U.S. patent application number 12/422385 was filed with the patent office on 2009-11-05 for nd-fe-b permanent magnetic material.
This patent application is currently assigned to BYD COMPANY LIMITED. Invention is credited to XiaoFeng CHENG, Xin DU, FaLiang ZHANG.
Application Number | 20090274571 12/422385 |
Document ID | / |
Family ID | 41231467 |
Filed Date | 2009-11-05 |
United States Patent
Application |
20090274571 |
Kind Code |
A1 |
DU; Xin ; et al. |
November 5, 2009 |
Nd-Fe-B Permanent Magnetic Material
Abstract
Permanent magnetic materials comprising an Nd--Fe--B alloy and
an additive comprising at least one boride are disclosed. The
boride may be a lanthanide boride being about 0.01% to about 5% of
the alloy by weight. In some instances, the lanthanide boride may
be at least one of DyB.sub.6, GdB.sub.6, TbB.sub.6, SmB.sub.6, or
mixtures thereof.
Inventors: |
DU; Xin; (Shenzhen, CN)
; CHENG; XiaoFeng; (Shenzhen, CN) ; ZHANG;
FaLiang; (Shenzhen, CN) |
Correspondence
Address: |
GREENBERG TRAURIG, LLP (SV);IP DOCKETING
2450 COLORADO AVENUE, SUITE 400E
SANTA MONICA
CA
90404
US
|
Assignee: |
BYD COMPANY LIMITED
Shenzhen
CN
|
Family ID: |
41231467 |
Appl. No.: |
12/422385 |
Filed: |
April 13, 2009 |
Current U.S.
Class: |
420/83 ;
419/29 |
Current CPC
Class: |
C22C 33/0278 20130101;
C22C 33/0228 20130101; C22C 2202/02 20130101; H01F 41/0266
20130101; H01F 1/0577 20130101 |
Class at
Publication: |
420/83 ;
419/29 |
International
Class: |
C22C 38/00 20060101
C22C038/00; C21D 1/00 20060101 C21D001/00; B22F 3/24 20060101
B22F003/24 |
Foreign Application Data
Date |
Code |
Application Number |
May 4, 2008 |
CN |
200810094116.0 |
Claims
1. A permanent magnetic material comprising: an Nd--Fe--B alloy;
and an additive comprising at least one boride.
2. The material of claim 1, wherein the amount of boride is from
about 0.01% to about 5% of the alloy by weight.
3. The material of claim 1, wherein the boride is a lanthanide
boride.
4. The material of claim 3, wherein the lanthanide boride includes
at least one member selected from the group consisting of
DyB.sub.6, GdB.sub.6, TbB.sub.6 and SmB.sub.6.
5. The material of claim 3, wherein the lanthanide boride includes
TbB.sub.6 and a first compound selected from the group consisting
of DyB.sub.6, GdB.sub.6 and SmB.sub.6, and wherein the weight ratio
of the TbB.sub.6 to the first compound is from about 1:1 to about
50:1.
6. The material of claim 1, wherein the alloy has the following
general formula: Nd.sub.aR.sub.bFe.sub.100-a-b-c-dM.sub.cB.sub.d,
wherein: R is at least one element selected from the group
consisting of Pr, Dy and Tb; M is at least one element selected
from the group consisting of Nb, Co, Ga, Zr, Al, Cu and Ti; and
10.ltoreq.a.ltoreq.20, 0.ltoreq.b.ltoreq.8, 0.ltoreq.c.ltoreq.6 and
5.ltoreq.d.ltoreq.7.
7. A permanent magnetic material comprising: an Nd--Fe--B alloy,
wherein the alloy has the following general formula:
Nd.sub.aR.sub.bFe.sub.100-a-b-c-dM.sub.cB.sub.d, wherein: R is at
least one element selected from the group consisting of Pr, Dy and
Tb; M is at least one element selected from the group consisting of
Nb, Co, Ga, Zr, Al, Cu and Ti; and 10.ltoreq.a.ltoreq.20,
0.ltoreq.b.ltoreq.8, 0.ltoreq.c.ltoreq.6 and 5.ltoreq.d.ltoreq.7;
and an additive comprising at least one lanthanide boride.
