A lightweight high-temperature medium-entropy alloy resistant to high-temperature brittleness, its preparation method and application

Abstract

This invention provides a lightweight, high-temperature medium-entropy alloy resistant to high-temperature brittleness, its preparation method, and its applications, belonging to the field of high-temperature medium-entropy alloys. The raw materials for this lightweight, high-temperature medium-entropy alloy resistant to high-temperature brittleness include at least one of elemental titanium, vanadium, and niobium, as well as metal nitrides of titanium, vanadium, and niobium. The atomic percentages of the four elements are as follows: titanium: 31-34%, vanadium: 31-34%, niobium: 31-34%, 0 < nitrogen < 2%, with the balance being unavoidable impurities. This alloy has a crystal structure dominated by the BCC phase and a density of less than 6.4 g / cm³. 3 The alloy has a Vickers hardness of 250-400 HV, a room temperature compressive yield strength of 870-1300 MPa with strain >50%, and a compressive yield strength of 520-720 MPa with strain >70% at 800℃. Its room temperature tensile yield strength is 880-1300 MPa with strain >6%, a 600℃ tensile yield strength of 520-700 MPa with strain >10%, and an 800℃ tensile yield strength of 500-650 MPa with strain >10%. This alloy can be used in both room temperature processing and high-temperature load-bearing applications.

Description

Technical Field

[0001] This invention belongs to the field of high-temperature medium-entropy alloys, specifically relating to a lightweight high-temperature medium-entropy alloy resistant to high-temperature brittleness, its preparation method, and its application. Background Technology

[0002] Medium / high entropy alloys, due to their unique multi-principal element mixed solid solution strengthening mechanism, exhibit thermodynamic properties different from traditional materials, making them promising candidates for high-temperature components in aerospace and nuclear power fields. To reduce component weight, the demand for lightweight, high-strength medium / high entropy alloys is becoming increasingly urgent. These lightweight, high-strength medium / high entropy alloys primarily incorporate Cr, Ni, Co, Ti, and Al. To reduce room-temperature processing brittleness, they feature a high titanium content and a low aluminum content. Their crystal structure is dominated by BCC and FCC solid solutions, and includes a small amount of precipitated phases, such as the BCC+Laves-type TiVCrNbAl system (density < 6 g / cm³). 3 BCC type TiVNbZr system (density < 6.5 g / cm³) 3 FCC-type CrMnFeCoNi system (density < 8 g / cm³) 3 FCC+L12 type NiFeCoTiAl system (density < 7.8 g / cm³) 3 These alloys possess high strength at high temperatures and toughness at room temperature. However, most of these alloys exhibit plasticity at room temperature and higher temperatures, but near a certain temperature point in the medium-high temperature range (600-800℃), a common phenomenon of toughness-brittle transition occurs, which is completely different from traditional alloys—whose plasticity increases with increasing temperature, and the higher the temperature, the more tough the alloy becomes.

[0003] The previously reported BCC-based TiVNbZr equal-proportion medium-entropy alloy (Journal of Alloys and Compounds, 937(2023)168458) exhibits brittle fracture at 600℃, while maintaining tensile plasticity at room temperature and 800℃. The FCC-based Ni-30Co-13Fe-15Cr-6Al-6Ti-0.1B high-entropy alloy experiences tensile brittle fracture in the 750-800℃ temperature range (ScriptaMaterialia 194,(2021)113622,Materials Today Physics, 24(2022)100653). 600-800℃ is the primary service temperature range for high-temperature materials; brittleness under stress in this range is detrimental to high-temperature use and may lead to significant losses due to catastrophic failure. However, methods and high-performance alloys to address this problem are still lacking. This invention addresses this critical issue by providing a lightweight, high-strength medium-entropy alloy resistant to high-temperature brittleness.

[0004] Chinese patent application number 2023104627374 discloses a TiVNb-based oxygen-containing high-temperature medium-entropy alloy, comprising elemental titanium, vanadium, and niobium, as well as oxides. The atomic percentages of the four elements are as follows: titanium: 31-34%; vanadium: 31-34%; niobium: 31-34%; oxygen: 0.01-1.5%. Although this alloy possesses low density, room-temperature compressive strength and toughness, and high-temperature compressive strength, it undergoes tensile brittle fracture at 800℃, making it unsuitable for use as a high-temperature load-bearing material. Summary of the Invention

[0005] To address the problem of brittle fracture in existing medium / high entropy alloys in the medium-to-high temperature range, this invention provides a lightweight high-temperature medium-entropy alloy resistant to high-temperature brittleness, its preparation method, and its applications. The lightweight high-temperature medium-entropy alloy is lightweight, high-strength, and maintains good plasticity over a wide temperature range.

