A eutectic high-entropy soft magnetic alloy, a preparation method and application thereof

Abstract

The application provides a eutectic high-entropy soft magnetic alloy and a preparation method and application thereof, and relates to the technical field of high-entropy alloys. a M b )Nb c B d C e , M is at least one of Co and Ni; a, b, c, d and e are the molar percentage contents of corresponding elements, 20 <= a <= 45, 20 <= b <= 60, 5 <= c <= 15, 5 <= d <= 15, 0 < e <= 1, and a + b + c + d + e = 100. The application obtains a eutectic high-entropy alloy material with excellent soft magnetic properties, mechanical properties and plastic deformation capacity through unique alloy component design and specific preparation process; meanwhile, the preparation process is simple and easy to implement, the flow is short, meets the requirements of industrial production, and has a wide application prospect.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of high-entropy alloys, in particular to a eutectic high-entropy soft magnetic alloy and a preparation method and application thereof. BACKGROUND

[0002] High-entropy alloys (also known as multi-principal element alloys, HEA) are alloys formed by five or more than five equal or approximately equal amounts of metals; due to the fact that high-entropy alloys can have many desirable properties, they have attracted considerable attention in the field of materials science and engineering, and have become a new research frontier in the field of metal materials. However, due to the limitation of raw material cost, its application is mostly limited to high-end advanced systems such as airplanes or submarines. On the other hand, compared with traditional alloys, most high-entropy alloys do not show particularly superior mechanical properties if they only have a single solid solution structure; therefore, researchers have turned to developing high-entropy alloys with multi-phase solid solution structures to improve their mechanical properties, but this often leads to the problem of poor castability of high-entropy alloys.

[0003] In fact, the casting of high-entropy alloys, especially large-scale casting (kilogram level or above), is often a challenge because most high-entropy alloys do not have good castability and show considerable chemical heterogeneity in the high-entropy alloys obtained by direct casting, which hinders their industrial application. At the same time, another technical problem related to the casting of high-entropy alloys is its coarse grain and precipitate microstructure, as well as relatively poor mechanical properties. The currently widely used cast high-entropy alloys, even if they have matching strength, show significantly lower tensile ductility and strength than their forged counterparts; this is because most high-entropy alloys, due to their poor castability, are often designed for forging and subsequent heat treatment processes, and their microstructure in the cast state is not designed and optimized.

[0004] Eutectic alloy refers to an alloy at eutectic composition, whose solidification structure is entirely composed of eutectic; the components constituting the eutectic phase diagram can be infinitely soluble in liquid state, but can only be partially soluble or even completely insoluble in solid state. Generally, the eutectic alloy has the following characteristics: 1, near-equilibrium microstructure; 2, low-energy phase interface; 3, controllable microstructure; 4, high fracture strength; 5, good high-temperature creep resistance; 6, regular sheet or rod-shaped eutectic structure formed in situ composite; 7, good castability; 8, since the eutectic reaction is an isothermal transformation without solidification temperature range, segregation and shrinkage can be greatly alleviated. From the perspective of mechanical properties, generally, high-entropy alloys with single-phase body-centered cubic (BCC) structure have limited ductility, while high-entropy alloys with single-phase face-centered cubic (FCC) structure can have higher ductility, but their strength is very low. How to achieve high strength and high ductility at the same time is another challenge for the engineering application of high-entropy alloys. At the same time, the processability of most high-entropy alloys is relatively poor, which greatly increases their production cost in the manufacturing process. It can be seen that the eutectic alloy has a theoretically feasible improvement and compensation for the defects of high-entropy alloys, and it is imperative to develop low-cost and high-performance eutectic high-entropy alloys with near-net-shape manufacturing capability.

[0005] Many metal parts of industrial equipment are directly cast, such as propellers, generator housings, engine housings, and various metal ball valves, adapters, etc. If the casting quality is poor, it is impossible to eliminate casting defects through thermal mechanical treatment, especially for complex or large ingots. At the same time, eutectic high-entropy alloys are rarely studied in terms of function, and existing technologies in this regard are not mature. There is no detailed research on how to design the composition and optimize the performance of magnetic eutectic high-entropy alloys. Therefore, if a eutectic high-entropy alloy with a composite phase structure can be prepared, it is foreseeable that it will have excellent mechanical properties and castability.

[0006] In view of this, the present application is proposed. SUMMARY

[0007] The first object of the present application is to provide a eutectic high-entropy soft magnetic alloy, which fully utilizes and combines the advantages of eutectic alloys and high-entropy alloys, and obtains a new alloy with high yield strength, strong plasticity and good magnetic properties.

