U.S. patent application number 17/313604 was filed with the patent office on 2022-04-14 for high entropy alloy with low specific gravity.
The applicant listed for this patent is Hyundai Motor Company, Kia Corporation. Invention is credited to Kyung Sik Choi, Hoo Dam Lee, Tae Gyu Lee, Byung Ho Min.
Application Number | 20220112580 17/313604 |
Document ID | / |
Family ID | 1000005723237 |
Filed Date | 2022-04-14 |
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United States Patent
Application |
20220112580 |
Kind Code |
A1 |
Lee; Hoo Dam ; et
al. |
April 14, 2022 |
High Entropy Alloy with Low Specific Gravity
Abstract
A high-entropy alloy with a low specific gravity includes Fe:
16.7 to 25 at %, Cr: 10.5 to 20.6 at %, Al: 12.7 to 18 at %,
remaining Ni, and impurities. The high-entropy alloy includes
microstructures of a body-centered cubic (BCC) and a face-centered
cubic (FCC) formed together, wherein a fraction of the FCC of the
high-entropy alloy is 50 to 80%.
Inventors: |
Lee; Hoo Dam; (Seongnam-si,
KR) ; Choi; Kyung Sik; (Seoul, KR) ; Lee; Tae
Gyu; (Seoul, KR) ; Min; Byung Ho; (Suwon-si,
KR) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Hyundai Motor Company
Kia Corporation |
Seoul
Seoul |
|
KR
KR |
|
|
Family ID: |
1000005723237 |
Appl. No.: |
17/313604 |
Filed: |
May 6, 2021 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
C22C 19/056
20130101 |
International
Class: |
C22C 19/05 20060101
C22C019/05 |
Foreign Application Data
Date |
Code |
Application Number |
Oct 13, 2020 |
KR |
10-2020-0132078 |
Claims
1. A high-entropy alloy with a low specific gravity, the
high-entropy alloy comprising Fe: 16.7 to 25 at %, Cr: 10.5 to 20.6
at %, Al: 12.7 to 18 at %, remaining Ni, and impurities.
2. The high-entropy alloy according to claim 1, wherein the
high-entropy alloy comprises Cr: 15 to 18 at %.
3. The high-entropy alloy according to claim 1, wherein the
high-entropy alloy comprises Al: 16 to 17 at %.
4. The high-entropy alloy according to claim 1, wherein the
high-entropy alloy further comprises Ti: 0.8 to 1 at %.
5. The high-entropy alloy according to claim 1, wherein the
high-entropy alloy contains the impurities of 0.1 at % or less.
6. The high-entropy alloy according to claim 1, wherein a Ni:Fe
content (at %) ratio of the high-entropy alloy is 2:1 to 3:1.
7. The high-entropy alloy according to claim 1, wherein the
high-entropy alloy includes microstructures of a body-centered
cubic (BCC) and a face-centered cubic (FCC) formed together.
8. The high-entropy alloy according to claim 7, wherein a fraction
of the FCC of the high-entropy alloy is 50 to 80%.
9. The high-entropy alloy according to claim 8, wherein a sigma
phase is not formed in the high-entropy alloy.
10. The high-entropy alloy according to claim 8, wherein an
intermetallic compound is not formed in the high-entropy alloy.
11. The high-entropy alloy according to claim 1, wherein the
high-entropy alloy has a specific gravity of 6.92 to 7.04
g/cm.sup.3.
12. The high-entropy alloy according to claim 1, wherein the
high-entropy alloy has a yield strength at room temperature of 670
to 700 MPa, and a tensile strength of 880 to 920 MPa.
13. The high-entropy alloy according to claim 1, wherein a Rockwell
hardness of the high-entropy alloy at 600.degree. C. is 20 to 43
HRC.
14. The high-entropy alloy according to claim 13, wherein the
Rockwell hardness at 600.degree. C. is 38 to 43 HRC.
