Note: Descriptions are shown in the official language in which they were submitted.
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IMPROVED ALUMINUM-MAGNESIUM-LITHIUM ALLOYS, AND METHODS
FOR PRODUCING THE SAME
BACKGROUND
[001] Aluminum alloys are useful in a variety of applications. However,
improving one
property of an aluminum alloy without degrading another property is elusive.
For example, it
is difficult to increase the strength of an alloy without decreasing the
toughness of an alloy.
Other properties of interest for aluminum alloys include corrosion resistance
and fatigue
resistance, to name two.
SUMMARY OF THE DISCLOSURE
[002] Broadly, the present patent application relates to new aluminum-
magnesium-
lithium alloys, and methods for producing the same. The alloys generally
contain 2.0 - 3.9
wt. % Mg, 0.1 - 1.8 wt. % Li, up to 1.5 wt. % Cu, up to 2.0 wt. % Zn, up to
1.0 wt. % Ag, up
to 1.5 wt. % Mn, up to 0.5 wt. % Si, up to 0.35 wt. % Fe, 0.05 to 0.50 wt. %
of a grain
structure control element (defined below), up to 0.10 wt. % Ti, and up to 0.10
wt. % of any
other element, with the total of these other elements not exceeding 0.35 wt.
%, the balance
being aluminum.
[003] The new aluminum-magnesium-lithium generally contain 2.0 to 3.9 wt. %
Mg.
Magnesium may help improve strength, but too much magnesium may degrade
corrosion
resistance. In one embodiment, the new alloys include at least 2.25 wt. % Mg.
In another
embodiment, the new alloys contain at least 2.5 wt. % Mg. In yet another
embodiment, the
new alloys include at least 2.75 wt. % Mg. In one embodiment, the new alloys
include not
greater than 3.75 wt. % Mg. In another embodiment, the new alloys include not
greater than
3.5 wt. % Mg. In yet another embodiment, the new alloys include not greater
than 3.25 wt.
% Mg.
[004] The new aluminum-magnesium-lithium generally contain 0.1 to 1.8 wt. %
Li.
Lithium helps reduce density and may help improve strength, but too much
lithium may
reduce ductility. In one embodiment, the new alloys include at least 0.4 wt. %
Li. In another
embodiment, the new alloys include at least 0.6 wt. % Li. In yet another
embodiment, the
new alloys include at least 0.8 wt. % Li. In another embodiment, the new
alloys include at
least 1.0 wt. % Li. In yet another embodiment, the new alloys include at least
1.05 wt. % Li.
In another embodiment, the new alloys include at least 1.10 wt. % Li. In yet
another
embodiment, the new alloys include at least 1.20 wt. % Li. In one embodiment,
the new
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alloys include not greater than 1.5 wt. % Li. In another embodiment, the new
alloys include
not greater than 1.45 wt. % Li. In yet another embodiment, the new alloys
include not greater
than 1.4 wt. % Li.
[005] The new alloys may contain up to about 1.5 wt. % Cu. Copper may
improve
strength but increases density. In one embodiment, the new alloys contain not
greater than
1.0 wt. % Cu. In another embodiment, the new alloys contain not greater than
0.9 wt. % Cu.
In yet another embodiment, the new alloys contain not greater than 0.6 wt. %
Cu. In another
embodiment, the new alloys contain not greater than 0.5 wt. % Cu. In
embodiments where
copper is used, the new alloys generally contain at least 0.05 wt. % Cu. In
one embodiment,
the new alloys include at least 0.10 wt. % Cu. In embodiments where copper is
not used, the
new alloys include less than 0.05 wt. % Cu.
[006] The new alloys may contain up to about 2.0 wt. % Zn. Zinc may improve
strength, but increases density. In one embodiment, the new alloys contain not
greater than
1.5 wt. % Zn. In another embodiment, the new alloys contain not greater than
1.0 wt. % Zn.
In embodiments where zinc is used, the new alloys generally contain at least
0.20 wt. % Zn.
In one embodiment, the new alloys contain at least 0.4 wt. % Zn. In another
embodiment, the
new alloys contain at least 0.5 wt. % Zn. In embodiments where zinc is not
used, the new
alloys include less than 0.20 wt. % Zn.
[007] The new alloys may contain up to 1.5 wt. % Mn. Manganese may improve
strength, but increases density. In one embodiment, the new alloys contain not
greater than
1.0 wt. % Mn. In another embodiment, the new alloys contain not greater than
0.9 wt. % Mn.
In yet another embodiment, the new alloys contain not greater than 0.7 wt. %
Mn. In
embodiments where manganese is used, the new alloys generally contain at least
0.05 wt. %
Mn. In one embodiment, the new alloys include at least 0.20 wt. % Mn. In
embodiments
where manganese is not used, the new alloys include not greater than 0.04 wt.
% Mn.
[008] The new alloys may contain up to 1.0 wt. % Ag. Silver may improve
strength, but
silver decreases density and is expensive. In one embodiment, the new alloys
contain not
greater than 0.9 wt. % Ag. In another embodiment, the new alloys contain not
greater than
0.6 wt. % Ag. In embodiments where silver is used, the new alloys generally
contain at least
0.05 wt. % Ag. In one embodiment, the new alloys include at least 0.20 wt. %
Ag. In
embodiments where silver is not used, the new alloys include not greater than
0.04 wt. % Ag.
[009] The new alloys may contain up to 0.5 wt. % Si. Silicon may improve
corrosion
resistance, but may decrease fracture toughness. In one embodiment, the new
alloys contain
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not greater than 0.35 wt. % Si. In another embodiment, the new alloys contain
not greater
than 0.25 wt. % Si. In embodiments where silicon is used, the new alloys
generally contain
at least 0.10 wt. % Si. In embodiments where silicon is not used, the new
alloys include not
greater than 0.09 vvt. % Si.
[0010] The new alloys may optionally include at least one secondary element
selected
from the group consisting of Zr, Sc, Cr, Hf, V, Ti, and rare earth elements.
