U.S. patent application number 15/754161 was filed with the patent office on 2018-08-23 for aluminum alloy extruded material and method of manufacturing the same.
The applicant listed for this patent is UACJ Corporation, UACJ Extrusion Corporation. Invention is credited to Hidenori Hatta, Koichi Ishida, Yuko Tamada.
Application Number | 20180237889 15/754161 |
Document ID | / |
Family ID | 58099964 |
Filed Date | 2018-08-23 |
United States Patent
Application |
20180237889 |
Kind Code |
A1 |
Tamada; Yuko ; et
al. |
August 23, 2018 |
ALUMINUM ALLOY EXTRUDED MATERIAL AND METHOD OF MANUFACTURING THE
SAME
Abstract
An aluminum alloy extruded material having chemical composition
that includes Cu by 2.5 to 3.3%, Mg by 1.3 to 2.5%, Ni by 0.50 to
1.3%, Fe by 0.50 to 1.5%, Mn by less than 0.50%, Si by 0.15 to
0.40%, Zr by 0.06 to 0.20%, and Ti by less than 0.05% in mass
percentage, and the remaining part that includes Al and inevitable
impurities. On a cross-section of the aluminum alloy extruded
material, a grain diameter of an intermetallic compound is 20.mu.m
or less in equivalent circle diameter; density of an intermetallic
compound, whose grain diameter is 0.3 to 20.mu.m in equivalent
circle diameter, is 5.times.10.sup.3 piece/mm.sup.2 or more; and,
an average grain diameter of sub-crystal grains is 20.mu.m or less
in equivalent circle diameter.
Inventors: |
Tamada; Yuko; (Tokyo,
JP) ; Hatta; Hidenori; (Tokyo, JP) ; Ishida;
Koichi; (Tochigi, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
UACJ Corporation
UACJ Extrusion Corporation |
Tokyo
Tokyo |
|
JP
JP |
|
|
Family ID: |
58099964 |
Appl. No.: |
15/754161 |
Filed: |
July 28, 2016 |
PCT Filed: |
July 28, 2016 |
PCT NO: |
PCT/JP2016/072198 |
371 Date: |
February 21, 2018 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
C22F 1/057 20130101;
C22C 21/16 20130101; C22C 21/14 20130101; C22C 21/12 20130101 |
International
Class: |
C22C 21/16 20060101
C22C021/16; C22C 21/14 20060101 C22C021/14; C22F 1/057 20060101
C22F001/057 |
Foreign Application Data
Date |
Code |
Application Number |
Aug 25, 2015 |
JP |
2015-165985 |
Claims
1. An aluminum alloy extruded material, comprising: chemical
composition that comprises Cu by 2.5 to 3.3%, Mg by 1.3 to 2.5%, Ni
by 0.50 to 1.3%, Fe by 0.50 to 1.5%, Mn by less than 0.50%, Si by
0.15 to 0.40%, Zr by 0.06 to 0.20%, and Ti by less than 0.05% in
mass percentage, and a remaining part that comprises Al and
inevitable impurities, wherein, on a cross-section of the aluminum
alloy extruded material, a grain diameter of an intermetallic
compound is 20 .mu.m or less in equivalent circle diameter; density
of an intermetallic compound whose grain diameter is 0.3 to 20
.mu.m in equivalent circle diameter is 5.times.10.sup.3
piece/mm.sup.2 or more; and, an average grain diameter of
sub-crystal grains is 20 .mu.m or less in equivalent circle
diameter.
2. A method of manufacturing the aluminum alloy extruded material
according to claim 1, the method comprising: processing an ingot of
an aluminum alloy that comprises the chemical composition with
homogenizing treatment at a temperature from 400 to 500.degree. C.;
cooling the ingot from the temperature of the homogenizing
treatment to 200.degree. C. or less at an average cooling speed of
0.01.degree. C./s or more; extruding the ingot at 310 to
450.degree. C.; processing an intermediate extruded material
obtained by the extruding with solution treatment and quenching;
processing the intermediate extruded material with stretch
levelling at 2 to 4% strain within 48 hours after the solution
treatment and quenching; and, processing the intermediate extruded
material with aging treatment at 160 to 220.degree. C.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This international application claims the benefit of
Japanese Patent Application No. 2015-165985 filed on August 25,
2015 with the Japan Patent Office, and the entire disclosure of
Japanese Patent Application No. 2015-165985 is incorporated herein
by reference.
Technical Field
[0002] The present disclosure relates to an aluminum alloy extruded
material and a method of manufacturing the same.
Background Art
[0003] From the standpoint of environmental preservation, there is
a recent demand for improvement in fuel consumption of internal
combustion engines of automobiles. Aluminum alloy materials that
are applied to automobile parts, such as parts for internal
combustion engines (pistons, for example) and parts for
superchargers (compressor wheels, for example), are required to
have strength under a high-temperature range and a creep resistance
enough to endure long use under a high-temperature range to achieve
a high output of internal combustion engines.
[0004] For example, Patent Document 1 suggests to control the
conductivity and the average grain diameter of intermetallic
compounds of an aluminum alloy material within a specified range to
improve the strength of the aluminum alloy material under a
high-temperature range (from 100 to 180.degree. C.). Moreover,
Patent Document 2 suggests that the content relation of Fe and Ni
satisfy a specified relation to improve the strength of an aluminum
alloy material under a high-temperature range (200.degree. C. or
higher).
