Iron-based nanocrystalline soft magnetic alloy powder, soft magnetic composite material and preparation method of iron-based nanocrystalline soft magnetic alloy powder

Abstract

The invention provides iron-based nanocrystalline soft magnetic alloy powder, a soft magnetic composite material and a preparation method of the iron-based nanocrystalline soft magnetic alloy powder and the soft magnetic composite material, and belongs to the technical field of soft magnetic materials. The iron-based nanocrystalline soft magnetic alloy powder is of a heterogeneous nanocrystalline structure comprising a three-dimensional island-shaped amorphous region and a nanocrystalline region, the diameter of the three-dimensional island-shaped amorphous region is 50-100 nm, and the number density of the three-dimensional island-shaped amorphous region is in the order of magnitude of 1019-1020 m <-3 >. The iron-based nanocrystalline soft magnetic alloy powder has the advantages of being high in sphericity degree, high in saturation magnetization intensity, low in coercive force and the like. The soft magnetic composite material comprises soft magnetic powder and a coating layer coating the surface of the soft magnetic powder, the coating layer comprises a binder, and the soft magnetic powder is formed by compounding the iron-based nanocrystalline soft magnetic alloy powder provided by the invention with at least one of iron nickel, iron nickel molybdenum, iron silicon, iron silicon aluminum, iron silicon chromium, carbonyl iron and pure iron powder. And the magnetic core has the advantages of low high-frequency loss, high magnetic conductivity, high direct-current bias and the like.

Description

Technical Field

[0001] The present invention relates to the technical field of soft magnetic materials, and more particularly, to iron-based nanocrystalline soft magnetic alloy powders, soft magnetic composite materials and methods for preparing the same. Background Art

[0002] With the progress and innovation of technology, electronic devices and magnetic devices are developing towards the directions of large capacity, miniaturization, high efficiency and high-frequency stability. Magnetic materials are essential materials in the fields of electronic devices and magnetic devices, and have huge application space and innovative significance. Soft magnetic materials are one of the most widely used and most diverse materials among them. Soft magnetic materials have low coercivity ( H c ), high magnetic permeability ( μ e ), high saturation magnetization intensity ( M s ) and low power loss ( P cv ), etc. They are important components of electromagnetic conversion devices, and can also be used in signal processing equipment, and are widely used in various transformers, controllers, sensors and magnetic recording equipment. Soft magnetic materials include crystalline soft magnetic materials, ferrite soft magnetic materials, metal magnetic powder materials, magnetic thin films, and amorphous and nanocrystalline soft magnetic materials, etc. Soft magnetic composite materials are a kind of metal soft magnetic materials formed by mixing ferromagnetic powders with insulating media and pressing them to have distributed air gaps, and have unique advantages such as low eddy current loss, high resistivity, good DC bias performance, easy machining, three-dimensional isotropy and wide working frequency range, and are widely used in fields such as switching power supplies, filter inductors, main transformers, inductors and high-frequency chokes.

[0003] Iron-based nanocrystalline alloys generally refer to composite alloys in which the microstructure is a nanoscale α-Fe crystal phase (including α-Fe crystal phases solid-solved with other elements such as Si, Co, and Ni) uniformly distributed in an amorphous matrix phase. Preparing iron-based nanocrystalline alloys into powders and using powder metallurgy technology to prepare them into soft magnetic composites can combine the dual advantages of iron-based nanocrystalline alloys and soft magnetic composites, becoming a new generation of high-performance soft magnetic materials - nanocrystalline soft magnetic composites, and promoting the development of high-frequency and high-performance electronic devices, power equipment, and related industries. Since the invention of FeSiBNbCu nanocrystalline alloys by Yoshizawa et al. in Japan in 1988, the academic and industrial communities have conducted extensive research and industrialization exploration on iron-based nanocrystalline alloys. Literature (Journal of Applied Physics 64 (1988) 6044, Journal of Alloys and Compounds 810 (2019) 151754, Journal of Magnetism and Magnetic Materials 501 (2020) 166457) and patents (CN10126324B, CN104934179B) etc. have all disclosed iron-based nanocrystalline alloys in the form of tapes or powders. Through transmission electron microscopy analysis, it is found that their microstructures are all uniform nanocrystalline structures, that is, a composite structure in which the nanoscale α-Fe crystal phase is uniformly distributed in the amorphous matrix. Since the resistivity of the crystal phase is lower than that of the amorphous phase, the resistivity of nanocrystalline alloys with a uniform structure is generally lower than that of amorphous alloys. The Fe 73.5 Si 13.5 B9Cu1Nb3 alloy has a resistivity of 1.15 μΩ·m, while Fe 78 Si9B 13 The resistivity of the amorphous alloy is 1.35 μΩ·m. The relatively low resistivity is not conducive to reducing eddy current losses in high-frequency application scenarios and is difficult to adapt to the high-frequency trend of future power electronic devices.

[0004] The shape of the iron-based nanocrystalline soft magnetic alloy powder has a crucial influence on its high-frequency magnetic properties. Due to the weak amorphous formation ability of the iron-based nanocrystalline alloy, a fully amorphous precursor ribbon can usually only be obtained by the single-roll casting method with a high cooling rate. After heat treatment, the ribbon is crushed by ball milling to obtain the nanocrystalline soft magnetic alloy powder. However, these powders have sharp edges and corners, making it difficult to insulate and coat them, resulting in very high high-frequency losses of the soft magnetic composite material, severely limiting its application in higher frequency bands. The spherical or ellipsoidal alkali metal powders prepared by the atomization method have good coatability and can effectively reduce the losses of the soft magnetic composite material at high frequencies. However, the traditional gas atomization method has poor cooling ability and it is difficult to obtain a fully amorphous precursor powder, resulting in the deterioration of the properties of the prepared nanocrystalline alloy powder. Although the water atomization and water-gas combined atomization methods have better cooling ability, the powders prepared by them have problems of high oxygen content and poor sphericity. Patent CN202311271977.2 discloses an iron-based nanocrystalline soft magnetic alloy powder, but its preparation method is the ball milling method, resulting in relatively high high-frequency losses.

[0005] In summary, in order to promote the development of power equipment and magnetic devices towards high frequency and high power, it is necessary to develop nanocrystalline soft magnetic alloy spherical powders with excellent soft magnetic properties, high resistivity and high sphericity, and to develop soft magnetic composite materials with high-frequency low loss, high magnetic permeability and high DC bias performance. Summary of the Invention

[0006] Aiming at the deficiencies in the prior art, the present invention provides an iron-based nanocrystalline soft magnetic alloy powder, a soft magnetic composite material and their preparation methods. The iron-based nanocrystalline soft magnetic alloy powder has both excellent soft magnetic properties and high resistivity, and the soft magnetic composite material has high-frequency low loss, high magnetic permeability and high DC bias performance.

[0007] The specific technical solutions of the present invention are as follows: In the first aspect, the present invention provides an iron-based nanocrystalline soft magnetic alloy powder. The powder particles have a heterogeneous nanocrystalline structure, and the heterogeneous nanocrystalline structure includes a three-dimensional island-shaped amorphous region and a nanocrystalline region. The diameter of the three-dimensional island-shaped amorphous region is 50-100 nm, and the number density of the three-dimensional island-shaped amorphous region is in the order of 10 19-20 m -3 order of magnitude.

[0008] The iron-based nanocrystalline soft magnetic alloy powder provided by the present invention has a special heterogeneous nanocrystalline structure. In the heterogeneous nanocrystalline structure, in addition to the nanocrystalline region composed of conventional nanoscale α-Fe crystal phase and amorphous matrix phase, there is also a three-dimensional island-shaped amorphous region. The amorphous matrix phase in the heterogeneous nanocrystalline structure is isotropic and has no magnetic anisotropy; the amorphous matrix phase has a large positive magnetostriction coefficient, while the α-Fe crystal phase has a small negative magnetostriction coefficient. When the heterogeneous nanocrystalline structure contains a three-dimensional island-shaped amorphous region, it can balance the amorphous matrix phase and the α-Fe crystal phase, so that the iron-based nanocrystalline soft magnetic alloy powder has a magnetostriction coefficient close to 0, reduces the remanence of the iron-based nanocrystalline soft magnetic alloy powder and increases its magnetic permeability, and also helps the iron-based nanocrystalline soft magnetic alloy powder to obtain excellent soft magnetic properties; further combining with controlling the diameter of the three-dimensional island-shaped amorphous region in the heterogeneous nanocrystalline structure to be 50-100 nm and the number density to be 10 19 -10 20 m -3 order of magnitude, while making the magnetostriction coefficient of the nanocrystalline soft magnetic alloy powder closest to 0 to the greatest extent, it can also overcome the problem of low resistivity caused by the α-Fe crystal phase, significantly increase the resistivity of the iron-based nanocrystalline soft magnetic alloy powder, and help reduce the high-frequency loss of the soft magnetic composite material; the iron-based nanocrystalline soft magnetic alloy powder provided by the present invention combines the synergistic cooperation of the three-dimensional island-shaped amorphous region and the nanocrystalline region in the heterogeneous nanocrystalline structure, so that the iron-based nanocrystalline soft magnetic alloy powder has both excellent soft magnetic properties and high resistivity.

[0009] In a possible implementation manner, the nanocrystalline region includes a nanoscale α-Fe crystal phase and an amorphous matrix phase, the average diameter of the α-Fe crystal phase is 8-14 nm, and the number density of the α-Fe crystal phase is 10 22 -10 23 m -3 order of magnitude. Generally, the α-Fe crystal phase has magnetocrystalline anisotropy, and when the average diameter of the α-Fe crystal phase in the heterogeneous nanocrystalline structure is 8-14 nm and the number density is 10 22 -10 23 m -3 order of magnitude, the magnetic exchange coupling effect between the α-Fe crystal phases can significantly reduce the magnetocrystalline anisotropy, which is beneficial to reducing the coercivity and remanence of the iron-based nanocrystalline soft magnetic alloy powder and increasing its magnetic permeability, so that the iron-based nanocrystalline soft magnetic alloy powder has excellent soft magnetic properties.

