CN115449691B - Ultrahigh-strength-plasticity matched high-entropy alloy and preparation method thereof - Google Patents

Abstract

A high-entropy alloy with ultra-high strength-plasticity matching and a preparation method thereof, the high-entropy alloy includes a main element and an auxiliary element, the main element includes Ni, Fe, Co, Cr, and the auxiliary element Including Al, Ti, W, Mo, Nb, by adding the auxiliary element, the main element is introduced into different precipitates. The high-entropy alloy is processed by a specific heat treatment process, which can make the alloy grain size, dislocation quantity, and precipitated phase morphology achieve excellent coordination. The yield strength of the high-entropy alloy of the present application can reach more than 1700 MPa, and the tensile strength is 1700 MPa. Most of the strengths have reached above 2.0GPa, with good toughness and high yield strength, meeting the requirements of the mechanical properties of modern industrial materials.

Description

A high-entropy alloy with ultra-high strength-plasticity matching and its preparation method

technical field

The application relates to the technical field of metal materials, in particular to an ultra-high strength-plastic matching high-entropy alloy and a preparation method thereof.

Background technique

The number of elements in high-entropy alloys (HEA) is large and the content of each alloy element is relatively high, which makes the mixing entropy of the alloy larger, which makes the alloy elements tend to be chaotically arranged to form a simple body-centered cubic (BCC) or face-centered cubic ( FCC) phase, this new alloy material has aroused widespread interest in the research field because of its excellent comprehensive properties such as high hardness, high strength, high temperature creep resistance, high temperature oxidation resistance, corrosion resistance, high resistivity and good electromagnetic properties. attention, and has broad application prospects.

In recent years, FCC-type FeCoCrNi-based high-entropy alloys (that is, multi-element high-entropy alloys formed with iron, cobalt, chromium, and nickel as the main elements, the matrix components are mainly iron, cobalt, chromium, and nickel, and the lattice type of face-centered cubic FCC lattice) has been extensively studied. The results show that promoting the formation of precipitates by doping with alloying elements and thermomechanical working is very effective in strengthening such alloys. However, the precipitates can also easily lead to a decrease in ductility, which limits the alloy to obtain excellent tensile properties with the ideal strength-ductility "tradeoff".

The most commonly used alloying elements in high entropy alloys are aluminum (Al) or titanium (Ti). The addition of these elements usually results in geometrically close-packed phases (GCP phases, including γ′-Ni3Al phases, η-Ni3Ti phases, and α-Ni2AlTi phases, among them, γ′-Ni3Al phases, whose lattice type is LI2 (ordered body-centered Cubic lattice), chemical composition is Ni3Al; η-Ni3Ti phase, its lattice type is ordered hexagonal close-packed lattice, chemical composition is Ni3Ti; α-Ni2AlTi phase, its lattice type is face-centered cubic structure, chemical composition For Ni2AlTi) formation. The lattice of these phases is consistent with the matrix. The study by Zhaoping Lu et al. showed that the low lattice mismatch reduces the nucleation barrier of the precipitated phase, thus enabling the generation and stabilization of the nano-precipitated phase. By optimizing the concentrations of Al and Ti, the nanoscale coherent LI2-γ′ phase (γ′-LI2-Ni3Al phase, whose lattice type is LI2 (ordered body-centered cubic lattice) and whose chemical composition is Ni3Al, is a precipitated phase, Distributed in the matrix of the alloy) particles precipitate in the CoCrFeNi-based high-entropy alloy. The fine coherent precipitate phase is beneficial to enhance the strength-ductility synergistic effect. For example, the (FeCoNi)86-Al7Ti7 HEA reinforced by LI2 nanoparticles (i.e. strengthened by the γ′-LI2-Ni3Al phase has a coherent relationship between the lattice and the matrix, which is coherent strengthening, which not only improves the strength, High-entropy alloys, which also do not adversely affect plasticity, can have a yield strength of about 1.0 GPa and a ductility of about 50%. The formation of LI2-γ′ nanoprecipitates provides an outstanding contribution to the strengthening of high-entropy alloys, resulting in a combination of good strength and ductility, where Ti is precipitated in the γ′ phase (i.e., the γ′-LI2-Ni3Al phase) Plays a key role, while Al improves the stability of the γ′ phase.

