Method for brazing AlxCoCrFeNi high entropy alloy using composite foil and brazed joint prepared therefrom

Abstract

The present application proposes a method for multi-stage contact reaction brazing of an AlxCoCrFeNi high-entropy alloy using a composite foil, comprising the following steps: providing a composite foil and two AlxCoCrFeNi high-entropy alloys, wherein 0 < x < 0.3, the composite foil being composed of elemental Ni and elemental Nb, with the atomic ratio of Ni to Nb ranging from 50% to 73.5%; separately polishing the welded portions of the two AlxCoCrFeNi high-entropy alloys to obtain two base materials to be welded; cleaning the welded portions of the two base materials and the composite foil; sequentially stacking one base material to be welded, the composite foil, and the other base material to be welded to form a welded assembly; placing a pressing block on one side of the welded assembly to compress the welded assembly; placing the compressed assembly to be welded in a brazing furnace for brazing, heating to a temperature of 1200°C to 1320°C, and holding the temperature for 2 min to 150 min to obtain a brazed joint. The present application also proposes a brazed joint. The brazed joint prepared in this application has high connection strength, good radiation resistance and low temperature resistance, and can be used in extreme service environments such as aerospace and nuclear energy.

Description

Technical Field

[0001] The present application relates to the field of welding technology, and in particular to a method for brazing AlxCoCrFeNi high-entropy alloy using composite foil and a brazed joint prepared therefrom. Background Art

[0002] High-entropy alloy is a new type of alloy material formed by introducing "chemical disorder" through the mixing of multiple principal elements. It has the characteristics of radiation resistance, extreme low temperature resistance, oxidation resistance, corrosion resistance, high temperature resistance, and good structural stability. As a low-temperature and radiation-resistant material, it has great application value in nuclear energy, aerospace, civil and other fields. In the nuclear energy field, it can be used as a helium-cooled divertor material.

[0003] The AlxCoCrFeNi high-entropy alloy has a face-centered cubic crystal structure, offering excellent radiation resistance and low-temperature toughness. Reportedly, AlxCoCrFeNi exhibits significantly superior radiation resistance to conventional nuclear materials such as M316 stainless steel, zirconium alloys, and nickel-based alloys. After thermodynamic processing, AlxCoCrFeNi fibers exhibit room-temperature and low-temperature tensile strengths and elongations of 1207 MPa / 7.8 and 1600 MPa / 17.5%, respectively, making them suitable for use in extremely low-temperature components.

[0004] Due to the current limitations of equipment and processes, it is difficult to directly manufacture complex AlxCoCrFeNi high entropy alloy structures. Therefore, achieving reliable connection of AlxCoCrFeNi high entropy alloys has important application value. Since AlxCoCrFeNi high entropy alloys have five components, ordinary fusion welding, such as MIG welding, laser welding, electron beam welding and other high temperature conditions, often produces complex physical and chemical reactions in the welded joints, which easily generate a variety of intermetallic compound phases that weaken the joint strength. At the same time, Al X The CoCrFeNi system high entropy alloy has poor electrical conductivity and heat resistance, and is prone to thermal cracking after traditional fusion welding. Summary of the Invention

[0005] To this end, the present application provides a method for brazing AlxCoCrFeNi high entropy alloy using composite foil multi-stage contact reaction and a brazed joint prepared thereby, in order to solve the problem that thermal cracks are easily generated after traditional fusion welding.

[0006] This application proposes a method for brazing AlxCoCrFeNi high entropy alloy using composite foil multi-stage contact reaction, comprising the following steps:

[0007] A composite foil and two AlxCoCrFeNi high entropy alloys are provided, wherein 0<x<0.3, the composite foil is composed of elemental Ni and elemental Nb, and the atomic ratio of Ni to Nb ranges from 50% to 73.5%;

[0008] grinding the two to-be-welded portions of the AlxCoCrFeNi high-entropy alloy respectively to obtain two to-be-welded parent materials;

[0009] Cleaning the to-be-welded portions of the two base materials and the composite foil;

[0010] stacking one of the base materials to be welded, the composite foil and another of the base materials to be welded in sequence to form a component to be welded;

[0011] Placing a pressing block on one side of the component to be welded to compress the component to be welded;

[0012] The compressed components to be welded are placed in a brazing furnace for brazing, heated to a temperature of 1200° C.-1320° C., and kept warm for 2 min-150 min to obtain a brazed joint.

[0013] In some embodiments, the step of separately grinding the two to-be-welded portions of the AlxCoCrFeNi high-entropy alloy to obtain two base materials to be welded specifically includes:

[0014] The welded portion of the AlxCoCrFeNi high entropy alloy was polished using sandpapers of 400 mesh, 800 mesh, 1200 mesh, and 2000 mesh in sequence.

[0015] In some embodiments, the composite foil includes two Ni foil layers and a Nb foil layer, and the Nb foil layer is connected between the two Ni foil layers.

[0016] In some embodiments, the purity of the Nb foil layer is not less than 95%, and the thickness ranges from 10 μm to 50 μm.

[0017] In some embodiments, the purity of the Ni foil layer is not less than 98%, and the thickness ranges from 10 μm to 50 μm.

[0018] In some embodiments, the step of cleaning the to-be-welded portions of the two base materials and the composite foil specifically includes:

[0019] Immerse the base metal to be welded and the composite foil in an acetone solution, clean them by ultrasonic means for 10 minutes to 30 minutes, and then dry them;

[0020] The dried base metal to be welded and the composite foil are immersed in an ethanol solution, cleaned by ultrasonic means for 10 minutes to 20 minutes, and then dried.

[0021] In some embodiments, the pressure applied by the pressing block to the component to be welded is 0.25N-1N.

[0022] In some embodiments, the Nb foil and the Ni foil are fixedly connected by an adhesive.

[0023] In some embodiments, the furnace chamber of the brazing furnace is evacuated to 2×10 -3 Pa-5.0×10 -3 Pa, before the brazing, the heating rate of the assembly to be welded is 5°C / min-20°C / min, and after the brazing, the cooling rate of the assembly to be welded after welding is 5°C / min-10°C / min.

[0024] In some embodiments, during brazing, the assembly to be welded is heated to 1240° C. and kept warm for 10 minutes.

