A preparation method and product of high-entropy alloy powder

Abstract

The present invention provides a method for preparing a high-entropy alloy powder and a product thereof, belonging to the field of high-entropy alloy powder synthesis. First, a high-entropy alloy precursor is prepared. The alloy precursor is set as an electrode in a hollow container with a through hole. Then, a radio frequency matcher is connected to the part of the electrode located outside the through hole of the hollow container. The radio frequency power supply is connected to the radio frequency matcher. A grounding electrode is wound around the outer wall of the hollow container. Then, a protective discharge gas is introduced into the hollow container through another through hole of the hollow container, and the gas flow rate is controlled. Finally, the radio frequency power supply is turned on, and a radio frequency power is applied to the electrode. Plasma will be generated at the electrode, and high-entropy alloy powder will be obtained on the inner wall of the hollow container. The present invention also provides a product prepared by the above method. The above method does not require expensive equipment, the process is simple, does not require chemical reagents, is environmentally friendly and pollution-free, has low cost, and the obtained high-entropy alloy powder has good sphericity and fluidity.

Description

Technical Field

[0001] The present invention belongs to the field of synthesis of high-entropy alloy powders, and more specifically, relates to a method for preparing high-entropy alloy powders and products. Background Art

[0002] High-entropy alloys are a class of emerging metallic materials composed of equimolar or near-equimolar amounts of multiple major elements, which have excellent mechanical properties and have received increasing attention as structural materials.

[0003] Currently, the methods for preparing high-entropy alloys mainly include arc melting, induction melting, powder metallurgy, and additive manufacturing. Among them, the precursors of powder metallurgy and additive manufacturing are both metal powders, and the properties of the powders largely determine the properties of the final products. Therefore, there are relatively strict requirements for the particle size, sphericity, and oxygen content of the powders. However, it is difficult and costly to prepare high-melting-point high-entropy alloys by traditional gas atomization method, and impurities such as O and C are easily introduced during the preparation of alloy powders by mechanical alloying.

[0004] Chinese Patent Application No. 202211340484.5 discloses a method and device for preparing metal nanowires, which uses a radio frequency voltage acting on an alloy electrode, and the atmosphere around the alloy electrode is a protective discharge gas. Through discharge, an atmospheric pressure radio frequency plasma is formed in the protective discharge gas at the alloy electrode. The atmospheric pressure radio frequency plasma will form a high-voltage capacitive sheath layer on the surface of the alloy electrode, so that the alloy is heated to the solid-liquid coexistence region in a short time, and the grain boundaries are preferentially melted to form microchannels. The melted alloy in the microchannels is charged and then drawn out directionally under the action of the electric field force to form metal nanowires. In fact, it is a dealloying process, and the dealloyed alloy forms nanowires in the atmosphere. However, there are requirements for the composition of the alloy. The alloy precursor is a binary or multi-component alloy, and the alloy precursor is denoted as SM, where S is the element of the obtained nanowires and M is the alloy element. Among them, S is a low-melting-point metal element, preferably Zn, Al, Mg, Sn, Cu, Ag, Au, etc.; M is an alloy element, preferably an element with a melting point higher than S, which is one or more of Cr, Mn, Fe, Co, Ni, Cu, Mo, Zr, Ti, V, Pt, Pd, Ru, Rh, Ir, W, Ta, Ge, Si, and the phase diagram of the alloy precursor SM has a solid-liquid coexistence region. It does not disclose that the method can be used to prepare powders instead of nanowires, nor does it disclose how to prepare metal powders, let alone how to prepare powders for high-entropy alloys.

[0005] Therefore, there is an urgent need for a new method for preparing high-entropy alloy powders, which requires the preparation method to be simple, feasible, easy to implement, low-cost, and have good powder properties. Summary of the Invention

[0006] Aiming at the defects of the prior art, the purpose of the present invention is to provide a preparation method and product of high-entropy alloy powder. By matching a high-entropy alloy with a suitable composition, applying a suitable radio frequency voltage to the high-entropy alloy, and controlling the power of the radio frequency voltage and the flow rate of the introduced protective gas, the viscosity and tension of the molten high-entropy alloy can be controlled, and finally high-entropy alloy powder can be prepared.

