Field of the Invention
[0001] The invention relates to metallic glasses having high permeability, low magnetostriction,
low coercivity, low ac core loss, low exciting power and high thermal stability.
Description of the Prior Art
[0002] As is known, metallic glasses are metastable materials lacking any long range order.
X-ray diffraction scans of glassy metal alloys show only a diffuse halo similar to
that observed for inorganic oxide glasses.
[0003] Metallic glasses (amorphous metal alloys) have been disclosed in U.S. Patent 3,856,513,
issued December 24, 1974 to H.S. Chen et al. These alloys include compositions having
the formula M
aY
bZ
c, where M is a metal selected from the group consisting of iron, nickel, cobalt, vanadium
and chromium, Y is an element selected from the group consisting of phosphorus, boron
and carbon and Z is an element selected from the group consisting of aluminum, silicon,
tin, germanium, indium, antimony and beryllium, "a" ranges from about 60 to 90 atom
percent, "b" ranges from about 10 to 30 atom percent and "c" ranges from about 0.1
to 15 atom percent. Also disclosed are metallic glassy wires having the formula T
iX
j' where T is at least one transition metal and X is an element selected from the group
consisting of phosphorus, boron, carbon, aluminum, silicon, tin, germanium, indium,
beryllium and antimony, "i" ranges from about 70 to 87 atom percent and "j" ranges
from about 13 to 30 atom percent. Such materials are conveniently prepared by rapid
quenching from the melt using processing techniques that are now well-known in the
art.
[0004] Metallic glasses are also disclosed in U.S. Patent No. 4,067,732 issued January 10,
1978. These glassy alloys include compositions having the formula M
aM'
bCr
cM"
dB
e, where M is one iron group element (iron, cobalt and nickel), M' is at least one
of the two remaining iron group elements, M" is at least one element of vanadium,
manganese, molybdenum, tungsten, niobium and tantalum, B is boron, "a" ranges from
about 40 to 85 atom percent, "b" ranges from 0 to about 45 atom percent, "c" and "d"
both range from 0 to about 20 atom percent and "e" ranges from about 15 to 25 atom
percent, with the provision that "b", "c" and "d" cannot be zero simultaneously. Such
glassy alloys are disclosed as having an unexpected combination of improved ultimate
tensile strength, improved hardness and improved thermal stability.
[0005] These disclosures also mention unusual or unique magnetic properties for many metallic
glasses which fall within the scope of the broad claims. However, metallic glasses
possessing a combination of higher permeability, lower magnetostriction, lower coercivity,
lower core loss, lower exciting power and higher thermal stability than prior art
metallic glasses are required for specific applications such as tape recorder head,
relay cores, transformers and the like.
SUMMARY OF THE INVENTION
[0006] In accordance with the invention, metallic glasses having a combination of high permeability,
low magnetostriction, low coercivity, low ac core loss, low exciting power and high
thermal stability are provided. The metallic glasses consist essentially of about
66 to 82 atom percent of iron, from 1 to about 8 atom percent of which metal may be
replaced with at least one of nickel and cobalt, about 1 to about 6 atom percent of
at least one element selected from the group consisting of chromium, molybdenum, tungsten,
vanadium, niobium, tantalum, titanium, zirconium and hafnium, about 17 to 28 atom
percent of boron, from 0.5 to about 6 atom percent of boron being, optionally, replaced
with silicon and up to about 2 atom percent of boron being, optionally, replaced with
carbon, plus incidental impurities. The metallic glasses of the invention are suitable
for use in tape recorder heads, relay cores, transformers and the like.
