Method for joining titanium alloy and high-entropy alloy based on interlayer and composite substrate

Abstract

A method for connecting titanium alloy and high-entropy alloy based on an intermediate layer, comprising: pre-providing an intermediate layer and a base material to be welded, wherein the intermediate layer comprises Nb foil layers and Ni foil layers arranged in layers, and the base material to be welded comprises TC4 titanium alloy and AlxCoCrFeNi high-entropy alloy, wherein 0

Description

Technical Field

[0001] This application relates to the field of welding technology, specifically to a method for joining titanium alloy and high-entropy alloy based on an intermediate layer and a composite substrate. Background Technology

[0002] High-entropy alloys are generally composed of five or more main elements in near-equal atomic ratios. They are advanced materials with multiple key elements, exhibiting unique microstructures and excellent properties, such as superior high-temperature mechanical properties, radiation resistance, corrosion resistance, and wear resistance. They have broad application prospects in aerospace, energy, nuclear industry, and automotive turbine components.

[0003] Titanium alloys possess high strength, low density, high basic strength, wide adjustable range, good mid-temperature stability, and excellent synergy with other properties. This makes them one of the preferred materials for "high-strength lightweight structures" in aerospace, marine engineering, and high-end equipment manufacturing, especially suitable for key components with strict requirements for strength, weight, and reliability.

[0004] Achieving a connection between titanium alloys and high-entropy alloys can leverage the advantages of both materials, broadening their application range. Therefore, as a structural material, connecting titanium alloys and high-entropy alloys is crucial for promoting the application of high-entropy alloys in the automotive and aerospace fields, and for obtaining highly reliable, long-life spacecraft. However, the mismatch in thermal expansion coefficients between titanium alloys and high-entropy alloys can easily induce significant residual stress during welding, thus affecting the mechanical properties of the welded joint. Summary of the Invention

[0005] Therefore, this application provides a connection method and composite substrate based on an intermediate layer of titanium alloy and high-entropy alloy to improve the mechanical properties of the brazed joint.

[0006] This application proposes a method for joining titanium alloys and high-entropy alloys based on an intermediate layer, including: An intermediate layer and a base material to be soldered are provided, wherein the intermediate layer comprises a stacked Nb foil layer and a Ni foil layer, and the base material to be soldered comprises a TC4 titanium alloy and an AlxCoCrFeNi high-entropy alloy, wherein 0 < x ≤ 0.3; The welding areas of the AlxCoCrFeNi high-entropy alloy and the welding areas of the TC4 titanium alloy were ground separately. Clean the intermediate layer, the areas of the AlxCoCrFeNi high-entropy alloy to be welded, and the areas of the TC4 titanium alloy to be welded; The intermediate layer is placed between the AlxCoCrFeNi high-entropy alloy and the TC4 titanium alloy to form a structure to be welded, wherein the Nb foil layer contacts the weldable part of the AlxCoCrFeNi high-entropy alloy and the Ni foil layer contacts the weldable part of the TC4 titanium alloy. A pressure block is placed on one side of the structure to be welded to press the structure to be welded. The compressed structure to be welded is placed in a high-temperature vacuum brazing furnace and heated to a brazing temperature of 1080℃-1200℃ in a vacuum environment. After holding at the brazing temperature for 1 min-20 min, it is cooled to room temperature to obtain a brazed joint, wherein the brazed joint includes a portion of the unmelted Nb foil layer.

[0007] The interlayer-based joining method for titanium alloys and high-entropy alloys in this application enables a high-strength and effective connection between TC4 titanium alloy and AlxCoCrFeNi high-entropy alloy. This method leverages the complete dissolution and instantaneous exothermic reaction of the Ni foil layer during the diffusion reaction between Ni and TC4 titanium alloys at a relatively low Ti / Ni eutectic temperature (942℃). This promotes a local diffusion reaction in the Nb foil / AlxCoCrFeNi high-entropy alloy, causing local dissolution at the interface and forming a TiNi+Laves eutectic structure and a TiNiNb reaction layer. The incompletely dissolved Nb foil layer acts as a barrier to Ti and possesses good deformability. During cooling, plastic deformation effectively alleviates residual stress in the brazed joint, thereby improving its strength. The brazed joint formed through the Nb foil / Ni foil contact reaction exhibits high connection strength, with a maximum room-temperature shear strength of 289 MPa.

[0008] In some possible implementations, the partially unmelted Nb foil layer, the AlxCoCrFeNi high-entropy alloy, and the TC4 titanium alloy have equal projected areas on a plane parallel to the intermediate layer.

