U.S. patent application number 14/945820 was filed with the patent office on 2016-05-26 for titanium-aluminum-based alloy.
This patent application is currently assigned to KOREA INSTITUTE OF MACHINERY & MATERIALS. The applicant listed for this patent is KOREA INSTITUTE OF MACHINERY & MATERIALS. Invention is credited to Jae Keun HONG, Seong Woong KIM, Seung Eon KIM, Young Sang NA.
Application Number | 20160145721 14/945820 |
Document ID | / |
Family ID | 55918050 |
Filed Date | 2016-05-26 |
United States Patent
Application |
20160145721 |
Kind Code |
A1 |
KIM; Seong Woong ; et
al. |
May 26, 2016 |
TITANIUM-ALUMINUM-BASED ALLOY
Abstract
The present invention relates to A titanium-aluminum-based alloy
comprising: 40 to 46 at % of aluminum (Al); 3 to 6 at % of niobium
(Nb); 0.3 to 0.5 at % of creep-property enhancer; at least any one
of 1 to 3 at % of tungsten (W) and 1 to 3 at % of chrome (Cr); and
the balance of titanium (Ti), wherein the creep-property enhancer
comprises silicon (Si) and boron (B), wherein the boron is added at
0.05 to 0.2 at %.
Inventors: |
KIM; Seong Woong;
(Changwon-si, KR) ; NA; Young Sang; (Changwon-si,
KR) ; KIM; Seung Eon; (Changwon-si, KR) ;
HONG; Jae Keun; (Changwon-si, KR) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
KOREA INSTITUTE OF MACHINERY & MATERIALS |
Yuseong-gu Daejeon |
|
KR |
|
|
Assignee: |
KOREA INSTITUTE OF MACHINERY &
MATERIALS
Yuseong-gu Daejeon
KR
|
Family ID: |
55918050 |
Appl. No.: |
14/945820 |
Filed: |
November 19, 2015 |
Current U.S.
Class: |
420/418 |
Current CPC
Class: |
C22C 21/00 20130101;
C22C 14/00 20130101 |
International
Class: |
C22C 14/00 20060101
C22C014/00 |
Foreign Application Data
Date |
Code |
Application Number |
Nov 24, 2014 |
KR |
10-2014-0164660 |
Claims
1. A titanium-aluminum-based alloy comprising: 40 to 46 at % of
aluminum (Al); 3 to 6 at % of niobium (Nb); 0.3 to 0.5 at % of
creep-property enhancer; at least any one of 1 to 3 at % of
tungsten (W) and 1 to 3 at % of chrome (Cr); and the balance of
titanium (Ti), wherein the creep-property enhancer comprises
silicon (Si) and boron (B), wherein the boron is added at 0.05 to
0.2 at %.
2. The titanium-aluminum-based alloy of claim 1, wherein the
creep-property enhancer further comprises carbon (C), in which case
the sum of contents of the boron and the carbon is in a range of
0.05 to 0.2 at %.
3. The titanium-aluminum-based alloy of claim 1, having a lamellar
structure in which a .alpha.2 phase and a .gamma. phase are
regularly and sequentially arranged, wherein a width ratio of the
.alpha.2 phase and the .gamma. phase is in a range of 2.17 to 2.22.
Description
[0001] This application claims priority from Korean Patent
Application No. 10-2014-0164660 filed on Nov. 24, 2014 in the
Korean Intellectual Property Office, the disclosure of which is
incorporated herein by reference in its entirety.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates to a titanium-aluminum-based
alloy, and more particularly, to a titanium-aluminum-based alloy
having improved tensile strength characteristics.
[0004] 2. Description of the Related Art
[0005] A titanium-aluminum-based alloy is a kind of intermetallic
compound drawing attention as a next-generation light-weight,
heat-resistant material. The titanium-aluminum-based alloy is a
two-phase alloy that contains approximately 10% of Ti.sub.3Al.
[0006] When the titanium-aluminum-based alloy is prepared using a
conventional melt solidification method, an ingot of a lamellar
structure composed of two phases of
TiAl(.gamma.)+Ti.sub.3Al(.alpha..sub.2) is obtained.
