Note: Descriptions are shown in the official language in which they were submitted.
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METALLIC GLASS ALLOYS FOR MECHANICALLY
RESONANT MARKER SURVEILLANCE SYSTEMS
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to metallic glass alloys; and more particularly to
metallic glass alloys suited for use in mechanically resonant markers of
article
surveillance systems.
2. Description of the Prior Art
Numerous article surveillance systems are available in the market today to
help identify andJor secure various animate and inanimate objects.
Identification of
personnel for controlled access to limited areas, and securing articles of
merchandise against pilferage are examples of purposes for which such systems
are
etriployed.
An essential component of all surveillance systems is a sensing unit or
"marker", that is attached to the object to be detected. Other components of
the
system include a transmitter and a receiver that are suitably disposed in an
"interrogation" zone. When the object carrying the marker enters the
interrogation
zone, the functional part of the marker responds to a signal from the
transmitter,
which response is detected in the receiver. The information contained in the
response signal is then processed for actions appropriate to the application:
denial
of access, triggering of an alarm, and the like.
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Several different types of markers have been disclosed and are in
use. In one type, the functional portion of the marker consists of either an
antenna
and diode or an antenna and capacitors forming a resonant circuit. When placed
in
an electromagnetic field transmitted by the interrogation apparatus, the
antenna-
diode marker generates harmonics of the interrogation frequency in the
receiving
antenna. The detection of the harmonic or signal level change indicates the
presence of the marker. With this type of system, however, reliability of the
marker identification is relatively low due to the broad bandwidth of the
simple
resonant circuit. Moreover, the marker must be removed after identification,
which is not desirable in such cases as antipilferage systems.
A second type of rriarker consists of a first elongated element of high
magnetic permeability ferromagnetic material disposed adjacent to at least a
second
element of ferromagnetic material having higher coercivity than the first
element.
When subjected to an interrogation frequency of electromagnetic radiation, the
marker generates harmonics of the interrogation frequency due to the non-
linear
characteristics of the marker. The detection of such harmonics in the
receiving coil
indicates the presence of the marker. Deactivation of the marker is
accomplished
by changing the state of magnetization of the second element, which can be
easily
achieved, for example, by passing the marker through a dc magnetic field.
Harmonic marker systems are superior to the aforementioned radio-frequency
resonant systems due to improved reliability of marker identification and
simpler
deactivation method. Two major problems, however, exist with this type of
system: one is the difficulty of detecting the marker signal at remote
distances. The
amplitude of the harmonics generated by the marker is much smaller than the
amplitude of the interrogation signal, limiting the detection aisle widths to
less than
about three feet. Another problem is the difficulty of distinguishing the
marker
signal from pseudo signals generated by other ferromagnetic objects such as
belt
buckles, pens, clips, etc.
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Surveillance systems that employ detection modes incorporating the
fundamental mechanical resonance frequency of the marker material are
especially
advantageous systems, in that they offer a combination of high detection
sensitivity, high operating reliability, and low operating costs. Examples of
such
=
systems are disclosed in U.S. Patent Nos. 4,510,489 and 4,510,490 (hereinafter
the
'489 and '490 patents).
The marker in such systems is a strip, or a plurality of strips, of known
length of a ferromagnetic material, packaged with a magnetically harder
ferromagnet (material with a higher coercivity) that provides a biasing field
to
establish peak magneto-mechanical coupling. The ferromagnetic marker material
is
preferably a metallic glass alloy ribbon, since the efficiency of magneto-
mechanical
coupling in these alloys is very high. The mechanical resonance frequency of
the
marker material is dictated essentially by the length of the alloy ribbon and
the
biasing field strength. When an interrogating signal tuned to this resonance
frequency is encountered, the marker material responds with a large signal
field
which is detected by the receiver. The large signal field. is partially
attributable to
an enhanced magnetic permeability of the marker material at the resonance
frequency. Various marker configurations and systems for the interrogation and
detection that utilize the above principle have been taught in the '489 and
'490
patents.
In one particularly useful system, the marker material is excited into
oscillations by pulses, or bursts, of signal at its resonance frequency
generated by
the transmitter. When the exciting pulse is over, the marker material will
undergo
damped oscillations at its resonance frequency, i.e., the marker material
"rings
down" following the termination of the exciting pulse. The receiver "listens"
to the
response signal during this ring down period. Under this arrangement, the
= surveillance system is relatively immune to interference from various
radiated or
power line sources and, therefore, the potential for false alarms is
essentially
eliminated.
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A broad range of alloys have been claimed in the '489 and '490 patents as
suitable for marker material, for the various detection systems disclosed.
Other
metallic glass alloys bearing high permeability are disclosed in U.S. Patent
No.
4,152,144.
