Lightweight high-entropy alloy and preparation method thereof

Abstract

The application relates to a light high-entropy alloy and a preparation method thereof. The preparation method comprises the following steps: adding Ta powder and Nb powder into a phenolic resin solution, performing coating treatment and pre-solidification to obtain polymer-coated ceramic powder; mixing Mo powder, W powder, Al powder and the polymer-coated ceramic powder, performing ball milling, sintering and annealing to obtain the light high-entropy alloy. By introducing the Al element into the Mo-Ta-W-Nb type high-entropy alloy, the density of the Mo-Ta-W-Nb type high-entropy alloy can be reduced, and the high-temperature oxidation resistance of the Mo-Ta-W-Nb type high-entropy alloy can be improved; by performing the coating and pre-solidification of the Ta powder and the Nb powder with the phenolic resin, a carbide ceramic phase can be generated in situ, and the plasticity and the high-temperature strength of the Mo-Ta-W-Nb type high-entropy alloy can be simultaneously improved.

Description

Technical Field

[0001] This application belongs to the field of high-entropy alloy and powder metallurgy technology, and relates to a high-entropy alloy, and more particularly to a lightweight high-entropy alloy and its preparation method. Background Technology

[0002] With the rapid development of modern industrial technology, fields such as aerospace, nuclear reactors, and chemical processing require high-temperature alloys capable of withstanding ultra-high temperature environments. High-entropy alloys possess high strength at room temperature and high-temperature resistance, offering broad application prospects. High-entropy alloys refer to solid solutions where multiple metal atoms are highly mixed, resulting in a high-entropy effect in the microstructure. The extremely high degree of disorder among the various metal atoms produced by this high-entropy effect directly leads to a decrease in the Gibbs free energy of the atomic system within the microstructure, enabling interdiffusion between the metal atoms and thus forming a simple, single-crystal structure.

[0003] Among them, Mo-Ta-W-Nb high-entropy alloys with body-centered cubic (BCC) structure still have high strength at 1600℃ and are high-temperature resistant materials with excellent performance. However, their density is too high, making it difficult to achieve lightweighting, and their oxidation resistance is poor.

[0004] CN114855050A discloses a high-strength, lightweight, refractory high-entropy alloy and its preparation method. This method reduces the density of the high-entropy alloy system and increases its specific strength by adding the lightweight element Al to a high-density Mo-Nb-V-Ta refractory high-entropy alloy, while maintaining the alloy structure as a single-phase solid solution. However, Al has a significantly different melting point from Mo, Nb, V, and Ta. To avoid Al loss due to burning, the preparation method of this high-strength, lightweight, refractory high-entropy alloy is complex, and adding only Al may sacrifice high-temperature strength.

[0005] CN115094291A discloses a Ti-V-Al-Cr-M system lightweight, high-strength, high-entropy alloy and its preparation method. Ti is the main element, ensuring low density; V is a minor element, preventing excessive density while also introducing lattice distortion. Al and Cr readily form oxide films to prevent corrosion, improving corrosion resistance and high-temperature oxidation resistance. M elements (such as Mo, Hf, Nb, and Ta) have melting points exceeding 2500℃, increasing the average melting point and facilitating high-temperature applications. However, the significant differences in atomic sizes among these elements can increase lattice distortion and even generate harmful phases, affecting the alloy's plasticity.

[0006] Therefore, how to simultaneously reduce density, improve oxidation resistance and plasticity while maintaining the high-temperature strength of Mo-Ta-W-Nb type high-entropy alloys is an urgent problem to be solved in this field. Summary of the Invention

[0007] To address the shortcomings of existing technologies, the purpose of this application is to provide a lightweight high-entropy alloy and its preparation method. This application introduces Al into Mo-Ta-W-Nb type high-entropy alloys, which simultaneously reduces the density and improves their high-temperature oxidation resistance. Furthermore, by coating and pre-curing Ta and Nb powders with phenolic resin, a carbide ceramic phase can be generated in situ, simultaneously enhancing the plasticity and high-temperature strength of the Mo-Ta-W-Nb type high-entropy alloy.

[0008] To achieve this objective, the present application adopts the following technical solution:

[0009] In a first aspect, this application provides a method for preparing a lightweight high-entropy alloy, comprising the following steps:

[0010] Ta powder and Nb powder are added to a phenolic resin solution for coating and pre-curing to obtain polymer-coated ceramic powder; Mo powder, W powder, Al powder and the polymer-coated ceramic powder are mixed and ball-milled, sintered and annealed to obtain the lightweight high-entropy alloy.

[0011] This application introduces Al into Mo-Ta-W-Nb type high-entropy alloys. The lightweighting of Al can significantly reduce the density of Mo-Ta-W-Nb type high-entropy alloys. At the same time, Al easily forms an oxide film, which can prevent the oxidation of Mo-Ta-W-Nb type high-entropy alloys and improve their high-temperature oxidation resistance.