[0025] The present application also proposes a brazing joint, comprising a composite foil and two AlxCoCrFeNi high-entropy alloys, wherein the composite foil is connected between the two AlxCoCrFeNi high-entropy alloys, wherein 0<x<0.3, the composite foil is composed of elemental Ni and elemental Nb, and the atomic ratio of Ni and Nb ranges from 50% to 73.5%.

[0026] In the brazed joint prepared by the above method, since 0<x<0.3, the atomic ratio of Ni and Nb in the composite foil ranges from 50% to 73.5%, the Nb metal has good radiation resistance, and can undergo a eutectic reaction with metallic Ni at 1184°C to form a eutectic liquid phase. The formation of the eutectic liquid phase accelerates the diffusion of Nb atoms toward the AlxCoCrFeNi high-entropy alloy, thereby initiating a secondary eutectic reaction between Nb and the AlxCoCrFeNi high-entropy alloy base material. After welding, the joint generates a face-centered cubic (FCC) matrix and a Laves phase lamellar eutectic structure. The FCC matrix has radiation resistance and low-temperature resistance. The FCC phase and Laves phase of the welded joint can improve the mechanical properties of the joint by alternating sliding when subjected to force. The obtained brazed joint has a uniform interface structure and no cracks. No other brittle and hard phases are produced in the joint after welding, and a Ni-rich Ni(s,s) transition layer is formed between the brazing seam and the base material. Compared with the AlxCoCrFeNi joint after pure Nb brazing, the brazing temperature is lower and the joint strength is higher. It has good radiation resistance and low-temperature resistance and can be used in extreme service environments such as aerospace and nuclear energy. When x is greater than or equal to 0.3, the high-entropy alloy has a face-centered cubic and body-centered cubic dual-phase structure. The high-entropy alloy has a high Al content. After dissolving into the Ni-Nb liquid phase, Al is easy to react with Ni in the Ni foil during the cooling process, forming a brittle and hard B2 phase structure in the brazing seam, which is prone to microcracks and weakening the mechanical properties of the joint. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 This is a schematic diagram of the cross-sectional structure of the brazing joint proposed in this application.

[0028] Figure 2Backscattered photograph of the brazed joint proposed in this application.

[0029] Figure 3 This is the shear fracture morphology of the brazed joint proposed in this application.

[0030] Figure 4 This is a flow chart of the method for brazing AlxCoCrFeNi high entropy alloy using composite foil proposed in this application.

[0031] Figure 5 for Figure 4 A flow chart of the steps of cleaning the two to-be-welded parts of the base materials, the Nb foil and the two Ni foils. DETAILED DESCRIPTION

[0032] The embodiments of the present application are described in detail below, and examples of the embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present application, and should not be understood as limiting the present application.

[0033] In the description of the present application, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", clockwise", "counterclockwise" and the like, indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present application. In addition, the terms "first" and "second" are used for descriptive purposes only, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include one or more of the said features. In the description of the present application, "multiple" means two or more, unless otherwise clearly and specifically defined.

[0034] In the description of this application, it should be noted that, unless otherwise expressly specified or limited, the terms "installed," "connected," and "connected" should be understood in a broad sense. For example, they can refer to fixed connections, detachable connections, or integral connections; they can refer to mechanical connections, electrical connections, or mutual communication; they can refer to direct connections or indirect connections through an intermediate medium; they can refer to internal communication between two components or the interaction between two components. Those skilled in the art will understand the specific meanings of the above terms in this application based on specific circumstances.

[0035] In this application, unless otherwise expressly specified or limited, a first feature being "above" or "below" a second feature may include the first and second features being in direct contact, or may include the first and second features being in contact not directly but through another feature between them. Moreover, a first feature being "above," "above," and "above" a second feature includes the first feature being directly above and obliquely above the second feature, or simply indicates that the first feature is higher in level than the second feature. A first feature being "below," "below," and "below" a second feature includes the first feature being directly above and obliquely above the second feature, or simply indicates that the first feature is lower in level than the second feature.

[0036] The disclosure below provides many different embodiments or examples for realizing different structures of the present application. In order to simplify the disclosure of the present application, the components and settings of specific examples are described below. Of course, they are merely examples and are not intended to limit the present application. In addition, the present application may repeat reference numbers and / or reference letters in different examples, and such repetition is for the purpose of simplicity and clarity, and does not itself indicate the relationship between the various embodiments and / or settings discussed. In addition, the present application provides examples of various specific processes and materials, but those of ordinary skill in the art will appreciate the application of other processes and / or the use of other materials.

[0037] See Figures 1 to 3 , an embodiment of the present application proposes a brazing joint 100, comprising a composite foil and two AlxCoCrFeNi high entropy alloys 30, wherein the composite foil is connected between the two AlxCoCrFeNi high entropy alloys 30, wherein 0<x<0.3, the composite foil is composed of elemental Ni and elemental Nb, and the atomic ratio of Ni and Nb ranges from 50% to 73.5%.

[0038] When 0 < x < 0.3, the AlxCoCrFeNi high-entropy alloy 30 is a single-phase face-centered cubic (FCC) base material with good toughness, radiation resistance, and low-temperature resistance. When x is greater than or equal to 0.3, the high-entropy alloy has a dual-phase structure of face-centered cubic and body-centered cubic. The high-entropy alloy contains a large amount of Al. After dissolving into a Ni-Nb liquid phase, Al easily reacts with Ni in the Ni foil during cooling, forming a brittle B2 phase structure in the brazing seam, which is prone to microcracks and weakens the mechanical properties of the joint.

[0039] Among them, the atomic ratio of Ni to Nb in the composite foil is between 50% and 73.5%, and the mechanical properties of the joint are good. When the atomic ratio of Ni to Nb is less than 50%, Nb7Ni6 intermetallic compounds may exist in the generated Ni-Nb liquid phase, the filling liquid phase has poor fluidity, and the mechanical properties of the joint are low. When the atomic ratio of Ni to Nb foil is greater than 50%, NbNi3 intermetallic compounds may exist in the generated Ni-Nb liquid phase, the filling liquid phase has poor fluidity, and the mechanical properties of the joint are low.

[0040] In some embodiments, the composite foil includes a Nb foil layer 10 and two Ni foil layers 20 .

