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

Abstract

The present application relates to the technical field of aluminum alloy brazing plate, and particularly relates to a pre-embedded brazing agent aluminum alloy composite material and a preparation method thereof. The method comprises the following steps: sequentially stacking and fixing an Al-Si alloy plate, a brazing agent / Al-Si alloy plate and an aluminum alloy plate to form a laminated structure; using a stirring pin of a friction stir processing tool to stir and frictionally composite the laminated structure, the stirring pin penetrating the Al-Si alloy plate and extending into the aluminum alloy plate, so that the laminated structure is solid-phase compounded into one body to form a composite plate; and stacking the aluminum alloy bottom layer of the composite plate on at least one surface of an aluminum alloy ingot, and then performing hot rolling to obtain the pre-embedded brazing agent aluminum alloy composite material. The preparation method can solve the problems of low bonding strength of the composite interface between the pre-embedded brazing agent layer and the core material layer, poor ductility, and easy cracking of the powder metallurgy blank ingot under high brazing agent content.

Description

Technical Field

[0001] This invention relates to the field of aluminum alloy brazing plate technology, and in particular 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, water-cooled plates, etc.). These heat exchangers are usually connected using brazing. Currently, the mainstream aluminum alloy brazing technology is controlled atmosphere brazing, the process of which includes: coating or spraying flux on the surface of the aluminum alloy components to be welded, followed by heating under inert gas protection to melt the brazing filler metal and fill the weld seam, thereby achieving the connection. However, this traditional process has the following problems: (1) Flux residue and waste: During the brazing process, flux needs to be sprayed / coated on the surface to be welded, but the actual weld seam area where the connection occurs only accounts for a small part of the component surface area. This results in a large amount of flux being wasted, affecting the product appearance, and even entering the coolant to accelerate the corrosion of aluminum components, reducing the service life and reliability of the heat exchanger. (2) Poor flux accessibility leads to poor soldering: As heat exchangers become smaller, lighter, and more complex (such as components with complex flow channels and fin structures), traditional spraying / coating methods cannot ensure that the flux evenly and effectively covers all areas to be soldered, especially "shadow" areas such as deep holes and narrow gaps. Poor flux accessibility directly leads to the inability to effectively remove the oxide film in these areas, resulting in soldering defects such as incomplete soldering and low solder joint rate, which seriously affects product yield and performance.

[0003] To overcome the aforementioned problems, researchers in the industry have proposed the concept of "pre-embedded flux," which involves pre-compositing the flux within the brazing filler metal layer. This allows the filler metal itself to function as both a film-breaking agent and a filler, eliminating the need for additional flux application during brazing. Specifically, flux powder is typically mixed with aluminum alloy powder and then hot isostatic pressing or other powder sintering methods to create a brazing layer ingot with pre-embedded flux. This ingot is then hot-rolled with an aluminum alloy ingot as the core material to obtain the final composite material. However, the composite interface of this method is mostly mechanically bonded, resulting in low bonding strength and poor ductility. Especially when the flux content needs to be increased to meet specific brazing requirements, the brittleness of the powder metallurgy ingot increases dramatically, thus limiting the stable preparation of high flux content materials.

[0004] While the aforementioned technologies have provided valuable insights for the development of pre-embedded flux composite materials, they still have shortcomings in terms of technical pathways, particularly in meeting the needs of large-scale, high-quality industrial production. These shortcomings mainly include low interfacial bonding strength, limited processing performance, cumbersome process steps, and high costs. Summary of the Invention

[0005] The purpose of this invention is to overcome the problems in existing technologies that rely on powder metallurgy sintering to prepare pre-embedded flux ingots, resulting in high brittleness and easy cracking of ingots with high flux content, as well as low interfacial bonding strength and poor ductility due to large differences in rheological stress during hot rolling composite with the core material. This invention provides a method for preparing pre-embedded flux aluminum alloy composite materials that does not require powder sintering and can achieve interlayer solid-state metallurgical bonding in a non-molten state. This method solves the problems of low interfacial bonding strength between the pre-embedded flux layer and the core material layer, poor ductility, and easy cracking of powder metallurgy ingots with high flux content in the preparation of existing pre-embedded flux composite materials. Furthermore, it simplifies the preparation process and reduces equipment investment and production costs.

[0006] The first aspect of this invention provides a method for preparing a pre-embedded flux aluminum alloy composite material, comprising the following steps: S1. Stack and fix the Al-Si alloy plate, the flux / Al-Si alloy plate and the aluminum alloy plate in sequence to form a laminated structure. S2. The stirring needle of the stirring friction processing tool is used to stir and friction composite the laminated structure. The stirring needle penetrates the Al-Si alloy plate and extends into the aluminum alloy plate, so that the laminated structure is solid-phase composited into one, forming a composite plate including an Al-Si alloy surface layer, a flux / Al-Si alloy intermediate layer and an aluminum alloy bottom layer. S3. The aluminum alloy bottom layer of the composite plate is laminated on at least one surface of the aluminum alloy ingot, and then hot-rolled to obtain a pre-embedded flux aluminum alloy composite material.

[0007] In some embodiments, the preparation method further includes: pressing a mixed powder containing flux and Al-Si alloy into shape to obtain the flux / Al-Si alloy plate.

[0008] In some embodiments, the preparation method does not include the step of powder metallurgy sintering the flux / Al-Si alloy plate.

[0009] In some embodiments, the conditions for the friction stir molding in step S2 include: a tool head rotation speed of 800 rpm to 2000 rpm, a welding speed of 100 mm / min to 500 mm / min, an axial pressure of 5 kN to 15 kN, and a tool head tilt angle of 1° to 3°.

[0010] In some embodiments, the stirring needle extends into the aluminum alloy plate to a depth of 0.25-0.5 times the thickness of the aluminum alloy plate.

[0011] In some of these embodiments, in step S2, the friction stir tool moves along a serpentine reciprocating scanning path on the surface of the Al-Si alloy plate, with an overlap rate of 20%-30% between adjacent welding trajectories.

[0012] In some of these embodiments, step S3, the hot rolling composite method includes: holding at 450℃-500℃ for 4h-6h followed by multiple hot rolling passes, with a final rolling temperature greater than 300℃.

[0013] In some embodiments, the preparation method further includes hot rolling followed by cold rolling and annealing.

[0014] In some of these embodiments, the cold rolling conditions include a single-pass reduction of 20%-30%.

[0015] In some of these embodiments, the annealing conditions include holding at 380°C-400°C for 2-4 hours.

[0016] In some embodiments, the mass content of Si in the Al-Si alloy plate is 7%-12.5%.

[0017] In some embodiments, the flux / Al-Si alloy plate contains 7%-12.5% ​​Si by mass in the Al-Si alloy.

[0018] In some embodiments, the flux / Al-Si alloy plate has a weight ratio of flux to Al-Si alloy of (80-95):(5-20).

[0019] In some embodiments, the flux in the flux / Al-Si alloy plate includes potassium fluoroaluminate-based fluxes, which include KAlF4 and K2AlF5.

[0020] In some embodiments, the aluminum alloy sheet is made of 3-series aluminum alloys and / or 4-series aluminum alloys.

[0021] In some embodiments, the aluminum alloy ingot is made of 3-series aluminum alloys and / or 4-series aluminum alloys.

[0022] In some embodiments, the aluminum alloy plate and the aluminum alloy ingot are made of the same material.

[0023] In some of these embodiments, the thickness ratio of the Al-Si alloy plate, the flux / Al-Si alloy plate, and the aluminum alloy plate is (30-50):(10-30):(20-40).

[0024] In some embodiments, the thickness of the Al-Si alloy plate, the flux / Al-Si alloy plate, the aluminum alloy plate, and the aluminum alloy ingot is 8%-15% based on the total thickness of the Al-Si alloy plate, the flux / Al-Si alloy plate, the aluminum alloy plate, and the aluminum alloy ingot.

[0025] The second aspect of the present invention provides a pre-embedded flux aluminum alloy composite material prepared by the preparation method of the pre-embedded flux aluminum alloy composite material described in the first aspect of the present invention.

[0026] Through the above technical solution, the preparation method of pre-embedded flux aluminum alloy composite material provided by the present invention has at least the following advantages: (1) No need for high-temperature sintering: Existing processes require high-temperature sintering at 550℃-620℃, while the present invention can complete solid-phase composite at room temperature to 300℃, saving energy and avoiding thermal decomposition of flux.

[0027] (2) Higher interfacial bonding strength: Friction stirring process causes intense plastic flow and mechanical mixing of different materials between layers, which can obtain fine grain structure and achieve true metallurgical bonding. The interfacial strength is far greater than that of powder metallurgy interlayer bonding.

