Iron-based soft magnetic composite material and preparation method and application thereof

Abstract

The invention provides an iron-based soft magnetic composite material and a preparation method and application thereof, the iron-based soft magnetic composite material comprises an iron matrix phase and iron-silicon-boron particles distributed in the iron matrix phase and having a heterostructure, and the heterostructure comprises a composite phase formed by an amorphous phase and an iron-boron crystal phase; the amorphous phase comprises a mixed phase formed by an iron-silicon crystal phase and an iron-based amorphous phase; and a crystal phase interface is arranged between the iron matrix phase and the iron-silicon-boron particles. The iron-based soft magnetic composite material satisfies the following conditions: the thickness of the crystal phase interface is 0.2-0.5 [mu] m, and / or the size of the gradient crystal grains is 0.1-2 [mu] m. Through a heterostructure formed by an amorphous phase and an iron-boron crystal phase, excellent mechanical strength can be achieved while excellent soft magnetic performance is guaranteed.

Description

Technical Field

[0001] The present invention relates to the technical field of soft magnetic composite materials, and particularly relates to an iron-based soft magnetic composite material, a preparation method thereof, and an application thereof. Background Art

[0002] Soft magnetic materials can rapidly change their magnetic properties under a relatively low magnetic field intensity, usually having a low coercivity and a high saturation magnetic induction intensity, and are widely used in fields such as power equipment, magnetic storage, and sensors, and are regarded as the basic materials in the power era and the artificial intelligence era. The history of soft magnetic materials can be traced back to the early 1990s. After years of development, various types have been developed, such as silicon steel, permalloy, soft ferrite, amorphous alloy, and amorphous nanocrystalline alloy.

[0003] With the continuous development of the electronic power industry and the increasing demand for energy conservation and emission reduction, further improving the saturation magnetic induction intensity (Bs) of soft magnetic materials and reducing the coercivity (Hc) can effectively improve the magnetic field utilization rate and reduce energy loss. In addition, in extreme working environments such as mechanical loads where a large centrifugal force is generated by the rotation of the rotor, soft magnetic materials also need to have sufficient mechanical properties. Although traditional silicon steel has a high saturation magnetic induction intensity, its resistivity is low, resulting in large eddy current losses. In contrast, due to the disordered atomic arrangement characteristics of amorphous / nanocrystalline materials, they have an extremely low coercivity, high resistivity, and excellent strength.

[0004] However, amorphous materials cannot dissipate energy through dislocations like crystalline materials during the deformation process, but can only generate brittle fractures through shear localization, and have poor thermal stability, which limits their application in high-temperature environments.

[0005] Soft magnetic composite materials are regarded as an important direction for the development of soft magnetic materials. They combine the excellent magnetic properties of soft magnetic materials and the good mechanical properties of composite materials, and thus have broad application prospects in modern high-performance magnetic devices.

[0006] However, existing soft magnetic composite materials still have problems of relatively low mechanical strength and relatively inferior magnetic properties. Summary of the Invention

[0007] Aiming at the deficiencies of the existing technology, the purpose of the present invention is to provide an iron-based soft magnetic composite material, a preparation method thereof, and an application thereof. By directly ball milling, pre-pressing, and spark plasma sintering soft magnetic amorphous powder and crystalline powder to form a heterogeneous structure, the magnetic properties and mechanical strength of the iron-based soft magnetic composite material can be taken into account.

[0008] To achieve this purpose, the present invention adopts the following technical solutions:

[0009] In a first aspect, the present invention provides an iron-based soft magnetic composite material, which includes an iron matrix phase and iron-silicon-boron particles with a heterogeneous structure distributed in the iron matrix phase. The heterogeneous structure includes a composite phase formed by an amorphous phase and an iron-boron crystal phase; the amorphous phase includes a mixed phase formed by an iron-silicon crystal phase and an iron-based amorphous phase; there is a crystal phase interface between the iron matrix phase and the iron-silicon-boron particles. The iron-based soft magnetic composite material satisfies that the thickness of the crystal phase interface is 0.2 to 0.5 μm, and / or the size of the gradient grains is 0.1 to 2 μm.

[0010] The iron-based soft magnetic composite material provided by the present invention forms a heterogeneous structure with an amorphous phase and an iron-boron crystal phase. In this heterogeneous structure, the iron-silicon-boron amorphous phase and the iron crystal phase are intertwined, which can take into account both mechanical strength and soft magnetic properties; moreover, the iron-based soft magnetic composite material also includes gradient grains near the crystal phase interface, and these gradient grains can play a role in improving strength. In the present invention, the thickness of the crystal phase interface is within the range of 0.2 to 0.5 μm and / or the size of the gradient grains is within the range of 0.1 to 2 μm, which can better improve mechanical strength and soft magnetic properties.

[0011] Preferably, the thickness of the crystal phase interface is 0.2 to 0.5 μm, for example, it can be 0.2 μm, 0.22 μm, 0.23 μm, 0.24 μm, 0.25 μm, 0.28 μm, 0.30 μm, 0.32 μm, 0.33 μm, 0.35 μm, 0.38 μm, 0.4 μm, 0.42 μm, 0.45 μm, 0.48 μm or 0.5 μm, etc., but not limited to the listed values, and other unlisted values within this range are equally applicable.

[0012] Preferably, the size of the gradient grains is 0.1 to 2 μm, for example, it can be 0.1 μm, 0.4 μm, 0.6 μm, 0.8 μm, 1 μm, 1.2 μm, 1.4 μm, 1.6 μm, 1.8 μm or 2 μm, etc., but not limited to the listed values, and other unlisted values within this range are equally applicable. Further, the size of these gradient grains is 0.1 to 2 μm, and controlling the size within this range can effectively coordinate stress, prevent premature interface failure, and thus improve mechanical strength and soft magnetic properties.

