# US 8,771,441 B2 · High fracture toughness aluminum-copper-lithium sheet or light-gauge plates suitable for fuselage panels

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- Number: US 8,771,441 B2
- Document ID: US8771441B2
- Status: Granted
- Kind: B2
- Application number: 11/612,131
- Filed: 2006-12-18
- Published: 2007-08-09
- Granted: 2014-07-08
- Earliest claimed: 2005-12-20
- Applicants: Bernard Bes; Herve Ribes; Christophe Sigli; Timothy Warner
- Inventors: Bernard Bes; Herve Ribes; Christophe Sigli; Timothy Warner
- Web page: https://patentgrep.com/patent/US8771441B2

## CPC

- C22F 1/057: of alloys with copper as the next major constituent
- C22C 21/16: with magnesium
- 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)

## Abstract

An aluminum alloy comprising 2.1 to 2.8 wt. % Cu, 1.1 to 1.7 wt. % Li, 0.1 to 0.8 wt. % Ag, 0.2 to 0.6 wt. % Mg, 0.2 to 0.6 wt. % Mn, a content of Fe and Si less or equal to 0.1 wt. % each, and a content of unavoidable impurities less than or equal to 0.05 wt. % each and 0.15 wt. % total, and the alloy being substantially zirconium free.

## Claims

### Claim 1

An aluminum alloy rolled product not exceeding 0.5 inch in thickness comprising 2.3 to 2.5 wt. % Cu, 0.2 to 0.6 wt. % Li, 0.1 to 0.4 wt. % Ag, 0.2 to 0.4 wt. % Mg, 0.2 to 0.4 wt. % Mn, a content of Fe and Si less or equal to 0.05 wt. % each, and a content of unavoidable impurities less than or equal to 0.05 wt. % each and 0.15 wt. % total, and the alloy being substantially zirconium free, wherein said zirconium is present an amount of not more than about 0.04 wt. %, wherein said product comprises
a difference between the tensile yield strength at 45° to the rolling direction and the tensile yield strength in the LT direction as defined by (TYS (TL)−TYS))(45° /TYS (TL) from +5% to -5%, an ultimate tensile strength in the L-direction of at least 420 MPa, and
the fracture toughness using CCT760 (2a0=253 mm), including a crack extension of the last valid point of the R-curve Δaeff(max), in the T-L direction, of at least 60 mm and Kapp in T-L direction of at least 100 MPa√m, and wherein the product has a recrystallization rate of at least 80%.

### Claim 2 (depends on 1)

An aluminum alloy product according to claim 1 comprising 2.3 to 2.5 wt. % Cu, 1.3 to 1.5 wt. % Li, 0.2 to 0.4 wt. % Ag, 0.3 to 0.4 wt. % Mg, and 0.3 to 0.4 wt. % Mn.

### Claim 3 (depends on 1)

A method for producing an aluminum alloy sheet or light gauge plate comprising a product of claim 1 having high fracture toughness and strength, said method comprising:
(a) casting an ingot consisting essentially of 2.3 to 2.5 wt. % Cu, 1.2 to 1.6 wt. % Li, 0.1 to 0.4 wt. % Ag, 0.2 to 0.4 wt. % Mg, and 0.2 to 0.4 wt. % Mn, a content of Fe and Si less than or equal to 0.1 wt. % each, and a content of unavoidable impurities less than or equal to 0.05 wt. % each and 0.15 wt. % total, and wherein said alloy is substantially zirconium free, wherein said zirconium is present an amount of not more than about 0.04 wt %,
(b) homogenizing said ingot at 480-520° C. for about 5 to about 60 hours,
(c) hot rolling said ingot to a slab, with an hot rolling initial temperature of about 450° C. to about 490° C. and optionally cold rolling said slabs,
(d) solution heat treating said slabs at about 480° C. to about 520° C. for about 15 min. to about 4 hours,
(e) quenching said slabs,
(f) stretching said slabs with a permanent set from about 1 to about 5%,
(g) aging said slab by heating at about 140° C. to about 170° C. for about 5 to about 80 hours
(h) resulting in a sheet or light gauge plate comprising a product of claim 1.

### Claim 4 (depends on 3)

A method according to claim 3, wherein the thickness of said sheet or light gauge plate is from 0.8 mm to 12.7 mm.

### Claim 5 (depends on 3)

A rolled product produced by a method of claim 3, wherein said rolled product comprises
(a) a tensile yield strength in the L-direction of at least 390 MPa, a difference between the tensile yield strength at 45° to the rolling direction and the tensile yield strength in the LT direction as defined by (TYS (TL)−TYS(45°))/TYS (TL) from +5% to −5%,
(b) a plane stress fracture toughness Kapp, measured on CCT760 (2ao=253 mm) specimens, of at least 100 MPa√m,
(c) and/or a crack extension of the last valid point of the R-curve Δaeff(max)in the T-L direction of at least 60 mm,
(d) an ultimate tensile strength in the L-direction of at least 420 MPa.

### Claim 6 (depends on 5)

An aircraft fuselage panel comprising at least one rolled product according to claim 5.

### Claim 7 (depends on 1)

A structural member for aeronautical construction comprising at least one product according to claim 1.

### Claim 8 (depends on 1)

An aluminum alloy product according to claim 1 wherein zirconium is less than or equal to 0.01 wt. %.

### Claim 9 (depends on 4)

A method according to claim 4, wherein said thickness is from 1.6 mm to 9 mm.

### Claim 10 (depends on 5)

A rolled product of claim 5, wherein said difference is from +3% to −3%, said plane stress fracture toughness is at least 120 MPa√m in the T-L direction and said crack extension is at least 80 mm.

### Claim 11 (depends on 1)

A product of claim 1, wherein said crack extension of the last valid point of the R-curve Δaeff(max), in the T-L direction is at least 80 mm.