Method for manufacturing aluminum alloy by permeating molten aluminum alloy containing silicon through preform containing metallic oxide and more finely divided substance

In this method for manufacturing an aluminum alloy, a porous preform is manufactured from a mixture of a finely divided oxide of a metallic element which has a weaker tendency to form oxide than does aluminum, and an additional substance substantially more finely divided than that metallic oxide. Then an aluminum alloy containing a substantial quantity of silicon is permeated in the molten state through the porous preform. This causes the metallic oxide to be reduced by a thermite reaction, to leave the metal which it included as alloyed with the aluminum alloy. At this time, the silicon in the aluminum alloy does not tend to crystallize out upon the particles of the metallic oxide, which would interfere with such a reduction reaction by forming crystalline silicon shells around such metallic oxide particles and would lead to a poor final product, because instead the silicon tends to crystallize out upon the particles of the additional substance. This alloying method is effective even if the average particle diameter of the finely divided metallic oxide, on the assumption that it is in the form of globular particles, is less than about 10 microns. The melting point of the additional substance should desirably be substantially higher than the melting point of the aluminum alloy. The silicon content of the aluminum alloy may freely be greater than about 1.65% by weight. Desirably, the preform may further contain reinforcing fibrous material. And, particularly, the additional substance may be Al.sub.2 O.sub.3.

BACKGROUND OF THE INVENTION 
The present invention relates to a method for manufacturing an aluminum 
alloy, and more particularly relates to such a method for manufacturing an 
aluminum alloy through the use of a reduction type reaction. 
Further, the present inventors wish hereby to attract the attention of the 
examining authorities to copending U.S. patent application Ser. Nos. 
820,886 and 888,650, which may be considered to be material to the 
examination of the present patent application. 
In the prior art, there have been proposed various types of method for 
manufacturing an aluminum alloy. In particular, in Japanese Patent 
Application Laying Open Publication Serial No. 59-256336 (1984), which it 
is not intended hereby to admit as prior art to the present patent 
application except to the extent in any case required by applicable law, 
there is disclosed a method for manufacturing an alloy of a first base 
metal which for example may be aluminum and a second additive metal which 
has a weaker affinity for oxygen than said first base metal (but may have 
a much higher melting point than said first base metal), in which a porous 
block like preform is made of an oxide of the second additive metal, and 
then a quantity of the first base metal in molten form is permeated 
through the interstices of this porous preform, so as to come into 
intimate contact with the material thereof which is the oxide of the 
second additive metal. As this occurs, said molten first base metal 
reduces this oxide of said second metal, due to the fact that said first 
metal has a greater affinity for oxygen, i.e. has a greater oxide 
formation tendency, than does said second metal. Accordingly, said oxide 
of said second additive metal is, hopefully, all reduced, so as to leave 
said second additive metal in alloyed form with said first base metal, 
while of course producing a certain quantity of the oxide of said first 
base metal which need not present any problem. And a distinguished 
advantage of this alloying process is that it is not necessary to raise 
the working temperature so high as to melt said second additive metal, 
which may be a very high melting point metal such as nickel or titanium or 
the like, but it is on the contrary only necessary to melt the first base 
metal which may be a relatively low melting point metal such as aluminum 
or aluminum alloy. And in the case of this alloying method there are no 
substantial limitations on the type or the quantity of the second additive 
metal which is to be alloyed to the first base metal, and it is thus 
possible to manufacture an alloy of any desired composition, as opposed to 
the case of a conventional type of allowing process in which there are 
various inevitable restrictions due to reasons including but not limited 
to rise in the dissolution temperature of the alloy or of its materials, 
degradation of alloying characteristics, and differences in the specific 
gravities of the materials to be alloyed. Further, in the case of the 
above outlined alloying method it is possible to regulate a specific part 
of a cast object to be of substantially any desired composition. 
In the case of the above outlined alloying method, in the case that the 
first base metal is aluminum or an alloy thereof, the reduction of the 
second additive metal is brought about by means of a thermite reaction 
that occurs between the molten aluminum or aluminum alloy base metal and 
the oxide or oxides of the porous perform including the second additive 
metal. This enables the manufacture of aluminum alloys that may be of 
substantially any desired composition, and whose composition may be 
locally varied as desired. 
However, there is a disadvantage with the above outlined alloying method in 
its form as described above, as follows. If a conventionally available 
aluminum alloy is selected as the first base metal to be alloyed, as is 
per se desirable on the grounds of cost and convenience, there are many 
cases in which a satisfactory thermite reaction is not produced, and there 
is in practice no assurance that a satisfactory alloying process will 
occur and that the first base metal and the second additive metal will be 
properly alloyed together and will be properly commingled. In detail, if 
substantially pure aluminum is used as the first base, metal, than no 
substantial problem tends to arise: thus, if pressurized infiltration of 
molten substantially pure aluminum alloy into a high porosity block formed 
of powdered oxide of another metal, such as Fe.sub.2 O.sub.3, NiO, or MnO, 
which has a particle diameter of less than one micron, is conducted, then 
indeed a sufficiently effective thermite reaction occurs, and the powdered 
oxide of said other metal is indeed satisfactorily reduced, so as to 
produce a quantity of aluminum oxide which presents no substantial 
problem, and so as to release a quantity of said other metal, such as Fe, 
Ni, or Mn, into the aluminum alloy to be alloyed therewith. Thereby, the 
desired high quality alloy, such as an Al-Fe alloy, and Al-Ni alloy, or an 
Al-Mn alloy, can be satisfactorily produced. However, in the more common 
case that it is desired to utilized as the material for being infiltrated 
in said high porosity preform an alloy of aluminum containing a 
substantial amount of silicon, such as aluminum alloy of type JIS standard 
AC8b 8A, then there is a tendency for the silicon in the molten aluminum 
alloy mixture to crystallize out on the surfaces of the small particles of 
the oxide of the additive metal that make up the preform, and this can 
impede the thermite reaction between the aluminum alloy and said small 
oxide particles, and can result in the incomplete reduction of said oxide 
of said second additive metal. Experimental results verifying this 
phenomenon are presented later in the specification under the title of 
"Background Experiments". This can present a serious problem in 
circumstances of actual industrial application. 