[0012] Furthermore, this application utilizes phenolic resin coating to coat Ta and Nb powders, enabling the in-situ generation of carbide ceramic phases during subsequent sintering. On one hand, the carbide ceramic phase effectively hinders dislocation movement, significantly enhancing plasticity through second-phase strengthening. On the other hand, the nanoparticles of the carbide ceramic phase pinning grain boundaries suppress excessive grain growth during sintering and hinder grain boundary slip at high temperatures, synergistically improving the high-temperature strength of Mo-Ta-W-Nb type high-entropy alloys.

[0013] Furthermore, this application obtains polymer-coated ceramic powder by pre-curing after coating treatment, thus avoiding the breakage of the phenolic resin coating layer during ball milling.

[0014] In some embodiments, the average particle size of the Mo powder, Ta powder, W powder, Nb powder and Al powder is independently 2μm to 3μm, for example, it can be 2μm, 2.2μm, 2.5μm, 2.8μm or 3μm, etc.

[0015] In some embodiments, the Mo powder, Ta powder, W powder, and Nb powder are in an equimolar ratio.

[0016] In some embodiments, the molar ratio of Al powder to Mo powder is (0.5~2):1, for example, it can be 0.5:1, 0.8:1, 1:1, 1.2:1, 1.5:1, 1.8:1 or 2:1, etc.

[0017] This application aims to control the molar ratio of Al powder to Mo powder to be (0.5~2):1. If the amount of Al powder added is too small, it will not be able to effectively reduce the density of Mo-Ta-W-Nb high-entropy alloys and improve their high-temperature oxidation resistance; if the amount of Al powder added is too large, it may reduce the high-temperature strength and other properties of Mo-Ta-W-Nb high-entropy alloys.

[0018] In some embodiments, the phenolic resin solution includes phenolic resin and a solvent.

[0019] In some embodiments, the solid content of the phenolic resin solution is 5% to 40%, for example, it can be 5%, 10%, 15%, 20%, 25%, 30%, 35% or 40%, etc.

[0020] In some embodiments, the solvent includes any one or a combination of at least two of ethanol, isopropanol, acetone, butanol, or xylene. Typical but non-limiting combinations include combinations of ethanol and isopropanol, acetone and butanol, ethanol and xylene, ethanol, isopropanol and acetone, ethanol, butanol and xylene, and combinations of ethanol, isopropanol, acetone, butanol and xylene.

[0021] In some embodiments, the number-average molecular weight Mn of the phenolic resin is 450 g / mol to 750 g / mol, for example, it can be 450 g / mol, 500 g / mol, 550 g / mol, 600 g / mol, 650 g / mol, 700 g / mol or 750 g / mol.

[0022] In some embodiments, the mass of the phenolic resin is 0.5% to 2% of the total mass of the Ta powder and the Nb powder, for example, it can be 0.5%, 1%, 1.5% or 2%.

[0023] This application requires controlling the mass of phenolic resin to be 0.5% to 2% of the total mass of Ta powder and Nb powder. If the amount of phenolic resin added is too small, it is difficult to achieve uniform coating of Ta powder and Nb powder, resulting in a low content of in-situ generated carbide ceramic phase, which cannot effectively improve the plasticity and high-temperature strength of Mo-Ta-W-Nb type high-entropy alloys. If the amount of phenolic resin added is too large, the phenolic resin is prone to agglomeration or uneven coating, resulting in larger in-situ generated carbide ceramic phase particles, which become crack sources and reduce both plasticity and high-temperature strength.

[0024] In some embodiments, the atmosphere of the coating treatment includes any one or a combination of at least two of nitrogen, argon, or helium. Typical but non-limiting combinations include combinations of nitrogen and argon, argon and helium, nitrogen and helium, nitrogen, argon, and helium, etc.

[0025] In some embodiments, the coating treatment temperature is 25°C to 50°C, for example, it can be 25°C, 30°C, 35°C, 40°C, 45°C or 50°C.

[0026] In some implementations, the coating process takes 3 to 6 hours, for example, 3 hours, 4 hours, 5 hours, or 6 hours.

[0027] In some embodiments, the coating process is carried out under stirring conditions, and the stirring speed is 300 rpm to 500 rpm, for example, 300 rpm, 350 rpm, 400 rpm, 450 rpm or 500 rpm.

[0028] In some embodiments, drying is further performed after the coating process is completed and before the pre-curing.

[0029] In some embodiments, the drying temperature is 60°C to 100°C, for example, it can be 60°C, 70°C, 80°C, 90°C or 100°C.

[0030] In some embodiments, the drying time is 8h to 12h, for example, it can be 8h, 9h, 10h, 11h or 12h.

[0031] In some embodiments, the pre-curing atmosphere includes any one or a combination of at least two of nitrogen, argon, or helium. Typical but non-limiting combinations include combinations of nitrogen and argon, argon and helium, nitrogen and helium, nitrogen, argon, and helium, etc.

[0032] In some embodiments, the pre-curing heating rate is 5℃ / min to 10℃ / min, for example, it can be 5℃ / min, 6℃ / min, 7℃ / min, 8℃ / min, 9℃ / min or 10℃ / min, etc.

[0033] In some embodiments, the pre-curing temperature is 120°C to 180°C, for example, it can be 120°C, 130°C, 140°C, 150°C, 160°C, 170°C or 180°C.