[0013] Preferably, the width of the crystal phase interface is 0.3 to 0.5 μm, for example, it can be 0.3 μm, 0.33 μm, 0.35 μm, 0.37 μm, 0.39 μm, 0.42 μm, 0.44 μm, 0.46 μm, 0.48 μm or 0.5 μm, etc., but not limited to the listed values, and other unlisted values within this range are equally applicable.

[0014] Preferably, the width of the crystal phase interface in the present invention is within the above range. When the width of the crystal phase interface is relatively large, it is necessary to extend the sintering time and sintering temperature, which will cause serious crystallization of the amorphous phase, resulting in a decrease in magnetic properties. When the width of the crystal phase interface is relatively small, there is insufficient bonding force, and the interface is prone to cracking and debonding when subjected to a load, and brittle fracture is likely to occur.

[0015] Preferably, the width of the amorphous phase-containing is 160-230 nm. For example, it can be 160 nm, 168 nm, 176 nm, 184 nm, 192 nm, 199 nm, 207 nm, 215 nm, 223 nm or 230 nm, etc., but not limited to the listed values. Other unlisted values within this range are equally applicable.

[0016] Preferably, the width of the iron-boron crystal phase is 80-120 nm. For example, it can be 80 nm, 85 nm, 89 nm, 94 nm, 98 nm, 103 nm, 107 nm, 112 nm, 116 nm or 120 nm, etc., but not limited to the listed values. Other unlisted values within this range are equally applicable.

[0017] Preferably, the width of the amorphous phase-containing and the width of the iron-boron crystal phase in the present invention are within the above range. Beyond this width, there are defects that hinder the expansion of magnetic domains and cause an increase in coercivity. Below this width, the amorphous content increases, and the brittleness increases significantly, deteriorating the mechanical properties.

[0018] Preferably, in the X-ray diffraction pattern when measuring the iron-based soft magnetic composite material by an X-ray diffraction apparatus using CuKα1 radiation, the diffraction peaks observed at the positions of 2θ = 43-47°, for example, can be 43°, 43.5°, 43.9°, 44.4°, 44.8°, 45.3°, 45.7°, 46.2°, 46.6° or 47°, etc., but not limited to the listed values. Other unlisted values within this range are equally applicable.

[0019] Preferably, in the X-ray diffraction pattern when measuring the iron-based soft magnetic composite material by an X-ray diffraction apparatus using CuKα1 radiation, the diffraction peaks observed at the positions of 2θ = 64-66°, for example, can be 64°, 64.3°, 64.5°, 64.7°, 64.9°, 65.2°, 65.4°, 65.6°, 65.8° or 66°, etc., but not limited to the listed values. Other unlisted values within this range are equally applicable.

[0020] Preferably, in the X-ray diffraction pattern obtained when measuring the iron-based soft magnetic composite material by an X-ray diffractometer using CuKα1 radiation, the diffraction peak observed at the position of 2θ = 81 - 84° can be, for example, 81°, 81.4°, 81.7°, 82°, 82.4°, 82.7°, 83°, 83.4°, 83.7°, or 84°, etc., but is not limited to the listed values, and other unlisted values within this range are equally applicable.

[0021] Preferably, the content of iron in the iron-based soft magnetic composite material is 94.9 - 97.5 wt%, and can be, for example, 94.9 wt%, 95.2 wt%, 95.5 wt%, 95.8 wt%, 96.1 wt%, 96.4 wt%, 96.7 wt%, 97 wt%, 97.3 wt%, or 97.5 wt%, etc., but is not limited to the listed values, and other unlisted values within this range are equally applicable.

[0022] Preferably, the content of silicon in the iron-based soft magnetic composite material is 1.2 - 2.4 wt%, and can be, for example, 1.2 wt%, 1.4 wt%, 1.5 wt%, 1.6 wt%, 1.8 wt%, 1.9 wt%, 2 wt%, 2.2 wt%, 2.3 wt%, or 2.4 wt%, etc., but is not limited to the listed values, and other unlisted values within this range are equally applicable.

[0023] Preferably, the content of boron in the iron-based soft magnetic composite material is 1.3 - 2.7 wt%, and can be, for example, 1.3 wt%, 1.5 wt%, 1.7 wt%, 1.8 wt%, 2 wt%, 2.1 wt%, 2.3 wt%, 2.4 wt%, 2.6 wt%, or 2.7 wt%, etc., but is not limited to the listed values, and other unlisted values within this range are equally applicable.

[0024] Preferably, the particle size of the iron-based soft magnetic composite material is 2 - 24 μm, and can be, for example, 2 μm, 5 μm, 7 μm, 10 μm, 12 μm, 15 μm, 17 μm, 20 μm, 22 μm, or 24 μm, etc., but is not limited to the listed values, and other unlisted values within this range are equally applicable.

[0025] In a second aspect, the present invention provides a method for preparing the iron-based soft magnetic composite material described in the first aspect, and the preparation method includes the following steps:

[0026] (1) Mix soft magnetic amorphous powder and crystalline powder, and the obtained mixed powder is ball-milled to obtain mechanically treated powder;

[0027] (2) Pre-press the mechanically treated powder obtained in step (1) to obtain a green compact;

[0028] (3) Sinter the green body described in step (3) by spark plasma sintering to obtain an iron-based soft magnetic composite material.

[0029] The preparation method of the iron-based soft magnetic composite material provided by the second aspect of the present invention has the following advantages:

[0030] A. In the present invention, no precious metals Cu and Nb are added, so the cost is low.

