CA3227929A1 - Methods of producing 2xxx aluminum alloys - Google Patents

Abstract

Methods of making new 2xxx aluminum alloy sheet products are disclosed. In one approach, a method comprises artificially aging a 2xxx aluminum alloy in at least two-steps. In one embodiment, the first aging step comprises first aging a 2xxx aluminum alloy at a first temperature of from 300ºF to 450ºF and for a first aging time of from 4 to 120 hours, and second aging the 2xxx aluminum alloy at a second temperature for a second aging time of from 30 minutes to 120 hours, wherein the second temperature is from 20°F to 150°F lower than the first temperature. The new two-step artificial aging step may facilitate an improved combination of properties, such as an improved combination of two or more of strength, ductility, fracture toughness, and corrosion resistance.

Description

CROSS-REFERENCE TO RELATED APPLICATION
[001] The present patent application claims priority to U.S. Provisional Patent Application No. 63/236,614 entitled "METHODS OF PRODUCING 2XXX ALUMINUM ALLOYS" filed August 24, 2021, which application is incorporated herein by reference in its entirety.
BACKGROUND

[002] Aluminum alloys are useful in a variety of applications. However, improving one property of an aluminum alloy without degrading another property often proves elusive. For example, it is difficult to increase the strength of an alloy without decreasing the toughness of an alloy. Other properties of interest for aluminum alloys include corrosion resistance and fatigue crack growth rate resistance, to name two.
SUMMARY OF THE DISCLOSURE

[003] Broadly, the present patent application relates to methods of producing 2xxx aluminum alloys. In one approach, a method comprises artificially aging a 2xxx aluminum alloy in at least two-steps ("two-step artificial aging"). In one embodiment, the artificial aging comprises (a) first aging a 2xxx aluminum alloy at a first temperature of from 300 F to 450 F and for a first aging time of from 4 to 120 hours, and (b) second aging the 2xxx aluminum alloy at a second temperature for a second aging time of from 30 minutes to 120 hours, wherein the second temperature is from 20 F to 150 F lower than the first temperature. The new two-step artificial aging step may facilitate an improved combination of properties, such as an improved combination of two or more of strength, ductility, fracture toughness, and corrosion resistance. In one embodiment, at least partially due to the first aging and second aging steps, the 2xxx aluminum alloy is (i) LT stress corrosion cracking resistant (defined below), (ii) ST stress corrosion cracking resistant (defined below), or (iii) both LT stress corrosion cracking resistant and ST stress corrosion cracking resistant. Additional details are provided in the sections that follow.
1. Composition

[004] The new methods described herein are applicable to 2xxx aluminum alloys (defined below). Some useful 2xxx aluminum alloys include those described in International Patent Application Publication No. W02020/123096 A2, filed November 15, 2019 by Arconic Inc., currently assigned to Arconic Technologies LLC.

[005] In one embodiment, a 2xxx aluminum alloy comprises (and in some instances consists essentially of, or consists of) from 0.08 to 0.20 wt. 0/0 Ti, from 4.5 to 5.5 wt. % Cu, from 0.20 to 0.6 wt. % Mn, from 0.20 to 0.8 wt. % Mg, from 0.05 to 0.60 wt. % Ag, up to 1.0 wt. % Zn, up to 0.30 wt. % Fe, up to 0.20 wt. % Si, up to 0.25 wt. 9/0Zr, up to 0.25 wt. % Cr, and up to 0.25 wt. %
V, the balance being aluminum, incidental elements and impurities. In one embodiment, the 2xxx aluminum alloy is a 2039 alloy (as defined by the Aluminum Association Teal Sheets document, described below) modified to include 0.08 to 0.20 wt. % Ti, such as any of the titanium limits/ranges described below. In one embodiment, the 2xxx aluminum alloy is a 2039 alloy modified to include 0.08 to 0.20 wt. % Ti and from 0 to 0.10 wt. % Zr. The teachings of this paragraph also apply to other 2x39 alloys, such as 2139. The 2xxx aluminum alloys described herein may realize an improved combination of at least two of strength, ductility, fracture toughness, and corrosion resistance (e.g., stress corrosion cracking resistance), among others.

[006] As noted above, the 2xxx aluminum alloys generally include 0.08 to 0.20 wt. % Ti.
The use of titanium in combination with other elements of the 2xxx aluminum alloys may result in 2xxx aluminum alloys products having an improved combination of properties, such as an improved combination of two or more of strength, ductility (elongation), fracture toughness and corrosion resistance (e.g., stress corrosion cracking resistance), among others. The amount of titanium present in the 2xxx aluminum alloys should be limited such that large primary particles do not form in the alloy. In one embodiment, a 2xxx aluminum alloy includes at least 0.09 wt. %
Ti. In another embodiment, a 2xxx aluminum alloy includes at least 0.10 wt. %
Ti. In yet another embodiment, a 2xxx aluminum alloy includes at least 0.11 wt. % Ti. In one embodiment, a 2xxx aluminum alloy includes not greater than 0.18 wt. % Ti. In another embodiment, a 2xxx aluminum alloy includes not greater than 0.16 wt. % Ti. In yet another embodiment, a 2xxx aluminum alloy includes not greater than 0.15 wt. % Ti. In another embodiment, a 2xxx aluminum alloy includes not greater than 0.14 wt. % Ti. In yet another embodiment, a 2xxx aluminum alloy includes not greater than 0.13 wt. % Ti. The titanium may facilitate improved stress corrosion cracking resistance properties while also facilitating, for instance, grain refining, among other things.
Titanium may be added as a separate element and/or as part of a grain refining compound.
Examples of grain refiners include Ti combined with B (e.g., TiB2) or carbon (TiC), although other grain refiners, such as Al-Ti master alloys may be utilized. Grain refiners in combination with elemental titanium may be used in the 2xxx aluminum alloys in any appropriate amount, and generally depending on the desired as-cast grain size.

[007] As noted above, a 2xxx aluminum alloy may include from 4.5 to 5.5 wt.
% Cu. In one embodiment, a 2xxx aluminum alloy includes at least 4.6 wt. % Cu. In another embodiment, a 2xxx aluminum alloy includes at least 4.7 wt. % Cu. In yet another embodiment, a 2xxx aluminum alloy includes at least 4.8 wt. % Cu. In one embodiment, a 2xxx aluminum alloy includes not greater than 5.4 wt. % Cu. In another embodiment, a 2xxx aluminum alloy includes not greater than 5.3 wt. `)/0 Cu. In yet another embodiment, a 2xxx aluminum alloy includes not greater than 5.2 wt. % Cu. In another embodiment, a 2xxx aluminum alloy includes not greater than 5.1 wt. %
Cu. In yet another embodiment, a 2xxx aluminum alloy includes not greater than 5.0 wt. % Cu.

[008] As noted above, a 2xxx aluminum alloy may include from 0.20 to 0.6 wt. % Mn. In one embodiment, a 2xxx aluminum alloy includes at least 0.25 wt. % Mn. In another embodiment, a 2xxx aluminum alloy includes at least 0.30 wt. % Mn. In one embodiment, a 2xxx aluminum alloy includes not greater than 0.55 wt. % Mn. In another embodiment, a 2xxx aluminum alloy includes not greater than 0.50 wt. % Mn. In yet another embodiment, a 2xxx aluminum alloy includes not greater than 0.45 wt. % Mn. In another embodiment, a 2xxx aluminum alloy includes not greater than 0.40 wt. % Mn.

[009] As noted above, a 2xxx aluminum alloy may include from 0.20 to 0.6 wt. % Mg. In one embodiment, a 2xxx aluminum alloy includes at least 0.25 wt. % Mg. In another embodiment, a 2xxx aluminum alloy includes at least 0.30 wt. % Mg. In one embodiment, a 2xxx aluminum alloy includes not greater than 0.55 wt. % Mg. In another embodiment, a 2xxx aluminum alloy includes not greater than 0,50 wt. % Mg.

[0010] As noted above, a 2xxx aluminum alloy may include from 0.05 to 0.6 wt. % Ag. In one embodiment, a 2xxx aluminum alloy includes at least 0.10 wt. (21/0 Ag. In another embodiment, a 2xxx aluminum alloy includes at least 0.15 wt. % Ag. In yet another embodiment, a 2xxx aluminum alloy includes at least 0.20 wt. % Ag. In another embodiment, a 2xxx aluminum alloy includes at least 0.25 wt. % Ag. In yet another embodiment, a 2xxx aluminum alloy includes at least 0.30 wt. % Ag. In one embodiment, a 2xxx aluminum alloy includes not greater than 0.55 wt. % Ag. In another embodiment, a 2xxx aluminum alloy includes not greater than 0.50 wt. %
Ag. In yet another embodiment, a 2xxx aluminum alloy includes not greater than 0.45 wt. % Ag.
In another embodiment, a 2xxx aluminum alloy includes not greater than 0.40 wt. % Ag.

[0011] As noted above, a 2xxx aluminum alloy may include up to 1.0 wt. % Zn. In one embodiment, a 2xxx aluminum alloy includes at least 0.10 wt. % Zn. In another embodiment, a 2xxx aluminum alloy includes at least 0.20 wt. % Zn. In yet another embodiment, a 2xxx aluminum alloy includes at least 0.30 wt. % Zn. In another embodiment, a 2xxx aluminum alloy includes at least 0.40 wt. % Zn. In yet another embodiment, a 2xxx aluminum alloy includes at least 0.50 wt. % Zn. In one embodiment, a 2xxx aluminum alloy includes not greater than 0.90 wt. % Zn. In another embodiment, a 2xxx aluminum alloy includes not greater than 0.80 wt. %
Zn. In yet another embodiment, a 2xxx aluminum alloy includes not greater than 0.70 wt. % Zn.
In another embodiment, a 2xxx aluminum alloy includes not greater than 0.60 wt. % Zn.

[0012] As noted above, a 2xxx aluminum alloy may include up to 0.25 wt. % Zr. In some embodiments, the combination of both (a) elevated levels of titanium, and (b) use of zirconium may facilitate the realization of improved 2xxx aluminum alloy products having an improved combination of at least two of strength, elongation, fracture toughness and corrosion resistance (e.g., stress corrosion cracking resistance), among others. In one embodiment, a 2xxx aluminum alloy includes at least 0.05 wt. % Zr. In another embodiment, a 2xxx aluminum alloy includes at least 0.06 wt. % Zr. In yet another embodiment, a 2xxx aluminum alloy includes at least 0.07 wt.
% Zr. In another embodiment, a 2xxx aluminum alloy includes at least 0.08 wt.
% Zr. In one embodiment, a 2xxx aluminum alloy includes not greater than 0.18 wt. % Zr. In another embodiment, a 2xxx aluminum alloy includes not greater than 0.16 wt. % Zr. In yet another embodiment, a 2xxx aluminum alloy includes not greater than 0.15 wt. % Zr. In another embodiment, a 2xxx aluminum alloy includes not greater than 0.14 wt. % Zr. In yet another embodiment, a 2xxx aluminum alloy includes not greater than 0.13 wt. % Zr. In another embodiment, a 2xxx aluminum alloy includes not greater than 0.12 wt. % Zr. In yet another embodiment, a 2xxx aluminum alloy includes not greater than 0.11 wt. % Zr. In another embodiment, a 2xxx aluminum alloy includes not greater than 0.10 wt. % Zr. In yet another embodiment, a 2xxx aluminum alloy includes not greater than 0.09 wt. % Zr. In another embodiment, a 2xxx aluminum alloy includes not greater than 0.08 wt. % Zr.