8. The material of claim 7, wherein the amount of lanthanide boride
is from about 0.01% to about 5% of the alloy by weight.
9. The material of claim 7, wherein the lanthanide boride includes
at least one member selected from the group consisting of
DyB.sub.6, GdB.sub.6, TbB.sub.6 and SmB.sub.6.
10. The material of claim 7, wherein the lanthanide boride includes
TbB.sub.6 and a first compound selected from the group consisting
of DyB.sub.6, GdB.sub.6 and SmB.sub.6, and wherein the weight ratio
of the TbB.sub.6 to the first compound is from about 1:1 to about
50:1.
11. A method of preparing a permanent magnetic material, the method
comprising: mixing an Nd--Fe--B alloy and an additive to form a
mixture; pressing the mixture in a magnetic field to form a
composition; sintering the composition to a first temperature; and
tempering the composition to a second temperature, wherein the
sintering and tempering steps can occur under a first
atmosphere.
12. The method of claim 11, wherein the first atmosphere is at
least one of vacuum or inert gas.
13. The method of claim 11, wherein the additive comprises at least
one boride, and wherein the amount of boride is from about 0.01% to
about 5% of the alloy by weight.
14. The method of claim 13, wherein the boride includes at least
one member selected from the group consisting of DyB.sub.6,
GdB.sub.6, TbB.sub.6 and SmB.sub.6.
15. The material of claim 13, wherein the boride includes TbB.sub.6
and a first compound selected from the group consisting of
DyB.sub.6, GdB.sub.6 and SmB.sub.6, and wherein the weight ratio of
the TbB.sub.6 to the first compound is from about 1:1 to about
50:1.
16. The method of claim 11, further comprising mixing the alloy and
the additive with an antioxidant and a lubricant, wherein the
amount of antioxidant is from about 0.01% to about 5% of the alloy
by weight, and wherein the amount of lubricant is from about 0% to
about 5% of the alloy by weight.
17. The method of claim 11, wherein the alloy has the following
general formula: Nd.sub.aR.sub.bFe.sub.100-a-b-c-dM.sub.cB.sub.d,
wherein: R is at least one element selected from the group
consisting of Pr, Dy and Tb; M is at least one element selected
from the group consisting of Nb, Co, Ga, Zr, Al, Cu and Ti; and
10.ltoreq.a.ltoreq.20, 0.ltoreq.b.ltoreq.8, 0.ltoreq.c.ltoreq.6 and
5.ltoreq.d.ltoreq.7.
18. The method of claim 11, wherein the average particle diameter
of the alloy is from about 2 to about 10 microns, and wherein the
average particle diameter of the additive is from about 2 to about
1000 nanometers.
19. The method of claim 11, wherein the pressing step has an
intensity of from about 1.2 to about 2.0 T, a pressure of from
about 10 to about 200 MPa, and a period of from about 10 to about
60 seconds.
20. The method of claim 11, wherein the first temperature is from
about 1030 to about 1120.degree. C. for a period of from about 2 to
about 4 hours, and wherein the second temperature is from about 500
to about 920.degree. C. for a period of from about 2 to about 8
hours.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This application claims priority to Chinese Patent
Application No. 200810094116.0, filed May 4, 2008.
BACKGROUND
[0002] Because of its magnetic properties, low cost and ample
reserves, Nd--Fe--B permanent magnets are widely used in vehicles,
computers, electronics, mechanical and medical devices, to name a
few. In addition, because of its performance to price ratio,
Nd--Fe--B materials have been favored to produce magnetic devices
with high efficiency, small volume and light mass. However,
Nd--Fe--B materials are also known to have poor coercivity and
mechanical properties thereby limiting its applications to some
extent.
