Methods for artificially aging aluminum-zinc-magnesium alloys, and products based on the same

Abstract

New methods for aging aluminum alloys having zinc and magnesium are disclosed. The methods may include first aging the aluminum alloy at a first temperature of from about 310° F. to 530° F. and for a first aging time of from 1 minute to 6 hours, and then second aging the aluminum alloy at a second temperature for a second aging time of at least 30 minutes, with the second temperature being lower than the first temperature.

Claims

1. A method comprising: (a) casting an aluminum alloy having from 4.0 to 9.5 wt. % Zn, from 1.2 to 3.0 wt. % Mg, and from 1.0 to 2.6 wt. % Cu; (b) optionally hot working or cold working the aluminum alloy; (c) after the casting step (a) and the optional step (b), solution heat treating and then quenching the aluminum alloy; (d) after step (c), optionally working the aluminum alloy; (e) after step (c) and the optional step (d), artificially aging the aluminum alloy, wherein the artificial aging step (e) comprises: (i) first aging the aluminum alloy at a first temperature of from 310° F. to 400° F. and for a first aging time of from 1 minute to 120 minutes; wherein the first aging comprises heating the aluminum alloy to the first temperature at a heating rate of at least 388° F. per hour; wherein the first aging is the first aging step of the artificial aging; (ii) second aging the aluminum alloy at a second temperature for a second aging time of at least 30 minutes, wherein the second temperature is lower than the first temperature, wherein the second aging is the second aging step of the artificial aging.

2. The method of claim 1, wherein the first temperature is from 320° to 390° F., and the first aging time is not greater than 90 minutes.

3. The method of claim 1, wherein the first temperature is from 330° to 385° F., and wherein the first aging time is not greater than 60 minutes.

4. The method of claim 1, wherein the first temperature is from 340° to 380° F., and the first aging time is not greater than 30 minutes.

5. The method of claim 1, wherein the second aging temperature is from 250° to 350° F., and the second aging time is from 0.5 to 12 hours.

6. The method of claim 2, wherein the second aging temperature is from 270° to 340° F., and the second aging time is from 1 to 12 hours.

7. The method of claim 3, wherein the second aging temperature is from 280° to 335° F., and the second aging time is from 2 to 8 hours.

8. The method of claim 4, wherein the second aging temperature is from 290° to 330° F., and wherein the second aging time is from 2 to 8 hours.

9. The method of claim 4, wherein the second aging temperature is from 300° to 325° F., and wherein the second aging time is from 2 to 8 hours.

10. The method of claim 1, wherein the aluminum alloy includes from 5.7- 8.4 wt. % Zn, from 1.3 to 2.3 wt. % Mg, and from 1.3 to 2.6 wt. % Cu.

11. The method of claim 10, wherein the aluminum alloy includes from 7.0 to 8.4 wt. % Zn.

12. The method of claim 1, wherein the aluminum alloy is selected from the group consisting of 7×85, 7×55, 7×50, 7×40, 7×99, 7×65, 7×78, 7×36, 7×37, 7×49, and 7×75.

13. The method of claim 1, wherein the aluminum alloy selected from the group consisting of 7×85, 7×55, and 7×65.

14. A method comprising: (a) casting an aluminum alloy having from 4.0 to 9.5 wt. % Zn, from 1.2 to 3.0 wt. % Mg, and from 0.25 to less than 1.0 wt. % Cu; (b) optionally hot working or cold working the aluminum alloy; (c) after the casting step (a) and the optional step (b), solution heat treating and then quenching the aluminum alloy; (d) after step (c), optionally working the aluminum alloy; (e) after step (c) and the optional step (d), artificially aging the aluminum alloy, wherein the artificial aging step (e) comprises: (i) first aging the aluminum alloy at a first temperature of from 330° F. to 430° F. and for a first aging time of from 1 minute to 120 minutes; wherein the first aging comprises heating the aluminum alloy to the first temperature at a heating rate of at least 388° F. per hour; wherein the first aging is the first aging step of the artificial aging; (ii) second aging the aluminum alloy at a second temperature for a second aging time of at least 30 minutes, wherein the second temperature is lower than the first temperature, wherein the second aging is the second aging step of the artificial aging.

15. The method of claim 14, wherein the first temperature is from 340° to 425° F., and the first aging time is not greater than 90 minutes.

16. The method of claim 14, wherein the first temperature is from 350° to 420° F., and the first aging time is not greater than 60 minutes.

17. The method of claim 14, wherein the first temperature is from 360° to 415° F., and the first aging time is not greater than 30 minutes.

18. The method of claim 14, wherein the second aging temperature is from 250° to 370° F., and the second aging time is from 0.5 to 12 hours.

19. The method of claim 14, wherein the second aging temperature is from 270° to 360° F., and the second aging time is from 1 to 12 hours.

20. The method of claim 15, wherein the second aging temperature is from 280° to 355° F., and the second aging time is from 2 to 8 hours.

21. The method of claim 16, wherein the second aging temperature is from 290° to 350° F., and the second aging time is from 2 to 8 hours.

