U.S. patent application number 11/182653 was filed with the patent office on 2006-01-19 for wear-resistant sintered aluminum alloy with high strength and manufacturing method thereof.
Invention is credited to Junichi Ichikawa, Kenzo Morita.
Application Number | 20060013719 11/182653 |
Document ID | / |
Family ID | 35508837 |
Filed Date | 2006-01-19 |
United States Patent
Application |
20060013719 |
Kind Code |
A1 |
Ichikawa; Junichi ; et
al. |
January 19, 2006 |
Wear-resistant sintered aluminum alloy with high strength and
manufacturing method thereof
Abstract
Disclosed is a wear-resistant sintered aluminum alloy with high
strength and a manufacturing method thereof. The sintered aluminum
alloy contains, by mass: 3.0-10% zinc; 0.5-5.0% magnesium; 0.5-5.0%
copper; 0.1-10% hard particles; impurities; and aluminum. The
metallographic structure has an aluminum alloy matrix in which the
hard particles dispersed; and an intermetallic compound phase being
dispersedly precipitated in the aluminum alloy matrix. Using an
aluminum powder, a hard particles powder and other powders, a
compact is formed and sintered at 580-610 degrees C., then cooled
and subjected to heat treatment at a temperature of 460-490 degrees
C., including water-quenching and aging at 110-200 degrees C.
Inventors: |
Ichikawa; Junichi;
(Matsudo-shi, JP) ; Morita; Kenzo; (Matsudo-shi,
JP) |
Correspondence
Address: |
JOHN S. PRATT, ESQ;KILPATRICK STOCKTON, LLP
1100 PEACHTREE STREET
ATLANTA
GA
30309
US
|
Family ID: |
35508837 |
Appl. No.: |
11/182653 |
Filed: |
July 14, 2005 |
Current U.S.
Class: |
419/29 ;
75/249 |
Current CPC
Class: |
C22C 32/0047 20130101;
B22F 2998/10 20130101; C22C 21/10 20130101; B22F 3/24 20130101;
B22F 3/16 20130101; B22F 3/17 20130101; B22F 2003/248 20130101;
B22F 2998/10 20130101 |
Class at
Publication: |
419/029 ;
075/249 |
International
Class: |
B22F 3/24 20060101
B22F003/24 |
Foreign Application Data
Date |
Code |
Application Number |
Jul 14, 2004 |
JP |
P2004-207586 |
May 12, 2005 |
JP |
P2005-139397 |
Claims
1. A wear-resistant sintered aluminum alloy having high strength,
comprising, by mass: 3.0 to 10% zinc; 0.5 to 5.0% magnesium; 0.5 to
5.0% copper; 0.1 to 10% hard particles; an inevitable amount of
impurities; and aluminum, and having a metallographic structure
comprising: an aluminum alloy matrix in which the hard particles
dispersed; and an intermetallic compound phase being dispersedly
precipitated in the aluminum alloy matrix.
2. The wear-resistant sintered aluminum alloy of claim 1, wherein
the hard particles have a mean particle size of 1 to 100
microns.
3. The wear-resistant sintered aluminum alloy of claim 1, wherein
the hard particles are composed of a material having a Vickers
hardness of 600 Hv or more and having substantially no reactivity
with aluminum.
4. The wear-resistant sintered aluminum alloy of claim 1, wherein
the hard particles are composed of at least one material selected
from the group consisting of silicon carbide, chromium boride and
boron carbide, and the intermetallic compound phase includes at
least one selected from the group consisting of MgZn.sub.2,
Al.sub.2Mg.sub.3Zn.sub.3 and CuAl.sub.2.
5. The wear-resistant sintered aluminum alloy of claim 1, further
comprising at least one reagent which is selected from the group
consisting of tin, bismuth, indium and both of an eutectic compound
and a monotactic compound both of which comprise at least one
element of tin, bismuth and indium as a main component, and the
content of the reagent in the wear-resistant sintered aluminum
alloy is 0.01 to 0.5 mass %.
6. A method of manufacturing a wear-resistant sintered aluminum
alloy with high strength, comprising: preparing a raw material
powder comprising, by mass: 3.0 to 10% zinc; 0.5 to 5.0% magnesium;
0.5 to 5.0% copper; 0.1 to 10% hard particles; inevitable amount of
impurities; and the balance aluminum, by using: an aluminum powder
having a particle size of 140 microns or less; a powder for the
hard particles, having a particle size of 113 microns or less; and
one of combination of simple metal powders, combination of binary
alloy powders and combination of a simple metal powder and a binary
alloy powder, containing zinc, magnesium and copper and having a
particle size of 74 microns or less; pressing the raw material
powder in a die at a compacting pressure of 200 MPa or more to form
a compact having a predetermined shape; sintering the compact in a
non-oxidizing atmosphere in such a manner as to heat the compact
from 400 degrees C. to a sintering temperature of 590 to 610
degrees C. at an temperature-elevating rate of 10 degrees C./min or
more and keep the sintering temperature for 10 minutes or more,
before cooling the sintered compact to a room temperature; and
subjecting the compact after the sintering, to heat treatment
comprising: heating the compact at a temperature of 460 to 490
degrees C. and water-quenching so as to dissolve a precipitation
phase in the aluminum base of the compact to produce solid
solution; and keeping the temperature in a range of 110 to 200
degrees C. for 3 to 28 hours to produce a precipitation phase from
the solid solution.
7. The manufacturing method of claim 6, further comprising, before
the heat treatment, subjecting the sintered compact to cold forging
or hot forging, the cold forging comprising pressing the sintered
compact at a room temperature with an upsetting ratio being in a
range of 3 to 40%, and the hot forging comprising pressing the
sintered compact at a temperature of 100 to 450 degrees C. with an
upsetting ratio being in a range of 3 to 70%.
8. The manufacturing method of claim 6, wherein the hard particles
are composed of a material having a Vickers hardness of 600 H.sub.v
or more and having substantially no reactivity with aluminum.
9. The manufacturing method of claim 6, wherein the hard particles
are composed of at least one material selected from the group
consisting of silicon carbide, chromium boride and boron
carbide.
10. The manufacturing method of claim 6, further comprising, before
the pressing, adding to the raw material powder at least one
reagent which is selected from the group consisting of tin,
bismuth, indium and both of an eutectic compound and a monotactic
compound both of which comprise at least one element of tin,
bismuth and indium as a main component, at the content of the
reagent being 0.01 to 0.5 mass % in the total of the reagent and
the raw material powder.
11. The manufacturing method of claim 6, wherein the non-oxidizing
atmosphere at the sintering is a nitrogen gas atmosphere having a
dew point of -40 degrees C. or less.
12. A method of manufacturing a wear-resistant sintered aluminum
alloy with high strength, comprising: preparing a raw material
powder comprising, by mass: 3.0 to 10% zinc; 0.5 to 5.0% magnesium;
0.5 to 5.0% copper; 0.1 to 10% hard particles; inevitable amount of
impurities; and the balance aluminum, by using: a simple aluminum
powder of at least 15 mass % of the raw material powder; an
aluminum alloy powder containing the whole of zinc which the raw
material powder comprises; and a powder for the hard particles at
0.1 to 10 mass % of the raw material powder; pressing the raw
material powder in a die at a compacting pressure of 200 MPa or
more to form a compact having a predetermined shape; sintering the
compact in a non-oxidizing atmosphere at a sintering temperature of
580 to 610 degrees C. for 10 minutes or more, before cooling the
sintered compact to a room temperature; and subjecting the compact
after the sintering, to heat treatment comprising: heating the
compact at a temperature of 460 to 490 degrees C. and
water-quenching so as to dissolve a precipitation phase in the
aluminum base of the compact to produce solid solution; and keeping
the temperature in a range of 110 to 200 degrees C. for 2 to 28
hours to produce a precipitation phase from the solid solution.
13. The manufacturing method of claim 12, further comprising,
before the heat treatment, subjecting the sintered compact to cold
forging or hot forging, the cold forging comprising pressing the
sintered compact at a room temperature with an upsetting ratio
being in a range of 3 to 40%, and the hot forging comprising
pressing the sintered compact at a temperature of 100 to 450
degrees C. with an upsetting ratio being in a range of 3 to
70%.
14. The manufacturing method of claim 12, wherein the aluminum
alloy powder has a composition comprising 10 to 30 mass % of zinc,
an inevitable amount of impurities and the balance aluminum.
15. The manufacturing method of claim 12, wherein, at the
preparing, the aluminum alloy powder contains 10 mass % or less of
copper.
16. The manufacturing method of claim 12, wherein the hard
particles are composed of a material having a Vickers hardness of
1000 H.sub.v or more and having substantially no reactivity with
aluminum.
17. The manufacturing method of claim 12, wherein the hard
particles are composed of at least one material selected from the
group consisting of silicon carbide, chromium boride and boron
carbide.
18. The manufacturing method of claim 12, further comprising,
before the pressing, adding to the raw material powder at least one
reagent which is selected from the group consisting of tin,
bismuth, indium and both of an eutectic compound and a monotactic
compound both of which comprise at least one element of tin,
bismuth and indium as a main component, at the content of the
reagent being 0.01 to 0.5 mass % in the total of the reagent and
the raw material powder.
19. The manufacturing method of claim 12, wherein, at the
preparing, the aluminum powder and the aluminum alloy powder have a
particle size of 140 microns or less, a powder for the hard
particles has a particle size of 113 microns or less, and the
preparing further comprises using at least one powder having a
particle size of 74 microns or less is used for magnesium and
copper.
20. The manufacturing method of claim 12, wherein the non-oxidizing
atmosphere at the sintering is a nitrogen gas atmosphere having a
dew point of -40 degrees C. or less.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to a wear-resistant sintered
aluminum alloy with high strength that is suitable for various
kinds of sliding parts such as connecting rods, pistons and the
like, and a method of manufacturing thereof. More particularly, the
invention concerns a wear-resistant sintered aluminum alloy with
high strength that is improved in tensile strength and elongation
as well as wear resistance, and a manufacturing method thereof.
[0003] 2. Related Art
[0004] Regarding the aluminum sintered parts manufactured with the
use of a powder-metallurgical method, there has been an increasing
demand in recent years, since they are not only light in weight but
also possible to possess preferable properties that cannot be
obtained with cast materials, such as strength, wear resistance and
the like. Specifically, in a case of wrought alloy containing a
large amount of silicon, only alloy having metallographic structure
in which primary silicon grains are coarse is obtained. In
contrast, in a case of sintered aluminum alloy, it has been
accomplished to obtain a sintered aluminum alloy which has
metallographic structure that Al--Si alloy phase having fine
primary silicon grains dispersed therein and aluminum solid
solution phase having no primary silicon grains are dispersed in
spots, and which is excellent in strength and wear resistance (ref.
publications of Japanese Laid-Open Patent applications,
JPA-H04-365382, JPA-H07-197168, JPA-H07-197163, and
JPA-H07-224341). These sintered aluminum alloys are excellent in
wear resistant. However, they are to an extent of 360 MPa or so in
terms of the strength even when they are subjected to forging and
heat treatment, and the application of them is limited and a
sintered aluminum alloy with a higher level of strength has been
therefore expected to be produced.
[0005] In short, it is not such a material that exhibits a high
level of property in terms of both of the tensile strength and the
elongation.
BRIEF SUMMARY OF THE INVENTION
[0006] With the above problems in mind, it is therefore an object
of the present invention to provide a novel sintered aluminum alloy
having a wear resistance and simultaneously having a higher tensile
strength and a high elongation, and a method of manufacturing the
same.
[0007] It is also an object of the present invention to provide a
manufacturing method of a sintered aluminum alloy, wherein the zinc
content of the sintered aluminum alloy after the sintering is not
fluctuate to achieve a constant mechanical strength and realize
stable mass production thereof.
[0008] In order to achieve the above-mentioned object, a
wear-resistant sintered aluminum alloy having high strength,
according to one aspect of the present invention, comprises, by
mass: 3.0 to 10% zinc; 0.5 to 5.0% magnesium; 0.5 to 5.0% copper;
0.1 to 10% hard particles; an inevitable amount of impurities; and
aluminum, and having a metallographic structure comprising: an
aluminum alloy matrix in which the hard particles dispersed; and an
intermetallic compound phase being dispersedly precipitated in the
aluminum alloy matrix.
[0009] A method of manufacturing a wear-resistant sintered aluminum
alloy with high strength, according to one aspect of the invention
comprises: preparing a raw material powder comprising, by mass: 3.0
to 10% zinc; 0.5 to 5.0% magnesium; 0.5 to 5.0% copper; 0.1 to 10%
hard particles; inevitable amount of impurities; and the balance
aluminum, by using: an aluminum powder having a particle size of
140 microns or less; a powder for the hard particles, having a
particle size of 113 microns or less; and one of combination of
simple metal powders, combination of binary alloy powders and
combination of a simple metal powder and a binary alloy powder,
containing zinc, magnesium and copper and having a particle size of
74 microns or less; pressing the raw material powder in a die at a
compacting pressure of 200 MPa or more to form a compact having a
predetermined shape; sintering the compact in a non-oxidizing
atmosphere in such a manner as to heat the compact from 400 degrees
C. to a sintering temperature of 590 to 610 degrees C. at an
temperature-elevating rate of 10 degrees C./min or more and keep
the sintering temperature for 10 minutes or more, before cooling
the sintered compact to a room temperature; and subjecting the
compact after the sintering, to heat treatment comprising: heating
the compact at a temperature of 460 to 490 degrees C. and
water-quenching so as to dissolve a precipitation phase in the
aluminum base of the compact to produce solid solution; and keeping
the temperature in a range of 110 to 200 degrees C. for 2 to 28
hours to produce a precipitation phase from the solid solution.
[0010] A method of manufacturing a wear-resistant sintered aluminum
alloy with high strength, according to another aspect of the
invention, comprises: preparing a raw material powder comprising,
by mass: 3.0 to 10% zinc; 0.5 to 5.0% magnesium; 0.5 to 5.0%
copper; 0.1 to 10% hard particles; inevitable amount of impurities;
and the balance aluminum, by using: a simple aluminum powder of at
least 15 mass % of the raw material powder; an aluminum alloy
powder containing the whole of zinc which the raw material powder
comprises; and a powder for the hard particles at 0.1 to 10 mass %
of the raw material powder; pressing the raw material powder in a
die at a compacting pressure of 200 MPa or more to form a compact
having a predetermined shape; sintering the compact in a
non-oxidizing atmosphere at a sintering temperature of 580 to 610
degrees C. for 10 minutes or more, before cooling the sintered
compact to a room temperature; and subjecting the compact after the
sintering, to heat treatment comprising: heating the compact at a
temperature of 460 to 490 degrees C. and water-quenching so as to
dissolve a precipitation phase in the aluminum base of the compact
to produce solid solution; and keeping the temperature in a range
of 110 to 200 degrees C. for 2 to 28 hours to produce a
precipitation phase from the solid solution.
[0011] In accordance with the above construction, the sintered
aluminum alloy of the present invention is excellent to have high
tensile strength and elongation as well as high wear resistance. In
the manufacturing method of a sintered aluminum alloy of the
present invention, the tensile strength and the elongation are
especially improved for wear resistant sintered aluminum alloys, to
enable application to various kinds of sliding members used in
vehicles and realize various sliding members of small weight.
[0012] The features and advantages of the manufacturing method
according to the present invention over the conventional art will
be more clearly understood from the following description of the
preferred embodiments of the present invention.
DETAILED DESCRIPTION OF THE INVENTION
[0013] The inventors of the present application has developed and
proposed in Japanese Patent Applications of No. 2003-345001 and No.
2004-206957, a manufacturing method of an aluminum alloy having
composition of ASM (American Society for Metals) 7xxx series that
are known as extra super duralumin, by a powder metallurgical
process. In this application, a wear-resistant sintered aluminum
alloy simultaneously having a high strength is accomplished, based
on the above sintered alloy, by the addition of hard particles in
the composition. Moreover, the manufacturing method is further
improved to prevent vaporization of zinc and variation of the zinc
content by incorporating the whole amount of zinc in the form of
aluminum alloy, and to prevent decrease of compressibility of the
raw material powder mixture, by use of at least 15 mass % of a
simple aluminum powder in combination with the aluminum alloy
powder as raw material powders.
