A high-entropy alloy and a preparation method thereof

Abstract

The application discloses a kind of high-entropy alloy and preparation method thereof, it is related to high-entropy alloy and tungsten alloy material field, the high-entropy alloy, its composition includes 20~50%W, 20~50%Ta, 2~20%Cr, 2~15%V, 0~15%Ti, 0~15%Mo and unavoidable impurities according to mole, impurity is C, N, H, O element.High-entropy alloy preparation method includes the following steps: S1.mixed material is carried out to obtain powder raw material;S2.powder raw material is pressed to obtain rod blank;S3.the rod blank is pre-sintered;S4.after pre-sintering the rod blank is smelted to obtain ingot S5.sampling is carried out to solid solution treatment.The advantage of this method is that: alloy material element is evenly distributed, basic element is not segregated;Element oxidation is lighter;It can be applied in the process of large-scale production, meet industrial demand.

Description

Technical Field

[0001] This invention belongs to the technical field of high-entropy alloys and tungsten alloy materials, specifically relating to a high-entropy alloy and its preparation method. Background Technology

[0002] Controlled nuclear fusion is considered the ultimate solution to humanity's energy problems, and tungsten-based alloys are seen as the preferred plasma material in fusion reactors. However, tungsten-based alloys still face some pressing issues, such as low-temperature brittleness, recrystallization brittleness, plasma irradiation brittleness, and thermal damage.

[0003] High-entropy alloys, also known as single-phase multi-component alloys, are a novel type of metallic material that breaks through traditional material design concepts. Composed of multiple main elements, they exhibit high lattice disorder and the ability to suppress atomic diffusion. Numerous studies have demonstrated that high-entropy alloys possess advantages such as high mixing entropy and resistance to neutron irradiation (resistance to exposition damage), thus they are considered a promising new type of radiation-resistant tungsten-based alloy material. Controlling the interface or precipitated phases within the material to prevent the diffusion and aggregation of gas atoms is an effective method for combating radiation swelling.

[0004] Among these, single-phase multi-component tungsten-based alloys developed based on tungsten are a popular radiation-resistant material research topic in academia. Tungsten possesses characteristics such as high melting point, low sputtering rate, and high thermal conductivity. Currently, Los Alamos National Laboratory in the United States has prepared W-Ta-V-Cr alloy thin film materials using magnetron sputtering, but this method has high production costs and is difficult to industrialize. However, there are currently few research reports on tungsten-based high-entropy alloys, with elemental segregation, titanium oxidation, and the inability to achieve industrial production being the main problems. Summary of the Invention

[0005] The technical problem solved by this invention is to overcome the limitation of existing products in industrial-scale production by providing a high-entropy alloy and its preparation method. The preparation method of this invention is simple, suitable for industrial production, and the resulting high-entropy alloy material is characterized by uniform composition and minimal oxidation.

[0006] The present invention solves the above-mentioned technical problems through the following technical solutions.

[0007] The present invention provides a high-entropy alloy, the composition of which, by molar weight, includes 20-50% W, 20-50% Ta, 2-20% Cr, 2-15% V, 0-15% Ti, 0-15% Mo and unavoidable impurities.

[0008] The impurities are C, N, H, and O elements; the O element content in the high-entropy alloy is ≤0.5wt%.

[0009] The high-entropy alloy has a BCC single-phase crystal structure.

[0010] This invention also provides a method for preparing a high-entropy alloy, which includes the following steps:

[0011] S1. Prepare and mix W, Ta, Cr, V, Ti and Mo in proportion to obtain powder raw materials;

[0012] S2. The powdered raw material is pressed to obtain a rod-shaped blank;

[0013] S3. Pre-sinter the rod-shaped billet;

[0014] S4. The pre-sintered rod-shaped billet is melted to obtain an ingot;

[0015] S5. Take a sample of the ingot and perform solid solution treatment to obtain a high-entropy alloy.

[0016] In S1, the purity of the prepared material is ≥99.95%; the weight of the prepared material is greater than 1kg.

