U.S. patent application number 15/886189 was filed with the patent office on 2019-08-01 for low cost, low density, substantially ag-free and zn-free aluminum-lithium plate alloy for aerospace application.
This patent application is currently assigned to Kaiser Aluminum Fabricated Products, LLC. The applicant listed for this patent is Kaiser Aluminum Fabricated Products, LLC. Invention is credited to Florence Andrea Baldwin, Philippe Lassince, Zhengdong Long, Robert A. Matuska, Roy A. Nash, Ravi Rastogi, David J. Shoemaker.
Application Number | 20190233921 15/886189 |
Document ID | / |
Family ID | 65351866 |
Filed Date | 2019-08-01 |
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United States Patent
Application |
20190233921 |
Kind Code |
A1 |
Long; Zhengdong ; et
al. |
August 1, 2019 |
Low Cost, Low Density, Substantially Ag-Free and Zn-Free
Aluminum-Lithium Plate Alloy for Aerospace Application
Abstract
The present invention is directed to aluminum-lithium alloys,
specifically aluminum--copper--lithium--magnesium--manganese
alloys. The aluminum-lithium alloy of the present invention
comprises from 3.6 to 4.1 wt. % Cu, 0.8 to 1.05 wt. % Li, 0.6 to
1.0 wt. % Mg, 0.2 to 0.6 wt. % Mn, up to 0.12 wt. % Si, up to 0.15
wt. % Fe, from 0.03 to 0.16 wt. % of at least one grain structure
control element selected from the group consisting of Zr, Sc, Cr,
V, Hf, and other rare earth elements, up to 0.10 wt. % Ti, up to
0.15 wt. % incidental elements with the total of incidental
elements not exceeding 0.35 wt. %, and the balance being aluminum.
Preferably, Ag is not intentionally added and should not be more
than 0.05 wt. % as a non-intentionally added element. Preferably,
Zn is not intentionally added and should not be more than 0.2 wt. %
as a non-intentionally added element. The amount of Cu in weight
percent is at least equal to or higher than four times the amount
of Li in weight percent.
Inventors: |
Long; Zhengdong; (Sokane,
WA) ; Lassince; Philippe; (Albi, FR) ;
Matuska; Robert A.; (Heath, OH) ; Baldwin; Florence
Andrea; (Mead, WA) ; Shoemaker; David J.;
(Heath, OH) ; Rastogi; Ravi; (Liberty Lake,
WA) ; Nash; Roy A.; (Spokane, WA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Kaiser Aluminum Fabricated Products, LLC |
Foothill Ranch |
CA |
US |
|
|
Assignee: |
Kaiser Aluminum Fabricated
Products, LLC
Foothill Ranch
CA
|
Family ID: |
65351866 |
Appl. No.: |
15/886189 |
Filed: |
February 1, 2018 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
C22F 1/057 20130101;
C22F 1/002 20130101; C22C 21/16 20130101; C22C 21/14 20130101; C22C
21/18 20130101; C22C 21/12 20130101 |
International
Class: |
C22C 21/16 20060101
C22C021/16; C22C 21/18 20060101 C22C021/18; C22C 21/14 20060101
C22C021/14; C22F 1/057 20060101 C22F001/057 |
Claims
1-20. (canceled)
21. A low cost, low density, and high performance Al--Li alloy
comprising: from 3.6 to 4.1 wt. % Cu, from 0.8 to 1.05 wt. % Li,
from 0.6 to 1.0 wt.% Mg, from 0.2 to 0.6 wt.% Mn, less than 0.05
wt.% Ag, less than 0.2 wt.% Zn, from 0.03 to 0.16 wt. % of at least
one grain structure control element selected from the group
consisting of Zr, Sc, Cr, V, Hf, and other rare earth elements up
to 0.10 wt.% Ti, up to 0.12 wt.% Si, up to 0.15 wt.% Fe, up to 0.15
wt. % each incidental elements, with the total incidental elements
not exceeding 0.35 wt. %, with the balance being aluminum, and
wherein the amount of Cu in weight percent is at least equal to or
higher than four times the amount of Li in weight percent.
22. The aluminum-lithium alloy of claim 21, comprising 3.7 to 4.0
wt. % Cu.
23. The aluminum-lithium alloy of claim 21, comprising 0.9 to 1.0
wt. % Li.
24. The aluminum-lithium alloy of claim 21, comprising 0.7 to 0.9
wt. % Mg.
25. The aluminum-lithium alloy of claim 21, wherein no Ag is
intentionally added to the aluminum alloy.
26. The aluminum-lithium alloy of claim 21, wherein no Zn is
intentionally added to the aluminum alloy.
27. The aluminum-lithium alloy of claim 21, comprising less than
0.10 wt % Zn.
28. The aluminum-lithium alloy of claim 21, comprising less than
0.05 wt % Zn.
29. The aluminum-lithium alloy of claim 21, comprising a maximum of
0.05 wt. % Si.
30. The aluminum-lithium alloy of claim 21, comprising a maximum of
0.08 wt.% Fe.
31. A low cost, low density, and high performance Al--Li alloy
comprising: from 3.7 to 4.0 wt. % Cu, from 0.9 to 1.0 wt. % Li,
from 0.7 to 0.9 wt.% Mg, from 0.2 to 0.6 wt.% Mn, less than 0.05
wt.% Ag, less than 0.2 wt.% Zn, from 0.03 to 0.16 wt. % of at least
one grain structure control element selected from the group
consisting of Zr, Sc, Cr, V, Hf, and other rare earth elements up
to 0.10 wt.% Ti, up to 0.12 wt.% Si, up to 0.15 wt.% Fe, up to 0.15
wt. % each incidental elements, with the total of these incidental
elements not exceeding 0.35 wt. %, with the balance being aluminum,
and wherein the amount of Cu in weight percent is at least equal to
or higher than four times the amount of Li in weight percent.
32. The aluminum-lithium alloy of claim 21, wherein said
aluminum-lithium alloy is in the form of a rolled, extruded, or
forged product, and has a thickness from about 0.5 to about 8.0
inch.
33. The aluminum-lithium alloy of claim 32, wherein said
aluminum-lithium alloy has a thickness from about 0.5 to about 6.0
inch.
34. A rolled product comprising an aluminum-lithium alloy of claim
21, having a thickness from about 0.5 to about 8.0 inch.,
exhibiting in a solution heat-treated, quenched, stretched and
artificially aged condition: a minimum Tensile Yield Strength (TYS)
along rolling (L) direction as function of plate gage (ga) of
75.0-1.4*ga., a minimum Tensile Yield Strength (TYS) along long
transverse (LT) direction of 71.2-1.4*ga., a minimum Fracture
Toughness (K1c) along the orientation of Long Transverse--Rolling
(T-L) of 28-1.0*ga., and a minimum Fracture Toughness (K1c) along
the orientation of Rolling--Long Transverse (L-T) of 28.8-0.6*ga,
wherein the units for gage (ga), strength, and fracture toughness
are inch, ksi, and ksi*in.sup.1/2 respectively.
35. A rolled product comprising an aluminum-lithium alloy of claim
21, having a thickness from about 0.5 to about 8.0 inch.,
exhibiting in a solution heat-treated, quenched, stretched and
artificially aged condition: a minimum Tensile Yield Strength (TYS)
along rolling (L) direction as function of plate gage (ga) of
76.2-1.4*ga., a minimum Tensile Yield Strength (TYS) along long
transverse (LT) direction of 72.2-1.4*ga., a minimum Fracture
Toughness (K1c) along the orientation of Long Transverse--Rolling
(T-L) of 29-1.0*ga., and a minimum Fracture Toughness (K1c) along
the orientation of Rolling--Long Transverse (L-T) of 30.8-0.6*ga,
wherein the units for gage (ga), strength, and fracture toughness
are inch, ksi, and ksi*in.sup.1/2 respectively.
36. A rolled product comprising an aluminum-lithium alloy of claim
21, having a thickness from about 0.5 to about 8.0 inch.,
exhibiting in a solution heat-treated, quenched, stretched and
artificially aged condition: a minimum Tensile Yield Strength (TYS)
along rolling (L) direction as function of plate gage (ga) of
77.0-1.4*ga., a minimum Tensile Yield Strength (TYS) along long
transverse (LT) direction of 72.7-1.4*ga., a minimum Fracture
Toughness (K1c) along the orientation of Long Transverse--Rolling
(T-L) of 29.5-1.0*ga., and a minimum Fracture Toughness (K1c) along
the orientation of Rolling--Long Transverse (L-T) of 31.8-0.6*ga,
wherein the units for gage (ga), strength, and fracture toughness
are inch, ksi, and ksi*in.sup.1/2 respectively.
