NiCrFeMo eutectic high-entropy alloy system and preparation method thereof

Abstract

The invention relates to the technical field of material processing, in particular to a NiCrFeMo eutectic high-entropy alloy system and a preparation method thereof. The NiCrFeMo eutectic high-entropy alloy system comprises the following elements of Ni, Cr, Fe, Mo and a toughening element, the total mass of the NiCrFeMo eutectic high-entropy alloy system is 100%, the mass percent of the toughening element is 3%-10%, and the toughening element is selected from at least one of Ti, Zr and Hf. The method has the effect of improving the fracture toughness and the high-temperature service strength of the NiCrFeMo eutectic high-entropy alloy system.

Description

Technical Field

[0001] The present invention relates to the technical field of material processing, and in particular to a NiCrFeMo eutectic high entropy alloy system and a preparation method thereof. Background Art

[0002] High-entropy alloys (HEAs), a new type of multi-principal alloy system, exhibit significant advantages in high-temperature strength, corrosion resistance, oxidation resistance, and microstructure stability due to their high mixing entropy, slow diffusion effect, and severe lattice distortion. They have become a hot topic in the research of structurally integrated materials. Among them, NiCrFeMo eutectic high-entropy alloys, due to their naturally formed "soft-hard phase" composite structure, achieve a balance between strength and ductility, and possess excellent castability and microstructure stability.

[0003] However, the high Mo content in existing NiCrFeMo eutectic high-entropy alloys easily leads to the formation of brittle intermetallic compounds such as σ, μ, or Laves phases within the eutectic structure. These phases often exhibit brittle fracture behavior and easily serve as crack initiators under load, resulting in a lack of fracture toughness and impact resistance in the overall material. Especially under high-temperature service environments, these brittle intermetallic phases are prone to fracture or cracking, making it difficult to meet the service requirements of structural components subjected to the combined effects of high stress and high temperature. Summary of the Invention

[0004] The present invention aims to improve the fracture toughness and high-temperature service strength of a NiCrFeMo-based eutectic high-entropy alloy system.

[0005] As a first aspect, the present invention provides a NiCrFeMo eutectic high entropy alloy system, which includes the following elements: Ni, Cr, Fe, Mo and a toughening element, wherein, based on the total mass of the NiCrFeMo eutectic high entropy alloy system as 100%, the mass percentage of the toughening element is 3% to 10%, and the toughening element is selected from at least one of Ti, Zr and Hf.

[0006] Optionally, the NiCrFeMo eutectic high entropy alloy system further includes the following elements in percentage by mass: Ni: 25% to 35%, Cr: 20% to 30%, Fe: 15% to 25% and Mo: 10% to 20%.

[0007] As a second aspect, the present invention also provides a method for preparing a NiCrFeMo eutectic high entropy alloy system, which is used to prepare the NiCrFeMo eutectic high entropy alloy system as described in the first aspect. The preparation method includes: the NiCrFeMo eutectic high entropy alloy system is prepared by vacuum arc melting.

[0008] Optionally, the vacuum arc melting method includes: Ni, Cr, Fe, Mo and Ti are mixed in proportion, vacuumed and repeatedly melted in an inert gas atmosphere for multiple times, and then rapidly cooled and cast to form a NiCrFeMo eutectic high entropy alloy system.

[0009] Optionally, the rapid cooling and casting to form the NiCrFeMo eutectic high entropy alloy system includes: a cooling rate of 1000 to 2000 K / s.

[0010] Optionally, the rapid cooling and pouring to form the NiCrFeMo eutectic high entropy alloy system includes: melting for 3 to 5 times.

[0011] Optionally, after the Ni, Cr, Fe, Mo and Ti are proportioned and mixed, vacuumed and repeatedly melted multiple times in an inert gas atmosphere, and then rapidly cooled and cast to form a NiCrFeMo eutectic high entropy alloy system, the process further includes: The NiCrFeMo eutectic high entropy alloy system is heat-treated in a vacuum or inert gas atmosphere, wherein the heat treatment temperature is 800 to 1000° C. and the heat treatment time is 1 to 10 hours.

