Preparation method of tungsten-copper alloy and tungsten-copper alloy

Abstract

The embodiment of the invention provides a preparation method of a tungsten-copper alloy and the tungsten-copper alloy, and relates to the technical field of alloy preparation.The method comprises the steps that superfine tungsten oxide powder, tungsten salt, copper salt and a polymer additive are added into deionized water to be evenly mixed, and a precursor mixed solution is obtained; carrying out spray granulation on the precursor mixed solution by adopting a spray dryer to obtain spherical tungsten-copper precursor composite powder; roasting the spherical tungsten-copper precursor composite powder to obtain tungsten-copper oxide composite powder, and carrying out segmented reduction on the tungsten-copper oxide composite powder to obtain tungsten-copper composite powder with tungsten grains having a nanocrystalline / ultra-fine grain bimodal distribution characteristic; and the tungsten-copper composite powder is pressed to obtain an alloy blank, the alloy blank is sintered, and the tungsten-copper alloy is prepared. According to the double-peak distribution tungsten-copper composite powder, full densification of the alloy can be promoted through coupling rearrangement of large and small tungsten particles in the sintering process, and the compactness, the heat conductivity and the electric conductivity of the tungsten-copper alloy can be improved.

Description

Technical Field

[0001] The embodiments of the present disclosure relate to the technical field of alloy preparation, and in particular, to a preparation method of a tungsten-copper alloy and a tungsten-copper alloy. Background Art

[0002] Tungsten copper alloy is often used as packaging and heat dissipation materials for high-power devices such as radio frequency microwaves and semiconductor lasers. Tungsten copper alloy can also be used as electrical contact materials for high-voltage electrical switches. It is also a key material for rocket nozzle throat linings and other parts that are resistant to short-term high-temperature thermal erosion in aerospace technology. In recent years, with the continuous expansion and development of electronic information, new energy power, aerospace, wireless communications and other fields to a higher level, the demand for high thermal conductivity and high electrical conductivity tungsten copper alloy has continued to rise.

[0003] At present, there are two main methods for preparing tungsten copper alloys: melt infiltration method and mixed powder sintering method. The tungsten copper alloy prepared by the melt infiltration method has problems such as coarse grains, uneven tissue distribution, insufficient thermal conductivity, electrical conductivity and ablation resistance, low material utilization rate and complex preparation process. Moreover, since it is difficult to obtain a continuous tungsten skeleton by firing when the tungsten content is too high or too low, the melt infiltration method is not suitable for preparing tungsten copper alloys with high tungsten or low tungsten (high copper) content, and its application range is limited. The mixed powder sintering method is to mix tungsten powder and copper powder in a certain proportion, press them into shape, and then sinter them under a protective atmosphere to obtain a tungsten copper alloy. However, due to the large difference in density and poor wettability between tungsten and copper, it is difficult to achieve uniform compounding between tungsten powder and copper powder, which leads to abnormal grain structure and phase segregation of the sintered alloy, affecting the thermal conductivity and electrical conductivity of the alloy. In addition, the particle size of industrial tungsten powder and copper powder is coarse, and the tungsten grains are usually distributed in a single size. The powder has poor fluidity, low bulk density, insufficient sintering activity, and high temperature and time required for sintering the alloy, resulting in coarse grain structure and low density of the sintered body, which limits the significant improvement of the thermal conductivity and electrical conductivity of the tungsten-copper alloy. Summary of the invention

[0004] The purpose of the present disclosure is to provide a preparation method of tungsten-copper alloy and tungsten-copper alloy, thereby overcoming the problem of poor performance of tungsten-copper alloy caused by limitations and defects of related technologies to at least a certain extent.

[0005] According to one aspect of the present disclosure, a preparation method of a tungsten-copper alloy is provided, comprising: adding ultrafine tungsten oxide powder, tungsten salt, copper salt and polymer additives to deionized water and mixing them evenly to obtain a precursor mixed solution; spray granulating the precursor mixed solution with a spray dryer to obtain a spherical tungsten-copper precursor composite powder; roasting the spherical tungsten-copper precursor composite powder to obtain a tungsten-copper oxide composite powder, and performing segmented reduction on the tungsten-copper oxide composite powder to obtain a tungsten-copper composite powder having a nanocrystalline / ultrafine crystal bimodal distribution characteristic of tungsten grains; pressing the tungsten-copper composite powder to obtain an alloy blank and sintering the blank to prepare a tungsten-copper alloy.

[0006] In an exemplary embodiment of the present disclosure, the particle size of the ultrafine tungsten oxide powder is 100-700 nm; the tungsten oxide is any one of yellow tungsten oxide, blue tungsten oxide, purple tungsten oxide, and tungsten dioxide.

[0007] In an exemplary embodiment of the present disclosure, the amount of the polymer additive added to the precursor mixed solution is 0.5~10wt% of the total mass of the ultrafine tungsten oxide powder, tungsten salt and copper salt; the tungsten salt is a water-soluble salt, and the concentration of the tungsten salt is 0.02~1.5mol / L; the tungsten salt includes one or more of ammonium tungstate, sodium tungstate, and potassium tungstate; the copper salt is a water-soluble salt, and the concentration of the copper salt is 0.05~2.5mol / L; the copper salt includes one or more of copper chloride, copper nitrate, copper oxalate, and copper acetate.

[0008] In an exemplary embodiment of the present disclosure, the polymer additive is a water-soluble polymer, and the polymer additive includes one or more of cellulose, polyvinyl alcohol, polyethylene glycol, and polyvinyl pyrrolidone.