[0031] B. The preparation method provided by the present invention can not only make the powder mixture uniform by ball milling the mixed powder, but also the ball milling process can promote the mechanical action between the amorphous powder FeSiB and the carbonyl iron powder. Among them, the amorphous powder FeSiB has extremely high strength and remains spherical particles during the ball milling process, while the carbonyl iron powder has low strength and is extruded and deformed during the ball milling process, adhering to the surface of the spherical FeSiB particles, which helps to obtain a dense sample during the subsequent pre-pressing process.

[0032] C. The present invention adopts a pre-pressing and forming step, which has the effect of compressing the powder into a more compact structure, thereby improving its fluidity and density.

[0033] D. The present invention uses spark plasma for vacuum sintering, which has the advantages of fast heating and high efficiency. Moreover, sintering in the supercooled liquid phase region makes use of the good fluidity of the amorphous phase to promote interface diffusion during the sintering process, promote interface bonding, and improve mechanical strength.

[0034] The formation principle of the heterogeneous structure in the present invention is as follows:

[0035] (1) Gradient grains. The grains near the crystal phase interface between the iron-silicon-boron particles and the iron matrix phase are finer, and the grains away from the interface gradually become coarser. This gradient structure is mainly due to the difference in the grain growth rate during the sintering process, and the grain growth near the interface is restricted. In addition, during the sintering process, Si and B elements at the interface diffuse into the iron particles in a gradient manner as solute atoms, inhibiting the diffusion of iron atoms, and finally forming a gradient structure.

[0036] (2) A double-layer structure composed of ultrafine columnar grains and equiaxed grains. The formation mechanism of this structure is related to the diffusion of elements at the interface. During the sintering process, Si and B elements diffuse into the iron particles. Since the mixing enthalpy of Si and Fe is more negative Si preferentially combines with Fe to form columnar grains, and then Fe combines with B to generate equiaxed grains.

[0037] (3) A heterogeneous structure composed of Fe2B, FeSi, and an amorphous phase. This structure is formed during the sintering process when the amorphous FeSiB particles partially crystallize. The atomic radius of the B atom is relatively small, making it easier to occupy interstitial positions, and thus more likely to transform from a disordered state to an ordered state at high temperatures, promoting the formation of Fe2B. In contrast, due to the relatively large atomic radius of the Si atom, the sorting process is slower, resulting in the coexistence of the amorphous phase and the crystal phase.

[0038] Preferably, the soft magnetic amorphous powder in step (1) includes amorphous FeSiB powder.

[0039] Preferably, in the amorphous FeSiB powder, the molar ratio of Fe:Si:B = (5.0 - 5.5):(0.3 - 0.5):1, where the molar fraction of Fe is 5.0, 5.1, 5.2, 5.3, 5.4, or 5.5, etc., and the molar fraction of Si is 0.3, 0.32, 0.35, 0.38, 0.39, 0.40, 0.41, 0.42, 0.45, 0.48, or 0.5, etc.

[0040] Preferably, the particle size range of the soft magnetic amorphous powder is 3 - 22 μm. For example, it can be 3 μm, 6 μm, 8 μm, 10 μm, 12 μm, 14 μm, 16 μm, 18 μm, 20 μm, or 22 μm, etc., but is not limited to the listed values, and other unlisted values within this range are equally applicable.

[0041] Preferably, the crystal powder includes carbonyl iron powder.

[0042] In the present invention, the raw materials used are amorphous powder FeSiB and carbonyl iron powder. Among them, FeSiB is a commercial amorphous powder with excellent soft magnetic properties, without adding precious metals Cu and Nb, and has a low cost. Carbonyl iron powder is widely used in industry, with high purity and low price.

[0043] Preferably, the particle size range of the crystal powder is 1 - 6 μm. For example, it can be 1 μm, 1.6 μm, 2.2 μm, 2.7 μm, 3.3 μm, 3.8 μm, 4.4 μm, 4.9 μm, 5.5 μm, or 6 μm, etc., but is not limited to the listed values, and other unlisted values within this range are equally applicable.

[0044] Preferably, the mass ratio of the amorphous FeSiB powder to the crystalline powder in step (1) is (0.5 - 0.8):1. For example, it can be 0.5:1, 0.52:1, 0.53:1, 0.54:1, 0.55:1, 0.57:1, 0.58:1, 0.6:1, 0.62:1, 0.65:1, 0.68:1, 0.7:1, 0.72:1, 0.75:1, 0.78:1 or 0.8:1, etc. However, it is not limited to the listed values, and other unlisted values within this range are equally applicable.

[0045] The present invention preferably has the mass ratio of the amorphous FeSiB powder to the crystalline powder as (0.5 - 0.8):1, which can better balance the soft magnetic properties and mechanical properties of the composite material.

[0046] Preferably, the ball milling medium for the ball milling in step (1) includes stainless steel grinding balls.

[0047] Preferably, the ball milling is carried out in a protective atmosphere.

[0048] Preferably, the protective atmosphere includes argon and / or nitrogen.

[0049] Preferably, the rotation speed of the ball milling is 200 - 300 r / min. For example, it can be 200 r / min, 212 r / min, 223 r / min, 234 r / min, 245 r / min, 256 r / min, 267 r / min, 278 r / min, 289 r / min or 300 r / min, etc. However, it is not limited to the listed values, and other unlisted values within this range are equally applicable.

[0050] The present invention preferably controls the rotation speed of the ball milling within the above range, which can better improve the bonding effect between the amorphous powder and the carbonyl iron powder, thereby promoting the formation of the heterogeneous structure.

