A dual-nanoscale phase doped ultrafine-grained tungsten alloy, a preparation method and application thereof

Abstract

The application relates to the technical field of plasma-facing materials in a fusion reactor, and discloses a double-nano-phase doped ultrafine-grain tungsten alloy as well as a preparation method and application thereof, which comprises the following raw material components: chromium: 5.0wt-10.0wt%, yttrium: 0.5wt-5.0wt%, and tungsten: the balance; wherein the matrix phase particles are tungsten, the second phase particles are chromium and yttrium, the grain size of the matrix phase particles tungsten is in the ultrafine-grain range, and the grain size of the second phase particles is in the nanocrystalline range. The double-nano-phase doped ultrafine-grain tungsten alloy is prepared by the following method: (1) raw material ball milling mechanical alloying; (2) cold pressing forming; and (3) hot isostatic pressing sintering. The prepared double-nano-phase doped ultrafine-grain tungsten alloy has the advantages of high compactness, good thermal stability, grain size in the ultrafine-grain range, and the like, can meet the severe irradiation service environment in a nuclear fusion reactor, can be used on weapons and equipment such as armor-piercing bullets to improve the destruction capacity, and can be applied to the preparation of high-temperature-resistant parts.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of powder metallurgy preparation, in particular to a kind of double nano-phase doped ultra-fine grain tungsten alloy and its preparation method and application. BACKGROUND

[0002] The statements in this section merely provide background information related to the present application and can not constitute prior art.

[0003] Nuclear fusion reactor facing plasma materials face high-energy (14.1 MeV) neutron irradiation, low-energy (first wall: 100 eV, divertor: 1-10 eV) high-flux (first wall: 10 20 ~10 21 m -2 s -1 , divertor: 10 25 m -2 s -1 ) D / T + 5% He plasma irradiation and other particle flow synergistic irradiation, which can cause materials to occur off-site damage (vacancies, interstitial atoms, dislocations, etc.), hydrogen helium effect (hydrogen helium bubble, swelling, embrittlement, etc.), secondly, facing plasma materials face steady-state high heat flow environment. Tungsten (W) due to its high melting point (3410℃), low thermal expansion coefficient (4.5×10 -6 / K at 25℃), high thermal conductivity (173W / m / K at 25℃), low sputtering rate and low hydrogen retention and a series of advantages, and become the most promising application in fusion reactor facing plasma materials (PFMs). However, as a tungsten material facing plasma materials still exist off-site damage, hydrogen helium effect and other irradiation effects, which lead to the problem of material performance degradation, poor thermal stability, and there is an urgent need to prepare high radiation resistance performance, high thermal stability of ultra-fine grain tungsten alloy material.

[0004] Refining the grain size can increase the volume fraction of grain boundaries, which can absorb defects generated by irradiation as dislocation traps, thereby significantly improving the radiation resistance of the material. In order to obtain ultra-fine-grained tungsten alloy (ultra-fine-grained grain size range: 100 nm-500 nm), it is common to refine the grain size by high-energy ball milling and to inhibit the growth of tungsten grains during sintering by doping with second-phase particles. However, due to the high melting point (3410°C) and low recrystallization temperature (1150°C-1350°C) of tungsten, there is a contradiction between high density and easy grain growth during the preparation of ultra-fine-grained tungsten alloy. The high melting point of tungsten requires a very high temperature for densification, and the sintering densification temperature often needs to reach more than 70% of the melting point temperature. The finer the grain size, the lower the recrystallization temperature, and the grain will begin to abnormally grow at a lower temperature. Therefore, it is difficult to simultaneously achieve high density and small grain size of tungsten alloy. During the preparation process, the tungsten grains will abnormally grow, and the prepared ultra-fine-grained tungsten alloy will have second-phase segregation, uneven structure, and low density.

