A heat-resisting aluminum alloy contains manganese ranging from 6 to 8% by weight, iron ranging from 0.5 to 2% by weight, zirconium ranging from 0.03 to 0.5% by weight, and copper ranging from 2 to 5% by weight, the balance being essentially aluminum. The aluminum alloy has been confirmed to be high in mechanical strength both at ordinary temperatures and at high temperatures while to be suitable for producing an article by using so-called atomization process.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
This invention relates, in general, to a heat-resisting aluminum alloy 
which is high in mechanical strength not only at ordinary temperatures but 
also at high temperatures, and more particularly to the heat-resisting 
aluminum alloy suitable for the material of automotive engine component 
parts subjected to ordinary to high temperatures. 
2. Description of the Prior Art 
It is a recent tendency that improved fuel economy has been eagerly desired 
particularly in the field of automotive vehicles. As a measure for 
attaining the improved fuel economy, weight reduction of the automotive 
vehicles has been made by using light weight component parts made, for 
example, of aluminum alloy. Thus, aluminum alloy has been extensively used 
as the material of the automotive vehicle component parts, particularly of 
engine component parts. 
However, it is difficult to employ usual aluminum alloy for the material of 
the engine component parts which are required to have a high mechanical 
strength throughout a wide temperature range from normal temperatures to 
about 250.degree. C. 
More specifically, so-called high strength aluminum alloy such as one whose 
designation number is 7075 has a good strength characteristics at normal 
temperatures but is sharply lowered in strength in a temperature range 
from normal temperatures to 200.degree. C. In this regard, such high 
strength aluminum alloy is not suitable for the material of the component 
parts of automotive engines. The designation numbers of aluminum alloys 
mentioned hereinabove and hereinafter are adopted by the Aluminum 
Association in the United States of America. 
Regarding so-called heat-resisting aluminum alloy such as one whose 
designation number is 2218, it is excellent in strength at high 
temperatures but is lower in strength at normal temperatures. As a result, 
such heat-resisting aluminum alloy is also not suitable for the material 
of automotive engine component parts. 
SUMMARY OF THE INVENTION 
A heat-resisting aluminum alloy according to the present invention contains 
manganese ranging from 6 to 8% by weight, iron ranging from 0.5 to 2% by 
weight, zirconium ranging from 0.03 to 0.5% by weight, and copper ranging 
from 2 to 5% by weight. The balance is essentially aluminum. By virtue 
particularly of the lowered upper limit of content of manganese and iron 
and the increased content of copper, the aluminum alloy becomes high both 
in strength at ordinary and high temperatures and becomes suitable for the 
material of an article produced by using so-called atomization process in 
which molten metal of the parent metal is sprayed to obtain powder 
particles which will be finally compression-formed into a desired article. 
DESCRIPTION OF THE INVENTION 
According to the present invention, a heat-resisting aluminum alloy 
comprises manganese ranging from 6 to 8% by weight, iron ranging from 0.5 
to 2% by weight, zirconium ranging from 0.03 to 0.5, copper ranging from 
2 to 5% by weight, and the balance essentially aluminum in which the 
balance may include impurities. In this aluminum alloy, the upper limit of 
the added amount or content of manganese (Mn) and iron (Fe) is kept lower 
thereby to suppress cystallization of bulky phase and segregation of Mn 
compound, while increasing the added amount or content of copper (Cu) 
which is an additive element for improving mechanical strength throughout 
a wide temperature range from ordinary temperatures to about 250.degree. 
C. without affecting Mn compound. This make possible to obtain the 
heat-resisting aluminum which is high in mechanical strength both at 
ordinary temperatures and high temperatures without using quench 
solidification such as so-called splat cooling process which will 
complicate production processes thereafter. 
The above-stated range of content of the components of the heat-resisting 
aluminum alloy of the present invention has been limited for the reasons 
discussed hereinafter. 
Mn:6 to 8% by weight. 
Mn is an element effective for improving heat resistance and wear 
resistance of aluminum alloy. However, if the content of Mn is less than 
6%, sufficient heat resistance cannot be obtained, while if it exceeds 8%, 
there occurs crystallization of the bulky phase and segregation of Mn 
compound at the cooling rate obtained by the atomization process. As a 
result, the content of Mn has been limited within the range from 6 to 8% 
by weight. 
Fe:0.5 to 2% by weight. 
Fe is an element effective for improving high temperature stability of 
supersaturated solid solution (obtained by quenching) of Al-Mn alloy and 
fine Al-Mn intermetallic compound. However, if the content of Fe is less 
than 0.5%, such an effect cannot be obtained, while if it exceeds 2%, 
brittle phase of Al-Mn-Fe and Al-Fe is crystallized in the atomization 
process. As a result, the content of Fe has been limited within the range 
from 0.5 to 2% by weight. 
