A method for preparing medium-entropy micro-nano alloys using refractory metals

Abstract

The present invention belongs to the technical field of refractory metal alloy preparation, and specifically relates to a method for preparing medium-entropy micro-nano alloys using refractory metals. The invention adopts a laser irradiation method, using a refractory first metal, a second metal that is mutually soluble in the refractory first metal, and a third metal that is immiscible with the refractory first metal but mutually soluble in the second metal as raw materials. The refractory first metal and the second metal are first subjected to non-focused laser irradiation in a liquid phase to form alloy nanoparticles. The alloy nanoparticles and the third metal are then subjected to non-focused laser irradiation in a liquid phase to obtain a medium-entropy micro-nano alloy. The medium-entropy micro-nano alloy obtained by the method of the present invention is dense and has a uniform distribution of components, and overcomes the technical defects of the existing preparation methods that introduce impurities such as surfactants.

Description

Technical Field

[0001] The present invention relates to the technical field of preparation of refractory metal alloys, and in particular to a method for preparing medium-entropy micro-nano alloys by using refractory metals. Background Art

[0002] Refractory metal alloys are made by combining a high-melting-point, highly corrosion-resistant refractory metal with a low-melting-point, highly conductive and thermally conductive intermediate-entropy alloy. They combine the unique properties of both metals, making them widely used in the fields of transudative materials, armor-piercing materials, and electrical contact materials. However, alloying the two metals is difficult due to their significant melting point difference, poor wettability, and immiscibility.

[0003] The existing routes for preparing refractory metal alloys are divided into vacuum infiltration and liquid phase sintering. Taking Cu-W alloy as an example, in vacuum infiltration, Ni-W alloy is prepared by pre-pressing and pre-sintering, and then the Ni-W alloy block material is infiltrated into molten liquid Cu, which is then solidified to form a layered Cu-Ni-W alloy. The refractory alloy prepared by this method often has problems such as large pores and uneven particle size distribution. In liquid phase sintering, the elemental Cu, Ni and W powders are mixed, cold compressed, and then sintered at a temperature above the melting point of Cu. Due to the immiscibility of the system between W and Cu, poor wettability and large difference in melting temperature, it is difficult to achieve complete densification and sufficient uniformity of the Cu-W composite material prepared by this method, which is necessary to obtain an ideal high-comprehensive performance alloy.

[0004] Furthermore, micro-nano medium-entropy alloys, due to their unique microstructure and properties, have broad application prospects, such as 3D-printed metal materials, high-temperature structural materials, thermal barrier coatings, and thermoelectric materials. However, current physical or chemical methods for preparing micro-nano medium-entropy alloys often introduce impurities such as surfactants, which can affect the physical, chemical, and mechanical properties of the micro-nano alloys. For example, impurity atoms, due to differences in size or electronegativity compared to the matrix metal atoms, can cause lattice distortion in the alloyed micro-nano particles. Furthermore, when impurity atoms are insoluble in the micro-nano alloy, they can form independent secondary phases or precipitate as particles, altering the microstructure of the micro-nano alloy and, in turn, affecting the overall performance of the micro-nano material. Summary of the Invention

[0005] In response to the shortcomings of the above-mentioned prior art, the purpose of the present invention is to provide a method for preparing medium-entropy micro-nano alloys using refractory metals. The present invention adopts a laser irradiation method, using a refractory first metal, a second metal that is mutually soluble in the refractory first metal, and a third metal that is immiscible with the refractory first metal but mutually soluble in the second metal as raw materials. The refractory first metal and the second metal are first subjected to unfocused laser irradiation in a liquid phase to form alloy nanoparticles. The alloy nanoparticles and the third metal are then subjected to unfocused laser irradiation in a liquid phase to obtain a medium-entropy micro-nano alloy. The medium-entropy micro-nano alloy obtained by the method of the present invention is dense and has a uniform distribution of components, and overcomes the technical defects of the existing preparation methods that introduce impurities such as surfactants.

[0006] To achieve the above object, the present invention adopts the following technical solutions:

[0007] A method for preparing a medium-entropy micro-nano alloy using a refractory metal comprises the following steps:

[0008] Nanoparticles of a refractory first metal and nanoparticles of a second metal that is mutually soluble in the first metal are mixed by ball milling, and then dispersed together in an organic solvent to obtain a mixed colloidal precursor solution.