A major problem in use of electronic article surveillance systems is the
tendency for markers of surveillance systems based on mechanical resonance to
accidentally trigger detection systems that are based an alternate technology,
such
as the harmonic marker systems described above: The non-linear magnetic
response of the marker is strong enough to generate harmonics in the alternate
system, thereby accidentally creating a pseudo response, or "false" alarm. The
importance of avoiding interference among, or "pollution" of, different
surveillance
systems is readily apparent. Consequently, there exists a need in the art for
a
resonant marker that can be detected in a highly reliable manner without
polluting
systems based on alternate technologies, such as harmonic re-radiance.
SUMMARY OF INVENTION
The present invention provides magnetic alloys that are at least 70% glassy
and, upon being annealed to enhance magnetic properties, are characterized by
relatively linear magnetic responses in a frequency regime wherein harmonic
marker systems operate magnetically. Such alloys can be cast into ribbon using
rapid solidification, or otherwise formed into markers having magnetic and
mechanical characteristics especially suited for use in surveillance systems
based on
magneto-mechanical actuation of the markers. Generally stated the glassy metal
alloys of the present invention have a composition consisting essentially of
the
formula Fea Cob Ni,_ Md B~ Sif Cg , where M is selected from molybdenum,
chromium and manganese and "a", "b", "c", "d", "e", "f' and "g" are in atom
percent, "a" ranges from about 30 to about 45, "b" ranges from about 4 to
about
40 and "c" ranges from about 5 to about 45, "d" ranges from about 0 to about
3,
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"e" ranges from about 10 to about 25 , "f' ranges from about 0 to about 15 and
"g" ranges from about 0 to about 2. Ribbons of these alloys, when mechanically
resonant at frequencies ranging from about 48 to about 66 kHz, evidence
relatively
linear magnetization behavior up to an applied field of 8 Oe or more as well
as the
slope of resonant frequency versus bias field close to or exceeding the level
of
about 400 Hz/Oe exhibited by a conventional mechanical-resonant marker.
Moreover, voltage amplitudes detected at the receiving coil of a typical
resonant-
marker system for the markers made from the alloys of the present invention
are
comparable to or higher than those of the existing resonant marker. These
features
assure that interference among systems based on mechanical resonance and
harmonic re-radiance is avoided
The metallic glasses of this invention are especially suitable for use as the
active elements in markers associated with article surveillance systems that
employ
excitation and detection of the magneto-mechanical resonance described above.
Other uses may be found in sensors utilizing magneto-mechanical actuation and
its
related effects and in magnetic components requiring high magnetic
permeability.
BRIEF DESCRIPTION OF THE DRAWINGS
The invention will be more fully understood and further advantages will
become apparent when reference is made to the following detailed description
of
the preferred embodiments of the invention and the accompanying drawings in
which:
Fig. 1(a) is a schematic representation of the magnetization curve taken
along the length of a conventional resonant marker, where B is the magnetic
induction and H is the applied magnetic field;
Fig. 1(b) is a schematic representation of the magnetization curve taken
along the length of the marker of the present invention, where Ha is a field
above
which B saturates;
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Fig. 2 is a schematic representation of signal profile detected at the
receiving coil depicting mechanical resonance excitation, termination of
excitation
at time to and subsequent ring-down, wherein V. and V, are the signal
amplitudes
at the receiving coil at t = to and t = ti (1 msec after to ), respectively;
and
Fig. 3 is a schematic representation of the mechanical resonance frequency,
fT , and response signal, Vl , detected in the receiving coil at I msec after
the
termination of the exciting ac field as a function of the bias magnetic field,
Hb,
wherein Hbl and Hb2 are the bias fields at which Vl is a maximum and fr is a
minimum, respectively.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
In accordance with the present invention, there are provided magnetic
metallic glass alloys that are characterized by relatively linear magnetic
responses in
the frequency region where harmonic marker systems operate magnetically. Such
alloys evidence all the features necessary to meet the requirements of markers
for
surveillance systems based on magneto-mechanical actuation. Generally stated
the
glassy metal alloys of the present invention have a composition consisting
essentially of the formula Fe, COb Ni. Md Be Sif Cg, where M is selected from
molybdenum, chromium and manganese and "a", "b", "c", "d", "e", "f' and "g"
are
in atom percent, "a" ranges from about 30 to about 45, "b" ranges from about 4
to
about 40 and "c" ranges from about 5 to about 45, "d" ranges from about 0 to
about 3, "e" ranges from about 10 to about 25 , "f' ranges from about 0 to
about
15 and "g" ranges from about 0 to about 2. The purity of the above
compositions
is that found in normal commercial practice. Ribbons of these alloys are
annealed
with a magnetic field applied across the width of the ribbons at elevated
temperatures for a given period of time. Ribbon temperatures should be below
its
crystalization temperature and the ribbon, upon being heat treated, should be
ductile enough to be cut up. The field strength during the annealing is such
that
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the ribbons saturate magnetically along the field direction. Annealing time
depends
on the annealing temperature and typically ranges from about a few minutes to
a
few hours. For commercial production, a continuous reel-to-reel annealing
furace
is preferred. In such cases, ribbon travelling speeds may be set at about
between
0.5 and about 12 meter per minute. The annealed ribbons having, for example, a
length of about 38 mm, exhibit relatively linear magnetic response for
magnetic
fields of up to 8 Oe or more applied parallel to the marker length direction
and
mechanical resonance in a range of frequencies from about 48 kHz to about 66
kHz. The linear magnetic response region extending to the level of 8 Oe is
sufficient to avoid triggering some of the harmonic marker systems. For more
stringent cases, the linear magnetic response region is extended beyond 8 Oe
by
changing the chemical composition of the alloy of the present invention. The
annealed ribbons at lengths shorter or longer than 38 mm evidence higher or
lower
mechanical resonance frequencies than 48-66 kHz range.