[0051] Preferably, the ball milling time is 10 - 20 h. For example, it can be 10 h, 12 h, 13 h, 14 h, 15 h, 16 h, 17 h, 18 h, 19 h or 20 h, etc. However, it is not limited to the listed values, and other unlisted values within this range are equally applicable.

[0052] Preferably, the mass ratio of the ball milling medium to the mixed powder for the ball milling is 5 - 10:1. For example, it can be 5:1, 5.6:1, 6.2:1, 6.7:1, 7.3:1, 7.8:1, 8.4:1, 8.9:1, 9.5:1 or 10:1, etc. However, it is not limited to the listed values, and other unlisted values within this range are equally applicable.

[0053] Preferably, the mold material for the pre - pressing and forming in step (2) is tungsten steel.

[0054] The present invention has no special requirements for the quality of the mechanically treated powder added in the pre-pressing forming, and can be adaptively adjusted according to requirements such as the size of the final iron-based soft magnetic composite material. For example, the quality of the mechanically treated powder in the pre-pressing forming can be 5 to 10 g.

[0055] Preferably, the pressure of the pre-pressing forming is 30 to 50 MPa. For example, it can be 30 MPa, 33 MPa, 35 MPa, 37 MPa, 39 MPa, 42 MPa, 44 MPa, 46 MPa, 48 MPa or 50 MPa, etc., but is not limited to the listed values, and other unlisted values within this range are equally applicable.

[0056] Preferably, the pressure holding time of the pre-pressing forming is 1 to 5 min. For example, it can be 1 min, 1.5 min, 1.9 min, 2.4 min, 2.8 min, 3.3 min, 3.7 min, 4.2 min, 4.6 min or 5 min, etc., but is not limited to the listed values, and other unlisted values within this range are equally applicable.

[0057] Preferably, the temperature of the spark plasma sintering in step (3) is 450 to 600 °C. For example, it can be 450 °C, 467 °C, 484 °C, 500 °C, 517 °C, 534 °C, 550 °C, 567 °C, 584 °C or 600 °C, etc., but is not limited to the listed values, and other unlisted values within this range are equally applicable.

[0058] Preferably, the pressure of the spark plasma sintering is 200 to 500 MPa. For example, it can be 200 MPa, 234 MPa, 267 MPa, 300 MPa, 334 MPa, 367 MPa, 400 MPa, 434 MPa, 467 MPa or 500 MPa, etc., but is not limited to the listed values, and other unlisted values within this range are equally applicable.

[0059] The present invention preferably controls the pressure and temperature of the spark plasma sintering within the above ranges, so that the density of the sample can be significantly improved, and thus a composite material with a heterogeneous structure can be better obtained, and the mechanical properties and soft magnetic properties of the final composite material are more excellent.

[0060] Preferably, the heat preservation and pressure holding time of the spark plasma sintering is 10 to 30 min. For example, it can be 10 min, 13 min, 15 min, 17 min, 19 min, 22 min, 24 min, 26 min, 28 min or 30 min, etc., but is not limited to the listed values, and other unlisted values within this range are equally applicable.

[0061] Preferably, the heating rate of the spark plasma sintering is 50-100 °C / min. For example, it can be 50 °C / min, 56 °C / min, 62 °C / min, 67 °C / min, 73 °C / min, 78 °C / min, 84 °C / min, 89 °C / min, 95 °C / min or 100 °C / min, etc., but is not limited to the listed values, and other unlisted values within this range are equally applicable.

[0062] The present invention has no requirement for the order of heating and pressure boosting. Generally, the time required for heating is 5-6 min, and the time required for pressure boosting is about 0.5-2 min. Heating or pressure boosting can be carried out synchronously, or heating can be carried out first and then pressure boosting, or pressure boosting can be carried out first and then heating. As long as the final holding time of pressure is ensured, a better spark plasma sintering effect can be obtained.

[0063] As a preferred technical solution of the present invention, the preparation method includes the following steps:

[0064] (1) Mix amorphous FeSiB powder and crystalline powder with a mass ratio of amorphous FeSiB powder to crystalline powder of (0.5-0.8):1, and the particle size range of the amorphous FeSiB powder is 3-22 μm and the particle size range of the crystalline powder is 1-6 μm to obtain a mixed powder; wherein, in the amorphous FeSiB powder, the molar ratio of Fe:Si:B=(5.0-5.5):(0.3-0.5):1;

[0065] According to the mass ratio of stainless steel grinding balls to the mixed powder of (5-10):1, the mixed powder is ball-milled at 200-300 r / min for 10-20 h in a protective atmosphere to obtain a mechanically treated powder;

[0066] (2) Pre-press the mechanically treated powder obtained in step (1), the pressure of the pre-pressing is 30-50 MPa, and the pressure holding time is 1-5 min to obtain a green compact;

[0067] (3) Heat the green compact obtained in step (3) to 450-600 °C at a heating rate of 50-100 °C / min, and hold for 10-30 min under a pressure of 200-500 MPa for spark plasma sintering to obtain an iron-based soft magnetic composite material.

[0068] In the third aspect, the present invention provides an application of the iron-based soft magnetic composite material described in the first aspect in power equipment, magnetic storage or sensors.

[0069] Due to the combination of high strength and high saturation magnetic induction intensity, the iron-based soft magnetic composite material provided in the first aspect of the present invention can be widely used in fields with certain mechanical strength requirements for soft magnetic materials, such as power equipment, magnetic storage or sensors, etc.

