Single crystal tungsten (W) preparation method and device based on multi-physics field (force-heat-electricity) coupling

Abstract

The invention discloses a single crystal tungsten (W) preparation method and device based on multi-physics field (force-heat-electricity) coupling, and the method comprises the following steps: (1) sample preparation: carrying out stress relief annealing on a deformed W plate, cutting the deformed W plate into a round sample, and cleaning and drying the round sample; (2) heat treatment: placing the sample in a graphite mold of a multi-physics field coupling device, regulating and controlling the working load, the heat treatment temperature and the current, and preparing a single crystal W in the sample; and (3) cutting: cutting the single crystal W in the obtained sample by adopting a linear cutting technology. According to the method, the abnormal growth behavior of the deformed W plate in the grain growth stage is strengthened through cooperation of a stress field generated by an external load, a temperature field generated by the thermal effect of current and a current field generated by a non-thermal effect, and the single crystal W with considerable size, low dislocation density, small sub-crystal number and small orientation difference among sub-grains can be obtained within the loading time of less than 20 min; and a brand-new method is provided for rapidly preparing the single crystal W with considerable size.

Description

Technical Field

[0001] The present invention relates to a method for preparing single crystal tungsten, belonging to the technical field of microstructure design of refractory (high melting point) metal materials, and specifically relates to a method and device for preparing single crystal tungsten (W) based on the coupling of multiple physical fields (force-thermal-electricity). Background Technique

[0002] Single crystal tungsten (W) is a high-performance refractory metal material with a single crystal structure, and shows irreplaceable application value in extreme working conditions such as high temperature, high stress and strong irradiation due to its special physical and chemical properties. As a metal material with the highest melting point (3422 °C), pure W has unique physical and chemical properties such as high density (19.3 g / cm 3 )、high thermal stability, high creep resistance, low coefficient of thermal expansion (close to ceramics) and high thermal conductivity. Therefore, on the basis of pure W materials, single crystal W with further eliminated grain boundary defects has better creep resistance than pure W materials above 1600 °C, and also has higher thermal stability and thermal conductivity, making it have high dimensional thermal stability and maintain efficient heat dissipation in working conditions of severe thermal cycling. In addition, the high density characteristic of pure W materials gives it excellent anti-irradiation performance, while single crystal W shows more excellent anti-irradiation performance in strong irradiation working conditions, which is mainly attributed to the fact that the single crystal structure can effectively inhibit the expansion of irradiation defects. These unique physical and chemical characteristics make it widely used in aerospace (such as rocket engine nozzles, ultra-high temperature furnace elements), nuclear energy technology (first wall materials of fusion devices, reactor shielding components), electronic industry (heat sinks for high-power devices, crucibles for single crystal silicon growth), medical equipment (radiotherapy collimators, CT targets) and scientific research instruments (synchrotron radiation mirrors, electron microscope filaments) and other fields. Single crystal W has become an important application material in extreme working conditions such as high temperature, high stress and strong radiation by breaking through the "bottleneck" of grain boundary constraints of traditional polycrystalline materials, continuously promoting the boundary expansion of frontier science and technology.

[0003] There are many methods for preparing refractory metal single crystals, such as directional crystallization methods (including Bridgman method, Stepanov method, Czochralski method, etc.), zone melting methods (including electron beam floating zone melting method, light beam floating zone melting method, plasma arc melting method, etc.), strain annealing method, etc. Among them, although the directional crystallization method has the advantages of controllable crystal orientation, suitability for large-scale production and mature process in the preparation of metal single crystals, the preparation cycle ranges from several hours to hundreds of hours, has strict requirements for the temperature field uniformity and may have residual stress or sub-grain boundaries, and may also introduce crucible contamination, affecting the quality of single crystals; although the zone melting method can prepare high-purity and pollution-free single crystals, especially suitable for refractory metal materials, its preparation cycle ranges from several hours to dozens of hours and has the disadvantages of complex equipment, high cost, low material utilization rate and difficulty in preparing large-size single crystals. Although the strain annealing method can prepare high-quality single crystals, the preparation cycle is as long as dozens of hours, the process is complex, the efficiency is low, and the cost is relatively high. Therefore, although the above methods have all been developed for a long time and can prepare large-size single crystal refractory metal materials with relatively high quality, they usually have high requirements for the environment, equipment, raw materials, process, etc., and the time consumption is relatively long.

