Rare earth permanent magnet material and preparation method thereof

Abstract

The present invention discloses a rare earth permanent magnet material and a preparation method thereof. The method includes a sintering treatment step performed by laying a composite powder for diffusion on the surface of a neodymium iron boron magnetic powder layer and carrying out spark plasma sintering treatment to obtain a neodymium iron boron magnet with a diffusion layer solidified on the surface thereof, and diffusion heat treatment and tempering steps. The method of the present invention has high efficiency, good diffusion effects, and reduced quantities of heavy rare earth elements.

Claims

1. A preparation method of a rare earth permanent magnet material, characterized by comprising: a sintering treatment step performed by laying a composite powder for diffusion on the surface of a neodymium iron boron magnetic powder layer and carrying out spark plasma sintering treatment to obtain a neodymium iron boron magnet with a diffusion layer solidified on the surface thereof, wherein a compositional proportional formula of the composite powder for diffusion is (TbF.sub.3).sub.95Nd.sub.2Al.sub.3, (DyF.sub.3).sub.95Nd.sub.1Al.sub.4, (DyF.sub.3).sub.85Nd.sub.5Al.sub.10, (DyF.sub.3).sub.83Nd.sub.10Al.sub.7 or (DyF.sub.3).sub.75Nd.sub.18Al.sub.7; a diffusion heat treatment step performed by carrying out a diffusion heat treatment on the neodymium iron boron magnet with the diffusion layer solidified on the surface thereof and performing a cooling to obtain a diffused neodymium iron boron magnet; and a tempering treatment step performed by carrying out a tempering treatment on the diffused neodymium iron boron magnet to obtain the rare earth permanent magnet material.

2. The preparation method of a rare earth permanent magnet material according to claim 1, characterized in that a thickness of the neodymium iron boron magnetic powder layer is controlled to 1-12 mm in an orientation direction.

3. The preparation method of a rare earth permanent magnet material according to claim 1, characterized in that conditions of the diffusion heat treatment are that a vacuum degree is not lower than 10.sup.?3 Pa, a temperature is 700-950? C., a temperature holding time is 2?30 hours.

4. The preparation method of a rare earth permanent magnet material according to claim 1, characterized in that the cooling means furnace cooling to not higher than 50? C.

5. The preparation method of a rare earth permanent magnet material according to claim 1 characterized in that a temperature of the tempering treatment is 420-640? C., and a temperature holding time of the tempering treatment is 2-10 hours.

6. The preparation method of a rare earth permanent magnet material according to claim 1, characterized in that conditions of the spark plasma sintering treatment are that a vacuum degree is not lower than 10.sup.?3 Pa, a pressure is 20-60 MPa, and a temperature is 700-900? C.

7. The preparation method of a rare earth permanent magnet material according to claim 1, characterized in that a particle size of the composite powder for diffusion is smaller than 150 mesh.

8. The preparation method of a rare earth permanent magnet material according to claim 7, characterized in that conditions of the spark plasma sintering treatment are that a vacuum degree is not lower than 10.sup.?3 Pa, a pressure is 20-60 MPa, and a temperature is 700-900? C.

9. The preparation method of a rare earth permanent magnet material according to claim 1, characterized in that a thickness of the composite powder for diffusion laid on the surface of the neodymium iron boron magnetic powder layer is 5-30 ?m.

10. The preparation method of a rare earth permanent magnet material according to claim 9, characterized in that the surface on which the composite powder for diffusion is laid is perpendicular to an orientation of the neodymium iron boron magnetic powder.

11. The preparation method of a rare earth permanent magnet material according to claim 9, characterized in that conditions of the spark plasma sintering treatment are that a vacuum degree is not lower than 10.sup.?3 Pa, a pressure is 20-60 MPa, and a temperature is 700-900? C.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is a comprehensive magnetic performance diagram of the magnet prepared by example 1.

DETAILED DESCRIPTION OF THE EMBODIMENTS

(2) The present invention will be further described in combination with examples below. Examples of the present invention are only used to describe the present invention, not to limit the present invention.

(3) The neodymium iron boron magnetic powder used in the following examples is prepared by air flow milling. It can be a commercial product, or it can be prepared according to common methods.

