Ceramic-metal composite thermal protection system and prediction method of wetting and filling behavior of brazing interface

Abstract

A ceramic-metal composite thermal protection system and a method for predicting the wetting and caulking behavior of a brazing interface are disclosed. The system comprises an upper honeycomb panel, a middle ceramic insulation layer, and a lower honeycomb panel, with adjacent layers connected by welding. The upper honeycomb panel is made of a zirconium-based high-temperature alloy, with honeycomb cells in the shape of regular hexagons with equal wall thickness and a side length of 4-6 mm. The ceramic insulation layer is made of alumina ceramic with a thickness of 40-60 mm. The lower honeycomb panel is made of a titanium-based high-temperature alloy, with honeycomb cells in the shape of regular hexagons with equal wall thickness of 0.05-0.1 mm. The honeycomb panel is 3-6 mm high and the side length of the regular hexagons is 4-6 mm. A method for predicting the wetting and caulking behavior of a brazing interface is also disclosed. The present invention utilizes a connection method different from that of traditional thermal protection systems, brazing to connect the various layers of insulation material in the thermal protection system. This connection is lighter and less expensive, meeting the design requirements of lightweight, high strength, high toughness, and good flexibility.

Description

Technical Field

[0001] The present invention relates to the field of welding, and more specifically, to a ceramic / metal composite thermal protection system and a method for predicting wetting and filling behaviors of a brazing interface. Background Art

[0002] Hypersonic vehicles are of vital military significance. Friction between the aircraft and the air at several times the speed of sound generates enormous heat. To ensure the normal operation of the aircraft's interior, thermal protection systems have emerged. Traditional superheat-resistant alloy honeycomb thermal protection systems are mechanically connected, consisting of a titanium alloy honeycomb, an alumina insulation layer, a surface titanium alloy foil, and an outer layer of nickel-based high-temperature alloy. Compared with mechanical connections, welding manufacturing technology offers lighter connections and lower costs, meeting the design requirements of lightweight, high strength, high toughness, and good flexibility. The alumina ceramic layer, titanium alloy honeycomb, and nickel-based high-temperature alloy are complex structural connections between ceramics and metals. The linear expansion coefficients and physical and chemical properties of titanium, nickel alloys, and ceramics differ significantly, leading to the generation of residual thermal stresses at the connection interface during high-temperature flight.

[0003] The research goal is to develop new concept thermal protection structural materials, replace nickel with zirconium, and build a new thermal protection system. Zirconium alloy has the advantages of excellent thermal stability, corrosion resistance, ductility, etc. When brazing ceramic materials, the difficulty of molten brazing material wetting the ceramic surface is one of the difficulties in ceramic brazing. Zirconium, as an active element, has better weldability with ceramics than nickel alloys.

[0004] The brazing principles such as the connection mechanism of the brazing interface, the wetting mechanism of the brazing filler metal and the diffusion behavior of the interface atoms are difficult to understand in depth or are costly through experimental means. Based on the high-throughput method, high-entropy (amorphous) brazing filler metals are designed, and the wetting and filling mechanism of high-entropy alloy (amorphous) brazing filler metals at the zirconium alloy / ceramic / titanium alloy interface is studied. The design criteria of the brazing filler metals are determined, the interface behavior is precisely regulated, the residual stress of the joint is effectively relieved, and the high-temperature thermal protection stability of the interface is improved. The regulation mechanism of high-entropy alloy (amorphous) brazing filler metals on the interface behavior and comprehensive performance of the zirconium alloy / ceramic / titanium alloy thermal protection system is revealed, which has important research value for the development of hypersonic aircraft and new concept thermal protection structural materials. Summary of the Invention

[0005] In view of this, in order to address the deficiencies of the above-mentioned prior art, the purpose of the present invention is to provide a method for predicting the wetting and filling behavior of the brazing interface of a ceramic-metal composite thermal protection system, in order to solve the problems of high cost and poor connection quality in mechanical connections in traditional thermal protection systems; to solve the problems of poor weldability of nickel alloy / ceramic, large differences in linear expansion coefficients after welding, and thermal stress generation; and to solve the problem of the difficulty in studying the wetting and filling mechanism of amorphous alloy brazing materials.

