U.S. patent application number 15/838608 was filed with the patent office on 2018-10-18 for al-zn-cu alloy and manufacturing method thereof.
The applicant listed for this patent is KOREA INSTITUTE OF MACHINERY & MATERIALS. Invention is credited to Jee-Hyuk AHN, Eun-Ae CHOI, Seung-Zeon HAN, Kwang-Ho KIM.
Application Number | 20180298474 15/838608 |
Document ID | / |
Family ID | 63792010 |
Filed Date | 2018-10-18 |
United States Patent
Application |
20180298474 |
Kind Code |
A1 |
HAN; Seung-Zeon ; et
al. |
October 18, 2018 |
AL-ZN-CU ALLOY AND MANUFACTURING METHOD THEREOF
Abstract
The present invention relates to an Al--Zn--Cu alloy comprising:
18 to 50 parts by weight of zinc; 0.05 to 5 parts by weight of
copper; and the rest being aluminum, based on the total weight of
the alloy, wherein a tensile strength is 230 to 450 MPa and an
elongation is 2.75 to 10% in the cast state. According to the
present invention, it is possible to provide an Al--Zn--Cu alloy
having improved casting property, strength and elongation at the
same time.
Inventors: |
HAN; Seung-Zeon;
(Changwon-si, KR) ; KIM; Kwang-Ho; (Busan, KR)
; AHN; Jee-Hyuk; (Changwon-si, KR) ; CHOI;
Eun-Ae; (Gimhae-si, KR) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
KOREA INSTITUTE OF MACHINERY & MATERIALS |
Daejeon |
|
KR |
|
|
Family ID: |
63792010 |
Appl. No.: |
15/838608 |
Filed: |
December 12, 2017 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
C22C 21/10 20130101;
C22C 1/026 20130101; C22C 30/02 20130101; C22C 30/06 20130101; C22F
1/053 20130101 |
International
Class: |
C22C 21/10 20060101
C22C021/10; C22F 1/053 20060101 C22F001/053 |
Foreign Application Data
Date |
Code |
Application Number |
Apr 13, 2017 |
KR |
10-2017-0048119 |
Claims
1. An Al--Zn--Cu alloy comprising: 18 to 50 parts by weight of
zinc; 0.05 to 5 parts by weight of copper; and the rest being
aluminum, based on the total weight of the alloy, wherein the
Al--Zn--Cu alloy has at least one of the following features: 1) a
tensile strength of 230 to 450 MPa and an elongation of 2.75 to 10%
in the cast state; 2) 2.theta. of a Zn(0002) plane of a lattice
constant in the X-ray diffraction of 36.3 to 36.9; and 3) 2.theta.
of a Zn(1000) plane of the lattice constant in the X-ray
diffraction of 38.7 to 38.9.
2. The Al--Zn--Cu alloy of claim 1, wherein the tensile strength in
the cast state is 310 to 450 Mpa.
3. The Al--Zn--Cu alloy of claim 1, wherein the elongation in the
cast state is 4 to 10%.
4. The Al--Zn--Cu alloy of claim 1, wherein a conductivity is 37%
IACS (International Annealed Copper Standard) or more.
5. The Al--Zn--Cu alloy of claim 1, wherein at least one of the
diameter and the length of a Zn phase in an Al matrix is 10 to 100
nm.
6. The Al--Zn--Cu alloy of claim 1, further comprising at least one
of more than 0 to less than 1 part by weight of magnesium and more
than 0 to less than 0.5 parts by weight of silicon, based on the
total weight of the alloy.
7. An Al--Zn--Cu alloy heat-treated with the Al--Zn--Cu alloy of
claim 1 to have a tensile strength of 330 to 600 Mpa.
8. The Al--Zn--Cu alloy of claim 7, wherein the Al--Zn--Cu alloy
has elongation of 4 to 12%.
9. The Al--Zn--Cu alloy of claim 7, wherein the heat-treatment is
performed at a temperature of 150 to 500.degree. C.
10. A method for manufacturing an Al--Zn--Cu alloy of claim 1
comprising: preparing an alloy molten comprising: 18 to 50 parts by
weight of zinc; 0.05 to 5 parts by weight of copper; and the rest
being aluminum, based on the total weight of the alloy; and casting
by filling the alloy molten into a metallic mold or a sand
mold.
11. The method of claim 10, wherein the step for preparing an alloy
molten is performed at 650 to 750.degree. C. and comprises
degassing after the alloy is completely melted.
12. The method of claim 10, wherein tensile strength of the
Al--Zn--Cu alloy is 230 to 450 MPa and elongation is 2.75 to 10% in
the cast state.
13. The method of claim 10, wherein the Al--Zn--Cu alloy has
2.theta. of a Zn(0002) plane of the lattice constant in the X-ray
diffraction of 36.3 to 36.9.
14. The method of claim 10, wherein the Al--Zn--Cu alloy has
2.theta. of a Zn(1000) plane of the lattice constant in the X-ray
diffraction of 38.7 to 38.9.
15. The method of claim 10, wherein the Al--Zn--Cu alloy has at
least one of the diameter and the length of the Zn phase in the Al
matrix of 10 to 100 nm.
16. The method of claim 10, further comprising forming a solid
solution by heat-treating the Al--Zn--Cu alloy at a temperature of
150 to 500 IC.
17. The method of claim 16, wherein the heat-treatment is performed
for 30 minutes or more.
18. A cast product manufactured from the alloy of claim 1.
19. A machined aluminum alloy product manufactured from the alloy
of claim 1.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This application claims the benefit under 35 USC .sctn.
119(a) of Korean Patent Application No. 10-2017-0048119 filed on
Apr. 13, 2017 in the Korean Intellectual Property Office, the
entire disclosure of which is incorporated herein by reference for
all purposes.
BACKGROUND
1. Field
[0002] The following description relates to an Al--Zn--Cu alloy and
a manufacturing method thereof and more particularly, to an
Al--Zn--Cu casting alloy, a heat-treated alloy and a wrought alloy
having improved castability, tensile strength and elongation at the
same time, and a manufacturing method thereof.
