High-strength heat-resistant high-entropy stainless steel as well as preparation method and application thereof

Abstract

The invention provides high-strength heat-resistant high-entropy stainless steel. The chemical composition of the high-strength stainless steel is FeaN ibCrcAl dTieNbfNg, wherein a is equal to 30 to 33 at%, b is equal to 25 to 30 at%, c is equal to 13 to 18 at%, d is equal to 10 to 16 at%, e is equal to 2 to 8 at%, f is equal to 0 to 8 at%, and g is equal to 1 to 3 at%. The invention further provides a preparation method and application of the high-strength heat-resistant high-entropy stainless steel. The problem that an existing stainless steel material is insufficient in normal-temperature and high-temperature mechanical property is solved.

Description

Technical Field

[0001] This invention belongs to the field of metal materials technology, specifically relating to a high-strength, heat-resistant, high-entropy stainless steel, its preparation method, and its applications. Background Technology

[0002] In modern industrial systems, traditional austenitic stainless steel with a face-centered cubic (FCC) crystal structure has become an indispensable key structural material in many fields such as chemical engineering, transportation, metallurgy, energy, and medical devices due to its balanced mechanical properties—possessing both the strength and ductility required for conventional working conditions, as well as excellent resistance to electrochemical corrosion, oxidation, and wear, while also taking into account the ease of obtaining raw materials and controllable production costs. For example, in the chemical industry's reaction vessels and piping systems, its resistance to acid and alkali corrosion ensures the stability of the production process; in the body structure and key connecting components of rail transit, its good ductility and processing properties can adapt to complex forming process requirements.

[0003] However, as industrial technology advances towards high-end and extreme applications, the performance limitations of traditional austenitic stainless steel are becoming increasingly apparent. Firstly, its strengthening methods are relatively singular, primarily relying on traditional mechanisms such as solid solution strengthening, cold working strengthening, and precipitation strengthening, with weak synergistic effects between these mechanisms. This directly results in generally low room-temperature mechanical strength; for example, the room-temperature tensile strength of 304 austenitic stainless steel is typically only 500-600 MPa, failing to meet the urgent demands for lightweight and high-strength structural materials in aerospace, high-end equipment manufacturing, and other fields. Secondly, under high-temperature service environments, the grains of traditional austenitic stainless steel are prone to significant growth, reducing dislocation movement resistance and leading to a sharp decline in its high-temperature strength, creep resistance, and thermal stability. Taking 310S stainless steel, commonly used in medium- and high-temperature applications, as an example, when the service temperature exceeds 800℃, its tensile strength is less than 40% of its room-temperature strength, making it unsuitable for extreme high-temperature applications such as gas turbine blades and nuclear reactor pressure vessels. In addition, the composition design of traditional stainless steel is mostly based on the theory of mixing enthalpy, which optimizes the microstructure by controlling the interaction energy between alloying elements. However, this design concept has gradually reached the ceiling of performance improvement and it is difficult to achieve a breakthrough in mechanical and service performance.

[0004] In recent years, the emergence of multi-principal element alloys (also known as high-entropy alloys) has opened up new pathways for the design and development of metallic materials. Unlike traditional single-principal or dual-principal element alloys, high-entropy alloys are typically composed of five or more principal elements, each with a molar fraction of 5%-35%. The core design concept lies in utilizing the high configurational entropy effect to suppress the excessive formation of intermetallic compounds, thereby forming single-phase or multi-phase solid solution structures dominated by simple FCC, body-centered cubic (BCC), or hexagonal close-packed (HCP). Numerous studies have shown that high-entropy alloys possess a series of excellent comprehensive properties, such as high strength (the room temperature tensile strength of some FCC-based high-entropy alloys can exceed 1000 MPa), high hardness, good room temperature and low temperature plasticity, and excellent wear resistance, corrosion resistance, and high-temperature oxidation resistance. They are considered to be a next-generation advanced structural material with great development potential.

