Note: Descriptions are shown in the official language in which they were submitted.
IMPROVED WROUGHT 7X.XX ALUMINUM ALLOYS, AND METHODS FOR
MAKING THE SAME
CROSS-REFERENCE TO RELATED APPLICATIONS
[001] This patent application is related to commonly-owned U.S. Patent
Application No.
14/694,109, filed April 23, 2015, entitled "IMPROVED 7XX ALUMINUM CASTING
ALLOYS, AND METHODS FOR MAKING THE SAME".
BACKGROUND
[002] 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 or corrosion resistance of a wrought 7xxx
aluminum alloy
without affecting other properties.
SUMMARY OF THE DISCLOSURE
[003] Broadly, the present patent application relates to improved wrought
7xxx aluminum
alloys, and methods for producing the same. The new wrought 7xxx aluminum
alloys may
realize, for instance, an improved combination of at least two of strength,
corrosion resistance,
fatigue failure resistance, and quench insensitivity, among other properties.
[004] The new wrought 7xxx aluminum alloys generally comprise (and in some
instance
consist essentially of, or consist of), zinc (Zn), magnesium (Mg), copper
(Cu), vanadium (V),
zirconium (Zr), and titanium (Ti), as primary alloying elements, optionally
with manganese (Mn)
and/or chromium (Cr), the balance being aluminum (Al), iron (Fe), silicon
(Si), and unavoidable
impurities, as defined below. Some embodiments of new wrought 7xxx aluminum
alloy
compositions are shown in FIG. 1.
[005] Regarding zinc, the new wrought 7xxx aluminum alloys generally
include from 3.75
to 8.0 wt. % Zn. In one embodiment, a new wrought 7xxx aluminum alloy includes
not greater
than 7.5 wt. % Zn. In another embodiment, a new wrought 7xxx aluminum alloy
includes not
greater than 7.0 wt. % Zn. In yet another embodiment, a new wrought 7xxx
aluminum alloy
includes not greater than 6.5 wt. % Zn. In another embodiment, a new wrought
7xxx aluminum
alloy includes not greater than 6.0 wt. % Zn. In yet another embodiment, a new
wrought 7xxx
aluminum alloy includes not greater than 5.5 wt. % Zn. In another embodiment,
a new wrought
7xxx aluminum alloy includes not greater than 5.0 wt. % Zn. In another
embodiment, a new
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wrought 7xxx aluminum alloy includes not greater than 4.75 wt. % Zn. In one
embodiment, a
new wrought 7xxx aluminum alloy includes at least 4.0 wt. % Zn. In another
embodiment, a
new wrought 7xxx aluminum alloy includes at least 4.25 wt. % Zn. In yet
another embodiment,
a new wrought 7xxx aluminum alloy includes at least 4.35 wt. % Zn.
[006] The new wrought 7xxx aluminum alloys generally include magnesium in
the range of
from 1.25 to 3.0 wt. % Mg. In one embodiment, a new wrought 7xxx aluminum
alloy includes
not greater than 2.75 wt. % Mg. In another embodiment, a new wrought 7xxx
aluminum alloy
includes not greater than 2.5 wt. % Mg. In yet another embodiment, a new
wrought 7xxx
aluminum alloy includes not greater than 2.25 wt. % Mg. In another embodiment,
a new wrought
7xxx aluminum alloy includes not greater than 2.0 wt. % Mg. In yet another
embodiment, a new
wrought 7xxx aluminum alloy includes not greater than 1.8 wt. % Mg. In one
embodiment, a
new wrought 7xxx aluminum alloy includes at least 1.35 wt. % Mg. In another
embodiment, a
new wrought 7xxx aluminum alloy includes at least 1.40 wt. % Mg. In yet
another embodiment,
a new wrought 7xxx aluminum alloy includes at least 1.45 wt. % Mg. In another
embodiment, a
new wrought 7xxx aluminum alloy includes at least 1.50 wt. % Mg.
[007] In some embodiments, the amount of zinc and magnesium may be limited
(e.g., to
improve corrosion resistance). Thus, in one embodiment, the combined amount of
zinc and
magnesium in a new wrought 7xxx aluminum alloy may be not greater than 7.0 wt.
% (i.e., wt.
