High-plasticity mixed crystal structure tungsten and preparation method thereof

Abstract

The invention provides high-plasticity mixed crystal structure tungsten and a preparation method thereof. The method comprises the following steps: growing tungsten on a deposition substrate by adopting a chemical vapor deposition method to obtain a high-purity tungsten raw material; the high-purity tungsten raw material is subjected to cogging hot rolling and stress relief annealing treatment, and a tungsten plate blank is obtained; the tungsten plate blank is subjected to multi-step cross rolling and stress relief annealing treatment, and then is subjected to vacuum high-temperature annealing treatment. Compared with a tungsten material prepared through a traditional method, the tungsten plate prepared through the method is of a unique mixed crystal structure with coarse grains and fine grains combined, has the advantages of being high in purity and density and good in room-temperature machinability and is excellent in performance. The tensile strain of the tungsten plate is high, and the stability and durability of a tungsten material in a high-temperature environment are remarkably improved. The preparation method is simple in process and high in repeatability, and a new thought is provided for improving the durability and reliability of the metal tungsten.

Description

Technical Field

[0001] The present invention relates to the technical field of nonferrous metal rolling processing, in particular to a high-plasticity mixed crystal structure tungsten and a preparation method thereof. Background Art

[0002] Tungsten is a refractory metal with the highest melting point of any metal, reaching 3422°C. It also possesses numerous physical properties, including excellent creep resistance, high hardness, high-temperature strength, and radiation resistance. Its unique properties have led to its widespread application in aerospace, military, electronics, and nuclear industries. However, tungsten exhibits a high ductile-brittle transition temperature (Tg). Below this temperature, it exhibits brittleness, making it difficult to plastically process, significantly limiting its application. Current methods for improving tungsten's plasticity include: 1) Alloying: Adding rhenium to form a tungsten-rhenium alloy can reduce room-temperature hardness by 16%. However, because rhenium is a precious metal, the preparation cost of this alloy is high, making it unsuitable for large-scale industrial production. 2) Grain refinement: Ultrafine-grained tungsten produced using powder metallurgy has a hardness of up to 7.8 GPa, but the effect of the ultrafine grain structure on plasticity improvement is not significant. 3) Hot deformation: Hot rolling, in particular, has been shown to significantly improve the room-temperature brittleness of pure tungsten, lowering the Tg to approximately 100°C.

[0003] As an important refractory metal, tungsten is the material of choice for high-temperature applications. Under service conditions above the recrystallization temperature, impurity segregation at grain boundaries weakens intergranular bonding, leading to brittle fracture and a decrease in plasticity even above the ductile-brittle transition temperature. Tungsten produced by traditional powder metallurgy methods has a low purity, which severely affects its plasticity to a certain extent. Ultra-high-purity tungsten is typically produced by chemical vapor deposition. Ultra-high-purity tungsten can be produced by chemical vapor deposition and exhibits a certain degree of plasticity after hot rolling. However, hot rolling increases internal deformation defects, preventing the full plasticity of rolled chemical vapor deposited tungsten at high temperatures. In recent years, magnesium alloys with a mixed crystal structure combining coarse and fine grains have been able to achieve synergistic enhancements in strength and plasticity. In a mixed crystal structure, fine grains preferentially undergo plastic deformation, while coarse grains effectively alleviate local stress concentrations through dislocation accumulation, significantly improving the overall plasticity of the material. This provides a new direction for optimizing the plasticity of tungsten materials. Introducing a mixed crystal structure into high-purity tungsten through hot rolling with large deformation and long-term vacuum treatment is expected to significantly improve the plasticity of tungsten materials, while overcoming the shortcomings of traditional methods and opening up new paths for the stable preparation of high-performance tungsten materials. Summary of the Invention

[0004] To address the above technical issues, the present invention provides a high-plasticity mixed-crystal structure, high-purity tungsten plate and a method for preparing the same. The method produces high-plasticity mixed-crystal structure, high-purity tungsten. This mixed-crystal structure offers advantages such as high purity, high density, and excellent room-temperature processing properties. It can operate stably in high-temperature environments for long periods of time, making it suitable for a variety of industrial applications.

[0005] In a first aspect, the present invention provides a method for preparing high-plasticity mixed crystal structure tungsten, comprising: 1) Chemical vapor deposition is used to grow tungsten on a deposition substrate to obtain high-purity tungsten raw material.

