Refractory high-entropy alloy porous material and method of making same

Abstract

This invention discloses a method for preparing a porous refractory high-entropy alloy material, comprising the following steps: 1. Mixing refractory metal element powder and low-melting-point metal element powder uniformly to obtain a mixed powder; 2. Cold isostatically pressing the mixed powder to obtain a green compact; 3. Under a vacuum degree not exceeding 1×10⁻⁶. ‑2 Under certain conditions, the green compact is heated to 1000℃~1400℃ and sintered for 0.5h~10h, followed by furnace cooling to obtain a refractory high-entropy alloy porous material. This invention utilizes low-melting-point metals to promote the diffusion of refractory metals and lowers the sintering temperature and activation energy to inhibit grain growth. By controlling the type and content of refractory and low-melting-point metal element powders and subsequent preparation processes, the properties of the refractory high-entropy alloy porous material can be flexibly controlled, achieving a porosity of 20%~40%, a maximum pore size of 1µm~20µm, and a room temperature compressive strength of 100MPa~900MPa.

Description

Technical Field

[0001] This invention belongs to the field of porous metal materials technology, specifically relating to a refractory high-entropy alloy porous material and its preparation method. Background Technology

[0002] Refractory high-entropy porous alloys are a new type of advanced material that combines porous structure, refractory properties, and high-entropy effects. Using refractory metals such as zirconium, niobium, tantalum, molybdenum, and tungsten as main components, they achieve excellent high-temperature stability, high strength, and corrosion resistance through the lattice distortion effect, hysteresis diffusion effect, and "cocktail" effect of high-entropy alloys. Simultaneously, the porous structure endows them with lightweight, high specific surface area, and good energy absorption capacity. These materials combine the high-temperature resistance advantages of refractory metals with the comprehensive performance control potential of high-entropy alloys, showing great application prospects in aerospace thermal protection, high-temperature filtration, catalyst supports, and thermal structural components in the nuclear energy field. They represent an important research direction for functional and structural materials in extreme environments.

[0003] Currently, the preparation of refractory high-entropy porous alloy materials using powder metallurgy technology still faces multiple challenges. First, refractory metals have extremely high melting points (often exceeding 1800℃), requiring not only extremely high sintering temperatures but also easily leading to grain coarsening and severely deteriorating mechanical properties. Second, precise control of the pore size and porosity of porous structures is difficult, easily resulting in uneven pore distribution and poor connectivity. Furthermore, large differences in density and diffusion coefficients between components easily induce segregation, making it difficult to achieve compositional homogenization. These challenges significantly limit its large-scale preparation and performance optimization.

[0004] Therefore, it is of great significance to develop a refractory high-entropy alloy porous material with both good pore structure and excellent mechanical properties, and to explore a low-cost and efficient preparation method. Summary of the Invention

[0005] The technical problem to be solved by this invention is to provide a method for preparing refractory high-entropy alloy porous materials, addressing the shortcomings of the prior art. This method involves uniformly mixing refractory metal element powder and low-melting-point metal element powder, followed by cold isostatic pressing and sintering. This process controls the porosity, pore size, and mechanical properties of the refractory high-entropy alloy porous material, enabling metallurgical bonding between the powder particles to form a porous structure, thus obtaining the refractory high-entropy alloy porous material.

[0006] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is: a method for preparing a refractory high-entropy porous alloy material, characterized in that the method includes the following steps: Step 1: Mix the refractory metal element powder and the low melting point metal element powder evenly to obtain a mixed powder; Step 2: The mixed powder obtained in Step 1 is subjected to cold isostatic pressing to obtain a green body; Step 3: Under a vacuum degree not exceeding 1×10 -2 Under the condition of Pa, the green blank obtained in step 2 is heated to 1000℃~1400℃ and sintered for 0.5h~10h, and then cooled in the furnace to obtain a refractory high entropy alloy porous material.

