Note: Descriptions are shown in the official language in which they were submitted.
CA 02886124 2015-03-23
TITLE: LITHIUM FREE ELEVATED TEMPERATURE ALUMINUM
COPPER MAGNESIUM SILVER ALLOY FOR FORGED
AEROSPACE PRODUCTS
INVENTORS: LESLIE STEELE
AWADH B. PANDEY
ASSIGNEE: GOODRICH CORPORATION
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a nonprovisional application of and claims
priority to U.S.
Provisional Patent Application Serial Number 61/989,326, filed May 6, 2014,
entitled
"LITHIUM FREE ELEVATED TEMPERATURE ALUMINUM COPPER MAGNESIUM
SILVER TYPE ALLOY FOR FORGED AEROSPACE PRODUCTS," which is hereby
incorporated by reference in its entirety.
FIELD OF INVENTION
[0002] The present disclosure relates to high-temperature alloys, and,
more specifically, to a
substantially lithium-free elevated-temperature aluminum based alloy.
BACKGROUND OF THE INVENTION
[0003] Aircraft components may be subjected to high airspeeds and
elevated temperatures as
result of flight. Load bearing structures (e.g., wheels and landing gear) may
also be put
under immense weight during taxi, takeoff, and landing. Materials used to make
components (e.g. main wheels) support aircraft weights and withstand inflight
wind
conditions. Many of the components (such as piston housings) may also be
subject to
elevated temperatures. As a result, components may be subject to stress
corrosion and
ultimately failure over time.
SUMMARY OF THE INVENTION
[0004] In various embodiments, a substantially lithium-free alloy may
comprise copper
from 4.8 wt.% to 5.4 wt.%, magnesium from 0.7 wt.% to 1.1 wt.%, silver from
0.55 wt.% to
0.7 wt.%, and lithium at or below 0.005 wt.%. The substantially lithium-free
alloy may
1
CA 02886124 2015-03-23
further comprise silver from 0.56 wt.% to 0.7 wt.%. The substantially lithium-
free alloy
may also comprise zirconium from 0.08 wt.% to 0.15 wt.%. The substantially
lithium-free
alloy may include titanium at or below 0.06 wt.%, iron at or below 0.1 wt.%,
silicon at or
below 0.08 wt.%, beryllium at or below 0.0001 wt.%, chromium at or below 0.05
wt.%, and
zinc at or below 0.25 wt.%. The silver may be from 0.6 wt.% to 0.7 wt.%.
Manganese may
be from 0.45 wt.% to 0.8 wt.%. The lithium may be at or below 0.003%.
[0005] In various embodiments, a worked aircraft component may comprise
an alloy
including silver from 0.55 wt.% to 0.7 wt.% and lithium at or below 0.005
wt.%. The
worked aircraft component may further comprise the silver from 0.56 wt.% to
0.7 wt.%.
The worked aircraft component may be a wheel or a piston housing. The alloy
may further
comprise titanium at or below 0.06 wt.%, iron at or below 0.1 wt.%, silicon at
or below 0.08
wt.%, beryllium at or below 0.0001 wt.%, chromium at or below 0.05 wt.%, and
zinc at or
below 0.25 wt.%. The worked aircraft component may be hardened by a
precipitation heat
treatment. The alloy may further comprise copper from 4.8 wt.% to 5.4 wt.%,
and
magnesium from 0.7 wt.% to 1.1 wt.%. The worked aircraft component may further
comprise silver from 0.6 wt.% to 0.7 wt.%.
[0006] The forgoing features and elements may be combined in various
combinations
without exclusivity, unless expressly indicated herein otherwise. These
features and
elements as well as the operation of the disclosed embodiments will become
more apparent
in light of the following description and accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0007] The subject matter of the present disclosure is particularly
pointed out and distinctly
claimed in the concluding portion of the specification. A more complete
understanding of
the present disclosure, however, may best be obtained by referring to the
detailed description
2
CA 02886124 2015-03-23
and claims when considered in connection with the figures, wherein like
numerals denote
like elements.
[0008] FIG. 1 illustrates a process of making a worked aluminum aircraft
component from a
substantially lithium-free aluminum alloy, in accordance with various
embodiments.
DETAILED DESCRIPTION
[0009] The detailed description of exemplary embodiments herein makes
reference to the
accompanying drawings, which show exemplary embodiments by way of
illustration. While
these exemplary embodiments are described in sufficient detail to enable those
skilled in the
art to practice the inventions, it should be understood that other embodiments
may be
realized and that logical changes and adaptations in design and construction
may be made in
accordance with this invention and the teachings herein. Thus, the detailed
description
herein is presented for purposes of illustration only and not of limitation.
