A method for directional direct diffusion bonding of refractory metal or alloy single crystal materials

Abstract

The application discloses a method for directional direct diffusion connection of refractory metal or alloy single crystal materials, and comprises the following steps: 1, grinding and polishing the refractory metal or alloy single crystal materials into cylindrical blocks; 2, electrolytic polishing the polished cylindrical blocks; 3, using an X-ray single crystal orientation instrument to mark the crystal faces of the polished cylindrical blocks to obtain the actual positions of the specified crystal faces on the cylindrical blocks; and 4, directionally assembling and fixing the two cylindrical blocks with marked crystal faces, and obtaining a refractory metal or alloy welded joint through vacuum diffusion connection. The method realizes the directional assembly of the to-be-connected samples through crystal face marking, combines the solid-phase diffusion connection process, makes the to-be-connected surfaces closely combined and the connection interface holes efficiently closed, and inhibits the generation of small-angle grain boundaries, recrystallized grains and mixed crystals at the interface, so that the refractory metal and alloy welded joint with the single crystal organization characteristics, the well-welded interface, the few defects and the high welding rate is obtained, and the refractory metal and alloy welded joint is suitable for the fields of nuclear reactors and medical devices.

Description

Technical Field

[0001] This invention relates to the field of welding technology for refractory metals and alloys, and specifically to a method for directional direct diffusion bonding of single crystal materials of refractory metals or alloys. Background Technology

[0002] Space-based thermionic reactors can provide the energy needed for deep space probes, space stations, and other space bases. The thermionic energy converter is the core of the space-based thermionic nuclear reactor. Refractory metals or alloys such as W and Mo possess excellent properties, including no grain boundary sliding during high-temperature deformation, stable microstructure, low plastic / brittle transition temperature, and high vacuum work function, making them ideal emitter materials for the thermionic energy converter in space nuclear reactors. In practical applications, the single-crystal materials need to be welded to meet the size requirements of the thermionic elements, which also broadens the application fields of refractory metal or alloy single-crystal materials.

[0003] Li Xin et al. from the China Institute of Atomic Energy achieved directional welding of Mo3Nb single crystal rods using electron beam welding technology (Li Xin, Jiang Wei, Chen Shengjie et al., Research on directional welding technology of Mo-3Nb single crystal, Rare Metal Materials and Engineering, 2015(44)1:1002-185X(2015)01-0189-05). Although the large-angle grain boundaries at the interface were eliminated by directional welding, a small number of substructures still exist in the center of the weld due to the movement of dislocations during the solidification of the molten pool, which affects the long-term creep performance of the material.

[0004] Currently, there are few publicly reported studies on welding technologies for refractory metals or alloy single-crystal materials, with electron beam welding being the most common. The high-energy heat input and varying cooling rates at different locations in electron beam welding lead to the formation of low-angle grain boundaries and impurities at the weld joint, simultaneously creating a heat-affected zone that damages the joint's mechanical properties. Therefore, fusion welding is not the most ideal welding method. Summary of the Invention

[0005] The technical problem to be solved by this invention is to provide a method for directional direct diffusion bonding of refractory metal or alloy single crystal materials, addressing the shortcomings of the prior art. This method achieves directional assembly by calibrating the crystal planes of the single crystal material samples to be bonded. Combined with solid-state diffusion bonding technology, it ensures tight bonding of the surfaces to be bonded and efficient closure of pores at the bonding interface, suppressing the generation of small-angle grain boundaries, recrystallized grains, and impurities. This enables the welding and forming of refractory metal or alloy single crystal materials, solving the problems of low-angle grain boundaries and impurities in existing electron beam welding joints of refractory metal or alloy single crystal materials.