SUMMARY
[0003] Nd--Fe--B permanent magnetic materials are disclosed. One
embodiment discloses a permanent magnetic material comprising an
Nd--Fe--B alloy and an additive comprising at least one boride. The
amount of boride may range from about 0.01% to about 5% of the
alloy by weight. In one embodiment, the boride is a lanthanide
boride. In some embodiments, the lanthanide boride includes at
least one member selected from the group consisting of DyB.sub.6,
GdB.sub.6, TbB.sub.6 and SmB.sub.6. In some embodiments, the
lanthanide boride includes TbB.sub.6 and a first compound selected
from the group consisting of DyB.sub.6, GdB.sub.6 and SmB.sub.6. In
these embodiments, the weight ratio of the TbB.sub.6 to the first
compound is from about 1:1 to about 50:1.
[0004] In one embodiment, the alloy has the following general
formula: Nd.sub.aR.sub.bFe.sub.100-a-b-c-dM.sub.cB.sub.d. In some
embodiments, R is at least one element selected from the group
consisting of Pr, Dy and Tb, M is at least one element selected
from the group consisting of Nb, Co, Ga, Zr, Al, Cu and Ti, and
10.ltoreq.a.ltoreq.20, 0.ltoreq.b.ltoreq.8, 0.ltoreq.c.ltoreq.6 and
5.ltoreq.d.ltoreq.7.
[0005] One embodiment discloses a method of preparing a permanent
magnetic material, the method comprising mixing an Nd--Fe--B alloy
and an additive to form a mixture, pressing the mixture in a
magnetic field to form a composition, sintering the composition to
a first temperature, and tempering the composition to a second
temperature. In one embodiment, the sintering and tempering steps
can occur under vacuum. In one embodiment, the sintering and
tempering steps can occur under an inert gas atmosphere.
[0006] In one embodiment, the method includes mixing the alloy and
the additive with an antioxidant and a lubricant. In one
embodiment, the amount of antioxidant is from about 0.01% to about
5% of the alloy by weight. In one embodiment, the amount of
lubricant is from about 0% to about 5% of the alloy by weight.
[0007] In some embodiments, the average particle diameter of the
alloy is from about 2 to about 10 microns, while the average
particle diameter of the additive is from about 2 to about 1000
nanometers. In some embodiments, the pressing step has an intensity
of from about 1.2 to about 2.0 T, a pressure of from about 10 to
about 200 MPa, and a period of from about 10 to about 60 seconds.
In some embodiments, the first temperature is from about 1030 to
about 1120.degree. C. for a period of from about 2 to about 4
hours, while the second temperature is from about 500 to about
920.degree. C. for a period of from about 2 to about 8 hours.
[0008] Other variations, embodiments and features of the presently
disclosed permanent magnetic materials will become evident from the
following detailed description, drawings and claims.
DETAILED DESCRIPTION
[0009] It will be appreciated by those of ordinary skill in the art
that the permanent magnetic materials can be embodied in other
specific forms without departing from the spirit or essential
character thereof. The presently disclosed embodiments are
therefore considered in all respects to be illustrative and not
restrictive.
[0010] One embodiment of the present disclosure discloses a
permanent magnetic material comprising an Nd--Fe--B
(neodymium-iron-boron) alloy and an additive comprising at least
one boride. As used herein, "boride" and the like means a chemical
compound between boron and a less electronegative element. In one
embodiment, a small quantity of boride may advance the coercivity
and mechanical properties of the permanent magnetic material. In
one embodiment, the amount of boride may be from about 0.01% to
about 5% of the alloy by weight.
