U.S. patent application number 15/495411 was filed with the patent office on 2017-11-02 for high-strength and ultra heat-resistant high entropy alloy (hea) matrix composites and method of preparing the same.
This patent application is currently assigned to Korea Advanced Institute of Science and Technology. The applicant listed for this patent is Korea Advanced Institute of Science and Technology. Invention is credited to Soon Hyung Hong, Bin Lee, Jun Ho Lee, Rizaldy Muhammad Pohan, Ho Jin Ryu.
Application Number | 20170314097 15/495411 |
Document ID | / |
Family ID | 60158187 |
Filed Date | 2017-11-02 |
United States Patent
Application |
20170314097 |
Kind Code |
A1 |
Hong; Soon Hyung ; et
al. |
November 2, 2017 |
HIGH-STRENGTH AND ULTRA HEAT-RESISTANT HIGH ENTROPY ALLOY (HEA)
MATRIX COMPOSITES AND METHOD OF PREPARING THE SAME
Abstract
A high-strength and ultra heat-resistant high entropy alloy
(HEA) matrix composite material and a method of preparing the HEA
matrix composite material are provided. The HEA matrix composite
material may include at least four matrix elements among Co, Cr,
Fe, Ni, Mn, Cu, Mo, V, Nb, Ta, Ti, Zr, W, Si, Hf and Al, and a
body-centered cubic (BCC) forming alloy element.
Inventors: |
Hong; Soon Hyung; (Daejeon,
KR) ; Ryu; Ho Jin; (Daejeon, KR) ; Lee;
Bin; (Daejeon, KR) ; Lee; Jun Ho; (Daejeon,
KR) ; Pohan; Rizaldy Muhammad; (Daejeon, KR) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Korea Advanced Institute of Science and Technology |
Daejeon |
|
KR |
|
|
Assignee: |
Korea Advanced Institute of Science
and Technology
Daejeon
KR
|
Family ID: |
60158187 |
Appl. No.: |
15/495411 |
Filed: |
April 24, 2017 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
C22C 21/00 20130101;
C22C 32/0015 20130101; C22C 1/0433 20130101; C22C 32/0089 20130101;
B22F 3/105 20130101; B22F 2003/1051 20130101; C22C 1/1084 20130101;
B22F 2998/10 20130101; B22F 2998/10 20130101; C22C 32/0047
20130101; C22C 1/1084 20130101; C22C 33/0257 20130101 |
International
Class: |
C22C 1/05 20060101
C22C001/05; C22C 21/00 20060101 C22C021/00; C22C 1/04 20060101
C22C001/04 |
Foreign Application Data
Date |
Code |
Application Number |
May 2, 2016 |
KR |
1020160053871 |
Mar 21, 2017 |
KR |
1020170035200 |
Claims
1. A high entropy alloy (HEA) matrix composite material comprising:
at least four matrix elements selected from the group consisting of
Co, Cr, Fe, Ni, Mn, Cu, Mo, V, Nb, Ta, Ti, Zr, W, Si, Hf and Al;
and a body-centered cubic (BCC) forming alloy element.
2. The HEA matrix composite material of claim 1, further
comprising: a reinforcing material comprising at least one selected
from the group consisting of a metal oxide, a metal silicide, a
metal carbide, a metal nitride and a metal boride, wherein each of
the metal oxide, the metal silicide, the metal carbide, the metal
nitride and the metal boride comprises at least one selected from
the group consisting of Al, Si, Ti, Zr, Ta, Mg, Be, Ba, Zn, Cr, Y,
Sn, W, Hf, V, Nb, Mo, W, La and B.
3. The HEA matrix composite material of claim 2, wherein the
reinforcing material is present in an amount of 0.01% by volume
(vol %) to 50 vol % in the HEA matrix composite material.
4. The HEA matrix composite material of claim 1, wherein a valence
electron concentration (VEC) of the BCC forming alloy element is
less than or equal to "7."
5. The HEA matrix composite material of claim 1, wherein the BCC
forming alloy element is different from the matrix elements, and
comprises at least one selected from the group consisting of, Al,
Cr, Mn, Mo, Nb, Ta, Ti, V and W.
6. The HEA matrix composite material of claim 1, wherein the BCC
forming alloy element is present in an amount of 0.01% by moles
(mol %) to 90 mol % in the HEA matrix composite material.
7. The HEA matrix composite material of claim 1, wherein a VEC of
the HEA matrix composite material is less than or equal to
"10."
