Ti-mn-fe-ni-co-cr medium-entropy alloy brazing filler metal and use thereof in brazing connection

Abstract

A Ti-Mn-Fe-Ni-Co-Cr medium-entropy alloy brazing filler metal, comprising the following components in percentages by mass: 16.0-22.0% of Mn, 12.0-18.0% of Fe, 2.0-10.0% of Ni, 2.0-10.0% of Co, less than or equal to 6.0% of Cr, and the balance of Ti. The brazing filler metal can achieve vacuum brazing connection of TiAl at a brazing temperature of 1170-1180ºC; and a brazed joint obtained under specific conditions has a tensile strength at room temperature of 495-518 MPa, a tensile strength at 700ºC of 530-563 MPa, a tensile strength at 750ºC of 517-566 MPa, a tensile strength at 850ºC of 411-420 MPa, and a high-temperature strength coefficient of more than 0.87 within a wide temperature range of 700-850ºC. The present invention further relates to a preparation method for the Ti-Mn-Fe-Ni-Co-Cr medium-entropy alloy brazing filler metal, the use of the Ti-Mn-Fe-Ni-Co-Cr medium-entropy alloy brazing filler metal in brazing connection, and a brazing method for a TiAl alloy.

Description

A Ti-Mn-Fe-Ni-Co-Cr medium-entropy alloy brazing filler metal and its application in brazing joints

[0001] This application claims priority to Chinese Patent Application No. 202410514165.4, filed on April 26, 2024, entitled "A Ti-Mn-Fe-Ni-Co-Cr Medium Entropy Alloy Brazing Alloy and Its Application in Brazing Connection", the entire contents of which are incorporated herein by reference. Technical Field

[0002] This invention relates to the field of aerospace brazing technology, and in particular to a Ti-Mn-Fe-Ni-Co-Cr medium-entropy alloy brazing filler metal and its application in TiAl brazing joints. Background Technology

[0003] The main advantages of titanium-aluminum (TiAl-based) alloys include: low density (3.9–4.2 g / cm³). 3 TiAl-based alloys possess high specific strength and specific stiffness, as well as excellent creep resistance, oxidation resistance, and flame retardancy below 800℃. In the aerospace field, parts made from TiAl-based alloys can withstand long-term high-temperature operating temperatures of 700–850℃, significantly increasing the long-term service temperature of components compared to traditional titanium alloys. Furthermore, compared to traditional nickel-based superalloys, TiAl-based alloys have lower density and higher specific strength. Therefore, TiAl-based alloys have broad prospects for high-temperature applications in the aerospace field.

[0004] However, TiAl-based alloys are inherently brittle, with room temperature plasticity of only 1-3%, making them highly susceptible to cracking during welding. From a feasibility and cost-effectiveness perspective, brazing is a highly suitable joining technique for TiAl-based alloys. Brazing involves heating a filler metal with a lower melting point than the base metal and the workpiece together. The workpiece does not melt, while the filler metal melts, wetting and filling the gaps between the base metals. The filler metal and base metal diffuse into each other, forming a strong bond. Currently, research on brazing technology for TiAl-based alloys focuses on improving brazing methods, filler metals, process control, and room temperature / high temperature strength of brazed joints. However, the brazing temperature of the filler metal and the strength of the brazed joint remain inconsistent.

[0005] Ag-based or Al-based brazing alloys have low brazing temperatures, but the high-temperature strength of the brazed joints is significantly insufficient. Although Ti-based brazing alloys improve the room temperature strength of the brazed joints, the high-temperature strength remains insufficient. Moreover, some Ti-based brazing alloys have very high brazing temperatures, such as exceeding 1200℃, which can easily damage the properties of the base material. Therefore, the key to coordinating TiAl-based alloy brazing alloys lies in how to achieve brazing at relatively low brazing temperatures (below 1200℃) while also ensuring that the brazed joints possess high room temperature / high-temperature strength. Summary of the Invention

[0006] In view of this, the present invention provides a Ti-Mn-Fe-Ni-Co-Cr medium-entropy alloy brazing filler metal and its application in TiAl brazing. The brazing filler metal provided by the present invention can effectively solve the problems of excessively high brazing temperature and insufficient room temperature / high temperature strength of brazed joints in existing TiAl brazing technology.

