High-performance NdFeB rare earth permanent magnet with composite main phase and manufacturing method thereof

Abstract

A NdFeB rare earth permanent magnet with composite main phase and a manufacturing method thereof are provided. In the composite main phase, a PR.sub.2(Fe.sub.1-x-yCo.sub.xAl.sub.y).sub.14B main phase is the core, ZR.sub.2(Fe.sub.1-w-nCo.sub.wAl.sub.n).sub.14B main phase surrounds a periphery of the PR.sub.2(Fe.sub.1-x-yCo.sub.xAl.sub.y).sub.14B main phase, and no grain boundary phase exists between ZR.sub.2(Fe.sub.1-w-nCo.sub.wAl.sub.n).sub.14B main phase and the PR.sub.2(Fe.sub.1-x-yCo.sub.xAl.sub.y).sub.14B main phase, wherein ZR represents a group of rare earth elements in which a content of heavy rare earth is higher than an average content of heavy rare earth in the composite main phase, PR represents a group of rare earth elements in which a content of heavy rare earth is lower than an average content of heavy rare earth in the composite main phase. The manufacturing method includes steps of LRFeB-Ma alloy melting, HRFeB-Mb alloy melting, alloy hydrogen decrepitating, metal oxide micro-powder surface absorbing and powdering, magnetic field pressing, sintering and ageing.

Claims

1. A method of manufacturing an NdFeB rare earth permanent magnet with a composite main phase, wherein a raw material comprises LRFeB-Ma alloy, HRFeB-Mb alloy and metal oxide micro-powder, wherein the LR comprises at least two rare earth elements, and at least comprises Nd and Pr, the HR is selected from rare earth elements and comprises at least Dv, the Ma is selected from the group consisting of Al, Co, Nb, Ga, Zr, Cu, V and Mo, the Mb is selected from the group consisting of Al, Co, Nb, Ga, Zr, Cu, V, Ti, Cr, Ni, Hf, Y and Mo; wherein the method comprises steps of: (1) melting the LRFeB-Ma alloy which comprises: firstly melting an LRFeB-Ma raw material under vacuum or argon protection with induction heating for forming an alloy, refining before casting the alloy in a melted state onto a rotation roller with water cooling function through a tundish, and cooling the alloy with the rotation roller for forming alloy flakes, wherein an average grain size of each of the alloy flakes is 1.5-3.5 m; (2) melting the HRFeB-Mb alloy which comprises: firstly melting an HRFeB-Mb raw material under vacuum or argon protection with induction heating for forming an alloy, refining before casting the alloy in a melted state onto a rotation roller with water cooling function through a tundish, and cooling the alloy with the rotation roller for forming alloy flakes, wherein an average grain size of each of the alloy flakes is 0.1-2.9 m; (3) alloy hydrogen decrepitating which comprises: sending the LRFeB-Ma alloy and the HRFeB-Mb alloy into a vacuum hydrogen decrepitation device, evacuating before injecting hydrogen for hydrogen absorption, wherein a hydrogen absorption temperature is 80-300 C.; heating after hydrogen absorption and evacuating for dehydrogenating, wherein a dehydrogenating temperature is 350-900 C., a dehydrogenating time is 3-15 h; and then cooling the alloy; (4) metal oxide powder surface adsorbing and powdering which comprises: adding the LRFeB-Ma alloy and the HRFeB-Mb alloy which are hydrogen decrepitated in the step (3), and the metal oxide micro-powder into a mixer for mixing, wherein the mixing is made under nitrogen protection, lubricant or anti-oxidant may be added; and then powdering with jet milling after the mixing for obtaining alloy powder; and (5) magnetic field pressing, sintering and ageing which comprises: under nitrogen protection, magnetic field pressing the obtained alloy powder in the step (4), and then sintering and ageing under vacuum or argon protection for manufacturing the NdFeB rare earth permanent magnet, wherein the powdering with jet milling comprises: under nitrogen atmosphere, adding the mixed powder into a hopper on a top portion of a feeder; moving the mixed powder into a milling room through the feeder; milling with air flow from a spray nozzle, wherein the powder milled rises with the air flow; sorting the milled powder with a sorting wheel and collecting in a cyclone collector; discharging powder coated with the metal oxide micro-powder from an air exhaust pipe of the cyclone collector with the air flow; collecting the powder coated with the metal oxide micro-powder in a collector after the cyclone collector, and then mixing under nitrogen protection.

