NANOCRYSTALLINE SOFT MAGNETIC ALLOY WITH HIGH MAGNETIC INDUCTION AND HIGH FREQUENCY AND PREPARATION METHOD THEREOF

Abstract

Disclosed in the present invention is a nanocrystalline soft magnetic alloy with high magnetic induction and high frequency. The nanocrystalline soft magnetic alloy has a molecular formula of Fe.sub.aSi.sub.bB.sub.cMa.sub.dCu.sub.eP.sub.f, in which M includes one or more of Nb, Mo, V, Mn, and Cr, molar percent contents of elements are as follows: 6?b?15, 5?c?12, 0.5?d?3, 0.5?e?1.5, and 0.5?f?3, and the balance includes Fe and impurities. A difference between an induced anisotropy value and an average magnetocrystalline anisotropy value is 0.1-1 J/m.sup.3. The soft magnetic alloy has high magnetic permeability and low magnetic loss at high frequency. Further disclosed in the present disclosure is a method for preparing the nanocrystalline soft magnetic alloy with high magnetic induction and high frequency. Based on a repeated cycle of a thermal field, a transverse magnetic field, and a cold field, the induced anisotropy value (K.sub.u) is similar to the average magnetocrystalline anisotropy value (<K.sub.1>), so that soft magnetic properties at high frequency are improved.

Claims

1. A nanocrystalline soft magnetic alloy with high magnetic induction and high frequency, wherein the nanocrystalline soft magnetic alloy has a molecular formula of Fe.sub.aSi.sub.bB.sub.cM.sub.dCu.sub.eP.sub.f, in which M comprises one or more of Nb, Mo, V, Mn, and Cr, molar percent contents of elements are as follows: 6?b?15, 5?c?12, 0.5?d?3, 0.5?e?1.5, and 0.5?f?3, and the balance comprises Fe and impurities; and a difference between an induced anisotropy value and an average magnetocrystalline anisotropy value is 0.1-1 J/m.sup.3.

2. The nanocrystalline soft magnetic alloy with high magnetic induction and high frequency according to claim 1, wherein both the induced anisotropy value and the average magnetocrystalline anisotropy value are greater than 5 J/m.sup.3 and less than 20 J/m.sup.3.

3. The nanocrystalline soft magnetic alloy with high magnetic induction and high frequency according to claim 1, wherein the nanocrystalline soft magnetic alloy with high magnetic induction and high frequency has a saturation magnetic induction intensity B.sub.s of greater than 1.45 T and a coercivity of less than 2 A/m.

4. The nanocrystalline soft magnetic alloy with high magnetic induction and high frequency according to claim 1, wherein the nanocrystalline soft magnetic alloy with high magnetic induction and high frequency has a magnetic permeability of greater than 20,000 at a frequency of less than 100 kHz.

5. The nanocrystalline soft magnetic alloy with high magnetic induction and high frequency according to claim 1, wherein the nanocrystalline soft magnetic alloy with high magnetic induction and high frequency has a loss of less than 250 kW/m.sup.3 at a frequency of less than 100 kHz in a transverse magnetic field of less than 0.2 T.

6. A method for preparing the nanocrystalline soft magnetic alloy with high magnetic induction and high frequency according to claim 1, comprising: (1) performing compounding according to the atomic percent molecular formula of the nanocrystalline soft magnetic alloy with high magnetic induction and high frequency so as to obtain a master alloy; melting the master alloy to obtain a melt, and spraying the melt onto a rotating cooling copper roller for cooling and solidification to obtain an amorphous alloy with a long-range disordered structure, namely a quenched alloy strip; and preparing a magnetic core from the quenched alloy strip by a superimposed cutting method and a winding method; (2) putting the magnetic core in a thermal field for heat preservation at 480-640? C. for 0.5-1.5 hours; putting the magnetic core in a 0-1 T transverse magnetic field for heat preservation at 380-420? C. for 0.5-1.5 hours; putting the magnetic core in a liquid nitrogen environment for cooling for 0.5-1 hour; taking the magnetic core out of the liquid nitrogen environment; and then putting the magnetic core in an environment for heat preservation at 200-300? C. for 0.5-1 hour; and (3) repeating step (2) for 1-5 times to obtain the nanocrystalline soft magnetic alloy with high magnetic induction and high frequency.

7. The method for preparing the nanocrystalline soft magnetic alloy with high magnetic induction and high frequency according to claim 6, wherein the magnetic core is a cylinder.

8. The method for preparing the nanocrystalline soft magnetic alloy with high magnetic induction and high frequency according to claim 6, wherein the magnetic core is a cylinder with an outer diameter of 21-23 mm and an inner diameter of 18-20 mm.

9. The method for preparing the nanocrystalline soft magnetic alloy with high magnetic induction and high frequency according to claim 6, wherein the cooling copper roller is rotated at a speed of 25 m/s to 40 m/s.

10. The method for preparing the nanocrystalline soft magnetic alloy with high magnetic induction and high frequency according to claim 6, wherein before the magnetic core is put in the transverse magnetic field, the magnetic core has a grain size of 10-20 nm.

11. The method for preparing the nanocrystalline soft magnetic alloy with high magnetic induction and high frequency according to claim 7, wherein the magnetic core is a cylinder with an outer diameter of 21-23 mm and an inner diameter of 18-20 mm.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0030] FIG. 1 is a diagram showing comparison of the average magnetocrystalline anisotropy and the induced anisotropy of Fe.sub.77.8Si.sub.10B.sub.8Nb.sub.2.6Cu.sub.0.6P.sub.1 prepared in Comparative Examples 1 and 2, Example 2, and Comparative Examples 3 and 4.

[0031] FIG. 2 is a diagram showing comparison of soft magnetic properties including the magnetic permeability ?, the coercivity H.sub.c, and the loss P.sub.s of the Fe.sub.77.8Si.sub.10B.sub.8Nb.sub.2.6Cu.sub.0.6P.sub.1 prepared in Comparative Examples 1 and 2, Example 2, and Comparative Examples 3 and 4.

[0032] FIG. 3 is a diagram showing transmission electron micrographs, selected diffraction patterns, and statistical distribution charts of grain size (D) of samples prepared in Example 1, Example 2, Comparative Example 1, and Comparative Example 5.

DESCRIPTION OF THE EMBODIMENTS

[0033] The present disclosure is further described in detail below in conjunction with embodiments and accompanying drawings. It should be noted that the following embodiments are merely intended to facilitate the understanding of the present disclosure without any limitation to the present disclosure.

Example 1

[0034] In the example, an iron-based nanocrystalline soft magnetic alloy material has a molecular formula of Fe.sub.76Si.sub.11B.sub.8Nb.sub.2Cu.sub.1Mo.sub.1P.sub.1.

