Method for preparing neodymium-iron-boron (Nd—Fe—B)-based sintered magnet

Abstract

A method for preparing a Nd—Fe—B-based sintered magnet. The method includes: 1) providing a master alloy and an auxiliary alloy, the master alloy being a Nd—Fe—B alloy ingot or cast strip, the auxiliary alloy being a heavy rare earth alloy; 2) breaking up the master alloy using a hydrogen decrepitation process to yield a crude powder, conducting hydrogen absorption treatment on the auxiliary alloy and breaking up the hydrogenated auxiliary alloy to yield hydride particles; 3) uniformly mixing and stirring the crude powder of the master alloy and the hydride particles of the auxiliary alloy to yield a mixture; 4) milling the mixture obtained in step 3) to yield powders; 5) uniformly stirring the powders obtained in step 4) and conducting orientation forming treatment on the powders, to yield a raw body of a Nd—Fe—B based magnet; and 6) sintering the raw body of the Nd—Fe—B based magnet.

Claims

1. A method for preparing a Neodymium-Iron-Boron (Nd—Fe—B) based sintered magnet, the method comprising: 1) providing a master alloy and an auxiliary alloy, the master alloy being a Nd—Fe—B alloy ingot or cast strip, the auxiliary alloy being a heavy rare earth alloy having a formula of R.sub.aM.sub.bFe.sub.100−a−b, wherein R represents Gd, Tb, Dy, Ho, or a mixture thereof, M represents Co, Mn, Cu, Al, Ti, Ga, Zr, V, Hf, W, B, Nb, or a mixture thereof, a and b are both expressed in percentage by weight, 30≦a<100, 0≦b<70; 2) breaking up the master alloy using a hydrogen decrepitation process to yield a crude powder, conducting hydrogen absorption treatment on the auxiliary alloy and breaking up the hydrogenated auxiliary alloy to yield hydride particles; 3) uniformly mixing and stirring the crude powder of the master alloy and the hydride particles of the auxiliary alloy to yield a mixture, wherein a weight percentage of the crude powder of the master alloy is greater than or equal to 75% and less than 100% of a total weight of the mixture, and a weight percentage of the hydride particles of the auxiliary alloy is greater than 0 and less than or equal to 25% of a total weight of the mixture; 4) milling the mixture obtained in step 3) to yield powders having a surface area mean diameter of between 1 and 5 μm; 5) uniformly stirring the powders obtained in step 4) and conducting orientation forming treatment on the powders, to yield a raw body of a Nd—Fe—B based magnet; and 6) sintering the raw body of the Nd—Fe—B based magnet.

2. The method of claim 1, wherein the orientation forming treatment in step 5) employs an orientation magnetic field of between 1 and 5 T.

3. The method of claim 1, wherein a sintering process in step 6) comprises the following steps: 6-1) introducing the raw body of the Nd—Fe—B based magnet to a vacuum sintering furnace, heating the furnace from 800° C. to 1000° C. for dehydrogenation for 2 hours; 6-2) heating the vacuum sintering furnace to a temperature between 1010 and 1120° C., and sintering the raw body for between 1 and 4 hours; and 6-3) allowing the raw body for a primary tempering at 850-950° C. for between 1 and 4 hours and for a secondary tempering at 450-600° C. for between 1 and 4 hours, to yield the Nd—Fe—B based sintered magnet.

4. The method of claim 1, wherein the master alloy in step 1) has a formula of Nd.sub.mN.sub.nX.sub.tFe.sub.100−m−n−k−tB.sub.k, N represents La, Ce, Pr, Dy, Tb, or a mixture thereof, X represents Co, Mn, Cu, Al, Ti, Ga, Zr, V, Hf, W, Nb, or a mixture thereof, m, n, t, and k are all expressed in percentage by weight, 28.5≦m+n≦33, 0≦t≦5, 0.9≦k≦1.2.

5. The method of claim 4, wherein the orientation forming treatment in step 5) employs an orientation magnetic field of between 1 and 5 T.

6. The method of claim 4, wherein a sintering process in step 6) comprises the following steps: 6-1) introducing the raw body of the Nd—Fe—B based magnet to a vacuum sintering furnace, heating the furnace from 800° C. to 1000° C. for dehydrogenation for 2 hours; 6-2) heating the vacuum sintering furnace to a temperature between 1010 and 1120° C., and sintering the raw body for between 1 and 4 hours; and 6-3) allowing the raw body for a primary tempering at 850-950° C. for between 1 and 4 hours and for a secondary tempering at 450-600° C. for between 1 and 4 hours, to yield the Nd—Fe—B based sintered magnet.

