A Si-doped AlCoCrFeNi 2.1 Si x Preparation method of eutectic high-entropy alloy and its synergistic improvement of strength and plasticity

Abstract

This invention relates to a eutectic high-entropy alloy, specifically a Si-doped AlCoCrFeNi alloy. 2.1 Si x A method for preparing a eutectic high-entropy alloy and its synergistic enhancement of strength and plasticity, wherein the chemical formula of the eutectic high-entropy alloy is AlCoCrFeNi. 2.1 Si x The alloy composition is 0 ≤ x ≤ 0.5. Its preparation method includes the following steps: weighing raw materials according to the proportions; obtaining a cast alloy through vacuum arc melting; and obtaining a eutectic high-entropy alloy through thermomechanical treatment. The thermomechanical treatment method includes two rolling processes and two annealing processes. The rolling process adopts multi-pass cold rolling with non-fixed deformation. The total rolling amount of the first multi-pass cold rolling of the cast alloy is 30%, followed by high-temperature annealing. Subsequently, a second multi-pass cold rolling with non-fixed deformation is performed, with a total rolling amount of 0~40%, followed by another high-temperature annealing to refine and recrystallize the grains in the alloy. The alloy treated by the thermomechanical method, compared to the cast AlCoCrFeNi alloy, exhibits higher yields. 2.1 Eutectic high-entropy alloys can improve fracture toughness by up to 47% and fracture toughness by up to 110%, further achieving a synergistic improvement in strength and plasticity.

Description

Technical Field

[0001] This invention relates to the field of eutectic high-entropy alloy materials, specifically to a Si-doped AlCoCrFeNi alloy. 2.1 Si x Preparation method of eutectic high-entropy alloy and its synergistic enhancement of strength and plasticity. Background Technology

[0002] Since Lu Yiping and others proposed the concept of eutectic high-entropy alloys in 2014, the field has attracted increasing attention. Eutectic high-entropy alloys combine the advantages of traditional eutectic alloys and high-entropy alloys, typically exhibiting excellent comprehensive properties such as a good balance between strength and plasticity, high oxidation resistance, superior high-temperature creep resistance, excellent fluidity, and a uniform microstructure. Currently, eutectic high-entropy alloy systems are continuously being developed and expanded. However, existing eutectic high-entropy alloy systems with a good balance between strength and plasticity are relatively few, and post-processing is required to improve their performance. Traditional methods for improving the mechanical properties of alloys often sacrifice plasticity to increase strength. Experimental studies have shown that by adjusting the composition ratio of eutectic high-entropy alloys or doping with trace elements, a synergistic improvement in strength and plasticity can be directly achieved. Currently reported eutectic high-entropy alloy compositions mostly select metallic elements or dopants of trace rare earth elements to improve the comprehensive mechanical properties of eutectic high-entropy alloys, while research on the non-metallic design of eutectic high-entropy alloys is limited. As an inorganic non-metallic element, silicon (Si) possesses excellent advantages such as oxidation resistance, corrosion resistance, and wear resistance. Furthermore, its low density and low cost have led to its widespread research and application in traditional alloys. Based on this, this project prepared AlCoCrFeNi alloy by adding trace amounts of the non-metallic element Si. 2.1 Si x The eutectic high-entropy alloy directly achieves a synergistic improvement in strength and plasticity. Furthermore, by subjecting the alloy to thermomechanical treatment, including multiple passes of non-fixed deformation cold rolling and recrystallization heat treatment, its comprehensive mechanical properties are further enhanced. This alloy can be processed into various product types and has wide applications in the manufacture of high-strength structural components for aerospace, future marine equipment, and the petrochemical industry. Summary of the Invention

[0003] To address the problems of existing technologies, this invention provides a Si-doped AlCoCrFeNi 2.1 Si x The preparation methods and applications of eutectic high-entropy alloys and their synergistic enhancement of strength and plasticity are widely used in high-strength structural components for aerospace, future marine equipment, petrochemicals, and other fields, providing valuable theoretical guidance and reference for the development of metallic materials.

[0004] This alloy consists of FCC and BCC phases. With increasing Si content, its microstructure gradually evolves from a typical lamellar eutectic structure to a structure where lamellar eutectic structure and irregular petal-like structures coexist, eventually evolving into a completely irregular petal-like structure. Si promotes the formation of the BCC phase and regulates the volume ratio of the hard BCC phase to the tough FCC phase in the microstructure. The volume changes of the two phases are as follows: Figure 2 As shown, the Si concentration significantly affects the microhardness and wear resistance of the alloy. On the other hand, increasing the Si concentration accelerates grain growth, gradually increasing the average grain size in the alloy and improving its work hardening ability. The change in the two-phase grain size in the alloy with Si content is shown in the figure. Figure 3 As shown. In summary, the addition of Si solves the key problem of the difficulty in synergistically improving the strength and plasticity of eutectic high-entropy alloys, thus achieving an improvement in the overall mechanical properties of the alloy. Furthermore, thermomechanical treatment of the alloy yields a refined eutectic microstructure. Subsequent control of heat treatment time and temperature allows for the formation of a micro / nano-ultrafine dual-phase (FCC+BCC) heterostructure with matching mechanical properties. The change in grain size of the two phases in the alloy with Si content after thermomechanical treatment is shown in the figure. Figure 4 As shown.

