A refractory high-entropy alloy based on HfNbTaTiZrWV and its preparation method

Abstract

This invention relates to a refractory high-entropy alloy based on the HfNbTaTiZrWV system and its preparation method, belonging to the field of metallic materials. The alloying expression for the HfNbTaTiZrWV system refractory high-entropy alloy is Hf a Nb b Ta c Ti d Zr e W f V g In the expression, a, b, c, d, e, f, and g represent the atomic percentages of their respective components, satisfying the following conditions: a is 5–20, b is 5–20, c is 5–20, d is 5–20, e is 5–20, f is 5–35, g is 5–35, and the sum of a, b, c, d, e, f, and g is 100. The HfNbTaTiZrWV refractory high-entropy alloy of this invention possesses good plasticity and excellent room-temperature and high-temperature mechanical properties.

Description

Technical Field

[0001] This invention relates to a refractory high-entropy alloy based on HfNbTaTiZrWV and its preparation method, belonging to the field of metallic materials. Background Technology

[0002] High-entropy alloys (HEAs) generally refer to alloys containing five or more alloying elements, with each element comprising 5% to 35% (mole fraction). HEAs break through the traditional alloying design concept of single main elements in metallic materials, such as iron-based alloys, nickel-based alloys, and cobalt-based alloys. Compared to alloys with a single main element, HEAs extend from the edges and corners of the phase diagram to the center, significantly expanding the range of alloy design compositions. This has opened up entirely new avenues for the research and development of high-performance metallic materials, earning them the title of "King of Future Materials."

[0003] High-entropy alloys possess numerous superior properties due to their thermodynamic high-entropy effect, slow diffusion effect, lattice distortion effect, and cocktail effect. Refractory high-entropy alloys, primarily composed of refractory elements, exhibit good high-temperature strength and excellent fatigue resistance, making them promising high-temperature structural materials for next-generation aero-engines, such as turbine disks and turbine blades. They hold significant research value and have substantial potential for major applications.

[0004] However, refractory high-entropy alloy systems have a significant drawback: apart from HfNbTaTiZr alloys and their derivatives, which exhibit good room-temperature tensile plasticity, other alloy systems generally have relatively poor plasticity. Furthermore, while HfNbTaTiZr alloys show good plasticity, their strength at high temperatures is low, with compressive yield strengths of only 295 MPa and 92 MPa at 1000℃ and 1200℃, respectively (Microstructure and elevated temperature properties of a refractory TaNbHfZrTi alloy, 2012). This severely limits their application as high-temperature structural components in aerospace applications. Therefore, developing refractory high-entropy alloys that simultaneously possess good plasticity and high-temperature strength is of great importance. Summary of the Invention

[0005] The purpose of this invention is to provide a refractory high-entropy alloy based on the HfNbTaTiZrWV system, which solves the problem of low compressive yield strength of HfNbTaTiZr alloys at high temperatures in the prior art.

[0006] The second objective of this invention is to provide a method for preparing HfNbTaTiZrWV refractory high-entropy alloys, which is simple to operate, has precise composition control, uniform microstructure, and low impurity content.

[0007] To achieve the above objectives, the first technical solution of the present invention is as follows:

[0008] A refractory high-entropy alloy based on the HfNbTaTiZrWV system, with the alloy formula Hf a Nb b Ta c Ti d Zr e W f V g In the expression, a, b, c, d, e, f, and g represent the atomic percentages of each corresponding component, and satisfy the following conditions: a is 5–20, b is 5–20, c is 5–20, d is 5–20, e is 5–20, f is 5–35, g is 5–35, and the sum of a, b, c, d, e, f, and g is 100.

[0009] The HfNbTaTiZrWV-based refractory high-entropy alloy of this invention possesses good plasticity and excellent room-temperature and high-temperature mechanical properties. This invention utilizes HfNbTaTiZr as the matrix element, adds W to increase the alloy's melting point, thereby improving its high-temperature performance, and adds V to create uniformly distributed nanoparticles in the dendritic regions, refining the alloy microstructure and thus promoting increased hardness and strength.

[0010] More preferably, a is 7-19, b is 5-20, c is 7-18, d is 5-20, e is 7-18, f is 9-30, g is 5-30, and the sum of a, b, c, d, e, f, and g is 100.

