A soft magnetic high entropy alloy with high thermal stability and preparation method thereof

Abstract

The invention discloses a soft magnetic high entropy alloy with high thermal stability and a preparation method thereof, belonging to the technical field of alloy materials. The chemical formula of the soft magnetic high entropy alloy with high thermal stability is Fe 40 Co 40‑ x Ni 10 Al 10 Si x , where 0≤x≤10, and the subscript is the atomic percentage. The soft magnetic high entropy alloy with high thermal stability has a saturation magnetization of ≥155emu / g and a coercive force of ≤3Oe under high temperature and long-term heat treatment conditions. The present invention also discloses a method for preparing a soft magnetic high entropy alloy with high thermal stability, comprising the following steps: stacking Fe, Co, Ni, Al, and Si according to their melting points according to a proportion, and then melting and casting them into alloy ingots by vacuum arc melting; and heat treating the alloy ingots at different temperatures and times. The alloy of the present invention has superior magnetic properties and excellent mechanical properties, and has broad application prospects in the fields of generators and motors.

Description

Technical Field

[0001] The invention relates to a soft magnetic high entropy alloy with high thermal stability and a preparation method thereof, belonging to the technical field of alloy materials. Background Art

[0002] Since the concept of high entropy alloy was proposed, it has attracted extensive attention from researchers due to its unique composition design theory, excellent mechanical properties, corrosion resistance, oxidation resistance and high temperature stability. Unlike traditional alloys with one element as the main component, high entropy alloys have multiple elements as the main component, so they are also called multi-principal element alloys. In recent years, the functional properties of high entropy alloys have gradually been discovered, among which magnetic properties have become one of the key concerns of researchers. Soft magnetic high entropy alloys not only have good soft magnetic properties, but also have excellent mechanical properties and high temperature stability.

[0003] With the rapid development of the new energy vehicle industry, the working conditions of its motor cores are becoming more and more demanding. Not only must it meet the conditions of high speed, light weight, and high efficiency, but it must also have the ability to operate stably under high frequency and high temperature conditions. This requires the motor core material to have high strength, high saturation magnetization, high resistivity, and high Curie temperature. Soft magnetic high entropy alloys not only have the excellent mechanical properties and high temperature stability commonly possessed by high entropy alloys, but also have good comprehensive soft magnetic properties, and are expected to develop into a new type of motor core material.

[0004] Although soft magnetic high entropy alloys have excellent mechanical properties, their saturation magnetization intensity and coercive force still have a lot of room for improvement compared with traditional soft magnetic materials, and have not yet demonstrated practical engineering application value. Summary of the invention

[0005] In order to overcome the shortcomings of the prior art, the purpose of the present invention is to provide a soft magnetic high entropy alloy with high thermal stability and a preparation method thereof, by adding Si element to reduce the mixing enthalpy and magnetostriction coefficient of the alloy, thereby improving the thermal stability of the alloy and further reducing the coercive force of the alloy.

[0006] In order to achieve the above-mentioned object of the invention, the present invention adopts the following technical solutions:

[0007] A soft magnetic high entropy alloy with high thermal stability, the chemical formula of the soft magnetic high entropy alloy is Fe 40 Co 40- x Ni 10 Al 10 Si x , where 0≤x≤10 and the subscript is atomic percentage.

[0008] Preferably, the chemical formula of the soft magnetic high entropy alloy is Fe 40 Co40-x Ni 10 Al 10 Si x , where 6≤x≤10, and the subscripts are atomic percentages.

[0009] The present invention also provides a method for preparing a soft magnetic high entropy alloy with high thermal stability, comprising the following steps:

[0010] (1) preparing Fe, Co, Ni, Al and Si raw materials according to atomic percentage;

[0011] (2) placing the raw materials prepared in step (1) into a smelting furnace for smelting to obtain an alloy ingot;

[0012] (3) subjecting the alloy ingot obtained in step (2) to high-temperature heat treatment, and then quenching it with water to room temperature to obtain a soft magnetic high-entropy alloy with high thermal stability; the temperature of the high-temperature heat treatment is 700°C-950°C, and the time is 2h-24h.