[0009] In some possible implementations, the Nb foil layer and the Ni foil layer are connected together.

[0010] In some possible implementations, the thickness ratio of the Nb foil layer to the Ni foil layer is greater than or equal to 5:1 and less than or equal to 8:1.

[0011] In some possible implementations, the purity of the Nb foil layer is not less than 95%, and the purity of the Ni foil layer is not less than 99%.

[0012] In some possible implementations, the steps of separately grinding the areas to be welded in the AlxCoCrFeNi high-entropy alloy and the TC4 titanium alloy include: The welding areas of the AlxCoCrFeNi high-entropy alloy and the welding areas of the TC4 titanium alloy were polished sequentially using metallographic sandpaper of grades 100#, 200#, 600#, and 1000#.

[0013] In some possible implementations, the step of cleaning the intermediate layer, the solderable areas of the AlxCoCrFeNi high-entropy alloy, and the solderable areas of the TC4 titanium alloy includes: Clean the intermediate layer, the areas to be welded of the AlxCoCrFeNi high-entropy alloy, and the areas to be welded of the TC4 titanium alloy for 5-10 minutes, and then blow them dry.

[0014] In some possible implementations, the step of placing a pressure block on one side of the structure to be welded to compress the structure includes: A graphite block is placed on one side of the structure to be welded to press the structure to be welded, so that the Nb foil layer abuts against the part of the AlxCoCrFeNi high-entropy alloy to be welded, and the Ni foil layer abuts against the part of the TC4 titanium alloy to be welded, wherein the pressure applied by the graphite block to the structure to be welded is 100Pa-400Pa.

[0015] In some possible implementations, the step of heating to a brazing temperature of 1080℃-1200℃ in a vacuum environment, holding at the brazing temperature for 1 min-20 min, and then cooling to room temperature includes: Heating is performed under vacuum conditions below 108 Pa, with the temperature increased to a brazing temperature of 1080℃-1200℃ at a rate of 8℃ / min-15℃ / min. After holding at the brazing temperature for 1min-20min, the temperature is reduced to 200℃ at a rate of 5-10℃ / min, and finally cooled to room temperature in the vacuum brazing furnace.

[0016] This application also proposes a composite substrate prepared using the method described above.

[0017] The composite substrate of this application is manufactured using the method described above. This method enables a high-strength and effective connection between TC4 titanium alloy and AlxCoCrFeNi high-entropy alloy. It utilizes the diffusion reaction between Ni and TC4 titanium alloy at a relatively low Ti / Ni eutectic temperature (942°C) to completely dissolve the Ni foil layer and release heat instantaneously. This promotes a local diffusion reaction between the Nb foil layer and the AlxCoCrFeNi high-entropy alloy, causing local dissolution at the interface and forming a TiNi+Laves eutectic structure and a TiNiNb reaction layer. The incompletely dissolved Nb foil layer acts as a barrier to Ti elements and has good deformability. During cooling, plastic deformation can effectively alleviate the residual stress of the brazed joint, thereby improving the strength of the brazed joint. The brazed joint formed by the contact reaction of the Nb foil layer and Ni foil layer has high connection strength, with a maximum room temperature shear strength of 289 MPa. Attached Figure Description

[0018] Figure 1 This is a flowchart of a method for joining titanium alloy and high-entropy alloy based on an intermediate layer, according to an embodiment of this application. Figure 2 This is a schematic diagram of the assembly structure of the intermediate layer and the base material to be welded in this application; Figure 3 A backscattered image of the brazed joint obtained in Embodiment 3 of this application; Figure 4 This is a shear strength diagram of the brazed joint obtained in Embodiment 3 of this application.

[0019] Figure label: 10-AlxCoCrFeNi high-entropy alloy; 20-TC4 titanium alloy; 30 - Intermediate layer; 31-Nb foil layer; 32-Ni foil layer; 40-Blocking. Detailed Implementation

[0020] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0021] In embodiments of this application, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes that element.

[0022] In the embodiments of this application, the terms "in some embodiments," "in some examples," or "for example" are used to indicate examples, illustrations, or descriptions. Any embodiment or design described as "in some embodiments," "in some examples," or "for example" in the embodiments of this application should not be construed as being more preferred or advantageous than other embodiments or design solutions. Specifically, the use of terms such as "in some embodiments," "in some examples," or "for example" is intended to present the relevant concepts in a specific manner.

