Note: Descriptions are shown in the official language in which they were submitted.
~22647
DESCRIPTION
NEAR~ZERO MAGNETOSTRICTIVE GLASSY METAL
ALLOYS WITH HIGH MAGNETIC AND THERMAL STABILITY
BACKGROUND OF THE INVEN~ION
1. Field of the Invention
_
This invention relates to glassy metal alloys
with near-zero magnetostriction, high magnetic and
thermal stability and excellent soft magnetic proper-
ties.
2. Description of the Prior Art
__ _
Saturation magnetostriction ~s is related to
the frac~ional change in length ~Q/Q that occurs in a
magnetic material on going from the demagnetized to the
saturated, ferromagnetic state. The value of magne-
tostriction, a dimensionless quantity, is often given
in units of microstrains ti.e-, a microstrain is a
fractional change in length of one part per million).
Ferromagnetic alloys of low magnetostriction
are desirable for several interre:Lated reasons:
1. Soft magnetic properties (low coercivity,
high permeability) are generally obtained when both the
saturation magnetostriction~sand the magnetocrystalline
anisotropy K approach zero. Therefore, given the same
anisotropy, alloys of lower magnetostriction will show
lower dc coercivities and higher permeabilities. Such
alloys are suitable for various soft magnetic applica-
tions.
2~ Magnetic properties of such zero magne-
toskrictive materials are insensitive to mechanical
strains. When this is the case, there is little need
~.
. .,
122;~64~
for stress-relief annealing after winding, punching or
other physical handling needed to form a device from
such material. In contrast, magnetic properties of
stress-sensitive materials, such as the crystalline
alloys, are seriously degraded by such cold working and
such materials must be carefully annealed.
3. The low dc coercivity of zero magneto-
strictive materials carries over to ac operating con-
ditions where again low coercivity and high
permeability are realized (provided the magneto-
crystalline anisotropy is not too lar~e and the
resistivity not too small). Also hecause energy is not
lost to mechanical vibrations when the saturation maga-
netostriction is zero, the core loss of zero magne-
tostrictive materials can be quite low~ Thus, zeromagnetostrictive magnetic alloys (of moderate or low
magnetocrystalline anisotropy) are useful where low
loss and high ac permeability are required. Such
applications include a variety of tape-wound and lami-
nated core devices, such as power transformers, signaltransformers, magnetic recording heads and the like.
4. Finally, electromagnetic devices con-
taining zero magnetostrictive materials generate no
acoustic noise under AC excitation. While thi~ is the
reason for the lower core loss mentioned above, it is
also a desirable characteristic in itsel~ because it
eliminates the hum inherent in many electromagnetic
devices.
There are three well-known crystalline alloys
of zero magnetostriction (in atom percent, unless
otherwise indicated)
(1) Nickel-iron alloys containing approxima-
tely 80% nickel ("80 nickel permalloys");
(2) Cobalt-iron alloys containing approxima-
tely 90% cobalt; and
(3) Iron-silicon alloys containing approxima-
tcly 6 wt. ~ silicon.
Also included in these categories are zero
` _3~ 6~7
magnetostrictive alloys based on the binaries but with
small additions of other elements such as molybdenum,
copper or aluminum to provide specific property chanyes.
These include, for example, 4~ Mo, 79% Ni, 17% Fe (sold
under the designation Moly Permalloy) for increased
resistivity and permeability; permalloy plus varying
amounts of copper (sold under the designation Mumetal,
a registered trademark of Spang Industries, Inc.) for
magnetic softness and improved ductility; and 85 wt. ~
Fe, 9 wt. % Si, 6 wt. % Al (sold under the designation
Sendust) for zero anisotropy.
The alloys included in category (1) are the
most widely used of the three classes listed above be-
cause they combine zero magnetostriction with low
anisotropy and are, therefore, extremely soft magneti-
cally; that is they have a low coercivity, a high
permeability and a low core loss. These permallays are
also relatively soft mechanically and their excellent
magnetic properties, achieved by high temperature
(about lOO~C) anneal, tend to be degraded by relatively
mild mechanical shock.