7. The method of claim 1, wherein the hydride particles in step 2) have hydrogen content by weight of being greater than or equal to 4000 ppm and less than or equal to 15000 ppm.

8. The method of claim 7, wherein the orientation forming treatment in step 5) employs an orientation magnetic field of between 1 and 5 T.

9. The method of claim 7, wherein a sintering process in step 6) comprises the following steps: 6-1) introducing the raw body of the Nd—Fe—B based magnet to a vacuum sintering furnace, heating the furnace from 800° C. to 1000° C. for dehydrogenation for 2 hours; 6-2) heating the vacuum sintering furnace to a temperature between 1010 and 1120° C., and sintering the raw body for between 1 and 4 hours; and 6-3) allowing the raw body for a primary tempering at 850-950° C. for between 1 and 4 hours and for a secondary tempering at 450-600° C. for between 1 and 4 hours, to yield the Nd—Fe—B based sintered magnet.

Description

DETAILED DESCRIPTION OF THE EMBODIMENTS

(1) For further illustrating the invention, experiments detailing a method for preparing a Nd—Fe—B based sintered magnet are described below. It should be noted that the following examples are intended to describe and not to limit the invention.

Example 1

(2) A method for preparing a Nd—Fe—B based sintered magnet, the method comprises:

(3) 1) Providing a master alloy and an auxiliary alloy. The master alloy was prepared using a strip casting technology, which was a Nd—Fe—B alloy cast strip. The auxiliary alloy was a Dy—Fe alloy. The master alloy comprised 32 wt. % of Nd, 1 wt. % of B, and 67 wt. % of Fe. The auxiliary alloy comprised 80 wt. % of Dy and 20 wt. % of Fe.

(4) 2) Breaking up the master alloy using a hydrogen decrepitation process to yield a crude powder, conducting hydrogen absorption treatment on the auxiliary alloy and breaking up the hydrogenated auxiliary alloy to yield hydride particles. The hydride particles had hydrogen content by weight of 4251 ppm.

(5) 3) Uniformly mixing and stirring the crude powder of the master alloy and the hydride particles of the auxiliary alloy to yield a mixture, a weight ratio of the crude powder of the master alloy to the hydride particles of the auxiliary alloy being 99:1.

(6) 4) Milling the mixture obtained in step 3) to yield powders having a surface area mean diameter of 3.22 μm.

(7) 5) Uniformly stirring the powders obtained in step 4) and conducting orientation forming treatment on the powders, to yield a raw body of a Nd—Fe—B based magnet, where the orientation forming treatment employed an orientation magnetic field of 1.6 T in the presence of nitrogen, followed by cold isostatic pressing treatment.

(8) 6) Sintering the raw body of the Nd—Fe—B based magnet.

(9) The sintering process in step 6) comprised the following steps:

(10) 6-1) introducing the raw body of the Nd—Fe—B based magnet to a vacuum sintering furnace, heating the furnace from 800° C. to 1000° C. for dehydrogenation for 2 hours;

(11) 6-2) heating the vacuum sintering furnace to a temperature of 1070° C., and sintering the raw body for 4 hours; and

(12) 6-3) allowing the raw body for a primary tempering at 890° C. for 2 hours and for a secondary tempering at 500° C. for 4 hours, to yield the Nd—Fe—B based sintered magnet.

(13) TABLE-US-00001 TABLE 1 Magnetic performance of Nd—Fe—B based sintered magnet after being added with 1 wt. % of heavy rare earth alloy (Dy.sub.80Fe.sub.20) Dy content B.sub.r H.sub.cB H.sub.cj (BH).sub.max H.sub.k (wt. %) (kGs) (kOe) (kOe) (MGsOe) (kOe) H.sub.k/H.sub.cj 0.8 11.8 11.47 18.61 33.84 17.74 0.95

Example 2

(14) A method for preparing a Nd—Fe—B based sintered magnet, the method comprises:

(15) 1) Providing a master alloy and an auxiliary alloy. The master alloy was prepared using a strip casting technology, which was a Nd—Fe—B alloy cast strip. The auxiliary alloy was a Dy—Fe alloy. The master alloy comprised 32 wt. % of Nd, 1 wt. % of B, and 67 wt. % of Fe. The auxiliary alloy comprised 80 wt. % of Dy and 20 wt. % of Fe.