[0007] To achieve the above object, according to the first aspect of the present invention, a preparation method of high-entropy alloy powder is provided, and the high-entropy alloy is (FeCoNi) 86 Al7Ti7, (HfZrTi) 90 Al6V4 or V 0.5 Nb 0.5 ZrTi, or the high-entropy alloy is composed of at least four elements among Fe, Co, Ni, Mn, Cu, Cr, Ti, Zr, Nb, Hf, Mo, V, Ta, W, Al, and the mass ratio of each element accounts for 5% - 35% of the mass of the entire high-entropy alloy.

[0008] First, melt the high-entropy alloy raw material, and obtain a high-entropy alloy with uniform composition after cooling.

[0009] Next, use the high-entropy alloy as an electrode, connect the electrode with a radio frequency power supply, place the high-entropy alloy used as the electrode in a set container, and introduce a protective discharge gas into the container so that the entire high-entropy alloy is completely surrounded by the protective gas.

[0010] Then, apply a radio frequency voltage to the high-entropy alloy, and control the power of the radio frequency voltage and the flow rate of the introduced protective gas to control not only the melting of the high-entropy alloy, but also its lower viscosity and tension, so that its surface tension is insufficient to resist the electric field force it receives, and finally it is ejected into droplets under the action of the electric field force and is cooled to form high-entropy alloy powder.

[0011] Electrospinning and electrospray are common methods for preparing nanowires or powders. Their basic principles are both to eject liquid materials from the substrate through the action of electric field force. The former is that the liquid material is ejected continuously and rapidly cooled to obtain continuous nanowires. The latter is that the liquid material is ejected discontinuously and rapidly cooled to obtain discontinuous powder materials. The ejection mode of the liquid material is determined by the mutual competition between the liquid surface instability brought by the electric field force and the liquid viscosity. Generally speaking, in the case of a stronger electric field force and a lower liquid viscosity, the liquid material will be ejected discontinuously and form powder. In the case of a weaker electric field force and a higher liquid viscosity, the liquid material will be ejected continuously and form continuous nanowires.

[0012] In the Chinese patent application with the application number 202211340484.5, a method for preparing metal nanowires based on an electrospinning mechanism is disclosed. Its important feature is that among the alloying elements of the precursor, one of the elements has a relatively low melting point, and there are significant differences in the melting points of the component elements. Particularly importantly, the precursor has a wide solid-liquid coexistence region. Based on this compositional feature, under the action of plasma, it can be melted at a relatively low temperature. At this time, the electric field is weak and the viscosity of the molten alloy is high, so only continuous metal nanowires can be obtained. The important feature of this application is that the precursor has more alloying elements, at least four or more, and it is required that the melting points of the elements are relatively high and the melting point differences are small. Particularly importantly, the precursor is a single-phase high-entropy alloy with a narrow solid-liquid coexistence region. Based on this compositional feature, the precursor needs to be melted at a relatively high temperature under the action of plasma. At this time, the electric field is strong and the viscosity of the molten alloy is small, so only discontinuous powders can be obtained.

[0013] In the above inventive concept, there are many influencing factors in the preparation method, including electric field force, temperature, surface tension, viscosity, etc. The lower the viscosity and surface tension of the molten metal, the more unstable it is, and the easier it is to be ejected under the action of the electric field force to form droplets. In addition to being determined by the material itself, the surface tension and viscosity are directly affected by temperature. Through research, it is found that for high-entropy alloys such as (FeCoNi) 86 Al7Ti7, (HfZrTi) 90 Al6V4 or V 0.5 Nb 0.5 ZrTi, or a high-entropy alloy composed of at least four elements among Fe, Co, Ni, Cu, Mn, Cr, Ti, Zr, Nb, Hf, Mo, V, Ta, W, Al, the higher the temperature, the lower its surface tension and viscosity, but the temperature cannot be too low. It is found in the research that under the condition of unchanged alloy composition, the tension and viscosity can be adjusted by controlling the temperature. The temperature is controlled by the externally applied excitation voltage and the flow rate of the protective discharge gas. The higher the voltage, the higher the temperature, and the lower the gas flow rate, the higher the temperature. The electric field force is controlled by the externally applied excitation voltage. By balancing the voltage, gas flow rate and electric field force, the preparation of high-entropy alloy powders can ultimately be achieved. More importantly, the high-entropy alloy powders prepared by the method of this invention application are spherical, with a very regular shape and excellent fluidity.

[0014] Furthermore, it includes the following steps:

[0015] S1: According to the required high-entropy alloy composition, put the high-entropy alloy raw materials into a vacuum melting furnace, and obtain a melted alloy by arc melting in a vacuum. After cooling, obtain the high-entropy alloy, cut off the defective part, polish and clean it to obtain the high-entropy alloy as the precursor.

