Nitrogen-doped high-entropy alloy with excellent room-temperature and low-temperature performance and preparation method of nitrogen-doped high-entropy alloy

Abstract

The invention discloses a nitrogen-doped high-entropy alloy with excellent room-temperature and low-temperature performance, the atomic percent expression of the high-entropy alloy is (Cr20Mn24Fe30Co20Ni6) xNy, x is more than or equal to 98 and less than 100, y is more than 0 and less than or equal to 2, and the sum of x and y is 100. According to the invention, the proportion of the main element of the alloy to the nitrogen element is regulated and controlled, the Cr20Mn24Fe30Co20Ni6 with a double-phase structure is added with interstitial N atoms, the deformation temperature is regulated and controlled, the stacking fault energy of the Cr20Mn24Fe30Co20Ni6 is regulated and controlled, and the generation of deformation twin crystals and martensite phase transformation is controlled, so that the face-centered cubic single-phase alloy material is obtained and has relatively high strength and plasticity under the conditions of room temperature and low temperature, the low-temperature tensile strength is close to 1GPa, and the tensile strength is close to 1GPa. The elongation rate exceeds 60%; the preparation process is simple in thermomechanical treatment procedure, few in heat treatment procedure, easy to operate and high in preparation efficiency.

Description

Technical Field

[0001] The present invention relates to the technical field of alloy material preparation, and in particular to a nitrogen-doped high-entropy alloy with excellent room temperature and low temperature performance and a preparation method thereof. Background Art

[0002] High entropy alloys are generally composed of 4 or more main elements, and can form single-phase or two-phase solid solutions without the appearance of complex intermetallic compounds. Compared with traditional alloys, this alloy has better performance in low-temperature toughness, high-temperature thermal stability, corrosion resistance, and radiation resistance, which makes the alloy have broad application prospects under extremely complex environmental conditions. The most widely studied equiatomic ratio CrMnFeCoNi high entropy alloy has a plasticity of more than 60%, but its yield strength is often less than 400MPa, which is difficult to meet the requirements of engineering applications. Therefore, the preparation of high-entropy alloys with high strength and high plasticity under extreme environments has become an urgent problem to be solved.

[0003] After the design concept of "metastable engineering" is introduced into high entropy alloys, the strength-plasticity of high entropy alloys can be effectively improved by adjusting the ratio of the main elements of the alloy. In addition, nitrogen, as a commonly used interstitial strengthening element in austenitic stainless steel, duplex stainless steel and other steels, can significantly improve the strength, corrosion resistance, biological application safety and other properties of steel, especially the low-temperature strength-toughness of austenitic stainless steel.

[0004] However, only a few studies have improved the room temperature mechanical properties of CrMnFeCoNi alloys by introducing interstitial atoms into equiatomic ratios, but it is difficult to achieve excellent mechanical properties at both room temperature and low temperature. For high entropy alloys, the optimization path for room temperature and low temperature mechanical properties is still focused on complex deformation and heat treatment processes, and these methods are difficult to improve strength and plasticity at the same time.

[0005] In summary, it is of great significance to study and develop a high-entropy alloy material that has excellent mechanical properties at both room temperature and low temperature. Summary of the invention

[0006] In view of the deficiencies in the prior art, the present invention provides a nitrogen-doped high entropy alloy with excellent room temperature and low temperature performance and a preparation method thereof, and regulates the ratio of the main element of the alloy to the nitrogen element. Under the premise of not introducing other precipitated phases, a single-phase alloy material with high strength and plasticity at both room temperature and low temperature is obtained, which opens up prospects for the application of high entropy alloys in extreme service environments and solves the problem that high entropy alloys cannot have both high strength and high plasticity under room temperature and low temperature conditions.

[0007] In order to solve the above technical problems, the first aspect of the present invention provides a nitrogen-doped high entropy alloy with excellent room temperature and low temperature performance, wherein the atomic percentage expression of the high entropy alloy is: (Cr 20Mn 24 Fe 30 Co 20 Ni 6 ) x N y , where 98≤x<100, 0<y≤2, and x+y=100.