15. A high-entropy alloy with a low specific gravity comprising Fe,
Cr, Al, and Ni, wherein microstructures of a body-centered cubic
(BCC) and a face-centered cubic (FCC) are formed together, and a
fraction of the FCC is 50 to 80%.
16. The high-entropy alloy according to claim 15, wherein a sigma
phase is not formed in the high-entropy alloy.
17. The high-entropy alloy according to claim 15, wherein an
intermetallic compound is not formed in the high-entropy alloy.
18. The high-entropy alloy according to claim 15, wherein the
high-entropy alloy comprises Fe: 16.7 to 25 at %, Cr: 10.5 to 20.6
at %, Al: 12.7 to 18 at %, remaining Ni, and impurities.
19. The high-entropy alloy according to claim 18, wherein the
high-entropy alloy further comprises Ti: 0.8 to 1 at %.
20. The high-entropy alloy according to claim 18, wherein the
high-entropy alloy contains the impurities of 0.1 at % or less.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application claims the benefit of Korean Patent
Application No. 10-2020-0132078, filed on Oct. 13, 2020, which
application is hereby incorporated herein by reference.
TECHNICAL FIELD
[0002] The present disclosure relates to a high-entropy alloy with
a low specific gravity.
BACKGROUND
[0003] In general, a turbine being applied to an automotive
turbocharger has been applied to diesel engines of all commercial
vehicles, such as an SUV, bus, and truck, and agricultural
machinery, and recently, it has also been applied to a gasoline
engine to improve vehicle fuel economy.
[0004] Since the turbocharger technology has an effect of reducing
an exhaust gas while functioning to exert a great power through an
increase of a car torque, the mounting rate thereof has been
increased at high speed.
[0005] The turbocharger is a kind of energy recycling device, and
is a technology to rotate a turbine using a flow energy being
thrown away as an engine exhaust gas and to supercharge an intake
air through rotation of a compressor connected to the turbine on
the same shaft.
[0006] Although the turbocharger enables a small engine to produce
a high output through supercharging of the intake air, it has been
pointed out that the turbocharger has the great disadvantage of the
transient driving response performance degradation called
turbo-lag.
[0007] Recently, in order to solve the problem of the turbo-lag as
described above, a high-entropy alloy capable of improving several
physical properties of the alloy has been used.
[0008] A general high-entropy alloy (HEA) is defined as a
multi-element alloy that is obtained by alloying various kinds of
constituent elements in similar proportions without primary
elements constituting an alloy, such as steel being a general
alloy, aluminum alloy, or titanium alloy. The high-entropy alloy as
described above is a metal material having a high mixed entropy in
the alloy, and having a single phase organization, such as
face-centered cubic (FCC) or body-centered cubic (BCC), without
forming an intermetallic compound or a middle phase.
[0009] For example, a CoCrFeMnNi alloy composed of the
face-centered cubic (FCC) has a high fracture toughness, and an
AlCrFeNi alloy composed of the body-centered cubic (BCC) has a high
strength.
[0010] The foregoing is intended merely to aid in the understanding
of the background of the present disclosure, and is not intended to
mean that the present disclosure falls within the purview of the
related art that is already known to those of ordinary skill in the
art.
SUMMARY
[0011] The present disclosure relates to a high-entropy alloy with
a low specific gravity. Particular embodiments relate to a
high-entropy alloy with a low specific gravity, which has an
excellent physical property at a high temperature and a low
specific gravity by controlling a fraction for generating a
microstructure of a face-centered cubic (FCC).
[0012] Embodiments of the present disclosure solve problems, and
provide a high-entropy alloy with a low specific gravity, which has
an excellent physical property at a high temperature and a low
specific gravity by controlling a ratio of a face-centered cubic
(FCC) to a body-centered cubic (BCC).
[0013] According to an embodiment of the present disclosure, a
high-entropy alloy with a low specific gravity includes Fe: 16.7 to
25 at %, Cr: 10.5 to 20.6 at %, Al: 12.7 to 18 at %, remaining Ni,
and inevitable impurities.
