High-strength heat-resistant medium-entropy alloy with high microstructure thermal stability

Abstract

This invention provides a high-strength, heat-resistant, medium-entropy alloy with high microstructure thermal stability, relating to the field of high-performance alloy materials technology. The medium-entropy alloy, based on atomic percentages, comprises Co: 30%-40%, Cr: ≤28%, Ti: 2%-4%, Al: 4%-6%, Mo: 0.3%-1.0%, Ta: 0.3%-1.0%, C: 0-3%, with Ni as the balance. After high-temperature short-time solution treatment and aging, the medium-entropy alloy constructs a cellular heterostructure. This structure exhibits extremely high thermal stability, overcoming the problem of the cellular structure of high-entropy alloys in additive manufacturing easily disappearing under medium- and high-temperature conditions. The alloy displays excellent comprehensive mechanical properties, with a room temperature yield strength as high as 1100-1200 MPa, a tensile strength exceeding 1460 MPa, a uniform elongation of over 15%, a yield strength of over 920 MPa at 700℃, and maintains over 8.0% plasticity, achieving an excellent combination of strength and plasticity, overcoming the problem of medium- and high-entropy alloys' medium-temperature brittleness.

Description

Technical Field

[0001] This invention relates to the field of high-performance alloy materials technology, and in particular to a high-strength, heat-resistant, medium-entropy alloy with high microstructure thermal stability. Background Technology

[0002] In recent years, medium-high entropy alloys have attracted much attention due to their excellent strength, plasticity, corrosion resistance, and oxidation resistance. However, these alloys often exhibit poor high-temperature microstructure stability and mechanical properties. For example, face-centered cubic single-phase medium-high entropy alloys have low high-temperature strength, while refractory body-centered cubic high-entropy alloys exhibit high high-temperature strength but extremely low high-temperature plasticity and fracture toughness. Some eutectic high-entropy alloys exhibit excellent strength-plasticity combination at room temperature, but show poor microstructure stability and mechanical properties at high temperatures. L12γ' precipitate-strengthened medium-high entropy alloys have excellent room-temperature strength and plasticity, but at higher temperatures (650–750 °C), they are prone to forming a σ-brittle phase, leading to alloy embrittlement. γ' precipitate-strengthened medium-high entropy alloys can be prepared by selective laser melting to obtain ultrafine cellular structures (hundreds of nanometers to one or two micrometers in scale), effectively improving the synergistic effect of strength and plasticity in this type of alloy. However, subsequent heat treatment often causes the cellular structure to disappear and forms a σ-brittle phase, significantly affecting the room-temperature and high-temperature properties of the alloy. Therefore, it is imperative to develop new high-microstructure thermal stability, high-strength, high-toughness, and heat-resistant medium-high entropy alloys.

[0003] Existing precipitation-strengthened medium-high entropy alloys exhibit poor microstructural stability at medium and high temperatures, readily forming chromium-rich brittle σ-phase at grain boundaries. Furthermore, under medium-high temperatures, oxygen readily diffuses from the surface along grain boundaries into the material's interior, causing grain boundary embrittlement and resulting in medium-temperature brittleness, thus limiting the application of such materials in medium-high temperature fields. Additionally, during additive manufacturing, the ultra-fast cooling and solidification rates of the molten pool in precipitation-strengthened medium-high entropy alloys often lead to the formation of microcellular structures. Dislocations and certain element segregation form at the cell boundaries. During deformation, these dislocation-rich and segregated cell boundaries effectively suppress dislocation movement without completely hindering it; therefore, this structure also contributes to improving the alloy's strength and ductility. However, under medium-high temperatures, this cellular structure disappears as the dislocation density decreases and elements diffuse, leading to a significant reduction in the alloy's yield strength. Therefore, it is necessary to develop high-strength medium-high entropy alloys with high microstructural thermal stability and resistance to high-temperature oxidation. Summary of the Invention

