U.S. patent application number 09/428480 was filed with the patent office on 2002-01-31 for aluminum alloy and method for manufacturing aluminum-alloy member.
Invention is credited to HASHIKURA, MANABU, HATTORI, HISAO, KAJI, TOSHIHIKO, TAKEDA, YOSHINOBU.
Application Number | 20020012606 09/428480 |
Document ID | / |
Family ID | 18014740 |
Filed Date | 2002-01-31 |
United States Patent
Application |
20020012606 |
Kind Code |
A1 |
HASHIKURA, MANABU ; et
al. |
January 31, 2002 |
ALUMINUM ALLOY AND METHOD FOR MANUFACTURING ALUMINUM-ALLOY
MEMBER
Abstract
The invention offers an aluminum alloy that not only has high
hardness accompanied by balanced ductility but also has high
toughness and superior processability. The invention also offers a
method for manufacturing an aluminum-alloy member that not only has
high hardness accompanied by balanced ductility but also has high
toughness and superior processability. The aluminum alloy comprises
(1) not less than 0.1 wt. % and not more than 8 wt. % Constituent A
comprising one or more kinds of elements selected from the group
consisting of titanium, vanadium, hafnium, and zirconium, (2) not
less than 0.1 wt. % and not more than 20 wt. % Constituent B
comprising one or more kinds of elements selected from the group
consisting of lanthanum, cerium, praseodymium, neodymium,
mischmetal, calcium, strontium, and barium, and (3) not less than
0.1 wt. % and not more than 20 wt. % Constituent C comprising one
or more kinds of elements selected from the group consisting of
magnesium and lithium.
Inventors: |
HASHIKURA, MANABU;
(ITAMI-SHI, JP) ; HATTORI, HISAO; (ITAMI-SHI,
JP) ; KAJI, TOSHIHIKO; (ITAMI-SHI, JP) ;
TAKEDA, YOSHINOBU; (ITAMI-SHI, JP) |
Correspondence
Address: |
MCDERMOTT WILL & EMERY
600 13TH STREET, N.W.
WASHINGTON
DC
20005-3096
US
|
Family ID: |
18014740 |
Appl. No.: |
09/428480 |
Filed: |
October 28, 1999 |
Current U.S.
Class: |
420/543 ;
148/440; 148/691 |
Current CPC
Class: |
B22F 2998/10 20130101;
B22F 2999/00 20130101; B22F 2998/00 20130101; B22F 2999/00
20130101; B22F 2009/041 20130101; C22C 1/0416 20130101; B22F
2998/10 20130101; B22F 3/14 20130101; B22F 2998/00 20130101; C25D
11/04 20130101; B22F 9/008 20130101; B22F 3/115 20130101; B22F 3/17
20130101; B22F 9/082 20130101; B22F 3/16 20130101; B22F 9/04
20130101 |
Class at
Publication: |
420/543 ;
148/440; 148/691 |
International
Class: |
C22C 021/06; C22F
001/04 |
Foreign Application Data
Date |
Code |
Application Number |
Oct 30, 1998 |
JP |
311236/1998 |
Claims
What is claimed is:
1. An aluminum alloy comprising: (1) not less than 0.1 wt. % and
not more than 8 wt. % Constituent A comprising one or more kinds of
elements selected from the group consisting of titanium, vanadium,
hafnium, and zirconium, (2) not less than 0.1 wt. % and not more
than 20 wt. % Constituent B comprising one or more kinds of
elements selected from the group consisting of lanthanum, cerium,
praseodymium, neodymium, mischmetal, calcium, strontium, and
barium, and (3) not less than 0.1 wt. % and not more than 20 wt. %
Constituent C comprising one or more kinds of elements selected
from the group consisting of magnesium and lithium.
2. An aluminum alloy as defined in claim 1, wherein Constituent C
constitutes not less than 5 wt. % and not more than 20 wt. %.
3. An aluminum alloy as defined in claim 1, the aluminum alloy
further comprising not less than 0.1 wt. % and not more than 5 wt.
% Constituent D comprising one or more kinds of elements selected
from the group consisting of niobium, molybdenum, silver, iron,
cobalt, tantalum, and tungsten.
4. An aluminum alloy as defined in claim 2, wherein: Constituent A
is zirconium, Constituent B is mischmetal, Constituent C is
magnesium, Constituent A constitutes not less than 0.1 wt. % and
not more than 3 wt. %, and Constituent B constitutes not less than
0.1 wt. % and not more than 15 wt. %.
5. An aluminum alloy comprising: (1) not less than 0.1 wt. % and
not more than 5 wt. % Constituent D comprising one or more kinds of
elements selected from the group consisting of niobium, molybdenum,
silver, iron, cobalt, tantalum, and tungsten, (2) not less than 0.1
wt. % and not more than 20 wt. % Constituent B comprising one or
more kinds of elements selected from the group consisting of
lanthanum, cerium, praseodymium, neodymium, mischmetal, calcium,
strontium, and barium, and (3) not less than 0.1 wt. % and not more
than 20 wt. % Constituent C comprising one or more kinds of
elements selected from the group consisting of magnesium and
lithium.
6. An aluminum alloy as defined in claim 5, wherein Constituent C
constitutes not less than 5 wt. % and not more than 20 wt. %.
7. An aluminum alloy as defined in one of the claims 1 to 6, the
aluminum alloy being further provided with an anodic oxide
coating.
8. An aluminum alloy as defined in claim 7, wherein the anodic
oxide coating has a lightness less than 50.
9. An aluminum alloy as defined in claim 8, wherein: the anodic
oxide coating is formed on the surface of a base material made of
the aluminum alloy, and the base material has an electrical
conductivity less than 20%IACS.
10. An aluminum alloy as defined in claim 8, wherein the anodic
oxide coating is a shade of brown, dark gray, or dark brown.
11. An aluminum alloy as defined in one of the claims 1 to 6, the
aluminum alloy having aluminum crystals and intermetallic
compounds, the aluminum crystals having an average grain diameter
of 1,000 nm or less, the intermetallic compounds having an average
grain diameter of 500 nm or less.
12. An aluminum alloy as defined in claim 11, wherein the aluminum
crystals have an average grain diameter of 500 nm or less and the
intermetallic compounds have an average grain diameter of 300 nm or
less.
13. An aluminum alloy as defined in one of the claims 1 to 6, the
aluminum alloy having: a hardness H.sub.RB not less than 50 and not
more than 100, a critical upsetting ratio of 70% or more at
temperatures not lower than 200.degree. C. and not higher than
600.degree. C., and an elongation of 10% or more at 20.degree.
C.
14. A method for manufacturing an aluminum-alloy member, the method
comprising the steps of: (1) producing a preform comprising an
aluminum alloy comprising: (a) not less than 0.1 wt. % and not more
than 8 wt. % Constituent A comprising one or more kinds of elements
selected from the group consisting of titanium, vanadium, hafnium,
and zirconium, (b) not less than 0.1 wt. % and not more than 20 wt.
% Constituent B comprising one or more kinds of elements selected
from the group consisting of lanthanum, cerium, praseodymium,
neodymium, mischmetal, calcium, strontium, and barium, and (c) not
less than 0.1 wt. % and not more than 20 wt. % Constituent C
comprising one or more kinds of elements selected from the group
consisting of magnesium and lithium; (2) heating the preform up to
a temperature not lower than 200.degree. C. and not higher than
600.degree. C. at a temperature rising rate of not less than
2.degree. C./sec and not more than 200.degree. C./sec; and (3)
subjecting the heated preform to hot-working.
