US20210340656A1

US20210340656A1 - 7xxx aluminum alloys

Info

Publication number: US20210340656A1
Application number: US17/308,794
Authority: US
Inventors: Julien Boselli; Jen C. Lin; Lynette M. Karabin; Severine Cambier; Francine S. Bovard; Wenping Zhang
Original assignee: Arconic Technologies LLC
Current assignee: Arconic Technologies LLC
Priority date: 2018-11-14
Filing date: 2021-05-05
Publication date: 2021-11-04
Also published as: EP3880857A4; WO2020102441A3; WO2020102441A2; CN113015816A; EP3880857A2; CA3118152A1; BR112021008744A2

Abstract

New 7xxx aluminum alloys are disclosed. The new 7xxx aluminum alloys generally include from 0.05 to 1.0 wt. % Ag. In one approach, a new 7xxx aluminum alloy includes from 0.05 to 1.0 wt. % Ag, from 5.5 to 9.0 wt. % Zn, from 1.2 to 2.6 wt. % Cu, from 1.3 to 2.5 wt. % Mg, up to 0.60 wt. % Mn, up to 1.0 wt. % of at least one grain structure control material, wherein the at least one grain structure control material is selected from the group consisting of Zr, Cr, V, Hf, other rare earth elements, and combinations thereof, up to 0.30 wt. % Fe, up to 0.30 wt. % Si, up to 0.15 wt. % Ti, not greater than 0.08 wt. % Sc, and not greater than 0.05 wt. % Li, the balance being aluminum, optional incidental elements and impurities.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of International Patent Application No. PCT/US2019/061305, filed Nov. 13, 2019, which claims the benefit of U.S. Provisional Patent Application No. 62/767,441 filed Nov. 14, 2018, entitled “IMPROVED 7XXX ALUMINUM ALLOYS,” each of which is incorporated herein by reference in its entirety.

FIELD OF THE INVENTION

The present patent application relates to improved 7xxx aluminum alloys and products made from the same.

BACKGROUND

Aluminum alloys are useful in a variety of applications. However, improving one property of an aluminum alloy without degrading another property is elusive. For example, it is difficult to increase the strength of a wrought aluminum alloy without affecting other properties such as fracture toughness or corrosion resistance. 7xxx (Al—Zn—Mg based) are prone to corrosion. See, e.g., Bonn, W. Gruhl, “The stress corrosion behaviour of high strength AIZnMg alloys,” Paper held at the International Meeting of Associazione Italiana di Metallurgie, “Aluminum Alloys in Aircraft Industries,” Turin, October 1976.
Patent Owner has described some 7xxx aluminum alloy products in, inter alia, U.S. Pat. Nos. 6,972,110, and 8,673,209, and International Patent Application Publication Nos. WO2016/183030 and WO2018/237196.