2. Description of Related Art
[0003] A casting process is widely used in various fields such as
in the production of electric parts, optical instruments, vehicles,
spinning machines, constructions, measuring instruments and the
like, particularly automobile parts.
[0004] Aluminum alloys such as Al--Si alloys and Al--Mg alloys,
which have excellent casting properties, have been generally used
as cast aluminum alloys, but their tensile strengths are low.
Therefore, aluminum alloys having a relatively high tensile
strength are used for plastic processing such as extrusion,
rolling, and forging. Such an aluminum alloy for plastic processing
is excellent in plastic workability, but has a problem of poor
castability in which cracking occurs during casting.
[0005] On the other hand, an aluminum alloy has been used as a
structural material since it is a lightweight alloy and has
excellent corrosion resistance and thermal conductivity. Since
aluminum has a low mechanical property, an aluminum alloy including
one or more of metals such as zinc, copper, silicon, magnesium,
nickel, cobalt, zirconium, cerium and the like is widely used as a
structural material such as an interior/exterior material in
various industrial fields such as automobiles, ships, aircrafts. An
aluminum-zinc alloy is used to improve aluminum hardness, usually
containing 10 to 14 wt % of zinc relative to the total weight of
the alloy.
[0006] In order to be used as a structural material for
automobiles, ships, aircrafts, etc., tensile strength, elongation,
and impact absorption energy are considered to be important
mechanical characteristics. Generally, there is a problem that it
is difficult to simultaneously improve the tensile strength and the
elongation because there is a trade-off relationship in which one
of the characteristics of the tensile strength and the elongation
is attenuated when the other is improved (FIG. 1).
[0007] Korean Patent No. 10-1387647 discloses an ultra-high tensile
strength aluminum casting alloy and manufacturing method
thereof.
SUMMARY
[0008] This Summary is provided to introduce a selection of
concepts in a simplified form that are further described below in
the Detailed Description. This Summary is not intended to identify
key features or essential features of the claimed subject matter,
nor is it intended to be used as an aid in determining the scope of
the claimed subject matter.
[0009] An object of the present invention is to provide an
Al--Zn--Cu alloy having an improved casting property by minimizing
cracking and the like.
[0010] Another object of the present invention is to provide an
Al--Zn--Cu cast alloy and a heat-treated alloy having improved
tensile strength and elongation at the same time.
[0011] Still another object of the present invention is to provide
a manufacturing method capable of efficiently producing an
Al--Zn--Cu cast alloy, a heat-treated alloy and a processing alloy
having improved casting property, tensile strength and elongation
at the same time.
[0012] According to an aspect of the present invention, there is
provided an Al--Zn--Cu alloy comprising: 18 to 50 parts by weight
of zinc; 0.05 to 5 parts by weight of copper; and the rest being
aluminum, based on the total weight of the alloy, wherein a tensile
strength is 230 to 450 MPa and an elongation is 2.75 to 10% in the
cast state.
[0013] According to an embodiment of the present invention, the
tensile strength in the cast state may be 310 to 450 Mpa.
[0014] According to an embodiment of the present invention, the
elongation in the cast state may be 4 to 10%.
[0015] According to another aspect of the present invention, there
is provided an Al--Zn--Cu alloy comprising: 18 to 50 parts by
weight of zinc; 0.05 to 5 parts by weight of copper; and the rest
being aluminum, based on the total weight of the alloy, wherein
2.theta. of a Zn(0002) plane of a lattice constant in the X-ray
diffraction is 36.3 to 36.9.
[0016] According to further another aspect of the present
invention, there is provided an Al--Zn--Cu alloy comprising: 18 to
50 parts by weight of zinc; 0.05 to 5 parts by weight of copper;
and the rest being aluminum, based on the total weight of the
alloy, wherein 2.theta. of a Zn(0002) plane of a lattice constant
in the X-ray diffraction is 38.7 to 38.9.
[0017] According to further another aspect of the present
invention, there is provided an Al--Zn--Cu alloy comprising: 18 to
50 parts by weight of zinc; 0.05 to 5 parts by weight of copper;
and the rest being aluminum, based on the total weight of the
alloy, wherein a conductivity is 37% IACS (International Annealed
Copper Standard) or more.
[0018] According to further another aspect of the present
invention, there is provided an Al--Zn--Cu alloy comprising: 18 to
50 parts by weight of zinc; 0.05 to 5 parts by weight of copper;
and the rest being aluminum, based on the total weight of the
alloy, wherein at least one of the diameter and the length of a Zn
phase in an Al matrix is 10 to 100 nm.
[0019] According to an embodiment of the present invention, the
Al--Zn--Cu alloy may further comprise at least one of more than 0
to less than 1 part by weight of magnesium and more than 0 to less
than 0.5 parts by weight of silicon, based on the total weight of
the alloy.
[0020] According to further another aspect of the present
invention, the Al--Zn--Cu alloy may be heat-treated to have a
tensile strength of 330 to 600 Mpa.
[0021] According to an embodiment of the present invention, the
Al--Zn--Cu alloy may have an elongation of 4 to 12%.
[0022] According to an embodiment of the present invention, the
heat-treatment may be performed at a temperature of 150 to
500.degree. C.
[0023] According to further another aspect of the present
invention, there is provided a method for manufacturing an
Al--Zn--Cu alloy comprising: preparing an alloy molten comprising:
18 to 50 parts by weight of zinc; 0.05 to 5 parts by weight of
copper; and the rest being aluminum, based on the total weight of
the alloy; and casting by filling the alloy molten into a metallic
mold or a sand mold.
[0024] According to an embodiment of the present invention, the
step for preparing an alloy molten may be performed at 650 to
750.degree. C. and comprises degassing after the alloy is
completely melted.
[0025] According to an embodiment of the present invention, tensile
strength of the Al--Zn--Cu alloy may be 230 to 450 MPa and
elongation may be 2.75 to 10% in the cast state.