[0005] A patent search on ultra-fine-grained tungsten alloy in China was conducted, and the following results were found:

[0006] (1) Some patents report that the grain size of ultra-fine-grained tungsten alloy is in the micron range, not in the range of 100 nm-500 nm of ultra-fine-grained tungsten alloy. For example:

[0007] a. An ultra-fine-grained tungsten-copper alloy part and its preparation, the prepared material has a grain size of 0.3-2 μm, not in the category of ultra-fine-grained tungsten alloy;

[0008] b. A method for preparing a nano-oxide dispersion strengthened enhanced ultra-fine-grained tungsten-based composite material, the prepared tungsten alloy has a grain size of ≤3 μm, not in the category of ultra-fine-grained tungsten alloy;

[0009] c. Ultra-fine-grained tungsten rod and its preparation method, the prepared tungsten alloy has a grain size of ≤10 μm, not in the category of ultra-fine-grained tungsten alloy;

[0010] d. Ultra-fine-grained high-specific-gravity tungsten alloy and its preparation method, the prepared tungsten alloy has a grain size of <5 μm, not in the category of ultra-fine-grained tungsten alloy.

[0011] (2) Some patents report that the grain size of ultra-fine-grained tungsten alloy meets the range of 100-500 nm, but the grain size of the second-phase particles is >100 nm, not in the category of nanocrystalline. For example:

[0012] a. A method for preparing high-density ultra-fine-grained rare earth oxide doped tungsten alloy, the second-phase particles in the prepared tungsten alloy are not in the category of nanocrystalline (<100 nm);

[0013] b. A high-strength and high-conductivity ultrafine-grained tungsten-copper composite material and a preparation method thereof. The second phase particles in the tungsten alloy prepared by the method are not in the nanocrystalline (<100 nm) range.

[0014] (3) The fine-grained or nanocrystalline tungsten alloy reported in part of the patent is essentially different from the double-nanophase doped ultrafine-grained tungsten alloy disclosed in the present application. The tungsten grain size in the ultrafine-grained tungsten alloy reported in the present patent is 100 nm-500 nm, and the second phase particle grain size is <100 nm, while the comparative documents are, for example:

[0015] a. A double-nanophase tungsten alloy with good high-temperature stability and a preparation method and application thereof. The tungsten alloy prepared by the method has a grain size of 20-100 nm, and the second phase grain size is 10-20 nm.

[0016] b. A preparation method of ultrafine nanocrystalline tungsten material. The pure tungsten thin film material prepared by the magnetron sputtering technology has an average grain size of 4 nm.

[0017] The grain sizes of the tungsten alloy materials prepared by the above patents do not belong to the ultrafine-grained range of 100 nm-500 nm, and the difference in grain size significantly affects the performance of the tungsten alloy material. Moreover, the preparation methods used in the above patents are different from those in the present application.

[0018] The prior art CN110273093B also provides a nanocrystalline tungsten alloy and a preparation method thereof. The tungsten powder and 1wt%-8wt% second phase metal nanoparticle powder are doped and mixed, then subjected to high-energy ball milling, and then subjected to ultra-high pressure electric sintering. By controlling the second phase to be nanoparticles and controlling the parameter settings during the sintering process, the growth of tungsten grains during sintering is effectively controlled. The device suppresses the growth of grain size by ultra-high pressure electric sintering, but ultra-high pressure electric sintering requires a high pressure of GPa order. The pressure F that the device can provide on the sample is certain. According to the calculation formula of pressure (the pressure that an object bears on a unit area), pressure p = pressure F / area S. To achieve a pressure (p) of GPa, the sample size (S) is limited, so that only small-sized (cylindrical with a diameter of 6 mm and a height of 5 mm) samples can be finally prepared, which cannot be put into industrial production to prepare large-sized samples. However, the existing method for preparing large-sized samples is difficult to prepare ultrafine-grained tungsten alloy. Therefore, a new method for preparing large-sized, high-density, and ultrafine-grained tungsten alloy material is needed. SUMMARY

[0019] The present application aims at the problem of contradiction between high density and easy growth of grains in the preparation process of ultra-fine tungsten alloy, and provides a double-nanophase doped ultra-fine grain tungsten alloy, a preparation method and application thereof, and prepares the ultra-fine grain tungsten alloy with high density, good thermal stability and large size in the ultra-fine grain range.

[0020] The technical scheme of the present application is as follows:

[0021] The present application provides a double-nanophase doped ultra-fine grain tungsten alloy, which comprises the following raw material components: chromium (Cr): 5.0wt-10.0wt%, yttrium (Y): 0.5wt-5.0wt%, tungsten (W): the balance.