SUMMARY OF THE INVENTION 
The inventors of the present invention have considered the various problems 
detailed above in the case when it is desired to utilize, as the molten 
first base metal for alloying, such an alloy of aluminum including 
silicon, from the point of view of the desirability of promoting the 
reduction reaction for the particles of the oxide of the second additive 
metal without any crystallization of silicon interfering with such 
reduction, and have discovered, as detailed later in this specification, 
that, if a quantity of another substance in a powder or other finely 
divided form, the particle size of which is even finer than the particle 
size of the oxide particles of the second additive metal, is added to the 
high porosity preform, then, during the process of infiltration by the 
aluminum alloy containing silicon, this silicon tends to crystallize out 
on the surfaces of said another substance in a preferential manner, and 
accordingly is prevented from crystallizing out upon the surfaces of the 
fine oxide powder particles. Accordingly, the thermite reaction between 
the aluminum alloy and said fine oxide powder particles is allowed to 
proceed to its culmination, and satisfactory alloying is enabled. 
Accordingly, it is the primary object of the present invention to provide a 
method for manufacturing an aluminum alloy, of the type in which a molten 
aluminum alloy which may contain silicon is infiltrated into the 
interstices of a preform containing fine particles of an oxide of another 
metal to be alloyed with said aluminum alloy in order to reduce them, 
which avoids the problems detailed above. 
It is a further object of the present invention to provide such a method 
for manufacturing an aluminum alloy, which prevents silicon 
crystallization from impeding the thermite reduction process of said oxide 
of another metal. 
It is a further object of the present invention to provide such a method 
for manufacturing an aluminum alloy, which avoids poor integrity of the 
finished product. 
It is further object of the present invention to provide such a method for 
manufacturing an aluminum alloy, which prevents the occurrence that 
particles of the oxide of the additive metal should remain in the finished 
product, perhaps as wholly or partly surrounded by shells of silicon. 
According to the most general aspect of the present invention, these and 
other objects are attained by a method for manufacturing an aluminum 
alloy, wherein: (a) a porous preform is manufactured from a mixture of: 
(a1) a finely divided oxide of a metallic element which has a weaker 
tendency to form oxide than does aluminum, and: (a2) an additional 
substance substantially more finely divided than said metallic oxide; and: 
(b) an aluminum alloy containing a substantial quantity of silicon is 
permeated in the molten state through said porous preform. And the process 
described above is particularly beneficial, in the case that the average 
particle diameter of said finely divided metallic oxide, on the assumption 
that said finely divided metallic oxide is in the form of globular 
particles, is less than about 10 microns. 
According to such a method for manufacturing an aluminum alloy as specified 
above, since the silicon in the aluminum alloy which is being permeated in 
the molten state through said porous preform tends preferentially to be 
crystallized out around the surfaces of the particles or flakes of said 
additional substance substantially more finely divided than said metallic 
oxide particles, therefore such silicon crystallization does not tend to 
occur to any great extent around the surfaces of the particles of the 
finely divided oxide of said metallic element, and accordingly the 
reduction reaction (or thermite reaction) between the molten aluminum 
alloy and said particles of said finely divided oxide of said metallic 
element is allowed to take place satisfactorily. This, in turn, 
facilitates the production of a satisfactory alloy of said aluminum alloy 
and said metallic element. Accordingly, poor integrity of the finished 
product is avoided, and this method for manufacturing an aluminum alloy 
therefore prevents the occurrence that particles of the oxide of the 
additive metal (said metallic element) should remain in the finished 
product perhaps as wholly or partly surrounded by shells of silicon. 
According to the results of experiments performed by the present inventors, 
when the molten aluminum alloy containing silicon is being infiltrated in 
the molten state through the interstices of the porous preform, if the 
particles or flakes of said additional substance which are substantially 
more finely divided than said metallic oxide particles tend to be melted 
by the molten aluminum alloy, the desired object of the present invention 
cannot be satisfactorily attained. Thus, it is considered to be very 
desirable, if not absolutely essential, to the present invention for said 
particles or flakes of said additional substance to be left as remaining 
in a state of fine dispersion in the final aluminum alloy produced, so as 
to be able to serve as the nuclei for the crystallization of silicon as 
explained above. Therefore, according to a particular and much desired 
specialization of the present invention, the above and other objects may 
more particularly be accomplished by such a method for manufacturing an 
aluminum alloy as first specified above, wherein the melting point of said 
additional substance is substantially higher than the melting point of 
said aluminum alloy. In this case, there will be no problem of said 
particles or flakes of said additional substance becoming melted away 
during the alloy infiltration process, and it is ensured that said 
particles or flakes of said additional substance are finally left as 
remaining in a state of fine dispersion in the final aluminum alloy 
produced. 
Further, according to the results of the various experiments performed by 
the present inventors, when the molten aluminum alloy containing silicon 
is being infiltrated in the molten state through the interstices of the 
porous preform, with regard to the risk identified above that the silicon 
in said molten aluminum alloy may crystallize out upon said metallic oxide 
particles, for the case of a bi elemental configuration in which the 
silicon content in the aluminum alloy is less than about 1.65% by weight, 
such silicon crystallization is not particularly likely to occur, although 
because of such factors as irregularities in the consistency or the 
density of such silicon content nevertheless some silicon crystallization 
may happen. However, the risk of this silicon crystallization phenomenon 
becomes much greater, when the silicon content in the aluminum alloy comes 
to be more than about 1.65% by weight. Accordingly, the above and other 
objects may even more desirably be accomplished by such a method for 
manufacturing an aluminum alloy as first specified above, when the silicon 
content of said aluminum alloy is greater than about 1.65% by weight. 