[0005] Despite the promising applications of high-entropy alloys, numerous key scientific and technological challenges remain to be addressed in their industrialization. One of the core challenges in high-entropy alloy research is achieving an optimal balance between strength and plasticity (i.e., a strength-plasticity tradeoff) through the synergistic regulation of multiple strengthening mechanisms, while ensuring stable mechanical properties and microstructure under high-temperature service conditions. Currently reported high-entropy alloys, while achieving high strength through mechanisms such as second-phase strengthening, dislocation strengthening, or grain refinement, often suffer from a significant decrease in plasticity; conversely, alloys with good plasticity often lack the strength required for high-end operating conditions. Furthermore, under high-temperature conditions, the solute atom diffusion behavior, grain growth kinetics, and phase structure stability of high-entropy alloys differ significantly from those of traditional alloys. The effectiveness of existing strengthening mechanisms is greatly reduced at high temperatures, limiting improvements in high-temperature strength and creep performance. Therefore, developing a high-entropy alloy material and design method that can achieve the synergistic effect of multiple strengthening mechanisms while maintaining excellent room-temperature strength and plasticity as well as high-temperature performance is crucial for promoting the practical application of high-entropy alloys under extreme conditions. Summary of the Invention

[0006] To address the aforementioned issues of insufficient mechanical properties at both room temperature and high temperature in existing stainless steel materials, this invention provides a high-strength, heat-resistant, and high-entropy stainless steel, its preparation method, and its applications. This high-strength, heat-resistant, and high-entropy stainless steel introduces an L21 nano-precipitated phase into the FCC+BCC dual-phase structure and utilizes interstitial atoms to achieve the synergistic effect of multiple strengthening mechanisms, enabling the nano-precipitated dual-phase high-entropy stainless steel to possess high strength, high plasticity, and heat resistance.

[0007] On one hand, the present invention provides a high-strength, heat-resistant, high-entropy stainless steel, wherein the chemical composition of the high-strength stainless steel is: Fe a Ni b Cr c Al d Tie Nb f N g ;

[0008] Where a = 30-33 at%, b = 25-30 at%, c = 13-18 at%, d = 10-16 at%, e = 2-8 at%, f = 0-8 at%, and g = 1-3 at%.

[0009] Furthermore, the value of e ranges from 6 to 8 at%.

[0010] Limiting the Ti content to 6–8 at% allows for a more complete reaction with elements such as Al and Nb to form stable L21-type intermetallic compounds. These compounds are also more uniform in quantity and distribution, avoiding insufficient second-phase strengthening due to excessively low Ti content, or decreased alloy plasticity and brittle phase precipitation due to excessively high Ti content. This optimization further improves the alloy's room temperature and high-temperature strength while ensuring good machinability, resulting in greater stability in high-temperature service environments requiring high strength.

[0011] Furthermore, the value of f ranges from 2 to 8 at%.

[0012] Setting the Nb content to 2–8 at% utilizes Nb's strong carbonitride forming ability and grain-refining effect. On the one hand, it can combine with N to form dispersed nitrides, enhancing high-temperature creep resistance; on the other hand, it can effectively inhibit grain growth at high temperatures, improving thermal stability. Compared to the alloy with 0 Nb content, this range of Nb content significantly improves the high-temperature mechanical properties of the alloy; at the same time, it avoids the formation of brittle phases caused by excessive Nb, ensuring a balance of the alloy's overall mechanical properties and broadening the alloy's high-temperature application range.

[0013] Furthermore, the chemical composition of the high-strength, heat-resistant, high-entropy stainless steel includes: Fe 30 Ni 28 Cr 13 Al 10 Ti8Nb8N3, Fe 30 Ni 28 Cr 14 Al 11 Ti8Nb7N2, Fe 31 Ni 30 Cr 15 Al 12 Ti8Nb2N2, Fe 31 Ni 27 Cr 16 Al 13 Ti7Nb4N2, Fe 32 Ni 26 Cr 17Al 14 Ti7Nb3N1 or Fe 33 Ni 25 Cr 17 Al 15 Ti6Nb3N1.

[0014] The six chemical composition formulations specifically defined are all optimal combinations obtained through extensive experimental optimization based on claim 1, exhibiting clear repeatability and stability. These formulations, by precisely matching the proportions of each element, achieve the best possible microstructure of the alloy (FCC matrix + dispersed L21 phase + BCC phase), realizing a precise balance of strength, plasticity, corrosion resistance, and high-temperature heat resistance.

