Ti-Al-Mo-Ta-Cr multi-element interlayer for titanium-aluminum dissimilar alloy diffusion welding and application of Ti-Al-Mo-Ta-Cr multi-element interlayer

Abstract

The invention discloses a Ti-Al-Mo-Ta-Cr multi-element interlayer for diffusion welding of titanium-aluminum series dissimilar alloys and application of the Ti-Al-Mo-Ta-Cr multi-element interlayer, and belongs to the field of diffusion welding of dissimilar metals. The middle layer is prepared from the following components in percentage by mass: 68.31 percent to 73.64 percent of Ti, 14.78 percent to 14.90 percent of Mo, 6.50 percent to 6.54 percent of Ta, 4.82 percent to 4.84 percent of Al and 0.13 percent to 5.54 percent of Cr, and the sum of the mass percent of all the components is 100 percent. According to the Ti-Mo-Ta-Al-Cr five-element interlayer alloy disclosed by the invention, the oxidation resistance of a diffusion welding joint can be effectively improved.

Description

Technical Field

[0001] The present invention belongs to the field of dissimilar alloy diffusion welding, and in particular relates to a novel multi-component intermediate layer for diffusion welding of TiAl and Ti2AlNb dissimilar alloys and applications thereof. Background Art

[0002] Thrust-to-weight ratio is a key technical indicator for assessing the industrial level and serviceability of aircraft engines. During engine development, increasing thrust and improving efficiency often involves raising engine operating temperatures and reducing vehicle weight. Overall, aircraft engine components are evolving toward higher temperatures, higher pressure ratios, and higher reliability, while aircraft engine structures are moving toward lightweight, integrated, and composite design. Advanced design concepts are based on higher operating temperatures, lower weight, and higher operating speeds. Over the past 50 years, the traditional metal systems currently in use have reached their limits. Further progress requires new materials. These materials must not only exhibit excellent high-temperature properties such as creep and oxidation resistance, but also possess high specific strength and modulus.

[0003] TiAl-based alloys possess high specific strength and modulus, maintaining sufficiently high strength and stiffness even at high temperatures. They also exhibit excellent resistance to creep, oxidation, and hydrogen embrittlement, making them promising lightweight, high-temperature structural materials. The major obstacle hindering the practical application of TiAl-based alloys is their lack of ductility and poor deformation processability at room temperature. In recent decades, extensive research has been conducted to improve the room-temperature ductility and hot-working plastic deformation properties of TiAl-based alloys, and significant progress has been made, driving their practical application. The practical engineering application of TiAl-based alloys inevitably involves joining them to other metal components, and researchers both domestically and internationally have conducted exploratory work in this area. Currently, research on joining techniques for TiAl-based alloys primarily encompasses fusion welding methods such as argon arc welding, electron beam welding, and laser welding, as well as solid-state welding methods such as diffusion welding, friction welding, and self-propagating high-temperature synthesis reaction welding. Studies on the weldability of fusion welds of TiAl-based alloys have revealed two prominent issues: a tendency to hot cracking; and a microstructure in the weld zone that differs from the matrix obtained through thermomechanical treatment and other processes, resulting in lower mechanical properties. Therefore, the weldability of low-ductility TiAl-based alloys using fusion welding is poor, especially when joining with dissimilar metals or alloys. Due to the inherent properties of TiAl-based alloys, solid-state welding can avoid the above-mentioned problems of fusion welding and shows good application prospects.

[0004] There are reports on diffusion welding of homogeneous TiAl alloys and TiAl / Ti2AlNb heterogeneous alloys.

[0005] The literature "Z.Du, K.Zhang, Z.Lu, et al.Microstructure and mechanical properties of vacuum diffusion bonding joints forγ-TiAl based alloy[J], Vacuum, 2018, 150:96-104." obtained excellent Ti-47.5Al-Cr-V (atomic percentage, the same below) alloy diffusion welded joints under the optimized welding process specifications, with a shear strength of 447MPa, which can reach 85% of the shear strength of the TiAl alloy base material.

