Products made of Al-Zn-Mg-Cu alloys with an improved compromise between static mechanical characteristics and damage tolerance

1. A structural element suitable for aeronautical construction made from at least one extruded product comprising an aluminum alloy of the following composition (by mass):

(a) Zn 6.9-7.3% Cu 2.0-2.8% Mg from 1.6 to less than 2.0% wherein Cu/Mg is at least 1.1

(b) at least one element selected from the group consisting of: Zr 0.08-0.20%, Cr 0.05-0.25%, Sc 0.01-0.50% Hf 0.05-0.60% and V 0.02-0.20%

(c) Fe+Si<0.20%

(d) other elements ≦0.05% each and ≦0.15% total,

(e) remainder aluminum, wherein said product possesses at least one of the following sets of properties measured at about 20° C.:

(a) a yield stress R p0.2(L) equal to at least 580 MPa and a measured K app(L-T) with W=100 mm equal to at least about 80 MPa√m;

(b) a yield stress R p0.2(L) equal to at least 580 MPa and a crack propagation rate da/dn not exceeding about 3×10 −3 mm/cycle for ΔK=27 MPa√m;

(c) a yield stress R p0.2(L) equal to at least 580 MPa, an ultimate strength R m(L) equal to at least 600 MPa and a K app(L-T) measured with W=100 mm equal to at least about 80 MPa√m;

(d) an ultimate strength Rm(L) equal to at least 600 MPa and a K app(L-T) measured with W=100 mm equal to at least about 80 MPa√m.

2. A structural element according to claim 1 , wherein 3.8<(Cu+Mg)<4.8.

3. A structural element of claim 1 , wherein 3.9<(Cu+Mg)<4.7.

4. A structural element of claim 1 , wherein 4.1<(Cu+Mg)<4.7.

5. A structural element according to claim 1 , wherein a Cu/Mg ratio in the composition is between 1.1 and 1.5.

6. A structural element according to claim 1 , wherein Cu is between 2.2 and 2.6%.

7. A structural element according to claim 1 , wherein Mg is from 1.7 to less than 2.0%.

8. A structural element according to claim 1 , further comprising up to 0.8% of manganese.

9. A structural element according to claim 1 , wherein the sum of the contents of the Zr, Cr, Sc, Hf, V and Mn elements does not exceed about 1.0%.

10. A structural element according to claim 1 , wherein Si+Fe does not exceed 0.15%.

11. A structural element according to claim 1 , wherein said product has been put into solution, quenched and annealed, by achieving a first plateau at a temperature of between about 110° C. and about 125° C., and a second plateau at a temperature of between about 150 and about 170° C.

12. A structural element according to claim 1 , further possessing at least one property selected from the group consisting of:

(a) elongation at failure A (L) equal to at least about 9%, and

(b) resistance to exfoliation corrosion measured according to ASTM G34 equal to at least about EB.

13. A structural element according to claim 1 , wherein the value of K app(L-T) at about −50° C. is at least about 98%, of a value measured at about 20° C.

14. A structural element according to claim 1 , comprising a wing stiffener obtained by extrusion.

15. A structural element according to claim 1 , comprising a fuselage frame stiffener.

16. A method for manufacturing an extruded product according to claim 1 , said method comprising:

(a) preparing said alloy,

(b) casting an as-cast product,

(c) homogenizing said as-cast product,

(d) hot transforming to obtain a first intermediate product,

(e) causing dissolution of said first intermediate product,

(f) quenching,

(g) optionally conducting controlled tension, and

(h) annealing.

17. A method according to claim 16 , wherein said method involves homogenizing in at least two steps, with a first plateau between about 452 and about 473° C., and a second plateau between about 465 and about 484° C.

18. A method according to claim 16 , wherein said hot transforming is carried out by extrusion at a temperature measured at a die utilized in said extrusion of between about 380° C. and about 430° C.

19. A method according to claim 16 , wherein the temperature during said dissolution does not exceed 485 ° C.

20. A method according to claim 19 , wherein said dissolution is terminated by a plateau between about 470 and about 485° C., for a duration of between about 1 and about 10 hours.

21. A method according to claim 16 , wherein the controlled tension leads to a permanent elongation between about 1 and about 5%.

22. A method according to claim 16 , wherein the annealing comprises:

a) a first plateau at a temperature of between about 110° C. and about 130° C.; and

b) a second plateau at a temperature of between about 150° C. and about 170° C.