[0014] It is preferable that the high-entropy alloy includes Cr: 15
to 18 at %.
[0015] It is preferable that the high-entropy alloy includes Al: 16
to 17 at %.
[0016] The high-entropy alloy further includes Ti: 0.8 to 1 at
%.
[0017] It is preferable that the high-entropy alloy contains
impurities of 0.1 at % or less.
[0018] It is preferable that a Ni:Fe content (at %) ratio of the
high-entropy alloy is 2:1 to 3:1.
[0019] The high-entropy alloy is characterized in that
microstructures of a body-centered cubic (BCC) and a face-centered
cubic (FCC) are formed together.
[0020] The high-entropy alloy is characterized in that a fraction
of the face-centered cubic (FCC) is 50 to 80%.
[0021] The high-entropy alloy is characterized in that a sigma
phase is not formed.
[0022] The high-entropy alloy is characterized in that an
intermetallic compound is not formed.
[0023] The high-entropy alloy is characterized in that a specific
gravity is 6.92 to 7.04 g/cm.sup.3.
[0024] The high-entropy alloy is characterized in that a yield
strength at a room temperature is 670 to 700 MPa, and a tensile
strength is 880 to 920 MPa.
[0025] The high-entropy alloy is characterized in that a Rockwell
hardness at 600.degree. C. is 20 to 43 HRC.
[0026] The high-entropy alloy is characterized in that the Rockwell
hardness at 600.degree. C. is 38 to 43 HRC.
[0027] Meanwhile, according to an embodiment of the present
disclosure, a high-entropy alloy with a low specific gravity is a
high-entropy alloy including Fe, Cr, Al, and Ni, wherein
microstructures of a body-centered cubic (BCC) and a face-centered
cubic (FCC) are formed together, and a fraction of the
face-centered cubic (FCC) is 50 to 80%.
[0028] The high-entropy alloy is characterized in that a sigma
phase is not formed.
[0029] The high-entropy alloy is characterized in that an
intermetallic compound is not formed.
[0030] The high-entropy alloy includes Fe: 16.7 to 25 at %, Cr:
10.5 to 20.6 at %, Al: 12.7 to 18 at %, remaining Ni, and
inevitable impurities.
[0031] The high-entropy alloy further includes Ti: 0.8 to 1 at
%.
[0032] It is preferable that the high-entropy alloy contains
impurities of 0.1 at % or less.
[0033] According to an embodiment of the present disclosure, it is
possible to implement the high-entropy alloy which can similarly
maintain the high-temperature characteristics with the low specific
gravity against Inconel 713 being a commercial good used for
high-temperature parts by adjusting the fraction of the
face-centered cubic (FCC) while forming the microstructures of the
body-centered cubic (BCC) and the face-centered cubic (FCC)
together through adjustment of the content of each element in the
high-entropy alloy including Fe, Cr, Al, and Ni.
[0034] In particular, since the high-entropy alloy having excellent
characteristics at the high temperature is implemented without
using expensive alloy elements, effects of saving the manufacturing
cost in case of manufacturing the parts for improving the vehicle
fuel economy can be expected, and effects of applying the alloy to
various parts can be expected since the existing precise alcoholic
method is possible.
