U.S. patent application number 14/410455 was filed with the patent office on 2015-11-12 for lamellar-structure titanium-aluminum based alloy having a beta-gamma phase.
This patent application is currently assigned to KOREA INSTITUTE OF MACHINERY & MATERIALS. The applicant listed for this patent is Seong Woong KIM, Seung Eon KIM, Young Sang NA, Jong Taek YEOM. Invention is credited to Seong Woong KIM, Seung Eon KIM, Young Sang NA, Jong Taek YEOM.
Application Number | 20150322549 14/410455 |
Document ID | / |
Family ID | 48665698 |
Filed Date | 2015-11-12 |
United States Patent
Application |
20150322549 |
Kind Code |
A1 |
KIM; Seong Woong ; et
al. |
November 12, 2015 |
LAMELLAR-STRUCTURE TITANIUM-ALUMINUM BASED ALLOY HAVING A
BETA-GAMMA PHASE
Abstract
A lamellar titanium-aluminium (TiAl) alloy having a beta-gamma
phase according to the present invention contains aluminum (Al) of
40.about.46 at %, niobium (Nb) of 3.about.6 at %, a creep
resistance enhancer of 0.2.about.0.4 at %, a softening resistance
enhancer of 2 at %, and the balance of titanium (Ti) and is
manufactured by vacuum arc melting.
Inventors: |
KIM; Seong Woong;
(Changwon-si, Gyeongsangnam-do, KR) ; NA; Young Sang;
(Changwon-si, Gyeongsangnam-do, KR) ; KIM; Seung Eon;
(Changwon-si, Gyeongsangnam-do, KR) ; YEOM; Jong
Taek; (Gimhae-si, Gyeongsangnam-do, KR) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
KIM; Seong Woong
NA; Young Sang
KIM; Seung Eon
YEOM; Jong Taek |
Changwon-si, Gyeongsangnam-do
Changwon-si, Gyeongsangnam-do
Changwon-si, Gyeongsangnam-do
Gimhae-si, Gyeongsangnam-do |
|
KR
KR
KR
KR |
|
|
Assignee: |
KOREA INSTITUTE OF MACHINERY &
MATERIALS
Yuseong-gu, Daejeon
KR
|
Family ID: |
48665698 |
Appl. No.: |
14/410455 |
Filed: |
August 30, 2012 |
PCT Filed: |
August 30, 2012 |
PCT NO: |
PCT/KR2012/006931 |
371 Date: |
December 22, 2014 |
Current U.S.
Class: |
420/418 |
Current CPC
Class: |
C22C 1/02 20130101; C22C
14/00 20130101 |
International
Class: |
C22C 14/00 20060101
C22C014/00 |
Foreign Application Data
Date |
Code |
Application Number |
Jul 25, 2012 |
KR |
10-2012-0081170 |
Claims
1. A lamellar titanium-aluminum (TiAl) alloy having a beta-gamma
phase that contains aluminum (Al) of 40.about.46 at %, niobium (Nb)
of 3.about.6 at %, a creep resistance enhancer of 0.2.about.0.4 at
%, a softening resistance enhancer of 1.about.3 at %, and the
balance of titanium (Ti) and is manufactured by solid-casting to
improve softening resistance and creep resistance.
2. The lamellar titanium-aluminum (TiAl) alloy of claim 1, wherein
the creep resistance enhancer includes one or more of carbon (C)
and silicon (Si).
3. The lamellar titanium-aluminum (TiAl) alloy of claim 2, wherein
the softening resistance enhancer is any one selected from tungsten
(W) and chromium (Cr).
4. The lamellar titanium-aluminum (TiAl) alloy of claim 3, wherein
average hardness is 335.6 Hv or more.
5. The lamellar titanium-aluminum (TiAl) alloy of claim 1, wherein
Young's modulus is 180.about.220 GPa.
6. The lamellar titanium-aluminum (TiAl) alloy of claim 5, wherein
tensile strength is 453.8.about.540 MPa.
7. The lamellar titanium-aluminum (TiAl) alloy of claim 2, wherein
Young's modulus is 180.about.220 GPa.
8. The lamellar titanium-aluminum (TiAl) alloy of claim 3, wherein
Young's modulus is 180.about.220 GPa.
