A rare earth tungsten-hafnium alloy and preparation method thereof

Abstract

The present invention provides a rare earth tungsten hafnium alloy and a preparation method thereof. The atomic percentages of the components of the rare earth tungsten hafnium alloy are as follows: Y 0.5%-2.5%, Hf 10%-30%, and the balance is W. When the rare earth tungsten hafnium alloy is plasma ablated at 2000°C for 60s, the mass ablation rate is ≤10.00×10 ‑3 g / (cm 2 ·s), line ablation rate ≤10.50×10 ‑3 mm / s. The present invention adopts a process flow combining wet ball milling, rapid hot pressing sintering and annealing to prepare a rare earth tungsten hafnium alloy. The preparation method is simple and controllable. The rare earth tungsten hafnium alloy has excellent high-temperature ablation resistance, a density of more than 95%, and a hardness of HV 0.2 Up to 1200.

Description

Technical Field

[0001] The invention belongs to the field of powder metallurgy, and in particular relates to a rare earth tungsten-hafnium alloy and a preparation method thereof. Background Art

[0002] The melting point of tungsten (W) is 3410℃, which is the highest melting point of metal elements. In addition, tungsten has the advantages of high density, good chemical stability, low vapor pressure and low thermal expansion coefficient, indicating that it has great development potential and application prospects. However, tungsten has poor high-temperature stability and lacks the ability to resist high-temperature ablation. Pure tungsten will oxidize above 400℃ and form loose and porous WO3 on the surface. The melting point of WO3 is only 1473℃, and it sublimates significantly at 850℃. Poor ablation resistance limits the further application of tungsten in high-temperature fields such as aerospace.

[0003] At present, the research on expanding the application space of tungsten mainly focuses on two aspects: one is to protect the tungsten matrix by constructing a surface layer, and the other is to improve the overall performance of the material by doping modification. Since the former faces the problems of interlayer bonding and thermal matching, the system design and implementation are difficult, and there is no perfect solution so far; the latter has high research value because it is simple, controllable, fast and effective.

[0004] Common metal elements have low melting points and will form low melting point phases with tungsten, making them difficult to withstand high temperature ablation. Most refractory metal elements are similar to tungsten, and their high temperature performance with the corresponding oxides is poor, limiting their applications. Refractory metal tungsten alloys have a series of excellent mechanical properties such as high density and high strength. They are widely used in the fields of national defense, aerospace, electronic information, energy, metallurgy and mechanical processing industries, and occupy an important position in the national economy.

[0005] Tungsten alloys include W-WC-TiC, W-WC-Cu, W-Cu and other alloy systems. These alloys have the advantages of high density (16.5-19.0g / cm), small thermal expansion coefficient, good corrosion resistance and oxidation resistance, good electrical and thermal conductivity, etc. Therefore, they have been widely used in cutting-edge scientific fields, defense industry and civilian industry. However, due to the high melting point of tungsten and the weak bonding force between atoms, it is difficult to form. Taking traditional hot pressing sintering as an example, to make tungsten alloys dense, the temperature must be above 2000℃. Due to the slow heating and cooling speed and long insulation time, the grains will grow significantly, resulting in reduced mechanical properties of the alloy.

[0006] With the rapid development of science and technology, the requirements for materials are getting higher and higher. However, the traditional refractory metal tungsten alloy is difficult to meet the further demand due to its own defects and preparation process limitations. Therefore, it is urgent to develop a tungsten alloy with simple and controllable preparation process, excellent mechanical properties, and especially good high-temperature ablation resistance. Summary of the invention

[0007] The purpose of the present invention is to provide a rare earth tungsten hafnium alloy and a preparation method thereof, wherein a tungsten hafnium alloy containing rare earth yttrium is prepared by a process flow combining wet ball milling-rapid hot pressing sintering-annealing heat treatment, wherein the rare earth tungsten hafnium alloy has excellent high temperature ablation resistance, a density of more than 95%, and a hardness of HV 0.2 Up to 1200.

