U.S. patent application number 11/216485 was filed with the patent office on 2007-03-01 for ti-based shape memory alloy article.
Invention is credited to Takashi Maeshima, Minoru Nishida, Hiroaki Uchiyama, Kiyoshi Yamauchi.
Application Number | 20070044868 11/216485 |
Document ID | / |
Family ID | 37802378 |
Filed Date | 2007-03-01 |
United States Patent
Application |
20070044868 |
Kind Code |
A1 |
Yamauchi; Kiyoshi ; et
al. |
March 1, 2007 |
Ti-based shape memory alloy article
Abstract
An article of Ti-based shape memory alloy is made of a Ti-based
alloy containing, by atomic percentage, 4 to 10 at % Mo, at least
one of 3 to 10 at % Sn and 1 to 10 at % Sc, and the balance Ti and
unavoidable impurities, or a Ti-based alloy containing 15 to 30 at
% Nb, 1 or more at % Sc, and the balance Ti and unavoidable
impurities.
Inventors: |
Yamauchi; Kiyoshi;
(Sendai-shi, JP) ; Uchiyama; Hiroaki; (Sendai-shi,
JP) ; Nishida; Minoru; (Kumamoto-shi, JP) ;
Maeshima; Takashi; (Kumamoto-shi, JP) |
Correspondence
Address: |
Bradley N. Ruben, PC
Suite 5A
463 First St.
Hoboken
NJ
07030-1859
US
|
Family ID: |
37802378 |
Appl. No.: |
11/216485 |
Filed: |
August 31, 2005 |
Current U.S.
Class: |
148/402 ;
420/417; 420/421 |
Current CPC
Class: |
C22C 14/00 20130101 |
Class at
Publication: |
148/402 ;
420/417; 420/421 |
International
Class: |
C22C 14/00 20060101
C22C014/00 |
Claims
1. An article of Ti-based shape memory alloy comprising a Ti-based
alloy which has a composition containing 4 to 10 at % Mo, at least
one of 3 to 10 at % Sn and 1 to 10 at % Sc, and the balance Ti and
unavoidable impurities.
2. An article according to claim 1, wherein said Ti-based alloy
contains 4 to 10 at % Mo, 3 to 10 at % Sn, and the balance Ti and
unavoidable impurities and has been subjected to an aging treatment
at a temperature of 500.degree. C. or more after a heat treatment
at a .beta.-transformation temperature or more.
3. An article according to claim 1, wherein said Ti-based alloy
contains 4 to 10 at % Mo, 1 to 10 at % Sc, and the balance Ti and
unavoidable impurities and has been subjected to an aging treatment
at a temperature of 150.degree. C. or more after a heat treatment
at a .beta.-transformation temperature or more.
4. An article according to claim 1, wherein said Ti-based shape
memory alloy article is used at at least a human body
temperature.
5. An article according to claim 1, wherein said Ti-based shape
memory alloy article has one of a plate shape, a tubular shape, and
a linear shape including a bar shape.
6. An article according to claim 1, wherein said Ti-based shape
memory alloy article has one of a shape memory function and a
superelasticity function.
7. A medical material or a medical instrument comprising the
article according to claim 1.
8. A consumer article comprising the article according to claim 1
which forms part or the whole of one of a golf club, eye glasss,
and a timepiece.
9. An article according to claim 1, wherein said Ti-based shape
memory alloy article is one of a heat exchanger, a heat insulator,
and a vibration suppressor.
10. An article of Ti-based shape memory alloy comprising a Ti-based
alloy having a composition containing 15 to 30 at % Nb, 1 or more
at % Sc, and the balance Ti and unavoidable impurities.
11. An article according to claim 10, wherein said Ti-based alloy
has been subjected to an aging treatment at a temperature of
500.degree. C. or more after a heat treatment at a
.beta.-transformation temperature or more.
12. An article according to claim 10, wherein said Ti-based shape
memory alloy article is used at at least a human body
temperature.
13. An article according to claim 10, wherein said Ti-based shape
memory alloy article has one of a plate shape, a tubular shape, and
a linear shape including a bar shape.