[0006] 2) The high-purity tungsten raw material is subjected to blanking hot rolling and stress relief annealing to obtain a tungsten slab.

[0007] 3) The tungsten slab is subjected to multi-step cross-rolling and stress-relief annealing, followed by vacuum high-temperature annealing; the vacuum high-temperature annealing is performed at a temperature of 1200-1600°C for 2-9 hours. In this invention, ultra-high-purity tungsten is first prepared using chemical vapor deposition technology. This is then hot-rolled to form a tungsten slab. A polycrystalline tungsten plate is then produced through a multi-step cross-rolling process. Finally, the polycrystalline tungsten plate is subjected to a long vacuum high-temperature annealing process under certain conditions to obtain a high-purity tungsten plate with a high-plasticity mixed crystal structure and excellent performance. Compared to tungsten materials prepared by traditional methods, the tungsten plate produced by this method exhibits a unique mixed crystal structure with a combination of coarse and fine grains. The proportion of coarse grains (diameter greater than 10 μm) ranges from 15% to 30%, while the proportion of fine grains (diameter less than 10 μm) ranges from 85% to 70%. Furthermore, the tungsten plate produced by this method exhibits the advantages of high purity, high density, good room-temperature workability, and excellent mechanical properties. At 300°C, the tungsten plate exhibits a quasi-static uniaxial tensile strain of up to 31.3%, significantly improving the stability and durability of tungsten in high-temperature environments. The preparation method employed in this invention offers a simple process and high repeatability, providing a new approach for improving the durability and reliability of tungsten metal.

[0008] Preferably, in step 1), the deposition substrate is selected from one or more of copper, molybdenum, tungsten, and carbon-carbon composite materials.

[0009] Preferably, in step 1), the reaction gases are tungsten halide and hydrogen, and the tungsten halide is WF6, WBr6 or WCl6, preferably WF6.

[0010] Preferably, in step 1), the temperature for growing tungsten is 450-600° C., the pressure is normal pressure, and the growth rate is 0.2-0.8 mm / h.

[0011] Further preferably, in step 1), the thickness of the high-purity tungsten raw material is 10 to 40 mm. Research conducted by the present invention has found that if the thickness of the high-purity tungsten raw material, i.e., chemically deposited tungsten, is less than 10 mm, the microstructure of the rolled tungsten plate is uneven; if the thickness of the chemically deposited tungsten is greater than 40 mm, the tungsten plate is prone to cracking during the rolling process.

[0012] Preferably, in step 1), the purity of the tungsten halide and hydrogen is ≥99.9%.

[0013] Preferably, in step 1), the purity of the high-purity tungsten raw material is greater than 99.9999%.

[0014] Preferably, step 1) further comprises peeling off the deposited substrate by cutting or acid treatment.

[0015] Preferably, in step 2), after the total deformation reaches 48% to 52%, preferably 50%, the rolled tungsten plate is subjected to stress relief annealing.

[0016] Preferably, in step 2), the rolling temperature of the bloom hot rolling is 1300-1600°C.

[0017] Preferably, in step 2), the number of rolling passes of the bloom hot rolling is 5 to 7.

[0018] Further preferably, in step 2), the deformation of each pass of the slab hot rolling is 5% to 15%. The present invention has found that if the deformation of each pass is too small, the rolling process becomes more complex; if the deformation of each pass is too large, the tungsten plate is prone to cracking, twisting, or deformation during the rolling process, reducing the surface quality of the rolled tungsten plate.

[0019] Preferably, in step 3), the multi-step cross rolling includes performing multiple passes of unidirectional rolling in each step, and rotating the rolling direction 90° clockwise and performing stress relief annealing between every two rolling steps.

[0020] Further preferably, in step 3), in the multi-step cross rolling, each step is performed with 2 to 5 rolling passes, the deformation amount of each pass is 10% to 20%, and the total deformation amount of each step does not exceed 70%.

[0021] Preferably, in step 3), the rolling temperature in the multi-step cross rolling is 1000-1300°C.

