U.S. patent application number 11/920090 was filed with the patent office on 2009-03-12 for aluminum-based alloy.
Invention is credited to Boris V. Ovsyannikov, Valeriy I. Popov, Victor M. Zamyatin.
Application Number | 20090068056 11/920090 |
Document ID | / |
Family ID | 38541383 |
Filed Date | 2009-03-12 |
United States Patent
Application |
20090068056 |
Kind Code |
A1 |
Popov; Valeriy I. ; et
al. |
March 12, 2009 |
Aluminum-based alloy
Abstract
The incorporation of calcium and at least one member selected
from the group consisting of vanadium and scandium into an aluminum
lithium alloy containing: lithium, copper, magnesium, zirconium,
beryllium, titanium, nickel, manganese, gallium, zinc, and sodium
provides an aluminum lithium alloy that: 1) exhibits improved
ductility; 2) exhibits improved processability resulting in the
capability to obtain higher yields of semi-finished products; 3)
provides the ability to fabricate thin sheets, thin walled sections
and forgings, all while preserving the inherent strength and
operating characteristics of such alloys when applied to
semi-finished products and parts thereof demanded by structural
applications in these fields.
Inventors: |
Popov; Valeriy I.;
(Kamensk-Uralsky, RU) ; Ovsyannikov; Boris V.;
(Kamensk-Uralsky, RU) ; Zamyatin; Victor M.;
(Ekaterinburg, RU) |
Correspondence
Address: |
AUZVILLE JACKSON, JR.
8652 RIO GRANDE ROAD
RICHMOND
VA
23229
US
|
Family ID: |
38541383 |
Appl. No.: |
11/920090 |
Filed: |
March 7, 2007 |
PCT Filed: |
March 7, 2007 |
PCT NO: |
PCT/RU2007/000109 |
371 Date: |
November 8, 2007 |
Current U.S.
Class: |
420/532 |
Current CPC
Class: |
C22C 21/12 20130101;
C22C 21/00 20130101; C22F 1/04 20130101; C22C 21/16 20130101 |
Class at
Publication: |
420/532 |
International
Class: |
C22C 21/00 20060101
C22C021/00 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 27, 2006 |
RU |
2006109658 |
Claims
1) An aluminum alloy having the following composition:
TABLE-US-00007 Element Percent by Weight Lithium 1.6-1.9 Copper
1.3-1.5 Magnesium 0.7-1.1 Zirconium 0.04-0.2 Beryllium 0.02-0.2
Titanium 0.01-0.1 Nickel 0.01-0.15 Manganese 0.01-0.2 Gallium up to
0.001 Zinc 0.01-0.3 Sodium up to 0.0005 Calcium 0.005-0.02 at least
one element selected from the group consisting of Vanadium
0.005-0.01 Scandium 0.005-0.01 Aluminum Balance.
2) The alloy of claim 1 comprising from 0.005 to 0.01 percent by
weight vanadium.
3) The alloy of claim 1 comprising from 0.005 to 0.01 weight
percent scandium.
Description
FIELD OF THE INVENTION
[0001] The present invention relates to aluminum lithium alloys and
more particularly to an aluminum-copper-magnesium-lithium alloy
that overcomes the shortcomings of prior such alloys.
BACKGROUND OF THE INVENTION
[0002] It is well known that aluminum lithium alloys possess a
unique combination of mechanical properties including; low density,
high modulus of elasticity, and high strength. These properties
contribute to the use of these alloys as structural materials in
aerospace applications that result in a number of improvements in
aircraft/aerospace vehicle performance including: reduction in
vehicle weight, fuel economy and increased load capacity.
[0003] However, aluminum lithium alloys as a group exhibit at least
one major disadvantage, low ductility under conditions at or near
their maximum strength. (N. I. Friedlander, K. V. Christos. A. L.
Berezina, N. I. Kolbe, Aluminum Lithium Alloys, Structure and
Properties, Kiev: Nauk. Dumka, 1992, page 177).
