Fe-ni based alloy with medium-range ordered structure for strengthening soft magnetic properties and preparation method thereof

Abstract

This invention relates to an Fe-Ni based alloy with enhanced soft magnetic properties utilizing a medium-range ordered structure and its preparation method. The chemical formula of the alloy is: Fe bal Ni a Cr y Si b B c M d Cu e X f Its microstructure is as follows: the alloy matrix is ​​mainly amorphous, with dispersed atomic-scale medium-range ordered (MRO) clusters comprising 15%–40% by volume. The size of these clusters is controlled between 1 nm and 5 nm, and no long-range crystalline phases larger than 10 nm are formed. By introducing Ni element to couple magnetic moments with Fe to reduce the saturation magnetostriction coefficient, and by using a low-temperature relaxation annealing process to control the pre-precipitation behavior of Cu element, a high-density MRO-reinforced framework is established in the amorphous matrix. This material possesses high saturation magnetic induction, low coercivity, and excellent high-frequency permeability, which can improve the problems of large magnetostriction coefficients and high high-frequency noise in existing high-Bs iron-based nanocrystalline alloys. It is particularly suitable for high-frequency high-power transformers and wireless charging magnetic shielding modules.

Description

Technical Field

[0001] This invention belongs to the field of amorphous and nanocrystalline soft magnetic materials technology, and relates to a Fe-Ni based alloy with enhanced soft magnetic properties using a medium range order (MRO) structure and its preparation method, especially a Fe-Ni based alloy with low magnetostriction and high saturation magnetic induction. Background Technology

[0002] With the widespread adoption of third-generation semiconductor (SiC / GaN) devices, the operating frequency of power electronic devices has increased to 100kHz or even MHz. This places stringent requirements on the core materials of magnetic components (such as high-frequency transformers and filter inductors): high saturation magnetic induction (Bs) is required to reduce device size, while extremely low loss and low magnetostriction are required to reduce heat generation and noise.

[0003] Existing technologies are mainly divided into two categories: (1) Fe-Si-B amorphous alloy: Bs is relatively high (~1.56T), but the magnetostriction coefficient is large (λs≈27 ppm), the working noise is large, and it is extremely sensitive to stress.

[0004] (2) Nanomet type (Fe-Si-BP-Cu) nanocrystalline alloy: Although Bs is increased to about 1.8T, in order to obtain excellent soft magnetic properties, the grains usually need to be grown to 10-20 nm. This type of alloy is extremely brittle and difficult to perform subsequent winding processing; and due to the extremely high Fe content, its coercivity Hc is difficult to reduce to below 5A / m, resulting in high high-frequency loss.

[0005] In recent years, a "medium-range order (MRO)" transition state has been discovered between amorphous and nanocrystalline materials. If the microstructure can be locked in the 1-5 nm cluster stage, it is possible to reduce magnetocrystalline anisotropy using clusters while retaining the high resistivity and toughness of amorphous materials. However, conventional Fe-based alloys are difficult to stably control in this state and are prone to explosive crystallization.

[0006] Therefore, developing a novel soft magnetic material that can stably obtain MRO structures and possesses high Bs, low Hc, and low noise characteristics is currently a key technological bottleneck in the field of high-end magnetic materials. Summary of the Invention

[0007] This invention aims to solve the existing high B s To address the technical contradictions of nanocrystalline alloys, such as high brittleness, high noise, and high coercivity, this paper proposes a Fe-Ni based alloy with enhanced soft magnetic properties using a mid-range ordered structure and its preparation method. This alloy is a mid-range ordered structure-enhanced alloy based on the Fe-Ni system.

[0008] In the Fe-Ni based alloy of this invention, the elements, through a unique synergistic ratio, jointly achieve precise control and stability of the medium-range ordered (MRO) heterostructure: the introduction of a specific ratio of Ni (4.0~8.0 at%) cleverly utilizes its negative magnetostrictive properties to neutralize the high positive magnetostriction of the iron matrix; a relatively high content of B (8.0~13.0 at%) constructs a robust amorphous network framework; by strictly limiting the Cu content to a low range of 0.6~1.2 at%, only a moderate local segregation driving force is provided; at the same time, the large atomic radius M elements (Nb, Mo, Zr) hinder the migration of cluster boundaries, helping to suppress further coarsening of clusters towards conventional nanocrystals (>10 nm). bal represents the balance Fe and unavoidable impurities.

[0009] In existing technologies, Cu is typically used to encourage the formation of numerous competing nuclei, ultimately resulting in conventional nanocrystalline structures with grain sizes exceeding 10 nm. The core of this invention is to obtain mid-range ordered (MRO) clusters of 1 nm to 5 nm, rather than fully crystallized nanocrystals. If the Cu content is too high (above 1.2%), it provides excessive nucleation sites and easily triggers explosive crystallization during heat treatment, leading to grain coarsening to over 10 nm, thus negating the high resistivity and low high-frequency loss advantages of the MRO structure. Therefore, controlling Cu at 0.6–1.2 at% helps achieve a "cluster + amorphous" two-phase heterostructure, and this is not a simple matter of adjusting conventional parameters.

[0010] The objective of this invention can be achieved through the following methods: This invention provides an Fe-Ni based alloy that enhances soft magnetic properties using a medium-range ordered structure. The chemical composition of the Fe-Ni based alloy, by atomic percentage, is: Fe bal Ni a Cr y Si b B c M d Cu e X f ; Wherein, 4.0 ≤ a ≤ 8.0, 0 ≤ y ≤ 1.5, 1.0 ≤ b ≤ 6.0, 8.0 ≤ c ≤ 13.0, 1.0 ≤ d ≤ 2.5, 0.6 ≤ e ≤ 1.2, 0 ≤ f ≤ 2.0, and bal is the margin; M is selected from one or more of Nb, Mo, and Zr; X is selected from one or more of C, P, Al, and Ga.

[0011] In this invention, the Ni content is preferably limited to 4.0%~8.0%. When the Ni content is below 4.0%, the positive magnetostriction of Fe cannot be effectively compensated, resulting in a still high λs in the material, which fails to solve the high-frequency howling problem. When the Ni content is above 8.0%, the strongly magnetic Fe atoms are excessively diluted, causing the saturation magnetic induction intensity Bs to drop significantly to below 1.75T, thus losing the advantage of high saturation magnetic induction. Therefore, 4.0%~8.0% is a better ratio range that balances higher Bs and lower magnetostriction.