Zr:0.03 to 0.5% by weight. 
Zr is an element effective for making fine crystal particles in addition 
for improving high temperature stability of supersaturated solid solution 
of Al-Mn alloy and fine Al-Mn intermetallic compound. However, the content 
of Zr is less than 0.03%, such an effect cannot be obtained, while if it 
exceeds 0.5%, there occurs enlargement of Al-Zr phase. As a result, the 
content of Zr has been limited within the range from 0.03 to 0.5% by 
weight. 
Cu:2 to 5% by weight. 
Cu is an element which is effective for improving mechanical strength at 
ordinary temperatures and by which the heat-resisting aluminum alloy 
according to the present invention is most characterized. In other words, 
the present invention is intended to improve the mechanical strength in a 
wide temperature range from ordinary temperatures to 250.degree. C. 
without affecting Mn compound, by increasing the content of Cu in order to 
compensate a decrease of Mn, Fe content which decrease is made for the 
purpose of suppressing coarsening and segregation of Mn compound in powder 
form produced by the atomization process. It will be noted that if the 
content of Cu is less than 2%, the effect of strength improvement cannot 
be expected, while if it exceeds 5%, corrosion resistance of the aluminum 
alloy is degraded, accompanied by deteriorating the high temperature 
stability of the supersaturated solid solution of Al-Mn alloy and very 
fine Al-Mn intermetallic compound. As a result, the content of Cu has been 
limited within the range from 2 to 5% by weight. 
Now, addition of silicon (Si) and magnesium (Mg) other than Cu is 
thinkable. However, if Si is added in a corresponding amount aiming the 
same degree strength improvement as in the case of Cu addition, Si is 
unavoidably contained in the form of .alpha.-Al(Fe,Mn)Si phase in Mn 
compound and therefore is less than Cu in strength improvement effect due 
to solid solution hardening and precipitation hardening. 
Mg is an element which improves mechanical strength at ordinary 
temperatures by age hardening upon binding of Mg with Si. However, as 
stated above, Si tends to take the form .alpha.-Al(Fe,Mn)Si phase and 
therefore the strength improvement due to the precipitation of Mg.sub.2 Si 
phase is degraded as compared with that due to Cu addition.

In order to evaluate the heat-resisting aluminum alloy according to the 
present invention, Examples (Sample Nos. 1 to 5) of the present invention 
will be discussed hereinafter in comparison with Comparative Examples 
(Sample Nos. 6 to 12) which are out of the scope of the present invention. 
The chemical compositions of the Examples and Comparative Examples are 
shown in Table 1. 
TABLE 1 
______________________________________ 
Chemical Composition (Wt. %) 
Al 
and im- 
Ref- 
No. Mn Fe Ni Zr Cu Mg Zn Cr purities 
erence 
______________________________________ 
1 6.5 1.5 -- 0.1 3.5 -- -- -- balance 
Ex- 
2 6.5 1.5 -- 0.1 5.0 -- -- -- balance 
amples 
3 7.0 2.0 -- 0.15 4.0 -- -- -- balance 
(Pre- 
4 8.0 1.0 -- 0.1 2.5 -- -- -- balance 
sent 
5 8.0 1.5 -- 0.05 4.0 -- -- -- balance 
Inven- 
tion) 
6 -- -- 2.0 -- 4.0 1.5 -- -- balance 
Com- 
7 -- -- -- -- 2.0 2.5 5.6 0.3 balance 
para- 
8 5.0 1.0 -- 0.1 2.0 -- -- -- balance 
tive 
9 4.0 0.5 -- 0.05 3.5 -- -- -- balance 
Ex- 
10 8.5 2.5 -- 0.15 -- -- -- -- balance 
amples 
11 8.5 2.5 -- 0.15 2.5 -- -- -- balance 
12 9.0 1.5 -- 0.2 -- -- -- -- balance 
______________________________________ 
The aluminum alloys of Sample Nos. 1 to 5 and of Sample Nos. 8 to 12 were 
prepared as follows: A binary alloy ingot containing Al and an individual 
component other than Al, and an Al ingot were weighed and molten to be 
mixed with each other thereby to produce a parent metal having a chemical 
composition shown in Table 1. Thereafter, the patent metal was molten in a 
melting furnace of an atomizing device, and the thus prepared molten metal 
was sprayed upon being superheated 150.degree. C. over the melting point 
of the parent metal, thereby obtaining atomized powder. The atomized 
powder having a particle size not larger than 120 mesh was used for 
preparing a specimen subjected to tests discussed below. Subsequently, the 
atomized powder was formed into a cylindrical shape under the compression 
of 3.5 tonf/cm.sup.2 to obtain a billet. The billet was then subjected to 
an extrusion process at a temperature lower than 400.degree. C. and at an 
extrusion ratio (the ratio between the cross-sectional areas of the billet 
and an extruded product) of 12:1. The extruded product was cut out into a 
predetermined shape to obtain the specimen for the tests. 
