NEODYMIUM-IRON-BORON MAGNET MATERIAL, RAW MATERIAL COMPOSITION PREPARATION METHOD THEREFOR AND USE THEREOF

Abstract

Disclosed are a neodymium-iron-boron magnet material, a raw material composition, a preparation method therefor and a use thereof. The raw material composition of the neodymium-iron-boron magnet material comprises the following components in weight content: R: 28-33%; R being rare earth elements, and comprising R1 and R2, R1 being a rare earth element added during smelting, R1 comprising Nd and Dy, R2 being a rare earth element added during grain boundary diffusion, R2 comprising Tb, and the content of R2 being 0.2-1%; M: ≤0.4% but not 0, M being one or more elements among Bi, Sn, Zn, Ga, In, Au and Pb; Cu: ≤0.15% but not 0; B: 0.9-1.1%; Fe: 60-70%; but not containing Co. The neodymium-iron-boron magnet material under the condition of adding a small amount of heavy rare earth elements and not adding cobalt, can still have a relatively high coercivity and remanence, and excellent thermal stability.

Claims

1. A raw material composition of neodymium-iron-boron magnet material, comprising the following components by mass content: R: 28-33%; R being rare earth element comprising R1 and R2, R1 being rare earth element added during smelting, and R1 comprising Nd and Dy; R2 being rare earth element added during grain boundary diffusion, R2 comprising Tb, and the content of R2 being 0.2-1%; M: ≤0.4%, but not 0, M being one or more of Bi, Sn, Zn, Ga, In, Au and Pb; Cu: ≤0.15%, but not 0; B: 0.9-1.1%; Fe: 60-70%; the raw material composition does not comprise Co; the percentage is the mass percentage of the mass of each component relative to the total mass of the raw material composition.

2. The raw material composition according to claim 1, wherein, the content of R is 29.5-32.6%, and the percentage is the mass percentage relative to the total mass of the raw material composition; or, in R1 of the raw material composition, the content of Nd is 28.5-32.5%, and the percentage is the mass percentage relative to the total mass of the raw material composition; or, in R1 of the raw material composition, the content of Dy is 0.3% or less, but not 0, and the percentage is the mass percentage relative to the total mass of the raw material composition; or, in R2, the content of Tb is 0.2%-1%, and the percentage is the mass percentage relative to the total mass of the raw material composition; or, the content of M is 0.35% or less, but not 0, and the percentage is the mass percentage relative to the total mass of the raw material composition; or, the content of Cu is 0.03-0.15%, or, the content of Cu is 0.08% or less, but not 0, and the percentage is the mass percentage relative to the total mass of the raw material composition; or, the content of B is 0.97-1.05%, and the percentage is the mass percentage relative to the total mass of the raw material composition; or, the content of Fe is 65-69.5%, and the percentage is the mass percentage relative to the total mass of the raw material composition.

3. The raw material composition according to claim 1, wherein, the raw material composition of the neodymium-iron-boron magnet material comprises the following components by mass content: R: 29.5-32.6%; R comprising R1 and R2, R1 comprising Nd and Dy, R1 being rare earth element added during smelting, the content of R2 being 0.2-0.9%, R2 comprising Tb, and R2 being rare earth element added during grain boundary diffusion; M: 0.35% or less, but not 0, M is one or more of Zn, Ga and Bi; Cu: 0.05-0.15%; B: 0.97-1.05%; Fe: 65-69.5%, the raw material composition does not comprise Co; the percentage is the mass percentage of the mass of each component relative to the total mass of the raw material composition; or, the raw material composition of the neodymium-iron-boron magnet material comprises the following components by mass content: R: 29.5-31%; R comprising R1 and R2, R1 comprising Nd and Dy, and R1 being rare earth element added during smelting, the content of R2 being 0.2-0.8%, R2 comprising Tb, and R2 being rare earth element added during grain boundary diffusion; M: 0.1-0.35%, M being one or more of Zn, Ga and Bi; Cu: 0.08% or less, but not 0; B: 0.97-1.05%; Fe: 65-69.5%, the raw material composition does not comprise Co; the percentage is the mass percentage of the mass of each component relative to the total mass of the raw material composition.

4. A preparation method for neodymium-iron-boron magnet material, which is carried out by using the raw material composition according to claim 1, and the preparation method is a preparation method with diffusion, wherein, R1 elements are added in smelting step, and R2 elements are added in grain boundary diffusion step.

