Iron-cobalt based nanocrystalline soft magnetic alloy with excellent comprehensive soft magnetic properties and its preparation method

Abstract

This invention discloses an iron-cobalt-based nanocrystalline soft magnetic alloy with excellent comprehensive soft magnetic properties and its preparation method. The chemical composition of the iron-cobalt-based nanocrystalline soft magnetic alloy is Fe. a Co b B c Si d P e Cu f The preparation method includes the following steps: (1) weighing and mixing raw materials iron, cobalt, boron, silicon, copper and iron-phosphorus master alloy according to atomic percentage; (2) induction melting of the prepared raw materials under inert protection, and obtaining a master alloy ingot with uniform composition after cooling; (3) preparing the above master alloy ingot into amorphous alloy strips by single-roll rapid cooling method; (4) subjecting the amorphous alloy strips to longitudinal magnetic field heat treatment, and obtaining iron-cobalt based nanocrystalline soft magnetic alloy. This invention effectively controls the microstructure and magnetic domain structure through longitudinal magnetic field heat treatment, and obtains an iron-cobalt based nanocrystalline soft magnetic alloy with high saturation magnetic induction intensity, low coercivity and high effective magnetic permeability.

Description

Technical Field

[0001] This invention relates to the field of soft magnetic materials technology, specifically to an iron-cobalt-based nanocrystalline soft magnetic alloy with excellent comprehensive soft magnetic properties and its preparation method. Background Technology

[0002] Soft magnetic materials are a crucial material foundation for modern information technology and power electronics, typically characterized by low loss, high permeability, and low coercivity. Based on their soft magnetic properties and different functional requirements, soft magnetic materials can be categorized into metallic soft magnetic materials, soft magnetic ferrites, and amorphous and nanocrystalline soft magnetic materials. With increasing application demands, modern industry is placing new requirements on the performance of soft magnetic materials.

[0003] Nanocrystalline soft magnetic alloys possess low mid-to-high frequency loss characteristics and have been widely used in power electronics, information communication, and new energy vehicles. However, the saturation magnetic induction of the widely used iron-based nanocrystalline soft magnetic alloys is still significantly lower than that of silicon steel. Currently, there are three main systems of nanocrystalline soft magnetic alloys: Finemet system (Fe-Si-B-Nb-Cu), Nanoperm system (Fe-MB-Cu, where M = Zr, Hf, Nb, etc.), and Hitperm system ((Fe, Co)-MB-Cu, where M = Zr, Hf, Nb). Finemet alloys have found some application in industrial production due to their low cost, ease of preparation, and excellent soft magnetic properties. However, their saturation magnetic induction is relatively low, only around 1.24T, far lower than that of silicon steel. Therefore, they require a larger volume for application under the same working conditions, greatly limiting their application range. Nanoperm alloys have higher saturation magnetic induction, but poorer soft magnetic properties. Both of these alloys have low Curie temperatures, causing them to become paramagnetic at high temperatures, thus limiting their application at high temperatures. The development of Hitperm alloys has solved this problem to some extent. The addition of cobalt to this alloy increases the Curie temperature, allowing it to be used at higher temperatures. However, this alloy has poor soft magnetic properties, with a coercivity as high as 200 A / m and high iron loss, which limits its application.

[0004] Therefore, developing nanocrystalline soft magnetic alloys with both high saturation magnetic induction and low coercivity is of great significance for realizing the miniaturization, energy saving, and high efficiency of electronic components. Researchers have conducted a number of studies on developing iron-cobalt-based nanocrystalline soft magnetic alloys with both high saturation magnetic induction and low coercivity, focusing on composition design and process optimization.

[0005] Patent CN102254665 discloses an iron-cobalt-based nanocrystalline soft magnetic alloy, comprising the following components and their molar percentages: Fe: 40%-42.8%; Co: 40%-42.8%; M: 5%-8%; B: 5%-12%; Cu: 0.1%-1.5%, wherein M is at least one of Nb, Zr, Hf, Mo, W, and Ta. While this material possesses a high saturation magnetic induction of 1.8-1.86T, its cobalt content is too high. Nb, Zr, Hf, Mo, W, and Ta are all rare and precious elements with high melting points, and their contents are also very high. This makes it easy for elemental segregation to occur during smelting, affecting the material's performance; furthermore, it results in excessively high industrialization costs.

[0006] Patent CN102828110 discloses a low-cobalt-nickel nanocrystalline iron-based soft magnetic alloy material and its preparation method. The weight percentage of each component in this material is as follows: Co: 4%-6.5%, Ni: 5%-8%, Gd: 3%-5%, Ir: 0.01%-0.05%, Tm: 0.1%-0.5%, Dy: 0.1%-0.5%, Al: 2%-4%, P: 0.1%-0.5%, B: 1%-3%, with the remainder being Fe. Although this material also has high saturation magnetic induction, the addition of rare earth elements such as Gd, Ir, Tm, and Dy increases the industrialization cost. Furthermore, its processing window is narrow, and excessive addition of elements such as B, Ni, P, Dy, Al, Cr, and Tm can react with Fe to form non-magnetic compounds, deteriorating the soft magnetic properties.