15. A method for manufacturing an aluminum-alloy member as defined
in claim 14, wherein the aluminum alloy further comprises not less
than 0.1 wt. % and not more than 5 wt. % Constituent D comprising
one or more kinds of elements selected from the group consisting of
niobium, molybdenum, silver, iron, cobalt, tantalum, and
tungsten.
16. A method for manufacturing an aluminum-alloy member, the method
comprising the steps of: (1) producing a preform comprising an
aluminum alloy comprising: (a) not less than 0.1 wt. % and not more
than 5 wt. % Constituent D comprising one or more kinds of elements
selected from the group consisting of niobium, molybdenum, silver,
iron, cobalt, tantalum, and tungsten, (b) not less than 0.1 wt. %
and not more than 20 wt. % Constituent B comprising one or more
kinds of elements selected from the group consisting of lanthanum,
cerium, praseodymium, neodymium, mischmetal, calcium, strontium,
and barium, and (c) not less than 0.1 wt. % and not more than 20
wt. % Constituent C comprising one or more kinds of elements
selected from the group consisting of magnesium and lithium; (2)
heating the preform up to a temperature not lower than 200.degree.
C. and not higher than 600.degree. C. at a temperature rising rate
of not less than 2.degree. C./sec and not more than 200.degree.
C./sec; and (3) subjecting the heated preform to hot-working.
17. A method for manufacturing an aluminum-alloy member as defined
in one of the claims 14 to 16, wherein the step of producing the
preform includes a step of forming rapidly solidified powders of
the aluminum alloy.
18. A method for manufacturing an aluminum-alloy member as defined
in one of the claims 14 to 16, wherein the step of producing the
preform employs the OSPREY method.
19. A method for manufacturing an aluminum-alloy member as defined
in one of the claims 14 to 16, wherein the step of producing the
preform includes a step of forming powders produced by pulverizing
rapidly solidified ribbons of the aluminum alloy.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to an aluminum alloy and a
method for manufacturing an aluminum-alloy member and, more
particularly, to an aluminum alloy combining good forgeability and
high hardness and a method for manufacturing an aluminum-alloy
member combining good forgeability and high hardness.
[0003] 2. Description of the Background Art
[0004] High-strength aluminum alloys have been in use in recent
years that are produced by adopting a rapid solidification
technique.
[0005] For instance, a published Japanese patent application
Tokukaihei 1-275732 has disclosed that rapid solidification of a
multi-element alloy expressed by a general formula
Al.sub.aM.sub.bX.sub.c produces a nanocrystalline aluminum alloy
having such mechanical properties as a tensile strength of 853 to
1,009 MPa, a yield strength of 804 to 941 MPa, and a hardness HV of
200 to 1,000. In the above formula Al.sub.aM.sub.bX.sub.c, (1) "M"
means one or more kinds of metal elements selected from the group
consisting of chrome (Cr), manganese (Mn), iron (Fe), cobalt (Co),
nickel (Ni), copper (Cu), zirconium (Zr), titanium (Ti), magnesium
(Mg), and silicon (Si), (2) "X" means one or more kinds of metal
elements selected from the group consisting of yttrium (Y),
lanthanum (La), cerium (Ce), samarium (Sm), neodymium (Nd), niobium
(Nb), and mischmetal (Mm), and (3) "a", "b", and "c" mean an atomic
percent, "a" lying in the range of 50 to 95 atm. %, "b" in the
range of 0.5 to 35 atm. %, and "c" 0.5 to 25 atm. %.
[0006] Another published Japanese patent application Tokukaihei
6-184712 has disclosed an aluminum alloy having the composition
expressed by a general formula Al.sub.aLn.sub.bM.sub.c, where (1)
"Ln" means one or more kinds of metal elements selected from the
group consisting of mischmetal, yttrium, lanthanum, cerium,
samarium, neodymium, hafnium, niobium, and tantalum, (2) "M" means
one or more kinds of metal elements selected from the group
consisting of vanadium, chrome, manganese, iron, cobalt, nickel,
copper, zirconium, titanium, molybdenum, tungsten, calcium,
lithium, magnesium, and silicon, and (3) "a", "b", and "c" mean an
atomic percent, "a" lying in the range of 50 to 97.5 atm. %, "b" in
the range of 0.5 to 30 atm. %, and "c" 0.5 to 30 atm. %. The
aluminum alloy is a rapidly solidified aluminum alloy that has a
cellular composite structure in which 5 to 50 vol. % amorphous
phases surround nanocrystalline phases. The aluminum alloy is
subjected to plastic working at a temperature higher than the
crystallization temperature of the amorphous phase. Intermetallic
compounds comprising two or more kinds of the above-described Al,
"Ln", and "M" are dispersed in the nanocrystalline matrix to form a
structure having such mechanical properties as a tensile strength
of 760 to 890 MPa and an elongation of 5.5 to 9.0%.
[0007] However, the aluminum alloy disclosed in the application
Tokukaihei 1-275732 has poor ductility and toughness, though it has
very high tensile strength and hardness. Because this lack of
sufficient ductility and toughness allows easy generation of cracks
at the time of processing such as forging and upsetting, it is
difficult to perform near-net-shape forging with complicated
shapes.
[0008] When forging is carried out by exploiting its
superplasticity resulting from its nanocrystallinity, it is
possible to impart complicated shapes. However, its poor ductility
and toughness requires prolonged time for a single step of forging,
causing a problem of reduced production efficiency, and hence an
increase in manufacturing costs. Such a problem becomes serious
when forming ornamental components that require complicated, fine
shapes such as embossed letters on the surface.
[0009] Although the aluminum alloy disclosed in the application
Tokukaihei 6-184712 ensures a certain amount of ductility, it does
not have sufficient mechanical properties to undergo near-net-shape
forging with complicated shapes. In addition to that, because it
uses material powders in which amorphous layers are formed, there
is a problem of increased material cost.
SUMMARY OF THE INVENTION
[0010] The present invention is aimed at solving the
above-described problems. An object of the present invention is to
offer an aluminum alloy that not only has high hardness accompanied
by balanced ductility but also has high toughness and superior
processability.
[0011] Another object of the present invention is to offer a method
for manufacturing an aluminum-alloy member that not only has high
hardness accompanied by balanced ductility but also has high
toughness and superior processability.
[0012] The first aspect of the present invention offers an aluminum
alloy that comprises (1) not less than 0.1 wt. % and not more than
8 wt. % Constituent A comprising one or more kinds of elements
selected from the group consisting of titanium (Ti), vanadium (V),
hafnium (Hf), and zirconium (Zr), (2) not less than 0.1 wt. % and
not more than 20 wt. % Constituent B comprising one or more kinds
of elements selected from the group consisting of lanthanum (La),
cerium (Ce), praseodymium (Pr), neodymium (Nd), mischmetal (Mm),
calcium (Ca), strontium (St), and barium (Ba), and (3) not less
than 0.1 wt. % and not more than 20 wt. % Constituent C comprising
one or more kinds of elements selected from the group consisting of
magnesium (Mg) and lithium (Li).
