Preparation of copper-indium-titanium active brazing filler metal and method for brazing yttrium-magnesium ceramic and TC4 titanium alloy

Abstract

The application relates to a preparation method of copper-indium-titanium active brazing filler metal and a method for brazing yttrium-magnesium ceramics and TC4 titanium alloy, and relates to the technical field of welding materials and heterogeneous material connection. The method is as follows: copper-indium-titanium active brazing filler metal is arranged between the connecting surfaces of the pretreated yttrium-magnesium ceramics and the TC4 titanium alloy to obtain a to-be-welded part; the to-be-welded part is placed in a vacuum furnace, and the temperature is first increased to 750-800 DEG C, and then the temperature is kept at 750-800 DEG C for 15-30 min; then the temperature is continuously increased to the brazing temperature and kept for 5-20 min; after the temperature keeping is completed, the temperature is first cooled to below 500 DEG C, and then the temperature is cooled to room temperature, and the brazing of the yttrium-magnesium ceramics and the TC4 titanium alloy by the copper-indium-titanium active brazing filler metal is completed. The application can obtain the preparation method of the copper-indium-titanium active brazing filler metal and the method for brazing the yttrium-magnesium ceramics and the TC4 titanium alloy.

Description

Technical Field

[0001] This invention relates to the field of welding materials and dissimilar material joining technology, specifically to the preparation of a copper indium titanium active brazing filler metal and its method for brazing yttrium magnesium ceramics and TC4 titanium alloy. Background Technology

[0002] With the development of high-tech fields such as aerospace, nuclear industry, and electronic packaging, ceramic materials are widely used due to their excellent high-temperature resistance, wear resistance, corrosion resistance, and insulation properties. Among them, yttrium oxide (Y₂O₃) has an extremely high melting point (2439℃), excellent thermal shock resistance, and chemical stability, making it an ideal high-temperature structural material; magnesium oxide (MgO) has good thermal conductivity and insulation properties. The composite ceramic formed by combining Y₂O₃ and MgO can combine the excellent properties of both, and has significant application value in extreme environments.

[0003] However, the inherent brittleness and processing difficulties of ceramic materials limit the fabrication of complex components. Reliably joining ceramics with metallic materials (especially titanium alloys) to form ceramic-metal composite components is an effective way to solve this problem. Titanium alloys possess high specific strength, good corrosion resistance, and excellent biocompatibility, making them key structural materials in aerospace and biomedical fields.

[0004] At present, active brazing is one of the main methods to achieve the connection between ceramics and metals. Although the traditional Ag-Cu-Ti active brazing alloy has mature technology, it has the following problems: (1) silver-based brazing alloy is expensive; (2) the brazing temperature is high (usually >850℃), which can easily lead to thermal damage to the ceramic matrix; (3) the reaction between the brazing alloy and the ceramic interface is difficult to control, and an excessively thick brittle reaction layer is easily formed.

[0005] Copper-titanium (Cu-Ti) solders have attracted attention due to their lower cost and good compatibility with titanium alloys. The Cu-Ti binary system undergoes a eutectic reaction at approximately 870℃ (containing about 17 at.%) Ti, forming a Cu-based solid solution + Cu3Ti eutectic structure. However, pure Cu-Ti eutectic solders suffer from problems such as a high melting point, insufficient wettability, and intense and difficult-to-control interfacial reactions.

[0006] Indium (In), a low-melting-point metal (melting point 156.6℃), can form an infinite solid solution with Cu and also has a certain solid solubility with Ti. Adding In to Cu-Ti alloys can effectively lower the melting point of the solder, improve wettability, and regulate the interface structure by altering the thermodynamic and kinetic conditions of the interfacial reaction. However, there is limited systematic research on Cu-In-Ti ternary solders in the current technology, especially regarding brazing of special systems such as Y₂O₃-MgO composite ceramics, which has not been reported.