[0012] This invention preferably controls the Cu content at 0.6~1.2 at%. Unlike the traditional design that adds high Cu content (usually >1.5 at%) to promote full nanocrystallization, this invention finds that when the Cu content is higher than 1.2 at%, it leads to too many nucleation sites, which easily induces explosive grain growth during annealing, forming conventional nanocrystals larger than 10 nm, resulting in alloy embrittlement and increased high-frequency losses. However, controlling the Cu content in the low range of 0.6~1.2 at% can induce an appropriate amount of local segregation in the amorphous matrix, forming ideal high-density 1 nm~5 nm bcc-Fe(Si) MRO precursor clusters, which not only prevents excessive grain growth but also retains the high resistivity advantage of the amorphous phase.

[0013] The chemical composition of the Fe-Ni based alloy, by atomic percentage, includes Ni 4-8%, Cr 0-1.5%, Si 1-6%, B 8-13%, M 1-2.5%, Cu 0.6-1.2%, X 0-2%, with the balance being Fe and unavoidable impurities.

[0014] The preferred Ni is 4.0 ≤ a ≤ 7.0; the preferred Si is 2.0 ≤ b ≤ 3.0; the preferred B is 8.0 ≤ c ≤ 10.0; the preferred M is 1.0 ≤ d ≤ 2.0; and the preferred Cu is 0.6 ≤ e ≤ 1.0.

[0015] The preferred values ​​for Cr are 0.5 ≤ y ≤ 1.0. The preferred values ​​for X are 0.1 ≤ f ≤ 1.0.

[0016] As one embodiment of the present invention, the total atomic percentage of Fe and Ni is: 82.0 ≤ Fe + Ni ≤ 87.0.

[0017] As one embodiment of the present invention, the microstructure of the Fe-Ni based alloy is a biphase heterostructure of “amorphous-medium-range ordered (MRO) clusters”. The medium-range ordered (MRO) clusters are dispersed in the amorphous matrix, with an average cluster size of 1 nm to 5 nm and no grains larger than 10 nm. The volume fraction of atomic-scale medium-range ordered (MRO) clusters is 15% to 40%.

[0018] The key factors influencing the average cluster size in this invention are the synergistic pinning effect of low Cu content and large atomic radius M (Nb, Mo, Zr) elements, as well as the strict pre-crystalline annealing temperature. This application further reduces the average cluster size by precisely limiting the number of Cu agglomeration nuclei and enriching the cluster periphery with M elements to form an "elastic shell" that hinders grain boundary migration. Combined with improvements in the pre-crystalline thermodynamic constraints of Tx1-60℃≤Ta≤Tx1-20℃, this successfully locks the cluster size within the MRO stage, avoiding grain coarsening phenomena common in conventional nanocrystal preparation.

[0019] When X is selected from one or more of C and P, it is preferably 0.1 ≤ f ≤ 1.0. When X is selected from one or more of Al and Ga, it is preferably 0.1 ≤ f ≤ 0.5.

[0020] This invention can also selectively introduce trace amounts of X elements (one or more of C, P, Al, and Ga, with the total amount controlled between 0 and 2.0 at%). Trace amounts of P help improve the amorphous forming ability of the alloy and synergistically refine clusters; trace amounts of C can increase the free volume of the amorphous matrix, further improving the winding toughness of the thin strip; while trace amounts of Al or Ga, although causing slight magnetic moment dilution, can significantly improve the interfacial resistivity of the alloy under strict control of the addition amount, thereby further reducing eddy current losses in ultra-high frequency environments and meeting the customized requirements for soft magnetic properties in different specific application scenarios.

[0021] The mid-range ordered clusters are Fe(Si)-rich locally ordered regions induced by Cu segregation; The Fe-Ni based alloy as a whole exhibits only amorphous diffuse peaks and no sharp crystallization peaks in the X-ray diffraction (XRD) pattern, but obvious lattice stripe regions are visible under transmission electron microscopy (HRTEM).

[0022] As one embodiment of the present invention, the Fe-Ni based alloy has a saturation magnetic induction intensity Bs ≥ 1.75T; coercivity Hc ≤ 4.0A / m; and saturation magnetostriction coefficient λs controlled within +2×10⁻⁶. -6 Up to +12×10 -6 Between; the effective permeability μe at 100 kHz is ≥15000.

[0023] This invention provides a method for preparing the Fe-Ni based alloy, comprising the following steps: S1. Master alloy smelting: Weigh the raw materials according to the atomic percentage of the Fe-Ni based alloy and smelt the raw materials into a master alloy ingot with uniform composition. S2. Rapid cooling strip preparation: Using single-roll melt spin quenching technology, a completely amorphous alloy thin strip is prepared. S3. Cluster-Induced Annealing: The completely amorphous alloy ribbon is subjected to isothermal heat treatment; the isothermal heat treatment temperature Ta is set as Tx1-60℃≤Ta≤Tx1-20℃, where Tx1 is the first crystallization temperature of the completely amorphous alloy ribbon with a defined chemical composition. S4 Field Cooling: After isothermal heat treatment, a longitudinal magnetic field is applied, and the Fe-Ni based alloy is obtained after cooling.

[0024] As one embodiment of the present invention, in step S1, the iron source in the raw materials includes one or more of pure iron, iron-boron (industrial grade Fe-B) master alloy, and iron-silicon (industrial grade Fe-Si) master alloy; Nickel sources include pure nickel; Chromium sources include pure chromium; Copper sources include pure copper; The M source includes bulk pure metal M (Nb, Mo, Zr); The silicon source includes one or more of pure silicon and iron-silicon (Fe-Si) master alloys; The boron source includes one or more of pure boron crystals and iron-boron (Fe-B) master alloys; The X source includes one or more of the following: high-purity graphite, pure metal Al, pure metal Ga, iron-carbon (Fe-C) master alloy, and iron-phosphorus (Fe-P) master alloy.

[0025] The purity of each raw material is not less than 99.9%. The smelting is carried out under the protection of high-purity argon gas.