2. A method of manufacturing an NdFeB rare earth permanent magnet with a composite main phase, wherein a raw material comprises LRFeB-Ma alloy, HRFeB-Mb alloy and metal oxide micro-powder, wherein the LR comprises at least two rare earth elements, and at least comprises Nd and Pr, the HR is selected from rare earth elements and comprises at least Dv, the Ma is selected from the group consisting of Al, Co, Nb, Ga, Zr, Cu, V and Mo, the Mb is selected from the group consisting of Al, Co, Nb, Ga, Zr, Cu, V, Ti, Cr, Ni, Hf, Y and Mo; wherein the method comprises steps of: (1) melting the LRFeB-Ma alloy which comprises: firstly melting an LRFeB-Ma raw material under vacuum or argon protection with induction heating for forming an alloy, refining before casting the alloy in a melted state onto a rotation roller with water cooling function through a tundish, and cooling the alloy with the rotation roller for forming alloy flakes, wherein an average grain size of each of the alloy flakes is 1.5-3.5 m; (2) melting the HRFeB-Mb alloy which comprises: firstly melting an HRFeB-Mb raw material under vacuum or argon protection with induction heating for forming an alloy, refining before casting the alloy in a melted state onto a rotation roller with water cooling function through a tundish, and cooling the alloy with the rotation roller for forming alloy flakes, wherein an average grain size of each of the alloy flakes is 0.1-2.9 m; (3) alloy hydrogen decrepitating which comprises: sending the LRFeB-Ma alloy and the HRFeB-Mb alloy into a vacuum hydrogen decrepitation device, evacuating before injecting hydrogen for hydrogen absorption, wherein a hydrogen absorption temperature is 80-300 C.; heating after hydrogen absorption and evacuating for dehydrogenating, wherein a dehydrogenating temperature is 350-900 C., a dehydrogenating time is 3-15 h; and then cooling the alloy; (4) metal oxide powder surface adsorbing and powdering which comprises: adding the LRFeB-Ma alloy and the HRFeB-Mb alloy which are hydrogen decrepitated in the step (3), and the metal oxide micro-powder into a mixer for mixing, wherein the mixing is made under nitrogen protection, lubricant or anti-oxidant may be added; and then powdering with jet milling after the mixing for obtaining alloy powder; and (5) magnetic field pressing, sintering and ageing which comprises: under nitrogen protection, magnetic field pressing the obtained alloy powder in the step (4), and then sintering and ageing under vacuum or argon protection for manufacturing the NdFeB rare earth permanent magnet, wherein the magnetic field pressing comprises sending the alloy powder into a nitrogen protection sealed magnetic field pressing machine under the nitrogen protection, weighting before adding to a cavity of a mould already assembled, then magnetic field pressing; after pressing, opening the mould and obtaining a magnetic block; wrapping the magnetic block with a plastic or rubber bag under the nitrogen protection, sending the magnetic block with the plastic or rubber bag into an isostatic pressing machine for isostatic pressing, then sending the magnetic block with the plastic or rubber bag into a nitrogen protection loading tank of a vacuum sintering furnace; then removing the plastic or rubber bag of the magnetic block with gloves in the nitrogen protection loading tank and sending the magnetic block to a sintering case.