[0009] In an exemplary embodiment of the present disclosure, the liquid inlet amount of the precursor mixed solution during the spray granulation process is 15-45%, the air inlet temperature is 200-350° C., the air outlet temperature is 100-180° C., and the nozzle rotation frequency is 25-55 Hz.

[0010] In an exemplary embodiment of the present disclosure, the calcination temperature is 250-500° C., the calcination time is 0.5-2 h, the calcination heating rate is 5-20° C. / min, and the calcination atmosphere is air, argon or nitrogen.

[0011] In an exemplary embodiment of the present disclosure, the staged reduction includes a first stage reduction and a second stage reduction, the atmospheres of the first stage reduction and the second stage reduction are hydrogen, decomposed ammonia or an argon-hydrogen mixture; the reduction temperature of the first stage reduction is 250~550°C, the reduction time is 0.5~2h, and the heating rate of the first stage reduction is 5~10°C / min; the reduction temperature of the second stage reduction is 550~850°C, the reduction time is 0.5~3h, and the heating rate of the second stage reduction is 3~10°C / min.

[0012] In an exemplary embodiment of the present disclosure, the tungsten-copper composite powder is spherical particles with a particle size of 20-50 μm, and the tungsten grains in the tungsten-copper composite powder have a nanocrystalline / ultrafine crystal bimodal distribution characteristic, the size of the nano tungsten grains is 20-70 nm, and the size of the ultrafine tungsten grains is 100-500 nm.

[0013] In an exemplary embodiment of the present disclosure, the sintering temperature of the tungsten copper alloy is 1100-1450° C., the sintering time is 0.5-3 hours, the sintering environment is normal pressure sintering, and the sintering atmosphere is hydrogen, decomposed ammonia or argon-hydrogen mixed gas.

[0014] According to one aspect of the present disclosure, a tungsten-copper alloy is provided, and the tungsten-copper alloy is prepared according to any one of the above-mentioned methods for preparing the tungsten-copper alloy.

[0015] In the technical solution provided in the embodiment of the present disclosure, on the one hand, the mixed solution of ultrafine tungsten oxide powder, soluble tungsten salt and copper salt is first sprayed and granulated under the bonding action of a polymer additive to obtain a composite uniform spherical tungsten-copper precursor composite powder, which avoids the segregation and phase separation of the tungsten source and the copper source, and improves the distribution uniformity of the components in the composite powder. On the other hand, by roasting and segmented reduction, a tungsten-copper composite powder with good sphericity, high sintering activity and tungsten grains having a bimodal distribution characteristic of nanocrystalline / ultrafine crystals is prepared. Compared with a single-scale distribution, the bimodal distribution powder not only has better fluidity and higher loose packing density, but also can promote the full densification of the alloy through the coupling rearrangement of large and small tungsten particles during the sintering process, and maintain the distribution uniformity of the alloy microstructure, thereby improving the density, thermal conductivity and electrical conductivity of the tungsten-copper alloy. On the other hand, the material utilization rate is improved, the preparation process is simplified, limitations are avoided, and the scope of application is increased.

[0016] It is to be understood that the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the present disclosure. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] The accompanying drawings herein are incorporated into the specification and constitute a part of the specification, illustrate embodiments consistent with the present disclosure, and together with the specification are used to explain the principles of the present disclosure. Obviously, the accompanying drawings described below are only some embodiments of the present disclosure, and for ordinary technicians in this field, other accompanying drawings can be obtained based on these accompanying drawings without creative work.

[0018] Figure 1 A flow chart schematically shows a method for preparing a tungsten-copper alloy in an embodiment of the present disclosure.

[0019] Figure 2This is a SEM image of the tungsten-copper alloy prepared in Example 1 of the present disclosure.

[0020] Figure 3 This is the EDS graph of W in the tungsten-copper alloy prepared in Example 1 of the present disclosure.

[0021] Figure 4 This is the EDS graph of Cu in the tungsten-copper alloy prepared in Example 1 of the present disclosure.

[0022] Figure 5 This is a SEM image of the tungsten-copper alloy prepared in Comparative Example 1 of the present disclosure.

[0023] Figure 6 This is a SEM image of the tungsten-copper alloy prepared in Comparative Example 2 of the present disclosure. DETAILED DESCRIPTION

[0024] Example embodiments will now be described more fully with reference to the accompanying drawings. However, example embodiments can be implemented in a variety of forms and should not be construed as being limited to the examples set forth herein; on the contrary, these embodiments are provided so that the present disclosure will be more comprehensive and complete, and the concepts of the example embodiments are fully conveyed to those skilled in the art. The described features, structures, or characteristics may be combined in one or more embodiments in any suitable manner. In the following description, many specific details are provided to provide a full understanding of the embodiments of the present disclosure. However, those skilled in the art will appreciate that the technical solutions of the present disclosure may be practiced while omitting one or more of the specific details, or other methods, components, devices, steps, etc. may be adopted. In other cases, known technical solutions are not shown or described in detail to avoid obscuring various aspects of the present disclosure.

[0025] The terms "a", "an", "the" and "said" used in this specification are used to indicate the presence of one or more elements / components, etc.; the terms "including" and "having" are used to express an open-ended inclusion and mean that there may be additional elements / components, etc. in addition to the listed elements / components, etc.; the terms "first" and "second" etc. are used only as labels and are not intended to limit the quantity of their objects.