SUMMARY OF THE DISCLOSURE

Broadly, the present patent application relates to improved 7xxx aluminum alloys, and products made from the same. The new 7xxx aluminum alloys generally comprise from 0.05 to 1.0 wt. % Ag. In one approach, a new 7xxx aluminum alloy comprises (and in some instances consist essentially of, or consist of) from 0.05 to 1.0 wt. % Ag, from 5.5 to 9.0 wt. % Zn, from 1.2 to 2.6 wt. % Cu, from 1.3 to 2.5 wt. % Mg, up to 0.60 wt. % Mn, up to 1.0 wt. % of at least one grain structure control material, wherein the at least one grain structure control material is selected from the group consisting of Zr, Cr, V, Hf, other rare earth elements, and combinations thereof, up to 0.15 wt. % Ti, up to 0.20 wt. % Fe, up to 0.15 wt. % Si, not greater than 0.08 wt. % Sc, and not greater than 0.05 wt. % Li. The balance of the new 7xxx aluminum alloys is generally aluminum, optional incidental elements and impurities. In one approach, a new 7xxx aluminum alloy includes high combined amounts of copper and magnesium, such as at least 3.0 wt. % (i.e., (wt. % Cu) +(wt. % Mg) >3.0 wt. %). The new 7xxx aluminum alloy may realize an improved combination of properties, such as an improved combination of two or more of strength, fracture toughness, elongation, and stress corrosion cracking resistance, among others.
i. Composition
As noted above, the new 7xxx aluminum alloys generally include 0.05 to 1.0 wt. % Ag. The use of silver in combination with other elements of the new 7xxx aluminum alloys may result in new 7xxx aluminum alloys products having an improved combination of properties, such as an improved combination of two or more of strength, elongation, fracture toughness and stress corrosion cracking resistance, among others. In one embodiment, a new 7xxx aluminum alloy includes at least 0.06 wt. % Ag. In another embodiment, a new 7xxx aluminum alloy includes at least 0.07 wt. % Ag. In yet another embodiment, a new 7xxx aluminum alloy includes at least 0.08 wt. % Ag. In another embodiment, a new 7xxx aluminum alloy includes at least 0.09 wt. % Ag. In yet another embodiment, a new 7xxx aluminum alloy includes at least 0.10 wt. % Ag. In another embodiment, a new 7xxx aluminum alloy includes at least 0.15 wt. % Ag. In yet another embodiment, a new 7xxx aluminum alloy includes at least 0.20 wt. % Ag. In another embodiment, a new 7xxx aluminum alloy includes at least 0.225 wt. % Ag. In yet another embodiment, a new 7xxx aluminum alloy includes at least 0.25 wt. % Ag. In one embodiment, a new 7xxx aluminum alloy includes not greater than 0.7 wt. % Ag. In another embodiment, a new 7xxx aluminum alloy includes not greater than 0.5 wt. % Ag. In yet another embodiment, a new 7xxx aluminum alloy includes not greater than 0.4 wt. % Ag. In another embodiment, a new 7xxx aluminum alloy includes not greater than 0.35 wt. % Ag. In yet another embodiment, a new 7xxx aluminum alloy includes not greater than 0.325 wt. % Ag. In another embodiment, a new 7xxx aluminum alloy includes not greater than 0.30 wt. % Ag.
As noted above, in one approach, a new 7xxx aluminum alloy may include from 5.5 to 9.0 wt. % Zn. In one embodiment, a new 7xxx aluminum alloy includes at least 5.75 wt. % Zn. In another embodiment, a new 7xxx aluminum alloy includes at least 6.0 wt. % Zn. In yet another embodiment, a new 7xxx aluminum alloy includes at least 6.25 wt. % Zn. In another embodiment, a new 7xxx aluminum alloy includes at least 6.5 wt. % Zn. In yet another embodiment, a new 7xxx aluminum alloy includes at least 6.75 wt. % Zn. In another embodiment, a new 7xxx aluminum alloy includes at least 7.0 wt. % Zn. In one embodiment, a new 7xxx aluminum alloy includes not greater than 8.75 wt. % Zn. In another embodiment, a new 7xxx aluminum alloy includes not greater than 8.5 wt. % Zn. In yet another embodiment, a new 7xxx aluminum alloy includes not greater than 8.25 wt. % Zn. In another embodiment, a new 7xxx aluminum alloy includes not greater than 8.0 wt. % Zn. In another embodiment, a new 7xxx aluminum alloy includes not greater than 7.75 wt. % Zn. In yet another embodiment, a new 7xxx aluminum alloy includes not greater than 7.5 wt. % Zn. In another embodiment, a new 7xxx aluminum alloy includes not greater than 7.25 wt. % Zn. In yet another embodiment, a new 7xxx aluminum alloy includes not greater than 7.0 wt. % Zn. In another embodiment, a new 7xxx aluminum alloy includes not greater than 6.75 wt. % Zn. In yet another embodiment, a new 7xxx aluminum alloy includes not greater than 6.5 wt. % Zn. In another embodiment, a new 7xxx aluminum alloy includes not greater than 6.25 wt. % Zn.
As noted above, in one approach, a new 7xxx aluminum alloy may include from 1.2 to 2.6 wt. % Cu. In one embodiment, a new 7xxx aluminum alloy includes at least 1.3 wt. % Cu. In another embodiment, a new 7xxx aluminum alloy includes at least 1.4 wt. % Cu. In yet another embodiment, a new 7xxx aluminum alloy includes at least 1.5 wt. % Cu. In another embodiment, a new 7xxx aluminum alloy includes at least 1.6 wt. % Cu. In yet another embodiment, a new 7xxx aluminum alloy includes at least 1.7 wt. % Cu. In another embodiment, a new 7xxx aluminum alloy includes at least 1.8 wt. % Cu. In one embodiment, a new 7xxx aluminum alloy includes not greater than 2.3 wt. % Cu. In another embodiment, a new 7xxx aluminum alloy includes not greater than 2.2 wt. % Cu. In yet another embodiment, a new 7xxx aluminum alloy includes not greater than 2.1 wt. % Cu. In another embodiment, a new 7xxx aluminum alloy includes not greater than 2.0 wt. % Cu. In yet another embodiment, a new 7xxx aluminum alloy includes not greater than 1.9 wt. % Cu. In another embodiment, a new 7xxx aluminum alloy includes not greater than 1.8 wt. % Cu.
As noted above, in one approach, a new 7xxx aluminum alloy may include from 1.3 to 2.5 wt. % Mg. In one embodiment, a new 7xxx aluminum alloy includes at least 1.4 wt. % Mg. In another embodiment, a new 7xxx aluminum alloy includes at least 1.45 wt. % Mg. In one embodiment, a new 7xxx aluminum alloy includes not greater than 2.2 wt. % Mg. In another embodiment, a new 7xxx aluminum alloy includes not greater than 2.1 wt. % Mg. In yet another embodiment, a new 7xxx aluminum alloy includes not greater than 2.0 wt. % Mg. In another embodiment, a new 7xxx aluminum alloy includes not greater than 1.9 wt. % Mg. In yet another embodiment, a new 7xxx aluminum alloy includes not greater than 1.8 wt. % Mg. In another embodiment, a new 7xxx aluminum alloy includes not greater than 1.7 wt. % Mg. In yet another embodiment, a new 7xxx aluminum alloy includes not greater than 1.65 wt. % Mg.
As noted above, in one approach, a new 7xxx aluminum alloy may include high combined amounts of copper and magnesium. In one embodiment, the combined amount of copper and magnesium in a new 7xxx aluminum alloy is at least 3.0 wt. % (i.e., (wt. % Cu)+(wt. % Mg)>3.0 wt. %). In another embodiment, the combined amount of copper and magnesium in a new 7xxx aluminum alloy is at least 3.25 wt. % (i.e., (wt. % Cu)+(wt. % Mg)>3.25 wt. %). In yet another embodiment, the combined amount of copper and magnesium in a new 7xxx aluminum alloy is at least 3.5 wt. % (i.e., (wt. % Cu)+(wt. % Mg)>3.5 wt. %). In another embodiment, the combined amount of copper and magnesium in a new 7xxx aluminum alloy is at least 3.75 wt. % (i.e., (wt. % Cu)+(wt. % Mg)>3.75 wt. %). In yet another embodiment, the combined amount of copper and magnesium in a new 7xxx aluminum alloy is at least 4.0 wt. % (i.e., (wt. % Cu)+(wt. % Mg)>4.0 wt. %).
As noted above, the new 7xxx aluminum alloys may include up to 0.60 wt. % Mn. In one embodiment, a new 7xxx aluminum alloy includes at least 0.05 wt. % Mn. In another embodiment, a new 7xxx aluminum alloy includes at least 0.10 wt. % Mn. In yet another embodiment, a new 7xxx aluminum alloy includes at least 0.15 wt. % Mn. In another embodiment, a new 7xxx aluminum alloy includes at least 0.20 wt. % Mn. In yet another embodiment, a new 7xxx aluminum alloy includes at least 0.25 wt. % Mn. In one embodiment, a new 7xxx aluminum alloy includes not greater than 0.55 wt. % Mn. In another embodiment, a new 7xxx aluminum alloy includes not greater than 0.50 wt. % Mn. In yet another embodiment, a new 7xxx aluminum alloy includes not greater than 0.45 wt. % Mn. In another embodiment, a new 7xxx aluminum alloy includes not greater than 0.40 wt. % Mn. In the aluminum alloy industry, manganese may be considered both an alloying ingredient and a grain structure control element—the manganese retained in solid solution may enhance a mechanical property of the alloy (e.g., strength and/or toughness), while the manganese in particulate form (e.g., as Al₆Mn, Al₁₂Mn₃Si₂, Al₂₀Cu₂Mn₃—sometimes referred to as dispersoids) may assist with grain structure control and may also improve damage tolerance properties, such as fracture toughness. However, since Mn is separately defined with its own composition limits in the present patent application, it is not within the definition of “grain structure control material” (described below) for the purposes of the present patent application.
In some embodiments, a new 7xxx aluminum alloy includes low amounts of manganese. In these embodiments, a new 7xxx aluminum alloy generally includes not greater than 0.04 wt. % Mn. In one embodiment, a new 7xxx aluminum alloy includes not greater than 0.03 wt. % Mn. In another embodiment, a new 7xxx aluminum alloy includes not greater than 0.02 wt. % Mn. In yet another embodiment, a new 7xxx aluminum alloy includes not greater than 0.01 wt. % Mn. In another embodiment, a new 7xxx aluminum alloy includes not greater than 0.005 wt. % Mn, or less.
As noted above, the new 7xxx aluminum alloys may include one or more of Zr, Cr, V, Hf, other rare earth elements, and combinations thereof as grain structure control materials (e.g., from 0.05-0.25 wt. % each of one or more of Zr, Cr, V, Hf, and other rare earth elements), limiting the total amounts of these elements such that large primary particles do not form in the alloy. Grain structure control materials may, for instance, facilitate an appropriate grain structure (e.g., an unrecrystallized grain structure). For purposes of the present patent application, grain structure control materials include Zr, Cr, V, Hf, and other rare earth elements, to name a few, but excludes Mn and Sc. When employed, a new 7xxx aluminum alloy product generally includes at least 0.05 wt. % of the grain structure control materials. In one embodiment, a new 7xxx aluminum alloy product includes at least 0.07 wt. % of the grain structure control materials. In another embodiment, a new 7xxx aluminum alloy product includes at least 0.09 wt. % of the grain structure control materials. When employed, a new 7xxx aluminum alloy product generally includes not greater than 1.0 wt. % of the grain structure control materials. In one embodiment, a new 7xxx aluminum alloy product includes not greater than 0.75 wt. % of the grain structure control materials. In yet another embodiment, a new 7xxx aluminum alloy product includes not greater than 0.50 wt. % of the grain structure control materials. In one embodiment, the grain structure control materials are selected from the group consisting of Zr, Cr, V and Hf. In another embodiment, the grain structure control materials are selected from the group consisting of Zr and Cr. In another embodiment, the grain structure control material is Zr. In another embodiment, the grain structure control material is Cr.