(16) 2) Breaking up the master alloy using a hydrogen decrepitation process to yield a crude powder, conducting hydrogen absorption treatment on the auxiliary alloy and breaking up the hydrogenated auxiliary alloy to yield hydride particles. The hydride particles had hydrogen content by weight of 4251 ppm.

(17) 3) Uniformly mixing and stirring the crude powder of the master alloy and the hydride particles of the auxiliary alloy to yield a mixture, a weight ratio of the crude powder of the master alloy to the hydride particles of the auxiliary alloy being 97.5:2.5.

(18) 4) Milling the mixture obtained in step 3) to yield powders having a surface area mean diameter of 2.97 μm.

(19) 5) Uniformly stirring the powders obtained in step 4) and conducting orientation forming treatment on the powders, to yield a raw body of a Nd—Fe—B based magnet, where the orientation forming treatment employed an orientation magnetic field of 1.6 T in the presence of nitrogen, followed by cold isostatic pressing treatment.

(20) 6) Sintering the raw body of the Nd—Fe—B based magnet.

(21) The sintering process in step 6) comprised the following steps:

(22) 6-1) introducing the raw body of the Nd—Fe—B based magnet to a vacuum sintering furnace, heating the furnace from 800° C. to 1000° C. for dehydrogenation for 2 hours;

(23) 6-2) heating the vacuum sintering furnace to a temperature of 1065° C., and sintering the raw body for 4 hours; and

(24) 6-3) allowing the raw body for a primary tempering at 890° C. for 2 hours and for a secondary tempering at 480° C. for 4 hours, to yield the Nd—Fe—B based sintered magnet.

(25) TABLE-US-00002 TABLE 2 Magnetic performance of Nd—Fe—B based sintered magnet after being added with 2.5 wt. % of heavy rare earth alloy (Dy.sub.80Fe.sub.20) Dy content B.sub.r H.sub.cB H.sub.cj (BH).sub.max H.sub.k (wt. %) (kGs) (kOe) (kOe) (MGsOe) (kOe) H.sub.k/H.sub.cj 2 11.24 10.96 21.29 30.77 20.43 0.96

Example 3

(26) A method for preparing a Nd—Fe—B based sintered magnet, the method comprises:

(27) 1) Providing a master alloy and an auxiliary alloy. The master alloy was prepared using a strip casting technology, which was a Nd—Fe—B alloy cast strip. The auxiliary alloy was a heavy rare earth alloy ingot. The master alloy comprised 29 wt. % of Pr—Nd alloy, 1.2 wt. % of Dy, 0.98 wt. % of B, 67.82 wt. % of Fe, and 1 wt. % of Co. The auxiliary alloy comprised 69.5 wt. % of Dy, 5 wt. % of Nd, 0.8 wt. % of Ga, 0.7 wt. % of Cu, 1.6 wt. % of Al, and 22.4 wt. % of Fe.

(28) 2) Breaking up the master alloy using a hydrogen decrepitation process to yield a crude powder, conducting hydrogen absorption treatment on the auxiliary alloy and breaking up the hydrogenated auxiliary alloy to yield hydride particles. The hydride particles had hydrogen content by weight of 10840 ppm.

(29) 3) Uniformly mixing and stirring the crude powder of the master alloy and the hydride particles of the auxiliary alloy to yield a mixture, a weight ratio of the crude powder of the master alloy to the hydride particles of the auxiliary alloy being 99:1.

(30) 4) Milling the mixture obtained in step 3) to yield powders having a surface area mean diameter of 2.88 μm.

(31) 5) Uniformly stirring the powders obtained in step 4) and conducting orientation forming treatment on the powders, to yield a raw body of a Nd—Fe—B based magnet, where the orientation forming treatment employed an orientation magnetic field of 1.8 T in the presence of nitrogen, followed by cold isostatic pressing treatment.

(32) 6) Sintering the raw body of the Nd—Fe—B based magnet.

(33) The sintering process in step 6) comprised the following steps:

(34) 6-1) introducing the raw body of the Nd—Fe—B based magnet to a vacuum sintering furnace, heating the furnace from 800° C. to 1000° C. for dehydrogenation for 2 hours;

(35) 6-2) heating the vacuum sintering furnace to a temperature of 1061° C., and sintering the raw body for 4 hours; and

(36) 6-3) allowing the raw body for a primary tempering at 890° C. for 2 hours and for a secondary tempering at 480° C. for 4 hours, to yield the Nd—Fe—B based sintered magnet.

