Preparation method of W-Cu composite powder with high sintering activity and corresponding material

Abstract

The invention relates to the technical field of powder metallurgy, discloses a preparation method of W-Cu composite powder with high sintering activity and a corresponding material, and aims to prepare a precursor of the W-Cu composite powder by adopting a wet chemical method, and obtain the W-Cu composite powder with high sintering activity after sintering by adopting a hydrogen atmosphere sectional hydrogen reduction method. And the W-Cu composite material which is high in density, uniform in structure distribution and excellent in performance is prepared through liquid-phase sintering. The preparation method is simple in process, high in connection efficiency, good in repeatability and suitable for industrial application and popularization.

Description

Technical Field

[0001] The present invention relates to the technical field of powder metallurgy, and in particular to a preparation method of a W-Cu composite powder with high sintering activity and corresponding materials. Background Art

[0002] W-Cu composites have excellent thermal and electrical conductivity, as well as an adjustable thermal expansion coefficient, making them suitable for use in various fields. However, due to the significant difference in the melting points of W and Cu and the near-absence of solid solution, obtaining dense W-Cu composites is extremely difficult. Powder metallurgy is a process that uses metal powders as raw materials to form and sinter composite materials. When preparing composite materials composed of two elements with significantly different melting points, powder metallurgy technology allows sintering below the melting point of the higher-melting-point component to obtain the composite material. Fine-particle powders help reduce the sintering activation energy and improve particle rearrangement, which helps reduce the sintering temperature and increase the density of the sintered body. Fine-grained W-Cu composite powders can be prepared through mechanical ball milling, oxide reduction, mechanochemical methods, and wet chemical methods.

[0003] Wet chemical methods include sol-gel, solution combustion synthesis, and chemical coprecipitation. Chemical coprecipitation involves uniformly mixing different chemical raw materials in solution, using a precipitation reaction to induce the precipitation of a precursor, and then filtering, drying, and reducing the precursor to obtain the final composite powder. This method allows precise control of the morphology, size, and distribution of nanoparticles by adjusting parameters such as the ion concentration in the solution and the type of precipitant. W-Cu composite powders prepared by chemical coprecipitation exhibit good dispersibility, uniform particle size distribution, low impurities, and high sintering activity.

[0004] Therefore, preparing a W-Cu composite powder with high sintering activity by chemical co-precipitation has become a technical problem that needs to be solved urgently. Summary of the Invention

[0005] The present invention aims to overcome the shortcomings of the prior art by providing a method for preparing a W-Cu composite powder with high sintering activity and corresponding materials. The W-Cu composite powder prepared in the present invention has uniform composition, low impurity content, and fine particle size. The powder exhibits high sintering activity, facilitating the production of a fine, dense W-Cu composite material. The fine-grained W-Cu composite material exhibits excellent performance. The preparation method of the present invention features simple process, high connection efficiency, and good repeatability, making it suitable for industrial application and promotion.

[0006] In order to achieve the above object, the technical solution adopted by the present invention is as follows: A method for preparing W-Cu composite powder comprises the following steps: Step (1), preparing a W-Cu precursor by a wet chemical method; Add the tungstate aqueous solution to the mixed solution of basic copper carbonate and ammonia water and stir evenly to obtain a precursor reaction mixture. Add water to adjust the Cu content in the precursor reaction mixture. 2+ concentration, heating and stirring until the solvent is completely evaporated to obtain a W-Cu precursor; Step (2), preparing W-Cu composite powder by a staged hydrogen reduction method; The W-Cu precursor is dried and ground, and reduced by a staged hydrogen reduction method to obtain a W-Cu composite powder.

[0007] Preferably, in step (1): the tungstate aqueous solution is prepared from ammonium metatungstate ((NH4)6H2W 12 O 40 ·H2O) are mixed and dissolved in water to prepare the

[0008] Preferably, in step (1), basic copper carbonate (Cu2(OH)2CO3·2H2O) and ammonia water (NH3·H2O) are uniformly mixed to obtain a mixed solution of basic copper carbonate and ammonia water.

[0009] Preferably, in the step (1): the Cu in the precursor reaction mixture is adjusted 2+ The concentration is 0.1mol / L.

[0010] Preferably, in step (1), the heating and stirring temperature is 65-95°C.

