A method for joining W / CuCrZr alloys

Abstract

This invention relates to a method for joining W / CuCrZr alloys. CNTs and a dispersant are added to a copper plating solution and ultrasonically dispersed to obtain a copper plating solution with uniformly dispersed CNTs. A W plate is then subjected to CNT-Cu co-deposition in the copper plating solution with uniformly dispersed CNTs, followed by annealing to obtain a W plate with a Cu / CNT composite film deposited on its surface. The W plate with the Cu / CNT composite film and a CuCrZr alloy plate are placed face-to-face, and pressure is applied to the resulting composite plate for high-temperature heating and joining to obtain a W / CuCrZr alloy connector. The joining strength can reach 201.8 MPa, and the thermal conductivity of the connector is approximately 250 W / (m·K). The joining method provided by this invention is simple and convenient, has high joining efficiency, low production cost, and is easy to implement in industrial applications.

Description

Technical Field

[0001] This invention relates to the field of dissimilar metal joining technology, specifically to a joining method for W / CuCrZr alloys. Background Technology

[0002] During the operation of a nuclear fusion reactor, a high-density ion flow (~10) is generated. 24 m -2 / s), high temperature (500~3200℃), thermal shock (10~20MW / m 2 Materials directly surrounding high-temperature plasma, such as those with high-flux neutrons (14 MeV), face extremely demanding service conditions. Tungsten, with its high melting point and excellent strength and thermal conductivity at high temperatures, along with low physical sputtering rate, non-reactive hydrogen, and extremely low hydrogen retention, is currently the preferred plasma-facing material in fusion reactors. Plasma-facing materials need to be connected to heat sinks to rapidly transfer the heat load from their surfaces. The heat sinks must also withstand periodic high heat loads and high-dose neutron irradiation; CuCrZr alloys have been used as heat sinks in the modern ITER tokamak device. Tungsten plasma-facing materials need to be connected to CuCrZr alloy heat sinks.

[0003] Current research on joining tungsten-based materials and CuCrZr alloys mainly focuses on improving the mechanical properties of the joiners, lacking research on their thermal conductivity. For example, patent CN111347147A discloses a method for hot isostatic pressing (HIP) joining tungsten and CuCrZr alloys using a pure iron interlayer, achieving a maximum shear strength of 200 MPa. However, the introduction of the pure iron interlayer leads to magnetic properties in the joiner and introduces a brittle phase at the interface, resulting in a complex interface and higher interfacial thermal resistance. Patent CN112359391A discloses a joining method using ODS-W with tungsten surface nano-activation technology to join CuCrZr alloys, achieving a shear strength of 201 MPa. However, this joining technology may introduce a brittle phase at the interface. The large specific surface area generated at the joint leads to an increase in the interfacial thermal resistance of the connector, which has an adverse effect on the thermal conductivity of the connector. In addition, since there is little attention paid to the thermal conductivity of the connector between tungsten-based materials and CuCrZr alloys, for reference, the patent document CN107740006A discloses a method for preparing a Cu / W composite material using a tungsten fiber layer and a Cu plate, and the thermal conductivity of the resulting composite material is 210 W / (m·K). The tungsten-copper gradient composite material prepared by the patent document CN115178740A also has a thermal conductivity of about 200 W / (m·K).

[0004] Given the high temperatures, extremely high thermal shocks, and heat loads encountered during fusion reactor operation, improving the thermal conductivity of the W-CuCrZr alloy connector is crucial for enhancing connector performance and ensuring stable operation. Existing technologies for joining tungsten-based materials and CuCrZr alloys have paid relatively little attention to the thermal conductivity of the connectors, and the thermal interface introduced during the joining process is also a significant factor negatively impacting the connector's thermal conductivity. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of the prior art and provide a joining method for W / CuCrZr alloys. The joining method provided by this invention can realize W / CuCrZr alloy connectors with both high joining strength and high thermal conductivity. The joining method provided by this invention is simple and convenient, has high joining efficiency, low production cost, and is easy to implement in industrial applications.

