THICK WROUGHT 7XXX ALUMINUM ALLOYS, AND METHODS FOR MAKING THE SAME

Disclosed are improved thick wrought 7xxx aluminum alloy products, and methods for producing the same. The new 7xxx aluminum alloy products may realize an improved combination of environmentally assisted crack resistance and at least one of strength, elongation, and fracture toughness, among other properties. The new 7xxx aluminum alloy products generally include high amounts of manganese. The new 7xxx aluminum alloy products thus generally include from 0.15 to 0.50 wt. % Mn in combination with 5.5-7.5 wt. % Zn, 0.95-2.20 wt. % Mg, and 1.50-2.40 wt. % Cu.

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Description
CROSS-REFERENCE TO RELATED APPLICATIONS

This patent application is a continuation of International Patent Application No. PCT/US2018/038838, filed Jun. 21, 2018, which claims priority to (a) U.S. Provisional Patent Application No. 62/523,128, filed Jun. 21, 2017, entitled “IMPROVED THICK WROUGHT 7XXX ALUMINUM ALLOYS, AND METHODS FOR MAKING THE SAME”, and (b) to U.S. Provisional Patent Application No. 62/571,401, filed Oct. 12, 2017, entitled “IMPROVED THICK WROUGHT 7XXX ALUMINUM ALLOYS, AND METHODS FOR MAKING THE SAME”. Each of the above identified patent applications are incorporated herein by reference in their entirety.

FIELD OF THE INVENTION

The present patent application relates to improved thick wrought 7xxx aluminum alloy products and methods for producing 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. Grubl, “The stress corrosion behaviour of high strength AlZnMg alloys,” Paper held at the International Meeting of Associazione Italiana di Metallurgie, “Aluminum Alloys in Aircraft Industries,” Turin, October 1976.

SUMMARY OF THE DISCLOSURE

Broadly, the present patent application relates to improved thick wrought 7xxx aluminum alloy products, and methods for producing the same. The new thick wrought 7xxx aluminum alloy products (“the new 7xxx aluminum alloy products”) may realize an improved combination of environmentally assisted crack resistance and at least one of strength, elongation, and fracture toughness, among other properties.

The new 7xxx aluminum alloy products generally include high amounts of manganese. Manganese in combination with appropriate amounts of zinc, magnesium, and copper has been found to facilitate production of thick 7xxx aluminum alloy products having a high resistance to environmentally assisted cracking. The new 7xxx aluminum alloy products thus generally include (and in some instances consist of, or consist essentially of) from 0.15 to 0.50 wt. % Mn in combination with 5.5-7.5 wt. % Zn, 0.95-2.20 wt. % Mg, and 1.50-2.40 wt. % Cu. The new wrought 7xxx aluminum alloy products are generally at least 1.5 inches thick, and may be up to 12 inches thick, and realize resistance to environmentally assisted cracking in the short transverse (ST) direction, which resistance is important for aerospace and other applications, especially those with structural loading in the short transverse (ST) direction. Such thick, wrought 7xxx aluminum alloy product generally also realize good strength, elongation, fracture toughness and crack-deviation resistance properties. Thus, the new wrought 7xxx aluminum alloy products generally realize an improved combination of corrosion resistance and at least one of strength, elongation, fracture toughness and crack-deviation resistance. In addition to manganese, zinc, magnesium and copper, the new 7xxx aluminum alloy products may include normal grain structure control materials, grain refiners, and impurities. For instance, the new 7xxx aluminum alloy products may include one or more of Zr, Cr, Sc, and Hf as grain structure control materials (e.g., from 0.05-0.25 wt. % each of one or more of Zr, Cr, Sc, and Hf), limiting the total amounts of these elements such that large primary particles do not form in the alloy. As another example, the new 7xxx aluminum alloy products may include up to 0.15 wt. % Ti as a grain refiner, optionally with some of the titanium in the form of TiB2 and/or TiC. The new 7xxx aluminum alloy products may include up to 0.20 wt. % Fe and up to 0.15 wt. % Si as impurities. Lower amounts of iron and silicon may be used. The balance of the new 7xxx aluminum alloy products is generally aluminum and other unavoidable impurities (other than iron and silicon).

As noted above, the new 7xxx aluminum alloy products generally include from 0.15 to 0.50 wt. % Mn. The new 7xxx aluminum alloy products generally include a sufficient amount of the manganese to facilitate realization of environmentally assisted crack resistance (EAC resistance) in the new 7xxx aluminum alloy products. In one embodiment, a new 7xxx aluminum alloy product includes at least 0.18 wt. % Mn to facilitate EAC resistance. In another embodiment, a new 7xxx aluminum alloy product includes at least 0.20 wt. % Mn. In yet another embodiment, a new 7xxx aluminum alloy product includes at least 0.22 wt. % Mn. In another embodiment, a new 7xxx aluminum alloy product includes at least 0.25 wt. % Mn. In yet another embodiment, a new 7xxx aluminum alloy product includes at least 0.275 wt. % Mn.

The amount of manganese should be limited to restrict imparting undue quench sensitivity to the new 7xxx aluminum alloy products. In one embodiment, a new 7xxx aluminum alloy product includes not greater than 0.45 wt. % Mn. In another embodiment, a new 7xxx aluminum alloy product includes not greater than 0.40 wt. % Mn. In yet another embodiment, a new 7xxx aluminum alloy product includes not greater than 0.375 wt. % Mn. In another embodiment, a new 7xxx aluminum alloy product includes not greater than 0.35 wt. % Mn. In another embodiment, a new 7xxx aluminum alloy product includes not greater than 0.325 wt. % Mn. In yet another embodiment, a new 7xxx aluminum alloy product includes not greater than 0.30 wt. % Mn.

As noted above, the new 7xxx aluminum alloy products generally include tailored amounts of zinc, magnesium and copper, in addition to the manganese, to facilitate realization of EAC resistance in combination with good strength and/or fracture toughness properties, among others. In this regard, the new 7xxx aluminum alloy products generally include from 0.15 to 0.50 wt. % Mn, such as any of the manganese limits/ranges described above, in combination with 5.5-7.5 wt. % Zn, 0.95-2.20 wt. % Mg, and 1.50-2.4 wt. % Cu. In one embodiment, the new 7xxx aluminum alloy products generally include from 0.15 to 0.50 wt. % Mn, such as any of the manganese limits/ranges described above, in combination with 5.5-7.2 wt. % Zn, 1.05-2.05 wt. % Mg, and 1.5-2.2 wt. % Cu.

As noted above, the new 7xxx aluminum alloy products generally include from 5.5 to 7.5 wt. % Zn. In one embodiment, a new alloy includes not greater than 7.4 wt. % Zn. In another embodiment, a new alloy includes not greater than 7.3 wt. % Zn. In yet another embodiment, a new alloy includes not greater than 7.2 wt. % Zn. In another embodiment, a new alloy includes not greater than 7.1 wt. % Zn. In another embodiment, a new alloy includes not greater than 7.0 wt. % Zn. In yet another embodiment, a new alloy includes not greater than 6.9 wt. % Zn. In another embodiment, a new alloy includes not greater than 6.8 wt. % Zn. In yet another embodiment, a new alloy includes not greater than 6.7 wt. % Zn. In one embodiment, a new alloy includes at least 5.5 wt. % Zn. In another embodiment, a new alloy includes at least 5.75 wt. % Zn. In yet another embodiment, a new alloy includes at least 6.0 wt. % Zn. In another embodiment, a new alloy includes at least 6.25 wt. % Zn. In another embodiment, a new alloy includes at least 6.375 wt. % Zn. In another embodiment, a new alloy includes at least 6.5 wt. % Zn.

As noted above, the new 7xxx aluminum alloy products generally include from 1.5 to 2.4 wt. % Cu. In one embodiment, a new alloy includes not greater than 2.3 wt. % Cu. In another embodiment, a new alloy includes not greater than 2.2 wt. % Cu. In one embodiment, a new alloy includes not greater than 2.1 wt. % Cu. In another embodiment, a new alloy includes not greater than 2.0 wt. % Cu. In one embodiment, a new alloy includes at least 1.55 wt. % Cu. In another embodiment, a new alloy includes at least 1.60 wt. % Cu. In yet another embodiment, a new alloy includes at least 1.65 wt. % Cu. In yet another embodiment, a new alloy includes at least 1.70 wt. % Cu. In yet another embodiment, a new alloy includes at least 1.75 wt. % Cu. In another embodiment, a new alloy includes at least 1.80 wt. % Cu.

As noted above, the new 7xxx aluminum alloy products generally include from 0.95 to 2.2 wt. % Mg. In one embodiment, a new alloy includes at least 1.05 wt. % Mg. In another embodiment, a new alloy includes at least 1.15 wt. % Mg. In yet another embodiment, a new alloy includes at least 1.25 wt. % Mg. In another embodiment, a new alloy includes at least 1.35 wt. % Mg. In yet another embodiment, a new alloy includes at least 1.40 wt. % Mg. In another embodiment, a new alloy includes at least 1.45 wt. % Mg. In yet another embodiment, a new alloy includes at least 1.50 wt. % Mg. In another embodiment, a new alloy includes at least 1.55 wt. % Mg. In another embodiment, a new alloy includes at least 1.60 wt. % Mg. In yet another embodiment, a new alloy includes at least 1.65 wt. % Mg. In another embodiment, a new alloy includes at least 1.70 wt. % Mg. In one embodiment, a new alloy includes not greater than 2.15 wt. % Mg. In another embodiment, a new alloy includes not greater than 2.10 wt. % Mg. In yet another embodiment, a new alloy includes not greater than 2.05 wt. % Mg. In another embodiment, a new alloy includes not greater than 2.00 wt. % Mg. In another embodiment, a new alloy includes not greater than 1.95 wt. % Mg. In yet another embodiment, a new alloy includes not greater than 1.90 wt. % Mg.