In one embodiment, the grain structure control material is at least chromium (Cr), and a new 7xxx aluminum alloy product includes from 0.05 to 0.25 wt. % Cr. In one embodiment, a new 7xxx aluminum alloy includes at least 0.07 wt. % Cr. In another embodiment, a new 7xxx aluminum alloy includes at least 0.10 wt. % Cr. In yet another embodiment, a new 7xxx aluminum alloy includes at least 0.12 wt. % Cr. In yet another embodiment, a new 7xxx aluminum alloy includes at least 0.14 wt. % Cr. In one embodiment, a new 7xxx aluminum alloy includes not greater than 0.24 wt. % Cr. In another embodiment, a new 7xxx aluminum alloy includes not greater than 0.22 wt. % Cr. In yet another embodiment, a new 7xxx aluminum alloy includes not greater than 0.20 wt. % Cr.
In some embodiments, a new 7xxx aluminum alloy contains low amounts of chromium (e.g., ≥0.04 wt. % Cr.) In one embodiment, a new 7xxx aluminum alloy contains not greater than 0.03 wt. % Cr. In another embodiment, a new 7xxx aluminum alloy contains not greater than 0.02 wt. % Cr. In yet another embodiment, a new 7xxx aluminum alloy contains not greater than 0.01 wt. % Cr. In another embodiment, a new 7xxx aluminum alloy contains not greater than 0.005 wt. % Cr, or less.
In one embodiment, the grain structure control material is Zr, and a new 7xxx aluminum alloy product includes from 0.05 to 0.20 wt. % Zr. In one embodiment, a new 7xxx aluminum alloy includes at least 0.06 wt. % Zr. In another embodiment, a new 7xxx aluminum alloy includes at least 0.07 wt. % Zr. In yet another embodiment, a new 7xxx aluminum alloy includes at least 0.08 wt. % Zr. In one embodiment, a new 7xxx aluminum alloy includes not greater than 0.18 wt. % Zr. In another embodiment, a new 7xxx aluminum alloy includes not greater than 0.16 wt. % Zr. In yet another embodiment, a new 7xxx aluminum alloy includes not greater than 0.15 wt. % Zr. In another embodiment, a new 7xxx aluminum alloy includes not greater than 0.14 wt. % Zr. In yet another embodiment, a new 7xxx aluminum alloy includes not greater than 0.13 wt. % Zr. In one embodiment, the grain structure control material is Zr, and a new 7xxx aluminum alloy product includes from 0.07 to 0.16 wt. % Zr. In another embodiment, the grain structure control material is Zr, and a new 7xxx aluminum alloy product includes from 0.08 to 0.15 wt. % Zr. In yet another embodiment, the grain structure control material is Zr, and a new 7xxx aluminum alloy product includes from 0.09 to 0.14 wt. % Zr. In embodiments where the grain structure control material is Zr, a new 7xxx aluminum alloy product may contain low amounts of the Cr, V, Hf, and other rare earth elements (e.g., ≥0.04 wt. % each of Cr, V, Hf, and the other rare earth elements.). In one embodiment, a new 7xxx aluminum alloy product contains not greater than 0.03 wt. % each of Cr, V, Hf, and the other rare earth elements. In another embodiment, a new 7xxx aluminum alloy product contains not greater than 0.02 wt. % each of Cr, V, Hf, and the other rare earth elements. In another embodiment, a new 7xxx aluminum alloy product contains not greater than 0.01 wt. % each of Cr, V, Hf, and the the other rare earth elements. In another embodiment, a new 7xxx aluminum alloy product contains not greater than 0.005 wt. % each of Cr, V, Hf and the other rare earth elements.
In some embodiments, a new 7xxx aluminum alloy includes low amounts of zirconium (e.g., ≥0.04 wt. % Zr). In one embodiment, a new 7xxx aluminum alloy product contains not greater than 0.03 wt. % Zr. In another embodiment, a new 7xxx aluminum alloy product contains not greater than 0.02 wt. % Zr. In yet another embodiment, a new 7xxx aluminum alloy product contains not greater than 0.01 wt. % Zr. In another embodiment, a new 7xxx aluminum alloy product contains not greater than 0.005 wt. % Zr, or less.
In one embodiment, the grain structure control materials comprise both Zr and Cr, and a new 7xxx aluminum alloy product includes at least 0.07 wt. % Zr and at least 0.07 wt. % Cr, wherein the wt. % Zr plus the wt. % Cr is not greater than 0.40 wt. % (i.e., wt. % Zr+wt. % Cr≥0.40 wt. %). In another embodiment, the grain structure control materials comprise both Zr and Cr, and a new 7xxx aluminum alloy product includes at least 0.07 wt. % Zr and at least 0.07 wt. % Cr, wherein the wt. % Zr plus the wt. % Cr is not greater than 0.35 wt. % (i.e., wt. % Zr+wt. % Cr≥0.35 wt. %). In another embodiment, the grain structure control materials comprise both Zr and Cr, and a new 7xxx aluminum alloy product includes at least 0.07 wt. % Zr and at least 0.07 wt. % Cr, wherein the wt. % Zr plus the wt. % Cr is not greater than 0.30 wt. % (i.e., wt. % Zr+wt. % Cr≥0.30 wt. %). In another embodiment, the grain structure control materials comprise both Zr and Cr, and a new 7xxx aluminum alloy product includes at least 0.07 wt. % Zr and at least 0.07 wt. % Cr, wherein the wt. % Zr plus the wt. % Cr is not greater than 0.25 wt. % (i.e., wt. % Zr+wt. % Cr≥0.25 wt. %). In another embodiment, the grain structure control materials comprise both Zr and Cr, and a new 7xxx aluminum alloy product includes at least 0.07 wt. % Zr and at least 0.07 wt. % Cr, wherein the wt. % Zr plus the wt. % Cr is not greater than 0.20 wt. % (i.e., wt. % Zr+wt. % Cr≥0.20 wt. %). In any of these embodiment, a new 7xxx aluminum alloy product may include at least 0.09 wt. % of at least one of Zr and Cr. In any of these embodiments, a new 7xxx aluminum alloy product may include at least 0.09 wt. % of both Zr and Cr.
As noted above, the new 7xxx aluminum alloy product may include up to 0.15 wt. % Ti, e.g., cumulatively for grain refining and/or other purposes. Grain refiners are inoculants or nuclei to seed new grains during solidification of the alloy. An example of a grain refiner is a 9.525 mm rod comprising 96% aluminum, 3% titanium (Ti) and 1% boron (B) (all in weight percent), where virtually all boron is present as finely dispersed TiB₂particles. During casting, a grain refining rod may be fed in-line into the molten alloy flowing into the casting pit at a controlled rate. The amount of grain refiner included in the alloy is generally dependent on the type of material utilized for grain refining and the alloy production process. 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. Generally, grain refiners are added in an amount ranging from 0.0003 wt. % to 0.005 wt. % to the alloy, depending on the desired as-cast grain size. In addition, Ti may be separately added to the alloy in an amount up to 0.15 wt. %, depending on product form, to increase the effectiveness of grain refiner, and typically in the range of 0.005 to 0.15 wt. % Ti. When Ti is included in the alloy, it is generally present in an amount of from 0.01 to 0.10 wt. %. In one embodiment, a new alloy includes at least 0.005 wt. % Ti. In another embodiment, a new alloy includes at least 0.01 wt. % Ti. In yet another embodiment, a new alloy includes at least 0.015 wt. % Ti. In another embodiment, a new alloy includes at least 0.020 wt. % Ti. In one embodiment, a new alloy includes not greater than 0.10 wt. % Ti. In another embodiment, a new alloy includes not greater than 0.08 wt. % Ti. In yet another embodiment, a new alloy includes not greater than 0.07 wt. % Ti. In another embodiment, a new alloy includes not greater than 0.06 wt. % Ti. In yet another embodiment, a new alloy includes not greater than 0.05 wt. % Ti. In one embodiment, the aluminum alloy includes a grain refiner, and the grain refiner is at least one of TiB₂and TiC, where the wt. % of Ti in the alloy is from 0.01 to 0.06 wt. %, or from 0.01 to 0.03 wt. %.
As noted above, a new 7xxx aluminum alloy may include up to 0.30 wt. % Fe. In one embodiment, a new alloy includes at least 0.01 wt. % Fe. In one embodiment, a new alloy includes not greater than 0.25 wt. % Fe. In another embodiment, a new alloy includes not greater than 0.20 wt. % Fe. In yet another embodiment, a new alloy includes not greater than 0.15 wt. % Fe. In another embodiment, a new alloy includes not greater than 0.12 wt. % Fe. In another embodiment, a new alloy includes not greater than 0.10 wt. % Fe. In yet another embodiment, a new alloy includes not greater than 0.08 wt. % Fe. In another embodiment, a new alloy includes not greater than 0.06 wt. % Fe. In yet another embodiment, a new alloy includes not greater than 0.04 wt. % Fe. Use of 0.12 wt. % Fe or less is preferred for aerospace applications.
As noted above, a new 7xxx aluminum alloy may include up to 0.30 wt. % Si. In one embodiment, a new alloy includes at least 0.01 wt. % Si. In one embodiment, a new alloy includes not greater than 0.25 wt. % Si. In another embodiment, a new alloy includes not greater than 0.20 wt. % Si. In yet another embodiment, a new alloy includes not greater than 0.15 wt. % Si. In another embodiment, a new alloy includes not greater than 0.12 wt. % Si. In yet another embodiment, a new alloy includes not greater than 0.10 wt. % Si. In another embodiment, a new alloy includes not greater than 0.08 wt. % Si. In yet another embodiment, a new alloy includes not greater than 0.06 wt. % Si. In another embodiment, a new alloy includes not greater than 0.04 wt. % Si. Use of 0.10 wt. % Si or less is preferred for aerospace applications.
As noted above, a new 7xxx aluminum alloy generally includes not greater than 0.08 wt. % Sc. Scandium may impact the grain structure of the 7xxx aluminum alloys. In one embodiment, a new 7xxx aluminum alloy includes not greater than 0.05 wt. % Sc. In another embodiment, a new 7xxx aluminum alloy includes not greater than 0.03 wt. % Sc. In yet another embodiment, a new 7xxx aluminum alloy includes not greater than 0.01 wt. % Sc. In another embodiment, a new 7xxx aluminum alloy includes not greater than 0.005 wt. % Sc, or less.
As noted above, a new 7xxx aluminum alloy includes not greater than 0.05 wt. % Li. Lithium handling is difficult and lithium may negatively impact the properties of the 7xxx aluminum alloys. In one embodiment, a new 7xxx aluminum alloy includes not greater than 0.03 wt. % Li. In another embodiment, a new 7xxx aluminum alloy includes not greater than 0.01 wt. % Li. In yet another embodiment, a new 7xxx aluminum alloy includes not greater than 0.005 wt. % Li, or less.
As noted above, the new 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 is 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 about 0.05 wt. %, or up to about 0.03 wt. %. In some embodiments, Ca is included in the alloy in an amount of about 0.001-0.03 wt % or about 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 about 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.
The new 7xxx aluminum alloys may contain low amounts of impurities. In one embodiment, a new 7xxx aluminum alloy includes not greater than 0.15 wt. %, in total, of the impurities, and wherein the 7xxx aluminum alloy includes not greater than 0.05 wt. % of each of the impurities. In another embodiment, a new 7xxx aluminum alloy includes not greater than 0.10 wt. %, in total, of the impurities, and wherein the 7xxx aluminum alloy includes not greater than 0.03 wt. % of each of the impurities.
In one embodiment, the new 7xxx aluminum alloy is a 7085 alloy (as defined by the Aluminum Association Teal Sheets document, described below) modified to include 0.05 to 1.0 wt. % Ag, such as any of the silver limits/ranges described above. The teachings of this paragraph also apply to other 7x85 alloys, such as 7185.