22. The method of claim 17, wherein the second aging temperature is from 300° to 345° F., and the second aging time is from 2 to 8 hours.

23. The method of claim 14, wherein the aluminum alloy is selected from the group consisting of 7×41 and. RU1953.

24. A method comprising: (a) casting an aluminum alloy having from 4.0 to 9.5 wt. % Zn, from 1.2 to 3.0 wt. % Mg, and less than 0.25 wt. % Cu; (b) optionally hot working or cold working the aluminum alloy; (c) after the casting step (a) and the optional step (b), solution heat treating and then quenching the aluminum alloy; (d) after step (c), optionally working the aluminum alloy; (e) after step (c) and the optional step (d), artificially aging the aluminum alloy, wherein the artificial aging step (e) comprises: (i) first aging the aluminum alloy at a first temperature of from 310° F. to 400° F. and for a first aging time of from 1 minute to 120 minutes; wherein the first aging comprises heating the aluminum alloy to the first temperature at a heating rate of at least 388° F. per hour; wherein the first aging is the first aging step of the artificial aging; (ii) second aging the aluminum alloy at a second temperature for a second aging time of at least 30 minutes, wherein the second temperature is lower than the first temperature, wherein the second aging is the second aging step of the artificial aging.

25. The method of claim 24, wherein the first temperature is from 320° to 390° F., and the first aging time is not greater than 90 minutes.

26. The method of claim 24, wherein the first temperature is from 330° to 385° F., and the first aging time is not greater than 60 minutes.

27. The method of claim 24, wherein the first temperature is from 340° to 380° F., and the first aging time is not greater than 30 minutes.

28. The method of claim 24, wherein the second aging temperature is from 250° to 350° F., and the second aging time is from 0.5 to 12 hours.

29. The method of claim 25, wherein the second aging temperature is from 270° to 340° F., and the second aging time is from 1 to 12 hours.

30. The method of claim 26, wherein the second aging temperature is from 280° to 335° F., and the second aging time is from 2 to 8 hours.

31. The method of claim 26, wherein the second aging temperature is from 290° to 330° F., and the second aging time is from 2 to 8 hours.

32. The method of claim 27, wherein the second aging temperature is from 300° to 325° F., and the second aging time is from 2 to 8 hours.

33. The method of claim 24, wherein the aluminum alloy is selected from the group consisting of 7×05, 7×39, and 7×47, and RU1980.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is a graph illustrating the electrical conductivity versus SCC performance for the Example 1 alloys.

DETAILED DESCRIPTION

EXAMPLE 1

(2) A 7xx casting aluminum alloy having the composition shown in Table 1, below, was cast via directional solidification.

(3) TABLE-US-00001 TABLE 1 Composition of Ex. 1 Alloy (in wt. %) Alloy Zn Mg Cu 1 4.24 1.52 0.80

(4) After casting, Alloy 1 was solution heat treated, and then quenched in boiling water. Alloy 1 was then stabilized by naturally aging for about 12-24 hours at room temperature. Next Alloy 1 was artificially aged at various times and temperatures, as shown in Table 2, below. For Alloys 1-A through 1-D, the alloys were heated from ambient to the first aging temperature in about 40 minutes, and then held at the first aging temperature for the stated duration; after the first aging step was completed, Alloys 1-A through 1-D were heated to the second aging temperature in about 45 minutes, and then held at the second aging temperature for the stated duration. Alloy 1-E was heated from ambient to the first aging temperature in about 50 minutes, and then held at the first aging temperature for the stated duration; after the first aging step was completed, power to the furnace was turned-off and the furnace was open to the air until the furnace reached the second target temperature (about 10 minutes), and after which Alloy 1-E was held at the second aging temperature for the stated duration.

(5) TABLE-US-00002 TABLE 2 Artificial Aging Practices Alloy 1.sup.st Step 2.sup.nd Step Note 1-A 250° F. for 3 hours 360° F. for 16 hours Non-Invention 1-B 250° F. for 3 hours 360° F. for 3 hours Non-Invention 1-C 250° F. for 3 hours 360° F. for 4 hours Non-Invention 1-D 250° F. for 3 hours 360° F. for 5 hours Non-Invention 1-E 400° F. for 10 mins. 360° F. for 4 hours Invention

(6) Various mechanical properties and the SCC (stress corrosion cracking) resistance of the alloys were then measured, the results of which are shown in Tables 3-5, below. Strength and elongation were measured in accordance with ASTM E8 and B557 (average of triplicate specimens). Fatigue performance was tested in accordance with ASTM E466 (Kt=1, R=−1, Stress=23.2 ksi, 25 Hz, in lab air) (average of triplicate specimens). SCC resistance was measured in accordance with ASTM G103 (stress=34.8 ksi).

