A low-density, ultrafine lamellar eutectic high-entropy alloy and its application in high-temperature structural materials.

Abstract

This invention discloses a low-density, ultrafine lamellar eutectic high-entropy alloy and its application in high-temperature structural materials. This eutectic high-entropy alloy is composed of a BCC+B2 lamellar structure. At room temperature, the Nb-rich BCC phase provides plastic deformation to ensure the alloy's ductility and toughness. At high temperatures, the B2 intermetallic compound phase, rich in Ti, V, and Fe / Co / Ni elements, exhibits higher strength to ensure the alloy possesses high-temperature strength. Simultaneously, the numerous interfaces between the two phases hinder inter-element diffusion, enhancing the alloy's high-temperature structural stability and mechanical properties. The eutectic high-entropy alloy of this invention exhibits a strength of 300 MPa and a strength retention rate of 20% at 1000°C, superior to classic nickel-based superalloys such as Inconel 718.

Description

Technical Field

[0001] This invention relates to the field of metallic materials and their preparation technology, and in particular to a low-density, ultrafine lamellar eutectic high-entropy alloy and its application in the field of high-temperature structural materials. Background Technology

[0002] High-temperature structural materials are materials that withstand static or dynamic mechanical loads under high-temperature conditions. These materials generally possess high high-temperature strength and good oxidation resistance to achieve high-temperature load-bearing capacity. Currently, the most widely used high-temperature structural materials are nickel-based superalloys, which have excellent high-temperature resistance and can operate at temperatures close to 90% of their melting point. Next-generation aerospace vehicles place even more stringent demands on thrust-to-weight ratios. On the one hand, engine weight needs to be reduced; on the other hand, the operating temperature of the thrust chamber needs to be increased. Therefore, there is a need to develop lighter and more heat-resistant high-temperature structural materials.

[0003] Eutectic high-entropy alloys are a new type of high-entropy alloy designed and developed based on the concept of eutectic alloys. They are characterized by low melting point and good casting fluidity, and can be used to prepare large-sized complex components. Traditional theory holds that metallic materials soften significantly at temperatures above 60% of their melting point. Eutectic high-entropy alloys have melting points lower than those of their pure components, making it difficult to maintain good performance at high temperatures and unsuitable for application in the field of high-temperature structural materials.

[0004] Therefore, it is necessary to develop a novel eutectic high-entropy alloy with low density (lower than nickel) and ultrafine lamellar structure to meet the requirements of next-generation high-temperature structural materials for low density, high strength and easy preparation. Summary of the Invention

[0005] This invention provides a low-density, ultra-fine lamellar eutectic high-entropy alloy and its application in the field of high-temperature structural materials, which overcomes the shortcomings of existing technologies such as insufficient high-temperature resistance.

[0006] To achieve the above objectives, this invention proposes a low-density, ultrafine lamellar eutectic high-entropy alloy, which is composed of Ti, V, Nb, and Fe / Co / Ni elements. The alloy phase structure includes a B2 intermetallic compound phase rich in Ti, V, Fe / Co / Ni elements and a BCC solid solution phase rich in Nb elements. The period of the lamellar eutectic structure formed by the two phases is 80-150 nm. Among them, Fe / Co / Ni represents one of Fe, Co, and Ni.

[0007] To achieve the above objectives, the present invention also proposes the application of a low-density, ultra-fine lamellar eutectic high-entropy alloy in the field of high-temperature structural materials, applying the aforementioned eutectic high-entropy alloy to fields such as thrust chambers of aerospace vehicles and aero engines.