[0007] This invention provides a Ti-Mn-Fe-Ni-Co-Cr medium-entropy alloy brazing filler metal, wherein the filler metal comprises the following components by mass percentage:

[0008] Mn 16.0–22.0%; Fe 12.0–18.0%; Ni 2.0–10.0%; Co 2.0–10.0%; Cr 0–6.0%; Ti balance.

[0009] Preferably, the brazing filler metal comprises the following components by weight percentage:

[0010] Mn 17.0–22.0%; Fe 13.0–18.0%; Ni 3.0–8.0%; Co 3.0–8.0%; Cr 0–5.0%; Ti balance.

[0011] Preferably, the brazing filler metal is used in one or more of the following forms: alloy block, alloy powder, and rapidly cooled foil strip.

[0012] This invention provides a method for preparing Ti-Mn-Fe-Ni-Co-Cr medium-entropy alloy solder as described above, comprising the following steps:

[0013] A) The ingredients are batched according to the mass percentage, and then the alloy ingots are melted by electric arc melting.

[0014] B) The alloy ingot is processed into brazing filler metals of different forms through different processes; the brazing filler metals are used in one or more of the following forms: alloy block, alloy powder, and rapidly cooled foil strip.

[0015] This invention provides the application of Ti-Mn-Fe-Ni-Co-Cr medium-entropy alloy brazing filler metal as described above in brazing connections.

[0016] This invention provides a brazing method for TiAl alloys, comprising the following steps:

[0017] S1. Pre-treat the welding positions on the surface of the TiAl alloy base material;

[0018] S2. Add brazing filler metal to the pre-treated base material at the welding position to obtain the assembled component; the brazing filler metal is the Ti-Mn-Fe-Ni-Co-Cr medium-entropy alloy brazing filler metal mentioned above;

[0019] S3. Brazing the assembled components to form TiAl alloy connectors.

[0020] Preferably, in step S1, oil and oxides are removed through pretreatment.

[0021] Preferably, step S2 includes controlling the brazing gap between the base materials to be welded to be 0.03 to 0.07 mm by machining or tooling fixtures.

[0022] Preferably, in step S3, the brazing temperature is 1170–1180°C; the brazing is vacuum brazing.

[0023] Preferably, the vacuum brazing includes: a furnace vacuum degree better than 8×10⁻⁶. -3 Pa, first heat to 600℃ at a rate of 10–40℃ / min, then heat to 900℃ at a rate of 10–30℃ / min, and finally heat to T at a rate of 10–25℃ / min. b Hold the temperature for 20–75 minutes; after holding, cool down at a rate of 10–40℃ / min until the furnace reaches room temperature.

[0024] The aforementioned brazing filler metal can be used for brazing TiAl alloys, but is not limited to the connection of TiAl as the only type of material.

[0025] Compared with existing technologies, the Ti-Mn-Fe-Ni-Co-Cr medium-entropy alloy brazing filler metal proposed in this invention has the following composition range: Mn: 16.0–22.0%; Fe: 12.0–18.0%; Ni: 2.0–10.0%; Co: 2.0–10.0%; Cr: 0–6.0%; Ti: balance. Among these, Ti exhibits good compatibility with Mn and Fe, and also possesses a ternary eutectic composition. Furthermore, based on the Ti-Fe-Mn base, Ni, Co, and Cr, elements commonly used in high-temperature alloys, are added. These elements not only have good compatibility with Fe and Mn but also provide solid solution strengthening and grain refinement, thereby improving the high-temperature resistance of the brazing filler metal and the brazed joint, and thus increasing the strength of the brazed joint. The brazing filler metal is a medium-entropy alloy, which will not undergo a violent chemical reaction with the TiAl base material being welded, thus facilitating a good metallurgical connection. Using the brazing filler metal of this invention, brazed joints are obtained at (1170~1180)℃ / (20-75)min, with a room temperature tensile strength of 495~518MPa and a joint strength coefficient that is basically stable in the range of 0.84~0.88; the high temperature tensile strength at 650℃ can reach 478~511MPa, at 700℃ it can reach 530~563MPa, at 750℃ it can reach 517~566MPa, at 800℃ it can reach 478~495MPa, and at 850℃ it can reach 411~420MPa. In this wide range of 700~850℃, the high temperature strength coefficient of the joint is basically stable above 0.87.

[0026] Furthermore, the components of the brazing filler metal described in this invention are all conventional metallic elements and do not contain precious metals, giving it a significant price advantage in terms of economics.