8. The HEA matrix composite material of claim 1, further
comprising: a precipitate(s) comprising at least one selected from
the group consisting of a metal oxide, a metal silicide, a metal
carbide, a metal nitride, a metal boride and an intermetallic
compound, wherein each of the metal oxide, the metal carbide, the
metal nitride, the metal boride and the intermetallic compound
comprises at least one selected from the group consisting of Co,
Cr, Fe, Ni, Mn, Cu, Mo, V, Nb, Al, Si, Ti, Zr, Ta, Mg, Be, Ba, Zn,
Cr, Y, Sn, W, Hf, Nb, Mo, W, La and B.
9. A method of preparing a high entropy alloy (HEA) matrix
composite material, the method comprising: preparing a powder
mixture by mixing a body-centered cubic (BCC) forming alloy element
and at least four matrix elements selected from the group
consisting of Co, Cr, Fe, Ni, Mn, Cu, Mo, V, Nb, Ta, Ti, Zr, W, Si,
Hf and Al; forming a mechanically alloyed powder by mechanically
alloying the powder mixture; and sintering the mechanically alloyed
powder at a high temperature, wherein the forming of the
mechanically alloyed powder comprises bonding the BCC forming alloy
element to at least a portion of the matrix elements.
10. The method of claim 9, wherein the forming of the mechanically
alloyed powder comprises acquiring a HEA matrix composite material
at a yield of 50% or greater using a high-energy ball mill.
11. The method of claim 9, wherein the preparing of the powder
mixture comprises adding a reinforcing material to the powder
mixture.
12. The method of claim 9, further comprising, after the preparing
of the powder mixture or the forming of the mechanically alloyed
powder: adding a precipitate(s) forming element, wherein the
precipitate(s) forming element comprises at least one selected from
the group consisting of Co, Cr, Fe, Ni, Mn, Cu, Mo, V, Nb, Al, Si,
Ti, Zr, Ta, Mg, Be, Ba, Zn, Cr, Y, Sn, W, Hf, Nb, Ta, Mo, W, Ta, La
and B.
13. The method of claim 9, further comprising, after the sintering
of the mechanically alloyed powder: forming a precipitate(s),
wherein the forming of the precipitate(s) comprises forming the
precipitate(s) by a heat treatment at a temperature of 300.degree.
C. to 1500.degree. C.
14. The method of claim 9, wherein the sintering of the
mechanically alloyed powder comprises sintering the mechanically
alloyed powder at a temperature corresponding to 50% to 99% of a
melting point of the mechanically alloyed powder.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This application claims the benefit of Korean Patent
Application No. 10-2016-0053871, filed on May 2, 2016, and Korean
Patent Application No. 10-2017-0035200 filed on Mar. 21, 2017, in
the Korean Intellectual Property Office, the disclosures of which
are incorporated herein by reference.
BACKGROUND
1. Field of the Invention
[0002] At least one example embodiment relates to a high-strength
and ultra heat-resistant high entropy alloy (HEA) matrix composite
material and a method of preparing the HEA matrix composite
material.
2. Description of the Related Art
[0003] Existing alloy materials have been developed to enhance
characteristics, for example, a hardness, a toughness, a heat
resistance, a corrosion resistance, and the like, by addition of
trace elements based on main metals, for example, Ti, Ni, and the
like. Currently, such development of alloy materials by addition of
trace elements has reached its limit.
[0004] Recently, research on high entropy alloys (HEAs) is being
actively conducted. HEAs are reported to have excellent mechanical
properties in comparison to existing metals due to effects of the
HEAs, for example, a sluggish diffusion, a lattice distortion
caused by a difference in size between elements, and a high mixing
entropy by mixing at least four or five metal elements in
near-equiatomic ratios.
[0005] A CoCrFeMnNi HEA reported in the journal Science in 2014
exhibits a fracture toughness of about 200 MPam.sup.0.5 and has
physical properties close to three times that of a titanium alloy,
and accordingly is gaining attention as next-generation extreme
environment materials that may replace existing alloys.
[0006] In a high-energy milling process using a face-centered cubic
(FCC) HEA with a high ductility, cold welding in a ball and a
container may occur, which may lead to a reduction in a powder
yield and a contamination by the ball.
[0007] In a composite HEA to which a reinforcing material is added,
the reinforcing material may tend to be a reactive site that causes
cold welding, and a yield may be severely reduced due to the cold
welding. Thus, there is a desire for a new technology for reducing
a cold welding phenomenon of a composite HEA using a powder
metallurgy process.
SUMMARY
[0008] The present disclosure is to solve the foregoing problems,
and an aspect provides a high entropy alloy (HEA) matrix composite
material and a method of preparing the HEA matrix composite
material which may significantly increase a yield by reducing a
cold welding phenomenon while enhancing mechanical properties and
heat resistance of an alloy.