[0007] Patent CN101260494 discloses a Ge-doped FeCo-based dual-phase soft magnetic alloy, in which the Fe... 44 Co 43- X Zr7B5Ge 1+X The atomic percentage of X in the soft magnetic alloy is 0-6. The Fe... 44 Co 43-X Zr7B5Ge 1+X The saturation magnetization of the alloy is 143-155 emu / g. After crystallization at 500-650℃, due to the precipitation of FeCo grains, the saturation magnetization reaches 166-178 emu / g. However, the coercivity after crystallization is 0.1-0.6 Oe, which cannot achieve both high saturation magnetic induction and low coercivity. Summary of the Invention

[0008] Purpose of the invention: In order to solve the technical problems existing in the prior art, the present invention aims to provide an iron-cobalt based nanocrystalline soft magnetic alloy with controllable structure and excellent comprehensive soft magnetic properties. Furthermore, the present invention also provides a method for preparing the iron-cobalt based nanocrystalline soft magnetic alloy.

[0009] Technical solution: The chemical composition of the iron-cobalt based nanocrystalline soft magnetic alloy with excellent comprehensive soft magnetic properties described in this invention is Fe. a Co b B c Si d P e Cu f Where a, b, c, d, e, and f represent the atomic percentages of the corresponding elements, 67≤a≤79, 4≤b≤20, 9≤c≤10, 2≤d≤3, 3≤e≤5, 0.5≤f≤1, and a+b+c+d+e+f=100.

[0010] Furthermore, the atomic percentage content of Fe and Co satisfies the following conditions: 83≤a+b≤84; 4.2≤a:b≤20.

[0011] Further, preferably, the atomic percentage of Co is 12. <b≤20。

[0012] Furthermore, the iron-cobalt based nanocrystalline soft magnetic alloy has a saturation magnetic induction of 1.78-1.86T and a coercivity of 1.8-4.5A / m, and an effective permeability of up to 20500-26500 at 1kHz and 5A / m.

[0013] The preparation method of the iron-cobalt based nanocrystalline alloy with excellent comprehensive soft magnetic properties according to the present invention includes the following steps:

[0014] (1) Weigh and mix the raw materials iron, cobalt, boron, silicon, copper and iron-phosphorus master alloy according to atomic percentage;

[0015] (2) The prepared raw materials are induction melted under inert gas protection and cooled to obtain a master alloy ingot with uniform composition.

[0016] (3) The above-mentioned master alloy ingot is prepared into amorphous alloy strip by single-roller rapid cooling method;

[0017] (4) The amorphous alloy strip is subjected to longitudinal magnetic field heat treatment, and the iron-cobalt based nanocrystalline soft magnetic alloy is obtained.

[0018] Further, in step (1), the mass percentage of phosphorus in the iron-phosphorus master alloy is 26.4%; the purity of the iron, cobalt, boron, silicon, copper and iron-phosphorus master alloy is greater than 99 wt.%.

[0019] Furthermore, in step (2), the temperature of the induction melting is 1250-1350℃.

[0020] Further, in step (3), the process parameters of the single-roller rapid cooling method are: spray pressure of 0.01-0.03MPa, spray temperature of 1000-1050℃, and surface linear velocity of the copper roller of 35-50m / s.

[0021] Further, in step (4), the specific method of the longitudinal magnetic field heat treatment is as follows: first, heat the amorphous alloy strip from room temperature to 420-540℃ and hold for 3-5 minutes, while applying a longitudinal magnetic field along the direction of the amorphous alloy strip with a magnetic field strength of 500-1500 Oe. Preferably, the heating temperature is 500℃ and the magnetic field strength is 1000 Oe. Then, water quench and cool to room temperature.

[0022] Furthermore, the longitudinal magnetic field heat treatment is carried out under vacuum conditions or inert atmosphere.

[0023] Invention Principle: This invention is based on research experience in the field of iron-based nanocrystalline soft magnetic materials. In terms of composition design, firstly, the total content of magnetic elements (Fe and Co) is selected to be between 83-84 at.%, as this composition point is the deep eutectic point of the system, and its formation ability is highest within this range. Secondly, by adding Co, a strong iron-cobalt exchange coupling effect is formed, effectively improving the saturation magnetic induction intensity of the iron-based nanocrystalline alloy, while simultaneously enhancing the alloy's amorphous formation ability and temperature stability. Adding P and Cu elements forms Cu-P clusters to inhibit nanocrystal growth; adding B ensures the alloy's amorphous formation ability; and adding Si reduces the magnetic anisotropy of the nanocrystals.

[0024] In terms of the preparation process, this invention employs a longitudinal magnetic field heat treatment method to effectively promote nanocrystal nucleation, forming a high-number-density nanocrystalline alloy; simultaneously, it inhibits nanocrystal growth, resulting in a significant reduction in grain size. Furthermore, the longitudinal magnetic field heat treatment induces the formation of regular magnetic domains in the iron-cobalt-based nanocrystalline soft magnetic alloy and regulates the alignment of these domains along the magnetic field direction. The domain width exceeds 200 μm, with straight and smooth domain walls. The magnetization mechanism shifts from being dominated by non-uniform domain rotation to being dominated by uniform domain wall displacement.