Category (2) alloys such as those based on
CogOFe10 have a much higher saturation induction (Bs about
1.9 Tesla) than the permalloys. However, they also have a
strong negative magnetocrystalline anisotropy, which
prevents them from being good soft magnetic materials. For
example, the initial permeability of Co90Fe10 is only about
100 to 200.
Category (3) alloys such as Fe/6 wt~ Si and the
related ternary alloy Sendust (mentioned above) also show
higher saturation inductions (Bs about 1.8 Tesla and 1.1
Tesla, respectively) than the permalloys. However these
alloys are extremely brittle and have, therefore, found
limited use in powder form only. Recently both Fe/6.5
wt% Si [IEEE Trans. M G-16, 728 (1980)] and Sendust alloys
[IEEE Trans. MAG-15, 1149 (1970)] have been made relatively
ductile by rapid solidification. However, compositional
dependence o~ the magnetostriction is very strong in
these materials,
~' ~ 4
-~ ~Z~Z~47
difficult precise tayloring of the alloy composition to
achieve near-zero maganetostriction.
It is known that magnetocrystalline anisotropy
i5 effectively eliminated in the glassy state. It is
therefore, desirable to seek glassy metal alloys of
zero magnetostriction. Such alloys might be found near
the compositions listed above. Because of the presence
of metalloids which tend to quench the magnetization by
the transfer of charge to the transition-metal d-
electron states, however, glassy metal alloys based onthe 80 nickel permalloys are either non-magnetic at
room temperature or have unacceptably lo~ saturation
induction~. For example, the glassy alloy Fe40Ni40P14B6
(the subscripts are in atom percent) has a saturation
induction of about 0.8 Tesla, while the glassy alloy
Ni49Fe29P14B6Si2 has a saturation induction of about
0.46 Tesla and the glassy alloy Ni80P~o is non-
magnetic. No glassy metal alloys having a saturation
magnetostriction approximately equal to zero have yet
been found near the iron-rich Sendust composition. A
number of near-zero magnetostrictive glassy metal
alloys based on the Co-Fe crystalline alloy mentioned
above in (2) have been reported in the literature.
These are, for example, Co72Fe3P16s6A13 (AIP ConferenCe
Proceedings, ~o. 24, pp. 745-746 (1975))
70.5Fe4.ssilsBlo (Vol- 14, Japanese ~ournal of
Appll Physics, pp. 1077-1078 (1975))
C31.2Fe7.8Ni39.0B14Sig [proceedings of 3rd
International Conference on Rapidly Quenched Metals, p.
183, (1979)] and CO74Fe6B20 [IEEE Trans. AG-12, 942
(1976)]. rrable I lists some of the magnetic properties
of these materials.
T le
Saturation induction (Bs), Curie temperature (~
the first crystallization temperature (TC1) r as-cast dc
coe~civity (HC), and dc coercivity and permeability
( ~ ) in the annealed states of some oE the prior art
zero magnetostrictive glassy alloys.
`-` 122;269~7
--5--
nnealed V lues
Alloy Bs ef TC H~ H~ ~
(Tesla) (K) (K~ ~A/m) (A~m) (at 1 ~z)
C72Fe3P16B6A13 0.63 600 - 1.8 1.0*
5 Co70~5Fe4~sBloSil5 0.65 688 - 8.0 1.2** 50 000
Co31.2Fe7.8N139 0.61 503690 - 0~16*** 50 000
B14Si8
CO74Fe6B20 1.18 7006~0 2.8
* annealed at 270~C for 45 min., in 2400 A/m field
10 (Hll) applied along the circumferential direction of
the toroidal sample.
** annealed at 350C and cooled at 175C/hour in Hll =
32 kA/m.
***annealed at about 330C.
The saturation induction (Bs) of these alloys ranges
between 0.6 and 1.2 Tesla. The glassy alloys with
Bs close to 0.6 T show low coercivities and high per-
meabilities comparable to crystalline supermalloys.
However, these alloys tend to be magnetically unstable
at relatively low ( 150C) temperatures. On the other
hand, the glassy alloys with Bs ~ 1.2 Tesla tend to have
their ferromagnetic Curie temperatures (ef) near or
above their first crystallization temperatures (TCl).
This makes heat-treatment of these materials very dif-
ficult to achieve desired soft magnetic propertiesbecause such annealing is most effective when carried
out at temperatures near ef.