[0006] To achieve the above-mentioned objectives, the present invention provides the following technical solution:

[0007] The present invention provides a method for joining W / CuCrZr alloys, comprising the following steps:

[0008] 1) Add carbon nanotubes (CNTs) and a dispersant to the copper plating solution, with a CNT mass fraction of 1-5 g / L, and then perform ultrasonic dispersion to obtain a copper plating solution with uniformly dispersed CNTs.

[0009] 2) The W plate is subjected to CNT-Cu co-deposition in the copper plating solution in which CNTs are uniformly dispersed, and then annealed at a temperature of 400-980℃ to obtain a W plate with a Cu / CNT composite film deposited on its surface.

[0010] 3) The surfaces of the W plate with Cu / CNT composite film deposited on its surface and the CuCrZr alloy plate to be joined are arranged opposite each other. Pressure is applied to the resulting composite plate, and high-temperature heating is performed to join them. The applied pressure is 80-130 MPa and the temperature is 800-1050℃ to obtain the W / CuCrZr alloy connector.

[0011] Preferably, the CNT is a hydroxylated multi-walled carbon nanotube with an outer diameter of 30-50 nm, an inner diameter of 5-12 nm, a length of less than 10 μm, a hydroxyl content of 0.70-1.50 wt.%, and a purity of greater than 95%.

[0012] Preferably, the dispersant used in step 1) is octadecyltrimethylammonium bromide (OTAB), and its mass fraction in the copper plating solution in which CNTs are uniformly dispersed is 0.1 to 1 g / L.

[0013] Preferably, the composition and content of the copper plating solution in step 1) are as follows: per liter of copper plating solution, there are 25-35g CuSO4·5H2O, 45-55g (NH4)2SO4, 20-26g citric acid, and 0.05-0.2g C7H5O3NS (saccharin).

[0014] Preferably, the total ultrasonic dispersion time in step 1) is 0.5 to 3 hours, and cooling is performed for 30 to 60 seconds after every 3 to 5 minutes of ultrasonication to avoid overheating of the copper plating solution.

[0015] Preferably, before the CNT-Cu co-deposition in step 2), the W plate is subjected to surface treatment, the surface treatment process including grinding and polishing and ultrasonic cleaning.

[0016] Preferably, the CNT-Cu co-deposition process in step 2) is performed using a pulsed power supply for electroplating, with a pulse width of 100–500 μs, a pulse period of 1–10 ms, an electroplating time of 3–10 min, and a current density of 1–5 A / dm³. 2 .

[0017] Preferably, in step 2), the annealing is carried out in a hydrogen atmosphere for 1 to 4 hours.

[0018] Preferably, before setting the surfaces of the W plate with the Cu / CNT composite film deposited on its surface and the CuCrZr alloy plate to be joined together in step 3), the CuCrZr alloy plate is subjected to surface treatment, the surface treatment process including grinding and polishing and ultrasonic cleaning.

[0019] Preferably, the surface of the W plate with a Cu / CNT composite film is the Cu / CNT composite film surface that has undergone surface treatment, and the surface of the CuCrZr alloy plate is the surface-treated surface.

[0020] Preferably, the method of applying pressure to the composite plate is to fix the composite plate with a high-temperature resistant stainless steel clamp and apply pressure to the composite plate through the clamp bolts.

[0021] Preferably, the high-temperature heating is carried out in a hydrogen atmosphere, and the holding time is 1 to 4 hours.