[0027] Furthermore, the brazing alloy of the present invention can be prepared in a wide range of forms. The Ti-Mn-Fe-Ni-Co-Cr multi-element alloy can be prepared into various application forms, and can be used in various forms during brazing. After the multi-element alloy is melted, it can be made into corresponding application forms by using different preparation methods, including alloy blocks or fragments or sheets, alloy powder, rapidly cooled foil strips, and powder sintered bodies. Attached Figure Description

[0028] To more clearly illustrate the technical solutions of the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the provided drawings through continuous creative work.

[0029] Figure 1 shows the Ti-Mn-Fe ternary phase diagram;

[0030] Figure 2 shows the Ti-Ni-Co ternary phase diagram;

[0031] Figure 3 shows the ternary phase diagram of Fe-Mn-Ni;

[0032] Figure 4 shows the Fe-Mn-Co ternary phase diagram;

[0033] Figure 5 shows the ternary phase diagram of Fe-Mn-Cr;

[0034] Figure 6 shows the Co-Ni-Cr ternary phase diagram;

[0035] Figure 7 shows the Co-Ni-Mn ternary phase diagram;

[0036] Figure 8 is a diagram showing the positions of each element in the brazing filler metal according to the periodic table in an embodiment of the present invention.

[0037] Figure 9 is a schematic diagram of the assembly structure in step S2 of the application method of this embodiment of the invention;

[0038] Figure 10 shows the front morphology of the sample after brazing in Example 5 of the present invention.

[0039] Figure 11 shows the cross-sectional microstructure of the brazed joint in Embodiment 5 of the present invention;

[0040] Figure 12 shows the average high-temperature tensile strength curve (650℃~850℃) of the brazing joint under the conditions of (1170~1180)℃ / (20-75)min according to the embodiment of the present invention. Detailed Implementation

[0041] The objectives, technical solutions, and advantages of this invention will become clearer below. The invention will be further described in detail below with reference to embodiments. Unless otherwise defined, all technical terms used herein have the same meaning as commonly understood by those skilled in the art. The technical terms used herein are for the purpose of describing specific embodiments only and are not intended to limit the scope of protection of this invention. Unless otherwise specified, all reagents and raw materials used in this invention are commercially available goods or products that can be prepared by recognized methods.

[0042] This invention provides a Ti-Mn-Fe-Ni-Co-Cr medium-entropy alloy brazing filler metal, wherein the filler metal comprises the following components by mass percentage:

[0043] Mn 16.0–22.0%; Fe 12.0–18.0%; Ni 2.0–10.0%; Co 2.0–10.0%; Cr 0–6.0%; Ti balance.

[0044] The brazing filler metal provided by this invention can not only achieve brazing at a lower brazing temperature, but also enable the brazed joint to have high room temperature / high temperature strength.

[0045] The solder system of this invention is mainly composed of titanium (Ti), with a significant amount of manganese (Mn) and iron (Fe). By mass percentage, the solder comprises 16.0–22.0% Mn, preferably 17.0–22.0% Mn; and 12.0–18.0% Fe, preferably 13.0–18.0% Fe.

[0046] According to the Ti-Mn-Fe ternary phase diagram shown in Figure 1, Ti, Mn, and Fe elements have good compatibility with each other, and there is also a ternary eutectic composition Ti-(19~24)Mn-(14~19)Fe (wt.%), with a eutectic temperature of about 1126℃.

[0047] Furthermore, in this embodiment of the invention, small amounts of nickel, cobalt, and chromium (Ni, Co, and Cr) are added to the Ti-Fe-Mn base. The solder comprises 2.0–10.0% Ni, preferably 3.0–8.0% Ni; the solder comprises 2.0–10.0% Co, preferably 3.0–8.0% Co, for example, at contents of 3.5%, 5.0%, 5.3%, or 8.0%.

[0048] According to the Ti-Ni-Co ternary phase diagram shown in Figure 2, a ternary eutectic composition of Ti-(2~6)Ni-(18~24)Co (wt.%) exists, with a eutectic temperature of 1025℃; the Ti-Ni-Co eutectic composition can lower the alloy's melting point. Furthermore, according to the Ti-Co binary phase diagram, a binary eutectic composition of Ti-(25~30)Co (wt.%) exists, with a eutectic temperature of 1015~1020℃; the Ti-Co eutectic composition can further lower the alloy's melting point. In addition, according to the Ti-Ni binary phase diagram, a binary eutectic composition of Ti-(25-30)Ni (wt.%) exists, with a eutectic temperature of 943℃; the Ti-Ni eutectic composition can further lower the alloy's melting point. Also, according to the Mn-Ni binary phase diagram, a low-melting-point composition of Mn-(40~50)Ni (wt.%) exists, with a corresponding temperature of 1020℃.