[0014] Hereinafter, the embodiments of the present invention will
be described, explaining every component and step of the
manufacturing method in detail. It is to be noted that, in the
description of the present application, Al, Zn, Mg and the like are
symbols of the elements used, and that the term, "aluminum
part(s)", should be read as meaning "aluminum-based part(s)" or
part(s) being composed mainly of aluminum and possibly containing
small amounts of other elements. Moreover, "sintering temperature"
means the maximum temperature at which the compact is sintered, and
"sintering time" means the time period during which the temperature
is in the range of the sintering temperature.
[0015] (1) Raw Material Powder Blending Step
[0016] In this step, a raw material powdery mixture to be compacted
is prepared by blending the respective powdered raw materials as to
which the details are described below.
[0017] (1)-1 Ingredient Composition
[0018] <Zinc>
[0019] Zinc, together with magnesium, is precipitated in the
aluminum matrix in the form of MgZn.sub.2 (.eta.-phase) or
Al.sub.2Mg.sub.3Zn.sub.3 (T-phase) to work to make an increase in
the strength. Also, zinc, when the temperature is elevated for
sintering, is molten to become a liquid phase and it wets the
surface of the aluminum particles to eliminate the oxide layer
thereon, and it is diffused into the aluminum matrix to also act to
accelerate the bonding of the aluminum particles resulting from
diffusion of them to each other due to such diffusion of zinc. If
the content of Zn is below 3 mass %, it is difficult to
sufficiently exhibit the above-described works, with the result
that the effect of making the enhancement in the strength becomes
poor. On the other hand, if the content is beyond 10 mass %, the
amount of Zn in the sintered mass or the amount of Zn-based
eutectoid liquid phase becomes excessively large, with the result
that it becomes impossible to maintain the shape of compact as is.
In addition, the portion where Zn is excessive or the diffusion of
Zn into the Al base is insufficient remains in the form of a
Zn-rich phase. Further, Zn volatilizes from inside the alloy and in
consequence contaminates the interior of the furnace and is
deposited there. Accordingly, the content of Zn is preferred to
range from 3 to 10 mass %.
[0020] <Magnesium>
[0021] Magnesium forms the above-described precipitation compound
together with zinc to contribute to enhancing the strength. Also,
Mg is also low in melting point, and in the course where the
temperature is elevated for performing the sintering, it produces a
liquid phase to eliminate the oxide layer to work to accelerate the
progress of the sintering. If the content of Mg is below 0.5 mass
%, that makes the above-described effect poor, and, if it is over
5.0 mass %, that increases the amount of liquid phase to become
excessively large, resulting in that it becomes impossible to
maintain the shape of compact as is. Accordingly, the content of Mg
is preferred to range from 0.5 to 5.0 mass %.
[0022] <Copper>
[0023] Copper is dissolved in the aluminum matrix to form solid
solution and precipitate a compound of CuAl.sub.2 (.theta.-phase),
thereby contributing to enhancing the strength. It also generates a
liquid phase, when performing the sintering step, and works to
accelerate the progress of the sintering. Regarding the content of
Cu, if it is below 0.5 mass %, that work is not sufficiently
attained, and, if it exceeds 5.0 mass %, copper forms an
unnecessary Cu--Zn alloy phase with zinc, which is precipitated
large along the grain boundary to cause the decrease in the
strength and elongation. Therefore, the amount of Cu is preferred
to range from 0.5 to 5.0 mass %.
[0024] <Hard Particles>
[0025] The metallographic structure of the aluminum alloy matrix
composed of the above-described components, having no hard
particles, exhibits excellent mechanical properties which are equal
to those of the general steel materials so that the tensile
strength is 500 MPa or more and the elongation is 4% or more, when
making proper the conditions for compacting, sintering, forging and
heat treatment.
[0026] In general, incorporation of a hard phase into an alloy
matrix leads to decrease in strength and elongation of the alloy.
However, since the aluminum alloy matrix as the base is made into
alloy with the above-described elements to impart strength,
extremely high strength and elongation in comparison with those of
the conventional wear-resistant sintered aluminum-silicon alloy are
possibly exhibited beyond a slight decrease in strength and
elongation by the addition of hard particles. Moreover, in the
present invention, it is advantageous in that the kind and amount
of the hard particle dispersed can be easily changed in accordance
with the sliding conditions (particularly, the sliding
counterpart). Specifically, the hard particles dispersed in the
conventional wear-resistant sintered aluminum-silicon alloy are
primary silicon crystal, and it tends to increase the coefficient
of friction when the sliding counterpart is made of ferrous
material, due to the affinity between iron and silicon. In
contrast, in the sintered aluminum alloy of the present invention,
it is possible to reduce the coefficient of friction and improve
wear resistance, by selecting a kind of hard particles having low
affinity to iron, such as chromium boride or the like. The hard
particles that can be used in the present invention includes
silicon carbide, chromium boride, boron carbide and the like.
[0027] When the content of the hard particles in the sintered
aluminum alloy is 0.1 mass % or more, the effect of improving wear
resistance is distinguished, and, if it is over 10 mass %, the
strength and elongation are remarkably reduced. Therefore, the
content of hard particles is preferably in a range of 0.1 to 10
mass %. If the hardness of hard particles is insufficient, the hard
particles themselves cause plastic flow, resulting in decrease of
wear resistance. Accordingly, the Vickers hardness of hard
particles is preferably 600 Hv or more, and more preferably 1,000
Hv or more, especially when an Al--Zn alloy powder is used as a raw
material.
[0028] <Sn, Bi, In >
[0029] Tin, bismuth and indium are low in melting point and
generate a liquid phase in the sintered mass, respectively. As a
result, they wet the surface of the aluminum particles and
eliminate the oxide layer from the surface of the aluminum
particles, to accelerate the progress of the sintering between the
Al powder particles without solution in aluminum. In addition, due
to the surface tension of liquid phase, the liquid phases cause
shrinkage, which works to contribute to densifying the resulting
mass. Therefore, it would be preferable if using the above elements
as a sintering auxiliary agent together with the above-described
Zn, Mg and Cu. When the length of the term during which the liquid
phase exists increases, the densifying attributable to the liquid
phase progresses further. Therefore, if the liquid phase generates
at an early stage of the sintering step so that the liquid phase
continues to exist during the almost entire step of sintering, the
densifying effect becomes great. In this view point, Sn (the
melting point: 232.degree. C.), Bi (the melting point: 271.degree.
C.), and In (the melting point: 155.4.degree. C.) are very
suitable, because they have a low melting point and they are hardly
dissolved into the main component, Al. Moreover, the liquid phase
of these low-melting-point metal components covers the surface of
the simple zinc powder or the zinc alloy powder to prevent
vaporization of zinc and fluctuation of zinc content in the
resulting sintered alloy.
[0030] Sn, Bi and In which are auxiliarily used as the sintering
aid agent may be used in the form of simple metal powder. If using
these elements as the main components and forming an eutectic
compound which would cause the production of an eutectic liquid
phase comprising those main components, its melting point is much
lower than that in the case of single substance. Therefore, making
into that eutectic compound is further preferable. This eutectic
liquid phase may be the one that is made by combining the main
component (Sn, Bi, In) and another element, or the one which is
made by combining the main component and an intermetallic compound
that comprises the main component and another element. Moreover,
there is also a compound having a line of eutectic reaction which
can be found in a part of the monotactic compounds, and it is also
possible to use such a monotactic compound causing the production
of a eutectic liquid phase that comprises Sn, Bi or In. As the
elements which form the eutectic liquid phase like that with Sn,
there are Ag, Au, Ce, Cu, La, Li, Mg, Pb, Pt, Tl, Zn and the like.
As the elements which form the eutectic liquid phase like that with
Bi there are Ag, Au, Ca, Cd, Ce, Co, Cu, Ga, K, Li, Mg, Mn, Na, Pb,
Rh, S, Se, Sn, Te, Tl, Zn and the like. As the elements which form
such a eutectic liquid phase as described above with In, there are
Ag, Au, Ca, Cd, Cu, Ga, Sb, Te, Zn and the like. Although these
respective groups of elements are an example of simple
two-elemental or binary system, the same effect can be obtained
even in a case of a three-elemental or ternary system, a
four-elemental or quaternary system or more-elemental system, as
long as the resulting eutectic liquid phase similarly has Sn, Bi or
In as the main component and has a composition causing the
production of a eutectic liquid phase that comprises the main
component. However, regarding Pb and Cd of the above elements,
although these elements also cause the production of a eutectic
liquid phase with Sn, Bi or In, it is preferable to abstain the use
of them from the standpoint of toxicity.
[0031] With the above-described standpoint also being taken into
consideration, as a multi-elemental system of eutectic alloy that
comprises Sn, Bi or In as the main component, a lead-free solder
the development of which has in recent years been urged can be
preferably used. As the lead-free solder, ones of Sn--Zn system,
Sn--Bi system, Sn--Zn--Bi system, Sn--Ag--Bi system or the like can
be given, and lead-free solders prepared by adding to the above
system a small amount of metal element such as In, Cu, Ni, Sb, Ga,
Ge or the like has been proposed. A part of them has actually been
put into practical use, and it is preferable to use such lead-free
solders that are commercially available, since this it is easy to
obtain.
[0032] The sintering auxiliary agent, when added 0.01 mass % or
more, exhibits a remarkable densifying effect. However, if used in
large amount, Sn, Bi and In become precipitated at the grain
boundary to cause the decrease in the strength, since they are not
dissolved with Al. Therefore, the use of them should be limited to
0.5 mass % or less at the most. Adding in an amount of 0.5 mass %
or more results in that the decrease in the strength due to the
precipitation of the Sn, Bi and In at the grain boundary becomes
larger in degree than the above-described effect of densification
due to the shrinkage of the liquid phase, resulting in more
decrease in strength.
[0033] (1)-2 Form of Powder
[0034] A. In a Case of Using a Simple Zinc Powder
[0035] Regarding the above-described Zn, Mg and Cu, no
inconvenience occurs when they are added to the zinc powder, in any
case of using simple element powder, alloy powder of two or more
kinds of these elements, or a powdery mixture of them. However, in
order to cause the above-described works uniformly in the base, it
is necessary to disperse the respective ingredient elements
uniformly in the matrix. For this reason, it is recommended that
those ingredient elements, as later described, are added in the
form of fine powder whose particle size is 200 meshes (74 microns)
or less. In a case where they are added like that, the simple
element powder or alloy powder is melted when the temperature is
elevated during sintering and becomes a liquid phase to wet the
surface of the aluminum powder to eliminate the oxide layer
thereon. They are then diffused into the aluminum matrix and, in
addition, accelerate the bond between the aluminum powder particles
due to such diffusion. If the particle size of the simple element
powder or alloy powders exceeds 200 meshes, local segregation
occurs to inhibit uniform diffusion of components.
[0036] In contrast, if the simple aluminum powder is also so fine
as the above, the flowability of the raw material powdery mixture
is reduced. Therefore, as for the aluminum powder, it is preferable
to use in a larger particle size than the powders for above
described elements. However, if the particle size exceeds 100
meshes (140 microns), the above-described components are difficult
to diffuse into the aluminum particles, resulting in
segregation.
[0037] B. In a Case of Using Aluminum Alloy Powder Containing the
Whole Amount of Zinc
[0038] Zinc is an element that is likely to volatilize at a high
temperature. Therefore, if Zn is added in the form of aluminum
alloy powder by alloying the whole amount of Zn with aluminum, the
amount of Zn that remaining through the volatilization of Zn
becomes more stable than that in a case where Zn is added as simple
zinc powder. As a result of this, the degree of fluctuation among
the products becomes small.
[0039] However, incorporation of Zn causes a hardening in the
aluminum alloy powder to decrease the compressibility of the
powder. Accordingly, if Zn is made into alloy with the whole amount
of aluminum, the compressibility of the raw material powder is
decreased. Therefore, it is necessary to limit the use of aluminum
alloy powder containing zinc to only a part of the whole powder for
aluminum and blend soft aluminum powder into the aluminum alloy
powder into which the whole amount of Zn is alloyed, in order to
raise the compressibility of the raw material powder. For
sufficiently achieving this purpose, the amount of used simple
aluminum powder is necessary set to be 15 mass % of the whole raw
material powder or more.
[0040] Regarding the aluminum alloy powder containing Zn, if it has
a composition such that causes the production of Al--Zn liquid
phase at a low temperature, Zn is likely to volatilize from this
Al--Zn liquid phase. Therefore, it is preferable that the aluminum
alloy powder has a composition with which the production of the
Al--Zn liquid phase is caused at a temperature that is as high as
possible, that is, only at a temperature of the final stage of the
sintering step. Moreover, if using an aluminum alloy powder
containing a large amount of Zn, this causes to relatively increase
the amount of simple aluminum powder with the result that Zn
dispersed in the sintered aluminum alloy matrix becomes likely not
to be uniform. This causes the occurrence of fluctuation in the
values of the obtained mechanical properties. In view of these
items, it is preferable that the content of Zn in the aluminum
alloy powder be 30 mass % or less. On the other hand, if the
content of Zn in the aluminum alloy powder falls below 10 mass %,
the difference in zinc concentration from the simple aluminum
powder becomes small, with the result that Zn comes to have
difficulty of being diffused and uniform dispersion is suppressed
by contraries. Accordingly, it is preferable that the content of Zn
in the aluminum alloy powder be in the range of from 10 to 30 mass
%.
[0041] C. Forms of Mg and Cu
[0042] Use of the aluminum alloy powder having a composition with
which the production of the Al--Zn liquid phase is caused only at a
high temperature is preferable for preventing volatilization of
zinc, but it is disadvantageous for uniform diffusion of the
components. Cu and Mg are used together with Zn, for the purpose of
causing the uniform diffusion of Zn into the above-described
matrix. Cu and Mg, in the process wherein the temperature is
elevated during sintering, cause the production of a Cu--Zn liquid
phase or Mg--Zn liquid phase together with Zn powder or Zn in the
aluminum alloy powder. These liquid phases are immediately
solidified by their components being absorbed into the aluminum
powder or aluminum alloy powder, and liquefaction and
solidification are repeated so that uniformity of the components
rapidly proceeds. Moreover, the liquid phase at this time gets
solidified so immediately that no problems with the volatilization
of Zn arise. The elements, Cu and Mg, each of which has the
above-described action may be added in the form of simple metal
powder, an alloy powder of the both elements, or an alloy powder
with aluminum, and no hindrance occurs in any of the above cases.
When the aluminum alloy powder containing Zn simultaneously
contains Cu at the content of 10 mass % or less, the
above-described effect becomes more enhanced. However, if the
amount of Cu added into the aluminum alloy powder exceeds 10 mass %
of the aluminum powder, the temperature at which Cu produces a
liquid phase together with Zn shifts to the high-temperature side,
and addition at more than 10 mass % is thus disadvantageous in
terms of the uniform diffusion of the components.
[0043] D. Forms of Sn, Bi and In
[0044] If Sn, Bi or In is used as the sintering aid agent, they may
be added in the form of simple metal powder, eutectic alloy powder
or monotectic alloy powder that would cause the production of an
eutectic liquid phase comprising those main components.
[0045] E. Powdered Material for Hard Particles
[0046] As the means for dispersing the hard particles into the
aluminum alloy matrix, it is convenient to add a powdered material
for the hard particles. If the powdered material reacts with the
main component of the matrix, Al, it becomes difficult to control
the amount and the range of particle size of the hard particles
dispersed in the aluminum alloy matrix after the sintering.
Therefore, it is preferred that the added powder, as the hard
particles, is made of a material that does not react with
aluminum.
[0047] For the hard particles as described above, silicon carbide,
chromium boride, boron carbide and the like are preferable
materials because they are extremely hard and does not react with
aluminum. Since the aluminum alloy matrix is somewhat soft, the
hard particles originated from a powder of the extremely hard
material are embedded in the aluminum alloy matrix during the
sliding operation, to suppress the wear of the sliding counterpart
member, and, at the same time, they present plastic flow of the
aluminum alloy matrix to contribute to improving wear resistance.
Moreover, even when they once fall off the aluminum alloy matrix
during the sliding operation, they are embedded again in the soft
aluminum alloy matrix to repeatedly exhibit the effect of
preventing plastic flow of the matrix.
