High Strength 7xxx Series Aluminum Alloy Products and Methods of Making Such Products

Abstract

The present invention is directed to a thick plate high strength 7xxx aluminum alloy product comprising 8.0 to 8.4 wt. % Zn, 1.5 to 2.0 wt. % Mg, 1.1 to 1.5 wt. % Cu, and 0.05 to 0.15 wt. % Zr, 4.0 to 5.3 of Zn/Mg weight percentage ratio, 0.14 to 0.19 of Cu/Zn weight percentage ratio, and 10.7 to 11.6 wt. % of Cu+Mg+Zn. This alloy can be fabricated to produce 3-10 inch thick plate, extrusion or forging products, and is especially suitable for aerospace structural components, especially large commercial airplane wing structure applications. The product provides high strength, high damage tolerance performance as well as better corrosion resistance performance suitable for aerospace application.

We claim: 
     
         1 . A thick plate high strength 7xxx aluminum alloy product comprising
 8.0 to 8.4 wt. % Zn,   1.5 to 2.0 wt. % Mg,   1.1 to 1.5 wt. % Cu, and   one or more elements selected from the group consisting of up to 0.2 wt. % Zr, up to 0.2% wt. Sc, and up to 0.2 wt. % Hf,   with the balance Al, and impurities   wherein said alloy product has a Zn/Mg weight percentage ratio between 4.0 to 5.3, a Cu/Zn weight percentage ratio between 0.14 to 0.19, and an amount of Cu+Mg+Zn between 10.7 to 11.6 wt. %.   
     
     
         2 . The aluminum alloy product of  claim 1  comprising ≦0.12 wt. % Si. 
     
     
         3 . The aluminum alloy product of  claim 2  comprising ≦0.05 wt. % Si. 
     
     
         4 . The aluminum alloy product of  claim 1  comprising ≦0.15 wt. % Fe. 
     
     
         5 . The aluminum alloy product of  claim 4  comprising ≦0.08 wt. % Fe. 
     
     
         6 . The aluminum alloy product of  claim 1  comprising ≦0.20 wt. % Mn. 
     
     
         7 . The aluminum alloy product of  claim 1  comprising ≦0.04 wt. % Cr. 
     
     
         8 . The aluminum alloy product of  claim 1  comprising ≦0.06 wt. % Ti. 
     
     
         9 . The aluminum alloy product of  claim 1  consisting essentially of
 8.0 to 8.4 wt. % Zn, 
 1.5 to 2.0 wt. % Mg, 
 1.1 to 1.5 wt. % Cu,
 one or more elements selected from the group consisting of up to 0.2 wt. % Zr, up to 0.2 wt. % Sc, and up to 0.2 wt. % Hf, 
 
 ≦0.12 wt. % Si, 
 ≦0.15 wt. % Fe, 
 ≦0.20 wt. % Mn, 
 ≦0.04 wt. % Cr, 
 and ≦0.06 wt. % Ti 
 with the balance Al, and impurities 
 wherein said alloy product has a Zn/Mg weight percentage ratio between 4.0 to 5.3, a Cu/Zn weight percentage ratio between 0.14 to 0.19, and an amount of Cu+Mg+Zn between 10.7 to 11.6 wt. %. 
 
     
     
         10 . The aluminum alloy product of  claim 1  wherein said aluminum alloy product is a 3-10 inches thick plate, extrusion, or forging product. 
     
     
         11 . The aluminum alloy product of  claim 9  wherein said aluminum alloy product is a 3-10 inches thick plate, extrusion, or forging product. 
     
     
         12 . The aluminum alloy product of  claim 1  wherein said aluminum alloy product is a 4-10 inches thick plate, extrusion, or forging product. 
     
     
         13 . The aluminum alloy product of  claim 1  wherein said aluminum alloy product is a 4-8 inches thick plate, extrusion, or forging product. 
     
     
         14 . The aluminum alloy product of  claim 1  wherein the aluminum alloy product has a minimum Long-Transverse (LT) yield strength at quarter-thickness (th/4) of (74−0.56*plate thickness in inch) ksi and a minimum LT ultimate strength at th/4 of (78−0.36*plate thickness in inch) ksi. 
     
     
         15 . A method of manufacturing a thick plate high strength 7xxx aluminum alloy product comprising the steps of:
 a. casting stock of an ingot of a 7xxx aluminum alloy comprising the aluminum alloy product of  claim 1     b. homogenizing the cast stock;   c. hot working the stock by one or more methods selected from the group consisting of rolling, extrusion, and forging;   d. solution heat treating (SHT) of the hot worked stock;   e. cold water quenching said SHT stock;   f. optionally stretching the SHT stock; and   h. ageing of the SHT, cold water quenched and optionally stretched stock to a desired temper.   
     
     
         16 . The method of  claim 15 , wherein said step of homogenizing includes homogenizing at temperatures from 454 to 491° C. (849 to 916° F.). 
     
     
         17 . The method of  claim 15 , wherein said step of hot working includes hot rolling at a temperature of 385 to 450° C. (725 to 842° F.). 
     
     
         18 . The method of  claim 15 , wherein said step of solution heat treating includes solution heat treated at temperature range from 454 to 491° C. (849 to 916° F.). 
     
     
         19 . The method of  claim 15 , wherein said step of optionally stretching includes stretching at about 1.5 to 3%. 
     
     
         20 . The method of  claim 15 , wherein said step of ageing includes a two-step T7651 ageing process wherein a first stage temperature ranges from 100 to 140° C. (212 to 284° F.) for 4 to 24 hours and a second stage temperature ranges from 135 to 200° C. (275 to 392° F.) for 5 to 20 hours. 
     
     
         21 . The method of  claim 15 , wherein
 b. said step of homogenizing includes homogenizing at temperatures from 454 to 491° C. (849 to 916° F.);   c. said step of hot working includes hot rolling at a temperature of 385 to 450° C. (725 to 842° F.);   d. said step of solution heat treating includes solution heat treated at temperature range from 454 to 491° C. (849 to 916° F.);   e. said step of cold water quenching includes cold water quenching to room temperature;   f. said step of optionally stretching includes stretching at about 1.5 to 3%;   g. said step of ageing includes a two-step T7651 ageing process wherein a first stage temperature ranges from 100 to 140° C. (212 to 284° F.) for 4 to 24 hours and a second stage temperature ranges from 135 to 200° C. (275 to 392° F.) for 5 to 20 hours.