Aluminum-zinc-magnesium-copper alloy extrusion

Abstract

An aluminum alloy extrusion product having improved strength and fracture toughness, the aluminum base alloy comprised of 1.95 to 2.5 wt. % Cu, 1.9 to 2.5 wt. % Mg, 8.2 to 10 wt. % Zn, 0.05 to 0.25 wt. % Zr, max. 0.15 wt. % Si, max. 0.15 wt. % Fe, max. 0.1 wt. % Mn, the remainder aluminum and incidental elements and impurities.

What is claimed is:  
     
         1 . A method of producing an aluminum alloy extrusion product having improved fracture toughness, the method comprising the steps of: 
 (a) providing a molten body of an aluminum base alloy comprised of 1.95 to 2.5 wt. % Cu, 1.9 to 2.5 wt. % Mg, 8.2 to 10 wt. % Zn, 0.05 to 0.25 wt. % Zr, max. 0.15 wt. % Si, max. 0.15 wt. % Fe, max. 0.1 wt. % Mn, the remainder aluminum and incidental elements and impurities;    (b) casting said molten body of said aluminum base alloy to provide a solidified body, said molten aluminum base alloy being cast at a rate in the range of 1 to 6 inches per minute;    (c) homogenizing said body by heating in a first temperature range of 840 to 860° F. followed by heating in a second temperature range of 860° to 880° F. to provide a homogenized body having a uniform distribution of η precipitate and zirconium containing dispersoids;    (d) extruding said homogenized body to provide an extrusion, said extruding being carried out in a temperature range of 6000° to 850° F. and at a rate sufficient to maintain at least 80% of the cross-sectional area of said extrusion in a non-recrystallized condition;    (e) solution heat treating said extrusion; and    (f) artificial aging said product to improve strength properties to provide an extrusion product having improved fracture toughness.    
     
     
         2 . The method in accordance with  claim 1  wherein the alloy contains 1.95 to 2.3 wt. % Cu.  
     
     
         3 . The method in accordance with  claim 1  wherein the alloy contains 1.9 to 2.3 wt. % Mg.  
     
     
         4 . The method in accordance with  claim 1  wherein the alloy contains 0.05 to 0.2 wt. % Cr.  
     
     
         5 . The method in accordance with  claim 1  wherein the alloy contains 8.45 to 9.4 wt. % Zn.  
     
     
         6 . The method in accordance with  claim 1  wherein the alloy contains 0.01 to 0.1 wt. % Sc.  
     
     
         7 . The method in accordance with  claim 1  wherein the alloy contains 0.01 to 0.2 wt. % Ti.  
     
     
         8 . The method in accordance with  claim 1  including heating in said first temperature range for 6 to 18 hours.  
     
     
         9 . The method in accordance with  claim 1  including heating in said second temperature range for 4 to 36 hours.  
     
     
         10 . The method in accordance with  claim 1  including rapidly quenching said extrusion.  
     
     
         11 . The method in accordance with  claim 1  wherein said extruding is carried out at a rate in the range of 0.5 to 8 ft/min.  
     
     
         12 . The method in accordance with  claim 1  wherein said solution heat treating is carried out in a temperature range of 870° to 890° F. for 5 to 120 minutes.  
     
     
         13 . The method in accordance with  claim 1  wherein said artificial aging is carried out by aging in a temperature range of 175° to 300° F. for 3 to 30 hours followed by aging at 280° to 360° F. for 3 to 24 hours.  
     
     
         14 . The method in accordance with  claim 1  wherein said artificial aging is carried out by aging in a temperature range of 210° to 280° F. for 4 to 24 hours followed by aging at 320° to 400° F. for 30 minutes to 14 hours.  
     
     
         15 . The method in accordance with  claim 1  wherein said artificial aging is carried out by aging in a temperature range of 150° to 325° F. for 2 to 30 hours followed by aging at 300° to 500° F. for 5 minutes to 3 hours followed by aging at 175° to 325° F. for 2 to 30 hours.  
     