[0012] As a third aspect, the present invention further provides a method for preparing a NiCrFeMo eutectic high entropy alloy system, which is used to prepare the NiCrFeMo eutectic high entropy alloy system as described in the first aspect, the preparation method comprising: Ni, Cr, Fe, Mo and Ti are mixed according to a certain proportion and ball milled to obtain a mixed alloy powder; The mixed alloy powder is subjected to spark plasma sintering in a vacuum or inert gas atmosphere to obtain a NiCrFeMo eutectic high entropy alloy system.

[0013] Optionally, the spark plasma sintering temperature is 1000 to 1150° C., the heating rate is 50 to 100° C. / min, the holding time is 5 to 10 min, and a pressure of 30 to 50 MPa is applied.

[0014] Optionally, after spark plasma sintering the mixed alloy powder under vacuum or inert gas atmosphere to obtain a NiCrFeMo eutectic high entropy alloy system, the method further comprises: The NiCrFeMo eutectic high entropy alloy system is heat-treated in a vacuum or inert gas atmosphere, wherein the heat treatment temperature is 800 to 1000° C. and the heat treatment time is 1 to 10 hours.

[0015] The beneficial effects of the present invention compared to the prior art are: The present invention incorporates toughening elements into the NiCrFeMo eutectic high-entropy alloy system. These toughening elements have limited solid solubility in the FCC matrix (FCC) (especially during cooling or annealing). Therefore, when their concentration exceeds the solubility limit, they precipitate from the solid solution. For example, Ti, a toughening element, partially dissolves in the FCC matrix at high temperatures and partially precipitates in the FCC structure, forming nanoscale FCC-Ti particles, specifically 10 to 200 nm in size, distributed at eutectic phase boundaries, within grains, or at grain boundaries. Furthermore, in complex eutectic high-entropy alloy systems, metastable FCC-Ti is more likely to precipitate at an early stage than stable phases (such as HCP α-Ti). Due to its smaller nanoscale size, the interfacial strain energy associated with FCC-Ti formation is lower, facilitating nucleation and growth. FCC-Ti nanoparticles typically significantly enhance the fracture toughness of NiCrFeMo eutectic alloys (by 30% to 80%) through dislocation pinning and the Orowan mechanism, while also improving their high-temperature strength, resulting in excellent structural stability and high-temperature yield strength. Furthermore, the FCC-Ti phase has an identical or similar structure to the parent FCC phase, providing excellent structural compatibility. This significantly reduces interfacial energy, making it less susceptible to cracking and contributing to improved toughness and ductility. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 This is a flow chart for preparing a NiCrFeMo eutectic high entropy alloy system in an exemplary embodiment of the present invention. DETAILED DESCRIPTION

[0017] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, specific embodiments of the present invention are described in detail below.

[0018] Unless otherwise defined, all technical and scientific terms used in this application have the same meanings as those commonly understood by those skilled in the art to which this application belongs. The terms used in the specification of this application are only for the purpose of describing specific embodiments and are not intended to limit this application. The term "including" and its variations used in this document are open inclusions, that is, "including but not limited to"; the term "based on" means "at least partially based on"; the term "one embodiment" means "at least one embodiment"; the term "another embodiment" means "at least one other embodiment"; the term "some embodiments" means "at least some embodiments"; the term "optionally" means "optional embodiments". The relevant definitions of other terms will be given in the following description. It should be noted that the concepts of "first" and "second" mentioned in the present invention are used to distinguish different objects, rather than to describe a specific order or a primary and secondary relationship. In addition, the terms "first" and "second" are used for descriptive purposes only and cannot be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Therefore, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features. In the description of this application, unless otherwise specified, "multiple" means two or more.

[0019] NiCrFeMo eutectic high-entropy alloys (HEAs) have become an important branch of HEA research due to their naturally formed "soft-hard phase" composite structure, which achieves a balance between strength and ductility, exhibiting excellent castability and structural stability. However, eutectic HEAs commonly exhibit defects such as the enrichment of brittle intermetallic compounds, coarse and rigid eutectic phase interfaces that are unable to effectively passivate or deflect cracks, resulting in poor interface continuity, and insufficient ductility under high-temperature conditions.