[0006] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is: a method for directional direct diffusion bonding of refractory metal or alloy single crystal materials, characterized in that the method includes the following steps: Step 1: [The text appears to be incomplete and contains several grammatical errors. A more accurate translation would require the full <111> Preferred orientation refractory metal or alloy single crystal materials are processed into cylindrical blocks by slow wire cutting, and then the end faces of the cylindrical blocks are ground and polished after hot mounting. Step 2: Hydrochloric acid, nitric acid, and methanol are mixed to obtain an electrolytic polishing solution. Using stainless steel as the cathode and the cylindrical block polished in Step 1 as the anode, the block is placed in the electrolytic polishing solution for electrolytic polishing to remove the surface oxide film and stress layer, resulting in a polished cylindrical block. The electrolytic polishing voltage is 20V~30V, the current is 0.5A~1A, and the time is 2min~4min. Step 3: Use an X-ray single crystal orientation instrument to calibrate the crystal planes of the polished cylindrical block in Step 2. First, calculate the θ angle of the specified crystal plane to be measured, and then rotate the cylindrical block until the diffraction intensity reading is greater than 80. Obtain the actual position of the specified crystal plane on the cylindrical block. Calibrate more than two crystal planes for each cylinder to ensure orientation accuracy. Step 4: Assemble the two cylindrical blocks whose crystal planes were calibrated in Step 3 according to the calibrated crystal planes, so that the surfaces to be joined are aligned. Fix them with tape and molds, then place the assembled cylindrical blocks in a vacuum diffusion furnace. After evacuation, heat and pressurize to perform vacuum diffusion joining. After furnace cooling to room temperature, remove the blocks to obtain a refractory metal or alloy welded joint. The vacuum diffusion joining temperature is 1100℃~1700℃, the pressure is 20MPa~80MPa, and the time is 2h. The refractory metal or alloy welded joint has single crystal structure characteristics, good interface welding, and no obvious defects.

[0007] The above-mentioned method for directional direct diffusion bonding of refractory metal or alloy single crystal materials is characterized in that the source of the refractory metal or alloy single crystal material in step one includes: W and Mo refractory metals, and refractory alloys alloyed with W and Mo as the matrix and Re, Hf or Nb alloying elements added, and the mass ratio of the matrix to the alloying elements is 1~30:1, wherein the refractory metal or alloy single crystal material has <111> Select single crystal rods, ingots, or bulk materials with the preferred growth orientation, and the orientation deflection angle of the (111) crystal plane shall not exceed 8°.

[0008] The above-mentioned method for directional direct diffusion bonding of refractory metal or alloy single crystal materials is characterized in that the diameter of the cylindrical block in step one is more than 20 mm and the end face is (111) crystal plane. The cylindrical block after thermal embedding is mechanically polished by an automatic metallographic polishing machine to ensure that the parallelism of the upper and lower surfaces is less than 0.005 mm.

[0009] The above-mentioned method for directional direct diffusion bonding of refractory metal or alloy single crystal materials is characterized in that the electrolytic polishing solution in step two is composed of 40% hydrochloric acid, 60% nitric acid, and anhydrous ethanol in a volume ratio of 30mL~50mL:10mL~20mL:130mL~160mL; the temperature of the electrolytic polishing solution during the electrolytic polishing process is not higher than 10℃, and the surface roughness Ra of the polished cylindrical block is ≤0.2μm.

[0010] The above-mentioned method for directional direct diffusion bonding of refractory metal or alloy single crystal materials is characterized in that, during the directional assembly in step four, positions with the same crystal plane index are joined together, the sides of the joint are fixed with high-temperature resistant tape, and the material is placed in a graphite sleeve mold.

[0011] The above-mentioned method for directional direct diffusion bonding of refractory metal or alloy single crystal materials is characterized in that the vacuum diffusion bonding in step four is performed at a vacuum degree not exceeding 5 × 10⁻⁶. -3 The process is carried out in the equipment of Pa, and the heating rate is controlled at 5℃ / min~20℃ / min; when the refractory metal or alloy single crystal material in step one is derived from refractory alloy W and W alloy, the temperature of the vacuum diffusion connection is 1400℃~1700℃; when the refractory metal or alloy single crystal material in step one is derived from refractory alloy Mo and Mo alloy, the temperature of the vacuum diffusion connection is 1100℃~1500℃.

[0012] The above-mentioned method for directional direct diffusion bonding of refractory metal or alloy single crystal materials is characterized in that the bonding rate of the diffusion bonding interface in the refractory metal or alloy welded joint in step four is higher than 99%.

[0013] Compared with the prior art, the present invention has the following advantages: 1. This invention uses slow wire cutting, mechanical grinding and polishing and electrolytic polishing in sequence to remove the oxide layer and stress layer on the surface of refractory metal or alloy single crystal material, and ensures the parallelism of the upper and lower end faces to achieve the surface quality requirements of diffusion bonding. The process is simple and easy to control.

