ALLOYS, MAGNETIC MATERIALS, BONDED MAGNETS AND METHODS FOR PRODUCING THE SAME

Abstract

The present invention relates to an alloy with composition of RE-Fe-M-B as defined herein, wherein said alloy comprises at least 80 vol % RE.sub.2Fe.sub.14B phase, the average crystal grain size of the RE.sub.2Fe.sub.14B phase is in the range of about 20 nm to about 40 nm, and the alloy is an alloy ribbon having a width measured from a left edge to a center portion to a right edge, and the average crystal RE.sub.2Fe.sub.14B grain size difference between the center portion, and left and right edges of said alloy ribbon is less than 20%. The present invention also relates to a method for preparing an alloy ribbon with composition of RE-Fe-M-B as defined herein comprising the steps of: (i) ejecting a melt of the alloy with composition of RE-Fe-M-B onto a rotating wheel at a mass flow rate of about 0.2 kg/min to about 1.0 kg/min; and (ii) quenching the melt using the rotating wheel to obtain said alloy ribbon

Claims

1. An alloy with composition of Formula (I):
RE-Fe-M-B Formula (I) wherein: RE is one or more rare earth metals; Fe is iron; M is absent or one or more metals; and B is boron; wherein: said alloy comprises at least 80 vol % RE.sub.2Fe.sub.14B phase; the average crystal grain size of the RE.sub.2Fe.sub.14B phase is in the range of 20 nm to 40 nm; and the alloy is an alloy ribbon having a width measured from a left edge to a center portion to a right edge, and the average crystal RE.sub.2Fe.sub.14B grain size difference between the center portion, and left and right edges of said alloy ribbon is less than 20%.

2. The alloy of claim 1, comprising at least 98 vol % RE.sub.2Fe.sub.14B phase.

3. The alloy of claim 1, wherein the left edge of the alloy ribbon comprises greater than 0% to 10% of the width, the right edge of the alloy ribbon comprises greater than 0% to 10% of the width, and the centre portion of the alloy ribbon comprises 1% to 40% of the width, or wherein the average crystal RE.sub.2Fe.sub.14B grain size at the center portion of said alloy ribbon is in the range of 25 nm to 40 nm, and the average crystal RE.sub.2Fe.sub.14B grain size at the left and right edges of said alloy ribbon is 20 nm to 30 nm.

4. (canceled)

5. The alloy of claim 1, wherein RE is one or more rare earth metals selected from the group consisting of lanthanum (La), cerium (Ce), neodymium (Nd), praseodymium (Pr), yttrium (Y), gadolinium (Gd), terbium (Tb), dysoprium (Dy), holmium (Ho), and ytterbium (Yb), or wherein RE is selected from the group consisting of: (i) Nd; (ii) Nd, Pr; (iii) Nd, Pr, La; (iv) Nd, Pr, Ce; (v) Nd, Pr, La, Ce; (vi) Nd, La; (vii) Nd, Ce; (viii) Nd, Ce, La; (ix) Pr; (x) Pr, La; (xi) Pr, Ce; and (xii) Pr, La, Ce.

6. (canceled)

7. The alloy of claim 1, wherein M is absent or wherein M is one or more metals selected from the group consisting of zirconium (Zr), niobium (Nb), molybdenum (Mo), titanium (Ti), vanadium (V), chromium (Cr), manganese (Mn), hafnium (Hf), tantalum (Ta), tungsten (W), cobalt (Co), copper (Cu), gallium (Ga) and aluminum (Al).

8. (canceled)

9. The alloy of claim 1, wherein Formula (I) is selected from the group consisting of: (i) NdFeNbB; (ii) NdFeCoB; (iii) (NdPrLa)FeAlB; (iv) (NdPr)FeZrB; (v) (NdPrCe)FeZrB; (vi) NdFeCoB; (vii) NdFeB; (viii) (NdPr)FeB; (ix) (NdPrLaCe)FeB; (x) (NdPr)FeCoB; and (xi) (NdPr)FeNbB.

