Low Cost, Low Density, Substantially Ag-Free and Zn-Free Aluminum-Lithium Plate Alloy for Aerospace Application

Abstract

The present invention is directed to aluminum-lithium alloys, specifically aluminum—copper—lithium—magnesium—manganese alloys. The aluminum-lithium alloy of the present invention comprises from 3.6 to 4.1 wt. % Cu, 0.8 to 1.05 wt. % Li, 0.6 to 1.0 wt. % Mg, 0.2 to 0.6 wt. % Mn, up to 0.12 wt. % Si, up to 0.15 wt. % Fe, from 0.03 to 0.16 wt. % of at least one grain structure control element selected from the group consisting of Zr, Sc, Cr, V, Hf, and other rare earth elements, up to 0.10 wt. % Ti, up to 0.15 wt. % incidental elements with the total of incidental elements not exceeding 0.35 wt. %, and the balance being aluminum. Preferably, Ag is not intentionally added and should not be more than 0.05 wt. % as a non-intentionally added element. Preferably, Zn is not intentionally added and should not be more than 0.2 wt. % as a non-intentionally added element. The amount of Cu in weight percent is at least equal to or higher than four times the amount of Li in weight percent.

1 - 20 . (canceled) 
     
     
         21 . A low cost, low density, and high performance Al—Li alloy comprising:
 from 3.6 to 4.1 wt. % Cu, from 0.8 to 1.05 wt. % Li, 
 from 0.6 to 1.0 wt.% Mg, from 0.2 to 0.6 wt.% Mn, 
 less than 0.05 wt.% Ag, less than 0.2 wt.% Zn, 
 from 0.03 to 0.16 wt. % of at least one grain structure control element selected from the group consisting of Zr, Sc, Cr, V, Hf, and other rare earth elements 
 up to 0.10 wt.% Ti, up to 0.12 wt.% Si, 
 up to 0.15 wt.% Fe, 
 up to 0.15 wt. % each incidental elements, with the total incidental elements not exceeding 0.35 wt. %, 
 with the balance being aluminum, and 
 wherein the amount of Cu in weight percent is at least equal to or higher than four times the amount of Li in weight percent. 
 
     
     
         22 . The aluminum-lithium alloy of  claim 21 , comprising 3.7 to 4.0 wt. % Cu. 
     
     
         23 . The aluminum-lithium alloy of  claim 21 , comprising 0.9 to 1.0 wt. % Li. 
     
     
         24 . The aluminum-lithium alloy of  claim 21 , comprising 0.7 to 0.9 wt. % Mg. 
     
     
         25 . The aluminum-lithium alloy of  claim 21 , wherein no Ag is intentionally added to the aluminum alloy. 
     
     
         26 . The aluminum-lithium alloy of  claim 21 , wherein no Zn is intentionally added to the aluminum alloy. 
     
     
         27 . The aluminum-lithium alloy of  claim 21 , comprising less than 0.10 wt % Zn. 
     
     
         28 . The aluminum-lithium alloy of  claim 21 , comprising less than 0.05 wt % Zn. 
     
     
         29 . The aluminum-lithium alloy of  claim 21 , comprising a maximum of 0.05 wt. % Si. 
     
     
         30 . The aluminum-lithium alloy of  claim 21 , comprising a maximum of 0.08 wt.% Fe. 
     
     
         31 . A low cost, low density, and high performance Al—Li alloy comprising:
 from 3.7 to 4.0 wt. % Cu, from 0.9 to 1.0 wt. % Li, 
 from 0.7 to 0.9 wt.% Mg, from 0.2 to 0.6 wt.% Mn, 
 less than 0.05 wt.% Ag, less than 0.2 wt.% Zn, 
 from 0.03 to 0.16 wt. % of at least one grain structure control element selected from the group consisting of Zr, Sc, Cr, V, Hf, and other rare earth elements 
 up to 0.10 wt.% Ti, up to 0.12 wt.% Si, 
 up to 0.15 wt.% Fe, 
 up to 0.15 wt. % each incidental elements, with the total of these incidental elements not exceeding 0.35 wt. %, 
 with the balance being aluminum, and 
 wherein the amount of Cu in weight percent is at least equal to or higher than four times the amount of Li in weight percent. 
 
     
     
         32 . The aluminum-lithium alloy of  claim 21 , wherein said aluminum-lithium alloy is in the form of a rolled, extruded, or forged product, and has a thickness from about 0.5 to about 8.0 inch. 
     
