flux for main materials with different Mg contents, which can optimize the amount of Cs salt added to reduce costs while ensuring the inhibition of Mg poisoning effect.

[0018] (3) This invention utilizes Cs in AlF3-CsF flux. + The unique mechanism of action of Cs + Preferential to Mg diffused from the core material 2+ The reaction produces a low-melting-point CsMgF3 eutectic, rather than a high-melting-point KMgF3 or MgF2. This mechanism is based on the physicochemical properties of the AlF3-KF-CsF and AlF3-CsF flux systems, in which the addition of CsF significantly lowers the flux melting point and has unique advantages for removing the coating from magnesium-aluminum alloys.

[0019] (4) The preparation method of the pre-embedded flux aluminum alloy composite material of the present invention first uses cold isostatic pressing (CIP) and vacuum sintering process to prepare a three-layer composite sintered blank, and pre-embeds the Cs / K composite flux inside the Al-Si solder layer. During CAB brazing, the pre-embedded Cs / K composite flux melts and escapes from the inside, without the need for external spraying, which fundamentally solves the problems of flux waste, residue and poor accessibility.

[0020] (5) The present invention presses the Al-Si powder and Cs / K composite flux mixed powder into a dense green blank by cold isostatic pressing, and then performs vacuum solid sintering at a temperature lower than the flux melting temperature (420-530℃) to ensure that the flux does not melt and lose during the sintering process and maintains the integrity of the layered structure.

[0021] Other features and advantages of the present invention will be described in detail in the following detailed description section. Attached Figure Description

[0022] The accompanying drawings are provided to further illustrate the invention and form part of the specification. They are used together with the following detailed description to explain the invention, but do not constitute a limitation thereof.

[0023] Figure 1 The image shows the metallographic structure of the double-sided composite pre-embedded flux composite material.

[0024] Figure 2 The diagram shows the process flow chart for preparing aluminum alloy composite materials with embedded flux.

[0025] Figure 3 The diagram shows the powder packing structure. 1- Aluminum-silicon alloy powder; 2- Double-zero aluminum foil; 3- Composite flux layer powder; 4- Flexible sheath.

[0026] Figure 4 The mechanical properties (O state) of the aluminum alloy composite material prepared in Example 3 and the aluminum alloy composite material in Comparative Example 1 are shown. Detailed Implementation

[0027] This invention discloses a pre-embedded flux aluminum alloy composite material and its preparation method. Those skilled in the art can refer to the content of this document and appropriately modify the process parameters to achieve the same result. It should be particularly noted that all similar substitutions and modifications are obvious to those skilled in the art and are considered to be included in this invention. The methods and applications of this invention have been described through preferred embodiments. Those skilled in the art can clearly modify or appropriately change and combine the methods and applications described herein without departing from the content, spirit, and scope of this invention to realize and apply the technology of this invention.

[0028] In the description of this invention, the list of items connected by the term "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.

[0029] 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.

[0030] Unless otherwise specified, all embodiments and optional embodiments of the present invention can be combined with each other to form new technical solutions.

[0031] Unless otherwise specified, all technical features and optional technical features of this invention can be combined to form new technical solutions.

[0032] 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.

[0033] The term "Cs / K composite flux" refers to the fact that, in contrast to single-component K salt flux and Cs salt flux, the Cs / K composite flux in this invention contains both K salt flux and Cs salt flux.

[0034] To address the problems of flux failure, residue, and poor accessibility in existing technologies, this invention adopts the following technical solution: The first aspect of the present invention provides a pre-embedded flux aluminum alloy composite material, such as... Figure 1 As shown, the pre-embedded flux aluminum alloy composite material includes a main body material and a pre-embedded flux disposed on at least one surface of the main body material along the thickness direction; The main material is aluminum alloy; The pre-embedded flux includes a first aluminum-silicon layer disposed on the surface of the main body material, a composite flux layer disposed on the surface of the first aluminum-silicon layer away from the main body material, and a second aluminum-silicon layer disposed on the surface of the composite flux layer away from the main body material. The composite flux layer includes a Cs / K composite flux; the Cs / K composite flux includes Cs salt flux and K salt flux.

[0035] The pre-embedded flux of the present invention includes a first aluminum-silicon layer disposed on the surface of the main material, a composite flux layer disposed on the surface of the first aluminum-silicon layer away from the main material, and a second aluminum-silicon layer disposed on the surface of the composite flux layer away from the main material. The first aluminum-silicon layer serves as a physical transition layer, which to some extent delays the diffusion of Mg from the core material to the flux layer. Cs in the Cs / K composite flux preferentially reacts with Mg to form a low-melting-point eutectic, thus maintaining the fluidity and activity of the flux.

[0036] In some embodiments of the present invention, the main aluminum alloy material is a brazed aluminum alloy, such as 3000 series aluminum alloy, 5000 series aluminum alloy, etc., which are well known to those skilled in the art.

[0037] This invention designs a gradient formulation of Cs / K composite flux for main materials with different Mg contents. It can optimize the amount of Cs salt added to reduce costs while ensuring that the reaction between Mg and K-based flux is suppressed to generate high-melting-point products.

[0038] In one embodiment of the present invention, based on the content of Mg element in the main material, when the content of Mg element is <0.5wt%, the mass proportion of Cs salt flux in the Cs / K composite flux is 10%~20%, and the mass proportion of K salt flux in the Cs / K composite flux is 80%~90%. For example, based on the content of Mg element in the main material, when the content of Mg element is <0.5wt%, the mass proportion of Cs salt flux in the Cs / K composite flux can be any value among 10%, 12%, 15%, 17%, and 20%, or any value within the range of any pair of the above values; the mass proportion of K salt flux in the Cs / K composite flux can be any value among 80%, 82%, 84%, 86%, 88%, and 90%, or any value within the range of any pair of the above values.

