U.S. patent application number 10/519255 was filed with the patent office on 2005-10-27 for method of thermo-mechanical-treatment for fe-mn-si shape-memory alloy doped with nbc.
This patent application is currently assigned to National Institute for Materials Science. Invention is credited to Baruj, Alberto, Kajiwara, Setsuo, Kikuchi, Takehiko, Ogawa, Kazuyuki, Shinya, Norio.
Application Number | 20050236077 10/519255 |
Document ID | / |
Family ID | 32588334 |
Filed Date | 2005-10-27 |
United States Patent
Application |
20050236077 |
Kind Code |
A1 |
Kikuchi, Takehiko ; et
al. |
October 27, 2005 |
Method of thermo-mechanical-treatment for fe-mn-si shape-memory
alloy doped with nbc
Abstract
The present invention provides a thermomechanical treatment
means for a Fe--Mn--Si-based shape memory alloy having specified
components with Nb, C addition with simple deformation prior to
aging. Such deformation treatment prior to aging is carried out in
the inventions of the prior applications in a temperature range of
from 500.degree. C. to 800.degree. C. According to the present
invention, however, the deformation treatment prior to the aging
treatment can be successfully carried out not at high temperature
but at room temperature, if the deformation ratio is in a specified
range. The technical meaning of the present invention must be
clearly understood as compared to the prior art and the inventions
of the prior applications because the present invention allows the
treatment at room temperature while the others require troublesome
treatment at high temperature so that there is significant
difference therebetween. That is, according to the present
invention, the remarkable improvement in shape memory property is
achieved first time by a combination of specified alloy components,
specified deformation ratio at room temperature, and setting of
aging condition to a certain range. With the development of the
present invention, it is expected that the use of shape memory
alloys will be accelerated toward the practical use in a wide
variety of fields.
Inventors: |
Kikuchi, Takehiko; (Ibaraki,
JP) ; Kajiwara, Setsuo; (Ibaraki, JP) ; Baruj,
Alberto; (Ibaraki, JP) ; Ogawa, Kazuyuki;
(Ibaraki, JP) ; Shinya, Norio; (Ibaraki,
JP) |
Correspondence
Address: |
WESTERMAN, HATTORI, DANIELS & ADRIAN, LLP
1250 CONNECTICUT AVENUE, NW
SUITE 700
WASHINGTON
DC
20036
US
|
Assignee: |
National Institute for Materials
Science
2-1, Sengen 1-chome
Tsukuba-shi, Ibaraki
JP
305-0047
|
Family ID: |
32588334 |
Appl. No.: |
10/519255 |
Filed: |
December 27, 2004 |
PCT Filed: |
December 17, 2003 |
PCT NO: |
PCT/JP03/16189 |
Current U.S.
Class: |
148/563 |
Current CPC
Class: |
C22C 38/12 20130101;
C21D 2201/01 20130101; C21D 8/005 20130101; C22C 22/00 20130101;
C22C 38/02 20130101; C22F 1/006 20130101; C22C 38/04 20130101 |
Class at
Publication: |
148/563 |
International
Class: |
C21D 008/00 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 18, 2002 |
JP |
2002-367062 |
Claims
1. A thermomechanical treatment method for a Fe--Mn--Si-based shape
memory alloy with Nb, C addition comprising: deforming a
Fe--Mn--Si-based shape memory alloy with Nb, C addition by a
deformation ratio of from 5% to 40% at room temperature, and
subjecting the deformed alloy to aging heating treatment to
precipitate NbC carbides.
2. A thermomechanical treatment method for a Fe--Mn--Si-based shape
memory alloy with Nb, C addition as claimed in claim 1, wherein the
Fe--Mn--Si-based shape memory alloy with Nb, C addition comprises,
as alloy components, Mn: 15% to 40% by weight, Si: 3% to 15% by
weight, Nb: 0.1% to 1.5% by weight, C: 0.01% to 0.2% by weight, and
Fe and inevitable impurities: residual amount, wherein the atomic
ratio Nb/C between Nb and C is 1 or more.
