WxNbZrTiTa high-entropy alloy and preparation method thereof

Abstract

The invention relates to the field of high-entropy alloy materials, in particular to a WxNbZrTiTa high-entropy alloy and a preparation method thereof. The alloy is composed of five elements of W, Nb, Zr, Ti and Ta, the chemical formula of the alloy is WxNbZrTiTa, and x is equal to 0.05-1. The alloy comprises the following chemical components in molar ratio: 0.05 to 1 percent of W, 0.9 to 1.2 percent of Nb, 0.9 to 1.2 percent of Zr, 0.9 to 1.2 percent of Ti and 0.9 to 1.2 percent of Ta. Elemental metal with the purity not lower than 99.9 wt% is taken and prepared according to nominal chemical components, alloy is prepared into an alloy ingot through vacuum electric arc melting, and the alloy ingot is condensed into a conical sample in a crucible. Compared with a traditional metal material, the high-entropy alloy is of a single centered cubic phase structure and has the excellent performance of high hardness, high density, high strength, high wear resistance, high corrosion resistance and the like at the room temperature.

Description

Technical Field

[0001] The present invention relates to the field of high-entropy alloy materials, and particularly to a W x NbZrTiTa high-entropy alloy and a preparation method thereof. Background Art

[0002] High-entropy alloys are a brand-new alloy design concept proposed in the 1960s of the last century. Their compositional feature is that they are formed by five or more alloying elements in an equiatomic ratio or close to an equiatomic ratio. The unique compositional feature of high-entropy alloys endows them with four core effects: high-entropy effect, lattice distortion effect, sluggish diffusion effect, and cocktail effect. These effects enable high-entropy alloys to have advantages such as high strength, high hardness, high-temperature oxidation resistance, excellent corrosion resistance, good plasticity and workability, and asymmetric deformation. High-entropy alloys mainly consist of high-entropy alloys composed of metal elements such as Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, and W, and have excellent properties such as high hardness, high density, high strength, high wear resistance, and high corrosion resistance at room temperature. They have broad application potential in the fields of aerospace, national defense, energy, chemical industry, and automobiles. Through further optimization of alloying elements and improvement of preparation processes, it is expected to further improve the service performance of high-entropy alloys.

[0003] The patent with the publication number CN115533100A proposes a porous Ti-Zr-Nb-Ta high-entropy alloy and a preparation method thereof, for preparing a porous Ti-Zr-Nb-Ta high-entropy alloy for biomedical use, using MgO as a pore-forming agent, and forming a porous structure through spark plasma sintering and acid etching. Since the alloy composition is a quaternary system of Ti-Zr-Nb-Ta and does not add the W element, the yield strength cannot be improved through the solid solution strengthening effect of W, and the application field is limited to low-strength bionic bone materials and cannot meet the high-strength requirements such as aerospace.

[0004] The patent with the publication number CN117900363A proposes a hot extrusion forming method for a NbZrTi-based refractory high-entropy alloy conical thin-walled part. Since the alloy composition is a ternary system of Nb-Zr-Ti and does not introduce the Ta element, the synergistic strengthening effect of high-melting-point elements is lacking; although the addition of the W element is allowed, the optimization effect of the W element on the room-temperature mechanical properties is not clear, and the core is to solve the problems of tissue uniformity and surface quality during the forming process. In addition, its preparation process focuses on the control of tissue uniformity after hot extrusion forming and does not involve the vacuum melting process, and cannot solve the problems of coarse as-cast structure and composition segregation.

[0005] The patent with the publication number CN118880150A proposes a W-Ti-Zr-Mo-based energetic high-entropy alloy with excellent strength and plasticity and its density adjustment method. Since the alloy composition is a quaternary system of W-Ti-Zr-Mo and does not contain Nb and Ta elements, the synergistic strengthening effect of W with Nb and Ta cannot be obtained, and aiming at forming a BCC+LAVES duplex structure, high strength under a single BCC structure has not been achieved. Summary of the Invention

[0006] The purpose of the present invention is to provide a W x NbZrTiTa high-entropy alloy and its preparation method, which solves the problem that it is difficult to balance the strength and plasticity of high-entropy alloys. By adding W element to the NbZrTiTa high-entropy alloy, the yield strength and room-temperature mechanical properties of the alloy are improved.

