Method for the production of a three-dimensional meshed magnesia-alumina composite interlayer for the brazing of dissimilar materials by means of joule heating and use thereof

Abstract

A method for preparing a three-dimensional grid magnesium aluminate composite interlayer for heterogeneous material brazing by joule heat shock and its application belong to the field of brazing connection of space mirrors. The present application solves the problem of uneven dispersion of the reinforcing phase of the brazing interlayer for the large-size SiC space mirror and the Al / SiC composite material support on the grid structure. The method comprises the following steps: 1. preparation of MgAl2O4 precursor solution; 2. impregnation; 3. preparation of three-dimensional grid MgAl2O4 composite interlayer by joule heat shock. Application: it is used for brazing of SiC and Al / SiC composite material. The present application is used for preparing a three-dimensional grid magnesium aluminate composite interlayer for heterogeneous material brazing by joule heat shock and its application.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of brazing connection of space mirrors. BACKGROUND

[0002] In order to cope with increasingly complex and precise space observation and detection tasks, the new generation of space mirrors selects lightweight SiC with excellent specific stiffness and thermal stability as the mirror material, and lightweight high-strength Al / SiC composite material with SiC content exceeding 40% as the annular support. Currently, SiC mirrors and Al / SiC composite material supports still use traditional mechanical flange connection method, which not only significantly increases the overall weight of the optical system, but also easily causes deformation at the connection, thereby affecting the optical accuracy and thermal stability, making it difficult to meet the increasingly stringent space mission requirements. In contrast, brazing connection technology can effectively reduce the structure weight, provide good connection strength, reduce deformation, and help improve the accuracy and thermal stability of the optical system, and is therefore considered a more ideal alternative.

[0003] Currently, there is little research on the brazing connection of SiC and Al / SiC composite material, and existing research mainly focuses on the brazing of each material with other materials. Al / SiC composite material usually uses Al-based filler metal, while SiC brazing uses AgCu-based, Ni-based, Ti-based and other filler metals, showing good mechanical properties. Although the research is limited, Al-based filler metal shows good compatibility and mechanical properties in the connection of SiC and Al / SiC composite material, especially AlSiMg filler metal. Due to the difference in thermal expansion coefficient between SiC (4.0×10 -6 / K) and Al / SiC composite material (12.0×10 -6 / K), the brazed joint is prone to generate large residual stress, especially in large-size joints, which is more prominent, leading to cracks and reduced mechanical properties. Therefore, relieving residual stress becomes a key problem. Particle reinforced phase can relieve residual stress by adjusting the thermal expansion coefficient, but there is currently no reinforcing phase suitable for Al-based filler metal. The grid structure of the porous metal skeleton loaded with reinforcing phase can uniformly distribute the reinforcing phase, but the tight connection between the particle reinforced phase and the grid skeleton is a key difficulty. If the particle reinforced phase separates from the grid skeleton during brazing, local agglomeration of the reinforcing phase will still occur. Therefore, the tight connection between the uniformly distributed reinforcing phase and the grid skeleton is a key link to ensure the effect of the composite interlayer on the gradient transition of the thermal expansion coefficient of the joint. SUMMARY

[0004] The present application aims to solve the problem of uneven distribution of the reinforcing phase in the brazing interlayer between the large-size SiC space mirror and the Al / SiC composite support, and further provides a method for preparing a three-dimensional grid magnesium aluminate composite interlayer for heterogeneous material brazing by joule heating impact and its application.

[0005] A method for preparing a three-dimensional grid magnesium aluminate composite interlayer for heterogeneous material brazing by joule heating impact, which is carried out according to the following steps:

[0006] I. Preparation of MgAl2O4 precursor solution:

[0007] Dissolve magnesium nitrate and aluminum nitrate in deionized water to obtain a MgAl2O4 precursor solution;

[0008] II. Immersion:

[0009] After acid washing, the porous Nb grid framework is immersed in the MgAl2O4 precursor solution, and finally dried to obtain the immersed grid framework;

[0010] III. Preparation of three-dimensional grid MgAl2O4 composite interlayer by joule heating impact:

[0011] The carbon fiber cloth, the immersed grid framework and the carbon fiber cloth are stacked in order, and the carbon fiber cloth on both sides is used as the joule heating heat source, under the conditions of vacuum, voltage of 15V-30V and current of 30A-90A, heat preservation for 5s-300s, then stop the current, to obtain a three-dimensional grid magnesium aluminate composite interlayer for heterogeneous material brazing.