[0017] In S1, the mixing operation involves adding the prepared materials into a horizontal ball mill jar for mixing.

[0018] In this invention, there is no need to add grinding balls during the mixing process, because the collision between the grinding balls and the inner wall of the grinding jar will carry iron elements into the powder, thereby reducing the purity of the alloy.

[0019] In S1, the mixing speed is 100-200 r / min.

[0020] In S1, the mixing time is 13 to 19 hours.

[0021] In S2, the pressing method is cold isostatic pressing; this method is used at room temperature, with rubber or plastic as the mold material and liquid as the pressure medium, mainly for the molding of powder materials, to provide blanks for further sintering, forging or hot isostatic pressing processes; the products pressed by this method have high density and uniform blank density.

[0022] In S2, the cold isostatic pressing includes a pressure increase process and a pressure holding process; the pressure increase rate is 10-15 MPa / min.

[0023] The pressure held is 160–200 MPa, preferably 180–200 MPa; the holding time is 9–30 min.

[0024] In step S3, the pre-sintering operation involves placing the rod-shaped billet into a medium-frequency sintering furnace. The medium-frequency sintering furnace utilizes the principle of electromagnetic induction, employing a thyristor switch to transmit the magnetic field generated by a high-frequency current to the interior of the object being heated, thus generating heat. Compared to traditional gas furnaces or resistance furnaces, medium-frequency sintering furnaces can achieve rapid and uniform heating. Due to the large size and weight of the samples in this invention, the bonding force between the raw material powders is enhanced after medium-frequency sintering, preventing sample collapse during the heating process of suspension melting.

[0025] In S3, the operating frequency of the pre-sintering is 1000Hz.

[0026] In S3, the pre-sintering includes heated sintering and high-temperature sintering; the heating rate of the heated sintering is 8-15℃ / min; the temperature of the high-temperature sintering is 1200-1650℃, preferably 1300-1500℃; and the time of the high-temperature sintering is 2h.

[0027] In this invention, since the melting point of Ti is 1668℃, the sintering temperature cannot be higher than the melting point of the component elements, so the maximum temperature is 1650℃.

[0028] In S4, the melting operation is to first evacuate the melting furnace to 1×10-3~5×10-3 Pa and fill it with argon gas to a pressure of 0.01~0.1 MPa; then place the sintered billet in the suspension melting furnace, flip the melting ingot up and down, and then cool it naturally.

[0029] In S4, the melting time is 3 minutes.

[0030] In S4, the melting process is performed ≥ 3 times.

[0031] In S4, the purpose of the melting is to make the components mix evenly.

[0032] In step S5, the solution treatment involves polishing the sample surface and then placing it in a vacuum annealing furnace for solution treatment. The sample is heated at a rate of 10°C / min before solution treatment.

[0033] In S5, the solution temperature is 1000–1500°C, preferably 1150–1300°C.

[0034] In S5, the solid solution time is 0.5 to 3 hours.

[0035] In S5, the vacuum degree of the solid solution is 1 to 5 Pa.

[0036] In this invention, the oxygen content in the high-entropy alloy product is below 0.1%; if the raw material contains Ti, since Ti is easily oxidized, Ti will inevitably be partially oxidized during the alloy preparation process, so the oxygen content in the Ti-containing high-entropy tungsten alloy is 0.3 to 0.5 wt%.

[0037] In this invention, the high-entropy alloy uses a body-centered cubic (BCC) melt as the matrix. The high-entropy alloy exhibits superior properties for two reasons. First, it possesses a strong lattice distortion effect, resulting in a higher atomic dislocation ability than pure tungsten when irradiated, making it less prone to irradiation defects. Second, even if irradiation creates vacancies and interstitial atoms within the material, their migration energies are relatively close, leading to a high recombination rate and a degree of "self-healing." Furthermore, W and Ta in the alloy components have high atomic numbers and low sputtering rates. V enhances the material's deformability at room temperature. Cr forms a protective oxide film in oxidizing environments. All components in the tungsten-based high-entropy alloy of this invention possess a BCC structure, thus forming a single BCC phase when dissolved together, further enhancing the material's properties.