[0009] However, the problems to be solved in the present disclosure
are not limited to the foregoing problems, and other problems not
mentioned herein would be clearly understood by one of ordinary
skill in the art from the following description.
[0010] According to an aspect, there is provided a HEA matrix
composite material including at least four matrix elements among
Co, Cr, Fe, Ni, Mn, Cu, Mo, V, Nb, Ta, Ti, Zr, W, Si, Hf and Al,
and a body-centered cubic (BCC) forming alloy element.
[0011] The HEA matrix composite material may further include a
reinforcing material. The reinforcing material may include at least
one of a metal oxide, a metal silicide, a metal carbide, a metal
nitride and a metal boride. Each of the metal oxide, the metal
silicide, the metal carbide, the metal nitride and the metal boride
may include at least one selected from the group consisting of Al,
Si, Ti, Zr, Ta, Mg, Be, Ba, Zn, Cr, Y, Sn, W, Hf, V, Nb, Mo, W, La
and B.
[0012] The reinforcing material may be present in an amount of
0.01% by volume (vol %) to 50 vol % in the HEA matrix composite
material.
[0013] A valence electron concentration (VEC) of the BCC forming
alloy element may be less than or equal to "7."
[0014] The BCC forming alloy element may be different from the
matrix elements, and may include at least one of, Al, Cr, Mn, Mo,
Nb, Ta, Ti, V and W.
[0015] The BCC forming alloy element may be present in an amount of
0.01% by moles (mol %) to 90 mol % in the HEA matrix composite
material.
[0016] A VEC of the HEA matrix composite material may be less than
or equal to "10."
[0017] The HEA matrix composite material may further include a
precipitate(s). The precipitate(s) may include at least one of a
metal oxide, a metal silicide, a metal carbide, a metal nitride, a
metal boride and an intermetallic compound. Each of the metal
oxide, the metal carbide, the metal nitride, the metal boride and
the intermetallic compound may include at least one of Co, Cr, Fe,
Ni, Mn, Cu, Mo, V, Nb, Al, Si, Ti, Zr, Ta, Mg, Be, Ba, Zn, Cr, Y,
Sn, W, Hf, Nb, Ta, Mo, W, Ta, La and B.
[0018] The precipitate(s) may include at least one of Ni.sub.3Nb,
TiC, MoC, CrC, Cr.sub.23C.sub.6, Mo.sub.23C.sub.6, W.sub.23C.sub.6,
Co.sub.23C.sub.6, Fe.sub.23C.sub.6, Mo.sub.6C, W.sub.6C, Co.sub.6C,
Ni.sub.6C, Ni.sub.3Al, Ni.sub.3Ti, TiAl and
Cr.sub.aMo.sub.bNi.sub.c in which a, b and c are rational
numbers.
[0019] According to another aspect, there is provided a method of
preparing a HEA matrix composite material, including preparing a
powder mixture by mixing a body-centered cubic (BCC) forming alloy
element and at least four matrix elements selected from the group
consisting of Co, Cr, Fe, Ni, Mn, Cu, Mo, V, Nb, Ta, Ti, Zr, W, Si,
Hf and Al, forming a mechanically alloyed powder by mechanically
alloying the powder mixture, and sintering the mechanically alloyed
powder at a high temperature, wherein the forming of the
mechanically alloyed powder includes bonding the BCC forming alloy
element to at least a portion of the matrix elements.
[0020] The forming of the mechanically alloyed powder may include
acquiring a HEA matrix composite material at a yield of 50% or
greater using a high-energy ball mill.
[0021] The preparing of the powder mixture may include adding
either a reinforcing material or a precipitate(s) forming element,
or both to the powder mixture.
[0022] The method may further include, after the preparing of the
powder mixture or the forming of the mechanically alloyed powder,
adding a precipitate(s) forming element. The precipitate(s) forming
element may include at least one of Co, Cr, Fe, Ni, Mn, Cu, Mo, V,
Nb, Al, Si, Ti, Z, Zr, Ta, Mg, Be, Ba, Zn, Cr, Y, Sn, W, Hf, Nb,
Mo, W, La and B.
[0023] The method may further include, after the sintering of the
mechanically alloyed powder, forming a precipitate(s). The forming
of the precipitate(s) may include forming the precipitate(s) by a
heat treatment at a temperature of 300.degree. C. to 1500.degree.
C.
[0024] The sintering of the mechanically alloyed powder may include
sintering the mechanically alloyed powder at a temperature
corresponding to 50% to 99% of a melting point of the mechanically
alloyed powder.
[0025] Additional aspects of example embodiments will be set forth
in part in the description which follows and, in part, will be
apparent from the description, or may be learned by practice of the
disclosure.