[0010] In a possible implementation manner, the chemical element composition of the iron-based nanocrystalline soft magnetic alloy powder satisfies the relational expression: Fe a Co b Ni c Si d B eP f C g Nb h Cu i , where the subscripts a, b, c, d, e, f, g, h, and i respectively represent the atomic percentages of the respective alloying elements, and the following conditions are satisfied: 59 ≤ a ≤ 72; 0 ≤ b ≤ 10; 0 ≤ c ≤ 5; 69 ≤ a + b + c ≤ 72; 12.5 ≤ d ≤ 15.5; 9 ≤ e ≤ 12; 0 ≤ f ≤ 2; 0 ≤ g ≤ 2; 3 ≤ h ≤ 5; 0.6 ≤ i ≤ 0.9; a + b + c + d + e + f + g + h + i = 100. The iron-based nanocrystalline soft magnetic alloy composition with the above composition has relatively high Si, B, and Nb contents, enabling the alloy to have good amorphous formation ability, and at the same time having a relatively low Cu content. Combining with the multi-stage atomization powder-making process provided by the present invention, the iron-based nanocrystalline soft magnetic alloy powder with a heterogeneous nanocrystalline structure described in the present invention can be obtained.

[0011] In a possible implementation manner, the shape of the powder particles is spherical or quasi-spherical, and the average sphericity of the powder particles ≥ 0.9. Spherical powder particles have a smooth surface, few defects, small resistance to the movement of magnetic domain walls during magnetization, better magnetic isotropy, less pinning effect between grains, and are easy to coat, which can reduce the hysteresis loss and eddy current loss between powder particles at high frequencies. By controlling the average sphericity of the powder particles ≥ 0.9, it is beneficial to reduce the hysteresis loss and eddy current loss of the iron-based nanocrystalline soft magnetic alloy powder, improve the magnetic permeability, and reduce the coercivity.

[0012] In a possible implementation manner, the saturation magnetization of the iron-based nanocrystalline soft magnetic alloy powder is 100 - 145 emu / g, and the coercivity < 2 Oe. The relatively high saturation magnetization of the iron-based nanocrystalline soft magnetic alloy powder helps to improve the power density of the soft magnetic composite material, and the relatively low coercivity is beneficial to reducing the hysteresis loss of the soft magnetic composite material.

[0013] In the second aspect, the present invention also provides a preparation method for the above iron-based nanocrystalline soft magnetic alloy powder, including the following steps: S1: Using a multi-stage crushing and atomization process to make the master alloy of the iron-based nanocrystalline soft magnetic alloy into an amorphous precursor powder. The multi-stage crushing and atomization process sequentially includes four main links, namely master alloy melting, alloy melt gas atomization, rotary disk mechanical atomization, and water cooling. Among them, the distance between the gas outlet in the alloy melt gas atomization and the rotary disk in the rotary disk mechanical atomization link is 110 - 130 mm, and the rotary disk speed in the rotary disk mechanical atomization is 6000 - 20000 rpm; S2: The amorphous precursor powder described in step S1 is subjected to heat treatment under vacuum or inert gas protection using a rotary annealing furnace to obtain an iron-based nanocrystalline soft magnetic alloy powder. The temperature of the heat treatment is 560 - 620 °C, the time is 0.5 - 2 hours, and the rotation rate of the sample chamber is 5 - 60 rpm.

[0014] The preparation method of the iron-based nanocrystalline soft magnetic alloy powder provided by the present invention adopts a multi-stage crushing and atomization process and controls key process parameters such as the distance between the gas outlet in the gas atomization stage and the turntable in the rotary mechanical atomization link and the rotation speed of the turntable in the high-speed rotary mechanical atomization link, so that the iron-based nanocrystalline soft magnetic alloy can obtain a completely amorphous precursor powder and form local depletion of Cu element therein. During the subsequent heat treatment process, the temperature and time of the heat treatment are controlled to form three-dimensional island-shaped amorphous regions in the local depletion region of Cu element and nanocrystalline regions containing α-Fe crystal phase in the Cu element enrichment region, thereby obtaining an iron-based nanocrystalline soft magnetic alloy powder with the heterogeneous nanocrystalline structure.

[0015] In a third aspect, the present invention also provides a soft magnetic composite material, which includes soft magnetic powder and a coating layer coated on the surface of the soft magnetic powder. The coating layer includes a binder. The soft magnetic powder is the iron-based nanocrystalline soft magnetic alloy powder provided by the present invention, or the soft magnetic powder is composed of the iron-based nanocrystalline soft magnetic alloy powder provided by the present invention and an alloy powder. The alloy powder includes at least one of iron-nickel powder, iron-nickel-molybdenum powder, iron-silicon powder, iron-silicon-aluminum powder, iron-silicon-chromium powder, carbonyl iron powder, and pure iron powder. The soft magnetic composite material has excellent magnetic properties such as high-frequency low loss, high magnetic permeability, and high DC bias performance.

[0016] In a possible implementation manner, the binder includes at least one of epoxy resin, silicone resin, and phenolic resin. The epoxy resin has a strong binding force with the soft magnetic powder, can reduce interface defects, and improve the mechanical properties of the soft magnetic composite material; the silicone resin has excellent high-temperature resistance performance, which is beneficial to improving the high-temperature stability of the soft magnetic composite material; the phenolic resin has a cost advantage, which is beneficial to reducing the preparation cost of the soft magnetic composite material.

[0017] In a possible implementation manner, the mass of the binder is 1% - 5% of the total mass of the soft magnetic composite material. Controlling the mass of the binder to be 1% - 5% of the total mass of the soft magnetic composite material can provide sufficient binding force to ensure the soft magnetic composite material maintains its complete shape during pressing and sintering, and can also make the soft magnetic composite material have high magnetic permeability and low eddy current loss.

[0018] In a possible implementation, the coating layer further includes at least one of an insulating material and a lubricant. When the coating layer contains an insulating material, the high-frequency eddy current loss of the soft magnetic composite material can be reduced and the high-temperature stability of the soft magnetic composite material can be enhanced; when the coating layer contains a lubricant, the lubricant is adsorbed on the surface of the soft magnetic powder, reducing the frictional resistance between the soft magnetic powder particles and between the soft magnetic powder and the mold during the pressing process, which is beneficial to improving the density of the soft magnetic composite material.

[0019] Further, when the coating layer contains an insulating material, the insulating material is selected from at least one of zinc oxide, silicon dioxide, zirconium dioxide, phosphate, aluminum oxide, titanium dioxide, and magnesium oxide. The above-mentioned insulating materials not only have good insulating properties, but also silicon dioxide and aluminum oxide have high dielectric strength, which are suitable for applications in high-frequency low-loss scenarios; zirconium dioxide and magnesium oxide also have excellent thermal stability, which is beneficial to improving the thermal stability of the soft magnetic composite material; zinc oxide and phosphate also have the advantage of low cost, which is beneficial to the large-scale production of the soft magnetic composite material.

[0020] Further, when the coating layer contains an insulating material, the thickness of the insulating material is 10-150 nm. Controlling the thickness of the insulating material within the range of 10-150 nm can achieve a balance in terms of loss and magnetic permeability of the soft magnetic composite material.

[0021] Further, when the coating layer contains a lubricant, the lubricant is selected from at least one of zinc stearate, magnesium stearate, aluminum stearate, calcium stearate, and graphite powder. The above-mentioned lubricants not only have good lubrication performance, but zinc stearate also has the characteristic of low-temperature decomposition, with a decomposition temperature of 120-160 °C, and less volatile residue during the pressing process, which can reduce the pollution to the soft magnetic composite material; magnesium stearate also has low hygroscopicity, which is beneficial to reducing the agglomeration of the soft magnetic powder caused by moisture absorption; calcium stearate also has biocompatibility, which can make the soft magnetic composite material suitable for applications in medical and food-grade equipment; graphite powder has an ultra-low friction coefficient, which can provide excellent lubrication effects.

[0022] Further, when the coating layer contains a lubricant, the mass of the lubricant is 0%-1% of the total mass of the soft magnetic composite material. Controlling the mass of the lubricant within the range of 0%-1% of the total mass of the soft magnetic composite material can optimize the forming process and improve the consistency of the soft magnetic composite material product without significantly sacrificing the electromagnetic properties of the soft magnetic composite material.

[0023] In a possible implementation, when the soft magnetic powder is the iron-based nanocrystalline soft magnetic alloy powder, and the pressing pressure of the soft magnetic composite material is 400 - 800 MPa and the heat treatment temperature is 150 - 250 °C, the loss of the soft magnetic composite material under the condition of 1 MHz / 10 mT is 80 - 120 mW / cm 3 、the loss under the condition of 1 MHz / 20 mT is 500 - 750 mW / cm 3 、the loss under the condition of 2 MHz / 30 mT is 2800 - 3800 mW / cm 3 ; the magnetic permeability of the soft magnetic composite material at 1 MHz is 25 - 32, and the DC bias performance of the soft magnetic composite material when the bias field is 100 Oe is 76% - 83%.

[0024] In a possible implementation, when the soft magnetic powder is composed of the iron-based nanocrystalline soft magnetic alloy powder and alloy powder, the alloy powder includes at least one of iron-nickel powder, iron-nickel-molybdenum powder, iron-silicon powder, iron-silicon-aluminum powder, iron-silicon-chromium powder, carbonyl iron powder and pure iron powder, and the pressing pressure of the soft magnetic composite material is 400 - 800 MPa and the heat treatment temperature is 150 - 250 °C, the loss of the soft magnetic composite material under the condition of 1 MHz / 20 mT is 200 - 700 mW / cm 3 ; the magnetic permeability of the soft magnetic composite material at 1 MHz is 40 - 50, and the DC bias performance of the soft magnetic composite material when the bias field is 100 Oe is 75% - 93%.

[0025] In a possible implementation, when the soft magnetic powder is the iron-based nanocrystalline soft magnetic alloy powder, the coating layer of the soft magnetic composite material contains an insulating material, and the pressing pressure of the soft magnetic composite material is 1600 - 2200 MPa and the heat treatment temperature is 560 - 620 °C, the loss of the soft magnetic composite material under the condition of 1 MHz / 20 mT is 250 - 450 mW / cm 3 、the loss under the condition of 3 MHz / 50 mT is 10000 - 18000 mW / cm 3 ; the magnetic permeability of the soft magnetic composite material at 1 MHz is 58 - 68, and the DC bias performance of the soft magnetic composite material when the bias field is 100 Oe is 48% - 58%.

[0026] Fourthly, the present invention also provides a preparation method of the above soft magnetic composite material, including the following steps: M1: Mix the soft magnetic powder with the raw materials for the coating layer to obtain composite magnetic powder; the soft magnetic powder is the above-mentioned iron-based nanocrystalline soft magnetic alloy powder, or is composed of a composite of the above-mentioned iron-based nanocrystalline soft magnetic alloy powder and alloy powder, and the alloy powder includes at least one of iron-nickel powder, iron-nickel-molybdenum powder, iron-silicon powder, iron-silicon-aluminum powder, iron-silicon-chromium powder, carbonyl iron powder, and pure iron powder; the raw materials for the coating layer contain a binder, or contain a lubricant at the same time; M2: Subject the composite magnetic powder to pressing and heat treatment to obtain a soft magnetic composite material, where the pressure of the pressing and the temperature of the heat treatment are 400 - 800 MPa and 150 - 250 °C respectively, or the pressure of the pressing and the temperature of the heat treatment are 1600 - 2200 MPa and 560 - 620 °C respectively.