10. The alloy of claim 1, comprising less than 10 at % boron.

11. The alloy of claim 1, wherein Formula (I) is of Formula (Ia):
RE.sub.x-Fe.sub.(100-x-y-z)-M.sub.y-B.sub.z Formula (Ia) wherein: RE is one or more rare earth metals; Fe is iron; M is absent or one or more metals; B is boron; and x, y, z are atom % in which 8.0x14.0, 0y2.0 and 5.0z7.0.

12. A method for preparing an alloy ribbon with composition comprising Formula (I):
RE-Fe-M-B Formula (I) wherein: RE is one or more rare earth metals; Fe is iron; M is absent or one or more metals; and B is boron, wherein: the alloy is an alloy ribbon having a width measured from a left edge to a center portion to a right edge, and the average crystal RE.sub.2Fe.sub.14B grain size difference between the center portion, and left and right edges of said alloy ribbon is less than 20%; comprising the steps of: (i) ejecting a melt of an alloy with composition of Formula (I) onto a rotating wheel at a mass flow rate in the range of 0.2 kg/min to 1.0 kg/min, wherein the ejection temperature is in the range of 1400 C. to 1600 C., and wherein the wheel is rotating at a speed in the range of 20 m/s to 45 m/s; and (ii) quenching the melt using the rotating wheel to obtain said alloy ribbon.

13. The method of claim 12, wherein the wheel is rotating at a speed in the range of 25 m/s to 45 m/s, or wherein the melt is ejected onto the rotating wheel through one or more nozzles, wherein the mass flow rate is controlled by controlling the diameter of said nozzle(s), and wherein the nozzle diameter is preferably in the range of 0.5 mm to 1.4 mm.

14. (canceled)

15. (canceled)

16. The method of claim 12, wherein step (ii) comprises a melt spinning process.

17. The method of claim 12, wherein the alloy comprises at least 80 vol % RE.sub.2Fe.sub.14B phase, preferably at least 98 vol % RE.sub.2Fe.sub.14B phase.

18. (canceled)

19. The method of claim 17, wherein the average crystal grain size of the RE.sub.2Fe.sub.14B phase is in the range of 20 nm to 40 nm, or wherein the average crystal RE.sub.2Fe.sub.14B grain size at the center portion of the alloy ribbon is in the range of 25 nm to 40 nm, and the average RE.sub.2Fe.sub.14B grain size at the left and right edges of the alloy ribbon is 20 nm to 30 nm.

20. (canceled)

21. The method of claim 12, wherein the alloy ribbon has a thickness in the range of 20 m to 50 m, or wherein the alloy ribbon has a width in the range of 1 mm to 5 mm.

22. (canceled)

23. The method of claim 12, wherein RE is one or more rare earth metals selected from the group consisting of lanthanum (La), cerium (Ce), neodymium (Nd), praseodymium (Pr), yttrium (Y), gadolinium (Gd), terbium (Tb), dysoprium (Dy), holmium (Ho), and ytterbium (Yb), or wherein RE is selected from the group consisting of: (i) Nd; (ii) Nd, Pr; (iii) Nd, Pr, La; (iv) Nd, Pr, Ce; (v) Nd, Pr, La, Ce; (vi) Nd, La; (vii) Nd, Ce; (viii) Nd, Ce, La, (ix) Pr; (x) Pr, La; (xi) Pr, Ce, and (xii) Pr, La, Ce.

24. (canceled)

25. The method of claim 12, wherein M is absent, or wherein M is one or more metals selected from the group consisting of zirconium (Zr), niobium (Nb), molybdenum (Mo), titanium (Ti), vanadium (V), chromium (Cr), manganese (Mn), hafnium (Hf), tantalum (Ta), tungsten (W), cobalt (Co), copper (Cu), gallium (Ga) and aluminum (Al).

26. (canceled)

27. The method of claim 12, wherein Formula (I) is selected from the group consisting of: (i) NdFeNbB; (ii) NdFeCoB; (iii) (NdPrLa)FeAlB; (iv) (NdPr)FeZrB; (v) (NdPrCe)FeZrB; (vi) NdFeCoB; (vii) NdFeB; (viii) (NdPr)FeB; (ix) (NdPrLaCe)FeB; (x) (NdPr)FeCoB; and (xi) (NdPr)FeNbB.

28. The method of claim 12any one of claims 12 to 27, wherein the rapidly solidified alloy comprises less than 10 at % boron.