3. A method of manufacturing an NdFeB rare earth permanent magnet with a composite main phase, wherein a raw material comprises LRFeB-Ma alloy, HRFeB-Mb alloy and metal oxide micro-powder, wherein the LR comprises at least two rare earth elements, and at least comprises Nd and Pr, the HR is selected from rare earth elements and comprises at least Dv, the Ma is selected from the group consisting of Al, Co, Nb, Ga, Zr, Cu, V and Mo, the Mb is selected from the group consisting of Al, Co, Nb, Ga, Zr, Cu, V, Ti, Cr, Ni, Hf, Y and Mo; wherein the method comprises steps of: (1) melting the LRFeB-Ma alloy which comprises: firstly melting an LRFeB-Ma raw material under vacuum or argon protection with induction heating for forming an alloy, refining before casting the alloy in a melted state onto a rotation roller with water cooling function through a tundish, and cooling the alloy with the rotation roller for forming alloy flakes, wherein an average grain size of each of the alloy flakes is 1.5-3.5 m; (2) melting the HRFeB-Mb alloy which comprises: firstly melting an HRFeB-Mb raw material under vacuum or argon protection with induction heating for forming an alloy, refining before casting the alloy in a melted state onto a rotation roller with water cooling function through a tundish, and cooling the alloy with the rotation roller for forming alloy flakes, wherein an average grain size of each of the alloy flakes is 0.1-2.9 m; (3) alloy hydrogen decrepitating which comprises: sending the LRFeB-Ma alloy and the HRFeB-Mb alloy into a vacuum hydrogen decrepitation device, evacuating before injecting hydrogen for hydrogen absorption, wherein a hydrogen absorption temperature is 80-300 C.; heating after hydrogen absorption and evacuating for dehydrogenating, wherein a dehydrogenating temperature is 350-900 C., a dehydrogenating time is 3-15 h; and then cooling the alloy; (4) metal oxide powder surface adsorbing and powdering which comprises: adding the LRFeB-Ma alloy and the HRFeB-Mb alloy which are hydrogen decrepitated in the step (3), and the metal oxide micro-powder into a mixer for mixing, wherein the mixing is made under nitrogen protection, lubricant or anti-oxidant may be added; and then powdering with jet milling after the mixing for obtaining alloy powder; and (5) magnetic field pressing, sintering and ageing which comprises: under nitrogen protection, magnetic field pressing the obtained alloy powder in the step (4) to obtain a magnetic block, and then sintering and ageing the magnetic block under vacuum or argon protection for manufacturing the NdFeB rare earth permanent magnet, wherein the sintering and ageing comprises sending a sintering case carrying the magnetic block in a nitrogen protection loading tank of a vacuum sintering furnace into a heating chamber of the vacuum sintering furnace under nitrogen protection, evacuating before heating, keeping a temperature at 200-400 C. for 2-10 h, then keeping the temperature at greater than 400 C. and less than or equal to 600 C. for 5-12 h, then pre-sintering by keeping the temperature at greater than 600 C. and less than or equal to 950 C. for 5-20 h to pre sinter, then sintering by keeping the temperature at greater than 950 C. and less than or equal to 1070 C. for 1-6 h to sinter, then first ageing at a temperature of 800-950 C. and second ageing at a temperature of 450-650 C., cooling after second ageing for manufacturing the sintered NdFeB permanent magnet, and then machining and surface-processing to manufacture various permanent magnetic devices.

4. The method, as recited in claim 3, wherein a density of the pre-sintered magnet is 7-7.4 g/cm.sup.3, and a density of the sintered magnet is 7.5-7.7 g/cm.sup.3.

5. The method, as recited in claim 3, wherein in the step of powdering with jet milling, powder collected by a cyclone collector and powder discharged from an air exhaust pipe of the cyclone collector are mixed under nitrogen protection, and then the mixed powder is for magnetic field pressing.

6. The method, as recited in claim 3, wherein the metal oxide micro-powder is Dy.sub.2O.sub.3 micro-powder heat-treated at a temperature of 600-1200 C.

7. The method, as recited in claim 3, wherein the metal oxide micro-powder is Al.sub.2O.sub.3 micro-powder.

8. The method, as recited in claim 3, wherein the metal oxide micro-powder is rare earth metal oxides except Lanthanum oxide and cerium oxide, or is selected from the group consisting of Al oxide, Co oxide, Nb oxide, Ga oxide, Zr oxide, Cu oxide, V oxide, Mo oxide, Fe oxide and Zn oxide.

9. The method, as recited in claim 3, wherein the metal oxide is selected from the group consisting of Dy.sub.2O.sub.3, Tb.sub.2O.sub.3 and Al.sub.2O.sub.3.

10. The method, as recited in claim 3, wherein after evacuating for dehydrogenating, a certain amount of hydrogen are injected within a temperature range of 100-600 C., and then the alloy is cooled.

11. The method, as recited in claim 3, wherein the LRFeB-Ma alloy and the HRFeB-Mb alloy which are hydrogen decrepitated, and the metal oxide micro-powder are added into the mixer for mixing, a certain amount of hydrogen is added while mixing.

12. The method, as recited in claim 3, wherein in the step (4), an average particle size of the obtained alloy powder is 1-3 m.

Description

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

(1) The significant effects of the present invention are further illustrated by comparative embodiments.