In one embodiment, a first 7xxx aluminum alloy product includes from 5.5-7.5 wt. % Zn, 1.7-2.2 wt. % Mg and 1.5-2.4 wt. % Cu. In one embodiment, the first 7xxx aluminum alloy product includes not greater than 7.2 wt. % Zn or not greater than 7.0 wt. % Zn (e.g., to facilitate improved EAC resistance). In one embodiment, the first 7xxx aluminum alloy product comprises 6.0-7.0 wt. % Zn.

In another embodiment, a second 7xxx aluminum alloy product includes from 5.5-7.5 wt. % Zn, 1.35-1.7 wt. % Mg and 1.5-2.1 wt. % Cu. The first 7xxx aluminum alloy product may realize, for instance, higher strength than the second aluminum alloy product, but possibly at the expense of reduced fracture toughness and/or reduced elongation. In one embodiment, the second 7xxx aluminum alloy product includes not greater than 7.2 wt. % Zn or not greater than 7.0 wt. % Zn (e.g., to facilitate improved EAC resistance). In one embodiment, the second 7xxx aluminum alloy product comprises 6.0-7.0 wt. % Zn.

In another embodiment, a third 7xxx aluminum alloy product includes from 5.5-7.5 wt. % Zn, 1.7-2.2 wt. % Mg and 1.5-1.8 wt. % Cu. This third 7xxx aluminum alloy product may be a lower strength zone of the first 7xxx aluminum alloy product region. In one embodiment, the third 7xxx aluminum alloy product includes not greater than 7.2 wt. % Zn or not greater than 7.0 wt. % Zn (e.g., to facilitate improved EAC resistance). In one embodiment, the third 7xxx aluminum alloy product comprises 6.0-7.0 wt. % Zn.

In another embodiment, a fourth 7xxx aluminum alloy product includes from 5.5-7.5 wt. % Zn, 1.7-2.2 wt. % Mg and 1.8-2.0 wt. % Cu. This forth 7xxx aluminum alloy product may be a middle strength zone of the first 7xxx aluminum alloy product region. In one embodiment, the fourth 7xxx aluminum alloy product includes not greater than 7.2 wt. % Zn or not greater than 7.0 wt. % Zn (e.g., to facilitate improved EAC resistance). In one embodiment, the fourth 7xxx aluminum alloy product comprises 6.0-7.0 wt. % Zn.

In another embodiment, a fifth 7xxx aluminum alloy product includes from 5.5-7.5 wt. % Zn, 1.7-2.2 wt. % Mg and 2.0-2.4 wt. % Cu. This fifth 7xxx aluminum alloy product may be a higher strength zone of the first 7xxx aluminum alloy product region. In one embodiment, a fifth 7xxx aluminum alloy product includes 2.0-2.2 wt. % Cu. In one embodiment, the fifth 7xxx aluminum alloy product includes not greater than 7.2 wt. % Zn or not greater than 7.0 wt. % Zn (e.g., to facilitate improved EAC resistance). In one embodiment, the fifth 7xxx aluminum alloy product comprises 6.0-7.0 wt. % Zn.

The third 7xxx aluminum alloy product may realize higher toughness and/or elongation as compared to the fourth or fifth aluminum alloy products. The fourth 7xxx aluminum alloy product may realize higher toughness and/or elongation as compared to the fifth aluminum alloy products.

In one embodiment, a new alloy includes a total amount of copper and magnesium such that (wt. % Cu+wt. % Mg)≥2.9 wt. %. In another embodiment, a new alloy includes a total amount of copper and magnesium such that (wt. % Cu+wt. % Mg)≥3.0 wt. %. In yet another embodiment, a new alloy includes a total amount of copper and magnesium such that (wt. % Cu+wt. % Mg)≥3.1 wt. %. In another embodiment, a new alloy includes a total amount of copper and magnesium such that (wt. % Cu+wt. % Mg)≥3.2 wt. %. In another embodiment, a new alloy includes a total amount of copper and magnesium such that (wt. % Cu+wt. % Mg)≥3.3 wt. %. In yet another embodiment, a new alloy includes a total amount of copper and magnesium such that (wt. % Cu+wt. % Mg)≥3.35 wt. %. In another embodiment, a new alloy includes a total amount of copper and magnesium such that (wt. % Cu+wt. % Mg)≥3.4 wt. %. In yet another embodiment, a new alloy includes a total amount of copper and magnesium such that (wt. % Cu+wt. % Mg)≥3.45 wt. %. In another embodiment, a new alloy includes a total amount of copper and magnesium such that (wt. % Cu+wt. % Mg)≥3.5 wt. %. In yet another embodiment, a new alloy includes a total amount of copper and magnesium such that (wt. % Cu+wt. % Mg)≥3.55 wt. %. In another embodiment, a new alloy includes a total amount of copper and magnesium such that (wt. % Cu+wt. % Mg)≥3.6 wt. %. In yet another embodiment, a new alloy includes a total amount of copper and magnesium such that (wt. % Cu+wt. % Mg)≥3.65 wt. %. In another embodiment, a new alloy includes a total amount of copper and magnesium such that (wt. % Cu+wt. % Mg)≥3.7 wt. %.

In one embodiment, a new alloy includes a total amount of copper and magnesium such that (wt. % Cu+wt. % Mg)≤4.5 wt. %. In another embodiment, a new alloy includes a total amount of copper and magnesium such that (wt. % Cu+wt. % Mg)≤4.4 wt. %. In yet another embodiment, a new alloy includes a total amount of copper and magnesium such that (wt. % Cu+wt. % Mg)≤4.3 wt. %. In another embodiment, a new alloy includes a total amount of copper and magnesium such that (wt. % Cu+wt. % Mg)≤4.2 wt. %. In yet another embodiment, a new alloy includes a total amount of copper and magnesium such that (wt. % Cu+wt. % Mg)≤4.1 wt. %. In another embodiment, a new alloy includes a total amount of copper and magnesium such that (wt. % Cu+wt. % Mg)≤4.0 wt. %.

In one embodiment, the amounts of zinc, magnesium and copper within the 7xxx aluminum alloy product satisfy the relationship: 2.362≤Mg+0.429*Cu+0.067*Zn≤3.062. In another embodiment, the amounts of zinc, magnesium and copper within the 7xxx aluminum alloy product satisfy the relationship: 2.502≤Mg+0.429*Cu+0.067*Zn≤2.912. In yet another embodiment, the amounts of zinc, magnesium and copper within the 7xxx aluminum alloy product satisfy the relationship: 2.662≤Mg+0.429*Cu+0.067*Zn≤3.062. In another embodiment, the amounts of zinc, magnesium and copper within the 7xxx aluminum alloy product satisfy the relationship: 2.662≤Mg+0.429*Cu+0.067*Zn≤2.912. Any of the zinc, magnesium, and copper amounts described in the preceding paragraphs may be used in combination with the above-shown empirical relationships.

In one approach, the amounts of zinc and magnesium within the 7xxx aluminum alloy product are such that the weight ratio of zinc-to-magnesium is not greater than 5.25:1 (i.e., (wt. % Zn/wt. % Mg)≤5.25:1). In one embodiment, a weight ratio of zinc-to-magnesium is not greater than 5.00:1 (i.e., (wt. % Zn/wt. % Mg)≤5.00:1). In another embodiment, a weight ratio of zinc-to-magnesium is not greater than 4.75:1 (i.e., (wt. % Zn/wt. % Mg)≤4.75:1). In yet another embodiment, a weight ratio of zinc-to-magnesium is not greater than 4.60:1 (i.e., (wt. % Zn/wt. % Mg)≤4.60:1). In another embodiment, a weight ratio of zinc-to-magnesium is not greater than 4.50:1 (i.e., (wt. % Zn/wt. % Mg)≤4.50:1).

In yet another embodiment, a weight ratio of zinc-to-magnesium is not greater than 4.40:1 (i.e., (wt. % Zn/wt. % Mg)≤4.40:1). In another embodiment, a weight ratio of zinc-to-magnesium is not greater than 4.35:1 (i.e., (wt. % Zn/wt. % Mg)≤4.35:1). In yet another embodiment, a weight ratio of zinc-to-magnesium is not greater than 4.30:1 (i.e., (wt. % Zn/wt. % Mg)≤4.30:1). In another embodiment, a weight ratio of zinc-to-magnesium is not greater than 4.25:1 (i.e., (wt. % Zn/wt. % Mg)≤4.25:1). In yet another embodiment, a weight ratio of zinc-to-magnesium is not greater than 4.20:1 (i.e., (wt. % Zn/wt. % Mg)≤4.20:1). In another embodiment, a weight ratio of zinc-to-magnesium is not greater than 4.15:1 (i.e., (wt. % Zn/wt. % Mg)≤4.15:1). In yet another embodiment, a weight ratio of zinc-to-magnesium is not greater than 4.10:1 (i.e., (wt. % Zn/wt. % Mg)≤4.10:1). In another embodiment, a weight ratio of zinc-to-magnesium is not greater than 4.00:1 (i.e., (wt. % Zn/wt. % Mg)≤4.00:1). In yet another embodiment, a weight ratio of zinc-to-magnesium is not greater than 3.95:1 (i.e., (wt. % Zn/wt. % Mg)≤3.95:1). In another embodiment, a weight ratio of zinc-to-magnesium is not greater than 3.90:1 (i.e., (wt. % Zn/wt. % Mg)≤3.90:1).

In one approach, the amounts of zinc and magnesium within the 7xxx aluminum alloy product are such that the weight ratio of zinc-to-magnesium is at least 3.0:1 (i.e., (wt. % Zn/wt. % Mg)≥3.0:1). In one embodiment, the amounts of zinc and magnesium within the 7xxx aluminum alloy product are such that the weight ratio of zinc-to-magnesium is at least 3.25:1 (i.e., (wt. % Zn/wt. % Mg)≥3.25:1). In another embodiment, the amounts of zinc and magnesium within the 7xxx aluminum alloy product are such that the weight ratio of zinc-to-magnesium is at least 3.33:1 (i.e., (wt. % Zn/wt. % Mg)≥3.33:1). In yet another embodiment, the amounts of zinc and magnesium within the 7xxx aluminum alloy product are such that the weight ratio of zinc-to-magnesium is at least 3.45:1 (i.e., (wt. % Zn/wt. % Mg)≥3.45:1). In another embodiment, the amounts of zinc and magnesium within the 7xxx aluminum alloy product are such that the weight ratio of zinc-to-magnesium is at least 3.55:1 (i.e., (wt. % Zn/wt. % Mg)≥3.55:1). In yet another embodiment, the amounts of zinc and magnesium within the 7xxx aluminum alloy product are such that the weight ratio of zinc-to-magnesium is at least 3.60:1 (i.e., (wt. % Zn/wt. % Mg)≥3.60:1).