In one embodiment, the new 7xxx aluminum alloy is a 7065 alloy (as defined by the Aluminum Association Teal Sheets document, described below) modified to include 0.05 to 1.0 wt. % Ag, such as any of the silver limits/ranges described above. The teachings of this paragraph also apply to other 7x65 alloys.
In one embodiment, the new 7xxx aluminum alloy is a 7040 alloy (as defined by the Aluminum Association Teal Sheets document, described below) modified to include 0.05 to 1.0 wt. % Ag, such as any of the silver limits/ranges described above. The teachings of this paragraph also apply to other 7x40 alloys, such as 7140.
In one embodiment, the new 7xxx aluminum alloy is a 7050 alloy (as defined by the Aluminum Association Teal Sheets document, described below) modified to include 0.05 to 1.0 wt. % Ag, such as any of the silver limits/ranges described above. The teachings of this paragraph also apply to other 7x50 alloys, such as 7150 and 7250.
In one embodiment, the new 7xxx aluminum alloy is a 7055 alloy (as defined by the Aluminum Association Teal Sheets document, described below) modified to include 0.05 to 1.0 wt. % Ag, such as any of the silver limits/ranges described above. The teachings of this paragraph also apply to other 7x50 alloys, such as 7155 and 7255.
In one embodiment, the new 7xxx aluminum alloy is a 7136 alloy (as defined by the Aluminum Association Teal Sheets document, described below) modified to include 0.05 to 1.0 wt. % Ag, such as any of the silver limits/ranges described above. The teachings of this paragraph also apply to other 7x36 alloys, such as 7036.
In one embodiment, the new 7xxx aluminum alloy is a 7037 alloy (as defined by the Aluminum Association Teal Sheets document, described below) modified to include 0.05 to 1.0 wt. % Ag, such as any of the silver limits/ranges described above. The teachings of this paragraph also apply to other 7x37 alloys.
In one embodiment, the new 7xxx aluminum alloy is a 7010 alloy (as defined by the Aluminum Association Teal Sheets document, described below) modified to include 0.05 to 1.0 wt. % Ag, such as any of the silver limits/ranges described above. The teachings of this paragraph also apply to other 7x10 alloys.
In one embodiment, the new 7xxx aluminum alloy is a 7081 alloy (as defined by the Aluminum Association Teal Sheets document, described below) modified to include 0.05 to 1.0 wt. % Ag, such as any of the silver limits/ranges described above. The teachings of this paragraph also apply to other 7x81 alloys, such as 7181.
In one embodiment, the new 7xxx aluminum alloy is a 7099 alloy (as defined by the Aluminum Association Teal Sheets document, described below) modified to include 0.05 to 1.0 wt. % Ag, such as any of the silver limits/ranges described above. The teachings of this paragraph also apply to other 7x99 alloys, such as 7199.
In one embodiment, the new 7xxx aluminum alloy is a 7449 alloy (as defined by the Aluminum Association Teal Sheets document, described below) modified to include 0.05 to 1.0 wt. % Ag, such as any of the silver limits/ranges described above. The teachings of this paragraph also apply to other 7x49 alloys, such as 7049, 7149, 7249, and 7349.
In one embodiment, the new 7xxx aluminum alloy is a 7075 alloy (as defined by the Aluminum Association Teal Sheets document, described below) modified to include 0.05 to 1.0 wt. % Ag, such as any of the silver limits/ranges described above. The teachings of this paragraph also apply to other 7x75 alloys, such as 7175 and 7475.
In one embodiment, the new 7xxx aluminum alloy is a 7097 alloy (as defined by the Aluminum Association Teal Sheets document, described below) modified to include 0.05 to 1.0 wt. % Ag, such as any of the silver limits/ranges described above. The teachings of this paragraph also apply to other 7x97 alloys.
ii. Product Forms
The new alloys may be useful in a variety of product forms, including ingot or billet, wrought product forms (sheet, plate, forgings and extrusions), shape castings, additively manufactured products, and powder metallurgy products, for instance.
In one embodiment, a new 7xxx 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 60 mm. In another embodiment, a thick wrought aluminum alloy product has a thickness of at least 80 mm. In yet another embodiment, a thick wrought aluminum alloy product has a thickness of at least 100 mm. In another embodiment, a thick wrought aluminum alloy product has a thickness of at least 120 mm. In another embodiment, a thick wrought aluminum alloy product has a thickness of at least 140 mm. 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 178 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.
iii. Wrought Processing
The new alloy can be prepared into wrought form, and in the appropriate temper, by more or less conventional practices, including direct chill (DC) casting the aluminum alloy into ingot form. After conventional scalping, lathing or peeling (if needed) and homogenization, which homogenization may be completed before or after scalping, these ingots may be further processed by hot working the product. The product may then be optionally cold worked and/or optionally annealed. After any cold work and any anneal (which may occur multiple times and in any order), the product may then be solution heat treated, quenched, such as in a gas (e.g. air), or a liquid (e.g., water) or both and to an appropriate temperature (e.g., quenched to ambient temperature), and then naturally and/or artificially aged. Thus, in some embodiments, the products may be produced in a T4, T6 or T7 temper. In other embodiments, other T tempers may be used (e.g., any of a T1, T2, T3, T5, T8 or T9 temper). Products may also be produced/shipped in the F or W tempers. In one approach, a new wrought aluminum alloy product is in a T7X temper, such as any of a T73, T74, T76, T79 or T77 temper. In one embodiment, a new wrought aluminum alloy product is in a T7X51 temper, such as any of a T7351, T7451, T7651, T7951 or T7751 temper. Tempers (F, W and T) are defined in ANSI H35.1 (2009).
iv. Properties
The new 7xxx aluminum alloys may realize an improved combination of at least two of strength, elongation, fracture toughness, and stress corrosion cracking resistance, among others.
a. Longitudinal (L)
In one embodiment, a new 7xxx aluminum alloy product has a thickness of at least 38 mm and realizes a typical tensile yield strength (L) of at least 400 MPa in a T7 temper. In another embodiment, a new 7xxx aluminum alloy product has a thickness of at least 38 mm and realizes a typical tensile yield strength (L) of at least 410 MPa in a T7 temper. In yet another embodiment, a new 7xxx aluminum alloy product has a thickness of at least 38 mm and realizes a typical tensile yield strength (L) of at least 420 MPa in a T7 temper. In another embodiment, a new 7xxx aluminum alloy product has a thickness of at least 38 mm and realizes a typical tensile yield strength (L) of at least 430 MPa in a T7 temper. In yet another embodiment, a new 7xxx aluminum alloy product has a thickness of at least 38 mm and realizes a typical tensile yield strength (L) of at least 440 MPa in a T7 temper. In another embodiment, a new 7xxx aluminum alloy product has a thickness of at least 38 mm and realizes a typical tensile yield strength (L) of at least 450 MPa in a T7 temper. In yet another embodiment, a new 7xxx aluminum alloy product has a thickness of at least 38 mm and realizes a typical tensile yield strength (L) of at least 460 MPa in a T7 temper. In another embodiment, a new 7xxx aluminum alloy product has a thickness of at least 38 mm and realizes a typical tensile yield strength (L) of at least 470 MPa in a T7 temper. In yet another embodiment, a new 7xxx aluminum alloy product has a thickness of at least 38 mm and realizes a typical tensile yield strength (L) of at least 480 MPa, or more, in a T7 temper. The above strength properties may be realized in products having a thickness of at least 60 mm, or at least 80 mm, or at least 100 mm, at least 120 mm, or at least 140 mm, or higher.
In one embodiment, a new 7xxx aluminum alloy product has a thickness of at least 38 mm and realizes an elongation (L) of at least 8.0% in a T7 temper. In another embodiment, a new 7xxx aluminum alloy product has a thickness of at least 38 mm and realizes an elongation (L) of at least 9.0% in a T7 temper. In yet another embodiment, a new 7xxx aluminum alloy product has a thickness of at least 38 mm and realizes an elongation (L) of at least 10.0% in a T7 temper. In another embodiment, a new 7xxx aluminum alloy product has a thickness of at least 38 mm and realizes an elongation (L) of at least 11.0% in a T7 temper. In yet another embodiment, a new 7xxx aluminum alloy product has a thickness of at least 38 mm and realizes an elongation (L) of at least 12.0%, or higher in a T7 temper. The above elongation properties may be realized in products having a thickness of at least 60 mm, or at least 80 mm, or at least 100 mm, at least 120 mm, or at least 140 mm, or higher.
b. Short Transverse (ST)
In one embodiment, a new 7xxx aluminum alloy product has a thickness of at least 38 mm and realizes a typical tensile yield strength (ST) of at least 400 MPa in a T7 temper. In another embodiment, a new 7xxx aluminum alloy product has a thickness of at least 38 mm and realizes a typical tensile yield strength (ST) of at least 410 MPa in a T7 temper. In yet another embodiment, a new 7xxx aluminum alloy product has a thickness of at least 38 mm and realizes a typical tensile yield strength (ST) of at least 420 MPa in a T7 temper. In another embodiment, a new 7xxx aluminum alloy product has a thickness of at least 38 mm and realizes a typical tensile yield strength (ST) of at least 430 MPa in a T7 temper. In yet another embodiment, a new 7xxx aluminum alloy product has a thickness of at least 38 mm and realizes a typical tensile yield strength (ST) of at least 440 MPa, or more, in a T7 temper. The above strength properties may be realized in products having a thickness of at least 60 mm, or at least 80 mm, or at least 100 mm, at least 120 mm, or at least 140 mm, or higher.
In one embodiment, a new 7xxx aluminum alloy product has a thickness of at least 38 mm and realizes a plane-strain (K_IC) fracture toughness (S-L) of at least 20 MPa-sqrt-m in a T7 temper. In another embodiment, a new 7xxx aluminum alloy product has a thickness of at least 38 mm and realizes a plane-strain (K_IC) fracture toughness (S-L) of at least 21 MPa-sqrt-m in a T7 temper. In yet another embodiment, a new 7xxx aluminum alloy product has a thickness of at least 38 mm and realizes a plane-strain (K_IC) fracture toughness (S-L) of at least 22 MPa-sqrt-m in a T7 temper. In another embodiment, a new 7xxx aluminum alloy product has a thickness of at least 38 mm and realizes a plane-strain (K_IC) fracture toughness (S-L) of at least 23 MPa-sqrt-m in a T7 temper. In yet another embodiment, a new 7xxx aluminum alloy product has a thickness of at least 38 mm and realizes a plane-strain (K_IC) fracture toughness (S-L) of at least 241V1Pa-sqrt-m in a T7 temper. In another embodiment, a new 7xxx aluminum alloy product has a thickness of at least 38 mm and realizes a plane-strain (K_IC) fracture toughness (S-L) of at least 25 MPa-sqrt-m, or higher, in a T7 temper. The above fracture toughness properties may be realized in products having a thickness of at least 60 mm, or at least 80 mm, or at least 100 mm, at least 120 mm, or at least 140 mm, or higher.
