FE-BASED AMORPHOUS ALLOY CONTAINING SUBNANOMETER-SCALE ORDERED CLUSTERS, AND PREPARATION METHOD AND NANOCRYSTALLINE ALLOY DERIVATIVE THEREOF

Abstract

A Fe-based amorphous alloy containing subnanometer-scale ordered clusters, and a preparation method and a nanocrystalline alloy derivative thereof. The composition expression of the Fe-based amorphous alloy is Fe.sub.aSi.sub.bB.sub.c(Cu.sub.dX.sub.e)M.sub.fM′.sub.g, and X is at least one of Ti, Zr and Hf, M is at least one of V, Ta and Nb, and M′ at least one of Co, Ni, C, P, Ge, Cr, Mn, W, Zn, Sn, Sb and Mo; a, b, c, d, e, f and g respectively represent the atomic percent (percentage of the number of atoms) of the corresponding element, and satisfy: 74≤a≤82, 8≤b≤15, 4≤c≤10, 0.5≤d≤1.2, 0.4≤e≤1.8, 1≤f≤3.5, 0≤g≤1, 0.8≤e/d≤1.5 and a+b+c+d+e+f+g=100; the Fe-based amorphous alloy is a composite material composed of an amorphous alloy matrix with atoms arranged in complete disorder and ordered atomic clusters having the size ranging from 0.5 nm to 2 nm uniformly dispersed and distributed in the matrix. The Fe-based amorphous alloy has ultrahigh permeability: the permeability at the frequency of 100 kHz is more than 35000, and the saturation flux density more than 1.3 T.

Claims

1. A Fe-based amorphous alloy containing subnanometer-scale ordered clusters, wherein the composition expression of the Fe-based amorphous alloy is Fe.sub.aSi.sub.bB.sub.c(Cu.sub.dX.sub.e)M.sub.fM′.sub.g, and Xis at least one of Ti, Zr and Hf, M is at least one of V, Ta and Nb, and M′ at least one of Co, Ni, C, P, Ge, Cr, Mn, W, Zn, Sn, Sb and Mo; a, b, c, d, e, f and g respectively represent the atomic percent (percentage of the number of atoms) of the corresponding element, and satisfy: 74≤a≤82, 8≤b≤15, 4≤c≤10, 0.5≤d≤1.2, 0.4≤e≤1.8, 1≤f≤3.5, 0≤g≤1, 0.8≤e/d≤1.5 and a+b+c+d+e+f+g=100; the Fe-based amorphous alloy is a composite material composed of an amorphous alloy matrix with atoms arranged in complete disorder and ordered atomic clusters having the size ranging from 0.5 nm to 2 nm uniformly dispersed and distributed in the matrix.

2. The Fe-based amorphous alloy containing subnanometer-scale ordered clusters of claim 1, wherein the ordered atom clusters in the Fe-based amorphous alloy are Cu—X body-centered cubic clusters formed by Cu atoms and X atoms.

3. The Fe-based amorphous alloy containing subnanometer-scale ordered clusters of claim 1, wherein the Fe-based amorphous alloy can be ribbon-like, powder-like or wire-like in shape.

4. A preparation method of the Fe-based amorphous alloy containing subnanometer-scale ordered clusters of claim 1, wherein the preparation method includes the following steps: (1) Proportioning: pure Cu and pure X are weighed according to a ratio of Cu to X in the composition expression of the alloy to formulate raw materials of a Cu—X intermediate alloy; other raw materials including Fe, Si, B, M and M′ are weighed according to the ratio of the remaining elements in the alloy composition to formulate raw materials of a Fe—Si—B-M-M′ alloy. (2) Smelting of Fe—Si—B-M-M′ master alloy: the raw materials of the Fe—Si—B-M-M′ alloy formulated in step (1) are homogeneously smelted and deslagged, and then the smelted liquid alloy is cooled to obtain a Fe—Si—B-M-M′ master alloy ingot with homogeneous ingredients. (3) Smelting of Cu—X intermediate alloy: the raw materials of the Cu—X intermediate alloy formulated in step (1) are smelted homogeneously and deslagged, and then the smelted Cu—X liquid intermediate alloy is cooled to obtain a Cu—X intermediate alloy ingot with homogeneous ingredients. (4) Preparation of amorphous alloy material: get proper amounts of the Fe—Si—B-M-M′ master alloy ingot prepared in step (2) and the Cu—X intermediate alloy ingot prepared in step (3) are weighed according to the contents of various elements in the composition expression of the alloy; re-melt the weighed master alloy ingot on a ribbon, powder or wire preparation apparatus; keep the master alloy warm for more than 5 minutes after completely molten; add the weighed Cu—X intermediate alloy ingot to the molten master alloy; after the intermediate alloy is completely molten, a material preparation apparatus is used to make the liquid alloy into an amorphous alloy ribbon, or an amorphous alloy powder or an amorphous alloy wire, obtaining the Fe-based amorphous alloy containing subnanometer-scale ordered clusters.

