Low-temperature impact-resistant multi-scale heterogeneous CoCrNi-based medium-entropy alloy and preparation method thereof

Abstract

The present application relates to a kind of low-temperature impact-resistant multiscale heterogeneous CoCrNi-based medium-entropy alloy and its preparation method, belong to low-temperature structural material technical field.The alloy of the present application is prepared using the method comprising the following steps: the raw materials containing Co, Cr, Ni, Al and Ti element are mixed, and alloy ingot is obtained by vacuum arc melting, wherein the molar content of Co, Cr, Ni, Al and Ti is 34.0%, 33.0%, 27.0%, 3.0%, 3.0% respectively;The alloy ingot is sequentially subjected to solid solution treatment, hot rolling treatment, recrystallization heat treatment, cryogenic rolling treatment and aging treatment, to obtain alloy product.The present application significantly improves the dynamic yield strength of medium-entropy alloy in low-temperature environment by the combined process of heat treatment and rolling without losing plasticity.

Description

Technical Field

[0001] This invention relates to the field of low-temperature structural materials technology, specifically to a low-temperature impact-resistant multi-scale heterogeneous CoCrNi-based medium-entropy alloy and its preparation method. Background Technology

[0002] Under extreme service conditions, metallic or alloy materials will inevitably be exposed to impact loads (such as bird strikes, hail impacts, and ballistic impacts) or cryogenic environments. There is an urgent need to develop materials that can maintain sufficient mechanical properties (including strength and toughness) from ambient temperature to cryogenic environments to ensure structural integrity during service. Typically, the mechanical properties of metals or alloys at room temperature to cryogenic conditions are dominated by the activation and migration of extended defects. At cryogenic environments, the thermal activation intensity decreases, leading to restricted defect activity and resulting in higher strength of metals or alloys at cryogenic temperatures compared to room temperature. However, this characteristic comes at the cost of toughness. This contradiction makes it difficult for many metals and alloys that perform well at room temperature to be fully utilized in cryogenic environments.

[0003] Alloys with a face-centered cubic (FCC) structure typically retain ductility at lower temperatures, especially the CoCrNi medium-entropy alloy, which exhibits a tensile strength of ~1.3 GPa and a tensile strength of ~270 MPa·m at 77 K. 1 / 2 The fracture toughness of these alloys is attributed to their abundant dislocation activity and deformation-induced twinning. Their excellent low-temperature performance rivals that of the highest-quality low-temperature steels (such as high-nickel steel and austenitic stainless steel), making them strong candidates for applications in extreme environments (such as ultra-high strain rates and low temperatures). However, these alloys still cannot provide sufficiently high yield strength at ambient and low temperatures, limiting their application as critical engineering components. In recent years, constructing heterogeneous structures has attracted widespread attention as a feasible solution to overcome the strength-toughness tradeoff. Depending on the scale, heterogeneity can be categorized into grain structures with uneven grain size distribution (such as multi-peaked grains and gradient grains), planar defects (such as twins and stacking faults), complexes and precipitates (such as ordered interstitial oxygen complexes and coherent ordered precipitates), multiphase structures (such as biphase eutectic structures and lamellar martensite), and locally chemically ordered structures (such as short / medium-range ordered structures). These heterogeneous components, ranging in size from nanometers to micrometers, exhibit deformation incompatibility, resulting in additional strengthening and strain-hardening effects. Compared to homogeneous structures, heterogeneous structures (including morphological and chemical structures) can endow metals or alloys with superior mechanical properties.