[0004] Electric current can promote the drastic evolution of the microstructure of metal materials, which is mainly attributed to the coupled action of the thermal effect and non-thermal effect of the electric current: a large number of directionally moving electrons collide with metal ions to generate Joule heat (i.e., the thermal effect), and at the same time, momentum exchange is carried out to strengthen the migration of metal atoms (i.e., the non-thermal effect). From the perspective of physical fields, the coupled action of the thermal effect and non-thermal effect generated by the interaction between the electric current and the metal is essentially the coupled action of the temperature field and the electric current field, and the strain annealing method is a single crystal preparation method with the coupled action of the stress field and the temperature field. Therefore, combining the theoretical knowledge of the coupled action of the temperature field, the electric current field and the stress field, a multi-physical field (electricity-thermal-force) coupled action mechanism is introduced on the basis of the strain annealing method by introducing high-density electric current, which not only further improves the preparation efficiency, but also further reduces the complexity of the process, and at the same time takes into account the advantages of low raw material requirements and high finished product quality of the strain annealing method.

[0005] In view of this, the present invention proposes a method for preparing single crystal W based on multi-physical field (force-thermal-electricity) coupling, and performs heat treatment for microstructural design on the deformed W plate in a multi-physical field (force-thermal-electricity) coupling device. Using the thermal effect of the electric current, the deformed W plate is quickly heated to a temperature above the abnormal grain growth temperature of the refractory metal, and then the abnormal grain growth of the deformed W plate is synergistically strengthened by the stress field generated by the working load parallel to the direction of the electric current, the temperature field generated by the thermal effect of the electric current, and the electric current field generated by the non-thermal effect, so as to quickly prepare single crystal W. Summary of the Invention

[0006] To solve the above problems existing in the prior art, based on the theoretical knowledge of the coupled action of stress field, temperature field and current field, the present invention proposes a method and device for preparing single-crystal tungsten (W) based on the coupling of multiple physical fields (force-thermal-electricity). Applying a certain working load to the deformed W plate and introducing a high-density current can accelerate the heat treatment process, promote the occurrence of abnormal grain growth of metals, and achieve the rapid preparation of single-crystal W.

[0007] To achieve the above object, the technical solution adopted by the present invention is as follows:

[0008] A method for preparing single-crystal W based on the coupling of multiple physical fields (force-thermal-electricity) uses the coupled action of multiple physical fields (force-thermal-electricity) to perform heat treatment on the deformed W plate. The stress field generated by the working load parallel to the current direction, the temperature field generated by the thermal effect of the high-density current, and the current field generated by the non-thermal effect synergistically strengthen the slip of grain boundaries and dislocations and atomic migration of metals during the grain growth stage, promoting abnormal grain growth of the deformed W plate and growing single-crystal W with considerable size, thereby achieving the rapid preparation of single-crystal W.

[0009] As a preferred technical solution of the present invention, the method for preparing single-crystal tungsten (W) includes the following steps:

[0010] (1) Sample preparation: First, perform stress relief annealing on the deformed W plate, then use wire electrical discharge machining technology to cut it into circular wafers with a certain diameter and thickness, and grind the upper and lower surfaces with sandpaper to reduce the surface roughness and improve the parallelism of the upper and lower surfaces of the sample. Then, clean and remove stains and dry it to obtain a deformed pure W circular wafer sample for heat treatment in a multi-physical field (force-thermal-electricity) coupling device;

[0011] (2) Heat treatment for microstructural design of the deformed pure W circular wafer sample: In a multi-physical field (force-thermal-electricity) coupling device, first install the pure W circular wafer sample obtained in step (1) in a graphite mold and make it in close contact with the electrode, then adjust the three heat treatment process parameters of working load, heat treatment temperature and current, and finally rapidly prepare single-crystal W with considerable size in the sample;

[0012] (3) Cutting: Cut the single-crystal W in the sample. The sample obtained in step (2) contains one or several large-size W grains. After cutting a plane and grinding and polishing it using wire cutting technology, etching the cut surface can reveal obvious grain boundaries. The range of the grain boundaries can be estimated through two perpendicular cut surfaces. Then, use wire cutting to separate each grain along the cutting line, and finally through polishing and cutting in various directions, so as to cut the abnormally grown large grains in the sample obtained in step (2) into single-crystal W.