[0041] The Nb foil layer 10 is arranged between two Ni foil layers 20, and an AlxCoCrFeNi high entropy alloy 30 is arranged on the side of the Ni foil layer 20 facing away from the Nb foil layer 10. Each AlxCoCrFeNi high entropy alloy 30 has a portion to be welded, and the side of the Ni foil layer 20 facing away from the Nb foil layer 10 is connected to the portion to be welded of the AlxCoCrFeNi high entropy alloy 30.

[0042] In some embodiments, the purity of the Nb foil layer 10 is not less than 95%. In this way, the liquid phase generated during the brazing process has good fluidity, the brazing seam filling effect is good, the interface structure is uniform, and there are no pores and cracks. When the purity of the Nb foil layer 10 is lower than 95%, defects such as pores and microcracks are likely to appear after welding, and the interface structure is uneven.

[0043] In some embodiments, the thickness range of the Nb foil layer 10 is 10 μm-50 μm. In this way, the brazing seam after welding is likely to form a lamellar eutectic structure composed of FCC phase and Laves phase, and the shear performance of the joint is significantly improved; when the thickness range of the Nb foil layer 10 is less than 10 μm, there is less Laves phase in the brazing seam, and it is difficult to form a eutectic structure; when the thickness range of the Nb foil layer 10 is greater than 50 μm, it is easy to cause the Nb foil layer 10 to not react completely, which is not conducive to the formation of a eutectic structure brazing seam.

[0044] In some embodiments, the purity of the Ni foil layer 20 is not less than 98%. In this way, the liquid phase generated during the brazing process has good fluidity, the brazing seam filling effect is good, the interface structure is uniform, and there are no pores and cracks. When the purity of the Ni foil layer 20 is less than 98%, the liquid phase generated during the brazing process has poor fluidity and the brazing seam filling effect is poor.

[0045] In some embodiments, the purity of the Ni foil layer 20 is not less than 98%. In this way, the liquid phase generated during the brazing process has good fluidity, the brazing seam filling effect is good, the interface structure is uniform, and there are no pores and cracks. When the purity of the Ni foil layer 20 is lower than 98%, the liquid phase generated during the brazing process has poor fluidity and the brazing seam filling effect is poor.

[0046] In some embodiments, the thickness range of the Ni foil layer 20 is 10 μm-50 μm, so that it can fully react with the Nb foil layer 10, and the formed Ni-Nb liquid phase has good fluidity, which is conducive to the formation of eutectic structure; when the thickness range of the Ni foil layer 20 is less than 10 μm, it is easy to cause the Nb foil layer 10 to not react completely or a large amount of Laves brittle hard phase to be generated in the brazing seam, thereby reducing the joint performance; when the thickness range of the Ni foil layer 20 is greater than 50 μm, the Ni foil layer 20 is prone to not being dissolved, which is not conducive to the formation of eutectic structure in the brazing seam and weakening the mechanical properties of the joint.

[0047] In some embodiments, the thickness range of the AlxCoCrFeNi high entropy alloy 30 is 2mm-20mm. In this way, the eutectic liquid phase formed in the joint after welding can effectively fill the brazing seam to form a lamellar eutectic structure joint with high joint connection strength; when the thickness range of the AlxCoCrFeNi high entropy alloy 30 is less than 2mm, the parent material near the interface dissolves and collapses, which is not conducive to the characterization of the shear performance of the joint; when the thickness range of the AlxCoCrFeNi high entropy alloy 30 is greater than 20mm, the formed liquid phase alloy is easily squeezed out under the action of the gravity of the parent material, resulting in uneven brazing seam thickness, and cracks are easily formed at the eutectic structure interface, which reduces the mechanical properties of the joint.

[0048] In the above-mentioned brazed joint 100, the Nb metal has good radiation resistance and can undergo a eutectic reaction with metal Ni at 1184°C to form a eutectic liquid phase. The formation of the eutectic liquid phase accelerates the diffusion of Nb atoms into the AlxCoCrFeNi high-entropy alloy 30, thereby initiating a secondary eutectic reaction between Nb and the AlxCoCrFeNi high-entropy alloy base material. After welding, the joint generates a face-centered cubic (FCC) matrix and a Laves phase lamellar eutectic structure. The FCC matrix has radiation resistance and low-temperature resistance. The FCC phase and Laves phase in the welded joint can improve the mechanical properties of the joint by alternating sliding under stress. The obtained brazed joint interface structure is uniform and crack-free. No other brittle and hard phases are generated in the welded joint, and a Ni-rich Ni(s,s) transition layer is formed between the brazing seam and the base material. Compared with the AlxCoCrFeNi joint after pure Nb brazing, the brazing temperature is lower, the joint strength is higher, and it has good radiation resistance and low-temperature resistance. It can be used in extreme service environments such as aerospace and nuclear energy.

[0049] See Figure 4 The present application also proposes a method for brazing AlxCoCrFeNi high entropy alloy using composite foil, comprising the following steps:

[0050] S10, providing a composite foil and two AlxCoCrFeNi high entropy alloys, wherein 0 < x < 0.3, the composite foil is composed of elemental Ni and elemental Nb, and the atomic ratio of Ni to Nb is in the range of 50% to 73.5%;

[0051] In some embodiments, the composite foil includes two Ni foil layers and a Nb foil layer, wherein the Nb foil layer is connected between the two Ni foil layers.

[0052] In some embodiments, the purity of the Nb foil layer is not less than 95%. In this way, the liquid phase generated during the brazing process has good fluidity, the brazing seam filling effect is good, the interface structure is uniform, and there are no pores and cracks. When the purity of the Nb foil layer is lower than 95%, defects such as pores and microcracks are likely to appear after welding, and the interface structure is uneven.

[0053] In some embodiments, the thickness range of the Nb foil layer is 10 μm-50 μm. In this way, the brazing seam after welding is likely to form a lamellar eutectic structure composed of FCC phase and Laves phase, and the shear performance of the joint is significantly improved; when the thickness range of the Nb foil is less than 10 μm, there is less Laves phase in the brazing seam, and it is difficult to form a eutectic structure; when the thickness range of the Nb foil is greater than 50 μm, it is easy to cause the Nb foil to not react completely, which is not conducive to the formation of a eutectic structure brazing seam.

[0054] In some embodiments, the purity of the Ni foil layer is not less than 98%. In this way, the liquid phase generated during the brazing process has good fluidity, the brazing seam filling effect is good, the interface structure is uniform, and there are no pores and cracks. When the purity of the Ni foil layer is lower than 98%, the liquid phase generated during the brazing process has poor fluidity and the brazing seam filling effect is poor.

