Bimodal tungsten-copper alloy and method for producing the same

Abstract

This invention relates to a bimodal tungsten-copper alloy and its preparation method. The preparation method includes: using water-soluble tungsten salt, water-soluble copper salt, and coarse tungsten powder with controllable particle size as raw materials, adding a solvent to prepare a suspension; subjecting the suspension to spray pyrolysis and in-situ reduction reaction to obtain tungsten-copper composite powder; and finally pressing the tungsten-copper composite powder into a green blank and sintering it to obtain a tungsten-copper alloy material with bimodal tungsten grain structure. In the tungsten-copper composite powder prepared by this invention, fine tungsten powder and copper powder are coupled to each other and uniformly distributed on the surface of coarse tungsten powder, forming a structure in which fine tungsten-copper composite powder coats coarse tungsten powder. This effectively improves the uniformity of W and Cu element distribution, thereby enhancing the overall properties of the tungsten-copper alloy, such as density, electrical conductivity, and thermal conductivity.

Description

Technical Field

[0001] This invention relates to the field of tungsten-copper composite materials; more specifically, it relates to a bimodal reinforced tungsten-copper alloy and its preparation method. Background Technology

[0002] Pure copper is widely used in electronics, power equipment, and rail transportation. It has excellent electrical conductivity, making it widely used in the manufacture of wires, cables, and generators; good thermal conductivity, often used in the manufacture of magnetic instruments requiring protection against magnetic interference, such as compasses and aerospace instruments; and excellent plasticity, making it easy to hot and cold press and process into copper wires, bars, plates, and foils. However, pure copper also has many drawbacks, such as low strength, low hardness, and poor wear resistance, which limit its wider application in industry.

[0003] Tungsten-copper alloys are composite materials composed of body-centered cubic tungsten particles and face-centered cubic copper binder phases that neither dissolve in each other nor form intermetallic compounds. Therefore, they possess both the high strength, high hardness, and low coefficient of thermal expansion of tungsten, and the high plasticity, good electrical and thermal conductivity of copper. These unique combined properties make tungsten-copper alloys widely used. Currently, tungsten-copper alloys are prepared using powder metallurgy or melt infiltration methods.

[0004] Chinese patent document CN109280833A discloses a method for preparing a tungsten-copper composite material. The method involves injection molding tungsten powder, copper powder, carbon nanotubes, and a binder, followed by degreasing and sintering in a hydrogen atmosphere to obtain a highly conductive and thermally conductive tungsten-copper composite material. By mass percentage, the composition is 74-84.8% tungsten, 15-25% copper, and 0.2-1% carbon nanotubes. The binder comprises: 60-70% paraffin wax, 10-16% high-density polyethylene, 15-20% ethylene-vinyl acetate copolymer, 1-4% stearic acid, and 0-0.5% antioxidant.

[0005] Chinese patent document CN111250720A discloses a method for preparing tungsten-copper composite materials. The method uses plasma to heat, melt, and atomize pure copper and pure tungsten respectively, and then deposits them by atomization to obtain tungsten-copper composite materials with different W (tungsten) contents. The deposited ingots are then hot-pressed in a hot press furnace at 1080°C to obtain the composite materials.

[0006] A comprehensive literature review reveals that current methods for preparing tungsten-copper alloys mostly employ single-size W powder as raw material, which is then ball-milled to mix with copper powder, followed by pressing and sintering to obtain the alloy; or single-size W powder is used as raw material, which is then pressed into a framework and infiltrated with copper to produce the alloy. These methods of preparing tungsten-copper alloys using single-size W powder often limit the improvement of properties such as alloy conductivity and density. Summary of the Invention

[0007] The main objective of this invention is to provide a bimodal tungsten-copper alloy with improved overall properties such as density, electrical conductivity, and thermal conductivity, as well as its preparation method.