[0008] The present invention adjusts the ratio of the main element and the nitrogen element of the alloy to form a dual-phase structure of Cr 20 Mn 24 Fe 30 Co 20 Ni 6 By adding interstitial N atoms, adjusting the deformation temperature, regulating the stacking fault energy, and controlling the generation of deformation twins and martensitic phase transformation, a face-centered cubic single-phase alloy material is obtained; the resulting high-entropy alloy material has high strength and plasticity both at room temperature and low temperature, which solves the problem that high-entropy alloys in the prior art cannot have both high strength and high plasticity under room temperature and low temperature conditions, and opens up prospects for the application of high-entropy alloys in extreme service environments.

[0009] Furthermore, x=99, and y=1.

[0010] Furthermore, the high entropy alloy is a face-centered cubic single-phase alloy.

[0011] The second aspect of the present invention provides a method for preparing the nitrogen-doped high entropy alloy with excellent room temperature and low temperature performance as described in the first aspect, comprising the following steps:

[0012] S1. Adding Cr, Mn, Fe, Co, Ni metal particles and chromium nitride into a magnetic suspension melting furnace, melting them under a protective atmosphere, cooling and solidifying them to obtain an alloy ingot;

[0013] S2, hot rolling the alloy ingot, and water cooling after final rolling to obtain an alloy plate;

[0014] S3. The alloy plate is subjected to high-temperature homogenization heat treatment, and water-cooled to obtain the nitrogen-doped high-entropy alloy with excellent room temperature and low temperature properties.

[0015] Furthermore, in S1, the purity of the Cr, Mn, Fe, Co, Ni metal particles and chromium nitride is ≥99.5wt%.

[0016] Furthermore, in S1, the smelting and cooling solidification are specifically as follows: after the alloy is melted and cooled, it is turned upside down and melted and cooled again, and this is repeated 3-8 times.

[0017] Furthermore, in S2, the hot rolling treatment is performed by 4-6 rolling passes, the reduction amount of each rolling pass is independently selected from 5%-20%, and the total reduction amount is 45%-55%.

[0018] Furthermore, in S2, annealing is performed during the hot rolling process, and the annealing temperature is 900-1000° C. and the time is 5-30 min.

[0019] Furthermore, in S3, the temperature of the high temperature homogenization heat treatment is 1200±20°C, and the time is 2-4h.

[0020] Furthermore, in S3, the high-temperature homogenization heat treatment is carried out under a protective atmosphere.

[0021] Furthermore, the protective atmosphere in S1 and S3 is argon.

[0022] Beneficial effects of the present invention:

[0023] The present invention adjusts the ratio of the main element and the nitrogen element of the alloy to form a dual-phase structure of Cr 20 Mn 24 Fe 30 Co 20 Ni 6 By adding interstitial N atoms, regulating their stacking fault energy, controlling the generation of deformation twins and martensitic phase transformation, a face-centered cubic single-phase alloy material is obtained. It has high strength and plasticity both at room temperature and low temperature conditions, with a low-temperature tensile strength close to 1 GPa and an elongation of more than 60%.

[0024] The method of the invention has simple deformation heat treatment process, fewer heat treatment processes, is easy to operate and has high preparation efficiency.

[0025] The nitrogen-doped CrMnFeCoNi high entropy alloy of the present invention reduces the amount of Ni added and reduces the alloy cost. At the same time, the addition of Cr and Co elements effectively improves the corrosion resistance and oxidation resistance of the alloy. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] In order to more clearly illustrate the technical solution of the present invention, the drawings required for use in the embodiments are briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0027] Figure 1 It is the XRD spectrum of the high entropy alloy obtained in Example 1 and Comparative Examples 1-2 of the present invention;

[0028] Figure 2 The tensile test results of the high entropy alloy obtained in Example 1 of the present invention at 293K and 200K;

[0029] Figure 3The tensile test results of the high entropy alloys obtained in Example 1 and Comparative Examples 1-2 of the present invention at a temperature of 293K are shown;

[0030] Figure 4 These are the tensile test results of the high entropy alloys obtained in Example 1 and Comparative Examples 1-2 of the present invention at a temperature of 200K. DETAILED DESCRIPTION

[0031] The technical solution of the present invention will be described clearly and completely below in conjunction with the specific embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0032] This embodiment provides a nitrogen-doped high entropy alloy with excellent room temperature and low temperature performance. The atomic percentage expression of the high entropy alloy is: (Cr 20 Mn 24 Fe 30 Co 20 Ni 6 ) x N y , where 98≤x<100, 0<y≤2, and x+y=100.