BRIEF DESCRIPTION OF THE DRAWINGS
[0026] These and/or other aspects, features, and advantages of the
invention will become apparent and more readily appreciated from
the following description of example embodiments, taken in
conjunction with the accompanying drawings of which:
[0027] FIG. 1 is a flowchart illustrating a method of preparing a
high entropy alloy (HEA) matrix composite material according to an
example embodiment;
[0028] FIG. 2 is a diagram illustrating yields of powders of HEA
matrix composite materials prepared in Examples 1, 2 and 3 and
Comparative Examples 1 and 2 according to an example
embodiment;
[0029] FIG. 3 is an X-ray diffraction (XRD) graph of HEA matrix
composite materials prepared in Examples 1 to 3 according to an
example embodiment;
[0030] FIG. 4 illustrates scanning electron microscopy (SEM) images
of HEA matrix composite materials prepared in Examples 1 and 2
according to an example embodiment;
[0031] FIG. 5 is a graph illustrating a hardness of HEA matrix
composite materials prepared in Examples 1 to 3 and Comparative
Examples 1 and 2 according to an example embodiment; and
[0032] FIG. 6 is a graph illustrating a compressive strength of a
HEA matrix composite material prepared in Example 1 according to an
example embodiment.
DETAILED DESCRIPTION
[0033] Hereinafter, example embodiments of the present disclosure
will be described in detail with reference to the accompanying
drawings. When it is determined detailed description related to a
related known function or configuration they may make the purpose
of the present disclosure unnecessarily ambiguous in describing the
present disclosure, the detailed description will be omitted here.
Also, terms used herein are defined to appropriately describe the
example embodiments and thus may be changed depending on a user,
the intent of an operator, or a custom of a field to which the
present disclosure pertains. Accordingly, the terms must be defined
based on the following overall description of this specification.
Like reference numerals present in the drawings refer to the like
elements throughout.
[0034] According to an example embodiment, a high entropy alloy
(HEA) matrix composite material may be provided. The HEA matrix
composite material may slightly increase a brittleness of a powder
by adding a body-centered cubic (BCC) forming alloy element to a
HEA matrix having a face-centered cubic (FCC) structure, to prevent
a cold welding phenomenon and to increase a yield of an alloyed
powder in a mechanical alloying process. Also, a precipitate(s) as
well as a .gamma.' phase, an oxide, a carbide, a nitride, a boride
and a silicide may be formed, and thus it is possible to enhance
both a high-temperature stability and mechanical properties of an
alloy.
[0035] The HEA matrix composite material may include a matrix
element, and a BCC forming alloy element. The HEA matrix composite
material may further include a reinforcing material and/or a
precipitate(s).
[0036] The matrix element may be used to form a matrix HEA of the
HEA matrix composite material, and may desirably be an element to
form an alloy with an FCC structure. For example, all elements
capable of forming an alloy with an FCC structure may be used as
the matrix element without a limitation. The matrix element may
include, for example, at least four of Co, Cr, Fe, Ni, Mn, Cu, Mo,
V, Nb, Ta, Ti, Zr, W, Si, Hf and Al, and may desirably include, for
example, a quaternary alloy such as CoCrFeNi, CoCrFeMn, CoCrFeCu,
CoCrFeMo, CoCrFeV, CoCrFeNb, CuCrFeNi and CoCrCuNi; a quinary alloy
such as CoCrFeNiMn, CoCrFeNiCu, CoCrFeNiMn, CoCrFeNiMo, CoCrFeNiV,
CuCrFeNiMn, CoCrCuFeNi and CoCrFeNiNb; and a senary alloy such as
CoCrFeNiMnMo, CoCrFeNiMnCu, CoCrFeNiMnV and CoCrFeNiMnNb.
[0037] The matrix element may be present in an amount of 5% by
moles (mol %) to 35 mol % in the matrix HEA.
[0038] The BCC forming alloy element may be used to prevent cold
welding and to enhance mechanical properties. For example, a BCC
forming alloy element for reducing an average valence electron
concentration (VEC) of an alloy to be less than or equal to "8" may
be added to an alloy matrix, for example, an FCC alloy matrix with
an average VEC greater than or equal to "8." Thus, cold welding may
be prevented in a mechanical alloying process and a yield of an
alloyed powder may be significantly enhanced. Also, a contamination
by a ball due to the cold welding may be prevented, and mechanical
properties of an alloy may be enhanced.
[0039] For example, the BCC forming alloy element may be an element
to reduce an average VEC of a HEA, and may have a VEC less than or
equal to "7," a VEC less than or equal to "6.8," or a VEC less than
or equal to "5." The BCC forming alloy element may include, for
example, at least one of Al, Cr, Mn, Mo, Nb, Ta, Ti, V and W. The
BCC forming alloy element may be different from the matrix element.