(4) The SPS technology adopted by the present invention is a pressure sintering method which uses direct-current pulse current for electrifying sintering. The basic principle is that the discharge plasma generated instantaneously by supplying a direct-current pulse current to the electrode causes each particle in the sintered body to generate Joule heat uniformly and activates the particle surface, and sintering is achieved while the pressure is applied. The application of the SPS technology to the present invention has the following characteristics that: (1) sintering temperature is low, generally as low as 700-900? C.; (2) temperature holding time for sintering is short, only 3-15 minutes; (3) fine and uniform structures can be obtained; (4) High density materials can be obtained.

Example 1

(5) (1) Preparation of the composite powder based on the compositional formula (component formula) of the powder (TbF.sub.3).sub.95Nd.sub.2Al.sub.3 (the subscript in the formula is the atomic percentage of the corresponding element): TbF.sub.3 powder (particle size: ?150 mesh), metal Nd powder (particle size: ?150 mesh), and metal Al powder (particle size: ?150 mesh) are weighed, and the above powder is mixed uniformly and passed through a sieve of 150 mesh, and the powder under the sieve (called as siftage hereafter) is taken as the composite powder, wherein the powder mixing and sieving process is performed under a nitrogen environment.

(6) (2) The neodymium iron boron magnetic powder for commerce (compositional ratio: Nd.sub.92Pr.sub.3Dy.sub.1.2Tb.sub.0.6Fe.sub.80B.sub.6, wherein the subscript is the atomic percentage of the corresponding element) obtained by air flow milling is placed in a cemented carbide mold, and at the same time the composite powder which has a thickness of 20 ?m is laid on the surface layer perpendicular to the orientation) prepared by step (1). The neodymium iron boron magnet with (TbF.sub.3).sub.95Nd.sub.2Al.sub.3 powder solidified layer solidified on the surface thereof is obtained by hot-pressing sintering under the 10.sup.?3 pa of vacuum degree, 30 Mpa of pressure, and 750? C. of temperature, using spark plasma sintering technology, wherein the thickness in the orientation direction is 6 mm.

(7) (3) The neodymium iron boron magnet with one uniform powder solidified layer on the surface obtained in step (2) is placed in a vacuum heat treatment furnace, and maintained under the 10.sup.?3 pa of vacuum and 800? C. of temperature for 6 hours for the diffusion heat treatment; and cooled with furnace to no higher than 50? C.

(8) (4) The magnet obtained in step (3) is further subjected to tempering treatment at 510? C. for 4 hours to obtain a magnet with improved performance, which is the rare earth permanent magnet material of the present invention.

(9) Control 1 is set when a magnet with improved performance is prepared according to the method of this example. The preparation method of control 1 is as follows: using traditional powder metallurgy technology (as for detailed preparation technology, refer to the contents in chapters 7-11 of Sintered neodymium iron boron rare earth permanent magnet material and technology Zhou Shouzeng, et al., 2012, Metallurgical Industry Press) to perform smelting, powdering, pressing, and sintering with the same composition formulation as example 1; the properties of magnet obtained are shown in Table 1.

(10) FIG. 1 is a BH curve of performance tests of the magnets of the example 1 of the present invention and control 1; it can be seen from FIG. 1 that after the technical treatment of steps (2), (3), and (4) of this example, the coercive force of the sintered neodymium iron boron increases from 25070 Oe to 41330 Oe, with an increase of 16260 Oe, and the residual magnetism of the sintered neodymium iron boron decreases slightly, that is, from 13010 Gs to 12790 Gs, with a decrease of 220 Gs. After processing, the coercive force of comprehensive magnetic properties Hcj+(BH).sub.max of the sintered neodymium iron boron is 80.66.

Example 2

(11) (1) Preparation of the composite powder based on the proportional formula of the powder (DyF.sub.3).sub.95Nd.sub.1Al.sub.4 (the subscript in the formula is the atomic percentage of the corresponding element): DyF.sub.3 powder (particle size: ?150 mesh), metal Nd powder (particle size: ?150 mesh), and metal Al powder (particle size: ?150 mesh) are weighed, and the above powder is mixed uniformly and passed through a sieve of 150 mesh, wherein the powder mixing and sieving process is performed under a nitrogen environment.