[0005] To achieve the above objectives, the present invention adopts the following technical solution:

[0006] A Si-doped AlCoCrFeNi 2.1 Si x Eutectic high-entropy alloys, with the general formula AlCoCrFeNi 2.1 Si x Where 0 ≤ x ≤ 0.5, and x is the molar percentage of the corresponding element. A Si-modified as-cast alloy with synergistically improved strength and ductility was obtained through vacuum arc melting, wherein the as-cast alloy AlCoCrFeNi... 2.1 Si 0.15 It exhibits the best strength-plasticity balance compared to the matrix AlCoCrFeNi. 2.1 Its strength and ductility were both improved by 45%. When x > 0.2, the ductility of the as-cast alloy began to decrease significantly, especially when x = 0.3, with only about 5% ductility remaining. Figure 1 As shown. Based on this, a eutectic high-entropy alloy with further synergistic improvement in strength and ductility is obtained through thermomechanical treatment. Compared to the as-cast AlCoCrFeNi2.1 eutectic high-entropy alloy, the alloy treated by the thermomechanical method exhibits a fracture toughness increase of up to 47% and a tensile strength increase of up to 110%, further achieving a strength enhancement, such as... Figure 14 As shown.

[0007] A Si-doped AlCoCrFeNi 2.1 Si xA method for synergistically improving the strength and plasticity of eutectic high-entropy alloys includes the following steps:

[0008] S1: Master alloy preparation: Al, Co, Cr, Fe, Ni, and non-metallic Si raw materials were accurately weighed according to the molar percentage of the eutectic high-entropy alloy, and then AlCoCrFeNi was obtained through a casting process. 2.1 Si x Eutectic high-entropy alloy master alloy;

[0009] S2: First cold deformation: The AlCoCrFeNi obtained in step S1 is subjected to cold deformation. 2.1 Si x The eutectic high-entropy alloy master alloy is cold-rolled to reduce the total thickness by 30%.

[0010] S3: First heat treatment: The AlCoCrFeNi alloy cold-rolled in step S2 is then subjected to heat treatment. 2.1 Si x Eutectic high-entropy alloys are annealed and water-quenched to remove internal stress and casting defects.

[0011] S4: Second cold deformation: The AlCoCrFeNi alloy annealed in step S3 is then subjected to a second cold deformation. 2.1 Si x The thickness of the eutectic high-entropy alloy is further reduced by 0-40% by cold rolling.

[0012] S5: Second annealing treatment: The cold-rolled AlCoCrFeNi from step S4... 2.1 Si x The eutectic high-entropy alloy is annealed and water-quenched to refine and recrystallize the grains in the alloy, thereby obtaining the eutectic high-entropy alloy with synergistic improvement in strength and plasticity.

[0013] In step S1, the purity of the metals Al, Co, Cr, Fe, and Ni is greater than or equal to 99.95%, and the purity of the non-metal Si is greater than or equal to 99.999%.

[0014] A Si-doped AlCoCrFeNi 2.1 Si x A method for synergistically improving the strength and plasticity of eutectic high-entropy alloys, the casting process being arc melting under inert gas protection, includes the following steps: evacuating the vacuum arc melting furnace to a vacuum level of 1×10⁻⁶. -3 Pa, then inert gas is injected into the furnace, and then the alloy melting begins. After arc initiation, the titanium ingot is first melted to absorb the residual oxygen in the furnace. Then, the raw materials weighed in S1 are added in order of element melting point from low to high. After the sample is melted and completely cooled, it is turned over and melted repeatedly more than 8 times to ensure the uniformity of the alloy ingot composition. After the melting is completed, the alloy ingot is obtained.

[0015] Furthermore, the inert gas is argon, the current of the electric arc melting is 400~600A, and the melting time for each melting is not less than 3 minutes.

[0016] Furthermore, in steps S2 and S4, the rolling process adopts multi-pass cold rolling with non-fixed deformation, that is: in the early stage, the deformation amount of each pass is maintained at about 5%, making full use of the plastic deformation of the material and reducing the edge crack rate of the billet; in the later stage, the deformation amount of each pass is not higher than 2%, thereby improving the sample quality and thickness accuracy.

[0017] Furthermore, the annealing temperature in step S3 is 1000-1200℃.

[0018] Furthermore, the annealing temperature range in step S5 is 600~900℃.

[0019] Compared with existing technologies, the beneficial effects of the invention are:

[0020] (1) The present invention is a high-strength and high-ductility AlCoCrFeNi modified by doping with trace amounts of Si. 2.1 Si x Eutectic high-entropy alloys are composed of six elements: Al, Co, Cr, Fe, Ni, and Si. All six elements have relatively low melting points, facilitating smelting. Furthermore, the alloys exhibit good casting properties, making them suitable for large-scale industrial production applications.

[0021] (2) This invention increases the volume fraction of the BCC phase by doping with trace amounts of Si, and fine particles precipitate within the BCC phase, thus achieving precipitation strengthening. Furthermore, the increased Si concentration accelerates grain growth, gradually increasing the average grain size in the alloy and improving its work hardening ability. This achieves a synergistic improvement in both strength and plasticity, resulting in excellent comprehensive mechanical properties in the as-cast state. The as-cast tensile strength increases from 765.5 MPa to 1112 MPa, and the plasticity increases from 13.5% to 19.5%, relative to the matrix AlCoCrFeNi. 2.1 Both tensile strength and plasticity were increased by 45%. Furthermore, by combining thermomechanical treatment processes, the tensile strength of the alloy was further increased to 1347.47 MPa without sacrificing plasticity, and the maximum tensile strength reached 1601.15 MPa.