% Zn + wt. % Mg < 7.0 wt. %). In another embodiment, the combined amount of
zinc and
magnesium in a new wrought 7xxx aluminum alloy is not greater than 6.75 wt. %
(i.e., wt. % Zn
+ wt. % Mg < 6.75 wt. %). In yet another embodiment, the combined amount of
zinc and
magnesium in a new wrought 7xxx aluminum alloy is not greater than 6.50 wt. %
(i.e., wt. % Zn
+ wt. % Mg < 6.50 wt. %). In another embodiment, the combined amount of
zinc and
magnesium in a new wrought 7xxx aluminum alloy is not greater than 6.25 wt. %
(i.e., wt. % Zn
+ wt. % Mg < 6.25 wt. %). In yet another embodiment, the combined amount of
zinc and
magnesium in a new wrought 7xxx aluminum alloy is not greater than 6.00 wt. %
(i.e., wt. % Zn
+ wt. % Mg < 6.00 wt. %).
[008] The new wrought 7xxx aluminum alloys generally include copper and in
the range of
from 0.35 to 1.35 wt. % Cu, and where the amount of magnesium exceeds the
amount of copper.
As shown below, copper may facilitate, for example, improved corrosion
resistance (e.g.,
improved SCC resistance) and/or strength. In one embodiment, a new wrought
7xxx aluminum
alloy includes not greater than 1.15 wt. % Cu. In another embodiment, a new
wrought 7xxx
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aluminum alloy includes not greater than 1.00 wt. % Cu. In yet another
embodiment, a new
wrought 7xxx aluminum alloy includes not greater than 0.95 wt. % Cu. In
another embodiment,
a new wrought 7xxx aluminum alloy includes not greater than 0.90 wt. % Cu. In
yet another
embodiment, a new wrought 7xxx aluminum alloy includes not greater than 0.85
wt. % Cu. In
another embodiment, a new wrought 7xxx aluminum alloy includes not greater
than 0.80 wt. %
Cu. In one embodiment, a new wrought 7xxx aluminum alloy includes at least
0.40 wt. % Cu.
In another embodiment, a new wrought 7xxx aluminum alloy includes at least
0.45 wt. ')/0 Cu.
In yet another embodiment, a new wrought 7xxx aluminum alloy includes at least
0.50 wt. %
Cu. In another embodiment, a new wrought 7xxx aluminum alloy includes at least
0.55 wt. %
Cu. In yet another embodiment, a new wrought 7xxx aluminum alloy includes at
least 0.60 wt.
% Cu.
[009] The new wrought 7xxx aluminum alloys generally include from 0.04 to
0.20 wt. % V.
As shown below, vanadium may facilitate, for example, improved corrosion
resistance and/or
quench insensitivity. In one embodiment, a new wrought 7xxx aluminum alloy
includes not
greater than 0.18 wt. % V. In another embodiment, a new wrought 7xxx aluminum
alloy
includes not greater than 0.16 wt. % V. In yet another embodiment, a new
wrought 7xxx
aluminum alloy includes not greater than 0.15 wt. % V. In another embodiment,
a new wrought
7xxx aluminum alloy includes not greater than 0.14 wt. % V. In yet another
embodiment, a new
wrought 7xxx aluminum alloy includes not greater than 0.13 wt. % V. In another
embodiment, a
new wrought 7xxx aluminum alloy includes not greater than 0.12 wt. % V. In yet
another
embodiment, a new wrought 7xxx aluminum alloy includes not greater than 0.11
wt. % V. In
one embodiment, a new wrought 7xxx aluminum alloy includes at least 0.05 wt. %
V. In another
embodiment, a new wrought 7xxx aluminum alloy includes at least 0.06 wt. % V.
In yet another
embodiment, a new wrought 7xxx aluminum alloy includes at least 0.07 wt. % V.
In another
embodiment, a new wrought 7xxx aluminum alloy includes at least 0.08 wt. % V.
[0010] The new wrought 7xxx aluminum alloys generally include from 0.06 to
0.20 wt. %
Zr. As shown by the below data, the combination of vanadium and zirconium may
facilitate, for
instance, improved fatigue failure resistance properties. In one embodiment, a
new wrought
7xxx aluminum alloy includes not greater than 0.18 wt. % Zr. In another
embodiment, a new
wrought 7xxx aluminum alloy includes not greater than 0.16 wt. % Zr. In yet
another
embodiment, a new wrought 7xxx aluminum alloy includes not greater than 0.15
wt. % Zr. In
another embodiment, a new wrought 7xxx aluminum alloy includes not greater
than 0.14 wt. %
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Zr. In yet another embodiment, a new wrought 7xxx aluminum alloy includes not
greater than
0.13 wt. % Zr. In one embodiment, a new wrought 7xxx aluminum alloy includes
at least 0.07
wt. % Zr. In another embodiment, a new wrought 7xxx aluminum alloy includes at
least 0.08 wt.
% Zr.