[0012] Application: It is used for brazing SiC and Al / SiC composite materials.

[0013] The beneficial effects of the present application are:

[0014] 1. The method for preparing a three-dimensional grid MgAl2O4 composite interlayer by joule heating impact. The method realizes the uniform distribution and close combination of MgAl2O4 particle reinforcing phase on the surface of the Nb grid framework, and avoids the particle agglomeration phenomenon caused by high temperature and long time treatment in the traditional heat treatment process. This uniform distribution significantly improves the structural performance and uniformity of the composite interlayer.

[0015] 2. The joule heating impact method significantly shortens the preparation period of the composite interlayer by rapidly heating (1000-3000℃) and rapidly cooling in a short time, avoids the problems of high energy consumption and long process time in the traditional heat treatment, and greatly improves the preparation efficiency.

[0016] 3. The joule heating shock technique not only avoids particle aggregation, but also can prepare nanoscale MgAl2O4 reinforcing phase particles, further improving the microstructure quality and mechanical properties of the composite interlayer, and providing superior performance support for the brazed joint. BRIEF DESCRIPTION OF DRAWINGS

[0017] Figure 1 Temperature curve of joule heating shock for step three of the embodiment;

[0018] Figure 2 Morphology and element distribution of the three-dimensional grid magnesium aluminate composite interlayer prepared in Example One for heterogeneous material brazing, (a) is the morphology, (b) is the distribution of Mg element in the composite interlayer, (c) is the distribution of Al element in the composite interlayer, and (d) is the distribution of O element in the composite interlayer;

[0019] Figure 3 Picture of the combination of the reinforcing phase and the matrix on the microstructure of the three-dimensional grid magnesium aluminate composite interlayer prepared in Example One for heterogeneous material brazing;

[0020] Figure 4 Shear strength and strain relationship curve of the brazed joint assisted by the three-dimensional grid magnesium aluminate composite interlayer prepared in Example One and the comparative experiment. DETAILED DESCRIPTION

[0021] Specific implementation one: the method for preparing a three-dimensional grid magnesium aluminate composite interlayer for heterogeneous material brazing by joule heating shock, which is carried out according to the following steps:

[0022] I. Preparation of MgAl2O4 precursor solution:

[0023] Dissolve magnesium nitrate and aluminum nitrate in deionized water to obtain a MgAl2O4 precursor solution;

[0024] II. Immersion:

[0025] Place the pickled porous Nb grid skeleton in the MgAl2O4 precursor solution for immersion, and finally dry to obtain the immersed grid skeleton;

[0026] III. Preparation of three-dimensional grid MgAl2O4 composite interlayer by joule heating shock:

[0027] Stack the carbon fiber cloth, the immersed grid skeleton, and the carbon fiber cloth in order, with the carbon fiber cloth on both sides as the joule heating heat source, under the conditions of vacuum, voltage of 15V-30V, and current of 30A-90A, heat for 5s-300s, then stop the current, to obtain a three-dimensional grid magnesium aluminate composite interlayer for heterogeneous material brazing.

[0028] The specific embodiment selects MgAl2O4(8.5x10 -6 / K) and Nb(7.5x10 -6 / K) with a thermal expansion coefficient matched, uses the gradient transition characteristics to relieve the residual stress of the large-size joint, improves the mechanical properties of the joint, and thus realizes high-quality brazing connection.

[0029] In step two of the specific embodiment, the soaked mesh skeleton is naturally dried at room temperature or treated by low-temperature drying (100°C). This step ensures that the precursor solution completely penetrates and adheres to the surface and pores of the Nb mesh skeleton.

[0030] The specific embodiment uses carbon fiber cloth as a heating element, which has high electrical conductivity and good thermal conductivity, ensuring that the sample can be uniformly heated during the joule heat shock process. The two ends of each piece of carbon fiber cloth are fixed to the heating electrode of the joule heat shock device through appropriate clamps or contact terminals. Ensure that the carbon fiber cloth is in close contact with the electrode port to avoid uneven heat transfer due to poor contact. Place the prepared impregnated sample between the two pieces of carbon fiber cloth to ensure uniform heating of the sample.