[0022] The matrix phase particles are tungsten, the second phase particles are chromium and yttrium, the grain size of the matrix phase particles tungsten is in the ultra-fine grain range (100nm-500nm), and the grain size of the second phase particles chromium and yttrium is in the nanocrystalline range (<100nm).

[0023] The second phase particles are nanocrystalline particles, which effectively inhibit the growth of tungsten grains during sintering. Meanwhile, the co-doping of chromium and yttrium can enhance the Zener pinning effect and reduce the Gibbs free energy of the system, effectively inhibiting the growth of tungsten grains at high temperatures, so that the material has excellent thermal stability. The chromium element can react with free oxygen in the powder to form chromium oxide compounds, which can purify and strengthen the grain boundary. The chromium element also plays a role in retarding the diffusion of tungsten atoms, thereby inhibiting grain growth. The addition of chromium element can reduce the Gibbs free energy of the system and form a stable ultra-fine grain structure with tungsten at a certain temperature. In addition, the dispersion of the second phase particles yttrium is uniformly distributed in and between tungsten grains, which inhibits the growth of tungsten grains through pinning effect. At the same time, the melting points of chromium and yttrium elements are lower than that of tungsten, and they are more likely to diffuse and fill pores than tungsten atoms, thereby improving the density of the material. The density of the double-nanophase doped ultra-fine grain tungsten alloy of the present application is 98.0%-99.9%.

[0024] The present application provides a preparation method of a double-nanophase doped ultra-fine grain tungsten alloy, which comprises the following steps:

[0025] (1) Raw material ball milling mechanical alloying: according to the formula, tungsten powder, chromium powder and yttrium powder are weighed and ball milled;

[0026] (2) Cold pressing forming: the ball milled powder obtained in step (1) is cold isostatic pressed to form a powder compact with certain strength;

[0027] (3) Hot isostatic pressing sintering: the powder compact obtained in step (2) is placed in a pure iron sleeve for hot isostatic pressing sintering to prepare a double-nanophase doped ultra-fine grain tungsten alloy bulk material.

[0028] The hot isostatic sintering method is beneficial to the preparation of large-size samples, but the tungsten alloy prepared by the hot isostatic sintering has a large particle size, which is out of the range of the ultra-fine grain tungsten alloy; and the existing methods capable of preparing the tungsten alloy, such as the ultra-high pressure electric sintering method, can prepare the ultra-fine grain tungsten alloy but cannot prepare large-size samples, which greatly limits the industrial application of the ultra-fine grain tungsten alloy. The method of the present application has prepared large-size ultra-fine grain tungsten alloy materials with a diameter of greater than or equal to 35 mm and a height of greater than or equal to 100 mm, and the volume of the materials is 96.2 cm 3 , and the samples with the required size can be prepared according to the requirements of industrial applications (the maximum size of the prepared sample depends on the size of the hot isostatic sintering furnace cavity, and the existing equipment can reach meter level), and meanwhile, the grain size of the tungsten particles in the matrix phase is in the ultra-fine grain range (100 nm-500 nm), and the grain size of the second phase particles is in the nanocrystalline range (<100 nm). According to a preferred embodiment, the tungsten raw material component is a high-purity raw material powder with a purity higher than 99.9% and a particle size of 10 nm-440 nm.

[0029] According to a preferred embodiment, the particle size of the raw material component chromium is 0.35 μm-22.50 μm, and the particle size of the raw material component yttrium is 0.18 μm-28.40 μm.

[0030] Preferably, in step (1), the ball milling rotation speed is 150 rpm-250 rpm, the ball-to-material ratio is 20:1-30:1, and the ball milling time is 5 h-10 h.

[0031] Preferably, in step (2), the powder cold isostatic pressing pressure is 180 MPa-280 MPa, and the pressure holding time is 3 min-8 min.

[0032] Preferably, in step (3), the hot isostatic sintering temperature is 1150℃-1250℃, the pressure is 150 MPa-180 MPa, and the sintering time is 1 h-2 h. The sintering temperature of the present application is lower than that of the existing direct hot isostatic sintering, which is beneficial to avoiding the grain size growth of the tungsten alloy, and meanwhile, based on the ball milling and the doping of the second phase particles, the high-density ultra-fine grain tungsten alloy is prepared at a lower temperature.