29. The method of claim 12, wherein Formula (I) is of Formula (Ia):
RE.sub.x-Fe.sub.(100-x-y-z)-M.sub.y-B.sub.z Formula (Ia) wherein: RE is one or more rare earth metals; Fe is iron; M is absent or one or more metals; B is boron; and x, y, z are atom % in which 8.0x14.0, 0y2.0 and 5.0z7.0.

30. A magnetic material comprising a powder of the alloy of claim 1.

31. (canceled)

Description

BRIEF DESCRIPTION OF DRAWINGS

[0209] The accompanying drawings illustrate a disclosed embodiment and serves to explain the principles of the disclosed embodiment. It is to be understood, however, that the drawings are designed for purposes of illustration only, and not as a definition of the limits of the invention.

[0210] FIG. 1 shows demagnetization curves for a: Nd.sub.11.6Fe.sub.80.3Co.sub.2.4B.sub.5.7 alloy (Sample 2 in Table 3); and b: Nd.sub.11.9Fe.sub.81Nb.sub.1.2B.sub.5.9 alloy (Sample 1 in Table 3), at different mass flow rates.

[0211] FIG. 2 is a graph showing (BH).sub.max (kJ/m.sup.3) against mass flow rate (kg/min) for a: Nd.sub.11.6Fe.sub.80.3Co.sub.2.4B.sub.5.7 alloy (Sample 2 in Table 3); and b: Nd.sub.11.9Fe.sub.81Nb.sub.1.2B.sub.5.9 alloy (Sample 1 in Table 3).

[0212] FIG. 3 is a graph showing wheel speed (m/s) against mass flow rate (kg/min) for a: Nd.sub.11.6Fe.sub.80.3Co.sub.2.4B.sub.5.7 alloy (Sample 2 in Table 3); and b: Nd.sub.11.9Fe.sub.81Nb.sub.1.2B.sub.5.9 alloy (Sample 1 in Table 3).

[0213] FIG. 4 is a graph showing ribbon thickness (m) or ribbon width (m) against mass flow rate (kg/min) for a: Nd.sub.11.6Fe.sub.80.3Co.sub.2.4B.sub.5.7 alloy (Sample 2 in Table 3); and b: Nd.sub.11.9Fe.sub.81Nb.sub.1.2B.sub.5.9 alloy (Sample 1 in Table 3).

[0214] FIG. 5 is a graph showing portion of crystalline RE.sub.2Fe.sub.14B phase (vol %) against mass flow rate (kg/min) for Nd.sub.11.6Fe.sub.80.3Co.sub.2.4B.sub.5.7 alloy (Sample 2 in Table 3).

[0215] FIG. 6 is a graph showing X-ray diffraction pattern against mass flow rate (kg/min) for Nd.sub.11.6Fe.sub.80.3Co.sub.2.4B.sub.5.7 alloy (Sample 2 in Table 3).

[0216] FIG. 7 is a graph showing average grain size of the RE.sub.2Fe.sub.14B phase (nm) against mass flow rate (kg/min) for Nd.sub.11.6Fe.sub.80.3Co.sub.2.4B.sub.5.7 alloy (Sample 2 in Table 3).

[0217] FIG. 8 shows the average grain size across the width of an alloy ribbon (from left-edge, center portion, to right-edge) at 0.2 kg/min mass flow rare, 0.5 kg/min mass flow rate, 0.8 kg/min mass flow rate, 1.3 kg/min mass flow rate and 1.9 kg/min mass flow rate for Nd.sub.11.6Fe.sub.80.3Co.sub.2.4B.sub.5.7 alloy (Sample 2 in Table 3).

[0218] FIG. 9 shows scanning electron microscope (SEM) images of an alloy ribbon (from left-edge, center portion, to right-edge) at 0.5 kg/min mass flow rate and 1.9 kg/min mass flow rate for Nd.sub.11.6Fe.sub.80.3Co.sub.2.4B.sub.5.7 alloy (Sample 2 in Table 3).

[0219] FIG. 10 is an exemplary depiction of the sections that make up the width of an alloy ribbon of the present invention.

EXAMPLES

[0220] Non-limiting examples of the invention will be further described in greater detail by reference to specific Examples, which should not be construed as in any way limiting the scope of the invention.