Now, it has been further determined by the present inventors that, if 
reinforcing fiber material is contained in the preform, the aluminum alloy 
that is produced as a result of the process of the present invention is 
produced as a fiber reinforced alloy, i.e. as a reinforced material. By 
this method, at the same time as this aluminum alloy which has a 
completely new composition is produced via the thermite reaction explained 
above, it is at the same time and concurrently provided with fiber 
reinforcement; and this is very beneficial with regard to production 
effectiveness. Therefore, according to a further specialization of the 
present invention, the above and other objects may more particularly be 
accomplished by such a method for manufacturing an aluminum alloy as first 
specified above, wherein said preform further contains reinforcing fibrous 
material. 
With regard to the material to be utilized for the aforementioned 
additional substance to be added to the preform, it has been particularly 
determined according to the results of the researches performed by the 
present inventors, as will be detailed shortly, that Al.sub.2 O.sub.3 is 
particularly effective as said additional substance. Therefore, according 
to a yet further specialization of the present invention, the above and 
other objects may more particularly be accomplished by such a method for 
manufacturing an aluminum alloy as first specified above, wherein said 
additional substance is Al.sub.2 O.sub.3. 
Now, if as suggested above the preform should contain reinforcing fibrous 
material, at least a portion of this reinforcing fibrous material may also 
fulfill the role of the additional substance substantially more finely 
divided than said metallic oxide; in other words, if the fibers of said 
reinforcing fibrous substance are finer, i.e. are smaller in size, than 
the particles or flakes or the like of said metallic oxide, then they may 
fulfill the role of the additional substance for promoting silicon 
crystallization upon themselves. By employing this method, the reinforcing 
fibers that are utilized as said additional substance perform two separate 
and disparate functions concurrently: they function as nuclei for silicon 
crystallization during the alloying process, and also they provide fiber 
reinforcement for the finally produced aluminum alloy material. As a 
result of this, it is not usually necessary to mix in any other additional 
substance, other than said fine reinforcing fibrous material, into the 
high porosity preform which is to be infiltrated. 
With regard to the amount of said additional substance which it is required 
to provide in said high porosity preform which is to be infiltrated with 
aluminum alloy containing silicon, it is desirable that this amount should 
be sufficient in order completely to prevent the crystallization of the 
silicon around the peripheral surfaces of the particles of the oxide of 
the additive metal. Even, however, if the amount of said additional 
substance which is provided is below this ideal value, the reduction 
thermite reaction between the aluminum alloy and the oxide of the additive 
material will be substantially promoted by such amount of said additional 
substance as in fact is provided. In other words, the intensity and the 
effectiveness of the thermite reaction generated increase, as the amount 
of said additional substance added to the preform is increased, up to the 
theoretically ideal amount therefor. In particular, when the oxide of the 
additive metal, and/or the amount of silicon present in the aluminum alloy 
for infiltration, are present only in relatively small quantities, 
nevertheless the reduction reaction can proceed satisfactorily, even if 
the additional substance contained in the preform is present only in a 
trace amount. 
The forms of the oxide of the additive metal present in the preform, and of 
the additional substance included therein, are not restricted to the 
globular particulate form. These substances may also be provided in any 
finely divided forms, such as the flake form, the non continuous fiber 
form, or the ultra thin flake form. Also, the oxide of the additive metal 
is not to be considered as being limited to being a simple oxide; it could 
be a compound oxide, i.e. an oxide of higher order, as shown by example in 
some of the preferred embodiments which will be disclosed hereinafter.

DESCRIPTION OF BACKGROUND EXPERIMENTS 
Before beginning the description of the preferred embodiments of the 
process for manufacturing an aluminum alloy of the present invention, it 
is appropriate to detail two of the sets of background experiments 
performed by the present inventors, relating to processes for manufacture 
of aluminum alloys not according to the present invention, by way of 
furnishing background as to the need for development of the process of 
manufacturing an aluminum alloy of the present invention. 
The First Set of Background Experiments 
In the first one of this first set of experiments performed for the sake of 
background, a quantity of approximately 35 grams of NiO powder having an 
average particle diameter of approximately 2 microns was mixed to an even 
consistency with approximately 33 grams of alumina short fiber material of 
a type manufactured by ICI Co. Ltd. under the trademark "Saffil RF", and 
having average fiber length of about 3 mm and average fiber diameter of 
about 2 microns. The resultant mixture was than compacted under pressure, 
to produce a block shaped preform with dimensions of approximately 100 
mm.times. 50 mm.times.20 mm and of relatively high porosity; this preform 
had density of approximately 0.68 gm/cm.sup.3. FIG. 1 is a perspective 
diagram of this preform, which is denoted as 2, and in this figure the 
reference numeral 4 denotes (schematically) the nickel oxide powder 
particles, while the reference numeral 6 denotes the alumina short fibers. 
Next, this high porosity preform 2 was preheated to a temperature of 
approximately 600.degree. C. in an air chamber; and then, as shown in 
schematic sectional view in FIG. 2, said perform 2 was placed into a mold 
cavity 10 of a mold 8, and a quantity 12 of molten aluminum alloy of type 
JIS standard AC8A was poured into said mold cavity, over and around the 
preform 2. And then a pressure plunger 14 was inserted into the upper 
portion of the mold 8, so as to press on the upper surface of the molten 
aluminum alloy mass 12 and so as closely and slidingly to cooperate with 
said mold upper portion, and said pressure plunger 14 was pressed 
downwards, so as to pressurize the molten aluminum alloy mass 12 around 
the preform 2 to a pressure of about 1000 kg/cm.sup.2. This pressure was 
maintained while said molten aluminum alloy mass 12 percolated and 
infiltrated into the interstices of the preform 2, and until said molten 
aluminum alloy mass 12 had completely solidified. Then the pressure 
plunger 14 was removed, and the solidified mass was removed from the mold 
cavity 10 of the mold 8 by being knocked out by a knock pin 16, and 
finally the portion of said solidified mass which corresponded to the 
original preform 2 was cut away from the rest of said solidified mass by 
means of a machine cutter. 
