A method for preparing a W-Cu composite powder with high sintering activity and a corresponding material

Abstract

The present application relates to the powder metallurgy technical field, and discloses a kind of preparation method of W-Cu composite powder with high sintering activity and corresponding material, the present application aims at using wet chemical method to prepare W-Cu composite powder precursor, obtains W-Cu composite powder with high sintering activity by hydrogen atmosphere segmented hydrogen reduction method sintering, and then high-density, uniform and excellent performance W-Cu composite material is prepared by liquid phase sintering.The preparation method of the present application is simple in process, high in connection efficiency, good in repeatability, and suitable for industrial application and popularization.

Description

TECHNICAL FIELD

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

[0002] W-Cu composite material has good thermal conductivity and electrical conductivity, and adjustable thermal expansion coefficient, which makes it be applied in various fields. However, it is very difficult to obtain dense W-Cu composite material due to the huge difference in melting point of W and Cu and almost no solid solution. Powder metallurgy is a process technology that uses metal powder as raw material to obtain composite material through forming and sintering. When preparing composite material composed of two elements with large difference in melting point, powder metallurgy technology can be used to sinter below the melting point of the element with higher melting point, so as to obtain the composite material. Fine particle powder helps to reduce sintering activation energy and improve particle rearrangement, which is beneficial to reduce sintering temperature and improve the density of sintered body. W-Cu composite powder with small particle size can be prepared by mechanical ball milling, oxide reduction, mechanochemistry and wet chemistry.

[0003] Wet chemical method includes sol-gel, solution combustion synthesis and chemical co-precipitation. Chemical co-precipitation method is to mix different chemical raw materials uniformly in the form of solution, use precipitation reaction to promote the precipitation of precursor, and then carry out subsequent steps such as filtration, drying and reduction to obtain the final composite powder. This method can precisely control the morphology, size and distribution of nanoparticles by adjusting the ion concentration in the solution, the type of precipitant and other parameters. The W-Cu composite powder prepared by chemical co-precipitation method has good dispersibility, uniform particle size distribution, less impurities and high sintering activity.

[0004] Therefore, it is a technical problem to be solved to prepare a W-Cu composite powder with high sintering activity by chemical co-precipitation method. SUMMARY

[0005] The present application aims to overcome the shortcomings of the prior art and provide a preparation method of W-Cu composite powder with high sintering activity and a corresponding material. The W-Cu composite powder prepared in the present application has uniform composition, low impurity content and small particle size, and the powder has high sintering activity, which is beneficial to obtain W-Cu composite material with small grain size and high density. The W-Cu composite material with small grain size has excellent performance. The preparation method of the present application is simple, has high connection efficiency and good repeatability, and is suitable for industrial application and popularization.

[0006] In order to achieve the above-mentioned purpose, the technical scheme adopted by the present application is as follows:

[0007] A preparation method of W-Cu composite powder, comprising the following steps:

[0008] Step (1), preparing W-Cu precursor by wet chemical method;

[0009] The aqueous tungstate solution is added to the mixed solution of basic copper carbonate and ammonia water and stirred uniformly to obtain a precursor reaction mixture, water is added, and the Cu 2+ concentration in the precursor reaction mixture is adjusted, and heating and stirring are performed until the solvent is completely evaporated to obtain a W-Cu precursor;

[0010] Step (2), preparing W-Cu composite powder by a segmented hydrogen reduction method;

[0011] The W-Cu precursor is dried and ground, and is reduced by the segmented hydrogen reduction method to obtain a W-Cu composite powder.

[0012] Preferably, in the step (1), the aqueous tungstate solution is prepared by completely mixing and dissolving ammonium metatungstate ((NH4)6H2W 12 O 40 ·H2O) in water.

[0013] Preferably, in the step (1), the mixed solution of basic copper carbonate and ammonia water is obtained after the basic copper carbonate (Cu2(OH)2CO3·2H2O) and the ammonia water (NH3·H2O) are uniformly mixed.

