Method for connecting Ti2AlNb alloy and TC20 alloy through composite interlayer brazing filler metal

Abstract

The invention provides a method for connecting Ti2AlNb alloy and TC20 alloy through composite interlayer brazing filler metal, and particularly provides Ni / TiH2-TiB2 / Ni composite interlayer brazing filler metal which is formed by mixing Ni powder, TiH2 powder and TiB2 powder, the average thickness of the Ni / TiH2-TiB2 / Ni composite interlayer brazing filler metal is 0.15 mm, and the volume fraction of theoretical in-situ synthesized TiB whiskers is 20%. The brazing filler metal is completely melted at the brazing temperature, element interdiffusion occurs between the brazing filler metal and brazing base metal in the heat preservation process, stable and reliable connection is formed, and connection of Ti2AlNb alloy and TC20 alloy heterogeneous materials is achieved.

Description

Technical Field

[0001] This invention belongs to the field of vacuum brazing technology. Specifically, this invention relates to a method for connecting Ti2AlNb alloy and TC20 alloy with a composite intermediate layer brazing filler metal. Background Technology

[0002] Technological advancements in advanced high thrust-to-weight ratio aero-engines heavily rely on new materials with superior comprehensive properties, including low density, high strength, high temperature resistance, and oxidation resistance. To meet the temperature resistance requirements of high-temperature structural components in aerospace vehicles and automotive engines, heat-resistant steel, Ni-based alloys, and Ti-based alloys are currently the primary materials used. However, the first two types of alloys, due to their high density and specific gravity, cannot meet the requirements for important parameters such as engine thermal efficiency and thrust-to-weight ratio. Many domestic and international scholars have focused their research on Ti-based alloys. TC20 (Ti-6Al-7Nb (wt.%)) alloy, as a second-generation α+β type titanium alloy, exhibits excellent corrosion resistance, comprehensive mechanical properties, and high-temperature plasticity, falling into the category of medium-to-high strength titanium alloys. However, its poor strength and creep resistance at high temperatures limit its further application in high-temperature environments. To address this issue, researchers have added Nb, a β-stabilizing element with high melting point characteristics, to Ti3Al alloys to achieve alloying and generate a second phase. This yields a new type of alloy material with high room temperature plasticity, fracture toughness, and resistance to crack propagation. However, it is very difficult and much more expensive to process integral components using Ti2AlNb alloys alone. From the perspective of comprehensive material utilization, if TC20 and Ti2AlNb-based alloys can be joined, the complementary advantages of the two materials in reducing costs and improving performance will be leveraged to obtain a composite component with high specific strength, strong corrosion resistance, light weight, and strong plastic deformation capacity. This will deepen and expand the application of both materials in aerospace and other fields.

[0003] Previous studies have shown that Ag-based brazing filler metals typically operate below 500 °C, which is unsuitable for the practical application environment of aerospace hot-end components. Ni-based and Cu-based brazing filler metals produce joints with high strength, but excessively high temperatures (above 1100 °C) can lead to over-wetting of the base metal by the brazing material, resulting in base metal corrosion. In contrast, Ti-based brazing filler metals possess a higher melting point, good high-temperature resistance, and excellent wettability and compatibility with titanium-aluminum and titanium-based alloys, effectively filling the weld and forming high-quality welded joints. Ti-based brazing filler metal joints between titanium-aluminum alloys and titanium-based alloys can be viewed as multilayer titanium alloys with a high coefficient of thermal expansion (CTE) mismatch, which are prone to generating large residual stresses. Furthermore, the presence of brittle intermetallic compounds (such as Ti₂Ni and Ti₂Cu) in the joint prevents effective release of residual stress. Currently, TiB whiskers, which have similar density, coefficient of thermal expansion and good compatibility with titanium alloys, are usually selected as reinforcing phases to reduce residual stress through in-situ synthesis technology. The resulting joints have good chemical properties and thermodynamic stability. However, existing research mainly emphasizes the introduction of a single intermediate layer brazing filler metal with reinforcing phases, which is difficult to apply to combinations of multiple materials, and the stability of the joints is also affected to some extent.

