AlCuMg ALLOYS WITH HIGH DAMAGE TOLERANCE SUITABLE FOR USE AS STRUCTURAL MEMBERS IN AIRCRAFTS

Abstract

New alloys for potential use in applications such as in lower wing skins and fuselage skins are disclosed. Specifically, Mn-free 2×24 alloys potentially suitable for thick plate and thin plate and sheet applications are believed to be novel and to provide unexpectedly superior properties.

1 . A method for obtaining a substantially manganese-free aluminum alloy rolled product consisting essentially of (in percent by weight): Cu 3.6-4.5%, Mg 1.0-1.6%, Zr 0.08-0.20%, Sc 0.02-0.05%, Fe up to 0.08%, Si up to 0.09%, Mn less than 0.05%, remainder aluminum and incident impurities, wherein said rolled product comprises a plate, said method comprising: 
 (a) casting a rolling ingot, followed by optional stress relieving, and scalping;    (b) homogenizing at a temperature between 450 and 510° C.;    (c) hot-rolling on a reversing mill, preferably with an exit temperature between 350 and 390° C.;    (d) optionally, for plate with a thickness of less than about 30 mm, conducting at least one intermediate reheating to about 480° C., followed by one or more hot-rolling passes, the final exit temperature optionally being between 350 and 370° C.;    (e) solution heat treating at a temperature between 490 and 510° C., followed by water quenching and natural aging; and    (f) cold working by stretching alone or cold rolling followed by stretching, optionally followed by artificial aging.    
   
   
       2 . The method of  claim 1 , wherein Zr is present in an amount from 0.08-0.14%.  
   
   
       3 . The method of  claim 1 , wherein Cu is present in an amount from 3.8-4.2%.  
   
   
       4 . The method of  claim 1 , wherein the aluminum alloy rolled product comprises a recrystallized volume fraction of 5% maximum.  
   
   
       5 . The method of  claim 1 , wherein Mn is present in an amount of <0.01%.  
   
   
       6 . The method of  claim 1 , wherein the aluminum alloy rolled product comprises one or more of the following combinations of properties: 
 a. a tensile strength in the longitudinal direction (TYS (L) ) of more than 400 MPa, and an apparent fracture toughness K app(T-L)  of more than 110 MPa√m, measured according ASTM E 561 in the T-L orientation on a specimen with a width of W=127 mm;    b. an ultimate tensile strength in the longitudinal direction (UTS (L) ) of more than 450 MPa, and an elongation at fracture in the longitudinal direction of more than 24%;    c. a tensile yield strength in the longitudinal direction (TYS (L) ) of more than 400 MPa, and a Kahn stress R e  of at least 180 MPa.    
   
   
       7 . The method of  claim 1 , wherein the aluminum alloy rolled product further comprises at least one of the following combinations of properties: 
 a. a (UTS (L) ) of more than 500 MPa, preferably more than 520 MPa, and even more preferably more than 530 MPa, and a K app(T-L)  of more than 75 MPa√m, measured according ASTM E 647 on a 6.35 mm thick C(T) specimen with a width of W=40 mm;    b. a tensile yield strength in the longitudinal direction (TYS (L) ) of more than 450 MPa, and preferably more than 460 MPa, and a K app(T-L)  of more than 77 MPa√m, measured according ASTM E 561 on a 6.35 mm thick C(T) specimen with a width of W=40 mm;    c. a tensile yield strength in the longitudinal direction (TYS (L) ) of more than 350 MPa, preferably more than 400 MPa and even more preferably more than 450 MPa, and a Kahn stress R e  of at least 190 MPa.    
   
   
       8 . The method of  claim 1 , wherein the aluminum alloy rolled product further comprises a sheet or thin plate with a thickness below about 12 mm in T351 temper, having a da/dn in T-L direction which fulfills at least one of the following conditions: 
 da/dn less than 1.3×10 −4  mm/cycles at ΔK=10 MP√am;    da/dn less than 4.0×10 −4  mm/cycles at ΔK=15 MPa√m;    da/dn less than 8.0×10 −4  mm/cycles at ΔK=20 MPa√m;    da/dn less than 16×10 −4  mm/cycles at ΔK=25 MPa√m; and    da/dn less than 25×10 −4  mm/cycles at ΔK=30 MPa√m.    
   
   
       9 . The method of  claim 1 , wherein the aluminum alloy rolled product further comprises a in T351 temper having a da/dn in T-L direction which fulfills at least one of the following conditions: 
 da/dn less than 3.0×10 −5  mm/cycles at ΔK=10 MPa√m;    da/dn less than 1.0×10 −4  mm/cycles at ΔK=15 MPa√m;    da/dn less than 1.0×10 −3  mm/cycles at ΔK=25 MPa√m; and    da/dn less than 3.0×10 −3  mm/cycles at ΔK=30 MPa√m.    
   
   
       10 . The method of  claim 1 , wherein the aluminum alloy rolled product exhibits a maximum intergranular attack of less than 80 μm in T39 temper, and/or less than 200 μm in T851 temper, and/or less than 250 μm in T89 temper, and/or less than 300 μm in T351 temper in a corrosion test according to ASTM G 110.  
   
   
       11 . The method of  claim 1 , wherein the aluminum alloy rolled product exhibits a maximum intergranular attack of less than 70 μm in T39 temper, and/or less than 180 μm in T851 temper, and/or less than 220 μm in T89 temper, and/or less than 270 μm in T351 temper in a corrosion test according to ASTM G 110.  
   
   
       12 . The method of  claim 1 , wherein the aluminum alloy rolled plate product is a lower wing skin structural member.  
   
   
       13 . The method of  claim 1 , wherein the aluminum alloy rolled plate or sheet product is a fuselage skin member.  
   