As noted above, the new 7xxx aluminum alloy product may include one or more of Zr, Cr, Sc, and Hf as grain structure control materials (e.g., from 0.05-0.25 wt. % each of one or more of Zr, Cr, Sc, and Hf), 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). 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, Sc, 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 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.

In one embodiment, the grain structure control material is Zr, and a new 7xxx aluminum alloy product includes from 0.07 to 0.18 wt. % Zr. In another 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 yet 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 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 generally contains low amounts of the Cr, Sc, and Hf (e.g., ≤0.04 wt. % each of Cr, Sc, and Hf). In one embodiment, a new 7xxx aluminum alloy product contains not greater than 0.03 wt. % each of Cr, Sc, and Hf. In another embodiment, a new 7xxx aluminum alloy product contains not greater than 0.02 wt. % each of Cr, Sc, and Hf In another embodiment, a new 7xxx aluminum alloy product contains not greater than 0.01 wt. % each of Cr, Sc, and Hf In another embodiment, a new 7xxx aluminum alloy product contains not greater than 0.005 wt. % each of Cr, Sc, and Hf

In one embodiment, the grain structure control material is Cr, and a new 7xxx aluminum alloy product includes from 0.07 to 0.25 wt. % Cr. In another embodiment, the grain structure control material is Cr, and a new 7xxx aluminum alloy product includes from 0.07 to 0.20 wt. % Cr. In yet another embodiment, the grain structure control material is Cr, and a new 7xxx aluminum alloy product includes from 0.08 to 0.15 wt. % Cr. In another embodiment, the grain structure control material is Cr, and a new 7xxx aluminum alloy product includes from 0.10 to 0.15 wt. % Cr. In other embodiments, a new 7xxx aluminum alloy product contains low amounts of Cr (e.g., ≤0.04 wt. % Cr.) In one embodiment, a new 7xxx aluminum alloy product contains not greater than 0.03 wt. % Cr. In another embodiment, a new 7xxx aluminum alloy product contains not greater than 0.02 wt. % Cr. In yet another embodiment, a new 7xxx aluminum alloy product contains not greater than 0.01 wt. % Cr. In another embodiment, a new 7xxx aluminum alloy product contains not greater than 0.005 wt. % Cr.

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.

As noted above, the new 7xxx aluminum alloy product may include up to 0.15 wt. % Ti. Titanium may be used to facilitate grain refining during casting, such as by using TiB2 or TiC. Elemental titanium may also or alternatively be used. In one embodiment, the new 7xxx aluminum alloy product includes from 0.005 to 0.025 wt. % Ti.

As noted above, the new 7xxx aluminum alloy product may include up to 0.15 wt. % Si and up to 0.20 wt. % Fe as impurities. The amount of silicon and iron may be limited so as to avoid detrimentally impacting the combination of strength, fracture toughness and crack deviation resistance. In one embodiment, the new 7xxx aluminum alloy product may include up to 0.12 wt. % Si and up to 0.15 wt. % Fe as impurities. In another embodiment, the new 7xxx aluminum alloy product may include up to 0.10 wt. % Si and up to 0.12 wt. % Fe as impurities. In another embodiment, the new 7xxx aluminum alloy product may include up to 0.08 wt. % Si and up to 0.10 wt. % Fe as impurities. In yet another embodiment, the new 7xxx aluminum alloy product may include up to 0.06 wt. % Si and up to 0.08 wt. % Fe as impurities. In yet another embodiment, the new 7xxx aluminum alloy product may include up to 0.04 wt. % Si and up to 0.06 wt. % Fe as impurities. In another embodiment, the new 7xxx aluminum alloy product may include up to 0.03 wt. % Si and up to 0.05 wt. % Fe as impurities.

As noted above, the new 7xxx aluminum alloy product has a thickness of from 1.5 to 12.0 inches. In one embodiment, the new 7xxx aluminum alloy product has a thickness of from 2.0 to 10.0 inches. In another embodiment, the new 7xxx aluminum alloy product has a thickness of from 3.0 to 8.0 inches (7.62-20.3 cm). In another embodiment, the new 7xxx aluminum alloy product has a thickness of from 1.5 to 8.0 inches. In another embodiment, the new 7xxx aluminum alloy product has a thickness of from 1.5 to 6.0 inches. In another embodiment, the new 7xxx aluminum alloy product has a thickness of from 1.5 to 4.0 inches. In another embodiment, the new 7xxx aluminum alloy product has a thickness of from 2.0 to 8.0 inches. In another embodiment, the new 7xxx aluminum alloy product has a thickness of from 2.0 to 6.0 inches. In another embodiment, the new 7xxx aluminum alloy product has a thickness of from 3.0 to 6.0 inches. In another embodiment, the new 7xxx aluminum alloy product has a thickness of from 4.0 to 10.0 inches. In another embodiment, the new 7xxx aluminum alloy product has a thickness of from 4.0 to 8.0 inches. In another embodiment, the new 7xxx aluminum alloy product has a thickness of from 4.0 to 6.0 inches.

In one embodiment, a new 7xxx aluminum alloy product is a rolled product (e.g., a plate product). In another embodiment, a new 7xxx aluminum alloy product is an extruded product. In yet another embodiment, a new 7xxx aluminum alloy product is a forged product (e.g., a hand forged product, a die forged product).

As mentioned above, the new 7xxx aluminum alloy products may realize an improved combination of properties. In one embodiment, a new 7xxx aluminum alloy product realizes a typical tensile yield strength (L) of at least 63 ksi as per ASTM E8 and B557. In another embodiment, a new 7xxx aluminum alloy product realizes a typical tensile yield strength (L) of at least 64 ksi. In yet another embodiment, a new 7xxx aluminum alloy product realizes a typical tensile yield strength (L) of at least 65 ksi. In another embodiment, a 7xxx aluminum alloy product may realize a typical tensile yield strength (L) of at least 66 ksi. In yet another embodiment, a 7xxx aluminum alloy product may realize a typical tensile yield strength (L) of at least 67 ksi. In another embodiment, a 7xxx aluminum alloy product may realize a typical tensile yield strength (L) of at least 68 ksi. In yet another embodiment, a 7xxx aluminum alloy product may realize a typical tensile yield strength (L) of at least 69 ksi. In another embodiment, a 7xxx aluminum alloy product may realize a typical tensile yield strength (L) of at least 70 ksi. In yet another embodiment, a 7xxx aluminum alloy product may realize a typical tensile yield strength (L) of at least 71 ksi. In another embodiment, a 7xxx aluminum alloy product may realize a typical tensile yield strength (L) of at least 72 ksi. In yet another embodiment, a 7xxx aluminum alloy product may realize a typical tensile yield strength (L) of at least 73 ksi.

In one embodiment, a new 7xxx aluminum alloy product realizes a typical tensile yield strength (ST) of at least 57 ksi as per ASTM E8 and B557. In another embodiment, a 7xxx aluminum alloy product may realize a typical tensile yield strength (ST) of at least 58 ksi. In yet another embodiment, a 7xxx aluminum alloy product may realize a typical tensile yield strength (ST) of at least 59 ksi. In another embodiment, a 7xxx aluminum alloy product may realize a typical tensile yield strength (ST) of at least 60 ksi. In yet another embodiment, a 7xxx aluminum alloy product may realize a typical tensile yield strength (ST) of at least 61 ksi. In another embodiment, a 7xxx aluminum alloy product may realize a typical tensile yield strength (ST) of at least 62 ksi. In yet another embodiment, a 7xxx aluminum alloy product may realize a typical tensile yield strength (ST) of at least 63 ksi. In another embodiment, a 7xxx aluminum alloy product may realize a typical tensile yield strength (ST) of at least 64 ksi. In yet another embodiment, a 7xxx aluminum alloy product may realize a typical tensile yield strength (ST) of at least 65 ksi. In another embodiment, a 7xxx aluminum alloy product may realize a typical tensile yield strength (ST) of at least 66 ksi.