[0025] Beneficial effects: Compared with the prior art, the present invention has the following significant advantages:

[0026] (1) The iron-cobalt based nanocrystalline alloy provided by the present invention effectively improves the saturation magnetic induction intensity to 1.78-1.86T by adding cobalt element to form strong iron-cobalt exchange coupling effect, while further improving the alloy's amorphous forming ability and Curie temperature, and broadening the process processing window.

[0027] (2) The preparation method provided by the present invention, especially the longitudinal magnetic field heat treatment method, can effectively reduce the coercivity of iron-cobalt based nanocrystalline alloys to 1.8-4.5 A / m and increase the permeability to 20500-26500 (1kHz, 5A / m) compared with ordinary nanocrystallization heat treatment.

[0028] (3) Through alloy composition design and preparation process optimization, this invention has obtained an iron-cobalt based nanocrystalline soft magnetic alloy with high saturation magnetic induction intensity, low coercivity and high effective magnetic permeability. The microstructure and magnetic domain structure of this alloy are adjustable, the process is simple, the applicability is wide, the cost is low, and the application prospects are broad. Attached Figure Description

[0029] Figure 1 The X-ray diffraction patterns of the quenched alloy strips prepared in Examples 1-4 of this invention are shown below.

[0030] Figure 2 The above are DSC curves of the quenched alloy strips prepared in Examples 1-4 of this invention.

[0031] Figure 3 The graphs show the changes in magnetic permeability and coercivity of Embodiment 4 and Comparative Example 4 after being kept at 420-540℃ for 3 minutes.

[0032] Figure 4 The HADDF pattern, selected area electron diffraction pattern, and nanocrystal size distribution diagram of the alloy sample after being held at 420°C for 3 minutes in Example 4 of this invention;

[0033] Figure 5 The HADDF pattern and selected area electron diffraction pattern of the alloy sample of Comparative Example 4 of this invention after being held at 420°C for 3 minutes are shown.

[0034] Figure 6 The TEM image, selected area electron diffraction pattern, and nanocrystal size distribution diagram of the alloy sample after holding at the optimal heat treatment temperature for 3 minutes in Example 4 of the present invention are shown.

[0035] Figure 7 The TEM image, selected area electron diffraction pattern and nanocrystal size distribution diagram of the alloy sample of Comparative Example 4 of the present invention after holding at the optimal heat treatment temperature for 3 minutes are shown.

[0036] Figure 8 These are images of the magnetic domain structure of the alloy sample of Example 4 of the present invention after holding at the optimal heat treatment temperature for 3 minutes under different external fields.

[0037] Figure 9 The images show the magnetic domain structure of the alloy sample of Comparative Example 4 of this invention after holding at the optimal heat treatment temperature for 3 minutes under different external fields. Detailed Implementation

[0038] The present invention will now be further described in conjunction with specific embodiments and accompanying drawings.

[0039] Example 1: Preparation of Fe 79.2 Co4B 9.5 Si 2.5 P4Cu 0.8 The steps for producing iron-cobalt based nanocrystalline soft magnetic alloys are as follows:

[0040] (1) Iron, cobalt, boron, silicon, copper and iron-phosphorus master alloy raw materials with a purity greater than 99wt.% were weighed according to atomic percentage to obtain 20g of mixture, of which the mass percentage of phosphorus in the iron-phosphorus master alloy was 26.4%.

[0041] (2) The prepared mixture is melted in an induction melting furnace under argon protection (temperature 1250-1350℃) to obtain a master alloy ingot with uniform composition.

[0042] (3) Single-roller rapid cooling belt spinning technology: After the master alloy ingot is crushed, it is loaded into a quartz tube with a nozzle at the bottom. The quartz tube is fixed in the induction coil. The upper and lower positions of the quartz tube are adjusted to control the distance between the tube opening and the roller surface to 0.25 mm. First, a low vacuum is drawn to below 5 Pa, and then a high vacuum is drawn to 8 × 10 Pa. -3 Pa, then fill with protective gas (high-purity argon) with a pressure difference of 0.01 MPa, set the surface linear velocity of the copper roller to about 50 m / s, turn on the heating current, and wait for the solenoid to heat the small alloy ingot to quickly reach the melting state through induction heating. Then turn off the heating power and wait for the alloy melt to cool to 1050℃. Press the spray button, and use the pressure difference between the quartz tube and the cavity to quickly spray the molten alloy liquid onto the surface of the high-speed rotating copper roller for rapid cooling, thus preparing an amorphous alloy strip with a width of 1 mm and a thickness of 17-19 μm.

[0043] (4) Cut a 6cm section from the prepared amorphous alloy strip and place it into the quartz tube matched with the tubular magnetic field annealing furnace. First, evacuate to a low vacuum of less than 5 Pa, then evacuate to a high vacuum of 5 × 10⁻⁶ Pa. -3 Pa; When the temperature of the tube furnace reaches the preset value (within the temperature range of 420-560℃, each 20℃ interval is a holding temperature), the quartz tube is pushed into the tube furnace, and the inverter is turned on to apply an external magnetic field. The direction of the magnetic field is parallel to the direction of the strip, and the magnetic field strength is 500 Oe. The temperature is held for 3 minutes, and then the obtained sample is water quenched and cooled to room temperature to obtain an iron-cobalt based nanocrystalline soft magnetic alloy.