3. A thermomechanical treatment method for a Fe--Mn--Si-based shape
memory alloy with Nb, C addition as claimed in claim 1, wherein the
Fe--Mn--Si-based shape memory alloy with Nb, C addition comprises,
as alloy components, Mn: 15% to 40% by weight, Si: 3% to 15% by
weight, Cr: 1% to 20% by weight, Nb: 0.1% to 1.5% by weight, C:
0.01% to 0.2% by weight, and Fe and inevitable impurities: residual
amount, wherein the atomic ratio Nb/C between Nb and C is 1 or
more.
4. A thermomechanical treatment method for a Fe--Mn--Si-based shape
memory alloy with Nb, C addition as claimed in claim 1, wherein the
Fe--Mn--Si-based shape memory alloy with Nb, C addition comprises,
as alloy components, Mn: 15% to 40% by weight, Si: 3% to 15% by
weight, Cr: 1% to 20% by weight, Ni: 0.1% to 20% by weight, Nb:
0.1% to 1.5% by weight, C: 0.01% to 0.2% by weight, and Fe and
inevitable impurities: residual amount, wherein the atomic ratio
Nb/C between Nb and C is 1 or more.
5. A thermomechanical treatment method for a Fe--Mn--Si-based shape
memory alloy with Nb, C addition as claimed in any one of claims 2
through 4, wherein the atomic ratio between Nb and C is set in a
range of from 1.0 to 1.2.
6. A thermomechanical treatment method for a Fe--Mn--Si-based shape
memory alloy with Nb, C addition as claimed in any one of claims 2
through 4, wherein the Fe--Mn--Si-based shape memory alloy with Nb,
C addition contains, as impurities, Cu: 3% by weight or less, Mo:
2% by weight or less, Al: 10% by weight or less, Co: 30% by weight
or less, and/or N: 5000 ppm or less.
7. A thermomechanical treatment method for a Fe--Mn--Si-based shape
memory alloy with Nb, C addition as claimed in any one of claims 1
through 4, wherein the conditions for the aging heating treatment
are a temperature range of 400.degree. C. to 1000.degree. C. and a
time period from 1 minute to 2 hours.
Description
TECHNICAL FIELD
[0001] The present invention relates to a thermomechanical
treatment method for a Fe--Mn--Si-based shape memory alloy with Nb,
C addition. More particularly, the present invention relates to a
thermomechanical treatment method for a Fe--Mn--Si-based shape
memory alloy with Nb, C addition which exhibits a satisfactory
shape memory effect without undergoing so-called training,
providing improved performance.
BACKGROUND OF THE INVENTION
[0002] It has been a long time since the Fe--Mn--Si-based shape
memory alloys had been proposed and invented. However,
unfortunately, the alloys of Fe--Mn--Si system may be currently in
a situation that the alloys are not sufficiently used yet and not
yet put to practical use. The main cause is that the alloys can not
exhibit satisfactory shape memory effect without undergoing a
special thermomechanical treatment called training.
[0003] Here, the training means a process sequence of repeating the
following treatment several times to improve shape memory effect.
The treatment consists of deforming an alloy by 2-3% at room
temperature and then heating it to around 600.degree. C. higher
than the reverse transformation temperature of the alloy.
[0004] In the face of the situation of prior art in which the
aforementioned troublesome training is indispensable, inventors of
this invention have earnestly studied aiming at developing a
treatment with simple process, especially not requiring the
training. As a result, the inventors have found a fact that if a
small amount of Nb and C elements is applied to a particular shape
memory alloy i.e. a Fe--Mn--Si-based shape memory alloy and a
suitable aging heating treatment is subjected to the alloy to
generate fine NbC carbides in structure of the alloy, a
sufficiently satisfactory shape memory effect is obtained without
undergoing the troublesome treatment called training, and thus
previously filed a patent application (see Patent Document 1). The
inventors have studied also about the thermomechanical treatments
for the alloy with Nb, C addition, and they found a fact that
pre-deformation in a temperature range of from 500.degree. C. to
800.degree. C. and a subsequent aging treatment lead to a further
improved shape memory effect and thus also filed patent
applications about this (see Patent Document 2, Patent Document
3).