[0028] (3) It can process materials with high flux content, and the process is simpler and the cost is lower: solid phase processing is not limited by the ductility of powder metallurgy billets, and can stably prepare composite materials with flux content of up to 20%. It does not require complex powder filling and vacuum sintering equipment, but only requires stirring friction processing equipment. It is easy to operate and has high production efficiency. Attached Figure Description

[0029] Figure 1 The diagram shown is a flowchart of the preparation process of a pre-embedded flux aluminum alloy composite material in one embodiment.

[0030] Figure 2 The diagram shown is a schematic diagram of the composite plate formed during the friction stir molding process in some embodiments.

[0031] Figure 3 The image shown is a metallographic photograph of the aluminum alloy composite material with single-sided pre-embedded flux in Example 2.

[0032] Explanation of reference numerals in the attached figures: 1. Al-Si alloy plate; 2. Flux / Al-Si alloy plate; 3. 3003 aluminum alloy plate; 4. Shoulder tool head with stirring pin. Detailed Implementation

[0033] 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 and 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.

[0034] In the preparation of pre-embedded flux aluminum alloy composites, to achieve the goal of pre-composite the flux within the brazing filler metal layer, thereby eliminating the need for additional flux spraying during brazing, a commonly used method is to pre-prepare a brazing layer ingot containing flux components using powder metallurgy sintering, and then roll-composite this ingot with an aluminum alloy core material layer. Specifically, the steps involve mixing flux powder and aluminum alloy powder, then forming a pre-embedded flux brazing layer ingot through hot isostatic pressing or other powder sintering methods. Subsequently, this ingot is hot-rolled and composited with an aluminum alloy ingot (such as 3003 aluminum alloy) as the core material to obtain the final composite material. This method solves the problems of significant flux waste and difficulty in integrating flux into complex cavity structures in traditional spraying processes.

[0035] The inventors of this invention found in their research that the above method is not ideal when applied to products that require a high flux content or need to be rolled into thinner specifications. After in-depth analysis, the main reasons are as follows: (1) The Al-Si alloy layer (powder metallurgy billet) with pre-embedded flux is directly hot-rolled and composited with the aluminum alloy ingot (melted billet). Due to the significant differences in composition, microstructure (powder metallurgy structure and as-cast structure) and high-temperature rheological stress between the two, the synergistic deformation ability under large deformation of hot rolling is poor, and the composite interface is prone to poor bonding, microcracks or even cracking. This problem is more prominent when it is necessary to roll into thinner specifications (such as 0.1mm-2mm). This limits its application in the preparation of high flux content (>10%) or ultra-thin composite materials. (2) In order to obtain a rollable billet, it is necessary to strictly control the amount of flux added (for example, some methods require strict control of the amount of flux added to 2%-4%). When the flux content needs to be increased (e.g., >10%) to meet specific brazing requirements, the ductility of the powder metallurgy billet decreases sharply, making it more prone to cracking when combined with the ingot, and making stable production difficult.

[0036] After in-depth research, this invention proposes a different technical approach. By introducing solid-state stirring friction processing technology, a multilayer structure containing pre-embedded flux components is directly plastically connected and composited. Under the action of frictional heat and mechanical stirring, plastic flow and atomic diffusion occur between the layers of the plate, forming a dense solid metallurgical bond, thus obtaining a composite plate. This composite plate is then treated as a whole and bonded to a metal core material through hot rolling.

[0037] In this invention, unless otherwise specified, "room temperature" refers to 20℃-25℃.

[0038] In a first aspect, the present invention provides a method for preparing a pre-embedded flux aluminum alloy composite material, which includes the following steps: S1. Stack and fix the Al-Si alloy plate, the flux / Al-Si alloy plate and the aluminum alloy plate in sequence to form a laminated structure. S2. The stirring needle of the stirring friction processing tool is used to stir and friction composite the laminated structure. The stirring needle penetrates the Al-Si alloy plate and extends into the aluminum alloy plate, so that the laminated structure is solid-phase composited into one, forming a composite plate containing an Al-Si alloy surface layer, a flux / Al-Si alloy intermediate layer and an aluminum alloy bottom layer. S3. The aluminum alloy bottom layer of the composite plate is laminated on at least one surface of the aluminum alloy ingot, and then hot-rolled to obtain a pre-embedded flux aluminum alloy composite material.

[0039] In this invention, a continuous solid-state metallurgical bond is formed between the Al-Si alloy plate, the flux / Al-Si alloy plate, and the aluminum alloy plate through friction stir compounding, resulting in an integrated functional layered structure. This layered structure is then bonded to the aluminum alloy ingot through hot rolling. This effectively avoids the problems of interface cracking and insufficient bonding force caused by poor synergistic deformation ability when the brittle powder metallurgy layer is directly hot rolled and bonded to the rolled / cast core material in the traditional powder metallurgy sintering process. This allows for the stable preparation of composite materials with high flux content, while eliminating multiple complex processes such as powder mixing, filling, and sintering, thus simplifying the process and reducing costs. Furthermore, the hot rolling composite achieves macroscopic bonding between the functional layered body and the core material, ensuring the overall interface strength of the composite plate.

[0040] According to the present invention, "Al-Si alloy plate" refers to a rolled plate with a dense structure made of aluminum-silicon alloy, which can directly withstand the upsetting and shearing of friction stir tools. It not only effectively prevents the loss of the underlying flux / Al-Si alloy plate during processing, but also provides stable mechanical support for the laminated structure through its sufficient mechanical strength, preventing overall deformation or penetration. Simultaneously, the silicon content of this Al-Si alloy plate can serve as the main source of brazing filler metal for the brazing functional layer, ensuring sufficient liquid filler metal is provided during subsequent brazing. As long as the objectives of the present invention are achieved, the Si content in the Al-Si alloy plate can be selected within a wide range. In some embodiments, the mass content of Si in the Al-Si alloy plate is 7%-12.5%, for example, 7%, 8%, 9%, 10%, 11%, 12%, 12.5%, or any combination of two of the above values. Controlling the mass content of Si in the Al-Si alloy plate within the aforementioned range ensures that the layer forms a sufficient amount of low-melting-point Al-Si eutectic liquid phase during brazing, providing sufficient liquid filler metal for the weld, thereby achieving a reliable brazed connection.

[0041] According to the present invention, "flux / Al-Si alloy plate" refers to a flux / Al-Si alloy plate containing flux and Al-Si alloy, which can be obtained by pressing a mixed powder containing flux powder and Al-Si alloy powder. That is, in some embodiments, the preparation method further includes: pressing the mixed powder containing flux and Al-Si alloy to obtain the flux / Al-Si alloy plate.

[0042] In some embodiments, the above-mentioned pressing molding can be performed using room temperature cold pressing. For example, the mixed powder, after being uniformly mixed according to a set weight ratio (e.g., the weight ratio of Al-Si alloy powder to flux powder is 80-95:5-20), is placed in a mold, and pressure is applied by a hydraulic press at room temperature to form a sheet with a set thickness and shape. Preferably, the cold pressing pressure is 100MPa-300MPa to ensure that the sheet obtains sufficient green strength to maintain its shape integrity during subsequent lamination and processing, while avoiding excessive wear of the mold or increased brittleness of the sheet due to excessive pressure. Furthermore, before pressing molding, the mixed powder needs to be thoroughly mixed (e.g., using a V-type powder mixer or a double cone powder mixer, mixing at a speed of 4r / min-6r / min for 3h-5h) to ensure that the Al-Si alloy powder and flux powder are uniformly distributed, preventing local flux agglomeration from affecting the brazing performance of the final product.

[0043] According to the present invention, the particle sizes of the flux powder and Al-Si alloy powder used in preparing the flux / Al-Si alloy plate can be selected according to actual process requirements, mixing uniformity requirements, and the performance targets of the final product. As an example, the Dv of the flux powder... 50The particle size is 10μm-50μm; as an example, the Dv of Al-Si alloy powder 50 The particle size is 20μm-60μm.

[0044] In some embodiments, the weight ratio of flux to Al-Si alloy in the flux / Al-Si alloy plate is (80-95):(5-20), for example, 80:20, 85:15, 90:10, or 95:5. Controlling the weight ratio of flux to Al-Si alloy within the aforementioned range ensures that the flux / Al-Si alloy layer has sufficient film removal and fluxing capabilities during brazing, enabling the formation of reliable weld joints. It also avoids the process risks of excessive flux content leading to a sharp increase in powder layer brittleness, difficulty in densification during friction stir processing, or cracking.

[0045] In some embodiments, the flux / Al-Si alloy plate contains 7%-12.5% ​​Si by mass, for example, 7%, 8%, 9%, 10%, 11%, 12%, 12.5%, or any combination of two of these values. Controlling the Si by mass content in the Al-Si alloy plate within the aforementioned range ensures that a sufficient amount of low-melting-point Al-Si eutectic liquid phase is formed during brazing, providing ample liquid filler metal for the weld and thus achieving a reliable brazed connection.