When the fine structure of the resultant material was studied by cutting a 
cross section thereof and studying it under an optical microscope, as 
shown in FIG. 3 there remained fine particles of NiO therein, designated 
as 18 in the figure, and said fine NiO particles 18 were surrounded with 
coatings 20 of crystallized silicon. The present inventors indeed verified 
by means of EPMA analysis and X-ray diffraction analysis that these fine 
particles 18 were indeed particles of NiO. This resulted in a base 
structure somewhat segregated from the matrix aluminum alloy 22 which was 
formed as surrounding the reinforcing alumina short fibers 6. It was 
considered that this undesirable fine structure was due to the fact that 
some of the particles of the NiO powder initially served as nuclei for 
crystallization of a portion of the silicon in the matrix AC8A aluminum 
alloy, and this crystallized silicon subsequently shielded said particles 
from being completely subjected to the thermite reaction, so that they 
remained unchanged in the final material produced, and were not reduced. 
Further, in two other background experiments similar to the one described 
above, as the aluminum alloy for infiltration into the porous preform 2, 
there were used, respectively, aluminum alloy of type JIS standard AC4C, 
and aluminum alloy of type JIS standard AC4A. The results were very 
similar to the above and as shown in cross sectional view in FIG. 3; the 
final material produced again contained a large number of NiO particles 
surrounded by silicon shells. Thus, the present inventors had again 
verified that some of the particles of the NiO powder had not been 
completely subjected to the thermite reaction, so that they remained 
unchanged in the final material produced and were not reduced. 
Further, when in another background experiment similar to the one described 
above there was used for infiltration into the porous preform 2, 
substantially pure aluminum containing substantially no silicon admixture, 
upon investigation of the finished product it was confirmed that there 
were substantially no NiO particles left remaining therein, and that 
therefore substantially complete alloying the nickel of said NiO particles 
into the aluminum matrix had occurred along with reduction of said NiO 
particles by a thermite reaction, with of course a quantity of aluminum 
oxide being produced. In fact, the macro composition of the aluminum alloy 
formed in this manner was Al with an admixture of about 10.7% Ni. 
As a result of these tests, the present inventors clarified the fact that, 
when the aluminum alloy used for infiltration into the porous preform has 
a comparatively large content of silicon, despite the structural formation 
of the final product that proceeds by means of a thermite reaction between 
the NiO particles and the aluminum in the aluminum alloy, due to the fact 
that the fine particles of NiO act as nuclei for the formation of silicon 
by crystallization, the is thermite reaction is not necessarily completed, 
and for these reasons there are instances in which complete and proper 
alloying is not achieved. 
The Second Set of Background Experiments 
In this second set of background experiments, seven types of NiO powder 
sample were used, having average particle diameters of approximately, 
respectively, 0.5, 1, 2, 3, 5, 10, and 15 microns. Using in each case as 
the molten material for infiltration a quantity of molten aluminum alloy 
of type JIS standard AC8A, substantially the same process as detailed 
above with regard to the first background experiment was carried out, for 
each such NiO powder sample, using the same quantities of NiO powder and 
other materials in each case. And in each case the resultant Al-Ni alloy 
material was examined, in the same manner as before. 
When the fine structure of the resultant materials, in each of the seven 
test cases, was studied by cutting a cross section thereof and studying it 
under an optical microscope, and was further subjected to exhaustive EPMA 
analysis and X-ray diffraction analysis, it was determined that, when the 
average diameter of the NiO particles was less than about 10 microns, 
there were as before left some of these fine particles of NiO remaining in 
the matrix aluminum alloy 22 which was formed as surrounding the 
reinforcing alumina short fibers 6; and it was again determined that these 
remaining fine NiO particles were surrounded by crystallized silicon 
shells, which had presumably shielded said fine NiO particles from being 
reduced by the thermite reaction. However, it was determined that, if on 
the other hand the diameter of the NiO particles was greater than about 10 
microns, no such problems tended to surface. 
Further, in other background experiments similar to the one described 
above, as the oxide powder for incorporation into the porous preform 2, 
there were used, respectively, Co.sub.3 O.sub.4 powder and Fe.sub.2 
O.sub.3 powder. The results were very similar to the above, and similarly 
indicated that, when the average diameter of the included oxide particles 
was less than about 10 microns, there were a before left some of these 
fine oxide particles remaining in the aluminum alloy which was formed; and 
it was again determined that these remaining fine oxide particles were 
surrounded by crystallized silicon shells, which had presumably shielded 
said fine oxide particles from being reduced by the thermite reaction. 
As a result of these background tests, the present inventors clarified the 
fact that, when the aluminum alloy used for infiltration into the porous 
preform had a comparatively large content of silicon, regardless of the 
species of metallic element of which fine oxide particles were used for 
manufacture of the porous preform 2, when the average particle diameter of 
said oxide particles was less than about 10 microns (assuming a globular 
shape for said oxide particles), this typically caused a satisfactory 
thermite reaction to fail to occur, and a proportion at least of the fine 
oxide particles remained unreduced in the resultant material, and for 
these reasons there were instances in which complete and proper alloying 
was noted achieved. 
DESCRIPTION OF THE PREFERRED EMBODIMENTS 
The present invention will now be described with reference to the various 
sets of preferred embodiments thereof, and with reference to the figures. 
The First Set Of Preferred Embodiments 
The Process 
For elaborating the first set of preferred embodiments of the method for 
manufacturing an aluminum alloy of the present invention, six experiments 
were conducted. Seven samples of each of six types of NiO powder having 
average particle diameters of approximately, respectively, 0.5, 1, 2, 3, 
5, and 10 microns were prepared, thus providing forty-two samples in all, 
and six samples of each of seven types of Al.sub.2 O.sub.3 powder (all 
with melting point approximately 2030.degree. C.) having average particle 
diameters of approximately, respectively, 0.1, 0.5, 1, 2, 3, 5, and 10 
microns were prepared, thus again providing forty-two samples in all. For 
all the forty-two combinations of particle diameters of the NiO powder and 
the Al.sub.2 O.sub.3 powder, approximately 35 grams of the appropriate NiO 
powder and approximately 19.5 grams of the appropriate Al.sub.2 O.sub.3 
powder were taken and were thoroughly mixed together along with 
approximately 33 grams of the same type of alumina short fiber material as 
used in the first set of background experiments described above, and then 
as in said first background experiment set the resultant mixed material 
was pressure formed into a high density block shaped preform like that 
illustrated in FIG. 1 again having dimensions of approximately 100 
mm.times.50 mm.times.20 mm and being of relatively high porosity; this 
preform had density of approximately 0.88 gm/cm.sup.3. 