[0006] The literature "D.Herrmann, F.Appel.Diffusion bonding ofγ(TiAl)alloys:influenceof composition,microstructure,and mechanical properties[J].Metallurgical and Materials Transactions A,2009,40:1881-190." obtained a Ti-45Al-5Nb-0.2C-0.2B alloy diffusion bonded joint with optimal tensile strength under the welding process specifications of welding temperature 1000℃, holding time 2h, and welding pressure 20MPa. Its room temperature tensile strength reached 850MPa.

[0007] The document "W. Glatz, H. Clemens. Diffusion bonding of intermetallic Ti-47Al-2Cr-0.2Si sheet material and mechanical properties of joints at room temperature and elevated temperatures [J], Intermetallics, 1997, 5: 415-423." obtained a Ti-47Al-2Cr-0.2Si alloy diffusion welded joint with a tensile strength comparable to that of the base material under the preferred welding process specifications.

[0008] Compared with the higher quality diffusion welding of the same TiAl alloy, the mechanical properties of the diffusion welding joints of TiAl and Ti2AlNb dissimilar alloys are still insufficient.

[0009] The paper "J.Zou, Y.Cui, R.Yang. Diffusion bonding of dissimilar intermetallic alloys based on Ti2AlNb and TiAl[J].Journal of Materials Science&Technology, 2009, 25(6):819-24" achieved diffusion bonding of Ti-46.2Al-2Cr-2Nb-0.15B alloy and Ti-22Al-23Nb-2Ta alloy. The results showed that a hard and brittle AlNb2 phase was generated at the bonding interface, seriously degrading the performance of the welded joint. Under the optimal process specifications, the shear strength of the TiAl / Ti2AlNb dissimilar alloy direct diffusion bonded joint was 260MPa.

[0010] The paper "ZC Wang, C. Li, JL Qi, et al. Characterization of hydrogenated niobium interlayer and its application in TiAl / Ti2AlNb diffusion bonding [J]. International Journal of Hydrogen Energy, 2019, 44, 13: 6929-6937" reports the use of a novel hydrogenated niobium foil as an interlayer to achieve reliable bonding of TiAl and Ti2AlNb alloys. Results show that the introduction of hydrogen increases the interfacial bonding area by enhancing the plastic deformation capacity of the welded surfaces and, by increasing the dislocation density in the niobium lattice, provides faster atomic pathways for interdiffusion between elements at the heterogeneous interface. The shear strength of the TiAl / Ti2AlNb diffusion-bonded joint produced under the optimal process specifications of 1.0 wt% hydrogen loading, 950°C welding temperature, 5 MPa welding pressure, and 40 min holding time was 259 MPa. However, residual hydrogen at the interface can easily lead to hydrogen embrittlement failure of the joint under internal residual stress or applied alternating loads.

[0011] The paper "L. Zhu, X. Wang, Y. Chen, et al. Enhanced tensile strength of TiAl / Ti2AlNb diffusion bonding joint by a novel post-bonded hot deformation [J]. Journal of Materials Research and Technology, 2024, 29: 3598-605" reports a novel post-bonded hot deformation (PBHD) process for improving the mechanical properties of TiAl / Ti2AlNb dissimilar alloy diffusion-bonded joints. Similar to the hot isostatic pressing (HIPP) process used in the metallurgical industry, the PBHD process aims to eliminate metallurgical defects in the reaction zone of the welded components. Combined with a heat treatment process, it improves the interface microstructure, densifying and homogenizing the interface, and thus enhancing the mechanical properties of the joint. Tensile tests show that the tensile strength of the TiAl / Ti2AlNb diffusion-bonded joint significantly increases from 325 MPa to 598 MPa after PBHD treatment. However, the cumbersome PBHD post-weld heat treatment process hinders its widespread industrial application.

[0012] In summary, for connections of the same TiAl-based alloy, the joint strength can reach the parent material level; however, for connections of TiAl alloys and Ti2AlNb alloys, the joint strength and reliability are still far from sufficient. Although pre-installed interlayers or post-weld heat treatment can reduce joint residual stress and brittle phase formation, thereby improving joint strength, the current choice of interlayers still focuses on pure metal single interlayers or composite interlayers of pure metal combinations, and there is a lack of design and related concepts for multi-component alloy interlayers. In addition, due to the limitations of filler metals, joint residual stress and interfacial brittle intermetallic compounds still restrict further improvements in the strength of TiAl-based heterogeneous alloy joints. Therefore, establishing a new interlayer design model and developing new alloy interlayers will help improve the interface structure, enhance the overall performance of the joint, and broaden the application range of TiAl / Ti2AlNb composite components. Summary of the Invention

[0013] Based on the above background technology, the present invention proposes a Ti-Mo-Ta-Al-Cr multi-component alloy intermediate layer and a preparation method thereof for preparing high-quality, high-performance titanium-aluminum dissimilar alloy (TiAl / Ti2AlNb dissimilar alloy) diffusion welding joints. The prepared diffusion welding joint is a high-strength and toughness diffusion welding joint.