5. A nanocrystalline alloy derivative of the Fe-based amorphous alloy containing subnanometer-scale ordered clusters of claim 1, wherein the composition expression of the nanocrystalline alloy derivative is Fe.sub.aSi.sub.bB.sub.c(Cu.sub.dX.sub.e)M.sub.fM′.sub.g, and X is at least one of Ti, Zr and Hf, M is at least one of V, Ta and Nb, and M′ at least one of Co, Ni, C, P, Ge, Cr, Mn, W, Zn, Sn, Sb and Mo; where a, b, c, d, e, f and g respectively represent the atomic percent (percentage of the number of atoms) of the corresponding element, and satisfy: 74≤a≤82, 8≤b≤15, 4≤c≤10, 0.5≤d≤1.2, 0.4≤e≤1.8, 1≤f≤3.5, 0≤g≤1, 0.8≤e/d≤1.5 and a+b+c+d+e+f+g=100; the nanocrystalline alloy derivative is a composite composed of an amorphous alloy matrix and grains with a size of 5-20 nm homogeneously dispersed in the matrix.

6. The nanocrystalline alloy derivative of claim 5, wherein the grains are α-Fe grains, and the size of the α-Fe grains is 6-16 nm.

7. The nanocrystalline alloy derivative of claim 5, wherein the nanocrystalline alloy derivative is ribbon-like, powder-like or wire-like in shape.

8. The nanocrystalline alloy derivative of claim 5, wherein the preparation method of the nanocrystalline alloy derivative includes: heat-treating the Fe-based amorphous alloy containing subnanometer-scale ordered clusters in a heat treatment furnace under proper conditions such that the amorphous alloy precipitates nanocrystalline grains with a size of 5-20 nm around the ordered atom clusters to form the nanocrystalline alloy.

9. The nanocrystalline alloy derivative of claim 8, wherein the heat treatment conditions include heating rate, holding temperature, holding time, direction and intensity of the applied magnetic field.

10. The nanocrystalline alloy derivative of claim 5, wherein the ribbon-like material of the nanocrystalline alloy derivative has ultrahigh permeability: the permeability at the frequency of 100 kHz is more than 35000, and the saturation flux density more than 1.3 T.

Description

BRIEF DESCRIPTIONS OF THE DRAWINGS

[0049] FIG. 1 shows a high-resolution transmission electron microscopy image and an electron diffraction pattern of an amorphous alloy ribbon of Embodiment 1 of the invention.

[0050] FIG. 2 shows an X-ray diffraction pattern of amorphous alloy ribbons of Embodiment 1, Embodiment 5 and Embodiment 8 of the invention.

[0051] FIG. 3 shows a transmission electron microscope image and an electron diffraction pattern of a nanocrystalline alloy ribbon prepared by heat-treating the amorphous alloy ribbon of Embodiment 1 of the invention.

[0052] FIG. 4 shows an X-ray diffraction pattern of nanocrystalline alloy ribbons of Embodiment 1, Embodiment 5 and Embodiment 8 of the invention.

[0053] FIG. 5 shows a pattern of the permeability of nanocrystalline alloy ribbons of Embodiments 1, 5 and 8 and Comparative Embodiments 1, 2 and 4 of the invention as a function of frequency.

[0054] FIG. 6 shows magnetic hysteresis loops of the nanocrystalline alloy ribbons of Embodiments 1, 5 and 8 and Comparative Embodiment 1 of the invention.

DETAILED DESCRIPTIONS OF EMBODIMENTS

[0055] The invention will be further described in detail below with reference to the accompanying drawing and specific embodiments. It should be noted that the following embodiments are intended to facilitate the understanding of the invention and do not limit the invention in any way.

Embodiment 1

[0056] In this embodiment, the composition expression of the Fe-based amorphous alloy containing subnanometer-scale ordered clusters is Fe.sub.74Si.sub.13B.sub.9Nb.sub.2.2Cu.sub.1Zr.sub.0.8.

[0057] The preparation and heat treatment method and steps of the Fe-based amorphous alloy were described as follows:

[0058] (1) Proportioning: Pure Cu and pure Zr (metals) with purities of not less than 99 wt % were weighed according to a ratio of Cu to Zr in the composition expression of the alloy to formulate raw materials of a Cu—Zr intermediate alloy. Pure iron, pure silicon, a boron-iron alloy and a niobium-iron alloy with purities of not less than 99 wt % were weighed according to the ratio of the remaining elements (Fe, Si, B and Nb) in the alloy composition to formulate raw materials of a Fe—Si—B—Nb alloy.

