CN115449691B - Ultrahigh-strength-plasticity matched high-entropy alloy and preparation method thereof - Google Patents
Ultrahigh-strength-plasticity matched high-entropy alloy and preparation method thereof Download PDFInfo
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Abstract
An ultrahigh-strength-plasticity matched high-entropy alloy and a preparation method thereof are provided, wherein the high-entropy alloy comprises main element and auxiliary element, the main element comprises Ni, fe, co, cr, the auxiliary element comprises Al, ti, W, mo, nb, and different precipitates are introduced into the main element by adding the auxiliary element. The high-entropy alloy is processed by a specific heat treatment process, so that the grain size, dislocation number and precipitated phase morphology of the alloy can be matched well, the yield strength of the high-entropy alloy reaches more than 1700MPa, the tensile strength of the high-entropy alloy reaches more than 2.0GPa, the high-entropy alloy has good toughness and higher yield strength, and the requirement of mechanical properties of modern industrial materials is met.
Description
Technical Field
The application relates to the technical field of metal materials, in particular to an ultrahigh-strength-plasticity matched high-entropy alloy and a preparation method thereof.
Background
The high-entropy alloy (HEA) has a plurality of elements and high content of each alloy element, so that the mixed entropy of the alloy is large, and the alloy elements tend to be arranged in a chaotic manner to form a simple body-centered cubic (BCC) or face-centered cubic (FCC) phase.
In recent years, strengthening of FCC type FeCoCrNi-based high-entropy alloys (i.e., multi-main element high-entropy alloys formed by using four metals of iron, cobalt, chromium and nickel as main elements, wherein the main matrix components are iron, cobalt, chromium and nickel, and the lattice type is face-centered cubic FCC lattice) has been widely studied. The results indicate that the formation of precipitates is promoted by doping with alloying elements and thermo-mechanical processing, which is very effective for strengthening such alloys. However, precipitates also tend to cause a decrease in ductility, which limits the alloy from achieving excellent tensile properties with the desired strength-ductility "trade-off".
The most commonly used alloying element in high entropy alloys is aluminum (Al) or titanium (Ti). The addition of these elements generally results in the formation of a geometrically closely packed phase (GCP phase, comprising a gamma '-Ni3Al phase, a eta-Ni 3Ti phase and an alpha-Ni 2AlTi phase being equal, wherein the gamma' -Ni3Al phase has a lattice type LI2 (ordered body-centered cubic lattice), a chemical composition of Ni3Al, a eta-Ni 3Ti phase has a lattice type of ordered closely packed hexagonal lattice, a chemical composition of Ni3Ti, and an alpha-Ni 2AlTi phase having a lattice type of face-centered cubic structure, and a chemical composition of Ni2 AlTi). The crystal lattice of these phases is consistent with the matrix phase. The Zhaoping Lu et al study showed that low lattice mismatch reduced the nucleation barrier of the precipitated phase, allowing the nano-precipitated phase to be generated and stabilized. By optimizing the Al and Ti concentrations, nanoscale coherent LI 2-gamma '-phase (gamma' -LI2-Ni3Al phase, its lattice type is LI2 (ordered body-centered cubic lattice), its chemical composition is Ni3Al, it is a precipitate phase, it is distributed in the matrix of the alloy) particles precipitate in CoCrFeNi-based high entropy alloys. The fine coherent precipitate phase contributes to the enhancement of the strength-ductility synergy. For example, LI 2-type nanoparticle-reinforced (FeCoNi) 86-Al7Ti7 HEA (i.e., reinforced by gamma' -LI2-Ni3Al phase, which has a lattice coherent relationship with the matrix, is a high-entropy alloy that not only enhances strength, but also does not adversely affect plasticity) can have a yield strength of about 1.0GPa and a ductility of about 50%. The formation of LI 2-gamma prime nano-precipitates provides a prominent contribution to the strengthening of the high entropy alloy, resulting in a combination of good strength and ductility, where Ti plays a key role in gamma prime phase (i.e. gamma' -LI2-Ni3Al phase) precipitation, while Al increases the stability of the gamma prime phase.