[0020] In NiCrFeMo eutectic high-entropy alloys, the FCC (Face-Centered Cubic) phase often becomes the dominant phase due to its low atomic stacking energy and high entropy effect. The FCC phase is often considered a "soft phase" relative to the coexisting hard phases, such as the BCC (Body-Centered Cubic) phase. This soft / hard phase combination is a key microstructural feature that enables eutectic high-entropy alloys to achieve excellent strength-ductility balance. The random solid solution of various elements in eutectic high-entropy alloys enhances the stability of the solid solution. Ni, Fe, and Cr all tend to form either FCC or BCC phases, while Mo tends to form the BCC phase but can dissolve into the FCC phase within the alloy. During deformation, the FCC phase undergoes plastic deformation first due to its face-centered cubic crystal structure, which offers a greater number of slip systems and lower dislocation slip resistance. It absorbs significant plastic strain energy through dislocation slip and multiplication, while also coordinating local strain around the hard phase, preventing premature stress concentration and thus delaying crack initiation. Therefore, the plastic deformation ability of the soft phase is the main source of the overall high toughness and ductility of the alloy.

[0021] Related technologies generally optimize the distribution ratio, microstructure, and organizational scale of the FCC phase in eutectic high-entropy alloys to improve the fracture toughness and plasticity of the material. For example, some related technologies achieve toughening by increasing the volume fraction of the FCC phase, refining its grain size, or improving the bonding state between the soft and hard phases. For example, in the NiCrFeCoMoAl system, the Mo or Al content is appropriately adjusted to suppress excessive Laves phase precipitation, maintain the continuity of the FCC phase, and thus achieve plasticization of the structure.

[0022] However, simply increasing the proportion of the FCC phase often comes at the expense of high-temperature strength or creep resistance. The increase in the proportion of the soft phase leads to a weakening of the hard phase support skeleton, and the overall mechanical properties fluctuate significantly. Secondly, the interface between FCC and intermetallic compounds such as Laves usually presents a high stress concentration area, which easily becomes a crack initiation point under load, and traditional composition control methods are difficult to effectively change its microstructural characteristics. In addition, the growth of the FCC phase is often accompanied by a grain coarsening effect, which makes the overall toughening effect of the material unstable, especially in high-temperature service environments. Its structural stability and performance durability still face great challenges. Therefore, it is difficult to simultaneously meet the comprehensive performance requirements of the NiCrFeMo eutectic high-entropy alloy system in terms of high strength, high-temperature stability and high toughness.

[0023] To solve the problems existing in the related art, an embodiment of the present invention provides a NiCrFeMo eutectic high entropy alloy system, which includes the following elements: Ni, Cr, Fe, Mo and a toughening element, wherein, based on the total mass of the NiCrFeMo eutectic high entropy alloy system as 100%, the mass percentage of the toughening element is 3% to 10%, and the toughening element is selected from at least one of Ti, Zr and Hf.

[0024] In the embodiments of the present invention, toughening elements are added to the NiCrFeMo eutectic high-entropy alloy system. The toughening elements have limited solid solubility in the FCC-structured NiCrFeMo parent phase (especially during cooling or annealing). Therefore, when the toughening element concentration exceeds the solubility limit, it precipitates from the solid solution. For example, under high temperature conditions, Ti partially dissolves in the FCC phase and partially precipitates in the FCC structure, forming nanoscale FCC-Ti particles, specifically 10 to 200 nm in size, distributed at eutectic phase boundaries, within grains, or at grain boundaries. Furthermore, in complex eutectic high-entropy alloy systems, metastable FCC-Ti is more likely to precipitate at an early stage than stable phases (such as HCP α-Ti). Due to its small nanoscale size, the interfacial strain energy associated with the formation of the FCC-Ti phase is low, facilitating nucleation and growth. FCC-Ti nanoparticles typically significantly enhance the fracture toughness of NiCrFeMo eutectic alloys (by 30% to 80%) through dislocation pinning and the Orowan mechanism, while also improving their high-temperature strength, resulting in excellent structural stability and high-temperature yield strength. Furthermore, the FCC-Ti phase has an identical or similar structure to the parent FCC phase, providing excellent structural compatibility. This significantly reduces interfacial energy, making it less susceptible to cracking and contributing to improved toughness and ductility.