[0046] Furthermore, the Al-Si alloy plate and the Al-Si alloy in the flux / Al-Si alloy plate can be controlled to be homogeneous materials. Because the dense Al-Si alloy plate at the top layer and the Al-Si matrix in the intermediate powder-pressed plate have a high degree of consistency in composition and microstructure, during friction stir processing, their plastic flow behavior, atomic diffusion rate, and recrystallization characteristics in the thermoplastic state tend to synchronize. This enables more uniform and continuous mechanical mixing and atomic-level metallurgical bonding, avoiding discontinuities or stress concentrations in the interface transition zone caused by differences in rheological stress between heterogeneous materials, effectively improving the uniformity and reliability of the interlayer interface bonding strength. Simultaneously, the homogeneous matrix can synergistically form liquid brazing filler metal with consistent melting behavior during subsequent brazing heating, ensuring that the flux components in the pre-embedded flux layer are fully integrated with the molten brazing filler metal, further optimizing the spreadability and filler quality during the brazing process.

[0047] According to the present invention, as long as the objectives of the present invention can be achieved, any flux suitable for brazing aluminum alloys, capable of effectively removing the oxide film on the surface of aluminum alloys at brazing temperatures, promoting the spread and filling of the filler metal, and not undergoing harmful chemical reactions with the processed material during mixing with Al-Si alloy powder and subsequent processing. In some embodiments, the flux in the flux / Al-Si alloy plate includes potassium fluoroaluminate-based flux. Potassium fluoroaluminate-based flux includes KAlF4 (potassium tetrafluoroaluminate) and K2AlF5 (potassium pentafluoroaluminate). As an example, the flux is a KAlF4-K2AlF5 mixed powder with a KAlF4:K2AlF5 weight ratio of (1.8-5.7):1. Those skilled in the art know that the KAlF4-K2AlF5 mixed powder can be obtained through the eutectic transformation reaction of KF and AlF3.

[0048] In some embodiments, the preparation method does not include the step of powder metallurgy sintering the flux / Al-Si alloy plate before performing friction stir compounding; that is, the flux / Al-Si alloy plate retains an unsintered powder morphology inside.

[0049] In existing processes, flux-containing powder metallurgy ingots are first formed through hot isostatic pressing or sintering, followed by rolling and composite processing. The sintered flux-embedded ingots develop brittle sintered necks due to high temperatures and contain a large amount of high-hardness flux phase and residual porosity, resulting in extremely low ductility. This brittleness increases dramatically, especially with high flux content, making them prone to cracking during subsequent hot rolling deformation. This invention eliminates the sintering step, ensuring the flux-embedded plate remains in an unsintered powder-pressed state before processing. This eliminates the brittle structure at its source, preventing cracking defects during the intense plastic deformation of high flux-content materials. Furthermore, in this invention, the flux / Al-Si alloy plate maintains an unsintered powder morphology. During the intense plastic flow of subsequent friction stirring processing, these unsintered powder particles can be more efficiently sheared, broken, mixed, and re-densified, allowing the flux particles to be uniformly "locked" within the dense Al-Si matrix. This results in superior interlayer metallurgical bonding and flux distribution uniformity.

[0050] Furthermore, the powder metallurgy sintering process itself requires high temperature and long heating time, which not only increases equipment investment, energy consumption, and process cycle, but also easily leads to thermal decomposition of the flux at the sintering temperature, reducing its activity during subsequent brazing. This invention directly presses and molds the flux / Al-Si alloy plate for friction stir solid-state processing, significantly simplifying the process while avoiding the risk of flux failure due to high-temperature sintering, thus ensuring the integrity of the flux.

[0051] According to the present invention, an "aluminum alloy sheet" is a sheet material made by adding alloying elements to aluminum as the base material. It is generally produced from semi-continuous casting ingots as raw materials, and undergoes complex processes such as homogenization annealing, hot rolling (heating and rolling the ingot), cold rolling, and heat treatment to obtain a rolled aluminum alloy sheet. As long as the purpose of the present invention can be achieved, the specific material of the aluminum alloy sheet is not particularly limited. In some embodiments, the material of the aluminum alloy sheet includes 3-series aluminum alloys and / or 4-series aluminum alloys.

[0052] According to the present invention, an "aluminum alloy ingot" is a block billet formed by pouring molten aluminum alloy liquid into a mold and solidifying it. It is generally formed by pouring liquid aluminum or aluminum alloy into a mold and cooling and solidifying it. The main processes include vertical semi-continuous casting, horizontal continuous casting, etc. As long as the purpose of the present invention can be achieved, the specific material of the aluminum alloy ingot is not particularly limited. In some embodiments, the material of the aluminum alloy ingot includes 3-series aluminum alloys and / or 4-series aluminum alloys.

[0053] The above-mentioned 3-series aluminum alloys are Al-Mn series aluminum alloys, and their specific grades include, but are not limited to, at least one of 3003 aluminum alloy and 3003mod aluminum alloy (Mg content less than 0.3wt%); the above-mentioned 4-series aluminum alloys are Al-Si series aluminum alloys, and their specific grades include, but are not limited to, at least one of 4045 aluminum alloy, 4047 aluminum alloy and 4343 aluminum alloy.

[0054] In some embodiments, the aluminum alloy sheet and the aluminum alloy ingot are homogeneous materials. "Homogeneous materials" means that the two have the same composition and microstructure. During the hot rolling composite process, because the materials on both sides of the interface are homogeneous, completely synchronized plastic deformation and sufficient atomic diffusion can be achieved, fundamentally eliminating defects such as interfacial microcracks and bonding lines caused by the incoordination of deformation of dissimilar materials, thereby obtaining an interfacial bonding strength far higher than that of dissimilar material rolling.

[0055] Furthermore, to ensure a high-strength metallurgical bond between the aluminum alloy base layer of the composite panel and the aluminum alloy ingot, the aluminum alloy ingot generally needs to be milled and flattened before use. Milling removes oxide scale, oil stains, casting defects, and rough layers from the surface of the ingot, resulting in a flat, clean, and uncontaminated fresh metal surface.

[0056] Furthermore, to ensure tight interlayer contact and interface bonding quality in subsequent processing, the surfaces of the Al-Si alloy plate and aluminum alloy plate need to be degreased before being used for lamination and fixation. The specific methods for degreasing are conventional techniques in the field, and will not be elaborated upon here.

[0057] In some embodiments, the thickness ratio of the Al-Si alloy plate, the flux / Al-Si alloy plate, and the aluminum alloy plate is (30-50):(10-30):(20-40). Controlling the thickness ratio between the three layers in the composite plate within the aforementioned range allows the material proportions of each layer to be in a better range of synergistic plasticizing flow during the friction stir molding process. This ensures that the surface Al-Si alloy and the intermediate flux layer (flux / Al-Si alloy plate) have sufficient material volume to participate in solid-state metallurgical bonding to form a dense functional layer. It also ensures that the bottom aluminum alloy has sufficient thickness to achieve uniform hot-rolled composite with the subsequent metal core material. This effectively avoids the problems of insufficient bonding due to an excessively thin layer or inconsistent deformation due to an excessively thick layer. Ultimately, a pre-embedded flux aluminum alloy composite material with a moderate proportion of brazed functional layer thickness, high interlayer interface bonding strength, and balanced overall mechanical properties is obtained stably.

[0058] According to the present invention, "friction stir compound forming" refers to a processing method or step in which, under solid conditions where the material does not reach its melting point, the material undergoes plastic flow and achieves bonding by utilizing the frictional heat and mechanical stirring between a rotating tool and the workpiece. Examples include, but are not limited to: using a shoulder tool head with a stirring pin to perform top-down penetrating stirring of a laminated structure; using a pinless shoulder for surface friction treatment only; or using a double-shoulder / double-sided stirring process. Here, "solid phase" can refer to a peak temperature in the processing area that is lower than the solidus temperature of any metallic component in the processed material, thereby avoiding the formation of a molten pool or liquid solidification structure; for example, in aluminum alloys, the processing temperature is typically controlled between 380°C and 500°C, below its solidus temperature (approximately 575°C).

[0059] According to the present invention, the process parameters for achieving friction stir molding can be adjusted according to the specific material thickness, tool head specifications, and equipment capabilities. In some embodiments, the conditions for friction stir molding in step S2 include: a tool head rotation speed of 800 rpm-2000 rpm (e.g., 800 rpm, 1000 rpm, 1200 rpm, 1500 rpm, 1800 rpm, or 2000 rpm), a welding speed of 100 mm / min-500 mm / min (e.g., 100 mm / min, 200 mm / min, 300 mm / min, 400 mm / min, or 500 mm / min), an axial pressure of 5 kN-15 kN (e.g., 5 kN, 7 kN, 10 kN, 12 kN, or 15 kN), and a tool head tilt angle of 1°-3° (e.g., 1°, 2°, or 3°).