[0022] Preferably, in step 3), the multi-step cross-rolling comprises 3 to 8 steps. In the present invention, rolling under these conditions can more effectively refine grains, homogenize the material's microstructure, and reduce anisotropy. Furthermore, it effectively improves the material's plasticity, reduces the degree of work hardening, and provides a more optimal initial microstructure for subsequent heat treatment and final plasticity optimization.

[0023] Preferably, in step 2) and step 3), the stress relief annealing treatment atmosphere is hydrogen, the treatment temperature is 950-1050°C, preferably 1000°C, and the holding time is 0.2-0.5 h.

[0024] Further preferably, in step 3), the vacuum high-temperature annealing treatment is performed at a temperature of 1200-1500°C for 2-8 hours, preferably 2-6 hours. Examples include 2 hours, 3 hours, 4 hours, 5 hours, and 6 hours. Research conducted by the present invention has found that shorter heat treatment times are insufficient to significantly improve the plasticity of the material; longer heat treatment times can lead to excessive grain growth, resulting in reduced plasticity.

[0025] In a second aspect, the present invention provides tungsten with a high-plasticity mixed crystal structure, wherein the proportion of coarse crystals ranges from 15% to 30%, and the proportion of fine crystals ranges from 85% to 70%. The diameter of the coarse crystals is greater than 10 μm, and the diameter of the fine crystals is no greater than 10 μm. The strain of the high-plasticity mixed crystal structure under quasi-static uniaxial tension at 300°C is ≥ 20%. For example, 25%, 25.4%, 26%, 28%, 31.3%, 32.5%, 33%, etc. The purity is not less than 99.99992%, for example, 99.99992%, 99.99994%, 99.99995%, 99.99996%, 99.99998%, 99.999999%, 99.999992%, 99.999995%, etc. Preferably, the high-plasticity mixed crystal structure is prepared according to the above-mentioned preparation method.

[0026] The present invention uses chemical vapor deposition technology to prepare metallic tungsten, which has high purity, no impurity segregation at the grain boundaries after recrystallization, and excellent plasticity. Multi-step cross-rolling technology is used to prepare high-purity tungsten with a high-plasticity mixed crystal structure. Compared with unidirectional rolling, multi-step cross-rolling solves the problem of homogenization of tungsten plate performance and significantly improves the plasticity and strength of the material. In addition, the multi-step cross-rolling process used to prepare high-plasticity mixed crystal structure tungsten strictly controls the deformation amount and stress relief annealing process of each pass, eliminating the need to change the rolling direction multiple times, simplifying the preparation process and reducing the complexity of the rolling process. In the present invention, the tungsten plate is subjected to high-temperature stress relief annealing treatment after each step of rolling deformation, reducing the stress accumulation of the tungsten plate along the rolling direction, which is beneficial for subsequent processing. After rolling, a long-term vacuum high-temperature heat treatment is carried out to eliminate the defects caused by the rolling deformation process of the tungsten plate, effectively improving the overall performance of the tungsten plate, and enhancing the stability and durability of the tungsten plate. Through multiple hot rolling processes, the tungsten plate has good room temperature processing performance and can be further processed to meet the requirements of various shapes and sizes. The method has a simple process flow, high controllability and good stability. In addition, the invention adopts a fully enclosed process, has almost no emissions, is environmentally friendly, and meets the requirements of sustainable development.

[0027] The present invention provides at least one beneficial effect: the method for preparing high-purity tungsten plates with a high-plasticity mixed-crystal structure employs chemical vapor deposition (CVD) tungsten as the raw material, employs multi-step cross-rolling for large deformation, and ultimately undergoes prolonged high-temperature vacuum heat treatment to obtain high-purity tungsten with a high-plasticity mixed-crystal structure. This mixed-crystal structure offers high purity, high density, and excellent room-temperature processability, enabling long-term, stable service in high-temperature environments and meeting the needs of a variety of industrial sectors. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] In order to more clearly illustrate the technical solutions in the present invention or the prior art, a brief introduction is given below to the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0029] Figure 1 A schematic flow chart of a method for preparing high-plasticity polycrystalline tungsten provided in an embodiment of the present invention.

[0030] Figure 2 This is a quasi-static uniaxial tensile stress-strain curve of high-purity tungsten with a high plasticity mixed crystal structure in Example 1 of the present invention.

[0031] Figure 3 These are sample photos of high-purity tungsten with a high plasticity mixed crystal structure before and after stretching in Example 1 of the present invention.

