A new type of high-strength and ductile single-phase refractory high-entropy alloy and its preparation method and application

Abstract

The present invention discloses a novel high-strength, high-ductility, single-phase refractory high-entropy alloy, its preparation method, and application, relating to the field of novel metal material technology. The high-entropy alloy is composed of the main elements Hf, Nb, Mo, Ta, and W; the composition of the high-entropy alloy is as follows: Hf: 2.5-40 at.%, Nb: 2.5-15 at.%, Mo: 2.5-40 at.%, Ta: 15-40 at.%, W: 2.5-40 at.%, totaling 100 at.%. The high-entropy alloy provided by the present invention has a simple, single-phase, body-centered cubic structure and exhibits high compressive strength and good compression plasticity at room temperature.

Description

Technical Field

[0001] The present invention relates to the technical field of novel metal materials, and in particular to a novel high-strength and plastic single-phase refractory high-entropy alloy, a preparation method thereof, and an application thereof. Background Art

[0002] High-entropy alloys (HEAs) have changed traditional design rules. They are typically composed of four or more alloy materials and possess unique structural characteristics and excellent mechanical properties. Existing HEAs can be divided into two categories based on their elements: one is composed of transition metals, such as Co, Cr, Cu, Fe, and Ni-based HEAs; the other is composed of refractory elements, such as molybdenum, titanium, vanadium, niobium, hafnium, tantalum, chromium, and tungsten. These alloys are called refractory HEAs, and are composed of high-melting-point elements like molybdenum, titanium, vanadium, niobium, hafnium, tantalum, chromium, and tungsten [Xiong W, Guo AXY, Zhan S, et al. Refractory high-entropy alloys: A focused review of preparation methods and properties [J]. Journal of Materials Science & Technology, 2023, 142:196-215.]. Due to the high melting points of their constituent elements, refractory HEAs generally exhibit excellent high-temperature performance and resistance to high-temperature oxidation. Refractory HEAs are considered a new class of alloys for high-temperature applications, potentially surpassing nickel-based superalloys. Therefore, the development of refractory HEAs is of great significance and holds broad application prospects in high-temperature applications.

[0003] Senkov et al. first proposed the concept of refractory high entropy alloys and designed Nb 25 Mo 25 Ta 25 W 25 andV 20 Nb 20 Mo 20 Ta 20 W 20Two refractory high entropy alloys can maintain good high-temperature properties at high temperatures, which are superior to conventional high-temperature alloys. However, they are prone to brittle fracture at room temperature and have a compression plasticity of less than 2%, which greatly limits the application of these alloys [Senkov ON, Wilks GB, Scott JM, et al. Mechanical properties of Nb25Mo25Ta25W25 and V20Nb20Mo20Ta20W20 refractory high entropy alloys [J]. Intermetallics, 2011, 19(5): 698-706.]. Many studies hope to improve the properties of NbMoTaW high entropy alloys by alloying. For the equiatomic ratio HfNbMoTaW high entropy alloy, by adding the high-melting-point Hf element, it is hoped that its room-temperature properties will be improved while maintaining its high-temperature properties. Studies have shown that although the room temperature performance of HfNbMoTaW has been slightly improved, its room temperature compressive strain is still less than 6% [Tong Y, Bai L, Liang X, et al. Influence of alloying elements on mechanical and electronic properties of NbMoTaWX (X = Cr, Zr, V, Hf and Re) refractory highentropy alloys [J]. Intermetallics, 2020, 126.], and further composition adjustment is needed to improve the performance of NbMoTaW high entropy alloys. Summary of the Invention

[0004] In order to solve the room temperature brittleness problem of HfNbMoTaW with equal atomic ratio in the prior art, the present invention provides a new high-strength and plastic single-phase refractory high-entropy alloy and its preparation method and application, which has high compressive strength and good compression plasticity at room temperature.

[0005] The first object of the present invention is to provide a new high-strength and high-ductility single-phase refractory high-entropy alloy, which is composed of the main elements Hf, Nb, Mo, Ta, and W; the high-entropy alloy composition is: Hf: 2.5-40at.%, Nb: 2.5-15at.%, Mo: 2.5-40at.%, Ta: 15-40at.%, W: 2.5-40at.%, totaling 100at.%.