[0008] The high-entropy alloy with single-phase structure is easy to migrate due to no pinning pressure of precipitated phase to interface, thus leading to grain coarsening, and according to Hall-Petch relationship, the single-phase high-entropy alloy tends to result in lower yield strength; while the eutectic structure tends to have fine lamellas, which is beneficial to improve the yield strength, and meanwhile, due to the existence of high-density interface, the dislocation accumulation on the interface is low, and the stress concentration is small, which is beneficial to improve the toughness of the material. The eutectic high-entropy soft magnetic alloy has a multiphase composition and a continuous lamellar network structure, and has the mechanical properties of eutectic alloy and high-entropy alloy, and has good magnetic properties, especially has a high saturation magnetic induction.

[0009] A eutectic high-entropy soft magnetic alloy, the alloy components are (Fe a M b )Nb c B d C e , M is at least one of Co and Ni; a, b, c, d and e are the molar percentage contents of the corresponding elements, 20≤a≤45, 20≤b≤60, 5≤c≤15, 5≤d≤15, 0<e≤1, and a+b+c+d+e=100.

[0010] Preferably, 25≤a≤42, 20≤b≤42, 7≤c≤11, 8≤d≤12, 0<e≤0.5;

[0011] Optionally, a includes but is not limited to 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, b includes but is not limited to 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, c includes but is not limited to 7, 8, 9, 10, 11, d includes but is not limited to 8, 9, 10, 11, 12, and e includes but is not limited to 0.01, 0.05, 0.1, 0.15, 0.2, 0.25, 0.3, 0.35, 0.4, 0.45, 0.5; it should be noted that a, b, c, d and e can adopt the point values as listed above, can adopt the numerical interval formed by the above point values, and can adopt any real number in the numerical interval;

[0012] More preferably, c=9; more preferably, d=10; more preferably, e=0.1.

[0013] In the present application, the niobium element can make the Fe-Co-Ni alloy have a higher liquidus slope during solidification, thus being beneficial to the generation of eutectic reaction. Meanwhile, the addition of niobium element is beneficial to improve the melting point of the alloy to a certain extent, thus generating a larger supercooling degree during solidification, which is beneficial to the refinement of eutectic structure.

[0014] In the present application, boron element can not only be used as interstitial solute to greatly improve the strength of the designed alloy, but also can optimize the soft magnetic properties of the alloy. The main reason is that the B s size is mainly determined by the average magnetic moment of the alloy, the larger the magnetic moment of the alloy, the higher the B s ; and the average magnetic moment is mainly related to the composition, the p energy band electron number of B element is 1, and 1.6 p energy band electrons can migrate to the d energy band of transition element, thereby improving the atomic magnetic moment.

[0015] In the present application, trace amount of carbon element can not only effectively refine the grain size of the alloy, but also effectively increase the atomic magnetic moment to improve the saturation magnetic induction strength; and it is found that trace amount of carbon element also has a positive effect on the coercive force of the soft magnetic alloy. However, it should be noted that too high carbon content will cause the decline of the soft magnetic properties of the material, so the molar percentage of carbon should be kept between 0 and 1%.

[0016] The second object of the present application is to provide a preparation method of the eutectic high-entropy soft magnetic alloy, which has simple process conditions, easy operation and is suitable for batch industrial production. The preparation method comprises the following steps:

[0017] S1, the raw material components include Fe, FeC, Nb and B, and at least one of Co or Ni;

[0018] S2, the raw material components are placed in a vacuum non-consumable arc melting furnace for melting, and after repeated melting for 4-8 times, an alloy ingot is obtained;

[0019] S3, the alloy ingot is melted by induction heating to obtain an alloy melt, and then the alloy melt is cooled by rapid quenching technology to obtain a eutectic high-entropy soft magnetic alloy.

[0020] Preferably, in step S1, the purity of Fe is 99.95wt.%, the purity of FeC is 99.5wt.%, the purity of Co is 99.99wt.%, the purity of Ni is 99.99wt.%, the purity of Nb is 99.99wt.%, and the purity of B is 99.9wt.%.

[0021] Preferably, in step S2, the temperature of each melting is 2400-3000℃, and the time of each melting is 5-10min.

[0022] More preferably, in step S2, the temperature of each of the melting includes but is not limited to 2400, 2450, 2500, 2550, 2600, 2650, 2700, 2750, 2800, 2850, 2900, 2950, 3000 (°C), and the time of each of the melting includes but is not limited to 5, 6, 7, 8, 9, 10 (min).

