A method for brazing dissimilar materials using a bionic structure intermediate layer

Abstract

A method for brazing dissimilar materials with the aid of a bionic structure intermediate layer relates to a method for brazing dissimilar materials. The purpose is to solve the problem of large residual stress and low joint strength in the brazing joint between ceramic or ceramic-based composite materials and metal materials. Method: The bamboo wall structure of bamboo in nature is composed of pores that are dense on the outside and sparse on the inside. Based on this, holes are punched in the metal or ceramic intermediate layer material to prepare a bionic structure intermediate layer, and then the brazing material, bionic structure intermediate layer and the parent material to be welded are assembled and brazed. The bionic structure intermediate layer of the present invention has a pore arrangement pattern similar to that of the bamboo wall, can absorb energy during the stress load transfer process, improve the stress bearing capacity of the intermediate layer material, improve the stress distribution form in the brazed joint, relieve the residual stress of the joint, and ultimately improve the mechanical properties of the brazed joint.

Description

Technical Field

[0001] The invention relates to a method for assisting brazing of dissimilar materials with a bionic structure intermediate layer. Background Art

[0002] Reliable connection of dissimilar materials can achieve complementary material advantages, give full play to their respective performance advantages, and better meet the needs of modern industry. In particular, the connection between metal materials and ceramics or ceramic-based composites can enable components to selectively achieve functions such as high temperature resistance, oxidation resistance, corrosion resistance, wave transmission and filtering. However, the large difference in thermal expansion coefficient between ceramics or ceramic-based composites and metal materials often leads to large residual stresses in brazed joints, especially at the edges and corners of ceramics or ceramic-based composites, which easily become stress concentration areas and weak points for joint failure, seriously affecting the connection strength of brazed joints. In addition, the metal base material reacts with the active elements in the brazing filler metal and excessively dissolves into the brazing seam, easily forming a large amount of brittle compounds in the brazing seam, which is also not conducive to improving the mechanical properties of the joint.

[0003] Adding an intermediate layer with a low thermal expansion coefficient to the brazing seam can create a gradient transition in the brazed joint, effectively alleviating residual stress in the brazed joint. Commonly used metal intermediate layer materials include Mo, W, and Nb. Although the thermal expansion coefficients of these materials are relatively low among metals, they are still larger than the ceramic or ceramic-based composite parent material to be welded. When ceramic materials with even lower thermal expansion coefficients are used as intermediate layers, the brittle ceramic intermediate layer will break under the action of residual stress, becoming a new weak link in the brazed joint. In current research, foam metals and porous ceramics are used as intermediate layer materials in brazed joints. Their common feature is that they both have a three-dimensional network structure that can be penetrated by liquid brazing material during the brazing process to form a relatively uniform composite interface. However, these intermediate layers are often thick and have a relatively random pore distribution, which is not conducive to the precise assembly of the brazed joint, and the uniformity and stability of the joint performance are also difficult to ensure. Summary of the Invention

[0004] To address the high residual stress, low joint strength, and poor joint performance uniformity and stability in existing dissimilar material brazing joints, this invention proposes a method for brazing dissimilar materials using a biomimetic structural interlayer. The biomimetic structural interlayer draws on the structural characteristics of bamboo walls found in nature. The interlayer is perforated to create a biomimetic structure, and the porosity decreases exponentially from the outside to the inside. The biomimetic structural interlayer absorbs more energy during joint stress load transfer, improving the stress-bearing capacity of the interlayer material. Furthermore, the biomimetic structural interlayer improves the stress distribution in the brazed joint, alleviating residual stress and enhancing the uniformity and stability of the joint performance, ultimately improving the mechanical properties of the brazed joint.