FIG. 4 shows a cross section of a portion 24 of this high porosity preform, 
as enlarged under an optical microscope. In this figure, the reference 
numeral 26 shows the NiO powder, the reference numeral 28 denotes the 
Al.sub.2 O.sub.3 powder, and the reference numeral 30 denotes the alumina 
short fibers, included in said preform portion 24. 
Next, in each of the forty-two cases, a high pressure infiltration alloying 
process like to that performed in the case of the first set of background 
experiments described above, in each case using a quantity of aluminum 
alloy of type JIS standard AC8A (with a melting point of approximately 
595.degree. C.) as molten metal for infiltration into the interstices of 
the porous preform 2, was performed; in other words, the present inventors 
attempted to form an Al-Ni alloy under conditions and guidelines 
essentially the same as utilized previously. 
The Results 
In substantially the same way as before, the effectiveness of the alloying 
and reduction process were checked by means of X-ray diffraction tests, so 
as to check whether or not complete alloying had been accomplished. The 
results of these tests are presented in Table 1, which is given at the end 
of this specification and before the claims thereof in the interests of 
ease of pagination. 
In this Table, for some particular ones of the tests, the sign "O" is used 
to indicate that no peaks for NiO were found as a result of the X-ray 
diffraction tests in these cases, although peaks for Ni and for NiAl.sub.3 
were determined. This indicates that the NiO particles in the original 
preforms 2 had in these cases been substantially completely reduced and 
alloyed into the aluminum alloy. 
On the other hand, in the Table, for some other particular ones of the 
tests, the sign "X" is used to indicate that no peaks for NiO were found 
as a result of the X-ray diffraction tests in these cases, although peaks 
for Ni and for NiAl.sub.3 were determined. This indicates that in these 
cases some of the NiO particles in the original preforms 2 remained after 
the pressure infiltration process, indicating that said NiO particles had 
not been completely reduced or alloyed into the aluminum alloy. 
Further, by combining the "O" signs in Table 1, it becomes clear that in 
these cases the silicon in the original aluminum alloy, rather than 
crystallizing around the surfaces of the NiO particles as was the case in 
the background experiments detailed above, had instead in these cases 
crystallized around the surfaces of the Al.sub.2 O.sub.3 powder particles, 
thus not causing any problem for the alloying process and instead allowing 
the thermite reduction reaction for the NiO particles to be completed 
satisfactorily. 
It is noted that these cases, which are the satisfactory ones, are 
precisely those ones in which the average particle diameter of the 
Al.sub.2 O.sub.3 powder particles included in the preform 2 was 
substantially less than the average particle diameter of the NiO particles 
included in said preform 2. 
Further Related Tests 
In addition to these tests described above, in other tests similar to the 
ones described above, as the oxide powder for incorporation into the 
porous preform 2, there were used, respectively, Co.sub.3 O.sub.4 powder 
and Fe.sub.2 O.sub.3 powder, instead of the NiO powder used in the 
forty-two tests detailed proximately above; and Al-Co and Al-Fe alloys 
were made in manners similar to the preceding. The results were very 
similar to the above, and similarly indicated that, when the average 
diameter of the included oxide particles (be they NiO particles, Co.sub.4 
O.sub.4 particles, or Fe.sub.2 O.sub.3 particles) included in the high 
porosity preform was less than about 10 microns, provided that other fine 
particles were included in said high porosity preform which had particle 
diameters substantially less than said oxide particles, there was not left 
remaining in the aluminum alloy which was formed any substantial quantity 
of the fine oxide particles which had been surrounded by crystallized 
silicon shells, as had undesirably happened in the case of the background 
experiments as detailed above and which had in those cases presumably 
shielded said fine oxide particles from being reduced by the thermite 
reaction; and on the contrary said crystallized silicon shells had (it is 
hypothesized) tended to form instead on the other fine particles included 
in said high porisity preform, which had acted as preferential nuclei for 
silicon crystallization. Accordingly, it was enabled to be possible to 
manufacture a good, complete, and well integrated alloy of aluminum with 
the metallic material included in the oxide material of the fine 
particles, which were reduced by the thermite reaction which had occurred 
satisfactorily, even though the average particle size of said oxide 
particles was less than about 10 microns (assuming a globular shape for 
said oxide particles), and even though the aluminum alloy used for 
alloying contained a substantial amount of silicon admixtured with it. 
The Second Set Of Preferred Embodiments 
The Process 
For elaborating the second set of preferred embodiments of the method for 
manufacturing an aluminum alloy of the present invention, twelve 
experiments were conducted. A sample of each of seven types of simple 
metallic oxide powder and also a sample of each of five types of compound 
metallic oxide powders were prepared, said twelve powders being of the 
types shown in Table 2 which is given at the end of this specification and 
before the claims thereof in the interests of ease of pagination, and 
having average particle diameters from approximately 1 micron to 
approximately 10 microns as shown in said Table and being prepared in 
quantities as also shown in said Table. Then, each of these twelve powder 
samples was mixed with approximately 19.5 grams of Al.sub.2 O.sub.3 powder 
(all with melting point approximately 2030.degree. C.) having average 
particle diameter substantially less than said sample, along with 
approximately 33 grams of the same type of alumina short fiber material as 
used in the first set of background experiment described above, and then 
as in said first background experiments set the resultant mixed material 
was pressure formed into a high density block shaped preform like the 
preform 2 illustrated in FIG. 1. 