[0035] A specific method for preparing the iron-based nanocrystalline alloy is as follows. [0036] (1) Compounding was performed according to the chemical 1 formula of Fe.sub.76Si.sub.11B.sub.8Nb.sub.2Cu.sub.1Mo.sub.1P.sub.1 with industrially pure Fe, Si, FeB, FeP, Cu, FeMo, and FeNb as raw materials so as to obtain a master alloy. The master alloy was subjected to melting and treatment by using a single-roller quenching technology to obtain a quenched amorphous strip with a width of about 60 mm and a thickness of about 18 ?m, wherein a copper roller was rotated at a speed of 30 m/s. The strip was cut and wound into a magnetic core with a width of 10 mm, an inner diameter of 19.7 mm, and an outer diameter of 22.6 mm. [0037] (2) The Fe.sub.76Si.sub.11B.sub.8Nb.sub.2Cu.sub.1Mo.sub.1P.sub.1 alloy was subjected to nanocrystalline heat treatment. The alloy strip was heated to 560? ? C. at a heating rate of 5? C./min for heat preservation for 0.5 hour, and then cooled to room temperature with a furnace. [0038] (3) An alloy magnetic core obtained after the heat treatment was uniformly divided into 8 parts, which were heated to 200? ? C. at a heating rate of 10? C./min, heated to 400? C. at a heating rate of 10? C./min for heat preservation for 1 hour in a 0.08 T transverse magnetic field, put in a liquid nitrogen environment for cooling for 0.5 hour, taken out, and then put in an environment for heat preservation at 250? ? C. for 0.5 hour. A cycle of cooling and heating was repeated for 3 times. [0039] (4) An initial magnetization curve of a magnetic ring was measured. In an initial magnetization curve stage, a tangent was obtained and extended to saturation magnetization. With the corresponding abscissa value as an anisotropy field (H.sub.k), an induced anisotropy value is calculated based on the formula K.sub.u=? H.sub.kB.sub.s. After the heat treatment in step (2) and step (3), it was calculated that the nanocrystalline magnetic core has a K.sub.u value of 12.8 J/m.sup.3. The crystallization volume fraction V.sub.cr and the grain size D were obtained according to analysis of XRD and TEM results. Based on the formula <K.sub.1>=K.sub.1V.sub.cr(D/L.sub.0).sup.6 (K.sub.1 refers to magnetocrystalline anisotropy of an ?-Fe(Si) phase and has a value of 8.2 KJ/m.sup.3; V.sub.cr refers to crystallization volume fraction; and L.sub.0 refers to ferromagnetic exchange length and has a value of about 35 nm), it was calculated that the <K.sub.1> value is 13 J/m.sup.3. The K.sub.u value is similar to the <K.sub.1> value. [0040] (5) A nanocrystalline obtained under the conditions of step (2) to step (4) has excellent soft magnetic properties at high frequency including a saturation magnetic induction intensity B.sub.s of 1.5 T, a coercivity H.sub.c of 1.5 A/m, a magnetic permeability u of 21,600 at 100 kHz, and a loss P.sub.s of 180 kW/m.sup.3 at 100 kHz and 0.2 T.

Example 2

[0041] In the example, an iron-based nanocrystalline soft magnetic alloy material has a molecular formula of Fe.sub.77.8Si.sub.10B.sub.8Nb.sub.2.6Cu.sub.0.6P.sub.1.

[0042] A specific method for preparing the iron-based nanocrystalline alloy is as follows. [0043] (1) Compounding was performed according to the chemical formula of Fe.sub.77.8Si.sub.10B.sub.8Nb.sub.2.6Cu.sub.0.6P.sub.1 with industrially pure Fe, Si, FeB, FeP, Cu, and FeNb as raw materials so as to obtain a master alloy. The master alloy was subjected to melting and treatment by using a single-roller quenching technology to obtain a quenched amorphous strip with a width of about 60 mm and a thickness of about 18 ?m, wherein a copper roller was rotated at a speed of 30 m/s. The strip was cut and wound into a magnetic core with a width of 10 mm, an inner diameter of 19.7 mm, and an outer diameter of 22.6 mm. [0044] (2) The Fe.sub.77.8Si.sub.10B.sub.8Nb.sub.2.6Cu.sub.0.6P.sub.1 alloy was subjected to nanocrystalline heat treatment. The alloy strip was heated to 560? C. at a heating rate of 5? C./min for heat preservation for 0.5 hour, and then cooled to room temperature with a furnace. [0045] (3) An alloy magnetic core obtained after the heat treatment was uniformly divided into 8 parts, which were heated to 200? ? C. at a heating rate of 10? C./min, heated to 400? C. at a heating rate of 10? C./min for heat preservation for 1 hour in a 0.08 T transverse magnetic field, put in a liquid nitrogen environment for 0.5 hour, taken out, and then put in an environment for heat preservation at 280? ? C. for 0.5 hour. A cycle of cooling and heating was repeated for 2 times. [0046] (4) An initial magnetization curve of a magnetic ring was measured. In an initial magnetization curve stage, a tangent was obtained and extended to saturation magnetization. With the corresponding abscissa value as an anisotropy field (H.sub.k), an induced anisotropy value is calculated based on the formula K.sub.u=? H.sub.kB.sub.s. After the heat treatment in step (2) and step (3), it was calculated that the nanocrystalline magnetic core has a K.sub.u value of 15.8 J/m.sup.3. The crystallization volume fraction V.sub.cr and the grain size D were obtained according to analysis of XRD and TEM results. Based on the formula <K.sub.1>=K.sub.1V.sub.cr(D/L.sub.0).sup.6 (K.sub.1 refers to magnetocrystalline anisotropy of an ?-Fe(Si) phase and has a value of 8.2 KJ/m.sup.3; V.sub.cr refers to crystallization volume fraction; and L.sub.0 refers to ferromagnetic exchange length and has a value of about 35 nm), it was calculated that the <K.sub.1> value is 16.1 J/m.sup.3. The K.sub.u value is similar to the <K.sub.1> value. [0047] (5) A nanocrystalline obtained under the conditions of step (2) to step (4) has excellent soft magnetic properties at high frequency including a saturation magnetic induction intensity B.sub.s of 1.5 T, a coercivity H.sub.c of 1.6 A/m, a magnetic permeability u of 20,000 at 100 kHz, and a loss P.sub.s of 205 kW/m.sup.3 at 100 kHz and 0.2 T.

Example 3

[0048] In the example, an iron-based nanocrystalline soft magnetic alloy material has a molecular formula of Fe.sub.77Si.sub.12B.sub.7Nb.sub.2Cu.sub.1P.sub.1.