[0034] In some embodiments, the pre-curing time is 1 hour to 3 hours, for example, it can be 1 hour, 1.5 hours, 2 hours, 2.5 hours or 3 hours.

[0035] In some embodiments, the atmosphere of the ball mill includes any one or a combination of at least two of nitrogen, argon, or helium. Typical but non-limiting combinations include combinations of nitrogen and argon, argon and helium, nitrogen and helium, nitrogen, argon, and helium, etc.

[0036] In some embodiments, the ball-to-material ratio of the ball mill is (8~12):1, for example, it can be 8:1, 9:1, 10:1, 11:1 or 12:1, etc.

[0037] In some embodiments, the rotational speed of the ball mill is 100 rpm to 300 rpm, for example, it can be 100 rpm, 150 rpm, 200 rpm, 250 rpm or 300 rpm.

[0038] In some embodiments, the ball milling time is 10h to 15h, for example, it can be 10h, 11h, 12h, 13h, 14h or 15h.

[0039] In some embodiments, the sintering includes a first sintering and a second sintering with stepped heating.

[0040] In some embodiments, the sintering atmosphere includes any one or a combination of at least two of nitrogen, argon, or helium. Typical but non-limiting combinations include combinations of nitrogen and argon, argon and helium, nitrogen and helium, nitrogen, argon, and helium, etc.

[0041] In some embodiments, the temperature of the first sintering is 500°C to 800°C, for example, it can be 500°C, 550°C, 600°C, 650°C, 700°C, 750°C or 800°C.

[0042] In some embodiments, the holding time for the first sintering is 20 min to 60 min, for example, it can be 20 min, 30 min, 40 min, 50 min or 60 min.

[0043] In some embodiments, the heating rate of the first sintering is 10°C / min to 30°C / min, for example, it can be 10°C / min, 15°C / min, 20°C / min, 25°C / min or 30°C / min.

[0044] In some embodiments, the absolute pressure of the first sintering is 30MPa to 80MPa, for example, it can be 30MPa, 40MPa, 50MPa, 60MPa, 70MPa or 80MPa.

[0045] In some embodiments, after the first sintering is completed and before the second sintering, a vacuuming process is further included.

[0046] In this application, by performing a vacuum process, the small molecules generated during the first sintering can be removed, leaving only residual carbon as the carbon source for the carbide ceramic phase.

[0047] In some embodiments, the second sintering temperature is 1200℃~1600℃, for example, it can be 1200℃, 1300℃, 1400℃, 1500℃ or 1600℃.

[0048] In some embodiments, the holding time for the second sintering is 5 min to 20 min, for example, it can be 5 min, 10 min, 15 min or 20 min.

[0049] In some embodiments, the heating rate of the second sintering is 50°C / min to 100°C / min, for example, it can be 50°C / min, 60°C / min, 70°C / min, 80°C / min, 90°C / min or 100°C / min.

[0050] In some embodiments, the absolute pressure of the second sintering is 30MPa to 80MPa, for example, it can be 30MPa, 40MPa, 50MPa, 60MPa, 70MPa or 80MPa.

[0051] In some embodiments, cooling is further performed after sintering and before annealing.

[0052] In some implementations, the cooling includes natural cooling to room temperature.

[0053] It should be noted that in this application, room temperature refers to 20℃~40℃.

[0054] In some embodiments, the annealing atmosphere includes any one or a combination of at least two of nitrogen, argon, or helium. Typical but non-limiting combinations include combinations of nitrogen and argon, argon and helium, nitrogen and helium, nitrogen, argon, and helium, etc.

[0055] In some embodiments, the annealing temperature is 900℃~1100℃, for example, it can be 900℃, 950℃, 1000℃, 1050℃ or 1100℃.

[0056] In some embodiments, the annealing holding time is 20 min to 40 min, for example, it can be 20 min, 25 min, 30 min, 35 min or 40 min.

[0057] In some embodiments, the annealing heating rate is 10℃ / min to 30℃ / min, for example, it can be 10℃ / min, 15℃ / min, 20℃ / min, 25℃ / min or 30℃ / min.

[0058] Secondly, this application provides a lightweight high-entropy alloy, which is prepared by the preparation method described in the first aspect.

[0059] In some embodiments, the compositional formula of the lightweight high-entropy alloy is MoTaWNbAl. x Where 0.5≤x≤1, the proportions in the composition expression are relative molar ratios.

[0060] The numerical range described in this application includes not only the point values ​​listed above, but also any point values ​​between the above numerical ranges that are not listed. Due to space limitations and for the sake of brevity, this application will not exhaustively list the specific point values ​​included in the range.

[0061] Compared with the prior art, this application has the following advantages:

[0062] This application introduces Al into Mo-Ta-W-Nb type high-entropy alloys. The lightweighting of Al can significantly reduce the density of Mo-Ta-W-Nb type high-entropy alloys. At the same time, Al easily forms an oxide film, which can prevent the oxidation of Mo-Ta-W-Nb type high-entropy alloys and improve their high-temperature oxidation resistance.