[0038] The positive and progressive effects of this invention are as follows:

[0039] (1) The alloy material has a uniform element distribution and no segregation of basic elements.

[0040] (2) The oxidation of elements is relatively mild; the oxygen content in the high-entropy alloy products of this invention is less than 0.1%; if the raw materials contain Ti, the oxygen content is 0.3-0.5%.

[0041] (3) The technical solution of the present invention can be applied in the process of large-scale production to meet industrial needs. Attached Figure Description

[0042] Figure 1 The image shows the XRD pattern of the tungsten-based high-entropy alloy prepared in Example 1 of this invention.

[0043] Figure 2 This is an EDS image of the tungsten-based high-entropy alloy prepared in Example 1 of the present invention.

[0044] Figure 3 This is a SEM image of the tungsten-based high-entropy alloy prepared in Example 2 of the present invention. Detailed Implementation

[0045] The present invention is further illustrated below by way of embodiments, but the invention is not limited to the scope of the embodiments described herein. Experimental methods in the following embodiments that do not specify specific conditions were performed according to conventional methods and conditions, or as selected according to the product instructions.

[0046] Unless otherwise specified, all raw materials and reagents used in the embodiments and comparative examples of this invention are commercially available.

[0047] Example 1

[0048] Ingredients: The raw material powder is prepared by mixing the raw material powder in a molar ratio of 44% W, 30% Ta, 9% Cr, 11% V and 6% Mo. The purity of the prepared material is 99.95% and the initial weight is 2 kg.

[0049] S1. Pour the above-mentioned materials into a horizontal ball mill jar for mixing. The rotation speed of the horizontal ball mill jar is 170 r / min, and the ball milling time is 15 h. The rotation direction remains unchanged during the ball milling process to obtain powder raw materials.

[0050] S2. The uniformly mixed powder raw material is subjected to cold isostatic pressing at a rate of 15 MPa / min. When the pressure reaches 180 MPa, it is held at this pressure for 10 minutes to form a rod-shaped blank.

[0051] S3. The rod-shaped pressed billet is placed in a medium-frequency sintering furnace for pre-sintering. The temperature is raised from room temperature at a rate of 10°C / min. When the temperature reaches 1400°C, it is sintered at this temperature for 2 hours, and then cooled with the furnace.

[0052] S4. The sintered billet is placed in a suspension melting furnace for melting. Before melting, the melting furnace is evacuated to a vacuum degree of 1x10⁻¹. -3 Pa, then argon gas is introduced to make the furnace pressure reach 0.01 MPa; each melting time is 3 minutes, and the ingots need to be turned upside down between each melting to make the components mix evenly; after melting 4 times, it is naturally cooled.

[0053] S5. Take samples of the smelted ingots, polish the surface of the samples, and then place them in a vacuum annealing furnace for solution treatment; heat from room temperature to 1150℃ at a heating rate of 10℃ / min, perform solution treatment at 1150℃ for 2 hours, and then cool with the furnace to obtain a high-entropy alloy; the oxygen content in the high-entropy alloy product is 0.03wt%.

[0054] Figure 1 This is the XRD pattern of the as-cast high-entropy tungsten alloy prepared in this embodiment. From... Figure 1 It can be seen that the modified cast high-entropy alloy (WTaCrVMo) is composed of a single BCC phase and belongs to a single-phase multi-component alloy.

[0055] Figure 2 This is the EDS energy dispersive spectroscopy (EDS) analysis of the solution-treated high-entropy alloy prepared in this embodiment. As can be seen from the figure, W, Ta, Mo, and other elements are uniformly distributed without segregation; Cr and V show slight segregation, but the overall elemental distribution remains relatively uniform with no macroscopic segregation.

[0056] Example 2

[0057] Ingredients: The raw material powder is prepared by mixing the raw material powder in a molar ratio of 41% W, 38% Ta, 11% Cr and 10% V. The purity of the prepared material is 99.95%, and the initial total weight is 3 kg.