[0007] This invention involves uniformly mixing refractory metal element powder and low-melting-point metal element powder, followed by cold isostatic pressing to mechanically interlock the powders, resulting in a green body. The green body is then sintered while controlling the vacuum degree to be no greater than 1×10⁻⁶. -2 To prevent the introduction of impurities and avoid oxidation, the sintering parameters are controlled to manage the porosity, pore size, and mechanical properties of the refractory high-entropy alloy porous material. During the sintering process, although the refractory metal element powder and the low-melting-point metal element powder in the cold isostatically pressed green body are mechanically interlocked, pores still remain. By controlling the sintering process, metallurgical bonding is formed between the powders, which reduces the pores but does not completely eliminate them, thus forming a porous structure. Finally, the low-melting-point metal elements and the refractory metal elements diffuse and combine with each other, remaining in the porous material to obtain the refractory high-entropy alloy porous material.

[0008] In this invention, the atomic radii of low-melting-point metals and refractory metals differ significantly. Therefore, low-melting-point metals diffuse rapidly and easily enter the crystal lattice of refractory metals to form substitutional solid solutions, leading to lattice distortion and the generation of numerous vacancies. Furthermore, the increase in vacancy concentration significantly accelerates the diffusion rate of refractory metal atoms, reducing the sintering activation energy. As a diffusion medium, low-melting-point metals significantly enhance the diffusion rate of refractory metal elements, not only lowering the sintering temperature but also effectively promoting the formation and growth of sintering necks and facilitating the homogenization of element distribution. In addition, low-melting-point metals readily adsorb onto the surface of refractory metals, reducing the surface energy of refractory metal powders through chemical adsorption, reducing interparticle repulsion, and promoting closer contact of the mixed powders during the pressing stage. With reduced surface energy, the atomic diffusion barrier decreases in the early stage of sintering (neck formation stage), allowing the refractory metals to bond at lower temperatures, shortening the sintering time. After sintering, low-melting-point metals are mainly distributed at the grain boundaries of refractory metals, forming continuous or discontinuous alloy phases. Through the pinning effect, they hinder the boundary migration of refractory metal grains and inhibit their excessive growth.

[0009] The above-mentioned method for preparing a refractory high-entropy alloy porous material is characterized in that the refractory metal element powder in step one is four or more selected from tungsten powder, molybdenum powder, tantalum powder, niobium powder, zirconium powder, vanadium powder, hafnium powder, rhenium powder, and chromium powder, and the atomic percentage of each powder is 10% to 30%. This invention ensures the high-temperature performance of the refractory high-entropy alloy porous material by controlling the composition of the refractory metal element powder. By controlling the atomic percentage of each powder, a refractory high-entropy alloy is formed, and its high-entropy effect, hysteresis diffusion effect, and lattice distortion effect can further improve its high-temperature performance.

[0010] The above-mentioned method for preparing a refractory high-entropy porous alloy material is characterized in that the low-melting-point metal element powder mentioned in step one is one or two of nickel powder, iron powder, tin powder, zinc powder, and silver powder. This invention, by controlling the types of powder used, ensures that all have low melting points and rapid diffusion rates during sintering. These powders serve as diffusion media for the refractory metal elements, increasing their diffusion rate and thus lowering the preparation temperature of the refractory high-entropy porous alloy material.

[0011] The method for preparing a refractory high-entropy alloy porous material, as described above, is characterized in that the mass ratio of the refractory metal element powder to the low-melting-point metal element powder in step one is 100:0.5~4. This invention, by controlling the mass ratio of the refractory metal element powder to the low-melting-point metal element powder, ensures the performance of the refractory high-entropy alloy porous material, preventing the problems of excessively high low-melting-point metal element powder content reducing the overall performance of the porous material and excessively low content leading to poor effects in reducing the preparation temperature.

[0012] The above-mentioned method for preparing a porous refractory high-entropy alloy is characterized in that the pressure of cold isostatic pressing in step two is 100MPa~300MPa, and the holding time is 1min~10min. This invention controls the degree of mechanical bonding of the powder and the number of retained pores by controlling the parameters of cold isostatic pressing, thereby affecting the densification behavior during sintering and thus controlling the porosity, pore size, and mechanical properties of the porous material.

[0013] In addition, the present invention also discloses a refractory high-entropy alloy porous material, characterized in that the refractory high-entropy alloy porous material is prepared by the above method.

[0014] The aforementioned refractory high-entropy alloy porous material is characterized in that the porosity of the refractory high-entropy alloy porous material is 20%~40%, the maximum pore size is 1µm~20µm, and the room temperature compressive strength is 100MPa~900MPa.