[0008] To achieve the aforementioned main objectives, a first aspect of the present invention discloses a method for preparing a bimodal reinforced tungsten-copper alloy, comprising the following steps:

[0009] (1) Add water-soluble tungsten salt, water-soluble copper salt, and coarse tungsten powder to a solvent in a predetermined ratio to obtain a suspension;

[0010] (2) The above suspension is atomized and pyrolyzed in a spray pyrolysis furnace to obtain a composite powder containing coarse tungsten powder and tungsten-copper oxide;

[0011] (3) The above composite powder is reduced in situ in a hydrogen furnace to obtain a tungsten-copper composite powder material containing coarse tungsten powder and fine tungsten powder; wherein the fine tungsten powder and copper powder are coupled to each other and are evenly distributed on the surface of the coarse tungsten powder.

[0012] (4) The above-mentioned tungsten-copper composite powder material is pressed into a green blank and then sintered to obtain a tungsten-copper alloy material with a bimodal structure of tungsten grains.

[0013] Tungsten and copper have significantly different densities, and traditional ball milling processes often result in stratification of these two elements, leading to uneven element distribution. In the preparation method of this invention, a suspension is prepared using coarse-grained tungsten powder, soluble tungsten salt, and soluble copper salt as raw materials. This suspension is then subjected to solution spray pyrolysis and in-situ reduction to obtain fine-grained tungsten-copper composite powder with a highly uniform distribution of tungsten and copper elements. In this composite powder, the fine-grained tungsten and copper particles are coupled together and coat or uniformly distributed on the surface of pre-added coarse tungsten particles, resulting in a core-shell structure with coarse-grained tungsten powder as the core and the fine-grained tungsten-copper composite powder obtained through spray pyrolysis and in-situ reduction as the shell. This structure helps improve the uniformity of W and Cu element distribution, thereby enhancing the density, electrical conductivity, thermal conductivity, and other comprehensive properties of the tungsten-copper alloy.

[0014] Preferably, the average particle size of the coarse tungsten powder is 3 μm to 15 μm, and the average particle size of the fine tungsten powder is 0.2 μm to 1.5 μm, more preferably 0.6 μm to 1.0 μm.

[0015] According to one specific embodiment of the present invention, the solvent is any one or two of deionized water and anhydrous ethanol; the tungsten salt is any one or two of ammonium metatungstate and / or ammonium paratungstate.

[0016] According to one specific embodiment of the present invention, the copper salt may be at least one selected from copper nitrate, copper sulfate, copper acetate, and copper chloride.

[0017] Preferably, in step (2), the feed inlet temperature of the spray pyrolysis furnace is controlled at 150–300°C, the pyrolysis temperature is controlled at 500–700°C, and the pyrolysis atmosphere is controlled at one or both of nitrogen and argon as protective atmospheres.

[0018] Preferably, in step (3), the heating rate of in-situ reduction is controlled at 3-10℃ / min, the holding temperature is 800-1100℃, and the holding time is 0.5-3h.

[0019] Preferably, in step (4), the green body is obtained by bidirectional molding or cold isostatic pressing, with a pressing pressure of 50-500 MPa, a pressing time of 10-30 s, and a holding time of 15-30 s.

[0020] Preferably, in step (4), the sintering temperature of the green compact is controlled at 1100–1350°C, the heating rate is 5–10°C / min, the holding time is 1–3 h, and the sintering atmosphere is a reducing atmosphere or an inert atmosphere. The reducing atmosphere is hydrogen and / or methane, and the inert atmosphere is argon and / or nitrogen.

[0021] To achieve the above-mentioned main objective, a second aspect of the present invention provides a bimodal tungsten-copper alloy material, which is obtained by sintering a tungsten-copper composite powder material with a copper mass fraction of 5 to 50 wt.%; wherein the tungsten-copper composite powder material includes coarse tungsten powder and fine tungsten powder in a mass fraction ratio of 1 to 5:1, and the fine tungsten powder and copper powder are coupled to each other and uniformly distributed on the surface of the coarse tungsten powder.

[0022] The tungsten-copper alloy of this invention is formed by pressing bimodal tungsten-copper composite powder into a green body and then sintering it. Fine tungsten and copper powder particles are coupled together and uniformly distributed on the surface of coarse tungsten powder particles, forming a structure where fine tungsten and copper powder particles coat the coarse tungsten powder particles. This reduces interfacial thermal resistance, strengthens interfacial bonding, and improves the material's density, wear resistance, and electrical and thermal conductivity. Furthermore, it reduces the driving force required for particle rearrangement during the liquid-phase sintering process of the tungsten-copper composite material, lowering the sintering temperature and reducing production energy consumption.