23. A structural element of claim 1 that is situated in an aeronautical construction.

24. A structural element suitable for aeronautical construction made from at least one extruded product comprising an aluminum alloy of the following composition (by mass):

(a) Zn 6.9-7.3% Cu 2.0-2.8% Mg from 1.6 to less than 2.0% wherein Cu/Mg is at least 1.1

(b) at least one element selected from the group consisting of: Zr 0.08-0.20% Cr 0.05-0.25% Sc 0.01-0.50% Hf 0.05-0.60% and V 0.02-0.20%

(c) Fe+Si<0.20%

(d) other elements ≦0.05% each and ≦0.15% total,

(e) remainder aluminum, wherein said product possesses the following set of properties measured at about 20° C.:

(f) a yield stress R p0.2(L) equal to at least 580 MPa, (ii) an ultimate strength R m(L) equal to at least 600 MPa and (iii) a K IC(L-T) equal to at least 31 MPa√m.

25. A structural element suitable for aeronautical construction made from at least one extruded product comprising an aluminum alloy of the following composition (by mass):

(a) Zn 6.9-7.3% Cu 2.0-2.8% Mg from 1.6% to less than 2.0% wherein Cu/Mg is at least 1.1

(b) at least one element selected from the group consisting of: Zr 0.08-0.20% Cr 0.05-0.25%Sc 0.01-0.50% Hf 0.05-0.60% and V 0.02-0.20%

(c) Fe +Si<0.20%

(d) other elements ≦0.05% each and ≦0.15% total,

(e) remainder aluminum, wherein said product possesses the following set of properties measured at about 20° C.:

(a) a yield stress R P0.2(L) equal to at least 580 MPa, and a measured K appl(L-T) with W=100 equal to at least about 80 Mpa√m;

(b) a yield stress R P0.2(L) equal to at least 580 MPa and a crack propagation rate da/dn not exceeding about 3×10 −3 mm/cycle for ΔK=27 MPa√m;

(c) a yield stress R P0.2(L) equal to at least 580 MPa, an ultimate strength R m(L) equal to at least 600 MPa and a K appl(L-T) measured with W=100 mm equal to at least about 80 MPa√m.

26. A structural element of claim 1 that is used as wing stiffener.

27. A structural element suitable for aeronautical construction made from at least one extruded product comprising an aluminum alloy of the following composition (by mass):

(a) Zn 6.9-7.3% Cu 2.0-2.8% Mg 1.8-1.91% wherein Cu/Mg is at least 1.1

(b) at least one element selected from the group consisting of: Zr 0.08-0.20% Cr 0.05-0.25%, Sc 0.01-0.50% Hf 0.05-0.60% and V 0.02-0.20%

(c) Fe +Si<0.20%

(d) other elements ≦0.05% each and ≦0.15% total,

(e) remainder aluminum, wherein said product possesses the following set of properties measured at about 20° C.:

(a) a yield stress R p0.2(L) equal to at least 580 MPa, and a measured K appl(L-T) with W=100 mm equal to at least about 80 Mpa√m;

(b) a yield stress R p0.2(L) equal to at least 580 MPa and a crack propagation rate da/dn not exceeding about 3×10 −3 mm/cycle for ΔK=27 MPa√m;

(c) a yield stress R p0.2(L) equal to at least 580 MPa, an ultimate strength R m(L) equal to at least about 580 MPa and a K appl(L-T) measured with W=100 mm equal to at least about 80 MPa√m;

(d) an ultimate strength R m(L) equal to at least 600 MPa and a K app(L-T) measured with W=100 mm equal to at least about 80 MPa√m.

28. A structural element of claim 27 , wherein Mg is about 1.9%.

29. A structural element of claim 24 , wherein Mg is from 1.6-1.91%.

30. A structural element of claim 24 , wherein Mg is about 1.9%

31. A structural element suitable for aeronautical construction made from at least one extruded product comprising an aluminum alloy of the following composition (by mass):

(a) Zn 6.9-7.3% Cu 2.0-2.8% Mg from 1.6 to less than 2.0% wherein Cu/Mg is at least 1.1

(b) at least one element selected from the group consisting of: Zr 0.08-0.20%, Sc 0.01-0.50% Hf 0.05-0.60% and V 0.02-0.20%

(c) Fe+Si<0.20%

(d) other elements≦0.05% each and≦0.15% total,

(e) remainder aluminum, wherein said product possesses the following set of properties measured at about 20 C.: a yield stress R p0.2(L) equal to at least 580 MPa, an ultimate strength R m(L) equal to at least 600 MPa and a measured K app(L-T) with W=100 mm equal to at least about 80MPa√m and a K IC(L-T) equal to at least 31 MPa√m.