[0025] Therefore, the embodiments of the present invention effectively control the crack propagation path at the microscale through the synergistic strengthening mechanism of the toughening element phase, thereby introducing a controllable micro / nano toughening mechanism without destroying the stability of the eutectic structure. By controlling the micro / nano precipitation behavior of the toughening elements, a uniformly distributed FCC-toughening phase is formed in the eutectic structure, thereby significantly improving the toughness, fracture toughness and impact properties of the alloy while maintaining excellent high-temperature yield strength.

[0026] In some optional embodiments, the NiCrFeMo eutectic high entropy alloy system further includes the following elements in percentage by mass: Ni: 25% to 35%, Cr: 20% to 30%, Fe: 15% to 25% and Mo: 10% to 20%.

[0027] In this embodiment, further regulating the ratio of the main elements is beneficial to suppressing the excessive precipitation of the Laves phase and maintaining the continuity of the FCC phase, thereby achieving plasticization and toughening of the structure.

[0028] Another embodiment of the present invention provides a method for preparing a NiCrFeMo eutectic high entropy alloy system, which is used to prepare the NiCrFeMo eutectic high entropy alloy system described above. In this embodiment, the NiCrFeMo eutectic high entropy alloy system is prepared by vacuum arc melting.

[0029] Specifically, the vacuum arc melting method for preparing a NiCrFeMo eutectic high-entropy alloy system includes: mixing Ni, Cr, Fe, Mo, and Ti in a certain proportion, evacuating the mixture, and repeatedly melting the mixture multiple times under an inert gas atmosphere, followed by rapid cooling to form the NiCrFeMo eutectic high-entropy alloy system. The melting process can be repeated 3 to 5 times at a cooling rate of 1000 to 2000 K / s. Furthermore, during the cooling and solidification process, rapid cooling can be achieved by rapid cooling casting or copper mold cooling.

[0030] In the embodiments of the present invention, if the cooling rate is controlled to be relatively fast, the toughening elements are less likely to diffuse over long distances and are more likely to accumulate locally and nucleate to form nanoparticles. Therefore, by controlling the rapid solidification, grain growth and element diffusion can be suppressed, significantly refining the grain size. The interlamellar spacing of the eutectic structure or the size of the precipitated phase is significantly reduced, suppressing the formation of coarse brittle phases and providing supersaturated solid solution conditions for subsequent precipitation phases.

[0031] In some optional embodiments, after forming the NiCrFeMo eutectic high entropy alloy system, the method further includes: heat treating the NiCrFeMo eutectic high entropy alloy system in a vacuum or inert gas atmosphere, wherein the heat treatment temperature is 800 to 1000° C. and the heat treatment time is 1 to 10 hours.

[0032] While rapid cooling suppresses segregation and refines the structure during the formation of a metastable microstructure, rapid solidification also introduces three drawbacks: insufficient atomic diffusion leading to a sub-equilibrium distribution of elements; the potential for residual non-equilibrium phases or defects; and the presence of internal stresses. In these examples, heat treatment of the NiCrFeMo eutectic high-entropy alloy system facilitates further control of the particle size and distribution of the FCC-toughening phase, releases residual stresses, and thus optimizes its microstructure and overall performance.

[0033] In the above-mentioned embodiment, the eutectic high-entropy alloy was prepared using vacuum arc melting, which eliminates the need for powder preparation and is suitable for mass production and industrialization. However, during the melting and solidification process, element segregation may occur, especially for elements with high melting points and high densities (such as Mo and Ti), which are prone to agglomeration. Therefore, for high-end applications requiring precise control of dispersed precipitates and maintaining a metastable structure, vacuum arc melting has certain limitations in terms of microstructure uniformity and stability.