[0060] The depth to which the stirring pin penetrates the aluminum alloy plate can be adjusted according to the thickness of the aluminum alloy plate. In some embodiments, in step S2, the depth of the stirring pin penetration into the aluminum alloy plate is 0.25-0.5 times the thickness of the aluminum alloy plate, for example, 0.25 times, 0.3 times, 0.375 times, 0.4 times, or 0.5 times, preferably 0.25-0.375 times. For example, when the thickness of the aluminum alloy plate is 4 mm, the penetration depth is 1 mm-2 mm. Controlling the depth of the stirring pin penetration into the aluminum alloy plate within the aforementioned range ensures that the stirring pin fully actuates the underlying interface material to undergo plastic flow, achieving a strong atomic-level metallurgical bond with the flux / Al-Si alloy plate, while effectively avoiding weak bonding due to shallow penetration or excessive thinning of the underlying layer, penetrating damage, or even contamination of the subsequent hot-rolled bonding surface due to excessive penetration.

[0061] In some embodiments, in step S2, the friction stir machining tool moves along a serpentine reciprocating scanning path on the surface of the Al-Si alloy plate. The "serpentine reciprocating scanning path" refers to the friction stir machining tool moving along a continuously zigzagging trajectory on the surface to be processed, thereby gradually covering the entire surface area and forming overlapping welding paths. For example, this may include, but is not limited to: moving in a zigzag pattern along parallel lines, making adjacent straight segments opposite in direction and adjacent to each other; or using a slightly curved reciprocating curve to ensure no missed areas between the trajectories.

[0062] Furthermore, the overlap rate between adjacent welding trajectories is 20%-30%. The serpentine path enables full-coverage scanning welding of the entire surface of the Al-Si alloy plate, ensuring no unbonded blind spots. "Overlap rate" refers to the degree of overlap in the width direction between two adjacent friction stir machining trajectories, characterizing the proportion of the processed area that is repeatedly stirred. Controlling the overlap rate at 20%-30% avoids incomplete coverage between adjacent welding trajectories, preventing defects or uneven strength in interlayer bonding. If the overlap rate is too high, although complete coverage is guaranteed, it increases unnecessary processing time and heat input, and may even cause defects due to over-stirring of the material, reducing processing efficiency.

[0063] According to the present invention, after processing in step S2, the originally separate layered structure becomes a single composite plate. Due to the friction stir processing, the original interfaces between the Al-Si alloy surface layer formed by the Al-Si alloy plate, the flux / Al-Si alloy intermediate layer formed by the flux / Al-Si alloy plate, and the aluminum alloy bottom layer formed by the aluminum alloy plate have completely disappeared, forming a tight solid-state metallurgical bond. "Solid-state metallurgical bond" refers to a connection method in which the joined materials do not undergo overall melting during processing, but rather achieve interfacial bonding through plastic deformation, mechanical mixing, and atomic diffusion in a thermoplastic state.

[0064] According to the present invention, the aluminum alloy underlayer of the composite plate is laminated on at least one surface of the aluminum alloy ingot, which means that a single-sided composite or a double-sided composite method can be adopted. Single-sided composite means that the aluminum alloy underlayer of a composite plate is laminated to one surface of an aluminum alloy ingot; double-sided composite means that the aluminum alloy underlayers of two composite plates are respectively laminated to two opposite surfaces of an aluminum alloy ingot.

[0065] In some embodiments, based on the total thickness of the Al-Si alloy plate, flux / Al-Si alloy plate, aluminum alloy plate, and aluminum alloy ingot, the thickness percentage of the Al-Si alloy plate and flux / Al-Si alloy plate is 8%-15%, for example, 8%, 9%, 10%, 11%, 12%, 13%, 14%, or 15%. This percentage ensures that the brazing functional layer has a sufficient volume fraction in the final product, allowing for the molten production of sufficient liquid brazing filler metal and active flux during brazing to fully fill the weld gap and form full rounded corners, meeting the requirements for reliable brazing connections. When using a double-sided composite, the thickness of the Al-Si alloy plate and flux / Al-Si alloy plate refers to the thickness of one side.

[0066] In some embodiments, step S3 involves hot rolling followed by multiple passes of hot rolling after holding at 450℃-500℃ for 4-6 hours, with a final rolling temperature greater than 300℃ (e.g., 330℃-380℃). Holding at 450-500℃ for 4-6 hours ensures the material uniformly reaches the required hot rolling temperature. Within this temperature range, the aluminum alloy exhibits good plasticity, facilitating deformation and promoting interfacial atomic diffusion. The final rolling temperature requirement of greater than 300℃ ensures the material retains a certain temperature after the final rolling pass, preventing severe work hardening or cracking due to excessively low temperatures.

[0067] In this invention, the composite material can be hot-rolled to an intermediate thickness according to the final required thickness. For example, when the laminated billet needs to be rolled to an intermediate thickness (e.g., 5mm-8mm), 5-9 passes of hot rolling can be performed, with the total reduction typically controlled between 80% and 95%. Those skilled in the art will understand that the specific selection of the number of passes needs to comprehensively consider the initial thickness of the billet, the target intermediate thickness, the mill capacity, and the high-temperature deformation characteristics of the material, and is not limited to the above example.

[0068] In some embodiments, the preparation method further includes cold rolling and annealing after hot rolling composite. Specifically, the hot-rolled composite plate is cooled to room temperature and then subjected to multiple cold rolling passes (e.g., 4-11 passes) to precisely roll the plate to the final finished thickness, e.g., 0.3mm-2mm, with the reduction per pass controlled at 20%-30%. After cold rolling, the finished product is annealed according to the product condition requirements, for example, held at 380℃-400℃ for 2-4 hours, followed by air cooling or furnace cooling. Annealing can eliminate cold rolling work hardening, restore the plasticity of the material, and homogenize the microstructure, thereby obtaining a final product with good mechanical properties and brazing performance. Those skilled in the art will understand that the specific cold rolling passes and annealing parameters can be adjusted according to the target thickness, material condition, and equipment capabilities, and are not limited to the examples above.

[0069] As an example, the preparation flow chart of the pre-embedded flux aluminum alloy composite material is as follows: Figure 1 As shown in the diagram, a composite plate is formed during the friction stir molding process. Figure 2 As shown.

[0070] The preparation of pre-embedded flux aluminum alloy composite material includes the following steps: Step 1: Preparation of precast panels Al-Si alloy plate 1: Rolled Al-(7wt%-12.5wt%)Si alloy plate (such as 4045, 4047) is used, with a thickness ratio of 30%-50%, and the surface is cleaned and degreased.

[0071] Flux / Al-Si alloy plate 2: Al-(7wt%-12.5wt%)Si alloy powder (Dv) 50 =20μm-60μm) and potassium fluoroaluminate flux powder (Dv) 50 =10μm-60μm) are mixed evenly by weight ratio (80-95):(5-20) and pressed into a sheet material by cold pressing (pressure 100MPa-300MPa) at room temperature, with a thickness ratio of 10%-30%.

[0072] 3003 Aluminum Alloy Plate 3: Rolled 3003 aluminum alloy plate with a thickness ratio of 20%-40%, and surface cleaned and degreased.

[0073] Step 2: Layering and fixing Stack the Al-Si alloy plate 1, flux / Al-Si alloy plate 2, and 3003 aluminum alloy plate 3 in a top-to-bottom order and fix them with clamps to ensure tight contact between the layers without gaps.

[0074] Step 3: Friction Stir Molding Equipment: Friction stir processing equipment, equipped with a tool head (4-piece tool head with a shoulder and stirring pin).

[0075] Process parameters: Tool head speed: 800rpm-2000rpm; Welding speed: 100mm / min-500mm / min; Axial pressure: 5kN-15kN; Tool head tilt angle: 1°-3°; Stirring pin length: designed according to the total thickness of the laminate to ensure penetration of Al-Si board and Al-Si+ flux board, and to a depth of 0.25-0.5 times the thickness of 3003 board; Shoulder diameter: 10-20mm; Motion path: serpentine path (reciprocating scan), with an overlap rate of 20%-30% between adjacent trajectories; Welding process: Start the equipment, the tool head rotates and presses down to the set depth, moving in a serpentine path to fully cover the surface of the Al-Si alloy plate 1. Under the action of frictional heat and mechanical stirring, the interlayer materials of Al-Si alloy plate 1, flux / Al-Si alloy plate 2, and 3003 aluminum alloy plate 3 undergo plastic flow and mixing, forming a dense solid metallurgical bond.

[0076] Post-soldering: A composite plate is obtained consisting of an Al-Si alloy surface layer, a flux / Al-Si alloy intermediate layer, and a 3003 aluminum alloy bottom layer.