[0023] To more clearly illustrate the purpose, technical solution, and advantages of the present invention, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. Attached Figure Description

[0024] Figure 1 SEM image of the tungsten-copper composite powder material prepared in Example 1;

[0025] Figure 2 The image shows the laser particle size distribution of the tungsten-copper composite powder material prepared in Example 1.

[0026] Figure 3 The image shows a SEM image of the bimodal tungsten-copper alloy prepared in Example 1. Detailed Implementation

[0027] This invention provides a bimodal reinforced tungsten-copper alloy, which is formed by pressing tungsten-copper composite powder into a green blank and then sintering it. The tungsten-copper composite powder contains 5-50 wt.% Cu powder, has a bimodal structure, and the ratio of coarse to fine tungsten powder particles is 1-5:1. The preparation method of this bimodal reinforced tungsten-copper alloy material may include the following steps:

[0028] (1) A water-soluble tungsten salt, a water-soluble copper salt, and coarse tungsten powder are added to a solvent in a predetermined ratio to obtain a suspension. Preferably, the pH of the suspension is adjusted to 3-4, and an appropriate amount of dispersant (e.g., citric acid, polyethylene glycol, stearic acid, etc.) is added. The amount of dispersant added can be 0.5-2 wt.%, for example, 1 wt.%, of the suspension. The solvent is any one or two of deionized water and anhydrous ethanol; the tungsten salt can be one or two of ammonium metatungstate and / or ammonium paratungstate; the copper salt can be at least one selected from copper nitrate, copper sulfate, copper acetate, and copper chloride; and the particle size of the coarse tungsten powder is preferably 3-15 μm. 。

[0029] (2) The above suspension is atomized and pyrolyzed in a spray pyrolysis furnace to obtain a composite powder containing coarse tungsten powder and tungsten-copper oxide; preferably, the feed inlet temperature of the spray pyrolysis furnace is controlled at 150-300°C, the pyrolysis temperature is 500-700°C, and the pyrolysis atmosphere is a nitrogen and / or argon atmosphere, for example, a protective atmosphere with an argon flow rate of 1-3 L / min.

[0030] (3) The above composite powder is reduced in situ in a hydrogen furnace to obtain a tungsten-copper composite powder material with a bimodal structure. The tungsten particles in the composite powder are composed of coarse tungsten powder from the raw material and fine tungsten powder obtained by in-situ reduction of tungsten salt through atomization. The average particle size of the fine tungsten powder is 0.2μm to 1.5μm, preferably 0.6μm to 1.0μm. The two types of coarse and fine tungsten powder have a typical bimodal structure. Preferably, the heating rate of the in-situ reduction is 3 to 10℃ / min, the reduction temperature is 800 to 1100℃, and the holding time is 0.5 to 3h.

[0031] (4) The tungsten-copper composite powder is pressed into a green body and then sintered to obtain a bimodal reinforced tungsten-copper composite material. The green body can be obtained by bidirectional molding or cold isostatic pressing, with a pressing pressure of 50–500 MPa, a pressing time of 10–30 s, and a holding time of 15–30 s. Preferably, the sintering temperature is controlled at 1100–1350 °C, the heating rate is 5–10 °C / min, the holding time is 1–3 h, and the sintering atmosphere is a reducing atmosphere or an inert atmosphere, such as a reducing atmosphere with a hydrogen flow rate of 0.5–2 L / min.

[0032] The following is a detailed description with reference to embodiments and comparative examples.

[0033] Example 1

[0034] The tungsten-copper composite material in Example 1 was prepared by pressing tungsten-copper composite powder with a Cu content of 20 wt.% into a green body and then sintering it. It exhibits a bimodal structure with a coarse W particle to fine W particle mass ratio of 2:1. Its preparation method includes the following steps:

[0035] (1) Weigh 17.97g of ammonium metatungstate, 31.40g of copper acetate, and 26.67g of 5μm coarse tungsten powder, dissolve them in 304ml of deionized water, and stir continuously with a glass rod to mix them, so as to prepare a suspension solution with a concentration of 20wt%.