Recently, some small atomic radius alloying elements, represented by molybdenum (Mo), have been used to strengthen HEA. Mo addition can produce different types of topologically close-packed phases (TCP phases including sigma phase, mu phase and Laves equal) depending on their doping content and heat treatment parameters. Unlike nickel-based superalloys, these phases in FCC-HEA can effectively strengthen the alloy without producing severe brittleness. This is because solid solution FCC matrices generally exhibit very high plasticity and remain somewhat ductile after precipitation strengthening. The results show that the sigma and mu phases precipitated in cocrfenimo0.3 HEA by thermo-mechanical processing effectively strengthen the alloy, resulting in good bond with tensile strength of 1.2GPa and elongation of 19%. In addition to Mo, HEA can be strengthened by adding elements such as niobium (Nb), manganese (Mn), and vanadium (V) to produce a TCP precipitate phase. Interestingly, the addition of Nb can form TCP in HEA while promoting the formation of geometrically closely packed phases of γ ', γ' and epsilon. However, nb does not fully exert its effect in terms of strengthening the strength-ductility synergistic effect. The tensile yield strength is generally lower than 1000MPa, and the tensile elongation is higher (15-55%).
In order to effectively strengthen FeCoCrNi HEA (namely the Fe-Cr-Co-Ni-based high-entropy alloy), the tissue design has important significance. A strategy for optimizing precipitation and introducing non-uniform microstructures by thermo-mechanical processing is proposed. The eutectic AlCoCrFeNi2.1 alloy with a non-uniform structure can achieve a tensile yield strength of about 1800MPa and an elongation of about 5% by cold rolling and warm rolling treatments. This increase in strength relies on dislocation strengthening and precipitation strengthening, exhibiting unprecedented strength-plastic matching.
Although the tensile properties described above have a good strength-plastic match, their low elongation, negative strain hardening and the difficult mass production limitations make them 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)
wherein 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 thermal mechanical processing, the high-entropy alloy can obtain a non-uniform microstructure, and has excellent strengthening effect.
Thus, obtaining a CoCrFeNi-based high entropy alloy with excellent combinations of strength and ductility remains a challenge in the research field. In practice, it is important that the high entropy alloys produced have sufficiently high strength, ductility and strain hardening rates.
Disclosure of Invention
The application aims to provide an ultrahigh-strength-plasticity matched high-entropy alloy and a preparation method thereof, so that the high-entropy alloy can maintain high elongation and positive hardening rate while greatly improving strength, and meets the requirements of modern industry on mechanical properties of materials, thereby solving the problems that the existing high-entropy alloy is insufficient in strength, poor in plasticity, poor in strength-plasticity matching and difficult to produce in a large scale.
The embodiment of the application can be realized by the following technical scheme:
an ultra-high strength-plasticity matched high-entropy alloy comprising a primary element comprising Ni, fe, co, cr and a secondary element comprising Al, ti, W, mo, nb, whereby by adding the secondary element,
so that the principal elements introduce different precipitations.
Further, the atomic percentage content of each element in the main element and the auxiliary element is as follows,
principal element, ni 22at.% to 25% at.%, fe 13at.% to 16at.%, co 32.5at.% to 35.5at.%, cr 12at.% to 15at.%;
by-element, 3.0at.% to 5.0at.% of Al, 1.5at.% to 3.5at.% of Ti, 0.5at.% to 2.0at.% of W, 1.0at.% to 2.5at.% of Mo, and 0.25at.% to 1.25at.% of Nb.