BRIEF DESCRIPTION OF THE DRAWINGS
[0035] The above and other objects, features and advantages of
embodiments of the present disclosure will be more clearly
understood from the following detailed description taken in
conjunction with the accompanying drawings, in which:
[0036] FIG. 1A is a state diagram for comparative example 2;
[0037] FIG. 1B is a state diagram for embodiment 1;
[0038] FIG. 1C is a state diagram for embodiment 2;
[0039] FIG. 2A is a state diagram according to the content of Cr in
[Ni.sub.33.3Fe.sub.33.3Al.sub.16.7];
[0040] FIG. 2B is a state diagram according to the content of Al in
[Ni.sub.33.3Fe.sub.33.3Cr.sub.16.7];
[0041] FIG. 3A is a state diagram for embodiment 3;
[0042] FIG. 3B is a state diagram for embodiment 4;
[0043] FIG. 3C is a state diagram for
[Ni.sub.38.6Fe.sub.25Cr.sub.16.7Al.sub.16.7Ti.sub.3];
[0044] FIG. 4A is a state diagram according to the addition of Mn
in [Ni.sub.49.1Fe.sub.16.7Cr.sub.16.7Al.sub.16.7Ti.sub.1]
alloy;
[0045] FIG. 4B is a state diagram according to the addition of Co
in [Ni.sub.49.1Fe.sub.16.7Cr.sub.16.7Al.sub.16.7Ti.sub.1]
alloy;
[0046] FIG. 5A is a microphotograph showing the surface of a
conventional material after heat treatment; and
[0047] FIG. 5B is a microphotograph showing the surface of
embodiment 4 after heat treatment.
DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS
[0048] Hereinafter, embodiments of the present disclosure will be
described in more detail with reference to the accompanying
drawings. However, the present disclosure is not limited to
embodiments as disclosed hereinafter, but may be embodied in
various different forms. However, the embodiments as described
hereinafter are only for specific details provided to complete the
present disclosure and to assist those of ordinary skill in the art
to which the present disclosure pertains in a comprehensive
understanding of the disclosure.
[0049] According to a high-entropy alloy according to an embodiment
of the present disclosure, it is possible to excellently maintain
the physical properties, such as hardness and strength, at room
temperature and at a high temperature since a ratio of a
face-centered cubic (FCC) is controlled through adjustment of the
content of alloy elements in Fe--Cr--Al--Ni alloy series in which
microstructures of a body-centered cubic (BCC) and the
face-centered cubic (FCC) are formed together.
[0050] Specifically, a high-entropy alloy according to an
embodiment of the present disclosure includes Fe: 16.7 to 25 at %,
Cr: 10.5 to 20.6 at %, Al: 12.7 to 18 at %, remaining Ni, and
inevitable impurities. Further, the high-entropy alloy further may
further include Ti: 0.8 to 1 at %, and it is preferable to adjust
the impurities to 0.1 at % or less.
[0051] In the following description, unless specially mentioned, %
that is described as a unit of a composition range means at %.
[0052] Fe, Cr, Al, and Ni are elements constituting a high-entropy
alloy, and through the content adjustment of alloy elements, the
microstructures of the body-centered cubic (BCC) and the
face-centered cubic (FCC) are formed together, and the ratio of the
face-centered cubic (FCC) is adjusted at the same time.
[0053] For example, it is preferable to control the ratio of the
face-centered cubic (FCC) to be at the level of 50 to 80% through
the content adjustment of the alloy elements.
[0054] Hereinafter, the reason to limit the ratio of a content of
each alloy element and a relative content will be described.
[0055] In the following measurement, a specimen was manufactured
while changing the content of respective ingredients as shown in
Table 1 below. For example, a high-entropy mother alloy molten
metal was prepared by dissolving and alloying the respective
ingredients in an Ar atmosphere using an are melter after
quantification while changing the content of the respective
ingredients as shown in Table 1. Then, the specimen was
manufactured by injecting the high-entropy mother alloy molten
metal into a mold.
TABLE-US-00001 TABLE 1 Classification Ni Fe Cr Al Ti conventional
material Inconel 713 (commercial material) comparative example 1 25
25 25 25 -- comparative example 2 33.3 33.3 16.7 16.7 -- embodiment
1 41.6 25 16.7 16.7 -- embodiment 2 50 16.7 16.7 16.7 -- embodiment
3 40.6 25 16.7 16.7 0.8 embodiment 4 49.9 16.7 16.7 16.7 1
[0056] Meanwhile, since the high-entropy alloy having a BCC
structure showed a higher strength than the strength of the
high-entropy alloy having an FCC structure as the room temperature
characteristics, the microstructures were observed with respect to
specimens according to the conventional material, comparative
example 1, and comparative example 2 of Table 1, and the Rockwell
hardness (HRC) for each temperature was measured. The results of
the measurement are shown in Table 2 below.