   
       14 . The method of  claim 1 , further comprising the step of cladding the aluminum alloy rolled product.  
   
   
       15 . A method for obtaining a substantially manganese-free aluminum alloy rolled product consisting essentially of (in percent by weight): Cu 3.6-4.5%, Mg 1.0-1.6%, Zr 0.08-0.20%, Sc 0.02-0.05%, Fe up to 0.08%, Si up to 0.09%, Mn less than 0.05%, remainder aluminum and incident impurities, wherein said rolled product comprises a sheet product, said method comprising: 
 (a) casting a rolling ingot, followed by optional stress relieving, and scalping;    (b) homogenizing at a temperature between 470 and 530° C.;    (c) hot-rolling down to a thickness of less than 12 mm, and not more than 200% of final thickness, with a final exit temperature between 230 and 350° C.;    (d) optionally cold rolling;    (e) solution heat treating at a temperature between 490 and 510° C., followed by water quenching;    (f) cold working by stretching alone or cold rolling followed by stretching, optionally followed by artificial aging.    
   
   
       16 . The method of  claim 15 , wherein Zr is present in an amount from 0.08-0.14%.  
   
   
       17 . The method of  claim 15 , wherein Cu is present in an amount from 3.8-4.2%.  
   
   
       18 . The method of  claim 15 , wherein the aluminum alloy rolled product comprises a recrystallized volume fraction of 5% maximum.  
   
   
       19 . The method of  claim 15 , wherein Mn is present in an amount of <0.01%.  
   
   
       20 . The method of  claim 15 , wherein the aluminum alloy rolled product comprises one or more of the following combinations of properties: 
 a. a tensile strength in the longitudinal direction (TYS (L) ) of more than 400 MPa, and an apparent fracture toughness K app(T-L)  of more than 110 MPa√m, measured according ASTM E 561 in the T-L orientation on a specimen with a width of W=127 mm;    b. an ultimate tensile strength in the longitudinal direction (UTS (L) ) of more than 450 MPa, and an elongation at fracture in the longitudinal direction of more than 24%;    c. a tensile yield strength in the longitudinal direction (TYS (L) ) of more than 400 MPa, and a Kahn stress R e  of at least 180 MPa.    
   
   
       21 . The method of  claim 15 , wherein the aluminum alloy rolled product further comprises a sheet comprising at least one of the following combinations of properties: 
 a. a (UTS (L) ) of more than 500 MPa, preferably more than 520 MPa, and even more preferably more than 530 MPa, and a K app(T-L)  of more than 75 MPa√m, measured according ASTM E 647 on a 6.35 mm thick C(T) specimen with a width of W=40 mm;    b. a tensile yield strength in the longitudinal direction (TYS (L) ) of more than 450 MPa, and preferably more than 460 MPa, and a K app(T-L)  of more than 77 MPa√m, measured according ASTM E 561 on a 6.35 mm thick C(T) specimen with a width of W=40 mm;    c. a tensile yield strength in the longitudinal direction (TYS (L) ) of more than 350 MPa, preferably more than 400 MPa and even more preferably more than 450 MPa, and a Kahn stress R e  of at least 190 MPa.    
   
   
       22 . The method of  claim 15 , wherein the aluminum alloy rolled product further comprises a sheet or thin plate with a thickness below about 12 mm in T351 temper, having a da/dn in T-L direction which fulfills at least one of the following conditions: 
 da/dn less than 1.3×10 −4  mm/cycles at ΔK=10 MPa√m;    da/dn less than 4.0×10 −4  mm/cycles at ΔK=15 MPa√m;    da/dn less than 8.0×10 −4  mm/cycles at ΔK=20 MPa√m;    da/dn less than 16×10 −4  mm/cycles at ΔK=25 MPa√m; and    da/dn less than 25×10 −4  mm/cycles at ΔK=30 MPa√m.    
   
   
       23 . The method of  claim 15 , wherein the aluminum alloy rolled product further comprises a in T351 temper having a da/dn in T-L direction which fulfills at least one of the following conditions: 
 da/dn less than 3.0×10 −5  mm/cycles at ΔK=10 MPa√m;    da/dn less than 1.0×10 −4  mm/cycles at ΔK=15 MPa√m;    da/dn less than 1.0×10 −3  mm/cycles at ΔK=25 MPa√m; and    da/dn less than 3.0×10 −3  mm/cycles at ΔK=30 MPa√m.    
   
   
       24 . The method of  claim 15 , wherein the aluminum alloy rolled product exhibits a maximum intergranular attack of less than 80 μm in T39 temper, and/or less than 200 μm in T851 temper, and/or less than 250 μm in T89 temper, and/or less than 300 μm in T351 temper in a corrosion test according to ASTM G 110.  
   
   
       25 . The method of  claim 15 , wherein the aluminum alloy rolled product exhibits a maximum intergranular attack of less than 70 μm in T39 temper, and/or less than 180 μm in T851 temper, and/or less than 220 μm in T89 temper, and/or less than 270 μm in T351 temper in a corrosion test according to ASTM G 110.  
   
   
       26 . The method of  claim 15 , wherein the aluminum alloy rolled plate product is a lower wing skin structural member.  
   
   
       27 . The method of  claim 15 , wherein the aluminum alloy rolled plate or sheet product is a fuselage skin member.  
   
   
       28 . The method of  claim 15 , wherein no reheating is involved between hot-rolling steps of said hot-rolling.  
   
   
       29 . The method of  claim 15 , wherein there is no additional step of recrystallization treatment.  
   
   
       30 . The method of  claim 15 , further comprising the step of cladding the aluminum alloy rolled product.