[0033] Preferably, 98.5≤x<99.5, 0<y≤1.5, and x+y=100.

[0034] As a specific example, x=99, y=1; the values ​​of x and y may also be: x=98.5, y=1.5; x=98.8, y=1.2; x=99.2, y=1.5; x=99.5, y=0.5, etc.

[0035] Specifically, the high entropy alloy is a face-centered cubic single-phase alloy.

[0036] Another embodiment provides a method for preparing the nitrogen-doped high entropy alloy having excellent room temperature and low temperature properties as described in the above embodiment, comprising the following steps:

[0037] S1. Adding Cr, Mn, Fe, Co, Ni metal particles and chromium nitride into a magnetic suspension melting furnace, melting them under a protective atmosphere, cooling and solidifying them to obtain an alloy ingot;

[0038] S2, hot rolling the alloy ingot, and water cooling after final rolling to obtain an alloy plate;

[0039] S3. The alloy plate is subjected to high-temperature homogenization heat treatment, and water-cooled to obtain the nitrogen-doped high-entropy alloy with excellent room temperature and low temperature properties.

[0040] Preferably, in S1, the purity of the Cr, Mn, Fe, Co, Ni metal particles and chromium nitride is ≥99.5wt%.

[0041] Preferably, in S1, the smelting and cooling solidification are specifically as follows: after the alloy is melted and cooled, it is turned upside down and melted and cooled again, and this is repeated 3-8 times, which can be 3, 4, 5, 6, 7, 8 times, and the uniformity of smelting is improved by repeated melting and cooling.

[0042] Preferably, in S2, the hot rolling treatment is performed by 4-6 rolling passes, the reduction amount of each rolling pass is independently selected from 5%-20%, and the total reduction amount is 45%-55%.

[0043] Preferably, in S2, annealing is performed during the hot rolling process, the annealing temperature is 900-1000° C., and the time is 5-30 min.

[0044] Preferably, in S3, the temperature of the high-temperature homogenization heat treatment is 1200±20° C., the time is 2-4 hours, and the high-temperature homogenization heat treatment is carried out under a protective atmosphere.

[0045] As a specific example, the protective atmosphere in S1 and S3 is argon.

[0046] Example 1

[0047] This embodiment relates to a method for preparing a nitrogen-doped high entropy alloy with excellent room temperature and low temperature performance. The atomic percentage expression of the alloy is (Cr 20 Mn 24 Fe 30 Co 20 Ni 6 ) 99 N 1 , the preparation method comprises the following steps:

[0048] (1) ultrasonically cleaning and drying metal particles of Cr, Mn, Fe, Co, Ni and chromium nitride with a purity of ≥99.5wt% using anhydrous ethanol;

[0049] (2) placing the cleaned raw materials in a magnetic suspension melting furnace, melting and cooling in an argon environment, turning them upside down and melting and cooling them again, and melting and cooling them four times to obtain an alloy ingot;

[0050] (3) hot rolling at 950°C with 5 passes and a final reduction of 50%;

[0051] (4) A nitrogen-doped high-entropy alloy with excellent room temperature and low-temperature properties is obtained by homogenizing the alloy at 1200°C in an argon atmosphere and cooling the alloy with water.

[0052] The nitrogen-doped high entropy alloy prepared in Example 1 was polished step by step using different types of sandpaper to 2000 mesh, and then subjected to XRD detection. The X-ray source was CuKa rays, the scanning range was 20° to 130°, and the scanning speed was 4° / min.