[0058] S1. Pour the above-prepared materials into a horizontal ball mill jar for mixing. The rotation speed of the horizontal ball mill jar is 150 r / min, and the ball milling time is 15 h to obtain powder raw materials.

[0059] S2. The uniformly mixed powder raw material is subjected to cold isostatic pressing at a rate of 10 MPa / min; when the pressure reaches 200 MPa, it is held at this pressure for 10 minutes to form a rod-shaped blank.

[0060] S3. The rod-shaped pressed billet is placed in a medium-frequency sintering furnace for pre-sintering. The temperature is raised from room temperature at a rate of 10°C / min. When the temperature reaches 1300°C, it is sintered at this temperature for 2 hours, and then cooled with the furnace.

[0061] S4. The sintered billet is placed in a suspension melting furnace for melting. Before melting, the melting furnace is evacuated to a vacuum degree of 2 x 10⁻⁶. -3 Pa, then argon gas is introduced to make the furnace pressure reach 0.02 MPa; each melting time is 3 minutes, and the ingots need to be turned upside down between each melting to make the components mix evenly; after melting 4 times, it is naturally cooled.

[0062] S5. Take samples of the smelted ingots, polish the surface of the samples, and then place them in a vacuum annealing furnace for solution treatment; heat from room temperature to 1250℃ at a heating rate of 10℃ / min, perform solution treatment at 1250℃ for 2 hours, and then cool with the furnace to obtain a high-entropy tungsten alloy with an oxygen content of 0.07wt%.

[0063] Figure 3 This is a low-magnification SEM image of the as-cast high-entropy tungsten alloy prepared in this embodiment. As can be seen from the image, the prepared high-entropy tungsten alloy sample has high density and is free of defects such as pores and cracks.

[0064] Example 3

[0065] Ingredients: The raw material powder is prepared by mixing the raw material powder in a molar ratio of 40% W, 24% Ta, 20% Cr, 7% V and 9% Ti. The purity of the prepared material is 99.95%, and the initial total weight is 3 kg.

[0066] S1. Pour the above-mentioned materials into a horizontal ball mill jar for mixing. The rotation speed of the horizontal ball mill jar is 190 r / min, and the ball milling time is 15 h to obtain powder raw materials.

[0067] S2. The uniformly mixed powder raw material is subjected to cold isostatic pressing at a rate of 15 MPa / min; when the pressure reaches 190 MPa, it is held at this pressure for 15 min to form a rod-shaped blank.

[0068] S3. The rod-shaped pressed billet is placed in a medium-frequency sintering furnace for pre-sintering. The temperature is raised from room temperature at a rate of 10°C / min. When the temperature reaches 1500°C, it is sintered at this temperature for 2 hours, and then cooled with the furnace.

[0069] S4. Place the sintered billet into a suspension melting furnace for melting. Before melting, evacuate the melting furnace to a vacuum degree of 3 x 10⁻⁶. -3 Pa, then argon gas is introduced to make the furnace pressure reach 0.02 MPa; each melting time is 3 minutes, and the ingots need to be turned upside down between each melting to make the components mix evenly; after melting 5 times, it is naturally cooled.

[0070] S5. Samples were taken from the smelted ingots, and the surfaces of the samples were polished. Then, the samples were placed in a vacuum annealing furnace for solution treatment. The temperature was raised from room temperature to 1300℃ at a rate of 10℃ / min, and the solution treatment was carried out at 1300℃ for 3 hours. The samples were then cooled in the furnace to obtain a high-entropy tungsten alloy with uniform composition. However, because Ti readily absorbs oxygen, the final high-entropy tungsten alloy sample contained 0.3–0.5 wt% oxygen.

[0071] Example 4

[0072] Ingredients: The raw material powder is prepared by mixing the raw material powder in the proportion of 33% W, 36% Ta, 15% Cr, 6% V and 10% Mo by molar amount. The purity of the prepared material is 99.95% and the initial total weight is 3 kg.