[0005] The method for assisting brazing of dissimilar materials with a biomimetic structure intermediate layer of the present invention is carried out by the following steps:

[0006] Step 1: Punch holes in the middle layer material with a hole diameter of 0.05 to 2 mm to prepare a bionic structure middle layer;

[0007] The intermediate layer material is a metal material or a ceramic material;

[0008] The method for punching the middle layer material is as follows: using several concentric rings to divide the surface of the middle layer material into a multi-layer structure, the width from the center of the innermost layer to the edge of the innermost layer is 4 to 10 times the punching diameter and the porosity of the innermost layer is 0.1% to 3%, the width of the outermost layer is 2 to 4 times the punching diameter and the porosity of the outermost layer is 5% to 10%, and the porosity of the middle layer is calculated according to the formula y = Ae -x / t +y0 is calculated, where x is the relative position from the center of the width of the middle layer to the center of the innermost layer, the center of the innermost layer is the starting point of the relative position and x=0, and the edge of the outermost layer is the end point of the relative position and x=1. A, t, and y0 are fitting constants. A, t, and y0 are determined by linearly fitting the porosity of the innermost layer and the porosity of the outermost layer to obtain array fitting constants. The array fitting constants are verified and retained to meet the average porosity of the entire surface of the middle layer material of 2-5%.

[0009] Step 2: Grind and clean the middle layer of the bionic structure and the surfaces of the two base materials to be welded;

[0010] Step 3: placing the bionic structure middle layer between two layers of solder to form a sandwich structure, and then placing the sandwich structure between the to-be-welded surfaces of two base materials to be welded to obtain a welded part;

[0011] Step 4: Place the assembled parts to be welded in a brazing furnace for brazing connection.

[0012] The principles and beneficial effects of the present invention are:

[0013] 1. The bionic structure intermediate layer of the present invention can effectively block the elements dissolved in the metal matrix from diffusing to the ceramic or ceramic-based composite material side, avoiding the formation of brittle intermetallic compounds at the interface between the intermediate layer and the ceramic or composite matrix material, while reducing the degree of dissolution of the metal matrix.

[0014] 2. The bionic structure intermediate layer of the present invention is well bonded with the solder, and the liquid solder completely fills the pores of the intermediate layer to form a composite interface structure, effectively reducing the thermal expansion coefficient of the brazing seam structure, reducing the residual stress of the joint in the brazing joint of dissimilar materials, and improving the mechanical properties of the joint.

[0015] 3. The bionic structure intermediate layer of the present invention has a pore arrangement pattern similar to that of bamboo wall, which can absorb energy during stress load transmission, improve the stress bearing capacity of the intermediate layer material, improve the stress distribution in the brazing joint, relieve stress concentration at the corners of ceramics or ceramic-based composite materials, and avoid the formation of through cracks at the interface of the intermediate layer material and the interface of the ceramic or ceramic-based composite material parent material.

[0016] 4. The mechanical or laser punching method of the present invention is used to prepare the bionic structure intermediate layer, which has the advantages of simplicity, high efficiency and low cost. The type, thickness and punching diameter of the intermediate layer are selected according to the shape and size of the surface to be connected and the assembly requirements. The punching design of the bionic structure intermediate layer is based on the formula of the pore distribution law of the bamboo wall.

[0017] 5. Using the bionic structure intermediate layer of the present invention, AgCuTi solder is used to braze SiO 2f / SiO2 composite material and Invar alloy, the brittle compounds in the brazed joint only exist at the interface between Invar alloy and the middle layer, and the stress concentration position is from SiO 2f The interface of the / SiO2 composite material is transferred to the pore position of the middle layer of the bionic structure, the stress at the corners of the brazed joint is relieved, and the shear strength of the brazed joint reaches 32 to 38 MPa. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 This is a schematic diagram of the bamboo wall structure in nature;

[0019] Figure 2 This is a schematic diagram of punching holes in the middle layer of the bionic structure in Example 1;

[0020] Figure 3 This is the interface morphology of the bionic structure intermediate layer auxiliary brazing joint in Example 1;

[0021] Figure 4 This is the interface morphology of the bionic structure intermediate layer auxiliary brazing joint in Example 1 (enlarged);

[0022] Figure 5 This is the interface structure morphology of the direct brazing joint without an intermediate layer in Comparative Example 1;

[0023] Figure 6 This is the interface microstructure of the direct brazing joint without an intermediate layer in Comparative Example 1 (enlarged);

[0024] Figure 7 This is the interface microstructure of the SiC intermediate layer assisted brazing joint in Comparative Example 2;

[0025] Figure 8 This is the interface microstructure of the SiC intermediate layer assisted brazing joint in comparative example 2 (enlarged). DETAILED DESCRIPTION

[0026] The technical solution of the present invention is not limited to the specific implementation methods listed below, but also includes any reasonable combination of the specific implementation methods.

