Method for preparing high-entropy alloy through multi-process cooperation

Abstract

The invention relates to the field of high-entropy alloy preparation, and discloses a method for preparing a high-entropy alloy through multi-process synergy, which comprises the following steps: S1, calculation; s2, taking metal elements of each principal component, and stacking and arranging the metal elements; s3, preheating and laminating at 70% + / -20 DEG C of the lowest melting point metal temperature; s4, rolling is conducted, the initial deformation quantity is 10%, and the initial deformation quantity is increased by 10% every time subsequently till the total deformation quantity is 40%; s5, annealing; and S6, folding the annealed material in half, and repeating the steps S3 to S5 for 30-150 times to form the high-entropy alloy plate with the multi-layer interface structure. According to the invention, through layered stacking-rolling-annealing multi-process cooperative treatment, grains are refined in the rolling process, alloying is realized in the preheating and hot rolling process, and the internal stress of the metal plate is eliminated through subsequent heat treatment, so that the high-entropy alloy plate with the multi-layer interface structure is obtained. And a soft phase and hard phase combined high-entropy alloy structure is obtained through regulation and control, so that the high-entropy alloy with excellent performance is obtained.

Description

Technical Field

[0001] The present invention relates to the technical field of high-entropy alloy preparation, and particularly relates to a method for preparing high-entropy alloys through multi-process collaboration. Background Art

[0002] The design concept of traditional metal materials is to form a simple solid solution structure composed of one matrix element and a small amount of alloying elements mixed in, and its mechanical properties have always been limited by the degree of alloying. Different from this, since the high-entropy alloy was proposed in 2004, it has quickly attracted people's attention. The high-entropy alloy contains multiple basic elements, and the elements are in equiatomic ratio or close to equiatomic ratio. The high-entropy effect formed by the mixing of these elements enables the material to still form a simple solid solution structure instead of forming complex intermetallic compounds. Moreover, the solid solution strengthening formed by multiple elements causes severe lattice distortion, making the high-entropy alloy have a special structure and effect in atomic structure.

[0003] Based on the preparation of traditional alloys, a variety of preparation techniques for high-entropy alloys have been developed. Currently, the preparation methods for high-entropy alloys include: melting method, powder metallurgy method, physical vapor deposition method, additive manufacturing (3D printing), sol-gel method, and electrochemistry, etc. Arc melting is a commonly used method for preparing high-entropy alloys. First, the elements mixed in proportion are placed in a water-cooled copper crucible, and then melted by arc heating. To ensure uniform composition, it usually needs to be remelted multiple times. The advantage of this method is that the operation process is relatively simple and large-sized alloy ingots can be prepared. However, it also has certain limitations. For example, some volatile elements may be lost during the melting process, and it needs to be operated in a vacuum or inert gas environment. Induction melting heats the metal by electromagnetic induction. This method is suitable for preparing high-entropy alloys with high melting points. Its advantages are fast heating speed and the ability to avoid contamination caused by the crucible. Induction melting heats the metal by electromagnetic induction. This method is suitable for preparing high-entropy alloys with high melting points. Its advantages are fast heating speed and the ability to avoid contamination caused by the crucible. Mechanical alloying places elemental powders in a high-energy ball mill for long-term grinding to form alloys through the collision and diffusion between powders. The advantage of mechanical alloying is that alloying can be achieved at room temperature and the grain size can be refined. However, this method requires subsequent sintering or hot pressing treatment to obtain dense materials. Spark plasma sintering (SPS) loads the powders obtained by mechanical alloying into a mold and then applies a pulsed current for rapid sintering. The advantage of this method is that dense materials can be prepared in a relatively short time and the nanostructure can be well retained. Magnetron sputtering is used to prepare high-entropy alloys. In a vacuum environment, ion bombardment is used to bombard the target, and the atoms in the target are deposited on the substrate to form a high-entropy alloy film. Magnetron sputtering is suitable for preparing thin film materials, such as applications in semiconductor devices or coating fields. Electron beam evaporation heats the metal by an electron beam, and after evaporation, it is deposited on the substrate to form a high-entropy alloy. Selective laser melting method spreads the high-entropy alloy powder into layers, and then selectively melts the powder with a laser to stack layer by layer to form a three-dimensional structure. The advantage of additive manufacturing (3D printing) is that it can achieve near-net shaping of complex shapes and can also precisely control the composition and structure. However, this method needs to solve the problem that high-entropy alloys are prone to cracking during solidification. Sol-gel method: The precursor is prepared through the reaction of chemical solutions, and then high-entropy alloys are obtained through heat treatment. This method is suitable for preparing nano powders or coatings. Laser cladding method uses a laser to melt the high-entropy alloy powder on the surface of the substrate to form a functional coating.

