EP3368702B1

EP3368702B1 - Improved wrought 7xxx aluminum alloys, and methods for making the same

Info

Publication number: EP3368702B1
Application number: EP16860785.1A
Authority: EP
Inventors: Xinyan Yan; James Daniel Bryant; Jen C. Lin; Wenping Zhang; Eider SIMIELLI
Original assignee: Howmet Aerospace Inc
Current assignee: Howmet Aerospace Inc
Priority date: 2015-10-29
Filing date: 2016-10-27
Publication date: 2023-08-16
Anticipated expiration: 2036-10-27
Also published as: CA3003158A1; EP3368702A4; EP3368702A1; WO2017075217A1; CA3003158C; CN108291280B; HUE063975T2; US20170121795A1; CN108291280A; EP3368702C0

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

This patent application claims priority to Prov. U.S. Pat. App. Ser. No. 62/248,165, filed Oct. 29, 2015 and entitled "WROUGHT 7XXX ALUMINUM ALLOYS, AND METHODS FOR MAKING THE SAME,"
This patent application is related to commonly-owned U.S. Patent Application No. 14/694,109, filed April 23, 2015 , entitled "IMPROVED 7XX ALUMINUM CASTING ALLOYS, AND METHODS FOR MAKING 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 or corrosion resistance of a wrought 7xxx aluminum alloy without affecting other properties.
WO 2015/167916 discloses wrought 7xxx aluminum alloys A2, A3, B3 and B4 comprising Zn, Mg, Cu, Fe, Si, Mn, Ti, V, Zr and B.