[0027] Specific embodiment 1: The method of assisting brazing of dissimilar materials with a biomimetic structure intermediate layer in this embodiment is carried out in the following steps:

[0028] Step 1: Punch holes in the middle layer material with a hole diameter of 0.05 to 2 mm to prepare a bionic structure middle layer;

[0029] The intermediate layer material is a metal material or a ceramic material;

[0030] The method for punching the middle layer material is as follows: using several concentric rings to divide the surface of the middle layer material into a multi-layer structure, the width from the center of the innermost layer to the edge of the innermost layer is 4 to 10 times the punching diameter and the porosity of the innermost layer is 0.1% to 3%, the width of the outermost layer is 2 to 4 times the punching diameter and the porosity of the outermost layer is 5% to 10%, and the porosity of the middle layer is calculated according to the formula y = Ae -x / t +y0 is calculated, where x is the relative position from the center of the width of the middle layer to the center of the innermost layer, the center of the innermost layer is the starting point of the relative position and x=0, and the edge of the outermost layer is the end point of the relative position and x=1. A, t, and y0 are fitting constants. A, t, and y0 are determined by linearly fitting the porosity of the innermost layer and the porosity of the outermost layer to obtain array fitting constants. The array fitting constants are verified and retained to meet the average porosity of the entire surface of the middle layer material of 2-5%.

[0031] Step 2: Grind and clean the middle layer of the bionic structure and the surfaces of the two base materials to be welded;

[0032] Step 3: placing the bionic structure middle layer between two layers of solder to form a sandwich structure, and then placing the sandwich structure between the to-be-welded surfaces of two base materials to be welded to obtain a welded part;

[0033] Step 4: Place the assembled parts to be welded in a brazing furnace for brazing connection.

[0034] This embodiment has the following beneficial effects:

[0035] 1. The bionic structure intermediate layer of this embodiment can effectively block the elements dissolved in the metal matrix from diffusing to the ceramic or ceramic-based composite material side, avoiding the formation of brittle intermetallic compounds at the interface between the intermediate layer and the ceramic or composite matrix, while reducing the degree of dissolution of the metal matrix.

[0036] 2. The bionic structure intermediate layer of this embodiment is well bonded with the solder, and the liquid solder completely fills the pores of the intermediate layer to form a composite interface structure, effectively reducing the thermal expansion coefficient of the brazing seam structure, reducing the residual stress of the joint in the brazing joint of dissimilar materials, and improving the mechanical properties of the joint.

[0037] 3. The bionic structure intermediate layer of this embodiment has a pore arrangement pattern similar to that of bamboo wall, which can absorb energy during stress load transmission, improve the stress bearing capacity of the intermediate layer material, improve the stress distribution in the brazing joint, alleviate the stress concentration at the corners of ceramics or ceramic-based composite materials, and avoid the formation of through cracks at the interface of the intermediate layer material and the interface of the ceramic or ceramic-based composite material base material.

[0038] 4. In this embodiment, the bionic structure intermediate layer is prepared by mechanical or laser punching method, which has the advantages of simplicity, high efficiency and low cost. The type, thickness and punching diameter of the intermediate layer are selected according to the shape and size of the surface to be connected and the assembly requirements. The punching design of the bionic structure intermediate layer is based on the formula of the pore distribution law of bamboo wall.

[0039] 5. Using the bionic structure intermediate layer of this embodiment, AgCuTi solder is used to braze SiO 2f / SiO2 composite material and Invar alloy, the brittle compounds in the brazed joint only exist at the interface between Invar alloy and the middle layer, and the stress concentration position is from SiO 2f The interface of the / SiO2 composite material is transferred to the pore position of the middle layer of the bionic structure, the stress at the corners of the brazed joint is relieved, and the shear strength of the brazed joint reaches 32 to 38 MPa.