[0036] (2) The above suspension solution is atomized and pyrolyzed in a spray pyrolysis furnace to obtain a composite powder containing coarse tungsten powder and tungsten-copper oxide. The feed rate is controlled at 3 ml / min, the feed inlet temperature is 240℃, the pyrolysis temperature is 650℃, the pyrolysis atmosphere is argon atmosphere, and the argon flow rate is 2 L / min.

[0037] (3) The above composite powder was reduced in situ in a hydrogen furnace to obtain a tungsten-copper composite powder material with a bimodal structure of tungsten powder; wherein the material layer thickness was 3 mm, the reduction temperature was 1000℃, the heating rate was 5℃ / min, the holding time was 1 h, and the hydrogen flow rate was 0.5 L / min; after the holding time was completed, the powder was cooled with the furnace to obtain the reduced powder.

[0038] (4) The tungsten-copper composite powder is pressed into a green body and then sintered to obtain a bimodal reinforced tungsten-copper composite material. The green body is obtained by bidirectional molding, with a pressing pressure of 50 MPa, a pressing time of 30 s, and a holding time of 30 s. The sintering temperature is controlled at 1250℃, the heating rate is 5℃ / min, the holding time is 2 h, and the sintering atmosphere is a hydrogen atmosphere with a hydrogen flow rate of 0.5 L / min.

[0039] Figure 1 This is a SEM image of the tungsten-copper composite powder material prepared in Example 1. Figure 2 The laser particle size distribution map shows that the W powder particles in the composite powder material vary in size. The size of the coarse W particles is determined by the 5μm coarse tungsten powder raw material, and the laser particle size analysis indicates that the coarse W powder particles are approximately 5–7μm in size. The size of the fine W powder particles is determined by the reduction process, and the laser particle size analysis indicates that the fine W powder particles are approximately 0.5–1.5μm in size. Furthermore, from... Figure 1 and 2 It can be seen that the coarse and fine tungsten powders are distributed relatively evenly, which is beneficial to the subsequent improvement of the overall performance of tungsten-copper alloys, such as hardness and strength. Figure 3The image shows the SEM image of the bimodal tungsten-copper alloy prepared in Example 1. It can be seen that the smaller W grains are mostly uniformly distributed around the larger W grains, and together with Cu, they fill the pores formed by the larger W grains, which improves the density of the alloy and is beneficial to enhancing the alloy's electrical and thermal conductivity.

[0040] Example 2

[0041] The tungsten-copper composite material in Example 2 was prepared by pressing tungsten-copper composite powder with a Cu content of 20 wt.% into a green body and then sintering it. It exhibits a bimodal structure with a coarse W particle to fine W particle mass ratio of 1:1. Its preparation method includes the following steps:

[0042] (1) Weigh 26.96g of ammonium metatungstate, 31.40g of copper acetate, and 20g of 5μm coarse tungsten powder, dissolve them in 313ml of deionized water, and stir continuously with a glass rod to mix them, so as to prepare a suspension solution with a concentration of 20wt.%.

[0043] (2) The above suspension solution is atomized and pyrolyzed in a spray pyrolysis furnace to obtain a composite powder containing coarse tungsten powder and tungsten-copper oxide. The feed rate is controlled at 3 ml / min, the feed inlet temperature is 240℃, the pyrolysis temperature is 650℃, the pyrolysis atmosphere is argon atmosphere, and the argon flow rate is 2 L / min.

[0044] (3) The above composite powder was reduced in situ in a hydrogen furnace to obtain a tungsten-copper composite powder material with a bimodal structure of tungsten powder; wherein the material layer thickness was 3 mm, the reduction temperature was 1000℃, the heating rate was 5℃ / min, the holding time was 1 h, and the hydrogen flow rate was 0.5 L / min; after the holding time was completed, the powder was cooled with the furnace to obtain the reduced powder.