[0032] Figure 4 This is the metallographic structure diagram of high-purity tungsten with high plasticity mixed crystal structure in Example 1 of the present invention.

[0033] Figure 5 This is a quasi-static uniaxial tensile stress-strain curve of high-purity tungsten with a high plasticity mixed crystal structure in Example 2 of the present invention.

[0034] Figure 6 This is a microstructure diagram of high-purity tungsten with a high plasticity mixed crystal structure in Example 2 of the present invention.

[0035] Figure 7 This is a quasi-static uniaxial tensile stress-strain curve of tungsten in Comparative Example 2 of the present invention.

[0036] Figure 8 This is a quasi-static uniaxial tensile stress-strain curve of tungsten in Comparative Example 3 of the present invention.

[0037] Figure 9 This is a quasi-static uniaxial tensile stress-strain curve of tungsten in Comparative Example 4 of the present invention. DETAILED DESCRIPTION

[0038] To make the objectives, technical solutions, and advantages of the present invention more clear, the technical solutions of the present invention are described clearly and completely below. Obviously, the embodiments described are only some of the embodiments of the present invention, not all of them. All other embodiments derived by persons of ordinary skill in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0039] The endpoints of the ranges and any values disclosed herein are not limited to the precise ranges or values, and these ranges or values should be understood to include values close to these ranges or values. For numerical ranges, the endpoints of each range, the endpoints of each range and individual point values, and the individual point values can be combined with each other to form one or more new numerical ranges, and these numerical ranges should be considered to be specifically disclosed in the present invention.

[0040] Where specific techniques or conditions are not specified in the examples of the present invention, the techniques or conditions described in literature in the field or in accordance with the product specifications were followed. Apparatus, instruments, reagents, etc. used, where the manufacturer is not specified, are conventional products available through regular channels. All experimental reagents and raw materials involved are commercially available.

[0041] Example 1 This embodiment provides a high-purity, high-plasticity mixed crystal structure tungsten, and its preparation method is as follows: Figure 1 As shown, the specific steps include: (1) A mixture of H2 and WF6 with a purity of 99.95% was introduced into the chemical vapor deposition chamber, with a molar ratio of H2 to WF6 of 3:1. The deposition substrate was copper. The reaction chamber was heated to 500 °C. The chemical vapor deposition reaction was carried out at atmospheric pressure. The deposition rate was 0.4 mm / h. The final deposition thickness was 20 mm.

[0042] (2) Use nitric acid to strip the copper substrate to obtain chemical vapor deposition high-purity tungsten material.

[0043] (3) The high-purity tungsten obtained in step (2) is subjected to slab hot rolling at a rolling temperature of 1400°C and five rolling passes; after the total deformation reaches 50%, the rolled tungsten plate is subjected to stress relief annealing at a temperature of 1000°C for 0.3 h.

[0044] (4) The tungsten plate obtained by the blank rolling in step (3) is subjected to a five-step cross rolling process, with four passes in each step and a rolling temperature of 1200°C. Between each two rolling steps, the rolling direction is rotated 90° clockwise and a stress relief annealing process is performed. The stress relief annealing process is 1000°C, kept warm for 0.2 h, and the atmosphere is hydrogen. The final tungsten plate thickness is 1.25 mm. After the rolling is completed, a vacuum heat treatment is performed at a temperature of 1500°C for 3.0 h to obtain high-plasticity tungsten with a mixed crystal structure.

[0045] Figure 2 This is the stress-strain curve of high-purity tungsten with high plasticity mixed crystal structure in Example 1. Figure 3 These are sample photos of high-purity tungsten with high plasticity mixed crystal structure before and after stretching in Example 1. Figure 4 This is the metallographic structure diagram of high-purity tungsten with high plasticity mixed crystal structure in Example 1.

[0046] The analysis and test results show that the purity of the obtained tungsten is 99.99999%; the metallographic results show that the tungsten plate has a uniform structure and a mixed crystal structure, of which coarse crystals (diameter greater than 10 μm) account for about 19% and fine crystals (diameter not greater than 10 μm) account for about 81%; the tungsten plate was processed into a tensile sample and subjected to a quasi-static uniaxial tensile test at 300 °C, with a strain of 25.4%.

