Note: Descriptions are shown in the official language in which they were submitted.
oo~~ ~0 4r
-1 -
AMORPHOUS ALUMINUM ALLOYS
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to novel amorphous
aluminum-valve metal alloys with special
characteristics such as high corrosion resistance, high
wear resistance and considerable toughness, which can
be used industrial plants such as chemical plants as
well as various fields of human life.
2. Description of the Prior Art
Since Ti and Zr are corrosion resistant metals,
the A1 alloys with Ti and/or Zr are expected to possess
a high corrosion resistance. However, various compound
phases exist in their crystalline alloys prepared by
conventional casting methods and hence the solubility
range of Ti and/or Zr in A1 is narrow.
On the other hand, Ti, Zr, Nb, Ta, Mo and W belong
to refractory metals. Melting points of Nb, Ta, Mo and
W are higher than the boiling point of A1. It is,
therefore, difficult to apply conventional casting
methodsfor production of A1-Ti, A1-Zr and A1-Ti-Zr
alloys with Nb, Ta, Mo and W. If these alloys are
successfully prepared not as heterogeneous crystalline
alloys but as homogeneous amorphous alloys, the alloys
have a bright future prospect as novel metallic
materials.
Most of the passive films, which can protect
metallic materials in mild environments, suffer break
down in hydrochloric acids. Because of severe
y~~~~ '~A
-2-
corrosiveness of hydrochloric acids, there are no
metallic materials which are corrosion resistant in
hydrochloric acids. Currently used aluminum alloys are
no exception.
In view of the above-foregoing, there has been a
strong demand for further new metallic materials which
can he used in such severe environments, that corrode
almost all currently used metallic material.
SUM MARY OF THE INVENTION
It is an objective of the present invention to
provide an aluminum-valve metal alloy, which is hardly
produced by conventional methods including melting, and
which is not a heterogeneous crystalline alloy but an
amorphous alloy having special characteristics such as
high corrosion resistance, high wear resistance and
considerable toughness.
The objective of the invention is achieved by an
amorphous A1 alloy with Ti and/or Zr as essential
components.
According to the present invention, the following
alloys are provided:
(1) An amorphous aluminum-valve metal alloy with
special characteristics such as high corrosion
resistance, high wear resistance and considerable
toughness, which consists of 40-60 ate of Ti, balance
being substantially A1.
(2) An amorphous aluminum-valve metal alloy with
special characteristics such as high corrosion
resistance, high wear resistance and considerable
toughness, which consists of less than 5 ate of at
least one element selected from the group of Mo, W, Ta
and Nb and 40-60 ate of the sum of Ti and at least one
a_
a
-3-
element selected from the group of Mo, W, Ta and Nb,
balance being substantially A1.
(3) An amorphous aluminum-valve metal alloy with
special characteristics such as high corrosion
resistance, high wear resistance and considerable
toughness, which consists of 40-75 ate of Zr, balance
being substantially A1.
(4) An amorphous aluminum-valve metal~~lloy with
special characteristics such as high corrosion
resistance, high wear resistance and considerable
toughness, which consists of at least 5~at~ of Zr and
40-75 ate of the sum of Zr and Ti, balance being
substantially A1.
(5) An amorphous aluminum-valve metal alloy with
special characteristics such as high corrosion
resistance, high wear resistance and considerable
toughness, which consists of less than 5 ate of at
least one element selected from the group of Mo, W, Ta
and Nb and 40-75 at$ of the sum of Zr and at least one
element selected from the group of Mo, W, Ta and Nb,
balance being substantially Al.
BRIEF DESCRIPTION OF THE DRAWINGS
FIGS. 1 and 2 show apparatuses for preparing an
alloy of the present invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
The present invention aims to provide novel
amorphous aluminum alloys of specific characteristics
such as high corrosion resistance, high wear resistance
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_.
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and considerable toughness.
It is generally known that an alloy has a
crystalline structure in the solid state. However, an
alloy having a specific composition becomes amorphous
by prevention of the formation of long-range order
structure during solidification through, for example,
rapid solidification from the liquid state, sputter
deposition or plating under the specific conditions; or
by destruction of the long-range order structure of the
solid alloy through ion implantation which is also
effective for supersaturation with necessary elements.
The amorphous alloy thus formed is a homogeneous single
phase supersaturated solid solution containing
sufficient amounts of various alloying elements
beneficial in providing specific characteristics, such
as high corrosion resistance, high mechanical strength
and high toughness.