[0014] 2. This invention utilizes an X-ray single-crystal orientation instrument to calibrate specific crystal planes on the sample to be joined, i.e., the polished cylindrical block, thereby realizing the directional assembly of single-crystal materials and laying the foundation for precise orientation in subsequent vacuum diffusion joining.

[0015] 3. This invention employs a vacuum diffusion bonding process, which, through strict control of temperature, pressure, and time, ensures a tight bond between the surfaces of the single-crystal materials to be bonded and efficient closure of the pores at the bonding interface. Solid-state diffusion bonding is carried out below the melting point, resulting in high dimensional accuracy and low residual stress. This process enables the welding and forming of refractory metal or alloy single-crystal materials, producing refractory metal and alloy welded joints with single-crystal microstructure characteristics, good interface bonding with few defects, and a high bonding rate (greater than 99%).

[0016] 4. The weld joints of refractory metals and alloys prepared by solid-phase diffusion bonding in this invention have a welding rate of over 99%, while suppressing the generation of small-angle grain boundaries, recrystallized grains, and impurities at the interface. The grain orientation difference on both sides of the weld joint interface is less than 5°, which meets the requirements of single-crystal materials and is suitable for fields such as nuclear reactors and medical equipment.

[0017] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the directional direct diffusion bonding process of Mo single crystal material in Embodiment 1 of the present invention.

[0019] Figure 2 The image shows a physical picture of the Mo single crystal material in Example 1 of this invention and the orientation deflection angle of the (111) crystal plane.

[0020] Figure 3 These are ultrasonic C-scan images of the diffusion connector interface in the welded joints obtained in Embodiments 1-3 of the present invention.

[0021] Figure 4 The images show scanning electron microscope (SEM) images of the microstructure of the diffusion connector interface in the welded joints obtained in Examples 1-3 of this invention, as well as the grain orientation difference diagrams on both sides of the interface.

[0022] Figure 5 This is a diagram of the interface defects, inclusions, and pores of the diffusion connector obtained in Comparative Example 1 of the present invention. Detailed Implementation

[0023] Example 1 like Figure 1 As shown, this embodiment includes the following steps: Step 1: [The text appears to be incomplete and contains several grammatical errors. A more accurate translation would require the full <111> Preferred-oriented Mo single crystal material was wire-cut into cylindrical blocks with a diameter × height of φ20mm × 5mm. The end face of the cylindrical block was a (111) crystal plane. Then, after hot mounting, the end face of the (111) crystal plane was mechanically polished using an automatic metallographic polishing machine. This included mechanical polishing with SiC sandpaper of 200#, 400#, 800#, 1500#, and 2000# in sequence, and nylon and silk polishing cloths equipped with 2.5μm polishing paste. After mechanical polishing, the parallelism of the upper and lower surfaces was 0.004mm. The material was then ultrasonically cleaned with deionized water and ethanol in sequence and dried. The Mo single crystal material has the following characteristics: <111> Single crystal rods with preferred growth orientation, such as Figure 2 As shown in Figure (a), the orientation deflection angle of the (111) crystal plane is 3.69°, as... Figure 2 As shown in Figure (b); Step 2: Mix 40% hydrochloric acid, 60% nitric acid, and anhydrous methanol in a volume ratio of 30 mL: 20 mL: 150 mL to obtain an electrolytic polishing solution. Then, using stainless steel as the cathode and the cylindrical block polished in Step 1 as the anode, place it in the electrolytic polishing solution for electrolytic polishing to remove the surface oxide film and stress layer. Control the anode and cathode to be parallel, with a vertical distance of 45 mm between their surfaces. The electrolytic polishing voltage is 30 V, the current is 0.5 A, the time is 2 min, and the temperature of the electrolytic polishing solution is 5 °C. Then, perform ultrasonic cleaning with ethanol and acetone in sequence to obtain the polished cylindrical block with a surface roughness Ra = 0.2 μm. Step 3: Use an X-ray single crystal orientation instrument to calibrate the crystal planes of the polished cylindrical block in Step 2. First, calculate the θ angles of the specified crystal planes (110) and (112) to be measured as 20.25° and 36.84° respectively. Then, rotate the sample stage to 20.25° and 36.84° respectively, place the cylindrical block on the receiver scanning bed, open the shutter, and slowly rotate the cylindrical block. When the diffraction intensity reading is 90, calibrate the planes formed by this position on the cylindrical block and the axis of the cylindrical block as planes (110) and (112) respectively. Step 4: Assemble the two cylindrical blocks whose crystal planes were calibrated in Step 3 according to the calibrated crystal planes. Connect the parts with the same crystal plane index and fix the sides of the connection with high-temperature resistant tape. Place the assembled cylindrical blocks in a graphite sleeve mold. Then, place the assembled cylindrical blocks in a vacuum diffusion furnace. When the vacuum degree of the vacuum diffusion connection equipment is 4.1×10-3Pa, turn on the heating and raise the temperature from room temperature to 1000℃ at 20℃ / min and hold for 10min. Then raise the temperature to 1400℃ at 5℃ / min and apply a pressure of 80MPa for vacuum diffusion connection for 2h. After completion, cool the furnace to room temperature and take it out to obtain a refractory metal Mo welded joint.