[0004] Therefore, obtaining a composite intermediate layer solder that is simple to process, low in preparation cost, and incorporates a reinforcing phase is the main problem that current technology needs to solve. Summary of the Invention

[0005] To address the above problems, this invention discloses a titanium-based composite intermediate layer brazing filler metal, its preparation method, and its application. Using this filler metal, a Ti2AlNb-TC20 joint with flexible preparation process and adaptability to various scenarios can be obtained by brazing, and the resulting brazed joint has good room temperature mechanical properties.

[0006] In one aspect of the invention, a Ni / TiH2-TiB2 / Ni composite interlayer solder is proposed. According to an embodiment of the invention, the Ni / TiH2-TiB2 / Ni composite interlayer solder is a Ni / TiH2-TiB2 / Ni composite interlayer solder with an average thickness of 0.15 mm and a theoretical in-situ self-generated TiB whisker volume fraction of 20%, formed by mixing Ni, TiH2, and TiB2 powders.

[0007] According to embodiments of the present invention, the Ni / TiH2-TiB2 / Ni composite interlayer solder may further include the following additional technical features: According to an embodiment of the present invention, the mass percentages of Ni, TiH2, and TiB2 powders are 25%:7%:68%.

[0008] In another aspect, the present invention provides a method for preparing a Ti2AlNb-TC20 brazed joint. According to an embodiment of the present invention, the method includes placing a Ni / TiH2-TiB2 / Ni composite interlayer solder between a Ti2AlNb alloy and a TC20 alloy to form a sandwich structure, and then performing brazing to obtain a Ti2AlNb-TC20 brazed joint. The Ni / TiH2-TiB2 / Ni composite intermediate layer solder is formed by mixing Ni, TiH2 and TiB2 powders.

[0009] According to embodiments of the present invention, the method may further include at least one of the following technical features: According to an embodiment of the present invention, the thickness of the Ni / TiH2-TiB2 / Ni composite intermediate layer solder is 0.15 mm.

[0010] According to an embodiment of the present invention, the theoretical in-situ self-generated TiB whisker volume fraction of the Ni / TiH2-TiB2 / Ni composite intermediate layer solder is 20%.

[0011] According to an embodiment of the present invention, the Ni / TiH2-TiB2 / Ni composite interlayer solder is obtained by the following method: Ni, TiH2, and TiB2 powders were weighed according to their respective mass percentages. TiH2 and TiB2 powders were then subjected to low-energy ball milling at a speed of 300 rpm, a ball-to-powder mass ratio of 4:1, and a ball milling time of 120 min to achieve mechanical mixing. The TiH2-TiB2 mixed powder layer and the Ni powder layer were then alternately stacked and compacted in a stainless steel mold to obtain the Ni / TiH2-TiB2 / Ni composite intermediate layer solder.

[0012] According to an embodiment of the present invention, the average particle sizes of the Ni, TiH2 and TiB2 powders are 48 μm, 45 μm and 3 μm, respectively.

[0013] According to an embodiment of the present invention, the Ni, TiH2 and TiB2 powder is composed of the following components in terms of mass content: TiH2 68%, Ni 25%, TiB2 7%.

[0014] According to an embodiment of the present invention, the surfaces of the Ti2AlNb alloy and the TC20 alloy to be welded are pre-polished, cleaned, and dried.

[0015] According to an embodiment of the present invention, the polishing process is carried out by polishing the surfaces to be welded of the Ti2AlNb alloy and the TC20 alloy sequentially with 300#, 800#, and 1200# sandpaper, respectively.

[0016] According to an embodiment of the present invention, the cleaning process is carried out by immersing the polished Ti2AlNb alloy and the TC20 alloy surfaces to be welded into a container containing ethanol, and then placing them in an ultrasonic cleaner for ultrasonic cleaning for 5 to 10 minutes.

[0017] According to an embodiment of the present invention, the drying process is carried out by transferring the cleaned Ti2AlNb alloy and TC20 alloy into an oven for drying.