Clearly desirable are zero magnetostrictive
glassy alloys with higher magnetic and thermal stability
and a saturation induction as high as possible.
SUMMARY OF THE INVENTION
In accordance with the invention, there is provided
a magnetic alloy that is at least 70% glassy~ and which
has a near-zero magnetostriction, high magnetic and
thermal stability and excellent soft magnetic proper-
ties. The glassy metal alloy has the composition
coaFebNicMo~Besi~ where A ranges ~rom about 58 to
70 atom percent, b ranges from about 2 to 7.5 atom
6~
percent, c ranges from about 0 to 8 atom percent,
d ranges from about 1 to about 2 atom percent, e ranges
from about 11 to lS atom percent and f ranges from about
9 to 1~ atom percent, with the proviso that the sum of
a, b and c ranges from about 72 to 76 atom percent and
the sum of e and f ranges from about 23 to 26 atom
percent. The glassy alloy has a value of magnetostric-
tion ranging from about -1 x 10-6 to +1 x 10-6 a
saturation induction ranging from about 0.6 to 0.8
Tesla, a Curie temperature ranging from about 550 to 670K
and a first crystallization temperature ranging from
about 790 to 870 X.
DETAILED DESCRIPTION OF THE INVENTION
~ ___ _
In accordance with the invention, there is
provided a magnetic alloy that is at least 70% glassy
and which has an outstanding combination of properties,
including a near-zero magnetostriction, high magnetic
and thermal stability and such soft magnetic properties
as high permeability, low core loss and low coercivity.
The glassy metal alloy has the composition
COaFebNicModBeSif, where a ranges from about 58 to 70
atom percent, b ranges from about 2 to 7.5 atom per-
cent, c ranges from about 0 to 8 ato~ percent and d
ranges from about 1 to about 2 atom percent, e ranges
from about 11 to 15 atom percent and ~ ranges from
about 9 to 14 atom percent, with ~he proviso that the
sum of a, b and c ranges from about 72 to 76 atom per-
cent and the sum of e and f ranges from about 23 to 26
atom percent. The glassy alloy has a value of magneto-
striction ranging from about -1 x 10-6 to +1 x 10-6 and
a saturation induction ranging from about 0.6 to 0.8
Tesla, Curie Temperature, ranging from 550 to 670K and
the first crystallization temperature ranging from
about 790 to 870 K.
The purity of the above composition is that
found in normal commercial practice. However, it will
be appreciated that molybdenum in the alloys of the
invention may be re~laced by at least one other tran-
l~ZZ64~7
sition metal element, such as tungsten, niobium, tan-
talum, titanium, zirconium and hafnium, and up to about
2 atom percent of Si may be replaced by carbon, alu-
minum or germanium without significantly degrading the
desirable magnetic properties of these glassy alloys.
Examples of essentially zero magnetostrictive
glassy metal alloys of the invention include
C67.4Fe4.1Ni3.0Ml.5B12.5Sill.5, Co67.lFe4.4Ni3.0Mol.s
B12.5Sill.5r C64.0Fe4.5Ni6.0M1O5B12.5Sill.5~ C67.0
Fe4.5Ni3.0M1.5B12Sil2r Co~7.oFe4.sNi3.oMol.sBl3sill and
Co67.5Fe4.5Ni3.0Mol.oBl2sil2. These glassy alloys
possess saturation induction between about 0.7 and 0.8
Tesla, Curie temperature between 600 and 670K, the
first crystallization temperature of about 800K and
excellent ductility. Some magnetic and thermal proper-
ties of these and some of other near-~ero magnetostric-
tive glassy alloys of the present invention are listed
in Table II. These may be compared with properties
listed in Table I for previously-reported glassy metal
alloys of zero magnetostriction.
The activation energy (Ea) for the reorien-
tation of the magnetization is listed in Table III
for some representative near-zero magnetostrictive
glassy alloys. This table indicates that Si tends to
increase Ea and also that Ea tends to be higher when
Si/B ratio is close to 1. The higher values of Ear
indicating higher magnetic stability of the system, is
desired. Combining these information based Table II
and III, preferred Si content is between 9 and 14 atom
percent when (Si ~ ~) is between 23 and 26 atom percent.