[0009] The mixed colloidal precursor liquid is subjected to a first unfocused laser irradiation. During the first unfocused laser irradiation, the refractory first metal and the second metal have strong absorption of the laser, while the organic solvent absorbs the laser very little. At this time, the refractory first metal and the second metal melt and evaporate, while the organic solvent hardly changes, thereby playing a role of rapid extraction and cooling, thereby obtaining an alloy colloidal solution, in which the solute is alloy nanoparticles.

[0010] After ball milling, nanoparticles of the third metal are uniformly dispersed in an organic solvent to obtain a colloidal precursor solution of the third metal; wherein the third metal is immiscible with the refractory first metal but miscible with the second metal.

[0011] The alloy colloid solution is mixed with a colloid precursor solution of a third metal to obtain a nano-colloid solution.

[0012] The nano-colloidal solution is subjected to a second unfocused laser irradiation. During the second unfocused laser irradiation process, the alloy nanoparticles and the third metal have strong absorption of the laser, while the organic solvent absorbs the laser very little. At this time, the alloy nanoparticles and the third metal melt and evaporate, while the organic solvent hardly changes, which plays a role of rapid cooling and obtains a medium-entropy micro-nano alloy.

[0013] Preferably, based on the optimal thermodynamic alloying conditions of the alloy nanoparticles, the optimal thermodynamic conditions refer to the change in free energy, which is a measure of the energy that a system can perform non-volume work under constant temperature and pressure conditions. By comparing the free energies of different phases at different molar ratios, it is determined which phases are stable phases at a given temperature and pressure. The stable phase is the state with the lowest free energy, and the molar ratio of the refractory first metal to the second metal is determined based on the stable phase.

[0014] Preferably, based on the optimal thermodynamic alloying conditions of the medium-entropy micro-nano alloy, by comparing the free energies of different phases at different molar ratios, it is determined which phases are stable phases at a given temperature and pressure. The stable phase is the state with the lowest free energy, and the molar ratio of the alloy nanoparticles to the third metal is determined based on the stable phase.

[0015] Preferably, the nanoparticles of the refractory first metal and the second metal that is miscible with it are ball-milled to a consistent particle size, and the third metal is ball-milled to a consistent particle size with the alloy nanoparticles. Ball milling makes the particle size uniform, which is more conducive to uniform phase change, such as vaporization, after laser irradiation. In addition, ball milling can make different nanoparticles evenly mixed, which is conducive to increasing the laser alloying of the nanoparticles, rather than partially alloying and partially forming pure nanoparticles after laser irradiation.

[0016] Preferably, the refractory first metal is tungsten, rhenium, tantalum, molybdenum, niobium, iridium or vanadium.

[0017] Preferably, the second metal is nickel, iron, palladium or titanium.

[0018] Preferably, the third metal is silver or copper.

[0019] Preferably, the organic solvent is selected from one or more of ethanol, acetone, butanol, and ethyl acetate.

[0020] Preferably, the conditions for the first unfocused laser irradiation are: using a 1064nm laser beam, a laser energy range of 350-500mJ, and a temperature higher than the vaporization temperature of the nanoparticles of the refractory first metal and the second metal. The conditions for the first unfocused laser irradiation are related to the absorption rate of the interaction between the refractory first metal and the second metal, the organic solvent, and the laser.

[0021] Preferably, the conditions for the second unfocused laser irradiation are: using a 1064nm laser beam, a laser energy range of 350-500mJ, and a temperature higher than the vaporization temperature of the alloy nanoparticles and the third metal. The selection of the conditions for the second unfocused laser irradiation is related to the absorption rate of the interaction between the alloy nanoparticles and the third metal, the organic solvent, and the laser.

[0022] Compared with the prior art, the present invention has the following beneficial effects:

[0023] 1. The present invention first irradiates a mutually soluble refractory first metal and a second metal under thermodynamically optimal alloying conditions, causing them to vaporize simultaneously. Under the rapid cooling action of the liquid medium, dense and uniform alloy nanoparticles are formed, which are referred to as an AB alloy. A colloidal precursor of a third metal is then mixed with the alloy colloidal solution and laser irradiated under optimal thermodynamic alloying conditions to achieve alloying of the refractory intermediate-entropy nanoalloy. Under these conditions, the third metal can more easily replace some of the B atoms in the AB alloy, resulting in a highly dense and uniformly sized intermediate-entropy micro-nanoalloy.