Example 1

General Method for Preparing Alloys

[0221] A rapidly solidified alloy of composition Nd.sub.11.6Fe.sub.80.3Co.sub.2.4B.sub.5.7 was prepared by weighing the appropriate amount of raw materials (Nd, Fe, Co, FeB) according to the composition formula with a total weight of 100 grams, placing all the raw materials into an arc-melter, melting the respective raw materials under argon atmosphere and cooling it to obtain ingots. 1% extra amount of Nd was added prior to melting to compensate for the melting loss. The alloy ingots were flipped and re-melted four times to ensure homogeneity.

[0222] The ingots were then broken into pieces and loaded into a crucible tube with a small nozzle underneath and placed into a melt-spinner. The alloy ingots were heated up and re-melted in argon atmosphere and ejected onto a rotating metal wheel to form ribbons. The ejection temperature was about 1400 C. to 1600 C., the ejection pressure was about 200 torr to 500 ton, the nozzle size was about 0.5 mm to 1.4 mm, and the wheel speed was about 20 m/s to 45 m/s. The ribbons were crushed to 40 mesh powder by a twin-roller crusher.

[0223] A rapidly solidified alloy of composition Nd.sub.11.9Fe.sub.81Nb.sub.1.2B.sub.5.9 was prepared in a similar way as described above.

[0224] Thereafter, the magnetic properties of the rapidly solidified Nd.sub.11.6Fe.sub.80.3Co.sub.2.4B.sub.5.7 alloy powder and Nd.sub.11.9Fe.sub.81Nb.sub.1.2B.sub.5.9 alloy powder were measured with a Lakeshore vibrating sample magnetometer (VSM). A demagnetization factor of 0.21 was used to correct the shape demagnetization effect in the powders. The results are shown in FIG. 1a, Table 1 (Nd.sub.11.6Fe.sub.80.3Co.sub.2.4B.sub.5.7 alloy) and FIG. 1b, Table 2 (Nd.sub.11.9Fe.sub.81Nb.sub.1.2B.sub.5.9 alloy):

TABLE-US-00001 TABLE 1 Mass flow rate B.sub.r H.sub.ci (BH).sub.max S.sub.q (kg/min) (mT) (kA/m) (kJ/m.sup.3) (%) 0.2 919 800 140 83.3 0.5 913 793 137 82.6 0.8 908 790 133 81.1 1.3 901 775 129 79.9 1.9 891 772 125 79.1

TABLE-US-00002 TABLE 2 Mass flow rate B.sub.r H.sub.ci (BH).sub.max S.sub.q (kg/min) (mT) (kA/m) (kJ/m.sup.3) (%) 0.2 869 1002 127 84.5 0.5 865 1001 125 84.0 0.8 857 977 123 84.2 1.3 848 978 119 83.2 1.9 835 967 115 82.9

[0225] It can be seen from Table 1 and Table 2 that higher magnetic properties (B.sub.r, H.sub.ci and (BH).sub.max) were obtained at lower mass flow rate for both Nd.sub.11.6Fe.sub.80.3Co.sub.2.4B.sub.5.7 alloy and Nd.sub.11.9Fe.sub.81Nb.sub.1.2B.sub.5.9 alloy. Additionally, as shown in the demagnetization curves of FIG. 1, squareness (S.sub.q, defined as (BH).sub.max/B.sub.r.sup.2) of the demagnetization curves improved with decreasing mass flow rate.

[0226] With reference to FIG. 2, it was also shown that (BH).sub.max increases linearly as mass flow rate decreases. It was shown that there is a 7 to 9 kJ/m.sup.3 increase per kg/min mass flow reduction.

Example 2

Magnetic Properties of Various other Alloys

[0227] Various other rapidly solidified alloys with various types of rare earth metals (Nd, Pr, NdPr, La, Ce, . . . ), various type of additives (Co, Nb, Zr,), and various amounts of constituting RE.sub.2Fe.sub.14B phase were made according to the method in Example 1. Thereafter, the (BH).sub.max of the rapidly solidified alloys at different mass flow rates were measured. The results are shown in Table 3.