[0013] Preferably, in step (1), the purity of the Fe, Co, Ni, Al and Si raw materials is greater than 99.5wt.%.

[0014] Preferably, in step (2), the Al, Si, Ni, Co, and Fe raw materials are placed into the smelting furnace in order from bottom to top according to the melting points of the elements from low to high.

[0015] Preferably, the melting furnace is a vacuum arc melting furnace.

[0016] Preferably, the vacuum arc melting furnace is evacuated to 6×10 -3 MPa, and then fill with Ar gas to 0.05-0.06MPa.

[0017] Preferably, the current during smelting is 100-400A, and the smelting time is 120-180 seconds.

[0018] Preferably, the ingot needs to be repeatedly turned over and melted 4-6 times during melting.

[0019] Preferably, before the high-temperature heat treatment, the alloy ingot is placed in a vacuum glass tube to be evacuated, the vacuum glass tube is then heated and sealed, and then the alloy ingot in the vacuum state is subjected to high-temperature heat treatment.

[0020] Compared with the prior art, the present invention has the following beneficial effects:

[0021] (1) After high temperature (700°C-950°C) and long time (2h-24h) heat treatment, the soft magnetic high entropy alloy with high thermal stability of the present invention does not increase drastically in grain size and the phase structure does not change, and has excellent thermal stability.

[0022] (2) The high thermal stability soft magnetic high entropy alloy of the present invention has excellent magnetic properties. After high temperature and long-term heat treatment, the coercivity is reduced, and the high thermal stability soft magnetic high entropy alloy obtained by the present invention is the soft magnetic high entropy alloy with the best comprehensive magnetic properties in the prior art.

[0023] (3) The preparation method and heat treatment process of the soft magnetic high entropy alloy with high thermal stability of the present invention are simple to operate. By controlling the vacuum degree and introducing protective gas, it is ensured that the alloy material will not be oxidized during the preparation and heat treatment process, thereby ensuring the accuracy of the alloy composition.

[0024] (4) The soft magnetic high entropy alloy with high thermal stability of the present invention does not contain precious metals, and the raw materials are non-toxic, harmless, low-cost and easy to obtain. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 The Fe as-cast and after heat treatment in Example 1 40 Co 32 Ni 10 Al 10 XRD spectrum of Si8 high entropy alloy.

[0026] Figure 2 The Fe as-cast and after heat treatment in Example 1 40 Co 32 Ni 10 Al 10 The metallographic structure and grain size of Si8 high entropy alloy, where (a) is the cast Fe 40 Co 32 Ni 10 Al 10 The metallographic structure of Si8 high entropy alloy, (b) is the cast Fe 40 Co 32 Ni 10 Al 10 Grain size diagram of Si8 high entropy alloy, (c) Fe after heat treatment 40 Co 32 Ni 10 Al 10 Metallographic structure of Si8 high entropy alloy, (d) is the Fe 40 Co 32 Ni 10 Al 10 Grain size diagram of Si8 high entropy alloy.

[0027] Figure 3 The Fe as-cast and after heat treatment in Example 1 40 Co 32 Ni 10 Al 10Magnetic hysteresis loop of Si8 high entropy alloy.

[0028] Among them, (a) is the cast and heat treated Fe 40 Co 32 Ni 10 Al 10 The hysteresis loop of Si8 high entropy alloy, (b) is the enlarged view of the hysteresis loop, in which the horizontal axis is the applied magnetic field and the vertical axis is the magnetization intensity.

[0029] Figure 4 The Fe in the as-cast state and after heat treatment in Example 2 40 Co 30 Ni 10 Al 10 Si 10 XRD spectrum of high entropy alloy.

[0030] Figure 5 The Fe in the as-cast state and after heat treatment in Example 2 40 Co 30 Ni 10 Al 10 Si 10 Metallographic structure and grain size of high entropy alloy, where (a) is cast Fe 40 Co 30 Ni 10 Al 10 Si 10 Metallographic structure diagram of high entropy alloy, (b) is cast Fe 40 Co 30 Ni 10 Al 10 Si 10 Grain size diagram of high entropy alloy, (c) is Fe after heat treatment 40 Co 30 Ni 10 Al 10 Si 10 Metallographic structure of high entropy alloy, (d) is Fe after heat treatment 40 Co 30 Ni 10 Al 10 Si 10 Grain size diagram of high entropy alloy.