[0023] The following disclosure provides many different embodiments or examples for implementing different structures of this application. To simplify the disclosure, specific examples of components and arrangements are described below. Of course, these are merely examples and are not intended to limit the scope of this application. Furthermore, reference numerals and / or letters may be repeated in different examples; such repetition is for simplification and clarity and does not in itself indicate a relationship between the various embodiments and / or arrangements discussed. In addition, various specific examples of processes and materials are provided in this application, but those skilled in the art will recognize the application of other processes and / or the use of other materials.

[0024] AlxCoCrFeNi high-entropy alloys are generally composed of five or more main elements in similar or equiatomic ratios. They are advanced materials with multiple main elements, exhibiting unique microstructures and excellent properties, such as superior high-temperature mechanical properties, radiation resistance, and corrosion resistance. They have broad application prospects in aerospace, energy, nuclear industry, and automotive turbine components.

[0025] TC4 titanium alloy has the characteristics of high strength and low density, high basic strength, wide adjustable range, good mid-temperature stability and excellent synergy with other properties. This makes it one of the preferred materials for "high strength and lightweight structure" in aerospace, marine engineering and high-end equipment manufacturing. It is especially suitable for key components with strict requirements for strength, weight and reliability.

[0026] If the connection between TC4 titanium alloy and AlxCoCrFeNi high-entropy alloy is achieved, the advantages of both materials can be brought into play, and their application range will be wider. Therefore, as a structural material, the connection between TC4 titanium alloy and AlxCoCrFeNi high-entropy alloy is of great significance for promoting the application of AlxCoCrFeNi high-entropy alloy in automobile manufacturing and space industry, and for obtaining highly reliable and long-life spacecraft.

[0027] In related technologies, the thermal expansion coefficients of AlxCoCrFeNi high-entropy alloy and TC4 titanium alloy are mismatched (TC4 titanium alloy: 8.6×10). -6 K -1 AlxCoCrFeNiHEA: 15×10 -6 K -1 During the welding process, large residual stresses can easily be generated, which can affect the mechanical properties of the welded joint.

[0028] To resolve the above issues, please refer to [link / reference]. Figure 1 and Figure 2 , Figure 1 This is a flowchart of a method for joining titanium alloy and high-entropy alloy based on intermediate layer 30, according to an embodiment of this application. Figure 2 This is a schematic diagram of the assembly structure of the intermediate layer 30 and the base material to be welded in this application. The connection method includes: S10 provides an intermediate layer 30 and a base material to be soldered, wherein the intermediate layer 30 includes a Nb foil layer 31 and a Ni foil layer 32 stacked together, and the base material to be soldered includes a TC4 titanium alloy 20 and an AlxCoCrFeNi high-entropy alloy 10, wherein 0 < x ≤ 0.3.

[0029] S20, grind the welding parts of AlxCoCrFeNi high-entropy alloy 10 and TC4 titanium alloy 20 respectively.

[0030] S30, clean the intermediate layer 30, the areas to be welded of AlxCoCrFeNi high-entropy alloy 10 and TC4 titanium alloy 20.

[0031] S40, an intermediate layer 30 is placed between the AlxCoCrFeNi high-entropy alloy 10 and the TC4 titanium alloy 20 to form a structure to be welded, wherein the Nb foil layer 31 contacts the part of the AlxCoCrFeNi high-entropy alloy 10 to be welded, and the Ni foil layer 32 contacts the part of the TC4 titanium alloy 20 to be welded.

[0032] S50, place a pressure block 40 on one side of the structure to be welded to press the structure to be welded.

[0033] S60, the compressed structure to be welded is placed in a high-temperature vacuum brazing furnace and heated to a brazing temperature of 1080℃-1200℃ in a vacuum environment. After holding at the brazing temperature for 1min-20min, it is cooled to room temperature to obtain a brazed joint, wherein the brazed joint includes a partially unmelted Nb foil layer 31.

[0034] The joining method of titanium alloy and high-entropy alloy based on intermediate layer 30 in this application can achieve a high-strength and effective connection between TC4 titanium alloy 20 and AlxCoCrFeNi high-entropy alloy 10. This is achieved by utilizing the diffusion reaction between Ni / TC4 titanium alloy 20 at a relatively low Ti / Ni eutectic temperature (942℃) during which the Ni foil layer 32 completely dissolves and instantly releases heat, promoting a local diffusion reaction between the Nb foil layer / AlxCoCrFeNi high-entropy alloy 10. This leads to local dissolution at the interface, forming a TiNi+Laves eutectic structure and a TiNiNb reaction layer. The incompletely dissolved Nb foil layer 31 acts as a barrier to Ti elements and has good deformability. During cooling, plastic deformation can effectively alleviate the residual stress of the brazed joint, thereby improving the strength of the brazed joint. The brazed joint formed by the contact reaction of Nb foil layer 31 / Ni foil layer 32 exhibits high connection strength, with a maximum room temperature shear strength of 289 MPa.