37. The rolled product of claim 34, wherein said product alloy has
a thickness from about 0.5 to about 6.0 inch.
38. A method of manufacturing a low cost, low density, and high
performance Al--Li alloy, the method comprising: a. casting stock
of an ingot of aluminum alloy comprising the aluminum-lithium alloy
product according to claim 21 producing a cast stock b.
homogenizing the cast stock producing a homogenized cast stock; c.
hot working the homogenized cast stock by one or more methods
selected from the group consisting of rolling, extrusion, and
forging forming a worked stock; d. solution heat treating (SHT) the
worked stock, producing a SHT stock; e. cold water quenching said
SHT stock to produce a cold water quenched SHT stock; f stretching
the cold water quenched SHT stock to produce stretched stock; and
g. artificially ageing of the stretched stock.
39. The method of claim 38, wherein said step of homogenizing
includes homogenizing at temperatures from 482 to 543.degree. C.
(900 to 1010.degree. F.); wherein said step of hot working includes
hot rolling at a temperature of 357 to 482.degree. C. (675 to
900.degree. F.); wherein said step of solution heat treating
includes solution heat treated at temperature range from 482 to
538.degree. C. (900 to 1000.degree. F.); wherein said step of
stretching includes stretching from 2% to up to 15%; and wherein
said step of artificially ageing includes aging at a temperature of
from 121 to 205.degree. C. (250 to 400.degree. F.) and the aging
time can be in the range of 2 to 60 hours.
40. The method of claim 39, wherein said step of artificially
ageing includes aging at a temperature of from 149 to 182.degree.
C. (300 to 360.degree. F.) and the aging time can be in the range
of 10 to 48 hours.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
[0001] The present invention generally relates to
Aluminum-Copper-Lithium-Magnesium based alloy products.
2. Description of Related Art
[0002] In order to reduce aircraft weight for better fuel
efficiency, low density aluminum-lithium alloys are being
aggressively pursued by airframe and aluminum material
manufacturers. Beside density, the material strength, fracture
toughness, fatigue resistance, and corrosion resistance are
required simultaneously for aerospace applications. In addition,
the cost of material has to be considered for the sustainable
solution of aluminum lithium products.
[0003] Therefore, it is an extreme challenge to produce
aluminum-lithium (Al--Li) plate products that meet all above
requirements. As a consequence, there are only limited registered
Al--Li alloys capable of producing higher than 0.5'' thickness
plate products. The examples of existing alloys are 2050 (up to
6.5'' thickness), 2195 (up to 2.25'' thickness), 2060 (up to 1.5''
thickness), 2395 (up to 1.5'' thickness) and 2196 (up to 1.0''
thickness) based on "Registration Record Series--Tempers for
Aluminum and Aluminum Alloys Production" published in 2011 and
"Addendum to 2011 Tan Sheets of Registration Record Series--Tempers
for Aluminum and Aluminum Alloys Production" published in 2017 by
The Aluminum Association. It should be mentioned that all above
Al--Li plate alloys are high cost Ag containing alloys. Silver (Ag)
is added to many new generation Al--Li alloys in order to improve
the final product properties.
[0004] In addition, the popularity of using high cost Ag in Al--Li
alloys can be demonstrated by a significant amount of Al--Li alloy
patents and patent applications. Thus, it is a significant
challenge to provide a low cost Al--Li sheet via eliminating Ag
addition while simultaneously maintaining the product performance
that Ag provides as demonstrated by these prior art examples.
[0005] Obviously, the Li is the most critical element for Al--Li
alloys. Too low of a level of Li cannot reduce the density and
improve the properties enough. However, too high of a level of Li
can cause undesirable performance such as low short transverse
fracture toughness, and high anisotropy of tensile properties.
[0006] The Cu is another important element and has to be controlled
within a certain range for desirable product performance.
[0007] The Mg is another element to be added in a certain range in
order to primarily enhance the strength and secondarily reduce the
density.
[0008] The Zn is also another element to be considered for Al--Li
alloy. However, the addition of Zn can also negatively impact the
density.
[0009] In general, prior Al--Li alloy compositions didn't succeed
to simultaneously achieve low density, low cost, high strength,
good damage tolerance, fatigue resistance, and corrosion properties
for Al--Li alloys capable of producing plate products. To achieve
all of these is an extreme metallurgical challenge, especially
without the use of Ag addition which significantly increase the
product cost.
BRIEF SUMMARY OF THE INVENTION
[0010] The present invention provides a low cost, high performance,
high Mg, substantially Ag-free and Zn-free, low density Al--Li
alloy suitable for making transportation components, such as
aerospace structural components. Aluminum-lithium alloys of the
present invention comprise from 3.6 to 4.1 wt. % Cu, 0.8 to 1.05
wt. % Li, 0.6 to 1.0 wt. % Mg, 0.2 to 0.6 wt. % Mn, up to 0.12 wt.
% Si, up to 0.15 wt. % Fe, from 0.03 to 0.16 wt. % of at least one
grain structure control element selected from the group consisting
of Zr, Sc, Cr, V, Hf, and other rare earth elements, up to 0.10 wt.
% Ti, up to 0.15 wt. % incidental elements with the total of
incidental elements not exceeding 0.35 wt. %, and the balance being
aluminum. Preferably, Ag is not intentionally added and should not
be more than 0.05 wt. % as a non-intentionally added element.
Preferably, Zn is not intentionally added and should not be more
than 0.2 wt. % as a non-intentionally added element. The amount of
Cu in weight percent is at least equal to or higher than 4 times
the amount of Li in weight percent in the inventive alloy.
[0011] The inventive alloy has improved properties over the prior
art. Preferably, the inventive alloy has a tensile yield strength
(TYS) along rolling (L) direction as function of plate gage (ga)
that is higher than 75.0-1.4*ga, preferably higher than
76.2-1.4*ga, and more preferably higher than 77.0-1.4*g .
Preferably, the inventive alloy has a tensile yield strength (TYS)
along long transverse (LT) direction that is higher than
71.2-1.4*ga, preferably higher than 72.2-1.4*ga, and more
preferably higher than 72.7-1.4*ga. Preferably, the inventive alloy
has a fracture toughness (K1c) along the orientation of Long
Transverse--Rolling (T-L) that is higher than 28-1.0*ga, preferably
higher than 29-1.0*ga, and more preferably higher than 29.5-1.0*ga.
Preferably, the inventive alloy has a fracture toughness (K1c)
along the orientation of Rolling--Long Transverse (L-T) that is
higher than 28.8-0.6*ga, preferably higher than 30.8-0.6*ga, and
more preferably higher than 31.8-0.6*ga. The units for gage (ga),
strength, and fracture toughness are inch, ksi, and
ksi*in.sup.1/2respectively. Methods for manufacturing wrought
aluminum-lithium alloy products of the present invention are also
provided.
[0012] The aluminum-lithium alloy of the present invention is a
plate, extrusion or forged wrought product having a thickness of
0.5 to 8.0 inch. It has been surprisingly discovered that the
aluminum-lithium alloy of the present invention having no Ag, or
very low amounts of non-intentionally added Ag, no Zn, or very low
amounts of non-intentionally added Zn, and high Mg content is
capable of producing 0.5 to 8.0 inch thickness plate products with
excellent strength and fracture toughness properties and desirable
corrosion resistance performance. Another aspect of the present
invention is a method to manufacture aluminum-lithium alloys of the
present invention.
BRIEF DESCRIPTION OF THE DRAWINGS
[0013] The features and advantages of the present invention will
become apparent from the following detailed description of a
preferred embodiment thereof, taken in conjunction with the
accompanying drawings, in which:
[0014] FIG. 1 is a graph showing the strength aging response
between invention alloys and non-invention alloys.
[0015] FIG. 2 is a graph showing the comparison of strength and
fracture toughness between a substantially Ag-free invention alloys
and Non-invention alloys (substantially Ag-free) of 3 inch plates;
The minimum LT TYS is 67 ksi; Preferred Minimum LT TYS is 68 ksi;
and more preferred Minimum LT TYS is 68.5 ksi; Minimum K1c T-L is
25 ksi*in.sup.1/2; Preferred Minimum K1c T-L is 26 ksi*in.sup.1/2;
More preferred Minimum K1c T-L is 26.5 ksi*in.sup.1/2.