[0063] Furthermore, this application utilizes phenolic resin coating to coat Ta and Nb powders, enabling the in-situ generation of carbide ceramic phases during subsequent sintering. On one hand, the carbide ceramic phase effectively hinders dislocation movement, significantly enhancing plasticity through second-phase strengthening. On the other hand, the nanoparticles of the carbide ceramic phase pinning grain boundaries suppress excessive grain growth during sintering and hinder grain boundary slip at high temperatures, synergistically improving the high-temperature strength of Mo-Ta-W-Nb type high-entropy alloys.

[0064] Furthermore, this application obtains polymer-coated ceramic powder by pre-curing after coating treatment, thus avoiding the breakage of the phenolic resin coating layer during ball milling. Attached Figure Description

[0065] Figure 1 This is a schematic flowchart of the preparation method of the lightweight high-entropy alloy provided in this application. Detailed Implementation

[0066] The technical solution of this application will be further described below through specific embodiments. Those skilled in the art should understand that the embodiments described are merely to help understand this application and should not be regarded as specific limitations on this application.

[0067] The scope of this application can be defined by lower and upper limits. The selected lower and upper limits define the boundaries of a specific range. The range defined in this way can be defined by the inclusion or exclusion of endpoints. Any endpoint can be independently selected for inclusion or exclusion, and all lower and upper limits can be arbitrarily combined to form new ranges. That is, any lower limit can be combined with any upper limit to form a valid range. For example, if the ranges of 60~120 and 80~110 are listed for specific parameters, it should be understood that the ranges of 60~110 and 80~120 also fall within the scope of this application. In addition, if the minimum range values ​​1 and 2 are listed, and the maximum range values ​​3, 4 and 5 are also listed, then all ranges of 1~3, 1~4, 1~5, 2~3, 2~4 and 2~5 fall within the scope of this application. In this application, the numerical range "a~b" represents a shortened representation of any combination of real numbers between a and b, where a and b are both real numbers. For example, the numerical range "0~5" means that all real numbers between 0 and 5 have been fully listed in this document, and "0~5" is only a shortened representation of this set of numerical combinations. When a parameter is expressed as an integer ≥2, it is equivalent to listing positive integers that meet the requirements, such as 2, 3, 4, 5, 6, 7, 8, 9, 10, etc. When a parameter is expressed as an integer selected from "2~10", it is equivalent to listing any integer among 2, 3, 4, 5, 6, 7, 8, 9, and 10.

[0068] Unless otherwise specified, the term "at least two combinations" in this application refers to a quantity greater than or equal to 2. For example, "any one or at least two combinations" means any one of the listed items, or a combination of at least two of the listed items in a manner that does not conflict and enables the implementation of this application.

[0069] In this application, unless otherwise specified, the features or solutions corresponding to "and / or" cover any one of two or more related listed items, as well as any and all combinations of the related listed items. These arbitrary and all combinations include any two related listed items, any more related listed items, or a combination of all related listed items. For example, "A and / or B" represents a set consisting of A, B, and combinations of A and B. "Including A and / or B" can be understood, depending on the context of the statement, as including A, including B, or including both A and B. In this application, "optional" means that the corresponding feature, component, step, or solution is not essential, i.e., selected from either "present" or "absent" parallel solutions. If multiple "optional" limitations appear in a technical solution, unless otherwise specified and without technical conflict or mutual constraint, each "optional" limitation is independent and does not affect the others.

[0070] In this application, technical features or solutions described using open-ended terms such as "comprising" or "including" do not exclude additional non-conflicting elements beyond those listed unless otherwise specified. They are considered to disclose both closed-ended features or solutions consisting solely of the listed elements and open-ended features or solutions that may include additional non-conflicting elements beyond those listed. For example, if A includes a1, a2, and a3, unless otherwise specified, this means that A may consist only of a1, a2, and a3, or it may include other non-conflicting elements based on a1, a2, and a3. This corresponds to the disclosure of technical solutions such as "A consists of a1, a2, and a3," "A is selected from a1, a2, and a3," and "A not only includes a1, a2, and a3, but may also include other non-conflicting elements."

[0071] All embodiments and optional embodiments of this application, unless otherwise specified and without technical conflict, can be combined to form new technical solutions, and such combinations fall within the scope of this application. The term "embodiment" mentioned in this application means that a specific feature, structure, or characteristic described in connection with an embodiment can be included in at least one embodiment or implementation of this application. The appearance of this phrase in various positions in the specification does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment mutually exclusive with other embodiments. Those skilled in the art can explicitly and implicitly understand that the embodiments described in this application can be combined with other embodiments without technical conflict.

[0072] In this application, the ordinal numbers “first,” “second,” “third,” and “fourth” used in expressions such as “first aspect,” “second aspect,” “third aspect,” and “fourth aspect” are used for descriptive purposes only and should not be construed as indicating or implying relative importance or quantity, nor should they be construed as implicitly indicating the importance or quantity of the indicated technical features. They serve only as a non-exhaustive enumeration and do not constitute a closed limitation on quantity.