[0015] In some embodiments, d / e = 1 to 3.

[0016] Furthermore, the present invention provides a method for preparing the high-strength, heat-resistant, high-entropy stainless steel as described above, comprising the following steps:

[0017] Under a protective atmosphere, elemental Fe, Cr, Ni, Al, Nb, Ti and CrN are induction melted to obtain a molten liquid; the molten liquid is cooled to obtain an alloy ingot; aging treatment is performed at 350-500℃ under a magnetic field, followed by furnace cooling to obtain FCC / L21+BCC structure high-strength heat-resistant high-entropy stainless steel.

[0018] Furthermore, the protective atmosphere is an argon atmosphere.

[0019] Furthermore, the pressure of the induction melting is -0.01 to -0.02 MPa, and the power is 75 to 110 kW.

[0020] Furthermore, an aging treatment is performed under a magnetic field, with the aging temperature being 350–500°C and the time being 4–10 hours.

[0021] Furthermore, this invention provides the application of a high-strength, heat-resistant, high-entropy stainless steel as described above in cookware manufacturing.

[0022] Compared with the prior art, the present invention has the following beneficial effects:

[0023] The high-entropy stainless steel of this invention has a Fe element content of 30-33 at% (a); 25-30 at% Ni element is added as a stabilizer for the FCC matrix; N element is added to the system, its small atomic radius (0.071 nm) allows it to fill the interatomic gaps in the metal, promoting interstitial solid solution strengthening; 0-8 at% Nb element is added to the alloy to reduce the formation of chromium-depleted regions at grain boundaries, significantly improving the stainless steel's resistance to intergranular corrosion; 13-18 at% Cr element is added to promote the formation and stabilization of the BCC phase and to give the stainless steel corrosion resistance; and 10-16 at% Al element is doped. Ni and Al have the most negative enthalpy of mixing and strong chemical affinity. The addition of these elements increases the concentration of free electrons, which helps to achieve short-range atomic ordering in Fe-based alloys, refining grain size after deformation and heat treatment. Ni, Al, and Ti readily form L21-Ni2AlTi nanoprecipitates. Furthermore, Nb has a similar atomic radius and electronegativity to Ti, facilitating the formation of L21 nanoprecipitates with a Ni2AlNb structure. Benefiting from the hysteresis diffusion effect of high-entropy alloys, after aging treatment, the precipitated L21 pins and hinders dislocation movement, suppressing grain growth and improving the alloy's mechanical properties. In addition, the L21 nanoprecipitates exhibit excellent thermal stability, enabling high-entropy stainless steel to operate under high-temperature conditions.

[0024] This invention, based on the concept of mixed entropy design, adjusts the principal components and proportions of the alloy. By adding Al, Ti, and Nb to FCC austenitic stainless steel, an FCC / L21+BCC structure is formed. The addition of a small amount of nitrogen achieves interstitial strengthening, thereby improving mechanical properties. Unlike the single strengthening mechanism in traditional alloys, this system utilizes fine-grain strengthening, interstitial solid solution strengthening, and precipitation strengthening to impart high strength to this heat-resistant high-entropy stainless steel. Its quasi-static uniaxial tensile strength at room temperature reaches 1120 MPa, with an elongation exceeding 25%, and a yield strength of 700 MPa at 500°C. Attached Figure Description

[0025] 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 these drawings without creative effort.

[0026] Figure 1 The XRD pattern of the high-strength, heat-resistant, high-entropy stainless steel obtained in Example 6 after aging;

[0027] Figure 2 The microstructure of the high-strength, heat-resistant, high-entropy stainless steel obtained in Example 6;

[0028] Figure 3 This is a schematic diagram of the FCC / L21+BCC structure of high-strength, heat-resistant, and high-entropy stainless steel. Detailed Implementation

[0029] This invention discloses a high-strength, heat-resistant, and high-entropy stainless steel. The high-strength, heat-resistant, and high-entropy stainless steel introduces an L21 nano-precipitated phase into the FCC+BCC dual-phase structure and utilizes interstitial atoms to achieve the synergistic effect of multiple strengthening mechanisms, so that the nano-precipitated dual-phase high-entropy stainless steel has high strength, high plasticity, and heat resistance.

