7XXX ALUMINUM ALLOYS

New 7xxx aluminum alloys alloys are disclosed. The new 7xxx aluminum alloys may include 5.0-9.0 wt. % Zn, 1.30-2.05 wt. % Mg, 1.10-2.10 wt. % Cu, wherein 2.55≤(wt. % Cu+wt. % Mg)≤3.85, at least one of (i) 0.03-0.40 wt. % Mn and 0.02-0.15 wt. % Zr, wherein 0.05≤(wt. % Zr+wt. % Mn)≤0.50, up to 0.20 wt. % Cr, up to 0.20 wt. % V, up to 0.20 wt. % Fe, up to 0.15 wt. % Si, up to 0.15 wt. % Ti, and up to 75 ppm B, the balance being aluminum, incidental elements and impurities. The new 7xxx aluminum alloys may be in the form of a 7xxx aluminum alloy sheet product having a thickness of from 0.5 to 4.0 mm and comprising at least 15 vol. % recrystallized grains. The new alloys may realize an improved combination of at least two of strength, elongation, fracture behavior and corrosion resistance.

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Description
CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of International Patent Application No. PCT/US2021/055655, filed Oct. 19, 2021, which claims the benefit of U.S. Provisional Patent Application No. 63/094,120, filed Oct. 20, 2020, entitled “IMPROVED 7XXX ALUMINUM ALLOYS,” each of which is incorporated herein by reference in its entirety.

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., W. Gruhl, “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 new 7xxx aluminum alloys and products made from the same. The new 7xxx aluminum alloys generally comprise (and in some instance consist of, or consist essentially of) 5.0-9.0 wt. % Zn, 1.30-2.05 wt. % Mg, 1.10-2.10 wt. % Cu, wherein 2.55≤(wt. % Cu+wt. % Mg)≤3.85, at least one of (i) 0.03-0.40 wt. % Mn and 0.02-0.15 wt. % Zr, wherein 0.05≤(wt. % Zr+wt. % Mn)≤0.50, up to 0.20 wt. % Cr, up to 0.20 wt. % V, up to 0.20 wt. % Fe, up to 0.15 wt. % Si, up to 0.15 wt. % Ti, and up to 75 ppm B, the balance being aluminum, incidental elements and impurities. In one approach, a new 7xxx aluminum alloy includes 5.8-7.5 wt. % Zn, 1.50-2.0 wt. % Mg, 1.30-2.05 wt. % Cu, wherein 2.55≤(wt. % Cu+wt. % Mg)≤3.80, at least one of (i) 0.03-0.40 wt. % Mn and 0.05-0.15 wt. % Zr, wherein 0.05≤(wt. % Zr+wt. % Mn)≤0.50, up to 0.20 wt. % Cr, up to 0.20 wt. % V, up to 0.20 wt. % Fe, up to 0.15 wt. % Si, up to 0.15 wt. % Ti, and up to 75 ppm B, the balance being aluminum, incidental elements and impurities. In another approach, a new 7xxx aluminum alloy includes 6.0-7.0 wt. % Zn, 1.50-1.65 wt. % Mg, 1.35-1.55 wt. % Cu, 0.15-0.35 wt. % Mn, 0.07-0.15 wt. % Zr, up to 0.20 wt. % Cr, up to 0.20 wt. % V, up to 0.20 wt. % Fe, up to 0.15 wt. % Si, up to 0.15 wt. % Ti, and up to 75 ppm B, the balance being aluminum, incidental elements and impurities. In one embodiment, the new 7xxx aluminum alloy is in the form of a rolled 7xxx aluminum alloy sheet product having a thickness of from 0.5 to 4.0 mm. In one embodiment, the 7xxx aluminum alloy sheet product comprises at least 15 vol. % recrystallized grains. In one embodiment, the 7xxx aluminum alloy sheet product comprises a dispersoid content of not greater than 1.95 vol. %, wherein the amount of dispersoids is calculated from the formula (wt. % Mn)*3.52+(wt. % Zr)*1.28+(wt. % Cr+wt. % V)*6.34. Products made from the new 7xxx aluminum alloys may realize an improved combination of properties, such as an improved combination of two or more of strength, ductility (elongation), fracture behavior and corrosion resistance.

I. Compositions

As noted above, the new 7xxx aluminum alloys generally comprise 5.0-9.0 wt. % Zn. In one embodiment, a 7xxx aluminum alloy includes at least 5.2 wt. % Zn. In another embodiment, a 7xxx aluminum alloy includes at least 5.4 wt. % Zn. In yet another embodiment, a 7xxx aluminum alloy includes at least 5.6 wt. % Zn. In another embodiment, a 7xxx aluminum alloy includes at least 5.8 wt. % Zn. In yet another embodiment, a 7xxx aluminum alloy includes at least 6.0 wt. % Zn. In another embodiment, a 7xxx aluminum alloy includes at least 6.2 wt. % Zn. In yet another embodiment, a 7xxx aluminum alloy includes at least 6.4 wt. % Zn. In another embodiment, a 7xxx aluminum alloy includes at least 6.6 wt. % Zn.

In one embodiment, a 7xxx aluminum alloy includes not greater than 8.8 wt. % Zn. In another embodiment, a 7xxx aluminum alloy includes not greater than 8.6 wt. % Zn. In yet another embodiment, a 7xxx aluminum alloy includes not greater than 8.4 wt. % Zn. In another embodiment, a 7xxx aluminum alloy includes not greater than 8.2 wt. % Zn. In yet another embodiment, a 7xxx aluminum alloy includes not greater than 8.0 wt. % Zn. In another embodiment, a 7xxx aluminum alloy includes not greater than 7.8 wt. % Zn. In yet another embodiment, a 7xxx aluminum alloy includes not greater than 7.6 wt. % Zn. In another embodiment, a 7xxx aluminum alloy includes not greater than 7.5 wt. % Zn. In yet another embodiment, a 7xxx aluminum alloy includes not greater than 7.4 wt. % Zn. In another embodiment, a 7xxx aluminum alloy includes not greater than 7.3 wt. % Zn. In yet another embodiment, a 7xxx aluminum alloy includes not greater than 7.2 wt. % Zn. In another embodiment, a 7xxx aluminum alloy includes not greater than 7.1 wt. % Zn. In yet another embodiment, a 7xxx aluminum alloy includes not greater than 7.0 wt. % Zn.

As noted above, the new 7xxx aluminum alloys generally comprise 1.30-2.05 wt. % Mg. In one embodiment, a 7xxx aluminum alloy includes at least 1.35 wt. % Mg. In another embodiment, a 7xxx aluminum alloy includes at least 1.40 wt. % Mg. In yet another embodiment, a 7xxx aluminum alloy includes at least 1.45 wt. % Mg. In another embodiment, a 7xxx aluminum alloy includes at least 1.50 wt. % Mg.

In one embodiment, a 7xxx aluminum alloy includes not greater than 2.0 wt. % Mg. In another embodiment, a 7xxx aluminum alloy includes not greater than 1.95 wt. % Mg. In yet another embodiment, a 7xxx aluminum alloy includes not greater than 1.90 wt. % Mg. In another embodiment, a 7xxx aluminum alloy includes not greater than 1.85 wt. % Mg. In yet another embodiment, a 7xxx aluminum alloy includes not greater than 1.80 wt. % Mg. In another embodiment, a 7xxx aluminum alloy includes not greater than 1.75 wt. % Mg. In yet another embodiment, a 7xxx aluminum alloy includes not greater than 1.70 wt. % Mg. In another embodiment, a 7xxx aluminum alloy includes not greater than 1.65 wt. % Mg. In yet another embodiment, a 7xxx aluminum alloy includes not greater than 1.60 wt. % Mg.

As noted above, the new 7xxx aluminum alloys generally comprise 1.10-2.10 wt. % Cu. In one embodiment, a 7xxx aluminum alloy includes at least 1.15 wt. % Cu. In another embodiment, a 7xxx aluminum alloy includes at least 1.20 wt. % Cu. In yet another embodiment, a 7xxx aluminum alloy includes at least 1.25 wt. % Cu. In another embodiment, a 7xxx aluminum alloy includes at least 1.30 wt. % Cu. In yet another embodiment, a 7xxx aluminum alloy includes at least 1.35 wt. % Cu. In another embodiment, a 7xxx aluminum alloy includes at least 1.40 wt. % Cu.

In one embodiment, a 7xxx aluminum alloy includes not greater than 2.05 wt. % Cu. In another embodiment, a 7xxx aluminum alloy includes not greater than 2.0 wt. % Cu. In another embodiment, a 7xxx aluminum alloy includes not greater than 1.95 wt. % Cu. In yet another embodiment, a 7xxx aluminum alloy includes not greater than 1.90 wt. % Cu. In another embodiment, a 7xxx aluminum alloy includes not greater than 1.85 wt. % Cu. In yet another embodiment, a 7xxx aluminum alloy includes not greater than 1.80 wt. % Cu. In another embodiment, a 7xxx aluminum alloy includes not greater than 1.75 wt. % Cu. In yet another embodiment, a 7xxx aluminum alloy includes not greater than 1.70 wt. % Cu. In another embodiment, a 7xxx aluminum alloy includes not greater than 1.65 wt. % Cu. In yet another embodiment, a 7xxx aluminum alloy includes not greater than 1.60 wt. % Cu.

As noted above, the combined amount of magnesium and copper used in the new 7xxx aluminum alloys is generally from 2.55 to 3.85 wt. %, i.e., 2.55≤(wt. % Cu+wt. % Mg)≤3.85. In one embodiment, the combined amount of magnesium and copper is at least 2.60 wt. %, i.e., (wt. % Cu+wt. % Mg) is at least 2.60. In another embodiment, the combined amount of magnesium and copper is at least 2.65 wt. %, i.e., (wt. % Cu+wt. % Mg) is at least 2.65. In yet another embodiment, the combined amount of magnesium and copper is at least 2.70 wt. %, i.e., (wt. % Cu+wt. % Mg) is at least 2.70. In another embodiment, the combined amount of magnesium and copper is at least 2.75 wt. %, i.e., (wt. % Cu+wt. % Mg) is at least 2.75. In yet another embodiment, the combined amount of magnesium and copper is at least 2.80 wt. %, i.e., (wt. % Cu+wt. % Mg) is at least 2.80. In another embodiment, the combined amount of magnesium and copper is at least 2.85 wt. %, i.e., (wt. % Cu+wt. % Mg) is at least 2.85. In yet another embodiment, the combined amount of magnesium and copper is at least 2.90 wt. %, i.e., (wt. % Cu+wt. % Mg) is at least 2.90. In another embodiment, the combined amount of magnesium and copper is at least 2.95 wt. %, i.e., (wt. % Cu+wt. % Mg) is at least 2.95.

In one embodiment, the combined amount of magnesium and copper is not greater than 3.80 wt. %, i.e., (wt. % Cu+wt. % Mg) is not greater than 3.80. In another embodiment, the combined amount of magnesium and copper is not greater than 3.75 wt. %, i.e., (wt. % Cu+wt. % Mg) is not greater than 3.75. In yet another embodiment, the combined amount of magnesium and copper in the 7xxx aluminum alloys is not greater than 3.70 wt. %, i.e., (wt. % Cu+wt. % Mg) is not greater than 3.70. In another embodiment, the combined amount of magnesium and copper is not greater than 3.65 wt. %, i.e., (wt. % Cu+wt. % Mg) is not greater than 3.65. In yet another embodiment, the combined amount of magnesium and copper is not greater than 3.60 wt. %, i.e., (wt. % Cu+wt. % Mg) is not greater than 3.60. In another embodiment, the combined amount of magnesium and copper is not greater than 3.55 wt. %, i.e., (wt. % Cu+wt. % Mg) is not greater than 3.55. In yet another embodiment, the combined amount of magnesium and copper is not greater than 3.50 wt. %, i.e., (wt. % Cu+wt. % Mg) is not greater than 3.50. In another embodiment, the combined amount of magnesium and copper is not greater than 3.45 wt. %, i.e., (wt. % Cu+wt. % Mg) is not greater than 3.45. In yet another embodiment, the combined amount of magnesium and copper is not greater than 3.40 wt. %, i.e., (wt. % Cu+wt. % Mg) is not greater than 3.40. In another embodiment, the combined amount of magnesium and copper is not greater than 3.35 wt. %, i.e., (wt. % Cu+wt. % Mg) is not greater than 3.35. In yet another embodiment, the combined amount of magnesium and copper is not greater than 3.30 wt. %, i.e., (wt. % Cu+wt. % Mg) is not greater than 3.30. In another embodiment, the combined amount of magnesium and copper is not greater than 3.25 wt. %, i.e., (wt. % Cu+wt. % Mg) is not greater than 3.25. In yet another embodiment, the combined amount of magnesium and copper is not greater than 3.20 wt. %, i.e., (wt. % Cu+wt. % Mg) is not greater than 3.20. In another embodiment, the combined amount of magnesium and copper is not greater than 3.15 wt. %, i.e., (wt. % Cu+wt. % Mg) is not greater than 3.15.

In one embodiment, a 7xxx aluminum alloy includes an amount of copper that is less than the amount of magnesium included in the 7xxx aluminum alloy, i.e., wt. % Cu≤wt. % Mg.