[0026] In one embodiment of the present invention, in step S1, the melting is performed using vacuum induction melting. The proportioned raw materials are placed in a crucible, and the melting is carried out under a vacuum degree better than 10. -2 After Pa, high-purity argon gas is introduced for protection; the temperature is raised to 1250℃~1350℃ to completely melt the raw materials, and electromagnetic stirring is performed for 5~10 minutes to ensure uniform alloy composition, thus obtaining the master alloy ingot.

[0027] As one embodiment of the present invention, in step S2, when preparing the completely amorphous alloy thin strip, the linear speed of the roller is controlled to be 25~35 m / s.

[0028] In one embodiment of the present invention, in step S3, the isothermal heat treatment time is 10~40 min; the isothermal heat treatment is carried out in a protective atmosphere. The isothermal heat treatment temperature Ta is set to Tx1-50℃≤Ta≤Tx1-30℃.

[0029] For any amorphous master alloy with a defined chemical composition, its first crystallization temperature (Tx1) is an inherent thermodynamic characteristic value, typically unique and definite under fixed test conditions (e.g., measured by differential thermal analysis (DSC) at a fixed heating rate). The setting of the heat treatment temperature Ta in this invention must depend on the Tx1 of that specific composition.

[0030] The preferred range for the first crystallization temperature (Tx1) is 435-465℃. In the composition range of this invention, when the content of element M (such as Nb or Zr) is at the upper limit of 2.5% and the total amount of metalloid elements (B+Si) is high, Tx1 can reach a maximum of approximately 485℃. The heat treatment temperature Ta is dynamically adjusted strictly according to the measured Tx1 of each component (i.e., Tx1-60℃≤Ta≤Tx1-20℃) to ensure that the energy is just sufficient to induce the formation of MRO clusters without triggering explosive crystallization.

[0031] As one embodiment of the present invention, in step S4, the intensity of the longitudinal magnetic field is ≥1000 Gs, preferably 1500~3000 Gs.

[0032] In this invention, after step S3, a two-phase heterostructure of "amorphous matrix-medium-range ordered (MRO) clusters" is formed inside the alloy. Studies have shown that if no longitudinal magnetic field is applied during cooling, the local magnetic moments of the MRO clusters and the local magnetic responses of the surrounding amorphous regions tend to be randomly distributed, leading to localized magnetic pinning during subsequent magnetization. This is detrimental to further reducing the coercivity Hc and increasing the effective permeability μe.

[0033] Therefore, the present invention applies a longitudinal magnetic field during the cooling process to induce the magnetic moments inside the alloy, especially the local magnetic moments associated with Fe-Ni atom pairs, to tend to be co-oriented along the direction of the magnetic field, so that the magnetic response between the MRO clusters and the amorphous matrix is ​​more consistent, reducing the local magnetization incoordination phenomenon, thereby reducing the coercivity Hc and increasing the effective permeability μe.

[0034] Furthermore, the longitudinal magnetic field treatment can be combined with the compensation effect of Ni element on the saturation magnetostriction coefficient λs to further reduce the vibration and noise of the material under high-frequency alternating magnetic field. Therefore, the longitudinal field cooling treatment in step S4 is not a normal field annealing step, but a key control step set up to fully utilize the unique MRO structure advantages of this invention.

[0035] In one embodiment of the present invention, in step S4, the cooling rate is ≥20°C / min, preferably 20~50°C / min. Cooling is performed to below 200°C.

[0036] The innovative points and technical principles of this invention are as follows: 1. Dual regulatory effect of Ni: This invention introduces 4-8 at% Ni into the Fe matrix. On the one hand, the negative magnetostriction property of Ni is used to compensate for the positive magnetostriction of Fe, reducing the overall λs to about 10 ppm, which significantly reduces device noise; on the other hand, Ni improves the stability of the supercooled liquid phase region, making the Cu clustering process more controllable and avoiding explosive grain growth.

[0037] 2. Synergistic Anti-eddy Current and Corrosion Protection Mechanism of Trace Cr: This invention optionally introduces trace amounts of Cr (≤1.5 at%) to construct Fe-Cr-Ni based alloys. Although the introduction of Cr will dilute the matrix magnetic moment to some extent, when it is strictly limited to within 1.5 at%, the gains far outweigh the losses. Cr not only significantly improves the corrosion resistance of the amorphous matrix framework, but more importantly, the addition of Cr can greatly increase the matrix resistivity. Combined with the high resistivity of the MRO cluster structure itself, the synergistic effect of trace Cr will further suppress eddy current losses at high frequencies (>100 kHz), making it more suitable for high-power, ultra-high-frequency applications driven by third-generation semiconductors.

[0038] 3. MRO Cluster Pinning Mechanism: In existing technologies, the pinning effect of large atoms (M) typically occurs at long-range nanograin boundaries of 10–50 nm. This invention weakens the kinetics of atomic segregation by strictly limiting the content of extremely low Cu (0.6 ≤ Cu ≤ 1.2) and innovatively performs annealing in the temperature range below Tx1 (subcrystalline region), ensuring that the provided thermodynamic driving force is insufficient to trigger explosive crystallization. In the budding stage of cluster growth, large atoms (M) with slower diffusion rates rapidly accumulate around extremely small clusters, forming a nanoscale "elastic shell" that stably pins them to the 1–5 nm MRO stage.

[0039] 4. Performance advantages: This structure is not a traditional "crystalline + amorphous" composite, but rather a "cluster + amorphous" structure. This structure helps maintain a high resistivity, thereby reducing high-frequency eddy current losses.

[0040] Compared with the prior art, the present invention has the following beneficial effects: (1) It solved the technical contradiction that high Bs and low magnetostriction could not be achieved simultaneously: such as Figure 2The figure shows a comparison of the saturation magnetic flux density (Bs) and saturation magnetostriction coefficient (λs) of the alloy of the present invention with those of typical existing iron-based soft magnetic materials. It can be seen that while traditional Fe-Si-B amorphous materials and existing nanocrystalline alloys can achieve high Bs, their λs are all above 25 ppm, classifying them as high-noise materials. However, the present invention, through a unique MRO structure and Ni element regulation, successfully locks the material properties in the excellent "high Bs-low λs" region in the upper left corner of the figure. While maintaining Bs at no less than 1.75T, it significantly reduces λs to around 10 ppm, effectively solving the howling problem of high-power magnetic devices.

