A CrNiFeCuTiB-based high-strength and high-toughness high-entropy alloy, its preparation method and application

Abstract

The present invention belongs to the technical field of alloy materials, and particularly relates to a CrNiFeCuTiB-based high-strength and high-toughness high-entropy alloy, its preparation method and application. The alloy is composed of Cr, Ni, Fe, Cu, Ti and B, wherein the atomic ratio of Cr:Ni:Fe:Cu:Ti:B is (0.1-1):(0.5-2):(0.5-1):(0.5-1.5):(0.1-0.5):(0.1-0.7), and at the same time, 0.028 ≤ (Ti + B) / (Cr + Ni + Fe + Cu) ≤ 0.25 in terms of atomic ratio. The CrNiFeCuTiB-based high-entropy alloy provided by the present invention is composed of a FCC matrix with good plasticity, and the precipitated Laves phase and δ phase improve the strength and hardness of the alloy. The alloy has a simple crystal structure and uniform composition; it has a relatively high hardness, up to 650 HV; the compressive strength can reach 1929 MPa, and the compressive strain can reach 55%.

Description

Technical Field

[0001] The present invention belongs to the technical field of alloy materials, and particularly relates to a CrNiFeCuTiB-based high-strength and high-toughness high-entropy alloy, a preparation method thereof, and an application thereof. Background Art

[0002] High-entropy alloys are multi-principal element alloys, usually consisting of at least 5 elements, and the content of each element is between 5% and 35%. Due to the high-entropy effect of high-entropy alloys, their multi-principal element metals tend to form simple solid solutions rather than many complex phases. This effect enables high-entropy alloys to avoid the formation of brittle intermetallic compounds, and they can have high strength, good wear resistance, and corrosion resistance, etc. For example, CN114058922 discloses a lightweight hard CoCrAlSiNi high-entropy alloy and a preparation method thereof, and a new type of lightweight hard high-entropy alloy with high hardness, low density, good mechanical properties, and thermal stability is obtained by vacuum arc melting method.

[0003] There are some systems in the prior art, such as AlCoCrFeNi, MoNbTaTiV, CoFeNi x VMo y and FeCoNiCuAl. However, due to the fact that FCC is relatively soft and BCC is relatively hard and brittle, high-entropy alloys with body-centered cubic, such as MoNiTaW, have high strength but poor ductility; high-entropy alloys with face-centered cubic, such as CoCrFeNi, have good ductility but low strength. Therefore, it is necessary to develop high-entropy alloy technologies with high strength, high hardness, and good plasticity at the same time. Summary of the Invention

[0004] To solve the deficiencies of the prior art, the present invention provides a CrNiFeCuTiB-based high-strength and high-toughness high-entropy alloy, a preparation method thereof, and an application thereof.

[0005] The technical solution provided by the present invention is as follows:

[0006] A CrNiFeCuTiB-based high-strength and high-toughness high-entropy alloy is composed of Cr, Ni, Fe, Cu, Ti, and B, wherein the atomic ratio of Cr:Ni:Fe:Cu:Ti:B is (0.1 - 1):(0.5 - 2):(0.5 - 1):(0.5 - 1.5):(0.1 - 0.5):(0.1 - 0.7), and at the same time, 0.028 ≤ (Ti + B) / (Cr + Ni + Fe + Cu) ≤ 0.25.

[0007] The CrNiFeCuTiB high-entropy alloy provided by the present invention is composed of a FCC matrix with good plasticity, and the precipitated Laves phase and δ phase improve the strength and hardness of the alloy. The crystal structure of the alloy is simple and the composition is uniform; the hardness is relatively high, reaching 650 HV; the compressive strength can reach 1929 MPa, and the compressive strain can reach 55%.