The preparation method of the ultra-high strength-plasticity matched high-entropy alloy comprises the following steps of:
firstly, alloy smelting: the method comprises the steps of (1) taking a metal simple substance Ni, fe, co, cr, al, ti, W, mo, nb as a raw material, designing component proportions according to the atomic percentage content of each element of the high-entropy alloy to obtain pure metal with the purity of more than 99.95 wt%, putting the pure metal into an induction smelting furnace for smelting to obtain a multi-main-element alloy melt, and casting the multi-main-element alloy melt into a die to form an ingot blank;
second, homogenizing: homogenizing the ingot blank in a vacuum heat treatment furnace at 1200 ℃ for 24 hours, and then taking out and air cooling to obtain a first alloy body;
thirdly, forging and forming: heating the first alloy body to 1200 ℃, and then performing hot forging to forge the first alloy body into a second alloy body with a specified size;
fourth, solution treatment: placing the second alloy body into a vacuum furnace with the temperature of 1200 ℃ for heat preservation for 2 hours, and then performing water quenching to obtain a third alloy body;
fifth, cold rolling: rolling the third alloy body by 75% -90% of pushing-down amount in multiple passes at room temperature, and rolling the third alloy body into a fourth alloy body with a specified size;
sixth, annealing: the fourth alloy body is subjected to water quenching after heat preservation for 30 minutes at 750-900 ℃ to obtain a fifth alloy body;
seventh, aging treatment: and (3) carrying out air cooling on the fifth alloy body after heat preservation for 48 hours at the temperature of 500-600 ℃ to obtain a high-entropy alloy finished product.
Further, the ingot blank includes an ingot body blank and an ingot plate body blank, the ingot plate blank being a blank obtained by cutting the ingot body blank.
Further, the cross-sectional area of the ingot rod body is as followsThe size of the cross-sectional area of the ingot plate body blank is +.>
Further, the fourth alloy body is subjected to water quenching after being subjected to heat preservation for 30 minutes at 800 ℃ or 825 ℃ or 850 ℃ to obtain a fifth alloy body.
The ultrahigh strength-plasticity matched high-entropy alloy and the preparation method thereof provided by the embodiment of the application have at least the following beneficial effects:
according to the application, different precipitates are introduced to obtain a multi-main element alloy product through adding the auxiliary element W, mo, al, ti and Nb, and the multi-main element alloy product is subjected to forging, rolling, annealing and aging processes, so that the high-entropy alloy has a heterogeneous microstructure, so that the precipitation strengthening is greatly improved, ultrafine recrystallized grains are generated and a certain number of dislocation is reserved, the high-entropy alloy is greatly improved, and meanwhile, the high elongation and the positive hardening rate are also maintained;
the high-entropy alloy prepared by the method can be used for preparing plates and bars with a certain volume, changes the condition that the traditional ultrahigh-strength high-entropy alloy can only be used for preparing high-entropy alloy button ingots with extremely small sizes by using an arc melting furnace, can be applied to the preparation of high-strength bolts and plates in the aviation industry and the like, and has excellent forming property;
the heat treatment process, especially the sixth annealing treatment and the seventh aging treatment, can lead the grain size of the alloy to be extremely fine, and a certain amount of dislocation is reserved to cause work hardening, so that the strength of the alloy is ensured to a certain extent. In addition, the precipitated phase of the alloy under the process can be controlled to the nanometer level, the alloy is strengthened and the plasticity is not reduced sharply, so that the heat treatment process can ensure that the grain size, dislocation number and precipitated phase morphology of the alloy are matched excellently, thereby producing excellent strength-plasticity matched alloy. The optimal strength plastic-matching of the obtained high-entropy alloy can reach rare yield strength of 2.2GPa and elongation of more than 10 percent, and the high-entropy alloy with different strength-plastic matching can be obtained by adjusting a heat treatment process, so that the high-entropy alloy has wide application prospect.
Drawings
FIG. 1 is a graph of the electron back scattering diffraction analysis of the sample prepared in example 1, example 8, example 9 of the present application under a scanning electron microscope;
fig. 2 to 4 are tensile engineering stress-strain curves of the high-entropy alloys prepared in example 1, example 8, and example 9, respectively.
Detailed Description
The present application will be further described below based on preferred embodiments with reference to the accompanying drawings.
In addition, various components on the drawings have been enlarged (thick) or reduced (thin) for ease of understanding, but this is not intended to limit the scope of the application.
The singular forms also include the plural and vice versa.