A VEC may refer to a sum of the number of peripheral electrons and
the number of electrons included in a d-orbital. Based on the paper
published by Guo et al. in the Journal of Applied Physics in 2011,
an FCC phase and a BCC phase of a HEA may be determined by a VEC of
a component of the HEA.
[0040] The BCC forming alloy element may be present in an amount of
0.01 mol % to 90 mol %, an amount of 0.1 mol % to 60 mol %, an
amount of 0.1 mol % to 30 mol %, an amount of 0.1 mol % to 20 mol
%, or an amount of 0.1 mol % to 5 mol % in the HEA matrix composite
material. When the amount of the BCC forming alloy element is
within the above ranges, a metal composite material that has
excellent mechanical properties and that is used to prevent cold
welding in a mechanical alloying process may be provided.
[0041] The reinforcing material may be used to enhance a strength
of the HEA matrix composite material. The reinforcing material may
include, for example, at least one of a metal oxide, a metal
silicide, a metal carbide, a metal nitride and a metal boride. Each
of the metal oxide, the metal silicide, the metal carbide, the
metal nitride and the metal boride may include, for example, at
least one of Al, Si, Ti, Zr, Ta, Mg, Be, Ba, Zn, Cr, Y, Sn, W, Hf,
V, Nb, Mo, W, La, and B.
[0042] The metal oxide may include, for example, at least one of
Al.sub.2O.sub.3, SiO.sub.2, TiO.sub.2, ZrO.sub.2, Ta.sub.2O.sub.5,
MgO, BeO, BaTiO.sub.3, ZnO, BaO, CrO.sub.2, Y.sub.2O.sub.3,
SnO.sub.2, WO.sub.2, W.sub.2O.sub.3, and WO.sub.3. The metal
carbide may include, for example, at least one of SiC, TiC, ZrC,
HfC, VC, NbC, TaC, Mo.sub.2C and WC. The metal nitride may include,
for example, at least one of TiN, ZrN, HfN, VN, NbN, TaN, AlN,
AlON, and Si.sub.3N.sub.4. The metal boride may include, for
example, at least one of TiB.sub.2, ZrB.sub.2, HfB.sub.2, VB.sub.2,
NbB.sub.2, TaB.sub.2, WB.sub.2, MoB.sub.2, B.sub.4C and
LaB.sub.6.
[0043] The reinforcing material may be present in an amount of
0.01% by volume (vol %) to 50 vol % and desirably in an amount of
0.05 vol % to 10 vol % in the HEA matrix composite material. When
the amount of the reinforcing material is within the above ranges,
the reinforcing material may be uniformly dispersed in an alloy
matrix and a strength of a metal composite material may be
enhanced.
[0044] The precipitate(s) may enhance high-temperature properties
of a metal composite material so that a HEA matrix composite
material applicable as a material for a high temperature may be
formed. The precipitate(s) may be formed by, for example, at least
one of a matrix element, a BCC forming alloy element and an added
precipitate(s) forming element or material. The precipitate(s) may
include a .gamma.' phase, and/or at least one of an oxide, a
carbide, a nitride, a boride, a silicide and an intermetallic
compound.
[0045] For example, the .gamma.' phase may be a crystalline phase
that includes at least one element or at least two elements among a
BCC forming alloy element, a precipitate(s) forming element and a
matrix element dispersed in a matrix HEA. The .gamma.' phase may
include, for example, at least one of Ni.sub.3Al, Ni.sub.3Ti and
TiAl.
[0046] The oxide, the carbide, the nitride, the boride, the
silicide and the intermetallic compound in the precipitate(s) may
include, for example, at least one of a metal oxide, a metal
silicide, a metal carbide, a metal nitride, a metal boride and an
intermetallic compound. Each of the metal oxide, the metal
silicide, the metal carbide, the metal nitride, the metal boride
and the intermetallic compound may include, for example, at least
one of Co, Cr, Fe, Ni, Mn, Cu, Mo, V, Nb, Al, Si, Ti, Zr, Ta, Mg,
Be, Ba, Zn, Cr, Y, Sn, W, If, Nb, Mo, W, La and B.
[0047] The metal carbide may include, for example, TiC, MoC, CrC,
Cr.sub.23C.sub.6, Mo.sub.23C.sub.6, W.sub.23C.sub.6,
Co.sub.23C.sub.6, Fe.sub.23C.sub.6, Mo.sub.6C, W.sub.6C, Co.sub.6C,
Ni.sub.6C, and the like.