[0018] According to an embodiment of the present invention, the brazing process is performed in a high-vacuum brazing furnace.

[0019] According to an embodiment of the present invention, the brazing process is performed by first heating to 700°C at a rate of 10°C / min and holding at that temperature for 10 min, then heating to the brazing temperature at a rate of 10°C / min and holding at that temperature for 10 min, and then cooling to room temperature in the furnace.

[0020] According to an embodiment of the present invention, the brazing temperature is 1020℃~1100℃.

[0021] In another aspect, the present invention also provides a method for preparing Ti2AlNb-TC20 brazed joints. According to an embodiment of the present invention, the method includes... S1: The surfaces of the Ti2AlNb alloy and TC20 alloy to be welded are polished with 300#, 800# and 1200# sandpaper respectively. Then, the polished surfaces are immersed in a container of ethanol and placed in an ultrasonic cleaner for ultrasonic cleaning for 5 min to 10 min. Then, they are taken out and dried in an oven to obtain the pretreated Ti2AlNb alloy and TC20 alloy. S2: Weigh out Ni, TiH2 and TiB2 powders of 68% TiH2, 25% Ni and 27% TiB2 by mass percentage, respectively, and perform low-energy ball milling on TiH2 and TiB2 powders at 300 rpm, ball-to-powder mass ratio of 4:1 and ball milling time of 120 min to achieve mechanical mixing. Then, stack and compact the TiH2-TiB2 mixed powder layer and Ni powder layer alternately in a stainless steel mold to obtain a Ni / TiH2-TiB2 / Ni composite intermediate layer solder with a theoretical in-situ self-generated TiB whisker volume fraction of 20% and an average thickness of about 0.15 mm. S3: Place the Ni / TiH2-TiB2 / Ni composite intermediate layer solder obtained in S2 between the Ti2AlNb alloy and TC20 alloy prepared in step one to form a sandwich structure of Ti2AlNb alloy / Ni / TiH2-TiB2 / Ni solder / TC20 alloy. S4: The assembled pre-welded parts obtained in S3 are placed in a high-vacuum brazing furnace for brazing connection. First, the temperature is raised to 700℃ at a rate of 10℃ / min and held for 10min. Then, the temperature is raised to the brazing temperature at a rate of 10℃ / min and held for 10min. The brazing is completed by cooling the furnace to room temperature to obtain a Ti2AlNb-TC20 brazed joint. The brazing temperature is 1020℃~1100℃.

[0022] In another aspect, the present invention also provides a Ti2AlNb-TC20 brazed joint. According to an embodiment of the present invention, the brazed joint is prepared by the welding method described above.

[0023] In another aspect, the present invention also proposes the application of the aforementioned method for preparing Ti2AlNb-TC20 brazed joints in vacuum brazing.

[0024] In another aspect, the present invention also provides a method for preparing Ti2AlNb-TC20 brazed joints. According to an embodiment of the present invention, the method includes: Step 1: Pretreatment of the parts to be welded: The surfaces of the Ti2AlNb alloy and TC20 alloy to be welded are polished with 300#, 800# and 1200# sandpaper respectively. Then, the polished surfaces are immersed in a container of ethanol and placed in an ultrasonic cleaner for ultrasonic cleaning for 5 to 10 minutes. After that, they are taken out and dried in an oven to obtain the pretreated Ti2AlNb alloy and TC20 alloy. Step 2: Prepare Ni / TiH2-TiB2 / Ni composite intermediate layer solder: Weigh Ni, TiH2 and TiB2 powders according to their mass percentages, and ball mill TiH2 and TiB2 powders at a speed of 300 rpm, a ball-to-powder mass ratio of 4:1 and a ball milling time of 120 min to achieve mechanical mixing. Then, alternately stack and compact the TiH2-TiB2 mixed powder layer and the Ni powder layer in a stainless steel mold to obtain a Ni / TiH2-TiB2 / Ni composite intermediate layer solder with a theoretical in-situ self-generated TiB whisker volume fraction of 20% and an average thickness of about 0.15 mm. Step 3, Assembly: Place the Ni / TiH2-TiB2 / Ni composite intermediate layer solder obtained in Step 2 between the Ti2AlNb alloy and TC20 alloy prepared in Step 1 to form a sandwich structure of Ti2AlNb alloy / Ni / TiH2-TiB2 / Ni solder / TC20 alloy. Step 4, Brazing in Furnace: Place the assembled pre-welded parts obtained in Step 3 into a high-vacuum brazing furnace for brazing connection. First, heat the furnace to 700℃ at a rate of 10℃ / min and hold for 10min. Then, heat the furnace to the brazing temperature at a rate of 10℃ / min and hold for 10min. Cool the furnace to room temperature to complete the brazing.