[0035] In other words, the brazed Nb foil layer 31 has high miscibility with the five elements Co, Cr, Mn, Fe, and Ni in the AlxCoCrFeNi high-entropy alloy 10, and no intermetallic compounds are formed. The Ni foil layer 32 melts at high temperature, and the Nb foil layer 31 acts as a barrier to Ti. The remaining Nb foil layer 31 has a plasticizing effect, which can effectively relieve the residual stress of the joint through plastic deformation during the brazing process, thereby improving the strength of the brazed joint. The joint brazed by the contact reaction of Nb foil layer 31 / Ni foil layer 32 has high connection strength, and the highest room temperature shear strength of the brazed joint is 289 MPa.

[0036] In related technologies, TC4 titanium alloy 20 and AlxCoCrFeNi high-entropy alloy 10 are brazed using binary or ternary brazing filler metals, such as a mixed filler metal composed of Nb and Ni, to weld AlxCoCrFeNi high-entropy alloy 10 and TC4 titanium alloy 20. However, during the brazing process, the mixed filler metal requires a very high temperature to dissolve, and Ni cannot dissolve to a limited extent. In addition, a large amount of active Ti elements in the TC4 titanium alloy 20 base material reacts with elements such as Co, Cr, Fe, and Ni in the AlxCoCrFeNi high-entropy alloy 10, easily generating a large number of intermetallic compound phases in the weld joint, which weakens the joint strength.

[0037] In some possible implementations, the projected areas of the partially unmelted Nb foil layer 31, the AlxCoCrFeNi high-entropy alloy 10, and the TC4 titanium alloy 20 on a plane parallel to the intermediate layer 30 are equal. In this way, the incompletely dissolved Nb foil layer 31 acts as a barrier to Ti elements and possesses good deformability; during cooling, it can effectively alleviate residual stress in the brazed joint through plastic deformation, thereby improving the strength of the brazed joint.

[0038] In some possible embodiments, the Nb foil layer 31 and the Ni foil layer 32 are connected. In some examples, the Nb foil layer 31 and the Ni foil layer 32 can be bonded together, using double-sided adhesive or 502 glue.

[0039] In some possible implementations, the thickness ratio of Nb foil layer 31 to Ni foil layer 32 is greater than or equal to 5:1 and less than or equal to 8:1. This ensures that Ni completely reacts and dissolves with TC4 titanium alloy 20 during welding, while Nb foil layer 31 remains, contacting the AlxCoCrFeNi high-entropy alloy 10 and undergoing a diffusion reaction with it. Simultaneously, it hinders the reaction of Ti elements with the AlxCoCrFeNi high-entropy alloy 10 base material to form a large amount of brittle reaction layer.

[0040] In some possible embodiments, the purity of the Nb foil layer 31 is not less than 95%, and the purity of the Ni foil layer 32 is not less than 99%.

[0041] In some possible embodiments, the steps of grinding the weldable areas of AlxCoCrFeNi high-entropy alloy 10 and TC4 titanium alloy 20 respectively include: The welding areas of AlxCoCrFeNi high-entropy alloy 10 and TC4 titanium alloy 20 were polished in sequence using metallographic sandpaper of 100#, 200#, 600# and 1000#.

[0042] In some possible embodiments, the steps of cleaning the intermediate layer 30, the solderable areas of the AlxCoCrFeNi high-entropy alloy 10, and the solderable areas of the TC4 titanium alloy 20 include: Clean the intermediate layer 30, the AlxCoCrFeNi high-entropy alloy 10 and the TC4 titanium alloy 20 to be welded areas for 5-10 minutes, and then blow them dry.

[0043] In some possible embodiments, the step of placing a pressure block 40 on one side of the structure to be welded to compress the structure includes: A graphite block 40 is placed on one side of the structure to be welded to press the structure to be welded. The pressure applied by the graphite block 40 to the structure to be welded is 100Pa-400Pa.

[0044] In some possible embodiments, the step of heating to a brazing temperature of 1080°C-1200°C in a vacuum environment, holding at the brazing temperature for 1 min-20 min, and then cooling to room temperature includes: Heating is performed under vacuum conditions below 108 Pa, with the temperature increased to a brazing temperature of 1080℃-1200℃ at a rate of 8℃ / min-15℃ / min. After holding at the brazing temperature for 1min-20min, the temperature is reduced to 200℃ at a rate of 5-10℃ / min, and finally cooled to room temperature in the vacuum brazing furnace.