[0011] The total amount of vanadium plus zirconium should be controlled to
restrict
formation of a high volume fraction of constituent particles (e.g., a high
volume fraction of
Al3Zr, A123V4, A17V and/or Alloy constituent particles). In one embodiment,
the total amount of
vanadium plus zirconium does not exceed 0.23 wt. % V + Zr. In another
embodiment, the total
amount of vanadium plus zirconium does not exceed 0.22 wt. % V + Zr. In yet
another
embodiment, the total amount of vanadium plus zirconium does not exceed 0.21
wt. % V + Zr.
In another embodiment, the total amount of vanadium plus zirconium does not
exceed 0.20 wt.
% V + Zr. In one embodiment, the total volume fraction of Al3Zr, A123V4, A17V
and AlioV
constituent particles does not exceed 0.07%. The total volume fraction of
these constituent
particles may be determined, for instance, by PandatTM software and the
PanAluminum
thermodynamic database (Compu'Therm LLC, 437 S. Yellowstone Dr. Suite 217,
Madison, WI,
USA). In one embodiment, the total volume fraction of Al3Zr, A123V4, A17V
and Al 10V
constituent particles does not exceed 0.06%. In another embodiment, the total
volume fraction
of A13Zr, A123V4, A17V and Al 10V constituent particles does not exceed 0.05%.
In yet another
embodiment, the total volume fraction of A13Zr, A123V4, A17V and AlioV
constituent particles
does not exceed 0.04%. In another embodiment, the total volume fraction of
Al3Zr, A123V4,
Al7V and Alloy constituent particles does not exceed 0.03%. In yet another
embodiment, the
total volume fraction of Al3Zr, A123V4, A17V and Al 10V constituent particles
does not exceed
0.02%. In another embodiment, the total volume fraction of A13Zr, A123V4, A17V
and Al ioV
constituent particles does not exceed 0.01%. In yet another embodiment, the
total volume
fraction of A13Zr, A123V4, A17V and AlloV constituent particles does not
exceed 0.005%.
[0012] The new wrought 7xxx aluminum alloys generally include from 0.01 to
0.25 wt. %
Ti. In one embodiment, a new wrought 7xxx aluminum alloy includes from 0.01 to
0.15 wt. %
Ti. In another embodiment, a new wrought 7xxx aluminum alloy includes from
0.01 to 0.10 wt.
% Ti. In yet another embodiment, a new wrought 7xxx aluminum alloy includes
from 0.01 to
0.08 wt. % Ti. In another embodiment, a new wrought 7xxx aluminum alloy
includes from 0.02
to 0.05 wt. % Ti. The titanium may be present (e.g., at least partially
present) in the form of TiB2
or TiC.
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[0013] In some embodiments, the new wrought 7xxx aluminum alloys may
include up to
0.50 wt. % Mn. In embodiments where manganese is utilized, the new wrought
7xxx aluminum
alloys generally include from 0.10 to 0.50 wt. % Mn. In one embodiment, a new
wrought 7xxx
aluminum alloy includes from 0.10 to 0.25 wt. % Mn. In some embodiments, the
new wrought
7xxx aluminum alloys are substantially free of manganese, and, in these
embodiments, contain
less than 0.10 wt. %. Mn (i.e., < 0.09 wt. % Mn), such as < 0.05 wt. % Mn, or
< 0.04 wt. % Mn,
or < 0.03 wt. % Mn.
[0014] In some embodiments, the new wrought 7xxx aluminum alloys may
include up to
0.40 wt. % Cr. In embodiments where chromium is utilized, the new wrought 7xxx
aluminum
alloys generally include from 0.10 to 0.40 wt. % Cr. In one embodiment, a new
wrought 7xxx
aluminum alloy includes from 0.10 to 0.35 wt. % Cr. In another embodiment, a
new wrought
7xxx aluminum alloy includes from 0.10 to 0.25 wt. % Cr. In some embodiments,
the new
wrought 7xxx aluminum alloys are substantially free of chromium, and, in these
embodiments,
contain less than 0.10 wt. %. Cr (i.e., < 0.09 wt. % Cr), such as < 0.05 wt. %
Cr, or < 0.04 wt. %
Cr, or < 0.03 wt. % Cr.
[0015] The new wrought 7xxx aluminum alloys may include iron, up to 0.35
wt. % Fe. In
one embodiment, a new wrought 7xxx aluminum alloy includes not greater than
0.25 wt. % Fe.
In another embodiment, a new wrought 7xxx aluminum alloy includes not greater
than 0.20 wt.