[0007] The lamellar structure of TiAl is superior in terms of
fracture toughness, fatigue strength, and creep strength.
Therefore, TiAl is known to provide useful properties for practical
use as a light-weight, high-temperature material. However, its lack
of ductility at room temperature is known to be the biggest
obstacle for use as a cast material.
[0008] The most likely cause of the lack of ductility is known to
be delamination at a boundary surface when stress acts in a
direction perpendicular to a lamellar boundary.
[0009] In addition, a large grain size is another cause of low
ductility. Therefore, superior high-temperature characteristics as
well as excellent strength and ductility can be obtained by
reducing the grain size and including beta and gamma phases having
relatively superior ductility compared with the lamellar
structure.
[0010] Previous studies have reported that a
Ti-(41.about.45)Al-(3.about.5)Nb--(Mo,V)--(B,C) alloy is used to
produce a lamellar structure TiAl alloy including beta and gamma
phases (H. Z. Niu et al, Intermetallics 21 (2012) 97 and T.
Sawatzky, Y. W. Kim et al., Mat. Sci. Forum 654-656 (2010)
500).
SUMMARY OF THE INVENTION
[0011] Aspects of the present invention provide a
titanium-aluminum-based alloy having improved tensile strength
characteristics.
[0012] However, aspects of the present invention are not restricted
to the one set forth herein. The above and other aspects of the
present invention will become more apparent to one of ordinary
skill in the art to which the present invention pertains by
referencing the detailed description of the present invention given
below.
[0013] According to an aspect of the present invention, there is
provided a titanium-aluminum-based alloy including: 40 to 46 at %
of aluminum (Al); 3 to 6 at % of niobium (Nb); 0.3 to 0.5 at % of
creep-property enhancer; 1 to 3 at % of anti-softening enhancer;
and the balance of titanium (Ti), wherein the creep-property
enhancer includes silicon (Si) and boron (B), wherein the boron is
added at 0.05 to 0.2 at %.
[0014] The creep-property enhancer further includes carbon (C), in
which case the sum of contents of the boron and the carbon is in a
range of 0.05 to 0.2 at %.
[0015] The anti-softening enhancer includes at least any one of
tungsten (W) and chrome (Cr).
[0016] The titanium-aluminum-based alloy has a lamellar structure
in which a .alpha.2 phase and a .gamma. phase are regularly and
sequentially arranged, wherein a width ratio of the .alpha.2 phase
and the .gamma. phase is in a range of 2.17 to 2.22.
BRIEF DESCRIPTION OF THE DRAWINGS
[0017] The above and other aspects and features of the present
invention will become more apparent by describing in detail
exemplary embodiments thereof with reference to the attached
drawings, in which:
[0018] FIG. 1A is an optical microscope photograph of the
microstructure of a first sample according to Embodiment 1;
[0019] FIG. 1B is an optical microscope photograph of the
microstructure of a second sample according to Embodiment 1;
[0020] FIG. 2A is an optical microscope photograph of the
microstructure of a first sample according to Embodiment 2;
[0021] FIG. 2B is an optical microscope photograph of the
microstructure of a second sample according to Embodiment 2;
[0022] FIG. 3A is an optical microscope photograph of the
microstructure of a first sample according to Comparative Example
1;
[0023] FIG. 3B is an optical microscope photograph of the
microstructure of a second sample according to Comparative Example
1;
[0024] FIG. 4A is an optical microscope photograph of the
microstructure of a first sample according to Comparative Example
2;
[0025] FIG. 4B is an optical microscope photograph of the
microstructure of a second sample according to Comparative Example
2;
[0026] FIG. 5 is a bright field image transmission electron
microscope photograph of the microstructure of the first sample
according to Embodiment 1;
[0027] FIG. 6A is a bright field image transmission electron
microscope photograph of the microstructure of the first sample
according to Embodiment 2;
[0028] FIG. 6B is a bright field image transmission electron
microscope photograph of the microstructure of the second sample
according to Embodiment 2;
[0029] FIG. 7 is a bright field image transmission electron
microscope photograph of the microstructure of the first sample
according to Comparative Example 1;
[0030] FIG. 8 is a bright field image transmission electron
microscope photograph of the microstructure of the first sample
according to Comparative Example 2;