[0049] The solder described in this embodiment of the invention comprises 0-6.0% Cr and the balance Ti, preferably 0-5.0% Cr, while the Ti content is, for example, 50.0%-58.0%. In some embodiments, the Cr content is 0; under the boundary condition of 0% Cr content, it behaves as a Cr-free pentagonal medium-entropy alloy solder. The Cr-free alloy is a pentagonal alloy, which is simply a special case of a hexaagonal alloy solder. In other embodiments, 0 < Cr content ≤ 6.0%, i.e., it behaves as a Ti-Mn-Fe-Ni-Co-Cr hexaagonal medium-entropy alloy solder.

[0050] The three elements Co, Ni, and Cr added in this embodiment of the invention are the three main elements commonly used in nickel-cobalt-based superalloys, and they have good compatibility with each other. Ni and Co are infinitely miscible, and both have good compatibility with Fe, Mn, and Cr. Moreover, Fe, Mn, and Cr also have good pairwise compatibility; see Figures 3 to 7.

[0051] According to the present invention, the solder preferably comprises the following components by mass percentage: Mn 17.0–22.0%; Fe 13.0–18.0%; Ni 3.0–8.0%; Co 3.0–8.0%; Cr 0–5.0%; and Ti as the balance. Figure 8 shows the positions of each element in the solder in the periodic table. Ti, Fe, Mn, Ni, Co, and Cr are all conventional metallic elements. The solder of the present invention does not contain precious metals and has good economic efficiency.

[0052] In an embodiment of the present invention, the solidus temperature of the brazing filler metal is 1023.2–1092.5 °C, and the liquidus temperature is 1046.8–1104.5 °C. The liquidus temperature of the Ti-Mn-Fe-Ni-Co-Cr multi-element alloy in this embodiment of the present invention is T... L : 1046.8~1104.5℃, which can achieve even lower temperature brazing (T b =1170~1180℃). Conversely, if the solder liquidus temperature T L Too high, natural brazing temperature T b This will also be higher, making the brazing production process not only excessively energy-intensive and environmentally unfriendly, but also resulting in excessively high T emissions. b It affects the structure of the near-joint zone and can also greatly damage the properties of the base material.

[0053] The brazing filler metal of this invention employs a combination of multiple eutectic components, including Ti-Mn-Fe, Ti-Ni-Co, Ti-Ni, and Ti-Co, along with low-melting-point Mn-Ni components, to achieve a lower melting point. The actual liquidus of the filler metal is 1046.8–1104.5°C, allowing brazing to be performed within the range of 1170–1180°C. This avoids overheating of the base material due to excessively high brazing temperatures and conserves energy. Furthermore, the excellent compatibility of elements in Fe-Mn-Cr and Fe-Ni-Co-Cr prevents the formation of complex brittle phases, resulting in a more uniform elemental distribution in the brazed weld.

[0054] The solder used in this invention is a multi-element medium-entropy alloy solder, which can significantly reduce the interfacial reaction between the solder and the TiAl base material. Thermodynamic calculations show that the mixing entropy of the hexa-element solder in some embodiments of this invention ranges from 9.18 to 10.92 J·mol⁻¹. -1 ·K -1The solder's properties, falling within the key parameters of a multi-principal alloy (1.0R to 1.5R), indicate that it is a medium-entropy alloy solder. This type of multi-element alloy solder does not undergo a violent chemical reaction with the TiAl base material being soldered, which is beneficial for achieving a good metallurgical connection.

[0055] In embodiments of the present invention, the brazing filler metal may be used in one or more of the following forms: alloy block (including sintered powder), alloy powder (including granular material), and rapidly cooled foil strip; the brazing filler metal forms of the embodiments of the present invention are wide-ranging and easy to apply.