[0014] The technical means adopted in the present invention are as follows:

[0015] A Ti-Al-Mo-Ta-Cr multi-component alloy intermediate layer for diffusion welding of titanium-aluminum dissimilar alloys (TiAl / Ti2AlNb dissimilar alloys), wherein the cluster expression of the intermediate layer is [Al 1.0 -Ti 12.9-x Mo 0.8 Ta 0.3 Cr x ]-Al 0.5 Mo 0.5 (x is between 0.02 and 0.9), and is composed of the following components in mass percentage: Ti is 68.31% to 73.64%, Mo is 14.78% to 14.90%, Ta is 6.50 to 6.54%, Al is 4.82 to 4.84%, and Cr is 0.13 to 5.54%. The sum of the mass percentages of the above components is 100%.

[0016] Design of Ti-Mo-Ta-Al-Cr five-element intermediate layer composition: Based on the cluster and connecting atom model and the composition range of β-type titanium alloy to maintain phase transformation diversity and deformation mode diversity, the β-Ti solid solution phase [M-Ti8Ti6]Ti1 is selected as the basic cluster formula, where M is the central atom of the cluster structural unit. Furthermore, the Ti atom in the cluster formula is partially replaced by Mo, Ta, Al and Cr atoms to obtain the cluster expression [Al 1.0 -Ti 12.9-x Mo 0.8 Ta 0.3 Cr x ]-Al 0.5 Mo 0.5 (x is between 0.02 and 0.9), the atomic percentage of each alloying element can be obtained by substituting it into the mass percentage of the corresponding element, and the mass percentage expression of the intermediate layer alloy Ti is obtained. a Mo b Ta c Al d Cr e , a is 68.31% to 73.64%, b is 14.78% to 14.90%, c is 6.50 to 6.54%, d is 4.82 to 4.84%, e is 0.13 to 5.54%, and a+b+c=100.

[0017] Specifically, when x = 0.1, the intermediate layer cluster expression is [Al 1.0 -Ti 12.8 Mo 0.8 Ta 0.3 Cr 0.1 ]-Al 0.5 Mo 0.5 , the atomic percentage expression is Ti 80.00 Mo 8.13Ta 1.88 Al 9.38 Cr 0.63 , converted into mass percentage expression is Ti 73.15 Mo 14.90 Ta 6.50 Al 4.83 Cr 0.63 , where the mass percentages are 73.15 + 14.90 + 6.50 + 4.83 + 0.63 = 100, satisfying a + b + c = 100. It should be emphasized that for values of x between 0.02 and 0.9 and other values other than x = 0.1, the conversion method remains the same as when x = 0.1.

[0018] Based on the above technical solution, preferably, the thickness of the intermediate layer should be ≤0.2 mm.

[0019] Based on the above technical solution, preferably, the Ti, Mo, Ta, Al and Cr are all high-purity metal particles with a purity of 99.99%, and are stored in a vacuum manner.

[0020] The present invention also provides a method for preparing the Ti-Al-Mo-Ta-Cr multi-component alloy intermediate layer for diffusion welding of titanium-aluminum dissimilar alloys (TiAl / Ti2AlNb dissimilar alloys), comprising the following steps:

[0021] Step 1: Based on the above-mentioned intermediate layer alloy design concept, the corresponding cluster expression can be obtained by assigning a value to x. A simple calculation can obtain the atomic percentage expression of the corresponding intermediate layer alloy, and then the corresponding mass percentage expression can be obtained by conversion. Using a precision electronic balance with an accuracy of one thousandth, the high-purity metal raw materials of each element are weighed out according to the mass percentage: Ti is 68.31% to 73.64%, Mo is 14.78% to 14.90%, Ta is 6.50% to 6.54%, Al is 4.82% to 4.84%, and Cr is 0.13% to 5.54%. The sum of the mass percentages of the above components is 100%;