[0047] Example 2 This embodiment provides a high-purity, high-plasticity mixed crystal structure tungsten, the preparation method of which includes the following steps: (1) A mixture of H2 and WF6 with a purity of 99.995% was introduced into the chemical vapor deposition chamber, with a molar ratio of H2 to WF6 of 3:1. The deposition substrate was copper. The reaction chamber was heated to 550 °C. The chemical vapor deposition reaction was carried out at atmospheric pressure. The deposition rate was 0.6 mm / h. The final deposition thickness was 25 mm.

[0048] (2) Use nitric acid to strip the copper substrate to obtain chemical vapor deposition high-purity tungsten material.

[0049] (3) The high-purity tungsten obtained in step (2) is subjected to slab hot rolling at a hot rolling temperature of 1450°C and 6 rolling passes; after the total deformation reaches 50%, the rolled tungsten plate is subjected to stress relief annealing treatment at a temperature of 1000°C for 0.5 h.

[0050] (4) The tungsten plate obtained by blank rolling in step (3) is subjected to 7-step cross rolling treatment at a rolling temperature of 1200°C; between each two rolling steps, the rolling direction is rotated 90° clockwise and stress relief annealing is performed, and the stress relief annealing process is 1000°C for 0.3 h in a hydrogen atmosphere, and the final thickness of the tungsten plate is 1.10 mm; after the rolling is completed, a vacuum heat treatment is performed at a temperature of 1200°C for 4 h to obtain high-purity tungsten with a high plasticity mixed crystal structure.

[0051] Figure 5 This is the stress-strain curve of high-purity tungsten with high plasticity mixed crystal structure in Example 2. Figure 6 This is the microstructure diagram of high-purity tungsten with high plasticity mixed crystal structure in Example 2.

[0052] The analysis and test results show that the purity of the obtained tungsten is 99.99995%; the test results show that the tungsten plate has a mixed crystal structure with a combination of coarse and fine grains, of which coarse grains (diameter greater than 10 μm) account for about 25% and fine grains (diameter not greater than 10 μm) account for about 75%; the tungsten plate was processed into a tensile sample and subjected to a quasi-static uniaxial tensile test at 300 °C, with a strain of 31.3%.

[0053] Comparative Example 1 This comparative example provides a mixed crystal structure tungsten, the preparation method of which includes the following steps: (1) A mixture of H2 and WF6 with a purity of 99.99% was introduced into the chemical vapor deposition chamber, with a molar ratio of H2 to WF6 of 3:1. The deposition substrate was copper. The reaction chamber was heated to 500 °C. The chemical vapor deposition reaction was carried out at atmospheric pressure. The deposition rate was 0.5 mm / h. The final deposition thickness was 20 mm.

[0054] (2) Use nitric acid to strip the copper substrate to obtain chemical vapor deposition high-purity tungsten material.

[0055] (3) The high-purity tungsten obtained in step (2) is subjected to slab hot rolling at a temperature of 1400°C and six rolling passes; after the total deformation reaches 50%, the rolled tungsten plate is subjected to stress relief annealing at a temperature of 1020°C for 0.3 h.

[0056] (4) The tungsten plate obtained by slab rolling in step (3) was subjected to unidirectional rolling at a rolling temperature of 1200°C for a total of 10 passes, with a deformation of 8% per pass and a total deformation of 80%. No stress relief annealing or cross rolling was performed during this period. Finally, a vacuum high-temperature annealing was performed at 1500°C for 8 hours.

[0057] After testing, the strain of the obtained tungsten under quasi-static uniaxial tension at 300 °C was 12.3%.

[0058] Comparative Example 2 Comparative Example 2 was the same as Example 1 in other conditions except that no vacuum heat treatment was performed after rolling. The metallographic results showed that the sample was mainly fine-grained. Figure 7 The quasi-static uniaxial tensile test results at 300°C are shown for the tungsten prepared in Comparative Example 2. The strain of the tested sample is only 6.4%, significantly lower than the tensile properties of the mixed crystal tungsten in Example 1.