Ribbons having mechanical resonance in the range from about 48 to 66 kHz
are preferred. Such ribbons are short enough to be used as disposable marker
materials. In addition, the resonance signals of such ribbons are well
separated
from the audio and commercial radio frequency ranges.
Most metallic glass alloys that are outside of the scope of this invention
typically exhibit either non-linear magnetic response regions below 8 Oe level
or H.
levels close to the operating magnetic excitation levels of many article
detection
systems utilizing harmonic markers. Resonant markers composed of these alloys
accidentally trigger, and thereby pollute, many article detection systems of
the
harmonic re-radiance variety.
There are a few metallic glass alloys outside of the scope of this invention
that do show linear magnetic response for an acceptable field range. These
alloys,
however, contain high levels of cobalt or molybdenum or chromium, resulting in
increased raw material costs and/or reduced ribbon castability owing to the
higher
melting temperatures of such constituent elements as molybdenum or chromium.
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The alloys of the present invention are advantageous, in that they afford, in
combination, extended linear magnetic response, improved mechanical resonance
performance, good ribbon castability and economy in production of usable
ribbon.
Apart from the avoidance of the interference among different systems, the
markers made from the alloys of the present invention generate larger signal
amplitudes at the receiving coil than conventional mechanical resonant
markers.
This makes it possible to reduce either the size of the marker or increase the
detection aisle widths, both of which are desirable features of article
surveillance
systems.
Examples of inetallic glass alloys of the invention include
Fe40 C034 Ni8 B13 Si5 , Fe 40 C030 Ni12 B13 Si5 , Fe40 Co26 Ni 16 B13 Sl 5,
Fe 40 Co22 Ni20 B13 Si5 , Fe 40 Co20 Ni22 B13 Si5 , Fe40 Co18 Ni24 B13 Si5 ,
Fe35 C018 N129 B13 Si5 , Fe32 C018 Ni32 B13 Si5 , Fe40 C016 Ni26 B13 Sls s
Fe40 C014 Ni28 B13 Sis , Fe4o C014 Ni28 B16 Si 2, Fe4o C014 Ni28 B11 Si 7,
Fe40 C014 N128 B13 Si 3 C 2, Fe 38 CO 14 Ni 30 B 13 Si 5, Fe36 CO 14 Ni 32 B
13 Si 5,
Fe34C014N134B 13 S15,Fe30C014Ni38B 13 S15,Fe42C014Ni26B 13 S15,
Fe 44 Co 14 Ni 24 B 13 Si 5, Fe4o Co14 Ni27 Mo1 B13 Si5, Fe4o Co14 Ni25 Mo3
B13 Si5,
Fe40 Co14 Ni27 Crl B13 Si5, Fe4o Co14 Ni25 Cr3 B13 Si5,
Fe40 Co14 Ni25 Mol B13 Si5 C 2, Fe 40 Co 12 Ni 3o B 13 Si 5,
Fe 38 CO 12 Ni 32 B 13 Si 5, Fe42 Co 12 Ni 30 B 13 Si 5, Fe40 Co 12 Ni 26 B 17
Si 5,
Fe 40 CO 12 Nl 28 B15 Sl 5, Fe40 CO 1o N132 B13 Sl5 , Fe42 CO 10 N130 B13 S15
,
Fe44 Co lo Ni28 B13 Si5, Fe4o Co lo Ni31 Mol B13 Si5, Fe4o Co lo Ni31 Crl B13
Si5,
Fe4o Co 10 Ni31 Mn1 B13 S15 , Fe40 Co 10 N129 Mn3 B13 S15 ,
Fe40 Co 10 N130 B13 Si5 C2, Fe4o Co8 Ni38 B13 Si5 , Fe40 C06 Ni36 B13 Si5 ,
and
Fe40 Co4 Ni38 B13 Si5 , wherein subscripts are in atom percent.
The magnetization behavior characterized by a B-H curve is shown in Fig.