[0006] The technical solution of the present invention is as follows:

[0007] This invention provides a lightweight high-temperature medium-entropy alloy resistant to high-temperature brittleness. Its raw materials include at least one of elemental titanium, vanadium, and niobium, as well as metal nitrides of titanium, vanadium, and niobium. The atomic percentages of the four elements titanium, vanadium, niobium, and nitrogen are as follows: titanium: 31-34%, vanadium: 31-34%, niobium: 31-34%, 0 < nitrogen < 2%, and the balance being unavoidable impurities.

[0008] In one specific embodiment, the atomic percentages of the four elements titanium, vanadium, niobium, and nitrogen are as follows: titanium: 32.84-33.2%; vanadium: 32.83-33.2%; niobium: 32.83-33.1%; nitrogen: 0.5-1.5%; preferably, the atomic percentages of the four elements titanium, vanadium, niobium, and nitrogen are as follows: titanium: 32.84%; vanadium: 32.83%; niobium: 32.83%; nitrogen: 1.5%.

[0009] In one specific embodiment, the metal nitride is niobium nitride.

[0010] In one specific embodiment, the purity of the metallic element exceeds 99%.

[0011] In one specific embodiment, the lightweight high-temperature medium-entropy alloy has a crystal structure dominated by the BCC phase and a density not exceeding 6.4 g / cm³. 3Vickers hardness 250-400 HV, room temperature compressive yield strength 870-1300 MPa, strain greater than 50%, compressive yield strength at 800℃ 520-720 MPa, strain greater than 70%; room temperature tensile yield strength 880-1300 MPa, strain greater than 6%, tensile yield strength at 600℃ 520-700 MPa, strain greater than 10%, tensile yield strength at 800℃ 500-650 MPa, strain greater than 10%.

[0012] This invention also provides a method for preparing a lightweight, high-temperature, medium-entropy alloy resistant to high-temperature brittleness, the method comprising the following steps:

[0013] (1) Weigh out the metallic elements of titanium, vanadium, and niobium, as well as niobium nitride, according to the atomic percentages of the four elements: titanium, vanadium, niobium, and nitrogen.

[0014] (2) Place the raw materials weighed in step (1) into the copper crucible of the electric arc melting furnace and clean the cavity;

[0015] (3) Adjust the current of the electric arc melting furnace to melt all the raw materials in the crucible, and at the same time turn on the magnetic stirring device. After the melting is completed, an alloy ingot is obtained.

[0016] (4) Repeat step (3) at least 4 times to repeatedly melt the alloy ingot obtained in step (3), and after cooling, obtain a lightweight high-temperature medium-entropy alloy resistant to high-temperature brittleness.

[0017] In one specific embodiment, in step (1), the purity of the metal element exceeds 99%, and the metal nitride is niobium nitride.

[0018] In one specific embodiment, the specific steps of cleaning the cavity in step (2) are as follows: evacuate to 10... -2 -10 -3 Pa, then fill with high-purity protective gas to make the gas pressure inside the cavity lower than the gas pressure outside the cavity.

[0019] The protective gas is an inert gas that does not participate in the reaction, such as high-purity argon, but nitrogen cannot be used in this invention.

[0020] In one specific implementation, step (3) is repeated 4 times in step (4).

[0021] This invention also provides the application of the above-mentioned lightweight high-temperature medium-entropy alloy with high-temperature brittleness resistance in room temperature processing and high-temperature load-bearing fields.

[0022] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0023] The lightweight, high-temperature, medium-entropy alloy of the present invention, which is resistant to high-temperature brittleness, has a crystal structure dominated by the BCC phase and a density of less than 6.4 g / cm³. 3Vickers hardness 250-400 HV, room temperature compressive yield strength 870-1300 MPa, strain > 50%; at 800℃, compressive yield strength 520-720 MPa, strain > 70%. Room temperature tensile yield strength 880-1300 MPa, strain > 6%; at 600℃, tensile yield strength 520-700 MPa, strain > 10%; at 800℃, tensile yield strength 500-650 MPa, strain > 10%. Attached Figure Description

[0024] Figure 1 The XRD crystal structure spectra of the alloys in Examples 1 and 2 are shown.