[0026] Tungsten copper alloy is a pseudo alloy material composed of two mutually immiscible metals, tungsten and copper. It combines the high strength, high temperature resistance, arc erosion resistance, low thermal expansion of tungsten with the high conductivity, high thermal conductivity and good processability of copper. The thermal conductivity, electrical conductivity, strength and thermal expansion properties of tungsten copper alloy can be comprehensively controlled through alloy composition design according to demand. Tungsten copper alloy can form a good thermal expansion match with ceramics, kovar and semiconductor materials, so it is often used as a packaging and heat dissipation material for high-power devices such as radio frequency microwaves and semiconductor lasers. In addition, due to its excellent electrical conductivity and arc erosion resistance, tungsten copper alloy is used in high-voltage electrical switch electrical contact materials. It is also a key material for rocket nozzle throat linings and other parts that are resistant to high temperature thermal erosion in aerospace technology for a short time. In recent years, with the continuous expansion and development of electronic information, new energy power, aerospace, wireless communications and other fields to a higher level, the demand for high thermal conductivity and high electrical conductivity tungsten copper alloy has continued to rise.

[0027] At present, there are two main methods for preparing tungsten-copper alloys: melt infiltration and mixed powder sintering. The melt infiltration method is a method in which a porous tungsten particle skeleton with a certain density and strength is first prepared, and then the metallic copper liquid flows along the gaps between the tungsten particles under the action of capillary force to fill and wet the porous tungsten skeleton. Limited by the pore structure of the tungsten skeleton and the difficulty in controlling the liquid copper infiltration process, the tungsten-copper alloy prepared by the melt infiltration method has problems such as coarse grains, uneven tissue distribution, insufficient thermal conductivity, electrical conductivity and ablation resistance, low material utilization rate and complex preparation process. Moreover, since it is difficult to obtain a continuous tungsten skeleton by firing when the tungsten content is too high or too low (tungsten content ≥90% or ≤50%), the melt infiltration method is not suitable for the preparation of tungsten-copper alloys with high tungsten or low tungsten (high copper) content, and its application range is limited.

[0028] The mixed powder sintering method is to mix tungsten powder and copper powder in a certain proportion, press them into shape, and then sinter them under a protective atmosphere to obtain a tungsten-copper alloy. The characteristics of this method are that the production process is simple and easy to control, and tungsten-copper alloys with any tungsten (copper) content can be prepared. However, due to the large difference in density and poor wettability between tungsten and copper, it is difficult to achieve uniform compounding between tungsten powder and copper powder, which leads to abnormal grain structure and phase segregation of the sintered alloy, affecting the thermal conductivity and electrical conductivity of the alloy. In addition, the particle size of industrial tungsten powder and copper powder is coarse (generally several to tens of microns), and the tungsten grains are usually distributed in a single particle size. The powder has poor fluidity, low bulk density, insufficient sintering activity, and high temperature and time required for sintering the alloy, resulting in coarse grain structure and low density of the sintered body (generally only 90%~95% of the theoretical density), which limits the significant improvement of the thermal conductivity and electrical conductivity of the tungsten-copper alloy.

[0029] In order to solve the above technical problems, the present invention provides a method for preparing a tungsten-copper alloy with high thermal conductivity and high electrical conductivity. Figure 1As shown in , the preparation method of the tungsten copper alloy mainly includes the following steps: In step S110, ultrafine tungsten oxide powder, tungsten salt, copper salt and polymer additive are added to deionized water and mixed evenly to obtain a precursor mixed solution; In step S120, a spray dryer is used to spray granulate the precursor mixed solution to obtain spherical tungsten-copper precursor composite powder; In step S130, the spherical tungsten-copper precursor composite powder is calcined to obtain a tungsten-copper oxide composite powder, and the tungsten-copper oxide composite powder is staged reduced to obtain a tungsten-copper composite powder having a nanocrystalline / ultrafine crystal bimodal distribution characteristic of tungsten grains; In step S140, the tungsten-copper composite powder is pressed into an alloy blank and sintered to prepare a tungsten-copper alloy.

[0030] The technical solution in the disclosed embodiment is to reduce ultrafine tungsten oxide powder to obtain ultrafine tungsten particles, and to obtain nanocrystalline tungsten particles by spray pyrolysis-calcination-reduction of tungsten salt. The two are coupled to form a bimodal distribution in the tungsten-copper composite powder, which helps to improve the fluidity of the composite powder and increase the packing density of the powder. During the sintering process, the coupled rearrangement of large and small tungsten particles promotes the full densification of the alloy, improves the uniformity of the alloy's microstructure, and thereby improves the density, thermal conductivity, electrical conductivity and other properties of the tungsten-copper alloy.

[0031] Next, the preparation method of the tungsten-copper alloy in the embodiment of the present disclosure is specifically described.

[0032] In step S110, ultrafine tungsten oxide powder, tungsten salt, copper salt and polymer additives are added into deionized water and mixed evenly to obtain a precursor mixed solution.

[0033] In the embodiment of the present disclosure, the particle size of the ultrafine tungsten oxide powder is 100-700 nm. The tungsten oxide in the ultrafine tungsten oxide powder can be yellow tungsten oxide (WO3), blue tungsten oxide or purple tungsten oxide (WO 2.72 ), tungsten dioxide (WO2). Ultrafine tungsten oxide is reduced to obtain ultrafine tungsten particles, which form a bimodal coupling distribution with the nano-tungsten grains obtained by tungsten salt spray pyrolysis-calcination-reduction, which helps to improve the fluidity of the tungsten-copper composite powder and increase the packing density of the powder. During the sintering process, the coupling rearrangement of large and small tungsten particles promotes the full densification of the alloy, improves the uniformity of the alloy's microstructure, and thus improves the thermal and electrical conductivity of the tungsten-copper alloy.