[0030] The technical solutions of this invention will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only a portion of the embodiments of this invention, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0031] This invention provides a high-strength, heat-resistant, high-entropy stainless steel, the chemical composition of which is: Fe a Ni b Cr c Al d Ti e Nb f N g ;

[0032] Where a = 30-33 at%, b = 25-30 at%, c = 13-18 at%, d = 10-16 at%, e = 2-8 at%, f = 0-8 at%, and g = 1-3 at%.

[0033] The high-entropy stainless steel of this invention has a Fe element content of 30-33 at% (a); 25-30 at% Ni element is added as a stabilizer for the FCC matrix; N element is added to the system, its small atomic radius (0.071 nm) allows it to fill the interatomic gaps in the metal, promoting interstitial solid solution strengthening; 0-8 at% Nb element is added to the alloy to reduce the formation of chromium-depleted regions at grain boundaries, significantly improving the stainless steel's resistance to intergranular corrosion; 13-18 at% Cr element is added to promote the formation and stabilization of the BCC phase and to give the stainless steel corrosion resistance; and 10-16 at% Al element is doped. Ni and Al have the most negative enthalpy of mixing and strong chemical affinity. The addition of these elements increases the concentration of free electrons, which helps to achieve short-range atomic ordering in Fe-based alloys, refining grain size after deformation and heat treatment. Ni, Al, and Ti readily form L21-Ni2AlTi nanoprecipitates. Furthermore, Nb has a similar atomic radius and electronegativity to Ti, facilitating the formation of L21 nanoprecipitates with a Ni2AlNb structure. Benefiting from the hysteresis diffusion effect of high-entropy alloys, after aging treatment, the precipitated L21 pins and hinders dislocation movement, suppressing grain growth and improving the alloy's mechanical properties. In addition, the L21 nanoprecipitates exhibit excellent thermal stability, enabling high-entropy stainless steel to operate under high-temperature conditions.

[0034] This invention, based on the concept of mixed entropy design, adjusts the principal components and proportions of the alloy. By adding Al, Ti, and Nb to FCC austenitic stainless steel, it forms a alloy with the following properties: Figure 3 The FCC / L21+BCC structure shown demonstrates how adding a small amount of nitrogen (N) achieves interstitial strengthening, thereby enhancing mechanical properties. Unlike the single strengthening mechanism in traditional alloys, this system utilizes grain refinement, interstitial solid solution strengthening, and precipitation strengthening to impart high strength to this heat-resistant high-entropy stainless steel. Its room temperature quasi-static uniaxial tensile strength reaches 1120 MPa, elongation exceeds 25%, and yield strength at 500°C reaches 700 MPa.

[0035] In some embodiments, e takes the value of 6 to 8 at%.

[0036] Limiting the Ti content to 6–8 at% allows for a more complete reaction with elements such as Al and Nb to form stable L21-type intermetallic compounds. These compounds are also more uniform in quantity and distribution, avoiding insufficient second-phase strengthening due to excessively low Ti content, or decreased alloy plasticity and brittle phase precipitation due to excessively high Ti content. This optimization further improves the alloy's room temperature and high-temperature strength while ensuring good machinability, resulting in greater stability in high-temperature service environments requiring high strength.

[0037] In some embodiments, f takes the value of 2 to 8 at%.

[0038] Setting the Nb content to 2–8 at% utilizes Nb's strong carbonitride forming ability and grain-refining effect. On the one hand, it can combine with N to form dispersed nitrides, enhancing high-temperature creep resistance; on the other hand, it can effectively inhibit grain growth at high temperatures, improving thermal stability. Compared to the alloy with 0 Nb content, this range of Nb content significantly improves the high-temperature mechanical properties of the alloy; at the same time, it avoids the formation of brittle phases caused by excessive Nb, ensuring a balance of the alloy's overall mechanical properties and broadening the alloy's high-temperature application range.