5. The preparation method according to claim 4, wherein, the preparation method comprises the following steps: subjecting the elements other than R2 in the raw material composition of the neodymium-iron-boron magnet material to smelting, powdering, forming, sintering to obtain a sintered body, and then subjecting the mixture of the sintered body and R2 to the grain boundary diffusion.

6. A neodymium-iron-boron magnet material made by the preparation method according to claim 4.

7. A neodymium-iron-boron magnet material, comprising the following components by mass content: R: 28-33%; R comprising R1 and R2, R1 comprising Nd and Dy, and R2 comprising Tb; the content of R2 being 0.2%-1%; M: ≤0.4%, but not 0, M being one or more of Bi, Sn, Zn, Ga, In, Au and Pb; Cu: ≤0.15%, but not 0; B: 0.9-1.1%; Fe: 60-70%; the neodymium-iron-boron magnet material does not comprise Co; the percentage is the mass percentage of the mass of each component relative to the total mass of the neodymium-iron-boron magnet material; the neodymium-iron-boron magnet material comprises Nd.sub.2Fe.sub.14B grains and their shells, a two-grain grain boundary and a grain boundary triangle region adjacent to the Nd.sub.2Fe.sub.14B grains, wherein the heavy rare earth elements in R1 are distributed in the Nd.sub.2Fe.sub.14B grains, and R2 is mainly distributed in the shells, the two-grain grain boundary and the grain boundary triangle region, the area ratio of the grain boundary triangle region is 2-3.12%; the grain boundary continuity of the two-grain grain boundary is 96% or more; the mass ratio of C and O in the grain boundary triangle region is 0.4-0.5%, and the mass ratio of C and O in the two-grain grain boundary is 0.3-0.4%.

8. The neodymium-iron-boron magnet material according to claim 7, wherein, the area ratio of the grain boundary triangle region is 2.07-2.84%; or, the grain boundary continuity is 97% or more; or, the mass ratio of C and O in the grain boundary triangle region is 0.41-0.48%; or, the mass ratio of C and O in the two-grain grain boundary is 0.32-0.39%.

9. The neodymium-iron-boron magnet material according to claim 7, wherein, the neodymium-iron-boron magnet material comprises the following components by mass content: R: 29.5-32.6%; R comprising R1 and R2, R1 comprising Nd and Dy, R1 being rare earth element added during smelting, the content of R2 being 0.2-0.9%, R2 comprising Tb, and R2 being rare earth element added during grain boundary diffusion; M: 0.35% or less, but not 0, M is one or more of Zn, Ga and Bi; Cu: 0.05-0.15%; B: 0.97-1.05%; Fe: 65-69.5%, the neodymium-iron-boron magnet material does not comprise Co; the percentage is the mass percentage of the mass of each component relative to the total mass of the neodymium-iron-boron magnet material; the neodymium-iron-boron magnet material comprises Nd.sub.2Fe.sub.14B grains and their shells, a two-grain grain boundary and a grain boundary triangle region adjacent to the Nd.sub.2Fe.sub.14B grains, wherein the heavy rare earth elements in R1 are distributed in the Nd.sub.2Fe.sub.14B grains, and R2 is mainly distributed in the shells, the two-grain grain boundary and the grain boundary triangle region, the area ratio of the grain boundary triangle region is 2-2.84%; the grain boundary continuity of the two-grain grain boundary is 97% or more; the mass ratio of C and O in the triangle region is 0.41-0.48%, and the mass ratio of C and O in the two-grain grain boundary is 0.32-0.39%; the two-grain grain boundary also comprises a new phase, the chemical composition of the new phase is R.sub.xFe.sub.100-x-y-zCu.sub.yM.sub.z; wherein, R in the R.sub.xFe.sub.100-x-y-zCu.sub.yM.sub.z comprises one or more of Nd, Dy and Tb, and M is one or more of Bi, Sn, Zn, Ga, In, Au and Pb, x is 78.1-79.5; y is 0.99-1.33; z is 0.26-0.38; the ratio of the area of the new phase in the two-grain grain boundary to the total area of the two-grain grain boundary is 0.25-1.65%; or, the neodymium-iron-boron magnet material comprises the following components by mass content: R: 29.5-31%; R comprising R1 and R2, R1 comprising Nd and Dy, R1 being rare earth element added during smelting, the content of R2 being 0.2-0.8%, R2 comprising Tb, and R2 being rare earth element added during grain boundary diffusion; M: 0.01-0.35%, M being one of Zn, Ga and Bi; Cu: 0.08% or less, but not 0; B: 0.97-1.05%; Fe: 65-69.5%, the neodymium-iron-boron magnet material does not comprise Co; the percentage is the mass percentage of the mass of each component relative to the total mass of the neodymium-iron-boron magnet material; the neodymium-iron-boron magnet material comprises Nd.sub.2Fe.sub.14B grains and their shells, a two-grain grain boundary and a grain boundary triangle region adjacent to the Nd.sub.2Fe.sub.14B grains, wherein the heavy rare earth elements in R1 are distributed in the Nd.sub.2Fe.sub.14B grains, and R2 is mainly distributed in the shells, the two-grain grain boundary and the grain boundary triangle region, the area ratio of the grain boundary triangle region is 2-2.6%; the grain boundary continuity of the two-grain grain boundary is 98% or more; the mass ratio of C and O in the triangle region is 0.41-0.46%, and the mass ratio of C and O in the two-grain grain boundary is 0.32-0.39%; the two-grain grain boundary comprises a new phase, the chemical composition of the new phase is R.sub.xFe.sub.100-x-y-zCu.sub.yM.sub.z; wherein, R in the R.sub.xFe.sub.100-x-y-zCu.sub.yM.sub.z comprises one or more of Nd, Dy and Tb, and M is one or more of Bi, Zn and Ga; x is 78.1-79.5; y is 0.99-1.33; z is 0.26-0.38; the ratio of the area of the new phase in the two-grain grain boundary to the total area of the two-grain grain boundary is 0.5-1.65%.