[0006] The object of the present invention is achieved in the following manner:

[0007] A ceramic-metal composite thermal protection system comprises an upper honeycomb panel, a middle ceramic insulation layer and a lower honeycomb panel, wherein adjacent layers are connected by welding. The upper honeycomb panel is made of a zirconium-based high-temperature alloy, the honeycomb cells are regular hexagons with equal wall thickness, the wall thickness is 0.05-0.1 mm, the honeycomb panel height is 4-8 mm, and the honeycomb cell regular hexagonal side length is 4-6 mm; the ceramic insulation layer is alumina ceramic with a thickness of 40-60 mm; the lower honeycomb panel is made of a titanium-based high-temperature alloy, the honeycomb cells are regular hexagons with equal wall thickness, the wall thickness is 0.05-0.1 mm, the honeycomb panel height is 3-6 mm, and the honeycomb cell regular hexagonal side length is 4-6 mm.

[0008] In the above-mentioned ceramic-metal composite thermal protection system, the adjacent layers are welded by vacuum thermoplastic brazing or laser thermoplastic brazing. The brazing temperature is higher than the crystallization temperature of the amorphous brazing material in the supercooled liquid phase and does not exceed the amorphous melting point of the amorphous brazing material in the supercooled liquid phase. The brazing temperature is 741-760°C.

[0009] In the above-mentioned ceramic-metal composite thermal protection system, the solder layers between adjacent layers are all silver-titanium-copper amorphous solder layers.

[0010] The above ceramic-metal composite thermal protection system is characterized in that the thickness of the brazing filling is 50-150 μm.

[0011] The above-mentioned method for predicting the filling behavior of the brazing interface of the ceramic-metal composite thermal protection system includes the following steps:

[0012] Step 1: Grind and polish the surface of the zirconium alloy / alumina ceramic and titanium alloy / alumina ceramic samples, ultrasonically clean them with alcohol or acetone for 5 to 10 minutes, dry them, and then corrode and characterize the samples. Characterize the phase precipitation at the interface layer of the brazing samples.

[0013] Step 2: Based on the characterized phase precipitation phase, a phase model is established and the structure is optimized; Step 3: Surface energy convergence test is performed on the phase model to calculate its surface energy;

[0014] Step 4: Establish a physical interface model and calculate the interfacial adhesion work based on the first-principles numerical calculation results;

[0015] Step 5: Calculate the interfacial energy of the phase interface based on the calculation results of step 4;

[0016] Step 6: Based on Laurent's theorem, predict the wetting and filling mechanism of the zirconium alloy / alumina ceramic or titanium alloy / alumina ceramic brazing interface.

[0017] In the above-mentioned method for predicting the filling behavior of the brazing interface of the ceramic-metal composite thermal protection system, the surface energy calculation formula in step 3 is:

[0018]

[0019] Wherein, E1 is the total energy of the surface structure model of the precipitate phase or alumina ceramics, N1 is the number of atoms contained in the surface structure model of the precipitate phase or alumina ceramics, N2 is the number of atoms contained in a unit cell of the precipitate phase or alumina ceramics, E2 is the total energy of a unit cell model of the precipitate phase or alumina ceramics, and A is the surface area of ​​the surface model.

[0020] In the above-mentioned method for predicting the filling behavior of the brazing interface of the ceramic-metal composite thermal protection system, the formula for calculating the interface adhesion work in step 4 is:

[0021] W ad =(E3+E4-E 34 ) / S

[0022] Where E3 and E4 are the energies that characterize the molecular model of the physical phase, E 34 is the total energy of the interface model, and S is the interface area of ​​the interface model.

[0023] In the above-mentioned method for predicting the filling behavior of the brazing interface of the ceramic-metal composite thermal protection system, the interface energy formula in step 5 is:

[0024] σ=γ1+γ2-W ad

[0025] Where γ1 and γ2 are the surface energies representing the physical model, W ad is the adhesion work of the interface model.