[0004] Currently, some literature has published studies on the introduction of coherent precipitated phases to enhance the mechanical properties of alloys, such as the literature Wang, JY et al. Ultrastrong and ductile (CoCrNi). 94A study on introducing multi-scale heterogeneous structures (CoCrNi) via Ti3Al3 medium-entropy alloys [J], Journal of Materials Science & Technology, 2023, 135: 241-249, reports a method for introducing multi-scale heterogeneous (CoCrNi) alloys. 94 The preparation process of Ti3Al3 medium-entropy alloys involves vacuum magnetic levitation melting, solution treatment, cold rolling, and aging treatment. Aging introduces spherical coherent precipitates, constructing a heterostructure with a minimum scale of nanometers. The literature Pan, RC et al., "Effect of minor elements Al and Ti on dynamic deformation and fracture of CoCrNi-based medium-entropy alloys [J]. Materials Science & Engineering, 2023, 884:145535," points out that cold rolling and high-temperature annealing effectively improve the entropy of (CoCrNi). 94 The impact resistance of Ti3Al3 medium-entropy alloys is shown by the fact that the alloy has a completely uniform grain structure and exhibits a micron-sized body-centered cubic phase transformation; reference: Bi, X Let al. Laser-directed energy deposition of a high performance additively manufactured (CoCrNi). 94 (TiAl)6 medium-entropy alloy with a novel core-shell structured strengthening phase[J]. Additive Manufacturing, 2024, 80: 103971. (CoCrNi) alloy was prepared by laser energy deposition. 94 (TiAl)6 medium entropy alloy, effectively improves the mechanical properties of the alloy.

[0005] However, the properties of alloys are related to multiple factors such as alloy composition and heterogeneity. Simply introducing heterogeneity does not always bring about the ideal strength-ductility synergy. How to optimize the microstructure of heterogeneous structures to effectively improve the strength, ductility and other properties of alloys has become the focus of current research. Summary of the Invention

[0006] The main objective of this invention is to provide a low-temperature impact-resistant multi-scale heterogeneous CoCrNi-based medium-entropy alloy and its preparation method. This invention combines the unique compositional design of medium-entropy alloys with the special microstructure engineering of heterogeneous materials. The complexity and multifunctionality of the multi-component alloy allow for the simultaneous superposition of multi-level heterogeneity, promoting heterogeneous deformation-induced strengthening and heterogeneous deformation-induced strain hardening. This enables the alloy to achieve ultra-high dynamic compressive strength without sacrificing low-temperature toughness, solving the challenge of its application as a key engineering component in extreme environments.

[0007] To achieve the above objectives, the present invention provides the following technical solution: A low-temperature impact-resistant multi-scale heterogeneous CoCrNi-based medium-entropy alloy and its preparation method include the following steps: S1. Raw materials containing cobalt (Co), chromium (Cr), nickel (Ni), aluminum (Al), and titanium (Ti) are mixed and alloy ingots are obtained by vacuum arc melting, wherein the molar contents of Co, Cr, Ni, Al, and Ti are 34.0%, 33.0%, 27.0%, 3.0%, and 3.0%, respectively. In this step, the raw materials include, but are not limited to, elemental powders, alloy powders, or mixtures thereof of the corresponding elements; S2. The alloy ingot is sequentially subjected to solution treatment, hot rolling treatment, recrystallization heat treatment, deep cryogenic rolling treatment and aging treatment to obtain the alloy product, namely, low-temperature impact-resistant multi-scale heterogeneous CoCrNi-based medium-entropy alloy.

[0008] In one specific embodiment of the present invention, vacuum arc melting is carried out in an argon atmosphere at a pressure of 0.05 MPa.

[0009] In one specific embodiment of the present invention, the solution treatment temperature is 1200℃, the holding time is 24h, and the cooling method is furnace cooling.

[0010] In one specific embodiment of the present invention, the deformation amount of hot rolling is 46.7% and the temperature is 1100℃.

[0011] In one specific embodiment of the present invention, the recrystallization heat treatment temperature is 1200℃, the time is 2h, and the cooling method is water cooling.

[0012] In one specific embodiment of the present invention, the deformation amount of the cryogenic rolling process is 60%, which is divided into 10 passes. The reduction amount of each pass is 0.5 mm. The alloy is immersed in liquid nitrogen for 10 minutes before and after each pass.