[0073] In this application, the order in which the steps are written in the methods described in the various embodiments does not imply a strict execution order. The actual execution order of each step should be determined according to its function and possible internal logic. Unless otherwise specified, all steps in this application can be executed in the order they are written, or in any order without technical conflict. For example, if the method includes steps (a) and (b), it means that the method may include steps (a) and (b) executed sequentially, or it may include steps (b) and (a) executed sequentially. If the method also includes step (c), then step (c) can be added to the method in any order without conflict, including but not limited to the execution order of steps (a), (b), and (c), steps (a), (c), and (b), steps (c), (a), and (b), etc.

[0074] Example 1

[0075] This embodiment provides a method for preparing a lightweight high-entropy alloy, the process flow diagram of which is shown below. Figure 1 As shown, it includes the following steps:

[0076] (1) Weigh out Mo powder, Ta powder, W powder, Nb powder and Al powder in a molar ratio of 1:1:1:1:1. The average particle size of Mo powder, Ta powder, W powder, Nb powder and Al powder is 2.5 μm.

[0077] (2) Weigh 1% of the total mass of Ta powder and Nb powder into phenolic resin and add it to an appropriate amount of ethanol to obtain a phenolic resin solution with a solid content of 20%. The number average molecular weight Mn of the phenolic resin is 450 g / mol to 750 g / mol.

[0078] (3) Under nitrogen atmosphere protection, Ta powder and Nb powder were added to the phenolic resin solution and coated for 4.5 h at a temperature of 40℃ and a stirring speed of 400 rpm. After the coating treatment, the mixture was dried at a temperature of 80℃ for 10 h. Finally, under nitrogen atmosphere protection, the temperature was raised to 150℃ at a heating rate of 8℃ / min and held for 2 h to complete the pre-curing, thus obtaining polymer-coated ceramic powder.

[0079] (4) Under nitrogen atmosphere protection, Mo powder, W powder, Al powder and polymer-coated ceramic powder were mixed and ball-milled for 12 hours at a ball-to-powder ratio of 10:1 and a rotation speed of 200 rpm. After ball milling, the mixture was heated to 700℃ at a heating rate of 20℃ / min and held for 30 minutes under nitrogen atmosphere and an absolute pressure of 50 MPa to complete the first sintering. After the first sintering, vacuum treatment was performed, and the mixture was heated to 1400℃ at a heating rate of 80℃ / min and held for 10 minutes under nitrogen atmosphere and an absolute pressure of 50 MPa to complete the second sintering. After the second sintering, the mixture was naturally cooled to room temperature. Finally, under nitrogen atmosphere protection, the mixture was heated to 1000℃ at a heating rate of 20℃ / min and held for 30 minutes to complete the annealing, resulting in a lightweight high-entropy alloy.

[0080] The lightweight high-entropy alloy provided in this embodiment has the composition formula MoTaWNbAl, where the proportions in the composition formula are relative molar ratios.

[0081] Example 2

[0082] This embodiment provides a method for preparing a lightweight high-entropy alloy, including the following steps:

[0083] (1) Weigh out Mo powder, Ta powder, W powder, Nb powder and Al powder in a molar ratio of 1:1:1:1:0.5. The average particle size of Mo powder, Ta powder, W powder, Nb powder and Al powder is 2 μm.

[0084] (2) Weigh 0.5% of the total mass of Ta powder and Nb powder into phenolic resin and add it to an appropriate amount of ethanol to obtain a phenolic resin solution with a solid content of 5%. The number average molecular weight Mn of the phenolic resin is 450 g / mol to 750 g / mol.

[0085] (3) Under nitrogen atmosphere protection, Ta powder and Nb powder were added to the phenolic resin solution and coated for 6 hours at 25℃ and 300 rpm. After coating, the mixture was dried at 60℃ for 12 hours. Finally, under nitrogen atmosphere protection, the temperature was increased to 120℃ at a rate of 5℃ / min and held for 3 hours to complete the pre-curing, resulting in polymer-coated ceramic powder.

[0086] (4) Under nitrogen atmosphere protection, Mo powder, W powder, Al powder and polymer-coated ceramic powder were mixed and ball-milled for 15 hours at a ball-to-powder ratio of 8:1 and a rotation speed of 100 rpm. After ball milling, the mixture was heated to 500°C at a heating rate of 10°C / min and held for 60 minutes under argon atmosphere and absolute pressure of 30 MPa to complete the first sintering. After the first sintering, vacuum treatment was performed, and the mixture was heated to 1200°C at a heating rate of 50°C / min and held for 20 minutes under argon atmosphere and absolute pressure of 30 MPa to complete the second sintering. After the second sintering, the mixture was naturally cooled to room temperature. Finally, under nitrogen atmosphere protection, the mixture was heated to 900°C at a heating rate of 10°C / min and held for 40 minutes to complete the annealing, resulting in a lightweight high-entropy alloy.

[0087] The lightweight, high-entropy alloy provided in this embodiment has the composition formula MoTaWNbAl 0.5 , where the proportions in the expression are relative molar ratios.

[0088] Example 3

[0089] This embodiment provides a method for preparing a lightweight high-entropy alloy, including the following steps:

[0090] (1) Weigh out Mo powder, Ta powder, W powder, Nb powder and Al powder in a molar ratio of 1:1:1:1:0.8. The average particle size of Mo powder, Ta powder, W powder, Nb powder and Al powder is 3 μm.