[0004] To address the aforementioned technical problems in the existing technology, this invention provides a high-strength, heat-resistant, medium-entropy alloy with high microstructure thermal stability. The aim is to improve the microstructure thermal stability of additively manufactured precipitation-strengthened medium-high entropy alloys, including improving the thermal stability of the cellular structure, preventing the disappearance of the cellular structure at medium and high temperatures, suppressing the precipitation of brittle phases such as σ at medium and high temperatures, and simultaneously enhancing the alloy's grain boundary oxidation resistance, suppressing grain boundary cracking at medium and high temperatures, thereby improving the medium- and high-temperature strength and plasticity of the precipitation-strengthened medium-high entropy alloy. The technical solution is as follows:

[0005] A high-strength, heat-resistant, medium-entropy alloy with high microstructure thermal stability, comprising, by atomic percentage, Co: 30%-40%, Cr: ≤28%, Ti: 2%-4%, Al: 4%-6%, Mo: 0.3%-1.0%, Ta: 0.3%-1.0%, C: 0-3%, with Ni as the balance.

[0006] The mass ratio of Ti to Al is 1.20-1.24.

[0007] Preferably, the Cr content is 20%-28%.

[0008] The medium-entropy alloy has a room temperature yield strength of 1100-1200 MPa, a tensile strength exceeding 1460 MPa, and a uniform elongation of over 15%. The medium-entropy alloy has a yield strength of not less than 920 MPa and a plasticity of not less than 8.0% at 700℃.

[0009] The preparation process of the medium-entropy alloy is as follows: S1. Mix the weighed raw material A evenly in argon gas according to the proportion; S2. Mix raw material A, which has been mixed evenly in S1, with raw material B to obtain a mixed powder; S3. The mixed powder obtained in S2 is subjected to selective laser melting in argon gas to prepare a printed medium-entropy alloy. S4. Heat-treat the printed medium-entropy alloy obtained in S3 to obtain the high-strength heat-resistant medium-entropy alloy.

[0010] In S1, raw material A is (CoCrNi). 94 (TiAl)6 alloy powder mixed with elemental Ni, Co, Ti, and Al powders, or elemental Ni, Co, Cr, Ti, and Al powders, with raw material A having a particle size of 15~53μm; In S1, mixing is carried out in a three-dimensional oscillating mixer at a speed of 25-30 rpm for 5-8 hours.

[0011] In S2, raw material B is fine Mo and Ta particles, or fine Mo, Ta particles and Cr3C2, wherein the particle size of Mo and Ta particles is 100~200nm, and the particle size of Cr3C2 is <1μm. The mixing in S2 is carried out in a horizontal high-energy ball mill at a mixing speed of 550~650 rpm and a mixing time of 10~20 min.

[0012] The specific process conditions for selective laser melting in S3 are: power 325W, exposure time 120μs, line spacing 60μm, dot spacing 50μm, and layer thickness 30μm.

[0013] When the raw material B is fine Mo and Ta particles, the heat treatment process in S4 is as follows: heat treatment at 1000℃ for 10 min followed by air cooling to room temperature, and then heat treatment at 800℃ for 2 h followed by air cooling to room temperature. When the raw material B is fine Mo, Ta particles and Cr3C2, the heat treatment process in S4 is: heat treatment at 800℃ for 2 hours followed by air cooling to room temperature.

[0014] The beneficial effects of the technical solutions provided in the embodiments of the present invention include at least the following: In the aforementioned scheme, the developed additive manufacturing medium-entropy alloy, when carbon-free, undergoes high-temperature short-time solid solution treatment (below the γ' dissolution temperature) and aging treatment. This transforms elements such as Ti and Ta that agglomerate at the cell boundaries into relatively coarse γ' precipitate clusters (hundreds of nanometers in scale) with high thermal stability, while ultrafine γ' precipitate particles (tens of nanometers in scale) precipitate within the cells, constructing a cellular heterostructure. This structure exhibits extremely high thermal stability, remaining intact even at 1000℃, overcoming the problem of the cellular structure of high-entropy alloys in additive manufacturing easily disappearing under medium- and high-temperature conditions. Due to advanced compositional design, this alloy also avoids the precipitation of the σ phase during heat treatment or heat exposure, ensuring high microstructural thermal stability. The cellular heterostructure obtained by this invention produces a significant back stress strengthening effect during plastic deformation. Combined with the strengthening effect of precipitated particles, the alloy exhibits excellent comprehensive mechanical properties, with a room temperature yield strength of up to 1100 MPa, a tensile strength of over 1460 MPa, and a uniform elongation of over 15%, achieving an excellent combination of strength and plasticity.