[0027] The preparation method of the soft magnetic composite material provided by the present invention uses the iron-based nanocrystalline soft magnetic alloy powder provided by the present invention as the soft magnetic powder or one of the soft magnetic powders, combines the above-mentioned binder and lubricant, and controls the pressure of pressing and the heat treatment temperature, and a soft magnetic composite material with high-frequency low loss, high magnetic permeability, and high DC bias performance can be obtained.

[0028] Further, when the pressure of the pressing and the temperature of the heat treatment in step M2 are 1600 - 2200 MPa and 560 - 620 °C respectively, the iron-based nanocrystalline soft magnetic alloy powder is an amorphous precursor powder, and the master alloy of the iron-based nanocrystalline soft magnetic alloy is made into the amorphous precursor powder through a multi-stage crushing and atomization process. The multi-stage crushing and atomization process successively includes four main links, namely master alloy melting, alloy melt gas atomization, rotary disk mechanical atomization, and water cooling. The distance between the gas outlet in the alloy melt gas atomization and the rotary disk in the rotary disk mechanical atomization link is 110 - 130 mm, and the rotational speed of the rotary disk in the rotary disk mechanical atomization is 6000 - 20000 rpm. When using the amorphous precursor powder as the soft magnetic powder, it is beneficial to further improve the soft magnetic properties of the soft magnetic composite material.

[0029] Further, when the raw materials for the coating layer in step M1 contain an insulating material, the insulating material is generated through a sol-gel reaction or a chemical in-situ reaction. The solvents used in the sol-gel reaction or the chemical in-situ reaction are acetone or ethanol, and the reaction temperature is 40 - 100 °C. The insulating material prepared under the above process conditions is beneficial to forming a more uniform and dense coating layer.

[0030] On the basis of conforming to common knowledge in the art, the above preferred conditions can be combined arbitrarily to obtain various preferred examples of the present invention.

[0031] The reagents and raw materials used in the present invention are all commercially available.

[0032] The positive and progressive effects of the present invention are as follows: The iron-based nanocrystalline soft magnetic alloy powder, soft magnetic composite material and preparation method provided by the present invention prepare an iron-based nanocrystalline soft magnetic alloy powder with a unique microstructure through the organic combination of alloy composition and powder preparation process. The iron-based nanocrystalline soft magnetic alloy powder has a heterogeneous nanocrystalline structure, and the heterogeneous nanocrystalline structure includes three-dimensional island-shaped amorphous regions and nanocrystalline regions. The diameter of the three-dimensional island-shaped amorphous regions is 50-100 nm, and the number density of the three-dimensional island-shaped amorphous regions is in the order of 10 19 -10 20 m -3 magnitude. The nanocrystalline region includes a nanoscale α-Fe crystal phase and an amorphous matrix phase. The iron-based nanocrystalline soft magnetic alloy powder has excellent magnetoelectric properties; the provided soft magnetic composite material has performance advantages such as low high-frequency loss, high magnetic permeability and high DC bias. Among them, the high-frequency loss is reduced by 20-60% compared with the similar powders at home and abroad, and it is very suitable for power electronic devices such as high-frequency miniaturized molded inductors. Description of the Drawings

[0033] Figure 1 It is a TEM image of the cross-sectional microstructure of the iron-based nanocrystalline soft magnetic alloy powder in Example 1.

[0034] Figure 2 It is an XRD diffraction pattern of the iron-based nanocrystalline soft magnetic alloy powder in Example 1.

[0035] Figure 3 It is an SEM image of the iron-based nanocrystalline soft magnetic alloy powder in Example 1.

[0036] Figure 4 It is a VSM curve of the iron-based nanocrystalline soft magnetic alloy powder in Example 1.

[0037] Figure 5 It is a curve of the power loss of the soft magnetic composite material in Example 1 varying with the maximum working magnetic density.

[0038] Figure 6 It is a curve of the magnetic permeability of the soft magnetic composite material in Example 1 varying with the frequency.

[0039] Figure 7 It is a curve of the DC bias performance of the soft magnetic composite material in Example 1 varying with the superimposed field strength.

[0040] Figure 8 It is an internal SEM image and main element distribution map of the soft magnetic composite material in Example 8.

[0041] Figure 9 It is the surface morphology, element distribution and cross-sectional SEM image of the iron-based nanocrystalline soft magnetic alloy powder coated with a ZnO insulating layer in Example 18. Detailed Embodiments

[0042] To make the above objects, features, and advantages of the present invention more obvious and understandable, the following provides a detailed description of specific embodiments of the present invention. It should be noted that the following embodiments are only used to illustrate the implementation methods and typical parameters of the present invention, and are not used to limit the parameter range described in the present invention. Reasonable variations derived therefrom are still within the protection scope of the claims of the present invention.

[0043] It should be noted that the endpoints and any values within the ranges disclosed herein are not limited to the exact ranges or values. These ranges or values should be understood to include values close to these ranges or values. For numerical ranges, between the endpoint values of each range, between the endpoint values of each range and individual point values, and between individual point values, they can be combined with each other to obtain one or more new numerical ranges, and these numerical ranges should be regarded as specifically disclosed herein.

[0044] Unless otherwise defined, all terms, symbols, and other scientific terms used herein are intended to have the same meaning as commonly understood by those skilled in the art to which the present invention belongs. In some cases, for the purpose of clarification or easy reference, terms with conventional understood meanings are defined herein. Such definitions herein should not be construed as indicating a significant difference from the conventional understanding in the art. The technical methods described or cited herein are generally well understood by those skilled in the art and are adopted by conventional methods. Unless otherwise stated, the use of commercially available kits, reagents, and instruments is carried out according to the protocols and parameters given by the manufacturers.

[0045] In a first aspect, the present invention provides an iron-based nanocrystalline soft magnetic alloy powder. The powder particles have a heterogeneous nanocrystalline structure, and the heterogeneous nanocrystalline structure includes a three-dimensional island-shaped amorphous region and a nanocrystalline region. The diameter of the three-dimensional island-shaped amorphous region D amo is 50 - 100 nm, and the number density of the three-dimensional island-shaped amorphous region N d, amo is in the order of 10 19 -10 20 m -3 order of magnitude.

[0046] The iron-based nanocrystalline soft magnetic alloy powder provided by the present invention has a special heterogeneous nanocrystalline structure. In the heterogeneous nanocrystalline structure, in addition to the nanocrystalline region composed of conventional nanoscale α-Fe crystal phase and amorphous matrix phase, there is also a three-dimensional island-shaped amorphous region. The amorphous matrix phase in the heterogeneous nanocrystalline structure is isotropic and has no magnetic anisotropy; the amorphous matrix phase in the nanocrystalline region has a large positive magnetostriction coefficient, while the α-Fe crystal phase has a small negative magnetostriction coefficient. When the heterogeneous nanocrystalline structure contains a three-dimensional island-shaped amorphous region, it can balance the amorphous matrix phase and the α-Fe crystal phase, so that the iron-based nanocrystalline soft magnetic alloy powder has a magnetostriction coefficient close to 0, reduces the remanence of the iron-based nanocrystalline soft magnetic alloy powder and increases its magnetic permeability, and also helps the iron-based nanocrystalline soft magnetic alloy powder to obtain excellent soft magnetic properties; further combining the regulation of the diameter of the three-dimensional island-shaped amorphous region in the heterogeneous nanocrystalline structure to be 50-100 nm and the number density to be 10 19 -10 20 m -3 order of magnitude, while making the magnetostriction coefficient of the base nanocrystalline soft magnetic alloy powder closest to 0 to the greatest extent, it can also overcome the problem of low resistivity caused by the α-Fe crystal phase, significantly increase the resistivity of the iron-based nanocrystalline soft magnetic alloy powder, and help reduce the high-frequency loss of the soft magnetic composite material; the iron-based nanocrystalline soft magnetic alloy powder provided by the present invention combines the three-dimensional island-shaped amorphous region and the nanocrystalline region in the heterogeneous nanocrystalline structure to make the iron-based nanocrystalline soft magnetic alloy powder have both excellent soft magnetic properties and high resistivity.

[0047] In a possible implementation manner, the average diameter of the α-Fe crystal phase in the nanocrystalline region D cry is 8-14 nm, and the number density of the α-Fe crystal phase N d, cry is in 10 22 -10 23 m -3 order of magnitude. Generally, the α-Fe crystal phase has magnetocrystalline anisotropy. When the average diameter of the α-Fe crystal phase in the heterogeneous nanocrystalline structure is 8-14 nm and the number density is in 10 22 -10 23 m -3 order of magnitude, the magnetic exchange coupling effect between the α-Fe crystal phases can significantly reduce the magnetocrystalline anisotropy, which is beneficial to reducing the coercivity and remanence of the iron-based nanocrystalline soft magnetic alloy powder and increasing its magnetic permeability, so that the iron-based nanocrystalline soft magnetic alloy powder has excellent soft magnetic properties.

[0048] In a possible implementation manner, the chemical element composition of the iron-based nanocrystalline soft magnetic alloy powder satisfies the relational expression: Fe a Co b Nic Si d B e P f C g Nb h Cu i , where the subscripts a, b, c, d, e, f, g, h, and i respectively represent the atomic percentages of the respective alloying elements, and satisfy the following conditions: 59 ≤ a ≤ 72; 0 ≤ b ≤ 10; 0 ≤ c ≤ 5; 69 ≤ a + b + c ≤ 72; 12.5 ≤ d ≤ 15.5; 9 ≤ e ≤ 12; 0 ≤ f ≤ 2; 0 ≤ g ≤ 2; 3 ≤ h ≤ 5; 0.6 ≤ i ≤ 0.9; a + b + c + d + e + f + g + h + i = 100. The iron-based nanocrystalline soft magnetic alloy composition with the above composition has relatively high Si, B, and Nb contents, enabling the alloy to have good amorphous formation ability, and at the same time having a relatively low Cu content. Combining with the multi-stage atomization powder-making process provided by the present invention, the iron-based nanocrystalline soft magnetic alloy powder with a heterogeneous nanocrystalline structure provided by the present invention can be obtained.