1(a) for a conventional mechanical resonant marker, where B is the magnetic
induction and H is the applied field. The overall B-H curve is sheared with a
non-
linear hysteresis loop existent in the low field region. This non-linear
feature of the =
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marker results in higher harmonics generation, which triggers some of the
harmonic marker systems, hence the interference among different article
surveillance systems.
The definition of the linear magnetic response is given in Fig. 1(b). As a
marker is magnetized along the length direction by an external magnetic field,
H,
the magnetic induction, B, results in the marker. The magnetic response is
relatively linear up to H$ , beyond which the marker saturates magnetically.
The
quantity H. depends on the physical dimension of the marker and its magnetic
anisotropy field. To prevent the resonant marker from accidentally triggering
a
surveillance system based on harmonic re-radiance, H. should be above the
operating field intensity region of the harmonic marker systems.
The marker material is exposed to a burst of exciting signal of constant
amplitude, referred to as the exciting pulse, tuned to the frequency of
mechanical
resonance of the marker material. The marker material responds to the exciting
pulse and generates output signal in the receiving coil following the curve
leading
to Vo in Fig. 2. At time to , excitation is terminated and the marker starts
to ring-
down, reflected in the output signal which is reduced from Vo to zero over a
period
of time. At time tl , which is 1 msec after the termination of excitation,
output
signal is measured and denoted by the quantity V 1. Thus V I/ V. is a measure
of
the ring-down. Although the principle of operation of the surveillance system
is
not dependent on the shape of the waves comprising the exciting pulse, the
wave
form of this signal is usually sinusoidal. The marker material resonates under
this
excitation.
The physical principle governing this resonance may be summarized as
follows: When a ferromagnetic material is subjected to a magnetizing magnetic
field, it experiences a change in length. The fractional change in length,
over the
original length, of the material is referred to as magnetostriction and
denoted by the
symbol X. A positive signature is assigned to k if an elongation occurs
parallel to
the magnetizing magnetic field.
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When a ribbon of a material with a positive magnetostriction is subjected to
a sinusoidally varying external field, applied along its length, the ribbon
will
undergo periodic changes in length, i.e., the ribbon will be driven into
oscillations.
The external field may be generated, for example, by a solenoid carrying a
sinusoidally varying current. When the half-wave length of the oscillating
wave of
the ribbon matches the length of the ribbon, mechanical resonance results. The
resonance frequency fr is given by the relation
fT = (1/2L)(E/D)o.s,
where L is the ribbon length, E is the Young's modulus of the ribbon, and D is
the
density of the ribbon.
Magnetostrictive effects are observed in a ferromagnetic material only
when the magnetization of the material proceeds through magnetization
rotation.
No magnetostriction is observed when the magnetization process is through
magnetic domain wall motion. Since the magnetic anisotropy of the marker of
the
alloy of the present invention is induced by field-annealing to be across the
marker
width direction, a dc magnetic field, referred to as bias field, applied along
the
marker length direction improves the efficiency of magneto-mechanical response
from the marker material. It is also well understood in the art that a bias
field
serves to change the effective value for E, the Young's modulus, in a
ferromagnetic material so that the mechanical resonance frequency of the
material
may be modified by a suitable choice of the bias field strength. The schematic
representation of Fig. 3 explains the situation further: The resonance
frequency, fr,
decreases with the bias field, Hb, reaching a minimum, (fr),,,;,,, at H62. The
signal
response, Vl , detected , say at t = tl at the receiving coil, increases with
Hb ,
reaching a maximum, V. , at Hbl. The slope, dfr /dHb, near the operating bias
field
is an important quantity, since it related to the sensitivity of the
surveillance system.
Summarizing the above, a ribbon of a positively magnetostrictive
ferromagnetic material, when exposed to a driving ac magnetic field in the
presence
of a dc bias field, will oscillate at the frequency of the driving ac field,
and when
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this frequency coincides with the mechanical resonance frequency, fT, of the
material, the ribbon will resonate and provide increased response signal
amplitudes.
In practice, the bias field is provided by a ferromagnet with higher
coercivity than
the marker material present in the "marker package".
Table I lists typical values for V. , Hb1, (fr ),,,;,, and Hb2 for a
conventional
mechanical resonant marker based on glassy Feao Ni38 Moa B18. The low value of
Hb2 , in conjunction with the existence of the non-linear B-H bahavior below
Hb2,
tends to cause a marker based on this alloy to accidentally trigger some of
the
harmonic marker systems, resulting in interference among article surveillance
systems based on mechanical resonance and harmonic re-radiance..