[0015] Compared with the prior art, the present invention has the following advantages: 1. This invention involves uniformly mixing refractory metal element powder and low-melting-point metal element powder, followed by cold isostatic pressing to form mechanical interlocking of the powders, resulting in a green body. By sintering the green body, the porosity, pore size, and mechanical properties of the refractory high-entropy alloy porous material are controlled, allowing metallurgical bonding between the powders to form a porous structure. Finally, the low-melting-point metal elements and refractory metal elements diffuse and combine with each other, remaining in the porous material, thus obtaining the refractory high-entropy alloy porous material.

[0016] 2. By adding low-melting-point metals, the present invention can significantly improve the diffusion rate of refractory metal elements during sintering due to the fast diffusion rate of low-melting-point metals, which can not only reduce the sintering temperature, but also effectively promote the formation and growth of sintering necks and facilitate the uniformity of element distribution.

[0017] 3. By adding a low-melting-point metal, the atomic radii of the low-melting-point metal and the refractory metal are significantly different. The low-melting-point metal atoms can easily enter the refractory metal lattice to form a substitutional solid solution, which leads to lattice distortion and generates a large number of vacancies. The increase in vacancy concentration will significantly accelerate the diffusion rate of refractory metal atoms and reduce the sintering activation energy.

[0018] 4. This invention adds low-melting-point metals, which are easily adsorbed onto the surface of refractory metal powder particles. Through chemical adsorption, the surface energy of the refractory metal powder is reduced, the repulsive force between particles is reduced, and the particles are more closely contacted during the pressing stage. After the surface energy is reduced, the atomic diffusion barrier in the early stage of sintering (neck formation stage) is reduced, so that the refractory metal powder particles can bond at a lower temperature, thus shortening the sintering time.

[0019] 5. This invention adds a low-melting-point metal, which is mainly distributed at the grain boundaries of the refractory metal after sintering, forming a continuous or discontinuous alloy phase. This phase inhibits the boundary migration of the refractory metal grains through a pinning effect, thereby suppressing their excessive growth.

[0020] 6. This invention controls the selection and mass percentage of low-melting-point metal elements, utilizes low-melting-point metals to promote the diffusion of refractory metals, reduce sintering temperature and activation energy, and inhibit grain growth, thereby flexibly regulating the properties of porous materials. In conjunction with subsequent cold isostatic pressing parameters and vacuum sintering parameters, the porosity, maximum pore size, and room temperature compressive strength of refractory high-entropy alloy porous materials can be flexibly controlled.

[0021] The technical solution of the present invention will be further described in detail below through embodiments. Detailed Implementation

[0022] Example 1 This embodiment includes the following steps: Step 1: Use tungsten powder, molybdenum powder, tantalum powder and niobium powder with an atomic percentage of 25:25:25:25 as refractory metal element powders, and nickel powder as low-melting-point metal element powders. Then mix the refractory metal element powders and low-melting-point metal element powders in a mass ratio of 100:0.6 evenly to obtain a mixed powder. Step 2: The mixed powder obtained in Step 1 is subjected to cold isostatic pressing at a pressure of 120 MPa and a holding time of 2 min to obtain a green body. Step 3: Under a vacuum of 9.3 × 10⁻⁶ -3Under the condition of Pa, the green blank obtained in step 2 is heated to 1050℃ and sintered for 0.7h, and then cooled in the furnace to obtain a refractory high-entropy alloy porous material.

[0023] Testing revealed that the porosity of the refractory high-entropy alloy porous material prepared in this embodiment was 39%, the maximum pore size was 20µm, and the room temperature compressive strength was 112MPa.

[0024] Example 2 This embodiment includes the following steps: Step 1: Use tungsten powder, molybdenum powder, tantalum powder and niobium powder with an atomic percentage of 10:30:30:30 as refractory metal element powders, and nickel powder and iron powder as low melting point metal element powders. Then mix the refractory metal element powder and the low melting point metal element powder with a mass ratio of 100:0.8 evenly to obtain a mixed powder. Step 2: The mixed powder obtained in Step 1 is subjected to cold isostatic pressing at a pressure of 200 MPa and a holding time of 6 min to obtain a green body. Step 3: Under a vacuum of 8.7 × 10⁻⁶ -3 Under the condition of Pa, the green blank obtained in step 2 is heated to 1200℃ and sintered for 6 hours, and then cooled in the furnace to obtain a refractory high-entropy alloy porous material.