[0026] According to an embodiment of the present invention, the
Al--Zn--Cu alloy may have 2.theta. of a Zn(0002) plane of the
lattice constant in the X-ray diffraction of 36.3 to 36.9.
[0027] According to an embodiment of the present invention, the
Al--Zn--Cu alloy may have 2.theta. of a Zn(1000) plane of the
lattice constant in the X-ray diffraction of 38.7 to 38.9.
[0028] According to an embodiment of the present invention, the
Al--Zn--Cu alloy may have at least one of the diameter and the
length of the Zn phase in the Al matrix of 10 to 100 nm.
[0029] According to an embodiment of the present invention, the
method may further comprise forming a solid solution by
heat-treating the Al--Zn--Cu alloy at a temperature of 150 to
500.degree. C.
[0030] According to an embodiment of the present invention, the
heat-treatment may be performed for 30 minutes or more.
[0031] According to further another aspect of the present
invention, there is provided a cast product manufactured from the
alloy.
[0032] According to further another aspect of the present
invention, there is provided an aluminum alloy product manufactured
from the alloy.
[0033] According to the present invention, it is possible to
provide an Al--Zn--Cu alloy having improved casting properties by
minimizing cracking and the like.
[0034] According to the present invention, it is possible to
provide an Al--Zn--Cu alloy and a heat-treated alloy having
improved strength and elongation at the same time.
[0035] According to the present invention, it is possible to
efficiently produce an Al--Zn--Cu cast alloy, a heat-treated alloy
and a processing alloy with improved casting properties, tensile
strength and elongation at the same time.
[0036] According to the present invention, it is possible to
efficiently produce an Al--Zn--Cu alloy having improved
moldability, tensile strength, elongation and conductivity at the
same time.
[0037] Other features and aspects will be apparent from the
following detailed description, the drawings, and the claims.
BRIEF DESCRIPTION OF THE DRAWINGS
[0038] FIG. 1 is graphs illustrating a trade-off relationship
between tensile strength and ductility of conventional aluminum
alloy for processing and aluminum alloy for casting.
[0039] FIG. 2 is an image illustrating that moldability of a cast
alloy according to an embodiment of the present invention is
excellent.
[0040] FIG. 3 is a graph illustrating that an Al--Zn--Cu alloy
according to an embodiment of the present invention is
simultaneously improved in tensile strength and elongation as
compared with a conventional alloy.
[0041] FIG. 4 is images illustrating improvement in mechanical
properties of a cast alloy according to an embodiment of the
present invention due to reduction in size of a zinc phase and
reduction in distance between particles.
[0042] FIG. 5 is images illustrating that copper is incorporated
into zinc particles when copper is added.
[0043] FIG. 6 is a diagram illustrating an interface of an
Al/Zn--Cu alloy according to an embodiment of the present invention
for calculating a change in interface energy between a zinc phase
and an aluminum phase by copper addition.
[0044] FIG. 7A is a graph illustrating a change in interface energy
of a zinc phase by copper addition.
[0045] FIG. 7B is a graph illustrating a change in lattice constant
of zinc by copper addition.
[0046] FIGS. 8A and 8B are graphs illustrating a change in lattice
constant of a zinc (0002) plane by copper addition.
[0047] FIGS. 9A and 9B are graphs illustrating changes in peak
angle (2.theta.) and lattice constant of a Zn(0002) plane depending
on Cu content of an alloy according to an embodiment of the present
invention.
[0048] FIGS. 10A and 10B are graphs illustrating changes in peak
angle (2.theta.) and lattice constant of a Zn(1000) plane depending
on Cu content of the alloy according to an embodiment of the
present invention.
[0049] FIGS. 11A and 11B are graphs illustrating changes in peak
angle (2.theta.) and lattice constant of an Al(111) plane depending
on Cu content of an alloy according to an embodiment of the present
invention.
[0050] FIGS. 12A and 12B are graphs illustrating changes in peak
angle (2.theta.) and lattice constant of an Al(200) depending on Cu
content of an alloy according to an embodiment of the present
invention.
[0051] FIGS. 13A and 13B are images illustrating a change in the
size of a zinc phase upon cooling after heat treatment of an alloy
according to an embodiment of the present invention by Cu
addition.
[0052] FIGS. 13C and 13D are graphs illustrating the zinc phase
size of the measurement site indicated in FIGS. 13A and 13B.
[0053] FIG. 14 is a flowchart illustrating a method for
manufacturing an Al--Zn--Cu alloy according to an embodiment of the
present invention.
[0054] FIG. 15 is diagrams illustrating a method for manufacturing
an Al--Zn--Cu alloy according to an embodiment of the present
invention and characteristics of the alloy by process.
[0055] FIG. 16 is a graph illustrating a change in conductivity
according to true strains of an Al--Zn--Cu alloy according to an
embodiment of the present invention.
DETAILED DESCRIPTION
[0056] The terms used in the description are intended to describe
certain embodiments only, and shall by no means restrict the
present disclosure. Unless clearly used otherwise, expressions in
the singular number include a plural meaning.
[0057] In the present description, an expression such as
"comprising" or "consisting of" is intended to designate a
characteristic, a number, a step, an operation, an element, a part
or combinations thereof, and shall not be construed to preclude any
presence or possibility of one or more other characteristics,
numbers, steps, operations, elements, parts or combinations
thereof.
[0058] In the present description, when a component is referred to
"comprising", it means that it can include other components as
well, without excluding other components unless particularly stated
otherwise. Also, throughout the specification, the term "on" means
to be located above or below a target portion, and does not
necessarily mean that it is located on the upper side with respect
to the gravitational direction.
[0059] While the present disclosure has been described with
reference to particular embodiments, it is to be appreciated that
various changes and modifications may be made by those skilled in
the art without departing from the spirit and scope of the present
disclosure, as defined by the appended claims and their
equivalents. Throughout the description of the present disclosure,
when describing a certain technology is determined to evade the
point of the present disclosure, the pertinent detailed description
will be omitted.
[0060] While such terms as "first" and "second," etc., may be used
to describe various components, such components must not be limited
to the above terms. The above terms are used only to distinguish
one component from another.
