7xxx aluminum alloys

Abstract

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.

What is claimed is: 
     
         1 . A 7xxx sheet product comprising:
 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;   
       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 . 
     
     
         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=− 0.02 X+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=− 0.039 X+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:
 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;   
       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. 
     
     
         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.