[0024] According to GJB 1580A-2004 "Ultrasonic Testing Methods for Wrought Metals", the interface of the diffusion connector in the welded joint obtained in this embodiment was subjected to ultrasonic C-scan, and microstructure scanning and grain orientation observation on both sides of the interface were performed. The results are as follows. Figure 3 and Figure 4 As shown. From Figure 3 and 4 It can be seen that the welded joint has single-crystal structure characteristics, the interface welding rate is higher than 99%, there are no obvious pores, and the crystal orientation deflection angle on both sides of the connection interface is less than 0.9°.

[0025] This embodiment has <111> Preferred-oriented Mo single crystal materials can also be in bulk or ingot form.

[0026] Example 2 This embodiment includes the following steps: Step 1: [The text appears to be incomplete and contains several grammatical errors. A more accurate translation would require the full <111> The preferred orientation Mo3Nb (the mass ratio of matrix Mo to alloying element Nb is 3:1) single crystal material was processed into cylindrical blocks with a diameter × height of φ20mm × 5mm by slow wire cutting. The end face of the cylindrical block is (111) crystal plane. Then, after the cylindrical block is hot-mounted, the end face of the (111) crystal plane is mechanically polished by an automatic metallographic polishing machine. This includes mechanical polishing with SiC sandpaper of 200#, 400#, 800#, 1500#, and 2000# in sequence and nylon and silk polishing cloth equipped with 2.5μm particle size polishing paste. After ultrasonic cleaning with deionized water and ethanol in sequence, the block is dried. Step 2: Mix 40% hydrochloric acid, 60% nitric acid, and anhydrous methanol in a volume ratio of 40 mL: 10 mL: 130 mL to obtain an electrolytic polishing solution. Then, using stainless steel as the cathode and the cylindrical block polished in Step 1 as the anode, place it in the electrolytic polishing solution for electrolytic polishing to remove the surface oxide film and stress layer. Control the anode and cathode to be parallel, with a vertical distance of 52 mm between their surfaces. The electrolytic polishing voltage is 20 V, the current is 1 A, the time is 3 min, and the temperature of the electrolytic polishing solution is 8 °C. Then, perform ultrasonic cleaning with ethanol and acetone in sequence to obtain the polished cylindrical block. Step 3: Use an X-ray single crystal orientation instrument to calibrate the crystal planes of the polished cylindrical block in Step 2. First, calculate the θ angles of the specified crystal planes (200) and (310) to be measured as 29.3° and 50.7° respectively. Then, rotate the sample stage to 29.3° and 50.7° respectively, place the cylindrical block on the receiver scanning bed, open the shutter, and slowly rotate the cylindrical block. When the diffraction intensity reading is 81, calibrate the planes formed by this position on the cylindrical block and the planes through the axis of the cylindrical block as (200) and (310) respectively. Step 4: Assemble the two cylindrical blocks whose crystal planes were calibrated in Step 3 according to the calibrated crystal planes, aligning the positions with the same crystal plane index. Secure the sides of the joint with high-temperature resistant tape and place it in a graphite sleeve mold. Then, place the assembled cylindrical blocks in a vacuum diffusion furnace. When the vacuum degree of the vacuum diffusion connection equipment is 4.0 × 10⁻⁶,... - 3 Heating was started at Pa, and the temperature was increased from room temperature to 1000℃ at 20℃ / min and held for 10min. Then the temperature was increased to 1500℃ at 5℃ / min, and a vacuum diffusion connection was performed with a pressure of 40MPa for 2h. After completion, the furnace was cooled to room temperature and the welded joint of refractory alloy Mo3Nb was obtained.

