Compacted and consolidated aluminum-based alloy material and production process thereof

The present invention provides a compacted and consolidated aluminum-based alloy material which has been obtained by compacting and consolidating a rapidly solidified material having a composition represented by the general formula: Al.sub.a Ni.sub.b X.sub.c wherein X is one or two elements selected from Zr and Ti and a, b and c are, in atomic percentages, 87.5.ltoreq.a.ltoreq.92.5, 5 .ltoreq.b.ltoreq.10, and 0.5.ltoreq.c.ltoreq.5; and a production process comprising melting a material of the above composition; quenching and solidifying the resultant molten material into powder or flakes; compacting, compressing, forming and consolidating the powder or flakes by conventional plastic working. The consolidated material of the present invention has. elongation (toughness) sufficient to withstand secondary working, even when secondary working is applied. Moreover, the material allows the secondary working to be performed easily while retaining the excellent properties of its raw material.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates to a compacted and consolidated 
aluminum-based alloy material having not only a high strength but also an 
elongation sufficient to withstand practically-employed working 
operations, and also to a process for the production of the material. 
2. Description of the Prior Art 
Aluminum-based alloys having high strength and high heat resistance have 
been produced to date by liquid quenching or the like. In particular, the 
aluminum alloys disclosed in Japanese Patent Application Laid-Open (Kokai) 
No. HEI 1-275732 and obtained by liquid quenching are amorphous or 
microcrystalline and are excellent alloys having a high strength, high 
heat resistance and high corrosion resistance. 
The conventional aluminum-based alloys referred to above exhibit a high 
strength, high heat resistance and high corrosion resistance and are 
excellent alloys. When they are each obtained in the form of powder or 
flakes by liquid quenching and the powder or flakes are then processed or 
worked as a raw material in one way or another to obtain a final product, 
in other words, the powder or flakes are converted into a final product by 
primary processing or working, they exhibit an excellent processability or 
workability. However, to form the powder or flakes as a raw material into 
a consolidated material and then to work the consolidated material, 
namely, to subject the consolidated material to secondary working, there 
is still room for improvement in their workability and also in the 
retention of their excellent properties after working. 
SUMMARY OF THE INVENTION 
An object of the present invention is, therefore, to provide a compacted 
and consolidated aluminum-based alloy material having a particular 
composition that permits easy working upon subjecting the material to 
secondary working (extrusion, cutting, forging or the like) and allows the 
retention of the excellent properties of the material even after working. 
The present invention provides a compacted and consolidated aluminum-based 
alloy material which has been obtained by compacting and consolidating a 
rapidly solidified material having a composition represented by the 
general formula: Al.sub.a Ni.sub.b X.sub.c, wherein X is one or two 
elements selected from Zr and Ti and a, b and c are, in atomic 
percentages, 87.5.ltoreq.a.ltoreq.92.5, 5.ltoreq.b.ltoreq.10, and 
0.5.ltoreq.c.ltoreq.5. 
More preferably, the above consolidated material is formed of a matrix of 
aluminum or a supersaturated aluminum solid solution, whose mean crystal 
grain size is 40-1000 nm, and grains made of a stable or metastable phase 
of various intermetallic compounds formed of the matrix element and the 
other alloying elements and/or of various intermetallic compounds formed 
of the other alloying elements are distributed evenly in the matrix, and 
the intermetallic compounds have a mean grain size of 10-800 nm. 
The present invention also provides a process in which a material 
represented by the above-specified general formula is molten and then 
quenched and solidified into powder or flakes and, thereafter, the powder 
or flakes are compacted and then compressed, formed and consolidated by 
conventional plastic working. In this case, the powder or flakes as the 
raw material are required to be amorphous, a supersaturated solid 
solution, or microcrystalline such that the mean crystal grain size of the 
matrix is not greater than 1000 nm and the mean grain size of 
intermetallic compounds is 1-800 nm; or to be in a mixed phase thereof. 
When the raw material is amorphous, it can be converted into such a 
microcrystalline or mixed phase as defined above by heating it to 
50.degree. C. to 400.degree. C. upon compaction. 
The term "conventional plastic working" as used herein should be 
interpreted in a broad sense and should embrace pressure forming 
techniques and powder metallurgical techniques.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
The proportions a, b and c are limited, in atomic percentages, to the 
ranges of 87.5-92.5%, 5-10% and 0.5-5% respectively, in the above general 
formula, because the alloys within the above ranges have higher strength 
than conventional (commercial) high-strength aluminum alloys over the 
temperature range of from room temperature to 200.degree. C. and are also 
equipped with a ductility sufficient to withstand practically-employed 
working. 