9. The lamellar titanium-aluminum (TiAl) alloy of claim 4, wherein
Young's modulus is 180.about.220 GPa.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to a lamellar
titanium-aluminum (TiAl) based alloy having a beta-gamma phase, and
more particularly, to a lamellar titanium-aluminum (TiAl) alloy
having a beta-gamma phase of which the effect of stabilizing a beta
phase is improved and the manufacturing cost is reduced, by adding
tungsten (W) and chromium (Cr) that are not expensive instead of
molybdenum (Mo) and vanadium (V) that are usually added to
stabilize a beta phase.
[0003] The present invention relates to a lamellar
titanium-aluminum (TiAl) alloy having a beta-gamma phase of which
mechanical properties are improved by adding a small amount of
carbon (C) and silicon (Si) that are effective in grain refinement
and creep resistance to suppress production of a deposit and of
which high-temperature oxidation resistance and ductility are
improved by adding niobium (Nb).
[0004] 2. Description of the Related Art
[0005] A titanium-aluminum (TiAl) based alloy, which is the next
generation light heat-resistant material as a kind of intermetallic
compounds, is a two-phase alloy containing Ti.sub.3Al of 10%.
[0006] A lamellar structure ingot having two phases of
TiAl(.gamma.)+Ti3Al(.alpha..sub.2) is obtained by common
melting-solidifying.
[0007] The titanium-aluminum (TiAl) lamellar structure has been
known as providing properties that are useful for the practical use
of titanium-aluminum (TiAl) as a light high-temperature material,
because it has high fracture toughness, fatigue strength, and creep
strength, but its insufficient ductility at a room temperature has
been known as the largest obstacle in use as a casting
material.
[0008] It has been known that the most important factor for the
insufficient ductility is delamination on the interface when stress
is exerted perpendicular to the lamellar boundary.
[0009] The rough grains also reduce the ductility. Accordingly,
high strength and ductility, in addition to excellent
high-temperature properties, can be obtained if it is possible to
reduce the grain size and contain beta and gamma phases having high
ductility relative to a lamellar structure.
[0010] The existing studies have reported that they have used
Ti-(41.about.45)Al-(3.about.5)Nb--(Mo,V)--(B,C)-based alloys to
manufacture a lamellar titanium-aluminum (TiAl) alloy having 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] An object of the present invention is to provide a lamellar
titanium-aluminum (TiAl) alloy having a beta-gamma phase of which
the effect of stabilizing a beta phase is improved and the
manufacturing cost is reduced, by adding tungsten (W) and chromium
(Cr) that are not expensive instead of molybdenum (Mo) and vanadium
(V) that are usually added to stabilize a beta phase.
[0012] Another object of the present invention is to provide a
lamellar titanium-aluminum (TiAl) alloy having a beta-gamma phase
of which mechanical properties are improved by adding a small
amount of carbon (C) and silicon (Si) that are effective in grain
refinement and creep resistance to suppress production of a deposit
and of which high-temperature oxidation resistance and ductility
are improved by adding niobium (Nb).
[0013] An aspect of the present invention provides a lamellar
titanium-aluminum (TiAl) alloy having a beta-gamma phase which
contains aluminum (Al) of 40.about.46 at %, niobium (Nb) of
3.about.6 at %, a creep resistance enhancer of 0.2.about.0.4 at %,
a softening resistance enhancer of 1.about.3 at %, and the balance
of titanium (Ti) and is manufactured by solid-casting.
[0014] The creep resistance enhancer may include one or more of
carbon (C) and silicon (Si).
[0015] The softening resistance enhancer may be any one selected
from tungsten (W) and chromium (Cr).
[0016] The average hardness may be 335.6 Hv or more.
[0017] Young's modulus may be 180.about.220 GPa.
[0018] Tensile strength may be 453.8.about.540 MPa.
[0019] According to the present invention, stabilization of a beta
phase is maximized by adding tungsten (W) and chromium (Cr) that
are inexpensive elements instead of molybdenum (Mo) and vanadium
(V) that are usually added to stabilize a beta phase.
[0020] Further, mechanical properties are improved by adding a
small amount of carbon (C) and silicon (Si) that are effective in
grain refinement and creep resistance to suppress production of a
deposit.
[0021] Further, high-temperature oxidation resistance and ductility
are improved by adding niobium (Nb) and the manufacturing cost is
reduced.
BRIEF DESCRIPTION OF THE DRAWINGS
[0022] FIG. 1 is a picture of the external appearances of lamellar
titanium-aluminum (TiAl) alloys having a beta-gamma phase according
to the present invention.
