A nano-scale ultrafine lamellar eutectic high entropy alloy and its preparation method

Abstract

A nano-scale ultra-fine lamellar eutectic high entropy alloy and its preparation method, relating to a nano-scale ultra-fine lamellar eutectic high entropy alloy and its preparation method. The purpose of the present invention is to solve the problem that the alloy grain size of the eutectic high entropy alloy is large and the lamellar spacing is wide, resulting in the inability to simultaneously obtain high strength and high plasticity. The chemical formula of the nano-scale ultra-fine lamellar eutectic high entropy alloy of the present invention is Al 1.25 CoCrFeNi3. The preparation method involves first melting an ingot in an electric arc furnace and using wire cutting to produce alloy bars. This is then induction-melted in a Bridgman furnace and then instantly quenched in a Ga-In solution to produce an ultrafine-grained eutectic high-entropy alloy. The eutectic high-entropy alloy prepared by the present invention has nanometer-scale flakes and exhibits excellent strength and ductility. The present invention has applications in the field of metal materials and their preparation.

Description

Technical Field

[0001] The invention relates to a nano-scale ultrafine lamellar eutectic high entropy alloy and a preparation method thereof. Background Art

[0002] As science and society progress, the demand for high-performance materials becomes increasingly stringent. Beyond meeting strength and ductility requirements, materials must also possess corrosion resistance, abrasion resistance, and oxidation resistance. Consequently, traditional metal design concepts are no longer able to keep pace with the times.

[0003] High-entropy alloys (HEAs) break with traditional alloy design concepts. Instead of using one or two principal elements as the primary component and adding trace elements to design the alloy, HEAs are composed of five or more elements, each of which can serve as a principal component. They are therefore also called multi-principal-component alloys. This cocktail effect allows HEAs to combine the excellent properties of each element. However, single-phase solid solutions, such as face-centered cubic HEAs, have high plasticity but low strength, while body-centered cubic HEAs have high strength but low plasticity. This mismatch between strength and plasticity has hindered the further development and engineering application of HEAs.

[0004] Eutectic high-entropy alloys (HEAs) typically consist of two phases, soft and hard, combining the strength and ductility advantages of both face-centered cubic and body-centered cubic HEAs. However, current methods for preparing eutectic HEAs, primarily arc melting and plasma sintering, result in large grain sizes and wide interlamellar spacing, making it difficult to achieve both strength and ductility. Due to these limitations, the compositional design of existing eutectic HEAs is primarily focused on maintaining a certain level of ductility, making it difficult to further enhance the alloy's strength. Summary of the Invention

[0005] The purpose of the present invention is to solve the problem that the alloy grain size of eutectic high entropy alloy is large and the interlamellar spacing is wide, which makes it impossible to obtain high strength and high plasticity at the same time. A nanoscale ultrafine lamellar eutectic high entropy alloy and its preparation method are provided.

[0006] The chemical formula of the nano-scale ultra-fine lamellar eutectic high entropy alloy of the present invention is Al 1.25 CoCrFeNi3.

[0007] The present invention provides a method for preparing a nano-scale ultrafine lamellar eutectic high entropy alloy, which is carried out according to the following steps:

[0008] 1. Weigh the raw materials according to the atomic ratio to obtain the raw materials;

[0009] 2. placing the raw materials into a tungsten electrode non-consumable vacuum melting furnace for ingot melting to obtain an ingot;

[0010] 3. cutting the ingot into metal rods, and then cleaning them to obtain cleaned metal rods;

[0011] Fourth, the metal rod is placed in a ceramic tube, which is then placed in a vacuum melting furnace. After heating and melting, it is immediately placed in a Ga-In liquid for quenching to obtain a eutectic high-entropy alloy with nano-scale ultrafine layers.

[0012] The present invention has the following beneficial effects:

[0013] First, the present invention provides a novel method for preparing nanoscale ultrafine lamellar eutectic high-entropy alloys. This method combines induction melting with quenching. This combined melting and solidification method achieves rapid solidification, small alloy grain size, and nanoscale eutectic lamellar thickness, achieving significant grain refinement and further improving the alloy's strength and plasticity based on its composition. The present invention features a simple preparation process, low production cost, and high production efficiency. This method can also be applied to the preparation of other eutectic high-entropy alloys, making it a highly promising preparation process.

