Low-heavy rare earth magnet and manufacturing method thereof

Abstract

The disclosure relates to a method of preparing a low-heavy rare earth magnet comprising the following steps: S1, smelting and strip casting of the raw materials of a NdFeB alloy to obtain a NdFeB alloy sheets, and mechanically crushing the NdFeB alloy sheets into flaky alloy sheets; S2, mechanically mixing the flaky alloy sheets, a low melting point powder and a lubricant to obtain a mixture, followed by hydrogen absorption and dehydrogenation treatment of the mixture and jet milling of the product to obtain a NdFeB magnet powder; S3, pressing, forming and sintering the NdFeB magnet powder to obtain a sintered NdFeB magnet; S4, mechanically processing the sintered NdFeB magnet to a desired shape, and then forming a diffusion source film on the surface of the sintered NdFeB magnet; and S5, performing a diffusion process and aging to obtain the low-heavy rare earth magnet.

Claims

1. A method of preparing a low-heavy rare earth magnet comprising the following steps: S1, smelting and strip casting of the raw materials of a NdFeB alloy to obtain a NdFeB alloy sheets, and mechanically crushing the NdFeB alloy sheets into flaky alloy sheets, wherein the NdFeB alloy has the following composition in weight percentage:28%≤R≤30%, 0.8%≤B≤1.2%, 0≤Gd≤5%, 0≤Ho≤5%, and 0≤M≤3%, wherein R is at least two or more elements of Nd, Pr, Ce, La, Tb, and Dy, M is at least one element of Co, Mg, Ti, Zr, Nb, and Mo, and the rest of the NdFeB alloy is Fe; S2, mechanically mixing the flaky alloy sheets, a low melting point powder and a lubricant to obtain a mixture, followed by hydrogen absorption and dehydrogenation treatment of the mixture and jet milling of the product to obtain a NdFeB magnet powder, wherein the low melting point powder contains at least one component selected from NdCu, NdAl and NdGa, and a weight percentage of the NdCu is 0% to 3%, a weight percentage of the NdAl is 0% to 3%, a weight percentage of the NdGa is 0% to 3%, each with respect to the total weight of the flaky alloy sheets and the low melting point powder; S3, pressing, forming and sintering the NdFeB magnet powder to obtain a sintered NdFeB magnet; S4, mechanically processing the sintered NdFeB magnet to a desired shape, and then forming a diffusion source film on the surface of the sintered NdFeB magnet, wherein the diffusion source film including a diffusion source of formula RxHyM1-x-y, wherein R is at least one of Nd, Pr, Ce, La, Ho, and Gd, H is at least one of Tb and Dy, M is at least one of Al, Cu, Ga, Ti, Co, Mg, Zn, and Sn, x and y are set to be 10%≤x≤50% and 40%≤y≤70% in weight percentage; and S5, performing a diffusion process and aging to obtain the low-heavy rare earth magnet.

2. The method of preparing a low-heavy rare earth magnet of claim 1, wherein in the step S2 a weight content of Cu is 0.1% to 0.5%, a weight content of Al is 0.2% to 0.9%, and a weight content of Ga is 0.01% to 0.4%, each with respect to the total weight of the flaky alloy sheets and the low melting point powder.

3. The method of preparing a low-heavy rare earth magnet of claim 1, wherein in the NdFeB alloy of the step S1, R is at least one element of Nd and Pr, and M is at least one element of Co and Ti.

4. The method of preparing a low-heavy rare earth magnet of claim 2, wherein in the NdFeB alloy of the step S1, R is at least one element of Nd and Pr, and M is at least one element of Co and Ti.

5. The method of preparing a low-heavy rare earth magnet of claim 1, wherein in the diffusion source film of the step S4, R is at least one of Nd and Pr, H is Dy, and M is at least one of Al, Cu, and Ga.

6. The method of preparing a low-heavy rare earth magnet of claim 1, wherein in the step S2, the dehydrogenation temperature is 400 to 600° C.

7. The method of preparing a low-heavy rare earth magnet of claim 1, wherein in the step S2, an average particle size D50 of the low melting point powder is 200 nm to 4 μm measured by laser diffraction (LD).

8. The method of preparing a low-heavy rare earth magnet of claim 1, wherein in the step S2, an average particle size D50 of the NdFeB magnet powder is 3 to 5 μm after jet milling measured by laser diffraction (LD).

9. The method of preparing a low-heavy rare earth magnet of claim 1, wherein in the step S3, the sintering temperature of the NdFeB magnet is 980 to 1060° C. and the sintering time is 6 to 15 h.

10. The method of preparing a low-heavy rare earth magnet of claim 1, wherein in the step S5, the diffusion temperature of NdFeB magnets is 850 to 930° C. and the diffusion time is 6 to 30 h.

11. The method of preparing a low-heavy rare earth magnet of claim 1, wherein in the step S5, an aging temperature is 420 to 680° C., an aging time is 3 to 10 h, an aging heating rate is 1 to 5° C./min, and an aging cooling rate is 5 to 20° C./min.

12. A sintered NdFeB magnet produced by the method of preparing a low-heavy rare earth magnet of claim 1.

13. The sintered NdFeB magnet of claim 12, wherein a phase structure of the sintered NdFeB magnet comprising: a main phase; an R shell consisting of at least one of Nd, Pr, Ce, La, Ho, and Gd and partially covering the main phase; a transition metal shell consisting of at least one of Cu, Al, and Ga and partially covering the main phase; and a triangular region consisting of at least one composition of Formulas 1 to 3: Formula 1, NdaFebRcMd, wherein R is at least one element of Pr, Ce, La, Ho, and Gd; M is at least three elements of Al, Cu, Ga, Ti, Co, Mg, Zn, and Sn; and a, b, c, and d are set to be 30%≤a≤70%, 5%≤b≤40%, 5%≤c≤35%, and 0%≤d≤15% in weight percentage; Formula 2, NdeFefRgHhKiMj, wherein R is at least one element of Pr, Ce, La; H is at least one element of Dy and Tb; M is at least three elements of Al, Cu, Ga, Ti, Co, Mg, Zn, and Sn; e, f, g, h, I, and j are set to be 25%≤e≤65%, 5%≤f≤35%, 5%≤g≤30%, 5%≤h≤30%, 5%≤i≤10%, and 0%≤j≤10% in weight percentage; Formula 3, NdkFelRmDnMo, wherein R is at least one element of Pr, Ce, La, Ho, and Gd; D is at least one element of Al, Cu, and Ga; M is at least one element of Ti, Co, Mg, Zn, and Sn; k, l, m, n, and o are set to be 30%≤k≤70%, 5%≤l≤35%, 5%≤m≤35%, 5%≤n≤25%, and 0%≤o≤10% in weight percentage.