     
         16 . The method in accordance with  claim 1  wherein said artificial aging is a three-step process wherein said first and third steps improve strength and a second step improves corrosion resistance.  
     
     
         17 . The method in accordance with  claim 1  wherein said artificial aging includes aging: (i) at a low temperature above room temperature to precipitation harden said extrusion; (ii) at temperatures to improve corrosion resistance properties of said extrusion; and (iii) at lower temperatures above room temperature to precipitation harden said extrusion.  
     
     
         18 . The method in accordance with  claim 1  wherein the extrusion has a fracture toughness at least 5% greater than a similar extrusion fabricated from 7075 alloy.  
     
     
         19 . The method in accordance with  claim 1  wherein the extrusion has a tensile strength at least 8% greater than a similar extrusion fabricated from 7075 alloy.  
     
     
         20 . A method of producing an aluminum alloy extrusion product having improved strength and fracture toughness, the method comprising the steps of: 
 (a) providing a molten body of an aluminum base alloy comprised of 1.95 to 2.3 wt. % Cu, 1.9 to 2.3 wt. % Mg, 8.2 to 9.4 wt. % Zn, 0.05 to 0.2 wt. % Cr, 0.05 to 0.15 wt. % Zr, max. 0.15 wt. % Si, max. 0.15 wt. % Fe, max. 0.1 wt. % Mn, the remainder aluminum and incidental elements and impurities;    (b) casting said molten body of said aluminum base alloy to provide a solidified body, said molten aluminum base alloy being cast at a rate in the range of 1 to 6 inches per minute;    (c) homogenizing said body by heating in a first temperature range of 840° to 860° F. for 6 to 24 hours followed by heating in a second temperature range of 860° to 880° F. for 4 to 36 hours to provide a homogenized body having a uniform distribution of η precipitate and zirconium and chromium containing dispersoids;    (d) extruding said homogenized body to provide an extrusion, said extruding being carried out in a temperature range of 600° to 850° F. and at a rate in the range of 0.5 to 8.0 ft/min to provide an extrusion with the non-recrystallized area representing at least 80% of the cross sectional area of the extrusion;    (e) rapidly quenching said extrusion;    (f) solution heat treating said extrusion; and    (g) artificial aging said product to improve strength properties to provide an extrusion product having improved fracture toughness.    
     
     
         21 . The method in accordance with  claim 20  wherein the alloy contains 0.01 to 0.1 wt. % Sc.  
     
     
         22 . The method in accordance with  claim 20  wherein the alloy contains 0.01 to 0.2 wt. % Ti.  
     
     
         23 . The method in accordance with  claim 20  wherein said solution heat treating is carried out in a temperature range of 870° to 890° F. for 5 to 120 minutes.  
     
     
         24 . The method in accordance with  claim 20  wherein said artificial aging is carried out by aging in a temperature range of 175° to 300° F. for 3 to 30 hours followed by aging at 280° to 360° F. for 3 to 24 hours.  
     
     
         25 . The method in accordance with  claim 20  wherein said artificial aging is carried out by aging in a temperature range of 245° to 255° F. for 6 to 24 hours followed by aging at 360° to 390° F. for 5 to 120 minutes.  
     
     
         26 . The method in accordance with  claim 20  wherein said artificial aging is a three-step process wherein said first and third steps improve strength and a second step improves corrosion resistance.  
     
     
         27 . The method in accordance with  claim 20  wherein said artificial aging includes aging: (i) at a low temperature above room temperature to precipitation harden said extrusion; (ii) at temperatures to improve corrosion resistance properties of said extrusion; and (iii) at lower temperatures above room temperature to precipitation harden said extrusion.  
     
     
         28 . The method in accordance with  claim 20  wherein the extrusion has a fracture toughness at least 5% greater than a similar extrusion fabricated from 7075 alloy.  
     
     
         29 . The method in accordance with  claim 20  wherein said artificial aging is carried out by aging in a temperature range of 150° to 325° F. for 2 to 30 hours followed by aging at 300° to 500° F. for 5 minutes to 3 hours followed by aging at 175° to 325° F. for 2 to 30 hours.  
     