[0039] In one embodiment of the present invention, based on the content of Mg in the main material, when 0.5wt% ≤ the content of Mg < 1.0wt%, the mass percentage of Cs salt flux in the Cs / K composite flux is 30%~40%, and the mass percentage of K salt flux in the Cs / K composite flux is 60%~70%. For example, based on the content of Mg in the main material, when 0.5wt% ≤ the content of Mg < 1.0wt%, the mass percentage of Cs salt flux in the Cs / K composite flux can be any value from 30%, 32%, 34%, 36%, 38%, and 40%, or any value within the range of any two of the above values; the mass percentage of K salt flux in the Cs / K composite flux can be any value from 60%, 62%, 64%, 66%, 68%, and 70%, or any value within the range of any two of the above values.

[0040] In one embodiment of the present invention, based on the Mg content in the main material, when 1.0 wt% ≤ Mg content ≤ 1.5 wt%, the Cs salt flux accounts for 50% to 70% of the mass of the Cs / K composite flux, and the K salt flux accounts for 30% to 50% of the mass of the Cs / K composite flux. For example, based on the Mg content in the main material, when 1.0 wt% ≤ Mg content ≤ 1.5 wt%, the mass percentage of the Cs salt flux in the Cs / K composite flux can be any value from 50%, 55%, 60%, 65%, and 70%, or any value within the range of any two of the above values; the mass percentage of the K salt flux in the Cs / K composite flux can be any value from 30%, 35%, 40%, 45%, and 50%, or any value within the range of any two of the above values.

[0041] In one embodiment of the present invention, the composite flux layer further includes Al and Si elements.

[0042] This invention uses a Cs / K composite flux (a mixture of CsF-AlF3 and KAlF4-K2AlF5), both of which are non-corrosive fluoroaluminate fluxes, chemically compatible, and do not produce harmful phases. At the brazing temperature, the CsF-AlF3 flux, due to the Cs... + It exhibits extremely strong polarization, preferentially reacting with Mg to form low-melting-point CsMgF3 (melting point approximately 500-550℃). This product remains liquid or semi-liquid at CAB brazing temperatures (570-600℃), without clogging flux channels or affecting flux flowability. This avoids the formation of high-melting-point KMgF3 and MgF2, while also reducing the F content in K- and Cs-based fluxes. -This invention rapidly removes Al2O3 from the surface of aluminum alloys through mechanisms such as reaction, dissolution, and peeling, thereby achieving high-quality CAB brazing connections for Mg-containing aluminum alloys. In one embodiment of the invention, the content of the Cs / K composite flux is 8wt% to 16wt%, based on the total mass of the composite flux layer. For example, the content of the Cs / K composite flux can be any value from 8%, 10%, 12%, 14%, and 16%, or any value within the range of any pair of values ​​mentioned above, based on the total mass of the composite flux layer. By controlling the content of the Cs / K composite flux within the above proportions, the reaction between Mg and K-based flux to generate high-melting-point products can be suppressed, and Al2O3 on the surface of the aluminum alloy can be removed, thereby achieving a brazing connection.

[0043] This invention utilizes Cs in CsF-AlF3 flux. + The unique mechanism of action of Cs + The flux preferentially reacts with Mg diffused from the core material to form a low-melting-point CsMgF3 eutectic, rather than forming a high-melting-point KMgF3 or MgF2. This mechanism is based on the physicochemical properties of the AlF3-KF and AlF3-CsF flux systems, where the addition of CsF significantly lowers the flux melting point and has unique advantages in removing the coating from magnesium-aluminum alloys. In one embodiment of the invention, the Cs salt flux is a eutectic reaction product of CsF and AlF3, and the mass ratio of CsF to AlF3 is (70~75):(25~30). By controlling the mass ratio of CsF to AlF3 within the above-mentioned ratio, the flux melting point can be reduced, Al2O3 can be removed from the surface of magnesium-aluminum alloys, thereby achieving brazing.

[0044] In one embodiment of the present invention, the K salt flux is a eutectic reaction product of KF and AlF3, wherein the mass ratio of the KF and AlF3 is (42~48):(52~58).

[0045] According to the present invention, the first aluminum-silicon layer may include a first aluminum-silicon alloy, wherein the Si content in the first aluminum-silicon alloy is 7~12.5 wt% based on the total mass of the first aluminum-silicon alloy; and / or; the second aluminum-silicon layer may include a second aluminum-silicon alloy, wherein the Si content in the second aluminum-silicon alloy is 7~12.5 wt% based on the total mass of the second aluminum-silicon alloy. By controlling the Si content in the first aluminum-silicon alloy and the second aluminum-silicon alloy to the above-mentioned proportions, the flux can be allowed to flow fully, wet and spread during the welding process, thereby effectively filling the weld and achieving brazing connection.

[0046] In one embodiment of the present invention, based on the total thickness of the pre-embedded flux, the thickness percentage of the first aluminum-silicon layer is 30%~50%, the thickness percentage of the composite flux layer is 20%~40%, and the thickness percentage of the second aluminum-silicon layer is 20%~50%. The first aluminum-silicon layer, as a physical transition layer, delays the diffusion of Mg from the core material to the flux layer to a certain extent. If the thickness percentage of the first aluminum-silicon layer is too large, it may lead to insufficient Cs / K composite flux, failing to inhibit Mg poisoning of the flux and remove surface Al2O3. If the thickness percentage of the first aluminum-silicon layer is too small, it may lead to insufficient aluminum-silicon solder for connection, resulting in incomplete filling or failure to achieve brazing. The composite flux layer, as the main functional component of the pre-embedded flux, also has this effect. If the thickness percentage of the composite flux layer is too large, it may lead to incomplete filling or failure to achieve brazing. If the thickness percentage of the composite flux layer is too small, it may lead to insufficient flux, failing to inhibit Mg poisoning of the flux and remove surface Al2O3.