[0045] This application also proposes a composite substrate prepared using the method described above.

[0046] The composite substrate of this application is manufactured using the method described above. This method enables a high-strength and effective connection between TC4 titanium alloy 20 and AlxCoCrFeNi high-entropy alloy 10. Specifically, the brazed Nb foil layer 31 exhibits high miscibility with the five elements Co, Cr, Mn, Fe, and Ni in the AlxCoCrFeNi high-entropy alloy 10, without the formation of intermetallic compounds. The Ni foil layer 32 melts at high temperatures, while the Nb foil layer 31 acts as a barrier to Ti elements. The remaining Nb foil layer 31 has a shaping effect, effectively alleviating residual stress in the joint through plastic deformation during brazing, thereby improving the strength of the brazed joint. The joint brazed via the contact reaction of Nb foil layer 31 / Ni foil layer 32 exhibits high connection strength, with a maximum room temperature shear strength of 289 MPa.

[0047] The technical solutions of this application are not limited to the specific embodiments exemplified below, but also include any combination of the specific embodiments.

[0048] Example 1 This embodiment proposes a method for joining titanium alloy and high-entropy alloy based on an intermediate layer, including the following steps: Step 1: Provide an intermediate layer and a base material to be soldered. The intermediate layer includes a stacked Nb foil layer and a Ni foil layer, which are bonded together. The thickness of the Nb foil layer is 100 μm, and the thickness of the Ni foil layer is 20 μm. The purity of the Nb foil is 99.5%, and the purity of the Ni foil is 99.95%. The base material to be soldered includes TC4 titanium alloy and AlxCoCrFeNi high-entropy alloy, where x = 0.3. Step 2: Use 100#, 200#, 600# and 1000# metallographic sandpaper in sequence to polish the welding parts of AlxCoCrFeNi high-entropy alloy and TC4 titanium alloy. Step 3: Use acetone solution to ultrasonically clean the intermediate layer, the areas to be welded in the AlxCoCrFeNi high-entropy alloy, and the areas to be welded in the TC4 titanium alloy for 10 minutes, and then blow dry. Step 4: Place the intermediate layer between the AlxCoCrFeNi high-entropy alloy and the TC4 titanium alloy to form a structure to be welded, wherein the Nb foil layer contacts the weldable part of the AlxCoCrFeNi high-entropy alloy, and the Ni foil layer contacts the weldable part of the TC4 titanium alloy. Step 5: Place a graphite block on one side of the structure to be welded to compress the structure. The pressure applied by the graphite block to the structure to be welded is 108 Pa. Step six: Place the compressed structure to be welded into a high-temperature vacuum brazing furnace, at a vacuum degree of 2.0 × 10⁻⁶. -3 The brazed joint is heated to 1080°C at a heating rate of 8°C / min under Pa conditions, held for 10 min, cooled to 200°C at a cooling rate of 5°C / min, and then cooled to room temperature to obtain a brazed joint. The brazed joint includes a partially unmelted Nb foil layer, and the projected areas of the partially unmelted Nb foil layer, AlxCoCrFeNi high-entropy alloy, and TC4 titanium alloy on a plane parallel to the intermediate layer are equal.

[0049] Experimental results show that during brazing, the Ni foil layer completely dissolves and releases heat instantaneously during the diffusion reaction between the Ni / TC4 titanium alloys at a relatively low Ti / Ni eutectic temperature (942℃). This promotes the local diffusion reaction of the Nb foil / AlxCoCrFeNi high-entropy alloy, causing local dissolution at the interface and forming a TiNi+Laves eutectic structure and a TiNiNb reaction layer. The incompletely dissolved Nb foil acts as a barrier to Ti elements and has good deformability. During cooling, it can effectively alleviate the residual stress of the brazed joint through plastic deformation, thereby improving the strength of the brazed joint. The brazed joint formed by the contact reaction of Nb foil / Ni foil has high connection strength, with a maximum room temperature shear strength of 156 MPa.