Next, in each of the twelve cases, a high pressure infiltration alloying 
process like to that performed in the case of the first set of background 
experiments described above, in each case again using a quantity of 
aluminum alloy of type JIS standard AC8A (with a melting point of 
approximately 595.degree. C.) as molten metal for infiltration into the 
interstices of the porous perform 2, was performed; in other words, the 
present inventors attempted, by performing a thermite reduction reaction, 
to form an alloy between aluminum and the metallic material or materials 
included in the oxide particles of the preforms 2, under conditions and 
guidelines essentially the same as utilized previously. 
The Results 
In substantially the same way as before, the effectiveness of the alloying 
and reduction process were checked by means of X-ray diffraction tests, so 
as to check whether or not complete alloying had been accomplished. The 
results of these tests were that, in all of these cases, it was verified 
that the silicon in the original aluminum alloy, rather than crystallizing 
around the surfaces of the oxide particles as was the case in the 
background experiments detailed above, had instead in these cases 
crystallized around the surfaces of the Al.sub.2 O.sub.3 powder particles, 
thus not causing any problem for the alloying process and instead allowing 
the thermite reduction reaction for the oxide particles to be completed 
satisfactorily. And it was verified that there was not left remaining in 
the aluminum alloy which was formed any substantial quantity of the fine 
oxide particles, as had undesirably happened in the case of the background 
experiments as detailed above. Accordingly, it was enabled to be possible 
to manufacture a good, complete, and well integrated alloy of aluminum 
with the metallic material or materials included in the oxide material of 
the fine particles, which were reduced by the thermite reaction which had 
occurred satisfactorily, even though the average particle size of said 
oxide particles was less than about 10 microns (assuming a globular shape 
for said oxide particles), and even though the aluminum alloy used for 
alloying contained a substantial amount of silicon admixtured with it. It 
is presumed that these satisfactory results were obtained because in each 
case the average particle diameter of the Al.sub.2 O.sub.3 powder 
particles included in the preform 2 was substantially less than the 
average particle diameter of the oxide particles included in said preform 
2. 
Further Related Tests 
In addition to these tests described above, in other tests similar to the 
ones described above, no admixture of Al.sub.2 O.sub.3 powder particles 
was employed; and aluminum alloys were attempted to be made in manners 
similar to the preceding. The results indicated that in each case there 
was left remaining in the aluminum alloy which was formed substantial 
quantities of the fine oxide particles, which had been surrounded by 
crystallized silicon shells, which had presumably shielded said fine oxide 
particles from being reduced by the thermite reaction. Accordingly, it was 
not possible to manufacture a good, complete, or well integrated alloy of 
aluminum with the metallic material or materials included in the oxide 
material of the fine particles, since the thermite reaction was not able 
to proceed satisfactorily to its conclusion. 
Thus, the present inventors clarified the fact that, regardless of the 
actual material incorporated in the quantity of fine particles of metallic 
oxide which was to be subjected to the reduction thermite reaction, if an 
admixture of even finer particles of another substance is added to the 
high porosity preform which is to be infiltrated in the high pressure 
infiltration alloying process, a complete and satisfactory alloying 
process can be accomplished even though there may be a substantial 
proportion of silicon in the aluminum alloy which is used for the pressure 
infiltration. It may also be inferred from these tests that the form of 
the fine oxide particles, while they were powder particles in the above 
preferred embodiments discussed, may in other cases be different; the fine 
oxide particles could be non continuous fibers, cut powder, ultra thin 
flakes, or of some other shape. 
The Third Set Of Preferred Embodiments 
The Process 
For elaborating the third set of preferred embodiments of the method for 
manufacturing an aluminum alloy of the present invention, the following 
experiments were conducted. A sample of each of fourteen types of material 
for admixture was prepared, to be used instead of the Al.sub.2 O.sub.3 
powder utilized in the case of the second preferred embodiments described 
above: these materials for admixture are described in detail in Table 3, 
which is given at the end of this specification and before the claims 
thereof in the interests of ease of pagination, and it will be seen that 
some of these materials for admixture were powder materials, while others 
were whisker materials. These materials for admixture were prepared in 
quantities as also shown in said Table. Then, in order, each of these 
material samples for admixture was mixed with a quantity of one of the 
oxide powders which were detailed in Table 2 with regard to the second set 
of preferred embodiments of the process for manufacturing an aluminum 
alloy of the present invention, and processes substantially the same as 
utilized in said second preferred embodiment set were conducted, so as in 
each case to form an alloy between aluminum and the metallic material or 
materials included in the oxide particles, by a similar type of thermite 
reduction process, under conditions and guidelines essentially the same as 
utilized previously. 
The Results 
In substantially the same was as before, the effectiveness of these 
alloying and reduction processes were checked by means of X-ray 
diffraction tests, so as to check whether or not complete alloying had 
been accomplished. The results of these tests were that, in all of these 
cases, it was vertified that the silicon in the original aluminum alloy, 
rather than crystallizing around the surfaces of the oxide particles as 
was the case in the background experiments detailed above, had instead in 
these cases crystallized around the surfaces of the admixture powder 
particles or whiskers, thus not causing any problem for the alloying 
process and instead allowing the thermite reduction reaction for the oxide 
particles to be completed satisfactorily. And it was verified that there 
was not left remaining in the aluminum alloy which was formed any 
substantial quantity of the fine oxide particles, as had undesirably 
happened in the case of the background experiments as detailed above. 
Accordingly, it was again enabled to be possible to manufacture a good, 
complete, and well integrated alloy of aluminum with the metallic material 
or materials included in the oxide material of the fine particles, which 
were reduced by the thermite reaction which had occurred satisfactorily, 
even though the average particle size of said oxide particles was less 
than about 10 microns (assuming a globular shape for said oxide 
particles), and even though the aluminum alloy used for alloying contained 
a substantial amount of silicon admixtured with it. It is presumed that 
these satisfactory results were obtained because in each case the average 
particle diameter or corresponding dimensional parameter of the admixtured 
powder particles or whiskers included in the preform was substantially 
less than the average particle diameter of the oxide particles included in 
said preform. 