In one embodiment, a new 7xxx aluminum alloy product has a thickness of at least 38 mm and realizes an elongation (ST) of at least 2.0% in a T7 temper. In another embodiment, a new 7xxx aluminum alloy product has a thickness of at least 38 mm and realizes an elongation (ST) of at least 3.0% in a T7 temper. In yet another embodiment, a new 7xxx aluminum alloy product has a thickness of at least 38 mm and realizes an elongation (ST) of at least 4.0% in a T7 temper. In another embodiment, a new 7xxx aluminum alloy product has a thickness of at least 38 mm and realizes an elongation (ST) of at least 5.0% in a T7 temper. In yet another embodiment, a new 7xxx aluminum alloy product has a thickness of at least 38 mm and realizes an elongation (ST) of at least 6.0% in a T7 temper. The above elongation properties may be realized in products having a thickness of at least 60 mm, or at least 80 mm, or at least 100 mm, at least 120 mm, or at least 140 mm, or higher.
In one embodiment, a new 7xxx aluminum alloy product has a thickness of at least 38 mm and passes Hot and Humid SCC (stress corrosion cracking) testing using standard stress-corrosion tension test specimens conforming to ASTM G49, as defined below (“HHSCC-G49”). To create the HHSCC-G49 test specimens, at least three short transverse (ST) samples are taken from mid-thickness of the final product and between W/4 and 3W/4 of the final product. The extracted samples are then machined into tensile specimens per ASTM E8 and matching the dimensions of FIG. 2 (the dimensions of FIG. 2 are in inches). If the final product thickness is at least 2.25 inches (57.15 mm), then the length of the tensile specimen is 2.00 inches (50.8 mm), as shown in FIG. 2. If the final product thickness is from 1.50 inches (38.1 mm) to less than 2.25 inches (<50.8 mm), the length of the specimen must be at least 1.25 inches (31.75 mm) and should be as close to 2.00 inches (50.8 mm) as possible. Prior to testing the tensile specimens are to be cleaned/degreased by washing in acetone. The tensile specimens are then strained in the short-transverse direction at 85% of their ST tensile yield strength at T/2. The alloy's ST tensile yield strength is measured at room temperature and in accordance with ASTM E8 and B557 prior to the HHSCC-G49 testing. The stressing frame used is a constant strain type per ASTM G49, section 7.2.2 (see, e.g., FIG. 4a of ASTM G49). The strained specimens are then placed into a controlled cabinet having air at 85% relative humidity (without additions to the air, such as chlorides) and a temperature of 70° C. or 90° C. At least three specimens must be tested. For purposes of this patent application, an alloy passes HHSCC-G49 testing at 70° C. when all specimens survive at least 100 days. For purposes of this patent application, an alloy passes HHSCC-G49 testing at 90° C. when all specimens survive at least 10 days. A failure is when the specimen breaks into two halves, either along the gauge length or at one of the specimen shoulders adjoining the gauge length. Shoulder failures are statistically equivalent to gauge length failures. Thread failures are only included when they are statistically equivalent to the gauge length failures when determining whether an alloy passes HHSCC-G49. A thread failure is when a crack occurs in a threaded end of a specimen as opposed to in the gauge length. In some instance, thread failures may not be detectable until the specimen is removed from the stressing frame. In one embodiment, a new 7xxx aluminum alloy passes 150 days of HHSCC-G49 testing at 70° C., wherein all samples survive 150 days of the HHSCC-G49 test defined above. In another embodiment, a new 7xxx aluminum alloy passes 15 days of HHSCC-G49 testing at 90° C., wherein all samples survive 15 days of the HHSCC-G49 test defined above. The above stress corrosion cracking resistance properties may be realized in products having a thickness of at least 60 mm, or at least 80 mm, or at least 100 mm, at least 120 mm, or at least 140 mm, or higher.
In one embodiment, a new 7xxx aluminum alloy product has a thickness of at least 38 mm and passes stress corrosion cracking, per ASTM G47 using standard stress-corrosion tension test specimens conforming to ASTM G49 under alternate immersion exposure conditions per ASTM G44 (“SCC alternate immersion testing”). For purposes of this patent application, a new 7xxx aluminum alloy passes SCC alternate immersion testing when all samples survive 20 days of the SCC alternate immersion testing at a net stress of 172 MPa in the ST direction, where the test environment is 3.5% NaCl, and with a minimum of five (5) samples required to be tested. In one embodiment, a new 7xxx aluminum alloy passes 30 days of SCC alternate immersion testing, as defined above. In another embodiment, a new 7xxx aluminum alloy passes 20 days of SCC alternate immersion testing, as defined above, but at a net stress of 241 MPa. In yet another embodiment, a new 7xxx aluminum alloy passes 30 days of SCC alternate immersion testing, as defined above, but at a net stress of 241 MPa. The above stress corrosion cracking resistance properties may be realized in products having a thickness of at least 60 mm, or at least 80 mm, or at least 100 mm, at least 120 mm, or at least 140 mm, or higher.
In one embodiment, a new 7xxx aluminum alloy product has a thickness of at least 38 mm and passes Hot and Humid SCC (stress corrosion cracking) testing under ASTM G168, as defined below (“HHSCC-G168”). For purpose of this patent application, a new 7xxx aluminum alloy passes HHSCC-G168 testing when (a) the stress intensity factor gives a crack growth rate of not greater than 10⁻⁷mm/s, and (b) the realized K value is at least 13 MPa-sqrt-m (MPa√m). The HHSCC-G168 testing is to be conducted at 70° C. and 85% relative humidity, at T/2 and with S-L specimens. In one embodiment, the realized K value is at least 14 MPa-sqrt-m at a crack growth rate of not greater than 10⁻⁷mm/s. In another embodiment, the realized K value is at least 15 MPa-sqrt-m at a crack growth rate of not greater than 10⁻⁷mm/s. In yet another embodiment, the realized K value is at least 16 MPa-sqrt-m at a crack growth rate of not greater than 10⁻⁷mm/s. In another embodiment, the realized K value is at least 17 MPa-sqrt-m at a crack growth rate of not greater than 10⁻⁷mm/s. In yet another embodiment, the realized K value is at least 18 MPa-sqrt-m, or higher, at a crack growth rate of not greater than 10⁻⁷mm/s. The above stress corrosion cracking resistance properties may be realized in products having a thickness of at least 60 mm, or at least 80 mm, or at least 100 mm, at least 120 mm, or at least 140 mm, or higher.
In one embodiment, a new 7xxx aluminum alloy passes at least two of the above-defined SCC tests (i.e., at least two of: (a) the HHSCC-G49 test, as defined above, (b) the SCC alternate immersion test, as defined above, and (c) the HHSCC-G168 test, as defined above). In another embodiment, a new 7xxx aluminum alloy passes all of the above-defined SCC tests.
While the above L and ST 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
Unless otherwise indicated, the following definitions apply to the present application:
“7xxx aluminum alloys” are aluminum alloys compositions having zinc 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,” (2015) a.k.a. the “Teal Sheets.” For purposes of this patent application, 7xxx aluminum alloy compositions may be used in non-wrought products, such as in shape castings, ingot/billet, and additively manufactured products, among others.
“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.
“Forged aluminum alloy product” means a wrought aluminum alloy product that is either die forged or hand forged.
“Solution heat treating” means exposure of an aluminum alloy to elevated temperature for the purpose of placing solute(s) into solid solution.
“Hot working” means working the aluminum alloy product at elevated temperature, generally at least 250° F.
“Cold working” means working the aluminum alloy product at temperatures that are not considered hot working temperatures, generally below about 250° F. (e.g., at ambient).
“Artificially aging” means exposure of an aluminum alloy to elevated temperature for the purpose of precipitating solute(s). Artificial aging may occur in one or a plurality of steps, which can include varying temperatures and/or exposure times.
Strength and elongation are measured in accordance with ASTM E8 and B557.
As used herein, “typical longitudinal (L) tensile yield strength” or TYS(L) is determined in accordance with ASTM B557-10 and by measuring the tensile yield strength (TYS) in the longitudinal direction (L) at the T/4 location from at least three different lots of material, and with at least duplicate specimens being tested for each lot, for a total of at least 6 different measured specimen values, with the typical TYS(L) being the average of the at least 6 different measured specimen values. Typical elongation (L) is measured during longitudinal tensile testing.
As used herein, “typical longitudinal (ST) tensile yield strength” or TYS(ST) is determined in accordance with ASTM B557-10 and by measuring the tensile yield strength (TYS) in the short transverse direction (ST) from at least three different lots of material, and with at least duplicate specimens being tested for each lot, for a total of at least 6 different measured specimen values, with the typical TYS(ST) being the average of the at least 6 different measured specimen values. Short transverse tensile specimens are taken so that the midpoint of the gage section coincides with the plate mid-thickness plane. Typical elongation (ST) is measured during short transverse tensile testing.
As used herein, “typical plane strain fracture toughness (K_IC) (L-T)” is determined in accordance with ASTM E399-12, by measuring the plane strain fracture toughness in the L-T direction at the T/2 location for plate thicknesses up to 4.0 inches and at the T/4 location for plate thicknesses above 4.0 inches from at least three different lots of material using a C(T) specimen, where “W” is 4.0 inches, and where “B” is 2.0 inches for products having a thickness of at least 2.0 inches and where “B” is 1.5 inches for products having a thickness less than 2.0 inches, with at least duplicate specimens being tested for each lot, for a total of at least 6 different measured specimen values, and with the typical plane strain fracture toughness (K_IC) (L-T) being the average of the at least 6 different valid K_ICmeasured specimen values.
As used herein, “typical plane strain fracture toughness (K_IC) (S-L)” is determined in accordance with ASTM E399-12, by measuring the plane strain fracture toughness in the S-L direction at the T/2 location from at least three different lots of material using a C(T) specimen, where “W” and “B” are per the below table, with at least duplicate specimens being tested for each lot, for a total of at least 6 different measured specimen values, and with the typical plane strain fracture toughness (K_IC) (S-L) being the average of the at least 6 different valid K_ICmeasured specimen values.