14. An article according to claim 10, wherein said Ti-based shape
memory alloy article has one of a shape memory function and a
superelasticity function.
15. A medical material or a medical instrument comprising the
article according to claim 10.
16. A consumer article comprising the article according to claim 10
which forms part or the whole of one of a golf club, eye glasss,
and a timepiece.
17. An article according to claim 10, wherein said Ti-based shape
memory alloy article is one of a heat exchanger, a heat insulator,
and a vibration suppressor.
Description
[0001] This application claims priority to prior Japanese patent
application JP 2004-93567, the disclosure of which is incorporated
herein by reference.
BACKGROUND OF THE INVENTION
[0002] This invention relates to a Ni-free shape memory alloy
material and, in particular, relates to a Ti-based shape memory
alloy article suitable as a biomaterial that is temporarily or
permanently used at every possible portion of a human body.
[0003] It is well known that Ti--Ni based shape memory alloys
exhibit a remarkable shape memory effect and superelasticity
following reverse transformation of the martensitic transformation.
Shape memory alloy articles made of those alloys are used in the
following applications.
[0004] For example, in the shape memory effect application, the
shape memory alloy articles are used as thermal actuators of air
conditioners, microwave ovens, and so on. In the superelasticity
application, the shape memory alloy articles are widely used as
medical supplies like catheter guide wires, stents, and so on and
as daily goods like eye glass frames, bracelets, and so on.
However, in view of concerns about occurrence of a problem of metal
allergy or cytotoxicity which would be otherwise caused by direct
contact between Ni and a human body, the Ti--Ni alloy is coated
with a resin or the like in the relevant application.
[0005] In recent years, studies have been made on Ti-based alloys
free of Ni and made of elements that do not cause metal
allergy.
[0006] For example, Japanese Unexamined Patent Application
Publication (JP-A) S53-123323 (hereinafter referred to as Patent
Document 1) discloses a corrosion-resistant titanium alloy
containing, by weight, 1 to 2 wt % Ag (silver) in a .beta.-Ti
alloy.
[0007] Japanese Unexamined Patent Application Publication (JP-A)
H01-129941 (hereinafter referred to as Patent Document 2) discloses
a cold-working low-strength high-ductility Ti alloy containing 6 wt
%.ltoreq.Mo (molybdenum).ltoreq.18 wt %, 0.5 wt
%.ltoreq.Sn.ltoreq.10 wt %, and the balance Ti.
[0008] Further, Japanese Unexamined PatentApplication Publication
(JP-A) H04-214830 (Japanese Patent (JP-B) No. 2936754; hereinafter
referred to as Patent Document 3) discloses a Ti alloy similar to
that in Patent Document 2.
[0009] On the other hand, Japanese Unexamined Patent Application
Publication (JP-A) S59-56554 (corresponding to Japanese Examined
Patent Application Publication (JP-B) S59-35978); hereinafter
referred to as Patent Document 4) discloses a shape memory titanium
alloy containing 10 to 15 wt % Mo in titanium.
[0010] However, in Patent Document 1, although an improvement in
corrosion resistance in several kinds of .beta.-Ti alloys is
confirmed as specific examples, the corrosion resistance of all
.beta.-Ti alloys is not necessarily improved and there is no
description at all about springiness.
[0011] In Patent Document 2, although a high-workability
low-strength alloy is introduced, there is no description about
springiness.
[0012] In Patent Document 3, an alloy with further improved
workability is discussed and whereupon description is given of an
alloy containing 0.5 to 6 wt % Sn, which, however, is merely a
low-strength alloy with improved workability and does not
necessarily have springiness.
[0013] Further, in Patent Document 4, although a stress-induced
martensite .alpha.-stabilized by addition of Al, being an alloy
having the shape memory properties, exhibits the shape memory
properties, there is no description at all about springiness.
Particularly, any of Patent Documents 1 to 4 gives no consideration
to adaptability to the human body.
[0014] In view of this, for the purpose of providing high-strength
Ti-based alloy spring materials having less indication of toxicity
and allergenicity and being human body alloys excellent in
workability and biocompatibility, the present inventors have
proposed a Ti--Mo based alloy spring (JP-A 2004-183014) and a
Ti--Sc based shape memory alloy (JP-A 2004-204245).