14. The sintered NdFeB magnet of claim 12, wherein a thickness of the sintered NdFeB magnet is 0.3 to 6 mm.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0036] FIG. 1 shows a SEM image using ZISS electron microscopy of the microstructure of an exemplary Nd—Fe—B permanent magnet after diffusion and aging.

DETAILED DESCRIPTION OF THE EMBODIMENTS

[0037] Reference will now be made in detail to embodiments. The present disclosure, however, may be embodied in various different forms, and should not be construed as being limited to only the illustrated embodiments herein. Rather, these embodiments are provided as examples so that this disclosure will be thorough and complete, and will fully convey the aspects and features of the present disclosure to those skilled in the art.

EXEMPLARY EMBODIMENTS

[0038] The preparation process of exemplary sintered NdFeB magnets will now be described in detail.

[0039] NdFeB alloy raw materials are mixed with different ratios of NdCu, NdAl, and NdGa and a conventional lubricant is added. Magnet compositions No. 1 to 22 are summarized in Table 1 below.

[0040] The preparation method of the low-heavy rare earth magnet was as follows:

[0041] (1) The raw materials of a NdFeB alloy are smelted and strip casted process to obtain a NdFeB alloy sheets, and the obtained NdFeB alloy sheets are mechanically crushed into flaky alloy sheets of 150 to 400 μm size;

[0042] (2) NdCu, NdAl and NdGa as low melting point powders with a particle size range of 200 nm to 4 μm are mixed and added to the flaky alloy sheets;

[0043] (3) The mixed materials of the flaky alloy sheets, a low melting point powders and lubricant are put into the hydrogen treatment furnace for hydrogen absorption and dehydrogenation treatment, where the dehydrogenation temperature is 400 to 600° C.; the low melting point alloy powders are coating the flaky alloy sheets; NdFeB powders are prepared by air milling and the NdFeB powder particle size is 3 to 5 μm;

[0044] The addition of a lubricant during the jet milling step is well-known; Any common type of lubricant and its dosage can be used; There is no specific restriction;

[0045] (4) The NdFeB magnet powders after the air flow grinding is oriented molding and pressed into the blank by isostatic pressure;

[0046] (5) The pressing blank of NdFeB is sintered in vacuum, and quickly cooled by argon, and then the blank is heat-treated including a primary tempering and secondary aging. The sintered magnet performance is tested, and the specific process conditions and magnet characteristic are shown in Table 2;

[0047] (6) The sintered NdFeB magnet is mechanically processed to obtain the desired shape and then a diffusion source film is coated on the sintered NdFeB magnet; The weight of Dy on the sintered NdFeB magnet is 1.0 wt. %, and the weight of Dy in Dy alloy on the sintered NdFeB magnet is 1.0 wt. %.

[0048] An increase in coercivity after diffusion of the Dy alloy reaches 636.8 to 756.2 kA/m, and the process allows reducing the production cost of the magnet due to the low Dy content.

[0049] The diffusion sources based on Dy alloys and magnet characteristics of the sintered NdFeB magnets are shown in Table 3.

[0050] Pure diffusion examples of Dy and magnet characteristics of the sintered NdFeB magnets are shown in Table 4.

TABLE-US-00001 TABLE 1 Magnet composition (%) Number Al B Co Cu Fe Ga Nd Pr Ti Ho TRE 1 0.30 0.97 1.00 0.15 Margin 0.05 29.52 29.52 2 0.59 0.95 1.00 0.15 Margin 0.11 31.23 31.23 3 0.87 0.93 1.00 0.14 Margin 0.21 33.19 33.19 4 0.83 0.95 1.00 0.29 Margin 0.05 31.51 31.51 5 0.41 0.92 1.00 0.29 Margin 0.10 26.35 6.59 0.05 32.94 6 0.53 0.95 1.00 0.29 Margin 0.21 24.81 6.20 0.05 31.02 7 0.82 0.94 1.00 0.44 Margin 0.05 25.61 6.40 0.05 32.02 8 0.53 0.95 1.00 0.44 Margin 0.11 24.74 6.19 0.06 30.93 9 0.35 0.92 1.00 0.43 Margin 0.21 26.19 6.55 0.05 32.73 10 0.42 0.97 1.00 0.15 Margin 0.11 23.89 5.97 0.10 29.86 11 0.59 0.94 1.00 0.15 Margin 0.21 31.82 0.10 31.82 12 0.86 0.92 1.00 0.14 Margin 0.31 33.76 0.10 33.76 13 0.82 0.94 1.00 0.29 Margin 0.11 23.86 7.95 0.10 31.81 14 0.41 0.91 1.00 0.29 Margin 0.21 25.14 8.38 0.10 33.52 15 0.53 0.94 1.00 0.29 Margin 0.32 23.71 7.90 0.20 31.61 16 0.81 0.94 1.00 0.43 Margin 0.11 32.31 0.20 32.31 17 0.53 0.94 1.00 0.44 Margin 0.21 31.52 0.20 31.52 18 0.35 0.91 1.00 0.43 Margin 0.31 33.31 0.20 33.31 19 0.31 0.97 0.91 0.20 Margin 0.18 24.83 6.39 0.20 31.22 20 0.70 1.00 1.00 0.15 Margin 0.20 25.00 6.20 0.10 31.20 21 0.34 0.91 1.00 0.15 Margin 0.20 22.00 5.50 0.15 3.37 30.87 22 0.28 0.87 0.80 0.38 Margin 0.37 23.62 7.60 0.10 31.22