TABLE-US-00003 TABLE 3 (BH).sub.max at (BH).sub.max at mass flow RE.sub.2Fe.sub.14B mass flow rate rate of 0.2 Sample Alloy amount of 1.9 kg/min kg/min (BH).sub.max no. (at %) (vol %) (kJ/m.sup.3) (kJ/m.sup.3) (kJ/m.sup.3) 1 Nd.sub.11.9Fe.sub.81.0Nb.sub.1.2B.sub.5.9 99.8 115 127 12 2 Nd.sub.11.6Fe.sub.80.3Co.sub.2.4B.sub.5.7 98.9 125 140 11 3 (Nd.sub.0.75Pr.sub.0.25).sub.9.9La.sub.1.9Fe.sub.81.6 99.9 106 116 10 Al.sub.1B.sub.5.6 4 (Nd.sub.0.75Pr.sub.0.25).sub.10.8Fe.sub.81.9 99.9 119 133 14 Zr.sub.1B.sub.6.3 5 (Nd.sub.0.75Pr.sub.0.25).sub.6.8Ce.sub.4.6Fe.sub.81.3 99.2 95 101 6 Zr.sub.1B.sub.6.3 6 Nd.sub.12.0Fe.sub.76.3Co.sub.5.9B.sub.5.8 99.7 130 142 12 7 Nd.sub.11.7Fe.sub.82.6B.sub.5.7 99.4 120 131 11 8 (Nd.sub.0.75Pr.sub.0.25).sub.11.2Fe.sub.83.4B.sub.5.4 95.4 120 129 9 9 (Nd.sub.0.75Pr.sub.0.25).sub.10.4Fe.sub.84.1B.sub.5.5 88.8 120 128 8 10 (Nd.sub.0.75Pr.sub.0.25).sub.6.0La.sub.3.0Ce.sub.3.0 99.7 89 98 9 Fe.sub.81.8B.sub.6.2

[0228] As shown in Table 3, remarkably higher (BH).sub.max values were achieved for all the alloys when melt-spun at a low mass flow rate. It was shown that a 6 to 14 kJ/m.sup.3 increase was achieved in (BH).sub.max by reducing mass flow rate from 1.9 kg/min to 0.2 kg/min.

Example 3

Wheel Speed Versus Mass Flow Rate

[0229] It was found that wheel speed could be adjusted to achieve optimal quenching of the alloy ribbon. By optimal quenching, it is meant that the ribbon was quenched at an optimal cooling rate by adjusting the wheel speed so that the obtained alloy ribbons had the finest and most uniform nanoscale grains and therefore highest magnetic properties. In contrast, under quench refers to a cooling rate that is too slow leading to a resultant grain size that is very large, whereas over-quench refers to a cooling rate that is too fast leading to the formation of an amorphous phase. Both under-quenching and over-quenching causes lower magnetic properties.

[0230] FIG. 3 and Table 4 show that the wheel speed for optimal quenching is in the range of 20 m/s to 45 m/s for the Nd.sub.11.6Fe.sub.80.3Co.sub.2.4B.sub.5.7 alloy, and 15 m/s to 30 m/s for the Nd.sub.11.9Fe.sub.81Nb.sub.1.2B.sub.5.9 alloy. Wheel speed increased as mass flow rate increased.

TABLE-US-00004 TABLE 4 Mass flow rate Nd.sub.11.6Fe.sub.80.3Co.sub.2.4B.sub.5.7 Nd.sub.11.9Fe.sub.81Nb.sub.1.2B.sub.5.9 (kg/min) Wheel Speed (m/s) Wheel Speed (m/s) 0.2 22.0 17.9 0.5 26.0 20.5 0.8 32.8 24.0 1.3 35.0 27.0 1.9 44.0 29.0

Example 4

Ribbon Dimension Versus Mass Flow Rate

[0231] Alloy ribbon dimensions were measured at different mass flow rates for all the alloy ribbons. As shown in FIG. 4a and Table 5, the ribbon thickness measured from ribbon surface contacting the rotating wheel surface (wheel side) to the ribbon free surface not contacting the rotating wheel surface (free side) for the Nd.sub.11.6Fe.sub.80.3Co.sub.2.4B.sub.5.7 alloy was in the range of 28 m to 32 m, and the ribbon width measured from ribbon left edge to right edge was in the range of 1 mm to 4 mm.