(12) (2) The neodymium iron boron magnetic powder for commerce (composition ratio: Nd.sub.10.8Pr.sub.3Tb.sub.0.4Fe.sub.79.8B.sub.6, wherein the subscript is the atomic percentage of the corresponding element) obtained by air flow milling is placed in a cemented carbide mold, and at the same time 25 ?m thickness of the powder prepared by step (1) is laid on the surface layer in the direction which is perpendicular to the orientation. The neodymium iron boron magnet with (DyF.sub.3).sub.95Nd.sub.1Al.sub.4 powder solidified layer solidified on the surface thereof is obtained by hot-pressing sintering under the 10.sup.?3 pa of vacuum, 30 Mpa of pressure, and 750? C. of temperature, using spark plasma sintering technology, wherein the thickness in the orientation direction is 7 mm.

(13) (3) The magnet with a uniform powder solidified layer on the surface thereof obtained in step (2) is placed in a vacuum heat treatment furnace, and maintained under the vacuum of 10.sup.?3 pa and the temperature of 800? C. for 6 hours; and cooled with furnace to no higher than 50? C.

(14) (4) The magnet obtained in step (3) is further subjected to tempering treatment at 510? C. for 4 hours to obtain a magnet with improved performance.

(15) Control 2 is set when a magnet with improved performance is prepared according to the method of this example. The preparation method of control 2 is as follows: using traditional powder metallurgy technology (as for detailed preparation technology, refer to the contents in chapters 7-11 of Sintered neodymium iron boron rare earth permanent magnet material and technology Zhou Shouzeng, et al., 2012, Metallurgical Industry Press) to perform smelting, powdering, molding, and sintering with the same composition formulation as example 2; the properties of the magnet obtained are shown in Table 1.

(16) The coercive force of the rare earth permanent magnet material prepared and obtained in this example increases by 7700 oe, and the residual magnetism decreases slightly by 185 Gs. The magnet performance test results of example 2 and control 2 are shown in Table 1.

Example 3

(17) (1) Preparation of the composite powder based on the proportional formula of the powder (TbF.sub.3).sub.95Cu.sub.5 (the subscript in the formula is the atomic percentage of the corresponding element): TbF.sub.3 powder (particle size: ?150 mesh) and metal Cu powder (particle size: ?150 mesh) are weighed, and the above powder is mixed uniformly and passed through a sieve of 150 mesh, wherein the powder mixing and sieving process is performed under a nitrogen environment.

(18) (2) The neodymium iron boron magnetic powder for commerce (composition ratio: Nd.sub.11.9Pr.sub.3Dy.sub.0.1Fe.sub.79B.sub.6, wherein the subscript is the atomic percentage of the corresponding element) obtained by air flow milling is placed in a cemented carbide mold, and at the same time, 30 ?m thickness of the powder prepared by step (1) is laid on the surface layer in the direction which is perpendicular to the orientation. The neodymium iron boron magnet with (TbF.sub.3).sub.95Cu.sub.5 powder solidified layer solidified on the surface thereof is obtained by hot-pressing sintering under the 10.sup.?3 pa of vacuum, 50 Mpa of pressure, and 780? C. of temperature, using spark plasma sintering technology, wherein the thickness in the orientation direction is 12 mm.

(19) (3) The magnet with a uniform powder solidified layer on the surface obtained in step (2) is placed in a vacuum heat treatment furnace, and maintained under the 10.sup.?3 pa of vacuum and 850? C. of temperature for 6 hours; and cooled with furnace to no higher than 50? C.

(20) (4) The magnet obtained in step (3) is further subjected to tempering treatment at 510? C. for 4 hours to obtain a magnet with improved performance.

(21) Control 3 is set when a magnet with improved performance is prepared according to the method of this example. The preparation method of control 3 is as follows: using traditional powder metallurgy technology (as for detailed preparation technology, refer to the contents in chapters 7-11 of Sintered neodymium iron boron rare earth permanent magnet material and technology Zhou Shouzeng, et al., 2012, Metallurgical Industry Press) to perform smelting, powdering, molding, and sintering with the same composition formulation as example 3; the properties of magnet obtained are shown in Table 1.

(22) The coercive force of the rare earth permanent magnet material prepared and obtained in this example increases by 14000 Oe, and the residual magnetism decreases slightly by 190 Gs. The magnet performance test results of example 3 and control 3 are shown in Table 1.