[0047] A second aspect of the present invention provides a method for preparing a pre-embedded flux aluminum alloy composite material, such as... Figure 2 As shown, the preparation method includes the following steps: S1. The first aluminum-silicon alloy powder, the first aluminum foil, the composite flux layer powder, the second aluminum foil, the second aluminum-silicon alloy powder, and the third aluminum foil are sequentially laid into the flexible sheath (e.g., Figure 3 (As shown) and then subjected to cold isostatic pressing to obtain a green blank; S2. Vacuum sintering is performed on the green blank to obtain a composite sintered blank; S3. The composite sintered billet is stacked with the main material to obtain a composite billet; the composite billet is subjected to heat treatment and hot rolling to obtain a hot-rolled plate; S4. After the hot-rolled plate is cooled, it undergoes cold rolling and annealing. The main material is aluminum alloy; The composite flux layer powder includes Cs / K composite flux; the Cs / K composite flux includes Cs salt flux and K salt flux.

[0048] The preparation method of the pre-embedded flux aluminum alloy composite material of the present invention first uses cold isostatic pressing (CIP) and vacuum sintering to prepare a three-layer composite sintered blank, and pre-embeds Cs / K composite flux inside the Al-Si solder layer. During CAB brazing, the pre-embedded Cs / K composite flux melts and escapes from the inside, eliminating the need for external spraying and fundamentally solving the problems of flux waste, residue, and poor accessibility. The present invention uses cold isostatic pressing to press the Al-Si powder and Cs / K composite flux mixture into a dense green blank, and then performs vacuum solid-state sintering at a temperature below the flux melting temperature (420-530℃), thereby ensuring that the flux does not melt and flow away during sintering and maintaining the integrity of the layered structure.

[0049] In one embodiment of the present invention, the first aluminum-silicon alloy powder has a D50 of 20 μm to 60 μm and an oxygen content of <300 ppm; and / or, the second aluminum-silicon alloy powder has a D50 of 20 μm to 60 μm and an oxygen content of <300 ppm; and / or, the composite flux layer powder further includes a third aluminum-silicon alloy powder, wherein, based on the total mass of the composite flux layer powder, the content of the third aluminum-silicon alloy powder is 84 wt% to 92 wt%, and the content of the Cs / K composite flux is 8 wt% to 16 wt%; and / or, the composite flux layer powder has a D50 of 20 μm to 60 μm.

[0050] In one embodiment of the present invention, the conditions for the cold isostatic pressing process in step S1 include: pressure of 150MPa to 300MPa, holding time of 5min to 15min, and temperature of 10℃ to 40℃.

[0051] In one embodiment of the present invention, the conditions for the vacuum sintering process in step S2 include: a vacuum degree lower than 1×10⁻⁶. -2 Pa, heating rate of 2℃ / min~5℃ / min, sintering temperature of 440℃~460℃, sintering time of 4h~10h.

[0052] In one embodiment of the present invention, in step S3, the conditions for the heat treatment include: a temperature of 440°C to 460°C and a time of 2h to 4h; and / or, the final rolling temperature of the hot rolling treatment is >300°C, and the intermediate thickness of the hot-rolled plate is 5mm to 8mm.

[0053] In one embodiment of the present invention, in step S4, the single-pass reduction of the cold rolling process is 20% to 30%, and the thickness of the composite material after the cold rolling process is 0.3 mm to 2.0 mm; and / or, the annealing conditions include: temperature 380℃ to 400℃, and time 2h to 4h.

[0054] For example, in step S3, the lamination can be selected as single-sided lamination or double-sided lamination according to the actual situation. Single-sided lamination includes laminating the Al-Si bottom layer of the composite sintered blank with the main body material (Al-Si surface facing outwards). Double-sided lamination includes laminating two composite sintered blanks on the upper and lower surfaces of the main body material, respectively.

[0055] The following describes embodiments of the present invention. The embodiments described below are exemplary and are only used to explain this application, and should not be construed as limiting the present invention. Where specific techniques or conditions are not specified in the embodiments, they shall be performed in accordance with the techniques or conditions described in the literature in the field or according to the product instructions. Reagents, materials, or instruments used, unless otherwise specified, are all conventional products that can be obtained commercially.

[0056] Example 1 This embodiment provides a method for preparing a pre-embedded Cs / K composite flux aluminum alloy composite material for controlled atmosphere brazing of magnesium-containing aluminum alloys. The core material is 3007 aluminum alloy (Mg content 0.6wt%). The specific steps are as follows: (1) Powder preparation The first powder layer (Al-Si surface layer) uses gas-atomized Al-10.0wt%Si alloy powder (Al powder is atomized with high-purity argon and then mixed with silicon powder, of which the mass percentage of silicon powder is 10.0%), D50=40μm, and oxygen content 250ppm.

[0057] The second powder layer (Al-Si+Cs / K composite flux mixture): Al-10.0wt%Si alloy powder, D50=40μm, oxygen content 250ppm; Cs / K composite flux: Cs salt flux and K salt flux are mixed at a mass ratio of 35:65; wherein, the Cs salt flux is a commercially available CsF-AlF3 eutectic reaction product (CsF and AlF3 mass ratio is 70:30), and the K salt flux is a commercially available KF-AlF3 eutectic reaction product (KF and AlF3 mass ratio is 42:58). Mixing ratio: Al-Si alloy powder 88wt%, Cs / K composite flux 12wt%. Mixing method: V-type powder mixer, speed 5r / min, mixing time 4h.