DETAILED DESCRIPTION OF THE INVENTION
[0007] The metallic glasses of the invention are characterized by a combination of high
permeability, low saturation magnetostriction, low coercivity, low ac core loss, low
exciting power and high thermal stability. The glassy alloys of the invention consist
essentially of about 66 to 82 atom percent iron, from 1 to about 8 atom percent of
which metal may be replaced with at least one of nickel and cobalt, about 1 to 6 atom
percent of at least one element selected from the group consisting of chromium, molybdenum,
tungsten, vanadium, niobium, tantalum, titanium, zirconium and hafnium, about 17 to
28 atom percent of boron, from 0.5 to about 6 atom percent of which metalloid may
be replaced with silicon and up to 2 atom percent of which metalloid may be replaced
with carbon, plus incidental impurities. A concentration of less than about 1 atom
percent of Cr, Mo, W, V, Nb, Ta, Ti, Zr and/or Hf does not result in sufficient improvement
of the properties of permeability, saturation magnetostriction, coercivity, ac core
loss and thermal stability. A concentration o greater than about 6 atom percent of
at least one of these elements results in an unacceptably low Curie temperature.
[0008] Iron provides high saturation magnetization at room temperature. Accordingly the
metal content is preferably substantially iron, with up to about 8 atom percent nickel
and/or cobalt in order to compensate the reduction of the room temperature saturation
magentiza- tion due to the presence of chromium, molybdenum, tungsten, niobium, tantalium,
titanium, zirconium and/or hafnium. The addition of nickel increases permeability.
[0009] Examples of metallic glasses of the invention include Fe
80Ni
1Mo
1B
16Si
2, Fe
76Ni
4Mo
2B
17.5Si
0.5 Fe
75 Ni
2Co
2Mo
3B
16Si
2, F
75Co
4Mo
3B
16Si
2, Fe75Ni4Mo3B16Si2, Fe
77Ni
2Mo
3B
16Si
2, Fe
75Ni
4Mo
3B
14Si
4, Fe
71Ni
4Mo
3B
17Si
5, Fe
74Ni
4Mo
4B
16Si
2, Fe
70Ni
6Mo
6B
15Si
3, Fe
75Ni
4V
3B
14Si
2C
2, Fe
71Ni
4Mo
3B
16Si
4C
2, Fe78Ni2Mo2B12Si4C2, Fe
78Ni
2Cr
2B
16Si
2, Fe
75Ni
4Nb
3B
16Si
2, Fe
75Ni
4W
3B
16Si
2, Fe75Ni4V3B16Si2' Fe
79Ni
4Ta
1B
16Si
2, Fe
75Ni
4Ti
3B
16Si
2, Fe
75Ni
4Zr
3B
16Si
2, Fe
79Ni
4Hf
1B
16Si
2, Fe
72Ni
2Mo
2B
22Si
2, Fe
70Ni
2Mo
2B
22Si
4, and Fe
70Ni
2Mo
2B
24Si
2 (the subscripts are in atom percent). The purity of all alloys is that found in normal
commercial practice.
[0010] The presence of chromium, molybdenum, tungsten, vanadium, niobium, tantalum, titanium,
zirconium and/or hafrium raises the crystallization temperature while simultaneously
lowering the Curie temperature of the glassy alloy. The increased separation of these
temperatures provides ease of magnetic annealing, that is, thermal annealing at a
temperature near the Curie temperature. As is well-known, annealing a magnetic material
close to its Curie temperature generally results in improved properties. As a consequence
of the increase in crystallization temperature with increase in the concentration
of chromium, molybdenum, tungsten, vanadium, niobium, tantalum, titanium, zirconium,
and/or hafnium, annealing can be easily accomplished at elevated temperatures near
the Curie temperature and below the crystallization temperature. Such annealing cannot
be carried out for many alloys similar to those of the invention but lacking these
elements. On the other hand, too high a concentration of chromium, molybdenum, tungsten,
vanadium, niobium, tantalum, titanium, zirconium and/or hafnium reduces the Curie
temperature to a level that may be undesirable in certain applications. For metallic
glasses in which boron and silicon are the major and minor metalloid constituents
respectively, a preferred range of chromium, molybdenum, tungsten, vanadium, niobium,
tantalum, titanium, zirconium and/or hafnium concentration is about 2 to 4 atom percent.
[0011] It is preferred that the metalloid content consist essentially of (1) substantially
boron with a small amount of silicon, (2) boron plus silicon and (3) boron and silicon
plus a small amount of carbon. Preferably, the metalloid content ranges from about
17 to 28 atom percent for maximum thermal stability.