[0091] (2) Weigh 2% of the total mass of Ta powder and Nb powder into phenolic resin and add it to an appropriate amount of ethanol to obtain a phenolic resin solution with a solid content of 40%. The number average molecular weight Mn of the phenolic resin is 450 g / mol to 750 g / mol.

[0092] (3) Under helium atmosphere protection, Ta powder and Nb powder were added to the phenolic resin solution and coated for 3 hours at 50℃ and 500 rpm. After coating, the mixture was dried at 100℃ for 8 hours. Finally, under helium atmosphere protection, the mixture was heated to 180℃ at a heating rate of 10℃ / min and held for 1 hour to complete pre-curing, thus obtaining polymer-coated ceramic powder.

[0093] (4) Under helium atmosphere protection, Mo powder, W powder, Al powder and polymer-coated ceramic powder were mixed and ball-milled for 10 hours at a ball-to-powder ratio of 12:1 and a rotation speed of 300 rpm. After ball milling, the mixture was heated to 800℃ at a heating rate of 30℃ / min and held for 20 minutes under helium atmosphere and absolute pressure of 80 MPa to complete the first sintering. After the first sintering, vacuum treatment was performed, and the mixture was heated to 1600℃ at a heating rate of 100℃ / min and held for 5 minutes under helium atmosphere and absolute pressure of 80 MPa to complete the second sintering. After the second sintering, the mixture was naturally cooled to room temperature. Finally, under helium atmosphere protection, the mixture was heated to 1100℃ at a heating rate of 30℃ / min and held for 20 minutes to complete the annealing, resulting in a lightweight high-entropy alloy.

[0094] The lightweight, high-entropy alloy provided in this embodiment has the composition formula MoTaWNbAl 0.8 , where the proportions in the expression are relative molar ratios.

[0095] Example 4

[0096] This embodiment provides a method for preparing a lightweight high-entropy alloy. Except for adjusting the molar ratio of Mo powder, Ta powder, W powder, Nb powder and Al powder in step (1) to 1:1:1:1:0.2, all other steps are the same as in Example 1.

[0097] The lightweight, high-entropy alloy provided in this embodiment has the composition formula MoTaWNbAl 0.2 , where the proportions in the expression are relative molar ratios.

[0098] Example 5

[0099] This embodiment provides a method for preparing a lightweight high-entropy alloy. Except for adjusting the molar ratio of Mo powder, Ta powder, W powder, Nb powder and Al powder in step (1) to 1:1:1:1:1.2, all other steps are the same as in Example 1.

[0100] The lightweight, high-entropy alloy provided in this embodiment has the composition formula MoTaWNbAl 1.2 , where the proportions in the expression are relative molar ratios.

[0101] Example 6

[0102] This embodiment provides a method for preparing a lightweight high-entropy alloy. Except for adjusting the mass of phenolic resin in step (2) to 0.2% of the total mass of Ta powder and Nb powder, all other steps are the same as in Example 1.

[0103] Example 7

[0104] This embodiment provides a method for preparing a lightweight high-entropy alloy. Except for adjusting the mass of phenolic resin in step (2) to 2.5% of the total mass of Ta powder and Nb powder, all other steps are the same as in Example 1.

[0105] Comparative Example 1

[0106] This comparative example provides a method for preparing a lightweight high-entropy alloy. Except for adjusting the molar ratio of Mo powder, Ta powder, W powder, Nb powder and Al powder in step (1) to 1:1:1:1:0 and not adding Al powder in step (4), everything else is the same as in Example 1.

[0107] The lightweight high-entropy alloy provided in this comparative example has the composition formula MoTaWNb, where the proportions in the composition formula are relative molar ratios.

[0108] Comparative Example 2

[0109] This comparative example provides a method for preparing a lightweight high-entropy alloy, except that steps (2) and (3) are omitted, that is, the Ta powder and Nb powder are not coated and pre-cured with phenolic resin. All other steps are the same as in Example 1.

[0110] Comparative Example 3

[0111] This comparative example provides a method for preparing a lightweight high-entropy alloy. Except for step (3), in which Mo powder, W powder and Al powder are added to the phenolic resin solution, i.e., Mo powder, Ta powder, W powder, Nb powder and Al powder are coated and pre-cured with phenolic resin, all other steps are the same as in Example 1.

[0112] Comparative Example 4

[0113] This comparative example provides a method for preparing a lightweight high-entropy alloy, which is the same as Example 1 except that pre-curing is not performed in step (3).

[0114] The following performance tests were performed on the lightweight high-entropy alloys prepared in Examples 1 to 7 and Comparative Examples 1 to 4:

[0115] (1) High temperature strength: The test was conducted in accordance with GB / T 4338-2006 "Metallic materials high temperature tensile test method" at a test temperature of 800℃, and the high temperature yield strength (unit is MPa) was recorded.

[0116] (2) Density: The density was determined using the Archimedes displacement method according to GB / T 3850-2015 "Method for Determination of Density of Dense Sintered Metallic Materials and Hard Alloys" (unit: g / cm³). 3 ).