[0034] In order to improve the above defects, another embodiment of the present invention further provides a method for preparing a NiCrFeMo eutectic high entropy alloy system, which is also used to prepare the NiCrFeMo eutectic high entropy alloy system as described above. Figure 1 As shown, the preparation method comprises the following steps: Step (1): Ni, Cr, Fe, Mo and Ti are mixed in proportion and ball milled to obtain a mixed alloy powder. The ball milling medium may be WC, ZrO2 or stainless steel balls, and the ball-to-powder ratio is 10:1 to 15:1. The ball milling time is 10 to 40 hours, preferably 20 to 30 hours, and the ball milling can be carried out in an inert gas atmosphere at a speed of 300 to 600 rpm. A pause of 10 to 15 minutes may be performed every 30 to 60 minutes of ball milling to prevent overheating.

[0035] Step (2): Spark plasma sintering the mixed alloy powder in a vacuum or inert gas atmosphere to obtain a NiCrFeMo eutectic high entropy alloy system. Specifically, the spark plasma sintering temperature is 1000 to 1150°C, the heating rate is 50 to 100°C / min, the holding time is 5 to 10 minutes, and a pressure of 30 to 50 MPa is applied.

[0036] In this embodiment, the preparation of eutectic high entropy alloy is achieved by combining mechanical alloying and spark plasma sintering. Among them, the mechanical alloying process can achieve atomic-scale mixing and effectively avoid macro-segregation. Toughening elements such as Ti are highly supersaturated during the ball milling process, and can be controlled to precipitate in the subsequent spark plasma sintering process to form nano-scale dispersed particles. Since the spark plasma sintering process has the characteristics of rapid heating, short-term heat preservation, and high-pressure pressing, it is possible to obtain a highly dense, ultrafine-grained or nanostructured NiCrFeMo eutectic high entropy alloy system while limiting grain growth. Therefore, this preparation method has higher control accuracy for the organization and strengthening phase.

[0037] In addition, as an option, after the above step (2), the following steps may also be included: Step (3): heat-treating the NiCrFeMo eutectic high entropy alloy system in a vacuum or inert gas atmosphere, wherein the heat-treating temperature is 800 to 1000° C. and the heat-treating time is 1 to 10 hours.

[0038] In this part of the embodiment, the NiCrFeMo eutectic high entropy alloy system is also heat treated to further control the particle size and distribution of the FCC-toughening phase, release the residual stress, and thus optimize its microstructure and comprehensive performance.

[0039] The present invention is described in detail below through specific examples and comparative examples: Example 1 In this embodiment, the NiCrFeMo eutectic high entropy alloy system includes the following elements in mass percentage: Ni: 30%, Cr: 30%, Fe: 20%, Mo: 15% and Ti: 5%. Its preparation process specifically includes the following steps: Step 1: Ni, Cr, Fe, Mo and Ti with purity ≥99.9% are mixed in the above proportions in an arc melting furnace and vacuumed to less than 10 -3 Pa, and then filled with argon (0.05 MPa). After melting 5 times in an argon atmosphere, a copper mold was used for rapid cooling to form a NiCrFeMo eutectic high entropy alloy system, wherein the cooling rate was 1500K / s.

[0040] Step 2: Heat-treating the NiCrFeMo eutectic high entropy alloy system in an argon atmosphere, wherein the heat treatment temperature is 1000° C. and the time is 1 h to obtain the NiCrFeMo eutectic high entropy alloy system.

[0041] Example 2 The difference between this embodiment and Example 1 is that the NiCrFeMo eutectic high entropy alloy system includes the following elements in mass percentage: Ni: 30%, Cr: 30%, Fe: 20%, Mo: 17% and Ti: 3%, and its preparation process is the same as that of Example 1.

[0042] Example 3 The difference between this embodiment and Example 1 is that the NiCrFeMo eutectic high entropy alloy system includes the following elements in mass percentage: Ni: 30%, Cr: 30%, Fe: 20%, Mo: 10% and Ti: 10%, and its preparation process is the same as that of Example 1.