[0006] Preferably, the high entropy alloy comprises: Hf 40 Ta 40 Nb 15 Mo 2.5 W 2.5 , Hf2.5 Nb 2.5 Mo 40 Ta 15 W 40 、Hf5Nb 12.5 Mo 25 Ta 27.5 W 30 , Hf 10 Nb5Mo 22.5 Ta 30 W 32.5 , Hf 12.5 Nb 15 Mo 27.5 Ta 32.5 W 12.5 , Hf 15 Nb 7.5 Mo 20 Ta 30 W 27.5 , Hf 25 Nb 10 Mo 35 Ta 10 W 20 , Hf 35 Nb 10 Mo 20 Ta 17.5 W 17.5 , Hf 17.5 Nb 12.5 Mo 22.5 Ta 7.5 W 40 , Hf 20 Nb 10 Mo 20 Ta 35 W 15 , Hf 22.5 Nb 7.5 Mo 15 Ta 22.5 TaW 32.5 .

[0007] Preferably, the high entropy alloy has a compressive strength of more than 1500 MPa at room temperature, a compressive strain energy of more than 30%, and a hardness of 4305 to 4580 MPa.

[0008] Preferably, the as-cast microstructure of the high entropy alloy is a single-phase body-centered cubic structure.

[0009] A second object of the present invention is to provide a method for preparing a novel high-strength, high-ductility, single-phase refractory high-entropy alloy, comprising the following steps:

[0010] The metal raw materials of each alloying element are weighed and placed in a crucible of a vacuum arc melting furnace. The sample chamber of the arc melting furnace is evacuated, and high-purity argon gas with a purity of ≥99.9% is filled into the sample chamber for vacuum arc melting. After the alloy raw materials are completely melted, smelting is carried out. Each alloy ingot is melted at least 5 times; thus, a new high-strength and high-ductility single-phase refractory high-entropy alloy is obtained.

[0011] Preferably, before placing the metal raw material in the vacuum arc melting furnace, the process further includes removing the oxide layer on the surface of the metal raw material with sandpaper, ultrasonically cleaning the polished raw material in ethanol, and finally taking out the raw material and air-drying or blow-drying it.

[0012] Preferably, in the process of weighing the metal raw materials of each alloying element, the masses of Hf, Nb, Mo, Ta and W required for each alloy are calculated according to the atomic ratio of the designed components, and then weighed and proportioned.

[0013] Preferably, the pressure of the sample chamber of the arc melting furnace is pumped down to 5×10 -3 Pa.

[0014] Preferably, the smelting temperature is 3000-3500°C.

[0015] The third object of the present invention is to provide a new type of high-strength and high-ductility single-phase refractory high-entropy alloy for use in the aerospace field.

[0016] Compared with the prior art, the present invention has the following beneficial effects:

[0017] The present invention provides a novel high-strength and plastic single-phase refractory high-entropy alloy. The five alloying elements Hf, Nb, Mo, Ta, and W are all refractory elements with relatively high melting points, and the prepared alloy may have good resistance to high-temperature softening. The cast microstructure of the high-entropy alloy provided by the present invention is a single-phase body-centered cubic structure with a simple structure. By selecting alloy components with high predicted Young's modulus and low valence electron concentration values, it is predicted that they will have high strength and good plasticity. Experiments have confirmed that the designed Hf-Nb-Mo-Ta-W system alloy has high compressive strength and good compression plasticity at room temperature. The alloy of the present invention is prepared by vacuum arc melting, the preparation method is simple, and it has prospects for large-scale application.

[0018] The novel high-strength, ductile, single-phase refractory high-entropy alloy provided by the present invention has potential application prospects in aerospace (turbines, engine blades), nuclear industry, biomedicine and other fields. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 This is the composition design diagram of a new type of high-strength and ductile single-phase refractory high-entropy alloy.

[0020] Figure 2is Hf in Example 1 40 Ta 40 Nb 15 Mo 2.5 W 2.5 X-ray diffraction (XRD) patterns of refractory high-entropy alloys.

[0021] Figure 3 is Hf in Example 1 40 Ta 40 Nb 15 Mo 2.5 W 2.5 EDS spectrum of refractory high entropy alloy.