[0008] The present invention also provides a preparation method of a CrNiFeCuTiB high-strength and high-toughness high-entropy alloy, including the following steps:

[0009] 1) Weigh clean Cr metal blocks, Ni metal blocks, Fe metal blocks, Cu metal blocks, Ti metal blocks and B particles according to the molar ratio of (0.1-1):(0.5-2):(0.5-1):(0.5-1.5):(0.1-0.5):(0.1-0.7) for batching;

[0010] 2) Place each raw material into a copper crucible in an arc melting furnace, and arrange the raw materials in the order of low melting point elements at the bottom and high melting point elements at the top;

[0011] 3) Adjust the vacuum degree in the arc melting furnace to -0.1 to -0.05 MPa, and use argon as the protective gas;

[0012] 4) Conduct arc melting to obtain a as-cast CrNiFeCuTiB high-strength and high-toughness high-entropy alloy.

[0013] Specifically, in step 2): Place a titanium ingot separately in the arc melting furnace to absorb the remaining oxygen during the melting process.

[0014] Specifically, in step 3): The protective gas is argon.

[0015] Specifically, in step 4):

[0016] The starting arc current is 60-80 A;

[0017] The melting current is 300-700 A;

[0018] The melting time is 30-90 s.

[0019] Specifically, in step 4): Repeatedly melt, and the number of times is 4-10 times.

[0020] Specifically, in step 4): The diameter of the obtained ingot is 20-90 mm, and the height is 5-200 mm.

[0021] The preparation method of the CrNiFeCuTiB high-strength and high-toughness high-entropy alloy may specifically include the following steps:

[0022] 1. Weigh raw materials:

[0023] 1a. Polish the Cr metal block, Ni metal block, Fe metal block, Cu metal block, Ti metal block, and B particles with 1000# sandpaper until the surfaces of the raw materials are bright and free of contamination. Put all the raw materials into a beaker containing acetone and wash them ultrasonically for 5 minutes. After taking them out, dry them and set them aside. The purity of the raw materials is above 99.999 wt.%.

[0024] 1b. Weigh the cleaned Cr metal block, Ni metal block, Fe metal block, Cu metal block, Ti metal block, and B particles according to the molar ratio of (0.1 - 1):(0.5 - 2):(0.5 - 1):(0.5 - 1.5):(0.1 - 2):(0.1 - 1.5) for preparation. The mass error during the preparation process should be controlled within 0.05 g.

[0025] 2. Place the raw materials:

[0026] 2a. Wipe the copper crucible and the inner wall of the furnace chamber clean with absolute ethanol to avoid the influence of contaminants on the alloy. Place a polished titanium ingot in one of the crucibles in the furnace to absorb the remaining oxygen.

[0027] 2b. Use tweezers to place the prepared alloy raw materials into the copper crucible in the arc melting furnace, and place them in the order of lower melting point elements at the bottom and higher melting point elements at the top. That is, the placement order is Cu, Ni, Fe, Ti, Cr, B.

[0028] 2c. Close the vacuum chamber, turn on the cooling water to continuously cool and protect the copper mold to prevent some elements in the copper mold from entering the ingot during the melting process due to high temperature.

[0029] 3. Evacuate the vacuum:

[0030] 3a. Turn on the mechanical pump and the molecular pump to evacuate the vacuum chamber. When the vacuum degree in the vacuum chamber reaches 5.5 - 6×10 -3 Pa, close the butterfly valve and stop the molecular pump. When the rotational speed of the molecular pump is zero, introduce high-purity argon gas into the furnace chamber through the pipeline. The purpose is to protect the alloy from oxidation and prevent the low-melting-point alloy from volatilizing during melting.

[0031] 3b. Repeat step 3a) 2 to 4 times, and then introduce argon gas until the vacuum degree is -0.1 to -0.05 MPa.

[0032] 4. Arc melting:

[0033] 4a. Turn on the arc melting button and first use the Ti ingot to strike an arc. Lower the tip of the arc gun vertically to a position 2 mm away from the surface of the Ti ingot and start striking the arc to melt it and absorb the remaining gas in the cavity. Stop until the surface of the Ti no longer changes color.