[0011] Preferably, in step (2), the steps of the staged hydrogen reduction method are as follows: in a hydrogen atmosphere, heating the temperature from room temperature to 350°C at a heating rate of 2-5°C / min in a sintering furnace and keeping the temperature for 30 min; after the first stage of heat preservation, heating the temperature to 560°C at a heating rate of 2-5°C / min and keeping the temperature for 60 min; after the second stage of heat preservation, heating the temperature to 660°C at a heating rate of 2-5°C / min and keeping the temperature for 60 min; after the third stage of heat preservation, heating the temperature to 760°C at a heating rate of 2-5°C / min and keeping the temperature for 30 min; after the fourth stage of heat preservation, cooling the temperature to 500°C at a cooling rate of 5°C / min, and then cooling to room temperature with the furnace.

[0012] Preferably, in step (2), the Cu content in the W-Cu composite powder is 25-90 wt.%.

[0013] Preferably, a W-Cu composite powder is prepared by the W-Cu composite powder preparation method as described above.

[0014] A method for preparing a W-Cu composite material comprises the following steps: The W-Cu composite powder prepared above is molded to obtain a W-Cu composite material compact; the compact is sintered, and after the sintering is completed, a W-Cu composite material is obtained.

[0015] Preferably, the compression molding pressure is 300-500 MPa.

[0016] Preferably, the sintering conditions are: in a hydrogen atmosphere, heating to 900-1050° C. at a heating rate of 5° C. / min, and keeping the temperature for 60-240 min.

[0017] Preferably, a W-Cu composite material is prepared by the preparation method of the W-Cu composite material as described above.

[0018] Compared with the prior art, the present invention has the following beneficial effects: 1. The present invention utilizes a staged hydrogen reduction process that facilitates the production of W-Cu composite powders with fine particle size and relatively complete crystallization. This is because sufficient reaction time is provided to aggregate and fuse fine particles that appear during the reduction process, thereby reducing the uneven particle size in the composite powder. In the staged hydrogen reduction process, the temperature and time of each holding stage are determined based on the type of product obtained by the chemical coprecipitation method. The reactions in each stage are as follows:

[0019] 2. When W-Cu composite powder is sintered to form a W-Cu composite material in the present invention, a composite material can be obtained by sintering at a temperature of 900-1050°C and holding for 60-240 min, which significantly reduces the sintering temperature of the composite material and exhibits excellent overall performance. This is because the W-Cu composite powder prepared by the present invention using a staged hydrogen reduction process has uniform composition, low impurity content, and fine particle size. As the powder particle size decreases, the surface activation energy of the composite powder is greatly increased, thereby improving the sintering activity of the composite powder, which is conducive to obtaining a dense W-Cu composite material with a fine grain size. The W-Cu composite material with a fine grain size has excellent performance because, according to the Hall-Petch relationship, the relationship between the yield strength σs of a polycrystal and the average grain diameter d can be described by the Hall-Petch formula:

[0020] In the formula , k——a constant related to the crystal type; It can be seen that the room temperature strength of polycrystals always increases with the refinement of grains.

