Process for manufacturing sheet metal made of aluminum-copper-lithium alloy for manufacturing an airplane fuselage
The subject of the invention is a process for manufacturing a wrought product made of aluminum alloy comprising the following steps: a) casting a plate made of alloy comprising, in percentages by weight, Cu: 2.1 to 2.8; Li: 1.1 to 1.7; Mg: 0.2 to 0.9; Mn: 0.2 to 0.6; Ti: 0.01-0.2; Ag<0.1; Zr<0.08; Fe and Si #0.1 each; unavoidable impurities #0.05% each and 0.15% in total; remainder aluminum; b) homogenizing said plate at 480-520° C. for 5 to 60 hours; c) hot-rolling and optionally cold-rolling said homogenized plate to give a sheet; d) solution annealing the sheet at 470-520° C. for 5 minutes to 4 hours; e) quenching the solution-annealed sheet; f) controlled tensioning of the solution-annealed and quenched sheet with a permanent set of 1 to 6%; g) tempering of the tensioned sheet by heating at a temperature of at least 160° C. for a maximum time of 30 hours.
1. A product obtained by a method comprising,
a. casting a rolling ingot made of an alloy comprising:
2.1 to 2.8% by weight of Cu;
1.1 to 1.7% by weight of Li;
0.2 to 0.9% by weight of Mg;
0.2 to 0.6% by weight of Mn;
0.01 to 0.2% by weight of Ti;
less than 0.1% by weight of Ag;
less than 0.08% by weight of Zr;
a quantity of Fe and of Si less than or equal to 0.1% by weight each, and inevitable impurities at a concentration less than or equal to 0.05% by weight each and 0.15% by weight in total;
the rest aluminum;
b. homogenizing said rolling ingot at 480-520° C. for 5 to 60 hours;
c. hot and optionally cold rolling said homogenized rolling ingot into sheet metal;
d. solution heat treatment of the sheet metal at 470-520° C. for 15 minutes to 4 hours;
e. quenching the solution heat treated sheet metal;
f. controlled stretching of the solution heat treated and quenched sheet metal with a permanent deformation of 1 to 6%;
g. aging of the stretched sheet metal by heating to a temperature of at least 170° C., for a maximum time of 30 hours,
wherein among phases containing lithium said phases do not contain the phase δ′ but only phase T 1 ,
wherein g of aging is carried out at an equivalent time t i at 165° C. between 20 and 30 hours,
the equivalent time t i at 165° C. being defined by formula:
t
i
=
∫
exp
(
-
1
6400
/
T
)
dt
exp
(
-
1
6400
/
T
r
e
f
)
wherein T (in Kelvin) is the instantaneous temperature of treatment of the metal, which changes with the time t (in hours), and T ref is a reference temperature set to 438K.
2. The product according to claim 1 , wherein the rolling ingot made of aluminum alloy comprises from 2.2 to 2.6% by weight of Cu.
3. The product according to claim 1 , wherein the rolling ingot made of aluminum alloy comprises from 1.2 to 1.6% by weight of Li.
4. The product according claim 1 , wherein the rolling ingot made of aluminum alloy comprises from 0.25 to 0.75% by weight of Mg.
5. The product according to claim 1 , wherein the rolling ingot made of aluminum alloy comprises from 0.25 to 0.45% by weight of Mn.
6. The product according to claim 1 , wherein the rolling ingot made of aluminum alloy comprises less than 0.05% by weight of Ag.
7. The product according to claim 1 , wherein the rolling ingot made of aluminum alloy comprises less than 0.05% by weight of Zr.
8. The product according to claim 1 , wherein the hot rolling is carried out at an initial temperature of 420 to 490° C.
9. The product according to claim 1 , wherein the controlled stretching of the sheet metal is carried out with a permanent deformation of between 2.5 and 5%.
10. The product according to claim 1 having at least one of the following properties:
conventional elastic limit, Rp0.2 (L), of at least 330 MPa;
conventional elastic limit, Rp0.2 (LT), of at least 325 MPa;
planar-stress toughness, Kapp (T-L), of at least 130 MPa m;
effective stress intensity factor for an effective crack extension Δa eff of 60 mm, Kr60 (T-L), of at least 175 MPa m.
11. The product according to claim 1 wherein at the end of a thermal treatment of 1000 h at 85° C., said product has a planar-stress toughness, Kapp (T-L), and/or an effective stress intensity factor for an effective crack extension Δa eff of 60 mm, Kr60 (T-L), that does not differ by more than 7%.
12. The product according to claim 10 , wherein the product has three or more of the properties.
13. The product according to claim 10 wherein:
the conventional elastic limit, Rp0.2 (L) is at least 335 MPa;
the conventional elastic limit, Rp0.2 (LT) is at least 330 MPa;
the planar-stress toughness, Kapp (T-L) is at least 135 MPa m;
the effective stress intensity factor for an effective crack extension Δa eff of 60 min, Kr60 (T-L), is at least 180 MPa m.
14. The product according to claim 10 wherein:
the conventional elastic limit, Rp0.2 (L) is at least 340 MPa;
the conventional elastic limit, Rp0.2 (LT) is at least 335 MPa;
the planar-stress toughness, Kapp (T-L) is at least 140 MPa m;
the effective stress intensity factor for an effective crack extension Δa eff of 60 mm, Kr60 (T-L), is at least 185 MPa m.
15. The product according to claim 1 wherein at the end of a thermal treatment of 1000 h at 85° C., said product has a planar-stress toughness, Kapp (T-L), and/or an effective stress intensity factor for an effective crack extension Δa eff of 60 mm, Kr60 (T-L), that does not differ by more than 5%.
16. The product according to claim 1 wherein at the end of a thermal treatment of 1000 h at 85° C., said product has a planar-stress toughness, Kapp (T-L), and/or an effective stress intensity factor for an effective crack extension Δa eff of 60 mm, Kr60 (T-L), that does not differ by more than 2%.