[0053] The nitrogen-doped high entropy alloy prepared in Example 1 was cut into tensile specimens using a wire-cut electric discharge machine. The tensile specimens were placed under 293K and 200K conditions for tensile property testing.

[0054] Comparative Example 1

[0055] This comparative example relates to a method for preparing a high entropy alloy, which differs from Example 1 in that: the high entropy alloy is Cr 20 Mn 24 Fe 30 Co 20 Ni 6 The raw materials for step (1) are: Cr, Mn, Fe, Co, Ni, and the other parameters and steps remain unchanged.

[0056] The high entropy alloy obtained in Comparative Example 1 was polished step by step using sandpaper of different types until it reached 2000 mesh, and then subjected to XRD detection. The X-ray source was CuKa ray, the scanning range was 20° to 130°, and the scanning speed was 4° / min.

[0057] The high entropy alloy prepared in Comparative Example 1 was cut into tensile specimens using an electric spark wire cutting machine, and the tensile specimens were placed under 293K and 200K conditions for tensile performance testing.

[0058] Comparative Example 2

[0059] This comparative example relates to a method for preparing a carbon-doped high entropy alloy, which differs from Example 1 in that: the high entropy alloy is (Cr 20 Mn 24 Fe 30 Co 20 Ni 6 ) 99 C 1 The raw materials for step (1) are: Cr, Mn, Fe, Co, Ni, C, and the other parameters and steps remain unchanged.

[0060] The high entropy alloy obtained in Comparative Example 2 was polished step by step using sandpaper of different types until it reached 2000 mesh, and then subjected to XRD detection. The X-ray source was CuKa ray, the scanning range was 20° to 130°, and the scanning speed was 4° / min.

[0061] The nitrogen-doped high entropy alloy prepared in Comparative Example 2 was cut into tensile specimens using a wire electric discharge machine, and the tensile specimens were placed under 293K and 200K conditions for tensile property testing.

[0062] The XRD test results of Example 1 (N1), Comparative Example 1 (Base), and Comparative Example 2 (C1) are as follows: Figure 1 As shown, it can be seen that the Cr 20 Mn 24 Fe 30 Co 20 Ni 6 It is a face-centered cubic (FCC) structure accompanied by a close-packed (HCP) structure; after adding interstitial atoms N in Example 1 and adding interstitial atoms C in Comparative Example 2, the stacking fault energy is increased, the structure changes, and the resulting high entropy alloy is a face-centered cubic single phase structure.

[0063] Example 1 Preparation of (Cr 20 Mn 24 Fe 30 Co 20 Ni 6 ) 99 N 1 High entropy alloys, tensile test results at 293K and 200K are shown in Figure 2 ,from Figure 2 It can be seen that when the sample is placed at 200K for tensile performance testing, the strength and plasticity of the alloy are improved compared to room temperature conditions. Among them, the yield strength of the alloy reaches 371MPa, the tensile strength reaches 910MPa, and the elongation reaches 60%.

[0064] Figure 3 The tensile test results of the high entropy alloys prepared in Example 1 and Comparative Examples 1-2 at 293K are shown in Table 1. Figure 3 It can be seen that after adding the N element, the yield strength, tensile strength and elongation of the alloy are significantly improved. It can be seen that the nitrogen-doped high entropy alloy of Example 1 has excellent high strength and high plasticity at low temperature.

[0065] Figure 4 The tensile test results of the high entropy alloys prepared in Example 1 and Comparative Examples 1-2 at 200K are shown in Table 1. Figure 4 It can be seen that after adding the N element, the yield strength, tensile strength and elongation of the alloy are significantly improved, among which the yield strength is increased by about 50 MPa, the tensile strength is increased by about 100 MPa, and the elongation is increased by about 18%. It can be seen that the nitrogen-doped high entropy alloy of Example 1 has excellent high strength and high plasticity properties at room temperature.

[0066] comprehensive Figure 3 and Figure 4It can be seen that the nitrogen-doped high entropy alloy prepared in Example 1 of the present invention has mechanical properties of high strength and high plasticity both at room temperature and low temperature conditions.