[0016] FIG. 3 is a graph showing the comparison of strength and
fracture toughness between a substantially Ag-free invention alloys
and Non-invention alloys (substantially Ag-free) of 3 inch plates.
Minimum L TYS is 70.8 ksi; Preferred Minimum L TYS is 72 ksi; More
preferred Minimum L TYS is 72.8 ksi; Minimum K1c L-T is 27
ksi*in.sup.1/2; Preferred Minimum K1c L-T is 29 ksi*in.sup.1/2;
More preferred Minimum K1c L-T is 30 ksi*in.sup.1/2.
[0017] FIG. 4 is a graph showing the comparison of LT TYS vs. K1c
T-L between a substantially Ag-free invention alloys and high cost
Ag-containing non-invention alloys of 3 inch plates.
[0018] FIG. 5 is a graph showing the comparison of L TYS vs. K1c
L-T between low cost substantially Ag-free invention alloys and
high cost Ag-containing non-invention alloys of 3 inch plates.
[0019] FIG. 6 is a graph showing the LT TYS as function of plate
thickness of invention alloy plates. Minimum is 71.2-1.4*ga;
Preferred Minimum is 72.2-1.4*ga; More preferred Minimum is
72.7-1.4*ga.
[0020] FIG. 7 is a graph showing the L TYS as function of plate
thickness of invention alloy plates. Minimum is 75.0-1.4*ga;
Preferred Minimum is 76.2-1.4*ga; More Preferred. Minimum is
77.0-1.4*ga.
[0021] FIG. 8 is a graph showing the K1c T-L as function of plate
thickness of invention alloy plates. Minimum is 28-1.0*ga;
Preferred Minimum is 29-1.0*ga; More Preferred Minimum is
29.5-1.0*ga.
[0022] FIG. 9 is a graph showing the K1c L-T as function of plate
thickness of invention alloy plates. Minimum is 28.8-0.6*ga;
Preferred Minimum is 30.8-0.6*ga; More preferred Minimum is
31.8-0.6*ga.
[0023] FIG. 10 are photos showing the typical surface appearances
after 672 hours MASTMASSIS testing exposure times (left Sample #6
with 3 inch plate thickness and right Sample #11 with 6 inch plate
thickness).
[0024] FIG. 11 are photos showing the grain structures of Sample
#1: 1'' thickness invention alloy plate.
[0025] FIG. 12 are photos showing the grain structures of Sample
#2: 2'' thickness invention alloy plate.
[0026] FIG. 13 are photos showing the grain structures of Sample
#3: 3'' thickness invention alloy plate.
[0027] FIG. 14 are photos showing the grain structures of Sample
#9: 4'' thickness invention alloy plate.
[0028] FIG. 15 are hotos showing the grain structures of Sample
#10: 6'' thickness invention alloy plate.
DETAILED DESCRIPTION OF THE INVENTION
[0029] The present invention is directed to aluminum-lithium
alloys, specifically
aluminum--copper--lithium--magnesium--manganese alloys. The
aluminum-lithium alloy of the present invention comprises from 3.6
to 4.1 wt. % Cu, 0.8 to 1.05 wt. % Li, 0.6 to 1.0 wt. % Mg, 0.2 to
0.6 wt. % Mn, up to 0.12 wt. % Si, up to 0.15 wt. % Fe, from 0.03
to 0.16 wt. % of at least one grain structure control element
selected from the group consisting of Zr, Sc, Cr, V, Hf, and other
rare earth elements, up to 0.10 wt. % Ti, up to 0.15 wt. %
incidental elements with the total of incidental elements not
exceeding 0.35 wt. %, and the balance being aluminum. Preferably,
Ag is not intentionally added and should not be more than 0.05 wt.
% as a non-intentionally added element. Preferably, Zn is not
intentionally added and should not be more than 0.2 wt. % as a
non-intentionally added element. The amount of Cu in weight percent
is at least equal to or higher than 4 times the amount of Li in
weight percent in the inventive alloy.
[0030] In an alternate preferred embodiment, the aluminum-lithium
alloy comprises from 3.7 to 4.0 wt. % Cu, 0.9 to 1.0 wt. % Li, 0.7
to 0.9 wt. % Mg along with 0.2 to 0.6 wt. % Mn, up to 0.12 wt. %
Si, up to 0.15 wt. % Fe, from 0.03 to 0.16 wt. % of at least one
grain structure control element selected from the group consisting
of Zr, Sc, Cr, V, Hf, and other rare earth elements, up to 0.10 wt.
% Ti, up to 0.15 wt. % incidental elements with the total of
incidental elements not exceeding 0.35 wt. %, and the balance being
aluminum. Preferably, Ag is not intentionally added and should not
be more than 0.05 wt. % as a non-intentionally added element.
Preferably, Zn is not intentionally added and should not be more
than 0.2 wt. % as a non-intentionally added element. The amount of
Cu in weight percent is at least equal to or higher than 4 times
the amount of Li in weight percent in the inventive alloy.
[0031] The aluminum-lithium alloy of the present invention can be
used to produce wrought products, having a thickness range of
0.5-8.0 inch. In addition to low density and low cost, the
aluminum-lithium alloys of the present invention are wrought
products having high strength, stronger damage tolerance, and
excellent fatigue and corrosion resistance properties.
[0032] Such products are suitable for use in many structural
applications, especially for aerospace structural components such
as spar, rib, and integrally machined structural parts. The
aluminum-lithium alloy of the present invention can be used for the
fabrication of components using several manufacturing processes
such as high speed machining.
[0033] Copper is added to the aluminum-lithium alloy in the present
invention in the range of 3.6 to 4.1 wt. %, mainly to enhance the
strength but also to improve the combination of strength and
fracture toughness. An excessive amount of Cu can result in
unfavorable intermetallic particles which can negatively affect
material properties such as ductility and fracture toughness. In
these cases the interaction of Cu with other elements such as Li
and Mg must also be considered. Thus in the alternative
embodiments, the upper or lower limit for the amount of Cu may be
selected from 3.6, 3.7, 3.8, 3.9, 4.0, and 4.1 wt. %. In the
preferred embodiment, the Cu is from 3.7 to 4.0 wt. % to provide
compositions that enhance specific product performance while
maintaining relatively high performance in the remaining attributes
as compared to the prior art.
[0034] Lithium is added to the aluminum-lithium alloy in the
present invention in the range of 0.8 to 1.05 wt. %. The primary
benefit for adding Li is to reduce the density and increase the
elastic modulus. Combined with other elements, such as Cu, Li is
critical in improving the strength, damage tolerance and corrosion
performance. Li contents that are too high, however, can negatively
impact fracture toughness, and anisotropy of tensile properties. In
addition to the upper and lower limits listed above for Cu, the
present invention includes the alternative embodiments wherein the
upper or lower limit for the amount of Li may be selected from 0.8,
0.9, 1.0, and 1.05 wt. %. In one preferred embodiment, Li is in the
range of 0.9 to 1.0 wt. %.
[0035] The Cu/Li ratio significantly affects the desirable T1
strengthening phase, which is critical for strength, fracture
toughness, and anisotropy of tensile properties. The present
invention requires the Cu/Li ratio should be higher than 4.0 in
terms of wt. % Cu/wt. % Li.
[0036] Mg is added to the aluminum-lithium alloy in the present
invention in the range of 0.6 to 1.0 wt. %. The primary purpose of
adding Mg is to enhance the strength with the secondary purpose of
reducing the density. However, Mg levels that are too high can
reduce Li solubility in the matrix, thus negatively impacting the
aging potential for higher strength. In addition to the upper and
lower limits listed above for Cu and Li, the present invention
includes alternative embodiments wherein the upper or lower limit
for the amount of Mg may be selected from 0.6, 0.7, 0.8, 0.9, and
1.0 wt. %. In one preferred embodiment, Mg is in the range of 0.7
to 0.9 wt. %.