[0014] 2. Design of new Al 1.25 CoCrFeNi3 eutectic high entropy alloy, in which the higher content of Al and Ni promotes the formation of high-strength BCC phase in the alloy, and the high content of BCC phase further improves the strength of the alloy.

[0015] 3. Al prepared by the novel preparation method provided by the present invention 1.25 The CoCrFeNi3 eutectic high-entropy alloy exhibits excellent properties at room temperature, with a tensile strength of 826.91 MPa and an elongation of 19.08%. Its compressive strain exceeds 55%, and its compressive strength exceeds 2.8 GPa. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 The nano-scale ultra-fine sheet Al in Example 1 1.25 Longitudinal cross-section microstructure of CoCrFeNi3 eutectic high entropy alloy;

[0017] Figure 2 The nano-scale ultra-fine sheet Al in Example 1 1.25 Electron backscatter diffraction pattern of CoCrFeNi3 eutectic high entropy alloy;

[0018] Figure 3 The nano-scale ultra-fine sheet Al in Example 1 1.25 Tensile stress-strain curve of CoCrFeNi3 eutectic high entropy alloy;

[0019] Figure 4 The nano-scale ultra-fine sheet Al in Example 1 1.25 Compressive stress-strain curves of CoCrFeNi3 eutectic high entropy alloy;

[0020] Figure 5The Al prepared by the directional solidification method in Example 2 1.25 Microstructure of CoCrFeNi3 eutectic high entropy alloy;

[0021] Figure 6 The Al prepared by the directional solidification method in Example 2 1.25 Tensile stress-strain curves of CoCrFeNi3 eutectic high entropy alloy. DETAILED DESCRIPTION

[0022] The technical solution of the present invention is not limited to the specific embodiments listed below, but also includes any combination of the specific embodiments. Specific embodiment 1: In this embodiment, a nano-scale ultra-fine lamellar eutectic high entropy alloy has the chemical formula of Al 1.25 CoCrFeNi3.

[0023] Specific embodiment 2: This embodiment differs from the specific embodiment 1 in that: the Al 1.25 The CoCrFeNi3 high entropy alloy is composed of 17.25% Al, 13.79% Co, 13.79% Cr, 13.79% Fe and 41.38% Ni in atomic percentage. The rest is the same as in the first embodiment.

[0024] Specific embodiment 3: This embodiment is a method for preparing a nano-scale ultra-fine lamellar eutectic high entropy alloy, which is carried out according to the following steps:

[0025] 1. Weigh the raw materials according to the atomic ratio to obtain the raw materials;

[0026] 2. placing the raw materials into a tungsten electrode non-consumable vacuum melting furnace for ingot melting to obtain an ingot;

[0027] 3. cutting the ingot into metal rods, and then cleaning them to obtain cleaned metal rods;

[0028] Fourth, the metal rod is placed in a ceramic tube, which is then placed in a vacuum melting furnace. After heating and melting, it is immediately placed in a Ga-In liquid for quenching to obtain a eutectic high-entropy alloy with nano-scale ultrafine layers.

[0029] In this embodiment, the diameter of the metal rod is equal to or close to the inner diameter of the ceramic tube, ensuring that the metal rod is in contact with the inner wall of the ceramic tube.

[0030] Specific embodiment 4: This embodiment differs from specific embodiment 3 in that: before step 2, the tungsten electrode non-consumable vacuum melting furnace is vacuumed to 6×10 -3 Pa, and then argon is introduced to 0.1 MPa. Other aspects are the same as those in the third embodiment.

[0031] Specific embodiment 5: This embodiment differs from specific embodiment 3 or 4 in that the number of smelting times is 7. Other aspects are the same as specific embodiment 3 or 4.

[0032] Specific embodiment 6: This embodiment differs from specific embodiments 3 to 5 in that the cleaning method of the metal rod in step 3 is to polish it with sandpaper and then ultrasonically clean it. Other aspects are the same as specific embodiments 3 to 5.

[0033] Specific embodiment 7: This embodiment differs from specific embodiments 3 to 6 in that the sandpaper is 400-2000 mesh. Other aspects are the same as specific embodiments 3 to 6.

[0034] Specific embodiment 8: This embodiment differs from specific embodiments 3 to 7 in that: in step 4, vacuum is evacuated to 20 Pa before smelting, and then protective gas is introduced to 0.1 MPa, and the purge is repeated three times. Other aspects are the same as specific embodiments 3 to 7.