[0011] In one embodiment, the boride may be a lanthanide boride. In
some embodiments, the lanthanide boride includes at least one
member selected from the group consisting of DyB.sub.6, GdB.sub.6,
TbB.sub.6 and SmB.sub.6. In some embodiments, the lanthanide boride
includes TbB.sub.6 and a first compound selected from the group
consisting of DyB.sub.6, GdB.sub.6 and SmB.sub.6. In these
embodiments, the weight ratio of the TbB.sub.6 to the first
compound may be from about 1:1 to about 50:1. In some embodiments,
the boride may be uniformly dispersed within the Nd--Fe--B alloy,
the boride having average particle diameters of from about 2 to
about 1000 nanometers. In some embodiments, the boride may have
average particle diameters of from about 2 to about 100
nanometers.
[0012] In one embodiment, the Nd--Fe--B alloy has the following
general formula: Nd.sub.aR.sub.bFe.sub.100-a-b-c-dM.sub.cB.sub.d.
In this embodiment, the R is at least one element selected from the
group consisting of Pr, Dy and Tb, the M is at least one element
selected from group consisting of Nb, Co, Ga, Zr, Al, Cu and Ti,
and 10.ltoreq.a.ltoreq.20, 0.ltoreq.b.ltoreq.8, 0.ltoreq.c.ltoreq.6
and 5.ltoreq.d.ltoreq.7. In some embodiments, the Nd--Fe--B alloy
may average particle diameters of from about 2 to about 10
microns.
[0013] One embodiment of the present disclosure discloses a method
of preparing a permanent magnetic material, the method comprising:
mixing an Nd--Fe--B alloy and an additive to form a mixture,
pressing the mixture in a magnetic field to form a composition,
sintering the composition to a first temperature, and tempering the
composition to a second temperature. In one embodiment, the
sintering and tempering can occur under vacuum. In one embodiment,
the sintering and tempering occur can under an inert gas. In some
embodiments, the inert gas includes at least one member selected
from the group consisting of nitrogen, helium, argon, neon, krypton
and xenon.
[0014] In some embodiments, the sintering process for preparing the
permanent magnetic material may include without limitation one or
more of the following steps: formulating, smelting, crushing,
milling, processing ultrafine powders, pressing in a magnetic
field, sintering in vacuum and electroplating. Some of the steps
are as follows:
[0015] (1) In one embodiment, the Nd--Fe--B alloy may be crushed
and grounded to form a powder. The crushing may include
hydrogen-induced cracking or mechanical crushing. In one
embodiment, jet milling may be utilized to produce powders with
average particle diameters of from about 2 to about 10 microns.
[0016] In some embodiments, the Nd--Fe--B alloy may be an alloy
ingot or a strip casting alloy. In one embodiment, the Nd--Fe--B
alloy may be acquired from a third party. In some embodiments, the
Nd--Fe--B alloy may be produced by casting or strip casting
processes. In one embodiment, the Nd--Fe--B alloy may have the
following general formula:
Nd.sub.aR.sub.bFe.sub.100-a-b-c-dM.sub.cB.sub.d where the R may be
at least one element selected from the group consisting of Pr, Dy
and Tb, the M may be at least one element selected from the group
consisting of Nb, Co, Ga, Zr, Al, Cu and Ti, and
10.ltoreq.a.ltoreq.20, 0.ltoreq.b.ltoreq.8, 0.ltoreq.c.ltoreq.6,
and 5.ltoreq.d.ltoreq.7.
[0017] In one embodiment, the casting process comprises casting a
smelted alloy molten in a water-cooled, copper mold. The Nd--Fe--B
alloy ingot may have a columnar, crystal structure, where the
columnar crystals are separated by Nd-rich phase layers. In these
instances, the distance between two Nd-rich phase layers may be
from about 100 to about 1500 microns.
[0018] In one embodiment, the strip casting process comprises
pouring a smelted alloy molten on a copper roller surface. In one
example, the rotational linear velocity of the copper roller
surface may vary from about 1 to about 2 meters per second. The
molten alloy may be cooled to form flakes in different breadths
with thicknesses ranging from about 0.2 to about 0.5 millimeter. In
some embodiments, the columnar crystals in the flakes may have
breadths ranging from about 5 to about 25 microns.