[0022] Figure 4 is Hf in Example 1 40 Ta 40 Nb 15 Mo 2.5 W 2.5 Room temperature compressive stress-strain curves of the refractory high entropy alloy and the high entropy alloy provided in Comparative Example 1.

[0023] Figure 5 is Hf in Example 2 2.5 Nb 2.5 Mo 40 Ta 15 W 40 X-ray diffraction (XRD) patterns of refractory high-entropy alloys.

[0024] Figure 6 is Hf in Example 2 2.5 Nb 2.5 Mo 40 Ta 15 W 40 EDS spectrum of refractory high entropy alloy.

[0025] Figure 7 is Hf in Example 2 2.5 Nb 2.5 Mo 40 Ta 15 W 40 Room temperature compressive stress-strain curves of the refractory high entropy alloy and the high entropy alloy provided in Comparative Example 2. DETAILED DESCRIPTION

[0026] The present invention is described in detail below with reference to the accompanying drawings and specific embodiments so that those skilled in the art can better understand the present invention and implement it. However, the embodiments are not intended to limit the present invention.

[0027] The present invention provides a novel high-strength and high-plasticity single-phase refractory high-entropy alloy, which is composed of the main elements Hf, Nb, Mo, Ta, and W. The high-entropy alloy composition is: Hf: 2.5-40 at.%, Nb: 2.5-15 at.%, Mo: 2.5-40 at.%, Ta: 15-40 at.%, W: 2.5-40 at.%, totaling 100 at.%.

[0028] The high entropy alloy comprises: Hf 40 Ta 40 Nb 15 Mo 2.5 W 2.5 , Hf 2.5 Nb 2.5 Mo 40 Ta 15 W 40 、Hf5Nb 12.5 Mo 25 Ta 27.5 W 30 , Hf 10 Nb5Mo 22.5 Ta 30 W 32.5 , Hf 12.5 Nb 15 Mo 27.5 Ta 32.5 W 12.5 , Hf 15 Nb 7.5 Mo 20 Ta 30 W 27.5 , Hf 25 Nb 10 Mo 35 Ta 10 W 20 , Hf 35 Nb 10 Mo 20 Ta 17.5 W 17.5 , Hf 17.5 Nb 12.5 Mo 22.5 Ta 7.5 W 40 , Hf 20 Nb 10 Mo 20 Ta 35 W 15 , Hf 22.5 Nb 7.5 Mo 15 Ta 22.5 TaW 32.5 .

[0029] The raw materials used in the following examples are all metal raw materials with a purity of ≥99.95%.

[0030] The cast structure of the high entropy alloy provided by the present invention is a single-phase body-centered cubic structure with a simple structure. By selecting alloy components with high predicted Young's modulus and low valence electron concentration values, such as Figure 1 As shown, they are predicted to have high strength and good plasticity. Experiments have confirmed that the designed Hf-Nb-Mo-Ta-W alloy has high compressive strength and good compression plasticity at room temperature. The alloy of the present invention is prepared by vacuum arc melting, which is simple and has the prospect of large-scale application.

[0031] Example 1

[0032] A new type of high-strength and high-ductility single-phase refractory high-entropy alloy, the chemical formula of which is Hf 40 Ta 40 Nb 15 Mo 2.5 W 2.5 , wherein the atomic percentages of the alloy elements are: Hf: 40 at.%, Nb: 15 at.%, Mo: 2.5 at.%, Ta: 40 at.%, and W: 2.5 at.%.

[0033] A type of Hf 40 Ta 40 Nb 15 Mo 2.5 W 2.5 A method for preparing a novel high-strength, high-ductility, single-phase refractory high-entropy alloy comprises the following steps:

[0034] 1) Using alloying elements with a purity of 99.9 wt.% or more as raw materials, remove the oxide layer on the surface of Hf, Nb, Mo, Ta, and W with sandpaper, then ultrasonically clean the polished raw materials in ethanol, and finally remove the raw materials and air-dry or blow-dry them;

[0035] 2) According to Hf 40 Ta 40 Nb 15 Mo 2.5 W 2.5 Calculate the mass of Hf, Nb, Mo, Ta and W required for each alloy by atomic ratio, and then weigh and proportion them;