[0034] 4b. Melting the alloy. At the beginning of melting, the current is 60 - 80 A, and gradually increase the melting current to 300 - 700 A, so that the arc sweeps back and forth across the entire surface of the sample, ensuring uniform heating of the sample, and the heating time is 60 s.

[0035] 4c. When the sample is completely melted, turn off the arc melting button and lift the arc gun. After the alloy cools and solidifies, use the robotic arm to turn the sample over, and repeat steps 4a, 4b, and 4c, melting 4 - 10 times repeatedly to obtain a sample with relatively uniform composition and microstructure.

[0036] 4d. After the melting is completed, wait for the alloy to cool completely, then open the vacuum inflation valve to inflate the vacuum chamber. When the pressure in the vacuum chamber is equal to the external atmospheric pressure, raise the furnace chamber, take out the alloy ingot, weigh it with an electronic balance, and bag and number it.

[0037] The present invention also provides the application of the above-mentioned high-strength, high-toughness CrNiFeCuTiB high-entropy alloy. According to its characteristics of high strength and high toughness, it can be used to prepare repair materials or structural materials for aerospace, ship equipment, etc.

[0038] The CrNiFeCuTiB high-entropy alloy provided by the present invention has outstanding performance in terms of strength, hardness and toughness. Therefore, it is particularly suitable as a repair material or structural material for special working condition equipment such as aerospace and ship equipment.

[0039] Advantages of the present invention:

[0040] The CrNiFeCuTiB high-entropy alloy prepared by the present invention has a complete microstructure. The main structure is the FCC matrix and a small amount of Laves phase and δ phase, mainly dendritic structure. The alloy has relatively high strength and hardness and good plasticity.

[0041] The compressive strength of the CrNiFeCuTiB high-entropy alloy prepared by the present invention can reach 1929 MPa, the compressive strain can reach 55%, and the hardness can reach 650 HV. While maintaining relatively high strength and hardness, it also has good plasticity. Compared with the MoNiTaW alloy, its plasticity is increased by 3 times; compared with the CoCrFeNi alloy, its strength is increased by 2.5 times.

[0042] The present invention can obtain a high-strength, high-toughness CrNiFeCuTiB high-entropy alloy and a preparation method thereof. The production process flow is simple, the mechanical properties of the alloy are excellent, and the production cost is low. Description of the drawings

[0043] Figure 1 It is an XRD picture of the CrNiFeCuTiB high-entropy alloy.

[0044] Figure 2 SEM image of the CrNiFeCuTiB-based high-entropy alloy. Specific implementation manners

[0045] The principles and features of the present invention are described below. The examples given are only used to explain the present invention and are not intended to limit the scope of the present invention.

[0046] In practical applications, when using the present invention to prepare the CrNiFeCuTiB-based high-strength and high-toughness high-entropy alloy, different component contents and process parameters will correspond to different mechanical property indexes. The component contents, process parameters and mechanical property data of the examples and comparative examples are listed in Tables 1-3 below.

[0047] Table 1 below is the chemical composition table (at%) of the alloys of the examples and comparative examples of the present invention;

[0048] Table 2 below is the process parameter table of the alloys of the examples and comparative examples of the present invention;

[0049] Table 3 below is the main mechanical property data table of the alloys of the examples and comparative examples of the present invention.

[0050] Table 1 Chemical composition table (at%) of the alloys of the examples and comparative examples of the present invention

[0051]

[0052] Table 2 Process parameter table of the alloys of the examples and comparative examples of the present invention

[0053]

[0054] Table 3 Main mechanical property data table of the alloys of the examples and comparative examples of the present invention

[0055]

[0056] It can be seen from the data in Table 3 that the CrNiFeCuTiB-based high-entropy alloy prepared by the present invention has high plasticity on the premise of having high hardness and strength.