SUMMARY OF THE INVENTION
[0015] It is an object of this invention to further extract
compositions and production conditions capable of achieving a shape
memory effect and compositions and production conditions capable of
achieving superelasticity to thereby provide practical shape memory
alloy articles.
[0016] According to this invention, there are obtained Ti-based
shape memory alloy articles made of alloys having the following
compositions.
[0017] According to one aspect of the present invnetion, there is
provided an article of Ti-based shape memory alloy which comprises
a Ti-based alloy having a composition containing 4 to 10 at % Mo,
at least one of 3 to 10 at % Sn and 1 to 10 at % Sc, and the
balance Ti and unavoidable impurities.
[0018] According to another aspect of the present invention an
article of Ti-based shape memory alloy which comprises a Ti-based
alloy having a composition containing 15 to 30 at % Nb, 1 or more
at % Sc, and the balance Ti and unavoidable impurities.
BRIEF DESCRIPTION OF THE DRAWINGS
[0019] FIG. 1 is photographs of metallurgical structures for
showing the results of shape memory property evaluation of
Ti-5Mo-(3-6)Sn (at %) alloys after a treatment at 1000.degree.
C.;
[0020] FIG. 2 is a diagram showing a relationship between aging
temperature and material hardness of the Ti-5Mo-5Sn alloy;
[0021] FIG. 3 is photographs of metallurgical structures for
showing the results of property evaluation of Ti-5Mo-(4,5)Sn alloy
aging-treatment materials at 600.degree. C. at 5 minutes;
[0022] FIG. 4 is a diagram showing the results of shape recovery
property evaluation of Ti-6Mo--Sc alloys following a change in Sc
concentration;
[0023] FIG. 5 is a diagram showing the influence of aging
conditions exerted on the material hardness of a Ti--Mo-7Sc
alloy;
[0024] FIG. 6 is photographs of metallurgical structures for
showing the results of property evaluation of Ti-6Sc-(18-24)Nb (at
%) alloys after a .beta.-transformation treatment;
[0025] FIG. 7 is photographs of metallurgical structures for
showing the results of property evaluation of a Ti-6Sc-26Nb alloy
aging-treatment material at 600.degree. C. at various times;
and
[0026] FIG. 8 is a diagram showing the influence of aging
conditions exerted on the material hardness of a Ti-6Sc-26Nb
alloy.
DESCRIPTION OF THE PREFERRED EMBODIMENT
[0027] At first, description will be given of compositions of
alloys used in shape memory alloy articles of this invention and
the reason for limiting aging conditions.
[0028] One shape memory alloy article of this invention comprises a
Ti--Mo--(Sn, Sc) based alloy. In this invention, the content of Mo
is set to 4 to 10, atomic percent, at %. This is because when it is
less than 4 at %, .beta.-stabilization is not sufficiently achieved
to thereby cause degradation in workability and properties, while,
when it exceeds 10 at %, it becomes difficult to obtain sufficient
shape memory properties. The content of Sn or Sc is also set in a
range where the effect of addition thereof is significant.
Particularly, since Sc is extremely expensive, the content of Sc is
limited to the range where the effect thereof is sufficient.
Further, the limitation on the aging conditions is for setting
conditions that do not affect an increase in hardness.
[0029] Further, this alloy can contain not only addition of Sn or
Sc outside the limited range, but also several at % of another
.beta.-stabilizing element, such as Nb, Hf, and the like or another
a-stabilizing element, such as Ag, Al, and the like.
[0030] Another shape memory alloy article of this invention
comprises a Ti--Nb--Sc based alloy. In this invention, the content
of Nb is set to 15 to 30 at %. This is because when it is less than
15 at % or exceeds 30 at %, it becomes difficult to obtain
sufficient shape memory properties. The content of Sc is also set
in a range where the effect of addition thereof is significant. The
limitation on the aging conditions is, as described above, for
setting conditions that do not affect an increase in hardness.