% Fe. In yet another embodiment, a new wrought 7xxx aluminum alloy includes
not greater than
0.15 wt. % Fe. In another embodiment, a new wrought 7xxx aluminum alloy
includes not
greater than 0.12 wt. % Fe. In yet another embodiment, a new wrought 7xxx
aluminum alloy
includes not greater than 0.10 wt. % Fe. In yet another embodiment, a new
wrought 7xxx
aluminum alloy includes not greater than 0.08 wt. % Fe. In one embodiment, a
new wrought
7xxx aluminum alloy includes at least 0.01 wt. % Fe.
[0016] The new wrought 7xxx aluminum alloys may include silicon, up to 0.25
wt. % Si. In
one embodiment, a new wrought 7xxx aluminum alloy includes not greater than
0.20 wt. % Si.
In another embodiment, a new wrought 7xxx aluminum alloy includes not greater
than 0.15 wt.
% Si. In yet another embodiment, a new wrought 7xxx aluminum alloy includes
not greater than
0.10 wt. % Si. In yet another embodiment, a new wrought 7xxx aluminum alloy
includes not
greater than 0.08 wt. % Si. In another embodiment, a new wrought 7xxx aluminum
alloy
includes not greater than 0.05 wt. % Si. In one embodiment, a new wrought 7xxx
aluminum
alloy includes at least 0.01 wt. % Si.
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[0017] The balance of the new wrought 7xxx aluminum alloy is generally
aluminum and
unavoidable impurities. In one embodiment, the new wrought 7xxx aluminum
alloys contain not
more than 0.10 wt. % each of any one impurity (measured on an elemental
basis), with the total
combined amount of these impurities not exceeding 0.35 wt. % in the new
wrought 7xxx
aluminum alloy (i.e., < 0.10 wt. % each of any one impurity, and with the
total impurities being
< 0.35 wt. %). In another embodiment, each one of the impurities,
individually, does not exceed
0.05 wt. % in the new wrought 7xxx aluminum alloy, and the total combined
amount of the
impurities does not exceed 0.15 wt. % in the new wrought 7xxx aluminum alloy
(i.e., < 0.05 wt.
% each of any one impurity, and with the total impurities being < 0.15 wt. %).
In another
embodiment, each one of these impurities, individually, does not exceed 0.03
wt. % in the new
wrought 7xxx aluminum alloy, and the total combined amount of these impurities
does not
exceed 0.10 wt. % in the new wrought 7xxx aluminum alloys (i.e., < 0.03 wt. %
each of any one
impurity, and with the total impurities being < 0.10 wt. %).
[0018] The new wrought 7xxx aluminum alloys described herein may be cast
(e.g., as ingot
or billet), then homogenized, and then hot worked to an intermediate or final
form (e.g., cold
working after the hot working when the hot working produces an intermediate
form). In one
embodiment, the hot working is forging. In one embodiment, the forging
produces a shaped
product, such as a wheel product. In another embodiment, the hot working is
rolling or
extruding. After the hot working (and any optional cold working), the new
alloy may be
tempered, such as by solution heat treating, and then quenching, and then
natural aging, followed
by artificial aging. Suitable tempers include the T4, T5, T6, and T7 tempers,
for instance, as
defined in ANSI H35.1 (2009). In one embodiment, the new alloy compositions
described
herein are processed into a forged wheel product per the processes described
in commonly-
owned U.S. Patent Application Publication No. 2006/0000094. In one embodiment,
the new
wrought 7xxx aluminum alloys described herein are processed to a T5 temper
(e.g., a T53
temper), which may include press quenching the new wrought 7xxx aluminum
alloys (e.g., in the
form of a forged wheel) after solution heat treatment.
[0019] As mentioned above, the new wrought 7xxx aluminum alloys may realize
improved
quench insensitivity. Quench insensitivity relates to an aluminum alloy's
sensitivity to the
quench conditions used after solution heat treatment. One indicator of quench
sensitivity is a
significant drop in strength with low quench rates as compared to high quench
rates. As shown
by the below examples, the new wrought 7xxx aluminum alloys described herein
may be
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relatively quench insensitive. For purposes of this application, quench
insensitivity is measured
by conventionally producing a new wrought 7xxx aluminum alloy as a rolled
plate having a final
gauge of 1.0 inch (2.54 mm), after which two identical pieces of this plate
are solution heat
treated, after which one piece is cold water quenched in 77 F (25 C) water and
the other piece is
boiling water quenched, both for a period of 10 minutes, after which the
pieces are allowed to air
dry. The two pieces are then both naturally aged for 24 hours and then both
two-step artificially
aged with a first step of 250 F for 3 hours (with a 2-hour heat up from
ambient to 250 F) and a
second step of 340 F for 8 hours. The longitudinal (L) tensile yield strengths
of these two pieces
are then measured at T/2 in accordance with ASTM B557 and E8, using at least
duplicate
specimens, after which the measured strengths are averaged for each piece. The
average TYS(L)
of the cold water quenched ("CWQ") piece is then compared to the average
TYS(L) of the
boiling water quenched (BWQ") TYS. The difference between the two average TYS
values (i.e.,
CWQ(TYS) - BWQ(TYS)) is the quench insensitivity of the alloy.