[0024] This invention combines theory and experimentation to prepare refractory metal medium-entropy micro-nano alloys in a liquid medium through a two-step process. Nanosecond pulsed lasers interact with the raw materials, generating high temperature and high pressure locally within the nanoparticles. Simultaneously, the liquid medium rapidly quenches and cools, creating an ideal extreme environment for preparing the refractory alloy. The first step, preparing an alloy of a refractory first metal and a miscible second metal, not only improves the mutual solubility between the first and second metals but also enhances wettability with the third metal in the second step, significantly increasing the compactness of the medium-entropy micro-nano alloy.

[0025] 2. The method of the present invention first obtains the thermodynamic conditions of metal alloys with a large difference in melting points through theoretical calculation. The large difference in melting points refers to refractory first metal and third metal, such as tungsten and copper, tungsten and silver. The large difference is due to the unique advantages of such alloys in the field of modern scientific and technological development. Such alloys can combine the respective advantages of the two metals. For example, tungsten-copper alloy combines the high hardness, low thermal expansion coefficient, and high stability of tungsten with the excellent electrical conductivity and thermal conductivity of copper, and can be applied to the fields of electrical materials, anti-perspirant materials, and armor-piercing materials; molybdenum-copper alloy has excellent high-temperature mechanical strength and low thermal expansion coefficient, and is widely used in the fields of electrical contact materials, perspiring materials, and electronic packaging materials; tungsten-silver composite materials combine the excellent electrical conductivity and thermal conductivity of silver with the high melting point and high corrosion resistance of tungsten, and are used as electrical contact materials for medium and low voltage electrical switches.

[0026] Free energy is used to determine under what conditions of temperature, composition, and particle size, micro-nanostructures are more likely to form a two-phase or single-phase structure. A lower single-phase free energy indicates a higher likelihood of forming a single-phase solid solution, or alloy. This allows us to identify the composition, temperature, or size that most easily forms an alloy. This simulation allows us to conduct experimental alloying experiments, using refractory metals to prepare medium-entropy micro-nanoalloys, making alloying more controllable.

[0027] 3. The present invention adopts non-focused laser irradiation to prepare alloy nanoparticles and medium-entropy micro-nano alloys, and utilizes laser melting and evaporation to realize the preparation of refractory metal alloys. Moreover, by simply changing the laser flux during the preparation process, the controllable preparation of refractory metal alloys of different sizes can be achieved.

[0028] 4. The present invention selects parameters of non-focused laser irradiation, such as laser wavelength and laser flux, to achieve the simultaneous melting and evaporation phase transition of the refractory first metal and the second metal or the alloy nanoparticles and the third metal under specific laser parameters, thereby realizing the controllable preparation of refractory metal alloys with uniform density.

[0029] 5. The method of preparing refractory metal alloys by non-focused laser irradiation in the present invention is simple and safe. No auxiliary reagents, such as surfactants, are required to directly alloy micro-nano materials. Laser irradiation technology is used in a liquid medium to prepare medium-entropy micro-nano alloys with uniform density and controllable particle size through discontinuity in time and space. The method is suitable for alloying a variety of refractory metals with different high melting points and low melting point metals, thereby improving the purity of medium-entropy micro-nano alloys.

[0030] 6. The present invention utilizes laser irradiation technology in a liquid medium to prepare intermediate-entropy micro-nano alloys because, based on the interaction between the laser and the particles dispersed in the liquid medium, by manipulating parameters such as laser wavelength and energy density, the controlled heating, melting, and evaporation of the micro-nano materials is achieved, thereby enabling the controllable preparation of ligand-free micro-nano materials. Existing technologies have only achieved the controllable preparation of metal, non-metal, and metal / semiconductor micro-nano particles. However, in this application, laser irradiation technology is utilized to achieve the controllable preparation of intermediate-entropy micro-nano alloys with significantly different melting points under extreme environments. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 Schematic diagram of the method for preparing medium-entropy micro-nano alloys using refractory metals according to Example 1 of the present invention.

[0032] Figure 2 In the figure, (a) is a relationship diagram between the free energy of the nickel-tungsten alloy forming a two-phase structure and a single-phase structure and the particle size of Example 1 of the present invention, and (b) is a relationship diagram between the free energy of the nickel-tungsten alloy forming a two-phase structure and a single-phase structure and the tungsten composition when the nickel-tungsten alloy particle size is 50nm.

[0033] Figure 3 In the figure, (a) is a relationship diagram between the free energy of the medium-entropy micro-nano alloy forming a two-phase structure and a single-phase structure and the particle size of Example 1 of the present invention, and (b) is a relationship diagram between the free energy of the medium-entropy micro-nano alloy forming a two-phase structure and a single-phase structure and the nickel-tungsten alloy when the size of the medium-entropy micro-nano alloy is 50nm.