[0016] S2: placing the precursor as an electrode in a hollow container having at least three through holes, and placing the precursor in the first through hole.

[0017] S3: The portion of the electrode located outside the through hole of the hollow container in step S2 is connected to a radio frequency matching device, the radio frequency matching device is connected to a radio frequency power supply, and a ground electrode is surrounded on the outer wall of the hollow container.

[0018] S4: introducing protective discharge gas into the hollow container through the second through hole of the hollow container and controlling the gas flow rate.

[0019] S5: Turn on the RF power supply and apply RF power to the precursor used as an electrode. Plasma is generated around the precursor used as an electrode. The temperature of the precursor used as an electrode is T m Less than the plasma temperature T gas , the temperature of the protective discharge gas outside the plasma is lower than the temperature T of the precursor used as the electrode m , high entropy alloy powder is obtained at the inner wall of the hollow container.

[0020] Furthermore, the protective discharge gas is a mixed gas of He and H 2 or a mixed gas of Ar and H 2 , and the volume ratio of H 2 in the two protective discharge gases is 1% to 5%.

[0021] Furthermore, the diameter of the high entropy alloy powder is 15 μm to 45 μm.

[0022] Furthermore, the high entropy alloy used as a precursor is in the shape of a rod, a bar, a sheet or a strip, so as to be conveniently used as an electrode and to be easily melted at a high temperature in a subsequent process.

[0023] Furthermore, the hollow container is a three-way ceramic tube, the RF matcher is connected to a precursor used as an electrode, the precursor is inserted into the first through hole of the three-way ceramic tube, a protective discharge gas is introduced into the second through hole of the three-way ceramic tube, the third through hole of the three-way ceramic tube is liquid-sealed, and the ground electrode is wrapped around the outer wall of the three-way ceramic tube.

[0024] Furthermore, a mass flow meter is used to control the flow of the protective discharge gas, and a water sealing device is used to achieve liquid sealing of the third through hole of the three-channel ceramic tube.

[0025] According to a second aspect of the present invention, a high entropy alloy powder prepared by the method described above is provided, wherein the particle size of the high entropy alloy powder is 15 μm to 45 μm.

[0026] In general, the above technical solutions conceived by the present invention have the following advantages compared with the prior art:

[0027] Beneficial effects:

[0028] 1. In the method of the present invention, a radio frequency voltage is applied to the electrode, and the atmosphere around the electrode is a protective discharge gas. Through discharge, atmospheric pressure radio frequency plasma is formed in the protective discharge gas at the alloy electrode. The atmospheric pressure radio frequency plasma will form a high-voltage capacitive sheath layer on the surface of the alloy electrode. This high-voltage capacitive sheath layer will rapidly raise the temperature of the electrode surface and its vicinity to the highest temperature after the start of discharge, and melt the entire alloy in a short time (for a high-entropy alloy, a material with a relatively complex composition and structure, it is not easy to control the overall heating and melting). At the same time, the area far from the metal surface remains at a relatively low temperature. Secondly, there is a strong electric field up to 10 kV / cm pointing from the plasma region to the electrode surface in the high-voltage capacitive sheath layer. The alloy precursor acts as an electrode and melts. Under the action of the electric field, an electric field force will be formed inside the liquid, and at the same time, the liquid is also affected by a surface tension opposite to the electric field force. The electric field force overcomes the surface tension, causing the liquid to undergo unstable ejection, forming micron-sized or nano-sized charged droplets. During this electrospray process, the tiny droplets solidify into micro / nano particles and are deposited on the inner wall of the hollow container to form alloy powder. The powder prepared in this way is spherical, with a very regular shape and excellent fluidity. In actual engineering practice, by controlling the process parameters, alloy powder with a diameter of 15 μm to 45 μm can be obtained.

[0029] 2. In the method of the present invention, the alloy electrode is directly in contact with the radio frequency plasma. The radio frequency plasma used can rapidly rise to the highest temperature after the start of discharge, and high-entropy alloy powder can be quickly formed in a short time. Its operation process is simple, easy to implement, time-saving and highly efficient.

[0030] 3. The method of the present invention does not require any polluting, complex and expensive devices such as chemical reagents, vacuum systems, heating systems, and atmosphere protection systems, greatly reducing the equipment cost.