[0004] Among the known aluminum lithium alloys are those having the
following compositions in percent by weight:
TABLE-US-00001 Lithium 1.7-2.0 Copper 1.6-2.0 Magnesium 0.7-1.1
Zirconium 0.04-0.16 Beryllium 0.02-0.2 Titanium 0.01-0.07 Nickel
0.02-0.15 Manganese 0.01-0.4 Aluminum Balance
(Inventor's Certificate of USSR No. 1767916, IPC C 22 C 21/16,
published Aug. 20, 1997)
[0005] The disadvantages of these alloys are their limited
processability, the high manufacturing costs associated therewith
that are dictated by the labor intensiveness of such activities,
low yields of satisfactory product obtained in the fabrication of
semi-finished products and parts and the difficulties encountered
when fabricating thin sheets, thin walled sections and forgings
therefrom.
[0006] These disadvantages are due, at least in part, to the fact
that the relatively high concentrations of copper in these alloys
contribute to hot brittleness and negatively affect the ductility
thereof. This leads to cracking, high rejection levels in folds and
non-flatness in finishing operations that include flattening and
stretching to form finished or semi-finished products.
[0007] Aluminum lithium alloy 8093 has the following composition
based upon percent by weight:
TABLE-US-00002 Lithium 1.9-2.6 Copper 1.0-1.6 Magnesium 0.9-1.6
Zirconium 0.04-0.14 Titanium up to 0.1 Manganese up to 0.1 Zinc up
to 0.25 Aluminum Balance
[0008] The disadvantages of this alloy include, high cost, their
limited processability, the high manufacturing costs associated
therewith that are dictated by the labor intensiveness of such
activities, low yields of satisfactory product obtained in the
fabrication of semi-finished products and parts and the
difficulties encountered when fabricating thin sheets, thin walled
sections and forgings therefrom.
[0009] The major cause of the aforementioned disadvantages is the
relatively elevated concentration of lithium in this alloy which
results in the formation of strengthening phases during forming
operations. The formation of these strengthening phases reduces the
alloy's ductility during casting and shaping. This, in turn,
results n increased cracking, higher rejections based on the
presence of folds and non-flatness in finishing operations that
include flattening and stretching during the fabrication of
semi-finished or finished products.
[0010] A further prior art aluminum lithium alloy comprises the
following elements in percent by weight:
TABLE-US-00003 Lithium 1.7-2.0 Copper 1.6-2.0 Magnesium 0.7-1.1
Zirconium 0.04-.2 Beryllium 0.02-0.2 Titanium 0.01-0.1 Nickel
0.01-0.15 Manganese 0.001-0.05 Gallium 0.001-0.05 Zinc 0.01-0.3
Sodium 0.0005-0.001 Aluminum Balance
(Russian Patent No. 2180928, IPC 7 C 22 C 21/00, C 22/21/16,
published Mar. 27, 2002).
[0011] Among the disadvantages of this alloy are its limited
processability, the high manufacturing costs associated therewith
that are dictated by the labor intensiveness of such activities,
low yields of satisfactory product obtained in the fabrication of
semi-finished products and parts and the difficulties encountered
when fabricating thin sheets, thin walled sections and forgings
therefrom.
[0012] These disadvantages are due, at least in part, to the fact
that the relatively high concentrations of copper in these alloys
contribute to hot brittleness and negatively affect the ductility
thereof. This leads to cracking, high rejection levels in folds and
non-flatness in finishing operations that include flattening and
stretching to form finished or semi-finished products.
Additionally, the relatively high levels of sodium and gallium lead
to a considerable increase in the hot brittleness of the alloy with
a consequent reduction in the ductility thereof. (A. V. Hurdyumov,
S. V. Inkin, V. S. Chulkov, G. G. Shadrin, Metallurgical Admixtures
in Aluminum Alloys, M,: Metallurgy, 1998, pp 90, 99). This
complicates considerably obtaining acceptable ingots and the
fabrication of various semi-finished products by shaping. This also
inhibits the production of quality claddings for rolled or
semi-finished products as a result of the formation of significant
areas of non-welded cladding on the surface.
OBJECT OF THE INVENTION
[0013] It is therefore an object of the present invention to
provide an aluminum lithium alloy for the fabrication of aircraft
and aerospace vehicles that does not exhibit the disadvantages of
prior art such alloys.
[0014] It is a further object of the present invention to provide
an aluminum lithium alloy that: 1) exhibits improved ductility; 2)
exhibits improved processability resulting in the capability to
obtain higher yields of semi-finished products; 3) provides the
ability to fabricate thin sheets, thin walled sections and
forgings, all while preserving the inherent strength and operating
characteristics of such alloys when applied to semi-finished
products and parts thereof demanded by structural applications in
these fields.