[0049] In a possible implementation, the shape of the powder particles is spherical or quasi-spherical, and the average sphericity of the iron-based nanocrystalline soft magnetic alloy powder ≥ 0.9. The spherical powder particles have a smooth surface, few defects, small resistance to the movement of magnetic domain walls during magnetization, better magnetic isotropy, less pinning effect between grains, and are easy to coat, which can reduce the hysteresis loss at high frequencies and the eddy current loss between powders. By controlling the average sphericity of the powder particles ≥ 0.9, it is beneficial to reduce the hysteresis loss and eddy current loss of the iron-based nanocrystalline soft magnetic alloy powder, improve the magnetic permeability, and reduce the coercivity.

[0050] In a possible implementation, the saturation magnetization intensity of the iron-based nanocrystalline soft magnetic alloy powder is 100 - 145 emu / g, and the coercivity < 2 Oe. The relatively high saturation magnetization intensity of the iron-based nanocrystalline soft magnetic alloy powder helps to improve the power density of the soft magnetic composite material, and the relatively low coercivity is beneficial to reducing the hysteresis loss of the soft magnetic composite material.

[0051] In the second aspect, the present invention also provides a preparation method for the above iron-based nanocrystalline soft magnetic alloy powder, including the following steps: S1: Using a multi-stage crushing and atomization process to make the master alloy of the iron-based nanocrystalline soft magnetic alloy into an amorphous precursor powder. The multi-stage crushing and atomization process successively includes four main links, namely master alloy melting, alloy melt gas atomization, rotary disk mechanical atomization, and water cooling. Among them, the distance between the gas outlet in the alloy melt gas atomization and the rotary disk in the rotary disk mechanical atomization is 110 - 130 mm, and the rotational speed of the rotary disk in the rotary disk mechanical atomization is 6000 - 20000 rpm; S2: The amorphous precursor powder in step S1 is subjected to heat treatment under vacuum or inert gas protection using a rotary annealing furnace to obtain an iron-based nanocrystalline soft magnetic alloy powder. The temperature of the heat treatment is 560 - 620 °C, the time is 0.5 - 2 hours, and the rotation rate of the sample chamber is 5 - 60 rpm.

[0052] The preparation method of the iron-based nanocrystalline soft magnetic alloy powder provided by the present invention adopts a multi-stage crushing and atomization process and controls key process parameters such as the distance between the gas outlet in the gas atomization stage and the turntable in the rotary mechanical atomization link and the rotation speed of the turntable in the high-speed rotary mechanical atomization link, so that the iron-based nanocrystalline soft magnetic alloy can obtain a completely amorphous precursor powder and form local depletion of Cu element therein. During the subsequent heat treatment process, the temperature and time of the heat treatment are controlled to form three-dimensional island-like amorphous regions in the local depletion region of Cu element and nanocrystalline regions containing α-Fe crystal phase in the Cu element enrichment region, thereby obtaining an iron-based nanocrystalline soft magnetic alloy powder with a heterogeneous nanocrystalline structure.

[0053] In a third aspect, the present invention also provides a soft magnetic composite material, which includes a soft magnetic powder and a coating layer coated on the surface of the soft magnetic powder. The coating layer includes a binder. The soft magnetic powder is the above-mentioned iron-based nanocrystalline soft magnetic alloy powder, or the soft magnetic powder is a composite composition of the above-mentioned iron-based nanocrystalline soft magnetic alloy powder and at least one of iron-nickel powder, iron-nickel-molybdenum powder, iron-silicon powder, iron-silicon-aluminum powder, iron-silicon-chromium powder, carbonyl iron powder, and pure iron powder. The soft magnetic composite material has excellent magnetic properties such as high-frequency low loss, high magnetic permeability, and high DC bias performance.

[0054] In a possible implementation manner, the binder is selected from at least one of epoxy resin, silicone resin, and phenolic resin. The epoxy resin has a strong binding force with the soft magnetic powder, which can reduce interface defects and improve the mechanical properties of the soft magnetic composite material; the silicone resin has excellent high-temperature resistance performance, which is beneficial to improving the high-temperature stability of the soft magnetic composite material; the phenolic resin has a cost advantage, which is beneficial to reducing the preparation cost of the soft magnetic composite material.

[0055] In a possible implementation manner, the mass of the binder is 1% - 5% of the total mass of the soft magnetic composite material. Controlling the mass of the binder to be 1% - 5% of the total mass of the soft magnetic composite material can not only provide sufficient binding force to ensure the integrity of the shape of the soft magnetic composite material during pressing and sintering, but also enable the soft magnetic composite material to have high magnetic permeability and low eddy current loss.

[0056] In a possible implementation, the coating layer further comprises at least one of an insulating material and a lubricant. When the coating layer contains an insulating material, the high-frequency eddy current loss of the soft magnetic composite material can be reduced and the high-temperature stability of the soft magnetic composite material can be enhanced; when the coating layer contains a lubricant, the lubricant is adsorbed on the surface of the soft magnetic powder, reducing the frictional resistance between the soft magnetic powder particles and between the soft magnetic powder and the mold during the pressing process, which is beneficial to improving the density of the soft magnetic composite material.

[0057] Further, when the coating layer contains an insulating material, the insulating material is selected from at least one of zinc oxide, silicon dioxide, zirconium dioxide, phosphate, aluminum oxide, titanium dioxide, and magnesium oxide. The above insulating materials not only have good insulation performance, but also silicon dioxide and aluminum oxide have high dielectric strength, which is suitable for applications in high-frequency low-loss scenarios; zirconium dioxide and magnesium oxide also have excellent thermal stability, which is beneficial to improving the thermal stability of the soft magnetic composite material; zinc oxide and phosphate also have the advantage of low cost, which is beneficial to the large-scale production of the soft magnetic composite material.

[0058] Further, when the coating layer contains an insulating material, the thickness of the insulating material is 10 - 150 nm. Controlling the thickness of the insulating material within the range of 10 - 150 nm can achieve a balance in terms of loss and magnetic permeability of the soft magnetic composite material.

[0059] Further, when the coating layer contains a lubricant, the lubricant is selected from at least one of zinc stearate, magnesium stearate, aluminum stearate, calcium stearate, and graphite powder. The above lubricants not only have good lubrication performance, but zinc stearate also has the characteristic of low-temperature decomposition, with a decomposition temperature of 120 - 160 °C, less volatile residue during the pressing process, and can reduce the pollution to the soft magnetic composite material; magnesium stearate also has low hygroscopicity, which is beneficial to reducing the agglomeration of the soft magnetic powder caused by moisture absorption; calcium stearate also has biocompatibility, enabling the soft magnetic composite material to be applicable to applications in medical and food-grade equipment; graphite powder has an ultra-low friction coefficient and can provide excellent lubrication effects.

[0060] Further, when the coating layer contains a lubricant, the mass of the lubricant is 0% - 1% of the total mass of the soft magnetic composite material. Controlling the mass of the lubricant within the range of 0% - 1% of the total mass of the soft magnetic composite material can optimize the forming process and improve the consistency of the soft magnetic composite material product without significantly sacrificing the electromagnetic performance of the soft magnetic composite material.

[0061] In a possible implementation, when the soft magnetic powder is the above-mentioned iron-based nanocrystalline soft magnetic alloy powder, and the pressing pressure of the soft magnetic composite material is 400 - 800 MPa and the heat treatment temperature is 150 - 250 °C, the loss of the soft magnetic composite material under the condition of 1 MHz / 10 mT is 80 - 120 mW / cm 3, the loss under the condition of 1 MHz / 20 mT is 500 - 750 mW / cm 3 , the loss under the condition of 2 MHz / 30 mT is 2800 - 3800 mW / cm 3 , the magnetic permeability of the soft magnetic composite material at 1 MHz is 25 - 32, and the DC bias performance of the soft magnetic composite material at a bias field of 100 Oe is 76% - 83%.

[0062] In a possible implementation manner, when the soft magnetic powder is composed of the above-mentioned iron-based nanocrystalline soft magnetic alloy powder and alloy powder, the alloy powder includes at least one of iron-nickel powder, iron-nickel-molybdenum powder, iron-silicon powder, iron-silicon-aluminum powder, iron-silicon-chromium powder, carbonyl iron powder and pure iron powder, and the pressing pressure of the soft magnetic composite material is 400 - 800 MPa and the heat treatment temperature is 150 - 250 °C, the loss of the soft magnetic composite material under the condition of 1 MHz / 20 mT is 200 - 700 mW / cm 3 , the magnetic permeability of the soft magnetic composite material at 1 MHz is 40 - 50, and the DC bias performance of the soft magnetic composite material at a bias field of 100 Oe is 75% - 93%.

[0063] In a possible implementation manner, when the soft magnetic powder is the above-mentioned iron-based nanocrystalline soft magnetic alloy powder and the coating layer contains an insulating material, and the pressing pressure of the soft magnetic composite material is 1600 - 2200 MPa and the heat treatment temperature is 560 - 620 °C, the loss of the soft magnetic composite material under the condition of 1 MHz / 20 mT is 250 - 450 mW / cm 3 , the loss under the condition of 3 MHz / 50 mT is 10000 - 18000 mW / cm 3 , the magnetic permeability of the soft magnetic composite material at 1 MHz is 58 - 68, and the DC bias performance of the soft magnetic composite material at a bias field of 100 Oe is 48% - 58%.

[0064] Fourthly, the present invention also provides a preparation method of the above-mentioned soft magnetic composite material, including the following steps: M1: Mix the soft magnetic powder and the coating layer raw materials to obtain a composite magnetic powder; the soft magnetic powder is the above-mentioned iron-based nanocrystalline soft magnetic alloy powder, or is composed of the above-mentioned iron-based nanocrystalline soft magnetic alloy powder and alloy powder, and the alloy powder includes at least one of iron-nickel powder, iron-nickel-molybdenum powder, iron-silicon powder, iron-silicon-aluminum powder, iron-silicon-chromium powder, carbonyl iron powder and pure iron powder; the coating layer raw materials contain a binder, or contain a lubricant at the same time; M2: The composite magnetic powder is pressed and heat-treated to obtain a soft magnetic composite material, where the pressing pressure and the heat treatment temperature are 400 - 800 MPa and 150 - 250 °C respectively, or the pressing pressure and the heat treatment temperature are 1600 - 2200 MPa and 560 - 620 °C respectively.

[0065] The preparation method of the soft magnetic composite material provided by the present invention uses the iron-based nanocrystalline soft magnetic alloy powder provided by the present invention as one of the soft magnetic powders or the soft magnetic powders, combines a binder and a lubricant, and controls the pressing pressure and the heat treatment temperature, so as to obtain a soft magnetic composite material with high-frequency low loss, high magnetic permeability and high DC bias performance.