[0022] This invention provides a method for joining W / CuCrZr alloys. CNTs and a dispersant are added to a copper plating solution and ultrasonically dispersed to obtain a copper plating solution with uniformly dispersed CNTs. A W plate is then subjected to CNT-Cu co-deposition in the copper plating solution with uniformly dispersed CNTs, followed by annealing to obtain a W plate with a Cu / CNT composite film deposited on its surface. The W plate with the Cu / CNT composite film deposited on its surface and a CuCrZr alloy plate are placed face-to-face, pressure is applied to the resulting composite plate, and high-temperature heating is performed to join them, resulting in a W / CuCrZr alloy connector. This invention utilizes CNT-Cu co-deposition, annealing, and diffusion bonding between the W plate and the CuCrZr alloy plate to achieve a high-strength and high-thermal-conductivity connection between the W plate and the CuCrZr alloy plate. Furthermore, the thickness of the Cu / CNT composite interlayer is only 0.4-1 μm, much thinner than the CuCrZr alloy plate itself, and will not affect the properties of the CuCrZr alloy plate. The W / CuCrZr alloy connector prepared using the joining method provided in this invention incorporates CNTs at the interface for enhanced bonding, which improves the bonding strength and thermal conductivity of the connector. The bonding strength reaches 201.8 MPa, approximately 1.4-2 times that of a direct W / CuCrZr alloy connector. Furthermore, the introduction of high thermal conductivity CNTs enhances the connector's thermal conductivity without the issue of increased surface area and thermal resistance caused by surface nano-activation. The resulting connector exhibits a thermal conductivity of approximately 250 W / (m·K), about 25% higher than the thermal conductivity of a direct W / CuCrZr alloy connector (approximately 200 W / (m·K)), and also surpasses the thermal conductivity of tungsten and copper alloy composites obtained using existing production technologies. The W and CuCrZr alloy bonding interface obtained by this invention is smooth and tightly bonded, with no significant Cu dewetting. The introduction of CNTs into the W / CuCrZr alloy connector does not introduce unnecessary properties (such as magnetism). The joining method provided in this invention is simple, convenient, highly efficient, low-cost, and easily applicable to industrial applications. Attached Figure Description

[0023] Figure 1 The diagram shows the fixtures used, where 1 is a nut, 2 is a high-temperature resistant stainless steel fixing plate, 3 is a partition plate, the main component of which is boron nitride, and 4 is a bolt.

[0024] Figure 2 The image shows a physical copy of the W / CuCrZr alloy connector prepared in Example 1.

[0025] Figure 3 The image shows the interface SEM image of the W / CuCrZr alloy connector prepared in Example 1.

[0026] Figure 4The stress-strain curves of the shear test of the W / CuCrZr alloy connector prepared in Example 1 are shown.

[0027] Figure 5 The stress-strain curve of the shear test of the W / CuCrZr alloy connector prepared in Example 2 is shown.

[0028] Figure 6 The stress-strain curve of the shear test of the W / CuCrZr alloy connector prepared in Example 3 is shown.

[0029] Figure 7 The thermal conductivity curves of the W / CuCrZr alloy connector prepared in Example 1 at different temperatures are shown.

[0030] Figure 8 This is a TEM image of the interface of the W / CuCrZr alloy connector prepared in Example 1. Detailed Implementation

[0031] The technical solutions of this invention will be clearly and completely described below with reference to the embodiments thereof. Obviously, the described embodiments are only a part of the embodiments of this invention, and not all of them. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0032] In the examples, CNTs were selected as hydroxylated multi-walled carbon nanotubes with an outer diameter of 30-50 nm, an inner diameter of 5-12 nm, a length of less than 10 μm, a hydroxyl content of 0.70-1.50 wt.%, and a purity of greater than 95%.

[0033] Example 1

[0034] Step 1: Place 28g CuSO4·5H2O, 50g (NH4)2SO4, 21g citric acid, and 0.1g / L C7H5O3NS in a beaker, add deionized water to make up to 1L, then add a cleaned stir bar and place it on a magnetic stirrer to stir for 12h to obtain copper plating solution.

[0035] 2g of CNT and 0.5g of OTAB were placed in the copper plating solution and ultrasonically dispersed in an ultrasonic disperser with a rated power of 1200W for 1 hour. The solution was cooled for 30 seconds after every 5 minutes of ultrasonic dispersion to obtain a copper plating solution with uniformly dispersed CNTs.

[0036] Step 2: Polish the W plate and CuCrZr alloy plate (30mm×10mm×2mm) sequentially with sandpaper of grades 100#, 150#, 240#, 400#, 600#, 800#, 1000#, 1200#, 1500#, and 2000#, so that one side of the W plate and CuCrZr alloy plate has a mirror finish. Then, ultrasonically clean them in acetone, isopropanol, and methanol for 15 minutes in sequence. After cleaning, dry them with high-pressure nitrogen and dry them in a vacuum drying oven at 30℃ for 12 hours.