[0039] In some embodiments, the chemical composition of the high-strength, heat-resistant, high-entropy stainless steel includes: Fe 30 Ni 28 Cr 13 Al 10 Ti8Nb8N3, Fe 30 Ni 28 Cr 14 Al 11 Ti8Nb7N2, Fe 31 Ni 30 Cr 15 Al 12 Ti8Nb2N2, Fe 31 Ni 27 Cr 16 Al 13 Ti7Nb4N2, Fe 32 Ni 26 Cr 17 Al 14 Ti7Nb3N1 or Fe 33 Ni 25 Cr 17 Al 15 Ti6Nb3N1.

[0040] The six chemical composition formulations specifically defined are all optimal combinations obtained through extensive experimental optimization based on claim 1, exhibiting clear repeatability and stability. These formulations, by precisely matching the proportions of each element, achieve the best possible microstructure of the alloy (FCC matrix + dispersed L21 phase + BCC phase), realizing a precise balance of strength, plasticity, corrosion resistance, and high-temperature heat resistance.

[0041] In some embodiments, d / e = 1 to 3.

[0042] When the Al / Ti ratio is in the range of 1-3, high-strength, heat-resistant, and high-entropy stainless steel has a microstructure of FCC+BCC+L21. When the ratio exceeds this range, a single FCC structure may be obtained, which does not have high mechanical strength. When the ratio is below this range, brittle phases such as the Laves phase and the η phase may precipitate, and the plasticity of the alloy will decrease significantly.

[0043] Another embodiment of the present invention provides a method for preparing high-strength, heat-resistant, high-entropy stainless steel as described above, comprising the following steps:

[0044] Under a protective atmosphere, elemental Fe, Cr, Ni, Al, Nb, Ti and CrN are induction melted to obtain a molten liquid; the molten liquid is cooled to obtain an alloy ingot; aging treatment is performed at 350-500℃ under a magnetic field, followed by furnace cooling to obtain FCC / L21+BCC structure high-strength heat-resistant high-entropy stainless steel.

[0045] In some embodiments, the protective atmosphere is an argon atmosphere.

[0046] Argon is used as a protective atmosphere because it is chemically stable and does not readily react with metal elements. It can effectively isolate air during induction melting, prevent the oxidation of active elements such as Fe, Al, and Ti to form oxide inclusions, and ensure the purity of the molten liquid.

[0047] In some embodiments, the pressure of the induction melting is -0.01 to -0.02 MPa, and the power is 75 to 110 kW.

[0048] In some embodiments, aging treatment is performed under a magnetic field, wherein the aging temperature is 350–500°C and the time is 4–10 hours.

[0049] Magnetic field-assisted aging can accelerate atomic diffusion, shorten aging time, improve production efficiency, and enable precipitated phases to be arranged in an orderly manner along the magnetic field direction, further enhancing the anisotropic strength and high-temperature stability of the alloy.

[0050] Another embodiment of the present invention provides the application of a high-strength, heat-resistant, high-entropy stainless steel as described above in the manufacture of cookware.

[0051] This high-strength, heat-resistant, high-entropy stainless steel is used in cookware manufacturing. Its excellent high-temperature strength can withstand the high-temperature deformation during heating, avoiding the deformation problems caused by high-temperature softening in traditional cookware. Its good plasticity and processing properties facilitate stamping, stretching, and other forming processes. The corrosion resistance provided by chromium prevents damage from acid and alkali corrosion during cooking, extending the cookware's lifespan. Simultaneously, the alloy's high thermal conductivity and uniform microstructure ensure even heating, improving cooking results. Furthermore, compared to traditional stainless steel cookware, this high-entropy stainless steel cookware is stronger, lighter, and thinner, combining practicality and economy.

[0052] The present invention will be further described below through specific embodiments:

[0053] Example 1

[0054] This embodiment provides a high-strength, heat-resistant, high-entropy stainless steel with the chemical formula Fe. 30 Ni 28 Cr 13 Al 10 Ti8Nb8N3.