[0040] Specific embodiment 2: This embodiment differs from specific embodiment 1 in that the thickness of the intermediate layer of the bionic structure described in step 1 is 0.05 mm to 1 mm.

[0041] Specific embodiment three: The difference between this embodiment and specific embodiment one or two is that the punching method described in step one is mechanical punching or laser punching, and the laser punching process parameters are: processing frequency 10~20KHz, processing speed 40~60mm / s, laser power 10~20W.

[0042] Specific embodiment 4: This embodiment differs from any one of specific embodiments 1 to 3 in that: the metal material in step 1 is W, Mo or Co, and the ceramic material is carbide ceramic, oxide ceramic or nitride ceramic.

[0043] Specific embodiment 5: This embodiment differs from any one of specific embodiments 1 to 4 in that: in step 2, 200#, 400#, 1000#, and 2000# sandpaper are used sequentially for polishing to remove dirt and oxide film.

[0044] Specific embodiment 6: This embodiment differs from any one of specific embodiments 1 to 5 in that: the cleaning method in step 2 is ultrasonic cleaning, the washing liquid is anhydrous ethanol or acetone, and the ultrasonic cleaning time is 10 to 20 minutes.

[0045] Specific embodiment seven: This embodiment differs from any one of specific embodiments one to six in that the two layers of solder in step three are solders of the same composition or solders of different compositions.

[0046] Specific embodiment eight: This embodiment differs from any one of specific embodiments one to seven in that the solder in step three is a Cu-based solder, an Ag-based solder, a Ni-based solder, a Ti-based solder, a Zr-based solder or a Sn-based solder.

[0047] Specific embodiment 9: This embodiment differs from any one of specific embodiments 1 to 8 in that: the two base materials to be welded in step 3 are base material 1 and base material 2, base material 1 is a C / C composite material, a C / SiC composite material, a SiO 2f / SiO2 composite material, SiO2-BN composite material or oxide ceramic; the base material 2 is Nb-based alloy, Ti-based alloy, Fe-based alloy or Ni-based high-temperature alloy.

[0048] Specific embodiment 10: The difference between this embodiment and the specific embodiments 1 to 9 is that the brazing process parameters in step 4 are: the vacuum degree is greater than 5×10 -3 Pa, the heating rate is 1-15℃ / min, the brazing temperature is 20-150℃ higher than the melting point of the brazing material, the holding time is 5-30min, and the cooling rate is 1-10℃ / min.

[0049] Example 1:

[0050] The method for assisting brazing of dissimilar materials with a biomimetic structure intermediate layer in this embodiment is carried out as follows:

[0051] Step 1: Punch holes in the middle layer material with a hole diameter of 0.3 mm to prepare a bionic structure middle layer;

[0052] The thickness of the middle layer of the bionic structure is 0.3 mm;

[0053] The method of punching the middle layer material is as follows: using several concentric rings to divide the surface of the middle layer material into a 4-layer structure, the width from the center of the innermost layer to the edge of the innermost layer is 1.1mm and the porosity of the innermost layer is 1.8%, the width of the outermost layer is 0.8mm and the porosity of the outermost layer is 8%, and the porosity of the middle layer is calculated according to the formula y=Ae -x / t+y0 is calculated, where x is the relative position from the center of the width of the middle layer to the center of the innermost layer, the center of the innermost layer is the starting point of the relative position and x=0, and the edge of the outermost layer is the end point of the relative position and x=1. A, t, and y0 are fitting constants; A=0.024, t=-0.179, y0=1.684; the average porosity of the surface of the middle layer material is 4.5%;

[0054] The punching method is laser punching, and the laser punching process parameters are: processing frequency 20KHz, processing speed 50mm / s, laser power 16W;

[0055] The bionic structure middle layer is made of SiC ceramic and has a size of 8mm×8mm×0.3mm;

[0056] Step 2: Grind and clean the middle layer of the bionic structure and the surfaces of the two base materials to be welded;

[0057] During the polishing, 200#, 400#, 1000#, and 2000# sandpaper are used in sequence to polish to remove dirt and oxide film;