TABLE-US-00002 TABLE 2 Performance Sintering holding One-level holding Secondary holding Heating Cooling Hcj Hk/ Number ° C. h ° C. h ° C. h ° C./min ° C./min Br(T) (kA/m) Hcj 1 980 15 850 3 450 3 5 5 14.55 14.29 0.99 2 980 15 850 3 450 3 5 5 13.86 16.72 0.99 3 980 15 850 3 450 3 5 10 13.17 19.42 0.97 4 980 15 850 3 450 3 5 15 13.56 17.48 0.98 5 980 15 850 3 480 3 3 15 13.67 16.49 0.98 6 1020 13 850 3 480 3 1 5 13.93 16.69 0.98 7 1020 13 850 3 480 3 1 20 13.47 17.68 0.97 8 1020 13 850 3 480 3 3 20 13.96 16.15 0.97 9 1020 13 850 3 510 3 3 20 13.74 16.65 0.98 10 1020 13 850 3 510 3 3 10 14.32 15.12 0.98 11 1040 9 850 3 510 3 1 10 13.71 17.26 0.97 12 1040 9 850 3 510 3 1 10 13.02 19.90 0.98 13 1040 9 850 3 550 3 5 10 13.45 18.90 0.98 14 1040 9 850 3 550 3 5 15 13.52 17.25 0.98 15 1040 9 850 3 550 3 5 15 13.77 17.52 0.98 16 1060 6 850 3 550 3 3 20 13.38 18.06 0.97 17 1060 6 850 3 580 3 1 20 13.80 16.93 0.97 18 1060 6 850 3 580 3 3 20 13.58 17.40 0.98 19 1060 6 850 3 580 3 3 5 13.70 18.50 0.98 20 1060 6 850 3 660 3 1 5 13.40 19.00 0.98 21 1050 12 850 3 660 3 1 5 13.30 18.00 0.99 22 1060 7 850 3 660 3 1 15 13.60 20.00 0.99

TABLE-US-00003 TABLE 3 Performance Diffusion holding Aging holding Heating Cooling after Diffusion Diffusion Temp. time Temp. time rate rate Hcj Hk/ Example Source Size(mm) ° C. hours ° C. hours ° C./min ° C./min Br(T) (kA/m) Hcj 1 PrDyCu 10*10*3 850 30 420 10 5 5 1.435 1950.2 0.97 2 PrDyCu 10*10*3 850 30 480 7 5 5 1.362 2029.8 0.97 3 PrDyCu 10*10*3 850 30 500 5 5 10 1.295 2149.2 0.96 4 PrDyCu 10*10*3 880 20 450 8 5 15 1.332 1990 0.96 5 NdDyCu 10*10*4 880 20 500 6 3 15 1.342 2069.6 0.96 6 NdDyCu 10*10*4 880 20 600 5 1 5 1.37 1990 0.97 7 NdDyCu 10*10*4 880 20 500 3 1 20 1.325 2109.4 0.96 8 PrDyCu 10*10*4 900 15 450 8 3 20 1.375 2029.8 0.96 9 PrDyCu 10*10*5 900 16 500 6 3 20 1.35 2069.6 0.97 10 PrDyCu 10*10*5 900 17 520 4 3 10 1.41 1990 0.97 11 PrDyCu 10*10*5 900 18 600 5 1 10 1.35 1990 0.97 12 PrDyCu 10*10*5 900 19 500 3 1 10 1.28 2189 0.97 13 PrDyCuGa 10*10*3 910 10 450 8 5 10 1.32 2109.4 0.96 14 PrDyCuGa 10*10*3 910 10 500 6 5 15 1.33 2029.8 0.97 15 PrDyCuGa 10*10*3 910 10 520 4 5 15 1.352 2109.4 0.97 16 PrDyCuAl 10*10*3 910 10 450 5 3 20 1.315 2149.2 0.97 17 PrDyCuAl 10*10*3 910 10 480 3 1 20 1.36 1990 0.96 18 PrDyCuAl 10*10*3 930 6 450 8 3 20 1.332 2069.6 0.98 19 PrDyCu 10*10*4 930 6 500 6 3 5 1.345 2149.2 0.97 20 PrDyCu 10*10*4 930 6 520 4 3 5 1.32 2109.4 0.97 21 PrDyCu 10*10*4 930 6 600 5 1 5 1.305 2189 0.98 22 PrDyCu 10*10*4 930 6 680 3 1 15 1.34 2189 0.98