[0070] Compared with the prior art, the present invention has at least the following beneficial effects:

[0071] (1) The iron-based soft magnetic composite material provided by the present invention does not add precious metals Cu and Nb, has low cost, high density, and significantly improved mechanical properties. Under preferred conditions, the strength of the iron-based soft magnetic composite material is above 1350 MPa, the plasticity is above 16.5%, while maintaining an extremely high saturation magnetic induction intensity above 2.0 T, and has a low coercive force within 240 A / m, which can meet the requirements of soft magnetic materials with mechanical strength requirements;

[0072] (2) The preparation method of the iron-based soft magnetic composite material provided by the present invention can make the powder mixture uniform by ball-milling the mixed powder. Among them, the amorphous has extremely high strength and remains spherical particles during the ball-milling process, while the carbonyl iron powder has low strength and is extruded and deformed during the ball-milling process, adhering to the surface of the spherical FeSiB particles, which helps to obtain a dense sample. The finally obtained iron-based soft magnetic composite material not only has excellent mechanical strength but also has excellent soft magnetic properties, and has broad application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0073] Figure 1 XRD diagram of the composite materials prepared in Examples 1-3 of the present invention.

[0074] Figure 2 SEM diagram of the composite material prepared in Example 1 of the present invention.

[0075] Figure 3 SEM diagram of the composite material prepared in Example 2 of the present invention.

[0076] Figure 4 SEM diagram of the composite material prepared in Example 3 of the present invention.

[0077] Figure 5 TEM analysis diagram of the composite material prepared in Example 3 of the present invention.

[0078] Figure 6 Magnified view of the interface of the composite material prepared in Example 3 of the present invention.

[0079] Figure 7 Schematic diagram of the internal composition of the composite material prepared in Example 3 of the present invention.

[0080] Figure 8 Compressive stress-strain curve diagram of the composite materials prepared in Examples 1-3 of the present invention.

[0081] Figure 9 Hysteresis loop of the composite material prepared in Example 3 of the present invention.

[0082] Figure 10 Performance comparison diagram of the composite material prepared in Example 3 of the present invention. Specific embodiments

[0083] To facilitate the understanding of the present invention, the following examples are listed. Those skilled in the art should understand that the examples are only for helping to understand the present invention and should not be regarded as specific limitations on the present invention.

[0084] Example 1

[0085] This example provides a preparation method of an iron-based soft magnetic composite material. The preparation method includes the following steps:

[0086] (1) According to the mass ratio of amorphous FeSiB powder to crystal powder being 4:1, mix amorphous FeSiB powder with a particle size range of 10 - 20 μm and crystal powder with a particle size range of 2 - 5 μm to obtain a mixed powder; wherein, in the amorphous FeSiB powder, the molar ratio of Fe:Si:B = 5.0:0.4:1;

[0087] According to the mass ratio of stainless steel grinding balls to the mixed powder being 10:1, ball-mill the mixed powder at 300 r / min for 10 h in a protective atmosphere to obtain mechanically treated powder;

[0088] (2) Perform pre-pressing on the mechanically treated powder obtained in step (1). The pressure for pre-pressing is 30 MPa, and the pressure holding time is 1 min to obtain a green compact;

[0089] (3) Heat the green compact obtained in step (3) to 550 °C at a heating rate of 100 °C / min and then to 600 °C at 50 °C / min, and keep it at a pressure of 200 MPa for 10 min for spark plasma sintering to obtain an iron-based soft magnetic composite material.

[0090] Example 2

[0091] This example provides a preparation method of an iron-based soft magnetic composite material. The preparation method includes the following steps:

[0092] (1) According to the mass ratio of amorphous FeSiB powder to crystal powder being 1.5:1, mix amorphous FeSiB powder with a particle size range of 3 - 16 μm and crystal powder with a particle size range of 1 - 5 μm to obtain a mixed powder; wherein, in the amorphous FeSiB powder, the molar ratio of Fe:Si:B = 5.5:0.5:1;

[0093] According to the mass ratio of stainless steel grinding balls to the mixed powder being 10:1, ball-mill the mixed powder at 250 r / min for 20 h in a protective atmosphere to obtain mechanically treated powder;

[0094] (2) Pre-press the powder after the mechanical treatment in step (1). The pressure for pre-pressing is 50 MPa, and the pressure holding time is 2 min to obtain a green compact.

[0095] (3) Heat the green compact in step (3) at a heating rate of 100 °C / min to 550 °C and then at 50 °C / min to 600 °C, and keep it at a pressure of 200 MPa for 10 min for spark plasma sintering to obtain an iron-based soft magnetic composite material.

[0096] Example 3

[0097] This example provides a method for preparing an iron-based soft magnetic composite material. The preparation method includes the following steps:

[0098] (1) Mix amorphous FeSiB powder and crystalline powder with a mass ratio of amorphous FeSiB powder to crystalline powder of 2:3. The particle size range of the mixed amorphous FeSiB powder is 10 - 22 μm, and the particle size range of the crystalline powder is 2 - 5 μm to obtain a mixed powder. Among them, in the amorphous FeSiB powder, the molar ratio of Fe:Si:B = 5.2:0.3:1;

[0099] With a mass ratio of stainless steel grinding balls to the mixed powder of 10:1, the mixed powder is ball-milled at 300 r / min for 10 h in a protective atmosphere to obtain the powder after mechanical treatment;

[0100] (2) Pre-press the powder after the mechanical treatment in step (1). The pressure for pre-pressing is 50 MPa, and the pressure holding time is 1 min to obtain a green compact.

[0101] (3) Heat the green compact in step (3) at a heating rate of 100 °C / min to 550 °C and then at 50 °C / min to 600 °C, and keep it at a pressure of 200 MPa for 10 min for spark plasma sintering to obtain an iron-based soft magnetic composite material.