[0026] In the above-mentioned method for predicting the filling behavior of the brazing interface of the ceramic-metal composite thermal protection system, the wetting mechanism described in step 6 is determined as follows: if the interface energy σ1 between the reaction layer and the brazing material is greater than the interface energy σ2 between the ceramic and the brazing material, then the wetting of the brazing material is dominated by the release of free energy; on the contrary, if the interface energy σ1 between the reaction layer and the brazing material is less than the interface energy σ2 between the ceramic and the brazing material, then the interface energy release plays a positive role in wetting.

[0027] Compared with the prior art, the present invention can have the following beneficial effects:

[0028] 1. The present invention adopts a connection method different from the traditional thermal protection system, brazing to connect the various layers of thermal insulation materials in the thermal protection system. The connection quality is lighter and the cost is lower, meeting the design requirements of lightweight, high strength, high toughness and good flexibility.

[0029] 2. The zirconium alloy used in the present invention has the advantages of excellent thermal stability, corrosion resistance, ductility, etc., has better weldability with ceramic materials, and its linear expansion coefficient is closer to that of ceramics, which solves the problems of residual thermal stress easily generated at the connection interface during high-temperature flight, short service life and unreliable reliability.

[0030] 3. The present invention uses the first-principles high-throughput calculation method to efficiently and accurately predict and study the wetting and filling mechanism of zirconium alloy / alumina ceramic or titanium alloy / alumina ceramic brazing, solving the problem of difficulty and high cost in revealing the brazing wetting mechanism by the "cooking-style" experimental method.

[0031] 4. The present invention organically combines the advantages of superplastic deformation with brazing and diffusion welding, uses bulk metallic glass as brazing material (that is, amorphous brazing material), and utilizes an amorphous alloy with a supercooled liquid phase region between the glass transition temperature and the crystallization temperature as an intermediate brazing material layer. Pre-bonding is achieved through superplastic flow in the supercooled liquid phase region (741-760°C), and then metallurgical bonding of the thermal protection system is achieved through appropriate diffusion treatment (not exceeding the amorphous melting point and higher than the crystallization temperature).

[0032] 5. The new amorphous solder of the present invention has an orderly arranged atomic structure and no grain boundaries, making the liquid solder seamless and drillable. After connection, the residual stress at the heterogeneous connection interface of the thermal protection system is effectively relieved. At the same time, thermoplastic brazing is a solid-state diffusion connection as a whole, with a large connection area, which can avoid thermal stress at the liquid connection interface, has no effect on the stability of the thermal protection system interface, and can be used in high-temperature environments.

[0033] 6. The melting temperature of the new amorphous solder of the present invention is at least 30 to 60°C lower than that of conventional active solder. It flows and spreads in the supercooled liquid phase without component segregation, and then is connected at low temperature, which can effectively inhibit the appearance of hard and brittle phases at the connection interface. At the same time, its good flexibility and ductility can effectively alleviate the residual stress at the heterogeneous interface and inhibit the influence of stress on the interface performance of the thermal protection system. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 It is a schematic structural diagram of the ceramic / metal composite thermal protection system of the present invention.

[0035] Figure 2 is a flow chart of the prediction method of the present invention;

[0036] Figure 3 It is the Ag, Ti3Al, Al2O3 crystal model of the present invention;

[0037] Figure 4 It is the model of Ag(111), Ti3Al(0001), and Al2O3(0001) surfaces of the present invention;

[0038] Figure 5It is the Ag(111) / Ti3Al(0001) interface and Ag(111) / Al2O3(0001) interface model of the present invention;

[0039] Figure 6 It is the DTA curve diagram of the silver-titanium-copper amorphous solder of the present invention. DETAILED DESCRIPTION

[0040] The following specific examples are given to further clearly, completely and in detail illustrate the technical solution of the present invention. This embodiment is the best embodiment based on the technical solution of the present invention, but the protection scope of the present invention is not limited to the following examples.