[0025] According to embodiments of the present invention, the method may further include at least one of the following technical features: According to an embodiment of the present invention, the average particle sizes of the Ni, TiH2, and TiB2 powders in step two are 48 μm, 45 μm, and 3 μm, respectively, and they are composed of the following components by mass percentage: TiH2 68%, Ni 25%, and TiB2 7%. The TiH2 powder is activated by thermal decomposition at 700°C. + Lowering the melting point of the brazing filler metal and improving its wettability are beneficial for improving the adhesion of the filler metal to the base material.

[0026] According to an embodiment of the present invention, in step two, the Ni / TiH2-TiB2 / Ni composite intermediate layer solder is mechanically mixed by low-energy ball milling in an inert gas environment. This preparation method has the advantages of fewer impurity elements, uniform chemical composition, and high production efficiency.

[0027] According to an embodiment of the present invention, in step two, Ni, TiH2 and TiB2 powders are weighed according to their respective mass percentages in the Ni / TiH2-TiB2 / Ni composite intermediate layer solder, and TiH2 and TiB2 powders are mixed at a rotation speed of 300 rpm, a ball-to-powder mass ratio of 4:1 and a ball milling time of 120 min.

[0028] According to an embodiment of the present invention, the brazing temperature in step four is 1020℃~1100℃. At this brazing temperature, the Ni / TiH2-TiB2 / Ni composite interlayer filler metal completely melts and undergoes elemental interdiffusion with the brazing base material, which is beneficial for obtaining a reliable brazed joint.

[0029] Compared with the prior art, the present invention has at least one of the following advantages: 1. This invention uses a Ni / TiH2-TiB2 / Ni composite intermediate layer, prepared by pressing TiH2-TiB2 composite intermediate layer powder and Ni powder into sheets, as a brazing material for vacuum brazing. The powdered brazing filler completely melts at the brazing temperature and undergoes elemental interdiffusion with the brazing base material during the heat preservation process, forming a stable and reliable connection, thus realizing the connection of Ti2AlNb alloy and TC20 alloy heterogeneous materials.

[0030] 2. The Ni / TiH2-TiB2 / Ni composite intermediate layer brazing filler used in this invention is obtained by pressing TiH2-TiB2 powder and Ni powder. The preparation method is simple, and the content of each component in the powder brazing filler can be controlled. The brazing temperature can be effectively adjusted according to the composition change, thus ensuring the weld quality between Ti2AlNb alloy and TC20 alloy heterogeneous materials.

[0031] 3. The Ni / TiH2-TiB2 / Ni composite intermediate layer brazing alloy used in this invention is simple to operate, requires no secondary processing before use, and its composition can be easily adjusted for the connection of various materials, simplifying the brazing process and easily meeting the brazing requirements of complex welds. Attached Figure Description

[0032] The above and / or additional aspects and advantages of the present invention will become apparent and readily understood from the description of the embodiments taken in conjunction with the following drawings, in which: Figure 1 The SEM morphology of the Ti2AlNb alloy / Ni / TiH2-TiB2 / Ni composite intermediate layer solder / TC20 alloy in Example 1 is shown. Figure 2 The SEM morphology of the joints at different brazing temperatures is shown.