(37) TABLE-US-00003 TABLE 3 Magnetic performance of Nd—Fe—B based sintered magnet after being added with 1 wt. % of heavy rare earth alloy (Dy.sub.69.5Nd.sub.5Ga.sub.0.8Cu.sub.0.7Al.sub.1.6Fe.sub.22.4) Dy content B.sub.r H.sub.cB H.sub.cj (BH).sub.max H.sub.k (wt. %) (kGs) (kOe) (kOe) (MGsOe) (kOe) H.sub.k/H.sub.cj 1.88 13.39 12.96 18.54 43.57 17.85 0.96

Example 4

(38) A method for preparing a Nd—Fe—B based sintered magnet, the method comprises:

(39) 1) Providing a master alloy and an auxiliary alloy. The master alloy was prepared using a strip casting technology, which was a Nd—Fe—B alloy cast strip. The auxiliary alloy was a heavy rare earth alloy ingot. The master alloy comprised 29 wt. % of Pr—Nd alloy, 1.2 wt. % of Dy, 0.98 wt. % of B, 67.82 wt. % of Fe, and 1 wt. % of Co. The auxiliary alloy comprised 69.5 wt. % of Dy, 5 wt. % of Nd, 0.8 wt. % of Ga, 0.7 wt. % of Cu, 1.6 wt. % of Al, and 22.4 wt. % of Fe.

(40) 2) Breaking up the master alloy using a hydrogen decrepitation process to yield a crude powder, conducting hydrogen absorption treatment on the auxiliary alloy and breaking up the hydrogenated auxiliary alloy to yield hydride particles. The hydride particles had hydrogen content by weight of 10840 ppm.

(41) 3) Uniformly mixing and stirring the crude powder of the master alloy and the hydride particles of the auxiliary alloy to yield a mixture, a weight ratio of the crude powder of the master alloy to the hydride particles of the auxiliary alloy being 97.3:2.7.

(42) 4) Milling the mixture obtained in step 3) to yield powders having a surface area mean diameter of 2.56 μm.

(43) 5) Uniformly stirring the powders obtained in step 4) and conducting orientation forming treatment on the powders, to yield a raw body of a Nd—Fe—B based magnet, where the orientation forming treatment employed an orientation magnetic field of 1.8 T in the presence of nitrogen, followed by cold isostatic pressing treatment.

(44) 6) Sintering the raw body of the Nd—Fe—B based magnet.

(45) The sintering process in step 6) comprised the following steps:

(46) 6-1) introducing the raw body of the Nd—Fe—B based magnet to a vacuum sintering furnace, heating the furnace from 800° C. to 1000° C. for dehydrogenation for 2 hours;

(47) 6-2) heating the vacuum sintering furnace to a temperature of 1030° C., and sintering the raw body for 4 hours; and

(48) 6-3) allowing the raw body for a primary tempering at 890° C. for 2 hours and for a secondary tempering at 450° C. for 4 hours, to yield the Nd—Fe—B based sintered magnet.

(49) TABLE-US-00004 TABLE 4 Magnetic performance of Nd—Fe—B based sintered magnet after being added with 2.7 wt. % of heavy rare earth alloy (Dy.sub.69.5Nd.sub.5Ga.sub.0.8Cu.sub.0.7Al.sub.1.6Fe.sub.22.4) Dy content B.sub.r H.sub.cB H.sub.cj (BH).sub.max H.sub.k (wt. %) (kGs) (kOe) (kOe) (MGsOe) (kOe) H.sub.k/H.sub.cj 3.04 12.71 12.34 22.69 39.46 21.69 0.96

Example 5

(50) A method for preparing a Nd—Fe—B based sintered magnet, the method comprises:

(51) 1) Providing a master alloy and an auxiliary alloy. The master alloy was prepared using a strip casting technology, which was a Nd—Fe—B alloy cast strip. The auxiliary alloy was a heavy rare earth alloy cast strip. The master alloy comprised 29.3 wt. % of Pr—Nd alloy, 0.2 wt. % of Nb, 1 wt. % of Co, 0.1 wt. % of Al, 0.15 wt. % of Cu, 1 wt. % of B, and 68.25 wt. % of Fe. The auxiliary alloy comprised 55 wt. % of Dy, 0.1 wt. % of Ga, 0.15 wt. % of Cu, 0.3 wt. % of Al, 1.4 wt. % of B, and 43.05 wt. % of Fe.