SUMMARY OF THE INVENTION
[0015] The foregoing objectives are obtained by the incorporation
of calcium and at least one member selected from the group
consisting of vanadium and scandium in an aluminum lithium alloy
containing: lithium, copper, magnesium, zirconium, beryllium,
titanium, nickel, manganese, gallium, zinc, and sodium.
Specifically, there is provided an aluminum lithium alloy having
the following composition in percent by weight:
TABLE-US-00004 Lithium 1.6-1.9 Copper 1.3-1.5 Magnesium 0.7-1.1
Zirconium 0.04-0.2 Beryllium 0.02-0.2 Titanium 0.01-0.1 Nickel
0.01-0.15 Manganese 0.01-0.2 Gallium up to 0.001 Zinc 0.01-0.3
Sodium up to 0.0005 Calcium 0.005-0.02 at least one element
selected from the group consisting of Vanadium 0.005-0.01 Scandium
0.005-0.01 Aluminum Balance
DETAILED DESCRIPTION
[0016] The present invention provides an aluminum lithium alloy
that: 1) exhibits improved ductility; 2) exhibits improved
processability resulting in the capability to obtain higher yields
of semi-finished products; 3) provides the ability to fabricate
thin sheets, thin walled sections and forgings, all while
preserving the inherent strength and operating characteristics of
such alloys when applied to semifinished products and parts thereof
demanded by structural applications in these fields.
[0017] The composition of this alloy comprises in percent by
weight:
TABLE-US-00005 Lithium 1.6-1.9 Copper 1.3-1.5 Magnesium 0.7-1.1
Zirconium 0.04-0.2 Beryllium 0.02-0.2 Titanium 0.01-0.1 Nickel
0.01-0.15 Manganese 0.01-0.2 Gallium up to 0.001 Zinc 0.01-0.3
Sodium up to 0.0005 Calcium 0.005-0.02 at least one element
selected from the group consisting of Vanadium 0.005-0.01 Scandium
0.005-0.01 Aluminum Balance.
[0018] The aluminum lithium alloy of the present invention differs
both quantitatively (reduced levels of copper, gallium and sodium)
and qualitatively (the addition of calcium and at least one member
selected from the group consisting of vanadium and scandium from
those of the prior art).
[0019] It has been determined that the incorporation of increased
contents of copper in aluminum lithium alloys results in the
formation of coarse irregularly shaped intermetallic compounds that
are copper bearing phases formed by alloy crystallization in areas
of increased copper content inside of grains and on their
boundaries. These phases are represented not by separate particles,
but rather by extensive accumulations that impair shear deformation
in shaping processes resulting in a significant reduction in alloy
ductility.
[0020] Scanning electron microscopic studies have determined that a
reduction in the copper content of aluminum lithium alloys to
within the limits of 1.3 to 1.5 weight percent result in a
virtually total conversion thereof to a solid solution. This
results in a significant reduction in the inclusion volume ratio of
coarse intermetallic compounds of copper bearing phases, thus,
enhancing the ductility of the alloy. At copper contents below
about 1.3 weight percent, no further improvement in ductility is
found, but strength is reduced considerably.
[0021] Additionally, it has been determined that gallium and sodium
do not form phases with aluminum, but rather accumulate at grain
boundaries resulting in brittle fracture along the grain boundaries
in fabrication processes involving alloy crystallization and
shaping.
[0022] It has been determined that with gallium and sodium contents
below about 0.001 and 0.0005 weight percent respectively, these
elements practically dissolve totally into solid solutions
resulting in a further enhancement in alloy ductility.
[0023] Calcium in quantities of less than about 0.005-0.2 weight
percent serves as a binding agent for excess sodium and other trace
elements resulting in the formation of rounder shaped isolated
intermetallic compounds and their coagulants resulting in more
favorable conditions for shear deformation, and, consequently and
enhancement in alloy ductility.
[0024] The introduction of vanadium and/or scandium in the
indicated amounts facilitates formation of homogeneous,
fine-grained structures that promote the role of zirconium as a
modifying agent that enhances structural strength.