In the description of the embodiments of the present application, it should be noted that, if the terms "upper," "lower," "inner," "outer," and the like indicate an azimuth or a positional relationship based on that shown in the drawings, or an azimuth or a positional relationship that a product of the embodiments of the present application conventionally put in use, it is merely for convenience of describing the present application and simplifying the description, and does not indicate or imply that the device or element to be referred to must have a specific azimuth, be configured and operated in a specific azimuth, and thus should not be construed as limiting the present application. Furthermore, in the description of the present application, terms first, second, etc. are used herein for distinguishing between different elements, but not limited to the order of manufacture, and should not be construed as indicating or implying any relative importance, as such may be different in terms of its detailed description and claims.
The terminology used in the description presented herein is for the purpose of describing embodiments of the application and is not intended to be limiting of the application. It should also be noted that unless explicitly stated or limited otherwise, the terms "disposed," "connected," and "connected" should be construed broadly, and may be, for example, fixedly connected, detachably connected, or integrally connected; the two components can be connected mechanically, directly or indirectly through an intermediate medium, and can be communicated internally. The specific meaning of the above terms in the present application will be specifically understood by those skilled in the art.
An ultra-high strength-plastic matched high-entropy alloy comprising a primary element comprising Ni, fe, co, cr and a secondary element comprising Al, ti, W, mo, nb, whereby the primary element incorporates different precipitates by addition of the secondary element.
The high-entropy alloy comprises the following elements in percentage by atom:
principal element, ni 22at.% to 25% at.%, fe 13at.% to 16at.%, co 32.5at.% to 35.5at.%, cr 12at.% to 15at.%;
by-element, 3.0at.% to 5.0at.% of Al, 1.5at.% to 3.5at.% of Ti, 0.5at.% to 2.0at.% of W, 1.0at.% to 2.5at.% of Mo, and 0.25at.% to 1.25at.% of Nb.
Wherein, the single impurity element in the impurity is less than or equal to 0.05at percent, and the total amount of all impurity elements is less than or equal to 0.15at percent.
Preferably, the purity of each elemental metal is 99.95wt.% or more.
The addition of W, mo, al, ti and Nb in the minor element is to introduce different precipitates to obtain a multi-main element alloy product for further playing the role of precipitation strengthening, and the high-entropy alloy presents a heterogeneous microstructure after the multi-main element alloy product is subjected to forging, rolling, annealing and aging processes, so that the high-entropy alloy can generate superfine recrystallized grains and retain a certain number of dislocation while the precipitation strengthening is greatly improved, and the high-entropy alloy not only greatly improves the strength, but also maintains the high elongation and the positive hardening rate.
The preparation method of the ultrahigh strength-plasticity matched high-entropy alloy comprises the following steps:
firstly, alloy smelting: the method comprises the steps of (1) taking a metal simple substance Ni, fe, co, cr, al, ti, W, mo, nb as a raw material, designing component proportions according to the atomic percentage content of each element of the high-entropy alloy to obtain pure metal with the purity of more than 99.95 wt%, putting the pure metal into an induction smelting furnace for smelting to obtain a multi-main-element alloy melt, and casting the multi-main-element alloy melt into a die to form an ingot blank;
second, homogenizing: homogenizing the ingot blank in a vacuum heat treatment furnace at 1200 ℃ for 24 hours, and then taking out and air cooling to obtain a first alloy body;
thirdly, forging and forming: heating the first alloy body to 1200 ℃, and then performing hot forging to forge the first alloy body into a second alloy body with a specified size;
fourth, solution treatment: placing the second alloy body into a vacuum furnace with the temperature of 1200 ℃ for heat preservation for 2 hours, and then performing water quenching to obtain a third alloy body;
fifth, cold rolling: rolling the third alloy body by 75% -90% of pushing-down amount in multiple passes at room temperature, and rolling the third alloy body into a fourth alloy body with a specified size;
in general, the total rolling reduction of the cold rolling treatment is generally 60% -90%, and the fourth alloy obtained after rolling with 75% -90% of the rolling reduction is measured by repeated experiments and has uniform structure, excellent surface quality and more excellent mechanical property and technological property.