[0048] (1)-3 Size of Powder
[0049] In order that the respective ingredient elements exhibit
their roles uniformly in the matrix, it is necessary to uniformly
diffuse those ingredient elements in the matrix. For this purpose,
it is preferable that each of those ingredient elements be added in
the form of fine powder whose particle size is as small as 74
microns (200 meshes) or less (i.e. 200 meshes minus sieve or the
powder having a particle size that passes through a comb screen of
200 meshes), except for the simple aluminum powder. The simple
metal powder or alloy powder, when the temperature is elevated
during sintering, is melted to become a liquid phase, which wets
the surface of the aluminum powder to eliminate the oxide layer and
which is diffused into the aluminum matrix and simultaneously to
accelerate the bond between the aluminum powder particles due to
the diffusion. However, if the particle size of the simple metal
powder or alloy powder exceeds 200 meshes, local segregation takes
place, and uniform diffusion of the ingredient elements is
obstructed.
[0050] However, if the aluminum powder is also made a fine powder,
the flowability of the raw material powder becomes inferior.
Therefore, it is suitable to use a powder for aluminum whose
particle size is greater than that of the above-described
respective ingredient element powder. Specifically, it is
preferable to use a powder for aluminum whose particle size is 140
microns (100 meshes) or less (i.e. 100 meshes minus sieve or the
powder whose particle is of a size having passed through a comb
screen of 100 meshes). If exceeding the size of 100 meshes, each
ingredient element has the difficulty of being diffused up to the
center of the powder, and the component comes to get segregated.
Therefore, such should be avoided.
[0051] Since the powdered material for the hard particles almost
does not react to the matrix, it is to be dispersed in the aluminum
alloy matrix and be left as it is added. Accordingly, the size of
the raw powder used for hard particles can be determined as that of
hard particles dispersed in the aluminum alloy matrix. The particle
size of the hard particles dispersed in the aluminum alloy matrix
is preferably 1 to 100 microns as the average. If the hard
particles are smaller than 1 micron, they are easily flown with the
matrix when the matrix flows plastically, and it is therefore
difficult to prevent plastic flow of the matrix. Moreover, if the
hard particles are larger than 100 microns, wear is easily caused
on the sliding counterpart member during the sliding operation,
depending on the sliding conditions. Therefore, in order to
uniformly disperse in the aluminum alloy matrix the hard particles
of a mean particle size in the above-mentioned range, it is
preferred to use a powder of a material which does not react with
aluminum, having a size of 113 microns (125 meshes) or less (i.e.
125 meshes minus sieve or the powder whose particle is of a size
having passed through a comb screen of 125 meshes).
[0052] (2) Compacting Step
[0053] In this step, the raw material powder prepared from the
above-described raw material powder blending step is filled into a
die of a predetermined configuration, and the powder is then formed
into a compact by compressing it under a compacting pressure of 200
MPa or more. As a result of this, a compact with a density ratio of
90% or more is obtained. If the compacting pressure falls below 200
MPa, the density of the compact becomes low, and, even after the
compact passes through the subsequent sintering step and forging
step, the pores of 2 vol % or more remain. This results in failure
to impart high strength and elongation. Such insufficient
compacting is not preferable also for the reason that dimensional
change during sintering becomes large. The higher the compacting
pressure is, the higher the density of the obtained compact
becomes. Therefore, high compacting pressure is preferable. When
the compacting pressure is 400 MPa or more, a compact whose density
ratio is 95% or more is obtained and this is suitable. However, a
compacting pressure exceeding 500 MPa easily causes adhesion of the
aluminum powder to the die and it is therefore undesirable.
[0054] (3) Sintering Step
[0055] If a large amount of the relevant liquid phase mentioned
above is produced during sintering, the amount of shrinkage of the
sintered mass becomes large, with the result that the dimensional
precision becomes inferior. Moreover, since zinc contained as an
ingredient is an element having a low melting point and is
therefore easy to volatilize in this sintering step, the amount of
zinc that is dissolved in the base to make solid solution is
reduced by the volatilization, resulting in failing to accomplish a
desired value of strength and elongation. Simultaneously, zinc
contaminates the sintering atmosphere and, in some cases, is
deposited within the furnace, resulting in raising a problem with
the working environment as well. To avoid inviting such bad
effects, in a case of using a simple zinc powder, it is then
recommended that elevation of the temperature up to the sintering
temperature be performed at a high rate.
[0056] Namely, at the step of sintering the compact obtained in the
above-described compacting step, it is recommended, in the course
of temperature elevation from room temperature to the sintering
temperature, that heating in the temperature range from at least
400 degrees C. being in the proximity of the melting point of zinc
up to the sintering temperature is rapidly proceeded at the
temperature-elevating rate of 10 degrees C./min or more to suppress
the volatilization of the relevant ingredient elements. Moreover,
sintering of the compact is developed by heating the compact at a
sintering temperature of 580 to 610 degrees C. (with use of
aluminum alloy powder containing zinc) or 590 to 610 degrees C.
(with no Zn-containing aluminum alloy powder), for a sintering time
of 10 minutes or more, so that, while the excessive decrease in the
dimensional precision due to the generation of a liquid phase is
being suppressed, uniform diffusion of the ingredient element is
possibly achieved. If the temperature-elevating rate for elevating
up to the sintering temperature is lower than 10 degrees C./min,
the problem concerning volatilization of zinc becomes remarkable.
If the sintering temperature exceeds 610 degrees C., the problems
concerning volatilization of zinc and over-shrinkage due to the
liquid phase become remarkable, and, in this case, the crystal
grains also grow and become large, causing the decrease in the
strength. It is necessary for uniform formation of solid solution
with the respective ingredient elements in the Al base that the
sintering temperature be settled to 580 degrees C. (using
Zn-containing Al alloy powder), 590 degrees C. (using no
Zn-containing Al alloy powder), or more, and that the sintering
time length be made 10 minutes or more. If the sintering conditions
fall below those ranges, diffusion of the respective ingredients
into the Al base becomes insufficient, resulting in that the
strength decreases.
[0057] By the above-described sintering, the respective ingredients
are each kept in the state of their being dissolved in the matrix.
The sintered compact is then cooled and the cooling rate had better
be high although not particularly limited. In detail, if the
cooling rate is low, in the high temperature range (450 degrees C.
or more) in particular, the increase in size of the crystal grains
proceeds. In addition, the component over-saturated in the course
of cooling sometimes gets precipitated along the grain boundary, to
cause the decrease in the strength and elongation. Also, that
portion where the over-saturated component has been precipitated
sometimes gets absorbed into the matrix by subjecting to a
subsequent heat treatment (solution treatment), to make pores that
cause the deterioration in the strength and elongation. Therefore,
it is better to cool in the high temperature range at a rate that
is as high as possible. Particularly, in the temperature range of
450 degrees C. or more, it is preferred that the sintered compact
is cooled at a rate of -10 degrees C./min.
[0058] In regard to the sintering atmosphere, non-oxidizing one is
suitable. Among various non-oxidizing gases, an atmosphere of
nitrogen gas wherein the dew point is made --40 degrees C. or less
is the most suitable. The dew point is an indicator that indicates
the amount of water in the atmosphere of gas, and a large amount of
water, that substantially means a large amount of oxygen, hinders
the progress of the sintering operation since the Al is likely to
have a bond to oxygen, to obstruct the densification of the mass.
Since nitrogen gas is also inexpensive and safe comparing to other
non-oxidizing gases, the nitrogen gas atmosphere that the dew point
is specified as above is therefore preferable.
[0059] In accordance with the above sintering, the ingredient
elements are uniformly dissolved in the Al matrix to make solid
solution through liquid phase sintering, and a sintered compact
such that the density ratio is 90% or more and the pores are closed
pores is possibly obtained.
[0060] (4) Heat-Treating (T6 Treatment) Step
[0061] The heat-treating (T6 treatment in accordance with the
regulation of JIS H 0001) step in the manufacturing method of the
present invention comprises a solution treatment and an aging
precipitation treatment. In the solution treatment, a precipitation
phase in the Al base is uniformly dissolved in the Al base to form
solid solution by heating at a temperature of from 460 to 490
degrees C., and the resulting mass is then water-quenched, thereby
making an over-saturated solid solution. In the aging precipitation
treatment, the resulting mass after the solution treatment is
maintained at a temperature of 110 to 200 degrees C. for 2 to 28
hours to precipitate the over-saturated solid solution and form the
precipitation phase dispersed in the Al base. If the temperature
for the solution treatment is below 460 degrees C., the
precipitated components does not uniformly form solid solution as a
whole into the Al matrix. On the other hand, if that temperature
exceeds 490 degrees C., although that effect almost does not
change, a liquid phase is produced at a temperature exceeding 500
degrees C., to cause the generation of pores. In regard to the
aging treatment, if the temperature is below 110 degrees C., or if
the treatment time does not reach 2 hours, a sufficient amount of
precipitated compound is not obtained, whereas, in a case where the
temperature exceeds 200 degrees C., or a case where the treatment
time exceeds 28 hours, the precipitated compound grows to become
excessively large, resulting in the decrease in the strength. In
regard to the length of time for the aging treatment, it is
approximately 2 to 28 hours. The temperature and time length can
suitably be adjusted, respectively, within the above-described
ranges according to the property that is required. By subjecting to
the above-described heat treatment, metallographic structure in
which intermetallic compounds such as MgZn.sub.2 (.eta.-phase),
Al.sub.2Mg.sub.3Zn.sub.3 (T-phase), CuAl.sub.2 (.theta.-phase) are
precipitated and dispersed in the aluminum alloy matrix is formed
to achieve improvement of mechanical properties.
[0062] Regarding the wear-resistant sintered aluminum alloy with
high strength, obtained through the above-described steps, it is so
densified that the density ratio is 90% or more and it exhibits
such an excellent property as a tensile strength of 450 MPa, as
well as elongation and wear resistance that are equal to the
conventional material. Moreover, it is possible to further improve
the mechanical property, by an additional step for subjecting
forging step between the sintering step and the heat treatment
step.
[0063] (5) Forging Step Causing Plastic Flow Under Pressure
[0064] In this step, sinter forged aluminum parts exhibiting high
tensile strength and high elongation can be obtained by subjecting
the sintered mass obtained through the above-described steps before
heat treatment and having a density ratio of 90%, to a cold forging
step where it is forged at a room temperature at an upsetting ratio
of 3 to 40%, or a hot forging step where it is forged at a
temperature of 100 to 450 degrees C. at an upsetting ratio of 3 to
70%, to obtain a sinter forged aluminum part which has an increased
density ratio of 98% or more. The resultant part has a high tensile
strength and elongation.
[0065] In general, it is known to possibly increase the density
through the execution of the forging treatment. However, in the
case of porous material, simply increasing the density only results
in that the pores get closed and no metallic bond is formed at the
pore walls. As a result, that is followed by the occurrence during
forging of cracks in the surface of the material or the remaining
the pores as the defects within the product, failing to enhance the
strength and elongation. Accordingly, in order to obtain a high
level of strength and elongation, it is necessary not only to close
the pores but also to form metallic bond there. To obtain this
metallic bond, in general, the forging has been performed through
two-divided sub-steps, one of which is a sub-step for performing
densification of the relevant material and the other of which is a
deforming sub-step for obtaining metallic bond by deforming the
densified material.
[0066] In the present invention, for the process to obtain metallic
bond, there is employed a technique of performing upsetting forging
that comprises applying pressure, from the above and below, to the
sintered porous material that has been obtained as above, to
compress it in the direction of height for closing the pores, and
also to deform the compressed material toward the space provided at
the lateral side of the material for causing plastic flow of the
material in the direction crossing to the direction in which the
pressure is applied, thereby compulsively forming material bond of
the original pore portions (i.e. the portion where the pore is
closed although no metallic bond is made), while metallic bond is
formed in these pore portions. Accordingly, the forging step of the
present invention comprises a single operation into which the works
of the two sub-steps that have been conventionally executed are
merged. In connection with the upsetting forging, the upsetting
ratio is determined as a ratio of the difference in the pressing
direction between the dimensions before and after forging of the
material relative to the dimension before forging of the material.
Here, it is noted that the importance of the forging step of the
present invention is to cause lateral plastic flow of the material
under pressure. Therefore, if the above-described upsetting
deformation is main work of the operation of the forging step, that
is acceptable and no hindrance exists even when the operation of
the forging step also locally or partially works as forward or
backward extrusion on the material. Namely, the forging operation
according to the present invention can include a technique wherein
the material is locally extruded. Moreover, the processing
operation that the area of material is reduced by means of a die,
such as forging with forward or backward extrusion and the like,
can also be included in the operation of the forging step, since
the pressing in that operation works in radial directions and the
direction in which the material is deformed is along the extruding
direction or the one that intersects the pressing directions at
right angles. Therefore, the above technique of working is also
included in the scope of the present invention. Also, by performing
the above forging operation for the compressing and plastically
material flowing works described above, it is also possible to
obtain, in addition to the above-described action, an action which
makes fine the crystal grains that grew during sintering, as well
as breaks the precipitate, whereby the strength and elongation are
more enhanced.
[0067] In the case of cold forging, it is necessary to forge so
that the upsetting ratio is 3 to 40%. If the upsetting ratio is
less than 3%, deformation occurs only locally when the diameter
after the forging is the same or larger in comparison with that
before the forging, with the result that the amount of residual
pores is increased to fail to enhance the strength and elongation.
Also, in a case where forging is done with a die whose diameter is
small such as forward extrusion forging, an upsetting ratio of 3%
or more is necessary for the reason described above. Incidentally,
if the upsetting ratio is 10% or more, the density ratio of the
forged mass can easily be made to be 98% or more. Therefore, that
setting is preferable. On the other hand, if the upsetting ratio
exceeds 40%, cracking is likely to occur on the forged mass. When
employing the cold forging operation, if upsetting forging is
designed in such a manner that the terminal end portions of the
material laterally extended during forging come to full contact
with the inner wall of the die at the finish of the forging
operation, the precision in dimension and shape of products
increases and defects have difficulty remaining on the uppermost
surface. Therefore, such way of upsetting forging is
preferable.
[0068] In the case of hot forging, if heating the material
(sintered mass) within a range of from 100 to 450 degrees C.,
preferably from 200 to 400 degrees C., forging at an upsetting
ratio within a range of from 3 up to 70% is allowed. When the
heating temperature for the material (sintered mass) is below 100
degrees C., almost no useful change is made in comparison with the
case of cold forging. That is, the deformability of the material is
still poor and it is therefore difficult to raise the upsetting
ratio. In a case where the heating temperature of the material
(sintered mass) is 200 degrees C. or more, the material becomes
soft and the deformability increases. Accordingly, it is possible
to decrease the forging pressure for performing hot forging at a
desired value of upsetting ratio. Therefore, such temperature range
is preferable. On the other hand, if the heating temperature
exceeds 450 degrees C., the adhesion between the die and the
material (sintered mass) remarkably occurs. Therefore, the upper
limit needs to be set at 450 degrees C. at maximum, and preferably
at 400 degrees C. However, even in the suitable temperature range
described above, if the upsetting ratio exceeds 70%, forging cracks
become likely to occur. Also in the case of hot forging, if
upsetting forging is performed in such a manner that the terminal
end portions of the material laterally extended during forging come
to contact with the inner wall of the die at the finish of the
forging operation, defects have difficulty remaining on the
uppermost surface. Therefore, such way of upsetting forging is
preferable.
[0069] The wear-resistant sinter forged aluminum alloy with high
strength that have been obtained through the above-described
process, as will be apparent from the following Examples, has a
density ratio of 98% or more and is improved to have a tensile
strength of 500 MPa or more and an elongation of 2% or more.
Therefore, it exhibits high mechanical characteristics that cannot
be expected from the one in the conventional art, as well as
excellent wear resistance.
EXAMPLES
Example 1
[0070] For each sample, the raw material powder blending step, the
compacting step, the sintering step, the forging step, and the heat
treatment step were sequentially performed to manufacture and
evaluate five kinds of samples of sintered aluminum alloy having a
overall composition shown in Table 2. Specifically, in the raw
material powder blending step, aluminum powder having a particle
size of minus sieve of 100 meshes screen; zinc powder, magnesium
powder, copper powder, tin powder, bismuth powder, indium powder,
lead-free solder powder containing 8 mass % Zn, 3 mass % Bi and the
balance Sn, each of which had a particle size of minus sieve of 250
meshes screen respectively; silicon carbide powder, chromium boride
powder and boron carbide powder, each of which had a particle size
of minus sieve of 125 meshes screen, were prepared to provide a raw
material powder by blending and mixing those powders together in
accordance with the blending ratio shown in Table 1.
