Uniform tungsten-copper bulk material based on short fiber preforms and methods of making the same

Abstract

The application provides a uniform tungsten-copper bulk material based on short fiber preforms and a preparation method thereof, and relates to the fields of non-ferrous metal composites and powder metallurgy technology. The material is formed by stacking a plurality of copper-coated tungsten short fibers into a stack through regular arrangement or disordered stacking, and then pressing and sintering. Each short fiber has a copper layer shell and a tungsten core inner core. After sintering, the adjacent copper layers are connected to form a continuous conductive and heat-conductive network, and each tungsten core is uniformly distributed in the network as an independent unit. The material has low porosity and excellent electrical conductivity and thermal conductivity. In the preparation, a copper layer is first electroplated on a tungsten wire and drawn to a fine diameter, then cut into short fibers, and then molded and pressed to obtain a preform, and finally sintered to densification under vacuum or hydrogen protection at a copper liquid phase temperature range. The method can effectively avoid the segregation problem caused by the density difference of tungsten and copper in traditional powder metallurgy, enhance the interface bonding, and flexibly adjust the arrangement mode of the short fibers to meet different performance requirements.

Description

Technical Field

[0001] This invention relates to the field of non-ferrous metal composite materials and powder metallurgy technology, specifically to a uniform tungsten-copper bulk material based on short fiber preforms and its preparation method. Background Technology

[0002] Tungsten-copper composites possess the high melting point and hardness of tungsten and the excellent electrical and thermal conductivity of copper, making them promising for applications in high-temperature electrodes, electrical contacts, and heat dissipation substrates for electronic packaging. Currently, the mainstream preparation method for these materials is powder metallurgy, including methods such as mechanically mixing tungsten and copper powders followed by pressing and sintering, and preparing a tungsten framework before infiltrating it with molten copper. However, these traditional processes still face several insurmountable technical bottlenecks in practical applications.

[0003] First, due to the significant density difference between tungsten and copper, segregation is highly likely to occur during the mechanical mixing of powders. This leads to the formation of localized copper-rich regions or tungsten particle agglomerations within the sintered material, resulting in poor microstructure uniformity and consequently affecting the consistency of electrical, thermal, and mechanical properties. Second, in traditional powder metallurgy methods, the tungsten and copper phases are mostly mechanically or weakly bonded, with limited interfacial bonding strength. Under high-temperature or cyclic stress service conditions, interfacial debonding easily occurs, reducing the long-term reliability of the material. Third, the irregular shape of powder particles makes densification difficult. Even after high-temperature sintering, a certain number of micropores often remain within the material, which are difficult to completely eliminate. These pores hinder the effective transport of electrons and phonons, causing the actual electrical and thermal conductivity of the material to be significantly lower than the theoretical values.

[0004] Furthermore, existing tungsten-copper bulk materials are mostly homogeneous structures, lacking the flexibility to control microstructure and properties through structural unit design. This makes it difficult to meet the differentiated requirements of isotropic or anisotropic properties in various application scenarios. Existing technologies also include schemes that use continuous tungsten fibers or tungsten wire mesh as the reinforcing phase, combined with copper melt infiltration or hot isostatic pressing processes to prepare tungsten fiber-reinforced copper matrix composites. While these schemes can achieve high strength, the fiber orientation is singular, exhibiting significant anisotropy, and they are not easy to fabricate bulk components with complex shapes or requiring isotropic properties. Similarly, they are difficult to meet the high requirements of microstructure uniformity and isotropic performance in applications such as heat dissipation substrates and electrical contacts.

[0005] In view of the above, this application is hereby submitted. Summary of the Invention

[0006] This invention provides a uniform tungsten-copper bulk material based on short fiber preforms and its preparation method, which can at least partially improve the above-mentioned problems.

[0007] To achieve the above objectives, the present invention adopts the following technical solution:

[0008] A uniform tungsten-copper bulk material based on a short fiber preform is disclosed. The uniform tungsten-copper bulk material is formed by stacking multiple micron-sized copper-clad tungsten short fibers in a regular or disordered manner, and then pressing and sintering them. The outer skin of the copper-clad tungsten short fibers is a copper layer, and the inner core is a tungsten core. The copper layers of adjacent copper-clad tungsten short fibers are interconnected during the sintering process to form a continuous conductive and thermally conductive network. Each tungsten core is uniformly distributed as an independent unit in the conductive and thermally conductive network.