10. A use of the neodymium-iron-boron magnet material according to claim 7 in the preparation of magnetic steel; the magnetic steel is high-performance magnetic steel of 54SH, 54UH, 56SH.

11. The raw material composition according to claim 1, wherein, R1 comprises Pr, Pr is added in the form of PrNd, or in the form of a mixture of pure Pr and pure Nd, or added in a combination of “a mixture of PrNd, pure Pr and pure Nd”; or, R1 comprises Ho, the content of Ho is 0.1-0.2%, and the percentage is the mass percentage relative to the total mass of the raw material composition; or, R1 comprises Gd, the content of Gd is 0.1-0.2%, and the percentage is the mass percentage relative to the total mass of the raw material composition; or, R1 comprises Y, the content of Y is 0.1-0.2%, and the percentage is the mass percentage relative to the total mass of the raw material composition.

12. The raw material composition according to claim 1, wherein, R2 comprises Pr, the content of Pr is 0.2% or less, but not 0, and the percentage is the mass percentage relative to the total mass of the raw material composition; or, R2 comprises Dy, the content of Dy is 0.3% or less, but not 0, and the percentage is the mass percentage relative to the total mass of the raw material composition.

13. The raw material composition according to claim 1, wherein, the raw material composition also comprises Al; the content of Al is 0.3% or less, but not 0, and the percentage is the mass percentage relative to the total mass of the raw material composition.

14. The preparation method according to claim 5, wherein, the operation of smelting is to smelt and cast the elements other than R2 in the neodymium-iron-boron magnet material by using ingot casting process and quick-setting flake process to obtain alloy flakes; the temperature of the smelting is 1300-1700° C.; the powdering comprises hydrogen decrepitation powdering and jet milling powdering; the hydrogen decrepitation powdering comprises hydrogen absorption, dehydrogenation and cooling treatment; the temperature of the hydrogen absorption is 20-200° C.; the temperature of the dehydrogenation is 400-650° C.; the pressure of the hydrogen absorption is 50-600 kPa; the jet milling powdering is carried out under the condition of 0.1-2 MPa, the airflow in the jet milling powdering is nitrogen; the time of the jet milling powdering is 2-4 h; the forming is a magnetic field forming method, and the magnetic field strength of the magnetic field forming method is 1.5 T or more; the sintering is carried out under the condition that the degree of vacuum is lower than 0.5 Pa; the temperature of sintering is 1000-1200° C.; the time of sintering is 0.5-10 h; the coating operation of R2 is comprised before the grain boundary diffusion; R2 is coated in the form of fluoride or alloy with low melting point; the temperature of the grain boundary diffusion is 800-1000° C.; the time of the grain boundary diffusion is 5-20 h; after the grain boundary diffusion, a low-temperature tempering treatment is performed; the temperature of the low-temperature tempering treatment is 460-560° C.; and the time of the low-temperature tempering treatment is 1-3 h.