[0059] (2) Smelting of Fe—Si—B—Nb master alloy: The raw materials of the Fe—Si—B—Nb alloy formulated in step (1) were added to a crucible of a vacuum induction smelting furnace, and the vacuum induction smelting furnace was vacuumized to 1 Pa or below and heated by energization to completely melt the raw materials of the alloy. After the raw materials of the alloy were completely molten, vacuum breaking and deslagging were carried out. After the completion of the deslagging, the “vacuumizing-smelting-deslagging” process was repeated until no impurities appeared in the liquid alloy any more. Then the furnace was cooled, and the smelted liquid alloy was poured into a cooling mold and was cooled to obtain the Fe—Si—B—Nb master alloy ingot with homogeneous ingredients.

[0060] (3) Smelting of Cu—Zr intermediate alloy: the raw materials of the Cu—Zr intermediate alloy formulated in step (1) were added to a crucible of a vacuum induction smelting furnace, and the vacuum induction smelting furnace was vacuumized to 1 Pa or below and heated by energization to completely melt the raw materials of the alloy. After the raw materials of the alloy were completely molten, vacuum breaking and deslagging were carried out. After the completion of the deslagging, the “vacuumizing-smelting-deslagging” process was repeated until no impurities appeared in the liquid alloy any more. Then the furnace was cooled, and the smelted liquid Cu—Zr intermediate alloy was poured into a cooling mold and was cooled to obtain the Cu—Zr intermediate alloy ingot with homogeneous ingredients.

[0061] (4) Preparation of amorphous alloy ribbon: A proper amount of the Fe—Si—B—Nb master alloy ingot prepared in step (2) was weighed, and then a corresponding weight of the Cu—Zr intermediate alloy prepared in step (3) was weighed according to the composition expression of the alloy and the weight of the weighed master alloy. The weighed Fe—Si—B—Nb master alloy ingot was added to a crucible of a vacuum induction smelting furnace of a ribbon making machine, and the vacuum induction smelting furnace was vacuumized to 1 Pa or below and heated by energization to re-melt the master alloy ingot. After the master alloy ingot was completely molten, the liquid alloy was held for 5 min. The weighed Cu—Zr intermediate alloy ingot was added to the molten master alloy. After the intermediate alloy was completely molten, the liquid alloy was poured into a tundish of the ribbon making machine. The liquid alloy was sprayed onto the surface of a rotating copper roll with a surface linear velocity of 30 m/s by single roll melt spinning to prepare the amorphous alloy ribbon. The ribbon had a width of 55 mm and a thickness of 18 μm.

[0062] (5) Determination of thermodynamic parameters: A differential scanning calorimeter (abbreviated as “DSC”, the same hereinafter) was used to measure thermodynamic parameters of the amorphous alloy ribbon prepared in step (4) at a heating rate of 20° C./min. The crystallization temperature of the amorphous alloy ribbon was determined to determine a range of heat treatment temperature.

[0063] (6) Preparation of magnetic core: The amorphous alloy ribbon prepared in step (4) was roll-cut into narrow ribbons with a width of 10 mm. The narrow ribbon was wound by a magnetic core winder into a circular magnetic core having an inner diameter of 20 mm, an outer diameter of 30 mm and a height of 10 mm.

[0064] (7) Heat treatment: The magnetic core prepared in step (6) was put in a vacuum heat treatment furnace. The vacuum heat treatment furnace was vacuumized and heated by energization. The magnetic core was heated to 400-550° C. at a heating rate of 5° C./min, subjected to multi-stage heat treatment at 400-550° C. for 200-300 min, and then cooled to room temperature. Then, the nanocrystalline magnetic core after vacuum heat treatment was placed in a vacuum magnetic field heat treatment furnace. The heat treatment furnace was vacuumized and heated by energization to 450-500° C. at a heating rate of 5° C./min. A 0.1 T transverse magnetic field (along a ribbon width direction) was externally applied in the furnace. The nanocrystalline magnetic core was held for 120-150 min, cooled to room temperature and discharged to obtain the nanocrystalline magnetic core with homogeneously distributed nanocrystalline grains.