[0007] In order to achieve the above purpose, the technical solutions adopted by the present invention are as follows:

[0008] A W x NbZrTiTa high-entropy alloy, which is composed of five elements: W, Nb, Zr, Ti, and Ta. The chemical formula of the alloy is W x NbZrTiTa, where x = 0.05 - 1.

[0009] The described W x NbZrTiTa high-entropy alloy, calculated by molar ratio, the chemical composition of the alloy is as follows: W 0.05 - 1, 0.9 - 1.2 Nb, 0.9 - 1.2 Zr, 0.9 - 1.2 Ti, 0.9 - 1.2 Ta.

[0010] The described W x NbZrTiTa high-entropy alloy, preferably, W 0.05 - 0.45.

[0011] The described W x NbZrTiTa high-entropy alloy, when the W content in the alloy is 0.1 - 0.4, with the increase of the W content, the yield strength of the alloy at room temperature increases from 1176.39 MPa to 1858.23 MPa, and when the W content is 0.3, the yield strength reaches the maximum of 1939.02 MPa.

[0012] The preparation method of the described W x NbZrTiTa high-entropy alloy, this method includes the following steps:

[0013] (1) Batching: Calculate and accurately weigh the raw materials of W, Nb, Zr, Ti, and Ta elements according to the molar ratio of each element in the alloy;

[0014] (2) Melting of alloy ingot: Place the elemental raw materials weighed in step (1) in a water-cooled copper crucible in ascending order of melting point from bottom to top; evacuate the furnace chamber to a pressure of 3×10 -3 Pa to 4×10 -3 Pa, and then introduce high-purity argon with a volume purity of 99.99% as the protective gas until the furnace pressure reaches -50 KPa to -100 KPa and stop inflation; when starting melting, first melt the elemental raw materials in the copper crucible; after all the raw materials are melted to form an alloy, wait for it to cool, use a robotic arm to flip the alloy ingot, and melt it again. The melting current is 1800 - 2400 A, and repeat melting 3 - 5 times to finally obtain the alloy ingot;

[0015] (3) Melting of master alloy: Place the melted alloy ingot in a water-cooled copper crucible of a large-sized conical mold, evacuate the furnace chamber to a pressure of 3×10 -3 Pa to 4×10 -3 Pa, and then fill with high-purity argon to -50 KPa to -100 KPa; melt the alloy ingot with a current of 1800 - 2400 A and repeat melting 3 - 5 times; after confirming uniformity, wait for it to cool to obtain the W x NbZrTiTa high-entropy alloy with uniform structure.

[0016] For the preparation method of the W x NbZrTiTa high-entropy alloy, in step (1), the elemental raw materials in the high-entropy alloy are single-element metals of W, Nb, Zr, Ti, and Ta with a purity not lower than 99.9 wt%.

[0017] For the preparation method of the W x NbZrTiTa high-entropy alloy, in step (1), before using each elemental raw material, first remove the oxide scale on the surfaces of the W, Nb, Zr, Ti, and Ta raw materials by mechanical polishing method, then ultrasonically clean them in ultrapure water and absolute ethanol in sequence, and finally take them out and dry.

[0018] The design concept of the present invention is as follows:

[0019] Based on the Nb-Zr-Ti-Ta quaternary alloy, the present invention first introduces the W element (x = 0.05 - 1). Through the solid solution strengthening effect of W, the yield strength and hardness are significantly improved, while maintaining the single-phase BCC structure and avoiding the decrease in plasticity caused by the duplex structure. In addition, the present invention adopts a multi-step vacuum melting process of "alloy ingot + master alloy melting", combined with high-purity argon protection, effectively eliminates composition segregation and realizes structural uniformity. Therefore, by introducing the W element into the Nb-Zr-Ti-Ta system and optimizing the melting process, the present invention solves the problem that it is difficult to balance the strength and plasticity of existing high-entropy alloys.