TABLE I
Typical values for V. , Hbl ,(fr ),n;,, and Hb2 for a conventional mechanical
resonant marker based on glassy Feao Ni38 Moa B18. This ribbon at a length of
38.1 mm has mechanical resonance frequencies ranging from about 57 and 60 kHz.
mV Hhl-(Oe) (kHz) HbZ (Oe2
150-250 4-6 57-58 5-7
Table II lists typical values for Ha, Vm, Hb1, (fr),,,;,, , HbZ and dfr /dHb
Hb for
the alloys outside the scope of this patent. Field-annealing was performed in
a
continuous reel-to-reel furnace on 12.7 mm wide ribbon where ribbon speed was
from about 0.6 m/min. to about 1.2 m/min.
TABLE II
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Values for H,, Vn,, Hbl, H62 and df, /dHb taken at Hb = 6 Oe for the
alloys outside the scope of this patent. Field-annealing was performed in a
continuous reel-to-reel furnace where ribbon speed was from about 0.6 ni/min.
to
about 1.2 m/min with a magnetic field of about 1.4 kOe applied perpendicular
to
the ribbon length direction.
Comoosition (at%) H. (Oe) y_ (mV) Hpa (00 (G1n:, (kHz) 1i Oe df, fdHe (HzlOo)
A C042 Fuo B,3 Sis 22 400 7.0 49.7 15.2 700
B. Co3*Fe4o Ni4B,sSis 20 420 9.3 53.8 16.4 500
C. Co2 Fe.o Ni4o B,3Sis 10 400 3.0 50.2 6.8 2,080
D. Co,oFe.4oNi2-7MnsB,3Sis 7.5 400 2.7 50.5 6.8 2.300
Although alloys A and B show linear magnetic responses for acceptable magnetic
field ranges, but contain high levels of cobalt, resulting in increased raw
material
costs. Alloys C and D have low Hbl values and high dit /dHb values,
combination
of which are not desirable from the standpoint of resonant marker system
operation.
EXAIVIPLES
Example 1: Fe-Co-Ni-B-Si metallic glasses
1. Sample Preparation
Glassy metal alloys in the Fe-Co-Ni-B-Si series, designated as samples No.
1 to 29 in Table III and IV, were rapidly quenched from the melt following the
techniques taught by Narasimhan in U.S. Patent No. 4,142,571.
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All casts were made in an inert
gas, using 100 g melts. The resulting ribbons, typically 25 m thick and about
12.7
mm wide, were determined to be free of significant crystallinity by x-ray
difi'ractometry using Cu-Ka radiation and differential scanning calorimetry.
Each
of the alloys was at least 70 % glassy and, in many instances, the alloys were
more
than 90 % glassy. Ribbons of these glassy metal alloys were strong, shiny,
hard
and ductile.
The ribbons were cut into small pieces for magnetization, magnetostriction,
Curie and crystallization temperature and density measurements. The ribbons
for -
magneto-mechanical resonance characterization were cut to a length of about
38.1
mm and were heat treated with a magnetic field applied across the width of the
ribbons. The strength of the magnetic field was 1.1 kOe or 1.4 kOe and its
direction was varied between 75 and 90 with respect to the ribbon length
direction. Some of the ribbons were heat-treated under tension ranging from
about
zero to 7.2 kg/mmZ applied along the direction of the ribbon. The speed of the
ribbon in the reel-to-reel annealing furnace was changed from about 0.5 meter
per
minute to about 12 meter per minute.
2. Characterization of in etic and thermal properties
Table III lists saturation induction (B, ), saturation magnetostriction Q, ),
and crystallization (T, ) temperature of the alloys. Magnetization was
measured by
a vibrating sample magnetometer, giving the saturation magnetization value in
emu/g which is converted to the saturation induction using density data.
Saturation magnetostriction was measured by a strain-gauge method, giving in
10~
'25 or in ppm. Curie and crystallization temperatures were measured by an
inductance
method and a differential scanning calorimetry, respectively.
TABLE ffi
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Magnetic and thermal properties of Fe-Co-Ni-B-Si glassy alloys. Curie
temperatures of alloy No. 22 (6f =447 C), No. 27 (6f =430 C), No. 28 (6f
=400
C) and 29 (Af =417 C) could be determined because they are below the first
crystallization temperatures (T. ).