[0071] In the compacting step, adjusting the compacting pressure to
300 MPa, the raw material powder was formed into compacts of
columnar shape having dimensions of +40 mm.times.28 mm for
measuring mechanical property. In the sintering step, the compact
was heated in an atmosphere of nitrogen gas, by elevating the
heating temperature within a range of from 400.degree. C. up to
sintering temperature of 600 degrees C. at a temperature-elevating
rate of 10 degrees C./min, and it was sintered by keeping it at the
sintering temperature for 20 minutes. After that, the compact was
cooled from the sintering temperature down to 450 degrees C. at a
cooling rate of -20 degrees C./min. In the forging step, thus
obtained sintered compact was heated at 400 degrees C. and put into
a die of the same temperature to perform hot forging at an
upsetting ratio of 40%. In the heat treatment step, the forged
compact was heated at 470 degrees C. to perform the solution
treatment, and it was then maintained at 130 degrees C. for 24
hours to perform aging precipitation treatment.
[0072] Moreover, as a conventional material, aluminum powder and
aluminum-silicon alloy powder containing 20 mass % Si and the
balance Al, each of which had a particle size of minus sieve of 100
meshes screen; nickel powder, copper-nickel alloy powder containing
4 mass % Ni and the balance Cu, and aluminum-magnesium alloy powder
containing 50 mass % Mg and the balance aluminum, each of which had
a particle size of minus sieve of 250 meshes screen, were prepared
to provide a raw material powder by blending and mixing those
powders together in accordance with the blending ratio shown in
Table 1. In the compacting step, the compacting pressure was
adjusted to 200 MPa, and, in the sintering step, the compact was
heated in an atmosphere of nitrogen gas, by elevating the heating
temperature within a range of from 400.degree. C. up to sintering
temperature of 550 degrees C. at a temperature-elevating rate of 10
degrees C./min, and the sintering temperature was kept for 20
minutes before cooling from the sintering temperature down to 450
degrees C. at a cooling rate of -20 degrees C./min. In the forging
step, the heating temperatures of the sintered compact and the die
were 450 degrees C., and the upsetting ratio was 40%. In the heat
treatment step, the temperature for solution treatment was 470
degrees C., and the aging precipitation was performed at 130
degrees C. for 24 hours, to produce an alloy disclosed in the
document of JPA No. H07-224341.
[0073] In the preparation of each sample, the density ratio was
measured for each of the green compact after the compacting step,
the sintered compact after the sintering step and the forged
compact after the forging step. The results are shown in Table 3.
For the evaluation of obtained samples of Nos. A01 to A34, five
columnar pieces of .phi.40 mm.times.28 mm were processed into a
tensile test piece and tensile test was conducted thereon to
measure the tensile strength and elongation. The result is shown as
an average value in Table 3. Moreover, each of another two columnar
pieces were cut into an wearing test piece having a columnar shape
of .phi. 7.98 mm.times.20 mm, sliding test was conducted thereon by
a pin-on-disk wear resistance test machine at a sliding speed of 5
m/s for 30 min., using a counterpart member made of S45C
heat-treated material under a constant load and supplying an engine
oil thereto. If drastic change in the coefficient of dynamic
friction was not observed during the sliding test, the test piece
was substituted with another one and the load was raised by 5 MPa
in every time. The load under which drastic increase in the
coefficient of dynamic friction was observed was determined as a
seizure pressure (critical bearing pressure). The results are shown
together in Table 3. TABLE-US-00001 TABLE 1 blending ratio mass %
hard praticles sample Al Zn Mg Cu powder low-melting-point No.
powder powder powder powder kind kind metal pwd. A01 balance 5.5
2.5 1.5 B.sub.4C powder 0.0 Sn powder 0.1 A02 balance 5.5 2.5 1.5
B.sub.4C powder 0.1 Sn powder 0.1 A03 balance 5.5 2.5 1.5 B.sub.4C
powder 0.5 Sn powder 0.1 A04 balance 5.5 2.5 1.5 B.sub.4C powder
1.0 Sn powder 0.1 A05 balance 5.5 2.5 1.5 B.sub.4C powder 2.5 Sn
powder 0.1 A06 balance 5.5 2.5 1.5 B.sub.4C powder 5.0 Sn powder
0.1 A07 balance 5.5 2.5 1.5 B.sub.4C powder 10.0 Sn powder 0.1 A08
balance 5.5 2.5 1.5 B.sub.4C powder 15.0 Sn powder 0.1 A09 balance
2.0 2.5 1.5 B.sub.4C powder 5.0 Sn powder 0.1 A10 balance 3.0 2.5
1.5 B.sub.4C powder 5.0 Sn powder 0.1 A06 balance 5.5 2.5 1.5
B.sub.4C powder 5.0 Sn powder 0.1 A11 balance 10.0 2.5 1.5 B.sub.4C
powder 5.0 Sn powder 0.1 A12 balance 15.0 2.5 1.5 B.sub.4C powder
5.0 Sn powder 0.1 A13 balance 5.5 0.1 1.5 B.sub.4C powder 5.0 Sn
powder 0.1 A14 balance 5.5 0.5 1.5 B.sub.4C powder 5.0 Sn powder
0.1 A15 balance 5.5 1.0 1.5 B.sub.4C powder 5.0 Sn powder 0.1 A06
balance 5.5 2.5 1.5 B.sub.4C powder 5.0 Sn powder 0.1 A16 balance
5.5 5.0 1.5 B.sub.4C powder 5.0 Sn powder 0.1 A17 balance 5.5 7.0
1.5 B.sub.4C powder 5.0 Sn powder 0.1 A18 balance 5.5 2.5 0.1
B.sub.4C powder 5.0 Sn powder 0.1 A19 balance 5.5 2.5 0.5 B.sub.4C
powder 5.0 Sn powder 0.1 A06 balance 5.5 2.5 1.5 B.sub.4C powder
5.0 Sn powder 0.1 A20 balance 5.5 2.5 2.5 B.sub.4C powder 5.0 Sn
powder 0.1 A21 balance 5.5 2.5 5.0 B.sub.4C powder 5.0 Sn powder
0.1 A22 balance 5.5 2.5 7.0 B.sub.4C powder 5.0 Sn powder 0.1 A06
balance 5.5 2.5 1.5 B.sub.4C powder 5.0 Sn powder 0.1 A23 balance
5.5 2.5 1.5 B.sub.4C powder 5.0 Sn powder 0.1 A24 balance 5.5 2.5
1.5 B.sub.4C powder 5.0 Sn powder 0.1 A25 balance 5.5 2.5 1.5
B.sub.4C powder 5.0 Sn powder 0.0 A26 balance 5.5 2.5 1.5 B.sub.4C
powder 5.0 Sn powder 0.01 A27 balance 5.5 2.5 1.5 B.sub.4C powder
5.0 Sn powder 0.05 A06 balance 5.5 2.5 1.5 B.sub.4C powder 5.0 Sn
powder 0.1 A28 balance 5.5 2.5 1.5 B.sub.4C powder 5.0 Sn powder
0.5 A29 balance 5.5 2.5 1.5 B.sub.4C powder 5.0 Sn powder 0.7 A06
balance 5.5 2.5 1.5 B.sub.4C powder 5.0 Sn powder 0.1 A30 balance
5.5 2.5 1.5 B.sub.4C powder 5.0 Bi powder 0.1 A31 balance 5.5 2.5
1.5 B.sub.4C powder 5.0 In powder 0.1 A32 balance 5.5 2.5 1.5
B.sub.4C powder 5.0 Sn--8Zn--3Bi 0.1 powder A33 Al--20Si pwd: 75%,
Cu--4Ni pwd: 4.2%, Al--50Mg pwd: 1%, Al pwd: balance
[0074] TABLE-US-00002 TABLE 2 overall composition mass % sample
hard praticles others No. Al Zn Mg Cu kind kind A01 balance 5.5 2.5
1.5 B.sub.4C 0.0 Sn 0.1 A02 balance 5.5 2.5 1.5 B.sub.4C 0.1 Sn 0.1
A03 balance 5.5 2.5 1.5 B.sub.4C 0.5 Sn 0.1 A04 balance 5.5 2.5 1.5
B.sub.4C 1.0 Sn 0.1 A05 balance 5.5 2.5 1.5 B.sub.4C 2.5 Sn 0.1 A06
balance 5.5 2.5 1.5 B.sub.4C 5.0 Sn 0.1 A07 balance 5.5 2.5 1.5
B.sub.4C 10.0 Sn 0.1 A08 balance 5.5 2.5 1.5 B.sub.4C 15.0 Sn 0.1
A09 balance 2.0 2.5 1.5 B.sub.4C 5.0 Sn 0.1 A10 balance 3.0 2.5 1.5
B.sub.4C 5.0 Sn 0.1 A06 balance 5.5 2.5 1.5 B.sub.4C 5.0 Sn 0.1 A11
balance 10.0 2.5 1.5 B.sub.4C 5.0 Sn 0.1 A12 balance 15.0 2.5 1.5
B.sub.4C 5.0 Sn 0.1 A13 balance 5.5 0.1 1.5 B.sub.4C 5.0 Sn 0.1 A14
balance 5.5 0.5 1.5 B.sub.4C 5.0 Sn 0.1 A15 balance 5.5 1.0 1.5
B.sub.4C 5.0 Sn 0.1 A06 balance 5.5 2.5 1.5 B.sub.4C 5.0 Sn 0.1 A16
balance 5.5 5.0 1.5 B.sub.4C 5.0 Sn 0.1 A17 balance 5.5 7.0 1.5
B.sub.4C 5.0 Sn 0.1 A18 balance 5.5 2.5 0.1 B.sub.4C 5.0 Sn 0.1 A19
balance 5.5 2.5 0.5 B.sub.4C 5.0 Sn 0.1 A06 balance 5.5 2.5 1.5
B.sub.4C 5.0 Sn 0.1 A20 balance 5.5 2.5 2.5 B.sub.4C 5.0 Sn 0.1 A21
balance 5.5 2.5 5.0 B.sub.4C 5.0 Sn 0.1 A22 balance 5.5 2.5 7.0
B.sub.4C 5.0 Sn 0.1 A06 balance 5.5 2.5 1.5 B.sub.4C 5.0 Sn 0.1 A23
balance 5.5 2.5 1.5 B.sub.4C 5.0 Sn 0.1 A24 balance 5.5 2.5 1.5
B.sub.4C 5.0 Sn 0.1 A25 balance 5.5 2.5 1.5 B.sub.4C 5.0 Sn 0.0 A26
balance 5.5 2.5 1.5 B.sub.4C 5.0 Sn 0.01 A27 balance 5.5 2.5 1.5
B.sub.4C 5.0 Sn 0.05 A06 balance 5.5 2.5 1.5 B.sub.4C 5.0 Sn 0.1
A28 balance 5.5 2.5 1.5 B.sub.4C 5.0 Sn 0.5 A29 balance 5.5 2.5 1.5
B.sub.4C 5.0 Sn 0.7 A06 balance 5.5 2.5 1.5 B.sub.4C 5.0 Sn 0.1 A30
balance 5.5 2.5 1.5 B.sub.4C 5.0 Bi 0.1 A31 balance 5.5 2.5 1.5
B.sub.4C 5.0 In 0.1 A32 balance 5.51 2.5 1.5 B.sub.4C 5.0 Sn 0.09
Bi 0.003 A33 Al--15% Si--4% Cu--0.17% Ni--0.5% Mg
[0075] TABLE-US-00003 TABLE 3 evaluation density ratio % tensile
seizure sample green sintered forged strength pressure No. compact
compact compact MPa elongation % MPa Remarks A01 93.6 97.9 99.3 530
4.2 20 A02 93.0 97.0 99.3 530 4.0 30 A03 93.0 97.0 99.3 530 4.0 35
A04 92.5 96.5 99.3 520 3.5 40 A05 92.5 96.5 99.3 520 3.5 40 A06
92.5 96.5 99.3 520 3.5 40 A07 90.0 96.0 99.3 500 2.8 40 A08 88.1
94.0 99.3 480 1.6 40 large wear on counterpart A09 92.5 90.1 99.5
461 4.3 20 A10 92.5 94.8 99.3 503 3.6 30 A06 92.5 96.5 99.3 520 3.5
40 A11 92.5 95.4 99.4 481 2.1 35 A12 92.5 -- -- -- -- -- sintered
mass melting A13 92.5 93.2 99.5 473 4.4 20 A14 92.5 94.8 99.5 501
4.2 35 A15 92.5 96.0 99.3 510 4.0 40 A06 92.5 96.5 99.3 520 3.5 40
A16 92.5 95.4 99.4 507 1.8 35 sintered mass deforming A17 92.5 --
-- -- -- -- A18 92.5 94.7 99.3 481 4.1 20 A19 92.5 94.9 99.4 508
3.8 35 A06 92.5 96.5 99.3 520 3.5 40 A20 92.5 96.2 99.5 503 2.4 40
A21 92.6 95.8 99.4 498 1.6 30 A22 92.7 92.1 99.4 472 0.3 --
elongation deteriorates A06 92.5 96.5 99.3 520 3.5 40 A23 91.8 96.3
99.4 525 3.2 45 A24 93.2 97.2 99.3 525 3.8 50 A25 92.5 90.4 99.3
470 2.6 30 A26 92.5 96.0 99.3 515 3.0 40 A27 92.5 96.5 99.3 520 3.2
40 A06 92.5 96.5 99.3 520 3.5 40 A28 92.5 96.5 99.3 500 3.0 40 A29
92.5 94.4 99.3 470 1.8 30 A06 92.5 96.5 99.3 520 3.5 40 A30 92.5
96.5 99.3 523 3.3 40 A31 92.5 96.5 99.3 512 3.8 40 A32 92.5 96.5
99.3 521 3.3 40 A33 85.0 87.0 99.8 360 2.5 50
[0076] Comparing samples of Nos. A01-A08 with one another, the
effect of the hard particles with the addition amount is possibly
researched. From the results, it is understood that the sample No.
A01 containing no had particles exhibits high tensile strength and
elongation but the seizure pressure is small, meaning a material
having a low wear resistance. Even in such a material, the wear
resistance can be improved by the hard particles at an amount of
0.1 mass % or more so that the seizure pressure rises to 30 MPa or
more, while suppressing fall of the tensile strength to a small
extent. In particular, addition at 1.0 mass % or more provides high
wear resistance. On the other hand, the elongation tends to
slightly decrease according as the amount of hard particles
increases, but it is still possible to exhibit sufficient
elongation, with an amount of 10 mass % or less of the hard
particles. However, if the amount of hard particles exceeds 10 mass
%, decrease in elongation becomes remarkable, and the wear amount
of the counterpart member increases simultaneously. From the above,
it is confirmed that, when the amount of hard particles is in a
range of 0.1 to 10 mass %, high tensile strength and high
elongation are exhibited, while the wear resistance is improved,
resulting in provision of a wear-resistant sintered aluminum alloy
exhibiting higher tensile strength than that of the wear-resistant
sintered aluminum alloy of sample No. A33 which is a conventional
aluminum-silicon alloy. It is also found that the effect of
improving wear resistance is especially great when the amount of
hard particles is in a range of 1.0 to 10 mass %.
[0077] Comparing sample of No. A06 with samples of Nos. A09-A12,
the effect of zinc with the addition amount is possibly researched.
From the results, it is understood that the amount of the
intermetallic compound precipitated in the aluminum alloy matrix in
the sample No. A09 containing 2.0 mass % zinc is so poor that the
tensile strength is small, though the elongation is great.
Moreover, its seizure pressure is of a low value, in spite of the
hard particles added at 5.0 mass %. In contrast, at the zinc
content of 3.0 mass % or more, although the elongation is reduced
by the increase in the amount of intermetallic zinc compound
precipitated in the aluminum alloy matrix, the tensile strength and
the seizure pressure are increased by the effect of this increased
amount of intermetallic compound and the effect of increased
density of the sintered mass that is caused by the increased amount
of Zn liquid phase and/or eutectic phase of Zn and other element.
However, if the amount of precipitated intermetallic zinc compound
is excessive, the strength is rather damaged, so that the tensile
strength and the seizure pressure tend to be at peaks on sample No.