[0015] When the additive manufacturing medium-entropy alloy contains carbon, MC carbide particles precipitate at grain boundaries and cell boundaries after direct aging treatment. During high-temperature stretching, these particles effectively inhibit the diffusion of oxygen from the material surface along the grain boundaries into the interior, thereby improving the grain boundary strength of the alloy, suppressing intergranular cracking, and enabling the alloy to achieve higher medium-temperature plasticity, thus overcoming the problem of medium-temperature brittleness in medium- and high-entropy alloys. Attached Figure Description

[0016] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying 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.

[0017] Figure 1 These are microstructure images of the medium-entropy alloy prepared in Example 1 of this invention before and after heat treatment, wherein (a) is a SEM image of the grain structure and cellular structure of the printed alloy; (b) is a high-magnification SEM image of the cellular structure of the printed alloy; (c) is a SEM image of the cellular structure and precipitate phase distribution of the heat-treated alloy; and (d) is a high-magnification SEM image of the precipitate phase distribution of the heat-treated alloy. Figure 2 These are SEM images of the medium-entropy alloy prepared in Example 1 of this invention at different heat treatment temperatures, wherein (a) is a SEM image of the alloy grain structure after heat treatment at 900℃; (b) is a SEM image of the alloy cellular structure after heat treatment at 900℃; (c) is a SEM image of the alloy grain structure after heat treatment at 1000℃; (d) is a SEM image of the alloy cellular structure after heat treatment at 1000℃; (e) is a SEM image of the alloy grain structure after heat treatment at 1050℃; and (f) is a magnified SEM image of the alloy grain structure after heat treatment at 1050℃. Figure 3 These are the tensile property curves of the medium-entropy alloy prepared in Example 1 of the present invention before and after heat treatment, wherein (a) is the engineering tensile stress-strain curve; (b) is the true stress-strain curve; (c) is the loading-unloading-reloading tensile curve; and (d) is the magnified first loading-unloading-reloading hysteresis loop. Figure 4 These are internal dislocation structure diagrams of the medium-entropy alloy prepared in Example 1 of this invention before and after heat treatment and stretching to 4% strain. Among them, (a) is a transmission electron microscopy (TEM) image of the dislocation distribution of the sample before stretching; (b) is a TEM image of the dislocation distribution and slip band of the sample after stretching; and (c) is a magnified TEM image of the dislocation distribution and slip band of the sample after stretching. Figure 5 These are microstructure images of the medium-entropy alloy prepared in Example 4 of the present invention after heat treatment, wherein (a) is a SEM image of the cellular structure of the alloy; and (b) is a SEM image of the distribution of ultrafine γ' precipitate phase and cell boundary carbides within the alloy cells. Figure 6 This is the tensile stress-strain curve of the medium-entropy alloy prepared in Example 4 of this invention after heat treatment at 700℃; Figure 7 This is the (CoCrNi) prepared in the comparative example of this invention. 94Microstructure of (TiAl)6 alloy, where (a) is SEM image of the cellular structure and grain boundary σ precipitate phase of the alloy; (b) is TEM image of the grain boundary σ precipitate phase of the alloy. Figure 8 This is the (CoCrNi) prepared in the comparative example of this invention. 94 Tensile stress-strain curve of (TiAl)6 alloy at 700℃; Figure 9 This is the (CoCrNi) prepared in the comparative example of this invention. 94 SEM image of secondary grain boundary cracks in (TiAl)6 alloy after tensile testing at 700℃. Detailed Implementation

[0018] The technical solution of the present invention will now be described with reference to the accompanying drawings.

[0019] In embodiments of the present invention, words such as "exemplarily," "for example," etc., are used to indicate that something is an example, illustration, or description. Any embodiment or design described as "exemplary" in the present invention should not be construed as being more preferred or advantageous than other embodiments or designs. Specifically, the use of the word "exemplary" is intended to present the concept in a concrete manner. Furthermore, in embodiments of the present invention, the meaning expressed by "and / or" can be both, or either one.