[0037] The surface-treated W plate was placed in the copper plating solution containing uniformly dispersed CNTs for pulse electrodeposition. A pure copper plate with dimensions of 30mm × 30mm × 2mm was used as the anode, and the surface-treated W plate was used as the cathode. The surface-treated surface of the W plate was positioned opposite the copper plate at a distance of 3cm. During the pulse electrodeposition process, the pulse width was 200μs, the pulse period was 1ms, and the current density was 1.7A / dm³. 2 The deposition time was 5 minutes. After that, the W plate was removed, rinsed with deionized water, and stored in a vacuum drying oven to prevent oxidation of the Cu / CNT composite film.

[0038] The W plate after CNT-Cu co-deposition was placed in a tube annealing furnace and annealed in a high-purity H2 atmosphere at a temperature of 400℃ for 3 hours to obtain a W plate with a Cu / CNT composite film on the surface.

[0039] Step 3: Position the Cu / CNT composite film side of the W plate (surface treated with Cu / CNT composite film) opposite the surface treated side of the CuCrZr alloy plate, and then proceed as follows: Figure 1 The clamp is used to fix the W / CuCrZr composite plate between two stainless steel fixing plates (2), and a partition plate (3) with boron nitride as the main component is inserted between the stainless steel fixing plate and the composite plate to prevent diffusion connection between the stainless steel fixing plate and the composite plate at high temperature. The clamp is locked with bolts (4) and nuts (1) and pressure is applied to the composite plate, with a pressure of 106 MPa. The W / CuCrZr composite plate fixed with the clamp is placed in a tubular annealing furnace and heated at 980°C for 3 hours in a high-purity H2 atmosphere to obtain a W / CuCrZr alloy connector. The actual picture of the obtained W / CuCrZr alloy connector is shown below. Figure 2 As shown.

[0040] Testing and Characterization:

[0041] The interface SEM of the W / CuCrZr alloy connector obtained in Example 1 is shown below. Figure 3 As shown. By Figure 3It can be seen that the interface between W and CuCrZr alloy is tightly bonded, with no obvious gaps or pores.

[0042] The stress-strain curve of the W / CuCrZr alloy connector obtained in Example 1 is shown in the figure. Figure 4 As shown, by Figure 4 It can be seen that the shear strength of the W / CuCrZr alloy connector is as high as 201.8 MPa.

[0043] The thermal conductivity of the W / CuCrZr alloy connector obtained in Example 1 was tested at different temperatures. A comparative sample without CNT-Cu co-deposition and directly bonded was also prepared for thermal conductivity testing. The thermal conductivity versus temperature curves are shown below. Figure 7 As shown, by Figure 7 It can be seen that the thermal conductivity of the W / CuCrZr alloy connector obtained by the method provided in this invention is increased by about 250 W / (m·K), which is significantly improved by about 25% compared with the thermal conductivity of the W / CuCrZr alloy direct connector (about 200 W / (m·K)).

[0044] The interface TEM image of the W / CuCrZr alloy connector obtained in Example 1 is shown below. Figure 8 As shown.

[0045] Example 2

[0046] Step 1: Place 25g CuSO4·5H2O, 45g (NH4)2SO4, 20g citric acid, and 0.05g / L C7H5O3NS in a beaker, add deionized water to make up to 1L, then add a cleaned stir bar and place it on a magnetic stirrer to stir for 12h to obtain copper plating solution.

[0047] 1g of CNT and 0.1g of OTAB were placed in the copper plating solution and ultrasonically dispersed for 0.5h in an ultrasonic disperser with a rated power of 1200W. The solution was cooled for 45s after every 4min of ultrasonic dispersion to obtain a copper plating solution with uniformly dispersed CNTs.

[0048] Step 2: Polish the W plate and CuCrZr alloy plate (30mm×10mm×2mm) sequentially with sandpaper of grades 100#, 150#, 240#, 400#, 600#, 800#, 1000#, 1200#, 1500#, and 2000#, so that one side of the W plate and CuCrZr alloy plate has a mirror finish. Then, ultrasonically clean them in acetone, isopropanol, and methanol for 15 minutes in sequence. After cleaning, dry them with high-pressure nitrogen and dry them in a vacuum drying oven at 30℃ for 12 hours.