[0014] Preferably, in the step (1), the Cu 2+ concentration in the precursor reaction mixture after adjustment is 0.1 mol / L.

[0015] Preferably, in the step (1), the heating and stirring temperature is 65-95 ℃.

[0016] Preferably, in the step (2), the segmented hydrogen reduction method comprises the following steps: under a hydrogen atmosphere, heating from room temperature to 350 ℃ at a heating rate of 2-5 ℃ / min in a sintering furnace and maintaining for 30 min, after the first stage of maintaining, heating to 560 ℃ at a heating rate of 2-5 ℃ / min and maintaining for 60 min, after the second stage of maintaining, heating to 660 ℃ at a heating rate of 2-5 ℃ / min and maintaining for 60 min, after the third stage of maintaining, heating to 760 ℃ at a heating rate of 2-5 ℃ / min and maintaining for 30 min, after the fourth stage of maintaining, cooling to 500 ℃ at a cooling rate of 5 ℃ / min, and then cooling to room temperature with the furnace.

[0017] Preferably, in the step (2), the Cu content in the W-Cu composite powder is 25-90 wt.%.

[0018] Preferably, the W-Cu composite powder is prepared by the preparation method of the W-Cu composite material.

[0019] A preparation method of a W-Cu composite material, comprising the following steps:

[0020] The W-Cu composite powder prepared above is formed by molding to obtain a W-Cu composite material compact, and the compact is sintered to obtain the W-Cu composite material.

[0021] Preferably, the molding pressure is 300-500 MPa.

[0022] Preferably, the sintering condition is: heating to 900-1050℃ at a heating rate of 5℃ / min in a hydrogen atmosphere, and holding for 60-240 min.

[0023] Preferably, the W-Cu composite material is prepared by the preparation method of the W-Cu composite material.

[0024] Compared with the prior art, the present application has the following beneficial effects:

[0025] 1. The process of the present application using segmented hydrogen reduction helps to obtain W-Cu composite powder with small particle size and relatively complete crystallization, because sufficient reaction time is provided to allow the aggregation and fusion of small particles generated during the reduction process, thereby reducing the phenomenon of uneven particle size in the composite powder. In the segmented hydrogen reduction process, the temperature and time of each holding stage are determined according to the types of products obtained by the chemical coprecipitation method, and the reactions of each stage are as follows:

[0026]

[0027] 2. In the present application, when the W-Cu composite powder is sintered to form a W-Cu composite material, the sintering temperature is 900-1050℃ and the holding time is 60-240 min, so that the composite material can be obtained, the sintering temperature of the composite material is significantly reduced, and the comprehensive performance of the composite material is excellent, because the W-Cu composite powder prepared by the segmented hydrogen reduction process of the present application has uniform composition, low impurity content and small particle size. With the decrease of the particle size of the powder, the surface activation energy of the composite powder is greatly improved, thereby improving the sintering activity of the composite powder, which is beneficial to obtain a dense W-Cu composite material with small grain size; the W-Cu composite material with small 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 diameter d of the grain can be described by the Hall-Petch formula:

[0028]

[0029] In the formula k - a constant related to the crystal type

[0030] It can be seen that the strength of the polycrystal at room temperature is always improved with the refinement of the crystal grains.