[0013] In one specific embodiment of the present invention, the aging treatment temperature is 700℃~900℃, the heat preservation time is 3~5h, and the cooling method is water cooling.

[0014] The advantages and beneficial effects of this invention are: This invention combines the unique compositional design of medium-entropy alloys with the special microstructure engineering of heterogeneous materials. The room temperature strength and ductility of CoCrNi-based alloys can be significantly improved at low temperatures without affecting toughness. At the same time, its low stacking fault energy helps promote the development of planar defects during low-temperature deformation. The enthalpy interaction between Ni, Co, and Cr, as well as their significant differences in electronegativity and shear modulus, are conducive to the formation of short-range order. The addition of appropriate amounts of 3 at% aluminum and 3 at% titanium to CoCrNi-based alloys can avoid the formation of brittle body-centered cubic phases and promote the precipitation of ordered phases. Overall, this invention introduces heterogeneity from the micrometer to the angstrom scale into medium-entropy alloys through unique compositional design and a series of rolling-annealing processes. This includes micrometer-scale heterogeneity involving grain size and microtwins, nanoscale heterogeneity involving nanoprecipitates, nanotwins, and the 9R phase, and atomic-level heterogeneity involving short-range order. These multi-scale heterostructures not only significantly improve the yield strength of the medium-entropy alloy, but also provide continuous strain hardening and deformation capabilities at different length scales, giving this medium-entropy alloy excellent low-temperature impact resistance. Attached Figure Description

[0015] Figure 1 The as-cast state of Co in Comparative Example 1 and the rolled-annealed state in Examples 1 and 2 of this invention. 34 C r33 Ni 27 Stress-strain curves of Al3Ti3 medium-entropy alloy under high strain rate compression at room temperature and 77 K; Figure 2 For the rolling-annealing Co in Examples 1 and 2 34 C r33 Ni 27 Schematic diagram of the preparation process of Al3Ti3 medium entropy alloy; Figure 3 For example, the rolling-annealing Co in Example 2 34 C r33 Ni 27 Synchrotron radiation X-ray diffraction analysis results of Al3Ti3 medium entropy alloy; Figure 4 For example, the rolling-annealing Co in Example 2 34 C r33 Ni 27 Grain distribution of Al3Ti3 medium entropy alloy; Figure 5 For example, the rolling-annealing Co in Example 2 34 C r33 Ni 27 Grain size statistics of Al3Ti3 medium entropy alloys; Figure 6 For example, the rolling-annealing Co in Example 2 34 C r33 Ni 27 Field emission transmission electron microscopy images of nano-precipitated phases, nanotwins and 9R phase in Al3Ti3 medium entropy alloy; Figure 7 For example, the rolling-annealing Co in Example 2 34 C r33 Ni 27 Short-range ordered spherical aberration transmission electron microscope image of Al3Ti3 medium-entropy alloy. Detailed Implementation

[0016] To more clearly illustrate the present invention, specific embodiments are described below. Those skilled in the art should understand that the following description is illustrative rather than restrictive and should not be construed as limiting the scope of protection of the present invention.

