U.S. patent application number 11/710937 was filed with the patent office on 2007-11-08 for nd-based two-phase separation amorphous alloy.
Invention is credited to Jung Chan Bae, Hye Jung Chang, Eun Young Jeong, Do Hyang Kim, Hwi Jun Kim, Jin Kyu Lee, Eun Soo Park.
Application Number | 20070258846 11/710937 |
Document ID | / |
Family ID | 38661345 |
Filed Date | 2007-11-08 |
United States Patent
Application |
20070258846 |
Kind Code |
A1 |
Park; Eun Soo ; et
al. |
November 8, 2007 |
Nd-based two-phase separation amorphous alloy
Abstract
Provided is a Nd-based two-phase separation amorphous alloy by
adding an element having a big difference in heat of mixing in a
Nd-based alloy with a superior amorphous formability through an
inherent characteristic of compositional elements and consideration
of thermodynamics, at the time of forming amorphous phase, to
thereby enable two-phase separation amorphous alloy during
solidification. The Nd-based two-phase separation amorphous alloy
which is represented as a general equation
Nd.sub.100-a-b(TM).sub.a(D).sub.b wherein TM is a transition metal
which is a combination of respective one selected from A-B, A-C and
B-C when a group of A consists of Y, Ti, Zr, La, Pr, Gd, and Hf, a
group of B consists of Fe, and Mn, and a group of C consists of Co,
Ni, Cu, and Ag, wherein the content of the element group which
constitutes each combination is 5 atomic weight % or greater, and
the element selected from each element group is at least one, and
wherein D is at least one selected from the group consisting of Al,
B, Si and P, and a and b have the range of 20.ltoreq.a.ltoreq.80,
and 5.ltoreq.b.ltoreq.30, respectively, in terms of atomic weight
%.
Inventors: |
Park; Eun Soo; (Suwon-si,
KR) ; Chang; Hye Jung; (Seoul, KR) ; Kim; Do
Hyang; (Seoul, KR) ; Jeong; Eun Young;
(Jeonju-si, KR) ; Lee; Jin Kyu; (Goyang-si,
KR) ; Kim; Hwi Jun; (Yongin-si, KR) ; Bae;
Jung Chan; (Gunpo-si, KR) |
Correspondence
Address: |
ROSENBERG, KLEIN & LEE
3458 ELLICOTT CENTER DRIVE-SUITE 101
ELLICOTT CITY
MD
21043
US
|
Family ID: |
38661345 |
Appl. No.: |
11/710937 |
Filed: |
February 27, 2007 |
Current U.S.
Class: |
420/416 |
Current CPC
Class: |
C22C 45/00 20130101;
C22C 1/002 20130101 |
Class at
Publication: |
420/416 |
International
Class: |
C22C 28/00 20060101
C22C028/00 |
Foreign Application Data
Date |
Code |
Application Number |
May 2, 2006 |
KR |
10-2006-0039614 |
Claims
1. A Nd-based two-phase separation amorphous alloy which is
represented as a general equation Nd.sub.100-a-b(TM).sub.a(D).sub.b
wherein TM is a transition metal which is one combination selected
from A-B, A-C and B-C when an element group of A consists of Y, Ti,
Zr, La, Pr, Gd and Hf, an element group of B consists of Fe and Mn,
and an element group of C consists of Co, Ni, Cu and Ag, wherein
the content of the element group which constitutes each combination
is 5 atomic weight % or greater, and the element selected from each
group is at least one, and wherein D is at least one selected from
the group consisting of Al, B, Si and P, and a and b have the range
of 20.ltoreq.a.ltoreq.80, and 5.ltoreq.b.ltoreq.30, respectively,
in terms of atomic weight %.
2. The Nd-based two-phase separation amorphous alloy according to
claim 1, wherein the amorphous alloy is a Nd--Zr--Co--Al alloy.
3. The Nd-based two-phase separation amorphous alloy according to
claim 1, wherein the amorphous alloy is a Nd--Hf--Co--Al alloy.
4. The Nd-based two-phase separation amorphous alloy according to
claim 1, wherein the amorphous alloy is a Nd--Zr--Hf--Co--Al
alloy.
5. The Nd-based two-phase separation amorphous alloy according to
claim 1, wherein the amorphous alloy is a Nd--Y--Co--Al alloy.
6. The Nd-based two-phase separation amorphous alloy according to
claim 1, wherein the amorphous alloy is a Nd--Ti--Co--Al alloy.
7. The Nd-based two-phase separation amorphous alloy according to
claim 1, wherein the amorphous alloy is a Nd--La--Co--Al alloy.
8. The Nd-based two-phase separation amorphous alloy according to
claim 1, wherein the amorphous alloy is a Nd--Pr--Co--Al alloy.
9. The Nd-based two-phase separation amorphous alloy according to
claim 1, wherein the amorphous alloy is a Nd--Ti--Fe--Al alloy.
10. The Nd-based two-phase separation amorphous alloy according to
claim 1, wherein the amorphous alloy is a Nd--Gd--Fe--Al alloy.
11. The Nd-based two-phase separation amorphous alloy according to
claim 1, wherein the amorphous alloy is a Nd--Pr--Fe--Al alloy.