[0033] Explanation of symbols in the diagram: A. α-Ti phase; B. β-Ti phase; C. Ti₂Ni phase; D. (Ti,Nb)B phase; E. Ti₂Ni phase; F. α-Ti phase; G. Ti₂Ni phase; H. α-Ti phase; I. (Ti,Nb)B phase; J. Ti₂Ni phase; K. Ti₂Ni phase; L. (Ti,Nb)B phase; M. α-Ti phase; N. Ti₂Ni phase; O. Ti₃Al phase; P. B₂ phase. Detailed Implementation

[0034] The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain the invention, and should not be construed as limiting the invention.

[0035] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this invention, "a plurality of" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0036] In this invention, unless otherwise explicitly specified and limited, "above" or "below" the second feature can mean that the first feature is in direct contact with the second feature, or that the first feature is in indirect contact with the second feature through an intermediate medium. Furthermore, "above," "over," and "on top" of the second feature can mean that the first feature is directly above or diagonally above the second feature, or simply that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature can mean that the first feature is directly below or diagonally below the second feature, or simply that the first feature is at a lower horizontal level than the second feature.

[0037] The present invention will now be described with reference to specific embodiments. It should be noted that these embodiments are merely descriptive and do not limit the present invention in any way.

[0038] Example 1 A brazing solder, its fabrication, and a brazing method for Ti2AlNb alloy and TC20 alloy: Step 1: Pretreatment of the parts to be welded: The surfaces of the Ti2AlNb alloy and TC20 alloy to be welded are polished with 300#, 800# and 1200# sandpaper respectively. Then, the polished surfaces are immersed in a container of ethanol and ultrasonically cleaned for 8 minutes. After that, they are taken out and dried in an oven at 70°C for 0.5 hours to obtain the pretreated Ti2AlNb alloy and TC20 alloy. Step 2: Prepare Ni / TiH2-TiB2 / Ni composite intermediate layer solder: Weigh Ni, TiH2 and TiB2 powders according to their mass percentages, and ball mill TiH2 and TiB2 powders at a speed of 300 rpm, a ball-to-powder mass ratio of 4:1 and a ball milling time of 120 min to achieve mechanical mixing. Then, alternately stack and compact the TiH2-TiB2 mixed powder layer and the Ni powder layer in a stainless steel mold to obtain a Ni / TiH2-TiB2 / Ni composite intermediate layer solder with a theoretical in-situ self-generated TiB whisker volume fraction of 20% and an average thickness of about 0.15 mm. Step 3, Assembly: Place the Ni / TiH2-TiB2 / Ni composite intermediate layer solder obtained in Step 2 between the Ti2AlNb alloy and TC20 alloy prepared in Step 1 to form a sandwich structure of Ti2AlNb alloy / Ni / TiH2-TiB2 / Ni solder / TC20 alloy. Step 4, Brazing in the furnace: Place the assembled pre-welded parts obtained in Step 3 into a high-vacuum brazing furnace for brazing connection. First, heat the furnace to 700℃ at a rate of 10℃ / min and hold for 10min. Then, heat the furnace to the brazing temperature of 1060℃ at a rate of 10℃ / min and hold for 10min. Cool the furnace to room temperature to complete the brazing.