[0034] Figure 4 This is the SEM image of the nickel-tungsten alloy of Example 1 of the present invention.

[0035] Figure 5 This is the SEM image of the copper-nickel-tungsten mesoentropy micro-nano alloy in Example 1 of the present invention. DETAILED DESCRIPTION

[0036] The specific embodiments of the present invention are described in detail below, but it should be understood that the scope of protection of the present invention is not limited by the specific embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention. The experimental methods described in the embodiments of the present invention are all conventional methods unless otherwise specified.

[0037] The present invention provides a method for preparing a medium-entropy micro-nano alloy using a refractory metal by laser irradiation, comprising:

[0038] The first step is to select a refractory first metal and a second metal that is miscible with it. By calculating the optimal thermodynamic conditions for the two metals to form an alloy, based on the simulation results, nanoparticles of the refractory first metal and the second metal are weighed, ball-milled and mixed, and then stirred and evenly dispersed in an organic solvent to obtain a mixed colloidal precursor solution.

[0039] Among them, the selection of nanoparticles of the refractory first metal and the second metal is related to the mutual solubility between the nanoparticles. Mutual solubility is also called solubility or solid solubility, which refers to the maximum amount of one metal that can be dissolved in another metal, usually in mass percentage, atomic percentage or volume percentage under specific temperature and pressure conditions.

[0040] The mixed colloidal precursor liquid is irradiated with a modulated unfocused laser to obtain an alloy colloidal solution containing alloy nanoparticles. The selection of the unfocused laser is related to the absorption rate of the interaction between the refractory first metal and the second metal, the organic solvent, and the laser. Specifically, the refractory first metal and the second metal have strong absorption of the laser, while the organic solvent has little absorption of the laser. The purpose is to melt and evaporate the refractory first metal and the second metal, while the organic solvent hardly changes, thereby achieving a rapid cooling effect.

[0041] In the second step, a third metal is selected that is immiscible with the refractory first metal but miscible with the second metal. The third metal is ball-milled and then uniformly dispersed in an organic solvent to obtain a colloidal precursor solution of the third metal.

[0042] The optimal thermodynamic conditions for the alloy nanoparticles and the formation of medium-entropy micro-nano alloys with the third metal are calculated. Based on the simulation results, the alloy colloidal solution is mixed with the colloidal precursor solution of the third metal to obtain a nano-colloidal solution.

[0043] After the nano-colloidal solution is irradiated with laser, it is dried to finally obtain a medium-entropy micro-nano alloy containing the first, second and third metal elements.

[0044] In summary, the present invention provides a method for preparing medium-entropy micro-nano alloys using refractory metals as raw materials and laser irradiation. The two-step method can be used to simply and efficiently prepare refractory metal alloys. The first step uses theoretical calculations of the thermodynamic conditions under which nanoparticles of a refractory first metal and a second metal that is mutually soluble therein can form an alloy. Under the photothermal effect of laser and nanoparticles, the refractory first metal and the second metal form alloy nanoparticles in a liquid medium. The second step uses theoretical calculations of the thermodynamic conditions under which alloy nanoparticles can form an alloy with a third metal. After mixing, the mixture is laser irradiated again, causing the metal particles to rapidly melt and alloy, and then condense, nucleate, and grow under the ultra-fast quenching mechanism of the liquid medium, thereby guiding the rapid synthesis of the refractory alloy on a kinetic scale.

[0045] The addition of a second metal that is miscible with the refractory first metal in the first step will increase the interfacial bonding strength between the refractory first metal and the immiscible third metal, relieve stress concentration at the interfacial interface, and thus enhance the solubility of the alloy nanoparticles and the third metal in the second step.

[0046] In order to more clearly demonstrate the technical solutions and technical effects provided by the present invention, the present invention is described in detail below with reference to specific embodiments.

[0047] Example 1

[0048] A method for preparing a medium-entropy micro-nano alloy using a refractory metal comprises the following steps:

[0049] (1) Preparation of nickel-tungsten mixed colloidal precursor solution: According to the theoretical calculation results, 2.5 mg of nickel powder and tungsten powder with a molar ratio of 7:3 were weighed, ball-milled and stirred for 20 min, and then placed in 5 mL of organic liquid medium ethanol. After sufficient stirring, a 0.5 mg / mL nickel-tungsten mixed colloidal precursor solution was obtained.