[0057] It can be seen from the content of Comparative Example 1 in Tables 1 to 3 that when (Ti + B) / (Cr + Ni + Fe + Cu) is 2.36%, the strength and hardness of the alloy both decrease. This is because the proportion of Ti and B is small, and the amount of the second phase generated is small, which cannot play a good role in improving the strength and hardness.

[0058] It can be seen from Comparative Example 2 from Table 1 to Table 3 that when (Ti + B) / (Cr + Ni + Fe + Cu) is 33%, the hardness and strength of the alloy do not increase significantly, but the toughness decreases severely. This is also because the increase in the amount of the second phase precipitated causes more brittle fractures in the alloy, affecting the toughness of the alloy.

[0059] Figure 1 XRD pattern of the CrNiFeCuTiB high-entropy alloy ingot prepared for Example 1. From Figure 1 Analysis of the XRD pattern shows that the alloy microstructure mainly consists of an FCC matrix and precipitated Laves phase and δ phase.

[0060] Figure 2 SEM image of the CrNiFeCuTiB high-entropy alloy ingot prepared for Example 1. From Figure 2 It can be seen from the SEM image that the microstructure of the alloy is clear and the structure is complete, mainly dendritic structure.

[0061] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A CrNiFeCuTiB-based high-strength and high-toughness high-entropy alloy, characterized in that: It is composed of Cr, Ni, Fe, Cu, Ti and B, where the atomic ratio of Cr:Ni:Fe:Cu:Ti:B is (0.1~1):(0.5~2):(0.5~1):(0.5~1.5):(0.1~0.5):(0.1~0.7), and at the same time, 0.028 ≤ (Ti + B) / (Cr + Ni + Fe + Cu) ≤ 0.25 in atomic ratio.

2. A method for preparing a CrNiFeCuTiB-based high-strength and high-toughness high-entropy alloy according to claim 1, characterized in that, It includes the following steps: 1) Weigh clean Cr metal blocks, Ni metal blocks, Fe metal blocks, Cu metal blocks, Ti metal blocks and B particles according to the molar ratio (0.1~1):(0.5~2):(0.5~1):(0.5~1.5):(0.1~0.5):(0.1~0.7) for batching; 2) Place each raw material into the copper crucible in the arc melting furnace, and arrange the raw materials in the order of lower melting point elements at the bottom and higher melting point elements at the top; 3) Adjust the vacuum degree in the arc melting furnace to -0.1~-0.05 MPa, with argon as the protective gas; 4) Conduct arc melting to obtain a cast CrNiFeCuTiB-based high-strength and high-toughness high-entropy alloy.

3. The preparation method of the CrNiFeCuTiB-based high-strength and high-toughness high-entropy alloy according to claim 2, wherein, In step 2): Place a titanium ingot separately in the arc melting furnace to absorb the remaining oxygen during the melting process.

4. The preparation method of the CrNiFeCuTiB-based high-strength and high-toughness high-entropy alloy according to claim 2, wherein, In step 3): The protective gas is argon.

5. The preparation method of the CrNiFeCuTiB-based high-strength and high-toughness high-entropy alloy according to claim 2, characterized in that, In step 4): The starting arc current is 60~80 A; The melting current is 300~700 A; The melting time is 30 - 90 s.

6. The preparation method of the CrNiFeCuTiB-based high-strength and high-toughness high-entropy alloy according to claim 5, characterized in that: Melt repeatedly for 4~10 times.

7. The preparation method of the CrNiFeCuTiB-based high-strength and high-toughness high-entropy alloy according to claim 2, wherein In step 4): The diameter of the obtained ingot is 20~90 mm, and the height is 5~200 mm.

8. An application of the CrNiFeCuTiB-based high-strength and high-toughness high-entropy alloy according to claim 1, characterized in that: It is used to prepare repair materials or structural materials for aerospace; Or, it is used to prepare repair materials or structural materials for ship equipment.

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