[0066] Furthermore, when the pressing pressure and the heat treatment temperature in step M2 are 1600 - 2200 MPa and 560 - 620 °C respectively, the iron-based nanocrystalline soft magnetic alloy powder is an amorphous precursor powder. The master alloy of the iron-based nanocrystalline soft magnetic alloy is made into an amorphous precursor powder through a multi-stage crushing and atomization process. The multi-stage crushing and atomization process successively includes four main links, namely master alloy melting, alloy melt gas atomization, rotary disk mechanical atomization and water cooling. The distance between the gas outlet in the alloy melt gas atomization and the rotary disk in the rotary disk mechanical atomization link is 110 - 130 mm, and the rotary disk speed in the rotary disk mechanical atomization is 6000 - 20000 rpm. When the amorphous precursor powder in step S1 of the preparation method of the above iron-based nanocrystalline soft magnetic alloy powder is used as the soft magnetic powder, it is beneficial to further improve the soft magnetic properties of the soft magnetic composite material.

[0067] Furthermore, when the raw material of the coating layer in step M1 contains an insulating material, the insulating material is generated through a sol-gel reaction or a chemical in-situ reaction. The solvents used in the sol-gel reaction or the chemical in-situ reaction are acetone or ethanol, and the reaction temperature is 40 - 100 °C. The insulating material prepared under the above process conditions is beneficial to form a more uniform and dense coating layer.

[0068] Hereinafter, the technical solution of the present invention will be further described in combination with specific embodiments. All reagents used in the embodiments can be commercially obtained or synthesized according to conventional methods, and can be directly used without further treatment, and the instruments used in the embodiments can be commercially obtained.

[0069] Examples 1 - 13 are examples of iron-based nanocrystalline soft magnetic alloy powders and their soft magnetic composite materials as soft magnetic powders. Examples 14 - 23 are examples of soft magnetic composite materials with iron-based nanocrystalline soft magnetic alloy powders and alloy powders as soft magnetic powders. Examples 24 - 29 are examples of soft magnetic composite materials with iron-based nanocrystalline soft magnetic alloy powders as soft magnetic powders and having insulating materials or lubricants.

[0070] Example 1

[0071] This embodiment provides an iron-based nanocrystalline soft magnetic alloy powder, which is prepared by the following method: S1: The atomic percentages of the iron-based nanocrystalline soft magnetic alloy are Fe 69.7 Si 15.5 B 10 Nb4Cu 0.8 . Put the master alloy into the crucible of the multi-stage crushing and atomizing equipment, gradually heat it up to 1500 °C, keep it warm for 5 minutes after the master alloy is completely melted, start the mechanical turntable and cooling water, start atomization until all the master alloy is sprayed out. The atomization pressure is 4 MPa, the nozzle diameter is 3 mm, the preferred distance between the gas atomization nozzle and the high-speed turntable is 120 mm, the turntable speed is 10000 rpm, and the cooling water flow rate is 12 L / minute; collect the powder from the powder and cooling water mixture, dehydrate and dry it to obtain the amorphous precursor powder; S2: Carry out vacuum rotary heat treatment on the amorphous precursor powder prepared in step S1 to obtain the iron-based nanocrystalline soft magnetic alloy powder. The rotation rate of the sample chamber is 30 rpm, the heat treatment temperature is 580 °C, the heat treatment time is 1 hour, and the vacuum degree is 10 -3 Pa.

[0072] This embodiment also provides a soft magnetic composite material, which is prepared by the following method: M1: Take an appropriate amount of the nanocrystalline soft magnetic alloy powder prepared in this embodiment. When the cumulative particle size distribution percentage reaches 50%, the particle size D 50 is 24.5 μm; Dissolve 2 wt.% of epoxy resin of the powder as a binder in acetone, pour the nanocrystalline soft magnetic alloy powder into the mixed solution of acetone and epoxy resin, continue to ultrasonically stir evenly, and obtain the composite magnetic powder after the acetone is completely volatilized, and dry it in an environment of 100 °C for 1 hour; M2: Take a small amount of the composite magnetic powder and put it into an annular sample mold with an inner diameter and an outer diameter of 4 mm and 8 mm respectively. Put the mold into a hydraulic press and press the composite magnetic powder into a magnetic ring under a pressure of 600 MPa. After the magnetic ring is heat-treated at 200 °C for 1 hour, a soft magnetic composite material is obtained.

[0073] Example 2

[0074] This embodiment provides an iron-based nanocrystalline soft magnetic alloy powder and a soft magnetic composite material. The difference in their preparation methods from those of Example 1 is that: the preferred distance between the gas atomization nozzle and the high-speed turntable is 110 mm, the turntable speed is 6000 rpm, the rotation rate of the rotary heat treatment sample chamber is 5 rpm, the heat treatment temperature is 560 °C, and the heat treatment time is 1 hour. Others are the same as those in Example 1.

[0075] Example 3

[0076] This example provides an iron-based nanocrystalline soft magnetic alloy powder and a soft magnetic composite material. The difference in its preparation method from Example 1 lies in that: the preferred distance between the gas atomization nozzle and the high-speed turntable is 130 mm, the turntable rotation speed is 20000 rpm, the rotation rate of the rotating heat treatment sample chamber is 60 rpm, the heat treatment temperature is 620 °C, and the heat treatment time is 0.5 hour. Others are the same as in Example 1.

[0077] Example 4

[0078] This example provides an iron-based nanocrystalline soft magnetic alloy powder and a soft magnetic composite material. The difference in its preparation method from Example 1 lies in that: the preferred distance between the gas atomization nozzle and the high-speed turntable is 120 mm, the turntable rotation speed is 8000 rpm, the rotation rate of the rotating heat treatment sample chamber is 20 rpm, the heat treatment temperature is 590 °C, and the heat treatment time is 0.75 hour. Others are the same as in Example 1.

[0079] Example 5

[0080] This example provides an iron-based nanocrystalline soft magnetic alloy powder and a soft magnetic composite material. The difference in its preparation method from Example 1 lies in that: the preferred distance between the gas atomization nozzle and the high-speed turntable is 120 mm, the turntable rotation speed is 12000 rpm, the rotation rate of the rotating heat treatment sample chamber is 30 rpm, the heat treatment temperature is 570 °C, and the heat treatment time is 1.5 hours. Others are the same as in Example 1.

[0081] Example 6

[0082] This example provides an iron-based nanocrystalline soft magnetic alloy powder and a soft magnetic composite material. The difference in its preparation method from Example 1 lies in that: the preferred distance between the gas atomization nozzle and the high-speed turntable is 120 mm, the turntable rotation speed is 15000 rpm, the rotation rate of the rotating heat treatment sample chamber is 15 rpm, the heat treatment temperature is 580 °C, and the heat treatment time is 1 hour. Others are the same as in Example 1.

[0083] Example 7

[0084] This example provides an iron-based nanocrystalline soft magnetic alloy powder and a soft magnetic composite material. The difference in its preparation method from Example 1 lies in that: the preferred distance between the gas atomization nozzle and the high-speed turntable is 120 mm, the turntable rotation speed is 10000 rpm, the rotation rate of the rotating heat treatment sample chamber is 50 rpm, the heat treatment temperature is 590 °C, and the heat treatment time is 1 hour. Others are the same as in Example 1.

[0085] Example 8

[0086] This embodiment provides an iron-based nanocrystalline soft magnetic alloy powder and a soft magnetic composite material. The difference in its preparation method from that of Embodiment 1 lies in that the atomic percentage of the iron-based nanocrystalline soft magnetic alloy is Fe 69.7 Si 15.5 B 10 Nb4Cu 0.8 Others are the same as those in Embodiment 1.

[0087] Embodiment 9

[0088] This embodiment provides an iron-based nanocrystalline soft magnetic alloy powder and a soft magnetic composite material. The difference in its preparation method from that of Embodiment 1 lies in that the atomic percentage of the iron-based nanocrystalline soft magnetic alloy is Fe 70.8 Si 13.5 B 12 Nb3Cu 0.7 Others are the same as those in Embodiment 1.

[0089] Embodiment 10

[0090] This embodiment provides an iron-based nanocrystalline soft magnetic alloy powder and a soft magnetic composite material. The difference in its preparation method from that of Embodiment 1 lies in that the atomic percentage of the iron-based nanocrystalline soft magnetic alloy is Fe 69.6 Si 14.5 B9P2Nb4Cu 0.9 Others are the same as those in Embodiment 1.

[0091] Embodiment 11

[0092] This embodiment provides an iron-based nanocrystalline soft magnetic alloy powder and a soft magnetic composite material. The difference in its preparation method from that of Embodiment 1 lies in that the atomic percentage of the iron-based nanocrystalline soft magnetic alloy is Fe 69.8 Si 14.5 B9C2Nb4Cu 0.7 Others are the same as those in Embodiment 1.

[0093] Embodiment 12

[0094] This embodiment provides an iron-based nanocrystalline soft magnetic alloy powder and a soft magnetic composite material. The difference in its preparation method from that of Embodiment 1 lies in that the atomic percentage of the iron-based nanocrystalline soft magnetic alloy is Fe 59.7 Co 10 Si 15.5 B 10 Nb4Cu 0.8 Others are the same as those in Embodiment 1.

[0095] Embodiment 13

[0096] This embodiment provides an iron-based nanocrystalline soft magnetic alloy powder and a soft magnetic composite material. The difference in its preparation method from that of Embodiment 1 lies in that the atomic percentage of the iron-based nanocrystalline soft magnetic alloy is Fe 64.7 Ni5Si 15.5 B 10 Nb4Cu 0.8 . Others are the same as those in Embodiment 1.

[0097] Comparative Example 1 The iron-based nanocrystalline soft magnetic alloy powder and the soft magnetic composite material provided in this comparative example are from Example 2 of Patent Document JP2019189928A. The microstructure of the iron-based nanocrystalline soft magnetic alloy powder is a nanocrystalline structure in which a uniform nanoscale crystal phase is distributed in an amorphous matrix.

[0098] Comparative Example 2 The iron-based nanocrystalline soft magnetic alloy powder and the soft magnetic composite material provided in this comparative example are from Example 2 of Patent Application Document JP2021086941A. The microstructure of the iron-based nanocrystalline soft magnetic alloy powder is a nanocrystalline structure in which a uniform nanoscale crystal phase is distributed in an amorphous matrix.

[0099] Comparative Example 3 The iron-based nanocrystalline soft magnetic alloy powder and the soft magnetic composite material provided in this comparative example are from Example 5 of Patent Document WO2019031462A1. The microstructure of the iron-based nanocrystalline soft magnetic alloy powder is a nanocrystalline structure in which a uniform nanoscale crystal phase is distributed in an amorphous matrix.

