Fe based hard magnetic alloy having super-cooled liquid region

Details Fe based hard magnetic alloy having super-cooled liquid region Fe based hard magnetic alloy having super-cooled liquid region

1998-03-25

2001-08-28

Sheehan, John (Department: 1742)

Metal treatment

Stock

Magnetic

C420S083000, C420S121000

Reexamination Certificate

active

06280536

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a Fe based hard magnetic alloy, especially to a Fe based hard magnetic alloy having a wide super-cooled liquid region, bearing a hard magnetism at room temperature after a heat treatment and being able to form into a bulky permanent magnet molded member.
2. Description of the Related Art
Some of conventional alloys composed of a plurality of elements have a wide temperature range to remain in a super-cooled liquid state prior to crystallization, so that these alloys can form glassy alloys. It is known in the art that this kind of glassy alloys can be molded into a bulky alloy far more thicker than thin films of amorphous alloys produced by a conventional melt quenching method.
While Fe—P—C amorphous alloys first produced in 1960's, (Fe, Co, Ni)—P—B alloys and (Fe, Co, Ni)—Si—B alloys first produced in 1970's, and (Fe, Co, Ni)—M (Zr, Hf, Nb) alloys and (Fe, Co, Ni)—M (Zr, Hf, Nb)—B alloys first produced in 1980's have been known as examples of amorphous alloy thin films, all of these alloys are inevitably produced by quenching at a cooling rate of the order of 10
5
K/s, thereby films with a thickness of 50 &mgr;m or less were produced.
Accordingly, production of thick and bulky bonded magnets have been devised. Since these bonded magnets were formed, however, by a compression molding or injection molding after mixing a magnetic powder, produced by quenching a molten liquid mainly composed of Nd
2
Fe
14
B phase, and an exchange spring magnetic powder of Fe
3
B—Nd
2
Fe
14
B
1
alloys with a binder comprising a rubber or plastic, their magnetic properties became poor besides having a weak strength as materials. In the glassy metal alloys, on the other hand, an alloy with a thickness of several mm can be formed. Alloys with compositions of Ln—Al—TM, Mg—Ln—TM and Zr—Al—TM (wherein Ln denotes a rare earth element while TM denotes a transition metal) were discovered in the years of 1988 to 1991 as these sort of glassy alloys described above.
However, since these conventional glassy metal alloys did not exhibit any magnetism at room temperature, industrial applications as hard magnetic materials were largely restricted.
Therefore, R & D of glassy metal alloys capable of obtaining thick bulky alloys with hard magnetism at room temperature have been carried out.
The temperature interval &Dgr; T
x
in the super-cooled liquid area, that is, an interval between crystallization temperature (T
x
) and glass transition temperature (T
g
), or a numerical value of (T
x
−T
g
), is usually small in alloys with a variety of composition even when a state of super-cooled liquid area exists in the alloy. By considering the fact that conventional alloys have actually a poor ability for forming glassy metals and are of little practical values, the presence of alloys having a wide temperature range in the super-cooled liquid region and being capable of forming a glassy alloy with a single amorphous phase by cooling can overcome the limitation in thickness of thin films in the conventional amorphous alloys. In addition, If the amorphous single phase can be obtained, the crystal texture can be fine and uniform after heat treatment. It is largely noticeable from metallurgical interests. And discovery of glassy metal alloys that exhibit ferromagnetism at room temperature would be a key problem whether the alloys could be developed as industrial materials or not.
SUMMARY OF THE INVENTION
The object of the present invention is to provide a Fe based hard magnetic alloy having a wide temperature interval in the super-cooled liquid area, having a hard magnetism at room temperature, being able to be processed thicker than thin films of amorphous alloys obtained by a conventional melt quenching method, and having a high strength as materials along with an excellent hard magnetism after a heat treatment.
In one aspect, the present invention provides a Fe based hard magnetic alloy having super-cooled liquid region, comprising Fe as a major component and containing one or a plurality of elements R selected from rare earth elements, one or a plurality of elements M selected from Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, W and Cu, and B, wherein the temperature interval &Dgr; T
x
in the super-cooled liquid region represented by the formula of &Dgr; T
x
=T
x
−T
g
(wherein T
x
and T
g
denote a crystallization temperature and glass transition temperature, respectively) is 20° C. or more.
The element M in the Fe based hard magnetic alloy according to the present invention contains Cr and &Dgr; T
x
is 40° C. or more.
The Fe based hard magnetic alloy having super-cooled liquid region according to the present invention may be represented by the following formula:
Fe
100−x−y−w
R
x
M
y
T
z
B
w
(wherein T is one or a plurality of elements selected from Co and Ni, with x, y, z and w representing composition ratios being in the range of 2≦x≦15, 2≦y≦20, 0≦z≦20 and 10≦W≦30 in atomic percentages, respectively)
The Fe based hard magnetic alloy having super-cooled region according to the present invention may be represented by the following formula:
Fe
100−x−y−w−t
R
x
M
y
T
z
B
w
L
t
(wherein T is one or a plurality of elements selected from Co and Ni with x, y, z, w and t representing composition ratios being in the range of 2≦x≦15, 2≦y≦20, 0≦z≦20, 10≦W≦30 and 0≦t≦0.5 in atomic percentages, respectively, and the element L is one or a plurality of elements selected from Ru, Rh, Pd, Os, Ir, Pt, Al, Si, Ge, Ga, Sn, C and P.)
It is preferable that, in the Fe based hard magnetic alloy having super-cooled region according to the present invention, x representing the composition ratios in the composition formula of Fe
100−x−y−w
R
x
M
y
Co
z
B
w
or Fe
100−x−y−w−t
R
x
M
y
T
z
B
w
L
t
is in the range of 2≦x≦12 in atomic percentage.
It is also preferable that, in the Fe based magnetic alloy having super-cooled region according to the present invention, y representing the composition ratios in the composition formula of Fe
100−x−y−w
R
x
M
y
T
z
B
w
or Fe
100−x−y−w−t
R
x
M
y
T
z
B
w
L
t
is in the range of 2≦y≦15 in atomic percentage.
It is further preferable that, in the Fe based hard magnetic alloy having super-cooled region according to the present invention, z representing the composition ratios in the composition formula of Fe
100−x−y−w
R
x
M
y
T
z
B
w
or Fe
100−x−y−w−t
R
x
M
y
T
z
B
w
L
t
is in the range of 0.1≦z≦20 in atomic percentage.
In the Fe based hard magnetic alloy having super-cooled region according to the present invention, the element M in the composition formula of Fe
100−x−y−w
R
x
M
y
T
z
B
w
or Fe
100−x−y−w−t
R
x
M
y
T
z
B
w
L
t
is represented by (Cr
1-a
M′
a
), wherein M′ is one or a plurality of elements selected from Ti, Zr, Hf, V, Nb, Ta, Mo, W and Cu and “a” is in the range of 0≦a≦1. It is further preferable that, in the Fe based hard magnetic alloy represented by the composition formula above, “a” representing the composition ratio in the foregoing structure formula is in the range of 0≦a≦0.5.
The Fe based hard magnetic alloy having super-cooled region described above may be subjected to a heat treatment in the present invention to precipitate a crystalline phase comprising one or two of &agr;-Fe phase and Fe
3
B phase, and a crystalline phase comprising Nd
2
Fe
14
B phase. It is preferable that the heat treatment described above is carried out by heating the Fe based hard magnetic alloy at 500 to 850° C. When the Fe based hard magnetic alloy according to the present invention is contaminated with a small amount of inevitable impurities such as oxides of rare earth elements in the production process, it should be considered to be within the technical concept of the present invention.


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