[0021] 3. The method of the present invention has simple process, high connection efficiency and good repeatability, and is suitable for industrial application and promotion. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 This is a scanning electron microscope image of the micromorphology of the W-Cu composite powder prepared in Example 1-2 of the present invention; Figure 2 This is a scanning electron microscope image of the microscopic morphology of the W-Cu composite powder prepared in Comparative Examples 1-4 of the present invention; Figure 3 This is a scanning electron microscope image of the microscopic morphology of the W-Cu composite powder prepared in Comparative Examples 5-6 of the present invention; Figure 4 is the XRD spectrum of the W-Cu composite powder prepared in Example 2 and Comparative Examples 5-6 of the present invention; Figure 5 is a density bar graph of the W-80Cu composite materials prepared in Examples 3-7 and Comparative Examples 7-10 of the present invention; Figure 6 is a tensile curve diagram of the W-Cu composite materials prepared in Examples 3, 6, 7 and Comparative Examples 7-10; Figure 7 1 is a scanning electron microscope image of the micromorphology of the tensile fracture of the W-Cu composite materials prepared in Examples 6-7 and Comparative Examples 7-10 of the present invention; Figure 8 is a histogram of the micro-Vickers hardness of the W-Cu composite materials prepared in Examples 3, 6, 7 and Comparative Examples 7-10 of the present invention; Figure 9 This is a process flow chart for preparing W-Cu composite powder and W-Cu composite material in the present invention; In the picture: Figure 1 In the figure, (a) is a scanning electron microscope image of the W-25Cu composite powder prepared in Example 1; (b) is a scanning electron microscope image of the W-80Cu composite powder prepared in Example 2; Figure 2 In the figure, (a) is a scanning electron microscope image of the W-80Cu composite powder prepared in Comparative Example 1; (b) is a scanning electron microscope image of the W-80Cu composite powder prepared in Comparative Example 2; (c) is a scanning electron microscope image of the W-80Cu composite powder prepared in Comparative Example 3; (d) is a scanning electron microscope image of the W-80Cu composite powder prepared in Comparative Example 4; Figure 3 In the figure, (a) is a scanning electron microscope image of the W-80Cu composite powder prepared in Comparative Example 5; (b) is a scanning electron microscope image of the W-80Cu composite powder prepared in Comparative Example 6; Figure 7In the figure, (a) is a scanning electron microscope image of the tensile fracture of the W-80Cu composite material prepared in Comparative Example 7; (b) is a scanning electron microscope image of the tensile fracture of the W-80Cu composite material prepared in Comparative Example 8; (c) is a scanning electron microscope image of the tensile fracture of the W-80Cu composite material prepared in Comparative Example 9; (d) is a scanning electron microscope image of the tensile fracture of the W-80Cu composite material prepared in Comparative Example 10; (e) is a scanning electron microscope image of the tensile fracture of the W-80Cu composite material prepared in Example 6; (f) is a scanning electron microscope image of the tensile fracture of the W-80Cu composite material prepared in Example 7. DETAILED DESCRIPTION

[0023] The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0024] Example 1

[0025] This embodiment discloses a method for preparing a W-25Cu composite powder, comprising the following steps: Step (1), preparing a W-25Cu precursor; 74.358 g of H 28 N6O 41 W 12 Mix H2O and 200 mL of deionized water to dissolve to obtain an aqueous solution of ammonium metatungstate; Mix and dissolve 38.574 g of Cu2(OH)2CO3·2H2O with 400 mL of aqueous ammonia to obtain a mixed solution of basic copper carbonate and aqueous ammonia. Add ammonium metatungstate aqueous solution to the mixed solution of basic copper carbonate and ammonia water and stir evenly to obtain a precursor reaction mixture. Add 2400 mL of deionized water to adjust the Cu content of the mixture. 2+ The concentration is 0.1 mol / L, and the mixture is heated and stirred by a heat collecting and stirring device until the solvent is completely evaporated to obtain a W-25Cu precursor; Step (2), preparing W-25Cu composite powder; The W-Cu precursor was dried and ground, and placed in a tubular atmosphere sintering furnace. Under a hydrogen atmosphere, it took 70 minutes to heat the temperature from room temperature to 350 °C and keep it for 30 minutes. After the first stage of heat preservation, it took 42 minutes to heat the temperature to 560 °C and keep it for 60 minutes. After the second stage of heat preservation, it took 20 minutes to heat the temperature to 660 °C and keep it for 60 minutes. After the third stage of heat preservation, it took 20 minutes to heat the temperature to 760 °C and keep it for 30 minutes. After the fourth stage of heat preservation, it took 52 minutes to cool it to 500 °C, and then cooled to room temperature with the furnace to obtain W-25Cu composite powder.

[0026] Example 2

[0027] The difference from Example 1 is that the aqueous solution of ammonium metatungstate is prepared by 6.42 g of H 28 N6O 41 W 12 ·H2O was mixed and dissolved with 200 mL of deionized water to obtain W-80Cu composite powder; in step (2), the temperature of the fourth stage was changed from 760°C to 700°C, and the other parameters and conditions were the same as those in Example 1.

[0028] Example 3

[0029] This embodiment discloses a method for preparing a W-25Cu composite material, comprising the following steps: The W-25Cu composite powder prepared in Example 1 was compression molded at a pressure of 500 MPa to obtain a W-25Cu composite material compact; The compact was heated at a heating rate of 5°C / min in a hydrogen atmosphere and sintered at 1010°C for 90 minutes. After the sintering, a W-25Cu composite material was obtained.