[0050] Example 2 This embodiment proposes a method for joining titanium alloy and high-entropy alloy based on an intermediate layer, including the following steps: Step 1: Provide an intermediate layer and a base material to be soldered. The intermediate layer includes a stacked Nb foil layer and a Ni foil layer, which are bonded together. The thickness of the Nb foil layer is 100 μm, and the thickness of the Ni foil layer is 20 μm. The purity of the Nb foil is 99.5%, and the purity of the Ni foil is 99.95%. The base material to be soldered includes TC4 titanium alloy and AlxCoCrFeNi high-entropy alloy, where x = 0.3. Step 2: Use 100#, 200#, 600# and 1000# metallographic sandpaper in sequence to polish the welding parts of AlxCoCrFeNi high-entropy alloy and TC4 titanium alloy. Step 3: Use acetone solution to ultrasonically clean the intermediate layer, the areas to be welded in the AlxCoCrFeNi high-entropy alloy, and the areas to be welded in the TC4 titanium alloy for 10 minutes, and then blow dry. Step 4: Place the intermediate layer between the AlxCoCrFeNi high-entropy alloy and the TC4 titanium alloy to form a structure to be welded, wherein the Nb foil layer contacts the weldable part of the AlxCoCrFeNi high-entropy alloy, and the Ni foil layer contacts the weldable part of the TC4 titanium alloy. Step 5: Place a graphite block on one side of the structure to be welded to compress the structure. The pressure applied by the graphite block to the structure to be welded is 108 Pa. Step six: Place the compressed structure to be welded into a high-temperature vacuum brazing furnace, at a vacuum degree of 2.0 × 10⁻⁶. -3 The brazed joint is heated to 1120°C at a heating rate of 8°C / min under Pa conditions, held for 10 min, cooled to 200°C at a cooling rate of 5°C / min, and then cooled to room temperature to obtain a brazed joint. The brazed joint includes a partially unmelted Nb foil layer, and the projected areas of the partially unmelted Nb foil layer, AlxCoCrFeNi high-entropy alloy, and TC4 titanium alloy on a plane parallel to the intermediate layer are equal.

[0051] Experimental results show that during brazing, the Ni foil layer completely dissolves and releases heat instantaneously during the diffusion reaction between the Ni / TC4 titanium alloys at a relatively low Ti / Ni eutectic temperature (942℃). This promotes the local diffusion reaction of the Nb foil / AlxCoCrFeNi high-entropy alloy, causing local dissolution at the interface and forming a TiNi+Laves eutectic structure and a TiNiNb reaction layer. The incompletely dissolved Nb foil acts as a barrier to Ti elements and has good deformability. During cooling, it can effectively alleviate the residual stress of the brazed joint through plastic deformation, thereby improving the strength of the brazed joint. The brazed joint formed by the Nb foil / Ni foil contact reaction has high connection strength, with a maximum room temperature shear strength of 189 MPa.

[0052] Example 3 This embodiment proposes a method for joining titanium alloy and high-entropy alloy based on an intermediate layer, including the following steps: Step 1: Provide an intermediate layer and a base material to be soldered. The intermediate layer includes a stacked Nb foil layer and a Ni foil layer, which are bonded together. The thickness of the Nb foil layer is 100 μm, and the thickness of the Ni foil layer is 20 μm. The purity of the Nb foil is 99.5%, and the purity of the Ni foil is 99.95%. The base material to be soldered includes TC4 titanium alloy and AlxCoCrFeNi high-entropy alloy, where x = 0.3. Step 2: Use 100#, 200#, 600# and 1000# metallographic sandpaper in sequence to polish the welding parts of AlxCoCrFeNi high-entropy alloy and TC4 titanium alloy. Step 3: Use acetone solution to ultrasonically clean the intermediate layer, the areas to be welded in the AlxCoCrFeNi high-entropy alloy, and the areas to be welded in the TC4 titanium alloy for 10 minutes, and then blow dry. Step 4: Place the intermediate layer between the AlxCoCrFeNi high-entropy alloy and the TC4 titanium alloy to form a structure to be welded, wherein the Nb foil layer contacts the weldable part of the AlxCoCrFeNi high-entropy alloy, and the Ni foil layer contacts the weldable part of the TC4 titanium alloy. Step 5: Place a graphite block on one side of the structure to be welded to compress the structure. The pressure applied by the graphite block to the structure to be welded is 108 Pa. Step six: Place the compressed structure to be welded into a high-temperature vacuum brazing furnace, at a vacuum degree of 2.0 × 10⁻⁶. -3 The brazed joint is heated to 1160°C at a heating rate of 8°C / min under Pa conditions, held for 10 min, cooled to 200°C at a cooling rate of 5°C / min, and then cooled to room temperature to obtain a brazed joint. The brazed joint includes a partially unmelted Nb foil layer, and the projected areas of the partially unmelted Nb foil layer, AlxCoCrFeNi high-entropy alloy, and TC4 titanium alloy on a plane parallel to the intermediate layer are equal.