[0013] The second aspect of the present invention offers another
aluminum alloy that comprises (1) not less than 0.1 wt. % and not
more than 5 wt. % Constituent D comprising one or more kinds of
elements selected from the group consisting of niobium (Nb),
molybdenum (Mo), silver (Ag), iron (Fe), cobalt (Co), tantalum
(Ta), and tungsten (W), (2) not less than 0.1 wt. % and not more
than 20 wt. % Constituent B comprising one or more kinds of
elements selected from the group consisting of lanthanum (La),
cerium (Ce), praseodymium (Pr), neodymium (Nd), mischmetal (Mm),
calcium (Ca), strontium (St), and barium (Ba), and (3) not less
than 0.1 wt. % and not more than 20 wt. % Constituent C comprising
one or more kinds of elements selected from the group consisting of
magnesium (Mg) and lithium (Li).
[0014] The third aspect of the present invention offers a method
for manufacturing an aluminum-alloy member made of the following
aluminum alloy: The aluminum alloy comprises (1) not less than 0.1
wt. % and not more than 8 wt. % Constituent A comprising one or
more kinds of elements selected from the group consisting of
titanium (Ti), vanadium (V), hafnium (Hf), and zirconium (Zr), (2)
not less than 0.1 wt. % and not more than 20 wt. % Constituent B
comprising one or more kinds of elements selected from the group
consisting of lanthanum (La), cerium (Ce), praseodymium (Pr),
neodymium (Nd), mischmetal (Mm), calcium (Ca), strontium (St), and
barium (Ba), and (3) not less than 0.1 wt. % and not more than 20
wt. % Constituent C comprising one or more kinds of elements
selected from the group consisting of magnesium (Mg) and lithium
(Li). First, a preform comprising the aluminum alloy is produced.
Next, the preform is heated up to a temperature not lower than
200.degree. C., and not higher than 600 .degree. at a temperature
rising rate of not less than 2.degree. C./sec and not more than
200.degree. C./sec. Then, the heated preform is subjected to
hot-working.
[0015] The fourth aspect of the present invention offers a method
for manufacturing an aluminum-alloy member made of the following
aluminum alloy: The aluminum alloy comprises (1) not less than 0.1
wt. % and not more than 5 wt. % Constituent D comprising one or
more kinds of elements selected from the group consisting of
niobium (Nb), molybdenum (Mo), silver (Ag), iron (Fe), cobalt (Co),
tantalum (Ta), and tungsten (W), (2) not less than 0.1 wt. % and
not more than 20 wt. % Constituent B comprising one or more kinds
of elements selected from the group consisting of lanthanum (La),
cerium (Ce), praseodymium (Pr), neodymium (Nd), mischmetal (Mm),
calcium (Ca), strontium (St), and barium (Ba), and (3) not less
than 0.1 wt. % and not more than 20 wt. % Constituent C comprising
one or more kinds of elements selected from the group consisting of
magnesium (Mg) and lithium (Li). First, a preform comprising the
aluminum alloy is produced. Next, the preform is heated up to a
temperature not lower than 200.degree. C. and not higher than
600.degree. C. at a temperature rising rate of not less than
2.degree. C./sec and not more than 200.degree. C./sec. Then, the
heated preform is subjected to hot-working.
[0016] The first to fourth aspects of the present invention offer
an aluminum alloy that not only has high hardness accompanied by
balanced ductility but also has high toughness and superior
processability and a method for manufacturing an aluminum-alloy
member that not only has high hardness accompanied by balanced
ductility but also has high toughness and superior
processability.
DETAILED DESCRIPTION OF THE INVENTION
[0017] The first aspect of the present invention offers an aluminum
alloy that comprises (1) not less than 0.1 wt. % and not more than
8 wt. % Constituent A comprising one or more kinds of elements
selected from the group consisting of titanium (Ti), vanadium (V),
hafnium (Hf), and zirconium (Zr), (2) not less than 0.1 wt. % and
not more than 20 wt. % Constituent B comprising one or more kinds
of elements selected from the group consisting of lanthanum (La),
cerium (Ce), praseodymium (Pr), neodymium (Nd), mischmetal (Mm),
calcium (Ca), strontium (St), and barium (Ba), and (3) not less
than 0.1 wt. % and not more than 20 wt. % Constituent C comprising
one or more kinds of elements selected from the group consisting of
magnesium (Mg) and lithium (Li).
[0018] Such a composition facilitates the formation of complicated
shapes because it reduces the strength of the aluminum alloy in the
temperature range for processing. This reduces the number of times
of forming (forging) until the last shape in comparison with the
conventional products, and therefore reduces the processing
cost.
[0019] This composition also increases the hardness of the aluminum
alloy, and increased hardness suppresses the generation of surface
flaws on members made of the aluminum alloy of the present
invention during their manufacturing processes, reducing the
fraction defective of the products.
[0020] The addition of a small amount of Ti, V, Hf, and Zr, which
are used in Constituent A, can reduce the grain size of aluminum,
increasing the hardness of the aluminum alloy. Intermetallic
compounds between these elements and aluminum are deposited or
crystallized out at the center of the individual crystal grains of
aluminum (one place per crystal grain). If the content of
Constituent A is less than 0.1 wt. %, the above-mentioned effect of
increased hardness cannot be obtained. If the content of
Constituent A is more than 8 wt. %, although the hardness of the
aluminum alloy increases, the ductility, critical up-setting ratio,
and other properties decrease, making it difficult to perform
near-net-shape forging with complicated shapes, resulting in the
reduction in forgeability.
[0021] The above-mentioned upsetting ratio is expressed in
(L0-L1)/L0.times.100 (%), where L0 is the sample length in the
upsetting direction before the upsetting work, and L1 after the
upsetting work. The critical upsetting ratio is defined as the
upsetting ratio at which cracks begin to develop at the periphery
of the workpiece when upsetting is performed at a forging rate of
0.5 mm/sec. If the critical upsetting ratio is 70% or more, the
sample is considered to have sufficient forgeability.
[0022] The elements La, Ce, Pr, Nd, Mm, Ca, Sr, and Ba, which are
used in Constituent B, have an effect that a small amount of their
addition can deposit a large amount of intermetallic compounds
having high hardness. The deposition of intermetallic compounds
increases the hardness of the aluminum alloy. The intermetallic
compounds between these elements and aluminum are deposited or
crystallized out at grain boundaries of aluminum. If the content of
Constituent B is less than 0.1 wt. %, the above-mentioned effect
cannot be obtained. If the content of Constituent B is more than 20
wt. %, although the hardness of the aluminum alloy increases, the
ductility and other properties deteriorate, reducing the
forgeability.
[0023] The elements Mg and Li, which are used in Constituent C,
have an effect that they can increase the hardness of the aluminum
alloy when they are rapidly solidified in .alpha.-aluminum to form
a supersaturated solid solution. If the content of Constituent C is
less than 0.1 wt. %, the above-mentioned effect cannot be obtained.
If the content of Constituent C is more than 20 wt. %, although the
hardness of the aluminum alloy increases, the ductility, critical
upsetting ratio, and other properties deteriorate, reducing the
forgeability.