[0023] Preferably, in step S2, the vacuum degree of the vacuum non-consumable arc melting furnace is 3.0 x 10 -3 Pa ~ 6.0 x 10 -3 Pa.

[0024] More preferably, in step S2, the vacuum degree of the vacuum non-consumable arc melting furnace includes but is not limited to 3.0 x 10 -3 , 4.0 x 10 -3 , 5.0 x 10 -3 , 6.0 x 10 -3 (Pa).

[0025] Preferably, in step S2, after vacuumizing and before heating and melting, the inert protective gas is filled at a pressure of 0.04 MPa ~ 0.06 MPa.

[0026] More preferably, the inert protective gas includes but is not limited to (high purity, 99.999%) helium, neon or argon, etc.

[0027] Preferably, in step S3, before the induction heating, the furnace cavity in which the alloy ingot is placed is vacuumized, and then the inert protective gas is filled.

[0028] More preferably, the type and pressure condition of the inert protective gas used in this step S3 are the same as the preferred conditions provided in step S2, and are independently selected according to the preferred conditions provided in step S2.

[0029] More preferably, the vacuum degree of the vacuumized furnace cavity is 3.0 x 10 -3 Pa ~ 9.0 x 10 -3 Pa.

[0030] Further preferably, the vacuum degree of the vacuumized furnace cavity includes but is not limited to 3.0 x 10 -3 , 4.0 x 10 -3 , 5.0 x 10 -3 , 6.0 x 10 -3 , 7.0 x 10 -3 , 8.0 x 10 -3 , 9.0 x 10 -3 (Pa).

[0031] Preferably, in step S3, the rapid quenching technology comprises the following steps: the alloy melt is sprayed into a copper mold by pressure difference, and the eutectic high-entropy soft magnetic alloy is obtained after cooling.

[0032] Preferably, in step S3, the following specific method can be used: the alloy ingot is broken and then placed into a quartz tube with a slit (or a through hole) at the bottom; the quartz tube is placed into an induction coil in a cavity of a rapid quenching device, and the nozzle of the quartz tube is about 1.0 mm away from the rapid quenching copper mold; the cavity of the rapid quenching device is pumped to a specific vacuum degree, and then inert protective gas is filled into the cavity; the induction heating power is turned on to completely melt the alloy ingot, and then the protective gas is blown in, and the alloy melt is sprayed into the rapid quenching copper mold by using the pressure difference between the inside and outside of the quartz tube, and the eutectic high-entropy soft magnetic alloy is obtained after cooling.

[0033] In the present application, the desired microstructure is obtained by the rapid quenching technology; the high-temperature alloy melt is sprayed into a water-cooled copper mold with a specific mold shape and cooled at a very fast speed, which greatly refines the eutectic lamellar size; at the same time, the faster cooling speed can reduce or even inhibit the composition segregation at the grain boundary, prevent the weakening of the grain boundary strength, and thus effectively improve the strength and toughness of the eutectic high-entropy alloy. Compared with the traditional casting method of eutectic alloy, the present application avoids the wide dual-phase lamellar structure in the grains, which leads to the defects of low plasticity and strength.

[0034] A third object of the present application is to provide an alloy casting comprising the eutectic high-entropy soft magnetic alloy.

[0035] A fourth object of the present application is to provide the application of the eutectic high-entropy soft magnetic alloy in the fields of structure monitoring, automobiles, aerospace, etc.

[0036] Compared with the prior art, the present application has the following advantages:

[0037] (1) The present application provides a eutectic high-entropy alloy material with a completely new element composition, which has excellent soft magnetic properties and mechanical properties (high yield strength or tensile strength), is composed of multiple phases and has a continuous lamellar network structure, and the microstructure is uniform and controllable; especially in terms of magnetic properties, the present application obtains the eutectic high-entropy alloy with the best soft magnetic properties in the prior art, which provides theoretical and experimental guidance for the further research and application of high-entropy alloys.

[0038] (2) Due to the unique alloy composition design of the present application, the micron-scale precipitated phase of the alloy has a certain plastic deformation capacity, so that the precipitated phase can not only provide sliding resistance during plastic deformation, but also prevent cracks from being generated due to stress concentration, so that the alloy has good strength and plasticity.