[0036] 3) The metal raw materials of each metallurgical element are placed in a crucible of a vacuum arc melting furnace, and the sample chamber of the arc melting furnace is evacuated. Finally, high-purity argon gas with a purity of ≥99.9% is filled into the sample chamber until the gauge pressure in the furnace reaches -0.05 MPa;

[0037] 4) Vacuum arc melting: to ensure uniform alloy composition, after the alloy raw materials are completely melted, heat at 3000℃

[0038] The smelting was repeated several times with a smelting current of 400-600A. Each alloy ingot was smelted 7 times with each smelting lasting 3 minutes. Electromagnetic stirring was also turned on for stirring. When the sample chamber cooled to room temperature, the smelted Hf 40 Ta 40 Nb 15 Mo 2.5 W 2.5 Refractory high entropy alloy; wherein each alloy ingot refers to the alloy ingot obtained after each smelting.

[0039] Example 2

[0040] A new type of high-strength and high-ductility single-phase refractory high-entropy alloy, the chemical formula of which is Hf 2.5 Nb 2.5 Mo 40 Ta 15 W 40 , wherein the atomic percentages of the alloy elements are: Hf: 2.5 at.%, Nb: 2.5 at.%, Mo: 40 at.%, Ta: 15 at.%, and W: 40 at.%.

[0041] A type of Hf 2.5 Nb 2.5 Mo 40 Ta 15 W 40 A method for preparing a novel high-strength, high-ductility, single-phase refractory high-entropy alloy comprises the following steps:

[0042] 1) Using alloying elements with a purity of 99.9 wt.% or more as raw materials, remove the oxide layer on the surface of Hf, Nb, Mo, Ta, and W with sandpaper, then ultrasonically clean the polished raw materials in ethanol, and finally remove the raw materials and air-dry or blow-dry them;

[0043] 2) According to Hf 2.5 Nb 2.5 Mo 40 Ta 15 W 40 Calculate the mass of Hf, Nb, Mo, Ta and W required for each alloy by atomic ratio, and then weigh and proportion them;

[0044] 3) The metal raw materials of each metallurgical element are placed in a crucible of a vacuum arc melting furnace, and the sample chamber of the arc melting furnace is evacuated. Finally, high-purity argon gas with a purity of ≥99.9% is filled into the sample chamber until the gauge pressure in the furnace reaches -0.05 MPa;

[0045] 4) Vacuum arc melting: to ensure uniform alloy composition, after the alloy raw materials are completely melted, heat at 3000℃

[0046] The smelting was repeated several times with a smelting current of 400-600A. Each alloy ingot was smelted 7 times with each smelting lasting 3 minutes. Electromagnetic stirring was also turned on for stirring. When the sample chamber cooled to room temperature, the smelted Hf 2.5 Nb 2.5 Mo 40 Ta 15 W 40 Refractory high entropy alloy; wherein each alloy ingot refers to the alloy ingot obtained after each smelting.

[0047] Comparative Example 1

[0048] A HfNbMoTaW high-entropy alloy, see the literature Tong Y, Bai L, Liang X, et al. Influence of alloying elements on mechanical and electronic properties of NbMoTaWX (X = Cr, Zr, V, Hf and Re) refractory high entropy alloys [J]. Intermetallics, 2020, 126. In the literature, HfNbMoTaW alloy was prepared by arc melting using alloying elements with a purity of more than 99.9wt.% as raw materials and subjected to compression testing. The compressive yield strength was 1252MPa, there was no compressive plastic strain, and brittle fracture quickly occurred under compression conditions.

[0049] Comparative Example 2

[0050] A NbMoTaWHf x High entropy alloys, see the literature Mo J, Liang X, Shen B, et al. Locallattice distortions, phase stability, and mechanical properties of NbMoTaWHfxalloys: A combined theoretical and experimental study[J]. Computational Materials Science, 2023, 217, 111891. NbMoTaWHf was prepared by vacuum arc melting. xHigh-entropy alloys (x = 0, 0.27, 0.57, 0.92, 1.33, 1.82), with a purity of 99.9 wt.% for each alloying element. Compression tests were used to measure the alloy properties. Compared with the equiatomic ratio HfNbMoTaW alloy, although the strength is improved, the compression plasticity is still poor.