[0031] Further, this alloy can contain several at % of another
.beta.-stabilizing element, such as Mo, Hf, and the like or another
.alpha.-stabilizing element, such as Sn, Ag, Al, and the like.
[0032] According to each of such Ti-based alloys of this invention,
there is obtained a shape memory alloy article having a recovery
strain of at least 2% and, by performing aging after a heat
treatment at or above a .beta.-transformation temperature, there is
obtained a shape memory element having a shape memory effect of a
3% or more recovery strain or a 2% or more superelasticity.
[0033] The shape memory alloy articles of this invention each have
a shape of a plate, a wire rod (linear shape) including a bar, a
tube, or the like and can be not only applied to Ni-free
biomaterials but also widely applied to eye glass frames, golf
supplies, and so on.
[0034] In this invention, medical materials and medical instruments
represent part or the whole of all metal articles that are buried
or brought into contact with human bodies temporarily or over the
long term.
[0035] In this invention, as shape memory articles each using a
shape memory alloy wire rod, there are catheters, guide wires for
use in catheters and so on, endoscopes, stents, orthodontic
appliances, scrub lines, bone joining wires, clips, and so on,
while, as plate-like or bar-like shape memory elements, there are
bone plates, artificial sphincters, fixing screws, artificial
bones, and so on. This invention, however, is not limited
thereto.
[0036] On the other hand, as consumer products, they can be used as
part or the whole of golf clubs, eye glasss, and timepieces, heat
exchangers, heat insulators, vibration suppressors, and so on. With
respect to the golf club, they can be used as a shaft, a crown, a
face, and so on. With respect to the timepiece, they can be used as
the whole thereof, a band piece, a pin, a case, and so on.
[0037] This invention will be described in further detail.
[0038] In this invention, attention is paid to alloys excellent in
biocompatibility and therefore use is made of Ti-based alloys each
containing at least two kinds of Mo, Sn, Nb, and Sc with no
indication of toxicity or allergenicity while excluding V, Ni, and
Co with indication of toxicity.
[0039] This invention provides Ti-based alloys each having a
crystal structure equivalent to a .beta.-Ti alloy and having a
shape memory effect or superelasticity.
[0040] Therefore, the Ti-based alloys aimed at by this invention
are each a .beta.-Ti alloy or a near .beta.-Ti alloy that is
excellent in workability among titanium alloys.
[0041] That is, in this invention, as elements contained in the
Ti-based alloy, selection is made of Mo, Sn, Nb, and Sc that are
elements with no indication of toxicity and excellent in
biocompatibility.
[0042] (1) Alloy Production
[0043] At first, selection was made of alloy compositions that
could be .beta.-type or near .beta.-type as shown in Tables 1 and 2
and alloys were produced by argon-arc melting. The melting was
performed in an argon atmosphere in an arc melting furnace using a
water-cooled copper hearth and non-consumable tungsten electrodes.
In order to reduce segregation of alloy components, ingots of the
alloys were turned upside down and subjected to melting and
freezing six times.
[0044] The produced ingots were subjected to a homogenizing
treatment in a vacuum atmosphere at 1000.degree. C. for 24 hours
and then to furnace cooling. TABLE-US-00001 TABLE 1 Shape Memory
Properties of Ti--Mo--(Sn, Sc) Alloys Shape Memory Properties
.beta.-phased at % Work- Cold Treat- No. Ti Mo Sn Sc ability
Working ment Examples 1 bal. 4 5 -- .DELTA. .largecircle.