[0022] (3) The present invention is a high-strength and high-plasticity AlCoCrFeNi modified by doping with trace amounts of Si. 2.1 Si x The elements in the eutectic high-entropy alloy system are all readily available, non-toxic and harmless, and the preparation method is simple, which can be achieved by vacuum arc melting.

[0023] (4) The AlCoCrFeNi of the present invention 2.1 Six The inorganic non-metallic element Si selected in eutectic high-entropy alloys not only reduces the overall density and manufacturing cost of the alloy, but also has excellent properties such as corrosion resistance, oxidation resistance and friction resistance.

[0024] In summary, this invention utilizes trace amounts of Si to modify high-strength, high-ductility AlCoCrFeNi alloys. 2.1 Si x Eutectic high-entropy alloys not only exhibit excellent comprehensive mechanical properties, casting fluidity, and uniform microstructure, but also possess potential wear resistance, oxidation resistance, and corrosion resistance. Attached Figure Description

[0025] Other features, objects, and advantages of the invention will become more apparent from the following detailed description of non-limiting embodiments with reference to the accompanying drawings.

[0026] Figure 1 As-cast AlCoCrFeNi 2.1 Si x Stress-strain curves of eutectic high-entropy alloys (x=0, 0.05, 0.1, 0.15, 0.2, 0.3).

[0027] Figure 2 As-cast AlCoCrFeNi 2.1 Si x (x=0, 0.05, 0.1, 0.15, 0.2) Bar chart showing the volume of FCC and BCC phases in eutectic high-entropy alloys as a function of Si content.

[0028] Figure 3 AlCoCrFeNi 2.1 Si x Line graphs showing the grain size of as-cast FCC and BCC eutectic high-entropy alloys as a function of Si content (x=0, 0.05, 0.1, 0.15, 0.2).

[0029] Figure 4 AlCoCrFeNi 2.1 Si x Line graphs showing the grain size of eutectic high-entropy alloys FCC and BCC as a function of Si content after thermomechanical treatment (x=0, 0.05, 0.1, 0.15, 0.2).

[0030] Figure 5 AlCoCrFeNi in Example 1 2.1 Si 0.1 Eutectic high-entropy alloy and matrix AlCoCrFeNi 2.1 Microstructure of eutectic high-entropy alloys in the as-cast state;

[0031] Figure 6AlCoCrFeNi in Example 1 2.1 Si 0.1 Eutectic high-entropy alloy and matrix AlCoCrFeNi 2.1 XRD patterns of eutectic high-entropy alloys in the as-cast state;

[0032] Figure 7 AlCoCrFeNi in Example 1 2.1 Si 0.1 Eutectic high-entropy alloy and matrix AlCoCrFeNi 2.1 DSC differential thermal analysis of eutectic high-entropy alloys in the as-cast state;

[0033] Figure 8 AlCoCrFeNi in Example 1 2.1 Si 0.1 Eutectic high-entropy alloy and matrix AlCoCrFeNi 2.1 Stress-strain curves of as-cast eutectic high-entropy alloys under tensile engineering conditions;

[0034] Figure 9 AlCoCrFeNi in Example 2 2.1 Si 0.15 Eutectic high-entropy alloy and matrix AlCoCrFeNi 2.1 Microstructure of eutectic high-entropy alloys in the as-cast state;

[0035] Figure 10 AlCoCrFeNi in Example 2 2.1 Si 0.15 Eutectic high-entropy alloy and matrix AlCoCrFeNi 2.1 XRD patterns of eutectic high-entropy alloys in the as-cast state;

[0036] Figure 11 AlCoCrFeNi in Example 2 2.1 Si 0.15 Eutectic high-entropy alloy and matrix AlCoCrFeNi 2.1 DSC differential thermal analysis of eutectic high-entropy alloys in the as-cast state;

[0037] Figure 12 AlCoCrFeNi in Example 2 2.1 Si 0.15 Eutectic high-entropy alloy and matrix AlCoCrFeNi 2.1 Stress-strain curves of eutectic high-entropy alloys in the as-cast state under tensile engineering conditions.

[0038] Figure 13 AlCoCrFeNi in Examples 1 and 2 2.1 Si xVickers hardness of the alloy system in the as-cast state.

[0039] Figure 14 AlCoCrFeNi in Example 3 2.1 Si 0.1 The tensile stress-strain curves of eutectic high-entropy alloys after thermomechanical treatment (exploring the temperature of the second heat treatment).

[0040] Figure 15 The AlCoCrFeNi obtained in Example 4 after thermomechanical treatment (investigating the second deformation) 2.1 Si 0.1 Tensile engineering stress-strain curves of eutectic high-entropy alloys.

[0041] Figure 16 The AlCoCrFeNi obtained in Example 4 after thermomechanical treatment (investigating the second deformation) 2.1 Si 0.1 Stress-strain curves of eutectic high-entropy alloys under tensile conditions (II).

[0042] Figure 17 The AlCoCrFeNi obtained in Example 4 after thermomechanical treatment (investigating the second deformation) 2.1 Si 0.1 Stress-strain curves of eutectic high-entropy alloys under tensile conditions (Part 3).

[0043] Figure 18 The tensile engineering stress-strain curves of alloy microstructure samples produced by arc melting with a current of 400–600 A are shown.

[0044] Figure 19 For samples with a single-pass deformation amount much greater than 5%.