In the consolidated alloy material according to this invention, Ni is an 
element having relatively small ability to diffuse into the A matrix and 
is distributed as fine intermetallic compounds in the Al matrix. Ni is 
therefore effective not only in strengthening the matrix but also in 
inhibiting growth of crystal grains. In other words, Ni improves the 
hardness, strength and rigidity of the alloy to significant extents, 
stabilizes the microcrystalline phase at elevated temperatures, to say 
nothing of room temperature, and imparts heat resistance. 
On the other hand, element X stands for one or two elements selected from 
Zr and Ti. It is an element having a small ability to diffuse in the Al 
matrix. It forms various metastable or stable intermetallic compounds, 
thereby contributing to the stabilization of the microcrystalline 
structure. 
In the consolidated aluminum-based alloy material according to the present 
invention, the mean crystal grain size of the matrix is limited to the 
range of 40-1000 nm for the following reasons. Mean crystal grain sizes of 
the matrix smaller than 40 nm are too small to provide a sufficient 
ductility, despite providing a high strength. To obtain ductility required 
for conventional working, a mean crystal grain size of the matrix of at 
least 40 nm is therefore needed. If the mean crystal grain size of the 
matrix exceeds 1000 nm, on the other hand, the strength drops abruptly, 
thereby making it impossible to obtain a consolidated material having a 
high strength. To obtain a consolidated material having a high strength, a 
mean crystal grain size of the matrix not greater than 1000 nm is needed. 
Further, the mean grain size of the intermetallic compounds is limited to 
the range of 10-800 nm because intermetallic compounds with a mean grain 
size outside the above range cannot serve as strengthening elements for 
the Al matrix. If the intermetallic compounds have a mean grain size 
smaller than 10 nm, they do not contribute to the strengthening of the Al 
matrix and, if they are present in the state of a solid solution in the 
matrix in an amount greater than that needed, there is the potential 
problem of embrittlement. Mean grain sizes greater than 800 nm, on the 
other hand, result in unduly large grains distributed in the Al matrix so 
that the Al matrix cannot retain its strength and the intermetallic 
compounds cannot serve as strengthening elements. The restriction to the 
above ranges, therefore, leads to improvements in Young's modulus, 
high-temperature strength and fatigue strength. 
In the consolidated aluminum-based alloy material according to the present 
invention, its mean crystal grain size and the dispersion state of the 
intermetallic compounds can be controlled by choosing suitable conditions 
for its production. The mean crystal grain size of the matrix and the mean 
grain size of the intermetallic compounds should be controlled to be small 
where an importance is placed on the alloy's strength. In contrast, they 
should be controlled to be large where the alloy's ductility is considered 
important. In this manner, it is possible to obtain consolidated 
aluminum-based alloy materials which are suited for various purposes, 
respectively. 
Further, the control of the mean crystal grain size of the matrix to the 
range of 40-1000 nm makes it possible to impart properties so that the 
resulting material can be used as an excellent superplastic working 
material. 
The present invention will hereinafter be described specifically on the 
basis of the following examples. 
EXAMPLE 1 
Aluminum-based alloy powders having desired compositions (Al.sub.92-x 
Ni.sub.8 Zr.sub.x) and (Al.sub.97.5-x Ni.sub.x Zr.sub.2.5) were produced 
by a gas atomizing apparatus. Each aluminum-based alloy powder so produced 
was filled in a metal capsule and, while being degassed, was formed into 
an extrusion billet. The billet was extruded at 200.degree.-550.degree. C. 
through an extruder. Mechanical properties (tensile strength and 
elongation) of the extruded materials (consolidated materials) obtained 
under the above production conditions are shown in FIG. 1 and FIG. 2, 
respectively. 
As is depicted in FIG. 1, it is understood that the tensile strength of the 
consolidated material at room temperature increased at Ni contents of 5 
at.% and higher but abruptly dropped at Ni contents higher than 10 at.%. 
It is also envisaged that the elongation dropped at Ni contents higher 
than 10 at.%, whereby it is seen that the minimum elongation (2%) required 
for ordinary working operations can be obtained at an Ni content of 10 
at.% or lower. 
As is illustrated in FIG. 2, it is seen that the tensile strength of the 
consolidated material at room temperature increased at Zr contents of 0.5 
at.% or higher but abruptly dropped at Zr contents higher than 5 at.%. It 
is also envisaged that the elongation dropped at Zr contents higher than 5 
at.%, whereby it is seen that the minimum elongation (2%) required for 
ordinary working can be obtained at a Zr content of 5 at.% or lower. For 
the sake of comparison, the tensile strength of a conventional 
high-strength aluminum-based alloy material (an extruded material of 
duralumin) was also measured at room temperature. As a result, the tensile 
strength was found to be about 650 MPa. It is also understood from this 
value that the above consolidated material of the present invention had an 
excellent strength at Ni and Zr contents in the above ranges. 