TABLE-US-00004 TABLE 4 Performance Diffusion holding Aging holding Heating Cooling after Diffusion Diffusion Size Temp. time Temp. time rate rate Hcj Hk/ proportionality Source (mm) ° C. hours ° C. hours ° C./min ° C./min Br(T) (kA/m) Hcj 1 Dy 10*10*3 850 30 420 10 5 5 1.436 1791.0 0.97 2 Dy 10*10*3 850 30 480 7 5 5 1.363 1870.6 0.97 3 Dy 10*10*3 850 30 500 5 5 10 1.297 1950.2 0.96 4 Dy 10*10*3 880 20 450 8 5 15 1.333 1791.0 0.96 5 Dy 10*10*4 880 20 500 6 3 15 1.344 1910.4 0.96 6 Dy 10*10*4 880 20 600 5 1 5 1.372 1870.6 0.97 7 Dy 10*10*4 880 20 500 3 1 20 1.326 1990.0 0.96 8 Dy 10*10*4 900 15 450 8 3 20 1.377 1910.4 0.96 9 Dy 10*10*5 900 16 500 6 3 20 1.352 1910.4 0.97 10 Dy 10*10*5 900 17 520 4 3 10 1.411 1830.8 0.97 11 Dy 10*10*5 900 18 600 5 1 10 1.351 1751.2 0.97 12 Dy 10*10*5 900 19 500 3 1 10 1.282 1990.0 0.97 13 Dy 10*10*3 910 10 450 8 5 10 1.322 1950.2 0.96 14 Dy 10*10*3 910 10 500 6 5 15 1.331 1910.4 0.97 15 Dy 10*10*3 910 10 520 4 5 15 1.354 1990.0 0.97 16 Dy 10*10*3 910 10 450 5 3 20 1.316 2029.8 0.96 17 Dy 10*10*3 910 10 480 3 1 20 1.360 1870.6 0.98 18 Dy 10*10*3 930 6 450 8 3 20 1.333 1950.2 0.97 19 Dy 10*10*4 930 6 500 6 3 5 1.346 1950.2 0.97 20 Dy 10*10*4 930 6 520 4 3 5 1.320 1990.0 0.98 21 Dy 10*10*4 930 6 600 5 1 5 1.306 1990.0 0.98 22 Dy 10*10*4 930 6 680 3 1 15 1.340 1990.0 0.98

[0051] Based on the above data, the NdCu, NdAl, NdGa phase powders are added to the grain boundary of the NdFeB alloy flakes, whose grain boundary has a low melting point. The grain boundary channel of NdFeB permanent magnets are suitable for the diffusion, especially when the diffusion source is a heavy rare earth alloys. The coercivity increases significantly to ΔHcj>597 kA/m after diffusion and the coercivity is significantly better than in case of diffusion of pure Dy.

[0052] Specifically, the various embodiments of Table 3 and the comparative examples of Table 4 are analyzed as follows:

[0053] Example 1, with the same NdFeB magnet composition and size, the same diffusion temperature and aging temperature, etc., the performance of example 1 by diffusion PrDyCu decreased by 0.02 T of Br, increased by 812 kA/m of Hcj compared with the pre-diffusion performance of NdFeB magnet. The performance of comparative example 1 by diffusion Dy decreased by 0.019 T of Br, increased by 653.5 kA/m of Hcj compared with the pre-diffusion performance of NdFeB magnet. Therefore, the Hcj of diffusion PrDyCu increased more significantly and the advantages were more pronounced.

[0054] Example 2, with the same NdFeB magnet composition and size, the same diffusion temperature and aging temperature, etc., the performance of example 2 by diffusion PrDyCu decreased by 0.024 T of Br, increased by 699 kA/m of Hcj compared with the pre-diffusion performance of NdFeB magnet. The performance of comparative example 2 by diffusion Dy decreased by 0.023 T of Br, increased by 539.7 kA/m of Hcj compared with the pre-diffusion performance of NdFeB magnet. Therefore, the Hcj of diffusion PrDyCu increased more significantly and the advantages were more pronounced.

[0055] Example 3, with the same NdFeB magnet composition and size, the same diffusion temperature and aging temperature, etc., the performance of example 3 by diffusion PrDyCu decreased by 0.022 T of Br, increased by 603.4 kA/m of Hcj compared with the pre-diffusion performance of NdFeB magnet. The performance of comparative example 3 by diffusion Dy decreased by 0.020 T of Br, increased by 404.4 kA/m of Hcj compared with the pre-diffusion performance of NdFeB magnet. Therefore, the Hcj of diffusion PrDyCu increased more significantly and the advantages were more pronounced.

[0056] Example 4, with the same NdFeB magnet composition and size, the same diffusion temperature and aging temperature, etc., the performance of example 4 by diffusion PrDyCu decreased by 0.024 T of Br, increased by 598.6 kA/m of Hcj compared with the pre-diffusion performance of NdFeB magnet. The performance of comparative example 4 by diffusion Dy decreased by 0.023 T of Br, increased by 400 kA/m of Hcj compared with the pre-diffusion performance of NdFeB magnet. Therefore, the Hcj of diffusion PrDyCu increased more significantly and the advantages were more pronounced.

[0057] Example 5, with the same NdFeB magnet composition and size, the same diffusion temperature and aging temperature, etc., the performance of example 5 by diffusion NdDyCu decreased by 0.025 T of Br, increased by 757 kA/m of Hcj compared with the pre-diffusion performance of NdFeB magnet. The performance of comparative example 5 by diffusion Dy decreased by 0.023 T of Br, increased by 597.8 kA/m of Hcj compared with the pre-diffusion performance of NdFeB magnet. Therefore, the Hcj of diffusion NdDyCu increased more significantly and the advantages were more pronounced.

[0058] Example 6, with the same NdFeB magnet composition and size, the same diffusion temperature and aging temperature, etc., the performance of example 6 by diffusion NdDyCu decreased by 0.023 T of Br, increased by 661.5 kA/m of Hcj compared with the pre-diffusion performance of NdFeB magnet. The performance of comparative example 6 by diffusion Dy decreased by 0.021 T of Br, increased by 542 kA/m of Hcj compared with the pre-diffusion performance of NdFeB magnet. Therefore, the Hcj of diffusion NdDyCu increased more significantly and the advantages were more pronounced.

[0059] Example 7, with the same NdFeB magnet composition and size, the same diffusion temperature and aging temperature, etc., the performance of example 7 by diffusion NdDyCu decreased by 0.022 T of Br, increased by 702.1 kA/m of Hcj compared with the pre-diffusion performance of NdFeB magnet. The performance of comparative example 7 by diffusion Dy decreased by 0.021 T of Br, increased by 582.7 kA/m of Hcj compared with the pre-diffusion performance of NdFeB magnet. Therefore, the Hcj of diffusion NdDyCu increased more significantly and the advantages were more pronounced.