[0045] Figure 20 The sample is the result of multiple passes with small deformations used in this patent (the deformation amount per pass in the early stage is about 5%, and the deformation amount per pass in the later stage is no more than 2%). Detailed Implementation

[0046] The present invention will be further described in detail below through embodiments. These embodiments are only used to illustrate the present invention and do not limit the scope of the present invention.

[0047] This invention relates to a eutectic high-entropy alloy, specifically to a Si-doped AlCoCrFeNi alloy. 2.1 Si x Preparation method and applications of eutectic high-entropy alloys and their synergistic enhancement of strength and plasticity. The chemical formula of the eutectic high-entropy alloy is AlCoCrFeNi. 2.1 Si xWhere 0≤x≤0.5. The process includes the following steps: S1: Master alloy preparation: Weigh Al, Co, Cr, Fe, Ni, and Si according to the specified proportions, and then obtain a Si-modified master alloy with synergistically improved strength and plasticity through a smelting process; S2: First cold deformation: Cold roll the master alloy to reduce its thickness by 30%; S3: First heat treatment: Anneal the eutectic high-entropy alloy after the first cold rolling; S4: Second cold deformation: Cold roll the eutectic high-entropy alloy after the first annealing a second time to further reduce its final thickness by 0-40%, resulting in a eutectic high-entropy alloy with further synergistically improved strength and plasticity.

[0048] Original eutectic high-entropy alloy AlCoCrFeNi 2.1 Composed of FCC and BCC phases, it exhibits a typical lamellar eutectic structure. A small amount of Si doping transforms the lamellar eutectic structure into a combination of lamellar and irregular petal-like structures. With further increases in Si content, the structure completely transforms into an irregular petal-like structure. This not only causes lattice distortion in the FCC and BCC phases but also increases the volume fraction of the hard BCC phase, achieving a synergistic improvement in strength and plasticity. Analysis shows that the addition of Si enhances the AlCoCrFeNi... 2.1 The stable mixed structure of FCC and BCC is disrupted, resulting in lattice distortion energy. To balance this energy change, significant lattice distortion occurs. Atomic density calculations show that BCC has an atomic density (the volume percentage of atoms in the unit cell) of 68%, while FCC has an atomic density of 74%. The lower atomic density releases some of the lattice distortion energy, leading to structural stabilization. Microscopically, this induces lattice distortion in both the FCC and BCC phases and increases the volume fraction of the hard BCC phase, resulting in a synergistic improvement in strength and plasticity macroscopically. Compared to existing technologies, the high-strength, high-plasticity eutectic high-entropy alloy of this invention exhibits excellent yield strength, tensile strength, and elongation, achieving a synergistic improvement in strength and plasticity; it also possesses excellent casting fluidity and a uniform microstructure, thus showing broad application prospects in the field of engineering structures. In this scheme, the alloy consists of FCC and BCC phases. With increasing Si content, its microstructure gradually evolves from a typical lamellar eutectic structure to a structure where lamellar eutectic structure and irregular petal-like structures coexist, eventually evolving into a completely irregular petal-like structure. Si promotes the formation of the BCC phase and regulates the volume ratio of the hard BCC phase to the tough FCC phase in the microstructure. The volume changes of the two phases are as follows: Figure 2 As shown, the Si concentration significantly affects the microhardness and wear resistance of the alloy. On the other hand, increasing the Si concentration accelerates grain growth, gradually increasing the average grain size in the alloy and improving its work hardening ability. The change in the two-phase grain size in the alloy with Si content is shown in the figure. Figure 3As shown. In summary, the addition of Si solves the key problem of the difficulty in synergistically improving the strength and plasticity of eutectic high-entropy alloys, thus achieving an improvement in the overall mechanical properties of the alloy. Furthermore, thermomechanical treatment of the alloy yields a refined eutectic microstructure. Subsequent control of heat treatment time and temperature allows for the formation of a micro / nano-ultrafine dual-phase (FCC+BCC) heterostructure with matching mechanical properties. The change in grain size of the two phases in the alloy with Si content after thermomechanical treatment is shown in the figure. Figure 4 As shown.

[0049] A Si-doped eutectic high-entropy alloy with synergistically enhanced plasticity, having the general formula AlCoCrFeNi 2.1 Si x Where 0 ≤ x ≤ 0.5, and x is the molar percentage of the corresponding element. The high-performance AlCoCrFeNi doped with trace amounts of Si described above... 2.1 Si x The as-cast tensile strength of the eutectic high-entropy alloy increased from 765.5 MPa to 1111.7 MPa, and its plasticity increased from 13.5% to 19.5% compared to the matrix AlCoCrFeNi. 2.1 Both tensile strength and plasticity have increased by 45%, such as Figure 1 As shown; further, by combining thermomechanical treatment processes, the tensile strength of the alloy was further increased to 1347.47 MPa without sacrificing plasticity, and the maximum tensile strength can reach 1601.15 MPa, as shown. Figure 14 As shown. It is worth noting that in the as-cast state, when x=0.15, the alloy exhibits the best mechanical properties. Special attention should be paid to the fact that when the Si content is greater than 0.2%, the alloy's plasticity begins to decrease, especially when x=0.3, where it has only about 5% plasticity. Figure 1 As shown; after thermomechanical treatment, the best mechanical properties are obtained when x=0.1, and the optimal heat treatment process is annealing at 800℃ after a second cold rolling of 30%, as shown. Figure 16 As shown.