[0008] In order to achieve the purpose of the invention, the present invention adopts the following technical solutions:

[0009] In a first aspect, the present invention provides a rare earth tungsten hafnium alloy, characterized in that the mass percentages of the components of the rare earth tungsten hafnium alloy are: Y 0.5%-2.5%, Hf 10%-30%, and the balance is W;

[0010] In the present invention, hafnium (Hf) itself has a high melting point. After being subjected to high-temperature oxidation and ablation, the oxide HfO2 is generated, and the melting point is as high as 2810°C, which has a good anti-ablation effect. The added Hf diffuses with the W matrix to form a tungsten-hafnium solid solution. The solid solution strengthening and the second phase strengthening will have a positive promoting effect on the alloy as a whole, so that the performance indicators such as hardness and ablation resistance are significantly improved; at the same time, the rare earth element yttrium (Y) can absorb impurities and oxygen elements in the powder, protect other elements from being oxidized, purify the grain boundaries, and also promote sintering, thereby improving the material's density, hardness and other properties.

[0011] In the present invention, the mass percentage of Y in the rare earth tungsten hafnium alloy is 0.5%-2.5%, for example, 0.5%, 0.7%, 0.9%, 1.0%, 1.3%, 1.5%, 1.7%, 1.9%, 2.0% or 2.5%, etc., but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0012] In the present invention, the mass percentage of Hf in the rare earth tungsten hafnium alloy is 10%-30%, such as 10%, 14%, 15%, 18%, 20%, 24%, 28% or 30%, etc., but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0013] As a preferred technical solution of the present invention, when the rare earth tungsten hafnium alloy is plasma ablated at 2000°C for 60s, the mass ablation rate is ≤10.00×10 -3 g / (cm2 ·s), line ablation rate ≤10.50×10 -3 mm / s.

[0014] Preferably, the density of the rare earth tungsten hafnium alloy is greater than 95%, such as 96%, 97%, 98%, 99% or 99.5%, etc., but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0015] Preferably, the hardness of the rare earth tungsten-hafnium alloy is HV 0.2 >700, for example, 720, 800, 900, 1000, 1100 or 1200, etc., but not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0016] In a second aspect, the present invention provides a method for preparing the rare earth tungsten-hafnium alloy according to the first aspect, the preparation method comprising the following steps:

[0017] (1) weighing a tungsten source, a hafnium source, and a yttrium source according to the mass percentage, mixing them, and then wet-milling them to obtain a precursor powder;

[0018] (2) The precursor powder of step (1) is subjected to rapid hot pressing sintering and annealing in sequence to obtain a rare earth tungsten-hafnium alloy.

[0019] The invention ball-mills alloy raw materials to obtain precursor powder for sintering and forming. The rare earth yttrium source can stably exist at low temperature. The precursor powder will not be oxidized after ball milling. The prepared precursor powder is placed in a rapid hot pressing sintering furnace for sintering and forming. The rare earth element Y will be decomposed at a higher temperature to absorb oxygen and impurities in a matrix, purify grain boundaries, avoid oxidation of tungsten and hafnium, and promote sintering. Since the tungsten and hafnium alloy obtained after sintering has large stress inside, annealing heat treatment is performed on the tungsten and hafnium alloy to avoid brittle cracking caused by stress.

[0020] As a preferred technical solution of the present invention, the tungsten source in step (1) includes tungsten powder.

[0021] Preferably, the hafnium source in step (1) comprises hafnium powder.

[0022] Preferably, the yttrium source in step (1) comprises yttrium hydride powder.

[0023] It is worth mentioning that Y, as a rare earth element, is easily oxidized, while YH2 can exist stably at a relatively low temperature and will not oxidize during the ball milling process. It can be decomposed and converted into element Y at a slightly higher temperature, thus ensuring the stability of the raw material.

