U.S. patent application number 10/419119 was filed with the patent office on 2003-09-25 for alloy-based nono-crystal texture and method of preparing same.
Invention is credited to Kajiwara, Setsuo, Kikuchi, Takehiro, Matsunaga, Takeshi, Miyazaki, Shuichi, Ogawa, Kazuyuki.
Application Number | 20030178109 10/419119 |
Document ID | / |
Family ID | 12144109 |
Filed Date | 2003-09-25 |
United States Patent
Application |
20030178109 |
Kind Code |
A1 |
Kajiwara, Setsuo ; et
al. |
September 25, 2003 |
Alloy-based nono-crystal texture and method of preparing same
Abstract
To provide a very tough material at a low manufacturing cost,
the present invention provides an alloy-based nano-crystal texture
in which, in an alloy system having a composition deviating from
the stoichiometric composition, and capable of forming an amorphous
state, nano-scale crystals are arranged in an identical crystal
orientation.
Inventors: |
Kajiwara, Setsuo; (Ibaraki,
JP) ; Kikuchi, Takehiro; (Ibaraki, JP) ;
Ogawa, Kazuyuki; (Ibaraki, JP) ; Miyazaki,
Shuichi; (Ibaraki, JP) ; Matsunaga, Takeshi;
(Ibaraki, JP) |
Correspondence
Address: |
WENDEROTH, LIND & PONACK, L.L.P.
2033 K STREET N. W.
SUITE 800
WASHINGTON
DC
20006-1021
US
|
Family ID: |
12144109 |
Appl. No.: |
10/419119 |
Filed: |
April 21, 2003 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
10419119 |
Apr 21, 2003 |
|
|
|
08938522 |
Sep 26, 1997 |
|
|
|
Current U.S.
Class: |
148/561 ;
148/403 |
Current CPC
Class: |
C22C 30/00 20130101;
C22C 45/10 20130101; C22C 45/008 20130101 |
Class at
Publication: |
148/561 ;
148/403 |
International
Class: |
C22C 045/00 |
Foreign Application Data
Date |
Code |
Application Number |
Feb 7, 1997 |
JP |
024653/1997 |
Claims
We claim:
1. A metallic alloy containing nano-crystals smaller than 100
nanometers having an identical crystal orientation, said alloy
having a composition which deviates from a stoichiometric
composition toward easier production of a precipitate by about 1 to
5%.
2. An alloy according to claim 1, wherein at least ten thousand of
the nano-crystals have the identical orientation.
3. An alloy according to claim 1, wherein said nano crystal has a
diameter within a range of from about 10 to 60 nm and the crystal
grain has a diameter within a range of from about 1 to 10
.mu.m.
4. An alloy according to claim 3, wherein said alloy is a Ti--Ni
alloy, a Ti--Co alloy, a Ti--Al alloy or an Fe--Al alloy.
5. An alloy according to claim 1, wherein said alloy is a Ti--Ni
alloy, a Ti--Co alloy, a Ti--Al alloy or an Fe--Al alloy.
6. A method of preparing an alloy-based nano-crystal texture in
which, in an alloy capable of forming an amorphous state,
nano-scale crystals are present as a crystal texture as arranged in
an identical crystal orientation, comprising the step of heating an
amorphous alloy at a temperature lower than the crystallization
temperature.
7. A method of preparing an alloy-based nano-crystal texture
according to claim 6, wherein the composition deviates from the
stoichiometric composition toward easier production of a
precipitate by about 1 to 5%.
Description
FIELD OF THE INVENTION
[0001] The present invention relates to a nano-crystal texture and
a method of preparing the same. More particularly, the present
invention relates to a nano-crystal texture which improves
ductility of a material and is useful for achievement of a material
known as a super-metal, and method of preparing the same.
RELATED ART
[0002] Reduction of the size of crystal grain has conventionally
been tried in various manners as a method for improving strength
and ductility of an alloy material. Materials having a high
strength have so far been achieved by the use of the thus developed
methods.
[0003] In spite of various contrivances made in the composition and
heat treatment, however, further remarkable improvement of the
strength level has been limited. With conventional techniques, it
is difficult to largely improve strength to, for example, ten times
as high. There is therefore a demand for quite new findings
essentially different from the conventional technical
knowledge.
[0004] The present invention has an object to overcome the
conventional technical limits as described above, and to provide a
novel practicable material permitting an epoch-making breakthrough
and a simple method for preparing the same.
SUMMARY OF THE INVENTION
[0005] The present invention provides an alloy-based nano-crystal
texture, wherein, in an alloy capable of forming an amorphous
state, nano-scale crystals are present as a crystal texture as
arranged in an identical orientation.