[0009] This invention can be further improved through the following technical measures: As a further improvement, the copper-clad tungsten short fibers have a diameter of 10 μm to 200 μm and a length of 0.5 mm to 5 mm.

[0010] As a further improvement, the relative density of the uniform tungsten-copper bulk material is greater than 98%, and the porosity is less than 2%.

[0011] As a further improvement, the volume ratio of the copper layer to the tungsten core in the copper-clad tungsten short fiber is 0.1:9.9 to 9:1. The uniform tungsten-copper bulk material formed by the copper-clad tungsten short fibers arranged in a regular unidirectional manner has anisotropic electrical and thermal conductivity. The uniform tungsten-copper bulk material formed by the copper-clad tungsten short fibers stacked in a disordered manner has isotropic electrical and thermal conductivity.

[0012] The present invention also provides a method for preparing a uniform tungsten-copper bulk material based on a short fiber preform as described in any one of the above claims, the steps of which are as follows: Step S1, Preparation of copper-clad tungsten composite wire: Select tungsten wire and electroplate a copper layer on its surface to obtain copper-clad tungsten composite wire; Step S2, drawing and forming: The copper-clad tungsten composite wire is drawn in multiple passes until the diameter of the copper-clad tungsten composite wire is reduced to the preset fine diameter to obtain copper-clad tungsten filament; Step S3, Cutting to prepare short fibers: Cut the copper-clad tungsten filaments to a preset length to obtain multiple copper-clad tungsten short fibers; Step S4, Mixing and Preforming: Multiple copper-clad tungsten short fibers are loaded into a mold in a regular or disordered manner, and then subjected to cold isostatic pressing or unidirectional pressing under vacuum or protective atmosphere to form a dense short fiber preform. Step S5, high-temperature sintering: Under vacuum or high-purity hydrogen protection, the short fiber preform is heated to a preset copper liquid phase temperature range, and after holding at the temperature for a preset time, sintering is performed. The copper layer fills the fiber gaps and achieves densification under the action of diffusion and capillary force. After cooling for a preset time, a dense and uniform tungsten-copper bulk material is obtained; wherein, the tungsten core maintains a fibrous morphology after sintering, with an aspect ratio ≥3.

[0013] As a further improvement, in step S3, laser cutting or precision mechanical cutting is used.

[0014] As a further improvement, in step S4, the pressing pressure is 50 MPa to 500 MPa, and the density of the short fiber preform reaches 90-99% of the theoretical density.

[0015] As a further improvement, in step S5, the preset sintering temperature range is 900-1100℃.

[0016] As a further improvement, in step S5, the sintering heating rate is 5-20℃ / min, the holding time is 1-4 hours, and the cooling method is furnace cooling or controlled cooling rate.

[0017] In summary, this invention achieves high uniformity and controllability of the microstructure by cutting copper-clad tungsten filaments into short fibers, utilizing their regular geometric shape and inherent copper-tungsten interface as basic "building blocks" for bulk materials. Specifically, the method first prepares copper-clad tungsten short fibers with small diameter and controllable length through drawing and cutting processes of copper-clad tungsten composite wires; then, a certain volume of these short fibers are uniformly mixed, and a preform is formed by cold isostatic pressing or unidirectional pressing, followed by high-temperature liquid-phase sintering under vacuum or a protective atmosphere.

[0018] This invention innovatively utilizes "short fibers" as the basic structural unit of bulk materials, rather than traditional powders or reinforcing phases. The resulting bulk materials contain no other matrix, binder, or additives, and the copper and tungsten phases are extremely uniformly distributed at the microscale. This achieves a continuous network construction of the copper phase and a uniform dispersion distribution of the tungsten phase, significantly improving the uniformity of the material's density, electrical conductivity, thermal conductivity, and mechanical properties. It overcomes the defects of segregation and porosity that are difficult to eliminate in traditional powder metallurgy methods. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of the structure of a uniform tungsten-copper bulk material based on a short fiber preform provided in an embodiment of the present invention. Detailed Implementation