[0049] A specific method for preparing the iron-based nanocrystalline alloy is as follows. [0050] (1) Compounding was performed according to the chemical formula of Fe.sub.77Si.sub.12B.sub.7Nb.sub.2Cu.sub.1P.sub.1 with industrially pure Fe, Si, FeB, FeP, Cu, and FeNb as raw materials so as to obtain a master alloy. The master alloy was subjected to melting and treatment by using a single-roller quenching technology to obtain a quenched amorphous strip with a width of about 60 mm and a thickness of about 18 ?m, wherein a copper roller was rotated at a speed of 30 m/s. The strip was cut and wound into a magnetic core with a width of 10 mm, an inner diameter of 19.7 mm, and an outer diameter of 22.6 mm. [0051] (2) The Fe.sub.77Si.sub.12B.sub.7Nb.sub.2Cu.sub.1P.sub.1 alloy was subjected to nanocrystalline heat treatment. The alloy strip was heated to 580? C. at a heating rate of 5? C./min for heat preservation for 0.5 hour, and then cooled to room temperature with a furnace. [0052] (3) An alloy magnetic core obtained after the heat treatment was uniformly divided into 8 parts, which were heated to 200? ? C. at a heating rate of 10? C./min, heated to 380? C. at a heating rate of 10? C./min for heat preservation for 1 hour in a 0.08 T transverse magnetic field, put in a liquid nitrogen environment for 0.5 hour, taken out, and then put in an environment for heat preservation at 220? ? C. for 0.5 hour. A cycle of cooling and heating was repeated for 4 times. [0053] (4) An initial magnetization curve of a magnetic ring was measured. In an initial magnetization curve stage, a tangent was obtained and extended to saturation magnetization. With the corresponding abscissa value as an anisotropy field (H.sub.k), an induced anisotropy value is calculated based on the formula K.sub.u=? H.sub.kB.sub.s. After the heat treatment in step (2) and step (3), it was calculated that the nanocrystalline magnetic core has a K.sub.u value of 8.6 J/m.sup.3. The crystallization volume fraction V.sub.cr and the grain size D were obtained according to analysis of XRD and TEM results. Based on the formula <K.sub.1>=K.sub.1V.sub.cr(D/L.sub.0).sup.6 (K.sub.1 refers to magnetocrystalline anisotropy of an ?-Fe(Si) phase and has a value of 8.2 KJ/m.sup.3; V.sub.cr refers to crystallization volume fraction; and L.sub.0 refers to ferromagnetic exchange length and has a value of about 35 nm), it was calculated that the <K.sub.1> value is 8.3 J/m.sup.3. The K.sub.u value is similar to the <K.sub.1> value. [0054] (5) A nanocrystalline obtained under the conditions of step (2) to step (4) has excellent soft magnetic properties at high frequency including a saturation magnetic induction intensity B.sub.s of 1.46 T, a coercivity H.sub.c of 2 A/m, a magnetic permeability u of 25,000 at 100 kHz, and a loss P.sub.s of 220 kW/m.sup.3 at 100 kHz and 0.2 T.

Example 4

[0055] In the example, an iron-based nanocrystalline soft magnetic alloy material has a molecular formula of Fe.sub.73.7Si.sub.11B.sub.10Nb.sub.2.5Cu.sub.1Mn.sub.1P.sub.0.8.

[0056] A specific method for preparing the iron-based nanocrystalline alloy is as follows. [0057] (1) Compounding was performed according to the chemical formula of Fe.sub.73.7Si.sub.11B.sub.10Nb.sub.2.5Cu.sub.1Mn.sub.1P.sub.0.8 with industrially pure Fe, Si, FeB, FeP, Cu, Mn, and FeNb as raw materials so as to obtain a master alloy. The master alloy was subjected to melting and treatment by using a single-roller quenching technology to obtain a quenched amorphous strip with a width of about 60 mm and a thickness of about 18 ?m, wherein a copper roller was rotated at a speed of 30 m/s. The strip was cut and wound into a magnetic core with a width of 10 mm, an inner diameter of 19.7 mm, and an outer diameter of 22.6 mm. [0058] (2) The Fe.sub.73.7Si.sub.11B.sub.10Nb.sub.2.5Cu.sub.1Mn.sub.1P.sub.0.8 alloy was subjected to nanocrystalline heat treatment. The alloy strip was heated to 580? C. at a heating rate of 5? C./min for heat preservation for 0.5 hour, and then cooled to room temperature with a furnace. [0059] (3) An alloy magnetic core obtained after the heat treatment was uniformly divided into 8 parts, which were heated to 200? C. at a heating rate of 10? C./min, heated to 380? C. at a heating rate of 10? C./min for heat preservation for 1 hour in a 0.08 T transverse magnetic field, put in a liquid nitrogen environment for 0.5 hour, taken out, and then put in an environment for heat preservation at 260? C. for 1 hour. A cycle of cooling and heating was repeated for 2 times. [0060] (4) An initial magnetization curve of a magnetic ring was measured. In an initial magnetization curve stage, a tangent was obtained and extended to saturation magnetization. With the corresponding abscissa value as an anisotropy field (H.sub.k), an induced anisotropy value is calculated based on the formula K.sub.u=? H.sub.kB.sub.s. After the heat treatment in step (2) and step (3), it was calculated that the nanocrystalline magnetic core has a K.sub.u value of 12.2 J/m.sup.3. The crystallization volume fraction V.sub.cr and the grain size D were obtained according to analysis of XRD and TEM results. Based on the formula <K.sub.1>=K.sub.1V.sub.cr(D/L.sub.0).sup.6 (K.sub.1 refers to magnetocrystalline anisotropy of an ?-Fe(Si) phase and has a value of 8.2 KJ/m.sup.3; V.sub.cr refers to crystallization volume fraction; and L.sub.0 refers to ferromagnetic exchange length and has a value of about 35 nm), it was calculated that the <K.sub.1> value is 11.7 J/m.sup.3. The K.sub.u value is similar to the <K.sub.1> value. [0061] (5) A nanocrystalline obtained under the conditions of step (2) to step (4) has excellent soft magnetic properties at high frequency including a saturation magnetic induction intensity B.sub.s of 1.45 T, a coercivity H.sub.c of 1.8 A/m, a magnetic permeability u of 23,400 at 100 kHz, and a loss P.sub.s of 250 kW/m.sup.3 at 100 kHz and 0.2 T.

Example 5

[0062] In the example, an iron-based nanocrystalline soft magnetic alloy material has a molecular formula of Fe.sub.77.5Si.sub.12B.sub.6Nb.sub.1Cu.sub.1.5Mo.sub.0.5V.sub.0.5P.sub.1.