[0050] The aforementioned Si-doped AlCoCrFeNi 2.1 Si x A method for synergistically improving the strength and plasticity of eutectic high-entropy alloys includes the following steps:

[0051] S1: Preparation of the master alloy: Al, Co, Cr, Fe, Ni, and non-metallic Si raw materials were accurately weighed according to the molar percentage of the eutectic high-entropy alloy. The purity of Al, Co, Cr, Fe, Ni, and Si was all greater than or equal to 99.95 wt.%. Subsequently, AlCoCrFeNi was obtained through a casting process. 2.1 Si x Eutectic high-entropy alloy master alloy;

[0052] S2: First cold deformation: The AlCoCrFeNi obtained in step S1 is subjected to cold deformation. 2.1 Si x The eutectic high-entropy alloy master alloy is cold-rolled to reduce the total thickness by 30%.

[0053] S3: First annealing treatment: The AlCoCrFeNi alloy cold-rolled in step S2 is then subjected to annealing. 2.1 Si x The eutectic high-entropy alloy is annealed and water-quenched; specifically, the AlCoCrFeNi alloy after the first cold rolling is... 2.1 Si x Eutectic high-entropy alloys are annealed at 1000-1200℃; preferably at 1050℃.

[0054] S4: Second cold deformation: The AlCoCrFeNi alloy annealed in step S3 is then subjected to a second cold deformation. 2.1 Si x The thickness of the eutectic high-entropy alloy is further reduced by 0-40% by cold rolling.

[0055] S5: Second annealing treatment: The cold-rolled AlCoCrFeNi from step S4... 2.1 Si x The eutectic high-entropy alloy was annealed and water-quenched to obtain the Si-modified eutectic high-entropy alloy. Specifically, the AlCoCrFeNi alloy was cold-rolled a second time. 2.1 Si x The eutectic high-entropy alloy was annealed at 600℃~900℃ to obtain the Si-modified eutectic high-entropy alloy.

[0056] In step S1, the purity of the metals Al, Co, Cr, Fe, and Ni is greater than or equal to 99.95%, and the purity of the non-metal Si is greater than or equal to 99.999%.

[0057] The casting process involves arc melting under inert gas protection, including the following steps: evacuating the vacuum arc melting furnace to a vacuum level of 1×10⁻⁶. -3 Pa, then inert gas is injected into the furnace, and then the alloy melting begins. After arc initiation, the titanium ingot is first melted to absorb the residual oxygen in the furnace. Then, the raw materials weighed in S1 are added in order of element melting point from low to high. After the sample is melted and completely cooled, it is turned over and melted repeatedly more than 8 times to ensure the uniformity of the alloy ingot composition. After the melting is completed, the alloy ingot is obtained.

[0058] The inert gas is argon, and the current for arc melting is 400–600 A. To ensure the uniformity of the melt composition, the current is increased sequentially with increasing Si content in each system. Specifically, as the Si content increases, a current of 400 A is no longer sufficient for the experiment. Increasing the current ensures the uniformity of the melt composition, resulting in a more uniform alloy microstructure and improved mechanical properties of the alloy macroscopically. Figure 18 (As shown).

[0059] In steps S2 and S4, the cold rolling process involves multi-pass, non-fixed deformation cold rolling. In the early stages, each pass maintains approximately 5% deformation to fully utilize the material's plastic deformation, reduce billet scrap length, and improve utilization. In the later stages, the deformation per pass is no more than 2%, improving sample quality and thickness accuracy. Ultimately, the total deformation after two cold rolling passes is 40% of the original. This alloy system has high hardness but relatively low overall plasticity. Multi-pass, low-deformation cold rolling can reduce the crack rate and improve alloy utilization. Furthermore, multi-pass, low-deformation cold rolling can also control the sample thickness accuracy and avoid over-rolling. Figure 19 The image shows a sample with a single-pass deformation amount much greater than 5%. Figure 20 The samples used in this patent, after multiple passes with small deformation (the deformation amount per pass in the early stage is about 5%, and the deformation amount per pass in the later stage is no more than 2%), show a significant reduction in cracks.

[0060] The annealing temperature range in step S5 is 600~900℃. This process is a key and core step in the heat treatment process, and is one of the original and innovative parts. After two cold rolling processes, annealing can improve the microstructure and properties of the cold-rolled alloy. It can improve internal stress, hardness, and elastic modulus, while also enhancing tensile strength, ductility, and fatigue strength. Furthermore, annealing can improve the surface quality of the rolled billet, making it smoother and more even. Experiments were conducted to explore the optimal second heat treatment temperature within the range of 600-900℃, using the Si0.1 system as an example. Figure 14 As shown, when the temperature is too low, the alloy has the highest strength but less than 10% plasticity; when the temperature is too high, it has high plasticity but low strength. Neither of these conditions can achieve a good balance between strength and plasticity.

[0061] Implementation Case 1

[0062] This example discloses a high-strength, high-ductility, as-cast eutectic high-entropy alloy modified by doping with trace amounts of Si, with the general formula AlCoCrFeNi. 2.1 Si 0.1 Abbreviated as AS-Si0.1, matrix AlCoCrFeNi 2.1 It is abbreviated as AS-Si0.