[0027] According to GJB 1580A-2004 "Ultrasonic Testing Methods for Wrought Metals", the interface of the diffusion connector in the welded joint obtained in this embodiment was subjected to ultrasonic C-scan, and microstructure scanning and grain orientation observation on both sides of the interface were performed. The results are as follows. Figure 3 and Figure 4 As shown. From Figure 3 and 4 It can be seen that the welded joint has single-crystal structure characteristics, the interface welding rate is higher than 99%, there are no obvious pores, and the crystal orientation deflection angle on both sides of the connection interface is less than 2.2°.

[0028] In this embodiment, the Mo3Nb single crystal material can also be replaced with a refractory alloy alloyed with W and Mo as the matrix and Re, Hf or Nb alloying elements added, and the mass ratio of the matrix to the alloying elements is 1~30:1. Comparative Example 1 This comparative example includes the following steps: Step 1: [The text appears to be incomplete and contains several grammatical errors. A more accurate translation would require the full <111> The preferred orientation Mo3Nb (the mass ratio of matrix Mo to alloying element Nb is 3:1) single crystal material was processed into cylindrical blocks with a diameter × height of φ20mm × 5mm by slow wire cutting. The end face of the cylindrical block is (111) crystal plane. Then, after the cylindrical block is hot-mounted, the end face of the (111) crystal plane is mechanically polished by an automatic metallographic polishing machine. This includes mechanical polishing with SiC sandpaper of 200#, 400#, 800#, 1500#, and 2000# in sequence and nylon and silk polishing cloth equipped with 2.5μm particle size polishing paste. After ultrasonic cleaning with deionized water and ethanol in sequence, the block is dried. Step 2: Mix 40% hydrochloric acid, 60% nitric acid, and anhydrous methanol in a volume ratio of 40 mL: 10 mL: 130 mL to obtain an electrolytic polishing solution. Then, using stainless steel as the cathode and the cylindrical block polished in Step 1 as the anode, place it in the electrolytic polishing solution for electrolytic polishing to remove the surface oxide film and stress layer. Control the anode and cathode to be parallel, with a vertical distance of 52 mm between their surfaces. The electrolytic polishing voltage is 20 V, the current is 1 A, the time is 3 min, and the temperature of the electrolytic polishing solution is 8 °C. Then, perform ultrasonic cleaning with ethanol and acetone in sequence to obtain the polished cylindrical block. Step 3: Use an X-ray single crystal orientation instrument to calibrate the crystal planes of the polished cylindrical block in Step 2. First, calculate the θ angles of the specified crystal planes (200) and (310) to be measured as 29.3° and 50.7° respectively. Then, rotate the sample stage to 29.3° and 50.7° respectively, place the cylindrical block on the receiver scanning bed, open the shutter, and slowly rotate the cylindrical block. When the diffraction intensity reading is 81, calibrate the planes formed by this position on the cylindrical block and the planes through the axis of the cylindrical block as (200) and (310) respectively. Step 4: Assemble the two cylindrical blocks whose crystal planes were calibrated in Step 3 according to the calibrated crystal planes, aligning the positions with the same crystal plane index. Secure the sides of the joint with high-temperature resistant tape and place it in a graphite sleeve mold. Then, place the assembled cylindrical blocks in a vacuum diffusion furnace. When the vacuum degree of the vacuum diffusion connection equipment is 4.0 × 10⁻⁶,... - 3 Heating was started at Pa, and the temperature was increased from room temperature to 1000℃ at 20℃ / min and held for 10min. Then the temperature was increased to 1050℃ at 5℃ / min, and a pressure of 10MPa was applied for vacuum diffusion bonding for 2h. After completion, the furnace was cooled to room temperature and the welded joint of refractory alloy Mo3Nb was obtained.