In one embodiment, a new 7xxx aluminum alloy product realizes a typical KIC plane-strain fracture toughness (L-T) of at least 25 ksi-sqrt-inch as per ASTM E8 and E399-12. In yet another embodiment, a new 7xxx aluminum alloy product realizes a typical KIC plane-stain fracture toughness (L-T) of at least 27 ksi-sqrt-inch. In another embodiment, a new 7xxx aluminum alloy product realizes a typical KIC plane-stain fracture toughness (L-T) of at least 28 ksi-sqrt-inch. In yet another embodiment, a new 7xxx aluminum alloy product realizes a typical KIC plane-stain fracture toughness (L-T) of at least 29 ksi-sqrt-inch. In another embodiment, a new 7xxx aluminum alloy product realizes a typical KIC plane-stain fracture toughness (L-T) of at least 30 ksi-sqrt-inch. In yet another embodiment, a new 7xxx aluminum alloy product realizes a typical KIC plane-stain fracture toughness (L-T) of at least 31 ksi-sqrt-inch. In another embodiment, a new 7xxx aluminum alloy product realizes a typical KIC plane-stain fracture toughness (L-T) of at least 32 ksi-sqrt-inch. In yet another embodiment, a new 7xxx aluminum alloy product realizes a typical KIC plane-stain fracture toughness (L-T) of at least 33 ksi-sqrt-inch. In another embodiment, a new 7xxx aluminum alloy product realizes a typical KIC plane-stain fracture toughness (L-T) of at least 34 ksi-sqrt-inch. In yet another embodiment, a new 7xxx aluminum alloy product realizes a typical KIC plane-stain fracture toughness (L-T) of at least 35 ksi-sqrt-inch. In another embodiment, a new 7xxx aluminum alloy product realizes a typical KIC plane-stain fracture toughness (L-T) of at least 36 ksi-sqrt-inch. In yet another embodiment, a new 7xxx aluminum alloy product realizes a typical KIC plane-stain fracture toughness (L-T) of at least 37 ksi-sqrt-inch. In another embodiment, a new 7xxx aluminum alloy product realizes a typical KIC plane-stain fracture toughness (L-T) of at least 38 ksi-sqrt-inch. In yet another embodiment, a new 7xxx aluminum alloy product realizes a typical KIC plane-stain fracture toughness (L-T) of at least 39 ksi-sqrt-inch. In another embodiment, a new 7xxx aluminum alloy product realizes a typical KIC plane-stain fracture toughness (L-T) of at least 40 ksi-sqrt-inch. In yet another embodiment, a new 7xxx aluminum alloy product realizes a typical KIC plane-stain fracture toughness (L-T) of at least 41 ksi-sqrt-inch. In another embodiment, a new 7xxx aluminum alloy product realizes a typical KIC plane-stain fracture toughness (L-T) of at least 42 ksi-sqrt-inch. In yet another embodiment, a new 7xxx aluminum alloy product realizes a typical KIC plane-stain fracture toughness (L-T) of at least 43 ksi-sqrt-inch. In another embodiment, a new 7xxx aluminum alloy product realizes a typical KIC plane-stain fracture toughness (L-T) of at least 44 ksi-sqrt-inch. In yet another embodiment, a new 7xxx aluminum alloy product realizes a typical KIC plane-stain fracture toughness (L-T) of at least 45 ksi-sqrt-inch.

In one embodiment, a new 7xxx aluminum alloy product realizes a typical KIC plane-strain fracture toughness (S-L) of at least 20 ksi-sqrt-inch as per ASTM E8 and E399-12. In another embodiment, a new 7xxx aluminum alloy product realizes a typical KIC plane-strain fracture toughness (S-L) of at least 22 ksi-sqrt-inch. In another embodiment, a new 7xxx aluminum alloy product realizes a typical KIC plane-strain fracture toughness (S-L) of at least 24 ksi-sqrt-inch. In another embodiment, a new 7xxx aluminum alloy product realizes a typical KIC plane-strain fracture toughness (S-L) of at least 26 ksi-sqrt-inch. In another embodiment, a new 7xxx aluminum alloy product realizes a typical KIC plane-strain fracture toughness (S-L) of at least 28 ksi-sqrt-inch. In another embodiment, a new 7xxx aluminum alloy product realizes a typical KIC plane-strain fracture toughness (S-L) of at least 30 ksi-sqrt-inch. In another embodiment, a new 7xxx aluminum alloy product realizes a typical KIC plane-strain fracture toughness (S-L) of at least 32 ksi-sqrt-inch. In another embodiment, a new 7xxx aluminum alloy product realizes a typical KIC plane-strain fracture toughness (S-L) of at least 34 ksi-sqrt-inch. In another embodiment, a new 7xxx aluminum alloy product realizes a typical KIC plane-strain fracture toughness (S-L) of at least 36 ksi-sqrt-inch. In another embodiment, a new 7xxx aluminum alloy product realizes a typical KIC plane-strain fracture toughness (S-L) of at least 38 ksi-sqrt-inch. In another embodiment, a new 7xxx aluminum alloy product realizes a typical KIC plane-strain fracture toughness (S-L) of at least 40 ksi-sqrt-inch.

In one embodiment, a new 7xxx aluminum alloy product realizes a typical elongation (L) of at least 8% as per ASTM E8 and B557. In another embodiment, a new 7xxx aluminum alloy product realizes a typical elongation (L) of at least 9%. In yet another embodiment, a new 7xxx aluminum alloy product realizes a typical elongation (L) of at least 10%. In another embodiment, a new 7xxx aluminum alloy product realizes a typical elongation (L) of at least 11%. In yet another embodiment, a new 7xxx aluminum alloy product realizes a typical elongation (L) of at least 12%. In another embodiment, a new 7xxx aluminum alloy product realizes a typical elongation (L) of at least 13%. In yet another embodiment, a new 7xxx aluminum alloy product realizes a typical elongation (L) of at least 14%. In another embodiment, a new 7xxx aluminum alloy product realizes a typical elongation (L) of at least 15%. In yet another embodiment, a new 7xxx aluminum alloy product realizes a typical elongation (L) of at least 16%.

In one embodiment, a new 7xxx aluminum alloy product realizes a typical elongation (ST) of at least 3% as per ASTM E8 and B557. In another embodiment, a new 7xxx aluminum alloy product realizes a typical elongation (ST) of at least 4%. In yet another embodiment, a new 7xxx aluminum alloy product realizes a typical elongation (ST) of at least 5%. In another embodiment, a new 7xxx aluminum alloy product realizes a typical elongation (ST) of at least 6%. In yet another embodiment, a new 7xxx aluminum alloy product realizes a typical elongation (ST) of at least 7%. In another embodiment, a new 7xxx aluminum alloy product realizes a typical elongation (ST) of at least 8%. In yet another embodiment, a new 7xxx aluminum alloy product realizes a typical elongation (ST) of at least 9%. In another embodiment, a new 7xxx aluminum alloy product realizes a typical elongation (ST) of at least 10%.

In one embodiment, a new 7xxx aluminum alloy product realizes a typical L-S crack deviation resistance (Kmax-dev) of at least 25 ksi-sqrt-in. In another embodiment, a new 7xxx aluminum alloy product realizes a typical L-S crack deviation resistance (Kmax-dev) of at least 27 ksi-sqrt-in. In yet another embodiment, a new 7xxx aluminum alloy product realizes a typical L-S crack deviation resistance (max-dev) of at least 29 ksi-sqrt-in. In another embodiment, a new 7xxx aluminum alloy product realizes a typical L-S crack deviation resistance (Kmax-dev) of at least 31 ksi-sqrt-in. In yet another embodiment, a new 7xxx aluminum alloy product realizes a typical L-S crack deviation resistance (Kmax-dev) of at least 33 ksi-sqrt-in. In another embodiment, a new 7xxx aluminum alloy product realizes a typical L-S crack deviation resistance (Kmax-dev) of at least 35 ksi-sqrt-in. In yet another embodiment, a new 7xxx aluminum alloy product realizes a typical L-S crack deviation resistance (Kmax-dev) of at least 37 ksi-sqrt-in. In another embodiment, a new 7xxx aluminum alloy product realizes a typical L-S crack deviation resistance (Kmax-dev) of at least 39 ksi-sqrt-in. In yet another embodiment, a new 7xxx aluminum alloy product realizes a typical L-S crack deviation resistance (Kmax-dev) of at least 41 ksi-sqrt-in. In another embodiment, a new 7xxx aluminum alloy product realizes a typical L-S crack deviation resistance (Kmax-dev) of at least 43 ksi-sqrt-in. In yet another embodiment, a new 7xxx aluminum alloy product realizes a typical L-S crack deviation resistance (Kmax-dev) of at least 45 ksi-sqrt-in. In another embodiment, a new 7xxx aluminum alloy product realizes a typical L-S crack deviation resistance (Kmax-dev) of at least 47 ksi-sqrt-in. In yet another embodiment, a new 7xxx aluminum alloy product realizes a typical L-S crack deviation resistance (Kmax-dev) of at least 49 ksi-sqrt-in. In another embodiment, a new 7xxx aluminum alloy product realizes a typical L-S crack deviation resistance (Kmax-dev) of at least 50 ksi-sqrt-in.

In one embodiment, a new 7xxx aluminum alloy product realizes a typical EAC resistance at 85% of TYS-ST of at least 80 days. In another embodiment, a new 7xxx aluminum alloy product realizes a typical EAC resistance at 85% of TYS-ST of at least 100 days. In another embodiment, a new 7xxx aluminum alloy product realizes a typical EAC resistance at 85% of TYS-ST of at least 120 days. In another embodiment, a new 7xxx aluminum alloy product realizes a typical EAC resistance at 85% of TYS-ST of at least 140 days. In another embodiment, a new 7xxx aluminum alloy product realizes a typical EAC resistance at 85% of TYS-ST of at least 160 days. In another embodiment, a new 7xxx aluminum alloy product realizes a typical EAC resistance at 85% of TYS-ST of at least 180 days. In another embodiment, a new 7xxx aluminum alloy product realizes a typical EAC resistance at 85% of TYS-ST of at least 200 days. In another embodiment, a new 7xxx aluminum alloy product realizes a typical EAC resistance at 85% of TYS-ST of at least 220 days. In another embodiment, a new 7xxx aluminum alloy product realizes a typical EAC resistance at 85% of TYS-ST of at least 240 days. In another embodiment, a new 7xxx aluminum alloy product realizes a typical EAC resistance at 85% of TYS-ST of at least 260 days. In another embodiment, a new 7xxx aluminum alloy product realizes a typical EAC resistance at 85% of TYS-ST of at least 280 days. In another embodiment, a new 7xxx aluminum alloy product realizes a typical EAC resistance at 85% of TYS-ST of at least 300 days.