[0045] (4) The tungsten-copper composite powder is pressed into a green body and then sintered to obtain a bimodal reinforced tungsten-copper composite material. The green body is obtained by bidirectional molding, with a pressing pressure of 50 MPa, a pressing time of 30 s, and a holding time of 30 s. The sintering temperature is controlled at 1250℃, the heating rate is 5℃ / min, the holding time is 2 h, and the sintering atmosphere is a hydrogen atmosphere with a hydrogen flow rate of 0.5 L / min.

[0046] Example 3

[0047] The tungsten-copper composite material in Example 3 was prepared by pressing tungsten-copper composite powder with a Cu content of 20 wt.% into a green body and then sintering it. It exhibits a bimodal structure with a coarse W particle to fine W particle mass ratio of 2:1. Its preparation method includes the following steps:

[0048] (1) Weigh 17.97g of ammonium metatungstate, 31.40g of copper acetate, and 26.67g of 12μm crude tungsten powder, dissolve them in 304ml of deionized water, and stir continuously with a glass rod to mix them, so as to prepare a suspension solution with a concentration of 20wt%.

[0049] (2) The above suspension solution is atomized and pyrolyzed in a spray pyrolysis furnace to obtain a composite powder containing coarse tungsten powder and tungsten-copper oxide. The feed rate is controlled at 3 ml / min, the feed inlet temperature is 280℃, the pyrolysis temperature is 700℃, the pyrolysis atmosphere is argon atmosphere, and the argon flow rate is 2 L / min.

[0050] (3) The above composite powder was reduced in situ in a hydrogen furnace to obtain a tungsten copper composite powder material with a bimodal structure. The material layer thickness was 3 mm, the reduction temperature was 900℃, the heating rate was 3℃ / min, the holding time was 1 h, and the hydrogen flow rate was 0.5 L / min. After the holding time was completed, the powder was cooled with the furnace to obtain the reduced powder.

[0051] (4) The tungsten-copper composite powder is pressed into a green body and then sintered to obtain a bimodal reinforced tungsten-copper composite material. The green body is obtained by bidirectional molding, with a pressing pressure of 50 MPa, a pressing time of 30 s, and a holding time of 30 s. The sintering temperature is controlled at 1250℃, the heating rate is 5℃ / min, the holding time is 2 h, and the sintering atmosphere is a hydrogen atmosphere with a hydrogen flow rate of 0.5 L / min.

[0052] Example 4

[0053] The tungsten-copper composite material in Example 4 was prepared by pressing tungsten-copper composite powder with a Cu content of 20 wt.% into a green body and then sintering it. It exhibits a bimodal structure with a coarse W particle to fine W particle mass ratio of 2:1. Its preparation method includes the following steps:

[0054] (1) Weigh 17.97g of ammonium metatungstate, 31.40g of copper acetate, and 26.67g of 3μm coarse tungsten powder, dissolve them in 304ml of deionized water, and stir continuously with a glass rod to mix them, so as to prepare a suspension solution with a concentration of 20wt%.

[0055] (2) The above suspension solution is atomized and pyrolyzed in a spray pyrolysis furnace to obtain a composite powder containing coarse tungsten powder and tungsten-copper oxide. The feed rate is controlled at 3 ml / min, the feed inlet temperature is 180℃, the pyrolysis temperature is 550℃, the pyrolysis atmosphere is argon atmosphere, and the argon flow rate is 2 L / min.

[0056] (3) The above composite powder was reduced in situ in a hydrogen furnace to obtain a tungsten-copper composite powder material with a bimodal structure of tungsten powder; wherein the material layer thickness was 3 mm, the reduction temperature was 900℃, the heating rate was 6℃ / min, the holding time was 1 h, and the hydrogen flow rate was 0.5 L / min; after the holding time was completed, the powder was cooled with the furnace to obtain the reduced powder.

[0057] (4) The tungsten-copper composite powder is pressed into a green body and then sintered to obtain a bimodal reinforced tungsten-copper composite material. The green body is obtained by bidirectional molding, with a pressing pressure of 50 MPa, a pressing time of 30 s, and a holding time of 30 s. The sintering temperature is controlled at 1250℃, the heating rate is 5℃ / min, the holding time is 2 h, and the sintering atmosphere is a hydrogen atmosphere with a hydrogen flow rate of 0.5 L / min.