TABLE-US-00002 TABLE 2 Rockwell hardness(HRC) Classification
microstructure 25.degree. C. 400.degree. C. 600.degree. C.
700.degree. C. 800.degree. C. commercial material FCC +
precipitation 44 45 43 42 39 phase comparative example 1 BCC 40 37
28 10 1 or less comparative example 2 BCC + FCC 33.6 27 22 15
3.8
[0057] As can be known from Table 2, in case of comparative example
1 based on BCC being known to have excellent hardness at room
temperature (25.degree. C.), it was able to be confirmed that the
hardness similar to the hardness at room temperature was maintained
until 600.degree. C., but the physical property was abruptly
decreased at a temperature exceeding 600.degree. C., and at a high
temperature (700.degree. C. and 800.degree. C.), hardness
characteristics lower than those of Inconel 713 material that is
the conventional material were shown.
[0058] In contrast, in case of comparative example 2 in which the
BCC and the FCC were formed together, low hardness was shown as a
whole in the whole temperature zone due to the forming of the FCC,
but it was able to be confirmed that high hardness characteristics
were shown due to the containing of the FCC as the temperature went
higher.
[0059] Accordingly, it was able to be confirmed that the physical
property at the high temperature could be improved by controlling
the FCC generation fraction.
[0060] Next, the reason to determine the ratio of another alloy
element to Ni for entropy control will be described.
[0061] First, the content ratio of Fe to Ni that is a base alloy
element will be described.
[0062] In order to find out the fraction relationship between the
hardness at a high temperature and FCC (ordered FCC
(.gamma.')+disordered FCC (.gamma.)), the microstructure fraction,
hardness, and ductility of specimens according to comparative
examples 1 and 2 and embodiments 1 and 2 were measured, and the
results of the measurement are shown in Table 3 below.
[0063] Further, state diagrams of comparative example 2, and
embodiments 1 and 2 are shown in FIGS. 1A to 1C, respectively. FIG.
1A is a state diagram for comparative example 2, FIG. 1B is a state
diagram for embodiment 1, and FIG. 1C is a state diagram for
embodiment 2.
TABLE-US-00003 TABLE 3 ORD constitutive fraction (600.degree. C.
reference fraction) FCC fraction elongation Ordered Disordered
Ordered Disordered fraction in FCC HRC (at (at room Classification
BCC BCC FCC(.gamma.') FCC(.gamma.) (%) (%) 800.degree. C.) temp)
comparative example 1 28 72 -- -- -- -- 1 about 2% comparative
example 2 45 13 -- 42 42% 0% 3.8 15% or more embodiment 1 31 15 22
32 54% 40% 15.2 about 2.5% embodiment 2 10 18 72 0 72% 100% 30
about 1.5%
[0064] As can be known from Table 3 and FIG. 1A, in case of
comparative example 2 corresponding to an AlCrFe.sub.2Ni.sub.2
alloy, it was able to be confirmed that the Fe:Ni content ratio (at
%) was 2:2. As the microstructure, an ordered BCC, disordered BCC,
and disordered FCC were mixed and created.
[0065] Meanwhile, as can be known from Table 3 and FIGS. 1B and 1C,
it was able to be confirmed that ordered FCC (.gamma.')+disordered
FCC(.gamma.), being a new phase, could be formed through the Fe
content control.
[0066] In particular, if the Fe:Ni content ratio (at %) is 2:2 as
in comparative example 2, only the disordered FCC(.gamma.) was
created, and the hardness improvement effect at a high temperature
was incomplete.