Sixth, annealing: the fourth alloy body is subjected to water quenching after heat preservation for 30 minutes at 750-900 ℃ to obtain a fifth alloy body, and the fifth alloy body is used for recrystallizing a cold rolling deformation structure of the alloy through high-temperature annealing to improve the plasticity of the alloy, slightly reduce the strength and keep the heat for 30 minutes for a short time, so that the excessive growth of crystal grains is prevented, fine grain strengthening is not facilitated, and the strength and the plasticity are positively influenced by the fine grain strengthening;
seventh, aging treatment: and (3) carrying out air cooling on the fifth alloy body after heat preservation for 48 hours at the temperature of 500-600 ℃ to obtain a high-entropy alloy finished product, wherein the long-time aging at low temperature is in the meaning of slowly precipitating a precipitated phase of the alloy at low temperature, and the strength of the alloy is further improved without generating severe reduction of plasticity in order to generate a large amount of fine second-phase precipitates.
Further, in the first step of the above preparation method, the ingot blank includes an ingot body blank and an ingot plate body blank, wherein the ingot plate blank is a blank obtained by cutting the ingot body blank in a wire cutting manner.
In some preferred embodiments, the ingot body billet cross-sectional area is of the size ofThe size of the cross-sectional area of the ingot plate body blank is +.>
Correspondingly, in the second step of the preparation method, the first alloy body comprises a first alloy rod body and a first alloy plate body, wherein the first alloy rod body and the first alloy plate body are alloy bodies obtained by homogenizing ingot rod body blanks and ingot plate body blanks respectively.
Correspondingly, in the third step of the preparation method, the second alloy body comprises 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 alloy bodies obtained by forging and forming 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 body is a short bar of 60mm diameter, and the second alloy plate body is a square plate of 15mm thickness.
Correspondingly, in the fourth step of the preparation method, the third alloy body comprises 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 alloy bodies obtained by solution treatment of the second alloy rod body and the second alloy plate body.
Correspondingly, in the fifth step of the preparation method, the fourth alloy body comprises a fourth alloy rod body and a fourth alloy plate body, and the fourth alloy rod body and the fourth alloy plate body are alloy bodies obtained by cold rolling treatment of the third alloy rod body and the third alloy plate body respectively.
In some preferred embodiments, after the fifth rolling step, the fourth alloy rod has a diameter of 19mm and the fourth alloy plate has a thickness of 1.5mm.
Correspondingly, in the sixth step of the preparation method, the fifth alloy body comprises 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 obtained by annealing the fourth alloy rod body and the fourth alloy plate body.
Correspondingly, in the seventh step of the preparation method, the high-entropy alloy finished product comprises a high-entropy alloy rod body finished product and a high-entropy alloy plate body finished product, wherein the high-entropy alloy rod body finished product and the high-entropy alloy plate body finished product are finished products obtained by ageing treatment of the fifth alloy rod body and the fifth alloy plate body respectively.
Through the heat treatment process of the specific process, the grain size of the alloy is extremely fine, and a certain volume fraction of deformed tissue is reserved for certain work hardening, so that the strength of the alloy is ensured to a certain extent. The alloy is aged for a long time at a low temperature, so that the precipitated phase can be controlled to the nanometer level, the alloy is strengthened and the plasticity is not reduced, and therefore, the grain size, dislocation number and precipitated phase morphology of the alloy can be perfectly matched by using a specific heat treatment process, and the high-entropy alloy with excellent strength-plasticity matching is produced. The heat treatment has the meaning of enabling the grain size, dislocation density, recrystallization percentage and morphology of a precipitated phase in the structure of the alloy to achieve good matching, thereby generating excellent strength plastic matching performance.