[0031] Figure 6 The Fe in the as-cast state and after heat treatment in Example 2 40 Co 30 Ni 10 Al 10 Si 10 Hysteresis loop diagram of high entropy alloy. (a) is the hysteresis loop of Fe in the cast state and after heat treatment. 40 Co 30 Ni10 Al 10 Si 10 Hysteresis loop of high entropy alloy, (b) is an enlarged view of the hysteresis loop, in which the horizontal axis is the applied magnetic field and the vertical axis is the magnetization intensity. DETAILED DESCRIPTION

[0032] In order to better explain the present invention and facilitate understanding, the present invention is described in detail below through specific implementation modes in conjunction with the accompanying drawings.

[0033] In order to better understand the above technical scheme, exemplary embodiments of the present invention will be described in more detail below. It should be understood that the present invention can be implemented in various forms and should not be limited by the embodiments set forth herein. On the contrary, these embodiments are provided in order to enable a clearer and more thorough understanding of the present invention, and to be able to fully convey the scope of the present invention to those skilled in the art.

[0034] Example 1

[0035] This embodiment discloses a soft magnetic high entropy alloy with high thermal stability, the general formula of which is Fe 40 Co 32 Ni 10 Al 10 Si8.

[0036] A soft magnetic Fe with high thermal stability 40 Co 32 Ni 10 Al 10 Si8 high entropy alloy, the preparation method thereof is as follows:

[0037] The first step is to select Fe, Co, Ni, Al, and Si with a purity of more than 99.5wt% as raw materials, and mix them according to the atomic percentage of Fe:Co:Ni:Al:Si=40:32:10:10:8. Put 40g of the prepared mixture into the water-cooled copper crucible of the arc melting furnace in the following order: according to the melting point of the elements from low to high, put Al, Si, Ni, Co, and Fe raw materials from bottom to top into the copper crucible of the vacuum arc melting furnace. Then evacuate to 6×10 -3 MPa, and then fill the furnace chamber with Ar gas to a vacuum degree of 0.05MPa. Then, smelting is carried out under the protective atmosphere of Ar gas. During smelting, the alloy ingot is repeatedly smelted five times to ensure uniform composition and obtain an alloy ingot.

[0038] The second step is to cut the smelted alloy ingot into 5mm×4mm×1mm thin slices and grind the high entropy alloy thin slice samples roughly. Then put the high entropy alloy thin slice samples into a vacuum glass tube for vacuuming to a vacuum degree of 2×10 - 3MPa and then the vacuum glass tube is heated and sealed.

[0039] In the third step, when the temperature in the heat treatment furnace rises to 950°C, the vacuum glass tube containing the high entropy alloy thin film sample is placed in the heat treatment furnace. After keeping it at 950°C for 24 hours, the sample is quickly taken out and quenched with water to room temperature to obtain a soft magnetic high entropy alloy with high thermal stability.

[0040] The cast state (alloy ingot obtained in the first step) and the heat treated Fe 40 Co 32 Ni 10 Al 10 The Si8 high entropy alloy thin film (the soft magnetic high entropy alloy obtained in the third step) sample was subjected to XRD analysis, such as Figure 1 As shown, Fe in the cast state and after heat treatment 40 Co 32 Ni 10 Al 10 Si8 high entropy alloys all have a single BCC phase structure, which indicates that after the alloy ingot is subjected to high temperature and long-term heat treatment, the phase structure does not change.

[0041] For cast and heat treated Fe 40 Co 32 Ni 10 Al 10 The metallographic microstructure of Si8 high entropy alloy thin slice samples was analyzed. Figure 2 As shown, Fe in the cast state and after heat treatment 40 Co 32 Ni 10 Al 10 The Si8 high entropy alloys all have an equiaxed crystal structure, and the average grain size increases from 149.2 μm to 250.7 μm, indicating that after the alloy ingot is subjected to high-temperature and long-term heat treatment, the grain size does not change dramatically.