[0020]
In one embodiment, a new wrought 7xxx aluminum alloy realizes a quench
insensitivity (as defined above) of not greater than 7 ksi (i.e., CWQ(TYS) -
BWQ(TYS) < 7 ksi).
In another embodiment, a new wrought 7xxx aluminum alloy realizes a quench
insensitivity of
not greater than 6 ksi. In yet another embodiment, a new wrought 7xxx aluminum
alloy realizes
a quench insensitivity of not greater than 5 ksi. In another embodiment, a new
wrought 7xxx
aluminum alloy realizes a quench insensitivity of not greater than 4 ksi. In
yet another
embodiment, a new wrought 7xxx aluminum alloy realizes a quench insensitivity
of not greater
than 3 ksi. In another embodiment, a new wrought 7xxx aluminum alloy realizes
a quench
insensitivity of not greater than 2 ksi. In yet another embodiment, a new
wrought 7xxx
aluminum alloy realizes a quench insensitivity of not greater than 1 ksi. In
another embodiment,
a new wrought 7xxx aluminum alloy realizes a quench insensitivity of not
greater than 0 ksi,
meaning the boiling water quenched alloy realizes at least equivalent strength
to the cold water
quenched alloy. In yet another embodiment, a new wrought 7xxx aluminum alloy
realizes a
quench insensitivity of not greater than -1 ksi, meaning the boiling water
quenched alloy realizes
higher strength than the cold water quenched alloy. In another embodiment, a
new wrought
7xxx aluminum alloy realizes a quench insensitivity of not greater than -2
ksi. In another
embodiment, a new wrought 7xxx aluminum alloy realizes a quench insensitivity
of not greater
than -3 ksi. In another embodiment, a new wrought 7xxx aluminum alloy realizes
a quench
insensitivity of not greater than -4 ksi. In another embodiment, a new wrought
7xxx aluminum
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alloy realizes a quench insensitivity of not greater than -5 ksi. In another
embodiment, a new
wrought 7xxx aluminum alloy realizes a quench insensitivity of not greater
than -6 ksi. In
another embodiment, a new wrought 7xxx aluminum alloy realizes a quench
insensitivity of not
greater than -7 ksi. In another embodiment, a new wrought 7xxx aluminum alloy
realizes a
quench insensitivity of not greater than -8 ksi. In another embodiment, a new
wrought 7xxx
aluminum alloy realizes a quench insensitivity of not greater than -9 ksi, or
more.
[0021] The quench insensitivity of the new wrought 7xxx aluminum alloys may
facilitate
improved strength. Likewise, when using a hot quench media, a new wrought 7xxx
aluminum
alloy may realize less distortion.
[0022] The new wrought 7xxx aluminum alloys may be post-solution heat
treatment
quenched with any applicable fluid or media. In one embodiment, a new wrought
7xxx
aluminum alloy is water quenched (cold water quenched, hot water quenched, or
boiling water
quenched). In one embodiment, the new wrought 7xxx aluminum alloy is hot or
boiling water
quenched. A hot water quench is a quenching using water having a temperature
of from 150 F to
boiling (212 F at standard temperature and pressure). A boiling water quench
uses boiling water.
A boiling water quench is a species of the hot water quench genus. As shown by
the below data,
use of a hot water quench (including a boiling water quench) may facilitate
improved SCC
resistance. In another embodiment, a new wrought 7xxx aluminum alloy is air
quenched (e.g.,
via a forced air quench). In yet another embodiment, a new wrought 7xxx
aluminum alloy is
press-quenched. In one embodiment, the quenching step results in an average
cooling rate of
from 1 F to 25 F per second as measured during the first 60 seconds of the
quench. In another
embodiment, the quenching step results in an average cooling rate of not
greater than 22.5 F per
second as measured during the first 60 seconds of the quench. In yet another
embodiment, the
quenching step results in an average cooling rate of not greater than 20 F per
second as measured
during the first 60 seconds of the quench. In another embodiment, the
quenching step results in
an average cooling rate of not greater than 17.5 F per second as measured
during the first 60
seconds of the quench. In yet another embodiment, the quenching step results
in an average
cooling rate of not greater than 15 F per second as measured during the first
60 seconds of the
quench. In another embodiment, the quenching step results in an average
cooling rate of not
greater than 12.5 F per second as measured during the first 60 seconds of the
quench. In yet
another embodiment, the quenching step results in an average cooling rate of
not greater than
F per second as measured during the first 60 seconds of the quench. In another
embodiment,
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the quenching step results in an average cooling rate of not greater than 9.0
F per second as
measured during the first 60 seconds of the quench. In yet another embodiment,
the quenching
step results in an average cooling rate of not greater than 8.0 F per second
as measured during
the first 60 seconds of the quench. In another embodiment, the quenching step
results in an
average cooling rate of not greater than 7.0 F per second as measured during
the first 60 seconds
of the quench. In yet another embodiment, the quenching step results in an
average cooling rate
of not greater than 6.0 F per second as measured during the first 60 seconds
of the quench.