     
         33 . The aluminum-lithium alloy of  claim 32 , wherein said aluminum-lithium alloy has a thickness from about 0.5 to about 6.0 inch. 
     
     
         34 . A rolled product comprising an aluminum-lithium alloy of  claim 21 , having a thickness from about 0.5 to about 8.0 inch., exhibiting in a solution heat-treated, quenched, stretched and artificially aged condition:
 a minimum Tensile Yield Strength (TYS) along rolling (L) direction as function of plate gage (ga) of 75.0-1.4*ga.,   a minimum Tensile Yield Strength (TYS) along long transverse (LT) direction of 71.2-1.4*ga.,   a minimum Fracture Toughness (K1c) along the orientation of Long Transverse—Rolling (T-L) of 28-1.0*ga.,   and a minimum Fracture Toughness (K1c) along the orientation of Rolling—Long Transverse (L-T) of 28.8-0.6*ga,   wherein the units for gage (ga), strength, and fracture toughness are inch, ksi, and ksi*in 1/2  respectively.   
     
     
         35 . A rolled product comprising an aluminum-lithium alloy of  claim 21 , having a thickness from about 0.5 to about 8.0 inch., exhibiting in a solution heat-treated, quenched, stretched and artificially aged condition:
 a minimum Tensile Yield Strength (TYS) along rolling (L) direction as function of plate gage (ga) of 76.2-1.4*ga.,   a minimum Tensile Yield Strength (TYS) along long transverse (LT) direction of 72.2-1.4*ga.,   a minimum Fracture Toughness (K1c) along the orientation of Long Transverse—Rolling (T-L) of 29-1.0*ga.,   and a minimum Fracture Toughness (K1c) along the orientation of Rolling—Long Transverse (L-T) of 30.8-0.6*ga,   wherein the units for gage (ga), strength, and fracture toughness are inch, ksi, and ksi*in 1/2  respectively.   
     
     
         36 . A rolled product comprising an aluminum-lithium alloy of  claim 21 , having a thickness from about 0.5 to about 8.0 inch., exhibiting in a solution heat-treated, quenched, stretched and artificially aged condition:
 a minimum Tensile Yield Strength (TYS) along rolling (L) direction as function of plate gage (ga) of 77.0-1.4*ga.,   a minimum Tensile Yield Strength (TYS) along long transverse (LT) direction of 72.7-1.4*ga.,   a minimum Fracture Toughness (K1c) along the orientation of Long Transverse—Rolling (T-L) of 29.5-1.0*ga.,   and a minimum Fracture Toughness (K1c) along the orientation of Rolling—Long Transverse (L-T) of 31.8-0.6*ga,   wherein the units for gage (ga), strength, and fracture toughness are inch, ksi, and ksi*in 1/2  respectively.   
     
     
         37 . The rolled product of  claim 34 , wherein said product alloy has a thickness from about 0.5 to about 6.0 inch. 
     
     
         38 . A method of manufacturing a low cost, low density, and high performance Al—Li alloy, the method comprising:
 a. casting stock of an ingot of aluminum alloy comprising the aluminum-lithium alloy product according to  claim 21  producing a cast stock 
 b. homogenizing the cast stock producing a homogenized cast stock; 
 c. hot working the homogenized cast stock by one or more methods selected from the group consisting of rolling, extrusion, and forging forming a worked stock; 
 d. solution heat treating (SHT) the worked stock, producing a SHT stock; 
 e. cold water quenching said SHT stock to produce a cold water quenched SHT stock; 
 f stretching the cold water quenched SHT stock to produce stretched stock; and 
 g. artificially ageing of the stretched stock. 
 
     
     
         39 . The method of  claim 38 , wherein said step of homogenizing includes homogenizing at temperatures from 482 to 543° C. (900 to 1010° F.); wherein said step of hot working includes hot rolling at a temperature of 357 to 482° C. (675 to 900° F.); wherein said step of solution heat treating includes solution heat treated at temperature range from 482 to 538° C. (900 to 1000° F.); wherein said step of stretching includes stretching from 2% to up to 15%; and wherein said step of artificially ageing includes aging at a temperature of from 121 to 205° C. (250 to 400° F.) and the aging time can be in the range of 2 to 60 hours. 
     
     
         40 . The method of  claim 39 , wherein said step of artificially ageing includes aging at a temperature of from 149 to 182° C. (300 to 360° F.) and the aging time can be in the range of 10 to 48 hours.