[0077] Step 4: Hot rolling composite Core material preparation: 3003 aluminum alloy ingot, surface milled flat.

[0078] Composite board: Surface milled flat.

[0079] Design of the thickness ratio between the composite plate and the ingot: The total thickness ratio of the single-sided brazed functional layer (Al-Si alloy surface layer + flux / Al-Si alloy intermediate layer) is required to be 8%-15%. After hot rolling composite, the thickness ratio between the composite plate and the ingot is basically the same.

[0080] Single-sided composite: The 3003 aluminum alloy bottom layer of the above composite plate is stacked with a 3003 aluminum alloy ingot (Al-Si alloy surface layer facing out).

[0081] Double-sided composite: Two composite plates are stacked on the top and bottom sides of a 3003 aluminum alloy ingot.

[0082] Heat the stacked billets to 450℃-500℃ and hold for 4-6 hours.

[0083] Multiple hot rolling passes are performed on a hot rolling mill, with a final rolling temperature greater than 300℃, and the thickness is 5mm-8mm.

[0084] Step 5: Cold rolling and finished product annealing Cool the hot-rolled plate to room temperature.

[0085] Multiple cold rolling passes are performed to achieve a final product thickness of 0.3mm-2.0mm, with a single pass reduction of 20%-30%.

[0086] Anneal the finished product according to the product condition requirements: temperature 380℃-400℃, hold for 2h-4h.

[0087] The final product obtained is a pre-embedded flux aluminum alloy composite material.

[0088] In a second aspect, the present invention provides a pre-embedded flux aluminum alloy composite material prepared by the preparation method of the pre-embedded flux aluminum alloy composite material provided in the first aspect above.

[0089] In the pre-embedded flux aluminum alloy composite material, the Al-Si alloy surface layer and the flux / Al-Si alloy intermediate layer together serve as the brazing functional layer, while the aluminum alloy layer and the aluminum alloy ingot layer together serve as the core material layer.

[0090] The pre-embedded flux aluminum alloy composite material provided by this invention has achieved a dense internal structure, uniform flux distribution, and high-strength solid metallurgical bonding at the interlayer interface through the preparation method of this invention. It also achieves homogeneous high-strength hot-rolled composite with the core material. Thus, it can still avoid processing cracking under high flux content and has significant advantages such as excellent brazing performance and interface bonding strength.

[0091] The present invention will be described in detail below through embodiments.

[0092] In the following examples and comparative examples: The characteristics of the composite interface can be observed by metallographic photographs of aluminum alloy composite materials with pre-embedded flux.

[0093] The interfacial bonding strength of the final pre-embedded flux aluminum alloy composite material was tested using an electronic universal testing machine at a tensile speed of 5 mm / min.

[0094] The pre-embedded flux aluminum alloy composite material was heated from room temperature to a specified temperature and held at that temperature for a specified time to simulate CAB brazing. Its spread area was tested in accordance with GB / T 11364-2020.

[0095] Example 1 This embodiment provides a method for friction stir molding of double-sided pre-embedded flux aluminum alloy composite materials, including the following steps: (1) Preparation of precast panels Al-Si alloy plate: Made of 4045 aluminum alloy rolled plate (Al-10.0wt%Si), 4mm thick, surface cleaned and degreased.

[0096] Flux / Al-Si alloy plate: Al-10.0wt%Si alloy powder (Dv) 50 =40μm, oxygen content 250ppm) and potassium fluoroaluminate flux powder (KAlF4-K2AlF5 mixed powder, KAlF4:K2AlF5 weight ratio is 5.7:1, Dv 50 =25μm) were mixed uniformly at a weight ratio of 88:12. A V-type powder mixer was used at a speed of 5 r / min for 4 h. The uniformly mixed powder was then pressed into flux / Al-Si alloy plates with a thickness of 2 mm using a mold at room temperature.

[0097] 3003 aluminum alloy sheet: Made of rolled 3003 aluminum alloy sheet, 4mm thick, surface cleaned and degreased.

[0098] The total thickness of the composite plate is 10mm, of which the thickness of the brazing functional layer (Al-Si alloy plate + flux / Al-Si alloy plate) is 6mm.

[0099] (2) Layered fixing The Al-Si alloy plate, flux / Al-Si alloy plate, and 3003 aluminum alloy plate are stacked in a top-to-bottom order and fixed with a clamp to ensure tight contact between the layers without gaps, thus obtaining a laminated structure.

[0100] (3) Stir-friction composite molding Friction stir welding equipment, equipped with a shoulder tool head with a stirring pin, was used to perform friction stir composite forming of the laminated structure. The tool head rotation speed was 1200 rpm, the welding speed was 300 mm / min, the axial pressure was 10 kN, the tool head tilt angle was 2°, the stirring pin length was designed to be 7.5 mm (ensuring penetration of the Al-Si alloy plate (4 mm) and the flux / Al-Si alloy plate (2 mm) and a depth of 1.5 mm into the 3003 aluminum alloy plate), and the shoulder diameter was 16 mm. The tool head moved along a serpentine reciprocating scanning path on the surface of the Al-Si alloy plate, with an overlap rate of 30% between adjacent trajectories, performing full-coverage welding on the entire plate surface. After welding, a composite plate was obtained, consisting of an Al-Si alloy surface layer, a flux / Al-Si alloy intermediate layer, and a 3003 aluminum alloy bottom layer, with a total thickness of approximately 10 mm.

[0101] (4) Hot-rolled composite (double-sided) Prepare two milled and smoothed composite plates and a 40mm thick 3003 aluminum alloy ingot. Stack the 3003 aluminum alloy bottom layer of the composite plate onto the top and bottom surfaces of the 3003 aluminum alloy ingot, with the Al-Si alloy surface layer of the composite plate facing outwards, to obtain a laminated billet. The total thickness of the single-sided brazed functional layer (Al-Si alloy surface layer and flux / Al-Si alloy intermediate layer) is approximately 6mm, and the proportion of the single-sided brazed functional layer to the final product thickness is 6mm / 60mm × 100% = 10%. Heat the laminated billet to 480℃ and hold for 5 hours. Perform 7 passes of hot rolling on a hot rolling mill, with a total reduction of approximately 90%, a final rolled thickness of 6mm, and a final rolling temperature of 350℃ to obtain a hot-rolled plate.

[0102] (5) Cold rolling and annealing The hot-rolled plate was cooled to room temperature and then cold-rolled in 6 passes, with the reduction per pass controlled at 25%-30%, 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 to obtain a double-sided symmetrical aluminum alloy composite material with embedded flux.

[0103] (6) Product structure and performance A double-sided symmetrical pre-embedded flux aluminum alloy composite material with a total thickness of 0.8 mm was obtained. The single-sided brazing functional layer (Al-Si alloy surface layer + flux / Al-Si alloy intermediate layer) has a thickness of approximately 0.08 mm, accounting for 10% of the total thickness; of which the Al-Si alloy surface layer is approximately 0.053 mm and the flux / Al-Si alloy intermediate layer is approximately 0.027 mm; the core material layer (3003 aluminum alloy layer + 3003 aluminum alloy ingot) has a thickness of approximately 0.64 mm, accounting for 80% of the total thickness.

[0104] The composite interface showed no cracks or pores; the interfacial bonding strength, as measured by the T-type peel test, averaged 45 N / mm; and the average spread area in simulated CAB brazing (600℃ × 5 min) was 524 mm². 2 No obvious flux residue was found on the surface after brazing.

[0105] Example 2 This embodiment provides a method for friction stir molding of single-sided pre-embedded flux aluminum alloy composite materials, including the following steps: (1) Preparation of precast panels Al-Si alloy plate: Made of 4047 aluminum alloy rolled plate (Al-12.0wt%Si), 5mm thick.

[0106] Flux / Al-Si alloy plate: Al-12.0wt%Si alloy powder (Dv) 50 =50μm, oxygen content 280ppm) and potassium fluoroaluminate flux powder (KAlF4-K2AlF5 mixed powder, KAlF4 and K2AlF5 weight ratio is 1.8:1, Dv 50=35μm) were mixed evenly at a weight ratio of 85:15. A double cone mixer was used at a speed of 4 r / min for 5 h. The evenly mixed powder was then pressed into 1 mm thick plates at room temperature using a mold.

[0107] 3003 aluminum alloy sheet: Rolled 3003 aluminum alloy sheet, 4mm thick.

[0108] The total thickness of the composite plate is 10mm, and the thickness of the brazing functional layer (Al-Si plate alloy + flux / Al-Si alloy plate) is 6mm.

[0109] (2) Layered fixing The Al-Si alloy plate, flux / Al-Si alloy plate, and 3003 aluminum alloy plate are stacked in a top-to-bottom order and fixed with a clamp to ensure tight contact between the layers without gaps, thus obtaining a laminated structure.