Such elements
may be used, for instance, to facilitate the appropriate grain structure in
the resultant
aluminum alloy product. The secondary elements may optionally be present as
follows: up to
0.20 wt. % Zr, up to 0.30 wt. % Sc, up to 0.50 wt. % of Cr, up to 0.25 wt. %
each of any of
Hf, V, and rare earth elements, and up to 0.10 wt. % Ti. Zirconium (Zr) and/or
scandium are
preferred for grain structure control. When zirconium is used, it is generally
included in the
new aluminum alloys at 0.05 to 0.20 wt. % Zr. In one embodiment, the new
aluminum alloys
include 0.07 to 0.16 wt. % Zr. Scandium (Sc) may be used in addition to, or as
a substitute
for zirconium, and, when present, is generally included in the new aluminum
alloys at 0.05 to
0.30 wt. % Sc. In one embodiment, the new aluminum alloys include 0.07 to 0.25
wt. % Sc.
Chromium (Cr) may also be used in addition to, or as a substitute for
zirconium, and/or
scandium, and when present is generally included in the new alloys at 0.05 to
0.50 wt. % Cr.
In one embodiment, the new aluminum alloys include 0.05 to 0.35 wt. % Cr. In
another
embodiment, the new aluminum alloys include 0.05 to 0.25 wt. % Cr. In other
embodiments,
any of zirconium, scandium, and/or chromium may be included in the alloy as an
impurity,
and in these embodiments such elements would be included in the alloy at less
than 0.05 wt.
%.
[0011] Hf, V and rare earth elements may be included an in an amount of up
to 0.25 wt.
% each of any of Hf, V, and rare earth elements (0.25 wt. % each of any rare
earth element
may be included). In one embodiment, the new aluminum alloys include not
greater than
0.05 wt. % each of Hf, V, and rare earth elements (< 0.05 wt. % each of any
rare earth
element).
[0012] Titanium is preferred for grain refining during casting, and, when
present is
generally included in the new aluminum alloys at 0.005 to 0.10 wt. % Ti. In
one
embodiment, the new aluminum alloys include 0.01 to 0.05 wt. % Ti. In another
embodiment, the aluminum alloys include 0.01 to 0.03 wt. % Ti.
[0013] The new alloys may include up to 0.35 wt. % Fe. In some embodiments,
the iron
content of the new aluminum alloys is not greater than about 0.25 wt. % Fe, or
not greater
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than about 0.15 wt. % Fe, or not greater than about 0.10 wt. % Fe, or not
greater than about
0.08 wt. % Fe, or not greater than 0.05 wt. % Fe, or less.
[0014]
Aside from the above-listed elements, the balance (remainder) of the new
aluminum alloys is generally aluminum and other elements, where the new
aluminum alloys
include not greater than 0.15 wt. % each of these other elements, and where
the total of these
other elements does not exceed 0.35 wt. %. As used herein, "other elements"
includes any
elements of the periodic table other than the above-identified elements, i.e.,
any elements
other than Al, Mg, Li, Cu, Zn, Mn, Si, Fe, Zr, Sc, Cr, Ti, Hf, V. and rare
earth elements. In
one embodiment, the new aluminum alloys include not greater than 0.10 wt. %
each of other
elements, and with the total of these other elements not exceeding 0.25 wt. %.
In another
embodiment, the new aluminum alloys include not greater than 0.05 wt. % each
of other
elements, and with the total of these other elements not exceeding 0.15 wt. %.
In yet another
embodiment, the new aluminum alloys include not- greater than 0.03 wt. % each
of other
elements, and with the total of these other elements not exceeding 0.10 wt. %.
[0015]
Except where stated otherwise, the expression "up to" when referring to the
amount of an element means that that elemental composition is optional and
includes a zero
amount of that particular compositional component.
Unless stated otherwise, all
compositional percentages are in weight percent (wt. %).
[0016] In
one specific embodiment, an aluminum alloy includes zinc, and includes 2.0 -
3.9 wt. % Mg, 0.1 - 1.8 wt. % Li, 0.4 to 2.0 wt. % Zn, up to 1.5 wt. % Cu, up
to 1.0 wt. % Ag,
up to 1.5 wt. % Mn, up to 0.5 wt. % Si, up to 0.35 wt. % Fe, optionally at
least one secondary
element, as described above, up to 0.10 wt. % of any other element, with the
total of these
other elements not exceeding 0.35 wt. %, the balance being aluminum. This
alloy may be
modified to any of the above-described Mg, Li, Zn, Cu, Ag, Mn, Si, Fe,
secondary elements
and other elements amounts, described above.
[0017] In
another specific embodiment, the aluminum alloy is a high-lithium alloy, and
includes 2.5 - 3.9 wt. % Mg, 1.05 - 1.8 wt. % Li, up to 2.0 wt. % Zn, up to
1.5 wt. % Cu, up
to 1.0 wt. % Ag, up to 1.5 wt. % Mn, up to 0.5 wt. % Si, up to 0.35 wt. % Fe,
optionally at
least one secondary element, as described above, up to 0.10 wt. % of any other
element, with
the total of these other elements not exceeding 0.35 wt. %, the balance being
aluminum. This
alloy may be modified to any of the above-described Mg, Li, Zn, Cu, Ag, Mn,
Si, Fe,
secondary elements and other elements amounts, described above.
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[0018] In
embodiments where the aluminum alloy is solution heat treated (described
below), the total amount of magnesium, lithium, copper, zinc, silicon, iron,
the secondary
elements and the other elements should be chosen so that the aluminum alloy
can be
appropriately solutionized (e.g., to promote hardening while restricting the
amount of
constituent particles). In one embodiment, the aluminum alloy includes an
amount of
alloying elements that leaves the aluminum alloy free of, or substantially
free of, soluble
constituent particles after solutionizing. In one embodiment, the aluminum
alloy includes an
amount of alloying elements that leaves the aluminum alloy with low amounts of
(e.g.,
restricted / minimized) insoluble constituent particles after solutionizing.
In other
embodiments, the aluminum alloy may benefit from controlled amounts of
insoluble
constituent particles.
[0019] The
new aluminum alloys may be processed into a variety of wrought forms, such
as in rolled form (sheet, plate), as an extrusion, or as a forging, and in a
variety of tempers.
In this regard, new aluminum alloys may be cast (e.g., direct chill cast or
continuously cast),
and then worked (hot and/or cold worked) into the appropriate product form
(sheet, plate,
extrusion, or forging). After working, the new aluminum alloys may be
processed into one of
an H temper, T temper or a W temper, as defined by the Aluminum Association.