PRIOR ART DOCUMENTS
Patent Documents
[0005] Patent Document 1: Japanese Unexamined Patent Application
Publication No. H01-152237
[0006] Patent Document 2: Japanese Unexamined Patent Application
Publication No. H07-242976
SUMMARY OF THE INVENTION
Problems to be Solved by the Invention
[0007] Although the strength of an aluminum alloy material under a
high-temperature range is discussed in the aforementioned Patent
Documents 1 and 2, no discussion is given to the creep resistance
under a high-temperature range. This means that, previously, there
has been no sufficient discussion about the creep resistance of an
aluminum alloy material under a high-temperature range.
[0008] It is desirable that one aspect of the present disclosure
provides an aluminum alloy extruded material that has excellent
strength and creep resistance under a high temperature and a method
of manufacturing the same.
Means for Solving the Problems
[0009] One aspect of the present disclosure is an aluminum alloy
extruded material having chemical composition that comprises Cu by
2.5 to 3.3%, Mg by 1.3 to 2.5%, Ni by 0.50 to 1.3%, Fe by 0.50 to
1.5%, Mn by less than 0.50%, Si by 0.15 to 0.40%, Zr by 0.06 to
0.20%, and Ti by less than 0.05% in mass percentage, and the
remaining part that comprises Al and inevitable impurities. On a
cross-section of the aluminum alloy extruded material, a grain
diameter of an intermetallic compound is 20 .mu.m or less in
equivalent circle diameter; density of an intermetallic compound,
whose grain diameter is 0.3 to 20 .mu.m in equivalent circle
diameter, is 5.times.10.sup.3 piece/mm.sup.2 or more; and, an
average grain diameter of sub-crystal grains is 20 .mu.m or less in
equivalent circle diameter.
[0010] This aluminum alloy extruded material can have an improved
strength and creep resistance in a high-temperature range of
200.degree. C. or more for example. The strength that can be
improved here is not only the strength in a direction of extrusion
(hereinafter optionally referred to as "L direction") but also the
strength in a direction orthogonal to the direction of extrusion
(hereinafter optionally referred to as "LT direction"). The creep
resistance that can be improved here is the creep resistance in the
LT direction in particular. Accordingly, the aluminum alloy
extruded material of the present disclosure may be applied, for
example, to automobile parts such as parts for internal combustion
engines and parts for superchargers that are used under a high
temperature environment.
[0011] Another aspect of the present disclosure is a method of
manufacturing the aforementioned aluminum alloy extruded material.
The method comprises processing an ingot of an aluminum alloy that
comprises the aforementioned chemical composition with homogenizing
treatment at a temperature from 400 to 500.degree. C.; then,
cooling the ingot from the temperature of the homogenizing
treatment to 200.degree. C. or less at an average cooling speed of
0.01.degree. C./s or more; then, extruding the ingot at 310 to
450.degree. C.; then, processing an intermediate extruded material
obtained by the extruding with solution treatment and quenching;
then, processing the intermediate extruded material with stretch
levelling at 2 to 4% strain within 48 hours after the solution
treatment and quenching; and then, processing the intermediate
extruded material with aging treatment at 160 to 220.degree. C.
[0012] According to this method of manufacturing an aluminum alloy
extruded material, it is possible to manufacture an aluminum alloy
extruded material that has an excellent strength (strength in the L
direction and the LT direction) and creep resistance (creep
resistance in the LT direction in particular) under a
high-temperature range of 200.degree. C. or more for example. The
aluminum alloy extruded material thus manufactured can be applied,
for example, to automobile parts such as parts for internal
combustion engines and parts for superchargers that are used under
a high temperature environment.
MODE FOR CARRYING OUT THE INVENTION
[0013] Embodiments of the present disclosure will be described
hereinafter. It goes without saying that the present disclosure is
not limited to the embodiments described hereinafter and may be
implemented in various manners within the scope of the spirit of
the present disclosure.
[0014] <Chemical Composition of Aluminum Alloy Extruded
Material>
[0015] Cu: 2.5 to 3.3%
[0016] Cu contributes to an improvement in strength of an aluminum
alloy extruded material under a normal temperature and under a high
temperature. When Cu content is less than 2.5%, an effect of
improving the strength cannot be obtained sufficiently. When the Cu
content is more than 3.3%, a commencing temperature of eutectic
fusion drops, and thus a decrease in a temperature of the solution
treatment is required; therefore, the solid solubility of Cu in the
matrix decreases, and the effect of improving the strength cannot
be expected.
[0017] Mg: 1.3 to 2.5%
[0018] Mg coexists with Cu and contributes to an improvement in
strength of the aluminum alloy extruded material under a normal
temperature and under a high temperature. When Mg content is less
than 1.3%, an effect of improving the strength is low. When the Mg
content is more than 2.5%, a deformation resistance of the material
in hot working processes such as extrusion increases, which results
in a decrease in productivity.