[0055] In some embodiments, the thickness range of the Ni foil layer is 10 μm-50 μm. In this way, the brazing seam after welding is likely to form a lamellar eutectic structure composed of FCC phase and Laves phase, and the shear performance of the joint is significantly improved; when the thickness range of the Ni foil layer is less than 10 μm, it is easy to cause the Nb foil layer 10 to not react completely or the brazing seam to generate more Laves brittle and hard phases, thereby reducing the joint performance; when the thickness range of the Ni foil 20 is greater than 50 μm, the Ni foil is likely to be unmelted, which is not conducive to the formation of eutectic structure in the brazing seam and weakens the mechanical properties of the joint.

[0056] In some embodiments, the thickness range of the AlxCoCrFeNi high entropy alloy is 2mm-20mm. In this way, the eutectic liquid phase formed in the joint after welding can effectively fill the brazing seam to form a lamellar eutectic structure joint with high joint connection strength; when the thickness range of the AlxCoCrFeNi high entropy alloy is less than 2mm, the parent material near the interface dissolves and collapses, which is not conducive to the characterization of the shear performance of the joint; when the thickness range of the AlxCoCrFeNi high entropy alloy is greater than 20mm, the formed liquid phase alloy is easily squeezed out under the action of the gravity of the parent material, resulting in uneven brazing seam thickness, and cracks are easily formed at the eutectic structure interface, which reduces the mechanical properties of the joint.

[0057] S20, grinding two AlxCoCrFeNi high entropy alloy parts to be welded respectively to obtain two base materials to be welded;

[0058] The AlxCoCrFeNi high entropy alloy welded parts were polished using 400-mesh, 800-mesh, 1200-mesh, and 2000-mesh sandpapers, respectively. It is understood that the sandpaper includes, but is not limited to, SiC sandpaper, diamond sandpaper, or white corundum sandpaper.

[0059] S30, cleaning the parts to be welded of the two base materials to be welded and the composite foil;

[0060] In some embodiments, see Figure 5 , the cleaning steps specifically include:

[0061] S31, immersing the base metal to be welded and the composite foil in an acetone solution, cleaning them by ultrasonic means for 10 minutes to 30 minutes, and drying them;

[0062] Among them, after cleaning, the surface of the base material to be welded is free of oil and dirt.

[0063] S32, immersing the dried base metal to be welded and the composite foil in an ethanol solution, cleaning them by ultrasonic means for 10 minutes to 20 minutes, and drying them.

[0064] Among them, after cleaning, it shows that it is clean and free of any stains. Acetone is mainly used to remove surface oil stains, and then alcohol ultrasonic cleaning is used to clean the surface, which is clean and free of impurities.

[0065] S40, stacking a base material to be welded, a composite foil, and another base material to be welded in sequence to form a component to be welded;

[0066] In one embodiment, the composite foil includes two Ni foil layers and one Nb foil layer. A Ni foil, a Nb foil, and another Ni foil can be stacked to form a structural component. Subsequently, a base metal to be welded, the structural component, and another base metal to be welded can be stacked in this order. In some embodiments, the Nb foil and the Ni foil are fixedly connected by an adhesive, which includes, but is not limited to, glue and resin.

[0067] S50, placing a pressing block on one side of the component to be welded to press the component to be welded;

[0068] The pressed block includes but is not limited to a graphite pressed block.

[0069] In some embodiments, the pressure applied by the pressing block to the assembly to be welded is 0.25N-1N. In this way, the generated eutectic liquid phase is not easily squeezed out, and the eutectic interface after welding is uniform and crack-free. When the applied pressure is less than 0.25N, the joint after welding is prone to pores, cracks, and uneven brazing seam thickness. When the applied pressure is greater than 10×103 Pa, the generated liquid filler metal is easily squeezed out, the brazing seam becomes narrower, and it is easy to crack.

[0070] S60, placing the compressed components to be welded into a brazing furnace for brazing, heating the temperature to 1200° C.-1320° C., and holding the temperature for 2 min-150 min to obtain a brazed joint.

[0071] Among them, the heating temperature is to 1200℃-1320℃, so that the interface of the joint after welding is a lamellar eutectic structure interface composed of FCC phase and Laves phase; when the heating temperature is lower than 1200℃, only diffusion occurs between Ni and Nb, and the eutectic liquid phase cannot be generated to fill the brazing seam; when the heating temperature is higher than 1320℃, there are more Laves phases in the brazing seam and more microcracks are easily formed.

[0072] In this embodiment, during brazing, the components to be welded are heated to 1240° C. and kept warm for 10 minutes.

[0073] In some embodiments, when brazing is performed in a brazing furnace, the furnace chamber of the brazing furnace is evacuated to a vacuum of 2×10 -3 Pa-5.0×10 -3 Pa, the liquid filling metal thus formed has good fluidity, and the generated interface structure is uniform and crack-free; when the furnace chamber is vacuumed to less than 2×10 -3 Pa, the liquid filler metal is easily oxidized, the fluidity is poor, and the brazing seam is prone to pores and cracks; when the furnace chamber is vacuumed to more than 2.5×10 -3 Pa, the vacuuming time is longer and energy is consumed.

[0074] Before brazing, the heating rate of the components to be welded is 5℃ / min-20℃ / min, so that the liquid metal generated has a good filling effect and the interface structure is uniform; when the heating rate is less than 5℃ / min, the brazing process consumes energy, the amount of base material dissolved is large, and the brazing material is easy to overflow; when the heating rate is greater than 20℃ / min, the temperature in the furnace is uneven and the welding rate is low.

[0075] After brazing, the cooling rate of the welded components is 5℃ / min-10℃ / min, so that the welded structure is uniform and no microcracks are generated at the eutectic structure interface; when the cooling rate is less than 5℃ / min, the cooling time is long and energy is consumed; when the cooling rate is greater than 10℃ / min, the residual stress between the brazing seam base material and the brazing seam is large, and microcracks are easily generated at the interface structure.