[0020] The advantages and beneficial effects of the present invention are as follows:

[0021] 1. The present invention is based on a Nb-Zr-Ti-Ta quaternary alloy. By adding an appropriate proportion of W element to the quaternary alloy and eliminating composition segregation through a two-step melting process, the synergistic improvement of yield strength and plasticity is achieved, thereby enhancing the yield strength and room-temperature mechanical properties of the alloy.

[0022] 2. The W x NbZrTiTa high-entropy alloy has a single body-centered cubic phase structure. Through the synergistic effect of Nb, Ta, and W, a higher yield strength is achieved in the single BCC structure, avoiding performance fluctuations that may be brought about by a duplex structure. Compared with traditional metal materials, it has excellent properties such as high hardness, high density, high strength, high wear resistance, and high corrosion resistance at room temperature, providing a more superior material choice for the application of high-entropy alloys in high-end fields such as aerospace. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 is the XRD pattern of as-cast W x NbZrTiTa high-entropy alloy.

[0024] Figure 2 is the microstructure diagram of as-cast W x NbZrTiTa high-entropy alloy; among them, (a) W 0.1 NbZrTiTa microstructure, (b) W 0.2 NbZrTiTa microstructure, (c) W 0.3 NbZrTiTa microstructure, (d) W 0.4 NbZrTiTa microstructure.

[0025] Figure 3 is the compressive stress-strain curve of as-cast W x NbZrTiTa high-entropy alloy at room temperature.

[0026] Figure 4 is the variation curve of the yield strength of as-cast W x NbZrTiTa high-entropy alloy with the W content.

[0027] Figure 5 is the variation curve of the hardness of as-cast W x NbZrTiTa high-entropy alloy with the W content.

[0028] Figure 6 is the variation curve of the density of as-cast W x NbZrTiTa high-entropy alloy with the W content. DETAILED DESCRIPTION OF THE INVENTION

[0029] In a specific implementation process, a single metal with a purity of not less than 99.9 wt% is taken and configured according to the nominal chemical composition. The alloy is made into an alloy ingot by vacuum arc melting and condensed into a cone-shaped sample in a crucible.

[0030] Hereinafter, the present invention will be further described in detail with reference to the accompanying drawings and embodiments.

[0031] Example

[0032] This embodiment is W x The preparation method of NbZrTiTa high entropy alloy includes the following steps:

[0033] Step 1: Prepare the ingredients, remove the oxide scale on the surface of the pure metal raw materials of W, Nb, Zr, Ti and Ta by mechanical grinding, and then add ultrapure water and then add anhydrous ethanol for ultrasonic cleaning;

[0034] According to W 0.1 NbZrTiTa, W 0.2 NbZrTiTa、W 0.3 NbZrTiTa、W 0.4 To calculate the molar percentage of each element in the four alloys NbZrTiTa, the raw materials W, Nb, Zr, Ti and Ta were accurately weighed respectively.

[0035] Step 2: Melting of small alloy ingots: Place the raw materials of each element weighed in step (1) in a water-cooled small copper crucible in order from low to high melting point and from bottom to top; evacuate the furnace chamber to a pressure of 3.2×10 -3 Pa, and then introduce high-purity argon with a volume purity of 99.99% as a protective gas until the pressure in the furnace reaches a vacuum degree of -70KPa (relative pressure) and the inflation is stopped; when starting smelting, first melt the elemental raw materials in the copper crucible; after all the raw materials are melted to form an alloy, wait for it to cool, use a mechanical arm to turn the alloy ingot over, and smelt again, the smelting current is 1800-2400A, and repeat 4 times (smelting currents are 2400A, 2200A, 2000A, and 1800A respectively) to finally obtain a small alloy ingot;

[0036] Step 3: Master alloy smelting: Place the smelted small alloy ingots in a large-sized conical mold water-cooled copper crucible, and evacuate the furnace chamber to a pressure of 3.2×10 -3 Pa and then filled with high-purity argon to -70KPa; the small alloy ingot was quickly melted with a current of 1800-2400A and smelted four times (smelting currents were 2400A, 2200A, 2000A, and 1800A respectively); after cooling, four WxNbZrTiTa high-entropy alloy cone-shaped samples with uniform structure were obtained.