[0034] Tungsten salt is a water-soluble salt, including but not limited to one or more of ammonium tungstate, sodium tungstate, potassium tungstate, etc. The concentration of tungsten salt is 0.02~1.5mol / L. Copper salt is a water-soluble salt, including but not limited to one or more of copper chloride, copper nitrate, copper oxalate, and copper acetate. The concentration of copper salt is 0.05~2.5mol / L. The total mass ratio of tungsten to copper in the precursor mixed solution is 95:5~10:90, and the total mass ratio refers to the total mass ratio of tungsten to copper. The present invention realizes precise control of the mass ratio of tungsten and copper in the system by controlling the concentration and addition amount of tungsten source and copper source in the precursor mixed solution. Among them, tungsten salt is sprayed pyrolysis-roasting-reduction to obtain nanocrystalline tungsten particles, and ultrafine tungsten particles obtained by reduction of tungsten oxide form a bimodal coupled distribution; copper salt is sprayed pyrolysis-roasting-reduction to obtain ultrafine crystalline copper particles, and is uniformly in-situ compounded with bimodal distribution tungsten particles to form high-quality tungsten-copper composite powder.

[0035] The polymer additive is a water-soluble polymer, including but not limited to one or more of cellulose, polyvinyl alcohol, polyethylene glycol, polyvinyl pyrrolidone, etc. The amount of polymer additive added to the precursor mixed solution is 0.5~10wt% of the total mass of ultrafine tungsten oxide powder, tungsten salt and copper salt. The main functions of the polymer additive are thickening, dispersion and bonding, promoting the full dissolution of ultrafine tungsten oxide powder, tungsten salt and copper salt, and avoiding phase separation of each component due to excessive physical property differences during the spray drying process. The present invention introduces a water-soluble polymer as a dispersant and adhesive, and effectively promotes the uniform dispersion of tungsten oxide and tungsten and copper precursor metal salts by regulating the type, amount and method of addition of the polymer, while avoiding phase separation between the components due to large density differences and poor wettability during the spray drying process, which is beneficial to improve the distribution uniformity of tungsten and copper, and thus improve the density, uniformity of organizational structure, thermal conductivity and electrical conductivity of tungsten-copper alloy.

[0036] In step S120, a spray dryer is used to spray granulate the precursor mixed solution to obtain spherical tungsten-copper precursor composite powder.

[0037] In the embodiment of the present disclosure, the liquid inlet amount of the precursor mixed solution during the spray granulation process is 15-45%, the air inlet temperature is 200-350°C, the air outlet temperature is 100-180°C, and the nozzle rotation frequency is 25-55Hz. The present disclosure controls the process conditions during the spray granulation process to promote the rapid evaporation of the solution, while avoiding the segregation and agglomeration of the components during the solution drying process, and improving the sphericity of the powder particles after drying, which is conducive to obtaining a high-activity spherical tungsten-copper precursor composite powder with high sphericity and uniform component distribution.

[0038] In step S130, the spherical tungsten-copper precursor composite powder is calcined to obtain a tungsten-copper oxide composite powder and then subjected to staged reduction to obtain a tungsten-copper composite powder having a nanocrystalline / ultrafine crystal bimodal distribution characteristic of tungsten grains.

[0039] In the embodiment of the present disclosure, the calcination temperature of the spherical tungsten-copper precursor composite powder is 250-500°C, the calcination time is 0.5-2h, and the calcination atmosphere can be air, argon or nitrogen. The heating rate during the calcination process can be 5-20°C / min. The present disclosure controls the calcination temperature, time and atmosphere to ensure that the polymer additives are completely removed and the spherical tungsten-copper precursor composite powder is fully converted into tungsten-copper oxide composite powder, while inheriting the spherical morphology and particle size of the spherical tungsten-copper precursor composite powder, which is conducive to obtaining a spherical tungsten-copper composite powder with high sintering activity.

[0040] The segmented reduction of tungsten copper oxide composite powder is divided into two stages, specifically including the first stage reduction and the second stage reduction. Among them, the reduction temperature of the second stage reduction is higher than the reduction temperature of the first stage reduction, and the heating rate of the second stage reduction is less than the heating rate of the first stage reduction. Exemplarily, the reduction temperature of the first stage is 250~550℃, and the reduction time is 0.5~2h. The reduction temperature of the second stage is 550~850℃, and the reduction time is 0.5~3h. The reducing atmosphere of the first stage reduction and the second stage reduction can be hydrogen, decomposed ammonia or argon hydrogen mixture. The present disclosure proposes a segmented reduction process for tungsten copper oxide composite powder, and by regulating the process parameters in the segmented reduction process, while ensuring that the tungsten copper oxide composite powder is fully reduced, the spherical morphology of the spherical tungsten copper precursor composite powder and the tungsten copper oxide composite powder is inherited, and the agglomeration and growth of tungsten powder are avoided, which is conducive to reducing the particle size of the composite powder and obtaining a spherical tungsten copper composite powder with high sintering activity.

[0041] The tungsten-copper composite powder is a spherical particle with a particle size of 20-50 μm, wherein the tungsten grains have a bimodal distribution characteristic of nanocrystalline / ultrafine crystals, that is, nano-tungsten grains and ultrafine tungsten grains. The size of the nano-tungsten grains is 20-70 nm, and the size of the ultrafine tungsten grains is 100-500 nm. The mass ratio of tungsten to copper in the tungsten-copper composite powder is 95:5-10:90. The present invention obtains a tungsten-copper composite powder with good sphericity and uniform dispersion by spray granulation, roasting and reduction of a mixed solution of ultrafine tungsten oxide powder, tungsten salt and copper salt, wherein the ultrafine tungsten particles obtained by reducing ultrafine tungsten oxide and the nano-tungsten particles obtained by spray pyrolysis-roasting-reduction of tungsten salt are coupled with each other to form a bimodal distribution, which is conducive to sintering to obtain a high-density and high-performance tungsten-copper alloy.