TABLE-US-00005 TABLE 5 Mass flow Ribbon Ribbon Normalized Normalized rate thickness width ribbon ribbon (kg/min) (m) (mm) thickness width 0.2 28.1 0.90 1.00 1.00 0.5 31.2 1.64 1.11 1.47 0.8 31.5 2.29 1.11 2.44 1.3 31.6 2.79 1.15 3.15 1.9 31.2 3.28 1.11 3.60

[0232] Also as shown in FIG. 4b and Table 6, the ribbon thickness for the Nd.sub.11.9Fe.sub.81Nb.sub.1.2B.sub.5.9 alloy was in the range of 35 m to 47 m, and the ribbon width was in the range of 1 mm to 4 mm.

TABLE-US-00006 TABLE 6 Mass flow Ribbon Ribbon Normalized rate thickness width ribbon Normalized (kg/min) (m) (mm) thickness ribbon width 0.2 34.7 1.06 1.00 1.00 0.5 43.0 1.70 1.24 1.61 0.8 44.4 2.31 1.28 2.18 1.3 46.7 2.78 1.35 2.63 1.9 46.3 3.79 1.34 3.58

[0233] Table 7 further summarizes the various alloy ribbon dimensions at different mass flow rates. It was found that a higher mass flow rate led to a wider ribbon width, but the ribbon thickness did not change significantly.

TABLE-US-00007 TABLE 7 Rib- Rib- bon Rib- bon Rib- thick- bon thick- bon ness width ness width @ @ @ @ 1.9 1.9 0.2 0.2 Sam- kg/ kg/ kg/ kg/ ple min min min min no. Alloy (at %) (m) (mm) (m) (mm) 1 Nd.sub.11.9Fe.sub.81Nb.sub.1.2B.sub.5.9 46.3 3.79 34.7 1.06 2 Nd.sub.11.6Fe.sub.80.3Co.sub.2.4B.sub.5.7 31.2 3.28 28.1 0.90 3 (Nd.sub.0.75Pr.sub.0.25).sub.9.9La.sub.1.9Fe.sub.81.6Al.sub.1B.sub.5.6 31.0 4.02 28.2 1.13 4 (Nd.sub.0.75Pr.sub.0.25).sub.10.8Fe.sub.81.9Zr.sub.1B.sub.6.3 32.4 3.80 30.5 1.06 5 (Nd.sub.0.75Pr.sub.0.25).sub.6.8Ce.sub.4.6Fe.sub.81.3Zr.sub.1B.sub.6.3 33.0 3.42 30.9 0.95 6 Nd.sub.12Fe.sub.76.3Co.sub.5.9B.sub.5.8 32.6 3.78 29.3 1.05 7 Nd.sub.11.7Fe.sub.82.6B.sub.5.7 30.2 3.45 27.6 0.97 8 (Nd.sub.0.75Pr.sub.0.25).sub.11.2Fe.sub.83.4B.sub.5.4 30.3 3.80 27.6 1.06 9 (Nd.sub.0.75Pr.sub.0.25).sub.10.4Fe.sub.84.1B.sub.5.5 32.3 3.76 29.0 1.04 10 (Nd.sub.0.75Pr.sub.0.25).sub.6.0La.sub.3.0Ce.sub.3.0Fe.sub.81.8B.sub.6.2 32.5 3.75 29.1 1.03

[0234] The most significant observation from Tables 5 to 7 is that a higher mass flow rate leads to a significantly wider ribbon width (an about 260% increase) when the mass flow rate increased from 0.2 kg/min to 1.9 kg/min; however the ribbon thickness did not change significantly (an only 10-35% increase) when the mass flow rate increased from 0.2 kg/min to 1.9 kg/min. This behaviour has an important impact on the microstructure homogeneity of the rapidly quenched ribbon, which is further discussed in Example 7.