[0067] In summary, the present invention adjusts the ratio of the main elements and nitrogen elements in the alloy to form a dual-phase structure of Cr 20 Mn 24 Fe 30 Co 20 Ni 6 By adding interstitial N atoms, regulating their stacking fault energy, controlling the generation of deformation twins and martensitic phase transformation, a face-centered cubic single-phase alloy material is obtained, which has high strength and plasticity at room temperature and low temperature conditions, with a low-temperature tensile strength close to 1GPa and an elongation of more than 60%; the deformation heat treatment process is simple, the heat treatment process is few, easy to operate, and the preparation efficiency is high; nitrogen-doped CrMnFeCoNi high-entropy alloy reduces the amount of Ni added and reduces the alloy cost. At the same time, the addition of Cr and Co elements effectively improves the corrosion resistance and oxidation resistance of the alloy.

[0068] The present invention has been described in detail above in conjunction with specific implementations and exemplary examples, but these descriptions cannot be understood as limiting the present invention. Those skilled in the art understand that, without departing from the spirit and scope of the present invention, a variety of equivalent substitutions, modifications or improvements may be made to the technical solution of the present invention and its implementation methods, all of which fall within the scope of the present invention. The scope of protection of the present invention shall be subject to the attached claims.

Claims

1. A nitrogen-doped high entropy alloy with excellent room temperature and low temperature performance, characterized in that: The atomic percentage expression of the high entropy alloy is: (Cr 20 Mn 24 Fe 30 Co 20 Ni6) x N y , where 98≤x<100, 0<y≤2, and x+y=100.

2. The nitrogen-doped high entropy alloy with excellent room temperature and low temperature performance according to claim 1, characterized in that: The x=99, and the y=1.

3. The nitrogen-doped high entropy alloy with excellent room temperature and low temperature performance according to claim 1, characterized in that: The high entropy alloy is a face-centered cubic single-phase alloy.

4. A method for preparing a nitrogen-doped high entropy alloy having excellent room temperature and low temperature properties according to any one of claims 1 to 3, characterized in that: The steps include: S1. Adding Cr, Mn, Fe, Co, Ni metal particles and chromium nitride into a magnetic suspension melting furnace, melting, cooling and solidifying under a protective atmosphere to obtain an alloy ingot; S2, hot rolling the alloy ingot, and water cooling after final rolling to obtain an alloy plate; S3. The alloy plate is subjected to high-temperature homogenization heat treatment, and water-cooled to obtain the nitrogen-doped high-entropy alloy with excellent room temperature and low temperature properties.

5. The method for preparing a nitrogen-doped high entropy alloy having excellent room temperature and low temperature properties as claimed in claim 4, characterized in that: In S1, the purity of the Cr, Mn, Fe, Co, Ni metal particles and chromium nitride is ≥99.5wt%.

6. The method for preparing a nitrogen-doped high entropy alloy having excellent room temperature and low temperature properties as claimed in claim 4, characterized in that: In S1, the smelting and cooling solidification specifically include: after the alloy is melted and cooled, it is turned upside down and melted and cooled again, and this is repeated 3-8 times.

7. The method for preparing a nitrogen-doped high entropy alloy having excellent room temperature and low temperature properties as claimed in claim 4, characterized in that: In S2, the hot rolling treatment adopts 4-6 rolling passes, the reduction amount of each rolling pass is independently selected from 5%-20%, and the total reduction amount is 45%-55%.

8. The method for preparing a nitrogen-doped high entropy alloy having excellent room temperature and low temperature properties as claimed in claim 4, characterized in that: In S2, annealing is performed during the hot rolling process, the annealing temperature is 900-1000° C., and the time is 5-30 minutes.

9. The method for preparing a nitrogen-doped high entropy alloy having excellent room temperature and low temperature properties as claimed in claim 4, characterized in that: In S3, the temperature of the high temperature homogenization heat treatment is 1200±20°C and the time is 2-4h.

10. The method for preparing a nitrogen-doped high entropy alloy having excellent room temperature and low temperature properties as claimed in claim 4, characterized in that: In S3, the high-temperature homogenization heat treatment is performed under a protective atmosphere.

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