[0019] Ni: 0.50 to 1.3%
[0020] Ni forms an Fe--Ni compound with Fe and improves a heat
resistance of the aluminum alloy extruded material. When Ni content
is less than 0.50%, an effect of improving the heat resistance
cannot be obtained sufficiently. When the Ni content is more than
1.3%, Ni-based compounds, such as Al--Ni based and Al--Ni--Cu based
compounds, which disperse in the matrix are formed; thus the effect
of improving the heat resistance becomes low. Moreover, formation
of a coarse Fe--Ni based compound increases a tendency of cracking
in hot working processes such as extrusion, which results in a
decrease in productivity.
[0021] Fe: 0.50 to 1.5%
[0022] Fe forms an Fe--Ni compound with Ni and improves a heat
resistance of the aluminum alloy extruded material. When Fe content
is less than 0.50%, an effect of improving the heat resistance
cannot be obtained sufficiently. When the Fe content is more than
1.5%, Fe based compounds, such as Al--Fe based and Al--Fe--Cu based
compounds, which disperse in the matrix are formed; thus the effect
of improving the heat resistance becomes low.
[0023] Mn: less than 0.50%
[0024] Mn causes precipitation and dispersion of an Al--Mn--Si
based compound to reduce recrystallization that occurs during the
solution treatment to form fine sub-crystal grains, and thereby
contributes to an improvement in strength of the aluminum alloy
extruded material under a normal temperature and under a high
temperature. When Mg content is 0.50% or more, a giant crystallized
product is easily formed during casting, which results in a
decrease in the strength.
[0025] Si: 0.15 to 0.40%
[0026] Si causes, together with Mn, precipitation of fine dispersed
phase of an Al--Mn--Si based compound and increases pinning effect
of dislocation to reduce coarsening of recrystallized grains during
the solution treatment, and thereby helps to improve strength of
the aluminum alloy extruded material. When Si content is less than
0.15%, an effect of improving the strength cannot be obtained
sufficiently. When the Si content is more than 0.40%, a compound of
Mg and Si is formed, which results in a decrease in the heat
resistance.
[0027] Zr: 0.06 to 0.20%
[0028] Zr contributes to fining of a casted structure. Moreover, Zr
causes, together with Al, fine dispersion of an Al.sub.3Zr compound
to reduce recrystallization that occurs during the solution
treatment to form fine sub-crystal grains, and thereby contributes
to an improvement in strength of the aluminum alloy extruded
material. When Zr content is less than 0.06%, an effect of fining
the casted structure and an effect of improving the strength cannot
be obtained sufficiently. When the Zr content is more than 0.20%, a
giant crystallized product is easily formed during casting; thus
the effect of fining the casted structure and the effect of
improving the strength become low.
[0029] Ti: less than 0.05%
[0030] Ti is added to stably obtain fine crystal grain structures
as Zr is. Ti content should be less than 0.05%. When the Ti content
is 0.05% or more, a giant Zr--Ti compound is formed during casting,
which results in a decrease in the strength.
[0031] Other Elements:
[0032] Al and inevitable impurities may basically be included
besides the aforementioned elements. Elements other than the
aforementioned elements that are added to an aluminum alloy may
usually be allowed to be included as inevitable impurities to an
extent that they do not influence significantly on the
characteristics of the aluminum alloy.
[0033] <Structure of Aluminum Alloy Extruded Material>
[0034] To reduce coarsening of sub-crystal grain diameters under a
high temperature and achieve an excellent strength and creep
resistance of the aluminum, alloy extruded material, it is
necessary that crystallized products exist finely on sub-crystal
grain boundaries so that a dislocation does not move easily under
the high temperature. For this reason, a grain diameter of an
intermetallic compound should be 20 .mu.m or less in equivalent
circle diameter (preferably 10 .mu.m or less), and density of an
intermetallic compound, whose grain diameter is 0.3 to 20 .mu.m in
equivalent circle diameter, should be 5.times.10.sup.3
piece/mm.sup.2 or more on a cross-section of the aluminum alloy
extruded material.
[0035] When the grain diameter of the intermetallic compound is
more than 20 .mu.m in equivalent circle diameter on a cross-section
of the aluminum alloy extruded material, the intermetallic compound
becomes the starting point of a crack, which results in a decrease
in the strength of the aluminum alloy extruded material. When the
density of the intermetallic compound, whose grain diameter is 0.3
to 20 .mu.m in equivalent circle diameter, is less than
5.times.10.sup.3 piece/mm.sup.2 on a cross-section of the aluminum
alloy extruded material, precipitates on the grain boundaries
become coarse and grain boundary sliding is not reduced, which
result in a decrease in the heat resistance of the aluminum alloy
extruded material.
[0036] To improve the strength of the aluminum alloy extruded
material under a high temperature (particularly the strength in LT
direction), the average grain diameter of sub-crystal grains should
be 20 .mu.m or less in equivalent circle diameter on a
cross-section of the aluminum alloy extruded material. When the
average grain diameter of sub-crystal grains is more than 20 .mu.m
in equivalent circle diameter on a cross-section of the aluminum
alloy extruded material, the effect of improving the strength under
a high temperature (particularly the strength in the LT direction)
becomes low.
[0037] A cross-section of the aluminum alloy extruded material here
refers to a cross-section on the aluminum alloy extruded material
in a given direction. The direction of the cross-section should not
be limited to any direction; for example, the cross-section may be
taken in a direction parallel to the direction of extrusion, or may
be taken in a direction orthogonal to the direction of extrusion.