DETAILED DESCRIPTION
[0023]
The following illustrates various embodiments of new 7xxx wrought aluminum
alloy
compositions:
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,
C)
L)
0
0
w (all values in weight
percent)
1-.
in
co
Iv Embod-
o iment Zn Mg Cu V Zr
V+Zr Ti
1-.
to .
1-
1 . 1 3.75 - 8.0 1.25 - 3.0 0.35- 1.35
0.04 - 0.20 0.06 - 0.20 <0.23 0.01 -0.25
Iv
1 2 3.75 - 7.0 1.25 - 2.75 0.35 - 1.15
0.05 - 0.18 _ 0.06 - 0.18 <0.23 0.01 -0.15
1-.
_
Iv 3 3.75 - 6.0 1.25 - 2.5 0.40- 0.95
0.05 - 0.16 0.06 -0.17 <0.22 0.01 -0.10
4 3.75 -6.5 1.35 -2.25 0.45 - 0.90 0.06 - 0.15 0.06
-0.16 <0.22 0.01 -0.08
5 4.0 - 5.5 1.40 - 2.0 0.50 - 0.85 _ 0.06 - 0.14
0.07 - 0.16 <0.21 0.01 -0.08
6 4.0 - 5.0 1.45 - 2.0 0.55 - 0.80 0.06 - 0.13 0.07 -
0.15 <0.21 0.01 -0.08
7 4.25 - 4.75 1.50- 1.8 0.60 - 0.80 _ 0.07 - 0.12
0.07 - 0.14 <0.20 0.02 - 0.05
..
_
Embod- Imp.,
Imp.,
Mn Cr, Fe Si Bal.
iment each
total ,
c) 1 Opt. Opt. 0.01 -0.35 , 0.01 -0.25
_ <0.10 <0.35 , Al
2 Opt. Opt. 0.01 - 0.25 0.01 -0.20 <0.05 <0.15
Al .
3 Opt. Opt. 0.01 - 0.20 0.01 -0.20 <0.05 <0.15
Al
_
4 Opt. Opt. 0.01 -0.15 0.01 -0.15 <0.05 <0.15
Al
5 <0.10 <0.10 0.01 -0.12 0.01 -0.10 <0.03 <0.10
Al
_
6 <0.10 <0.10 - 0.01 -0.10 0.01 -0.10 <0.03 <0.10
Al
7 <0.05 <0.05 0.01 -0.08 0.01 -0.08 <0.03 <0.10
Al
Example 1
[0024] Several 7xxx aluminum alloys having the compositions shown in Table
1, below,
were cast as lab-scale, 2.5 inch (6.35 cm) thick ingots (nominal). The ingots
were then scalped,
homogenized, and hot rolled to a final gauge of 1.25 inch (3.175 cm). After
hot rolling, the
plates were metallographically inspected. The inspection revealed that plates
2, 14, 15, 17 and
18 contained a high volume fraction of constituent particles due to excess V +
Zr + Ti content
relative to the amount of Zn+Mg+Cu content of those alloys.
[0025] The hot rolled plates were then solution heat treated, cold water
quenched, and then
allowed to naturally age for about 24-hours. After natural aging, the plates
were then two-step
artificially aged at 250 F for 3 hours and then 340 F for 8 hours. Several of
the alloy samples in
the naturally aged condition were also artificially aged at 250 F for 3 hours
and then 340 F for 16
hours. The longitudinal (L) mechanical properties of the artificially aged
plates were then
measured at T/2 and in accordance with ASTM B557 and E8, the results of which
are shown in
Table 2, below (average of duplicate specimens).