[0041] Experimental description: Use amorphous solder silver titanium copper, vacuum thermoplastic brazing, brazing temperature 741 ~ 760 ℃ (according to Figure 6 Determine), keep warm for 10 minutes, the interface reaction layer between zirconium alloy / alumina ceramics, alumina ceramics and solder contains Ti3Al and Ti3Cu3O; the close-packed planes of Ag crystal with space group Fm-3m, Ti3Al crystal with P63 / mmc and Al2O3 crystal with R-3C are (111), (0001) and (0001), respectively. The close-packed plane has the lowest surface energy among all crystal planes, which means that the close-packed plane is the most stable crystal plane and has the greatest interface formation tendency.

[0042] Example 1: Figure 1 The ceramic-metal composite thermal protection system comprises an upper honeycomb panel 1, a middle ceramic insulation layer 2 and a lower honeycomb panel 3, and adjacent layers are connected by welding. The upper honeycomb panel material is a zirconium-based high-temperature alloy, the honeycomb unit cell is a regular hexagon with equal wall thickness, the wall thickness is 0.05-0.1mm, the honeycomb panel height is 4-8mm, and the honeycomb unit cell regular hexagonal side length is 4-6mm; the ceramic insulation layer is alumina ceramic with a thickness of 40-60mm; the lower honeycomb panel material is a titanium-based high-temperature alloy, the honeycomb unit cell is a regular hexagon with equal wall thickness, the wall thickness is 0.05-0.1mm, the honeycomb panel height is 3-6mm, and the honeycomb unit cell regular hexagonal side length is 4-6mm; the adjacent layers are welded by vacuum thermoplastic brazing or laser thermoplastic brazing, and the brazing temperature is higher than the crystallization temperature of the amorphous brazing material in the supercooled liquid phase and does not exceed the amorphous melting point of the amorphous brazing material in the supercooled liquid phase, that is, 741-760°C (according to Figure 6 ); the solder layers between the adjacent layers are all silver-titanium-copper amorphous solder layers; the thickness of the brazing filling is 50-150μm.

[0043] The method for predicting the filling behavior of the brazing interface of the ceramic-metal composite thermal protection system comprises the following steps:

[0044] Step 1: Grind and polish the surfaces of the zirconium alloy / alumina ceramic and titanium alloy / alumina ceramic connector samples, ultrasonically clean them with alcohol or acetone for 5 to 10 minutes, and dry them. Then, corrode and characterize the samples, and characterize the phase precipitation at the interface layer of the brazed samples. Step 2: Establish a phase model structure optimization based on the characterized phase precipitation.

[0045] Step 3: Perform surface energy convergence test on the phase model and calculate its surface energy. The surface energy calculation formula is:

[0046]

[0047] Wherein, E1 is the total energy of the surface structure model of the precipitate phase or alumina ceramic, N1 is the number of atoms contained in the surface structure model of the precipitate phase or alumina ceramic, N2 is the number of atoms contained in a unit cell of the precipitate phase or alumina ceramic, E2 is the total energy of a unit cell model of the precipitate phase or alumina ceramic, and A is the surface area of ​​the surface model of the precipitate phase or alumina ceramic;

[0048] Step 4: Establish a physical interface model and calculate the interfacial adhesion work based on the first-principles numerical calculation results. The formula for calculating the interfacial adhesion work is:

[0049] W ad =(E3+E4-E 34 ) / S

[0050] Where E3 and E4 are the energies that characterize the molecular model of the physical phase, E 34 is the total energy of the interface model, S is the interface area of ​​the interface model;

[0051] Step 5: Calculate the interfacial energy of the phase interface based on the calculation results of step 4. The interfacial energy formula is:

[0052] σ=γ1+γ2-W ad

[0053] Where γ1 and γ2 are the surface energies representing the physical model, W ad is the adhesion work of the interface model;

[0054] Step 6: Based on Laurent's theorem, predict the wetting and filling mechanism of the zirconium alloy / alumina ceramic or titanium alloy / alumina ceramic brazing interface;

[0055] The basis for judging the wetting mechanism is: if the interface energy σ1 between the reaction layer and the solder is greater than the interface energy σ2 between the ceramic and the solder, the solder wetting is dominated by the free energy release; on the contrary, if the interface energy σ1 between the reaction layer and the solder is less than the interface energy σ2 between the ceramic and the solder, the interface energy release plays a positive role in wetting.