[0044] Example 2: Preparation of Fe 75.2 Co8B 9.5 Si 2.5 P4Cu 0.8 The steps for producing iron-cobalt based nanocrystalline soft magnetic alloys are as follows:

[0045] (1) Iron, cobalt, boron, silicon, copper and iron-phosphorus master alloy raw materials with a purity greater than 99wt.% were weighed according to atomic percentage to obtain 20g of mixture, of which the mass percentage of phosphorus in the iron-phosphorus master alloy was 26.4%.

[0046] (2) The prepared mixture is melted in an induction melting furnace under argon protection (temperature 1250-1350℃) to obtain a master alloy ingot with uniform composition.

[0047] (3) Single-roller rapid cooling belt spinning technology: After the master alloy ingot is crushed, it is loaded into a quartz tube with a nozzle at the bottom. The quartz tube is fixed in the induction coil. The upper and lower positions of the quartz tube are adjusted to control the distance between the tube opening and the roller surface to 0.25 mm. First, a low vacuum is drawn to below 5 Pa, and then a high vacuum is drawn to 8 × 10 Pa. -3 Pa, then fill with protective gas (high-purity argon) with a pressure difference of 0.015 MPa, set the surface linear velocity of the copper roller to about 45 m / s, turn on the heating current, and wait for the solenoid to heat the small alloy ingot to quickly reach the melting state through induction heating. Then turn off the heating power and wait for the alloy melt to cool to 1050℃. Press the spray button, and use the pressure difference between the quartz tube and the cavity to quickly spray the molten alloy liquid onto the surface of the high-speed rotating copper roller for rapid cooling, thus preparing an amorphous alloy strip with a width of 1 mm and a thickness of 18-20 μm.

[0048] (4) Cut a 6cm section from the prepared amorphous alloy strip and place it into the quartz tube matched with the tubular magnetic field annealing furnace. First, evacuate to a low vacuum of less than 5 Pa, then evacuate to a high vacuum of 5 × 10⁻⁶ Pa. -3 Pa; When the temperature of the tube furnace reaches the preset value (within the temperature range of 420-560℃, each 20℃ interval is a holding temperature), the quartz tube is pushed into the tube furnace, and the inverter is turned on to apply an external magnetic field. The direction of the magnetic field is parallel to the direction of the strip, and the magnetic field strength is 1500 Oe. The temperature is held for 3 minutes, and then the obtained sample is water quenched and cooled to room temperature to obtain an iron-cobalt based nanocrystalline soft magnetic alloy.

[0049] Example 3: Preparation of Fe 71.2 Co 12 B 9.5 Si 2.5 P4Cu 0.8 The steps for producing iron-cobalt based nanocrystalline soft magnetic alloys are as follows:

[0050] (1) Iron, cobalt, boron, silicon, copper and iron-phosphorus master alloy raw materials with a purity greater than 99wt.% were weighed according to atomic percentage to obtain 20g of mixture, of which the mass percentage of phosphorus in the iron-phosphorus master alloy was 26.4%.

[0051] (2) The prepared mixture is melted in an induction melting furnace under argon protection (temperature 1250-1350℃) to obtain a master alloy ingot with uniform composition.

[0052] (3) Single-roller rapid cooling belt spinning technology: After the master alloy ingot is crushed, it is loaded into a quartz tube with a nozzle at the bottom. The quartz tube is fixed in the induction coil. The upper and lower positions of the quartz tube are adjusted to control the distance between the tube opening and the roller surface to 0.25 mm. First, a low vacuum is drawn to below 5 Pa, and then a high vacuum is drawn to 8 × 10 Pa. -3 Pa, then fill with protective gas (high-purity argon) with a pressure difference of 0.03 MPa, set the surface linear velocity of the copper roller to about 40 m / s, turn on the heating current, and wait for the solenoid to heat the small alloy ingot to quickly reach the melting state through induction heating. Then turn off the heating power and wait for the alloy melt to cool to 1000℃. Press the spray button, and use the pressure difference between the quartz tube and the cavity to quickly spray the molten alloy liquid onto the surface of the high-speed rotating copper roller for rapid cooling, thus preparing an amorphous alloy strip with a width of 1 mm and a thickness of 20-23 μm.

[0053] (4) Cut a 6cm section from the prepared amorphous alloy strip and place it into the quartz tube matched with the tubular magnetic field annealing furnace. First, evacuate to a low vacuum of less than 5 Pa, then evacuate to a high vacuum of 5 × 10⁻⁶ Pa. -3 Pa; When the temperature of the tube furnace reaches the preset value (within the temperature range of 420-560℃, each 20℃ interval is a holding temperature), the quartz tube is pushed into the tube furnace, and at the same time the inverter is turned on to apply an external magnetic field. The direction of the magnetic field is parallel to the direction of the strip, and the magnetic field strength is 1000Oe. The temperature is held for 3 minutes, and then the obtained sample is water quenched and cooled to room temperature to obtain an iron-cobalt based nanocrystalline soft magnetic alloy.