[0100] The microstructure and magnetic property data of the iron-based nanocrystalline soft magnetic alloy powders prepared in Examples 1-13 and Comparative Examples 1-3 are shown in Table 1. From the data in Table 1, it can be seen that the diameter of the three-dimensional island-shaped amorphous region of the iron-based nanocrystalline soft magnetic alloy powders prepared in Examples 1-3 D amo is 50-100 nm, the number density of the three-dimensional island-shaped amorphous region N d, amo is in the order of 10 19 -10 20 m -3 , the average diameter of the α-Fe crystal phase D cry is 8-14 nm, the number density of the α-Fe crystal phase N d, cry is in the order of 10 22 -10 23 m -3 , while there is no three-dimensional island-shaped amorphous region in the iron-based nanocrystalline soft magnetic alloy powders in Comparative Examples 1-3.

[0101] The magnetic property data of the soft magnetic composites prepared in Examples 1-13 and Comparative Examples 1-3 are shown in Table 2. From the data in Table 2, it can be seen that the loss of the soft magnetic composites prepared in Examples 1-13 under the condition of 1 MHz / 10 mT is 85-117 mW / cm 3 and the loss under the condition of 1 MHz / 20 mT is 553-716 mW / cm 3 and the loss under the condition of 2 MHz / 30 mT is 2981-3655 mW / cm 3 . The magnetic permeability of the soft magnetic composites at 1 MHz is 26.3-30.3, and the DC bias performance of the soft magnetic composites when the bias field is 100 Oe is 78-81%; while the loss of the soft magnetic composite prepared in Comparative Example 1 under the condition of 1 MHz / 10 mT is 215 mW / cm 3 , which is significantly higher than that of the soft magnetic composites in Examples 1-13; the losses of the soft magnetic composites prepared in Comparative Examples 2 and 3 under the condition of 2 MHz / 30 mT are 4796 mW / cm 3 and 3739 mW / cm 3 respectively, which are significantly higher than that of the soft magnetic composites in Examples 1-13; and the magnetic permeability of the soft magnetic composite prepared in Comparative Example 2 is 16.3, which is significantly lower than that of the soft magnetic composites in Examples 1-13.

[0102] Table 1 Microstructural and magnetic property data of iron-based nanocrystalline soft magnetic alloy powders prepared in Examples 1-13 and Comparative Examples 1-3

[0103] Table 2 Magnetic property data of soft magnetic composites prepared in Examples 1-13 and Comparative Examples 1-3

[0104] Example 14 This example provides a soft magnetic composite, which is prepared by the following method: M1: The iron-based nanocrystalline powder prepared in Example 1 is compounded with an alloy powder. The alloy powder is Fe 50 Ni 50 (wt.%) iron-nickel powder. The D 50 of the alloy powder is 3.1 μm to obtain a composite powder; the mass percentage of the alloy powder in the composite powder is 30%; 2 wt% of epoxy resin of the powder is dissolved in acetone to form a mixed solution. The composite powder is poured into the mixed solution and ultrasonicated and stirred evenly. After the acetone is completely volatilized, a composite magnetic powder is obtained, and it is dried in an environment of 60 °C for 1 hour; M2: Take the composite magnetic powder in step M1 and place it into an annular sample mold with inner and outer diameters of 4 and 8 mm respectively. Put the annular sample mold into a hydraulic press and press the composite magnetic powder into a magnetic ring sample under a pressure of 600 MPa. Prepare 3 - 5 magnetic ring samples per batch and heat-treat them at 200 °C for 1 hour to obtain the soft magnetic composite material.

[0105] Example 15

[0106] This example provides a soft magnetic composite material, which is different from Example 14 in that the mass percentage of the alloy powder in the composite powder is 35%. Others are the same as Example 14.

[0107] Example 16

[0108] This example provides a soft magnetic composite material, which is different from Example 14 in that the alloy powder is iron-nickel-molybdenum powder, and the D 50 is 9.2 μm, and the mass percentage of the alloy powder in the composite powder is 20%. Others are the same as Example 14.

[0109] Example 17

[0110] This example provides a soft magnetic composite material, which is different from Example 8 in that the alloy powder is iron-nickel-molybdenum powder, and the D 50 is 9.2 μm. Others are the same as Example 8.

[0111] Example 18

[0112] This example provides a soft magnetic composite material, which is different from Example 14 in that the alloy powder is carbonyl iron powder, and the D 50 is 4.4 μm. Others are the same as Example 14.

[0113] Example 19

[0114] This example provides a soft magnetic composite material, which is different from Example 14 in that the alloy powder is carbonyl iron powder, and the D 50 is 4.4 μm, and the mass percentage of the alloy powder in the composite powder is 40%. Others are the same as Example 14.

[0115] Example 20

[0116] This example provides a soft magnetic composite material, which is different from Example 14 in that the alloy powder is iron-silicon-aluminum powder, and the D 50It is 7.9 μm, and the mass percentage of the alloy powder in the composite powder is 25%. Others are the same as in Example 14.

[0117] Example 21

[0118] This example provides a soft magnetic composite material, which is different from Example 14 in that the alloy powder is an iron-silicon-aluminum powder, and the D 50 is 7.9 μm. Others are the same as in Example 14.

[0119] Example 22

[0120] This example provides a soft magnetic composite material, which is different from Example 14 in that the alloy powder is an iron-silicon-aluminum powder, and the D 50 is 8.6 μm, and the mass percentage of the alloy powder in the composite powder is 35%. Others are the same as in Example 14.

[0121] Example 23

[0122] This example provides a soft magnetic composite material, which is different from Example 14 in that the alloy powder is an iron-silicon-aluminum powder, and the D 50 is 8.6 μm, and the mass percentage of the alloy powder in the composite powder is 40%. Others are the same as in Example 14.

[0123] Table 3 shows the soft magnetic property data of the soft magnetic composite materials prepared in Examples 14 - 23. From the data in the table, it can be seen that the loss of the soft magnetic composite materials prepared in Examples 14 - 23 under the conditions of 1 MHz / 20 mT is 219 - 654 mW / cm 3 , the magnetic permeability under the condition of 1 MHz is 41.4 - 48.6, and the DC bias performance of the soft magnetic composite material when the bias field is 100 Oe is 78 - 91%.

[0124] Table 3 Soft Magnetic Property Data of Soft Magnetic Composite Materials Prepared in Examples 14 - 23

[0125] Example 24 This example provides a soft magnetic composite material containing an insulating material, which is prepared by the following method: M1: Take an appropriate amount of the amorphous precursor powder of the iron-based nanocrystalline soft magnetic alloy powder in Example 1, put it into absolute ethanol together with 1 wt.% of polyvinylpyrrolidone (PVP) powder, and form a uniform absolute ethanol mixture of magnetic powder and PVP through ultrasonic dispersion stirring for 0.5 hours; dissolve 1.75 wt.% of zinc acetate dihydrate powder in absolute ethanol, completely dissolve it through ultrasonic dispersion, and dropwise add it to the stirred absolute ethanol mixture of magnetic powder and PVP. Then add 50 ml of deionized water, and adjust the pH of the mixture to 8 - 9 using ammonia water. Under the water bath condition of 60 °C, continuously stir for 5 hours to complete the reaction. The amorphous precursor powder after the reaction is filtered and washed 3 - 5 times, and then dried at 60 °C for 3 hours to obtain the amorphous precursor powder coated with ZnO. M2: Weigh 2 wt.% of epoxy resin powder as a binder and dissolve it in acetone. Pour the amorphous precursor powder coated with ZnO in step M1 into the mixed solution of acetone and epoxy resin, continue ultrasonic treatment and stir evenly. After the acetone completely volatilizes, obtain the amorphous precursor powder containing insulating materials, and dry it in an environment of 60 °C for 1 hour. Subsequently, add 0.5 wt.% of zinc stearate powder as a lubricant to it, and mix it evenly. M3: Take the powder containing insulating layer and lubricant in M2, put it into an annular sample mold with inner and outer diameters of 4 and 8 mm respectively, put the annular sample mold into a hydraulic press, and press it into a magnetic ring sample under a pressure of 1800 MPa; prepare 3 - 5 magnetic ring samples for each batch, and anneal them at 600 °C under vacuum for 1 hour to obtain a soft magnetic composite material containing insulating materials.

[0126] Example 25

[0127] This example provides a soft magnetic composite material containing insulating materials, which is different from Example 24 in that: M1: Mix absolute ethanol and polyvinylpyrrolidone in a ratio of 50:1 to form a mixed solution. Add the amorphous precursor powder of the iron-based nanocrystalline soft magnetic alloy powder prepared in Example 1 into the mixed solution and stir and disperse for 0.5 hours to obtain a magnetic powder mixed solution; dissolve 1 wt.% of K2ZrF6 of the magnetic powder in absolute ethanol, and gradually drop it into the magnetic powder mixed solution. Subsequently, adjust the pH value to 9 - 10 with NH3·H2O solution, and react at 50 °C for 3 hours; the powder after the reaction is filtered and washed 3 - 5 times, and then dried at 60 °C for 3 hours to obtain the amorphous precursor powder coated with an insulating layer.

[0128] Others are the same as Example 24.

[0129] Example 26 This embodiment provides a soft magnetic composite material containing an insulating material, which is different from Embodiment 24 in that: M1: Mix 3-aminopropyltriethoxysilane (APTES) and absolute ethanol in a ratio of 1:125 to form a mixed solution; take the amorphous precursor powder of the iron-based nanocrystalline soft magnetic alloy powder in Embodiment 1, add it to the above mixed solution, and perform ultrasonic treatment and mechanical stirring for 0.5 hours to obtain a magnetic powder mixed solution; then quickly drop ammonia water into the magnetic powder mixed solution, adjust the pH value to about 9, and perform mechanical stirring in a constant water bath at 50 °C for 4 hours; the reacted powder is first filtered and washed with ethanol 2-4 times, and then vacuum dried at 60 °C for 2 hours to obtain an amorphous precursor powder coated with an insulating layer.

[0130] Others are the same as Embodiment 24.

[0131] Embodiment 27

[0132] This embodiment provides a soft magnetic composite material containing an insulating material, which is different from Embodiment 24 in that: M1: Mix 3-aminopropyltriethoxysilane (APTES) and absolute ethanol in a ratio of 1:100 to form a mixed solution; add the amorphous precursor powder of the iron-based nanocrystalline soft magnetic alloy powder in Embodiment 1 to the mixed solution, and perform ultrasonic treatment and mechanical stirring for 0.5 hours to obtain a magnetic powder mixed solution; dissolve 6 wt.% of tetraethyl orthosilicate and 7 wt.% of ZrOCl2·8H2O of the magnetic powder in deionized water, and gradually drop it into the magnetic powder mixed solution, then adjust the pH value to about 9 with ammonia water, and perform mechanical stirring in a constant water bath at 50 °C for 4 hours; the reacted powder is first filtered and washed with ethanol 2−4 times, and then vacuum dried at 60 °C for 2 hours to obtain an amorphous precursor powder coated with an insulating layer.