[0042] In step S140, the tungsten-copper composite powder is pressed into an alloy blank and sintered to prepare a tungsten-copper alloy.

[0043] In the embodiment of the present disclosure, the sintering temperature of the alloy blank is 1100-1450°C, the sintering time is 0.5-3h, the sintering environment is normal pressure sintering, and the sintering atmosphere can be hydrogen, decomposed ammonia or argon hydrogen mixture. The present disclosure promotes gas removal, impurity removal and shrinkage and rearrangement of large and small tungsten particles during the sintering process by controlling the temperature, time and atmosphere of the alloy sintering, which is conducive to achieving full sintering and densification of the tungsten copper alloy.

[0044] The tungsten and copper phases in the prepared tungsten-copper alloy are evenly distributed and highly connected in three dimensions. The tungsten grains are fine and uniform, the alloy density is ≥98.5%, and the alloy has excellent thermal conductivity and electrical conductivity.

[0045] Compared with the direct mixing of tungsten powder and copper powder, the technical solution provided in the embodiment of the present disclosure sprays and granulates a mixed solution of ultrafine tungsten oxide, soluble tungsten salt and copper salt under the bonding action of a polymer to obtain a composite and uniform spherical tungsten-copper precursor composite powder, thereby avoiding the segregation and phase separation of the tungsten source and the copper source, and is beneficial to improving the distribution uniformity of the tungsten and copper phases, thereby improving the density, uniformity of the organizational structure, thermal conductivity, electrical conductivity and other properties of the tungsten-copper alloy.

[0046] The ultrafine tungsten oxide used is reduced to obtain ultrafine tungsten particles, which form a bimodal coupled distribution with the nano-tungsten grains obtained by tungsten salt spray pyrolysis-calcination-reduction, which helps to improve the fluidity of the tungsten-copper composite powder and increase the packing density of the powder. During the sintering process, the coupled rearrangement of large and small tungsten particles promotes the full densification of the alloy, improves the uniformity of the alloy's microstructure, and thereby improves the density, thermal conductivity, electrical conductivity and other properties of the tungsten-copper alloy.

[0047] The spherical tungsten-copper nanocomposite powder with adjustable composition and particle size, uniform compound, high sintering activity, good fluidity and formability obtained by spray granulation combined with roasting and staged reduction reduces the additional granulation link in the later stage, avoids the introduction of impurities, and simplifies the process steps. Compared with the traditional melt infiltration method and mixed powder sintering method, it can significantly reduce the sintering temperature, shorten the sintering time, save the sintering cost, and improve the comprehensive properties of the tungsten-copper alloy such as density, thermal conductivity and electrical conductivity.

[0048] The ratio of tungsten to copper in the prepared tungsten-copper composite powder and tungsten-copper alloy can be precisely controlled by adjusting the mass ratio of tungsten to copper in tungsten oxide powder and the mixed solution of tungsten salt and copper salt, so that the preparation of a full range of tungsten-copper alloys with any tungsten (copper) content can be achieved.

[0049] Compared with the tungsten-copper alloy prepared by the melt infiltration method and the mixed powder sintering method, the tungsten-copper alloy prepared by the present invention has a high density (≥98%), a fine and uniform tungsten grain structure, and a high degree of connectivity between the tungsten and copper phases in three-dimensional space. The tungsten-copper alloy has higher thermal conductivity, electrical conductivity and other properties.

[0050] The raw materials used are cheap and easy to obtain, and the proposed process method and the equipment used can be promoted for large-scale industrial production. The prepared tungsten-copper alloy has broad application prospects in many fields such as high-power device packaging and heat dissipation materials, high-voltage resistant electrical contact materials, etc.

[0051] Next, the preparation method of the tungsten-copper alloy disclosed in the present invention is specifically described in conjunction with an embodiment.

[0052] Example 1 Step 1: First, add 5g of polyvinyl alcohol into 500mL of deionized water, stir and heat until it is fully dissolved, then add 37.83g of tungsten trioxide, 80.87g of ammonium metatungstate, and 26.64g of copper chloride and mix well to obtain a precursor mixed solution.

[0053] Step 2: Use a spray dryer to spray granulate the precursor mixed solution obtained in step 1 to obtain spherical tungsten-copper precursor composite powder. The liquid inlet volume of the mixed solution in the spray drying is 40%, the air inlet temperature is 250°C, the air outlet temperature is 120°C, and the nozzle rotation frequency is 35Hz.

[0054] Step 3: calcine the spherical tungsten-copper precursor composite powder obtained in step 2 to obtain a tungsten-copper oxide composite powder; then perform a staged reduction treatment on the tungsten-copper oxide composite powder to obtain a W90Cu10 composite powder, in which the mass ratio of W to Cu in the composite powder is 9:1. The calcination process is: heating to 350°C at a heating rate of 10°C / min and then keeping warm for 2h, and the calcination atmosphere is air. The staged reduction treatment is: first heating to 500°C at a rate of 10°C / min and then keeping warm for 1h for the first stage reduction, then heating to 750°C at a rate of 5°C / min and then keeping warm for 2h for the second stage reduction; the atmosphere for the first stage reduction and the second stage reduction is hydrogen.

[0055] Step 4: Use a cold isostatic press to press the W90Cu10 composite powder obtained in step 3 to obtain a W90Cu10 alloy billet, and then transfer it to a sintering furnace for sintering to obtain a W90Cu10 alloy. The molding pressure is 300MPa, and the holding time is 10min. The sintering process is: first increase the temperature to 800℃ at 10℃ / min and keep it for 30min, then increase the temperature to 1000℃ at 10℃ / min and keep it for 30min, and finally increase the temperature to 1400℃ at 5℃ / min and keep it for 3h; the sintering atmosphere is hydrogen.