Example 1
Firstly, alloy smelting: using a metal simple substance Ni, fe, co, cr, al, ti, W, mo, nb as a raw material according to Co: cr: fe: ni: w: mo: al: ti: nb=34.25%: 15%:15%:24%:1.5%:1.5%:5%:3%: proportioning 0.75 atomic percent, accurately weighing 20kg of mixed raw materials, putting into an induction smelting furnace, smelting and casting to obtain the alloy with the cross-sectional area size ofIs cut into a cross-sectional area size by wire cutting>Is a cast ingot plate blank;
second, homogenizing: homogenizing the ingot plate blank in a vacuum heat treatment furnace at 1200 ℃ for 24 hours, and then taking out and air cooling to obtain a first alloy plate body;
thirdly, forging and forming: heating the first alloy plate body to 1200 ℃, and then performing hot forging to forge the first alloy plate body into a second alloy plate body with the thickness of 15 mm;
fourth, solution treatment: placing the second alloy plate body into a vacuum furnace at 1200 ℃ for heat preservation for 2 hours, and then performing water quenching to obtain a third alloy plate body;
fifth, cold rolling: rolling the third alloy plate body by 90% pressing quantity in multiple passes at room temperature until a fourth alloy plate body with the thickness of 1.5mm is obtained;
sixth, annealing: the fourth alloy plate body is subjected to water quenching after heat preservation for 30 minutes at 800 ℃ to obtain a fifth alloy plate body;
seventh, aging treatment: and (3) carrying out air cooling on the fifth alloy plate body after heat preservation for 48 hours at 500 ℃ to obtain a high-entropy alloy plate body finished product, and marking the high-entropy alloy plate body finished product as the high-entropy alloy 1.
Examples 2 to 6:
based on example 1, only the atomic percentages between Ni, fe, co, cr, al, ti, W, mo, nb were changed,
other steps and conditions are the same as those in example 1, and high-entropy alloys 2 to 6 are prepared respectively; wherein, the atomic percentages between Ni, fe, co, cr, al, ti, W, mo, nb are shown in Table 1:
TABLE 1
Examples 7 to 10
On the basis of the embodiment 1, the atomic percentage of Ni, fe, co, cr, al, ti, W, mo, nb is not changed, the heat preservation temperature in the sixth step is only changed, the fourth alloy plate body obtained through the fifth step is respectively subjected to water quenching after being subjected to heat preservation at 750 ℃, 825 ℃, 850 ℃ and 900 ℃ for 30 minutes, and the rest steps and conditions are the same as those of the embodiment 1, so that the high-entropy alloy 7, the high-entropy alloy 8, the high-entropy alloy 9 and the high-entropy alloy 10 are respectively prepared.
Example 11
On the basis of example 1, the atom percentage of Ni, fe, co, cr, al, ti, W, mo, nb is not changed, only the cold rolling reduction in the fifth step is changed, the third alloy plate body obtained through the fourth step is rolled by 75% reduction in multiple passes at room temperature, and the rest steps are the same as in example 1, so that the high-entropy alloy 11 is prepared.
Example 12
Based on example 1, the heat preservation temperature in the seventh step is only changed without changing the atomic percentage between Ni, fe, co, cr, al, ti, W, mo, nb, the fifth alloy plate body obtained by the sixth step is subjected to air cooling after being subjected to heat preservation at 600 ℃ for 48 hours, and the rest steps are the same as those in example 1, so that the high-entropy alloy 12 is prepared.
The high-entropy alloys 1 to 12 prepared in the above examples were respectively subjected to room temperature quasi-static tensile mechanical property test, and the results are shown in Table 2.
TABLE 2
Analysis of Table 2 shows that the yield strength of the high-entropy alloy in each example of the application is over 1700MPa, the tensile strength is over 2.0GPa, and comparison of analysis examples 1 and examples 7-10 shows that the cold-rolled deformation structure of the alloy can be recrystallized through high-temperature annealing, so that the plasticity of the alloy is improved, and the strength is slightly reduced; comparative analysis of example 1, example 12 shows that aging is carried out for a long time at low temperature, and the strength of the alloy is further improved at low temperature without causing a drastic decrease in plasticity; comparative analysis example 1 and example 11 showed that the fourth alloy obtained after rolling had a uniform structure and a superior surface quality as the pressing amount was larger, and the high-entropy alloy had a higher strength and a lower molding.