[0067] Further, if Fe was replaced by Ni and the Fe:Ni content
ratio (at %) was 1:2 as in embodiment 1, it was able to be
confirmed that ordered FCC(.gamma.') was created together with the
ordered BCC, disordered BCC, and disordered FCC, and the hardness
at the high temperature was improved.
[0068] Further, if the Fe:Ni content ratio (at %) is 1:3 as in
embodiment 2, the disordered FCC(.gamma.) fraction capable of
securing the ductility was reduced as the temperature went lower,
and only ordered FCC(.gamma.') remained to cause an abrupt
brittleness to occur.
[0069] Meanwhile, if the disordered FCC fraction in the FCC
(ordered FCC+disordered FCC) in the microstructural crystalline
structure disappears, the brittleness is increased. Accordingly, it
is preferable that the FCC total fraction is 50 to 80% to suppress
the occurrence of the abrupt brittleness in the high-entropy alloy.
More preferably, the maximum value of the FCC total fraction does
not exceed 72%.
[0070] For this, it was able to be confirmed that it was preferable
to maintain the Fe content equal to or higher than 16.7 at % and
equal to or lower than 25 at %.
[0071] Next, the reason to limit the content of Cr and Al will be
described.
[0072] FIG. 2A is a state diagram according to the content of Cr in
[Ni.sub.33.3Fe.sub.33.3Al.sub.16.7], and FIG. 2B is a state diagram
according to the content of Al in
[Ni.sub.33.3Fe.sub.33.3Cr.sub.16.7].
[0073] As can be known from FIG. 2A, if the content of Cr becomes
less than 16.7 at %, the FCC content is increased, and in addition,
the ordered FCC (.gamma.') is increased. Further, the specific
gravity is increased. In particular, if the Cr content is less than
10.5 at %, the ordered BCC is newly created in the neighborhood of
650.degree. C., and thus the lowest value of the content is limited
to 10.5 at %.
[0074] Further, if the Cr content is increased, the FCC content is
reduced, and if the FCC content exceeds 20.6 at %, the disordered
FCC disappears, and thus the phase control is unable to be
performed.
[0075] Accordingly, by limiting the Cr content to 10.5 to 20.6 at
%, it is possible to control the FCC/BCC phase fraction, and
preferably, by controlling the same to be 15 to 18 at %, a stable
physical property can be secured within the range in which the
characteristic change is not big.
[0076] As can be known from FIG. 2B, if the content of Al becomes
lower than 16.7 at %, the FCC content is increased, and the
specific gravity is increased. In accordance with the increase of
the specific gravity, the effect is halved when being applied to
the parts. In particular, if the content of Al is lower than 12.7
at %, the BCC phase disappears to make the phase control
impossible.
[0077] Further, if the content of Al is higher than 18 at %, the
BCC phase disappears, and thus it is preferable to limit the
content of Al to 12.7 to 18 at %, and more preferably, in case of
the control to 16 to 17 at %, a stable physical property can be
secured within the range in which the characteristic change is not
big.
[0078] Meanwhile, in order to maintain the characteristics of the
high-entropy alloy, it is preferable to maintain the content of Cr
and Al to Cr: 10.5 to 20.6 at % and Al: 12.7 to 18 at %.
Preferably, it is good to maintain the content of Cr and Al to Cr:
15 to 18 at % and Al: 16 to 17 at %. Most preferably, it is good to
maintain the content of Cr and Al to 16.7 at %, respectively.
[0079] If the content of Cr and Al deviates from a suggested range,
the set ratio of ordered FCC (.gamma.')+disordered FCC(.gamma.) is
changed, and thus the phase control becomes impossible.
[0080] In order to find out the reason to limit the content of Cr
and Al as described above, content-adjusted specimens were prepared
as shown in Table 4, and the microstructural fraction and hardness
of the prepared specimens were measured. The results of the
measurement are shown in Table 5.