[0037] In one embodiment, Ag is not intentionally added in the
aluminum-lithium alloy of the present invention. Ag may exist in
the alloy as a result of a non-intentional addition. In this case,
the Ag should not be more than 0.05 wt. %. In addition to the upper
and lower limits listed above for Cu, Li, and Mg, the present
invention includes alternate embodiments wherein the upper or limit
for the amount of Ag may be selected from 0.05, 0.04, 0.03, 0.02,
and 0.01 wt.% The prior art teaches that Ag is necessary to improve
the final product properties and is therefore included in many
aluminum-lithium alloys as well as many patents and patent
applications. However, Ag significantly increases the cost of the
alloys. In the embodiment of the aluminum-lithium alloy of the
present invention, Ag is not intentionally included in order to
reduce the cost. It is surprising to find that the aluminum-lithium
alloy of the present invention, without the addition of Ag for
providing low cost, can be used to produce high strength, high
fracture toughness, and excellent corrosion resistance plate
products suitable for structural applications particularly in
aerospace.
[0038] The addition of Zn can negatively affect the density and
therefore Zn is not added in the present invention. Zn may exist in
the alloy as a result of a non-intentional addition. In this case,
the Zn should not be more than 0.2 wt. %. In addition to the upper
and lower limits listed above for Cu, Li, Mg, and Ag, the present
invention includes alternate embodiments having less than 0.15 wt.
% Zn, less than 0.10 wt.% Zn, less than 0.05 wt.% Zn.
[0039] Mn is intentionally added to improve the grain structure for
better mechanical isotropy and formability. In addition to the
upper and lower limits listed above for Cu, Li, Mg, Ag, and Zn, the
present invention includes alternative embodiments wherein the
upper or lower limits for the amounts of Mn may be selected from
0.2, 0.3, 0.4, 0.5, and 0.6 wt. %.
[0040] Ti can be added up to 0.10 wt. %. The purpose of adding Ti
is mainly for grain refinement in casting. In addition to the upper
and lower limits listed above for Cu, Li, Mg, Ag, Zn, and Mn, the
present invention includes alternative embodiments wherein the
upper limit for the amount of Ti may be selected from 0.01, 0.02,
0.05, 0.06, 0.07, 0.08, 0.09, and 0.10 wt. % Ti.
[0041] Si and Fe may be present in the aluminum-lithium alloy of
the present invention as impurities but are not intentionally
added. In addition to the upper and lower limits listed above for
Cu, Li, Mg, Ag, Zn, Mn, and Ti, the present invention includes
alternate embodiments wherein the alloy includes .ltoreq.0.12 wt. %
for Si, and .ltoreq.0.15 wt. % for Fe, preferably .ltoreq.0.05 wt.
% for Si and .ltoreq.0.08 wt. % for Fe. In one embodiment, the
aluminum-lithium alloy of the present invention includes a maximum
content of 0.12 wt. % for Si, and 0.15 wt. % for Fe. In one
preferred embodiment, the maximum contents are 0.05 wt. % A for Si
and 0.08 wt. % for Fe.
[0042] The aluminum-lithium alloy of the present invention may also
include low levels of "incidental elements" that are not included
intentionally. The "incidental elements" means any other elements
except Al, Cu, Li, Mg, Zr, Zn, Mn, Ag, Fe, Si, and Ti.
[0043] The low cost, high performance, high Mg content Al--Li alloy
of the present invention may be used to produce wrought products.
In one embodiment, the aluminum-lithium alloy of the present
invention is capable of producing rolled products, preferably, a
plate product in the thickness range of 0.5 to 8.0 inch. In the
alternative embodiments, the upper or lower limit for the thickness
may be selected from 0.5, 1.0, 2.0, 3.0, 4.0, 5.0, 6.0, 7.0 and 8.0
inch
[0044] The rolled products may be manufactured using known
processes such as casting, homogenization, hot rolling, solution
heat treating and quenching, stretching, and ageing treatments. The
ingot may be cast by traditional direct chill (DC) casting method.
The ingot may be homogenized at temperatures from 482 to
543.degree. C. (900 to 1010.degree. F.). The hot rolling
temperature may be from 357 to 482.degree. C. (675 to 900.degree.
F.). The products may be solution heat treated at temperature range
of 482 to 538.degree. C. (900 to 1000.degree. F.). The wrought
products are cold water quenched to room temperature and may be
stretched up to 15%, preferably from 2 to 8%. The quenched and
stretched product may be subjected to any aging practices known by
those skilled in the art including, but not limited to, one-step
aging practices that produce a final desirable temper, such as T8
temper, for better combination of strength, fracture toughness, and
corrosion resistance which are highly desirable for aerospace
members. The aging temperature can be in the range of 121 to
205.degree. C. (250 to 400.degree. F.) and preferably from 149 to
182.degree. C. (300 to 360.degree. F.) and the aging time can be in
the range of 2 to 60 hours, preferably from 10 to 48 hours.
[0045] The unique chemistry along with proper processing of present
patent application results in plate products with surprising novel
and basic material characteristics. In one embodiment, the tensile
yield strength (TYS) along rolling (L) direction as function of
plate gage (ga) is higher than 75.0-1.4*ga, preferably higher than
76.2-1.4*ga, and more preferably higher than 77.0-1.4*ga. The
tensile yield strength (TYS) along long transverse (LT) direction
is higher than 71.2-1.4*ga, preferably higher than 72.2-1.4*ga, and
more preferably higher than 72.7-1.4*ga. The fracture toughness
(K1c) along the orientation of Long Transverse--Rolling (T-L) is
higher than 28-1.0*ga, preferably higher than 29-1.0*ga, and more
preferably higher than 29.5-1.0*ga. The fracture toughness (K1c)
along the orientation of Rolling--Long Transverse (L-T) is higher
than 28.8-0.6*ga, preferably higher than 30.8-0.6*ga, and more
preferably higher than 31.8-0.6*ga. The units for gage (ga),
strength, and fracture toughness are inch, ksi, and ksi*in.sup.1/2
respectively.
[0046] The following examples illustrate various aspects of the
invention and are not intended to limit the scope of the
invention.
EXAMPLES
Industrial Scale Ingots--1 to 6 Inches Thick Plates
[0047] Twenty seven (27) industrial scale 16'' (406 mm) thick
ingots of Al--Li alloys were cast by DC (Direct Chill) casting
process and produced to 1'' to 6'' thickness plates. It is well
known that the properties of final plate products are strongly
affected by the processing. The properties of plates from
industrial scale process can be dramatically different from that
from lab scale processing due to different chemistry segregation,
as-cast structure, hot rolling related crystallographic texture,
and solution heat treatment quenching rate.
[0048] Table 1 gives the chemical compositions and final plate
thickness. There are three groups: (1) "Invention", (2)
"Non-Invention (Substantially Ag-free)" and (3) "Non-Invention
(Ag)". The third group is obviously not the invention alloy due to
the high cost Ag element and/or along with other conditions that do
not meet invention alloy chemical composition limits. In the second
group, samples are not invention alloys due to the combination of
Cu/Li ratio, Cu, Li, and Zn limits. For example, the Cu/Li ratios
for sample 12, 13 14, and 16 are lower than 4.0. The Cu contents in
sample 13 and 15 are lower than 3.6 wt. %. The Li content in Sample
13 is higher than 1.05 wt. %. The Zn content in Sample 16 is higher
than 0.2 wt. %.