[0005] Patent Document 1;
[0006] Japanese Patent Unexamined Publication No. 2001-226747
[0007] Patent Document 2;
[0008] Japanese Patent Unexamined Publication No. 2001-296901
[0009] Patent Document 3;
[0010] Japanese Patent Unexamined Publication No. 2002-79295
[0011] We believe that the inventions proposed in the
aforementioned prior applications facilitate astonishing progress
in the shape memory alloy technology, contribute to put the shape
memory alloy to practical use for the future, and greatly
contribute to the development of industry. However, there are still
some points to be improved in proposed inventions. As for the two
latter prior applications (Patent Document 2, Patent Document 3),
the inventions proposed in these applications are significantly
meaningful because the quite easy treatment process is achieved as
well as further improved shape memory performance of alloy. In
addition, it was recognized that the shape memory performance is
therefore dramatically improved, thus dramatically increasing the
degree of practical use That is, the works and effects of the
inventions of these applications are quite noticeable. However,
there still remains a problem that the treatment process requires a
heating treatment in a high temperature range of from 500.degree.
C. to 800.degree. C., which causes difficulties in most cases. It
is undeniable that this point makes it difficult to put the shape
memory alloys to practical use.
DISCLOSURE OF THE INVENTION
[0012] The object of the present invention is to fundamentally
solve the aforementioned problems.
[0013] The inventors of this invention has earnestly studied aiming
at developing and ensuring good shape memory properties for a shape
memory alloy of specified components even with deformation at low
temperatures. As a result, they found that the satisfactory shape
memory properties can be sufficiently ensured even with deformation
at room temperature so as to achieve the aforementioned object.
[0014] That is, they found amazing fact that the excellent shape
memory property of alloy can be developed just by applying a basic
operation comprising deforming a Fe--Mn--Si-based shape memory
alloy with Nb, C addition at room temperature and then subjecting
the deformed alloy to aging heating treatment to precipitate NbC
carbides. In brief, the aforementioned object is achieved by the
present invention.
[0015] The present invention was made on the basis of the
aforementioned knowledge and success. The solving means to solve
the problems are the followings (1)-(7).
[0016] (1) A thermomechanical treatment method for a
Fe--Mn--Si-based shape memory alloy with Nb, C addition comprising:
deforming a Fe--Mn--Si-based shape memory alloy with Nb, C addition
by a deformation ratio of from 5% to 40% at room temperature, and
subjecting the deformed alloy to aging treatment to precipitate NbC
carbides.
[0017] (2) A thermomechanical treatment method for a
Fe--Mn--Si-based shape memory alloy with Nb, C addition according
to the above (1), wherein the Fe--Mn--Si-based shape memory alloy
with Nb, C addition comprises, as alloy components, Mn: 15% to 40%
by weight, Si: 3% to 15% by weight, Nb: 0.1% to 1.5% by weight, C:
0.01% to 0.2% by weight, and Fe and inevitable impurities: residual
amount, wherein the atomic ratio Nb/C between Nb and C is 1 or
more.
[0018] (3) A thermomechanical treatment method for a
Fe--Mn--Si-based shape memory alloy with Nb, C addition according
to the above (1), wherein the Fe--Mn--Si-based shape memory alloy
with Nb, C addition comprises, as alloy components, Mn: 15% to 40%
by weight, Si: 3% to 15% by weight, Cr: 1% to 20% by weight, Nb:
0.1% to 1.5% by weight, C: 0.01% to 0.2% by weight, and Fe and
inevitable impurities: residual amount, wherein the atomic ratio
Nb/C between Nb and C is 1 or more.
[0019] (4) A thermomechanical treatment method for a
Fe--Mn--Si-based shape memory alloy with Nb, C addition according
to the above (1), wherein the Fe--Mn--Si-based shape memory alloy
with Nb, C addition comprises, as alloy components, Mn: 15% to 40%
by weight, Si: 3% to 15% by weight, Cr: 1% to 20% by weight, Ni:
0.1% to 20% by weight, Nb: 0.1% to 1.5% by weight, C: 0.01% to 0.2%
by weight, and Fe and inevitable impurities: residual amount,
wherein the atomic ratio Nb/C between Nb and C is 1 or more.
[0020] (5) A thermomechanical treatment method for a
Fe--Mn--Si-based shape memory alloy with Nb, C addition according
to any one of the above (2) through (4), wherein the atomic ratio
between Nb and C is set in a range of from 1.0 to 1.2.