[0004] However, traditional arc melting and induction melting rely on high temperatures for melting, which easily leads to element segregation, coarse grains, and uneven alloy composition, and is prone to forming an equiaxed crystal structure with single performance. Traditional powder metallurgy methods rely on long-term ball milling or high-temperature sintering, and it is still difficult to completely eliminate composition segregation. Vapor deposition and additive manufacturing (3D printing) equipment are expensive and the processes are complex, making large-scale production difficult. Summary of the Invention

[0005] To solve the above problems, the present invention provides a method for preparing high-entropy alloys through multi-process collaboration.

[0006] The technical solution to achieve the object of the present invention is as follows:

[0007] A method for preparing high-entropy alloys through multi-process collaboration, comprising the following steps:

[0008] S1. Calculate the composition and corresponding atomic percentages of high-entropy alloys containing more than 5 main elements;

[0009] S2. Take the metal elements of each main element, make the metal elements into metal foils with a thickness of 10 - 50 μm, and stack them from the inside to the outside in the order of increasing metal melting point;

[0010] S3. Perform preheating lamination at 70% ± 20 °C of the melting point temperature corresponding to the metal with the lowest melting point;

[0011] S4. Roll the preheated laminated material, with an initial deformation of 10%, and each subsequent increase of 10% until the total deformation reaches 40%;

[0012] S5. Anneal the rolled material at the preheating temperature for 5 - 10 hours;

[0013] S6. Fold the annealed material, and repeat steps S3 to S5 for 30 - 150 times to form a high-entropy alloy sheet with a multi-layer interface structure.

[0014] As a preferred technical solution, in step S1, the main elements are at least five of the metals Fe, Co, Ni, Cr, Mn, Al, Ti, Cu, Zn, Zr, Bi, In, Pb, Mg, and the atomic percentages of each main element are 5 - 35%.

[0015] As a preferred technical solution, in step S2, the number of laminated layers of the stacked material is 20 - 50 layers, and vacuum electron beam welding or high-temperature jigs are used for lamination fixation, and a pre-tightening pressure of 0.1 - 0.5 MPa is applied between adjacent metal foil layers.

[0016] As a preferred technical solution, in the step S4, multi-pass hot rolling process is adopted for rolling, and the reduction of material thickness after each rolling is 10-15% of the previous thickness; an asynchronous rolling mill is used in the rolling process, the upper and lower roll speed ratio is set to 1.05-1.20, and the rolling linear speed is maintained at 0.5-2 m / s.

[0017] As a preferred technical solution, in the step S5, the annealing process is carried out in a vacuum or inert gas protective atmosphere, and the material after annealing is cooled in the furnace, and the cooling rate is controlled at 10-80 °C / min.

[0018] As a preferred technical solution, in the step S6, the steps S4 to S5 are repeated 20-150 times, and the temperature selection in the annealing process is carried out in stages: the first stage is 70% ± 20 °C of the melting point temperature corresponding to the lowest melting point metal, the second stage is 70% ± 20 °C of the melting point temperature corresponding to the intermediate melting point metal, and the third stage is 70% ± 20 °C of the melting point temperature corresponding to the highest melting point metal, and the holding time is 5-10 hours for all.

[0019] As a preferred technical solution, the surface of the metal foil is pre-treated by sandblasting and degreasing, and the surface roughness Ra is controlled at 0.5-2.0 μm; the difference in melting point temperature between adjacent metal foils in the step S2 is within 500 °C.

[0020] As a preferred technical solution, a gradient annealing process is adopted in the heat treatment process of the annealing in the step S5.