TABLE-US-00001 TABLE 1 Chemical compositions of samples Gage,
Invention? Sample ID Lot in Si Fe Cu Mn Mg Ti Zr Li Ag Zn Cu/Li
Invention 1 130432B8 1 0.03 0.05 3.85 0.36 0.71 0.03 0.10 0.92 0.00
0.05 4.2 2 130408B8 2 0.03 0.04 3.80 0.36 0.70 0.02 0.10 0.86 0.00
0.05 4.4 3 130275B1 3 0.04 0.04 3.88 0.36 0.74 0.02 0.11 0.84 0.00
0.04 4.6 4 130285B0 3 0.03 0.04 3.74 0.35 0.70 0.03 0.10 0.90 0.00
0.06 4.1 5 187413B0 3 0.03 0.06 3.64 0.35 0.77 0.00 0.11 0.92 0.00
0.04 4.0 6 187292B8 3 0.02 0.06 3.74 0.33 0.68 0.03 0.11 0.92 0.00
0.03 4.1 7 652929A1 3 0.03 0.05 3.80 0.34 0.61 0.03 0.10 0.76 0.00
0.00 5.0 8 187267B0 3.2 0.03 0.04 3.98 0.42 0.72 0.02 0.10 0.88
0.00 0.01 4.5 9 130415B3 4 0.03 0.05 3.73 0.34 0.70 0.02 0.10 0.86
0.00 0.03 4.3 10 130369B2 6 0.03 0.04 3.73 0.35 0.72 0.02 0.10 0.88
0.00 0.03 4.2 11 187382B7 6 0.03 0.56 3.80 0.32 0.70 0.04 0.10 0.87
0.00 0.05 4.4 Non-Invention 12 187432B0 3 0.02 0.05 3.94 0.33 0.92
0.03 0.11 1.00 0.00 0.03 3.9 (No Ag) 13 652851A7 3 0.03 0.08 3.36
0.35 0.96 0.02 0.10 1.21 0.00 0.00 2.8 14 652867A3 3 0.03 0.07 3.62
0.36 1.02 0.02 0.10 1.07 0.00 0.00 3.4 15 652868A1 3 0.03 0.05 3.39
0.35 0.99 0.02 0.10 0.80 0.00 0.00 4.2 16 652950A7 3 0.03 0.05 3.70
0.36 1.05 0.03 0.10 1.01 0.00 0.51 3.7 Non-Invention 17 115697B5 1
0.03 0.05 3.84 0.35 0.40 0.02 0.10 1.15 0.28 0.03 3.3 (Ag) 18
652795A6 1 0.03 0.05 3.79 0.00 0.42 0.02 0.09 1.19 0.44 0.53 3.2 19
115621B5 2 0.03 0.05 3.82 0.35 0.41 0.02 0.10 1.00 0.28 0.06 3.8 20
187433B8 3 0.02 0.05 4.35 0.04 0.56 0.03 0.11 0.89 0.19 0.06 4.9 21
652784A0 3 0.04 0.05 3.88 0.33 0.90 0.02 0.09 0.80 0.26 0.37 4.8 22
652916A8 3 0.03 0.05 3.71 0.36 1.05 0.02 0.09 1.02 0.28 0.00 3.6 23
534647A3 3 0.02 0.04 3.67 0.37 0.37 0.03 0.08 0.92 0.31 0.07 4.0 24
652850A9 4 0.03 0.05 3.84 0.35 0.40 0.02 0.10 0.99 0.27 0.00 3.9 25
115664B5 5 0.03 0.05 3.78 0.34 0.45 0.02 0.10 1.05 0.28 0.02 3.6 26
652790A7 5 0.03 0.05 3.72 0.34 0.42 0.02 0.09 0.99 0.28 0.04 3.8 27
115615B7 6 0.03 0.05 3.77 0.34 0.38 0.02 0.10 0.98 0.28 0.03
3.9
[0049] The ingots were homogenized at temperatures from 496 to
538.degree. C. (925 to 1000.degree. F.). The hot rolling
temperatures were from 371 to 466.degree. C. (700 to 870''F), The
ingots were hot rolled at multiple passes into 1'' to 6''
thickness. The rolled plates were solution heat treated at a
temperature range from 493 to 532.degree. C. (920 to 990.degree.
F.). The plates were cold water quenched to room temperature. All
example plates were stretched by 2 to 7% in terms of plastic
strain. The stretched plates were further aged to T8 temper for
strength, fracture, fatigue resistance, and corrosion resistance
performance evaluation. The aging temperature was from 160.degree.
C. (320.degree. F.) to 171.degree. C. (340.degree. F.) for 8 to 70
hours.
[0050] The strength and fracture toughness as a function of aging
process is one critical characteristic for alloy performance. The
selected substantially Ag-free addition 3'' invention and
non-invention alloy plates were evaluated under 166.degree. C.
(330.degree. F.) aging temperature at different aging times. Table
2 gives the tensile and fracture toughness testing results. Tensile
in LT direction at quarter thickness (T/4) was conducted under ASTM
B557 specification. The plane strain fracture toughness (K1c) in
T-L orientations at middle thickness (T/2) was measured under ASTM
E399 using CT specimens.
[0051] For the same substantially Ag-free alloys, as demonstrated
in FIG. 1, invention alloys have much faster/better strength
response as aging time increases than non-invention alloys. Such
significant difference is mainly due to the distinctive chemical
composition difference between invention alloys and non-invention
alloys.
TABLE-US-00002 TABLE 2 The strength and fracture toughness as
function of aging time at 330.degree. F. Aging T/2 K1c Time at T/4
LT T/4 LT T/4 LT T-L Invention? Sample ID Lot 330 F., hours UTS,
Ksi TYS, Ksi EL, % ksi- in Invention 3 130275B1 18 77.0 70.5 8.0
30.3 18 76.8 70.3 7.5 29.3 31 78.5 72.7 6.5 30.7 31 78.6 72.3 6.5
30.9 31 78.3 72.2 7.5 28.1 31 78.2 72.1 7.5 27.2 50 78.5 72.9 8.0
26.2 50 78.4 73.0 8.0 25.9 4 130285B0 18 76.2 69.7 9.0 31.2 18 76.0
69.5 8.5 31.4 31 77.6 71.5 8.0 28.6 31 77.3 71.3 8.0 29.1 31 77.4
71.7 7.0 28.5 31 77.5 71.5 7.5 29.0 50 78.2 72.7 8.0 26.5 50 77.9
72.3 6.5 26.7 7 652929A1 9 66.0 53.5 15.0 43.9 11 58.0 58.2 13.5
41.3 14 71.3 62.2 11.5 36.2 18 73.2 65.2 9.0 33.6 24 74.9 67.5 7.5
31.3 31 76.8 69.5 8.0 28.8 31 76.5 69.0 7.5 29.0 32 75.7 69.4 7.3
29.5 41 73.9 69.4 5.8 44 76.2 70.3 4.0 27.4 48 75.8 70.4 7.0 67
75.4 69.8 7.5 26.1 Non-Invention 13 652851A7 9 63.9 47.3 19.0 43.6
(No Ag) 11 64.4 48.0 18.5 42.4 14 64.8 49.4 17.5 41.7 18 65.8 52.0
17.5 39.6 24 65.8 54.5 14.0 36.8 32 73.9 58.4 10.5 3 .4 41 71.6
64.8 7.3 44 73.5 68.1 5.0 25.1 44 72.8 64.9 6.0 26.6 44 73.1 66.2
4.5 26.5 48 73.3 67.4 6.0 67 73.0 66.6 6.0 23.2 14 652867A3 9 65.7
47.6 19.5 45.9 11 65.2 48.9 17.5 46.4 14 66.2 49.8 17.5 43.5 18
67.4 52.5 16.5 41.0 24 68.4 54.7 13.5 38.6 32 70.3 59.8 11.5 34.4
41 72.9 65.9 6.3 44 73.2 67.5 5.0 27.2 44 74.5 66.7 6.5 28.6 44
74.0 66.1 5.5 48 73.9 67.9 6.0 67 74.5 68.8 4.5 25.1 15 652868A1 9
52.5 45.6 20.0 51.7 11 52.8 46.4 23.0 51.6 14 53.5 48.1 21.0 50.0
18 64.0 49.2 20.0 48.8 24 64.9 51.4 18.5 45.7 32 65.9 54.0 16.0
43.0 44 69.6 62.9 10.0 33.9 44 69.5 62.8 9.0 33.9 16 652950A7 9
66.2 49.4 18.5 48.0 11 67.5 50.9 19.0 48.1 14 67.8 51.9 18.0 47.5
18 68.6 54.9 16.0 44.5 24 69.5 56.0 13.5 32 71.9 60.3 11.5 41 73.6
65.7 5.7 44 73.2 67.9 4.8 26.1 48 75.4 69.8 5.5 67 72.8 69.7 4.5
24.5 indicates data missing or illegible when filed
[0052] Based on the lab aging results, the desired aging practice
with balanced strength and fracture toughness was selected for
production aging treatment. The production aged plates were
comprehensively evaluated for tensile, fracture, corrosion and
fatigue resistance.
[0053] Table 3 and 4 give the tensile properties along L, LT, and
L45 (45.degree. off the rolling direction) directions at quarter
thickness (T/4) and middle thickness (T/2) for all production aged
plates. Table 5 gives the fracture toughness at the orientations of
L-T, T-L and S-L at quarter thickness (T/4) and middle thickness
(T/2) for all production aged plates.