[0063] A specific method for preparing the iron-based nanocrystalline alloy is as follows. [0064] (1) Compounding was performed according to the chemical formula of Fe.sub.77.5Si.sub.12B.sub.6Nb.sub.1Cu.sub.1.5Mo.sub.0.5V.sub.0.5P.sub.1 with industrially pure Fe, Si, FeB, FeP, Cu, V, FeMo, and FeNb as raw materials so as to obtain a master alloy. The master alloy was subjected to melting and treatment by using a single-roller quenching technology to obtain a quenched amorphous strip with a width of about 60 mm and a thickness of about 18 ?m, wherein a copper roller was rotated at a speed of 30 m/s. The strip was cut and wound into a magnetic core with a width of 10 mm, an inner diameter of 19.7 mm, and an outer diameter of 22.6 mm. [0065] (2) The Fe.sub.77.5Si.sub.12B.sub.6Nb.sub.1Cu.sub.1.5Mo.sub.0.5V.sub.0.5P.sub.1 alloy was subjected to nanocrystalline heat treatment. The alloy strip was heated to 580? C. at a heating rate of 5? C./min for heat preservation for 0.5 hour, and then cooled to room temperature with a furnace. [0066] (3) An alloy magnetic core obtained after the heat treatment was uniformly divided into 8 parts, which were heated to 200? ? C. at a heating rate of 10? C./min, heated to 380? C. at a heating rate of 10? C./min for heat preservation for 1 hour in a 0.08 T transverse magnetic field, put in a liquid nitrogen environment for 0.5 hour, taken out, and then put in an environment for heat preservation at 260? C. for 0.5 hour. A cycle of cooling and heating was repeated for 2 times. [0067] (4) An initial magnetization curve of a magnetic ring was measured. In an initial magnetization curve stage, a tangent was obtained and extended to saturation magnetization. With the corresponding abscissa value as an anisotropy field (H.sub.k), an induced anisotropy value is calculated based on the formula K.sub.u=? H.sub.kB.sub.s. After the heat treatment in step (2) and step (3), it was calculated that the nanocrystalline magnetic core has a K.sub.u value of 19 J/m.sup.3. The crystallization volume fraction V.sub.cr and the grain size D were obtained according to analysis of XRD and TEM results. Based on the formula <K.sub.1>=K.sub.1V.sub.cr(D/L.sub.0).sup.6 (K.sub.1 refers to magnetocrystalline anisotropy of an ?-Fe(Si) phase and has a value of 8.2 KJ/m.sup.3; V.sub.cr refers to crystallization volume fraction; and L.sub.0 refers to ferromagnetic exchange length and has a value of about 35 nm), it was calculated that the <K.sub.1> value is 18.9 J/m.sup.3. The K.sub.u value is similar to the <K.sub.1> value. [0068] (5) A nanocrystalline obtained under the conditions of step (2) to step (4) has excellent soft magnetic properties at high frequency including a saturation magnetic induction intensity B.sub.s of 1.52 T, a coercivity H.sub.c of 1.5 A/m, a magnetic permeability ? of 20,300 at 100 kHz, and a loss P.sub.s of 190 kW/m.sup.3 at 100 kHz and 0.2 T.

Example 6

[0069] In the example, an iron-based nanocrystalline soft magnetic alloy material has a molecular formula of Fe.sub.76.5Si.sub.10B.sub.8Nb.sub.1Cu.sub.1.5Cr.sub.1V.sub.1P.sub.1.

[0070] A specific method for preparing the iron-based nanocrystalline alloy is as follows. [0071] (1) Compounding was performed according to the chemical formula of Fe.sub.76.5Si.sub.10B.sub.8Nb.sub.1Cu.sub.1.5Cr.sub.1V.sub.1P.sub.1 with industrially pure Fe, Si, FeB, FeP, Cu, V, Cr, and FeNb as raw materials so as to obtain a master alloy. The master alloy was subjected to melting and treatment by using a single-roller quenching technology to obtain a quenched amorphous strip with a width of about 60 mm and a thickness of about 18 ?m, wherein a copper roller was rotated at a speed of 30 m/s. The strip was cut and wound into a magnetic core with a width of 10 mm, an inner diameter of 19.7 mm, and an outer diameter of 22.6 mm. [0072] (2) The Fe.sub.76.5Si.sub.10B.sub.8Nb.sub.1Cu.sub.1.5Cr.sub.1V.sub.1P.sub.1 alloy was subjected to nanocrystalline heat treatment. The alloy strip was heated to 580? C. at a heating rate of 5? C./min for heat preservation for 0.5 hour, and then cooled to room temperature with a furnace. [0073] (3) An alloy magnetic core obtained after the heat treatment was uniformly divided into 8 parts, which were heated to 200? ? C. at a heating rate of 10? C./min, heated to 380? C. at a heating rate of 10? C./min for heat preservation for 1 hour in a 0.08 T transverse magnetic field, put in a liquid nitrogen environment for 0.5 hour, taken out, and then put in an environment for heat preservation at 280? ? C. for 0.5 hour. A cycle of cooling and heating was repeated for 2 times. [0074] (4) An initial magnetization curve of a magnetic ring was measured. In an initial magnetization curve stage, a tangent was obtained and extended to saturation magnetization. With the corresponding abscissa value as an anisotropy field (H.sub.k), an induced anisotropy value is calculated based on the formula K.sub.u=? H.sub.kB.sub.s. After the heat treatment in step (2) and step (3), it was calculated that the nanocrystalline magnetic core has a K.sub.u value of 9 J/m.sup.3. The crystallization volume fraction V.sub.cr and the grain size D were obtained according to analysis of XRD and TEM results. Based on the formula <K.sub.1>=K.sub.1V.sub.cr(D/L.sub.0).sup.6 (K.sub.1 refers to magnetocrystalline anisotropy of an ?-Fe(Si) phase and has a value of 8.2 KJ/m.sup.3; V.sub.cr refers to crystallization volume fraction; and L.sub.0 refers to ferromagnetic exchange length and has a value of about 35 nm), it was calculated that the <K.sub.1> value is 8.3 J/m.sup.3. The K.sub.u value is similar to the <K.sub.1> value. [0075] (5) A nanocrystalline obtained under the conditions of step (2) to step (4) has excellent soft magnetic properties at high frequency including a saturation magnetic induction intensity B.sub.s of 1.45 T, a coercivity H.sub.c of 2 A/m, a magnetic permeability ? of 22,000 at 100 kHz, and a loss P.sub.s of 230 kW/m.sup.3 at 100 kHz and 0.2 T.

Comparative Example 1

[0076] (1) In Comparative Example 1, an alloy with a composition chemical formula of Fe.sub.77.8Si.sub.10B.sub.8Nb.sub.2.6Cu.sub.0.6P.sub.1 was subjected to treatment as step (1) in Example 1 to obtain a magnetic core, followed by conventional nanocrystalline heat treatment as step (2). That is to say, a Fe.sub.77.8Si.sub.10B.sub.8Nb.sub.2.6Cu.sub.0.6P.sub.1 alloy strip sample was heated to 560? C. at a heating rate of 5? C./min for heat preservation for 0.5 hour, and then cooled to room temperature with a furnace. As step (3) in Examples, the magnetic core was heated to 320? C. for heat preservation for 1 hour in a 0.08 T transverse magnetic field, put in a liquid nitrogen environment for 0.5 hour, taken out, and then put in an environment for heat preservation at 280? C. for 0.5 hour. A cycle of cooling and heating was repeated for 3 times. [0077] (2) After the heat treatment in the magnetic field, the alloy has an average magnetic anisotropy <K.sub.1> value of 14.6 J/m.sup.3 and an induced anisotropy K.sub.u value of 8.9 J/m.sup.3, and the <K.sub.1> value and the K.sub.u value have a large difference. [0078] (3) Under the conditions of step (1) to step (2), the saturation magnetic induction intensity B.sub.s is 1.49 T, the coercivity H.sub.c is 10 A/m, the magnetic permeability ? at 100 kHz is 7,000, and the loss P.sub.s at 100 kHz and 0.2 T is 640 kW/m.sup.3.