[0031] The specific embodiment uses the joule heat shock method, which can heat up to 1000-3000°C in a very short time and rapidly cool down after heating, achieving rapid quenching. This technology avoids the problem of agglomeration of reinforcing phases caused by long-time high-temperature heat treatment, realizes the close connection of uniformly distributed reinforcing phases and mesh skeletons, and is very suitable for the preparation of high-melting-point oxides. The three-dimensional mesh MgAl2O4 composite interlayer prepared by the joule heat shock method not only realizes the close connection of the particle reinforcing phase and the matrix, but also effectively inhibits the aggregation and movement of the particle reinforcing phase, ensuring the uniform dispersion of the particle reinforcing phase on the matrix, and can also prepare nano-scale reinforcing phases, greatly improving the quality of the three-dimensional mesh composite interlayer.

[0032] In the joule heat shock process, the specific embodiment makes the metal ions in the sample react to form magnesium aluminate (MgAl2O4) particles and deposit them on the surface of the porous Nb skeleton. After heating is completed, the current is stopped quickly and rapid cooling is performed. Due to the characteristics of the joule heat shock method itself, the material can be rapidly cooled in a short time after heating, avoiding excessive oxidation or physical property changes of the material at high temperatures.

[0033] The specific embodiment has the following beneficial effects:

[0034] 1. The method for preparing three-dimensional grid MgAl2O4 composite interlayer by Joule heat shock in the embodiment. The uniform distribution and close combination of MgAl2O4 particle reinforced phase on the surface of Nb grid skeleton are realized, and the particle agglomeration phenomenon caused by high-temperature and long-time treatment in the traditional heat treatment process is avoided. The uniform distribution significantly improves the structural performance and uniformity of the composite interlayer.

[0035] 2. The Joule heat shock method significantly shortens the preparation period of the composite interlayer by rapid heating (1000-3000℃) and rapid cooling in a short time, avoids the problems of high energy consumption and long process time in the traditional heat treatment, and greatly improves the preparation efficiency.

[0036] 3. The Joule heat shock technology not only avoids particle aggregation, but also can prepare nano-level MgAl2O4 reinforced phase particles, further improving the microstructure quality and mechanical properties of the composite interlayer, and providing more superior performance support for the brazed joint.

[0037] Specific implementation method two: The difference between the embodiment and the specific implementation method one is that the concentration of magnesium nitrate in the MgAl2O4 precursor solution in step one is 0.01 mol / L-0.5 mol / L. The others are the same as the specific implementation method one.

[0038] Specific implementation method three: The difference between the embodiment and the specific implementation method one or two is that the molar ratio of magnesium nitrate to aluminum nitrate in step one is 1:2. The others are the same as the specific implementation method one or two.

[0039] Specific implementation method four: The difference between the embodiment and the specific implementation method one to three is that the acid-washed porous Nb grid skeleton in step two is prepared according to the following steps: immersing the porous Nb grid skeleton in a mixed solution containing hydrofluoric acid and nitric acid for 1 min-10 min, then rinsing with deionized water, and finally natural drying or low-temperature drying to obtain the acid-washed porous Nb grid skeleton; the mixed solution containing hydrofluoric acid and nitric acid is prepared by mixing hydrofluoric acid and nitric acid, the mass percentage of hydrofluoric acid is 10%-30%, the mass percentage of nitric acid is 10%-30%, and the volume ratio of hydrofluoric acid to nitric acid is 1:(3-5). The others are the same as the specific implementation method three.

[0040] The acid pickling in the specific implementation method removes the oxides and impurities on the surface of the porous Nb, significantly enhances the activity of the surface. The clean surface can better combine with the MgAl2O4 precursor, laying a foundation for the subsequent deposition and uniform distribution of particles, and reducing the formation of interface defects. The drying step after acid pickling ensures that there is no water and acid residue on the surface, avoiding the instability of the reaction in the subsequent processing process.

[0041] Specific embodiment 5: This embodiment differs from specific embodiments 1 to 4 in that the porosity of the porous Nb grid skeleton is 30% to 70%, and the average pore size of the grid is 50 μm to 300 μm. Other aspects are the same as specific embodiments 1 to 4.

[0042] In this embodiment, porous Nb is selected as the grid skeleton to ensure uniform distribution of structural strength and reinforcement phase.

[0043] Specific embodiment 6: This embodiment differs from specific embodiments 1 to 5 in that in step 2, the acid-washed porous Nb grid skeleton is immersed in a MgAl2O4 precursor solution for 5 to 30 minutes. Other aspects are the same as specific embodiments 1 to 5.