[0041] (2) High frequency, extremely low loss and high environmental adaptability: Utilizing the high resistivity of the MRO structure and the electron scattering effect of optional trace amounts of Cr, the alloy of this invention exhibits superior high-frequency magnetic properties above 100 kHz. At the same time, the Fe-Cr-Ni system endows the material with excellent oxidation and rust resistance, which helps reduce the material's dependence on additional protective treatments and is expected to simplify the device manufacturing process.

[0042] (3) Low noise and environmentally friendly: By doping with Ni, the magnetostriction coefficient is reduced to below 12 ppm, which solves the whistling problem of high Bs transformers.

[0043] (4) Wide process window: Compared with some existing Fe-Si-BP-Cu systems, the present invention has a relatively wide sub-crystalline annealing process window, which is more conducive to industrial control. Attached Figure Description

[0044] Other features, objects, and advantages of the present invention will become more apparent from the following detailed description of non-limiting embodiments with reference to the accompanying drawings: Figure 1 This is a process flow diagram for preparing an Fe-Ni based alloy, provided in an embodiment of the present invention. Figure 2 This is a comparison graph showing the relationship between the saturation magnetic induction intensity (Bs) and the saturation magnetostriction coefficient (λs) of the alloy of the present invention and a typical existing iron-based soft magnetic material; Figure 3 This is a transmission electron microscope (TEM) image of the Fe-Ni based alloy prepared in Example 1. Detailed Implementation

[0045] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments. The following examples are implemented under the premise of the technical solution of the present invention, providing detailed implementation methods and specific operating procedures, which will help those skilled in the art to further understand the present invention. It should be noted that the scope of protection of the present invention is not limited to the following embodiments; any adjustments and improvements made under the concept of the present invention are all within the scope of protection of the present invention.

[0046] This invention provides a method for preparing the Fe-Ni based alloy, such as... Figure 1 As shown, it includes the following steps: S1 Master alloy smelting: Under the protection of high-purity argon gas, the raw materials are smelted into a master alloy ingot with uniform composition; S2 Rapid Cooling Strip Preparation: Using single-roll melt spin quenching technology, the roller linear speed is controlled at 25 ~ 35 m / s to prepare a completely amorphous alloy thin strip; S3 Cluster-Induced Annealing: The amorphous ribbon is placed in a protective atmosphere for isothermal heat treatment. The heat treatment temperature Ta is set to Tx1-60℃≤Ta≤Tx1-20℃, and the holding time is 10~40min. S4 Field Cooling Treatment: After the heat preservation is completed, a longitudinal magnetic field with an intensity of ≥1000 Gs is applied, and the temperature is cooled to below 200℃ at a rate of ≥20℃ / min.

[0047] This invention belongs to the technical field of amorphous and nanocrystalline soft magnetic materials, specifically relating to a mid-range ordered structure-reinforced Fe-Ni based alloy with low magnetostriction and high saturation magnetic induction, and its preparation method. The chemical formula of the alloy is: Fe bal Ni a Cr y Si b B c M d Cu e X f Its microstructure is characterized by a predominantly amorphous alloy matrix with dispersed atomic-scale medium-range ordered (MRO) clusters comprising 15%–40% by volume. These clusters are controlled to a size of 1–5 nm, and no long-range crystalline phases larger than 10 nm are formed. The saturation magnetostriction coefficient (λs < 12 × 10⁻⁶) is reduced by introducing Ni element for magnetic moment coupling with Fe. -6The material utilizes a low-temperature relaxation annealing process to control the pre-precipitation behavior of Cu, establishing a high-density MRO (Magnetic Restriction and Repair) reinforcement framework in an amorphous matrix. This material possesses high saturation magnetic induction (Bs≥1.75T), low coercivity (Hc≤4.0A / m), and excellent high-frequency permeability, effectively solving the problems of high magnetostriction coefficient and high high-frequency noise in existing high-Bs iron-based nanocrystalline alloys. It is particularly suitable for high-frequency high-power transformers and wireless charging magnetic shielding modules.

[0048] Unless otherwise specified, the purity of raw materials, protective atmosphere, strip width and other preparation conditions not particularly limited in each embodiment and comparative example can be performed in accordance with Example 1.

[0049] Example 1 The alloy composition, prepared by atomic percentage, is as follows: Fe82Ni5Cr0Si3B8.4Nb1Cu0.6, as shown in Table 1.

[0050] (1) Smelting and belt making: Vacuum induction melting is employed, where the proportioned raw materials are placed in a crucible and melted under a vacuum degree better than 10. -2 After Pa, high-purity argon gas is introduced for protection; the temperature is raised to 1300℃ to completely melt the raw material, and electromagnetic stirring is performed for 8 minutes to ensure uniform alloy composition, thus obtaining a master alloy ingot. A 24µm thick and 5mm wide amorphous strip is produced by single-roll quenching (roller linear speed is 30m / s).

[0051] (2) Heat treatment: The first crystallization temperature Tx1 of the amorphous ribbon was determined to be 445℃ by differential thermal analysis (DSC). The ribbon was placed in a vacuum heat treatment furnace and held at 400℃ (Tx1-45℃) for 20 min. A longitudinal magnetic field of 2000 Gs was applied from the holding stage and continued throughout the entire subsequent cooling process until the sample was cooled to below 200℃ after holding. The magnetic field was then removed. The cooling process was carried out at a rate of 20℃ / min to obtain the Fe-Ni based alloy.

[0052] (3) Performance tests are shown in Table 3: Transmission electron microscopy (TEM) revealed a large number of tiny clusters (approximately ~3 nm in size, 28% by volume) diffusely distributed within the matrix. Figure 3 No obvious crystallization peak was observed in the XRD.

[0053] Magnetic properties: Bs = 1.78 T, coercivity Hc = 2.8 A / m, λs = +9 × 10 -6 The effective permeability at 100 kHz is μe = 16500.

[0054] Mechanical properties: It can withstand 180-degree folding without breaking and has better toughness than similar Nanomet alloys.

[0055] Example 2 The alloy composition, prepared by atomic percentage, is as follows: Fe 79.9Ni 7Cr 0Si 2B 9Mo 1.5Cu 0.6, as shown in Table 1.

[0056] Preparation process: The first crystallization temperature of the alloy, Tx1, was determined to be 440℃ by differential thermal analysis (DSC). The annealing temperature was set to Tx1-50℃ (i.e., 390℃) and held for 20 min.