[0022] Step 2: Place the high-purity metal raw materials weighed in step 1 into the copper crucible in the order of "low melting point elements at the bottom and high melting point elements at the top". Use vacuum arc melting to melt the high-purity metal raw materials in the copper crucible. The vacuum degree in the furnace chamber must be maintained at 5×10 -3 Pa or less, and each button ingot must be repeatedly smelted more than 6 times;

[0023] Step 3: Place the button ingot obtained in Step 2 in a vacuum quartz tube for homogenization. Heat treatment is performed by furnace heating at a temperature of 800-1000°C for 6-10 hours. Furthermore, wire cutting is used to separate the button ingot into intermediate foil sheets that meet welding dimensions. Step 4: Grind the intermediate foil sheets obtained in Step 3 with sandpaper to remove any traces of wire cutting from the surface to be welded.

[0024] Based on the above technical solution, preferably, in step 3, in order to effectively control the warping deformation of the intermediate layer foil during the mechanical polishing process, the thickness of the intermediate layer foil separated in this step should be ≥0.4 mm.

[0025] Based on the above technical solution, preferably, in step 4, the intermediate layer foil obtained in step 3 is ground step by step using 400# to 2000# sandpaper to a thickness of ≤0.2 mm, and its flatness must be ensured to be ≤0.05 mm.

[0026] An application of the above-mentioned Ti-Al-Mo-Ta-Cr multi-element alloy intermediate layer in the diffusion welding of titanium-aluminum dissimilar alloys (TiAl / Ti2AlNb dissimilar alloys).

[0027] A welding process for diffusion welding of titanium-aluminum dissimilar alloys (TiAl / Ti2AlNb dissimilar alloys) using the Ti-Mo-Ta-Al-Cr multi-element intermediate layer comprises the following steps:

[0028] Step 1: Before welding, use 400#~2000# sandpaper to grind the surface of the base material to be welded to ensure that the base material is flat, bright and scratch-free, with a flatness of ≤0.05mm. After the treatment is completed, place the intermediate layer foil (Ti-Mo-Ta-Al-Cr five-element intermediate layer) and the base material to be welded in a dry and clean beaker, pour in an appropriate amount of anhydrous ethanol, and place the beaker in an ultrasonic cleaner for 10 to 30 minutes. After cleaning, remove the sample to be welded and use a hair dryer to dry it for later use;

[0029] Step 2: Place the cleaned Ti-Mo-Ta-Al-Cr five-element intermediate layer between the base materials to be welded (TiAl and Ti2AlNb) to form a "sandwich" assembly. After assembly, place it in the center of the graphite platform of the vacuum diffusion welding furnace, and then close the furnace door to prepare for welding;

[0030] Step 3: Wait until the vacuum degree in the furnace is less than 6×10 -3Pa, the welding heating program is started: set the initial welding pressure to 0.5~5MPa, heat up to 250~300℃ and keep warm for 5~10min; heat up to 450~500℃ and keep warm for 5~10min, increase the welding pressure to 5~10MPa; heat up to 550~600℃ and keep warm for 5~10min, increase the welding pressure to 10~15MPa; heat up to 650~700℃ and keep warm for 10~30min, increase the welding pressure to 15~20MPa; heat up to 950-1000℃ and keep warm for 60~90min, and keep the welding pressure at 15~20MPa; after the heat and pressure holding period, stop heating, turn off the heating and closed-loop pressurization in the furnace in turn, take out the sample after the furnace cools to room temperature, and the welding is completed.

[0031] Based on the above technical solution, preferably, in step 1, 400# to 2000# sandpaper is used to grind the surface of the base material to be welded step by step to ensure that the surface of the base material to be welded is smooth, bright and scratch-free, and the flatness is ≤0.05mm.

[0032] Based on the above technical solution, preferably, in step 1, the beaker is placed in an ultrasonic cleaning machine and cleaned for about 10 to 30 minutes.