[0051] In order to illustrate the various properties of the novel high-strength and high-ductility single-phase refractory high-entropy alloy provided by the present invention, the novel high-strength and high-ductility single-phase refractory high-entropy alloy provided by Examples 1 and 2 and the high-entropy alloy provided by Comparative Examples 1 and 2 were analyzed for their relevant properties. Figures 2 to 7 shown.

[0052] (1) XRD analysis of alloy phase structure

[0053] Small cubes measuring 2 mm × 2 mm × 4 mm were cut from the resulting alloy ingot using an electric discharge cutter. These cubes were then sanded and polished using 400#, 800#, 1200#, and 2000# sandpaper, followed by cleaning with water and alcohol. The phase composition of the prepared samples was then analyzed using an X-ray diffractometer, scanning at a 2θ angle ranging from 20° to 100°.

[0054] like Figure 2 and Figure 5 As shown, from the XRD diffraction peak distribution, it can be concluded that Hf 40 Ta 40 Nb 15 Mo 2.5 W 2.5 and Hf 2.5 Nb 2.5 Mo 40 Ta 15 W 40 The high-entropy alloys all have a single-phase BCC structure. Jade software fitting calculations show that the lattice constants of the BCC phases of the two alloys are 2.938nm and 2.751nm, respectively.

[0055] (2) EDS energy spectrum analysis of alloy

[0056] The alloy ingot was cut into small cubes of 5mm×5mm×4mm using an electric spark cutting machine. These cubes were then sanded and polished with 400#, 800#, 1200#, and 2000# sandpaper, and cleaned with water and alcohol. The Hf was then analyzed using a scanning electron microscope. 40 Ta 40 Nb 15 Mo 2.5 W 2.5 and Hf 2.5 Nb 2.5 Mo 40 Ta 15 W40 The EDS patterns of the alloys are as follows: Figure 3 and Figure 6 shown.

[0057] Table 1 shows Hf 40 Nb 15 Mo 2.5 Ta 40 W 2.5 Actual elemental composition of cast refractory high entropy alloys (at.%)

[0058]

[0059] Table 2 shows Hf 2.5 Nb 2.5 Mo 40 Ta 15 W 40 Actual elemental composition of cast refractory high entropy alloys (at.%)

[0060]

[0061] (3) Hardness analysis of alloy

[0062] The sample size for alloy hardness analysis is a small square of 5mm×5mm×4mm. The sample is ground and polished with 400#, 800#, 1200# and 2000# sandpaper in sequence, and then rinsed with water and alcohol. The microhardness of the alloy is tested using a Vickers hardness tester. The load during the test is HV1, and the average value of the four points is taken as the final result. The test results show that Hf 40 Ta 40 Nb 15 Mo 2.5 W 2.5 and Hf 2.5 Nb 2.5 Mo 40 Ta 15 W 40 The hardness values ​​of the two alloys are 439.3±3.1HV and 467±7.4HV, respectively, which are converted into stress units as: 4305±38MPa and 4580±73MPa.

[0063] (4) Room temperature compression performance test of alloy

[0064] The room temperature compression test was conducted on a small square of 2 mm × 2 mm × 4 mm. The samples were sanded and polished with 400#, 800#, 1200#, and 2000# sandpaper, then ultrasonically treated with alcohol for 5 minutes and dried. The room temperature compression test was conducted using an Instron 5967 universal testing machine with a compression strain rate of 5×10 -4 / s, and three parallel samples were used for the test. Since a video extensometer was not used, the measured compressive strain was not accurate. We measured the Young's modulus of the alloy through nanoindentation experiments, and then used the Young's modulus calibration curve to calculate Hf. 40 Ta 40 Nb 15 Mo 2.5 W 2.5 and Hf 2.5 Nb 2.5 Mo 40 Ta 15 W 40 The compressive stress-strain curves of the alloys are shown in Figure 4 and Figure 7 The specific compression performance is shown in Table 3. Figure 4 Hf in Example 1 40 Ta 40 Nb 15 Mo 2.5 W 2.5 The compression strength and plasticity of the alloy are much higher than those of HfNbMoTaW and other atomic ratio alloys; Figure 7 In Example 2, Hf 2.5 Nb 2.5 Mo 40 Ta 15 W 40 Although the strength of the alloy is slightly lower than that of the Hf2.5NbMoTaW alloy in Comparative Example 2, the Hf 2.5 Nb 2.5 Mo 40 Ta 15 W 40 The compression plasticity is much higher than that of the alloy in Comparative Example 2.