A06 containing 5.5 mass % of Zn and then turn to decrease on sample
No. All containing 10 mass % of Zn. Moreover, it has found, in
sample No. A12 in which the Zn content exceeds 10 mass %, that the
sintered compact was molten with excessive amount of
zinc-containing liquid phase produced during sintering, resulting
in canceling the subsequent forging step, heat treatment and tests.
From the above, it can be confirmed that the zinc content of 3.0 to
10 mass % is effective in improvement of tensile strength and
seizure pressure.
[0078] Comparing sample of No. A06 with samples of Nos. A13-A17,
the effect of magnesium with the addition amount is possibly
researched. From the results, it is understood that the amount of
the intermetallic compound precipitated in the aluminum alloy
matrix in the sample No. A13 containing 0.1 mass % Mg is so poor
that the tensile strength is small, though the elongation is great.
Moreover, its seizure pressure is of a low value, in spite of the
hard particles added at 5.0 mass %. In contrast, at the magnesium
content of 0.5 mass % or more, although the elongation is reduced
by the increase in the amount of intermetallic compound
precipitated in the aluminum alloy matrix, the tensile strength and
the seizure pressure are increased by the effect of this increased
amount of intermetallic compound and the effect of increased
density of the sintered mass that is caused by the increased amount
of Mg liquid phase and/or eutectic phase of Mg and other element.
However, if the amount of precipitated intermetallic compound is
excessive, the strength is rather damaged, so that the tensile
strength and the seizure pressure tend to be at peaks on sample No.
A06 containing 2.5 mass % of Mg and then turn to decrease on sample
No. A16 containing 5 mass % of Mg. Moreover, it has found, in
sample No. A17 in which the Mg content exceeds 5.0 mass %, that the
sintered compact was deformed with excessive amount of
zinc-containing liquid phase produced during sintering, resulting
in canceling the subsequent forging step, heat treatment and tests.
From the above, it can be confirmed that the magnesium content of
0.5 to 5.0 mass % is effective in improvement of tensile strength
and seizure pressure.
[0079] Comparing sample of No. A06 with Nos. A18-A22, the effect of
copper with the addition amount is possibly researched. From the
results, it is understood that the amount of the intermetallic
compound precipitated in the aluminum alloy matrix in the sample
No. A18 containing 0.1 mass % Cu is so poor that the tensile
strength is small, though the elongation is great. Moreover, its
seizure pressure is of a low value, in spite of the hard particles
added at 5.0 mass %. In contrast, at the copper content of 0.5 mass
% or more, although the elongation is reduced by the increase in
the amount of intermetallic compound precipitated in the aluminum
alloy matrix, the tensile strength and the seizure pressure are
increased by the effect of this increased amount of intermetallic
compound and the effect of increased density of the sintered mass
that is caused by the increased amount of Cu liquid phase and/or
eutectic phase of Cu and other element. However, if the amount of
precipitated intermetallic compound is excessive, the strength is
rather damaged, so that the tensile strength and the seizure
pressure tend to be at peaks on sample No. A06 containing 1.5 mass
% of Cu and then turn to decrease on sample No. A21 containing 5.0
mass % of Cu. Moreover, it has found, in sample No. A22 in which
the Cu content exceeds 5.0 mass %, that the sintered compact was
deformed with excessive amount of zinc-containing liquid phase
produced during sintering, resulting in canceling the subsequent
forging step, heat treatment and tests. From the above, it can be
confirmed that the copper content of 0.5 to 5.0 mass % is effective
in improvement of tensile strength and seizure pressure.
[0080] Comparing sample of No. A06 with Nos. A23 and A24 in Tables
1-3, the effect of the hard particles with the kind of them is
possibly researched. From the results, it is understood that
sufficient wear resistance (seizure pressure) is possibly achieved
even if the kind of hard particles is changed from boron carbide to
silicon carbide or chromium boride. It has been found that,
especially when chromium boride is used, it is possible to provide
an excellent wear-resistant sintered aluminum alloy which exhibits
not only a higher tensile strength than that of the wear-resistant
sintered aluminum alloy (sample No. A33) of the conventional
aluminum-silicon type, but also an equal seizure pressure.
[0081] Comparing sample of No. A06 with Nos. A25-A29 in Tables 1-3,
the effect of the low-melting-point metal powder with the addition
amount is possibly researched. From the results, it is understood
that sufficient tensile strength, elongation and seizure pressure
are possibly achieved even if the low-melting-point metal powder is
not added, and that, in particular, the tensile strength and the
elongation are higher than those of the wear-resistant sintered
aluminum alloy (sample No. A33) of the conventional
aluminum-silicon type. Moreover, it is also understood that these
characteristics are improved by adding 0.01 to 0.5 mass % of
low-melting-point metal powder to the wear-resistant sintered
aluminum alloy of the present invention. However, if its addition
exceeds 0.5 mass %, the low-melting-point metal precipitates in the
grain boundary of the aluminum alloy matrix and the above
characteristics rather deteriorate. From the above, it can be
confirmed that, though no addition of the low-melting-point metal
powder is allowable, its addition at 0.01 to 0.5 mass % is
effective to improve the tensile strength elongation and seizure
pressure.
[0082] Comparing sample of No. A06 with Nos. A30-A32 in Tables 1-3,
the effect of the low-melting-point metal powder with the kind of
it is possibly researched. From the results, it is understood that,
even if the kind of the low-melting-point metal powder is changed
from tin to bismuth, indium or eutectic compounds thereof
(lead-free solder), the same improving effect as that with tin can
be obtained in tensile strength, elongation and seizure
pressure.
Example 2
[0083] In this example, using the raw material powder prepared in
Example 1 and the same blending ratio for sample No. A03: 5.5 mass
% zinc powder; 2.5 mass % magnesium powder; 1.5 mass % copper
powder; 5 mass % boron carbide powder; 0.1 mass % tin powder; and
the balance aluminum powder, sintered aluminum alloy samples were
manufactured by performing the same operation of Example 1,
excepting that the compacting pressure, the sintering conditions
(temperature-elevating rate in the range from 400 degrees C. to the
sintering temperature, the sintering temperature and time), and the
forging conditions (the heating temperatures of the sintered
compact and the forging die, the upsetting ratio) were changed to
those shown in Table 4. Regarding each of these samples, the same
estimation in Example 1 was executed. The results are shown in
Table 5. TABLE-US-00004 TABLE 4 sintering compacting elevat. sint.
forging sample pressure rate sint. temp. time temp. upsetting No.
MPa .degree. C./min .degree. C. min .degree. C. ratio % A34 100 10
600 20 400 40 A35 200 10 600 20 400 40 A06 300 10 600 20 400 40 A36
400 10 600 20 400 40 A37 300 10 600 20 400 40 A38 300 5 600 20 400
40 A06 300 10 600 20 400 40 A39 300 15 600 20 400 40 A40 300 20 600
20 400 40 A41 300 10 580 20 400 40 A42 300 10 590 20 400 40 A06 300
10 600 20 400 40 A43 300 10 610 20 400 40 A44 300 10 620 20 400 40
A45 300 10 600 0 400 40 A46 300 10 600 10 400 40 A06 300 10 600 20
400 40 A47 300 10 600 30 400 40 A48 300 10 600 40 400 40 A49 300 10
600 20 -- -- A50 300 10 600 20 r.t. 3 A51 300 10 600 20 r.t. 10 A52
300 10 600 20 r.t. 20 A53 300 10 600 20 r.t. 40 A54 300 10 600 20
r.t. 45 A53 300 10 600 20 r.t. 40 A55 300 10 600 20 100 40 A56 300
10 600 20 150 40 A57 300 10 600 20 200 40 A58 300 10 600 20 300 40
A06 300 10 600 20 400 40 A59 300 10 600 20 450 40 A60 300 10 600 20
500 40 A61 300 10 600 20 400 3 A62 300 10 600 20 400 10 A63 300 10
600 20 400 20 A06 300 10 600 20 400 40 A64 300 10 600 20 400 70 A65
300 10 600 20 400 80 A66 200 10 550 60 -- -- A33 200 10 550 60 450
40
[0084] TABLE-US-00005 TABLE 5 evaluation density ratio % tensile
seizure sample green sintered forged strength pressure No. compact
compact compact MPa elongation % MPa Remarks A34 90.5 -- -- -- --
-- sintered mass deform. A35 92.4 96.5 99.3 520 3.5 40 A06 92.5
96.5 99.3 520 3.5 40 A36 94.2 97.8 99.3 520 3.1 40 A37 -- -- -- --
-- -- die galling A38 92.5 95.0 98.8 473 1.8 30 A06 92.5 96.5 99.3
520 3.5 40 A39 92.5 96.2 99.2 510 3.3 40 A40 92.5 96.8 99.3 523 3.4
40 A41 92.5 88.0 99.3 410 2.6 25 A42 92.5 96.2 99.3 482 3 35 A06
92.5 96.5 99.3 50 3.5 40 A43 92.5 96.8 99.3 515 3.1 40 A44 92.5 --
-- -- -- -- sintered mass melting A45 92.5 95.5 99.3 410 2.4 25 A46
92.5 96.1 99.3 512 3.4 40 A06 92.5 96.5 99.3 520 3.5 40 A47 92.5
96.3 99.3 515 3.3 40 A48 92.5 96.8 99.3 521 3.2 40 A49 92.5 96.5 --
450 1.1 20 A50 92.5 96.5 99.3 480 1.2 35 A51 92.5 96.5 99.3 483 1.2
40 A52 92.5 96.5 99.4 488 1.4 40 A53 92.5 96.5 99.3 495 1.3 40 A54
92.5 96.5 -- -- -- -- cracking A53 92.5 96.5 99.3 495 1.3 40 A55
92.5 96.5 99.3 505 2.6 40 A56 92.5 96.5 99.3 510 3 40 A57 92.5 96.5
99.3 522 3.2 40 A58 92.5 96.5 99.3 520 3.4 40 A06 92.5 96.5 99.3
520 3.5 40 A59 92.5 96.5 99.3 523 3.6 40 A60 92.5 96.5 99.3 -- --
-- adhesion to punch A61 92.5 96.5 99.3 485 2.8 40 A62 92.5 96.5
99.3 492 3 40 A63 92.5 96.5 99.3 518 3.2 40 A06 92.5 96.5 99.3 520
3.5 40 A64 92.5 96.5 99.3 511 3.3 40 A65 92.5 96.5 -- -- -- --
cracking A66 85.0 87.0 -- 300 1.3 20 alloy in JPA-H7-224341 A33
85.0 87.0 99.8 360 2.5 50 alloy in JPA-H7-224341
[0085] Comparing sample of No. A06 with Nos. A34-A37 in Tables 4
and 5, the effect of the compacting pressure is possibly
researched. From the results, it is understood that a compacting
pressure in a rage of 200 to 400 MPa provides a green compact
sample having a high density ratio, which results in a sintered
aluminum alloy exhibiting high tensile strength and high elongation
through the process of sintering-forging-heat treatment. In
contrast, the green compact of sample No. A34 in which the
compacting pressure is less than 200 MPa has a low density, and its
sintered mass thus caused deformation by large shrinkage due to
generation of liquid phase, resulting in canceling the subsequent
forging step, heat treatment and tests. On the other hand, in the
green compact of sample No. A37 in which the compacting pressure
exceeds 400 MPa, adhesion (die galling) of the sintered compact to
the die has occurred when taking the compact out of the die, also
resulting in canceling the subsequent forging step, heat treatment
and tests. From the above, it is confirmed that the compacting is
necessarily conducted at a compacting pressure of 200 to 400
MPa.
[0086] Comparing sample of No. A06 with Nos. A38-A40 in Tables 4
and 5, the effect of the temperature-elevating rate in the range of
400 degrees C. up to the sintering temperature is possibly
researched. From the results, it is understood that, in regard to
the sample of No. A38 in which the temperature-elevating rate is
less than 10 degrees C./min, the Zn component volatilizes from the
compact during sintering and the quantity of precipitation phase
decreases, resulting in deterioration in tensile strength,
elongation and seizure pressure. On the other hand, regarding the
samples in which the temperature-elevating rate is 10 degrees
C./min or more, it is seen that each of them exhibits a high level
of tensile strength, elongation and seizure pressure. From the
above, it is confirmed that the temperature-elevating rate in the
range of 400 degrees C. to the sintering temperature is necessarily
10 degrees C./min.
[0087] Comparing sample of No. A06 with Nos. A41-A44 in Tables 4
and 5, the effect of the sintering temperature is possibly
researched. From the results, it is understood that, regarding each
of the samples in which the sintering temperature is within a range
of from 590 to 610 degrees C., the sample exhibits high levels of
tensile strength, elongation and seizure pressure. In contrast,
regarding the sample of No. A41 in which the sintering temperature
is lower than 590 degrees C., both the tensile strength and the
elongation are decreased. The reason for this is considered that
the ingredient element added in the form of a simple metal powder
is not completely dissolved in the Al base and forms solid solution
which is locally segregated to remain, with the result that the
relevant sample has a small value of mechanical property.
Conversely, in the sample of No. A44 in which the sintering
temperature is over 610 degrees C., melting of the sintered compact
occurs due to the liquid phase generating in excess. The succeeding
test for evaluation has been therefore canceled. From the above, it
is confirmed that the sintering temperature is necessarily in a
range of 590 to 610 degrees C.
[0088] Comparing sample of No. A06 with Nos. A45-A48 in Tables 4
and 5, the effect of the sintering time is possibly researched.
From the results, it is understood that, in the sample of No. A45
in which the sintering time is less than 10 minutes, it is low in
terms of all of tensile strength, elongation and seizure pressure.
The reason of this is considered that, when the sintering time is
short, the ingredient is not sufficiently dissolved in the Al base
and forms solid solution which is locally segregated to remain,
with the result that the relevant sample has a small value of
mechanical property. On the other hand, in the samples in which the
sintering time is 10 minutes or more, the ingredient is uniformly
dissolved in the Al base to form solid solution. Therefore, the
relevant samples exhibit high levels of tensile strength,
elongation and seizure pressure. However, even if the sintering
time exceeds 30 minutes, these properties are not changed very
much. Therefore, the setting of the sintering time being 30 minutes
or less will be sufficient.
[0089] Comparing samples of Nos. A49-A66 in Tables 4 and 5 with one
another, the effect of performing the forging or not, and the
effects of forging temperature and upsetting ratio are possibly
researched.
[0090] First, by comparing the sample of No. A49 that is the
wear-resistant sintered aluminum alloy according to the present
invention, with the sample of No. A66 that is a wear-resistant
sintered aluminum alloy of the conventional aluminum-silicon type,
in both of which the forging is not carried out, each of the
elongation and the seizure pressure is of the same level in both
samples. However, in regard to the tensile strength, it is
confirmed that the sample of No. A49 of the present invention is
excellent to exhibit a higher value than that of the conventional
one.
[0091] Moreover, comparing with the sample of No. A49 in which the
forging has not been carried out, the samples of Nos. A50-65
(excepting ones that the test for evaluation was canceled for
improperness) in which the forging has been performed are improved
in all of tensile strength, elongation and seizure pressure.
Therefore, the effect of adding the forging step has been
confirmed.
[0092] Second, the forging conditions are searched. Comparing the
samples of Nos. A49-A54 with one another, if the upsetting ratio is
in a range from 3 to 40% in the case of cold forging, it is found
that the improving effect can be seen in all of tensile strength,
elongation and seizure pressure. In contrast, if the upsetting
ratio exceeds 40% such as in the sample of No. A54, cracks occur in
the sample due to forging. The test for evaluation of the sample
was therefore canceled.
[0093] Comparing the sample of No. A35 (cold forging) with Nos. A06
and A55-A60, it is also understood that, in the case of hot forging
with changing the temperatures of the sintered mass and the forging
die, the tensile strength is possibly improved, while the
elongation is largely improved. This is attributable to the fact
that, although in the case of cold forging hair cracks very
slightly remain within the sample, followed by decrease in the
elongation, carrying out hot forging of the material with the
heating temperature being set to 100 degrees C. or more makes the
hair cracks removed. On the other hand, when the forging
temperature exceeds 450 degrees C., adhesion (die galling) of the
sintered compact to the die occurs. Therefore, the test in such a
case has been cancelled.