.largecircle. 2 bal. 5 3 -- .DELTA. .largecircle. .largecircle. 3
bal. 5 4 -- .largecircle. .largecircle. .largecircle. 4 bal. 5 5 --
.largecircle. .largecircle. .largecircle. 5 bal. 5 10 --
.largecircle. .largecircle. .largecircle. 6 bal. 10 -- 5
.largecircle. .largecircle. .largecircle. 7 bal. 4 -- 5
.largecircle. .largecircle. .largecircle. 8 bal. 6 -- 2
.largecircle. .largecircle. .largecircle. 9 bal. 6 -- 7
.largecircle. .largecircle. .largecircle. 10 bal. 6 -- 10
.largecircle. .largecircle. .largecircle. 11 bal. 10 -- 5
.largecircle. .largecircle. .largecircle. 12 bal. 5 5 1
.largecircle. .largecircle. .largecircle. 13 bal. 6 1 5
.largecircle. .largecircle. .largecircle. Compara- 14 bal. 3 5 -- X
.largecircle. .largecircle. tive 15 bal. 15 5 -- .largecircle. X X
Examples 16 bal. 5 2 -- .largecircle. X X 17 bal. 5 15 --
.largecircle. X X 18 bal. 3 -- 5 .largecircle. X X 19 bal. 15 -- 5
.largecircle. X X 20 bal. 5 -- 0.5 .largecircle. X X bal.: balance
--: 0 at %
[0045] TABLE-US-00002 TABLE 2 Shape Memory Properties of Ti--Nb--Sc
Alloys Shape Memory Properties at % Work- Cold .beta.-phased No. Ti
Nb Sc ability Working Treatment Examples 21 bal. 15 3 .DELTA.
.largecircle. .largecircle. 22 bal. 18 2 .DELTA. .largecircle.
.largecircle. 23 bal. 18 1 .largecircle. .largecircle.
.largecircle. 24 bal. 18 4 .largecircle. .largecircle.
.largecircle. 25 bal. 18 8 .largecircle. .largecircle.
.largecircle. 26 bal. 18 10 .largecircle. .largecircle.
.largecircle. 27 bal. 18 6 .largecircle. .largecircle.
.largecircle. 28 bal. 20 6 .largecircle. .largecircle.
.largecircle. 29 bal. 22 6 .largecircle. .largecircle.
.largecircle. 30 bal. 24 6 .largecircle. .largecircle.
.largecircle. 31 bal. 26 6 .largecircle. .largecircle.
.largecircle. 32 bal. 30 6 .largecircle. .largecircle.
.largecircle. Compara- 33 bal. 10 6 .largecircle. X X tive 34 bal.
35 6 .largecircle. X X Examples 35 bal. 18 0.5 .largecircle. X X
bal.: balance
[0046] (2) Sample Production
[0047] Subsequently, plates each having a thickness of 2 to 3 mm
were cut from the homogenized ingots and then cold-rolled to 0.3 to
0.5 mm. Thereafter, part of each sample was subjected to a heat
treatment at 1000.degree. C. for one hour and then quenched in an
ice brine so as to be subjected to a .beta. single-phase
transformation treatment. Although the cold rolling was carried
out, it may be replaced with hot rolling, hot rolling and then cold
rolling, or repetition of hot rolling and cold rolling.
[0048] (3) Shape Memory Property Evaluation
[0049] Property evaluation was conducted on the basis of a simple
bending test using the foregoing test pieces. At first, each of the
plates having the thickness of 0.3 to 0.5 mm was wound round a
cylinder with a radius of 3 to 4 mm. In this event, a strain of
about 4 to 5% was applied. Thereafter, unwinding and lighter
heating were carried out. The shape memory properties were
evaluated according to the total amount of a springback
(superelasticity) after the unwinding and a residual strain
cancellation (shape memory effect) caused by the heating, wherein a
recovery amount of 2% or more was evaluated as good (identified by
O in Tables) while a recovery amount of 1 to 2% was evaluated as
normal (identified by .DELTA. in Tables).
[0050] (4) Aging Property Evaluation
[0051] The samples in Tables 1 and 2 having been subjected to the
.beta.-transformation treatment at 1000.degree. C. were each
subjected to an aging treatment at 100.degree. C. to 700.degree. C.
for 5 minutes, thereby evaluating the shape memory properties
thereof. The evaluation was conducted like in the foregoing manner.
Some of the results are shown in Table 3. TABLE-US-00003 TABLE 3
Shape Memory Properties of Ti--(Mo, Nb)--(Sn, Sc) Alloy Shape
Memory Properties 100.degree. 150.degree. 200.degree. 400.degree.
500.degree. 600.degree. 700.degree. No. Alloy C. C. C. C. C. C. C.