Recently, some alloying elements with small atomic radius represented by molybdenum (Mo) have been used to strengthen HEA. The addition of Mo can produce different types of topological close-packed phases (TCP phase, including σ phase, μ phase, and Laves equal), depending on its doping content and heat treatment parameters. Unlike nickel-based superalloys, these phases in FCC-HEA effectively strengthen the alloy without developing severe brittleness. This is due to the fact that the solid solution FCC matrix phase usually exhibits very high plasticity and still maintains some toughness after precipitation strengthening. The results show that the σ and μ phases precipitated in CoCrFeNiMo0.3 HEA by thermomechanical processing effectively strengthen the alloy, resulting in a good combination of tensile strength of 1.2 GPa and elongation of 19%. In addition to Mo, HEA can also be strengthened by adding elements such as niobium (Nb), manganese (Mn), and vanadium (V) to generate a TCP precipitated phase. Interestingly, the addition of Nb can form TCP in HEA while promoting the formation of geometrically close-packed phases of γ′, γ′, and ε. However, Nb does not fully exert its role in strengthening the strength-ductility synergistic effect. In general, the tensile yield strength is lower than 1000MPa, but has a higher elongation (15-55%).

In order to effectively strengthen FeCoCrNi HEA (that is, iron-chromium-cobalt-nickel-based high-entropy alloy), microstructure design is of great significance. A strategy to optimize precipitation and introduce a heterogeneous microstructure by thermomechanical processing is proposed. The eutectic AlCoCrFeNi2.1 alloy with heterogeneous structure can reach a tensile yield strength of about 1800MPa and an elongation of about 5% through low temperature rolling and warm rolling treatment. This strength enhancement relies on dislocation strengthening and precipitation strengthening, showing unprecedented strength-plastic matching.

Although the above-mentioned tensile properties have good strength-plastic matching, their low elongation, negative strain hardening rate, and limitations in mass production make it difficult to apply to practical industrial structural materials.

However, heterogeneous microstructures may produce synergistic strengthening effects, which follow:

σ _0.2 ＝σ ₁ +Δσ _G +Δσ _S +Δσ _P +Δσ _D (1)

Among them, σ0.2 is the enhanced yield strength; σ1 is the original yield strength; ΔσS, ΔσG, ΔσD and ΔσP represent solid solution strengthening, grain boundary hardening, dislocation strengthening and precipitation strengthening, respectively. After thermomechanical processing, high-entropy alloys can obtain non-uniform microstructures and exhibit excellent strengthening effects.

Therefore, obtaining CoCrFeNi-based high-entropy alloys with an excellent combination of strength and ductility remains a challenge in the research field. In practice, it is of great importance to prepare high-entropy alloys with sufficiently high strength, ductility, and strain hardening rate.

Contents of the invention

The purpose of this application is to provide a high-entropy alloy with ultra-high strength-plasticity matching and its preparation method, so that the high-entropy alloy can maintain high elongation and positive hardening rate while the strength is greatly improved, and meet the modern industry's requirements for materials. Requirements for mechanical properties to solve the problems of insufficient strength, poor plasticity, poor strength-plasticity matching, and difficulty in mass production of existing high-entropy alloys.

Embodiments of the application can be achieved through the following technical solutions:

A high-entropy alloy with ultra-high strength-plasticity matching, the high-entropy alloy includes a main element and an auxiliary element, the main element includes Ni, Fe, Co, Cr, and the auxiliary element includes Al, Ti , W, Mo, Nb, by adding the secondary elements,

Such that the principal element introduces different precipitates.

Further, the atomic percentage content of each element in the main element and the auxiliary element is,

Main element, Ni 22at.%～25%at.%, Fe 13at.%～16at.%, Co 32.5at.%～35.5at.%, Cr 12at.%～15at.%;

Auxiliary element, Al 3.0at.%～5.0at.%, Ti 1.5at.%～3.5at.%, W 0.5at.%～2.0at.%, Mo 1.0at.%～2.5at.%, Nb 0.25 at.%～1.25at.%.