To more intuitively demonstrate the fact that the multi-principal element alloy product is obtained by adding W, mo, al, ti and Nb in the secondary element to the principal element, and the strength of the obtained high-entropy alloy is greatly improved while maintaining the high elongation and positive hardening rate after forging, rolling, annealing and aging the multi-principal element alloy product, the following is further described with reference to fig. 1 to 4:
fig. 1 is a graph of a Scanning Electron Microscope (SEM) image and an electron back-scattering diffraction analysis graph of samples prepared in example 1, example 8 and example 9 according to the present application, wherein (a), (b) and (c) represent the high-entropy alloy 1 in example 1, the high-entropy alloy 8 in example 8 and the high-entropy alloy 9 in example 9, respectively, and after 90% rolling, annealing and aging, as shown in fig. 1, phase particles rich in (Ti, nb) were observed to be aligned in the rolling direction (indicated by yellow arrows) in the SEM image, and no cracks were found around them.
After annealing and aging, the shear band recrystallized and the sigma phase precipitated in submicron size (indicated by the red arrows). In this case, shear bands were still observed under SEM.
After annealing and aging, recrystallized grains are well observed in the EBSD-IPF pattern (electron back-scattered-reverse polar pattern). KAM plot (Kernel Average Misorientation local orientation difference) shows that dislocation strain in recrystallized regions is reduced and recrystallized areas are smaller. Under SEM observation, as the annealing temperature increases, the recrystallized region expands, the shear band disappears, and the number of submicron sigma phase particles is maximized at 825 ℃, the annealing yield is increased to 850 ℃, and the content is reduced. Annealing at high temperature, EBSD pattern clearly shows recrystallized grains with very Gao Fendu rate due to more adequate recrystallization. KAM plots show a further reduction in dislocation strain, indicating that the alloy is more fully recrystallized after annealing at higher temperatures.
Fig. 2 to fig. 4 show tensile engineering stress-strain curves of the high-entropy alloys prepared in examples 1, 8 and 9, wherein the ordinate is stress and the abscissa is strain, and as shown in fig. 2 to fig. 4, the yield strengths of the high-entropy alloys in examples 1, 8 and 9 of the present application reach 1700MPa or more, the tensile strengths reach 2.0GPa or more, and the strength is high. Regarding plasticity, after the alloy is subjected to thermal mechanical treatment, certain plasticity is still reserved, so that certain engineering application can be met.
Comparing the three stress strain curves, it can be seen that the high-entropy alloy 1 subjected to water quenching after heat preservation at 800 ℃ for 30 minutes and air cooling aging treatment after heat preservation at 500 ℃ for 48 hours has the highest strength, the tensile strength is 2606MPa, the yield strength is 2486MPa, and the plasticity is lower than 3.5%.
The high-entropy alloy with the best plasticity is the high-entropy alloy 9 which is water quenched after being kept at 850 ℃ for 30 minutes, and the elongation percentage is 17.9 percent, but the yield strength is only 1138MPa. The alloy with better strong plastic bonding is the high-entropy alloy 8 which is water quenched after being preserved for 30 minutes at 825 ℃, the yield strength is 2221MPa, and the elongation percentage is 11.2%.
While the foregoing is directed to embodiments of the present application, other and further embodiments of the application may be devised without departing from the basic scope thereof, and the scope thereof is determined by the claims that follow.
Claims (5)
1. An ultra-high strength-plasticity matched high entropy alloy, characterized by:
the high-entropy alloy comprises a main element and a minor element, wherein the main element comprises Ni, fe, co, cr, the minor element comprises Al, ti, W, mo, nb, and different precipitates are introduced into the main element by adding the minor element;
the atomic percentage content of each element in the main element and the auxiliary element is as follows,
principal element, ni 22at.% to 25% at.%, fe 13at.% to 16at.%, co 32.5at.% to 35.5at.%, cr 12at.% to 15at.%;
by-element, 3.0at.% to 5.0at.% of Al, 1.5at.% to 3.5at.% of Ti, 0.5at.% to 2.0at.% of W, 1.0at.% to 2.5at.% of Mo, and 0.25at.% to 1.25at.% of Nb.