The grain diameter (in equivalent circle diameter) of the
above-described intermetallic compound, the density of the
intermetallic compound whose grain diameter (in equivalent circle
diameter) is 0.3 to 20 .mu.m, and the average grain diameter (in
equivalent circle diameter) of sub-crystal grains can be obtained
by randomly observing a region of a cross-section of the aluminum
alloy extruded material, where the cross-section is taken in a
given direction and the region excludes a surface layer (for
example, an area from the surface to a depth of 2 to 5 mm) of the
cross-section, by means of an optical microscope for example.
[0038] <Method of Manufacturing Aluminum Alloy Extruded
Material>
[0039] Manufacturing of an aluminum alloy extruded material begins
with melting of an aluminum alloy that comprises the aforementioned
chemical composition by a conventional method and processing thus
casted ingot of the aluminum alloy with homogenizing treatment at
400 to 500.degree. C. If the treatment temperature is less than
400.degree. C. in the homogenizing treatment, then homogenization
of the structure will be insufficient. If the treatment temperature
is more than 500.degree. C., then a eutectic fusion takes place
where elements are segregated.
[0040] After the homogenizing treatment, the ingot of the aluminum
alloy is cooled from the homogenizing treatment temperature to a
specified temperature, which is 200.degree. C. or less, at an
average cooling speed of 0.01.degree. C./s or more. When the
temperature of the homogenizing treatment is A.degree. C. and the
time required to cool the ingot from A.degree. C. to 200.degree. C.
is B second, the average cooling speed is represented as (A.degree.
C.-200.degree. C.)/B second. When the average cooling speed is less
than 0.01.degree. C./s (slower than 0.01.degree. C./s), an S-phase
(Al2CuMg) and/or an Fe--Ni based compound grow/grows coarsely
during the cooling.
[0041] For example, if an extrusion is carried out at 450.degree.
C. or less while a coarse compound is being formed, then a
dislocation introduced by the extrusion disappears in the vicinity
of the coarse compound, and thus sub-crystal grain diameters become
coarse. In particular, an Fe--Ni based compound remains in the
final product since it does not easily dissolve during a solution
treatment, which is a process after the extrusion. Since a coarse
compound degrades the creep characteristics of the aluminum alloy
extruded material, the cooling speed needs to be controlled so as
not to produce a coarse compound during the homogenizing treatment.
Accordingly, by setting the average cooling speed after the
homogenizing treatment at 0.01.degree. C./s or more to produce fine
Fe--Ni based and Cu--Mg based compounds to consequently produce
uniform and fine precipitates in subsequent stretch levelling and
aging treatment, an aluminum alloy extruded material that has an
excellent heat resistance can be obtained. Note that the "coarse
compound" here refers to a compound that, for example, may keep its
grain diameter in the size of 20 .mu.m or more (in equivalent
circle diameter) after the extrusion.
[0042] The cooled ingot is reheated at 310 to 450.degree. C. and
subsequently extruded at the same temperature to obtain an
intermediate extruded material. Since a use of a furnace requires
time to increase the temperature of the ingot and thus results in
coarsening of crystallized products, it is preferable to perform
extrusion of the ingot immediately after increasing its temperature
by an induction heater (induction heating) or by other manners.
When the temperature of extrusion is less than 310.degree. C., a
deformation resistance of the material increases and speed of
extrusion decreases during the extrusion, which results in a
decrease in productivity. When the temperature of extrusion is more
than 450.degree. C., dynamic recovery occurs during the extrusion,
and therefore, fine sub-crystal grains cannot be obtained.
[0043] The intermediate extruded material that is obtained by the
extrusion is subsequently processed with solution treatment and
quenching. The temperature of the solution treatment is preferably
in a temperature range that is lower by 3 to 10.degree. C. than the
commencing temperature of eutectic fusion. When the temperature of
the solution treatment is higher than the aforementioned
temperature range, eutectic fusion may easily occur occasionally in
the material due to variations in temperatures inside the furnace.
When the temperature of the solution treatment is lower than the
aforementioned temperature range, solution treatment of the
structure will not be performed sufficiently and thus sufficient
strength may not be obtained occasionally.
[0044] The intermediate extruded material is subsequently processed
with stretch levelling at 2 to 4% within 48 hours after the
solution treatment and quenching. The stretch levelling is for
removing residual stress and improving yield strength. Moreover, an
introduction of a dislocation enables compounds to be precipitated
finely in subsequent aging treatment; thus fine sub-crystal grains
can be maintained in a high temperature. In particular, by finely
precipitating compounds on the sub-crystal grain boundaries,
movement of the dislocations is reduced and thereby an excellent
high-temperature creep characteristics can be obtained.
[0045] If the time from after performing the solution treatment and
quenching till performing the stretch levelling is more than 48
hours, precipitation is significantly promoted on an area where the
residual stress remains. Since dislocations are prone to be
introduced in a neighborhood of fine precipitates, partially
promoted precipitation causes a partial introduction of
dislocations by the stretch levelling, and therefore, uniform
sub-crystal grains cannot be maintained afterward. If a stretch
levelling amount (strain amount in the stretch levelling) is less
than 2%, then effects of the above-described stretch levelling
become low. If the stretch levelling amount is more than 4%, then
introduced dislocations increase in excess and precipitation is
promoted consequently, which results in a decrease in the
high-temperature creep characteristics.