Comparative Example 2

[0079] (1) As a contrast, in Comparative Example 2, an alloy with a composition chemical formula of Fe.sub.77.8Si.sub.10B.sub.8Nb.sub.2.6Cu.sub.0.6P.sub.1 was subjected to treatment as step (1) in Example 1 to obtain a magnetic core, followed by conventional nanocrystalline heat treatment as step (2). That is to say, a Fe.sub.77.8Si.sub.10B.sub.8Nb.sub.2.6Cu.sub.0.6P.sub.1 alloy strip sample was heated to 560? C. at a heating rate of 5? C./min for heat preservation for 0.5 hour, and then cooled to room temperature with a furnace. As step (3) in Examples, the magnetic core was heated to 360? C. for heat preservation for 1 hour in a 0.08 T transverse magnetic field, put in a liquid nitrogen environment for 0.5 hour, taken out, and then put in an environment for heat preservation at 280? C. for 0.5 hour. A cycle of cooling and heating was repeated for 3 times. [0080] (2) After the heat treatment in the magnetic field, the alloy has an average magnetic anisotropy <K.sub.1> value of 15.1 J/m.sup.3 and an induced anisotropy K.sub.u value of 10.9 J/m.sup.3, and the <K.sub.1> value and the K.sub.u value have a large difference. [0081] (3) Under the conditions of step (1) to step (2), the saturation magnetic induction intensity B.sub.s is 1.49 T, the coercivity H.sub.c is 3.6 A/m, the magnetic permeability ? at 100 kHz is 10,000, and the loss P.sub.s at 100 kHz and 0.2 Tis 380 kW/m.sup.3.

Comparative Example 3

[0082] (1) In Comparative Example 3, an alloy with a composition chemical formula of Fe.sub.77.8Si.sub.10B.sub.8Nb.sub.2.6Cu.sub.0.6P.sub.1 was subjected to treatment as step (1) in Example 1 to obtain a magnetic core, followed by conventional nanocrystalline heat treatment as step (2). That is to say, a Fe.sub.77.8Si.sub.10B.sub.8Nb.sub.2.6Cu.sub.0.6P.sub.1 alloy strip sample was heated to 560? C. at a heating rate of 5? C./min for heat preservation for 0.5 hour, and then cooled to room temperature with a furnace. As step (3) in Examples, the magnetic core was heated to 440? C. for heat preservation for 1 hour in a 0.08 T transverse magnetic field, put in a liquid nitrogen environment for 0.5 hour, taken out, and then put in an environment for heat preservation at 280? C. for 0.5 hour. A cycle of cooling and heating was repeated for 3 times. [0083] (2) After the heat treatment in the magnetic field, the alloy has an average magnetic anisotropy <K.sub.1> value of 16.7 J/m.sup.3 and an induced anisotropy K.sub.u value of 22.8 J/m.sup.3, and the <K.sub.1> value and the K.sub.u value have a large difference. [0084] (3) Under the conditions of step (1) to step (2), the saturation magnetic induction intensity B.sub.s is 1.49 T, the coercivity H.sub.c is 5 A/m, the magnetic permeability ? at 100 kHz is 15,000, and the loss P.sub.s at 100 kHz and 0.2 T is 540 kW/m.sup.3.

Comparative Example 4

[0085] (1) In Comparative Example 4, an alloy with a composition chemical formula of Fe.sub.77.8Si.sub.10B.sub.8Nb.sub.2.6Cu.sub.0.6P.sub.1 was subjected to treatment as step (1) in Example 1 to obtain a magnetic core, followed by conventional nanocrystalline heat treatment as step (2). That is to say, a Fe.sub.77.8Si.sub.10B.sub.8Nb.sub.2.6Cu.sub.0.6P.sub.1 alloy strip sample was heated to 560? C. at a heating rate of 5? C./min for heat preservation for 0.5 hour, and then cooled to room temperature with a furnace. As step (3) in Examples, the magnetic core was heated to 500? C. for heat preservation for 1 hour in a 0.08 T transverse magnetic field, put in a liquid nitrogen environment for 0.5 hour, taken out, and then put in an environment for heat preservation at 280? ? C. for 0.5 hour. A cycle of cooling and heating was repeated for 3 times. [0086] (2) After the heat treatment in the magnetic field, the alloy has an average magnetic anisotropy <K.sub.1> value of 20.1 J/m.sup.3 and an induced anisotropy K.sub.u value of 25.1 J/m.sup.3, and the <K.sub.1> value and the K.sub.u value have a large difference. [0087] (3) Under the conditions of step (1) to step (2), the saturation magnetic induction intensity B.sub.s is 1.49 T, the coercivity H.sub.c is 11 A/m, the magnetic permeability ? at 100 kHz is 8,000, and the loss P.sub.s at 100 kHz and 0.2 T is 600 kW/m.sup.3.

Comparative Examples 1-4

[0088] The alloys in Comparative Examples 1-4 and Example 2 have the composition of Fe.sub.77.8Si.sub.10B.sub.8Nb.sub.2.6Cu.sub.0.6P.sub.1, and preparation methods and methods for testing soft magnetic properties of the alloys were basically the same as those in Example 2. Different from Example 2, a process for heat treatment of the alloys in Comparative Examples 1-4 was carried out at a temperature of 320? C., 360? C., 440? C., and 480? C. respectively. Specific results are as shown in Table 1.

TABLE-US-00001 TABLE 1 Comparative Heat preservation <K.sub.1> K.sub.u P.sub.s Example temperature (? C.) (J/m.sup.3) (J/m.sup.3) ? (kW/m.sup.3) 1 320 14.6 8.9 7000 640 2 360 15.1 10.9 10000 380 3 440 16.7 22.8 15000 540 4 480 20.1 25.1 8000 600