In one embodiment, a new 7xxx aluminum alloy product realizes a typical EAC resistance at 60% of TYS-ST of at least 90 days. In another embodiment, a new 7xxx aluminum alloy product realizes a typical EAC resistance at 60% of TYS-ST of at least 120 days. In another embodiment, a new 7xxx aluminum alloy product realizes a typical EAC resistance at 60% of TYS-ST of at least 150 days. In another embodiment, a new 7xxx aluminum alloy product realizes a typical EAC resistance at 60% of TYS-ST of at least 180 days. In another embodiment, a new 7xxx aluminum alloy product realizes a typical EAC resistance at 60% of TYS-ST of at least 210 days. In another embodiment, a new 7xxx aluminum alloy product realizes a typical EAC resistance at 60% of TYS-ST of at least 240 days. In another embodiment, a new 7xxx aluminum alloy product realizes a typical EAC resistance at 60% of TYS-ST of at least 270 days. In another embodiment, a new 7xxx aluminum alloy product realizes a typical EAC resistance at 60% of TYS-ST of at least 300 days. In another embodiment, a new 7xxx aluminum alloy product realizes a typical EAC resistance at 60% of TYS-ST of at least 330 days. In another embodiment, a new 7xxx aluminum alloy product realizes a typical EAC resistance at 60% of TYS-ST of at least 360 days. In another embodiment, a new 7xxx aluminum alloy product realizes a typical EAC resistance at 60% of TYS-ST of at least 390 days. In another embodiment, a new 7xxx aluminum alloy product realizes a typical EAC resistance at 60% of TYS-ST of at least 420 days. In another embodiment, a new 7xxx aluminum alloy product realizes a typical EAC resistance at 60% of TYS-ST of at least 450 days. In another embodiment, a new 7xxx aluminum alloy product realizes a typical EAC resistance at 60% of TYS-ST of at least 480 days. In another embodiment, a new 7xxx aluminum alloy product realizes a typical EAC resistance at 60% of TYS-ST of at least 500 days.

As noted above, the new thick 7xxx aluminum alloy products may be suitable for parts in various aerospace applications. In one embodiment, the alloy product is an aerospace structural component. The aircraft structural component may be any of an upper wing panel (skin), an upper wing stringer, an upper wing cover with integral stringers, a spar, a spar cap, a spar web, a rib, rib feet or a rib web, stiffening elements, frames, a landing gear component (e.g., a cylinders, beams), drag braces, bulkheads, flap track assemblies, fuselage and windshield frames, gear ribs, side stays, fittings, a fuselage component (e.g., a fuselage skin), and space components (e.g., for rockets and other vehicles that may exit the earth). In one embodiment, the alloy product is an armor component (e.g., of a motorized vehicle). In one embodiment, the alloy product is used in the oil and gas industry (e.g., as pipes, structural components). In one embodiment, the alloy product is a thick mold block/mold plate product (e.g., for injection molding). In one embodiment, the alloy product is an automotive product.

The new thick 7xxx aluminum alloy products may be made into wrought products by casting an aluminum alloy having any of the aforementioned compositions into an ingot or billet, followed by homogenizing of the ingot or billet. The homogenized ingot or billet may worked by rolling, extruding, or forging to final gauge, generally by hot working, optionally with some cold working. The final gauge product may be solution heat treated, and then quenched, and then stress relieved (e.g., by stretching or compression) and then artificially aged.

Aside from traditional wrought products, the new 7xxx aluminum alloys may be made into shape castings or by additive manufacturing into additively manufactured products. The additively manufactured products may be used as-is, or may be subsequently processed, e.g., processed via mechanical, thermal, or thermomechanical treatment.

Definitions

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 (KIC) (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/4 location 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 (KIC) (L-T) being the average of the at least 6 different valid KIC measured specimen values.

As used herein, “typical plane strain fracture toughness (KIC) (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 (KIC) (S-L) being the average of the at least 6 different valid KIC measured 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

The typical L-S crack deviation resistance properties (Kmax-dev) are to be determined per the procedure described in commonly-owned U.S. Patent Application Publication No. 2017/0088920, paragraph 0058, which procedure is incorporated herein by reference, except: (a) the “W” dimension of the specimen shall be 2.0 inches (5.08 cm), (b) the specimen shall be centered at T/2 (as opposed to the notch tip), and (c) the test specimens may be tested in lab air as opposed to high humidity air.

As used herein, “EAC resistance” is tested per ASTM G49 and per the conditions defined below. 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. 3 (the dimensions of FIG. 3 are in inches). If the final product thickness is at least 2.25 inches, then the length of the tensile specimen is 2.00 inches, as shown in FIG. 3. If the final product thickness is from 1.50 inches to less than 2.25 inches, the length of the specimen must be at least 1.25 inches and should be as close to 2.00 inches 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% or 60% of their ST tensile yield strength (strength being measured at room temperature). 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. At least three specimens must be tested. The “typical EAC resistance” is the lowest failure date of the at least three specimens. For instance, if specimen A fails at 76 days, but specimens B and C fail at 140 and 180 days, respectively, the “typical EAC resistance” is 76 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 not included when determining typical EAC resistance. A thread failure is when a crack occurs in a threaded end of a specimen as opposed to in the gauge length. Thread failures are generally not detectable until the specimen is removed from the stressing frame.

The term “square root” may be abbreviated herein as “sqrt.”

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, as described below, 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 showing EAC resistance properties of Example 1 alloys at 85% of its TYS-ST.

FIG. 2 is a graph showing EAC resistance properties of Example 1 alloys at 60% of its TYS-ST.

FIG. 3 is an illustration of a tensile specimen for testing EAC resistance properties.

FIG. 4 is a graph showing EAC resistance properties of Example 3 alloys at 85% of its TYS-ST.

FIG. 5 is a graph showing EAC resistance properties of Example 3 alloys at 60% of its TYS-ST.

FIG. 6 is a graph showing EAC resistance properties of Example 4 alloys at 85% of its TYS-ST.

FIG. 7 is a graph showing EAC resistance properties of Example 4 alloys at 60% of its TYS-ST.

 DETAILED DESCRIPTION Example 1

Various 7xxx aluminum alloys were cast as six inch (15.24 cm) thick ingots (nominal). The actual compositions of the cast ingots are shown in Table 1, below. 7085-LS is a lab scale version of a conventional aluminum alloy, registered with the Aluminum Association as aluminum alloy 7085. The registered version of the 7085 alloy requires, among other things, 0.08-0.15 wt. % Zr, not greater than 0.04 wt. % Mn and not greater than 0.04 wt. % Cr, as shown by the document “International Alloy Designations and Chemical Composition Limits for Wrought Aluminum and Wrought Aluminum Alloys”, The Aluminum Association (2009), page 12. Commonly-owned U.S. Pat. No. 6,972,110 (among others) also relates to the 7085 alloy. Alloys 1-7 are new alloys having lower amounts of zinc (Zn) and/or also having manganese (Mn).

TABLE 1 Composition of Example 1 Alloys (wt. %) - Lab Scale Materials Alloy Si Fe Cu Mn Mg Cr Zn Ti Zr 1 0.02 0.04 1.68 0.23 1.55 — 7.42 0.03 0.11 2 0.02 0.05 1.59 0.35 1.47 — 6.48 0.03 0.11 3 0.02 0.04 1.62 0.35 1.39 0.12 6.43 0.02 0.11 4 0.03 0.04 1.74 0.34 1.34 — 7.44 0.03 0.10 5 0.02 0.04 1.67 0.36 1.33 0.15 7.52 0.02 0.11 6 0.02 0.04 1.92 0.36 1.53 — 6.41 0.02 0.11 7 0.02 0.04 1.69 0.35 1.71 — 6.43 0.02 0.11 7085-LS 0.02 0.04 1.67 — 1.51 — 7.64 0.02 0.11

The balance of each alloy was aluminum and unavoidable impurities (≤0.03 wt. % each, ≤0.10 wt. % total). After casting, the ingots were stress-relieved, sawed into multiple sections, scalped, homogenized, and then hot rolled to plate having a final gauge of about 1.75 inches (4.445 cm). The alloy plates were then solution heat treated and then hot water quenched in 190° F. water (87.8° C.) to simulate cooling conditions at T/2 (mid-thickness) for 5 inch plate relative to cold water (ambient) quenching. The plates were then stretched about 2.25% and then artificially aged. Table 2, below, provides the aging conditions for the various alloys. Samples of alloys 4, 6 and 7 were aged using two different aging practices. The 7085 plates were aged to a T7451-type or a T7651-type temper (see, ANSI H35.1, AMS-4329A).

TABLE 2 Aging Practice for Various Alloys Alloy Aging Practice Alloy 1 6 h/250 F. + 14-15 h/310 F. + Air Cool + 24 h/250 F. Alloy 2 6 h/250 F. + 10-11 h/320 F. + Air Cool + 24 h/250 F. Alloy 3 6 h/250 F. + 7 h/320 F. + Air Cool + 24 h/250 F. Alloy 4-1 6 h/250 F. + 6-7 h/320 F. + Air Cool + 24 h/250 F. Alloy 4-2 6 h/250 F. + 10 h/320 F. + Air Cool + 24 h/250 F. Alloy 5 6 h/250 F. + 4-5 h/320 F. + Air Cool + 24 h/250 F. Alloy 6-1 6 h/250 F.+ 12-13 h/320 F. + Air Cool + 24 h/250 F. Alloy 6-2 6 h/250 F.+ 13-14 h/320 F. + Air Cool + 24 h/250 F. Alloy 7-1 6 h/250 F. + 14-15 h/320 F. + Air Cool + 24 h/250 F. Alloy 7-2 6 h/250 F.+ 16-17 h/320 F. + Air Cool + 24 h/250 F.

Various properties of the aluminum alloy plates were then tested. Specifically, the strength and elongation properties were tested in accordance with ASTM E8 and B557 at the T/2 location of the material. Plane strain fracture toughness properties were tested in the L-T direction and in accordance with ASTM E399 using a C(T) specimen taken from the T/2 location of the material, where the “B” dimension of the specimen was 0.25 inch (6.35 mm) and the “W” dimension of the specimen was 2.5 inches (63.5 mm). The typical L-S crack deviation resistance properties (Kmax-dev) were determined per the procedure described in commonly-owned U.S. Patent Application Publication No. 2017/0088920, paragraph 0058, which procedure is incorporated herein by reference, except, for this Example 1, the “W” dimension of the specimen was 1.3 inches (33.02 mm). The test is started using a Kmax of approximately 20 ksi√in.

The test results are shown in Table 3, below. The shown strength and elongation values are averages of duplicate specimens. The fracture toughness values are taken from a single specimen. The crack deviation values are averages of triplicate specimens.