3 Ti--5Mo--4Sn X X X X .largecircle. .largecircle. .DELTA. 4
Ti--5Mo--5Sn X X X X .largecircle. .largecircle. .DELTA. 9
Ti--6Mo--7Sc X .largecircle. .largecircle. .largecircle.
.largecircle. .largecircle. .DELTA. 31 Ti--26Nb--6Sc X
.largecircle. .largecircle. .largecircle. .largecircle.
.largecircle. .DELTA.
[0052] (5) Shape Memory Effect and Superelasticity
[0053] At first, description will be given with respect to
Ti--Mo--Sn based alloys.
[0054] FIG. 1 shows the results of property evaluation of the
Ti-5Mo-(3-6)Sn (at %) alloys after the treatment at 1000.degree.
C., where .epsilon..sub.d represents a deformation strain,
.epsilon..sub.s a residual strain after the springback
(superelasticity), and .epsilon..sub.r a residual strain after the
heating (shape memory effect), respectively. In addition, a
standard temperature which will be hereinafter referred to as
"S.T.".
[0055] From the results shown in FIG. 1, it is understood that the
alloy with lower content of Sn tends to exhibit the shape memory
effect, that the superelasticity becomes maximum at 5Sn, and that
both properties are degraded at 6Sn.
[0056] In the case of Mo, the low content of Mo cannot sufficiently
achieve .beta.-stabilization of the alloy and induces generation of
an .omega. phase in the solution treatment or the aging treatment
to thereby cause difficulty in workability. On the other hand, the
high content of Mo can sufficiently achieve .beta.-stabilization of
the alloy, but it becomes difficult to hold a shape memory property
of 2% or more.
[0057] FIG. 2 shows a relationship between aging temperature and
material hardness of the Ti-5Mo-5Sn alloy. From FIG. 2, it is
understood that, in the case of holding for 5 minutes (300 seconds)
where the aging effect is easily achievable, a significant increase
in hardness is observed when the temperature is less than
500.degree. C., thereby causing degradation in properties.
[0058] FIG. 3 shows, at (a) and (b), the results of property
evaluation of the Ti-5Mo4Sn alloy aging-treatment material and the
Ti-5Mo-5Sn alloy aging-treatment material at 600.degree. C. at 5
minutes, respectively. From FIG. 3, it is understood that there is
observed significant property change and improvement caused by the
aging.
[0059] Now, description will be given with respect to Ti--Mo--Sc
based alloys.
[0060] FIG. 4 shows the shape recovery properties of the Ti-6Mo--Sc
alloys following a change in Sc concentration. From FIG. 4, it is
understood that the addition effect of Sc is small when Sc is 1 at
% or less, while the addition of Sc exceeding 8 at % impedes the
properties.
[0061] FIG. 5 shows the influence of aging conditions exerted on
the material hardness of the Ti--Mo-7Sc alloy. It is understood
that, as different from the foregoing case of FIG. 2, an increase
in hardness is not observed even at 200.degree. C. and therefore
wide condition setting is enabled.
[0062] Now, description will be given with respect to Ti--Nb--Sc
based alloys.
[0063] FIG. 6 shows the results of property evaluation of the
Ti-6Sc-(18-24)Nb (at %) alloys after the .beta.-transformation
treatment. From FIG. 6, it is understood that the alloy with lower
content of Nb tends to exhibit the shape memory effect.
[0064] FIG. 7 shows the results of an aging treatment of the
Ti-6Sc-26Nb alloy at 600.degree. C. for 7 minutes. From FIG. 7, it
is understood that the superelasticity properties are improved by
the aging.
[0065] FIG. 8 shows the influence of aging conditions exerted on
the material hardness of the Ti-6Sc-26Nb alloy. It is understood
that, like in the foregoing case of FIG. 2, a significant increase
in hardness is observed at less than 500.degree. C.
[0066] In the foregoing examples of this invention, the description
has been given of the plate-like shape memory alloy articles.
However, this invention is not limited to the plate shape but can
be modified in various ways depending on the purpose and use. For
example, this invention is also applicable to wire rods including
bars, tubes, and so on.
* * * * *