[0017] Comparative Example 1 (cast Co) 34 Cr 33 Ni 27 Al3Ti3) This comparative as-cast Co 34 Cr 33 Ni 27 Al3Ti3 medium entropy alloys are prepared by a method including the following steps: Arc melting: Five elemental metals are mixed according to the target molar percentages (Co-34.0%, Cr-33.0%, Ni-27.0%, Al-3.0%, Ti-3.0%). Before melting, the furnace cavity is pre-evacuated to a pressure below 8 × 10⁻⁶. -4 The pressure was initially set at 0.05 MPa, then argon gas was introduced twice to purge the gas environment. Argon gas was then introduced again to maintain the pressure at 0.05 MPa as a protective atmosphere. At the start of melting, pure titanium was used to remove oxygen, and a small current (60 A) was used to ignite the arc to prevent raw material splashing. The current was then gradually increased to 200 A, and further increased until the raw material was completely liquefied. This state was maintained for 5 minutes, then the current was gradually reduced. After cooling, the material was flipped, and the arc was ignited again for melting until a liquid was formed. At this point, magnetic stirring was activated, and the current intensity was adjusted according to the melt flow. Each melting process lasted 5 minutes, then was stopped and allowed to cool. This melting process was repeated 6 times. Finally, the resulting molten alloy was poured into a water-cooled copper mold to solidify, thus obtaining a medium-entropy alloy plate with dimensions of 80 mm (length) × 80 mm (width) × 15 mm (thickness). Mechanical testing: Cylindrical samples with a height and diameter of 3 mm were cut from the cast alloy sheet obtained by arc melting using wire cutting. The sample size was 3.2 × 10⁻⁶ mm. 3 s -1The compressive strain rate of the obtained cylindrical samples was subjected to high-strain rate compression tests on a Hopkinson system equipped with a cryogenic cooling system. Before each loading, the contact interface between the rod and the sample was thoroughly lubricated with molybdenum disulfide to minimize friction. High-strain rate compressive stress-strain curves of the alloy at room temperature and 77 K were output using Origin software; see [link to Origin software]. Figure 1 As shown, the low-temperature yield strength of the as-cast medium-entropy alloy obtained by arc melting is 0.76 GPa, the low-temperature maximum compressive strength is 1.69 GPa, and the low-temperature maximum compressive plasticity is 25.4%; the yield strength at room temperature is 0.66 GPa, the maximum compressive strength is 1.31 GPa, and the maximum compressive plasticity is 25.1%.

[0018] Comparative Example 2 This comparative example is based on the literature Pan, RC et al. Effects of strain rate, temperature and microstructure on mechanical properties of (CoCrNi)94Al3Ti3 medium-entropy alloy: Experiments and constitutive modeling [J]. Journal of Alloys and Compounds, 2025, 1010: 177551. (Medium annealed (CoCrNi)) 94 Al3Ti3 medium-entropy alloy, which is prepared by a method including the following steps: 1) Solution treatment: The solution treatment temperature is 1050℃, the time is 2h, the cooling method is water cooling, and the treatment atmosphere is air; 2) Aging treatment: The aging treatment temperature is 800℃, the holding time is 55h, the cooling method is water cooling, and the treatment atmosphere is air; Mechanical testing: Cylindrical samples with a height and diameter of 5 mm were cut from the annealed alloy sheet obtained in steps 1) to 2) using electrical discharge machining (EDM). The samples were then tested at a depth of 3.0 × 10⁻⁶ mm. 3 s -1 The obtained cylindrical samples were subjected to high-strain-rate compression tests at a Hopkinson scale equipped with a cryogenic cooling system. High-strain-rate compressive stress-strain curves of the alloy at room temperature and 123 K were output using Origin software, obtained through solution treatment and aging treatment of (CoCrNi). 94The Al3Ti3 medium entropy alloy has a yield strength of 0.93 GPa, a maximum compressive strength of 1.95 GPa, and a maximum compressive plasticity of 24.4% at 123 K; and a yield strength of 0.9 GPa, a maximum compressive strength of 1.51 GPa, and a maximum compressive plasticity of 13.7% at room temperature.