[0024] When Constituents A, B, and C are added with the specified
contents as shown above, because the aluminum having Constituent C
as a solid solution has fine crystal grains and because the
intermetallic compounds are deposited or crystallized out at grain
boundaries, a structure is formed that has less tendency to
overgrow with temperature. The formation of this structure enables
the production of an aluminum alloy with superior balance between
the hardness and forgeability.
[0025] If any one of Constituents A, B, and C lies beyond the
specified range of content, the balance between the hardness and
forgeability is destroyed, producing high hardness with low
forgeability or high forgeability with low hardness.
[0026] When an aluminum alloy having the above-described structure
is hot-worked and then its surface is polished by buffing or other
means, the surface of the member made of this hot-worked aluminum
alloy can easily obtain metallic luster.
[0027] In the aluminum alloy of the first aspect of the present
invention, it is more desirable that the content of Constituent C
be more than 5 wt. % and not more than 20 wt. %.
[0028] This content range, when the surface of the aluminum alloy
is anodized to form an anodic oxide coating, enables the anodic
oxide coating to obtain a shade of relatively low brightness such
as brown or dark gray.
[0029] The shade of the anodic oxide coating can be changed by
adjusting the kind and content of elements used in Constituent C
and other Constituents.
[0030] The aluminum alloy of the first aspect of the present
invention may further comprise not less than 0.1 wt. % and not more
than 5 wt. % Constituent D comprising one or more kinds of elements
selected from the group consisting of niobium (Nb), molybdenum
(Mo), silver (Ag), iron (Fe), cobalt (Co), tantalum (Ta), and
tungsten (W).
[0031] This can offer an aluminum alloy having good forgeablity and
higher hardness.
[0032] The elements Nb, Mo, Ag, Fe, Co, Ta, and W, which are used
in Constituent D, have an effect that they can not only reduce the
grain size of aluminum but also deposit a large amount of
intermetallic compounds. As a result, the hardness of the aluminum
alloy can be further increased. In this case, the intermetallic
compounds are deposited or crystallized out at a plurality of
places inside the individual crystal grains of the aluminum.
[0033] If the content of Constituent D is less than 0.1 wt. %, the
above-mentioned effect cannot be obtained. If the content of
Constituent D is more than 5 wt. %, although the hardness of the
aluminum alloy increases, the ductility, critical upsetting ratio,
and other properties deteriorate, reducing the forgeability.
[0034] In the aluminum alloy of the first aspect of the present
invention, it is more desirable that Constituent A be Zr,
Constituent B be Mm, and Constituent C be Mg. In this case, it is
more desirable that the content of Constituent A be not less than
0.1 wt. % and not more than 3 wt. % and the content of Constituent
B be not less than 0.1 wt. % and not more than 15 wt. %.
[0035] The respective use of Zr, Mm, and Mg as Constituents A, B,
and C can offer an aluminum alloy with further enhanced balance
between the hardness and forgeability.
[0036] The second aspect of the present invention offers another
aluminum alloy that comprises (1) not less than 0.1 wt. % and not
more than 5 wt. % Constituent D comprising one or more kinds of
elements selected from the group consisting of niobium (Nb),
molybdenum (Mo), silver (Ag), iron (Fe), cobalt (Co), tantalum
(Ta), and tungsten (W), (2) not less than 0.1 wt. % and not more
than 20 wt. % Constituent B comprising one or more kinds of
elements selected from the group consisting of lanthanum (La),
cerium (Ce), praseodymium (Pr), neodymium (Nd), mischmetal (Mm),
calcium (Ca), strontium (St), and barium (Ba), and (3) not less
than 0.1 wt. % and not more than 20 wt. % Constituent C comprising
one or more kinds of elements selected from the group consisting of
magnesium (Mg) and lithium (Li).
[0037] Such a composition facilitates the formation of complicated
shapes because it reduces the strength of the aluminum alloy in the
temperature range for processing. This reduces the number of times
of forming (forging) until the last shape in comparison with the
conventional products, and therefore reduces the processing
cost.
[0038] This composition also increases the hardness of the aluminum
alloy. Increased hardness suppresses the generation of surface
flaws on members made of the aluminum alloy of the present
invention during their manufacturing processes, reducing the
fraction defective of the products.
[0039] The elements Nb, Mo, Ag, Fe, Co, Ta, and W, which are used
in Constituent D, have an effect that they can not only reduce the
grain size of aluminum but also deposit a large amount of
intermetallic compounds. As a result, the hardness of the aluminum
alloy can be further increased. The intermetallic compounds
produced by Constituent D are deposited or crystallized out at a
plurality of places inside the individual crystal grains of the
aluminum. If the content of Constituent D is less than 0.1 wt. %,
the above-mentioned effect cannot be obtained. If the content of
Constituent D is more than 5 wt. %, although the hardness of the
aluminum alloy increases, the ductility, critical upsetting ratio,
and other properties deteriorate, reducing the forgeability.
[0040] The elements La, Ce, Pr, Nd, Mm, Ca, Sr, and Ba, which are
used in Constituent B, have an effect that a small amount of their
addition can deposit a large amount of intermetallic compounds
having high hardness. The deposition of intermetallic compounds
increases the hardness of the aluminum alloy. The intermetallic
compounds produced by Constituent B are deposited or crystallized
out at grain boundaries of aluminum.
[0041] If the content of Constituent B is less than 0.1 wt. %, the
above-mentioned effect cannot be obtained. If the content of
Constituent B is more than 20 wt. %, although the hardness of the
aluminum alloy increases, the ductility, critical upsetting ratio,
and other properties deteriorate, reducing the forgeability.
[0042] The elements Mg and Li, which are used in Constituent C,
have an effect that they can increase the hardness of the aluminum
alloy when they are rapidly solidified in .alpha.-aluminum to form
a supersaturated solid solution. If the content of Constituent C is
less than 0.1 wt. %, the above-mentioned effect cannot be obtained.
If the content of Constituent C is more than 20 wt. %, although the
hardness of the aluminum alloy increases, the ductility, critical
upsetting ratio, and other properties deteriorate, reducing the
forgeability.
[0043] When Constituents D, B, and C are added with the specified
contents as shown above, because the aluminum having Constituent C
as a solid solution has fine crystal grains and because the
intermetallic compounds are deposited or crystallized out at grain
boundaries, a structure is formed that has less tendency to
overgrow with temperature. The formation of this structure enables
the production of an aluminum alloy with superior balance between
the hardness and forgeability.
[0044] If any one of Constituents D, B, and C lies beyond the
specified range of content, the balance between the hardness and
forgeability is destroyed, producing high hardness with low
forgeability or high forgeability with low hardness.
[0045] In the aluminum alloy of the second aspect of the present
invention, it is more desirable that the content of Constituent C
be more than 5 wt. % and not more than 20 wt. %.
[0046] This content range, when the surface of the aluminum alloy
is anodized to form an anodic oxide coating, enables the anodic
oxide coating to obtain a shade of relatively low brightness such
as brown or dark gray. The shade of the anodic oxide coating can be
changed by adjusting the kind and content of elements used in
Constituent C and other Constituents.
[0047] In the aluminum alloys of the first and second aspects of
the present invention, it is more desirable that the aluminum
alloys be further provided with an anodic oxide coating.