[0054] Example 4: Preparation of Fe 67.2 Co 16 B 9.5 Si 2.5 P4Cu 0.8 The steps for producing iron-cobalt based nanocrystalline soft magnetic alloys are as follows:

[0055] (1) Iron, cobalt, boron, silicon, copper and iron-phosphorus master alloy raw materials with a purity greater than 99wt.% were weighed according to atomic percentage to obtain 20g of mixture, of which the mass percentage of phosphorus in the iron-phosphorus master alloy was 26.4%.

[0056] (2) The prepared mixture is melted in an induction melting furnace under argon protection (temperature 1250-1350℃) to obtain a master alloy ingot with uniform composition.

[0057] (3) Single-roller rapid cooling belt spinning technology: After the master alloy ingot is crushed, it is loaded into a quartz tube with a nozzle at the bottom. The quartz tube is fixed in the induction coil. The upper and lower positions of the quartz tube are adjusted to control the distance between the tube opening and the roller surface to 0.25 mm. First, a low vacuum is drawn to below 5 Pa, and then a high vacuum is drawn to 8 × 10 Pa. -3 Pa, then fill with protective gas (high-purity argon) with a pressure difference of 0.03 MPa, set the surface linear velocity of the copper roller to about 35 m / s, turn on the heating current, and wait for the solenoid to heat the small alloy ingot to quickly reach the melting state through induction heating. Then turn off the heating power and wait for the alloy melt to cool to 1050℃. Press the spray button, and use the pressure difference between the quartz tube and the cavity to quickly spray the molten alloy liquid onto the surface of the high-speed rotating copper roller for rapid cooling, thus preparing an amorphous alloy strip with a width of 1 mm and a thickness of 22-25 μm.

[0058] (4) Cut a 6cm section from the prepared amorphous alloy strip and place it into the quartz tube matched with the tubular magnetic field annealing furnace. First, evacuate to a low vacuum of less than 5 Pa, then evacuate to a high vacuum of 5 × 10⁻⁶ Pa. -3 Pa; When the temperature of the tube furnace reaches the preset value (within the temperature range of 420-560℃, each 20℃ interval is a holding temperature), the quartz tube is pushed into the tube furnace, and at the same time the inverter is turned on to apply an external magnetic field. The direction of the magnetic field is parallel to the direction of the strip, and the magnetic field strength is 1000Oe. The temperature is held for 3 minutes, and then the obtained sample is water quenched and cooled to room temperature to obtain an iron-cobalt based nanocrystalline soft magnetic alloy.

[0059] Comparative Examples 1-4 were set up. The difference between them and Examples 1-4 is that step (4) only performed ordinary heat treatment. The effects of longitudinal magnetic field heat treatment method and ordinary heat treatment method on the soft magnetic properties of alloy were analyzed and compared.

[0060] Comparative Example 1: The difference from Example 1 lies in step (4): a 6cm section is cut from the prepared amorphous alloy strip and placed into a quartz tube matched with the tubular magnetic field annealing furnace. First, a low vacuum is drawn to below 5Pa, and then a high vacuum is drawn to 5×10. -3 Pa; When the temperature of the tube furnace reaches the preset value (within the temperature range of 420-560℃, each 20℃ interval is a holding temperature), the quartz tube is pushed into the tube furnace and held for 3 minutes without an external magnetic field. Then the obtained sample is water quenched and cooled to room temperature to obtain an iron-cobalt based nanocrystalline soft magnetic alloy.

[0061] Comparative Example 2: The difference from Example 2 lies in step (4): a 6cm section is cut from the prepared amorphous alloy strip and placed into a quartz tube matched with the tubular magnetic field annealing furnace. First, a low vacuum is drawn to below 5Pa, and then a high vacuum is drawn to 5×10. -3Pa; When the temperature of the tube furnace reaches the preset value (within the temperature range of 420-560℃, each 20℃ interval is a holding temperature), the quartz tube is pushed into the tube furnace and held for 3 minutes without an external magnetic field. Then the obtained sample is water quenched and cooled to room temperature to obtain an iron-cobalt based nanocrystalline soft magnetic alloy.

[0062] Comparative Example 3: The difference from Example 3 lies in step (4): a 6cm section is cut from the prepared amorphous alloy strip and placed into a quartz tube matched with the tubular magnetic field annealing furnace. First, a low vacuum is drawn to below 5Pa, and then a high vacuum is drawn to 5×10. -3 Pa; When the temperature of the tube furnace reaches the preset value (within the temperature range of 420-560℃, each 20℃ interval is a holding temperature), the quartz tube is pushed into the tube furnace and held for 3 minutes without an external magnetic field. Then the obtained sample is water quenched and cooled to room temperature to obtain an iron-cobalt based nanocrystalline soft magnetic alloy.

[0063] Comparative Example 4: The difference from Example 4 lies in step (4): a 6cm section is cut from the prepared amorphous alloy strip and placed into a quartz tube matched with the tubular magnetic field annealing furnace. First, a low vacuum is drawn to below 5 Pa, and then a high vacuum is drawn to 5 × 10 Pa. -3 Pa; When the temperature of the tube furnace reaches the preset value (within the temperature range of 420-560℃, each 20℃ interval is a holding temperature), the quartz tube is pushed into the tube furnace and held for 3 minutes without an external magnetic field. Then the obtained sample is water quenched and cooled to room temperature to obtain an iron-cobalt based nanocrystalline soft magnetic alloy.