[0025] The aluminum lithium alloys of the present invention permit
the manufacture and fabrication of a wide variety of semi-finished
products including: sheet and plate, forgings and extrusions. From
these semi-finished products it is therefore possible to fabricate
finished fuselage skin panels for aircraft, bulkhead elements,
welded fuel tank assemblies and a wide variety of other aircraft
and aerospace vehicle parts and assemblies.
EXAMPLES
Example 1
[0026] Alloys having a chemical composition within the range
described for the prior art sodium and gallium containing alloys
described above and those of the present invention were cast into
rectangular ingots 300.times.1 and 100 mm in length and round
ingots in diameters of 190 mm and 350 mm. All casting operations
were performed in the temperature range of from 710 to 730.degree.
C. The prior art material is identified hereinafter as sample 1
while those specimens produced from the alloys of the present
invention are identified as samples 2-4.
[0027] Cladding sheets were fabricated from flat ingots in each of
the alloys. These sheets were produced by hot rolling to 6.5 mm at
a temperature 430.degree. C., coiling and annealing at a
temperature of 400.degree. C. by means of cold rolling.
[0028] Sample 1 could only be rolled to a thickness of 90 mm
because of the presence of tears 30 mm deep on the edges of the
coil and 2 breakages of the coil. Sheets of samples 2-4 were
reduced to a thickness of 0.5 mm with no cracking or
separation.
[0029] The sheets of samples 2-4 were then finished in flattening
and stretching operations with minimal rejection because of folds,
non-flatness or cracks. Yields of sheets from samples 2-4 were 30%
higher than those experienced with sheets of sample 1 which were
produced from the minimum thickness rolled sheets previously
obtained.
[0030] Specimens cut at a 45.degree. angle lengthwise and subjected
to mechanical testing to determine, mechanical strength, yield
strength and elongation showed the results indicated in attached
Table 1. As shown in this Table, the properties of the alloy,
tensile strength (.sigma.), yield strength (.sigma..sub.0.2) and
percent elongation (.delta.%) of the present invention equal or
surpass those of the prior art alloy.
TABLE-US-00006 TABLE 1 Mechanical Properties Sample No. Sampling
Direction .sigma..sub.B, MP.sub.a .sigma..sub.0.2, MP.sub.a
.delta., % 1 Longitudinal 432 347.5 13.5 Transverse 440 343 10.7 At
45.degree. Angle 419 323 13.9 2 Longitudinal 430 349 14.6
Transverse 438 352 13.8 At 45.degree. Angle 424 328 14.5 3
Longitudinal 431 351 14.8 Transverse 438 345 13.9 At 45.degree.
Angle 425 329 14.9 4 Longitudinal 432 345 14.9 Transverse 439 339
14.1 At 45.degree. Angle 423 328 15.1
Example 2
[0031] Extruded sections up to 5 mm thick with flanges have been
extruded from ingots 190 mm in diameter in each of the alloys.
These sections were manufactured by extruding at a temperature of
400.degree. C., cold water quenching and aging for 24 hours at a
temperature of 150.degree. C. The yields obtained from samples 2-4
were demonstrated to be 15% higher than those obtained from sample
1.
Example 3
[0032] Forgings with wall thicknesses of 40 mm were fabricated from
round ingots with a diameter of 350 mm in each of the alloys.
Samples were prepared by blanking the forging at a temperature of
410.degree. C., preliminarily forging at this same temperature,
final forging at a temperature of 400.degree. C., quenching at a
temperature of 500.degree. C. for two hours and aging at a
temperature of 150.degree. C. for 24 hours. The forgings thus
produced indicated that fabrication yields for samples 2-4 were 10%
higher than those for sample 1.
[0033] There has thus been described an aluminum lithium alloy that
an aluminum lithium alloy that: 1) exhibits improved ductility; 2)
exhibits improved processability resulting in the capability to
obtain higher yields of semi-finished products; 3) provides the
ability to fabricate thin sheets, thin walled sections and
forgings, all while preserving the inherent strength and operating
characteristics of such alloys when applied to semi-finished
products and parts thereof demanded by structural applications in
these fields.
[0034] As the invention has been described, it will be apparent to
those skilled in the art that the same may be varied in many ways
without departing from the spirit and scope of the invention. Any
and all such modifications are intended to be included within the
scope of the appended claims.
* * * * *