[0063] In this embodiment, a Si-doped AlCoCrFeNi2.1 Si 0.1 A method for synergistically improving the strength and plasticity of a eutectic high-entropy alloy includes the following steps: Ni, Co, Fe, Cr, Al, and non-metallic Si raw materials are accurately weighed according to the molar percentage of the eutectic high-entropy alloy, wherein the purity of metallic Al, Co, Cr, Fe, and Ni is greater than or equal to 99.95%, and the purity of non-metallic Si is greater than or equal to 99.999%. Subsequently, the Si-modified AlCoCrFeNi alloy is obtained by vacuum arc melting. 2.1 Si 0.1 Eutectic high-entropy alloy. The specific operation is as follows: Evacuate the vacuum arc melting furnace to a vacuum level of 1×10⁻⁶. -3 Pa, then inert argon gas is injected into the furnace, and the alloy melting begins. After arc ignition, the titanium ingot is first melted to absorb residual oxygen in the furnace, and then the mixed raw materials are melted at a current of 400~600A. After the sample is melted and completely cooled, it is turned over and melted repeatedly more than 8 times to ensure the uniformity of the alloy ingot composition. After melting, a cast alloy ingot is obtained.

[0064] Figure 5 The as-cast AlCoCrFeNi obtained in Example 1 2.1 Si 0.1 Eutectic high-entropy alloy and matrix AlCoCrFeNi 2.1 Microstructure of eutectic high-entropy alloy. It can be observed that with the addition of Si, the alloy changes from a typical layered eutectic microstructure to a combination of lamellar and irregular petal-like structures. The addition of Si reduces the volume fraction of FCC and increases the volume fraction of BCC. Furthermore, fine particles precipitate within the BCC phase, which plays a role in precipitation strengthening and achieves a synergistic improvement in the strength and plasticity of the alloy.

[0065] Figure 6 The as-cast AlCoCrFeNi obtained in Example 1 2.1 Si 0.1 Eutectic high-entropy alloy and matrix AlCoCrFeNi 2.1 The XRD diffraction patterns of the eutectic high-entropy alloy show that the alloy consists of FCC and BCC phases, indicating that changes in Si content do not alter the crystal structure. However, the patterns reveal a rightward shift in the diffraction peaks of the BCC phase after the addition of Si. This suggests that the smaller radius of Si atoms causes lattice contraction in the BCC solid solution by replacing larger atoms, resulting in a decrease in the lattice constant and a rightward shift of the BCC diffraction peaks.

[0066] Figure 7 The as-cast AlCoCrFeNi obtained in Example 1 2.1 Si 0.1DSC differential thermal analysis of the as-cast eutectic high-entropy alloy showed only a single endothermic / exothermic peak, indicating that the alloy is a eutectic alloy composition.

[0067] Figure 8 The as-cast AlCoCrFeNi obtained in Example 1 2.1 Si 0.1 Eutectic high-entropy alloy and matrix AlCoCrFeNi 2.1 The tensile stress-strain curves of the eutectic high-entropy alloy in the as-cast state reveal a synergistic improvement in strength and plasticity. (AlCoCrFeNi) 2.1 The eutectic high-entropy alloy has a tensile strength of 765.5 MPa and an elongation of 13.5%, with a Vickers hardness of 258 HV; AlCoCrFeNi 2.1 Si 0.1 The eutectic high-entropy alloy has a tensile strength of 979.2 MPa and an elongation of 16.7%, and a Vickers hardness of 298 HV.

[0068] Implementation Case 2

[0069] This example discloses a high-strength, high-ductility, as-cast eutectic high-entropy alloy modified by doping with trace amounts of Si, with the general formula AlCoCrFeNi. 2.1 Si 0.15 , abbreviated as AS-Si0.15.

[0070] In this embodiment, a Si-doped AlCoCrFeNi 2.1 Si 0.15 A method for synergistically improving the strength and plasticity of eutectic high-entropy alloys includes the following steps: Accurately weigh Ni, Co, Fe, Cr, Al, and non-metallic Si raw materials according to the molar percentage of the high-entropy alloy, wherein the purity of metallic Al, Co, Cr, Fe, and Ni is greater than or equal to 99.95%, and the purity of non-metallic Si is greater than or equal to 99.999%. Subsequently, the Si-modified AlCoCrFeNi alloy is obtained by vacuum arc melting. 2.1 Si 0.15 High-entropy alloys. The specific operation is as follows: Evacuate the vacuum arc melting furnace to a vacuum level of 1×10⁻⁶. -3 Pa, then inert argon gas is injected into the furnace, and the alloy melting begins. After arc ignition, the titanium ingot is first melted to absorb residual oxygen in the furnace, and then the mixed raw materials are melted at a current of 400~600A. After the sample is melted and completely cooled, it is turned over and melted repeatedly more than 8 times to ensure the uniformity of the alloy ingot composition. After melting, a cast alloy ingot is obtained.

[0071] Figure 9 The as-cast AlCoCrFeNi obtained in Example 22.1 Si 0.15 Eutectic high-entropy alloy and matrix AlCoCrFeNi 2.1 Microstructure of eutectic high-entropy alloy. It can be observed that when X is greater than 0.1, the layered structure completely disappears, and the alloy completely transforms from a typical layered eutectic microstructure into an irregular petal-like structure. Furthermore, the volume fraction of the hard BCC phase further increases, and the strength of the alloy is further improved.