[0110] (3) Stir-friction composite molding Friction stir welding equipment, equipped with a shoulder tool head featuring a stirring pin, was used to perform friction stir composite forming of the laminated structure. The tool head rotated at 1000 rpm, the welding speed was 250 mm / min, the axial pressure was 12 kN, the tool head tilt angle was 1°, and the stirring pin length was designed to be 7 mm (ensuring penetration of the Al-Si alloy plate (5 mm) + flux / Al-Si alloy plate (1 mm) and a depth of 1 mm into the 3003 aluminum alloy plate). The shoulder diameter was 14 mm. The tool head moved in a serpentine reciprocating scanning path across the Al-Si alloy plate surface, with an overlap rate of 20% between adjacent tracks, achieving full coverage welding across the entire plate surface. After welding, a composite plate was obtained, comprising an Al-Si alloy surface layer, a flux / Al-Si alloy intermediate layer, and a 3003 aluminum alloy bottom layer, with a total thickness of approximately 10 mm.

[0111] Prepare a composite plate with a milled and smooth surface and a 65mm thick 3003 aluminum alloy ingot. Lay the 3003 aluminum alloy bottom layer of the composite plate onto one surface of the 3003 aluminum alloy ingot, with the Al-Si alloy surface layer of the composite plate facing outwards, to obtain the laminated billet. The brazed functional layer accounts for 8% of the final product thickness (6mm / 75mm × 100%). Heat the laminated billet to 470℃ and hold for 6 hours. Perform 9 passes of hot rolling, with a total reduction of approximately 89.3%, a final rolled thickness of 8mm, and a final rolling temperature of 330℃ to obtain the hot-rolled plate.

[0112] (5) Cold rolling and annealing The hot-rolled plate was cooled to room temperature and then cold-rolled in 8 passes, with the reduction per pass controlled at 20%-25% for a final rolled thickness of 1.2 mm. The finished product was then annealed: held at 380℃ for 4 hours and air-cooled to obtain a single-sided pre-embedded flux aluminum alloy composite material.

[0113] (6) Product structure and performance A single-sided pre-embedded flux aluminum alloy composite material with a total thickness of 1.2 mm was obtained. The single-sided brazing functional layer (Al-Si alloy surface layer + flux / Al-Si alloy intermediate layer) has a thickness of approximately 0.096 mm, accounting for 8% of the total thickness; of which the Al-Si alloy surface layer is approximately 0.08 mm and the flux / Al-Si alloy intermediate layer is approximately 0.016 mm; the core material layer (3003 aluminum alloy layer + 3003 aluminum alloy ingot) has a thickness of approximately 1.104 mm, accounting for 92% of the total thickness.

[0114] Metallographic photographs of single-sided pre-embedded flux aluminum alloy composite materials are shown below. Figure 3 As shown, the composite interface showed no cracks or pores; the average interfacial bonding strength, as demonstrated by the T-type peel test, was 48 N / mm; and the average spread area in simulated CAB brazing (598℃ × 6 min) was 513 mm². 2 No obvious flux residue was found on the surface after brazing.

[0115] Example 3 This embodiment provides a method for friction stir molding of thin-gauge double-sided pre-embedded flux aluminum alloy composite materials, including the following steps: (1) Preparation of precast panels Al-Si alloy plate: Made of 4343 aluminum alloy rolled plate (Al-7.5wt%Si), 3mm thick.

[0116] Flux / Al-Si alloy plate: Al-7.5wt%Si alloy powder (Dv) 50 =30μm, oxygen content 220ppm) and potassium fluoroaluminate flux powder (KAlF4-K2AlF5 mixed powder, KAlF4 and K2AlF5 weight ratio is 4:1, Dv 50 =15μm) were mixed uniformly at a weight ratio of 91:9. A V-type powder mixer was used at a speed of 6 r / min for 3 hours. The uniformly mixed powder was then pressed into 3 mm thick plates at room temperature using a mold.

[0117] 3003 aluminum alloy sheet: Rolled 3003 aluminum alloy sheet, 4mm thick.

[0118] The total thickness of the composite plate is 10mm, and the thickness of the brazing functional layer (Al-Si alloy plate + flux / Al-Si alloy plate) is 6mm.

[0119] (2) Layered fixing The Al-Si alloy plate, flux / Al-Si alloy plate, and 3003 aluminum alloy plate are stacked in a top-to-bottom order and fixed with a clamp to ensure tight contact between the layers without gaps, thus obtaining a laminated structure.

[0120] (3) Stir-friction composite molding Friction stir welding equipment, equipped with a shoulder tool head featuring a stirring pin, was used to perform friction stir composite forming of the laminated structure. The tool head rotated at 1500 rpm, the welding speed was 350 mm / min, the axial pressure was 8 kN, the tool head tilt angle was 3°, and the stirring pin length was designed to be 7.5 mm (ensuring penetration of the Al-Si alloy plate (3 mm) + flux / Al-Si alloy plate (3 mm) and reaching 1.5 mm into the 3003 aluminum alloy plate). The shoulder diameter was 16 mm. The tool head moved along a serpentine reciprocating scanning path on the Al-Si alloy plate surface, with an overlap rate of 30% between adjacent tracks, achieving full coverage welding across the entire plate surface. After welding, a composite plate was obtained, comprising an Al-Si alloy surface layer, a flux / Al-Si alloy intermediate layer, and a 3003 aluminum alloy bottom layer, with a total thickness of approximately 10 mm.

[0121] (4) Hot-rolled composite (double-sided) Prepare two milled and smoothed composite plates and a 30mm thick 3003 aluminum alloy ingot. Stack the 3003 aluminum alloy bottom layer of the composite plate onto the top and bottom surfaces of the 3003 aluminum alloy ingot, with the Al-Si alloy surface layer of the composite plate facing outwards, to obtain a laminated billet. The total thickness of the single-sided brazed functional layer (Al-Si alloy surface layer and flux / Al-Si alloy intermediate layer) is 6mm, accounting for 12% of the final product thickness (6mm / 50mm × 100%). Heat the laminated billet to 500℃ and hold for 4 hours. Perform 6 passes of hot rolling with a total reduction of approximately 90%, a final rolled thickness of 5mm, and a final rolling temperature of 380℃ to obtain a hot-rolled plate.

[0122] (5) Cold rolling and annealing The hot-rolled plate was cooled to room temperature and then cold-rolled in 9 passes, with the reduction per pass controlled at 20%-25%, resulting in a final rolled thickness of 0.5 mm. The finished product was then annealed: held at 400℃ for 2 hours and air-cooled to obtain a double-sided symmetrical aluminum alloy composite material with embedded flux.

[0123] (6) Product structure and performance A double-sided symmetrical pre-embedded flux aluminum alloy composite material with a total thickness of 0.5 mm was obtained. The single-sided brazing functional layer (Al-Si alloy surface layer + flux / Al-Si alloy intermediate layer) has a thickness of approximately 0.06 mm, accounting for 12% of the total thickness; of which the Al-Si alloy surface layer is approximately 0.03 mm and the flux / Al-Si alloy intermediate layer is approximately 0.03 mm; the core material layer (3003 aluminum alloy layer + 3003 aluminum alloy ingot) has a thickness of approximately 0.38 mm, accounting for 76% of the total thickness.

[0124] The composite interface exhibited good bonding with no peeling; the average interfacial bonding strength, as demonstrated by the T-type peel test, was 42 N / mm. Simulated CAB brazing (605℃ × 4 min) resulted in an average spread area of ​​438 mm². 2 No obvious flux residue was found on the surface after brazing.

[0125] Example 4 This embodiment follows the steps of Embodiment 1, except that the proportions of each layer and the length of the stirring pin are changed. Specifically, the thickness of the Al-Si alloy plate is adjusted to 2mm, the thickness of the flux / Al-Si alloy plate is adjusted to 2mm, the thickness of the 3003 aluminum alloy plate is adjusted to 6mm, the total thickness of the composite plate remains 10mm, and the length of the stirring pin is adjusted to 6mm.

[0126] The rest is the same as in Example 1, and the final result is a double-sided symmetrical pre-embedded flux aluminum alloy composite material.

[0127] Product structure and performance A double-sided symmetrical pre-embedded flux aluminum alloy composite material with a total thickness of 0.8 mm was obtained. The single-sided brazing functional layer (Al-Si alloy surface layer + flux / Al-Si alloy intermediate layer) has a thickness of approximately 0.053 mm, accounting for 6.67% of the total thickness; of which the Al-Si alloy surface layer is approximately 0.0265 mm and the flux / Al-Si alloy intermediate layer is approximately 0.0265 mm; the core material layer (3003 aluminum alloy layer + 3003 aluminum alloy ingot) has a thickness of approximately 0.694 mm, accounting for 86.66% of the total thickness.