[0033] The present application also provides the application of the double-nanophase doped ultra-fine grain tungsten alloy as described above as a plasma-facing material in a fusion reactor.

[0034] The present application also provides the application of the double-nanophase doped ultra-fine grain tungsten alloy as described above in the preparation of weapon equipment.

[0035] The present application also provides the application of the double-nanophase doped ultra-fine grain tungsten alloy as described above in the preparation of high-temperature resistant components.

[0036] The beneficial effects of the present application compared with the prior art are:

[0037] 1. The second phase particles are uniformly distributed and the material has high density and improved mechanical properties: The second phase particles include intracrystalline and intercrystalline doping, and the material has high density. The double-phase nano-doped ultra-fine tungsten alloy obtained by co-doping of chromium and yttrium effectively inhibits the growth of grains during sintering by enhancing pinning effect and reducing Gibbs free energy of the system. Meanwhile, the second phase doping can react with free oxygen to purify and strengthen the grain boundary, and the doping of the second phase improves the density of the material.

[0038] 2. Large-size bulk materials can be prepared by ball milling, cold isostatic pressing and hot isostatic sintering technology, and the obtained bulk materials have uniform composition and high density, and the grain size does not significantly grow at 1000℃ and 1100℃, and the thermal stability is good. BRIEF DESCRIPTION OF DRAWINGS

[0039] Figure 1 It is a process schematic diagram of the preparation method of the double nano-doped ultra-fine tungsten alloy.

[0040] Figure 2 It is a scanning electron microscope (SEM) image of the powder raw material, (a) is tungsten powder, (b) is chromium powder and (c) is yttrium powder.

[0041] Figure 3 It is a scanning electron microscope (SEM) image and grain size statistical diagram of the double-phase nano-doped ultra-fine tungsten alloy, (a) and (b) are SEM images, (c) is a tungsten grain size statistical diagram, and (d) is a second phase particle grain size statistical diagram.

[0042] Figure 4 It is an energy spectrum analysis diagram of the double-phase nano-doped ultra-fine tungsten alloy, (a) is an SEM image with element distribution, (b) is an SEM image, (c) is a tungsten (W) element distribution diagram, (d) is a chromium (Cr) element distribution diagram, (e) is a yttrium (Y) element distribution diagram, and (f) is an oxygen (O) element distribution diagram.

[0043] Figure 5 The change of Vickers hardness of the double-phase nano-doped ultra-fine tungsten alloy before and after annealing, Vickers hardness indentation and micro-fracture morphology (RT is room temperature). DETAILED DESCRIPTION

[0044] It should be noted that relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0045] The features and performance of the present invention will be further described in detail below with reference to embodiments.

[0046] Example 1

[0047] refer to Figure 1 This embodiment provides a method for preparing a dual-nanophase-doped ultrafine-grained tungsten alloy:

[0048] Step (1): Step (1.1): Under a nitrogen atmosphere (nitrogen purity 99.999%) in a glove box, tungsten powder and two second-phase powders (chromium powder and yttrium powder) are placed in a high-energy ball mill jar at a certain mass ratio. The chromium powder doping ratio of the second-phase particles is 10 wt%, and the yttrium powder doping ratio of the second-phase particles is 5 wt%. Figure 2 The images shown are scanning electron microscope (SEM) images of the powder materials. The images show the particle size of each powder material at this time. Figure (a) shows tungsten powder with a particle size of 10 nm-440 nm, Figure (b) shows chromium powder with a particle size of 0.35 μm-22.50 μm, and Figure (c) shows yttrium with a particle size of 0.18 μm-28.40 μm.

[0049] Step (1.2): Add a certain amount of tungsten carbide cemented carbide balls to the grinding jar. The diameter of the tungsten carbide cemented carbide balls is 3mm-10mm. The ratio of the mass of the grinding balls to the mass of the powder is 20:1. Add a sealing rubber ring to the grinding jar, cover the grinding jar with the lid, and take it out of the glove box.

[0050] Step (1.3): The ball mill jar is loaded into a ball mill for high-energy ball milling. The ball mill speed is set to 250 rpm, and the milling time is 10 hours. High-energy ball milling refines the grain size of the powder and simultaneously ensures uniform mixing of the second-phase particles and tungsten powder.