The presence of Mo is to increase TC1 and
hence the thermal stability of the alloy system. The
content of Mo beyond 2 atom percent, however, reduces
the Curie temperature to a level lower than 550 K,
which is undesirab]e in convention magnetic devices.
~-`` lZ~26~7
Table II
Saturation induction ~Bs), Curie temperature (a~),
saturation magnetostriction ( ~s) and the first
~rystallization tempera~ure (TCl) of near-zero
magnetostrictive glassy alloys.
Ccmposl ons
Co Fe Ni Mo B Si B~(Tesla) ~(K) S(10-6) T ~K)
._ c
67.4 4.1 3.0 1,5 12.5 11.5 0.72 603 -0.0 798
67.1 4~4 3.0 1.5 12.5 11.5 0.75 626 +0.0 798
64.0 4.5 6.0 1.5 1205 11.5 0.70 620 -0.0 796
10 65.5 4.5 4.5 1.5 12.5 11.5 0.74 620 +0.8 799
70.0 4.5 0 1.5 12.5 11.5 0.77 649 +0.8 800
68.5 4.5 1.5 1.5 12.5 11.5 0.78 639 -0.9 801
63.3 3.7 7.5 1.5 12.5 11.5 ~.66 575 -0.7 798
67.0 4.5 3.0 1.511 13 0.72 582 +0.4 801
15 67.0 4.5 3O0 1~512 12 0.70 598 +0.0 803
67.0 4.5 3.0 1.513 11 0.74 654 +0.0 797
67.0 4.5 3.0 1.514 10 0.74 637 +0.4 800
67.8 3.7 3.0 1.511 13 0.70 558 -0.4 7g9
67.8 3.7 3.0 1.512 12 0.70 585 -0.2 804
20 67.8 3.7 3.0 1.513 11 0.70 600 -0.4 797
67.8 3.7 3.0 1.514 10 0.72 Ç23 -0.6 798
67.8 3.7 3.0 1.515 9 0.72 640 -0.6 794
66.3 5.2 3.0 1.512 12 0.72 586 +0.6 800
68.5 3.0 3.0 1.512 12 0.70 609 -0.3 796
25 69.3 2.2 3.0 1.512 12 0.70 580 -1.1 794
~7.5 4.5 3.0 1.012 1~ 0.75 672 +0.0 810
66.6 4.4 3.0 2.012 12 0.69 610 +0.6 802
68.0 3.0 3.0 2.012 12 0.68 567 +0.8 867
62.2 5.9 5.9 2.012 12 0.69 578 +1.1 806
30 63.6 5.9 4.4 2.012 12 0.65 563 +0~8 808
65.1 5.9 3.0 2.012 12 0.68 549 +0.8 810
66.6 5.9 1.5 2.012 12 0.71 581 +1.1 808
63.0 6.0 6.0 2.012 11 0.71 673 +0.? 795
67.1 5.4 0 2.0 12.5 13 0.72 643 +0.5 820
35 58.4 7.3 7~3 2.013 12 0.62 570 +0.7 824
'7
TABLE III
Activation energy (Ea) for reorientation of the
magnetic anisotropy of representative near-zero
magnetostrive glassy alloys.
Alloy Compositions Ea
Co Fe Ni Mo B Si (10-19J)
64.0 8.0 8.0 2.0 18 0 1.1
64.0 ~.0 8.0 2.0 16 2 1.2
64.0 8.0 8.0 2.0 10 8 2.6
60.0 7.5 7.5 2.0 17 6 0.82
60.0 7.5 7.5 2.0 11 lZ 2.1
For some applications, it may be desirable or
acceptable to use a material with a small positive or a
small negative magnetostri~tion. Such near-zero magne-
tostrictive glassy metal alloys are obtained for a, band c in the ranges of about 58 to 70, 2 to 7.5 and 0
to 8 atom percent respectively, with the provision that
the sum of a, b and c ranges between 72 and 76 atom
percent. The absolute value of saturation magne-
tostriction l~sl of these glassy metal alloys is less
than about 1 x 10-6 (i.e., the saturation magnetostric-
tion ranges from about -1 x 10-6 to ~1 x 10-6, or -1 to
+l microstrains). The saturation induction of these
glassy alloys ranges between about 0.6 and 0.8 Tesla.