12. The Nd-based two-phase separation amorphous alloy according to
claim 1, wherein the amorphous alloy is a Nd--Gd--Pr--Fe--Al
alloy.
13. The Nd-based two-phase separation amorphous alloy according to
claim 1, wherein the amorphous alloy is a Nd--Fe--Co--Al alloy.
14. The Nd-based two-phase separation amorphous alloy according to
claim 1, wherein the amorphous alloy is a Nd--Fe--Co--Al--B
alloy.
15. The Nd-based two-phase separation amorphous alloy according to
claim 1, wherein the amorphous alloy is a Nd--Fe--Co--Al--Si
alloy.
16. The Nd-based two-phase separation amorphous alloy according to
claim 1, wherein the amorphous alloy is a Nd--Fe--Ni--Al alloy.
17. The Nd-based two-phase separation amorphous alloy according to
claim 1, wherein the amorphous alloy is a Nd--Fe--Co--Ni--Al
alloy.
18. The Nd-based two-phase separation amorphous alloy according to
claim 1, wherein the amorphous alloy is a Nd--Fe--Cu--Al alloy.
19. The Nd-based two-phase separation amorphous alloy according to
claim 1, wherein the amorphous alloy is a Nd--Fe--Ag--Al alloy.
20. The Nd-based two-phase separation amorphous alloy according to
claim 1, wherein the amorphous alloy is a Nd--Fe--Ag--Cu--Al alloy.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to a neodymium-based
(Nd-based) two-phase separation amorphous alloy, and more
particularly, to a Nd-based two-phase separation amorphous alloy by
adding an element having a big difference in heat of mixing in a
Nd-based alloy with excellent glass forming ability through an
inherent characteristic of compositional elements and consideration
of thermodynamics, at the time of forming amorphous phase, to
thereby obtain a two-phase separation amorphous alloy during
solidification.
[0003] 2. Description of the Related Art
[0004] Amorphous metal can be defined as the atomic positions of
the liquid phase are conceptually stopped in view of the structural
analysis. Researches on the structural analysis of initial
amorphous metal materials have been performed through Roentgen rays
or electron diffraction based on a controversy whether the
structure of the initial amorphous metal materials are amorphous or
crystalline, but the research on the property of materials have not
been performed. After 1970, Masumoto and Maddin have succeeded in
manufacturing the uniform amorphous ribbon shape with a centrifugal
quenching method. Accordingly, measurement about the property of
the amorphous material has been facilitated. Since the different
magnetic, electric, and mechanical properties are contained in the
amorphous materials, in comparison with the conventional metal
material, it has been reported that the amorphous materials are the
dream metal, to thereby draw the attention of world wide metal and
property researchers.
[0005] The most important one in the property of the amorphous
alloy is the magnetism. The amorphous alloy has been currently
developed as practical soft magnetic materials. The reasons why the
amorphous alloy is suitable for the magnetic material are as
follows.
[0006] 1) The smaller the crystal magnetic anisotropy constant (K)
and magnetism negative constant (.lamda.) may be, the better the
magnetic material, may be. It is ideally best that they become all
zero. In the case of crystalline materials, Sendust (one of
Fe--Al--Si alloys), and Permalloy (one of Fe--Ni alloys) are famous
since the values of the crystal magnetic anisotropy constant (K)
and magnetism negative constant (.lamda.) are small. However, the
composition having the values of zero in these alloys exists as
only a point. However, since the amorphous composition meets
.lamda..apprxeq.0, the group of the composition of
.lamda..apprxeq.0 has a high-permeability and low iron loss
characteristic
[0007] 2) Since the amorphous material is intrinsically of a big
electric resistance, the low iron loss can be easily obtained.
[0008] 3) Since the amorphous material can be made into thin
ribbons of 20-30 .mu.m, the low iron loss can be easily
obtained.
[0009] Research and development on the amorphous materials proceed
in the field of the following applications, due to the
above-described magnetic property.
[0010] a. iron cores of a transformer using a high saturation
magnetic flux density, and low iron loss (Fe--B--C or Fe--Si--B
alloy)
[0011] b. Co-based amorphous alloy (Fe-95Co, Fe--Ni--Co, (Co,
Fe)--B--Si) for making a magnetic head, and a magnetic portion for
controlling a magnetic core of a switching power supply be near to
zero (0)
[0012] c. Products including magnetic heads for video cassette
recorders (VCR) having many advantages including a
high-permeability, a less hysteresis loss, a high electric
resistance to thereby cause a low overcurrent loss and an excellent
high frequency property, and a high intensity to thereby cause an
excellent abrasion resistance
[0013] One of the currently developed Nd-based amorphous alloys is
a Nd--Fe--B material which is used as a hyper-strong magnet in
1980's. It is known that a very high coercive force can be obtained
in a Nd--Fe alloy which has been rapidly cooled. The Nd--Fe alloy
has the advantage having the magnetic property which is more
excellent than a Sm--Co magnetic material in the room temperature
and a price competitive power since the raw material is
inexpensive. However, the general chemical composition is near to a
Fe-rich composition of Nd.sub.15Fe.sub.77B.sub.8. Moreover, The
Nd--Fe alloy has the disadvantage that the magnetic property is
drastically lowered according to an increase in the temperature.