Comparative Example 5

[0089] In Comparative Example 5, an alloy has a composition chemical formula of

[0090] A specific method for preparing the iron-based nanocrystalline alloy is as follows. [0091] (1) Compounding was performed according to the chemical formula of Fe.sub.77Si.sub.12B.sub.7Nb.sub.2Cu.sub.1Al.sub.1 with industrially pure Fe, Si, FeB, Al, Cu, and Nb as raw materials so as to obtain a master alloy. The master alloy was subjected to melting and treatment by using a single-roller quenching technology to obtain a quenched amorphous strip with a width of about 60 mm and a thickness of about 18 ?m, wherein a copper roller was rotated at a speed of 30 m/s. The strip was cut and wound into a magnetic core with a width of 10 mm, an inner diameter of 19.7 mm, and an outer diameter of 22.6 mm. [0092] (2) The Fe.sub.77Si.sub.12B.sub.7Nb.sub.2Cu.sub.1P.sub.1 alloy was subjected to nanocrystalline heat treatment. The alloy strip was heated to 560? C. at a heating rate of 5? C./min for heat preservation for 0.5 hour, and then cooled to room temperature with a furnace. [0093] (3) An alloy magnetic core obtained after the heat treatment was uniformly divided into 8 parts, which were heated to 200? ? C. at a heating rate of 10? C./min, heated to 420? C. at a heating rate of 10? C./min for heat preservation for 1 hour in a 0.08 T transverse magnetic field, put in a liquid nitrogen environment for 0.5 hour, taken out, and then put in an environment for heat preservation at 200? ? C. for 0.5 hour. A cycle of cooling and heating was repeated for 2 times. [0094] (4) After the heat treatment in the magnetic field in step (2) and step (3), the alloy has an average magnetic anisotropy <K.sub.1> value of 36.6 J/m.sup.3 and an induced anisotropy K.sub.u value of 42.9 J/m.sup.3, and the <K.sub.1> value and the K.sub.u value have a large difference and large values. [0095] (5) Under the conditions of step (1) to step (4), the saturation magnetic induction intensity B.sub.s is 1.4 T, the coercivity H.sub.c is 26 A/m, the magnetic permeability ? at 100 kHz is 8,000, and the loss P.sub.s at 100 kHz and 0.2 T is 750 kW/m.sup.3.

Comparative Example 6

[0096] In Comparative Example 6, an alloy has a composition chemical formula of Fe.sub.74Si.sub.13B.sub.6P.sub.4Cu.sub.2C.sub.1.

[0097] A specific method for preparing the iron-based nanocrystalline alloy is as follows. [0098] (1) Compounding was performed according to the chemical formula of Fe.sub.74Si.sub.13B.sub.6P.sub.4Cu.sub.2C.sub.1 with industrially pure Fe, Si, FeB, FeP, Cu, and FeC as raw materials so as to obtain a master alloy. The master alloy was subjected to melting and treatment by using a single-roller quenching technology to obtain a quenched amorphous strip with a width of about 60 mm and a thickness of about 18 ?m, wherein a copper roller was rotated at a speed of 30 m/s. The strip was cut and wound into a magnetic core with a width of 10 mm, an inner diameter of 19.7 mm, and an outer diameter of 22.6 mm. [0099] (2) The Fe.sub.74Si.sub.13B.sub.6P.sub.4Cu.sub.2C.sub.1 alloy was subjected to nanocrystalline heat treatment. The alloy strip was heated to 540? ? C. at a heating rate of 5? C./min for heat preservation for 0.5 hour, and then cooled to room temperature with a furnace. [0100] (3) An alloy magnetic core obtained after the heat treatment was uniformly divided into 8 parts, which were heated to 200? ? C. at a heating rate of 10? C./min, heated to 400? C. at a heating rate of 10? C./min for heat preservation for 1 hour in a 0.08 T transverse magnetic field, put in a liquid nitrogen environment for 0.5 hour, taken out, and then put in an environment for heat preservation at 240? ? C. for 1 hour. A cycle of cooling and heating was repeated for 2 times. [0101] (4) After the heat treatment in the magnetic field in step (2) and step (3), the alloy has an average magnetic anisotropy <K.sub.1> value of 4.6 J/m.sup.3 and an induced anisotropy K.sub.u value of 6.9 J/m.sup.3, and the <K.sub.1> value and the K.sub.u value have a large difference and small values. [0102] (5) Under the conditions of step (1) to step (4), the saturation magnetic induction intensity B.sub.s is 1.42 T, the coercivity H.sub.c is 34 A/m, the magnetic permeability ? at 100 kHz is 7,000, and the loss P.sub.s at 100 kHz and 0.2 T is 630 kW/m.sup.3.

Comparative Examples 5 and 6 and Examples 1-6

[0103] In Comparative Examples 5 and 6, preparation methods and methods for testing soft magnetic properties of the alloys were basically the same as those in Examples 1-6. The differences are that the alloys were different in composition and were subjected to heat treatment at different temperatures under different conditions to obtain optimal anisotropy values and soft magnetic properties. Specific results are as shown in Table 2.

TABLE-US-00002 TABLE 2 <K.sub.1> K.sub.u B.sub.s P.sub.s Example Composition of alloy (J/m.sup.3) (J/m.sup.3) (T) ? (kW/m.sup.3) Example 1 Fe.sub.76Si.sub.11B.sub.8Nb.sub.2Cu.sub.1Mo.sub.1P.sub.1 12.8 13 1.5 21600 180 Example 2 Fe.sub.77.8Si.sub.10B.sub.8Nb.sub.2.6Cu.sub.0.6P.sub.1 16.1 15.8 1.5 20000 205 Example 3 Fe.sub.77Si.sub.12B.sub.7Nb.sub.2Cu.sub.1P.sub.1 8.6 8.3 1.46 25000 220 Example 4 Fe.sub.73.7Si.sub.11B.sub.10Nb.sub.2.5Cu.sub.1Mn.sub.1P.sub.0.8 11.7 12.2 1.45 23400 250 Example 5 Fe.sub.77.5Si.sub.12B.sub.6Nb.sub.1Cu.sub.1.5Mo.sub.0.5V.sub.0.5P.sub.1 18.9 19 1.52 20300 190 Example 6 Fe.sub.76.5Si.sub.10B.sub.8Nb.sub.1Cu.sub.1.5Cr.sub.1V.sub.1P.sub.1 8.3 9 1.45 22000 230 Comparative Fe.sub.77Si.sub.12B.sub.7Nb.sub.2Cu.sub.1Al.sub.1 36.6 42.9 1.4 8000 750 Example 5 Comparative Fe.sub.74Si.sub.13B.sub.6P.sub.4Cu.sub.2C.sub.1 4.6 6.9 1.42 7000 630 Example 6

Comparative Example 7

[0104] (1) As a contrast, in Comparative Example 7, an alloy with a composition chemical formula of Fe.sub.77Si.sub.12B.sub.7Nb.sub.2Cu.sub.1P.sub.1 was subjected to treatment as step (1) in Example 1 to obtain a magnetic core, followed by conventional nanocrystalline heat treatment as step (2). That is to say, a Fe.sub.77Si.sub.12B.sub.7Nb.sub.2Cu.sub.1P.sub.1 alloy strip sample was heated to 580? C. at a heating rate of 5? C./min for heat preservation for 0.5 hour, and then cooled to room temperature with a furnace. As step (3) in Examples, the magnetic core was heated to 380? C. for heat preservation for 1 hour in a 0.08 T transverse magnetic field, and then cooled to room temperature with a furnace. [0105] (2) After the heat treatment in the magnetic field, the alloy has an average magnetic anisotropy <K.sub.1> value of 10.6 J/m.sup.3 and an induced anisotropy K.sub.u value of 8.1 J/m.sup.3, and the <K.sub.1> value and the K.sub.u value have a large difference. [0106] (3) Under the conditions of step (1) to step (2), the saturation magnetic induction intensity B.sub.s is 1.42 T, the coercivity H.sub.c is 5 A/m, the magnetic permeability ? at 100 kHz is 11,000, and the loss P.sub.s at 100 kHz and 0.2 T is 440 kW/m.sup.3.