A method for preparing a high-entropy alloy according to the above-mentioned ultrahigh strength-plasticity matching, comprising the following steps:

The first step, alloy smelting: use metal elemental Ni, Fe, Co, Cr, Al, Ti, W, Mo, Nb as raw materials, design the distribution ratio according to the atomic percentage content of each element of the above-mentioned high-entropy alloy, and obtain a purity of 99.95wt .% or more pure metal, put the pure metal into an induction melting furnace for melting to obtain a multi-principal element alloy melt, and then cast the multi-principal element alloy melt in a mold to form an ingot blank;

The second step, homogenization treatment: the ingot billet is subjected to a homogenization treatment for 24 hours in a vacuum heat treatment furnace at 1200°C, and then taken out and air-cooled to obtain the first alloy body;

The third step is forging forming: heating the first alloy body to 1200°C, and then performing hot forging to hot forge the first alloy body into a second alloy body of a specified size;

The fourth step, solid solution treatment: put the second alloy body in a vacuum furnace at 1200°C for 2 hours, and then perform water quenching to obtain the third alloy body;

The fifth step, cold rolling treatment: the third alloy body is subjected to multi-pass rolling of 75%-90% reduction at room temperature, and the third alloy body is rolled into a fourth alloy with a specified size body;

The sixth step, annealing treatment: heat the fourth alloy body at 750°C-900°C for 30 minutes and then water quench to obtain the fifth alloy body;

The seventh step, aging treatment: heat the fifth alloy body under the condition of 500°C-600°C for 48 hours, then air-cool to obtain a finished high-entropy alloy.

Further, the ingot billet includes an ingot rod body billet and an ingot plate body billet, and the ingot plate body billet is a billet obtained by cutting the ingot bar body billet.

Further, the size of the cross-sectional area of the ingot rod blank is The size of the cross-sectional area of the ingot plate body blank is />

Further, the fourth alloy body is water-quenched after being kept at 800°C, 825°C, or 850°C for 30 minutes to obtain the fifth alloy body.

An ultra-high strength-plastic matching high-entropy alloy and its preparation method provided by the embodiments of the present application have at least the following beneficial effects:

In this application, through the addition of auxiliary element elements W, Mo, Al, Ti and Nb, different precipitates are introduced to obtain multi-main element alloy products. After forging, rolling, annealing and aging processes for multi-main element alloy products , the high-entropy alloy presents a heterogeneous microstructure, which makes the high-entropy alloy produce ultra-fine recrystallized grains and retain a certain number of dislocations while the precipitation strengthening of the high-entropy alloy is greatly improved, so that the strength of the high-entropy alloy is not only greatly improved, At the same time, it also maintains high elongation and positive hardening rate;

The high-entropy alloy prepared by the method of the present application can produce plates and rods with a certain volume, which changes the traditional ultra-high-strength high-entropy alloy that can only use an arc melting furnace to prepare extremely small high-entropy alloy button ingots. It is used in the preparation of high-strength bolts and plates in the aviation industry, with excellent formability;

Through the heat treatment process of this application, especially the sixth step annealing treatment and the seventh step aging treatment, the grain size of the alloy will be extremely small, and a certain number of dislocations will be retained to cause work hardening, so that the strength of the alloy can be guaranteed to a certain extent . In addition, the precipitation phase of the alloy under this process can be controlled to the nanometer level, and the alloy will be strengthened without a sharp drop in plasticity. Therefore, the heat treatment process of the application can make the grain size, dislocation number, and precipitation of the alloy The phase morphology achieves excellent coordination, which can produce excellent strength-plasticity matching alloys. The optimal strength-plasticity matching of the obtained high-entropy alloy can reach a rare yield strength of 2.2GPa, and the elongation rate is more than 10%, and the high-entropy alloy with different strength-plasticity matching can be obtained by adjusting the heat treatment process, showing a broad field of view. Application prospect.

Description of drawings

Fig. 1 is the picture and electron backscatter diffraction analysis diagram of the sample prepared by embodiment 1, embodiment 8 and embodiment 9 of the present application under the scanning electron microscope;

Figures 2-4 are the tensile engineering stress-strain curves of the high-entropy alloys prepared in Example 1, Example 8, and Example 9, respectively.

Detailed ways

Hereinafter, the present application will be further described based on preferred embodiments with reference to the drawings.