[0020] In this embodiment of the invention, sometimes a subscript such as W1 may be written in a non-subscript form such as W1. When the difference is not emphasized, the meaning they express is the same.

[0021] To make the technical problems, technical solutions and advantages of the present invention clearer, a detailed description will be given below in conjunction with the accompanying drawings and specific embodiments.

[0022] This invention provides a high-strength, heat-resistant, medium-entropy alloy with high microstructure thermal stability.

[0023] To develop medium-high entropy alloys with high microstructural thermal stability, this invention uses a CoCrNi medium-entropy alloy as a base. Through phase diagram calculations, approximately 10 at.% of Al and Ti elements are added to the alloy, with the Ti / Al mass ratio strictly controlled at around 1.22 to prevent the precipitation of brittle phases such as σ during heat treatment, while ensuring a high γ' volume fraction for high strength. Furthermore, through phase diagram calculations, the Cr content is controlled below 28 at.%, ensuring high oxidation resistance while avoiding the precipitation of brittle phases. Small amounts of Mo and Ta are also added to promote the segregation of cell boundary elements during additive manufacturing, improving the thermal stability of the cellular structure. Additionally, an appropriate amount of interstitial element C is added to the alloy to promote the precipitation of fine carbide particles at grain boundaries and cell boundaries, improving the alloy's oxidation resistance. Based on this, this invention designs various additive manufacturing medium-entropy alloys with high microstructural thermal stability, high strength and toughness, and high heat resistance.

[0024] The high-strength, heat-resistant, medium-entropy alloy with high microstructure thermal stability comprises, by atomic percentage, Co: 30%-40%, Cr: ≤28%, Ti: 2%-4%, Al: 4%-6%, Mo: 0.3%-1.0%, Ta: 0.3%-1.0%, C: 0-3%, with Ni as the balance.

[0025] Preferably, the Cr content is 20%-28%.

[0026] The preparation process of the medium-entropy alloy is as follows: S1. Mix the weighed raw material A evenly in argon gas according to the proportion; S2. Mix raw material A, which has been mixed evenly in S1, with raw material B to obtain a mixed powder; S3. The mixed powder obtained in S2 is subjected to selective laser melting in argon gas to prepare a printed medium-entropy alloy. S4. Heat-treat the printed medium-entropy alloy obtained in S3 to obtain the high-strength heat-resistant medium-entropy alloy.

[0027] In S1, raw material A is (CoCrNi). 94 (TiAl)6 alloy powder mixed with elemental Ni, Co, Ti, and Al powders, or elemental Ni, Co, Cr, Ti, and Al powders, with raw material A having a particle size of 15~53 μm; In S2, raw material B is fine Mo and Ta particles, or fine Mo, Ta particles and Cr3C2, wherein the particle size of Mo and Ta particles is 100~200nm, and the particle size of Cr3C2 is <1μm.

[0028] The following description, in conjunction with specific embodiments, illustrates this point.

[0029] Example 1 A three-dimensional oscillating mixer was used to mix (CoCrNi) particles with similar diameters (15–53 μm). 94 (TiAl)6) alloy particles and elemental metal powders Ni, Co, Ti, and Al powders were mixed in argon gas at a ratio of 28 rpm for 6 hours.

[0030] The mixed powder was then mixed with fine Mo and Ta particles (~100 nm) using a horizontal high-energy ball mill at a speed of 600 rpm for 10 min.

[0031] After mixing, the master alloy (CoCrNi) 94 The content of (TiAl)6 powder is 62.9 wt.%, and the content of elemental powder is 16.16 wt., 16.09 wt., 0.92 wt., 1.47 wt., 0.85 wt., and 1.61 wt.

[0032] Subsequently, the mixed powder was melted and sampled using a selective laser melting device under the following conditions: 325W power, 120μs exposure time, 60μm line spacing, 50μm dot spacing, and 30μm layer thickness, to obtain the additive manufacturing alloy. The specific heat treatment process was as follows: holding at 1000℃ for 10 min, air cooling to room temperature, and then holding at 800℃ for 2 h and air cooling to room temperature.