[0046] After the stretch levelling, the intermediate extruded
material is subsequently processed with aging treatment at 160 to
220.degree. C. If the temperature of the aging treatment is less
than 160.degree. C., then precipitation does not progress
sufficiently. If the temperature of the aging treatment is more
than 220.degree. C., then precipitates become coarse, and thus
sufficient strength cannot be obtained.
[0047] An aluminum alloy extruded material that includes the
aforementioned chemical composition and the aforementioned
structure can be obtained through the steps as described above.
EXAMPLES
[0048] Examples of the present disclosure will be explained
hereinafter along with comparison with comparative examples to
substantiate effects of the present disclosure. These examples show
some of the modes of the present disclosure. The present disclosure
is therefore not limited by these examples.
[0049] First, aluminum alloys (alloys A1 to A14, and B1 to B4) that
include chemical composition as shown in Table 1 were casted by
continuous casting to obtain billets with a diameter of 90 mm
(ingots modified for extrusion). Note that, in Table 1, the
remaining part besides the chemical components comprises Al and
inevitable impurities, which are not shown in the table. Moreover,
when the contents of the chemical components are not within the
scope of the present disclosure, such contents are shown
underlined.
[0050] The obtained billets were processed with the homogenizing
treatment under the conditions that the treatment was conducted at
470.degree. C. for 15 hours and cooled under the condition that the
average cooling speed was 0.012.degree. C./s, and subsequently
processed with hot extrusion under the condition that the extrusion
was conducted at 440.degree. C. Through these processings, a round
bar material (intermediate extruded material) with a diameter of 28
mm was obtained. The obtained round bar material was processed with
the solution treatment under the conditions that the treatment was
conducted at 525.degree. C. for 2 hours, and subsequently processed
with the quenching; 12 hours later, the material was processed with
the stretch levelling at a strain amount of 2.4% and then processed
with artificial aging treatment under the conditions that the
treatment was conducted at 190.degree. C. for 18 hours. Aluminum
alloy extruded materials (hereinafter optionally referred to simply
as "extruded materials") of examples 1 to 14 and comparative
examples 15 to 18 were thus prepared through the aforementioned
processings.
TABLE-US-00001 TABLE 1 Alloy Chemical Components (in mass
percentage) No. Cu Mg Ni Fe Si Mn Zr Ti Example 1 A1 3.2 2.0 1.1
1.1 0.29 0.30 0.14 0.03 2 A2 2.5 2.0 1.1 1.1 0.29 0.30 0.14 0.03 3
A3 3.0 2.4 1.1 1.1 0.29 0.30 0.14 0.03 4 A4 3.0 1.4 1.1 1.1 0.29
0.30 0.14 0.03 5 A5 3.0 2.0 1.3 1.1 0.29 0.30 0.14 0.03 6 A6 3.0
2.0 0.6 1.1 0.29 0.30 0.14 0.03 7 A7 3.0 2.0 1.1 1.3 0.29 0.30 0.14
0.03 8 A8 3.0 2.0 1.1 0.58 0.29 0.30 0.14 0.03 9 A9 3.0 2.0 1.1 1.1
0.38 0.30 0.14 0.03 10 A10 3.0 2.0 1.1 1.1 0.15 0.30 0.14 0.03 11
A11 3.0 2.0 1.1 1.1 0.29 0.45 0.14 0.03 12 A12 3.0 2.0 1.1 1.1 0.29
0.30 0.19 0.03 13 A13 3.0 2.0 1.1 1.1 0.29 0.30 0.06 0.03 14 A14
3.0 2.0 1.1 1.1 0.29 0.30 0.14 0.03 Compar- 15 B1 2.2 2.0 1.1 1.1
0.29 0.30 0.14 0.03 ative 16 B2 3.0 2.0 0.4 1.1 0.29 0.30 0.14 0.03
Example 17 B3 3.0 2.0 1.1 0.4 0.29 0.30 0.14 0.03 18 B4 3.0 2.0 1.1
1.1 0.29 0.30 0.04 0.03
[0051] On a cross-section of each prepared extruded material, the
maximum grain diameter (in equivalent circle diameter) of the
intermetallic compounds; density of the intermetallic compound,
whose grain diameter (in equivalent circle diameter) is 0.3 to 20
.mu.m; and, the average grain diameter (in equivalent circle
diameter) of sub-crystal grains were measured. For each prepared
extruded material, 0.2% yield strength (in L direction and LT
direction) at room temperature and at 200.degree. C. were measured
by a tensile test, and a creep resistance (in LT direction) was
evaluated by a creep rupture test. Methods of the measurements and
evaluation will be explained hereinafter.
[0052] <Maximum Grain Diameter (in Equivalent Circle Diameter)
and Density of Intermetallic Compounds>
[0053] To enable an observation of the structure of the extruded
material in the direction of extrusion (L direction), the extruded
material was cut so as to be evenly divided into two pieces in a
direction parallel to the direction of extrusion (L direction) (so
that the cut surfaces include the central axis of the extruded
material). The cut surfaces were polished using a waterproof
sandpaper, and further polished to a mirror-finish using a buff
with a polish applied thereon. The central part of the cut surfaces
of the extruded material (the middle point in the direction (in
width direction) orthogonal to the Long direction (direction of
extrusion) on the cut surface) was subsequently magnified to 200
times by an optical microscope and observed. The maximum grain
diameter of the intermetallic compounds (in equivalent circle
diameter) and the density of the intermetallic compound, whose
grain diameter (in equivalent circle diameter) was 0.3 to 20 .mu.m,
were measured thereby.
