Shielding piece made of tungsten-based alloy material, preparation method and application

Abstract

The invention discloses a shielding part made of a tungsten-based alloy material, a preparation method and application, the tungsten-based alloy comprises a tungsten matrix and lanthanum hexaboride dispersed in the tungsten matrix, and the content of boron in the tungsten-based alloy is 0.01 wt%-0.5 wt%. Lanthanum hexaboride is introduced into the tungsten-based alloy, so that refining of tungsten grains in the tungsten-based alloy is facilitated, the toughness of the tungsten-based alloy is enhanced, the ductile-brittle transition temperature is reduced, and the absorption capacity of the tungsten-based alloy to neutron irradiation is improved; meanwhile, the introduction of lanthanum hexaboride not only does not reduce the heat-conducting property of the tungsten matrix, but also contributes to the improvement of the heat-conducting property of the material, so that the service life of the shielding piece is prolonged.

Description

Technical Field

[0001] The present invention relates to the technical field of nuclear ray shielding materials, and in particular to a shielding component made of tungsten-based alloy, a preparation method and an application thereof. Background Art

[0002] Traditional nuclear radiation shielding materials are mainly composed of metallic lead and its polymer composite materials, which have good shielding effects on low-energy and high-energy X-rays and gamma rays, and are low-cost and easy to process. However, lead itself has a low melting point and certain biological toxicity, which limits its application in nuclear radiation shielding materials.

[0003] Tungsten has good radiation shielding properties and does not produce secondary electron radiation, but pure tungsten is difficult to process, has a high ductile-brittle transition temperature, a low recrystallization temperature, and high brittleness after irradiation. Although there have been studies on doping tungsten with rare earth oxides, the high temperature resistance and recrystallization temperature of the prepared tungsten-based alloys have been improved, the brittleness of the material will be increased, and its ability to absorb neutron radiation still cannot meet the needs of the first wall in the tokamak device.

[0004] In view of this, the present invention is proposed. Summary of the invention

[0005] The purpose of the present invention is to provide a shielding component made of tungsten-based alloy, a preparation method and an application thereof, and to provide a shielding component with strong absorption capacity for neutron radiation, good toughness, low ductile-brittle transition temperature and high recrystallization temperature.

[0006] The present invention is achieved in that:

[0007] In a first aspect, the present invention provides a shielding component made of a tungsten-based alloy, wherein the tungsten-based alloy comprises a tungsten matrix and lanthanum hexaboride dispersed in the tungsten matrix, and the content of boron in the tungsten-based alloy is 0.01wt%-0.5wt%.

[0008] In an optional embodiment, the tungsten-based alloy satisfies at least one of the following features AE:

[0009] A boron content is 0.03wt%-0.1wt%;

[0010] B Thermal conductivity is greater than 130W / mK at 800℃;

[0011] C recrystallization temperature is greater than 1500℃;

[0012] D The average grain size is 10μm-15μm;

[0013] E ductile-brittle transition temperature ≤200℃.

[0014] In a second aspect, the present invention provides a method for preparing a shielding member made of a tungsten-based alloy as described in the aforementioned embodiment, comprising the following steps:

[0015] Pressing, pressing the mixed material containing metal tungsten and lanthanum hexaboride to obtain a pressed part;

[0016] Sintering, sintering and rolling or rotary forging the pressed part to obtain a rolled part;

[0017] Annealing: annealing the rolled piece to obtain the shielding piece.

[0018] In an optional embodiment, the mixed material is at least one of a first mixed material and a second mixed material:

[0019] The preparation method of the first mixed material comprises: ball-milling lanthanum hexaboride and part of tungsten powder to obtain a premix, and then adding the remaining tungsten powder to the premix to obtain a first mixed material;

[0020] The preparation method of the second mixed material comprises: mixing ammonium paratungstate and lanthanum hexaboride in a liquid to obtain a mixed liquid, drying the mixed liquid to obtain a mixed powder, and reducing and sintering the mixed powder to obtain the second mixed material.