[0020] For
any of the H temper, T temper or W temper products, the aluminum alloy may
be hot worked, such as by rolling, extruding and/or forging. In one
embodiment, the hot
working temperature is maintained below the recrystallization temperature of
the alloy. In
one embodiment, the hot working exit temperature is not greater than 600 F. In
another
embodiment, the hot working exit temperature is not greater than 550 F. In yet
another
embodiment, the hot working exit temperature is not greater than 500 F. In
another
embodiment, the hot working exit temperature is not greater than 450 F. In yet
another
embodiment, the hot working exit temperature is not greater than 400 F.
[0021] In
one embodiment, the new alloy is processed to an H temper. In these
embodiments, the processing may include casting the new aluminum alloy,
including any
version of the aluminum alloy described above, after which the aluminum alloy
is hot rolled
to an intermediate gauge or final gauge. In instances where the alloy is hot
rolled to an
intermediate gauge, it will then be cold rolled to final gauge (e.g., cold
rolled 2-25%), and
then optionally stretched (e.g., 1-10%), for instance, for flatness and/or for
stress relief. In
instances where the alloy is hot rolled to final gauge, it may be stretched
(e.g., 1-10%), for
instance, for flatness and/or for stress relief.
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[0022] In embodiments where the aluminum alloy is cold rolled and/or
stretched, the
aluminum alloy may be cooled to a temperature of not greater than 400 F prior
to the cold
rolling and/or the stretching. In one embodiment, the aluminum alloy is cooled
to a
temperature of not greater than 250 F prior to the cold rolling and/or the
stretching. In
another embodiment, the aluminum alloy is cooled to a temperature of not
greater than 200 F
prior to the cold rolling and/or the stretching. In yet another embodiment,
the aluminum
alloy is cooled to a temperature of not greater than 150 F prior to the cold
rolling and/or the
stretching. In yet another embodiment, the aluminum alloy is cooled to ambient
temperature
prior to the cold rolling and/or the stretching.
[0023] When producing the aluminum alloy in an H temper, it may be
detrimental to
anneal the product. Thus, in some H-temper embodiments, the process includes
maintaining
the aluminum alloy at a temperature below 400 F between the hot rolling step
and any cold
rolling and/or stretching step. In one H-temper embodiment, the process
includes
maintaining the aluminum alloy at a temperature of net 250 F between the hot
rolling step
and/or any cold rolling and/or stretching step. In another H-temper
embodiment, the process
includes maintaining the aluminum alloy at a temperature of net 200 F between
the hot
rolling step and/or any cold rolling and/or stretching step. In yet another H-
temper
embodiment, the process includes maintaining the aluminum alloy at a
temperature of net
150 F between the hot rolling step and/or any cold rolling and/or stretching
step. In another
H-temper embodiment, the process includes maintaining the aluminum alloy at
ambient
temperature between the hot rolling step and/or any cold rolling and/or
stretching step.
[0024] In some embodiments, when producing the aluminum alloy in an H
temper, it may
be detrimental to apply any thermal treatment to the product after any cold
rolling and/or
stretching step. Thus, in some embodiments, an H-temper processing method is
absent of
any thermal treatments after any cold rolling step and/or any stretching step.
However, in
other embodiments, one or more anneal steps could be used, such as before or
after hot and/or
cold rolling.
[0025] In some embodiments when cold rolling is used as a part of H-temper
processing,
the cold rolling may be restricted to so as to facilitate good strength,
ductility and/or
corrosion resistance. In one embodiment, the cold rolling comprises cold
rolling the
intermediate gauge product by 1-25%, i.e., the thickness of the intermediate
gauge product is
reduced by 1-25% by cold rolling. In one embodiment, the cold rolling is 2-
22%, i.e., the
thickness of the intermediate gauge product is reduced by 2-22% by cold
rolling. In another
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embodiment, the cold rolling is 3-20%, i.e., the thickness of the intermediate
gauge product is
reduced by 3-20% by cold rolling.
[0026] In another embodiment, the new aluminum alloy is processed to a "T
temper"
(thermally treated). In this regard, during or after the hot working (as
appropriate), the new
aluminum alloys may be processed to any of a Ti, '12, T3, T4, T5, T6,17, T8 or
T9 temper,
as defined by the Aluminum Association. In one embodiment, the new aluminum
alloys are
processed to one of a T4, T6 or T7 temper, where the new aluminum alloys are
solution heat
treated, and then quenched, and then either naturally aged (T4) or
artificially aged (T6 or T7).
In one embodiment, the new aluminum alloys are processed to one of a T3 or T8
temper,
where the new aluminum alloys are solution heat treated, and then quenched,
and then cold
worked, and then either naturally aged (T3) or artificially aged (T8). In
another embodiment,
the new aluminum alloy is processed to an "W temper" (solution heat treated),
as defined by
the Aluminum Association. In yet another embodiment, no solution heat
treatment is applied
after the hot working, and thus the new aluminum alloy may be processed to an
"F temper"
(as fabricated), as defined by the Aluminum Association. The alloys may also
be processed
with high cold work after the solution heat treatment and quench, e.g., 25% or
more cold
work, as described in commonly-owned U.S. Patent Publication No. 2012/0055590.
[0027] The new aluminum alloys may achieve an improved combination of
properties.
For example, the new aluminum alloys may achieve an improved combination of
strength,
corrosion resistance and/or ductility, among others.
[0028] In one approach, the new aluminum alloys are in an H-temper, are hot
rolled, and
then stretched 1-10%, (no cold rolling step) and realize a tensile yield
strength (L) of at least
35 ksi (tested via ASTM E8 and B557). In one embodiment, the new aluminum
alloys
realize a tensile yield strength (L) of at least 36 ksi. In another
embodiment, the new
aluminum alloys realize a tensile yield strength (L) of at least 38 ksi. In
yet another
embodiment, the new aluminum alloys realize a tensile yield strength (L) of at
least 40 ksi.
