Aluminum alloy products having improved property combinations and method for artificially aging same

Abstract

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 three stage method of preferred embodiments, this alloy also achieves superior SCC performance, including under seacoast conditions.

1 . A mold plate made from a thick aluminum alloy product consisting essentially of: 7 to 9.5 wt. % Zn; 1.3 to 1.68 wt. % Mg; and 1.3 to 1.9 wt. % Cu; up to about 0.4 wt. % Zr, less than 0.3 wt. % Mn, less than 0.1 wt. % Cr, the balance Al, incidental elements and impurities.  
     
     
         2 . The mold plate of  claim 1  wherein said alloy contains 0.25 wt. % or less Fe and 0.25 wt. % or less Si.  
     
     
         3 . The mold plate of  claim 1  wherein said alloy contains 7 to 8.5 wt. % Zn, 1.3 to 1.65 wt. % Mg and about 1.4 to 1.9 wt. % Cu.  
     
     
         4 . The mold plate of  claim 1  wherein said product is a rolled plate or forging and said alloy contains about 0.05 to 0.2 wt. % Zr.  
     
     
         5 . The mold plate of  claim 1  wherein said product is a casting.  
     
     
         6 . The mold plate of  claim 1  wherein said product is 2 inches or more in thickness.  
     
     
         7 . The mold plate of  claim 1  wherein said product is 4 inches or more in thickness.  
     
     
         8 . The mold plate of  claim 1  wherein said product is 6 inches or more in thickness.  
     
     
         9 . The mold plate of  claim 1 , wherein said product is 8 inches or more in thickness.  
     
     
         10 . The mold plate of  claim 1 , wherein said product is 12 inches or more in thickness.  
     
     
         11 . The mold plate of  claim 1 , wherein said product is from about 2 to about 12 inches thick.  
     
     
         12 . The mold plate of  claim 1 , wherein said plate is solution heat treated (SHT) and quenched, then mechanically stress relieved.  
     
     
         13 . The mold plate of  claim 12 , wherein said mechanical stress relief includes stretching up to about 8%.  
     
     
         14 . The mold plate of  claim 12 , wherein said mechanical stress relief includes stretching and compression up to about 8%.  
     
     
         15 . The mold plate of  claim 12 , wherein said mechanical stress relief includes stretching from about 1 to 3%.  
     
     
         16 . The mold plate of  claim 12 , wherein said mechanical stress relief includes compression from about 1 to 3%.  
     
     
         17 . The mold plate of  claim 12 , wherein said mechanical stress relief includes stretching and compression from about 1 to 3%.  
     
     
         18 . A product for use in mold and die manufacturing comprising an aluminum alloy consisting essentially of 7 to 9.5 wt. % Zn; 1.3 to 1.68 wt. % Mg; and 1.3 to 1.9 wt. % Cu; up to about 0.4 wt. % Zr, less than 0.3 wt. % Mn, less than 0.1 wt. % Cr, the balance Al, incidental elements and impurities.  
     
     
         19 . The product of  claim 18 , wherein said alloy contains 7 to 8.5 wt. % Zn, 1.3 to 1.65 wt. % Mg and about 1.4 to 1.9 wt. % Cu.  
     
     
         20 . The product of  claim 19 , wherein said product is a rolled product, a cast product or a forged product.  
     
     
         21 . The product of  claim 18  wherein said product is 2 inches or more in thickness.  
     
     
         22 . The product of  claim 18  wherein said product is 4 inches or more in thickness.  
     
     
         23 . The product of  claim 18  wherein said product is 6 inches or more in thickness.  
     
     
         24 . The product of  claim 18  wherein said product is 8 inches or more in thickness.  
     
     
         25 . The product of  claim 18 , wherein said product is solution heat treated (SHT) and quenched, then mechanically stress relieved as part of its manufacture.  
     
     
         26 . The mold plate of  claim 18 , wherein said mechanical stress relief includes stretching or compression from 1% to 3%.  
     
     
         27 . A thick wrought aluminum mold plate for use in mold and die manufacturing, consisting essentially of 7 to 9.5 wt. % Zn; 1.3 to 1.68 wt. % Mg; and 1.3 to 1.9 wt. % Cu; up to about 0.4 wt. % Zr, less than 0.3 wt. % Mn, less than 0.1 wt. % Cr, the balance Al, incidental elements and impurities.  
     
     
         28 . The wrought plate of  claim 18 , wherein said plate is a forged product.  
     
     
         29 . The wrought plate of  claim 18 , wherein said plate is a cast product.  
     
     
         30 . The wrought plate of  claim 18 , wherein said plate is a rolled product.