(7) TABLE-US-00003 TABLE 3 Strength and Elongation Properties of Ex. 1 Alloys TYS UTS Total El Alloy (ksi) (ksi) (%) 1-A 47.4 55.4 9.3 1-B 49.9 56.5 6.7 1-C 48.5 56.3 9.3 1-D 47.4 53.9 6.3 1-E 46.8 54.7 8.7

(8) TABLE-US-00004 TABLE 4 Fatigue Properties of Ex. 1 Alloys Average Cycles Standard Alloy to Fail Deviation 1-A 105,421 27,715 1-B 109,519 58,674 1-C 142,187 105,362 1-D 90,002 22,694 1-E 144,611 35,256

(9) TABLE-US-00005 TABLE 5 SCC resistance of Ex. 1 Alloys Hours to Average hours Alloy Specimen Failure to Failure 1-A 1 45 111 2 96 3 96 4 150 5 168 1-B 1 21 60.2 2 45 3 45 4 72 5 118 1-C 1 24 47.8 2 30 3 45 4 68 5 72 1-D 1 68 80.4 2 72 3 72 4 72 5 118 1-E 1 142 154 2 142 3 150 4 168 5 168

(10) As shown above, the invention alloy (1-E) achieves about the same strength but better fatigue resistance as compared to the non-invention alloys. The invention alloy also achieves much better stress corrosion cracking resistance as compared to the non-invention alloys. Furthermore, the invention alloy achieves its improved properties with only about 4 hours, 10 minutes of artificial aging time, whereas the non-invention alloys all required at least 6 or more hours of artificial aging time.

(11) The electrical conductivity of the alloys was also measured using a HOCKing electric conductivity meter (AutoSigma 3000DL), the results of which are shown in Table 6, below (average of quadruplicate specimens). As shown in FIG. 1, the invention alloy unexpectedly achieves better SCC performance at lower electrical conductivity. The lower electrical conductivity of the invention alloy indicates that it has not been overly aged, but yet still improved SCC performance is achieved.

(12) TABLE-US-00006 TABLE 6 Electrical conductivity of Ex. 1 Alloys Average EC Alloy (% IACS) Stdev 1-A 42.0 0.55 1-B 40.9 0.15 1-C 41.4 0.05 1-D 41.6 0.01 1-E 41.2 0.06

EXAMPLE 2

(13) Alloy 1 from Example 1 was processed similar to Example 1, but was artificially aged for various times as shown in Table 7, below.

(14) TABLE-US-00007 TABLE 7 Artificial Aging Practices Alloy 1.sup.st Step 2.sup.nd Step Note 1-F 400° F. for 10 mins. 360° F. for 3 hours Invention 1-G 400° F. for 10 mins. 360° F. for 4 hours Invention 1-H 400° F. for 10 mins. 360° F. for 6 hours Invention 1-I 400° F. for 5 mins. 360° F. for 4 hours Invention 1-J 400° F. for 20 mins. 360° F. for 4 hours Invention

(15) Various mechanical properties and the SCC (stress corrosion cracking) resistance of the alloys were then measured, the results of which are shown in Tables 8-10, below. Strength and elongation were measured in accordance with ASTM E8 and B557 (average of triplicate specimens). Fatigue performance was tested in accordance with ASTM E466 (Kt=1, R=−1, Stress=23.2 ksi, 25 Hz, in lab air) (average of triplicate specimens). SCC resistance was measured in accordance with ASTM G103 (stress=34.8 ksi).

(16) TABLE-US-00008 TABLE 8 Strength and Elongation Properties of Ex. 2 Alloys TYS UTS Alloy (ksi) (ksi) Total El (%) 1-F 48.7 55.5 7.3 1-G 48.0 55.1 7.3 1-H 48.0 54.7 7.0 1-I 46.9 53.6 6.3 1-J 47.5 54.5 8.0

(17) TABLE-US-00009 TABLE 9 Fatigue Properties of Ex. 2 Alloys Average Cycles Standard Alloy to Fail Deviation 1-F 112,269 48,630 1-G 144,611 35,256 1-H 94,599 49,852 1-I 103,367 31,106 1-J 107,605 16,369

(18) TABLE-US-00010 TABLE 10 SCC resistance of Ex. 2 Alloys Hours to Average hours Alloy Specimen Failure to Failure 1-F 1 72 102.3 2 72 3 96 4 124.08 5 147.6 1-G 1 96 142.8 2 113.76 3 168 4 168 5 168 1-H 1 96 124.8 2 96 3 96 4 168 5 168 1-I 1 42 118.8 2 96 3 120 4 168 5 168 1-J 1 96 138.0 2 114 3 144 4 168 5 168

(19) Similar to Example 1, the invention alloys achieve a good combination of strength, fatigue resistance and stress corrosion cracking resistance.

EXAMPLE 3

(20) Alloy 1 from Example 1 was processed similar to Example 1, but was artificially aged for various times as shown in Table 11, below.

(21) TABLE-US-00011 TABLE 11 Artificial Aging Practices Alloy 1.sup.st Step 2.sup.nd Step Note 1-K 390° F. for 10 mins. 360° F. for 4 hours Invention 1-L 400° F. for 10 mins. 360° F. for 4 hours Invention 1-M 420° F. for 10 mins. 360° F. for 4 hours Invention

(22) Various mechanical properties and the SCC (stress corrosion cracking) resistance of the alloys were then measured, the results of which are shown in Tables 12-14, below. Strength and elongation were measured in accordance with ASTM E8 and B557 (average of triplicate specimens, except Alloy 1-K, which was the average of duplicate specimens). Fatigue performance was tested in accordance with ASTM E466 (Kt=1, R=−1, Stress=23.2 ksi, 25 Hz, in lab air) (average of triplicate specimens). SCC resistance was measured in accordance with ASTM G103 (stress=34.8 ksi).