No. Composition (at.%) B (Tesla) L" (ppm) Tc ( C)
Fe Co Ni B Si
1 40 34 8 13 5 1.46 23 456
2 40 30 12 13 5 1.42 22 455
3 40 26 16 13 5 1.38 22 450
4 40 22 20 13 5 1.32 20 458
5 40 20 22 13 5 1.28 19 452
6 40 18 24 13 5 1.25 20 449
7 35 18 29 13 5 1.17 17 441
8 32 18 32 13 5 1.07 13 435
9 40 16 26 13 5 1.21 18 448
10 40 14 28 13 5 1.22 19 444
11 40 14 28 16 2 1.25 19 441
12 40 14 28 11 7 1.20 15 444
13 38 14 30 13 5 1.19 18 441
14 36 14 32 13 5 1.14 17 437
15 34 14 34 13 5 1.09 17 434
16 30 14 38 13 5 1.00 10 426
17 42 14 26 13 5 1.27 21 448
18 44 14 24 13 5 1.31 21 453
19 40 12 30 13 5 1.20 18 442
20 38 12 32 13 5 1.14 18 440
21 42 12 30 13 3 1.29 21 415
22 40 12 26 17 5 1.12 17 498
23 40 12 28 15 5 1.20 19 480
24 40 10 32 13 5 1.16 17 439
25 42 10 30 13 5 1.15 19 443
26 44 10 28 13 5 1.25 20 446
27 40 8 34 13 5 1.11 17 437
28 40 6 36 13 5 1.12 17 433
29 40 4 38 13 5 1.09 17 430
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Each marker material having a dimension of about 38.1mnix12.7mmx20 m
was tested by a conventional B-H loop tracer to measure the quantity of H. and
then was placed in a sensing coil with 221 turns. An ac magnetic field was
applied
along the longitudinal direction of each alloy marker with a dc bias field
changing
from 0 to about 20 Oe. The sensing coil detected the magneto-mechanical
response of the alloy marker to the ac excitation. These marker materials
mechanically resonate between about 48 and 66 kHz. The quantities
characterizing
the magneto-mechanical response were measured and are listed in Table IV for
the
alloys listed in Table III.
TABLE IV
Values of H. , V. , Hbi (f r),r,;,, , Hb2 and dfr /dHb taken at Hb = 6 Oe for
the alloys of Table III heat-treated at 380 C in a continuous reel-to-reel
furnace
with a ribbon steed of about 1.2 m/minute and at 415 C for 30 min (indicated
by
asterisks *). The annealing field was about 1.4 kOe applied perpendicular to
the
ribbon length direction.
Allov No. H, (Oe) V m Hbi Oe L~, (kHzl H, Oe df /dH,, (Hz/Oe)
1 21 415 10.3 54.2 16.5 460
2 20 370 10.7 54.2 16.0 560
3 20 370 10.0 53.8 16.5 430
4* 20 250 10.5 49.8 17.7 450
4 18 330 8.0 53.6 14.2 590
5 17 270 9.0 52.0 14.5 710
6 17 340 7.8 53.4 14.2 620
7 16 300 8.6 53.5 14.3 550
8 15 380 8.0 54.1 13.0 580
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9 16 450 7.8 51.3 14.2 880
10* 17 390 8.9 49.3 15.9 550
16 390 7.0 52.3 13.4 810
11 15 350 8.0 52.3 13.9 750
5 12 14 350 7.0 52.5 12.4 830
13 14 400 7.3 52.5 13.1 780 =
14 13 330 6.5 54.2 12.6 670
13 270 6.2 53.0 11.5 820
16 10 230 5.0 56.0 9.3 1430
10 17 15 415 7.2 51.2 14.3 740
18 15 350 7.7 50.4 12.9 1080
19 14 440 6.5 50.6 11.6 960
14 330 6.6 52.9 11.3 900
21 19_ 325 9.3 53.9 14.8 490
15 22 9 260 3.5 55.8 8.0 1700
23 11 310 5.4 52.2 10.5 1380
24* 15 220 8.2 48.5 13.7 740
24 14 410 7.5 51.8 13.5 800
13 420 6.2 49.5 12.2 1270
20 26 14 400 6.0 50.2 12.8 1050
27 10 250 4.0 51.9 8.5 1490
28 12 440 4.0 49.7 9.0 1790
29 11 380 5.2_ 51.5 9.8 1220
All the alloys listed in Table IV exhibit H. values exceeding 8 Oe, which
make them possible to avoid the interference problem mentioned above. Good
sensitivity ( df, /dHb ) and large response signal ( Vm ) result in smaller
markers for
resonant marker systems.
The quantities characterizing the magneto-mechanical resonance of the
marker material of Table III heat-treated under different annealing conditions
are
summarized in Tables V, VI, VII, VIII and IX.
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TABLE V
Values of V. , Hb1 ,(fr)n,iõ , dfr /dHb taken at Hb = 6 Oe for alloy No. 8 of
Table III heat-treated under different conditions in a reel-to-reel annealing
furnace.
Applied field direction indicated is the angle btween the ribbon length
direction and
-
the field direction.
Annealing Temperature: 440 C Applied Field/Direction: 1.1 kOe / 90
Hb~2 df / dFib
Ribbon Speed Tension V H tL)~.
(m/minute) (kg/mm2) (mV) (Oe) (kHz) (Oe) (Hz/Oe)
9.0 1.4 360 3.9 55.3 8.5 590
10.5 1.4 340 3.8 55.4 8.5 540
10.5 6.0 225 5.0 55.8 9.8 690
1= t 1'_a.' t l 1_/l_ /!lA
-on .