[0073] S1. Pour the above-prepared materials into a horizontal ball mill jar for mixing. The rotation speed of the horizontal ball mill jar is 170 r / min, and the ball milling time is 18 h to obtain powder raw materials.

[0074] S2. The uniformly mixed powder raw material is subjected to cold isostatic pressing at a rate of 16 MPa / min; when the pressure reaches 180 MPa, it is held at this pressure for 20 minutes to form a rod-shaped blank.

[0075] S3. The rod-shaped pressed billet is placed in a medium-frequency sintering furnace for pre-sintering. The temperature is raised from room temperature at a rate of 13°C / min. When the temperature reaches 1550°C, it is sintered at this temperature for 2 hours and then cooled with the furnace.

[0076] S4. Place the sintered billet into a suspension melting furnace for melting. Before melting, evacuate the melting furnace to a vacuum degree of 3 x 10⁻⁶. -3 Pa, then argon gas is introduced to make the furnace pressure reach 0.03 MPa; each melting time is 3 minutes, and the ingots need to be turned upside down between each melting to make the components mix evenly; after melting 3 times, it is naturally cooled.

[0077] S5. Samples were taken from the smelted ingots, and the surfaces of the samples were polished. Then, the samples were placed in a vacuum annealing furnace for solution treatment. The temperature was raised from room temperature to 1250℃ at a rate of 10℃ / min, and the solution treatment was carried out at 1250℃ for 3 hours. The samples were then cooled in the furnace to obtain a high-entropy tungsten alloy with uniform composition and no obvious segregation. The high-entropy tungsten alloy sample contained 0.1 wt% oxygen.

[0078] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above descriptions are merely specific embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A high-entropy alloy, characterized in that, The molar mass contains 20-50% W, 20-50% Ta, 2-20% Cr, 2-15% V, 0-15% Ti, 0-15% Mo and unavoidable impurities; The impurities are C, N, H, and O elements; the O element content in the high-entropy alloy is ≤0.5wt%; the high-entropy alloy has a BCC single-phase crystal structure. The method for preparing the high-entropy alloy includes the following steps: S1. Prepare and mix W, Ta, Cr, V, Ti and Mo in proportion to obtain powder raw materials; S2. The powdered raw material is pressed to obtain a rod-shaped blank; S3. Pre-sinter the rod-shaped billet; the pre-sintering includes heating sintering and high-temperature sintering; the heating rate of the heating sintering is 8~15℃ / min; the temperature of the high-temperature sintering is 1200~1650℃, and the high-temperature sintering time is 2h; S4. The pre-sintered rod-shaped billet is melted to obtain an ingot; S5. Take a sample of the ingot and perform solid solution treatment at 1000~1500℃ to obtain a high-entropy alloy; The temperature is increased at a rate of 10℃ / min before solid solution treatment; the solid solution time is 0.5~3h; and the vacuum degree of solid solution treatment is 1~5Pa.

2. The high-entropy alloy as described in claim 1, characterized in that, The purity of the raw materials is ≥99.95%; The weight of the prepared materials is greater than 1 kg; The mixing time is 13-19 hours.

3. The high-entropy alloy as described in claim 1, characterized in that, The pressing method is cold isostatic pressing; the cold isostatic pressing includes a pressure increase process and a pressure holding process.

4. The high-entropy alloy as described in claim 3, characterized in that, The rate of pressure increase is 10~15 MPa / min; The pressure for holding pressure is 160~200 MPa; The pressure holding time is 9 to 30 minutes.

5. The high-entropy alloy as described in claim 1, characterized in that, The smelting operation involves first evacuating the smelting furnace to a vacuum level of 1×10⁻⁶. -3 ~5×10 -3 Pa, and argon gas is introduced to a pressure of 0.01~0.1MPa; then the sintered billet is placed in a suspension melting furnace, the melting ingot is turned upside down, and then cooled naturally; The melting time is 3 minutes; The number of smelting operations is ≥3.

Images