[0012] Preferred metallic glass systems are as follows:
1. Fe-M-Mo-B-Si: Fe100-a-b-c-dMaMobBcSid, where M is at least one of nickel and cobalt. When (c+d) is about 18, the preferred ranges
of a,b,c and d are from about 2 to 8, from about 1 to 4, from about 14 to 17.5 and
from about 0.5 to 4, respectively. When (c+d) is about 22, the preferred ranges for
a,b,c and d are from about 2 to 8, from about 1 to 6, from about 15 to 20.5 and from
about 0.5 to 6, respectively. When (c+d) is close to 25, the preferred ranges of a,
b, c and d are from about 2 to 8, from about 1 to 6, from about 21 to 25 and from
about 1 to 6 respectively. These metallic glasses have a combination of saturation
induction (Bs) of 1.0-1.4 Tesla, saturation magnetostriction (Às) between 12 and 24 ppm, Curie temperature (ef) between about 475 and 705 K and first crystallization temperature of 750-880 K.
When optimally heat-treated, these alloys have excellent ac magnetic properties especially
at high frequencies (f>103 Hz). The ac core loss (L) and exciting power (P ) taken at f = 50 kHzfand the induction level of Bm = 0.1 Tesla of, for example, a heat-treated Fe75Ni4Mo3B16Si2 metallic glass are 6.5 W/kg and 13.4 VA/kg, respectively. These values are to be
compared with L = 7W/kg and Pe = 20 VA/kg for a a heat-treated prior art metallic glass of the same thickness having
the composition Fe79B16Si5. The permeability P at Bm = 0.01 Tesla is 10 500 and 8000 for the heat-treated Fe75Ni3Mo4B16Si2 and Fe79B16Si5, respectively. The smaller saturation magnetostriction (λs) of about 20 ppm of the present alloy as compared to s λs = 30 ppm for the aforesaid prior art alloy makes the alloys of the present invention
especially suited for magnetic device applications such as cores for high frequency
transformers. Beyond f = 50 kHz, the alloys of the present invention have permeabilities
comparable or higher than those for crystalline supermalloys which have Bs near 0.8 Tesla. The higher values of B for the present alloys make these alloys better
suited than supermalloys for magnetic applications of f>50 kHz. Fe-M-M'-B-Si: Fe100-a-b-c-dMaM'bBcSid where M is nickel and/or cobalt and M' is selected from Cr, W, V, Nb, Ta, Ti, Zr
or Hf. When (c+d) is about 18, the preferred ranges of a,b,c and d are about 2 to
8, from about 1 to 4, from about 14 to 17.5 and from about 0.5 to 4, respectively.
When (c+d) is about 22, the preferred ranges for a,b,c and d are from about 2 to 8,
from about 1 to 6, from about 16 to 21.5 and from about 0.5 to 6, respectively. When
(c+d) is close to 25, the preferred ranges for a, b, c and d are from about 2 to 8,
from about 1 to 6, from about 21 to 25 and from about 1 to 6 respectively. Fe-M-M'-B-Si-C:
Fe100-a-b-c-d-eM aM'bBcSidCe wherein M is nickel and/or cobalt, and M' is selected from the group consisting of
Cr, Mo, W, V, Nb, Ta, Ti, Zr or Hf. When (c+d) is about 18, the preferred ranges for
a,b,c,d and e are from about 2 to 8, from about 1 to 4, from about 12 to 17.5, from
about 0.5 to 4 and from 0 to 2, respectively. When (c+d) is about 22, the preferred
ranges for a,b,c,d and e are from about 2 to 8, from about 1 to 6, from about 14 to
21.5, from about 0.5 to 6 and from about 0 to 2, respectively. When (c+d) is close
to 25, the preferred ranges for a, b, c, d and e are from about 2 to 8, from about
1 to 6, from'about 20 to 27, from about 1 to 6 and from about 0 to 2 respectively.