[0056] The density of the W90Cu10 alloy prepared in Example 1 was 17.15 g / cm 3 , converted to a density of 98.9%, the tungsten grain size in the prepared alloy is 0.7~2.5μm, the thermal conductivity is 203W / (m·K), and the electrical conductivity is 39.2%IACS.

[0057] Figure 2 The surface SEM image of the W90Cu10 alloy prepared in Example 1 is shown in FIG. Figure 2 It can be seen that the grain structure of the W90Cu10 alloy is fine and uniform, and there is no phase segregation.

[0058] Figure 3 and Figure 4 1 and 2 are EDS distribution diagrams of W and Cu in the W90Cu10 alloy prepared in Example 1. It can be seen that the W and Cu phases in the W90Cu10 alloy are evenly distributed.

[0059] Example 2 This embodiment includes the following steps: Step 1: First, add 2.5g polyethylene glycol into 500mL deionized water, stir and heat until it is fully dissolved, then add 24.73g purple tungsten oxide (WO 2.72 ), 107.64 g of sodium tungstate, and 62.39 g of copper acetate are mixed to obtain a precursor mixed solution.

[0060] Step 2: Use a spray dryer to spray granulate the precursor mixed solution obtained in step 1 to obtain spherical tungsten-copper precursor composite powder. The liquid inlet amount of the precursor mixed solution in the spray drying is 30%, the air inlet temperature is 260°C, the air outlet temperature is 110°C, and the nozzle rotation frequency is 40Hz.

[0061] Step 3: calcine the spherical tungsten-copper precursor composite powder obtained in step 2 to obtain a tungsten-copper oxide composite powder; then perform a staged reduction treatment on the tungsten-copper oxide composite powder to obtain a W80Cu20 composite powder, in which the mass ratio of W to Cu is 8:2. The calcination process is: heating to 400°C at a heating rate of 15°C / min and then keeping warm for 2h, and the calcination atmosphere is argon. The staged reduction treatment is: first heating to 450°C at a rate of 10°C / min and then keeping warm for 0.5h for the first stage reduction, and then heating to 700°C at a rate of 3°C / min and then keeping warm for 2h for the second stage reduction; the atmosphere for the first stage reduction and the second stage reduction is decomposed ammonia.

[0062] Step 4: Use a cold isostatic press to press the W80Cu20 composite powder obtained in step 3 to obtain a W80Cu20 alloy billet, and then transfer it to a sintering furnace for sintering to obtain a W80Cu20 alloy; the molding pressure is 250MPa, and the holding time is 10min. The sintering process is: first increase the temperature to 800℃ at 10℃ / min and keep it for 30min, then increase the temperature to 1000℃ at 10℃ / min and keep it for 30min, and then increase the temperature to 1300℃ at 3℃ / min and keep it for 3h; the sintering atmosphere is an argon-hydrogen mixture.

[0063] After testing, the density of the W80Cu20 alloy prepared in Example 2 is 15.50 g / cm 3 , which translates to a density of 98.6%, a tungsten grain size of 0.7~1.7μm, a thermal conductivity of 230W / (m·K), and an electrical conductivity of 45.2%IACS.

[0064] Example 3 This embodiment includes the following steps: Step 1: First, add 10g of sodium carboxymethyl cellulose into 500mL of deionized water, stir and heat until it is fully dissolved, then add 17.61g of tungsten dioxide, 98.43g of potassium tungstate, and 82.89g of copper oxalate and mix well to obtain a precursor mixed solution.

[0065] Step 2: Use a spray dryer to spray granulate the precursor mixed solution obtained in step 1 to obtain spherical tungsten-copper precursor composite powder; the liquid inlet volume of the mixed solution in the spray drying is 30%, the air inlet temperature is 230°C, the air outlet temperature is 130°C, and the nozzle rotation frequency is 35Hz.

[0066] Step 3: calcine the spherical tungsten-copper precursor composite powder obtained in step 2 to obtain a tungsten-copper oxide composite powder; then perform a staged reduction treatment on the tungsten-copper oxide composite powder to obtain a W65Cu35 composite powder, in which the mass ratio of W to Cu in the composite powder is 6.5:3.5. The calcination process is: heating to 500°C at a heating rate of 20°C / min and then keeping warm for 1.5 hours, and the calcination atmosphere is nitrogen. The staged reduction treatment is: first heating to 400°C at 10°C / min and keeping warm for 1 hour for the first stage reduction, and then heating to 650°C at 5°C / min and keeping warm for 1.5 hours for the second stage reduction. The atmosphere for the first stage reduction and the second stage reduction is an argon-hydrogen mixture.

[0067] Step 4: Use a cold isostatic press to press the W65Cu35 composite powder obtained in step 3 to obtain a W65Cu35 alloy blank, and then transfer it to a sintering furnace for sintering to obtain a W65Cu35 alloy. The molding pressure is 200MPa, and the holding time is 10min; the sintering process is: first increase the temperature to 800℃ at 10℃ / min and keep it for 30min, then increase the temperature to 1000℃ at 10℃ / min and keep it for 30min, and then increase the temperature to 1200℃ at 5℃ / min and keep it for 2h; the sintering atmosphere is a hydrogen-argon mixture.

[0068] After testing, the density of the W65Cu35 alloy prepared in Example 3 is 13.69 g / cm 3 , which is converted into a density of 99.5%. The tungsten grain size in the prepared alloy is 0.5~1.2μm, the thermal conductivity is 262W / (m·K), and the electrical conductivity is 60.3%IACS.