[0053] The experimental structural results are shown in the following figure. Figure 3 and Figure 4 , Figure 3 A backscattered image of the brazed joint obtained in Embodiment 3 of this application; Figure 4 This is a shear strength diagram of the brazed joint obtained in Embodiment 3 of this application. Figure 3 The microstructure of the joint interface shows that the Nb foil layer and TC4 interface are metallurgically bonded to form a Ti-based solid solution. The AlxCoCrFeNi high-entropy alloy matrix forms a solid solution of a small amount of Ti and Nb. The residual Nb foil layer reacts with the AlxCoCrFeNi high-entropy alloy interface and then dissolves and solidifies to form the TiNi matrix phase, TiNiNb reaction layer and Laves phase. This brittle and hard phase structure helps to improve the mechanical properties of the joint. The joint interface microstructure is uniform and crack-free. The room temperature shear strength of the brazed joint is 289 MPa.

[0054] Example 4: This embodiment proposes a method for joining titanium alloy and high-entropy alloy based on an intermediate layer, including the following steps: Step 1: Provide an intermediate layer and a base material to be soldered. The intermediate layer includes a stacked Nb foil layer and a Ni foil layer, which are bonded together. The thickness of the Nb foil layer is 100 μm, and the thickness of the Ni foil layer is 20 μm. The purity of the Nb foil is 99.5%, and the purity of the Ni foil is 99.95%. The base material to be soldered includes TC4 titanium alloy and AlxCoCrFeNi high-entropy alloy, where x = 0.3. Step 2: Use 100#, 200#, 600# and 1000# metallographic sandpaper in sequence to polish the welding parts of AlxCoCrFeNi high-entropy alloy and TC4 titanium alloy. Step 3: Use acetone solution to ultrasonically clean the intermediate layer, the areas to be welded in the AlxCoCrFeNi high-entropy alloy, and the areas to be welded in the TC4 titanium alloy for 10 minutes, and then blow dry. Step 4: Place the intermediate layer between the AlxCoCrFeNi high-entropy alloy and the TC4 titanium alloy to form a structure to be welded, wherein the Nb foil layer contacts the weldable part of the AlxCoCrFeNi high-entropy alloy, and the Ni foil layer contacts the weldable part of the TC4 titanium alloy. Step 5: Place a graphite block on one side of the structure to be welded to compress the structure. The pressure applied by the graphite block to the structure to be welded is 108 Pa. Step six: Place the compressed structure to be welded into a high-temperature vacuum brazing furnace, at a vacuum degree of 2.0 × 10⁻⁶. -3 The brazed joint is heated to 1200℃ at a heating rate of 8℃ / min under Pa environment, held for 10 min, cooled to 200℃ at a cooling rate of 5℃ / min, and then cooled to room temperature to obtain a brazed joint. The brazed joint includes a partially unmelted Nb foil layer, and the projected areas of the partially unmelted Nb foil layer, AlxCoCrFeNi high-entropy alloy, and TC4 titanium alloy on a plane parallel to the intermediate layer are equal.

[0055] Experimental results show that during brazing, the Ni foil layer completely dissolves and releases heat instantaneously during the diffusion reaction between the Ni / TC4 titanium alloys at a relatively low Ti / Ni eutectic temperature (942℃). This promotes the local diffusion reaction of the Nb foil / AlxCoCrFeNi high-entropy alloy, causing local dissolution at the interface and forming a TiNi+Laves eutectic structure and a TiNiNb reaction layer. The incompletely dissolved Nb foil acts as a barrier to Ti elements and has good deformability. During cooling, it can effectively alleviate the residual stress of the brazed joint through plastic deformation, thereby improving the strength of the brazed joint. The brazed joint formed by the Nb foil / Ni foil contact reaction has high connection strength, with a maximum room temperature shear strength of 228 MPa.

[0056] It will be apparent to those skilled in the art that this application is not limited to the details of the exemplary embodiments described above, and that this application can be implemented in other specific forms without departing from the spirit or essential characteristics of this application. Therefore, the embodiments should be regarded as exemplary and non-limiting in all respects, and the scope of this application is defined by the appended claims rather than the foregoing description. Thus, all variations falling within the meaning and scope of equivalents of the claims are intended to be embraced within this application.

[0057] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application and are not intended to limit it. Although this application has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of this application without departing from the spirit and scope of the technical solutions of this application.