[0061] The disclosure will be described below in more detail with
reference to the accompanying drawings, in which those components
are rendered the same reference number that are the same or are in
correspondence, regardless of the figure number, and redundant
explanations are omitted.
[0062] An Al--Zn--Cu alloy of the present invention comprises 18 to
50 parts by weight of zinc; 0.05 to 5 parts by weight of copper;
and the balance of aluminum, wherein a tensile strength is 230 to
450 MPa and an elongation is 2.75 to 10% in the cast state.
[0063] The Al--Zn--Cu alloy of the present invention has a
remarkable improved moldability as compared with a conventional
cast alloy at the above compositional amounts. That is, the cast
alloy according to the present invention does not cause cracks even
when a cross-sectional area is reduced by 75% in the cold working
(FIG. 2).
[0064] In addition, the Al--Zn--Cu alloy of the present invention
can simultaneously improve tensile strength and elongation in the
cast state (FIG. 3).
[0065] In the present invention, zinc (Zn) is added to aluminum as
an alloy element to effectively increase tensile strength and
hardness. In the Al--Zn--Cu alloy for casting according to the
present invention, zinc is added in an amount of 18 to 50 parts by
weight based on the total weight of the alloy, but it is not
limited thereto. When the content of zinc is less than 18 parts by
weight, the effect of increasing the tensile strength is
insignificant. When the content of zinc is more than 50 parts by
weight, the casting property is lowered and may cause hot
shortness.
[0066] The zinc content may be 20 to 50 parts by weight, 20 to 45
parts by weight, 20 to 40 parts by weight, 30 to 50 parts by
weight, 30 to 45 parts by weight, or 30 to 40 parts by weight, but
it is not limited thereto. The zinc content may be in the range of
30 to 45 parts by weight based on the total weight of the alloy,
but it is not limited thereto. In this case, the Al--Zn--Cu alloy
may have a tensile strength of 350 to 450 MPa and an elongation of
4 to 10% in the cast state (FIG. 3).
[0067] In the present invention, copper (Cu) is added to aluminum
as an alloy element to make the largest contribution to the
increase in tensile strength. The addition of copper to the
aluminum-zinc alloy reduces the size of the zinc particle during
cooling after the heat treatment, thereby significantly reducing
the distance between the particles (FIG. 4 and FIG. 5).
[0068] Copper added in the present invention is incorporated in
zinc to lower the interface energy on a Zn precipitate phase/an Al
matrix phase (FIG. 6). As the interface energy on the precipitation
phase and the matrix phase decreases, the average size of
precipitates decreases. Thus, the addition of copper reduces the
average size of the precipitate zinc. As a result, the spacing
between the zinc particles is greatly reduced and the tensile
strength of the cast alloy is increased.
[0069] Referring to FIG. 6, the closest surfaces of the Al phase
and the Zn phase, which are the surfaces with low energy, are
bonded to each other. The Zn(0002) and Al(100) planes are bonded,
and have the most Al--Zn bonds. When the content of copper is
increased to 6 wt %, the interface energy (E.sub.inter) between
Al(111) and Zn(0001) can be defined by the following Equation
1.
Equation 1 E inter = E Al / zn ( cu ) - ( E Al + E zn ( cu ) ) A (
1 ) ##EQU00001##
[0070] E.sub.AlZn(Cu), E.sub.Al and E.sub.Zn(Cu) are the total
energies of interface structure of Al/Zn(Cu), bulk Al and bulk
Zn(Cu), respectively, and A is the total area of the Al/Zn(Cu)
interface.
[0071] (References: Equation: Perdew-Burke-Emzerhof approximation
(PBE) [1] for the exchange-correlation potential as implanted in
the Vienna Ab-initio Simulation Package code (VASP).[2,3] [1] J. P.
Perdew, K. Burke, and M. Ernzerhof, Phys. Rev. Lett. 77, 3865
(1996) [2] G. Kresse and J. Hafner, Phys. Rev. B 47, 558 (1993) [3]
G. Kresse and J. Furthmuller, Phys. Rev. B 54, 11169 (1996))
[0072] In the Al--Zn--Cu alloy for casting according to the present
invention, copper is added in an amount of 0.05 to 5 parts by
weight based on the total weight of the alloy, but it is not
limited thereto. When the content of copper is less than 0.05 parts
by weight, the effect of increasing the tensile strength is
insignificant. When the content of copper is more than 5 parts by
weight, the castability may be lowered and may cause hot
shortness.
[0073] The content of copper may be 0.05 to 5 parts by weight, 0.05
to 4 parts by weight, 0.05 to 3 parts by weight, 0.05 to 2 parts by
weight, 0.1 to 5 parts by weight, 0.1 to 4 parts by weight, 0.1 to
3 parts by weight, 0.1 to 2 parts by weight, 0.5 to 5 parts by
weight, 0.5 to 4 parts by weight, 0.5 to 3 parts by weight, 0.5 to
2 parts by weight, 1 to 5 parts by weight, 1 to 4 parts by weight,
1 to 3 parts by weight, 1 to 2 parts by weight, 2 to 5 parts by
weight, 2 to 4 parts by weight, 2 to 3 parts by weight, 3 to 5
parts by weight, or 3 to 4 parts by weight, but it is not limited
thereto.
[0074] The content of copper may be in the range of 1 to 4 parts by
weight based on the total weight of the alloy, though it is not
limited thereto. In this case, the Al--Zn--Cu alloy may have a
tensile strength of 310 to 450 MPa and an elongation of 4 to 10% in
the cast state.
[0075] The Al--Zn--Cu alloy of the present invention has 2.theta.
of a Zn(0002) plane of a lattice constant of 36.3 to 36.9 in X-ray
diffraction.
[0076] As described above, Cu in the Al--Zn--Cu alloy of the
present invention remarkably reduces the interface energy on the Zn
precipitation phase/the Al matrix phase. Therefore, the addition of
copper to the aluminum-zinc alloy sharply reduces the interface
energy of the Zn(0002)/Al(100) plane within a certain range (FIG.