[0050] (2) Preparation of nickel-tungsten alloy colloidal solution by laser irradiation: the wavelength is 1064 nm and the energy density is 500 mJ / pulse*cm 2 The nickel-tungsten mixed colloidal precursor solution was irradiated with an unfocused laser for 5 minutes with continuous stirring during the irradiation process to obtain a nickel-tungsten alloy colloidal solution, in which the solute is nickel-tungsten alloy.

[0051] (3) Preparation of a copper colloidal precursor solution: 2.5 mg of copper nanopowder was weighed, ball-milled and stirred for 20 min, and then placed in 5 mL of organic liquid medium ethanol. After sufficient stirring, a 0.5 mg / mL copper colloidal precursor solution was obtained.

[0052] (4) Preparation of nano-colloidal solution: According to the theoretical calculation results, the nickel-tungsten alloy colloidal solution and the copper colloidal precursor solution are evenly mixed in a liquid medium, and the molar ratio of nickel-tungsten alloy to copper is 5:5, to obtain a 0.5 mg / mL nano-colloidal solution.

[0053] (5) Preparation of copper-nickel-tungsten alloy powder by laser irradiation: the wavelength is 1064 nm and the energy density is 500 mJ / pulse*cm 2 The nanocolloidal solution was irradiated with an unfocused laser for 5 minutes, with continuous stirring during the irradiation process. Finally, after drying and other treatments, the copper-nickel-tungsten medium-entropy micro-nano alloy was obtained.

[0054] The following study is conducted using the copper-nickel-tungsten medium-entropy micro-nano alloy obtained in Example 1 as an example. The specific research methods and results are as follows:

[0055] like Figure 1 As shown, the technical solution of the present invention is universal in the preparation of medium-entropy micro-nano alloys.

[0056] Figure 2 The thermodynamic free energy calculation diagram of the refractory metal tungsten and the metal nickel miscible with it in Example 1 is shown in FIG. Figure 2 Figure (a) shows the relationship between the free energy for forming a two-phase structure and a single-phase structure and particle size when the nickel-tungsten molar ratio is 7:3. At this ratio, for nickel-tungsten alloy particles ranging in size from a few nanometers to 200 nanometers, the free energy for forming a single-phase structure is lower than the free energy for forming a two-phase structure, so the formation of a micro-nanostructure is more inclined towards a single-phase solid solution structure. Figure 2 Figure (b) shows the relationship between the free energy for forming two-phase and single-phase structures and the tungsten composition when the nickel-tungsten alloy particle size is 50 nm. At this particle size, the free energy for forming a single-phase solid solution of micro-nanoparticles with different compositions is lower than the free energy for forming a two-phase structure. The free energy for forming a single-phase structure is lowest at a nickel-tungsten molar ratio of 7:3, which represents the optimal composition ratio for alloy formation. The free energy difference is also greatest at a nickel-tungsten molar ratio of 7:3.

[0057] Figure 3 Figure (a) shows the relationship between the free energy and particle size for the formation of two-phase and single-phase structures, after nickel and tungsten are alloyed at a molar ratio of 7:3 and then mixed with metallic copper at a molar ratio of 5:5. At this ratio, the free energy for the formation of a single-phase structure is lower than that for the formation of a two-phase structure for medium-entropy micro-nano alloy particles ranging in size from a few nanometers to 200 nanometers, favoring a single-phase solid solution structure. Figure 3Figure (b) shows the relationship between the free energy for forming two-phase and single-phase structures and the composition of the alloyed nickel-tungsten alloy at a molar ratio of 7:3 for a 50nm medium-entropy micro-nano alloy particle. At this particle size, the free energy for forming a single-phase solid solution of medium-entropy micro-nano alloy particles of varying compositions is lower than the free energy for forming a two-phase structure. The free energy for forming a single phase is lowest at a molar ratio of 5:5, indicating the optimal composition ratio for alloy formation.

[0058] Figure 4 This is a scanning electron microscope image of the nickel-tungsten alloy prepared in Example 1. Figure 4 It can be seen that the particle size of the nickel-tungsten alloy nanoparticles is several hundred nanometers. The corresponding energy spectrum distribution results in Table 1 show that these nanoparticles still contain NiW elements, indicating that the nickel powder and tungsten powder have undergone decomposition / separation during the photothermal process and maintained their original properties.