[0044] This embodiment fully impregnates the porous Nb skeleton to ensure that the precursor solution can completely penetrate the pores of the skeleton and achieve uniform deposition of the reinforcement phase particles. After soaking, the grid skeleton is removed and gently shaken to remove excess precursor solution.

[0045] Specific embodiment 7: This embodiment differs from specific embodiments 1 to 6 in that the drying in step 2 is carried out at room temperature to 100° C. for 1 to 3 hours. Other aspects are the same as specific embodiments 1 to 6.

[0046] In this embodiment, drying at room temperature or low temperature ensures the firm attachment of the solution to the skeleton, while avoiding uneven particle distribution caused by premature decomposition of the precursor at high temperature.

[0047] Specific embodiment 8: This embodiment differs from specific embodiments 1 to 7 in that the thickness of the carbon fiber cloth in step 3 is 0.1 mm to 1 mm. Other aspects are the same as specific embodiments 1 to 7.

[0048] Specific embodiment 9: This embodiment differs from specific embodiments 1 to 8 in that: the vacuum in step 3 is a vacuum degree of 10 -2 The vacuum environment is 10 Pa to 10 Pa. Other aspects are the same as those in the first to eighth embodiments.

[0049] In this specific embodiment, the device is evacuated to effectively suppress excessive oxidation caused by high temperature during the Joule thermal shock process, thereby protecting the microstructural integrity of the three-dimensional grid MgAl2O4 composite intermediate layer.

[0050] Specific embodiment 10: This embodiment is used for the application of a three-dimensional grid magnesium aluminate composite intermediate layer for brazing dissimilar materials, and is used for brazing SiC and Al / SiC composite materials.

[0051] The following examples are used to verify the beneficial effects of the present invention:

[0052] Embodiment one:

[0053] A method for preparing a three-dimensional grid magnesium aluminate composite interlayer for heterogeneous material brazing by means of joule heat shock, which is carried out according to the following steps:

[0054] I. Preparation of MgAl2O4 precursor solution:

[0055] Dissolve magnesium nitrate and aluminum nitrate in deionized water to obtain the MgAl2O4 precursor solution;

[0056] The concentration of magnesium nitrate in the MgAl2O4 precursor solution is 0.1 mol / L;

[0057] The molar ratio of magnesium nitrate to aluminum nitrate is 1:2;

[0058] II. Immersion:

[0059] After pickling, the porous Nb grid skeleton is immersed in the MgAl2O4 precursor solution for 15 min, and finally dried at a temperature of 100℃ for 2h to obtain the immersed grid skeleton;

[0060] The size of the porous Nb grid skeleton is 10mm×10mm×1mm, the porosity is 60%, and the average pore size of the grid is 200μm;

[0061] III. Preparation of three-dimensional grid MgAl2O4 composite interlayer by joule heat shock:

[0062] The carbon fiber cloth, the immersed grid skeleton, and the carbon fiber cloth are stacked in order, with the carbon fiber cloth on both sides as the joule heat heating source, under the conditions of a vacuum degree of 5×10 -2 Pa, a voltage of 30V, and a current of 60A, heat for 10s, then stop the current, to obtain a three-dimensional grid magnesium aluminate composite interlayer for heterogeneous material brazing.

[0063] The pickled porous Nb grid skeleton in step two is prepared according to the following steps: immerse the porous Nb grid skeleton in a mixed solution containing hydrofluoric acid and nitric acid for 5min, then rinse with deionized water, and finally dry at a temperature of 100℃ for 2h to obtain the pickled porous Nb grid skeleton; the mixed solution containing hydrofluoric acid and nitric acid is prepared by mixing hydrofluoric acid and nitric acid, the mass percentage of hydrofluoric acid is 10%, the mass percentage of nitric acid is 10%, and the volume ratio of hydrofluoric acid to nitric acid is 1:3.

[0064] The size of the carbon fiber cloth in step three is 40mm×10mm×0.5mm.

[0065] Comparative experiment:

[0066] MgAl2O4 particles are immersed in ethanol to form a MgAl2O4 suspension, a porous Nb grid skeleton is immersed in the MgAl2O4 suspension and ultrasonically dispersed, and excess solvent is removed by drying after soaking to obtain a three-dimensional grid magnesium aluminate composite intermediate layer.