[0031] FIG. 9A is a dark field image transmission electron
microscope photograph of the microstructure of the first sample
according to Embodiment 1;
[0032] FIG. 9B is a dark field image transmission electron
microscope photograph of the microstructure of the second sample
according to Embodiment 1;
[0033] FIG. 10A is a dark field image transmission electron
microscope photograph of the microstructure of the first sample
according to Embodiment 2;
[0034] FIG. 10B is a dark field image transmission electron
microscope photograph of the microstructure of the second sample
according to Embodiment 2;
[0035] FIG. 11 is a dark field image transmission electron
microscope photograph of the microstructure of the first sample
according to Comparative Example 1;
[0036] FIG. 12A is a dark field image transmission electron
microscope photograph of the microstructure of the first sample
according to Comparative Example 2;
[0037] FIG. 12B is a dark field image transmission electron
microscope photograph of the microstructure of the second sample
according to Comparative Example 2;
[0038] FIG. 13A is a graph illustrating the stress-strain curve of
the first sample of Embodiment 1;
[0039] FIG. 13B is a graph illustrating the stress-strain curve of
the second sample according to Embodiment 1;
[0040] FIG. 14A is a graph illustrating the stress-strain curve of
the first sample according to Embodiment 2;
[0041] FIG. 14B is a graph illustrating the stress-strain curve of
the second sample according to Embodiment 2;
[0042] FIG. 15A is a graph illustrating the stress-strain curve of
the first sample according to Comparative Example 1;
[0043] FIG. 15B is a graph illustrating the stress-strain curve of
the second sample according to Comparative Example 1;
[0044] FIG. 16A is a graph illustrating the stress-strain curve of
the first sample according to Comparative Example 2; and
[0045] FIG. 16B is a graph illustrating the stress-strain curve of
the second sample according to Comparative Example 2.
DETAILED DESCRIPTION OF THE INVENTION
[0046] Advantages and features of the present invention and methods
of accomplishing the same may be understood more readily by
reference to the following detailed description of exemplary
embodiments and the accompanying drawings. The present invention
may, however, be embodied in many different forms and should not be
construed as being limited to the embodiments set forth herein.
Rather, these embodiments are provided so that this disclosure will
be thorough and complete and will fully convey the concept of the
invention to those skilled in the art, and the present invention
will only be defined by the appended claims.
[0047] The present invention will be described more fully with
reference to the accompanying drawings. Like reference numerals
refer to like elements regardless of the drawings. As used herein,
the term "and/or" includes any and all combinations of one or more
of the associated listed items.
[0048] It will be understood that, although the terms first,
second, third, etc., may be used herein to describe various
elements, these elements should not be limited by these terms.
These terms are only used to distinguish one element from another
element. Thus, a first element discussed below could be termed a
second element without departing from the teachings of the present
invention.
[0049] The terminology used herein is for the purpose of describing
particular embodiments only and is not intended to be limiting of
the invention. As used herein, the singular forms "a", "an" and
"the" are intended to include the plural forms as well, unless the
context clearly indicates otherwise. It will be further understood
that the terms "comprises" and/or "comprising," when used in this
specification, specify the presence of stated elements, but do not
preclude the presence or addition of one or more other elements,
and/or groups thereof.
[0050] Unless otherwise defined, all terms (including technical and
scientific terms) used herein have the same meaning as commonly
understood by one of ordinary skill in the art to which this
invention belongs. It will be further understood that terms, such
as those defined in commonly used dictionaries, should be
interpreted as having a meaning that is consistent with their
meaning in the context of the relevant art and will not be
interpreted in an idealized or overly formal sense unless expressly
so defined herein.
[0051] Hereinafter, the present invention will be described more
fully with reference to the accompanying drawings, in which
exemplary embodiments of the invention are shown.