[0019] In one embodiment, hydrogen-induced cracking comprises
placing an Nd--Fe--B alloy in a stainless steel case, filling the
case with high purity hydrogen after vacuumizing, and maintaining
at an atmospheric pressure for about 20 to about 30 minutes. In one
instance, the alloy may blow out because of hydrogen absorption and
produce a hydride. In one embodiment, the hydride may be vacuumized
for dehydrogenation for from about 2 to about 10 hours at from
about 400 to about 600.degree. C.
[0020] In one embodiment, mechanical crushing comprises rough
crushing in a jaw crusher, followed by mechanical crushing in a
fine crusher. In one embodiment, jet milling comprises accelerating
powder grains to supersonic speed in air, and allowing the grains
to clash with each other and fall to pieces.
[0021] (2) The Nd--Fe--B alloy and the additive may be mixed using
a mixer to obtain a powder composition. In one embodiment, the
additive comprises at least one boride. The amount of boride may be
from about 0.01% to about 5% of the alloy by weight. In some
embodiments, the boride may be processed in advance by dispersion
treatment. In some embodiments, the boride may include at least one
member selected from the group consisting of DyB.sub.6, GdB.sub.6,
TbB.sub.6 and SmB.sub.6. In some embodiments, the alloy may have an
average particle diameter of from about 2 to about 10 microns. In
some embodiments, the additive or boride may have an average
particle diameter of from about 2 to about 1000 nanometers. In some
embodiments, the boride may include TbB.sub.6 and a first compound
selected from the group consisting of DyB.sub.6, GdB.sub.6 and
SmB.sub.6, where the weight ratio of the TbB.sub.6 to the first
compound may be from about 1:1 to about 50:1.
[0022] In one embodiment, the alloy/additive mixture may further
include an antioxidant and a lubricant. In some embodiments, the
amount of antioxidant may be about 0.01% to about 5% of the alloy
by weight, and the amount of lubricant may be about 0% to about 5%
of the alloy by weight. In some embodiments, the antioxidant
includes at least one member selected from the group consisting of
polyethylene oxide alkyl ether, polyethylene oxide single fatty
ester and polyethylene oxide alkenyl ether. In some embodiments,
the lubricant includes at least one member selected from group
consisting of gasoline, oleic acid, stearic acid, polyhydric
alcohol, polyethylene glycol, sorbitan and stearin.
[0023] (3) The alloy/additive mixture may be pressed in a magnetic
field to form a composition. In some embodiments, the pressing
comprises pressing in a closed glove box with a magnetic field. In
some embodiments, the magnetic field has an intensity of from about
1.2 to about 2.0 T and a pressure of from about 10 to about 200
MPa. In some embodiments, the pressing step may take anywhere from
about 10 to about 60 seconds.
[0024] (4) The composition may be sintered to a first temperature,
and tempered to a second temperature. In one embodiment, the
sintering and tempering may occur under vacuum. In one embodiment,
the sintering and tempering may occur under an inert gas. In some
embodiments, the inert gas includes at least one member selected
from the group consisting of nitrogen, helium, argon, neon, krypton
and xenon. In some embodiments, the mixture may be sintered at
temperatures ranging from about 1030 to about 1120.degree. C. for a
period of from about 2 to about 4 hours. In some embodiments, the
mixture may be tempered at temperatures ranging from about 500 to
about 920.degree. C. for a period of from about 2 to about 8 hours.
In some embodiments, the mixture may be tempered in two steps, the
first tempering at temperatures ranging from about 800 to about
920.degree. C. for a period of from about 1 to about 3 hours
followed by a second tempering at temperatures ranging from about
500 to about 650.degree. C. for a period of from about 2 to about 4
hours.
[0025] The following provides additional details on some
embodiments of the present disclosure.