[0023] FIG. 2 is a table showing the components of lamellar
titanium-aluminum (TiAl) alloys having a beta-gamma phase according
to the present invention and a comparative example.
[0024] FIG. 3 is a picture of a fine structure in a lamellar
titanium-aluminum (TiAl) alloy having a beta-gamma phase according
to a first embodiment of the present invention.
[0025] FIG. 4 is a picture of a fine structure in a lamellar
titanium-aluminum (TiAl) alloy having a beta-gamma phase according
to a second embodiment of the present invention.
[0026] FIG. 5 is a picture of a fine structure in a lamellar
titanium-aluminum (TiAl) alloy having a beta-gamma phase according
to a third embodiment of the present invention.
[0027] FIG. 6 is a picture of a fine structure according to a
comparative example.
[0028] FIG. 7 is a table comparing tensile strengths of the
lamellar titanium-aluminum (TiAl) alloys having a beta-gamma phase
according to the second and third embodiments of the present
invention and a comparative example.
[0029] FIG. 8 is a table comparing Vickers hardness of the lamellar
titanium-aluminum (TiAl) alloys having a beta-gamma phase according
to the first to third embodiments of the present invention and a
comparative example.
[0030] FIG. 9 is a graph comparing the result of tensile test on
the lamellar titanium-aluminum (TiAl) alloys having a beta-gamma
phase according to the second and third embodiments of the present
invention and a comparative example.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0031] A lamellar titanium-aluminum (TiAl) alloy having a
beta-gamma phase according to the present invention is described
hereafter with reference to FIGS. 1 and 2.
[0032] The terms and words used in the present specification and
claims should not be interpreted as being limited to typical
meanings or dictionary definitions, but should be interpreted as
having meanings and concepts relevant to the technical scope of the
present invention based on the rule according to which an inventor
can appropriately define the concept of the term to describe most
appropriately the best method he or she knows for carrying out the
invention.
[0033] Therefore, the configurations described in the embodiments
and drawings of the present invention are merely most preferable
embodiments but do not represent all of the technical spirit of the
present invention. Thus, the present invention should be construed
as including all the changes, equivalents, and substitutions
included in the spirit and scope of the present invention at the
time of filing this application.
[0034] FIG. 1 is a picture of the external appearances of lamellar
titanium-aluminum (TiAl) alloys having a beta-gamma phase according
to the present invention and FIG. 2 is a table showing the
components of lamellar titanium-aluminum (TiAl) alloys having a
beta-gamma phase according to the present invention and a
comparative example.
[0035] The lamellar titanium-aluminum (TiAl) alloy having a
beta-gamma phase (hereafter, referred to as a titanium-aluminum
(TiAl) alloy 10) according to the present invention shown in the
figure has been manufactured by performing solid-casting on the
metallic components shown in FIG. 2 and have not undergone post
processes such as heat treatment, hot isostatic pressing, rolling,
and forging.
[0036] In detail, it is apparent that the hardness, softening
resistance, and creep resistance of the titanium-aluminum (TiAl)
alloy 10 are improved, when post processes such as heat treatment
are applied, but in the present invention, hardness and tensile
tests were performed on an embodiment having the shape of a button
manufactured by solid-casting and having a diameter of 60 mm and
was compared with a comparative example.
[0037] The comparative example is based on the components of the
titanium-aluminum (TiAl) heat resisting alloy disclosed in
JP-A-10-220236 and JP-A-10-193087 by Daido Steel, Japan.
[0038] The present invention may be classified into first to third
embodiments.
[0039] The first embodiment was manufactured by changing the
amounts of aluminum (Al) and niobium (Nb) with the composition
ratio of tungsten (W) and carbon (C) maintained at a predetermined
level, the second embodiment was manufactured by changing the
amount of niobium (Nb), and the third embodiment was manufactured
by changing the amounts of aluminum (Al) and niobium (Nb) with the
amounts of chromium (Cr), silicon (Si), and carbon (C) maintained
at a predetermined level.
[0040] The composition of the TiAl alloy 10, based on Table 2,
contains aluminum (Al) of 40.about.46 at %, niobium (Nb) of
3.about.6 at %, a creep resistance enhancer of 0.2.about.0.4 at %,
a softening resistance enhancer of 1.about.3 at %, and the balance
of titanium.