[0013] As noted above, a 2xxx aluminum alloy may include up to 0.30 wt. % Fe In one embodiment, a 2xxx aluminum alloy includes at least 0.01 wt. % Fe. In another embodiment, a 2xxx aluminum alloy includes at least 0.02 wt. % Fe. In one embodiment, a 2xxx aluminum alloy includes not greater than 0.25 wt. % Fe. In another embodiment, a 2xxx aluminum alloy includes not greater than 0.20 wt. % Fe. In yet another embodiment, a 2xxx aluminum alloy includes not greater than 0.15 wt. % Fe. In another embodiment, a 2xxx aluminum alloy includes not greater than 0.10 wt. % Fe. in yet another embodiment, a 2xxx aluminum alloy includes not greater than 0.08 wt. % Fe. In another embodiment, a 2xxx aluminum alloy includes not greater than 0.06 wt.
% Fe. In yet another embodiment, a 2xxx aluminum alloy includes not greater than 0.04 wt. %
Fe.

[0014] As noted above, a 2xxx aluminum alloy may include up to 0.20 wt. % Si. In one embodiment, a 2xxx aluminum alloy includes at least 0.01 wt. % Si. In another embodiment, a 2xxx aluminum alloy includes at least 0.02 wt. % Si. In one embodiment, a 2xxx aluminum alloy includes not greater than 0.15 wt. % Si. In another embodiment, a 2xxx aluminum alloy includes not greater than 0.10 wt. % Si. In yet another embodiment, a 2xxx aluminum alloy includes not greater than 0.07 wt. % Si. In another embodiment, a 2xxx aluminum alloy includes not greater than 0.05 wt. % Si. In yet another embodiment, a 2xxx aluminum alloy includes not greater than 0.03 wt. % Si.

[0015] As noted above, a 2xxx aluminum alloy may include up to 0.25 wt. % Cr. In one embodiment, a 2xxx aluminum alloy includes not greater than 0.20 wt. % Cr. In another embodiment, a 2xxx aluminum alloy includes not greater than 0.15 wt. % Cr. In another embodiment, a 2xxx aluminum alloy includes not greater than 0.10 wt. % Cr. In yet another embodiment, a 2xxx aluminum alloy includes not greater than 0.05 wt. % Cr. In another embodiment, a 2xxx aluminum alloy includes not greater than 0.03 wt. % Cr. In yet another embodiment, a 2xxx aluminum alloy includes not greater than 0.01 wt. % Cr.

[0016] As noted above, a 2xxx aluminum alloy may include up to 0.25 wt. % V. In one embodiment, a 2xxx aluminum alloy includes not greater than 0.20 wt. % V. In another embodiment, a 2xxx aluminum alloy includes not greater than 0.15 wt. % V. In another embodiment, a 2xxx aluminum alloy includes not greater than 0.10 wt. % V. In yet another embodiment, a 2xxx aluminum alloy includes not greater than 0.05 wt. % V. In another embodiment, a 2xxx aluminum alloy includes not greater than 0.03 wt. % V. In yet another embodiment, a 2xxx aluminum alloy includes not greater than 0.01 wt. % V.

[0017] Some embodiments of useful alloys in accordance with the present disclosure are provided below (all values in weight percent).

Alloy Cu Mn Mg Zn Ag Ti A 4.5 - 5.5 0.20 - 0.60 0.20 - 0.60 0.10- 1.0 ..
0.05 -0.60 .. 0.08 -0.20 4.6 - 5.4 0.20 - 0.55 0.25 - 0.55 0.20- 0.80 0.10 - 0.55 0.08- 0.18 4.7- 5.3 0.25 -0.50 0.30 - 0.55 0.30 - 0.70 0.15 -0.50 0.08 -0.16 4.8- 5.2 0.25 -0.45 0.35 -0.55 0.30 - 0.60 0.20 - 0.45 0.08 -0.15 4.8- 5.1 0.25 -0.40 0.35 -0.50 0.40 -0.60 0.25 -0.40 0.08 - 0.14 4.8 - 5.0 0.30 - 0.40 0.40 - 0.50 0.40- 0.60 0.30 - 0.40 0.08 -0.13 Alloy Zr Fe Si Cr V Balance (cont.) A <0.25 <0.30 <0.25 <0.25 <0.25 Aluminum, 0.05-0.18 0.01 -0.25 0.01 -0.25 <0.15 <0.15 incidental 0.05-0.16 0.01 -0.20 0.01 -0.20 <0.10 <0.10 elements 0.06-0.14 0.01 -0.15 0.01 -0.15 < 0.05 < 0.05 and 0.07-0.13 0.02 - 0.10 0.02 - 0.10 < 0.03 < 0.03 impurities.
0.08-0.12 0.02 - 0.08 0.02 - 0.07 < 0.03 < 0.03

[0018] As noted above, in one approach, the 2xxx aluminum alloy is a 2039 aluminum alloy modified to include 0.08 to 0.20 wt. % Ti, such as any of the titanium limits/ranges described above. Per the Aluminum Association Teal Sheets (2015), a 2039 aluminum alloy comprises 4.5 to 5.5 wt. % Cu, 0.20 to 0.50 wt. % Mn, 0.40 to 0.8 wt. % Mg, 0.05 to 0.50 wt.
% Ag, 0.10 to 0.25 wt. % Zr, up to 0.20 wt. % Si, up to 0.30 wt. % Fe, up to 0.15 wt. % Ti, the balance being aluminum, incidental elements and impurities, wherein the 2xxx aluminum alloy includes not greater than 0.15 wt. %, in total, of the impurities, and wherein the 2xxx aluminum alloy includes not greater than 0.05 wt. % of each of the impurities.

[0019] As noted above, in one approach, the 2xxx aluminum alloy is a 2139 aluminum alloy modified to include 0.08 to 0.20 wt. % Ti, such as any of the titanium limits/ranges described above. Per the Aluminum Association Teal Sheets (2015), a 2139 aluminum alloy comprises 4.5 to 5.5 wt. % Cu, 0.20 to 0.6 wt. % Mn, 0.20 to 0.8 wt. % Mg, 0.15 to 0.60 wt.
% Ag, up to 0.10 wt. % Si, up to 0.15 wt. % Fe, up to 0.05 wt. % Cr, up to 0.25 wt. % Zn, up to 0.15 wt. % Ti, up to 0.05 wt. % V, the balance being aluminum, incidental elements and impurities, wherein the 2xxx aluminum alloy includes not greater than 0.15 wt. %, in total, of the impurities, and wherein the 2xxx aluminum alloy includes not greater than 0.05 wt. % of each of the impurities.

[0020] In one embodiment, a 2039 aluminum alloy or 2139 aluminum alloy is modified to include from 0.08 to 0.20 wt. % Ti, such as any of the titanium limits/ranges described above ("a modified 2039/2139 aluminum alloy"), and is further modified to include zinc (Zn). In one embodiment, a modified 2039/2139 aluminum alloy includes from 0.08 to 0.20 wt.
% Ti and includes from 0.10 to 1.0 wt. % Zn. In one embodiment, a modified 2039/2139 aluminum alloy includes at least 0.20 wt. % Zn. In another embodiment, a modified 2039/2139 aluminum alloy includes at least 0.30 wt. % Zn. In another embodiment, a modified 2039/2139 aluminum alloy includes at least 0.40 wt. % Zn. In another embodiment, a modified 2039/2139 aluminum alloy includes at least 0.50 wt. % Zn. In one embodiment, a modified 2039/2139 aluminum alloy includes not greater than 0.90 wt. % Zn. In another embodiment, a modified 2039/2139 aluminum alloy includes not greater than 0.80 wt. % Zn. In another embodiment, a modified 2039/2139 aluminum alloy includes not greater than 0.70 wt. % Zn. In another embodiment, a modified 2039/2139 aluminum alloy includes not greater than 0.60 wt. % Zn.

[0021] In one embodiment, a 2039/2139 aluminum alloy is modified to include from 0.08 to 0.20 wt. % Ti, such as any of the titanium limits/ranges described above ("a modified 2139 aluminum alloy"), and is further modified to include appropriate amounts of zirconium. (2039, as specified by the Aluminum Association Teal Sheets, includes 0.10 - 0.25 wt. %
Zr, and 2139, as specified by the Aluminum Association Teal Sheets, includes zirconium as an impurity only.) The combination of both (a) elevated levels of titanium, and (b) use of zirconium may facilitate the realization of improved 2039/2139 aluminum alloy products having an improved combination of at least two of strength, elongation, fracture toughness and corrosion resistance (e.g., stress corrosion cracking resistance), among others. In one embodiment, a modified aluminum alloy includes from 0.05 to 0.20 wt. % Zr. In one embodiment, a modified 2039/2139 aluminum alloy includes at least 0.06 wt. % Zr. In another embodiment, a modified 2039/2139 aluminum alloy includes at least 0.07 wt. % Zr. In yet another embodiment, a modified 2039/2139 aluminum alloy includes at least 0.08 wt. % Zr. In one embodiment, a modified aluminum alloy includes not greater than 0.18 wt. % Zr. In another embodiment, a modified 2039/2139 aluminum alloy includes not greater than 0.16 wt. % Zr. In another embodiment, a modified 2039/2139 aluminum alloy includes not greater than 0.15 wt. % Zr. In yet another embodiment, a modified 2039/2139 aluminum alloy includes not greater than 0.14 wt. % Zr. In another embodiment, a modified 2039/2139 aluminum alloy includes not greater than 0.13 wt. %
Zr. In another embodiment, a modified 2039/2139 aluminum alloy includes not greater than 0.12 wt. % Zr. In another embodiment, a modified 2039/2139 aluminum alloy includes not greater than 0.11 wt. % Zr. In yet another embodiment, a modified 2039/2139 aluminum alloy includes not greater than 0.10 wt. % Zr. In another embodiment, a modified 2039/2139 aluminum alloy includes not greater than 0.09 wt. % Zr. In another embodiment, a modified 2039/2139 aluminum alloy includes not greater than 0.08 wt. % Zr. In one embodiment, a modified aluminum alloy includes from 0.05 wt. % to 0.15 wt. % Zr. In another embodiment, a modified 2039/2139 aluminum alloy includes from 0.07 wt. % to 0.14 wt. % Zr. In another embodiment, a modified 2039/2139 aluminum alloy includes from 0.08 wt. % to 0.13 wt. % Zr.
The amount of zirconium present in the 2xxx aluminum alloys should be limited such that large primary particles do not form in the alloy.