As noted above, the new 7xxx aluminum alloys include at least one of 0.03-0.40 wt. % Mn and 0.02-0.15 wt. % Zr, wherein 0.05≤(wt. % Zr+wt. % Mn)≤0.50, i.e., the combined amount of manganese and zirconium is from 0.05 to 0.50 wt. %. In one embodiment, the combined amount of manganese and zirconium is at least 0.08 wt. %, i.e., (wt. % Zr+wt. % Mn)≥0.08 wt. %. In another embodiment, the combined amount of manganese and zirconium is at least 0.10 wt. %, i.e., (wt. % Zr+wt. % Mn)≥0.10 wt. %. In yet another embodiment, the combined amount of manganese and zirconium is at least 0.12 wt. %, i.e., (wt. % Zr+wt. % Mn)≥0.12 wt. %. In another embodiment, the combined amount of manganese and zirconium is at least 0.14 wt. %, i.e., (wt. % Zr+wt. % Mn)≥0.14 wt. %. In yet another embodiment, the combined amount of manganese and zirconium is at least 0.16 wt. %, i.e., (wt. % Zr+wt. % Mn)≥0.16 wt. %. In another embodiment, the combined amount of manganese and zirconium is at least 0.18 wt. %, i.e., (wt. % Zr+wt. % Mn)≥0.18 wt. %. In yet another embodiment, the combined amount of manganese and zirconium is at least 0.20 wt. %, i.e., (wt. % Zr+wt. % Mn)≥0.20 wt. %. In another embodiment, the combined amount of manganese and zirconium is at least 0.22 wt. %, i.e., (wt. % Zr+wt. % Mn)≥0.22 wt. %. In yet another embodiment, the combined amount of manganese and zirconium is at least 0.24 wt. %, i.e., (wt. % Zr+wt. % Mn)≥0.24 wt. %. In another embodiment, the combined amount of manganese and zirconium is at least 0.26 wt. %, i.e., (wt. % Zr+wt. % Mn)≥0.26 wt. %. In yet another embodiment, the combined amount of manganese and zirconium is at least 0.28 wt. %, i.e., (wt. % Zr+wt. % Mn)≥0.28 wt. %. In another embodiment, the combined amount of manganese and zirconium is at least 0.30 wt. %, i.e., (wt. % Zr+wt. % Mn)≥0.30 wt. %.

In one embodiment, the combined amount of manganese and zirconium is not greater than 0.45 wt. %, i.e., (wt. % Zr+wt. % Mn)≤0.45 wt. %. In another embodiment, the combined amount of manganese and zirconium is not greater than 0.40 wt. %, i.e., (wt. % Zr+wt. % Mn)≤0.40 wt. %. In yet another embodiment, the combined amount of manganese and zirconium is not greater than 0.38 wt. %, i.e., (wt. % Zr+wt. % Mn)≤0.38 wt. %.

As noted above, the new 7xxx aluminum alloys may include 0.02-0.15 wt. % Zr. In one embodiment, a 7xxx aluminum alloy includes at least 0.08 wt. %. Zr. In another embodiment, a new 7xxx aluminum alloy includes at least 0.10 wt. % Zr. In one embodiment, the zirconium content is below the peritectic of the 7xxx aluminum alloy composition (e.g., to restrict/avoid primary particulates formed during casting, such as Al3Zr primary particulates). In one embodiment, a new 7xxx aluminum alloy includes not greater than 0.13 wt. % Zr. In another embodiment, a new 7xxx aluminum alloy includes not greater than 0.12 wt. % Zr. In yet another embodiment, a new 7xxx aluminum alloy includes not greater than 0.11 wt. % Zr.

As noted above, the new 7xxx aluminum alloys may include 0.03-0.50 wt. % Mn. In one embodiment, a 7xxx aluminum alloy includes at least 0.08 wt. %. Mn. In another embodiment, a new 7xxx aluminum alloy includes at least 0.10 wt. % Mn. In yet another embodiment, a new 7xxx aluminum alloy includes at least 0.12 wt. % Mn. In another embodiment, a new 7xxx aluminum alloy includes at least 0.15 wt. % Mn. In yet another embodiment, a new 7xxx aluminum alloy includes at least 0.18 wt. % Mn. In another embodiment, a new 7xxx aluminum alloy includes at least 0.20 wt. % Mn. In yet another embodiment, a new 7xxx aluminum alloy includes at least 0.22 wt. % Mn. In another embodiment, a new 7xxx aluminum alloy includes at least 0.25 wt. % Mn.

In one embodiment, a 7xxx aluminum alloy includes not greater than 0.45 wt. % Mn. In another embodiment, a 7xxx aluminum alloy includes not greater than 0.40 wt. % Mn. In yet another embodiment, a 7xxx aluminum alloy includes not greater than 0.35 wt. % Mn. In another embodiment, a 7xxx aluminum alloy includes not greater than 0.30 wt. % Mn. In yet another embodiment, a 7xxx aluminum alloy includes not greater than 0.28 wt. % Mn.

In one embodiment, a 7xxx aluminum alloy includes 0.20-0.30 wt. % Mn. In one embodiment, a 7xxx aluminum alloy includes 0.08-0.13 wt. % Zr. In one embodiment, a 7xxx aluminum alloy includes 0.20-0.30 wt. % Mn and 0.08-0.13 wt. % Zr. In another embodiment, a 7xxx aluminum alloy includes 0.20-0.30 wt. % Mn and 0.08-0.12 wt. % Zr, wherein the zirconium content is below the peritectic of the 7xxx aluminum alloy composition. In yet another embodiment, a 7xxx aluminum alloy includes 0.20-0.30 wt. % Mn and 0.08-0.11 wt. % Zr, wherein the zirconium content is below the peritectic of the 7xxx aluminum alloy composition.

As noted above, the new 7xxx aluminum alloys may include up to 0.20 wt. % Cr. In one approach, a 7xxx aluminum alloy includes from 0.05 to 0.20 wt. % Cr. In another approach, a 7xxx aluminum alloy includes not greater than 0.15 wt. % Cr. In one embodiment, a 7xxx aluminum alloy includes not greater than 0.10 wt. % Cr. In another embodiment, a 7xxx aluminum alloy includes not greater than 0.08 wt. % Cr. In yet another embodiment, a 7xxx aluminum alloy includes not greater than 0.05 wt. % Cr. In another embodiment, a 7xxx aluminum alloy includes not greater than 0.04 wt. % Cr. In yet another embodiment, a 7xxx aluminum alloy includes not greater than 0.03 wt. % Cr. In another embodiment, a 7xxx aluminum alloy includes not greater than 0.02 wt. % Cr. In yet another embodiment, a 7xxx aluminum alloy includes not greater than 0.01 wt. % Cr. In another embodiment, a 7xxx aluminum alloy includes not greater than 0.005 wt. % Cr.

As noted above, the new 7xxx aluminum alloys may include up to 0.20 wt. % V. In one approach, a 7xxx aluminum alloy includes from 0.05 to 0.20 wt. % V. In another approach, a 7xxx aluminum alloy includes not greater than 0.15 wt. % V. In one embodiment, a 7xxx aluminum alloy includes not greater than 0.10 wt. % V. In another embodiment, a 7xxx aluminum alloy includes not greater than 0.08 wt. % V. In yet another embodiment, a 7xxx aluminum alloy includes not greater than 0.05 wt. % V. In another embodiment, a 7xxx aluminum alloy includes not greater than 0.04 wt. % V. In yet another embodiment, a 7xxx aluminum alloy includes not greater than 0.03 wt. % V. In another embodiment, a 7xxx aluminum alloy includes not greater than 0.02 wt. % V. In yet another embodiment, a 7xxx aluminum alloy includes not greater than 0.01 wt. % V. In another embodiment, a 7xxx aluminum alloy includes not greater than 0.005 wt. % V.

As noted above, the new 7xxx aluminum alloys may include up to 0.20 wt. % Fe. In one embodiment, a 7xxx aluminum alloy includes at least 0.01 wt. % Fe. In another embodiment, a 7xxx aluminum alloy includes at least 0.03 wt. % Fe. In yet another embodiment, a 7xxx aluminum alloy includes at least 0.05 wt. % Fe. In another embodiment, a 7xxx aluminum alloy includes at least 0.07 wt. % Fe. In yet another embodiment, a 7xxx aluminum alloy includes at least 0.09 wt. % Fe.

In one embodiment, a 7xxx aluminum alloy includes not greater than 0.18 wt. % Fe. In another embodiment, a 7xxx aluminum alloy includes not greater than 0.16 wt. % Fe. In yet another embodiment, a 7xxx aluminum alloy includes not greater than 0.14 wt. % Fe. In another embodiment, a 7xxx aluminum alloy includes not greater than 0.12 wt. % Fe. In some embodiments, iron is restricted to fairly low levels, which may facilitate improved bend properties. In one embodiment, a 7xxx aluminum alloy includes not greater than 0.10 wt. % Fe. In another embodiment, a 7xxx aluminum alloy includes not greater than 0.08 wt. % Fe. In yet another embodiment, a 7xxx aluminum alloy includes not greater than 0.06 wt. % Fe. In another embodiment, a 7xxx aluminum alloy includes not greater than 0.05 wt. % Fe. In yet another embodiment, a 7xxx aluminum alloy includes not greater than 0.04 wt. % Fe.

As noted above, the new 7xxx aluminum alloys may include up to 0.15 wt. % Si. In one embodiment, a 7xxx aluminum alloy includes at least 0.01 wt. % Si. In another embodiment, a 7xxx aluminum alloy includes at least 0.03 wt. % Si. In yet another embodiment, a 7xxx aluminum alloy includes at least 0.05 wt. % Si.

In one embodiment, a 7xxx aluminum alloy includes not greater than 0.12 wt. % Si. In another embodiment, a 7xxx aluminum alloy includes not greater than 0.10 wt. % Si. In yet another embodiment, a 7xxx aluminum alloy includes not greater than 0.08 wt. % Si. In some embodiments, silicon is restricted to fairly low levels, which may facilitate improved bend properties. In one embodiment, a 7xxx aluminum alloy includes not greater than 0.07 wt. % Si. In another embodiment, a 7xxx aluminum alloy includes not greater than 0.06 wt. % Si. In yet another embodiment, a 7xxx aluminum alloy includes not greater than 0.05 wt. % Si. In another embodiment, a 7xxx aluminum alloy includes not greater than 0.04 wt. % Si. In yet another embodiment, a 7xxx aluminum alloy includes not greater than 0.03 wt. % Si.

As noted above, the new 7xxx aluminum alloys may include up to 0.15 wt. % Ti. In one embodiment, a 7xxx aluminum alloy includes at least 0.005 wt. % Ti. In another embodiment, a 7xxx aluminum alloy includes at least 0.01 wt. % Ti. In yet another embodiment, a 7xxx aluminum alloy includes at least 0.015 wt. % Ti. In another embodiment, a 7xxx aluminum alloy includes at least 0.020 wt. % Ti. In yet another embodiment, a 7xxx aluminum alloy includes at least 0.025 wt. % Ti

In one embodiment, a 7xxx aluminum alloy includes not greater than 0.12 wt. % Ti. In another embodiment, a 7xxx aluminum alloy includes not greater than 0.10 wt. % Ti. In yet another embodiment, a 7xxx aluminum alloy includes not greater than 0.08 wt. % Ti. In yet another embodiment, a 7xxx aluminum alloy includes not greater than 0.05 wt. % Ti.

As noted above, the new 7xxx aluminum alloys may include up to 75 ppm B (boron). The boron may be in the form of titanium diboride. In one embodiment, a 7xxx aluminum alloy includes at least 1 ppm B. In another embodiment, a 7xxx aluminum alloy includes at least 3 ppm B. In yet another embodiment, a 7xxx aluminum alloy includes at least 5 ppm B. In another embodiment, a 7xxx aluminum alloy includes at least 8 ppm B. In yet another embodiment, a 7xxx aluminum alloy includes at least 10 ppm B.

In one embodiment, a 7xxx aluminum alloy includes not greater than 70 ppm B. In another embodiment, a 7xxx aluminum alloy includes not greater than 60 ppm B. In yet another embodiment, a 7xxx aluminum alloy includes not greater than 50 ppm B. In another embodiment, a 7xxx aluminum alloy includes not greater than 40 ppm B.