In addition, for the convenience of understanding, various components on the drawings are enlarged (thick) or reduced (thin), but this approach is not intended to limit the scope of protection of the present application.

Words in the singular include the plural and vice versa.

In the description of the embodiments of the present application, it should be noted that if the orientation or positional relationship indicated by the terms "upper", "lower", "inner" and "outer" appear, it is based on the orientation or position shown in the drawings relationship, or the usual orientation or positional relationship of the products in the embodiments of the application when used, is only for the convenience of describing the application and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, in order to Specific orientation configurations and operations, therefore, are not to be construed as limitations on the application. In addition, in the description of the present application, in order to distinguish different units, words such as first and second are used in this specification, but these are not limited by the order of manufacture, nor can they be interpreted as indicating or implying relative importance. The titles in the detailed description of the application may be different from those in the claims.

The terms used in this specification are used to describe the embodiments of the present application, but are not intended to limit the present application. It should also be noted that, unless otherwise clearly stipulated and limited, the terms "set", "connected" and "connected" should be interpreted in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral Ground connection; it can be a mechanical connection, a direct connection, or an indirect connection through an intermediary, or an internal connection between two components. Those skilled in the art can specifically understand the specific meanings of the above terms in this application.

A high-entropy alloy with ultra-high strength-plasticity matching, the high-entropy alloy includes a main element and an auxiliary element, the main element includes Ni, Fe, Co, Cr, and the auxiliary element includes Al, Ti , W, Mo, Nb, by adding the auxiliary element, the main element introduces different precipitates.

The atomic percent content of each element of the high-entropy alloy is:

Main element, Ni 22at.%～25%at.%, Fe 13at.%～16at.%, Co 32.5at.%～35.5at.%, Cr 12at.%～15at.%;

Auxiliary element, Al 3.0at.%～5.0at.%, Ti 1.5at.%～3.5at.%, W 0.5at.%～2.0at.%, Mo 1.0at.%～2.5at.%, Nb 0.25 at.%～1.25at.%;

Among them, a single impurity element in the impurities is ≤0.05 at.%, and the total amount of all impurity elements is ≤0.15 at.%.

Preferably, the purity of each element metal is above 99.95wt.%.

The addition of W, Mo, Al, Ti and Nb in the auxiliary elements is to introduce different precipitates to obtain multi-primary element alloy products, which are used to further exert the effect of precipitation strengthening, and then through forging the multi-main element alloy products , after rolling, annealing and aging treatment, the high-entropy alloy presents a heterogeneous microstructure, which makes the high-entropy alloy greatly improve the precipitation strengthening, and at the same time produce ultra-fine recrystallized grains and retain a certain number of dislocations, so as to realize The high-entropy alloy not only greatly improves the strength, but also maintains high elongation and positive hardening rate.

A method for preparing a high-entropy alloy with ultra-high strength-plasticity matching, comprising the following steps:

The first step, alloy smelting: use metal elemental Ni, Fe, Co, Cr, Al, Ti, W, Mo, Nb as raw materials, design the distribution ratio according to the atomic percentage content of each element of the above-mentioned high-entropy alloy, and obtain a purity of 99.95wt .% or more pure metal, put the pure metal into an induction melting furnace for melting to obtain a multi-principal element alloy melt, and then cast the multi-principal element alloy melt in a mold to form an ingot blank;

The second step, homogenization treatment: the ingot billet is subjected to a homogenization treatment for 24 hours in a vacuum heat treatment furnace at 1200°C, and then taken out and air-cooled to obtain the first alloy body;

The third step is forging forming: heating the first alloy body to 1200°C, and then performing hot forging to hot forge the first alloy body into a second alloy body of a specified size;

The fourth step, solid solution treatment: put the second alloy body in a vacuum furnace at 1200°C for 2 hours, and then perform water quenching to obtain the third alloy body;

The fifth step, cold rolling treatment: the third alloy body is subjected to multi-pass rolling of 75%-90% reduction at room temperature, and the third alloy body is rolled into a fourth alloy with a specified size body;

Under normal circumstances, the total reduction rate of cold rolling treatment is generally 60% to 90%. It is measured through repeated tests that the structure of the fourth alloy obtained after rolling with a reduction rate of 75% to 90% is uniform and the surface quality is uniform. Superior, more excellent mechanical properties and process performance.