[0007] Furthermore, Y₂O₃-MgO composite ceramics contain two oxide phases with distinctly different chemical properties: Y₂O₃ is an acidic oxide, and MgO is a basic oxide. The introduction of a third component (such as indium) to construct a ternary system and the systematic study of the influence of the third component content on brazing characteristics, interface microstructure, and final joint performance, leading to the acquisition of an optimized brazing filler metal suitable for yttrium magnesium ceramic / TC4 connections, have not yet been publicly reported. Summary of the Invention

[0008] The purpose of this invention is to solve the above-mentioned technical problems by providing a method for preparing copper indium titanium active brazing filler metal and its application in brazing yttrium magnesium ceramics and TC4 titanium alloy.

[0009] A copper-indium-titanium active solder, wherein the copper-indium-titanium active solder comprises indium, copper and titanium, wherein the mass fraction of indium is 3.0~25.0%, and the balance is copper and titanium, and the mass ratio of copper to titanium is (72~80):(20~28).

[0010] A method for preparing a copper-indium-titanium active solder, comprising the following steps:

[0011] Step 1: Alloy smelting;

[0012] Indium, copper, and titanium are placed in a vacuum melting furnace, and the vacuum level is ≤5×10⁻⁶. -3 After Pa, induction melting is carried out in an inert gas atmosphere, and the master alloy is obtained by casting after melting.

[0013] Step 2: Preparation of copper indium titanium active solder;

[0014] The master alloy obtained in step one is made into copper indium titanium active solder foil strip by rapid cooling and spinning method, or into copper indium titanium active solder spherical powder by gas atomization method.

[0015] The method of brazing yttrium magnesium ceramics to TC4 titanium alloy using copper indium titanium active solder is carried out according to the following steps:

[0016] Step S1:

[0017] The surfaces of the yttrium magnesium ceramic and TC4 titanium alloy to be joined are pretreated to obtain pretreated yttrium magnesium ceramic and TC4 titanium alloy.

[0018] Step S2:

[0019] The copper indium titanium active brazing filler metal is placed between the pretreated yttrium magnesium ceramic and TC4 titanium alloy surfaces obtained in step S1 to be joined, thus obtaining the workpiece to be welded.

[0020] Step S3:

[0021] The workpiece to be welded obtained in step S2 is placed in a vacuum furnace, heated to 750~800℃ and held at 750~800℃ for 15~30 minutes, then heated to the brazing temperature and held for 5~20 minutes; after the holding period, it is cooled to below 500℃ and then cooled to room temperature to complete the brazing of yttrium magnesium ceramic and TC4 titanium alloy using copper indium titanium active brazing filler metal.

[0022] The core of this invention lies in the original composition design of the brazing filler metal: the mass ratio of copper to titanium is fixed as the lowest eutectic point ratio in its binary alloy phase diagram, and on this basis, a variable amount of indium is introduced.

[0023] 1. Composition of a novel copper-indium-titanium solder;

[0024] The brazing filler metal consists of the following components by mass percentage:

[0025] The mass ratio of copper (Cu) to titanium (Ti) is kept constant at 77:23. This ratio strictly corresponds to the lowest eutectic point composition in the Cu-Ti binary phase diagram, ensuring that the alloy base has a minimum and well-defined eutectic melting temperature (~875℃), a narrow melting range, and excellent fluidity.

[0026] Indium (In): 3.0% to 25.0%;

[0027] Unavoidable impurities: ≤0.5%;

[0028] Ingredient design principles and scope limitations:

[0029] A fixed eutectic ratio of Cu to Ti (Cu:Ti = 77:23): This is the technical cornerstone of this invention and a key feature distinguishing it from Cu-In-Ti alloys with arbitrary ratios. Using this fixed ratio means that regardless of changes in In content, the relative content of Cu and Ti in the solder remains at their binary eutectic point. This brings two major advantages: First, the solder has a definite and low melting initiation point, resulting in excellent process repeatability; second, it provides a stable and optimal Ti activity source for interfacial reactions, which is beneficial for forming a uniform interfacial reaction layer.