[0056] Example 2:

[0057] A ceramic / metal composite thermal protection system and a method for predicting the wetting and filling behavior of a brazing interface. The ceramic / metal composite thermal protection system comprises an upper honeycomb panel, a ceramic insulation layer and a lower honeycomb panel, and adjacent layers are connected by welding.

[0058] The upper honeycomb panel material is zirconium-based high-temperature alloy, the honeycomb unit cell is a regular hexagon with equal wall thickness, the wall thickness is 0.08mm, the honeycomb panel height is 6mm, and the side length of the regular hexagon of the honeycomb unit cell is 6mm;

[0059] The ceramic insulation layer is alumina ceramic with a thickness of 50 mm;

[0060] The lower honeycomb panel material is titanium-based high-temperature alloy, the honeycomb unit cell is a regular hexagon with equal wall thickness, the wall thickness is 0.05mm, the honeycomb panel height is 4mm, and the side length of the honeycomb unit cell regular hexagon is 6mm;

[0061] The ceramic / metal composite thermal protection system and brazing interface wetting and filling behavior prediction method, the welding method of the adjacent layers is vacuum thermoplastic brazing or laser thermoplastic brazing, according to Figure 6 Determine the brazing temperature to be 741-760°C;

[0062] The ceramic / metal composite thermal protection system and brazing interface wetting and filling behavior prediction method, wherein the brazing seam thickness is 100 μm;

[0063] The ceramic / metal composite thermal protection system and the brazing interface wetting and filling behavior prediction method include the following steps:

[0064] Step 1: Use 1500# silicon carbide sandpaper to grind and polish the surface of the zirconium alloy / alumina ceramic connector sample, ultrasonically clean it with alcohol or acetone for 10 minutes, and dry it. Then, corrode the sample and characterize the sample. Characterize the phase (precipitate phase) at the zirconium alloy / alumina ceramic interface.

[0065] Step 2: Based on the characterized phase interfaces Ti3Cu3O, Ti3Al, etc., the phase model of amorphous Ag solder, alumina ceramics and Ti3Al interface reactants is established. The space groups of Ag, Ti3Al and α-Al2O3 crystals are Fm-3m, P63 / mmc and R-3C respectively. Figure 3 As shown, the structure is optimized for standby use;

[0066] Step 3: Process the crystal surface of Ag, Ti3Al and α-Al2O3 crystal models, such as Figure 4As shown, the surface energy convergence test of the phase model was performed to calculate the surface energy of the Ag (111) surface, Ti3Al (001) surface and Al2O3 (001) surface; the surface energy convergence test calculation results are shown in Table 1; the surface energy calculation formula is:

[0067]

[0068] Where E1 is the total energy of the surface structure of Ag, Ti3Al and α-Al2O3, N1 is the number of atoms contained in the surface structure of Ag, Ti3Al and α-Al2O3, N2 is the number of atoms contained in a unit cell of Ag, Ti3Al and α-Al2O3, E2 is the total energy of a unit cell of Ag, Ti3Al and α-Al2O3, and A is the area of ​​the surface.

[0069] Table 1. Surface energies of different Ag(111) surfaces, Ti3Al(0001) surfaces, and Al2O3(0001) surfaces

[0070]

[0071] Step 4: Establish the Ag(111) / Ti3Al(0001) and Ag(111) / Al2O3(0001) interface models, such as Figure 5 As shown in the figure, according to the first principle numerical calculation results, the interface adhesion work is calculated; the calculation formula of the interface adhesion work is: W ad =(E3+E4-E 34 ) / S, where W ad is the interfacial adhesion work, E3 and E4 are the energies representing the molecular model of the physical phase, and E 34 is the total energy of the interface model, and S is the interface area of ​​the interface model.