(23) TABLE-US-00012 TABLE 12 Strength and Elongation Properties of Ex. 3 Alloys TYS UTS Total El Alloy (ksi) (ksi) (%) 1-K 48.2 53.6 5.5 1-L 48.0 54.1 5.7 1-M 46.9 52.6 5.3

(24) TABLE-US-00013 TABLE 13 Fatigue Properties of Ex. 3 Alloys Average Cycles Standard Alloy to Fail Deviation 1-K 110423 41955 1-L 110362 36083 1-M 103406 23128

(25) TABLE-US-00014 TABLE 14 SCC resistance of Ex. 3 Alloys Hours to Average hours Alloy Specimen Failure to Failure 1-K 1 46 104 2 94 3 94 4 118 5 168 1-L 1 48 117.4 2 79 3 146 4 146 5 168 1-M 1 94 153.2 2 168 3 168 4 168 5 168

(26) Similar to Examples 1-2, the invention alloys achieve a good combination of strength, fatigue resistance and stress corrosion cracking resistance.

EXAMPLE 4

Aging of Wrought Aluminum Alloy 7085

(27) Aluminum alloy 7085 having the composition shown in Table 15 was produced as a conventional plate product (e.g., homogenized, rolled to final gauge, solution heat treated and cold water quenched, stress relieved by stretching (2%)) having a thickness of 2 inches. After about four days of natural aging, the 7085 plate was multi-step aged for various times at various temperatures, as shown in Table 16. After aging, mechanical properties were measured in accordance with ASTM E8 and B557, the results of which are shown in Table 17. Stress corrosion cracking (SCC) resistance was also measured in accordance with ASTM G44, 3.5% NaCl, Alternate Immersion, the results of which are shown in Table 18 (stress in the ST direction).

(28) TABLE-US-00015 TABLE 15 Composition of the 7085 Alloy (in wt. %)* Alloy Zn Mg Cu Zr Si Fe Mn Cr Ti 7085 7.39 1.54 1.66 0.11 0.02 0.03 <0.01 <0.01 0.02 *The balance of the alloy is aluminum and other elements, with the aluminum alloy containing not more than 0.05 wt. % each of any other element, and with the aluminum alloy containing not more than 0.15 wt. % in total of the other elements.

(29) TABLE-US-00016 TABLE 16 Artificial Aging Practices Alloy 1.sup.st Step 2.sup.nd Step 7085-1 N/A - Conventional 3-step aging practice of 250° F. for 6 hours, then 310° F. for 18 hours, and then 250° F. for 24 hours 7085-2 400° F. for 10 mins. 310° F. for 4 hour 7085-3 400° F. for 10 mins. 310° F. for 6 hours 7085-4 400° F. for 10 mins. 310° F. for 8 hours 7085-5 460° F. for 5 mins. 310° F. for 8 hours 7085-6 430° F. for 7.5 mins. 310° F. for 8 hours 7085-7 400° F. for 5 mins. 310° F. for 8 hours 7085-8 400° F. for 15 mins. 310° F. for 8 hours 7085-9 460° F. for 5 mins. 310° F. for 4 hours 7085-10 460° F. for 5 mins. 310° F. for 6 hours 7085-11 375° F. for 10 mins. 310° F. for 4 hours 7085-12 375° F. for 20 mins. 310° F. for 4 hours 7085-13 375° F. for 30 mins. 310° F. for 4 hours 7085-14 345° F. for 15 mins. 310° F. for 6 hours 7085-15 345° F. for 30 mins. 310° F. for 6 hours 7085-16 345° F. for 72 mins. 310° F. for 6 hours 7085-17 345° F. for 90 mins. 310° F. for 6 hours 7085-18 345° F. for 72 mins. 310° F. for 4 hours
For the artificial aging, the samples were heated to the first temperature in about 50 minutes and then held at the stated temperature for the stated amount of time. The samples were then cooled to the second temperature by changing the furnace set-point and opening the furnace door until the second temperature was reached. The specimens were then held at the second temperature for the stated amount of time, after which the samples were removed from the furnace and allowed to air cool to room temperature.