[0030] The effects and scope of In (3~25%):

[0031] Function: Adding In to a fixed Cu-Ti eutectic framework primarily serves as an alloying modification. In lowers the overall liquidus temperature of the ternary alloy, allowing the actual brazing temperature to be below the binary eutectic temperature of 875°C, achieving an even lower joining temperature (as low as 840°C). In significantly improves the fluidity of the molten solder and its wettability to ceramics. Furthermore, In dissolves in Cu or forms specific intermetallic compounds, which can adjust the plasticity and coefficient of thermal expansion of the brazed joint, helping to alleviate residual stress in the joint.

[0032] Lower limit (3%): If the In content is less than 3%, its effect on lowering the overall melting point and improving processability is negligible, and it cannot reflect the core advantages of low-temperature bonding and improved wetting.

[0033] Upper limit (25%): If the In content exceeds 25%, excessive low-melting-point In-rich phases or brittle Cu-In intermetallic compounds (such as CuIn2) will form in the solder. These phases are prone to becoming pathways for crack initiation and propagation when the joint is subjected to mechanical loads or high-temperature service, severely impairing the room temperature and high-temperature strength, ductility, and long-term reliability of the joint. At the same time, excessively high In content will over-dilute the Ti concentration in the solder, potentially weakening its ability to form an effective reaction layer at the ceramic interface.

[0034] 2. Optimal formulation:

[0035] Based on the above principles and experimental verification, this invention discloses the following three preferred ratio ranges for application scenarios with different performance focuses:

[0036] Type I (Low Indium, High Strength / High Temperature): In content is 3.0~10.0%. Within this range, the overall melting point of the brazing filler metal decreases only slightly, but the brazing joint structure is based on Cu-Ti eutectic with few brittle phases. The resulting joint has the highest room temperature and high temperature shear strength, making it suitable for applications with extremely high strength requirements and high operating temperatures.

[0037] Type II (medium indium, comprehensive optimization): In content is 10.1~18.0%. Within this range, the solder achieves a balance between low-temperature performance, wettability, joint strength, and toughness.

[0038] Type III (High Indium, Ultra-Low Temperature / High Wetting Type): In content is 18.1~25.0%. This brazing filler metal has the lowest melting point and the strongest wetting and spreading ability on ceramics. It is suitable for connecting precision components where the heat input of the connection is extremely strictly controlled or the component shape is complex and requires excellent filler metal flowability. However, it is necessary to optimize the brazing process (such as precisely controlling the holding time) to suppress the adverse effects of the brittle phase.

[0039] Note: In all types, the mass ratio of Cu to Ti remains constant at 77:23. When calculating the actual composition, this ratio must be met first, and then a specified range of In is added. For example, for a solder with a target composition of Cu-23Ti-12In (Type II), its nominal total mass is: assuming Ti is 23 parts, then Cu is 77 parts, In is 12 parts, and the total mass is 112 parts. Therefore, the actual mass percentages are: Cu = (77 / 112)100%≈68.75%, Ti = (23 / 112)100%≈20.54%, In =10.71%.

[0040] 3. Preparation method of brazing filler metal:

[0041] The brazing filler metal is preferably prepared using a vacuum induction melting method. High-purity Cu, Ti, and In raw materials are melted uniformly in a designed ratio under vacuum or inert gas protection, and then shaped using any of the following methods:

[0042] Rapid cooling and spinning method: Molten alloy liquid is sprayed onto a high-speed rotating copper roller, where it rapidly solidifies to form an amorphous or microcrystalline foil strip with a thickness of 20~100μm. This method produces uniform composition and is suitable for automated assembly.

[0043] Gas atomization method: Molten alloy is atomized into fine droplets by an inert gas (such as argon) and rapidly solidified to obtain spherical powder with a particle size range of 150-500 mesh. The powder can be mixed with organic binders to form a paste-like brazing filler metal, suitable for complex or irregular joint surfaces.

[0044] 4. Matching brazing process:

[0045] To fully utilize the performance advantages of the brazing filler metal of this invention, the following vacuum brazing process is recommended for joining yttrium magnesium ceramic and TC4 titanium alloy:

[0046] 1. Surface pretreatment:

[0047] Yttrium magnesium ceramics: Polished sequentially with diamond polishing paste of different particle sizes until the surface roughness Ra≤0.1μm, then ultrasonically cleaned in acetone for 15~20 minutes, and dried.

