A method for preparing a refractory metal / copper alloy double-layer composite material

Abstract

The application provides a preparation method of a refractory metal / copper alloy double-layer composite material, which comprises the following steps: roughening the surface of a plate of refractory metal to be coated with copper by machining, and performing heat treatment under a protective atmosphere; placing the plate after the heat treatment into a mold, and sequentially laying electrolytic copper powder and a copper plate on the surface of the plate; heating and heat-insulating the mold under a protective atmosphere, and then replacing the protective atmosphere; after the first temperature rising and heat-insulating, closing the gas outlet and the gas inlet, the first temperature falling, the second temperature rising and heat-insulating, and the second temperature falling; and demolding. By using the electrolytic copper powder+copper plate composite laying, the multi-section heat-insulating and temperature rising and falling processes, and the segmented switching of hydrogen / argon protection, the gas at the refractory metal / copper interface is effectively discharged, the formation of pores on the interface is avoided, and the double-layer composite material with a clean interface and dense combination is obtained.

Description

Technical Field

[0001] This invention relates to the field of powder metallurgy technology, specifically to a method for preparing a refractory metal / copper alloy bilayer composite material. Background Technology

[0002] Refractory metals such as tungsten and molybdenum possess characteristics such as high melting points, low coefficients of thermal expansion, excellent thermal shock resistance, and high-temperature strength, while copper exhibits superior thermal and electrical conductivity. The combination of tungsten, molybdenum, and copper to form bilayer or multilayer composite materials achieves a synergistic effect of low expansion and high thermal conductivity, making them key materials for high-power electronic components, nuclear fusion devices, and aerospace applications.

[0003] Currently, the main methods for preparing tungsten / copper or molybdenum / copper bilayer composites include high-temperature copper cladding and thermopressed diffusion welding. The traditional high-temperature copper cladding method involves directly melting copper onto a tungsten / molybdenum substrate to form the composite. In this method, when the molten copper has insufficient wettability on the tungsten / molybdenum substrate, pores and un-copper-permeated areas easily form at the interface, leading to microscopic defects that severely affect the material's thermal conductivity and bonding strength. Thermopressed diffusion welding requires applying mechanical pressure to promote interfacial atomic diffusion, but this method is poorly suited to complex shapes, and refractory metals are prone to grain growth at high temperatures, resulting in decreased mechanical properties. Furthermore, the pressurization equipment is complex and costly, making it unsuitable for large-scale production. In addition, most existing preparation processes use a single atmosphere for continuous protection—while hydrogen has good reducing properties, hydrogen atoms may penetrate the metal lattice at high temperatures, causing hydrogen embrittlement; argon and nitrogen, although inert, cannot effectively reduce interfacial oxides. Existing technologies fail to fully utilize atmosphere switching to synergistically address the problems of interfacial oxidation and gas residue.

[0004] In summary, in existing technologies, pores and bonding defects easily form at the interface between refractory metals and copper in composite materials. These interfacial pores significantly reduce the thermal conductivity, mechanical strength, and service reliability of the material, representing a core technological bottleneck restricting the engineering applications of such materials. Furthermore, existing methods for preparing tungsten / copper or molybdenum / copper bilayer composites have failed to address the problem of interfacial pores in composite materials, resulting in interfacial bonding quality that does not meet market demands.

[0005] In view of this, the present invention is hereby proposed. Summary of the Invention

[0006] This invention provides a method for preparing a refractory metal / copper alloy bilayer composite material. By using a composite layering of copper powder and copper plate, a multi-stage heat preservation and heating / cooling process, and segmented switching of protective atmospheres such as hydrogen / argon, the gas at the refractory metal / copper interface is effectively discharged, avoiding the formation of pores at the interface, and obtaining a clean interface and densely bonded refractory metal / copper alloy bilayer composite material to meet market demand.

[0007] To achieve the above objectives, the present invention employs the following technical solution: This invention provides a method for preparing a refractory metal / copper alloy bilayer composite material, which includes the following steps: The surface of the refractory metal plate to be coated with copper is machined to roughen and then heat-treated under a protective atmosphere. The heat-treated plate is placed in a mold, and electrolytic copper powder and copper plate are sequentially laid on the surface of the plate. The mold is heated and kept at a temperature under a protective atmosphere, and then the protective atmosphere is changed. After the first heating and holding, the outlet and inlet are closed. After the first cooling, argon gas is introduced. After the second heating and holding, the second cooling is performed. Demolding.

