Aluminum—copper—lithium products
View Patent ↗The present invention relates to extruded, rolled and/or forged products. Also provided are methods of making such products based on aluminum alloy wherein a liquid metal bath is prepared comprising 2.0 to 3.5% by weight of Cu, 1.4 to 1.8% by weight of Li, 0.1 to 0.5% by weight of Ag, 0.1 to 1.0% by weight of Mg, 0.05 to 0.18% by weight of Zr, 0.2 to 0.6% by weight of Mn and at least one element selected from Cr, Sc, Hf and Ti, the quantity of said element, if it is selected, being 0.05 to 0.3% by weight for Cr and for Sc, 0.05 to 0.5% by weight for Hf and 0.01 to 0.15% by weight for Ti, the remainder being aluminum and inevitable impurities. The products and methods of the present invention offer a particularly advantageous compromise between static mechanical strength and damage tolerance and are particularly useful in the field of aeronautical design.
1. Extruded aluminum alloy product having a density less than 2.67 g/cm 3 obtained by a method comprising:
a) preparing a liquid metal bath comprising 2.45 to 2.65% by weight of Cu, 1.4 to 1.5% by weight of Li, 0.1 to 0.5% by weight of Ag, 0.1 to 1.0% by weight of Mg, 0.05 to 0.18% by weight of Zr, 0.2 to 0.6% by weight of Mn and at least one element selected from Cr, Sc, Hf or Ti, the quantity of said element being 0.05 to 0.3% by weight for Cr and for Sc, 0.05 to 0.5% by weight for Hf and 0.01 to 0.15% by weight for Ti, remainder aluminum and inevitable impurities;
b) casting an unwrought shape from said liquid metal bath;
c) homogenizing said unwrought shape at a temperature from 515° C. to 525° C. such that the equivalent time for homogenization
t
(
eq
)
=
∫
exp
(
-
26100
/
T
)
ⅆ
t
exp
(
-
26100
/
T
ref
)
is from 5 to 20 hours, where T (in Kelvin) is the instantaneous treatment temperature, which varies with the time t (in hours), and T ref is a reference temperature set at 793 K;
d) hot working and optionally cold working said unwrought shape into an extruded product;
e) subjecting the product to a solution treatment and quenching;
f) stretching said product with a permanent set of 1 to 5%;
g) artificially aging said product by heating at 140 to 170° C. for 5 to 70 hours, wherein the toughness K Q (L-T) is at least 52 MPa√{square root over (m)} and the yield strength is at least 490 MPa.
2. Extruded product according to claim 1 comprising:
(a) the yield strength measured at 0.2% elongation in the L direction Rp 0.2 (L) expressed in MPa and the toughness thereof K Q (L-T), in the L-T direction expressed in MPa√{square root over (m)} are such that K Q (L-T)>132−0.17 Rp 0.2 (L); and/or
(b) the fracture strength thereof in the L direction R m (L) expressed in MPa and the toughness thereof K Q (L-T), in the L-T direction expressed in MPa√{square root over (m)} are such that
K Q (L-T)>182−0.25 R m (L).
3. Extruded product according to claim 1 wherein the thickness of at least one elementary rectangle thereof is at least 8 mm.
4. Structural element comprising and/or manufactured using at least one product according to claim 1 .
5. Structural element comprising at least one extruded product according to claim 1 used as a stiffener or frame for the manufacture of fuselage panels and/or aircraft wings.
6. Extruded aluminum alloy product having a density less than 2.67 g/cm 3 obtained by a method comprising:
a) preparing a liquid metal bath comprising 2.65 to 2.85% by weight of Cu, 1.5 to 1.7% by weight of Li, 0.1 to 0.5% by weight of Ag, 0.1 to 1.0% by weight of Mg, 0.05 to 0.18% by weight of Zr, 0.2 to 0.6% by weight of Mn and at least one element selected from Cr, Sc, Hf or Ti, the quantity of said element being 0.05 to 0.3% by weight for Cr and for Sc, 0.05 to 0.5% by weight for Hf and 0.01 to 0.15% by weight for Ti, remainder aluminum and inevitable impurities;
b) casting an unwrought shape from said liquid metal bath;
c) homogenizing said unwrought shape at a temperature from 515° C. to 525° C. such that the equivalent time for homogenization
t
(
eq
)
=
∫
exp
(
-
26100
/
T
)
ⅆ
t
exp
(
-
26100
/
T
ref
)
is from 5 to 20 hours, where T (in Kelvin) is the instantaneous treatment temperature, which varies with the time t (in hours), and T ref is a reference temperature set at 793 K;
d) hot working and optionally cold working said unwrought shape into an extruded product;
e) subjecting the product to a solution treatment and quenching;
f) stretching said product with a permanent set of 1 to 5%;
g) artificially aging said product by heating at 140 to 170° C. for 5 to 70 hours, wherein the toughness K Q (L-T) is at least 45 MPa√{square root over (m)} and the yield strength is at least 520 MPa.