Thereafter, the alloy of the Nd--Al-TM (TM=transition metal) has
been reported. Nd--Al--Fe ternary alloys are under the active
research on applications as the ferromagnetic materials (Materials
Science and Engineering A Volumes 226-228, 15 Jun. 1997, Pages
393-396).
[0014] Particularly, in the case of the conventional Nd-based
amorphous alloys as described above, there have been the efforts of
controlling alloying elements or a cooling speed for the
application of the magnetic material to thereby improve a magnetic
property through nano-crystallizing of the whole or the part
thereof (Journal of Magnetism and Magnetic Materials Volume 261,
Issues 1-2, April 2003, Pages 122-130; Journal of Magnetism and
Magnetic Materials Volumes 290-291, Part 2, April 2005, Pages
1214-1216; and Materials Science and Engineering A Volume 385,
Issues 1-2, 15 Nov. 2004, Pages 38-43). Here, the nano-crystalline
structure in the material suppresses movement of domain walls
efficiently, to thereby increase a coercive force and magnetic
susceptibility. Demagnetization has a positive effect on a magnetic
property through a pinning effect that a corresponding external
magnetic field is required. However, the form of precipitate is
being limited to a crystal phase through crystallization of the
material inside. So far, there have been no reports that the
magnetic property can be improved by forming an amorphous phase of
a second phase.
[0015] In the meantime, in the case of the currently developed
two-phase separation amorphous alloys, there have been reports that
a phase separation phenomenon is found only in the limited
compositional range of Zr--La--Al--Cu--Ni, Y--Ti--Al--Co and
Ni--Nb--Y based alloys through a rapid solidification process using
a melt spinning process. As a result, while the two-phase
separation amorphous alloy needs a higher cooling speed in
comparison with a single-phase amorphous alloy. This means that the
compositional range of alloy for obtaining amorphous microstructure
is limited.
SUMMARY Of THE INVENTION
[0016] To solve the above problems, it is an object of the present
invention to provide a Nd-based two-phase separation amorphous
alloy in which elements having a big difference of heat of mixing
are added in a Nd-based bulk amorphous alloy composition which has
been reported to have an excellent glass forming ability through an
inherent characteristic of compositional elements and consideration
of thermodynamics, to thereby enable two-phase separation amorphous
alloy during solidification, and the two-phase separated amorphous
phase shows up a conspicuously separated crystallization behavior
according to an inherent crystallization temperature difference of
main elements, respectively, with a result that 1) manufacturing of
the composite material is facilitated through nano-crystallization,
2) a multi-stage forming can be performed in a supercooled liquid
region corresponding to the amorphous phase, respectively, and 3) a
magnetic property can be improved by the amorphous phase of the
second phase, or the nano-phase which can be easily formed through
a thermal process.
[0017] To accomplish the above object of the present invention,
there is provided a A Nd-based two-phase separation amorphous alloy
which is represented as a general equation
Nd.sub.100-a-b(TM).sub.a(D).sub.b, wherein TM is transition metals
which are one combination selected from A-B, A-C and B-C when an
element group of A consists of Y, Ti, Zr, La, Pr, Gd and Hf, an
element group of B consists of Fe and Mn, and an element group of C
consists of Co, Ni, Cu and Ag, wherein the content of the element
group which constitutes each combination is five atomic weight % or
greater, and the element selected from each group is at least one,
and wherein D is at least one selected from the group consisting of
Al, B, Si and P, and a and b have the range of
20.ltoreq.a.ltoreq.80, and 5.ltoreq.b.ltoreq.30, respectively, in
terms of atomic weight %.
[0018] In more detail, an equilibrium condition is generally
determined by free energy calculation through thermodynamics
consideration in the respective states of the metal materials.
Particularly, mixing of two elements having a positive heat of
mixing relationship forms an immiscibility gap which is an
immiscible area between the two elements so that two solid
solutions can be stabilized in a specific composition range.
[0019] Based on this fact, the present invention has made every
effort in order to manufacture a neodymium (Nd)-based two-phase
amorphous alloy. As a result, a Nd-TM group (TM is a transition
element) is formed in which a base element is an element of Nd, a
group of A consists of transition elements such as Y, Ti, Zr, La,
Pr, Gd, and Hf having a positive heat of mixing relationship with
respect to Nd, a group of B consists of transition elements such as
Fe and Mn having an excellent glass forming ability together with a
high crystallization temperature in a Nd-based amorphous alloy, and
a group of C consists of transition elements such as Co, Ni, Cu,
and Ag having a negative heat of mixing relationship with respect
to Nd. Here, the two-phase separation amorphous alloy can be
obtained during solidification by a positive heat of mixing
relationship between Nd and the element of the A group in the TM,
or between the element of B and the element of C group in the
TM.
[0020] For this, the element of TM consists necessarily of any one
selected from a combination of an element group among A-B, A-C and
B-C, when a group of A consists of a group of elements such as Y,
Ti, Zr, La, Pr, Gd and Hf having a positive heat of mixing
relationship with respect to Nd, a group of B consists of
transition elements such as Fe and Mn enhancing the glass forming
ability and increasing the crystallization temperature in a
Nd-based amorphous alloy, and a group of C consists of transition
elements such as Co, Ni, Cu, and Ag having a negative heat of
mixing relationship with respect to Nd, so as to match the purport
of the present invention.