[0008] The preparation method provided by this invention employs a composite structure of copper powder and copper plate. Electrolytic copper layers serve as a transition buffer layer, and their porous structure enhances the wettability of molten copper on the surface of refractory metals and adsorbs trace impurities at the interface. Simultaneously, the copper plate provides the thickness of the main copper coating, avoiding the problems of poor dimensional accuracy and low density caused by sintering shrinkage when using only copper powder. The capillary force formed by the copper powder layer during the melting and infiltration process helps to evenly spread the molten copper on the surface of the refractory metal. This invention overcomes the limitations of traditional single-atmosphere protection by changing the protective atmosphere, employing an asymmetric atmosphere control strategy of "hydrogen-argon-sealed-argon." It also utilizes multi-stage heat preservation and heating / cooling processes. The combination of these two methods allows for the removal of residual gases, elimination of interfacial porosity, and densification of the interface.

[0009] In one specific implementation, the step of roughening the surface of the refractory metal plate to be coated with copper and then heat-treating it under a protective atmosphere includes the following steps: The roughness standard is a roughness of 1.5-6.0 μm, the protective atmosphere is hydrogen, the heat treatment temperature is 1150-1350℃, and the heat treatment holding time is 30-120 min.

[0010] In this invention, the roughness is set to less than 6.0 μm. This is because during the machining process of refractory metals, an oxide layer and a work-hardened layer inevitably form on the surface, while residual stress is generated. If the surface roughness of the refractory metal plate is too large (Ra greater than or equal to 6.0 μm), it will lead to uneven thickness when electrolytic copper powder is laid, and the flow of copper liquid will be obstructed during melting and infiltration, easily forming local un-infiltrated areas. If the roughness is too small (Ra less than 1.5 μm), the processing cost will increase, and the improvement on the interfacial bonding strength will be limited. This invention limits the roughness to less than 6.0 μm, which can ensure the mechanical interlocking effect of the interfacial bonding and also take into account the processing economy.

[0011] Meanwhile, the present invention also selected hydrogen as a protective atmosphere. Hydrogen atmosphere heat treatment is a key means to remove oxides from the surface of refractory metals. Hydrogen can react with WO3 and MoO3 at high temperature to generate metallic elements and water vapor. At the same time, high temperature holding can release residual stress.

[0012] In one specific implementation scheme, placing the heat-treated plate in a mold and sequentially coating the surface of the plate with electrolytic copper powder and a copper plate includes the following steps: The standard for laying the electrolytic copper powder is to lay it evenly and flat, with a thickness of 0.5-1mm.

[0013] In one specific feasible implementation, the electrolytic copper powder has a particle size of 200-400 mesh and a purity of ≥99.5%. The copper plate is one or a combination of two of oxygen-free copper plates and pure copper plates, with a thickness of 1-5mm.

[0014] This invention limits the thickness of the electrolytic copper powder to 0.5-1 mm. If the thickness is less than 0.5 mm, the electrolytic copper powder layer cannot form a continuous transition buffer structure, limiting its capillary flow effect on molten copper. If the thickness exceeds 1 mm, the self-sintering shrinkage of the electrolytic copper powder layer is too large, affecting the dimensional accuracy and density of the copper-clad layer. Simultaneously, this invention also limits the particle size of the electrolytic copper powder to 200-400 mesh. Electrolytic copper powder within this particle size range has suitable bulk density and flowability, ensuring uniformity when spreading the electrolytic copper powder and forming interconnected pores during sintering, providing capillary channels for molten copper. This invention further specifies that electrolytic copper powder is first laid on the surface of the plate, and then a copper plate is laid on top of the electrolytic copper powder. This arrangement creates a porous transition layer on the surface of the refractory metal. When the copper plate melts, the electrolytic copper powder layer guides the molten copper evenly to the surface of the refractory metal through capillary action, improving the wettability of the molten copper to tungsten and molybdenum, while simultaneously absorbing trace impurities and residual gases at the interface. The copper plate of this invention has a thickness of 1-5 mm, providing sufficient thickness for the main copper cladding and avoiding defects such as large dimensional deviations and low density caused by sintering shrinkage when using only copper powder. Furthermore, graphite templates are used because they have good high-temperature chemical stability, do not react with the plate, and are easy to demold.