[0048] As mentioned above, the shade of an anodic oxide coating can
be changed by adjusting the kind and content of elements used in
the individual Constituents. This enables the production of
aluminum alloys provided with anodic oxide coatings having
different shades. As a result, the painting process of the product
can be omitted by using an anodic oxide coating having relatively
high hardness as the protective coating of the aluminum alloy and
by adjusting the shade of the anodic oxide coating so as to conform
to the shade required in the product using the aluminum alloy.
Consequently, the manufacturing cost of the product using the
aluminum alloy can be reduced.
[0049] In the aluminum alloys of the first and second aspects of
the present invention, it is more desirable that the anodic oxide
coating have a lightness less than 50.
[0050] The lightness is measured by spectrophotometric colorimetry
using a chromaticity meter (Japanese Industrial Standard JIS Z
8729: the L*a*b* color-expressing system). The light source for the
measurement is D65 (the International Lighting Committee: the ISO
standard light) with a color temperature of 6,504 K.
[0051] In the aluminum alloys of the first and second aspects of
the present invention, the anodic oxide coating may be formed on
the surface of an aluminum-alloy base material. In this case, the
base material may have an electrical conductivity less than 20%IACS
(International Annealed Copper Standard).
[0052] The present inventors have found that as the electrical
conductivity of a base material decreases, the base-material
element forms more solid solutions with the anodic oxide coating,
giving a shade of relatively low brightness such as brown to the
anodic oxide coating. The present inventors have also found that
the base material requires to have an electrical conductivity less
than 20%IACS in order to give a shade of relatively low brightness
such as brown to the anodic oxide coating.
[0053] In the aluminum alloys of the first and second aspects of
the present invention, the anodic oxide coating may have a shade of
brown, dark gray, or dark brown.
[0054] When a component is required to have a low-bright shade such
as brown in the final product, the use of the aluminum alloy of the
present invention makes it possible to obtain the required shade by
adjusting the kind and content of elements used in the individual
Constituents. This simplifies the traditionally required painting
process of the component. Consequently, the manufacturing cost of
the component can be reduced.
[0055] The aluminum alloys of the first and second aspects of the
present invention may have aluminum crystals and intermetallic
compounds. In this case, the aluminum crystals may have an average
grain diameter of 1,000 nm or less and the intermetallic compounds
may have an average grain diameter of 500 nm or less.
[0056] This enables the aluminum alloy to obtain high forgeability
without losing the high hardness.
[0057] If the aluminum crystals have an average grain diameter more
than 1,000 nm or the intermetallic compounds have an average grain
diameter more than 500 nm, although the aluminum alloy improves its
forgeability by improving its ductility, critical upsetting ratio,
and other properties, it decreases its hardness.
[0058] In the aluminum alloys of the first and second aspects of
the present invention, it is more desirable that the aluminum
crystals have an average grain diameter of 500 nm or less and that
the intermetallic compounds have an average grain diameter of 300
nm or less.
[0059] This enables the aluminum alloy to obtain higher hardness
without losing its forgeability such as ductility and critical
upsetting ratio when higher hardness is required.
[0060] The aluminum alloys of the first and second aspects of the
present invention may have a Rockwell B hardness (H.sub.RB) not
less than 50 and not more than 100. In this case, the aluminum
alloy may have a critical upsetting ratio of 70% or more at
temperatures not lower than 200.degree. C. and not higher than 600
.degree. and an elongation of 10% or more at 20.degree. C.
[0061] The hardness H.sub.RB not less than 50 and not more than 100
means sufficiently high hardness in comparison with the
conventional ingot aluminum alloys such as A5052. This high
hardness suppresses the generation of surface flaws during the
manufacturing process, thereby significantly reducing the ratio of
defective products due to the surface flaws. If the hardness
H.sub.RB is less than 50, as in the conventional ingot aluminum
alloys, it is difficult to suppress the generation of surface flaws
during the manufacturing process. If the hardness H.sub.RB is more
than 100, such properties as the elongation at 20.degree. C. and
critical upsetting ratio deteriorate, reducing the
forgeability.
[0062] The use of an aluminum alloy having the above-described
critical upsetting ratio and elongation allows one or two processes
of hot-working at temperatures not lower than 200.degree. C. and
not higher than 600.degree. C., facilitating the near-net-shape
forging of components with complicated shapes. If the aluminum
alloy has a critical upsetting ratio less than 70% at temperatures
not lower than 200.degree. C. and not higher than 600.degree. C. or
an elongation less than 10% at room temperature (20.degree. C.),
one or two processes of hot-working (near-net-shape forging) for
obtaining components with complicated shapes generates work
cracking of the components during the forging.
[0063] It is more desirable that the aluminum alloy of the first
aspect of the present invention comprises (1) not less than 1.5 wt.
% and not more than 2.5 wt. % Constituent A, (2) not less than 3
wt. % and not more than 6 wt. % Constituent B, (3) not less than 4
wt. % and not more than 6 wt. % Constituent C, and (4) not less
than 1 wt. % and not more than 1.5 wt. % Constituent D.
[0064] The above-mentioned selection of the content ranges of
Constituents A, B, C, and D enables the aluminum alloy to obtain a
more enhanced balance between the hardness and workability
(forgeability).
[0065] It is more desirable that the aluminum alloy of the second
aspect of the present invention comprises (1) not less than 1.5 wt.
% and not more than 2.5 wt. % Constituent D, (2) not less than 3
wt. % and not more than 6 wt. % Constituent B, and (3) not less
than 4 wt. % and not more than 6 wt. % Constituent C.
[0066] The above-mentioned selection of the content ranges of
Constituents D, B, and C enables the aluminum alloy to obtain a
more enhanced balance between the hardness and workability
(forgeability).
[0067] The third aspect of the present invention offers a method
for manufacturing an aluminum-alloy member made of the following
aluminum alloy: The aluminum alloy comprises (1) not less than 0.1
wt. % and not more than 8 wt. % Constituent A comprising one or
more kinds of elements selected from the group consisting of
titanium (Ti), vanadium (V), hafnium (Hf), and zirconium (Zr), (2)
not less than 0.1 wt. % and not more than 20 wt. % Constituent B
comprising one or more kinds of elements selected from the group
consisting of lanthanum (La), cerium (Ce), praseodymium (Pr),
neodymium (Nd), mischmetal (Mm), calcium (Ca), strontium (St), and
barium (Ba), and (3) not less than 0.1 wt. % and not more than 20
wt. % Constituent C comprising one or more kinds of elements
selected from the group consisting of magnesium (Mg) and lithium
(Li). First, a preform comprising the aluminum alloy is produced.
Next, the preform is heated up to a temperature not lower than 200
.degree. and not higher than 600.degree. C. at a temperature rising
rate of not less than 2.degree. C./sec and not more than
200.degree. C./sec. Then, the heated preform is subjected to
hot-working.
[0068] This procedure enables the easy production of an
aluminum-alloy member having high hardness and a complicated shape
notwithstanding the considerably reduced number of times of working
during the hot-working process in comparison with the conventional
methods.
[0069] If the temperature during the heating process
(degasification process) of the preform is higher than 600.degree.
C. or the temperature-rising rate is less than 2.degree. C./sec or
more than 200.degree. C./sec, the hot-working produces an aluminum
alloy with sec or more than 200.degree. C./sec, the hot-working
produces an aluminum alloy with reduced hardness resulting from the
coarsened grains of aluminum crystals and intermetallic compounds.
If the heating temperature of the preform is lower than 200.degree.