[0021] Furthermore, the semi-metal and non-metal elements which are
known to contribute to improve the glass forming ability in the
Nd-based amorphous alloy are classified as a group of D such as Al,
B, Si, and P, to thereby have an excellent glass forming ability
after the two-phase separation.
[0022] In the present invention, a heat of mixing relationship of
an element pair which forms an immiscible area is as follows.
[0023] <Nd-A Group>
[0024] Nd--(Y or Gd): 0 KJ/mole, Nd--Ti: 17 KJ/mole, Nd--Zr: 10
KJ/mole, Nd--Hf: 13 KJ/mole, Nd--La: 0 KJ/mole, Nd--Pr: 0
KJ/mole
[0025] <B-C Group>
[0026] Fe--Co: -1 KJ/mole, Fe--Ni: -2 KJ/mole, Fe--Cu: 13 KJ/mole,
Fe--Ag: 28 KJ/mole
[0027] Mn--Co: -2 KJ/mole, Mn--Ni: -4 KJ/mole, Mn--Cu: 4 KJ/mole,
Mn--Ag: 13 KJ/mole
[0028] In the present invention, because TM gets to deviate from a
eutectic composition with Nd in the case that TM is added to Nd by
less than 20% or in excess of 80% in units of atomic weight %, the
glass forming ability is decreased. Particularly, in the case that
the elements of the A group, B group, and C group of TM are added
by less than five atomic weight %, it is thermodynamically
imperfect to form an miscibility gap which is an immiscible area
between the element groups which have the positive heat of mixing
relationship.
[0029] In order to perform the two-phase separation amorphous
alloy, the glass forming ability becomes an important factor in
addition to the two-phase separation of the main elements.
Therefore, the elements of the D group have been selected
considering the empirical formula for improving the glass forming
ability (1) a multi-component system of a ternary component or
greater, (2) a big difference of 12% or greater between
compositional elements, (3) a composition of elements having a
negative heat of mixing, and (4) the condition of the deep eutectic
composition neighborhood. Here, in the case of the D group elements
are added by less than five atomic weight %, this violates a
confusion theory which is the glass forming ability improvement
concept through the multi-component system of the empirical
formula. In the case that the D group elements are added in excess
of thirty atomic weight %, a big change is induced in the amorphous
formation combination consisting of Nd-TM-D to rather drastically
reduce the glass forming ability.
BRIEF DESCRIPTION OF THE DRAWINGS
[0030] The above and other objects and advantages of the present
invention will become more apparent by describing the preferred
embodiment thereof in more detail with reference to the
accompanying drawings in which:
[0031] FIGS. 1A and 1B are graphical views illustrating
differential thermal analysis results and X-ray diffraction
analysis results with respect to a two-phase separation amorphous
alloy of Nd.sub.25Zr.sub.35Co.sub.30Al.sub.10 according to the
present invention, respectively;
[0032] FIG. 2 is a photographical view illustrating transmission
electron microscope analysis results with respect to a two-phase
separation amorphous alloy of Nd.sub.25Zr.sub.35Co.sub.30Al.sub.10
according to the present invention;
[0033] FIG. 3 is a graphical view illustrating differential thermal
analysis results with respect to alloys of Nd--Fe--X--Al according
to the present invention;
[0034] FIG. 4 is a photographical view illustrating transmission
electron microscope analysis results with respect to a two-phase
separation amorphous alloy of Nd.sub.30Ti.sub.30Co.sub.30Al.sub.10
after having undergone selective nano-crystallization through a
thermal process according to the present invention;
[0035] FIG. 5 is a graphical view illustrating height variation
measurement results of a specimen according to temperature using a
thermo-mechanical analyzer (TMA) with respect to an alloy of
Nd.sub.30Ti.sub.30Co.sub.30Al.sub.10 according to the present
invention;
[0036] FIG. 6 is a graphical view illustrating results which is
obtained by measuring a magnetic field versus magnetization
behavior according to temperature using a vibrating sample
magnetometer (VSM) with respect to an alloy of
Nd.sub.30Ti.sub.30Co.sub.30Al.sub.10 according to the present
invention.
DETAILED DESCRIPTION OF THE INVENTION
[0037] A neodymium-based (Nd-based) two-phase separation amorphous
alloy according to preferred embodiments of the present invention
will be described below with reference to the accompanying
drawings.
[0038] (Manufacturing of a Specimen)
[0039] 1. Manufacturing of a Mother Alloy
[0040] In order to obtain a mother alloy of a desired alloy
composition in the present invention, Nd which has a purity of
99.8%-99.99%, and elements selected from a group of A such as Y,
Ti, Zr, La, Pr, Gd, and Hf, a group of B such as Fe and Mn, a group
of C such as Co, Ni, Cu, and Ag, and a group of D such as Al, B,
Si, and P elements have been arc-melted under a high purity argon
gas atmosphere of 99.99%. Moreover, in order to remove any
segregation of the alloy component during the arc-melting, a sample
has been repeatedly melted three times while inverting.
[0041] 2. Manufacturing of a Specimen Using a Melt Spinning
Method
[0042] The prepared mother alloy has been manufactured into a
specimen of a ribbon-shape by using a melt spinning method whose
cooling rate is 10.sup.4-10.sup.6 K/s.