[0020] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0021] refer to Figure 1As shown, the first embodiment of the present invention discloses a uniform tungsten-copper bulk material based on a short fiber preform. The uniform tungsten-copper bulk material is formed by stacking multiple micron-sized copper-clad tungsten short fibers 3 in a regular or disordered manner, and then pressing and sintering them (without other matrix materials, binders or additives). The outer skin of the copper-clad tungsten short fiber 3 is a copper layer 1, and the inner core is a tungsten core 2. The copper layers of adjacent copper-clad tungsten short fibers 3 are interconnected during the sintering process to form a continuous conductive and thermally conductive network. Each tungsten core 2 is uniformly distributed in the conductive and thermally conductive network as an independent unit, forming a "fibrous" microstructure.

[0022] In a preferred embodiment, the copper-clad tungsten short fiber 3 has a diameter of 10 μm to 200 μm and a length of 0.5 mm to 5 mm.

[0023] The relative density of the uniform tungsten-copper bulk material is greater than 98%, and the porosity is less than 2%.

[0024] The volume ratio of copper layer 1 to tungsten core 2 in the copper-clad tungsten short fiber 3 is 0.1:9.9 to 9:1. The uniform tungsten-copper bulk material formed by the copper-clad tungsten short fiber 3 arranged in the same direction has anisotropic electrical and thermal conductivity. The uniform tungsten-copper bulk material formed by the copper-clad tungsten short fiber 3 stacked in a disordered manner has isotropic electrical and thermal conductivity. In this embodiment, the uniform tungsten-copper bulk material based on the short fiber preform is formed by stacking multiple micron-sized copper-clad tungsten short fibers 3 in a regular or disordered manner, and then pressing and sintering to form a dense bulk. Each copper-clad tungsten short fiber 3 has a copper outer shell and a tungsten core. After sintering, the copper layers 1 of adjacent fibers are interconnected to form a continuous conductive and thermally conductive network, while each tungsten core 2 is uniformly distributed as an independent unit within this network. This structure effectively avoids the segregation problem caused by the density difference between tungsten and copper in traditional powder metallurgy, making the internal structure of the material highly uniform, thereby ensuring the consistency of macroscopic properties.

[0025] Specifically, the diameter of the copper-clad tungsten short fibers 3 is controlled within the range of 10μm to 200μm, and the length is controlled within the range of 0.5mm to 5mm. Using finer and moderately long short fibers facilitates a more uniform spatial distribution during stacking, resulting in a more continuous and denser copper layer network after sintering, significantly improving the material's electrical and thermal conductivity. Testing showed that the relative density of the obtained tungsten-copper bulk material was greater than 98%, and the porosity was less than 2%, indicating that there are almost no residual pores inside the material, minimal obstruction to electron and phonon transport paths, and that the actual electrical and thermal conductivity are close to the theoretical values.

[0026] Furthermore, the volume fraction of copper-clad tungsten short fibers 3 can be flexibly adjusted between 10% and 90%, and the volume ratio of copper layer 1 to tungsten core 2 can be selected within a wide range from 0.1:9.9 to 9:1. For example, a higher copper volume fraction can be selected when high electrical and thermal conductivity is required; a higher tungsten volume fraction can be selected when high hardness and high temperature resistance are required. Since each tungsten core 2 is independently wrapped and uniformly distributed by the copper layer network, tungsten particle agglomeration can be avoided even at high tungsten content, maintaining the uniformity of the microstructure. At the same time, a good metallurgical bond is achieved between the continuous copper phase and the discrete tungsten phase, with high interfacial strength, making it less prone to debonding under high temperature or cyclic stress conditions, significantly improving the long-term service reliability of the material.