Example 4

(23) (1) Preparation of the composite powder based on the proportional formula of the powder (HoF.sub.3).sub.97Pr.sub.1Cu.sub.2 (the subscript in the formula is the atomic percentage of the corresponding element): HoF.sub.3 powder (particle size: ?150 mesh), metal Pr powder (particle size: ?150 mesh) and metal Cu powder (particle size: ?150 mesh) are weighed, and the above powder is mixed uniformly and passed through a sieve of 150 mesh, wherein the powder mixing and sieving process is performed under a nitrogen gas environment.

(24) (2) The neodymium iron boron magnetic powder for commerce (composition ratio: Nd.sub.11.8Pr.sub.3Dy.sub.0.1Fe.sub.79B.sub.6.1, wherein the subscript is the atomic percentage of the corresponding element) obtained by air flow milling is placed in a cemented carbide mold, and at the same time, 20 ?m thickness of the powder prepared by step (1) is laid on the surface layer in the direction which is perpendicular to orientation. The neodymium iron boron magnet with (HoF.sub.3).sub.97Pr.sub.1Cu.sub.2 powder solidified layer solidified on the surface thereof is obtained by hot-pressing sintering under the 10.sup.?3 pa of vacuum, 20 Mpa of pressure, and 750? C. of temperature, using spark plasma sintering technology, wherein the thickness in the orientation direction is 3 mm.

(25) (3) The magnet with a uniform powder solidified layer on the surface obtained in step (2) is placed in a vacuum heat treatment furnace, and maintained under the less than 10.sup.?3 pa of vacuum and 800? C. of temperature for 6 hours; and cooled with furnace to no higher than 50? C.

(26) (4) The magnet obtained in step (3) is further subjected to tempering treatment at 510? C. for 4 hours to obtain a magnet with improved performance.

(27) Control 4 is set when a magnet with improved performance is prepared according to the method of this example. The preparation method of control 4 is as follows: using traditional powder metallurgy technology (as for detailed preparation technology, refer to the contents in chapters 7-11 of Sintered neodymium iron boron rare earth permanent magnet material and technology Zhou Shouzeng, et al., 2012, Metallurgical Industry Press) to perform smelting, powdering, molding, and sintering with the same composition formulation as example 4; the properties of magnet obtained are shown in Table 1.

(28) The coercive force of the rare earth permanent magnet material prepared and obtained in this example increases by 4500 Oe, and the residual magnetism decreases slightly by 215 Gs. The magnet performance test results of example 4 and control 4 are shown in Table 1.

Example 5

(29) (1) Preparation of the composite powder based on the proportional formula of the powder (DyTb)F.sub.3).sub.96Cu.sub.1Al.sub.3 (the subscript in the formula is the atomic percentage of the corresponding element): (DyTb)F.sub.3 powder (particle size: ?150 mesh), metal Cu powder (particle size: ?150 mesh) and metal Al powder (particle size: ?150 mesh) are weighed, and the above powder is mixed uniformly and passed through a sieve of 150 mesh, wherein the powder mixing and sieving process is performed under a nitrogen environment.

(30) (2) The neodymium iron boron magnetic powder for commerce (composition ratio: Nd.sub.14.6Tb.sub.0.3Fe.sub.79B.sub.6.1, wherein the subscript is the atomic percentage of the corresponding element) obtained by air flow milling is placed in a cemented carbide mold, and at the same time, 30 ?m thickness of the powder prepared by step (1) is laid on the surface layer in the direction which is perpendicular to the orientation. The neodymium iron boron magnet with ((DyTb)F.sub.3).sub.96Cu.sub.1Al.sub.3 powder solidified layer solidified on the surface thereof is obtained by hot-pressing sintering under the 10.sup.?3 pa of vacuum, 20 Mpa of pressure, and 750? C. of temperature, using spark plasma sintering technology, wherein the thickness in the orientation direction is 8 mm.

(31) (3) The magnet with a uniform powder solidified layer on the surface obtained in step (2) is placed in a vacuum heat treatment furnace, and maintained under the 10.sup.?3 pa of vacuum and 800? C. of temperature for 6 hours; and cooled with furnace to no higher than 50? C.

(32) (4) The magnet obtained in step (3) is further subjected to tempering treatment at 510? C. for 4 hours to obtain a magnet with improved performance.