[0064] Comparative Example 5: Preparation of a molecular formula of Fe 83.2 B 9.5 Si 2.5 P4Cu 0.8 The iron-based nanocrystalline soft magnetic alloy is produced through the following steps:

[0065] (1) Iron, boron, silicon, copper and iron-phosphorus master alloy raw materials with a purity greater than 99wt.% were weighed according to atomic percentage to obtain 20g of mixture, of which the mass percentage of phosphorus in the iron-phosphorus master alloy was 26.4%.

[0066] (2) The prepared mixture is melted in an induction melting furnace under argon protection (temperature 1250-1350℃) to obtain a master alloy ingot with uniform composition.

[0067] (3) Single-roller rapid cooling belt spinning technology: After the master alloy ingot is crushed, it is loaded into a quartz tube with a nozzle at the bottom. The quartz tube is fixed in the induction coil. The upper and lower positions of the quartz tube are adjusted to control the distance between the tube opening and the roller surface to 0.25 mm. First, a low vacuum is drawn to below 5 Pa, and then a high vacuum is drawn to 8 × 10 Pa. -3Pa, then fill with protective gas (high-purity argon) with a pressure difference of 0.015 MPa, set the surface linear velocity of the copper roller to about 50 m / s, turn on the heating current, and wait for the solenoid to quickly melt the small alloy ingot through induction heating. Then turn off the heating power and wait for the alloy melt to cool to 1050℃. Press the spray button, and use the pressure difference between the quartz tube and the cavity to quickly spray the molten alloy liquid onto the surface of the high-speed rotating copper roller for rapid cooling, thus preparing an amorphous alloy strip with a width of 1 mm and a thickness of 17-19 μm.

[0068] (4) Cut a 6cm section from the prepared amorphous alloy strip and place it into the quartz tube matched with the tubular magnetic field annealing furnace. First, evacuate to a low vacuum of less than 5 Pa, then evacuate to a high vacuum of 5 × 10⁻⁶ Pa. -3 Pa; When the temperature of the tube furnace reaches 500℃, the quartz tube is pushed into the tube furnace and kept at that temperature for 3 minutes without an external magnetic field. Then the obtained sample is water quenched and cooled to room temperature to obtain an iron-based nanocrystalline soft magnetic alloy.

[0069] Comparative Example 6: Preparation of Fe 83.2 B 13.5 Si 2.5 Cu 0.8 The iron-based nanocrystalline soft magnetic alloy is produced through the following steps:

[0070] (1) Iron, boron, silicon and copper alloy raw materials with a purity greater than 99wt.% were mixed according to atomic percentage to obtain 20g of mixture;

[0071] (2) The prepared mixture is melted in an induction melting furnace under argon protection (temperature 1250-1350℃) to obtain a master alloy ingot with uniform composition.

[0072] (3) Single-roller rapid cooling belt spinning technology: After the master alloy ingot is crushed, it is loaded into a quartz tube with a nozzle at the bottom. The quartz tube is fixed in the induction coil. The upper and lower positions of the quartz tube are adjusted to control the distance between the tube opening and the roller surface to 0.25 mm. First, a low vacuum is drawn to below 5 Pa, and then a high vacuum is drawn to 8 × 10 Pa. -3 Pa, then fill with protective gas (high-purity argon) with a pressure difference of 0.015 MPa, set the surface linear velocity of the copper roller to about 50 m / s, turn on the heating current, and wait for the solenoid to quickly melt the small alloy ingot through induction heating. Then turn off the heating power and wait for the alloy melt to cool to 1050℃. Press the spray button, and use the pressure difference between the quartz tube and the cavity to quickly spray the molten alloy liquid onto the surface of the high-speed rotating copper roller for rapid cooling, thus preparing an amorphous alloy strip with a width of 1 mm and a thickness of 17-19 μm.

[0073] (4) Cut a 6cm section from the prepared amorphous alloy strip and place it into the quartz tube matched with the tubular magnetic field annealing furnace. First, evacuate to a low vacuum of less than 5 Pa, then evacuate to a high vacuum of 5 × 10⁻⁶ Pa. -3Pa; When the temperature of the tube furnace reaches 500℃, the quartz tube is pushed into the tube furnace and kept at that temperature for 3 minutes without an external magnetic field. Then the obtained sample is water quenched and cooled to room temperature to obtain an iron-based nanocrystalline soft magnetic alloy.

[0074] Comparative Example 7: The difference from Example 1 lies in step (4): a 6cm section is cut from the prepared amorphous alloy strip and placed into a quartz tube matched with the tubular magnetic field annealing furnace. First, a low vacuum is drawn to below 5Pa, and then a high vacuum is drawn to 5×10. -3 Pa; When the temperature of the tube furnace reaches the preset value (within the temperature range of 420-560℃, each 20℃ interval is a holding temperature), the quartz tube is pushed into the tube furnace, and at the same time the inverter is turned on to apply an external magnetic field. The direction of the magnetic field is parallel to the direction of the strip, and the magnetic field strength is 500 Oe. The temperature is held for 10 minutes, and then the obtained sample is water quenched and cooled to room temperature to obtain an iron-cobalt based nanocrystalline soft magnetic alloy.