[0048] TC4 titanium alloy: Grind with SiC sandpaper to a certain roughness to increase mechanical interlocking, then immerse in pickling solution (HF:HNO3:H2O=1:3:10, volume ratio) for 30~60 seconds to remove oxide film, then rinse with deionized water and alcohol and dry.

[0049] 2. Assembly: Place the prepared brazing foil or uniformly applied brazing paste between the treated yttrium magnesium ceramic and the TC4 alloy surfaces to be joined, and apply a slight pressure of 0.2~1.0 MPa to ensure good initial contact.

[0050] 3. Vacuum brazing process: Performed in a cold-wall vacuum brazing furnace, the working vacuum level should be better than 5.0 × 10⁻⁶. -3 Pa.

[0051] First stage (preheating and temperature equalization): Raise the furnace temperature to 750-800℃ at a rate of 8-15℃ / min (this temperature is lower than the actual melting temperature of all brazing filler metals), and hold for 15-30 minutes to ensure that the entire workpiece is heated evenly and to fully remove the gas and moisture adsorbed on the surface.

[0052] Second stage (brazing): Continue heating at a slower rate of 3~8℃ / min to the brazing temperature. The brazing temperature needs to be optimized according to the In content type of the selected filler metal.

[0053] For type I (3~10%In): the brazing temperature is 870~885℃, and the holding time is 5~20 minutes.

[0054] For type II (10.1~18%In): the brazing temperature is 870~885℃, and the holding time is 5~20 minutes.

[0055] For type III (18.1~25%In): the brazing temperature is 870~885℃, and the holding time is 5~20 minutes.

[0056] The heat preservation stage allows the brazing filler metal to fully melt, spread, and react with the base material at the interface.

[0057] The third stage (cooling): After the heat preservation is completed, the furnace is cooled to below 500°C at a rate of ≤5°C / min. This slow cooling process helps to reduce thermal stress caused by the difference in the coefficient of thermal expansion. Then, a high-purity inert gas (such as Ar) can be introduced for rapid cooling to room temperature.

[0058] The principle of this invention:

[0059] In this invention, the brazing filler metal uses the lowest eutectic point composition of copper and titanium (Cu:Ti≈77:23, mass ratio) as an invariable basic framework. By introducing a specific mass percentage of indium (In) element, a ternary alloy is formed, aiming to achieve the following objectives: (1) While maintaining the high activity advantage of the Cu-Ti system, In is used to further reduce the brazing temperature and reduce thermal stress; (2) The addition of In improves the wetting and spreading ability of the brazing filler metal on yttrium magnesium ceramics; (3) By controlling the In content, the brazing seam structure is optimized, and the joint strength and toughness are balanced, thereby obtaining a high-strength and high-reliability yttrium magnesium ceramic / TC4 titanium alloy brazed joint at a relatively low temperature.

[0060] The beneficial effects of this invention are:

[0061] 1. A clear and low process window was achieved: the eutectic composition-based brazing filler metal has sharp melting characteristics and high process repeatability. The addition of In further reduces the actual brazing temperature to the range of 840~885℃, which is significantly lower than conventional Ag-Cu-Ti brazing filler metal and ordinary Cu-Ti brazing filler metal, minimizing thermal damage to the TC4 titanium alloy base material (such as grain growth and phase transformation) and residual thermal stress throughout the joint.

[0062] 2. Excellent interfacial metallurgical bonding was achieved: A constant and optimal Ti content (from a 77:23 ratio) ensures the formation of a continuous, dense, and moderately thick (typically 1~3 μm) active reaction layer at the yttrium magnesium ceramic interface. This layer is mainly composed of compounds such as Ti-YO and Ti-Mg-O, achieving a gradient transition in chemical bonding and mechanical properties from ceramic to metal, which is the fundamental guarantee of high bonding strength. The addition of In improves wettability, making the reaction layer more uniform.

[0063] 3. Excellent and controllable joint mechanical properties: Joint performance can be optimized by selecting different types of In content. Using the optimal Type II solder (such as Cu-Ti-15In, nominal composition), under an optimized process of 860℃ / 15min, the following results can be obtained:

[0064] 1) Excellent wettability: Spreading contact angle on yttrium magnesium ceramic surface ≤40°.