The sixth step, annealing treatment: the fourth alloy body is kept at 750°C-900°C for 30 minutes and then water quenched to obtain the fifth alloy body, which is used to generate the cold-rolled deformed structure of the alloy through high-temperature annealing Recrystallization improves the plasticity of the alloy and slightly reduces the strength. The reason for keeping the temperature for 30 minutes is short is to prevent excessive growth of grains, which is not conducive to fine-grain strengthening, because fine-grain strengthening has a positive impact on both strength and plasticity. ;

The seventh step, aging treatment: the fifth alloy body is kept at 500°C-600°C for 48 hours and then air-cooled to obtain a finished high-entropy alloy. The meaning of long-term aging at low temperature is to make the alloy at low temperature The slow precipitation of the precipitated phase is also to produce a large amount of fine second phase precipitation, so that the strength of the alloy can be further improved without a sharp drop in plasticity.

Further, in the first step of the above preparation method, the ingot blank includes an ingot rod body blank and an ingot plate body blank, wherein the ingot plate blank is cut by wire cutting. A blank obtained from a body blank.

In some preferred embodiments, the size of the cross-sectional area of the ingot rod blank is The size of the cross-sectional area of the ingot plate body blank is />

Correspondingly, in the second step of the above-mentioned preparation method, the first alloy body includes a first alloy rod body and a first alloy plate body, wherein the first alloy rod body and the first alloy plate body are respectively It is an alloy body obtained by homogenizing the ingot rod body blank and the ingot plate body blank.

Correspondingly, in the third step of the above preparation method, the second alloy body includes a second alloy rod body and a second alloy plate body, and the second alloy rod body and the second alloy plate body are respectively the An alloy body obtained by forging the first alloy rod body and the first alloy plate body.

In some preferred embodiments, after the third step of hot forging, the second alloy rod body is a short rod with a diameter of 60 mm, and the second alloy plate body is a square plate with a thickness of 15 mm.

Correspondingly, in the fourth step of the above preparation method, the third alloy body includes a third alloy rod body and a third alloy plate body, and the third alloy rod body and the third alloy plate body are respectively the third alloy rod body and the third alloy plate body. The alloy body obtained after the second alloy rod body and the second alloy plate body are subjected to solid solution treatment.

Correspondingly, in the fifth step of the above preparation method, the fourth alloy body includes a fourth alloy rod body and a fourth alloy plate body, and the fourth alloy rod body and the fourth alloy plate body are formed by An alloy body obtained by cold rolling the third alloy rod body and the third alloy plate body.

In some preferred embodiments, after the fifth step of rolling, the diameter of the fourth alloy rod body is 19 mm, and the thickness of the fourth alloy plate body is 1.5 mm.

Correspondingly, in the sixth step of the above preparation method, the fifth alloy body includes a fifth alloy rod body and a fifth alloy plate body, and the fifth alloy rod body and the fifth alloy plate body are respectively the first The four-alloy rod body and the fourth alloy plate body are obtained through annealing treatment.

Correspondingly, in the seventh step of the above preparation method, the finished high-entropy alloy includes finished high-entropy alloy rods and finished high-entropy alloy plates, the finished high-entropy alloy rods, the finished high-entropy alloy plates The finished product is a finished product obtained from the fifth alloy rod body and the fifth alloy plate body after aging treatment respectively.

Through the heat treatment process of the above specific process, the grain size of the alloy will be extremely small, and a certain volume fraction of the deformed structure will be retained to retain a certain amount of work hardening, so that the strength of the alloy can be guaranteed to a certain extent. Long-term aging alloys at low temperatures can control the precipitated phases to the nanometer level, which can strengthen the alloy without reducing the plasticity. Therefore, only by using a specific heat treatment process can the grain size, number of dislocations, and precipitated phases of the alloy be reduced. The appearance can be perfectly matched, resulting in a high-entropy alloy with excellent strength-plasticity matching. The significance of heat treatment is to achieve a good match between the grain size, dislocation density, recrystallization percentage, and the morphology of the precipitated phase in the structure of the alloy, thereby producing excellent strength-plastic matching properties.