SUMMARY OF THE DISCLOSURE

Broadly, the present patent application relates to improved wrought 7xxx aluminum alloys, and methods for producing the same. The new wrought 7xxx aluminum alloys may realize, for instance, an improved combination of at least two of strength, corrosion resistance, fatigue failure resistance, and quench insensitivity, among other properties.
The new wrought 7xxx aluminum alloys generally comprise (and in some instance consist essentially of, or consist of), zinc (Zn), magnesium (Mg), copper (Cu), vanadium (V), zirconium (Zr), and titanium (Ti), as primary alloying elements, optionally with manganese (Mn) and/or chromium (Cr), the balance being aluminum (Al), iron (Fe), silicon (Si), and unavoidable impurities, as defined below. Some embodiments of new wrought 7xxx aluminum alloy compositions are shown in FIG. 1.
Regarding zinc, the new wrought 7xxx aluminum alloys generally include from 3.75 to 8.0 wt. % Zn. In one embodiment, a new wrought 7xxx aluminum alloy includes not greater than 7.5 wt. % Zn. In another embodiment, a new wrought 7xxx aluminum alloy includes not greater than 7.0 wt. % Zn. In yet another embodiment, a new wrought 7xxx aluminum alloy includes not greater than 6.5 wt. % Zn. In another embodiment, a new wrought 7xxx aluminum alloy includes not greater than 6.0 wt. % Zn. In yet another embodiment, a new wrought 7xxx aluminum alloy includes not greater than 5.5 wt. % Zn. In another embodiment, a new wrought 7xxx aluminum alloy includes not greater than 5.0 wt. % Zn. In another embodiment, a new wrought 7xxx aluminum alloy includes not greater than 4.75 wt. % Zn. In one embodiment, a new wrought 7xxx aluminum alloy includes at least 4.0 wt. % Zn. In another embodiment, a new wrought 7xxx aluminum alloy includes at least 4.25 wt. % Zn. In yet another embodiment, a new wrought 7xxx aluminum alloy includes at least 4.35 wt. % Zn.
The new wrought 7xxx aluminum alloys generally include magnesium in the range of from 1.25 to 3.0 wt. % Mg. In one embodiment, a new wrought 7xxx aluminum alloy includes not greater than 2.75 wt. % Mg. In another embodiment, a new wrought 7xxx aluminum alloy includes not greater than 2.5 wt. % Mg. In yet another embodiment, a new wrought 7xxx aluminum alloy includes not greater than 2.25 wt. % Mg. In another embodiment, a new wrought 7xxx aluminum alloy includes not greater than 2.0 wt. % Mg. In yet another embodiment, a new wrought 7xxx aluminum alloy includes not greater than 1.8 wt. % Mg. In one embodiment, a new wrought 7xxx aluminum alloy includes at least 1.35 wt. % Mg. In another embodiment, a new wrought 7xxx aluminum alloy includes at least 1.40 wt. % Mg. In yet another embodiment, a new wrought 7xxx aluminum alloy includes at least 1.45 wt. % Mg. In another embodiment, a new wrought 7xxx aluminum alloy includes at least 1.50 wt. % Mg.
In some embodiments, the amount of zinc and magnesium may be limited (e.g., to improve corrosion resistance). Thus, in one embodiment, the combined amount of zinc and magnesium in a new wrought 7xxx aluminum alloy may be not greater than 7.0 wt. % (i.e., wt. % Zn + wt. % Mg ≤ 7.0 wt. %). In another embodiment, the combined amount of zinc and magnesium in a new wrought 7xxx aluminum alloy is not greater than 6.75 wt. % (i.e., wt. % Zn + wt. % Mg ≤ 6.75 wt. %). In yet another embodiment, the combined amount of zinc and magnesium in a new wrought 7xxx aluminum alloy is not greater than 6.50 wt. % (i.e., wt. % Zn + wt. % Mg ≤ 6.50 wt. %). In another embodiment, the combined amount of zinc and magnesium in a new wrought 7xxx aluminum alloy is not greater than 6.25 wt. % (i.e., wt. % Zn + wt. % Mg ≤ 6.25 wt. %). In yet another embodiment, the combined amount of zinc and magnesium in a new wrought 7xxx aluminum alloy is not greater than 6.00 wt. % (i.e., wt. % Zn + wt. % Mg ≤ 6.00 wt. %).
The new wrought 7xxx aluminum alloys generally include copper and in the range of from 0.35 to 1.35 wt. % Cu, and where the amount of magnesium exceeds the amount of copper. As shown below, copper may facilitate, for example, improved corrosion resistance (e.g., improved SCC resistance) and/or strength. In one embodiment, a new wrought 7xxx aluminum alloy includes not greater than 1.15 wt. % Cu. In another embodiment, a new wrought 7xxx aluminum alloy includes not greater than 1.00 wt. % Cu. In yet another embodiment, a new wrought 7xxx aluminum alloy includes not greater than 0.95 wt. % Cu. In another embodiment, a new wrought 7xxx aluminum alloy includes not greater than 0.90 wt. % Cu. In yet another embodiment, a new wrought 7xxx aluminum alloy includes not greater than 0.85 wt. % Cu. In another embodiment, a new wrought 7xxx aluminum alloy includes not greater than 0.80 wt. % Cu. In one embodiment, a new wrought 7xxx aluminum alloy includes at least 0.40 wt. % Cu. In another embodiment, a new wrought 7xxx aluminum alloy includes at least 0.45 wt. % Cu. In yet another embodiment, a new wrought 7xxx aluminum alloy includes at least 0.50 wt. % Cu. In another embodiment, a new wrought 7xxx aluminum alloy includes at least 0.55 wt. % Cu. In yet another embodiment, a new wrought 7xxx aluminum alloy includes at least 0.60 wt. % Cu.