[0094] Third, comparing the sample of No. A06 and the samples of
Nos. A61-A65, it is understood, even when the upsetting ratio
within a wide range of 3 to 70% is employed, the effect of
improvement can be seen in each of tensile strength, elongation and
seizure pressure. On the other hand, when the upsetting ratio
exceeds 70% such as the sample of No. A65, forging causes cracks in
the sample. Therefore, the test in such a case has been
cancelled.
[0095] As described above, it is confirmed that the effect of
improvement is obtained in tensile strength, elongation and seizure
pressure, by adding, after the sintering step, either of the cold
forging step where the sintered compact is forged at a room
temperature and an upsetting ratio of 3 to 40%, and the hot forging
step where the sintered compact is forged at a temperature of 100
to 450 degrees C. and an upsetting ratio of 3 to 70%.
Example 3
[0096] In this example, comparison was made between the case where
zinc is incorporated in the form of aluminum alloy powder (No. B01)
and the case where it is in the form simple zinc powder (No. B02).
Specifically, in the raw material powder blending step for No. B01,
aluminum powder having a particle size of minus sieve of 100 meshes
screen; aluminum alloy powder containing 12 mass % Zn; boron
carbide powder having a particle size of minus sieve of 125 meshes
screen as a powder for the hard particles; zinc powder, magnesium
powder, copper powder and tin powder, each of which had a particle
size of minus sieve of 250 meshes screen respectively, were
prepared to provide a raw material powder having a overall
composition of Zn: 5.5%, Mg: 2.5%, Cu: 1.5%, Sn: 0.1%, hard
particles (boron carbide): 5.0% and the balance Al and inevitable
impurities, by blending and mixing those powders together in
accordance with the blending ratio shown in Table 6.
[0097] In the compacting step, adjusting the compacting pressure to
300 MPa, the raw material powder was formed into compacts of
columnar shape having dimensions of .phi.40 mm.times.28 mm. In the
sintering step, the compact was heated in an atmosphere of nitrogen
gas, by elevating the heating temperature within a range of from
400.degree. C. up to sintering temperature of 600 degrees C. at a
temperature-elevating rate of 10 degrees C./min, and it was
sintered by keeping it at the sintering temperature for 20 minutes.
After that, the compact was cooled from the sintering temperature
down to 450 degrees C. at a cooling rate of -20 degrees C./min. In
the forging step, thus obtained sintered compact was heated at 400
degrees C. and put into a die of the same temperature to perform
hot forging at an upsetting ratio of 40%. In the heat treatment
step, the forged compact was heated at 470 degrees C. to perform
the solution treatment, and it was then maintained at 130 degrees
C. for 24 hours to perform aging precipitation treatment.
[0098] For the evaluation of each of the obtained samples of Nos.
B01 and B02, five columnar pieces of .phi.40 mm.times.28 mm were
processed into a tensile test piece and tensile test was conducted
thereon to measure the tensile strength and elongation. The result
is shown as an average value and a value 3a in Table 7. Moreover,
each of another two columnar pieces were cut into an wearing test
piece having a columnar shape of .phi.7.98 mm.times.20 mm, and
sliding test was conducted thereon by a pin-on-disk wear resistance
test machine at a sliding speed of 5 m/s for 30 min., using a
counterpart member made of S45C heat-treated material under a
constant load and supplying an engine oil thereto. If drastic
change in the coefficient of dynamic friction was not observed
during the sliding test, the test piece was substituted with
another one and the load was raised by 5 MPa in every time. The
load under which drastic increase in the coefficient of dynamic
friction was observed was determined as a seizure pressure
(critical bearing pressure). The results are shown together in
Table 7. Moreover, in the preparation of each sample, the density
ratio was measured for each of the green compact after the
compacting step, the sintered compact after the sintering step and
the forged compact after the forging step. The results are shown in
Table 7. It is noted that the conditions in the compacting to aging
precipitation treatment for sample No. B02 are the same as those
for sample No. A06. TABLE-US-00006 TABLE 6 blending ratio mass %
sample Al Al alloy powder Zn Mg Cu hard praticles low-melting-point
No. powder Al Zn pwd. pwd. pwd. kind pwd. kind metal pwd. B01 45
Balance balance 12.0 2.5 1.5 B.sub.4C pwd. 5.0 Sn pwd. 0.1 B02
balance 5.5 2.5 1.5 B.sub.4C pwd. 5.0 Sn pwd. 0.1
[0099] TABLE-US-00007 TABLE 7 evaluation sam- Density ratio %
tensile seizure ple green sintered forged strength MPa elongation %
pressure No. compact compact compact average 3 .sigma. average 3
.sigma. MPa B01 85.0 93.0 99.0 525 18 4.0 1.0 40 B02 87.0 93.0 99.0
520 28 3.5 1.2 40
[0100] From the results in Tables 6 and 7, it is confirmed that the
tensile strength becomes slightly higher and that the fluctuation
in terms of the tensile strength can be particularly suppressed to
a smaller range of values in a case where Zn is added in the form
of the alloyed powder with Al (the sample No. B01), than in a case
where Zn is added in the form of simple component powder (the
sample No. B02). Moreover, the elongation is also improved and its
fluctuation is suppressed to a small range. This is considered as
the effect of that volatilization of zinc is prevented by adding in
the alloy form the zinc component which is easily volatilized and
the zinc content in the sample is thus not fluctuated. In contrast,
an equivalent value is obtained for the seizure pressure. In this
example, it is confirmed that improvement and suppressing of
fluctuation in tensile strength and elongation can be achieved,
without leading to decrease in seizure pressure, by adding zinc in
the alloy form.
Example 4
[0101] In the raw material powder blending step, aluminum powder
having a particle size of minus sieve of 100 meshes screen;
aluminum alloy powder of the composition shown in Table 8;
magnesium powder, copper powder, and tin powder as a
low-melting-point metal powder, each of which had a particle size
of minus sieve of 250 meshes screen respectively; and boron carbide
powder having a particle size of minus sieve of 125 meshes screen
as a powder for the hard particles, were prepared to provide a raw
material powder, by blending and mixing those powders together in
accordance with the blending ratio shown in Table 8. Using each of
these raw material powders, the compacting step, sintering step,
forging step and heat treatment step were executed under the same
conditions as in Example 3 to prepare each of samples having a
overall composition shown in Table 9.
[0102] In the preparation of each sample, the density ratio was
measured for each of the green compact after the compacting step,
the sintered compact after the sintering step and the forged
compact after the forging step, and measurement of tensile
strength, elongation and seizure pressure (critical bearing
pressure) was also conducted, the results of which are shown in
Table 10. TABLE-US-00008 TABLE 8 blending ratio mass % sample Al Al
alloy powder Mg Cu hard praticles low-melting-point No. powder Al
Zn pwd. pwd. kind pwd. kind metal pwd. B03 0.0 balance balance 12.0
2.5 1.5 B.sub.4C pwd. 5.0 Sn pwd. 0.1 B04 1.0 balance balance 12.0
2.5 1.5 B.sub.4C pwd. 5.0 Sn pwd. 0.1 B05 15.0 balance balance 12.0
2.5 1.5 B.sub.4C pwd. 5.0 Sn pwd. 0.1 B06 25.0 balance balance 12.0
2.5 1.5 B.sub.4C pwd. 5.0 Sn pwd. 0.1 B01 45.0 balance balance 12.0
2.5 1.5 B.sub.4C pwd. 5.0 Sn pwd. 0.1 B07 65.0 balance balance 12.0
2.5 1.5 B.sub.4C pwd. 5.0 Sn pwd. 0.1 B08 75.0 balance balance 12.0
2.5 1.5 B.sub.4C pwd. 5.0 Sn pwd. 0.1 B09 17.5 balance balance 7.5
2.5 1.5 B.sub.4C pwd. 5.0 Sn pwd. 0.1 B10 35.8 balance balance 10.0
2.5 1.5 B.sub.4C pwd. 5.0 Sn pwd. 0.1 B01 45.0 balance balance 12.0
2.5 1.5 B.sub.4C pwd. 5.0 Sn pwd. 0.1 B11 54.2 balance balance 15.0
2.5 1.5 B.sub.4C pwd. 5.0 Sn pwd. 0.1 B12 63.3 balance balance 20.0
2.5 1.5 B.sub.4C pwd. 5.0 Sn pwd. 0.1 B13 72.5 balance balance 30.0
2.5 1.5 B.sub.4C pwd. 5.0 Sn pwd. 0.1 B14 77.1 balance balance 40.0
2.5 1.5 B.sub.4C pwd. 5.0 Sn pwd. 0.1 B15 60.9 balance balance 10.0
2.5 1.5 B.sub.4C pwd. 5.0 Sn pwd. 0.1 B16 57.5 balance balance 30.0
2.5 1.5 B.sub.4C pwd. 5.0 Sn pwd. 0.1
[0103] TABLE-US-00009 TABLE 9 overall composition mass % sample
hard praticles others No. Al Zn Mg Cu kind kind B03 balance 10.9
2.5 1.5 B.sub.4C 5.0 Sn 0.1 B04 balance 10.8 2.5 1.5 B.sub.4C 5.0
Sn 0.1 B05 balance 9.1 2.5 1.5 B.sub.4C 5.0 Sn 0.1 B06 balance 7.9
2.5 1.5 B.sub.4C 5.0 Sn 0.1 B01 balance 5.5 2.5 1.5 B.sub.4C 5.0 Sn
0.1 B07 balance 3.1 2.5 1.5 B.sub.4C 5.0 Sn 0.1 B08 balance 1.9 2.5
1.5 B.sub.4C 5.0 Sn 0.1 B09 balance 5.5 2.5 1.5 B.sub.4C 5.0 Sn 0.1
B10 balance 5.5 2.5 1.5 B.sub.4C 5.0 Sn 0.1 B01 balance 5.5 2.5 1.5
B.sub.4C 5.0 Sn 0.1 B11 balance 5.5 2.5 1.5 B.sub.4C 5.0 Sn 0.1 B12
balance 5.5 2.5 1.5 B.sub.4C 5.0 Sn 0.1 B13 balance 5.5 2.5 1.5
B.sub.4C 5.0 Sn 0.1 B14 balance 5.5 2.5 1.5 B.sub.4C 5.0 Sn 0.1 B15
balance 3.0 2.5 1.5 B.sub.4C 5.0 Sn 0.1 B16 balance 10.0 2.5 1.5
B.sub.4C 5.0 Sn 0.1
[0104] TABLE-US-00010 TABLE 10 evaluation density ratio % tensile
seizure sample green sintered forged strength pressure No. compact
compact compact MPa elongation % MPa Remarks B03 72.0 -- -- -- --
-- severe deform. on sinterng. B04 76.0 -- -- -- -- -- severe
deform. on sinterng. B05 80.0 92.0 99.0 510 2.0 40 B06 83.0 92.0
99.0 514 2.6 40 B01 85.0 93.0 99.0 525 4.0 40 B07 87.0 93.0 99.0
501 4.0 40 B08 90.0 93.0 99.3 475 4.0 30 B09 74.0 88.0 99.0 510 0.7
35 B10 80.0 91.0 99.0 520 2.0 40 B01 85.0 93.0 99.0 525 4.0 40 B11
56.0 93.0 99.0 515 3.5 40 B12 88.0 93.0 99.0 507 3.0 40 B13 90.0
92.0 99.0 500 2.0 40 B14 92.0 90.0 99.0 240 0.9 30 B15 87.0 91.0
99.0 515 3.8 40 B16 86.0 90.0 99.0 507 1.0 40
[0105] Comparing the samples of Nos. B01 and B03-B08 in Tables 8 to
10, the effect of the amount of aluminum powder added is searched.
In the samples of Nos. B03, and B04 wherein the amount of aluminum
powder added is less than 15 mass %, as a result of the fact that
the amount of Zn in the overall composition of the raw material
powder becomes excessively large to such an extent as it exceeds 10
mass %, the sintered compact is largely deformed due to the liquid
phase occurring from inside the aluminum alloy powder. The
subsequent steps have therefore been canceled. On the other hand,
when the amount of aluminum powder added is over 15 mass %, it
becomes possible to sinter without occurring deformation of the
sintered mass and the sample exhibits high levels of tensile
strength, elongation and seizure pressure. From the above-mentioned
results, it is confirmed that, in a case where Zn is wholly added
in the form of aluminum alloy powder, it is necessary to
simultaneously use the aluminum powder of 15 mass % or more. If the
amount of aluminum powder added exceeds 15 mass %, the relevant
sample also tends to exhibit enhanced values of tensile strength
and elongation as the amount of aluminum powder increases. However,
if the amount of Zn in the overall composition of the raw material
powder exceeds 5.5 mass % (of sample No. B01), the tensile strength
tends to fall on the contrary. In the sample of No. B08 wherein the
amount of Zn in the overall composition of the raw material powder
is lower than 3 mass %, with the result that the amount of zinc is
poor, the decrease in the tensile strength and seizure pressure of
the relevant sample is seen.
[0106] By comparing the samples of Nos. B01 and B09 to B14 in
Tables 8 to 10, the effect of the content of Zn in the aluminum
alloy powder is searched. In these comparisons, the amount of Zn in
the overall composition of the raw material powder in each sample
has been adjusted to a fixed value. From the results of these
samples, it is found that, in the sample of No. B09, wherein the
content of Zn in the aluminum alloy powder is less than 10 mass %,
the product exhibits a high value of tensile strength whereas the
elongation value thereof is small or 0.7%. On the other hand, in a
case where the content of Zn in the aluminum alloy powder is 10
mass % or more, it is found that not only does the relevant sample
exhibit a high tensile strength but is the value of elongation also
enhanced. However, when the content of Zn in the aluminum alloy
powder exceeds 30 mass %, both the decrease in the tensile strength
and the decrease in the elongation are seen to occur (sample No.
B14). Moreover, in regard to the seizure pressure, a preferable
value is obtained when the content of Zn in the aluminum alloy
powder is in a range of 10 to 30 mass %, but the decrease in the
seizure pressure is seen when the content of Zn in the aluminum
alloy powder exceeds 30 mass %. Accordingly, it is confirmed that,
when the amount of Zn in the aluminum alloy powder is in the range
of from 10 to 30 mass %, the relevant sample exhibits high values
of tensile strength, elongation and seizure pressure.
[0107] In the optimum range confirmed as above of Zn content in the
aluminum alloy powder, the lower limit value of Zn in the overall
composition of the raw material powder, and the upper limit value
thereof, can be searched, respectively, by the sample No. B15 and
the sample No.B16. As a result, it is confirmed that, when the
amount of Zn is in the range of from 3 to 10 mass % in the overall
composition of the raw material powder, the relevant samples
exhibit a high tensile strength, high elongation together and high
seizure pressure with the above-described effect.
Example 5
[0108] Example 5 is an embodiment wherein examination has been
performed of the amounts of Mg and Cu added and the forms in which
Mg and Cu were added. In this example, together with the aluminum
powder, aluminum alloy powder, magnesium powder, copper powder, tin
powder and boron carbide powder used in Example 3, mixed together
were the aluminum alloy powders each having a composition shown in
Table 11 and a particle size of 100 meshes minus sieve and the
aluminum-magnesium alloy powder wherein the content of Mg was 50
mass %, the balance being Al and inevitable impurities and the
particle size was 250 meshes minus sieve. The blending proportion
is shown in Table 11, and the raw material powders each having an
overall composition shown in Table 12 were prepared. Using these
raw material powders, there were executed the compacting step,
sintering step, forging step, heat-treating step and test piece
processing step, under the same conditions as those in Example 3.
Regarding the samples of Nos. B-17 to B-32 that were obtained
above, the density ratios in each step as well as the mechanical
properties, namely, tensile strength, elongation and seizure
pressure, were measured, the results being shown in Table 13
together with the measured result (average value) of the sample No.