[0031] 3、 The method of the application has simple process, high connection efficiency and good repeatability, and is suitable for industrial application and popularization. BRIEF DESCRIPTION OF DRAWINGS

[0032] Figure 1 is the scanning electron microscope image of the W-Cu composite powder prepared in Examples 1-2 of the application;

[0033] Figure 2 is the scanning electron microscope image of the W-Cu composite powder prepared in Comparative Examples 1-4 of the application;

[0034] Figure 3 is the scanning electron microscope image of the W-Cu composite powder prepared in Comparative Examples 5-6 of the application;

[0035] Figure 4 is the XRD spectrum of the W-Cu composite powder prepared in Examples 2 and Comparative Examples 5-6 of the application;

[0036] Figure 5 is the densification column chart of the W-80Cu composite material prepared in Examples 3-7 and Comparative Examples 7-10 of the application;

[0037] Figure 6 is the tensile curve chart of the W-Cu composite material prepared in Examples 3, 6, 7 and Comparative Examples 7-10;

[0038] Figure 7 is the scanning electron microscope image of the tensile fracture of the W-Cu composite material prepared in Examples 6-7 and Comparative Examples 7-10 of the application;

[0039] Figure 8 is the micro Vickers hardness column chart of the W-Cu composite material prepared in Examples 3, 6, 7 and Comparative Examples 7-10 of the application;

[0040] Figure 9 is the process flow chart of the preparation of the W-Cu composite powder and the W-Cu composite material in the application;

[0041] In the figure:

[0042] Figure 1 In the figure, (a) is the scanning electron microscope image of the W-25Cu composite powder prepared in Example 1; (b) is the scanning electron microscope image of the W-80Cu composite powder prepared in Example 2;

[0043] 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;

[0044] 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;

[0045] Figure 7 In 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

[0046] The technical solutions in the embodiments of the present application will be clearly and completely described in combination with the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, and not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by a person of ordinary skill in the art without creative labor fall within the scope of protection of the present application.

[0047] Example 1

[0048] The present embodiment discloses a preparation method of a W-25Cu composite powder, comprising the following steps:

[0049] Step (1), preparing a W-25Cu precursor;

[0050] 74.358 g of H 28 N6O 41 W 12 ·H2O was mixed and dissolved with 200 mL of deionized water to obtain an ammonium metatungstate aqueous solution;

[0051] 38.574 g of Cu2(OH)2CO3·2H2O was mixed and dissolved with 400 mL of ammonia water to obtain a mixed solution of basic copper carbonate and ammonia water;

[0052] The ammonium metatungstate aqueous solution was added into the mixed solution of basic copper carbonate and ammonia water to be stirred uniformly to obtain a precursor reaction mixture, 2400 mL of deionized water was added, and the Cu 2+ The concentration was 0.1 mol / L, and the W-25Cu precursor was obtained by heating and stirring through a heat collecting stirring device until the solvent was completely evaporated.

[0053] Step (2), preparation of W-25Cu composite powder;

[0054] The W-Cu precursor was dried and ground, and was placed in a tube-type atmosphere sintering furnace, and was heated from room temperature to 350 ℃ at a rate of 70 min, and was kept for 30 min, and was heated to 560 ℃ at a rate of 42 min after the first stage of keeping was finished, and was kept for 60 min, and was heated to 660 ℃ at a rate of 20 min after the second stage of keeping was finished, and was kept for 60 min, and was heated to 760 ℃ at a rate of 20 min after the third stage of keeping was finished, and was kept for 30 min, and was cooled to 500 ℃ at a rate of 52 min after the fourth stage of keeping was finished, and then was cooled to room temperature in the furnace, to obtain the W-25Cu composite powder.

[0055] Example 2

[0056] The difference from example 1 is that the ammonium metatungstate aqueous solution is prepared by mixing and dissolving 6.42 g of H 28 N6O 41 W 12 ·H2O and 200 mL of deionized water, and the W-80Cu composite powder is prepared; in step (2), the fourth stage temperature is changed from 760 ℃ to 700 ℃, and the other parameters and conditions are the same as those in example 1.

[0057] Example 3

[0058] The embodiment discloses a preparation method of a W-25Cu composite material, comprising the following steps:

[0059] The W-25Cu composite powder prepared in example 1 was die formed under a pressure of 500 MPa to obtain a W-25Cu composite material compact;

[0060] The compact was heated in a hydrogen atmosphere at a heating rate of 5 ℃ / min, and was sintered at a temperature of 1010 ℃ for 90 min, and then the W-25Cu composite material was obtained after sintering.