[0008] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0009] 1. The low-density, ultrafine lamellar eutectic high-entropy alloy provided by this invention is composed of a BCC+B2 lamellar structure. At room temperature, the Nb-rich BCC phase provides plastic deformation to ensure the alloy's ductility and toughness. At high temperature, the B2 intermetallic compound phase, rich in Ti, V, and Fe / Co / Ni elements, has higher strength to ensure the alloy possesses high-temperature strength. This is because V and Ti can be infinitely dissolved, significantly expanding the temperature range and stability of the alloy's BCC structure. Furthermore, the Ti-V BCC solid solution can form B2 intermetallic compounds with Fe / Co / Ni elements. These intermetallic compounds have ordered covalent bonds and stronger chemical bonds, maintaining structural temperature and high strength at high temperatures. Simultaneously, the numerous interfaces between the two phases hinder inter-element diffusion, improving the alloy's high-temperature structural stability and high-temperature mechanical properties. The eutectic high-entropy alloy of this invention has a strength of 300 MPa at 1000℃ (95% of the melting point) and a strength retention rate (high-temperature yield strength / room temperature yield strength) of 20%, which is superior to classic nickel-based high-temperature alloys such as Inconel 718.

[0010] 2. The eutectic high-entropy alloy of the present invention has a melting point of around 1050°C, a low melting point and a very narrow liquid-solid two-phase region, and can form complex structural parts through simple casting, which can greatly reduce the cost in the preparation process and facilitate large-scale industrial production.

[0011] 3. The density of the eutectic high-entropy alloy of the present invention is 7–7.25 g / cm³. 3 It is far lower than that of nickel-based superalloys (density higher than 8 g / cm³). 3 Furthermore, the oxidation rate of the eutectic high-entropy alloy of the present invention is close to that of nickel-based alloys, and far lower than that of traditional titanium alloys and niobium alloys. Attached Figure Description

[0012] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the structures shown in these drawings without creative effort.

[0013] Figure 1 The room temperature stress-strain curve of the Ti2VNbNi3 alloy provided in Example 1;

[0014] Figure 2 The X-ray diffraction pattern of the Ti2VNbFe3 alloy provided in Example 1;

[0015] Figure 3 SEM image of the Ti2VNbFe3 alloy provided in Example 1;

[0016] Figure 4 TEM image of the Ti2VNbFe3 alloy provided in Example 1;

[0017] Figure 5 The DSC curve of the Ti2VNbFe3 alloy provided in Example 1;

[0018] Figure 6 The stress-strain curve of the Ti2VNbFe3 alloy provided in Example 1 at 1000℃;

[0019] Figure 7 Macroscopic image of the surface of the Ti2VNbNi3 alloy oxide sample provided in Example 1;

[0020] Figure 8 The oxidation weight gain curve of the Ti2VNbNi3 alloy provided in Example 1;

[0021] Figure 9 Ti2VNbFe provided in Example 2 3.2 Room temperature stress-strain curve of the alloy;

[0022] Figure 10 Ti2VNbFe provided in Example 2 3.2 X-ray diffraction pattern of the alloy;

[0023] Figure 11 Ti2VNbFe provided in Example 2 3.2 SEM images of the alloy;

[0024] Figure 12 Ti2VNbFe provided in Example 2 3.2 Stress-strain curve of the alloy at 800℃;

[0025] Figure 13 Ti2VNbFe provided in Example 3 2.8 Room temperature stress-strain curve of the alloy;

[0026] Figure 14 Ti2VNbFe provided in Example 3 2.8 X-ray diffraction pattern of the alloy;

[0027] Figure 15 Ti2VNbFe provided in Example 3 2.8 SEM images of the alloy;

[0028] Figure 16 Ti2VNbFe provided in Example 3 2.8Stress-strain curve of the alloy at 800℃;

[0029] Figure 17 TiVNbFe provided in Example 4 2.3 Room temperature stress-strain curve of the alloy;

[0030] Figure 18 TiVNbFe provided in Example 4 2.3 X-ray diffraction pattern of the alloy;

[0031] Figure 19 TiVNbFe provided in Example 4 2.3 SEM images of the alloy;

[0032] Figure 20 TiVNbFe provided in Example 4 2.3 Stress-strain curve of the alloy at 800℃.

[0033] The realization of the objective, functional features and advantages of the present invention will be further explained in conjunction with the embodiments and with reference to the accompanying drawings. Detailed Implementation

[0034] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0035] Furthermore, the technical solutions of the various embodiments of the present invention can be combined with each other, but only if they are feasible for those skilled in the art. If the combination of technical solutions is contradictory or cannot be implemented, it should be considered that such combination of technical solutions does not exist and is not within the scope of protection claimed by the present invention.