[0027] The present invention also provides a method for preparing a uniform tungsten-copper bulk material based on a short fiber preform as described in any one of the above claims, the method comprising the following steps: Step S1, Preparation of copper-clad tungsten composite wire: Select tungsten wire and electroplate a copper layer 1 on its surface to obtain copper-clad tungsten composite wire; Step S2, drawing and forming: The copper-clad tungsten composite wire is drawn in multiple passes until the diameter of the copper-clad tungsten composite wire is reduced to the preset fine diameter to obtain copper-clad tungsten filament; Step S3, Cutting to prepare short fibers: Cut the copper-clad tungsten filaments according to the preset length to obtain multiple copper-clad tungsten short fibers 3; Step S4, Mixing and Preforming: Multiple copper-clad tungsten short fibers 3 are loaded into a mold in a regular or disordered manner, and cold isostatic pressing or unidirectional pressing is performed under vacuum or protective atmosphere to form a dense short fiber preform. Step S5, high-temperature sintering: Under vacuum or high-purity hydrogen protection, the short fiber preform is heated to a preset copper liquid phase temperature range, and after holding at the temperature for a preset time, sintering is performed. The copper layer 1 fills the fiber gaps and achieves densification under the action of diffusion and capillary force. After cooling for a preset time, a dense and uniform tungsten copper bulk material is obtained; wherein, the tungsten core 2 maintains a fibrous morphology after sintering, with an aspect ratio ≥3.

[0028] In a preferred embodiment, in step S3, laser cutting or precision mechanical cutting is used to produce a smooth cut without burrs.

[0029] In step S4, the pressing pressure is 50 MPa to 500 MPa, and the density of the short fiber preform reaches 90-99% of the theoretical density.

[0030] In step S5, the preset sintering temperature range is 900-1100℃.

[0031] In step S5, the sintering heating rate is 5-20℃ / min, the holding time is 1-4 hours, and the cooling method is furnace cooling or controlled cooling rate.

[0032] In steps S1 to S3, the bonding strength between the copper layer 1 and the tungsten core 2 is controlled by the electroplating process to ensure that delamination does not occur during drawing and cutting. Step S1 is equivalent to preliminary bonding, step S2, during the drawing deformation process, not only reduces the diameter but also further promotes bonding, and step S3 simply cuts out the bonded short fibers. Specifically, in this embodiment, firstly, step S1 is performed to prepare a copper-clad tungsten composite wire: a tungsten wire is selected, and a copper layer 1 is deposited on its surface by electroplating to obtain a copper-clad tungsten composite wire. The electroplating process can form a uniform and dense copper layer 1 on the surface of the tungsten wire, ensuring that the copper phase can be continuously distributed during subsequent sintering, laying the foundation for forming a good conductive and thermally conductive network. Next, step S2 is performed for drawing: the copper-clad tungsten composite wire is drawn in multiple passes, gradually reducing its diameter until a preset fine diameter is reached, resulting in a copper-clad tungsten filament. Multiple drawing passes not only allow for precise control of the final wire size but also make the bond between the copper layer 1 and the tungsten core 2 tighter, which is beneficial for improving the interfacial bonding strength of the material after subsequent sintering. Before electroplating, the surface of the tungsten wire is subjected to alkaline degreasing, acid deoxidation, and activation treatment in sequence to ensure a strong metallurgical bond between the copper layer and the tungsten substrate. During the electroplating process, the copper layer thickness is made uniform by controlling the current density (typical value 1-5 A / dm²) and the composition of the plating solution (such as acidic copper sulfate plating solution supplemented with a small amount of brightener). The copper layer thickness accounts for 5% to 30% of the diameter of the composite wire. More specifically, the electroplating uses an acidic copper sulfate plating solution, which comprises: 180-240 g / L copper sulfate pentahydrate, 50-80 mL / L concentrated sulfuric acid (98%), 40-80 mg / L chloride ions, and a brightener system. The brightener system consists of three components: an inhibitor, an accelerator, and a leveling agent. The inhibitor is polyethylene glycol (PEG) (number average molecular weight 2000-8000, added at 100-500 mg / L), the accelerator is sodium 3-mercaptopropane sulfonate (MPS) or disodium bis(3-sulfopropyl)disulfide (SPS) (added at 1-10 mg / L), and the leveling agent is a nitrogen-containing quaternary ammonium salt dye molecule (such as Janus Green B or a polyquaternized leveling agent, added at 1-10 mg / L). The electroplating process parameters are: temperature 22-32℃, cathode current density 2-6... A / dm², using phosphorus-deoxidized copper anodes containing 0.04%-0.06% phosphorus and combined with air agitation or plating solution spraying; to avoid Cu² in acidic copper sulfate plating solution + A loose "contact copper" layer is generated by directly replacing the tungsten substrate. Before the acidic copper sulfate electroplating, the tungsten wire is first pre-plated with nickel or copper pyrophosphate using alkaline chemical / electrochemical methods to form a 1-3 μm transition layer, so that a strong metallurgical bond is formed between the subsequent thick copper plating layer and the tungsten core. The final copper layer thickness accounts for 5%-30% of the diameter of the composite wire.