[0022] In one embodiment, a 2139 aluminum alloy is modified to include from 0.08 to 0.20 wt. % Ti, such as any of the titanium limits/ranges described above ("a modified 2139 aluminum alloy"), and is further modified to include zirconium, such as any of the zirconium limits/ranges described above, and is further modified to include zinc, such as any of the zinc limits/ranges described above.

[0023] As noted above, the alloys generally include the stated alloying ingredients, the balance being aluminum, optional incidental elements, and impurities. As used herein, "incidental elements" means those elements or materials, other than the above listed elements, that may optionally be added to the alloy to assist in the production of the alloy.
Examples of incidental elements include casting aids, such as grain refiners and deoxidizers.
Optional incidental elements may be included in the alloy in a cumulative amount of up to 1.0 wt. %. As one non-limiting example, one or more incidental elements may be added to the alloy during casting to reduce or restrict (and in some instances eliminate) ingot cracking due to, for example, oxide fold, pit and oxide patches. These types of incidental elements are generally referred to herein as deoxidizers.
Examples of some deoxidizers include Ca, Sr, and Be. When calcium (Ca) is included in the alloy, it is generally present in an amount of up to 0.05 wt. %, or up to 0.03 wt. %
In some embodiments, Ca is included in the alloy in an amount of 0.001-0.03 wt. % or 0.05 wt. %, such as 0.001-0.008 wt. % (or 10 to 80 ppm). Strontium (Sr) may be included in the alloy as a substitute for Ca (in whole or in part), and thus may be included in the alloy in the same or similar amounts as Ca Traditionally, beryllium (Be) additions have helped to reduce the tendency of ingot cracking, though for environmental, health and safety reasons, some embodiments of the alloy are substantially Be-free. When Be is included in the alloy, it is generally present in an amount of up to 20 ppm. Incidental elements may be present in minor amounts, or may be present in significant amounts, and may add desirable or other characteristics on their own without departing from the alloy described herein, so long as the alloy retains the desirable characteristics described herein. It is to be understood, however, that the scope of this disclosure should not/cannot be avoided through the mere addition of an element or elements in quantities that would not otherwise impact on the combinations of properties desired and attained herein.

[0024] The 2xxx aluminum alloys generally contain low amounts of impurities. In one embodiment, a 2xxx aluminum alloy includes not greater than 0.15 wt. %, in total, of the impurities, and wherein the 2xxx aluminum alloy includes not greater than 0.05 wt. % of each of the impurities. In another embodiment, a 2xxx aluminum alloy includes not greater than 0.10 wt.
%, in total, of the impurities, and wherein the 2xxx aluminum alloy includes not greater than 0.03 wt. % of each of the impurities.
ii. Product Forms

[0025] The new alloys may be useful in a variety of product forms, including ingot or billet, wrought product forms (plate, forgings and extrusions), shape castings, additively manufactured products, and powder metallurgy products, for instance.

[0026] In one embodiment, a new 2xxx aluminum alloy is in the form of a thick wrought product. Thick wrought aluminum alloy products are those wrought products having a cross-sectional thickness of at least 12.7 mm. The wrought products may be rolled products, forged products or extruded products. In one embodiment, a thick wrought aluminum alloy product has a thickness of at least 25 mm. In another embodiment, a thick wrought aluminum alloy product has a thickness of at least 38 mm. In yet another embodiment, a thick wrought aluminum alloy product has a thickness of at least 50 mm. In another embodiment, a thick wrought aluminum alloy product has a thickness of at least 76 mm. In yet another embodiment, a thick wrought aluminum alloy product has a thickness of at least 102 mm, or higher.

[0027] The improved properties described herein may be achieved with thick wrought products having a thickness of up to 305 mm In one embodiment, a thick wrought aluminum alloy product has a thickness of not greater than 254 mm. In another embodiment, a thick wrought aluminum alloy product has a thickness of not greater than 203 mm. In yet another embodiment, a thick wrought aluminum alloy product has a thickness of not greater than 17S
mm In another embodiment, a thick wrought aluminum alloy product has a thickness of not greater than 152 mm.
As used in this paragraph, thickness refers to the minimum thickness of the product, realizing that some portions of the product may realize slightly larger thicknesses than the minimum stated.

[0028] In another approach, a new 2xxx aluminum alloy is a thin wrought product having a thickness of less than 12.7 mm. Thin wrought products have a thickness of less than 12.7 mm. In one embodiment, a thin wrought product has a thickness of from 0.5 mm to 12.6 mm. In another embodiment, a thin wrought product has a thickness of from 1.0 mm to 12.6 mm.
In yet another embodiment, a thin wrought product has a thickness of from 2.0 mm to 12.6 mm.
In another embodiment, a thin wrought product has a thickness of from 3.0 mm to 12.6 mm.
In yet another embodiment, a thin wrought product has a thickness of from 4.0 mm to 12.6 mm.
In another embodiment, a thin wrought product has a thickness of from 5.0 mm to 12.6 mm.
In yet another embodiment, a thin wrought product has a thickness of from 6.0 mm to 12.6 mm.
In another embodiment, a thin wrought product has a thickness of from 7.0 mm to 12.6 mm.
In yet another embodiment, a thin wrought product has a thickness of from 8.0 mm to 12.6 mm.
iii. Methods ofMaking

[0029] As noted above, new methods of producing 2xxx aluminum alloys are disclosed. In one approach, a method comprises artificially aging a 2xxx aluminum alloy in at least two-steps ("two-step artificial aging"). As shown below, 2xxx aluminum alloys aged using a first step aging practice of 350 F for 24 hours and a second step aging practice of 270 F for 24 hours realized an unexpected combination of at least two of strength, ductility, fracture toughness, and corrosion resistance. As appreciated by those skilled in the art, aging temperatures and/or times may be adjusted based on well-known aluminum alloy aging principles and/or formulas.
Thus, those skilled in the art could increase the aging temperature but decrease the aging time, or vice-versa, or only slightly change only one of these parameters and still achieve the same result as aging at 350 F for 24 hours and then at 270 F for 24 hours. Accordingly, some embodiments disclosed herein are directed to first artificially aging at 350 F for 24 hours, or a substantially equivalent artificial aging temperature and duration, and second artificially aging at 270 F for 24 hours, or a substantially equivalent artificial aging temperature and duration. The amount of artificial aging practices that could achieve the same result as this specific practice is numerous, and therefore all such substitute aging practices are not listed herein, even though they are within the scope of the present invention. The use of the phrase "or a substantially equivalent artificial aging temperature and duration" or the phrase "or a substantially equivalent practice" is used to capture all such substitute aging practices. As may be appreciated, these substitute artificial aging steps can occur in one or multiple steps, and at one or multiple temperatures. That is, multiple sub-steps may be used to accomplish the first aging step and/or the second aging step, which sub-steps may include age integration. In one embodiment, the artificial aging practice consists only of two-steps, i.e., no additional artificial aging steps are completed after the second artificial aging step.

[0030] In one approach, an artificial aging practice comprises (a) first aging a 2xxx aluminum alloy at a first temperature of from 300 F to 450 F and for a first aging time of from 4 to 120 hours, and (b) second aging the 2xxx aluminum alloy at a second temperature for a second aging time of from 30 minutes to 120 hours, wherein the second temperature is from 20 F to 150 F lower than the first temperature. In one embodiment, at least partially due to the first aging and second aging steps, the 2xxx aluminum alloy is (i) LT stress corrosion cracking resistant (defined below), (ii) ST stress corrosion cracking resistant (defined below), or (iii) both LT
stress corrosion cracking resistant and ST stress corrosion cracking resistant.

[0031] As noted above, the first step of the artificial aging process generally comprises aging the 2xxx aluminum alloy at a first temperature for a first period of time, such as from 300 F to 450 F and for a first aging time of from 4 to 120 hours. In one embodiment, the first temperature is at least 310 F. In another embodiment, the first temperature is at least 320 F. In yet another embodiment, the first temperature is at least 330 F. In another embodiment, the first temperature is at least 340 F. In yet another embodiment, the first temperature is at least 350 F. In one embodiment, the first temperature is not greater than 440 F. In another embodiment, the first temperature is not greater than 430 F. In yet another embodiment, the first temperature is not greater than 420 F. In another embodiment, the first temperature is not greater than 410 F. In yet another embodiment, the first temperature is not greater than 400 F. In another embodiment, the first temperature is not greater than 390 F. In yet another embodiment, the first temperature is not greater than 380 F. In another embodiment, the first temperature is not greater than 370 F. In one embodiment, the first period of time of the first artificial aging step (i.e., the first aging time) is at least 8 hours In another embodiment, the first aging time is at least 12 hours In yet another embodiment, the first aging time is at least 16 hours In another embodiment, the first aging time is at least 20 hours. In yet another embodiment, the first aging time is at least 24 hours. In one embodiment, the first aging time is not greater than 96 hours. In another embodiment, the first aging time is not greater than 72 hours. In yet another embodiment, the first aging time is not greater than 48 hours. In another embodiment, the first aging time is not greater than 40 hours. In yet another embodiment, the first aging time is not greater than 36 hours. In another embodiment, the first aging time is not greater than 32 hours. In yet another embodiment, the first aging time is not greater than 28 hours.

[0032] In one embodiment, the first temperature is from 330 F to 370 F and the first aging time is from 12 to 36 hours.

[0033] In one approach, the amount of time of the first step is determined according to an equivalent time at 350 F. In this approach, the first step time (ti'al) is in accordance with the below formula:
t350 F eq. actual 156000 1 1 1 = t1 * exp 8.314 * 5 "F 5 g wherein (a) T;F is the actual temperature of the first step in Fahrenheit, wherein T;Fis from 300 to 450 F, (b) tactual is the actual amount of time at the first temperature, wherein ti'ctuth is from 10 to 120 hours, and (c) ti30 F eq. is the equivalent amount of time at a first step temperature of 350 F.

[0034] In one approach, t135" eq- is from 20 to 30 hours. In one embodiment, t13501. eq- is at least 20.5 hours. In another embodiment, t13500Feq- is at least 21 hours. In yet another embodiment, t135wF eq- is at least 21.5 hours. In another embodiment, t13'"'q- is at least 22 hours. In yet another embodiment, t1350Feq. is at least 22.5 hours. In another embodiment, t1350T eq-is at least 23 hours.
In yet another embodiment, ti35 T eq. is at least 23.5 hours. In another embodiment, ti350T eq. is at least 24 hours. In one embodiment, t13500F eq- is not greater than 29 hours.
In another embodiment, ti35 F eq- is not greater than 28 hours. In yet another embodiment, ti35 'F
eq- is not greater than 27 hours. In another embodiment, t1350 F' eq. is not greater than 26 hours. In yet another embodiment, ti35wF eq- is not greater than 25 hours. In another embodiment, t135" eq- is not greater than 24.5 hours. In yet another embodiment, t1350 Fcq. is not greater than 24 hours. In one embodiment, t1350 F
'I- is from 20.5 to 24 hours. In another embodiment, t135" eq- is from 21 to 24 hours. In another embodiment, t1350 ' eq. is from 21.5 to 24 hours. In yet another embodiment, t1350 F eq- is from 22 to 24 hours. In another embodiment, t135" eq is from 22.5 to 24 hours.