The new wrought 7xxx aluminum alloys generally include from 0.04 to 0.20 wt. % V. As shown below, vanadium may facilitate, for example, improved corrosion resistance and/or quench insensitivity. In one embodiment, a new wrought 7xxx aluminum alloy includes not greater than 0.18 wt. % V. In another embodiment, a new wrought 7xxx aluminum alloy includes not greater than 0.16 wt. % V. In yet another embodiment, a new wrought 7xxx aluminum alloy includes not greater than 0.15 wt. % V. In another embodiment, a new wrought 7xxx aluminum alloy includes not greater than 0.14 wt. % V. In yet another embodiment, a new wrought 7xxx aluminum alloy includes not greater than 0.13 wt. % V. In another embodiment, a new wrought 7xxx aluminum alloy includes not greater than 0.12 wt. % V. In yet another embodiment, a new wrought 7xxx aluminum alloy includes not greater than 0.11 wt. % V. In one embodiment, a new wrought 7xxx aluminum alloy includes at least 0.05 wt. % V. In another embodiment, a new wrought 7xxx aluminum alloy includes at least 0.06 wt. % V. In yet another embodiment, a new wrought 7xxx aluminum alloy includes at least 0.07 wt. % V. In another embodiment, a new wrought 7xxx aluminum alloy includes at least 0.08 wt. % V.
The new wrought 7xxx aluminum alloys generally include from 0.06 to 0.20 wt. % Zr. As shown by the below data, the combination of vanadium and zirconium may facilitate, for instance, improved fatigue failure resistance properties. In one embodiment, a new wrought 7xxx aluminum alloy includes not greater than 0.18 wt. % Zr. In another embodiment, a new wrought 7xxx aluminum alloy includes not greater than 0.16 wt. % Zr. In yet another embodiment, a new wrought 7xxx aluminum alloy includes not greater than 0.15 wt. % Zr. In another embodiment, a new wrought 7xxx aluminum alloy includes not greater than 0.14 wt. % Zr. In yet another embodiment, a new wrought 7xxx aluminum alloy includes not greater than 0.13 wt. % Zr. In one embodiment, a new wrought 7xxx aluminum alloy includes at least 0.07 wt. % Zr. In another embodiment, a new wrought 7xxx aluminum alloy includes at least 0.08 wt. % Zr.
The total amount of vanadium plus zirconium should be controlled to restrict formation of a high volume fraction of constituent particles (e.g., a high volume fraction of Al₃Zr, Al₂₃V₄, Al₇V and/or Al₁₀V constituent particles). In one embodiment, the total amount of vanadium plus zirconium does not exceed 0.23 wt. % V + Zr. In another embodiment, the total amount of vanadium plus zirconium does not exceed 0.22 wt. % V + Zr. In yet another embodiment, the total amount of vanadium plus zirconium does not exceed 0.21 wt. % V + Zr. In another embodiment, the total amount of vanadium plus zirconium does not exceed 0.20 wt. % V + Zr. In one embodiment, the total volume fraction of Al₃Zr, Al₂₃V₄, Al₇V and Al₁₀V constituent particles does not exceed 0.07%. The total volume fraction of these constituent particles may be determined, for instance, by Pandat^™ software and the PanAluminum thermodynamic database (CompuTherm LLC, 437 S. Yellowstone Dr. Suite 217, Madison, WI, USA). In one embodiment, the total volume fraction of Al₃Zr, Al₂₃V₄, Al₇V and Al₁₀V constituent particles does not exceed 0.06%. In another embodiment, the total volume fraction of Al₃Zr, Al₂₃V₄, Al₇V and Al₁₀V constituent particles does not exceed 0.05%. In yet another embodiment, the total volume fraction of Al₃Zr, Al₂₃V₄, Al₇V and Al₁₀V constituent particles does not exceed 0.04%. In another embodiment, the total volume fraction of Al₃Zr, Al₂₃V₄, Al₇V and Al₁₀V constituent particles does not exceed 0.03%. In yet another embodiment, the total volume fraction of Al₃Zr, Al₂₃V₄, Al₇V and Al₁₀V constituent particles does not exceed 0.02%. In another embodiment, the total volume fraction of Al₃Zr, Al₂₃V₄, Al₇V and Al₁₀V constituent particles does not exceed 0.01%. In yet another embodiment, the total volume fraction of Al₃Zr, Al₂₃V₄, Al₇V and Al₁₀V constituent particles does not exceed 0.005%.
The new wrought 7xxx aluminum alloys generally include from 0.01 to 0.25 wt. % Ti. In one embodiment, a new wrought 7xxx aluminum alloy includes from 0.01 to 0.15 wt. % Ti. In another embodiment, a new wrought 7xxx aluminum alloy includes from 0.01 to 0.10 wt. % Ti. In yet another embodiment, a new wrought 7xxx aluminum alloy includes from 0.01 to 0.08 wt. % Ti. In another embodiment, a new wrought 7xxx aluminum alloy includes from 0.02 to 0.05 wt. % Ti. The titanium may be present (e.g., at least partially present) in the form of TiB₂ or TiC.
In some embodiments, the new wrought 7xxx aluminum alloys may include up to 0.50 wt. % Mn. In embodiments where manganese is utilized, the new wrought 7xxx aluminum alloys generally include from 0.10 to 0.50 wt. % Mn. In one embodiment, a new wrought 7xxx aluminum alloy includes from 0.10 to 0.25 wt. % Mn. In some embodiments, the new wrought 7xxx aluminum alloys are substantially free of manganese, and, in these embodiments, contain less than 0.10 wt. %. Mn (i.e., ≤ 0.09 wt. % Mn), such as ≤ 0.05 wt. % Mn, or ≤ 0.04 wt. % Mn, or ≤ 0.03 wt. % Mn.
In some embodiments, the new wrought 7xxx aluminum alloys may include up to 0.40 wt. % Cr. In embodiments where chromium is utilized, the new wrought 7xxx aluminum alloys generally include from 0.10 to 0.40 wt. % Cr. In one embodiment, a new wrought 7xxx aluminum alloy includes from 0.10 to 0.35 wt. % Cr. In another embodiment, a new wrought 7xxx aluminum alloy includes from 0.10 to 0.25 wt. % Cr. In some embodiments, the new wrought 7xxx aluminum alloys are substantially free of chromium, and, in these embodiments, contain less than 0.10 wt. %. Cr (i.e., ≤ 0.09 wt. % Cr), such as ≤ 0.05 wt. % Cr, or ≤ 0.04 wt. % Cr, or ≤ 0.03 wt. % Cr.