[0039] Example 2 Step 1: Pretreatment of the parts to be welded: The surfaces of the Ti2AlNb alloy and TC20 alloy to be welded are polished with 300#, 800# and 1200# sandpaper respectively. Then, the polished surfaces are immersed in a container of ethanol and ultrasonically cleaned for 8 minutes. After that, they are taken out and dried in an oven at 70°C for 0.5 hours to obtain the pretreated Ti2AlNb alloy and TC20 alloy. Step 2: Prepare Ni / TiH2-TiB2 / Ni composite intermediate layer solder: Weigh Ni, TiH2 and TiB2 powders according to their mass percentages, and ball mill TiH2 and TiB2 powders at a speed of 300 rpm, a ball-to-powder mass ratio of 4:1 and a ball milling time of 120 min to achieve mechanical mixing. Then, alternately stack and compact the TiH2-TiB2 mixed powder layer and the Ni powder layer in a stainless steel mold to obtain a Ni / TiH2-TiB2 / Ni composite intermediate layer solder with a theoretical in-situ self-generated TiB whisker volume fraction of 20% and an average thickness of about 0.15 mm. Step 3, Assembly: Place the Ni / TiH2-TiB2 / Ni composite intermediate layer solder obtained in Step 2 between the Ti2AlNb alloy and TC20 alloy prepared in Step 1 to form a sandwich structure of Ti2AlNb alloy / Ni / TiH2-TiB2 / Ni solder / TC20 alloy. Step 4, Brazing in the furnace: Place the assembled pre-welded parts obtained in Step 3 into a high-vacuum brazing furnace for brazing connection. First, heat the furnace to 700℃ at a rate of 10℃ / min and hold for 10min. Then, heat the furnace to the brazing temperature of 1020℃ at a rate of 10℃ / min and hold for 10min. Cool the furnace to room temperature to complete the brazing.

[0040] Example 3 Step 1: Pretreatment of the parts to be welded: The surfaces of the Ti2AlNb alloy and TC20 alloy to be welded are polished with 300#, 800# and 1200# sandpaper respectively. Then, the polished surfaces are immersed in a container of ethanol and ultrasonically cleaned for 8 minutes. After that, they are taken out and dried in an oven at 70°C for 0.5 hours to obtain the pretreated Ti2AlNb alloy and TC20 alloy. Step 2: Prepare Ni / TiH2-TiB2 / Ni composite intermediate layer solder: Weigh Ni, TiH2 and TiB2 powders according to their mass percentages, and ball mill TiH2 and TiB2 powders at a speed of 300 rpm, a ball-to-powder mass ratio of 4:1 and a ball milling time of 120 min to achieve mechanical mixing. Then, alternately stack and compact the TiH2-TiB2 mixed powder layer and the Ni powder layer in a stainless steel mold to obtain a Ni / TiH2-TiB2 / Ni composite intermediate layer solder with a theoretical in-situ self-generated TiB whisker volume fraction of 20% and an average thickness of about 0.15 mm. Step 3, Assembly: Place the Ni / TiH2-TiB2 / Ni composite intermediate layer solder obtained in Step 2 between the Ti2AlNb alloy and TC20 alloy prepared in Step 1 to form a sandwich structure of Ti2AlNb alloy / Ni / TiH2-TiB2 / Ni solder / TC20 alloy. Step 4, Brazing in Furnace: Place the assembled pre-welded parts obtained in Step 3 into a high-vacuum brazing furnace for brazing connection. First, heat the furnace to 700℃ at a rate of 10℃ / min and hold for 10min. Then, heat the furnace to the brazing temperature of 1040℃ at a rate of 10℃ / min and hold for 10min. Cool the furnace to room temperature to complete the brazing.

[0041] Example 4 Step 1: Pretreatment of the parts to be welded: The surfaces of the Ti2AlNb alloy and TC20 alloy to be welded are polished with 300#, 800# and 1200# sandpaper respectively. Then, the polished surfaces are immersed in a container of ethanol and ultrasonically cleaned for 8 minutes. After that, they are taken out and dried in an oven at 70°C for 0.5 hours to obtain the pretreated Ti2AlNb alloy and TC20 alloy. Step 2: Prepare Ni / TiH2-TiB2 / Ni composite intermediate layer solder: Weigh Ni, TiH2 and TiB2 powders according to their mass percentages, and ball mill TiH2 and TiB2 powders at a speed of 300 rpm, a ball-to-powder mass ratio of 4:1 and a ball milling time of 120 min to achieve mechanical mixing. Then, alternately stack and compact the TiH2-TiB2 mixed powder layer and the Ni powder layer in a stainless steel mold to obtain a Ni / TiH2-TiB2 / Ni composite intermediate layer solder with a theoretical in-situ self-generated TiB whisker volume fraction of 20% and an average thickness of about 0.15 mm. Step 3, Assembly: Place the Ni / TiH2-TiB2 / Ni composite intermediate layer solder obtained in Step 2 between the Ti2AlNb alloy and TC20 alloy prepared in Step 1 to form a sandwich structure of Ti2AlNb alloy / Ni / TiH2-TiB2 / Ni solder / TC20 alloy. Step 4, Brazing in Furnace: Place the assembled pre-welded parts obtained in Step 3 into a high-vacuum brazing furnace for brazing connection. First, heat the furnace to 700℃ at a rate of 10℃ / min and hold for 10min. Then, heat the furnace to the brazing temperature of 1080℃ at a rate of 10℃ / min and hold for 10min. Cool the furnace to room temperature to complete the brazing.