[0035] Specific embodiment 9: This embodiment differs from specific embodiments 5 to 8 in that the shielding gas is argon. Other aspects are the same as specific embodiments 5 to 8.

[0036] Specific embodiment 11: This embodiment differs from specific embodiments 5 to 9 in that: in step 4, the temperature is raised to 2000° C. and then kept at this temperature for 50 minutes for smelting. Other aspects are the same as specific embodiments 5 to 9.

[0037] The following examples are used to verify the beneficial effects of the present invention:

[0038] Example 1

[0039] The chemical formula of a nano-scale ultrafine lamellar eutectic high entropy alloy in this embodiment is Al 1.25 CoCrFeNi3.

[0040] The preparation process is as follows:

[0041] Step 1: According to the atomic formula Al 1.25 CoCrFeNi3, converted into mass ratio, Al is 8.96%, Co is 15.65%, Cr is 13.81%, Fe is 14.83%, Ni is 46.75%, weigh out the metal element particles with a purity of 99.5%;

[0042] Taking into account the burn-off during smelting, the mass is weighed according to 103% of the nominal composition mass, with the mass accurate to 0.01 g;

[0043] Step 2: Use a tungsten electrode non-consumable vacuum melting furnace to melt the ingot. Place the Al metal particles with the lowest density and melting point at the bottom of the crucible in the melting furnace. From bottom to top, they are Al, Ni, Co, Fe, and Cr. Before melting, vacuum should be drawn to 6×10 -3 Pa, then 0.1MPa argon was introduced as a protective gas, and then the smelting was repeated 7 times to ensure uniform distribution of components;

[0044] Step 3: Cut the ingot into bars with a diameter of 8 mm, polish the surface impurities with 400-2000 mesh sandpaper, and clean them with ultrasonic wave;

[0045] Step 4. Place the metal rod into a ceramic tube with an inner diameter of 8mm and place it in a vacuum Bridgman melting furnace. The melting method of the vacuum Bridgman melting furnace is vacuum induction melting. There is a Ga-In liquid under the melt, and carbon felt is used to isolate the temperature. Before melting in a vacuum Bridgman melting furnace, it is necessary to evacuate the vacuum to 20Pa, and then introduce argon as a protective gas to 0.1MPa to complete a purge. The purge operation needs to be repeated three times. After starting the smelting, the temperature is raised to 2000℃ and kept warm for 50 minutes. After ensuring that the alloy is completely melted, the alloy melt is instantly quenched in the Ga-In liquid to obtain a eutectic high entropy alloy with nano-scale ultrafine layers.

[0046] Experimental test analysis:

[0047] The nano-scale ultra-fine sheet Al prepared in this embodiment 1.25 CoCrFeNi3 eutectic high entropy alloy was used as the test sample for experimental test and analysis. Figure 1 It can be seen from the scanning organization diagram that the thickness of the lamellar structure of the longitudinal section of the eutectic high entropy alloy prepared by this method is at the nanometer level. Figure 2 Nano-scale ultra-fine sheet Al 1.25 Electron backscatter diffraction pattern of CoCrFeNi3 eutectic high entropy alloy; the alloy composition of this embodiment obtains a high content of BCC phase, the content of BCC phase is about 42%, which improves the strength of the alloy.

[0048] Figure 3 This is the tensile engineering stress-strain curve of the alloy. The tensile strength of the alloy is 826.91 MPa and the elongation is 19.08%. Figure 4 The compressive engineering stress-strain curve for the alloy shows exceptionally good compressive plasticity, with the alloy remaining intact even at a compressive strain exceeding 55%. The compressive strength of the alloy at 55% exceeds 2.8 GPa. This demonstrates that the eutectic high-entropy alloy prepared by this method possesses a nanoscale, ultrafine lamellar structure and excellent strength and plasticity.

[0049] Example 2

[0050] This example is an Al2O3 prepared by directional solidification method. 1.25 The process of CoCrFeNi3 eutectic high entropy alloy is as follows:

[0051] Step 1: According to the atomic formula Al 1.25 CoCrFeNi3, converted into mass ratio, Al is 8.96%, Co is 15.65%, Cr is 13.81%, Fe is 14.83%, Ni is 46.75%, weigh out the metal element particles with a purity of 99.5%;

[0052] Taking into account the burn-off during smelting, the mass is weighed according to 103% of the nominal composition mass, with the mass accurate to 0.01 g;

[0053] Step 2: Use a tungsten electrode non-consumable vacuum melting furnace to melt the ingot, and place the Al metal particles with the lowest density and lowest melting point at the bottom of the crucible in the melting furnace. Before melting, it is necessary to evacuate to 6×10 -3 Pa, then 0.1MPa argon is introduced as a protective gas. The melting is repeated 7 times to ensure uniform distribution of components.