[0033] Step S3 is then performed to cut and prepare short fibers: the copper-clad tungsten filaments are cut according to a preset length to obtain multiple copper-clad tungsten short fibers 3. In a preferred embodiment, laser cutting or precision mechanical cutting is used for cutting. Laser cutting can obtain short fibers with flat end faces and uniform lengths, avoiding burrs or deformation, thereby ensuring that the fibers are evenly arranged when stacked, and the internal structure of the final bulk material is more consistent. Step S4 is mixing and preforming: multiple copper-clad tungsten short fibers 3 are loaded into a mold in a regular or disordered arrangement, and cold isostatic pressing or unidirectional pressing is performed under vacuum or a protective atmosphere to form a dense short fiber preform. The pressing pressure is controlled in the range of 50MPa to 500MPa, so that the density of the short fiber preform reaches 90-99% of the theoretical density. Under this pressure, the short fibers achieve close contact without excessive deformation, providing a good capillary channel for subsequent liquid phase sintering. Since the pressing is carried out under vacuum or a protective atmosphere, oxidation of the fiber surface is effectively avoided, ensuring the activity of the copper layer 1 during sintering.

[0034] Finally, step S5, high-temperature sintering, is performed: Under vacuum or high-purity hydrogen protection, the short fiber preform is heated to a preset copper liquid phase temperature range, preferably 900-1100℃. At this temperature, the copper layer 1 melts into a liquid phase, while the tungsten core 2 remains solid. The sintering heating rate is controlled at 5-20℃ / min, and the holding time is 1-4 hours. During the holding process, the liquid copper actively fills the gaps between the fibers under the action of diffusion and capillary force, and encapsulates and uniformly disperses the tungsten core 2. At the same time, the liquid copper interconnects to form a continuous conductive and thermally conductive network. Cooling is achieved by furnace cooling or controlled cooling rate, resulting in a dense and uniform tungsten-copper bulk material. Because the copper liquid fully fills the gaps under the action of capillary force, the internal pores of the material are effectively eliminated, and the relative density of the resulting bulk material can reach over 98%, with a porosity of less than 2%. Meanwhile, each tungsten core 2 is uniformly distributed as an independent unit within the copper network, avoiding the tungsten particle agglomeration and copper segregation problems common in traditional powder metallurgy. This results in a high degree of consistency in the material's electrical conductivity, thermal conductivity, and mechanical properties on a macroscopic scale. Furthermore, a good metallurgical bond is achieved between the copper and tungsten phases, resulting in high interfacial strength and significantly improving the material's long-term reliability under high-temperature or cyclic stress service conditions. By adjusting the arrangement of the short fibers (regular arrangement yields anisotropic properties, while disordered stacking yields isotropic properties) and controlling the volume ratio of the copper layer 1 to the tungsten core 2 in the copper-clad tungsten short fiber 3 (0.1:9.9 to 9:1), the differentiated requirements for thermal conductivity, electrical conductivity, hardness, and high-temperature resistance in various application scenarios can be flexibly met.

[0035] In this embodiment, to further verify the effect of the uniform tungsten-copper bulk material based on short fiber preforms, uniform tungsten-copper bulk materials were prepared using raw materials with different proportions.

[0036] In Example 1, a uniform tungsten-copper bulk material with high tungsten content was prepared. Specifically, a high-purity tungsten wire with a diameter of 3.0 mm was selected. An acidic copper sulfate electroplating process was used to electroplat a copper layer 1 with a thickness of 0.1 mm onto the surface of the tungsten wire, resulting in a copper-clad tungsten composite wire with a diameter of 3.2 mm. Subsequently, the composite wire was drawn multiple times until its final diameter reached 50 μm. A precision laser cutting machine was used to cut the copper-clad tungsten wire into short fiber units with a length of 2 mm. At this point, the copper layer 1 thickness was approximately 3 μm, and the tungsten core 2 diameter was approximately 44 μm. Approximately 500 g of copper-clad tungsten short fibers 3 were prepared, with a tungsten-copper volume ratio of approximately 85:15.