The new wrought 7xxx aluminum alloys may include iron, up to 0.35 wt. % Fe. In one embodiment, a new wrought 7xxx aluminum alloy includes not greater than 0.25 wt. % Fe. In another embodiment, a new wrought 7xxx aluminum alloy includes not greater than 0.20 wt. % Fe. In yet another embodiment, a new wrought 7xxx aluminum alloy includes not greater than 0.15 wt. % Fe. In another embodiment, a new wrought 7xxx aluminum alloy includes not greater than 0.12 wt. % Fe. In yet another embodiment, a new wrought 7xxx aluminum alloy includes not greater than 0.10 wt. % Fe. In yet another embodiment, a new wrought 7xxx aluminum alloy includes not greater than 0.08 wt. % Fe. In one embodiment, a new wrought 7xxx aluminum alloy includes at least 0.01 wt. % Fe.
The new wrought 7xxx aluminum alloys may include silicon, up to 0.25 wt. % Si. In one embodiment, a new wrought 7xxx aluminum alloy includes not greater than 0.20 wt. % Si. In another embodiment, a new wrought 7xxx aluminum alloy includes not greater than 0.15 wt. % Si. In yet another embodiment, a new wrought 7xxx aluminum alloy includes not greater than 0.10 wt. % Si. In yet another embodiment, a new wrought 7xxx aluminum alloy includes not greater than 0.08 wt. % Si. In another embodiment, a new wrought 7xxx aluminum alloy includes not greater than 0.05 wt. % Si. In one embodiment, a new wrought 7xxx aluminum alloy includes at least 0.01 wt. % Si.
The balance of the new wrought 7xxx aluminum alloy is generally aluminum and unavoidable impurities. In one embodiment, the new wrought 7xxx aluminum alloys contain not more than 0.10 wt. % each of any one impurity (measured on an elemental basis), with the total combined amount of these impurities not exceeding 0.35 wt. % in the new wrought 7xxx aluminum alloy (i.e., ≤ 0.10 wt. % each of any one impurity, and with the total impurities being ≤ 0.35 wt. %). In another embodiment, each one of the impurities, individually, does not exceed 0.05 wt. % in the new wrought 7xxx aluminum alloy, and the total combined amount of the impurities does not exceed 0.15 wt. % in the new wrought 7xxx aluminum alloy (i.e., ≤ 0.05 wt. % each of any one impurity, and with the total impurities being ≤ 0.15 wt. %). In another embodiment, each one of these impurities, individually, does not exceed 0.03 wt. % in the new wrought 7xxx aluminum alloy, and the total combined amount of these impurities does not exceed 0.10 wt. % in the new wrought 7xxx aluminum alloys (i.e., ≤ 0.03 wt. % each of any one impurity, and with the total impurities being ≤ 0.10 wt. %).
The new wrought 7xxx aluminum alloys described herein may be cast (e.g., as ingot or billet), then homogenized, and then hot worked to an intermediate or final form (e.g., cold working after the hot working when the hot working produces an intermediate form). In one embodiment, the hot working is forging. In one embodiment, the forging produces a shaped product, such as a wheel product. In another embodiment, the hot working is rolling or extruding. After the hot working (and any optional cold working), the new alloy may be tempered, such as by solution heat treating, and then quenching, and then natural aging, followed by artificial aging. Suitable tempers include the T4, T5, T6, and T7 tempers, for instance, as defined in ANSI H35.1 (2009). In one embodiment, the new alloy compositions described herein are processed into a forged wheel product per the processes described in commonly-owned U.S. Patent Application Publication No. 2006/0000094 , which is incorporated herein by reference in its entirety. In one embodiment, the new wrought 7xxx aluminum alloys described herein are processed to a T5 temper (e.g., a T53 temper), which may include press quenching the new wrought 7xxx aluminum alloys (e.g., in the form of a forged wheel) after solution heat treatment.
As mentioned above, the new wrought 7xxx aluminum alloys may realize improved quench insensitivity. Quench insensitivity relates to an aluminum alloy's sensitivity to the quench conditions used after solution heat treatment. One indicator of quench sensitivity is a significant drop in strength with low quench rates as compared to high quench rates. As shown by the below examples, the new wrought 7xxx aluminum alloys described herein may be relatively quench insensitive. For purposes of this application, quench insensitivity is measured by conventionally producing a new wrought 7xxx aluminum alloy as a rolled plate having a final gauge of 2.54 mm (1.0 inch), after which two identical pieces of this plate are solution heat treated, after which one piece is cold water quenched in 25°C (77°F) water and the other piece is boiling water quenched, both for a period of 10 minutes, after which the pieces are allowed to air dry. The two pieces are then both naturally aged for 24 hours and then both two-step artificially aged with a first step of 121°C (250°F) for 3 hours (with a 2-hour heat up from ambient to 121°C (250°F)) and a second step of 171°C (340°F) for 8 hours. The longitudinal (L) tensile yield strengths of these two pieces are then measured at T/2 in accordance with ASTM B557 and E8, using at least duplicate specimens, after which the measured strengths are averaged for each piece. The average TYS(L) of the cold water quenched ("CWQ") piece is then compared to the average TYS(L) of the boiling water quenched (BWQ") TYS. The difference between the two average TYS values (i.e., CWQ(TYS) - BWQ(TYS)) is the quench insensitivity of the alloy.