[0060] Example 8, with the same NdFeB magnet composition and size, the same diffusion temperature and aging temperature, etc., the performance of example 8 by diffusion PrDyCu decreased by 0.021 T of Br, increased by 744.3 kA/m of Hcj compared with the pre-diffusion performance of NdFeB magnet. The performance of comparative example 8 by diffusion Dy decreased by 0.019 T of Br, increased by 642.8 kA/m of Hcj compared with the pre-diffusion performance of NdFeB magnet. Therefore, the Hcj of diffusion PrDyCu increased more significantly and the advantages were more pronounced.

[0061] Example 9, with the same NdFeB magnet composition and size, the same diffusion temperature and aging temperature, etc., the performance of example 9 by diffusion PrDyCu decreased by 0.024 T of Br, increased by 744.3 kA/m of Hcj compared with the pre-diffusion performance of NdFeB magnet. The performance of comparative example 9 by diffusion Dy decreased by 0.022 T of Br, increased by 585.1 kA/m of Hcj compared with the pre-diffusion performance of NdFeB magnet. Therefore, the Hcj of diffusion PrDyCu increased more significantly and the advantages were more pronounced.

[0062] Example 10, with the same NdFeB magnet composition and size, the same diffusion temperature and aging temperature, etc., the performance of example 10 by diffusion PrDyCu decreased by 0.022 T of Br, increased by 786.4 kA/m of Hcj compared with the pre-diffusion performance of NdFeB magnet. The performance of comparative example 10 by diffusion Dy decreased by 0.021 T of Br, increased by 627.2 kA/m of Hcj compared with the pre-diffusion performance of NdFeB magnet. Therefore, the Hcj of diffusion PrDyCu increased more significantly and the advantages were more pronounced.

[0063] Example 11, with the same NdFeB magnet composition and size, the same diffusion temperature and aging temperature, etc., the performance of example 11 by diffusion PrDyCu decreased by 0.021 T of Br, increased by 616.1 kA/m of Hcj compared with the pre-diffusion performance of NdFeB magnet. The performance of comparative example 11 by diffusion Dy decreased by 0.02 T of Br, increased by 377.3 kA/m of Hcj compared with the pre-diffusion performance of NdFeB magnet. Therefore, the Hcj of diffusion PrDyCu increased more significantly and the advantages were more pronounced.

[0064] Example 12, with the same NdFeB magnet composition and size, the same diffusion temperature and aging temperature, etc., the performance of example 12 by diffusion PrDyCu decreased by 0.022 T of Br, increased by 605 kA/m of Hcj compared with the pre-diffusion performance of NdFeB magnet. The performance of comparative example 12 by diffusion Dy decreased by 0.02 T of Br, increased by 406 kA/m of Hcj compared with the pre-diffusion performance of NdFeB magnet. Therefore, the Hcj of diffusion PrDyCu increased more significantly and the advantages were more pronounced.

[0065] Example 13, with the same NdFeB magnet composition and size, the same diffusion temperature and aging temperature, etc., the performance of example 13 by diffusion PrDyCuGa decreased by 0.025 T of Br, increased by 605 kA/m of Hcj compared with the pre-diffusion performance of NdFeB magnet. The performance of comparative example 13 by diffusion Dy decreased by 0.023 T of Br, increased by 445.8 kA/m of Hcj compared with the pre-diffusion performance of NdFeB magnet. Therefore, the Hcj of diffusion PrDyCuGa increased more significantly and the advantages were more pronounced.

[0066] Example 14, with the same NdFeB magnet composition and size, the same diffusion temperature and aging temperature, etc., the performance of example 14 by diffusion PrDyCuGa decreased by 0.022 T of Br, increased by 656.7 kA/m of Hcj compared with the pre-diffusion performance of NdFeB magnet. The performance of comparative example 14 by diffusion Dy decreased by 0.021 T of Br, increased by 537.3 kA/m of Hcj compared with the pre-diffusion performance of NdFeB magnet. Therefore, the Hcj of diffusion PrDyCuGa increased more significantly and the advantages were more pronounced.

[0067] Example 15, with the same NdFeB magnet composition and size, the same diffusion temperature and aging temperature, etc., the performance of example 15 by diffusion PrDyCuGa decreased by 0.025 T of Br, increased by 714.8 kA/m e of Hcj compared with the pre-diffusion performance of NdFeB magnet. The performance of comparative example 15 by diffusion Dy decreased by 0.023 T of Br, increased by 595.4 kA/m of Hcj compared with the pre-diffusion performance of NdFeB magnet. Therefore, the Hcj of diffusion PrDyCuGa increased more significantly and the advantages were more pronounced.

[0068] Example 16, with the same NdFeB magnet composition and size, the same diffusion temperature and aging temperature, etc., the performance of example 16 by diffusion PrDyCuAl decreased by 0.023 T of Br, increased by 711.6 kA/m of Hcj compared with the pre-diffusion performance of NdFeB magnet. The performance of comparative example 16 by diffusion Dy decreased by 0.022 T of Br, increased by 592.2 kA/m of Hcj compared with the pre-diffusion performance of NdFeB magnet. Therefore, the Hcj of diffusion PrDyCuAl increased more significantly and the advantages were more pronounced.

[0069] Example 17, with the same NdFeB magnet composition and size, the same diffusion temperature and aging temperature, etc., the performance of example 17 by diffusion PrDyCuAl decreased by 0.02 T of Br, increased by 642.4 kA/m of Hcj compared with the pre-diffusion performance of NdFeB magnet. The performance of comparative example 17 by diffusion Dy decreased by 0.02 T of Br, increased by 523 kA/m of Hcj compared with the pre-diffusion performance of NdFeB magnet. Therefore, the Hcj of diffusion PrDyCuAl increased more significantly and the advantages were more pronounced.