Thus, the present inventors clarified the fact that, regardless of the 
actual details of the fine structure of the finely divided material 
incorporated in the quantity of admixed other substance which was added to 
the high porisity preform which was to be infiltrated in the high pressure 
infiltration alloying process, a complete and satisfactory alloying 
process can be accomplished even though there may be a substantial 
proportion of silicon in the aluminum alloy which is used for the pressure 
infiltration. It may also be inferred from these tests that the admixtured 
substance, so long as it remains unreacted and does not become dissolved 
into trace elements within the aluminum alloy, may be a compound--either a 
stable compound that does not react with aluminum or a compound that can 
react with aluminum--or any desired substance, such as for example a 
metallic material. Further, the form of the admixtured substance may in 
various cases be different from the powder form; said admixtured substance 
may be in the form of short non continuous fibers such as whiskers, or may 
be in some other form. 
The Fourth Set Of Preferred Embodiments 
The Process 
For elaborating the fourth set of preferred embodiments of the method for 
manufacturing an aluminum alloy of the present invention, various sets of 
experiments were conducted. In each such experiment, a quantity of 
approximately 35 grams of NiO powder having average particle diameter of 
approximately 2 microns was mixed with approximately 33 grams of the same 
type of alumina short fiber material as used in the various sets of 
experiments described above, and this mixture was then further mixed with, 
in the various different cases, various different amounts of a type of 
Al.sub.2 O.sub.3 powder having average particle diameter of approximately 
0.5 microns, thus providing various mixed samples. In each case, the 
resultant mixed material was pressure formed into a high density block 
shaped preform like that illustrated in FIG. 1, and was subjected to a 
high pressure infiltration alloying process like to that performed in the 
case of the first set of background experiments described above, using 
quantities of aluminum alloy of various different types and various 
different JIS standards, i.e. containing various different amounts of 
silicon, as molten metal for infiltration into the interstices of the 
porous preforms. This was done to determine, for each case of a particular 
quantity of silicon present in the aluminum alloy which was pressure 
infiltrated into the interstices of the preforms, what was the minimum 
quantity of admixtured Al.sub.2 O.sub.3 powder which was sufficient for 
providing complete alloying without any portions of the NiO oxide 
particles remaining in the finished product. 
The Results 
In substantially the same way as before, the effectiveness of the alloying 
the reduction process were checked by means of X-ray diffraction tests, so 
as to check whether or not complete alloying had been accomplished. The 
results of these tests are presented in Table 4, which is again given at 
the end of this specification and before the claims thereof in the 
interests of ease of pagination. 
In this Table, for each type of aluminum alloy, there is shown the minimum 
quantity of admixtured Al.sub.2 O.sub.3 powder which was sufficient for 
providing complete alloying without any portions of the NiO oxide 
particles remaining in the finished product, in order to ensure that the 
silicon in the original aluminum alloy, rather than crystallizing around 
the surfaces of the NiO particles as was the case in the background 
experiments detailed earlier in this specification, should instead 
crystallize around the surfaces of the Al.sub.2 O.sub.3 powder particles, 
thus not causing any problem for the alloying process and instead allowing 
the thermite reduction reaction for the NiO particles to be completed 
satisfactorily. It may be seen from this Table that, when the aluminum 
alloy conformed to JIS standard AC1A, i.e. had a silicon content of 
approximately 1%, no particular amount of admixtured Al.sub.2 O.sub.3 
powder was required, since in fact no problem of silicon crystallization 
occurred even if no admixtured Al.sub.2 O.sub.3 powder at all was 
utilized; and it is considered that this is because in this case the 
silicon content was less than the solution limit for silicon of 
alpha-Al.sub.2 O.sub.3 (which is approximately 1.65% by weight). Complete 
alloying could therefore be achieved satisfactorily, even if no admixtured 
Al.sub.2 O.sub.3 powder at all was utilized. This illustrates the point 
that the process for manufacturing an aluminum alloy of the present 
invention is particularly beneficial when the silicon content in the 
aluminum alloy utilized is greater than about 1.65% by weight. 
Moreover from Table 4 it will be understood that, the greater is silicon 
content in the aluminum alloy utilized, the greater is the amount of 
admixtured Al.sub.2 O.sub.3 powder required, in order to provide complete 
alloying without any portions of the NiO oxide particles remaining in the 
finished product. Therefore, it is seen that, according to a particular 
specialization of the process for manufacturing an aluminum alloy of the 
present invention, it is desirable to adjust the amount of the added 
material such as Al.sub.2 O.sub.3 powder, according to the silicon content 
of the aluminum alloy utilized. 
The required minimum quantities of admixtured Al.sub.2 O.sub.3 powder which 
were just sufficient for providing complete alloying without any portions 
of the NiO oxide particles remaining in the finished product, and which 
are presented in Table 4, are in fact precisely the quantities of Al.sub.2 
O.sub.3 powder which are necessary to bring about a complete reaction of 
the NiO powder. However, even if the quantity of Al.sub.2 O.sub.3 powder 
actually utilized is below the required minimum value for complete 
alloying without any portions of the NiO oxide particles remaining in the 
finished product, nevertheless it is clear that the admixture of such an 
inadequate amount of Al.sub.2 O.sub.3 powder will still have the 
beneficial effect of promoting the reaction. The present inventors also 
verified that, when the quantity of admixtured Al.sub.2 O.sub.3 powder was 
increased, the quantity of NiO powder that was reacted also increased. 
Particularly in cases wherein the quantity of NiO powder utilized and also 
the silicon content of the aluminum alloy utilized are both relatively 
small, the present inventors verified the fact that, even if the quantity 
of Al.sub. 2 O.sub.3 powder contained in the high porosity preform is only 
a small quantity such as a trace quantity, a very clear reaction promotion 
effect can be obtained. 