The present inventors carried out a series of
searches and directed their attention to the outstanding
properties of amorphous alloys. They found that
amorphous alloys consisting of metals having high
melting points and metals having low melting points can
be prepared by sputter deposition method which does not
require mixing of metallic elements by melting.
Furthermore, the present inventors found that those
alloys possess extremely high corrosion resistance due
to formation of protective surface films by spontaneous
passivation even in very corrosive acids having a poor
oxidizing power such as hydrochloric acids.
The U.S. patent application serial No. 07/183,981
consists of the following 6 claims:
1. An amorphous aluminum-refractory metal alloy
-5-
with special characteristics such as high corrosion
resistance, high wear resistance and considerable
toughness, which consists of 7-75 ate of at least one
element selected from the group of Ta and Nb, with
balance being substantially A1.
2. An amorphous aluminum-refractory metal alloy
with special characteristics such as high corrosion
resistance, high wear resistance and considerable
toughness, which consists of at :Least 5 ate of at least
one element selected from the group of Ta and Nb and 7-
75 ate of the sum of at least one element selected from
the group of Ta and Nb and at least one element
selected from the group of Ti and Zr, with balance
being substantially A1.
3. An amorphous aluminum-r~sfractory metal alloy
with special characteristics such as high corrosion
resistance, high wear resistance and considerable
toughness, which consists of 7-50 ate of at least one
element selected from the group of Mo and W, with
balance being substantially A1.
4. An amorphous aluminum-refractory metal alloy
with special characteristics such as high corrosion
resistance, high wear resistance and considerable
toughness, which consists of at least 5 ate of at least
one element selected from the group of Mo and W and 7-
50 ate of the sum of at least one element selected from
the group of Mo and W and at least one element selected
from the group of Ti and Zr, with balance being
substantially A1.
5. An amorphous aluminum-refractory metal alloy
with special characteristics such as high corrosion
resistance, high wear resistance and considerable
toughness, which consists of less than 50 ate of at
least one element selected from the group of Mo and W
..
-6-
and 7-75 ate of the sum of at least one element
selected from the group of Mo and W and at least one
element selected from the group of Ta and Nb, with
balance being substantially Al.
6. An amorphous aluminum-refractory metal alloy
with special characteristics such as high corrosion
resistance, high wear resistance and considerable
toughness, which consists of less than 50 at~s of at
least one element selected from the group of Mo and W,
at least 5 at$ in the sum of at least one element
selected from Ta and Nb and at least one element
selected from Mo and W and 7-75 ate in total of
elements in three groups, that is, at least one element
selected from the group of Ta and Nb, at least one
element selected from the group of Mo and W, and at
least one element selected from the group of Ti and Zr,
with balance being substantially Al.
The present inventors further continued the
investigations and directed their attention to the
outstanding properties of amorphous alloys. They found
that sputter deposition enables the production of the
amorphous A1 alloys containing Ti and/or Zr as the
maj or alloying elements and furthermore, the amorphous
A1 alloys containing Ti and/or Zr as the major alloying
elements and refractory metals such as Mo, W, Ta and Nb
as the minor alloying elements, without requiring
mixing of these metallic elements by melting.
Furthermore, the present inventors found that these
alloys possess extremely high corrosion resistance due
to formation of protective surface films by spontaneous
passivation even in very corrosive acids having a poor
oxidizing power such as hydrochloric acids. The alloys
of the present invention has been accomplished on the
basis of this finding.
Table 1 shows the components and compositions of
the alloys set forth in Claims.
Table 1
(atomic
Ti Zr Mo, W, Ta and Nb (*1) A1(*2)
40-60 Balance
40-60 (*3) less than 5 Balance
40-75 Balance
40-75 (*4) at least 5 Balance
40-75 (*5) less than 5 Balance
*1 : At least one element selected from the group of
Mo, W, Ta and Nb.
*2: Substantially Al.
*3: The sum of Ti and at least one element selected
from the group of Mo, W, Ta and Nb.
*4: The sum of Ti and Zr.
*5: The sum of Zr and at least one element selected
from the group of Mo, W, Ta and Nb.
The amorphous alloys produced by sputter
deposition are single-phase alloys in which the
alloying elements exist in a state of uniform solid
solution. Accordingly, they form an extremely uniform
and highly corrosion-resistant protective passive film
in a poorly oxidizing environment.
Metallic materials are readily dissolved in a
poorly oxidizing very aggressive hydrochloric acid.