[0024] As a preferred technical solution of the present invention, the particle size of the tungsten source in step (1) is 1-3 μm, for example, it can be 1 μm, 1.4 μm, 1.8 μm, 2 μm, 2.4 μm, 2.8 μm or 3 μm, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0025] Preferably, the purity of the tungsten source in step (1) is ≥99.9%, for example, it can be 99.91%, 99.93%, 99.95%, 99.97%, 99.98% or 99.99%, etc., but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0026] Preferably, the particle size of the hafnium source in step (1) is 5-15 μm, for example, 5 μm, 6 μm, 7 μm, 9 μm, 10 μm, 12 μm or 15 μm, etc., but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0027] Preferably, the purity of the hafnium source in step (1) is ≥99.9%, for example, it can be 99.91%, 99.93%, 99.95%, 99.97%, 99.98% or 99.99%, etc., but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0028] Preferably, the particle size of the yttrium source in step (1) is 38-74 μm, for example, it can be 38 μm, 40 μm, 45 μm, 50 μm, 55 μm, 60 μm, 65 μm, 70 μm or 74 μm, etc., but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0029] Preferably, the purity of the yttrium source in step (1) is ≥99%, for example, it can be 99%, 99.1%, 99.3%, 99.5%, 99.7% or 99.9%, etc., but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0030] As a preferred technical solution of the present invention, the medium for wet ball milling in step (1) includes anhydrous ethanol.

[0031] Preferably, the ball-to-material ratio of the wet ball milling in step (1) is (4-10):1, for example, it can be 4:1, 4.5:1, 5:1, 5.5:1, 6:1, 6.5:1, 7:1, 7.5:1, 8:1, 8.5:1, 9:1, 9.5:1 or 10:1, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0032] Preferably, the rotation speed of the wet ball milling in step (1) is 250-320 rad / min, for example, it can be 250 rad / min, 270 rad / min, 290 rad / min, 300 rad / min or 320 rad / min, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0033] Preferably, the wet ball milling time in step (1) is 6-10 h, for example, 6 h, 6.5 h, 7 h, 7.5 h, 8 h, 8.5 h, 9 h, 9.5 h or 10 h, etc., but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0034] As a preferred technical solution of the present invention, the wet ball milling in step (1) further includes separation, drying and screening performed in sequence.

[0035] As a preferred technical solution of the present invention, the rapid hot pressing sintering in step (2) is carried out under an inert atmosphere.

[0036] It is worth mentioning that, compared with traditional hot pressing sintering, fast hot pressing sintering (FHP) uses electric field to assist sintering and directly heats the mold, with faster sintering speed and shorter sintering time. The activation effect of electric current can promote sintering and reduce the sintering temperature, so it is easier to sinter and densify. Sintering can be completed within a few minutes, avoiding grain growth. Fast hot pressing sintering uses ordinary direct current. Compared with SPS, which uses expensive pulse power supply, it can accurately control parameters to ensure the smooth progress of the sintering process and reduce production costs.

[0037] In the present invention, the inert atmosphere includes argon, and the process is carried out in an inert atmosphere to avoid oxidation of the material.

[0038] Preferably, the rapid hot pressing sintering in step (2) includes heating to 1600°C at a heating rate of 80-120°C / min or heating to 1600°C at a heating rate of 80-120°C / min, and then heating to 1600-1800°C (excluding 1600°C) at a heating rate of 40-60°C / min.

[0039] In the present invention, the rapid hot pressing sintering includes heating the temperature to 1600°C at a heating rate of 80-120°C / min, for example, it can be 80°C / min, 85°C / min, 90°C / min, 95°C / min, 100°C / min, 110°C / min or 120°C / min, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0040] In the present invention, the rapid hot pressing sintering further includes heating to 1600°C at a heating rate of 80-120°C / min, and then heating to 1600-1800°C (excluding 1600°C) at a heating rate of 40-60°C / min.