As noted above, the new 7xxx aluminum alloys generally include the stated alloying ingredients, the balance being aluminum, optional incidental elements, and impurities. As used herein, “incidental elements” means those elements or materials, other than the above listed elements, that may optionally be added to the alloy to assist in the production of the alloy. Examples of incidental elements include casting aids, such as deoxidizers. Optional incidental elements may be included in the alloy in a cumulative amount of up to 1.0 wt. %. As one non-limiting example, one or more incidental elements may be added to the alloy during casting to reduce or restrict (and in some instances eliminate) ingot cracking due to, for example, oxide fold, pit and oxide patches. These types of incidental elements are generally referred to herein as deoxidizers. Examples of some deoxidizers include Ca, Sr, and Be. When calcium (Ca) is included in the alloy, it is generally present in an amount of up to about 0.05 wt. %, or up to about 0.03 wt. %. In some embodiments, Ca is included in the alloy in an amount of about 0.001-0.03 wt % or about 0.05 wt. %, such as 0.001-0.008 wt. % (or 10 to 80 ppm). Strontium (Sr) may be included in the alloy as a substitute for Ca (in whole or in part), and thus may be included in the alloy in the same or similar amounts as Ca. Traditionally, beryllium (Be) additions have helped to reduce the tendency of ingot cracking, though for environmental, health and safety reasons, some embodiments of the alloy are substantially Be-free. When Be is included in the alloy, it is generally present in an amount of up to about 20 ppm. Incidental elements may be present in minor amounts, or may be present in significant amounts, and may add desirable or other characteristics on their own without departing from the alloy described herein, so long as the alloy retains the desirable characteristics described herein. It is to be understood, however, that the scope of this disclosure should not/cannot be avoided through the mere addition of an element or elements in quantities that would not otherwise impact on the combinations of properties desired and attained herein.

The new 7xxx aluminum alloys may contain low amounts of impurities. In one embodiment, a new 7xxx aluminum alloy includes not greater than 0.15 wt. %, in total, of the impurities, and wherein the aluminum alloy includes not greater than 0.05 wt. % of each of the impurities. In another embodiment, a new 7xxx aluminum alloy includes not greater than 0.10 wt. %, in total, of the impurities, and wherein the aluminum alloy includes not greater than 0.03 wt. % of each of the impurities.

The new 7xxx aluminum alloys are generally substantially free of lithium, i.e., lithium is included only as an impurity, and generally at less than 0.04 wt. % Li, or less than 0.01 wt. % Li. The new 7xxx aluminum alloys are generally substantially free of silver, i.e., silver is included only as an impurity, and generally at less than 0.04 wt. % Ag, or less than 0.01 wt. % Ag. The new 7xxx aluminum alloys are generally substantially free of lead, i.e., lead is included only as an impurity, and generally at less than 0.04 wt. % Pb, or less than 0.01 wt. % Pb. The new 7xxx aluminum alloys are generally substantially free of cadmium, i.e., cadmium is included only as an impurity, and generally at less than 0.04 wt. % Cd, or less than 0.01 wt. % Cd. The new 7xxx aluminum alloys are generally substantially free of thallium, i.e., thallium is included only as an impurity, and generally at less than 0.04 wt. % Tl, or less than 0.01 wt. % Tl. The new 7xxx aluminum alloys are generally substantially free of scandium, i.e., scandium is included only as an impurity, and generally at less than 0.04 wt. % Sc, or less than 0.01 wt. % Sc. The new 7xxx aluminum alloys are generally substantially free of nickel, i.e., nickel is included only as an impurity, and generally at less than 0.04 wt. % Ni, or less than 0.01 wt. % Ni.

II. Methods of Production

The new 7xxx aluminum alloys may be produced by casting (e.g., direct chill casting or continuously casting) into an ingot or strip followed by appropriate processing to achieve a variety of tempers, such as one of a T temper, a W temper, an O temper, or an F temper as per ANSI H35.1 (2009). In one embodiment, a new aluminum alloy is processed to a “T temper” (thermally treated), such as into any of a T1, T2, T3, T4, T5, T6, T7, T8, T9 or T10 temper as per ANSI H35.1 (2009). Of these, T6 and T7 tempers may be particularly relevant.

In one embodiment, and referring now to FIG. 1, a method (100) may include casting (105) an ingot or strip of any of the aluminum alloys described in Section I, above. After casting, an ingot may be homogenized (110), which homogenization may include scalping, lathing or peeling (if needed). The homogenization step (110) may be skipped with continuously cast strips, such as those described in U.S. Pat. No. 6,672,368. Next, the ingot/strip is then rolled (115) to final gauge. In one embodiment, the final gauge sheet product has a thickness of from 0.5 to 4.0 mm. The rolling step (115) generally includes hot rolling to an intermediate gauge (117) and then cold rolling to final gauge (121). An intermediate anneal (119) may optionally be completed between hot rolling (117) and cold rolling (121). After the rolling step (115), the product may be solution heat treated and then rapidly quenched (125). The solution heat treating portion of this step (125) generally comprises heating the final gauge product to a temperature sufficient and for a time sufficient to dissolve a large volume fraction of precipitation hardened phases (e.g., 11 (eta) phase). The quenching portion of this step (125) generally involves cooling the solution heat treated material rapidly to less than 200° F. (e.g., less than 100° F.), and generally at a cooling rate of at least 100° F. per second, such as by water immersion and/or spraying. In one embodiment, the quench rate of step 125 is at least 1000° F. per second. In another embodiment, the quench rate of step 125 is at least 10,000° F. per second.

After the solution heat treating and quenching step (125), the material may be artificially aged (130), such as by heating to one or more temperatures within the range of 200-450° F. In one embodiment, the artificial aging comprises peak strength aging to a T6 temper. A peak strength aged temper is where a product realizes a strength within about 20 MPa (≈3 ksi) of its peak strength, as determined by appropriate aging curves. In one embodiment, the artificial aging comprises overaging to a T7 or T77 temper. An overaged temper is where a product is aged past peak strength and to a strength more than 20 MPa (≈3 ksi) less than its peak strength, as determined by appropriate aging curves. Overaging may facilitate improved corrosion resistance. The artificial aging step (130) may be completed by the aluminum sheet manufacturer, or the artificial aging step (130) may be completed by an automotive manufacturer (e.g., as a part of paint baking).

In one embodiment, the artificial age step (130) is a two-step aging practice, optionally followed by a paint baking step, wherein the alloy is held at a first temperature for a first period of time and then held at a second temperature for a second period of time. In one embodiment, the first temperature is within the range of 225-275° F. and the first period of time is from 2 to 16 hours (e.g., from 6 to 10 hours). The second temperature is generally higher than the first temperature, e.g. from 25° to 100° F. higher than the first temperature. In one embodiment, the second temperature is within the range of 300-350° F. and the second period of time is from 2 to 16 hours (e.g., from 6 to 10 hours). Two-step aging practices differ from conventional three-step aging practices, such as those described in U.S. Pat. No. 6,972,110, because two-step aging practices only include two-steps, i.e., after conclusion of the second step there are no additional artificial aging steps applied to the product, except for an optional paint baking step.

In one embodiment, and referring now to FIG. 2, alternate processing is used. In this embodiment (100′), the same steps as FIG. 1 apply, except a new post-rolling anneal (200) is completed after the rolling step (115) and prior to the solution heat treatment and quenching step (125). In this embodiment, the final gauge materials are annealed (200) at one or more anneal temperatures (210) within the range of from 525° F. to 850° F. and at one or more anneal times (220) within the range of from 0.5 to 50 hours. The anneal products are then slowly cooled to a temperature of not greater than 200° F. at a cooling rate (230) of not greater than 500° F. per minute. The time-temperature profile may be selected to achieve a desired amount of recrystallization in the final product, as described below. In one embodiment, the new anneal process (200) facilitates partially recrystallized final products having from 15-95 vol. % recrystallized grains (240), as described in further detail below. Such tailored final products may realize an improved combination of properties, as shown by the examples herein. In one embodiment, the annealing is completed via an induction furnace and corresponding induction heating.

In one embodiment, the anneal (200) is completed by heating a coil of the final gauge 7xxx sheet product to the anneal temperature (210) using an appropriate heat-up rate (212), after which the product is held at the anneal temperature for the anneal time (220). The coil may then be cooled by removing it from the furnace and allowing it to sit in ambient conditions until it reaches ambient temperature, i.e., is coil cooled. The coil cooling may result in the slow cooling rates (230) described herein.

As noted above, the anneal temperature (210) may be from 525° F. to 850° F., depending on the amount of recrystallization and/or grain size desired in the final product. Grain size is defined in the Definitions section, below. In cases where the microstructure is partially recrystallized, grain size refers to values obtained considering both recrystallized and unrecrystallized grains. Multiple anneal temperatures within the above-noted temperature range may be selected. In one embodiment, the anneal temperature is at least 575° F. In another embodiment, the anneal temperature is at least 625° F. In yet another embodiment, the anneal temperature is at least 675° F. In one embodiment, the anneal temperature is not greater than 825° F. In another embodiment, the anneal temperature is not greater than 775° F. In one embodiment, the anneal temperature is from 650-800° F. In another embodiment, the anneal temperature is from 675-750° F. The heat-up rate (212) may be any suitable heat-up rate that facilitates achievement of the appropriate amount and/or size of recrystallized grains, such as any of the heat-up rates described in Example 1, Table 2, below. In one embodiment, the anneal heat-up rate (as measured from ambient temperature until the product is within 10° F. of the anneal temperature) is from 25° to 50° C. per hour (linear calculation employed for ease of determination).

As noted above, the anneal time (220) may be from 0.5 to 50 hours, depending on the amount of recrystallization and/or grain size desired in the final product, and multiple anneal times may be selected. In one embodiment, the anneal time is at least 1 hour. In another embodiment, the anneal time is at least 2 hours. In one embodiment, the anneal time is not greater than 40 hours. In another embodiment, the anneal time is not greater than 30 hours.

As noted above, the anneal cooling rate (230) is generally not greater than 500° F. per minute as measured by the time it takes the material to cool from the anneal temperature (210) to 200° F. In one embodiment, the anneal cooling rate (230) is not greater than 100° F. per minute. In another embodiment, the anneal cooling rate (230) is not greater than 10° F. per minute. In yet another embodiment, the anneal cooling rate (230) is not greater than 5° F. per minute. In another embodiment, the anneal cooling rate (230) is not greater than 2° F. per minute. As noted above, the anneal cooling rate (230) may be accomplished by coil cooling.

As noted above, the new anneal process (200) facilitates partially recrystallized final products having from 15-95 vol. % recrystallized grains (240), as described in further detail below. In one embodiment, the annealing process (200) produces materials having at least 20 vol. % recrystallized grains. In another embodiment, the annealing process (200) produces materials having at least 25 vol. % recrystallized grains.

In one embodiment, the annealing process (200) produces materials having not greater than 95 vol. % recrystallized grains. In another embodiment, the annealing process (200) produces materials having not greater than 90 vol. % recrystallized grains. In yet another embodiment, the annealing process (200) produces materials having not greater than 85 vol. % recrystallized grains. In another embodiment, the annealing process (200) produces materials having not greater than 80 vol. % recrystallized grains. In yet another embodiment, the annealing process (200) produces materials having not greater than 75 vol. % recrystallized grains. In another embodiment, the annealing process (200) produces materials having not greater than 70 vol. % recrystallized grains.

Referring now to FIGS. 2-3, as mentioned above, it has been surprisingly found that an anneal (200) may be completed after rolling (115) and prior to solution heat treating (125) to produce 7xxx sheet products having tailored amounts of recrystallized grains and/or a tailored average grain size. As the below examples show, tailoring the amount of recrystallization and/or grain size may facilitate the realization of an improved combination of properties, such as an improved combination of at least two of strength, elongation, fracture behavior (evaluated using the three-point bending test described herein), and corrosion resistance. Referring now to FIG. 3, in one embodiment, a method (300) includes preselecting an amount of recrystallization (305) to achieve in a rolled 7xxx sheet product. The preselected amount of recrystallization may be 15-95% recrystallization (308), or any of the recrystallization amounts described in the preceding paragraphs. The method (300) further includes, at least partially based on the recrystallization preselecting step (305), preselecting the anneal conditions (315) to complete relative to the rolled 7xxx sheet product, which preselected anneal conditions include preselecting one or more anneal temperatures (317) and/or one or more anneal times (319) to be used for the anneal (200). A preselected heat-up rate (318) may also be selected, which heat-up rate may affect the amount of recrystallization and/or average grain size of the microstructure. A preselected anneal quench rate (321) may also be selected. The method may further comprise completing the anneal (200) using the preselected anneal conditions (315). At least partially due to the preselected anneal conditions (315), the rolled 7xxx sheet product may realize (325) the selected amount of recrystallization (i.e., amount of recrystallized grains), such as any of the recrystallization amounts described in the preceding paragraph. Similarly, although not illustrated, a grain size may be preselected, such as any of the grain sizes shown in Example 1, Table 3, below. At least partially due to the preselected anneal conditions (315), the rolled 7xxx sheet product may realize the preselected grain size.

As one example, and referring now to FIG. 4, Alloy E of Example 1 (below) achieved a 70% recrystallized microstructure by heating to 625° F. at a heat-up rate of 60.9° F./hour (linear), holding at 625° F. for 2 hours followed by slow cooling to room temperature, followed by solution heat treating at 870° F. for 7 minutes followed by water quenching. As shown, recrystallized grains are generally homogenously intermixed with unrecrystallized grains through the thickness. This is completely different than known unrecrystallized sheet products where some recrystallized grains may be found near the surface but the interior is unrecrystallized. The grain size of the microstructure of FIG. 4 was 56.4 micrometers (includes both recrystallized and unrecrystallized grain sizes).

As another example, and referring now to FIG. 5, a 99% recrystallized microstructure was achieved in Alloy G by heating to 525° F. at a heat-up rate of 49.8° F./hour (linear), holding at 525° F. for 24 hours, followed by slow cooling to room temperature, followed by solution heat treating at 870° F. for 7 minutes followed by water quenching. The grain size of the microstructure of FIG. 5 was 65.2 micrometers.