[0030] Example 4

[0031] The difference from Example 3 is that when preparing the W-80Cu composite material compact, the W-80Cu composite powder prepared in Example 2 was used, the molding pressure was 400 MPa, and the compact sintering conditions were changed to: heating at a heating rate of 5°C / min in a hydrogen atmosphere and sintering at 900°C for 90 min; the obtained W-80Cu composite material; other parameters and conditions were the same as in Example 3.

[0032] Example 5

[0033] The difference from Example 3 is that the W-80Cu composite material green sheet was prepared using the W-80Cu composite powder prepared in Example 2, and the molding pressure was 400 MPa; the green sheet sintering conditions were changed to: heating at a heating rate of 5°C / min in a hydrogen atmosphere and sintering at 930°C for 90 min; the obtained material was a W-80Cu composite material; the other parameters and conditions were the same as those in Example 3.

[0034] Example 6

[0035] The difference from Example 3 is that, when preparing the W-80Cu composite material compact, the W-80Cu composite powder prepared in Example 2 was used, and the molding pressure was 400 MPa; the compact sintering conditions were changed to: heating at a heating rate of 5°C / min in a hydrogen atmosphere and sintering at 960°C for 90 min, to obtain a W-80Cu composite material; other parameters and conditions were the same as those in Example 3.

[0036] Example 7

[0037] The difference from Example 3 is that the W-80Cu composite powder prepared in Example 2 was used in preparing the W-80Cu composite material compact; the molding pressure was 400 MPa; the compact sintering conditions were changed to: heating at a heating rate of 5°C / min in a hydrogen atmosphere and sintering at 990°C for 90 min, to obtain a W-80Cu composite material; other parameters and conditions were the same as in Example 3.

[0038] Comparative Example 1 This comparative example discloses a method for preparing a W-80Cu composite powder, comprising the following steps: 80 g of W powder with a particle size of 0.2 μm and 20 g of electrolytic copper powder were mechanically ball-milled in a planetary ball mill using cemented carbide grinding balls and alcohol for 6 h. After the ball milling, the powders were dried and ground to obtain W-80Cu composite powders. Among them, the ball-to-material ratio is 4:1, and the ball mill speed is 200 r / min.

[0039] Comparative Example 2 The difference from Comparative Example 1 is that the mechanical ball milling time is changed to 12 h; other parameters and conditions are the same as those in Comparative Example 1.

[0040] Comparative Example 3 The difference from Comparative Example 1 is that the mechanical ball milling time is changed to 24 h; other parameters and conditions are the same as those in Comparative Example 1.

[0041] Comparative Example 4 The difference from Comparative Example 1 is that the mechanical ball milling time is changed to 48 h; other parameters and conditions are the same as those in Comparative Example 1.

[0042] Comparative Example 5 The difference from Example 1 is that the aqueous solution of ammonium metatungstate is prepared by 6.42 g of H 28 N6O 41 W 12 ·H2O was mixed and dissolved in 200 mL of deionized water; when preparing the W-80Cu composite powder, the sintering conditions were changed as follows: in a hydrogen atmosphere, the temperature was raised from room temperature to 700°C in 140 minutes and kept at this temperature for 30 minutes. After the first stage of holding, the temperature was lowered to 500°C in 40 minutes, and then cooled to room temperature in the furnace; other parameters and conditions were the same as those in Example 1.

[0043] Comparative Example 6 The difference from Example 1 is that the aqueous solution of ammonium metatungstate is prepared by 6.42 g of H 28 N6O 41 W 12 ·H2O was mixed and dissolved in 200 mL of deionized water; when preparing the W-80Cu composite powder, the sintering conditions were changed as follows: in a hydrogen atmosphere, the temperature was raised from room temperature to 550°C in 110 minutes and kept at this temperature for 90 minutes. After the first stage of holding, the temperature was lowered to 500°C in 10 minutes, and then cooled to room temperature in the furnace; other parameters and conditions were the same as those in Example 1.

[0044] Comparative Example 7 This comparative example discloses a method for preparing a W-80Cu composite material, comprising the following steps: The W-80Cu composite powder prepared in Comparative Example 1 was compression molded at a pressure of 400 MPa to obtain a W-80Cu composite material compact; The compact was heated at a heating rate of 5 ℃ / min in a hydrogen atmosphere and sintered at 960 ℃ for 90 min to obtain a W-80Cu composite material.