[0033] Based on the above technical solution, preferably, the strength coefficient of the TiAl / Ti2AlNb diffusion welded joint is greater than 0.95, and the oxidation weight gain of the welded joint after oxidation for 96 hours in an extreme high temperature environment (800°C) is less than 5 mg·cm -2 The oxidation resistance of the welded joint is comparable to that of TiAl alloy and better than that of Ti2AlNb alloy.

[0034] Beneficial effects

[0035] 1. The Ti-Mo-Ta-Al-Cr quinary interlayer alloy of the present invention has a molybdenum equivalent (MoE) between 10 and 20, representing a typical β-type titanium alloy. This interlayer alloy inherently possesses excellent heat treatment strengthening capabilities. By adjusting the welding process specifications, it can be ensured that it maintains a solid solution structure before and after welding, thereby achieving a good match between strength and plasticity. Furthermore, the good matching between the various elements in the interlayer alloy effectively improves the alloy's high-temperature thermal strength and stability, resulting in excellent properties such as high specific strength, excellent fracture toughness, high hardenability, good forgeability, and low sensitivity to segregation, facilitating industrial application.

[0036] 2. The Ti-Mo-Ta-Al-Cr quinary interlayer designed by this invention, through optimized process specifications, effectively controls the formation of fine secondary α phase in the interface reaction zone of TiAl / Ti2AlNb diffusion welds. Under applied load, this discontinuous distribution of fine α phase effectively hinders crack propagation along grain boundaries, thereby improving the deformation capacity of the weld joint. Simultaneously, a large number of fine, needle-like secondary α phases uniformly disperse and precipitate within the β grains, significantly increasing the number of α / β phase interfaces and significantly hindering dislocation movement, thereby strengthening the weld joint.

[0037] 3. By adopting the technical solution set forth in the present invention and using a Ti-Mo-Ta-Al-Cr five-element intermediate layer alloy foil as a preset intermediate layer and optimizing the process parameters, the formation of hard and brittle intermetallic compounds at the interface can be significantly suppressed, the interface bonding quality can be improved, and the overall interface performance can be improved. The average tensile strength of the TiAl / Ti2AlNb diffusion welded joint can reach 757 MPa, and the joint strength coefficient is greater than 0.95.

[0038] 4. The preferred Mo, Ta, Al, and Cr elements in the Ti-Mo-Ta-Al-Cr quinary interlayer alloy of the present invention can effectively improve the oxidation resistance of diffusion-welded joints. Specifically, doping TiO2 with Nb and Ta inhibits the diffusion of O and stimulates the migration of Al. This doping effect inhibits the growth of TiO2 and promotes the formation of a TiO2+Al2O3 nanolayer. Al and Cr contribute to the continuous generation of protective oxidation products and significantly enhance their adhesion. After high-temperature oxidation at 800°C for 96 hours, the joint exhibits an oxidation thickening of less than 15.0 μm. The joint exhibits superior oxidation resistance to the Ti2AlNb alloy parent material and is comparable to that of a TiAl alloy. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 [Al 1.0 -Ti 12.8 Mo 0.8 Ta 0.3 Cr 0.1 ]-Al 0.5 Mo 0.5 Preparation flow chart of the intermediate layer (a), XRD pattern (b) and EPMA surface scanning results (c).

[0040] Figure 2 This is the microstructure diagram of the TiAl / Ti2AlNb diffusion welded joint obtained according to Example 2.

[0041] Figure 3 FIG1 is a force-displacement loading curve of the TiAl / Ti2AlNb diffusion-bonded joint obtained according to Example 3 at room temperature.

[0042] Figure 4 The weight gain (a) and thickness gain (b) kinetic curves of the TiAl / Ti2AlNb diffusion-bonded joint obtained in Example 4 oxidized at 800°C for 96 hours and the microstructure of the oxidation product (c) are shown. DETAILED DESCRIPTION

[0043] The present invention will now be further described with reference to specific embodiments and accompanying drawings:

[0044] Example 1

[0045] The composition of the intermediate layer was designed. Based on the cluster and connecting atom model and the composition range that maintains phase transformation diversity and deformation mode diversity of β-type titanium alloy, the β-Ti solid solution phase [M-Ti8Ti6]Ti1 was selected as the basic cluster formula, where M is the central atom of the cluster structural unit. Furthermore, the Ti atom in the cluster formula was partially replaced by Mo, Ta, Al and Cr atoms to obtain the cluster expression [Al 1.0 -Ti 12.9-x Mo 0.8 Ta 0.3 Cr x ]-Al 0.5 Mo 0.5 (x is between 0.02 and 0.9), the atomic percentage of each alloying element can be obtained by substituting it into the mass percentage of the corresponding element, and the mass percentage expression of the intermediate layer alloy Ti is obtained. a Mo b Ta c Al d Cr e , a is 68.31% to 73.64%, b is 14.78% to 14.90%, c is 6.50 to 6.54%, d is 4.82 to 4.84%, e is 0.13 to 5.54%, and a+b+c=100.

[0046] In this embodiment, x is assigned to x=0.1, and x=0.1 is substituted into the cluster expression [Al 1.0 -Ti 12.9- x Mo 0.8 Ta 0.3 Cr x ]-Al 0.5 Mo 0.5 The cluster expression can be obtained as [Al 1.0 -Ti 12.8 Mo 0.8 Ta 0.3 Cr 0.1 ]-Al 0.5 Mo 0.5 , the mass percentage expression can be converted to Ti73.15 Mo 14.90 Ta 6.50 Al 4.83 Cr 0.63 .

[0047] Melting alloy ingots: weigh out high-purity (99.99%) element particles of Ti, Mo, Ta, Al, and Cr according to the predetermined mass percentage, and place the weighed pure element particles in the order of melting point from low to high in a copper crucible for vacuum arc melting. The vacuum degree of the furnace chamber is required to reach 5×10 -3 Below Pa, forward and reverse melting 6 times.

[0048] Preparation of the intermediate layer foil: The melted button ingot was placed in a vacuum quartz tube and heated to 1000°C in a furnace and then kept at this temperature for 6 hours for homogenization. Furthermore, the button ingot was cut into 15×15×0.4mm thick foils by wire cutting. 3 The middle layer foil is then ground step by step using 400#, 800#, 1000#, 1500# and 2000# sandpaper, and both sides are mechanically polished to a thickness of 0.2mm, and its flatness must be ensured to be ≤0.05mm.

[0049] The intermediate layer alloy preparation process adopted in this embodiment and the obtained intermediate layer alloy XRD spectrum and EPMA surface scanning results are as follows: Figure 1 As shown in the figure, [Al 1.0 -Ti 12.8 Mo 0.8 Ta 0.3 Cr 0.1 ]-Al 0.5 Mo 0.5 The interlayer alloy is a single-phase β solid solution, with uniform distribution of alloying elements within each grain. β-type alloys inherently possess low density, high strength, good ductility, and a wide range of deformation modes. Furthermore, the interlayer alloying elements Mo and Ta have a positive impact on the thermal stability and ductility of both the TiAl and Ti2AlNb alloys, effectively improving the interface structure in the reaction zone and thereby enhancing the mechanical properties of the TiAl / Ti2AlNb diffusion-bonded joint.

[0050] Example 2

[0051] Before welding, the surfaces of TiAl alloy (Ti-45Al-2Cr-2Nb (at.%)) and Ti2AlNb alloy (Ti-23Al-26Nb (at.%)) were ground step by step using 400#, 800#, 1000#, 1500# and 2000# sandpaper to ensure that the surface of the base material to be welded was flat, bright and scratch-free, with a flatness of ≤0.05mm. The intermediate layer preparation method in Example 1 was used to process [Al1.0 -Ti 12.8 Mo 0.8 Ta 0.3 Cr 0.1 ]-Al 0.5 Mo 0.5 Middle layer, place the middle layer to be welded and the base material to be welded in a dry and clean beaker respectively, pour in an appropriate amount of anhydrous ethanol to place the middle layer to be welded and the base material to be welded in anhydrous ethanol, place the beaker in an ultrasonic cleaner for cleaning for 10 minutes, take out the sample to be welded after cleaning, use a hair dryer to dry it for standby use; then place the cleaned middle layer to be welded between the TiAl alloy and the Ti2AlNb alloy to form a "sandwich" type assembly, after assembly is completed, according to the set heating program, place the above assembly in the center of the graphite platform of the vacuum diffusion welding furnace, and then close the furnace door for diffusion welding. The welding temperature was raised from room temperature to 250°C and held for 5 minutes, with an initial pressure of 5 MPa. The temperature was then raised to 500°C and held for 10 minutes, with the welding pressure increased to 10 MPa. The temperature was then raised to 600°C and held for 10 minutes, with the welding pressure increased to 15 MPa. The temperature was then raised to 700°C and held for 30 minutes, with the welding pressure increased to 20 MPa. Finally, the temperature was raised to 975°C and held for 60 minutes before welding. The welding pressure was maintained at 20 MPa. After the welding process was completed, the heating and closed-loop pressurization in the furnace were turned off in sequence. The sample was removed after the furnace cooled to room temperature, and the welding was complete.