[0021] In an optional embodiment, the Fischer-Tropsch particle size of lanthanum hexaboride in the first mixed material is 0.8 μm-1.2 μm, and the Fischer-Tropsch particle size of the tungsten powder is less than 2.5 μm-3.5 μm;

[0022] And / or, the ball milling mixing time is 30h-72h, the rotation speed is 40rpm-100rpm, and the ball-to-material ratio is 8-12:1;

[0023] And / or, the mass ratio of the tungsten powder in the premix to the tungsten powder in the first mixed material is 5%-10%.

[0024] In an optional embodiment, the preparation method of the second mixed material satisfies at least one of the following features ad:

[0025] a. The ratio of the total mass of ammonium paratungstate and lanthanum hexaboride in the mixed solution to the mass of the liquid is 2.5-3.5:1;

[0026] b. Drying the mixed liquid by a spray drying device, wherein the inlet temperature of the spray drying device is 290°C-300°C, the outlet temperature is 120°C-130°C, and the feed pump frequency is 70Hz-90Hz;

[0027] c. The reduction sintering atmosphere is hydrogen, the reduction sintering temperature is 900°C-1000°C, and the reduction sintering time is 6h-9h.

[0028] In an optional embodiment, the mixture is pressed using a cold isostatic press at a pressure of 200 MPa-250 MPa for a time of 80 s-120 s.

[0029] In an optional embodiment, the sintering temperature is 2100° C.-2300° C., and the sintering time is 5 h-8 h.

[0030] In an optional embodiment, the rolling temperature is 1500° C.-1600° C., and the rolling deformation is 52%-88%;

[0031] And / or, the annealing temperature is 1150° C.-1250° C., and the time is 1 h-2 h.

[0032] In a third aspect, the present invention provides an application of the shielding element described in the aforementioned embodiment or the shielding element prepared by the method described in any one of the aforementioned embodiments as a first wall of nuclear fusion.

[0033] The present invention has the following beneficial effects:

[0034] The introduction of lanthanum hexaboride into the tungsten-based alloy in the embodiment of the present invention is beneficial to the refinement of tungsten grains in the tungsten-based alloy, enhancing the toughness of the tungsten-based alloy, reducing the ductile-brittle transition temperature, and improving its absorption capacity for neutron irradiation; at the same time, the introduction of lanthanum hexaboride not only does not reduce the thermal conductivity of the tungsten matrix, but helps to improve the thermal conductivity of the material, all of which are beneficial to increasing the service life of the shielding component. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for use in the embodiments are briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present invention and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without creative work.

[0036] Figure 1 is a metallographic structure diagram of the shielding member in Example 1;

[0037] Figure 2 is a surface morphology diagram of the shielding member in Example 1;

[0038] Figure 3 is the XRD pattern of the shielding member in Example 1;

[0039] Figure 4 is a metallographic structure diagram of the shielding member in Example 2;

[0040] Figure 5 is a surface topography image of the shielding member in Example 2;

[0041] Figure 6is the XRD pattern of the shielding member in Example 2;

[0042] Figure 7 This is a fracture morphology diagram of the shielding component in Example 2. DETAILED DESCRIPTION

[0043] In order to make the purpose, technical scheme and advantages of the embodiments of the present invention clearer, the technical scheme in the embodiments of the present invention will be described clearly and completely below. If the specific conditions are not specified in the embodiments, they are carried out according to conventional conditions or conditions recommended by the manufacturer. If the manufacturer of the reagents or instruments used is not specified, they are all conventional products that can be purchased commercially.

[0044] An embodiment of the present invention provides a shielding component made of a tungsten-based alloy. The tungsten-based alloy includes a tungsten matrix and lanthanum hexaboride dispersed in the tungsten matrix. The content of boron in the tungsten-based alloy is 0.01wt%-0.5wt%.

[0045] The introduction of lanthanum hexaboride into the tungsten-based alloy in the embodiment of the present invention is beneficial to the refinement of tungsten grains in the tungsten-based alloy, enhancing the toughness of the tungsten-based alloy, reducing the ductile-brittle transition temperature, and improving its absorption capacity for neutron irradiation; at the same time, the introduction of lanthanum hexaboride not only does not reduce the thermal conductivity of the tungsten matrix, but helps to improve the thermal conductivity of the material, all of which are beneficial to increasing the service life of the shielding component.