[0045] Comparative Example 8 The difference from Comparative Example 7 is that the W-80Cu composite powder prepared in Comparative Example 2 is used in preparing the W-80Cu composite compact, and the other parameters and conditions are the same as those in Comparative Example 7.

[0046] Comparative Example 9 The difference from Comparative Example 7 is that the W-80Cu composite powder prepared in Comparative Example 3 is used in preparing the W-80Cu composite compact, and the other parameters and conditions are the same as those in Comparative Example 7.

[0047] Comparative Example 10 The difference from Comparative Example 7 is that the W-80Cu composite powder prepared in Comparative Example 4 is used in preparing the W-80Cu composite compact, and the other parameters and conditions are the same as those in Comparative Example 7.

[0048] In the above examples and comparative examples: ammonium metatungstate ((NH4)6H2W 12 O 40 ·xH2O, x=1; AMT, Sinopharm, analytical grade); basic copper carbonate (Cu2(OH)2CO3·2H2O, Sinopharm, analytical grade); ammonia water (NH4·OH, Sinopharm, analytical grade).

[0049] Experimental data characterization and performance testing like Figure 1 As shown, the micromorphology of the W-Cu composite powder prepared in Example 1-2 was characterized by field emission scanning electron microscopy.

[0050] according to Figure 1 The test results show that the W-Cu composite powders prepared in Examples 1 and 2 have a particle size range of 200-500 nm, and the powder morphology varies slightly depending on the Cu content. The W-80Cu composite powder prepared in Example 2 has a moderate particle size distribution and an ellipsoidal shape, consisting of smaller Cu and larger W.

[0051] like Figure 2 As shown, the micromorphology of the W-Cu composite powders prepared in Comparative Examples 1-4 was characterized by a field emission scanning electron microscope.

[0052] according to Figure 2 The test results show that the W-80Cu composite powder prepared by mechanical ball milling presents a flaky morphology. This is mainly due to the poor strength and good plasticity of Cu, which will produce large plastic deformation during the ball milling process to form a flaky structure. The powder particle size distribution is below 50 μm, the particle size distribution is wide, and there is agglomeration phenomenon.

[0053] like Figure 3 As shown, the micromorphology of the W-Cu composite powder prepared in Comparative Examples 5-6 was characterized by field emission scanning electron microscopy; Figure 4 As shown, the W-Cu composite powders prepared in Example 2 and Comparative Examples 5-6 were subjected to XRD testing.

[0054] according to Figure 3 The test results show that Figure 3 As shown in (a), the particle size of the W-80Cu composite powder prepared in Comparative Example 5 is too concentrated, and it can be seen that the Cu in the powder is larger than that in Example 2; Figure 3As shown in (b), the W-80Cu composite powder prepared in Comparative Example 6 has a wide particle size distribution and is in the shape of elongated strips, polygons or nearly spheres, etc., and is composed of Cu with small particle size and W with large particle size.

[0055] according to Figure 4 The test results show that the W-Cu composite powders prepared in Example 2 and Comparative Examples 5-6 all have obvious W and Cu characteristic peaks in their XRD spectra, corresponding to the W and Cu in the standard card. The W-80Cu composite powder prepared in Comparative Example 6 has a lower intensity of the W phase in the XRD spectrum, and the diffraction peak is broadened. In addition, the peaks in the XRD spectra of the powders prepared in Example 2 and Comparative Example 5 are sharper than those in Comparative Example 6, indicating that the powders prepared in Example 2 and Comparative Example 5 have better crystallinity.

[0056] The staged hydrogen reduction method used in Example 2 provides sufficient reaction time, which can aggregate and fuse the fine particles generated during the reduction process, thereby reducing the uneven particle size in the composite powder. However, the reduction method used in Comparative Example 5 is to directly heat the temperature to 700°C and maintain the temperature. The W and Cu obtained by partial preferential decomposition and reduction have sufficient time to melt and grow. Moreover, the volatile tungsten oxide hydrate at high temperature for a long time will be adsorbed on the W particles, resulting in the growth of the W particles. In addition, it may also cause the melting of Cu particles, resulting in coarse-grained W-Cu composite powder.