[0058] The third powder layer (Al-Si bottom layer): is the same as the first powder layer.

[0059] (2) Layered powder spreading and cold isostatic pressing A flexible rubber sheath with an internal height of 22mm is used. The flux is applied in the following order: The third layer (Al-Si bottom layer powder) is applied, accounting for 30% of the total pre-embedded flux thickness, and leveled. A 0.005mm thick double-zero aluminum foil layer is placed. The second layer (Al-Si + Cs / K composite flux mixed powder) is applied, accounting for 40% of the total pre-embedded flux thickness, and leveled. Another double-zero aluminum foil layer of the same thickness is placed. The first layer (Al-Si surface layer powder) is applied, accounting for 30% of the total pre-embedded flux thickness, and leveled. The sheath opening is sealed, and then cold isostatic pressing is performed at room temperature at a pressure of 200MPa for 10 minutes to obtain a green compact with a density of approximately 88%.

[0060] (3) 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 The material was heated to 460℃ at a heating rate of 3℃ / min and held for 4 hours for solid-state diffusion sintering. After holding, it was cooled to room temperature in the furnace to obtain a three-layer composite sintered blank. The sintered blank was measured to be approximately 11 mm thick with a density of 96%. The thickness ratio of each layer remained basically unchanged (30:40:30), the interlayer bonding was good, and the Cs / K composite flux was uniformly distributed in the Al-Si matrix without melting or loss.

[0061] (4) Hot-rolled composite (double-sided) Core material preparation: 3007 aluminum alloy ingot, Mg content 0.6%, thickness 60mm, surface milled flat.

[0062] The composite sintered billet is flattened and shaped to a total thickness of 10mm (3mm for the first layer, 4mm for the second layer, and 3mm for the third layer).

[0063] Two composite sintered blanks are stacked on the upper and lower sides of the 3007 ingot, respectively, so that the Al-Si bottom layer (third layer) of the composite sintered blank is in contact with the 3007 ingot, with the Al-Si surface layer facing outward.

[0064] Total thickness of the stacked blanks: 10mm + 60mm + 10mm = 80mm.

[0065] Heat the stacked blanks to 450℃ and hold for 5 hours.

[0066] Eight passes of hot rolling were performed on a hot rolling mill, with a total reduction rate of 92.5%, a final rolling thickness of 6 mm, and a final rolling temperature of 340℃.

[0067] (5) Cold rolling and finished product annealing Cool the hot-rolled plate to room temperature.

[0068] Nine cold rolling passes are performed, with a reduction of 20-30% per pass, resulting in a final rolling thickness of 0.5 mm.

[0069] Finished product annealing: Hold at 380℃ for 3 hours, then air cool.

[0070] A high-strength brazed aluminum alloy composite material with double-sided pre-embedded Cs / K composite flux was obtained.

[0071] (6) Product structure and performance: Total thickness: 0.5mm The thickness of the single-sided brazed functional layer (first layer + second layer + third layer) is 0.063mm (accounting for 12.5% ​​of the total thickness). The thickness of the first and third Al-Si layers is approximately 0.019 mm. The thickness of the pre-embedded Cs / K composite flux layer (second layer) is approximately 0.025 mm. Core material layer (3007): 0.375mm (accounting for 75% of the total thickness); Composite interface: No cracks, no pores, and good interface bonding.

[0072] Mechanical properties (O-state composite board): Using an electronic universal testing machine at a tensile speed of 5 mm / min, the tensile strength of the composite material was measured to be 134 MPa, the yield strength to be 56 MPa, and the elongation to be 24%.

[0073] 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. The sample was heated from room temperature to 600℃ in a nitrogen protective atmosphere for 24 minutes, and held at that temperature for 5 minutes. The spreading area was measured using image analysis software. The average value of three tests was approximately 538mm². 2 The brazing rate was 99%. Metallographic observation and surface scanning electron microscopy energy dispersive spectroscopy analysis of the cross-section of the brazed joint showed that the brazing seam was full and there was no high melting point KMgF3 / MgF2 residue.

[0074] Example 2 This embodiment provides a method for preparing a pre-embedded Cs / K composite flux aluminum alloy composite material for controlled atmosphere brazing of magnesium-containing aluminum alloys. The core material is 3005 aluminum alloy (Mg content 0.4wt%). The specific steps are as follows: (1) Powder preparation First powder layer (Al-Si surface layer): gas-atomized Al-10.0wt%Si alloy powder, D50=45μm, oxygen content 260ppm.

[0075] The second powder layer (Al-Si+Cs / K composite flux mixture layer): Al-10.0wt%Si alloy powder, D50=45μm, oxygen content 260ppm.

[0076] Cs / K composite flux: Cs salt flux and K salt flux are mixed at a mass ratio of 15:85; wherein, the Cs salt flux is a commercially available CsF-AlF3 eutectic reaction product (CsF and AlF3 mass ratio of 75:25), and the K salt flux is a commercially available KF-AlF3 eutectic reaction product (KF and AlF3 mass ratio of 48:52). Mixing ratio: 90wt% Al-Si alloy powder, 10wt% Cs / K composite flux. Mixing method: Double cone mixer, speed 4r / min, mixing time 5h.

[0077] The third layer of powder (Al-Si bottom layer): same as the first layer of powder.