[0039] (3) The preparation process of the eutectic high-entropy soft magnetic alloy of the present application can be obtained by near-net forming casting, without the need for forging and subsequent complex heat treatment process (such as the need for complex annealing process treatment, etc.), short process, in line with the requirements of industrial production, providing more material selection space for the upgrading of traditional industry and the development of high-tech industry. BRIEF DESCRIPTION OF DRAWINGS

[0040] In order to more clearly illustrate the technical solutions in the specific embodiments or prior art of the present application, the drawings needed in the specific embodiments or prior art description will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present application, and those skilled in the art can obtain other drawings based on these drawings without creative labor.

[0041] Figure 1 The XRD curve of the alloy prepared in Example 1-3 of the present application is provided;

[0042] Figure 2 The micro scanning electron microscope image of the alloy prepared in Example 2 of the present application is provided. DETAILED DESCRIPTION

[0043] The technical solutions of the present application will be described clearly and completely below in combination with the drawings and specific embodiments, but those skilled in the art will understand that the following described embodiments are part of the embodiments of the present application, not all the embodiments, and should not be regarded as limiting the scope of the present application. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor are within the scope of protection of the present application. The specific conditions are not specified in the embodiments, which are carried out according to the conventional conditions or the conditions recommended by the manufacturer. The reagents or instruments used are not specified by the manufacturer, which are conventional products that can be purchased on the market.

[0044] EMBODIMENT

[0045] The present embodiment provides a (FeCoNi)NbBC eutectic high-entropy soft magnetic alloy with high strength, and the preparation method thereof comprises the following steps:

[0046] (1) Selecting Fe with a purity of 99.95wt.%, FeC with a purity of 99.5wt.%, Co with a purity of 99.99wt.%, Ni with a purity of 99.99wt.%, Nb with a purity of 99.99wt.% and B with a purity of 99.9wt.% as raw materials, and weighing and batching according to the atomic percentage content in the above alloy expression;

[0047] (2) Placing the prepared raw materials into a vacuum non-consumable arc melting furnace, and vacuumizing to a vacuum degree of 5.0×10-3 Pa, the argon protective gas with a pressure of 0.05 MPa, the smelting temperature is 2600℃, each smelting is 8 min, and the composition is ensured to be uniform after repeated smelting for 6 times, and the master alloy ingot is obtained by cooling in the furnace;

[0048] (3) The smelted master alloy is broken into small pieces, the master alloy is clamped into a quartz tube with a slit at the bottom, the quartz tube is placed in the induction coil of the melt rapid quenching equipment cavity, the nozzle of the quartz tube is about 1.0 mm away from the rapid quenching copper mold; the induction melt rapid quenching equipment cavity is pumped to 6.0 x 10 -3 Pa vacuum degree, 0.05 MPa of 99.999% pure argon is filled into the rear cavity; the induction heating power is turned on to completely melt the master alloy in the quartz tube, argon is blown to use the pressure difference between the inside and outside of the quartz tube to spray the completely melted master alloy melt into the rapid quenching copper mold, thereby preparing a eutectic high-entropy alloy rod with a diameter of 2.0 mm.

[0049] According to the preparation method described in the present embodiment, different element mole percentage ratios are used to obtain the following examples 1-5 with different alloy expressions, and the specific alloy expressions are recorded in Table 1 below.

[0050] Table 1

[0051] Example 1 Fe 40.4 Co 40.5 Nb9B 10 C 0.1 ]]> Example 2 Fe 26.9 Co 27 Ni 27 Nb9B 10 C 0.1 ]]> Example 3 Fe 40.4 Ni 40.5 Nb9B 10 C 0.1 ]]> Example 4 Fe 20 Co 29.5 Ni 30 Nb5B 15 C 0.5 ]]> Example 5 Fe 45 Co 17 Ni 17.7 Nb 15 B5C 0.3 ]]>

[0052] At the same time, Figure 1 The XRD curve of the eutectic high-entropy alloy rod obtained in examples 1, 2 and 3 is provided. From the XRD curve, Figure 1 It can be seen that the XRD curve of the alloy is a Nb(Fe, Co, Ni)B cubic structure (BCC or FCC) dual-phase structure.

[0053] Figure 2 The microstructure electron microscope graph of the eutectic high-entropy alloy rod obtained in example 2 at 2 μm is also provided.