[0057] The performance results are shown in Table 3: Bs = 1.82 T, coercivity Hc = 1.9 A / m, λs = +9×10 -6 The effective permeability at 100 kHz is μe = 18000. Its extremely low coercivity makes it ideal for precision transformer applications.

[0058] Example 3 The alloy composition was prepared according to atomic percentage as follows: Fe81Ni4Cr0Si2B10Zr2Cu1, as shown in Table 1.

[0059] Preparation process: The first crystallization temperature Tx1 was determined to be 450℃, the annealing temperature was set to Tx1-40℃ (i.e., 410℃), the holding temperature was 25 min, and the field cooling magnetic field strength was 1500 Gs.

[0060] The performance results are shown in Table 3: Bs = 1.76 T, coercivity Hc = 3.2 A / m, λs = +6×10 -6 The effective permeability at 100 kHz is μe = 15800, and the grain size is approximately 2 nm.

[0061] Example 4 The alloy composition was prepared according to atomic percentage as follows: Fe81Ni5Cr1Si3B8.4Nb1Cu0.6 (based on Example 1, 1% Cr was used to replace 1% Fe), as shown in Table 1.

[0062] Preparation process: The first crystallization temperature Tx1 was determined to be 452℃ by differential thermal analysis (DSC). The annealing temperature was set to Tx1-42℃ (i.e., 410℃), held for 20 min, and the field cooling magnetic field strength was 2000 Gs.

[0063] The performance results are shown in Table 3: Due to the slight dilution effect of Cr, Bs decreased slightly to 1.75 T (still meeting the standard), coercivity Hc = 3.0 A / m, λs = +8×10 -6 However, the effective permeability at 100 kHz is further increased to 17500, and no visible rust is observed on the surface after being left to stand in a humid environment for 30 days, demonstrating excellent high-frequency characteristics and weather resistance.

[0064] Introducing trace amounts of Cr into the system of this invention not only has a positive effect on corrosion resistance, but may also help improve high-frequency magnetic properties by influencing local electron scattering and interface characteristics. Compared with elements such as Al and Ti, Cr has a relatively smaller adverse effect on saturation magnetic induction at lower addition levels, making it more suitable as one of the optional microalloying elements in this invention.

[0065] Although many elements (such as Al, Si, and Ti) can form films for corrosion protection, the Cr added in this embodiment has a synergistic effect compared to other elements: (1) High segregation tendency under extremely low solid solubility: In the Fe-Ni matrix, trace amounts of Cr may tend to distribute around MRO clusters or in local areas of the amorphous matrix during annealing, thereby helping to improve the interfacial resistivity and corrosion resistance. This "atomic-level coating" not only forms an anti-corrosion layer, but more importantly, it significantly improves the resistivity of the inter-cluster boundary, thereby effectively suppressing micro-eddy current loss at high frequencies.

[0066] (2) Minimization of magnetic moment effect: Compared with strongly paramagnetic elements such as Al and Ti, the weakening effect of trace amounts of Cr (≤1.5%) on the saturation magnetic induction intensity (Bs) of the Fe-Ni system is relatively mild.

[0067] (3) Self-healing properties of passivation film: On the surface of extremely thin strips (20-30 μm), Cr can form a dense Cr2O3 passivation film at the nanoscale, which is crucial for protecting materials with such a high specific surface area.

[0068] Other corrosion-resistant elements, such as Al (aluminum), while possessing corrosion-resistant properties, exhibit a non-magnetic dilution effect that is extremely sensitive to the saturation magnetic induction intensity Bs. In the system of this invention, the addition of Al significantly weakens magnetic moment coupling; if the content is slightly high (e.g., exceeding 0.5 at%), it leads to a drastic decrease in Bs, making it difficult to maintain a stable value above 1.75 T. Furthermore, Al is easily oxidized during smelting, which can increase the surface roughness of the thin strip and deteriorate the magnetic permeability. Therefore, if Al is selected as the X element, it must be strictly limited to an extremely small amount (as shown in Example 6, although the addition of 0.5 at% Al can maintain Bs at 1.77 T, it already shows a decreasing trend in magnetic properties compared to the Cr addition group under the same conditions). In contrast, the Cr element preferred in this invention has a wider process window (up to 1.5 at%), significantly improving corrosion resistance while having a relatively mild weakening effect on Bs. It can also more effectively accumulate at the MRO interface to improve resistivity and suppress high-frequency losses, demonstrating superior overall technical advantages. In addition, Ti (titanium) tends to form coarse, hard phases with Si and B, which destroys the 1-5 nm MRO cluster structure sought in this invention; V (vanadium) is extremely expensive and its enrichment effect at the MRO interface is not as significant as that of Cr in improving resistivity.

[0069] Example 5 The alloy composition is prepared by atomic percentage as follows: Fe82Ni5Cr0Si3B8.4Mo1Cu0.6. (1) Melting and strip making: Vacuum induction melting is adopted. The raw materials are placed in a crucible and the vacuum degree is better than 10. -2 After Pa, high-purity argon gas was introduced for protection; the temperature was raised to 1350℃ to completely melt the raw materials, and electromagnetic stirring was carried out for 8 minutes to ensure uniform composition, and the master alloy ingot was cast. Subsequently, a single-roll quenching technique was used to control the roller linear speed at 32 m / s to prepare a completely amorphous alloy strip with a thickness of about 24 μm and a width of 5 mm.

[0070] (2) Heat treatment: Differential thermal analysis determined that the first crystallization temperature Tx1 of the Mo-containing amorphous ribbon was 442℃. The ribbon was placed in a vacuum heat treatment furnace, and the heat treatment temperature was set to Ta = 400℃ (i.e., Tx1 - 42℃), and held for 25 min. A longitudinal magnetic field of 2500 Gs was applied from the holding stage and continued throughout the subsequent cooling process; the magnetic field was removed after the sample was cooled to below 200℃ at a rate of 30℃ / min.

[0071] (3) Performance testing: Microstructure: Transmission electron microscopy revealed that the amorphous matrix contained diffusely distributed microclusters with an average size of approximately 3.2 nm, and the cluster volume fraction was approximately 30%; XRD patterns showed only diffuse peaks in the amorphous matrix.