[0058] The cleaning method is ultrasonic cleaning, the cleaning liquid is acetone, and the ultrasonic cleaning time is 10 minutes;

[0059] Step 3: placing the bionic structure middle layer between two layers of solder to form a sandwich structure, and then placing the sandwich structure between the to-be-welded surfaces of two base materials to be welded to obtain a welded part;

[0060] The two layers of solder are made of the same composition of AgCuTi solder;

[0061] The two base materials to be welded in step 3 are base material 1 and base material 2. Base material 1 is SiO 2f / SiO2 composite material, the base material 2 is Invar alloy; SiO 2f The size of the / SiO2 composite material is 5mm×5mm×5mm, and the size of the Invar alloy is 15mm×10mm×3mm.

[0062] Step 4: Place the assembled parts to be welded in a brazing furnace for brazing connection.

[0063] The brazing process parameters are as follows: vacuuming the furnace until the vacuum rate reaches 5×10 -3 Pa, start heating, increase the temperature to 900℃ at a rate of 10℃ / min and keep it for 10min, then reduce the temperature to 200℃ at a rate of 5℃ / min, and finally turn off the heating and cool it to room temperature with the furnace.

[0064] Comparative Example 1: The method for brazing dissimilar materials is carried out according to the following steps:

[0065] AgCuTi solder is coated on SiO 2f Brazing connection between / SiO2 composite material and Invar alloy;

[0066] The brazing process parameters are as follows: vacuuming the furnace until the vacuum rate reaches 5×10 -3 Pa, start heating, heat up to 450℃ at a rate of 15℃ / min, then heat up to 800℃ at a rate of 10℃ / min, then heat up to 900℃ at a rate of 5℃ / min and keep warm for 10min, then cool down to 200℃ at a rate of 5℃ / min, finally turn off heating and cool to room temperature with the furnace. Before brazing, SiO 2f The surfaces to be welded of the SiO2 composite material and Invar alloy were polished with 240#, 400#, 600# and 1000# sandpaper in sequence, then ultrasonically cleaned in acetone for 10 min and taken out to dry.

[0067] Comparative Example 2: The method for brazing dissimilar materials is carried out according to the following steps:

[0068] AgCuTi brazing filler metal is coated on both sides of the unperforated SiC ceramic intermediate layer and placed on the SiO 2f Brazing connection between / SiO2 composite material and Invar alloy;

[0069] The SiC ceramic intermediate layer has a size of 8 mm × 8 mm × 0.3 mm;

[0070] The brazing process parameters are as follows: vacuuming the furnace until the vacuum rate reaches 5×10 -3 Pa, start heating, heat up to 450℃ at a rate of 15℃ / min, then heat up to 800℃ at a rate of 10℃ / min, then heat up to 900℃ at a rate of 5℃ / min and keep warm for 10min, then cool down to 200℃ at a rate of 5℃ / min, finally turn off heating and cool to room temperature with the furnace. Before brazing, SiO 2f The surfaces to be welded of the SiO2 composite material, SiC ceramic intermediate layer and Invar alloy were polished with 240#, 400#, 600# and 1000# sandpaper in sequence, then ultrasonically cleaned in acetone for 10 min and taken out to dry.

[0071] exist Figure 3 and Figure 4 In the experiment, the bionic structure SiC ceramic intermediate layer assisted brazing, which changed the distribution of residual stress in the joint. The joint was crack-free and the interface was well bonded. The perforated intermediate layer could block the diffusion of brittle compounds to the composite material side, thus improving the mechanical properties of the joint. The shear strength of the joint was 35MPa. Figure 5 and Figure 6 In SiO2f When brazing SiO2 and Invar alloy without an intermediate layer, the difference in thermal expansion coefficients between the two is too large, resulting in large residual stress in the joint and obvious cracks on the composite material side. Figure 7 and Figure 8 In the case of unperforated SiC ceramic assisted brazing, the brazed joint is 2f Obvious cracks were found on both the composite / SiO2 sides. The reason was that the residual stress on the composite side was transferred to the SiC ceramic, and cracks occurred on both the composite and SiC sides.