[0011] The second technical solution of the present invention is:

[0012] A method for preparing an HfNbTaTiZrWV refractory high-entropy alloy includes the following steps: vacuum arc melting of raw materials Hf, Nb, Ta, Ti, Zr, W, and V. This invention obtains the HfNbTaTiZrWV refractory high-entropy alloy through vacuum arc melting. This preparation method is simple to operate, allows for precise composition control, produces uniform microstructure, and has low impurity content.

[0013] Preferably, during the smelting process, the high-melting-point raw material is placed on top of the low-melting-point raw material. This invention, by placing the high-melting-point raw material on top of the low-melting-point raw material during smelting, ensures that the high-melting-point alloying elements are fully melted, while reducing the volatilization of the low-melting-point alloying elements. This guarantees a more accurate and uniform alloy composition during smelting, thereby obtaining a high-performance HfNbTaTiZrWV series refractory high-entropy alloy.

[0014] To further reduce raw material loss and ensure accurate and uniform smelting, it is further preferred that the raw materials Hf, Nb, Ta, Ti, Zr, W, and V are arranged in descending order of melting point, from top to bottom as W, Ta, Nb, Hf, V, Zr, and Ti.

[0015] Preferably, the raw material is in granular and / or flake form.

[0016] More preferably, the purity of the raw material is >99.9%.

[0017] To ensure that the alloy is fully and uniformly melted, the melting current is preferably 200-500A.

[0018] To prevent oxidation of raw materials, preferably, during vacuum arc melting, a vacuum is first drawn and then an inert gas is introduced for melting.

[0019] Preferably, the pressure of the inert gas is controlled at 0.04-0.05 MPa.

[0020] To control the content of impurities such as oxygen in the alloy, preferably, the vacuum degree of the vacuuming is less than 3 × 10⁻⁶. -3 Pa.

[0021] To ensure that the alloy is fully and uniformly melted, it is further preferred that the alloy ingot be melted again after being obtained by melting, and the melting is repeated 7-9 times, with each melting lasting 1-2 minutes. Attached Figure Description

[0022] Figure 1 Example 1Hf of the present invention 15 Nb 15 Ta 15 Ti 15 Zr 15 W 15 V 10 Microstructure of a refractory high-entropy alloy;

[0023] Figure 2 Example 1Hf of the present invention 15 Nb 15 Ta 15 Ti 15 Zr 15 W 15 V 10 Compression curves of refractory high-entropy alloys at different temperatures. Detailed Implementation

[0024] This invention uses vacuum arc melting to prepare HfNbTaTiZrWV-based refractory high-entropy alloys.

[0025] In order to remove oxides from the surface of the metal raw materials, the preparation method of the present invention preferably includes the following steps: grinding, cleaning and drying the raw materials Hf, Nb, Ta, Ti, Zr, W and V before smelting.

[0026] Preferably, the cleaning is ultrasonic cleaning in anhydrous ethanol. This removes impurities and dirt from the surface of the raw materials.

[0027] To obtain metal raw materials with higher purity, the cleaning time is preferably 180-300 seconds.

[0028] Ti balls are placed separately in the electric arc furnace. Before alloy melting, the Ti balls are melted first to further consume the residual oxygen in the furnace. Specifically, after the arc is ignited, the high-purity titanium balls are melted until the titanium balls are melted and the liquid is observed to rotate uniformly for about 5 seconds. Then the sample (i.e., the Ti balls) is flipped and melted again.

[0029] The technical solution of the present invention will be further described below with reference to specific embodiments.

[0030] I. Specific embodiments of the HfNbTaTiZrWV refractory high-entropy alloy and its preparation method of the present invention are as follows:

[0031] Example 1

[0032] The HfNbTaTiZrWV refractory high-entropy alloy of this embodiment has the following alloying expression: Hf 15 Nb 15 Ta 15 Ti 15 Zr 15 W 15 V 10 .

[0033] The preparation method of the HfNbTaTiZrWV refractory high-entropy alloy in this embodiment adopts the following steps:

[0034] (1) Use a file to polish the surface of raw materials Hf, Nb, Ta, Ti, Zr, W and V with a purity greater than 99.9% to remove the oxide film and impurities on the surface;

[0035] (2) The polished materials were ultrasonically cleaned in anhydrous ethanol for 240 seconds; then they were placed in a drying oven to dry at 120°C for 10 minutes.