[0052] This implementation method is used to preset [Al 1.0 -Ti 12.8 Mo 0.8 Ta 0.3 Cr 0.1 ]-Al 0.5 Mo 0.5 After the intermediate layer is welded, the effective control of fine secondary α phase is achieved in the interface reaction area of TiAl / Ti2AlNb diffusion welded joint, and its interface structure is as follows: Figure 2 As shown in Figure 2, under applied load, this discontinuous distribution of fine α phase effectively hinders crack propagation along grain boundaries, thereby improving the deformation capacity of the weld joint. Simultaneously, a large number of fine, needle-like secondary α phases uniformly disperse and precipitate within the β grains, significantly increasing the number of α / β phase interfaces and significantly hindering dislocation movement, thereby strengthening the weld joint.

[0053] Example 3

[0054] Satisfactory TiAl / Ti2AlNb diffusion-bonded joints were fabricated using the welding process specifications described in Example 2 and subjected to static room-temperature tensile testing. The test specimens were dog-bone rod-shaped tensile specimens with dimensions of 30 mm × 4 mm; a clamping end diameter of 4 mm and a clamping length of 7.5 mm; a central test section with a diameter of 2 mm and a length of 10 mm; and a transition arc radius of 3 mm.

[0055] The force-displacement loading curves of the TiAl / Ti2AlNb diffusion welded joint and the TiAl base material obtained in this embodiment are shown in FIG. Figure 3 As shown in the figure, it can be seen that the TiAl / Ti2AlNb diffusion welded joint with both high strength and high plasticity can be obtained by using this embodiment method. The tensile test results show that the joint breaks at the TiAl alloy base material, the tensile strength of the joint can reach 757 MPa, the strength coefficient can reach 0.96, and its plasticity is greatly improved compared to the TiAl alloy base material.

[0056] Example 4

[0057] A satisfactory TiAl / Ti2AlNb diffusion-bonded joint was fabricated using the welding process specifications described in Example 2 and then subjected to high-temperature oxidation performance testing. This testing was conducted in accordance with HB5258-2000, "Test Methods for Determination of Oxidation Resistance of Steel and High-Temperature Alloys." The oxidation temperature was 800°C, the sampling interval was 12 hours, and the total oxidation time was 96 hours.

[0058] The present method can be used to obtain a TiAl / Ti2AlNb diffusion welded joint with excellent oxidation resistance. The thickening kinetic curve of the joint after cyclic oxidation at 800℃ for 96h and the cross-sectional morphology of the oxidation product at 36h and 96h are shown in FIG. Figure 4 The oxidation weight gain of the entire joint can be divided into two stages. Stage I consists of three periods from 0h to 36h, and Stage II consists of five periods from 36h to 96h. It can be seen that the TiAl / Ti2AlNb diffusion welded joint obtained in this example has an oxidation weight gain of 4.69mg·cm after high-temperature oxidation at 800℃ for 96h. -2 , oxidation thickening is less than 15.0μm, and the oxidation resistance of the joint is better than that of Ti2AlNb alloy parent material and is equivalent to that of TiAl alloy parent material.

Claims

1. A Ti-Al-Mo-Ta-Cr multi-component alloy intermediate layer for diffusion welding of titanium-aluminum dissimilar alloys, characterized in that: The material is composed of the following components in mass percentage: Ti is 68.31% to 73.64%, Mo is 14.78% to 14.90%, Ta is 6.50% to 6.54%, Al is 4.82% to 4.84%, and Cr is 0.13% to 5.54%. The sum of the mass percentages of the above components is 100%.