[0037] The microstructure formation test of the prepared alloy cone-shaped sample is as follows:

[0038] 1. Phase analysis was carried out using XRD, SmartLab SE, and Rigaku.

[0039] A cylindrical specimen with a diameter of Φ7mm and a height of 7mm was cut out along the axis from the high-entropy alloy conical-shaped sample. It was ground step by step with sandpapers of 240#, 600#, 1000#, 1500#, and 2000# to remove the oxide film on the matrix surface, polished with a polishing paste with a particle size of 2.5μm, then ultrasonically cleaned with absolute ethanol for 5 - 15 min to remove surface oil stains, and then tested. The X-ray source was Cu Kα ray, the scanning range was 10° - 90°, and the scanning speed was 5° / min.

[0040] As Figure 1 shown, it can be judged from the XRD pattern that the alloy is a single body-centered cubic structure (BCC), and with the increase of the W element, the alloy phase structure remains unchanged.

[0041] 2. Microstructure observation was carried out using a GeminiSEM 360 scanning electron microscope.

[0042] A cylindrical specimen with a diameter of Φ7mm and a height of 7mm was cut out along the axis from the high-entropy alloy conical-shaped sample. It was ground step by step with sandpapers of 240#, 600#, 1000#, 1500#, and 2000# to remove the oxide film on the matrix surface, polished with a diamond grinding and mechanical vibration paste with a particle size of 2.5μm, and the backscattered probe of scanning electron was used to observe the sample. As Figure 2 shown, it can be seen from the microstructure diagram that the matrix is a dendritic phase of BBC structure.

[0043] 3. Room-temperature static tests were carried out using a UTM-2000 universal testing machine.

[0044] A cylinder with a diameter of 3mm was cut out along the axis from the high-entropy alloy conical-shaped sample, and after being ground with a centerless grinder, it was cut into a cylindrical compression sample with a diameter of 3mm and a height of 9mm. The strain rate was 1×10 -3 , and a quasi-static compression test was carried out at room temperature. The results are as Figures 3 - 4 shown. It can be seen from the figure that among the four high-entropy alloys of W 0.1 NbZrTiTa, W 02 NbZrTiTa, W 03 NbZrTiTa, W 04 NbZrTiTa, adding W (the content x of the W element is 0.1, 0.2, 0.3, 0.4) can improve the yield strength of the alloy. The yield strength increases from 1176.39 MPa to 1858.23 MPa, and a small amount of addition can ensure the plasticity of the alloy, and the compression strain (deformation amount) reaches 8.24 - 17.06%. Especially when the content x of the W element is 0.3, W0.3 The yield strength of the NbZrTiTa high-entropy alloy reaches 1939.02 MPa, and the compressive strain (deformation amount) reaches 13.38%, showing better strength and plasticity.

[0045] 4. A Vickers hardness test was carried out using an HV-1000 manual turret microhardness tester.

[0046] A cylindrical specimen with a diameter of Φ7 mm and a height of 7 mm was cut out along the axis from the conical-shaped sample of the high-entropy alloy, and was ground step by step with sandpapers of 240#, 600#, 1000#, 1500# and 2000# to remove the oxide film on the substrate surface, and was polished with a polishing paste with a particle size of 2.5 μm. Then, it was ultrasonically cleaned with absolute ethanol for 5 - 15 min to remove the surface oil stain, and then the Vickers hardness test was carried out. The results are as Figure 5 shown. It can be seen from the figure that adding W (the content of W element x is 0.1, 0.2, 0.3, 0.4) can increase the Vickers hardness of the alloy, and the Vickers hardness reaches 394.88 - 533.5 HV. When the content of W element x is 0.3, the 0.3 Vickers hardness of the NbZrTiTa high-entropy alloy reaches a maximum of 555.12 HV.

[0047] 5. The density test was carried out using Archimedes' principle.