[0036] (3) Weigh each dried material using an electronic balance with an accuracy of 0.001g according to the mass fraction corresponding to the mole fraction (i.e. atomic percentage) in the alloy expression;

[0037] (4) According to their melting points, Ti, Zr, V, Hf, Nb, Ta, and W granular metal raw materials are placed into a water-cooled copper crucible in a non-consumable vacuum arc furnace in order of increasing melting point. A vacuum is then drawn until the vacuum level reaches 3 × 10⁻⁶. -3 The pressure is below 0.05 MPa, and then argon gas is introduced to make the furnace chamber pressure 0.05 MPa to start melting. The melting current is 400 A, and the melting time is 2 minutes. After the alloy cools down, the alloy is flipped using a flipping rod. This melting process is repeated 8 times to ensure that the alloy is fully and uniformly melted.

[0038] Example 2

[0039] The HfNbTaTiZrWV refractory high-entropy alloy of this embodiment has the following alloying expression: Hf 15 Nb 15 Ta 15 Ti 15 Zr 15 W 10 V 15 .

[0040] The preparation method of the HfNbTaTiZrWV refractory high-entropy alloy in this embodiment adopts the following steps:

[0041] (1) Use a file to polish the surface of raw materials Hf, Nb, Ta, Ti, Zr, W and V with a purity greater than 99.9% to remove the oxide film on the surface;

[0042] (2) The polished materials were ultrasonically cleaned in anhydrous ethanol for 180 seconds; then they were placed in a drying oven to dry at 120°C for 10 minutes.

[0043] (3) Weigh each dried material using an electronic balance with an accuracy of 0.001g according to the mass fraction corresponding to the mole fraction (i.e. atomic percentage) in the alloy expression;

[0044] (4) The weighed materials, in order of increasing melting point, are Ti, Zr, V, Hf, Nb, Ta, and W sheet metal raw materials and placed into a water-cooled copper crucible in a non-consumable vacuum arc furnace. A vacuum is then drawn until the vacuum level reaches 3 × 10⁻⁶. -3 The pressure is below 0.045 MPa, and then argon gas is introduced to make the furnace chamber pressure 0.045 MPa for melting. The melting current is 300 A, and the melting time is 1 minute. After the alloy cools, the alloy is flipped using a flipping rod. This melting process is repeated 7 times to ensure that the alloy is fully and uniformly melted.

[0045] Example 3

[0046] The HfNbTaTiZrWV refractory high-entropy alloy of this embodiment has the following alloying expression: Hf 19 Nb5Ta 18 Ti5Zr 18 W 30 V5.

[0047] The preparation method of the HfNbTaTiZrWV refractory high-entropy alloy in this embodiment is basically the same as that in Example 1, except that the melting current is 500A, the melting time is 2 minutes, and after the alloy cools down, the alloy is flipped using a flipping rod. This melting process is repeated 9 times.

[0048] Example 4

[0049] The HfNbTaTiZrWV refractory high-entropy alloy of this embodiment has the alloy formula Hf7Nb. 20 Ta7Ti 20 Zr7W9V 30 .

[0050] The preparation method of the HfNbTaTiZrWV refractory high-entropy alloy in this embodiment is basically the same as that in Example 1, except that the melting current is 200A, the melting time is 1 minute, and after the alloy cools, the alloy is flipped using a flipping rod. This melting process is repeated 9 times.

[0051] II. Comparative Example

[0052] Comparative Example 1

[0053] The HfNbTaTiZrW series refractory high-entropy alloy in this comparative example has the following alloying expression: Hf 15 Nb 15 Ta 15 Ti 15 Zr 15 W 25 .

[0054] The preparation method of the HfNbTaTiZrW refractory high-entropy alloy in this comparative example is the same as that in Example 1.

[0055] Comparative Example 2

[0056] The HfNbTaTiZrV system refractory high-entropy alloy in this comparative example has the following alloying expression: Hf 15 Nb 15 Ta 15 Ti 15 Zr 15 V 25 .

[0057] The preparation method of the HfNbTaTiZrV refractory high-entropy alloy in this comparative example is the same as that in Example 1.

[0058] Comparative Example 3

[0059] The HfNbTaTiZrWV system refractory high-entropy alloy in this comparative example has the following alloying expression: Hf 15 Nb 15 Ta 15 Ti 15 Zr 15 W 15 V 10 .