[0031] 4. The method of the present invention uses radio frequency plasma to directly prepare high-entropy alloy powder in one step, without multiple steps and post-treatment. High-entropy alloy powder with a diameter of about 15 μm to 45 μm can be obtained in about 2 minutes. Its shape is extremely regular and its fluidity is good, truly realizing a simple, easy-to-implement, time-saving and highly efficient operation process. Description of the Drawings

[0032] Figure 1 is the flow chart of the method for preparing high-entropy alloy powder provided by the embodiment of the present invention;

[0033] Figure 2 is the schematic diagram of the device for preparing high-entropy alloy powder provided by the embodiment of the present invention;

[0034] Figure 3 is the scanning electron micrograph of the high-entropy alloy powder prepared by the embodiment of the present invention;

[0035] Figure 4 X-ray diffraction pattern of the high-entropy alloy powder prepared in the embodiment of the present invention. Specific embodiments

[0036] In order to make the objectives, technical solutions and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0037] The objective of the present invention is to provide a method for preparing high-entropy alloy powder. By designing a novel method, an alloy is used as an electrode, and atmospheric pressure radio frequency plasma is applied to the electrode to obtain high-entropy alloy powder prepared from the alloy serving as the electrode. The present invention utilizes the synergistic effect of the rapid heating effect of atmospheric pressure radio frequency plasma and the sheath electric field to achieve the rapid preparation of high-entropy alloy powder. Taking advantage of this feature, when the alloy precursor is rapidly heated by atmospheric pressure radio frequency plasma in the present invention, the alloy precursor can be melted. At the same time, at the plasma boundary, due to the influence of the "instantaneous" electric field generated by the radio frequency power supply, the mobile electrons will perform periodic motion within the space charge cloud composed of positive ions. Ions with very high mass are only affected by the time-averaged electric field. The periodic motion of the electron cloud generates a sheath near the electrode. In this sheath, the average number of positive charges in one period is more than that of negative charges in one period, resulting in a net positive charge in the sheath region. This net charge generates a strong oscillating electric field in the sheath that points from the plasma to the electrode direction. The molten liquid will form an electric field force inside the liquid under the action of the electric field, and at the same time, the liquid is also affected by a surface tension force that is opposite to the electric field force. The electric field force overcomes the surface tension, causing the liquid to undergo unstable ejection, forming micron-sized or nano-sized charged droplets. The tiny droplets solidify into micro / nano particles and are deposited on the inner wall of the hollow container to form alloy powder, and its particle size is extremely uniform and regular, presenting a spherical shape.

[0038] The plasma temperature in the present invention can be regulated by the radio frequency voltage and the flow rate of the protective discharge gas. Under the same excitation voltage, the greater the gas flow, the lower the temperature. The sheath electric field strength can be regulated by the radio frequency voltage: where V0 is the amplitude of the radio frequency voltage, ω is the angular frequency of the radio frequency voltage, is the sheath voltage. The higher the excitation voltage, the higher the sheath voltage. For alloy systems with different melting points, the critical field strength for electrohydrodynamic jetting (corresponding to the radio frequency excitation voltage V c)There will be differences, depending on the surface tension of the melt. Therefore, during the experiment, it is necessary to preferentially use a higher gas flow and radio frequency voltage to excite the plasma, ensure that the plasma temperature is lower than the melting point (solidus line) of the alloy, and then reduce the gas flow to rapidly melt the alloy temperature. After a period of time, high-entropy alloy powder is obtained.

[0039] Figure 1 is the flow chart of the method for preparing high-entropy alloy powder provided by the embodiment of the present invention. It can be seen from Figure 1 that the method of the present invention mainly includes the following core steps:

[0040] S1: Prepare a high-entropy alloy precursor. The composition of the alloy precursor can be (FeCoNi) 86 Al7Ti7, (HfZrTi) 90 Al6V4, V 0.5 Nb 0.5 ZrTi and other high-entropy alloys. In addition, high-entropy alloys composed of multiple alloys among Fe, Co, Ni, Cu, Mn, Cr, Ti, Zr, Nb, Hf, Mo, V, Ta, W, Al can also be used as precursors. The prepared alloy precursor is in the shape of a rod, bar, sheet or strip, which is convenient to be used as an electrode and is easily melted by high temperature in the subsequent process.

[0041] S2: Set the alloy precursor as an electrode in a hollow container with a through hole.