[0051] Step (1.4): After the powder ball milling is completed, transfer the ball mill jar to the glove box, separate the powder and grinding balls through the mesh screen, and vacuum seal the powder in a vacuum plastic bag to prevent it from being oxidized by contact with air.

[0052] Step (2): Step (2.1): Load the obtained ball mill powder into a PVC mold with a diameter of 35mm, and insert a rubber plug with a vacuum port into the PVC mold. Wrap the PVC opening with iron wire and tighten it. Use a mechanical pump to vacuum the powder through the vacuum port for 2 hours until the vacuum degree reaches below 10Pa. After vacuuming is completed, use a strip to bind and seal the vacuum port.

[0053] Step (2.2): Place the PVC mold containing alloy powder after vacuuming into a cold isostatic press for cold isostatic pressing. The cold pressing pressure is 280 MPa and the cold pressing time is 3 min.

[0054] Step (3): Step (3.1): Take out the cold-pressed molded powder blank, put it into a cylindrical pure iron sleeve with a bottom, and weld the pure iron cover with the air extraction port to seal the sleeve.

[0055] Step (3.2): Degas the pressed powder in the package. Place the package containing the pressed powder in the heating furnace cavity. Connect the evacuation port to the vacuum system (two stages: mechanical pump and turbomolecular pump) for evacuation. Simultaneously, heat the package to 200℃ and hold until the vacuum reaches 10. -3 Pa is used to extract the residual water vapor in the pressed powder blank. Then, the temperature is heated to 800℃ and held for 1 hour to complete the degassing. The heating system is turned off and the sample is allowed to cool. The vacuum tube near the casing is quickly heated until it turns red. The heated part of the vacuum tube is clamped and sealed with pliers. The vacuum system is turned off and the casing is allowed to cool. The excess vacuum tube is then cut off.

[0056] Step (3.3): The degassed cladding is placed in a hot isostatic pressing (HIP) furnace for HIP sintering. The HIP sintering parameters are set as follows: sintering temperature 1200℃, holding time 2h, holding pressure 180MPa, with simultaneous heating and pressurization at a heating rate of 400℃ / h. After holding, the cladding is allowed to cool naturally to room temperature. The pure iron cladding is then opened, and the sintered bulk sample is removed, thus obtaining the dual-nanophase doped ultrafine-grained tungsten alloy.

[0057] The density of the obtained bulk material was measured using Archimedes' displacement method. Through density measurement and calculation, the compactness of the bulk material was found to be 99.9%. The fracture morphology and energy dispersive spectroscopy (EDS) of the material were characterized using scanning electron microscopy (SEM) to obtain the grain size, second-phase particle composition, and doping mode. The SEM images are shown below. Figure 3 (a) and Figure 3(b) shown. By statistics of the grain size, it is found that the grain size of tungsten ranges from 104 nm to 336 nm, as shown in Figure 3 (c) shown, the grain size of the second phase particles ranges from 14 nm to 89 nm, as shown in Figure 3 (d) shown. The obtained ultrafine-grained tungsten alloy material is uniform in composition, as shown in Figure 4 The energy spectrum analysis diagram thereof is shown, (a) is an SEM diagram with element distribution, (b) is an SEM diagram, (c) is a tungsten (W) element distribution diagram, (d) is a chromium (Cr) element distribution diagram, (e) is a yttrium (Y) element distribution diagram, and (f) is an oxygen (O) element distribution diagram. It can be seen from the diagram that the second phase is uniformly distributed, and exists in the form of CrOx compound and yttrium. The second phase particles include intracrystalline doping and intercrystalline doping. The obtained bulk material is vacuum annealed at 1000℃ and 1100℃ for 1h, the Vickers hardness of the material before and after annealing is tested, and the fracture morphology of the material before and after annealing is analyzed, Figure 5 The Vickers hardness of the unannealed material is 1312±12 kgf / mm 2 The Vickers hardness of the material annealed at 1000℃ is 1244±13 kgf / mm 2 The Vickers hardness of the material annealed at 1100℃ is 1265±7 kgf / mm 2 It can be found that the Vickers hardness decreases slightly, and the decrease in Vickers hardness may be due to the disappearance of micro defects such as dislocations in the material caused by annealing. Through the micro fracture morphology characterization, it can be found that the average grain size changes by no more than 12 nm compared with the unannealed sample, which has excellent thermal stability. The sample prepared in this embodiment has a size of a cylinder with a diameter of 35mm-50mm and a height of 100mm, which is larger than the sample prepared by spark plasma sintering and ultra-high pressure current sintering.