[0013] As a further preferred technical solution of the present invention, in the method for preparing single-crystal tungsten (W):

[0014] In step (1), the plastic deformation amount of the deformed W plate used is greater than 50%, and the impurity content should be within 5%. The annealing temperature during stress relief annealing is 900 - 1100 °C, and the annealing time is 1 - 3 h. The upper and lower surfaces of the obtained deformed pure W wafer sample should be clean and have low surface roughness and high parallelism.

[0015] In step (2), in order to prevent the pure W wafer sample from being oxidized during annealing, the vacuum degree in the multi-physical field (force-thermal-electricity) coupling device is ≤ 10 Pa. In order to ensure that the electrodes do not contaminate the sample, pure W foils are placed between the upper and lower surfaces of the wafer sample and the two electrodes on both sides as isolation layers. In order to reduce contamination, the isolation layers are also ground, polished, and cleaned.

[0016] In step (2), the heat treatment process parameters of the multi-physical field (force-thermal-electricity) coupling device are as follows: first, apply a working load of 10 - 30 Mpa parallel to the current direction (which can not only provide a stress field but also is conducive to good contact between the electrodes in the device and the pure W wafer sample), then gradually increase the current to 800 - 1100 A and keep it constant, then stop loading the current immediately after the temperature reaches 1600 - 1700 °C without heat preservation, and finally let the sample cool in the furnace to below 100 °C and take it out.

[0017] In step (2), the structure of the multi-physical field (force-thermal-electricity) coupling device includes an infrared thermometer, an upper pressure head, a vacuum chamber, electrodes, a graphite mold, and a lower pressure head. The infrared thermometer is used to measure the temperature, the infrared thermometer is connected to the upper pressure head, the vacuum chamber is used for vacuum pumping, the upper pressure head and the lower pressure head are used to apply an external load, and the electrodes are connected to the graphite mold and are used to pass current through the sample.

[0018] The present invention proposes a new method for rapidly preparing single-crystalline W. This method is based on the theoretical knowledge of the coupled action of stress field, temperature field, and current field, and designs the microstructure of refractory metal materials at the microscale in a multi-physical field (force-thermal-electricity) coupling device. Based on the Joule effect, the multi-physical field (force-thermal-electricity) coupling device passes a high-density current into the sample to generate a large amount of uniformly distributed Joule heat, which rapidly raises the temperature uniformly to the temperature at which abnormal growth of refractory metals occurs, thereby accelerating the processes of recovery, recrystallization, and grain growth of the material, and significantly reducing the preparation cycle of single-crystalline W. Moreover, the stress field generated by the working load, the temperature field generated by the current thermal effect, and the current field generated by the non-thermal effect are all uniformly distributed inside the sample. They not only synergistically strengthen atomic migration and dislocation slip, accelerate the evolution of the material microstructure, further reduce the preparation cycle of single-crystalline W, but also facilitate a small number of grains to break the pinning effect of grain boundaries to generate large grains with a volume advantage relative to the surrounding grains, undergo abnormal growth, and rapidly grow into single-crystalline W, thereby realizing the rapid preparation of single-crystalline W.

[0019] Compared with the prior art, the beneficial technical effects of the present invention are as follows:

[0020] 1. The present invention uses a multi-physical field (force-thermal-electricity) coupling device to pass a high-density direct current into the sample, and generates a large amount of Joule heat through the thermal effect of the current in the metal, realizing uniform and rapid heating of the sample to the temperature at which abnormal growth of refractory metals occurs, thereby promoting dislocation slip and atomic migration, accelerating the recovery and recrystallization processes of the sample, and improving the working efficiency of single-crystalline preparation.