[0076] In the brazed joint prepared by the above method, the Nb metal has good radiation resistance and can undergo a eutectic reaction with metallic Ni at 1184°C to form a eutectic liquid phase. The formation of the eutectic liquid phase accelerates the diffusion of Nb atoms into the AlxCoCrFeNi high-entropy alloy 30, thereby initiating a secondary eutectic reaction between Nb and the AlxCoCrFeNi high-entropy alloy base material. After welding, the joint produces a face-centered cubic (FCC) matrix and a Laves phase lamellar eutectic structure. The FCC matrix has radiation resistance and low-temperature resistance. The FCC phase and Laves phase in the welded joint can improve the mechanical properties of the joint by alternating sliding under stress. The obtained brazed joint interface structure is uniform and crack-free. No other brittle and hard phases are generated in the welded joint, and a Ni-rich Ni(s,s) transition layer is formed between the braze seam and the base material. Compared with the AlxCoCrFeNi joint brazed with pure Nb, the brazing temperature is lower and the joint strength is higher. It has good radiation resistance and low-temperature resistance and can be used in extreme service environments such as aerospace and nuclear energy.

[0077] Furthermore, a Ni / Nb / Ni foil layer was used as the intermediate layer for contact reaction brazing. To reduce the brazing temperature, Ni and Nb first underwent a eutectic reaction above 1184°C during the heating process, forming a eutectic liquid phase. This accelerated the diffusion of Nb from the eutectic liquid phase into the AlxCoCrFeNi high-entropy alloy base material, prompting a secondary eutectic reaction between Nb and the AlxCoCrFeNi alloy. Consequently, metallurgical bonding between the base materials was achieved at a brazing temperature of 1200°C. With continued temperature increases or extended holding times, the base material dissolved and diffused into the molten liquid phase. By controlling process parameters, the aggregation and growth of brittle phases in the braze joint were controlled. Consequently, in addition to the formation of a lamellar eutectic structure composed of a face-centered cubic matrix (FCC phase) and Laves phase at the interface, a Ni(s,s) reaction layer formed between the braze joint and base material, promoting a transition in mechanical properties between the base material and the braze joint. After welding, the Laves brittle phase was evenly distributed within the face-centered cubic matrix, resulting in excellent joint performance. The connection method of the present application is simple, economical and applicable. The average shear strength of the obtained AlxCoCrFeNi high-entropy alloy joint is as high as 592 MPa, which has great promotion and application value.

[0078] The technical solution of the present application is not limited to the specific implementation methods given below, but also includes any combination of the specific implementation methods.

[0079] Example 1

[0080] Example 1 of the present application proposes a method for brazing an AlxCoCrFeNi high entropy alloy using a composite foil, comprising the following steps:

[0081] A composite foil and two AlxCoCrFeNi high-entropy alloys are provided, wherein X=0.28, the composite foil is composed of elemental Ni and elemental Nb, the atomic ratio of Ni to Nb is in the range of 50%, the thickness of the Nb foil is 30 μm, the purity of the Nb foil is 99.5%, the thickness of the Ni foil is 20 μm, the purity of the Ni foil is 99.5%, and the thickness of the AlxCoCrFeNi high-entropy alloy is 5 mm;

[0082] The welded parts of the AlxCoCrFeNi high entropy alloy were polished using 400-mesh, 800-mesh, 1200-mesh and 2000-mesh sandpapers in sequence to obtain two base materials to be welded.

[0083] Immerse the base metal and composite foil to be welded in acetone solution, clean them by ultrasonic method for 20 minutes and dry them;

[0084] The dried base metal and composite foil to be welded are immersed in an ethanol solution, cleaned by ultrasonic method for 15 minutes and dried;

[0085] A base material to be welded, a composite foil and another base material to be welded are stacked in sequence to form a component to be welded;

[0086] Place a pressing block on one side of the component to be welded to press the component to be welded;

[0087] The compressed components to be welded are placed in a brazing furnace for brazing, heated to 1320°C, and kept warm for 10 minutes to obtain a brazed joint.

[0088] The experimental results show that Nb metal and metal Ni undergo a eutectic reaction at 1184℃ to form a eutectic liquid phase. The formation of the eutectic liquid phase accelerates the diffusion of Nb atoms into the AlxCoCrFeNi high-entropy alloy 30, thereby initiating a secondary eutectic reaction between Nb and the AlxCoCrFeNi high-entropy alloy base material. After welding, the joint generates a face-centered cubic (FCC) matrix and Laves phase lamellar eutectic structure. The FCC phase and Laves phase in the welded joint can improve the mechanical properties of the joint by alternately sliding under stress. The obtained brazed joint interface structure is uniform and crack-free, and no other brittle and hard phases are generated. The brazed joint has high connection strength, and the average shear strength of the brazed joint at room temperature is as high as 484MPa.

[0089] Example 2

[0090] Example 2 of the present application proposes a method for brazing AlxCoCrFeNi high entropy alloy using composite foil. Example 2 of the present application is substantially the same as Example 1, except that:

[0091] The atomic ratio of Ni to Nb in the composite foil selected in Example 2 is in the range of 58.5%.

[0092] The experimental results show that Nb metal and metal Ni undergo a eutectic reaction at 1184℃ to form a eutectic liquid phase. The formation of the eutectic liquid phase accelerates the diffusion of Nb atoms into the AlxCoCrFeNi high-entropy alloy 30, thereby initiating a secondary eutectic reaction between Nb and the AlxCoCrFeNi high-entropy alloy base material. After welding, the joint generates a face-centered cubic (FCC) matrix and Laves phase lamellar eutectic structure. The FCC phase and Laves phase in the welded joint can improve the mechanical properties of the joint by alternately sliding under stress. The obtained brazed joint interface structure is uniform and crack-free, and no other brittle and hard phases are generated. The brazed joint has high connection strength, and the average shear strength of the brazed joint at room temperature is as high as 572MPa.

[0093] Example 3

[0094] Example 3 of the present application proposes a method for brazing AlxCoCrFeNi high entropy alloy using composite foil. Example 3 of the present application is substantially the same as Example 1, except that:

[0095] The atomic ratio of Ni to Nb in the composite foil selected in Example 3 is in the range of 73.5%.