Embodiment 1

(2) Melting 600 Kg LRFeB-Ma alloy and 600 Kg HRFeB-Mb alloy respectively selected from the components of embodiment 1 in Table 1; casting the alloys in a melted state onto a rotation copper roller with water cooling function, so as to be cooled for forming alloy flakes; adjusting a cooling speed of the LRFeB-Ma alloy and the HRFeB-Mb alloy by adjusting a rotation speed of the rotation copper roller for obtaining the LRFeB-Ma alloy with an average grain size of 2.8 m and the HRFeB-Mb alloy with an average grain size of 1.8 m; selecting the LRFeB-Ma alloy flakes and HRFeB-Mb alloy flakes with a ratio in Table 1 for hydrogen decrepitating; after hydrogen decrepitating, sending the alloy flakes and metal oxides with a ratio in Table 1 into a mixer, mixing under nitrogen protection for 60 min before powdering with jet milling; sending the powder from a cyclone collector and the super-fine powder from the filter into a post-mixer for post-mixing, wherein post-mixing is provided under nitrogen protection with a mixing time of 90 min; an oxygen content in protection atmosphere is less than 100 ppm; then sending into a nitrogen protection magnetic field orientation pressing machine for pressing, wherein an orientation magnetic field strength is 1.8 T, an in-cavity temperature is 3 C., a size of a magnet is 403020 mm, and an orientation direction is a 20 size direction; packaging in a protection tank after pressing, then outputting for isostatic pressing; sending into a sintering furnace for pre-sintering, wherein a pre-sintering temperature is kept at 940 C. for 15 h and a pre-sintering density is 7.3 g/cm.sup.3; then sintering, firstly ageing and secondly ageing, wherein a sintering temperature is kept at 1070 C. for 1 h; taking out the magnetic block for being machined, then measuring magnetic performance and weight loss, recording results in Table 1, wherein a weight percentage ratio of the sintered magnet after testing is (Nd.sub.0.7Pr.sub.0.3).sub.29.5Dy.sub.1.0B.sub.0.9Al.sub.0.1Co.sub.1.2Cu.sub.0.15Fe.sub.residual, and the measurement results of magnetic energy product, coercivity and weight loss also are recorded in Table 1.

Contrast Example 1

(3) Selecting the magnet with a composition of (Nd.sub.0.7Pr.sub.0.3).sub.29.5Dy.sub.1.0B.sub.0.9Al.sub.0.1Co.sub.1.2Cu.sub.0.15Fe.sub.residual of the contrast example 1 in Table 2, firstly melting alloy, casting the alloy in a melted state onto a rotation copper roller with water cooling function, so as to be cooled for forming alloy flakes; then hydrogen decrepitating, powdering with jet milling, pressing by a magnetic field orientation pressing machine, isostatic pressing, sintering, firstly ageing and secondly ageing the alloy flakes, machining, measuring magnetic properties and weight loss, and recording results in Table 1.

(4) In spite that the embodiment 1 and the contrast example 1 has same magnetic composition, the magnetic energy product, coercivity and weight loss of the present invention of the embodiment 1 of the present invention are significantly higher than those of the contrast example 1.

(5) The other compositions of embodiment 1 are unchanged, the content of Co is changed, when 0Co5, the metal oxide is in a range of 0.01-0.05%, the magnetic performance is changed with the increase of the content of Co, the change range is less than 4%, the performance is significantly higher than that of the contrast example 1. Preferably, the content of Co is 0Co3, the performance change is smaller. Further preferably, the content of Co is 1.0Co2.4, the performance change is much smaller and lower than 2%. The content of Co is unchangeable, the content of Cu is adjusted, when 0Cu0.3, the metal oxide is in a range of 0.01-0.05%, the performance is changed with the change of the content of Cu, the change range is less than 3%, the performance is significantly higher than that of the contrast example 1. Preferably, the content of Cu is 0.1Cu0.3, the performance is changed with the change of the content of Cu, and the change range is less than 2%. Further preferably, the content of Cu is 0.1Co0.2, the performance is changed with the change of the content of Cu, and the change range is less than 1%. Experiments show that when both Co and Cu are added, the content of Co meets 0.8Co2.4, and the content of Cu meets 0.1Cu0.2, the magnetic performance and corrosion resistance are best.