(52) 2) Breaking up the master alloy using a hydrogen decrepitation process to yield a crude powder, conducting hydrogen absorption treatment on the auxiliary alloy and breaking up the hydrogenated auxiliary alloy to yield hydride particles. The hydride particles had hydrogen content by weight of 8086 ppm.

(53) 3) Uniformly mixing and stirring the crude powder of the master alloy and the hydride particles of the auxiliary alloy to yield a mixture, a weight ratio of the crude powder of the master alloy to the hydride particles of the auxiliary alloy being 92.2:7.8.

(54) 4) Milling the mixture obtained in step 3) to yield powders having a surface area mean diameter of 2.44 μm.

(55) 5) Uniformly stirring the powders obtained in step 4) and conducting orientation forming treatment on the powders, to yield a raw body of a Nd—Fe—B based magnet, where the orientation forming treatment employed an orientation magnetic field of 1.8 T in the presence of nitrogen, followed by cold isostatic pressing treatment.

(56) 6) Sintering the raw body of the Nd—Fe—B based magnet.

(57) The sintering process in step 6) comprised the following steps:

(58) 6-1) introducing the raw body of the Nd—Fe—B based magnet to a vacuum sintering furnace, heating the furnace from 800° C. to 1000° C. for dehydrogenation for 2 hours;

(59) 6-2) heating the vacuum sintering furnace to a temperature of 1030° C., and sintering the raw body for 4 hours; and

(60) 6-3) allowing the raw body for a primary tempering at 890° C. for 2 hours and for a secondary tempering at 500° C. for 4 hours, to yield the Nd—Fe—B based sintered magnet.

(61) TABLE-US-00005 TABLE 5 Magnetic performance of Nd—Fe—B based sintered magnet after being added with 7.8 wt. % of heavy rare earth alloy (Dy.sub.55Ga.sub.0.1Cu.sub.0.15Al.sub.0.3Fe.sub.43.05B.sub.1.4) Dy content B.sub.r H.sub.cB H.sub.cj (BH).sub.max H.sub.k (wt. %) (kGs) (kOe) (kOe) (MGsOe) (kOe) H.sub.k/H.sub.cj 4.3 12.82 12.49 23.70 40.19 22.43 0.95

Example 6

(62) A method for preparing a Nd—Fe—B based sintered magnet, the method comprises:

(63) 1) Providing a master alloy and an auxiliary alloy. The master alloy was prepared using a strip casting technology, which was a Nd—Fe—B alloy cast strip. The auxiliary alloy was a heavy rare earth alloy cast strip. The master alloy comprised 29.3 wt. % of Pr—Nd alloy, 0.2 wt. % of Nb, 1 wt. % of Co, 0.1 wt. % of Al, 0.15 wt. % of Cu, 1 wt. % of B, and 68.25 wt. % of Fe. The auxiliary alloy comprised 45 wt. % of Dy, 0.1 wt. % of Ga, 0.15 wt. % of Cu, 0.3 wt. % of Al, 1.4 wt. % of B, and 53.05 wt. % of Fe.

(64) 2) Breaking up the master alloy using a hydrogen decrepitation process to yield a crude powder, conducting hydrogen absorption treatment on the auxiliary alloy and breaking up the hydrogenated auxiliary alloy to yield hydride particles. The hydride particles had hydrogen content by weight of 8911 ppm.

(65) 3) Uniformly mixing and stirring the crude powder of the master alloy and the hydride particles of the auxiliary alloy to yield a mixture, a weight ratio of the crude powder of the master alloy to the hydride particles of the auxiliary alloy being 85.1:14.9.

(66) 4) Milling the mixture obtained in step 3) to yield powders having a surface area mean diameter of 2.49 μm.

(67) 5) Uniformly stirring the powders obtained in step 4) and conducting orientation forming treatment on the powders, to yield a raw body of a Nd—Fe—B based magnet, where the orientation forming treatment employed an orientation magnetic field of 1.8 T in the presence of nitrogen, followed by cold isostatic pressing treatment.

(68) 6) Sintering the raw body of the Nd—Fe—B based magnet.