[0025] Figure 2 The compression curve of the alloy in Example 1 at room temperature and 800°C is shown.

[0026] Figure 3 The tensile curves of the alloy in Example 1 at room temperature, 600°C, and 800°C are shown.

[0027] Figure 4 The compression curve of the alloy in Example 2 at room temperature and 800°C is shown.

[0028] Figure 5 The tensile curves of the alloy in Example 2 at room temperature, 600°C, and 800°C are shown.

[0029] Figure 6 The tensile properties of the alloy in Comparative Example 3 at room temperature, 600°C, and 800°C are shown in the graph.

[0030] Figure 7 For Comparative Example 4, TiVNbO 0.5 Tensile properties of the alloy at room temperature, 600℃, and 800℃;

[0031] Figure 8 For Comparative Example 4, TiVNbO 1.5 Tensile properties of the alloy at room temperature, 600℃, and 800℃. Detailed Implementation

[0032] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0033] Example 1

[0034] This embodiment provides a lightweight, high-temperature, medium-entropy alloy resistant to high-temperature brittleness, with atomic percentages of Ti: 33.2 at%, V: 33.2 at%, Nb: 33.1 at%, and N: 0.5 at%. Its preparation method is as follows:

[0035] (1) Weigh out elemental titanium, vanadium, and niobium, as well as niobium nitride, with a purity of over 99% according to the atomic percentages of Ti: 33.2at%, V: 33.2at%, Nb: 33.1at%, and N: 0.5at%.

[0036] (2) Place the raw materials weighed in step (1) into the copper crucible of the electric arc melting furnace, and clean the cavity to reduce impurities such as oxygen. The cleaning method is as follows: evacuate to (10) -1 -10 -3 Then, high-purity argon gas is introduced to maintain the pressure inside the cavity within the range of 0.01-0.05 MPa.

[0037] (3) Adjust the current of the electric arc melting furnace to melt all the raw materials in the crucible, and at the same time turn on the magnetic stirring device to make the materials mix more evenly. After the melting is completed, an alloy ingot is obtained.

[0038] (4) Repeat step (3) four times to repeatedly melt the alloy ingot obtained in step (3) so that the material is mixed evenly, and a lightweight high-temperature medium-entropy alloy with high temperature brittleness can be obtained.

[0039] The alloy density obtained in this embodiment is approximately 6.40 g / cm³. 3 The average hardness is 288 HV, and the alloy has a crystal structure dominated by the BCC phase. (See...) Figure 1 The compression curves of the alloy at room temperature and 800℃ are as follows: Figure 2 As shown, the compressive yield strength of the alloy at room temperature is 874 MPa, with a strain greater than 50%; at 800℃, the compressive yield strength of the alloy is approximately 522 MPa, with a strain greater than 70%. The tensile curves of the alloy at room temperature, 600℃, and 800℃ are shown below. Figure 3 As shown, the room temperature tensile yield strength is 884 MPa with strain > 15%; the 600℃ tensile yield strength is 527 MPa with strain > 17%; and the 800℃ tensile yield strength is 508 MPa with strain > 12%. This demonstrates that the alloy exhibits good plasticity in both room temperature and medium-high temperature ranges.

[0040] Example 2

[0041] This embodiment provides a lightweight, high-temperature, medium-entropy alloy resistant to high-temperature brittleness, with the following atomic percentages: Ti: 32.84 at%, V: 32.83 at%, Nb: 32.83 at%, N: 1.5 at%. Its preparation method is as follows:

[0042] (1) Weigh out elemental titanium, vanadium, and niobium with a purity of over 99% according to the atomic percentages of Ti: 32.84at%, V: 32.83at%, Nb: 32.83at%, and N: 1.5at%.

[0043] (2) Place the raw materials weighed in step (1) into the copper crucible of the electric arc melting furnace, and clean the cavity to reduce impurities such as oxygen. The cleaning method is as follows: evacuate to (10) -1 -10 -3 Then, high-purity argon gas is introduced to maintain the pressure inside the cavity within the range of 0.01-0.05 MPa.