(33) Control 5 is set when a magnet with improved performance is prepared according to the method of this example. The preparation method of control 5 is as follows: using traditional powder metallurgy technology (as for detailed preparation technology, refer to the contents in chapters 7-11 of Sintered neodymium iron boron rare earth permanent magnet material and technology Zhou Shouzeng, et al., 2012, Metallurgical Industry Press) to perform smelting, powdering, molding, and sintering with the same composition formulation as example 5; the properties of magnet obtained are shown in Table 1.

(34) The coercive force of the rare earth permanent magnet material prepared and obtained in this example increases by 12000 Oe, and the residual magnetism decreases slightly by 188 Gs. The magnet performance test results of example 5 and control 5 are shown in Table 1.

Example 6

(35) (1) Preparation of the composite powder based on the proportional formula of the powder (GdF.sub.3).sub.98Cu.sub.2 (the subscript in the formula is the atomic percentage of the corresponding element): GdF.sub.3 powder (particle size: ?150 mesh) and metal Cu powder (particle size: ?150 mesh) are weighed, and the above powder is mixed uniformly and passed through a sieve of 150 mesh, wherein the powder mixing and sieving process is performed under a nitrogen environment.

(36) (2) The neodymium iron boron magnetic powder for commerce (composition ratio: Nd.sub.11.5Pr.sub.3Dy.sub.0.3Fe.sub.79.2B.sub.6, wherein the subscript is the atomic percentage of the corresponding element) obtained by air flow milling is placed in a cemented carbide mold, and at the same time, 20 ?m thickness of the powder prepared by step (1) is laid on the surface layer in the direction which is perpendicular to the orientation. The neodymium iron boron magnet with (GdF.sub.3).sub.98Cu.sub.2 powder solidified layer solidified on the surface thereof is obtained by hot-pressing sintering under the 10.sup.?3 pa of vacuum, 20 Mpa of pressure, and 750? C. of temperature, using spark plasma sintering technology, wherein the thickness in the orientation direction is 4 mm.

(37) (3) The magnet with a uniform powder solidified layer on the surface obtained in step (2) is placed in a vacuum heat treatment furnace, and maintained under the less than 10.sup.?3 pa of vacuum and 800? C. of temperature for 6 hours; and cooled with furnace to no higher than 50? C.

(38) (4) The magnet obtained in step (3) is further subjected to tempering treatment at 510? C. for 4 hours to obtain a magnet with improved performance.

(39) Control 6 is set when a magnet with improved performance is prepared according to the method of this example. The preparation method of control 6 is as follows: using traditional powder metallurgy technology (as for detailed preparation technology, refer to the contents in chapters 7-11 of Sintered neodymium iron boron rare earth permanent magnet material and technology Zhou Shouzeng, et al., 2012, Metallurgical Industry Press) to perform smelting, powdering, molding, and sintering with the same composition formulation as example 6; the properties of magnet obtained are shown in Table 1.

(40) The coercive force of the rare earth permanent magnet material prepared and obtained in this example increases by 4600 Oe, and the residual magnetism decreases slightly by 218 Gs. The magnet performance test results of example 6 and control 6 are shown in Table 1.

Example 7

(41) (1) Preparation of the composite powder based on the proportional formula of the powder (TbO.sub.3).sub.94Nd.sub.1Al.sub.5 (the subscript in the formula is the atomic percentage of the corresponding element): TbO.sub.3 powder (particle size: ?150 mesh), metal Nd powder (particle size: ?150 mesh) and metal Al powder (particle size: ?150 mesh) are weighed, and the above powder is mixed uniformly and passed through a sieve of 150 mesh, wherein the powder mixing and sieving process is performed under a nitrogen environment.

(42) (2) The neodymium iron boron magnetic powder for commerce (composition ratio: Nd.sub.10.7Pr.sub.3Tb.sub.0.5Fe.sub.80B.sub.5.8, wherein the subscript is the atomic percentage of the corresponding element) obtained by air flow milling is placed in a cemented carbide mold, and at the same time, 30 ?m thickness of the powder prepared by step (1) is laid on the surface layer in the direction which is perpendicular to the orientation. The neodymium iron boron magnet with (TbO.sub.3).sub.94Nd.sub.1Al.sub.5 powder solidified layer solidified on the surface thereof is obtained by hot-pressing sintering under the 10.sup.?3 pa of vacuum, 50 Mpa of pressure, and 780? C. of temperature, using spark plasma sintering technology, wherein the thickness in the orientation direction is 12 mm.