B01 in Example 3. TABLE-US-00011 TABLE 11 Blending ratio mass %
low-melting- point sample Al Al alloy powder Mg Al--50Mg Cu hard
praticles metal No. Pwd. Al Zn Cu pwd. pwd. pwd. kind pwd. kind
pwd. B17 47.5 balance balance 12.0 0.0 1.5 B.sub.4C pwd. 5.0 Sn
pwd. 0.1 B18 4.0 balance balance 12.0 0.5 1.5 B.sub.4C pwd. 5.0 Sn
pwd. 0.1 B19 46.5 balance balance 12.0 1.0 1.5 B.sub.4C pwd. 5.0 Sn
pwd. 0.1 B01 45.0 balance balance 12.0 2.5 1.5 B.sub.4C pwd. 5.0 Sn
pwd. 0.1 B20 42.5 balance balance 12.0 5.0 1.5 B.sub.4C pwd. 5.0 Sn
pwd. 0.1 B21 42.5 balance balance 12.0 5.0 1.5 B.sub.4C pwd. 5.0 Sn
pwd. 0.1 B22 39.5 balance balance 12.0 8.0 1.5 B.sub.4C pwd. 5.0 Sn
pwd. 0.1 B23 46.5 balance balance 12.0 2.5 0.0 B.sub.4C pwd. 5.0 Sn
pwd. 0.1 B24 46.0 balance balance 12.0 2.5 0.5 B.sub.4C pwd. 5.0 Sn
pwd. 0.1 B01 45.0 balance balance 12.0 2.5 1.5 B.sub.4C pwd. 5.0 Sn
pwd. 0.1 B25 44.0 balance balance 12.0 2.5 2.5 B.sub.4C pwd. 5.0 Sn
pwd. 0.1 B26 41.5 balance balance 12.0 2.5 5.0 B.sub.4C pwd. 5.0 Sn
pwd. 0.1 B27 38.5 balance balance 12.0 2.5 8.0 B.sub.4C pwd. 5.0 Sn
pwd. 0.1 B28 61.0 balance balance 12.0 2.0 2.5 B.sub.4C pwd. 5.0 Sn
pwd. 0.1 B29 61.0 balance balance 12.0 5.0 2.5 B.sub.4C pwd. 5.0 Sn
pwd. 0.1 B30 61.0 balance balance 12.0 8.0 2.5 B.sub.4C pwd. 5.0 Sn
pwd. 0.1 B31 61.0 balance balance 12.0 10.0 2.5 B.sub.4C pwd. 5.0
Sn pwd. 0.1 B32 61.0 balance balance 12.0 15.0 2.5 B.sub.4C pwd.
5.0 Sn pwd. 0.1
[0109] TABLE-US-00012 TABLE 12 overall composition mass % sample
hard praticles others No. Al Zn Mg Cu Kind Kind B17 balance 5.5 0.0
1.5 B.sub.4C 5.0 Sn 0.1 B18 balance 5.5 0.5 1.5 B.sub.4C 5.0 Sn 0.1
B19 balance 5.5 1.0 1.5 B.sub.4C 5.0 Sn 0.1 B01 balance 5.5 2.5 1.5
B.sub.4C 5.0 Sn 0.1 B20 balance 5.5 2.5 1.5 B.sub.4C 5.0 Sn 0.1 B21
balance 5.5 5.0 1.5 B.sub.4C 5.0 Sn 0.1 B22 balance 5.5 8.0 1.5
B.sub.4C 5.0 Sn 0.1 B23 balance 5.5 2.5 0.0 B.sub.4C 5.0 Sn 0.1 B24
balance 5.5 2.5 0.5 B.sub.4C 5.0 Sn 0.1 B01 balance 5.5 2.5 1.5
B.sub.4C 5.0 Sn 0.1 B25 balance 5.5 2.5 2.5 B.sub.4C 5.0 Sn 0.1 B26
balance 5.5 2.5 5.0 B.sub.4C 5.0 Sn 0.1 B27 balance 5.5 2.5 8.0
B.sub.4C 5.0 Sn 0.1 B28 balance 3.8 2.5 0.6 B.sub.4C 5.0 Sn 0.1 B29
balance 3.8 2.5 1.6 B.sub.4C 5.0 Sn 0.1 B30 balance 3.8 2.5 2.5
B.sub.4C 5.0 Sn 0.1 B31 balance 3.8 2.5 3.1 B.sub.4C 5.0 Sn 0.1 B32
balance 3.8 2.5 4.7 B.sub.4C 5.0 Sn 0.1
[0110] TABLE-US-00013 TABLE 13 evaluation density ratio % tensile
seizure sample green Sintered forged strength elongation pressure
No. compact compact compact MPa % MPa Remarks B17 86.0 88.0 99.0
380 1.0 25 B18 85.0 90.0 99.0 490 1.8 35 B19 85.0 90.0 99.0 510 3.0
40 B01 85.0 93.0 99.0 525 4.0 40 B20 85.0 93.0 99.0 520 3.8 40 B21
85.0 82.0 99.0 505 1.6 40 B22 84.0 -- -- -- -- -- sintrd. mass
deform. severely B23 85.0 91.0 99.0 400 3.8 25 B24 85.0 92.0 99.0
495 3.8 30 B01 85.0 93.0 99.0 525 4.0 40 B25 84.0 93.0 99.0 510 2.0
40 B26 81.0 93.0 99.0 501 1.2 35 B27 83.0 -- -- -- -- -- sintrd.
mass deform. severely B28 84.0 91.0 99.0 518 2.1 40 B29 85.0 93.0
99.0 531 3.0 40 B30 85.0 93.0 99.0 520 3.2 40 B31 84.0 91.0 99.0
505 1.8 35 B32 84.0 88.0 99.0 450 0.7 35
[0111] By comparing the samples of Nos. B01, B17-B19, B21 and B22
in Tables 11 to 13, the effect of the amount of Mg powder that is
added in the form of a simple metal powder is searched. From the
results, it is found that, in the case of the Mg being not added
whatsoever (the sample No. B17), where the liquid phase that Mg
would otherwise participate in does not occur, the tensile
strength, the elongation and the seizure pressure are reduced. In
contrast, in a case where Mg is added in the form of a simple metal
powder, the tensile strength, the elongation and the seizure
pressure are enhanced when the amount of Mg is 0.5 mass % or more.
However, in the case of sample No. B22 wherein the amount of Mg
exceeds 5 mass %, the amount of liquid phase occurring becomes
excessively large, with the result that the sintered compact is
deformed. From these items, it is confirmed that, regarding the
amount of Mg in the overall composition of the raw material powder,
there is the effect of enhancing all of the tensile strength, the
elongation and the seizure pressure when the amount of Mg is in the
range of from 0.5 to 5 mass %.
[0112] Sample No. B20 is an example wherein Mg is added in the form
of aluminum-magnesium alloy powder. Comparing it with the sample of
No. B01, it is found that, if the amount of Mg is equal in the
overall composition of the raw powder, the equivalent values of
tensile strength, elongation and seizure pressure are obtained even
when Mg is added in the form of aluminum-magnesium alloy
powder.
[0113] By comparing the samples of Nos. B01 and B23-B27 in Tables
11 to 13, the effect of the amount of Cu powder that is added in
the form of a simple metal powder is searched. From the results, it
is found that, in the case of the Cu being not added whatsoever
(sample No. B23), wherein the liquid phase that Cu would otherwise
participate in does not occur, both of the tensile strength and the
seizure pressure has a low value. In contrast, in a case where Cu
is added in the form of a simple metal powder, the tensile strength
and the seizure pressure are enhanced when the amount of Cu is 0.5
mass % or more. However, in the case of sample No. B27 wherein the
amount of Cu exceeds 5 mass %, the amount of liquid phase occurring
becomes excessively large, with the result that the sintered
compact is deformed. On the other hand, regarding the elongation,
as the amount of Cu increases, the elongation tends to decrease,
but it is possibly held to be 1.0% or more at the amount of Cu in a
range of up to 5 mass %. From these items, it is confirmed that,
regarding the amount of Cu in the overall composition of the raw
material powder, there is the effect of enhancing the tensile
strength and the seizure pressure when the amount of Cu is in the
range of from 0.5 to 5 mass %, and the amount of Cu in this range
is preferable, because a sufficient value of elongation is
obtainable.
[0114] By comparing the samples of Nos. B28-B32 in Tables 11 to 13,
the effect of the amount of Cu in a case where Cu is added in the
form of an aluminum alloy powder containing Zn therein is searched.
In this case, as in the case where Cu is added in the form of a
simple metal powder, the enhancement in the tensile strength and
the seizure pressure is seen in comparison with the product wherein
Cu is not added at all (the sample No. B23). However, regarding the
amount of Cu in the overall composition of the raw material powder,
even when it falls within the range of from 0.5 to 5 mass % that
has been confirmed above, it is seen that, if the amount of Cu in
the aluminum alloy powder exceeds 10 mass %, the tensile strength
and elongation become contrarily decreased. From this result, it is
further confirmed that, in a case where Cu is added in a form
wherein it is alloyed into the aluminum alloy powder containing Zn
therein, the upper limit of Cu in the alloy needed to be 10 mass
%.
Example 6
[0115] Example 6 is an embodiment wherein examination has been
performed of the amount of hard particles and the kind thereof.
Together with the aluminum powder, aluminum alloy powder, magnesium
powder, copper powder, tin powder and boron carbide powder of the
Example 3, used were the silicon carbide powder and the chromium
boride powder each having a particle size of 125 meshes minus
sieve. These powders were mixed together in the proportion for
blending shown in Table 14, to prepare raw material powders each
having an overall composition shown in Table 15. Using these raw
material powders, there were executed the compacting step,
sintering step, forging step, heat-treating step and test piece
processing step, under the same conditions as those in Example 3,
to obtain the products of sample Nos. B33-B42. Regarding the
obtained samples, measurement of the density ratios in each step as
well as the tensile strength, elongation and seizure pressure was
carried out, the results being shown in Table 16 together with the
measured result (average value) of the sample No.B01 in Example
3.
[0116] Moreover, as a conventional material, aluminum powder and
aluminum-silicon alloy powder containing 20 mass % Si and the
balance Al, each of which had a particle size of minus sieve of 100
meshes screen; nickel powder, copper-nickel alloy powder containing
4 mass % Ni and the balance Cu, and aluminum-magnesium alloy powder
containing 50 mass % Mg and the balance aluminum, each of which had
a particle size of minus sieve of 250 meshes screen, were prepared
to provide a raw material powder by blending and mixing those
powders together in accordance with the blending ratio shown in
Table 6. In the compacting step, the compacting pressure was
adjusted to 200 MPa, and, in the sintering step, the compact was
heated in an atmosphere of nitrogen gas, by elevating the heating
temperature within a range of from 400.degree. C. up to sintering
temperature of 550 degrees C. at a temperature-elevating rate of 10
degrees C./min, and the sintering temperature was kept for 60
minutes before cooling from the sintering temperature down to 450
degrees C. at a cooling rate of -20 degrees C./min. In the forging
step, the heating temperatures of the sintered compact and the die
were 450 degrees C., and the upsetting ratio was 40%. In the heat
treatment step, the temperature for solution treatment was 470
degrees C., and the aging precipitation was performed at 130
degrees C. for 24 hours, to produce an alloy disclosed in the
document of JPA No. H07-224341. Also for this sample (No. B43),
measurement of the density ratio after each step as well as
mechanical properties, namely, the tensile strength, elongation and
seizure pressure was carried out. These results are also shown in
Table 16. TABLE-US-00014 TABLE 14 blending ratio mass % sample Al
Al alloy powder Mg Cu hard praticles low-melting-point No. Pwd. Al
Zn pwd. pwd. kind pwd. kind metal pwd. B33 45.0 balance balance
12.0 2.5 1.5 B.sub.4C pwd. 0.0 Sn pwd. 0.1 B34 45.0 balance balance
12.0 2.5 1.5 B.sub.4C pwd. 0.1 Sn pwd. 0.1 B35 45.0 balance balance
12.0 2.5 1.5 B.sub.4C pwd. 0.5 Sn pwd. 0.1 B36 45.0 balance balance
12.0 2.5 1.5 B.sub.4C pwd. 1.0 Sn pwd. 0.1 B37 45.0 balance balance
12.0 2.5 1.5 B.sub.4C pwd. 2.5 Sn pwd. 0.1 B01 45.0 balance balance
12.0 2.5 1.5 B.sub.4C pwd. 5.0 Sn pwd. 0.1 B38 45.0 balance balance
12.0 2.5 1.5 B.sub.4C pwd. 7.5 Sn pwd. 0.1 B39 45.0 balance balance
12.0 2.5 1.5 B.sub.4C pwd. 10.0 Sn pwd. 0.1 B40 45.0 balance
balance 12.0 2.5 1.5 B.sub.4C pwd. 12.5 Sn pwd. 0.1 B01 45.0
balance balance 12.0 2.5 1.5 B.sub.4C pwd. 5.0 Sn pwd. 0.1 B41 45.0
balance balance 12.0 2.5 1.5 SiC pwd. 5.0 Sn pwd. 0.1 B42 45.0
balance balance 12.0 2.5 1.5 CrB.sub.2 pwd. 5.0 Sn pwd. 0.1 B43
Al--20Si pwd: 75%, Cu--4Ni pwd: 4.2%, Al--50Mg pwd: 1%, Al pwd:
balance
[0117] TABLE-US-00015 TABLE 15 overall composition mass % hard
sample praticles low-melting-point No. Al Zn Mg Cu kind kind metal
pwd. B33 balance 6.1 2.5 1.5 B.sub.4C 5.0 Sn 0.1 B34 balance 6.1
2.5 1.5 B.sub.4C 5.0 Sn 0.1 B35 balance 6.0 2.5 1.5 B.sub.4C 5.0 Sn
0.1 B36 balance 6.0 2.5 1.5 B.sub.4C 5.0 Sn 0.1 B37 balance 5.8 2.5
1.5 B.sub.4C 5.0 Sn 0.1 B01 balance 5.5 2.5 1.5 B.sub.4C 5.0 Sn 0.1
B38 balance 5.2 2.5 1.5 B.sub.4C 5.0 Sn 0.1 B39 balance 4.9 2.5 1.5
B.sub.4C 5.0 Sn 0.1 B40 balance 4.6 2.5 1.5 B.sub.4C 5.0 Sn 0.1 B01
balance 5.5 2.5 1.5 B.sub.4C 5.0 Sn 0.1 B41 balance 5.5 2.5 1.5 SiC
5.0 Sn 0.1 B42 balance 5.5 2.5 1.5 CrB.sub.2 5.0 Sn 0.1 B43 Al--15%
Si--4% Cu--0.17% Ni--0.5% Mg
[0118] TABLE-US-00016 TABLE 16 evaluation density ratio % tensile
seizure sample green sintered forged strength pressure No. compact
compact compact MPa elongation % MPa Remarks B33 88.0 93.0 99.0 560
11.0 20 B34 86.0 93.0 99.0 550 8.6 30 B35 86.0 93.0 99.0 545 7.1 35
B36 86.0 93.0 99.0 540 6.0 40 B37 85.0 93.0 99.0 530 5.4 40 B01
85.0 93.0 99.0 525 4.0 40 B38 85.0 93.0 99.0 506 3.1 40 B39 84.0
92.0 99.0 501 1.6 35 B40 82.0 91.0 99.0 485 0.8 30 large wear on
counterpart B01 85.0 93.0 99.0 525 4.0 40 B41 85.0 93.0 99.0 535
5.6 45 B42 85.0 93.0 99.0 548 7.0 50 B43 85.0 87.0 99.0 360 2.5
50
[0119] Comparing the samples of Nos.B01 and B33-B40 in Tables 15 to
16, the effect of the amount of the hard particles is searched.
From the results, it is understood that the sample No. B33
containing no had particles exhibits high tensile strength and
elongation but the seizure pressure is small, meaning a material
having a low wear resistance. Even in such a material, the wear
resistance can be improved by the hard particles at an amount of
0.1 mass % or more so that the seizure pressure is raised, while
suppressing fall of the tensile strength to a small extent. In
particular, addition at 1.0 mass % or more provides high wear
resistance. On the other hand, the elongation tends to slightly
decrease according as the amount of hard particles increases, but
it is still possible to exhibit sufficient elongation of 1% or
more, with an amount of 10 mass % or less of the hard particles.
However, if the amount of hard particles exceeds 10 mass % (sample
No. B40), decrease in elongation becomes remarkable to fall below
1%, and it has bee simultaneously observed that the wear amount of
the counterpart member has increased. From the above, it is
confirmed that, when the amount of hard particles is in a range of
0.1 to 10 mass %, high tensile strength and high elongation are
exhibited, while the wear resistance is improved, resulting in
provision of a wear-resistant sintered aluminum alloy exhibiting
higher tensile strength than that of the wear-resistant sintered
aluminum alloy of sample No. B43 which is a conventional
aluminum-silicon alloy. It is also found that the effect of
improving wear resistance is especially great when the amount of
hard particles is in a range of 1.0 to 10 mass %.