Values of ~s even closer to zero may be
obtained for values of a, b and c ranging respectively
from about 63 to 69, 3 to 6 and 0 to 6, with the provi-
sion that the sum of a, b and c ranges between about 72
and 76 atom percent. For such preferred compositions,
l~5l is less than 0.5 x 10-6. Essentially zero values
of magnetostriction are obtained for values of a, b and
c ranging from about 64 to 68, 4 to 5 and 0 to 6 atom
percent respectively with the provision that the sum of
a, b and c ranges between about 72 and 76 atom percent
and also when f is between 11 and 12 atom percent and
(e ~ f) is close to 24 atom percent and, accordingly,
such compositions are most preferred.
The ylassy metal alloys of the invention are
12~ZZ64~
10--
conveniently prepared by techniques readily available
elsewhere; see, e.g., U.S. Patents 3,845,805, issued
November 5, 1974 and 3,856,513, issued December 24,
1974O In general, the glassy alloys, in the form of
continuous ribbon, wire, etc., are rapidly quenched
from a melt of the desired composition at a rate of at
least about 105 K/sec.
A metalloid content of boron, and silicon in
the range of about 23 to 26 atom percent of the total
alloy composition is sufficient for glass formation,
with boron ranging from about 11 to 15 atom percent and
silicon ranging from about 9 to about 14 atom percent.
As noted hereinabove, a ratio Si/B close to 1 and a Si
content ("f") between 11 and 12 atom percent are most
favorable because they lead to higher stability and
relative insensitiveness of the ~agnetostriction value
(which is close to zero) to the metalloid composition.
For example, the rate of change of magnetostriction
value with respect to silicon content, d~S/df, i5 close
to zero for "f" between 11 and 12 atom percent while
Id~s/dfl is about o.8xlo-6~at.%si near f=10 or 13 atom
percent when a=67.1, b=4.5, c=3.0 and d=1.5 atom per-
cent. The quantity Id~S/dfl becomes zero near f=12
atom percent and about O.lxlO-6/at.%Si near f=10 or 13
atom percent when a=67.8, b=3.7,c=3.0 and d=1.5 atom
percent.
The small amount of Ni is relatively ineffec-
tive to alter the magnetostriction values in the pre-
sent alloy system and Co;Fe ratios essentially
determine the resultant maganetostriction values. Zero
magnetostriction is realized for the Co:Fe ratio of
about (14 ~16.5) to 1 in the present alloy system. In
the prior art glassy metal alloys such as
C70.5Fe4.5B10Sil5 and Co7~Fe6B20/ the ratios are
narrowly set at about 14 and 12 respectively. The
above range of the Co:Fe ratio between about 14:1 to
16.5:1 and the tolerance of abol~t +0.5 atom percent
z~
near f-11.5 atom percent to achieve ~s= and d~S/df
=0 are advantageous from materials synthesis stand-
point.
Table IV gives ac core loss ~L), exciting
power (Pe) and permeability (~ ) at 0.1 Tesla induction
and at 50 kHz of the near-zero magnetostrictive glassy
alloys of the present invention annealed at different
temperatures (Ta)~
Table IV
Examples of core loss (L), exciting power (Pe) and
permeability of near-zero magnetostrictive glassy
alloys annealed at different temperatures (Ta)~
Composition
Co Fe Ni M~ B Si L(W/kg) Pe(Va/kg) ~ Ta(C)
67.4 4.1 3,0 1.5 12.5 11.5 5.07O 8 21300 375
15 67.1 4.4 3.0 1.5 12.5 11.5 8.3 12 14400 400
68.5 4.5 1.5 1.5 12.5 11~5 5.2 7.4 21200 400
70.0 ~.5 0 1.5 12.5 11.5 7.9 1213000 400
65.5 4.5 4~5 1.5 12.5 11.5 5.1 7.5 20900 400
6~.0 4.5 6.0 1.5 12.5 11.5 6. 89.3 16900 400
20 63.3 3.7 7.5 1.5 12.5 11.5 6. 812 13500 400
67.1 5.4 0 2.0 12.5 13 7.0 12 11000 300 *
58.4 7. 3 7.3 2.0 13 12 10 11 8200 350**
* Holding time = 5 min.;
Co~ling rate = ~0.5C/min.; ~11 = 20 Ce and Hl = 350
**Holding time = 2 hours;
Cooling rate = -0.5C/min.7 Hll = 20 Oe and Hl = 35 Oe
Table V shows the effects of the annealing
temperature (Ta) and annealing field (~11) applied
along the circumferential cirection of the toroidal
samples on the dc coercivity (Hc) and remanence (Br)~
ac coercivity (Hc~) and squareness ratio (Br/Bl), where
Bl is the induction at an applied field ofl Oeat 50
kHz and ~at 50 kHz and 0.1 T induction for one of the
æero magnetostrictive alloys of the present invention.