(69) The sintering process in step 6) comprised the following steps:

(70) 6-1) introducing the raw body of the Nd—Fe—B based magnet to a vacuum sintering furnace, heating the furnace from 800° C. to 1000° C. for dehydrogenation for 2 hours;

(71) 6-2) heating the vacuum sintering furnace to a temperature of 1030° C., and sintering the raw body for 4 hours; and

(72) 6-3) allowing the raw body for a primary tempering at 890° C. for 2 hours and for a secondary tempering at 530° C. for 4 hours, to yield the Nd—Fe—B based sintered magnet.

(73) TABLE-US-00006 TABLE 6 Magnetic performance of Nd—Fe—B based sintered magnet after being added with 14.9 wt. % of heavy rare earth alloy (Dy.sub.45Ga.sub.0.1Cu.sub.0.15Al.sub.0.3Fe.sub.53.05B.sub.1.4) Dy content B.sub.r H.sub.cB H.sub.cj (BH).sub.max H.sub.k (wt. %) (kGs) (kOe) (kOe) (MGsOe) (kOe) H.sub.k/H.sub.cj 6.7 11.24 10.86 30.04 31.15 29.14 0.97

Example 7

(74) A method for preparing a Nd—Fe—B based sintered magnet, the method comprises:

(75) 1) Providing a master alloy and an auxiliary alloy. The master alloy was prepared using a strip casting technology, which was a Nd—Fe—B alloy cast strip. The auxiliary alloy was a heavy rare earth alloy cast strip. The master alloy comprised 29.3 wt. % of Pr—Nd alloy, 0.2 wt. % of Nb, 1 wt. % of Co, 0.1 wt. % of Al, 0.15 wt. % of Cu, 1 wt. % of B, and 68.25 wt. % of Fe. The auxiliary alloy comprised 35 wt. % of Dy, 0.1 wt. % of Ga, 0.15 wt. % of Cu, 0.3 wt. % of Al, 1.4 wt. % of B, and 63.05 wt. % of Fe.

(76) 2) Breaking up the master alloy using a hydrogen decrepitation process to yield a crude powder, conducting hydrogen absorption treatment on the auxiliary alloy and breaking up the hydrogenated auxiliary alloy to yield hydride particles. The hydride particles had hydrogen content by weight of 7423 ppm.

(77) 3) Uniformly mixing and stirring the crude powder of the master alloy and the hydride particles of the auxiliary alloy to yield a mixture, a weight ratio of the crude powder of the master alloy to the hydride particles of the auxiliary alloy being 75:25.

(78) 4) Milling the mixture obtained in step 3) to yield powders having a surface area mean diameter of 2.51 μm.

(79) 5) Uniformly stirring the powders obtained in step 4) and conducting orientation forming treatment on the powders, to yield a raw body of a Nd—Fe—B based magnet, where the orientation forming treatment employed an orientation magnetic field of 1.8 T in the presence of nitrogen, followed by cold isostatic pressing treatment.

(80) 6) Sintering the raw body of the Nd—Fe—B based magnet.

(81) The sintering process in step 6) comprised the following steps:

(82) 6-1) introducing the raw body of the Nd—Fe—B based magnet to a vacuum sintering furnace, heating the furnace from 800° C. to 1000° C. for dehydrogenation for 2 hours;

(83) 6-2) heating the vacuum sintering furnace to a temperature of 1030° C., and sintering the raw body for 4 hours; and

(84) 6-3) allowing the raw body for a primary tempering at 890° C. for 2 hours and for a secondary tempering at 530° C. for 4 hours, to yield the Nd—Fe—B based sintered magnet.

(85) TABLE-US-00007 TABLE 7 Magnetic performance of Nd—Fe—B based sintered magnet after being added with 25 wt. % of heavy rare earth alloy (Dy.sub.35Ga.sub.0.1Cu.sub.0.15Al.sub.0.3Fe.sub.63.05B.sub.1.4) Dy content B.sub.r H.sub.cB H.sub.cj (BH).sub.max H.sub.k (wt. %) (kGs) (kOe) (kOe) (MGsOe) (kOe) H.sub.k/H.sub.cj 8.75 11.10 10.77 32.43 30.40 31.45 0.97

(86) Unless otherwise indicated, the numerical ranges involved in the invention include the end values.

(87) While particular embodiments of the invention have been shown and described, it will be obvious to those skilled in the art that changes and modifications may be made without departing from the invention in its broader aspects, and therefore, the aim in the appended claims is to cover all such changes and modifications as fall within the true spirit and scope of the invention.