[0055] Fe 30 Ni 28 Cr 13 Al 10 The preparation method of Ti8Nb8N3 includes the following steps:

[0056] The surfaces of the raw materials Fe, Cr, Ni, Al, Nb, Ti, and CrN were cleaned by grinding, ultrasonically treated in anhydrous ethanol, and then dried. The raw materials were then weighed according to the designed composition and placed in a crucible in order of increasing melting point and from bottom to top. After evacuation, high-purity argon gas was introduced, and multiple induction melting processes were performed at a pressure of -0.014 MPa and a power of 80 kW to ensure uniform composition, resulting in a molten liquid. The molten liquid was cooled to obtain a cast alloy. This alloy was then aged at 480℃ for 6 hours under a magnetic field and cooled in the furnace to obtain Fe. 30 Ni 28 Cr 13 Al 10 Ti8Nb8N3 high-strength, heat-resistant, high-entropy stainless steel.

[0057] Tests showed that the alloy has a room temperature tensile strength of 650 MPa, a uniform strain of over 45%, and a yield strength of 690 MPa at 500°C.

[0058] Example 2

[0059] This embodiment provides a high-strength, heat-resistant, high-entropy stainless steel with the chemical formula Fe. 30 Ni 28 Cr 14 Al 11 Ti8Nb7N2.

[0060] Fe 30 Ni 28 Cr 14 Al 11 The preparation method of Ti8Nb7N2 includes the following steps:

[0061] The surfaces of the raw materials Fe, Cr, Ni, Al, Nb, Ti, and CrN were cleaned by grinding, ultrasonically treated in anhydrous ethanol, and then dried. The raw materials were then weighed according to the designed composition and placed in a crucible in order of increasing melting point and from bottom to top. After evacuation, high-purity argon gas was introduced, and multiple induction melting processes were performed at a pressure of -0.015 MPa and a power of 90 kW to ensure uniform composition, resulting in a molten liquid. The molten liquid was cooled to obtain an ingot. This ingot was then aged at 500℃ for 5 hours under a magnetic field and cooled in the furnace to obtain Fe. 30 Ni 28 Cr 14 Al 11 Ti8Nb7N2 high-strength, heat-resistant, high-entropy stainless steel.

[0062] Tests showed that the alloy has a room temperature tensile strength of 912 MPa, a uniform strain of over 25%, and a yield strength of 680 MPa at 500°C.

[0063] Example 3

[0064] This embodiment provides a high-strength, heat-resistant, high-entropy stainless steel with the chemical formula Fe. 31 Ni 30 Cr 15 Al 12 Ti8Nb2N2.

[0065] Fe 31 Ni 30 Cr 15 Al 12 The preparation method of Ti8Nb2N2 includes the following steps:

[0066] The surfaces of the raw materials Fe, Cr, Ni, Al, Nb, Ti, and CrN were cleaned by grinding, ultrasonically treated in anhydrous ethanol, and then dried. The raw materials were then weighed according to the designed composition and placed in a crucible in order of increasing melting point and from bottom to top. After evacuation, high-purity argon gas was introduced, and multiple induction melting processes were performed at a pressure of -0.014 MPa and a power of 95 kW to ensure uniform composition, resulting in a molten liquid. The molten liquid was cooled to obtain an ingot. This ingot was then aged at 450℃ for 5 hours under a magnetic field and cooled in the furnace to obtain Fe. 31 Ni 30 Cr 15 Al 12 Ti8Nb2N2 high-strength, heat-resistant, high-entropy stainless steel.

[0067] Tests showed that the alloy has a room temperature tensile strength of 910 MPa, a uniform strain of over 30%, and a yield strength of 685 MPa at 500℃, demonstrating excellent mechanical properties.

[0068] Example 4

[0069] This embodiment provides a high-strength, heat-resistant, high-entropy stainless steel with the chemical formula Fe. 31 Ni 27 Cr 16 Al 13 Ti7Nb4N2.