[0072] Figure 10 The as-cast AlCoCrFeNi obtained in Example 2 2.1 Si 0.15 Eutectic high-entropy alloy and matrix AlCoCrFeNi 2.1 XRD diffraction patterns of the eutectic high-entropy alloys show that the alloys are composed of FCC and BCC phases, indicating that changes in Si content do not alter the crystal structure. However, as the Si content increases, the tendency for FCC phase formation decreases compared to the relatively stable BCC structure; the FCC phase gradually disappears, and the BCC phase gradually becomes the dominant phase. Furthermore, due to the small radius of Si atoms, the substitution of larger atoms in the solid solution causes lattice contraction in the BCC solid solution, reducing the lattice constant and shifting the BCC diffraction peaks to the right.

[0073] Figure 11 The as-cast AlCoCrFeNi obtained in Example 2 2.1 Si 0.15 Differential thermal analysis (DSC) of the eutectic high-entropy alloy showed two sets of endothermic / exothermic peaks in the image.

[0074] Figure 12 The as-cast AlCoCrFeNi obtained in Example 2 2.1 Si 0.15 Eutectic high-entropy alloy and matrix AlCoCrFeNi 2.1 The tensile stress-strain curves of the eutectic high-entropy alloy in the as-cast state reveal a synergistic improvement in strength and plasticity. With further addition of Si content, AlCoCrFeNi... 2.1 Si 0.15 The eutectic high-entropy alloy has a tensile strength of 1111.7 MPa and an elongation of 19.5%, and a Vickers hardness of 331 HV.

[0075] Implementation Case 3

[0076] Based on Example 1, this example, combined with thermomechanical treatment processes (alloys abbreviated as CR-Si0.1-600, CR-Si0.1-700, CR-Si0.1-750, CR-Si0.1-800, CR-Si0.1-850, CR-Si0.1-900), further enhances the strength of the alloy without sacrificing its plasticity.

[0077] In this embodiment, the subsequent thermomechanical treatment process steps are as follows:

[0078] S1: Cold deformation: transforming the as-cast AlCoCrFeNi 2.1 Si 0.1 The eutectic high-entropy alloy master alloy is cold-rolled to reduce its thickness by 30%; S2: Annealing treatment: the AlCoCrFeNi alloy cold-rolled in step S1 is then annealed. 2.1 Si 0.1 The eutectic high-entropy alloy was annealed at 1050℃ for 5 hours; S3: Cold deformation: the AlCoCrFeNi alloy annealed in step S2 was subjected to cold deformation. 2.1 Si 0.1 The eutectic high-entropy alloy is cold-rolled to further reduce the thickness by 40%; S4: Annealing treatment: the cold-rolled AlCoCrFeNi alloy from step S3 is then annealed. 2.1 Si 0.1 The eutectic high-entropy alloy was annealed at 600℃~900℃ for 30 min to obtain the eutectic high-entropy alloy with further improved strength and plasticity.

[0079] Figure 14 The thermomechanically treated AlCoCrFeNi obtained in Example 3 2.1 Si 0.1 The tensile stress-strain curves of the eutectic high-entropy alloy reveal that thermomechanical treatment further enhances its strength without sacrificing plasticity. After multiple rolling processes and annealing at different temperatures, AlCoCrFeNi... 2.1 Si 0.1 The tensile strength of the eutectic high-entropy alloy is increased by 2 times compared to the matrix.

[0080] Implementation Case 4

[0081] Building upon Example 3, this example explores the effect of the second cold rolling amount on the mechanical properties of the alloy (alloys abbreviated as CR0%-Si0.1-800, CR10%-Si0.1-800, CR20%-Si0.1-800, CR30%-Si0.1-800, CR40%-Si0.1-800), thereby achieving a further improvement in the strength of the alloy.

[0082] In this embodiment, the subsequent thermomechanical treatment process steps are as follows:

[0083] S1: Cold deformation: transforming the as-cast AlCoCrFeNi 2.1 Si 0.1 The eutectic high-entropy alloy master alloy is cold-rolled to reduce its thickness by 30%; S2: Annealing treatment: the AlCoCrFeNi alloy cold-rolled in step S1 is then annealed. 2.1 Si 0.1 The eutectic high-entropy alloy was annealed at 1050℃ for 5 hours; S3: Cold deformation: the AlCoCrFeNi alloy annealed in step S2 was subjected to cold deformation. 2.1 Si 0.1 The eutectic high-entropy alloy is cold-rolled to reduce the thickness by 0-40%; S4: Annealing treatment: the cold-rolled AlCoCrFeNi alloy from step S3 is then annealed. 2.1 Si 0.1 The eutectic high-entropy alloy was annealed at 750℃-850℃ for 30 min to obtain the eutectic high-entropy alloy with further improved comprehensive mechanical properties.

[0084] Figures 15-17 The thermomechanically treated AlCoCrFeNi obtained in Example 4 2.1 Si 0.1 The tensile stress-strain curves of the eutectic high-entropy alloy reveal that the alloy exhibits optimal mechanical properties under the conditions of a second rolling process with a 30% rolling allowance and a second annealing temperature of 800°C.

[0085] While specific embodiments of the present invention have been described above, those skilled in the art should understand that these are merely illustrative examples, and the scope of protection of the present invention is defined by the appended claims. Those skilled in the art can make various changes or modifications to these embodiments without departing from the principles and essence of the present invention, but all such changes and modifications fall within the scope of protection of the present invention.