C., it is difficult to give the preform sufficient strength because
of the insufficient bonding between the grains constituting the
preform. This reduces the critical upsetting ratio at temperatures
not lower than 200.degree. C. and not higher than 600.degree. C.
and an elongation at room temperature (20.degree. C.),
deteriorating the forgeability.
[0070] In the method for manufacturing an aluminum-alloy member in
the third aspect of the present invention, the aluminum alloy may
further comprise not less than 0.1 wt. % and not more than 5 wt. %
Constituent D comprising one or more kinds of elements selected
from the group consisting of niobium (Nb), molybdenum (Mo), silver
(Ag), iron (Fe), cobalt (Co), tantalum (Ta), and tungsten (W).
[0071] The fourth aspect of the present invention offers a method
for manufacturing an aluminum-alloy member made of the following
aluminum alloy: The aluminum alloy comprises (1) not less than 0.1
wt. % and not more than 5 wt. % Constituent D comprising one or
more kinds of elements selected from the group consisting of
niobium (Nb), molybdenum (Mo), silver (Ag), iron (Fe), cobalt (Co),
tantalum (Ta), and tungsten (W), (2) not less than 0.1 wt. % and
not more than 20 wt. % Constituent B comprising one or more kinds
of elements selected from the group consisting of lanthanum (La),
cerium (Ce), praseodymium (Pr), neodymium (Nd), mischmetal (Mm),
calcium (Ca), strontium (St), and barium (Ba), and (3) not less
than 0.1 wt. % and not more than 20 wt. % Constituent C comprising
one or more kinds of elements selected from the group consisting of
magnesium (Mg) and lithium (Li). First, a preform comprising the
aluminum alloy is produced. Next, the preform is heated up to a
temperature not lower than 200.degree. C. and not higher than
600.degree. C. at a temperature rising rate of not less than
2.degree. C./sec and not more than 200.degree. C./sec. Then, the
heated preform is subjected to hot-working.
[0072] This procedure enables the easy production of an
aluminum-alloy member having high hardness and a complicated shape
notwithstanding the considerably reduced number of times of working
during the hot-working process in comparison with the conventional
methods.
[0073] If the heating temperature of the preform is higher than
600.degree. C. or the temperature-rising rate is less than
2.degree. C./sec or more than 200.degree. C./sec, the hot working
produces an aluminum alloy with reduced hardness resulting from the
coarsened grains of aluminum crystals and intermetallic compounds.
If the heating temperature of the preform is lower than 200.degree.
C., the preform becomes brittle because of the insufficient bonding
between the grains constituting the preform. This reduces the
critical upsetting ratio at temperatures not lower than 200.degree.
C. and not higher than 600.degree. C. and an elongation at room
temperature (20.degree. C.), deteriorating the forgeability.
[0074] In the methods for manufacturing aluminum-alloy members in
the third and fourth aspects of the present invention, it is more
desirable that the heating temperature of the preform be not lower
than 350.degree. C., and not higher than 450.degree. C.
[0075] The above-mentioned selection of the heating temperature
enables the aluminum-alloy member to easily obtain a more enhanced
balance between the hardness and forgeability.
[0076] In the methods for manufacturing aluminum-alloy members in
the third and fourth aspects of the present invention, it is
desirable that the die temperature for the hot-working be about
400.degree. C.
[0077] In the methods for manufacturing aluminum-alloy members in
the third and fourth aspects of the present invention, the step for
producing the preform may include a step for forming rapidly
solidified powders of aluminum alloy.
[0078] In the methods for manufacturing aluminum-alloy members in
the third and fourth aspects of the present invention, the step for
producing the preform may employ the OSPREY method.
[0079] In the methods for manufacturing aluminum-alloy members in
the third and fourth aspects of the present invention, the step for
producing the preform may include a step for forming powders
produced by pulverizing rapidly solidified ribbons of aluminum
alloy.
PREFERRED EMBODIMENTS OF THE INVENTION
[0080] The following is an explanation of the preferred embodiments
of the present invention.
Embodiment 1
[0081] Aluminum-alloy powders having a composition shown in the
columns for Experimental Examples 1 to 11 in Table 1 were produced
by using a gas-atomization device. In the gas-atomization method, a
nitrogen gas was blown onto a molten aluminum alloy dropping from a
nozzle having a hole 2 mm in diameter. The nitrogen gas was
pressurized at 100 kgf/cm.sup.2. In this case, air or an inert gas
such as argon may be used in place of the nitrogen gas.
[0082] Powders of a 2014 aluminum alloy were also produced under
the same condition of gas atomization as described above. The
spacing between dendrite arms in the powder structure of the 2014
aluminum alloy was measured to estimate the cooling rate in the
foregoing process. The result demonstrates that the production of
powders having a particle diameter of 150 .mu.m corresponds to a
cooling rate of 1.0.times.10.sup.3.degree. C./sec.
[0083] The aluminum-alloy powders were sieved out to obtain powders
having a diameter less than 150 .mu.m. The obtained aluminum-alloy
powders were press-formed to produce preforms. The preforms were
heated up to temperatures of 350 to 400.degree. C. at a temperature
rising rate more than 2.degree. C./sec, actually at 10.degree.
C./sec, as shown in Table 1 as the heating and degasifying
treatments.
[0084] Subsequently, the preforms were inserted into a die kept at
400.degree. C. to solidify the powders under a surface pressure of
9 t/cm.sup.2. The fine structure and mechanical properties of the
obtained solidified bodies were examined. The results are shown in
Tables 1 and 2.
[0085] The grain diameters shown in Table 1 were determined by the
following method: First, a section of a solidified body was mirror
polished. Second, micrographs of the fine structure were taken by
using a high-resolution scanning electron microscope (SEN) at
50,000 power. Finally, the individual micrographs were input into a
personal computer to process the pictures for measuring the grain
diameters of the aluminum crystals and intermetallic compounds.
Because the aluminum crystals and intermetallic compounds have a
different contrast on the micrograph, they are easily
distinguished. The grain diameters were measured on three visual
fields of each Experimental Example. Table 1 shows the average
value of the measured results.