[0058] Example 5

[0059] The tungsten-copper composite material of Example 5 was prepared by pressing tungsten-copper composite powder with a Cu content of 20 wt.% into a green body and then sintering it. It exhibits a bimodal structure with a coarse W particle to fine W particle mass ratio of 5:1. Its preparation method includes the following steps:

[0060] (1) Weigh 8.99g of ammonium metatungstate, 31.40g of copper acetate, and 33.33g of 8μm coarse tungsten powder, dissolve them in 295ml of deionized water, and stir continuously with a glass rod to mix them, so as to prepare a suspension solution with a concentration of 20wt.%.

[0061] (2) The above suspension solution is atomized and pyrolyzed in a spray pyrolysis furnace to obtain a composite powder containing coarse tungsten powder and tungsten-copper oxide. The feed rate is controlled at 3 ml / min, the feed inlet temperature is 220℃, the pyrolysis temperature is 660℃, the pyrolysis atmosphere is argon atmosphere, and the argon flow rate is 2 L / min.

[0062] (3) The above composite powder was reduced in situ in a hydrogen furnace to obtain a tungsten copper composite powder material with a bimodal structure of tungsten powder; wherein the material layer thickness was 3 mm, the reduction temperature was 900℃, the heating rate was 6℃ / min, the holding time was 3 h, and the hydrogen flow rate was 0.5 L / min; after the holding time was completed, the powder was cooled with the furnace to obtain the reduced powder.

[0063] (4) The tungsten-copper composite powder is pressed into a green body and then sintered to obtain a bimodal reinforced tungsten-copper composite material. The green body is obtained by bidirectional molding, with a pressing pressure of 50 MPa, a pressing time of 30 s, and a holding time of 30 s. The sintering temperature is controlled at 1250℃, the heating rate is 5℃ / min, the holding time is 2 h, and the sintering atmosphere is a hydrogen atmosphere with a hydrogen flow rate of 0.5 L / min.

[0064] Comparative Example 1

[0065] The only difference between Comparative Example 1 and Example 1 is that only crude tungsten powder was used as raw material to prepare tungsten-copper composite powder with a Cu content of 20 wt.%. The preparation method includes the following steps:

[0066] (1) Weigh 31.40g of copper acetate and 40g of 5μm coarse tungsten powder, dissolve them in 285ml of deionized water, and stir continuously with a glass rod to mix them, so as to prepare a suspension solution with a concentration of 20wt.%.

[0067] (2) The above suspension solution is atomized and pyrolyzed in a spray pyrolysis furnace to obtain a composite powder containing coarse tungsten powder and copper oxide. The feed rate is controlled at 3 ml / min, the feed inlet temperature is 240℃, the pyrolysis temperature is 650℃, the pyrolysis atmosphere is argon atmosphere, and the argon flow rate is 2 L / min.

[0068] (3) The above composite powder is reduced in situ in a hydrogen furnace to obtain a tungsten-copper composite powder material with coarse tungsten powder and copper powder; wherein the material layer thickness is 3 mm, the reduction temperature is 1000℃, the heating rate is 5℃ / min, the holding time is 1 h, and the hydrogen flow rate is 0.5 L / min; after the holding time is completed, the powder is cooled with the furnace to obtain the reduced powder.

[0069] (4) The tungsten-copper composite powder is pressed into a green body and then sintered to obtain a tungsten-copper composite material. The green body is obtained by bidirectional molding, with a pressing pressure of 50 MPa, a pressing time of 30 s, and a holding time of 30 s. The sintering temperature is controlled at 1250℃, the heating rate is 5℃ / min, the holding time is 2 h, and the sintering atmosphere is a hydrogen atmosphere with a hydrogen flow rate of 0.5 L / min.

[0070] Comparative Example 2

[0071] The only difference between Comparative Example 2 and Example 1 is that only ammonium metatungstate was used as a raw material to prepare tungsten-copper composite powder with a Cu content of 20 wt.%. The preparation method includes the following steps:

[0072] (1) Weigh 31.40g of copper acetate and 53.93g of ammonium metatungstate, dissolve them in 341ml of deionized water, and stir continuously with a glass rod to mix them, so as to prepare a suspension with a concentration of 20wt.%.