[0025] Testing revealed that the porosity of the refractory high-entropy alloy porous material prepared in this embodiment was 31%, the maximum pore size was 11µm, and the room temperature compressive strength was 510MPa.

[0026] Example 3 This embodiment includes the following steps: Step 1: Use tungsten powder, molybdenum powder, tantalum powder and niobium powder with an atomic percentage of 30:20:30:20 as refractory metal element powders, and zinc powder and tin powder as low-melting-point metal element powders. Then mix the refractory metal element powders and low-melting-point metal element powders with a mass ratio of 100:3.9 evenly to obtain a mixed powder. Step 2: The mixed powder obtained in Step 1 is subjected to cold isostatic pressing at a pressure of 290 MPa and a holding time of 9 min to obtain a green body; Step 3: Under a vacuum of 6.5 × 10⁻⁶ -3 Under the condition of Pa, the green blank obtained in step 2 is heated to 1400℃ and sintered for 10h, and then cooled in the furnace to obtain a refractory high-entropy alloy porous material.

[0027] Testing revealed that the porosity of the refractory high-entropy alloy porous material prepared in this embodiment was 22%, the maximum pore size was 2µm, and the room temperature compressive strength was 885MPa.

[0028] Example 4 This embodiment includes the following steps: Step 1: Take tungsten powder, molybdenum powder, tantalum powder, niobium powder, zirconium powder and hafnium powder with an atomic percentage of 15:20:20:25:10:10 as refractory metal element powders, and silver powder and iron powder as low melting point metal element powders. Then mix the refractory metal element powder and the low melting point metal element powder in a mass ratio of 100:0.5 evenly to obtain a mixed powder. Step 2: The mixed powder obtained in Step 1 is subjected to cold isostatic pressing at a pressure of 200 MPa and a holding time of 6 min to obtain a green body. Step 3: Under a vacuum of 8.7 × 10⁻⁶ -3 Under the condition of Pa, the green blank obtained in step 2 is heated to 1200℃ and sintered for 6 hours, and then cooled in the furnace to obtain a refractory high-entropy alloy porous material.

[0029] Testing revealed that the porosity of the refractory high-entropy alloy porous material prepared in this embodiment was 36%, the maximum pore size was 16µm, and the room temperature compressive strength was 443MPa.

[0030] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention in any way. Any simple modifications, alterations, and equivalent changes made to the above embodiments based on the technical essence of the present invention shall still fall within the protection scope of the present invention.

Claims

1. A method for preparing a refractory high-entropy porous alloy material, characterized in that, The method includes the following steps: Step 1: Mix refractory metal element powder and low-melting-point metal element powder evenly to obtain a mixed powder; the refractory metal element powder is four or more of the following: tungsten powder, molybdenum powder, tantalum powder, niobium powder, zirconium powder, vanadium powder, hafnium powder, rhenium powder, and chromium powder, and the atomic percentage of each of the refractory metal element powders is 10%~30%; the low-melting-point metal element powder is one or two of the following: nickel powder, iron powder, tin powder, zinc powder, and silver powder; the mass ratio of the refractory metal element powder to the low-melting-point metal element powder is 100:0.5~4; Step 2: The mixed powder obtained in Step 1 is subjected to cold isostatic pressing to obtain a green body; Step 3: Under a vacuum degree not exceeding 1×10 -2 Under the condition of Pa, the green blank obtained in step 2 is heated to 1000℃~1400℃ and sintered for 0.5h~10h, and then cooled in the furnace to obtain a refractory high entropy alloy porous material.

2. The method for preparing a refractory high-entropy alloy porous material according to claim 1, characterized in that, The pressure of the cold isostatic pressing in step two is 100MPa~300MPa, and the holding time is 1min~10min.

3. A refractory high-entropy porous alloy material, characterized in that, The refractory high-entropy alloy porous material is prepared by the method described in any one of claims 1 or 2.

4. The refractory high-entropy porous alloy material according to claim 3, characterized in that, The porosity of the refractory high-entropy alloy porous material is 22%~40%, the maximum pore size is 1µm~20µm, and the room temperature compressive strength is 112MPa~900MPa.