1 TABLE 1 Preform-heating condition Grain diameter of Grain
diameter of Powder- Ultimate Temperature- aluminum intermetallic
solidified Composition temperature rising rate crystals compounds
body (wt. %) (.degree. C.) (.degree. C./sec) (nm) (nm) 1
Al--2Zr--8Mm--18Mg 400 10 600 300 2 Al--3Zr--8Mm--10Mg 400 10 500
200 3 Al--2Ti--4.5Mm--9Mg 350 10 500 200 4 Al--2Mo--3Mm--11Mg 400
10 650 400 5 Al--5V--2Nb--3Mm--8Mg 350 10 700 300 6
Al--6Zr--3Mm--2Ta--6Mg 400 10 850 400 7 Al--2Zr--8Mm--8Mg 400 10
500 300 8 Al--2Zr--8Mm--16Mg 400 10 500 300 9 Al--3Zr--4.5Mm--8Mg
400 10 500 300 10 Al--2Zr--8Mm--8Mg--3Mo 400 10 500 300 11
Al--2Zr--8Mm--8Mg--3Ta 400 10 500 300 12 400 0.5 1,200 700 13
Al--2Zr--8Mm--16Mg 180 10 300 200 14 650 10 2,000 600 15
Al--2Zr--8Mm--25Mg 400 10 600 200 16 Al--10Zr--8Mm--8Mg 400 10 600
600 17 Al--3Zr--21Mm--6Mg 400 10 500 750 18 Al--2Zr--3Mm--6Mg--10Mo
400 10 700 900 19 Al--10Ti--6Mm--10Mg--8Nb 400 10 600 800
[0086]
2TABLE 2 Room- Room- Upsetting Electrical Powder- temperature
temperature tempera- Critical conductiv- Lightness of solidified
hardness elongation ture upsetting ratio Shade of ity alumite body
H.sub.RB (%) (.degree. C.) (%) alumite (% IACS) L* 1 91 10 400 81
Brown 12.6 22.5 2 94 10 400 75 Dark gray 13.0 23.6 3 95 15 300 80
Brown 12.0 21.5 4 91 11 600 85 Dark gray 16.0 33.5 5 89 13 300 75
Dark gray 17.0 30.5 6 95 11 400 80 Dark gray 9.0 20.5 7 84 11 400
88 Dark gray 18.2 45.8 8 91 10 400 81 Brown 15.2 43.1 9 82 10 400
71 Brown 17.3 47.5 10 78 13 400 86 Dark gray 14.2 36.9 11 81 12 400
81 Dark gray 11.6 33.2 12 49 18 400 90 Light gray 25.0 63.9 13 103
0 400 50 Dark gray 10.5 31.8 14 46 21 400 95 Light gray 24.0 65.1
15 110 0 400 45 Dark gray 10.0 21.6 16 85 5 400 65 Dark gray 18.0
28.4 17 91 3 400 67 Dark gray 15.0 27.3 18 91 8 500 68 Dark gray
12.0 32.4 19 92 6 500 71 Dark 14.0 26.5 brown
[0087] The fine structures of the solidified bodies of Experimental
Examples 1 to 11 were examined by the above-described method.
[0088] As is seen in Table 1, it was confirmed that all the
Experimental Examples 1 to 11 have both aluminum crystals and
intermetallic compounds. It was also confirmed that all the
Experimental Examples 1 to 11 have aluminum crystals less than
1,000 nm in grain diameter and intermetallic compounds less than
500 nm in grain diameter.
[0089] Next, aluminum-alloy powders having a composition shown in
the columns for Experimental Examples 12 to 19 in Table 1 were
produced by a method similar to that used for Experimental Examples
1 to 11. Experimental Examples 12 to 19 were produced by using
these powders. The heating conditions for the preforms of
Experimental Examples 12 to 19 are also shown in Table 1. The fine
structures of Experimental Examples 12 to 19 were also examined by
the same method as in Experimental Examples 1 to 11.
[0090] The following measurements were carried out on Experimental
Examples 1 to 19 shown in Table 1: hardness HRB at room temperature
(20.degree. C.), tensile strength at room temperature, critical
upsetting ratio, and the shade of an anodic oxide coating (alumite)
and other properties when the anodic oxide coating was formed on
the surface.
[0091] As shown in Table 2, all the Experimental Examples 1 to 11
have a room-temperature hardness H.sub.RB more than 50 and less
than 100, an elongation not less than 10%, and a critical upsetting
ratio more than 70%.
[0092] The surfaces of the solid bodies of Experimental Examples 1
to 11 were anodized to form an anodic oxide coating (alumite). The
shade of the alumite was examined. As is seen in Table 2, the
results showed that all the Experimental Examples 1 to 11 have a
dark shade such as brown or dark gray. The lightness of the alumite
was measured; the result showed that all the Experimental Examples
1 to 11 have a lightness less than 50. The electrical conductivity
of the matrices of the solidified bodies of Experimental Examples 1
to 19 was measured. As is seen in Table 2, the result showed that
when the electrical conductivity is less than 20%IACS, the shade of
the alumite is dark (less than 50 in lightness) such as brown.
Incidentally, all the Experimental Examples 1 to 11 have an
electrical conductivity less than 20%IACS.
[0093] The fine structures and mechanical properties of
Experimental Examples 12 to 19 are discussed in the following:
[0094] Experimental Example 12 has a room-temperature hardness as
low as 49, as is seen in Table 2. This is attributable to the grain
diameter of the aluminum crystals as large as 1,200 nm resulting
from the temperature-rising rate as low as 0.5.degree. C./sec in
the preform-heating conditions as can be seen in Table 1. If the
room-temperature hardness is less than 50, surface flaws and other
defects tend to be generated during the manufacturing process,
causing a yield reduction as in the conventional products.
[0095] Experimental Example 13, although having a room-temperature
hardness exceeding 100, has practically no elongation and a
critical upsetting ratio as low as 50%. This is attributable to the
fact that the ultimate temperature was 180.degree. C. in the
preform-heating conditions, i.e., the preform was not heated up to
a temperature exceeding 200.degree. C.
[0096] Experimental Example 14 also has a room-temperature hardness
as low as 46, as is seen in Table 2. This is attributable to the
grain diameter of the aluminum crystals as large as 2,000 nm, which
is more than necessary, resulting from the ultimate temperature as
high as 650.degree. C. in the preform-heating conditions as can be
seen in Table 1.
[0097] Experimental Example 15 contains, in its composition, more
Mg than the content specified for the aluminum alloy of the present
invention as is seen in Table 1. Consequently, as shown in Table 2,
although sufficiently high in room-temperature hardness,
Experimental Example 15 has low elongation and critical upsetting
ratio, and hence low forgeability.
[0098] Experimental Example 16 contains more Zr than the content
specified for the aluminum alloy of the present invention as is
seen in Table 1. Consequently, as shown in Table 2, although
sufficiently high in room-temperature hardness, Experimental
Example 16 has low elongation and critical upsetting ratio.
[0099] Experimental Example 17 contains more Mm than the content
specified for the aluminum alloy of the present invention as is
seen in Table 1. Consequently, as shown in Table 2, although
sufficiently high in room-temperature hardness, Experimental
Example 17 has low elongation and critical upsetting ratio.
[0100] Experimental Example 18 contains more Mo than the content
specified for the aluminum alloy of the present invention as is
seen in Table 1. Consequently, as shown in Table 2, although
sufficiently high in room-temperature hardness, Experimental
Example 18 has low elongation and critical upsetting ratio.
[0101] Experimental Example 19 contains more Ti and Nb than the
contents specified for the aluminum alloy of the present invention
as is seen in Table 1. Consequently, as shown in Table 2, although
sufficiently high in room-temperature hardness, Experimental
Example 19 has low elongation.
[0102] The anodizing was carried out by the following process:
First, the surface of a solidified body was cut. Second, the
solidified body subjected to the cutting work was cleaned by
caustic soda. Finally, anodizing was conducted up to a coating
thickness of about 10 .mu.m.
[0103] The structure in the vicinity of the boundary between the
anodic oxide coating and base material (matrix) was examined on the
individual Experimental Examples 1 to 19 by using a high-resolution
scanning electron microscope. The result was that the reflected
electron image of the structure demonstrates the existence of
intermetallic compounds in the anodic oxide coating. When the shade
of an anodic oxide coating (alumite) becomes brown or dark gray,
the alumite has an increased amount of the intermetallic compounds
to a certain extent. More specifically, the intermetallic compounds
occupy more than 20% of the area of the alumite.