Example 1
[0026] (1) An Nd--Fe--B alloy is made by strip casting with a
rotational linear velocity of a copper roller surface at about 1.5
meters per second. The strip casting alloy has a thickness of about
0.3 mm with the formula
Nd.sub.10.2(Dy.sub.2.8Tb.sub.1.3)Fe.sub.75.5(CO.sub.2.3Al.sub.0.7-
Nb.sub.0.3Ga.sub.0.4)B.sub.6.5.
[0027] (2) The alloy is crushed by hydrogen-induced cracking.
First, by absorbing hydrogen to saturation at room temperature.
Next, by dehydrogenation at 550.degree. C. for about 6 hours. The
alloy is milled to produce a powder with an average particle
diameter of about microns by jet milling under a nitrogen
atmosphere.
[0028] (3) An TbB.sub.6 additive and an antioxidant are added to
the powder. The additive is about 3% of the alloy by weight and has
an average particle diameter of about 20 nanometers. The
composition is mixed by adding gasoline, which is about 3% of the
alloy by weight.
[0029] (4) The composition may be pressed by a forming press in a
closed glove box under nitrogen gas in a magnetic field. The
intensity of the magnetic field is about 1.6 T, the pressure is at
about 100 MPa, and the isostatic pressing time is about 30
seconds.
[0030] (5) The composition is sintered in a vacuum sintering
furnace under an atmospheric pressure of 2.times.10.sup.-2 Pa, the
sintering temperature at about 1080.degree. C. for about 3 hours.
The composition is subsequently tempered at about 850.degree. C.
for about 2 hours followed by tempering at about 550.degree. C. for
about 3 hours.
[0031] The Nd--Fe--B permanent magnetic material can be labeled as
T1.
[0032] Reference 1
[0033] The sample is substantially similar in all respect to that
of EXAMPLE 1 with the exception of the TbB.sub.6 additive.
[0034] The Nd--Fe--B permanent magnetic material can be labeled as
TC1.
Example 2
[0035] The sample is substantially similar in all respect to that
of EXAMPLE 1 with the exception that the average particle diameter
of the TbB.sub.6 additive is about 1.2 microns.
[0036] The Nd--Fe--B permanent magnetic material can be labeled as
T2.
Example 3
[0037] The sample is substantially similar in all respect to that
of EXAMPLE 1 with the exception that the amount of TbB.sub.6
additive is about 6% of the alloy by weight.
[0038] The Nd--Fe--B permanent magnetic material can be labeled as
T3.
Example 4
[0039] The sample is substantially similar in all respect to that
of EXAMPLE 1 with the exception of the antioxidant and
gasoline.
[0040] The Nd--Fe--B permanent magnetic material can be labeled as
T4.
Example 5
[0041] The sample is substantially similar in all respect to that
of EXAMPLE 1 with the exception that DyB.sub.6 is incorporated as
the additive instead of TbB.sub.6.
[0042] The Nd--Fe--B permanent magnetic material can be labeled as
T5.
Example 6
[0043] The sample is substantially similar in all respect to that
of EXAMPLE 1 with the exception that GdB.sub.6 is incorporated as
the additive instead of TbB.sub.6.
[0044] The Nd--Fe--B permanent magnetic material can be labeled as
T6.
Example 7
[0045] The sample is substantially similar in all respect to that
of EXAMPLE 1 with the exception that SmB.sub.6 is incorporated as
the additive instead of TbB.sub.6.
[0046] The Nd--Fe--B permanent magnetic material can be labeled as
T7.
Example 8
[0047] The sample is substantially similar in all respect to that
of EXAMPLE 1 with the exception that:
[0048] (1) The average particle diameter of the TbB.sub.6 additive
is about 1000 nanometers;
[0049] (2) The amount of TbB.sub.6 additive is about 6% of the
alloy by weight;
[0050] (3) The average particle diameter of the powder alloy is
about 7 microns;
[0051] (4) The amount of antioxidant is about 5% of the alloy by
weight;
[0052] (5) The intensity of the magnetic field is about 1.2 T, the
pressure is about 200 MPa, and the isostatic pressing time is about
10 seconds;
[0053] (6) The vacuum sintering temperature is about 1030.degree.