[0054] Step 3: Cut the ingot into bars with a diameter of 8 mm, polish the surface impurities with 400-2000 mesh sandpaper, and clean them with ultrasonic wave;

[0055] Step 4. Place the metal rod into a ceramic tube with an inner diameter of 8mm and place it in a vacuum Bridgman melting furnace. The melting method of the vacuum Bridgman melting furnace is vacuum induction melting. There is a Ga-In liquid under the melt, and carbon felt is used to isolate the temperature. Before melting in a vacuum Bridgman melting furnace, it is necessary to evacuate the vacuum to 20Pa, and then introduce argon as a protective gas to 0.1MPa to complete a purge. The purge operation needs to be repeated three times. After starting the smelting, the temperature is raised to 2000℃ and kept warm for 50 minutes. After ensuring that the alloy is completely melted, the melt is slowly pulled into the Ga-In liquid at a pulling speed of 5μm / s to obtain a directionally solidified eutectic high entropy alloy.

[0056] Experimental test analysis:

[0057] The Al 1.25 CoCrFeNi3 eutectic high entropy was used as a control test sample for experimental testing and analysis. Figure 5 It can be seen from the scanning organization diagram that the lamellar structure of the eutectic high entropy alloy prepared by this method is relatively Figure 1 The nanosheet structure in the α-H2O2O3 ... Figure 6The engineering stress-strain curves show that the strength of the eutectic high-entropy alloy prepared by directional solidification is similar to that of a eutectic high-entropy alloy with nanoscale lamellar thickness, but the elongation is 14.22%, significantly lower than that of the eutectic high-entropy alloy prepared by the new preparation method. This shows that the eutectic high-entropy alloy prepared by the preparation method of Example 1 has a nanoscale ultrafine lamellar structure, which can simultaneously improve the strength and plasticity of the alloy.

Claims

1. A nanoscale ultrafine lamellar eutectic high entropy alloy, characterized in that: The chemical formula of the high entropy alloy is Al 1.25 CoCrFeNi3, composed by atomic percentage of 17.25% Al, 13.79% Co, 13.79% Cr, 13.79% Fe and 41.38% Ni; The preparation method of the high entropy alloy is carried out according to the following steps:

1. Weigh the raw materials according to the atomic ratio to obtain the raw materials; 2. placing the raw materials into a tungsten electrode non-consumable vacuum melting furnace for ingot melting to obtain an ingot; 3. cutting the ingot into metal rods, and then cleaning them to obtain cleaned metal rods; Fourth, the metal rod is placed in a ceramic tube, which is then placed in a vacuum melting furnace. After heating and melting, it is immediately placed in a Ga-In liquid for quenching to obtain a eutectic high-entropy alloy with nano-scale ultrafine layers.

2. The nanoscale ultrafine lamellar eutectic high entropy alloy according to claim 1, characterized in that Step 2 Before melting, evacuate the tungsten electrode non-consumable vacuum melting furnace to 6×10 -3 Pa, and then argon was introduced to 0.1 MPa.

3. The nanoscale ultrafine lamellar eutectic high entropy alloy according to claim 1, characterized in that The number of smelting times is 7 times.

4. The nanoscale ultrafine lamellar eutectic high entropy alloy according to claim 1, characterized in that The cleaning method of the metal rod in step 3 is: polishing with sandpaper and then ultrasonic cleaning.

5. The nanoscale ultrafine lamellar eutectic high entropy alloy according to claim 4, characterized in that The sandpaper is 400-2000 grit.

6. The nanoscale ultrafine lamellar eutectic high entropy alloy according to claim 1, characterized in that Step 4: Before smelting, evacuate to 20 Pa, then introduce protective gas to 0.1 MPa, and repeat the purge 3 times.

7. The nanoscale ultrafine lamellar eutectic high entropy alloy according to claim 6, characterized in that The shielding gas is argon.

8. The nanoscale ultrafine lamellar eutectic high entropy alloy according to claim 1, characterized in that Step 4: Raise the temperature to 2000°C and keep it at this temperature for 50 minutes for smelting.

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