Claims

1. A Si-doped AlCoCrFeNi 2.1 Si x Eutectic high-entropy alloy, characterized in that, The general formula is AlCoCrFeNi 2.1 Si x , where 0≤x≤0.5, and x is the mole percentage of the corresponding element; Among them, Si-doped AlCoCrFeNi 2.1 Si x Eutectic high-entropy alloys are prepared by a synergistic enhancement method of strong plasticity, including the following steps: S1: Master alloy preparation: Al, Co, Cr, Fe, Ni, and non-metallic Si raw materials were accurately weighed according to the molar percentage of the eutectic high-entropy alloy, and then AlCoCrFeNi was obtained through a casting process. 2.1 Si x Eutectic high-entropy alloy master alloy; S2: First cold deformation: The AlCoCrFeNi obtained in step S1 is subjected to cold deformation. 2.1 Si x The eutectic high-entropy alloy master alloy is cold-rolled to reduce the total thickness by 30%. S3: First heat treatment: The AlCoCrFeNi alloy cold-rolled in step S2 is then subjected to heat treatment. 2.1 Si x The eutectic high-entropy alloy was annealed and water-quenched. S4: Second cold deformation: The AlCoCrFeNi alloy annealed and water-quenched in step S3 is subjected to a second cold deformation. 2.1 Si x The thickness of the eutectic high-entropy alloy is further reduced by 0-40% by cold rolling. S5: Second annealing treatment: The AlCoCrFeNi alloy cold-rolled in step S4 is then subjected to a second annealing process. 2.1 Si x Annealing and water quenching of eutectic high-entropy alloys yield eutectic high-entropy alloys with synergistic improvement in strength and plasticity.

2. Preparation of Si-doped AlCoCrFeNi as described in claim 1 2.1 Si x A method for synergistically improving the strength and plasticity of eutectic high-entropy alloys includes the following steps: S1: Master alloy preparation: Al, Co, Cr, Fe, Ni, and non-metallic Si raw materials were accurately weighed according to the molar percentage of the eutectic high-entropy alloy, and then AlCoCrFeNi was obtained through a casting process. 2.1 Si x Eutectic high-entropy alloy master alloy; S2: First cold deformation: The AlCoCrFeNi obtained in step S1 is subjected to cold deformation. 2.1 Si x The eutectic high-entropy alloy master alloy is cold-rolled to reduce the total thickness by 30%. S3: First heat treatment: The AlCoCrFeNi alloy cold-rolled in step S2 is then subjected to heat treatment. 2.1 Si x The eutectic high-entropy alloy was annealed and water-quenched. S4: Second cold deformation: The AlCoCrFeNi alloy annealed and water-quenched in step S3 is subjected to a second cold deformation. 2.1 Si x The thickness of the eutectic high-entropy alloy is further reduced by 0-40% by cold rolling. S5: Second annealing treatment: The AlCoCrFeNi alloy cold-rolled in step S4 is then subjected to a second annealing process. 2.1 Si x Annealing and water quenching of eutectic high-entropy alloys yield eutectic high-entropy alloys with synergistic improvement in strength and plasticity.

3. The Si-doped AlCoCrFeNi according to claim 2 2.1 Si x A method for synergistically improving the strength and plasticity of eutectic high-entropy alloys, characterized in that: In step S1, the purity of the metals Al, Co, Cr, Fe, and Ni is greater than or equal to 99.95%, and the purity of the non-metal Si is greater than or equal to 99.999%.

4. The Si-doped AlCoCrFeNi according to claim 2 2.1 Si x A method for synergistically improving the strength and plasticity of eutectic high-entropy alloys, characterized in that: The casting process involves arc melting under inert gas protection, including the following steps: evacuating the vacuum arc melting furnace to a vacuum level of 1×10⁻⁶. -3 Pa, then inert gas is introduced into the furnace, and then the alloy is melted.

5. The Si-doped AlCoCrFeNi according to claim 4 2.1 Si x A method for synergistically improving the strength and plasticity of eutectic high-entropy alloys, characterized in that: After the arc is started, the titanium ingot is first melted to absorb the residual oxygen in the furnace. Then, the raw materials weighed in S1 are put into the vacuum arc melting furnace in order of element melting point from low to high. After the sample is melted and completely cooled, it is turned over and melted repeatedly more than 8 times to ensure the uniformity of the alloy ingot composition. After the melting is completed, the alloy ingot is obtained.

6. The Si-doped AlCoCrFeNi according to claim 4 2.1 Si x A method for synergistically improving the strength and plasticity of eutectic high-entropy alloys, characterized in that: The inert gas is argon, the current for arc melting is 400~600A, and the melting time for each melting is not less than 3 minutes.

7. The Si-doped AlCoCrFeNi according to claim 2 2.1 Si x A method for synergistically improving the strength and plasticity of eutectic high-entropy alloys, characterized in that: In steps S2 and S4, the cold rolling process is a multi-pass cold rolling with non-fixed deformation. In the early stage, the deformation amount of a single pass is maintained at 5%, which makes full use of the plastic deformation of the material and reduces the length of geometric waste at the beginning and end. In the later stage, the deformation amount of a single pass is not higher than 2%, which improves the sample quality and thickness accuracy.

8. The Si-doped AlCoCrFeNi according to claim 2 2.1 Si x A method for synergistically improving the strength and plasticity of eutectic high-entropy alloys, characterized in that: The annealing temperature in step S3 is 1000-1200℃.

9. The Si-doped AlCoCrFeNi according to claim 2 2.1 Si x A method for synergistically improving the strength and plasticity of eutectic high-entropy alloys, characterized in that: The annealing temperature range in step S5 is 600~900℃.

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