[0021] (6) A thermomechanical treatment method for a
Fe--Mn--Si-based shape memory alloy with Nb, C addition according
to any one of the above (2) through (5), wherein the
Fe--Mn--Si-based shape memory alloy with Nb, C addition contains,
as impurities, Cu: 3% by weight or less, Mo: 2% by weight or less,
Al: 10% by weight or less, Co: 30% by weight or less, and/or N:
5000 ppm or less.
[0022] (7) A thermomechanical treatment method for a
Fe--Mn--Si-based shape memory alloy with Nb, C addition according
to any one of the above (1) through (6), wherein the conditions for
the aging treatment are a temperature range of 400.degree. C. to
1000.degree. C. and an aging time from 1 minute to 2 hours.
EFFECT OF THE INVENTION
[0023] As a thermomechanical treatment for a Fe--Mn--Si-based shape
memory alloy having specified components with Nb, C addition,
conventionally, the processing treatment prior to aging is carried
out by training. Alternatively, in the inventions of the prior
applications, the processing treatment prior to aging is carried
out in a temperature range of from 500.degree. C. to 800.degree. C.
According to the present invention, however, the processing
treatment prior to the aging treatment can be successfully carried
out without high temperature, i.e. at room temperature, by setting
a processing ratio in a specified range.
[0024] The technical meaning of the present invention must be
clearly understood as compared to the prior art and the inventions
of the prior applications on which the present invention is based
because there are obvious difference therebetween. That is,
according to the present invention, the remarkable improvement in
shape memory property is achieved first time by a combination of
specified alloy components, specified deformation ratio at room
temperature, and setting of aging condition to a certain range.
Amazingly by run-of-the-mill thermomechanical treatment comprising
a deformation at room temperature and then aging, the shape
recovery ratio equivalent to that of the sample subjected to the
training can be obtained and, in addition, the shape recovery
stress significantly larger than that of the sample subjected to
the training can be obtained. With development of the present
invention, it is expected that the use of shape memory alloys will
be accelerated toward the practical use in a wide variety of
fields.
BRIEF DESCRIPTION OF THE DRAWINGS
[0025] FIG. 1 is a diagram showing relations between the amount of
initial deformation and the shape recovery ratio depending on the
thermomechanical treatment of Fe--Mn--Si-based shape memory alloys
with Nb, C addition of the present invention; and
[0026] FIG. 2 is a diagram showing the relation between the
recovered shape strain and shape recovery stress depending on the
thermomechanical treatment of Fe--Mn--Si-based shape memory alloys
with Nb, C addition of the present invention.
BEST MODE FOR CARRYING OUT THE INVENTION
[0027] The reason why the deformation ratio at room temperature is
specified to be from 5% to 40% comes from the fact that the
deformation ratio lower than 5% does not effectively contribute to
improvement in shape memory property while the deformation ratio
over 40% makes a sample too hard so that it is extremely difficult
to deform the sample after subjected to an aging treatment.
[0028] An alloy as to be subjected to the thermomechanical
treatment method for a Fe--Mn--Si-based shape memory alloy with Nb,
C addition of the present invention has the following chemical
compositions, just as specified in the prior applications, 1) Mn:
15% to 40% by weight, Si: 3% to 15% by weight, Nb: 0.1% to 1.5% by
weight, C: 0.01% to 0.2% by weight, and Fe and inevitable
impurities: residual amount, wherein the atomic ratio Nb/C between
Nb and C is 1 or more;
[0029] 2) The Fe--Mn--Si-based shape memory alloy with Nb, C
addition has the following compositions Mn: 15% to 40% by weight,
Si: 3% to 15% by weight, Cr: 1% to 20% by weight, Nb: 0.1% to 1.5%
by weight, C: 0.01% to 0.2% by weight, and Fe and inevitable
impurities: residual amount, wherein the atomic ratio Nb/C between
Nb and C is 1 or more; has the following compositions Mn: 15% to
40% by weight, Si: 3% to 15% by weight, Cr: 1% to 20% by weight,
Ni: 0.1% to 20% by weight, Nb: 0.1% to 1.5% by weight, C: 0.01% to
0.2% by weight, and Fe and inevitable impurities: residual amount,
wherein the atomic ratio Nb/C between Nb and C is 1 or more.