[0102] Example 4

[0103] This example provides a method for preparing an iron-based soft magnetic composite material. The preparation method includes the following steps:

[0104] (1) Mix amorphous FeSiB powder and crystalline powder with a mass ratio of amorphous FeSiB powder to crystalline powder of 0.8:1. The particle size range of the mixed amorphous FeSiB powder is 18 - 22 μm, and the particle size range of the crystalline powder is 1 - 6 μm to obtain a mixed powder. Among them, in the amorphous FeSiB powder, the molar ratio of Fe:Si:B = 5.3:0.45:1;

[0105] According to the mass ratio of stainless steel grinding balls to the mixed powder being 5:1, the mixed powder is ball-milled at 200 r / min for 20 h in a protective atmosphere to obtain the mechanically treated powder;

[0106] (2) The mechanically treated powder obtained in step (1) is pre-pressed and formed. The pressure for the pre-pressing and forming is 30 MPa, and the pressure holding time is 5 min to obtain a green compact;

[0107] (3) The green compact in step (3) is heated to 520 °C at a heating rate of 90 °C / min and then to 580 °C at a heating rate of 55 °C / min, and is kept at a pressure of 300 MPa for 12 min to perform spark plasma sintering to obtain an iron-based soft magnetic composite material.

[0108] Example 5

[0109] This example provides a preparation method of an iron-based soft magnetic composite material. The preparation method includes the following steps:

[0110] (1) According to the mass ratio of amorphous FeSiB powder and crystal powder being 0.5:1, amorphous FeSiB powder with a mixed particle size range of 3 - 22 μm and crystal powder with a particle size range of 1 - 6 μm are mixed to obtain a mixed powder; among them, in the amorphous FeSiB powder, the molar ratio of Fe:Si:B = 5.3:0.45:1;

[0111] According to the mass ratio of stainless steel grinding balls to the mixed powder being 8:1, the mixed powder is ball-milled at 250 r / min for 15 h in a protective atmosphere to obtain the mechanically treated powder;

[0112] (2) The mechanically treated powder obtained in step (1) is pre-pressed and formed. The pressure for the pre-pressing and forming is 40 MPa, and the pressure holding time is 3 min to obtain a green compact;

[0113] (3) The green compact in step (3) is heated to 480 °C at a heating rate of 95 °C / min and then to 580 °C at a heating rate of 60 °C / min, and is kept at a pressure of 500 MPa for 10 min to perform spark plasma sintering to obtain an iron-based soft magnetic composite material.

[0114] Example 6

[0115] This example provides a preparation method of an iron-based soft magnetic composite material. Except that the rotation speed of ball milling is 400 r / min, the rest are the same as those in Example 3 and will not be elaborated here.

[0116] Example 7

[0117] This embodiment provides a method for preparing an iron-based soft magnetic composite material. Except that the rotation speed of ball milling is 100 r / min, the rest are the same as those in Embodiment 3 and will not be elaborated here.

[0118] Example 8

[0119] This embodiment provides a method for preparing an iron-based soft magnetic composite material. Except that the pressure of spark plasma sintering is 100 MPa, the rest are the same as those in Embodiment 3 and will not be elaborated here.

[0120] Example 9

[0121] This embodiment provides a method for preparing an iron-based soft magnetic composite material. Except that the pressure of spark plasma sintering is 600 MPa, the rest are the same as those in Embodiment 3 and will not be elaborated here.

[0122] Example 10

[0123] This embodiment provides a method for preparing an iron-based soft magnetic composite material. Except that the mass ratio of amorphous FeSiB powder to crystalline powder is 0.3:1, the rest are the same as those in Embodiment 3 and will not be elaborated here.

[0124] Example 11

[0125] This embodiment provides a method for preparing an iron-based soft magnetic composite material. Except that the mass ratio of amorphous FeSiB powder to crystalline powder is 8:1, the rest are the same as those in Embodiment 3 and will not be elaborated here.

[0126] Comparative Example 1

[0127] This comparative example provides a method for preparing an iron-based soft magnetic composite material. Except that no ball milling is performed and only simple mixing is carried out, the rest are the same as those in Embodiment 3 and will not be elaborated here.

[0128] Comparative Example 2

[0129] This comparative example provides a method for preparing an iron-based soft magnetic composite material. Except that spark plasma sintering is replaced by sintering in a tube furnace according to the same heating curve, the rest are the same as those in Embodiment 3 and will not be elaborated here.

[0130] Test method: After mechanical grinding and polishing of the sintered samples, a scanning electron microscope (SEM) was used to test the microstructure of the iron-based soft magnetic composite material, and a transmission electron microscope (TEM) was used to test the size of each microstructure in the iron-based soft magnetic composite material. An X-ray diffractometer using CuKα1 rays was used to measure the X-ray diffraction pattern of the iron-based soft magnetic composite material, and the peak positions were recorded. A scanning electron microscope was used to test the particle size of the iron-based soft magnetic composite material itself.

