# US 10,501,835 B2 · Thin sheets made of an aluminium-copper-lithium alloy for producing airplane fuselages

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- Number: US 10,501,835 B2
- Document ID: US10501835B2
- Status: Granted
- Kind: B2
- Application number: 14/781,096
- Filed: 2014-04-01
- Published: 2016-02-25
- Granted: 2019-12-10
- Earliest claimed: 2013-04-03
- Assignees: Constellium Issoire
- Applicants: Constellium Issoire
- Inventors: Bernard Bes; Juliette Chevy; Frank Eberl
- Web page: https://patentgrep.com/patent/US10501835B2

## CPC

- C22F 1/057: of alloys with copper as the next major constituent
- C22C 21/14: with silicon
- C22C 21/16: with magnesium
- C22F 1/002: {by rapid cooling or quenching; cooling agents used therefor}
- B64C 2001/0081: {from metallic materials}
- C22F: CHANGING THE PHYSICAL STRUCTURE OF NON-FERROUS METALS AND NON-FERROUS ALLOYS (surface treatment of metallic material involving at least one process provided for in class C23 and at least one process covered by this subclass, C23F17/00)
- C22C: ALLOYS (treatment of alloys C21D, C22F)
- B64C: AEROPLANES; HELICOPTERS

## Abstract

The invention relates to a method for manufacturing a thin sheet having a thickness of 0.5 to 3.3 mm and an essentially non-recrystallized structure made of aluminum-based alloy.

## Claims

### Claim 1

A method for producing a sheet of thickness 0.5 to 3.3 mm of essentially unrecrystallized structure made of an aluminum-based alloy said method comprising, successively
a) a molten metal bath is prepared comprising
2.6 to 3.4% by weight of Cu,
0.5 to 1.1% by weight of Li,
0.1 to 0.4% by weight of Ag,
0.2 to 0.8% by weight of Mg,
0.11 to 0.20% by weight of Zr,
0.01 to 0.15% by weight of Ti,
optionally at least one element chosen among Mn, V, Cr, Sc, and Hf, the quantity of element, if chosen, being from 0.01 to 0.8% by weight for Mn, 0.05 to 0.2% by weight for V, 0.05 to 0.3% by weight for Cr, 0.02 to 0.3% by weight for Sc, 0.05 to 0.5% by weight for Hf,
a quantity of Zn less than 0.6% by weight, a quantity of Fe and Si less than or equal to 0.1% by weight each, and inevitable impurities with a content less than or equal to 0.05% by weight each and 0.15% by weight in total,
b) casting a slab from said molten metal bath
c) homogenizing said slab at a temperature between 450° C. and 515° C.;
d) hot rolling said slab into a plate of thickness between 4 and 12 mm;
e) cold rolling said plate into a sheet of final thickness between 0.5 and 3.3 mm, the reduction in thickness by cold rolling being between 1 and 3.5 mm;
f) performing heat treatment during which the sheet reaches a temperature between 300° C. and 450° C. for at least thirty minutes;
g) solution heat treating said sheet at a temperature between 450° C. and 515° C. and quenching;
h) controlled stretching said sheet with a permanent deformation of 0.5 to 5%, cold working after solution heat treatment being less than 15%;
i) performing aging at a temperature between 130° C. and 170° C. and optionally between 150° C. and 160° C. for 5 to 100 hours and preferably for 10 to 40 hours.

### Claim 2 (depends on 1)

The method according to claim 1, wherein the copper content lies between 2.8 and 3.1% by weight and optionally between 2.8 and 3.0% by weight.

### Claim 3 (depends on 1)

The method according to claim 1, wherein the lithium content lies between 0.55 and 0.75% by weight and optionally between 0.60 and 0.73% by weight.

### Claim 4

A sheet of essentially unrecrystallized granular structure, wherein the sheet is obtained by a process comprising the following performed in succession,
a) preparing a molten metal bath comprising
2.6 to 3.4% by weight of Cu,
0.5 to 1.1% by weight of Li,
0.1 to 0.4% by weight of Ag,
0.2 to 0.8% by weight of Mg,
0.11 to 0.20% by weight of Zr,
0.1 to 0.15% by weight of Ti,
optionally at least one element chosen among Mn, V, Cr, Sc, and Hf, the quantity of element, if chosen, being from 0.01 to 0.8% by weight for Mn, 0.05 to 0.2% by weight for V, 0.05 to 0.3% by weight for Cr, 0.02 to 0.3% by weight for Sc, 0.05 to 0.5% by weight for Hf,
a quantity of Zn less than 0.6% by weight, a quantity of Fe and Si less than equal to 0.1by weight each, and inevitable impurities with a content less than or equal to 0.05% by weight each and 0.15% by weight in total,
e) casting a slab from said molten metal bath
f) homogenizing said slab at a temperature between 450° C. and 515° C.;
g) hot rolling said slab into a plate of thickness between 4 and 12 mm;
e) cold rolling said plate into a sheet of final thickness between 0.5 and 3.3 mm, the reduction in thickness by cold rolling being between 1 and 3.5 mm;
f) performing heat treatment during which the sheet reaches a temperature between 300° C. and 450° C. for at least thirty minutes;
g) solution heat treating said sheet at a temperature between 450° C. and 515° C. and quenching;
h) controlled stretching said sheet with a permanent deformation of 0.5 to 5%, cold working after solution heat treatment being less than 15%;
i) performing aging at a temperature between 130° C. and 170° C. and optionally between 150° C. and 160° C. for 5 to 100 hours and preferable for 10 to 40 hours,
wherein the yield stress Rp0.2 in the T-L direction is at least 395 MPa, and the fracture toughness in plane strain Kapp, measured on test pieces of type CCT760 (2ao=253 mm) in the T-L direction is at least 150 MPa√m.