Conclusion 
In the experiments and preferred embodiments of the process for 
manufacturing an aluminum alloy of the present invention described above, 
in the high porosity preforms that were manufactured for being subjected 
to high pressure infiltration alloying, in addition to the oxide material 
utilized for being reduced to provide the material to be alloyed with the 
aluminum alloy, and in addition to the finely divided material such as 
Al.sub.2 O.sub.3 powder that was used for providing crystallization nuclei 
for the silicon contained in the aluminum alloy, there were additionally 
contained alumina short fibers. However, these alumina short fibers are 
not considered to have made any substantial contribution to the oxygen 
reduction reaction by which the alloying was accomplished, but only 
functioned as reinforcing material for the preform block and then for the 
finally produced alloy material, which thus finally functioned as a matrix 
metal in cooperation with said alumina short fibers. The alumina short 
fibers, in other words, fulfilled the following quite distinct functions: 
(a) they provided a skeleton material for the high porosity preform block, 
and functioned for helping with the adjustment of the density of the oxide 
material and the admixtured material such as Al.sub.2 O.sub.3 powder, and 
further were helpful with the event distribution of said oxide material 
and said admixtured material; and: 
(b) they functioned to reinforce the finally alloyed aluminum alloy with 
reinforcing material. 
Therefore, the type, size, shape, and quantity of the added fiber material 
such as short alumina fiber material that is utilized, in addition to the 
oxide material utilized for being reduced to provide the material to be 
alloyed with the aluminum alloy, and in addition to the finely divided 
material such as Al.sub.2 O.sub.3 powder that is used for providing 
crystallization nuclei for the silicon contained in the aluminum alloy, do 
not make any direct contribution to the process for manufacturing an 
aluminum alloy of the present invention. Any type of reinforcing fibers, 
such as for example alumina-silica short fibers, silicon carbide fibers, 
or carbon fibers might be used, instead of the alumina short fibers that 
were described in, for example, the second set of preferred embodiments. 
Furthermore, this additional reinforcing material does not have to be 
provided in the form of fibers; it could take the form of powder particles 
or ultra thin flake material, and moreover need not be provided at all: it 
would be perfectly possible to form the high porosity preforms without the 
use of any such reinforcing material, which is helpful for providing body 
but however is not essential. In the case of the fourth set of preferred 
embodiments described above, for example, if silicon carbide whiskers and 
silicon nitride whiskers are used instead of alumina short fibers, not 
only was complete alloying achieved, but these whiskers acted as 
reinforcing fibers, and the aluminum alloy that resulted from the alloying 
process was manufactured in situ as the matrix metal of a fiber reinforced 
metallic compound material. 
Although the present invention has been shown and described in terms of the 
preferred embodiments thereof and in terms of the background experiments 
related thereto, and with reference to the appended drawings, it should 
not be considered as being particularly limited thereby, since the details 
of any particular embodiment, or of the drawings, could be varied without, 
in many cases, departing from the ambit of the present invention. 
Accordingly, the scope of the present invention is to be considered as 
being delimited, not by any particular perhaps entirely fortuitous details 
of the disclosed preferred embodiments, or of the drawings, but solely by 
the scope of the accompanying claims, which follow after the Tables. 
TABLE 1 
______________________________________ 
Al.sub.2 O.sub.3 powder 
NiO powder average 
average particle 
particle diameter 
diameter 0.5 1 2 3 5 10 
______________________________________ 
0.1 O O O O O O 
0.5 X O O O O O 
1 X X O O O O 
2 X X X O O O 
3 X X X X O O 
5 X X X X X O 
10 X X X X X X 
______________________________________ 
TABLE 2 
______________________________________ 
Oxide Average particle 
Quantity 
material diameter (microns) 
used (gm) 
______________________________________ 
Ta.sub.2 O.sub.5 
5 44 
CoO 3 29 
SnO 4 32 
Fe.sub.2 O.sub.3 
5 26 
WO.sub.3 5 36 
V.sub.2 O.sub.5 
8 17 
Mn.sub.3 O.sub.4 
10 24 
Fe.sub.2 O.sub.3.MnO.sub.2 
5 26 
Fe.sub.2 O.sub.3.NiO 
2 31 
ZnO.PbO 5 34 
CoO.NiO 1 32 
SnO.V.sub.2 O.sub.5 
4 25 
______________________________________ 
TABLE 3 
______________________________________ 
Admixtured Melting Average particle 
Quantity 
material point diameter (microns) 
used (gm) 
______________________________________ 
SiO.sub.2 powder 
1610.degree. C. 
0.3 12 
MgO powder 2800.degree. C. 
0.2 18 
TiO.sub.2 powder 
1670.degree. C. 
0.2 20 
SiC whiskers 
(note 1) (note 3) 10 
VC powder 3123.degree. C. 
0.1 29 
W.sub.2 C powder 
2800.degree. C. 
0.1 86 
Si.sub.3 N.sub.4 whiskers 
(note 2) (note 4) 10 
BN powder 2730.degree. C. 
0.2 12 
Fe powder 1536.degree. C. 
0.5 39 
Ni powder 1453.degree. C. 
0.5 45 
Ti powder 1680.degree. C. 
0.5 24 
Co powder 1492.degree. C. 
0.3 45 
Fe.sub.2 O.sub.3 powder 
1597.degree. C. 
0.1 26 
NiO powder 1984.degree. C. 
0.2 35 
______________________________________ 
note 1: 2700.degree. C. (decomposition) 
note 2: 1900.degree. C. (decomposition) 
note 3: average fiber diameter 0.2 microns, average fiber length 100 
microns 
note 4: average fiber diameter 0.3 microns, average fiber length 20 
microns 
TABLE 4 
______________________________________ 
Aluminum alloy 
Si content JIS standard Al.sub.2 O.sub.3 powder 
(wt %) satisfied quantity required 
______________________________________ 
1% AC1A (none required) 
2% (none) 1 gram or more 
5% AC4D 6 grams or more 
7% AC4C 9 grams or more 
10% AC4A 15 grams or more 
12% AC8A 18 grams or more 
______________________________________