[0035] As noted above, the second step of the artificial aging process generally comprises aging the 2xxx aluminum alloy at a second temperature for a second period of time, such as at a temperature that is at least 20 F lower than, but not more than 150 F lower than, the first aging temperature and for a period of time of from 30 minutes to 120 hours. For instance, if the first aging temperature is 350 F, the second aging temperature would be no higher than 330 F (i.e., 20 F lower than the first temperature), but the second aging temperature would be at least 200 F
(i.e., not more than 150 F lower than the first aging temperature).

[0036] In one embodiment, the second temperature is at least at least 30 F lower than the first temperature In another embodiment, the second temperature is at least 40 F
lower than the first temperature. In yet another embodiment, the second temperature is at least 50 F lower than the first temperature. In another embodiment, the second temperature is at least 60 F lower than the first temperature. In yet another embodiment, the second temperature is at least 70 F lower than the first temperature. In another embodiment, the second temperature is at least 80 F lower than the first temperature. In one embodiment, the second temperature is not greater than 140 F lower than the first temperature. In another embodiment, the second temperature is not greater than 130 F lower than the first temperature. In yet another embodiment, the second temperature is not greater than 120 F lower than the first temperature. In another embodiment, the second temperature is not greater than 110 F lower than the first temperature. In yet another embodiment, the second temperature is not greater than 100 F lower than the first temperature.

[0037] In one embodiment, the second period of time of the second artificial aging step (i.e., the second aging time) is at least 8 hours. In another embodiment, the second aging time is at least 12 hours. In yet another embodiment, the second aging time is at least 16 hours. In another embodiment, the second aging time is at least 20 hours. In yet another embodiment, the second aging time is at least 24 hours. In one embodiment, the second aging time is not greater than 96 hours. In another embodiment, the second aging time is not greater than 72 hours. In yet another embodiment, the second aging time is not greater than 48 hours. In another embodiment, the second aging time is not greater than 40 hours. In yet another embodiment, the second aging time is not greater than 36 hours In another embodiment, the second aging time is not greater than 32 hours. In yet another embodiment, the second aging time is not greater than 28 hours.

[0038] In one embodiment, the second aging temperature is from 250 to 290 F and the second aging time is from 12 to 36 hours.

[0039] The two-step aging practices described herein may be conducted in a conventional fashion, such as by the use of temperature controlled furnaces. In one embodiment, after the first aging step, the 2xxx aluminum alloy is allowed to cool to room temperature (e.g., by turning off the furnace and/or removing the material from the furnace, after which the material is allowed to cool to room temperature.) The material may then be reheated from room temperature to complete the second aging step, e.g., reheated to the second temperature of the second aging step.

[0040] In another embodiment, the material is cooled from the first temperature to the second temperature. In this embodiment, the furnace set-point may be changed and/or the furnace may be turned off and allowed to cool to the second temperature, after which the second aging step is initiated (e.g., due to achievement of the second temperature). In this embodiment, cooling below the second step is not completed.

[0041] Variations of the above may also be practiced where the material is allowed to cool somewhat below the second temperature, but not all the way to room temperature, and such variations are within the scope of the present disclosure.

[0042] In one embodiment, a method comprises preparing a 2xxx aluminum alloy for artificial aging. The preparing step may include, for instance, casting a 2xxx aluminum alloy into an ingot or billet (e.g., via direct chill (DC) casting). After conventional scalping, lathing or peeling (if needed) and homogenization, which homogenization may be completed before or after scalping, the ingots/billets may be further processed by hot working the product. The product may then be optionally cold worked, solution heat treated, quenched, and final cold worked (e.g., by stretching or compression of from 0.5% to 15%). After the final cold working step, the product may be artificially aged, as provided above. Thus, in some embodiments, the products may be produced in a T3 or T8 temper. In other embodiments, other T tempers may be used (e.g., any of a Ti, T2, T4, T5, T6, T7 or T9 temper). T tempers are defined in ANSI H35.1 (2009).

[0043] In some embodiments, forming operations may be completed concomitant to artificial aging, for instance, by forming the alloy into a predetermined shaped product before artificial aging, during artificial aging, after artificial aging, and combinations thereof. In such cases, the accumulated amount of cold work completed after solution heat treatment may be higher, such as from 10-15% cold work, or more.

[0044] As noted above, as part of processing to a T temper, the wrought product may be solution heat treated and then optionally cold worked, such as by stretching.
In one approach, a wrought product is processed to a T temper and part of that processing includes stretching by from 0.5 to 10% after solution heat treatment. As shown by the below examples, in some instances, appropriate amounts of stretch may facilitate realization of an improved combination of properties, such as an improved combination of two or more of strength, ductility, fracture toughness and corrosion resistance (e.g., stress corrosion cracking resistance) properties.
In one embodiment, a wrought product is stretched at least 1% after solution heat treatment. In another embodiment, a wrought product is stretched at least 1.5% after solution heat treatment. In yet another embodiment, a wrought product is stretched at least 2% after solution heat treatment. In one embodiment, a wrought product is stretched not greater than 9% after solution heat treatment. In another embodiment, a wrought product is stretched not greater than 8% after solution heat treatment.
iv. Properties

[0045] The new 2xxx aluminum alloys generally realize an improved combination of at least two of strength, elongation, fracture toughness, and corrosion resistance (e.g., stress corrosion cracking resistance).

[0046] For purposes of this patent application, the "T8 temper" is per ANSI H35.1(2009), and includes all artificial aging conditions, including underaged, peak or near peak aged, and overaged aging conditions.

[0047] In one embodiment, a new 2xxx aluminum alloy has a thickness of at least 12.7 mm and realizes a tensile yield strength (L) of at least 390 MPa in the T8 temper. In another embodiment, a new 2xxx aluminum alloy has a thickness of at least 12.7 mm and realizes a tensile yield strength (L) of at least 400 MPa in the T8 temper. In yet another embodiment, a new 2xxx aluminum alloy has a thickness of at least 12.7 mm and realizes a tensile yield strength (L) of at least 410 MPa in the T8 temper. In another embodiment, a new 2xxx aluminum alloy has a thickness of at least 12.7 mm and realizes a tensile yield strength (L) of at least 420 MPa in the T8 temper. In yet another embodiment, a new 2xxx aluminum alloy has a thickness of at least 12.7 mm and realizes a tensile yield strength (L) of at least 430 MPa in the T8 temper. In another embodiment, a new 2xxx aluminum alloy has a thickness of at least 12.7 mm and realizes a tensile yield strength (L) of at least 440 MPa in the T8 temper. In yet another embodiment, a new 2xxx aluminum alloy has a thickness of at least 12.7 mm and realizes a tensile yield strength (L) of at least 450 MPa in the T8 temper. In another embodiment, a new 2xxx aluminum alloy has a thickness of at least 12.7 mm and realizes a tensile yield strength (L) of at least 460 MPa, or more, in the T8 temper. The above strength properties may be realized in products having a thickness of at least 25 mm, or at least 38 mm, or at least 50 mm, or at least 76 mm, or at least 108 mm, or higher. The above strength properties may be realized in thin wrought products having a thickness of 0.5 to 12.6 mm.

[0048] In one embodiment, a new 2xxx aluminum alloy has a thickness of at least 12.7 mm and realizes a plane-strain (Kic) fracture toughness (L-T) of at least 30 MPa-sqrt-m in the T8 temper. In another embodiment, a new 2xxx aluminum alloy has a thickness of at least 12.7 mm and realizes a plane-strain (Kw) fracture toughness (L-T) of at least 31 MPa-sqrt-m in the T8 temper. In yet another embodiment, a new 2xxx aluminum alloy has a thickness of at least 12.7 mm and realizes a plane-strain (Kic) fracture toughness (L-T) of at least 32 MPa-sqrt-m in the T8 temper. In another embodiment, a new 2xxx aluminum alloy has a thickness of at least 12.7 mm and realizes a plane-strain (Kic) fracture toughness (L-T) of at least 33 MPa-sqrt-m in the T8 temper. In yet another embodiment, a new 2xxx aluminum alloy has a thickness of at least 12.7 mm and realizes a plane-strain (KT) fracture toughness (L-T) of at least 34 MPa-sqrt-m in the T8 temper. In another embodiment, a new 2xxx aluminum alloy has a thickness of at least 12.7 mm and realizes a plane-strain (Kw) fracture toughness (L-T) of at least 35 MPa-sqrt-m in the T8 temper. In yet another embodiment, a new 2xxx aluminum alloy has a thickness of at least 12.7 mm and realizes a plane-strain (Kic) fracture toughness (L-T) of at least 36 MPa-sqrt-m in the T8 temper. In another embodiment, a new 2xxx aluminum alloy has a thickness of at least 12.7 mm and realizes a plane-strain (Kic) fracture toughness (L-T) of at least 37 MPa-sqrt-m in the T8 temper. In yet another embodiment, a new 2xxx aluminum alloy has a thickness of at least 12.7 mm and realizes a plane-strain (Kic) fracture toughness (L-T) of at least 38 MPa-sqrt-m in the T8 temper. In another embodiment, a new 2xxx aluminum alloy has a thickness of at least 12.7 mm and realizes a plane-strain (Kw) fracture toughness (L-T) of at least 39 MPa-sqrt-m in the T8 temper. In yet another embodiment, a new 2xxx aluminum alloy has a thickness of at least 12.7 mm and realizes a plane-strain (KT) fracture toughness (L-T) of at least 40 MPa-sqrt-m in the T8 temper. In another embodiment, a new 2xxx aluminum alloy has a thickness of at least 12.7 mm and realizes a plane-strain (Kic) fracture toughness (L-T) of at least 41 MPa-sqrt-m in the T8 temper. In yet another embodiment, a new 2xxx aluminum alloy has a thickness of at least 12.7 mm and realizes a plane-strain (Kic) fracture toughness (L-T) of at least 42 MPa-sqrt-m in the T8 temper. In another embodiment, a new 2xxx aluminum alloy has a thickness of at least 12.7 mm and realizes a plane-strain (Kic) fracture toughness (L-T) of at least 43 MPa-sqrt-m in the T8 temper. In yet another embodiment, a new 2xxx aluminum alloy has a thickness of at least 12.7 mm and realizes a plane-strain (Kic) fracture toughness (L-T) of at least 44 MPa-sqrt-m in the T8 temper. In another embodiment, a new 2xxx aluminum alloy has a thickness of at least 12.7 mm and realizes a plane-strain (Kic) fracture toughness (L-T) of at least 45 MPa-sqrt-m in the T8 temper. In yet another embodiment, a new 2xxx aluminum alloy has a thickness of at least 12.7 mm and realizes a plane-strain (Kic) fracture toughness (L-T) of at least 46 MPa-sqrt-m in the T8 temper. In another embodiment, a new 2xxx aluminum alloy has a thickness of at least 12.7 mm and realizes a plane-strain (Kic) fracture toughness (L-T) of at least 47 MPa-sqrt-m in the T8 temper. In yet another embodiment, a new 2xxx aluminum alloy has a thickness of at least 12.7 mm and realizes a plane-strain (Kr) fracture toughness (L-T) of at least 48 WiPa-sqrt-m in the T8 tcmper. In anothcr cmbodimcnt, a ncw 2xxx aluminum alloy has a thickness of at least 12.7 mm and realizes a plane-strain (Kw) fracture toughness (L-T) of at least 49 MPa-sqrt-m in the T8 temper. In yet another embodiment, a new 2xxx aluminum alloy has a thickness of at least 12.7 mm and realizes a plane-strain (KT) fracture toughness (L-T) of at least 50 MPa-sqrt-m, or more, in the T8 temper. The above fracture toughness properties may be realized in products having a thickness of at least 25 mm, or at least 38 mm, or at least 50 mm, or at least 76 mm, or at least 108 mm, or higher. The above fracture toughness properties may be realized in thin wrought products having a thickness of 0.5 to 12.6 min.