TABLE 3 Measured Properties KQ L-T TYS- UTS- Kmax-dev (ksi- TYS- UTS- elong- ST ST Elong- (ksi- sqrt- Alloy L (ksi) L (ksi) L (%) (ksi) (ksi) ST (%) sqrt-in.) in.) 1 71.2 77.9 13.5 64.5 75.9 9.4 29.4 32.0 2 67.3 75.3 15.0 60.5 72.8 10.2 40.9 39.7 3 66.4 74.5 14.5 61.9 73.4 10.2 45.3 42.5 4-1 70.9 77.2 14.0 63.7 75.0 10.2 31.6 34.9 4-2 65.8 73.2 13.3 59.8 71.2 10.2 N/A N/A 5 68.2 75.6 14.0 61.1 72.8 10.9 41.4 41.0 6-1 68.9 77.2 14.0 61.8 74.4 10.2 32.4 37.9 6-2 67.0 75.7 12.5 60.2 72.8 10.9 N/A N/A 7-1 69.0 77.5 14.0 62.2 74.8 9.4 34.6 38.3 7-2 65.7 75.0 14.1 60.0 73.1 10.9 N/A N/A 7085(LS) 69.6 76.6 15.5 64.3 74.7 9.4 33.5 36.2 (T7451) 7085(LS) 74.1 79.9 14.0 67.2 77.3 9.4 27.0 36.2 (T7651)

The EAC resistance of the materials were also tested, the results of which are shown in Tables 4a-4b, below. Days in test are included for materials that have not yet failed (T=still in test at the stated number of days).

TABLE 4a EAC Properties - First Test 70° C./85% RH Days Stress Stress Stress in Days to failure Alloy (% TYS-ST) (ksi) (Mpa) test rep 1 rep 2 rep 3 2 60 36.3 250 697 592 N/A T 85 51.4 354 — 291 199 178 4-1 60 38.2 263 — N/A N/A  38 85 54.1 373 — N/A  35 N/A 6-1 60 37.1 256 697 604 T T 85 52.5 362 — 221 312 337 7-1 60 37.4 258 697 T T 611 85 52.9 365 — N/A 220 N/A 7085(LS)- 60 38.2 263 — 119  46  53 T7451 85 54.1 373 —  46  53  44

TABLE 4b EAC Properties - Second Test 70° C./85% RH Stress Stress Stress Days in Days to failure Alloy (% TYS-ST) (ksi) (Mpa) test rep 1 rep 2 rep 3 1 60 38.7 267 — 192 282 N/A 85 54.8 378 — 84 106 147 3 60 37.2 256 533 T T 480 85 52.7 363 — 198 N/A 333 4-2 60 35.8 247 — 66 105 156 85 50.7 350 — 51 53 63 5 (Test 1) 60 36.9 254 — 144 189 169 85 52.2 360 — 79 66 87 5 (Test 2) 60 36.6 252 — 130 206 291 85 51.8 357 — 120 137 127 6-2 60 36.1 249 533 T T T 85 51.2 353 — 326 518 326 7-2 60 36 248 533 T T T 85 51 352 533 T T 441 7085(LS)- 60 40.3 278 — 73 123 109 T7651 85 57 393 — 39 45 51 7085(LS)- 60 38.5 265 — 120 106 129 T7451 85 54.5 376 — 60 53 60 “N/A” means specimen data not applicable due to thread failure.

As shown, the new alloys with manganese and having zinc, magnesium, and copper within the scope of the formula 2.362≤Mg+0.429*Cu+0.067*Zn≤3.062 realize an improved combination of properties, including EAC resistance properties, over the conventional 7085 materials. This data also suggests that using a Zn/Mg (wt. % ratio) of not greater than 5.25:1 in combination with the use of manganese may lead to an improved combination of properties.

As a comparison, mechanical properties and EAC resistance of plant produced 7050 and 7085 materials in the T7451 and T7651 tempers were also measured, the results of which are provided in Tables 5a-5b, below.

TABLE 5a Plant Mechanical Property Data Kmax- dev KQ L- TYS- UTS- elong- (ksi- T (ksi- Alloy- Gauge TYS-L UTS-L elong- ST ST ST sqrt- sqrt- Temper (in) (ksi) (ksi) L (%) (ksi) (ksi) (%) in.) in.) 7085- 4.331 73.8 76.6 12.1 67.4 77.0 5.95 N/A N/A T7651 7085- 4.3 71.2 74.8 15.1 66.0 76.0 7.85 N/A N/A T7451 7050- 5.42 68.2 76.0 12.5 60.9 72.4 8 27.5 33.4 T7651 7050- 3.92 68.9 77.2 12.45 62.9 74.4 5.8 N/A N/A T7451

TABLE 5b Plant EAC Data Stress 70° C./85% RH (% Days Alloy/ Gauge TYS- Stress Stress in Days to failure Temper (in.) ST) (ksi) (Mpa) test rep 1 rep 2 rep 3 rep 4 rep 5 7085- 4.331 60 40.5 279 — 68 N/A 42 N/A 39 T7651  85** 57.4 396 — 35 26 57 43 N/A 7085- 4.3 60 39.6 273 — 92 71 46 53 92 T7451 85 56.1 387 — 57 42 56 N/A 46 7050- 5.42 50 30.45 210 614 T T T T T T7651 85 51.765 357 — 203 401 260 246 147 7050- 3.92 60 37.7 260 — 292 180 540 393 330 T7451 85 53.4 368 — 292 292 386 162 469 **Three additional replicates of this material failed in 18, 14 and 26 days.

As shown in Tables 5a-5b, the EAC resistance of the conventional 7085 materials are consistent with the results of the lab-scale materials.

FIGS. 1-2 illustrate the tensile strength versus EAC results. As shown, alloys falling within the scope of the composition ranges defined herein realize an improved combination of EAC resistance and strength. The plant produced materials include the label PP. The lab scale materials include the label LS. The plant produced materials have a dark border on the data markers.

Example 2

Additional testing was completed on Alloys 2, 3, 6 and 7 of Example 1. Specifically, samples of Alloys 2, 3, 6, and 7 were artificially aged to different conditions, after which mechanical and corrosion properties were tested. The aging conditions and results are shown in Tables 6-8, below.

TABLE 6 Aging Practices for Example 2 Alloys Alloy Aging Practice Alloy 2 6 h/250 F. + 7-8 h/320 F. + Air Cool + 24 h/250 F. Alloy 3 6 h/250 F. + 2 h/320 F. + Air Cool + 24 h/250 F. Alloy 6 6 h/250 F. + 10-11 h/320 F. + Air Cool + 24 h/250 F. Alloy 7 6 h/250 F. + 12 h/320 F. + Air Cool + 24 h/250 F.

TABLE 7 Measured Properties - Example 2 Kmax-dev KQ L-T TYS- UTS- elong- TYS-ST UTS-ST Elong- (ksi- (ksi- Alloy  L (ksi) L (ksi) L (%) (ksi) (ksi) ST (%) sqrt-in.) sqrt-in.) 2 68.5 76.3 11.7 61.6 73.7 9.4 32.3 37.3 3 69.8 77.4 12.5 62.4 74.5 11.7 31.7 43.7 6 68 76 12.5 60 73 9.4 31.8 36.4 7 69 78 12.5 62 75 9.4 31.8 37.3

TABLE 8 EAC Properties - Example 2 Stress 70° C./85% RH (% TYS- Stress Stress Days Days to failure Alloy ST) (ksi) (Mpa) in test rep 1 rep 2 rep 3 2 60 37 255 449 T 424 412 85 52.4 361 449 T 197 190 3 60 37.4 258 449 T 288 291 85 53 365 449 T 137 N/A 6 60 36.2 250 449 T T T 85 51.3 354 449 T T T 7 60 37.4 258 449 T T 70 85 53 365 — 242 344 340

As shown, Alloys 2, 3, 6 and 7 achieve an improved combination of mechanical and corrosion properties over the conventional 7085-T7451 alloy.

Example 3 Additional Lab Scale Testing

Various 7xxx aluminum alloys were cast as six inch (15.24 cm) thick ingots (nominal). The actual compositions of the cast ingots are shown in Table 9, below. Conventional alloys 7085 and 7050 were also produced.

TABLE 9 Composition of Example 3 Alloys (wt. %) - Lab Scale Materials Alloy Si Fe Cu Mn Mg Cr Zn Ti Zr 7085 0.02 0.03 1.64 — 1.52 — 7.59 0.02 0.11 7050 0.05 0.08 2.22 — 2.09 — 6.10 0.02 0.11 8 0.02 0.03 1.69 0.36 1.29 — 6.55 0.02 0.11 9 0.03 0.03 1.89 0.35 1.30 — 6.49 0.02 0.11 10 0.02 0.03 2.10 0.36 1.31 — 6.57 0.02 0.11 11 0.02 0.03 2.06 0.34 1.55 — 5.98 0.02 0.12

The balance of each alloy was aluminum and unavoidable impurities (≤0.03 wt. % each, ≤0.10 wt. % total). The ingots were then hot rolled to a final gauge of 1.75 inches, and then solution heat treated, and then hot water quenched to simulate cooling conditions at T/2 (mid-thickness) for approximately 8-inch thick plate. The plates were then stretched about 2.25% and then artificially aged, after which mechanical and corrosion properties were tested. The aging conditions and results are shown in Tables 10-13, below.

For this Example 3, the same testing standards as Example 1 were used for strength, fracture toughness, EAC resistance and L-S crack deviation resistance (Kmax-dev). The shown strength and elongation values are averages of duplicate specimens. The fracture toughness values are taken from a single specimen. The crack deviation values are averages of triplicate specimens.