[0042] Example 5 Step 1: Pretreatment of the parts to be welded: The surfaces of the Ti2AlNb alloy and TC20 alloy to be welded are polished with 300#, 800# and 1200# sandpaper respectively. Then, the polished surfaces are immersed in a container of ethanol and ultrasonically cleaned for 8 minutes. After that, they are taken out and dried in an oven at 70°C for 0.5 hours to obtain the pretreated Ti2AlNb alloy and TC20 alloy. Step 2: Prepare Ni / TiH2-TiB2 / Ni composite intermediate layer solder: Weigh Ni, TiH2 and TiB2 powders according to their mass percentages, and ball mill TiH2 and TiB2 powders at a speed of 300 rpm, a ball-to-powder mass ratio of 4:1 and a ball milling time of 120 min to achieve mechanical mixing. Then, alternately stack and compact the TiH2-TiB2 mixed powder layer and the Ni powder layer in a stainless steel mold to obtain a Ni / TiH2-TiB2 / Ni composite intermediate layer solder with a theoretical in-situ self-generated TiB whisker volume fraction of 20% and an average thickness of about 0.15 mm. Step 3, Assembly: Place the Ni / TiH2-TiB2 / Ni composite intermediate layer solder obtained in Step 2 between the Ti2AlNb alloy and TC20 alloy prepared in Step 1 to form a sandwich structure of Ti2AlNb alloy / Ni / TiH2-TiB2 / Ni solder / TC20 alloy. Step 4, Brazing in Furnace: Place the assembled pre-welded parts obtained in Step 3 into a high-vacuum brazing furnace for brazing connection. First, heat the furnace to 700℃ at a rate of 10℃ / min and hold for 10 minutes. Then, heat the furnace to the brazing temperature of 1100℃ at a rate of 10℃ / min and hold for 10 minutes. Cool the furnace to room temperature to complete the brazing.

[0043] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0044] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention.

Claims

1. A Ni / TiH2-TiB2 / Ni composite interlayer brazing material, characterized by, The Ni / TiH2-TiB2 / Ni composite interlayer filler is a Ni / TiH2-TiB2 / Ni composite interlayer filler with an average thickness of 0.15 mm and a theoretical in-situ self-grown TiB whisker volume fraction of 20% formed by mixing Ni, TiH2 and TiB2 powders.

2. A method for preparing a Ti2AlNb-TC20 brazed joint, characterized in that, The method comprises placing the Ni / TiH2-TiB2 / Ni composite interlayer filler between the Ti2AlNb alloy and the TC20 alloy to form a sandwich structure, and performing a brazing process to obtain a Ti2AlNb-TC20 brazed joint, The Ni / TiH2-TiB2 / Ni composite interlayer filler is formed by mixing Ni, TiH2 and TiB2 powders.

3. The method of claim 2, wherein, The thickness of the Ni / TiH2-TiB2 / Ni composite interlayer filler is 0.15 mm. Optionally, the theoretical in-situ self-grown TiB whisker volume fraction of the Ni / TiH2-TiB2 / Ni composite interlayer filler is 20%.