[0030] In either of the Fe--Mn--Si-based shape memory alloys with
Nb, C addition, the atomic ratio Nb/C between Nb and C in the alloy
is preferably from 1.0 to 1.2.
[0031] Further, the alloy as to be subjected to a thermomechanical
treatment method for the Fe--Mn--Si-based shape memory alloy of the
present invention is permitted to contain, as impurities, one or
more of a group consisting of Cu of 3% by weight or less, Mo of 2%
by weight or less, Al of 10% by weight or less, Co of 30% by weight
or less, and N of 5000 ppm or less.
EMBODIMENTS OF THE INVENTION
[0032] Hereinafter, the invention will be specifically described on
the basis of FIG. 1 and FIG. 2. It should be noted that examples
shown in the drawings are for the purpose of disclosure for helping
the easy understanding of the present invention and are not
intended to limit the scope of the present invention.
EXAMPLES
[0033] First, a Fe-28Mn-6Si-5Cr-0.53Nb-0.06C alloy (% by weight)
with Nb, C addition of the present invention was prepared by
melting. How the shape memory property is improved by rolling at
room temperature and then subjecting it to an aging treatment in a
temperature range of 400.degree. C. to 1000.degree. C. for a time
period from 1 minute to 2 hours, is shown below.
[0034] FIG. 1 is a graph showing differences in shape recovery
ratio among a case in which only aging was conducted (0% rolling)
and cases in which aging was conducted after rolling by 10%, 20%
and 30% at room temperature. In all of the cases, the aging
treatment was conducted at 800.degree. C. for 10 minutes. For
comparison, results of samples of the Fe-28Mn-6Si-5Cr alloy with no
Nb, C addition prepared only by annealing and samples of the alloy
prepared after subjected to the training five times are shown. The
abscissa shows the initial strain (%) by tensile deformation at
room temperature, and the ordinate shows the recovery ratio of
strain when the sample is heated to 600.degree. C. When heated to
400.degree. C., approximately the same shape recovery ratio is also
obtained. The samples used in tests were test pieces having a
thickness of 0.6 mm, a width of 1 to 4 mm, and a length (gage
length) of 15 mm.
[0035] As is known from this figure, the sample rolled by 10% has
shape memory recovery ratios nearly equivalent to or slightly lower
than those of the alloy with no Nb, C addition which was subjected
to training five times. Practically the necessary initial strain is
believed to be about 4%. A shape memory recovery ratio of about 90%
shown at this strain strongly suggests that it is used as a
practically applicable alloy. Training of at least five times is
necessary for obtaining the same shape recovery ratio as this
sample, with a conventional Fe--Mn--Si-based shape memory alloy
with no Nb, C addition. As is understood from this, the present
invention exhibits shape memory properties with a simple
method.
[0036] The sample with a higher rolling ratio of 20% has shape
memory recovery ratios nearly equivalent to or slightly higher than
those of the case without rolling (only aged). However, the sample
with a further higher rolling ratio of 30% has shape memory
recovery ratios lower than those of the case which was only aged in
a range with large initial strain.
[0037] On the other hand, as for shape recovery stress which is one
of the important shape memory properties for practical use, the
shape recovery stresses of samples aged after rolling by 20% and
30% are remarkably improved. FIG. 2 is a graph showing the degrees
of improvement in shape recovery stress of these samples, in
comparison with the case in which only aging was conducted (0%
rolling) and a case in which the aging was conducted after rolling
by 10%. The recovery stress when recovered strain on the abscissa
is zero means the stress generated when a sample is
tensile-deformed at room temperature, then, heated to the reverse
transformation temperature or more in a state that the both ends of
the sample are fixed without any recovery, and returned to room
temperature again. The recovery stress at recovered strain of 2%,
for example, means the stress generated in case that the both ends
of the sample are fixed after a recovery of strain by 2%. Tests
were conducted with the initial strain given at room temperature of
from 4% to 6%.