[0069] Example 4 This embodiment includes the following steps: Step 1: First, add 8g of polyvinyl pyrrolidone into 500mL of deionized water, stir and heat until it is fully dissolved, then add 12.61g of tungsten trioxide, 54g of ammonium metatungstate, and 231.25g of copper nitrate and mix well to obtain a precursor mixed solution.

[0070] Step 2: Use a spray dryer to spray granulate the precursor mixed solution obtained in step 1 to obtain spherical tungsten-copper precursor composite powder. The liquid inlet volume of the precursor mixed solution in the spray drying is 20%, the air inlet temperature is 200°C, the air outlet temperature is 120°C, and the nozzle rotation frequency is 25Hz.

[0071] Step three, calcine the spherical tungsten-copper precursor composite powder obtained in step two to obtain a tungsten-copper oxide composite powder, such as a W50Cu50 composite powder. The tungsten-copper oxide composite powder is subjected to a staged reduction treatment to obtain a tungsten-copper composite powder, which may be a W50Cu50 composite powder, and the mass ratio of W to Cu in the composite powder is 5:5. The calcination process is: heating to 300°C at a heating rate of 10°C / min and then keeping warm for 1h. The calcination atmosphere is air. The staged reduction treatment is: first heating to 350°C at 10°C / min and keeping warm for 0.5h for the first stage reduction, then heating to 650°C at 5°C / min and keeping warm for 1h for the second stage reduction; the atmosphere for the first stage reduction and the second stage reduction is hydrogen.

[0072] Step 4: Use a cold isostatic press to press the W50Cu50 composite powder obtained in step 3 to obtain a W50Cu50 alloy billet, and then transfer it to a sintering furnace for sintering to obtain a W50Cu50 alloy. The molding pressure is 200MPa, and the holding time is 5min. The sintering process is: first increase the temperature to 800℃ at 10℃ / min and keep it for 30min, then increase the temperature to 1000℃ at 10℃ / min and keep it for 30min, and finally increase the temperature to 1125℃ at 5℃ / min and keep it for 1.5h; the sintering atmosphere is hydrogen.

[0073] After testing, the density of the W50Cu50 alloy prepared in Example 4 is 12.20 g / cm 3 , which is converted into a density of 99.6%. The tungsten grain size in the prepared alloy is 0.3~0.9μm, the thermal conductivity is 296W / (m·K), and the electrical conductivity is 70.9%IACS.

[0074] Comparative Example 1 The W90Cu10 alloy was prepared by melt infiltration, which specifically includes the following steps: tungsten powder with an average particle size of 10 μm was loaded into a mold, preformed by molding and then isostatically pressed to obtain a green body, and then pre-sintered at 1350°C in a hydrogen atmosphere to obtain a tungsten skeleton. The amount of pure copper added in the copper infiltration process was determined according to the proportion of copper in W90Cu10, and then copper was melt-infiltrated at 1300°C in a hydrogen atmosphere. After the melt infiltration, the surface of the sample was processed to remove the excess infiltrated copper to obtain the W90Cu10 alloy.

[0075] After testing, the density of the W90Cu10 alloy prepared in Comparative Example 1 is 16.71 g / cm 3 , which translates to a density of 96.4%, a tungsten grain size of 1.1~22.5μm, a thermal conductivity of 169W / (m·K), and an electrical conductivity of 32.2%IACS.

[0076] Figure 5 The surface SEM image of the W90Cu10 alloy prepared in Comparative Example 1 is shown in FIG. Figure 5 It can be seen that the tungsten grains in the W90Cu10 alloy are coarse and unevenly distributed, and there is serious phase segregation.

[0077] Comparative Example 2 The W90Cu10 alloy was prepared by a conventional mixed powder sintering method, which specifically included the following steps: using a planetary ball mill, tungsten powder with an average particle size of 10 μm and copper powder with an average particle size of 5 μm were mixed in a mass ratio of 9:1 to obtain W90Cu10 composite powder, and then a cold isostatic press was used to press the W90Cu10 billet, which was then transferred to a molybdenum wire heating furnace and sintered at 1800°C for 4 hours in a hydrogen atmosphere to obtain the W90Cu10 alloy.

[0078] After testing, the density of the W90Cu10 alloy prepared in Comparative Example 2 is 16.56 g / cm 3 , which translates to a density of 95.5%, a tungsten grain size of 5.1~15.6μm, a thermal conductivity of 152W / (m·K), and an electrical conductivity of 31.4%IACS.

[0079] Figure 6 The surface SEM image of the W90Cu10 alloy prepared in Comparative Example 2 is shown in FIG. Figure 6 It can be seen that the tungsten grain structure in the W90Cu10 alloy is coarse and uneven, and there is a serious phase segregation phenomenon.

[0080] By comparing Comparative Examples 1 and 2 with Examples 1 to 4, it can be learned that the tungsten grains prepared by the method in the disclosed embodiments have a high-activity spherical tungsten-copper composite powder with a nanocrystalline / ultrafine crystal bimodal distribution characteristic, which can be sintered at low temperature and in a short time to obtain a tungsten-copper alloy with fine and uniformly distributed grain structure, and the density, thermal conductivity, electrical conductivity and other properties of the alloy are greatly improved.

[0081] In the embodiment of the present disclosure, a tungsten-copper alloy is also provided. The tungsten-copper alloy can be prepared according to the method of step S110 to step S140.