[0046] In an optional embodiment, the tungsten-based alloy satisfies at least one of the following features AE:

[0047] A boron content is 0.03wt%-0.1wt%;

[0048] B Thermal conductivity is greater than 130W / mK at 800℃;

[0049] C recrystallization temperature is greater than 1500℃;

[0050] D The average grain size is 10μm-15μm;

[0051] E ductile-brittle transition temperature ≤200℃.

[0052] The embodiment of the present invention further provides a method for preparing the shielding member made of tungsten-based alloy as described in the above embodiment, comprising the following steps:

[0053] Pressing, pressing the mixed material containing metal tungsten and lanthanum hexaboride to obtain a pressed part;

[0054] Sintering, sintering and rolling or rotary forging the pressed part to obtain a rolled part;

[0055] Annealing: annealing the rolled piece to obtain the shielding piece.

[0056] In an optional embodiment, the mixed material is at least one of a first mixed material and a second mixed material.

[0057] In an optional embodiment, the preparation method of the first mixed material includes: ball-milling lanthanum hexaboride and a portion of tungsten powder to obtain a premix, and then adding the remaining tungsten powder to the premix to obtain the first mixed material.

[0058] There are two ways to prepare the mixture in the embodiment of the present invention. One is to directly mix and ball-mill lanthanum hexaboride and part of tungsten powder to obtain a premix, and then mix the premix with the remaining tungsten powder. If there is no secondary mixing, it will be difficult to form after pressing. In this method, on the one hand, the particle size of the raw materials needs to be controlled; on the other hand, the conditions of ball milling need to be controlled.

[0059] In an optional embodiment, the Fisher particle size of lanthanum hexaboride in the first mixture is 0.8μm-1.2μm, and the Fisher particle size of the tungsten powder is less than 2.5μm-3.5μm; if the particle size of the raw material is too large, the uniformity of the mixture will be reduced, which will in turn reduce the performance of the tungsten-based alloy; if the particle size of the raw material is too small, it will increase the difficulty of processing.

[0060] In an optional embodiment, the ball milling mixing time is 30h-72h, the rotation speed is 40rpm-100rpm, and the ball-to-material ratio is 8-12:1 to ensure uniform mixing of tungsten powder and lanthanum hexaboride. In particular, a higher ball-to-material ratio is conducive to sufficient mixing of the raw materials.

[0061] In an optional embodiment, the mass ratio of the tungsten powder in the premix to the tungsten powder in the first mixed material is 5%-10%, and lanthanum hexaboride and a small amount of tungsten powder are first ball-milled to facilitate pressing and molding.

[0062] In an optional embodiment, the preparation method of the second mixture includes: mixing ammonium paratungstate and lanthanum hexaboride in a liquid to obtain a mixed liquid, drying the mixed liquid to obtain a mixed powder, and reducing and sintering the mixed powder to obtain a second mixture.

[0063] Generally, when the content of lanthanum hexaboride in tungsten-based alloy is too high, if lanthanum hexaboride and tungsten powder are directly mixed and ball-milled to obtain a mixture, cracks are more likely to appear on the prepared shielding parts, resulting in an increase in the failure rate. If the second mixture is pressed, sintered, rolled and annealed, it can maintain a high pass rate while having a higher boron content; at the same time, the second mixture is also suitable for the preparation of tungsten-based alloys with low boron content, and is more universal.

[0064] In an optional embodiment, the preparation method of the second mixed material satisfies at least one of the following features ad:

[0065] a The ratio of the total mass of ammonium paratungstate and lanthanum hexaboride in the mixed solution to the mass of the liquid is 2.5-3.5:1. Usually, the liquid can be water. A certain amount of water is conducive to the uniform mixing of the raw materials. Excessive water will greatly increase the subsequent drying cost.