Comparative Example 8

[0107] (1) As a contrast, in Comparative Example 8, an alloy with a composition chemical formula of Fe.sub.77Si.sub.12B.sub.7Nb.sub.2Cu.sub.1P.sub.1 was subjected to treatment as step (1) in Example 1 to obtain a magnetic core, followed by conventional nanocrystalline heat treatment as step (2). That is to say, a Fe.sub.77Si.sub.12B.sub.7Nb.sub.2Cu.sub.1P.sub.1 alloy strip sample was heated to 580? C. at a heating rate of 5? C./min for heat preservation for 0.5 hour, and then cooled to room temperature with a furnace. As step (3) in Examples, the magnetic core was heated to 380? C. for heat preservation for 1 hour in a 0.08 T transverse magnetic field, put in a liquid nitrogen environment for 0.5 hour, taken out, and then put in an environment for heat preservation at 150? C. for 1 hour. A cycle of cooling and heating was repeated for 2 times. [0108] (2) After the heat treatment in the magnetic field, the alloy has an average magnetic anisotropy <K.sub.1> value of 11.5 J/m.sup.3 and an induced anisotropy K.sub.u value of 9.2 J/m.sup.3, and the <K.sub.1> value and the K.sub.u value have a large difference. [0109] (3) Under the conditions of step (1) to step (2), the saturation magnetic induction intensity B.sub.s is 1.41 T, the coercivity H.sub.c is 3 A/m, the magnetic permeability ? at 100 kHz is 15.000, and the loss P.sub.s at 100 kHz and 0.2 T is 420 kW/m.sup.3.

Comparative Examples 7 and 8 and Example 3

[0110] In Comparative Examples 7 and 8, the composition, the thermal field, and the heat treatment in the magnetic field were basically the same as those in Example 3. The difference was a process for treatment in a cold field. In Comparative Example 7, treatment in a cold field was not conducted. In Comparative Example 8, treatment in a cold field was not conducted under limited conditions, and was conducted at different temperatures under different treatment conditions to obtain anisotropy values and soft magnetic properties. Specific results are as shown in Table 3.

TABLE-US-00003 TABLE 3 <K.sub.1> K.sub.u B.sub.s P.sub.s Example Composition of alloy (J/m.sup.3) (J/m.sup.3) (T) ? (kW/m.sup.3) Example Fe.sub.77Si.sub.12B.sub.7Nb.sub.2Cu.sub.1P.sub.1 (cooled to 8.6 8.3 1.46 25000 220 3 220? C.) Comparative Fe.sub.77Si.sub.12B.sub.7Nb.sub.2Cu.sub.1P.sub.1 (without a 10.6 8.1 1.42 11000 440 Example cold field) 7 Comparative Fe.sub.77Si.sub.12B.sub.7Nb.sub.2Cu.sub.1P.sub.1 (cooled to 11.5 9.2 1.41 15000 420 Example 150? C.) 8

Analysis of Test Results of Properties in Examples 1-6 and Comparative Examples 1-8

1. Magnetic Anisotropy of Alloys

[0111] An initial magnetization curve of a magnetic ring is measured. In an initial magnetization curve stage, a tangent was obtained and extended to saturation magnetization. With the corresponding abscissa value as an anisotropy field (H.sub.k), an induced anisotropy K.sub.u value was calculated based on the formula K.sub.u=? H.sub.kB.sub.s. The crystallization volume fraction V.sub.cr and the grain size D were obtained according to analysis of XRD and TEM results. Based on the formula <K.sub.1>=K.sub.1V.sub.cr(D/L.sub.0).sup.6, the <K.sub.1> value was calculated. Results of the magnetic anisotropy of the alloys in Examples 1-6 and Comparative Examples 1-8 after heat treatment at different temperatures for different times are as shown in Table 4.

TABLE-US-00004 TABLE 4 <K.sub.1> K.sub.u Example Composition of alloy (J/m.sup.3) (J/m.sup.3) Example 1 Fe.sub.76Si.sub.11B.sub.8Nb.sub.2Cu.sub.1Mo.sub.1P.sub.1 12.8 13 Example 2 Fe.sub.77.8Si.sub.10B.sub.8Nb.sub.2.6Cu.sub.0.6P.sub.1 16.1 15.8 Example 3 Fe.sub.77Si.sub.12B.sub.7Nb.sub.2Cu.sub.1P.sub.1 8.3 8.6 Example 4 Fe.sub.73.7Si.sub.11B.sub.10Nb.sub.2.5Cu.sub.1Mn.sub.1P.sub.0.8 11.7 12.2 Example 5 Fe.sub.77.5Si.sub.12B.sub.6Nb.sub.1Cu.sub.1.5Mo.sub.0.5V.sub.0.5P.sub.1 18.9 19 Example 6 Fe.sub.76.5Si.sub.10B.sub.8Nb.sub.1Cu.sub.1.5Cr.sub.1V.sub.1P.sub.1 8.3 9 Comparative Fe.sub.77.8Si.sub.10B.sub.8Nb.sub.2.6Cu.sub.0.6P.sub.1 14.6 8.9 Example 1 Comparative Fe.sub.77.8Si.sub.10B.sub.8Nb.sub.2.6Cu.sub.0.6P.sub.1 15.1 10.9 Example 2 Comparative Fe.sub.77.8Si.sub.10B.sub.8Nb.sub.2.6Cu.sub.0.6P.sub.1 16.7 22.8 Example 3 Comparative Fe.sub.77.8Si.sub.10B.sub.8Nb.sub.2.6Cu.sub.0.6P.sub.1 20.1 25.1 Example 4 Comparative Fe.sub.77Si.sub.12B.sub.7Nb.sub.2Cu.sub.1Al.sub.1 36.6 42.9 Example 5 Comparative Fe.sub.74Si.sub.13B.sub.6P.sub.4Cu.sub.2C.sub.1 4.6 6.9 Example 6 Comparative Fe.sub.77Si.sub.12B.sub.7Nb.sub.2Cu.sub.1P.sub.1 10.6 8.1 Example 7 Comparative Fe.sub.77Si.sub.12B.sub.7Nb.sub.2Cu.sub.1P.sub.1 11.5 9.2 Example 8

[0112] In Comparative Example 5 and Examples 1-6, the alloys were compared in composition. In Examples 1-6, the element P was used for doping, so that the <K.sub.1> value was effectively decreased, and was less than 20 J/m.sup.3. In Comparative Example 5, the grain size was large, as shown in FIG. 3, and it was calculated that the <K.sub.1> value was large, and was greater than 20 J/m.sup.3. In Comparative Example 6, the value was too small, and the K.sub.u value was not similar to the <K.sub.1> value. It was indicated that due to the doping with the element P, the nucleation rate of a grain was increased under the condition of ensuring the saturation magnetic induction intensity, the growth rate of the grain was inhibited, and convenience was provided for obtaining a fine and uniform nanocrystalline structure. A nanocrystalline alloy with a low <K.sub.1> value was obtained, convenience was provided for adjusting the ratio of the K.sub.u value to the <K.sub.1> value, and soft magnetic properties of the alloy at high frequency were improved. In Examples 1-6, after the doping with P, the nanocrystalline alloys with a low <K.sub.1> value were subjected to annealing in a magnetic field, and the K.sub.u value was similar to the <K.sub.1> value.