[0042] For cast and heat treated Fe 40 Co 32 Ni 10 Al 10 Magnetic properties of Si8 high entropy alloy thin slice samples were analyzed, such as Figure 3 As shown, Fe 40 Co 32 Ni 10 Al 10 Saturation magnetization M of Si8 high entropy alloy S =168emu / g, coercive force H C =1.39Oe, Fe after heat treatment 40 Co 32 Ni 10 Al 10Saturation magnetization M of Si8 high entropy alloy S =173emu / g, coercive force H C =1.01Oe.

[0043] Example 2

[0044] This embodiment discloses a soft magnetic high entropy alloy with high thermal stability, the general formula of which is Fe 40 Co 30 Ni 10 Al 10 Si 10 .

[0045] A soft magnetic Fe with high thermal stability 40 Co 30 Ni 10 Al 10 Si 10 High entropy alloy, the preparation method thereof is as follows:

[0046] The first step is to select Fe, Co, Ni, Al, and Si with a purity of more than 99.5wt% as raw materials, and mix them according to the atomic percentage of Fe:Co:Ni:Al:Si=40:30:10:10:10. Put 40g of the prepared mixture into the water-cooled copper crucible of the arc melting furnace in the following order: according to the melting point of the elements from low to high, put Al, Si, Ni, Co, and Fe raw materials from bottom to top into the copper crucible of the vacuum arc melting furnace. Then evacuate to 6×10 -3 MPa, and then fill the furnace chamber with Ar gas to a vacuum degree of 0.05MPa. Then, smelting is carried out under the protective atmosphere of Ar gas. During smelting, the alloy ingot is repeatedly smelted five times to ensure uniform composition and obtain an alloy ingot.

[0047] The second step is to cut the smelted alloy ingot into 5mm×4mm×1mm thin slices and grind the high entropy alloy thin slice samples roughly. Then put the high entropy alloy thin slice samples into a vacuum glass tube for vacuuming to a vacuum degree of 2×10 - 3 MPa and then the vacuum glass tube is heated and sealed.

[0048] In the third step, when the temperature in the heat treatment furnace rises to 950°C, the vacuum glass tube containing the high entropy alloy thin sheet sample is placed in the heat treatment furnace. After keeping it at 950°C for 10 hours, the sample is quickly taken out and quenched in water to obtain an alloy ingot.

[0049] For cast and heat treated Fe 40 Co 30 Ni 10 Al 10 Si 10 XRD analysis of high entropy alloy thin film samples, such as Figure 4 As shown, Fe in the cast state and after heat treatment 40 Co 30 Ni 10 Al 10 Si 10 The phase structure of the high entropy alloy does not change, which indicates that after the alloy ingot is subjected to high temperature and long-term heat treatment, the phase structure does not change.

[0050] For cast and heat treated Fe 40 Co 30 Ni 10 Al 10 Si 10 Metallographic microstructure analysis of high entropy alloy thin slice samples, such as Figure 5 As shown, Fe in the cast state and after heat treatment 40 Co 30 Ni 10 Al 10 Si 10 The high entropy alloys all have an equiaxed crystal structure, and the average grain size increases from 71.9 μm to 105.3 μm, indicating that after the alloy ingot is subjected to high-temperature and long-term heat treatment, the grain size does not change dramatically.

[0051] For cast and heat treated Fe 40 Co 30 Ni 10 Al 10 Si 10 High entropy alloy thin film samples were subjected to magnetic property analysis, such as Figure 6 As shown, Fe 40 Co 30 Ni 10 Al 10 Si 10 Saturation magnetization M of high entropy alloy S =166emu / g, coercive force H C =1.80Oe, Fe after heat treatment 40 Co 30 Ni 10 Al 10 Si 10 Saturation magnetization M of high entropy alloy S =161emu / g, coercive force H C =1.36Oe.

[0052] Table 1 is a comparison of the magnetic properties of the high thermal stability soft magnetic high entropy alloys of Example 1 and Example 2 and other soft magnetic high entropy alloys in the cast state and after high temperature and long-term heat treatment (the alloy components in bold are the example alloys of the present invention).