[0133] Others are the same as Embodiment 24.

[0134] Embodiment 28

[0135] This embodiment provides a soft magnetic composite material containing an insulating material, which is different from Embodiment 24 in that: M1: Take the amorphous precursor powder of the iron-based nanocrystalline soft magnetic alloy powder in Example 1, mix it with 0.5 wt.% of polyvinylpyrrolidone (PVP) powder in an anhydrous ethanol solution, and ultrasonically stir for 0.5 hours to obtain a magnetic powder mixture; then add 10 wt.% of tetrabutyl titanate (TBOT) to the magnetic powder mixture and stir well, then dropwise add deionized water, and mechanically stir in a 50 °C water bath for 4 hours; the reacted powder is washed 2-3 times with ethanol and filtered by suction, and then dried in a vacuum atmosphere at 60 °C for 12 hours to obtain an amorphous precursor powder coated with an insulating layer; add epoxy resin to acetone and dissolve it by ultrasonic dispersion to obtain an epoxy resin solution, and the mass of the epoxy resin is 3% of the mass of the amorphous precursor powder coated with an insulating layer; then add the amorphous precursor powder coated with an insulating layer to the epoxy resin solution, continuously stir under ultrasonic dispersion until the acetone completely evaporates, and dry at 60 °C for 1 hour to obtain composite magnetic powder.

[0136] Others are the same as in Example 24.

[0137] Example 29

[0138] This example provides a soft magnetic composite material containing an insulating material, which is different from Example 24 in that: M1: Take the amorphous precursor powder of the iron-based nanocrystalline soft magnetic alloy powder in Example 1, disperse it in a mixed solution of phosphoric acid, ethanol and deionized water, and the amount of phosphoric acid used in the mixed solution is 1 wt% of the powder; ultrasonically stir mechanically in a 50 °C water bath for 0.25 hours, mix the phosphated powder with 0.5 wt.% of polyvinylpyrrolidone (PVP) in a 60 ml anhydrous ethanol solution and ultrasonically stir for 0.5 hours, then add 20 wt.% of tetrabutyl titanate (TBOT) of the magnetic powder and stir well, dropwise add deionized water, and mechanically stir in a 50 °C water bath for 4 hours; the reacted powder is first washed 2-3 times with ethanol and filtered by suction, and then dried in a vacuum atmosphere at 60 °C for 12 hours to obtain an amorphous precursor powder coated with an insulating layer.

[0139] Others are the same as in Example 24.

[0140] The magnetic property data of the soft magnetic composite materials containing insulating materials prepared in Examples 24-29 are shown in Table 4. It can be seen from the data in Table 4 that the soft magnetic composite materials containing insulating materials prepared in Examples 24-29 have a loss of 296-328 mW / cm under the conditions of 1 MHz / 20 mT 3 and a loss of 10372-16864 mW / cm under the conditions of 3 MHz / 50 mT 3 , the magnetic permeability is 61.2-64, and the DC bias performance at a bias field of 100 Oe is 50-54%.

[0141] Magnetic property data of soft magnetic composite materials containing insulating materials prepared in Examples 24 - 29, shown in Table 4

[0142] The following tests were conducted on the iron - based nanocrystalline soft magnetic alloy powders and soft magnetic composite materials prepared in Examples 1 - 13, the soft magnetic composite materials prepared in Examples 14 - 23, and the soft magnetic composite materials containing insulating materials prepared in Examples 24 - 29.

[0143] XRD test: Using an XRD powder diffractometer, a radial scan was performed from 20° to 90° scattering angle, and the scanning speed was 4° / min. θ

[0144] Transmission electron microscope images: Using a ThermoFisher Talos F200x transmission electron microscope, the microstructure of the iron - based nanocrystalline soft magnetic alloy powders was observed.

[0145] Scanning electron microscope images and sphericity test: Using an FEI Quanta FEG 250 scanning electron microscope (SEM), the morphology, element distribution, cross - sectional structure of the powders were observed and their sphericity was calibrated. Using the image - processing software of the SEM, the powder contour was captured, the projected area A and perimeter B of the particles were measured, and the sphericity formula Φ: Φ = 4π*A / B². The number - weighted average of the sphericity of all powders in the sample is the average sphericity.

[0146] Particle size test of powders: Using a new Patech HELOS - OASIS laser particle size analyzer to measure the particle size distribution of the powders, and the measurement method is dry method.

[0147] Magnetic property test of powders: Using a Lakeshore 7410 vibrating sample magnetometer to test the magnetic properties of the iron - based nanocrystalline soft magnetic alloy powders.

[0148] Loss test of soft magnetic composite materials: The magnetic ring samples prepared in the examples were wound, with 20 and 5 turns for the primary and secondary respectively, and an Iwasaki 8218 alternating - current hysteresis loop tracer was used to test the magnetic ring loss.

[0149] Permeability test of soft magnetic composite materials: Using an Agilent 4294A to test the variation law of the permeability of the soft magnetic composite materials with frequency.

[0150] DC bias performance test of soft magnetic composite materials: ​The DC bias performance of the soft magnetic composite material was measured using a Tonghui TH28339 impedance analyzer with a DC bias power supply.

[0151] Test effect description: Figure 1 It is a TEM image of the cross-sectional microstructure of the iron-based nanocrystalline soft magnetic alloy powder in Example 1. As can be seen from the figure, the microstructure of the iron-based nanocrystalline soft magnetic alloy powder has a heterogeneous nanocrystalline structure. The heterogeneous nanocrystalline structure is divided into a three-dimensional island-shaped amorphous region (marked by the white dotted line) and a nanocrystalline region. The nanocrystalline region contains a nanoscale α-Fe crystal phase and an amorphous matrix phase. The nanoscale α-Fe crystal phase is distributed in the amorphous matrix; after measurement and calculation, the average diameter of the island-shaped amorphous region is 80 nm, and the number density is 1.6×10 20 m -3 , the average diameter of the crystal phase in the nanocrystalline region is about 10 nm, and the number density is 2.1×10 23 m -3 .

[0152] Figure 2 It is the XRD diffraction pattern of the iron-based nanocrystalline soft magnetic alloy powder in Example 1. As can be seen from the figure, the XRD pattern of the iron-based nanocrystalline soft magnetic alloy powder contains a diffuse scattering peak symbolizing the amorphous state and a diffraction peak corresponding to the α-Fe crystal, indicating the presence of an amorphous phase and an α-Fe crystal phase in the powder. Combining the TEM image and the XRD diffraction pattern, the microstructure of the powder is a composite structure of an island-shaped amorphous region and a nanocrystalline region where nanoscale α-Fe crystal phases are distributed in the amorphous matrix. The microstructure data of the iron-based nanocrystalline soft magnetic alloy powder in Examples 1-7 are shown in Table 1.

[0153] Figure 3 It is the SEM image of the iron-based nanocrystalline soft magnetic alloy powder in Example 1. As can be seen from the figure, most of the iron-based nanocrystalline soft magnetic alloy powder is spherical, and a few are quasi-spherical or rod-shaped. After calibration, the average sphericity of the iron-based nanocrystalline soft magnetic alloy powder is 0.91. The sphericity data of the iron-based nanocrystalline soft magnetic alloy powder in Examples 1-7 are listed in Table 1.

[0154] Figure 4 It is the VSM curve of the iron-based nanocrystalline soft magnetic alloy powder in Example 1. As can be seen from the figure, the VSM curve of the powder is of typical soft magnetic characteristics, where the M s and H c are 125.0 emu / g and 0.8 Oe respectively.

[0155] Figure 5It is the curve of the power loss of the soft magnetic composite material in Example 1 varying with the maximum working magnetic flux density at a frequency of 1 MHz. It can be seen from the figure that the 1 MHz / 10 mT loss of the soft magnetic composite material in Example 1 is 85 mW / cm 3 、the 1 MHz / 20 mT loss is 553 mW / cm 3 、the 2 MHz / 30 mT loss is 2981 mW / cm 3 。The power loss data of the soft magnetic composite materials prepared in Examples 8 - 17 are listed in Table 2.

[0156] Figure 6 It is the curve of the permeability of the soft magnetic composite material in Example 1 varying with the frequency. It can be seen from the figure that the permeability of the soft magnetic composite material prepared in Example 1 remains stable in the range of 1k - 10 MHz, and the permeability at 1 MHz is 30.3. The permeability data of the soft magnetic composite materials prepared in Examples 8 - 17 are listed in Table 2.

[0157] Figure 7 It is the curve of the DC bias performance of the soft magnetic composite material in Example 1 varying with the superimposed field strength. It can be seen from the figure that the DC bias performance of the soft magnetic composite material prepared in Example 1 is 80% when the DC superimposed field is 100 Oe. The DC bias performance data of the soft magnetic composite materials prepared in Examples 8 - 17 are listed in Table 2.

[0158] Figure 8 It is the internal SEM image and the main element distribution map of the soft magnetic composite material in Example 14. Figure 8 In (a) is the internal SEM image of the soft magnetic composite material, Figure 8 in (b), (c) and (d) are the distribution maps of Fe element, Si element and Ni element in the corresponding regions respectively. It can be seen from the figure that the Si element is mainly contained in the nanocrystalline soft magnetic alloy powder, the Ni element is mainly distributed in the iron-nickel powder, and the Fe element content in the nanocrystalline soft magnetic alloy powder is higher than that in the iron-nickel powder.

[0159] The soft magnetic properties of the soft magnetic composite materials prepared in Examples 14 - 23 are shown in Table 3. It can be seen from the table that the loss of the soft magnetic composite material prepared in Example 14 at 1 MHz / 20 mT is 248 mW / cm 3 ,the permeability at 1 MHz is 43.6, and the DC bias performance is 86% when the bias field is 100 Oe.

[0160] Figure 9 It is the surface morphology, element distribution and cross-section SEM image of the iron-based nanocrystalline soft magnetic alloy powder coated with ZnO insulating layer in Example 24. Figure 9 In (a) is the surface morphology of the iron-based nanocrystalline soft magnetic alloy powder coated with ZnO insulating layer, Figure 9In (b), (c), (d), and (e) are the distribution diagrams of Fe element, Si element, O element, and Zn element respectively. Figure 9 In (f) is the cross-sectional SEM image of the iron-based nanocrystalline soft magnetic alloy powder coated with a ZnO insulating layer. It can be seen from the figure that a uniform and dense ZnO layer (the area marked by the white dotted line) is formed on the surface of the powder. It can be known from the cross-sectional SEM image that the average thickness of the ZnO layer is about 110 nm.