[0061] Example 4

[0062] The difference from Example 3 is that the W-80Cu composite powder prepared in Example 2 is used in preparing the W-80Cu composite compact, the pressure of the die compaction is 400 MPa; the sintering condition of the compact is changed as follows: sintering at 900 ℃ for 90 min in hydrogen atmosphere with a heating rate of 5 ℃ / min, and a W-80Cu composite material is prepared; and the other parameters and conditions are the same as those in Example 3.

[0063] Example 5

[0064] The difference from Example 3 is that the W-80Cu composite powder prepared in Example 2 is used in preparing the W-80Cu composite compact, the pressure of the die compaction is 400 MPa; the sintering condition of the compact is changed as follows: sintering at 930 ℃ for 90 min in hydrogen atmosphere with a heating rate of 5 ℃ / min, and a W-80Cu composite material is prepared; and the other parameters and conditions are the same as those in Example 3.

[0065] Example 6

[0066] The difference from Example 3 is that the W-80Cu composite powder prepared in Example 2 is used in preparing the W-80Cu composite compact, the pressure of the die compaction is 400 MPa; the sintering condition of the compact is changed as follows: sintering at 960 ℃ for 90 min in hydrogen atmosphere with a heating rate of 5 ℃ / min, and a W-80Cu composite material is prepared; and the other parameters and conditions are the same as those in Example 3.

[0067] Example 7

[0068] The difference from Example 3 is that the W-80Cu composite powder prepared in Example 2 is used in preparing the W-80Cu composite compact, the pressure of the die compaction is 400 MPa; the sintering condition of the compact is changed as follows: sintering at 990 ℃ for 90 min in hydrogen atmosphere with a heating rate of 5 ℃ / min, and a W-80Cu composite material is prepared; and the other parameters and conditions are the same as those in Example 3.

[0069] Comparative Example 1

[0070] This comparative example discloses a preparation method of a W-80Cu composite powder, comprising the following steps:

[0071] 80 g of W powder with a particle size of 0.2 μm and 20 g of electrolytic copper powder are mechanically ball milled on a planetary ball mill with hard alloy grinding balls and alcohol as the medium for 6 h, and after the ball milling, the W-80Cu composite powder is obtained by drying and grinding;

[0072] Wherein, the ball-to-material ratio is 4:1, and the ball milling speed is 200 r / min.

[0073] Comparative Example 2

[0074] The difference from Comparative Example 1 is that the mechanical ball milling time is changed to 12 h; and other parameters and conditions are the same as those in Comparative Example 1.

[0075] Comparative Example 3

[0076] The difference from Comparative Example 1 is that the mechanical ball milling time is changed to 24 h; and other parameters and conditions are the same as those in Comparative Example 1.

[0077] Comparative Example 4

[0078] The difference from Comparative Example 1 is that the mechanical ball milling time is changed to 48 h; and other parameters and conditions are the same as those in Comparative Example 1.

[0079] Comparative Example 5

[0080] The difference from Example 1 is that the aqueous solution of ammonium metatungstate is prepared by mixing and dissolving 6.42 g of H 28 N6O 41 W 12 ·H2O with 200 mL of deionized water; and the sintering condition is changed to: under a hydrogen atmosphere, heating from room temperature to 700 ℃ for 140 min and maintaining for 30 min, then cooling to 500 ℃ for 40 min, and then cooling to room temperature; and other parameters and conditions are the same as those in Example 1.

[0081] Comparative Example 6

[0082] The difference from Example 1 is that the aqueous solution of ammonium metatungstate is prepared by mixing and dissolving 6.42 g of H 28 N6O 41 W 12 ·H2O with 200 mL of deionized water; and the sintering condition is changed to: under a hydrogen atmosphere, heating from room temperature to 550 ℃ for 110 min and maintaining for 90 min, then cooling to 500 ℃ for 10 min, and then cooling to room temperature; and other parameters and conditions are the same as those in Example 1.