[0054] <Average Grain Diameter (in Equivalent Circle Diameter)
of Sub-Crystal Grains>
[0055] To enable an observation of the structure of the extruded
material in the direction of extrusion (L direction), the extruded
material was cut to be evenly divided into two pieces in the
direction parallel to the direction of extrusion (L direction) (so
that the cut surfaces include the central axis of the extruded
material). The cut surfaces were polished using a waterproof
sandpaper, and further polished to a mirror-finish using a buff
with a polish applied thereon. The cut surfaces of the extruded
material were then etched using Keller's reagent. The central part
of the cut surfaces of the extruded material (the middle point in
the direction (width direction) orthogonal to the Long direction
(direction of extrusion) on the cut surface) was subsequently
magnified to 200 times by an optical microscope and observed. The
average grain diameter (in equivalent circle diameter) of the
sub-crystal grains was measured thereby.
[0056] <0.2% Yield Strength>
[0057] With regard to the 0.2% yield strength at a room
temperature, test pieces were prepared from each extruded material.
Specifically, a test piece whose axis direction (Long direction)
was the direction of extrusion (L direction) and a test piece whose
axis direction (Long direction) was the direction orthogonal to the
direction of extrusion (LT direction) were prepared for each
extruded material. The test pieces were prepared to have a diameter
of 5 mm at the parallel portion, the gauge length of 15 mm, and a
radius of 10 mm at the shoulder portion. The test pieces were
placed to a tensile test device, then tensile tests (JIS Z2241
(year 2011)) were conducted in the room temperature. In the tensile
test for the LT direction, common materials are joined to both ends
of an evaluation area of the test piece by friction welding to
ensure the necessary length as a test piece. The 0.2% yield
strength at the room temperature (in L direction and LT direction)
was calculated from the result of the aforementioned tensile tests.
The 0.2% yield strength at the room temperature was evaluated by
using conventional values (for example, those values that are
disclosed in the aforementioned Patent Document 2) as comparisons;
a pass was given if the value of the 0.2% yield strength at the
room temperature was 410 MPa or more.
[0058] With regard to 0.2% yield strength at 200.degree. C., the
same test pieces as those used in the aforementioned 0.2% yield
strength at the room temperature were prepared from each extruded
material. The test pieces were heated to 200.degree. C. as they
were placed to the tensile test device. The test pieces were
maintained for 10 minutes after reaching 200.degree. C.; then the
tensile tests (JIS Z2241 (year 2011)) were conducted. The 0.2%
yield strength at 200.degree. C. (in L direction and LT direction)
was calculated from the result of the aforementioned tensile tests.
The 0.2% yield strength at 200.degree. C. was evaluated by using
conventional values (for example, those values that are disclosed
in the aforementioned Patent Document 2) as comparisons; a pass was
given if the value of the 0.2% yield strength at 200.degree. C. was
310 MPa or more.
[0059] <Creep Resistance>
[0060] Test pieces whose axis direction (Long direction) were the
direction orthogonal to the direction of extrusion (LT direction)
were prepared from each extruded material in the same manner as in
the aforementioned measurements of 0.2% yield strength. The test
pieces were heated to 200.degree. C. as they were placed to a creep
rupture test device. The test pieces were maintained for 60 minutes
after reaching 200.degree. C.; then creep rupture tests were
conducted at 200.degree. C. Each test piece was loaded with a load
of 200 MPa for 100 hours in the creep rupture tests. The load was
decided to be 200 MPa based on the recent values at which high
temperature properties are required. With respect to evaluations of
the creep resistance (in LT direction), a pass was given if the
test piece did not fracture in 100 hours with a load of 200 MPa,
and a fail was given if the test piece fractured.
TABLE-US-00002 TABLE 2 Sub-crystal Intermetallic Compound Grains
Maximum Density when Average Creep Resistance grain grain diameter
grain 0.2% Yield Strength (MPa) (200 MPa/100 h) diameter is 0.3 to
20 .mu.m diameter Room Temperature 200.degree. C. 200.degree. C.
(.mu.m) (.times.10.sup.3/mm.sup.2) (.mu.m) L direction LT direction
L direction LT direction LT direction Example 1 8.1 6.5 9.5 472 445
313 318 Pass 2 8.3 6.2 12 455 427 310 314 Pass 3 8.2 7.1 7.7 468
435 317 316 Pass 4 7.7 5.6 11 457 427 315 315 Pass 5 10 6.0 10 466
431 320 322 Pass 6 7.3 5.1 8.9 462 429 312 315 Pass 7 15 5.1 18 470
441 318 318 Pass 8 7.2 5.4 13 460 432 311 315 Pass 9 11 5.8 7.6 458
428 311 312 Pass 10 9.8 5.3 7.4 460 429 310 313 Pass 11 8.2 7.6 8.6
465 433 313 318 Pass 12 8.3 6.2 7.6 469 444 318 321 Pass 13 8.2 5.7
18 459 430 310 312 Pass 14 7.0 5.4 7.6 464 434 312 313 Pass
Comparative 15 8.6 6.6 9.5 400 386 289 288 Fail Example 16 7.9 4.9
8.4 449 422 276 275 Fail 17 8.0 5.0 12 451 428 290 290 Fail 18 18
5.0 85 428 392 295 278 Fail
[0061] Table 2 shows the results of the aforementioned measurements
and evaluations. When values for each item are not within the scope
of the present disclosure, such values are shown underlined in
Table 2.