[0015] In one specific implementation, heating and holding the mold in a protective atmosphere, followed by changing the protective atmosphere, includes the following steps: Heat the mold to 780-850 degrees Celsius under a hydrogen protective atmosphere and hold for 1-3 hours, then replace the protective atmosphere with argon.

[0016] In this invention, the electrolytic copper powder is heated to 780-850°C under a hydrogen protective atmosphere. This temperature range is lower than the melting point of copper (1083°C). Holding the temperature within this range allows for pre-sintering of the electrolytic copper powder, forming a porous framework with a certain strength. Simultaneously, it promotes interfacial sparking between the electrolytic copper powder and the refractory metal plate. If the temperature is below 780°C, the sintering activity of the electrolytic copper powder is insufficient, making it difficult to form an effective porous transition layer. If the temperature is above 830°C, the electrolytic copper powder undergoes over-sintering, leading to a decrease in porosity and affecting the subsequent capillary penetration of the copper liquid. The holding time is limited to 1-3 hours. Too short a holding time will result in insufficient pre-sintering, increased energy consumption, and potential coarsening of the W / Mo grains. Furthermore, this invention switches the protective atmosphere after the holding time. This is because hydrogen has strong reducing properties, which can continuously reduce trace oxides (such as CuO, WO3, and MoO3) on the surface of the refractory metal, electrolytic copper powder, and copper plate during heating, creating a clean surface condition for subsequent interfacial bonding. After the heating and holding period is complete (after the reduction reaction has fully occurred), the protective atmosphere is switched to argon. This is to prevent hydrogen atoms from penetrating into the metal lattice and causing hydrogen embrittlement during the subsequent high-temperature stage (above 1080 °C). At the same time, argon, as an inert gas, can prevent copper from being oxidized at high temperatures. If hydrogen is used throughout the process, there is a risk of hydrogen embrittlement; if argon is used throughout the process, the surface oxides cannot be effectively reduced, and a residual oxide layer at the interface will affect the bonding quality.

[0017] In one specific implementation scheme, after the first heating and holding, the outlet and inlet are closed, followed by the first cooling and the introduction of argon gas. After the second heating and holding, the second cooling includes the following steps: In the first heating and holding process, the heating temperature is 1085-1090℃, and the holding time is 10-20 minutes. The temperature for the first cooling is 550-600℃.

[0018] In this invention, the initial heating temperature in this step is limited to 1085-1090℃, which is slightly higher than the melting point of copper (1083℃), ensuring complete melting of the electrolytic copper powder layer. The holding time is limited to 10-20 minutes. If the holding time is too short (less than 10 minutes), the electrolytic copper powder may not melt sufficiently, making it difficult to completely wet the surface of the refractory metal plate. If the holding time is too long, both the electrolytic copper powder and the copper plate will melt, and the gas at the interface will need to pass through a thick layer of molten copper to be expelled. Therefore, the "high temperature, short time" holding strategy ensures that the electrolytic copper powder melts sufficiently while preventing the copper plate from melting in large quantities. Simultaneously, this invention also uses a closed-loop cooling system. By closing the inlet and outlet, a closed environment is formed. As the temperature naturally decreases, the atmospheric pressure within the closed environment decreases accordingly (according to the ideal gas law PV=nRT, the pressure decreases synchronously with the temperature decrease). Residual gases at the interface (such as hydrogen and water vapor) are effectively expelled under the drive of the pressure difference and temperature gradient. The closed-environment "pressureless self-venting" mechanism employed in this invention eliminates the need for mechanical pressure, avoiding equipment complexity and sample deformation risks, and is a core technical means to eliminate interfacial porosity. If the atmosphere is kept flowing during the cooling process, the interfacial gas cannot escape sufficiently and is prone to forming closed pores during solidification.