[0049] In one embodiment, a new 2xxx aluminum alloy has a thickness of at least 12.7 mm and realizes an elongation (L) of at least 6.0% in the T8 temper. In another embodiment, a new 2xxx aluminum alloy has a thickness of at least 12.7 mm and realizes an elongation (L) of at least 8.0% in the T8 temper. In yet another embodiment, a new 2xxx aluminum alloy has a thickness of at least 12.7 mm and realizes an elongation (L) of at least 10.0% in the T8 temper. In another embodiment, a new 2xxx aluminum alloy has a thickness of at least 12.7 mm and realizes an elongation (L) of at least 12.0% in the T8 temper. In yet another embodiment, a new 2xxx aluminum alloy has a thickness of at least 12.7 mm and realizes an elongation (L) of at least 14.0%
in the T8 temper. In another embodiment, a new 2xxx aluminum alloy has a thickness of at least 12.7 mm and realizes an elongation (L) of at least 16.0%, or more, in the T8 temper. The above elongation properties may be realized in products having a thickness of at least 25 mm, or at least 38 mm, or at least 50 mm, or at least 76 mm, or at least 108 mm, or higher.
The above elongation properties may be realized in thin wrought products having a thickness of 0.5 to 12.6 mm.

[0050] In one embodiment, a new 2xxx aluminum alloy has a thickness of at least 12.7 mm and realizes a tensile yield strength (LT) of at least 390 MPa in the T8 temper. In another embodiment, a new 2xxx aluminum alloy has a thickness of at least 12.7 mm and realizes a tensile yield strength (LT) of at least 400 MPa in the T8 temper. In yet another embodiment, a new 2xxx aluminum alloy has a thickness of at least 12.7 mm and realizes a tensile yield strength (LT) of at least 410 MPa in the T8 temper. In another embodiment, a new 2xxx aluminum alloy has a thickness of at least 12.7 mm and realizes a tensile yield strength (LT) of at least 420 MPa in the T8 temper. In yet another embodiment, a new 2xxx aluminum alloy has a thickness of at least 12.7 mm and realizes a tensile yield strength (LT) of at least 430 lVfPa in the T8 temper. In another embodiment, a new 2xxx aluminum alloy has a thickness of at least 12.7 mm and realizes a tensile yield strength (LT) of at least 440 MPa in the T8 temper. In yet another embodiment, a new 2xxx aluminum alloy has a thickness of at least 12.7 mm and realizes a tensile yield strength (LT) of at least 450 MPa in the T8 temper. In another embodiment, a new 2xxx aluminum alloy has a thickness of at least 12.7 mm and realizes a tensile yield strength (LT) of at least 460 MPa, or more, in the T8 temper. The above strength properties may be realized in products having a thickness of at least 25 mm, or at least 38 mm, or at least 50 mm, or at least 76 mm, or at least 108 mm, or higher. The above strength properties may be realized in thin wrought products having a thickness of 0.5 to 12.6 mm.

[0051] In one embodiment, a new 2xxx aluminum alloy has a thickness of at least 12.7 mm and realizes a plane-strain (Kw) fracture toughness (T-L) of at least 30 MPa-sqrt-m in the T8 temper. In another embodiment, a new 2xxx aluminum alloy has a thickness of at least 12.7 mm and realizes a plane-strain (Kic) fracture toughness (T-L) of at least 31 MPa-sqrt-m in the T8 temper. In yet another embodiment, a new 2xxx aluminum alloy has a thickness of at least 12.7 mm and realizes a plane-strain (Kic) fracture toughness (T-L) of at least 32 MPa-sqrt-m in the T8 temper. In another embodiment, a new 2xxx aluminum alloy has a thickness of at least 12.7 mm and realizes a plane-strain (Kw) fracture toughness (T-L) of at least 33 MPa-sqrt-m in the T8 temper. In yet another embodiment, a new 2xxx aluminum alloy has a thickness of at least 12.7 mm and realizes a plane-strain (Kic) fracture toughness (T-L) of at least 34 MPa-sqrt-m in the T8 temper. In another embodiment, a new 2xxx aluminum alloy has a thickness of at least 12.7 mm and realizes a plane-strain (Kic) fracture toughness (T-L) of at least 35 MPa-sqrt-m in the T8 temper. In yet another embodiment, a new 2xxx aluminum alloy has a thickness of at least 12.7 mm and realizes a plane-strain (Kw) fracture toughness (T-L) of at least 36 NiPa-sqrt-m in the T8 temper. In another embodiment, a new 2xxx aluminum alloy has a thickness of at least 12.7 mm and realizes a plane-strain (Kw) fracture toughness (T-L) of at least 37 MPa-sqrt-m in the T8 temper. In yet another embodiment, a new 2xxx aluminum alloy has a thickness of at least 12.7 mm and realizes a plane-strain (Kic) fracture toughness (T-L) of at least 38 NiPa-sqrt-m in the T8 temper. In another embodiment, a new 2xxx aluminum alloy has a thickness of at least 12.7 mm and realizes a plane-strain (Kw) fracture toughness (T-L) of at least 39 MPa-sqrt-m in the T8 temper. In yet another embodiment, a new 2xxx aluminum alloy has a thickness of at least 12.7 mm and realizes a plane-strain (Kic) fracture toughness (T-L) of at least 40 MPa-sqrt-m in the T8 temper. In another embodiment, a new 2xxx aluminum alloy has a thickness of at least 12.7 mm and realizes a plane-strain (Kw) fracture toughness (T-L) of at least 41 MPa-sqrt-m in the T8 temper. In yet another embodiment, a new 2xxx aluminum alloy has a thickness of at least 12.7 mm and realizes a plane-strain (Kic) fracture toughness (T-L) of at least 42 MPa-sqrt-m in the T8 temper. In another embodiment, a new 2xxx aluminum alloy has a thickness of at least 12.7 mm and realizes a plane-strain (Kic) fracture toughness (T-L) of at least 43 MPa-sqrt-m in the T8 temper. In yet another embodiment, a new 2xxx aluminum alloy has a thickness of at least 12.7 mm and realizes a plane-strain (Kic) fracture toughness (T-L) of at least 44 MPa-sqrt-m in the T8 temper. In another embodiment, a new 2xxx aluminum alloy has a thickness of at least 12.7 mm and realizes a plane-strain (Kw) fracture toughness (T-L) of at least 45 MPa-sqrt-m in the T8 temper. In yet another embodiment, a new 2xxx aluminum alloy has a thickness of at least 12.7 mm and realizes a plane-strain (Kfc) fracture toughness (T-L) of at least 46 I\SPa-sqrt-m in the T8 temper. In another embodiment, a new 2xxx aluminum alloy has a thickness of at least 12.7 mm and realizes a plane-strain (Kw) fracture toughness (T-L) of at least 47 MPa-sqrt-m in the T8 temper. In yet another embodiment, a new 2xxx aluminum alloy has a thickness of at least 12.7 mm and realizes a plane-strain (KT) fracture toughness (T-L) of at least 48 MPa-sqrt-m in the T8 temper. In another embodiment, a new 2xxx aluminum alloy has a thickness of at least 12.7 mm and realizes a plane-strain (Kic) fracture toughness (T-L) of at least 49 MPa-sqrt-m in the T8 temper. In yet another embodiment, a new 2xxx aluminum alloy has a thickness of at least 12.7 mm and realizes a plane-strain (Kic) fracture toughness (T-L) of at least 50 MPa-scirt-m, or more, in the T8 temper. The above fracture toughness properties may be realized in products having a thickness of at least 25 mm, or at least 38 mm, or at least 50 mm, or at least 76 mm, or at least 108 mm, or higher. The above fracture toughness properties may be realized in thin wrought products having a thickness of 0.5 to 12.6 mm.

[0052] In one embodiment, a new 2xxx aluminum alloy has a thickness of at least 12.7 mm and realizes an elongation (LT) of at least 6.0% in the T8 temper. In another embodiment, a new 2xxx aluminum alloy has a thickness of at least 12.7 mm and realizes an elongation (LT) of at least 8.0% in the T8 temper. In yet another embodiment, a new 2xxx aluminum alloy has a thickness of at least 12.7 mm and realizes an elongation (LT) of at least 10.0% in the T8 temper. In another embodiment, a new 2xxx aluminum alloy has a thickness of at least 12.7 mm and realizes an elongation (LT) of at least 12.0% in the T8 temper. In yet another embodiment, a new 2xxx aluminum alloy has a thickness of at least 12.7 mm and realizes an elongation (LT) of at least 14.0% in the T8 temper. In another embodiment, a new 2xxx aluminum alloy has a thickness of at least 12.7 mm and realizes an elongation (LT) of at least 16.0%, or more, in the T8 temper. The above elongation properties may be realized in products having a thickness of at least 25 mm, or at least 38 mm, or at least 50 mm, or at least 76 mm, or at least 108 mm, or higher. The above elongation properties may be realized in thin wrought products having a thickness of 0.5 to 12.6 mm.