[0065] The amorphous alloy ribbon, and the nanocrystalline ribbon and the magnetic core obtained after heat treatment described above were tested as follows:

[0066] (a) A transmission electron microscope (abbreviated as “TEM”, the same hereinafter) was used to test the microstructure of the amorphous alloy ribbon prepared in step (4) and the nanocrystalline alloy ribbon prepared in step (7), as shown in FIG. 1 and FIG. 3. FIG. 1 shows a high-resolution TEM morphology image and a selected area electron diffraction pattern of the amorphous alloy ribbon. The selected area electron diffraction pattern shows a diffraction halo unique to an amorphous solid with atoms arranged disorderly. As can be seen from the TEM morphology image, ordered atom clusters with a size of 2 nm or below (shown as the white circle in the figure) are dispersed in the amorphous matrix with atoms arranged disorderly. FIG. 3 shows a TEM morphology image and a selected area electron diffraction pattern of a nanocrystalline alloy ribbon prepared after heat treatment. As can be seen from the selected area electron diffraction pattern, the halo in FIG. 1 changed to diffraction spots of a typical polycrystalline structure. As can be seen from the TEM morphology image, the nanocrystalline alloy ribbon was composed of nanocrystalline grains with a size of 20 nm or below. According to statistical analysis, the grain size was in the range of 8-16 nm.

[0067] (b) A D8Advance polycrystalline X-ray diffractometer (abbreviated as “XRD”, the same hereinafter) was used to test the amorphous alloy ribbon in step (4) and the nanocrystalline alloy ribbon prepared in step (7) to obtain the XRD patterns. FIG. 2 shows the XRD pattern of the amorphous alloy ribbon. In the figure, there is only one broadened dispersion diffraction peak, and there is no obvious crystal peak, which indicates that most of the ribbon is amorphous and no crystal phase can be detected by XRD. FIG. 4 shows an XRD pattern of the nanocrystalline alloy ribbon prepared after heat treatment. In the figure, crystal peaks appear near 45°, 66° and 84°. According to analysis, a crystallization phase is a single body-centered cubic structure, that is, α-Fe.

[0068] (c) An impedance analyzer was used to test the nanocrystalline magnetic core subjected to magnetic field heat treatment to obtain a pattern of permeability as a function of frequency. FIG. 5 shows typical variation curve of effective permeability, at a frequency of 10-1000 kHz, of the nanocrystalline magnetic core. The permeability, at 100 kHz, of the nanocrystalline magnetic core reached 36100, and was significantly higher than that of all comparative embodiments within the entire frequency range of 10-1000 kHz.

[0069] (d) A vibrating sample magnetometer (abbreviated as “VSM”, the same hereinafter) was used to measure the ribbon samples of the nanocrystalline magnetic cores prepared in step (7) above to obtain magnetic hysteresis loops, as shown in FIG. 6. The saturation flux density Bs reached 1.31 T.

[0070] The saturation flux density Bs, the effective permeability μ at 100 kHz (@100 kHz) and the internal grain size D of the nanocrystalline alloy prepared after magnetic field heat treatment in step (7) in this embodiment are listed in Table 1.

Embodiments 2-14

[0071] The specific ingredients of each alloy, that is, the composition expression, are shown in Table 1.

[0072] The preparation and heat treatment methods and steps of the amorphous alloy ribbons of this series of embodiments were basically the same as in Embodiment 1. Except that the raw materials and proportioning thereof, the smelting temperature of the alloy, the remelting temperature, the ribbon spraying temperature and the heat treatment process parameters were different from those in Embodiment 1 due to different alloy ingredients, other methods and process parameters were the same as those in Embodiment 1. In the embodiments, an amorphous alloy ribbon with a thickness of 18 μm was prepared, and roll-cut and wound into a circular magnetic core having an inner diameter of 20 mm, an outer diameter of 30 mm and a height of 10 mm, the circular magnetic core was subjected to vacuum heat treatment and transverse magnetic field heat treatment, and a 0.1 T transverse magnetic field was applied during the magnetic field heat treatment.

[0073] The amorphous alloy ribbons, and the nanocrystalline alloy ribbons and the magnetic cores obtained after heat treatment in the embodiments were tested as in Embodiment 1, and the saturation flux density Bs, the effective permeability μ at 100 kHz (@100 kHz) and the internal grain size D are listed in Table 1. As for Embodiment 5 and Embodiment 8, the XRD pattern of the amorphous alloy ribbon is shown in FIG. 2, the XRD pattern of the nanocrystalline alloy ribbon prepared after heat treatment is shown in FIG. 4, the typical variation curve of the permeability, at the frequency of 10-1000 kHz, of the nanocrystalline magnetic core prepared after magnetic field heat treatment is shown in FIG. 5, and the magnetic hysteresis loop of the nanocrystalline ribbon is shown in FIG. 6. Other test results of the other embodiments are not shown one by one.