[0044] (3) Adjust the current of the electric arc melting furnace to melt all the materials in the crucible, and at the same time turn on the magnetic stirring device to make the materials mix more evenly. After the melting is completed, an alloy ingot is obtained.

[0045] (4) Repeat step (3) four times to repeatedly melt the alloy ingot obtained in step (3) so that the material is mixed evenly, and a lightweight high-temperature medium-entropy alloy with high temperature brittleness can be obtained.

[0046] The alloy density obtained in this embodiment is approximately 6.39 g / cm³. 3 The average hardness is 378 HV. The alloy has a crystal structure dominated by the BCC phase. (See...) Figure 1 The compression curves of the alloy at room temperature and 800℃ are as follows: Figure 4 As shown: the compressive yield strength of the alloy at room temperature is 1263 MPa, with a strain greater than 50%; the compressive yield strength of the alloy at 800℃ is approximately 712 MPa, with a strain greater than 80%; the tensile curves of the alloy at room temperature, 600℃, and 800℃ are shown below. Figure 5 As shown: room temperature tensile yield strength 1295 MPa, strain > 6%; 600℃ tensile yield strength 700 MPa, strain > 10%; 800℃ tensile yield strength 647 MPa, strain > 10%. It is evident that the alloy exhibits high strength and good plasticity in both room temperature and medium-high temperature ranges.

[0047] Comparative Example 1

[0048] The scheme in this comparative example is the patent application number 201910673106.0: A MoVNbTiZrx high-entropy alloy for nuclear power and its preparation method.

[0049] Compared with Comparative Example 1, the advantages of this invention are: 1. Lower density, with some alloys having comparable strength and hardness; 2. Better room temperature plasticity; 3. Simple and rapid preparation method, reducing hot isostatic pressing and annealing heat treatment.

[0050] Comparative Example 2

[0051] The scheme in this comparative example is the patent application number 201310690502.7: an oxygen-strengthened TiZrNbHfO high-entropy alloy and its preparation method.

[0052] Compared with Comparative Example 2, the advantages of the present invention are: 1. Lower alloy density; 2. The room temperature compressive yield strength (1263 MPa) of Example 2 of the present invention is higher than that of TiZrNbHfO. 1.5 The alloy (1075MPa) is higher.

[0053] Since neither Comparative Example 1 nor Comparative Example 2 provided performance at 600℃ and 800℃, high-temperature plasticity could not be compared.

[0054] Comparative Example 3

[0055] This comparative example provides a TiVNb alloy with atomic percentages of Ti: 33.4 at%, V: 33.3 at%, and Nb: 33.3 at%, and its preparation method is as follows:

[0056] (1) Weigh out elemental titanium, vanadium, and niobium with a purity of over 99% according to the atomic percentages of Ti: 33.4at%, V: 33.3at%, and Nb: 33.3at%.

[0057] (2) Place the raw materials weighed in step (1) into the copper crucible of the electric arc melting furnace, and clean the cavity to reduce impurities such as oxygen. The cleaning method is as follows: evacuate to (10) -1 -10 -3 Then, high-purity argon gas is introduced to maintain the pressure inside the cavity within the range of 0.01-0.05 MPa.

[0058] (3) Adjust the current of the electric arc melting furnace to melt all the materials in the crucible, and at the same time turn on the magnetic stirring device to make the materials mix more evenly. After the melting is completed, an alloy ingot is obtained.

[0059] (4) Repeat step (3) four times to repeatedly melt the alloy ingot obtained in step (3) so that the material is evenly mixed and TiVNb alloy can be obtained.

[0060] The tensile properties of the alloy prepared in this comparative example at room temperature, 600℃, and 800℃ are as follows. Figure 6 As shown, it has low strength and low plasticity at 800℃, and fractures rapidly after yielding.

[0061] Compared with Comparative Example 3, the strength and plasticity at 800°C of the alloy are greatly improved after adding trace amounts of nitrogen to the raw materials in this invention.