[0117] (3) High-temperature oxidation resistance: According to GB / T 13303-1991 "Determination of high-temperature oxidation resistance of steel", the test was carried out in a static air atmosphere. The specific conditions were constant temperature oxidation at 1000℃ for 100h, and the oxidation weight gain rate was calculated (unit: g / (m)). 2 The smaller the value of h), the better the high-temperature antioxidant performance.

[0118] (4) Plasticity: The test shall be conducted in accordance with GB / T 228.1-2021 "Metallic Materials - Tensile Testing" Part 1: Room Temperature Test Method, and the elongation after fracture (in %) shall be recorded. The larger the value, the better the plasticity.

[0119] The test results are shown in Table 1.

[0120]

[0121] As shown in Table 1, the lightweight high-entropy alloys prepared in Examples 1-3 possess both low density and excellent high-temperature strength, high-temperature oxidation resistance, and plasticity. This indicates that by introducing Al into Mo-Ta-W-Nb high-entropy alloys, the lightweighting of Al can significantly reduce the density of Mo-Ta-W-Nb high-entropy alloys. Simultaneously, Al readily forms an oxide film, preventing oxidation of Mo-Ta-W-Nb high-entropy alloys and improving their high-temperature oxidation resistance. Furthermore, by coating Ta and Nb powders with phenolic resin, a carbide ceramic phase can be generated in situ during subsequent sintering. On one hand, the carbide ceramic phase effectively hinders dislocation movement, achieving improved plasticity through significant second-phase strengthening. On the other hand, the nanoparticles of the carbide ceramic phase pinning grain boundaries can suppress excessive grain growth during sintering and hinder grain boundary slip behavior at high temperatures, synergistically improving the high-temperature strength of Mo-Ta-W-Nb high-entropy alloys.

[0122] Compared to Example 1, Examples 4 and 5 adjusted the amount of Al powder added. For example, in Example 4, insufficient Al powder was added, failing to effectively reduce the density of the Mo-Ta-W-Nb high-entropy alloy and improve its high-temperature oxidation resistance. Therefore, the resulting lightweight high-entropy alloy had a high density and poor high-temperature oxidation resistance. Similarly, in Example 5, excessive Al powder was added, affecting the high-temperature strength of the Mo-Ta-W-Nb high-entropy alloy. Therefore, the high-temperature strength of the resulting lightweight high-entropy alloy was reduced.

[0123] Compared to Example 1, Examples 6 and 7 adjusted the amount of phenolic resin added. In Example 6, insufficient phenolic resin made it difficult to achieve uniform coating of Ta and Nb powders, resulting in a low content of in-situ generated carbide ceramic phase, which failed to effectively improve the plasticity and high-temperature strength of the Mo-Ta-W-Nb type high-entropy alloy. In Example 7, excessive phenolic resin caused agglomeration or uneven coating, resulting in larger in-situ generated carbide ceramic phase particles that became crack initiation sites, reducing both plasticity and high-temperature strength. Therefore, the high-temperature strength and plasticity of the lightweight high-entropy alloys prepared in Examples 6 and 7 were reduced.

[0124] Compared to Example 1, Comparative Example 1, lacking the addition of Al powder, cannot utilize the lightweight nature of Al to reduce the density of the Mo-Ta-W-Nb high-entropy alloy, nor can it leverage the ease with which Al forms an oxide film to prevent oxidation of the Mo-Ta-W-Nb high-entropy alloy. Therefore, the lightweight high-entropy alloy prepared in Comparative Example 1 has an extremely high density and extremely poor high-temperature oxidation resistance.

[0125] Compared to Example 1, Comparative Example 2, due to the lack of prior phenolic resin coating and pre-curing of Ta and Nb powders, failed to generate a carbide ceramic phase in situ during subsequent sintering, thus hindering the improvement of plasticity by impeding dislocation movement and failing to improve high-temperature strength by pinning grain boundaries. Therefore, the lightweight high-entropy alloy prepared in Comparative Example 2 exhibited extremely poor high-temperature strength and plasticity.

[0126] Compared to Example 1, Comparative Example 3 involved coating and pre-curing Mo, Ta, W, Nb, and Al powders with phenolic resin. While Mo and W can also form carbides, these carbides exhibit poor stability at high temperatures. Coating Mo and W indiscriminately would lead to the formation of large amounts of carbides, causing excessive hardening and brittleness of the matrix, ultimately impairing high-temperature strength and plasticity. Therefore, the lightweight high-entropy alloy prepared in Comparative Example 3 exhibits extremely poor high-temperature strength and plasticity.

[0127] Compared to Example 1, Comparative Example 4, due to the lack of pre-curing after phenolic resin coating, resulted in the phenolic resin coating layer breaking down during ball milling. This made it difficult to generate a carbide ceramic phase in situ during subsequent sintering, and also prevented the improvement of plasticity by hindering dislocation movement, as well as the improvement of high-temperature strength by pinning grain boundaries. Therefore, the lightweight high-entropy alloy prepared in Comparative Example 4 exhibited extremely poor high-temperature strength and plasticity.