In one embodiment, a new wrought 7xxx aluminum alloy realizes a quench insensitivity (as defined above) of not greater than 48 MPa (7 ksi) (i.e., CWQ(TYS) - BWQ(TYS) < 7 ksi). In another embodiment, a new wrought 7xxx aluminum alloy realizes a quench insensitivity of not greater than 41 MPa (6 ksi). In yet another embodiment, a new wrought 7xxx aluminum alloy realizes a quench insensitivity of not greater than 34 MPa (5 ksi). In another embodiment, a new wrought 7xxx aluminum alloy realizes a quench insensitivity of not greater than 28 MPa (4 ksi). In yet another embodiment, a new wrought 7xxx aluminum alloy realizes a quench insensitivity of not greater than 21 MPa (3 ksi). In another embodiment, a new wrought 7xxx aluminum alloy realizes a quench insensitivity of not greater than 14 MPa (2 ksi). In yet another embodiment, a new wrought 7xxx aluminum alloy realizes a quench insensitivity of not greater than 7 MPa (1 ksi). In another embodiment, a new wrought 7xxx aluminum alloy realizes a quench insensitivity of not greater than 0 MPa (0 ksi), meaning the boiling water quenched alloy realizes at least equivalent strength to the cold water quenched alloy. In yet another embodiment, a new wrought 7xxx aluminum alloy realizes a quench insensitivity of not greater than -7 MPa (-1 ksi), meaning the boiling water quenched alloy realizes higher strength than the cold water quenched alloy. In another embodiment, a new wrought 7xxx aluminum alloy realizes a quench insensitivity of not greater than -14 MPa (-2 ksi). In another embodiment, a new wrought 7xxx aluminum alloy realizes a quench insensitivity of not greater than -21 MPa (-3 ksi). In another embodiment, a new wrought 7xxx aluminum alloy realizes a quench insensitivity of not greater than -28 MPa (-4 ksi). In another embodiment, a new wrought 7xxx aluminum alloy realizes a quench insensitivity of not greater than -34 MPa (-5 ksi). In another embodiment, a new wrought 7xxx aluminum alloy realizes a quench insensitivity of not greater than -41 MPa (-6 ksi). In another embodiment, a new wrought 7xxx aluminum alloy realizes a quench insensitivity of not greater than -48 MPa (-7 ksi). In another embodiment, a new wrought 7xxx aluminum alloy realizes a quench insensitivity of not greater than -55 MPa (-8 ksi). In another embodiment, a new wrought 7xxx aluminum alloy realizes a quench insensitivity of not greater than -62 MPa (-9 ksi), or more.
The quench insensitivity of the new wrought 7xxx aluminum alloys may facilitate improved strength. Likewise, when using a hot quench media, a new wrought 7xxx aluminum alloy may realize less distortion.
The new wrought 7xxx aluminum alloys may be post-solution heat treatment quenched with any applicable fluid or media. In one embodiment, a new wrought 7xxx aluminum alloy is water quenched (cold water quenched, hot water quenched, or boiling water quenched). In one embodiment, the new wrought 7xxx aluminum alloy is hot or boiling water quenched. A hot water quench is a quenching using water having a temperature of from 66°C (150°F) to boiling (100°C (212°F) at standard temperature and pressure). A boiling water quench uses boiling water. A boiling water quench is a species of the hot water quench genus. As shown by the below data, use of a hot water quench (including a boiling water quench) may facilitate improved SCC resistance. In another embodiment, a new wrought 7xxx aluminum alloy is air quenched (e.g., via a forced air quench). In yet another embodiment, a new wrought 7xxx aluminum alloy is press-quenched. In one embodiment, the quenching step results in an average cooling rate of from -17.2°C to -3.9°C (1°F to 25°F) per second as measured during the first 60 seconds of the quench. In another embodiment, the quenching step results in an average cooling rate of not greater than -5.3°C (22.5°F) per second as measured during the first 60 seconds of the quench. In yet another embodiment, the quenching step results in an average cooling rate of not greater than -6.7°C (20°F) per second as measured during the first 60 seconds of the quench. In another embodiment, the quenching step results in an average cooling rate of not greater than -8.1°C (17.5°F) per second as measured during the first 60 seconds of the quench. In yet another embodiment, the quenching step results in an average cooling rate of not greater than -9.4°C (15°F) per second as measured during the first 60 seconds of the quench. In another embodiment, the quenching step results in an average cooling rate of not greater than -10.8°C (12.5°F) per second as measured during the first 60 seconds of the quench. In yet another embodiment, the quenching step results in an average cooling rate of not greater than -12.2°C (10°F) per second as measured during the first 60 seconds of the quench. In another embodiment, the quenching step results in an average cooling rate of not greater than -12.8°C (9.0°F) per second as measured during the first 60 seconds of the quench. In yet another embodiment, the quenching step results in an average cooling rate of not greater than -13.3°C (8.0°F) per second as measured during the first 60 seconds of the quench. In another embodiment, the quenching step results in an average cooling rate of not greater than -13.9°C (7.0°F) per second as measured during the first 60 seconds of the quench. In yet another embodiment, the quenching step results in an average cooling rate of not greater than -14.4°C (6.0°F) per second as measured during the first 60 seconds of the quench.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG 1 is a table illustrating various embodiments of new 7xxx wrought aluminum alloy compositions.