2. The Ti-Al-Mo-Ta-Cr multi-element alloy intermediate layer according to claim 1, characterized in that: The intermediate layer cluster expression is [Al 1.0 -Ti 12.9-x Mo 0.8 Ta 0.3 Cr x ]-Al 0.5 Mo 0.5 , where x is between 0.02 and 0.

9.

3. The Ti-Al-Mo-Ta-Cr multi-element alloy intermediate layer according to claim 1, characterized in that: The thickness of the intermediate layer is ≤0.2 mm.

4. The Ti-Al-Mo-Ta-Cr multi-element alloy intermediate layer according to claim 1, characterized in that: The Ti, Mo, Ta, Al and Cr are all high-purity metal particles with a purity of 99.99%, and are stored in a vacuum manner.

5. The Ti-Al-Mo-Ta-Cr multi-element alloy intermediate layer according to claim 1, characterized in that: The titanium-aluminum dissimilar alloy is a TiAl / Ti2AlNb dissimilar alloy.

6. The method for preparing the Ti-Al-Mo-Ta-Cr multi-element alloy intermediate layer according to any one of claims 1 to 5, characterized in that: The steps include: Step 1: Weigh out the pure metal raw materials of each element according to the mass percentage; Step 2: Place the pure metal raw materials weighed in step 1 into the copper crucible in the order of "low melting point elements at the bottom and high melting point elements at the top"; use vacuum arc melting to melt the high purity metal raw materials in the copper crucible, and the vacuum degree in the furnace chamber must be maintained at 5×10 -3 Pa or less, and each button ingot must be repeatedly smelted more than 6 times; Step 3: The button ingot obtained in step 2 is placed in a vacuum quartz tube for homogenization treatment at a heating temperature of 800-1000° C. for a holding time of 6-10 hours; an intermediate layer foil that meets welding size requirements is cut from the button ingot using a wire cutting method; Step 4: Use sandpaper to grind the middle layer foil obtained in step 3.

7. The preparation method according to claim 6, characterized in that In step 3, the thickness of the separated intermediate layer foil is ≥ 0.4 mm; In step 4, the intermediate layer foil obtained in step 3 is ground step by step using 400# to 2000# sandpaper to a thickness of ≤0.2 mm, and its flatness is ensured to be ≤0.05 mm.

8. Use of the Ti-Al-Mo-Ta-Cr multi-element alloy intermediate layer according to any one of claims 1 to 5 in diffusion welding of titanium-aluminum dissimilar alloys.

9. A titanium-aluminum dissimilar alloy diffusion welding process, characterized in that: The following steps are involved: Step 1: Before welding, use sandpaper to grind the surface of the base material to be welded; after the treatment, place the intermediate layer according to any one of claims 1 to 5 and the base material to be welded in anhydrous ethanol, and use an ultrasonic cleaner to clean them. After cleaning, take out the sample to be welded and use a hair dryer to dry them for later use; Step 2: Place the intermediate layer in the middle of the base material to be welded to form a "sandwich" assembly; after assembly, place it in the center of the graphite platform of the vacuum diffusion welding furnace, and then close the furnace door to prepare for welding; Step 3: Wait until the vacuum degree in the furnace is less than 6×10 -3 Pa, the welding heating program is started: set the initial welding pressure to 0.5~5MPa, heat up to 250~300℃ and keep warm for 5~10min; heat up to 450~500℃ and keep warm for 5~10min, increase the welding pressure to 5~10MPa; heat up to 550~600℃ and keep warm for 5~10min, increase the welding pressure to 10~15MPa; heat up to 650~700℃ and keep warm for 10~30min, increase the welding pressure to 15~20MPa; heat up to 950-1000℃ and keep warm for 60~90min, and keep the welding pressure at 15~20MPa; after the welding program is completed, turn off the heating and closed-loop pressurization in the furnace in turn, take out the sample after the furnace cools to room temperature, and the welding is completed.

10. The welding process according to claim 9, characterized in that: In step 1, use 400# to 2000# sandpaper to grind the surface of the base material to be welded step by step to ensure that the surface of the base material to be welded is flat, bright and scratch-free, with a flatness of ≤0.05mm; use an ultrasonic cleaner to clean it for 10 to 30 minutes.

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