S-L Specimen Parameters


Product Thickness	“W”	“B”

≥5.0 inches	4.0 inches	2.0 inches
<5.0 inches to ≥3.8 inches	3.0 inches	1.5 inches
<3.8 inches to ≥3.2 inches	2.5 inches	1.25 inches
<3.2 inches to ≥2.6 inches	2.0 inches	1.0 inches
<2.6 inches to ≥2.0 inches	1.5 inches	0.75 inches
<2.0 inches to ≥1.5 inches	1.0 inches	0.5 inches

As used herein, “additive manufacturing” means “a process of joining materials to make objects from 3D model data, usually layer upon layer, as opposed to subtractive manufacturing methodologies”, as defined in ASTM F2792-12a entitled “Standard Terminology for Additively Manufacturing Technologies”. Non-limiting examples of additive manufacturing processes useful in producing aluminum alloy products include, for instance, DMLS (direct metal laser sintering), SLM (selective laser melting), SLS (selective laser sintering), and EBM (electron beam melting), among others. Any suitable feedstocks made from the above new 7xxx aluminum alloys may be used, including one or more powders, one or more wires, one or more sheets, and combinations thereof In some embodiments the additive manufacturing feedstock is comprised of one or more powders comprising the new 7xxx aluminum alloys. Shavings are types of particles. In some embodiments, the additive manufacturing feedstock is comprised of one or more wires comprising the new 7xxx aluminum alloys. A ribbon is a type of wire. In some embodiments, the additive manufacturing feedstock is comprised of one or more sheets comprising the new 7xxx aluminum alloys. Foil is a type of sheet.
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.
The figures constitute a part of this specification and include illustrative embodiments of the present disclosure and illustrate various objects and features thereof. In addition, any measurements, specifications and the like shown in the figures are intended to be illustrative, and not restrictive. Therefore, specific structural and functional details disclosed herein are not to be interpreted as limiting, but merely as a representative basis for teaching one skilled in the art to variously employ the present invention.
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.
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.
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.
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

FIG. 1 is a graph illustrating the hot and humid stress corrosion cracking (SCC) G168 performance of the Example 1 alloys.

FIG. 2 is an illustration of a tensile specimen for testing HHSCC-G49 resistance properties.

FIG. 3 is a graph illustrating the hot and humid stress corrosion cracking (SCC) G168 performance of the Example 2 alloys.

DETAILED DESCRIPTION

Example 1

Multiple 7xxx aluminum alloy compositions were cast as rectangular ingots with a thickness of 2.875 inches: a new invention alloy having silver along with two conventional 7050 alloys and two conventional 7085 alloys. The compositions of the alloys are provided in Table 1, below.

TABLE 1

Composition of Example 1 Alloys (wt. %)

Alloy	Si	Fe	Cu	Mg	Zn	Zr	Ag	Balance

7085 + Ag	0.02	0.04	1.60	1.52	7.7	0.12	0.48	Aluminum,
7050-1	0.05	0.08	2.23	2.19	6.0	0.11	—	incidental
7050-2	0.05	0.10	2.19	2.14	5.9	0.11	—	elements,
7085-1	0.02	0.09	1.64	1.52	7.4	0.10	—	and
7085-2	0.02	0.04	1.61	1.49	7.3	0.11	—	impurities*

*Each alloy contained from 0.02-0.03 wt. % Ti as an incidental element; no one impurity exceeded 0.05 wt. %, and the total amount of impurities did not exceed 0.15 wt. % for each alloy.

After casting, the ingots were homogenized, scalped, and then hot rolled into plate. The plates had a final gauge of about 1.125 inches (28.575 mm). The plates were then flattened and then solution heat treated and then quenched in 195° F. water. The 195° F. water quench simulates quench conditions for thick plates (e.g., plates having a final gauge thickness of about 8-12 inches). After quenching, the plates were stretched and then artificially aged to a T7 temper. Mechanical properties of the plates were then evaluated. Strength and elongation properties were measured in accordance with ASTM B557 and E8. Fracture toughness properties were measured in accordance with ASTM E399. The results are provided in Tables 2-3, below.