[0033] like Figure 1 As shown, the printed alloy is mainly composed of single-phase γ-cell structure. After heat treatment, large-sized γ' precipitate particle clusters are precipitated at the cell boundaries, while ultrafine γ' precipitate particles are precipitated inside the cells, forming a cellular heterostructure.

[0034] like Figure 2 As shown, the cellular structure, in which the cell boundaries are pinned by clusters of large-sized γ' precipitate particles, was maintained until 1000℃ and did not disappear until 1050℃, demonstrating excellent thermal stability.

[0035] like Figure 3 As shown, the printed alloy exhibits excellent strong-ductile bonding, with a significant increase in strength after heat treatment while maintaining a high elongation. Due to the presence of the cellular heterostructure, back stress is activated, becoming one of the important sources of alloy strength. Figures ①-⑦ represent deformation at different stages. It can be seen that as deformation progresses, the hysteresis loops become increasingly prominent, indicating a continuous increase in back stress.

[0036] like Figure 4As shown, during deformation, the deformation is mainly characterized by dislocation slip, and a large number of dislocations are concentrated at the cell boundaries, meaning that the cell boundaries effectively hinder the movement of dislocations. At the same time, a large number of slip bands pass through the cellular structure, which helps to maintain good plastic deformation.

[0037] Example 2 Metal elemental powders of similar particle size (15-53 μm), namely Ni, Co, Cr, Ti, and Al, were mixed in argon gas at a ratio using a three-dimensional oscillating powder mixer. The mixing speed was 28 rpm and the mixing time was 6 hours.

[0038] The mixed powder was then mixed with fine Mo and Ta particles (~100 nm) using a horizontal high-energy ball mill at a speed of 600 rpm for 10 min.

[0039] After mixing, the alloy powder contains 36.99 wt.% Ni powder, 37.14 wt.% Co powder, 18.46 wt.% Cr powder, 2.55 wt.% Ti powder, 2.4 wt.% Al powder, 0.85 wt.% Mo powder, and 1.61 wt.% Ta powder.

[0040] Subsequently, the mixed powder was melted and sampled using a selective laser melting device under the following conditions: 325W power, 120μs exposure time, 60μm line spacing, 50μm dot spacing, and 30μm layer thickness, to obtain the additive manufacturing alloy. The specific heat treatment process was as follows: holding at 1000℃ for 10 min, air cooling to room temperature, and then holding at 800℃ for 2 h and air cooling to room temperature.

[0041] Example 3 In addition to preparing medium-entropy alloys by mixing elemental metal powders as described in the above embodiments, pre-alloying can also be performed first, and medium-entropy alloys can be prepared using pre-alloyed powders, as detailed below: According to the designed alloy composition, raw materials are proportioned, and pre-alloyed rods are prepared by melting and casting. Then, pre-alloyed powder is prepared by inert gas atomization, plasma atomization or rotating electrode powder preparation method.

[0042] The pre-alloyed powder contains 36.99 wt.% Ni, 37.14 wt.% Co, 18.46 wt.% Cr, 2.55 wt.% Ti, 2.4 wt.% Al, 0.85 wt.% Mo, and 1.61 wt.% Ta.

[0043] Subsequently, the pre-alloyed powder was melted and sampled using a selective laser melting device under the following conditions: 325W power, 120μs exposure time, 60μm line spacing, 50μm dot spacing, and 30μm layer thickness, to obtain the additive manufacturing alloy. The specific heat treatment process was as follows: holding at 1000℃ for 10 min, air cooling to room temperature, and then holding at 800℃ for 2 h and air cooling to room temperature.

[0044] Example 4 A three-dimensional oscillating mixer was used to mix (CoCrNi) particles with similar diameters (15–53 μm). 94 (TiAl)6) alloy particles and elemental metal powders Ni, Co, Ti, and Al powders were mixed in argon gas at a ratio of 28 rpm for 6 hours.

[0045] The mixed powder was then mixed with fine Mo, Ta (~100 nm) and carbide particles (<1 μm) using a horizontal high-energy ball mill at a speed of 600 rpm for 10 min.