[0072] Magnetic properties: Saturation magnetic induction Bs = 1.79 T, coercivity Hc = 2.5 A / m, saturation magnetostriction coefficient λs = +8.5 × 10⁻⁶ -6 The effective permeability at 100 kHz is μe = 17200.

[0073] Mechanical properties: The thin strip exhibits good toughness and does not break when bent at 180 degrees.

[0074] Example 6 The alloy composition is prepared by atomic percentage as follows: Fe 78.9, Ni 7.5, Cr 0.5, Si 2B 9, Zr 1, Cu 0.6, Al 0.5.

[0075] (1) Melting and Strip Making: Vacuum induction melting is used. High-purity Fe, Ni, Cr, Cu, Zr bulk materials, Si, B crystals, and pure metallic Al (X source) are placed in a crucible. The melting is carried out under a vacuum degree better than 10... -2 After Pa, high-purity argon gas was introduced for protection, and the temperature was raised to 1350℃ to completely melt the raw material. Electromagnetic stirring was maintained for 10 min to ensure uniform distribution of all elements (especially high-melting-point Zr and easily oxidized Al). Subsequently, a single-roller spin quenching technique was used, with the roller linear speed controlled at 30 m / s, to prepare a completely amorphous alloy strip with a thickness of approximately 22 μm and a width of 5 mm.

[0076] (2) Heat treatment: Differential thermal analysis determined that the first crystallization temperature Tx1 of the Zr and Al-containing amorphous ribbon was 455℃. The ribbon was placed in a vacuum heat treatment furnace, and the heat treatment temperature was set to Ta = 415℃ (i.e., Tx1 - 40℃), and held for 20 min. A longitudinal magnetic field of 2000 Gs was applied from the holding stage and continued throughout the subsequent cooling process; the sample was rapidly cooled to below 200℃ at a rate of 20℃ / min, and then the magnetic field was removed.

[0077] (3) Performance testing: Microstructure: Transmission electron microscopy revealed that the amorphous matrix contained diffusely distributed microclusters with an average size of approximately 2.5 nm, and the cluster volume fraction was approximately 32%; the XRD pattern showed typical diffuse peaks typical of amorphous matrix.

[0078] Magnetic properties: Due to the increased Ni content to 7.5% and the introduction of Zr pinning, the alloy exhibits excellent overall performance: saturation magnetic induction Bs = 1.77 T, coercivity Hc = 1.8 A / m, and the saturation magnetostriction coefficient is significantly reduced to λs = +5 × 10⁻⁵.-6 The effective permeability at 100 kHz is μe = 18500.

[0079] Mechanical properties: Despite containing solute element X, the strip still maintains good plasticity and does not break when bent at 180 degrees.

[0080] Example 7 The alloy composition is prepared by atomic percentage as follows: Fe 75.4Ni 8Cr 1Si 2.5B 10Mo 1.5Cu 0.6P 1.0. (1) Melting and Strip Making: Vacuum induction melting is used. The raw materials are placed in a crucible, and the P source is an iron-phosphorus master alloy. The vacuum degree is better than 10... -2 After Pa, high-purity argon gas was introduced for protection, and the temperature was raised to 1360℃ to completely melt the raw material and electromagnetically stirred for 8 min. Subsequently, a single-roller spin quenching technique was used to control the roller linear speed at 30 m / s, and a completely amorphous alloy strip with a thickness of about 24 μm and a width of 5 mm was prepared. (2) Heat treatment: The first crystallization temperature Tx1 of the amorphous ribbon of this composition was determined by differential thermal analysis (DSC) to be 458℃. The ribbon was placed in a vacuum heat treatment furnace, and the heat treatment temperature was set to Ta = 410℃ and held for 20 min. A longitudinal magnetic field of 2000 Gs was applied from the holding stage and continued throughout the subsequent cooling process until the sample cooled to below 200℃ at a rate of 20℃ / min, after which the magnetic field was removed.

[0081] (3) Performance testing: TEM observation showed that MRO clusters with a size of approximately 2.8 nm were diffusely distributed in the matrix, with a volume fraction of 35%. The magnetic properties were tested as follows: Bs = 1.76 T, Hc = 1.5 A / m, λs = +2×10 -6 The effective permeability at 100 kHz is μe = 18800.

[0082] Example 8 The alloy composition is prepared according to atomic percentage: Fe80Ni6Cr0.5Si3B8Nb1.5Cu0.7C0.3. (1) Melting and ribbon making: In the vacuum induction melting process, high-purity graphite is added as the C source. The temperature is raised to 1380℃ to completely melt the raw materials and stir them evenly; the linear speed of the single-roller quenching roller is controlled at 30 m / s to prepare a completely amorphous ribbon with a thickness of about 24 μm and a width of 5 mm. (2) Heat treatment: The Tx1 of the component was measured to be 448℃. The annealing temperature was set to Ta = 410℃ and held for 20 min. A longitudinal magnetic field of 2000 Gs was applied throughout the process for field cooling treatment, and the cooling rate was 30℃ / min.

[0083] (3) Performance testing: The average size of the MRO clusters is approximately 3.0 nm, with a volume fraction of 28%. The magnetic properties are: Bs = 1.80 T, Hc = 2.1 A / m, λs = +6×10 -6 The effective permeability at 100 kHz is μe = 17600.

[0084] Example 9 The alloy composition is prepared according to atomic percentage: Fe 81.5 Ni 4.5 Cr 0 Si 3 B 8.1 Nb 2 Cu 0.8 Ga 0.1.

[0085] (1) Melting and ribbon preparation: Pure metallic Ga was added to the X source. The raw materials were melted uniformly at 1400℃; the roller linear speed was controlled at 30 m / s to prepare an amorphous ribbon with a thickness of about 24 μm and a width of 5 mm. (2) Heat treatment: The Tx1 of the component was measured to be 465℃. The annealing temperature was set to Ta = 420℃ and held for 20 min. A longitudinal magnetic field of 2000 Gs was applied and held until the end of cooling. The cooling rate was 20℃ / min. (3) Performance testing: The MRO cluster size is approximately 2.2 nm, and the magnetic properties are: Bs = 1.81 T, Hc = 2.4 A / m, λs = +9×10 -6 The effective permeability at 100 kHz is μe = 17000.

[0086] Example 10 The alloy composition is prepared according to atomic percentage: Fe 79.3 Ni 7Cr 1 Si 2B 8.5 Zr 1.5 Cu 0.6 P 0.1.