[0021] 2. The present invention uses a multi-physical field (force-thermal-electricity) coupling device to apply a certain working load to the sample, and promotes the directional migration of W atoms through the stress parallel to the current direction, further accelerating the recovery and recrystallization processes of the sample, and improving the working efficiency of single-crystalline W preparation. Moreover, the applied working load, the thermal effect and non-thermal effect generated by the passed direct current synergistically strengthen dislocation slip and atomic migration, are conducive to breaking the pinning effect of grain boundaries, promoting abnormal grain growth of the deformed W raw material, and realizing the rapid preparation of single-crystalline W with a considerable size.

[0022] 3. By performing multi-physical field (force-thermal-electricity) coupling heat treatment on the deformed pure W plate, the present invention can reduce the temperature at which abnormal growth of refractory metals occurs while shortening the time required to form a single crystal through abnormal growth, and rapidly prepare single-crystalline W with a considerable size and a low dislocation density when the heat treatment time is controlled within 20 minutes.

[0023] 4. The key to the method of the present invention for improving the recrystallization annealing of refractory metals lies in controlling three technical process parameters: working load, heat treatment temperature, and current, to form a coupled physical field of the most appropriate stress field, temperature field, and current field, which not only accelerates the recovery and recrystallization processes of the sample and shortens the heat treatment time, but also promotes the growth of abnormal grains during the grain growth stage, achieving the rapid preparation of single-crystal W with a considerable size.

[0024] 5. The solution of the present invention has strong operability and low requirements for equipment. It is proposed to apply a certain working load and pass a high-density current on the deformed W raw material in a short time, so that the temperature quickly reaches the abnormal growth temperature of the refractory metal, and promotes the abnormal grain growth behavior during the grain growth stage, shortening the cycle of preparing W single crystal by the strain annealing method, improving the efficiency, and reducing the required cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or in the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the drawings in the following description are some embodiments of the present invention.

[0026] Figure 1 is a multi-physical field (force - heat - electricity) coupling device for preparing single-crystal W provided by an embodiment of the present invention.

[0027] Figure 2 is a metallographic micrograph of large-sized grains that appear inside the sample after the deformed W raw material in Example 1 is heated to 1700 °C under the condition of a current that is gradually increased to 1000 A and then remains unchanged.

[0028] Figure 3 is collected by the electron backscatter diffraction (EBSD) technique Figure 2 the orientation imaging map (OIM) of the inside and edge of the large grain in, the grains are colored according to the grain orientation along the current direction, the low-angle grain boundaries with an orientation difference greater than 2° and less than 15° are represented by white lines, and the high-angle grain boundaries with an orientation difference greater than 15° are represented by black lines.

[0029] Figure 4 is a metallographic micrograph of three large-sized grains that appear inside the sample after the deformed W raw material in Example 2 is heated to 1700 °C under the condition of a current that is gradually increased to 900 A and then remains unchanged.

[0030] Figure 5 is Figure 4 the orientation imaging map (OIM) of the inside and edge of a certain large grain in.

[0031] Figure 6It is the orientation imaging map (OIM) and metallographic micrograph of large-sized grains that appeared inside the sample after the deformed W raw material in Example 3 was heated to 1600°C under the condition of gradually increasing the current to 800 A and then keeping it unchanged.

[0032] Figure 7 It is a schematic diagram of single crystal cutting; the green is the obvious grain boundary after corrosion, and the red is the cutting line.

[0033] Figure 8 It is a physical photo and scale comparison of the W single crystal cut out in Example 2.

[0034] Figure 1 The meanings of the reference numerals in the figure are as follows:

[0035] 1 - Infrared thermometer; 2 - Upper pressure head; 3 - Vacuum chamber; 4 - Electrode; 5 - Graphite mold; 6 - Lower pressure head. Specific embodiments

[0036] The following elaborates on the preferred embodiments and comparative embodiments of the present invention in conjunction with the accompanying drawings, so that the advantages and features of the present invention can be more easily understood by those skilled in the art, thereby making the protection scope of the present invention more clearly defined.

[0037] Please refer to Figure 1 As shown, the multi - physical - field force - heat - electricity coupling device adopted by the present invention has a structure including an infrared thermometer 1, an upper pressure head 2, a vacuum chamber 3, an electrode 4, a graphite mold 5, and a lower pressure head 6. The infrared thermometer 1 is used to measure the temperature, the infrared thermometer 1 is connected to the upper pressure head 2, the vacuum chamber 3 is used for vacuum pumping, the upper pressure head 1 and the lower pressure head 5 are used to apply external loads, and the electrode 4 is connected to the graphite mold 5 and is used to pass current through the sample.