As another example, and referring now to FIG. 6, a 60% recrystallized microstructure was achieved in Alloy E by heating to 725° F. at a heat-up rate of 72.0° F./hour (linear), holding at 725° F. for 2 hours, followed by slow cooling to room temperature, followed by solution heat treating at 870° F. for 7 minutes followed by water quenching. The grain size of the microstructure of FIG. 6 was 67.1 micrometers. Upon subsequent aging, this microstructure realizes an improved combination of mechanical properties (see Example 1 below).

As another example, and referring now to FIG. 7, a 92% recrystallized microstructure was achieved in Alloy G by heating to 725° F. at a heat-up rate of 72.0° F./hour (linear), holding at 725° F. for 2 hours, followed by slow cooling to room temperature, followed by solution heat treating at 870° F. for 7 minutes followed by water quenching. The grain size of the microstructure of FIG. 7 was 100.5 micrometers. Upon subsequent aging, this microstructure realizes an improved combination of mechanical properties (see Example 1 below).

Referring back to FIGS. 1-2, as described above, after rolling (FIG. 1) and any post-roll annealing (FIG. 2), the final gauge sheet product is solution heat treated and quenched (125). In one embodiment, the solution heat treating and quenching step is accomplished by the manufacturer of the final gauge 7xxx aluminum alloy sheet product, after which the product is either (i) shipped to the customer (e.g., in the W-temper) or (ii) is artificially aged (130), as described above, and then shipped to the customer.

In another embodiment, the manufacturer of the final gauge 7xxx aluminum alloy sheet product ships the final gauge 7xxx aluminum alloy sheet product in the F temper (as fabricated) or O temper (as annealed) to a customer, such as an automotive manufacturer, who completes the solution heat treating and quenching step (125) and any artificial aging step (130). In one embodiment, the customer completes the solution heat treating and quenching step (125) as part of a hot forming operation, wherein the final gauge 7xxx aluminum alloy sheet product is heated to a solution heat treatment temperature and then formed into a component (e.g., an automotive component). The tooling used to form the final gauge 7xxx aluminum alloy sheet product into the component generally deforms the material into a complex shape. In one embodiment, the hot forming comprises forming the final gauge 7xxx aluminum alloy sheet product in one or more dies. The tooling temperature may be substantially below the solution heat treatment temperature. Thus, quenching of the final gauge 7xxx aluminum alloy sheet product may occur due to contact contact with the tooling. In some embodiments, the tooling can be water or air cooled. The formed 7xxx aluminum alloy sheet product may then be artificially aged (130) in one or more steps. In one embodiment, at least one of the artificial aging steps includes paint baking (e.g., for 20-40 minutes at 180-190° C.).

III. Microstructure

As noted above, the 7xxx aluminum alloy products may realize a unique microstructure, which may at least partially give rise to the unique properties shown herein. For instance, the 7xxx aluminum alloys may be partially recrystallized or fully recrystallized. As used herein, “partially recrystallized” means a product realizes 15-95% recrystallization (i.e., contains 15-95 vol. % recrystallized grains), as determined using the Recrystallization Determination Procedure, described in the Definitions section, below. As used herein, a fully recrystallized product is 96-100% recrystallized (i.e., contains 96-100 vol. % recrystallized grains), as determined using the Recrystallization Determination Procedure, described in the Definitions section, below.

In one embodiment, the 7xxx aluminum alloy product is a fully recrystallized sheet product. In another embodiment, the 7xxx aluminum alloy product is a partially recrystallized sheet product having 15-95 vol. % recrystallized grains. In one embodiment, a partially recrystallized 7xxx aluminum alloy sheet product comprises at least 20 vol. % recrystallized grains. In another embodiment, a partially recrystallized 7xxx aluminum alloy sheet product comprises at least 25 vol. % recrystallized grains. In yet another embodiment, a partially recrystallized 7xxx aluminum alloy sheet product comprises at least 30 vol. % recrystallized grains. In another embodiment, a partially recrystallized 7xxx aluminum alloy sheet product comprises at least 35 vol. % recrystallized grains. In one embodiment, a partially recrystallized 7xxx aluminum alloy sheet product comprises not greater than 90 vol. % recrystallized grains. In another embodiment, a partially recrystallized 7xxx aluminum alloy sheet product comprises not greater than 85 vol. % recrystallized grains. In yet another embodiment, a partially recrystallized 7xxx aluminum alloy sheet product comprises not greater than 80 vol. % recrystallized grains. In another embodiment, a partially recrystallized 7xxx aluminum alloy sheet product comprises not greater than 75 vol. % recrystallized grains. In yet another embodiment, a partially recrystallized 7xxx aluminum alloy sheet product comprises not greater than 70 vol. % recrystallized grains.

In one embodiment, a 7xxx aluminum alloy sheet product from 30 to 80 vol. % recrystallized grains. In another embodiment, a 7xxx aluminum alloy sheet product comprises from 35 to 75 vol. % recrystallized grains.

The 7xxx aluminum alloy products may contain an appropriate amount of dispersoids, wherein the amount of dispersoids is calculated from the formula (wt. % Mn)*3.52+(wt. % Zr)*1.28+(wt. % Cr+wt. % V)*6.34. In one approach, a 7xxx aluminum alloy sheet product comprises from 0.07 to 1.95 vol. % of dispersoids. In one embodiment, a 7xxx aluminum alloy sheet product comprises at least 0.08 vol. % dispersoids. In another embodiment, a 7xxx aluminum alloy sheet product comprises at least 0.09 vol. % dispersoids. In yet another embodiment, a 7xxx aluminum alloy sheet product comprises at least 0.10 vol. % dispersoids. In another embodiment, a 7xxx aluminum alloy sheet product comprises at least 0.11 vol. % dispersoids. In yet another embodiment, a 7xxx aluminum alloy sheet product comprises at least 0.12 vol. % dispersoids. In another embodiment, a 7xxx aluminum alloy sheet product comprises at least 0.13 vol. % dispersoids.

In one embodiment, a 7xxx aluminum alloy sheet product comprises not greater than 1.90 vol. % dispersoids. In another embodiment, a 7xxx aluminum alloy sheet product comprises not greater than 1.85 vol. % dispersoids. In yet another embodiment, a 7xxx aluminum alloy sheet product comprises not greater than 1.80 vol. % dispersoids. In another embodiment, a 7xxx aluminum alloy sheet product comprises not greater than 1.70 vol. % dispersoids. In another embodiment, a 7xxx aluminum alloy sheet product comprises not greater than 1.60 vol. % dispersoids. In yet another embodiment, a 7xxx aluminum alloy sheet product comprises not greater than 1.50 vol. % dispersoids. In another embodiment, a 7xxx aluminum alloy sheet product comprises not greater than 1.40 vol. % dispersoids. In yet another embodiment, a 7xxx aluminum alloy sheet product comprises not greater than 1.30 vol. % dispersoids. In another embodiment, a 7xxx aluminum alloy sheet product comprises not greater than 1.20 vol. % dispersoids. In yet another embodiment, a 7xxx aluminum alloy sheet product comprises not greater than 1.10 vol. % dispersoids. In one approach, a 7xxx aluminum alloy sheet product comprises 0.80 to 1.20 vol. % dispersoids.

The 7xxx aluminum alloy sheet products may contain precipitate hardening phases. In one embodiment, a 7xxx aluminum alloy sheet product contains at least one of M-phase and S-phase precipitates. In one embodiment, a 7xxx aluminum alloy sheet product is absent of T-phase precipitates. The presence or absence of M-phase, S-phase and T-phase precipitates, and their corresponding solvus temperature(s), is to be determined using THERMO-CALC software (hitps://www.thermocalc.com/, Therom-Calc, Råsundavagen 18, SE-169 67 Solna, Sweden) using the THERMO-CALC Aluminum Database, Version 5, “TCAL5,” or an equivalent software program and database, based on the actual composition of the 7xxx aluminum alloy. In one aspect, a 7xxx aluminum alloy sheet product at least contains M-phase precipitates and the M-phase precipitates have a solvus temperature in the range of 744-810° F. (395.6-413.9° C.).

In one approach, a 7xxx aluminum alloy sheet product contains both M-phase and S-phase precipitates and the S-phase precipitates of the 7xxx aluminum alloy sheet product have a solvus temperature of not greater than 850° F. (454.4° C.). In another embodiment, the S-phase precipitates have a solvus temperature of not greater than 845° F. In yet another embodiment, the S-phase precipitates have a solvus temperature of not greater than 840° F. In another embodiment, the S-phase precipitates have a solvus temperature of not greater than 835° F. In yet another embodiment, the S-phase precipitates have a solvus temperature of not greater than 830° F. In another embodiment, the S-phase precipitates have a solvus temperature of not greater than 825° F. In one embodiment, the S-phase precipitates have a solvus temperature of not greater than 820° F. In another embodiment, the S-phase precipitates have a solvus temperature of not greater than 815° F. In yet another embodiment, the S-phase precipitates have a solvus temperature of not greater than 810° F. In another embodiment, the S-phase precipitates have a solvus temperature of not greater than 805° F. In yet another embodiment, the S-phase precipitates have a solvus temperature of not greater than 800° F. In another embodiment, the S-phase precipitates have a solvus temperature of not greater than 795° F.

In one embodiment, a 7xxx aluminum alloy sheet product contains both M-phase and S-phase precipitates, the M-phase precipitates have a solvus temperature in the range of 744-810° F. (395.6-413.9° C.), the S-phase precipitates of the 7xxx aluminum alloy sheet product have a solvus temperature of not greater than 850° F. (454.4° C.), such as any of the solvus temperatures described above, and the 7xxx aluminum alloy sheet product is absent of T-phase precipitates.

IV. Properties

As noted above, the new 7xxx aluminum alloys may realize an improved combination of properties, such as an improved combination of two or more of strength, ductility, fracture behavior (e.g., as evaluated using a three-point bending test), and corrosion resistance.

In one embodiment, a 7xxx aluminum alloy sheet product has a thickness of from 0.5 to 4.0 mm and realizes a tensile yield strength (LT) of at least 450 MPa. In another embodiment, a 7xxx aluminum alloy sheet product has a thickness of from 0.5 to 4.0 mm and realizes a tensile yield strength (LT) of at least 460 MPa. In yet another embodiment, a 7xxx aluminum alloy sheet product has a thickness of from 0.5 to 4.0 mm and realizes a tensile yield strength (LT) of at least 470 MPa. In some embodiments, the above strength values are consistent with continuously cast materials. In another embodiment, a 7xxx aluminum alloy sheet product is cast as an ingot (e.g., using DC (direct-chill) or electromagnetic casting) and then wrought processed to a final gauge material having a thickness of from 0.5 to 4.0 mm. In the ingot cast embodiments, the strength values may be higher. In one embodiment, a 7xxx aluminum alloy sheet product has a thickness of from 0.5 to 4.0 mm and realizes a tensile yield strength (LT) of at least 480 MPa. In another embodiment, a 7xxx aluminum alloy sheet product has a thickness of from 0.5 to 4.0 mm and realizes a tensile yield strength (LT) of at least 490 MPa. In yet another embodiment, a 7xxx aluminum alloy sheet product has a thickness of from 0.5 to 4.0 mm and realizes a tensile yield strength (LT) of at least 500 MPa. In another embodiment, a 7xxx aluminum alloy sheet product has a thickness of from 0.5 to 4.0 mm and realizes a tensile yield strength (LT) of at least 510 MPa. In yet another embodiment, a 7xxx aluminum alloy sheet product has a thickness of from 0.5 to 4.0 mm and realizes a tensile yield strength (LT) of at least 520 MPa. In another embodiment, a 7xxx aluminum alloy sheet product has a thickness of from 0.5 to 4.0 mm and realizes a tensile yield strength (LT) of at least 530 MPa. In yet another embodiment, a 7xxx aluminum alloy sheet product has a thickness of from 0.5 to 4.0 mm and realizes a tensile yield strength (LT) of at least 540 MPa, or higher.