[0070] Example 18, with the same NdFeB magnet composition and size, the same diffusion temperature and aging temperature, etc., the performance of example 17 by diffusion PrDyCuAl decreased by 0.026 T of Br, increased by 684.6 kA/m of Hcj compared with the pre-diffusion performance of NdFeB magnet. The performance of comparative example 18 by diffusion Dy decreased by 0.025 T of Br, increased by 565.2 kA/m of Hcj compared with the pre-diffusion performance of NdFeB magnet. Therefore, the Hcj of diffusion PrDyCuAl increased more significantly and the advantages were more pronounced.

[0071] Example 19, with the same NdFeB magnet composition and size, the same diffusion temperature and aging temperature, etc., the performance of example 19 by diffusion PrDyCu decreased by 0.025 T of Br, increased by 676.6 kA/m of Hcj compared with the pre-diffusion performance of NdFeB magnet. The performance of comparative example 19 by diffusion Dy decreased by 0.024 T of Br, increased by 477.6 kA/m of Hcj compared with the pre-diffusion performance of NdFeB magnet. Therefore, the Hcj of diffusion PrDyCu increased more significantly and the advantages were more pronounced.

[0072] Example 20, with the same NdFeB magnet composition and size, the same diffusion temperature and aging temperature, etc., the performance of example 20 by diffusion PrDyCu decreased by 0.02 T of Br, increased by 597 kA/m of Hcj compared with the pre-diffusion performance of NdFeB magnet. The performance of comparative example 20 by diffusion Dy decreased by 0.02 T of Br, increased by 477.6 kA/m of Hcj compared with the pre-diffusion performance of NdFeB magnet. Therefore, the Hcj of diffusion PrDyCu increased more significantly and the advantages were more pronounced.

[0073] Example 21, with the same NdFeB magnet composition and size, the same diffusion temperature and aging temperature, etc., the performance of example 21 by diffusion PrDyCu decreased by 0.025 T of Br, increased by 756.2 kA/m of Hcj compared with the pre-diffusion performance of NdFeB magnet. The performance of comparative example 21 by diffusion Dy decreased by 0.024 T of Br, increased by 557.2 kA/m of Hcj compared with the pre-diffusion performance of NdFeB magnet. Therefore, the Hcj of diffusion PrDyCu increased more significantly and the advantages were more pronounced.

[0074] Example 22, with the same NdFeB magnet composition and size, the same diffusion temperature and aging temperature, etc., the performance of example 22 by diffusion PrDyCu decreased by 0.02 T of Br, increased by 597 kA/m of Hcj compared with the pre-diffusion performance of NdFeB magnet. The performance of comparative example 22 by diffusion Dy decreased by 0.02 T of Br, increased by 398 kA/m of Hcj compared with the pre-diffusion performance of NdFeB magnet. Therefore, the Hcj of diffusion PrDyCu increased more significantly and the advantages were more pronounced.

[0075] From the above, it can be seen that after diffusion and aging the coercivity of the examples of Table 3 is significantly better than the coercivity of the comparative examples of Table 4.

[0076] Microstructure assays of the magnets of Table 3 are determined by SEM with a ZISS electron microscopy and EDS of Oxford. The following can be seen: A rare earth shell, that is to say, R shell, is around of more than 60% of the grain, and a transition metal shell is around of more than 40% of the grain. In addition, three sampling points (a), (b), (c) are determined at different locations. However, the small triangle area with a size <1 μm is characterized by a 6:14 phase type rich Cu, that is, the chemical formula of EDS is: Fe.sub.30-51(NdPr).sub.45-60Cu.sub.2-15Ga.sub.0-5Co.sub.0-5 or Fe.sub.30-51(NdPr).sub.45-60Dy.sub.2-15Cu.sub.2-15Ga.sub.0-5Co.sub.0-5, where the number is the percentage of weight at the foot of the element. The three points are shown in FIG. 1. White phase area of the point composition a, which is sample point composition 1 are summarized as Formula 1. Grey phase area of the point composition b, which is sample point composition 2 are summarized as Formula 3. Sandwich shape area including heavy rare earth element of the point composition c, which is sample point composition 3 are summarized as Formula 2.

Example 1

[0077] The magnet diffused with PrDyCu has the following microstructure: Pr, Dy rare earth shell and transition metal shell Cu, and the formation of sample point composition 1: Nd.sub.50-70Fe.sub.10-30Pr.sub.10-20Cu.sub.0-5, sample point composition 2: Nd.sub.50-70Fe.sub.10-35Pr.sub.10-20Cu.sub.10-20Co.sub.0-5, sample point composition 3: Nd.sub.50-55Fe.sub.10-30Pr.sub.5-15Dy.sub.5-15Cu.sub.0-5.

Example 2

[0078] The magnet diffused with PrDyCu has the following microstructure: Pr, Dy rare earth shell and transition metal shell Cu, and the formation of sample point composition 1: Nd.sub.50-65Fe.sub.10-30Pr.sub.10-25Cu.sub.0-5Ga.sub.0-5Al.sub.0-3, sample point composition 2: Nd.sub.50-70Fe.sub.10-35Pr.sub.10-20Cu.sub.10-15Co.sub.0-5, sample point composition 3: Nd.sub.50-55Fe.sub.10-30Pr.sub.5-15Dy.sub.5-15Cu.sub.0-5.