[0065] 2) High static strength: room temperature shear strength ≥25MPa.

[0066] 3) Good high-temperature performance: at a test temperature of 400℃, the shear strength retention rate is >70%.

[0067] 4) Improved toughness: Fracture surface analysis shows an increased proportion of ductile fracture characteristics, and improved joint resistance to impact and thermal shock.

[0068] 4. Provides material selection for different service requirements: Three types (I, II, III) of brazing filler metal provide a clear material selection guide for engineering applications. Users can flexibly select the most suitable brazing filler metal ratio according to the component's emphasis on connection temperature, joint strength, high-temperature performance or wetting and spreading requirements.

[0069] This invention provides a method for preparing a copper indium titanium active brazing filler metal and its application in brazing yttrium magnesium ceramics and TC4 titanium alloys. Attached Figure Description

[0070] Figure 1 This diagram illustrates the design of the Cu-In-Ti ternary solder composition based on the Cu-Ti eutectic ratio according to the present invention.

[0071] Figure 2 A comparison chart showing typical differential scanning calorimetry (DSC) curves of low indium content I solder;

[0072] Figure 3 A comparison chart of typical differential scanning calorimetry (DSC) curves for indium content II solder;

[0073] Figure 4A comparison chart showing typical differential scanning calorimetry (DSC) curves of high indium content III solder;

[0074] Figure 5 This image shows backscattered electron (BSE) images of typical interface microstructures of yttrium magnesium ceramic / TC4 joints obtained using three types of brazing filler metals according to the present invention.

[0075] Figure 6 The bar chart shows the comparison of room temperature shear strength of joints obtained by the three types of brazing filler metals of the present invention and comparative brazing filler metals. Detailed Implementation

[0076] Specific Implementation Method 1: This implementation method provides a copper-indium-titanium active solder, comprising indium, copper, and titanium. The mass fraction of indium is 3.0% to 25.0%, with the balance being copper and titanium, and unavoidable impurities totaling no more than 0.5%, such as... Figure 1 As shown, the mass ratio of copper to titanium is (72~80):(20~28).

[0077] Specific Implementation Method Two: This implementation method differs from Specific Implementation Method One in that the mass fraction of indium is 3.0~10.0%, 10.1~18.0%, or 18.1~25.0%, and the melting point is as follows: Figure 2-4 As shown.

[0078] The other steps are the same as in Specific Implementation Method 1.

[0079] Specific Implementation Method 3: This implementation method describes a method for preparing a copper-indium-titanium active solder, which is carried out according to the following steps:

[0080] Step 1: Alloy smelting;

[0081] Indium, copper, and titanium are placed in a vacuum melting furnace, and the vacuum level is ≤5×10⁻⁶. -3 After Pa, induction melting is carried out in an inert gas atmosphere to fully alloy the elements; after melting, a master alloy ingot with uniform composition is obtained by casting.

[0082] Step 2: Preparation of copper indium titanium active solder;

[0083] The master alloy obtained in step one is made into copper indium titanium active solder foil strip by rapid cooling and spinning method, or into copper indium titanium active solder spherical powder by gas atomization method.

[0084] Specific Implementation Method Four: The difference between this implementation method and Specific Implementation Method Three is that the inert gas mentioned in step one is one or both of argon and helium; the alloy melt is turned over and remelted 2 to 4 times during the smelting process;

[0085] The rapid cooling and belt-throwing method described in step two is carried out as follows:

[0086] The master alloy is placed in the quartz tube of a rapid cooling and spinning device and heated under a protective atmosphere until the alloy is completely melted. It is then allowed to stand and maintain a uniform temperature. The quartz tube is pressurized, causing the molten alloy to be sprayed from a nozzle at the bottom of the tube onto the surface of a high-speed rotating metal cooling roller, which is a copper roller or a chromium-zirconium copper roller. The molten alloy rapidly cools and solidifies on the roller surface, forming a continuous amorphous or microcrystalline thin strip, resulting in a copper-indium-titanium active solder foil. The thickness of the thin strip can be controlled by adjusting the linear speed of the cooling roller; the preferred thickness is 30-80 μm, more preferably 40-60 μm.