[0058] Example 2

[0059] Reference Figure 1 The embodiment provides a preparation method of a dual-nano-phase doped ultrafine-grained tungsten alloy.

[0060] Step (1): Step (1.1): In a glove box under a nitrogen atmosphere (nitrogen purity 99.999%), tungsten powder and two second phase powders (chromium powder and yttrium powder) are placed in a high-energy ball milling tank in a certain mass ratio. The doping ratio of the second phase particle chromium powder is 5wt%, and the doping ratio of the second phase particle yttrium powder is 0.5wt%.

[0061] Step (1.2): A certain amount of tungsten carbide hard alloy balls with a diameter of 3-10 mm is added to the ball mill jar, the ratio of the mass of the grinding balls to the mass of the powder is 30:1, a sealing rubber ring is added to the ball mill jar, and the lid of the ball mill jar is covered.

[0062] Step (1.3): The ball mill jar is loaded into a ball mill for high-energy ball milling, the rotation speed of the ball mill is set to 150 rpm, and the ball milling time is 8 h. The high-energy ball milling method refines the grain size of the powder and uniformly mixes the second phase particles and the tungsten powder.

[0063] Step (1.4): After the powder is ball milled, the ball mill jar is transferred to the glove box, the powder and the grinding balls are separated through a mesh screen, and the powder is stored in a vacuum plastic bag to avoid oxidation by contacting air.

[0064] Step (2): Step (2.1): The obtained ball milled powder is loaded into a PVC mold with a diameter of 35 mm, a rubber plug with a suction port is inserted into the PVC mold, the PVC port is tightly wrapped with iron wire, a mechanical pump is used to vacuum the powder through the suction port for 2 h until the vacuum degree reaches below 10 Pa, and after the vacuuming is completed, the suction port is sealed by banding.

[0065] Step (2.2): The PVC mold containing the alloy powder after vacuumizing is placed in a cold isostatic pressing machine for cold isostatic pressing, the cold pressing pressure is 180 MPa, and the cold pressing time is 8 min.

[0066] Step (3): Step (3.1): The cold-pressed formed powder compact is taken out and placed in a cylindrical pure iron sleeve with a bottom, and the pure iron cover with a suction port is electrically welded to seal the sleeve.

[0067] Step (3.2): The pressed powder compact in the sleeve is degassed, the sleeve containing the pressed powder compact is placed in a heating furnace cavity, the suction port is connected to a vacuum system (two-stage mechanical pump and turbo molecular pump) for pumping, and heating is performed at the same time, the temperature is heated to 200°C, and the vacuum degree is maintained at 10 -3 Pa, so that the residual water vapor in the pressed powder compact is pumped out, and then the temperature is heated to 800°C, and the temperature is maintained for 1 h to complete the degassing, the heating system is turned off, the sample is cooled, the suction tube near the sleeve is quickly heated to red, and the suction tube is clamped and sealed at the red heated part by using pliers, the clamping and sealing are performed twice, the vacuum system is turned off, the sleeve is cooled, and the excess suction tube is cut off.

[0068] Step (3.3): Put the de-gassed package into the hot isostatic sintering furnace for hot isostatic sintering, set the hot isostatic sintering parameters, the sintering temperature is 1250℃, the holding time is 2h, the holding pressure is 150MPa, the temperature is raised and the pressure is increased at the same time, the temperature rising rate is 400℃ / h. After holding, the sample is naturally cooled to room temperature, the pure iron package is opened, and the sintered bulk sample is taken out, that is, the dual-nanophase doped ultrafine-grained tungsten alloy is prepared.

[0069] The density of the obtained bulk material is measured by the Archimedes drainage method, the fracture morphology and energy spectrum of the material are characterized by a scanning electron microscope, and the grain size, second phase particle composition and doping method are obtained. The second phase particles include intracrystalline doping and intercrystalline doping. Through density measurement and calculation, the density of the bulk material is 98.6%, and by counting the grain size, it is found that the tungsten grain size ranges from 110nm to 340nm, and the second phase particle grain size ranges from 16nm to 91nm. The second phase is uniformly distributed and exists in the form of CrOx compound and yttrium. Under the annealing conditions of 1000℃ and 1100℃, the average grain size changes by no more than 12nm compared with the unannealed sample, which has excellent thermal stability. The sample prepared in this embodiment has a size of a cylinder with a diameter of 35mm-50mm and a height of 100mm, which is larger than the size of the samples prepared by spark plasma sintering and ultra-high pressure current sintering.