[0104] It was also confirmed that when a sample made of the
aluminum alloy of the present invention is upset at high
temperature and then its surface is polished by buffing or another
simple means, the surface of the sample can easily obtain metallic
luster.
Embodiment 2
[0105] Aluminum-alloy powders having a composition shown in the
columns for Experimental Examples 20 to 27 in Table 3 were produced
by a method similar to that used for Embodiment 1 of the present
invention. Experimental Examples 20 to 27 were produced by using
these powders. Samples of solidified bodies were formed by a method
basically similar to that used for Embodiment 1 of the present
invention. The heating conditions for the preforms are shown in
Table 3. The fine structures and mechanical properties of the
solidified bodies were examined by a method similar to that used
for Embodiment 1 of the present invention. The results are shown in
Tables 3 and 4.
3 TABLE 3 Preform-heating condition Grain diameter of Grain
diameter of Powder- Ultimate Temperature- aluminum intermetallic
solidified Composition temperature rising rate crystals compounds
body (wt. %) (.degree. C.) (.degree. C./sec) (nm) (nm) 20
Al--2Mo--3Mm--3Mg 400 10 650 400 21 Al--1V--1Nb--3Mm--3Mg 350 10
700 300 22 Al--3Ti--13Mm--3Mg 400 10 400 300 23 Al--1Hf--5Mm--3Mg
400 10 500 300 24 Al--3Ag--Mm--2Mg 400 10 400 250 25
Al--2V--9Mm--2Mg--3Mo 350 10 500 300 26 Al--2V--9Mm--2Mg--3W 400 10
500 300 27 Al--3Zr--13.5Mm--2Li 400 10 400 500 28 400 0.5 1,200 600
29 Al--2Mo--3Mm--3Mg 180 10 500 300 30 650 10 2,000 700 31
Al--2Mo--8Mm--25Mg 400 10 500 200 32 Al--5Ti--5V--8Mm--8Mg 400 10
600 600 33 Al--3Zr--10Mm--11La--6Mg 400 10 500 1,000 34
Al--10Mo--3Mm--3Mg 400 10 1,000 800 35 Al--10W--2Mm--4Mg 400 10
1,200 900
[0106]
4TABLE 4 Room- Room- Upsetting Electrical Powder- temperature
temperature tempera- Critical conductiv- Lightness of solidified
hardness elongation ture upsetting ratio Shade of ity alumite body
H.sub.RB (%) (.degree. C.) (%) alumite (% IACS) L* 20 88 11 500 65
Light gray 24.3 65.2 21 78 13 300 76 Light gray 26.8 69.8 22 74 13
400 81 Light 26.5 68.2 yellow 23 73 20 400 92 Light 24.0 61.4
yellow 24 84 14 400 85 Light 24.5 59.8 yellow 25 88 12 500 92 Light
gray 20.0 68.3 26 87 11 500 85 Light gray 21.8 69.2 27 85 10 400 79
Dark gray 18.9 36.3 28 44 25 400 90 Light gray 30.0 60.2 29 101 2
400 50 Dark gray 10.6 20.4 30 48 22 400 95 Light gray 32.0 59.8 31
112 0 400 45 Dark gray 9.0 15.8 32 91 3 400 55 Dark gray 11.0 20.6
33 91 1 400 45 Dark gray 8.0 17.8 34 81 7 400 80 Dark gray 18.6
45.6 35 82 8 400 76 Dark gray 19.2 48.9
[0107] As is seen in Tables 3 and 4, the measured items for
Experimental Examples 20 to 27 are the same as those for Embodiment
1 of the present invention. The measured results for all the items
of Experimental Examples 20 to 27 are within the range specified
for the aluminum alloy of the present invention. The surfaces of
the samples were anodized similarly to Embodiment 1 of the present
invention to form an anodic oxide coating (alumite). The shade and
lightness of the alumite were examined. The electrical conductivity
of the base material was also measured. As can be seen in Tables 3
and 4, the shade of the aluminum alloy can be changed to one such
as dark gray or light yellow by adjusting the composition of the
aluminum alloy.
[0108] Aluminum-alloy powders having a composition shown in the
columns for Experimental Examples 28 to 35 in Table 3 were produced
similarly to Experimental Examples 20 to 27. The powders were used
to produce solidified bodies under the heating conditions for the
preforms shown in Table 3. The fine structures and mechanical
properties of the solidified bodies were examined similarly to
Experimental Examples 20 to 27.
[0109] Experimental Example 28 was prepared by a temperature-rising
rate lower than 2.degree. C./sec. Experimental Example 30 was
prepared at an ultimate temperature higher than 600.degree. C. As a
result, Experimental Examples 28 and 30 have aluminum-crystal
grains and intermetallic compounds both larger in diameter than the
values desirable for the aluminum alloy of the present invention.
Consequently, both Examples have a considerably low
room-temperature hardness as shown in Table 4.
[0110] Experimental Example 29 was prepared at an ultimate
temperature lower than 200.degree. C. Consequently, although high
in room-temperature hardness, Experimental Example 29 has low
elongation and critical upsetting ratio.
[0111] Experimental Example 31 contains Constituent C of which Mg
exceeds 20 wt. % in content. Consequently, although sufficiently
high in room-temperature hardness, Experimental Example 31 has
considerably low elongation and critical upsetting ratio.
[0112] Experimental Example 32 contains Constituent A of which the
sum of Ti and V exceeds 8 wt. % in content. As a result,
Experimental Example 32 has inter-metallic compounds not only
increased in the amount of deposition but also excessively grown.
Consequently, although sufficiently high in room-temperature
hardness, Experimental Example 32 has considerably low elongation
and critical upsetting ratio.
[0113] Experimental Example 33 contains Constituent B of which the
sum of Mm and La exceeds 20 wt. % in content. As a result,
Experimental Example 33 also has intermetallic compounds not only
increased in the amount of deposition but also excessively grown.
Consequently, although sufficiently high in room-temperature
hardness, Experimental Example 33 has considerably low elongation
and critical upsetting ratio.
[0114] Experimental Example 34 contains more Mo than 5 wt. %. In
this case also, the intermetallic compounds are excessively grown.
Consequently, although the room-temperature hardness becomes high,
the elongation decreases.
[0115] Experimental Example 35 contains more W than 5 wt. %. In
this case also, the intermetallic compounds are not only increased
in the amount of deposition but also excessively grown.
Consequently, although the room-temperature hardness increases to a
certain extent, the elongation decreases.
[0116] As described above, the aluminum alloy of the present
invention has high hardness and good elongation and critical
upsetting ratio (forgeability). It is also possible to obtain a
member having metal luster by giving it simple polishing after
hot-working.
[0117] Because the shade of the alumite can be changed by adjusting
additive elements, a highly hard anodic oxide coating can be used
not only as a protective coating but also as a colored layer that
gives necessary coloring.
[0118] The aluminum alloy of the present invention can be used both
as an exterior component of electronic devices, for example, and as
a component of household electrical appliances, ornamental objects,
cars, and other objects.
[0119] The present embodiments are to be considered in all respects
as illustrative and not restrictive. The scope of the present
invention is indicated by the appended claims rather than by the
above-described embodiments. All changes that come within the
meaning and range of equivalency of the claims are therefore
intended to be embraced by the claims.
* * * * *