TABLE-US-00004 TABLE 4 Classification Ni Fe Cr Al embodiment 1 41.6
25 16.7 16.7 embodiment 1-1 43.3 25 15 16.7 embodiment 1-2 40.3 25
18 16.7 embodiment 1-3 42.3 25 16.7 16 embodiment 1-4 41.3 25 16.7
17 embodiment 2 50 16.7 16.7 16.7 embodiment 2-1 51.6 16.7 15 16.7
embodiment 2-2 48.6 16.7 18 16.7 embodiment 2-3 50.6 16.7 16.7 16
embodiment 2-4 49.6 16.7 16.7 17
TABLE-US-00005 TABLE 5 FCC fraction (%) (ORD FCC/ constitutive
fraction (600.degree. C. reference fraction) ORD FCC + FCC Ordered
Disordered Ordered Disordered DISORD FCC fraction HRC (at HRC at
Classification BCC BCC FCC(.gamma.') FCC(.gamma.) fraction) change
room temp) 800.degree. C. embodiment 1 31 15 22 32 55 (59) -- 25.4
15.2 embodiment 1-1 28 12 31 29 60 (48) 9.1% 24 16 embodiment 1-2
32 15 24 29 53 (54) -3.6% 26 14 embodiment 1-3 27 14 29 30 59 (50)
7.3% 24.5 15.5 embodiment 1-4 34 16 19 31 50 (62) -9.1% 27 13
embodiment 2 10 18 72 0 72 (100) -- 30.5 30.1 embodiment 2-1 15 7
76 0 76 (100) 5.6% 29 31 embodiment 2-2 19 12 68 0 68 (100) -5.6%
31 29 embodiment 2-3 6 18 76 0 76 (100) 5.6% 29.5 31 embodiment 2-4
12 18 70 0 70 (100) -2.8% 30.5 30
[0081] As can be known from Table 4 and Table 5, in order to
maintain the change of the set FCC fraction within 10%, as
suggested, it is preferable to maintain Cr: 15 to 18 at % and Al:
16 to 17 at %, and in this case, it was able to be confirmed that
the hardness change at room temperature and at a high temperature
was incomplete.
[0082] Further, as can be confirmed from Table 5, it was able to be
confirmed that the FCC fraction could be maintained 50 to 80%, and
preferably, 50 to 76%, in case of maintaining Cr: 15 to 18 at % and
Al: 16 to 17 at %.
[0083] Next, the influence on alloy elements additionally contained
in the high-entropy alloy according to embodiments of the present
disclosure, which is a quaternary high-entropy alloy, will be
described.
[0084] FIG. 3A is a state diagram for embodiment 3, FIG. 3B is a
state diagram for embodiment 4, and FIG. 3C is a state diagram for
[Ni.sub.38.6Fe.sub.25Cr.sub.16.7Al.sub.16.7Ti.sub.3].
[0085] As can be known from FIGS. 3A to 3C, it was able to be
confirmed that the ordered FCC(.gamma.') precipitation temperature
was changed in accordance with the Ti addition, and in case of
improving the ordered FCC(.gamma.') precipitation temperature, it
can be analogized that the hardness will be improved at a higher
temperature.
[0086] However, as can be known from FIG. 3C, if Ti was added over
a predetermined range, it was able to be confirmed that a sigma
phase was created and thus the precipitation temperature of the
ordered FCC(.gamma.') was abruptly increased.
[0087] However, the sigma phase corresponds to needle-shaped
particles, and since the creation thereof may cause the alloy
brittleness, it is required to control the Ti content.
[0088] Accordingly, it is preferable that the content of Ti is
added with 0.8 to 1 at %, and in accordance with the addition of
Ti, the precipitation temperature of the ordered FCC(.gamma.') can
be increased to about 150 to 200.degree. C.
[0089] However, if the content of Ti exceeds the suggested range,
there occurs a problem in that the needle-shaped signal phase is
formed and thus the brittleness is abruptly increased.
[0090] Next, the influence exerted on the microstructure by
impurities contained in the high-entropy alloy will be
described.