[0082] In the disclosed embodiment, unlike directly mixing tungsten powder with copper powder, this method first sprays and granulates a mixed solution of ultrafine tungsten oxide powder, soluble tungsten salt and copper salt under the bonding action of a polymer to obtain a composite uniform spherical tungsten-copper precursor composite powder, thereby avoiding segregation and phase separation of the tungsten source and the copper source. Further, through roasting and segmented reduction, a tungsten-copper composite powder with good sphericity, high sintering activity, and tungsten grains having a bimodal distribution characteristic of nanocrystalline / ultrafine crystals is prepared. Compared with a single-scale distribution, a powder with a bimodal distribution not only has better fluidity and a higher loose bulk density, but also can promote the full densification of the alloy and maintain the uniformity of the alloy microstructure through the coupling rearrangement of large and small tungsten particles during the sintering process, which helps to improve the density, thermal conductivity, electrical conductivity and other properties of the tungsten-copper alloy.

[0083] In addition, the above-mentioned figures are only schematic illustrations of the processes included in the method according to the exemplary embodiments of the present disclosure, and are not intended to be limiting. It is easy to understand that the processes shown in the above-mentioned figures do not indicate or limit the time sequence of these processes. In addition, it is also easy to understand that these processes can be performed synchronously or asynchronously, for example, in multiple modules.

[0084] Those skilled in the art will readily appreciate other embodiments of the present disclosure after considering the specification and practicing the invention disclosed herein. This application is intended to cover any modification, use or adaptation of the present disclosure, which follows the general principles of the present disclosure and includes common knowledge or customary techniques in the art that are not disclosed in the present disclosure. The specification and examples are intended to be exemplary only, and the true scope and spirit of the present disclosure are indicated by the appended claims.

[0085] It should be understood that the present disclosure is not limited to the exact structures that have been described above and shown in the drawings, and that various modifications and changes may be made without departing from the scope thereof. The scope of the present disclosure is limited only by the appended claims.

Claims

1. A method for preparing a tungsten-copper alloy, characterized in that: include: Add ultrafine tungsten oxide powder, tungsten salt, copper salt and polymer additives into deionized water and mix them evenly to obtain a precursor mixed solution; The precursor mixed solution is sprayed and granulated by a spray dryer to obtain a spherical tungsten-copper precursor composite powder; The spherical tungsten-copper precursor composite powder is calcined to obtain a tungsten-copper oxide composite powder, and the tungsten-copper oxide composite powder is staged reduced to obtain a tungsten-copper composite powder having a nanocrystalline / ultrafine crystal bimodal distribution characteristic of tungsten grains; The tungsten-copper composite powder is pressed into an alloy blank and sintered to prepare a tungsten-copper alloy.

2. The method for preparing tungsten-copper alloy according to claim 1, characterized in that: The particle size of the ultrafine tungsten oxide powder is 100-700 nm; the tungsten oxide is any one of yellow tungsten oxide, blue tungsten oxide, purple tungsten oxide, and tungsten dioxide.

3. The method for preparing tungsten-copper alloy according to claim 1, characterized in that: The amount of the polymer additive added to the precursor mixed solution is 0.5-10wt% of the total mass of the ultrafine tungsten oxide powder, tungsten salt and copper salt; The tungsten salt is a water-soluble salt, and the concentration of the tungsten salt is 0.02-1.5 mol / L; the tungsten salt includes one or more of ammonium tungstate, sodium tungstate, and potassium tungstate; The copper salt is a water-soluble salt, and the concentration of the copper salt is 0.05-2.5 mol / L; the copper salt includes one or more of copper chloride, copper nitrate, copper oxalate, and copper acetate.

4. The method for preparing tungsten-copper alloy according to claim 1, characterized in that: The polymer additive is a water-soluble polymer, and the polymer additive includes one or more of cellulose, polyvinyl alcohol, polyethylene glycol, and polyvinyl pyrrolidone.

5. The method for preparing tungsten-copper alloy according to claim 1, characterized in that: In the spray granulation process, the liquid inlet amount of the precursor mixed solution is 15-45%, the air inlet temperature is 200-350° C., the air outlet temperature is 100-180° C., and the nozzle rotation frequency is 25-55 Hz.

6. The method for preparing tungsten-copper alloy according to claim 1, characterized in that: The calcination temperature is 250-500° C., the calcination time is 0.5-2 h, the calcination heating rate is 5-20° C. / min, and the calcination atmosphere is air, argon or nitrogen.

7. The method for preparing tungsten-copper alloy according to claim 1, characterized in that: The staged reduction includes a first stage reduction and a second stage reduction, wherein the atmospheres of the first stage reduction and the second stage reduction are hydrogen, decomposed ammonia or argon-hydrogen mixed gas; The reduction temperature of the first stage reduction is 250-550°C, the reduction time is 0.5-2h, and the heating rate of the first stage reduction is 5-10°C / min; The reduction temperature of the second stage reduction is 550-850° C., the reduction time is 0.5-3 h, and the heating rate of the second stage reduction is 3-10° C. / min.

8. The method for preparing tungsten-copper alloy according to claim 1, characterized in that: The tungsten-copper composite powder is spherical particles with a particle size of 20-50 μm. The tungsten grains in the tungsten-copper composite powder have a nanocrystalline / ultrafine crystal bimodal distribution characteristic. The size of the nano tungsten grains is 20-70 nm, and the size of the ultrafine tungsten grains is 100-500 nm.

9. The method for preparing tungsten-copper alloy according to claim 1, characterized in that: The sintering temperature is 1100~1450℃, the sintering time is 0.5~3h, the sintering environment is normal pressure sintering, and the sintering atmosphere is hydrogen, decomposed ammonia or argon hydrogen mixed gas.

10. A tungsten copper alloy, characterized in that: The tungsten-copper alloy is prepared according to the preparation method of the tungsten-copper alloy according to any one of claims 1-9.

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