[0072] Step 5: Calculate the interface energy of Ag(111) / Ti3Al(0001) and Ag(111) / Al2O3(0001) interfaces based on the calculation results of step 4;

[0073] The interface energy formula is:

[0074] σ=γ1+γ2-W ad

[0075] Where γ1 and γ2 are the surface energies representing the physical model, W ad is the adhesion work of the interface model.

[0076] Table 2. Calculation results of interface adhesion work and interface energy of Ag(111) / Ti3Al(0001) and Ag(111) / Al2O3(0001)

[0077]

[0078] Step 6: During the brazing of alumina ceramics, Ti3Al, one of the products of the interfacial reaction, is generated. The Ag / Al2O3 interface has a lower interfacial energy than the Ag / Ti3Al interface. According to Laurent's theorem, the interfacial energy of Ti3Al is higher, which has an adverse effect on wetting. This shows that the free energy released by the Ti3Al generation reaction plays a positive role in the wetting of the brazing material.

[0079] Example 3

[0080] The ceramic / metal composite thermal protection system comprises an upper honeycomb panel, a ceramic insulation layer and a lower honeycomb panel, and adjacent layers are connected by welding.

[0081] The upper honeycomb panel material is zirconium-based high-temperature alloy, the honeycomb unit cell is a regular hexagon with equal wall thickness, the wall thickness is 0.05mm, the honeycomb panel height is 4mm, and the side length of the regular hexagon of the honeycomb unit cell is 4mm;

[0082] The ceramic insulation layer is alumina ceramic with a thickness of 40 mm;

[0083] The lower honeycomb panel material is titanium-based high-temperature alloy, the honeycomb unit cell is a regular hexagon with equal wall thickness, the wall thickness is 0.05mm, the honeycomb panel height is 3mm, and the side length of the honeycomb unit cell regular hexagon is 4mm;

[0084] The ceramic / metal composite thermal protection system and brazing preparation method, the welding method of the adjacent layers is vacuum thermoplastic brazing, according to Figure 6 Determine the brazing temperature to be 741-760°C;

[0085] The ceramic / metal composite thermal protection system and brazing preparation method, wherein the brazing seam thickness is 80 μm;

[0086] Other implementations are the same as those in Example 2.

[0087] Example 4

[0088] The ceramic / metal composite thermal protection system comprises an upper honeycomb panel, a ceramic insulation layer and a lower honeycomb panel, and adjacent layers are connected by welding.

[0089] The upper honeycomb panel material is zirconium-based high-temperature alloy, the honeycomb unit cell is a regular hexagon with equal wall thickness, the wall thickness is 0.1mm, the honeycomb panel height is 6mm, and the side length of the regular hexagon of the honeycomb unit cell is 6mm;

[0090] The ceramic insulation layer is alumina ceramic with a thickness of 60 mm;

[0091] The lower honeycomb panel material is titanium-based high-temperature alloy, the honeycomb unit cell is a regular hexagon with equal wall thickness, the wall thickness is 0.1mm, the honeycomb panel height is 6mm, and the side length of the honeycomb unit cell regular hexagon is 6mm;

[0092] The ceramic / metal composite thermal protection system and brazing preparation method, the welding method of the adjacent layers is laser thermoplastic brazing, according to Figure 6 Determine the brazing temperature to be 741-760°C;

[0093] The ceramic / metal composite thermal protection system and brazing preparation method, the brazing seam thickness is 150 μm.

[0094] Other implementations are the same as those in Example 2.

[0095] The above is only a preferred embodiment of the present invention. It should be pointed out that for those skilled in the art, several changes and improvements can be made without departing from the overall concept of the present invention, and these should also be regarded as the scope of protection of the present invention.