In another embodiment, the new aluminum alloys realize a tensile yield
strength (L) of at
least 42 ksi. In yet another embodiment, the new aluminum alloys realize a
tensile yield
strength (L) of at least 44 ksi. In another embodiment, the new aluminum
alloys realize a
tensile yield strength (L) of at least 46 ksi. In yet another embodiment, the
new aluminum
alloys realize a tensile yield strength (L) of at least 48 ksi. In another
embodiment, the new
aluminum alloys realize a tensile yield strength (L) of at least 50 ksi. In
yet another
embodiment, the new aluminum alloys realize a tensile yield strength (L) of at
least 51 ksi, or
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more. In these H-temper and stretching embodiments, the new aluminum alloys
may realize
an elongation (L) of at least 10% (tested via ASTM E8 and B557). In one
embodiment, the
new aluminum alloys realize an elongation (L) of at least 12%. In another
embodiment, the
new aluminum alloys realize an elongation (L) of at least 14%. In yet another
embodiment,
the new aluminum alloys realize an elongation (L) of at least 16%. In another
embodiment,
the new aluminum alloys realize an elongation (L) of at least 18%, or more. In
these II-
temper and stretching embodiments, the new aluminum alloys may realize a mass
loss of not
greater than 25 mg/cm2 (tested in accordance with ASMT G67, and with 1 week of
exposure
to 100 C). In one embodiment, the new aluminum alloys realize a mass loss of
not greater
than 15 mglem2. In these H-temper and stretching embodiments, the new aluminum
alloys
may realize an EXCO rating of at least EB (at T/10 and/or at surface, and as
tested in
accordance with ASMT G66, and with 1 week of exposure to 100"C). In one
embodiment,
the new aluminum alloys realize an EXCO rating of at least EA. In another
embodiment, the
new aluminum alloys realize an EXCO rating of at least PC. In yet another
embodiment, the
new aluminum alloys realize an EXCO rating of at least PB. In another
embodiment, the new
aluminum alloys realize an EXCO rating of at least PA.
[0029] In another approach, the new aluminum alloys are in an H-temper, are
hot rolled,
and then cold rolled 1-25% and realize a tensile yield strength (L) of at
least 40 ksi (tested via
ASTM E8 and B557). In one embodiment, the new aluminum alloys realize a
tensile yield
strength (L) of at least 42 ksi. In another embodiment, the new aluminum
alloys realize a
tensile yield strength (L) of at least 44 ksi. In yet another embodiment, the
new aluminum
alloys realize a tensile yield strength (L) of at least 46 ksi. In another
embodiment, the new
aluminum alloys realize a tensile yield strength (L) of at least 48 ksi. In
yet another
embodiment, the new aluminum alloys realize a tensile yield strength (L) of at
least 50 ksi.
In another embodiment, the new aluminum alloys realize a tensile yield
strength (L) of at
least 52 ksi. In yet another embodiment, the new aluminum alloy's realize a
tensile yield
strength (L) of at least 54 ksi. In another embodiment, the new aluminum
alloys realize a
tensile yield strength (L) of at least 56 ksi.. In yet another embodiment, the
new aluminum
alloys realize a tensile yield strength (L) of at least 58 ksi, or more. In
these LI-temper and
cold rolling embodiments, the new aluminum alloys may realize an elongation
(L) of at least
6% (tested via ASTM E8 and B557), In one embodiment, the new aluminum alloys
realize
an elongation (L) of at least 8%. In another embodiment, the new aluminum
alloys realize an
elongation (L) of at least 10%. In yet another embodiment, the new aluminum
alloys realize
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an elongation (L) of at least 12%. In another embodiment, the new aluminum
alloys realize
an elongation (L) of at least 14%, or more. In these II-temper and cold
rolling embodiments,
the new aluminum alloys may realize a mass loss of not greater than 25 mg/cm2
(tested in
accordance with ASMT (367, and with 1 week of exposure to 100 C). In these H-
temper and
cold rolling embodiments, the new aluminum alloys may realize a mass loss of
not greater
than 15 mg/cm2. In these H-temper and cold rolling embodiments, the new
aluminum alloys
may realize an EXCO rating of at least EB (at T/10 and/or at surface, and as
tested in
accordance with ASMT (366, and with 1 week of exposure to 100 C). In one
embodiment,
the new aluminum alloys realize an EXCO rating of at least EA. In another
embodiment, the
new aluminum alloys realize an EXCO rating of at least PC. In yet another
embodiment, the
new aluminum alloys realize an EXCO rating of at least PB. In another
embodiment, the new
aluminum alloys realize an EXCO rating of at least PA.
[0030] In yet another approach, the new aluminum alloys are in an T-temper,
and realize
a tensile yield strength (L) of at least 45 ksi (tested via ASTM E8 and B557).
In one
embodiment, the new aluminum alloys realize a tensile yield strength (L) of at
least 46 ksi.
In another embodiment, the new aluminum alloys realize a tensile yield
strength (L) of at
least 48 ksi. In yet another embodiment, the new aluminum alloys realize a
tensile yield
strength (L) of at least 50 ksi. In another embodiment, the new aluminum
alloys realize a
tensile yield strength (L) of at least 52 ksi. In yet another embodiment, the
new aluminum
alloys realize a tensile yield strength (L) of at least 54 ksi. In another
embodiment, the new
aluminum alloys realize a tensile yield strength (L) of at least 56 ksi. In
yet another
embodiment, the new aluminum alloys realize a tensile yield strength (L) of at
least 58 ksi.
In another embodiment, the new aluminum alloys realize a tensile yield
strength (L) of at
least 60 ksi. In yet another embodiment, the new aluminum alloys realize a
tensile yield
strength (L) of at least 62 ksi, or more. In these T-temper embodiments, new
aluminum
alloys may realize an elongation (L) of at least 6% (tested via ASTM E8 and
B557). In one
embodiment, the new aluminum alloys realize an elongation (L) of at least 8%.
In another
embodiment, the new aluminum alloys realize an 'elongation (L) of at least
10%. In yet
another embodiment, the new aluminum alloys realize an elongation (L) of at
least 12%. In
another embodiment, the new aluminum alloys realize an elongation (L) of at
least 14%, or
more. In these T-temper embodiments, the new aluminum alloys may realize a
mass loss of
not greater than 25 mg/cm2 (tested in accordance with ASMT G67, and with 1
week of
exposure to 100 C). In one embodiment, the new aluminum alloys realize mass
loss of not
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greater than 15 mg/cm2. In these T-temper embodiments, the new aluminum alloys
may
realize an EXCO rating of at least EB (at T/10 and/or at surface, and as
tested in accordance
with ASMT G66, and with 1 week of exposure to 100 C). In one embodiment, the
new
aluminum alloys realize an EXCO rating of at least EA. In another embodiment,
the new
aluminum alloys realize an EXCO rating of at least pc. In yet another
embodiment, the new
aluminum alloys realize an EXCO rating of at least PB. In another embodiment,
the new
aluminum alloys realize an EXCO rating of at least PA.