Example 1

The first step, alloy smelting: use metal elemental Ni, Fe, Co, Cr, Al, Ti, W, Mo, Nb as raw materials, according to Co: Cr: Fe: Ni: W: Mo: Al: Ti: Nb = 34.25 %: 15%: 15%: 24%: 1.5%: 1.5%: 5%: 3%: 0.75% atomic percentage for proportioning, accurately weigh 20kg of mixed raw materials, put them into the induction melting furnace, and cast after melting Obtain the cross-sectional area size as The ingot rod blank, and then use wire cutting to cut the ingot rod blank into a cross-sectional area size of /> Ingot plate blanks;

The second step, homogenization treatment: the ingot plate blank is subjected to a homogenization treatment for 24 hours in a vacuum heat treatment furnace at 1200° C., and then taken out and air-cooled to obtain the first alloy plate body;

The third step is forging forming: the first alloy plate body is heated to 1200° C., and then hot forged to forge the first alloy plate body into a second alloy plate body with a thickness of 15 mm;

The fourth step, solution treatment: put the second alloy plate body in a vacuum furnace at 1200°C for 2 hours and then water quench to obtain the third alloy plate body;

The fifth step, cold rolling treatment: rolling the third alloy plate body with a 90% downdraft for multiple passes at room temperature until a fourth alloy plate body with a thickness of 1.5 mm is obtained;

The sixth step, annealing treatment: heat the fourth alloy plate body at 800°C for 30 minutes and then water quench to obtain the fifth alloy plate body;

The seventh step, aging treatment: heat the fifth alloy plate body at 500° C. for 48 hours and then air-cool to obtain a finished high-entropy alloy plate body, which is denoted as high-entropy alloy 1.

Embodiment 2-6:

On the basis of embodiment 1, only change the atomic percent among Ni, Fe, Co, Cr, Al, Ti, W, Mo, Nb,

Other steps and conditions are the same as in Example 1, and high-entropy alloys 2-6 are prepared respectively; wherein, the atomic percentages among Ni, Fe, Co, Cr, Al, Ti, W, Mo, and Nb are shown in Table 1:

Table 1

Example 7-10

On the basis of Example 1, without changing the atomic percentage between Ni, Fe, Co, Cr, Al, Ti, W, Mo, Nb, only changing the holding temperature in the sixth step, the fifth step will be processed to obtain The fourth alloy plate body was kept at 750°C, 825°C, 850°C, and 900°C for 30 minutes, and then quenched in water. The rest of the steps and conditions were the same as in Example 1, and high-entropy alloy 7, high-entropy alloy 8, and High entropy alloy 9, high entropy alloy 10.

Example 11

On the basis of Example 1, do not change the atomic percentage between Ni, Fe, Co, Cr, Al, Ti, W, Mo, Nb, only change the cold rolling reduction in the fifth step, at room temperature The third alloy plate body obtained through the fourth step treatment was subjected to multi-pass rolling with a 75% downdraft, and the rest of the steps and conditions were the same as those in Implementation 1, and the high entropy alloy 11 was prepared.

Example 12

On the basis of Example 1, do not change the atomic percentage between Ni, Fe, Co, Cr, Al, Ti, W, Mo, Nb, only change the holding temperature in the seventh step, and obtain The fifth alloy plate body was kept at 600° C. for 48 hours and then air-cooled. The rest of the steps and conditions were the same as in Example 1 to prepare high-entropy alloy 12.

The quasi-static tensile mechanical properties at room temperature were tested on the high-entropy alloys 1-12 prepared in the above examples, and the results are shown in Table 2.

Table 2

Analysis of Table 2 shows that the yield strength of the high-entropy alloys in each embodiment of the present application has reached more than 1700MPa, and most of the tensile strengths have reached more than 2.0GPa. Comparative analysis of Example 1 and Examples 7-10 shows that through high-temperature annealing It can recrystallize the cold-rolled deformed structure of the alloy, improve the plasticity of the alloy, and slightly decrease the strength; comparative analysis of Example 1 and Example 12 shows that aging at low temperature for a long time, low temperature can further improve the strength of the alloy without producing Sharp decrease in plasticity; comparative analysis of Example 1 and Example 11 shows that the greater the amount of pressing force, the more uniform the structure of the fourth alloy obtained after rolling, the better the surface quality, the higher the strength of the high-entropy alloy, and the lower the plasticity .