[0070] Example 3

[0071] Reference Figure 1 The embodiment provides a preparation method of a dual-nanophase doped ultrafine-grained tungsten alloy:

[0072] Step (1): Step (1.1): In a nitrogen atmosphere (nitrogen purity 99.999%) in a glove box, tungsten powder and two second phase powders of chromium powder and yttrium powder are put into a high-energy ball milling jar in a certain mass ratio. The doping proportion of the second phase particle chromium powder is 8wt%, and the doping proportion of the second phase particle yttrium powder is 4wt%.

[0073] Step (1.2): A certain amount of tungsten carbide hard alloy balls with a diameter of 3mm-10mm are added to the ball milling jar, and the mass ratio of the tungsten carbide hard alloy balls to the powder is 25:1. A sealing rubber ring is added to the ball milling jar, and the cover of the ball milling jar is covered. The ball milling jar is taken out from the glove box.

[0074] Step (1.3): The ball milling jar is loaded into a ball mill for high-energy ball milling, and the rotation speed of the ball mill is set to 200rpm. The ball milling time is 5h. The grain size of the powder is refined by high-energy ball milling, and the second phase particles and the tungsten powder are uniformly mixed.

[0075] Step (1.4): After the powder ball milling is completed, transfer the ball mill jar to the glove box, separate the powder and grinding balls through the mesh screen, and vacuum seal the powder in a vacuum plastic bag to prevent it from being oxidized by contact with air.

[0076] Step (2): Step (2.1): Load the obtained ball mill powder into a PVC mold with a diameter of 35mm, and insert a rubber plug with a vacuum port into the PVC mold. Wrap the PVC opening with iron wire and tighten it. Use a mechanical pump to vacuum the powder through the vacuum port for 2 hours until the vacuum degree reaches below 10Pa. After the vacuum is completed, use a strip to bind and seal the vacuum port.

[0077] Step (2.2): Place the PVC mold containing alloy powder after vacuuming into a cold isostatic press for cold isostatic pressing. The cold pressing pressure is 230 MPa and the cold pressing time is 6 min.

[0078] Step (3): Step (3.1): Take out the cold-pressed molded powder blank and put it into a cylindrical pure iron sleeve with a bottom. Weld the pure iron cover with the air extraction port to seal the sleeve.

[0079] Step (3.2): Degas the pressed powder in the package. Place the package containing the pressed powder in the heating furnace cavity. Connect the evacuation port to the vacuum system (two stages: mechanical pump and turbomolecular pump) for evacuation. Simultaneously, heat the package to 200℃ and hold until the vacuum reaches 10. -3 Pa is used to extract residual water vapor from the pressed powder, and then the temperature is heated to 800℃ and held for 1 hour to complete degassing. The heating system is then turned off, and the sample is allowed to cool. The vacuum tube near the sheath is then rapidly heated until it turns red. The heated part of the vacuum tube is then clamped and sealed with pliers. The vacuum system is then turned off, and the sheath is allowed to cool. The excess vacuum tube is then cut off.

[0080] Step (3.3): The degassed cladding is placed in a hot isostatic pressing (HIP) furnace for HIP sintering. The HIP sintering parameters are set as follows: sintering temperature 1150℃, holding time 1h, holding pressure 170MPa, with simultaneous heating and pressurization at a heating rate of 400℃ / h. After holding, the cladding is allowed to cool naturally to room temperature. The pure iron cladding is then opened, and the sintered bulk sample is removed, thus obtaining the dual-nanophase doped ultrafine-grained tungsten alloy.