DETAILED DESCRIPTION

Example 1

Several 7xxx aluminum alloys having the compositions shown in Table 1, below, were cast as lab-scale, 6.35 cm (2.5 inch) thick ingots (nominal). The ingots were then scalped, homogenized, and hot rolled to a final gauge of 3.175 cm (1.25 inch). After hot rolling, the plates were metallographically inspected. The inspection revealed that plates 2, 14, 15, 17 and 18 contained a high volume fraction of constituent particles due to excess V + Zr + Ti content relative to the amount of Zn+Mg+Cu content of those alloys.

The hot rolled plates were then solution heat treated, cold water quenched, and then allowed to naturally age for about 24-hours. After natural aging, the plates were then two-step artificially aged at 121°C (250°F) for 3 hours and then 171°C (340°F) for 8 hours. Several of the alloy samples in the naturally aged condition were also artificially aged at 121°C (250°F) for 3 hours and then 171°C (340°F) for 16 hours. The longitudinal (L) mechanical properties of the artificially aged plates were then measured at T/2 and in accordance with ASTM B557 and E8, the results of which are shown in Table 2, below (average of duplicate specimens).

Table 1 - Composition of the Example 1 Alloys (all values in weight percent) ^∗

Alloy #	Si	Fe	Zn	Mg	Cu	V	Zr	V+Zr
1**	0.056	0.087	4.25	1.59	0.57	0.079	0.10	0.179
2	0.059	0.094	4.83	1.67	0.65	0.120	0.19	0.310
3**	0.057	0.095	5.20	1.60	0.64	0.082	0.10	0.182
4**	0.056	0.094	6.02	1.57	0.64	0.086	0.10	0.186
5	0.057	0.085	3.65	1.66	0.62	0.080	0.11	0.190
6	0.059	0.092	2.83	1.61	0.60	0.080	0.10	0.180
7**	0.064	0.093	4.39	1.99	0.62	0.088	0.10	0.188
8**	0.057	0.092	4.38	2.37	0.61	0.089	0.10	0.189
9	0.052	0.072	4.53	1.20	0.55	0.083	0.10	0.183
10	0.050	0.080	4.40	0.85	0.60	0.080	0.10	0.180
11**	0.058	0.084	4.41	1.63	0.88	0.084	0.10	0.184
12**	0.054	0.088	4.38	1.64	1.26	0.083	0.10	0.183
13**	0.055	0.088	4.35	1.63	0.42	0.082	0.12	0.202
14	0.059	0.092	4.44	1.67	0.61	0.200	0.10	0.300
15	0.059	0.086	4.46	1.62	0.61	0.160	0.11	0.270
16**	0.058	0.100	4.41	1.55	0.64	0.056	0.10	0.156
17	0.057	0.089	4.39	1.65	0.61	0.088	0.15	0.238
18	0.059	0.092	4.44	1.61	0.62	0.086	0.19	0.276
19**	0.054	0.084	4.36	1.62	0.59	0.086	0.06	0.146
20	0.056	0.088	4.31	1.6	0.61	0.078	0	0.078

* = The balance of the alloys was Ti, Al and impurities; all alloys contained 0.02 - 0.03 wt. % Ti, except alloy 2 which contained 0.055 wt. % Ti ; all alloys contained < 0.03 wt. % of any one impurity and < 0.10 wt. % in total of all impurities; impurities included Mn and Cr in this example.
^∗∗ = invention alloy

Table 2 - Measured Mechanical Properties of the Example 1 Alloys

Alloy #	Artificial Aging Practice	TYS (MPa)	UTS (MPa)	Elong. (%
1	250F/3hrs + 340F/8hrs	332.5	395.3	17.0
1	250F/3hrs + 340F/16hrs	323.8	389.3	16.0
3	250F/3hrs + 340F/8hrs	399.0	447.5	17.0
3	250F/3hrs + 340F/16hrs	371.3	428.3	18.0
4	250F/3hrs + 340F/16hrs	416.3	459.0	16.5
5	250F/3hrs + 340F/8hrs	285.8	365.3	17.5
5	250F/3hrs + 340F/16hrs	299.0	378.5	18.0
6	250F/3hrs + 340F/16hrs	224.5	317.0	21.5
7	250F/3hrs + 340F/8hrs	383.3	440.3	16.0
7	250F/3hrs + 340F/16hrs	383.8	444.0	15.5
8	250F/3hrs + 340F/16hrs	399.8	455.3	13.5
9	250F/3hrs + 340F/8hrs	304.5	360.5	15.0
9	250F/3hrs + 340F/16hrs	275.0	340.0	15.0
10	250F/3hrs + 340F/16hrs	231.0	298.0	19.5
11	250F/3hrs + 340F/8hrs	344.3	411.0	15.5
11	250F/3hrs + 340F/16hrs	358.3	424.8	16.0
12	250F/3hrs + 340F/16hrs	357.5	433.0	15.0
13	250F/3hrs + 340F/8hrs	332.8	391.3	17.0
13	250F/3hrs + 340F/16hrs	333.3	397.3	17.0
16	250F/3hrs + 340F/8hrs	368.8	424.8	16.5
16	250F/3hrs + 340F/16hrs	325.8	392.0	14.5
19	250F/3hrs + 340F/8hrs	336.5	393.8	17.0
19	250F/3hrs + 340F/16hrs	326.5	389.0	16.0
20	250F/3hrs + 340F/8hrs	345.3	399.8	16.0
20	250F/3hrs + 340F/16hrs	337.0	396.5	13.0

As shown, alloys 5-6 and 9-10 with low zinc (alloys 5-6) or low magnesium (9-10) have low strength, not achieving a tensile yield strength (TYS) of at least 320 MPa in combination with an elongation of at least 12%.