[0019] In one specific implementation scheme, during the second heating and heat preservation, the heating temperature is 1090-1120℃, and the heat preservation time is 2-3 hours; The second cooling temperature is room temperature.

[0020] The second heating temperature of this invention is limited to 1090-1120℃. Its main purpose is to promote the melting of a large amount of copper and accelerate the interdiffusion of interfacial elements, forming a more complete metallurgical bonding layer. Simultaneously, this invention also limits the holding time to 2-3 hours. Longer holding time allows copper atoms to diffuse towards the grain boundaries of refractory metals and refractory metal atoms (tungsten / molybdenum atoms) to dissolve into the copper layer, forming a transition diffusion layer and significantly improving the interfacial bonding strength. If the holding time is too short (less than 2 hours), element diffusion is insufficient, and the interface remains primarily mechanically bonded with insufficient shear strength; if the holding time is too long (more than 3 hours), energy consumption increases, and grains may grow further. This invention uses a second heating after cooling because during the closed cooling process, the interfacial gas is largely expelled. After the first cooling, the copper layer has completely solidified. The second heating then melts the copper layer again, and the fluidity during the second melting process can further fill interfacial micro-defects, achieving secondary densification of the interface. Meanwhile, the second heating process was carried out entirely under an argon protective atmosphere, which avoided the risk of hydrogen embrittlement at high temperatures. Argon protection also prevented the copper liquid from oxidizing.

[0021] In one specific implementation, the demolding includes the following steps: Remove the sheet material from the mold, remove the excess copper layer, and obtain a refractory metal / copper alloy double-layer composite material.

[0022] It is important to note that during demolding, due to the difference in thermal expansion coefficients between the graphite mold and the refractory metal sheet, the sample can usually be demolded naturally or gently tapped out after cooling to room temperature. When machining to remove excess copper layer, the machining allowance should be controlled to avoid damaging the interface bonding layer. The final product can be further processed into the required shape and size according to the actual application requirements.

[0023] In one specific implementation, the protective atmosphere includes both hydrogen and argon, with the hydrogen flow rate being 5-20 L / min and the argon flow rate being 3-12 L / min.

[0024] This invention breaks through the limitations of traditional single-atmosphere protection by adopting an asymmetric atmosphere control strategy of "hydrogen-argon-sealed-argon". In the hydrogen protection stage, the strong reducing properties of hydrogen can reduce trace oxides on the surface of electrolytic copper powder and copper plates to metallic elements, while promoting the release of residual stress and creating a clean surface state for subsequent interface bonding. In the argon protection stage, argon, as an inert gas, can prevent copper from being oxidized at high temperatures and prevent hydrogen atoms from penetrating into the metal lattice and causing hydrogen embrittlement. At the same time, the sealed environment cooling allows the pressure of the protective atmosphere to decrease as the temperature decreases. The residual gas at the interface is effectively eliminated under the drive of pressure difference and temperature gradient, eliminating interface porosity.

[0025] In one specific feasible implementation, the refractory metal is tungsten, molybdenum, or their alloys.

[0026] Compared with the prior art, the present invention has at least the following advantages: 1. This invention overcomes the limitations of traditional single-atmosphere protection by using a three-stage thermal cycle, which involves switching the protective atmosphere, first heating and cooling, and second heating and cooling. It adopts an asymmetric atmosphere control strategy of "hydrogen → argon → sealed → argon" and, combined with temperature changes, allows residual gas at the interface to be fully eliminated. The tungsten-molybdenum / copper composite material prepared by this method has a dense interface and a porosity of less than 0.3%, which is a significant improvement over the traditional melt infiltration method (porosity is usually 1-5%). 2. The preparation method provided by this invention uses a composite structure of "copper powder bottom layer + copper plate top layer". Electrolytic copper is layered as a transition buffer layer. Its porous structure enhances the wettability of molten copper on the surface of refractory metals and adsorbs trace impurities at the interface. The copper plate provides the thickness of the main copper coating, avoiding the problems of poor dimensional accuracy and low density caused by sintering shrinkage when using electrolytic copper powder alone. The capillary force formed during the melting and infiltration process of the electrolytic copper powder layer helps to evenly spread the molten copper on the surface of the refractory metal. By using the copper powder transition layer and thermal cycling, the interdiffusion of interfacial elements is promoted, forming a metallurgical bonding layer. Interfacial shear strength tests show that the interfacial bonding strength of the material of this invention can reach 80-120 MPa.