[0128] The interfacial bonding strength, as measured by T-peel testing, averaged 42 N / mm. Simulated CAB brazing (600℃ × 5 min) resulted in an average spread area of ​​approximately 456 mm². 2 No obvious flux residue was found on the surface after brazing.

[0129] Example 5 This embodiment follows the steps of Embodiment 1, except that the proportions of each layer and the length of the stirring pin are changed. Specifically, the thickness of the Al-Si alloy plate is adjusted to 6mm, the thickness of the flux / Al-Si alloy plate is adjusted to 2mm, the thickness of the 3003 aluminum alloy plate is adjusted to 2mm, the total thickness of the composite plate remains 10mm, and the length of the stirring pin is adjusted to 9mm.

[0130] The rest is the same as in Example 1, and the final result is a double-sided symmetrical pre-embedded flux aluminum alloy composite material.

[0131] Product structure and performance A double-sided symmetrical pre-embedded flux aluminum alloy composite material with a total thickness of 0.8 mm was obtained. The single-sided brazing functional layer (Al-Si alloy surface layer + flux / Al-Si alloy intermediate layer) has a thickness of approximately 0.107 mm, accounting for 13.3% of the total thickness; of which the Al-Si alloy surface layer is approximately 0.08 mm and the flux / Al-Si alloy intermediate layer is approximately 0.027 mm; the core material layer (3003 aluminum alloy layer + 3003 aluminum alloy ingot) has a thickness of approximately 0.586 mm, accounting for 73.4% of the total thickness.

[0132] The interfacial bonding strength, as measured by T-peel testing, averaged 32 N / mm. Simulated CAB brazing (600℃ × 5 min) resulted in an average spread area of ​​480 mm². 2 No obvious flux residue was found on the surface after brazing.

[0133] Example 6 This embodiment follows the steps of Embodiment 1, except that the proportions of each layer are adjusted. Specifically, the thickness of the Al-Si alloy plate is adjusted to 5mm, the thickness of the flux / Al-Si alloy plate is adjusted to 1mm, the thickness of the 3003 aluminum alloy plate is adjusted to 4mm, and the total thickness of the composite plate remains 10mm.

[0134] The rest is the same as in Example 1, and the final result is a double-sided symmetrical pre-embedded flux aluminum alloy composite material.

[0135] Product structure and performance A double-sided symmetrical pre-embedded flux aluminum alloy composite material with a total thickness of 0.8 mm was obtained. The single-sided brazing functional layer (Al-Si alloy surface layer + flux / Al-Si alloy intermediate layer) has a thickness of approximately 0.08 mm, accounting for 10% of the total thickness; of which the Al-Si alloy surface layer is approximately 0.067 mm and the flux / Al-Si alloy intermediate layer is approximately 0.013 mm; the core material layer (3003 aluminum alloy layer + 3003 aluminum alloy ingot) has a thickness of approximately 0.64 mm, accounting for 80% of the total thickness.

[0136] The interfacial bonding strength, as measured by T-peel testing, averaged 42 N / mm. Simulated CAB brazing (600℃ × 5 min) resulted in an average spread area of ​​367 mm². 2 No obvious flux residue was found on the surface after brazing.

[0137] Example 7 This embodiment follows the steps of Embodiment 1, except that the preparation of the flux / Al-Si alloy plate is different from that in Embodiment 1. Specifically, the flux / Al-Si alloy plate is prepared as follows: the mixed powder is prepared according to the method of Embodiment 1 and pressed into a plate with a thickness of 2 mm. Then, the pressed plate is sintered under nitrogen protection at a sintering temperature of 420°C and a holding time of 2 h to obtain the flux / Al-Si alloy plate.

[0138] Product Performance The interfacial bonding strength, as measured by the T-type peel test, averaged 30 N / mm. Simulated CAB brazing (600℃ × 5 min) resulted in an average spread area of ​​412 mm². 2 Furthermore, a small amount of flux residue remains.

[0139] Example 8 This embodiment follows the steps of Embodiment 1, except that the preparation of the flux / Al-Si alloy plate differs from that in Embodiment 1. Specifically, the preparation steps of the flux / Al-Si alloy plate are as follows: Al-10.0wt%Si alloy powder (Dv... 50 =40μm, oxygen content 250ppm) and potassium fluoroaluminate flux powder (KAlF4-K2AlF5 mixed powder, KAlF4:K2AlF5 weight ratio is 5.7:1, Dv 50 =25μm) were mixed uniformly at a weight ratio of 88:12. A V-type powder mixer was used at a speed of 5 r / min for 4 hours. The uniformly mixed powder was placed into a stainless steel sleeve, sealed, and then pressed in a hot isostatic press to obtain a hot isostatic ingot. The pressing process parameters were: vacuum to 2 Pa, temperature 470℃, pressure 120 MPa, and holding time for 4 hours. After pressing, the hot isostatic ingot was machined (milled) to remove the stainless steel sleeve, and further processed (preliminary milling, precision milling, surface cleaning) into a flux / Al-Si alloy plate with a thickness of 2 mm.

[0140] Product Performance The interfacial bonding strength, as measured by the T-type peel test, averaged 35 N / mm. Simulated CAB brazing (600℃ × 5 min) resulted in an average spread area of ​​430 mm². 2 Furthermore, a small amount of flux residue remains.

[0141] Comparative Example 1 This comparative example provides a friction stir molding method for double-sided pre-embedded flux aluminum alloy composite materials, including the following steps: (1) Preparation of precast panels Al-Si alloy plate: Same as in Example 1.

[0142] Flux / Al-Si alloy plate: Same as in Example 1.

[0143] The total thickness of the composite plate is 6mm, of which the thickness of the brazing functional layer (Al-Si alloy plate + flux / Al-Si alloy plate) is 6mm.

[0144] (2) Layered fixing Al-Si alloy plates and flux / Al-Si alloy plates are stacked from top to bottom and fixed with clamps to ensure tight contact between layers without gaps, thus obtaining a laminated structure.

[0145] (3) Stir-friction composite molding Referring to Example 1, the difference is that the stirring needle is designed to be 5.5 mm long (to ensure penetration of the Al-Si alloy plate (4 mm) and penetration into the flux / Al-Si alloy plate by 1.5 mm), resulting in a composite plate containing an Al-Si alloy surface layer and a pre-embedded flux aluminum alloy base, with a total thickness of approximately 6 mm.

[0146] (4) Hot-rolled composite (double-sided) Referring to Example 1, the difference is that two composite plates with milled and flat surfaces and a 3003 aluminum alloy ingot with a thickness of 48mm are prepared. The pre-embedded flux aluminum alloy bottom layer of the composite plate is stacked on the upper and lower surfaces of the 3003 aluminum alloy ingot, with the Al-Si alloy surface layer of the composite plate facing outward, to obtain the stacked blank. The rest is the same as in Example 1, and finally a hot-rolled plate is obtained.

[0147] (5) Cold rolling and annealing Referring to Example 1, a double-sided symmetrical pre-embedded flux aluminum alloy composite material was obtained.

[0148] (6) Product structure and performance A double-sided symmetrical pre-embedded flux aluminum alloy composite material with a total thickness of 0.8 mm was obtained. The single-sided brazing functional layer (Al-Si alloy surface layer + flux / Al-Si alloy intermediate layer) has a thickness of approximately 0.08 mm, accounting for 10% of the total thickness; of which the Al-Si alloy surface layer is approximately 0.053 mm and the flux / Al-Si alloy intermediate layer is approximately 0.027 mm; the core material layer (3003 aluminum alloy ingot) has a thickness of approximately 0.64 mm, accounting for 80% of the total thickness.

[0149] Simulated CAB brazing (600℃×5min), average spread area 350mm. 2 A small amount of flux residue remains on the surface after brazing.

[0150] Comparative Example 2 This comparative example provides a friction stir molding method for double-sided pre-embedded flux aluminum alloy composite materials, including the following steps: (1) Preparation of precast panels Flux / Al-Si alloy plate: Al-10.0wt%Si alloy powder (Dv) 50 =40μm, oxygen content 250ppm) and potassium fluoroaluminate flux powder (KAlF4-K2AlF5 mixed powder, Dv) 50 =25μm) were mixed uniformly at a weight ratio of 88:12. A V-type powder mixer was used at a speed of 5 r / min for 4 h. The uniformly mixed powder was then pressed into a 6 mm thick flux / Al-Si alloy plate at room temperature using a mold.

[0151] 3003 aluminum alloy sheet: Same as Example 1.

[0152] The total thickness of the composite plate is 10mm, of which the thickness of the brazing functional layer (flux / Al-Si alloy plate) is 6mm.

[0153] (2) Layered fixing The flux / Al-Si alloy plate and the 3003 aluminum alloy plate are stacked in order from top to bottom and fixed with a clamp to ensure tight contact between the layers without gaps, thus obtaining a laminated structure.