[0070] Fe 31 Ni 27 Cr 16 Al 13 The preparation method of Ti7Nb4N2 includes the following steps:

[0071] The surfaces of the raw materials Fe, Cr, Ni, Al, Nb, Ti, and CrN were cleaned by grinding, ultrasonically treated in anhydrous ethanol, and then dried. The raw materials were then weighed according to the designed composition and placed in a crucible in order of increasing melting point and from bottom to top. After evacuation, high-purity argon gas was introduced, and multiple induction melting processes were performed at a pressure of -0.015 MPa and a power of 93 kW to ensure uniform composition, resulting in a molten liquid. The molten liquid was cooled to obtain an ingot. This ingot was then aged at 650℃ for 5.5 hours under a magnetic field and cooled in the furnace to obtain Fe. 31 Ni 27 Cr 16 Al 13 Ti7Nb4N2 high-strength, heat-resistant, high-entropy stainless steel.

[0072] Tests showed that the alloy has a room temperature tensile strength of 800 MPa, a uniform strain of over 32%, and a yield strength of 635 MPa at 500℃, demonstrating excellent mechanical properties.

[0073] Example 5

[0074] This embodiment provides a high-strength, heat-resistant, high-entropy stainless steel with the chemical formula Fe. 32 Ni 26 Cr 17 Al 14 Ti7Nb3N1.

[0075] Fe 32 Ni 26 Cr 17 Al 14 The preparation method of Ti7Nb3N1 includes the following steps:

[0076] The surfaces of the raw materials Fe, Cr, Ni, Al, Nb, Ti, and CrN were cleaned by grinding, ultrasonically treated in anhydrous ethanol, and then dried. The raw materials were then weighed according to the designed composition and placed in a crucible in order of increasing melting point and from bottom to top. After evacuation, high-purity argon gas was introduced, and multiple induction melting processes were performed at a pressure of -0.017 MPa and a power of 94 kW to ensure uniform composition, resulting in a molten liquid. The molten liquid was cooled to obtain an ingot. This ingot was then aged at 700℃ for 5 hours under a magnetic field and cooled in the furnace to obtain Fe. 32 Ni 26 Cr 17 Al 14 Ti7Nb3N1 high-strength, heat-resistant, high-entropy stainless steel.

[0077] Tests showed that the alloy has a room temperature tensile strength of 790 MPa, a uniform strain of over 30%, and a yield strength of 650 MPa at 500℃, demonstrating excellent mechanical properties.

[0078] Example 6

[0079] This embodiment provides a high-strength, heat-resistant, high-entropy stainless steel with the chemical formula Fe. 33 Ni 25 Cr 17 Al 15 Ti6Nb3N1.

[0080] Fe 33 Ni 25 Cr 17 Al 15 The preparation method of Ti6Nb3N1 includes the following steps:

[0081] The surfaces of the raw materials Fe, Cr, Ni, Al, Nb, Ti, and CrN were cleaned by grinding, ultrasonically treated in anhydrous ethanol, and then dried. The raw materials were then weighed according to the designed composition and placed in a crucible in order of increasing melting point and from bottom to top. After evacuation, high-purity argon gas was introduced, and multiple induction melting processes were performed at a pressure of -0.02 MPa and a power of 95 kW to ensure uniform composition and obtain a molten liquid. The molten liquid was cooled to obtain an ingot. This ingot was then aged at 680℃ for 5 hours under a magnetic field and cooled in the furnace to obtain Fe. 33 Ni 25 Cr 17 Al 15 Ti6Nb3N1 high-strength, heat-resistant, high-entropy stainless steel.

[0082] The alloy was tested and found to have a room temperature tensile strength of 1120 MPa, a uniform strain exceeding 25%, and a yield strength of 700 MPa at 500°C, exhibiting excellent comprehensive mechanical properties. XRD pattern analysis and microstructure observation of the high-entropy stainless steel prepared in Example 6 yielded the following results: Figure 1 and Figure 2 As shown.

[0083] Comparative Examples 1-6

[0084] Comparative Examples 1-6 are used to illustrate the high-strength, heat-resistant, high-entropy stainless steel and its preparation method of the present invention. They include most of the operation steps in Examples 1-6, except that the alloy composition shown in Comparative Examples 1-6 in Table 1 is used, and the other operation steps are the same as in Examples 1-6.

[0085] Table 1

[0086]

[0087] As can be seen from the test results in Table 1, the high-strength, heat-resistant, high-entropy stainless steel designed and prepared in this application possesses excellent comprehensive properties such as room temperature tensile strength, plasticity, and high-temperature strength, which are superior to traditional stainless steel. Meanwhile, the addition and adjustment of aluminum significantly affect the microstructure of the high-entropy steel, thereby influencing its mechanical properties.