[0062] Comparative Example 4

[0063] The comparative example is based on patent application number 2023104627374: A TiVNb-based oxygen-containing high-temperature medium-entropy alloy and its preparation method. The TiVNbO material disclosed in this patent was tested. 0.5(Atomic percentages: Ti: 33.17%, V: 33.17%, Nb: 33.16%, O: 0.5%) and TiVNbO 1.5 The tensile properties (atomic percentages: Ti: 32.84%, V: 32.83%, Nb: 32.83%, O: 1.5%) are shown in the figure. Figure 7 and Figure 8 As shown in the figure, TiVNbO 0.5 With TiVNbO 1.5 All alloys undergo brittle fracture at 800℃.

[0064] Compared with Comparative Example 4, the advantages of this invention are: higher tensile strength and plasticity at room temperature, 600°C and 800°C, and strain exceeding 10% at 800°C, making it suitable for room temperature processing and high temperature load-bearing applications.

[0065] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A lightweight high-temperature medium-entropy alloy with high-temperature brittleness resistance, characterized in that, The raw materials include at least one of titanium, vanadium, niobium metal elements and titanium, vanadium, niobium metal nitrides, wherein the atomic percentage of titanium, vanadium, niobium and nitrogen is as follows: titanium: 32.84-33.2%; vanadium: 32.83-33.2%; niobium: 32.83-33.1%; nitrogen: 0.5-1.5%, the balance is inevitable impurities; the lightweight high-temperature medium-entropy alloy has a tensile strain of more than 10% at 800 DEG C.

2. The lightweight high-temperature medium-entropy alloy with high-temperature brittleness resistance according to claim 1, characterized in that: The atomic percentage of titanium, vanadium, niobium and nitrogen is as follows: titanium: 32.84%; vanadium: 32.83%; niobium: 32.83%; nitrogen: 1.5%.

3. The lightweight high-temperature medium-entropy alloy with high-temperature brittleness resistance according to claim 1, characterized in that, The metal nitride is niobium nitride.

4. The lightweight high-temperature medium-entropy alloy with high-temperature brittleness resistance according to claim 1, characterized in that, The purity of the metal element is more than 99%.

5. The lightweight high-temperature medium-entropy alloy with high-temperature brittleness resistance according to claim 1, characterized in that, The lightweight high-temperature medium-entropy alloy has a crystal structure mainly in BCC phase, a density not greater than 6.4 g / cm 3 , a Vickers hardness of 250-400 HV, a room temperature compression yield strength of 870-1300 MPa, a strain greater than 50%, an 800 ℃ compression yield strength of 520-720 MPa, a strain greater than 70%; a room temperature tensile yield strength of 880-1300 MPa, a strain greater than 6%, a 600 ℃ tensile yield strength of 520-700 MPa, a strain greater than 10%, and an 800 ℃ tensile yield strength of 500-650 MPa.

6. A method of preparing a lightweight high-entropy alloy with high-temperature brittleness resistance according to any one of claims 1-5, characterized in that, The method comprises the following steps: (1) according to the atomic percentage of titanium, vanadium, niobium and nitrogen, at least one of titanium, vanadium, niobium metal elements and titanium, vanadium, niobium metal nitrides is weighed; (2) the raw materials weighed in step (1) are put into the copper crucible of the electric arc furnace together, and the cavity is cleaned; (3) adjust the current of the electric arc furnace to make the raw materials in the crucible melt, and open the magnetic stirring device, and the alloy ingot is obtained after melting; (4) the alloy ingot obtained in step (3) is repeatedly melted at least 4 times according to step (3), and after cooling, the lightweight high-temperature medium-entropy alloy with high-temperature brittleness resistance is obtained.

7. The preparation method of the lightweight high-temperature medium-entropy alloy with high-temperature brittleness resistance according to claim 6, characterized in that, In step (1), the purity of the metal element is more than 99%, and the metal nitride is niobium nitride.

8. The method for preparing a lightweight, high-temperature, medium-entropy alloy resistant to high-temperature brittleness according to claim 6, characterized in that, The specific steps of cleaning the chamber in step (2) are: vacuumizing to 10 -2 -10 -3 Pa, and then filling high-purity protective gas to make the gas pressure in the chamber less than the gas pressure outside the chamber.

9. The method for preparing a lightweight, high-temperature, medium-entropy alloy resistant to high-temperature brittleness according to claim 6, characterized in that, In step (4), step (3) is repeated 4 times.

10. The application of a lightweight high-temperature medium-entropy alloy with high-temperature brittleness resistance according to any one of claims 1-5 in the field of room temperature processing and high-temperature load bearing.

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