Therefore, the metallic materials intended for use in
_g_
such an environment should have an ability to form a
stable protective passive film. This objective is
achieved by an alloy containing effective elements as
much as necessary. However, it is not desirable to add
various alloying elements in large quantities to a
crystalline metal, because the resulting alloys is of a
multiple phase mixture, with each phase having
different chemical properties, and is not so'
satisfactory in corrosion resistance as intended.
Moreover, the chemical heterogeneity is rather harmful
to corrosion resistance.
By contrast, the amorphous alloys of this
invention are of homogeneous solid solution.
Therefore, they homogeneously contain effective
elements as much as required to form uniformly a stable
passive film. Owing to the formation of this uniform
passive film, the amorphous alloys of this invention
exhibit a sufficiently high corrosion resistance.
In other words, metallic materials to withstand
poorly oxidizing hydrochloric acids should form a
uniform, stable passive film in such an environment.
Alloys of amorphous structure permit many alloying
elements to exist in a form of single-phase solid
solution, and also permit the formation of a uniform
passive film.
The components and compositions of the alloys of
this invention are specified as above for the following
reasons:
Ti, Zr, Ta, Nb, Mo and W are able to form the
amorphous structure when they coexist with A1. For the
formation of the amorphous structure by sputtering. the
A1 alloys consisting of A1 and Ti are required to
contain 25-60 ate Ti, and the A1 alloys consisting of
A1 and Zr are required to contain 10-75 ate Zr. The
_g_
amorphous structure for the ternary Al-Zr-Ti alloys is
formed by sputtering if the sum of Ti and at least 5 at
Zr is 10-75 ate. Among these amorphous alloys the A1
alloys containing at least 40 ate of Ti and/or Zr
possess particularly high corrosion resistance.
Consequently the alloys in the present invention are
required to contain at least 40 at ~ Ti and/or Zr.
The A1 alloys with Mo, W, Ta and/or Nb form the
amorphous structure in wide composition ranges, and the
addition of Mo, W, Ta and/or Nb to the A1 alloys
containing Ti and/or Zr as the major alloying elements
results in the formation of the amorphous structure in
wide composition ranges. However, the A1 alloys
containing at least 5 ate of at least one element
selected from the group of Mo, W, Ta and Nb are
included in our Canadian Pat. App. 564,867 which issued as
Patent 1,329,711. And hence in the present invention the
content of at least one element selected from the group of
Mo, W, Ta and Nb is restricted to less than 5 ato.
Ti, Zr, Mo, W, Ta and Nb are able to form a
protective passive film in a poorly oxidizing acid, and
hence the amorphous alloys of the present invention
have a sufficiently high corrosion resistance in
corrosive environments such as hydrochloric acids.
Preparation of the alloys of the present invention
is carried out by sputter deposition method.
Sputtering is performed by using a sintered or alloyed
crystalline target of multiple phases whose average
composition is the same as the amorphous alloy to be
prepared. Sputtering is also performed by using a
target consisting of a metal sheet of one of
constituents in the amorphous alloy to be prepared and
other metal constituents placed on the metal sheet.
In the present invention, it is difficult to form
-10-
alloy targets of aluminum with valve metals, and hence
targets consisting of an A1 disc on which at least one
element selected from valve metals is placed are used.
The alloys of the present invention can be produced by
using the valve-metal placed A1 sheet target. The
apparatus shown in F:IC. 1 can be used. In order to
avoid local compositional heterogeneity of sputtered
alloys, it is desirable to carry out revolution of the
substrate disc 2 around a central axis 1 of the
sputtering chamber 6 in addition to revolution of the
substrate disc itself around the center.of the
substrate disc. The orbit of the substrate disc is
just above the center of the target 3.
In order to change widely the composition of the
amorphous alloy formed, the apparatus shown in FIB. 2
can be used. For instance if an A1 disc is used as a
target 4, a Ti-embedded A1 disc is used as a target 5.
These two targets are installed obliquely in the
sputtering chamber 6, in such a way that the
intersection of the normals to the centers of these two
targets is on the orbit of the center of the substrate
disc 2 revolving around a central axis 1 of the
sputtering chamber 6 in addition to revolving the
substrate disc itself around the center of the
substrate disc. When these two targets are
independently operated by two independent power
sources, amorphous A1-Ta alloys are formed whose
compositions are dependent upon the relative powers of
two targets. In this manner when different various
combinations of two targets are used, different
amorphous alloy such as A1-Ti, A1-Zr, A1-Ti-Zr, A1-Ti-
Mo, A1-Ti-W, A1-Ti-Ta, A1-Ti-Nb, A1-Zr-Mo, A1-Zr-W, A1-
Zr-Ta, A1-Zr-Nb, A1-Ti-Mo-W, Al-Ti-Mo-Ta, A1-Ti-Mo-Nb,
A1-Ti-Mo-W-Ta, A1-Ti-Mo-W-Nb, A1-Ti-Mo-W-Ta-Nb, A1-Zr-
~~~~~ ~4w
-1 1 -
Mo-W, A1-Zr-Mo-Ta, A1-Zr-Mo-Nb, A1-Zr-Mo-W-Ta, A1-Zr-
Mo-W-Nb and A1-Zr-Mo-W-Ta-Nb are formed.