[0060] The preparation method of the HfNbTaTiZrWV system refractory high-entropy alloy in this comparative example adopts the following steps:

[0061] (1) Weigh and mix the elemental powders of Hf, Nb, Ta, Ti, Zr, W and V with a purity greater than 99.9% according to the proportion, and the powder particle size is 45-75μm;

[0062] (2) Place the weighed powder into a V-shaped powder mixer for mixing for 8 hours;

[0063] (3) The mixed powder is subjected to high-energy ball milling. The ball milling jar and grinding balls are made of stainless steel. The average diameter of the grinding balls is 10 mm. The ball-to-material mass ratio is 13:1. The speed of the ball milling jar is controlled at 120 r / min. The ball milling time is 30 h.

[0064] (4) The ball-milled powder is placed in a graphite mold for spark plasma sintering at a pressure of 25 MPa. The powder is held at 1400℃ for 10 min and then cooled to room temperature in the furnace.

[0065] III. Experimental Examples

[0066] This experiment determined the microstructure, morphology, and mechanical properties at room temperature and high temperature of the refractory high-entropy alloys obtained in Examples 1-4 and Comparative Examples 1-3.

[0067] Specific method: The microstructure of Example 1 was observed using a Phenom-XL scanning electron microscope (SEM), and the results are as follows. Figure 1 As shown.

[0068] An HV-1000A microhardness tester was used, with a load set to 1 kg and a loading time of 10 s. Nine points were randomly selected and evenly distributed on the test surface for testing, and the average value was taken as the test result. The results are shown in Table 1. Room temperature compression tests were performed using an E45-105 electronic universal testing machine at a strain rate of 10... -3 / s, deformation amount 40%, the results are shown in Table 1. Among them, ">40%" means that the sample has not been crushed when the compression amount is 40%.

[0069] As shown in Table 1, the refractory high-entropy alloy prepared by the method of the present application has better mechanical properties at room temperature and high temperature.

[0070] A high-temperature compression test was conducted on Example 1 using a Gleeble-3500 thermal simulation testing machine. Platinum-rhodium thermocouples were selected, the heating rate was 10℃ / s, the holding time was 5 min, and the vacuum degree was 10. -3 Pa, strain rate 10 -3 / s, deformation 50%. The dimensions of the room temperature high-temperature compression test specimens are all... The results are as follows Figure 2 As shown.

[0071] Table 1 Mechanical Properties

[0072]

[0073]

Claims

1. A HfNbTaTiZrWV system refractory high-entropy alloy, characterized in that, The alloy formula is Hf a Nb b Ta c Ti d Zr e W f V g In the expression, a, b, c, d, e, f, and g represent the atomic percentages of each corresponding component, and satisfy the following conditions: a is 19, b is 5, c is 18, d is 5, e is 18, f is 30, and g is 5; the alloy is prepared by vacuum arc melting, wherein the melting current is 500A and the number of repeated melting cycles is 9.

2. A method for preparing the HfNbTaTiZrWV system refractory high-entropy alloy as described in claim 1, characterized in that, The process includes the following steps: vacuum arc melting of raw materials Hf, Nb, Ta, Ti, Zr, W, and V.

3. The method for preparing the HfNbTaTiZrWV system refractory high-entropy alloy according to claim 2, characterized in that, During the smelting process, high-melting-point raw materials are smelted on top of low-melting-point raw materials.

4. The method for preparing the HfNbTaTiZrWV system refractory high-entropy alloy according to claim 3, characterized in that, When the raw materials Hf, Nb, Ta, Ti, Zr, W, and V are smelted, they are arranged in descending order of melting point, from top to bottom as W, Ta, Nb, Hf, V, Zr, and Ti.

5. The method for preparing the HfNbTaTiZrWV system refractory high-entropy alloy according to any one of claims 2-4, characterized in that, In vacuum arc melting, a vacuum is first drawn and then an inert gas is introduced for melting.

6. The method for preparing the HfNbTaTiZrWV system refractory high-entropy alloy according to claim 5, characterized in that, The pressure of the inert gas is controlled at 0.05 MPa.

7. The method for preparing the HfNbTaTiZrWV system refractory high-entropy alloy according to claim 5, characterized in that, The vacuum level of the vacuum pump is less than 3 × 10⁻⁶. -3 Pa.

8. The method for preparing the HfNbTaTiZrWV refractory high-entropy alloy according to any one of claims 2-4, characterized in that, After obtaining the alloy ingot through smelting, it is smelted again, and the smelting process is repeated 9 times, with each smelting lasting 2 minutes.

Images