[0013] Magnetic permeability is the ratio of induction to applied magnetic field. A higher
permeability renders a material more useful in certain applications such as tape recorder
heads, due to the increased response. The frequency dependence of permeability of
the glassy alloys of the invention is similar to that of the 4-79 Permalloys in the
medium-to-high frequency range (1-50 kHz), and at higher frequencies (about 50 kHz
to 1 MHz), the permeability is comparable to that of the supermalloys. Especially
noted is the fact that a heat-treated Fe
7sNi
4Mo
3B
16si
2 metallic glass has permeability of 24,000 while the best-heat-treated prior art Fe40Ni36M04B20
metallic glass has a permeability of 14,000 at 1 kHz and the induction level of 0.01
Tesla.
[0014] Saturation magnetostriction is the change in length under the influence of a saturating
magnetic field. A lower saturation magnetostriction renders a material more useful
in certain application such as tape recorder heads. Magnetostriction is usually discussed
in terms of the ratio of the change in length to the original length, and is given
in ppm. Prior art iron with metallic glasses evidence saturation magnetostric- tions
of about 30 ppm as do metallic glasses without the presence of the any of the elements
belonging to the IVB, VB and VIB columns of the periodic table such as molybdenum.
For example, a prior art iron rich metallic glass designated for use in high frequency
applications and having the composition Fe
79B
16Si
5 has a saturation magnetostriction of about 30 ppm. In contract, a metallic glass
of the invention having the composition Fe
75Ni
4Mo
3B
16Si
2 has a saturation magnetostriction of about 20 ppm. A lower saturation magnetostriction
leads to a lower phase angle between the exciting field and the resulting induction.
This results in lower exciting power as discussed below.
[0015] Ac core loss i's that energy loss dissipated as heat. It is the hysteresis in an
ac field and is measured by the area of a B-H loop for low frequencies (less than
about 1 kHz) and from the complex imput power in the exciting coil for high frequencies
(about 1 kHz to 1 MHz). The major portion of the ac core loss at high frequencies
arises from the eddy current generated during flux change. However, a smaller hystersis
loss and hence a smaller coercivity is desirable. A lower core loss renders a material
more useful in certain applications such as tape recorder heads and transformers.
Core loss is discussed in units of watts/kg. Prior art heat-treated metallic glasses
typically evidence ac core losses of about 0.05 to 0.1 watts/kg at an induction of
0.1 Tesla and at the frequency range of 1 kHz. For example, a prior art heat-treated
metallic glass having the composition Fe40Ni36Mo4B20, has an
ac core loss of 0.07 watts/kg at an induction of 0.1 Tesla and at the frequency of
1 kHz, while a metallic glass having the composition Fe
76Mo
4B
20 has an ac core loss of 0.08 watts/kg at an induction of 0.1 Tesla and at the same
frequency. In contrast, a metallic glass alloy of the invention having the composition
Fe
75Ni
4Mo
3B
16Si
2 has an ac core loss of 0.02 watts/kg at an induction of 0.1 Tesla and at the same
frequency.
[0016] Exciting power is a measure of power required to maintain a certain flux density
in a magnetic material. It is therefore desirable that a magnetic material to be used
in magnetic devices has an exciting power as low as possible. Exciting power (P )
is related to the above-mentioned core loss (L) through the relationship L = P
e cos δ where δ is the phase shift between the exciting field and the resultant induction.
The phase shift is also related to the magnetostriction in such a way that a lower
magnetostriction value leads to a lower phase shift. It is then advantageous to have
the magnetostriction value as low as possible. As mentioned earlier, prior art iron-rich
metallic glasses such as
Fe79B16Si
5 have the magnetostriction value near 30 pp
m, in contract to the magnetostriction value of about 20 ppm of the metallic glasses
of the present invention. This difference results in a considerable phase shift difference.
For example, optimally annealed prior art metallic glass Fe
79B
16Si
5 has δ near 70° while the metallic glasses of the present invention have 6 near 50°.
This results, for a given core loss, in a higher exciting power by a factor of two
for the prior art metallic glass than the metallic glass of the present invention.
[0017] Crystallization temperature is the temperature at which a metallic glass begins to
crystallize. A higher crystallization temperature renders a material more useful in
high temperature applications and, in conjunction with a Curie temperature that is
substantially lower than the crystallization temperature, permits magnetic annealing
just above the Curie temperature. Some metallic glasses crystallize in multiple steps.