[0052] A titanium-aluminum-based alloy according to the present
invention includes 40 to 46 at % of aluminum (Al), 3 to 6 at % of
niobium (Nb), 0.3 to 0.5 at % of creep-property enhancer, 1 to 3 at
% of anti-softening enhancer, and the balance of titanium (Ti). The
titanium-aluminum-based alloy includes beta-gamma phases to enhance
an anti-softening property and a creep property.
[0053] Here, the creep-property enhancer includes silicon (Si) and
boron (B) and may further include carbon (C). Here, the boron may
be added at 0.05 to 0.2 at %. When the creep-property enhancer
further includes carbon, the sum of contents of the boron and the
carbon may be controlled to be 0.05 to 0.2 at %.
[0054] In addition, the anti-softening enhancer may include at
least any one of tungsten (W) and chrome (Cr).
[0055] The titanium-aluminum-based alloy according to the present
invention has a lamellar structure in which a .alpha.2 phase and a
.gamma. phase are regularly and sequentially arranged. A width
ratio .gamma./.alpha.2 of the .alpha.2 phase and the .gamma. phase
may be in a range of 2.17 to 2.22
[0056] Table 1 below shows embodiments and comparative examples of
the titanium-aluminum-based alloy according to the present
invention.
TABLE-US-00001 TABLE 1 Category Composition (at %) Embodiment 1
Ti--46Al--6Nb--0.5W--0.5Cr--0.3Si--0.1B Embodiment 2
Ti--46Al--6Nb--0.5W--0.5Cr--0.3Si--0.1B--0.1C Comparative
Ti--48Al--6Nb--0.5W--0.5Cr--0.3Si--0.1C Example 1 Comparative
Ti--48Al--6Nb--0.5W--0.5Cr--0.3Si--0.1B Example 2
[0057] That is, as apparent from Embodiment 1 and Embodiment 2, the
present invention may include 46 at % of aluminum, 6 at % of
niobium, and 1 at % of anti-softening enhancer. Here, the
creep-property enhancer includes silicon and boron.
[0058] In addition, as apparent from Embodiment 2, the
creep-property enhancer may further include carbon.
[0059] Comparative Example 2 includes 48 at % of aluminum, whereas
Embodiment 1 includes 46 at % of aluminum.
[0060] In addition, Comparative Example 1 includes silicon and
carbon as the creep-property enhancer, whereas Embodiment 1
includes 46 at % of aluminum and silicon and boron as the
creep-property enhancer.
[0061] Microstructure properties of Embodiments 1 and 2 and
Comparative Examples 1 and 2 will now be described.
[0062] FIG. 1A is an optical microscope photograph of the
microstructure of a first sample according to Embodiment 1. FIG. 1B
is an optical microscope photograph of the microstructure of a
second sample according to Embodiment 1. In addition, FIG. 2A is an
optical microscope photograph of the microstructure of a first
sample according to Embodiment 2. FIG. 2B is an optical microscope
photograph of the microstructure of a second sample according to
Embodiment 2.
[0063] In addition, FIG. 3A is an optical microscope photograph of
the microstructure of a first sample according to Comparative
Example 1. FIG. 3B is an optical microscope photograph of the
microstructure of a second sample according to Comparative Example
1. In addition, FIG. 4A is an optical microscope photograph of the
microstructure of a first sample according to Comparative Example
2. FIG. 4B is an optical microscope photograph of the
microstructure of a second sample according to Comparative Example
2.
[0064] FIG. 5 is a bright field image transmission electron
microscope photograph of the microstructure of the first sample
according to Embodiment 1. In addition, FIG. 6A is a bright field
image transmission electron microscope photograph of the
microstructure of the first sample according to Embodiment 2. FIG.
6B is a bright field image transmission electron microscope
photograph of the microstructure of the second sample according to
Embodiment 2.
[0065] In addition, FIG. 7 is a bright field image transmission
electron microscope photograph of the microstructure of the first
sample according to Comparative Example 1. In addition, FIG. 8 is a
bright field image transmission electron microscope photograph of
the microstructure of the first sample according to Comparative
Example 2.
[0066] FIG. 9A is a dark field image transmission electron
microscope photograph of the microstructure of the first sample
according to Embodiment 1. FIG. 9B is a dark field image
transmission electron microscope photograph of the microstructure
of the second sample according to Embodiment 1. In addition, FIG.