[0029] Microstructure scanning was performed on the interface of the diffusion connector in the welded joint obtained in this embodiment, and the results are as follows: Figure 5 As shown. From Figure 5 It can be seen that there are obvious pores and inclusions at the interface of the welded joint.

[0030] Comparing Example 2 of the present invention with Comparative Example 1, it can be seen that welding single crystal materials under the diffusion connection parameters of Example 2 (i.e., the present invention) can yield a welded joint without defects such as pores or inclusions at the interface.

[0031] Example 3 This embodiment includes the following steps: Step 1: [The text appears to be incomplete and contains several grammatical errors. A more accurate translation would require the full <111> The preferred orientation W single crystal material is processed into a cylindrical block with a diameter × height of φ20mm × 5mm by slow wire cutting. The end face of the cylindrical block is the (111) crystal plane. Then, after the cylindrical block is hot-mounted, the (111) crystal plane end face is mechanically polished by an automatic metallographic polishing machine. This includes mechanical polishing with SiC sandpaper of 200#, 400#, 800#, 1500# and 2000# in sequence and nylon and silk polishing cloth equipped with 2.5μm particle size polishing paste. After ultrasonic cleaning with deionized water and ethanol in sequence, it is dried. Step 2: Mix 40% hydrochloric acid, 60% nitric acid, and anhydrous methanol in a volume ratio of 50 mL: 10 mL: 130 mL to obtain an electrolytic polishing solution. Then, using stainless steel as the cathode and the cylindrical block polished in Step 1 as the anode, place it in the electrolytic polishing solution for electrolytic polishing to remove the surface oxide film and stress layer. Control the anode and cathode to be parallel, with a vertical distance of 45 mm between their surfaces. The electrolytic polishing voltage is 25 V, the current is 1 A, the time is 2 min, and the temperature of the electrolytic polishing solution is 7 °C. Then, perform ultrasonic cleaning with ethanol and acetone in sequence to obtain the polished cylindrical block. Step 3: Use an X-ray single crystal orientation instrument to calibrate the crystal planes of the polished cylindrical block in Step 2. First, calculate the θ angles of the specified crystal planes (110) and (200) to be measured as 20.25° and 29.3° respectively. Then, rotate the sample stage to 20.25° and 29.3° respectively, place the cylindrical block on the receiver scanning bed, open the shutter, and slowly rotate the cylindrical block. When the diffraction intensity reading is 90, calibrate the planes formed by this position on the cylindrical block and the axis of the cylindrical block as (110) and (200) respectively. Step 4: Assemble the two cylindrical blocks whose crystal planes were calibrated in Step 3 according to the calibrated crystal planes, aligning the positions with the same crystal plane index. Secure the sides of the joint with high-temperature resistant tape. Place the assembled cylindrical blocks in a graphite sleeve mold, and then place the assembled cylindrical blocks in a vacuum diffusion furnace. The vacuum degree of the vacuum diffusion connection equipment should be 5.0 × 10⁻⁶. - 3 Heating was started at Pa, and the temperature was increased from room temperature to 1000℃ at 20℃ / min and held for 10min. Then the temperature was increased to 1600℃ at 5℃ / min, and a vacuum diffusion connection was performed with a pressure of 20MPa for 2h. After completion, the furnace was cooled to room temperature and the welded joint of refractory metal W was obtained.

[0032] According to GJB 1580A-2004 "Ultrasonic Testing Methods for Wrought Metals", the interface of the diffusion connector in the welded joint obtained in this embodiment was subjected to ultrasonic C-scan, and microstructure scanning and grain orientation observation on both sides of the interface were performed. The results are as follows. Figure 3 and Figure 4 As shown. From Figure 3 and4 It can be seen that the welded joint has single-crystal structure characteristics, the interface welding rate is higher than 99%, there are no obvious pores, and the crystal orientation deflection angle on both sides of the connection interface is less than 1.4°.

[0033] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention in any way. Any simple modifications, alterations, and equivalent changes made to the above embodiments based on the inventive essence shall still fall within the protection scope of the present invention.