15. The neodymium-iron-boron magnet material according to claim 7, wherein, the two-grain grain boundary also comprises a phase with a chemical composition of R.sub.xFe.sub.100-x-y-zCu.sub.yM.sub.z; wherein R comprises one or more of Nd, Dy and Tb, and M is one or more of Bi, Sn, Zn, Ga, In, Au and Pb, x is 78-80; y is 0.8-1.5; z is 0.1 or less, but not 0.

16. The neodymium-iron-boron magnet material according to claim 15, wherein, in the two-grain grain boundary, the ratio of the area of the new phase to the total area of the two-grain grain boundary is 0.25-1.65%.

17. The neodymium-iron-boron magnet material according to claim 7, wherein, R1 comprises Pr, Pr is added in the form of PrNd, or in the form of a mixture of pure Pr and pure Nd, or added in a combination of “a mixture of PrNd, pure Pr and pure Nd”; or, R1 comprises Ho, the content of Ho is 0.1-0.2%, and the percentage is the mass percentage relative to the total mass of the neodymium-iron-boron magnet material; or, R1 comprises Gd, the content of Gd is 0.1-0.2%, and the percentage is the mass percentage relative to the total mass of the neodymium-iron-boron magnet material; or, R1 comprises Y, the content of Y is 0.1-0.2%, and the percentage is the mass percentage relative to the total mass of the neodymium-iron-boron magnet material.

18. The neodymium-iron-boron magnet material according to claim 7, wherein, in the neodymium-iron-boron magnet material, R2 comprises Pr, the content of Pr is 0.2% or less, but not 0, and the percentage is the mass percentage relative to the total mass of the neodymium-iron-boron magnet material; or, R2 comprises Dy, the content of Dy is 0.3% or less, but not 0, and the percentage is the mass percentage relative to the total mass of the neodymium-iron-boron magnet material.

19. The neodymium-iron-boron magnet material according to claim 7, wherein, M comprises Ga, the content of Ga is 0.35% or less, but not 0, and the percentage is the mass percentage relative to the total mass of the neodymium-iron-boron magnet material; or, M comprises Zn, the content of Zn is 0.35% or less, but not 0, and the percentage is the mass percentage relative to the total mass of the neodymium-iron-boron magnet material; or, M comprises Bi, the content of Bi is 0.35% or less, but not 0, and the percentage is the mass percentage relative to the total mass of the neodymium-iron-boron magnet material.

20. The neodymium-iron-boron magnet material according to claim 7, wherein, the neodymium-iron-boron magnet material also comprises Al; the content of Al is 0.3% or less, but not 0, and the percentage is the mass percentage relative to the total mass of the neodymium-iron-boron magnet material.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0148] FIG. 1 shows the EPMA microstructure of the neodymium-iron-boron magnet material of Example 4. The point pointed by arrow 1 in the figure is the new phase of R.sub.xFe.sub.100-x-y-zCu.sub.yM.sub.z contained in the two-grain grain boundary, the position pointed by arrow 2 is the grain boundary triangle region, and the position pointed by arrow 3 is the main phase of Nd.sub.2Fe.sub.14B.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

[0149] The following embodiments further illustrate the present disclosure, but the present disclosure is not limited thereto. Experiment methods in which specific conditions are not indicated in the following embodiments are selected according to conventional methods and conditions, or according to the product specification.

[0150] 1. The raw material compositions of the neodymium-iron-boron magnet materials for Embodiments 1-10 and Comparative Embodiments 1-3 of the present disclosure are shown in Table 1 below.