[0043] Concretely, the mother alloy has been firstly charged into a
quartz tube. Then, the mother alloy has been melted to liquid state
under the argon atmosphere of 7-9 KPa with a microwave induction
heating after having maintained a degree of vacuum in a chamber
into about 10.sup.-4 Torr. Here, the molten metal is being
maintained by a surface tension in the quartz tube. Then, the
quartz tube has rapidly fallen before the reaction of the quartz
tube has occurred after the mother alloy has been completely
melted, and simultaneously the argon gas of about 50 KPa has been
injected into the quartz tube. Accordingly, the molten metal is
melt-spinned on the Cu roll surface (wheel surface velocity: about
40 m/s) which rotates at a high speed, to thereby manufacture a
ribbon-shaped specimen of the thickness of about 30 .mu.m and the
width of about 2 mm.
[0044] 3. Manufacturing of a Specimen Using an Injection Casting
Method
[0045] In the present invention, the mother alloy has been
manufactured into a bulk specimen through an injection casting
method while changing a cooling speed by using a copper mold of
various diameters. The high purity argon gas is charged at the high
vacuum state. The mother alloy has been melted with a high
frequency induction under the argon atmosphere. Then, the melted
mother alloy has been charged a water-cooled copper mold through a
certain fixed injection pressure, to thereby manufacture a
rod-shaped specimen of a fixed length of 50 mm.
[0046] The analysis of the amorphous alloy composition according to
the present invention is as follows.
[0047] (Specimen Analysis)
[0048] 1. Transmission Electron Microscope Analysis
[0049] The transmission electron microscope (TEM) analysis has been
conducted in order to observe the phase separation phenomenon of a
bulk amorphous alloy. The specimen manufactured using an injection
casting has been mechanically grinded and prepared by ion milling
method. An angle between an ion beam and a specimen surface has
been polished while changing into 4-8.degree. by using the ion
milling method.
[0050] Under the same condition as the above-described condition, a
bright field image (BF image) and a limit viewing direction
selected area diffraction pattern (SADP) has been obtained at the
acceleration voltage of 200 kV using JEM 2000EX.
[0051] 2. Differential Thermal Analysis
[0052] In general, in order to estimate thermodynamic properties
which relate to a glass transition temperature (Tg) of an amorphous
phase, and a crystallization temperature (Tc), a differential
scanning calorimetry (Perkin Elmer, DSC7) has been used.
[0053] In this experiment, a sample has been put into a copper fan,
and then put in a platinum holder. Then, an empty pan has been put
into a reference. The thermodynamic properties have been measured
under the high purity argon atmosphere of 99.999% at the
temperature range of 373-953 K in order to prevent the oxidation of
the specimen. The DSC analysis has been performed under the 99.99%
purity argon atmosphere after having charged a sample of about 20
mg at a constant temperature-up rate of 40 K/min(0.667 K/s).
[0054] 3. X-Ray Diffraction Analysis
[0055] In order to identify whether the manufactured specimen has
an amorphous phase, an X-ray diffractometry (M18XHF.sup.22-SRA,
monochromatic Cu K radiation) has been used to irradiate X-rays
onto the specimen. The X-ray diffraction analysis has been
performed with the condition of a tube voltage of 50 kV and current
of 200 mA of a Cu target (.lamda.=1.5406, Ka.sub.1 ray). X-ray
diffraction spectrum has been obtained within the range of a
scanning range of 20.degree.-80.degree. with a sequential scanning
method, at the speed of 4.degree./min while maintaining
0.02.degree. interval.
[0056] In general, in the case of an amorphous specimen, a broad
diffraction pattern with no crystalline picks has been obtained in
the X-ray diffraction analysis. Differently from the general
amorphous alloy, the diffraction patterns regarding the two
amorphous phases have been overlapped in the two-phase amorphous
alloy. As a result, it can be confirmed that the present invention
has a relatively wider diffraction angle region.
[0057] 4. TMA Analysis
[0058] In a supercooled liquid region, TMA (TMA-7, Perkin-Elmer)
has been used in order to measure viscosity of the amorphous alloy.
By using a specimen of a rod-shape and a ribbon-shape, a certain
compressive load is applied by a ceramic probe whose diameter is 3
mm at a compressed mode, and then a change in length of a specimen
has been measured while increasing the temperature. Correction for
temperature has been performed using In and Zn specimens before all
the experiments. The experiment has been progressed under the Ar
atmosphere.
[0059] 5. VSM (Vibrating Sample Magnetometer) Analysis
[0060] A macroscopic magnetism change has been measured according
to temperature in the form of a ribbon or powder with respect to
the two-phase amorphous alloy according to the invention using a
VSM (Vibrating Sample Magnetometer). A change in a magnetic
property (or magnetization) according to temperature has been
measured with a magnetic force of 2 tesla at maximum and at the
range of the temperature of 10 K to 300 K.