[0083] Comparative Example 7

[0084] This comparative example discloses a preparation method of a W-80Cu composite material, comprising the following steps:

[0085] The W-80Cu composite powder obtained in Comparative Example 1 was molded under a pressure of 400 MPa to obtain a W-80Cu composite material compact.

[0086] The compact was heated in a hydrogen atmosphere at a heating rate of 5 °C / min and sintered at 960 °C for 90 min to obtain the W-80Cu composite material.

[0087] Comparative Example 8

[0088] The difference from Comparative Example 7 is that the W-80Cu composite powder obtained in Comparative Example 2 was used when preparing the W-80Cu composite compact, while the other parameters and conditions were the same as those in Comparative Example 7.

[0089] Comparative Example 9

[0090] The difference from Comparative Example 7 is that the W-80Cu composite powder obtained in Comparative Example 3 was used when preparing the W-80Cu composite compact, while the other parameters and conditions were the same as those in Comparative Example 7.

[0091] Comparative Example 10

[0092] The difference from Comparative Example 7 is that the W-80Cu composite powder obtained in Comparative Example 4 was used when preparing the W-80Cu composite compact, while the other parameters and conditions were the same as those in Comparative Example 7.

[0093] 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).

[0094] Experimental data characterization and performance testing

[0095] like Figure 1 As shown, the microstructure of the W-Cu composite powders prepared in Examples 1-2 was characterized using field emission scanning electron microscopy.

[0096] according to Figure 1 The test results show that the W-Cu composite powder prepared in Examples 1-2 has a particle size between 200-500 nm, and the morphology of the powder varies slightly depending on the Cu content. Among them, the W-80Cu composite powder prepared in Example 2 has a more moderate particle size distribution, an ellipsoidal shape, and is composed of smaller Cu particles and larger W particles.

[0097] like Figure 2The micro-morphology of the W-Cu composite powder prepared in Comparative Example 1-4 was characterized by a field emission scanning electron microscope.

[0098] According to the test results of Figure 2 It can be seen that the W-80Cu composite powder prepared by the mechanical ball milling method presents a flaky morphology, which is mainly due to the poor strength and good plasticity of Cu, which will produce large plastic deformation during ball milling and form a flaky structure. The powder particle size distribution is below 50 μm, the particle size distribution is extensive, and there is an agglomeration phenomenon.

[0099] As shown in Figure 3 The micro-morphology of the W-Cu composite powder prepared in Comparative Example 5-6 was characterized by a field emission scanning electron microscope; as shown in Figure 4 The W-Cu composite powder prepared in Example 2 and Comparative Examples 5-6 was subjected to XRD test.

[0100] According to the test results of Figure 3 As shown in Figure 3 (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 phase in the powder has a larger particle size than that in Example 2; as shown in Figure 3 (b), the particle size distribution of the W-80Cu composite powder prepared in Comparative Example 6 is extensive, and the shape is long strip, polygon or approximately spherical, etc., which is composed of Cu with small particle size and W with large particle size.

[0101] According to the test results of Figure 4 It can be seen that the W-Cu composite powder prepared in Example 2 and Comparative Examples 5-6 has obvious W and Cu characteristic peaks on the XRD spectrum, which corresponds to W and Cu in the standard card. The intensity of the W phase in the XRD spectrum of the W-80Cu composite powder prepared in Comparative Example 6 is low, the diffraction peak is widened, and the peaks on the XRD spectrum of the powder prepared in Example 2 and Comparative Example 5 are sharper than that of Comparative Example 6, indicating that the powder prepared in Example 2 and Comparative Example 5 has better crystallinity.