[0053] In one embodiment, a new 2xxx aluminum alloy has a thickness of at least 12.7 mm and realizes a tensile yield strength (ST) of at least 350 MPa in the T8 temper. In another embodiment, a new 2xxx aluminum alloy has a thickness of at least 12.7 mm and realizes a tensile yield strength (ST) of at least 360 MPa in the T8 temper. In yet another embodiment, a new 2xxx aluminum alloy has a thickness of at least 12.7 mm and realizes a tensile yield strength (ST) of at least 370 MPa in the T8 temper. In another embodiment, a new 2xxx aluminum alloy has a thickness of at least 12.7 mm and realizes a tensile yield strength (ST) of at least 380 MPa in the T8 temper. In yet another embodiment, a new 2xxx aluminum alloy has a thickness of at least 12.7 mm and realizes a tensile yield strength (ST) of at least 390 MPa in the T8 temper. In another embodiment, a new 2xxx aluminum alloy has a thickness of at least 12.7 mm and realizes a tensile yield strength (ST) of at least 400 MPa in the T8 temper. In yet another embodiment, a new 2xxx aluminum alloy has a thickness of at least 12.7 mm and realizes a tensile yield strength (ST) of at least 410 MPa in the T8 temper. In another embodiment, a new 2xxx aluminum alloy has a thickness of at least 12.7 mm and realizes a tensile yield strength (ST) of at least 420 MPa, or more, in the T8 temper. The above strength properties may be realized in products having a thickness of at least 25 mm, or at least 38 mm, or at least 50 mm, or at least 76 mm, or at least 108 mm, or higher. The above strength properties may be realized in thin wrought products having a thickness of 7.0 to 12.6 mm.

[0054] In one embodiment, a new 2xxx aluminum alloy has a thickness of at least 12.7 mm and realizes a plane-strain (Kic) fracture toughness (S-L) of at least 30 MPa-sqrt-m in the T8 temper. In another embodiment, a new 2xxx aluminum alloy has a thickness of at least 12.7 mm and realizes a plane-strain (Kw) fracture toughness (S-L) of at least 31 MPa-sqrt-m in the T8 temper. In yet another embodiment, a new 2xxx aluminum alloy has a thickness of at least 12.7 mm and realizes a plane-strain (Km.) fracture toughness (S-L) of at least 32 MPa-sqrt-m in the T8 temper. In another embodiment, a new 2xxx aluminum alloy has a thickness of at least 12.7 mm and realizes a plane-strain (Kic) fracture toughness (S-L) of at least 33 MPa-sqrt-m in the T8 temper. In yet another embodiment, a new 2xxx aluminum alloy has a thickness of at least 12.7 mm and realizes a plane-strain (KT) fracture toughness (S-L) of at least 34 MPa-sqrt-m in the T8 temper. In another embodiment, a new 2xxx aluminum alloy has a thickness of at least 12.7 mm and realizes a plane-strain (Kw) fracture toughness (S-L) of at least 35 MPa-sqrt-m in the T8 temper. In yet another embodiment, a new 2xxx aluminum alloy has a thickness of at least 12.7 mm and realizes a plane-strain (Kic) fracture toughness (S-L) of at least 36 MPa-sqrt-m in the T8 temper. In another embodiment, a new 2xxx aluminum alloy has a thickness of at least 12.7 mm and realizes a plane-strain (Kic) fracture toughness (S-L) of at least 37 MPa-sqrt-m in the T8 temper. In yet another embodiment, a new 2xxx aluminum alloy has a thickness of at least 12.7 mm and realizes a plane-strain (Kic) fracture toughness (S-L) of at least 38 MPa-sqrt-m in the T8 temper. In another embodiment, a new 2xxx aluminum alloy has a thickness of at least 12.7 mm and realizes a plane-strain (Kw) fracture toughness (S-L) of at least 39 MPa-sqrt-m in the T8 temper. In yet another embodiment, a new 2xxx aluminum alloy has a thickness of at least 12.7 mm and realizes a plane-strain (Km) fracture toughness (S-L) of at least 40 MPa-sqrt-m in the T8 temper. In another embodiment, a new 2xxx aluminum alloy has a thickness of at least 12.7 mm and realizes a plane-strain (Kic) fracture toughness (S-L) of at least 41 MPa-sqrt-m in the T8 temper. In yet another embodiment, a new 2xxx aluminum alloy has a thickness of at least 12.7 mm and realizes a plane-strain (Kic) fracture toughness (S-L) of at least 42 MPa-sqrt-m in the T8 temper. In another embodiment, a new 2xxx aluminum alloy has a thickness of at least 12.7 mm and realizes a plane-strain (Kic) fracture toughness (S-L) of at least 43 MPa-sqrt-m in the T8 temper. In yet another embodiment, a new 2xxx aluminum alloy has a thickness of at least 12.7 mm and realizes a plane-strain (Kic) fracture toughness (S-L) of at least 44 MPa-sqrt-m in the T8 temper. In another embodiment, a new 2xxx aluminum alloy has a thickness of at least 12.7 mm and realizes a plane-strain (Kic) fracture toughness (S-L) of at least 45 MPa-sqrt-m in the T8 temper. In yet another embodiment, a new 2xxx aluminum alloy has a thickness of at least 12.7 mm and realizes a plane-strain (Kic) fracture toughness (S-L) of at least 46 MPa-sqrt-m in the T8 temper. In another embodiment, a new 2xxx aluminum alloy has a thickness of at least 12.7 mm and realizes a plane-strain (Kw) fracture toughness (S-L) of at least 47 MPa-sqrt-m in the T8 temper. In yet another embodiment, a new 2xxx aluminum alloy has a thickness of at least 12.7 mm and realizes a plane-strain (Kr) fracture toughness (S-L) of at least 48 MPa-sqrt-m in the T8 temper. In another embodiment, a new 2xxx aluminum alloy has a thickness of at least 12.7 mm and realizes a plane-strain (Kw) fracture toughness (S-L) of at least 49 MPa-sqrt-m in the T8 temper. In yet another embodiment, a new 2xxx aluminum alloy has a thickness of at least 12.7 mm and realizes a plane-strain (KT) fracture toughness (S-L) of at least 50 MPa-sqrt-m, or more, in the T8 temper. The above fracture toughness properties may be realized in products having a thickness of at least 25 mm, or at least 38 mm, or at least 50 mm, or at least 76 mm, or at least 108 mm, or higher. The above fracture toughness properties may be realized in thin wrought products haying a thickness of 7.0 to 12.6 min.

[0055] In one embodiment, a new 2xxx aluminum alloy has a thickness of at least 12.7 mm and realizes an elongation (ST) of at least 3.0% in the T8 temper. In another embodiment, a new 2xxx aluminum alloy has a thickness of at least 12.7 mm and realizes an elongation (ST) of at least 4.0% in the T8 temper. In yet another embodiment, a new 2xxx aluminum alloy has a thickness of at least 12.7 mm and realizes an elongation (ST) of at least 5.0% in the T8 temper. In another embodiment, a new 2xxx aluminum alloy has a thickness of at least 12.7 mm and realizes an elongation (ST) of at least 6.0% in the T8 temper. In yet another embodiment, a new 2xxx aluminum alloy has a thickness of at least 12.7 mm and realizes an elongation (ST) of at least 7.0%
in the T8 temper. The above elongation properties may be realized in products having a thickness of at least 25 mm, or at least 38 mm, or at least 50 mm, or at least 76 mm, or at least 108 mm, or higher. The above elongation properties may be realized in thin wrought products having a thickness of 7.0 to 12.6 mm.

[0056] In one embodiment, a new 2xxx aluminum alloy has a thickness of at least 12.7 mm and is LT stress corrosion cracking resistant (defined below) in the T8 temper. The LT stress corrosion cracking resistance properties may be realized in products having a thickness of at least 25 mm, or at least 38 mm, or at least 50 mm, or at least 76 mm, or at least 108 mm, or higher. The LT stress corrosion cracking resistance properties may be realized in thin wrought products having a thickness of 0.5 to 12.6 mm.

[0057] In one embodiment, a new 2xxx aluminum alloy has a thickness of at least 12.7 mm and is ST stress corrosion cracking resistant (defined below) in the T8 temper. The ST stress corrosion cracking resistance properties may be realized in products having a thickness of at least 25 mm, or at least 38 mm, or at least 50 mm, or at least 76 mm, or at least 108 mm, or higher. The ST stress corrosion cracking resistance properties may be realized in thin wrought products having a thickness of 7.0 to 12.6 mm.

[0058] In one embodiment, a new 2xxx aluminum alloy has a thickness of at least 12.7 mm and is both LT stress corrosion cracking resistant and ST stress corrosion cracking resistant in the T8 temper.

[0059] While the above properties generally relate to thick plate products, similar properties may also be realized in thick forged product and thick extruded products.
Further, many of the above properties may be realized in combination, as shown by the below examples.
v. Definitions

[0060] Unless otherwise indicated, the following definitions apply to the present application:

[0061] "2xxx aluminum alloys" are aluminum alloys compositions having copper as the major alloying element as per the Aluminum Association definition provided in "International Alloy Designations and Chemical Composition Limits for Wrought Aluminum and Wrought Aluminum Alloys," a.k.a. the "Teal Sheets" (2015). For purposes of this patent application, 2xxx aluminum alloy compositions may be used in non-wrought products, such as in shape castings, ingot/billet, and additively manufactured products, among others. The 2xxx aluminum alloys of the present patent application are generally lithium-free, having less than 0.05 wt. % Li, and generally less than 0.03 wt. % Li, or less than 0.01 wt. % Li.

[0062] "Wrought aluminum alloy product" means an aluminum alloy product that is hot worked after casting, and includes rolled products (sheet or plate), forged products, and extruded products.

[0063] "Forged aluminum alloy product" means a wrought aluminum alloy product that is either die forged or hand forged.

[0064] "Solution heat treating" means exposure of an aluminum alloy to elevated temperature for the purpose of placing solute(s) into solid solution.

[0065] "Hot working" such as by hot rolling means working the aluminum alloy product at elevated temperature. Strain-hardening is restricted / avoided during hot working, which generally differentiates hot working from cold working.

[0066] "Cold working" such as by cold rolling means working the aluminum alloy product at temperatures that are not considered hot working temperatures.

[0067] Temper definitions are per ANSI H35.1 (2009), entitled "American National Standard Alloy and Temper Designation Systems for Aluminum," published by The Aluminum Association.

[0068] Strength and elongation are measured in accordance with ASTM
E8/E8M-16ael and B557-15. Plane-strain fracture toughness is determine in accordance with ASTM
339-20.

[0069] "LT Stress corrosion cracking resistant" means that at least two-out-of-three specimens of a 2xxx aluminum alloy product do not fail after 60 days of alternate immersion testing at a net stress of 300 MPa in the LT direction and in accordance with ASTM G47 using constant-strain type stressing frame fixtures according to Figure 4 of ASTM G49, and with three replicate specimens being required for testing. In one embodiment, all three specimens do not fail after 60 days of alternate immersion testing at a net stress of 300 MPa in the LT
direction and in accordance with ASTM G47. In another embodiment, all three specimens do not fail after 90 days of alternate immersion testing at a net stress of 300 MPa in the LT direction and in accordance with ASTM
G47. In one embodiment, all three specimens do not fail after 60 days of alternate immersion testing at a net stress of 350 MPa in the LT direction and in accordance with ASTM G47. In

70 another embodiment, all three specimens do not fail after 90 days of alternate immersion testing at a net stress of 350 MPa in the LT direction and in accordance with ASTM
G47.
[0070] "ST Stress corrosion cracking resistant" means that at least two-out-of-three specimens of a 2xxx aluminum alloy product do not fail after 60 days of alternate immersion testing at a net stress of 250 MPa in the ST direction and in accordance with ASTM G47 and using fixtures according to G49, and with at least 3 specimens being required for testing. In one embodiment, all three specimens do not fail after 60 days of alternate immersion testing at a net stress of 250 MPa in the ST direction and in accordance with ASTM G47. In another embodiment, all three specimens do not fail after 90 days of alternate immersion testing at a net stress of 250 MPa in the ST direction and in accordance with ASTM G47. In one embodiment, all three specimens do not fail after 60 days of alternate immersion testing at a net stress of 300 MPa in the ST direction and in accordance with ASTM G47. In another embodiment, all three specimens do not fail after 90 days of alternate immersion testing at a net stress of 300 MPa in the ST
direction and in accordance with ASTM G47.
vi. Miscellaneous

[0071] These and other aspects, advantages, and novel features of this new technology are set forth in part in the description that follows and will become apparent to those skilled in the art upon examination of the following description and figures, or may be learned by practicing one or more embodiments of the technology provided for by the present disclosure.