[0066] b. Use spray drying equipment to dry the mixed liquid. The inlet temperature of the spray drying equipment is 290℃-300℃, the outlet temperature is 120℃-130℃, and the feed pump frequency is 70Hz-90Hz. The drying method can be selected from the existing technology. On the one hand, spray drying is beneficial to improving the drying efficiency. On the other hand, the particle size of the obtained mixed powder is relatively uniform and controllable, which is beneficial to improving the quality of subsequent pressed parts.

[0067] c The reduction sintering atmosphere is hydrogen, the reduction sintering temperature is 900°C-1000°C, and the reduction sintering time is 6h-9h. In theory, the reduction sintering can also be carried out under vacuum conditions to obtain a mixed powder, but the oxygen content in the mixed powder obtained under vacuum conditions is higher than that in a hydrogen atmosphere, which is not conducive to improving the toughness of tungsten-based alloys. In the embodiment of the present invention, a hydrogen atmosphere is selected, and the reduction sintering temperature and time are matched to control the oxygen content in the mixture to be less than 300ppm.

[0068] In an optional embodiment, the mixture is pressed using a cold isostatic press at a pressure of 200 MPa-250 MPa for a time of 80 s-120 s.

[0069] In the implementation manner of the present invention, both the first mixed material and the second mixed material can be pressed by a cold isostatic press.

[0070] In an optional embodiment, the sintering temperature is 2100° C.-2300° C., and the sintering time is 5 h-8 h.

[0071] In an optional embodiment, the rolling temperature is 1500° C.-1600° C., and the rolling deformation is 52%-88%;

[0072] And / or, the annealing temperature is 1150° C.-1250° C., and the time is 1 h-2 h.

[0073] An embodiment of the present invention further provides an application of the shielding element described in the aforementioned embodiment or the shielding element prepared by the method described in any one of the aforementioned embodiments as a first wall of nuclear fusion.

[0074] The features and performance of the present invention are further described in detail below in conjunction with the embodiments.

[0075] Example 1

[0076] This embodiment provides a method for preparing a shielding member made of a tungsten-based alloy, which specifically includes the following steps:

[0077] 1. Mixing powder: lanthanum hexaboride and tungsten powder are mixed at a weight ratio of 1:50, wherein the lanthanum hexaboride has a Fischer-Tropsch particle size of 1μm and the tungsten powder has a Fischer-Tropsch particle size of 3μm. The mixed powder is put into a ball mill with a ball-to-material ratio of 10:1; ball milling is performed at a speed of 50RPM for 72 hours to obtain a premix, and then the ball-milled premix is ​​poured into a V-type powder mixer, and tungsten powder of the same particle size is continued to be added. After mixing for 4 hours, it is taken out for use to obtain a first mixture, and the mass ratio of tungsten powder in the premix to the mass ratio of tungsten powder in the first mixture is 5%, and the boron content in the first mixture is 0.0318wt%.

[0078] 2. Pressing: put the mixed tungsten powder into the cold isostatic pressing mold. The size of the polyurethane mold is 32*200*250mm, and the size of the stainless steel sleeve is 40*230*200mm. Put the mold filled with materials into the cold isostatic press for pressing. The pressing force is 250MPa and the pressure is maintained for 90s. After demolding, a 30*180*180 compact is obtained.

[0079] 3. Sintering: Place the pressed blank into a medium frequency induction furnace for sintering in a hydrogen atmosphere at a sintering temperature of 2200°C for 8 hours;

[0080] 4. Rolling: The sintered sample is heated to 1500-1600℃ for rolling, and the rolling deformation is 52%;

[0081] 5. The rolled sample is annealed at a temperature of 1200° C. for 1 hour to obtain the shielding component.