In order to more intuitively show that W, Mo, Al, Ti and Nb in the auxiliary elements are added after the main elements to obtain multi-principal element alloy products, and then through forging, rolling and annealing the multi-principal element alloy products After treatment with the aging process, the obtained high-entropy alloy not only has a greatly improved strength, but also maintains a high elongation and positive hardening rate. The following is further explained in conjunction with Figures 1 to 4:

Fig. 1 is the picture and the electron backscatter diffraction analysis figure of the sample prepared by embodiment 1, embodiment 8 and embodiment 9 of the present application under the scanning electron microscope, wherein, (a), (b), and (c) represent respectively High-entropy alloy 1 in Example 1, high-entropy alloy 8 in Example 8, and high-entropy alloy 9 in Example 9, as shown in Figure 1, after 90% rolling, annealing and aging, in the scanning electron microscope (SEM) figure It was observed that the (Ti, Nb)-rich phase particles (indicated by yellow arrows) were aligned along the rolling direction, and no cracks were found around them.

After annealing and aging treatment, the shear bands recrystallized and the σ phase precipitated in submicron size (indicated by the red arrow). In this case, shear bands can still be observed under SEM.

After annealing and aging treatment, the recrystallized grains can be well observed in the EBSD-IPF diagram (electron backscattering-inverse pole figure). The KAM diagram (Kernel Average Misorientation local misorientation) shows that the dislocation strain in the recrystallized region decreases and the recrystallized area is smaller. Under SEM observation, as the annealing temperature increases, the recrystallization region expands and the shear band disappears. At the same time, the number of submicron σ phase particles annealed at 825°C is the largest, and the content decreases after rising to 850°C. Annealed at high temperature, the EBSD map clearly shows recrystallized grains with a very high division rate due to more complete recrystallization. The KAM diagram shows that the dislocation strain is further reduced, which indicates that the alloy is recrystallized more fully after annealing at a higher temperature.

Fig. 2-Fig. 4 is the tensile engineering stress-strain curve of the high-entropy alloy prepared by each embodiment 1, embodiment 8, and embodiment 9, wherein, the ordinate is the stress, and the abscissa is the strain, as shown in Fig. 2-Fig. As shown in 4, the yield strength of the high-entropy alloys in Example 1, Example 8, and Example 9 of the present application all reached more than 1700 MPa, and the tensile strength reached more than 2.0 GPa, and the strength was relatively high. With regard to plasticity, after thermomechanical treatment, the alloy still retains a certain degree of plasticity to meet certain engineering applications.

Comparing the three stress-strain curves, it can be seen that the high-entropy alloy 1 after heat preservation at 800°C for 30 minutes, water quenching, and air cooling and aging treatment at 500°C for 48 hours has the highest strength, with a tensile strength of 2606MPa and a yield strength of 2486MPa, but The plasticity is as low as 3.5%.

The high-entropy alloy with the best plasticity is the high-entropy alloy 9 which has been water-quenched at 850°C for 30 minutes. Its elongation is 17.9%, but its yield strength is only 1138MPa. The alloy with better strong-plastic combination is high-entropy alloy 8, which is water-quenched after holding at 825°C for 30 minutes. Its yield strength is 2221MPa, combined with an elongation of 11.2%.

The specific implementation of the application has been described in detail above. For those skilled in the art, without departing from the principle of the application, some improvements and modifications can be made to the application, and these improvements and modifications also belong to the application. The scope of the claims.