Example 5

Percentage of RE.SUB.2.Fe.SUB.14.B Crystalline Phase Versus Mass Flow Rate

[0235] As discussed above, the alloys disclosed herein have a RE.sub.2Fe.sub.14B phase as the main constituent phase. In a melt-spinning process, it is desirable for the alloy to be quenched uniformly so that the entire RE.sub.2Fe.sub.14B phase is solidified into very fine and uniform RE.sub.2Fe.sub.14B grains. Under this condition, the volume percentage of RE.sub.2Fe.sub.14B crystalline phase is also maximized. In other words, a higher percentage of the RE.sub.2Fe.sub.14B crystalline phase indicates more uniform quenching in the alloy ribbon.

[0236] The percentage volume of RE.sub.2Fe.sub.14B crystalline phase was measured at different mass flow rates. It was found that a higher percentage volume of RE.sub.2Fe.sub.14B crystalline phase was obtained at a lower mass flow rate. This indicated that there was more uniform quenching at a lower mass flow rate.

[0237] As shown in FIG. 5 and Table 8, more than 98 vol % of the as-quenched powders of the Nd.sub.11.6Fe.sub.80.3Co.sub.2.4B.sub.5.7 alloy were in crystalline RE.sub.2Fe.sub.14B phase, with the remaining vol % being amorphous.

TABLE-US-00008 TABLE 8 Mass flow Crystalline RE.sub.2Fe.sub.14B rate (kg/min) phase (vol %) 0.2 99.9 0.5 99.6 0.8 98.4 1.3 98.4 1.9 98.3

Example 6

Ribbon and Crushed Powder Average Grain Size Versus Mass Flow Rate

[0238] X-ray diffraction (XRD) tests were performed on alloy ribbons and crushed powders produced at different mass flow rates. As an example, FIG. 6 shows the typical XRD patterns of Nd.sub.11.6Fe.sub.80.3Co.sub.2.4B.sub.5.7 alloy powders produced at different mass flow rates. It was found that all peaks can be indexed to Nd.sub.2Fe.sub.14B crystal structure, meaning the crystalline phase is the Nd.sub.2Fe.sub.14B type phase. Significant peak broadening was also observed, indicating that the Nd.sub.2Fe.sub.14B grain size was very small.

[0239] The Nd.sub.2Fe.sub.14B grain size can be calculated from XRD data using the Scherrer equation:

Mean grain size=K/ cos

[0240] where K is a dimensionless shape factor, and has a typical value of about 0.9; is the X-ray wavelength and has a value of 1.5405 for Cu K as the X-ray source; is the peak full width at half maximum (FWHM) in radians; and is the Bragg angle.

[0241] The grain size of the RE.sub.2Fe.sub.14B phase was calculated from XRD data at different mass flow rates using the Scherrer equation as described above. As shown in FIG. 7 and Table 9, the average grain size of crushed powder of the Nd.sub.11.6Fe.sub.80.3Co.sub.2.4B.sub.5.7 alloy was about 20 nm to 30 nm. It was further found that the lower mass flow rate led to smaller grain size, which in turn led to higher magnetic properties as shown in Examples 1 and 2. However, the grain size difference between the wheel side of the alloy ribbon, and the free side of the alloy ribbon remained about the same at different mass flow rates. This can be understood from the ribbon thickness data shown in Example 4 where it was found that ribbon thickness was essentially kept unchanged as mass flow rate changed. As the grain size difference between ribbon wheel side and free side was mainly caused by cooling rate difference between wheel side and free side and was proportional to the ribbon thickness, nearly unchanged ribbon thickness at various mass flow rate indicates a similar grain size difference between the ribbon wheel side and free side.

TABLE-US-00009 TABLE 9 Mass Wheel Free Powder flow rate side grain side grain grain size (kg/min) size (nm) size (nm) (nm) 0.2 19.4 24.5 21.8 0.5 20.9 24.4 23.3 0.8 22.5 27.4 23.7 1.3 23.3 27.8 25.1 1.9 23.4 29.4 26.2

Example 7

Grain Size Uniformity Across Ribbon Width Direction

[0242] As discussed above, a uniform grain size across ribbon width direction (from ribbon left edge to central portion then to right edge) is critical for achieving high-performance alloy ribbons. In this example, ribbon cross section areas were observed under a field-emission scanning electronic microscope (SEM) from the ribbon left edge to center portion to right edge. The average grain size of the RE.sub.2Fe.sub.14B phase at each area was calculated using ImageJ software (Image Processing and Analysis in Java, http://rsb.info.nih.gov.ij, version 1.51j8) The results are summarized in FIGS. 8, 9 and Table 10. It was found that lower mass flow rates produced more uniform grain sizes when measured across the width of the alloy ribbon.