[0074] It can be seen from data in Table 1 that in the nanocrystalline alloys of all above embodiments, the grain size is basically within the range of 6-16 nm, the permeability at the frequency of 100 kHz reaches 35000 or above, and the saturation flux density reaches 1.3 T or above.

Comparative Embodiment 1

[0075] The alloy in this comparative embodiment is a FINEMET nanocrystalline alloy currently industrially produced and applied, and its composition is Fe.sub.73.5Si.sub.13.5B.sub.9Nb.sub.3Cu.sub.1.

[0076] The wide ribbon having a thickness of 18 μm and a width of 10 mm of Comparative Embodiment 1 was wound by a magnetic core winder into a circular magnetic core having an inner diameter of 20 mm, an outer diameter of 30 mm and a height of 10 mm. Then the circular magnetic core was heat-treated as follows: The magnetic core was placed in a vacuum heat treatment furnace. The vacuum heat treatment furnace was vacuumized and heated by energization. The magnetic core was heated to 380-540° C. at a heating rate of 5° C./min, subjected to multi-stage heat treatment at 380-540° C. for 300-350 min, and then cooled to room temperature. Then, the nanocrystalline magnetic core after vacuum heat treatment was placed in a vacuum magnetic field heat treatment furnace. The heat treatment furnace was vacuumized and heated by energization to 450-500° C. at a heating rate of 5° C./min. A 0.1 T transverse magnetic field (along a ribbon width direction) was externally applied in the furnace. The nanocrystalline magnetic core was held for 120-150 min, then cooled to room temperature and discharged.

[0077] The amorphous alloy ribbon, and the nanocrystalline alloy ribbon and the magnetic core obtained after heat treatment in Comparative Embodiment 1 were tested as in Embodiment 1. The high-resolution transmission electron microscopy picture of the amorphous ribbon shows that in the amorphous alloy ribbon of this comparative embodiment, the atoms are arranged completely disorderly, and there are no ordered atom clusters. The saturation flux density, the effective permeability at 100 kHz and the internal grain size of the nanocrystalline magnetic core and ribbon obtained after magnetic field heat treatment are listed in Table 1. The typical variation curve of the permeability, at 10-1000 kHz, of the nanocrystalline magnetic core is shown in FIG. 5, and the magnetic hysteresis loop of the nanocrystalline ribbon is shown in FIG. 6.

[0078] As can be seen from the comparison of data in Table 1, FIG. 5 and FIG. 6, the saturation flux density and the permeability of the nanocrystalline alloy ribbons of the embodiments of the invention are significantly higher than those of Comparative Embodiment 1, and the internal grain size of the nanocrystalline alloys of the embodiments of the invention is smaller than that of Comparative Embodiment 1, which should be the main reason why the permeability of the alloy of the invention is higher than that of Comparative Embodiment 1.

Comparative Embodiment 2

[0079] The composition expression of the alloy of this comparative embodiment is Fe.sub.76Si.sub.13B.sub.8Nb.sub.1Cu.sub.1Mo.sub.1.

[0080] The preparation and heat treatment method and steps of the Fe-based amorphous alloy ribbon were as follows:

[0081] (1) Proportioning: Pure iron, pure silicon, a boron-iron alloy, a niobium-iron alloy, pure copper and pure molybdenum with purities of greater than 99 wt % were proportioned according to the composition expression of the alloy.

[0082] (2) Smelting of master alloy: The raw materials of the alloy formulated in step (1) were added to a crucible of a vacuum induction smelting furnace, and the vacuum induction smelting furnace was vacuumized to 1 Pa or below and heated by energization to completely melt the raw materials of the alloy. After the raw materials of the alloy were completely molten, vacuum breaking and deslagging were carried out. After the completion of the deslagging, the “vacuumizing-smelting-deslagging” process was repeated until no impurities appeared in the liquid alloy any more. Then the furnace was cooled, and the smelted liquid alloy was poured into a cooling mold and was cooled to obtain the master alloy ingot with homogeneous ingredients.

[0083] (3) Preparation of ribbon: A proper amount of the master alloy ingot prepared in step (2) was weighed and added to a crucible of a vacuum induction smelting furnace of a ribbon making machine, and the vacuum induction smelting furnace was vacuumized to 1 Pa or below and heated by energization to remelt the master alloy ingot. After the master alloy ingot was completely molten, the liquid alloy was held for 5 min. Then the liquid alloy was poured into a tundish of the ribbon making machine. The liquid alloy was sprayed onto the surface of a rotating copper roll with a surface linear velocity of 30 m/s by single roll melt spinning to prepare the amorphous alloy ribbon. The ribbon had a width of 25 mm and a thickness of 18 μm.