In one approach, a 7xxx aluminum alloy sheet product has a thickness of 0.5 to 4.0 mm and is capable of realizing a three-point bend extension of at least 5.8 mm as per the “three-point bending test” described in the Definitions section, below. As noted below, all three-point bend testing is to be conducted at 2.0±0.05 mm. Thus, for a 7xxx aluminum alloy sheet product having a thickness of from 0.5 to 1.94 mm or 2.06 to 4.0 mm, the bend extension for such a product is determined by reproducing the product at 2.0±0.05 mm, after which its three-point bend extension is measured. In one embodiment, a 7xxx aluminum alloy sheet product realizes a three-point bend extension of at least 6.0 mm. In yet another embodiment, a 7xxx aluminum alloy sheet product realizes a three-point bend extension of at least 6.1 mm. In another embodiment, a 7xxx aluminum alloy sheet product realizes a three-point bend extension of at least 6.2 mm. In yet another embodiment, a 7xxx aluminum alloy sheet product realizes a three-point bend extension of at least 6.3 mm. In another embodiment, a 7xxx aluminum alloy sheet product realizes a three-point bend extension of at least 6.4 mm. In yet another embodiment, a 7xxx aluminum alloy sheet product realizes a three-point bend extension of at least 6.5 mm. In another embodiment, a 7xxx aluminum alloy sheet product realizes a three-point bend extension of at least 6.6 mm. In some embodiments, the above three-point bend extension values are consistent with continuously cast materials. In another embodiment, a 7xxx aluminum alloy sheet product is cast as a DC ingot and then wrought processed to a final gauge material having a thickness of from 0.5 to 4.0 mm. In another embodiment, a 7xxx aluminum alloy sheet product is cast as an ingot (e.g., using DC (direct-chill) or electromagnetic casting) and then wrought processed to a final gauge material having a thickness of from 0.5 to 4.0 mm, in which case the three-point bend extension values may be higher. In one embodiment, a 7xxx aluminum alloy sheet product has a thickness of from 0.5 to 4.0 mm and realizes a three-point bend extension of at least 6.7 mm. In another, a 7xxx aluminum alloy sheet product has a thickness of from 0.5 to 4.0 mm and realizes a three-point bend extension of at least 6.8 mm. In yet another, a 7xxx aluminum alloy sheet product has a thickness of from 0.5 to 4.0 mm and realizes a three-point bend extension of at least 7.0 mm. In another, a 7xxx aluminum alloy sheet product has a thickness of from 0.5 to 4.0 mm and realizes a three-point bend extension of at least 7.2 mm. In yet another, a 7xxx aluminum alloy sheet product has a thickness of from 0.5 to 4.0 mm and realizes a three-point bend extension of at least 7.4 mm. In another, a 7xxx aluminum alloy sheet product has a thickness of from 0.5 to 4.0 mm and realizes a three-point bend extension of at least 7.6 mm. In yet another, a 7xxx aluminum alloy sheet product has a thickness of from 0.5 to 4.0 mm and realizes a three-point bend extension of at least 7.8 mm. In another, a 7xxx aluminum alloy sheet product has a thickness of from 0.5 to 4.0 mm and realizes a three-point bend extension of at least 8.0 mm. In yet another, a 7xxx aluminum alloy sheet product has a thickness of from 0.5 to 4.0 mm and realizes a three-point bend extension of at least 8.2 mm. In another, a 7xxx aluminum alloy sheet product has a thickness of from 0.5 to 4.0 mm and realizes a three-point bend extension of at least 8.4 mm. In yet another, a 7xxx aluminum alloy sheet product has a thickness of from 0.5 to 4.0 mm and realizes a three-point bend extension of at least 8.6 mm. In another, a 7xxx aluminum alloy sheet product has a thickness of from 0.5 to 4.0 mm and realizes a three-point bend extension of at least 8.8 mm. In yet another, a 7xxx aluminum alloy sheet product has a thickness of from 0.5 to 4.0 mm and realizes a three-point bend extension of at least 9.0 mm. In another, a 7xxx aluminum alloy sheet product has a thickness of from 0.5 to 4.0 mm and realizes a three-point bend extension of at least 9.2 mm. In yet another, a 7xxx aluminum alloy sheet product has a thickness of from 0.5 to 4.0 mm and realizes a three-point bend extension of at least 9.4 mm. In another, a 7xxx aluminum alloy sheet product has a thickness of from 0.5 to 4.0 mm and realizes a three-point bend extension of at least 9.5 mm. In yet another, a 7xxx aluminum alloy sheet product has a thickness of from 0.5 to 4.0 mm and realizes a three-point bend extension of at least 9.6 mm. In another, a 7xxx aluminum alloy sheet product has a thickness of from 0.5 to 4.0 mm and realizes a three-point bend extension of at least 9.7 mm. In yet another, a 7xxx aluminum alloy sheet product has a thickness of from 0.5 to 4.0 mm and realizes a three-point bend extension of at least 9.8 mm. In another, a 7xxx aluminum alloy sheet product has a thickness of from 0.5 to 4.0 mm and realizes a three-point bend extension of at least 9.9 mm. In yet another, a 7xxx aluminum alloy sheet product has a thickness of from 0.5 to 4.0 mm and realizes a three-point bend extension of at least 10.0 mm.

In one approach, a 7xxx aluminum alloy sheet product is produced from a continuously cast strip and realizes a strength to three-point bend at extension relationship above a line defined by the formula Y=−0.02X+Z, wherein X is the TYS(LT) (MPa) of the 7xxx aluminum alloy sheet product is at least 450 MPa, wherein Y is the LT three-point bend extension (mm) of the 7xxx aluminum alloy sheet product and is at least 5.8 mm, and wherein Z is 15.0. In one embodiment, Z is 15.25. In another embodiment, Z is 15.5. In yet another embodiment, Z is 15.75. In another embodiment, Z is 16.0. In yet another embodiment, Z is 16.25. In another embodiment, Z is 16.5. In yet another embodiment, Z is 16.75. As an example, when Z is 16.0 and the TYS(LT) of the alloy is 450 MPa, the three-point bend extension would be at least 7.0 mm. As another example, when Z is 16.25 and the three-point bend extension is 6.6 mm, the TYS(LT) would be at least 482 MPa (LT).

In another approach, the 7xxx aluminum alloy sheet product is produced from an ingot and realizes a strength to three-point bend at extension relationship above a line defined by the formula Y=−0.039X+Z, wherein X is the TYS(LT) (MPa) of the 7xxx aluminum alloy sheet product is at least 450 MPa, wherein Y is the LT three-point bend extension (mm) of the 7xxx aluminum alloy sheet product and is at least 7.0 mm, and wherein Z is 25.25. In one embodiment, Z is 25.5. In another embodiment, Z is 25.75. In yet another embodiment, Z is 26.0. In another embodiment, Z is 26.25. In yet another embodiment, Z is 26.5. In another embodiment, Z is 26.75. In yet another embodiment, Z is 27.0. In another embodiment, Z is 27.25. In yet another embodiment, Z is 27.5. In another embodiment, Z is 27.75. In yet another embodiment, Z is 28.0. In another embodiment, Z is 28.25. In yet another embodiment, Z is 28.5. As an example, when Z is 26.25 and the TYS(LT) of the alloy is 470 MPa, the three-point bend extension would be at least 7.9 mm. As another example, when Z is 27.75 and the three-point bend extension is 8.9 mm, the TYS(LT) would be at least 483 MPa (LT).

In one embodiment, a 7xxx aluminum alloy sheet product has a thickness of from 0.5 to 4.0 mm and realizes an exfoliation rating of at least EB when tested in accordance with ASTM G34-01(2018). In another embodiment, a 7xxx aluminum alloy sheet product has a thickness of from 0.5 to 4.0 mm and realizes an exfoliation rating of at least EA when tested in accordance with ASTM G34-01(2018). In yet another embodiment, a 7xxx aluminum alloy sheet product has a thickness of from 0.5 to 4.0 mm and realizes an exfoliation rating of at least P when tested in accordance with ASTM G34-01(2018).

In one embodiment, a 7xxx aluminum alloy sheet product has a thickness of from 0.5 to 4.0 mm and passes at least 20 days of ASTM G44-99(2013) testing in the LT direction at a net stress of 353 MPa, wherein all 5 specimens of the 7xxx aluminum alloy sheet survive the ASTM G44 testing for 20 days.

In one embodiment, a 7xxx aluminum alloy sheet product has a thickness of from 0.5 to 4.0 mm and realizes an average depth of attack of not greater than 50 micrometers when tested in accordance with ASTM G110-92(2015) for 6 hours. In another embodiment, a 7xxx aluminum alloy sheet product has a thickness of from 0.5 to 4.0 mm and realizes an average depth of attack of not greater than 40 micrometers when tested in accordance with ASTM G110-92(2015) for 6 hours. In another embodiment, a 7xxx aluminum alloy sheet product has a thickness of from 0.5 to 4.0 mm and realizes an average depth of attack of not greater than 30 micrometers when tested in accordance with ASTM G110-92(2015) for 6 hours. In another embodiment, a 7xxx aluminum alloy sheet product has a thickness of from 0.5 to 4.0 mm and realizes an average depth of attack of not greater than 25 micrometers when tested in accordance with ASTM G110-92(2015) for 6 hours.

V. Product Applications

The new aluminum alloys described herein may be used in a variety of product applications, such as in automotive and/or industrial applications. For instance, the new alloys may be used in body-in-white components or other structural components of an automobile (e.g., B-pillars, door beams, roof rails).

VI. Definitions

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

“Hot working” such as by hot rolling means working the aluminum alloy product at elevated temperature, and generally at least 250° F. Strain-hardening is restricted/avoided during hot working, which generally differentiates hot working from cold working.

“Cold working” such as by cold rolling means working the aluminum alloy product at temperatures that are not considered hot working temperatures, generally below about 250° F. (e.g., at ambient).

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

Strength and elongation are measured in accordance with ASTM E8/E8M-16a and B557-15.

“Three-point bending tests” (sometimes called 3-point bending tests) are measured in accordance with VDA 238-100, entitled, Plate bending test for metallic materials, Validation Rule, 1 Jun. 2017 (see https://www.vda.de/en/services/Publications/vda-238-100-plate-bending-test-for-metallic-materials.html), where the final gauge (thickness) of the sheet is 2.0±0.05 mm, the coupon is fixed in the test frame, and a punch radius of 0.2 mm is used, except the VDA test is modified as follows:

    • the specimen size is 25 mm wide and 51 mm long;
    • the extension at 70% load drop is used as a metric, with higher extensions representing greater fracture toughness or crash resistance (the normal test VDA 238-100 utilizes the bend angle measured after 5% drop in load as a metric for comparing materials).

Ten replicate three-point bending coupons are tested for each test. Longitudinal (L) specimens are oriented such that the bend line is perpendicular to the rolling direction and transverse (LT) specimens are oriented such that the bend line is parallel to the rolling direction.

“Percent recrystallized” and the like means the volume percent of a wrought aluminum alloy product having recrystallized grains. The amount of recrystallized grains is determined by EBSD (electron backscatter diffraction) analysis of a suitable number of SEM micrographs of the wrought aluminum alloy product, as per the Recrystallization Determination Procedure, below. Generally at least 5 micrographs should be analyzed.

Recrystallization Determination Procedure

“Recrystallized grains” means those grains of a crystalline microstructure that meet the “first grain criteria”, defined below, and as measured using the OIM (Orientation Imaging Microscopy) sampling procedure, described below.

The OIM analysis is to be completed through the full thickness of the sheet sample on the L-ST plane, using the OIM sample procedure, below. The size of the sample to be analyzed will generally vary by gauge. Prior to measurement, the OIM samples are prepared by standard metallographic sample preparation methods. For example, the OIM samples are metallographically prepared and then polished (e.g., using 0.05 micron colloidal silica). The samples are then anodized in Barker's reagent, a diluted fluoroboric acid solution, for 90 seconds. The samples are then stripped using an aqueous phosphoric acid solution containing chromium trioxide, and then rinsed and dried.

The “OIM sample procedure” is as follows:

    • The software used is OIM Data Collection Software version 7 (EDAX Inc., New Jersey, U.S.A.), or equivalent, which is connected to a Hikari EBSD camera (EDAX Inc., New Jersey, U.S.A.), or equivalent. The SEM is an APREO S Field Emission Gun (Thermo Fisher Scientific. Waltham, Mass., U.S.A.), or equivalent.
    • OIM run conditions are 65° tilt with a 17 mm working distance and an accelerating voltage of 20 kV with dynamic focusing and an instrument-specified beam current of 13 nA (nanoamps). The mode of collection is hexagonal grid. A selection is made such that orientations are collected in the analysis (i.e., Hough peaks information is not collected). The area size per scan (i.e., the frame) is 2.0 mm by 1 mm for 2 mm gauge samples at 1 micron steps at 40×. Different frame sizes can be used depending upon gauge. The collected data is output in an *.osc file. This data may be used to calculate the volume fraction of first type grains, as described below.
    • Calculation of volume fraction of first type grains: The volume fraction of first type grains is calculated using the data of the *.osc file and the OIM/TSL Analysis Software version 8, or equivalent. Prior to calculation, two-step data cleanup may be performed. First, for any points whose confidence index is below a threshold of 0.08, a neighbor orientation correlation clean-up is performed. Second, a grain dilation clean-up is performed for any grain smaller than 3 data points. Then, the amount of first type grains is calculated by the software using the first grain criteria (below).
    • First grain criteria: Grain average misorientation (GAM) is calculated. All of “apply partition before calculation”, “include edge grains”, and “ignore twin boundary definitions” should be required. Any grain whose GAM is ≤1° is a first type grain.

“First grain volume” (FGV) means the volume fraction of first type grains of the crystalline material.

“Percent Recrystallized” is determined via the formula: FGV*100%.

The term “grain” has the meaning defined in ASTM E112 § 3.2.2, i.e., “the area within the confines of the original (primary) boundary observed on the two-dimensional plane of-polish or that volume enclosed by the original (primary) boundary in the three-dimensional object”.

“Grain size” is calculated by the following equation:

d i = square ⁢ root ⁢ ( 4 ⁢ A ⁢ i π )

    • wherein Ai is the area of the individual grain as measured using commercial software OIM/TSL version 8.0 or equivalent; and
    • wherein di is the calculated individual grain size assuming the grain is a circle.