4. The method of claim 2, wherein, The Ni / TiH2-TiB2 / Ni composite interlayer filler is obtained by the following method: The Ni, TiH2 and TiB2 powders are weighed according to the mass percentage, and the TiH2 and TiB2 powders are subjected to low-energy ball milling to achieve mechanical mixing under the conditions of a rotation speed of 300 rpm, a ball-to-powder mass ratio of 4:1 and a ball milling time of 120 min. Then, the TiH2-TiB2 mixed powder layer and the Ni powder layer are alternately stacked and compacted in a stainless steel mold to obtain the Ni / TiH2-TiB2 / Ni composite interlayer filler.

5. The method of claim 4, wherein, The average particle sizes of the Ni, TiH2 and TiB2 powders are 48 μm, 45 μm and 3 μm, respectively. Optionally, the Ni, TiH2 and TiB2 powders are composed of the following components with the following mass contents: TiH268%, Ni 25%, TiB27%.

6. The method of claim 2, wherein, The surfaces to be welded of the Ti2AlNb alloy and the TC20 alloy are subjected to pre-grinding treatment, cleaning treatment and drying treatment; Optionally, the grinding treatment is performed by grinding the surfaces to be welded of the Ti2AlNb alloy and the TC20 alloy with sandpaper of 300#, 800# and 1200# in sequence. Optionally, the cleaning treatment is performed by immersing the surfaces to be welded of the Ti2AlNb alloy and the TC20 alloy after the grinding treatment in a container containing ethanol, and then placing them in an ultrasonic cleaner for ultrasonic cleaning treatment for 5-10 min. Optionally, the drying treatment is performed by transferring the Ti2AlNb alloy and the TC20 alloy after the cleaning treatment into an oven for drying.

7. The method of claim 2, wherein, The brazing process is performed in a high-vacuum brazing furnace. Optionally, the brazing process is performed by first increasing the temperature to 700°C at a rate of 10°C / min and maintaining the temperature for 10 min, then increasing the temperature to the brazing temperature at a rate of 10°C / min and maintaining the temperature for 10 min, and then cooling the furnace to room temperature. Optionally, the brazing temperature is 1020-1100°C.

8. A method for preparing a Ti2AlNb-TC20 brazed joint, characterized in that S1: the welding surface of the Ti2AlNb alloy and the TC20 alloy to be welded is polished with 300#, 800# and 1200# sandpaper respectively, then the polished welding surface is immersed in a container containing ethanol, and then placed in an ultrasonic cleaner for ultrasonic cleaning treatment for 5-10 min, and then taken out and transferred to an oven for drying, to obtain the pretreated Ti2AlNb alloy and TC20 alloy; S2: according to the mass percentage, Ni, TiH2 and TiB2 powders of TiH268%, Ni 25%, TiB2 7% are weighed, and the TiH2 and TiB2 powders are mechanically mixed by low-energy ball milling at a speed of 300 rpm, a ball-powder mass ratio of 4:1 and a ball milling time of 120 min, then the TiH2-TiB2 mixed powder layer and the Ni powder layer are alternately stacked and compacted in a stainless steel mold to obtain a Ni / TiH2-TiB2 / Ni composite interlayer filler with a theoretical in-situ TiB whisker volume fraction of 20% and an average thickness of about 0.15 mm; S3: the Ni / TiH2-TiB2 / Ni composite interlayer filler obtained in S2 is placed between the Ti2AlNb alloy and the TC20 alloy prepared in step one to form a sandwich structure of Ti2AlNb alloy / Ni / TiH2-TiB2 / Ni filler / TC20 alloy; S4: the assembled pre-welding part obtained in S3 is placed in a high vacuum brazing furnace for brazing connection, first heated to 700℃ at a rate of 10℃ / min and held for 10 min, then heated to the brazing temperature at a rate of 10℃ / min and held for 10 min, and then cooled to room temperature in the furnace to complete the brazing, to obtain a Ti2AlNb-TC20 brazed joint, and the brazing temperature is 1020-1100℃.

9. A Ti2AlNb-TC20 brazed joint, characterized in that, The brazed joint is prepared by the welding method of any one of claims 2-8.

10. The use of the method for preparing a Ti2AlNb-TC20 brazed joint according to any one of claims 2-8 in vacuum brazing.

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