[0082] Example 2

[0083] This embodiment provides a method for preparing a shielding member made of a tungsten-based alloy, which specifically includes the following steps:

[0084] 1. Mixing powder: Mix ammonium paratungstate and lanthanum hexaboride according to the ratio of 0.1wt% of boron content in the shielding part, then add water and stir evenly to form a slurry with a weight ratio of 3:1; spray granulate the mixed slurry with an inlet temperature of 290-300℃, an outlet temperature of 120-130℃ and a feed pump frequency of 80Hz;

[0085] 2. Reduction: Put the sprayed powder into a clean molybdenum boat and put it into a continuous furnace for reduction treatment. The atmosphere is hydrogen, the hydrogen flow rate is 3-5L / min, the maximum temperature is 900-1000℃, and the temperature is kept for 8h to obtain a powder with an oxygen content of less than 300ppm;

[0086] 3. Pressing: put the reduced tungsten powder into the cold isostatic pressing mold. The size of the polyurethane mold is 32*200*250mm, and the size of the stainless steel sleeve is 40*230*200mm. Put the mold filled with materials into the cold isostatic press for pressing. The pressing force is 250MPa and the pressure is maintained for 90s. After demolding, a 30*180*180 compact is obtained.

[0087] 4. Sintering: Place the pressed blank into a medium frequency induction furnace for sintering in a hydrogen atmosphere at a sintering temperature of 2100°C for 8 hours;

[0088] 6. Rolling: The sintered sample is heated to 1500-1600℃ for rolling, and the rolling deformation is 52%;

[0089] 7. The rolled sample is annealed at a temperature of 1200° C. for 1 hour to obtain the shielding component.

[0090] Example 3

[0091] This embodiment provides a method for preparing a shielding component made of a tungsten-based alloy, which is different from Embodiment 2 only in that the boron content in the tungsten-based alloy is 0.01 wt %.

[0092] Example 4

[0093] This embodiment provides a method for preparing a shielding member made of a tungsten-based alloy, which is different from the embodiment 2 only in that the boron content in the tungsten-based alloy is 0.5wt%.

[0094] Example 5

[0095] This embodiment provides a method for preparing a shielding component made of a tungsten-based alloy, which is different from the embodiment 1 only in that the boron content in the tungsten-based alloy is 0.5wt%.

[0096] Example 6

[0097] This embodiment provides a method for preparing a shielding component made of tungsten-based alloy material, which differs from Embodiment 1 only in that in the powder mixing step, lanthanum hexaboride and tungsten powder are mixed in a ratio of 0.0318wt% boron content in the powder and then ball-milled, and then the ball-milled material is directly pressed.

[0098] Example 7

[0099] This embodiment provides a method for preparing a shielding component made of tungsten-based alloy material, which differs from Embodiment 1 only in that in the powder mixing step, the mass ratio of the tungsten powder in the premix to the mass ratio of the tungsten powder in the first mixture is 7%.

[0100] Example 8

[0101] This embodiment provides a method for preparing a shielding component made of tungsten-based alloy material, which differs from Embodiment 1 only in that in the powder mixing step, the mass ratio of the tungsten powder in the premix to the mass ratio of the tungsten powder in the first mixture is 10%.

[0102] Comparative Example 1

[0103] This comparative example provides a method for preparing a shielding member made of a tungsten-based alloy, which differs from Example 2 only in that lanthanum hexaboride is not added.

[0104] Comparative Example 2

[0105] This comparative example provides a method for preparing a shielding member made of a tungsten-based alloy, which differs from Example 2 only in that lanthanum hexaboride is replaced with an equal molar amount of lanthanum oxide.

[0106] Comparative Example 3

[0107] This comparative example provides a method for preparing a shielding member made of a tungsten-based alloy material, which is different from Example 2 only in that lanthanum hexaboride is replaced with an equal molar amount of boron oxide.

[0108] Comparative Example 4

[0109] This comparative example provides a method for preparing a shielding member made of a tungsten-based alloy, which is different from Example 1 only in that the boron content in the tungsten-based alloy is 0.005wt%.

[0110] Comparative Example 5

[0111] This comparative example provides a method for preparing a shielding member made of a tungsten-based alloy, which is different from Example 1 only in that the boron content in the tungsten-based alloy is 0.8 wt %.