TABLE-US-00001 TABLE 1 (Unit: Kelvin Temp.) Manufacturing/ Items
Composition (at %) T.sub.g1 T.sub.x1 T.sub.g2 T.sub.x2 form
Examples 1 Nd.sub.25Zr.sub.35Co.sub.30Al.sub.10 468 488 671 719
M/DA 2 Nd.sub.30Zr.sub.25Hf.sub.5Co.sub.30Al.sub.10 477 501 667 712
M/DA 3 Nd.sub.50Ti.sub.10Co.sub.30Al.sub.10 496 519 562 587 M/DA 4
Nd.sub.15Y.sub.40Co.sub.25Al.sub.20 598 646 810 848 M/DA 5
Nd.sub.30La.sub.30Co.sub.30Al.sub.10 462 498 554 586 M/DA 6
Nd.sub.30Ti.sub.30Fe.sub.30Al.sub.10 470 498 705 727 M/DA 7
Nd.sub.30Gd.sub.30Fe.sub.30Al.sub.10 472 508 823 857 M/DA 8
Nd.sub.50Mn.sub.20Co.sub.15Al.sub.15 534 562 682 715 M/DA 9
Nd.sub.50Fe.sub.10Co.sub.25Al.sub.15 528 570 752 782 I/DA 10
Nd.sub.50Fe.sub.5Co.sub.30Al.sub.12B.sub.3 527 560 769 789 I/DA 11
Nd.sub.57Fe.sub.10Co.sub.15Al.sub.15Si.sub.3 478 507 688 727 M/DA
12 Nd.sub.60Fe.sub.10Ni.sub.15Al.sub.15 471 499 717 762 I/DA 13
Nd.sub.50Fe.sub.5Ni.sub.30Al.sub.12P.sub.3 530 561 752 766 M/DA 14
Nd.sub.50Fe.sub.20Ag.sub.15Al.sub.15 492 522 716 784 I/DA 15
Nd.sub.50Fe.sub.10Ag.sub.20Cu.sub.5Al.sub.15 499 524 735 758 M/DA
Comparative 1 Nd.sub.60Fe.sub.30Al.sub.10 -- -- 712 797 M/SA
Examples 2 Nd.sub.70Fe.sub.10Co.sub.5Al.sub.15 -- -- -- 734 M/Comp.
3 Nd.sub.10Fe.sub.75Co.sub.7B.sub.8 -- -- -- 870 M/Comp. 4
Nd.sub.56Zr.sub.4Co.sub.30Al.sub.10 496 521 -- -- M/SA 5
Nd.sub.30V.sub.30Fe.sub.30Al.sub.10 -- -- 732 776 M/Comp. 6
Nd.sub.30Nb.sub.30Co.sub.30Al.sub.10 -- -- -- -- M/Cryst. 7
Nd.sub.60Fe.sub.15Mn.sub.15Al.sub.10 -- -- -- -- M/Cryst. 8
Nd.sub.50Ni.sub.20Cu.sub.15Al.sub.15 503 542 -- -- M/SA 9
Nd.sub.50Fe.sub.20Zn.sub.15Al.sub.15 -- -- -- -- M/Cryst. 10
Nd.sub.65Mn.sub.17Co.sub.15Si.sub.3 -- -- -- -- M/Cryst. 11
Nd.sub.40Mn.sub.15Cu.sub.10Al.sub.35 -- -- -- -- M/Cryst. 12
Nd.sub.25Zr.sub.35Co.sub.30C.sub.10 -- -- -- -- M/Cryst.
[0061] Here, M=Melt spinning method, I.=Injection casting method,
SA=single amorphous state, DA=two-phase amorphous state,
Cryst.=crystallization, and Comp.=SA+Cryst.
[0062] As can be seen from Table 1, the alloys according to the
present invention have two-phase separation amorphous
microstructure (DA) during solidification. The glass forming
ability of the two-phase separation amorphous alloy depends on
cooling rates greater than that of the single amorphous alloy.
However, in the case of the Nd--Fe--Co--Al group, the
Nd--Fe--Ni--Al group, and the Nd--Fe--Ag--Al group amorphous alloy
according to the present invention, the two-phase amorphous can be
obtained through an injection casting method having a relatively
small cooling rate of about 10-100 K/S.
[0063] In Comparative Example 1, only the element of the B group
among the TM is selected. This violates the present invention
requirement that at least two groups should be selected among the
TM. The immiscible area is not formed due to the absence of the
elements which has a positive heat of mixing. Thus, the Comparative
Example 1 shows an example in which the amorphous alloy of the
simple Nd-based single phase is formed.
[0064] In Comparative Example 2, the elements of TM are added by
less than 20 wt %. In this case, the TM gets to deviate from a
eutectic composition with Nd. Then, the glass forming ability of
this alloy is reduced. As a result, a complete amorphous phase is
not obtained even through a rapid solidification process.
[0065] In Comparative Example 3, the elements of TM are added in
excess of 80 wt %. The TM element (Fe) becomes a main component in
this composition. Accordingly, the TM gets to deviate from a
eutectic composition in a combination of Nd-TM-(D group), to
thereby greatly reduce the glass forming ability. As a result, a
complete amorphous phase is not obtained even through a rapid
solidification process.
[0066] In Comparative Example 4, the element of the A group among
the TM is added by less than 5 wt % which is presented on the basis
of a minimum standard. In this case, an element of the A group, Zr
is insufficient in quantity to form an immiscible area together
with the main element Nd. Thus, the Comparative Example 4 shows an
example in which the amorphous alloy of the Nd-based single phase
is formed.