[0087] (1) Melting and Strip Making: Vacuum induction melting is used. The raw materials are placed in a crucible, and the P source is an iron-phosphorus master alloy. The vacuum degree is better than 10... -2 After Pa, high-purity argon gas was introduced for protection, and the temperature was raised to 1350 ℃ to completely melt the raw material and electromagnetically stirred for 8 min. Subsequently, a single-roller spin quenching technique was used to control the roller linear speed at 30 m / s, and a completely amorphous alloy strip with a thickness of about 24 μm and a width of 5 mm was prepared.

[0088] (2) Heat treatment: The temperature of the component Tx1 was measured to be 452℃. The annealing temperature was set to Ta = 415℃ and held for 20 min. The field cooling magnetic field strength was 2000 Gs and the cooling rate was 20℃ / min.

[0089] (3) Performance test: The cluster size is 2.5 nm, and the magnetic properties are: Bs = 1.78 T, Hc = 1.7 A / m, λs = +4 × 10-6 The effective permeability at 100 kHz is μe = 19000.

[0090] Table 1 Alloy composition and preparation parameters of the examples

[0091] Comparative Example 1 This comparative example serves as a benchmark reference for the prior art, using the traditional Nanomet type Fe-Si-B-Cu alloy composition: Fe83Si4B12Cu1 (without the addition of the Ni and M elements of this invention) as shown in Table 2. Preparation process: Differential thermal analysis determined that the Tx1 of this composition is approximately 430℃. A traditional fully crystallized annealing process was adopted, with the annealing temperature set at 450℃ (i.e., Ta>Tx1, which does not fall within the subcrystallization temperature range required by this invention), and the holding time was 60 min. The results and performance are shown in Table 3. Due to the lack of magnetostrictive compensation from Ni and the pinning effect of M, coupled with an excessively high annealing temperature, a large number of crystal nuclei grew rapidly, forming conventional nanocrystals with an average size of approximately 18 nm. Tests showed that Bs = 1.82 T, but the coercivity Hc soared to 12.5 A / m, and λs reached +25 × 10⁻⁶. -6 (Extremely noisy). Furthermore, due to the formation of coarse grains, the strip is extremely brittle and has completely lost its toughness.

[0092] Comparative Example 2 (Process temperature too high) The composition and preparation method of the comparative Fe-Ni based alloy are basically the same as those in Example 1, except that the annealing temperature is 460℃, as shown in Table 2.

[0093] The results are shown in Table 3: the grains coarsened to 25 nm, Hc surged to 35 A / m, and the soft magnetic properties deteriorated.

[0094] Comparative Example 3 (Cu content too high) The alloy composition is prepared according to atomic percentage as follows: Fe81Ni5Si3B8.4Nb1Cu1.6 (Cu content exceeds the limits of this invention), as shown in Table 2.

[0095] Preparation process: The first crystallization temperature Tx1 was determined to be 435℃, the annealing temperature was set to 400℃, and the holding time was 20 min.

[0096] The performance results are shown in Table 3: Due to the high Cu content of 1.6%, excessive nucleation sites led to explosive crystallization, resulting in grain coarsening to 22 nm. Although Bs was 1.78 T, the coercivity Hc deteriorated to 21.5 A / m, completely deviating from the low-loss design goal of this invention.

[0097] Comparative Example 4 (Cu content too low) The composition and preparation method of the comparative Fe-Ni based alloy are basically the same as those of Example 1, as shown in Table 2. The only difference is that the Cu content is only 0.3%.

[0098] Preparation process: The first crystallization temperature Tx1 was determined to be 448℃, the annealing temperature was set to 400℃, and the holding time was 20 min.

[0099] Comparative Example 5 (excessive Nb content) The composition and preparation method of this comparative Fe-Ni based alloy are basically the same as those in Example 1, except that the Nb content is increased to 3.0 at.

[0100] Preparation process: The first crystallization temperature Tx1 was determined to be 455℃, the annealing temperature was set to Ta = 415℃, the holding temperature was 20 min, and the field cooling magnetic field strength was 2000 Gs.

[0101] The performance results are shown in Table 3. Although the high Nb content suppressed grain coarsening to some extent and kept the feature size at about 2 nm, the high Nb content had a significant dilution effect on the Fe-based magnetic matrix, causing the saturation magnetic induction intensity Bs to drop to 1.65 T, which is lower than the target range of this invention. This shows that the M element content is not necessarily better the higher it is.

[0102] Comparative Example 6 (lacking Cu) The composition and preparation method of this comparative Fe-Ni based alloy are basically the same as those in Example 1, except that Cu element is not added and its proportion is supplemented to Fe.

[0103] Preparation process: The first crystallization temperature Tx1 was determined to be 442℃, the annealing temperature was set to Ta = 400℃, the holding temperature was 20 min, and the field cooling magnetic field strength was 2000 Gs.

[0104] The performance results are shown in Table 3. Due to the lack of Cu to provide local segregation induction, the material is unable to form MRO clusters with sufficient density and controlled size, and eventually exhibits a large characteristic scale structure. This results in the coercivity Hc increasing to 15.6 A / m and the effective permeability μe decreasing to 8300, indicating that Cu plays an important role in constructing a stable "amorphous-MRO cluster" heterostructure.

[0105] Comparative Example 7 (lacking Ni) The composition of this comparative example is basically the same as that of Example 1, except that Ni element was not added, but its proportion was added to Fe. The chemical composition by atomic percentage is: Fe 87Cr 0Si 3B 8.4Nb 1Cu 0.6. Preparation process: The first crystallization temperature Tx1 was determined to be 440℃, the annealing temperature was set to Ta = 400℃, the holding temperature was 20 min, and the field cooling magnetic field was 2000 Gs. Performance results: Due to the lack of negative magnetostriction compensation effect of Ni, although the MRO cluster structure was obtained and Bs was maintained at 1.80 T, the saturation magnetostriction coefficient λs soared to +22×10⁻⁶. -6 This approach fails to address the acoustic howling problem of high-frequency, high-power transformers, deviating from the low-noise design goal of this invention.