[0120] By comparing samples of Nos. B01, B41 and B42 in Tables 14
to 16, the effect of the hard particles with the kind of them is
possibly researched. From the results, it is understood that
sufficient wear resistance (seizure pressure) is possibly achieved
even if the kind of hard particles is changed from boron carbide to
silicon carbide or chromium boride. It has been found that,
especially when chromium boride is used, it is possible to provide
an excellent wear-resistant sintered aluminum alloy which exhibits
not only a higher tensile strength than that of the wear-resistant
sintered aluminum alloy (sample No. B43) of the conventional
aluminum-silicon type, but also an equivalent value of seizure
pressure.
Example 7
[0121] Example 7 is an embodiment wherein examination has been
performed of the amounts of sintering aid powder and the kind
thereof. Together with the aluminum powder, aluminum alloy powder,
magnesium powder, copper powder, boron carbide powder and tin
powder of the Example 3, used were the bismuth powder, indium
powder and the lead-free solder powder each having a particle size
of 250 meshes minus sieve, and the lead-free solder powder had a
composition wherein the content of Zn was 8 mass % and the amount
of Bi was 3 mass %, the balance being Sn and inevitable impurities.
These powders were mixed together in the proportion for blending
shown in Table 17, to prepare raw material powders each having an
overall composition shown in Table 17. Using these raw material
powders, there were executed the compacting step, sintering step,
forging step, heat-treating step and test piece processing step,
under the same conditions as those in Example 3, to obtain the
products of sample Nos. B44 to B51. Regarding the obtained samples,
measurement of the density ratios in each step as well as the
tensile strength, elongation and seizure pressure was carried out,
the results being shown in Table 19 together with the measured
result (average value) of the sample No.B01 in Example 3.
TABLE-US-00017 TABLE 17 blending ratio mass % sample Al Al alloy
powder Mg Cu hard praticles low-melting-point No. pwd. Al Zn pwd.
pwd. kind pwd. kind metal pwd. B44 45.0 balance balance 12.0 2.5
1.5 B.sub.4C pwd. 5.0 -- -- B45 45.0 balance balance 12.0 2.5 1.5
B.sub.4C pwd. 5.0 Sn pwd. 0.01 B46 45.0 balance balance 12.0 2.5
1.5 B.sub.4C pwd. 5.0 Sn pwd. 0.05 B01 45.0 balance balance 12.0
2.5 1.5 B.sub.4C pwd. 5.0 Sn pwd. 0.1 B47 45.0 balance balance 12.0
2.5 1.5 B.sub.4C pwd. 5.0 Sn pwd. 0.5 B48 45.0 balance balance 12.0
2.5 1.5 B.sub.4C pwd. 5.0 Sn pwd. 0.7 B01 45.0 balance balance 12.0
2.5 1.5 B.sub.4C pwd. 5.0 Sn pwd. 0.1 B49 45.0 balance balance 12.0
2.5 1.5 B.sub.4C pwd. 5.0 Bi pwd. 0.1 B50 45.0 balance balance 12.0
2.5 1.5 B.sub.4C pwd. 5.0 In pwd. 0.1 B51 45.0 balance balance 12.0
2.5 1.5 B.sub.4C pwd. 5.0 Sn--8Zn--4Bi pwd. 0.1
[0122] TABLE-US-00018 TABLE 18 overall composition mass % hard
sample praticles low-melting-point No. Al Zn Mg Cu kind kind metal
pwd. B44 balance 5.5 2.5 1.5 B.sub.4C 5.0 -- -- B45 balance 5.5 2.5
1.5 B.sub.4C 5.0 Sn 0.0 B46 balance 5.5 2.5 1.5 B.sub.4C 5.0 Sn 0.1
B01 balance 5.5 2.5 1.5 B.sub.4C 5.0 Sn 0.1 B47 balance 5.5 2.5 1.5
B.sub.4C 5.0 Sn 0.5 B48 balance 5.4 2.5 1.5 B.sub.4C 5.0 Sn 0.7 B01
balance 5.5 2.5 1.5 B.sub.4C 5.0 Sn 0.1 B49 balance 5.5 2.5 1.5
B.sub.4C 5.0 Bi 0.1 B50 balance 5.5 2.5 1.5 B.sub.4C 5.0 In 0.1 B51
balance 5.5 2.5 1.5 B.sub.4C 5.0 Sn 0.09 Bi 0.003
[0123] TABLE-US-00019 TABLE 19 evaluation sam- density ratio %
tensile elon- seizure ple green sintered forged strength gation
pressure Re- No. compact compact compact MPa % MPa marks B44 85.0
90.0 99.0 501 3.1 35 B45 85.0 93.0 99.0 520 3.6 40 B46 85.0 93.0
99.0 525 4.0 40 B01 85.0 93.0 99.0 525 4.0 40 B47 85.0 93.0 99.0
515 3.1 40 B48 85.0 93.0 99.0 495 2.3 30 B01 85.0 93.0 99.0 525 4.0
40 B49 85.0 93.0 99.0 528 4.2 40 B50 85.0 93.0 99.0 520 3.8 40 B51
85.0 93.0 99.0 528 4.0 40
[0124] Here, comparing the samples of Nos. B01 and B44-B48 in
Tables 17 to 19, the effect of the amount of the low-melting-point
metal powder. Comparing with the product (sample No. B44) wherein
no low-melting-point metal is added, it is found that, when the
low-melting-point metal is added, the tensile strength, elongation
and seizure pressure are improved. It is also found that, regarding
that amount of addition, the effect of that is seen when that is in
the range of from 0.01 to 0.5 mass %; and the effect is the highest
when the adding amount thereof is in the range of from 0.05 to 0.1
mass %. However, if the adding amount thereof exceeds 0.5 mass %,
the decrease in the elongation is outstanding, simultaneously
accompanied by the decrease in the seizure pressure. Accordingly,
it is confirmed that, regarding the addition of the
low-melting-point metal powder, the effect of enhancing the
mechanical properties is brought about when that addition is in the
range of from 0.01 to 0.5 mass %.
[0125] Also, comparing the samples of Nos. B01 and B49-B51 in
Tables 17 to 19, wherein the kind of the low-melting-point metal
powder is changed, the effect of the kind of the low-melting-point
metal powder is searched. From the results of them, it is confirmed
that the same effect as described above is obtained even when the
bismuth powder, indium powder or lead-free solder powder is used in
place of tin powder.
Example 8
[0126] Example 8 is an embodiment wherein examination is performed
on a case where the compacting pressure is changed as a compacting
condition, or one of the sintering temperature and sintering time
is changed as a sintering condition.
[0127] Using the raw material powder which was prepared by using
aluminum powder, aluminum alloy powder, magnesium powder, copper
powder and tin powder and by adjusting to the same ingredient
composition as that in Example 3, there were executed the
compacting step and sintering step with the use of the compacting
pressure, sintering temperature and sintering time shown in Table
20. Then, under the same conditions as those in Example 3, the
forging step, heat-treating step and test piece processing step
were performed. Regarding each of the obtained products,
measurement of the density ratio in each step and the tensile
strength, elongation and seizure pressure was carried out. The
results are shown in Table 21 together with the result (average
value) of sample No. B01 in Example 3. TABLE-US-00020 TABLE 20
compacting sintering sample pressure Sint. temp. sint. time No. MPa
.degree. C. min B52 100 600 20 B53 200 600 20 B01 300 600 20 B54
400 600 20 B55 500 600 20 B56 300 550 20 B57 300 580 20 B01 300 600
20 B58 300 610 20 B59 300 620 20 B60 300 -- 0 B61 300 600 10 B01
300 600 20 B62 300 600 30 B63 300 600 40
[0128] TABLE-US-00021 TABLE 21 evaluation density ratio % tensile
seizure sample green sintered forged strength elongation pressure
No. compact compact compact MPa % MPa Remarks B52 75.0 -- -- -- --
-- severe deform. on sinterng. B53 83.0 90.0 99.0 527 3.8 40 B01
85.0 93.0 99.0 525 4.0 40 B54 85.0 93.0 99.0 530 4.2 40 B55 86.0 --
-- -- -- -- die galling B56 85.0 86.0 99.0 415 1.0 20 B57 85.0 92.0
99.0 520 2.6 35 B01 85.0 93.0 99.0 525 4.0 40 B58 85.0 93.0 99.0
525 3.2 40 B59 85.0 -- -- -- -- -- sintered mass melting B60 85.0
91.0 99.0 418 1.2 20 B61 85.0 92.0 99.0 520 3.2 40 B01 85.0 93.0
99.0 525 4.0 40 B62 85.0 93.0 99.0 526 3.8 40 B63 85.0 94.0 99.0
525 3.6 40
[0129] From the results of samples of Nos. B01 and B52-B55 in
Tables 20 and 21, it is found that, when the compacting pressure is
in the range of from 200 to 400 MPa, a compacted compact sample in
which the density ratio thereof is 80% or more, and that, by
passing through the sintering-forging-heat treating steps, the
product of the relevant sample exhibits a high level of tensile
strength and high values of elongation and seizure pressure.
Moreover, in the sample of No. B52 wherein the compacting pressure
is below 200 MPa, the amount of shrinkage due to the occurrence of
the liquid phase is large, because the density of the green compact
is low. This has caused to lose the shape. As a result of this, the
succeeding forging and heat-treating steps have been canceled and
the relevant test has also been stopped. On the other hand, if the
compacting pressure exceeds 400 MPa (in sample No. B55), die
galling occurs, whereby the succeeding sintering step and the steps
thereafter have been canceled and the test has been stopped.
[0130] Moreover, comparing the samples of Nos. B01 and B56-B59 in
Tables 20 and 21, the effect of the sintering temperature is
searched. From those results, it is found that the samples of Nos.
B01, B67 and B58 wherein the sintering temperature is in the range
of from 580 to 610 degrees C. exhibit a high level of tensile
strength and a high value of elongation. On the other hand, in the
sample of No. B56 wherein the sintering temperature is lower than
580 degrees C., both of the tensile strength and elongation are
deteriorated. This is considered, because the ingredient element is
not completely be dissolved in the Al base to form solid solution
and it is locally segregated to remain, with the result that the
mechanical properties deteriorate to a low value. Contrary to the
above, in the sample of No. B59 wherein the sintering temperature
is higher than 610 degrees C., the sintered compact is deformed
with melting, because the amount of liquid phase excessively
occurred. The succeeding test has been therefore canceled.
[0131] Comparing the samples of Nos. B01 and B60-B63 in Tables 20
and 21, the effect of the sintering time is searched. From the
results of those, it is found that, in the sample of No. B60
wherein the sintering time is shorter than 10 minutes, both of the
tensile strength and elongation are deteriorated. This is
considered because the ingredient element is not sufficiently
dissolved in the Al base to form solid solution and it is locally
segregated to remain, with the result that the mechanical
properties come to a low value. Opposite to the above, in the
samples of Nos. B01 and B61-B63 wherein the length of sintering
time is longer than 10 minutes, the ingredient is evenly dissolved
in the Al base to form solid solution, whereby the relevant product
exhibits a high level of mechanical property that, while the
tensile strength is 500 MPa or more, the elongation exceeds 3%.
Here, it is noted that, even when the sintering time exceeds 30
minutes, the mechanical property that the product exhibits has no
change. Therefore, a sintering time of 30 min or less can be
regarded as being sufficient.
Example 9
[0132] In Example 9, the operation of Example 3 was repeated under
the same conditions for sample production as those in Example 3,
excepting that the forging conditions were changed to those shown
in Table 22, to prepare product samples of Nos. B-53 to B-69, using
the aluminum powder, aluminum alloy powder, magnesium powder,
copper powder and tin powder used for the Sample No. B01 in Example
3 and preparing the raw material powders that were adjusted to the
same ingredient composition as that in Example 3. Regarding each of
these samples, the density ratio after executing each step as well
as the tensile strength, elongation and seizure pressure was
measured, the results being shown in Table 23 together with the
measured results concerning the sample No. B01 in Example 3. Here,
in Table 22, regarding the field "Forging Temperature", the term
"R.T. (Room Temperature)" designates the case of cold forging, and,
in the case of hot forging, the heating temperature for a sintered
compact sample as a material to be forged is shown. The sample of
No. B64 is prepared for comparison with a specimen of a
conventional material that is similar to the material of Japanese
Laid-Open Patent Application of Publication No. JPA H04-365832 with
no forging. TABLE-US-00022 TABLE 22 forging sample forging temp.
No. .degree. C. upsetting ratio % B64 -- -- B65 r.t. 3 B66 r.t. 10
B67 r.t. 20 B68 r.t. 40 B69 r.t. 45 B68 r.t. 40 B70 100 40 B71 150
40 B72 200 40 B73 300 40 B01 400 40 B74 450 40 B75 500 40 B76 400 3
B77 400 10 B78 400 20 B01 400 40 B79 400 70 B80 400 80
[0133] TABLE-US-00023 TABLE 23 evaluation density ratio % tensile
seizure sample green sintered forged strength pressure No. compact
compact compact MPa elongation % MPa Remarks B64 85.0 93.0 99.0 405
0.5 15 B65 85.0 93.0 99.0 475 0.6 20 B66 85.0 93.0 99.0 480 0.8 25
B67 85.0 93.0 99.0 480 0.8 25 B68 85.0 93.0 99.0 485 1.1 30 B69
85.0 93.0 -- -- -- -- forging crack occurred B68 85.0 93.0 99.0 485
1.1 30 B70 85.0 93.0 99.0 510 1.9 35 B71 85.0 93.0 99.0 515 2.8 40
B72 85.0 93.0 99.0 520 3.4 40 B73 85.0 93.0 99.0 525 4.0 40 B01
85.0 93.0 99.0 525 4.0 40 B74 85.0 93.0 99.0 526 3.2 40 B75 85.0
93.0 -- -- -- -- die adhesion on forging B76 85.0 93.0 99.0 520 1.9
40 B77 85.0 93.0 99.0 522 3.3 40 B78 85.0 93.0 99.0 525 3.6 40 B01
85.0 93.0 99.0 525 4.0 40 B79 85.0 93.0 99.0 524 4.2 40 B80 85.0
93.0 -- -- -- -- disuniform forg. & cracks
[0134] Here, comparing the samples of Nos. B64-B69 in Tables 22 and
23, the effect of the upsetting ratio that is brought about when
cold forging is done at room temperature is searched. From those
results, it is found that, in the case of cold forging, the sample
has high levels of tensile strength, elongation and seizure
pressure, if the upsetting ratio is set in a range of from 3 to 40.
Contrary to the above, if the upsetting ratio exceeds 40% (in
sample No. B69), cracks occur in the sample due to forging. The
performance of the test in such a case has been cancelled.
[0135] Also, the effect of the heating temperature in a case where
hot forging is performed is searched by comparing the samples of
Nos. B68 (cold forging), B01 and B70-B75 in Tables 22 and 23
wherein that heating temperature for sintered compact is changed.
From those results, it is found that, the values of tensile
strength, elongation and seizure pressure are possibly improved by
turning to the hot forging. This is attributable to the fact that,
although in the case of cold forging hair cracks very slightly
remain within the sample, followed by decrease in the elongation,
carrying out hot forging of the material with the heating
temperature being set to 100 degrees C. or more makes the hair
cracks removed. On the other hand, when the forging temperature
exceeds 400 degrees C., adhesion (die galling) of the sintered
compact to the die occurs. The succeeding test in such a case has
been therefore cancelled.
[0136] Also, comparing the samples of Nos.65 to 69 in Table 18, the
effect of the upsetting ratio in the case where hot forging is done
is searched. From those results, it is found that, in the case of
hot forging, the samples have high levels of tensile strength and
seizure pressure and a high value of elongation even when the
upsetting ratio is extended to a wide range of 3 to 70%. However,
if the upsetting ratio exceeds 70% (in sample No. B80), forging
causes the occurrence of cracks on the samples. The succeeding test
in such a case has been therefore cancelled.
[0137] It must be understood that the invention is in no way
limited to the above embodiments and that many changes may be
brought about therein without departing from the scope of the
invention as defined by the appended claims.
* * * * *