The invention is now illustrated by the following
examples:
Example 1
The targets consisted of 7 and 8 Ti discs of 20 mm
diameter and 1 m m thickness placed sym metrically on an
A1 disc of 1 00 mm diameter and 6 mm thickness so as to
place the center of Ti discs on a concentric circle of
58 mm diameter on the surface of the A1 disc. The
sputtering apparatus shown in FIG. 1 was used.
Substrates were an A1 disc and two glasses which were
revolved around the central axis of the sputtering
chamber during~revolution of the substrates themselves
around the center of the substrates. Sputtering was
carried out at the power of 240-200 watts under
purified Ar stream of 5 ml/min at a vacuum of 2 x 10-4
Torr.
X-ray diffraction of the sputter deposits thus
prepared revealed the formation of amorphous alloys.
Electron probe microanalysis showed that the amorphous
alloys consisted of A1-49 ate Ti and A1-60 ate Ti
alloys.
These alloys were spontaneously passive in 0.075
M/1 Na2B407-0.3 M/1 H3B03-0.5 M/1 NaCl at 25°C, and the
passivity breakdown potentials of the alloys measured
by anodic polarization in this solution were 0.73 and
0.80 V(SCE) which were very high. Consequently, these
amorphous alloys are highly corrosion-resistant.
Example 2
-1 2-
The sputtering apparatus shown in FIG. 2 was used
in which various kinds of A1 targets discs placing
various metals were installed. Substrates were an A1
disc and two glasses which were revolved around the
5 central axis of the sputtering chamber during
revolution of the substrates themselves around the
center of the substrates. Sputtering was .carried out
at various powers of the two targets under purified Ar
stream of 5 ml/min at a vacuum of 1 x 10-4 Torr.
10 X-ray diffraction of the sputter-deposits thus
prepared revealed the formation of amorphous alloys.
The compositions of these amorphous alloys analyzed by
electron probe microanalysis are shown in Table 2.
These alloys were spontaneously passive in 0.075
15 M/1 Na2B407-0.3 M/1 H3B03-0.5 M/1 NaCl at 25°C, and the
passivity breakdown potentials of the alloys measured
by anodic polarization in this solution and in 1 N HC1 at
30°C are shown in Table 2. Consequently, these
amorphous alloys are highly corrosion-resistant.
-13-
Table 2
Pitting potentials of amorphous alloys measured in
0.075 M/1 Na2B407-0.3M/1 H3B03-0.5M/1 NaCl at 25°C and in
1 N HC1 at 30°C.
Alloy Pittinq Potential mV(SCE)
5 (at ~) 0.075 M/1 Na2B407- 1 N HC1
0.3 M/1 H3B03-0.5 M/1 NaCl
at 25°C at 30°C
A1-40Ti 650 170
A1-50Ti-1Ta 810 300
10 A1-50Ti-3Nb 850 320
A1-50Ti-3Mo 750 210
Al-50Ti-1 W 730 200
A1-50Ti-1Nb-2Mo 770 250
A1-50Ti-1Nb-2W 760 250
15 A1-50Ti-1Nb-1Mo-1W 780 280
A1-50Ti-2Mo-2W 750 180
A1-50Ti-1 Ta-1 Nb-1 Mo-1 W 800 300
Crystalline Metals
20 A1 -900 -930
A1-50Ti-2Mo-2W -800 -850
A1-50Ti-1 Ta-1 Nb-1 Mo-1 W 1 00 -620
Example 3
The targets consisted of 4 - 8 Zr discs of 20 mm
25 diameter and 1 m m thickness placed symmetrically on an
A1 disc of 1 00 mm diameter and 6 mm thickness so as to
place the center of Zr discs on a concentric circle of
-1 4-
58 mm diameter on the surface of the Al disc. The
sputtering apparatus shown in FIG. 1 was used.