[0031] The new aluminum alloys described herein may be used in a variety of
applications, such as in automotive and/or aerospace applications, among
others. In one
embodiment, the new aluminum alloys are used in an aerospace application, such
as wing
skins (upper and lower) or stringers / stiffeners, fuselage skin or stringers,
ribs, frames, spars,
bulkheads, circumferential frames, empennage (such as horizontal and vertical
stabilizers),
floor beams, seat tracks, doors, and control surface components (e.g.,
rudders, ailerons)
among others. In another embodiment, the new aluminum alloys are used in an
automotive
application, such as closure panels (e.g., hoods, fenders, doors, roofs, and
trunk lids, among
others), wheels, and critical strength applications, such as in body-in-white
(e.g., pillars,
reinforcements) applications, among others. In yet another embodiment, the new
aluminum
alloys are used in a marine application, such as for ships and boats (e.g.,
hulls, decks, masts,
and superstructures, among others). In another embodiment, the new aluminum
alloys are
used in a munitions / ballistics / military application, such as in ammunition
cartridges and
armor, among others. Ammunition cartridges may include those used in small
arms and
cannons or for artillery or tank rounds. Other possible ammunition components
would
include sabots and fins. Artillery, fuse components are another possible
application as are
fins and control surfaces for precision guided bombs and missiles. Armor
components could
include armor plates or structural components for military vehicles.
BRIEF DESCRIPTION OF THE DRAWINGS
[0032] FIGS. 1-12 are graphs illustrating results of Example 1.
[0033] FIGS. 13 is a graph illustrating results of Example 2.
[0034] FIGS. 14-21 are graphs illustrating results of Example 3.
DETAILED DESCRIPTION
[0035] Example 1
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[0036] Twelve book mold ingots were produced, the compositions of which are
provided
in Table 1, below (all values in weight percent).
Table 1 - Example 1 Alloy Compositions
Alloy Mg Li Cu Zn
1 2.89 0.00 0 0
2 ........................... 2.80 0.21 0
3 ........................... 2.90 0.87 0 0
4 2.80 1.20 0 0
2.70 1.60 0 0
6 5.03 0.00
7 4.75 0.23 0 0
8 4.75 0.87 0
9 ........................... 4.55 1.20 0 0
5.55 0.85 0 0
11 5.04 0.00 0.19 0.54
12 4.50 0.86 0.18 0.46
[0037] Unless otherwise indicated, all alloys contained the listed
elements, from about
0.10 to 0.13 wt. % Zr, about 0.60 wt. % Mn, not more than about 0.04 wt. % Fe,
not more
than 0.03 wt. % Si, about 0.02 wt. % Ti, the balance being aluminum and other
elements,
where the other elements did not exceed more than 0.05 wt. % each, and not
more than 0.15
wt. % total of the other elements.
[0038] The alloys were cast as approximately 2.875 inch (ST) x 4.75 inch
(LT) x 17 inch
(L) ingots that were scalped (machined) to about 2 inches thick. Alloys 10-12
were then
homogenized. Each ingot was then hot rolled to a gauge of about 0.25 inch. The
finish hot
rolling temperature varied as shown below (the starting hot rolling
temperature was about
850 F). Part of these hot rolled pieces were then cold rolled to a gauge of
about 0.1875 inch
(about a 25% reduction in thickness). For Alloys 1-5, other parts of the hot
rolled pieces
were stretched about 2% for flatness. The mechanical properties of the as hot
rolled (HR),
the as cold rolled materials (CR) and hot rolled and 2% stretched material (HR-
2%S) were
then tested, the results of which are provided in Tables 2-4, below. Strength
and elongation
properties were measured in accordance with ASTM E8 and B557 -- all test
values relative to
the longitudinal (L) direction, unless otherwise indicated.
Table 2 - Mechanical Properties of Hot Rolled (HR) Alloys
1 Hot Rolling
TYS UTS Elong.
Alloy Finish Temp.
1 (ksi) I (ksi) (%)
CF)
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r ...... -
Hot Rolling
TYS UTS Elong.
Alloy Finish Temp.
000 OW) (%)
CF)
1 500-550 25.2 35.8 28.4
1 400-450 28.7 38.3 I 26.1
2 500-550 24.3 37.9 24.9
3 400-450 32.5 46.2 15.2
4 400-450 35.0 48.5 =12.9
400-450 35.7 53.0 11.8
6 400-450 35.0 50.0 1 24.1
6 500-550 32.4 49.7 1 23.2
7 400-450 36.8 53.2 1 17.0
8 500-550 31.5 51.8 23.5
9 400-450 38:3 1 55.8 19.1
400-450 .... 39.0 1 57.5 18.9
_____________ 11 400-450 40.4 1 56.5 17.5
12 400-450 39.1 56.8 16.4
Table 3 - Mechanical Properties of HR +25% CR Alloys
Hot Rolling
TYS UTS Elong.
Alloy Finish Temp.
000 000 (%)
......................... CF)
1 500-550 37.6 41.9 14.1
1 400-450 41.4 43.7 10.7
2 500-550 39.0 42.6 13.5
3 400-450 48.8 50.4 7.2
4 400-450 51.5 53.2 5.7
5 400-450 55.1 57.7 I __ 5.0
r 6 400-450
51.2 57.9 11.6
6 500-550 48.9 57.4 12.2
7 400-450 53.3 60.5 8.0
8 500-550 51.0 59.0 11.0
9 400-450 56.2 64.4 7.7
10 400-450 60.4 67.1 8.8
11 400-450 --t--
56.5 63.7 8.5
12 400-450 59.3 66.4 6.8
Table 4 - Mechanical Properties of HR + 2% Stretch Alloys
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Alloy Hot Rolling Finish TYS UTS Elong.
Temp. ( F) (ksi) (ksi) (%)
1 500-550 ............................. 27.4 35.5 24.3
1 400-450 30.7 37.8 23.9
2 500-550 31.8 38.4 22.5
3 400-450 39.8 44.9 1 15.4
4 400-450 1 43.4 47.9 12.6
400-450 1 48.8 53.2 , 10.3
[0039] As shown in FIGS. 1-3, lower hot rolling exit temperatures resulted
in better
properties. As shown in FIGS. 4-5, the cold rolled alloys generally realize
better strength
than the hot-rolled only alloys. As shown in FIGS. 6-7, the hot rolled alloys
without cold
rolling generally realized good ductility at all lithium levels. As shown in
FIGS. 8-9, higher
levels of magnesium and lithium generally result in higher strengths.