[0087] The gas atomization method described in step two is performed as follows:

[0088] The master alloy is placed in the crucible of the atomizing device and heated under a protective atmosphere until it is completely melted and held at that temperature. The alloy melt is then fed into the atomizing chamber through a guide pipe, while a high-pressure inert gas is introduced into the atomizing chamber to impact and disperse the molten metal, resulting in fine droplets. The high-pressure inert gas is one or more of argon, nitrogen, and helium, with a pressure of 2-10 MPa. The fine droplets are cooled and solidified during flight, forming spherical powder. After collection, the powder is sieved and graded according to the target particle size to obtain copper indium titanium active solder spherical powder.

[0089] Specific Implementation Method Five: This implementation method uses copper indium titanium active solder to braze yttrium magnesium ceramic to TC4 titanium alloy, and is carried out according to the following steps:

[0090] Step S1:

[0091] The surfaces of the yttrium magnesium ceramic and TC4 titanium alloy to be joined are pretreated to obtain pretreated yttrium magnesium ceramic and TC4 titanium alloy.

[0092] Step S2:

[0093] The copper indium titanium active brazing filler metal is placed between the pretreated yttrium magnesium ceramic and TC4 titanium alloy surfaces obtained in step S1 to be joined, thus obtaining the workpiece to be welded.

[0094] Step S3:

[0095] The workpiece to be welded obtained in step S2 is placed in a vacuum furnace, heated to 750~800℃ and held at 750~800℃ for 15~30 minutes, then heated to the brazing temperature and held for 5~20 minutes; after the holding period, it is cooled to below 500℃ and then cooled to room temperature to complete the brazing of yttrium magnesium ceramic and TC4 titanium alloy using copper indium titanium active brazing filler metal.

[0096] Specific Implementation Method Six: The difference between this implementation method and Specific Implementation Method Five is that in step S1, the surface of the yttrium magnesium ceramic to be joined is polished to Ra≤0.1μm and ultrasonically cleaned; the surface of the TC4 titanium alloy to be joined is immersed in an acid pickling solution, which is composed of hydrofluoric acid, nitric acid and water, and the volume ratio of hydrofluoric acid, nitric acid and water is 1:(2.5~3.5):(8~12).

[0097] The other steps are the same as in Specific Implementation Method Four.

[0098] Specific Implementation Method Seven: This implementation method differs from Specific Implementation Methods Five or Six in that the vacuum degree in step S3 is less than 5.0 × 10⁻⁶. -3 Pa.

[0099] The other steps are the same as in specific implementation methods four or five.

[0100] Specific Implementation Method Eight: The difference between this implementation method and one of the specific implementation methods five to seven is that in step S3, the temperature is increased to 750-800℃ at a rate of 8-15℃ / min.

[0101] The other steps are the same as those in specific implementation methods five to seven.

[0102] Specific Implementation Method Nine: The difference between this implementation method and Specific Implementation Methods Five to Eight is that in step S3, the temperature is increased to the brazing temperature at a rate of 3~8℃ / min, and the brazing temperature is 870~885℃.

[0103] The other steps are the same as those in specific implementation methods five to eight.

[0104] Specific Implementation Method 10: The difference between this implementation method and Specific Implementation Methods 5 to 9 is that in step S3, the temperature is cooled to below 500°C at a rate of ≤5°C / min.

[0105] The other steps are the same as those in Specific Implementation Methods 5 to 9.

[0106] The beneficial effects of the present invention are verified using the following embodiments:

[0107] Example 1: Using Type I solder (low indium); --- Optimal example;

[0108] I. Solder preparation: The raw materials were weighed according to the ratio of Cu:Ti = 77:23, with 5% In added (by mass). Vacuum induction melting was followed by rapid cooling and spinning to obtain a foil strip with a thickness of approximately 50 μm.

[0109] II. Base materials to be welded: Yttrium magnesium ceramic sheet (4mm×4mm×3mm) and TC4 titanium alloy sheet (8mm×10mm×3mm).