[0067] In Comparative Examples 5 and 6, the other elements of V and
Nb are added instead of the A group element according to the
present invention. In these cases, although they have the positive
heat of mixing value of 18 KJ/mole and 32 KJ/mole with respect to
Nd, respectively, they have a relatively high melting temperature
when the elements of V and Nb are combined with the other
compositional elements. Accordingly, the Comparative Examples 5 and
6 violate the empirical formula for amorphous phase formation that
they have to have the deep eutectic composition. Thus, the
Comparative Examples 5 and 6 show an example that formation of
amorphous phase is not facilitated even through a rapid
solidification process, respectively.
[0068] In Comparative Example 7, only the element of the B group
among the TM is selected. This violates the present invention
requirement that at least two groups should be selected among the
TM. Thus, the Comparative Example 7 shows an example in which
two-phase separation of amorphous are not facilitated even through
a rapid solidification process.
[0069] In Comparative Example 8, only the element of the C group
among the TM is selected. This violates the present invention
requirement that at least two groups should be selected among the
TM. Thus, Comparative Example 8 shows an example that the Nd-based
single phase of amorphous is made since it has a difficulty in
forming an immiscible area.
[0070] In Comparative Example 9, zinc (Zn) which is an element
other than those of the present invention is added as an element of
TM. The Comparative Example 9 shows an example that amorphous is
not achieved even through a rapid solidification since the glass
forming ability is very reduced.
[0071] In Comparative Examples 10 and 11, the element of the D
group is added by less than 5 wt % or in excess of 30 wt %. These
show that the element of the D group which has been added by less
than 5 wt % or in excess of 30 wt % plays a negative role in a
correlation between the existing elements and thus amorphous is not
achieved even through a rapid solidification since the glass
forming ability is abruptly reduced.
[0072] In Comparative Example 12, a semi-metal or non-metal element
different from the D group elements is added. Accordingly, when
carbon (C) is added, the Comparative Example 12 violates the
empirical formula for enhancing glass forming ability glass forming
ability in the Nd-based alloy. Thus, the Comparative Example 12
shows an example that amorphous is not obtained even through a
rapid solidification process.
[0073] Hereinbelow, a Nd-based two-phase separation amorphous alloy
according to the present invention will be described in more detail
with reference to the accompanying drawings.
[0074] FIGS. 1A and 1B are graphical views illustrating
differential thermal analysis results and X-ray diffraction
analysis results with respect to a two-phase separation amorphous
alloy of Nd.sub.25Zr.sub.35Co.sub.30Al.sub.10 according to the
present invention, respectively. As can be seen from FIG. 1A, the
two-phase separation amorphous alloy of the present invention shows
a crystallization behavior conspicuously separated by the
difference in the crystallization temperature range of main
elements with a positive heat of mixing relationship. Moreover, as
can be seen from FIG. 1B, the two-phase separation amorphous alloy
of the present invention shows a typical amorphous halo pattern in
an inherent two-theta (20) section which has been determined by the
inherent atom radius of main elements whose two phases have been
separated by a positive heat of mixing relationship from an X-ray
diffraction analysis result. As a result, a diffraction pattern
which two halo patterns have been overlapped can be obtained.
[0075] FIG. 2 is a photographical view illustrating transmission
electron microscope analysis results with respect to a two-phase
separation amorphous alloy of Nd.sub.25Zr.sub.35Co.sub.30Al.sub.10
according to the present invention. As can be seen from FIG. 2, in
the case of a two-phase separation amorphous alloy of
Nd.sub.25Zr.sub.35Co.sub.30Al.sub.10 according to the present
invention, two halo rings which are separated by the atom radius
difference of a respectively separated amorphous main element are
obtained similarly to the X-ray diffraction analysis results. The
shape of amorphous phases obtained in this two-phase separation
alloy of Nd.sub.25Zr.sub.35Co.sub.30Al.sub.10 is indistinguishable
through a Bright Field Image due to a similar density value of the
separated amorphous phase, but definitively distinguishable through
a Dark Field Image.
[0076] FIG. 3 is a graphical view illustrating differential thermal
analysis results with respect to alloys of Nd--Fe--X--Al according
to the present invention. As can be seen from FIG. 3, it can be
confirmed that a crystallization behavior for each separated ally
occurs in two divided temperature ranges by a positive heat of
mixing relationship. In this way, the alloy composition having the
separated crystallization behavior has a supercooled liquid region
of a certain temperature area showing a super plasticity behavior
before the crystallization behavior, respectively.
[0077] FIG. 4 is a photographical view illustrating transmission
electron microscope analysis results of a sample which has
undergone a thermal process up to 600 K, with respect to a
two-phase separation amorphous alloy of
Nd.sub.30Ti.sub.30Co.sub.30Al.sub.10 according to the present
invention. As can be seen from FIG. 4, in the case that the
two-phase separation alloy of Nd.sub.30Ti.sub.30Co.sub.30Al.sub.10
according to the present invention is thermally treated up to 600
K, it can be confirmed that nano-crystalline phase having particle
size of several tens of nano-meters have partially appeared by a
first crystallization behavior relating to a Nd-based amorphous
phase, and an amorphous phase is maintained for the other regions.
That is, it can be confirmed that the crystallized region and the
amorphous region have a composite form of a nano-scale. As a
result, it is possible to perform a selective crystallization due
to the separated crystallization behavior of the two-phase
separation amorphous alloy, to thereby manufacture nano-composite
materials.