[0036] Unless otherwise specified, all medicines / reagents used are commercially available.

[0037] This invention proposes a low-density, ultrafine lamellar eutectic high-entropy alloy, which is composed of Ti, V, Nb and Fe / Co / Ni elements. The alloy phase structure includes a B2 intermetallic compound phase rich in Ti, V, Fe / Co / Ni elements and a BCC solid solution phase rich in Nb elements. The period of the lamellar eutectic structure formed by the two phases is 80-150 nm. Among them, Fe / Co / Ni represents one of Fe, Co and Ni.

[0038] Preferably, the general formula of the eutectic high-entropy alloy is Ti. a V b Nbc (Fe / Co / Ni) d , where 1≤a≤2, 0.5≤b≤1.5, 0.5≤c≤1.5, 2.3≤d≤3.2, and a, b, c, and d are all mole percentages.

[0039] Preferably, the eutectic high-entropy alloy is Ti2VNbNi3, with a compressive strength of 2202 MPa, a compressive fracture deformation rate of 11.5%, and a density of 7.23 g / cm³. 3 It has a melting point of 1040℃ and a microstructure of BCC+B2 lamellar structure with a wavelength of 100nm.

[0040] Preferably, the eutectic high-entropy alloy has a strength of approximately 1030 MPa and a room temperature yield strength of 68% at 600°C and 57% of its melting point.

[0041] The strength is approximately 500 MPa at 800℃ and 76% of the melting point, with a room temperature yield strength of 33%.

[0042] The strength is approximately 300 MPa at 1000℃ and 95% of the melting point, with a yield strength of 20% at room temperature.

[0043] Preferably, the eutectic high-entropy alloy is Ti2VNbFe. 3.2 The alloy has a compressive strength of 1800 MPa, a compressive fracture deformation rate of 4%, and a density of 7.30 g / cm³. 3 The microstructure is hypereutectic, and the strength is approximately 200 MPa at 800℃.

[0044] Preferably, the eutectic high-entropy alloy is Ti2VNbCo. 2.8 The alloy has a compressive strength of 1870 MPa, a compressive fracture deformation rate of 6%, and a density of 7.20 g / cm³. 3 The microstructure is hypoeutectic, and the strength is approximately 200 MPa at 800℃.

[0045] Preferably, the eutectic high-entropy alloy is TiVNbNi. 2.3 The alloy has a compressive strength of 2140 MPa, a compressive fracture deformation rate of 4%, and a density of 7.56 g / cm³. 3 Its microstructure is dendritic, and its strength is approximately 370 MPa at 800℃.

[0046] Preferably, the preparation method of the eutectic high-entropy alloy includes the following steps:

[0047] S1. Place the solid pure raw materials of Ti, V, Nb, Fe, Co and Ni into different containers, add alcohol solution, and ultrasonically clean and dry them.

[0048] S2: According to Ti a V b Nb c (Fe / Co / Ni) d The molar percentage of the multi-principal element alloy was precisely measured using an analytical balance, and the Ti and V raw materials were mixed, while the Nb and (Fe / Co / Ni) raw materials were placed in separate containers.

[0049] S3: Place the TiV mixed raw material in a crucible, place the Nb raw material on top of the TiV mixed raw material, melt it in a vacuum arc furnace, then add the (Fe / Co / Ni) raw material and continue melting to obtain the eutectic high-entropy alloy.

[0050] Preferably, step S3 specifically comprises:

[0051] S31: Place the TiV mixed raw material in a crucible, place the Nb raw material on top of the TiV mixed raw material, and place the (Fe / Co / Ni) raw material in another crucible;

[0052] S32: Close the furnace door and evacuate to a vacuum level of 3-4 × 10⁻⁴. -3 After Pa, backflush with argon gas to 0.05–0.06 MPa;

[0053] S33: Turn on the melting power supply, and after igniting the arc, first purify the intracranial atmosphere by melting titanium ingots. Repeat the melting process twice to ensure that the oxygen in the cavity is absorbed by the titanium ingots.