[0049] The surface-treated W plate was placed in the copper plating solution containing uniformly dispersed CNTs for pulse electrodeposition. A pure copper plate with dimensions of 30mm × 30mm × 2mm was used as the anode, and the surface-treated W plate was used as the cathode. The surface-treated surface of the W plate was positioned opposite the copper plate at a distance of 3cm. During the pulse electrodeposition process, the pulse width was 100μs, the pulse period was 5ms, and the current density was 1A / dm³. 2 The deposition time was 10 minutes. After that, the W plate was removed, rinsed with deionized water, and stored in a vacuum drying oven to prevent oxidation of the Cu / CNT composite film.

[0050] The W plate after CNT-Cu co-deposition was placed in a tube annealing furnace and annealed in a high-purity H2 atmosphere at a temperature of 700℃ for 1 hour to obtain a W plate with a Cu / CNT composite film on the surface.

[0051] Step 3: Position the Cu / CNT composite film side of the W plate (surface treated with Cu / CNT composite film) opposite the surface treated side of the CuCrZr alloy plate, and then proceed as follows: Figure 1 The clamps shown are used to fix the composite plate, and a pressure of 80 MPa is applied to the composite plate using the same method as in Example 1. Then, the W / CuCrZr composite plate fixed with the clamps is placed in a tubular annealing furnace and subjected to high-temperature heating at 1050°C for 1 hour in a high-purity H2 atmosphere to obtain a W / CuCrZr alloy connector.

[0052] Testing and Characterization:

[0053] The stress-strain curve of the W / CuCrZr alloy connector obtained in Example 2 is shown in the figure. Figure 5 As shown, by Figure 5 It can be seen that the shear strength of the W / CuCrZr alloy connector is as high as 140MPa.

[0054] Example 3

[0055] Step 1: Place 35g CuSO4·5H2O, 55g (NH4)2SO4, 26g citric acid, and 0.2g C7H5O3NS in a beaker, add deionized water to make up to 1L, then add a cleaned stir bar and place it on a magnetic stirrer to stir for 12h to obtain copper plating solution.

[0056] 5g of CNT and 1g of OTAB were placed in the copper plating solution and ultrasonically dispersed for 3 hours in an ultrasonic disperser with a rated power of 1200W. The solution was cooled for 60 seconds after every 3 minutes of ultrasonic dispersion to obtain a copper plating solution with uniformly dispersed CNTs.

[0057] Step 2: Polish the W plate and CuCrZr alloy plate (30mm×10mm×2mm) sequentially with sandpaper of grades 100#, 150#, 240#, 400#, 600#, 800#, 1000#, 1200#, 1500#, and 2000#, so that one side of the W plate and CuCrZr alloy plate has a mirror finish. Then, ultrasonically clean them in acetone, isopropanol, and methanol for 15 minutes in sequence. After cleaning, dry them with high-pressure nitrogen and dry them in a vacuum drying oven at 30℃ for 12 hours.

[0058] The surface-treated W plate was placed in the copper plating solution containing uniformly dispersed CNTs for pulse electrodeposition. A pure copper plate with dimensions of 30mm × 30mm × 2mm was used as the anode, and the surface-treated W plate was used as the cathode. The surface-treated surface of the W plate was positioned opposite the copper plate at a distance of 3cm. During the pulse electrodeposition process, the pulse width was 500μs, the pulse period was 10ms, and the current density was 5A / dm³. 2 The deposition time was 3 minutes. After that, the W plate was removed, rinsed with deionized water, and stored in a vacuum drying oven to prevent oxidation of the Cu / CNT composite film.

[0059] The W plate after CNT-Cu co-deposition was placed in a tube annealing furnace and annealed in a high-purity H2 atmosphere at a temperature of 980℃ for 4 hours to obtain a W plate with a Cu / CNT composite film on the surface.

[0060] Step 3: Position the Cu / CNT composite film side of the W plate (surface treated with Cu / CNT composite film) opposite the surface treated side of the CuCrZr alloy plate, and then proceed as follows: Figure 1 The clamps shown are used to fix the composite plate, and a pressure of 130 MPa is applied to the composite plate using the same method as in Example 1. Then, the W / CuCrZr composite plate fixed with the clamps is placed in a tubular annealing furnace and subjected to high-temperature heating at 800°C for 4 hours in a high-purity H2 atmosphere to obtain a W / CuCrZr alloy connector.