(30) TABLE-US-00017 TABLE 17 Mechanical Properties Tensile Yield Strength Ultimate Tensile Strength Elongation, Alloy (TYS), ksi (ST) (UTS), ksi (ST) % (ST) 7085-1 67.7 76.3 10.9 7085-2 61.3 70.8 10.9 7085-3 60.3 70.5 10.9 7085-4 61.2 71.3 11.4 7085-5 46.1 59.1 14.1 7085-6 51.8 63.7 14.1 7085-7 60.5 70.5 11.4 7085-8 57.8 68.4 10.4 7085-9 46.9 59.8 15.1 7085-10 46.3 59.1 14.6 7085-11 65.5 74.2 12.0 7085-12 65.2 73.8 10.9 7085-13 64.2 73.0 10.9 7085-14 67.3 75.5 9.4 7085-15 66.2 74.6 10.4 7085-16 65.5 74.4 9.9 7085-17 65.5 74.3 9.4 7085-18 66.2 74.8 9.4

(31) TABLE-US-00018 TABLE 18 SCC Results Days to Failure Stress Spec- Spec- Spec- Spec- Spec- Alloy (ksi) imen 1 imen 2 imen 3 imen 4 imen 5 7085-1 45 DNF 50 42 86 89 7085-1 55 DNF 89 44 33 29 7085-2 45 DNF DNF DNF DNF N/A 7085-2 55 DNF DNF 90 DNF N/A 7085-3 45 DNF DNF DNF 77 N/A 7085-3 55 DNF DNF DNF DNF N/A 7085-4 45 DNF DNF DNF DNF N/A 7085-4 55 DNF DNF DNF DNF N/A 7085-5 45 DNF DNF DNF DNF N/A 7085-5 55 DNF DNF DNF DNF N/A 7085-6 45 DNF DNF DNF DNF N/A 7085-6 55 DNF DNF DNF DNF N/A 7085-7 45 DNF DNF DNF DNF N/A 7085-7 55 DNF DNF DNF DNF N/A 7085-8 45 DNF DNF DNF DNF N/A 7085-8 55 DNF DNF DNF DNF N/A 7085-9 45 DNF DNF DNF DNF N/A 7085-9 55 DNF DNF DNF DNF N/A 7085-10 45 DNF DNF DNF DNF N/A 7085-10 55 DNF DNF DNF DNF N/A 7085-11 45 DNF 51 59 50 N/A (66) 7085-11 55 DNF DNF 43 DNF N/A (66) (66) (66) 7085-14 45 50 50 59 40 N/A 7085-14 55 40 DNF 44 44 43 (66) 7085-12 55 DNF 58 DNF 48 54 (66) (66) 7085-13 55 58 57 DNF DNF 65 (66) (66) 7085-15 55 54 47 DNF DNF DNF (66) (66) (66) 7085-16 55 64 DNF DNF 64 DNF (66) (66) (66) 7085-17 55 64 DNF 62 DNF DNF (66) (66) (66) 7085-18 55 DNF 54 DNF 52 59 (66) (66) * DNF = did not fail after 90 days ** DNF(66) = did not fail after 66 days

(32) As shown, the new aging practice yields significant improvement in throughput via decreased total aging time, and with similar strength and corrosion resistance. Indeed, alloy 7085-14 realizes about the same strength as conventionally aged 7085-1, but with only 6.25 hours of total aging time (not including ramp-up time and cool down time) as compared to the total aging time of 48 hours (not including ramp-up time and cool down time) for alloy 7085-1.

EXAMPLE 5

Aging of Alloy 7255

(33) Aluminum alloy 7255 having the composition shown in Table 19 was produced as a conventional plate product (e.g., homogenized, rolled to final gauge, solution heat treated and cold water quenched, stress relieved by stretching (2%)) having a thickness of 1.5 inches. After about four days of natural aging, the 7255 plate was multi-step aged for various times at various temperatures, as shown in Table 20. After aging, mechanical properties were measured in accordance with ASTM E8 and B557, the results of which are shown in Table 21. Stress corrosion cracking (SCC) resistance was also measured in accordance with ASTM G44, 3.5% NaCl, Alternate Immersion, the results of which are shown in Table 22 (stress in the ST direction and with a stress of 35 ksi). For some of the alloys, electrical conductivity (% IACS) was measured in accordance with ASTM E1004-09, Standard Test Method for Determining Electrical Conductivity Using the Electromagnetic (Eddy-Current) Method, using a 1 inch by 1.5 inch by 4 inch block, the results of which are shown in Table 23, below.

(34) TABLE-US-00019 TABLE 19 Composition of the 7255 Alloy (in wt. %)* Alloy Zn Mg Cu Zr Si Fe Mn Cr Ti 7255 7.98 1.91 2.18 0.11 0.02 0.03 <0.01 <0.01 0.02 *The balance of the alloy is aluminum and other elements, with the aluminum alloy containing not more than 0.05 wt. % each of any other element, and with the aluminum alloy containing not more than 0.15 wt. % in total of the other elements.