7. Extruded product according to claim 6 comprising:
(a) the yield strength measured at 0.2% elongation in the L direction Rp 0.2 (L) expressed in MPa and the toughness thereof K Q (L-T), in the L-T direction expressed in MPa√{square root over (m)} are such that K Q (L-T)>132−0.17 Rp 0.2 (L); and/or
(b) the fracture strength thereof in the L direction R m (L) expressed in MPa and the toughness thereof K Q (L-T), in the L-T direction expressed in MPa√{square root over (m)} are such that
K Q (L-T)>182−0.25 R m (L).
8. Extruded product according to claim 1 wherein the thickness of at least one elementary rectangle thereof is at least 8 mm.
9. Method to manufacture an extruded product based on an aluminum alloy, said method comprising:
a) preparing a liquid metal bath comprising 2.45 to 2.65% by weight of Cu, 1.4 to 1.5% by weight of Li, 0.1 to 0.5% by weight of Ag, 0.1 to 1.0% by weight of Mg, 0.05 to 0.18% by weight of Zr, 0.2 to 0.6% by weight of Mn and at least one element selected from Cr, Sc, Hf or Ti, the quantity of said element being 0.05 to 0.3% by weight for Cr and for Sc, 0.05 to 0.5% by weight for Hf and 0.01 to 0.15% by weight for Ti, remainder aluminum and inevitable impurities;
b) casting an unwrought shape from said liquid metal bath;
c) homogenizing said unwrought shape at a temperature from 515° C. to 525° C. such that the equivalent time for homogenization
t
(
eq
)
=
∫
exp
(
-
26100
/
T
)
ⅆ
t
exp
(
-
26100
/
T
ref
)
is from 5 to 20 hours, where T (in Kelvin) is the instantaneous treatment temperature, which varies with the time t (in hours), and T ref is a reference temperature set at 793 K;
d) hot working and optionally cold working said unwrought shape into an extruded product;
e) subjecting the product to a solution treatment and quenching;
f) stretching said product with a permanent set of 1 to 5%;
g) artificially aging said product by heating at 140 to 170° C. for 5 to 70 hours; and
wherein the toughness K Q (L-T) is at least 52 MPa√{square root over (m)} and the yield strength is at least 490 MPa.
10. Method according claim 9 , wherein the silver content of said liquid metal bath is from 0.15 to 0.35% by weight.
11. Method according to claim 9 wherein the magnesium content of said liquid metal bath is less than 0.4% by weight.
12. Method according to claim 9 wherein the manganese of said liquid metal bath is not more than 0.35% by weight.
13. Method according to claim 9 wherein said inevitable impurities comprise iron and silicon, said impurities having a content less than 0.08% by weight and 0.06% by weight for iron and silicon, respectively, the other impurities having a content less than 0.05% by weight each and 0.15% by weight in total.
14. Method according to claim 9 wherein said equivalent time for homogenization is between 6 and 15 hours.
15. Method according to claim 9 wherein the homogenization temperature is about 520° C. and the treatment time is from 8 to 20 hours.
16. Method according to claim 9 wherein said artificial aging is carried out by heating at 148 to 155° C. for 10 to 40 hours.
17. Method to manufacture an extruded product based on an aluminum alloy, said method comprising:
a) preparing a liquid metal bath comprising 2.65 to 2.85% by weight of Cu, 1.5 to 1.7% by weight of Li, 0.1 to 0.5% by weight of Ag, 0.1 to 1.0% by weight of Mg, 0.05 to 0.18% by weight of Zr, 0.2 to 0.6% by weight of Mn and at least one element selected from Cr, Sc, Hf or Ti, the quantity of said element being 0.05 to 0.3% by weight for Cr and for Sc, 0.05 to 0.5% by weight for Hf and 0.01 to 0.15% by weight for Ti, remainder aluminum and inevitable impurities;
b) casting an unwrought shape from said liquid metal bath;
c) homogenizing said unwrought shape at a temperature from 515° C. to 525° C. such that the equivalent time for homogenization
t
(
eq
)
=
∫
exp
(
-
26100
/
T
)
ⅆ
t
exp
(
-
26100
/
T
ref
)
is from 5 to 20 hours, where T (in Kelvin) is the instantaneous treatment temperature, which varies with the time t (in hours), and T ref is a reference temperature set at 793 K;
d) hot working and optionally cold working said unwrought shape into an extruded product;
e) subjecting the product to a solution treatment and quenching;
f) stretching said product with a permanent set of 1 to 5%;
g) artificially aging said product by heating at 140 to 170° C. for 5 to 70 hours; and
wherein the toughness K Q (L-T) is at least 45 MPa√{square root over (m)} and the yield strength is at least 520 MPa.