Table 1 - Composition of the Example 1 Alloys (all values in weight percent)*
Alloy # Si Fe Zn Mg Cu V Zr
V+Zr
1** 0.056
0.087 4.25 1.59 0.57 0.079 0.10 0.179
2 0.059
0.094 4.83 1.67 0.65 0.120 0.19 0.310
3** 0.057
0.095 5.20 1.60 0.64 0.082 0.10 0.182
4** 0.056
0.094 6.02 1.57 0.64 0.086 0.10 0.186
0.057 0.085 3.65 1.66 0.62 0.080 0.11 0.190
6 0.059
0.092 2.83 1.61 0.60 0.080 0.10 0.180
7** 0.064
0.093 4.39 1.99 0.62 0.088 0.10 0.188
8** 0.057
0.092 4.38 2.37 0.61 0.089 0.10 0.189
9 0.052
0.072 4.53 1.20 0.55 0.083 0.10 0.183
0.050 0.080 4.40 0.85 0.60 0.080 0.10 0.180
11** 0.058 0.084 4.41 1.63 0.88 0.084 0.10 0.184
12** 0.054 0.088 4.38 1.64 1.26 0.083 0.10 0.183
13** 0.055 0.088 4.35 1.63 0.42 0.082 0.12 0.202
14 0.059
0.092 4.44 1.67 0.61 0.200 0.10 0.300
0.059 0.086 4.46 1.62 0.61 0.160 0.11 0.270
16** 0.058 0.100 4.41 1.55 0.64 0.056 0.10 0.156
17 0.057
0.089 4.39 1.65 0.61 0.088 0.15 0.238
18 0.059
0.092 4.44 1.61 0.62 0.086 0.19 0.276
19** 0.054 0.084 4.36 1.62 0.59 0.086 0.06 0.146
0.056 0.088 4.31 1.6 0.61 0.078 0 0.078
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CA 3003158 2019-12-12
* = The balance of the alloys was Ti, Al and impurities; all alloys contained
0.02 - 0.03
wt. % Ti, except alloy 2 which contained 0.055 wt. % Ti ; all alloys contained
0.03 wt.
% of any one impurity and < 0.10 wt. % in total of all impurities; impurities
included Mn
and Cr in this example.
** = invention alloy
Table 2 - Measured Mechanical Properties of the Example 1 Alloys
All Artificial Aging TYS UTS Elong.
#
Practice (MPa) (MPa) (%
1 250F/3hrs + 340F/8hrs 332.5 395.3 17.0
1 250F/3hrs + 340F/16hrs 323.8 389.3 16.0
3 250F/3hrs + 340F/8hrs 399.0 447.5 17.0
3 250F/3hrs + 340F/16hrs 371.3 428.3 18.0
4 250F/3hrs + 340F/16hrs 416.3 459.0
16.5
5 250F/3hrs + 340F/8hrs 285.8 365.3 17.5
5 250F/3hrs + 340F/16hrs 299.0 378.5
18.0
6 250F/3hrs + 340F/16hrs 224.5 317.0
21.5
7 250F/3hrs + 340F/8hrs 383.3 440.3 16.0
7 250F/3hrs + 340F/16hrs 383.8 444.0
15.5
8 250F/3hrs + 340F/16hrs 399.8 455.3
13.5
9 250F/3hrs + 340F/8hrs 304.5 360.5 15.0
9 250F/3hrs + 340F/16hrs 275.0 340.0
15.0
250F/3hrs + 340F/16hrs 231.0 298.0 19.5
11 250F/3hrs + 340F/8hrs 344.3 411.0 15.5
11 250F/3hrs + 340F/16hrs 358.3 424.8
16.0
12 250F/3hrs + 340F/16hrs 357.5 433.0
15.0
13 250F/3hrs + 340F/8hrs 332.8 391.3 17.0
13 250F/3hrs + 340F/16hrs 333.3 397.3 17.0
16 250F/3hrs + 340F/8hrs 368.8 424.8 16.5
16 250F/3hrs + 340F/16hrs 325.8 392.0
14.5
19 250F/3hrs + 340F/8hrs 336.5 393.8 17.0
19 250F/3hrs + 340F/16hrs 326.5 389.0
16.0
20 250F/3hrs + 340F/8hrs 345.3 399.8 16.0
20 250F/3hrs + 340F/16hrs 337.0 396.5
13.0
[0026] As shown, alloys 5-6 and 9-10 with low zinc (alloys 5-6) or low
magnesium (9-10)
have low strength, not achieving a tensile yield strength (TYS) of at least
320 MPa in
combination with an elongation of at least 12%.