[0084] (4) Determination of thermodynamic parameters: A differential scanning calorimeter was used to measure thermodynamic parameters of the amorphous alloy ribbon prepared in step (3) at a heating rate of 20° C./min. The crystallization temperature of the amorphous alloy ribbon was determined to determine a range of heat treatment temperature.

[0085] (5) Preparation of magnetic core: The amorphous alloy ribbon prepared in step (3) was roll-cut into narrow ribbons with a width of 10 mm. The narrow ribbon was wound by a magnetic core winder into a circular magnetic core having an inner diameter of 20 mm, an outer diameter of 30 mm and a height of 10 mm.

[0086] (6) Heat treatment: The magnetic core prepared in step (5) was put in a vacuum heat treatment furnace. The vacuum heat treatment furnace was vacuumized and heated by energization. The magnetic core was heated to 450-560° C. at a heating rate of 5° C./min, subjected to multi-stage heat treatment at 450-560° C. for 200-250 min, and then cooled to room temperature. Then, the nanocrystalline magnetic core after vacuum heat treatment was placed in a vacuum magnetic field heat treatment furnace. The heat treatment furnace was vacuumized and heated by energization to 450-500° C. at a heating rate of 5° C./min. A 0.1 T transverse magnetic field (along a ribbon width direction) was externally applied in the furnace. The nanocrystalline magnetic core was held for 120-150 min, cooled to room temperature and discharged to obtain the nanocrystalline magnetic core with homogeneously distributed nanocrystalline grains.

[0087] The amorphous alloy ribbon, and the nanocrystalline alloy ribbon and the magnetic core obtained after heat treatment in Comparative Embodiment 2 were tested as in Embodiment 1. The high-resolution transmission electron microscopy picture of the amorphous ribbon shows that in the amorphous alloy ribbon of this comparative embodiment, the atoms are arranged completely disorderly, and there are no ordered atom clusters. The saturation flux density, the effective permeability at 100 kHz and the internal grain size of the nanocrystalline magnetic core and ribbon obtained after magnetic field heat treatment are listed in Table 1. The typical variation curve of the permeability, at 10-1000 kHz, of the nanocrystalline magnetic core is shown in FIG. 5.

[0088] As can be seen from the comparison of data in Table 1 and FIG. 5, compared with Comparative Embodiment 2, the internal grain size of the nanocrystalline alloys of the embodiments of the invention is smaller, and the permeability at each frequency is significantly higher than that of the alloy of Comparative Embodiment 2.

Comparative Embodiment 3

[0089] The alloy of this comparative embodiment has the same composition expression as Embodiment 3: Fe.sub.75Si.sub.12B.sub.8.5Nb.sub.2.5Cu.sub.1Zr.sub.1. The difference from Embodiment 3 is that: during the preparation process of the amorphous alloy ribbon, the ribbon preparation method as described in Comparative Embodiment 2 was used instead of the use of the Cu—Zr intermediate alloy.

[0090] The preparation and heat treatment method and steps of the Fe-based amorphous alloy ribbon were described as follows:

[0091] (1) Proportioning: Pure iron, pure silicon, a boron-iron alloy, a niobium-iron alloy, pure copper and pure zirconium with purities of greater than 99 wt % were proportioned according to the composition expression of the alloy.

[0092] (2) Smelting of master alloy: The raw materials of the alloy formulated in step (1) were added to a crucible of a vacuum induction smelting furnace, and the vacuum induction smelting furnace was vacuumized to 1 Pa or below and heated by energization to completely melt the raw materials of the alloy. After the raw materials of the alloy were completely molten, vacuum breaking and deslagging were carried out. After the completion of the deslagging, the “vacuumizing-smelting-deslagging” process was repeated until no impurities appeared in the liquid alloy any more. Then the furnace was cooled, and the smelted liquid alloy was poured into a cooling mold and was cooled to obtain the master alloy ingot with homogeneous ingredients.

[0093] (3) Preparation of ribbon: A proper amount of the master alloy ingot prepared in step (2) was weighed and added to a crucible of a vacuum induction smelting furnace of a ribbon making machine, and the vacuum induction smelting furnace was vacuumized to 1 Pa or below and heated by energization to remelt the master alloy ingot. After the master alloy ingot was completely molten, the liquid alloy was held for 5 min. Then the liquid alloy was poured into a tundish of the ribbon making machine. The liquid alloy was sprayed onto the surface of a rotating copper roll with a surface linear velocity of 30 m/s by single roll melt spinning to prepare the amorphous alloy ribbon. The ribbon had a width of 55 mm and a thickness of 18 μm.