[0021] As a preferred technical solution, the high-entropy alloy sheet in the step S6 includes the following structural characteristics:

[0022] 1) Fine grain phases of 50-200 nm and coarse grain phases of 1-5 μm, and the volume fraction of the coarse grain phase is 15-40%;

[0023] 2) A nano-scale mixed transition layer is formed at the adjacent layer interfaces;

[0024] 3) There are simultaneously soft and hard bimodal grain structures inside the material; the soft phase includes FCC (face-centered cubic lattice) structure, and the hard phase includes BCC (body-centered cubic lattice) structure.

[0025] The present invention also discloses a high-entropy alloy sheet with a multi-layer interface structure. For the high-entropy alloy sheet prepared, its hardness is increased by ≥ 30% and its elongation is ≥ 15%.

[0026] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0027] 1. The present invention prepares high-entropy alloys by means of a synergistic approach of layered stacking-rolling-annealing. By controlling the rolling passes and annealing parameters, the layered structure, grain boundary density, and precipitate phase distribution can be precisely regulated, achieving an integrated optimization of design-fabrication-performance. The layered structure can hinder dislocation movement, further enhancing the material strength, regulating the structure combining soft and hard phases, and obtaining high-performance high-entropy alloys.

[0028] 2. The present invention prepares high-entropy alloys by means of a synergistic approach of layered stacking-rolling-annealing. Through repeated rolling and annealing at room temperature or a relatively low temperature, element diffusion is driven by mechanical force to achieve atomic-level mixing. Meanwhile, severe plastic deformation (ECAP) can refine the grains to the nanoscale, significantly enhancing the material strength and toughness.

[0029] 3. By stacking different metal foils layer by layer and repeatedly rolling, the interfacial layers are broken and mixed under shear stress to form a uniformly distributed nanostructure, effectively suppressing element segregation.

[0030] 4. The present invention is not restricted to the existing high-entropy alloy systems and can effectively alloy refractory metals and low-melting-point volatile metals. The process designed by the present invention is simple, requires low demands on production equipment, is easy to operate, and is easy to industrialize. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 is a flow chart for preparing high-entropy alloy sheets according to the present invention.

[0032] Figure 2 is a microscopic structure diagram of the multi-layer interface of the high-entropy alloy sheet in Example 1. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0033] In order to make the technical means, creative features, achieved purposes, and functions of the present invention easy to understand, the present invention will be further described below in conjunction with specific embodiments.

[0034] Example 1

[0035] (1) Calculation and material preparation: Al, Sn, Bi, Pb, and In are calculated according to a molar ratio of 1:1:1:1:1, and their ideal entropy value is 13.38 J / (mol·K), meeting the definition of high-entropy alloys (entropy value ≥ 12.47 J / (mol·K)). Metal foils with a thickness of 10 μm of the above metal elements are cut into rectangles of 10 cm × 10 cm; the surfaces of the metal foils are pre-treated by sandblasting and degreasing, and the surface roughness Ra is controlled within 0.5 - 1.0 μm.

[0036] (2) Stacking and fixing: Stack the prepared rectangular metal foils in the order of increasing melting point from low to high and from inside to outside. Stack In (157 °C), Sn (232 °C), Bi (271.3 °C), Pb (327.5 °C), and Al (660 °C) in sequence to form a single-layer stacked structure. Then stack 50 layers according to the single-layer stacked structure. Use a high-temperature fixture and apply a pre-tightening pressure of 0.1 MPa between adjacent foil layers.

[0037] (3) Layered stacking and hot rolling: Preheat the stacked plates at 123 °C, and then perform rolling. The upper and lower roll speed ratio is 1, the rolling linear speed is 0.5 m / s, and the deformation amount is sequentially stacked from 10% to 40% by 10%;

[0038] (4) Post-treatment: Fold the plates in half and repeat step (3) for a total of 30 times. Anneal once after each hot rolling. During annealing, place the plates at 123 °C - 460 °C in stages. The annealing process is carried out under vacuum, and the annealing process is controlled in segments: the annealing temperature for the first 10 times is 123 °C, the middle 10 times is 200 °C, and the last 10 times is 460 °C. The annealing time for each time is 5 h. After annealing, the material is cooled in the furnace, and the cooling rate is controlled at 10 °C / min. After annealing, the plates are air-cooled to room temperature to obtain high-quality SnAlBiPbIn high-entropy alloy plates containing multiple interfaces. The microstructure of its multiple interfaces is as Figure 2 shown. Compared with the traditional ball milling process (Comparative Example 1), the hardness of the high-entropy alloy plates is increased by 30% (reaching 235 HV), and the elongation is increased by 17% (reaching 21%).