[0131] Taking Examples 1 to 3 as an example, the XRD patterns of the obtained iron-based soft magnetic composite materials are as Figure 1 shown. It can be clearly seen from Figure 1 that the peak positions of the XRD fall within the preferred range defined in this application. The SEM images of the obtained iron-based soft magnetic composite materials are respectively as Figures 2 - 4 shown. It can be seen from Figures 2 - 4 that the sintered samples are basically composed of FeSiB particles, deformed iron-based crystal phase particles, and the interface between the two. Among them, the interface in Example 3 is the most obvious, and the width of the interface is the thickest. Figure 5 This is the TEM analysis image of the composite material prepared in Example 3 of the present invention. It can be seen from Figure 5 that the iron-based soft magnetic composite material prepared in Example 3 has an obvious heterogeneous structure, where Figure 5 a is the TEM image of the iron-based soft magnetic composite material. After magnifying part I, it is Figure 5 b. After magnifying part II, it is Figure 5 c. After magnifying part III, it is Figure 5 d. Among them, Figure 5 b represents the interface formed between the sintered particles, Figure 5 c material represents the iron crystal phase, Figure 5 d represents the internal phase composition of the FeSiB particles. It can be seen from Figure 6 that the composite material obtained in Example 3 has an obvious gradient grain structure near the interface. Figure 7 This is a schematic diagram of the internal composition of the composite material in Example 3. It can be seen from Figure 7 that part a is the iron crystal phase, and the specific composition is Fe2B. Part b is the amorphous phase, and the specific composition includes iron, silicon, and boron, that is, a heterogeneous structure including the coexistence of amorphous and crystal phases is formed. Figure 8 This is the compressive stress-strain curve diagram of Examples 1 to 3. It can be seen from Figure 8 that Example 3 has the best mechanical properties. From Figure 9 the hysteresis loop and Figure 10 by comparing the iron-based soft magnetic composite material in Example 3 with other soft magnetic materials, it can be seen that the iron-based soft magnetic composite material obtained in Example 3 has excellent soft magnetic properties, where the other soft magnetic materials are from the prior art.

[0132] The test results of the above examples and comparative examples are shown in Table 1 below.

[0133] Table 1

[0134]

[0135] The iron-based soft magnetic composites obtained from the above examples and comparative examples were subjected to compression stress-strain tests, and the magnetic hysteresis loop tests of the above iron-based soft magnetic composites were carried out using the magnetic measurement system MPMS3.

[0136] The test results are shown in Table 2 below.

[0137] Table 2

[0138]

[0139]

[0140] It can be seen from Tables 1 to 2 as follows:

[0141] (1) From Examples 3 to 5, it can be seen that the iron-based soft magnetic composite provided by the present invention can control the thickness of the crystal phase interface within the range of 0.2 - 0.5 μm, the size of the amorphous phase-containing region within the range of 120 - 230 nm, the size of the iron-boron crystal phase within the range of 80 - 150 nm, and the size range of the gradient grains within the range of 0.1 - 2.5 μm, and can have both excellent magnetic properties and mechanical properties, where the saturation magnetic induction intensity is above 2.0 T, the coercivity is above 240 A / m, the compressive strength is above 1350 MPa, and the elongation is above 16.5%.

[0142] (2) From Examples 3 and 6 to 7, it can be seen that the rotation speed of the ball milling in Example 3 is 300 r / min. Compared with Examples 6 to 7 where 400 r / min and 100 r / min are used respectively, the coercivity in Example 3 is only 245 A / m. In Examples 6 to 7, although the thickness of the crystal phase interface in the finally obtained product is slightly higher or lower due to the relatively decreased mixing effect compared with Example 3, the coercivities of the finally obtained iron-based soft magnetic composites are as high as 331 A / m and 435 A / m respectively. This shows that by preferably selecting a specific ball milling range, the present invention not only achieves the effect of uniform mixing, but also can improve the microstructure and soft magnetic properties of the iron-based soft magnetic composite.

[0143] (3) It can be seen from the comprehensive implementation of Example 3 and Examples 8 to 9 that the pressure of spark plasma sintering in Example 3 is 200 MPa. Compared with Examples 8 to 9 where 100 MPa and 600 MPa are used respectively, the coercivity in Example 3 is only 245 A / m, and the saturation magnetic induction intensity is 2.05 T. However, in Example 8, the low sintering pressure leads to insufficient fluidity of the powder during sintering, forming voids during sintering, low density, and finally the thickness of the crystal phase interface is 0.1 - 0.3 μm, and the size range of gradient grains reaches 0.1 - 3.0 μm. Eventually, the mechanical and magnetic properties are significantly lower than those in Example 3; in Example 9, the pressure of spark plasma sintering is too high. Although it will improve the density, the size range of the FeB crystal phase is 100 - 140 nm, the magnetic properties decline, and the coercivity rises to 392 A / m. Thus, it shows that by optimizing the specific pressure of spark plasma sintering, the present invention can take into account the improvement of the mechanical properties and soft magnetic properties of the iron-based soft magnetic composite material.

[0144] (4) It can be seen from the comprehensive implementation of Example 3 and Examples 10 to 11 and Examples 1 to 2 that an increase in the content of iron carbonyl will lead to a decrease in the strength of the material, an increase in plasticity, but a decrease in magnetic properties; if the content of iron carbonyl powder is too low, the proportion of the soft matrix is small, and the amorphous phase content of the hard phase increases, which will cause the sample to crack and fail prematurely before the strength reaches the highest point during the compression process. Moreover, if the content of the soft phase iron carbonyl is too low, the binder of the soft phase is insufficient, the formed density is poor, the pores increase, and the coercivity also increases. By optimizing the specific mass ratio of iron carbonyl powder and amorphous particles, the present invention can better improve the soft magnetic properties and mechanical properties.

[0145] (5) It can be seen from the comprehensive implementation of Example 1 and Comparative Examples 1 to 2 that in Comparative Example 1, no ball milling is carried out, only simple mixing is performed, which will result in uneven distribution. At the same time, it will also reduce the flow degree of metal powder during sintering, increase the porosity, reduce the density, and deteriorate the mechanical and magnetic properties; while in Comparative Example 2, a tube furnace is used, and it is difficult to apply pressure during sintering, and the sintered sample will have very poor density, and the mechanical and magnetic properties will deteriorate significantly.