[0096] The experimental results show that Nb metal and metallic Ni undergo a eutectic reaction at 1184℃ to form a eutectic liquid phase. The formation of the eutectic liquid phase accelerates the diffusion of Nb atoms into the AlxCoCrFeNi high-entropy alloy 30, thereby initiating a secondary eutectic reaction between Nb and the AlxCoCrFeNi high-entropy alloy base material. After welding, the joint generates a face-centered cubic (FCC) matrix and Laves phase lamellar eutectic structure. The FCC phase and Laves phase in the welded joint can improve the mechanical properties of the joint by alternately sliding under stress. The obtained brazed joint interface structure is uniform and crack-free, and no other brittle and hard phases are generated. The brazed joint has high connection strength, and the average shear strength of the brazed joint at room temperature is as high as 521MPa.

[0097] Example 4

[0098] Example 4 of the present application proposes a method for brazing an AlxCoCrFeNi high entropy alloy using a composite foil, comprising the following steps:

[0099] Providing a Nb foil, two Ni foils, and two AlxCoCrFeNi high-entropy alloys, wherein X=0.28, the thickness of the Nb foil is 30 μm, the purity of the Nb foil is 99.5%, the thickness of the Ni foil is 20 μm, the purity of the Ni foil is 99.5%, and the thickness of the AlxCoCrFeNi high-entropy alloy is 5 mm;

[0100] The welded parts of the AlxCoCrFeNi high entropy alloy were polished using 400-mesh, 800-mesh, 1200-mesh and 2000-mesh sandpapers in sequence to obtain two base materials to be welded.

[0101] The base metal to be welded, Nb foil and Ni foil were immersed in acetone solution, ultrasonically cleaned for 20 minutes and dried; then the dried base metal to be welded, Nb foil and Ni foil were immersed in ethanol solution, ultrasonically cleaned for 15 minutes and dried;

[0102] First, a Ni foil, a Nb foil, and another Ni foil are stacked to form a structural member, and then a base material to be welded, a structural member, and another base material to be welded are stacked in this order;

[0103] Place a pressing block on one side of the assembly to be welded to compress the assembly to be welded. The pressure exerted by the pressing block on the assembly to be welded is 1N.

[0104] The compressed components to be welded are placed in a vacuum brazing furnace for brazing. -3 The solder joint was obtained by heating to 1320 °C in a Pa environment with a heating rate of 10 °C / min and a holding time of 10 min. After brazing, the solder joint was cooled to room temperature with a cooling rate of 10 °C / min.

[0105] The experimental results show that Nb metal and metallic Ni undergo a eutectic reaction at 1184℃ to form a eutectic liquid phase. The formation of the eutectic liquid phase accelerates the diffusion of Nb atoms into the AlxCoCrFeNi high-entropy alloy 30, thereby initiating a secondary eutectic reaction between Nb and the AlxCoCrFeNi high-entropy alloy base material. After welding, the joint generates a face-centered cubic (FCC) matrix and Laves phase lamellar eutectic structure. The FCC phase and Laves phase in the welded joint can improve the mechanical properties of the joint by alternately sliding under stress. The obtained brazed joint interface structure is uniform and crack-free, and no other brittle and hard phases are generated. The brazed joint has high connection strength, and the average shear strength of the brazed joint at room temperature is as high as 592MPa.

[0106] Example 5

[0107] Example 5 of the present application proposes a method for brazing AlxCoCrFeNi high entropy alloy using composite foil. Example 5 of the present application is substantially the same as Example 4, except that:

[0108] In Example 5, the AlxCoCrFeNi high entropy alloy base material is selected, and x=0.1.

[0109] The experimental results show that Nb metal and metal Ni undergo a eutectic reaction at 1184℃ to form a eutectic liquid phase. The formation of the eutectic liquid phase accelerates the diffusion of Nb atoms into the AlxCoCrFeNi high-entropy alloy 30, thereby initiating a secondary eutectic reaction between Nb and the AlxCoCrFeNi high-entropy alloy base material. After welding, the joint generates a face-centered cubic (FCC) matrix and Laves phase lamellar eutectic structure. The FCC phase and Laves phase in the welded joint can improve the mechanical properties of the joint by alternately sliding under stress. The obtained brazed joint interface structure is uniform and crack-free, and no other brittle and hard phases are generated. The brazed joint has high connection strength, and the average shear strength of the brazed joint at room temperature is as high as 472MPa.

[0110] Example 6

[0111] Example 6 of the present application proposes a method for brazing AlxCoCrFeNi high entropy alloy using composite foil. Example 6 of the present application is substantially the same as Example 4, except that:

[0112] In Example 6, the AlxCoCrFeNi high entropy alloy base material is selected, and x=0.15.

[0113] The experimental results show that Nb metal and metal Ni undergo a eutectic reaction at 1184℃ to form a eutectic liquid phase. The formation of the eutectic liquid phase accelerates the diffusion of Nb atoms into the AlxCoCrFeNi high-entropy alloy 30, thereby initiating a secondary eutectic reaction between Nb and the AlxCoCrFeNi high-entropy alloy base material. After welding, the joint generates a face-centered cubic (FCC) matrix and Laves phase lamellar eutectic structure. The FCC phase and Laves phase in the welded joint can improve the mechanical properties of the joint by alternately sliding under stress. The obtained brazed joint interface structure is uniform and crack-free, and no other brittle and hard phases are generated. The brazed joint has high connection strength, and the average shear strength of the brazed joint at room temperature is as high as 511 MPa.

[0114] Example 7

[0115] Example 7 of the present application proposes a method for brazing AlxCoCrFeNi high entropy alloy using composite foil. Example 7 of the present application is substantially the same as Example 4, except that:

[0116] In Example 7, the purity of the Nb foil was 99% and the thickness was 20 μm.

[0117] The experimental results show that Nb metal and metallic Ni undergo a eutectic reaction at 1184℃ to form a eutectic liquid phase. The formation of the eutectic liquid phase accelerates the diffusion of Nb atoms into the AlxCoCrFeNi high-entropy alloy 30, thereby initiating a secondary eutectic reaction between Nb and the AlxCoCrFeNi high-entropy alloy base material. After welding, the joint generates a face-centered cubic (FCC) matrix and Laves phase lamellar eutectic structure. The FCC phase and Laves phase in the welded joint can improve the mechanical properties of the joint by alternately sliding under stress. The obtained brazed joint interface structure is uniform and crack-free, and no other brittle and hard phases are generated. The brazed joint has high connection strength, and the average shear strength of the brazed joint at room temperature is as high as 532MPa.