“Area weighted average grain size” is calculated by the following equation:


d-bar=(Σi=1nAidi)/(Σi=1ndi)

    • wherein Ai is the area of each individual grain as measured using commercial software Edax OIM version 8.0 or equivalent;
    • wherein di is the calculated individual grain size assuming the grain is a circle; and
    • wherein d-bar is the area weighted average grain size.

VII. Miscellaneous

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

The figures constitute a part of this specification and include illustrative embodiments of the present disclosure and illustrate various objects and features thereof. In addition, any measurements, specifications and the like shown in the figures are intended to be illustrative, and not restrictive. Therefore, specific structural and functional details disclosed herein are not to be interpreted as limiting, but merely as a representative basis for teaching one skilled in the art to variously employ the present invention.

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

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

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

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

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a flow chart showing one embodiment of a method for making rolled 7xxx aluminum alloy sheet products.

FIG. 2 is a flow chart showing another embodiment of a method for making rolled 7xxx aluminum alloy sheet products.

FIG. 3 is a flow chart showing one embodiment of a preselecting step relating to the anneal step (200) of FIG. 2.

FIG. 4 is a micrograph showing a Kernel Average Misorientation (KAM) map from EBSD analyses of the grain structures of Alloy E of Example 1. This image is from a rolled 7xxx aluminum alloy sheet annealed at 625° F. for 2 hours, followed by slow cooling to room temperature, followed by solution heat treating at 870° F. for 7 minutes followed by water quenching.

FIG. 5 is a micrograph showing Kernel Average Misorientation (KAM) maps from EBSD analyses of the grain structures of Alloy G of Example 1. This image is from a rolled 7xxx aluminum alloy sheet annealed at 525° F. for 24 hours, followed by slow cooling to room temperature, followed by solution heat treating at 870° F. for 7 minutes followed by water quenching.

FIG. 6 is a micrograph showing a Kernel Average Misorientation (KAM) map from EBSD analyses of the grain structures of Alloy E of Example 1. This image is from a rolled 7xxx aluminum alloy sheet annealed at 725° F. for 2 hours, followed by slow cooling to room temperature, followed by solution heat treating at 870° F. for 7 minutes followed by water quenching.

FIG. 7 is a micrograph showing Kernel Average Misorientation (KAM) maps from EBSD analyses of the grain structures of Alloy G of Example 1. This image is from a rolled 7xxx aluminum alloy sheet annealed at 725° F. for 2 hours, followed by slow cooling to room temperature, followed by solution heat treating at 870° F. for 7 minutes followed by water quenching.

    • NOTE: for FIGS. 4-7, recrystallized grains appear white and unrecrystallized grains appear black. The left side of the image is one surface of the sheet and the right is the other surface. Rolling direction is vertical.

DETAILED DESCRIPTION Example 1

Sixteen aluminum alloy strips were produced, the compositions of which are provided in Table 1, below.

TABLE 1 Composition of Experimental 7xxx Alloys (all values in wt. %)* Alloy Si Fe Cu Mn Mg Cr Zn Zr Ti A 0.07 0.11 1.31 0.01 1.77 0.01 6.34 0.11 0.02 B 0.09 0.09 1.22 — 1.62 — 5.90 0.13 0.02 C 0.05 0.09 1.39 0.25 1.85 — 6.36 — 0.02 D 0.08 0.09 1.28 0.03 1.77 — 6.54 0.02 0.02 E 0.11 0.11 1.40 0.25 1.56 — 6.61 0.11 0.02 F 0.07 0.11 1.94 — 1.47 — 6.46 0.10 0.02 G 0.07 0.11 1.61 — 1.49 — 7.46 0.10 0.09 H 0.12 0.12 1.37 — 1.74 — 6.53 0.11 0.02 I** 0.06 0.09 1.31 0.25 1.73 — 8.03 — 0.03 J 0.08 0.10 1.57 0.71 1.74 — 6.61 — 0.02 K 0.11 0.11 1.30 0.27 1.76 0.13 6.54 0.11 0.02 L 0.08 0.11 1.26 0.01 1.78 — 6.62 0.17 0.02 M** 0.06 0.10 1.25 0.25 1.74 0.01 6.51 — 0.05 N 0.14 0.23 1.30 — 1.69 — 6.67 0.11 0.02 O (7050) 0.07 0.10 2.22 — 2.01 — 5.77 0.11 0.03 P (7075) 0.17 0.25 1.54 — 2.52 0.18 5.75 — 0.02 *The balance of all alloys was aluminum and impurities, wherein the impurities in the aluminum alloy are limited to not greater than 0.05 wt. % (max) each, and wherein the total amount of impurities in the aluminum alloy is not greater than 0.15 wt. % (max). **All alloys except alloys I and M contained about 10 ppm of boron; alloy I contained about 40 ppm of boron; alloy M contained about 120 ppm of boron.

All alloys were continuously cast on a pilot scale version of the apparatus described in commonly-owned U.S. Pat. No. 6,672,368, which is incorporated herein by reference in its entirely. Specifically, the alloys were cast to a gauge of from 0.156-0.166 inch (3.964-4.216 mm) at a casting rate of about 53-57 feet per minute (16.2-17.4 meters per minute) and then hot rolled in-line to an intermediate gauge of about 0.125 inch (3.175 mm) and then cooled to room temperature. The intermediate gauge products were then subjected to an intermediate anneal and then cold rolled to a final gauge of about 0.080 inch (2.032 mm).

The cold rolled products were then subjected to various post-rolling anneal conditions (shown in Table 2, below). After the post-rolling anneal was completed, the products were slow cooled by turning off the furnace and then removing the products from the furnace once the temperature reached about 300° F. (148.9° C.), after which the products were allowed to air cool to ambient (room) temperature.

TABLE 2 Post-Rolling Anneal Conditions Anneal Anneal Soak Code Temperature Approx. Heat-up Rate Time AN-01 525° F. (273.9° C.) 49.8° F./hour 2 hours (27.7° C./hour) AN-02 525° F. (273.9° C.) 49.8° F./hour 24 hours (27.7° C./hour) AN-03 625° F. (329.4° C.) 60.9° F./hour 2 hours (33.8° C./hour) AN-04 625° F. (329.4° C.) 60.9° F./hour 24 hours (33.8° C./hour) AN-05 725° F. (385° C.) 72.0° F./hour 2 hours (40.0° C./hour) AN-06 725° F. (385° C.) 72.0° F./hour 24 hours (40.0° C./hour) AN-07 820° F. (437.8° C.) 82.6° F./hour 2 hours (45.9° C./hour) AN-08 820° F. (437.8° C.) 82.6° F./hour 24 hours (45.9° C./hour) AN-09 850° F. (454.4° C.) 85.9° F./hour 2 hours (47.7° C./hour) AN-10 850° F. (454.4° C.) 85.9° F./hour 24 hours (47.7° C./hour)

Next, the final gauge products were solution heat treated at 870° F. (465.6° C.) for 7 minutes and then cold water quenched. After quenching, the alloys were stretched about 0.5% for flatness and then allowed to naturally age for about 4 days. The naturally aged alloys were then subjected to metallographic analysis. Specifically, electron backscattered diffraction (EBSD) via SEM was used to determine the extent of recrystallization and the area weighted grain size of the alloys, the results of which are shown in the Table 3, below. The grain size shown in the table is the area weighted grain size in micrometers.

TABLE 3 Microstructure Results Anneal Percent (%) Grain Size Alloy Code Recrystallized (micrometers) A AN-01 99 41.2 A AN-02 100 52.8 A AN-03 99 56.0 A AN-04 97 73.4 A AN-05 100 123.4 A AN-06 64 113.8 A AN-07 88 114.8 A AN-08 93 128.6 A AN-09 95 126.1 A AN-10 92 119.5 B AN-05 67 116.4 B AN-07 65 111.0 C AN-01 99 42.7 C AN-02 99 42.4 C AN-03 99 54.0 C AN-04 99 59.9 C AN-05 99 97.3 C AN-06 99 78.0 C AN-07 99 89.3 C AN-08 99 76.3 C AN-09 98 93.8 C AN-10 100 73.5 D AN-01 99 54.4 D AN-02 99 52.1 D AN-03 98 59.1 D AN-04 99 84.9 D AN-05 98 107.1 D AN-06 100 99.8 D AN-07 96 105.1 D AN-08 99 96.5 D AN-09 92 90.4 D AN-10 99 95.0 E AN-01 88 45.3 E AN-02 79 49.2 E AN-03 70 56.4 E AN-04 53 58.6 E AN-05 60 67.1 E AN-06 20 60.2 E AN-07 34 60.3 E AN-08 56 67.7 E AN-09 43 64.1 E AN-10 73 75.4 F AN-01 99 43.9 F AN-02 99 56.5 F AN-03 100 63.2 F AN-04 98 86.3 F AN-05 99 130.1 F AN-06 91 109.9 F AN-07 96 115.8 F AN-08 97 117.0 F AN-09 97 104.1 F AN-10 99 111.8 G AN-01 99 43.5 G AN-02 99 65.2 G AN-03 99 58.5 G AN-04 93 71.9 G AN-05 92 100.5 G AN-06 39 68.0 G AN-07 72 109.4 G AN-08 84 117.5 G AN-09 83 121.0 G AN-10 94 130.1 H AN-01 99 45.9 H AN-02 100 52.1 H AN-03 99 66.9 H AN-04 91 79.7 H AN-05 90 125.9 H AN-06 56 115.9 H AN-07 73 122.5 H AN-08 84 128.7 H AN-09 83 128.3 H AN-10 98 51.9 I AN-01 99 38.3 I AN-02 99 37.1 I AN-03 99 39.0 I AN-04 98 51.5 I AN-05 99 72.0 I AN-06 99 72.5 I AN-07 99 73.1 I AN-08 99 73.8 I AN-09 99 69.1 I AN-10 99 71.5 J AN-01 31 35.87 J AN-02 38 36.45 J AN-03 33 37.18 J AN-04 61 36.16 J AN-05 45 37.12 J AN-06 71 41.82 J AN-07 52 36.56 J AN-08 81 38.77 J AN-09 58 35.24 J AN-10 83 40.36 K AN-01 84 43.68 K AN-02 81 49.07 K AN-03 70 54.88 K AN-04 55 64.75 K AN-05 46 61.08 K AN-06 32 60.88 K AN-07 32 67.15 K AN-08 43 71.18 K AN-09 43 58.47 K AN-10 59 72.22 L AN-01 83 84.68 L AN-02 10 69.5 L AN-03 7 79.55 L AN-04 4 75.94 L AN-05 3 81.72 L AN-06 3 67.54 L AN-07 7 80.79 L AN-08 5 79.03 L AN-09 3 83.39 L AN-10 9 75.12 M AN-01 97 40.12 M AN-02 99 33.79 M AN-03 98 45.04 M AN-04 100 70.48 M AN-05 96 84.54 M AN-06 100 70.42 M AN-07 97 77.18 M AN-08 100 69.33 M AN-09 98 75.88 M AN-10 100 68.08 N NO DATA O AN-01 99 37.39 O AN-02 99 44.63 O AN-03 99 52.39 O AN-04 94 71.73 O AN-05 98 94.94 O AN-06 40 66.23 O AN-07 80 88.05 O AN-08 81 87.51 O AN-09 88 87.74 O AN-10 93 83.84 P AN-01 88 22.81 P AN-02 88 26.42 P AN-03 89 31.18 P AN-04 89 41.82 P AN-05 87 61.71 P AN-06 85 58.98 P AN-07 80 55.95 P AN-08 91 71.41 P AN-09 89 62.12 P AN-10 95 69.03

Next, the final gauge products were artificially aged to a T7-type temper by first aging for 8 hours at 250° F. (121.1° C.) and then aging at 320° F. (160° C.) for either 8 or 16 hours. After aging, the products were subjected to various analyses, including mechanical property analyses.

As it relates to mechanical properties, strength and elongation in the transverse orientation (LT) were tested at various final anneal and artificial aging conditions in accordance with ASTM E8/E8M-16a and B557-15. Duplicate specimens were used for all strength/elongation testing. The results are provided in the Table 4, below.

Fracture behavior was also evaluated using three-point bending tests (as defined in the Definitions section), the test results of which are provided in Table 4, below. The tests were conducted relative to the transverse orientation (LT), and the reported values are based on the average of ten specimens used for each alloy tested.