[0065] Table 3 Hf 40 Ta 40 Nb 15 Mo 2.5 W 2.5 Room temperature compression properties of as-cast refractory high entropy alloys

[0066]

[0067] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as within the scope of protection of the present invention.

Claims

1. A new type of high-strength, high-ductility, single-phase refractory high-entropy alloy, characterized in that: The high entropy alloy is composed of main elements Hf, Nb, Mo, Ta, and W; the high entropy alloy composition is: Hf: 2.5-40 at.%, Nb: 2.5-15 at.%, Mo: 2.5-40 at.%, Ta: 15-40 at.%, W: 2.5-40 at.%, totaling 100 at.%; The high entropy alloy has a compressive strength of more than 1500 MPa at room temperature, a compressive strain energy of more than 30%, and a hardness of 4305 to 4580 MPa; The as-cast microstructure of the high entropy alloy is a single-phase body-centered cubic structure.

2. The novel high-strength and high-ductility single-phase refractory high-entropy alloy according to claim 1, characterized in that: Including high-strength alloys: Hf 40 Ta 40 Nb 15 Mo 2.5 W 2.5 , Hf 2.5 Nb 2.5 Mo 40 Ta 15 W 40 , Hf5Nb 12.5 Mo 25 Ta 27.5 W 30 , Hf 10 Nb5Mo 22.5 Ta 30 W 32.5 , Hf 12.5 Nb 15 Mo 27.5 Ta 32.5 W 12.5 , Hf 15 Nb 7.5 Mo 20 Ta 30 W 27.5 , Hf 35 Nb 10 Mo 20 Ta 17.5 W 17.5 , Hf 20 Nb 10 Mo 20 Ta 35 W 15 , Hf 22.5 Nb 7.5 Mo 15 Ta 22.5 W 32.5 .

3. A method for preparing the novel high-strength, high-ductility, single-phase refractory high-entropy alloy according to claim 1 or 2, characterized in that: The following steps are involved: The metal raw materials of each alloying element are weighed and placed in a crucible of a vacuum arc melting furnace. The sample chamber of the arc melting furnace is evacuated, and high-purity argon gas with a purity of ≥99.9% is filled into the sample chamber for vacuum arc melting. After the alloy raw materials are completely melted, smelting is carried out. Each alloy ingot is melted at least 5 times; thus, a new high-strength and high-ductility single-phase refractory high-entropy alloy is obtained.

4. The method for preparing the novel high-strength and high-ductility single-phase refractory high-entropy alloy according to claim 3, characterized in that: Before placing the metal raw materials in the vacuum arc melting furnace, the oxide layer on the surface of the metal raw materials is removed with sandpaper, the polished raw materials are then ultrasonically cleaned in ethanol, and finally the raw materials are taken out and air-dried or blow-dried.

5. The method for preparing the novel high-strength and high-ductility single-phase refractory high-entropy alloy according to claim 3, characterized in that: In the process of weighing the metal raw materials of each alloy element, the mass of Hf, Nb, Mo, Ta and W required for each alloy is calculated according to the atomic ratio of the designed composition, and then weighed and proportioned.

6. The method for preparing the novel high-strength and high-ductility single-phase refractory high-entropy alloy according to claim 3, characterized in that: The pressure of the sample chamber of the arc melting furnace was pumped down to 5×10 -3 Pa.

7. The method for preparing the novel high-strength and high-ductility single-phase refractory high-entropy alloy according to claim 3, characterized in that: The smelting temperature is 3000-3500°C.

8. Use of the novel high-strength, high-ductility, single-phase refractory high-entropy alloy according to claim 1 or 2 in the field of aerospace.

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