Claims

1. A method for directional direct diffusion bonding of refractory metal or alloy single crystal materials, characterized in that, The method includes the following steps: Step 1: [The text appears to be incomplete and contains several grammatical errors. A more accurate translation would require the full <111> Preferred orientation refractory metal or alloy single crystal materials are processed into cylindrical blocks by slow wire cutting, and then the end faces of the cylindrical blocks are ground and polished after hot mounting. Step 2: Mix hydrochloric acid, nitric acid, and methanol to obtain an electrolytic polishing solution. Then, using stainless steel as the cathode and the cylindrical block polished in Step 1 as the anode, place it in the electrolytic polishing solution for electrolytic polishing to remove the surface oxide film and stress layer, obtaining a polished cylindrical block. The voltage of the electrolytic polishing is 20V~30V, the current is 0.5A~1A, and the time is 2min~4min. Step 3: Use an X-ray single crystal orientation instrument to calibrate the crystal planes of the polished cylindrical block in Step 2. First, calculate the θ angle of the specified crystal plane to be measured, and then rotate the cylindrical block until the diffraction intensity reading is greater than 80. Obtain the actual position of the specified crystal plane on the cylindrical block. Calibrate more than two crystal planes for each cylinder to ensure orientation accuracy. Step 4: Assemble the two cylindrical blocks whose crystal planes were calibrated in Step 3 according to the calibrated crystal planes, so that the surfaces to be joined are aligned. Fix them with tape and molds, then place the assembled cylindrical blocks in a vacuum diffusion furnace. After evacuation, heat and pressurize to perform vacuum diffusion joining. After furnace cooling to room temperature, remove the blocks to obtain a refractory metal or alloy welded joint. The vacuum diffusion joining temperature is 1100℃~1700℃, the pressure is 20MPa~80MPa, and the time is 2h. The refractory metal or alloy welded joint has single crystal structure characteristics, good interface welding, and no obvious defects.

2. The method for directional direct diffusion bonding of refractory metal or alloy single crystal materials according to claim 1, characterized in that, The sources of the refractory metal or alloy single crystal material mentioned in step one include: W and Mo refractory metals, and refractory alloys alloyed with W and Mo as the matrix and adding Re, Hf, or Nb alloying elements, and the mass ratio of the matrix to the alloying elements is 1~30:

1. The refractory metal or alloy single crystal material has the following properties: <111> Select single crystal rods, ingots, or bulk materials with the preferred growth orientation, and the orientation deflection angle of the (111) crystal plane shall not exceed 8°.

3. The method for directional direct diffusion bonding of refractory metal or alloy single crystal materials according to claim 1, characterized in that, The diameter of the cylindrical block in step one is more than 20 mm and the end face is (111) crystal plane. The cylindrical block after hot mounting is mechanically polished by an automatic metallographic polishing machine to ensure that the parallelism of the upper and lower surfaces is less than 0.005 mm.

4. The method for directional direct diffusion bonding of refractory metal or alloy single crystal materials according to claim 1, characterized in that, The electrolytic polishing solution in step two is composed of 40% hydrochloric acid, 60% nitric acid, and anhydrous ethanol in a volume ratio of 30mL~50mL: 10mL~20mL: 130mL~160mL; the temperature of the electrolytic polishing solution during the electrolytic polishing process is not higher than 10℃, and the surface roughness Ra of the polished cylindrical block is ≤0.2μm.

5. The method for directional direct diffusion bonding of refractory metal or alloy single crystal materials according to claim 1, characterized in that, During the directional assembly described in step four, positions with the same crystal plane index are joined together, and the sides of the joint are fixed with high-temperature resistant tape and placed in a graphite sleeve mold.

6. The method for directional direct diffusion bonding of refractory metal or alloy single crystal materials according to claim 1, characterized in that, The vacuum diffusion connection described in step four is performed under a vacuum level not exceeding 5 × 10⁻⁶. -3 The process is carried out in the equipment of Pa, and the heating rate is controlled at 5℃ / min~20℃ / min; when the refractory metal or alloy single crystal material in step one is derived from refractory alloy W and W alloy, the temperature of the vacuum diffusion connection is 1400℃~1700℃; when the refractory metal or alloy single crystal material in step one is derived from refractory alloy Mo and Mo alloy, the temperature of the vacuum diffusion connection is 1100℃~1500℃.

7. The method for directional direct diffusion bonding of refractory metal or alloy single crystal materials according to claim 1, characterized in that, The diffusion bonding interface bonding rate in the refractory metal or alloy welded joint described in step four is higher than 99%.

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