(35) TABLE-US-00020 TABLE 20 Artificial Aging Practices Alloy 1.sup.st Step 2.sup.nd Step 7255-1 N/A - Conventional 3-step aging practice of 250° F. for 6 hours, then 400° F. for 3 minutes (≈30 minute ramp to 400° F.), and then 250° F. for 24 hours 7255-2 400° F. for 10 mins. 310° F. for 4 hours 7255-3 400° F. for 10 mins. 310° F. for 6 hours 7255-4 400° F. for 10 mins. 310° F. for 8 hours 7255-5 480° F. for 5 mins. 310° F. for 8 hours 7255-6 440° F. for 10 mins. 310° F. for 8 hours 7255-7 400° F. for 5 mins. 310° F. for 8 hours 7255-8 400° F. for 15 mins. 310° F. for 8 hours 7255-9 480° F. for 5 mins. 310° F. for 4 hours 7255-10 480° F. for 5 mins. 310° F. for 6 hours 7255-11 370° F. for 5 mins. 310° F. for 4 hours 7255-12 370° F. for 10 mins. 310° F. for 4 hours 7255-13 370° F. for 20 mins. 310° F. for 4 hours 7255-14 345° F. for 15 mins. 310° F. for 4 hours 7255-15 345° F. for 30 mins. 310° F. for 4 hours 7255-16 345° F. for 60 mins. 310° F. for 4 hours 7255-17 370° F. for 10 mins. N/A
For the artificial aging, unless otherwise stated, the samples were heated to the first temperature in about 50 minutes and then held at the stated temperature for the stated amount of time. The samples were then cooled to the second temperature by changing the furnace set-point and opening the furnace door until the second temperature was reached. The specimens were then held at the second temperature for the stated amount of time, after which the samples were removed from the furnace and allowed to air cool to room temperature.

(36) TABLE-US-00021 TABLE 21 Mechanical Properties Tensile Yield Strength Ultimate Tensile Strength Elongation, Alloy (TYS), ksi (ST) (UTS), ksi (ST) % 7255-1 77.9 88.9 4.7 7255-2 68.8 79.6 9.4 7255-3 67.7 78.7 9.4 7255-4 67.6 79.0 9.4 7255-5 44.0 59.3 13.6 7255-6 54.2 68.3 12.5 7255-7 70.0 81.2 7.8 7255-8 65.0 76.9 9.4 7255-9 43.5 59.1 12.5 7255-10 43.8 59.5 12.5 7255-11 75.7 85.8 7.8 7255-12 75.1 84.4 6.7 7255-13 75.2 84.4 5.7 7255-14 76.1 85.3 6.2 7255-15 75.8 85.0 6.2 7255-16 75.5 84.3 5.7 7255-17 74.6 84.9 6.2

(37) TABLE-US-00022 TABLE 22 SCC Results Days to Failure Specimen Specimen Specimen Specimen Specimen Alloy 1 2 3 4 5 7255-1 5 71 6 8 5 7255-2 88 42 88 74 43 7255-3 63 70 74 54 53 7255-4 49 88 88 88 88 7255-5 DNF DNF DNF DNF DNF 7255-6 DNF DNF DNF DNF DNF 7255-7 60 63 88 47 46 7255-8 88 71 DNF 90 90 7255-9 DNF DNF DNF DNF DNF 7255-10 DNF DNF DNF DNF DNF 7255-11 48 32 26 25 22 7255-12 45 41 51 52 52 7255-13 51 DNF(66) 53 53 57 7255-14 8 8 8 32 24 7255-15 24 43 48 8 32 7255-16 53 32 47 41 DNF(66) 7255-17 8 8 8 8 8 * DNF = did not fail after 90 days ** DNF(66) = did not fail after 66 days

(38) As shown, the new aging practice yields significant improvement in throughput via decreased total aging time, and with similar strength and corrosion resistance. Indeed, alloy 7255-14 realizes about the same strength as conventionally aged 7255-1, but with only 4.25 hours of total aging time (not including ramp-up time and cool down time) as compared to the total aging time of about 30 hours (not including ramp-up time and cool down time) for alloy 7255-1. The 7255-14 alloy also realizes comparable corrosion resistance to alloy 7255-1. Improved corrosion resistance is realized by alloys 7255-15 and 7255-16 over alloy 7255-1, with comparable strength, and with only 4.5-5.0 hours of total aging time (not including ramp-up time and cool down time).

(39) TABLE-US-00023 TABLE 23 Electrical Conductivity + SCC Results Ave. SCC EC Alloy (days to failure) (% IACS) 7255-1 19 37.5 7255-11 30.6 37.2 7255-12 48.2 37.6 7255-13 56 38.8 7255-14 16 37.0 7255-15 31 37.1 7255-16 47.8 38.5 7255-17 8 36.2

EXAMPLE 6

Aging of Alloy 1980

(40) Russian alloy 1980 having the composition shown in Table 24 was produced as a conventional rod product (e.g., homogenized, extruded to rod, solution heat treated and cold water quenched) having an outer diameter of about 7.0 inches and a thickness of about 1.3 inches. After about 0.5-1 days of natural aging, the 1980 alloy rod was multi-step aged for various times at various temperatures, as shown in Table 25. After aging, mechanical properties were measured in accordance with ASTM E8 and B557, the results of which are shown in Table 26. Stress corrosion cracking (SCC) resistance for some of the alloys was also measured in accordance with ASTM G103, Boiling Salt Test, the results of which are shown in Table 27 (stress in the ST direction and with a stress of 16.2 ksi).

