Aluminum-copper-lithium alloy thin sheets with improved toughness, and process for manufacturing an aluminum-copper-lithium alloy thin sheet
View Patent ↗The invention relates to a method for manufacturing a thin sheet made from aluminum-based alloy comprising, as % by weight, 2.2 to 2.7% Cu, 1.3 to 1.6% Li, less than 0.1% Ag, 0.2 to 0.5% Mg, 0.1 to 0.5% Mn, 0.01 to 0.15% Ti, a quantity of Zn of less than 0.3, a quantity of Fe and of Si of less than or equal to 0.1% each, and unavoidable impurities with a content of less than or equal to 0.05% by weight each and 0.15% by weight in total, the remainder aluminum, wherein optionally the hot-rolling input temperature being between 400° C. and 460° C. and the hot-rolling output temperature being less than 300° C. and the mean heating speed during the solution heat treatment is at least approximately 17° C./min between 300° C. and 400° C., aging conditions such that the yield strength in the long-transverse direction Rp0.2 is between 350 and 380 MPa.
1 . A method for manufacturing a sheet with a thickness of between 4 and 12.7 mm made from aluminum-based alloy wherein, successively,
a) producing a liquid metal bath consisting of
2.2 to 2.7% by weight Cu,
1.3 to 1.6% by weight Li,
no more than 0.1% by weight Ag,
0.2 to 0.5% by weight Mg,
0.1 to 0.5% by weight Mn,
0.01 to 0.15% by weight Ti,
a quantity of Zn of less than or equal to 0.3% by weight, a quantity of Fe and of Si of less than or equal to 0.1% by weight each, the remainder being aluminum and unavoidable impurities with a content of less than or equal to 0.05% by weight each, and 0.15% by weight in total, the remainder aluminum,
b) casting a slab from said liquid-metal bath;
c) homogenizing said slab at a temperature of between 490° C. and 535 ° C.;
d) rolling said homogenized slab by hot rolling into a sheet having a thickness of between 4 and 12.7 mm, a hot-rolling input temperature being between 420° C. and 445° C. and a hot-rolling output temperature being less than 300° C.;
e) solution heat treating said sheet at a temperature of between 450° C. and 535° C. for at least 5 min, with a mean rate of heating of said sheet of at least 17° C./min between 300° C. and 400° C., and said solution heat treated sheet is quenched in water;
f) stretching said quenched sheet in a controlled manner with a permanent deformation of 0.5 to 6%, a cold deformation after solution heat treatment being less than 15%;
g) aging said sheet, said aging comprising heating at a temperature of between 130 and 170° C. so that yield strength in a long-transverse direction Rp0.2 (LT) is between 350 and 380 MPa, and wherein the sheet is recrystallized.
2 . The method according to claim 1 , wherein the copper content is between 2.45 and 2.55% by weight.
3 . The method according to claim 1 , wherein the lithium content is between 1.35 and 1.55% by weight.
4 . The method according to claim 1 , wherein the magnesium content is between 0.25 and 0.45% by weight.
5 . The method according to claim 1 , wherein the manganese content is between 0.2 and 0.4% by weight.
6 . The method according to claim 1 , wherein the zinc content is less than 0.1% by weight.
7 . The method according to claim 1 , wherein the silver content is less than 0.05% by weight.
8 . The method according to claim 1 , wherein hot-rolling input temperature is between 420° C. and 440° C. and/or hot-rolling output temperature is less than 290° C.
9 . The method according to claim 1 , wherein the copper content is between 2.20 and 2.35% by weight.
10 . The method according to claim 1 , wherein the Fe content and the Si content are no more than 0.08% by weight each.
11 . The method according to claim 1 , wherein the homogenization temperature is between 500° C. and 515° C.
12 . The method according to claim 1 , wherein the temperature of the solution heat treatment is between 450° C. and 525° C.
13 . The method according to claim 1 , wherein the aging comprising heating at a temperature of between 145 and 155° C.