[0039] The structural characteristics of the high-entropy alloy plates are as follows:

[0040] 1) Fine grain phases of 50 - 200 nm and coarse grain phases of 1 - 5 μm, and the volume fraction of the coarse grain phase is 35%;

[0041] 2) A nano-scale mixed transition layer is formed at the interface between adjacent layers;

[0042] 3) There are simultaneously soft and hard bimodal grain structures inside the material; the soft phase includes the FCC structure (with a proportion of 42%), and the hard phase includes the BCC structure (with a proportion of 58%).

[0043] Example 2

[0044] (1) Calculation and material preparation: Calculate the ideal entropy value of Zn, Sn, Bi, Al, and Pb according to the mass percentages of 20%, 25%, 30%, 5%, and 20% to be 12.81 J / (mol·K), which meets the definition of high-entropy alloys (entropy value ≥ 12.47 J / (mol·K)). Cut the 20-μm-thick metal foil of the above metal elements into rectangles of 10 cm × 10 cm;

[0045] (2) Stacking and fixing: Stack the prepared rectangular metal foils in the order of increasing melting point from low to high and from inside to outside. Stack Sn (232 °C), Bi (271.3 °C), Pb (327.5 °C), Zn (419.6 °C), and Al (660 °C) in sequence to form a single-layer stacked structure. Stack 40 layers, use a high-temperature fixture, and apply a pre-tightening pressure of 0.1 MPa between adjacent foil layers.

[0046] (3) Layered stacking and hot rolling: Preheat the stacked sheets at 180 °C, and then perform rolling. The upper and lower roll speed ratio is 1, the rolling linear speed is 1.0 m / s, and the deformation amount is sequentially stacked from 10% to 40% by 10%.

[0047] (4) Post-treatment: Fold the sheets in half and repeat step (3) for a total of 50 times. Place the sheets in an annealing furnace at 180 °C - 480 °C in stages. The annealing process is carried out under vacuum, and the annealing process is controlled in sections: the annealing temperature for the first 20 times is 180 °C, the annealing temperature for the middle 10 times is 240 °C, and the annealing temperature for the last 20 times is 480 °C. The annealing time for each time is 8 h, the cooling rate is controlled at 20 °C / min, and the annealed material is cooled in the furnace. After annealing, the sheets are air-cooled to room temperature to obtain high-quality AlSnZnBiPb high-entropy alloy sheets with multiple interfaces. Compared with the traditional ball milling process, the hardness of the high-entropy alloy sheets is increased by 32%, and the elongation is increased by 16%.

[0048] Example 3

[0049] (1) Calculation and material preparation: Calculate the ideal entropy value of Cu, Fe, Ti, Co, and Ni according to the mass percentages of 20%, 20%, 30%, 15%, and 15% to be 12.75 J / (mol·K), which meets the definition of high-entropy alloy (entropy value ≥ 12.47 J / (mol·K)). Cut 30-μm metal foil into rectangles of 10 cm × 10 cm.

[0050] (2) Stacking and fixing: Stack the prepared rectangular metal foils in the order of increasing melting point from low to high and from inside to outside. Stack Cu (1083 °C), Ni (1455 °C), Co (1495 °C), Fe (1535 °C), and Ti (1675 °C) in sequence to form a single-layer stacked structure. Stack 50 layers, use vacuum electron beam welding, and apply a pre-tightening pressure of 0.5 MPa between adjacent foil layers.

[0051] (3) Layered stacking and hot rolling: Preheat the stacked sheets at 760 °C, and then perform rolling. The upper and lower roll speed ratio is 1.08, the rolling linear speed is 1.5 m / s, and the deformation amount is sequentially stacked from 10% to 40% by 10%.