Example 3

[0079] The magnet diffused with PrDyCu has the following microstructure: Pr, Dy rare earth shell and transition metal shell Cu and Al, and the formation of sample point composition 1: Nd.sub.45-60Fe.sub.10-35Pr.sub.10-20Cu.sub.3-8Ga.sub.0-5Al.sub.3-5, sample point composition 2: Nd.sub.45-65Fe.sub.10-30Pr.sub.10-20Cu.sub.10-25Co.sub.0-5Al.sub.0-5, sample point composition 3: Nd.sub.45-55Fe.sub.10-30Pr.sub.5-20Dy.sub.5-10Cu.sub.2-5Al.sub.2-10

Example 4

[0080] The magnet diffused with PrDyCu has the following microstructure: Pr, Dy rare earth shell and transition metal shell Cu and Al, and the formation of sample point composition 1: Nd.sub.45-60Fe.sub.10-35Pr.sub.10-20Cu.sub.3-8Ga.sub.0-5Al.sub.3-5, sample point composition 2: Nd.sub.45-65Fe.sub.10-30Pr.sub.10-20Cu.sub.10-25Co.sub.0-5Al.sub.0-5, sample point composition 3: Nd.sub.45-55Fe.sub.10-30Pr.sub.5-20Dy.sub.5-10Cu.sub.2-5Al.sub.2-10

Example 5

[0081] The magnet diffused with NdDyCu has the following microstructure: Nd, Dy rare earth shell and transition metal shell Cu, and the formation of sample point composition 1: Nd.sub.50-65Pr.sub.10-15Fe.sub.10-30Cu.sub.2-6Go.sub.0-5, sample point composition 2: Nd.sub.45-60Pr.sub.10-20Fe.sub.5-30Cn.sub.10-20Co.sub.0-5, sample point composition 3: Nd.sub.45-60Pr.sub.5-15Dy.sub.5-15Fe.sub.5-30

Example 6

[0082] The magnet diffused with NdDyCu has the following microstructure: Nd, Dy rare earth shell and transition metal shell Cu, and the formation of sample point composition 1: Nd.sub.45-60Pr.sub.10-20Fe.sub.10-30Cu.sub.2-5Ga.sub.0-5 sample point composition 2: Nd.sub.50-60Pr.sub.10-15Fe.sub.5-25Cu.sub.5-25Co.sub.0-5, sample point composition 3: Nd.sub.45-60Pr.sub.5-12Dy.sub.5-20Fe.sub.5-25

Example 7

[0083] The magnet diffused with NdDyCu has the following microstructure: Nd, Dy rare earth shell and transition metal shell Cu and Al, and the formation of sample point composition 1: Nd.sub.50-65Pr.sub.10-15Fe.sub.10-40Cu.sub.5-10Al.sub.0-5 sample point composition 2: Nd.sub.50-60Pr.sub.10-15Fe.sub.5-25Cu.sub.5-15Co.sub.0-5Al.sub.0-5, sample point composition 3: Nd.sub.50-60Pr.sub.5-15Dy.sub.5-25Fe.sub.5-30Al.sub.2-10

Example 8

[0084] The magnet diffused with PrDyCu has the following microstructure: Pr, Dy rare earth shell and transition metal shell Cu, and the formation of sample point composition 1: Nd.sub.40-60Pr.sub.20-30Fe.sub.10-30Cu.sub.3-8 sample point composition 2: Nd.sub.35-50Pr.sub.15-30Fe.sub.5-25Cu.sub.5-20Co.sub.0-5, sample point composition 3: Nd.sub.35-45Pr.sub.10-25Dy.sub.5-25Fe.sub.10-30Co.sub.0-5Cu.sub.0-5

Example 9

[0085] The magnet diffused with PrDyCu has the following microstructure: Pr, Dy rare earth shell and transition metal shell Cu, and the formation of sample point composition 1: Nd.sub.40-60Pr.sub.20-30Fe.sub.10-30Cu.sub.3-8 sample point composition 2: Nd.sub.35-50Pr.sub.15-30Fe.sub.5-25Cu.sub.5-20Co.sub.0-5, sample point composition 3: Nd.sub.35-45Pr.sub.15-25Dy.sub.5-25Fe.sub.10-30Co.sub.0-5Cu.sub.0-5

Example 10

[0086] The magnet diffused with PrDyCu has the following microstructure: Pr, Dy rare earth shell and transition metal shell Cu, and the formation of sample point composition 1: Nd.sub.40-60Pr.sub.20-35Fe.sub.10-30Cu.sub.0-5 sample point composition 2: Nd.sub.35-45Pr.sub.15-35Fe.sub.5-30Cu.sub.5-20Co.sub.0-5, sample point composition 3: Nd.sub.25-40Pr.sub.10-25Dy.sub.5-15Fe.sub.10-30Co.sub.0-5Cu.sub.0-5

Example 11

[0087] The magnet diffused with PrDyCu has the following microstructure: Pr, Dy rare earth shell and transition metal shell Cu, and the formation of sample point composition 1: Nd.sub.50-65Fe.sub.10-25Pr.sub.10-20Cu.sub.0-5Ga.sub.0-5Al.sub.0-5 sample point composition 2: Nd.sub.45-70Fe.sub.10-30Pr.sub.10-25Cu.sub.10-25Co.sub.0-5Ga.sub.0-5, sample point composition 3: Nd.sup.45-55Fe.sub.10-30Pr.sub.5-20Dy.sub.5-20Cu.sub.0-5

Example 12

[0088] The magnet diffused with PrDyCu has the following microstructure: Pr, Dy rare earth shell and transition metal shell Cu, and the formation of sample point composition 1: Nd.sub.50-65Fe.sub.10-30Pr.sub.10-25Cu.sub.0-5Ga.sub.2-7Al.sub.3-7 sample point composition 2: Nd.sub.50-65Fe.sub.10-35Pr.sub.5-20Cu.sub.10-20Cu.sub.0-5Al.sub.0-5, sample point composition 3: Nd.sub.45-55Fe.sub.10-30Pr.sub.5-20Dy.sub.5-10Cu.sub.0-5Ga.sub.0-5

Example 13

[0089] The magnet diffused with PrDyCuGa has the following microstructure: Pr, Dy rare earth shell and transition metal shell Cu and Ga, and the formation of sample point composition 1: Nd.sub.45-55Pr.sub.20-25Fe.sub.15-30Ga.sub.2-10Cu.sub.3-5 sample point composition 2: Nd.sub.35-45Pr.sub.25-35Fe.sub.10-35Cu.sub.5-15Ga.sub.5-10Co.sub.2-5, sample point composition 3: Nd.sub.30-45Pr.sub.25-30Dy.sub.5-15Fe.sub.5-25Cu.sub.0-5