[0048] The intermetallic compound may be, for example, an
intermetallic compound with at least two elements. The
intermetallic compound with at least two elements may include, for
example, M1.sub.aM2.sub.b and M1.sub.aM2.sub.bM3.sub.c (in which
M1, M2 and M3 are selected from Co, Cr, Fe, Ni, Mn, Cu, Mo, V, Nb,
Al, Si, Ti, Zr, Ta, Mg, Bo, Ba, Zn, Cr, Y, Sn, W, Hf, Nb, Mo, W,
La, and B, and a, b and c denote the same rational number or
different rational numbers and may be a rational number less than
or equal to "100"). For example, M1.sub.aM2.sub.b may be
Ni.sub.3Nb, Ni.sub.3Al, Ni.sub.3Ti, TiAl, and the like, and
M1.sub.aM2.sub.bM3.sub.c may be a CrMoNi-based compound, such as
Cr.sub.aMo.sub.bNi.sub.c, and the like.
[0049] In an example, the precipitate(s) may be formed by either a
matrix element or a BCC forming alloy element, or both in a process
of alloying the HEA matrix composite material, and/or may be formed
by adding a precipitate(s) forming element before or after a
mechanically alloyed powder is formed. In another example, the
precipitate(s) may be formed by sintering the mechanically alloyed
powder and/or by a heat treatment after the sintering.
[0050] For example, the precipitate(s) forming element may be the
same as or different from a matrix element. The precipitate(s)
forming may include, for example, at least one of Co, Cr, Fe, Mn,
Cu, Mo, V, Nb, Ni, Al, Si, Ti, Zr, Ta, Mg, Be, Ba, Zn, Cr, Y, Sn,
W, Hf, V, Nb, Ta, Mo, W, Ta, La, and B. The precipitate(s) forming
element may be present in an amount exceeding 0 mol % and less than
or equal to 300 mol %, and desirably in an amount of 1 mol % to 100
mol % with respect to the matrix element and/or the BCC forming
alloy element.
[0051] The HEA matrix composite material may have an average VEC
less than or equal to "10," an average VEC of "5" to "8," or an
average VEC of "6" to "7.5." For example, the matrix element may
form an FCC structure. Accordingly, when a BCC forming alloy
element with a lower VEC than that of the matrix element is added,
an average VEC of an alloy matrix composite material may be reduced
and the alloy matrix composite material may have both a BCC
structure and an FCC structure. Also, by reducing the average VEC
of the alloy matrix composite material, it is possible to prevent
cold welding between matrix alloy elements in a mechanical alloying
process.
[0052] According to an example embodiment, a method of preparing a
HEA matrix composite material may be provided. In the method, a BCC
forming alloy element may be added to a matrix element or a
reinforcing material may be additionally added, and thus it is
possible to enhance a mechanical strength and a yield of the HEA
matrix composite material. Also, a precipitate(s) may be
additionally added, and thus it is possible to enhance a
high-temperature characteristic of the HEA matrix composite
material.
[0053] FIG. 1 is a flowchart illustrating a method of preparing a
HEA matrix composite material according to an example embodiment.
The method of FIG. 1 may include operation 110 of preparing a
powder mixture, operation 120 of forming a mechanically alloyed
powder, and operation 130 of sintering the mechanically alloyed
powder at a high temperature.
[0054] In operation 110, the powder mixture may be prepared by
mixing a matrix element and a BCC forming alloy element. The matrix
element and the BCC forming alloy element have been described above
in the description of the HEA matrix composite material. A powder
mixing method applicable in the technical field of the present
disclosure may be used in operation 110, and accordingly further
description thereof is not repeated herein.
[0055] In operation 120, the mechanically alloyed powder may be
formed by mechanically alloying the powder mixture. Operation 120
may be performed to prevent cold welding of powders in a mechanical
alloying process by adding the BCC forming alloy element so as to
increase a yield of an alloy, and to prevent impurities from
flowing into the alloy by preventing a contamination by a ball
mill.
[0056] In an example, in operation 120, the BCC forming alloy
element may be bonded to at least a portion of the matrix element
and may be dispersed in the alloy matrix. In another example, the
BCC forming alloy element may be bonded to at least a portion of
the matrix element, to form a BCC alloy. The BCC alloy may also be
dispersed in the alloy matrix.
[0057] In operation 110, a reinforcing material (for example, a
reinforcing material forming element and/or material) may be
additionally added to the powder mixture. The reinforcing material
has been described above.
[0058] For example, operation 120 may be performed within 120
hours, for a period of 1 hour to 120 hours, or a period of 10 hours
to 50 hours.