[0059] Comparative Example 3 Comparative Example 3 is the same as Example 1 in other conditions, except that the vacuum heat treatment time after rolling is extended to 24 hours. Figure 8 The tungsten plate prepared in Comparative Example 3 was subjected to quasi-static uniaxial tensile testing at 300°C. The strain of the test sample was 19.7%, lower than the tensile properties of the mixed-crystal tungsten in Example 1. The material in Comparative Example 3 exhibited poor plasticity. The processing conditions of the present invention play a significant role in forming an optimized mixed-crystal structure and improving the plasticity of tungsten.

[0060] Comparative Example 4 Comparative Example 4 is the same as Example 2 in other conditions, except that the raw tungsten is adjusted to a commercially available powder metallurgy tungsten raw material with a purity of 99.97%. Figure 9 The tungsten plate prepared in Comparative Example 4 was subjected to a quasi-static uniaxial tensile test at 300°C. The strain of the test sample was 11.9%, significantly lower than the tensile properties of the high-purity tungsten plate prepared in Example 2. The high-purity raw materials used in this invention play an important role in improving the plasticity of tungsten.

[0061] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the various embodiments of the present invention.

Claims

1. A method for preparing high plasticity mixed crystal structure tungsten, characterized in that: include: 1) Using chemical vapor deposition to grow tungsten on a deposition substrate to obtain high-purity tungsten raw material; 2) subjecting the high-purity tungsten raw material to slab hot rolling and stress relief annealing to obtain a tungsten slab; 3) performing multi-step cross rolling and stress relief annealing on the tungsten slab, and then performing vacuum high-temperature annealing; the vacuum high-temperature annealing is performed at a temperature of 1200-1600° C. and for a time of 2-9 hours.

2. The method for preparing high plasticity mixed crystal structure tungsten according to claim 1, characterized in that: In step 1), the deposition substrate is selected from one or more of copper, molybdenum, tungsten, and carbon-carbon composite materials; And / or, in step 1), the reaction gas is tungsten halide and hydrogen, and the tungsten halide is WF6, WBr6 or WCl6; And / or, in step 1), the temperature of growing tungsten is 450-600°C, and the growth rate is 0.2-0.8 mm / h.

3. The method for preparing high plasticity mixed crystal structure tungsten according to claim 2, characterized in that: In step 1), the thickness of the high-purity tungsten raw material is 10-40 mm.

4. The method for preparing high plasticity mixed crystal structure tungsten according to claim 1, characterized in that: In step 2), after the total deformation reaches 48% to 52%, the rolled tungsten plate is subjected to stress relief annealing.

5. The method for preparing high plasticity mixed crystal structure tungsten according to claim 4, characterized in that: In step 2), the rolling temperature of the slab hot rolling is 1300-1600°C.

6. The method for preparing high plasticity mixed crystal structure tungsten according to claim 5, characterized in that: In step 2), the slab hot rolling is performed in 5 to 7 passes; And / or, in step 2), the deformation amount of each pass of the slab hot rolling is 5% to 15%.

7. The method for preparing high plasticity mixed crystal structure tungsten according to any one of claims 1 to 6, characterized in that: In step 3), the multi-step cross rolling includes performing multiple passes of unidirectional rolling in each step, rotating the rolling direction 90° clockwise and performing stress relief annealing between each two rolling steps; And / or, in the multi-step cross rolling, 2 to 5 rolling passes are performed in each step, the deformation amount of each pass is 10% to 20%, and the total deformation amount of each step does not exceed 70%. and / or, in the multi-step cross rolling, the rolling temperature is 1000-1300° C.; And / or, the multi-step cross rolling is 3 to 8 steps.

8. The method for preparing high plasticity mixed crystal structure tungsten according to claim 7, characterized in that: In step 2) and step 3), the stress relief annealing treatment atmosphere is hydrogen, the treatment temperature is 950-1050° C., and the holding time is 0.2-0.5 h.

9. The method for preparing high plasticity mixed crystal structure tungsten according to claim 8, characterized in that: In step 3), the vacuum high temperature annealing treatment is performed at a temperature of 1200-1500° C. for 2-8 hours.

10. A high plasticity mixed crystal structure tungsten, characterized in that: In the high-plasticity mixed crystal structure, the proportion of coarse crystals is in the range of 15% to 30%, the proportion of fine crystals is in the range of 85% to 70%, the diameter of the coarse crystals is greater than 10 μm, and the diameter of the fine crystals is not greater than 10 μm; the strain under quasi-static uniaxial tension at 300 °C is ≥20%.

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