[0040] The HR only alloys and the HR + 25% CR alloys were also tested for
corrosion
resistance in accordance with ASTM G66 (exfoliation resistance) and G67 (mass
loss).
Specifically, the alloys were tested for corrosion resistance before and after
exposure to a
temperature of about 100 C for about 1 week. Alloys 1-5 that were hot rolled
and then
stretched 2% were also tested for corrosion resistance in accordance with ASTM
G67 (mass
loss). The corrosion resistance results are shown in Tables 5-7, below.
Table 5- Corrosion Resistance Results - Hot Rolled (HR) Alloys
Before Thermal Exiosure After Thermal Exposure -
Hot
G67 G66 G66
Rolling 1 G66
Mass Ratin Rating G67 Mass G66 Rating
Alloy Finish
Loss g Loss Rating
Temp.
(mg/cm @ Surfac (mg/cm2) @
T/10 @
( F) 2) ... T/10 S Surface
1 500-550 1.11 PB PB 1.75 PB PB
1 400-450 1.47 PB PB 1.90 PB ... PB
2 500-550 1.26 PB PB 1.79 PB ... PB
3 400-450 1.38 PA PA 3.06 PB PB
4 400-450 1,21 PB PB 2.99 PB PB
5 400-450 1.64 PB PB 2.48 EA PB
6 400-450 1.74 PB PB 40.05 EA EC
6 500-550 1.90 PB PB 49.23 EA EC
16 400-450 1.30 PB PB 49.17 PB PB
1 7 400-450 1.65 PB PB 31.11 1B ED
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_____________ 1
i Before Thermal Exposure ' After Thermal Exposure ..
Hot
G67 G66 G66
Rolling 1 G66
Mass Ratin Rating G67 Mass G66
Alloy FinishRating
T
Loss g (ii) Loss Rating
emp . @
(mg/cm @ Surfac (mg/cm2) @
T/10
cF)T/10 ........................... e surface
z)
7 400-450 1.66 PB PB 33.68 EB EB
8 500-550 2.36 PB ' PB 55.61 EB EB
: 9 400-450 3.55 EA EA 33.18 I EC. ED
.. ,
9 400-450 2.31 PB PB 29.68 PB PB
400-450 7.70 PB PB ! 46.20 EB I EC
10 400-450 6.84 PB PB 73.16 EA EA
11 400-450 2.99 EC EC 13.73 EC EC
-- 11 400-450 1.72 EC EC 15.72 EC EC
12 400-450 2.20 EC EC j ................ 14 .. 98 EF EC
4 ...
_......_....
12 400-450 2.31 i ...................... EC L EC I 17.77 ED t ED
Table 6 - Corrosion Resistance Results - HR + 25% CR Alloys
Hot I. .. Before Thermal Ex . osure ! After
Thermal Exposure
Rolling ' G66
G67-Z- G66 G67
1 G66 G66
Alloy Finish Mass Rating
T
Loss Rating Rating Loss
Rating @
emp.
............... ( (mg/cm2) T/10
Surface (mg/cm2) @ T/10
1-1 Surface
1 500-550 1.16 PA PA 1.49 PA PA -
-,
1 400-450 ' 1.55 PA PA 1.68 PA PA
2 : 500-550 1.33 PB PB 2.03 PA PA
3 400-450 1.26 PA PA 4.58 EA I
EA
4 : 400-450 1.25 PB PB 4.20 EA ...... EA
I 5 400-450 ...
1.37 PA PA 2.29 PA ]:
PA
1.--
1 6 400-450 1.48 PB PB 38.29 ED ED
I-6-i 500-550 1.34 PA PA 53.10 ED ]
ED
I
16 4007450 1.37 PA PA 56.63 EA i
EA
1.7 400-450 1.49 PB PB 36.46 ED ED
7 400-450 1.76 PA PA 35.72 ED ED
, . ___
8 500-550 2.08 I PB PB 54.86 ED I
ED
9 400-450 2.70 EA EA 33.47 ED ED
9 400-450 2.08 PA PA 44.44 ED ED
_
10 .. 400-450 5.01 PB VA 43.08 ED ED
10 400-450 4.11 PA PA 68.24 ED ED
11 400-450 1.77 EC EC 29.55 ED ED
EC .
11 400-450 1.63 .. EC i----
30.67 ED ED
1-
[ 12 400-4501 2.31 EC __ EC I 26.13 ED ED
-
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Hot Before Thermal Exposure After
Thermal Exposure
Rolling G67 = G66
G67 Mass G66 G66 G66
Alloy FinishMass Rating
T
Loss Rating Rating @ Loss Rating
emp.
(ing/cm2) T/10 Surface ongicm2.1 (0) T/10
Surface
12 400-450 2.251 EC EC 28.01 ED ED
Table 7 - Corrosion Resistance Results - Hot Rolled (HR) + 2% Stretch Alloys
Hot Before After
Roiling Thermal Thermal I
Alloy Finish Exposure Exposure j
Temp. G67 Mass Loss
( F) cm2)
1 500-550 1.59 I 2.09
1 400-450 1.33 1.92
2 500-550 1.31 2.04
3 400-450 1.29 3.62
4 400-450 1.28 4.50
5 _400-450 1.41 2.36
[0041] As shown in FIG. 10, all alloys realize low (good) mass loss prior
to thermal
exposure realizing less than 15 mg/cm2 mass loss during the ASTM G67 test.
However, after
thermal exposure, the about 3 wt. % Mg alloys realize low mass loss, but many
of Alloys 6-
12 with magnesium realize high mass loss (See, FIG. 11). FIG. 12 illustrates
mass loss as a
function of lithium for high magnesium alloys. As shown above, the higher
magnesium
alloys also realize worse exfoliation resistance.
[0042] Example 2
[0043] Fourteen book mold ingots were produced, the compositions of which
are
provided in Table 8, below (all values in weight percent).