[0110] III. Brazing Process: The surfaces of the yttrium magnesium ceramic and TC4 titanium alloy to be joined are pretreated. Then, copper indium titanium active brazing filler metal is placed between the pretreated surfaces of the yttrium magnesium ceramic and TC4 titanium alloy for assembly. The process is carried out under a vacuum of 2×10⁻⁶. -3 At Pa, the temperature was increased to 780℃ at 10℃ / min and held for 20min, then increased to 880℃ at 5℃ / min and held for 8min. Subsequently, the temperature was cooled to 500℃ in the furnace at 3℃ / min and then rapidly cooled by argon.

[0111] Results and characterization: such as Figure 5 As shown in (a), the brazing filler metal melts and spreads well. The interfacial reaction layer is continuous and approximately 1.2 μm thick. The average room temperature shear strength is 35 MPa. Fracture occurs at the interface between the ceramic near-seam region and the reaction layer, exhibiting predominantly brittle fracture.

[0112] Example 2: Using Type II solder (medium indium);

[0113] I. Preparation of brazing filler metal: Weigh according to the proportion and prepare spherical powder with a particle size of 300-400 mesh by gas atomization.

[0114] II. Brazing Process: Mix the brazing filler metal powder with rosin ethanol solution to form a paste and apply it. Vacuum degree 1×10 -3 Pa, the same temperature rise procedure as in Example 1, brazing temperature 865℃, hold for 12 min.

[0115] Results and Characterization: Excellent wettability, with a wetting angle of approximately 16°. Figure 5 As shown in (b), the interfacial reaction layer is uniform with a thickness of approximately 1.8 μm, exhibiting a good gradient structure. The average room temperature shear strength is 30 MPa, and the fracture surface shows obvious dimples and tear ridges, indicating a ductile-brittle mixed fracture, suggesting improved joint toughness.

[0116] Example 3: Using Type III solder (high indium);

[0117] 1. Preparation of brazing filler metal: After vacuum melting, the filler metal is spun into an 80μm foil strip.

[0118] II. Brazing process: Brazing temperature 850℃, holding time 15min, other procedures are the same as in Example 1.

[0119] Results and characterization: such as Figure 5 As shown in (c), the interfacial reaction layer is intact, with a thickness of approximately 2.0 μm. The average room temperature shear strength is 20 MPa. Microstructural analysis reveals a small amount of network-like In-rich phase in the central region of the brazed joint. The joint exhibits good plasticity, but its strength is lower than that of types I and II.

[0120] Comparative example: Ag-Cu-Ti solder (Ag-26.7Cu-4.5Ti);

[0121] like Figure 6 As shown, the brazing temperature is 900℃ and the shear strength is 28 MPa, but the cost is 4 times that of the brazing filler metal of this invention, and the high temperature causes the titanium alloy grains to coarsen.

[0122] The most critical technical feature of this invention lies in locking the Cu to Ti ratio in the solder at the eutectic point of its binary system, which is a fundamental innovation. Based on this immutable ratio, In is introduced as a performance adjustment variable, thereby systematically resolving the contradictions between low-temperature bonding, wetting and spreading, and interface toughening.

Claims

1. A copper-indium-titanium active solder, characterized in that, The copper-indium-titanium active solder comprises indium, copper, and titanium, with an indium mass fraction of 3.0-25.0% and the remainder being copper and titanium, wherein the mass ratio of copper to titanium is (72-80):(20-28).

2. The copper-indium-titanium active solder according to claim 1, characterized in that, The mass fraction of indium is 3.0~10.0%, 10.1~18.0%, or 18.1~25.0%.

3. The method for preparing a copper-indium-titanium active solder as described in any one of claims 1-2, characterized in that, The preparation method is carried out according to the following steps: Step 1: Alloy smelting; Indium, copper, and titanium are placed in a vacuum melting furnace, and the vacuum level is ≤5×10⁻⁶. -3 After Pa, induction melting is carried out in an inert gas atmosphere, and the master alloy is obtained by casting after melting. Step 2: Preparation of copper indium titanium active solder; The master alloy obtained in step one is made into copper indium titanium active solder foil strip by rapid cooling and spinning method, or into copper indium titanium active solder spherical powder by gas atomization method.