[0112] Comparative Example 6

[0113] This comparative example provides a method for preparing a shielding component made of a tungsten-based alloy material, which differs from Example 2 only in that lanthanum hexaboride is replaced by lanthanum oxide and boron, the lanthanum addition amount of lanthanum oxide and lanthanum hexaboride is the same, and the boron addition amount of boron and lanthanum hexaboride is the same, wherein the mass percentage of lanthanum oxide is 0.251wt%, and the mass percentage of boron is 0.1wt%.

[0114] The thermal conductivity of the shielding members prepared in Example 2 and Comparative Example 1 was tested according to GB / T 22588-2008 “Flash Method for Measurement of Thermal Diffusivity or Thermal Conductivity”. The results are shown in Table 1.

[0115] Table 1

[0116]

[0117] The hardness of the shielding components prepared in Example 2 and Comparative Example 1 was measured according to GB / T2411, wherein the core and the edge are used to divide the shielding components into three parts of equal area, and the surface and the interior of each part are sampled for hardness testing. The results are shown in Table 2.

[0118] Table 2

[0119]

[0120] The performance of the shielding components prepared in the above-mentioned embodiment and the comparative example is compared, wherein the neutron shielding coefficient is measured according to the enterprise standard "Q / CYSXY 001-2016" of Beijing Radiation Application Research Center, and the results are shown in Table 3.

[0121] Table 3

[0122]

[0123] The crack rate in the table is P1 / P, where P1 refers to the number of cracks in the shielding parts after sintering or thermal stress processing (the cracks must meet any of the following conditions: ① greater than 20μm in length; ② greater than 1μm in width; ③ greater than 1μm in depth); P refers to the total number of shielding parts prepared.

[0124] The metallographic structure, surface morphology and XRD pattern of the shielding member in Example 1 are shown in FIG. Figure 1-3 As shown in the figure, it can be seen that lanthanum hexaboride is evenly distributed in the tungsten-based alloy of the shield, a small part of lanthanum hexaboride is concentratedly distributed, and XRD can clearly scan the lanthanum hexaboride phase.

[0125] The metallographic structure, surface morphology and XRD pattern of the shielding member in Example 2 are shown in FIG. Figure 4-6 As shown in the figure, it can be seen that the lanthanum hexaboride particles in the tungsten-based alloy of the shield are dissolved in the matrix and evenly distributed. It is difficult to scan the lanthanum hexaboride phase using XRD, and it can only be confirmed from the SEM element distribution, indicating that lanthanum hexaboride can be dissolved in the tungsten matrix during the sintering process.

[0126] In Comparative Example 1, lanthanum hexaboride is not added, and the strengthening effect of lanthanum hexaboride is not achieved, and the effect is consistent with that of pure tungsten.

[0127] In Comparative Example 2, only lanthanum oxide is added, which does not significantly improve the hardness, has a significant effect on the ductile-brittle transition temperature and the recrystallization temperature, but cannot improve the neutron shielding effect of the tungsten alloy.

[0128] In Comparative Example 3, only boron oxide is added. Boron oxide exists in the form of foreign matter at the grain boundary and has no wettability to the grain boundary, which reduces the toughness and plasticity. This will cause cracks during the processing.

[0129] In Comparative Example 4, since the amount of lanthanum hexaboride added is too small, the grain refining effect of lanthanum and the neutron shielding effect of boron are not significantly improved.

[0130] In Comparative Example 5, the lanthanum hexaboride content is relatively high. Calculated based on the boron content of 0.8%, the lanthanum content is 1.715%. During the sintering process at 2100-2300°C, the high-content lanthanum will volatilize to a certain extent. The volatilized lanthanum hexaboride will further react with the tungsten matrix to form tungsten boride or boron particles. Both tungsten boride and boron are particles with higher hardness and are mostly present in grain boundaries. The material is prone to severe cracking during thermal stress processing.

[0131] In Comparative Example 6, lanthanum oxide and boron are added. Although lanthanum oxide can refine the grains and reduce the ductile-brittle transition temperature, due to the presence of elemental boron, borides or boron oxides are easily formed on the grain boundaries during sintering, which have no wettability on the grain boundaries, resulting in reduced toughness and plasticity, causing the material to crack easily during hot pressure processing, and other tests cannot be performed; while lanthanum hexaboride has a stable structure and is not easily decomposed into other products during the sintering process, so this problem does not exist. In addition, lanthanum hexaboride plays a pinning role at the grain boundaries and has a certain wettability, which can prevent crack propagation, such as Figure 7 .