[0059] In operation 120, the HEA matrix composite material may be
provided at a yield greater than or equal to 50%, a yield greater
than or equal to 60%, a yield greater than or equal to 80%, or a
yield greater than or equal to 90%.
[0060] In operation 120, a high-energy ball mill may be used. For
example, a vibration mill, a planetary mill, an attrition mill, and
the like may be used, however, there is no limitation thereto.
[0061] In operation 130, the mechanically alloyed powder may be
sintered at a high temperature so that the mechanically alloyed
powder may be formed of bulk materials. For example, in operation
130, a normal sintering method, a reaction sintering method, a
pressurizing sintering method, an isostatic pressure sintering
method, a gas pressure sintering method, or a high-temperature
pressurizing sintering method may be used, however, there is no
limitation thereto.
[0062] In operation 130, the mechanically alloyed powder may be
sintered at a temperature that corresponds to 50% to 99%, 50% to
80%, 60% to 80%, 70% to 80%, 50% to 70%, 60% to 70%, or 50% to 60%
of a melting point of the mechanically alloyed powder.
[0063] Operation 130 may be performed in an atmosphere including at
least one of air, nitrogen, carbon and boron for 60 hours or less,
for a period of 1 minute to 60 hours, a period of 5 minutes to 10
hours, a period of 5 minutes to 5 hours or a period of 5 minutes to
1 hour.
[0064] The method may further include operation 140 of adding a
precipitate(s) forming element. Operation 140 may be performed
after operation 110 to add and mix the precipitate(s) forming
element and the powder mixture, and/or operation 140 may be
performed after operation 120 to add and mix the precipitate(s)
forming element and the mechanically alloyed powder and to further
perform mechanical alloying as necessary.
[0065] In operation 140, the precipitate(s) forming element may be
added in an amount exceeding 0 mol % and less than or equal to 300
mol %, and desirably in an amount of 1 mol % to 100 mol %, with
respect to the matrix element and/or the BCC forming alloy
element.
[0066] The method may further include operation 150 of forming a
precipitate(s). In operation 150, the precipitate(s) may be formed
by a heat treatment of the mechanically alloyed powder sintered in
operation 130. For example, the heat treatment may be performed at
a temperature of 300.degree. C. to 1500.degree. C. for 60 hours or
less, for a period of 1 minute to 60 hours, a period of 10 minutes
to 50 hours, a period of 1 hour to 20 hours, or a period of 1 hour
to 10 hours. When a temperature and a period of time for the heat
treatment are within the above ranges, the precipitate(s) may be
efficiently formed, and a high-temperature characteristic of an
alloy material may be enhanced. For example, in operation 150, the
heat treatment may be performed in an atmosphere including at least
one of air, nitrogen, carbon and boron.
Example 1
[0067] Mechanical alloying was performed using a planetary mill for
24 hours, to prepare an Al.sub.0.3CoCrFeMnNi HEA powder to which 3
vol % of Y.sub.2O.sub.3 was added. About 5.7 mol % of Al was added
as a BCC forming alloy element. A yield of the prepared
Al.sub.0.3CoCrFeMnNi HEA powder is shown in FIG. 2.
[0068] The prepared 3 vol % Y.sub.2O.sub.3/Al.sub.0.3CrCrFeMnNi HEA
powder was sintered at 900.degree. C. for 5 minutes using a spark
plasma sintering method, to prepare a sintered alloy. A phase and a
microstructure of the sintered alloy were analyzed and a hardness
and a compressive strength of the sintered alloy were measured as
shown in FIGS. 3 to 6. The microstructure was obtained by a
scanning electron microscope (SEM).
Example 2
[0069] Mechanical alloying was performed using a planetary mill for
24 hours, to prepare an Al.sub.0.3CoCrFeMnNi HEA powder to which 5
vol % of TiC was added. About 5.7 mol % of Al was added as a BCC
forming alloy element. A yield of the prepared Al.sub.0.3CoCrFeMnNi
HEA powder is shown in FIG. 2.
[0070] The prepared 5 vol % TiC/Al.sub.0.3CoCrFeMnNi HEA powder was
sintered at 900.degree. C. for 5 minutes using a spark plasma
sintering method, to prepare a sintered alloy. A phase and a
microstructure of the sintered alloy were analyzed and a hardness
of the sintered alloy was measured as shown in FIGS. 3 to 5.
Example 3
[0071] Mechanical alloying was performed using a planetary mill for
24 hours, to prepare a Mo.sub.0.8CoCrFeMnNi HEA powder. About 13.8
mol % of Mo was added as a BCC forming alloy element. A yield of
the prepared Mo.sub.0.8CoCrFeMnNi HEA powder is shown in FIG.
2.