(6) The material compositions and experimental method of embodiment 1 are unchangeable, the variety and content of the metal oxide are changed. Experiments show that when the metal oxide micro-powder is Al.sub.2O.sub.3, the content thereof is 0.01-0.05%, the magnetic performance is increased with the increase of the content, the content is 0.01-0.08%, the magnetic performance keeps higher than the performance with the content of 0.01; when the metal oxide micro-powder is replaced by Dy.sub.2O.sub.3 and Tb.sub.2O.sub.3, the same rules exist, the performance of Dy.sub.2O.sub.3 is higher than that of Al.sub.2O.sub.3, the performance of Tb.sub.2O.sub.3 is higher than Dy.sub.2O.sub.3. Preferably, the content of the metal oxide micro-powder is 0.01-0.05%. Further preferably, the content of the metal oxide micro-powder is 0.02-0.03%. Preferably, the metal oxide is Al.sub.2O.sub.3; and more preferably, Dy.sub.2O.sub.3, and even more preferably, Tb.sub.2O.sub.3. Preferably, both Dy.sub.2O.sub.3 and Al.sub.2O.sub.3 are added to further improve the performance of the magnet. More preferably, both Al.sub.2O.sub.3 and Tb.sub.2O.sub.3 or both Tb.sub.2O.sub.3 and Dy.sub.2O.sub.3 are added to further improve the performance of the magnet. Even more preferably, Dy.sub.2O.sub.3, Al.sub.2O.sub.3 and Tb.sub.2O.sub.3 are added to further improve the performance of the magnet.

Embodiment 2

(7) Melting 600 Kg LRFeB-Ma alloy and 600 Kg HRFeB-Mb alloy respectively selected from the components of embodiment 2 in Table 1; casting the alloys in a melted state onto a rotation copper roller with water cooling function, so as to be cooled for forming alloy flakes; adjusting a cooling speed of the LRFeB-Ma alloy and the HRFeB-Mb alloy by adjusting a rotation speed of the rotation copper roller for obtaining the LRFeB-Ma alloy with an average grain size of 2.3 m and the HRFeB-Mb alloy with an average grain size of 1.3 m; selecting the LRFeB-Ma alloy flakes and HRFeB-Mb alloy flakes with a ratio in Table 1 for hydrogen decrepitating; after hydrogen decrepitating, sending the alloy flakes and metal oxides with a ratio in Table 1 into a mixer, mixing under nitrogen protection for 40 min before powdering with jet milling; sending the powder from a cyclone collector and the super-fine powder from the filter into a post-mixer for post-mixing, wherein post-mixing is provided under nitrogen protection with a mixing time of 70 min; an oxygen content in protection atmosphere is less than 50 ppm; then sending into a nitrogen protection magnetic field orientation pressing machine for pressing, wherein an orientation magnetic field strength is 1.8 T, an in-cavity temperature is 4 C., a size of a magnet is 403020 mm, and an orientation direction is a 20 size direction; packaging in a protection tank after pressing, then outputting for isostatic pressing; sending into a sintering furnace for pre-sintering, wherein a pre-sintering temperature is kept at 910 C. for 10 h and a pre-sintering density is 7.2 g/cm.sup.3; then sintering, firstly ageing and secondly ageing, wherein a sintering temperature is kept at 1060 C. for 1 h; taking out the magnetic block for being machined, then measuring magnetic performance and weight loss, recording results in Table 1, wherein a weight percentage ratio of the sintered magnet after testing is La.sub.1(Nd.sub.0.75Pr.sub.0.25).sub.24Dy.sub.4Tb.sub.2Co.sub.1Cu.sub.0.1B.sub.0.95Al.sub.0.2Ga.sub.0.1Fe.sub.residual, and the measurement results also are recorded in Table 1.

Contrast Example 2

(8) Selecting the magnet with a composition of La.sub.1(Nd.sub.0.75Pr.sub.0.25).sub.24Dy.sub.4Tb.sub.2Co.sub.1Cu.sub.0.1B.sub.0.95Al.sub.0.2Ga.sub.0.1Fe.sub.residual in Table 2 to compare, the experimental method is same as that in the comparative 1, the measurement results also are recorded in Table 1.

(9) Generally, when Pr or Nd is replaced by La, the magnetic performance is significantly reduced. It can be seen from Table 1, when 1% (Nd.sub.0.75Pr.sub.0.25) is replaced by 1% La, the magnetic performance is significantly improved by the technical process of the present invention. The contents of other compositions are unchanged, only the content of La is changed. Experiments show when 0La2.4, the magnetic performance and the corrosion resistance are unchanged; when 2.5La3, the magnetic performance and the corrosion resistance are slightly decreased; when 3.1La4.5, the magnetic performance and the corrosion resistance can be decreased to less than 3%; when 5La9, the magnetic performance and the corrosion resistance can be decreased to less than 5%. Therefore, preferably, the content of La is 5La9, and further preferably, 3.1La4.5, and further preferably, 2.5La3.