(43) (3) The magnet with a uniform powder solidified layer on the surface obtained in step (2) is placed in a vacuum heat treatment furnace, and maintained under the 10.sup.?3 pa of vacuum and 800? C. of temperature for 6 hours; and cooled with furnace to no higher than 50? C.

(44) (4) The magnet obtained in step (3) is further subjected to tempering treatment at 510? C. for 4 hours to obtain a magnet with improved performance.

(45) Control 7 is set when a magnet with improved performance is prepared according to the method of this example. The preparation method of control 7 is as follows: using traditional powder metallurgy technology (as for detailed preparation technology, refer to the contents in chapters 7-11 of Sintered neodymium iron boron rare earth permanent magnet material and technology Zhou Shouzeng, et al., 2012, Metallurgical Industry Press) to perform smelting, powdering, molding, and sintering with the same composition formulation as example 7; the properties of magnet obtained are shown in Table 1.

(46) The coercive force of the rare earth permanent magnet material prepared and obtained in this example increases by 9000 Oe, and the residual magnetism decreases slightly by 195 Gs. The magnet performance test results of example 7 and control 7 are shown in Table 1.

Example 8

(47) (1) Preparation of the composite powder based on the proportional formula of the powder (DyO.sub.3).sub.97(PrNd).sub.2Al.sub.1 (the subscript in the formula is the atomic percentage of the corresponding element): DyO.sub.3 powder (particle size: ?150 mesh), metal PrNd powder (the ratio of Pr and Nd by weight is 1:4, particle size: ?150 mesh) and metal Al powder (particle size: ?150 mesh) are weighed, and the above powder is mixed uniformly and passed through a sieve of 150 mesh, wherein the powder mixing and sieving process is performed under a nitrogen environment.

(48) (2) The neodymium iron boron magnetic powder for commerce (composition ratio: Nd.sub.12.2Pr.sub.3.1Fe.sub.78.6B.sub.6.1, wherein the subscript is the atomic percentage of the corresponding element) obtained by air flow milling is placed in a cemented carbide mold, and at the same time, 23 ?m thickness of the powder prepared by step (1) is laid on the surface layer in the direction which is perpendicular to the orientation. The neodymium iron boron magnet with (DyO.sub.3).sub.97(PrNd).sub.2Al.sub.1 powder solidified layer solidified on the surface thereof is obtained by hot-pressing sintering under the 10.sup.?3 pa of vacuum, 40 Mpa of pressure, and 760? C. of temperature, using spark plasma sintering technology, wherein the thickness in the orientation direction is 6.5 mm.

(49) (3) The magnet with a uniform powder solidified layer on the surface obtained in step (2) is placed in a vacuum heat treatment furnace, and maintained under the less than 10.sup.?3 pa of vacuum and the 800? C. of temperature for 6 hours; and cooled with furnace to no higher than 50? C.

(50) (4) The magnet obtained in step (3) is further subjected to tempering treatment at 510? C. for 4 hours to obtain a magnet with improved performance.

(51) Control 8 is set when a magnet with improved performance is prepared according to the method of this example. The preparation method of control 8 is as follows: using traditional powder metallurgy technology (as for detailed preparation technology, refer to the contents in chapters 7-11 of Sintered neodymium iron boron rare earth permanent magnet material and technology Zhou Shouzeng, et al., 2012, Metallurgical Industry Press) to perform smelting, powdering, molding, and sintering with the same composition formulation as example 8; the properties of magnet obtained are shown in Table 1.

(52) The coercive force of the rare earth permanent magnet material prepared and obtained in this example increases by 7700 Oe, and the residual magnetism decreases slightly by 197 Gs. The magnet performance test results of example 8 and control 8 are shown in Table 1.

Example 9

(53) (1) Preparation of the composite powder based on the proportional formula of the powder (TbF.sub.3).sub.46(DyO.sub.3).sub.48Nd.sub.2ZnSnCu.sub.2 (the subscript in the formula is the atomic percentage of the corresponding element): TbF.sub.3 and DyO.sub.3 powder (particle size: ?150 mesh), metal Nd powder (particle size: ?150 mesh), and metal Zn, Sn, Cu powder (particle size: ?150 mesh) are weighed, and the above powder is mixed uniformly and passed through a sieve of 150 mesh, wherein the powder mixing and sieving process is performed under a nitrogen environment.