[0043] Example 4 The difference between this embodiment and Example 1 is that the NiCrFeMo eutectic high entropy alloy system includes the following elements in mass percentage: Ni: 30%, Cr: 30%, Fe: 20%, Mo: 12% and Hf: 8%, and its preparation process is the same as that of Example 1.

[0044] Example 5 The difference between this embodiment and Example 1 is that the NiCrFeMo eutectic high entropy alloy system includes the following elements in mass percentage: Ni: 30%, Cr: 30%, Fe: 20%, Mo: 14% and Zr: 6%, and its preparation process is the same as that of Example 1.

[0045] Example 6 The difference between this embodiment and embodiment 1 is that the preparation process of the NiCrFeMo eutectic high entropy alloy system specifically includes the following steps: Step (1): Ni, Cr, Fe, Mo, and Ti with a purity of ≥99.9% were prepared in the proportions given in Example 1 and mixed by ball milling to obtain a mixed alloy powder. The milling media was WC and ZrO2, the ball-to-powder ratio was 10:1, the milling time was 20 h, and the milling process was carried out under an argon atmosphere. The milling speed was 500 rpm, and the milling was performed at a frequency of 30 min followed by a 10 min pause.

[0046] Step (2): In an argon atmosphere, the ball-milled mixed alloy powder is placed into a graphite mold and subjected to spark plasma sintering to obtain a NiCrFeMo eutectic high-entropy alloy system. The spark plasma sintering temperature is 1000°C, the heating rate is 100°C / min, the holding time is 10 min, and a pressure of 45 MPa is applied.

[0047] Comparative Example 1 This comparative example differs from Example 1 in that the NiCrFeMo eutectic high-entropy alloy system includes the following elements in percentage by mass: Ni: 30%, Cr: 30%, Fe: 20%, and Mo: 20%, i.e., no Ti element is added. The preparation process is the same as that of Example 1.

[0048] Comparative Example 2 This comparative example differs from Example 1 in that the NiCrFeMo eutectic high-entropy alloy system includes the following elements in percentage by mass: Ni: 30%, Cr: 30%, Fe: 20%, Mo: 18%, and Ti: 2%. The preparation process is the same as that of Example 1.

[0049] Comparative Example 3 This comparative example differs from Example 1 in that the NiCrFeMo eutectic high-entropy alloy system includes the following elements in percentage by mass: Ni: 30%, Cr: 30%, Fe: 20%, Mo: 9%, and Ti: 12%. The preparation process is the same as that of Example 1.

[0050] The yield strength of the NiCrFeMo eutectic high entropy alloy system in Examples 1 to 6 and Comparative Examples 1 to 3 at room temperature and high temperature (800°C) is shown in Table 1: Table 1 Yield strength and elongation data of NiCrFeMo eutectic high entropy alloy systems in Examples 1 to 6 and Comparative Examples 1 to 3

[0051] As shown in Table 1, the NiCrFeMo eutectic high-entropy alloy system in the embodiments of the present invention has excellent tensile strength and yield strength. Even at a high temperature of 800°C, its yield strength can still be maintained above 600 MPa. When no toughening element is added (Comparative Example 1), the yield strength of the NiCrFeMo eutectic high-entropy alloy system at room temperature can still reach above 800 MPa, but the high-temperature yield strength drops to below 500 MPa. When the toughening element content is less than 3% (Comparative Example 2), the toughening element does not precipitate and is completely dissolved in the FCC parent phase of the NiCrFeMo eutectic high-entropy alloy system, resulting in a similar microstructure and properties to those of Comparative Example 1. However, when the toughening element content is greater than 10% (Comparative Example 3), the Ti content is too high, forming a large number of secondary phases, such as Ti-rich Laves phase (NiTi2, etc.) and brittle σ phase (Cr / Ti / Mo-rich). These phases precipitate along grain boundaries and become crack initiation sources, resulting in a significant decrease in the alloy's fracture toughness, reduced room temperature plasticity, and elongation falling below 3%.

[0052] Although the present invention is disclosed as above, the protection scope of the present invention is not limited thereto. Those skilled in the art may make various changes and modifications without departing from the spirit and scope of the present invention, and these changes and modifications will fall within the protection scope of the present invention.