[0038] Example 1

[0039] This example proposes a method for preparing single - crystal tungsten, and the steps are as follows:

[0040] (1) Sample preparation: First, anneal the deformed pure tungsten (W) plate at 950°C for 3 h to remove stress, then use electrical discharge wire - cutting technology to cut it into pure W circular - sheet samples with a diameter of 13 mm and a thickness of 2.8 mm, and grind the upper and lower surfaces with sandpaper to reduce the surface roughness and improve the parallelism of the upper and lower surfaces of the sample. Then place it in ethanol and ultrasonically clean it for 5 min to remove stains, obtaining deformed pure W circular - sheet samples for heat treatment in a multi - physical - field (force - heat - electricity) coupling device; the plastic deformation amount of the deformed W plate in the present invention is greater than 50%, and the impurity content should be within 5%.

[0041] (2) Heat treatment: In the multi-physical field (force-thermal-electricity) coupling device, first install the pure W wafer sample obtained in step (1) in a graphite mold and make it in close contact with the electrode. The parameters during the heat treatment under the multi-physical field (force-thermal-electricity) coupling action are as follows: the vacuum degree is less than 10 Pa, the working load is 15 MPa, the current loading rate is 200 A / min, the target current is 1000 A, the target temperature is 1700 °C, the loading time is 10 min, and the holding time is 0 min. Finally, let the sample cool in the furnace to below 100 °C and then take it out.

[0042] The metallographic micrograph of the large-sized grains that appear inside the specimen after electro-assisted heat treatment is as Figure 2 shown. There is no grain boundary inside this grain, and its size in the RD direction of the specimen reaches 4.95 mm. Figure 3 (a-b) are the orientation imaging maps (OIM) of two places at the edge of the large grain, Figure 3 (c-d) are the orientation imaging maps (OIM) of two places inside the large grain. It can be seen that the orientations of all parts of this large grain are consistent, and no small-angle grain boundaries with an orientation difference higher than 2° are seen inside, that is, there are no sub-grains or the orientation difference between sub-grains is less than 2°.

[0043] (3) Cutting: Cut the single-crystal W in the sample. The sample obtained in step (2) contains one or several large-sized W grains. After using wire cutting technology to cut out a plane and grinding and polishing it, when the cutting surface is corroded with boiled hydrogen peroxide solution, obvious grain boundaries can be seen ( Figure 7 shown). The range of the grain boundary can be estimated through two perpendicular cutting surfaces. Then use wire cutting to separate each grain along the cutting line. Finally, through polishing and cutting in various directions, the abnormally grown large grains in the sample subjected to the multi-physical field (force-thermal-electricity) coupling action are cut into single-crystal W. Figure 8 The physical photograph of the cut single-crystal W is shown.

[0044] Example 2

[0045] This example proposes a method for preparing single-crystal tungsten, and the steps are as follows:

[0046] (1) Sample preparation: First, perform stress relief annealing on the deformed pure tungsten (W) plate at 950 °C for 3 h. Then use wire electrical discharge machining technology to cut it into pure W wafer samples with a diameter of 13 mm and a thickness of 2.8 mm. Grind the upper and lower surfaces with sandpaper to reduce the surface roughness and improve the parallelism of the upper and lower surfaces of the sample. Then place it in ethanol and ultrasonically clean it for 5 min to remove stains, so as to obtain the deformed pure W wafer sample for heat treatment in the multi-physical field (force-thermal-electricity) coupling device; the plastic deformation amount of the deformed W plate in the present invention is greater than 50%, and the impurity content should be within 5%.

[0047] (2) Heat treatment: In the multi-physical field (force-thermal-electricity) coupling device, first install the pure W wafer sample obtained in step (1) in a graphite mold and make close contact with the electrode. The parameters during the heat treatment under the multi-physical field (force-thermal-electricity) coupling action are as follows: the vacuum degree is less than 10 Pa, the working load is 30 MPa, the current loading rate is 200 A / min, the target current is 900 A, the target temperature is 1700 °C, the loading time is 15 min, and the heat preservation time is 0 min. Finally, let the sample cool in the furnace to below 100 °C and then take it out.