(41) TABLE-US-00024 TABLE 24 Composition of the 1980 Alloy (in wt. %)* Alloy Zn Mg Cu Zr Si Fe Mn Cr Ti 1980 4.25 2.00 0.07 0.12 0.12 0.20 0.38 0.13 <0.01 *The balance of the alloy is aluminum and other elements, with the aluminum alloy containing not more than 0.05 wt. % each of any other element, and with the aluminum alloy containing not more than 0.15 wt. % in total of the other elements.

(42) TABLE-US-00025 TABLE 25 Artificial Aging Practices Alloy 1.sup.st Step 2.sup.nd Step 1980-1 250° F. for 24 hours 350° F. for 6 hours 1980-2 400° F. for 10 mins. 350° F. for 2 hours 1980-3 400° F. for 10 mins. 350° F. for 4 hours 1980-4 400° F. for 10 mins. 350° F. for 6 hours 1980-5 420° F. for 7.5 mins. 350° F. for 4 hours 1980-6 380° F. for 10 mins. 350° F. for 4 hours 1980-7 400° F. for 5 mins. 350° F. for 4 hours 1980-8 400° F. for 15 mins. 350° F. for 4 hours 1980-9 420° F. for 7.5 mins. 350° F. for 2 hours 1980-10 420° F. for 7.5 mins. 350° F. for 6 hours 1980-11 370° F. for 10 mins. N/A 1980-12 370° F. for 10 mins. 310° F. for 2 hours 1980-13 360° F. for 10 mins. 310° F. for 2 hours 1980-14 350° F. for 10 mins. 310° F. for 2 hours 1980-15 350° F. for 10 mins. 310° F. for 4 hours 1980-16 350° F. for 30 mins. 310° F. for 2 hours 1980-17 350° F. for 30 mins. 310° F. for 4 hours 1980-18 330° F. for 20 mins. 310° F. for 2 hours 1980-19 330° F. for 20 mins. 310° F. for 4 hours 1980-20 330° F. for 50 mins. 310° F. for 2 hours 1980-21 330° F. for 50 mins. 310° F. for 4 hours
For the artificial aging, unless otherwise stated, the samples were heated to the first temperature in about 50 minutes and then held at the stated temperature for the stated amount of time. The samples were then cooled to the second temperature by changing the furnace set-point and opening the furnace door until the second temperature was reached. The specimens were then held at the second temperature for the stated amount of time, after which the samples were removed from the furnace and allowed to air cool to room temperature.

(43) TABLE-US-00026 TABLE 26 Mechanical Properties Tensile Yield Strength Ultimate Tensile Strength Elongation, Alloy (TYS), ksi (UTS), ksi % 1980-1 46.3 57.9 14.0 1980-2 35.5 48.9 14.0 1980-3 35.9 49.0 14.0 1980-4 35.5 48.4 12.0 1980-5 33.4 46.7 12.0 1980-6 36.6 49.3 12.0 1980-7 35.2 48.3 12.0 1980-8 35.0 48.0 12.7 1980-9 34.3 47.6 12.7 1980-10 34.1 47.4 12.0 1980-11 41.5 54.2 12.0 1980-12 44.7 56.4 10.7 1980-13 46.2 56.8 10.7 1980-14 44.7 56.3 10.7 1980-15 47.2 57.9 10.0 1980-16 46.4 57.2 10.0 1980-17 48.1 58.7 10.0 1980-18 45.7 56.8 9.3 1980-19 48.5 58.6 10.7 1980-20 47.8 58.2 10.0 1980-21 49.0 59.1 11.3

(44) TABLE-US-00027 TABLE 27 SCC Results Hours to Failure Spec- Spec- Spec- Spec- Spec- Spec- Alloy imen 1 imen 2 imen 3 imen 4 imen 5 imen 6 1980-1 1 1 1 1 1 1 1980-3 1.5 1.5 1.5 1.5 2.5 2.5 1980-6 1.5 2 2 2.5 3 3.5 1980-8 1.5 1.5 1.5 2 2 N/A 1980-10 1.5 1.5 2 2 3.5 8 1980-11 1 1 1 44 N/A N/A 1980-12 1 1 0.5 1 N/A N/A 1980-13 1 0.5 0.5 1 N/A N/A 1980-14 0.5 0.5 0.5 0.5 N/A N/A 1980-15 20.5 1 0.5 0.5 N/A N/A 1980-16 1.5 20.5 0.5 0.5 N/A N/A 1980-17 0.5 1 0.5 1 N/A N/A 1980-18 0.5 20.5 1 1 N/A N/A 1980-19 0.5 0.5 0.5 2.5 N/A N/A 1980-20 1 1.5 1 1 N/A N/A 1980-21 1 1 1 1 N/A N/A

(45) As shown, the new aging practice yields significant improvement in throughput via decreased total aging time, and with similar strength and corrosion resistance. Indeed, alloy 1980-21 realizes higher strength than conventionally aged 1980-1, but with only about 4.83 hours of total aging time (not including ramp-up time and cool down time) as compared to the total aging time of 30 hours (not including ramp-up time and cool down time) for alloy 1980-1. The 1980-21 alloy also realizes comparable corrosion resistance to alloy 1980-1.