The scope of the
invention is defined by the appended claims. For example, the steps recited in
any of the
method or process descriptions may be executed in any order and are not
necessarily limited
to the order presented. Furthermore, any reference to singular includes plural
embodiments,
and any reference to more than one component or step may include a singular
embodiment
or step. Also, any reference to attached, fixed, connected or the like may
include permanent,
removable, temporary, partial, full and/or any other possible attachment
option.
Additionally, any reference to without contact (or similar phrases) may also
include reduced
contact or minimal contact.
[0010] Furthermore, any reference to singular includes plural
embodiments, and any
reference to more than one component or step may include a singular embodiment
or step.
Surface shading lines may be used throughout the figures to denote different
parts but not
necessarily to denote the same or different materials.
3
CA 02886124 2015-03-23
[0011] As used herein, the term "% wt," "wt.%" or "% by weight," used in
reference to a
substantially lithium-free aluminum alloy, may refer to the percentage weight
of the
substantially lithium-free aluminum alloy or a constituent of the
substantially lithium-free
aluminum alloy or a group of constituents of the substantially lithium-free
aluminum alloy
over the weight of the entire substantially lithium-free aluminum alloy.
[0012] In various embodiments, FIG. 1 depicts a method 100 of making
aircraft components
using a worked aluminum alloy. A substantially lithium-free aluminum alloy may
be
formed, for example by casting, such as by heating and melting one or more
metals to form a
homogenous solution (Step 102). The solution may be cooled to solidify the
substantially
lithium-free aluminum alloy. The substantially lithium-free aluminum alloy may
comprise
copper (Cu) ranging from 4.8 wt.% to 5.4 wt.%, magnesium (Mg) ranging from 0.7
to 1.1
wt.%, and silver (Ag) ranging from 0.55 to 0.7 wt.%. Ag may preferably range
from 0.56 to
0.7 wt.%, and Ag may further range from 0.6 wt.% to 0.7 wt.%. The
substantially lithium-
free aluminum alloy may further comprise zirconium (Zr) ranging from 0.08 to
0.15 wt.%,
and manganese (Mn) ranging from 0.45 to 0.8 wt.%. Trace elements present in
the
substantially lithium-free aluminum alloy may include lithium (Li) not to
exceed 0.005
wt.%, titanium (Ti) not to exceed 0.06 wt.%, iron (Fe) not to exceed 0.10
wt.%, silicon (Si)
not to exceed 0.08 wt.%, beryllium (Be) not to exceed 0.0001 wt.%, chromium
(Cr) not to
exceed 0.05 wt.%, zinc (Zn) not to exceed 0.25 wt.%, and other individual
trace elements
each to not to exceed 0.05 wt.%, and other total trace elements not to exceed
0.15 wt.%. The
alloy may have a ratio between Cu and Mg that is closely controlled. The ratio
of Cu/Mg
may range from 6.5 to 7.5. In various embodiments, the Cu/Mg ratio may be
approximately
7. As used herein, the term "substantially lithium-free aluminum alloy" refers
to the
aluminum alloy at least partially comprising the foregoing composition.
4
CA 02886124 2015-03-23
[0013] In various embodiments, the substantially lithium-free aluminum
alloy may be
substantially free from lithium to reduce brittleness and improve the
toughness of the alloy.
Lithium may not be intentionally added to the substantially lithium-free
aluminum alloy,
though trace amounts (e.g., less than 0.005 wt.%, less than 0.003 wt.%, or
less than 0.001
wt.%) may be present and regarded impurities. Stated another way, the term
"substantially
lithium-free" may refer to an alloy having controlled amounts of lithium less
than 0.005
wt.%, less than 0.003 wt.%, or less than 0.001 wt.%. The amount of lithium
introduced to
the substantially lithium-free aluminum alloy may be tightly controlled by
inspecting any
aluminum prior to adding the aluminum to the substantially lithium-free
aluminum alloy.
For example, prior to using scrap aluminum to create the substantially lithium-
free
aluminum alloy, scrap aluminum should be inspected to determine the lithium
content in the
scrap aluminum. Scrap aluminum with excessive lithium content may not be used
to create
the substantially lithium-free aluminum alloy. Bauxite or aluminum oxide may
also be used
to produce a substantially lithium-free aluminum alloy without associated
inspection for
lithium.