10A is a dark field image transmission electron microscope
photograph of the microstructure of the first sample according to
Embodiment 2. FIG. 10B is a dark field image transmission electron
microscope photograph of the microstructure of the second sample
according to Embodiment 2.
[0067] In addition, FIG. 11 is a dark field image transmission
electron microscope photograph of the microstructure of the first
sample according to Comparative Example 1. In addition, FIG. 12A is
a dark field image transmission electron microscope photograph of
the microstructure of the first sample according to Comparative
Example 2. FIG. 12B is a dark field image transmission electron
microscope photograph of the microstructure of the second sample
according to Comparative Example 2.
[0068] Referring to FIGS. 1A and 1B, 5 and 9A and 9B which show the
microstructures of Embodiment 1, both the first and second samples
(?) of Embodiment 1 form a lamellar structure.
[0069] In addition, referring to FIGS. 2A and 2B, 6A and 6B, and
10A and 10B which show the microstructures of Embodiment 2, both
the first and second samples of Embodiment 2 form a lamellar
structure.
[0070] In Embodiments 1 and 2, bright areas have a .beta..sub.2
phase, dark areas are areas in which a .alpha. phase and a .gamma.
phase form a lamellar structure, and gray areas mainly indicate
gamma-phase areas.
[0071] However, referring to FIGS. 3A and 3B, 7 and 11 which show
the microstructures of Comparative Example 1 and FIGS. 4A and 4B, 8
and 12A and 12B which show the microstructures of Comparative
Example 2, a grain size is small, but the lamellar structure in a
grain is not seen clearly, and a weak .alpha..sub.2(Ti.sub.3Al)
phase is distributed along the grain boundary in the case of
Comparative Examples 1 and 2.
[0072] Table 2 below shows major factors of the microstructures of
Embodiments 1 and 2 and Comparative Examples 1 and 2 of the
titanium-aluminum-based alloy according to the present
invention.
TABLE-US-00002 TABLE 2 Compar- Compar- Embodi- Embodi- ative ative
Category ment 1 ment 2 Example 1 Example 2 Grain size(.mu.m) 288
358.4 213.3 109.3 .gamma.lamellar width(.mu.m) 258.6 162.3 313.6
270.6 .alpha.2 lamellar width(.mu.m) 116.2 74.9 175.1 147.9
.gamma./.alpha.2 lamellar width ratio 2.22 2.17 1.79 1.54
.alpha.2-.alpha.1 spacing(.mu.m) 339.6 146 583.2 549.1
[0073] As apparent from Table 2, Embodiments 1 and 2 have a larger
grain size than Comparative Examples 1 and 2.
[0074] However, while the width ratio .gamma./.alpha.2 of the
.alpha.2 phase and the .gamma. phase is in a range of 2.17 to 2.22
in the case of the alloy according to Embodiments 1 and 2 of the
present invention, it is only 1.79 in the case of Comparative
Example 1 and only 1.54 in the case of Comparative Example 2.
[0075] As described above, Embodiment 1 includes 46 at % of
aluminum, but Comparative Example 2 includes 48 at % of aluminum.
Therefore, it can be understood that the difference in the aluminum
content results in a significant difference in the width ratio
.gamma./.alpha.2 of the .alpha.2 phase and the .gamma. phase.
[0076] In addition, while Embodiment 1 includes silicon and boron
as the creep-property enhancer as well as 46 at % of aluminum,
Comparative Example 1 includes silicon and carbon as the
creep-property enhancer. Therefore, it can be understood that
whether boron is added as the creep-property enhancer results in a
significant difference in the width ratio .gamma./.alpha.2 of the
.alpha.2 phase and the .gamma. phase.
[0077] The above difference between the microstructures leads to a
difference between the strengths of the samples. Strength
characteristics of each sample will hereinafter be described.
[0078] FIG. 13A is a graph illustrating the stress-strain curve of
the first sample of Embodiment 1. FIG. 13B is a graph illustrating
the stress-strain curve of the second sample according to
Embodiment 1. In addition, FIG. 14A is a graph illustrating the
stress-strain curve of the first sample according to Embodiment 2.
