Aluminum-copper-lithium alloys
View Patent ↗Improved aluminum-copper-lithium alloys are disclosed. The alloys may include 3.4-4.2 wt. % Cu, 0.9-1.4 wt. % Li, 0.3-0.7 wt. % Ag, 0.1-0.6 wt. % Mg, 0.2-0.8 wt. % Zn, 0.1-0.6 wt. % Mn, and 0.01-0.6 wt. % of at least one grain structure control element, the balance being aluminum and incidental elements and impurities. The alloys achieve an improved combination of properties over prior art alloys.
1. A method comprising:
(a) casting an aluminum alloy ingot comprising:
3.6 - 4.0 wt. % Cu;
1.1 - 1.2 wt. % Li;
0.4 - 0.55 wt. % Ag;
0.25 - 0.45 wt. % Mg;
0.4 - 0.6 wt. % Zn;
0.2 - 0.4 wt. % Mn; and
0.05 - 0.15 wt. % Zr;
the balance being aluminum and incidental elements and impurities;
(b) homogenizing the aluminum alloy ingot, wherein the homogenizing step (b) comprises:
first heating the aluminum alloy ingot to a first temperature and for a first period of time, wherein the first temperature is from 900° F. to 940° F., and wherein the first period of time is at least 2 hours;
second heating the aluminum alloy ingot to a second temperature and for a second period of time, wherein the second temperature is higher than the first temperature, and wherein the second period of time is at least two hours;
(c) extruding the aluminum alloy ingot into an extruded product;
(d) solution heat treating and quenching the extruded product;
(e) mechanically stress relieving the extruded product by cold working the extruded product 1-4%, wherein the total amount of cold work does not exceed 4%; and
(f) artificially aging the extruded product.
2. The method of claim 1 , wherein the alloy contains at least 3.7 wt. % Cu.
3. The method of claim 1 , wherein the alloy contains at least 3.8 wt. % Cu.
4. The method of any of claims 1 - 3 , wherein the alloy contains not greater than 3.95 wt. % Cu.
5. The method of claim 1 , wherein the alloy contains at least 0.45wt. % Zn.
6. The method of claim 1 , wherein the alloy contains not greater than 0.55 wt, % Zn.
7. The method of claim 1 , wherein the alloy contains at least 0.45wt. % Ag.
8. The method of claim 1 , wherein the second heating occurs at a temperature of from 940° F. to 955° F.
9. The method of claim 1 , wherein the first period of time is at least 7 hours.
10. The method of claim 1 , wherein the solution heat treating and quenching step (d) comprises solution heat treating the extruded product at a temperature of from 940° F. to 955° F.
11. The method of claim 1 , wherein total amount of the cold work of step (e) does not exceed 3.0%.
12. The method of claim 1 , wherein the total amount of the cold work of step (e) does not exceed 2.5%.
13. The method of claim 1 , wherein the artificially aging step (f) comprises:
first aging the extruded product at a first artificial aging temperature for a first period of artificial aging time;
second aging the extruded product at a second artificial aging temperature for a second period of artificial aging time, wherein the second artificial aging temperature is different than the first artificial aging temperature.
14. The method of claim 13 , wherein the second artificial aging temperature is higher than the first artificial aging temperature.
15. The method of claim 14 , wherein the first artificial aging temperature is from 200° F. to 275° F.
16. The method of claim 15 , wherein the second artificial aging temperature is from 290° F. to 325° F.
17. The method of any of claims 15 - 16 , wherein the first period of artificial aging time is at least 12 hours.
18. The method of claim 17 , wherein the second period of artificial aging time is at least 16 hours.
19. The method of any of claims 1 , 11 , and 12 , wherein the extruded product realizes a tensile yield strength of at least 84 ksi.
20. The method of any of claims 1 , 11 , and 12 , wherein the extruded product realizes a tensile yield strength of at least 86 ksi.
21. The method of any of claims 1 , 11 and 12 , wherein the extruded product realizes a tensile yield strength of at least 88 ksi.
22. The method of any of claims 1 , 11 and 12 , wherein the extruded product realizes a tensile yield strength of at least 90 ksi.
23. The method of any of claims 1 , 11 and 12 , wherein the extruded product realizes a tensile yield strength of at least 97 ksi.
24. The method of claim 18 , wherein the first period of time is from 12 to 17 hours, and wherein the second period of time is from 16 to 22 hours.