C. for about 4 hours; and
[0054] (7) The first tempering is at about 920.degree. C. for about
1 hour and the second tempering is at about 650.degree. C. for
about 2 hours.
[0055] The Nd--Fe--B permanent magnetic material can be labeled as
T8.
Example 9
[0056] The sample is substantially similar in all respect to that
of EXAMPLE 1 with the exception that:
[0057] (1) A mixture of DyB.sub.6 and TbB.sub.6 is incorporated as
the additive instead of TbB.sub.6;
[0058] (2) The average particle diameter of the DyB.sub.6 and
TbB.sub.6 mixture additive is about 20 nanometers; and
[0059] (3) The amount of the DyB.sub.6 is about 0.2% of the alloy
by weight and the amount of the TbB.sub.6 is about 4% of the alloy
by weight.
[0060] The Nd--Fe--B permanent magnetic material can be labeled as
T9.
Example 10
[0061] The sample is substantially similar in all respect to that
of EXAMPLE 1 with the exception that:
[0062] (1) A mixture of GdB.sub.6 and TbB.sub.6 is incorporated as
the additive instead of TbB.sub.6;
[0063] (2) The average particle diameter of the GdB.sub.6 and
TbB.sub.6 mixture additive is about 20 nanometers; and
[0064] (3) The amount of the GdB.sub.6 is about 1% of the alloy by
weight and the amount of the TbB.sub.6 is about 2% of the alloy by
weight.
[0065] The Nd--Fe--B permanent magnetic material can be labeled as
T10.
Example 11
[0066] The sample is substantially similar in all respect to that
of EXAMPLE 1 with the exception that:
[0067] (1) A mixture of SmB.sub.6 and TbB.sub.6 is incorporated as
the additive instead of TbB.sub.6;
[0068] (2) The average particle diameter of the SmB.sub.6 and
TbB.sub.6 mixture additive is about 20 nanometers; and
[0069] (3) The amount of the SmB.sub.6 is about 0.01% of the alloy
by weight and the amount of the TbB.sub.6 is about 0.5% of the
alloy by weight.
[0070] The Nd--Fe--B permanent magnetic material can be labeled as
T11.
Example 12
[0071] The sample is substantially similar in all respect to that
of EXAMPLE 1 with the exception that:
[0072] (1) The average particle diameter of the TbB.sub.6 additive
is about 100 nanometers;
[0073] (2) The amount of TbB.sub.6 additive is about 0.1% of the
alloy by weight;
[0074] (3) The average particle diameter of the powder alloy is
about 10 microns;
[0075] (4) The amount of antioxidant is about 1% of the alloy by
weight; and
[0076] (5) The intensity of the magnetic field is about 1.8 T, the
pressure is about 10 MPa, and the isostatic pressing time is about
60 seconds.
[0077] The Nd--Fe--B permanent magnetic material can be labeled as
T12.
Example 13
[0078] (1) An Nd--Fe--B alloy is made by casting, the smelted
molten alloy being cooled and solidified in a water-cooling cooper
mold. The cast alloy has a general chemical formula
Nd.sub.10.25(Pr.sub.3.30Dy.sub.1.15)Fe.sub.78.33(Al.sub.0.75Cu.sub.0.05)B-
.sub.6.17.
[0079] (2) The alloy is rough crushed in a jaw crusher, followed by
mechanical crushing in a fine crusher, and milled to powder form
with an average particle diameter of about 3.5 microns by jet
milling under a nitrogen atmosphere.
[0080] (3) An TbB.sub.6 additive and an antioxidant are added to
the powder. The additive is about 0.1% of the alloy by weight and
has an average particle diameter of about 100 nanometers. The
amount of antioxidant is about 1% of the alloy by weight.