[0041] In the present invention, when the temperature is increased to 1600-1800°C but not including 1600°C at a heating rate of 40-60°C / min, the heating rate is 40-60°C / min, for example, it can be 40°C / min, 44°C / min, 48°C / min, 50°C / min, 54°C / min, 58°C / min or 60°C / min, and the heating end point is 1600-1800°C but not including 1600°C, for example, it can be 1650°C, 1670°C, 1700°C, 1740°C, 1780°C or 1800°C, but it is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0042] Preferably, the pressure of the rapid hot pressing sintering in step (2) is 40-60 MPa, for example, it can be 40 MPa, 42 MPa, 44 MPa, 46 MPa, 48 MPa, 50 MPa, 52 MPa, 54 MPa, 56 MPa, 58 MPa or 60 MPa, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0043] Preferably, the time for rapid hot pressing sintering in step (2) is 3-5 min, for example, 3 min, 3.4 min, 3.8 min, 4 min, 4.4 min, 4.8 min or 5 min, etc., but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0044] In the present invention, the rapid hot pressing sintering time is: the holding time after reaching the temperature rising end point and the predetermined sintering pressure.

[0045] As a preferred technical solution of the present invention, the annealing in step (2) is carried out under an inert atmosphere.

[0046] In the present invention, annealing treatment is performed in an inert atmosphere to eliminate stress caused by rapid sintering, so that the rare earth tungsten-hafnium alloy can remain stable at high temperatures or even during ablation.

[0047] Preferably, the annealing temperature in step (2) is 1000-1600°C, for example, it can be 1000°C, 1100°C, 1200°C, 1300°C, 1400°C, 1500°C or 1600°C, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0048] In the present invention, the cooling method after annealing in step (2) is adjusted according to actual conditions; the annealing temperature in step (2) is lower than the endpoint temperature of the rapid hot pressing sintering.

[0049] Preferably, the annealing time in step (2) is 1-10 h, for example, 1 h, 2 h, 3 h, 4 h, 5 h, 6 h, 7 h, 8 h, 9 h or 10 h, etc., but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0050] As a preferred technical solution of the present invention, the preparation method comprises the following steps:

[0051] (1) mixing a tungsten source with a particle size of 1-3 μm, a hafnium source with a particle size of 5-15 μm, and a yttrium source with a particle size of 38-74 μm according to the mass percentage, and then wet-milling the mixture using anhydrous ethanol as a ball milling medium, and then separating, drying, and sieving the mixture in sequence to obtain a precursor powder;

[0052] The ball-to-material ratio of the wet ball milling in step (1) is (4-10): 1. The rotation speed is 250-320 rad / min and the time is 6-10 h;

[0053] (2) rapidly hot pressing and sintering the precursor powder of step (1) in an inert atmosphere at a pressure of 40-60 MPa for 3-5 min, and then annealing at 1000-1600° C. for 1-10 h in an inert atmosphere to obtain a rare earth tungsten-hafnium alloy;

[0054] The rapid hot pressing sintering in step (2) includes heating the temperature to 1600°C at a heating rate of 80-120°C / min or heating the temperature to 1600°C at a heating rate of 80-120°C / min, and then heating the temperature to 1600-1800°C (excluding 1600°C) at a heating rate of 40-60°C / min.

[0055] The numerical range described in the present invention not only includes the point values ​​listed above, but also includes any point values ​​between the above numerical ranges that are not listed. Due to space limitations and for the sake of simplicity, the present invention no longer exhaustively lists the specific point values ​​included in the range.