[0054] S34: Melt the TiVNb mixed raw material with a melting current of 350-500A and a melting time of 80-100s, repeating the melting process 4-5 times;

[0055] S35: Mix the cast TiVNb alloy ingot and (Fe / Co / Ni) raw material in the same crucible;

[0056] S36: Melt according to step S34. After the alloy ingot has completely cooled, turn it over and repeat the melting process twice.

[0057] S37: Place the alloy ingot on its side against the crucible wall and melt it according to step S34. Repeat the melting process 6 times to obtain a eutectic high-entropy alloy.

[0058] This invention also proposes the application of a low-density, ultra-fine lamellar eutectic high-entropy alloy in the field of high-temperature structural materials, applying the aforementioned eutectic high-entropy alloy to fields such as thrust chambers of aerospace vehicles and aero engines.

[0059] Example 1

[0060] This embodiment provides a low-density, ultrafine lamellar eutectic high-entropy alloy, which is Ti2VNbNi3, with the molar ratio of active metal elements Ti, V, Nb to Ni being 2:1:1:3.

[0061] The Ti2VNbNi3 alloy provided in this embodiment is prepared using the traditional electric arc melting method.

[0062] The Ti2VNbNi3 alloy provided in this embodiment has a compressive strength of 2202 MPa, a compressive fracture deformation rate of 11.5%, a density of 7.23 g / cm3, a melting point of 1040℃, and a microstructure of BCC+B2 lamellar structure with a lamellar structure wavelength of approximately 100 nm. Under the conditions of 600℃ (57% melting point), 800℃ (76% melting point), and 1000℃ (95% melting point), the strengths are 1030 MPa (68% yield strength), 500 MPa (33% yield strength), and 300 MPa (20% yield strength), respectively.

[0063] Figure 1 The room temperature stress-strain curve of the Ti2VNbNi3 alloy provided in Example 1 shows that the maximum compressive strength is 2202 MPa.

[0064] Figure 2 The X-ray diffraction pattern of the Ti2VNbNi3 alloy provided in Example 1 shows that the alloy in this example is composed of BCC+B2.

[0065] Figure 3 The image shows a SEM image of the Ti2VNbNi3 alloy provided in Example 1. As can be seen from the image, the alloy in this example is composed of obvious lamellar structure.

[0066] Figure 4 The image shows a TEM image of the Ti2VNbNi3 alloy provided in Example 1. As can be seen from the image, the lamellar structure of the alloy in this example is about 100 nm (the sum of the two phase lamellars).

[0067] Figure 5 The figure shows the DSC curve of the Ti2VNbNi3 alloy provided in Example 1. As can be seen from the figure, the melting point of the alloy in this example is 1087℃.

[0068] Figure 6 The figure shows the high-temperature stress-strain curve of the Ti2VNbNi3 alloy provided in Example 1. As can be seen from the figure, the alloy in this example still maintains a strength of 300 MPa at 92% melting point.

[0069] Figure 7 Macroscopic image of the surface of the Ti2VNbNi3 alloy oxide sample provided in Example 1.

[0070] Figure 8The oxidation weight gain curve of the Ti2VNbNi3 alloy provided in Example 1.

[0071] Example 2

[0072] This embodiment provides a eutectic high-entropy alloy containing highly active elements, specifically Ti₂VNbFe. 3.2 The molar ratio of active metal elements Ti, V, Nb to Fe is 2:1:1:3.2.

[0073] The Ti2VNbFe provided in this embodiment 3.2 The alloy was prepared using the traditional electric arc melting method.

[0074] The Ti2VNbFe provided in this embodiment 3.2 The alloy has a compressive strength of 1800 MPa, a compression fracture deformation rate of 4%, a density of 7.30 g / cm3, a hypereutectic microstructure, and a strength of 200 MPa at 800℃.

[0075] Figure 9 Ti2VNbFe provided in Example 2 3.2 The room temperature stress-strain curve of the alloy shows that the maximum compressive strength of the alloy in this embodiment is 1800 MPa.