[0072] Example 2

[0073] The method for assisting brazing of dissimilar materials with a biomimetic structure intermediate layer in this embodiment is carried out as follows:

[0074] Step 1: Punch holes in the middle layer material with a hole diameter of 0.3 mm to prepare a bionic structure middle layer;

[0075] The thickness of the middle layer of the bionic structure is 0.3 mm;

[0076] The method of punching the middle layer material is as follows: using several concentric rings to divide the surface of the middle layer material into 10 layers, the width from the center of the innermost layer to the edge of the innermost layer is 1.2mm and the porosity of the innermost layer is 1.6%, the width of the outermost layer is 0.8mm and the porosity of the outermost layer is 7%, and the porosity of the middle layer is calculated according to the formula y=Ae -x / t +y0 is calculated, where x is the relative position from the center of the width of the middle layer to the center of the innermost layer, the center of the innermost layer is the starting point of the relative position and x=0, and the edge of the outermost layer is the end point of the relative position and x=1. A, t, and y0 are fitting constants; A=0.058, t=-0.220, y0=1.485; the average porosity of the surface of the middle layer material is 3.5%;

[0077] The punching method is laser punching, and the laser punching process parameters are: processing frequency 20KHz, processing speed 50mm / s, laser power 16W;

[0078] The bionic structure middle layer is made of SiC ceramic and has a size of 20mm×20mm×0.3mm;

[0079] Step 2: Grind and clean the middle layer of the bionic structure and the surfaces of the two base materials to be welded;

[0080] During the polishing, 200#, 400#, 1000#, and 2000# sandpaper are used in sequence to polish to remove dirt and oxide film;

[0081] The cleaning method is ultrasonic cleaning, the cleaning liquid is acetone, and the ultrasonic cleaning time is 10 minutes;

[0082] Step 3: placing the bionic structure middle layer between two layers of solder to form a sandwich structure, and then placing the sandwich structure between the to-be-welded surfaces of two base materials to be welded to obtain a welded part;

[0083] The two layers of solder are made of the same composition of AgCuTi solder;

[0084] The two base materials to be welded in step 3 are base material 1 and base material 2. Base material 1 is SiO 2f / SiO2 composite material, the base material 2 is Invar alloy; SiO 2f The dimensions of the / SiO2 composite material are 20mm×20mm×5mm, and the dimensions of the Invar alloy are 35mm×35mm×3mm

[0085] Step 4: Place the assembled parts to be welded in a brazing furnace for brazing connection.

[0086] The brazing process parameters are as follows: vacuuming the furnace until the vacuum rate reaches 5×10 -3 Pa, start heating, increase the temperature to 900℃ at a rate of 10℃ / min and keep it for 10min, then reduce the temperature to 200℃ at a rate of 5℃ / min, and finally turn off the heating and cool it to room temperature with the furnace.

[0087] Comparative Example 3: The method for brazing dissimilar materials is carried out according to the following steps:

[0088] AgCuTi brazing filler metal is coated on both sides of the unperforated SiC ceramic intermediate layer and placed on the SiO 2f Brazing connection between / SiO2 composite material and Invar alloy;

[0089] The size of the SiC ceramic intermediate layer is 20 mm × 20 mm × 0.3 mm;

[0090] The brazing process parameters are as follows: vacuuming the furnace until the vacuum rate reaches 5×10 -3 Pa, start heating, heat up to 450℃ at a rate of 15℃ / min, then heat up to 800℃ at a rate of 10℃ / min, then heat up to 900℃ at a rate of 5℃ / min and keep warm for 10min, then cool down to 200℃ at a rate of 5℃ / min, finally turn off heating and cool to room temperature with the furnace. Before brazing, SiO 2f The surfaces to be welded of the SiO2 composite material, SiC ceramic intermediate layer and Invar alloy were polished with 240#, 400#, 600# and 1000# sandpaper in sequence, then ultrasonically cleaned in acetone for 10 min and taken out to dry.

[0091] As the welding area increases, the influence of the residual stress of the joint on the mechanical properties becomes more obvious. The shear strength of the joint in Example 3 using an unperforated intermediate layer is 6 MPa, while the shear strength of the joint in Example 2 using a bionic structure intermediate layer is 9 MPa, an increase of 50%.