[0243] FIG. 10 is an exemplary depiction of the sections that make up the width of an alloy ribbon of the present invention. As shown in FIG. 10, the left-edge of the alloy ribbon comprises the first 5% of the width (i.e. 0% to 5%), the center-left portion comprises the next 30% of the width (i.e. 5% to 35%), the center portion comprises the next 30% of the width (i.e. 35% to 65%), the center-right portion comprises the next 30% of the width (i.e. 65% to 95%), and the right-edge portion of the alloy ribbon comprises the last 5% of the width (i.e. 95% to 100%).

[0244] As shown in FIGS. 8, 9 and Table 10, lower mass flow rate at 0.2 to 0.8 kg/min produced more uniform grain sizes from left to right edge for the Nd.sub.11.6Fe.sub.80.3Co.sub.2.4B.sub.5.7 alloy ribbon, with grain size ranging from 21 to 27 nm and the grain size difference between center portion and left/right edges being only 2 to 4% for 0.2 kg/min mass flow rate, 8 to 12% for 0.5 kg/min mass flow rate and 17 to19% for 0.8 kg/min mass flow rate, respectively.

[0245] At higher mass flow rate of 1.3 kg/min and 1.9 kg/min, however, it was seen that both edges had much smaller grains when compared to the center portion, with the grain size ranging from 15 to 29 nm and the grain size difference between the center portion and the left and right edges being 27 to 31% for 1.3 kg/min mass flow rate and 36 to 48% for 1.9 kg/min mass flow rate.

[0246] It is therefore evident that lower mass flow rate produces much more uniform grain sizes when measured across the width of the alloy ribbon. This indicates that the cooling rate across the ribbon width is more uniform at lower mass flow rate, and it becomes less uniform as mass flow rate increases. Specifically, at high mass flow rate, the edge areas were over-quenched (i.e. cooling rate is too fast) leading to too small grains or even a partially amorphous phase (meaning no grains at all), and the central portion is under-quenched (i.e. cooling rate is too slow) leading to very large grains. This is also in good agreement with the fact that ribbon width increases significantly with mass flow rate as shown in Example 4. From the point of view of heat transfer between the alloy ribbon and the quenching wheel, a narrow ribbon produced at lower mass flow rate would have a more uniform temperature across the ribbon width and therefore a uniform cooling rate. However, for a wider ribbon, its edge area will have lower temperature than the center portion as it is further away from the source of the heat (i.e. the alloy stream). This will cause a non-uniform cooling rate with the edges being cooled down much faster than the center portion.

TABLE-US-00010 TABLE 10 Left- Center- Right- Grain size edge Left- Center- right edge difference ribbon center portion ribbon ribbon between Mass grain ribbon ribbon grain grain center flow rate size grain size grain size size size and edges (kg/min) (nm) (nm) (nm) (nm) (nm) (%) 0.2 24.3 23.6 25.4 24.1 24.8 2 to 4 0.5 22.5 26.7 25.5 25.4 23.4 8 to 12 0.8 21.5 22.7 26.5 25.1 21.9 17 to 19 1.3 19.1 24.8 27.6 25.7 20.2 27 to 31 1.9 15.0 26.6 29.0 26.9 18.6 36 to 48

INDUSTRIAL APPLICABILITY

[0247] The disclosed alloy compositions, magnetic materials, bonded magnets may advantageously exhibit improved magnetic properties, for example, high B.sub.r, (BH).sub.max and H.sub.ci values.

[0248] Advantageously, the methods for making the disclosed alloys of the present disclosure may produce alloys with a substantially uniform ribbon microstructure.

[0249] More advantageously, the method of the present disclosure may produce alloys with primarily RE.sub.2Fe.sub.14B phase.

[0250] Further advantageously, the method of the present disclosure may result in substantially uniform quenching.

[0251] It will be apparent that various other modifications and adaptations of the invention will be apparent to the person skilled in the art after reading the foregoing disclosure without departing from the spirit and scope of the invention and it is intended that all such modifications and adaptations come within the scope of the appended claims.