In such cases, the first crystallization temperature (the lowest value of the crystallization
temperatures) is the meaningful one as far as the materials' thermal stability is
concerned. The crystallization temperature as discussed herein is measured by differential
scanning calorimetry. Prior art glassy alloys evidence crystallization temperatures
of about 660 K to 750 K. For example, a metallic glass having the compo-
sition Fe
78Mo
2B
20 has a crystallization temperature of 680 K, while a metallic glass having the composition
Fe74Mo6B20 has a crystallization temperature of 750
K. In contrast, metallic glasses of the invention evidence increases in crystallization
temperatures to a level above 750 K.
[0018] The magnetic properties of the metallic glasses of the present invention are improved
by thermal treatment, characterized by choice of annealing temperatures (T
a), holding time (ta), applied magnetic field (either parallel or perpendicular to
the ribbon direction and in the ribbon plane), and post-treatment cooling rate. For
the present alloys, the optimal properties are obtained after an anneal which causes
the controlled precipitation of a certain number of crystalline particles from the
glassy matrix. Under these conditions, for compositions having boron content ranging
from about 17 to 20 atom percent, the discrete particles have a body-centered cubic
structure. The particles are composed essentially of iron, up to 22 atom percent of
the iron being adapted to be replaced by at least one of nickel, cobalt, chromium,
molybdenum, tungsten, vanadium, niobium, tantalum, titanium, zirconium, hafnium, silicon
and carbon. For compositions having boron content ranging from about 21 to 25 atom
percent and iron content ranging from about 69 to 78 atom percent, the discrete particles
consist essentially of a mixture of particles, a major portion of which mixture contains
particles having a crystalline Fe
3B structure. The particles of such portion are composed of iron and boron, up to 14
atom percent of the iron being adapted to be replaced by at least one of nickel, cobalt,
chromium, molybdenum, tungsten, vanadium, niobium, tantalum, titanium, zirconium and
hafnium and up to 2 atom percent of the boron being adapted to be replaced by carbon.
A small number of such particles introduces a certain decrease in the average domain
wall spacing with concomitant decrease in core loss. Too large a number of particles
increases the coercivity and thus the hysteresis loss. A metallic glass of the present
invention with composition Fe75Ni4Mo3B16Si2 has a combination of low loss and high
permeability with a coercivity of only 2 A/m when optimally annealed. In contrast
to this, an optimally annealed prior art metallic glass Fe79Bl6Sis has a coercivity
of about 8 A/m. The crystalline particle size in the optimally heat-treated materials
of the present invention ranges between 100 and 300nm, and their volume fraction is
less than 1%. The interparticle spacing is of the order of 1-10µm.
[0019] In summary, the metallic glasses of the invention have a combination of high permeability,
low saturation magnetostriction, low coercivity, low ac core loss, low exciting power
and high crystallization temperature and are useful as tape heads, relay cores, transformers
and the like.
[0020] The metallic glasses of the invention are prepared by cooling a melt of the desired
composition at a rate of at least about 10 "C/sec, employing quenching techniques
well known to the metallic glass art; see e.g., U.S. Patent 3,856,513. The metallic
glasses are substantially completely glassy, that is, at least 90% glassy, and consequently
possess lower coercivities and are more ductile than less glassy alloys.
[0021] A variety of techniques are available for fabricating continuous ribbon, wire, sheet,
etc. Typically, a particular composition is selected, powders or granules of the requisite
elements in the desired portions are melted and homogenized and the molten alloy is
rapidly quenched on a chill surface such as a rapidly rotating cylinder.
EXAMPLES
Example 1: Fe-Ni-Mo-B-Si
[0022] Ribbons having compositions given by Fe
100-a-b-c-dNi
aMo
bB
cSi
d and having dimensions about 1 to 2.5 cm wide and about 25 to 50 µm thick were formed
by squirting a melt of the particular composition by overpressure of argon onto a
rapidly rotating copper chill wheel (surface speed about 3000 to 6000 ft/min).
[0023] Molybdenum content was varied from 1 to 6 atom percent, for which substantially glassy
ribbons were obtained. Molybdenum content higher than 6 atom percent reduced the Curie
temperature to an unacceptable low value.