[0059] Table 1 EDS data of nickel-tungsten alloy

[0060] element Mass percentage Mass percentage error % Atomic percentage % Atomic percentage error % Ni 71.21 ±0.46 88.57 ±0.25 W 28.79 ±1.88 11.43 ±0.33 total 100 100

[0061] Figure 5 The scanning electron microscope image of the medium entropy micro-nano alloy of Example 1 is shown in FIG. Figure 5 It can be seen that the particle size of the nanoparticles is several hundred nanometers. The corresponding energy spectrum distribution results in Table 2 show that these nanoparticles still contain CuNiW elements, indicating that the nickel-tungsten alloy and copper powder undergo decomposition / separation during the photothermal process and maintain their original properties.

[0062] Table 2 EDS data of copper-nickel-tungsten medium-entropy micro-nano alloy

[0063] element Mass percentage Mass percentage error % Atomic percentage % Atomic percentage error % Ni 24.78 ±0.52 27.51 ±0.51 Cu 68.51 ±0.89 70.25 ±0.82 W 6.71 ±0.44 2.24 ±0.14 total 100 100

[0064] Obviously, those skilled in the art can make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention is also intended to include these changes and variations. The above-mentioned embodiments are only preferred embodiments for fully illustrating the present invention, and their scope of protection is not limited thereto. Equivalent substitutions or modifications made by those skilled in the art on the basis of the present invention are all within the scope of protection of the present invention, and the scope of protection of the present invention shall be subject to the claims.

Claims

1. A method for preparing medium-entropy micro-nano alloys using refractory metals, characterized in that: The steps include: Mixing nanoparticles of a refractory first metal and nanoparticles of a second metal that is mutually soluble therewith, and then dispersing the nanoparticles together in an organic solvent to obtain a mixed colloidal precursor solution; subjecting the mixed colloidal precursor solution to a first unfocused laser irradiation to obtain an alloy colloidal solution, wherein the solute in the alloy colloidal solution is alloy nanoparticles; uniformly dispersing nanoparticles of a third metal in an organic solvent to obtain a colloidal precursor solution of the third metal; wherein the third metal is immiscible with the refractory first metal but miscible with the second metal; mixing the alloy colloidal solution with a colloidal precursor solution of a third metal to obtain a nano-colloidal solution; The nano-colloidal solution is subjected to a second unfocused laser irradiation to obtain a medium-entropy micro-nano alloy.

2. The method for preparing medium-entropy micro-nano alloys using refractory metals according to claim 1, characterized in that: The molar ratio of the refractory first metal to the second metal is determined according to the optimal thermodynamic alloying conditions of the alloy nanoparticles.

3. The method for preparing medium-entropy micro-nano alloys using refractory metals according to claim 1, characterized in that: The molar ratio of the alloy nanoparticles to the third metal is determined according to the optimal thermodynamic alloying conditions of the medium-entropy micro-nano alloy.

4. The method for preparing medium-entropy micro-nano alloys using refractory metals according to claim 1, characterized in that: The nanoparticles of the refractory first metal and the second metal mutually soluble therein are ball-milled to have the same particle size, and the third metal is ball-milled to have the same particle size as the alloy nanoparticles.

5. The method for preparing medium-entropy micro-nano alloys using refractory metals according to claim 1, characterized in that: The refractory first metal is tungsten, rhenium, tantalum, molybdenum, niobium, iridium or vanadium.

6. The method for preparing medium-entropy micro-nano alloys using refractory metals according to claim 1, characterized in that: The second metal is nickel, iron, palladium or titanium.

7. The method for preparing medium-entropy micro-nano alloys using refractory metals according to claim 1, characterized in that: The third metal is silver or copper.

8. The method for preparing medium-entropy micro-nano alloys using refractory metals according to claim 1, characterized in that: The organic solvent is selected from one or more of ethanol, acetone, butanol and ethyl acetate.

9. The method for preparing medium-entropy micro-nano alloys using refractory metals according to claim 1, characterized in that: The conditions for the first unfocused laser irradiation are: using a 1064 nm laser beam, a laser energy range of 350-500 mJ, and a temperature higher than the vaporization temperature of the nanoparticles of the refractory first metal and the second metal.

10. The method for preparing medium-entropy micro-nano alloys using refractory metals according to claim 1, characterized in that: The conditions for the second unfocused laser irradiation are: using a 1064 nm laser beam, a laser energy range of 350-500 mJ, and a temperature higher than the vaporization temperature of the alloy nanoparticles and the third metal.

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