Table 8 - Example 2 Alloy Compositions
Alloy Mg Li Zn Cu Ag
13 4.42 2.01 0.96 0.35 0.24
14 4.33 2.09 .............. 1.871 0.35 0.23
15 4.53 2.13 0.97 0.95 0.24
16 4.48 2.18 1.92 0.95 0.24
17 4.41 2.03 0.97 0.35 0.65
18 4.38 2.04 1.90 0.36 0.65
19 4.41 2.06 0.98 0.95 0.66
20 4.36 2.12 1.89 L0.89 0.62
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---1 -
Alloy_ Mg .. Li Zn Cu AK
21 ...................... 4.37 2.08 1.44 0.65 0.44
22 ______________________ 4.31 .. 2.22 2.82 0.64 0.43
23 4.43 2.16 1.44 1.85 0.45
24 4.45 2.18 1.48 0.68 0.91
' 25 4 4A5 2.06 1A5 0.67 0.45
L ji
26 1 4.40 _ 2.13 1.45 , 0.67 i 0.44 I
[0044] Unless otherwise indicated, all alloys contained the listed
elements, from about
0.10 to 0.012 wt. % Zr, not more than about 0.03 wt. % Fe, not more than 0.04
wt. % Si,
about 0.02 wt. % Mn, about 0.02 wt. % Ti, the balance being aluminum and other
elements,
where the other elements did not exceed more than 0.05 wt. % each, and not
more than 0.15
wt. % total of the other elements. Alloy 25 contained about 0.24 wt. % Si.
Alloy 26
contained about 0.87 wt. % Si.
[0045] The alloys were cast as approximately 2.875 inch (ST) x 4.75 inch
(LT) x 17 inch
(L) ingots that were scalped to about 2 inches thick, and then homogenized.
After
homogenization, each ingot was hot rolled to a gauge of about 0.25 inch, and
then cold rolled
about 25% (reduced in thickness by 25%) to a final gauge of about 0.1875 inch.
Tensile
yield strength and corrosion resistance properties were then tested, the
results of which are
provided in Tables 9a-9b, below. Tensile yield strength properties were
measured in
accordance with ASTM E8 and B557 -- all test values relative to the
longitudinal (L)
direction, unless otherwise indicated. Corrosion resistance was tested in
accordance with
ASTM G66 (exfoliation resistance) and G67 (mass loss) -- the alloys were
tested for
corrosion resistance before and after exposure to a .temperature of about 100
C for about 1
week.
Table 9a - Mechanical Properties of Example 2 Alloys
TYS UTS Elong.
Alloy
(1139 (lisi) (%)
13 59.2 .. 66.0 6.4
14 60.1 65.7 3.9
15 1 55.6 62.1 5.2
L 16 57.3 62.0 5.2
17 64.3 68.9 3.7
18 59.4 - 64.2 4.5
........................................... ..--
19 54.2 59.5 5.9
20 52.9 59.4 4.6
L 21 55.7 61.8 7.1
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r __________________________ TYS UTS Elong.
Alloy
(ksi ksi (%) ..
.--
22 55.3 60.2 4.8
23 , 53.2 59.3 6.1
' 24 55.9 60.6 3.5
25 56.0 60.2 15.5
26 51.6 58.1 4.6
Table 9b - Corrosion Resistance Properties of Example 2 Alloys
1
1 Before Thermal Exposure After
Thermal Exposure I
1
Alloy G67 Mass G66 G66 G67 Mass G66 ' G66
Loss Rating Rating @ Loss Rating Rating @
I (mg/cm2) @ T/10 Surface .. (mg/cm2) @ T/10 Surface
13 ' 1.64 PC ..... PB 21.66 ED ED
1 14 2.26 PC PB 25.62 ED ED
15 2.43 PC PA 23.36 ED ED
16 248 ........ PC PC 28.80 ED ED
17 2.14 PC .............................................. PC 31.19 ED ED
18 2.72 PC PB 32.85 ED ED
19 ........ 3.71 PC , PA 23.99 ED EC
4
20 2.99 PC EC 34.99 ED F'...1)
21 2.48 ...... PC PC 29.38 ED ED
22 3.31 PC PC ... 43 ED ED
, 34
.,
23 4.09 PC PC r3286 ED ....... I ED
24 3.41 PC PA 28.25 ED EC
25 2.40 .*: PC * PA .... 25.59 1. ED
ED
26 : 3.41 I PC PA .................. L 17.45 I PC .. EC
,
[0046] As shown in FIG. 13, the strongest alloy contained about 1.0 wt. %
Zn, 0.35 wt. %
Cu and 0.65 wt. % Ag. In low silver alloys (- 0.25 wt. % Ag), increasing
copper from about
0.35 to 0.95 wt. % and/or increasing zinc did appear to benefit strength. In
medium silver
alloys (-- 0.45 wt. % Ag), increasing copper from about 0.65 to 1.85 wt. %
decreased
strength, and increasing zinc from about 1.45 to 2.82 wt. % had little effect
on strength. In
moderately-high silver alloys (- 0.65 wt. % Ag), increasing copper from about
0.35 to about
0.90 wt. % decreased strength, and increasing zinc also decreased strength.
Increasing silver
from about 0.45 to 0.91 wt. % did not appear to materially affect strength.
Increasing silicon
from about 0.04 wt. % to 0.24 wt. % also did not appear to materially affect
strength.
Increasing silicon to about 0.89 wt. %, however, did affect strength.
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[0047] Regarding ductility, all of the alloys have somewhat low elongation,
indicating
that less than 25% cold work may be required to achieve better ductility.
[0048] Regarding corrosion resistance, most of the alloys did not pass the
mass loss test,
all achieving a mass loss of more than 15 mg/cm2, and often a mass loss of
more than 25
mg/cm2. Increasing the silicon level did appear to help with mass loss.
[0049] Example 3
[0050] Twenty-three book mold ingots were produced, the compositions of
which are
provided in Table 9, below (all values in weight percent).
Table 10- Example 1 Alloy Compositions
Alloy I Mg Li Mn Cu Zn
27 1 2.2 1.1 0.55 0.05
28 2.5 1.0 0.58
29 3.3 1.0 0.54 --
30 3.5 1.1 0.56 --
31 4.1 1.1 0.57 --
32 2.9 1.1 0.54 --
33 3.1 1.0 0.29 -- --
32
=1.1 r -- 0.01 --
35 3.0 1.0 1.10 -
36 .................. 3.0 1 1.0 1.60 -
37 3.0 1-1.0 0.56 -- 0.10
38 3.0 1.1 0.56 -- 0.24
39 2.9 1.1 0.57 -- 0.51
40 3.0 1.1 0.56 -- 0.97
41 3.0 1.1 0.56 -- 1.90
42 2.9 1.0 0.57 0.14 0.02
43 3.1 1.1 0.56 0.29 --
44 2.9 1.1 0.56 1 0.48 --
45 j 3.1 1.0 0.56 0.25 0.50
46 2.8 1.1 0.56 --
i 47 2.94 -- 0.54 -- --
48 2.9 0.50 0.57 77-4
49 2.8 1.00 0.57 --
50 2.9 1.60 0.57 --
Unless otherwise indicated, all alloys contained the listed elements, from
about 0.10 to 0.14
wt. % Zr, not more than about 0.04 wt. % Fe, not more than 0.08 wt. % Si, the
balance being
aluminum and other elements, where the other elements did not exceed more than
0.05 wt. %
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each, and not more than 0.15 wt. % total of the other elements. Alloy 46
contained about
0.09 wt. % Zr, about 0.10 wt. % Fe and about 0.14 wt. % Si.