[0037] Furthermore, the short fibers were placed in a three-dimensional mixer and uniformly mixed for 30 minutes. The mixed short fibers were then loaded into a cemented carbide mold and subjected to cold isostatic pressing under vacuum at a pressure controlled at 200 MPa. After pressing, a cylindrical preform with a diameter of 30 mm and a height of 40 mm was obtained, with a relative density of approximately 80%. The preform was placed in a vacuum sintering furnace and protected with high-purity hydrogen gas. The temperature was increased to 1050 °C at a rate of 10 °C / min and held for 2 hours. During the holding process, the copper layer 1 melted to form a liquid phase, filling the gaps between the fibers and completely wetting the tungsten core 2. After the holding period, the preform was cooled to room temperature with the furnace. After demolding, a dense tungsten-copper composite block was obtained. Finally, metallographic observation showed that the microstructure was uniform and without segregation, with the copper phase continuously encapsulating the tungsten core 2 in a network pattern; the relative density reached over 98.5%; the tensile strength was approximately 900 MPa; and the electrical conductivity was approximately 45% IACS.

[0038] In Example 2, a uniform tungsten-copper bulk material with high copper content was prepared. Specifically, a tungsten wire with a diameter of 1.0 mm was selected, and a copper layer with a thickness of 0.08 mm was electroplated to obtain a copper-clad tungsten wire. This wire was drawn to a diameter of 20 μm and cut to a length of 1 mm, resulting in short fibers with a copper-tungsten volume ratio of 40:60. After mixing, the fibers were cold isostatically pressed at a pressure of 300 MPa. The temperature was then raised to 1100 °C and held for 1.5 hours. The resulting material had a high copper content and an electrical conductivity of 85% IACS, while maintaining good thermal shock resistance.

[0039] In Example 3, the effect of different aspect ratios on uniform tungsten-copper bulk material was determined. Specifically, a control group was set up with short fiber lengths maintained at 0.5 mm and volume ratios adjusted; an experimental group was set up with short fiber lengths maintained at 5 mm and volume ratios adjusted. Comparing the two, it was found that longer short fibers are easier to orient during pressing, resulting in slightly higher thermal conductivity parallel to the fiber direction and slightly lower thermal conductivity perpendicular to the fiber direction, exhibiting a certain degree of anisotropy; shorter short fibers exhibit better isotropy. By controlling the length of the short fibers, the material properties can be customized for different application scenarios (such as heat sinks requiring isotropy and electrodes requiring anisotropy).

[0040] In summary, this method employs an electroplating + drawing + slitting process to prepare a large number of precisely dimensional copper-clad tungsten short fibers 3. These short fibers themselves are miniature "copper-clad tungsten composite material units," with the copper layer 1 and tungsten core 2 firmly bonded together. After mixing a large number of short fibers, a preform is formed by high-pressure pressing. Due to the aspect ratio of the short fibers, they will orient or randomly stack during the pressing process, forming a porous skeleton with a specific pore structure. Finally, taking advantage of the low melting point of copper, the copper layer 1 melts during sintering, forming a continuous liquid-phase copper network. Under capillary action, the liquid-phase copper fills the gaps between the fibers and wets the tungsten core 2, ultimately achieving complete densification, with the copper phase distributed in a network pattern and the tungsten core 2 exhibiting a regular distribution.

[0041] Compared with existing technologies, this invention has the following advantages: 1. Extremely uniform microstructure: Short fibers, as pre-formed units, ensure the uniformity of the tungsten-copper ratio within each micro-volume, completely eliminating the segregation problem of traditional powder mixing. 2. High-performance interface bonding: The copper-tungsten interface inside the short fibers is a metallurgical bond formed by electroplating, which further diffuses during sintering. The interface bonding strength is far higher than that of the mechanical contact surface formed by powder pressing. 3. No additives, no impurities: The material is composed entirely of tungsten and copper phases, without binders or other matrices, ensuring high electrical conductivity, high thermal conductivity, and high resistance to electrolytic corrosion. 4. Strong process controllability: By adjusting the aspect ratio, volume fraction, and pressing process of the short fibers, the tungsten content, pore structure, and mechanical properties of the final bulk material can be precisely controlled.