TABLE 10 Aging Practices for Example 2 Alloys Alloy Aging Practice 1 Aging Practice 2 7085 Both T7451 7050 Both T7651 8 6 h/250 F. + 6.2 h/320 F. + 6 h/250 F. + 8.8 h/320 F. + Air Cool + 24 h/250 F. Air Cool + 24 h/250 F. 9 6 h/250 F. + 6.8 h/320 F. + 6 h/250 F. + 9.8 h/320 F. + Air Cool + 24 h/250 F. Air Cool + 24 h/250 F. 10 6 h/250 F. + 6.8 h/320 F. + 6 h/250 F. + 9.8 h/320 F. + Air Cool + 24 h/250 F. Air Cool + 24 h/250 F. 11 6 h/250 F. + 7.3 h/320 F. + 6 h/250 F.+ 11.1 h/320 F. + Air Cool + 24 h/250 F. Air Cool + 24 h/250 F.

TABLE 11 Mechanical Properties of Example 3 Alloys - Aging Practice 1 Elong- Kmax- KQ L-T TYS-L UTS-L Elong- TYS-ST UTS-ST ST dev (ksi- (ksi-sqrt- Alloy (ksi) (ksi) L (%) (ksi) (ksi) (%) sqrt-in) in) 7085 68.7 76.0 14.1 62.3 73.3 9.4 28.1 35.3 7050 61.6 72.3 11.7 56.3 70.4 9.4 26.6 30.7 8 71.1 77.6 12.5 63.4 74.4 10.9 28.9 36.0 9 70.2 77.1 12.5 62.0 73.6 10.9 25.9 35.2 10 71.9 78.5 12.5 63.1 74.6 8.6 27.7 35.7 11 71.0 78.6 11.7 62.5 74.2 7.8 25.4 32.7

TABLE 12 Mechanical Properties of Example 3 Alloys - Aging Practice 2 Elong- Kmax- KQ L-T TYS-L UTS-L Elong- TYS-ST UTS-ST ST dev (ksi- (ksi-sqrt- Alloy (ksi) (ksi) L (%) (ksi) (ksi) (%) sqrt-in) in) 7085 68.5 75.9 14.1 62.0 73.4 10.9 31.9 36.1 7050 61.2 72.2 12.5 56.2 70.3 10.2 29.0 28.2 8 66.9 74.4 13.3 59.0 71.2 10.9 30.4 40.7 9 66.7 74.4 14.9 59.2 71.4 10.2 30.8 38.2 10 66.2 74.3 13.3 59.0 71.4 10.2 32.6 40.0 11 67.6 76.2 14.1 60.4 71.8 7.1 29.6 36.0

TABLE 13 EAC Properties - Example 3 Stress 70° C./85% RH Alloy - (% TYS- Stress Stress Days Days to failure Aging ST) (ksi) (Mpa) in test rep1 rep2 rep3 7085-T7451 60 37.4 258 — 175 187 301 85 53 365 — 79 98 N/A 7085-T7451 60 37.2 256 — N/A N/A 173 85 52.7 363 — N/A 79 N/A 7050-T7651 60 33.8 233 301 T T T 85 47.9 330 301 T T T 7050-T7651 60 33.7 232 301 T T T 85 47.8 330 301 T T T Alloy 8 - 60 38 262 — N/A 56 159 Aging 1 85 53.9 372 — N/A N/A 68 Alloy 8 - 60 35.4 244 301 T 259 243 Aging 2 85 50.2 346 — N/A 146 121 Alloy 9 - 60 37.2 256 — 64 N/A 153 Aging 1 85 52.7 363 — N/A N/A 301 Alloy 9 - 60 35.5 245 301 273 T 180 Aging 2 85 50.3 347 — 231 198 180 Alloy 10 - 60 37.9 261 — 100 135 N/A Aging 1 85 53.6 370 — 65 100 79 Alloy 10 - 60 35.4 244 — 292 301 T Aging 2 85 50.2 346 — N/A 148 166 Alloy 11 - 60 37.5 259 301 T T T Aging 1 85 53.1 366 301 T T T Alloy 11 - 60 36.2 250 301 T T T Aging 2 85 51.3 354 301 T T T

As shown by the above data, alloy 7085 simulating around 8 inch thick plate realizes longer days to failure than alloy 7085 shown in Table 4a and 4b that simulated around 5 inch thick plate. As also shown, alloy 11 realizes no EAC failures after 300 days, but with significantly higher strength and fracture toughness than that of alloy 7050. Alloy 11 realizes significantly better EAC resistance properties than alloy 7085 and with similar strength and fracture toughness properties. Alloys 8-10 have slightly lower properties, but may realize properties similar to alloy 11 if alloys 8-10 had at least 1.35 wt. % Mg and/or a lower weight ratio of zinc-to-magnesium (e.g., a ratio of not greater than 4.75:1, (wt. % Zn)/(wt. % Mg)).

Example 4 Plant Scale Testing

Twenty industrial size ingots were cast, nine conventional 7085 ingots, two 7050 ingots, and nine experimental alloy ingots (three per alloy). The compositions of the experimental alloy ingots are provided in Table 14, below.

TABLE 14 Composition of Plant Scale Ingot - Invention Alloys Alloy Si Fe Cu Mn Mg Cr  Zn Ti Zr 12 0.02 0.04 1.68 0.27 1.53 — 6.62 0.02 0.11  13 0.02 0.04 1.87 0.25 1.52 — 6.43 0.02 0.11 14 0.02 0.04 1.64 0.25 1.65 — 6.37 0.02 0.11

The balance of each alloy was aluminum and unavoidable impurities (≤0.03 wt. % each, ≤0.10 wt. % total). The ingots were then hot rolled to various final gauges, and then solution heat treated and quenched in cold water. The plates were then stretched about 2.25-2.50% and then artificially aged. Table 15, below, provides the various conditions for the various alloys. Table 16 provides various artificial aging conditions listed in Table 15. The 7085 plates were aged to a T7451-type or a T7651-type temper (see, ANSI H35.1, AMS-4329A). The 7050 plates were also aged to a T7451-type or a T651-type temper.

TABLE 15 Alloy Conditions Final Gauge Artificial Alloy Plate (in.) Aging/Temper 7085 1 6.45 T7651 7085 2 6.50 T7651 7085 3 4.00 T7451 7085 4 6.00 T7451 7085 5 6.00 T7451 7085 6 7.00 T7451 7085 7 7.00 T7451 7085 8 8.50 T7451 7085 9 8.50 T7451 7050 1 4.40 T7651 7050 2 3.94 T7651 12 1 3.94 A 12 2 3.94 B 12 3 6.70 A 12 4 6.70 B 12 5 7.87 A 12 6 7.87 B 13 1 3.94 C 13 2 3.94 D 13 3 6.70 C 13 4 6.70 D 13 5 7.87 C 13 6 7.87 D 14 1 3.94 C 14 2 3.94 D 14 3 6.70 C 14 4 6.70 D 14 5 7.87 C 14 6 7.87 D

TABLE 16 Artificial Aging Practices for Table 15 Condition Aging Practice A 6 h/250 F. + 8 h/320 F. + Air Cool + 24 h/250 F. B 6 h/250 F. + 12.5 h/320 F. + Air Cool + 24 h/250 F. C 6 h/250 F. + 9 h/320 F. + Air Cool + 24 h/250 F. D 6 h/250 F. + 14 h/320 F. + Air Cool + 24 h/250 F.

For this Example 4, the same ASTM testing standards as Example 1 were used for strength, fracture toughness and EAC resistance. The typical L-S crack deviation resistance properties (Kmax-dev) were determined per the procedure described in commonly-owned U.S. Patent Application Publication No. 2017/0088920, paragraph 0058, as modified above per the Definitions section, above. The shown strength, elongation and fracture toughness values are averages of duplicate specimens. The crack deviation values are averages of triplicate specimens. The test results are shown in Tables 17-19, below.

TABLE 17 Mechanical Properties of Example 4 - Conventional Alloys TYS- UTS- Elong- KIC KIC TYS-L UTS-L Elong- ST ST ST L-T (ksi- S-L (ksi- Alloy (ksi) (ksi) L (%) (ksi) (ksi) (%) sqrt-in) sqrt-in) 7085-1 74.1 77.3 9.5 68.0 75.8 5.1 31.0 23.4 7085-2 73.4 76.3 10.1 67.2 75.2 5.1 30.7 26.7 7085-3 69.7 74.3 16.2 63.4 73.9 9.0 46.4 32.7 7085-4 71.5 75.7 12.6 65.4 73.7 6.3 33.9 30.1 7085-5 70.2 74.0 14.0 63.7 72.4 6.0 32.6 28.9 7085-6 69.0 73.8 12.7 62.5 71.1 6.0 32.7 31.6 7085-7 69.4 73.3 12.5 62.4 71.1 6.3 32.4 29.1 7085-8 67.4 73.0 11.6 60.2 69.5 5.9 31.3 28.8 7050-1 67.9 75.9 12 61.9 73 5.7 N/A 26.6 7050-2 67.65 75.25 10.5 62.7 73.8 4.7 33.6 N/A

TABLE 18 Mechanical Properties of Example 4 - Experimental Alloys Kmax- KIC TYS- UTS- Elong- dev L-T KIC S-L Alloy- TYS-L UTS-L Elong- ST ST ST (ksi- (ksi- (ksi- Specimen (ksi) (ksi) L (%) (ksi) (ksi) (%) sqrt-in) sqrt-in) sqrt-in) 12-1 71.3 75.3 15.0 64.5 75.4 6.8 33.3 41.4(*) 34.8 12-2 67.8 73.2 15.5 61.5 72.8 7.1 39.0 45.1 37.0 12-3 70.7 75.0 12.3 63.9 72.9 5.5 30.1 33.6 31.5 12-4 66.3 72.0 13.0 60.3 70.3 6.8 34.3 37.8 35.6 12-5 70.1 74.5 10.5 62.7 71.8 5.0 28.4 31.1 30.5 12-6 65.3 71.3 12.0 58.6 68.8 7.3 33.6 35.3 36.5 13-1 71.8 76.0 14.0 64.5 75.4 7.1 33.1 39.4(*) 34.9 13-2 68.9 75.3 13.0 61.0 72.8 7.1 42.3 44.8(*) 38.1 13-3 70.8 75.1 12.0 63.9 72.8 5.0 28.5 32.7 30.4 13-4 67.1 72.9 12.5 60.8 70.8 6.3 32.6 36.0 33.3 13-5 69.9 74.8 10.8 63.0 72.2 5.3 29.4 30.4 28.5 13-6 65.5 71.8 11.0 58.9 69.1 6.8 33.8 34.1 34.2 14-1 71.8 76.1 14.5 64.5 75.3 7.1 35.1 38.9(*) 34.7 14-2 67.5 73.4 15.0 60.8 72.5 7.1 37.2 44.2(*) 37.4 14-3 71.4 75.7 11.8 64.2 73.1 5.5 32.2 31.9 30.5 14-4 67.8 73.5 12.5 61.4 71.0 6.3 35.4 35.8 33.1 14-5 70.6 75.1 10.5 63.2 72.1 5.0 26.4 29.8 29.8 14-6 66.7 72.7 11.8 60.2 70.0 5.0 30.2 32.8 32.3 (*)= Test result was technically invalid per ASTM E399-17, and is thus a KQ value, as a result of Pmax/PQ being greater than 1.1. However, per ASTM B645-10, test result is usable for lot release given that B has been maximized at the specified test location.