TABLE 4 Mechanical Property Data for Example 1 Alloys Second Step UTS TYS Elong. Average Anneal Aging Time (LT) (LT) (LT) Extension Alloy Code (hrs.) (MPa) (MPa) (%) @70% (mm) A AN-05 8 511 471 12.2 6.29 A AN-05 16 492 443 8.9 6.72 H AN-01 8 513 475 9.4 5.92 H AN-01 16 490 431 7.9 6.41 H AN-04 8 515 476 7.1 5.90 H AN-04 16 490 437 8.2 6.06 H AN-07 8 506 470 10.0 5.87 H AN-07 16 480 432 10.3 6.20 B AN-05 8 500 460 11.4 5.93 B AN-05 16 461 429 6.6 6.29 B AN-06 8 497 459 7.2 6.01 B AN-06 16 473 428 7.1 6.42 C AN-05 8 525 486 10.7 5.76 C AN-05 16 512 463 10.9 5.85 C AN-06 8 530 488 12.4 5.92 C AN-06 16 512 462 8.7 6.15 D AN-05 8 506 465 10.7 6.03 D AN-05 16 484 434 10.9 6.49 D AN-06 8 503 466 5.6 6.23 D AN-06 16 485 435 9.1 6.84 E AN-01 8 508 470 7.2 6.53 E AN-01 16 483 435 7.8 7.53 E AN-04 8 518 474 8.8 6.81 E AN-04 16 485 440 6.1 7.32 E AN-04 8 515 471 9.1 6.91 E AN-04 16 494 438 10.8 7.55 E AN-05 8 509 472 6.4 7.14 E AN-05 16 486 432 9.4 7.89 E AN-07 8 513 469 9.2 7.23 E AN-07 16 480 427 7.7 7.87 F AN-05 8 490 450 11.4 6.37 F AN-05 16 474 423 10.9 6.59 G AN-05 8 506 468 10.9 6.84 G AN-05 16 473 427 6.8 8.24 I AN-06 8 531 491 12.2 5.85 I AN-06 16 501 449 11.2 6.61 N AN-05 8 494 461 4.7 4.98 N AN-05 16 473 421 8.3 4.77 J AN-01 8 529 469 8.0 4.79 J AN-01 16 499 431 8.7 5.40 J AN-04 8 534 484 5.2 5.02 J AN-04 16 515 452 9.9 5.21 J AN-04 8 539 482 9.4 4.79 J AN-04 16 513 449 7.5 5.02 J AN-05 8 533 477 6.3 4.59 J AN-05 16 494 444 3.9 5.21 J AN-07 8 536 479 10.2 4.84 J AN-07 16 507 442 10.2 4.95 K AN-01 8 523 480 11.1 5.49 K AN-01 16 501 430 8.9 6.51 K AN-04 16 500.6 450.2 6.8 5.98 K AN-04 8 524.7 477.1 10.25 5.08 K AN-04 16 499.2 443.0 10.6 5.94 K AN-05 8 523.0 477.1 11.65 5.50 K AN-05 16 494.4 432.6 9.85 5.85 K AN-07 8 519.2 470.9 9.9 5.57 K AN-07 16 496.1 437.8 8.95 6.17 L AN-05 8 518.5 474.7 8 4.66 L AN-05 16 487.5 433.7 7.8 5.34 L AN-06 8 516.1 471.9 9.8 4.47 L AN-06 16 487.5 432.6 10.3 5.56 M AN-05 8 525.7 485.0 6.75 5.30 M AN-05 16 500.9 452.3 8.5 5.58 M AN-06 8 521.2 477.1 12.05 5.32 M AN-06 16 496.8 445.1 9 5.84 O AN-05 8 550.2 511.9 7.5 4.34 O AN-05 16 537.8 488.8 9.15 4.84 P AN-05 8 542.6 491.6 7.8 3.53 P AN-05 16 529.5 480.6 5.85 4.00

As shown above, the invention alloys are capable of achieving a tensile yield strength (LT) of at least 450 MPa and a three-point bend extension of at least 5.8 mm. Alloy E is particularly high performing, realizing a very high combination of strength and three-point bend extension. It is hypothesized that Alloy E's microstructural features (e.g., its grain size, percent recrystallization, amount of Zr-bearing and Mn-bearing intermetallic particles), facilitates realization of the excellent properties.

Corrosion tests were also conducted on two alloys. Specifically, ASTM G34, G44 and ASTM G110 tests were conducted on specimens of Alloys E and G made in accordance with the production flow path shown in FIG. 1. Tables 5-7 show the results. All results are from artificial aging at 250° F. (121.1° C.) for 8 hours followed by artificial aging at 320° F. (160° C.) at 8 hours. As shown, the alloys exhibit good corrosion resistance properties. In the case of ASTM G44 testing (Table 6), the test was discontinued after 60 days, at which time two of the Alloy E samples had not failed.

TABLE 5 ASTM G34-01(2018) Results Exfoliation Rating Alloy Test Plane (48 hours) E Surface EA G Surface EA

TABLE 6 ASTM G44-99(2013) Results Days Test Stress in Alloy Direction (MPa) Test Days to fail E LT 353 59 52, 54, 59, OK, OK G LT 353 45 27, 29, 34, 38, 45

TABLE 7 ASTM G110-92(2015) Results (6 hours) Alloy Depth of attack (micrometers) Max. Avg. E 25.4 25.8 28.8 27.5 33.1 33.1 24.6 22.5 17 19.3 27 19.3 G 31.9 40.9 54.7 91.5 39.1 91.5 55.2 80.1 35.9 50 52.9 74.7

The Mn, Zr, Cr, and V dispersoid content of the Example 1 alloys was calculated using formula (1), below, which was developed by the inventors through thermodynamic estimations. The results are shown in Table 8, below.


Dispersoid (vol. %)=(wt. % Mn)*3.52+(wt. % Zr)*1.28+(wt. % Cr+wt. % V)*6.34  Formula (1):

TABLE 8 Mn, Zr, Cr, and V Dispersoid Content (Vol. %) for Example 1 Alloys Dispersoids Alloy Mn Cr Zr (Vol. %) A 0.01 0.01 0.11 0.24 B — — 0.13 0.17 C 0.25 — — 0.88 D 0.03 — 0.02 0.13 E 0.25 — 0.11 1.02 F — — 0.10 0.13 G — — 0.10 0.13 H — — 0.11 0.14 I 0.25 — — 0.88 J 0.71 — — 2.50 K 0.27 0.13 0.11 1.92 L 0.01 — 0.17 0.25 M 0.25 0.01 — 0.94 N — — 0.11 0.14 O (7050) — — 0.11 0.14 P (7075) — 0.18 — 1.14

As shown, the invention alloys contain a dispersoid content based on Mn, Zr, Cr, and V of from about 0.13 to 1.02 vol. %. Non-invention alloys J and K contain a high amount of dispersoids.

The solvus temperatures for various phases of the Example 1 alloys was calculated based on their alloy composition using THERMO-CALC software and the THERMO-CALC Aluminum Database, Version 5, “TCAL5,” the results of which are shown in Table 9, below.

TABLE 9 Solvus Temperatures of the Example 1 Alloys S-phase M-phase T-phase Alloy solvus ° F. solvus (° F.) solvus (° F.) A 787 769 — B 770 744 — C 825 774 — D 787 774 — E 792 755 — F 817 737 — G 792 777 — H 784 768 — I — 810 — J 830 773 — K 805 772 — L 781 779 — M 803 773 — N — 810 — O (7050) 880 750 — P (7075) 818 — 792

As shown, when present, the invention alloys have an S-phase solvus temperature in the range of 770-825° F. (410-440.6° C.), an M-phase solvus temperature in the range of 744-810° F. (395.6-413.9° C.), and have no T-phase precipitates. Conversely, some non-invention alloys may have an S-phase solvus temperature above 825° F. (440.6° C.) and/or contain T-phase precipitates.

Example 2

Fifteen pilot scale ingots (152 mm thick by 457 mm wide by 1270 mm long) were direct-chill (DC) cast, the compositions of which are provided in Table 10, below (all values in weight percent). The Mn, Zr and Cr dispersoid content of the alloys were calculated using formula (1) as done for the Example 1 alloys above, which values are also provided in Table 10 as volume percent.

TABLE 10 Example 2 Compositions (wt. %) and Dispersoid Content (vol. %) Alloy Si Fe Cu Mn Mg Cr Zn Zr Ti Dispersoids  1 0.07  0.097 1.77 — 1.78 — 6.64 0.11 0.02 0.14  2 0.13 0.16 1.74 — 1.75 — 6.58 0.11 0.02 0.15  3 0.18 0.19 1.76 — 1.75 — 6.6  0.11 0.04 0.15  4 0.07 0.10 1.72 — 1.75 — 6.53 0.13 0.02 0.17  5 0.06 0.10 1.79 0.10 1.77 — 6.77 0.10 0.02 0.48  6 0.07 0.11 1.76 0.24 1.76 — 6.58 0.11 0.03 0.99  7 0.07 0.10 1.74 0.26 1.78 0.13 6.61 0.11 0.02 1.88  8 0.07 0.10 1.58 — 1.59 — 6.23 0.10 0.02 0.14  9 0.07 0.11 1.61 — 1.61 — 6.92 0.11 0.02 0.15 10 0.07 0.11 1.6  — 1.9  — 6.4  0.11 0.02 0.14 11 0.07 0.10 1.58 — 1.85 — 6.91 0.10 0.02 0.13 12 0.07 0.10 1.82 — 1.61 — 6.22 0.11 0.02 0.14 13 0.06 0.11 1.89 — 1.62 — 6.97 0.11 0.02 0.14 14 0.07 0.11 1.88 — 1.89 — 6.24 0.11 0.02 0.14 15 0.07 0.11 1.92 — 1.84 — 6.92 0.11 0.02 0.14

After scalping, the ingots were homogenized and then hot rolled to 4.06 mm (0.160 inch). Some sheet samples annealed at 343.3° C. (650° F.) for 1 hour and then cold rolled to a final gauge of 2.03 mm (0.80 inch), while other samples skipped annealing and were simply cold rolled to the final gauge of 2.03 mm (0.80 inch). All final gauge samples were then solution heat treated, then cold water quenched, and then naturally aged for about 4 days. The naturally aged samples were then two-step artificially aged by first aging at 121.1° C. (250° F.) for 8 hours and then aging at 160° C. (320° F.) for 16 hours. After artificial aging, the products were subjected to various analyses, including mechanical property analyses.

As with Example 1, the mechanical properties, strength and elongation in the transverse orientations (LT) of the Example 2 alloys were tested in accordance with ASTM E8/E8M-16a and B557-15. Duplicate specimens were used for all strength/elongation testing. The results are provided in the Tables 11 and 12, below for the cases of no hot line anneal and with hot line anneal, respectively.

Fracture behavior was also evaluated using three-point bending tests (as defined in the Definitions section), the test results of which are provided in Table 11, below. As with Example 1, the tests were conducted relative to the transverse orientation (LT), and the reported values are based on the average of ten specimens used for each alloy tested.

TABLE 11 Mechanical Property Data for Example 2 Alloys (LT) (no hot line anneal) Average Total Extension UTS TYS Elongation at 70% Alloy (MPa) (MPa) (%) (mm) 1 522 475 12.2 8.11 2 510 467 11.7 6.45 3 500 459 10.7 6.30 4 514 468 13.7 6.81 5 530 488 11.8 8.16 6 535 490 11.1 7.12 7 530 482 12.1 7.28 8 500 458 9.7 8.23 9 508 464 13.0 8.15 10 519 478 10.4 7.43 11 524 485 11.3 7.43 12 503 458 9.2 8.23 13 509 462 11.9 8.12 14 535 496 10.9 7.51 15 535 494 12.6 7.34

TABLE 12 Mechanical Property Data for Example 2 Alloys (LT) (Hot Line Annealed) Average Total Extension UTS TYS Elongation at 70% Alloy (MPa) (MPa) (%) (mm) 1 521 476 12.1 7.85 2 500 450 11.6 5.78 3 491 443 11.4 5.59 4 520 474 12.0 6.22 5 539 500 12.1 7.32 6 536 492 12.3 7.18 7 521 466 11.6 6.35

As the data shows, alloys 2, 3, 4 and 7 realize an inferior strength/bend relationship. Alloys 2 and 3 are higher in iron and silicon than the others and therefore would not be expected to show excellent performance. Similarly, Alloy 4 had higher zirconium, and was determined to be beyond the peritectic composition (using the THERMO-CALC Aluminum Database, Version 5, “TCAL5,” based on alloy composition), which may have contributed to the formation of primary Al3Zr particles, which negatively affect performance. Alloy 7 contained a high amount of dispersoids.

Corrosion tests, specifically, ASTM G34, G110 and ASTM G44 tests, were also conducted on the Example 2 alloys fabricated using no hot line anneal and aged as described above. In ASTM G44, all Example 2 alloys received a rating of EA after 2 days of test. In ASTM G110 (6 hours of exposure), none of the alloys exhibited intergranular corrosion and for all the average depth of attack was less than 45 microns. In ASTM G44, the LT oriented specimens tested at 75% of tensile yield strength, all alloys passed more than 40 days in test.

The solvus temperatures for various phases of the Example 2 alloys were calculated based on their alloy composition using THERMO-CALC software and the THERMO-CALC Aluminum Database, Version 5, “TCAL5,” the results of which are shown in Table 13, below.

TABLE 13 Solvus Temperatures of the Example 2 Alloys S-phase M-phase T-phase Alloy solvus, (° F.) solvus, ° F. solvus, ° F. 1 830 769 — 2 808 762 — 3 797 759 — 4 824 765 — 5 833 772 — 6 838 765 — 7 843 770 — 8 801 747 — 9 802 769 — 10 823 773 — 11 818 785 — 12 822 743 — 13 825 766 — 14 845 763 — 15 843 779 —

As shown, the alloys have an S-phase solvus temperature in the range of 797-845° F., and an M-phase solvus temperature in the range of 743-785° F., and have no T-phase.