[0019] Example 1 This embodiment involves rolling-annealing Co. 34 Cr 33 Ni 27 Al3Ti3 medium-entropy alloy is prepared by a method including the following steps: 1) Arc melting: Five elemental metals are mixed according to the target molar percentage (Co-34.0%, Cr-33.0%, Ni-27.0%, Al-3.0%, Ti-3.0%). Before melting, the furnace cavity is pre-evacuated to a pressure below 8×10⁻⁶. -4 The pressure was initially set at 0.05 MPa, then argon gas was introduced twice to purge the gas environment. Argon gas was then introduced again to maintain the pressure at 0.05 MPa as a protective atmosphere. At the start of melting, pure titanium was used to remove oxygen, and a small current (60 A) was used to ignite the arc to prevent raw material splashing. The current was then gradually increased to 200 A, and further increased until the raw material was completely liquefied. This state was maintained for 5 minutes, then the current was gradually reduced. After cooling, the material was flipped, and the arc was ignited again for melting until a liquid was formed. At this point, magnetic stirring was activated, and the current intensity was adjusted according to the melt flow. Each melting process lasted 5 minutes, then was stopped and allowed to cool. This melting process was repeated 6 times. Finally, the resulting molten alloy was poured into a water-cooled copper mold to solidify, thus obtaining a medium-entropy alloy plate with dimensions of 80 mm (length) × 80 mm (width) × 15 mm (thickness). 2) Solution treatment: The solution treatment temperature is 1200℃, the holding time is 24h, and the cooling method is furnace cooling; 3) Hot rolling treatment: The deformation amount of hot rolling treatment is 46.7%, and the temperature is 1100℃; 4) Recrystallization heat treatment: The temperature of recrystallization heat treatment is 1200℃, the time is 2h, and the cooling method is water cooling; 5) Deep cryogenic rolling treatment: The deformation amount of the deep cryogenic rolling treatment is 60%, which is divided into 10 passes. The reduction amount of each pass is 0.5mm. The alloy is immersed in liquid nitrogen for 10 minutes before and after each pass. 6) Aging treatment: The aging treatment temperature is 900℃, the holding time is 3h, and the cooling method is water cooling; Mechanical testing: Cylindrical samples with a height and diameter of 3 mm were cut from the rolled-annealed alloy sheet obtained in steps 1) to 6) using wire cutting. The sample size was 3.2 × 10⁻⁶ mm. 3 s -1The compressive strain rate of the obtained cylindrical samples was subjected to high-strain rate compression tests on a Hopkinson system equipped with a cryogenic cooling system. Before each loading, the contact interface between the rod and the sample was thoroughly lubricated with molybdenum disulfide to minimize friction. High-strain rate compressive stress-strain curves of the alloy at room temperature and 77 K were output using Origin software; see [link to Origin software]. Figure 1 As shown, the Co obtained by selecting this aging parameter (900°C for 3 hours) 34 Cr 33 Ni 27 The Al3Ti3 medium-entropy alloy has a yield strength of 1.29 GPa, a maximum compressive strength of 2.8 GPa, and a maximum compressive plasticity of 25.1% at 77 K; and a yield strength of 1.17 GPa, a maximum compressive strength of 2.46 GPa, and a maximum compressive plasticity of 24.6% at room temperature.