[0128] In summary, this application introduces Al into Mo-Ta-W-Nb type high-entropy alloys. The lightweighting of Al can significantly reduce the density of Mo-Ta-W-Nb type high-entropy alloys. At the same time, Al easily forms an oxide film, which can prevent the oxidation of Mo-Ta-W-Nb type high-entropy alloys and improve their high-temperature oxidation resistance.

[0129] Furthermore, this application utilizes phenolic resin coating to coat Ta and Nb powders, enabling the in-situ generation of carbide ceramic phases during subsequent sintering. On one hand, the carbide ceramic phase effectively hinders dislocation movement, significantly enhancing plasticity through second-phase strengthening. On the other hand, the nanoparticles of the carbide ceramic phase pinning grain boundaries suppress excessive grain growth during sintering and hinder grain boundary slip at high temperatures, synergistically improving the high-temperature strength of Mo-Ta-W-Nb type high-entropy alloys.

[0130] Furthermore, by pre-curing after coating, this application can obtain polymer-coated ceramic powder, thus preventing the phenolic resin coating layer from breaking during ball milling.

[0131] The applicant declares that the above description is only a specific implementation of this application, but the protection scope of this application is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this application fall within the protection and disclosure scope of this application.

Claims

1. A method for preparing a lightweight high-entropy alloy, characterized in that, Includes the following steps: Ta powder and Nb powder are added to a phenolic resin solution for coating and pre-curing to obtain polymer-coated ceramic powder. Mo powder, W powder, Al powder and the polymer-coated ceramic powder are mixed, ball-milled, sintered and annealed to obtain the lightweight high-entropy alloy.

2. The preparation method according to claim 1, characterized in that, The average particle size of the Mo powder, Ta powder, W powder, Nb powder and Al powder is independently 2μm~3μm; And / or, the Mo powder, Ta powder, W powder and Nb powder are in an equimolar ratio; And / or, the molar ratio of the Al powder to the Mo powder is (0.5~2):1; And / or, the phenolic resin solution comprises phenolic resin and a solvent; And / or, the solid content of the phenolic resin solution is 5% to 40%.

3. The preparation method according to claim 2, characterized in that, The solvent includes any one or a combination of at least two of ethanol, isopropanol, acetone, butanol, or xylene; And / or, the number-average molecular weight Mn of the phenolic resin is 450 g / mol to 750 g / mol; And / or, the mass of the phenolic resin is 0.5% to 2% of the total mass of the Ta powder and the Nb powder.

4. The preparation method according to any one of claims 1 to 3, characterized in that, The atmosphere for the coating treatment includes any one or a combination of at least two of nitrogen, argon, or helium. And / or, the coating treatment temperature is 25℃~50℃; And / or, the coating treatment time is 3h~6h; And / or, the coating process is carried out under stirring conditions, wherein the stirring speed is 300 rpm to 500 rpm.

5. The preparation method according to any one of claims 1 to 4, characterized in that, The pre-curing atmosphere includes any one or a combination of at least two of nitrogen, argon, or helium. And / or, the pre-curing heating rate is 5℃ / min to 10℃ / min; And / or, the pre-curing temperature is 120℃~180℃; And / or, the pre-curing time is 1h to 3h; And / or, the atmosphere of the ball mill includes any one or a combination of at least two of nitrogen, argon or helium; And / or, the ball-to-material ratio of the ball mill is (8~12):1; And / or, the rotational speed of the ball mill is 100 rpm to 300 rpm; And / or, the ball milling time is 10h~15h.

6. The preparation method according to any one of claims 1 to 5, characterized in that, The sintering includes a first sintering and a second sintering with stepped heating; And / or, the sintering atmosphere includes any one or a combination of at least two of nitrogen, argon, or helium.

7. The preparation method according to claim 6, characterized in that, The first sintering temperature is 500℃~800℃; And / or, the holding time for the first sintering is 20 min to 60 min; And / or, the heating rate of the first sintering is 10℃ / min to 30℃ / min; And / or, the absolute pressure of the first sintering is 30MPa~80MPa; And / or, after the first sintering is completed and before the second sintering, a vacuuming process is also included; And / or, the second sintering temperature is 1200℃~1600℃; And / or, the holding time for the second sintering is 5 min to 20 min; And / or, the heating rate of the second sintering is 50℃ / min to 100℃ / min; And / or, the absolute pressure of the second sintering is 30MPa~80MPa.

8. The preparation method according to any one of claims 1 to 7, characterized in that, The annealing atmosphere includes any one or a combination of at least two of nitrogen, argon, or helium. And / or, the annealing temperature is 900℃~1100℃; And / or, the holding time for annealing is 20 min to 40 min; And / or, the annealing heating rate is 10℃ / min to 30℃ / min.

9. A lightweight high-entropy alloy, characterized in that, The lightweight high-entropy alloy is prepared by the preparation method according to any one of claims 1 to 8.

10. The lightweight high-entropy alloy according to claim 9, characterized in that, The compositional formula of the lightweight high-entropy alloy is MoTaWNbAl x Where 0.5≤x≤1, the proportions in the composition expression are relative molar ratios.

Images