[0076] Figure 10 Ti2VNbFe provided in Example 2 3.2 The X-ray diffraction pattern of the alloy shows that the alloy in this embodiment is composed of BCC+B2.

[0077] Figure 11 Ti2VNbFe provided in Example 2 3.2 The SEM image of the alloy shows that the alloy in this embodiment has a typical hypereutectic structure.

[0078] Figure 12 Ti2VNbFe provided in Example 2 3.2 The stress-strain curve of the alloy at 800℃ shows that the compressive strength of the alloy in this embodiment is 200MPa.

[0079] Example 3

[0080] This embodiment provides a eutectic high-entropy alloy containing highly active elements, the alloy being Ti2VNbCo. 3.2 The molar ratio of active metal elements Ti, V, Nb to Co is 2:1:1:2.8.

[0081] The Ti2VNbCo provided in this embodiment 2.8 The alloy was prepared using the traditional electric arc melting method.

[0082] The Ti2VNbCo provided in this embodiment 2.8 The alloy has a compressive strength of 1870 MPa, a compressive fracture deformation rate of 6%, a density of 7.20 g / cm3, a hypoeutectic microstructure, and a strength of 200 MPa at 800℃.

[0083] Figure 13 Ti2VNbCo provided in Example 3 2.8 The room temperature stress-strain curve of the alloy shows that the maximum compressive strength of the alloy in this embodiment is 1870 MPa.

[0084] Figure 14 Ti2VNbCo provided in Example 3 2.8 X-ray diffraction pattern of the alloy.

[0085] Figure 15 Ti2VNbCo provided in Example 3 2.8 The SEM image of the alloy shows that the alloy in this embodiment has a hypoeutectic structure.

[0086] Figure 16 Ti2VNbCo provided in Example 3 2.8 The stress-strain curve of the alloy at 800℃ shows that the compressive strength of this embodiment is 200MPa.

[0087] Example 4

[0088] This embodiment provides a eutectic high-entropy alloy containing highly active elements, the alloy being Ti2VNbNi. 3.2 The molar ratio of active metal elements Ti, V, Nb to Ni is 1:1:1:2.3.

[0089] The TiVNbNi provided in this embodiment 2.3 The alloy was prepared using the traditional electric arc melting method.

[0090] The TiVNbNi provided in this embodiment 2.3 The alloy has a compressive strength of 2140 MPa, a compressive fracture deformation rate of 4%, a density of 7.56 g / cm3, a dendritic microstructure, and a strength of 370 MPa at 800℃.

[0091] Figure 17 The TiVNbNi provided in Example 4 2.3 The room temperature stress-strain curve of the alloy shows that the compressive strength of the alloy in this embodiment is 2140 MPa.

[0092] Figure 18 The TiVNbNi provided in Example 4 2.3 X-ray diffraction pattern of the alloy.

[0093] Figure 19 The TiVNbNi provided in Example 4 2.3 The SEM image of the alloy shows that the alloy in this embodiment has a hypoeutectic structure.

[0094] Figure 20 The TiVNbNi provided in Example 4 2.3 The stress-strain curve of the alloy at 800℃. The above description is merely a preferred embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent structural transformations made using the description and drawings of the present invention under the inventive concept of the present invention, or direct / indirect applications in other related technical fields, are included within the patent protection scope of the present invention.