[0042] S3: Connect a radio frequency matcher to the part of the electrode in step S2 located outside the through hole of the hollow container. The radio frequency power supply is connected to the radio frequency matcher, and a grounding electrode is wound around the outer wall of the hollow container. The end of the hollow container has a through hole. The vacuum container with a through hole at the end is a three-way ceramic tube. The alloy precursor used as an electrode is inserted into one through hole of the three-way ceramic tube. The second through hole is used as an air inlet, and the third through hole is used as an air outlet. During operation, the air outlet is liquid-sealed.

[0043] S4: Introduce a protective discharge gas into the hollow container through another through hole of the hollow container, and control the gas flow rate. The protective discharge gas is a mixed gas of He and H2 or a mixed gas of Ar and H2. Among the two protective discharge gases, the volume ratio of H2 is 1% - 5%.

[0044] S5: Turn on the radio frequency power supply, apply radio frequency power to the electrode, and plasma will be generated at the electrode. The protective discharge gas is used to control the plasma temperature, and the flow rate of the protective discharge gas can be adjusted according to the plasma temperature. The power of the radio frequency power supply acting on the electrode through the radio frequency matcher can melt the alloy precursor used as an electrode. After a period of time, high-entropy alloy powder is obtained on the inner wall of the hollow container. The diameter of the high-entropy alloy powder is 15μm - 45μm.

[0045] Figure 2 The figure shows a schematic diagram of the apparatus for preparing high-entropy alloy powder provided by an embodiment of the present invention. As can be seen from the figure, 1 is a He / H2 gas mixture, 2 is a mass flowmeter, 3 is a radio frequency matcher, 4 is a radio frequency power supply, 6 is a radio frequency electrode connected to the sample, 5 is a three-channel ceramic tube, 7 is a grounding electrode, and in this embodiment, the grounding electrode is a grounded tantalum foil electrode, and 8 is a water sealing device. The radio frequency matcher 3 is connected to the alloy precursor used as an electrode, the radio frequency matcher 3 and the radio frequency power supply 4 are connected, the radio frequency power supply 4 is connected to the radio frequency electrode 6, the radio frequency electrode 6 is connected to the alloy precursor, and the alloy precursor is inserted into a through hole of the three-channel ceramic tube 5. A protective discharge gas He / H2 gas mixture is introduced into another through hole of the three-channel ceramic tube 5. The He / H2 gas mixture is placed in a gas storage tank. The third through hole of the three-channel ceramic tube 5 is liquid-sealed, and the grounding electrode is wound around the outer wall of the three-channel ceramic tube 5. A mass flowmeter 2 is provided on the pipeline connecting the gas storage tank and the three-channel ceramic tube for monitoring the flow rate of the protective discharge gas. The third through hole of the three-channel ceramic tube 5 is immersed in the water sealing device 8, and the grounding electrode 7 is wound around the outer wall of the three-channel ceramic tube 5.

[0046] In actual engineering practice, first, (FeCoNi) 86 Al7Ti7 high-entropy alloy can be used as an electrode, inserted into the three-channel ceramic tube and sealed at the tube mouth, and connected to a 13.56 MHz radio frequency matcher. The outside of the three-channel ceramic tube is surrounded by tantalum foil of the same length and grounded, and the other end of the three-channel ceramic tube is introduced into deionized water to isolate oxygen. Among them, the inner diameter of the ceramic tube is 6 - 8 mm, and in a preferred embodiment, it can be 6 mm, and the wall thickness of the ceramic tube is 0.5 mm - 2 mm, and in a preferred embodiment, it can be 1 mm. Then, He / H2 gas mixture is pre-introduced into the branch pipe of the ceramic tube for 1 - 3 minutes to remove the air in the device. Among them, the proportion of H2 is 1% - 5%, preferably 2%, and the gas flow rate is controlled at 100 - 400 mL / min, preferably 200 mL / min. Finally, turn on the radio frequency power supply and the matcher, adjust the power to 200 - 500 W, preferably 300 W. The He / H2 gas mixture in the ceramic tube discharges to form an atmospheric pressure radio frequency plasma, and after 1 - 5 minutes, (FeCoNi) 86 Al7Ti7 high-entropy alloy powder is collected on the ceramic tube wall.

[0047] Example 1

[0048] (1) Prepare a high-entropy alloy precursor. The composition and mass percentage of the alloy precursor are Fe: 29 - 30%, Co: 30 - 31%, Ni: 30 - 31%, Al: 3 - 4%, Ti: 6 - 7%. According to the required alloy composition for the above, put the raw materials into the crucible of the vacuum melting furnace, and arc melt the alloy in a vacuum. Cut off the defective part of the alloy, polish and clean it to be used as the precursor.

