Aluminum alloy products having improved property combinations and method for artificially aging same
View Patent ↗Aluminum alloy products, such as plate, forgings and extrusions, suitable for use in making aerospace structural components like integral wing spars, ribs and webs, comprises about: 6 to 10 wt. % Zn; 1.2 to 1.9 wt. % Mg; 1.2 to 2.2 wt. % Cu, with Mg≦(Cu+0.3); and 0.05 to 0.4 wt. % Zr, the balance Al, incidental elements and impurities. Preferably, the alloy contains about 6.9 to 8.5 wt. % Zn; 1.2 to 1.7 wt. % Mg; 1.3 to 2 wt. % Cu. This alloy provides improved combinations of strength and fracture toughness in thick gauges. When artificially aged per the 3-stage method of preferred embodiments, this alloy also achieves superior SCC performance, including under seacoast conditions.
1. An aluminum alloy consisting essentially of:
7.0-10.0 wt. % Zn;
1.3-1.7 wt. % Mg;
1.4-1.9 wt % Cu;
0.05-0.15 wt. % Zr;
the balance being essentially aluminum, incidental elements and impurities.
2. The aluminum alloy of claim 1 , wherein the alloy comprises 7.0-9.5 wt. % Zn.
3. The aluminum alloy of claim 1 , wherein the alloy comprises 7.0-9.0 wt. % Zn.
4. The aluminum alloy of claim 1 , wherein the alloy comprises 7.0-8.5 wt. % Zn.
5. The aluminum alloy of claim 1 , wherein the alloy comprises 7.0-8.0 wt. % Zn.
6. The aluminum alloy of claim 5 , wherein the alloy comprises 1.4-1.7 wt. % Mg.
7. The aluminum alloy of claim 1 or 6 , wherein the alloy comprises 1.4-1.8 wt. % Cu.
8. The alloy of claim 7 , wherein the alloy comprises a fracture toughness to tensile yield strength ratio that satisfies the expression FT≧−0.9*TYS+93.5, wherein FT is the K.sub.Ic L-T fracture toughness in ksi-in and TYS is the L tensile yield strength in ksi, wherein FT is measured in accordance with ASTM Standard E399 on an aluminum alloy specimen taken from the T/4location of a six-inch aluminum alloy plate, wherein the specimen has a thickness of 2.0 inches and a width of 4.0 inches, and wherein the specimen is fatigue pre-cracked to a crack length of 2.0 inches, and wherein TYS is measured in accordance with ASTM Standard E8.
9. The alloy of claim 8 , wherein the alloy has a visual exfoliation corrosion resistance rating of EB or better as measured in accordance with ASTM standard G34.
10. The alloy of claim 9 , wherein the alloy has an electrical conductivity value of at least about 36% IACS.
11. The alloy of claim 10 , wherein the alloy comprises a fracture toughness to tensile yield strength ratio that satisfies the expression FT≧−0.9*TYS+96.5.
12. The alloy of claim 10 , wherein the alloy comprises a fracture toughness to tensile yield strength ratio that satisfies the expression FT≧−0.9*TYS+99.5.
13. The alloy of claim 1 , wherein the alloy is included in an aerospace part.
14. The alloy of claim 1 , wherein the alloy is included in a non-aerospace part.
15. The alloy of claim 14 , wherein the non-aerospace part is a marine component.
16. The alloy of claim 1 , alloy is included in a mold plate.
17. The alloy of claim 1 , alloy is included in a cast plate.
18. The alloy of claim 1 , alloy is included in a forging.
19. The alloy of claim 1 , alloy is included in a extrusion.
20. The alloy of claim 1 , wherein the alloy is in the from of a plate.
21. The alloy of claim 1 , wherein the amount of Cu exceeds the amount of Mg in the alloy.
22. The alloy of claim 1 , wherein the incidental elements include at least one grain refiner.
23. The alloy of claim 22 , wherein the grain refiner comprises titanium with either boron or carbon.
24. The alloy of claim 1 , wherein the impurities comprise Fe and Si, and wherein the alloy includes not greater than 0.25 wt. % Si, and wherein the alloy comprises not greater than 0.25 wt. % Fe.
25. The alloy of claim 1 , or 23 , wherein the incidental elements includes at least one of the following elements or compounds:
up to 0.06 wt. % Ti;
up to 1.0 wt. % Mn;
up to 0.4 wt. % Cr;
up to 0.03 wt % Ca;
up to 0.03 wt. % Sr; and
up to 0.002 wt. % Be.