[0106] Comparative Example 8 (lacking element M) The composition of this comparative example is basically the same as that of Example 1, except that the large atomic element M (Nb) was not added, but its proportion was supplemented to Fe. The chemical composition by atomic percentage is: Fe 83Ni 5Cr 0Si 3B 8.4Cu 0.6.

[0107] Preparation process: The first crystallization temperature Tx1 was determined to be 435℃, the annealing temperature was set to Ta = 395℃, the holding temperature was 20 min, and the field cooling magnetic field was 2000 Gs. Performance results: Due to the lack of a "plastic shell" pinning effect formed by large Nb atoms around the clusters, the Cu-rich segregation regions are prone to engulfment and growth during annealing, leading to rapid grain coarsening to 16 nm, failing to lock into the 1-5 nm MRO stage. Tests show that its Bs = 1.78 T, but the coercivity Hc deteriorates to 14.5 A / m, and the high-frequency loss increases sharply.

[0108] Comparative Example 9 (Transverse Magnetic Field) The composition of this comparative example is basically the same as that of Example 1, and the preparation method is also basically the same. The only difference is that a transverse magnetic field is applied in step S4 instead of a longitudinal magnetic field, and the magnetic field strength is 2000 Gs. All other conditions remain the same.

[0109] The performance test results are shown in Table 3. Although an MRO cluster structure of about 3 nm was still formed, the sample treated with the transverse magnetic field was inferior to the sample treated with the longitudinal magnetic field in terms of coercivity and effective permeability, indicating that the longitudinal magnetic field treatment is more conducive to obtaining excellent soft magnetic properties.

[0110] Comparative Example 10 (No magnetic field) The composition of this comparative example is basically the same as that of Example 1, and the preparation method is also basically the same. The only difference is that no magnetic field is applied in step S4, while the other conditions remain the same.

[0111] The performance test results are shown in Table 3: Under the condition of no magnetic field applied, the local magnetic response distribution inside the material is relatively disordered, which leads to a further increase in coercivity to 7.1 A / m and a decrease in effective permeability at 100 kHz to 12800.

[0112] Table 2. Comparative alloy compositions and their preparation parameters

[0113] Performance tests are shown in Table 3: Table 3

[0114] The specific embodiments of the present invention have been described above. It should be understood that the present invention is not limited to the specific embodiments described above, and those skilled in the art can make various modifications or variations within the scope of the claims, which do not affect the essence of the present invention.

Claims

1. A method for preparing Fe-Ni based alloys with enhanced soft magnetic properties utilizing a medium-range ordered structure, characterized in that, Includes the following steps: S1. Master alloy smelting: Weigh the raw materials according to the atomic percentage of the Fe-Ni based alloy and smelt the raw materials into a master alloy ingot with uniform composition. S2. Rapid cooling strip preparation: Using single-roll melt spin quenching technology, a completely amorphous alloy thin strip is prepared; S3. Cluster-induced annealing: The completely amorphous alloy strip is subjected to isothermal heat treatment; the isothermal heat treatment temperature Ta is set to Tx1-60℃≤Ta≤Tx1-20℃, where Tx1 is the first crystallization temperature for determining the chemical composition of the completely amorphous alloy strip, and the isothermal heat treatment time is 10~40min. S4. Field cooling treatment: After isothermal heat treatment, a longitudinal magnetic field is applied, and the Fe-Ni based alloy is obtained after cooling. The chemical composition of the Fe-Ni based alloy, by atomic percentage, is: Fe bal Ni a Cr y Si b B c M d Cu e X f ; Where 4.0 ≤ a ≤ 8.0, 0 ≤ y ≤ 1.5, 1.0 ≤ b ≤ 6.0, 8.0 ≤ c ≤ 13.0, 1.0 ≤ d ≤ 2.5, 0.6 ≤ e ≤ 0.8, 0 ≤ f ≤ 2.0, and bal is the margin; M is selected from one or more of Nb, Mo, and Zr; X is selected from one or more of C, P, Al, and Ga.

2. The method for preparing the Fe-Ni based alloy according to claim 1, characterized in that, The total atomic percentage of Fe and Ni is: 82.0 ≤ Fe + Ni ≤ 87.

0.

3. The method for preparing the Fe-Ni based alloy according to claim 1, characterized in that, The microstructure of the Fe-Ni based alloy is an "amorphous-medium-range ordered cluster" biphase heterostructure; and the medium-range ordered clusters are dispersed in the amorphous matrix, with an average cluster size of 1 nm to 5 nm; the volume fraction of atomic-scale medium-range ordered clusters is 15% to 40%. And / or, the mid-range ordered clusters are Fe-rich (Si) locally ordered regions induced by Cu segregation; And / or, the Fe-Ni based alloy as a whole exhibits only amorphous diffuse peaks and no sharp crystallization peaks in the X-ray diffraction pattern, but obvious lattice stripe regions are visible under transmission electron microscopy.

4. The method for preparing the Fe-Ni based alloy according to claim 1, characterized in that, The Fe-Ni based alloy exhibits a saturation magnetic induction intensity Bs ≥ 1.75 T; coercivity Hc ≤ 4.0 A / m; and a saturation magnetostriction coefficient λs controlled within +2 × 10⁻⁶. -6 Up to +12×10 -6 Between; the effective permeability μe at 100 kHz is ≥15000.

5. The method for preparing the Fe-Ni based alloy according to claim 1, characterized in that, In step S1, the iron source in the raw materials includes one or more of pure iron, iron-boron master alloy, and iron-silicon master alloy; Nickel sources include pure nickel; Chromium sources include pure chromium; Copper sources include pure copper; The M source consists of a pure metal M block; Silicon sources include one or more of pure silicon and iron-silicon master alloys; Boron sources include one or more of pure boron crystals and iron-boron master alloys; The X source includes one or more of the following: high-purity graphite, pure aluminum, pure gallium, iron-carbon master alloy, and iron-phosphorus master alloy.

6. The method for preparing the Fe-Ni based alloy according to claim 1, characterized in that, In step S2, during the preparation of the fully amorphous alloy thin strip, the roller linear speed is controlled to be 25~35 m / s.

7. The method for preparing the Fe-Ni based alloy according to claim 1, characterized in that, In step S4, the intensity of the longitudinal magnetic field is ≥1000 Gs.

8. The method for preparing the Fe-Ni based alloy according to claim 1, characterized in that, In step S4, the cooling rate is ≥20℃ / min.

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