[0027] 3. This invention does not require complex pressurization equipment and can be completed in a conventional tube furnace or box furnace, making it suitable for large-scale production. Furthermore, the process parameters (temperature, time, atmosphere) for each stage can be flexibly adjusted within an optimal range, resulting in lower requirements for equipment and operation.

[0028] 4. The bilayer composite material prepared by this invention combines the low expansion characteristics of refractory metals with the high thermal conductivity of copper, which can meet the requirements of harsh service environments such as high-power electronic packaging and nuclear fusion divertors. 5. The method of the present invention is applicable to various refractory metal-copper composite systems such as tungsten / copper, molybdenum / copper, and tungsten-molybdenum alloy / copper, and can be extended to the preparation of three-layer and multi-layer composite materials. Attached Figure Description

[0029] Various other advantages and benefits will become apparent to those skilled in the art upon reading the following detailed description of preferred embodiments. The accompanying drawings are for illustrative purposes only and are not intended to limit the invention. Furthermore, the same reference numerals denote the same parts throughout the drawings. In the drawings:

[0030] Figure 1 These are microscopic images of the interface of the TZM / Cu alloy bilayer composite material prepared in Example 1 of this invention at a scale of 100 μm. Figure 2 This is a surface distribution diagram of Cu element at the interface of the TZM / Cu alloy bilayer composite material prepared in Example 1 of the present invention; Figure 3 This is a surface distribution diagram of Mo elements at the interface of the TZM / Cu alloy bilayer composite material prepared in Example 1 of the present invention; Figure 4 This is a surface distribution diagram of Ti element at the interface of the TZM / Cu alloy bilayer composite material prepared in Example 1 of the present invention; Figure 5This is a photograph of the microstructure of the TZM / Cu alloy bilayer composite material prepared in Comparative Example 1 of this invention at the interface at a scale of 100 μm. Figure 6 This is a photograph of the microstructure of the TZM / Cu alloy bilayer composite material prepared in Comparative Example 2 of this invention at the interface at a scale of 50 μm. Detailed Implementation

[0031] The technical solution of the present invention will be clearly and completely described below with reference to the accompanying drawings and specific embodiments. However, those skilled in the art will understand that the embodiments described below are some embodiments of the present invention, but not all embodiments, and are only used to illustrate the present invention, and should not be regarded as limiting the scope of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall be followed. Where the manufacturers of reagents or instruments are not specified, they are all conventional products that can be purchased commercially.

[0032] In the description of this invention, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing the invention and for simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the invention. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0033] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installed," "connected," and "connected" should be interpreted broadly. For example, they can refer to fixed connection, detachable connection, or integral connection; they can refer to mechanical connection or electrical connection; they can refer to direct connection or indirect connection through an intermediate medium; and they can refer to the connection within two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0034] To more clearly illustrate the technical solutions in this invention, specific embodiments are described below.

[0035] Example 1 This embodiment provides a method for preparing a refractory metal / copper alloy bilayer composite material. In this embodiment, the refractory metal plate is selected as a TZM plate (molybdenum-titanium-zirconium alloy plate), which includes the following steps: 1. Pretreatment: A TZM plate with dimensions of 50mm×50mm×2mm was machined to a rough surface with a surface roughness Ra of 5.5μm. The TZM plate was then placed in a tube furnace and hydrogen gas (flow rate of 10L / min) was introduced for heat treatment: the temperature was raised to 1350℃ and held for 120min to remove the surface oxide layer and residual stress of the TZM plate. 2. Loading: Place the TZM plate after pretreatment in step (1) into a graphite mold, and evenly spread 0.8 mm of electrolytic copper powder with a particle size of 300 mesh (purity of 99.7%) on the surface of the TZM plate. Then spread 2 mm of oxygen-free copper plate on the surface of the electrolytic copper powder. 3. Atmosphere shift: The graphite mold after loading is pushed into the heating furnace and heated to 800°C in a hydrogen atmosphere (flow rate of 10L / min). The temperature is held for 60 minutes, then the hydrogen is turned off and argon is introduced (flow rate of 5L / min). 4. First heating: The furnace is first heated to 1085℃ in an argon atmosphere and held for 10 minutes. Then, the outlet valve (outlet) and inlet valve (inlet) of the furnace body are closed in sequence to form a sealed environment. The furnace will then begin its first cooling process, cooling down to 600℃. 5. Second heating: When the furnace temperature drops to 600℃ for the first time, argon gas is reintroduced (flow rate of 5L / min), and a second heating is performed: the temperature is raised to 1100℃ and held for 2 hours. Then, the furnace is cooled down for the second time under the protection of argon gas. The graphite template is removed from the furnace when the temperature drops to room temperature. 6. Demolding: Remove the TZM board from the graphite mold and then remove the excess copper layer using mechanical processing to obtain the TZM / Cu alloy double-layer composite material.