[0052] (4) Post-treatment: Cut and fold the sheet metal, repeat step (3) for a total of 100 times. Anneal once after each hot rolling. The sheet metal is annealed in stages at 760°C - 1150°C. The annealing process is carried out under vacuum and is controlled in segments: the annealing temperature for the first 30 times is 760°C, the middle 40 times is 1060°C, and the last 30 times is 1150°C. The annealing time for each time is 10 h, and the cooling rate is controlled at 50°C / min. After annealing, the material is cooled in the furnace. Air-cool the annealed sheet metal to room temperature to obtain a high-quality CuFeTiCoNi high-entropy alloy sheet with multiple interfaces. Compared with the arc melting process, the hardness of the high-entropy alloy sheet is increased by 35% and the elongation is increased by 18%.

[0053] Example 4

[0054] (1) Calculation and material preparation: Calculate the ideal entropy value of Fe, Co, Ni, Cr, and Mn according to the mass percentages of 30%, 20%, 20%, 20%, and 10% to be 12.95 J / (mol·K), which meets the definition of high-entropy alloy (entropy value ≥ 12.47 J / (mol·K)). Cut the 50-μm metal foil into rectangles of 10 cm × 10 cm.

[0055] (2) Stacking and fixing: Stack the prepared rectangular metal foils in the order of increasing melting point from the inside to the outside, and stack Mn (1246°C), Ni (1455°C), Co (1495°C), Fe (1538°C), and Cr (1907°C) in turn to form a single-layer stacked structure. Stack 40 layers and use vacuum electron beam welding, applying a pre-tightening pressure of 0.3 MPa between adjacent foil layers.

[0056] (3) Layered stacking hot rolling: Preheat the stacked sheet metal at 890°C, and then carry out rolling. The upper and lower roll speed ratio is 1.2, the rolling linear speed is 0.5 m / s, and the deformation amount is sequentially superimposed from 10% to 50% by 10%.

[0057] (4) Post-treatment: Fold the sheet metal and repeat step (3) 100 times. Place the sheet metal in the range of 890°C - 1350°C for staged annealing. The annealing process is carried out under vacuum and is controlled in segments: the annealing temperature for the first 30 times is 890°C, the middle 40 times is 1050°C, and the last 30 times is 1350°C. The annealing time for each time is 8 h, and the cooling rate is controlled at 80°C / min. After annealing, the material is cooled in the furnace. Air-cool the annealed sheet metal to room temperature to obtain a high-quality FeCoZnSnIn high-entropy alloy sheet with multiple interfaces. Compared with the arc melting process, the hardness of the high-entropy alloy sheet is increased by 40% and the elongation is increased by 18%.

[0058] Example 5

[0059] (1) Calculation and material preparation: Ti, Zr, Cr, Fe, and Ni are calculated to have an ideal entropy value of 13.07 J / (mol·K) according to the mass percentages of 20%, 20%, 25%, 15%, and 20%, respectively, which meets the definition of high-entropy alloys (entropy value ≥ 12.47 J / (mol·K)). Cut 30-μm metal foil into rectangles of 10 cm × 10 cm;

[0060] (2) Stacking and fixing: Stack Ni (1455 °C), Fe (1538 °C), Ti (1675 °C), Zr (18525 °C), and Cr (1907 °C) in sequence from the lowest melting point to the highest and from the inside to the outside in the prepared rectangular metal foils to form a single-layer stacked structure. Stack 40 layers and use vacuum electron beam welding, applying a pre-tightening pressure of 0.3 MPa between adjacent foil layers;

[0061] (3) Layered stacking and hot rolling: Preheat the stacked plates at 1000 °C, and then perform rolling. The upper and lower roll speed ratio is 1.2, the rolling linear speed is 1.8 m / s, and the deformation amount is sequentially stacked from 10% to 40% by 10%;

[0062] (4) Subsequent treatment: Cut and fold the plates in half, repeat step (3) 80 times, place the plates in an annealing furnace at 1000 °C - 1350 °C in stages. The annealing process is carried out under vacuum, and the annealing process is controlled in segments: the annealing temperature for the first 30 times is 1000 °C, the annealing temperature for the middle 20 times is 1150 °C, and the annealing temperature for the last 30 times is 1350 °C. The annealing time for each time is 8 h, and the cooling rate is controlled at 50 °C / min. After annealing, the material is cooled in the furnace. Air-cool the annealed plates to room temperature to obtain high-quality TiZrCrFeNi high-entropy alloy plates with multiple interfaces. Compared with the arc melting process, the hardness of the high-entropy alloy plates is increased by 35%, and the elongation is increased by 20%.