[0102] The segmented hydrogen reduction method adopted in Example 2 can provide sufficient reaction time to aggregate and fuse the fine particles occurring during the reduction process, reduce the phenomenon of uneven particle size in the composite powder; while the reduction method adopted in Comparative Example 5 is to directly heat to 700℃ and keep warm, and the W and Cu obtained by preferential decomposition and reduction have enough time to melt and grow, and the volatile tungsten hydrate at high temperature for a long time will be adsorbed on the W particles, leading to the growth of W particles. In addition, it may also lead to the fusion of Cu particles, resulting in a coarse-grained W-Cu composite powder.

[0103] As shown in Figure 5As shown, the density of the W-80Cu composite materials prepared in Examples 3-7 and Comparative Examples 7-10 was compared. The density was calculated as follows:

[0104] The measured density (g / cm³) of W-80Cu composite material was calculated with reference to the national standard GB / T 3850-2015. 3 The density of the W-80Cu composite material was then calculated using a formula:

[0105]

[0106] In the formula, Ф s Density (%) of W-80Cu composite material; ρ s Measured density of W-80Cu composite material (g / cm³) 3 ); ρ m The theoretical density (g / cm³) of W-80Cu composite material 3 ).

[0107] according to Figure 5 The test results show that, due to the high activity of the W-80Cu composite powder prepared in Example 2, the sintered density of the W-80Cu composite material prepared in Example 6 using Example 2 as the 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 the different particle sizes of the composite powders; composite powders with smaller particle sizes have higher sintering activity. The sintering activity of composite powders obtained by chemical co-precipitation is generally higher than that of composite powders obtained by mechanical ball milling. Therefore, at the same sintering temperature, the sintered density of composite powders prepared by chemical co-precipitation is much higher than that prepared by mechanical ball milling.

[0108] like Figure 6 As shown, Example 3, which has a higher density among W-25Cu composite materials, and Examples 6 and 7, which have a higher density among W-80Cu composite materials, were selected. The tensile properties of the W-Cu composite materials prepared in Examples 3, 6, 7 and Comparative Examples 7-10 were tested.

[0109] 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 excellent tensile strength of the W-80Cu composite material prepared by chemical coprecipitation is mainly attributed to its density and the small and uniform particle size of the second phase W particles.

[0110] likeFigure 7 As shown, Examples 6 and 7, which have higher density among the W-80Cu composite materials, were selected. The microstructure of the tensile fracture surface of the W-80Cu composite materials prepared in Examples 6, 7, and Comparative Examples 7-10 was characterized by field emission scanning electron microscopy.

[0111] according to Figure 7 The test results show that the W-Cu composite material exhibits a typical dimple fracture, indicating ductile fracture. The density of the W-Cu composite materials prepared in Comparative Examples 7-10 differs significantly from that shown in Examples 6 and 7. This difference is attributed to the fact that the powder prepared by the mechanical mixing method in Comparative Examples 7-10 has a much lower sintering activity than the powder prepared by the chemical coprecipitation-reduction method used in the examples. Increased sintering activity, decreased diffusion activation energy, and accelerated surface and grain boundary diffusion rates further promote neck growth and pore shrinkage. Therefore, the Cu diffusion and liquid-phase Cu flowability of the powder obtained by the mechanical mixing method are much lower during sintering than those 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 5 Many black pores can also be seen in it.

[0112] like Figure 8 As shown, Example 3, which has a higher density among W-25Cu composite materials, and Examples 6 and 7, which have a higher density among W-80Cu composite materials, were selected. The micro Vickers hardness of the W-Cu composite materials prepared in Examples 3, 6, and 7 and Comparative Examples 7-10 were compared and tested.

[0113] according to Figure 8 The test results show that the micro Vickers hardness of the W-80Cu composite material prepared according to Example 6 can reach 143.89 HV.