TABLE-US-00003 TABLE 3 The tensile properties along L, LT, and L45
directions at quarter thickness (T/4) for production aged plates
Plate Information Aging T/4 Tensile Properties Temper- T/4 L T/4 L
T/4 L T/4 L45 T/4 L45 T/4 L45 T/4 LT T/4 LT T/4 LT Sample Gage,
ature, Aging UTS, TYS, EL, UTS, TYS, EL, UTS, TYS, EL, Invention?
Lot ID in .degree. F. hours Ksi Ksi % Ksi Ksi % Ksi Ksi % Invention
130408B8 2 2.0 330 32 77.3 74.3 11.0 75.1 68.8 7.5 77.2 71.7 9.5
78.6 75.2 11.0 75.2 68.7 13.0 77.1 71.5 10.0 130275B1 3 3.0 330 32
79.7 76.5 9.0 77.2 70.6 9.5 78.6 72.7 6.5 80.0 76.6 7.5 77.3 70.6
11.0 78.6 72.3 6.5 130285B0 4 3.0 330 32 78.9 75.7 8.5 76.1 69.6
11.0 77.6 71.5 8.0 78.0 74.7 9.5 76.3 69.4 11.0 77.3 71.3 8.0
187413B0 5 3.0 330 32 76.8 74.3 11.0 75.2 69.5 12.0 76.8 71.2 9.5
77.7 75.2 10.0 75.4 69.3 12.0 76.4 70.9 11.0 187292B8 6 3.0 330 32
77.6 74.3 11.0 76.0 69.5 11.0 76.6 70.9 8.0 77.4 74.1 9.0 76.1 69.6
11.0 76.9 71.2 8.5 652929A1 7 3.0 330 32 77.8 74.1 7.5 75.5 68.9
9.0 76.8 69.5 8.0 79.0 75.2 7.0 76.0 69.4 7.5 76.5 69.0 7.5
187267B0 8 3.2 330 32 76.7 75.5 9.5 76.0 69.3 9.0 77.3 71.0 7.5
76.8 73.8 11.0 76.1 69.6 12.0 77.2 71.0 8.5 130415B3 9 4.0 330 32
75.9 72.7 8.5 75.2 68.6 7.5 75.9 69.8 7.0 75.8 72.6 9.0 75.3 68.9
10.0 76.2 70.5 5.5 130369B2 10 6.0 330 32 74.1 70.6 8.0 73.0 66.1
6.0 73.4 66.4 4.5 74.0 70.4 6.5 72.6 66.0 3.5 73.1 66.5 4.5
187382B7 11 6.0 330 32 74.2 70.7 7.0 73.8 66.6 9.0 74.2 67.2 6.0
74.2 70.7 8.5 73.7 66.2 8.0 74.1 67.0 5.0 Non-Invention 187432B0 12
3.0 330 32 81.1 78.0 9.5 79.2 72.0 11.0 80.1 73.5 8.0 (No Ag) 80.3
77.0 10.0 78.7 71.3 11.0 79.7 73.0 8.5 652851A7 13 3.0 340 24 72.1
68.7 8.5 71.6 64.0 9.0 72.8 64.9 6.0 73.3 69.8 10.0 72.1 64.8 8.0
73.1 66.2 4.5 652867A3 14 3.0 340 24 74.2 69.6 7.5 73.2 65.0 10.0
74.5 66.7 6.5 75.9 70.2 9.5 73.2 64.9 8.0 74.0 66.1 5.5 652868A1 15
3.0 340 24 70.0 65.2 11.0 68.7 61.6 13.0 69.6 62.9 10.0 68.3 64.0
13.0 68.5 61.3 10.0 69.5 62.8 9.0 Non-Invention 115621B5 19 2 310
20 81.6 77.6 11.0 78.1 70.6 14.0 79.9 73.2 12.0 (Ag) 80.0 76.1 11.0
77.8 70.1 14.0 79.9 73.2 10.0 187433B8 20 3 330 18 84.3 80.4 8.5
83.4 75.9 9.5 84.4 77.6 5.5 84.1 80.1 9.0 83.3 75.9 9.0 84.3 77.8
5.5 652784A0 21 3 330 32 79.5 76.1 5.0 77.6 70.4 4.5 79.3 72.7 8.5
82.0 78.2 6.0 78.7 71.6 8.0 79.2 72.7 3.0 652916A8 22 3 340 24 76.5
71.6 7.0 75.1 67.8 5.5 75.5 69.0 3.5 78.0 74.3 6.0 75.3 68.0 5.5
75.0 69.2 4.0 534647A3 23 3.0 310 27 77.8 73.7 9.8 77.1 70.0 9.3
78.0 71.2 6.3 652850A9 24 4 320 24 79.1 74.6 7.5 78.2 70.1 7.5 78.8
71.4 4.2 79.5 74.6 8.0 78.3 69.4 7.5 78.7 71.1 5.0 115664B5 25 5
320 24 80.3 76.2 6.0 79.0 71.8 3.5 79.2 72.2 4.0 80.1 75.9 5.5 79.3
71.6 6.5 80.1 73.1 5.5 652790A7 26 5 320 24 78.3 73.8 6.5 76.9 70.5
3.0 76.6 69.5 3.5 78.5 73.9 7.5 77.2 70.1 3.5 77.0 69.8 3.5
115615B7 27 6 320 24 77.9 73.8 8.5 78.4 71.2 4.7 77.8 71.2 3.5 78.0
73.8 6.0 78.5 70.8 5.0 75.9 71.2 2.0
TABLE-US-00004 TABLE 4 The tensile properties along L, LT, and L45
directions at middle thickness (T/2) for production aged plates
Plate Information T/2 Tensile Properties Aging T/2 T/2 T/2 Temper-
T/2 L T/2 L T/2 L L45 L45 L46 Sample Gage, ature, Aging UTS, TYS,
EL, UTS, TYS, EL, Invention? Lot ID in .degree. F. hours Ksi Ksi %
Ksi Ksi % Invention 130432B8 1 1 330 18 81.4 77.7 11.0 72.6 67.0
15.0 81.3 77.8 11.0 72.5 66.9 14.0 130408B8 2 2 330 32 79.2 75.4
8.5 71.2 66.0 13.0 79.4 75.5 9.5 71.0 65.7 14.0 130275B1 3 3 330 32
80.7 77.2 7.5 73.5 68.1 9.5 80.8 77.1 8.5 73.6 68.4 9.0 130205B0 4
3 330 32 79.3 75.6 8.0 72.8 67.1 12.0 79.1 75.2 8.0 72.5 67.2 12.0
187413B0 5 3 330 32 79.2 78.4 10.0 71.9 67.8 12.0 79.2 78.3 8.5
71.9 67.6 13.0 187292B8 6 3 330 32 78.9 75.2 11.0 72.3 67.2 12.0
78.8 75.2 11.0 72.2 67.2 11.0 652929A1 7 3 330 32 79.7 74.4 8.0
73.2 66.0 9.5 80.0 75.7 7.0 72.2 65.5 11.0 187267B0 8 3.21 330 32
79.8 75.9 9.5 73.0 67.6 10.0 79.8 75.8 8.0 72.7 67.3 9.0 130415B3 9
4 330 32 77.3 73.4 8.5 74.9 68.2 9.0 77.2 73.3 7.5 71.8 66.4 9.5
130369B2 10 6 330 32 74.6 70.6 6.5 69.3 63.3 7.0 75.1 71.0 6.5 69.0
63.0 7.0 187382B7 11 6 330 32 75.4 71.2 8.5 70.7 64.5 7.5 75.3 71.1
8.5 71.4 65.2 10.0 Non-Invention 187432B0 12 3 330 32 81.7 78.3
10.0 75.1 69.7 9.0 (No Ag) 81.6 78.3 7.5 75.0 69.4 11.0 652851A7 13
3 340 24 75.7 71.6 7.0 69.4 62.2 9.5 75.6 71.6 6.0 69.3 62.5 8.0
652867A3 14 3 340 24 78.6 74.6 4.5 70.0 64.8 8.0 78.4 74.2 5.5 70.5
64.9 9.5 652868A1 15 3 340 24 73.4 69.2 9.0 66.4 60.1 14.0 74.2
69.9 8.0 65.8 60.5 9.5 Non-Invention 115697B5 17 1 310 15 85.6 81.2
11.0 76.9 70.4 15.0 (Ag) 85.7 81.3 10.0 76.5 70.2 13.0 652795A6 18
1 320 24 86.6 85.6 5.5 81.4 73.6 11.0 90.1 86.9 6.5 81.0 73.2 9.0
115621B5 19 2 310 20 83.7 79.0 10.0 75.1 68.8 13.0 84.0 79.3 10.0
74.9 68.1 15.0 187433B8 20 3 330 18 87.8 83.6 7.5 80.2 74.2 7.0
87.6 83.4 8.0 80.4 74.3 7.5 652784A0 21 3 330 32 80.9 77.0 7.5 74.6
68.6 5.5 81.4 77.4 6.5 75.6 68.2 8.5 652916A8 22 3 340 24 78.9 74.7
5.5 72.5 66.6 7.0 79.5 75.5 6.0 71.8 65.9 9.0 534647A3 23 3.0 310
27 78.2 73.4 9.3 71.5 65.1 9.3 652850A9 24 4 320 24 83.1 77.8 6.5
75.5 68.3 7.5 82.4 77.0 7.0 115664B5 25 5 320 24 81.2 77.1 4.7 76.1
69.4 5.5 81.5 77.5 4.0 75.9 69.3 5.5 652790A7 26 5 320 24 75.5 68.2