[0072] The prepared Mo.sub.0.8CoCrFeMnNi HEA powder was sintered at
900.degree. C. for 5 minutes using a spark plasma sintering method,
to prepare a sintered alloy. A phase and a microstructure of the
sintered alloy were analyzed and a hardness of the sintered alloy
was measured as shown in FIGS. 3 to 5.
Comparative Example 1
[0073] An alloyed powder was prepared in the same manner as in
Example 1 except that a CoCrFeNiMn HEA was formed. A yield of the
alloyed powder is shown in FIG. 2. The prepared CoCrFeNiMn HEA
powder was sintered at 900.degree. C. for 5 minutes using a spark
plasma sintering method, to prepare a sintered alloy. A hardness of
the sintered alloy was measured as shown in FIG. 5.
Comparative Example 2
[0074] An alloyed powder was prepared in the same manner as in
Example 1 except that a CoCrFeNiMn HEA to which 3 vol % of
Y.sub.2O.sub.3 was added was formed. A yield of the alloyed powder
is shown in FIG. 2. The prepared CoCrFeNiMn HEA was sintered at
900.degree. C. for 5 minutes using a spark plasma sintering method,
to prepare a sintered alloy. A hardness of the sintered alloy was
measured as shown in FIG. 5.
[0075] Referring to FIG. 2, the CoCrFeNiMn HEA of Comparative
Example 1 to which Al was not added as a BCC alloying element has a
yield of 17.6%, and the CoCrFeNiMn HEA of Comparative Example 2 to
which 3 vol % of Y.sub.2O.sub.3 was added has a yield of 16.4%,
whereas the Al.sub.0.3CoCrFeMnNi HEA powder of Example 1 to which 3
vol % of Y.sub.2O.sub.3 was added has a yield of 81.2% that is
superior to the yields of the CoCrFeNiMn HEAs of Comparative
Examples 1 and 2. This is because most of powders are entangled in
a ball and a container due to cold welding in a mechanical alloying
process, thereby lowering a yield of the alloyed powder. However,
since Al was added as a BCC alloying element to the 3 vol %
Y.sub.2O.sub.3/Al.sub.0.3CoCrFeMnNi HEA powder in Example 1, it is
possible to reduce the cold welding by enhancing a brittleness of
the powder, and possible to obtain an alloyed powder at a high
yield.
[0076] In an X-ray diffraction (XRD) graph of FIG. 3, a phase
analysis of the sintered alloy is shown. It can be found from the
XRD graph that Mo was added to the sintered alloy prepared in
Example 3, to form a BCC phase and to form a precipitate that
includes Cr, Mo and Ni.
[0077] Referring to FIG. 4, it can be found that reinforcing
materials are uniformly dispersed as shown in SEM images that show
the microstructures of the sintered alloys of Examples 1 and 2.
[0078] Referring to FIG. 5, it can be found that the hardness of
the Al.sub.0.3CoCrFeMnNi alloy to which 3 vol % of Y.sub.2O.sub.3
was added in Example 1 and the hardness of the Al.sub.0.3CoCrFeMnNi
alloy to which 5 vol % of TiC was added in Example 2 were enhanced
in comparison to the CoCrFeNiMn alloy of Comparative Example 1 and
the CoCrFeNiMn alloy of Comparative Example 2 to which 3 vol % of
Y.sub.2O.sub.3 was added. Referring to FIG. 6, it can be found that
the 3 vol % Y.sub.2O.sub.3/Al.sub.0.3CoCrFeMnNi alloy of Example 1
has a high compressive strength, which may indicate that mechanical
properties may be enhanced by adding Al and a reinforcing material
and a powder yield may also be enhanced by adding Al as a BCC
alloying element to a HEA.
[0079] Thus, a BCC forming alloy element and a reinforcing material
may be added, to enhance a heat resistance and mechanical
properties of a HEA matrix composite material, to prevent cold
welding in a mechanical alloying process, and to increase a yield
of an alloyed powder.
[0080] According to example embodiments, it is possible to prevent
cold welding by adding a BCC forming alloy element to a HEA matrix,
to increase a yield of an alloyed powder of a HEA matrix composite
material. Also, it is possible to enhance a heat resistance and
mechanical properties of the HEA matrix composite material by
additionally adding a reinforcing material.
[0081] Although the example embodiments have been described with
reference to the accompanying drawings, the present disclosure is
not limited to the described example embodiments. Instead, it would
be appreciated by one of ordinary skill in the art that various
modifications and changes may be made to these example embodiments
without departing from the principles and spirit of the present
disclosure. It is intended therefore that the scope of the present
invention not be limited to the foregoing embodiments, but be
defined by the claims appended hereto and their equivalents.
* * * * *