     
         30 . A method of producing an aluminum alloy extrusion product having improved strength and fracture toughness, the method comprising the steps of: 
 (a) providing a molten body of an aluminum base alloy comprised of 1.95 to 2.5 wt. % Cu, 1.9 to 2.5 wt. % Mg, 8.2 to 10 wt. % Zn, 0.05 to 0.25 wt. % Zr, max. 0.15 wt. % Si, max. 0.15 wt. % Fe, max. 0.1 wt. % Mn, the remainder aluminum and incidental elements and impurities;    (b) casting said molten body of said aluminum base alloy to provide a solidified body, said molten aluminum base alloy being cast at a rate in the range of 1 to 4 inches per minute;    (c) homogenizing said body to provide a homogenized body having a uniform distribution of η precipitate;    (d) extruding said homogenized body to provide an extrusion, said extruding being carried out in a temperature range of 600° to 850° F. at an extrusion ratio in the range of 10 to 60 and an extrusion rate in the range of 0.5 to 8.0 ft/min to provide said extrusion in a substantially non-recrystallized condition;    (e) rapidly quenching said extrusion;    (f) solution heat treating said extrusion; and    (g) artificial aging said product to improve strength properties to provide an extrusion product having improved fracture toughness.    
     
     
         31 . The method in accordance with  claim 30  wherein the alloy contains 0.05 to 0.2 wt. % Cr.  
     
     
         32 . The method in accordance with  claim 30  wherein the alloy contains 0.01 to 0.2 wt. % Ti.  
     
     
         33 . The method in accordance with  claim 30  wherein the alloy contains 0.01 to 0.2 wt. % Sc.  
     
     
         34 . The method in accordance with  claim 30  wherein said solution heat treating is carried out in a temperature range of 875° to 885° F. for 5 to 120 minutes.  
     
     
         35 . The method in accordance with  claim 30  wherein said artificial aging is carried out by aging in a temperature range of 175° to 300° F. for 3 to 30 hours followed by aging at 280° to 360° F. for 3 to 24 hours.  
     
     
         36 . The method in accordance with  claim 30  wherein said artificial aging is carried out by aging in a temperature range of 210° to 280° F. for 4 to 24 hours followed by aging at 300° to 400° F. for 1 to 14 hours.  
     
     
         37 . The method in accordance with  claim 30  wherein said artificial aging includes aging: (i) at a low temperature above room temperature to precipitation harden said extrusion; (ii) at temperatures to improve corrosion resistance properties of said extrusion; and (iii) at lower temperatures above room temperature to precipitation harden said extrusion.  
     
     
         38 . The method in accordance with  claim 30  wherein said artificial aging is carried out by aging in a temperature range of 150° to 325° F. for 2 to 30 hours followed by aging at 300° to 500° F. for 5 minutes to 3 hours followed by aging at 175° to 325° F. for 2 to 30 hours.  
     
     
         39 . An improved aluminum base alloy wrought product consisting essentially of 1.95 to 2.5 wt. % Cu, 1.9 to 2.5 wt. % Mg, 8.2 to 10 wt. % Zn, 0.05 to 0.25 wt. % Zr, max. 0.15 wt. % Si, max. 0.15 wt. % Fe, max. 0.1 wt. % Mn, the remainder aluminum and incidental elements and impurities, said alloy product having a fracture toughness of 5% or greater and a yield strength of 8% or greater than a similarly sized 7075 product.  
     
     
         40 . The alloy product in accordance with  claim 39  wherein the alloy contains 1.95 to 2.3 wt. % Cu.  
     
     
         41 . The alloy product in accordance with  claim 39  wherein the alloy contains 1.9 to 2.3 wt. % Mg.  
     
     
         42 . The alloy product in accordance with  claim 39  wherein the alloy contains 0.05 to 0.2 wt. % Cr.  
     
     
         43 . The alloy product in accordance with  claim 39  wherein the alloy contains 8.45 to 9.4 wt. % Zn.  
     
     
         44 . The alloy product in accordance with  claim 39  wherein the alloy contains 0.01 to 0.2 wt. % Sc.  
     