[0056] This invention provides a method for preparing Ti-Mn-Fe-Ni-Co-Cr medium-entropy alloy solder as described above, comprising the following steps:

[0057] A) Batching and smelting: After batching according to the percentage of brazing filler metal by mass, alloy ingots are smelted by electric arc melting; the embodiments of the present invention do not have special restrictions on the batching, and are conventional processes in the field;

[0058] B) Preparation of brazing filler metals in different application forms: The alloy ingots are processed into brazing filler metals in different forms through different processes; including one or more of the following shapes: alloy blocks, or crushed into granules, or made into thin sheets, alloy powders, rapidly cooled foil strips, or powder sintered bodies.

[0059] Furthermore, this invention provides the application of Ti-Mn-Fe-Ni-Co-Cr medium-entropy alloy brazing filler metal as described above in brazing connections.

[0060] This invention provides a brazing method for TiAl alloys, comprising the following steps:

[0061] S1. Preparation of base material to be welded: Pre-treatment of the welding position on the surface of the TiAl alloy base material;

[0062] S2. Assembly: Add solder to the welding position of the pretreated base material to obtain the assembled component; wherein, the solder is the solder described in the above technical solution or the solder obtained by the preparation method described in the above technical solution;

[0063] S3. Brazing: The assembled components are brazed to form TiAl alloy connectors.

[0064] The brazing method for TiAl alloy provided in this invention first involves preparing the base material to be welded. This pretreatment can be performed on the surface of the base material and the area to be welded. Specifically, the pretreatment removes oil and impurities from the surface of the base material and removes oxides from the area to be welded; this invention does not impose any particular limitations. In some embodiments, the TiAl alloy part can have any structure, including but not limited to TiAl-TiAl alloy.

[0065] In this embodiment of the invention, the aforementioned brazing filler metal is added to the pre-treated base material at the welding location to obtain an assembled component. Preferably, the brazing gap between the base materials to be welded is controlled to be 0.03–0.07 mm using machining or tooling fixtures, as shown in Figure 9. The method of adding brazing filler metal varies depending on its form: for rapidly cooled foil-shaped brazing filler metal, it can be directly placed between the base materials to be welded; while for alloy block, granular, or sheet-like alloy filler metal, alloy powder, or sintered powder filler metal, a pre-made gap should be established between the base materials before adding the brazing filler metal. The pre-made gap is 0.03–0.07 mm, and the latter brazing filler metal is placed using a pre-made bevel.

[0066] In this embodiment of the invention, the assembled components are placed in a vacuum brazing furnace, where the vacuum level is better than 8 × 10⁻⁶. -3 Pa; Select the brazing temperature based on the liquidus temperature of the brazing filler metal.

[0067] In some embodiments of the present invention, the brazing temperature is specifically: the brazing temperature T of the TiAl-based alloy. b The temperature is 1170–1180℃.

[0068] In some embodiments of the present invention, the specific parameters of the vacuum brazing are as follows: under a certain vacuum degree, the temperature is first increased at a rate of 10-40℃ / min to 600℃, then increased at a rate of 10-30℃ / min to 900℃, and then increased at a rate of 10-25℃ / min to T. b Hold the temperature for 20–75 minutes; after holding, cool down at a rate of 10–40℃ / min until the furnace reaches room temperature.

[0069] Regarding the connection performance of the brazing filler metal, this invention employs a multi-element medium-high entropy alloy design concept, innovatively adding five or more alloying elements to the filler metal. This comprehensively utilizes the solid solution strengthening and grain refinement strengthening effects of different elements to improve the strength of the brazed joint. In this embodiment of the multi-element medium-entropy alloy brazing filler metal, Fe and Mn elements can refine the grains and provide solid solution strengthening, thereby improving the room temperature and high temperature mechanical properties of the TiAl joint. Ni element promotes dynamic recrystallization, improving the hot working plasticity of the TiAl joint. Co element can refine the grains, improving the room temperature strength and plasticity of the TiAl joint, and also improving high temperature oxidation performance. Cr element can significantly improve the plasticity of the TiAl joint, and Cr, after coupling with Mn, can significantly refine the grains, thus significantly improving the room temperature / high temperature strength and toughness of the TiAl joint; however, Cr should not be added in excess, otherwise it will increase the melting point.

[0070] Brazed joints obtained using the brazing filler metal of this invention under brazing conditions of (1170~1180)℃ / (20-75)min exhibit relatively uniform diffusion of alloying elements in the brazed joint, achieving element content levels of 0.5%≤Fe≤4.0%, 0.5%≤Mn≤4.0%, 0.25%≤Ni≤2.0%, 0.25%≤Co≤2.0%, and 1.0%≤Cr≤6.0% (at.%), thus providing a small or trace strengthening effect of alloying elements. For example, the microstructure of brazed joints obtained using the brazing filler metal of this invention is mainly γ-TiAl and α2-Ti3Al.