[0067] Figure 1 This is the Joule thermal shock temperature curve of step three of Example 1; under the conditions of setting voltage 30V, current 60A, and holding time 10s, the temperature rises rapidly from 0s to 2s, and quickly rises from room temperature (about 25°C) to above 1050°C. After 2s, the temperature stabilizes at around 1050°C and remains constant. After the 10s holding time, the temperature drops rapidly, and the curve shows a trend of rapid cooling. This curve illustrates the characteristics of Joule thermal shock technology, namely rapid heating, precise temperature control, and rapid cooling.

[0068] Figure 2 The morphology and element distribution diagrams of the three-dimensional grid magnesium aluminate composite interlayer for dissimilar material brazing prepared in Example 1 are as follows: (a) is the morphology, (b) is the distribution of Mg in the composite, (c) is the distribution of Al in the composite, and (d) is the distribution of O in the composite. The cross-nodes and pore structure of the three-dimensional grid can be seen. The elemental scan ratio of Mg-Al-O here is close to 1:2:4, and the molar ratio of the precursor solution in the early stage is limited to Mg:Al=1:2. At the same time, Mg-Al oxide preferentially generates MgAl2O4, which can prove the formation of MgAl2O4. As can be seen from the figure, the covering layer of reinforcing phase particles (MgAl2O4) on the surface is tightly integrated with the grid skeleton and is evenly distributed on the surface of the pore structure. There is no obvious agglomeration between the particles, indicating that the Joule thermal shock method effectively avoids the particle aggregation problem caused by long-term high temperature in traditional heat treatment.

[0069] Figure 3 This is a picture of the bonding between the reinforcing phase and the matrix in the microstructure of the three-dimensional grid magnesium aluminate composite intermediate layer for brazing of dissimilar materials prepared in Example 1. The morphology of the MgAl2O4 reinforcing phase particles can be clearly observed in the figure. It presents a polyhedral structure and the particle shape is relatively regular, indicating that the crystal growth is stable during the Joule thermal shock process. The particle size of the reinforcing phase is about 100nm, which is consistent with the characteristics of nano-scale reinforced materials. The interface between the reinforcing phase MgAl2O4 and the porous Nb skeleton is clear and smooth, showing good bonding characteristics. There is no obvious delamination or gap at the interface, indicating that the Joule thermal shock method can achieve metallurgical bonding or chemical bonding between the reinforcing phase and the matrix in a short time, ensuring the overall strength and stability of the material. The figure shows that the reinforcing phase particles are evenly distributed and there is no particle agglomeration or accumulation.

[0070] The three-dimensional grid magnesium aluminate composite intermediate layer prepared in Example 1 and the comparative experiment was used to braze SiC and Al / SiC composite materials:

[0071] The brazing material is AlSiMg, the welding temperature is 620℃, the holding time is 10min, and the size is 10mm×10mm×1mm. First, ensure that the surface of SiC and Al / SiC composite materials are clean and free of impurities, which can be cleaned with alcohol or acetone. The three-dimensional grid magnesium aluminate composite interlayer and AlSiMg brazing filler powder are placed in a vacuum container, and the three-dimensional grid magnesium aluminate composite interlayer is buried in the AlSiMg brazing filler powder, and then evacuated to a pressure of 0.1MPa. Under the condition of a pressure of 0.1MPa, it is maintained for 5min, and then the vacuum is released at a speed of 0.05MPa / min until it returns to normal pressure, thereby obtaining a composite interlayer filled with AlSiMg brazing filler. Then, the composite interlayer filled with AlSiMg brazing filler is placed between the SiC and Al / SiC composite surfaces to be welded to obtain the welded parts, and the welded parts are placed in a brazing furnace and evacuated for 10min until the vacuum degree is 5×10 -3 Pa, heat to 620℃ and keep it for 10min. The solder will flow fully at this temperature, fill the joint and form a strong connection.

[0072] Tested according to GB / T 11363-2008 standard; Figure 4 The relationship curve between the shear strength and strain of the three-dimensional grid magnesium aluminate composite intermediate layer assisted brazing joint prepared in Example 1 and the comparative experiment; it can be seen from the figure that the composite intermediate layer prepared by the Joule thermal shock method has higher shear strength and ductility. The shear strength peak is close to 120MPa, which is significantly higher than the approximately 85MPa prepared by the original method. The material prepared by Joule thermal shock reaches fracture when the strain is close to 40%, while the material prepared by the original method breaks at about 20%. The Joule thermal shock preparation method significantly improves the shear strength and ductility of the composite intermediate layer assisted brazing joint, exhibits more superior mechanical properties, and is suitable for the preparation of high-performance materials.