Rotating beam fatigue testing in accordance with ISO 1143 was also conducted on alloy plates 1, 13, 16 and 20, the results of which are shown in Table 3, below. The stress level for the test was 103 MPa (15 ksi), with R = -1 and with the RPM being 10,000. Three test specimens per alloy were used, and the number of cycles to failure was measured for each specimen. The test run-out was 10,000,000 cycles.

Table 3 - Measured Fatigue Life of Alloys L 13, 16 and 20

Alloy #	Artificial Aging Practice	Cycles to Failure**
Alloy #	Artificial Aging Practice	Specimen 1	Specimen 2	Specimen 3
1	250F/3hrs + 340F/8hrs	10,000,000	10,000,000	10,000,000
13	250F/3hrs + 340F/8hrs	10,000,000	1,174,446	10,000,000
16	250F/3hrs + 340F/8hrs	10,000,000	10,000,000	10,000,000
20	250F/3hrs + 340F/8hrs	2,281,864	2,664,481	1,562,425

250°F is 121°C, 340°F is 171°F

As shown, alloy 20 with no zirconium realizes worse fatigue properties relative to alloys 1, 13 and 16.

Example 2

Three 7xxx aluminum alloys having the compositions shown in Table 4, below, were cast as industrial-scale billet. From these billets, 7.62 cm x 19.7 cm x 19.7 cm (3" x 7.75" x 7.75") samples were obtained from D/2 by machining. The samples were then hot rolled to a final gauge of about 2.54 cm (1.0 inch). The hot rolled plates were then solution heat treated, and then either cold water (CW) or boiling water (BW) quenched, and then allowed to naturally age for about 24-hours. Cold water quenched means the use of ambient temperature water. Boiling-water quench means the use of boiling water. After natural aging, the plates were then two-step artificially aged with a first step of 121°C (250°F) for 3 hours (with a 2-hour heat up from ambient to 121°C (250°F)) and a second step of 171°C (340°F) for 8 hours. The longitudinal (L) mechanical properties of the plates were then measured at T/2 and in accordance with ASTM B557 and E8, the results of which are shown in Table 5, below (average of duplicate specimens). SCC results were also measured in accordance with ASTM G103-97(2011), the "Standard Practice for Evaluating Stress-Corrosion Cracking Resistance of Low Copper 7XXX Series Al-Zn-Mg-Cu Alloys in Boiling 6% Sodium Chloride Solution," at 172 MPa and 241 MPa (25 ksi and 35 ksi) stress levels, the results of which are shown in Table 6, below.

Table 4 - Composition of the Example 2 Alloys (all values in weight percent)*

Alloy #	Si	Fe	Zn	Mg	Cu	V	Zr
A	0.062	0.065	4.38	1.54	0.63	0.06	0.08
B	0.078	0.061	4.60	1.72	0.61	0.01	0.11
C	0.060	0.068	4.43	1.71	0.89	0.01	0.10

* = The balance of the alloys was Ti, Al and impurities; all alloys contained 0.02 - 0.03 wt. % Ti; all alloys contained < 0.03 wt. % of any one impurity and < 0.10 wt. % in total of all impurities; impurities included Mn and Cr in this example.

Table 5 - Measured Mechanical Properties of the Example 2 Alloys

Alloy #	Quench	TYS (MPa)	UTS (MPa)	Elong. (%
A	CW	362.8	417.5	17.0
A	BW	370.5	423.0	16.5
B	CW	391.0	441.8	16.0
B	BW	400.8	448.3	15.8
C	CW	390.5	446.0	16.0
C	BW	401.3	450.5	16.3

Table 6 - SCC Properties of the Example 2 Alloys

Alloy #	Stress (ST) (ksi)	Quench	Days to Failure
Alloy #	Stress (ST) (ksi)	Quench	Specimen
1	Specimen 2	Specimen 3
A	25	CW	2.12	OK7	OK7
A	35	CW	6.06	3.01	2.12
A	25	BW	OK7	OK7	OK7
A	35	BW	OK7	OK7	OK7
B	25	CW	0.65	1.07	0.65
B	35	CW	0.65	0.65	0.65
B	25	BW	5.08	OK7	OK7
B	35	BW	0.65	1.7	1.07
C	25	CW	OK7	OK7	7.0
C	35	CW	3.01	0.65	2.12
C	25	BW	3.01	OK7	5.08
C	35	BW	2.67	2.12	OK7

OK7 = Passed the SCC test for the full 7 days
7.0 = failed on the 7^th day
25 ksi is 172 MPa, 35 ksi is 241 MPa