Example 3

Eight additional pilot scale ingots were cast, the compositions of which are provided in Table 14, below. In addition, the Mn, Zr and Cr dispersoid content was calculated using formula (1) as done for the Example 1 and Example 2 alloys above.

TABLE 14 Example 3 Compositions (wt. %) and Dispersoid Content (vol. %) Alloy Si Fe Cu Mn Mg Cr Zn Zr Ti Dispersoids 16 0.07 0.10 1.63 — 1.82 — 6.20 0.11 0.02 0.16 17 0.07 0.12 1.57 0.25 1.86 — 6.27 0.11 0.02 1.03 18 0.08 0.14 1.62 0.25 1.96 — 6.28 0.11 0.02 1.01 19 0.03 0.05 1.59 0.25 1.88 — 6.27 0.11 0.02 1.02 20 0.06 0.09 1.38 0.24 1.56 — 6.44 0.10 0.02 0.97 21 0.05 0.10 2.04 0.25 1.50 — 5.82 0.11 0.02 1.02 22 0.06 0.10 1.56 — 1.51 — 7.43 0.11 0.02 0.17 23 0.02 0.04 1.68 0.23 1.55 — 7.42 0.11 0.03 0.96

After scalping, the ingots were homogenized and then hot rolled to 4.06 mm (0.160 inch) and then cold rolled to a final gauge of 2.03 mm (0.80 inch). (No samples were annealed.) The final gauge samples were then solution heat treated, then cold water quenched, and then naturally aged for about 5 days. The naturally aged samples were then two-step artificially aged by first aging at 121.1° C. (250° F.) for 8 hours and then aging at 160° C. (320° F.) for 4 hours. After cooling to room temperature, the alloys were then given a simulated paint bake of 365° F. (185° C.).

After artificial aging and the simulated paint bake, the products were subjected to various analyses, including mechanical property analyses. Mechanical properties were again tested using the standards identified above, the results of which are provided in Table 15, below. Fracture behavior was also evaluated using three-point bending tests (as defined in the Definitions section), the test results of which are also provided in Table 15, below. As with Example, 1, the tests were conducted relative to the transverse orientations (LT), and the reported values are based on the average of ten specimens used for each alloy tested.

TABLE 15 Mechanical Property Data for Example 3 Alloys (LT) Average Total Extension UTS TYS Elongation at 70% Alloy (MPa) (MPa) (%) (mm) 16 556 523 11.8 6.81 17 567 533 11.8 6.95 18 564 523 11.2 6.53 19 565 529 10.8 7.96 20 526 495 11.2 9.10 21 516 477 11.8 9.09 22 540 514 12.0 7.77 23 542 512 8.2 9.81

As shown, alloys 17-21 and 23 contain about the same amount of manganese and zirconium as that of Alloy E of Example 1. As a comparison of the data shows, the ingot cast alloys realize about 70-80 MPa higher strength at about equivalent three-point bend extension relative to the continuous cast alloys. The ingot cast alloys also realize about 2.5-2.6 higher three-point bend extension at about equivalent strength.

The solvus temperatures for various phases of the Example 3 alloys was calculated based on their alloy composition using THERMO-CALC software and the THERMO-CALC Aluminum Database, Version 5, “TCAL5,” the results of which are shown in Table 16, below.

TABLE 16 Solvus Temperatures of the Example 3 Alloys S-phase M-phase T-phase Alloy solvus, ° F. solvus, ° F. solvus, ° F. 16 822 761 — 17 832 766 — 18 846 770 — 19 838 771 — 20 799 754 — 21 792 778 — 22 840 715 — 23 827 780 —

As shown, the alloys have an S-phase solvus temperature in the range of 792-846° F., an M-phase solvus temperature in the range of 715-780° F., and have no T-phase. Alloy 18 has the highest S-phase solvus temperatures and the poorest bend performance. Alloy 20 is similar to Alloy E of Example 1 and has a solvus temperature below 800° F. Lower S-phase solvus temperatures may facilitate improved properties due to, for instance, improved quench insensitivity properties.

While various embodiments of the new technology described herein 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 presently disclosed technology. Various ones of the unique aspects noted hereinabove may be combined to yield various new 7xxx aluminum alloy products having an improved combination of properties. Additionally, these and other aspects and advantages, and novel features of this new technology are set forth in part in the description that follows and will become apparent to those skilled in the art upon examination of the following description and figures, or may be learned by practicing one or more embodiments of the technology provided for by the present disclosure.

Claims

1. A 7xxx sheet product comprising: wherein the 7xxx aluminum alloy sheet product has a thickness of from 0.5 to 4.0 mm; wherein the 7xxx aluminum alloy sheet product comprises at least 15 vol. % recrystallized grains; and wherein the 7xxx aluminum alloy sheet product realizes a dispersoid content of not greater than 1.95 vol. %, wherein the amount of dispersoids is calculated from the formula (wt. % Mn)*3.52+(wt. % Zr)*1.28+(wt. % Cr+wt. % V)*6.34.

5.0-9.0 wt. % Zn;
1.30-2.05 wt. % Mg;
1.10-2.10 wt. % Cu; wherein 2.55≤(wt. % Cu+wt. % Mg)≤3.85
at least one of: 0.03-0.40 wt. % Mn; and 0.02-0.15 wt. % Zr; wherein 0.05≤(wt. % Zr+wt. % Mn)≤0.50;
up to 0.20 wt. % Cr;
up to 0.20 wt. % V;
up to 0.20 wt. % Fe;
up to 0.15 wt. % Si;
up to 0.15 wt. % Ti; and
up to 75 ppm B;
the balance being aluminum, incidental elements and impurities;

2. The 7xxx aluminum alloy sheet product of claim 1, wherein (wt. % Zr+wt. % Mn) is at least 0.08, or (wt. % Zr+wt. % Mn) is at least 0.10.

3. The 7xxx aluminum alloy sheet product of claim 2, wherein (wt. % Zr+wt. % Mn) is not greater than 0.45.

4. The 7xxx aluminum alloy sheet product of claim 3, wherein the 7xxx sheet product includes at least 0.08 wt. % Mn.

5. The 7xxx aluminum alloy sheet product of claim 4, wherein the 7xxx sheet product includes not greater than 0.45 wt. % Mn.

6. The 7xxx aluminum alloy sheet product of claim 1, wherein the 7xxx sheet product realizes a dispersoid content of at least 0.07 vol., wherein the amount of dispersoids is calculated from the formula (wt. % Mn)*3.52+(wt. % Zr)*1.28+(wt. % Cr+wt. % V)*6.34.

7. The 7xxx aluminum alloy sheet product of claim 6, wherein the 7xxx sheet product realizes a dispersoid content of not greater than 1.90 vol. %.

8. The 7xxx aluminum alloy sheet product of claim 1, wherein the 7xxx aluminum alloy sheet product comprises at least 20 vol. % recrystallized grains.

9. The 7xxx aluminum alloy sheet product of claim 8, wherein the 7xxx aluminum alloy sheet product comprises not greater than 95 vol. % recrystallized grains.

10. The 7xxx aluminum alloy sheet product of claim 1, wherein the 7xxx aluminum alloy sheet product contains S-phase precipitate and wherein the S-phase precipitates realize a solvus temperature of not greater than 850° F., wherein the solvus temperature is calculated using THERMO-CALC software and the THERMO-CALC Aluminum Database, Version 5.

11. The 7xxx aluminum alloy sheet product of claim 10, wherein the 7xxx aluminum alloy sheet product is absent of T-phase precipitates, wherein the presence of T-phase precipitates is determined using THERMO-CALC software and the THERMO-CALC Aluminum Database, Version 5.

12. The 7xxx aluminum alloy sheet product of claim 1, wherein the 7xxx aluminum alloy sheet product is produced from a continuously cast strip and realizes a strength to three-point bend at extension relationship at or above a line defined by the formula:

Y=−0.02X+Z;
wherein X is the LT-TYS (MPa) of the 7xxx aluminum alloy sheet product and wherein X is at least 450 MPa;
wherein Y is the LT three-point bend extension (mm) of the 7xxx aluminum alloy sheet product and wherein Y is at least 5.8 mm; and
wherein Z is 15.0.

13. The 7xxx aluminum alloy sheet product of claim 1, wherein the 7xxx aluminum alloy sheet product is produced from a direct cast ingot and realizes a strength to three-point bend at extension relationship at or above a line defined by the formula:

Y=−0.039X+Z;
wherein X is the LT-TYS (MPa) of the 7xxx aluminum alloy sheet product and wherein X is at least 450 MPa;
wherein Y is the LT three-point bend extension (mm) of the 7xxx aluminum alloy sheet product and wherein Y is at least 7.0 mm; and
wherein Z is 25.25.

14. A 7xxx sheet product comprising: wherein the 7xxx aluminum alloy sheet product has a thickness of from 0.5 to 4.0 mm; wherein the 7xxx aluminum alloy sheet product comprises from 20 to 90 vol. % recrystallized grains; and wherein the 7xxx aluminum alloy sheet product realizes a dispersoid content of from 0.65 to 1.45 vol. %, wherein the amount of dispersoids is calculated from the formula (wt. % Mn)*3.52+(wt. % Zr)*1.28+(wt. % Cr+wt. % V)*6.34.

6.0-7.0 wt. % Zn;
1.50-1.65 wt. % Mg;
1.35-1.55 wt. % Cu;
0.15-0.35 wt. % Mn;
0.07-0.15 wt. % Zr;
up to 0.20 wt. % Cr;
up to 0.20 wt. % V;
up to 0.20 wt. % Fe;
up to 0.15 wt. % Si;
up to 0.15 wt. % Ti; and
up to 75 ppm B;
the balance being aluminum, incidental elements and impurities;

15. A method of making a 7xxx aluminum alloy sheet product, comprising:

(a) hot rolling the 7xxx aluminum alloy to an intermediate gauge, wherein the 7xxx aluminum alloy comprises: 5.0-9.0 wt. % Zn; 1.30-2.05 wt. % Mg; 1.10-2.10 wt. % Cu; wherein 2.55≤(wt. % Cu+wt. % Mg)≤3.85 at least one of: 0.03-0.40 wt. % Mn; and 0.02-0.15 wt. % Zr; wherein 0.05≤(wt. % Zr+wt. % Mn)≤0.50; up to 0.20 wt. % Cr; up to 0.20 wt. % V; up to 0.20 wt. % Fe; up to 0.15 wt. % Si; up to 0.15 wt. % Ti; and up to 75 ppm B; the balance being aluminum, incidental elements and impurities;
(b) after the hot rolling, cold rolling the 7xxx aluminum alloy to a final gauge sheet product, wherein the final gauge sheet product has a thickness of from 0.50 to 4.0 mm;
(c) after the cold rolling, annealing the final gauge sheet product at an anneal temperature of from 525° F. to 850° F.; wherein at least partially due to the annealing, the final gauge sheet product contains at least 15% recrystallized grains; and
(d) after the annealing, solution heat treating and then quenching the final gauge sheet product, wherein the 7xxx aluminum alloy sheet product realizes a dispersoid content of not greater than 1.95 vol. %, wherein the amount of dispersoids is calculated from the formula (wt. % Mn)*3.52+(wt. % Zr)*1.28+(wt. % Cr+wt. % V)*6.34.

16. The method of claim 15, comprising, prior to the annealing step:

(i) selecting an amount of recrystallization to achieve in the final gauge sheet product, wherein the selected amount of recrystallization is from 15% to 95% recrystallization;
(ii) selecting the anneal time and the anneal temperature based on the selected amount of recrystallization;
(iii) after the selecting steps (i)-(ii), completing the annealing step using the selected anneal time and the selected anneal temperature;
wherein, after the completing step (iii) and at least partially due to the selected anneal time and the selected anneal temperature, the final gauge sheet product realizes the selected amount of recrystallization.

17. The method of claim 16, comprising, prior to the annealing step:

(i) selecting a grain size to achieve in the final gauge sheet product;
(ii) selecting at least one of an anneal heat-up rate, the anneal time and the anneal temperature based on the selected grain size;
(iii) after the selecting steps (i)-(ii), completing the annealing step using the selected anneal heat-up rate, the anneal time and/or the selected anneal temperature;
wherein, after the completing step (iii) and at least partially due to the selected anneal heat-up rate, the selected anneal time and the selected anneal temperature, the final gauge sheet product realizes the selected amount grain size.

18. The method of claim 17, wherein the anneal temperature is from 575° F. to 750° F.

19. The method of claim 18, wherein the anneal heat-up rate is from 25° C. to 50° C. per hour.

Patent History
Publication number: 20230250516
Type: Application
Filed: Apr 13, 2023
Publication Date: Aug 10, 2023
Inventors: Lynette M. Karabin (Ruffs Dale, PA), John M. Newman (Pittsburgh, PA), Carolyn G. Norwood (Pittsburgh, PA)
Application Number: 18/134,149
Classifications
International Classification: C22C 21/10 (20060101); C21D 8/02 (20060101); C22F 1/053 (20060101);