Example 14

[0090] The magnet diffused with PrDyCuGa has the following microstructure: Pr, Dy rare earth shell and transition metal shell Cu and Ga, and the formation of sample point composition 1: Nd.sub.40-55Pr.sub.20-30Fe.sub.15-30Ga.sub.2-10Cu.sub.3-5 sample point composition 2: Nd.sub.30-50Pr.sub.25-30Fe.sub.10-30Cu.sub.5-10Ga.sub.5-10Co.sub.2-5, sample point composition 3: Nd.sub.30-40Pr.sub.25-30Dy.sub.5-15Fe.sub.5-25Cu.sub.0-5

Example 15

[0091] The magnet diffused with PrDyCuGa has the following microstructure: Pr, Dy rare earth shell and transition metal shell Cu and Ga, and the formation of sample point composition 1: Nd.sub.40-55Pr.sub.20-30Fe.sub.15-25Ga.sub.5-10Cu.sub.3-10 sample point composition 2: Nd.sub.30-45Pr.sub.25-35Fe.sub.10-30Cu.sub.5-10Ga.sub.5-10Co.sub.2-5, sample point composition 3: Nd.sub.30-40Pr.sub.15-30Dy.sub.5-20Fe.sub.5-25Cu.sub.0-5

Example 16

[0092] The magnet diffused with PrDyCuAl has the following microstructure: Pr, Dy rare earth shell and transition metal shell Cu and Al, and the formation of sample point composition 1: Nd.sub.45-65Fe.sub.10-35Pr.sub.5-15Cu.sub.5-15Al.sub.5-10 sample point composition 2: Nd.sub.50-65Fe.sub.10-20Pr.sub.10-15Cu.sub.10-25Al.sub.0-5, sample point composition 3: Nd.sub.45-65Fe.sub.5-30Pr.sub.5-20Dy.sub.5-10Cu.sub.5-10Al.sub.2-10

Example 17

[0093] The magnet diffused with PrDyCuAl has the following microstructure: Pr, Dy rare earth shell and transition metal shell Cu and Al, and the formation of sample point composition 1: Nd.sub.45-55Fe.sub.10-30Pr.sub.5-20Cu.sub.5-10Al.sub.2-5 sample point composition 2: Nd.sub.45-60Fe.sub.10-20Pr.sub.10-20Cu.sub.10-20Ga.sub.0-5Al.sub.0-5, sample point composition 3: Nd.sub.45-60Fe.sub.5-25Pr.sub.5-25Dy.sub.5-15Cu.sub.5-10Al.sub.3-5

Example 18

[0094] The magnet diffused with PrDyCuAl has the following microstructure: Pr, Dy rare earth shell and transition metal shell Cu and Al, and the formation of sample point composition 1: Nd.sub.50-65Fe.sub.10-30Pr.sub.5-20Cu.sub.5-10Al.sub.2-5 sample point composition 2: Nd.sub.45-60Fe.sub.10-25Pr.sub.10-20Cu.sub.10-20Ga.sub.0-5Al.sub.0-5, sample point composition 3: Nd.sub.45-65Fe.sub.5-30Pr.sub.5-20Dy.sub.5-15Cu.sub.5-10Al.sub.5-10

Example 19

[0095] The magnet diffused with PrDyCu has the following microstructure: Pr, Dy rare earth shell and transition metal shell Cu, and the formation of sample point composition 1: Nd.sub.45-55Fe.sub.5-30Pr.sub.20-35Cu.sub.0-5 sample point composition 2: Nd.sub.35-55Fe.sub.5-30Pr.sub.10-35Cu.sub.5-10Ga.sub.0-5Co.sub.0-5 sample point composition 3: Nd.sub.45-55Fe.sub.5-10Pr.sub.10-30Dy.sub.5-20Cu.sub.0-5

Example 20

[0096] The magnet diffused with PrDyCu has the following microstructure: Pr, Dy rare earth shell and transition metal shell Cu, and the formation of sample point composition 1: Nd.sub.35-50Fe.sub.15-40Pr.sub.15-30Cu.sub.0-10Ga.sub.0-3Al.sub.0-3 sample point composition 2: Nd.sub.40-55Fe.sub.5-35Pr.sub.15-30Cu.sub.5-25Ga.sub.0-5Co.sub.0-5 sample point composition 3: Nd.sub.40-60Fe.sub.3-30Pr.sub.10-20Dy.sub.5-25

Example 21

[0097] The magnet diffused with PrDyCu has the following microstructure: Pr, Dy rare earth shell and transition metal shell Cu, and the formation of sample point composition 1: Nd.sub.30-45Fe.sub.10-30Pr.sub.20-25Cu.sub.5-10Ga.sub.0-5Co.sub.0-5Ti.sub.0-5 sample point composition 2: Nd.sub.35-45Fe.sub.5-30Pr.sub.15-30Cu.sub.5-25Ga.sub.0-3Co.sub.0-5 sample point composition 3: Nd.sub.30-40Fe.sub.5-25Pr.sub.10-15Dy.sub.10-30Ho.sub.5-10

Example 22

[0098] The magnet diffused with PrDyCu has the following microstructure: Pr, Dy rare earth shell and transition metal shell Cu, and the formation of sample point composition 1: Nd.sub.25-35Fe.sub.20-30Pr.sub.20-30Cu.sub.0-10Ga.sub.0-5 sample point composition 2: Nd.sub.40-55Fe.sub.10-25Pr.sub.15-40Cu.sub.5-20Ga.sub.0-10Co.sub.0-5, sample point composition 3: Nd.sub.45-55Fe.sub.10-20Pr.sub.20-30Dy.sub.5-20