As shown, Alloy A realizes a superior combination of strength, elongation and SCC resistance properties. As shown, Alloy A is generally quench insensitive, realizing about 55 MPa (8 ksi) higher tensile yield strength when boiling water quenched.
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. The invention is defined by the appended claims

Claims

A wrought 7xxx aluminum alloy product consisting of:
(a) from 3.75 to 8.0 wt. % Zn;

(b) from 1.25 to 3.0 wt. % Mg;

(c) from 0.35 to 1.35 wt. % Cu;

(d) from 0.04 to 0.20 wt. % V;

(e) from 0.06 to 0.20 wt. % Zr;
wherein V + Zr ≤ 0.23 wt. %;

(f) from 0.01 to 0.25 wt. % Ti;

(g) up to 0.50 wt. % Mn;

(h) up to 0.40 wt. % Cr;

(i) up to 0.35 wt. % Fe; and

(j) up to 0.25 wt. % Si;

(k) the balance being aluminum and impurities, wherein the wrought 7xxx aluminum alloy includes not greater than 0.10 wt. % each of any one impurity, and wherein the wrought 7xxx aluminum alloy includes not greater than 0.35 wt. % in total of the impurities,
with the exception that the wrought 7xxx aluminum alloy product does not consist of:
4.20 wt. % Zn, 1.56 wt. % Mg, 0.65 wt. % Cu, 0.057 wt. % V, 0.09 wt. % Zr, 0.07 wt. % Ti, 0.05 wt. % Mn, 0.08 wt. % Fe, 0.05 wt.% Si, and 0.02 wt. % B; or

4.35 wt. % Zn, 1.62 wt. % Mg, 0.63 wt. % Cu, 0.103 wt. % V, 0.09 wt. % Zr, 0.06 wt. % Ti, 0.05 wt. % Mn, 0.08 wt. % Fe, 0.05 wt. % Si, and 0.02 wt. % B; or

4.38 wt. % Zn, 1.62 wt. % Mg, 0.48 wt. % Cu, 0.10 wt. % V, 0.091 wt. % Zr, 0.07 wt. % Ti, 0.05 wt. % Mn, 0.10 wt. % Fe, 0.05 wt. % Si, and 0.02 wt. % B; or

4.39 wt. % Zn, 1.61 wt. % Mg, 0.78 wt. % Cu, 0.11 wt. % V, 0.091 wt. % Zr, 0.07 wt. % Ti, 0.05 wt. % Mn, 0.10 wt. % Fe, 0.05 wt. % Si, and 0.02 wt. % B.
The wrought 7xxx aluminum alloy product of claim 1, wherein the wrought 7xxx aluminum alloy is a forged wheel product.
The wrought 7xxx aluminum alloy product of claim 2, wherein the wrought 7xxx aluminum alloy is in the T5 temper.
The wrought 7xxx aluminum alloy product of claim 3, wherein the wrought 7xxx aluminum alloy realizes a quench insensitivity of not greater than 48 MPa (7 ksi).
The wrought 7xxx aluminum alloy product of any of the preceding claims, wherein the wrought aluminum alloy includes not greater than 5.5 wt. % Zn.
The wrought 7xxx aluminum alloy product of any of the preceding claims, wherein the wrought aluminum alloy includes not greater than 4.75 wt. % Zn.
The wrought 7xxx aluminum alloy product of any of the preceding claims, wherein the combined amount of zinc and magnesium is not greater than 7.0 wt. %.
The wrought 7xxx aluminum alloy product of any of the preceding claims, wherein the combined amount of zinc and magnesium is not greater than 6.0 wt. %.
The wrought 7xxx aluminum alloy product of any of the preceding claims, wherein the wrought 7xxx aluminum alloy includes not greater than 0.95 wt. % Cu.
The wrought 7xxx aluminum alloy product of any of the preceding claims, wherein the wrought 7xxx aluminum alloy includes at least 0.50 wt. % Cu.
The wrought 7xxx aluminum alloy product of any of the preceding claims, wherein the wrought 7xxx aluminum alloy includes 0.06 - 0.16 wt. %. V and 0.07 - 0.16 wt. % Zr.
The wrought 7xxx aluminum alloy product of any of the preceding claims, wherein the total volume fraction of Al₃Zr, Al₂₃V₄, Al₇V and Al₁₀V constituent particles does not exceed 0.07 vol. %; or does not exceed 0.01 vol. %.
The wrought 7xxx aluminum alloy product of any of the preceding claims, wherein the wrought 7xxx aluminum alloy includes not greater than 0.05 wt. % each of any one impurity, and wherein the wrought 7xxx aluminum alloy includes not greater than 0.15 wt. % in total of the impurities.
The wrought 7xxx aluminum alloy product of any of the preceding claims, wherein the wrought 7xxx aluminum alloy is a forged wheel product in the T5 temper, and wherein the wrought 7xxx aluminum alloy realizes a quench insensitivity of not greater than 0 MPa (0 ksi).
The wrought 7xxx aluminum alloy product of any of the preceding claims, wherein the wrought 7xxx aluminum all comprises 0.02-0.05 wt. % Ti.