[0048] The metallographic micrograph of large-sized grains that appear inside the specimen after electro-assisted heat treatment is as Figure 4 shown. There are three large grains inside this sample. It can be clearly seen that there are no grain boundaries inside the three grains, and the total size in the RD direction of the specimen reaches 11.3 mm. Figure 5 (a) is the orientation imaging map (OIM) at the edge of two large grains, Figure 5 (b-c) are the orientation imaging maps (OIM) at two certain positions inside the two large grains. It can be seen that there are no small-angle grain boundaries with an orientation difference higher than 2° inside the two large grains, that is, there are no sub-grains or the orientation difference between sub-grains is less than 2°.

[0049] (3) Cutting: Cut the single-crystal W in the sample. The sample obtained in step (2) contains one or several large-sized W grains. After using wire cutting technology to cut out a plane and grinding and polishing it, the cutting surface is corroded with boiling hydrogen peroxide solution, and obvious grain boundaries can be seen ( Figure 7 shown). The range of the grain boundaries can be estimated through two perpendicular cutting surfaces. Then use wire cutting to separate each grain along the cutting line. Finally, through polishing and cutting in various directions, the abnormally grown large grains in the sample subjected to the multi-physical field (force-thermal-electricity) coupling action are cut into single-crystal W. Figure 8 This is a physical photo of the cut single-crystal W.

[0050] Example 3

[0051] This example proposes a method for preparing single-crystal tungsten, and the steps are as follows:

[0052] (1) Sample preparation: First, perform stress relief annealing on the deformed pure W plate at 950 °C for 3 h. Then use electrical discharge wire cutting technology to cut it into pure W wafer samples with a diameter of 13 mm and a thickness of 2.8 mm. Grind the upper and lower surfaces with sandpaper to reduce the surface roughness and improve the parallelism of the upper and lower surfaces of the sample. Then place it in ethanol and ultrasonically clean it for 5 min to remove stains, obtaining a deformed pure W wafer sample for heat treatment in the multi-physical field (force-thermal-electricity) coupling device; the plastic deformation amount of the deformed W plate in the present invention is greater than 50%, and the impurity content should be within 5%.

[0053] (2) Heat treatment: In the multi-physical field (force-thermal-electricity) coupling device, first install the pure W wafer sample obtained in step (1) in a graphite mold and make it in close contact with the electrodes. The parameters for heat treatment under the multi-physical field (force-thermal-electricity) coupling effect are as follows: the vacuum degree is less than 10 Pa, the working load is 15 MPa, the current loading rate is 200 A / min, the target current is 800 A, the target temperature is 1600 °C, the loading time is 20 min, and the holding time is 0 min. Finally, cool the sample in the furnace to below 100 °C and take it out.

[0054] The metallographic micrograph of the large-sized grains that appear inside the specimen after electro-assisted heat treatment is as Figure 6 shown in (a), and there are no grain boundaries inside this grain. Figure 6 (b) is the orientation imaging map (OIM) of a certain part at the edge of the large grain. It can be seen that the orientations of all parts of this large grain are the same, and there are no small-angle grain boundaries with an orientation difference higher than 2° inside, that is, there are no sub-grains or the orientation difference between sub-grains is less than 2°.

[0055] (3) Cutting: Cut the single-crystal W in the sample. The sample obtained in step (2) contains one or several large-sized W grains. After cutting out a plane and grinding and polishing it using wire cutting technology, the cutting surface can be etched with boiling hydrogen peroxide solution to see obvious grain boundaries ( Figure 7 as shown). The range of the grain boundaries can be estimated through two perpendicular cutting surfaces. Then use wire cutting to separate each grain along the cutting line. Finally, through polishing and cutting in various directions, the abnormally grown large grains in the sample subjected to multi-physical field (force-thermal-electricity) coupling effect heat treatment are cut into single-crystal W. Figure 8 This is a physical photo of the cut single-crystal W.

[0056] The above content is only an example and illustration of the concept of the present invention. Those skilled in the art of this technology can make various modifications or supplements to the described specific embodiments or use similar methods for substitution. As long as they do not deviate from the concept of the invention or exceed the scope defined by this claim book, they should all fall within the protection scope of the present invention.