TABLE-US-00001 TABLE 1 Formulations and contents of raw material compositions of neodymium-iron-boron magnet materials (wt %) R1 R2 M Nd Dy Pr Tb Pr Dy Ga Zn Bi Al Cu B Fe Embodiment 1 28.6 0.05 0.1 1 / / 0.05 / / 0.1 0.05 0.99 69.06 Embodiment 2 28.6 0.1 0.2 0.9 / / 0.1 0.1 / / 0.05 1 68.95 Embodiment 3 28.6 0.08 / 0.9 / / 0.3 / / / 0.06 1.1 68.96 Embodiment 4 29.9 0.1 / 0.8 0.1 / 0.2 / / 0.2 0.08 0.99 67.63 Embodiment 5 30.4 0.05 / 0.8 0.1 0.35 / / / 0.1 0.99 67.21 Embodiment 6 29.9 0.1 0.1 0.6 / / 0.15 / / / 0.07 0.99 68.09 Embodiment 7 29.9 0.1 / 0.6 / / 0.15 / / / 0.07 0.99 68.19 Embodiment 8 30.4 0.05 / 0.3 0.2 / / 0.2 / / 0.15 0.99 67.71 Embodiment 9 32.1 0.3 / 0.2 / / / 0.08 0.08 / 0.15 1.1 65.99 Embodiment 10 28.6 0.05 0.1 1 / / 0.01 / / 0.03 0.03 0.99 69.19 Comparative 29.9 0.1 / 0.1 0.8 0.2 / / 0.2 0.08 0.99 67.63 Embodiment 1 Comparative 29.9 0.1 / 0.8 0.1 0 0.2 / / 0.2 0.25 0.99 67.46 Embodiment 2 Comparative 29.9 0.1 / 0.8 0.1 0 0.45 / / 0.2 0.08 0.99 67.38 Embodiment 3 Note: “/” refers to being without the element. (wt %) is the mass percentage.

[0151] 2. Preparation Method for the Neodymium-Iron-Boron Magnet Material in Embodiment 1

[0152] (1) Smelting and casting process: according to the formulation in Table 1, the prepared raw materials except R2 (R2 was added as PrCu in Embodiments 4 and 8, and in Embodiments 4 and 8, the contents of Cu added in the grain boundary diffusion step were respectively 0.05 wt % and 0.03 wt %, the contents of Cu added in the smelting step were respectively 0.03 wt % and 0.12 wt %) were placed into the crucible of alumina, and were vacuum smelted in a high-frequency vacuum smelting furnace with a vacuum of 0.05 Pa and 1500° C., and were cast in the medium-frequency vacuum induction quick-setting dumping belt furnace with argon gas, then quenched the alloy to obtain the alloy flakes.

[0153] (2) Hydrogen decrepitation powdering process: the furnace for hydrogen decrepitation with the quench alloy placed therein was evacuated at room temperature, and then hydrogen of 99.9% purity was introduced into the furnace for hydrogen decrepitation, the pressure of hydrogen was maintained at 90 kPa, and after sufficient hydrogen absorption, it was sufficiently dehydrogenated by heating while evacuating, and then it was cooled and the powder crushed by hydrogen decrepitation was taken out. Herein, the temperature of hydrogen absorption was the room temperature, and the temperature of dehydrogenation was 550° C.

[0154] (3) Jet milling process: the powder crushed by hydrogen decrepitation was crushed by jet milling for 3 h at the pressure of 0.6 MPa in the crushing chamber under nitrogen atmosphere to obtain fine powder.

[0155] (4) Forming process: the powder subjected to jet milling was formed under a magnetic field strength of 1.5 T or more.

[0156] (5) Sintering process: each forming body was moved to the sintering furnace for sintering, the sintering was carried out at 1030-1090° C. for 2-5 h under vacuum below 0.5 Pa to obtain the sintered body.

[0157] (6) Grain boundary diffusion process: the surface of the sintered body was purified and R2 (e.g. one or more of alloys or fluorides of Tb, alloys or fluorides of Dy and PrCu alloys, wherein Cu was added both in the smelting step and the grain boundary diffusion step) was coated on the surface of the sintered body and diffused at 850° C. for 5-15 h, and then it was cooled to room temperature, and was subjected to the low-temperature tempering treatment at 460-560° C. for 1-3 h.

[0158] The parameters in the preparation method for neodymium-iron-boron magnet material in Embodiments 2-10 and Comparative Embodiments 1-3 were the same as those in Embodiment 1. Herein, in Embodiments 4 and 8, the raw materials in the formulations in Table 1 except for R2 and Cu that needed to be added in the grain boundary diffusion were smelted and cast.

[0159] 3. Composition determination: The neodymium-iron-boron magnet material in Embodiments 1-10 and Comparative Embodiments 1-3 were determined by using high frequency inductively coupled plasma emission spectrometer (ICP-OES). The results are shown in Table 2 below.