TABLE 19 EAC Properties - Example 4 Stress 70° C./85% RH (% TYS- Stress Stress Days Days to failure Alloy ST) (ksi) (Mpa) in test rep 1 rep 2 rep 3  rep 4 rep 5 7085-1 60 40.8 281 — 78 87 N/A 87 87 7085-1 85 57.8 399 — 58 51 51 51 51 7085-2 60 40.3 278 — N/A N/A 68 69 53 7085-2 85 57.1 394 — N/A 38 56 N/A 46 7085-3 60 38.0 262 87 39 20 60 T 60 7085-3 85 53.9 372 87 39 15 T 25 25 7085-4 60 39.2 270 — 171 164 129 94 157 7085-4 85 55.5 383 — N/A 91 N/A 87 91 7085-5 60 39.2 270 — 120 198 92 105 105 7085-5 85 55.5 383 — 56 N/A 56 120 58 7085-6 60 37.9 261 327 81 T T T 91 7085-6 85 53.7 370 327 N/A T 55 67 67 7085-7 60 37.5 259 — 162 88 81 N/A 113 7085-7 85 53.1 366 327 70 T 57 57 70 7050-1 60 37.1 256 369 T T T T 225 7050-1 85 52.6 363 — 176 225 186 368 176 7050-2 60 37.6 259 124 T T T T T 7050-2 85 53.3 368 124 T T T T T 12-1 60 38.7 267 124 T 69 T T 111 12-1 85 54.8 378 124 43 T 36 41 83 12-2 60 36.9 254 124 T T T 97 T 12-2 85 52.3 361 124 69 80 T 69 69 13-1 60 38.7 267 — 62 90 62 83 115 13-1 85 54.8 378 — 41 48 52 64 52 13-2 60 36.6 252 124 T T T T T 13-2 85 51.9 358 124 T T T 97 97 14-1 60 38.7 267 124 T T T T T 14-1 85 54.8 378 124 29 T 48 34 T 14-2 60 36.5 252 124 T T T T T 14-2 85 51.7 356 124 90 T 83 T 69 12-3 60 38.3 264 115 T T T T T 12-3 85 54.3 374 115 T T T T T 12-4 60 36.2 250 115 T T T T T 12-4 85 51.2 353 115 T T T T T 13-3 60 38.3 264 115 T T T T T 13-3 85 54.3 374 115 T T T T T 13-4 60 36.5 252 115 T T T T T 13-4 85 51.7 356 115 T T T T T 14-3 60 38.5 265 115 T T T T T 14-3 85 54.6 376 115 T T T T T 14-4 60 36.8 254 115 T T T T T 14-4 85 52.2 360 115 T T T T T 12-5 60 37.6 259 117 T T T T T 12-5 85 53.3 368 117 T T T T T 12-6 60 35.2 243 117 T T T T T 12-6 85 49.8 343 117 T T T T T 13-5 60 37.8 261 117 T T T T T 13-5 85 53.5 369 117 T T T T T 13-6 60 35.3 243 117 T T T T T 13-6 85 50.1 345 117 T T T T T 14-5 60 37.9 261 117 T T T T T 14-5 85 53.7 370 117 T T T T T 14-6 60 36.1 249 117 T T T T T 14-6 85 51.1 352 117 T T T T T

As shown by the above data, alloys 12-14 show significantly improved EAC resistance over 7085 at equivalent gauge for at least one of the aging conditions. In addition, alloys 12-14 exhibit significantly better strength and fracture toughness relative to 7050 in similar gauges and a comparable strength and fracture toughness relative to 7085. As shown in Example 3, EAC resistance increases with increasing gauge for given aging practices.

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

1. A wrought 7xxx aluminum alloy product comprising:

0.15 to 0.50 wt. % Mn;
5.5-7.3 wt. % Zn;
0.95-2.2 wt. % Mg;
1.5-2.4 wt. % Cu;
up to 1.0 wt. % of grain structure control materials, wherein the grain structure control materials comprise at least one of Zr, Cr, Sc, and Hf; and
up to 0.15 wt. % Ti;
the balance being aluminum and unavoidable impurities;
wherein the wrought 7xxx aluminum alloy product has a thickness of from 1.5 to 12 inches.

2. The wrought 7xxx aluminum alloy product claim 1, wherein the wrought 7xxx aluminum alloy product includes from 0.25 to 0.40 wt. % Mn.

3. The wrought 7xxx aluminum alloy product of claim 2, wherein the wrought 7xxx aluminum alloy product includes from 6.25 to 7.0 wt. % Zn.

4. The wrought 7xxx aluminum alloy product of claim 3, wherein the wrought 7xxx aluminum alloy product includes from 1.70 to 2.0 wt. % Cu.

5. The wrought 7xxx aluminum alloy product of claim 4, wherein the wrought 7xxx aluminum alloy product includes from 1.40 to 1.90 wt. % Mg.

6. The wrought 7xxx aluminum alloy product of claim 1, wherein the wrought 7xxx aluminum alloy product includes a total amount of copper and magnesium such that (wt. % Cu+wt. % Mg)≥is from 3.5 to 4.5 wt. %.

8. The wrought 7xxx aluminum alloy product of claim 1, wherein the amounts of zinc, magnesium and copper within the 7xxx aluminum alloy product (in wt. %) satisfy the relationship 2.362≤Mg+0.429*Cu+0.067*Zn≤3.062.

9. The wrought 7xxx aluminum alloy product of claim 1, wherein the amounts of zinc and magnesium are such that a weight ratio of zinc-to-magnesium is from 3.00:1 to 5.25:1.

10. A wrought 7xxx aluminum alloy product comprising:

0.25 to 0.40 wt. % Mn;
6.0-7.0 wt. % Zn;
1.35-2.05 wt. % Mg;
1.5-2.2 wt. % Cu;
wherein (wt. % Cu+wt. % Mg)≥3.2 wt. %;
wherein the amounts of zinc, magnesium and copper within the 7xxx aluminum alloy product (in wt. %) satisfy the relationship 2.362≤Mg+0.429*Cu+0.067*Zn≤3.062;
wherein the amounts of zinc and magnesium are such that a weight ratio of zinc-to-magnesium is not greater than 5.25:1;
up to 1.0 wt. % of grain structure control materials, wherein the grain structure control materials comprise at least one of Zr, Cr, Sc, and Hf; and
up to 0.15 wt. % Ti;
the balance being aluminum and unavoidable impurities;
wherein the wrought 7xxx aluminum alloy product has a thickness of from 1.5 to 12 inches.

11. The wrought 7xxx aluminum alloy product of claim 10, comprising 0.25-0.35 wt. % Mn.

12. The wrought 7xxx alloy product of claim 11, wherein the amounts of zinc, magnesium and copper within the 7xxx aluminum alloy product (in wt. %) satisfy the relationship 2.662≤Mg+0.429*Cu+0.067*Zn≤2.912.

13. The wrought 7xxx aluminum alloy product of claim 12, wherein the 7xxx aluminum alloy product realizes a typical tensile yield strength (L) of at least 63 ksi.

14. The wrought 7xxx aluminum alloy product of claim 13, wherein the 7xxx aluminum alloy product realizes a typical tensile yield strength (ST) of at least 57 ksi.

15. The wrought 7xxx aluminum alloy product of claim 14, wherein the 7xxx aluminum alloy product realizes a typical KIC plane-strain fracture toughness (L-T) of at least 25 ksi-sqrt-inch.

16. The wrought 7xxx aluminum alloy product of claim 15, wherein the 7xxx aluminum alloy product realizes a typical KIC plane-strain fracture toughness (S-L) of at least 20 ksi-sqrt-inch.

17. The wrought 7xxx aluminum alloy product of claim 16, wherein the 7xxx aluminum alloy product realizes a typical elongation (L) of at least 8%.

18. The wrought 7xxx aluminum alloy product of claim 17, wherein the 7xxx aluminum alloy product realizes a typical elongation (ST) of at least 3%.

19. The wrought 7xxx aluminum alloy product of claim 18, wherein the 7xxx aluminum alloy product realizes a typical L-S crack deviation resistance (Kmax-dev) of at least 25 ksi-sqrt-in.

20. The wrought 7xxx aluminum alloy product of claim 19, wherein the 7xxx aluminum alloy product realizes a typical EAC resistance at 85% of TYS-ST of at least 80 days.

Patent History
Publication number: 20200115780
Type: Application
Filed: Dec 9, 2019
Publication Date: Apr 16, 2020
Inventors: Julien Boselli (Pittsburgh, PA), Gary H. Bray (Murrysville, PA), Cagatay Yanar (Pittsburgh, PA), Lynette M. Karabin (Ruffs Dale, PA), Severine Cambier (Pittsburgh, PA), Francine S. Bovard (Monroeville, PA), Jen C. Lin (Export, PA)
Application Number: 16/708,117
Classifications
International Classification: C22C 21/10 (20060101); C22F 1/053 (20060101);