7.5 74.0 66.7 5.0 84.2 79.3 5.5 73.7 66.9 4.5 115615B7 27 6 320 24
78.5 74.2 5.5 73.0 66.8 4.7 78.9 74.5 6.0 73.0 66.9 4.5 Plate
Information T/2 Tensile Properties Aging T/2 T/2 T/2 T/2 T/2 T/2
Temper- LT LT LT ST ST ST Sample Gage, ature, Aging UTS, TYS, EL,
UTS, TYS, EL, Invention? Lot ID in .degree. F. hours Ksi Ksi % Ksi
Ksi % Invention 130432B8 1 1 330 18 79.3 74.4 11.0 74.2 66.6 4.5
79.2 74.2 12.0 75.3 64.0 5.0 130408B8 2 2 330 32 77.3 72.2 11.0
75.6 65.1 8.5 77.0 71.8 10.0 74.9 64.3 8.0 130275b1 3 3 330 32 79.1
73.5 6.5 76.4 68.0 3.0 78.9 73.4 7.5 76.5 67.9 3.0 130205B0 4 3 330
32 77.9 72.4 8.0 75.5 66.4 4.0 78.1 72.4 8.5 75.6 66.9 4.0 187413B0
5 3 330 32 77.5 73.1 9.5 75.4 67.6 4.0 77.6 73.2 9.5 75.2 67.3 3.0
187292B8 6 3 330 32 77.7 72.3 8.0 75.5 66.6 4.0 77.8 72.6 8.5 75.6
66.7 5.0 652929A1 7 3 330 32 76.2 69.9 6.0 74.3 65.0 3.0 77.6 71.3
6.5 73.8 64.9 4.0 187267B0 8 3.21 330 32 77.7 72.1 7.5 75.9 66.7
4.0 77.6 71.7 8.0 75.4 67.2 4.0 130415B3 9 4 330 32 75.6 69.4 7.5
73.0 64.7 4.3 75.2 70.2 3.0 72.7 64.6 4.3 130369B2 10 6 330 32 70.5
64.1 4.0 70.6 62.3 3.5 70.4 84.3 5.0 70.4 62.1 2.5 187382B7 11 6
330 32 71.9 65.2 6.5 70.8 63.1 4.0 72.8 66.7 4.4 70.3 63.4 3.4
Non-Invention 187432B0 12 3 330 32 80.2 74.9 8.0 77.8 68.3 3.0 (No
Ag) 80.2 74.8 10.0 78.1 68.4 5.0 652851A7 13 3 340 24 73.2 67.6 4.5
70.7 62.9 1.0 74.0 67.8 7.0 70.6 62.9 2.0 652867A3 14 3 340 24 75.4
68.7 5.5 73.2 64.9 1.0 75.2 69.6 5.0 72.3 64.2 1.0 652B68A1 15 3
340 24 70.4 64.3 9.0 69.3 60.2 5.0 71.4 65.6 7.5 69.8 61.2 6.0
Non-Invention 115697B5 17 1 310 15 83.9 78.0 10.0 81.3 67.7 11.0
(Ag) 83.7 77.6 11.0 81.7 69.8 7.5 652795A6 18 1 320 24 88.7 83.7
4.5 88.9 74.1 8.0 88.7 83.8 5.5 87.7 75.4 6.5 115621B5 19 2 310 20
81.7 75.7 11.0 78.9 66.4 8.5 81.7 75.6 10.0 78.2 66.1 8.0 187433B8
20 3 330 18 85.6 81.0 4.5 82.4 72.8 2.0 86.7 81.2 6.0 82.7 72.8 1.0
652784A0 21 3 330 32 79.5 73.4 5.5 75.7 66.9 2.0 79.7 73.6 5.0 76.2
67.2 1.5 652916A8 22 3 340 24 76.0 69.9 6.5 73.1 64.7 1.0 77.3 69.9
5.0 73.8 65.5 1.0 534647A3 23 3.0 310 27 76.6 70.1 6.8 74.1 65.6
4.1 652850A9 24 4 320 24 79.9 72.7 5.0 77.7 66.6 3.0 79.0 73.0 2.5
77.7 66.3 2.0 115664B5 25 5 320 24 79.5 73.3 3.5 75.7 67.0 2.5 79.1
73.0 3.5 75.6 66.9 2.0 652790A7 26 5 320 24 78.8 71.3 4.5 77.5 87.0
3.0 78.6 71.5 4.2 78.5 67.8 2.5 115615B7 27 6 320 24 74.5 68.5 3.0
72.7 64.5 2.5 74.7 68.6 3.5 72.6 64.2 2.5
TABLE-US-00005 TABLE 5 Fracture toughness at the orientations of
L-T, T-L and S-L at quarter thickness (T/4) and middle thickness
(T/2) for all final production aged plates Plate Information
Fracture Toughness Aging T/2 T/2 T/2 T/4 T/4 Sample Gage,
Temperature, Aging L-T T-L S-L L-T T-L Invention? Lot ID in
.degree. F. hours ksi- in ksi- in ksi- in ksi- in ksi- in Invention
130432B8 1 1 330 18 33.0 30.2 25.9 31.9 30.6 29.2 130408B8 2 2 330
32 34.3 30.4 28.0 33.6 30.1 26.1 130275B1 3 3 330 32 30.7 27.4 25.1
27.8 25.5 30.9 26.8 23.9 27.7 26.1 130285B0 4 3 330 32 32.2 28.6
24.0 27.8 26.9 31.1 29.1 24.9 28.6 26.4 187413B0 5 3 330 32 32.6
28.1 24.7 29.7 28.2 32.1 28.0 25.5 28.6 27.0 187292B8 6 3 330 32
32.2 28.1 26.1 28.3 27.3 31.4 28.0 25.2 28.4 27.1 652929A1 7 3 330
32 33.9 28.8 25.7 32.3 28.3 33.8 29.0 27.0 187267B0 8 3.21 330 32
31.6 27.9 25.8 29.3 26.8 32.6 28.2 26.1 29.8 27.6 130415B3 9 4 330
32 31.5 28.5 26.0 29.7 27.4 31.2 29.0 25.9 29.6 27.5 130369B2 10 6
330 32 33.0 25.3 25.0 31.3 24.9 32.8 26.1 23.1 30.4 26.0 187382B7
11 6 330 32 30.0 26.2 25.4 29.7 25.0 30.0 25.7 26.1 28.9 25.1
Non-Invention 187432B0 12 3 330 32 25.3 24.3 23.6 23.6 23.4 (No Ag)
24.0 24.5 23.3 23.0 22.7 652851A7 13 3 340 24 31.6 26.6 20.8 25.3
30.6 26.5 22.4 652867A3 14 3 340 24 33.0 28.6 23.0 30.7 27.5 32.1
23.0 652868A1 15 3 340 24 42.9 33.9 31.6 40.7 34.0 42.5 33.9 29.7
Non-Invention 115697B5 17 1 310 15 34.0 32.6 28.8 (Ag) 33.3 32.3
27.9 652795A6 18 1 320 24 18.7 18.4 18.5 18.7 17.0 115621B5 19 2
310 20 32.8 31.5 27.9 33.4 30.9 28.7 187433B8 20 3 330 18 21.6 21.1
20.3 20.0 20.7 22.2 20.9 19.5 19.9 21.0 652784A0 21 3 330 32 27.5
25.8 25.6 26.7 23.7 27.1 25.4 24.2 652916A8 22 3 340 24 31.8 29.6
26.6 31.1 29.1 31.6 30.3 27.3 534647A3 23 3.0 310 27 35.9 30.9 28.2
652850A9 24 4 320 24 31.3 25.8 23.1 29.4 26.0 31.6 25.7 23.9
115664B5 25 5 320 24 26.8 25.2 23.0 25.0 24.2 26.7 24.9 22.6 25.1
24.3 652790A7 26 5 320 24 30.0 27.3 26.0 31.8 27.8 29.9 27.0 26.2
115615B7 27 6 320 24 29.0 24.3 23.9 28.0 24.4 28.5 24.6 22.7 27.3
23.5
[0054] Table 3 to 5 shows that the low cost invention alloy with
unique chemical composition has surprisingly better material
properties in terms of the combination of strength and fracture
toughness. As an example, FIG. 2 gives the comparison of LT TYS
strength and K1c T-L fracture toughness between substantially
Ag-free invention alloys and Non-invention alloys (No Ag) of 3 inch
plates. The invention alloys have a better combination of strength
and fracture toughness. The minimum LT TYS can be 67 ksi and
minimum K1c T-L can be 25 ksi*in.sup.1/2 for 3'' plate. Preferably,
the minimum LT TYS can be 68 ksi and minimum K1c T-L can be 26
ksi*in.sup.1/2 for 3'' plate. More preferably, the minimum LT TYS
can be 68.5 ksi and minimum K1c T-L can be 26.5 ksi*in.sup.1/2 for
3'' plate.