[0078] (2) Layered powder spreading and cold isostatic pressing A flexible rubber sheath with an internal height of 22mm is used. The flux is applied in the following order: The third layer (Al-Si bottom layer powder) is applied, accounting for 40% of the total pre-embedded flux thickness, and leveled. A layer of double-zero aluminum foil (0.005mm thick) is placed. The second layer (Al-Si + Cs / K composite flux mixed powder) is applied, accounting for 20% of the total pre-embedded flux thickness, and leveled. Another layer of double-zero aluminum foil is placed. The first layer (Al-Si surface layer powder) is applied, accounting for 40% of the total pre-embedded flux thickness, and leveled. After sealing the sheath opening, cold isostatic pressing is performed at room temperature at a pressure of 180MPa for 12 minutes to obtain a green compact with a density of approximately 87%.

[0079] (3) 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 2 × 10⁻⁶. -3 Pa was heated to 450℃ at a heating rate of 3℃ / min and held for 6 hours for solid-state diffusion sintering. After holding, the furnace was cooled to room temperature to obtain a three-layer composite sintered blank. The sintered blank was approximately 11 mm thick with a density of 96%. The thickness ratio of each layer remained basically unchanged (35:30:35), the interlayer bonding was good, and the Cs / K composite flux did not melt or leak.

[0080] (4) Hot-rolled composite (single-sided) Core material preparation: 3005 aluminum alloy ingot, Mg content 0.4%, thickness 90mm, surface milled flat.

[0081] The composite sintered billet is flattened and shaped to a total thickness of 10mm (the first layer is 4mm, the second layer is 2mm, and the third layer is 4mm).

[0082] The Al-Si bottom layer (third layer) of the composite sintered billet is stacked with the 3005 ingot, with the Al-Si surface layer of the composite sintered billet facing outward.

[0083] Total thickness of the stacked blanks: 10mm + 90mm = 100mm.

[0084] Heat the stacked billets to 460℃ and hold for 2 hours.

[0085] The hot rolling process was carried out in 7 passes on a hot rolling mill, with a total reduction rate of 91.7%, a final rolling thickness of 5 mm, and a final rolling temperature of 330℃.

[0086] (5) Cold rolling and finished product annealing Cool the hot-rolled plate to room temperature.

[0087] The material undergoes seven cold rolling passes, with a reduction of 20-25% per pass, resulting in a final rolling thickness of 1.2 mm.

[0088] Finished product annealing: Hold at 380℃ for 4 hours, then air cool.

[0089] A high-strength brazed aluminum alloy composite material with single-sided pre-embedded Cs / K composite flux was obtained.

[0090] (6) Product structure and performance Product structure: Total thickness: 1.2mm; The thickness of the single-sided brazed functional layer (first layer + second layer + third layer) is 0.12mm (accounting for 10% of the total thickness). The thickness of the first and third Al-Si layers is approximately 0.048 mm. The thickness of the pre-embedded Cs / K composite flux layer (second layer) is approximately 0.024 mm. Core material layer (3005): 1.08mm (accounting for 90% of the total thickness); Composite interface: flawless, with good interface integration.

[0091] Mechanical properties (O-state composite board): Using an electronic universal testing machine at a tensile speed of 5 mm / min, the tensile strength of the composite material was measured to be 124 MPa, the yield strength to be 52 MPa, and the elongation to be 25%.

[0092] 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. The sample was heated from room temperature to 600℃ in a nitrogen protective atmosphere for 24 minutes, and held at that temperature for 5 minutes. The spread area was measured using image analysis software. The average value of three tests was approximately 476mm². 2 The brazing rate was 98%. Metallographic observation and surface scanning electron microscopy energy dispersive spectroscopy analysis of the cross-section of the brazed joint showed that the brazed joint was full and there was no high-melting-point KMgF3 / MgF2 residue.

[0093] Example 3 This embodiment provides a method for preparing a pre-embedded Cs / K composite flux aluminum alloy composite material for controlled atmosphere brazing of magnesium-containing aluminum alloys. The core material is 3004 aluminum alloy (Mg content 1.2wt%). The specific steps are as follows: (1) Powder preparation First powder layer (Al-Si surface layer): gas-atomized Al-12.0%Si alloy powder with D50=35μm and oxygen content of 230ppm.

[0094] The second powder layer (Al-Si+Cs / K composite flux mixture): Al-12.0%Si alloy powder, D50=35μm, oxygen content 230ppm. Cs / K composite flux: Cs salt flux and K salt flux are mixed at a mass ratio of 60:40; wherein, the Cs salt flux is a commercially available CsF-AlF3 eutectic reaction product (CsF and AlF3 mass ratio is 72:28), and the K salt flux is a commercially available KF-AlF3 eutectic reaction product (KF and AlF3 mass ratio is 45:55). Mixing ratio: Al-Si alloy powder 86wt%, Cs / K composite flux 14wt%. Mixing method: V-type powder mixer, speed 5r / min, mixing time 5h.

[0095] The third layer of powder is the same as the first layer of powder.

[0096] (2) Layered powder spreading and cold isostatic pressing A flexible rubber sheath, 22mm thick, is used. The flux is laid in the following order: The third layer (Al-Si bottom layer powder), accounting for 20% of the total pre-embedded flux, is then smoothed. A layer of double-zero aluminum foil (0.005mm thick) is placed. The second layer (Al-Si + Cs / K composite flux mixed powder), accounting for 30% of the total pre-embedded flux, is then smoothed. Another layer of double-zero aluminum foil is placed. The first layer (Al-Si surface layer powder), accounting for 50% of the total pre-embedded flux, is then smoothed. After sealing the sheath opening, cold isostatic pressing is performed at room temperature at a pressure of 220MPa for 10 minutes. A green compact with a density of approximately 89% is obtained.

[0097] (3) 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 The material was heated to 440℃ at a heating rate of 2℃ / min and held for 10 hours for solid-state diffusion sintering. After holding, it was cooled to room temperature in the furnace to obtain a three-layer composite sintered blank. The sintered blank was approximately 11 mm thick with a density of 96%. The thickness ratio of each layer remained basically unchanged (50:30:20), the interlayer bonding was good, and the Cs / K composite flux was uniformly distributed in the Al-Si matrix without melting or loss.