[0048] A cylindrical specimen with a diameter of Φ7 mm and a height of 7 mm was cut out along the axis from the conical-shaped sample of the high-entropy alloy, and then the density test was carried out. The results are as Figure 6 shown. It can be seen from the figure that with the increase of the W content (the content of W element x is 0.1, 0.2, 0.3, 0.4), the density of the high-entropy alloy shows a trend of first increasing and then decreasing, and the density range reaches 9.025 - 9.676 g·cm -3 . When the content of W element x is 0.3, the density of the high-entropy alloy reaches a maximum of 9.989 g·cm -3 .

[0049] The implementation results show that through the innovative addition of W element and the optimization of the multi-step melting process in the present invention, when the compressive deformation amount is more than 8%, the yield strength reaches more than 1175 MPa, the Vickers hardness reaches more than 390 HV, and the density reaches more than 9.0 g·cm -3 above, solving the core problems such as the strength-plasticity contradiction, density-property imbalance and insufficient tissue uniformity in the existing high-entropy alloys. On the basis of enhancing the strength performance, a certain plasticity is retained, so that the alloy can withstand large external forces during actual use and will not be easily broken due to excessive brittleness, achieving a good balance between strength and plasticity.

Claims

1. A W x NbZrTiTa high-entropy alloy, characterized in that This alloy is composed of five elements: W, Nb, Zr, Ti, and Ta, and the chemical formula of this alloy is W x NbZrTiTa, where x = 0.05 - 1.

2. The W according to claim 1 x NbZrTiTa high-entropy alloy, characterized in that In terms of molar ratio, the chemical composition of the alloy is as follows: 0.05 - 1 W, 0.9 - 1.2 Nb, 0.9 - 1.2 Zr, 0.9 - 1.2 Ti, 0.9 - 1.2 Ta.

3. The W according to claim 2 x NbZrTiTa high-entropy alloy, characterized in that Preferably, 0.05 - 0.45 W.

4. The W according to claim 2 x NbZrTiTa high-entropy alloy, characterized in that: When the W content in the alloy is 0.1 - 0.4, with the increase of the W content, the yield strength of the alloy at room temperature increases from 1176.39 MPa to 1858.23 MPa, and the yield strength reaches the maximum of 1939.02 MPa when the W content is 0.

3.

5. The W according to any one of claims 1 to 4 x A method for preparing NbZrTiTa high-entropy alloy, characterized in that The method comprises the following steps: (1) Charging: Calculate and accurately weigh the raw materials of elements W, Nb, Zr, Ti and Ta according to the molar ratio of each element in the alloy; (2) Alloy ingot melting: Place the elemental raw materials weighed in step (1) in a water-cooled copper crucible in ascending order of melting point from bottom to top; evacuate the furnace chamber to a pressure of 3×10 -3 Pa to 4×10 -3 Pa, then introduce high-purity argon with a volume purity of 99.99% as the protective gas until the furnace pressure reaches -50KPa to -100KPa and stop inflating; at the start of melting, first melt the elemental raw materials in the copper crucible; after all the raw materials are melted to form an alloy, wait for it to cool, use a robotic arm to flip the alloy ingot, and melt it again. The melting current is 1800 - 2400A, and repeat the melting 3 - 5 times to finally obtain the alloy ingot; (3) Master alloy melting: Place the melted alloy ingot in a large-sized conical mold water-cooled copper crucible, evacuate the furnace cavity to a pressure of 3×10 -3 Pa to 4×10 -3 Pa, and then fill it with high-purity argon gas to -50 KPa to -100 KPa; melt the alloy ingot with a current of 1800 to 2400 A, and repeat the melting 3 to 5 times; after confirming uniformity, wait for it to cool to obtain the W x NbZrTiTa high-entropy alloy with uniform structure.

6. The W according to claim 5 x A method for preparing an NbZrTiTa high-entropy alloy, characterized in that In step (1), the raw materials of each element in the high-entropy alloy are single metals of W, Nb, Zr, Ti and Ta with a purity of not less than 99.9 wt%.

7. The W according to claim 5 x A method for preparing an NbZrTiTa high-entropy alloy, characterized in that In step (1), before using the raw materials of each element, first remove the oxide scale on the surfaces of the raw materials of W, Nb, Zr, Ti and Ta by mechanical grinding method, then ultrasonically clean them in ultrapure water and anhydrous ethanol in sequence, and finally take them out and dry them.

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