(54) (2) The neodymium iron boron magnetic powder for commerce (composition ratio: Nd.sub.11.5Tb.sub.1.6Fe.sub.80.9B.sub.6, wherein the subscript is the atomic percentage of the corresponding element) obtained by air flow milling is placed in a cemented carbide mold, and at the same time, 23 ?m thickness of the powder prepared by step (1) is laid on the surface layer in the direction which is perpendicular to the orientation. The neodymium iron boron magnet with (TbF.sub.3).sub.46(DyO.sub.3).sub.48Nd.sub.2ZnSnCu.sub.2 powder solidified layer solidified on the surface thereof is obtained by hot-pressing sintering under the 10.sup.?3 pa of vacuum, 40 Mpa of pressure, and 760? C. of temperature, using spark plasma sintering technology, wherein the thickness in the orientation direction is 6.5 mm.

(55) (3) The magnet with a uniform powder solidified layer on the surface obtained in step (2) is placed in a vacuum heat treatment furnace, and maintained under the less than 10.sup.?3 pa of vacuum and 800? C. of temperature for 6 hours; and cooled with furnace to no higher than 50? C.

(56) (4) The magnet obtained in step (3) is further subjected to tempering treatment at 510? C. for 4 hours to obtain a magnet with improved performance.

(57) Control 9 is set when a magnet with improved performance is prepared according to the method of this example. The preparation method of control 9 is as follows: using traditional powder metallurgy technology (as for detailed preparation technology, refer to the contents in chapters 7-11 of Sintered neodymium iron boron rare earth permanent magnet material and technology Zhou Shouzeng, et al., 2012, Metallurgical Industry Press) to perform smelting, powdering, molding, and sintering with the same composition formulation as example 9; the properties of magnet obtained are shown in Table 1.

(58) The coercive force of the rare earth permanent magnet material prepared and obtained in this example increases by 9100 Oe, and the residual magnetism decreases slightly by 190 Gs. The magnet performance test results of example 9 and control 9 are shown in Table 1.

(59) TABLE-US-00001 TABLE 1 The magnet performance test results of Examples 1-9 and controls 1-9 Dimension Br Hcj Dimension Br Hcj Item (mm.sup.3) (kGs) (kOe) Item (mm.sup.3) (kGs) (kOe) Example 1 20 * 15 * 1.96 12.79 41.33 Control 1 20 * 15 * 1.96 13.01 25.07 Example 2 25 * 15 * 3 13.625 25.53 Control 2 25 * 15 * 3 13.81 17.83 Example 3 25 * 15 * 5 13.13 27.28 Control 3 25 * 15 * 5 13.32 13.28 Example 4 25 * 15 * 3 13.095 17.68 Control 4 25 * 15 * 3 13.31 13.18 Example 5 30 * 15 * 6 14.012 32.2 Control 5 30 * 15 * 6 14.2 20.2 Example 6 25 * 15 * 3 11.612 20.5 Control 6 25 * 15 * 3 11.83 15.9 Example 7 35 * 15 * 8 13.505 27.5 Control 7 35 * 15 * 8 13.7 18.5 Example 8 35 * 15 * 6 13.003 21.15 Control 8 35 * 15 * 6 13.2 13.45 Example 9 35 * 15 * 4.5 13.48 33.9 Control 9 35 * 15 * 4.5 13.67 24.8

Examples 10-13

(60) Except that the thickness of the composite powder laid is different from that of example 2, other process parameters of Examples 10-13 are the same as example 2; wherein the thickness of the composite powder layer in example 10 is about 12 ?m, the thickness of the composite powder layer in example 11 is about 20 ?m, the thickness of the composite powder layer in example 12 is about 5 ?m, and the thickness of the composite powder layer in example 13 is about 30 ?m. The magnet performance test results of examples 10-13 and example 2 are shown in Table 2.