[0073] (2) The above suspension solution is atomized and pyrolyzed in a spray pyrolysis furnace to obtain tungsten-copper oxide composite powder. The feed rate is controlled at 3 ml / min, the feed inlet temperature is 240℃, the pyrolysis temperature is 650℃, the pyrolysis atmosphere is argon atmosphere, and the argon flow rate is 2 L / min.

[0074] (3) The above composite powder is reduced in situ in a hydrogen furnace to obtain a tungsten-copper composite powder material with fine tungsten powder and copper powder; wherein the material layer thickness is 3 mm, the reduction temperature is 1000℃, the heating rate is 5℃ / min, the holding time is 1 h, and the hydrogen flow rate is 0.5 L / min; after the holding time is completed, the powder is cooled with the furnace to obtain the reduced powder.

[0075] (4) The tungsten-copper composite powder is pressed into a green body and then sintered to obtain a tungsten-copper composite material. The green body is obtained by bidirectional molding, with a pressing pressure of 50 MPa, a pressing time of 30 s, and a holding time of 30 s. The sintering temperature is controlled at 1250℃, the heating rate is 5℃ / min, the holding time is 2 h, and the sintering atmosphere is a hydrogen atmosphere with a hydrogen flow rate of 0.5 L / min.

[0076] Comparative Example 3

[0077] The difference between Comparative Example 3 and Example 1 is that coarse tungsten powder with an average particle size of 5 μm and fine tungsten powder with an average particle size of 1 μm were used as raw materials to prepare a tungsten-copper composite powder with a Cu content of 20 wt.%, wherein the mass ratio of coarse tungsten powder to fine tungsten powder was 2:1. The preparation method includes the following steps:

[0078] (1) Weigh 31.40g of copper acetate, 26.67g of 5μm coarse tungsten powder, and 13.33g of 1μm fine tungsten powder, dissolve them in 286ml of deionized water, and stir continuously with a glass rod to mix them, so as to prepare a suspension solution with a concentration of 20wt.%.

[0079] (2) The above suspension solution is atomized and pyrolyzed in a spray pyrolysis furnace to obtain a composite powder containing coarse and fine tungsten powder and copper oxide. The feed rate is controlled at 3 ml / min, the feed inlet temperature is 240℃, the pyrolysis temperature is 650℃, the pyrolysis atmosphere is argon atmosphere, and the argon flow rate is 2 L / min.

[0080] (3) The above composite powder was reduced in situ in a hydrogen furnace to obtain a tungsten-copper composite powder material with a bimodal structure of tungsten powder; wherein the material layer thickness was 3 mm, the reduction temperature was 1000℃, the heating rate was 5℃ / min, the holding time was 1 h, and the hydrogen flow rate was 0.5 L / min; after the holding time was completed, the powder was cooled with the furnace to obtain the reduced powder.

[0081] (4) The tungsten-copper composite powder is pressed into a green body and then sintered to obtain a bimodal reinforced tungsten-copper composite material. The green body is obtained by bidirectional molding, with a pressing pressure of 50 MPa, a pressing time of 30 s, and a holding time of 30 s. The sintering temperature is controlled at 1250℃, the heating rate is 5℃ / min, the holding time is 2 h, and the sintering atmosphere is a hydrogen atmosphere with a hydrogen flow rate of 0.5 L / min.

[0082] The Vickers hardness, electrical conductivity, and density of the tungsten-copper alloys prepared in Examples 1-5 and Comparative Examples 1-3 were measured. The results are shown in Table 1.