Substrates were an A1 disc and two glasses which were
revolved around the central axis of the sputtering
chamber during revolution of the substrates themselves
around the center of the substrates. Sputtering was
carried out at the power of 560-200 watts under
purified Ar stream of 5 ml/min at a vacuum of 2 x 10-4
Torr.
X-ray diffraction of the sputter deposits thus
prepared revealed the formation of amorphous alloys.
Electron probe micro-analysis showed that the amorphous
alloys consisted of A1-40 ate Zr, Al-45 ate Zr, A1-57
ate Zr, A1-69 ate Zr and A1-75 ate Zr alloys.
These alloys were spontaneously passive in 1 N HC1
at 30°C, and their corrosion rates are shown in Table
3. Consequently, these amorphous alloys are highly
corrosion-resistant.
Table 3
Corrosion rates measured in 1 N HC1 at 30°C
Alloy(at~) Corrosion Rate (mm/year)
Al-40Zr 7.5 x 10-3
A1-45Zr 4.5 x 10-3
A1-57Zr 1.0 x 10-3
A1-69Zr 4.1 x 10-4
A1-75Zr 2.5 x 10-4
Example 4
-1 5-
The sputtering apparatus shown in FIG. 2 was used
in which various kinds of A1 targets discs placing
various metals were installed. Substrates were an A1
disc and two glasses which were revolved around the
5 central axis of the sputtering chamber during
revolution of the substrates themselves around the
center of the substrates. Sputtering was carried out
at various powers of the two targets under~purified Ar
stream of 5 ml/min at a vacuum of 2 x 10-4 Torr.
10 X-ray diffraction of the sputter deposits thus
prepared revealed the formation of amorphous alloys.
The compositions of these amorphous alloys analyzed by
electron probe microanalysis are shown in Table 4.
These alloys were spontaneously passive in 1 N HC1
15 at 30°C, and the corrosion rates of these alloys
measured in 1 N HC1 at 30°C are shown in Table 4.
Consequently, these amorphous alloys are highly
corrosion-resistant.
Table 4
20 Corrosion rates measured in 1 N HC1 at 30°C
Alloy(at.~) - Corrosion Rate (mm/year)
A1-40Zr-3Ta 4.0 x 10-3
A1-40Zr-5Nb 3.5 x 10-3
A1-60Zr-2Ta 8.0 x 10-4
25 A1-60Zr-2Nb 9.0 x 10-4
A1-60Zr-1 Mo 1 .0 x 1
0-3
A1-60Zr-1 W 1 .1 x 1
0-3
A1-60Zr-1 Ta-1 Nb-1 Mo-1 W 8.5 x 1
0-4
-1 6-
Example 5
The targets consisted of 1 -7 Zr discs of 20 mm
diameter and 1 mm thickness and 2-7 Ti discs of 20 mm
diameter and 1 mm thickness placed symmetrically on an
A1 disc of 100 mm diameter and 6 mm thickness so as to
place 3-8 of the sum of Zr and Ti. The sputtering
apparatus shown in FIG. 1 was used. Substrates were an
A1 disc and two glasses which were revolved around the
central axis of the sputtering chamber during
revolution of the substrates themselves around the
center of the substrates. Sputtering was carried out
at the power of 560-200 watts under purified Ar stream
of 5 ml/min at a vacuum of 2 x 10-4 Torr.
X-ray diffraction of the sputter deposits thus
prepared revealed the formation of amorphous alloys.
The compositions of these amorphous alloys were
analyzed by electron probe microanalysis and shown in
Table 5.
The pitting potentials of these alloys measured in
0.075 M/1 Na2B407-0.3 M/1 Fi3B03-0.5 M/1 NaCl at 25°C
and in 1 N HC1 at 30°C are shown in Table 5.
Consequently, these amorphous alloys are highly
corrosion-resistant.
Table 5 Pitting potentials of amorphous alloys
measured in 0.075 M/1 Na2B407-0.3 M/1 H3B03-0.5M/1
NaCl at 25°C and in 1 N HC1 at 30°C.
c
-1 7_
Table 5
Alloy Pitting Potential mV(SCE)
(at ~) 0.075 M/1 Na2B407- 1 N HC1
0.3 M/1 H3B03-0.5 M/1 NaCl
at 25°C at 30°C
Al-5Zr-50Ti 720 250
A1-10Zr-40Ti 530 100
A1-20Zr-30Ti -40 -220
A1-30Zr-10Ti -80 -250
A1-40Zr-10Ti 120 -180
A1-50Zr-10Ti 150 -160
A1-60Zr-10Ti 160 -150
A1-70Zr-5Ti 160 -150