[0024] Permeability, magnetostriction, core loss, magnetization and coercive force were
measured by conventional techniques employing B-H loops, metallic strain gauges and
a vibrating sample magnetometer. Curie temperature and crystallization temperature
were measured respectively by an induction method and differential scanning calorimetry.
The measured values at room temperature saturation induction, Curie temperature, room
temperature saturation magnetostriction and the first crystallization temperature
are summarized in Table I below. The magnetic properties of these glassy alloys after
annealing are presented in Table II. Optimum annealing conditions for the metallic
glass Fe
75Ni
4Mo
3B
16Si
2 and the obtained results are summarized in Table III. Frequency dependence of permability
and ac core loss of this optimally annealed alloy are listed in Table IV.
Example 2: Fe-Ni-M-B-Si System
[0026] Ribbons having compositions given by Fe
100-a-b-c-dM-M'-B-Si when M is nickel and/or cobalt, M' is one of the elements chromium, molybdenum,
tungsten, vanadium, niobium, tantalum, titanium, zirconium and hafnium, and having
dimensions about 1 cm wide and about 25 to 50Pm thick were formed as in Example 1.
[0027] Metal "M'" content was varied from 1 to 6 atom percent, for which substantially glassy
ribbons were obtained. Higher metal "M'" content reduced the Curie temperature to
an unacceptably low value.
[0028] The magnetic and thermal data are summarized in Table V below. The magnetic properties
of these glassy alloys after annealing are presented in Table VI.
[0029] Low field magnetic properties of these metallic glasses were comparable to those
for the metallic glasses containing molybdenum (Example 1).
[0030] A combination of low ac core loss and high permeability at high frequency is achieved
in the metallic glasses of the present invention. The thermal stability is also shown
to be excellent as evidenced by high crystallization temperature. These improved combination
of properties of the metallic glasses of the present invention renders these compositions
suitable in the magnetic cores of transformers, tape-recording heads and the like.
[0031] Table V. Examples of the room temperature saturation induction, B
s, Curie temperature, θ
f, saturation magnetostriction, X
s, and the first crystallization temperature, Tc, for the metallic glasses having the
composition Fe
100-a-b-c-dM
aM'
bB
cSi
d where M is at least one of nickel and cobalt, and M' = Cr, Mo, W, V, Nb, Ta, Ti,
Zr or Hf.

[0032] Table VI. Core loss (L), exciting power (P
e) and permeability (µ) taken at f = 50 kHz, and B
m= 0.1 Tesla on the heat-treated metallic glasses having the composition Fe
100-a-b-c-dM
aM'
bB
cSi
d where M = Ni, and/or Co, and M' = Cr, Mo
1, W, V,
Nb, Ta, Ti, Zr or Hf. The annealing temperatures are indicated by T
a and the holding time is 15 min. for allthe materials.

[0033] Table VII. Saturation induction (Bs), Curie temperature (θ
f), stauration magnetostriction (λ
s) and the first crystallization temperature (T
cl) of the metallic glasses having the composition Fe
100-a-b-c-d-eNi
aM
bB
cSi
dC
e Where M' = Cr, Mo, W, V, Nb, Ta, Ti, or Zr.

Example 3: Fe-Ni-M-B-Si-C System
[0034] Ribbons having compositions given by Fe
100-a-b-c-d-eNi
aM'
bB
cSi
dC
e where M = Cr, Mo, W, V,
Nb, Ta, Ti, or Zr and having dimensions about 1 cm wide and about 25 to 50 µm thick
were formed as in Example 1. The metal "M'" content was varied from 1 to 6 atom percent,
and the carbon content "e" was up to 2 atom percent for which substantially glassy
ribbons were obtained. The metal "M'" content greater than about 6 atom percent reduced
the Curie temperature to an unacceptably low value.
[0035] The magnetic and thermal data are summarized in Table VII below. The magnetic properties
of these metallic glasses after annealing are presented in Table VIII. A combination
of low ac core loss, high permeability, and high thermal stability of the metallic
glasses of the present invention renders these compositions suitable in the magnetic
cores of transformers, recording heads and the like.