[0161] The soft magnetic property data of the soft magnetic composite containing an insulating material prepared in Examples 24-29 are shown in Table 4. It can be seen from the table that the loss of the soft magnetic composite containing an insulating material prepared in Example 24 is 304 mW / cm under the conditions of 1 MHz / 20 mT 3 and the loss under the conditions of 3 MHz / 50 mT is 11520 mW / cm. 3 The magnetic permeability under the condition of 1 MHz is 62.0, and the DC bias performance is 54% when the bias field is 100 Oe.

[0162] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that: they can still modify the technical solutions recorded in the foregoing embodiments, or perform equivalent replacements on some or all of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A kind of iron-based nanocrystalline soft magnetic alloy powder, characterized in that, The powder particles have a heterogeneous nanocrystalline structure, and the heterogeneous nanocrystalline structure includes three-dimensional island-shaped amorphous regions and nanocrystalline regions. The average diameter of the three-dimensional island-shaped amorphous regions is 50-100 nm, and the number density of the three-dimensional island-shaped amorphous regions is at 10 19 -10 20 m -3 order of magnitude.

2. The iron-based nanocrystalline soft magnetic alloy powder according to claim 1, characterized in that, The nanocrystalline region contains a nanoscale α-Fe crystal phase and an amorphous matrix phase. The average diameter of the α-Fe crystal phase is 8-14 nm, and the number density of the α-Fe crystal phase is at 10 22 -10 23 m -3 order of magnitude.

3. The iron-based nanocrystalline soft magnetic alloy powder according to claim 1, characterized in that, The chemical element composition of the iron-based nanocrystalline soft magnetic alloy powder satisfies the relational expression: Fe a Co b Ni c Si d B e P f C g Nb h Cu i , where the subscripts a, b, c, d, e, f, g, h, i respectively represent the atomic percentages of the alloying elements, and satisfy the following conditions: 59 ≤ a ≤ 72; 0 ≤ b ≤ 10; 0 ≤ c ≤ 5; 69 ≤ a + b + c ≤ 72; 12.5 ≤ d ≤ 15.5; 9 ≤ e ≤ 12; 0 ≤ f ≤ 2; 0 ≤ g ≤ 2; 3 ≤ h ≤ 5; 0.6 ≤ i ≤ 0.9; a + b + c + d + e + f + g + h + i = 100.

4. The iron-based nanocrystalline soft magnetic alloy powder according to claim 1, characterized in that, The shape of the powder particles is spherical or quasi-spherical, and the average sphericity of the powder particles is ≥ 0.

9.

5. The iron-based nanocrystalline soft magnetic alloy powder according to claim 1, characterized in that, The saturation magnetization of the iron-based nanocrystalline soft magnetic alloy powder is 100 - 145 emu / g, and the coercivity is < 2 Oe.

6. A preparation method of the iron-based nanocrystalline soft magnetic alloy powder according to any one of claims 1-5, characterized in that, It includes the following steps: S1: Using a multi-stage crushing and atomization process to make the master alloy of the iron-based nanocrystalline soft magnetic alloy into an amorphous precursor powder. The multi-stage crushing and atomization process successively includes four main links, namely master alloy melting, alloy melt gas atomization, rotary mechanical atomization, and water cooling. Among them, the distance between the gas outlet in the alloy melt gas atomization and the rotary disk in the rotary mechanical atomization link is 110 - 130 mm, and the rotational speed of the rotary disk in the rotary mechanical atomization is 6000 - 20000 rpm; S2: Using a rotary annealing furnace to conduct heat treatment on the amorphous precursor powder obtained in step S1 under vacuum or inert gas protection to obtain the iron-based nanocrystalline soft magnetic alloy powder. The temperature of the heat treatment is 560 - 620 °C, the time is 0.5 - 2 hours, and the rotational speed of the sample chamber is 5 - 60 rpm.

7. A kind of soft magnetic composite material, characterized in that, It contains soft magnetic powder and a coating layer coated on the surface of the soft magnetic powder. The coating layer contains a binder. The soft magnetic powder is the iron-based nanocrystalline soft magnetic alloy powder according to any one of claims 1 - 5, or the soft magnetic powder is composed of the iron-based nanocrystalline soft magnetic alloy powder according to any one of claims 1 - 5 and alloy powder in combination. The alloy powder includes at least one of iron-nickel powder, iron-nickel-molybdenum powder, iron-silicon powder, iron-silicon-aluminum powder, iron-silicon-chromium powder, carbonyl iron powder, and pure iron powder.

8. The soft magnetic composite material according to claim 7, characterized in that, The binder is selected from at least one of epoxy resin, silicone resin, and phenolic resin.

9. The soft magnetic composite material according to claim 7, characterized in that, The mass of the binder is 1% - 5% of the total mass of the soft magnetic composite material.

10. The soft magnetic composite material according to claim 7, characterized in that, The coating layer further contains at least one of an insulating material and a lubricant.

11. The soft magnetic composite material according to claim 10, characterized in that, When the coating layer contains an insulating material, the insulating material is selected from at least one of zinc oxide, silicon dioxide, zirconium dioxide, phosphate, aluminum trioxide, titanium dioxide, and magnesium oxide.

12. The soft magnetic composite material according to claim 11, characterized in that, When the coating layer contains an insulating material, the thickness of the insulating material is 10 - 150 nm.

13. The soft magnetic composite material according to claim 10, characterized in that, When the coating layer contains a lubricant, the lubricant is selected from at least one of zinc stearate, magnesium stearate, aluminum stearate, calcium stearate, and graphite powder.

14. The soft magnetic composite material according to claim 13, characterized in that, When the coating layer contains a lubricant, the mass of the lubricant is 0% - 1% of the total mass of the soft magnetic composite material.

15. The soft magnetic composite material according to claim 7, characterized in that, When the soft magnetic powder is the iron-based nanocrystalline soft magnetic alloy powder according to any one of claims 1-5, and the pressing pressure and heat treatment temperature of the soft magnetic composite material are 400-800 MPa and 150-250 °C respectively, the loss of the soft magnetic composite material under the condition of 1 MHz / 10 mT is 80-120 mW / cm 3 , the loss under the condition of 1 MHz / 20 mT is 500-750 mW / cm 3 , the loss under the condition of 2 MHz / 30 mT is 2800-3800 mW / cm 3 , the magnetic permeability of the soft magnetic composite material at 1 MHz is 25-32, and the DC bias performance of the soft magnetic composite material at a bias field of 100 Oe is 76%-83%.

16. The soft magnetic composite material according to claim 7, characterized in that, When the soft magnetic powder is composed of the iron-based nanocrystalline soft magnetic alloy powder and alloy powder as described in any one of claims 1-5, the alloy powder includes at least one of iron-nickel powder, iron-nickel-molybdenum powder, iron-silicon powder, iron-silicon-aluminum powder, iron-silicon-chromium powder, carbonyl iron powder and pure iron powder, and when the pressing pressure and heat treatment temperature of the soft magnetic composite material are 400-800 MPa and 150-250 °C respectively, the loss of the soft magnetic composite material under the condition of 1 MHz / 20 mT is 200-700 mW / cm 3 , the magnetic permeability of the soft magnetic composite material under the condition of 1 MHz is 40-50, and the DC bias performance of the soft magnetic composite material when the bias field is 100 Oe is 75%-93%.

17. The soft magnetic composite material according to claim 7, characterized in that, When the soft magnetic powder is the iron-based nanocrystalline soft magnetic alloy powder according to any one of claims 1-5, the coating layer of the soft magnetic composite material contains an insulating material, and the pressing pressure and heat treatment temperature of the soft magnetic composite material are 1600-2200 MPa and 560-620 °C respectively, the loss of the soft magnetic composite material under the condition of 1 MHz / 20 mT is 250-450 mW / cm 3 , and the loss under the condition of 3 MHz / 50 mT is 10000-18000 mW / cm 3 . The magnetic permeability of the soft magnetic composite material at 1 MHz is 58-68, and the DC bias performance of the soft magnetic composite material when the bias field is 100 Oe is 48%-58%.

18. A preparation method of the soft magnetic composite material according to any one of claims 7-17, characterized in that,It includes the following steps: M1: Mix the soft magnetic powder and the coating layer raw materials to obtain a composite magnetic powder; the soft magnetic powder is the iron-based nanocrystalline soft magnetic alloy powder according to any one of claims 1 - 5, or is composed of the iron-based nanocrystalline soft magnetic alloy powder according to any one of claims 1 - 5 and alloy powder in combination. The alloy powder includes at least one of iron-nickel powder, iron-nickel-molybdenum powder, iron-silicon powder, iron-silicon-aluminum powder, iron-silicon-chromium powder, carbonyl iron powder, and pure iron powder; the coating layer raw materials contain a binder, or simultaneously contain a lubricant; M2: The composite magnetic powder is pressed and heat-treated to obtain a soft magnetic composite material, where the pressure of the pressing and the temperature of the heat treatment are 400 - 800 MPa and 150 - 250 °C respectively, or the pressure of the pressing and the temperature of the heat treatment are 1600 - 2200 MPa and 560 - 620 °C respectively.

19. The preparation method of the soft magnetic composite material according to claim 18, characterized in that, When the pressure of the pressing and the temperature of the heat treatment in step M2 are 1600 - 2200 MPa and 560 - 620 °C respectively, the iron-based nanocrystalline soft magnetic alloy powder is an amorphous precursor powder. The amorphous precursor powder is made from the master alloy of the iron-based nanocrystalline soft magnetic alloy through a multi-stage crushing and atomization process. The multi-stage crushing and atomization process successively includes four main links, namely master alloy melting, alloy melt gas atomization, rotary disk mechanical atomization, and water cooling. Among them, the distance between the gas outlet in the alloy melt gas atomization and the rotary disk in the rotary disk mechanical atomization link is 110 - 130 mm, and the rotational speed of the rotary disk in the rotary disk mechanical atomization is 6000 - 20000 rpm.

20. The preparation method of the soft magnetic composite material according to claim 18, characterized in that, When the raw material of the coating layer in step M1 contains an insulating material, the insulating material is generated through a sol-gel reaction or a chemical in-situ reaction. The solvent used in the sol-gel reaction or the chemical in-situ reaction is acetone or ethanol, and the reaction temperature is 40 - 100 °C.

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