Aluminum alloys

Abstract

The disclosure relates to an alloy comprising, by weight, about 5.8% to about 6.8% zinc, about 2.5% to about 3.0% magnesium, about 1.5% to about 2.3% copper, 0% to about 0.2% scandium, 0% to about 0.2% zirconium, and optionally less than about 0.50% silver, the balance essentially aluminum and incidental elements and impurities. In embodiments, the alloy has a stress-corrosion cracking threshold stress of at least about 240 MPa using an ASTM G47 short-transverse test specimen and a yield strength of at least about 510 MPa using an ASTM E8 longitudinal test specimen.

1 . An alloy comprising, by weight, about 5.8% to about 6.8% zinc, about 2.5% to about 3.0% magnesium, about 1.5% to about 2.3% copper, 0% to about 0.2% scandium, 0% to about 0.2% zirconium, and optionally less than about 0.50% silver, the balance essentially aluminum and incidental elements and impurities, wherein the alloy has a stress-corrosion cracking threshold stress of at least about 240 MPa using an ASTM G47 short-transverse test specimen and a yield strength of at least about 510 MPa using an ASTM E8 longitudinal test specimen. 
     
     
         2 . The alloy of  claim 1 , wherein the alloy comprises dispersed L1 2  phase particles including at least one of scandium and zirconium, constituting about 0.1% by volume of the alloy. 
     
     
         3 . The alloy of  claim 1 , wherein the alloy comprises an η-MgZn 2  phase that constitutes about 3% to about 8% by volume of the alloy. 
     
     
         4 . The alloy of  claim 1 , wherein the alloy comprises 6.3 Zn, 2.7 Mg, 1.6 Cu, 0.10 Sc, 0.05 Zr, and balance Al, in wt %, with the composition including a variation of ten percent of the nominal values. 
     
     
         5 . The alloy of  claim 1 , wherein the alloy comprises 5.8 Zn, 3.0 Mg, 2.2 Cu, 0.05 Sc, 0.05 Zr, and balance Al, in wt %, with the composition including a variation of ten percent of the nominal values. 
     
     
         6 . The alloy of  claim 1 , wherein the alloy comprises 6.3 Zn, 2.7 Mg, 1.6 Cu, 0.12 Zr, and balance Al, in wt %, with the composition including a variation of ten percent of the nominal values. 
     
     
         7 . A method for producing an alloy comprising:
 preparing a melt that includes, by weight, about 5.8% to about 6.8% zinc, about 2.5% to about 3.0% magnesium, about 1.5% to about 2.3% copper, 0% to about 0.2% scandium, 0% to about 0.2% zirconium, and optionally less than about 0.50% silver, the balance essentially aluminum and incidental elements and impurities;   cooling the melt to room temperature; and   homogenizing the alloy by heating it from room temperature to 400° C. at 1° C. per minute, holding it at 400° C. for 12 hours, heating it from 400° C. at 1° C. per minute, and holding it at 460° C.-480° C. for 24-48 hours.   
     
     
         8 . The method of  claim 7 , further comprising:
 hot-working the alloy to a change in cross section.   
     
     
         9 . The method of  claim 7 , further comprising:
 solution heat-treating the alloy at 460° C.-480° C. for 1-4 hours.   
     
     
         10 . The method of  claim 7 , further comprising:
 aging the alloy at a first temperature of 100° C.-120° C. for 6-12 hours, then heating the alloy to a second temperature of 160° C.-180° C. and holding the alloy at the second temperature for 8-30 hours, and quenching the alloy with water.   
     
     
         11 . An alloy produced according to the method of  claim 7 . 
     
     
         12 . A manufactured article comprising an alloy according to  claim 11 . 
     
     
         13 . A method for producing an aluminum alloy comprising:
 providing an alloy comprising an aluminum matrix;   adding to the aluminum matrix amounts of zinc, magnesium, and copper according to an SCC index of the equation:
   ( SCC  index)=2 ×wp Zn+ wp Mg− wp Cu
 
   
       where wpZn, wpMg, and wpCu are the weight percentages of Zn, Mg, and Cu, respectively, in the matrix of the alloy, and wherein the SCC index of the alloy is less than or equal to 1.6. 
     
     
         14 . The method of  claim 13 , wherein the alloy comprises about 5.8% to about 6.8% zinc, about 2.5% to about 3.0% magnesium, about 1.5% to about 2.3% copper, 0% to about 0.2% scandium, 0% to about 0.2% zirconium, and optionally less than about 0.50% silver, the balance essentially aluminum and incidental elements and impurities. 
     
     
         15 . The method of  claim 13 , further comprising:
 homogenizing the alloy by heating it from room temperature to 400° C. at 1° C. per minute, holding it at 400° C. for 12 hours, heating it from 400° C. at 1° C. per minute, and holding it at 460° C.-480° C. for 24-48 hours.   
     
     
         16 . The method of  claim 13 , further comprising:
 hot-working the alloy to a change in cross section.   
     
     
         17 . The method of  claim 13 , further comprising:
 solution heat-treating the alloy at 460° C.-480° C. for 1-4 hours.   
     
     
         18 . The method of  claim 13 , further comprising:
 aging the alloy at a first temperature of 100° C.-120° C. for 6-12 hours, then heating the alloy to a second temperature of 160° C.-180° C. and holding the alloy at the second temperature for 8-30 hours, and quenching the alloy with water.