[0042] The above description represents the preferred embodiments of the present invention. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principles of the present invention, and these improvements and modifications are also considered to be within the scope of protection of the present invention.

Claims

1. A uniform tungsten-copper bulk material based on short fiber preforms, characterized in that, The uniform tungsten-copper bulk material is formed by stacking multiple micron-sized copper-clad tungsten short fibers in a regular or disordered manner, and then pressing and sintering them. The outer skin of the copper-clad tungsten short fibers is a copper layer, and the inner core is a tungsten core. The copper layers of adjacent copper-clad tungsten short fibers are interconnected during the sintering process to form a continuous conductive and thermally conductive network. Each tungsten core is uniformly distributed as an independent unit in the conductive and thermally conductive network.

2. The uniform tungsten-copper bulk material based on short fiber preforms according to claim 1, characterized in that, The copper-clad tungsten short fibers have a diameter of 10 μm to 200 μm and a length of 0.5 mm to 5 mm.

3. The uniform tungsten-copper bulk material based on short fiber preforms according to claim 1, characterized in that, The relative density of the uniform tungsten-copper bulk material is greater than 98%, and the porosity is less than 2%.

4. The uniform tungsten-copper bulk material based on short fiber preforms according to claim 1, characterized in that, The volume ratio of the copper layer to the tungsten core in the copper-clad tungsten short fiber is 0.1:9.9 to 9:

1. The uniform tungsten-copper bulk material formed by the copper-clad tungsten short fibers arranged in the same direction has anisotropic electrical and thermal conductivity. The uniform tungsten-copper bulk material formed by the copper-clad tungsten short fibers stacked in a disordered manner has isotropic electrical and thermal conductivity.

5. The method for preparing a uniform tungsten-copper bulk material based on a short fiber preform according to any one of claims 1 to 4, characterized in that, The preparation method involves the following steps: Step S1, Preparation of copper-clad tungsten composite wire: Select tungsten wire and electroplate a copper layer on its surface to obtain copper-clad tungsten composite wire; Step S2, drawing and forming: The copper-clad tungsten composite wire is drawn in multiple passes until the diameter of the copper-clad tungsten composite wire is reduced to the preset fine diameter to obtain copper-clad tungsten filament; Step S3, Cutting to prepare short fibers: Cut the copper-clad tungsten filaments to a preset length to obtain multiple copper-clad tungsten short fibers; Step S4, Mixing and Preforming: Multiple copper-clad tungsten short fibers are loaded into a mold in a regular or disordered manner, and then subjected to cold isostatic pressing or unidirectional pressing under vacuum or protective atmosphere to form a dense short fiber preform. Step S5, high-temperature sintering: Under vacuum or high-purity hydrogen protection, the short fiber preform is heated to a preset copper liquid phase temperature range, and after holding at the temperature for a preset time, sintering is performed. The copper layer fills the fiber gaps and achieves densification under the action of diffusion and capillary force. After cooling for a preset time, a dense and uniform tungsten-copper bulk material is obtained; wherein, the tungsten core maintains a fibrous morphology after sintering, with an aspect ratio ≥3.

6. The method for preparing a uniform tungsten-copper bulk material based on a short fiber preform according to claim 5, characterized in that, In step S3, laser cutting or precision mechanical cutting is used.

7. The method for preparing a uniform tungsten-copper bulk material based on a short fiber preform according to claim 5, characterized in that, In step S4, the pressing pressure is 50 MPa to 500 MPa, and the density of the short fiber preform reaches 90-99% of the theoretical density.

8. The method for preparing a uniform tungsten-copper bulk material based on a short fiber preform according to claim 5, characterized in that, In step S5, the preset sintering temperature range is 900-1100℃.

9. The method for preparing a uniform tungsten-copper bulk material based on a short fiber preform according to claim 5, characterized in that, In step S5, the sintering heating rate is 5-20℃ / min, the holding time is 1-4 hours, and the cooling method is furnace cooling or controlled cooling rate.

Images