[0049] (2) Insert the (FeCoNi) 86 Al7Ti7 high-entropy alloy rod into a three-channel ceramic tube and seal the tube mouth. Connect the radio frequency matcher, place it in a ceramic tube with an inner diameter of 6 mm and a wall thickness of 1 mm and seal it. Turn on the mass flowmeter to adjust the gas flow rate to 1000 mL / min, and ventilate for 2 min to remove the air in the device. The proportion of H2 in the He / H2 mixed gas is 2%.

[0050] (3) Turn on the radio frequency power supply, adjust the power to 300 W, generate radio frequency plasma near the alloy electrode, quickly reduce the gas flow to 200 mL / min, turn off the power after 2 minutes, and take out the electrode after the device has cooled sufficiently. Collect the substances attached to the inner wall of the ceramic tube to obtain the (FeCoNi) 86 Al7Ti7 high-entropy alloy powder, and its scanning electron microscope image is as Figure 3 shown. As can be seen from Figure 3 it, the powder is micron-sized spherical powder with good sphericity and a diameter of 15 - 45 μm. Figure 4 For the (FeCoNi) 86 Al7Ti7 high-entropy alloy powder prepared in the embodiment of the present invention, the X-ray diffraction pattern shows that the powder is a single-phase FCC structure with good alloying degree.

[0051] Example 2

[0052] (1) Prepare a high-entropy alloy precursor. The composition and mass percentage of the alloy precursor are Hf: 54 - 55%, Zr: 27 - 28%, Ti: 14 - 15%, Al: 1 - 2%, V: 2 - 3%. According to the required alloy composition for batching, put the raw materials into the crucible of a vacuum melting furnace, arc melt the alloy in a vacuum, cut off the defective part of the alloy, and polish and clean it to obtain the precursor.

[0053] (2) Insert the (HfZrTi) 90 Al6V4 high-entropy alloy rod into a three-channel ceramic tube and seal the tube mouth. Connect the radio frequency matcher, place it in a ceramic tube with an inner diameter of 6 mm and a wall thickness of 1 mm and seal it. Turn on the mass flowmeter to adjust the gas flow rate to 1000 mL / min, and ventilate for 2 min to remove the air in the device. The proportion of H2 in the He / H2 mixed gas is 2%.

[0054] (3) Turn on the radio frequency power supply, adjust the power to 400 W, generate radio frequency plasma near the alloy electrode, quickly reduce the gas flow to 200 mL / min, turn off the power after 2 minutes, and take out the electrode after the device has cooled sufficiently. Collect the substances attached to the inner wall of the ceramic tube to obtain the (HfZrTi) 90Al6V4 high-entropy alloy powder with a diameter of 15 - 45 μm.

[0055] Example 3

[0056] (1) Prepare a high-entropy alloy precursor. The composition and mass percentage of the alloy precursor are: V: 12 - 13%, Zr: 43 - 44%, Ti: 22 - 23%, Nb: 22 - 23%. Weigh the raw materials according to the required alloy composition, put the raw materials into the crucible of a vacuum melting furnace, and obtain the alloy by arc melting in vacuum. Cut off the defective part of the alloy, polish and clean it to obtain the precursor.

[0057] (2) Insert the V 0.5 Nb 0.5 ZrTi high-entropy alloy bar into a three-channel ceramic tube and seal the tube mouth. Connect the radio frequency matcher, place it in a ceramic tube with an inner diameter of 6 mm and a wall thickness of 1 mm and seal it. Open the mass flowmeter to adjust the gas flow rate to 1000 mL / min, and ventilate for 2 minutes to remove the air in the device. The proportion of H2 in the He / H2 mixed gas is 2%.

[0058] (3) Turn on the radio frequency power supply, adjust the power to 400 W, generate radio frequency plasma near the alloy electrode, quickly reduce the gas flow to 200 mL / min, turn off the power after 2 minutes, and take out the electrode after the device has cooled down sufficiently. Collect the substances attached to the inner wall of the ceramic tube to obtain V 0.5 Nb 0.5 ZrTi high-entropy alloy powder with a diameter of 15 - 45 μm.