[0094] (4) Determination of thermodynamic parameters: A differential scanning calorimeter was used to measure thermodynamic parameters of the amorphous alloy ribbon prepared in step (3) at a heating rate of 20° C./min. The crystallization temperature of the amorphous alloy ribbon was determined to determine a range of heat treatment temperature.

[0095] (5) Preparation of magnetic core: The amorphous alloy ribbon prepared in step (3) was roll-cut into narrow ribbons with a width of 10 mm. The narrow ribbon was wound by a magnetic core winder into a circular magnetic core having an inner diameter of 20 mm, an outer diameter of 30 mm and a height of 10 mm.

[0096] (6) Heat treatment: The magnetic core prepared in step (5) was put in a vacuum heat treatment furnace. The vacuum heat treatment furnace was vacuumized and heated by energization. The magnetic core was heated to 420-550° C. at a heating rate of 5° C./min, subjected to multi-stage heat treatment at 420-550° C. for 200-300 min, and then cooled to room temperature. Then, the nanocrystalline magnetic core after vacuum heat treatment was placed in a vacuum magnetic field heat treatment furnace. The heat treatment furnace was vacuumized and heated by energization to 450-500° C. at a heating rate of 5° C./min. A 0.1 T transverse magnetic field (along a ribbon width direction) was externally applied in the furnace. The nanocrystalline magnetic core was held for 120-150 min, cooled to room temperature and discharged to obtain the nanocrystalline magnetic core with homogeneously distributed nanocrystalline grains.

[0097] The amorphous alloy ribbon, and the nanocrystalline alloy ribbon and the magnetic core obtained after heat treatment in Comparative Embodiment 3 were tested as in Embodiment 1. The high-resolution transmission electron microscopy picture of the amorphous alloy ribbon shows that in the amorphous alloy of this comparative embodiment, the atoms are basically arranged completely disorderly, and there are few ordered atom clusters. The saturation flux density, the effective permeability at 100 kHz and the internal grain size of the nanocrystalline magnetic core and ribbon of this comparative embodiment are listed in Table 1.

[0098] As can be seen from the table, the saturation flux density of the nanocrystalline alloy of this comparative embodiment is the same as that of Embodiment 3. However, since there are few subnanometer-scale ordered clusters in the amorphous alloy, the size of the grains precipitating from the nanocrystalline alloy is obviously larger than that of Embodiment 3, so that the permeability is also greatly lower than that of the nanocrystalline alloy of the Embodiment 3.

Comparative Embodiment 4

[0099] The alloy of this comparative embodiment has the same composition expression as Embodiment 8: Fe.sub.78Si.sub.10B.sub.8Nb.sub.2Cu.sub.1Zr.sub.1. The difference from Embodiment 8 is that: during the preparation process of the amorphous alloy ribbon, the ribbon preparation method as described in Comparative Embodiment 2 and Comparative Embodiment 3 was used instead of the use of the Cu—Zr intermediate alloy.

[0100] The preparation and heat treatment steps of the amorphous alloy ribbon and the magnetic core in this comparative embodiment will not be repeated here. Except that the raw material proportioning, the smelting temperature of the master alloy, the remelting temperature, the ribbon spraying temperature and the heat treatment process parameters were different from those in Comparative Embodiment 3 due to different alloy ingredients, the other methods and process parameters were the same as those in Comparative Embodiment 3.

[0101] The amorphous alloy ribbon, and the nanocrystalline alloy ribbon and the magnetic core obtained after heat treatment in Comparative Embodiment 4 were tested as in Embodiment 1. The high-resolution transmission electron microscopy picture of the amorphous alloy ribbon shows that in the amorphous alloy of this comparative embodiment, the atoms are basically arranged completely disorderly, and there are few ordered atom clusters. The saturation flux density, the effective permeability at 100 kHz and the internal grain size of the nanocrystalline magnetic core and ribbon of this comparative embodiment are listed in Table 1. The typical variation curve of the permeability, at 10-1000 kHz, of the nanocrystalline magnetic core is shown in FIG. 5.

[0102] As can be seen from data in Table 1 and FIG. 5, this comparative embodiment is similar to Comparative Embodiment 3: The saturation flux density of the nanocrystalline alloy is the same as that of Embodiment 8. However, since there are few subnanometer-scale ordered clusters in the amorphous alloy, the size of the nanocrystalline grains precipitating from the nanocrystalline alloy is obviously larger than that of Embodiment 8, so that the permeability is also greatly lower than that of the nanocrystalline alloy of the Embodiment 8.