[0071] The brazed joints obtained using the brazing filler metal of this invention at (1170~1180)℃ / (20-75)min have a room temperature tensile strength of 495~518MPa and a joint strength coefficient that is basically stable in the range of 0.84~0.88. The high-temperature tensile strength at 650℃ can reach 478~511MPa, at 700℃ it can reach 530~563MPa, at 750℃ it can reach 517~566MPa, at 800℃ it can reach 478~495MPa, and at 850℃ it can reach 411~420MPa. The high-temperature strength coefficient of the joint is basically stable above 0.87 in the wide range of 700~850℃. The TiAl / TiAl brazed joints obtained by applying the brazing filler metal in this embodiment of the invention exhibit higher high-temperature strength in a wide temperature range of 700–850°C than brazed joints corresponding to simple ternary or quaternary brazing filler metal alloys such as Ti-Fe-Mn, Ti-Zr-Ni-Cu, Ti-Ni-Nb, or Ti-Zr-Ni-Nb.

[0072] The brazing filler metal described in this invention is not only applicable to brazing of materials such as TiAl alloys, but can also be used for joining Ti-Al-Nb alloys, Ti-based composite materials, TiAl-based composite materials, and other multi-element medium-entropy or high-entropy alloy matrix materials containing only Ti or both Ti and Al.

[0073] To further understand the present invention, preferred embodiments of the present invention are described below in conjunction with examples. However, it should be understood that these descriptions are only for further illustrating the features and advantages of the present invention, and not for limiting the scope of the claims of the present invention.

[0074] Examples 1-3:

[0075] The chemical composition of the solder is shown in Table 1 (wt%).

[0076] The preparation method of the Ti-Mn-Fe-Ni-Co-Cr medium-entropy alloy solder includes:

[0077] A) Batching and smelting: After batching according to the percentage of brazing filler metal by mass, alloy ingots are smelted using an electric arc melting method;

[0078] B) Preparation of brazing filler metals in different application forms: alloy ingots are prepared into brazing filler metals of different shapes using different manufacturing processes; including alloy blocks, alloy powders, rapidly cooled foil strips, and powder sintered bodies.

[0079] Table 1. Solder composition of Examples 1-3 of the present invention

[0080] This document outlines the specifications and application methods for a Ti-Mn-Fe-Ni-Co pentagonal medium-entropy alloy solder. The solder composition by mass percentage is as follows: Mn: 16.0–22.0%; Fe: 12.0–18.0%; Ni: 2.0–10.0%; Co: 2.0–10.0%; Cr: 0–6.0%; Ti: balance. Furthermore, the solder's liquidus temperature is between 1046.8 and 1104.5 °C.

[0081] Using the solder compositions of Examples 1-3 (see Table 1), the following steps were performed:

[0082] (1) The base material is a TiAl-based alloy with a nominal composition of Ti-46Al-(3~4)Nb-(2~3)(Cr,Ta,B)(at.%). The surface of the base material is removed by pretreatment to remove oil and impurities and to remove oxides at the welding position.

[0083] Pure Ti foil strips with a thickness of 0.03–0.07 mm are cut into narrow strips with a width of 0.5–1 mm and spot-welded to one side of the base material to be welded using a spot welding machine. Then, the base materials on both sides are clamped with tooling to control the brazing gap to 0.03–0.07 mm. Then, brazing filler powder is pre-formed on the base material at the position to be welded to assemble the assembly.

[0084] (2) Place the assembled components into a vacuum furnace, with a vacuum level of 5.0 × 10⁻⁶. -3 Pa, the brazing temperature is selected as 1170~1180℃.

[0085] The performance of the brazed joints corresponding to Examples 1-3 is shown in Table 2:

[0086] Table 2 shows the brazed joint performance corresponding to Examples 1-3.

[0087] Note: The specimen performance includes room temperature and high temperature tensile tests. Tensile specimens are prepared using standard drawings and tensile tests are performed according to standard methods (the following tests are the same).

[0088] The brazing effect of Examples 1 to 3 is that the brazing temperature of the brazing filler metal of the present invention is 1170 to 1180°C; under suitable brazing specifications, the brazed joint has high room temperature / high temperature (750 to 850°C) tensile strength.

