Transformation process of Al—Cu—Li alloy sheets

1. A 3-dimensional formed fuselage skin sheet for the aeronautic industry manufactured by a process comprising:

a) preparing a molten metal bath comprising aluminum, said molten bath comprising from 3.0% to 3.5% Cu by weight, from 0.8% to 1.1% Li by weight, from 0.25% to 0.6% Mg by weight, from 0.10% to 0.50% Ag by weight, from 0% to 0.35% Zn by weight, at most 0.18% Fe+ Si by weight, 0.04% to 0.18% Zr by weight, other elements≤0.05% by weight each and ≤0.15% by weight in total, remainder aluminum;

b) casting a rolling ingot from said molten metal bath;

c) optionally, homogenizing said rolling ingot;

d) hot rolling the optionally homogenized rolling ingot, and optionally cold rolling, into a sheet having a thickness of from 1 mm to 8 mm;

e) solution heat treating and quenching said sheet;

f) flattening and/or stretching the solution heat treated and quenched sheet with a cumulated deformation of at least 0.5% and not more than 3%;

g) performing short heat-treatment, wherein said short heat-treatment is carried out to obtain an equivalent time at 150° C. from 0.5 hour to 5 hours, wherein equivalent time t i at 150° C. is defined by formula:

t

i

=

∫

exp

⁡

(

-

16400

/

T

)

⁢

d

⁢

⁢

t

exp

⁡

(

-

16400

/

T

ref

)

where T (in Kelvin) is instantaneous treatment temperature of the flattened and/or stretched sheet, which changes with time t (in hours), T ref is reference temperature set at 423 K, and t i is expressed in hours;

h) performing 3-dimensional forming operation with additional cold working of at least 4% and not more than 8% of the short heat-treated sheet to obtain the fuselage skin sheet; and

i) performing an artificial aging in which said 3-dimensional formed fuselage skin sheet reaches a temperature ranging between 130° C. and 170° C. for 5 to 100 hours;

wherein the 3-dimensional formed fuselage skin sheet is a 3-dimensional rolled product;

wherein the 3-dimensional formed fuselage skin sheet comprises a combination of:

at least one property selected from the group consisting of: (i) R p0.2 (L) of at least 500 MPa and (ii) R p0.2 (LT) of at least 480 MPa, and

at least one property measured on CCT760 (2ao=253 mm) test specimens selected from the group consisting of (1) K app in the T-L direction at least 160 MPa√{square root over (m)} and (2) K eff in the T-L direction at least 200 MPa√{square root over (m)}.

2. The 3-dimensional formed fuselage skin sheet according to claim 1 , wherein said short heat-treatment is carried out to obtain an equivalent time at 150° C. from 1 hour to 4 hours.

3. The 3-dimensional formed fuselage skin sheet according to claim 1 , wherein said short heat-treatment is carried out to obtain an equivalent time at 150° C. from 0.5 hour to 4 hours.

4. The 3-dimensional formed fuselage skin sheet according to claim 1 ,

wherein said product comprises a combination of:

at least one property selected from the group consisting of: (i) R p0.2 (L) of at least 510 MPa and (ii) R p0.2 (LT) of at least 490 MPa, and

at least one property measured on CCT760 (2ao=253 mm) test specimens selected from the group consisting of (1) K app in the T-L direction at least 170 MPa√{square root over (m)} and (2) K eff in the T-L direction at least 220 MPa√{square root over (m)}.

5. A 3-dimensional formed fuselage skin sheet for the aeronautic industry manufactured by a process comprising:

a) preparing a molten metal bath comprising aluminum, said molten bath comprising from 3.0% to 3.5% Cu by weight, from 0.8% to 1.1% Li by weight, from 0.25% to 0.6% Mg by weight, from 0.10% to 0.50% Ag by weight, from 0% to 0.35% Zn by weight, at most 0.18% Fe+ Si by weight, 0.04% to 0.18% Zr by weight, other elements≤0.05% by weight each and ≤0.15% by weight in total, remainder aluminum;

b) casting a rolling ingot from said molten metal bath;

c) optionally, homogenizing said rolling ingot;

d) hot rolling the optionally homogenized rolling ingot, and optionally cold rolling, into a sheet having a thickness of from 1 mm to 8 mm;

e) solution heat treating and quenching said sheet;

f) flattening and/or stretching the solution heat treated and quenched sheet with a cumulated deformation of at least 0.5% and not more than 3%;

g) performing short heat-treatment in which the flattened and/or stretched sheet reaches a temperature ranging from 130° C. to 170° C. for from 0.1 to 5 hours;

h) performing 3-dimensional operation with additional cold working of at least 4% and not more than 8% of the short heat-treated sheet to obtain the fuselage skin sheet; and

i) performing an artificial aging in which said 3-dimensional formed fuselage skin sheet reaches a temperature ranging between 130° C. and 170° C. for 5 to 100 hours;

wherein the 3-dimensional formed fuselage skin sheet is a 3-dimensional rolled product;

wherein the 3-dimensional formed fuselage skin sheet comprises a combination of:

at least one property selected from the group consisting of: (i) R p0.2 (L) of at least 500 MPa and (ii) R p0.2 (LT) of at least 480 MPa, and

at least one property measured on CCT760 (2ao=253 mm) test specimens selected from the group consisting of (1) K app in the T-L direction at least 160 MPa√{square root over (m)} and (2) K eff in the T-L direction at least 200 MPa√{square root over (m)}.

6. The 3-dimensional formed fuselage skin sheet according to claim 5 , wherein, at f, controlled stretching is performed with permanent deformation from 0.5% to 1.5%.

7. The 3-dimensional formed fuselage skin sheet according to claim 5 , wherein lithium is present in an amount of at least 0.85% by weight and at most 1.1% by weight.

8. The 3-dimensional formed fuselage skin sheet according to claim 5 , wherein zinc is present in an amount greater than 0% to 0.35% by weight.

9. The 3-dimensional formed fuselage skin sheet according to claim 5 , wherein the alloy comprises from 0.08% to 0.15% of zirconium by weight.

10. The 3-dimensional formed fuselage skin sheet according to claim 5 , wherein g) comprises performing short heat-treatment in which said sheet reaches a temperature ranging from 130° C. to 170° C. for from 1 to 5 hours.

11. The 3-dimensional formed fuselage skin sheet according to claim 5 , wherein g) comprises performing short heat-treatment in which said sheet reaches a temperature ranging from 150° C. to 160° C.

12. The 3-dimensional formed fuselage skin sheet according to claim 5 , wherein silver is present in an amount from 0.15% to 0.4% by weight.

13. The 3-dimensional formed fuselage skin sheet according to claim 12 , wherein zinc is present in an amount greater than 0% and less than 0.2% by weight.

14. The 3-dimensional formed fuselage skin sheet according to claim 5 , wherein said product comprises a combination of:

at least one property selected from the group consisting of: (i) R p0.2 (L) of at least 510 MPa and (ii) R p0.2 (LT) of at least 490 MPa, and

at least one property measured on CCT760 (2ao=253 mm) test specimens selected from the group consisting of (1) K app in the T-L direction at least 170 MPa√{square root over (m)} and (2) K eff in the T-L direction at least 220 MPa√{square root over (m)}.