[0114] from Figure 8 As can be seen from the data, in Comparative Examples 7-10 prepared from Comparative Examples 1-4 as raw materials, the microhardness of the W-80Cu composite material increases with increasing ball milling time. The composite materials obtained after ball milling for 24 h and 48 h and sintering at 960 ℃ have hardnesses of 60.676 HV and 65.530 HV, respectively. It can be seen that the increase in hardness with the extension of ball milling time is not significant, which is the same trend as the change in density. This is mainly because the mechanical mixing method has little effect on the particle size of the powder after 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 inside the material. When a load is applied, the indentation at the W position is small, while the indentation at the Cu position is large. Under the action of force, the pore part of the indenter at the pore position begins to expand, resulting in a lower and more volatile hardness value.

[0115] The hardness of the W-80Cu composite material prepared in Example 6 is much higher than that of Comparative Examples 7-10. In Example 6 and Example 7, the W-80Cu composite powder prepared from the raw material of Example 2, the hardness measured after sintering at 960 ℃ and 990 ℃ reaches 143.89 HV and 132.43 HV, respectively. This is because the powder obtained by the chemical coprecipitation-reduction method has a smaller particle size, the density of the composite material is higher, the grain boundary and the second phase W hinder the dislocation, and finally the microhardness is improved. It is worth noting that the hardness of the composite material obtained at 990 ℃ is lower than that obtained at 960 ℃, which shows that the hardness is reduced by 8.65%. This is because as the sintering temperature increases, part of the W in the sintered body quickly engulfs the surrounding small particles through the Ostwald ripening mechanism, leading to particle coarsening, weakening the strengthening effect of the second phase W, and causing the hardness of the composite material to decrease.

[0116] Although embodiments of the present application have been shown and described, it is to be understood that various modifications, substitutions, replacements and changes can be made to these embodiments without departing from the principles and spirit of the present application, and the scope of the present application is defined by the appended claims and their equivalents.

Claims

1. A method for preparing a W-Cu composite material, characterized in that, Includes the following steps: Step (1): Add the tungstate aqueous solution to the mixed solution of basic copper carbonate and ammonia and stir until homogeneous to obtain the precursor reaction mixture. Add an appropriate amount of deionized water to adjust the Cu content in the precursor reaction mixture. 2+ The concentration was 0.1 mol / L, and the mixture was heated and stirred until the solvent was completely evaporated to obtain the W-Cu precursor. Step (2): Dry and grind the W-Cu precursor, and reduce it by a segmented hydrogen reduction method to obtain W-Cu composite powder with a Cu content of 25-90 wt.%; The steps of the segmented hydrogen reduction method are as follows: Under a hydrogen atmosphere, the temperature is increased from room temperature to 350℃ in a sintering furnace at a heating rate of 2-5℃ / min and held for 30 min. After the first stage of holding, the temperature is increased to 560℃ at a heating rate of 2-5℃ / min and held for 60 min. After the second stage of holding, the temperature is increased to 660℃ at a heating rate of 2-5℃ / min and held for 60 min. After the third stage of holding, the temperature is increased to 700℃ or 760℃ at a heating rate of 2-5℃ / min and held for 30 min. After the fourth stage of holding, the temperature is decreased to 500℃ at a cooling rate of 5℃ / min. Then, the W-Cu composite powder is cooled to room temperature with the furnace. Step (3): The W-Cu composite powder is molded into a W-Cu composite material compact; the compact is sintered to obtain the W-Cu composite material. The sintering conditions are as follows: in a hydrogen atmosphere, the temperature is increased to 900-1050 ℃ at a heating rate of 5 ℃ / min, and held for 60-240 min.

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

3. The method for preparing a W-Cu composite material according to claim 1, characterized in that, In step (1), the heating and stirring temperature is 65-95 ℃.

4. The method for preparing a W-Cu composite material according to claim 1, characterized in that, The compression molding pressure is 300-500 MPa.

5. A W-Cu composite material prepared by the method for preparing W-Cu composite material as described in any one of claims 1-4.

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