Claims

1. A method for preparing single-crystal tungsten (W) based on the coupling of multiple physical fields (force-thermal-electricity), characterized in that, The deformed W plate is heat-treated by the coupling action of multiple physical fields (force-thermal-electricity). The stress field generated by the working load parallel to the current direction, the temperature field generated by the thermal effect of the high-density current, and the current field generated by the non-thermal effect synergistically strengthen the slip of grain boundaries and dislocations and atomic migration of the metal during the grain growth stage, promoting the abnormal grain growth of the deformed W plate and growing out single-crystal W with considerable size, thereby realizing the rapid preparation of single-crystal W.

2. The method for preparing single-crystalline tungsten (W) according to claim 1, wherein It includes the following steps: (1) Sample preparation: First, the deformed W plate is subjected to stress relief annealing, and then it is cut into circular wafers with a certain diameter and thickness by wire electrical discharge machining technology. The upper and lower surfaces are ground with sandpaper to reduce the surface roughness and improve the parallelism of the upper and lower surfaces of the sample. Then, the stains are removed by cleaning and dried to obtain a deformed pure W circular wafer sample for heat treatment in a multiple physical field (force-thermal-electricity) coupling device. (2) Heat treatment for the microstructure design of the deformed pure W circular wafer sample: In a multiple physical field (force-thermal-electricity) coupling device, first, the pure W circular wafer sample obtained in step (1) is installed in a graphite mold and in close contact with the electrodes. Then, the three heat treatment process parameters of the working load, heat treatment temperature, and current are adjusted. Finally, single-crystal W with considerable size is rapidly prepared in the sample. (3) Cutting: Cut the single-crystal W in the sample. The sample obtained in step (2) contains one or several large-size W grains. After cutting a plane and grinding and polishing it by wire cutting technology, the obvious grain boundaries can be seen by etching the cutting surface. The range of the grain boundaries can be estimated through two perpendicular cutting surfaces. Then, each grain is separated along the cutting line by wire cutting. Finally, through polishing and cutting in all directions, the abnormally grown large grains in the sample obtained in step (2) are cut into single-crystal W.

3. The method for preparing single crystal tungsten (W) according to claim 2, wherein In step (1), the plastic deformation amount of the deformed W plate used is greater than 50%, and the impurity content is within 5%.

4. The method for preparing single-crystalline tungsten (W) according to claim 2, characterized in that, In step (1), the annealing temperature during stress relief annealing is 900 - 1100 °C, and the annealing time is 1 - 3 h.

5. The method for preparing single crystal tungsten (W) according to claim 2, wherein, In step (2), the vacuum degree in the multiple physical field (force-thermal-electricity) coupling device is ≤ 10 Pa.

6. The method for preparing single crystal tungsten (W) according to claim 2, wherein, In step (2), pure W foils are placed between the upper and lower surfaces of the circular wafer sample and the two electrodes on both sides as isolation layers.

7. The method for preparing single crystal tungsten (W) according to claim 2, wherein, In step (2), the heat treatment process parameters of the multiple physical field (force-thermal-electricity) coupling device are as follows: First, apply a working load of 10 - 30 Mpa parallel to the current direction, then gradually increase the current to 800 - 1100 A and keep it constant. Then, stop loading the current immediately after the temperature reaches 1600 - 1700 °C without heat preservation. Finally, let the sample cool in the furnace to below 100 °C and take it out.

8. The method for preparing single crystal tungsten (W) according to claim 2, wherein, The structure of the multi-physical-field (force-thermal-electricity) coupling device includes an infrared thermometer (1), an upper punch (2), a vacuum chamber (3), an electrode (4), a graphite mold (5), and a lower punch (6). The infrared thermometer (1) is used to measure temperature, and the infrared thermometer (1) is connected to the upper punch (2). The vacuum chamber (3) is used for vacuum pumping. The upper punch (1) and the lower punch (5) are used to apply an external load. The electrode (4) is connected to the graphite mold (5) and is used to pass an electric current through the sample.

9. A single crystal W prepared by the method according to any one of claims 1 to 8.

Images