[0072] Among those benefits and improvements that have been disclosed, other objects and advantages of this invention will become apparent from the following description taken in conjunction with the accompanying figures. Detailed embodiments of the present invention are disclosed herein; however, it is to be understood that the disclosed embodiments are merely illustrative of the invention that may be embodied in various forms. In addition, each of the examples given in connection with the various embodiments of the invention is intended to be illustrative, and not restrictive.

[0073] Throughout the specification and claims, the following terms take the meanings explicitly associated herein, unless the context clearly dictates otherwise.
The phrases "in one embodiment" and "in some embodiments" as used herein do not necessarily refer to the same embodiment(s), though they may Furthermore, the phrases "in another embodiment" and "in some other embodiments" as used herein do not necessarily refer to a different embodiment, although they may. Thus, various embodiments of the invention may be readily combined, without departing from the scope or spirit of the invention.

[0074] In addition, as used herein, the term "or" is an inclusive "or" operator, and is equivalent to the term "and/or," unless the context clearly dictates otherwise. The term "based on" is not exclusive and allows for being based on additional factors not described, unless the context clearly dictates otherwise. In addition, throughout the specification, the meaning of "a," "an," and "the"
include plural references, unless the context clearly dictates otherwise. The meaning of "in"
includes "in" and "on", unless the context clearly dictates otherwise.

[0075] While a number of embodiments of the present invention have been described, it is understood that these embodiments are illustrative only, and not restrictive, and that many modifications may become apparent to those of ordinary skill in the art.
Further still, unless the context clearly requires otherwise, the various steps may be carried out in any desired order, and any applicable steps may be added and/or eliminated.
BRIEF DESCRIPTION OF THE DRAWINGS

[0076] FIG. 1 is a graph illustrating TYS(L) versus Kic(L-T) for the Example 1 alloys.

[0077] FIG. 2 is a graph illustrating TYS(LT) versus Kic(T-L) for the Example 1 alloys.

[0078] FIG. 3 is a graph illustrating TYS(ST) versus Kic(S-L) for the Example 1 alloys.
DETAILED DESCRIPTION
Example 1

[0079] Several industrial scale DC ingots (18-inch x 80-inch) of the 2xxx aluminum alloy shown in Table 1 were homogenized and then conventionally scalped / peeled.
Table 1 - Composition of Ex. 1 Alloy (in wt. %)*
Si Fe Cu Mn Mg Zn Ti Zr Ag 0.02 0.05 4.9 0.35 0.4 0.5 0.11 0.07 0.35 * Nominal composition; the balance of the alloy was incidental elements and impurities, where the alloy contained not greater than 0.03 wt. % of any one impurity, and where the alloy contained not greater than 0.10 wt. %, in total, of all impurities.

The ingots were then hot rolled to a final gauge of 4.9 inches (124.5 mm) and then cooled to room temperature. The 2xxx aluminum alloy was then solution heat treated at 975 F
(523 C), water quenched and then naturally aged for 10 hours. The final gauge materials were then either stretched either 2% or 8% and then artificially aged as shown in Table 2, below.
Table 2 ¨Stretch and Artificial Aging Practices of the Ex. 1 Alloys Stretch Alloy (%) Aging Practice Single step age:
la 2 = 16 hours at 350 F (176.7 C) Single step age:
lb 2 = 24 hours at 350 F (176.7 C) Single step age:
lc 2 = 36 hours at 350 F (176.7 C) Single step age:
3a 8 = 16 hours at 350 F (176.7 C) Single step age:
3b 8 = 24 hours at 350 F (176.7 C) Single step age:
3c 8 = 36 hours at 350 F (176.7 C) Multi-step aging:
2 2 = 24 hours at 350 F (176.7 C);
= Air cool to room temperature;
4 8 = Reheat - 24 hours at 270 F
The mechanical properties of the alloys were then tested. Strength and elongation were determined in accordance with ASTM E8/E8M-16ae1 and B557-15. Plane-strain fracture toughness (Kic) was determined in accordance with ASTM E399-20. The test results are shown in Table 3, below and are also shown in FIGS. 1-3.
Table 3 ¨ Mechanical Properties of Ex. 1 Alloys Test Test TYS UTS Elong.
Alloy Loc. Dir. (MPa) (MPa) (%) (MPn\ltn) orient.
la T/4 L 430 472 8.1 47.5 L-T
lb T/4 L 424 469 8.1 47.9 L-T
c T/4 L 414 463 7.8 48.3 L-T
2 T/4 L 428 474 8.1 46.5 L-T
la T/4 LT 427 480 7.4 46 T-L
lb T/4 LT 419 476 7.2 47.1 T-L
lc T/4 LT 412 471 7.1 45.8 T-L
2 T/4 LT 426 481 7.2 44.3 T-L

la T/2 ST 399 447 5.5 49.1 S-L
lb T/2 ST 393 447 5.2 47.8 S-L
lc T/2 ST 385 440 5.3 49.4 S-L
2 T/2 ST 396 447 5.3 48.1 S-L
3a T/4 L 441 477 9.5 45.6 L-T
3b T/4 L 432 473 8.4 46.3 L-T
3c T/4 L 423 467 8.1 44.6 L-T
4 T/4 L 436 476 8.2 43.2 L-T
3a T/4 LT 438 487 7.6 40.4 T-L
3b T/4 LT 430 481 7 41.1 T-L
3c T/4 LT 420 477 6,6 41.8 T-L
4 T/4 LT 434 484 6.8 42.1 T-L
3a T/2 ST 402 458 5.9 39.4 S-L
3b T/2 ST 400 456 5.5 41.9 S-L
3c T/2 ST 389 447 6 39.9 S-L
4 T/2 ST 396 455 5.5 40.1 S-L

[0080] As shown in FIG. 2, the multistep practice demonstrates higher yield strength than the 350 F/24h aged condition. Also, the difference in properties is lower between the 2% and 8%-stretch for both strength and toughness, indicating the two-step aged materials may be suited for hydroforming applications (e.g., where a single hydroformed component may contain regions of variable strain and therefore variation in properties as a function of location within the plate).

[0081] The SCC (stress corrosion cracking) properties of the alloys in the ST direction were also measured as per the "ST Stress corrosion cracking resistance" definition provided above. The SCC results are shown in Table 4, below. The specimen type was T-bar and the location was T/2 for all tests.
Table 4 ¨ ASTM G44 SCC test results for Ex. 1 Alloys (ST direction) Altern. Immer. ASTM G44 Stress Alloy (MPa) .Days Days to failure in test rep 1 rep 2 rep 3 3a l 210 90 0K90 31 0K90 a 3b 210 90 0K90 32 90 lb 210 90 0K90 90 0K90 3c lc 210 90 01(90 0K90 01(9090 As shown, the multi-step aged alloys (both the 2% and 8% stretched materials) did not realize any failures over the 90-day test period at both the 210 MPa and the 250 MPa net-stress levels.
Conversely, the single-step aged alloys realized multiple failures.

[0082] The SCC resistance of the alloys in the ST direction were also tested at the seacoast to test the alloys against corrosion in natural saltwater conditions. The specimens for the seacoast environment SCC testing are tested in constant strain fixtures (e.g., similar to those use in accelerated laboratory SCC testing). The seacoast SCC testing conditions include continuously exposing the samples via racks to a seacoast environment, where the samples are ,=,' 1.5 meters from the ground, the samples are oriented 45 from the horizontal, and a face of the sample face the prevailing winds. The samples are located 100 meters from the coastline. In one embodiment, the coastline is of a rocky nature, with the prevailing winds oriented toward the samples so as to provide an aggressive salt-mist exposure (e.g., a location similar to the seacoast exposure station, Pt Judith, Rhode Island, USA of Arconic Corp.). The test results are shown in Table 5, below.
The specimen type was T-bar and the location was T/2 for all tests.
Table 5 ¨ Seacoast Testing SCC results for Ex. 1 Alloys (ST direction) Point Judith, RI
Stress Alloy (1V1Pa) Days in Days to failure test rep 1 rep 2 rep 3 rep 4 rep 5 lb 250 201 77 T T T T

3c 250 201 T T T 45 T

= "T" = still in test Again, the multi-step aged alloys (both the 2% and 8% stretched materials) did not realize any failures after 596 days in test at the 210 MPa and 250 MPa net-stress levels.
Conversely, the single-step aged alloys realized multiple failures. At the 300 MPa net stress level, only a single specimen of the multi-step aged alloys failed (the specimen had 8% stretch) at 192 days of testing.
Conversely, at the 300 MPa net stress level, the single-step aged alloys realized multiple failures, most occurring in 60 days or less.

[0083] 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.

Claims (42)

What is claimed is:

1. A method comprising:
(a) first aging a 2xxx aluminum alloy at a first temperature of from 300 F to 450 F and for a first aging time of from 4 to 120 hours;
(b) second aging the 2xxx aluminum alloy at a second temperature for a second aging time of from 30 minutes to 120 hours, wherein the second temperature is from 20 F to 150 F
lower than the first temperature;
wherein, at least partially due to the first aging and second aging steps, the 2xxx aluminum alloy is (i) LT stress corrosion cracking resistant, (ii) ST stress corrosion cracking resistant, or (iii) both LT stress corrosion cracking resistant and ST stress corrosion cracking resistant.

2. The method of claim 1, wherein the first temperature is at least 310 F, or at least 320 F, or at least 330 F, or at least 340 F, or at least 350 F.

3. The method of any of the preceding claims, wherein the first temperature is not greater than 440 F, or not greater than 430 F, or not greater than 420 F, or not greater than 410 F, or not greater than 400 F, or not greater than 390 F, or not greater than 380 F, or not greater than 370 F.

4 The method of any of the preceding claims, wherein the first aging time is at least 8 hours, or at least 12 hours, or at least 16 hours, or at least 20 hours, or at least 24 hours.

5. The method of any of the preceding claims, wherein the first aging time is not greater than 96 hours, or not greater than 72 hours, or not greater than 48 hours, or not greater than 40 hours, or not greater than 36 hours, or not greater than 32 hours, or not greater than 28 hours.