TABLE 2

Longitudinal Properties

	TYS(L)	UTS(L)	Elong. (L)
Alloy	(MPa)	(MPa)	(%)

7085 + Ag	475.0	513.0	12.0
7050-1	459.2	516.4	14.0
7050-2	456.8	515.4	9.0
7085-1	460.6	498.8	11.0
7085-2	462.3	500.2	10.0

TABLE 3

Short Transverse Properties

	TYS(ST)	UTS(ST)	Elong. (ST)	S-L K_IC
Alloy	(MPa)	(MPa)	(%)	(MPa-sqrt-m)

7085 + Ag	441.3	501.9	6	24.3
7050-1	N/A	N/A	N/A	20.9
7050-2	429.2	481.6	4	20.5
7085-1	406.8	422.6	2	25.1
7085-2	424.0	425.4	4	27.0

As shown, the new invention alloy realizes improved strength, elongation, and fracture toughness as compared to the conventional alloys.
The corrosion resistance of the alloys was also tested. Specifically, double cantilever beam (DCB) specimens in S-L orientation were tested according to ASTM G168 to measure each alloy's stress corrosion cracking (SCC) resistance. The temperature during the SCC testing was 70° C. and the relative humidity (RH) was 85%. Two replicates per alloy were tested. FIG. 1 shows the results. Data for conventional plant produced 7050 and 7085 plate products are also provided in FIG. 1 for comparison purposes. As a baseline, C-ring specimens were also placed into test to measure the stress corrosion cracking SCC initiation based on time to failure at 60% of TYS in 70° C. and 85% RH. No failures in any of the composition have occurred after 87 days in test.
The DCB curves for the 7085 and the 7050 bookmold alloys are consistent with those for the plant produced 7085-T7451 (152 mm) and 7050-T7451 (100 mm) plates. However, the crack growth rate is much lower and the threshold stress intensity (K_ISCC) is much higher for the invention alloy (7085+Ag). Thus, the invention alloy realizes improved strength, elongation, toughness, and SCC resistance as compared to the conventional alloys.

Example 2

Seven additional 7xxx aluminum alloys were cast as ingots (6-inches thick (152.4 mm)), the composition of which are shown in Table 4, below

TABLE 4

Composition of Example 2 Alloys (wt. %)**

Alloy	Si	Fe	Cu	Mg	Zn	Zr	Ag	Balance

1	0.02	0.04	1.63	1.48	7.53	0.11	0.11	Aluminum,
2	0.02	0.04	1.62	1.49	7.54	0.11	0.18	incidental
3	0.02	0.04	1.59	1.45	7.54	0.11	0.10	elements,
4	0.02	0.04	1.64	1.50	7.51	0.11	0.50	and
5	0.02	0.04	1.86	1.51	6.32	0.11	0.15	impurities*
7085	0.02	0.03	1.64	1.52	7.59	0.11	—
7050	0.05	0.08	2.22	2.09	6.10	0.11	—

*Each alloy contained from 0.02-0.03 wt. % Ti as an incidental element; no one impurity exceeded 0.05 wt. %, and the total amount of impurities did not exceed 0.15 wt. % for each alloy.
**Alloys 3 and 5 also contained about 0.25 wt. % Mn.

After scalping and homogenization, the ingots were hot rolled to a final gauge of about 1.75 inches (44.45 mm). The alloys were then solution heat treated and then quenched in hot water (190° F./87.8° C.), which simulates about 8-12 inch (20.32-30.48 cm) thick plate. After quenching, the plates were stretched and then artificially aged to various versions of a T7 temper. Mechanical properties of the plates were then evaluated. Strength and elongation properties were measured in accordance with ASTM B557 and E8. Fracture toughness properties were measured in accordance with ASTM E399. The results are provided in Tables 5-6, below. (The terminology “Alloy-Version of _-_,” below, indicates the alloy number per Table 4, above, followed by the aging condition of that alloy. For instance, Alloy 1-1 means Alloy 1 shown in Table 4, above, aged per Aging practice 1.)

TABLE 5

Short Transverse Properties

Alloy-		TYS (ST)	UTS (ST)	Elong. (ST)	S-L K_IC
Version	Aging	(ksi)	(ksi)	(%)	(ksi-sqrt-in)

Alloy 1-1	Aging 1	65.7	76.4	7.8	N/A
Alloy 1-2	Aging 2	62.6	73.5	9.4	N/A
Alloy 1-3	Aging 1	64.7	75.0	10.9	N/A
Alloy 1-4	Aging 2	61.3	71.2	11.7	N/A
Alloy 2-1	Aging 1	64.2	75.0	9.4	N/A
Alloy 2-2	Aging 2	60.9	72.7	10.9	N/A
Alloy 2-3	Aging 1	65.8	76.0	9.4	22.4
Alloy 2-4	Aging 2	62.3	73.3	9.4	24.6
Alloy 3-1	Aging 1	63.1	74.6	9.4	N/A
Alloy 3-2	Aging 2	60.0	71.6	9.4	N/A
Alloy 4-1	Aging 1	61.9	73.5	9.4	N/A
Alloy 4-2	Aging 2	59.5	71.1	10.9	N/A
Alloy 4-3	Aging 1	62.8	73.9	7.0	19.4
Alloy 4-4	Aging 2	59.9	71.5	8.6	22.8
Alloy 5-1	Aging 1	62.9	74.8	9.4	N/A
Alloy 5-2	Aging 2	61.2	73.4	9.4	N/A
Alloy 5-3	Aging 1	64.6	76.0	9.4	22.8
Alloy 5-4	Aging 2	61.7	74.0	9.4	22.5
7085-1	T7651	65.6	75.6	12.5	N/A
7085-2	T7451	62.3	73.1	10.9	N/A
7085-3	T7651	66.5	76.8	9.4	23.3*
7085-4	T7451	63.0	73.6	7.8	N/A
7085-5	T7451	62.4	73.3	10.8	N/A
7085-6	T7451	62.3	73.3	9.4	25.1
7085-7	T7451	62.0	73.4	10.9	26.9
7050-1	T7651	57.7	71.6	9.4	N/A
7050-2	T7451	57.1	70.9	9.4	N/A
7050-3	T7651	58.1	70.9	6.2	N/A
7050-4	T7451	56.5	70.9	9.4	N/A
7050-5	T7651	56.5	69.6	7.3	N/A
7050-6	T7651	56.3	70.4	9.4	18.5
7050-7	T7651	56.2	70.3	10.2	18.4

*= K_Qvalue

TABLE 6

Longitudinal Properties

Alloy-		TYS(L)	UTS(L)	Elong. (L)	L-T K_IC
Version	Aging	(ksi)	(ksi)	(%)	(ksi-sqrt-in)

Alloy 1-1	Aging 1	73.5	79.7	12.5	N/A
Alloy 1-2	Aging 2	68.5	75.9	12.5	N/A
Alloy 2-1	Aging 1	71.7	78.0	13.3	N/A
Alloy 2-2	Aging 2	67.9	75.3	14.1	N/A
Alloy 2-3	Aging 1	73.6	79.8	12.5	28.4
Alloy 2-4	Aging 2	66.7	75.6	12.5	31.1
Alloy 3-1	Aging 1	70.6	77.6	12.5	N/A
Alloy 3-2	Aging 2	66.3	74.2	12.5	N/A
Alloy 4-1	Aging 1	71.0	77.5	12.5	N/A
Alloy 4-2	Aging 2	67.5	74.9	13.3	N/A
Alloy 4-3	Aging 1	71.9	78.5	12.5	26.0
Alloy 4-4	Aging 2	67.8	75.2	12.5	29.8
Alloy 5-1	Aging 1	71.7	78.6	12.5	N/A
Alloy 5-2	Aging 2	68.9	76.6	13.3	N/A
Alloy 5-3	Aging 1	71.4	78.6	12.5	28.3
Alloy 5-4	Aging 2	71.6	78.8	12.5	29.6
7085-1	T7651	73.0	78.9	13.3	N/A
7085-2	T7451	68.8	75.7	14.1	N/A
7085-3	T7651	73.6	80.1	12.5	28.9
7085-6	T7451	68.7	76.0	14.1	35.3*
7085-7	T7451	68.5	75.9	14.1	36.1*
7050-1	T7651	63.9	74.2	12.5	N/A
7050-2	T7451	62.5	73.2	11.7	N/A
7050-6	T7651	61.6	72.3	11.7	30.7*
7050-7	T7651	61.2	72.2	12.5	28.2*

*= K_Qvalue

Various ones of the Example 2 alloys were also subjected to Hot and Humid SCC (stress corrosion cracking) ASTM G49 testing (“HHSCC-G49”), as defined in the Summary of the Disclosure section, above, but with some specimens being tested at 90° C. instead of 70° C. The results are shown in Tables 7-8, below. As noted in the Summary of the Disclosure section, above, for purposes of this patent application, an alloy passes HHSCC-G49 testing at 70° C. when all specimens survive at least 100 days, and an alloy passes HHSCC-G49 testing at 90° C. when all specimens survive at least 10 days.