[0036] It should be noted that during demolding, due to the difference in thermal expansion coefficients between the graphite mold and the metal sample (TZM plate), the metal sample can usually be demolded naturally or gently tapped out after cooling to room temperature; when machining to remove excess copper layer, the machining allowance should be controlled to avoid damaging the interface bonding layer; the final refractory metal / copper alloy bilayer composite material can be further processed into the required shape and size according to the actual application requirements.

[0037] in, Figure 1 This is a photograph of the microstructure of the interface of the TZM / Cu alloy bilayer composite material prepared in this embodiment at a scale of 100 μm. Figure 2 This is a surface distribution diagram of Cu element at the interface of the TZM / Cu alloy bilayer composite material prepared in Example 1 of the present invention; Figure 3 This is a surface distribution diagram of Mo elements at the interface of the TZM / Cu alloy bilayer composite material prepared in Example 1 of the present invention; Figure 4 This is a surface distribution diagram of Ti element at the interface of the TZM / Cu alloy bilayer composite material prepared in Example 1 of this invention. (The diagram is presented in the original text.) Figures 1-4 As can be seen from the content, the microstructure of the TZM / Cu alloy bilayer composite material prepared in Example 1 is relatively uniform, the interface is densely bonded, no pores or microcracks are observed under scanning electron microscopy, and there are no oxide inclusions between the copper layer and the TZM matrix, which is beneficial to improving the tensile strength and other mechanical properties of the TZM / Cu alloy bilayer composite material.

[0038] Example 2-3 The specific implementation method is the same as in Example 1, the only difference being the different preparation conditions in the preparation method, as shown in Table 1 below: Table 1. Differences in preparation conditions Example 4 This embodiment provides a method for preparing a refractory metal / copper alloy bilayer composite material. In this embodiment, the refractory metal plate is selected as a pure molybdenum plate, and the method includes the following steps: 1. Pretreatment: A pure molybdenum plate with dimensions of 150mm×80mm×3mm was machined to a rough surface with a surface roughness Ra of 4.8μm. The pure molybdenum plate was then placed in a tube furnace and hydrogen gas (flow rate of 10L / min) was introduced for heat treatment: the temperature was raised to 1250℃ and held for 90min to remove the surface oxide layer and residual stress of the pure molybdenum plate. 2. Loading: Place the pretreated pure molybdenum plate from step (1) into a graphite mold, and evenly spread 0.5 mm of electrolytic copper powder (99.7% purity) with a particle size of 300 mesh on the surface of the pure molybdenum plate. Then spread 5 mm of oxygen-free copper plate on the surface of the electrolytic copper powder. 3. Atmosphere shift: The graphite mold after loading is pushed into the heating furnace and heated to 830°C in a hydrogen atmosphere (flow rate of 12L / min). It is held for 120 minutes, then the hydrogen is turned off and argon is introduced (flow rate of 10L / min). 4. First heating: The furnace is first heated to 1085℃ in an argon atmosphere and held for 15 minutes. Then, the outlet valve (outlet) and inlet valve (inlet) of the furnace body are closed in sequence to form a sealed environment. The furnace will then begin its first cooling process, cooling down to 560℃. 5. Second heating: When the furnace temperature drops to 560℃ for the first time, argon gas is reintroduced (flow rate of 10L / min), and a second heating is carried out: the temperature is raised to 1100℃ and held for 3 hours. Then, under the protective atmosphere of argon gas, the furnace is cooled down for the second time until the temperature drops to room temperature, and the graphite template is removed. 6. Demolding: The graphite template is removed, and the processed pure molybdenum plate is taken out of the graphite mold. The excess copper layer is removed by mechanical processing to obtain the Mo / Cu alloy double-layer composite material.