6. The method of claim 1, wherein the first temperature is from 330 F to 370 F
and the first time is from 12 to 36 hours.

7. The method of any of the preceding claims, wherein the second temperature is at least 30 F
lower than the first temperature, or at least 40 F lower than the first temperature, or at least 50 F

lower than the first temperature, or at least 60 F lower than the first temperature, or at least 70 F
lower than the first temperature, or at least 80 F lower than the first temperature.

8. The method of any of the preceding claims, wherein the second temperature is not greater than 140 F lower than the first temperature, or not greater than 130 F lower than the first temperature, or not greater than 120 F lower than the first temperature, or not greater than 110 F
lower than the first temperature, or not greater than 100 F lower than the first temperature.

9. The method of any of the preceding claims, wherein the second aging time is at least 2 hours, or at least 4 hours, or at least 8 hours, or at least 12 hours, or at least 16 hours, or at least 20 hours, or at least 24 hours.

10. The method of any of the preceding claims, wherein the second aging time is not greater than 96 hours, or not greater than 72 hours, or not greater than 48 hours, or not greater than 40 hours, or not greater than 36 hours, or not greater than 32 hours, or not greater than 28 hours.

11. The method of claim 1, wherein the first aging temperature is from 330 F
to 370 F, wherein the first aging time is from 12 to 36 hours, wherein the second aging temperature is from 250 to 290 F, and wherein the second aging time is from 12 to 36 hours.

12. The method of claim 1, wherein the first temperature is 350 F and the first aging time is 24 hours, or a substantially equivalent aging temperature and duration.

13. The method of claim 1 or 12, wherein the second temperature is 270 F and the second aging time is 24 hours, or a substantially equivalent aging temperature and duration.

14. The method of any of claims 1-11, wherein the first aging time is tactual, wherein ti"thal is determined according to an equivalent time at 350 F in accordance with the below formula:
wherein (a) Ti7 is the first temperature of the first aging step in Fahrenheit, wherein nFis from 300 to 450 F, (b) ti"mal is from 10 to 120 hours, and (c) ti3500. eq is the equivalent amount of time at a first step temperature of 350 F.

15. The method of claim 14, wherein ti35 F eq- is from 20 to 30 hours.

16. The method of claim 15, wherein ti3500F eq- is at least 20.5 hours, or at least 21 hours, or at least 21.5 hours, or at least 22 hours, or at least 22.5 hours, or at least 23 hours, or at least 23.5 hours, or at least 24 hours.

17. The method of any of claims 15-16, wherein ti35 T eq is not greater than 29 hours, or not greater than 28 hours, or not greater than 27 hours, or not greater than 26 hours, or not greater than 25 hours, or not greater than 24.5 hours, or not greater than 24 hours.

18. The method of claim 15, wherein t135O1' eq- is from 20.5 to 24 hours, or from 21 to 24 hours, or from 21.5 to 24 hours, or from 22 to 24 hours, or from 22.5 to 24 hours.

19. The method of any of the preceding claims, wherein the LT stress corrosion cracking resistance is two-out-of-three specimens of the 2xxx aluminum alloy do not fail after 60 days of alternate immersion testing at a net stress of 300 MPa in the LT direction and in accordance with A STM G47 using constant-strain type stressing frame fixtures according to Figure 4 of A STM
G49.

20. The method of claim 19, wherein the all three specimens do not fail after 60 days of alternate immersion testing at a net stress of 300 MPa in the LT direction, or wherein all three specimens do not fail after 90 days of alternate immersion testing at a net stress of 300 A/Pa, or wherein all three specimens do not fail after 60 days of alternate immersion testing at a net stress of 350 MPa in the LT direction, or wherein all three specimens do not fail after 90 days of alternate immersion testing at a net stress of 350 MPa in the LT direction.

21. The method of any of the preceding claims, wherein the ST stress corrosion cracking resistance is two-out-of-three specimens of the 2xxx aluminum alloy do not fail after 60 days of alternate immersion testing at a net stress of 250 MPa in the ST direction and in accordance with ASTM G47 using constant-strain type stressing frame fixtures according to Figure 4 of ASTM
G49.

22. l'he method of claim 21, wherein the all three specimens do not fail after 60 days of alternate immersion testing at a net stress of 250 MPa in the ST direction, or wherein all three specimens do not fail after 90 days of alternate immersion testing at a net stress of 250 NiPa, or wherein all three specimens do not fail after 60 days of altemate immersion testing at a net stress of 300 MPa in the ST direction, or wherein all three specimens do not fail after 90 days of alternate immersion testing at a net stress of 300 MPa in the ST direction.

23. The method of any of the preceding claims, comprising:
after the first aging step, cooling the 2xxx aluminum alloy to room temperature; and reheating the 2xxx aluminum alloy from room temperature to the second temperature of the second aging step.

24. The method of any of claims 1-22, comprising:
after the first aging step, cooling the 2xxx aluminum alloy to the second temperature of the second aging step.

25. The method of any of the preceding claims, comprising:
preparing a wrought 2xxx aluminum alloy for solution heat treating; and then solution heat treating and then quenching the wrought 2xxx aluminum alloy; and then completing the first aging step and the second aging step.

26. The method of claim 25, wherein the preparing comprising:
casting the 2xxx aluminum alloy as in ingot or billet;
working the ingot or billet to the final gauge product, wherein the working comprises hot working.

27. The method of claim 26, wherein the working further comprises cold working.

28. The method of any of the preceding claims, wherein the 2xxx aluminum alloy comprises from 0.08 to 0.20 wt. % Ti, from 4.5 to 5.5 wt. % Cu, from 0.20 to 0.6 wt. %
Mn, from 0.20 to 0.8 wt. % Mg, from 0.05 to 0.60 wt. % Ag, up to 1.0 wt. % Zn, up to 0.30 wt. %
Fe, up to 0.20 wt. % Si, up to 0.25 wt. % Zr, up to 0 25 wt. % Cr, and up to 0.25 wt. % V, the balance being aluminum, incidental elements and impurities.

29. The method of claim 28, wherein the 2xxx aluminum alloy is a 2x39 alloy modified to include 0.08 to 0.20 wt. % Ti.

30. The method of any of claims 25-29, wherein the wrought 2xxx aluminum alloy is one of a plate product, an extruded product, or a forged product.

31. The wrought 2xxx aluminum alloy of claim 30, wherein the wrought 2xxx aluminum alloy is a plate product.

32. The wrought 2xxx aluminum alloy of any of claims 30-31, wherein the wrought 2xxx aluminum alloy has a cross-sectional thickness of at least 12.7 mm, or at least 25 mm, or at least 38 mm, or at least 50 mm, or at least 76 mm, or at least 108 mm.

33. The wrought 2xxx aluminum alloy of claim 32, wherein the wrought 2xxx aluminum alloy has a cross-sectional thickness of not greater than 305 mm, or not greater than 254 mm, or not greater than 203 mm, or not greater than 178 mm, or not greater than 152 mm.

34. The wrought 2xxx aluminum alloy of any of claims 30-31, wherein the wrought 2xxx aluminum alloy has a cross-sectional thickness of from 7.0 to 12.6 mm.

35. The wrought 2xxx aluminum alloy of any of claims 30-34, wherein the wrought 2xxx aluminum alloy is in the T3 or T8 temper.

36. The wrought 2xxx aluminum alloy of claim 35, wherein the wrought 2xxx aluminum alloy is in the T8 temper and is stretched from 0.5-15% after solution heat treatment.

37. The wrought 2xxx aluminum alloy of claim 35, wherein the wrought 2xxx aluminum alloy is stretched at least 1% after solution heat treatment, or at least 1.5% after solution heat treatment, or at least 2% after solution heat treatment.

38. The wrought 2xxx aluminum alloy of claim 37, wherein the wrought 2xxx aluminum alloy is stretched not greater than 12% after solution heat treatment, or not greater than 9% after solution heat treatment.

39. The wrought 2xxx aluminum alloy of any of claims 30-38, wherein the wrought 2xxx aluminum alloy is in the T8 temper and wherein the wrought 2xxx aluminum alloy realizes a tensile yield strength (LT) of at least 390 MPa, or at least 400 MPa, or at least 410 MP, or at least 420 MPa, or at least 430 MPa, or at least 440 MPa, or at least 450 NfPa.

40. The wrought 2xxx aluminum alloy of any of claims 30-39, wherein the wrought 2xxx aluminum alloy is in the T8 temper and wherein the wrought 2xxx aluminum alloy realizes a plane-strain (Kw) fracture toughness (T-L) of at least 3 0 MPa-sqrt-m, or at least 31 MPa-sqrt-m, or at least 32 MPa-sqrt-m, or at least 33 MPa-sqrt-m, or at least 34 MPa-sqrt-m, or at least 35 MPa-sqrt-m, or at least 36 MPa-sqrt-m, or at least 37 MPa-sqrt-m, or at least 38 MPa-sqrt-m, or at least 39 MPa-sqrt-m, or at least 40 MPa-sqrt-m, or at least or at least 41 MPa-sqrt-m, or at least 42 MPa-sqrt-m, or at least 43 MPa-sqrt-m, or at least 44 MPa-sqrt-m, or at least 45 MPa-sqrt-m, or at least 46 MPa-sqrt-m, or at least 47 MPa-sqrt-m, or at least 48 MPa-sqrt-m, or at least 49 MPa-sqrt-m, or at least 50 MPa-sqrt-m.

41. The wrought 2xxx aluminum alloy of any of claims 30-40, wherein the wrought 2xxx aluminum alloy is in the T8 temper and wherein the wrought 2xxx aluminum alloy realizes an elongation (LT) of at least 6.0%, or at least 8.0%, or at least 10.0%, or at least 12.0%, or at least 14%, or at least 16%.

42. A method comprising:
(a) first aging a 2xxx aluminum alloy at a first temperature of 350 F for 24 hours, or a substantially equivalent artificial aging temperature and duration;
(b) second aging the 2xxx aluminum alloy at a second temperature of 270 F for 24 hours, or a substantially equivalent artificial aging temperature and duration;
wherein the 2xxx aluminum alloy comprises from 0.08 to 0.20 wt. % Ti, from 4.5 to 5.5 wt. % Cu, from 0.20 to 0.6 wt. % Mn, from 0.20 to 0.8 wt. % Mg, from 0.05 to 0.60 wt. % Ag, up to 1.0 wt. % Zn, up to 0.30 wt. % Fe, up to 0.20 wt. % Si, up to 0.25 wt. %
Zr, up to 0.25 wt.
% Cr, and up to 0.25 wt. % V, the balance being aluminum, incidental elements and impurities.
24; and wherein, at least partially due to the first aging and second aging steps, the 2xxx aluminum alloy is (i) LT stress corrosion cracking resistant, (ii) ST stress corrosion cracking resistant, or (iii) both LT stress corrosion cracking resistant and ST stress corrosion cracking resistant.