[0098] (4) Hot-rolled composite (double-sided) Core material preparation: 3004 aluminum alloy ingot, Mg content 1.2%, thickness 105mm, surface milled flat.

[0099] The composite sintered billet is flattened and shaped to a total thickness of 10mm (5mm for the first layer, 3mm for the second layer, and 2mm for the third layer).

[0100] Two composite sintered billets are stacked on the upper and lower sides of a 3004 ingot, respectively, so that the Al-Si bottom layer (third layer) of the composite sintered billet is in contact with the 3004 ingot, and the Al-Si surface layer (first layer) faces outward.

[0101] Total thickness of the stacked blanks: 10mm + 105mm + 10mm = 125mm.

[0102] Heat the stacked blanks to 450℃ and hold for 3 hours.

[0103] Eight passes of hot rolling were performed on a hot rolling mill, with a total reduction rate of 93.6%, a final rolling thickness of 8 mm, and a final rolling temperature of 320℃.

[0104] (5) Cold rolling and finished product annealing Cool the hot-rolled plate to room temperature.

[0105] The material undergoes five cold rolling passes, with a reduction of 20-30% per pass, resulting in a final rolling thickness of 2.0 mm.

[0106] Finished product annealing: Hold at 400℃ for 2.5 hours, then air cool to obtain a high-strength brazed aluminum alloy composite material with double-sided pre-embedded Cs / K composite flux.

[0107] (6) Product structure and performance Product structure: Total thickness: 2.0mm; The thickness of the single-sided brazed functional layer (first layer + second layer + third layer) is 0.16mm (accounting for 8% of the total thickness). The Al-Si surface layer (first layer) is approximately 0.08 mm thick, and the third layer is approximately 0.032 mm thick.

[0108] The thickness of the pre-embedded Cs / K composite flux layer (second layer) is approximately 0.048 mm. Core material layer (third layer + 3004 ingot): 1.68mm (accounting for 84% of the total thickness); Composite interface: No cracks, no pores, and good interface bonding.

[0109] Mechanical properties (O-state composite board): Using an electronic universal testing machine at a tensile speed of 5 mm / min, the tensile strength of the composite material was measured to be 160 MPa, the yield strength to be 68 MPa, and the elongation to be 24%.

[0110] 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. The sample was heated from room temperature to 600℃ in a nitrogen protective atmosphere for 24 minutes, and held at that temperature for 5 minutes. The spread area was measured using image analysis software. The average value of three tests was approximately 512mm². 2 The brazing rate was 99%. Metallographic observation and surface scanning electron microscopy energy dispersive spectroscopy analysis of the cross-section of the brazed joint showed that the brazing seam was full and there was no high melting point KMgF3 / MgF2 residue.

[0111] Comparative Example 1 This comparative example describes a conventional method for preparing brazed aluminum alloy composite materials. The core material is 3003 aluminum alloy (containing 1.17wt% Mn, 0.15wt% Si, 0.5wt% Fe, 0.1wt% copper, with the remainder being Al and no Mg). The double-sided brazing layer is made of 4045 aluminum alloy with a Si content of 10.5wt%. The specific steps are as follows: (1) Semi-continuous casting of aluminum alloy 3003 aluminum alloy and 4045 aluminum alloy were smelted and semi-continuously cast according to the alloy element ratio. After surface milling, the ingot thickness was 80mm and the length was 400mm.

[0112] (2) Rolling and segmentation of 4045 aluminum alloy The 4045 aluminum alloy ingot is heated to 450℃ and held for 3 hours. It is then hot-rolled to 10mm in 5 passes on a reciprocating hot rolling mill. The ends are sheared, and the hot-rolled plate is cut into 400mm segments, each of which is then milled.

[0113] (3) Hot rolling composite billet 4045 aluminum alloy hot-rolled plate and 3003 aluminum alloy are placed from top to bottom in the order of 4045, 3003 and 4045, with a total thickness of 100mm. Then they are loaded into the furnace and heated to 450℃ and held for 3 hours. Subsequently, they are hot rolled to 5mm in 7 passes in a reciprocating hot rolling mill, with a final rolling temperature of 320℃.

[0114] (4) Cold rolling and finished product annealing Cool the hot-rolled plate to room temperature. Perform 5 passes of cold rolling, with a reduction of 20-30% per pass, and a final rolling thickness of 1.20 mm.

[0115] Finished product annealing: Hold at 400℃ for 2.5 hours, then air cool to obtain a brazed aluminum alloy composite material with double-sided composite brazing filler metal.

[0116] (5) Product structure and performance Product structure: Total thickness: 1.20mm; Thickness of single-sided brazed functional layer: 0.12mm (accounting for 10% of the total thickness); Core material layer (3003 alloy): 0.96mm (accounting for 80% of the total thickness); Composite interface: Metallographic images show that the brazing layer and the core material layer are free of cracks and pores, and the interface is well bonded.

[0117] Mechanical properties (O-state composite board): Using an electronic universal testing machine at a tensile speed of 5 mm / min, the tensile strength of the composite material was measured to be 108 MPa, the yield strength to be 38 MPa, and the elongation to be 34%.

[0118] Brazing performance: Tests were conducted 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. A flux consisting of the eutectic reaction product of KF and AlF3 (mass ratio of KF to AlF3 45:55) was coated on the surface. The sample was heated from room temperature to 600℃ for 24 minutes under a nitrogen protective atmosphere and held at that temperature for 5 minutes. The spread area was measured using image analysis software. The average value of three tests was approximately 518 mm². 2 Meanwhile, metallographic observation and surface scanning electron microscopy energy dispersive spectroscopy analysis were performed on the cross-section of the brazed joint. The brazed joint was full and continuous, with a welding rate of 98%, and obvious flux residue was visible on the surface.