[0056] Compared with the prior art, the present invention has the following beneficial effects:

[0057] (1) The rare earth tungsten hafnium alloy provided by the present invention has a density of >95% and a hardness of HV 0.2 >700, with excellent high temperature ablation resistance, when plasma ablation is carried out at 2000℃ for 60s, the mass ablation rate is ≤10.00×10 -3 g / (cm 2 ·s), line ablation rate ≤10.50×10 -3mm / s;

[0058] (2) The preparation method provided by the present invention adopts a process flow combining wet ball milling-rapid hot pressing sintering-annealing heat treatment to prepare a tungsten-hafnium alloy containing rare earth yttrium. The sintering speed is fast, the temperature rise and fall speed is fast, the sintering time is short, the grains will not grow excessively, and the mechanical properties of the alloy will not be reduced. The preparation method is simple and has the conditions for large-scale application. BRIEF DESCRIPTION OF THE DRAWINGS

[0059] Figure 1 The XRD diagram of the precursor powder in step (1) in Examples 1-3 and Comparative Example 1 of the present invention;

[0060] Figure 2 The XRD diagram of the alloy after sintering in step (2) in Examples 1-3 of the present invention and Comparative Example 1;

[0061] Figure 3 This is a SEM image of the alloy surface after sintering in step (2) of Example 1 of the present invention;

[0062] Figure 4 This is a SEM image of the alloy surface after sintering in step (2) of Example 2 of the present invention;

[0063] Figure 5 This is a SEM image of the alloy surface after sintering in step (2) of Example 3 of the present invention;

[0064] Figure 6 This is a SEM image of the alloy surface after sintering in step (2) of comparative example 1 of the present invention. DETAILED DESCRIPTION

[0065] The technical solution of the present invention is further described below by specific implementation methods. It should be understood by those skilled in the art that the embodiments are only to help understand the present invention and should not be regarded as specific limitations of the present invention.

[0066] Example 1

[0067] This embodiment provides a method for preparing a rare earth tungsten-hafnium alloy, the preparation method comprising the following steps:

[0068] (1) 88.5 g of W powder with a particle size of 2 μm, 10 g of Hf powder with a particle size of 10 μm, and 1.53 g of YH2 powder with a particle size of 74 μm were mixed in a ball mill, and then wet-milled using anhydrous ethanol as a ball milling medium, and then filtered, dried and sieved in a vacuum drying oven to obtain a precursor powder;

[0069] The purity of the W powder and Hf powder in step (1) is 99.9%, and the purity of the YH2 powder is 99%; the ball-to-material ratio of the wet ball milling in step (1) is 5:1, the rotation speed is 280 rad / min, and the time is 8 hours;

[0070] (2) placing the precursor powder of step (1) in a rapid hot pressing sintering furnace, heating the mixture to 1600° C. at a heating rate of 100° C. / min in an argon atmosphere at a pressure of 50 MPa, and sintering the mixture for 5 min. Then, annealing the sintered material in a tubular furnace at 1000° C. for 1 h in an argon atmosphere to obtain a rare earth tungsten hafnium alloy.

[0071] Example 2

[0072] This embodiment provides a method for preparing a rare earth tungsten hafnium alloy. Except that the raw material composition in step (1) is replaced with "78.5 g W powder with a particle size of 2 μm, 20 g Hf powder with a particle size of 10 μm, and 1.53 g YH2 powder with a particle size of 74 μm in a ball mill", the other conditions are the same as those in Example 1.

[0073] Example 3

[0074] This embodiment provides a method for preparing a rare earth tungsten hafnium alloy. Except that the raw material composition in step (1) is replaced with "68.5 g W powder with a particle size of 2 μm, 30 g Hf powder with a particle size of 10 μm, and 1.53 g YH2 powder with a particle size of 74 μm in a ball mill", the other conditions are the same as those in Example 1.

[0075] Comparative Example 1

[0076] This comparative example provides a method for preparing a rare earth tungsten alloy. Except that the raw material composition in step (1) is replaced with "98.5 g W powder with a particle size of 2 μm and 1.53 g YH2 powder with a particle size of 74 μm", other conditions are the same as those in Example 1.