(10) When La is replaced by Ce, that is to say, that when the magnet with a composition of Ce.sub.1(Nd.sub.0.75Pr.sub.0.25).sub.24Dy.sub.4Tb.sub.2Co.sub.1Cu.sub.0.1B.sub.0.95Al.sub.0.2Ga.sub.0.1Fe.sub.residual is selected to test, the same rules are obtained. Therefore, preferably, the content of Ce is 5Ce9, and more preferably, 3.1Ce4.5, and even more preferably, 2.5Ce3.

Embodiment 3

(11) Melting 600 Kg LRFeB-Ma alloy and 600 Kg HRFeB-Mb alloy respectively selected from the components of embodiment 3 in Table 1; casting the alloys in a melted state onto a rotation copper roller with water cooling function, so as to be cooled for forming alloy flakes; adjusting a cooling speed of the LRFeB-Ma alloy and the HRFeB-Mb alloy by adjusting a rotation speed of the rotation copper roller for obtaining the LRFeB-Ma alloy with an average grain size of 2.8-3.2 m and the HRFeB-Mb alloy with an average grain size of 2.1-2.4 m; selecting the LRFeB-Ma alloy flakes and HRFeB-Mb alloy flakes with a ratio in Table 1 for hydrogen decrepitating; after hydrogen decrepitating, sending the alloy flakes and metal oxides with a ratio in Table 1 into a mixer, mixing under nitrogen protection for 90 min before powdering with jet milling; sending the powder from a cyclone collector and the super-fine powder from the filter into a post-mixer for post-mixing, wherein post-mixing is provided under nitrogen protection with a mixing time of 60 min; an oxygen content in protection atmosphere is less than 150 ppm; then sending into a nitrogen protection magnetic field orientation pressing machine for pressing, wherein an orientation magnetic field strength is 1.5 T, a size of a magnet is 403020 mm, and an orientation direction is a 20 size direction; packaging in a protection tank after pressing, then outputting for isostatic pressing; sending into a sintering furnace for pre-sintering, wherein a pre-sintering temperature is kept at 990 C. for 8 h and a pre-sintering density is 7.4 g/cm.sup.3; then sintering, firstly ageing and secondly ageing, wherein a sintering temperature is kept at 1080 C. for 1 h; taking out the magnetic block for being machined, then measuring magnetic performance and weight loss, recording results in Table 1, wherein the composition of the sintered magnet after testing is Ce.sub.1.5(Nd.sub.0.8Pr.sub.0.2).sub.20Dy.sub.6Ho.sub.2Gd.sub.2Co.sub.2.4Cu.sub.0.2B.sub.1.0Al.sub.0.3Ga.sub.0.1Zr.sub.0.1Nb.sub.0.1Fe.sub.residual, and the measurement results also are recorded in Table 1.

Contrast Example 3

(12) Selecting the magnet with a composition of Ce.sub.1.5(Nd.sub.0.8Pr.sub.0.2).sub.20Dy.sub.6Ho.sub.2Gd.sub.2Co.sub.2.4Cu.sub.0.2B.sub.1.0Al.sub.0.3Ga.sub.0.1Zr.sub.0.1Nb.sub.0.1Fe.sub.residual according to the contrast example 3 in Table 2, firstly melting alloy, casting the alloy in a melted state onto a rotation copper roller with water cooling function, so as to be cooled for forming alloy flakes; then hydrogen decrepitating, powdering with jet milling, pressing by a magnetic field orientation pressing machine, isostatic pressing, sintering, firstly ageing and secondly ageing the alloy flakes, machining, measuring magnetic performance and weight loss, and recording results in Table 1.

(13) Compare the measurement results of embodiment 3 with those of the contrast example 3, the magnetic performance and corrosion resistance of embodiment 3 are significantly higher than those of the contrast example 3, which further illustrates the advantages of the present invention.