[0036] Table VIII. Core loss (L), exciting power (P
e) and permeability (µ) taken at f = 50 kHz and B = 0.1 Tesla on the heat-treated metallic
glasses having the composition Fe
100-a-b-c-d-eNi
aM'
bB
cSi
dC
e where
M' = Cr, Mo, W, V, Nb or Ta. Annealing temperatures are indicated by T
a and the holding time is 15 min. for all the materials.

[0037] Having thus described the invention in rather full detail, it will be understood
that this detail need not be strictly adhered to but that various changes and modifications
may suggest themselves to one skilled in the art, all falling within the scope of
the present invention as defined by the subjoined claims.
1. A metallic glass that is substantially completely glassy having a combination of
high permability, low magnetostriction, low coercivity, low ac core loss, low exciting
power and high thermal stability consisting essentially of 66 to 82 atom percent of
iron, from 1 to 8 atom percent of said iron being, optionally, replaced with at least
one element selected from the group consisting of nickel, cobalt and mixtures thereof,
1 to 6 atom percent of at least one element selected from the group consisting of
chromium, molybdenum, tungsten, vanadium, niobium, tantalum, titanium, zirconium and
hafnium, 17 to 28 atom percent of boron, from 0.5 to 6 atom percent of said boron
being, optionally, replaced with silicon and up to 2 atom percent of boron being,
optionally, replaced with carbon, plus incidental impurities.
2. The metallic glass of claim 1, in which the metal consists essentially of 62 to
79 atom percent iron, 2 to 8 atom percent of at least one element selected from the
group consisting of nickel, cobalt and mixtures thereof, and 2 to 4 atom percent of
at least one element selected from the group consisting of chromium, molybdenum, tungsten,
vanadium, niobium, tantalum, titanium, zirconium and hafnium.
3. The metallic glass of claim 1, in which the replacement of boron with silicon and
carbon provides said glass with a metalloid element selected from the group consisting
of substantially boron and from .5 to 4 atom percent silicon, and boron plus silicon
together with from 0 to 2 atom percent carbon.
4. The metallic glass of claim 3, in which said metalloid element ranges from 17 to
26 atom percent.
5. The metallic glass of claim 1, consisting essentially of 70 to 79 atom percent
iron, about 2 to 4 atom percent of at least one element selected from the group consisting
of nickel, cobalt and mixtures thereof, 2 to 4 atom percent of an element selected
from the group consisting of molybdenum and chromium and 17 to 22 percent of an element
selected from the group consisting of boron, silicon and mixtures thereof.
6. An alloy of claim 1 which is at least 85 percent amorphous, said alloy being characterized
by the presence therein of discrete particles of its constituents, said particles
having an average size ranging from about 0.1 µm to 0.3 µm and an average interparticle
spacing of about 1 pm to 10 µm.
7. An alloy of claim 6, in which said discrete particles occupy and an average volume
fraction of 0.005 to 0.01.
8. The method of enhancing the magnetic properties of the alloy recited in claim 1,
comprising the step of annealing said alloy at a temperature and for a time sufficient
to induce precipitation of discrete particles in said amorphous metal matrix.
9. A method as recited in claim 8, wherein the discrete particles consist essentially
of a mixture of particles a portion of which mixture contains particles having a body-centered
cubic structure, said particles being composed essentially of iron, up to 22 atom
percent of said iron being adapted to be replaced by at least one of nickel, cobalt,
chromium, molybdenum, tungsten, vanadium, niobium, tantalum, titanium, zirconium,
havnium, silicon, and carbon.
10. A method as recited in claim 8, wherein the discrete particles consist essentially
of a mixture of particles a portion of which mixture contains particles having a crystalline
Fe3B structure, said particles of said portion being composed of iron and boron, up to
14 atom percent of said iron being adapted to be replaced by at least one of nickel,
cobalt, chromium, molybdenum, tungsten, vanadium, niobium, tantalum, titanium, zirconium,
and hafnium, and up to 2 atom percent of said boron being adapted to be replaced by
carbon.