[0081] The density of the obtained bulk material is measured by Archimedes drainage method, and the fracture morphology and energy spectrum of the material are characterized by scanning electron microscope to obtain the grain size, second phase particle composition and doping method. Through density measurement and calculation, the bulk material density is 98.0%, and through grain size statistics, it is found that the tungsten grain size ranges from 105nm to 330nm, and the second phase particle grain size ranges from 15nm to 85nm. The second phase is uniformly distributed, and exists in the form of CrOx compound and yttrium. Under the annealing conditions of 1000℃ and 1100℃, the average grain size changes by no more than 12nm compared with the unannealed sample, which has excellent thermal stability.

[0082] The sample prepared in this embodiment has a size of a cylinder with a diameter of 35mm-50mm and a height of 100mm, which is larger than the sample size prepared by spark plasma sintering and superhigh pressure current sintering. The volume is at least 96.2cm 3 .

[0083] The above-described embodiments only express the specific implementation of the present application, which is described in detail and specifically, but it cannot be understood as a limitation on the protection scope of the present application. It should be noted that for ordinary skilled in the art, without departing from the technical concept of the present application, a number of modifications and improvements can be made, which are all within the protection scope of the present application.

[0084] This background section is provided to generally present the context of the application, the work of the current named inventors, the work described in this background section to the extent described in this section, and the work described in this section at the time of filing, neither expressly nor implicitly, is recognized as prior art of the present application.

Claims

1. A dual nanophase doped ultrafine crystalline tungsten alloy characterized in that, The raw material components are as follows: chromium powder 5.0wt-10.0wt%, yttrium powder 0.5wt-5.0wt%, and tungsten powder the rest; The base phase particles are tungsten, the second phase particles are chromium and yttrium, the grain size of the base phase particles tungsten is in the ultra-fine crystal range: 100nm-500nm, and the grain size of the second phase particles chromium and yttrium is in the nanocrystal range: both less than 100nm; The volume of the ultrafine-grained tungsten alloy bulk material is not less than 96.2 cm 3 ; The preparation method of the ultra-fine crystal tungsten alloy is as follows: (1) Raw material ball milling mechanical alloying: according to the formula, tungsten powder, chromium powder and yttrium powder are weighed and ball milled; (2) Cold pressing forming: the ball milled powder obtained in step (1) is cold isostatic pressing forming to obtain a powder compact; (3) Hot isostatic pressing sintering: the powder compact obtained in step (2) is hot isostatic pressing sintering to prepare a double-nanophase doped ultra-fine crystal tungsten alloy bulk material; The temperature of the hot isostatic pressing sintering in step (3) is 1150℃-1250℃, the pressure is 150MPa-180MPa, and the time is 1h-2h.

2. A dual nanophase doped ultrafine crystalline tungsten alloy as in claim 1, wherein, The density is 98.0%-99.9%.

3. The method for preparing a dual-nanophase-doped ultrafine-grained tungsten alloy as described in claim 1, characterized in that, The preparation method is as follows: (1) Raw material ball milling mechanical alloying: according to the formula, tungsten powder, chromium powder and yttrium powder are weighed and ball milled; (2) Cold pressing forming: the ball milled powder obtained in step (1) is cold isostatic pressing forming to obtain a powder compact; (3) Hot isostatic pressing sintering: the powder compact obtained in step (2) is hot isostatic pressing sintering to prepare a double-nanophase doped ultra-fine crystal tungsten alloy bulk material.

4. The method of claim 3, wherein the method further comprises the step of: The raw material component tungsten powder in step (1) is a high-purity raw material powder with a purity higher than 99.9% and a particle size of 10nm-440nm.

5. The method of claim 3, wherein the method further comprises the step of: The particle size of the raw material component chromium powder in step (1) is 0.35μm-22.50μm, and the particle size of the raw material component yttrium powder is 0.18μm-28.40μm.

6. The method of claim 3, wherein the method further comprises the step of: The ball milling speed in step (1) is 150rpm-250rpm, the ball-to-material ratio is 20:1-30:1, and the ball milling time is 5h-10h.

7. The method of claim 3, wherein the method further comprises the step of: The cold isostatic pressing forming pressure in step (2) is 180MPa-280MPa, and the holding time is 3min-8min.

8. The double-nanophase doped ultra-fine crystal tungsten alloy of any one of claims 1-7 as a plasma-facing material for fusion reactors.

9. The double-nanophase doped ultra-fine crystal tungsten alloy of any one of claims 1-7 for preparing weapons and high-temperature resistant parts.

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