[0057] like Figure 5 As shown, the density of the W-80Cu composite materials prepared in Examples 3-7 and Comparative Examples 7-10 was compared and tested. The density was calculated as follows: The measured density of W-80Cu composite material (g / cm 3 ); The density of the W-80Cu composite material was then calculated using the formula:

[0058] Where, Ф s is the density of W-80Cu composite material (%); ρ s is the measured density of W-80Cu composite material (g / cm 3 );ρ m is the theoretical density of W-80Cu composite material (g / cm 3 ).

[0059] according to Figure 5The test results show that due to the high activity of the W-80Cu composite powder prepared in Example 2, the density of the sintered body of the W-80Cu composite material in Example 6 prepared using Example 2 as raw material can reach 93.79%. Compared with Comparative Examples 7-10 prepared using Comparative Examples 1-4 as raw materials under the same sintering conditions, the density of the sintered body increased by 10.86%, 9.10%, 8.20% and 6.71% respectively. The main reason for this difference is that the particle size of the composite powder is different. The composite powder with a smaller particle size has a higher sintering activity. The sintering activity of the composite powder obtained by the chemical coprecipitation method is generally higher than that of the composite powder obtained by the mechanical ball milling method. Therefore, the sintered body density of the composite powder prepared by the chemical coprecipitation method at the same sintering temperature is much higher than that prepared by the mechanical ball milling method.

[0060] like Figure 6 As shown, Example 3 with higher density among the W-25Cu composite materials, and Example 6 and Example 7 with higher density among the W-80Cu composite materials were selected, and the tensile properties of the W-Cu composite materials prepared by Examples 3, 6, 7 and Comparative Examples 7-10 were tested.

[0061] according to Figure 6 The test results show that the tensile strength of the W-80Cu composite material prepared in Example 6 can reach 379.56 MPa at room temperature. The main reason why the W-80Cu composite material prepared by the chemical coprecipitation method has such excellent tensile strength is attributed to its high density and the small and uniform distribution of the second phase W particles.

[0062] like Figure 7 As shown, Example 6 and Example 7, which have higher density among the W-80Cu composite materials, were selected, and the micromorphology of the tensile fracture of the W-80Cu composite materials prepared in Example 6, Example 7, and Comparative Examples 7-10 was characterized by field emission scanning electron microscopy; according to Figure 7 It can be seen from the test results that the W-Cu composite material has a relatively typical dimple fracture, which is a ductile fracture. The density of the W-Cu composite material prepared by comparative examples 7-10 is quite different from the density shown in Examples 6 and 7. The reason for this difference is that the powders prepared by the mechanical mixing method in comparative examples 7-10 have a much lower sintering activity than the powders prepared by the chemical coprecipitation-reduction method used in the examples. As the sintering activity increases, the diffusion activation energy decreases, and the surface diffusion and grain boundary diffusion rates accelerate, further promoting neck growth and pore shrinkage. Therefore, the diffusion of Cu and the fluidity of liquid Cu in the powder obtained by the mechanical mixing method during the sintering process are much lower than those of the powder obtained by the chemical coprecipitation-reduction method, resulting in only a high degree of surface densification, while the internal pores cannot be well filled. Figure 5Many black pores can also be seen in the

[0063] like Figure 8 As shown, Example 3 with higher density among the W-25Cu composite materials and Examples 6 and 7 with higher density among the W-80Cu composite materials were selected, and the micro-Vickers hardness of the W-Cu composite materials prepared by Examples 3, 6, 7 and Comparative Examples 7-10 was compared and tested; according to Figure 8 It can be seen from the test results that the micro Vickers hardness of the W-80Cu composite material prepared according to Example 6 can reach 143.89 HV.

[0064] from Figure 8 As can be seen from the results, the microhardness of the W-80Cu composites prepared from Comparative Examples 7-10 using Comparative Examples 1-4 as raw materials increases with ball milling time. The hardness of the composites obtained after 24 h and 48 h of ball milling and sintering at 960 ° C can reach 60.676 HV and 65.530 HV, respectively. It can be seen that the hardness of the two increases slightly with the extension of ball milling time, which is consistent with the change trend of density. This is mainly due to the fact that the mechanical mixing method has little effect on the powder particle size after the ball milling time exceeds 24 h, resulting in almost no difference in density between the two. When the overall density of the composite material is relatively low, there are a large number of pores and defects within the material. When a load is applied, the indentation at the W position is small, and the indentation at the Cu position is large. The pore portion of the indenter at the pore position begins to expand under the action of force, resulting in a low hardness value and large fluctuations.