FIG. 14B is a graph illustrating the stress-strain curve of the
second sample according to Embodiment 2.
[0079] In addition, FIG. 15A is a graph illustrating the
stress-strain curve of the first sample according to Comparative
Example 1. FIG. 15B is a graph illustrating the stress-strain curve
of the second sample according to Comparative Example 1. In
addition, FIG. 16A is a graph illustrating the stress-strain curve
of the first sample according to Comparative Example 2. FIG. 16B is
a graph illustrating the stress-strain curve of the second sample
according to Comparative Example 2.
[0080] First, referring to FIG. 13, the first sample according to
Embodiment 1 had an ultimate tensile strength (UTS) of 490.1 MPa
and a strain of 0.3%, and the second sample according to Embodiment
1 had an UTS of 553.4 MPa and a strain of 0.4%.
[0081] In addition, referring to FIG. 14, the first sample
according to Embodiment 2 had an UTS of 527.4 MPa and a strain of
0.3%, and the second sample according to Embodiment 2 had an UTS of
545.1 MPa and a strain of 0.4%.
[0082] However, referring to FIG. 15, the first sample according to
Comparative Example 1 had an UTS of 151 MPa and a strain of 0.1%,
and the second sample according to Comparative Example 1 had an UTS
of 309.9 MPa and a strain of 0.2%.
[0083] In addition, referring to FIG. 16, the first sample
according to Comparative Example 2 had an UTS of 445.0 MPa and a
strain of 0.3%, and the second sample according to Comparative
Example 2 had an UTS of 429.7 MPa and a strain of 0.3%.
[0084] As described above, Embodiment 1 includes 46 at % of
aluminum, but Comparative Example 2 includes 48 at % of aluminum.
Therefore, it can be understood that the difference in the aluminum
content improves the UTS in the present invention.
[0085] In addition, while Embodiment 1 includes silicon and boron
as the creep-property enhancer as well as 46 at % of aluminum,
Comparative Example 1 includes silicon and carbon as the
creep-property enhancer. Therefore, it can be understood that boron
added as the creep-property enhancer significantly improves the UTS
in the present invention.
[0086] As described above, the titanium-aluminum-based alloy
according to the present invention includes 40 to 46 at % of
aluminum and silicon and boron as the creep-property enhancer.
Here, the boron may be added at 0.05 to 0.2 at %.
[0087] That is, the present invention includes boron as the
creep-property enhancer and 40 to 46 at % of aluminum, thereby
producing a titanium-aluminum-based alloy having superior tensile
strength characteristics.
[0088] In addition, in the present invention, inexpensive tungsten
and chrome are added instead of molybdenum (Mo) and vanadium (V)
typically added to stabilize the beta phase. Therefore, the
stabilization effect of the beta phase can be maximized.
[0089] Also, boron and silicon effective for grain refinement and
creep resistance are added. Here, since inexpensive boron is used
instead of carbon, the manufacturing costs can be reduced.
[0090] Further, niobium is added in the present invention to
improve high-temperature oxidation resistance and ductility.
[0091] As described above, the present invention includes boron as
a creep-property enhancer and 40 to 46 at % of aluminum. Therefore,
a titanium-aluminum-based alloy having superior tensile strength
characteristics can be prepared.
[0092] In addition, in the present invention, inexpensive tungsten
and chrome are added instead of molybdenum and vanadium typically
added to stabilize the beta phase. Therefore, the stabilization
effect of the beta phase can be maximized.
[0093] Also, boron and silicon effective for grain refinement and
creep resistance are added.
[0094] Here, since inexpensive boron is used instead of carbon, the
manufacturing costs can be reduced.
[0095] While the present invention has been particularly shown and
described with reference to exemplary embodiments thereof, it will
be understood by those of ordinary skill in the art that various
changes in form and detail may be made therein without departing
from the spirit and scope of the present invention as defined by
the following claims. The exemplary embodiments should be
considered in a descriptive sense only and not for purposes of
limitation.
* * * * *