TABLE-US-00002 TABLE 2 Components and contents of neodymium-iron-boron magnet materials (wt %) R1 R2 M Nd Dy Pr Tb Pr Dy Ga Zn Bi Al Cu B Fe Embodiment 1 28.6 0.05 0.1 1 / / 0.05 / / 0.1 0.05 0.99 69.06 Embodiment 2 28.6 0.1 0.2 0.9 / / 0.1 0.1 / / 0.05 1 68.95 Embodiment 3 28.6 0.08 / 0.9 / / 0.3 / / / 0.06 1.1 68.96 Embodiment 4 29.9 0.1 / 0.8 0.1 / 0.2 / / 0.2 0.08 0.99 67.63 Embodiment 5 30.4 0.05 / 0.8 0.1 0.35 / / / 0.1 0.99 67.21 Embodiment 6 29.9 0.1 0.1 0.6 / / 0.15 / / / 0.07 0.99 68.09 Embodiment 7 29.9 0.1 / 0.6 / / 0.15 / / / 0.07 0.99 68.19 Embodiment 8 30.4 0.05 / 0.3 0.2 / / 0.2 / / 0.15 0.99 67.71 Embodiment 9 32.1 0.3 / 0.2 / / / 0.08 0.08 / 0.15 1.1 65.99 Embodiment 10 28.6 0.05 0.1 1 / / 0.01 / / 0.03 0.03 0.99 69.19 Comparative 29.9 0.1 / 0.1 0.8 0.2 / / 0.2 0.08 0.99 67.63 Embodiment 1 Comparative 29.9 0.1 / 0.8 0.1 0 0.2 / / 0.2 0.25 0.99 67.46 Embodiment 2 Comparative 29.9 0.1 / 0.8 0.1 0 0.45 / / 0.2 0.08 0.99 67.38 Embodiment 3 Note: “/” refers to being without the element. (wt %) is the mass percentage.

Effect Embodiment 1

[0160] The neodymium-iron-boron magnet materials of Embodiments 1-9 and Comparative Embodiments 1-3 were tested as follows.

[0161] 1. Magnetic property test: The sintered magnets were tested for magnetic properties using PFM-14 magnetic property measuring instrument of Hirs, UK. The magnetic properties tested included remanence at 20° C. and 120° C., coercivity at 20° C. and 120° C., and the corresponding remanence temperature coefficient. Herein, the formula for calculating the temperature coefficient of remanence is: (Br.sub.high temperature−Br.sub.room temperature)/(Br.sub.room temperature(high temperature−room temperature))×100%, and the results are shown in Table 3 below.

[0162] 2. FE-EPMA testing: the perpendicular orientation surface of neodymium-iron-boron magnet material was polished and tested by field emission electron probe microanalyzer (FE-EPMA) (Japan Electronics Company (JEOL), 8530F). The area ratio of the grain boundary triangle, continuity of the two-grain grain boundary, mass ratio of C and O, and new phases were tested.

[0163] The continuity of the two-grain grain boundary was calculated according to the backscattered images of EPMA; the mass ratio of C and O in the two-grain grain boundary and grain boundary triangle and the new phase were measured by elemental analysis of EPMA.

[0164] The area ratio of the grain boundary triangle (%) refers to the ratio of the area of the grain boundary triangle to the total area of the “grain and grain boundary”.

[0165] The continuity of the grain boundary (%) refers to the ratio of the length occupied by the phases except for voids (phases such as B-rich phase, rare-earth-rich phase, rare earth oxides, rare earth carbides, etc.) in the grain boundary to the length of the total grain boundary.

[0166] The mass ratio of C and O in the grain boundary triangle (%) refers to the ratio of the mass of C and O in the grain boundary triangle to the total mass of all elements in the grain boundary.

[0167] The mass ratio (%) of C and O in the two-grain grain boundary refers to the ratio of the mass of C and O in the two-grain grain boundary to the total mass of all elements in the grain boundary.

[0168] The ratio of the area of the new phase in the two-grain grain boundary (%) refers to the ratio of the area of the new phase in the two-grain grain boundary to the total area of the two-grain grain boundary.