Claims

1. A method for preparing a three-dimensional grid magnesium aluminate composite intermediate layer for brazing dissimilar materials by Joule thermal shock, characterized in that It is carried out in the following steps:

1. Preparation of MgAl2O4 precursor solution: dissolving magnesium nitrate and aluminum nitrate in deionized water to obtain a MgAl2O4 precursor solution; 2. Impregnation: The acid-washed porous Nb grid skeleton is immersed in a MgAl2O4 precursor solution and finally dried to obtain an immersed grid skeleton; 3. Preparation of three-dimensional grid MgAl2O4 composite intermediate layer by Joule thermal shock: The carbon fiber cloth, the soaked grid skeleton and the carbon fiber cloth are stacked in this order. The carbon fiber cloths on both sides are used as Joule heat sources. Under vacuum, a voltage of 15V to 30V and a current of 30A to 90A, the heat is kept for 5s to 300s, and then the current is stopped to obtain a three-dimensional grid magnesium aluminate composite intermediate layer for brazing dissimilar materials.

2. The method for preparing a three-dimensional grid magnesium aluminate composite intermediate layer for brazing dissimilar materials by Joule thermal shock according to claim 1, characterized in that The concentration of magnesium nitrate in the MgAl2O4 precursor solution described in step 1 is 0.01 mol / L to 0.5 mol / L.

3. The method for preparing a three-dimensional grid magnesium aluminate composite intermediate layer for brazing dissimilar materials by Joule thermal shock according to claim 1, characterized in that The molar ratio of magnesium nitrate to aluminum nitrate described in step 1 is 1:

2.

4. The method for preparing a three-dimensional grid magnesium aluminate composite intermediate layer for brazing dissimilar materials by Joule thermal shock according to claim 1, characterized in that The pickled porous Nb mesh skeleton described in step 2 is specifically prepared according to the following steps: immersing the porous Nb mesh skeleton in a mixed solution containing hydrofluoric acid and nitric acid for 1 minute to 10 minutes, then rinsing with deionized water, and finally drying naturally or drying at low temperature to obtain a pickled porous Nb mesh skeleton; the mixed solution containing hydrofluoric acid and nitric acid is specifically prepared by mixing hydrofluoric acid and nitric acid, the mass percentage of the hydrofluoric acid is 10% to 30%; the mass percentage of the nitric acid is 10% to 30%, and the volume ratio of hydrofluoric acid to nitric acid is 1: (3 to 5).

5. The method for preparing a three-dimensional grid magnesium aluminate composite intermediate layer for brazing dissimilar materials by Joule thermal shock according to claim 4, characterized in that The porosity of the porous Nb grid skeleton is 30% to 70%, and the average pore size of the grid is 50 μm to 300 μm.

6. The method of preparing a three-dimensional grid magnesium aluminate composite intermediate layer for brazing dissimilar materials by Joule thermal shock according to claim 1, characterized in that In step 2, the acid-washed porous Nb grid skeleton is immersed in a MgAl2O4 precursor solution for 5 to 30 minutes.

7. The method for preparing a three-dimensional grid magnesium aluminate composite intermediate layer for brazing dissimilar materials by Joule thermal shock according to claim 1, characterized in that The drying in step 2 is specifically performed at room temperature to 100° C. for 1 to 3 hours.

8. The method of preparing a three-dimensional grid magnesium aluminate composite intermediate layer for brazing dissimilar materials by Joule thermal shock according to claim 1, characterized in that The thickness of the carbon fiber cloth described in step 3 is 0.1 mm to 1 mm.

9. The method of preparing a three-dimensional grid magnesium aluminate composite intermediate layer for brazing dissimilar materials by Joule thermal shock according to claim 1, characterized in that The vacuum degree in step 3 is 10 -2 Vacuum environment of Pa~10Pa.

10. Application of the three-dimensional grid magnesium aluminate composite intermediate layer for brazing dissimilar materials prepared as claimed in claim 1, characterized in that It is used for brazing SiC and Al / SiC composite materials.

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