[0089] Examples 4-5:

[0090] The chemical composition of the solder is shown in Table 3 (by mass percentage, wt%):

[0091] Table 3. Solder composition of embodiments 4-5 of the present invention

[0092] This paper addresses the application of a Ti-Mn-Fe-Ni-Co-Cr hexa-element medium-entropy alloy solder. The solder composition by mass percentage is as follows: Mn: 16.0–22.0%; Fe: 12.0–18.0%; Ni: 2.0–10.0%; Co: 2.0–10.0%; Cr: 0–6.0%; Ti: balance. The liquidus temperature of the solder is between 1046.8 and 1104.5 °C.

[0093] Using the solder composition of Examples 4-5 (see Table 3), the following steps were performed:

[0094] (1) Preparation of different brazing filler metal forms, including powder, quenched state, block, powder sintered body, etc. The preparation methods are the same as in Examples 1 to 3.

[0095] (2) The base material is a TiAl-based alloy with a nominal composition of Ti-46Al-(3~4)Nb-(2~3)(Cr,Ta,B)(at.%). The surface oil and impurities of the base material are removed by pretreatment, and the oxides at the welding position are removed.

[0096] Pure Ti foil strips with a thickness of 0.03–0.07 mm are cut into narrow strips with a width of 0.5–1 mm and spot-welded to one side of the base material to be welded using a spot welding machine. Then, the base materials on both sides are clamped with tooling to control the brazing gap to 0.03–0.07 mm. Then, brazing filler powder is pre-formed on the base material at the position to be welded to assemble the assembly.

[0097] (3) Place the assembled components into a vacuum furnace, with a vacuum level of 5.0 × 10⁻⁶. -3 Pa, the brazing temperature was selected as 1170~1180℃; Figure 10 shows the front morphology of the sample after brazing in Example 5.

[0098] The performance of the brazed joints corresponding to Examples 4 and 5 is shown in Table 4:

[0099] Table 4 shows the brazed joint performance corresponding to Examples 4-5.

[0100] The brazing results of Examples 4 and 5 are that the brazing temperature of the brazing filler metal of the present invention is 1170-1180℃; under suitable brazing specifications, the brazed joint has high room temperature / high temperature (750-850℃) tensile strength.

[0101] Figure 11 shows the cross-sectional microstructure of the brazed joint in Example 5; the microstructure of the brazed joint obtained using the brazing filler metal of the present invention is mainly γ-TiAl and α2-Ti3Al.

[0102] Figure 12 shows the average high-temperature tensile strength curve (650℃~850℃) of the brazing joints of the embodiment of the present invention under the conditions of (1170~1180)℃ / (20-75)min. The black line represents the TiAl base material (the high-temperature tensile strength at 650℃ is 567.25MPa), and the blue line represents the brazing alloy of the present invention (the average value of the performance of Examples 1 to 5). In addition, there are curves for Ti-Fe-Mn brazing alloy and Ti-Zr-Cu-Ni brazing alloy (for the key components of ternary and quaternary brazing alloys, see the literature: Vacuum brazing TiAl-based intermetallics using novel Ti-Fe-Mn eutectic brazing alloy, YSCai et al., Intermetallics 136, 2021).

[0103] The brazed joints obtained using the brazing filler metal of this invention at (1170~1180)℃ / (20-75)min exhibit a room temperature tensile strength of 495~518MPa, with the joint strength coefficient remaining relatively stable in the range of 0.84~0.88. At 650℃, the high-temperature tensile strength reaches 478~511MPa; at 700℃, it reaches 530~563MPa; at 750℃, it reaches 517~566MPa; at 800℃, it reaches 478~495MPa; and at 850℃, it reaches 411~420MPa. Within this wide temperature range of 700~850℃, the high-temperature strength coefficient of the joint remains relatively stable above 0.87. The average high-temperature tensile strength (Tensile strength) at 650~850℃ is shown in Figure 12. The TiAl / TiAl brazed joints obtained by applying the brazing filler metal in this embodiment of the invention exhibit higher high-temperature strength in a wide temperature range of 700–850°C than brazed joints corresponding to simple ternary or quaternary brazing filler metal alloys such as Ti-Fe-Mn, Ti-Zr-Ni-Cu, Ti-Ni-Nb, or Ti-Zr-Ni-Nb.