[0078] FIG. 5 is a graphical view illustrating height variation
measurement results of a specimen according to temperature using a
thermo-mechanical analyzer (TMA) with respect to an alloy of
Nd.sub.30Ti.sub.30Co.sub.30Al.sub.10 according to the present
invention. In the case of the alloy of
Nd.sub.30Ti.sub.30Co.sub.30Al.sub.10 according to the present
invention, it can be confirmed that a sudden height variation is
undergone in a first supercooled liquid region (450-500 K) which
relates to the Nd-based amorphous phase. This is the same result as
that of the previously known super plastic deformation of the
amorphous alloy. However, in the case of the two-phase separation
amorphous alloy composition of the present invention, it can be
confirmed that a step portion (a sudden height decreasing area
according to the temperature increment) which has implied that a
second variation is possible in a supercooled liquid region
(680-740 K) relating to a second crystallization behavior relating
to Zr differently from a single amorphous phase. In the vicinity of
about 900 K (that is, at the solidus melting temperature (Ts), a
sudden height reduction is initiated in connection with the melting
of the Nd-based amorphous alloy.
[0079] FIG. 6 is a graphical view illustrating results which is
obtained by measuring a magnetic field versus magnetization
behavior according to temperature using a vibrating sample
magnetometer (VSM) with respect to an alloy of
Nd.sub.30Ti.sub.30Co.sub.30Al.sub.10 according to the present
invention. In the case of the two-phase separation alloy of
Nd.sub.30Ti.sub.30Co.sub.30Al.sub.10 according to the present
invention, as shown in FIG. 6, a spin reorientation temperature in
which orientation of spins begins to be changed is about 30 K. That
is, in the room temperature, the spins are oriented to an
out-of-plane direction. If the temperature gets to fall down to 30
K or less, the spins rotate while forming a cone. As a result, an
in-plane component of the spins is generated so that a
magnetization value increases in an in-plane direction. This
phenomenon is one of the general properties which show up in the
magnetic materials. However, in the case of the two-phase
separation alloy of the present invention, it can be confirmed that
the magnetic property drastically changes from the soft magnetic
characteristic to the hard magnetic characteristic, at the spin
reorientation temperature due to the presence of a second amorphous
phase. This phenomenon is taken into consideration that the
two-phase separation alloy of Nd.sub.30Ti.sub.30Co.sub.30Al.sub.10
according to the present invention can be used as a data storage
medium etc., since spins are firstly oriented in an in-plane
direction at the low temperature, a preference magnetization
direction is changed according to a temperature, and a magnetism
switching is possible at the time of applications with a little
temperature change.
[0080] As described above, a Nd-based alloy which enables two-phase
amorphous alloy according to the present invention has the
following effects.
[0081] 1) An amorphous alloy composition can be manufactured in an
in-situ manner through a thermodynamic access, in which a two-phase
amorphous material having an excellent glass forming ability is
phase-separated from the amorphous alloy composition and then
phase-separated amorphous material exists.
[0082] 2) A phase separation mechanism applied in the amorphous
alloy composition according to the present invention, presents
standards designing an amorphous material in a new concept
differing from previously proposed empirical formulas as well as
opposing the general empirical formulas regarding the amorphous
formation. Furthermore, two-phase bulk amorphous alloy compositions
by the phase separation can be easily developed in the other alloy
systems in the future.
[0083] 3) The two-phase separation amorphous alloy according to the
present invention exhibits a phase separation having a quite fine
connection structure of a nano-scale. Thus, a two-phase separated
composition can be selectively nano-crystallized through a
selective thermal process or a control of a cooling rate, to
thereby easily manufacture an amorphous based nano-composite
material.
[0084] 4) The two-phase separation amorphous alloy according to the
present invention shows two supercooled liquid regions in respect
of both of the two amorphous phases. Accordingly, a multi-stage
deformational behavior is available in the supercooled liquid
region. In more detail, a supercooled liquid region using the
super-plasticity of the amorphous material for the existing micro
electro mechanical systems (MEMS), including, the processing of the
material through microforming etc., is mainly used, but the two
amorphous phases of the invention have the supercooled liquid
region separately with respect to the respective amorphous phase in
the case of the alloy according to the present invention. It is
possible to obtain an amorphous based composite material through a
nano-crystallization process by appearance of the second
supercooled liquid region, to accordingly be applicable as a new
processing method for a nano-composite material.
[0085] 5) In the case of the Nd-based two-phase amorphous alloy
according to the present invention, a magnetic property is improved
by a nano-phase which can be easily formed through the second
amorphous phase or a thermal process of the two-phase amorphous
alloy. In this way, a neodymium-based amorphous alloy which enables
a nano-structure control has a big potential in view of high
value-added industry applications including electric and electronic
industries etc., differently from the existing concept for
enhancing the magnetic property through nano-crystallization
relying upon various kinds of thermal treatments and processes.
[0086] As described above, the present invention has been described
with respect to particularly preferred embodiments. However, the
present invention is not limited to the above embodiments, and it
is possible for one who has an ordinary skill in the art to make
various modifications and variations, without departing off the
spirit of the present invention.
* * * * *