With respect to extruded materials (consolidated materials) obtained under 
the above production conditions, their mechanical properties (tensile 
strength and elongation) were investigated at 200.degree. C. or lower 
after they were held at 200.degree. C. for 100 hours. The results are 
diagrammatically shown in FIG. 3 and FIG. 4, respectively. 
As is indicated in FIG. 3, it is understood that the tensile strength at 
200.degree. C. abruptly dropped at Ni contents less than 5 at.% and 
gradually dropped when the Ni content exceeded 10 at.%. In contrast, the 
elongation remained at a large value over the entire range of the Ni 
content. 
As is shown in FIG. 4, it is understood that the tensile strength at 
200.degree. C. abruptly dropped at Zr contents lower than 0.5 at.% and 
gradually dropped when the Zr content exceeded 5 at.%. In contrast, the 
elongation remained at a large value over the entire range of the Zr 
content. 
For the sake of comparison, the tensile strength of the conventional 
high-strength aluminum-based alloy material (an extruded material of 
duralumin) was also measured at 200.degree. C. As a result, its tensile 
strength was found to be about 200 MPa. From this value, it is understood 
that the consolidated materials according to the present invention are 
excellent in strength at 200.degree. C. 
EXAMPLE 2 
Extruded materials (consolidated materials) having the various compositions 
shown in Table I were produced in a similar manner to Example 1. Their 
mechanical properties (tensile strength, Young's modulus, hardness) at 
room temperature were investigated. The results are also presented in 
Table 1. It is to be noted that the minimum elongation (2%) required for 
ordinary working was obtained by all the consolidated materials shown in 
Table 1. 
It is understood from Table 1 that the alloys of the present invention have 
excellent properties with respect to tensile strength, Young's modulus and 
hardness. 
The Young's modulus of the conventional high-strength aluminum-based alloy 
material (an extruded material of duralumin) is about 70 (GPa). In 
comparison with conventional material, the consolidated materials 
according to the present invention have been found to exhibit the 
advantages that their deflection and deformation are smaller under the 
same load. 
TABLE 1 
__________________________________________________________________________ 
Tensile 
Young's 
Composition (at %) 
strength 
Modulus 
Hardness 
Al Ni Ti, Zr (MPa) 
(GPa) 
(Hv) 
__________________________________________________________________________ 
Invention Sample 1 
Balance 
10 Zr = 1 928 99 223 
Invention Sample 2 
Balance 
9 Zr = 4 983 107 235 
Invention Sample 3 
Balance 
9 Zr = 2 945 95 217 
Invention Sample 4 
Balance 
8 Zr = 4.5 950 104 200 
Invention Sample 5 
Balance 
8 Zr = 3.6 970 103 212 
Invention Sample 6 
Balance 
7 Zr = 3 920 91 192 
Invention Sample 7 
Balance 
6 Zr = 0.5 701 89 152 
Invention Sample 8 
Balance 
5 Zr = 5 742 97 161 
Invention Sample 9 
Balance 
5 Zr = 3 715 87 155 
Invention Sample 10 
Balance 
10 Ti = 2 900 92 217 
Invention Sample 11 
Balance 
9 Ti = 3 933 97 224 
Invention Sample 12 
Balance 
8 Ti = 4 969 102 232 
Invention Sample 13 
Balance 
8 Ti = 0.5 908 89 197 
Invention Sample 14 
Balance 
7 Ti = 2 848 82 184 
Invention Sample 15 
Balance 
6 Ti = 5 788 88 171 
Invention Sample 16 
Balance 
5 Ti = 3 747 91 162 
Invention Sample 17 
Balance 
8 Zr = 2, Ti = 1.5 
933 105 224 
Invention Sample 18 
Balance 
7 Zr = 1, Ti = 1 
899 92 195 
Invention Sample 19 
Balance 
6 Zr = 3, Ti = 2 
816 90 177 
Invention Sample 20 
Balance 
5 Zr = 1.5, Ti = 2 
686 86 149 
__________________________________________________________________________ 
Consolidated aluminum-based alloy materials according to the present 
invention have an excellent elongation (toughness) so they can withstand 
secondary working when the secondary working is applied. The secondary 
working can therefore be performed with ease while retaining the excellent 
properties of the raw materials as they are. Owing to the inclusion of at 
least one of Zr and Ti as the element X, the consolidated aluminum-based 
alloy materials according to the present invention have a large specific 
strength and, therefore, are useful as high specific-strength materials. 
In addition, such consolidated materials can be obtained by a simple 
process, that is, by simply compacting powder or flakes, which have been 
obtained by quench solidification, and then subjecting the thus-compacted 
powder or flakes to plastic working.