[0077] The precursor powders and sintered alloys in Examples 1-3 and Comparative Example 1 were characterized. The characterization results are as follows: Figure 1-6 shown.

[0078] Depend on Figure 1-2 It can be seen that compared with the tungsten-yttrium alloy, the powder composition of the rare earth tungsten-hafnium alloy prepared by the present invention does not change before and after ball milling, indicating that the powder is not oxidized; after rapid hot pressing sintering, due to the small amount of yttrium element added, the relative peak intensity is weak, and the characteristic peak information is not obvious; with the increase of hafnium content, an obvious HfW2 phase appears, the peak intensity of tungsten weakens, and the number and intensity of the HfW2 characteristic peaks increase.

[0079] Depend on Figure 3-6 It can be seen that compared with the tungsten-yttrium alloy, the rare earth tungsten-hafnium alloy prepared by the present invention gradually changes its morphology after adding hafnium, and the phase changes from two phases to four phases. One added phase is the hafnium phase remaining after doping with hafnium, and the other added phase is the HfW2 phase, and the content increases with the increase of the amount of hafnium added.

[0080] The samples after rapid hot pressing sintering of the above embodiments and comparative examples were subjected to performance tests of density and hardness, and the alloys prepared in the above embodiments and comparative examples were subjected to high temperature ablation resistance test by ablation at 2000°C plasma ablation for 60s. The test results are shown in Table 1.

[0081] Table 1

[0082]

[0083] From Table 1 we can conclude that:

[0084] The hardness of the rare earth tungsten-hafnium alloy prepared by the preparation method provided in Examples 1-5 of the present invention is HV 0.2 As high as 740 or above, with excellent high temperature ablation resistance, when plasma ablation is carried out at 2000℃ for 60s, the mass ablation rate is ≤10.00×10 - 3 g / (cm 2 ·s), line ablation rate ≤10.50×10 -3 mm / s; in contrast, the hardness of the tungsten-yttrium alloy without hafnium is lower, and because there is no protective layer on the surface to resist ablation during the ablation process, the high-temperature ablation resistance is poor. Under the same ablation conditions, the mass ablation rate of the tungsten-yttrium alloy without hafnium is greater than 30.00×10 -3 g / (cm 2 ·s), line ablation rate>25.00×10 -3 mm / s.

[0085] The applicant declares that the present invention illustrates the detailed structural features of the present invention through the above-mentioned embodiments, but the present invention is not limited to the above-mentioned detailed structural features, that is, it does not mean that the present invention must rely on the above-mentioned detailed structural features to be implemented. Those skilled in the art should understand that any improvement of the present invention, equivalent replacement of the components selected by the present invention, addition of auxiliary components, selection of specific methods, etc., all fall within the protection scope and disclosure scope of the present invention.

Claims

1. A rare earth tungsten-hafnium alloy, characterized in that: The mass percentages of the components of the rare earth tungsten-hafnium alloy are: Y0.5%-2.5%, Hf 24%-30%, and the balance is W; When the rare earth tungsten hafnium alloy is plasma ablated at 2000°C for 60 seconds, the mass ablation rate is ≤2.47×10 -3 g / (cm 2 ·s), line ablation rate ≤1.44×10 -3 mm / s; The density of the rare earth tungsten-hafnium alloy is greater than 98%; The hardness of the rare earth tungsten-hafnium alloy is HV 0.2 >1200; The rare earth tungsten-hafnium alloy is prepared by the following method: (1) weighing a tungsten source, a hafnium source, and a yttrium source according to the mass percentage, mixing them, and then wet-milling them to obtain a precursor powder; (2) subjecting the precursor powder of step (1) to rapid hot pressing sintering and annealing in sequence to obtain a rare earth tungsten-hafnium alloy; In step (1), the tungsten source comprises tungsten powder; the hafnium source comprises hafnium powder; and the yttrium source comprises yttrium hydride powder.