[0091] FIG. 4A is a state diagram according to addition of Mn in
[Ni.sub.49.1Fe.sub.16.7Cr.sub.16.7Al.sub.16.7Ti.sub.1] alloy, and
FIG. 4B is a state diagram according to addition of Co in
[Ni.sub.49.1Fe.sub.16.7Cr.sub.16.7Al.sub.16.7Ti.sub.1] alloy.
[0092] It is preferable that the content of the remaining
impurities except the primary alloy ingredients of the high-entropy
alloy according to an embodiment of the present disclosure is
limited to 0.1 at % or less.
[0093] As can be known from FIGS. 4A and 4B, the high-entropy alloy
is configured as a single phase by an interaction of elements of
the same element group (similar atomic radius and weight required)
in the periodic table, but if another element is added, there is a
high probability that an intermetallic compound rather than the BCC
or FCC is created, and since the addition of the same group
elements, such as Mn and Co, may not only hurt the phase fraction
characteristics but also make a phase having high brittleness, such
as the sigma phase, it is preferable to limit the content to 0.1 at
% or less.
[0094] Next, the hardness characteristics according to the
temperature of the high-entropy alloy according to embodiments of
the present disclosure and the physical properties of the yield
strength and the tensile strength at room temperature were
evaluated, and the specific gravity was measured. The results of
the measurement are shown in Table 6 and Table 7.
TABLE-US-00006 TABLE 6 Rockwell hardness(HRC) Classification
25.degree. C. 400.degree. C. 600.degree. C. 700.degree. C.
800.degree. C. embodiment 1 25.4 26 20 17 15.2 embodiment 2 30.5 33
32 31 30.1 embodiment 3 36 37 38 38 35.1 embodiment 4 40 42 43 43
39.7 commercial 44 45 43 42 39 material
TABLE-US-00007 TABLE 7 specific gravity yield tensile specific
ratio against strength strength gravity conventional Classification
(MPa) (MPa) (g/cm.sup.3) material embodiment 1 670 900 6.96 12.1%
embodiment 2 685 880 7.04 11.1% embodiment 3 680 920 6.92 12.6%
embodiment 4 700 890 6.99 11.7% commercial 650 900 7.91 --
material
[0095] As can be known from Table 6 and Table 7, according to
embodiments of the present disclosure, it was able to be confirmed
that the high hardness could be secured at 600.degree. C. or more,
and the yield strength and the tensile strength having a level
similar to the conventional material or an improved level at room
temperature could be secured.
[0096] Further, it was able to be confirmed that the embodiments
had a lower specific gravity than that of Inconel 713 being a
commercial good by about 10% or more, and thus the light weight
could be achieved.
[0097] Next, in order to find out the oxidation resistance
characteristics of the high-entropy alloy according to embodiments
of the present disclosure, heat treatment was performed for 100 hr.
at 900.degree. C. with respect to specimens of the conventional
material and embodiment 4, and thereafter, the depth of an oxide
layer formed on the surface of the specimen was measured.
[0098] FIG. 5A is a microphotograph showing the surface of a
conventional material after heat treatment, and FIG. 5B is a
microphotograph showing the surface of embodiment 4 after heat
treatment.
[0099] As can be known from FIGS. 5A and 5B, it was able to be
confirmed that an oxide layer was formed with a depth of about 10
.mu.m on the surfaces of the specimens of both the conventional
material and embodiment 4.
[0100] Through the above-described results, it was able to be
confirmed that the high-temperature oxidation amount according to
the embodiment of the present disclosure was similar to that of
Inconel 713 being the conventional material.
[0101] Although the present disclosure has been described with
reference to the accompanying drawings and the preferred
embodiments as described above, the present disclosure is not
limited thereto, but also encompasses claims to be described later.
Accordingly, those of ordinary skill in the art to which the
present disclosure pertains will appreciate that various
modifications, additions and substitutions are possible, without
departing from the scope and spirit of the disclosure as disclosed
in the appended claims.
* * * * *