[0020] Example 2 This embodiment involves rolling-annealing Co. 34 Cr 33 Ni 27 Al3Ti3 medium-entropy alloy is prepared by a method including the following steps: 1) Arc melting: Five elemental metals are mixed according to the target molar percentage (Co-34.0%, Cr-33.0%, Ni-27.0%, Al-3.0%, Ti-3.0%). Before melting, the furnace cavity is pre-evacuated to a pressure below 8×10⁻⁶. -4 The pressure was initially set at 0.05 MPa, then argon gas was introduced twice to purge the gas environment. Argon gas was then introduced again to maintain the pressure at 0.05 MPa as a protective atmosphere. At the start of melting, pure titanium was used to remove oxygen, and a small current (60 A) was used to ignite the arc to prevent raw material splashing. The current was then gradually increased to 200 A, and further increased until the raw material was completely liquefied. This state was maintained for 5 minutes, then the current was gradually reduced. After cooling, the material was flipped, and the arc was ignited again for melting until a liquid was formed. At this point, magnetic stirring was activated, and the current intensity was adjusted according to the melt flow. Each melting process lasted 5 minutes, then was stopped and allowed to cool. This melting process was repeated 6 times. Finally, the resulting molten alloy was poured into a water-cooled copper mold to solidify, thus obtaining a medium-entropy alloy plate with dimensions of 80 mm (length) × 80 mm (width) × 15 mm (thickness). 2) Solution treatment: The solution treatment temperature is 1200℃, the holding time is 24h, and the cooling method is furnace cooling; 3) Hot rolling treatment: The deformation amount of hot rolling treatment is 46.7%, and the temperature is 1100℃; 4) Recrystallization heat treatment: The temperature of recrystallization heat treatment is 1200℃, the time is 2h, and the cooling method is water cooling; 5) Deep cryogenic rolling treatment: The deformation amount of the deep cryogenic rolling treatment is 60%, which is divided into 10 passes. The reduction amount of each pass is 0.5mm. The alloy is immersed in liquid nitrogen for 10 minutes before and after each pass. 6) Aging treatment: The aging treatment temperature is 700℃, the holding time is 5h, and the cooling method is water cooling; Mechanical testing: Cylindrical samples with a height and diameter of 3 mm were cut from the rolled-annealed alloy sheet obtained in steps 1) to 6) using wire cutting. The sample was measured at 3.2 × 10⁻⁶ mm. 3 s -1 The compressive strain rate of the obtained cylindrical samples was subjected to high-strain rate compression tests on a Hopkinson system equipped with a cryogenic cooling system. Before each loading, the contact interface between the rod and the sample was thoroughly lubricated with molybdenum disulfide to minimize friction. High-strain rate compressive stress-strain curves of the alloy at room temperature and 77 K were output using Origin software; see [link to Origin software]. Figure 1 As shown, the Co obtained by selecting this aging parameter (700°C for 5 hours) 34 Cr 33 Ni 27 The Al3Ti3 medium-entropy alloy exhibits a yield strength of 2.19 GPa, a maximum compressive strength of 3.38 GPa, and a maximum compressive plasticity of 25.1% at 77 K; at room temperature, it has a yield strength of 1.87 GPa, a maximum compressive strength of 2.9 GPa, and a maximum compressive plasticity of 25.7%. Phase composition analysis of the rolled-annealed alloy (Example 2) was performed using synchrotron X-ray diffraction at a scanning angle of 2-10° and an incident energy of 75 eV. The results were analyzed using pyFAI software and are available in the [link to pyFAI software]. Figure 3 As shown, the rolled-annealed alloy exhibited characteristic peaks of FCC and L12 structures, indicating that ordered L12 precipitates coherent with the matrix were formed through aging treatment. A small amount of σ phase was also found, which was unintentionally formed during the heat treatment process. Electron backscatter diffraction was used to perform crystallographic analysis on the rolled-annealed alloy (Example 2) with a step size of 0.1 μm. The results are shown in [reference needed]. Figure 4 As shown, the rolled-annealed alloy exhibits grain size inhomogeneity. Specifically, some nanoscale ultrafine grains are distributed laterally, forming bands, while micron-scale fine grains tend to be distributed above and below these bands. Simultaneously, a small number of ultrafine grains are randomly embedded between these larger grains. See crystallographic statistics for details. Figure 5 As shown, the results indicate that the average grain size of these ultrafine grains is 0.79 μm (accounting for approximately 39.2% of the total volume), the average grain size of the larger grains is 3.05 μm (accounting for approximately 60.8% of the total volume), and the microtwin fraction is 41%. Nanoscale analysis of the rolled-annealed alloy (Example 2) was performed using field emission transmission electron microscopy. The results are shown in [reference needed]. Figure 6 As shown, the presence of the coherent L12 precipitate phase in the rolled-annealed alloy was further confirmed. These precipitates were approximately rod-shaped, with a length of 20-45 μm, a width of 8-20 μm, and a volume fraction of 25.31%. Nanotwins and the 9R phase, with a thickness of approximately 10 nm, were also observed. Atomic-scale analysis of the rolled-annealed alloy was performed using aberration-corrected transmission electron microscopy; the results are shown in [reference needed]. Figure 7 As shown, short-range order was found in the rolled-annealed alloy, with an average size of 0.67 nm.