[0039] It should be noted that during demolding, due to the difference in thermal expansion coefficients between the graphite mold and the metal sample (pure molybdenum plate), the metal sample can usually be demolded naturally or gently tapped out after cooling to room temperature; when machining to remove excess copper layer, the machining allowance should be controlled to avoid damaging the interface bonding layer; the final refractory metal / copper alloy bilayer composite material can be further processed into the required shape and size according to the actual application requirements.

[0040] Example 5 This embodiment provides a method for preparing a refractory metal / copper alloy bilayer composite material. In this embodiment, the refractory metal plate is selected as a pure tungsten plate, and the method includes the following steps: 1. Pretreatment: A pure tungsten plate with dimensions of 150mm × 60mm × 4mm was machined until the surface was rough, with a surface roughness Ra of 4.5μm. The pure tungsten plate was then placed in a tube furnace and hydrogen gas (flow rate of 10L / min) was introduced for heat treatment: the temperature was raised to 1200℃ and held for 120min to remove the surface oxide layer and residual stress of the pure tungsten plate. 2. Loading: Place the pretreated pure tungsten plate from step (1) into a graphite mold, and evenly spread 1.0 mm of electrolytic copper powder (99.6% purity) with a particle size of 400 mesh on the surface of the pure tungsten plate. Then spread 3 mm of oxygen-free copper plate on the surface of the electrolytic copper powder. 3. Atmosphere shift: The graphite mold after loading is pushed into the heating furnace and heated to 800°C in a hydrogen atmosphere (flow rate of 20L / min). It is held for 180 minutes, then the hydrogen is turned off and argon is introduced (flow rate of 12L / min). 4. First heating: The furnace is first heated to 1090℃ in an argon atmosphere and held for 10 minutes. Then, the outlet valve (outlet) and inlet valve (inlet) of the furnace body are closed in sequence to form a sealed environment. The furnace will then begin its first cooling process, cooling down to 580℃. 5. Second heating: When the furnace temperature drops to 580℃ for the first time, argon gas is reintroduced (flow rate of 12L / min), and a second heating is performed: the temperature is raised to 1112℃ and held for 2 hours. Then, under the protective atmosphere of argon gas, the furnace is cooled down for the second time. When the temperature drops to 50℃, the graphite template is removed. 6. Demolding: Remove the graphite template, take out the processed pure tungsten plate from the graphite mold, and remove the excess copper layer by mechanical processing to obtain the W / Cu alloy double-layer composite material.

[0041] It should be noted that during demolding, due to the difference in thermal expansion coefficients between the graphite mold and the metal sample (pure tungsten plate), the metal sample can usually be demolded naturally or gently tapped out after cooling to room temperature; when machining to remove excess copper layer, the machining allowance should be controlled to avoid damaging the interface bonding layer; the final refractory metal / copper alloy bilayer composite material can be further processed into the required shape and size according to the actual application requirements.

[0042] Example 6 The specific implementation method is the same as in Example 1, except that the thickness of the electrolytic copper powder is selected as 0.8 mm.

[0043] Example 7 The specific implementation method is the same as that in Example 1, except that the temperature of the second heating in step (5) is set to 1099°C.

[0044] Comparative Example 1 The specific implementation method is the same as that in Example 1, except that electrolytic copper powder is not used, the protective atmosphere is not switched, hydrogen protective atmosphere is used, the gas outlet valve (gas outlet) and gas inlet valve (gas inlet) of the heating furnace body are not closed, and the first cooling is not performed.

[0045] Comparative Example 2 The specific implementation method is the same as in Example 1, except that electrolytic copper powder is not used.

[0046] Comparative Example 3 The specific implementation method is the same as that in Example 1, except that the gas outlet valve (gas outlet) and gas inlet valve (gas inlet) of the heating furnace body are not closed in step (4).