(14) It can be proved by embodiments 1-3 and contrast examples 1-3 that the technical solution of the present invention has obvious advantages. Adding Al, Ga, Zr and Nb can significantly improve the magnetic performance and corrosion resistance of the magnet. Preferably, the contents of Al, Ga, Zr and Nb are respectively 0Al0.6, 0Ga0.2, 0Zr0.3, 0Nb0.3; and further preferably, 0.1Al0.3, 0.05Ga0.15, 0.1Zr0.2, 0.1Nb0.2,

(15) TABLE-US-00001 TABLE 1 compound and performance in embodiments and contrast example Contrast Contrast Contrast Embodiment 1 example 1 Embodiment 2 example 2 Embodiment 3 example 3 LR- Pr 9.15 9 7.5 5 6 4.3 Fe-B- Nd 21.35 21 22.5 20 24 17.2 Ma La 1.0 (Wt %) Ce 1.5 Dy 0 1 0 4 6 Tb 0 0 0 2 Ho 2 Gd 2 Co 1.0 1.0 1.2 1.2 2.4 2.4 Cu 0.1 0.1 0.15 0.15 0.2 0.2 B 0.9 0.9 0.95 0.95 1.0 1.0 Al 0.1 0.1 0.2 0.2 0.3 0.3 Ga 0.1 0.1 0.1 0.1 Zr 0.1 0.1 Nb 0.1 0.1 Fe residual residual residual residual residual residual Alloy 90% 100% 80% 100% 60% 100% ratio HR- Dy 10 20 15 Fe-B- La 1 Ma Ce 1.5 alloy Pr 6.15 0.25 1 (Wt %) Nd 14.35 0.75 4 Tb 0 10 Ho 5 Gd 5 Co 1.0 1.2 2.4 Cu 0.1 0.15 0.2 B 0.9 0.95 1.0 Al 0.1 0.2 0.3 Ga 0.1 0.1 Zr 0.1 Nb 0.1 Fe residual residual Alloy 10% 0 20% 0 40% 0 ratio Oxide Dy.sub.2O.sub.3 0.01 0.02 0.03 micro- Tb.sub.2O.sub.3 0.01 0.01 powder Al.sub.2O.sub.3 0.01 0.01 (Wt %) total 0.02 0.03 0.05 Magnetic 48 46 43 38 30 27 energy product (MGOe) Coercivity 21 15 33 27 36 31 (KOe) Magnetic 69 61 76 65 66 58 energy product + coercivity Weight loss 1 4 2 6 3 5 (mg/cm.sup.2)

(16) TABLE-US-00002 TABLE 2 Composition of rare earth permanent magnet alloy in contrast example No Composition Contrast example 1 (Nd.sub.0.7Pr.sub.0.3).sub.29.5Dy.sub.1.0B.sub.0.9Al.sub.0.1Co.sub.1.2Cu.sub.0.15Feresidual Contrast example 2 (Nd.sub.0.75Pr.sub.0.25).sub.25Dy.sub.4Tb.sub.2Co.sub.1Cu.sub.0.1B.sub.0.95Al.sub.0.2Ga.sub.0.1Fe.sub.residual Contrast example 3 (Nd.sub.0.8Pr.sub.0.2).sub.21.5Dy.sub.6Ho.sub.2Gd.sub.2Co.sub.2.4Cu.sub.0.2B.sub.1.0Al.sub.0.3Ga.sub.0.1Zr.sub.0.1Nb.sub.0.1Fe.sub.residual

(17) It is further illustrated by the embodiments and the contrast examples that the method and the device according to the present invention significantly improve the magnetic performance, coercivity and corrosion resistance of the magnet. By respectively melting two alloys, one decrepitating and adding metal oxide micro-powder while jet milling, the present invention improves the structure of the powder, and forms the ground surface of the metal oxide for reducing the further oxidation of the magnetic powder. HRFeB-Mb alloy powder absorbs around LRFeB-Ma alloy powder, it is alloyed while sintering to form the special metallurgical structure of the present invention. Compared with Dy infiltration technique, the present invention is not limited by the shape and size of the magnet and is a very promising technology.

(18) One skilled in the art will understand that the embodiment of the present invention as shown in the drawings and described above is exemplary only and not intended to be limiting.

(19) It will thus be seen that the objects of the present invention have been fully and effectively accomplished. Its embodiments have been shown and described for the purposes of illustrating the functional and structural principles of the present invention and is subject to change without departure from such principles. Therefore, this invention includes all modifications encompassed within the spirit and scope of the following claims.