[0113] In Comparative Examples 1 and 2, Example 2, and Comparative Examples 3 and 4, the alloys have the composition of Fe.sub.77.8Si.sub.10B.sub.8Nb.sub.2.6Cu.sub.0.6P.sub.1, the process for heat treatment in a magnetic field was carried out at a temperature of 320? C., 360 ? C, 400? C., 440? C., and 480? C. respectively, and anisotropic values were as shown in FIG. 1. With increase of the annealing temperature, the K.sub.u value and the <K.sub.1> value were increased. However, the increasing trend of the K.sub.u value was higher than that of the <K.sub.1> value. It can be seen obviously that when the annealing temperature was 400? C. (in Example 2), the K.sub.u value was nearly equal to the <K.sub.1> value.

[0114] In Comparative Examples 7 and 8 and Example 3, the alloys have the composition of Fe.sub.77Si.sub.12B.sub.7Nb.sub.2Cu.sub.1P.sub.1, and the thermal field and the heat treatment in the magnetic field were the same. The difference was a process for treatment in a cold field. In Comparative Example 7, treatment in a cold field was not conducted. In Comparative Example 8, treatment in a cold field was not conducted under limited conditions, and the K.sub.u value was not similar to the <K.sub.1> value.

2. Soft Magnetic Properties of Alloys

[0115] The saturation magnetic induction intensity B.sub.s, coercivity P.sub.s, and magnetic permeability ? of the nanocrystalline soft magnetic alloys after heat treatment at different temperatures for different times in Examples 1-6 and Comparative Examples 1-8 were tested by using a vibrating sample magnetometer (Lakeshore7410), a direct current B-H tester (EXPH-100), and an impedance analyzer (Agilent 4294 A) respectively. Results are as shown in FIG. 2 and Table 5.

TABLE-US-00005 TABLE 5 B.sub.s H.sub.c P.sub.s Example Composition of alloy (T) (A/m) ? (kW/m.sup.3) Example 1 Fe.sub.76Si.sub.11B.sub.8Nb.sub.2Cu.sub.1Mo.sub.1P.sub.1 1.5 1.5 21600 180 Example 2 Fe.sub.77.8Si.sub.10B.sub.8Nb.sub.2.6Cu.sub.0.6P.sub.1 1.5 1.6 20000 205 Example 3 Fe.sub.77Si.sub.12B.sub.7Nb.sub.2Cu.sub.1P.sub.1 1.46 2 25000 220 Example 4 Fe.sub.73.7Si.sub.11B.sub.10Nb.sub.2.5Cu.sub.1Mn.sub.1P.sub.0.8 1.45 1.8 23400 250 Example 5 Fe.sub.77.5Si.sub.12B.sub.6Nb.sub.1Cu.sub.1.5Mo.sub.0.5V.sub.0.5P.sub.1 1.52 1.5 20300 190 Example 6 Fe.sub.76.5Si.sub.10B.sub.8Nb.sub.1Cu.sub.1.5Cr.sub.1V.sub.1P.sub.1 1.45 2 22000 230 Comparative Fe.sub.77.8Si.sub.10B.sub.8Nb.sub.2.6Cu.sub.0.6P.sub.1 1.49 10 7000 640 Example 1 Comparative Fe.sub.77.8Si.sub.10B.sub.8Nb.sub.2.6Cu.sub.0.6P.sub.1 1.49 3.6 10000 380 Example 2 Comparative Fe.sub.77.8Si.sub.10B.sub.8Nb.sub.2.6Cu.sub.0.6P.sub.1 1.49 5 15000 540 Example 3 Comparative Fe.sub.77.8Si.sub.10B.sub.8Nb.sub.2.6Cu.sub.0.6P.sub.1 1.49 11 8000 600 Example 4 Comparative Fe.sub.77Si.sub.12B.sub.7Nb.sub.2Cu.sub.1Al.sub.1 1.4 26 8000 750 Example 5 Comparative Fe.sub.74Si.sub.13B.sub.6P.sub.4Cu.sub.2C.sub.1 1.42 34 7000 630 Example 6 Comparative Fe.sub.77Si.sub.12B.sub.7Nb.sub.2Cu.sub.1P.sub.1 1.42 5 11000 440 Example 7 Comparative Fe.sub.77Si.sub.12B.sub.7Nb.sub.2Cu.sub.1P.sub.1 1.41 3 15000 420 Example 8

[0116] In Comparative Examples 1 and 2, Example 2, and Comparative Examples 3 and 4, the alloys have the composition of Fe.sub.77.8Si.sub.10B.sub.8Nb.sub.2.6Cu.sub.0.6P.sub.1, the process for heat treatment in a magnetic field was carried out at a temperature of 320? C., 360 ? C, 400? C., 440? C., and 480? C. respectively, and soft magnetic properties are as shown in FIG. 2. When the annealing temperature was 400? ? C. (in Example 2), the soft magnetic properties are optimal.

3. Microstructures of Alloys

[0117] In order to further explain why the nanocrystalline soft magnetic alloy of the present disclosure has excellent soft magnetic properties at high frequency, microstructures of samples in Example 1 (Fe.sub.76Si.sub.11B.sub.8Nb.sub.2Cu.sub.1Mo.sub.1P.sub.1), Example 2 (Fe.sub.77.8Si.sub.10B.sub.8Nb.sub.2.6Cu.sub.0.6P.sub.1 at 400? C.), Comparative Example 1 (Fe.sub.77.8Si.sub.10B.sub.8Nb.sub.2.6Cu.sub.0.6P.sub.1 at 320? C.), and Comparative Example 5 (Fe.sub.77Si.sub.12B.sub.7Nb.sub.2Cu.sub.1Al.sub.1) were analyzed by using a Talos transmission electron microscope.

[0118] Results are as shown in FIG. 3. All crystal phases consist of amorphous phases and nanometer ?-Fe grains. In Examples 1 and 2, due to the addition of a trace amount of the element P, the magnetocrystalline anisotropy was reduced, and the growth of a grain was inhibited. According to morphology maps and selected diffraction patterns, it was shown that fine and uniform grains precipitated are embedded on amorphous matrices at optimal annealing temperatures. The grains are ?-Fe grains, and have a grain size (D) of 11.7 nm and 12.1 nm respectively. In Comparative Example 1 and Example 2, the nanocrystallines obtained from the alloy with the same composition in a magnetic field at different annealing temperatures are compared. In Example 2, the D value was 12.6 nm, indicating that the grain size was basically unchanged after annealing in a magnetic field. In Comparative Example 5, the D value was 15.5 nm. The grain size was slightly large, the magnetocrystalline anisotropy is large, and the soft magnetic properties are poor.