Claims

1. A NiCrFeMo eutectic high entropy alloy system, characterized in that: The invention comprises the following elements: Ni, Cr, Fe, Mo and toughening elements, wherein, based on the total mass of the NiCrFeMo eutectic high entropy alloy system as 100%, the mass percentage of the toughening elements is 3% to 10%, and the toughening elements are selected from at least one of Ti, Zr and Hf.

2. The NiCrFeMo eutectic high entropy alloy system according to claim 1, characterized in that The NiCrFeMo eutectic high entropy alloy system further includes the following elements in percentage by mass: Ni: 25% to 35%, Cr: 20% to 30%, Fe: 15% to 25% and Mo: 10% to 20%.

3. A method for preparing a NiCrFeMo eutectic high entropy alloy system, characterized in that: Used to prepare the NiCrFeMo eutectic high entropy alloy system as described in claim 1 or 2, the NiCrFeMo eutectic high entropy alloy system is prepared by vacuum arc melting.

4. The method for preparing the NiCrFeMo eutectic high entropy alloy system according to claim 3, characterized in that: The vacuum arc melting method comprises: Ni, Cr, Fe, Mo and Ti are mixed in proportion, vacuumed and repeatedly melted in an inert gas atmosphere for multiple times, and then rapidly cooled and cast to form a NiCrFeMo eutectic high entropy alloy system.

5. The method for preparing the NiCrFeMo eutectic high entropy alloy system according to claim 4, characterized in that: The Ni, Cr, Fe, Mo and Ti are proportioned and mixed, vacuumed and repeatedly melted multiple times in an inert gas atmosphere, and then rapidly cooled and cast to form a NiCrFeMo eutectic high entropy alloy system, including: a cooling rate of 1000 to 2000K / s.

6. The method for preparing the NiCrFeMo eutectic high entropy alloy system according to claim 4, characterized in that: The method comprises the steps of mixing Ni, Cr, Fe, Mo and Ti in proportion, repeatedly melting the mixture in an inert gas atmosphere under vacuum for multiple times, and then rapidly cooling and pouring the mixture to form a NiCrFeMo eutectic high entropy alloy system, wherein the melting times are 3 to 5 times.

7. The method for preparing the NiCrFeMo eutectic high entropy alloy system according to claim 4, characterized in that: After mixing Ni, Cr, Fe, Mo and Ti in proportion, vacuuming and repeatedly melting multiple times in an inert gas atmosphere, and rapidly cooling and pouring to form a NiCrFeMo eutectic high entropy alloy system, the method further includes: The NiCrFeMo eutectic high entropy alloy system is heat-treated in a vacuum or inert gas atmosphere, wherein the heat treatment temperature is 800 to 1000° C. and the heat treatment time is 1 to 10 hours.

8. A method for preparing a NiCrFeMo eutectic high entropy alloy system, characterized in that: For preparing the NiCrFeMo eutectic high entropy alloy system according to claim 1 or 2, the preparation method comprises: Ni, Cr, Fe, Mo and Ti are mixed according to a certain proportion and ball milled to obtain a mixed alloy powder; The mixed alloy powder is subjected to spark plasma sintering in a vacuum or inert gas atmosphere to obtain a NiCrFeMo eutectic high entropy alloy system.

9. The method for preparing the NiCrFeMo eutectic high entropy alloy system according to claim 8, characterized in that: The spark plasma sintering temperature is 1000 to 1150° C., the heating rate is 50 to 100° C. / min, the holding time is 5 to 10 min, and a pressure of 30 to 50 MPa is applied.

10. The method for preparing the NiCrFeMo eutectic high entropy alloy system according to claim 8, characterized in that: After the mixed alloy powder is subjected to spark plasma sintering under vacuum or inert gas atmosphere to obtain a NiCrFeMo eutectic high entropy alloy system, the method further comprises: The NiCrFeMo eutectic high entropy alloy system is heat-treated in a vacuum or inert gas atmosphere, wherein the heat treatment temperature is 800 to 1000° C. and the heat treatment time is 1 to 10 hours.

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