TABLE-US-00001 TABLE 1 Summary of alloy composition, main soft magnetic properties and grain size distribution of embodiments and comparative embodiment of the invention Alloy Ingredients (at %) Bs(T) μ(@100 kHz) D(nm) Embodiment 1 Fe.sub.74Si.sub.13B.sub.9Nb.sub.2.2Cu.sub.1Zr.sub.0.8 1.31 36100 8-16 Embodiment 2 Fe.sub.74.5Si.sub.12.5B.sub.8.8Nb.sub.2Cu.sub.1.2Zr.sub.1 1.32 38500 9-15 Embodiment 3 Fe.sub.75Si.sub.12B.sub.8.5Nb.sub.2.5Cu.sub.1Zr.sub.1 1.35 35400 10-15  Embodiment 4 Fe.sub.75.5Si.sub.12.5B.sub.8 Nb.sub.2Cu.sub.1Hf.sub.1 1.38 37000 9-14 Embodiment 5 Fe.sub.76Si.sub.12.2B.sub.8Nb.sub.2Cu.sub.1Zr.sub.0.8 1.41 38300 6-13 Embodiment 6 Fe.sub.76.5Si.sub.11.8B.sub.8Nb.sub.2Cu.sub.0.9Ti.sub.0.8 1.41 36000 8-16 Embodiment 7 Fe.sub.77Si.sub.10.5B.sub.8Nb.sub.2.5Cu.sub.1Zr.sub.1 1.45 37600 9-15 Embodiment 8 Fe.sub.78Si.sub.10B.sub.8Nb.sub.2Cu.sub.1Zr.sub.1 1.51 35700 7-16 Embodiment 9 Fe.sub.79Si.sub.10B.sub.7Nb.sub.2.3Cu.sub.0.8Ti.sub.0.9 1.56 35000 6-16 Embodiment 10 Fe.sub.80Si.sub.9B.sub.7.2Nb.sub.2 Cu.sub.1Ti.sub.0.8 1.60 35200 8-17 Embodiment 11 Fe.sub.79.5Si.sub.9B.sub.7.2Nb.sub.2Cu.sub.1Ti.sub.0.8C.sub.0.5 1.58 36600 8-16 Embodiment 12 Fe.sub.80Si.sub.9B.sub.7Nb.sub.1.8Cu.sub.0.9Ti.sub.1Co.sub.0.3 1.62 35100 7-15 Embodiment 13 Fe.sub.76Si.sub.12B.sub.7.5Nb.sub.2Cu.sub.1Hf.sub.1.1Cr.sub.0.4 1.40 37400 9-16 Embodiment 14 Fe.sub.77Si.sub.10B.sub.7.5Nb.sub.2Cu.sub.1.2Zr.sub.1.3P.sub.1 1.45 36500 9-16 Comparative Fe.sub.73.5Si.sub.13.5B.sub.9Nb.sub.3Cu.sub.1 1.25 26000 10-20  Embodiment 1 Comparative Fe.sub.76Si.sub.13B.sub.8Nb.sub.1Cu.sub.1Mo.sub.1 1.39 15200 14-25  Embodiment 2 Comparative Fe.sub.75Si.sub.12B.sub.8.5Nb.sub.2.5Cu.sub.1 Zr.sub.1 1.35 24300 15-25  Embodiment 3 (no intermediate alloy used) Comparative Fe.sub.78Si.sub.10B.sub.8Nb.sub.2Cu.sub.1 Zr.sub.1 1.51 20100 14-22  Embodiment 4 (no intermediate alloy used)

[0103] Through the comparison of the amorphous alloys and nanocrystalline alloy derivatives in the embodiments and the comparative embodiments of the invention in the aspects of microstructure and main soft magnetic properties, it can be seen that the Fe-based amorphous alloy containing subnanometer-scale ordered clusters and the preparation method thereof provided by the invention provide an effective method for preparing a nanocrystalline alloy with high saturation flux density and high permeability: Through the design of the alloy ingredients and the amorphous alloy preparation method matched therewith, the Fe-based amorphous alloy containing a large number of subnanometer-scale ordered atom clusters is prepared, and thereby can precipitate more homogeneous and smaller nanocrystalline grains during the subsequent heat treatment process, so that the soft magnetic properties of the nanocrystalline alloy are greatly improved and the high-frequency permeability is significantly increased (the permeability at 100 kHz is up to 35000 or above). At the same time, since the Fe content in the alloy is higher than that in the commercial FINEMET alloy, a higher saturation flux density is also obtained, reaching 1.3 T or above.

[0104] The above embodiments systematically describe the technical solutions of the invention in detail, but it should not be considered that the specific implementation of the invention is limited to these descriptions. A person of ordinary skill in the technical field to which the invention belongs can also make some simple deductions or substitutions without departing from the concept of the invention, all of which should be regarded as falling within the protection scope of the invention.