[0006] The invention provides also a method of preparing an
alloy-based nano-crystal texture in which, in an alloy capable of
forming an amorphous state, nano-scale crystals are present as a
crystal texture as arranged in an identical orientation, comprising
the step of heating an amorphous alloy at a temperature lower than
the crystallization temperature.
BRIEF DESCRIPTION OF THE DRAWINGS
[0007] FIG. 1 is an ordinary electron micrograph of a crystal grain
formed when annealing the material at 687 K for two hours;
[0008] FIG. 2 is an electron micrograph illustrating that one of
the crystal grains shown in FIG. 1 is composed of nano-crystals of
20 to 40 nm;
[0009] FIG. 3 is a high-resolution electron micrograph when an
electron beam is irradiated from the [111] bcc orientation to show
a nano-crystal texture in an embodiment of the invention;
[0010] FIG. 4 is an enlarged electron micrograph of the box portion
shown in FIG. 3;
[0011] FIG. 5 is a high-resolution electron micrograph when an
electron beam is irradiated from the [001] bcc orientation to show
the nano-crystal texture;
[0012] FIG. 6 is an enlarged electron micrograph of the box portion
shown in FIG. 5;
[0013] FIG. 7 is a diagram illustrating the atomic arrangement of a
precipitate produced on the interface between adjacent
nano-crystals;
[0014] FIG. 8 is a schematic view illustrating the process of
formation of a nano-crystal texture having an identical
orientation, as viewed from the [001] bcc orientation;
[0015] FIG. 9 is a schematic view illustrating the process of
formation of a nano-crystal texture having an identical
orientation, as viewed from the [111] bcc orientation; and
[0016] FIG. 10 is a schematic view illustrating the process of
formation of a nano-crystal texture having an identical
orientation, showing the whole view three-dimensionally.
DETAILED DESCRIPTION OF THE INVENTION
[0017] Now, the present invention will be described below further
in detail by means of embodiments. First, the nano-crystal texture
of the invention has a unique structure in which as many as several
tens of thousand nano-crystals having a nano-scale size, i.e., a
size of an extra-fine diameter represented in units smaller than
100 nano-meter (nm), have an identical orientation in fine grains
in the common meaning, for example, of a micron-meter
(.mu.m)-scale.
[0018] Such a nano-crystal texture has a composition deviated from
the stoichiometric composition, and further, is characterized by
falling under an alloy system capable of forming an amorphous
state. When the composition deviates toward the side of easier
production of precipitate, it is very difficult, upon transition
from amorphous to crystalline state, to contain excessive atoms in
the form of a uniform solid solution. Immediately upon
crystallization, therefore, the crystallized portion becomes a
regular ordered alloy having a stoichiometric composition, and
excessive atoms of elements on the excessive component side, are
released into the amorphous phase. When this exceeds a certain
amount, a thin plate-shaped precipitate is formed, while making
boundaries, thus resulting in nano-crystals. A nano-crystal texture
having an identical orientation is prepared by repeating this
process.
[0019] More specifically, the composition of the alloy-based
nano-crystal texture of the invention deviates toward the side of
easier production of precipitate, preferably by about 1 to 5% from
the stoichiometric composition. In a Ti--Ni alloy, for example,
deviation toward Ti side (Ti excess side) is conceived. Such a
deviation is appropriately determined from the phase diagram of the
alloy. Applicable alloys include, for example, Ti--Ni alloys,
Ti--Co alloys, Ti--Al alloys and Fe--Al alloys. The diameter of a
nano-scale crystal is within a range of from about 10 to 60 nm, and
the diameter of a crystal grain in the conventional sense is within
a range of from about 1 to 10 .mu.m.
[0020] The nano-crystal texture of the invention is produced in the
process of crystallization from an amorphous state. The alloy
should therefore fall under an alloy system capable of achieving an
amorphous state. That is, for example, preparation of a
nano-crystal texture of the invention can be prepared in Ti--Ni,
Ti--Al, Ti--Co and Fe--Al alloy systems and alloy systems showing a
phase diagram similar to those of these alloys, in which the
amorphous states are capable to be produced.
[0021] Production of the nano-crystal texture of the invention is
based on a mechanism in which a regular ordered lattice having a
stoichiometric composition is formed simultaneously with
crystallization, and excessive alloy elements are released as a
precipitate into the interface between the nano-crystal grains and
the amorphous phase. It is therefore necessary that the alloy
system has a composition slightly deviated from the stoichiometric
composition toward easier formation of a precipitate.
[0022] The formation thereof is made possible by heating the
amorphous alloy at a temperature lower than the crystallization
temperature.