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CA 3003158 2019-12-12
[0027] Rotating beam fatigue testing in accordance with ISO 1143 was also
conducted on
alloy plates 1, 13, 16 and 20, the results of which are shown in Table 3,
below. The stress level
for the test was 15 ksi, with R = -1 and with the RPM being 10,000. Three test
specimens per
alloy were used, and the number of cycles to failure was measured for each
specimen. The test
run-out was 10,000,000 cycles.
Table 3 - Measured Fatigue Life of Alloys 1, 13, 16 and 20
Alloy # Artificial Aging Cycles to Failure**
Practice Specimen 1 Specimen 2 Specimen 3
250F/3hrs +
1
340F/8hrs 10,000,000 10,000,000 10,000,000
250F/3hrs +
13
340F/8hrs 10,000,000 1,174,446 10,000,000
250F/3hrs +
16
340F/8hrs 10,000,000 10,000,000 10,000,000
250F/3hrs +
340F/8hrs 2,281,864 2,664,481 1,562,425
[0028] As shown, alloy 20 with no zirconium realizes worse fatigue
properties relative to
alloys 1, 13 and 16.
Example 2
[0029] Three 7xxx aluminum alloys having the compositions shown in Table 4,
below, were
cast as industrial-scale billet. From these billets, 3" x 7.75" x 7.75"
samples were obtained from
D/2 by machining. The samples were then hot rolled to a final gauge of about
1.0 inch (2.54
cm). The hot rolled plates were then solution heat treated, and then either
cold water (CW) or
boiling water (BW) quenched, and then allowed to naturally age for about 24-
hours. Cold water
quenched means the use of ambient temperature water. Boiling-water quench
means the use of
boiling water. After natural aging, the plates were then two-step artificially
aged with a first step
of 250 F for 3 hours (with a 2-hour heat up from ambient to 250 F) and a
second step of 340 F
for 8 hours. The longitudinal (L) mechanical properties of the plates were
then measured at T/2
and in accordance with ASTM B557 and E8, the results of which are shown in
Table 5, below
(average of duplicate specimens). SCC results were also measured in accordance
with ASTM
G103-97(2011), the "Standard Practice for Evaluating Stress-Corrosion Cracking
Resistance of
Low Copper 7XXX Series Al-Zn-Mg-Cu Alloys in Boiling 6% Sodium Chloride
Solution," at 25
ksi and 35 ksi stress levels, the results of which are shown in Table 6,
below.
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CA 3003158 2019-12-12
,
Table 4 - Composition of the Example 2 Alloys (all values in weight percent)*
Alloy # Si Fe Zn Mg Cu V Zr
A 0.062 0.065 4.38 1.54 0.63 0.06 0.08
B 0.078 0.061 4.60 1.72 0.61 0.01
0.11
C 0.060 0.068 4.43 1.71 0.89 0.01
0.10
* = The balance of the alloys was Ti, Al and impurities; all alloys contained
0.02 - 0.03
wt. % Ti; all alloys contained < 0.03 wt. % of any one impurity and < 0.10 wt.
% in total
of all impurities; impurities included Mn and Cr in this example.
Table 5 - Measured Mechanical Properties of the Example 2 Alloys
Quench TYS UTS Elong.
Alloy #
(MPa) (MPa) (%
A CW 362.8 417.5 17.0
A BW 370.5 423.0 16.5
B CW 391.0 441.8 16.0
B BW 400.8 448.3 15.8
C CW 390.5 446.0 16.0
C BW 401.3 450.5 16.3
Table 6 - SCC Properties of the Example 2 Alloys
Stress (ST) Days to Failure
Alloy # Quench
(ksi) Specimen 1 Specimen 2 Specimen 3
25 2.12 0K7 0K7
A CW
35 6.06 3.01 2.12
25 0K7 0K7 0K7
A BW
35 0K7 0K7 0K7
25 0.65 1.07 0.65
B CW
35 0.65 0.65 0.65
25 5.08 0K7 0K7
B BW
35 0.65 1.7 1.07
25 0K7 0K7 7.0
C CW
35 3.01 0.65 2.12
25 3.01 0K7 5.08
C BW
35 2.67 2.12 0K7
0K7 = Passed the SCC test for the full 7 days
7.0 = failed on the 7th day
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[0030] As shown, Alloy A realizes a superior combination of strength,
elongation and SCC
resistance properties. As shown, Alloy A is generally quench insensitive,
realizing about 8 ksi
higher tensile yield strength when boiling water quenched.
[0031] While various embodiments of the present disclosure have been
described in detail, it
is apparent that modifications and adaptations of those embodiments will occur
to those skilled
in the art. However, it is to be expressly understood that such modifications
and adaptations are
within the spirit and scope of the present disclosure.
CA 3003158 2019-12-12