EXAMPLE 6

Aging of Alloy 1953

(46) Russian alloy 1953 having the composition shown in Table 28 was produced as a conventional rod product (e.g., homogenized, extruded to rod, solution heat treated and cold water quenched) having an outer diameter of about 7.0 inches and a thickness of about 1.3 inches. After about 0.5-1 days of natural aging, the 1953 alloy rod was multi-step aged for various times at various temperatures, as shown in Table 29. After aging, mechanical properties were measured in accordance with ASTM E8 and B557, the results of which are shown in Table 30. Stress corrosion cracking (SCC) resistance was also measured in accordance with ASTM G103, Boiling Salt Test, the results of which are shown in Table 31 (stress in the ST direction and with a stress of 20 ksi), and in accordance with ASTM G44, 3.5% NaCl, Alternate Immersion, the results of which are shown in Table 32 (stress in the ST direction and with a stress of 35 ksi).

(47) TABLE-US-00028 TABLE 28 Composition of the 1953 Alloy (in wt. %)* Alloy Zn Mg Cu Zr Si Fe Mn Cr Ti 1953 5.76 2.65 0.55 0.02 0.04 0.08 0.17 0.20 <0.01 *The balance of the alloy is aluminum and other elements, with the aluminum alloy containing not more than 0.05 wt. % each of any other element, and with the aluminum alloy containing not more than 0.15 wt. % in total of the other elements.

(48) TABLE-US-00029 TABLE 29 Artificial Aging Practices Alloy 1.sup.st Step 2.sup.nd Step 1953-1 230° F. for 5 hours 330° F. for 5 hours 1953-2 400° F. for 10 mins. 330° F. for 2 hours 1953-3 400° F. for 10 mins. 330° F. for 4 hours 1953-4 400° F. for 10 mins. 330° F. for 6 hours 1953-5 460° F. for 5 mins. 330° F. for 4 hours 1953-6 430° F. for 7.5 mins. 330° F. for 4 hours 1953-7 400° F. for 5 mins. 330° F. for 4 hours 1953-8 400° F. for 15 mins. 330° F. for 4 hours 1953-9 460° F. for 5 mins. 330° F. for 2 hours 1953-10 460° F. for 7.5 mins. 330° F. for 6 hours
For the artificial aging, unless otherwise stated, the samples were heated to the first temperature in about 50 minutes and then held at the stated temperature for the stated amount of time. The samples were then cooled to the second temperature by changing the furnace set-point and opening the furnace door until the second temperature was reached. The specimens were then held at the second temperature for the stated amount of time, after which the samples were removed from the furnace and allowed to air cool to room

(49) TABLE-US-00030 TABLE 30 Mechanical Properties Tensile Yield Strength Ultimate Tensile Strength Elongation, Alloy (TYS), ksi (UTS), ksi % 1953-1 69.0 78.0 12.0 1953-2 67.0 75.7 12.0 1953-3 66.0 75.4 12.0 1953-4 65.1 74.3 12.0 1953-5 53.0 65.8 12.0 1953-6 59.7 70.9 12.0 1953-7 64.9 75.0 12.0 1953-8 63.0 73.6 12.0 1953-9 52.3 66.1 13.3 1953-10 51.1 65.1 12.0

(50) TABLE-US-00031 TABLE 31 SCC Results - ASTM G103 Days to Failure Alloy Specimen 1 Specimen 2 Specimen 3 1953-1 0.08 0.17 0.17 1953-2 0.17 0.17 0.17 1953-3 0.17 0.17 0.17 1953-4 0.17 0.08 0.08

(51) TABLE-US-00032 TABLE 32 SCC Results - ASTM G44 Days to Failure Spec- Spec- Spec- Spec- Spec- Spec- Alloy imen 1 imen 2 imen 3 imen 4 imen 5 imen 6 1953-1 DNF 90 90 N/A N/A N/A 1953-2 DNF 90 90 N/A N/A N/A 1953-3 90 DNF DNF N/A N/A N/A 1953-4 90 DNF N/A N/A N/A N/A 1953-5 DNF 99 DNF DNF DNF DNF 1953-6 DNF DNF DNF 90 90 N/A 1953-7 90 DNF 90 90 DNF DNF 1953-8 75 90 DNF 90 DNF 90 1953-9 DNF DNF DNF DNF DNF DNF 1953-10 DNF DNF DNF DNF DNF DNF * DNF = did not fail after 140 days

(52) As shown, the new aging practice yields significant improvement in throughput via decreased total aging time, and with similar strength and corrosion resistance. Indeed, alloy 1953-2 realizes about the same strength as conventionally aged 1953-1, but with only about 2.17 hours of total aging time (not including ramp-up time and cool down time) as compared to the total aging time of 10 hours (not including ramp-up time and cool down time) for alloy 1953-1.

(53) While various embodiments of the present disclosure have been described in detail, it is apparent that modifications and adaptations of those embodiments will occur to those skilled in the art. However, it is to be expressly understood that such modifications and adaptations are within the spirit and scope of the present disclosure.