[0023] The material provided by the invention is theoretically
expected to have a yield strength about ten times as high even as
compared with a material composed of an extra-fine grain size of 1
to 2 .mu.m, and about 30 times as high as compared with an ordinary
crystal grain size of 20 to 40 .mu.m. In addition, the material of
the invention, composed of nano-crystals with an identical
orientation, can be extended by large amounts and is highly
resistant to rupture.
[0024] Further, the method of the present invention is based on a
subtle combination of the tendency toward ordering and the tendency
of precipitation in the process of crystallization from the
amorphous state. It is therefore very easy to industrialize only if
an appropriate alloy system is available, and to achieve properties
known as the super-metal.
[0025] Now, the present invention will be described further in
detail below by means of examples.
EXAMPLES
[0026] A nano-crystal having a diameter of from 20 to 40 nm was
produced by heating a Ti-48.2 at % Ni alloy in the amorphous state,
of which the composition deviates from the stoichiometric one
toward Ti side (Ti excessive), at a temperature lower by about 50 K
than the crystallization temperature (737 K). The resulting
crystals were confirmed to have formed crystal grains having a
diameter of about 1 to 2 .mu.m. FIG. 1 is a micrograph through an
ordinary electron microscope of crystal grains formed when
annealing at a temperature of 687 K for two hours; and FIG. 2 is an
electron micrograph showing that a crystal grain shown in FIG. 1 is
composed of numerous nano-scale crystals having a diameter of 20 to
40 nm.
[0027] More specifically, FIG. 3 is a high-resolution electron
micrograph of a produced nano-crystal texture when an electron beam
is irradiated in the [111] bcc orientation; and FIG. 4 is an
enlarged view of the box portion in FIG. 3. It is known from the
images of the atomic array and lattice plane that adjacent
nano-crystals are arranged in the same orientation. Further, it is
also known that a small amorphous portion is existent between
adjacent nano-crystals.
[0028] FIG. 5 is a high-resolution electron micrograph of a
produced nano-crystal texture when an electron beam is irradiated
in the [001] bcc orientation; and FIG. 6 is an enlarged view of the
box portion in FIG. 5. Plate-shaped precipitate is confirmed on the
boundary between adjacent nano-crystals. As can be seen in FIG. 6,
the bright portion is precipitate, suggesting that this has a
b.c.t. lattice, and amorphous portions are also observed on the
boundaries.
[0029] FIG. 7 illustrates an atomic arrangement of a precipitate
(b.c.t.) produced on a boundary between adjacent nano-crystals,
which is deduced the structure images such as shown in the upper
left framed region of FIG. 6; and FIGS. 8 to 10 are schematic views
illustrating the process of formation of nano-crystals arranged in
an identical orientation.
[0030] FIG. 8 is as viewed from the [001] bcc orientation, and FIG.
9 is as viewed from the [111] bcc orientation. The shadowed
portions represent precipitates. FIG. 10 three-dimensionally
illustrates the whole view.
[0031] The forming process of nano-crystal will first be described
for FIG. 8 having the [001] orientation. The crystallized portion
(1) grows into a spherical shape. When the diameter reaches 20 to
40 nm, a plate-shaped coherent precipitate is formed on the
interface with the amorphous region(shadowed portions). Then, a new
crystal grain aligned coherently with the precipitate is nucleated
from the interface, and grows into crystal grain(2). Subsequently,
this process is repeated. A Ti--Ni alloy has a high-temperature
phase of body-centered cubic lattice (b.c.c), and the plate-shaped
precipitate is formed on the {100} plane. There are therefore three
variants: in FIG. 8, crystal grain (2) may grow into (3).
Nano-crystal grains thus three-dimensionally grow. FIG. 8 is a view
projected from the [001] orientation, and FIG. 9 is a view
projected from the [111] orientation.
[0032] FIG. 10 three-dimensionally represents such a nano-crystal
texture as a whole: large circles are individual nano-crystal
grains. For easier understanding, however, each nano-crystal grain
is drawn in a form separated from the adjacent nano-crystal grains.
The plate-shaped precipitate, not shown in FIG. 10, is present at a
contact point of adjacent nano-crystal grains.
[0033] It is needless to mention that the present invention is not
limited to the above example. Various nano-crystal textures are
provided.
[0034] According to the present invention, as described above in
detail, a nano-crystal texture composed of nano-crystals arranged
in an identical orientation, which cannot be anticipated by
conventional technology, is provided.
[0035] It is thus possible to manufacture a very tough material at
a low manufacturing cost, and to incorporate properties known as a
super-metal.
* * * * *