[0132] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A shielding member made of tungsten-based alloy, characterized in that: The tungsten-based alloy comprises a tungsten matrix and lanthanum hexaboride dispersed in the tungsten matrix. The content of boron in the tungsten-based alloy is 0.01wt%-0.5wt%.

2. The shielding member made of tungsten-based alloy according to claim 1, characterized in that: The tungsten-based alloy satisfies at least one of the following features AE: A boron content is 0.03wt%-0.1wt%; B Thermal conductivity is greater than 130W / mK at 800℃; C recrystallization temperature is greater than 1500℃; D The average grain size is 10μm-15μm; E ductile-brittle transition temperature ≤200℃.

3. A method for preparing a shielding member made of tungsten-based alloy according to claim 1 or 2, characterized in that: The following steps are involved: Pressing, pressing the mixed material containing metal tungsten and lanthanum hexaboride to obtain a pressed part; Sintering, sintering and rolling or rotary forging the pressed part to obtain a rolled part; Annealing: annealing the rolled piece to obtain the shielding piece.

4. The method for preparing a shielding member made of tungsten-based alloy according to claim 3, characterized in that: The mixed material is at least one of a first mixed material and a second mixed material: The preparation method of the first mixed material comprises: ball-milling lanthanum hexaboride and part of tungsten powder to obtain a premix, and then adding the remaining tungsten powder to the premix to obtain a first mixed material; The preparation method of the second mixed material comprises: mixing ammonium paratungstate and lanthanum hexaboride in a liquid to obtain a mixed liquid, drying the mixed liquid to obtain a mixed powder, and reducing and sintering the mixed powder to obtain the second mixed material.

5. The method for preparing a shielding member made of tungsten-based alloy according to claim 4, characterized in that: The Fischer-Tropsch particle size of lanthanum hexaboride in the first mixed material is 0.8 μm-1.2 μm, and the Fischer-Tropsch particle size of the tungsten powder is less than 2.5 μm-3.5 μm; And / or, the ball milling mixing time is 30h-72h, the rotation speed is 40rpm-100rpm, and the ball-to-material ratio is 8-12:1; And / or, the mass ratio of the tungsten powder in the premix to the tungsten powder in the first mixed material is 5%-10%.

6. The method for preparing a shielding member made of tungsten-based alloy according to claim 4, characterized in that: The preparation method of the second mixed material satisfies at least one of the following features ad: a. The ratio of the total mass of ammonium paratungstate and lanthanum hexaboride in the mixed solution to the mass of the liquid is 2.5-3.5:1; b. Drying the mixed liquid by a spray drying device, wherein the inlet temperature of the spray drying device is 290°C-300°C, the outlet temperature is 120°C-130°C, and the feed pump frequency is 70Hz-90Hz; c. The reduction sintering atmosphere is hydrogen, the reduction sintering temperature is 900°C-1000°C, and the reduction sintering time is 6h-9h.

7. The method for preparing a shielding member made of tungsten-based alloy according to claim 3, characterized in that: The mixture is pressed by a cold isostatic press at a pressure of 200MPa-250MPa for 80s-120s.

8. The method for preparing a shielding member made of tungsten-based alloy according to claim 3, characterized in that: The sintering temperature is 2100° C.-2300° C., and the sintering time is 5 h-8 h.

9. The method for preparing a shielding member made of tungsten-based alloy according to claim 3, characterized in that: The rolling temperature is 1500℃-1600℃, and the rolling deformation is 52%-88%; And / or, the annealing temperature is 1150° C.-1250° C., and the time is 1 h-2 h.

10. Use of the shielding element according to claim 1 or 2 or the shielding element prepared by the method according to any one of claims 3 to 9 as a first wall of nuclear fusion.

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