[0065] The hardness of the W-80Cu composite material prepared in Example 6 is much higher than that of Comparative Examples 7-10. In Examples 6 and 7, prepared using Example 2 as raw material, the hardness of the W-80Cu composite powder measured after sintering at 960°C and 990°C reached 143.89 HV and 132.43 HV, respectively. This is because the powder particle size obtained by the chemical coprecipitation-reduction method is finer, the density of the composite material is higher, and the grain boundaries and the second phase W have an obstructive effect on dislocations, ultimately improving the microhardness. It is worth noting that the hardness of the composite material obtained at 990°C is lower than that of the composite material obtained at 960°C, showing a decrease of 8.65%. This is because as the sintering temperature increases, some W in the sintered body quickly swallows up surrounding small particles through the Ostwald ripening mechanism, resulting in particle coarsening, weakening the strengthening effect of the second phase W, and causing a decrease in the hardness of the composite material.

[0066] While embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions, and variations may be made to these embodiments without departing from the principles and spirit of the invention, and that the scope of the invention is defined by the appended claims and their equivalents.

Claims

1. A method for preparing W-Cu composite powder, characterized in that: The following steps are involved: Step (1), add the tungstate aqueous solution to the mixed solution of basic copper carbonate and ammonia water and stir evenly to obtain a precursor reaction mixture, add an appropriate amount of deionized water to adjust the Cu content in the precursor reaction mixture. 2+ concentration, heating and stirring until the solvent is completely evaporated to obtain a W-Cu precursor; Step (2): drying and grinding the W-Cu precursor, and reducing it by a staged hydrogen reduction method to obtain a W-Cu composite powder.

2. The method for preparing a W-Cu composite powder according to claim 1, characterized in that: In the step (1), the tungstate aqueous solution is prepared by completely dissolving ammonium metatungstate in water; and a mixed solution of basic copper carbonate and ammonia water is obtained by uniformly mixing basic copper carbonate and ammonia water.

3. The method for preparing a W-Cu composite powder according to claim 1, characterized in that: In the step (1): after adjusting the precursor reaction mixture, Cu 2+ The concentration is 0.1 mol / L.

4. The method for preparing a W-Cu composite powder according to claim 1, wherein: In the step (1), the heating and stirring temperature is 65-95°C.

5. The method for preparing a W-Cu composite powder according to claim 1, characterized in that: In the step (2), the steps of the staged hydrogen reduction method are as follows: in a hydrogen atmosphere, the temperature is raised from room temperature to 350°C at a heating rate of 2-5°C / min in a sintering furnace and kept warm for 30 min; after the first stage of heat preservation, the temperature is raised to 560°C at a heating rate of 2-5°C / min and kept warm for 60 min; after the second stage of heat preservation, the temperature is raised to 660°C at a heating rate of 2-5°C / min and kept warm for 60 min; after the third stage of heat preservation, the temperature is raised to 760°C at a heating rate of 2-5°C / min and kept warm for 30 min; after the fourth stage of heat preservation, the temperature is lowered to 500°C at a cooling rate of 5°C / min, and the W-Cu composite powder is then cooled to room temperature with the furnace.

6. The method for preparing a W-Cu composite powder according to claim 1, characterized in that: In the step (2), the Cu content in the W-Cu composite powder is 25-90 wt.%.

7. A W-Cu composite powder prepared by the method for preparing a W-Cu composite powder according to any one of claims 1 to 6.

8. A method for preparing a W-Cu composite material using the W-Cu composite powder according to claim 7, comprising the following steps: The W-Cu composite powder is molded to obtain a W-Cu composite material compact; and the compact is sintered to obtain a W-Cu composite material.

9. The method for preparing a W-Cu composite material according to claim 8, characterized in that: The pressure of the compression molding is 300-500 MPa; the sintering conditions are: heating to 900-1050°C at a heating rate of 5°C / min in a hydrogen atmosphere and keeping the temperature for 60-240 minutes.

10. A W-Cu composite material prepared by the method for preparing a W-Cu composite material according to any one of claims 8 to 9.

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