[0021] The results of the embodiments show that the present invention, through a series of rolling-annealing processes, especially the careful selection of aging treatment parameters, achieves optimal performance in Co... 34 Cr 33 Ni 27 The Al3Ti3 medium-entropy alloy introduces heterogeneity ranging from micrometers to angstroms, including micrometer-scale heterogeneity involving grain size and microtwins, nanometer-scale heterogeneity involving nanoprecipitates, nanotwins, and the 9R phase, and atomic-scale heterogeneity involving short-range order. These multi-scale heterostructures not only significantly enhance the yield strength of the medium-entropy alloy but also provide sustained strain hardening and deformation capabilities across different length scales, endowing rolled-annealed Co alloys with... 34 Cr 33 Ni 27 Al3Ti3 medium-entropy alloys exhibit excellent low-temperature impact resistance.

[0022] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for preparing a low-temperature impact-resistant multi-scale heterogeneous CoCrNi-based medium-entropy alloy, characterized in that, Includes the following steps: S1. Raw materials containing Co, Cr, Ni, Al and Ti are mixed and alloy ingots are obtained by vacuum arc melting, wherein the molar contents of Co, Cr, Ni, Al and Ti are 34.0%, 33.0%, 27.0%, 3.0% and 3.0%, respectively. S2. The alloy ingot is subjected to solution treatment, hot rolling, recrystallization heat treatment, deep cryogenic rolling and aging treatment in sequence to obtain the alloy product.

2. The method for preparing a low-temperature impact-resistant multi-scale heterogeneous CoCrNi-based medium-entropy alloy according to claim 1, characterized in that, The raw materials contain 34.0% Co, 33.0% Cr and 27.0% Ni in molar amounts, respectively.

3. The method for preparing a low-temperature impact-resistant multi-scale heterogeneous CoCrNi-based medium-entropy alloy according to claim 1, characterized in that, The vacuum arc melting is carried out in an argon atmosphere at a pressure of 0.05 MPa.

4. The method for preparing a low-temperature impact-resistant multi-scale heterogeneous CoCrNi-based medium-entropy alloy according to claim 1, characterized in that, The solution treatment temperature is 1200℃, the holding time is 24h, and the cooling method is furnace cooling.

5. The method for preparing a low-temperature impact-resistant multi-scale heterogeneous CoCrNi-based medium-entropy alloy according to claim 1, characterized in that, The deformation amount of the hot rolling process is 46.7%, and the temperature is 1100℃.

6. The method for preparing a low-temperature impact-resistant multi-scale heterogeneous CoCrNi-based medium-entropy alloy according to claim 1, characterized in that, The recrystallization heat treatment was performed at a temperature of 1200℃ for 2 hours, and the cooling method was water cooling.

7. The method for preparing a low-temperature impact-resistant multi-scale heterogeneous CoCrNi-based medium-entropy alloy according to claim 1, characterized in that, The deep cryogenic rolling process involves a deformation of 60%, divided into 10 passes, with a reduction of 0.5 mm per pass. The alloy is immersed in liquid nitrogen for 10 minutes before and after each pass.

8. The method for preparing a low-temperature impact-resistant multi-scale heterogeneous CoCrNi-based medium-entropy alloy according to claim 1, characterized in that, The aging treatment temperature is 700℃~900℃, the holding time is 3~5h, and the cooling method is water cooling.

9. A low-temperature impact-resistant multi-scale heterogeneous CoCrNi-based medium-entropy alloy, characterized in that, It is prepared by any one of the preparation methods described in claims 1-8.

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