[0118] Example 8

[0119] Example 8 of the present application proposes a method for brazing AlxCoCrFeNi high entropy alloy using composite foil. Example 8 of the present application is substantially the same as Example 4, except that:

[0120] In Example 8, the purity of the Ni foil was 99% and the thickness was 30 μm.

[0121] The experimental results show that Nb metal and metal Ni undergo a eutectic reaction at 1184℃ to form a eutectic liquid phase. The formation of the eutectic liquid phase accelerates the diffusion of Nb atoms into the AlxCoCrFeNi high-entropy alloy 30, thereby initiating a secondary eutectic reaction between Nb and the AlxCoCrFeNi high-entropy alloy base material. After welding, the joint generates a face-centered cubic (FCC) matrix and Laves phase lamellar eutectic structure. The FCC phase and Laves phase in the welded joint can improve the mechanical properties of the joint by alternately sliding under stress. The obtained brazed joint interface structure is uniform and crack-free, and no other brittle and hard phases are generated. The brazed joint has high connection strength, and the average shear strength of the brazed joint at room temperature is as high as 511 MPa.

[0122] Example 9

[0123] Example 9 of the present application proposes a method for brazing AlxCoCrFeNi high entropy alloy using composite foil. Example 8 of the present application is substantially the same as Example 4, except that:

[0124] In Example 9, a Ni foil, a Nb foil, and another Ni foil are first stacked to form a structural member, wherein the Nb foil and the Ni foil are fixedly connected by glue; then, a base material to be welded, the structural member, and another base material to be welded are stacked in this order.

[0125] The experimental results show that Nb metal and metal Ni undergo a eutectic reaction at 1184℃ to form a eutectic liquid phase. The formation of the eutectic liquid phase accelerates the diffusion of Nb atoms into the AlxCoCrFeNi high-entropy alloy 30, thereby initiating a secondary eutectic reaction between Nb and the AlxCoCrFeNi high-entropy alloy base material. After welding, the joint generates a face-centered cubic (FCC) matrix and Laves phase lamellar eutectic structure. The FCC phase and Laves phase in the welded joint can improve the mechanical properties of the joint by alternately sliding under stress. The obtained brazed joint interface structure is uniform and crack-free, and no other brittle and hard phases are generated. The brazed joint has high connection strength, and the average shear strength of the brazed joint at room temperature is as high as 572MPa.

[0126] Example 10

[0127] Example 10 of the present application proposes a method for brazing AlxCoCrFeNi high entropy alloy using composite foil. Example 10 of the present application is substantially the same as Example 4, except that:

[0128] In Example 10, the base metal to be welded, Nb foil and Ni foil were immersed in an acetone solution, ultrasonically cleaned for 10 minutes and dried; then the dried base metal to be welded, Nb foil and Ni foil were immersed in an ethanol solution, ultrasonically cleaned for 10 minutes and dried.

[0129] The experimental results show that Nb metal and metallic Ni undergo a eutectic reaction at 1184℃ to form a eutectic liquid phase. The formation of the eutectic liquid phase accelerates the diffusion of Nb atoms into the AlxCoCrFeNi high-entropy alloy 30, thereby initiating a secondary eutectic reaction between Nb and the AlxCoCrFeNi high-entropy alloy base material. After welding, the joint generates a face-centered cubic (FCC) matrix and Laves phase lamellar eutectic structure. The FCC phase and Laves phase in the welded joint can improve the mechanical properties of the joint by alternately sliding under stress. The obtained brazed joint interface structure is uniform and crack-free, and no other brittle and hard phases are generated. The brazed joint has high connection strength, and the average shear strength of the brazed joint at room temperature is as high as 584MPa.

[0130] Example 11

[0131] Example 11 of the present application proposes a method for brazing AlxCoCrFeNi high entropy alloy using Nb foil. Example 11 of the present application is substantially the same as Example 7, except that:

[0132] In Example 11, the pressure applied by the pressing block to the assembly to be welded is 0.5N.

[0133] The experimental results show that Nb metal and metallic Ni undergo a eutectic reaction at 1184℃ to form a eutectic liquid phase. The formation of the eutectic liquid phase accelerates the diffusion of Nb atoms into the AlxCoCrFeNi high-entropy alloy 30, thereby initiating a secondary eutectic reaction between Nb and the AlxCoCrFeNi high-entropy alloy base material. After welding, the joint generates a face-centered cubic (FCC) matrix and Laves phase lamellar eutectic structure. The FCC phase and Laves phase in the welded joint can improve the mechanical properties of the joint by alternately sliding under stress. The obtained brazed joint interface structure is uniform and crack-free, and no other brittle and hard phases are generated. The brazed joint has high connection strength, and the average shear strength of the brazed joint at room temperature is as high as 543MPa.

[0134] Example 12

[0135] Example 12 of the present application proposes a method for brazing AlxCoCrFeNi high entropy alloy using Nb foil. Example 12 of the present application is substantially the same as Example 7, except that:

[0136] In Example 12, the heating temperature during brazing is 1240°C, the heating rate is set to 10°C / min, the holding time is 2 minutes, and the cooling rate to room temperature after brazing is 5°C / min to obtain a brazed joint.

[0137] The experimental results show that Nb metal and metallic Ni undergo a eutectic reaction at 1184℃ to form a eutectic liquid phase. The formation of the eutectic liquid phase accelerates the diffusion of Nb atoms into the AlxCoCrFeNi high-entropy alloy 30, thereby initiating a secondary eutectic reaction between Nb and the AlxCoCrFeNi high-entropy alloy base material. After welding, the joint generates a face-centered cubic (FCC) matrix and Laves phase lamellar eutectic structure. The FCC phase and Laves phase in the welded joint can improve the mechanical properties of the joint by alternately sliding under stress. The obtained brazed joint interface structure is uniform and crack-free, and no other brittle and hard phases are generated. The brazed joint has high connection strength, and the average shear strength of the brazed joint at room temperature is as high as 385MPa.

[0138] Example 13

[0139] Example 13 of the present application proposes a method for brazing AlxCoCrFeNi high entropy alloy using Nb foil. Example 13 of the present application is substantially the same as Example 10, except that:

[0140] In Example 13, the heating temperature during brazing was 1240°C, the heating rate was set to 20°C / min, the holding time was 30 min, and the cooling rate to room temperature after brazing was 10°C / min to obtain a brazed joint.