[0063] Example 6

[0064] (1) Calculation and material preparation: Zn, Bi, Mg, Sn, Al, and Pb are calculated to have an ideal entropy value of 13.80 J / (mol·K) according to the mass percentages of 10%, 25%, 10%, 20%, 10%, and 25%, respectively, which meets the definition of high-entropy alloys (entropy value ≥ 12.47 J / (mol·K)). Cut 20-μm metal foil into rectangles of 10 cm × 10 cm;

[0065] (2) Stacking and fixing: Stack the prepared rectangular sheet metal foils in the order of increasing melting point from the inside to the outside, stacking Sn (232 °C), Bi (271.3 °C), Pb (327.5 °C), Zn (419.6 °C), Mg (650 °C), and Al (660 °C) in sequence to form a single-layer stacked structure. Stack 30 layers, use a high-temperature fixture, and apply a pre-tightening pressure of 0.5 MPa between adjacent foil layers;

[0066] (3) Layered stacking hot rolling: Preheat the stacked sheet at 180 °C, and then perform rolling. The upper and lower roll speed ratio is 1.2, the rolling linear speed is 1.5 m / s, and the strain is sequentially stacked from 10% to 40% by 10%;

[0067] (4) Post-treatment: Cut and fold the sheet in half, repeat step (3) 80 times, place the sheet in an annealing furnace at 180 °C - 460 °C in stages. The annealing process is carried out under vacuum, and the annealing process is controlled in segments: the annealing temperature for the first 30 times is 180 °C, the middle 20 times is 240 °C, and the last 30 times is 460 °C. The annealing time for each time is 10 h, and the cooling rate is controlled at 60 °C / min. After annealing, the material is cooled in the furnace. After annealing, the sheet is air-cooled to room temperature to obtain a high-quality ZnBiMgSnAlPb high-entropy alloy sheet containing multiple interfaces. Compared with the arc melting process, the hardness of the high-entropy alloy sheet is increased by 38%, and the elongation is increased by 22%.

[0068] Example 7

[0069] (1) Calculation and material preparation: Co, Ni, Cr, Fe, Mn, and Ti are calculated according to the mass percentages of 25%, 20%, 15%, 15%, 10%, and 15%, and their ideal entropy value is 14.66 J / (mol·K), which meets the definition of high-entropy alloy (entropy value ≥ 12.47 J / (mol·K)). Cut 40-μm metal foil into rectangles of 10 cm × 10 cm;

[0070] (2) Stacking and fixing: Stack the prepared rectangular plate metal foils in the order of increasing melting point from the inside to the outside: Mn (1246 °C) - Ni (1455 °C) - Co (1495 °C) - Fe (1538 °C) - Ti (1675 °C) - Cr (1907 °C) in sequence to form a single-layer stacked structure. Stack 20 layers, use vacuum electron beam welding, and apply a pre-tightening pressure of 0.5 MPa between adjacent foil layers;

[0071] (3) Layered stacking hot rolling: Preheat the stacked sheet at 890 °C, and then perform rolling. The upper and lower roll speed ratio is 1.1, the rolling linear speed is 1.5 m / s, and the strain is sequentially stacked from 10% to 40% by 10%;

[0072] (4) Post-treatment: Cut and fold the sheet metal, repeat step (3) 100 times, place the sheet metal in an annealing furnace at 890 °C - 1350 °C in stages. The annealing process is carried out under vacuum and is controlled in segments: the annealing temperature for the first 30 times is 890 °C, the middle 40 times is 1100 °C, and the last 30 times is 1350 °C. The annealing time for each time is 10 h, and the cooling rate is controlled at 50 °C / min. After annealing, the material is cooled in the furnace. After air-cooling the annealed sheet metal to room temperature, a high-quality CoNiCrFeMnTi high-entropy alloy sheet with multiple interfaces can be obtained. Compared with the arc melting process, the hardness of the high-entropy alloy sheet is increased by 33% and the elongation is increased by 17%.