Claims

1. A method for brazing dissimilar materials using a bionic structure intermediate layer, characterized in that: The method for brazing dissimilar materials with a bionic structure intermediate layer is carried out in the following steps: Step 1: Punch holes in the middle layer material with a hole diameter of 0.05 to 2 mm to prepare a bionic structure middle layer; The method for punching the middle layer material is as follows: using several concentric rings to divide the surface of the middle layer material into a multi-layer structure, the width from the center of the innermost layer to the edge of the innermost layer is 4 to 10 times the punching diameter and the porosity of the innermost layer is 0.1% to 3%, the width of the outermost layer is 2 to 4 times the punching diameter and the porosity of the outermost layer is 5% to 10%, and the porosity of the middle layer is calculated according to the formula y = Ae -x / t +y0 is calculated, where x is the relative position from the center of the width of the middle layer to the center of the innermost layer, the center of the innermost layer is the starting point of the relative position and x=0, and the edge of the outermost layer is the end point of the relative position and x=1. A, t, and y0 are fitting constants. A, t, and y0 are determined by linearly fitting the porosity of the innermost layer and the porosity of the outermost layer to obtain array fitting constants. The array fitting constants are verified and retained to meet the average porosity of the entire surface of the middle layer material of 2-5%. The intermediate layer material is a metal material or a ceramic material; Step 2: Grind and clean the middle layer of the bionic structure and the surfaces of the two base materials to be welded; Step 3: placing the bionic structure middle layer between two layers of solder to form a sandwich structure, and then placing the sandwich structure between the to-be-welded surfaces of two base materials to be welded to obtain a welded part; Step 4: Place the assembled parts to be welded in a brazing furnace for brazing connection; The solder in step 3 is a Cu-based solder, an Ag-based solder, a Ni-based solder, a Ti-based solder, a Zr-based solder or a Sn-based solder; The two base materials to be welded in step 3 are base material 1 and base material 2, base material 1 is C / C composite material, C / SiC composite material, SiO 2f / SiO2 composite material, SiO2-BN composite material or oxide ceramic; the base material 2 is Nb-based alloy, Ti-based alloy, Fe-based alloy or Ni-based high-temperature alloy.

2. The method for brazing dissimilar materials using a biomimetic structure intermediate layer as claimed in claim 1, characterized in that: The thickness of the middle layer of the bionic structure described in step 1 is 0.05 mm to 1 mm.

3. The method for brazing dissimilar materials using a biomimetic structure intermediate layer as claimed in claim 1, characterized in that: The punching method described in step 1 is mechanical punching or laser punching, and the laser punching process parameters are: processing frequency 10-20KHz, processing speed 40-60mm / s, and laser power 10-20W.

4. The method for brazing dissimilar materials using a biomimetic structure intermediate layer as claimed in claim 1, characterized in that: The metal material in step 1 is W, Mo or Co, and the ceramic material is carbide ceramic, oxide ceramic or nitride ceramic.

5. The method for brazing dissimilar materials using a biomimetic structure intermediate layer as claimed in claim 1, characterized in that: During the polishing process in step 2, use 200#, 400#, 1000#, and 2000# sandpaper in sequence to remove dirt and oxide film.

6. The method for brazing dissimilar materials using a biomimetic structure intermediate layer as claimed in claim 1, characterized in that: The cleaning method described in step 2 is ultrasonic cleaning, the cleaning liquid is anhydrous ethanol or acetone, and the ultrasonic cleaning time is 10 to 20 minutes.

7. The method for brazing dissimilar materials using a biomimetic structure intermediate layer as claimed in claim 1, characterized in that: The two layers of solder in step 3 may be solders of the same composition or solders of different compositions.

8. The method for brazing dissimilar materials using a biomimetic structure intermediate layer as claimed in claim 1, characterized in that: The brazing process parameters described in step 4 are: vacuum degree greater than 5×10 -3 Pa, the heating rate is 1-15℃ / min, the brazing temperature is 20-150℃ higher than the melting point of the brazing material, the holding time is 5-30min, and the cooling rate is 1-10℃ / min.

Images