TABLE 7

HHSCC-G49 test results at 70° C. (85% TYS, 85% RH)*

Alloy-

Days to failure (per specimen, below)

Version	1st	2nd	3rd	4th	5th

Alloy 1-3	T(42)	T(42)	T(42)	T(42)	T(42)
Alloy 1-4	T(42)	T(42)	T(42)	T(42)	T(42)
Alloy 1-1	68	68	89	101	T(180)
Alloy 1-2	124	140	145	145	T(180)
Alloy 3-1	61	63	104	108	T(180)
Alloy 3-2	157	161	171	T(180)	T(180)
Alloy 2-3	40	54	87	136	T(215)
Alloy 2-4	103	122	136	175	T(215)
Alloy 4-3	136	187	T(215)	T(215)	T(215)
Alloy 4-4	T(215)	T(215)	T(215)	T(215)	T(215)
Alloy 5-3	T(215)	T(215)	T(215)	T(215)	T(215)
Alloy 5-4	T(215)	T(215)	T(215)	T(215)	T(215)
7085-3	24	24	24	31	T(215)
7085-5	28	T(42)	T(42)	T(42)	T(42)
7085-6	79	98	N/A	N/A	N/A
7085-7	79	N/A	N/A	N/A	N/A
7050-5	T(42)	T(42)	T(42)	T(42)	T(42)
7050-6	T(301)	T(301)	T(301)	N/A	N/A
7050-7	T(301)	T(301)	T(301)	N/A	N/A

*T(#) means the indicated specimen did not failed after the specified number of days in testing, e.g., “T(42)” means the specimen did not failed after 42 days of testing.

TABLE 8

HHSCC-G49 test results at 90° C. (85% TYS, 85% RH)*

Alloy-

Days to failure (per specimen, below)

Version	1st	2nd	3rd	4th	5th	6th	7th	8th

Alloy 1-3	7	10	10	17	19	N/A	N/A	N/A
Alloy 1-4	14	17	19	21	21	N/A	N/A	N/A
Alloy 2-3	8	11	12	12	22	N/A	N/A	N/A
Alloy 2-4	12	14	20	22	N/A	N/A	N/A	N/A
Alloy 4-3	12	14	21	26	27	29	34	40
Alloy 4-4	16	32	39	40	41	41	N/A	N/A
Alloy 5-3	28	39	41	44	50	57	N/A	N/A
Alloy 5-4	44	65	65	75	117	148	T(216)	N/A
7085-3	4	4	4	6	8	8	14	N/A
7085-4	9	N/A	N/A	N/A	N/A	N/A	N/A	N/A
7085-5	5	5	7	10	T(40)	N/A	N/A	N/A
7085-6	7	12	N/A	N/A	N/A	N/A	N/A	N/A
7085-7	8	14	N/A	N/A	N/A	N/A	N/A	N/A
7050-3	47	47	61	84	86	N/A	N/A	N/A
7050-4	77	90	98	103	117	N/A	N/A	N/A
7050-5	T(40)	T(40)	T(40)	T(40)	T(40)	N/A	N/A	N/A
7050-6	90	107	117	N/A	N/A	N/A	N/A	N/A
7050-7	69	100	100	N/A	N/A	N/A	N/A	N/A

*T(#) means the indicated specimen did not failed after the specified number of days in testing, e.g., “T(7)” means the specimen did not failed after 7 days of testing.

Various ones of the Example 2 alloys were also subjected to stress corrosion cracking (SCC) resistance in accordance with ASTM G44, 3.5% NaCl, Alternate Immersion, the results of which are shown in Table 9, below.

TABLE 9

ASTM G44 Results*

Alloy-

Days to failure (per specimen, below)

Version	1st	2nd	3rd	4th	5th

Alloy 2-3	64	83	69	83	58
Alloy 2-4	OK90	90	90	90	90
Alloy 4-3	90	OK90	90	90	90
Alloy 4-4	90	85	77	86	85
Alloy 5-3	OK90	OK90	OK90	47	OK90
Alloy 5-4	OK90	OK90	OK90	OK90	OK90
7085-3	90	56	61	83	44

*“OK90” means the sample passed final examination after 90 days of testing as per ASTM G47.

ASTM G168 testing per Example 1 was also tested on various ones of the Example 2 alloys. FIG. 3 shows the results. Data for a conventional 7085 plate product (plant produced) is also provided in FIG. 3 for comparison purposes. Similar to the Example 1 results, the alloys having silver realized a much lower crack growth rate and a much higher threshold stress intensity (K_ISCC).
These above results of Example 2 show that the new 7xxx+Ag alloys realize an improved combination of at least two of strength, ductility, fracture toughness and corrosion resistance.
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

What is claimed is:

1. A wrought 7xxx aluminum alloy product, wherein the wrought 7xxx aluminum alloy product comprises:

from 0.05 to 1.0 wt. % Ag;

from 1.2 to 2.6 wt. % Cu;

from 1.3 to 2.5 wt. % Mg;

from 5.5 to 9.0 wt. % Zn;

up to 0.60 wt. % Mn;

up to 1.0 wt. % of at least one grain structure control material, wherein the at least one grain structure control material is selected from the group consisting of Zr, Cr, V, Hf, other rare earth elements, and combinations thereof,

up to 0.30 wt. % Fe;

up to 0.30 wt. % Si;

up to 0.15 wt. % Ti;

not greater than 0.08 wt. % Sc;

not greater than 0.05 wt. % Li;

the balance being aluminum, optional incidental elements and impurities;

wherein the wrought 7xxx aluminum alloy product has a thickness of from 12.7 to 305 mm.

2. The wrought 7xxx aluminum alloy product of claim 1, wherein the 7xxx aluminum alloy comprises from 6.0 to 8.5 wt. % Zn.

3. The wrought 7xxx aluminum alloy product of claim 2, wherein the 7xxx aluminum alloy comprises from 1.5 to 2.0 wt. % Cu.

4. The wrought 7xxx aluminum alloy product of claim 3, wherein the 7xxx aluminum alloy comprises from 1.4 to 2.0 wt. % Mg.

5. The wrought 7xxx aluminum alloy product of claim 1, wherein (wt. % Cu)+(wt. % Mg)≥3.0 wt. %.

6. The wrought 7xxx aluminum alloy product of claim 1, wherein the 7xxx aluminum alloy comprises at least 0.10 wt. % Ag.

7. The wrought 7xxx aluminum alloy product of claim 1, wherein the 7xxx aluminum alloy comprises not greater than 0.7 wt. % Ag.

8. The wrought 7xxx aluminum alloy product of claim 1, wherein the 7xxx aluminum alloy comprises from 0.10 to 0.50 wt. % Mn.

9. The wrought 7xxx aluminum alloy product of claim 1, wherein the 7xxx aluminum alloy comprises not greater than 0.01 wt. % Mn.

10. The wrought 7xxx aluminum alloy product of claim 1, wherein the at least one grain structure control material is at least chromium, and wherein the 7xxx aluminum alloy comprises from 0.05 to 0.24 wt. % Cr.

11. The wrought 7xxx aluminum alloy product of claim 1, wherein the 7xxx aluminum alloy comprises not greater than 0.01 wt. % Cr.

12. The wrought 7xxx aluminum alloy product of claim 1, wherein the 7xxx aluminum alloy includes from 0.010 to 0.10 wt. % Ti.

13. The wrought 7xxx aluminum alloy product of claim 1, wherein the grain structure control material is at least Zr, and wherein the alloy includes 0.05 to 0.20 wt. % Zr.

14. The wrought 7xxx aluminum alloy product of claim 1, wherein the wrought aluminum alloy product realizes a typical tensile yield strength (ST) of at least 400 MPa in a T7 temper.

15. The wrought 7xxx aluminum alloy product of claim 14, wherein the wrought aluminum alloy product realizes a plane-strain (K_IC) fracture toughness (S-L) of at least 20 MPa-sqrt-m in a T7 temper.

16. The wrought 7xxx aluminum alloy product of claim 15, wherein the wrought aluminum alloy product realizes an elongation (ST) of at least 2.0% in a T7 temper.

17. The wrought 7xxx aluminum alloy product of claim 16, wherein the wrought aluminum alloy product passes HHSCC-G49 testing at 70° C. at 100 days or at 90° C. for 10 days.

18. The wrought 7xxx aluminum alloy product of claim 17, wherein the wrought aluminum alloy product passes SCC alternate immersion testing at 20 days and a net stress (ST) of 172 MPa.

19. The wrought 7xxx aluminum alloy product of claim 18, wherein the wrought aluminum alloy product passes HHSCC-G168, wherein the stress intensity factor gives a crack growth rate of not greater than 10⁻⁷mm/s, and wherein the realized K value is at least 13 MPa-sqrt-m (MPa√m).