7A). In addition, the addition of copper to the aluminum-zinc alloy
significantly reduces the lattice constant of the Zn(0002) plane,
while the lattice constant of the Zn(1000) plane increases gently
with increasing copper solubility (FIG. 7B). Therefore, according
to the present invention, a sharp reduction in the interface energy
of the Zn(0002)/Al(100) plane due to the addition of copper to the
aluminum-zinc alloy is a direct cause of a significant reduction in
the lattice constant of the Zn(0002) plane.
[0077] The lattice constant as described above corresponds to the
maximum peak angle on X-ray diffraction. Thus, the addition of
copper to the aluminum-zinc alloy significantly reduces the lattice
constant of the Zn(0002) plane and increases 2.theta. of the
Zn(0002) plane during X-ray measurement (FIGS. 8A and 8B).
[0078] Accordingly, the Al--Zn--Cu alloy of the present invention
exhibits an increase in 2.theta. of a Zn(0002) plane of a lattice
constant in the X-ray diffraction to the range of 36.3 to 36.9
(FIGS. 9A and 9B).
[0079] As described above, the lattice constant corresponds to the
maximum peak angle on X-ray diffraction. In addition, the addition
of copper to the aluminum-zinc alloy increases a lattice constant
of the Zn(1000) plane and decreases the 2.theta. of the Zn(1000)
plane during X-ray measurement.
[0080] Accordingly, the Al--Zn--Cu alloy of the present invention
exhibits a reduction in 2.theta. of a Zn(1000) plane of a lattice
constant in the X-ray diffraction to the range of 38.7 to 38.9
(FIGS. 10A and 10B).
[0081] On the other hand, the position of the Al peak is not
directly affected by the addition of Cu, since copper is not
incorporated in the aluminum matrix (FIG. 11A-FIG. 12B).
[0082] The Al--Zn--Cu alloy of the present invention may have at
least one of a diameter and a length of a Zn phase in an Al matrix
of 10 to 100 nm. As described above, when copper is added to the
aluminum-zinc alloy, the average size of zinc, which is a
precipitation phase, decreases (FIG. 13A-FIG. 13D). As a result,
the distance between the zinc particles is greatly reduced and the
tensile strength of the cast alloy is increased. When at least one
of the diameter and the length of the Zn phase in the Al matrix is
less than 10 nm or exceeds 100 nm, the increase in the tensile
strength of the alloy due to the addition of copper may be
insignificant.
[0083] The Al--Zn--Cu alloy of the present invention comprises 18
to 50 parts by weight of zinc; 0.05 to 5 parts by weight of copper;
and the rest being aluminum based on the total weight of the alloy,
and the conductivity may be higher than 37% International Annealed
Copper Standard (IACS). The Al--Zn--Cu alloy according to the
present invention improves the tensile strength and elongation as
well as the conductivity (FIG. 16).
[0084] According to one embodiment of the present invention, the
Al--Zn--Cu alloy may further comprise at least one of more than 0
to less than 1 part by weight of magnesium and more than 0 to less
than 0.5 parts by weight of silicon based on the total weight of
the alloy.
[0085] In the present invention, magnesium (Mg) is added to
aluminum as an alloy element to effectively increase tensile
strength and hardness. In the Al--Zn--Cu alloy according to the
present invention, magnesium is added in an amount of more than 0
parts by weight to less than 1 part by weight based on the total
weight of the alloy, but it is not limited thereto. When the
magnesium content is 1 part by weight or more, grain boundary
corrosion and stress corrosion occur, thereby causing deterioration
of corrosion resistance and rapid decrease of elongation.
[0086] The content of magnesium may be 0.1 to 0.9 parts by weight,
0.1 to 0.7 parts by weight, 0.1 to 0.5 parts by weight, 0.1 to 0.3
parts by weight, 0.2 to 0.9 parts by weight, 0.2 to 0.7 parts by
weight, 0.2 to 0.5 parts by weight, or 0.2 to 0.3 parts by weight,
but it is not limited thereto. The magnesium content may be 0.1 to
0.3 parts by weight based on the total weight of the alloy. In this
case, the Al--Zn--Cu alloy may have a tensile strength of 380 to
450 MPa and an elongation of 4 to 10% in the cast state.
[0087] In the present invention, silicon (Si) is an added to
aluminum as an alloy element to contribute to improvement in
casting and mechanical properties. In the Al--Zn--Cu alloy for
casting according to the present invention, silicon is added in an
amount of more than 0 parts by weight to less than 0.5 parts by
weight based on the total weight of the alloy. When the content of
silicon exceeds 0.5 parts by weight, it may cause the elongation to
drop sharply without increasing the tensile strength.
[0088] The content of silicon may be 0.05 to 0.4 parts by weight,
0.05 to 0.3 parts by weight, 0.05 to 0.2 parts by weight, 0.05 to
0.1 part by weight, 0.1 to 0.4 parts by weight, 0.1 to 0.3 parts by
weight, or 0.1 to 0.2 parts by weight, but it is not limited
thereto. The content of silicon is preferably 0.05 to 0.2 part by
weight based on the total weight of the alloy. In this case, the
Al--Zn--Cu alloy may have a tensile strength of 380 to 450 MPa and
an elongation of 4 to 10% in the cast state.
[0089] A heat-treated Al--Zn--Cu alloy of the present invention has
a tensile strength of 330 to 600 MPa. The tensile strength of the
alloy can be remarkably increased by heat treatment.
[0090] In addition, the heat-treated Al--Zn--Cu alloy of the
present invention may have an elongation of 4 to 12%. The tensile
strength and the elongation of the alloy can be remarkably
increased simultaneously by the heat treatment.
[0091] In the present invention, the heat treatment temperature may
be 150 to 500.degree. C., but it is not limited thereto. If the
heat treatment temperature is lower than 150.degree. C., the
elongation can be improved but the tensile strength may be lowered.
If the heat treatment temperature is higher than 500.degree. C.,
the tensile strength can be improved but the elongation can be
lowered.