TABLE-US-00003 TABLE 3 mass mass percentage percentage Area Continuity of C of C percentage of Area of the and O in and O in new phase in Temperaturecoefficient percentage two-grain the two-grain the the two-grain of of the grain grain triangle grain Br(k Hcj(k 120-Br(k 20-120° C. Br triangle boundary boundary region boundary Gs) Oe) Gs) α(Br)%/° C. region % phase % (%) (%) new phase (%) Embodiment 1 14.51 25.23 12.94 −0.108 2.84 98.11 0.39 0.44 R.sub.78.89Fe.sub.19.59 0.85 Cu.sub.1.17M.sub.0.35 Embodiment 2 14.58 24.82 12.99 −0.109 2.65 98.09 0.32 0.41 R.sub.78.17Fe.sub.20.50 0.56 Cu.sub.1.07M.sub.0.26 Embodiment 3 14.53 24.75 12.97 −0.107 2.67 97.92 0.34 0.42 R.sub.77.87Fe.sub.20.50 0.58 Cu.sub.1.33M.sub.0.30 Embodiment 4 14.42 26.35 12.86 −0.108 2.54 98.22 0.33 0.48 R.sub.79.42Fe.sub.19.16 1.65 Cu.sub.1.07M.sub.0.35 Embodiment 5 14.45 26.21 12.91 −0.107 2.07 98.04 0.35 0.46 R.sub.78.68Fe.sub.19.77 1.54 Cu.sub.1.17M.sub.0.38 Embodiment 6 14.61 25.92 13.07 −0.105 2.45 98.08 0.35 0.44 R.sub.78.50Fe.sub.20.13 1.62 Cu.sub.1.03M.sub.0.34 Embodiment 7 14.61 25.6 13.02 −0.109 2.67 98.13 0.37 0.47 R.sub.78.87Fe.sub.19.79 0.97 Cu.sub.0.99M.sub.0.35 Embodiment 8 14.46 24.21 12.92 −0.107 2.65 98.21 0.36 0.42 R.sub.78.14Fe.sub.20.34 0.25 Cu.sub.1.23M.sub.0.29 Embodiment 9 14.31 24.11 12.78 −0.107 3.12 97.88 0.37 0.45 R.sub.78.68Fe.sub.19.80 0.35 Cu.sub.1.20M.sub.0.32 Embodiment 10 14.53 25.68 13.01 −0.105 2.79 98.16 0.34 0.42 R.sub.79.41Fe.sub.19.09 0.78 Cu.sub.1.17M.sub.0.33 Comparative 14.39 22.16 12.81 −0.110 3.86 96.45 0.21 0.54 × 0 Embodiment 1 Comparative 14.35 23.37 12.82 −0.107 3.92 96.51 0.25 0.52 × 0 Embodiment 2 Comparative 14.26 23.99 12.72 −0.108 3.78 96.34 0.24 0.56 × 0 Embodiment 3 Note: “×” refers to that the new phase with chemical composition of R.sub.xFe.sub.100-x-y-zCu.sub.yM.sub.z was not contained in the two-grain grain boundary phase.

[0169] From Table 3 mentioned above, the present disclosure, with the addition of a small amount of heavy rare earth elements and without the addition of Co element, can reach a comparable level to those with addition of a large amount of Co and heavy rare earth elements at present. In addition, due to the high content of the rare earth in the grain boundary, C and O are more distributed in the grain boundary and exist in the form of rare earth carbides and rare earth oxides, respectively. The difference values of the “mass ratio of C and O in the grain boundary triangle region” minus the “mass ratio (%) of C and O in the two-grain grain boundary” in Embodiments 1-10 reduce compared to those in the Comparative Embodiments 1-3, based on which the conclusion that the hetero-phases (rare earth carbides and rare earth oxides) migrate from the grain boundary triangle region to the two-grain grain boundary can be obtained, which mechanically explains the improvement of the continuity of the two-grain grain boundary.

Effect Embodiment 2

[0170] As shown in FIG. 1, the EPMA microstructure of the neodymium-iron-boron magnet material prepared in Embodiment 4 is shown. The point pointed by arrow 1 in the figure is the new phase of R.sub.xFe.sub.100-x-y-zCu.sub.yM.sub.z contained in the two-grain grain boundary (light gray area), the position pointed by arrow 2 is the grain boundary triangle region (silver-white area), and the position pointed by arrow 3 is the main phase of Nd.sub.2Fe.sub.14B (dark gray area). Combined with the data in Table 3, it can be further seen that the area of the grain boundary triangle region is smaller than that of the conventional magnet material.