Claims (5)

1. A high-entropy alloy with ultra-high strength-plasticity matching, characterized in that: The high-entropy alloy includes main elements and auxiliary elements, the main elements include Ni, Fe, Co, Cr, and the auxiliary elements include Al, Ti, W, Mo, Nb, by adding the auxiliary elements elements such that the principal element introduces different precipitates; The atomic percentage content of each element in the main element and the auxiliary element is, Main element, Ni 22at.%～25%at.%, Fe 13at.%～16at.%, Co 32.5at.%～35.5at.%, Cr 12at.%～15at.%; Auxiliary element, Al 3.0at.%～5.0at.%, Ti 1.5at.%～3.5at.%, W 0.5at.%～2.0at.%, Mo 1.0at.%～2.5at.%, Nb 0.25 at.%～1.25at.%; The high-entropy alloy is prepared by the following steps: The first step, alloy smelting: use metal elemental Ni, Fe, Co, Cr, Al, Ti, W, Mo, Nb as raw materials, design the distribution ratio according to the atomic percentage content of each element of the above-mentioned high-entropy alloy, and obtain a purity of 99.95wt .% or more pure metal, put the pure metal into an induction melting furnace for melting to obtain a multi-principal element alloy melt, and then cast the multi-principal element alloy melt in a mold to form an ingot blank; The second step, homogenization treatment: the ingot billet is subjected to a homogenization treatment for 24 hours in a vacuum heat treatment furnace at 1200°C, and then taken out and air-cooled to obtain the first alloy body; The third step is forging forming: heating the first alloy body to 1200°C, and then performing hot forging to hot forge the first alloy body into a second alloy body of a specified size; The fourth step, solid solution treatment: put the second alloy body in a vacuum furnace at 1200°C for 2 hours, and then perform water quenching to obtain the third alloy body; The fifth step, cold rolling treatment: the third alloy body is subjected to multi-pass rolling of 75%-90% reduction at room temperature, and the third alloy body is rolled into a fourth alloy with a specified size body; The sixth step, annealing treatment: heat the fourth alloy body at 750°C-900°C for 30 minutes and then water quench to obtain the fifth alloy body; The seventh step, aging treatment: heat the fifth alloy body under the condition of 500°C-600°C for 48 hours, then air-cool to obtain a finished high-entropy alloy. 2. a method for preparing the high-entropy alloy of ultrahigh strength-plasticity matching according to claim 1, is characterized in that, comprises the following steps: The first step, alloy smelting: use metal elemental Ni, Fe, Co, Cr, Al, Ti, W, Mo, Nb as raw materials, design the distribution ratio according to the atomic percentage content of each element of the above-mentioned high-entropy alloy, and obtain a purity of 99.95wt .% or more pure metal, put the pure metal into an induction melting furnace for melting to obtain a multi-principal element alloy melt, and then cast the multi-principal element alloy melt in a mold to form an ingot blank; The second step, homogenization treatment: the ingot billet is subjected to a homogenization treatment for 24 hours in a vacuum heat treatment furnace at 1200°C, and then taken out and air-cooled to obtain the first alloy body; The third step is forging forming: heating the first alloy body to 1200°C, and then performing hot forging to hot forge the first alloy body into a second alloy body of a specified size; The fourth step, solid solution treatment: put the second alloy body in a vacuum furnace at 1200°C for 2 hours, and then perform water quenching to obtain the third alloy body; The fifth step, cold rolling treatment: the third alloy body is subjected to multi-pass rolling of 75%-90% reduction at room temperature, and the third alloy body is rolled into a fourth alloy with a specified size body; The sixth step, annealing treatment: heat the fourth alloy body at 750°C-900°C for 30 minutes and then water quench to obtain the fifth alloy body; The seventh step, aging treatment: heat the fifth alloy body under the condition of 500°C-600°C for 48 hours, then air-cool to obtain a finished high-entropy alloy. 3. according to the preparation method of the high-entropy alloy of a kind of ultrahigh strength-plasticity matching described in claim 2, it is characterized in that: The ingot stock includes an ingot bar stock and an ingot slab stock which is a stock obtained by cutting the ingot bar stock. 4. according to the preparation method of the high-entropy alloy of a kind of ultrahigh strength-plasticity matching described in claim 3, it is characterized in that: The size of the cross-sectional area of the ingot rod blank is φ180mm×350mm, and the size of the cross-sectional area of the ingot plate body blank is φ180mm×50mm. 5. according to the preparation method of the high-entropy alloy of a kind of ultrahigh strength-plasticity matching described in claim 2, it is characterized in that: The fourth alloy body is kept at 800° C. or 825° C. or 850° C. for 30 minutes and then water quenched to obtain the fifth alloy body.