[0053] Table 1

[0054]

[0055]

[0056] Table 1 is a comparison of the magnetic properties of the soft magnetic high entropy alloys with high thermal stability in Example 1 and Example 2 and other soft magnetic high entropy alloys in the cast state and after heat treatment. The comprehensive magnetic properties of the soft magnetic high entropy alloy with high thermal stability in this example are superior to almost all the soft magnetic high entropy alloys reported so far. The high content of ferromagnetic elements (Fe, Co, Ni) ensures the high saturation magnetization intensity of the soft magnetic high entropy alloy with high thermal stability in this example, the addition of Al elements promotes the formation of ferromagnetic BCC phases, and the addition of Si elements reduces the magnetostriction coefficient of the soft magnetic high entropy alloy with high thermal stability in this example, thereby significantly reducing the coercive force.

[0057] The soft magnetic high entropy alloy with high thermal stability in this example has no phase structure change under high temperature and long-term heat treatment conditions, and the microstructure is always a uniform equiaxed crystal structure, and the grain size increases slowly with the increase of heat treatment time, indicating that the soft magnetic high entropy alloy with high thermal stability provided by the present invention has excellent thermal stability. The addition of Si element reduces the mixing enthalpy of the soft magnetic high entropy alloy with high thermal stability in this example, so that the element diffusion needs to absorb more heat, thereby improving the thermal stability of the alloy.

[0058] The above-described embodiments only provide a detailed description of the implementation methods of the present invention, but do not limit the present invention. For ordinary technicians in this field, based on the concept and ideas provided by the present invention, several modifications and improvements can be made in the specific implementation, and these modifications and improvements should also be regarded as the scope of protection of the present invention.

Claims

1. A soft magnetic high entropy alloy with high thermal stability, characterized in that: The chemical formula of the soft magnetic high entropy alloy is Fe 40 Co 40-x Ni 10 Al 10 Si x , where 6≤x≤10, and the subscripts are atomic percentages.

2. A method for preparing the soft magnetic high entropy alloy with high thermal stability according to claim 1, characterized in that: The following steps are involved: (1) preparing Fe, Co, Ni, Al and Si raw materials according to atomic percentage; (2) placing the raw materials prepared in step (1) into a smelting furnace for smelting to obtain an alloy ingot; (3) subjecting the alloy ingot obtained in step (2) to high-temperature heat treatment, and then quenching it with water to room temperature to obtain a soft magnetic high-entropy alloy with high thermal stability; the temperature of the high-temperature heat treatment is 700°C-950°C, and the time is 2h-24h.

3. The method for preparing a soft magnetic high entropy alloy with high thermal stability according to claim 2, characterized in that: In step (1), the purity of the Fe, Co, Ni, Al and Si raw materials is greater than 99.5wt.%.

4. The method for preparing a soft magnetic high entropy alloy with high thermal stability according to claim 2, characterized in that: In step (2), the Al, Si, Ni, Co, and Fe raw materials are placed into the smelting furnace in order from bottom to top according to the melting points of the elements from low to high.

5. The method for preparing a soft magnetic high entropy alloy with high thermal stability according to claim 4, characterized in that: The melting furnace is a vacuum arc melting furnace.

6. The method for preparing a soft magnetic high entropy alloy with high thermal stability according to claim 2, characterized in that: In step (2), the smelting furnace is evacuated to a vacuum of 6×10 -3 MPa, and then fill with Ar gas to 0.05-0.06MPa.

7. The method for preparing a soft magnetic high entropy alloy with high thermal stability according to claim 2, characterized in that: In step (2), the current during smelting is 100-400A, and the smelting time is 120-180 seconds.

8. The method for preparing a soft magnetic high entropy alloy with high thermal stability according to claim 2, characterized in that: In step (2), the ingot needs to be repeatedly turned over and melted 4-6 times during melting.

9. The method for preparing a soft magnetic high entropy alloy with high thermal stability according to claim 2, characterized in that: In step (3), the alloy ingot is placed in a vacuum glass tube for evacuation before high-temperature heat treatment, and then the vacuum glass tube is heated and sealed, and then the alloy ingot in the vacuum state is subjected to high-temperature heat treatment.

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