[0104] Taking into account the metallurgical effects of the above elements, the brazing alloy provided in this embodiment of the invention can achieve brazing at lower temperatures (T). b=1170~1180℃), which improves the strength of the brazed joint, thereby effectively solving the problems of excessively high brazing temperature of brazing filler metal and insufficient room temperature / high temperature (750~850℃) strength of brazed joints in the existing TiAl brazing technology.

[0105] This article uses specific examples to illustrate the principles and implementation methods of the present invention. The above description of the embodiments is only for the purpose of helping to understand the method and core ideas of the present invention, including the best mode, and also enables any person skilled in the art to practice the present invention, including manufacturing and using any device or system, and implementing any combination of methods.

[0106] The brazing filler metal of this invention is not only applicable to brazing of materials such as TiAl alloys, but also to the joining of Ti-Al-Nb alloys, Ti-based composite materials, TiAl-based composite materials, and other multi-element medium-entropy or high-entropy alloy matrix materials containing only Ti or both Ti and Al.

[0107] It should be noted that those skilled in the art can make various improvements and modifications to this invention without departing from its principles, and these improvements and modifications also fall within the scope of protection of the claims. The scope of protection of this patent is defined by the claims and may include other embodiments that can be conceived by those skilled in the art. If these other embodiments have structural elements similar to those expressed in the claims, or if they include equivalent structural elements that are not substantially different from those expressed in the claims, then these other embodiments should also be included within the scope of the claims.

Claims

1. A Ti-Mn-Fe-Ni-Co-Cr medium-entropy alloy solder, characterized in that, The brazing filler metal comprises the following components by weight percentage: Mn 16.0–22.0%; Fe 12.0–18.0%; Ni 2.0–10.0%; Co 2.0–10.0%; Cr 0–6.0%; Ti balance.

2. The Ti-Mn-Fe-Ni-Co-Cr medium-entropy alloy solder according to claim 1, characterized in that, The brazing filler metal comprises the following components by weight percentage: Mn 17.0–22.0%; Fe 13.0–18.0%; Ni 3.0–8.0%; Co 3.0–8.0%; Cr 0–5.0%; Ti balance.

3. The Ti-Mn-Fe-Ni-Co-Cr medium-entropy alloy solder according to claim 1, characterized in that, The brazing filler metal is used in one or more of the following forms: alloy block, alloy powder, and rapidly cooled foil strip.

4. The method for preparing Ti-Mn-Fe-Ni-Co-Cr medium-entropy alloy solder as described in any one of claims 1-3, characterized in that, Includes the following steps: A) The ingredients are batched according to the mass percentage, and then the alloy ingots are melted by electric arc melting. B) The alloy ingot is processed into brazing filler metals of different forms through different processes; the brazing filler metals are used in one or more of the following forms: alloy block, alloy powder, and rapidly cooled foil strip.

5. The application of the Ti-Mn-Fe-Ni-Co-Cr medium-entropy alloy brazing filler metal as described in any one of claims 1-3 in brazing connections.

6. A brazing method for TiAl alloy, characterized in that, Includes the following steps: S1. Pre-treat the welding positions on the surface of the TiAl alloy base material; S2. Add brazing filler metal to the pretreated base material at the welding position to obtain the assembled component; the brazing filler metal is the Ti-Mn-Fe-Ni-Co-Cr medium-entropy alloy brazing filler metal according to any one of claims 1 to 3; S3. Brazing the assembled components to form TiAl alloy connectors.

7. The brazing method according to claim 6, characterized in that, In step S1, oil and oxides are removed through pretreatment.

8. The brazing method according to claim 6, characterized in that, Step S2 includes controlling the brazing gap between the base materials to be welded to be 0.03 to 0.07 mm through machining or tooling fixtures.

9. The brazing method according to claim 6, characterized in that, In step S3, the brazing temperature is 1170–1180°C; the brazing is vacuum brazing.

10. The brazing method according to claim 9, characterized in that, The vacuum brazing includes: a furnace vacuum degree better than 8×10⁻⁶. -3 Pa, first heat to 600℃ at a rate of 10–40℃ / min, then heat to 900℃ at a rate of 10–30℃ / min, and finally heat to T at a rate of 10–25℃ / min. b Hold the temperature for 20–75 minutes; after holding, cool down at a rate of 10–40℃ / min until the furnace reaches room temperature.

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