[0088] Comparative Examples 7-13

[0089] Comparative Examples 7-13 are used to illustrate the high-strength, heat-resistant, high-entropy stainless steel and its preparation method of the present invention. They include most of the operation steps in Examples 1-6, except that the alloy composition shown in Comparative Examples 7-13 in Table 2 is used, but the ratio of Al and Ti elements in the alloy is adjusted. Other operation steps are the same as in Examples 1-6.

[0090] Table 2

[0091]

[0092]

[0093] The test results in Tables 1 and 2 show that when the Al / Ti ratio is in the range of 1-3, the high-strength, heat-resistant, and high-entropy stainless steel has a microstructure of FCC+BCC+L21. When the ratio exceeds this range, a single FCC structure may be obtained, which does not have high mechanical strength. When the ratio is below this range, brittle phases such as the Laves phase and the η phase may precipitate, and the plasticity of the alloy will decrease significantly.

[0094] The above is a further detailed description of the present invention in conjunction with specific preferred embodiments, and the specific implementation of the present invention should not be considered to be limited to these descriptions. For those skilled in the art of the present invention, without departing from the concept of the present invention, several simple deductions or substitutions can be made, which should be considered to fall within the scope of protection of the present invention.

Claims

1. A high-strength, heat-resistant, high-entropy stainless steel, characterized in that, The chemical composition of the high-strength stainless steel is: Fe a Ni b Cr c Al d Ti e Nb f N g ; Where a = 30-33 at%, b = 25-30 at%, c = 13-18 at%, d = 10-16 at%, e = 2-8 at%, f = 0-8 at%, and g = 1-3 at%.

2. The high-strength, heat-resistant, high-entropy stainless steel according to claim 1, characterized in that, The value of e ranges from 6 to 8 at%.

3. The high-strength, heat-resistant, high-entropy stainless steel according to claim 1, characterized in that, The value of f ranges from 2 to 8 at%.

4. The high-strength, heat-resistant, high-entropy stainless steel according to claim 1, characterized in that, The chemical composition of the high-strength, heat-resistant, high-entropy stainless steel includes: Fe 30 Ni 28 Cr 13 Al 10 Ti8Nb8N3, Fe 30 Ni 28 Cr 14 Al 11 Ti8Nb7N2, Fe 31 Ni 30 Cr 15 Al 12 Ti8Nb2N2, Fe 31 Ni 27 Cr 16 Al 13 Ti7Nb4N2, Fe 32 Ni 26 Cr 17 Al 14 Ti7Nb3N1 or Fe 33 Ni 25 Cr 17 Al 15 Ti6Nb3N1.

5. A high-strength, heat-resistant, high-entropy stainless steel according to claim 1, characterized in that, d / e = 1 to 3.

6. A method for preparing a high-strength, heat-resistant, high-entropy stainless steel according to any one of claims 1 to 5, characterized in that, The following steps are included: Under a protective atmosphere, elemental Fe, Cr, Ni, Al, Nb, Ti and CrN are induction melted to obtain a molten liquid; the molten liquid is cooled to obtain an alloy ingot; aging treatment is performed at 350-500℃ under a magnetic field, followed by furnace cooling to obtain FCC / L21+BCC structure high-strength heat-resistant high-entropy stainless steel.

7. The method for preparing a high-strength, heat-resistant, high-entropy stainless steel according to claim 6, characterized in that, The protective atmosphere is an argon atmosphere.

8. The method for preparing high-strength, heat-resistant, high-entropy stainless steel according to claim 6, characterized in that, The induction melting pressure is -0.01 to -0.02 MPa, and the power is 75 to 110 kW.

9. The method for preparing high-strength, heat-resistant, high-entropy stainless steel according to claim 6, characterized in that, The aging process is carried out under a magnetic field at a temperature of 350–500°C for 4–10 hours.

10. The application of the high-strength, heat-resistant, high-entropy stainless steel according to any one of claims 1 to 5 in the preparation of cookware.

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