[0014] In various embodiments, the substantially lithium-free aluminum
alloy may then be
worked into a component (Step 104). For example, extrusion, folding, or heat
forging may
be used to work the substantially lithium-free aluminum alloy into the desired
shape. For
example, the substantially lithium-free aluminum alloy may be hot forged into
a wheel,
brake piston housing or any other component for use on an aircraft. If forging
is used to
shape the component, the component may then be quenched to precipitate harden
the
component (Step 106). The copper and magnesium may precipitate out of solution
with the
metal as it is quenched to harden the substantially lithium-free aluminum
alloy as well as
improve strength and fatigue characteristics. The substantially lithium-free
aluminum alloy
may then be aged to complete the precipitation hardening process.
CA 02886124 2015-03-23
[0015] The substantially lithium-free aluminum alloy may display
increased strength
characteristics compared an aluminum alloy having a composition, in weight
percent, of
about 4 percent copper, about 0.5 percent magnesium, about 0.8 percent
manganese, and
about 0.8 percent silicon, and the remainder aluminum, which is commonly known
by the
industry standard designation of aluminum 2014. The term "about" in this
context only
refers to +/- 0.15%. The substantially lithium-free aluminum alloy may also
have improved
toughness compared to aluminum 2014, for example, and be more resistant to
deformation
or fracturing under load. The substantially lithium-free aluminum alloy may
further have
improved thermal stability over aluminum 2014 in response to higher silver
levels contained
in the substantially lithium-free aluminum alloy. For example, aluminum 2014
may be used
in environments that repeatedly reach temperatures of approximately 300 F (149
C). The
substantially lithium-free aluminum alloy may be used at higher temperatures,
up to 350 F
(176 C) or higher, while substantially maintaining strength and toughness. The
substantially
lithium-free aluminum alloy displays improved fracture toughness, for example
over
aluminum 2014, as the amount of silver in the substantially lithium-free
aluminum alloy
increases. Similarly, the substantially lithium-free aluminum alloy is more
resistant to stress
corrosion cracking than aluminum 2014 because of the higher silver content in
the
substantially lithium-free aluminum alloy. The substantially lithium-free
aluminum alloy
may also be substantially vanadium free. The substantially lithium-free
aluminum alloy may
further have reduced weight and improved fatigue characteristics over aluminum
2014.
[0016] Benefits, other advantages, and solutions to problems have been
described herein
with regard to specific embodiments. Furthermore, the connecting lines shown
in the
various figures contained herein are intended to represent exemplary
functional relationships
and/or physical couplings between the various elements. It should be noted
that many
alternative or additional functional relationships or physical connections may
be present in a
6
CA 02886124 2015-03-23
practical system. However, the benefits, advantages, solutions to problems,
and any
elements that may cause any benefit, advantage, or solution to occur or become
more
pronounced are not to be construed as critical, required, or essential
features or elements of
the inventions. The scope of the inventions is accordingly to be limited by
nothing other
than the appended claims, in which reference to an element in the singular is
not intended to
mean "one and only one" unless explicitly so stated, but rather "one or more."
Moreover,
where a phrase similar to "at least one of A, B, or C" is used in the claims,
it is intended that
the phrase be interpreted to mean that A alone may be present in an
embodiment, B alone
may be present in an embodiment, C alone may be present in an embodiment, or
that any
combination of the elements A, B and C may be present in a single embodiment;
for
example, A and B, A and C, B and C, or A and B and C.
[0017] Systems, methods and apparatus are provided herein. In the
detailed description
herein, references to "various embodiments", "one embodiment", "an
embodiment", "an
example embodiment", etc., indicate that the embodiment described may include
a particular
feature, structure, or characteristic, but every embodiment may not
necessarily include the
particular feature, structure, or characteristic. Moreover, such phrases are
not necessarily
referring to the same embodiment. Further, when a particular feature,
structure, or
characteristic is described in connection with an embodiment, it is submitted
that it is within
the knowledge of one skilled in the art to affect such feature, structure, or
characteristic in
connection with other embodiments whether or not explicitly described. After
reading the
description, it will be apparent to one skilled in the relevant art(s) how to
implement the
disclosure in alternative embodiments.
[0018] Furthermore, no element, component, or method step in the present
disclosure is
intended to be dedicated to the public regardless of whether the element,
component, or
method step is explicitly recited in the claims. No claim element herein is to
be construed
7
CA 02886124 2015-03-23
under the provisions of 35 U.S.C. 112(0, unless the element is expressly
recited using the
phrase "means for." As used herein, the terms "comprises", "comprising", or
any other
variation thereof, are intended to cover a non-exclusive inclusion, such that
a process,
method, article, or apparatus that comprises a list of elements does not
include only those
elements but may include other elements not expressly listed or inherent to
such process,
method, article, or apparatus.
8