[0062] As represented in Table 2, comparative examples 15 to 18
were not within the scope of the present disclosure; thus, these
examples were given a fail in at least one of the 0.2% yield
strength or the creep resistance.
[0063] Specifically, due to its low Cu content, comparative example
15 failed in the 0.2% yield strength at the room temperature (in L
direction and LT direction) for not satisfying the reference value
(410 MPa), failed in the 0.2% yield strength at 200.degree. C. (in
L direction and LT direction) for not satisfying the reference
value (310 MPa), and failed in the creep resistance (in LT
direction).
[0064] With respect to comparative example 16, density of the
intermetallic compound whose grain diameter is 0.3 to 20 .mu.m was
low due to its low Ni content; thus, comparative example 16 failed
in the 0.2% yield strength at 200.degree. C. (in L direction and LT
direction) for not satisfying the reference value, and failed in
the creep resistance (in LT direction).
[0065] Comparative example 17 failed the 0.2% yield strength at
200.degree. C. (in L direction and LT direction) for not satisfying
the reference value and failed in the creep resistance (in LT
direction) due to its low Fe content.
[0066] Comparative example 18 recrystallized due to its low Zr
content, and thus failed in the 0.2% yield strength at the room
temperature (in LT direction) and in the 0.2% yield strength at
200.degree. C. (in L direction and LT direction) for not satisfying
the reference value, and failed in the creep resistance (in LT
direction). The value shown in the section for the average grain
diameter of sub-crystal grains for comparative example 18 in Table
2 is the average grain diameter of recrystallized grains.
[0067] Meanwhile, examples 1 to 14 passed in all of the 0.2% yield
strength at the room temperature (in L direction and LT direction),
the 0.2% yield strength at 200.degree. C. (in L direction and LT
direction), and the creep resistance (in LT direction), since these
examples were within the scope of the present disclosure. In other
words, it was revealed that the aluminum alloy extruded material of
the present disclosure was excellent in the strength and the creep
resistance under a high temperature.
[0068] Next, an aluminum alloy (Alloy A14: see Table 1 for its
chemical composition) was casted by continuous casting to obtain a
billet (356 mm in diameter). The obtained billet was processed with
the homogenizing treatment under specified conditions, cooled at a
specified average cooling speed, and subsequently processed with
hot extrusion under specified conditions. Through these
processings, a round bar material (intermediate extruded material)
with a diameter of 58 mm was obtained. The obtained round bar
material was processed with the solution treatment under the
conditions that the treatment was conducted at 525.degree. C. for 2
hours, and processed with the quenching; specified hours later, the
material was processed with the stretch levelling at a specified
strain amount and then processed with the artificial aging
treatment under specified conditions. Aluminum alloy extruded
materials (hereinafter optionally referred to simply as "extruded
materials") of examples 21 to 23 and comparative examples 24 to 31
were thus prepared through the aforementioned processings.
[0069] Table 3 shows temperature and duration of the homogenizing
treatment, average cooling speed, extruding temperature, duration
from after the solution treatment and quenching to the stretch
levelling, strain amount during the stretch levelling, and
temperature and duration of the aging treatment. When conditions in
each processing in the method of manufacturing are not within the
scope of the present disclosure, such conditions are shown
underlined in Table 3.
TABLE-US-00003 TABLE 3 Average Time after Solution Homogenizing
Cooling Extruding Treatment and Strain Amount Alloy Treatment Speed
Temperature Quenching till Stretch in Stretch Aging Treatment No.
(temperature/hour) (.degree. C./s) (.degree. C.) Levelling (h)
Levelling (%) (Temperature/hour) Example 21 A14 470.degree. C.
.times. 15 h 0.012 440 12 2.0 190.degree. C. .times. 18 h 22 A14
470.degree. C. .times. 15 h 0.012 440 12 4.0 190.degree. C. .times.
18 h 23 A14 470.degree. C. .times. 15 h 0.012 440 12 2.5
165.degree. C. .times. 48 h Comparative 24 A14 470.degree. C.
.times. 15 h 0.012 440 12 1.3 190.degree. C. .times. 18 h Example
25 A14 470.degree. C. .times. 15 h 0.012 440 12 6.0 190.degree. C.
.times. 12 h 26 A14 350.degree. C. .times. 25 h 0.014 440 12 2.4
190.degree. C. .times. 18 h 27 A14 520.degree. C. .times. 15 h
0.011 440 12 2.4 190.degree. C. .times. 18 h 28 A14 470.degree. C.
.times. 15 h 0.005 440 12 2.4 190.degree. C. .times. 18 h 29 A14
470.degree. C. .times. 15 h 0.013 300 x x x 30 A14 470.degree. C.