[0141] The experimental results show that Nb metal and metallic Ni undergo a eutectic reaction at 1184℃ to form a eutectic liquid phase. The formation of the eutectic liquid phase accelerates the diffusion of Nb atoms into the AlxCoCrFeNi high-entropy alloy 30, thereby initiating a secondary eutectic reaction between Nb and the AlxCoCrFeNi high-entropy alloy base material. After welding, the joint generates a face-centered cubic (FCC) matrix and Laves phase lamellar eutectic structure. The FCC phase and Laves phase in the welded joint can improve the mechanical properties of the joint by alternately sliding under stress. The obtained brazed joint interface structure is uniform and crack-free, and no other brittle and hard phases are generated. The brazed joint has high connection strength, and the average shear strength of the brazed joint at room temperature is as high as 428MPa.

[0142] Example 14

[0143] Example 14 of the present application proposes a method for brazing AlxCoCrFeNi high entropy alloy using Nb foil. Example 14 of the present application is substantially the same as Example 11, except that:

[0144] In Example 14, the heating temperature during brazing was 1280°C, the heating rate was set to 5°C / min, the holding time was 20 min, and the cooling rate to room temperature after brazing was 20°C / min to obtain a brazed joint.

[0145] The experimental results show that after the Nb foil contacts the AlxCoCrFeNi high-entropy alloy, a eutectic reaction is formed to generate a face-centered cubic (FCC) matrix and a Laves phase lamellar eutectic structure. When the welded joint is subjected to stress, the FCC phase and the Laves phase can alternately slip to improve the mechanical properties of the joint. The obtained brazed joint interface structure is uniform and crack-free, and no other brittle and hard phases are generated. The brazed joint has high connection strength. The average shear strength of the brazed joint at room temperature is 485 MPa, and the shear strength at liquid nitrogen temperature (77K) is 968 MPa.

[0146] In summary, the average shear strength of the brazed joint prepared by the above method at room temperature can reach 385MPa-592MPa, which has great promotion and application value.

[0147] It will be apparent to those skilled in the art that the present application is not limited to the details of the exemplary embodiments described above, and that the present application can be implemented in other specific forms without departing from the spirit or essential characteristics of the present application. Therefore, the embodiments should be considered in all respects as illustrative and non-restrictive, and the scope of the present application is defined by the appended claims rather than the foregoing description, and all variations that come within the meaning and range of equivalents of the claims are intended to be embraced herein.

[0148] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application and are not limiting. Although the present application has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present application may be modified or replaced by equivalents without departing from the spirit and scope of the technical solutions of the present application.

Claims

1. A multi-stage contact reaction brazing method for Al using composite foil x The method for making a CoCrFeNi high entropy alloy is characterized in that The steps include: Provide a composite foil and two Al x CoCrFeNi high entropy alloy, wherein 0 < x < 0.3, the atomic ratio of Ni to Nb ranges from 50% to 73.5%, the composite foil comprises two Ni foil layers and one Nb foil layer, the Nb foil layer is connected between the two Ni foil layers; Polish the two Al x The welded part of the CoCrFeNi high entropy alloy is obtained to obtain two base materials to be welded; Cleaning the to-be-welded portions of the two base materials and the composite foil; stacking one of the base materials to be welded, the composite foil and another of the base materials to be welded in sequence to form a component to be welded; Placing a pressing block on one side of the component to be welded to compress the component to be welded; The compressed components to be welded are placed in a brazing furnace for brazing, heated to a temperature of 1200° C.-1320° C., and kept warm for 2 min-150 min to obtain a brazed joint.

2. The multi-stage contact reaction brazing method using composite foil according to claim 1 x The method for making a CoCrFeNi high entropy alloy is characterized in that The two Al x The steps of obtaining two base materials to be welded at the parts to be welded of the CoCrFeNi high entropy alloy include: The Al x The welded parts of the CoCrFeNi high entropy alloy are ground.

3. The multi-stage contact reaction brazing method of Al using composite foil as claimed in claim 2 x The method for making a CoCrFeNi high entropy alloy is characterized in that The purity of the Nb foil layer is not less than 95%, and the thickness ranges from 10 μm to 50 μm.

4. The multi-stage contact reaction brazing method of Al using composite foil as claimed in claim 2 x The method for making a CoCrFeNi high entropy alloy is characterized in that The purity of the Ni foil layer is not less than 98%, and the thickness ranges from 10 μm to 50 μm.

5. The multi-stage contact reaction brazing method of Al using composite foil as claimed in claim 1 x The method for making a CoCrFeNi high entropy alloy is characterized in that The step of cleaning the to-be-welded portions of the two to-be-welded base materials and the composite foil specifically includes: Immerse the base metal to be welded and the composite foil in an acetone solution, clean them by ultrasonic means for 10 minutes to 30 minutes, and then dry them; The dried base metal to be welded and the composite foil are immersed in an ethanol solution, cleaned by ultrasonic means for 10 minutes to 20 minutes, and then dried.

6. The multi-stage contact reaction brazing method using composite foil according to claim 1 x The method for making a CoCrFeNi high entropy alloy is characterized in that The pressure exerted by the pressing block on the assembly to be welded is 0.25N-1N.

7. The multi-stage contact reaction brazing method of Al using composite foil as claimed in claim 1 x The method for making a CoCrFeNi high entropy alloy is characterized in that The furnace chamber of the brazing furnace is evacuated to 2×10 -3 Pa-5.0×10 -3 Pa, before the brazing, the heating rate of the assembly to be welded is 5°C / min-20°C / min, and after the brazing, the cooling rate of the assembly to be welded after welding is 5°C / min-10°C / min.

8. The multi-stage contact reaction brazing method of Al using composite foil according to claim 1 or 7. x The method for making a CoCrFeNi high entropy alloy is characterized in that During the brazing, the assembly to be welded is heated to a temperature of 1240° C. and the holding time is 10 minutes.

9. A brazing joint, characterized in that: Comprising a composite foil and two Al x CoCrFeNi high entropy alloy, the composite foil is connected to the two Al x CoCrFeNi high entropy alloy, wherein 0<x<0.3, the atomic ratio of Ni and Nb ranges from 50% to 73.5%, and the composite foil includes two Ni foil layers and a Nb foil layer, and the Nb foil layer is connected between the two Ni foil layers.

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