[0083] Table 1: Test results of Vickers hardness, electrical conductivity and density of tungsten-copper alloys in the examples and comparative examples

[0084]

[0085] As shown in Table 1, the hardness, conductivity, and density of Examples 1-5 are all higher than those of Comparative Example 1 (which uses coarser tungsten powder). Although Comparative Example 2 (using finer tungsten powder) has the highest hardness, its conductivity and density are significantly lower than those of Examples 1-5. It should be particularly noted that although Comparative Example 3 uses both coarse and fine tungsten powder to prepare the tungsten-copper alloy, the mechanical mixing of the fine and coarse tungsten powders results in lower conductivity and density compared to Examples 1-5. Overall, the conductivity and density of the tungsten-copper alloys in the five examples are higher than those in the three comparative examples, indicating that the bimodal tungsten-copper alloy prepared by the method of this invention maintains high hardness while also exhibiting significant advantages in improved conductivity and density, resulting in superior overall performance.

[0086] In summary, the tungsten-copper alloy with a bimodal structure contains tungsten particles of two different sizes. The fine grains ensure high hardness, while the coarse grains provide diffusion channels for dislocations, resulting in high electrical conductivity. Furthermore, the appropriate ratio of fine to coarse particles allows the fine W powder to fully fill the pores formed by the coarse W powder, thereby increasing the alloy density. As a result, this tungsten-copper alloy simultaneously possesses high hardness, high density, and good electrical conductivity.

[0087] While the present invention has been disclosed above with reference to specific embodiments, it should be understood that the above specific embodiments are not intended to limit the scope of the present invention. Any person skilled in the art can make some modifications without departing from the scope of the invention; that is, all equivalent modifications made in accordance with the present invention should be covered by the protection scope of the present invention.

Claims

1. A method for preparing a bimodal tungsten-copper alloy, comprising the following steps: (1) A suspension is obtained by adding water-soluble tungsten salt, water-soluble copper salt and coarse tungsten powder to a solvent in a predetermined ratio; (2) The above suspension is atomized and pyrolyzed in a spray pyrolysis furnace to obtain a composite powder containing coarse tungsten powder and tungsten-copper oxide. (3) The above composite powder is reduced in situ in a hydrogen furnace to obtain a tungsten-copper composite powder material containing coarse tungsten powder and fine tungsten powder; wherein the fine tungsten powder and copper powder are coupled to each other and are evenly distributed on the surface of the coarse tungsten powder. (4) The above-mentioned tungsten-copper composite powder material is pressed into a green blank and then sintered to obtain a tungsten-copper alloy material with a bimodal structure of tungsten grains; The coarse tungsten powder has an average particle size of 3 μm to 15 μm, and the fine tungsten powder has an average particle size of 0.2 μm to 1.5 μm.

2. The preparation method according to claim 1, wherein, The solvent is any one or two of deionized water and anhydrous ethanol; the tungsten salt is any one or two of ammonium metatungstate and ammonium paratungstate.

3. The preparation method according to claim 1, wherein, The copper salt is selected from at least one of copper nitrate, copper sulfate, copper acetate, and copper chloride.

4. According to the preparation method of claim 1, in step (2), the feed inlet temperature of the spray pyrolysis furnace is controlled to be 150~300 ℃, the pyrolysis temperature is 500~700 ℃, and the pyrolysis atmosphere is one or two protective atmospheres selected from nitrogen and argon.

5. The preparation method according to claim 1, wherein in step (3), the heating rate for in-situ reduction is controlled at 3~10℃ / min, the holding temperature is 800~1100℃, and the holding time is 0.5~3 h.

6. According to the preparation method of claim 1, in step (4), the sintering temperature of the green body is controlled at 1100~1350 ℃, the heating rate is 5~10 ℃ / min, the holding time is 1~3 h, and the sintering atmosphere is a reducing atmosphere or an inert atmosphere.

7. The preparation method according to claim 6, wherein, The reducing atmosphere is hydrogen and / or methane, and the inert atmosphere is argon and / or nitrogen.

8. A bimodal tungsten-copper alloy material, obtained by sintering tungsten-copper composite powder material with a copper mass fraction of 5-50 wt.%; wherein, The tungsten-copper composite powder material comprises coarse tungsten powder and fine tungsten powder in a mass fraction ratio of 1 to 5:1, wherein the fine tungsten powder and copper powder are coupled to each other and uniformly distributed on the surface of the coarse tungsten powder; the bimodal tungsten-copper alloy material is obtained by the preparation method described in any one of claims 1-7.

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