[0081] (4) The composition may be pressed by a forming press in a
closed glove box under nitrogen gas in a magnetic field. The
intensity of the magnetic field is about 2.0 T, the pressure at
about 10 MPa, and the isostatic pressing time is about 60
seconds.
[0082] (5) The composition is sintered in a vacuum sintering
furnace under an atmospheric pressure of 2.times.10.sup.-2 Pa, the
sintering temperature at about 1120.degree. C. for about 2 hours.
The composition is first tempered at about 800.degree. C. for about
3 hours followed by second tempering at about 500.degree. C. for
about 4 hours.
[0083] The Nd--Fe--B permanent magnetic material can be labeled as
T13.
[0084] Reference 2
[0085] The sample is substantially similar in all respect to that
of EXAMPLE 13 with the exception of the TbB.sub.6 additive.
[0086] The Nd--Fe--B permanent magnetic material can be labeled as
TC2.
[0087] Testing
[0088] 1. Magnetic Property
[0089] Using a curve measurement system for permanent magnetic
materials (NIM200C/China National Institute of Metrology), the
magnetic properties of materials T1-T13, TC1 and TC2 were carried
out and recorded in Table 1. The magnetic properties tested
included remnant magnetism (Br) and maximum magnetic energy product
(BHmax).
[0090] 2. Mechanical Property
[0091] Using a universal testing machine (CMT5105/XinSanSi
(ShenZhen) Group
[0092] Company), the mechanical properties of materials T1-T13, TC1
and TC2 were carried out and recorded in Table 1. The mechanical
properties tested included coercive force (Hcj) and bending
strength (MPa).
TABLE-US-00001 TABLE 1 Magnetic and mechanical properties of
materials T1-T13, TC1 and TC2. Bending BHmax Hcj Strength No. Br
(KGs) (MGOe) (KOe) (MPa) T1 11.66 32.80 27.95 188.21 TC1 11.68
33.11 25.46 179.37 T2 11.59 32.75 26.62 186.37 T3 11.43 31.40 25.96
182.78 T4 11.59 32.13 26.10 183.48 T5 11.64 32.72 26.45 187.68 T6
11.57 32.50 26.19 187.36 T7 11.56 32.43 26.08 186.41 T8 11.59 32.79
26.60 185.74 T9 11.64 32.81 27.46 188.03 T10 11.60 32.77 27.09
187.76 T11 11.67 32.87 26.75 187.66 T12 11.66 32.91 26.89 187.80
T13 11.78 34.76 18.92 193.19 TC2 11.75 34.51 17.43 186.42
[0093] Based on the results of Table 1, T1 exhibited better
coercive force (27.95 KOe v. 25.46 KOe) and improved bending
strength (188.21 MPa v. 179.37 MPa) than its counterpart TC1
without the TbB.sub.6 additive, while T13 likewise performed the
same versus its counterpart TC2 (18.92 KOe v. 17.43 KOe and 193.19
MPa v. 186.42 MPa). At the same time, the permanent magnetic
materials T1 and T13 are able to maintain comparable magnetic
properties (remnant magnetism of 11.66 KGs v. 11.68 KGs for T1 v.
TC1 and 11.78 KGs v. 11.75 KGs for T13 v. TC2; maximum magnetic
energy product of 32.80 MGOe v. 33.11 MGOe for T1 v. TC1 and 34.76
MGOe v. 34.51 MGOe for T13 v. TC2). In addition, the permanent
magnetic materials according to the presently disclosed embodiments
are also able to maintain comparable mechanical properties
including coercive force and bending strength against the reference
samples while keeping magnetic properties including remnant
magnetism and maximum magnetic energy product substantially
invariant.
[0094] Although the permanent magnetic materials have been
described in detail with reference to several embodiments,
additional variations and modifications exist within the scope and
spirit as described and defined in the following claims.
* * * * *