[0092] FIG. 14 is a flowchart illustrating a method for
manufacturing an Al--Zn--Cu alloy according to an embodiment of the
present invention. FIG. 15 is diagrams illustrating a method for
manufacturing an Al--Zn--Cu alloy according to an embodiment of the
present invention and characteristics of the alloy by process.
[0093] Referring to FIG. 14 and FIG. 15, an alloy material for
casting is prepared to provide a molten alloy (S100).
[0094] More particularly, the alloy molten including 18 to 50 parts
by weight of zinc; 0.05 to 5 parts by weight of copper; and the
rest being aluminum, based on the total weight of the alloy is
prepared.
[0095] The step for preparing an alloy molten of S100 is performed
at 650 to 750.degree. C., and a degassing operation may be
performed after the alloy is completely melted.
[0096] In S200, the produced molten alloy is cast by filling it to
a metallic mold or a sand mold. The cast alloy has the following
properties which are as described above.
[0097] A tensile strength may be 230 to 450 MPa in the cast state,
and an elongation may be 2.75 to 10%. Further, 2.theta. of a
Zn(0002) plane of a lattice constant in the X-ray diffraction may
be 36.3 to 36.9. 2.theta. Of a Zn(1000) plane of a lattice constant
in the X-ray diffraction may be 38.7 to 38.9. At least one of the
diameter and the length of the Zn phase in the Al matrix may be 10
to 100 nm.
[0098] Thus, according to the present invention, there is provided
a cast article produced from the alloy. Also provided is an
aluminum alloy product manufactured from the alloy.
[0099] The method may further include forming a solid solution by
heat-treating the Al--Zn--Cu alloy at a temperature of 150 to
500.degree. C. of S300.
[0100] The solid solution may be formed by heat-treating the
Al--Zn--Cu. The heat treatment may be a homogenization treatment
and/or a solubilization treatment. Due to the generation of the
solid solution, the Al--Zn--Cu alloy becomes a state containing the
solid solution.
[0101] The temperature range of forming a solid solution may be 150
to 500.degree. C. The temperature range can be determined in
consideration of the maximum employment limit temperature at which
the liquid phase of the Al--Zn--Cu alloy is not formed and the
solid solution can be formed. In the case of an Al--Zn--Cu alloy,
discontinuous precipitates are not produced because a poly-phase is
formed without forming a single phase at a temperature exceeding
500.degree. C. The step of forming a solid solution may be
performed by heating for 30 minutes or more. Although it is not
limited thereto, the heat treatment is preferably carried out at
450.degree. C. for 120 minutes to form a solid solution.
[0102] The method may further include forcibly forming
discontinuous precipitates using the Al--Zn--Cu alloy including the
solid solution (S400).
[0103] The step of forcibly forming discontinuous precipitates is a
step of forming discontinuous precipitates or lamellar precipitates
in the alloy. The aluminum alloy containing the solid solution is
tempered to forcibly form discontinuous precipitates or lamellar
precipitates of 5% or more per unit area. The tempering treatment
may be performed at 120 to 200.degree. C. which is lower than that
of forming the solid solution. For example, the tempering treatment
may be performed at 160.degree. C. The tempering treatment may be
performed for 5 minutes to 400 minutes.
[0104] For example, when the alloy material includes a
precipitation-accelerating metal, water quenching or air quenching
may be performed after the solid solution is formed. By tempering
for more than 2 hours, discontinuous precipitates may be forcibly
produced.
[0105] As described above, water quenching or air quenching before
the tempering treatment can form oriented type precipitates by
rapidly quenching the temperature lowering speed very quickly. When
the temperature is lowered slowly, these precipitates may not be
oriented even if the discontinuous precipitates or lamellar
precipitates are forcibly formed.
[0106] After the discontinuous precipitates or the lamellar
precipitates are forcibly formed as described above, the
aluminum-zinc alloy containing the precipitates is calcined to form
oriented precipitates (S500).
[0107] The step for forming oriented precipitates is a step of
artificially orienting the forcibly formed discontinuous
precipitates, and may be carried out through rolling, drawing
and/or extrusion.
[0108] A drawing ratio, which is a reduction rate of the
cross-sectional area, may be at least 50%. As the drawing ratio
increases, the thickness of the oriented precipitates itself and
the distance between the oriented precipitates may decrease, and
the tensile strength may be improved.
[0109] The step for orientation may be performed in a liquid
nitrogen atmosphere. When oriented in a liquid nitrogen atmosphere,
the heat generated in the step for orientation may be minimized to
facilitate orientation of the discontinuous precipitates, resulting
in increased tensile strength.
[0110] The Al--Zn--Cu alloy may have one or more of the following
characteristics (1) to (5):
[0111] 1) The Al--Zn--Cu alloy includes discontinuous precipitates
or lamellar precipitates forcibly produced at 5% or more per unit
area of the Al--Zn--Cu alloy;
[0112] 2) The average aspect ratio of the discontinuous
precipitates or the lamellar precipitates is 20 or more;
[0113] 3) The average length of the discontinuous precipitates or
the lamellar precipitates is 1.4 .mu.m or more:
[0114] 4) The average interval of the discontinuous precipitates or
the lamellar precipitates is 105 nm or less; and
[0115] 5) The average thickness of the discontinuous precipitates
or the lamellar precipitates is 55 nm or less.
[0116] As described above, the Al--Zn--Cu alloy of the present
invention forcibly forms discontinuous precipitates or lamellar
precipitates during the manufacturing process, and includes
oriented precipitates formed by using the same, so that the tensile
strength, the elongation and the conductivity can be improved at
the same time to be provided as an excellent metal material.
[0117] Therefore, the Al--Zn--Cu alloy of the present invention can
improve both tensile strength and elongation at the same time only
by casting, and can further improve strength and elongation at the
time of processing, so that it can be usefully used in the
production of casting and processing materials.
EXAMPLES
[0118] Hereinafter, the present invention will be described in more
detail with reference to specific production examples and
comparative examples of the present invention.