[0051] The alloys were cast as 2.875 inch (ST) x 4.75 inch (LT) x 17
inch (L) ingots that
were scalped to 2 inches thick and then homogenized. After homogenization,
each ingot was
hot rolled to a gauge of about 0.25 inch (Alloy 36 could not be rolled due to
too much
manganese). Part of these hot rolled pieces were then cold rolled to a gauge
of about 0.1875
inch (about 25% reduction in thickness). Other parts of the hot rolled pieces
were stretched
about 2% for flatness. The mechanical properties and corrosion resistance
properties of the
hot rolled and cold rolled materials were then tested, the results of which
are provided in
Tables 11-14, below. Strength and elongation properties were measured in
accordance with
ASTM E8 and B557 -- all test values relative to the longitudinal (L)
direction, unless
otherwise indicated. Corrosion resistance was tested in accordance with ASTM
G67 (mass
loss) -- the alloys were tested for corrosion resistance before and after
exposure to a
temperature of about 100 C for about 1 week.
Table 11 - Mechanical Properties of Hot Rolled + 2% Stretch Alloys
TYS UTS Elong.
Alloy _Aks:11 (1_(.1!) (%)
27 38.3 41.3 13.5
1_28 38.1 42.6 15.0
I29 45.5 15.0 15.0
30 40.3 .. 46.7 15.5
31 40.7 47.4 14.5
32 39.1 43.6 14.0
33 37.3 41.3 16.0
34 35.7 40.5 16.0
35 42.6 47.9 13.0
37 39.4 44.7 15.5
38 39.4 44.9 15.5
39.7 45.0 15.0
40 39.9 45.5 15.5 -I
41 42.6 49.3 15.0
42 41.7 46.3 15.0
43 44.9 50.4 13.0
44 49.4 53.3 __ 10.0
45 42.5 48.4 15.0
46 40.1 44.8 15.5
47 37.0 41.0 18.5
48 38.0 42.7 15.0
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TYS UTS Elong.
Alloy
(ksi) (ksi) (%)
t
, 49 40.3 44.7 i 15.5
?
50 44.5 , 49.9 i 14.0
Table 12 - Mechanical Properties of Hot Rolled + Cold Rolled Alloys
TYS UTS Elong.
Alloy
(ksi) (ksi) (%)
.. .,
27 45.5 46.7 7.0
,
28 47.4 49.1 8.5
29 45.3 153.6 8.0
30 ...... 51.4 55.7 8.0
31 52.2 57.2 9.0
32 51.3 52.2 8.0
33 46.9 49.4 10.0
34 43.0 1 45.4 .. 9.5
35 51.9 56.7 6.0
=
3'7 48.5 52.0 9.0
... . ...........................................
38 49.2 52.8 8.0 1
39 49.0 52.4 8.0
40 49.6 53.4 8.0
41 48.5 , 56.0 7.5
42 44.5 53.3 8.0
43 55.9 56.9 8.0
44 57.5 59.7 7.5
L.... 45 52.7 55.0 8.5
! 46 1 50.5 51.7 7.0
47 43.7 47.1 L 10.5
...
48 45.2 48.4 1 8.5
49 48.9 51.2 8.5
,. 50 57.9 59.6 7.5
Table 13 - Corrosion Resistance Results - Hot Rolled (HR) Alloys
r-
Before After
Thermal Thermal
Alloy Exposure .......................... Exposure
G67 Mass Loss
(ms/cm2)
......................... , .................... _
27 1.29 1.57
28 1.25 2.48
29 1.32 8.96
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Before After
Alloy Thermal Thermal
Exposure Exposure
30 1.66 17.2
31 1.59 30.23
32 1.28 5.34
33 1.37 6.29
34 1.51 9.68
35 1.49 8.12
37
1.62
1.73 11.8
38
.................................................. =
10.39
39 1.53 2.9
40 1.72 2.52
41 1 1.87 2.61
42 1.18 1 3.5
43 1.17 1 3.41
44 1.5 3.51
45 1.29 3.3
46 1.77 6.68
47 1.46 2.24
48 1.72 3.28
49 1.47 L6'71
50 11.73 3.97
Table 14 - Corrosion Resistance Results - Hot Rolled (BR) + 25% CR Alloys
Before After
Thermal Thermal
Alloy Exposure Exposure
G67 Mass Loss
(mg/em) ..........................................
27 .... 1.28 1.81
28 1.2 2.79
29 1.35 11.26
30 ---- 1.63 18.2
31 1.72 32.45
32 1.31
33 1.3 8.711
9.97
34 1.25 ..... 10.23
35 1.76 14.96
37 1.64 1 12.884
[ 38 L72 12.22 j
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r-
Before After
Alloy Thermal Thermal
Exposure Exposure
39 1.55 4.11
40 ................................. 1.63 3.14
41 1.92 2.67
42 1.22 5.17
43 1.31 ... 5.96
44 1, 1.461 4.91
45 1.28 5.13
46 1.82 9.32
47 1.46 2.57
48 1 1.57 4.58
49 1 1.59 11.51
1._ .............................. 1.63 r 3.97
[0052] As shown in FIGS. 14-18, increasing levels of Mg, Li, Mn and Cu
resulted in
increased strength. Increasing zinc may increase strength in hot rolled only
alloys. However,
as shown in FIG. 19, poor corrosion resistance is realized in alloys having
more than about
4.0 wt. % Mg, indicating that the alloys should include not greater than 3.9
wt. % Mg for
good corrosion resistance. As shown in FIG. 20, higher levels of copper tend
to improve
corrosion. As shown in FIG. 21, higher levels of zinc (e.g., at or above 0.4
wt. % Zn) also
tend to improve corrosion resistance. Manganese above about 1.0 wt. % tends to
degrade
corrosion resistance.