[0046] After mixing, the master alloy (CoCrNi) 94 The content of (TiAl)6 powder is 60.91 wt.%, and the content of elemental powder is 15.65 wt.%, Ni powder is 15.58 wt.%, Ti powder is 0.89 wt.%, Al powder is 1.42 wt.%, Mo powder is 0.82 wt.%, Ta powder is 1.56 wt.%, and Cr3C2 powder is 3.17 wt.%.

[0047] Subsequently, the mixed powder was melted and sampled using a selective laser melting device under the following conditions: 325W power, 120μs exposure time, 60μm line spacing, 50μm dot spacing, and 30μm layer thickness, to obtain the additive manufacturing alloy. The specific heat treatment process was: holding at 800℃ for 2 hours and then air cooling to room temperature.

[0048] like Figure 5 As shown, the alloy still has a cellular structure after heat treatment, with discontinuous TiC particles at the cell boundaries and a large number of ultrafine γ' precipitates inside the cells.

[0049] like Figure 6 As shown, the alloy exhibits high strength and good elongation at 700℃, overcoming the mid-temperature brittleness of medium-high entropy alloys.

[0050] Example 5 Metal elemental powders of similar particle size (15-53 μm), namely Ni, Co, Cr, Ti, and Al, were mixed in argon gas at a ratio using a three-dimensional oscillating powder mixer. The mixing speed was 28 rpm and the mixing time was 6 hours.

[0051] The mixed powder was then mixed with fine Mo, Ta (~100 nm) and carbide particles (<1 μm) using a horizontal high-energy ball mill at a speed of 600 rpm for 10 min.

[0052] After mixing, the alloy powder contains 35.82 wt.% Ni powder, 35.97 wt.% Co powder, 17.87 wt.% Cr powder, 2.47 wt.% Ti powder, 2.32 wt.% Al powder, 0.82 wt.% Mo powder, 1.56 wt.% Ta powder, and 3.17 wt.% Cr3C2 powder.

[0053] Subsequently, the mixed powder was melted and sampled using a selective laser melting device under the following conditions: 325W power, 120μs exposure time, 60μm line spacing, 50μm dot spacing, and 30μm layer thickness, to obtain the additive manufacturing alloy. The specific heat treatment process was: holding at 800℃ for 2 hours and then air cooling to room temperature.

[0054] Example 6 According to the designed alloy composition, raw materials are proportioned, and pre-alloyed rods are prepared by melting and casting. Then, pre-alloyed powder is prepared by inert gas atomization, plasma atomization or rotating electrode powder preparation method.

[0055] The pre-alloyed powder contains 35.79 wt.% Ni, 35.94 wt.% Co, 20.68 wt.% Cr, 2.47 wt.% Ti, 2.32 wt.% Al, 0.82 wt.% Mo, 1.55 wt.% Ta, and 0.43 wt.% C.

[0056] Subsequently, the pre-alloyed powder was melted and sampled using a selective laser melting device under the following conditions: 325W power, 120μs exposure time, 60μm line spacing, 50μm dot spacing, and 30μm layer thickness, to obtain the additive manufacturing alloy. The specific heat treatment process was: holding at 800℃ for 2 hours and then air cooling to room temperature.

[0057] Comparative Example Selective laser melting equipment was used to process pre-alloyed (CoCrNi). 94 (TiAl)6) alloy powder (15-53μm) was melted and sampled under the following process conditions: 325W power, 120μs exposure time, 60μm line spacing, 50μm dot spacing, and 30μm layer thickness, to obtain the additive manufacturing alloy. The specific heat treatment process was: holding at 800℃ for 2h and air cooling to room temperature.

[0058] Figure 7 This is a comparative preparation of (CoCrNi). 94 Microstructure diagrams of the (TiAl)6 alloy are shown, where (a) is a SEM image of the alloy's cellular structure and grain boundary σ precipitate phase; and (b) is a TEM image of the alloy's grain boundary σ precipitate phase. It can be seen that after heat treatment, this medium-entropy alloy precipitates a large amount of brittle σ precipitate phase along the grain boundaries.