[0119] Comparative Example 2 This comparative example provides a method for preparing a pre-embedded K-salt flux aluminum alloy composite material for controlled atmosphere brazing of magnesium-containing aluminum alloys. The core material is 3007 aluminum alloy (Mg content 0.6wt%). The specific steps are as follows: (1) Powder preparation The first powder layer (Al-Si surface layer) uses gas-atomized Al-10.0%wtSi alloy powder (Al powder is atomized with high-purity argon and then mixed with silicon powder, wherein the mass percentage of silicon powder is 10.0wt%), D50=40μm, and oxygen content 250ppm.

[0120] The second powder layer (Al-Si + K salt flux mixed layer): Al-10.0%wtSi alloy powder, D50=40μm, oxygen content 250ppm; K salt flux: commercially available KF-AlF3 eutectic reaction product (KF and AlF3 mass ratio 45:55). Mixing ratio: Al-Si alloy powder 88wt%, K salt flux 12wt%. Mixing method: V-type powder mixer, speed 5r / min, mixing time 4h.

[0121] The third powder layer (Al-Si bottom layer): is the same as the first powder layer.

[0122] (2) Layered powder spreading and cold isostatic pressing A flexible rubber sheath with an internal height of 22mm is used. The flux is applied in the following order: The third layer (Al-Si bottom layer powder) is applied, accounting for 30% of the total pre-embedded flux thickness, and leveled. A 0.005mm thick double-zero aluminum foil layer is placed. The second layer (Al-Si + K salt flux mixed powder) is applied, accounting for 40% of the total pre-embedded flux thickness, and leveled. Another double-zero aluminum foil layer of the same thickness is placed. The first layer (Al-Si surface layer powder) is applied, accounting for 30% of the total pre-embedded flux thickness, and leveled. The sheath opening is sealed, and then cold isostatic pressing is performed at room temperature at a pressure of 200MPa for 10 minutes to obtain a green compact with a density of approximately 88%.

[0123] (3) 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 The material was heated to 460℃ at a heating rate of 3℃ / min and held for 4 hours for solid-state diffusion sintering. After holding, it was cooled to room temperature in the furnace to obtain a three-layer composite sintered blank. The sintered blank was measured to be approximately 11 mm thick with a density of 98%. The thickness ratio of each layer remained basically unchanged (30:40:30), the interlayer bonding was good, and the K salt flux was uniformly distributed in the Al-Si matrix without melting or loss.

[0124] (4) Hot-rolled composite (double-sided) Core material preparation: 3007 aluminum alloy ingot, Mg content 0.6%, thickness 60mm, surface milled flat.

[0125] The composite sintered billet is flattened and shaped to a total thickness of 10mm (3mm for the first layer, 4mm for the second layer, and 3mm for the third layer).

[0126] Two composite sintered blanks are stacked on the upper and lower sides of the 3007 ingot, respectively, so that the Al-Si bottom layer (third layer) of the composite sintered blank is in contact with the 3007 ingot, with the Al-Si surface layer facing outward.

[0127] Total thickness of the stacked blanks: 10mm + 60mm + 10mm = 80mm.

[0128] Heat the stacked blanks to 450℃ and hold for 5 hours.

[0129] Eight passes of hot rolling were performed on a hot rolling mill, with a total reduction rate of 92.5%, a final rolling thickness of 6 mm, and a final rolling temperature of 340℃.

[0130] (5) Cold rolling and finished product annealing Cool the hot-rolled plate to room temperature.

[0131] Nine cold rolling passes are performed, with a reduction of 20-30% per pass, resulting in a final rolling thickness of 0.5 mm.

[0132] Finished product annealing: Hold at 380℃ for 3 hours, then air cool.

[0133] A brazed aluminum alloy composite material with double-sided pre-embedded K-salt flux was obtained.

[0134] (6) Product structure and performance: Total thickness: 0.5mm; The thickness of the single-sided brazed functional layer (first layer + second layer + third layer) is 0.063mm (accounting for 12.5% ​​of the total thickness). The thickness of the first and third Al-Si layers is approximately 0.019 mm. The thickness of the pre-embedded K-salt flux layer (second layer) is approximately 0.025 mm. Core material layer (3007): 0.375mm (accounting for 75% of the total thickness); Composite interface: No cracks, no pores, and good interface bonding.

[0135] Mechanical properties (O-state composite board): Using an electronic universal testing machine at a tensile speed of 5 mm / min, the tensile strength of the composite material was measured to be 136 MPa, the yield strength to be 57 MPa, and the elongation to be 23%.

[0136] 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. The sample was heated from room temperature to 600℃ in a nitrogen protective atmosphere for 24 minutes, and held at that temperature for 5 minutes. The spreading area was measured using image analysis software. The average value of three tests was approximately 83mm². 2 The brazing rate was 8%. Metallographic observation and surface scanning electron microscopy energy dispersive spectroscopy analysis of the cross-section of the brazed joint revealed numerous pores in the brazed joint, localized non-connection, and the presence of high-melting-point KMgF3 and MgF2 at the weld.

[0137] Table 1 shows a comparison of parameters and performance between Examples 1-3 and Comparative Examples 1-2. The parts of this invention not described in detail are techniques known to those skilled in the art.

[0138] 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.

[0139] In the above description of the present invention, the reference to terms such as "one embodiment," "another embodiment," etc., indicates that a specific feature, structure, material, or characteristic described in connection with that embodiment is included in at least one embodiment of this application. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, those skilled in the art can combine and integrate different embodiments or examples and features of different embodiments or examples described in the present invention without contradiction. Additionally, it should be noted that in the present invention, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features.