Claims

1. A method for joining titanium alloy and high-entropy alloy based on an intermediate layer, characterized in that, include: An intermediate layer and a base material to be soldered are provided, wherein the intermediate layer comprises a stacked Nb foil layer and a Ni foil layer, and the base material to be soldered comprises a TC4 titanium alloy and an AlxCoCrFeNi high-entropy alloy, wherein 0 < x ≤ 0.3; The welding areas of the AlxCoCrFeNi high-entropy alloy and the welding areas of the TC4 titanium alloy were ground separately. Clean the intermediate layer, the areas of the AlxCoCrFeNi high-entropy alloy to be welded, and the areas of the TC4 titanium alloy to be welded; The intermediate layer is placed between the AlxCoCrFeNi high-entropy alloy and the TC4 titanium alloy to form a structure to be welded, wherein the Nb foil layer contacts the weldable part of the AlxCoCrFeNi high-entropy alloy and the Ni foil layer contacts the weldable part of the TC4 titanium alloy. A pressure block is placed on one side of the structure to be welded to press the structure to be welded. The compressed structure to be welded is placed in a high-temperature vacuum brazing furnace and heated to a brazing temperature of 1080℃-1200℃ in a vacuum environment. After holding at the brazing temperature for 1 min-20 min, it is cooled to room temperature to obtain a brazed joint, wherein the brazed joint includes a portion of the unmelted Nb foil layer.

2. The joining method for titanium alloy and high-entropy alloy based on an intermediate layer according to claim 1, characterized in that, The unmelted Nb foil layer, the AlxCoCrFeNi high-entropy alloy, and the TC4 titanium alloy have equal projected areas on a plane parallel to the intermediate layer.

3. The joining method for titanium alloy and high-entropy alloy based on an intermediate layer according to claim 1, characterized in that, The Nb foil layer and the Ni foil layer are connected.

4. The joining method for titanium alloy and high-entropy alloy based on an intermediate layer according to claim 1, characterized in that, The thickness ratio of the Nb foil layer to the Ni foil layer is greater than or equal to 5:1 and less than or equal to 8:

1.

5. The joining method for titanium alloy and high-entropy alloy based on an intermediate layer according to claim 1, characterized in that, The purity of the Nb foil layer is not less than 95%, and the purity of the Ni foil layer is not less than 99%.

6. The joining method for titanium alloy and high-entropy alloy based on an intermediate layer according to claim 1, characterized in that, The steps of grinding the welding areas of the AlxCoCrFeNi high-entropy alloy and the welding areas of the TC4 titanium alloy respectively include: The welding areas of the AlxCoCrFeNi high-entropy alloy and the welding areas of the TC4 titanium alloy were polished sequentially using metallographic sandpaper of grades 100#, 200#, 600#, and 1000#.

7. The joining method for titanium alloy and high-entropy alloy based on an intermediate layer according to claim 1, characterized in that, The steps of cleaning the intermediate layer, the areas to be welded in the AlxCoCrFeNi high-entropy alloy, and the areas to be welded in the TC4 titanium alloy include: Clean the intermediate layer, the areas to be welded of the AlxCoCrFeNi high-entropy alloy, and the areas to be welded of the TC4 titanium alloy for 5-10 minutes, and then blow them dry.

8. The joining method for titanium alloy and high-entropy alloy based on an intermediate layer according to claim 1, characterized in that, The step of placing a pressure block on one side of the structure to be welded to compress the structure includes: A graphite block is placed on one side of the structure to be welded to press the structure to be welded, so that the Nb foil layer abuts against the part of the AlxCoCrFeNi high-entropy alloy to be welded, and the Ni foil layer abuts against the part of the TC4 titanium alloy to be welded, wherein the pressure applied by the graphite block to the structure to be welded is 100Pa-400Pa.

9. The joining method for titanium alloy and high-entropy alloy based on an intermediate layer according to claim 1, characterized in that, The step of heating to a brazing temperature of 1080℃-1200℃ in a vacuum environment, holding at the brazing temperature for 1 min-20 min, and then cooling to room temperature includes: Heating is performed under vacuum conditions below 108 Pa, with the temperature increased to a brazing temperature of 1080℃-1200℃ at a rate of 8℃ / min-15℃ / min. After holding at the brazing temperature for 1min-20min, the temperature is reduced to 200℃ at a rate of 5-10℃ / min, and finally cooled to room temperature in the vacuum brazing furnace.

10. A composite substrate, characterized in that, Prepared using the connection method described in any one of claims 1-9.

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