Examples 1-46 and Comparative Examples 1-10
[0119] Table 1 shows contents of elements of an aluminum-zinc alloy
of Examples and Comparative Examples.
[0120] The Al--Zn--Cu alloy having the content of each element in
Table 1 was melted by electric furnace melting and high-frequency
induction melting. All alloys were cast using a 99.9% pure raw
material. Using an electric furnace, 5 kg of each specimen was
melted and temperature was maintained at 700.degree. C. After
complete melting, A degassing operation was performed with Ar gas
for 10 minutes. After molten state was maintained for 10 minutes,
it was filled into a metallic mold or a sand mold. Five minutes
after filling, the ingot was taken out of the mold.
[0121] Homogenization treatment was carried out at 450.degree. C.
for 120 minutes in order to remove impurities generated during
casting. Subsequently, annealing was performed at a reduction rate
of 20% at 400.degree. C. every 15 minutes to perform swaging to a
total cold processing area reduction rate of 75%. After 1 hour, the
resulting solution was subjected to solution treatment at
450.degree. C. for 2 hours, followed by water-quenching treatment.
Then, precipitation treatment for producing discontinuous
precipitates was carried out at 160.degree. C. for 360 minutes.
TABLE-US-00001 TABLE 1 Heat-treatment Tensile Elongation Interface
energy(J/m.sup.2) (wt %) Al Zn Cu Mg Si Mold Temp. (.degree. C.)
Strength (MPa) (%) Zn(0002)/Al(100) Comparative Example 1 Bal. 45
-- Metallic Mold As cast 286 4 0.139 Comparative Example 2 Bal. 45
-- Metallic Mold 400 312 1.36 Comparative Example 3 Bal. 20 --
Metallic Mold As cast 290 3.8 Comparative Example 4 Bal. 20 --
Metallic Mold 400 199 16.3 Comparative Example 5 Bal. 25 --
Metallic Mold As cast 227 10.3 Comparative Example 6 Bal. 25 --
Metallic Mold 400 350 0.8 Comparative Example 7 Bal. 35 -- Metallic
Mold As cast 290 2.3 Comparative Example 8 Bal. 35 -- Metallic Mold
400 310 0.32 Example 1 Bal. 44.31 0.69 0.084 Example 2 Bal. 43.63
1.37 0.085 Example 3 Bal. 42.94 2.06 0.084 Example 4 Bal. 42.26
2.74 0.082 Example 5 Bal. 41.57 3.43 0.087 Example 6 Bal. 40.89
4.11 0.095 Example 7 Bal. 40.2 4.80 0.109 Example 8 Bal. 39.52 5.48
0.126 Example 9 Bal. 18 2 Metallic Mold As cast 337 4.1 Example 10
Bal. 23 2 Metallic Mold As cast 310 6.1 Example 11 Bal. 23 2
Metallic Mold 400 330 4.5 Example 12 Bal. 33 2 Metallic Mold As
cast 359 4.6 Example 13 Bal. 33 2 Metallic Mold 160 325 22 Example
14 Bal. 33 2 Metallic Mold 330 366 7.9 Example 15 Bal. 33 2
Metallic Mold 490 436 11.1 Example 16 Bal. 33 2 Sand Mold As cast
365 8.0 Example 17 Bal. 33 2 Sand Mold 160 307 13.4 Example 18 Bal.
33 2 Sand Mold 330 410 8.8 Example 19 Bal. 33 2 Sand Mold 490 430
9.7 Example 20 Bal. 39 2 Metallic Mold As cast 373 6.4 Example 21
Bal. 39 2 Metallic Mold 160 319 9.0 Example 22 Bal. 39 2 Metallic
Mold 350 414 6.3 Example 23 Bal. 39 2 Metallic Mold 430 441 8.2
Example 24 Bal. 39 2 Sand Mold As cast 350 6.6 Example 25 Bal. 39 2
Sand Mold 160 309 10.2 Example 26 Bal. 39 2 Sand Mold 350 416 6.7
Example 27 Bal. 39 2 Sand Mold 430 436 6.5 Example 28 Bal. 44.5 0.5
Metallic Mold As cast 322 7.8 Example 29 Bal. 44.5 0.5 Metallic
Mold 400 451 3.2 Example 30 Bal. 44 1 Metallic Mold As cast 315 3.1
Example 31 Bal. 44 1 Metallic Mold 160 320 20.5 Example 32 Bal. 44
1 Metallic Mold 400 437 6.2 Example 33 Bal. 43 2 Metallic Mold As
cast 338 3.9 Example 34 Bal. 43 2 Metallic Mold 160 315 24 Example
35 Bal. 43 2 Metallic Mold 160 320 25 Example 36 Bal. 43 2 Metallic
Mold 370 508 4.8 Example 37 Bal. 43 2 Metallic Mold 400 600 4.5
Example 38 Bal. 42 3 Metallic Mold As cast 401 6.7 Example 39 Bal.
42 3 Metallic Mold 160 300 6.5 Example 40 Bal. 42 3 Metallic Mold
400 554 4.8 Example 41 Bal. 33 2 0.2 0.1 Metallic Mold As cast 391
6.74 Example 42 Bal. 33 2 0.2 0.1 Metallic Mold 160 300 10 Example
43 Bal. 33 2 0.2 0.1 Metallic Mold 400 469 1.27 Example 44 Bal. 33
2 0.5 0.3 Metallic Mold As cast 341 2.59 Example 45 Bal. 33 2 0.5
0.3 Metallic Mold 160 285 4 Example 46 Bal. 33 2 0.5 0.3 Metallic
Mold 400 437 1.33 Comparative Example 9 Bal. 33 2 1 0.5 Metallic
Mold As cast 300 0.8 Comparative Example 10 Bal. 33 2 1 0.5
Metallic Mold 400 245 0.4
[0122] Evaluation of Cold Workability after Casting
[0123] FIG. 2 is an image illustrating that moldability of a cast
alloy according to an embodiment of the present invention is
excellent. As shown in FIG. 2, in the case of an aluminum-zinc
alloy containing no copper, cracks occurred from a reduction rate
of the sectional area of 17% in cold working after casting.