[0140] 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 pre-embedded flux aluminum alloy composite material, characterized in that, The pre-embedded flux aluminum alloy composite material includes a main material and a pre-embedded flux disposed on at least one surface of the main material along the thickness direction; The main material is aluminum alloy; The pre-embedded flux includes a first aluminum-silicon layer disposed on the surface of the main body material, a composite flux layer disposed on the surface of the first aluminum-silicon layer away from the main body material, and a second aluminum-silicon layer disposed on the surface of the composite flux layer away from the main body material. The composite flux layer comprises a Cs / K composite flux and an aluminum-silicon alloy; the Cs / K composite flux comprises a Cs salt flux and a K salt flux, wherein the Cs salt flux is a eutectic reaction product of CsF and AlF3, and the K salt flux is a eutectic reaction product of KF and AlF3; Based on the Mg content in the main material, gradient formulations of Cs / K composite flux were designed for main materials with different Mg contents, including: When the content of the Mg element is <0.5wt%, the Cs salt flux accounts for 10%~20% of the mass of the Cs / K composite flux, and the K salt flux accounts for 80%~90% of the mass of the Cs / K composite flux; and / or, When the content of the Mg element is less than 1.0 wt% and less than 0.5 wt%, the Cs salt flux accounts for 30% to 40% of the mass of the Cs / K composite flux, and the K salt flux accounts for 60% to 70% of the mass of the Cs / K composite flux; and / or, When the content of the Mg element is 1.0wt%≤1.5wt%, the mass percentage of the Cs salt flux in the Cs / K composite flux is 50%~70%, and the mass percentage of the K salt flux in the Cs / K composite flux is 30%~50%.

2. The pre-embedded flux aluminum alloy composite material according to claim 1, characterized in that, Based on the total mass of the composite flux layer, the content of the Cs / K composite flux is 8wt~16wt%.

3. The pre-embedded flux aluminum alloy composite material according to claim 1, characterized in that, The mass ratio of the CsF and AlF3 mixture is (70~75):(25~30); and / or, The mass ratio of the KF and AlF3 mixture is (42~48):(52~58).

4. The pre-embedded flux aluminum alloy composite material according to claim 1, characterized in that, The first aluminum-silicon layer comprises a first aluminum-silicon alloy, wherein, based on the total mass of the first aluminum-silicon alloy, the content of Si element in the first aluminum-silicon alloy is 7~12.5 wt%; and / or, The second aluminum-silicon layer comprises a second aluminum-silicon alloy, and based on the total mass of the second aluminum-silicon alloy, the content of Si element contained in the second aluminum-silicon alloy is 7~12.5wt%.

5. The pre-embedded flux aluminum alloy composite material according to claim 1, characterized in that, Based on the total thickness of the pre-embedded flux, the thickness of the first aluminum-silicon layer accounts for 30% to 50%, the thickness of the composite flux layer accounts for 20% to 40%, and the thickness of the second aluminum-silicon layer accounts for 20% to 50%.

6. A method for preparing a pre-embedded flux aluminum alloy composite material according to any one of claims 1 to 5, characterized in that, The preparation method includes the following steps: S1. The first aluminum-silicon alloy powder, the first aluminum foil, the composite flux layer powder, the second aluminum foil, the second aluminum-silicon alloy powder, and the third aluminum foil are sequentially laid into the flexible sleeve and subjected to cold isostatic pressing to obtain a green blank. S2. Vacuum sintering is performed on the green blank to obtain a composite sintered blank; S3. The composite sintered billet is stacked with the main material to obtain a composite billet; the composite billet is subjected to heat treatment and hot rolling to obtain a hot-rolled plate; S4. After the hot-rolled plate is cooled, it undergoes cold rolling and annealing. The main material is aluminum alloy; The composite flux layer powder includes Cs / K composite flux and a third aluminum-silicon alloy powder; the Cs / K composite flux includes Cs salt flux and K salt flux.

7. The preparation method according to claim 6, characterized in that, The first aluminum-silicon alloy powder has a D50 of 20μm to 60μm and an oxygen content of <300ppm; and / or, The second aluminum-silicon alloy powder has a D50 of 20μm to 60μm and an oxygen content of <300ppm; and / or, Based on the total mass of the composite flux layer powder, the content of the third aluminum-silicon alloy powder is 84wt%~92wt%, and the content of the Cs / K composite flux is 8wt%~16wt%; and / or, The D50 of the composite flux layer powder is 20μm~60μm.

8. The preparation method according to claim 6, characterized in that, In step S1, the conditions for the cold isostatic pressing treatment include: pressure of 150 MPa to 300 MPa, holding time of 5 min to 15 min, and temperature of 10℃ to 40℃; and / or, In step S2, the conditions for the vacuum sintering process include: a vacuum level lower than 1×10⁻⁶. -2 Pa, heating rate of 2℃ / min~5℃ / min, sintering temperature of 440℃~460℃, sintering time of 4h~10h; and / or, In step S3, the heat treatment conditions include: a temperature of 440℃~460℃ and a time of 2h~4h; and / or, the final rolling temperature of the hot rolling treatment is >300℃, and the intermediate thickness of the hot-rolled plate is 5 mm~8 mm; and / or, In step S4, the single-pass reduction of the cold rolling process is 20%~30%, and the thickness of the composite material after the cold rolling process is 0.3 mm~2.0 mm; and / or, the annealing conditions include: temperature 380℃~400℃, time 2h~4h.

9. The preparation method according to claim 6, characterized in that, In step S3, the overlapping is either single-sided or double-sided.

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