[0146] The present invention uses the above examples to illustrate the detailed features of the present invention, but the present invention is not limited to the above detailed features, that is, it does not mean that the present invention must rely on the above detailed features to be implemented. Those skilled in the art should understand that any improvement to the present invention, the equivalent replacement of the selected technical features of the present invention, and the addition of auxiliary technical features, the selection of specific methods, etc., all fall within the protection scope and disclosure scope of the present invention.

Claims

1. A kind of iron-based soft magnetic composite material, characterized in that, The iron-based soft magnetic composite material comprises an iron matrix phase, and iron-silicon-boron particles with a heterogeneous structure distributed in the iron matrix phase. The heterogeneous structure includes a composite phase formed by an amorphous phase and an iron boride crystal phase; the amorphous phase-containing phase includes a mixed phase formed by an iron-silicon crystal phase and an iron-based amorphous phase; there is a crystal phase interface between the iron matrix phase and the iron-silicon-boron particles; The iron-based soft magnetic composite material further includes gradient grains near the crystal phase interface; The iron-based soft magnetic composite material satisfies that the thickness of the crystal phase interface is 0.2 - 0.5 μm, and / or the size of the gradient grains is 0.1 - 2 μm.

2. The iron-based soft magnetic composite material according to claim 1, wherein The width of the crystal phase interface is 0.3 - 0.5 μm; Preferably, the width of the amorphous phase-containing phase is 120 - 230 nm; Preferably, the width of the iron boride crystal phase is 80 - 150 nm; Preferably, the iron content in the iron-based soft magnetic composite material is 94.9 - 97.5 wt%; Preferably, the silicon content in the iron-based soft magnetic composite material is 1.2 - 2.4 wt%; Preferably, the boron content in the iron-based soft magnetic composite material is 1.3 - 2.7 wt%; Preferably, the particle size of the iron-based soft magnetic composite material is 0.7 - 24 μm.

3. A method for preparing the iron-based soft magnetic composite material according to claim 1 or 2, characterized in that, The preparation method includes the following steps: (1) Mix soft magnetic amorphous powder and crystal powder, and the obtained mixed powder is ball-milled to obtain mechanically treated powder; (2) The mechanically treated powder in step (1) is pre-pressed into a green compact; (3) The green compact in step (3) is subjected to spark plasma sintering to obtain an iron-based soft magnetic composite material.

4. The preparation method according to claim 3, characterized in that The soft magnetic amorphous powder in step (1) includes amorphous FeSiB powder; Preferably, in the amorphous FeSiB powder, the molar ratio of Fe:Si:B = (5.0 - 5.5):(0.3 - 0.5):1; Preferably, the particle size range of the soft magnetic amorphous powder is 3 - 22 μm; Preferably, the crystal powder includes carbonyl iron powder; Preferably, the particle size range of the crystal powder is 1 - 6 μm.

5. The preparation method according to claim 3 or 4, characterized in that, The mass ratio of the amorphous FeSiB powder to the crystal powder in step (1) is (0.5 - 0.8):

1.

6. The preparation method according to any one of claims 3 to 5, characterized in that The ball-milling medium in step (1) for ball-milling includes stainless steel grinding balls; Preferably, the ball-milling is carried out in a protective atmosphere; Preferably, the protective atmosphere includes argon and / or nitrogen; Preferably, the rotation speed of the ball-milling is 200 - 300 r / min; Preferably, the ball-milling time is 10 - 20 h; Preferably, the mass ratio of the ball-milling medium to the mixed powder in the ball-milling is 5 - 10:

1.

7. The preparation method according to any one of claims 3 to 6, characterized in that, The mold material for the pre-pressing in step (2) is tungsten steel; Preferably, the pressure for the pre-pressing is 30 - 50 MPa; Preferably, the holding pressure time for the pre-pressing is 1 - 5 min.

8. The preparation method according to any one of claims 3 to 7, characterized in that, The temperature for the spark plasma sintering in step (3) is 450 - 600 °C; Preferably, the pressure for the spark plasma sintering is 200 - 500 MPa; Preferably, the holding pressure and holding time for the spark plasma sintering is 10 - 30 min; Preferably, the heating rate of the spark plasma sintering is 50-100 °C / min.

9. The preparation method according to any one of claims 3 to 8, characterized in that, The preparation method includes the following steps: (1) Mix amorphous FeSiB powder and crystalline powder with a mass ratio of amorphous FeSiB powder to crystalline powder of (0.5-0.8):1, where the particle size range of the amorphous FeSiB powder is 3-22 μm and the particle size range of the crystalline powder is 1-6 μm, to obtain a mixed powder; wherein, in the amorphous FeSiB powder, the molar ratio of Fe:Si:B = (5.0-5.5):(0.3-0.5):1; According to the mass ratio of stainless steel grinding balls to the mixed powder of (5-10):1, the mixed powder is ball-milled at 200-300 r / min for 10-20 h in a protective atmosphere to obtain the mechanically treated powder; (2) Pre-press the mechanically treated powder obtained in step (1), with the pre-pressing pressure of 30-50 MPa and the pressure holding time of 1-5 min, to obtain a green compact; (3) Heat the green compact obtained in step (3) to 450-600 °C at a heating rate of 50-100 °C / min, and keep it at a pressure of 200-500 MPa for 10-30 min for spark plasma sintering to obtain the iron-based soft magnetic composite material.

10. Application of the iron-based soft magnetic composite material according to claim 1 or 2 in power equipment, magnetic storage or sensors.

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