[0059] Figure 8 This is a comparative preparation of (CoCrNi). 94 The tensile stress-strain curve of (TiAl)6 alloy at 700℃ shows that the alloy exhibits high yield strength at 700℃, but extremely low elongation (<1.5%), demonstrating severe mid-temperature brittleness.

[0060] Figure 9 (CoCrNi) prepared in a comparative example 94 SEM images of secondary grain boundary cracks in (TiAl)6 alloy after tensile testing at 700℃. These images show that the alloy is prone to intergranular cracking under medium-temperature stress. The σ-precipitated phase at the grain boundaries promotes crack nucleation and propagation, leading to brittleness.

[0061] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A high-strength, heat-resistant, medium-entropy alloy with high microstructure thermal stability, characterized in that, Based on atomic percentages, it includes Co: 30%-40%, Cr: ≤28%, Ti: 2%-4%, Al: 4%-6%, Mo: 0.3%-1.0%, Ta: 0.3%-1.0%, C: 0-3%, and Ni as the balance.

2. The high-strength, heat-resistant, medium-entropy alloy with high microstructure thermal stability according to claim 1, characterized in that, The mass ratio of Ti to Al is 1.20-1.

24.

3. The high-strength, heat-resistant, medium-entropy alloy with high microstructure thermal stability according to claim 1, characterized in that, The Cr content is 20%-28%.

4. The high-strength, heat-resistant, medium-entropy alloy with high microstructure thermal stability according to claim 1, characterized in that, The medium-entropy alloy has a room temperature yield strength of 1100-1200 MPa, a tensile strength exceeding 1460 MPa, and a uniform elongation of over 15%. The medium-entropy alloy has a yield strength of not less than 920 MPa and a plasticity of not less than 8.0% at 700℃.

5. The high-strength, heat-resistant, medium-entropy alloy with high microstructure thermal stability according to claim 1, characterized in that, The preparation process of the medium-entropy alloy is as follows: S1. Mix the weighed raw material A evenly in argon gas according to the proportion; S2. Mix raw material A, which has been mixed evenly in S1, with raw material B to obtain a mixed powder; S3. The mixed powder obtained in S2 is subjected to selective laser melting in argon gas to prepare a printed medium-entropy alloy. S4. Heat-treat the printed medium-entropy alloy obtained in S3 to obtain the high-strength heat-resistant medium-entropy alloy.

6. The high-strength, heat-resistant, medium-entropy alloy with high microstructure thermal stability according to claim 5, characterized in that, In S1, raw material A is (CoCrNi). 94 (TiAl)6 alloy powder mixed with elemental Ni, Co, Ti, and Al powders, or elemental Ni, Co, Cr, Ti, and Al powders, with raw material A having a particle size of 15~53 μm; In S1, mixing is carried out in a three-dimensional oscillating mixer at a speed of 25-30 rpm for 5-8 hours.

7. The high-strength, heat-resistant, medium-entropy alloy with high microstructure thermal stability according to claim 5, characterized in that, In S2, raw material B is fine Mo and Ta particles, or fine Mo, Ta particles and Cr3C2, wherein the particle size of Mo and Ta particles is 100~200nm, and the particle size of Cr3C2 is <1μm. The mixing in S2 is carried out in a horizontal high-energy ball mill at a mixing speed of 550~650 rpm and a mixing time of 10~20 min.

8. The high-strength, heat-resistant, medium-entropy alloy with high microstructure thermal stability according to claim 5, characterized in that, The specific process conditions for selective laser melting in S3 are: power 325W, exposure time 120μs, line spacing 60μm, dot spacing 50μm, and layer thickness 30μm.

9. The high-strength, heat-resistant, medium-entropy alloy with high microstructure thermal stability according to claim 5, characterized in that, When the raw material B is fine Mo and Ta particles, the heat treatment process in S4 is as follows: heat treatment at 1000℃ for 10 min followed by air cooling to room temperature, and then heat treatment at 800℃ for 2 h followed by air cooling to room temperature. When the raw material B is fine Mo, Ta particles and Cr3C2, the heat treatment process in S4 is: heat treatment at 800℃ for 2 hours followed by air cooling to room temperature.

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