However, in the case of the Al--Zn--Cu alloy of the present
invention, cracks did not occur even at a reduction rate of the
sectional area of 75% and the moldability was excellent.
[0124] Evaluation of Mechanical Properties of Cast
[0125] FIG. 3 is a graph illustrating that an Al--Zn--Cu alloy
according to an embodiment of the present invention is
simultaneously improved in tensile strength and elongation as
compared with a conventional alloy.
[0126] FIG. 4 is images illustrating improvement in mechanical
properties of a cast alloy according to an embodiment of the
present invention due to reduction in size of a zinc phase and
reduction in distance between particles. The addition of Cu to the
Al--Zn alloy shows that the particle-to-particle spacing is greatly
reduced due to the decrease in the size of the zinc particles
during cooling after the heat treatment, thereby improving the
tensile strength of the particles in the alloy.
[0127] FIG. 5 is images illustrating that copper is incorporated
into zinc particles when copper is added. Copper is incorporated
within the zinc particles to reduce the interface energy on the
zinc precipitation phase/aluminum phase matrix.
[0128] Evaluation of Interfacial Enemies and Lattice Constants of
Zn Phase by Cu Addition
[0129] Table 2 and FIG. 7A show the change in the interface energy
of the zinc phase by the addition of copper. When the lattice
constant of Zn by DFT (Density Functional Theory) is calculated
(0.degree. K), the addition of Cu to the Al--Zn alloy significantly
reduces the interface energy of Zn and Al phases. The interface
energy of the Zn(0002)/Al(100) plane is significantly decreased by
Cu addition.
TABLE-US-00002 TABLE 2 Interface energy(J/m.sup.2) (wt %) Al Zn Cu
Zn(0002)/Al(100) Comparative Bal. 45 -- 0.139 Example 1 Example 1
Bal. 44.31 0.69 0.084 Example 2 Bal. 43.63 1.37 0.085 Example 3 Bal
42.94 2.06 0.084 Example 4 Bal. 42.26 2.74 0.082 Example 5 Bal.
41.57 3.43 0.087 Example 6 Bal. 40.89 4.11 0.095 Example 7 Bal.
40.2 4.80 0.109 Example 8 Bal. 39.52 5.48 0.126
[0130] FIG. 7B is a graph illustrating a change in lattice constant
of zinc by copper addition. The addition of Cu to the Al--Zn alloy
reduces the lattice constant of the Zn(0002) plane, and the
increase in the Cu concentration in the Zn phase reduces the
lattice constant of the Zn(0002) plane within a certain range. The
lattice constant of the Zn(1000) plane increases as the Cu content
increases. The reduction of the interface energy of the Zn(0002)
plane/Al(111) plane is a direct cause of the reduction of the
lattice constant of the Z (0002) plane.
[0131] FIGS. 8A and 8B are graphs illustrating a change in lattice
constant of a zinc (0002) plane by copper addition. The addition of
Cu to the Al--Zn alloy shows a decrease in the lattice constant of
the Zn(0002) plane, that is, an increase in 2.theta. of Zn(0002) in
X-ray measurement.
[0132] X-Ray Analysis of Alloy
[0133] FIGS. 9A and 9B are graphs illustrating changes in peak
angle (2.theta.) and lattice constant of a Zn(0002) plane depending
on Cu content of an alloy according to an embodiment of the present
invention. FIGS. 10A and 10B are graphs illustrating changes in
peak angle (2.theta.) and lattice constant of a Zn(1000) plane
depending on Cu content of the alloy according to an embodiment of
the present invention.
[0134] When the alloy according to the present invention was
analyzed by X-ray, 2.theta. of a Zn(0002) plane is decreased to
36.30 to 36.90 and the 2.theta. of a Zn(1000) plane is increased to
38.70 to 38.90.
[0135] 11A and 11B are graphs illustrating changes in peak angle
(2.theta.) and lattice constant of an Al(111) plane depending on Cu
content of an alloy according to an embodiment of the present
invention. FIGS. 12A and 12B are graphs illustrating changes in
peak angle (2.theta.) and lattice constant of an Al(200) depending
on Cu content of an alloy according to an embodiment of the present
invention. It is noted that the position of the Al peak is not
directly affected by Cu addition because Cu is not incorporated in
the Al matrix.
[0136] Microstructure Analysis of Alloy
[0137] FIGS. 13A and 13B is TEM images illustrating a change in the
size of a zinc phase upon cooling after heat treatment of an alloy
according to an embodiment of the present invention by Cu addition.
FIGS. 13C and 13D is graphs illustrating the zinc phase size of the
measurement site indicated in FIGS. 13A and 13B.
[0138] The size of the Zn phase in the Al matrix ranges from 10 nm
to 100 nm, and the size of the Zn phase is remarkably reduced by
the addition of copper.
[0139] Evaluation of Electrical Conductivity after Drawing
[0140] FIG. 16 is a graph illustrating a change in conductivity
according to true strains of an Al--Zn--Cu alloy according to an
embodiment of the present invention.
[0141] The conductivity of the alloy according to Example 13 and
Example 33 of the present invention after heat treatment was
measured to be 37% IACS (International Annealed Copper Standard) or
higher. In particular, the conductivity of the alloy according to
Example 13 increases to 53% IACS.
[0142] While this disclosure includes specific examples, it will be
apparent to one of ordinary skill in the art that various changes
in form and details may be made in these examples without departing
from the spirit and scope of the claims and their equivalents. The
examples described herein are to be considered in a descriptive
sense only, and not for purposes of limitation. Descriptions of
features or aspects in each example are to be considered as being
applicable to similar features or aspects in other examples.
Suitable results may be achieved if the described techniques are
performed in a different order, and/or if components in a described
system, architecture, device, or circuit are combined in a
different manner, and/or replaced or supplemented by other
components or their equivalents. Therefore, the scope of the
disclosure is defined not by the detailed description, but by the
claims and their equivalents, and all variations within the scope
of the claims and their equivalents are to be construed as being
included in the disclosure
* * * * *