     
         45 . The alloy product in accordance with  claim 39  wherein the alloy contains 0.01 to 0.2 wt. % Ti.  
     
     
         46 . The alloy product in accordance with  claim 39  wherein said product is an extrusion product.  
     
     
         47 . The alloy product in accordance with  claim 39  wherein the alloy product is an extrusion having an aspect ratio between the thinnest and the thickest section of 1:4 to 1:18.  
     
     
         48 . The alloy product in accordance with  claim 39  wherein said product is an aircraft stringer.  
     
     
         49 . The alloy product in accordance with  claim 39  wherein said product is an aircraft floor beam.  
     
     
         50 . The alloy product in accordance with  claim 39  wherein said product is an aircraft fuselage beam.  
     
     
         51 . The alloy product in accordance with  claim 39  wherein said product is a hollow extruded product.  
     
     
         52 . The alloy product in accordance with  claim 39  wherein said product is a hollow non-seamless extruded product.  
     
     
         53 . The alloy product in accordance with  claim 39  wherein said product is a hollow seamless extruded product.  
     
     
         54 . The alloy product in accordance with  claim 39  wherein said product is a baseball bat.  
     
     
         55 . The alloy product in accordance with  claim 39  wherein said product is an automobile rocker arm.  
     
     
         56 . An improved aluminum base alloy wrought product consisting essentially of 1.95 to 2.5 wt. % Cu, 1.9 to 2.5 wt. % Mg, 8.2 to 10 wt. % Zn, 0.05 to 0.25 wt. % Zr, 0.05 to 0.2 wt. % Sc, max 0.15 wt. % Si, max. 0.15 wt. % Fe, max. 0.1 wt. % Mn, the remainder aluminum and incidental elements and impurities.  
     
     
         57 . The alloy product in accordance with  claim 56  wherein the alloy contains 0.05 to 0.2 wt. % Cr.  
     
     
         58 . The alloy product in accordance with  claim 56  wherein the alloy contains 0.05 to 0.2 wt. % Ti.  
     
     
         59 . An improved aluminum base alloy wrought product consisting essentially of 1.95 to 2.5 wt. % Cu, 1.9 to 2.5 wt. % Mg, 8.2 to 10 wt. % Zn, 0.05 to 0.25 wt. % Zr, max. 0.15 wt. % Si, max. 0.15 wt. % Fe, max. 0.1 wt. % Mn, the remainder aluminum and incidental elements and impurities, said alloy product having a fracture toughness of 5% or greater, a yield strength of 8% or greater than a similarly sized 7075 product and having an exfoliation resistance of EB or better.  
     
     
         60 . An improved aluminum base alloy aircraft member consisting essentially of 1.95 to 2.5 wt. % Cu, 1.9 to 2.5 wt. % Mg, 8.2 to 10 wt. % Zn, 0.05 to 0.25 wt. % Zr, max. 0.15 wt. % Si, max. 0.15 wt. % Fe, max. 0.1 wt. % Mn, the remainder aluminum and incidental elements and impurities, said alloy product having a fracture toughness of 5% or greater and a yield strength of 8% or greater than a similarly sized 7075 product.  
     
     
         61 . The alloy product in accordance with  claim 60  wherein said member is an aircraft stringer.  
     
     
         62 . The alloy product in accordance with  claim 60  wherein said member is an aircraft floor beam.  
     
     
         63 . The alloy product in accordance with  claim 60  wherein said member is an aircraft fuselage beam.  
     
     
         64 . An improved aluminum base alloy aircraft member consisting essentially of 1.95 to 2.5 wt. % Cu, 1.9 to 2.5 wt. % Mg, 8.2 to 10 wt. % Zn, 0.05 to 0.25 wt. % Zr, max. 0.15 wt. % Si, max. 0.15 wt. % Fe, max. 0.1 wt. % Mn, the remainder aluminum and incidental elements and impurities, said alloy product having a fracture toughness of 5% or greater, a yield strength of 8% or greater than a similarly sized 7075 product and having an exfoliation resistance of EB or better.