[0059] There are many influencing factors in the above preparation method, including electric field force, temperature, surface tension, viscosity, etc. The lower the viscosity and surface tension of the molten metal, the more unstable it is, and the easier it is to spray under the action of electric field force to form droplets. In addition to being determined by the material itself, surface tension and viscosity are directly affected by temperature. The higher the temperature, the lower the surface tension and viscosity. Therefore, when the alloy composition remains unchanged, the influence of viscosity and other factors is unified as the influence of temperature, and it is directly adjusted by controlling the temperature. And the temperature is controlled by the applied excitation voltage and the flow rate of the protective gas. The higher the voltage, the higher the temperature, and the lower the gas flow rate, the higher the temperature. The electric field force is controlled by the applied excitation voltage. Through simulation, it can be known that when the applied voltage is 820 V, the electric field force on the alloy surface can reach up to 14 KV / cm, which is at least one order of magnitude higher than the electric field directly formed by the applied voltage. In addition, the higher the applied excitation voltage, the higher the internal electric field force.

[0060] The parameters that can be directly controlled in the present invention are the applied voltage (controlled by adjusting the power), and the gas flow rate. Because the melting point of the high-entropy alloy is relatively high, (FeCoNi) 86The melting point of Al7Ti7 is 1450 °C, which requires a relatively high voltage and a low gas flow rate. The temperature of the molten metal is measured by an infrared detector.

[0061] Table 1 shows that by adjusting the power to further adjust the voltage and controlling the gas flow rate, the temperature value is changed to be near the melting point of the high-entropy alloy with the composition of (FeCoNi) 86 Al7Ti7

[0062] Voltage V Gas flow rate ml / min Temperature °C 1420 100 1590 1420 200 1480 1420 300 1370 1490 200 1560 1490 300 1420 1490 400 1310 1560 200 1600 1560 300 1490 1560 400 1380

[0063] It can be seen from Table 1 that increasing the voltage and decreasing the gas flow density will both increase the temperature. Analyzing the results under different process parameters, it is found that when the voltage is 1420 V and 1490 V, there is no change on the alloy surface. When the voltage is increased to 1560 V and the gas flow rate is continuously adjusted to increase the temperature to the melting point (1450 °C), micron-sized metal powder is collected on the container wall. To produce the effect of electrospray, a critical point Vc is required, and this voltage is affected by the alloy composition. In addition, to prepare the metal powder, the temperature needs to be raised above the melting point of the alloy to reduce the surface tension and viscosity of the molten metal to meet the requirements of electrospray. Metal powder will be prepared if and only if T gas >T m ,V>V c . T m is the melting point of the alloy, and T gas is the plasma temperature. The plasma temperature is different from the gas temperature. It is only after the external electric field converts the gas around the alloy into plasma that the temperature of the plasma is T gas .

[0064] In the present invention, the composition of the high-entropy alloy powder is limited to (FeCoNi) 86 Al7Ti7, (HfZrTi) 90 Al6V4 or V 0.5 Nb 0.5One of Zr and Ti. Alternatively, the high-entropy alloy is composed of at least four elements among Fe, Co, Ni, Cu, Mn, Cr, Ti, Zr, Nb, Hf, Mo, V, Ta, W, and Al, and the mass percentage of each element accounts for 5% to 35% of the mass of the entire high-entropy alloy. Such a composition can successfully achieve powder preparation and obtain a spherical appearance. The diameter of the high-entropy alloy powder is easily formed to be 15 μm to 45 μm. The shape of the high-entropy alloy as a precursor is rod-shaped, bar-shaped, sheet-shaped, or strip-shaped to facilitate use as an electrode and be easily melted at high temperature in the subsequent process. It is not necessarily limited to the above shapes, and the shape can be flexibly determined according to needs as long as it is convenient to be used as an electrode. The protective discharge gas is a mixed gas of He and H2 or a mixed gas of Ar and H2. Among the two protective discharge gases, the volume ratio of H2 is 1% to 5%. The reason for setting the volume ratio of H2 to 1% to 5% is that as a protective gas, the presence of H2 plays a reducing role and further prevents the alloy from oxidizing. In addition, the proportion of H2 should not be too high because too high a proportion of H2 will affect the discharge effect.

[0065] Those skilled in the art can easily understand that the above are only preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, and improvements made within the spirit and principles of the present invention shall be included in the protection scope of the present invention.