The Sample Nos. 6 and 7 correspond to aluminum alloys whose designation 
numbers are 2218 and 7075, respectively. These were prepared as follows: 
The molten metal of the parent metal corresponding to each Sample No. was 
formed into an ingot for rolling which ingot thereafter underwent hot 
rolling. Subsequently, a product corresponding to Sample No. 6 was 
subjected to solid solution treatment at 510.degree. C. for 4 hours and to 
artificial aging treatment at 175.degree. C. for 4 hours, whereas a 
product corresponding to Sample No. 7 was subjected to solid solution 
treatment at 460.degree. C. for 4 hours and to artificial aging treatment 
at 120.degree. C. for 24 hours. Thereafter, each product were cut out into 
the predetermined shape to obtain each specimen for the tests. 
Next, a tension test was conducted on each of the thus obtained specimens 
at an ordinary (or room) temperature and at 200.degree. C., in which 
tension value measurement in test at 200.degree. C. was made after each 
specimen had been kept heated for 1 hour. The test result is shown in 
Table 2 in which Sample Nos. correspond to those in Table 1. 
TABLE 2 
______________________________________ 
Strength at room temp. 
Strength at 200.degree. C. 
Sam- tensile yield tensile yield 
ple strength strength strength 
strength 
Ref- 
No. (kgf/mm.sup.2) 
(kgf/mm.sup.2) 
(kgf/mm.sup.2) 
(kgf/mm.sup.2) 
erence 
______________________________________ 
1 54.3 45.7 42.7 34.2 Ex- 
2 57.7 48.9 40.9 34.6 amples 
3 57.4 48.9 43.1 35.7 (Pre- 
4 55.1 46.3 44.3 37.3 sent 
5 59.8 49.1 40.3 35.9 Inven- 
tion) 
6 41.0 30.5 32.6 27.5 Com- 
7 55.1 48.5 24.7 22.3 para- 
8 44.9 35.8 30.6 25.3 tive 
9 47.0 37.8 29.8 21.8 Ex- 
10 45.3 35.8 41.5 32.7 amples 
11 46.1 37.3 40.1 32.6 
12 39.7 32.4 37.4 31.7 
______________________________________ 
As shown in Table 2, all the Sample Nos. 1 to 5 aluminum alloys according 
to the present invention exhibit considerably higher tensile strengths at 
ordinary temperatures and at 200.degree. C. than the designation number 
2218 heat-resisting aluminum alloy (Sample No. 6). Particularly, the 
strength at ordinary temperatures of the aluminum alloys according to the 
present invention can stand comparison with that of the designation number 
7075 high strength aluminum alloy (Sample No. 7). Thus, it has been 
demonstrated that the aluminum alloy according to the present invention is 
excellent in strength at ordinary temperatures and at high temperatures. 
The Sample Nos. 8 and 9 aluminum alloys (Comparative Examples) whose Mn and 
Fe contents are less than those of the aluminum alloy of the present 
invention are slightly lower in strength at 200.degree. C. as compared 
with the aluminum alloy of the present invention. The Sample Nos. 10, 11 
and 12 aluminum alloys (Comparative Examples) whose Mn and Fe contents are 
more than those of the aluminum alloy of the present invention are 
degraded in strength as compared with the aluminum alloy of the present 
invention because coarsening and segregation of Mn compound unavoidably 
occurs at the cooling rate obtained by the atomization process. Thus, the 
Sample Nos. 8 to 12 aluminum alloys have been confirmed to be inferior as 
compared with the aluminum alloy according to the present invention. 
As will be appreciated from the above discussion, the aluminum alloy 
according to the present invention is a light alloy material which is 
excellent in mechanical strength both at ordinary temperatures and at high 
temperatures as compared with conventional aluminum alloys, so that it is 
widely applicable, for example, in engine component parts which are 
required not only to be heat-resistant but also to be high in ordinary 
temperature strength, while achieving weight reduction of the component 
parts and an assembled product. Additionally, an article made of the 
aluminum alloy of the present invention can be produced with powder 
particles prepared by the atomization process, thus offering an advantage 
of omitting quench solidification such as troublesome splat cooling 
process.