[0061] Testing and Characterization:

[0062] The stress-strain curve of the W / CuCrZr alloy connector obtained in Example 3 is shown in the figure. Figure 6 As shown, by Figure 6 It can be seen that the shear strength of the W / CuCrZr alloy connector is as high as 135 MPa.

[0063] The results of the examples show that when W and CuCrZr alloys are joined using the joining method provided by the present invention, the shear strength of the resulting joint can reach up to 201.8 MPa, and the thermal conductivity is about 250 W / (m·K), which is about 25% higher than that of the W / CuCrZr direct joint, and the interface connection is tight.

[0064] The technical solutions disclosed and proposed in this invention can be implemented by those skilled in the art by appropriately modifying the conditions and routes, etc. Although the methods and preparation techniques of this invention have been described through preferred embodiments, those skilled in the art can obviously modify or recombine the methods and technical routes described herein without departing from the content, spirit, and scope of this invention to achieve the final preparation technique. It should be particularly noted that all similar substitutions and modifications are obvious to those skilled in the art and are considered to be included within the spirit, scope, and content of this invention.

Claims

1. A method for joining W / CuCrZr alloys, characterized in that, Includes the following steps: 1) Add carbon nanotubes (CNTs) and a dispersant to the copper plating solution, with a CNT mass fraction of 1-5 g / L, and then perform ultrasonic dispersion to obtain a copper plating solution with uniformly dispersed CNTs. 2) The W plate is subjected to CNT-Cu co-deposition in the copper plating solution in which CNTs are uniformly dispersed, and then annealed at a temperature of 400-980℃ to obtain a W plate with a Cu / CNT composite film deposited on its surface. 3) The surfaces of the W plate with Cu / CNT composite film deposited on its surface and the CuCrZr alloy plate to be joined are arranged opposite each other. Pressure is applied to the resulting composite plate, and high-temperature heating is performed to join them. The applied pressure is 80-130 MPa and the temperature is 800-1050℃ to obtain the W / CuCrZr alloy connector.

2. The joining method of W / CuCrZr alloy as described in claim 1, characterized in that, CNTs are hydroxylated multi-walled carbon nanotubes with an outer diameter of 30-50 nm, an inner diameter of 5-12 nm, a length of less than 10 μm, a hydroxyl content of 0.70-1.50 wt.%, and a purity greater than 95%.

3. The joining method of W / CuCrZr alloy as described in claim 1, characterized in that, The dispersant used in step 1) is octadecyltrimethylammonium bromide (OTAB), and its mass fraction in the copper plating solution in which CNTs are uniformly dispersed is 0.1 to 1 g / L.

4. The joining method of W / CuCrZr alloy as described in claim 1, characterized in that, The composition and content of the copper plating solution are as follows: per liter of copper plating solution, there are 25-35g CuSO4·5H2O, 45-55g (NH4)2SO4, 20-26g citric acid, and 0.05-0.2g C7H5O3NS.

5. The joining method of W / CuCrZr alloy as described in claim 1, characterized in that, Step 1) The total ultrasonic dispersion time is 0.5 to 3 hours. After every 3 to 5 minutes of ultrasonication, the solution is cooled for 30 to 60 seconds to avoid overheating of the copper plating solution.

6. The joining method of W / CuCrZr alloy as described in claim 1, characterized in that, Step 2) The CNT-Cu co-deposition process uses a pulsed power supply for electroplating, with a pulse width of 100–500 μs, a pulse period of 1–10 ms, an electroplating time of 3–10 min, and a current density of 1–5 A / dm³. 2 .

7. The joining method of W / CuCrZr alloy as described in claim 1, characterized in that, In step 2), annealing is carried out in a hydrogen atmosphere for 1 to 4 hours.

8. The joining method of W / CuCrZr alloy as described in claim 1, characterized in that, The method of applying pressure to the composite plate is to fix the composite plate with a high-temperature resistant stainless steel clamp and apply pressure to the composite plate through the clamp bolts.

9. The joining method of W / CuCrZr alloy as described in claim 1, characterized in that, Step 3) The high-temperature heating connection is carried out in a hydrogen atmosphere, and the holding time is 1 to 4 hours.

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