~: 1. 1 Kve t 7v
Anneaiing l~emperature:-400O - C. Appued FieiaiTLire_ cLi -
Ribbon Speed Tension V H ~f )m Hh d-rf / dHb
(m/minute) (kg/mmZ) (mV) (Oe) (kHz) (Oe) (Hz/Oe)
9.0 0 300 4.1 53.7 8.3 1170
9.0 7.2 250 5.2 55.9 9.7
AnnealingTemperature: 340 C Applied Field Direction: 1.1 kOe / 75
Ribbon Speed Tension V H (f~ Hb= df / dHb
(m/minute) (kg/mrnz) (mV) (Oe) (kHz) (Oe) (Hz/Oe)
0.6 0 315 7.9 55.7 13.4 420
2.1 0 225 8.0 56.1 12.8 470
TABLE VI
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Values of V. , Hbl ,(Qn,;,, , df, /dHb taken at Hb = 6 Oe for alloy No. 17 of
Table III heat-treated under different conditions in a reel-to-reel annealing
furnace.
Applied field direction indicated is the angle btween the ribbon length
direction and
the field direction.
Annealing Temperature: 320 C Applied Field/Direction: 1.4 kOe / 90
Ribbon Speed Tension Vm H fLL1,,,,,, x, , d / dHb
(m/minute) (kg/mmZ) (mV) (Oe) (kHz) (Oe) (Hz/Oe)
0.6 0 250 6.0 55.3 13.0 670
0.6 1.4 320 6.0 54.0 14.1 620
0.6 3.6 370 7.0 52.2 14.0 630
Annealing Temperature: 280 C Applied Field/Direction: 1.1 kOe / 90
Ribbon Sueed Tension V H (f L1m;" Hh? drf dH
(m/minute) (kg/mm2) (mV) (Oe) (kHz) (Oe) (HzJOe)
0.6 7.2 390 7.0 53.2 13.9 615
2.1 7.2 240 5.0 53.6 11.5 760
Annealin,g Temperature: 280 C Applied Field/Direction: 1.1 kOe / 75
Ribbon Speed Tension V4. H (f ~ H,, df dHb
(m/minute) (kg/mm2) (mV) (Oe) (kHz) (Oe) (HzJOe)
0.6 7.2 360 6.3 52.9 13.2 630
2.1 7.2 270 5.2 53.2 11.2 860
TABLE VII
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Values of V. , Hbl ,(f,),,,;,, , df, /dHb taken at Hb = 6 Oe for alloy No. 24
of
Table III heat-treated under different conditions in a reel-to-reel annealing
furnace.
Applied field direction indicated is the angle btween the ribbon length
direction and
the field direction.
Annealing Temperature: 320 C Applied Field/Direction: 1.1 kOe / 90
Ribbon Speed Tension V H (f jm,,, H~, f / Hh
(m/minute) (kg/mm2) (mV) (Oe) (kHz) (Oe) (Hz/Oe)
0.6 0 280 8.0 54.7 13.1 450
2.1 0 310 7.6 54.7 12.0 500
2.1 7.2 275 8.0 55.1 14.5 450
Annealing Temperature: 320 C Aonlied Field/Direction: 1.1 kOe / 75
Ribbon Speed Tension V Hm ff r 1m;" HbZ d,f / dH
(m/minute) (kg/mm2) (mV) (Oe) (kHz) (Oe) (Hz/Oe)
0.6 0 310 8.2 54.7 13.0 530
0.6 7.2 275 8.2 55.2 15.0 430
2.1 0 290 7.2 54.8 12.0 550
2.1 7.2 270 7.0 55.6 13.5 480
Annealing Temperature: 300 C Applied Field/Direction: 1.1 kOe / 82.5
Ribbon Speed Tension Vm Hm If m HbQ df / dHb
(m/minute) (kg/mm') (mV) (Oe) (kHz) (Oe) (Hz/Oe)
0.6 2.1 300 8.3 54.9 13.7 410
2.1 2.1 300 7.0 54.4 11.8 480
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AnnealingTemperature: 280 C Applied Field/Direction: 1.1 kOe / 90
Ribbon Speed Tension V H LL)= Hu df, / dHb
(m/minute) (kg/mm') (mV) (Oe) (kHz) (Oe) (Hz/Oe)
0.6 0 265 8.4 55.2 12.6 430
2.1 7.2 255 6.8 55.9 12.0 490
TABLE VIII
Values of Vm , Hbi ,(fr)n,;n , df, /dHb taken at Hb = 6 Oe for alloy No. 27 of
Table III heat-treated under different conditions in a reel-to-reel annealing
furnace.
Applied field direction indicated is the angle btween the ribbon length
direction and
the field direction.