2. A method for preparing the rare earth tungsten-hafnium alloy as claimed in claim 1, characterized in that: The preparation method comprises the following steps: (1) weighing a tungsten source, a hafnium source, and a yttrium source according to the mass percentage, mixing them, and then wet-milling them to obtain a precursor powder; (2) subjecting the precursor powder of step (1) to rapid hot pressing sintering and annealing in sequence to obtain a rare earth tungsten-hafnium alloy; The tungsten source in step (1) comprises tungsten powder; The hafnium source in step (1) comprises hafnium powder; The yttrium source in step (1) includes yttrium hydride powder.

3. The preparation method according to claim 2, characterized in that: The particle size of the tungsten source in step (1) is 1-3 μm and the purity is ≥ 99.9%.

4. The preparation method according to claim 2, characterized in that: The hafnium source in step (1) has a particle size of 5-15 μm and a purity of ≥99.9%.

5. The preparation method according to claim 2, characterized in that: The particle size of the yttrium source in step (1) is 38-74 μm and the purity is ≥99%.

6. The preparation method according to claim 2, characterized in that: The medium for wet ball milling in step (1) includes anhydrous ethanol.

7. The preparation method according to claim 2, characterized in that: The ball-to-material ratio of the wet ball milling in step (1) is (4-10):

1.

8. The preparation method according to claim 2, characterized in that: The rotation speed of the wet ball milling in step (1) is 250-320 rad / min.

9. The preparation method according to claim 2, characterized in that: The time of wet ball milling in step (1) is 6-10 hours.

10. The preparation method according to claim 2, characterized in that: The wet ball milling in step (1) also includes separation, drying and screening in sequence.

11. The preparation method according to claim 2, characterized in that: The rapid hot pressing sintering in step (2) is carried out under an inert atmosphere.

12. The preparation method according to claim 2, characterized in that: The rapid hot pressing sintering in step (2) includes heating the temperature to 1600°C at a heating rate of 80-120°C / min or heating the temperature to 1600°C at a heating rate of 80-120°C / min, and then heating the temperature to 1600-1800°C (excluding 1600°C) at a heating rate of 40-60°C / min.

13. The preparation method according to claim 2, characterized in that: The pressure of the rapid hot pressing sintering in step (2) is 40-60 MPa.

14. The preparation method according to claim 2, characterized in that: The time of the rapid hot pressing sintering in step (2) is 3-5 minutes.

15. The preparation method according to claim 2, characterized in that: The annealing in step (2) is performed under an inert atmosphere.

16. The preparation method according to claim 2, characterized in that: The annealing temperature in step (2) is 1000-1600°C.

17. The preparation method according to claim 2, characterized in that: The annealing time in step (2) is 1-10 hours.

18. The preparation method according to claim 2, characterized in that: The preparation method comprises the following steps: (1) mixing a tungsten source with a particle size of 1-3 μm, a hafnium source with a particle size of 5-15 μm, and a yttrium source with a particle size of 38-74 μm according to the mass percentage, and then wet-milling the mixture using anhydrous ethanol as a ball milling medium, and then separating, drying, and sieving the mixture in sequence to obtain a precursor powder; The ball-to-material ratio of the wet ball milling in step (1) is (4-10):

1. The rotation speed is 250-320 rad / min and the time is 6-10 h; (2) rapidly hot pressing and sintering the precursor powder of step (1) in an inert atmosphere at a pressure of 40-60 MPa for 3-5 min, and then annealing at 1000-1600° C. for 1-10 h in an inert atmosphere to obtain a rare earth tungsten-hafnium alloy; The rapid hot pressing sintering in step (2) includes heating the temperature to 1600°C at a heating rate of 80-120°C / min or heating the temperature to 1600°C at a heating rate of 80-120°C / min, and then heating the temperature to 1600-1800°C (excluding 1600°C) at a heating rate of 40-60°C / min.

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