Examples 14-15

(61) Except for the holding temperature and the temperature holding time in the vacuum heat treatment in step (3) of examples 14-15, which are different from those of example 2, other process parameters of examples 14-15 are the same as example 2; wherein the condition of vacuum heat treatment in example 14 is: the 950? C. of holding temperature for 4 h, and the condition of vacuum heat treatment in example 15 is the 700? C. of holding temperature for 30 h. The magnet performance test results of examples 14-15 and example 2 are shown in Table 2.

Examples 16-17

(62) Except for the tempering treatment temperature and time in step (4) of examples 16-17, which are different from those of example 2, other process parameters of examples 16-17 are the same as example 2; wherein the tempering treatment condition in example 16 is: (tempering treatment at) 420? C. for 10 h, the tempering treatment condition in example 17 is: (tempering treatment) at 640? C. for 2 h. The magnet performance test results of examples 16-17 and example 2 are shown in Table 2.

(63) TABLE-US-00002 TABLE 2 The magnet performance test results of examples 10-17 and example 2 Item Dimension (mm.sup.3) Br (kGs) Hcj (kOe) Example 2 25 * 15 * 3 13.625 25.53 Example 10 25 * 15 * 3 13.75 20.55 Example 11 25 * 15 * 3 13.69 23.05 Example 12 25 * 15 * 3 13.78 19.24 Example 13 25 * 15 * 3 13.61 25.65 Example 14 25 * 15 * 3 13.55 25.02 Example 15 25 * 15 * 3 13.76 20.73 Example 16 25 * 15 * 3 13.64 24.52 Example 17 25 * 15 * 3 13.63 24.06

Examples 18-23

(64) Except that the composition of the composite powder used in examples 18-23 is different from that of example 2, other process parameters of examples 18-23 are the same as those of example 2; the specific composition of the composite powder and the magnet performance test results of examples 18-23 and example 2 are shown in Table 3.

(65) TABLE-US-00003 TABLE 3 The magnet performance test results of examples 18-23 and example 2 The composition of Dimension Br Hcj Item composite powder (mm.sup.3) (kGs) (kOe) Example 2 (DyF.sub.3).sub.95Nd.sub.1Al.sub.4 25*15*3 13.625 25.53 Example 18 (DyF.sub.3).sub.50Nd.sub.10Al.sub.40 25*15*3 13.71 22.09 Example 19 (DyF.sub.3).sub.55Nd.sub.20Al.sub.25 25*15*3 13.69 22.92 Example 20 (DyF.sub.3).sub.85Nd.sub.5Al.sub.10 25*15*3 13.66 24.96 Example 21 (DyF.sub.3).sub.70Nd.sub.10Al.sub.20 25*15*3 13.68 23.61 Example 22 (DyF.sub.3).sub.83Nd.sub.10Al.sub.17 25*15*3 13.66 24.8 Example 23 (DyF.sub.3).sub.75Nd.sub.18A.sub.17 25*15*3 13.67 24.32

Examples 24-26

(66) The composite powder used in examples 1-3 is added directly into the sintered neodymium iron boron powder, and after mixing, SPS hot pressing is performed, followed by sintering and aging in examples 24-26. The process parameters of SPS hot pressing, sintering and aging in examples 24-26 are the same as those of the corresponding example. The test results of examples 24-26, examples 1-3, and controls 1-3 are shown in Table 4.

(67) TABLE-US-00004 TABLE 4 The magnet performance test results of examples 1-3, examples 24-26 and controls 1-3 Item Dimension (mm.sup.3) Br (kGs) Hcj (kOe) Control 1 20 * 15 * 1.96 13.01 25.07 Example 1 20 * 15 * 1.96 12.79 41.33 Example 24 20 * 15 * 1.96 12.99 25.88 Control 2 25 * 15 * 3 13.81 17.83 Example 2 25 * 15 * 3 13.625 25.53 Example 25 25 * 15 * 3 13.8 18.35 Control 3 25 * 15 * 5 13.32 13.28 Example 3 25 * 15 * 5 13.13 27.28 Example 26 25 * 15 * 5 13.3 14.1

(68) Obviously, the above-mentioned examples are merely examples for clear description, and are not limitations on the embodiment. For those skilled in the art, other different forms of changes or modifications can be made on the basis of the above-mentioned description. There is no need and cannot be exhaustive for all embodiments. However, the obvious changes or modifications extended thereby are still within the protection scope created by the present invention.