[0047] Experimental Example 1 The performance of the refractory metal / copper alloy bilayer composite materials prepared in Examples 1-7 and Comparative Examples 1-3 was tested: The performance test results are shown in Table 2 below: Table 2 Performance Test Results in Figure 5 This is a photograph of the microstructure of the TZM / Cu alloy bilayer composite material prepared in Comparative Example 1 of the present invention at the interface at a scale of 100 μm. Figure 6 These are microscopic images of the interface of the TZM / Cu alloy bilayer composite material prepared in Comparative Example 2 of this invention at a scale of 50 μm. Figure 5 and Figure 6 It can be seen that there are a few irregular pores at the interface of the prepared TZM / Cu alloy bilayer composite material. The main reason is that it did not undergo a pressure-driven venting process, and some pores were sealed by the solidified copper layer, resulting in a lack of effective metallurgical connection between the copper layer and the TZM matrix.

[0048] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. The present invention is not limited to the exact structures described above and illustrated in the accompanying drawings, and it should not be considered that the specific implementation of the present invention is limited to these descriptions. For those skilled in the art, various changes and modifications made without departing from the concept of the present invention should be considered to fall within the protection scope of the present invention.

Claims

1. A method for preparing a refractory metal / copper alloy bilayer composite material, characterized in that, Includes the following steps: The surface of the refractory metal plate to be coated with copper is machined to roughen and then heat-treated under a protective atmosphere. The heat-treated plate is placed in a mold, and electrolytic copper powder and copper plate are sequentially laid on the surface of the plate. The mold is heated and kept at a temperature under a protective atmosphere, and then the protective atmosphere is changed. After the first heating and holding, the outlet and inlet are closed. After the first cooling, argon gas is introduced. After the second heating and holding, the second cooling is performed. Demolding.

2. The preparation method according to claim 1, characterized in that, The process of roughening the surface of the refractory metal plate to be coated with copper and then heat-treating it under a protective atmosphere includes the following steps: The roughness standard is a roughness of 1.5-6.0 μm, the protective atmosphere is hydrogen, the heat treatment temperature is 1150-1350℃, and the heat treatment holding time is 30-120 min.

3. The preparation method according to claim 1, characterized in that, The step of placing the heat-treated plate in a mold and sequentially laying electrolytic copper powder and copper plate on the surface of the plate includes the following steps: The standard for laying the electrolytic copper powder is to lay it evenly and flat, with a thickness of 0.5-1mm.

4. The preparation method according to claim 3, characterized in that, The electrolytic copper powder has a particle size of 200-400 mesh and a purity of ≥99.5%. The copper plate is one or a combination of two of oxygen-free copper plates and pure copper plates, with a thickness of 1-5mm.

5. The preparation method according to claim 1, characterized in that, The process of heating and holding the mold under a protective atmosphere, followed by changing the protective atmosphere, includes the following steps: Heat the mold to 780-850 degrees Celsius under a hydrogen protective atmosphere and hold for 1-3 hours, then replace the protective atmosphere with argon.

6. The preparation method according to claim 1, characterized in that, After the first heating and holding, the outlet and inlet are closed, followed by the first cooling and the introduction of argon gas. After the second heating and holding, the second cooling includes the following steps: In the first heating and holding process, the heating temperature is 1085-1090℃, and the holding time is 10-20 minutes. The temperature for the first cooling is 550-600℃.

7. The preparation method according to claim 6, characterized in that, In the second heating and heat preservation process, the heating temperature is 1090-1120℃, and the heat preservation time is 2-3 hours. The second cooling temperature is room temperature.

8. The preparation method according to claim 1, characterized in that, The demolding process includes the following steps: Remove the sheet material from the mold, remove the excess copper layer, and obtain a refractory metal / copper alloy double-layer composite material.

9. The preparation method according to claim 1, characterized in that, The protective atmosphere includes two gases: hydrogen and argon. The flow rate of hydrogen is 5-20 L / min, and the flow rate of argon is 3-12 L / min.

10. The preparation method according to claim 1, characterized in that, The refractory metals are tungsten, molybdenum, and their alloys.

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