The high-entropy alloy is prepared by the following steps:
firstly, alloy smelting: the method comprises the steps of (1) taking a metal simple substance Ni, fe, co, cr, al, ti, W, mo, nb as a raw material, designing component proportions according to the atomic percentage content of each element of the high-entropy alloy to obtain pure metal with the purity of more than 99.95 wt%, putting the pure metal into an induction smelting furnace for smelting to obtain a multi-main-element alloy melt, and casting the multi-main-element alloy melt into a die to form an ingot blank;
second, homogenizing: homogenizing the ingot blank in a vacuum heat treatment furnace at 1200 ℃ for 24 hours, and then taking out and air cooling to obtain a first alloy body;
thirdly, forging and forming: heating the first alloy body to 1200 ℃, and then performing hot forging to forge the first alloy body into a second alloy body with a specified size;
fourth, solution treatment: placing the second alloy body into a vacuum furnace with the temperature of 1200 ℃ for heat preservation for 2 hours, and then performing water quenching to obtain a third alloy body;
fifth, cold rolling: rolling the third alloy body by 75% -90% of pushing-down amount in multiple passes at room temperature, and rolling the third alloy body into a fourth alloy body with a specified size;
sixth, annealing: the fourth alloy body is subjected to water quenching after heat preservation for 30 minutes at 750-900 ℃ to obtain a fifth alloy body;
seventh, aging treatment: and (3) carrying out air cooling on the fifth alloy body after heat preservation for 48 hours at the temperature of 500-600 ℃ to obtain a high-entropy alloy finished product.
2. A method of preparing an ultra-high strength-plastic matched high entropy alloy according to claim 1, comprising the steps of:
firstly, alloy smelting: the method comprises the steps of (1) taking a metal simple substance Ni, fe, co, cr, al, ti, W, mo, nb as a raw material, designing component proportions according to the atomic percentage content of each element of the high-entropy alloy to obtain pure metal with the purity of more than 99.95 wt%, putting the pure metal into an induction smelting furnace for smelting to obtain a multi-main-element alloy melt, and casting the multi-main-element alloy melt into a die to form an ingot blank;
second, homogenizing: homogenizing the ingot blank in a vacuum heat treatment furnace at 1200 ℃ for 24 hours, and then taking out and air cooling to obtain a first alloy body;
thirdly, forging and forming: heating the first alloy body to 1200 ℃, and then performing hot forging to forge the first alloy body into a second alloy body with a specified size;
fourth, solution treatment: placing the second alloy body into a vacuum furnace with the temperature of 1200 ℃ for heat preservation for 2 hours, and then performing water quenching to obtain a third alloy body;
fifth, cold rolling: rolling the third alloy body by 75% -90% of pushing-down amount in multiple passes at room temperature, and rolling the third alloy body into a fourth alloy body with a specified size;
sixth, annealing: the fourth alloy body is subjected to water quenching after heat preservation for 30 minutes at 750-900 ℃ to obtain a fifth alloy body;
seventh, aging treatment: and (3) carrying out air cooling on the fifth alloy body after heat preservation for 48 hours at the temperature of 500-600 ℃ to obtain a high-entropy alloy finished product.
3. The method for preparing the ultrahigh strength-plasticity matched high-entropy alloy according to claim 2, wherein the method comprises the following steps:
the ingot blank includes an ingot body blank and an ingot plate body blank, which is a blank obtained by cutting the ingot body blank.
4. A method for preparing an ultra-high strength-plasticity matched high-entropy alloy according to claim 3, wherein:
the cross-sectional area of the ingot casting bar body blank is phi 180mm multiplied by 350mm, and the cross-sectional area of the ingot casting plate body blank is phi 180mm multiplied by 50mm.
5. The method for preparing the ultrahigh strength-plasticity matched high-entropy alloy according to claim 2, wherein the method comprises the following steps:
and (3) preserving the temperature of the fourth alloy body at 800 ℃, 825 ℃ or 850 ℃ for 30 minutes, and then carrying out water quenching to obtain a fifth alloy body.
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