[0041] The creep resistance enhancer contains one or more of carbon
(C) and silicon (Si), any one of tungsten (W) and chromium (Cr) is
selected as the softening resistance enhancer, and the alloy has an
average hardness over 335.6 Hv and a Young's modulus of
180.about.220 GPa, when post processes such as heat treatment is
not performed yet.
[0042] The fine structures of the first to third embodiments of the
present invention and a comparative example are described hereafter
with reference to FIGS. 3 to 6.
[0043] FIGS. 3 to 5 are pictures of fine structures in a lamellar
titanium-aluminum (TiAl) alloy having a beta-gamma phase according
to first to third embodiments of the present invention and FIG. 6
is a picture of a fine structure of a comparative example.
[0044] The fine structures shown in FIG. 3 were manufactured when
tungsten (W) was selected as a softening resistance enhancer and
carbon (C) was added as a creep resistance enhancer, and the all
have a lamellar structure.
[0045] The fine structures shown in FIG. 4 were manufactured when
tungsten (W) was selected as a softening resistance enhancer and
silicon (Si) was added as a creep resistance enhancer, and they
also have a lamellar structure.
[0046] The fine structures shown in FIG. 5 were manufactured when
chromium (Cr) was selected as a softening resistance enhancer and
carbon (C) and silicon (Si) were added as creep resistance
enhancers, and they have a lamellar structure.
[0047] The titanium-aluminum (TiAl) alloy according to a
comparative example, as shown in FIG. 6, has a low grain size, but
does not show a clear lamellar structure in the grains and a
vulnerable .alpha..sub.2 (Ti.sub.3Al) phase is distributed along
the grain boundary.
[0048] The embodiments of the present invention and the comparative
example have a difference in strength, as shown in FIG. 7, due to
the differences in fine structure described above.
[0049] That is, FIG. 7 is a table comparing tensile strengths of
lamellar titanium-aluminum (TiAl) alloys having a beta-gamma phase
according to the second and third embodiments of the present
invention and a comparative example. It could be seen that the
embodiments of the present invention had a tensile strength over
453.8 MPa, while the comparative example had a tensile strength of
384.5 MPa, so the strength of the titanium-aluminum (TiAl) alloys
according to the present invention was far superior.
[0050] FIG. 8 is a table comparing Vickers hardness of lamellar
titanium-aluminum (TiAl) alloys having a beta-gamma phase according
to the first to third embodiments of the present invention and a
comparative example.
[0051] As shown in FIG. 8, the specimens of first to third
embodiments of the present invention showed an average hardness
over 335.6 Hv, as the result of measuring Vickers hardness three
times for each of the specimens.
[0052] In contrast, it was seen that the specimen of the
comparative example had hardness of 268.4 Hv, considerably lower
than those of the embodiments of the present invention.
[0053] Finally, FIG. 9 is a graph comparing the result of tensile
test on the lamellar titanium-aluminum (TiAl) alloys having a
beta-gamma phase according to the second and third embodiments of
the present invention and a comparative example. As the result of
performing a tensile test on #7 of the second embodiment, #11 of
the third embodiment, and the comparative example, they showed
Young's modulus of 180.about.220 GPa.
[0054] The test results correspond to the first to third
embodiments manufactured by performing solid-casting on the
titanium-aluminum (TiAl) alloy having the composition shown in FIG.
2, without post processes such as heat treatment and plastic
working performed.
[0055] Accordingly, Young's modulus, hardness, and tensile strength
can be further improved if post processes are additionally
performed. Further, if the added amount is changed with the
composition range shown in FIG. 2 and a softening resistance
enhancer and a creep resistance enhancer are selectively added, it
is apparent that softening resistance and creep resistance are
selectively increased and desired properties can be obtained.
[0056] The scope of the present invention is not limited to the
embodiments described above and many other modifications based on
the present invention may be achieved by those skilled in the art
within the scope of the present invention.
[0057] In the present invention, molybdenum (Mo) and vanadium (V)
that are usually added to stabilize a beta phase were replaced by
tungsten (W) and chromium (Cr) that are inexpensive elements.
[0058] Accordingly, it is possible to reduce the manufacturing cost
and maximize the effect of stabilizing a beta phase.
[0059] Further, it is possible to manufacture a lamellar
titanium-aluminum (TiAl) alloy having a beta-gamma phase of which
mechanical properties are improved by adding a small amount of
carbon (C) and silicon (Si) for grain refinement to suppress
production of a deposit and of which high-temperature oxidation
resistance and strength are improved by adding niobium (Nb).
* * * * *