Claims

1. A preparation method of high-entropy alloy powder, characterized in that, The high-entropy alloy is (FeCoNi) 86 Al7Ti7, (HfZrTi) 90 Al6V4 or V 0.5 Nb 0.5 one of ZrTi First, melt the high-entropy alloy raw materials, and after cooling, obtain a high-entropy alloy with uniform composition. Next, use the high-entropy alloy as an electrode, connect the electrode with a radio frequency power supply, place the high-entropy alloy used as the electrode in a set container, and introduce a protective discharge gas into the container. The entire high-entropy alloy is completely surrounded by the protective gas. Then, apply a radio frequency voltage to the high-entropy alloy. By controlling the power of the radio frequency voltage and the flow rate of the introduced protective gas, control the high-entropy alloy to not only be melted but also have low viscosity and surface tension, so that its surface tension is insufficient to resist the electric field force it receives. Eventually, under the action of the electric field force, it is ejected into droplets, and thus is cooled to form high-entropy alloy powder, and the high-entropy alloy powder is spherical and regular in shape. Specifically, use the radio frequency voltage to act on the electrode. Through discharge, an atmospheric pressure radio frequency plasma is formed in the protective discharge gas at the electrode. The atmospheric pressure radio frequency plasma forms a high-voltage capacitive sheath layer on the electrode surface, melting the entire electrode in a short time. There is a strong electric field up to 10 kV / cm pointing from the plasma region to the electrode surface in the high-voltage capacitive sheath layer. Under the action of the electric field, an electric field force will be formed inside the molten liquid, and at the same time, the liquid is also affected by a surface tension opposite to the electric field force. The electric field force overcomes the surface tension, causing the liquid to undergo unstable ejection, forming micron-sized or nano-sized charged droplets, which are deposited on the inner wall of the hollow container to form alloy powder.

2. The preparation method of a high-entropy alloy powder according to claim 1, characterized in that, It includes the following steps: S1: According to the required composition of the high-entropy alloy for batching, put the high-entropy alloy raw materials into a vacuum melting furnace, melt them by arc melting in a vacuum, and after cooling, obtain the high-entropy alloy. Cut off the defective parts, polish and clean them to obtain the high-entropy alloy as the precursor. S2: Set the precursor as an electrode in a hollow container with at least three through holes and located in the first through hole among them. S3: Connect a radio frequency matcher to the part of the electrode in step S2 outside the through hole of the hollow container. The radio frequency matcher is connected to a radio frequency power supply, and a grounding electrode is wound around the outer wall of the hollow container. S4: Introduce a protective discharge gas into the hollow container through the second through hole of the hollow container and control the gas flow rate. S5: Turn on the radio frequency power supply, apply radio frequency power to the precursor used as the electrode, generate plasma around the precursor used as the electrode, and the temperature of the precursor used as the electrode T m is lower than the plasma temperature T gas , and the temperature of the protective discharge gas outside the plasma is lower than the temperature of the precursor used as the electrode T m , and high-entropy alloy powder is obtained at the inner wall of the hollow container.

3. The preparation method of a high-entropy alloy powder as described in claim 2, characterized in that, The protective discharge gas is a mixed gas of He and H2 or a mixed gas of Ar and H2. Among the two protective discharge gases, the volume ratio of H2 is 1% - 5%.

4. The preparation method of a high-entropy alloy powder as claimed in claim 3, wherein, The diameter of the high-entropy alloy powder is 15 μm - 45 μm.

5. The preparation method of a high-entropy alloy powder according to claim 4, characterized in that, The high-entropy alloy as the precursor is in the shape of a rod, bar, sheet or strip, which is convenient to be used as an electrode and is easily melted by high temperature in the subsequent process.

6. The preparation method of a high-entropy alloy powder according to claim 5, characterized in that, The hollow container is a three-way ceramic tube. The radio frequency matcher is connected to the precursor used as an electrode. The precursor is inserted into the first through hole of the three-channel ceramic tube. The second through hole of the three-channel ceramic tube is used to introduce the protective discharge gas, and the third through hole of the three-channel ceramic tube is liquid-sealed. The grounding electrode is wound around the outer wall of the three-way ceramic tube.

7. The preparation method of a high-entropy alloy powder according to claim 6, characterized in that Use a mass flow meter to control the flow rate of the protective discharge gas, and use a water sealing device to realize the liquid sealing of the third through hole of the three-channel ceramic tube.

8. High-entropy alloy powder prepared by the method according to any one of claims 1 - 7.

9. The high-entropy alloy powder according to claim 8, wherein Its particle size is 15μm to 45μm, and its shape is spherical.

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