[0054] Comparative example

[0055] The comparative example has the same element mole percentage ratio as example 2. However, the comparative example is prepared according to the following preparation method:

[0056] (1) Selecting Fe with a purity of 99.95wt.%, FeC with a purity of 99.5wt.%, Co with a purity of 99.99wt.%, Ni with a purity of 99.99wt.%, Nb with a purity of 99.99wt.% and B with a purity of 99.9wt.% as raw materials, weighing and batching according to the atomic percentage content in the above alloy expression;

[0057] (2) The prepared raw materials are placed in a vacuum non-consumable arc smelting furnace, and the vacuum degree is pumped to 5.0 x 10-3 Pa, argon protective gas with a filling pressure of 0.05 MPa, smelting temperature of 2600°C, 8 min for each smelting, 6 times of repeated smelting to ensure uniform composition, and then in-rack cooling to obtain the master alloy ingot;

[0058] (3) homogenization annealing at 1000°C for 1 h in a heat treatment furnace, and then water cooling to room temperature, thereby preparing the corresponding high-entropy alloy bulk, and then machining the alloy into a rod.

[0059] The alloy rods prepared in each example and the comparative example were tested for yield strength, fracture strength, ductility, and saturation magnetic induction, and the results are shown in Table 2 below.

[0060] Table 2

[0061]

[0062] Although the present application has been illustrated and described with reference to specific embodiments, it is to be understood that the above examples are merely illustrative of the principles of the application, and are not to be construed as limiting the scope of the application. Those skilled in the art should understand that various modifications of the above-described embodiments, equivalents thereof maybe made that still fall within the spirit and scope of the present application. Accordingly, the true scope of the present application should be determined only by reference to the appended claims.

Claims

1. A eutectic high-entropy soft magnetic alloy, characterized by, The alloy components of the eutectic high-entropy soft magnetic alloy are Fe a M b Nb c B d C e , M is at least one of Co and Ni; a, b, c, d, and e are the molar percentage contents of the corresponding elements, 20≤a≤45, 20≤b≤60, 5≤c≤15, 5≤d≤15, 0<e≤1, and a+b+c+d+e=100. 2.The co-crystal high-entropy soft magnetic alloy according to claim 1, characterized in that, 25≤a≤42, 20≤b≤42, 7≤c≤11, 8≤d≤12, 0 3. The eutectic high-entropy soft magnetic alloy according to claim 2, characterized in that, c=9; d=10; e=0.

1.

4. The preparation method of the eutectic high-entropy soft magnetic alloy according to any one of claims 1-3, characterized in that, The method comprises the following steps: S1, selecting and matching raw material components, the raw material components comprising Fe, FeC, Nb and B, and at least one of Co or Ni; S2, placing the raw material components into a vacuum non-consumable arc smelting furnace for smelting, and obtaining an alloy ingot after repeated smelting for 4-8 times; S3, melting the alloy ingot by induction heating to obtain an alloy melt, and then cooling the alloy melt by a rapid quenching technology to obtain a eutectic high-entropy soft magnetic alloy.

5. The preparation method of the eutectic high-entropy soft magnetic alloy according to claim 4, characterized in that, In step S1, the purity of Fe is 99.95wt.%, the purity of FeC is 99.5wt.%, the purity of Co is 99.99wt.%, the purity of Ni is 99.99wt.%, the purity of Nb is 99.99wt.% and the purity of B is 99.9wt.%.

6. The preparation method of the eutectic high-entropy soft magnetic alloy according to claim 4, characterized in that, In step S2, the temperature of each smelting is 2400-3000°C, and the time of each smelting is 5-10 min.

7. The preparation method of the eutectic high-entropy soft magnetic alloy according to claim 4, characterized in that, In step S2, the vacuum degree of the vacuum non-consumable arc melting furnace is 3.0 x 10 -3 Pa 6.0 x 10 -3 Pa. 8.The method of claim 7, wherein the method further comprises the step of: In step S2, after vacuumizing and before heating and smelting, 0.04-0.06 MPa of inert protective gas is filled. ​ 9.The method of claim 4, wherein the method further comprises the steps of: In step S3, before the induction heating, the furnace cavity where the alloy ingot is placed is vacuumized, and then inert protective gas is filled. ​ The furnace chamber vacuum degree is 3.0 x 10 -3 Pa~9.0 x 10 -3 Pa.

10. The preparation method of the eutectic high-entropy soft magnetic alloy according to claim 4, characterized in that, In step S3, the rapid quenching technology comprises the following steps: the alloy melt is sprayed into a copper mold by pressure difference, and the eutectic high-entropy soft magnetic alloy is obtained after cooling.

11. An alloy casting, characterized by The eutectic high-entropy soft magnetic alloy according to any one of claims 1-3.

12. Use of the eutectic high-entropy soft magnetic alloy according to any one of claims 1-3 in structural monitoring, automotive or aerospace fields.

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