4. The method for preparing a copper-indium-titanium active solder according to claim 3, characterized in that, The inert gas mentioned in step one is one or both of argon and helium; the alloy melt is remelted by turning over 2 to 4 times during the smelting process; The rapid cooling and belt-throwing method described in step two is carried out as follows: The master alloy is placed in the quartz tube of a rapid cooling and spinning equipment and heated under a protective atmosphere until the alloy is completely melted. After standing and holding at a constant temperature, the pressure in the quartz tube is increased, causing the alloy melt to be sprayed from the nozzle at the bottom of the quartz tube onto the surface of a high-speed rotating metal cooling roller. The metal cooling roller is a copper roller or a chromium-zirconium copper roller. After the alloy melt cools and solidifies, a copper-indium-titanium active solder foil is obtained, and the thickness of the copper-indium-titanium active solder foil is 30~80μm. The gas atomization method described in step two is performed as follows: The master alloy is placed in the crucible of the atomizing device and heated under a protective atmosphere until it is completely melted and held at that temperature. The alloy melt is then fed into the atomizing chamber through a guide tube, while a high-pressure inert gas is introduced into the atomizing chamber to impact and disperse the molten metal, resulting in fine droplets. The high-pressure inert gas is one or more of argon, nitrogen, and helium, with a pressure of 2-10 MPa. After the fine droplets cool and solidify, the spherical powder is collected and sieved to obtain copper indium titanium active solder spherical powder.

5. A method for brazing yttrium magnesium ceramic and TC4 titanium alloy using copper indium titanium active solder as described in any one of claims 1-2, characterized in that, This method is performed in the following steps: Step S1: The surfaces of the yttrium magnesium ceramic and TC4 titanium alloy to be joined are pretreated to obtain pretreated yttrium magnesium ceramic and TC4 titanium alloy. Step S2: The copper indium titanium active brazing filler metal is placed between the pretreated yttrium magnesium ceramic and TC4 titanium alloy surfaces obtained in step S1 to be joined, thus obtaining the workpiece to be welded. Step S3: The workpiece to be welded obtained in step S2 is placed in a vacuum furnace, heated to 750~800℃ and held at 750~800℃ for 15~30 minutes, then heated to the brazing temperature and held for 5~20 minutes; after the holding period, it is cooled to below 500℃ and then cooled to room temperature to complete the brazing of yttrium magnesium ceramic and TC4 titanium alloy using copper indium titanium active brazing filler metal.

6. The method for brazing yttrium magnesium ceramic and TC4 titanium alloy using copper indium titanium active solder according to claim 5, characterized in that, In step S1, the surface of the yttrium magnesium ceramic to be joined is polished to Ra≤0.1μm and ultrasonically cleaned; the surface of the TC4 titanium alloy to be joined is immersed in an acid pickling solution, which is composed of hydrofluoric acid, nitric acid and water, and the volume ratio of hydrofluoric acid, nitric acid and water is 1:(2.5~3.5):(8~12).

7. The method for brazing yttrium magnesium ceramic and TC4 titanium alloy using copper indium titanium active solder according to claim 5, characterized in that, In step S3, the vacuum degree is less than 5.0 × 10⁻⁶. -3 Pa.

8. The method for brazing yttrium magnesium ceramic and TC4 titanium alloy using copper indium titanium active solder according to claim 5, characterized in that, In step S3, the temperature is increased to 750-800℃ at a rate of 8-15℃ / min.

9. The method for brazing yttrium magnesium ceramic and TC4 titanium alloy using copper indium titanium active solder according to claim 5, characterized in that, In step S3, the temperature is increased to the brazing temperature at a rate of 3~8℃ / min, where the brazing temperature is 870~885℃.

10. The method for brazing yttrium magnesium ceramic and TC4 titanium alloy using copper indium titanium active solder according to claim 5, characterized in that, In step S3, the temperature is cooled to below 500°C at a rate of ≤5°C / min.

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