.times. 15 h 0.013 500 12 2.4 190.degree. C. .times. 18 h 31 A14
470.degree. C. .times. 15 h 0.014 440 55 2.2 190.degree. C. .times.
18 h
[0070] On a cross-section of each prepared extruded material, the
maximum grain diameter (in equivalent circle diameter) of the
intermetallic compound; density of the intermetallic compound,
whose grain diameter (in equivalent circle diameter) is 0.3 to
20.mu.m; and the average grain diameter (in equivalent circle
diameter) of sub-crystal grains were measured. For each prepared
extruded material, the 0.2% yield strength (in L direction and LT
direction) at the room temperature and at 200.degree. C. were
measured by the tensile test, and the creep resistance (in LT
direction) was evaluated by the creep rupture test. Methods of
these measurements and evaluation are the same as those explained
before.
TABLE-US-00004 TABLE 4 Sub-crystal Intermetallic Compound Grains
Maximum Density when Average Creep Resistance grain grain diameter
grain 0.2% Yield Strength (MPa) (200 MPa/100 h) diameter is 0.3 to
20 .mu.m diameter Room Temperature 200.degree. C. 200.degree. C.
(.mu.m) (.times.10.sup.3/mm.sup.2) (.mu.m) L direction LT direction
L direction LT direction LT direction Example 21 7.9 5.1 9.5 460
432 319 320 Pass 22 7.2 5.5 9.1 471 445 316 317 Pass 23 8.1 5.7 9.8
442 420 315 317 Pass Comparative 24 7.1 5.2 9.6 435 403 291 290
Fail Example 25 8.8 5.7 9.5 466 435 306 308 Fail 26 20 4.6 9.8 440
412 313 306 Fail 27 11 6.3 12 433 408 303 305 Fail 28 28 4.7 75 408
388 273 285 Fail 29 x x x x x x x x 30 15 6.2 28 444 420 310 306
Fail 31 7.3 6.8 21 437 408 312 295 Fail
[0071] Table 4 shows the results of the aforementioned measurements
and evaluation. When values for each item are not within the scope
of the present disclosure, such values are shown underlined in
Table 4.
[0072] As represented in Table 4, methods of manufacturing in
comparative examples 24 to 31 were not within the scope of the
present disclosure; thus, these examples were given a fail in at
least one of the 0.2% yield strength or the creep resistance.
[0073] Specifically, due to its low strain amount during the
stretch levelling, comparative example 24 failed in the 0.2% yield
strength at the room temperature (in LT direction) and in the 0.2%
yield strength at 200.degree. C. (in L direction and LT direction)
for not satisfying the reference value, and failed in the creep
resistance (in LT direction).
[0074] Comparative example 25 failed in the0.2% yield strength at
200.degree. C. (in L direction and LT direction) for not satisfying
the reference value and failed in the creep resistance (in LT
direction) due to its excess strain amount during the stretch
levelling.
[0075] With respect to comparative example 26, density of the
intermetallic compound whose grain diameter is 0.3 to 20 .mu.m was
low due to its low homogenizing treatment temperature; thus,
comparative example 26 failed in the 0.2% yield strength at
200.degree. C. (in LT direction) for not satisfying the reference
value, and failed in the creep resistance (in LT direction).
[0076] Comparative example 27 failed in the 0.2% yield strength at
the room temperature (in LT direction) and in the 0.2% yield
strength at 200.degree. C. (in L direction and LT direction) for
not satisfying the reference value and failed in the creep
resistance (in LT direction) due to its high homogenizing treatment
temperature.
[0077] With respect to comparative example 28, density of the
intermetallic compound, whose grain diameter is 0.3 to 20 .mu.m,
was low and the average grain diameter of sub-crystal grains were
large due to its low average cooling speed; thus, the comparative
example 28 failed in the 0.2% yield strength at the room
temperature (in L direction and LT direction) and in the 0.2% yield
strength at 200.degree. C. (in L direction and LT direction) for
not satisfying the reference value, and failed in the creep
resistance (in LT direction).
[0078] With respect to comparative example 29, extrusion failed due
to its low extruding temperature; thus, no evaluation could be
conducted on an extruded material.
[0079] With respect to comparative example 30, the average grain
diameter of sub-crystal grains became large due to its high
extruding temperature; thus, comparative example 30 failed in the
0.2% yield strength at 200.degree. C. (in LT direction) for not
satisfying the reference value, and failed in the creep resistance
(in LT direction).
[0080] With respect to comparative example 31, the average grain
diameter of sub-crystal grains became large since its duration from
after the solution treatment and quenching to the stretch levelling
was long; thus, comparative example 31 failed in the 0.2% yield
strength at the room temperature (in LT direction) and in the 0.2%
yield strength at 200.degree. C. (in LT direction) for not
satisfying the reference value, and failed in the creep resistance
(in LT direction).
[0081] Meanwhile, examples 21 to 23 passed in all of the 0.2% yield
strength at the room temperature (in L direction and LT direction),
the 0.2% yield strength at 200.degree. C. (in L direction and LT
direction), and the creep resistance (in LT direction) since these
examples were within the scope of the present disclosure. In other
words, it was revealed that the method of manufacturing of an
aluminum alloy extruded material in the present disclosure can
provide an aluminum alloy extruded material that is excellent in
the strength and the creep resistance under a high temperature.
* * * * *