[0075] The structure of the quenched alloy strips obtained in step (3) of Examples 1-4 was tested using an X-ray diffractometer, and the results are as follows: Figure 1 As shown, all the prepared quenched alloy samples exhibited only one diffuse diffraction peak, indicating that they were all amorphous structures.

[0076] The thermal properties of the quenched alloy strips obtained in step (3) of Examples 1-4 were measured using differential scanning calorimetry (DSC), and the initial crystallization temperature T was determined at a heating rate of 40 K / min. x1 and secondary crystallization temperature T x2 ,like Figure 2 As shown. The T of the alloy strip. x1 The temperature is 415-421℃, T x2 The annealing temperature range is 420-560℃, with each 20℃ interval serving as a holding temperature.

[0077] The magnetic permeability of the alloy samples was measured using an impedance analyzer at 1 kHz and 5 A / m, and the coercivity of the alloy samples was measured using a DC hysteresis loop meter under a 1 kA / m magnetic field. The measurement results of the quenched alloy sample in Example 4, the alloy sample after longitudinal magnetic field heat treatment, and Comparative Example 4 are as follows: Figure 3 As shown, Example 4, after longitudinal magnetic field heat treatment, exhibits good soft magnetic properties in the temperature range of 480-520℃, with a significant increase in permeability and a coercivity of less than 2.2 A / m. In contrast, Comparative Example 4 shows a significantly increased coercivity compared to the quenched sample. Example 4 achieves optimal soft magnetic properties at a heat treatment temperature of 500℃. When the heat treatment temperature is further increased to 560℃, both Example 4 and Comparative Example 4 show a significant deterioration in soft magnetic properties.

[0078] Appendix 1 of the instruction manual details the saturation magnetic flux density, coercivity, and permeability of the alloy samples from Examples 1-4 after longitudinal magnetic field heat treatment at the optimal heat treatment temperature, and the alloy samples from Comparative Examples 1-7 after ordinary heat treatment at the optimal heat treatment temperature. The saturation magnetic flux density was measured using a vibrating sample magnetometer under an 800 kA / m magnetic field. This series of iron-based amorphous alloys, optimized by longitudinal magnetic field heat treatment, exhibits excellent comprehensive soft magnetic properties, with a saturation magnetic flux density of 1.78-1.84 T, a coercivity of 1.8-4.5 A / m, and a permeability of 20500-26500 at 1 kHz and 5 A / m. The symbols in Table 1 have the following meanings: B s H is the saturation magnetic induction intensity. c For coercivity, μ e The effective permeability.

[0079] Table 1. Magnetic properties of the alloys prepared in Examples 1-4 and Comparative Examples 1-7.

[0080]

[0081] At the initial crystallization temperature T x1 The microstructures of the alloy strips after longitudinal magnetic field heat treatment and conventional heat treatment were observed using a high-resolution transmission microscope. The TEM images and selected area electron diffraction patterns of the alloy strips after longitudinal magnetic field heat treatment at 420℃ in Example 4 and after conventional heat treatment at 420℃ in Comparative Example 4 are shown below. Figure 4 and Figure 5 As shown, it is evident that after ordinary heat treatment at 420℃, Comparative Example 4 still maintains a long-range disordered amorphous structure; while Example 4, after longitudinal magnetic field heat treatment, has precipitated fine nanocrystals of about 3 nm, and selected area electron diffraction shows the (2 0 0) crystal plane. Therefore, the longitudinal magnetic field heat treatment process can effectively promote the nucleation of nanocrystals from the amorphous matrix.

[0082] The microstructures of the alloy strips after longitudinal magnetic field heat treatment at the optimal heat treatment temperature and after ordinary heat treatment were observed using a high-resolution transmission microscope. The TEM images of the alloy strips after longitudinal magnetic field heat treatment at the optimal heat treatment temperature in Example 4 and after ordinary heat treatment at the optimal heat treatment temperature in Comparative Example 4 are shown below. Figure 6 and Figure 7As shown, it is evident that after heat treatment, both Example 4 and Comparative Example 4 exhibit typical amorphous-nanocrystalline dual-phase structures. The difference lies in the nanocrystal size: Example 4, after longitudinal magnetic field heat treatment, has a nanocrystal size of only 12 nm, while Comparative Example 4, after ordinary heat treatment, has a nanocrystal size as high as 29 nm. For nanocrystalline soft magnetic alloys, the smaller the nanocrystal size, the lower the loss. Therefore, Example 4, after longitudinal magnetic field heat treatment, exhibits superior soft magnetic properties.