Low coercivity and high squareness ratio close to 1 at
high ~requencies (e.g. 50 kHz) are desirable in some
magnetic device applications such as switch-mode power
supplies.
:~2~26~'Y
-12-
Table V
Ef~ects of annealing temperature (Ta) and
circumferential field (Hll) on the dc coercivity
(Hc) and remanence ~Br)r ac (50 kHz) coercivity
(Hc') and BH loop squareness ratio (Br/Bl), and
permeability at 50 kHz and Bm=o~l T for
C67.4Fe4.1N13,0Mol.5B12.5Sill.5.
Annealing
Conditions dc _ 50 kHz
Ta (C) Hll(A/m) Hc(A/m) Br(T) Hc'(A/m) Br/Bl
350 0 0.56 0.54 24 1 15600
3501600 0.49 0.63 21 1 10000
375 0 0.49 0.38 18 1 21300
3751600 0.42 0.59 22 1 10900
400 0 0.42 0.38 17 1 20000
4001600 0.28 0.50 26 0.95 11300
425 0 0.56 0.40 21 0.89 14000
4251600 0.49 0.45 24 1 13300
4~0 0 0.56 0.39 21 0.92 14400
4401600 0.56 0.59 24 1 10600
Table VI shows the effects of the annealing
time (ta) on L, Pe and ~ for one of the zero magne-
tostrictive alloys of the present invention.
Table V
Effects on annealing time (ta) on core less (L),
exciting power (Pe) and permeability ( ~) at
induction of 0.1 Tesla and frequency of 1 kHz and
50 k~z for CO67.4Fe4.1Ni3.0Mol.sB12.sSill.s annealed
at Ta=380C.
Annealing
t~me 1 kHz _ 50 kHz _ _
ta (min.) L(W7~g) Pe(VA/kg) L(W/kg) Pe(VA/kg)
0.024 0.056 5~ 500 4.2 7.1 22 100
0.027 0.056 56 300 3.6 6.8 23 200
0.027 0.055 56 800 3.7 6.7 23 600
0.031 0.053 S9 000 4.9 7.2 21 700
The results set forth in Tables IV-VI above
in~icate that L=4 W/kg, Pe=7 Va/kg and ~=23 000 at 0.1
T and 50 kHz can be achieved for 25-30 ~m thick zero
4~7
-13-
magnetostrictive glassy alloys of the present inven-
tion. Compared with these values, a prior art
crystalline nonmagnetostrictive supermalloy of the
similar thickness (~5 ~m) gives L= 8 W/kg, Pe= 10 VA/kg
and ~ =19 000 at 0~1 T and 50 kHz. It is clear that
the properties o~ the nonmagnetostrictive glassy alloys
of the present invention are superior to those of the
crystalline supermalloys. Examples of amorphous alloys
outside the scope of the invention are set forth in
Table VII. The advantageous combination of properties
provided by the alloys of the present invention cannot
be achieved in the prior art nonmagnetostrictive glassy
alloys with high saturation induction such as
CO74Fe6B20 because their Curie temperatures are higher
than the first crystallization temperatures and the
heat-treatment to improve their properties are not so
effective as in those with lower saturation inductions.
The above properties, achieved in the glassy alloys of
the present invention, may be obtained in low induction
glassy alloys of the prior art. However, these alloys
of the prior art such as C31.2Fe7.sNi39.0B14Si8 tend
to be magnetically unstable at relatively low tem-
perature of about 150C as pointecl earlier.