### Claim 5 (depends on 4)

The sheet according to claim 4 wherein the lithium content lies between 0.55 and 0.75% by weight, the elongation of which is at least 14% in the T-L direction.

### Claim 6 (depends on 5)

The sheet according to claim 5, wherein the magnesium content lies between 0.40 and 0.65% by weight, whose yield stress Rp0.2 in the T-L direction is at least 405 MPa, whose fracture toughness in plane strain Kapp, measured on test pieces of type CCT760 (2ao=253 mm) in the T-L direction is at least 160 MPa√m.

### Claim 7 (depends on 5)

The sheet according to claim 5 wherein the copper content lies between 2.8 and 3.0% by weight, and the elongation of which is at least 15% in the T-L direction.

### Claim 8 (depends on 5)

The sheet according to claim 5, wherein the magnesium content lies between 0.40 and 0.65% by weight, the copper content of which lies between 2.8 and 3.0%, the yield stress Rp0.2 in the T-L direction is at least 410 MPa, whose fracture toughness in plane strain Kapp, measured on test pieces to type CCT760 (2ao=253 mm), in the T-L direction of at least 163 MPa√m and whose elongation in the T-L direction is at least 16%.

### Claim 9 (depends on 4)

A sheet according to claim 4 shaped into an aircraft fuselage panel.

### Claim 10 (depends on 4)

The sheet according to claim 4, wherein recrystallization rate at half thickness is less than 10%.

### Claim 11 (depends on 4)

The sheet according to claim 4, wherein the lithium content is between 0.60 and 0.73% by weight.

### Claim 12 (depends on 4)

The sheet according to claim 4, wherein the Ag content is between 0.2 and 0.3% by weight.

### Claim 13 (depends on 4)

The sheet according to claim 4, wherein the final thickness is between 1.2 and 2.8 mm.

### Claim 14 (depends on 4)

The sheet according to claim 4, wherein the reduction in thickness by cold rolling is between 1 and 3.0 mm.

### Claim 15 (depends on 4)

The sheet according to claim 4, wherein cold working after solution heat treatment is less than 10%.

### Claim 16 (depends on 4)

The sheet according according to claim 4, wherein the molten metal bath consists essentially of
a. 2.6 to 3.4% by weight of Cu,
b. 0.5 to 1.1% by weight of Li,
c. 0.1 to 0.4% by weight of Ag,
d. 0.2 to 0.8% by weight of Mg,
e. 0.11 to 0.20% by weight of Zr,
f. 0.01 to 0.15% by weight of Ti,
optionally at least one element chosen among Mn, V, Cr, Sc, and Hf, the quantity of element, if chosen, being from 0.01 to 0.8% by weight for Mn, 0.05 to 0.2% by weight for V, 0.05 to 0.3% by weight for Cr, 0.02 to 0.3% by weight for Sc, 0.05 to 0.5% by weight for Hf,
a quantity of Zn less than 0.6% by weight, a quantity of Fe and Si less than or equal to 0.1% by weight each, and inevitable impurities with a content less than or equal to 0.05% by weight each and 0.15% by weight in total.

### Claim 17 (depends on 4)

The sheet according according to claim 4, wherein the molten metal bath consists of
a. 2.6 to 3.4% by weight of Cu,
b. 0.5 to 1.1% by weight of Li,
c. 0.1 to 0.4% by weight of Ag,
d. 0.2 to 0.8% by weight of Mg,
e. 0.11 to 0.20% by weight of Zr,
f. 0.01 to 0.15% by weight of Ti,
optionally at least one element chosen among Mn, V, Cr, Sc, and Hf, the quantity of element, if chosen, being from 0.01 to 0.8% by weight for Mn, 0.05 to 0.2% by weight for V, 0.05 to 0.3% by weight for Cr, 0.02 to 0.3% by weight for Sc, 0.05 to 0.5% by weight for Hf,
a quantity of Zn less than 0.6% by weight, a quantity of Fe and Si less than or equal to 0.1% by weight each, and inevitable impurities with a content less than or equal to 0.05% by weight each and 0.15% by weight in total.

### Claim 18 (depends on 5)

The sheet according to claim 5, wherein the yield stress Rp0.2 in the T-L direction is at least 410 MPa, and the fracture toughness in plane strain Kapp, measured on test pieces to type CCT760 (2ao =253 mm), in the T-L direction is at least 165 MPa√m.

### Claim 19 (depends on 17)

The sheet according to claim 17, wherein the lithium content is from 0.55 and 0.75% by weight, the magnesium content is from 0.40 and 0.65% by weight, the copper content is from 2.8 and 3.0% by weight, the Ag content is from 0.2 and 0.3% by weight; and
wherein the yield stress Rp0.2 in the T-L direction is at least 410 MPa, whose fracture toughness in plane strain Kapp, measured on test pieces to type CCT760 (2ao =253 mm), in the T-L direction of at least 163 MPa√m and whose elongation in the T-L direction is at least 16%.

### Claim 20 (depends on 19)

The sheet according to claim 19, wherein the final thickness of the sheet is from 1.2 and 2.8 mm.