Annealing Temperature: 300 C Applied Field/Direction: 1.1 kOe / 82.5
Ribbon Sueed Tension Vm H f(lm , H, f dHh
(m/minute) (kg/mm2) (mV) (Oe) (kHz) (Oe) (HWOe)
0.6 2.1 270 6.2 53.8 11.9 690
2.1 2.1 270 5.2 52.9 10.5 870
Annealina Temperature: 280 C Applied Field/Direction: 1.1 kOe / 90
Ribbon Sueed Tension V H (f ? .. H Z df, / dHb
(m/minute) (kg/mm2) (mV) (Oe) (kHz) (Oe) (Hz/Oe)
0.6 7.2 290 5.8 53.8 12.0 670
2.1 0 230 6.0 54.3 11.0 720
TABLE IX
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Values of V,,, , Hb, ,(Q,,,iõ , dfr /dHb taken at Hb = 6 Oe for alloy No. 29
of
Table III heat-treated under different conditions in a reel-to-reel annealing
furnace.
Applied field direction indicated is the angle btween the ribbon length
direction and
the field direction.
Annealiniz Temperature: 320 C Applied Field/Direction: 1.1 kOe / 90
Ribbon Speed Tension V H !f E~ Hb, df, / dH
(m/minute) (kg/mm2) (mV) (Oe) (kHz) (Oe) (Hz/oe)
2.1 7.2 225 4.7 55.2 10.0 570
Annealing Temperature: 280 0 C Applied Field/Direction: 1.1 kOe / 75
Ribbon Speed Tension V H ff,)= H2 df / dHb
(m/minute) (kg/mmZ) (mV) (Oe) (kHz) (Oe) (HzJOe)
0.6 0 230 5.8 54.2 11.0 720
0.6 7.2 245 5.2 54.7 11.2 620
Above tables indicate that desired performance of a magneto-mechanical
resonant marker can be achieved by proper combination of alloy chemistry and
heat-treatment conditions.
Example 2: Fe-Co-Ni-Mo/Cr/Mn-B-Si-C metallic glasses
Glassy metal alloys in the Fe-Co-Ni-Mo/Cr/Mn-B-Si-C system were
prepared and characterized as detailed under Example 1. Table X lists chemical
compositions, magnetic and thermal properties and Table XI lists quantities
characterizing mechanical resonance responses of the alloys of Table X.
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TABLE X
Magnetic and thermal properties of low cobalt containing glassy alloys. T.
is the first crystallization temperature.
Alloy No. Composition (at.%) B L
Fe Co Ni Mo Cr Mn B Si C (Tesla) (ppm)
( C)
1 40 14 28 - - - 13 3 2 1.22 19 441
2 40 14 27 1 - - 13 5 1.18 18 451
3 40 14 25 3 - 13 5 - 1.07 13 462
4 40 14 27 - 1 - 13 5 1.18 20 462
5 40 14 25 - 3 - 13 5 1.07 15 451
6 40 14 25 1 - - 13 5 2 1.15 15 480
7 40 10 31 1 - - 13 5 - 1.12 18 447
8 40 10 31 - 1 - 13 5 - 1.13 18 441
9 40 10 31 - - 1 13 5 - 1.16 18 445
10 40 10 29 - - 3 13 5 - 1.19 17 454
11 40 10 30 - - - 13 5 2 1.13 16 465
TABLE XI
Values of Ha , V. , Hbl ,( fr ),,,;,, , Hb2 and dfr /dHb taken at Hb = 6 Oe
for
the alloys listed in Table X heat-treated at 380 C in a continuous reel-to-
reel
furnace with a ribbon speed of about 0.6 m/minute with a field of 1.4 kOe
applied
across the ribbon width.
Allov No. H. (Oe) V ,,CmN/j H,(Oe) (f~kHz Hhy fOe1 df /dHb (Hz/Oe1
1 14 310 8.3 52.5 13.1 870
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2 13 350 4.4 51.7 10.0 1640
3 12 250 3.0 51.7 6,4 1790
4 11 320 6.2 51.8 9.8 950
10 480 3.7 51.5 8.2 1780
5 6 9 390 4.1 52.0 8.5 1820
7 10 460 4.2 50.3 8.9 1730
8 10 480 5.2 51.6 9.8 1560
9 12 250 6.5 51.2 10.6 1000
10 380 3.5 51.0 7.8 1880
10 11 9 310 4.0 51.5 8.0 1880
All the alloys listed in Table XI exhibit H. values exceeding 8 Oe, which
make them possible to avoid the interference problems mentioned above. Good
sensitivity ( dfr /dHb ) and large magneto-mechanical resonance response
signal (
Vm ) result in smaller markers for resonant marker systems.
Having thus described the invention in rather full detail, it will be
understood that such detail need not be strictly adhered to but that further
changes
and modifications may suggest themselves to one skilled in the art, all
falling within
the scope of the invention as defined by the subjoined claims.