Table VII shows the magnetic properties of
some of the representative glassy alloys of the com-
position CoaFebNicM~dBesif in which at least one of a,
b, c, d, e, and f is outside the composition range
defined in the present invention. The table indicates
that the alloys with at least one of the constituents
outside the defined ranges exhibit at least one of the
following undesirable properties: ~i) The value of ¦~
is larger than lxlo-6~ (ii) The Curie temperature (~f)
is higher than the crystallization temperature (TCl),
which makes the post-fabrication field annealing less
effective and (iii) The Curie temperature and satura-
tion induction (Bs) become too low to be practicalO
-
2~Z~6~7
Table VII
_ _ _ _ .
Magnetic properties of some representative
CaFebNicMOdBeSif glassy alloys in which at
least one of a, b, c, d, e and f is outside
the range defined in the present invention.
Composition
____ ___________________
Co Fe Ni Mo B Si ~(Tesla) ~f(K) s(10~6) TCl(K)
69.4 5.6 0 0 25 0 1.0 760 ~0.0 715
64.0 8.0 8.0 2 10 8 0.97 725 +2.5 7~0
10 64.0 8.0 8.0 2 12 6 0.95 735 ~1.7 713
60.0 7.5 7.5 2 19 4 0.83 715 +1.6 760
43.8 7.3 14.~ 2 13 12 0.52 507 +2.7 817
The following examples are presented to pro-
vide a more complete understanding of the invention.
The specific techniques, conditions, materials, propor-
tions and reported data set forth to illustrate the
principles and practice of the invention are exemplary
and should not be construed as limiting the scope of
the invention.
EXAMPLES
1. ample Pr aration
The glassy alloys listed in Tables II-VII were
rapidly quenched (about 106 K/sec) from the melt
following the techniques taught by Chen and Polk in
25 U.S. Patent 3,856,513. The resulting ribbons, typi-
cally 25 to 30~ m thick and 0.5 to 2.5 cm wide, were
determined to be free of significant crystallinity by
X-ray diffractometry (using CuK radiation) and
scanning calorimetry. Ribbons of the glassy metal
alloys were strong, shiny, hard and ductileO
2. Magnetl _measurements
Continuous ribbons of the glassy metal alloys
prepared in accordance with the procedure described in
Example I were wound onto bobbins (3.8 cm O.D.) to form
closed-magnetic-path toroidal samples. Each sample
contained from 1 to 3 g of ribbon. Insulated primary
and secondary windings (numbering at least 10 each)
were applied to the toroids. These samples were used
:3 2~26~L~
-15~
to obtain hysteresis loops (coercivity and remanence)
and initial permeability with a commercial curve tracer
and core loss (IEEE Standard 106-1972).
The saturation magnetization, Ms, of each
sample, was measured with a commercial vibrating sample
magnetometer (Princeton Applied Research). In this
case, the ribbon was cut into several small squares
(approximately 2 mm x 2 mm). These were randomly
oriented about their normal direction, their plane
being parallel to the applied field (0 to 720 k~/m.
The saturation induction Bs (=4~MSD) was then calcu-
lated by using the measured mass density D.
The ferromagnetic Curie temperature (~f) was
measured by inductance method and also monitored by
differential scanning calorimetry, which was used pri-
marily to determine the crystallization temperatures.
The first or primary crystallization temperature (T
was used to compare ~he thermal stability of various
glassy alloys of the present and prior art inventions.
Magnetic stability was determined from the
reorientation kinetics of the magnetization, in accor-
dance with the method described in Journal of Applied
Physics, vol. 49, p. 6510 (1978), which method is
incorporated herein by reference thereto.
Magnetostriction measurements employed
metallic strain gauges (BLH Electronics), which were
bonded (Eastman - 910 Cement) between two short lengtlls
o~ ribbon. The ribbon axis and gauge axis were
parallel. The magneto~triction was determined as a
function of applied field ~rom the longitudinal strain
in the parallel (~Q/Qtland perpendicular(~Q/Q)l in-plain
fields, according to the formula ~ =2/3[~ ~Q/Q)I~ Q/Q)l]
Having thus described the invention in rather
full detail, it will be understood that this detail
need not be strictly adhered to but that further
changes and modifications ma~ suggest themselves to one
skilled in the art, all falling within the scope o~ the
invention as defined by the subjoined claims.