[0083] The magnetization process of the alloy sample was observed using a magneto-optical Kerr microscope. The dynamic magnetic domain evolution of the alloy sample after longitudinal magnetic field heat treatment at the optimal heat treatment temperature in Example 4 is shown below. Figure 8 As shown in the figure, the alloy after longitudinal magnetic field heat treatment exhibits a regular magnetic domain arrangement, with orientation largely consistent with the direction of the applied magnetic field. The domain width exceeds 200 μm, and the domain walls are straight and smooth, without obvious pinning points. The magnetization mechanism is dominated by uniform domain wall displacement. The dynamic magnetic domain evolution of the alloy sample in Comparative Example 4 after ordinary heat treatment at the optimal heat treatment temperature is shown in the figure. Figure 9 As shown, the alloy after ordinary heat treatment has relatively narrow and irregular magnetic domains with uneven domain walls and bifurcations. The magnetization process is dominated by the rotation of non-uniform magnetic domains, accompanied by a small amount of domain wall displacement, and the domain wall pinning effect is strong.

[0084] Furthermore, it can be seen from Comparative Examples 5 and 6 that the addition of P element has a promoting effect on its overall soft magnetic properties; it can be seen from Examples 1 and 7 that long-term heat treatment is not conducive to obtaining excellent soft magnetic properties of the composition system of the present invention.

[0085] In summary, this invention provides an iron-cobalt-based nanocrystalline alloy with excellent comprehensive soft magnetic properties and its preparation method. Specifically, by adding cobalt, a strong iron-cobalt exchange coupling effect is formed, effectively enhancing the saturation magnetic flux density. Simultaneously, a longitudinal magnetic field heat treatment method, compared to ordinary nanocrystallization heat treatment, effectively reduces the coercivity of the iron-cobalt-based nanocrystalline alloy and increases its permeability, achieving effective control over soft magnetic properties. Furthermore, the applied longitudinal magnetic field effectively controls the microstructure by promoting nanocrystal nucleation while inhibiting their growth; and by forming regular magnetic domains and transforming the magnetization mechanism, it effectively controls the microdomain structure. Through extensive experiments, the optimal heat treatment temperature and magnetic field strength matching were established, resulting in an alloy with excellent comprehensive soft magnetic properties. Examples show that the saturation magnetic flux density of the iron-based amorphous soft magnetic alloy of this invention is 1.78-1.84T, the coercivity is 1.8-4.5 A / m, and the permeability at 1 kHz and 5 A / m is 20500-26500. The heat treatment method of this invention is simple, widely applicable, and has broad application prospects.

Claims

1. A cobalt-based nanocrystalline soft magnetic alloy with excellent comprehensive soft magnetic properties, characterized in that, The chemical composition of the iron-cobalt-based nanocrystalline soft magnetic alloy is Fe a Co b B c Si d P e Cu f , where a, b, c, d, e, and f respectively represent the atomic percentages of the corresponding elements, 67 ≤ a ≤ 79, 12 < b ≤ 20, 9 ≤ c ≤ 10, 2 ≤ d ≤ 3, 3 ≤ e ≤ 5, 0.5 ≤ f ≤ 1, and a + b + c + d + e + f = 100; the atomic percentage contents of Fe and Co satisfy the following conditions: 83 ≤ a + b ≤ 84; 4.2 ≤ a:b ≤ 20; The preparation method of the iron-cobalt-based nanocrystalline alloy with excellent comprehensive soft magnetic properties includes the following steps: (1) Weigh and mix the raw materials iron, cobalt, boron, silicon, copper and iron-phosphorus master alloy according to atomic percentage; (2) The prepared raw materials are induction melted under inert gas protection and cooled to obtain a master alloy ingot with uniform composition; (3) The above-mentioned master alloy ingots were prepared into amorphous alloy strips by using a single-roller rapid cooling method; (4) The amorphous alloy strip is subjected to longitudinal magnetic field heat treatment to obtain iron-cobalt based nanocrystalline soft magnetic alloy. The specific method of longitudinal magnetic field heat treatment is as follows: the amorphous alloy strip is heated from room temperature to 420-540 ℃ and held for 3-5 minutes. At the same time, a longitudinal magnetic field with a magnetic field strength of 500-1500 Oe is applied along the direction of the amorphous alloy strip. Then, it is water quenched and cooled to room temperature.

2. The iron-cobalt-based nanocrystalline alloy with excellent comprehensive soft magnetic properties according to claim 1, characterized in that, The iron-cobalt based nanocrystalline soft magnetic alloy has a high saturation magnetic induction of 1.78-1.86 T, a low coercivity of 1.8-4.5 A / m, and a high effective permeability of 20500-26500 at 1 kHz.

3. The iron-cobalt-based nanocrystalline alloy with excellent comprehensive soft magnetic properties according to claim 1, characterized in that, In step (1), the purity of the raw material is greater than 99 wt.%.

4. The iron-cobalt-based nanocrystalline alloy with excellent comprehensive soft magnetic properties according to claim 1, characterized in that, In step (2), the temperature of induction melting is 1250-1350 ℃.

5. The iron-cobalt-based nanocrystalline alloy with excellent comprehensive soft magnetic properties according to claim 1, characterized in that, In step (3), the process parameters of the single-roller rapid cooling method are: spray pressure of 0.01-0.03 MPa, spray temperature of 1000-1050℃, and surface linear velocity of copper roller of 35-50 m / s.

6. The iron-cobalt-based nanocrystalline alloy with excellent comprehensive soft magnetic properties according to claim 1, characterized in that, In step (4), the longitudinal magnetic field heat treatment is carried out under vacuum conditions or inert atmosphere.

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