[0038] The test pieces used were the same as those used for
obtaining the results shown in FIG. 1. The recovered strain on the
abscissa in FIG. 2 is explained, taking a case where a shape memory
alloy is used as a coupling for examples. It is equivalent to the
ratio (%) of clearance between the pipes and the coupling part
(shape memory alloy) to the diameter. Remarkable increase in shape
recovery stress is observed in a range of high rolling ratio: a
shape recovery stress of 310 MPa is obtained at the recovered
strain of 0% when the rolling ratio is from 20% to 30% at room
temperature and a shape recovery stress of 200 MPa is obtained even
at the recovered strain of 2% for the same rolling ratio. It is
also found that the same shape recovery stress as the case
subjected to training is obtained even in a case that the rolling
ratio is 10%.
[0039] That is, as is known from the results of this figure (FIG.
2), remarkable increase in shape recovery stress is observed in
cases of high rolling ratios (20%, 30%) as compared to the cases of
a rolling ratio of 0% and a rolling ratio of 10%. For the sake of
comparison, FIG. 2 shows shape recovery stresss of the sample with
no Nb, C addition and the sample subjected to the training five
times. It is seem from this figure that the recovery stresses of
these samples are much smaller than those of the present
invention.
[0040] As described above, the present invention was made by
finding that the deformation treatment prior to the aging treatment
to a Fe--Mn--Si-based shape memory alloy having specified
components with Nb, C addition can be successfully carried out at
room temperature if the deformation ratio is in a specified range.
The technical meaning of the present invention must be clearly
understood because there are obvious advantages as compared to a
conventional one which requires the training accompanied by
troublesome operation and the inventions of the prior applications
which still require high-temperature deformation in a range of from
500.degree. C. to 800.degree. C.
[0041] That is, according to the present invention, the remarkable
improvement in shape memory property is achieved first time by a
combination of specified alloy components, specified deformation
ratio at room temperature, and setting of aging condition to a
certain range. Amazingly by run-of-the-mill thermomechanical
treatment comprising a deformation at room temperature and then
aging, the shape recovery ratio equivalent to that of the sample
subjected to the training can be obtained and, in addition, the
shape recovery stress significantly larger than that of the sample
subjected to the training can be obtained. Anyway, the meaning of
the present invention is significant. The shape memory alloy
according to the present invention can be used as tightening
materials for various applications, for example, for tightening
water pipes, tightening oil pipes, etc., which will produce great
economic effects.
[0042] It should be noted that the applications as tightening
materials mentioned above are just examples and the present
invention is not limited to such applications. With the development
of the present invention, it is expected that the shape memory
alloy will be put to practical use for various applications in a
wide variety of fields.
INDUSTRIAL APPLICABILITY
[0043] The present invention provides a thermomechanical treatment
means for a Fe--Mn--Si-based shape memory alloy having specified
components with Nb, C addition with simple processing treatment
prior to aging. Conventionally, the processing treatment prior to
aging is carried out by training. Alternatively, in the inventions
of the prior applications, the processing treatment prior to aging
is carried out in a temperature range of from 500.degree. C. to
800.degree. C. According to the present invention, however, the
processing treatment prior to the aging treatment can be
successfully carried out without high temperature, i.e. at room
temperature, if using a processing ratio in a specified range.
[0044] The technical meaning of the present invention must be
clearly understood as compared to the prior art and the inventions
of the prior applications because there are obvious difference
therebetween. That is, according to the present invention, the
remarkable improvement in shape memory property is achieved first
time by a combination of specified alloy components, specified
processing ratio at room temperature, and setting of aging
condition into a certain range.
[0045] The technical meaning of the present invention must be
clearly understood as compared to the prior art and the inventions
of the prior applications because there are obvious difference
therebetween. That is, according to the present invention, the
remarkable improvement in shape memory property is achieved first
time by a combination of specified alloy components, specified
deformation ratio at room temperature, and setting of aging
condition to a certain range. Amazingly by run-of-the-mill
thermomechanical treatment comprising a deformation at room
temperature and then aging, the shape recovery ratio equivalent to
that of the sample subjected to the training can be obtained and,
in addition, the shape recovery stress significantly larger than
that of the sample subjected to the training can be obtained. With
development of the present invention, it is expected that the use
of shape memory alloys will be accelerated toward the practical use
in a wide variety of fields.
* * * * *