Claims

1. A low-density, ultrafine lamellar eutectic high-entropy alloy, characterized in that, The eutectic high-entropy alloy is composed of Ti, V, Nb, and Fe / Co / Ni elements. The alloy phase structure includes a B2 intermetallic compound phase rich in Ti, V, and Fe / Co / Ni elements, and a BCC solid solution phase rich in Nb elements. The period of the lamellar eutectic structure formed by these two phases is 80–150 nm. Fe / Co / Ni represents one of Fe, Co, and Ni. The density of the eutectic high-entropy alloy is 7–7.25 g / cm³. 3 The general formula of the eutectic high-entropy alloy is Ti. a V b Nb c (Fe / Co / Ni) d Where 1≤a≤2, 0.5≤b≤1.5, 0.5≤c≤1.5, 2.3≤d≤3.2, and a, b, c, and d are all mole percentages; The preparation method of the eutectic high-entropy alloy includes the following steps: S1. Place Ti, V, Nb and (Fe / Co / Ni) solid pure raw materials into different containers, add alcohol solution, ultrasonically clean and dry; S2: According to Ti a V b Nb c (Fe / Co / Ni) d The molar percentage of the multi-principal element alloy was precisely measured using an analytical balance, and the Ti and V raw materials were mixed, while the Nb and (Fe / Co / Ni) raw materials were placed in separate containers. S3: Place the TiV mixed raw material in a crucible, place the Nb raw material on top of the TiV mixed raw material, melt it in a vacuum arc furnace, then add the (Fe / Co / Ni) raw material and continue melting to obtain the eutectic high entropy alloy; Step S3 specifically involves: S31: Place the TiV mixed raw material in a crucible, place the Nb raw material on top of the TiV mixed raw material, and place the (Fe / Co / Ni) raw material in another crucible; S32: Close the furnace door and evacuate to a vacuum level of 3~4×10⁻⁴. -3 After Pa, backflush with argon gas to 0.05~0.06 MPa; S33: Turn on the melting power supply, and after igniting the arc, first purify the intracranial atmosphere by melting titanium ingots. Repeat the melting process twice to ensure that the oxygen in the cavity is absorbed by the titanium ingots. S34: Melt the TiVNb mixed raw material with a melting current of 350~500A and a melting time of 80~100s, repeating the melting process 4~5 times; S35: Mix the cast TiVNb alloy ingot and (Fe / Co / Ni) raw material in the same crucible; S36: Melt according to step S34. After the alloy ingot has completely cooled, turn it over and repeat the melting process twice. S37: Place the alloy ingot on its side against the crucible wall and melt it according to step S34. Repeat the melting process 6 times to obtain a eutectic high-entropy alloy.

2. The eutectic high-entropy alloy as described in claim 1, characterized in that, The eutectic high-entropy alloy is Ti2VNbNi3, with a compressive strength of 2202 MPa, a compressive fracture deformation rate of 11.5%, and a density of 7.23 g / cm³. 3 It has a melting point of 1040℃ and a microstructure of BCC+B2 lamellar structure with a wavelength of 100 nm.

3. The eutectic high-entropy alloy as described in claim 2, characterized in that, The eutectic high-entropy alloy has a strength of 1030 MPa and a room temperature yield strength of 68% at 600℃ and 57% of its melting point. The strength is 500 MPa at 800℃ and 76% of the melting point, and the room temperature yield strength is 33%. The strength is 300 MPa at 1000℃ and 95% of the melting point, and the yield strength is 20% at room temperature.

4. The eutectic high-entropy alloy as described in claim 1, characterized in that, The eutectic high-entropy alloy is Ti2VNbFe 3.2 The alloy has a compressive strength of 1800 MPa, a compressive fracture deformation rate of 4%, and a density of 7.30 g / cm³. 3 The microstructure is hypereutectic, and the strength is 200 MPa at 800℃.

5. The eutectic high-entropy alloy as described in claim 1, characterized in that, The eutectic high-entropy alloy is Ti2VNbCo. 2.8 The alloy has a compressive strength of 1870 MPa, a compressive fracture deformation rate of 6%, and a density of 7.20 g / cm³. 3 The microstructure is hypoeutectic, and the strength is 200 MPa at 800℃.

6. The eutectic high-entropy alloy as described in claim 1, characterized in that, The eutectic high-entropy alloy is TiVNbNi. 2.3 The alloy has a compressive strength of 2140 MPa, a compressive fracture deformation rate of 4%, and a density of 7.56 g / cm³. 3 The microstructure is dendritic, and the strength is 370 MPa at 800℃.

7. The application of a low-density, ultrafine lamellar eutectic high-entropy alloy in the field of high-temperature structural materials, characterized in that, The eutectic high-entropy alloy described in any one of claims 1 to 6 is applied in the fields of aerospace vehicle thrust chambers and aero engines.

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