[0073] Example 8

[0074] (1) Calculation and material preparation: Fe, Ni, Cr, Ag, Ti, Co, and Zr are calculated according to the mass percentages of 20%, 15%, 15%, 15%, 10%, 10%, and 15%, and their ideal entropy value is 15.76 J / (mol·K), which meets the definition of high-entropy alloys (entropy value ≥ 12.47 J / (mol·K)). Cut the 30-μm metal foil into rectangles of 10 cm × 10 cm.

[0075] (2) Stacking and fixing: Stack the prepared rectangular metal foils in the order of increasing melting point from the inside to the outside, Ag (965 °C), Ni (1455 °C), Co (1495 °C), Fe (1538 °C), Ti (1675 °C), Zr (18525 °C), and Cr (1907 °C) in sequence to form a single-layer stacked structure. Stack 30 layers and use vacuum electron beam welding, applying a pre-tightening pressure of 0.5 MPa between adjacent foil layers.

[0076] (3) Layered stacking and hot rolling: Preheat the stacked sheet metal at 680 °C, and then carry out rolling. The upper and lower roll speed ratio is 1.2, the rolling linear speed is 1.8 m / s, and the deformation amount is sequentially superimposed from 10% to 40% by 10%.

[0077] (4) Post-treatment: Cut and fold the sheet metal, repeat step (3) 150 times, place the sheet metal in an annealing furnace at 680 °C - 1350 °C in stages. The annealing process is carried out under vacuum and is controlled in segments: the annealing temperature for the first 50 times is 680 °C, the middle 50 times is 1100 °C, and the last 50 times is 1350 °C. The annealing time for each time is 10 hours, and the cooling rate is controlled at 50 °C / min. After annealing, the material is cooled in the furnace. After air-cooling the annealed sheet metal to room temperature, a high-quality FeNiCrAgTiCoZr high-entropy alloy sheet with multiple interfaces can be obtained. Compared with the arc melting process, the hardness of the high-entropy alloy sheet is increased by 42% and the elongation is increased by 25%.

[0078] Comparative Example 1

[0079] Calculation and material preparation: Al, Sn, Bi, Pb, and In were calculated to have an ideal entropy value of 13.38 J / (mol·K) according to a molar ratio of 1:1:1:1:1, which meets the definition of high-entropy alloys (entropy value ≥ 12.47 J / (mol·K)).

[0080] Preparation method: The metal powders were loaded into a ball milling tank according to the ratio, and a high-energy ball milling process was used to prepare the high-entropy alloy;

[0081] Results: Due to the high specific surface area and surface energy of the metal powders, agglomeration easily occurred during the ball milling process, affecting subsequent processes such as forming and sintering, and it was difficult to obtain a completely dense material. Subsequent treatment was required to improve the density. Finally, the high-entropy alloy SnAlBiPbIn had a hardness of 180 HV and an elongation of 16%.

[0082] Comparative Example 2

[0083] Calculation and material preparation: Fe, Cr, Cu, Zn, Al, and In were calculated to have an ideal entropy value of 15.19 J / (mol·K) according to mass percentages of 10%, 10%, 10%, 20%, 25%, and 25%, which meets the definition of high-entropy alloys (entropy value ≥ 12.47 J / (mol·K)).

[0084] Preparation method: The metal powders were loaded into a crucible according to the ratio, and an arc melting process was used to prepare the high-entropy alloy;

[0085] Results: Due to the large difference in the melting points of the alloys and the high arc melting temperature, low-melting-point metals (In, Zn, Al) volatilized, while high-melting-point metals (Cu, Fe, Cr) were not completely melted, resulting in the alloy composition deviating from the designed value and it being difficult to ensure the composition uniformity. Finally, the high-entropy alloy FeCrCuInZnAl had a hardness of 538 HV and an elongation of 25%.

[0086] The above shows and describes the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited by the above embodiments. Without departing from the spirit and scope of the present invention, the present invention will have various changes and improvements, and these changes and improvements all fall within the protection scope. The scope of protection required by the present invention is defined by the appended claims and their equivalents.