[0055] The similar distinctiveness can be demonstrated in FIG. 3
for 3'' L TYS and K1c L-T properties. The minimum L TYS can be 70.8
ksi and minimum K1c L-T can be 27 ksi*in.sup.1/2 for 3'' plate.
Preferably, the minimum L TYS can be 72.0 ksi and minimum K1c L-T
can be 29 ksi*in.sup.1/2 for 3'' plate. More preferably, the
minimum L TYS can be 72.8 ksi and minimum K1c L-T can be 30
ksi*in.sup.1/2 for 3'' plate.
[0056] FIGS. 4 and 5 gives the comparison of LT TYS vs. K1c T-L and
L TYS vs. K1c L-T between low cost substantially Ag-free invention
alloys and high cost Ag containing non-invention alloys of 3 inch
plates. It surprisingly shows that there is no significant
difference between Ag containing non invention alloys and
substantially Ag-free invention alloys in terms of the combination
of strength and fracture toughness.
[0057] FIGS. 6 to 9 gives the strength and fracture toughness as a
function of plate thickness for invention alloy plates. The tensile
yield strength (TYS) along long transverse (LT) direction is higher
than 71.2-1.4*ga, preferably higher than 72.2-1.4*ga, and more
preferably higher than 72.7-1.4*ga. The tensile yield strength
(TYS) along rolling (L) direction as function of plate gage (ga) is
higher than 75.0-1.4*ga, preferably higher than 76.2-1.4*ga, and
more preferably higher than 77.0-1.4*ga. The fracture toughness
(K1c) along the orientation of Long Transverse--Rolling (T-L) is
higher than 28-1.0*ga, preferably higher than 29-1.0*ga, and more
preferably higher than 29.5-1.0*ga. The fracture toughness (K1c)
along the orientation of Rolling--Long Transverse (L-T) is higher
than 28.8-0.6*ga, preferably higher than 30.8-0.6*ga, and more
preferably higher than 31.8-0.6*ga. The units for gage (ga),
strength, and fracture toughness are inch, ksi, and ksi*in.sup.1/2
respectively.
[0058] Corrosion resistance is a key design consideration for
airframe manufacturers. The MASTMASSIS test is generally considered
to be a good representative accelerated corrosion test method for
Al--Li based alloys.
[0059] The MASTMASSIS test was based on ASTM G85-11 Annex-2 under
dry-bottom conditions. The sample size was 4.5'' L.times.4.5'' LT
at middle of sheet thickness. The temperature of the exposure
chamber through the duration of the test was 49.+-.2.degree. C. The
testing through thickness location is T/2 (center of thickness).
The testing plane is L-LT plane. The testing duration times were
24, 48, 96, 168, 336, 504, and 672 hrs.
[0060] FIG. 10 gives the typical surface appearances after 672
hours MASTMASSIS testing exposure times. The left photo is from
invention alloy Sample #6 with 3 inch plate thickness and right
photo is from invention alloy Sample #11 with 6 inch plate
thickness. The tested surfaces are very clean and shiny. No
exfoliation is evident for all the exposure times. The excellent
corrosion resistance of pitting/EA can be concluded for all
exposure times for all invention alloy plates.
[0061] Stress corrosion cracking (SCC) resistance is also critical
for aerospace application. The standard stress corrosion cracking
resistance testing was performed in accordance with the
requirements of ASTM G47 which is alternate immersion in a 3.5%
NaCl solution under constant deflection. Three specimens were
tested per sample. The stress levels are 45 ksi and 50 ksi.
[0062] Table 6 gives the SCC testing results for Sample 6, 7, 8, 10
with final production ageing treatment. All specimens survived 30
days testing without failures under 45 ksi or 50 ksi stress levels
in ST direction.
TABLE-US-00006 TABLE 6 The SCC testing results for Sample 6, 7, 8,
10 with final production ageing treatment Sample Gage, ID Lot in
Stress Repeat 1 Repeat 2 Repeat 3 6 187292B8 3.0 45 >30 days
>30 days >30 days 7 652929A1 3.0 45 >30 days >30 days
>30 days 7 652929A1 3.0 45 >30 days >30 days >30 days 8
187267B0 3.2 50 >30 days >30 days >30 days 10 130369B2 6.0
45 >30 days >30 days >30 days
[0063] The fatigue property was tested in accordance with the
requirements of ASTM E466. Four LT smooth specimens were tested
from each plate at plate thickness center along long transverse
(LT) direction. Specimen was tested at 240 MPa (35 ksi). Table 7
gives the fatigue testing results of invention alloy plates. The
majority of fatigue test specimens had no failures after 300,000
cycles and all plates met the common industrially accepted
criterion, i.e. 120,000 cycles of logarithm average of four
specimens.
TABLE-US-00007 TABLE 7 The smooth fatigue testing results of
invention alloy plates Sample ID Lot # Gage, in Specimen-1
Specimen-2 Specimen-3 Specimen-4 Log Average 1 130432B8 1
>300,000 >300,000 >300,000 >300,000 >300,000 2
130408B8 2 >300,000 >300,000 >300,000 >300,000
>300,000 3 130275B1 3 >300,000 >300,000 >300,000
>300,000 >300,000 4 130285B0 3 >300,000 >300,000
>300,000 >300,000 >300,000 5 187413B0 3 >300,000
>300,000 >300,000 >300,000 >300,000 6 187292B8 3
>300,000 >300,000 >300,000 >300,000 >300,000 7
652929A1 3 289,683 196,242 244,917 >300,000 >254,222 8
187267B0 3.2 >300,000 >300,000 >300,000 >300,000
>300,000 9 130415B3 4 >300,000 >300,000 >300,000
>300,000 >300,000 10 130369B2 6 126,731 157,529 117,225
121,511 129,858 11 187382B7 6 243,681 >300,000 285,136
>300,000 >281,209
[0064] The material performance is strongly related to material
grain structure, which is greatly affected by alloy chemical
composition along with thermal mechanical processing procedure.
Specifically for Al--Li plate products, an unrecrystallized grain
structure is desirable for better strength, fracture toughness and
corrosion resistance performance. FIGS. 11 to 15 gives the grain
structures of different thickness invention alloy plates. All the
invention alloy plates have unrecrystallized grain structures at
both quarter thickness (T/4) and middle thickness (T/2).
[0065] While specific embodiments of the invention have been
disclosed, it will be appreciated by those skilled in the art that
various modifications and alterations to those details could be
developed in light of the overall teachings of the disclosure.
Accordingly, the particular arrangements disclosed are meant to be
illustrative only and not limiting as to the scope of the invention
which is to be given the full breadth if the appended claims and
any and all equivalents thereof.
* * * * *