Claims

1. A ceramic-metal composite thermal protection system, characterized by: The invention comprises an upper honeycomb panel (1), a middle ceramic insulation layer (2) and a lower honeycomb panel (3), and adjacent layers are connected by welding. The upper honeycomb panel is made of zirconium-based high-temperature alloy, the honeycomb unit cell is a regular hexagon with equal wall thickness, the wall thickness is 0.05-0.1mm, the honeycomb panel height is 4-8mm, and the honeycomb unit cell regular hexagon side length is 4-6mm; the ceramic insulation layer is alumina ceramic with a thickness of 40-60mm; the lower honeycomb panel is made of titanium-based high-temperature alloy, the honeycomb unit cell is a regular hexagon with equal wall thickness, the wall thickness is 0.05-0.1mm, the honeycomb panel height is 3-6mm, and the honeycomb unit cell regular hexagon side length is 4-6mm; the adjacent layers are welded by vacuum thermoplastic brazing or laser thermoplastic brazing, and the specific brazing temperature is higher than the crystallization temperature of the amorphous brazing material in the supercooled liquid phase region and lower than or equal to the amorphous melting point of the amorphous brazing material in the supercooled liquid phase region.

2. The ceramic-metal composite thermal protection system according to claim 1, characterized in that: The solder layers between the adjacent layers are all silver-titanium-copper amorphous solder layers, and the soldering temperature is 741-760°C.

3. The ceramic-metal composite thermal protection system according to claim 1 or 2, characterized in that: The thickness of the brazing filling is 50-150 μm.

4. A method for predicting the filling behavior of the brazing interface of the ceramic-metal composite thermal protection system according to any one of claims 1 to 3, characterized in that: The following steps are involved: Step 1: Grind and polish the surface of the zirconium alloy / alumina ceramic and titanium alloy / alumina ceramic samples, ultrasonically clean them with alcohol or acetone for 5-10 minutes, dry them, and then corrode and characterize the samples. Characterize the phase precipitation at the interface layer of the brazing samples. Step 2: Based on the characterized phase precipitation phase, establish a phase model and optimize the structure; Step 3: Perform surface energy convergence test on the phase model and calculate its surface energy; Step 4: Establish a physical interface model and calculate the interfacial adhesion work based on the first-principles numerical calculation results; Step 5: Calculate the interfacial energy of the physical interface based on the calculation results of step 4; Step 6: Based on Laurent's theorem, predict the wetting and filling mechanism of the zirconium alloy / alumina ceramic or titanium alloy / alumina ceramic brazing interface.

5. The method for predicting the filling behavior of the brazing interface of the ceramic-metal composite thermal protection system according to claim 4, characterized in that: The surface energy calculation formula in step 3 is: Wherein, E1 is the total energy of the surface structure model of the precipitate phase or alumina ceramics, N1 is the number of atoms contained in the surface structure model of the precipitate phase or alumina ceramics, N2 is the number of atoms contained in a unit cell of the precipitate phase or alumina ceramics, E2 is the total energy of the unit cell model of the precipitate phase or alumina ceramics, and A is the surface area of ​​the surface model.

6. The method for predicting the filling behavior of the brazing interface of the ceramic-metal composite thermal protection system according to claim 4, characterized in that: The calculation formula for the interfacial adhesion work in step 4 is: W ad =(E3+E4-E 34 ) / S Where E3 and E4 are the energies that characterize the molecular model of the physical phase, E 34 is the total energy of the interface model, and S is the interface area of ​​the interface model.

7. The method for predicting the filling behavior of the brazing interface of the ceramic-metal composite thermal protection system according to claim 4, characterized in that: The interfacial energy formula in step 5 is: σ=γ1+γ2-W ad Where γ1 and γ2 are the surface energies representing the physical model, W ad is the adhesion work of the interface model.

8. The method for predicting the filling behavior of the brazing interface of the ceramic-metal composite thermal protection system according to claim 4, characterized in that: The basis for judging the wetting and filling mechanism described in step 6 is: if the interface energy σ1 between the reaction layer and the solder is greater than the interface energy σ2 between the ceramic and the solder, the solder wetting is dominated by the free energy release; on the contrary, if the interface energy σ1 between the reaction layer and the solder is less than the interface energy σ2 between the ceramic and the solder, the interface energy release plays a positive role in wetting.

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