Claims

1. A method for preparing high-entropy alloys by multi-process collaboration, characterized in that, It includes the following steps: S1. Calculate the composition of the high-entropy alloy containing more than 5 principal elements and the corresponding atomic percentages; S2. Take the metal elements of each principal element, make the metal elements into metal foils with a thickness of 10 - 50 μm, and stack them layer by layer from the inside to the outside in the order of increasing metal melting point; S3. Preheat the stack at 70% ± 20 °C of the melting point temperature of the metal with the lowest melting point; S4. Roll the preheated stacked material, with an initial deformation of 10%, and then increase it by 10% each time until the total deformation reaches 40%; S5. Anneal the rolled material at the preheating temperature for 5 - 10 hours; S6. Fold the annealed material, and repeat steps S3 to S5 for 30 - 150 times to form a high-entropy alloy sheet with a multi-layer interface structure.

2. The method for preparing a high-entropy alloy by multi-process collaboration according to claim 1, characterized in that: In step S1, the principal elements are at least five of the metals Fe, Co, Ni, Cr, Mn, Al, Ti, Cu, Zn, Zr, Bi, In, Pb, Mg, and the atomic percentage of each principal element is 5 - 35%.

3. The method for preparing a high-entropy alloy by multi-process collaboration according to claim 1, characterized in that: In step S2, a stacked material is formed by using a single-layer stacking structure of 20 - 50 layers, and vacuum electron beam welding or a high-temperature fixture is used for stacking and fixing, and a pre-tightening pressure of 0.1 - 0.5 MPa is applied between adjacent metal foil layers.

4. A method for preparing a high-entropy alloy by multi-process collaboration according to claim 1, characterized in that: In step S4, multi-pass hot rolling process is used for rolling, and the thickness reduction of the material after each rolling is 10 - 15% of the previous thickness; an asynchronous rolling mill is used in the rolling process, the upper and lower roll speed ratio is set to 1.05 - 1.20, and the rolling linear speed is maintained at 0.5 - 2 m / s.

5. A method for preparing a high-entropy alloy through multi-process collaboration as claimed in claim 1, characterized in that: In step S5, the annealing process is carried out in a vacuum or inert gas protection atmosphere, and the material after annealing is cooled in a furnace, and the cooling rate is controlled at 10 - 80 °C / min.

6. A method for preparing a high-entropy alloy by multi-process collaboration according to claim 1, characterized in that: In step S6, steps S4 to S5 are repeated for 30 - 150 times, and the temperature selection in the annealing process is carried out in stages: the first stage is 70% ± 20 °C of the melting point temperature of the metal with the lowest melting point, the second stage is 70% ± 20 °C of the melting point temperature of the metal with the intermediate melting point, and the third stage is 70% ± 20 °C of the melting point temperature of the metal with the highest melting point, and the holding time is 5 - 10 hours for all.

7. A method for preparing a high-entropy alloy through multi-process collaboration as described in claim 1, characterized in that: The surface of the metal foil is pre-treated by sandblasting and degreasing, and the surface roughness Ra is controlled within 0.5 - 2.0 μm; the difference in melting point temperature between adjacent metal foils in step S2 is within 500 °C.

8. A method for preparing a high-entropy alloy through multi-process collaboration as described in claim 1, characterized in that: In the annealing at the preheating temperature in step S5, a gradient annealing process is adopted in the heat treatment process.

9. The method for preparing a high-entropy alloy through multi-process collaboration according to claim 1, wherein, The high-entropy alloy sheet in S6 includes the following structural characteristics: 1) Fine grain phase of 50 - 200 nm and coarse grain phase of 1 - 5 μm, and the volume ratio of the coarse grain phase is 15 - 40%; 2) A nano-scale mixed transition layer is formed at the interface between adjacent layers; 3) There are both soft phase and hard phase bimodal grain structures inside the material; the soft phase includes FCC structure, and the hard phase includes BCC structure.

10. A high-entropy alloy sheet with a multi-layer interface structure, characterized in that: The high-entropy alloy sheet prepared by any one of claims 1 to 9 has a hardness increase of ≥ 30% and an elongation of ≥ 15%.

Images