[0154] (3) Stir-friction composite molding Referring to Example 1, a composite plate comprising a flux / Al-Si alloy surface layer and a 3003 aluminum alloy bottom layer was obtained, with a total thickness of approximately 10 mm.

[0155] (4) Hot-rolled composite (double-sided) Referring to Example 1, the difference is that the 3003 aluminum alloy bottom layer of the composite plate is stacked on the upper and lower sides of the 3003 aluminum alloy ingot, with the flux / Al-Si alloy surface layer of the composite plate facing outwards, to obtain a laminated billet. The total thickness of the single-sided brazed functional layer (flux / Al-Si alloy surface layer) is approximately 6 mm, and the rest is the same as in Example 1, finally yielding a hot-rolled plate.

[0156] (5) Cold rolling and annealing Referring to Example 1, a double-sided symmetrical pre-embedded flux aluminum alloy composite material was obtained.

[0157] (6) Product structure and performance A double-sided symmetrical pre-embedded flux aluminum alloy composite material with a total thickness of 0.8 mm was obtained. The single-sided brazing functional layer (flux / Al-Si alloy surface layer) is about 0.08 mm thick, accounting for 10% of the total thickness; the core material layer (3003 aluminum alloy layer + 3003 aluminum alloy ingot) is about 0.64 mm thick, accounting for 80% of the total thickness.

[0158] The interfacial bonding strength, as measured by the T-type peel test, is approximately 28 N / mm, and the average spread area in simulated CAB brazing (600℃ × 5 min) is 240 mm². 2 After brazing, there are obvious flux residues and unspread areas on the surface.

[0159] Comparative Example 3 This comparative example provides a double-sided symmetrical pre-embedded flux aluminum alloy composite material, including the following steps: (1) Preparation of pre-embedded flux billet Al-10.0wt%Si alloy powder (Dv) 50 =40μm, oxygen content 250ppm) and potassium fluoroaluminate flux powder (KAlF4-K2AlF5 mixed powder, KAlF4:K2AlF5 weight ratio is 5.7:1, Dv 50=25μm) were mixed uniformly at a weight ratio of 88:12. A V-type powder mixer was used at a speed of 5 r / min for 4 hours. The uniformly mixed powder was loaded into a stainless steel sleeve, sealed, and then placed in a hot isostatic press to obtain a hot isostatic ingot. The pressing process parameters were: vacuum to 2 Pa, temperature 470℃, pressure 120 MPa, and holding time for 4 hours. After pressing, the hot isostatic ingot was machined (milled) to remove the stainless steel sleeve. The thickness after milling was 6 mm, resulting in a flux-embedded ingot.

[0160] (2) Hot-rolled composite The aforementioned flux-embedded billets were stacked on both sides of a 48mm thick 3003 aluminum alloy ingot to obtain a stacked billet with a total thickness of 60mm (of which the single-sided flux-embedded billet is 6mm thick, accounting for 10% of the total thickness). After heating to 480℃ and holding for 5 hours, it underwent 7 passes of hot rolling with a total reduction of approximately 90%, aiming for a final rolled thickness of approximately 6mm. However, during the hot rolling process, macroscopic cracks appeared at multiple points at the interface between the billet and the core material, and cracks also formed inside the billet. Therefore, subsequent steps were not performed.

[0161] Comparative Example 4 This comparative example provides a double-sided symmetrical pre-embedded flux aluminum alloy composite material, including the following steps: (1) Preparation of pre-embedded flux billet Al-10.0wt%Si alloy powder (Dv) 50 =40μm, oxygen content 250ppm) and potassium fluoroaluminate flux powder (KAlF4-K2AlF5 mixed powder, KAlF4:K2AlF5 weight ratio is 5.7:1, Dv 50 =25μm) were mixed uniformly at a weight ratio of 96:4. A V-type powder mixer was used at a speed of 5 r / min for 4 hours. The uniformly mixed powder was placed into a stainless steel sleeve, sealed, and then placed in a hot isostatic press to obtain a hot isostatic ingot. The pressing process parameters were: vacuum to 2 Pa, temperature 470℃, pressure 120 MPa, and holding time for 4 hours. After pressing, the hot isostatic ingot was machined (milled) to remove the stainless steel sleeve. The thickness after milling was 6 mm, resulting in a flux-embedded ingot.

[0162] (2) Hot-rolled composite The above-mentioned flux-embedded billet is stacked on the upper and lower sides of a 48mm thick 3003 aluminum alloy ingot to obtain a stacked billet with a total thickness of 60mm (of which the thickness of the single-sided pre-embedded flux billet is 6mm, accounting for 10% of the total thickness). After heating to 480℃ and holding for 5 hours, it is hot rolled in 7 passes to obtain a hot-rolled plate with a total reduction rate of about 90% and a target final rolling thickness of about 6mm.

[0163] (3) Cold rolling and annealing The hot-rolled plate was cooled to room temperature and then cold-rolled in 6 passes, with the reduction per pass controlled at 25%-30%, 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 to obtain a double-sided symmetrical aluminum alloy composite material with embedded flux.

[0164] (4) Product performance Simulated CAB brazing (600℃×5min), average spread area 83mm. 2 Furthermore, a small amount of flux residue remains on the surface after brazing.

[0165] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope 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: S1. Stack and fix the Al-Si alloy plate, the flux / Al-Si alloy plate and the aluminum alloy plate in sequence to form a laminated structure. S2. The stirring needle of the stirring friction processing tool is used to stir and friction composite the laminated structure. The stirring needle penetrates the Al-Si alloy plate and extends into the aluminum alloy plate, so that the laminated structure is solid-phase composited into one, forming a composite plate including an Al-Si alloy surface layer, a flux / Al-Si alloy intermediate layer and an aluminum alloy bottom layer. S3. The aluminum alloy bottom layer of the composite plate is laminated on at least one surface of the aluminum alloy ingot, and then hot-rolled to obtain a pre-embedded flux aluminum alloy composite material.

2. The preparation method according to claim 1, characterized in that, The preparation method further includes: pressing a mixed powder containing flux and Al-Si alloy into shape to obtain the flux / Al-Si alloy plate; And / or, the preparation method does not include the step of powder metallurgy sintering the flux / Al-Si alloy plate.

3. The preparation method according to claim 1, characterized in that, In step S2, the conditions for friction stir molding include: tool head rotation speed of 800rpm-2000rpm, welding speed of 100mm / min-500mm / min, axial pressure of 5kN-15kN, and tool head tilt angle of 1°-3°. And / or, the stirring needle extends into the aluminum alloy plate to a depth of 0.25-0.5 times the thickness of the aluminum alloy plate; And / or, in step S2, the friction stir processing tool moves on the surface of the Al-Si alloy plate in a serpentine reciprocating scanning path, with an overlap rate of 20%-30% between adjacent welding trajectories.

4. The preparation method according to claim 1, characterized in that, In step S3, the hot rolling composite method includes: holding at 450℃-500℃ for 4h-6h and then performing multiple hot rolling passes, with a final rolling temperature greater than 300℃. And / or, the preparation method further includes hot rolling followed by cold rolling and annealing.

5. The preparation method according to claim 4, characterized in that, The conditions for cold rolling include: a single-pass reduction of 20%-30%; And / or, the annealing conditions include: holding at 380℃-400℃ for 2h-4h.

6. The preparation method according to claim 1, characterized in that, The mass content of Si in the Al-Si alloy plate is 7%-12.5%; And / or, in the flux / Al-Si alloy plate, the mass content of Si in the Al-Si alloy is 7%-12.5%.

7. The preparation method according to claim 1, characterized in that, In the flux / Al-Si alloy plate, the weight ratio of flux to Al-Si alloy is (80-95):(5-20); And / or, the flux in the flux / Al-Si alloy plate includes potassium fluoroaluminate-based flux, which includes KAlF4 and K2AlF5.

8. The preparation method according to claim 1, characterized in that, The aluminum alloy plate is made of 3-series aluminum alloy and / or 4-series aluminum alloy. And / or, the material of the aluminum alloy ingot includes 3-series aluminum alloys and / or 4-series aluminum alloys; And / or, the aluminum alloy plate and the aluminum alloy ingot are made of the same material.

9. The preparation method according to any one of claims 1-8, characterized in that, The thickness ratio of the Al-Si alloy plate, the flux / Al-Si alloy plate, and the aluminum alloy plate is (30-50):(10-30):(20-40). And / or, based on the total thickness of the Al-Si alloy plate, the flux / Al-Si alloy plate, the aluminum alloy plate, and the aluminum alloy ingot, the thickness ratio of the Al-Si alloy plate and the flux / Al-Si alloy plate is 8%-15%.

10. A pre-embedded flux aluminum alloy composite material, characterized in that, It is prepared by the method for preparing the pre-embedded flux aluminum alloy composite material according to any one of claims 1-9.

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