Annealing Aly 2024T3

[123Cat]

It anneals at higher temps than the other alys
But at what temp
Thanks in advance

 

[kenvlach]

For full anneal (to T-0 temper): 2-3 hours at a metal temperature of 775^oF (413 C), followed by slow cooling at 50^oF/hr to 500^oF. Faster cooling thereafter is permissible.

 

[123Cat]

Thanks Ken
Yes I used 2011 for model eng heads and its apparently not the done thing
,,,,, so 2024 is the go
I think its the manganese and chrome which gives the 2024 the heat resistance over the others like 2011 and suchlike
Great
These air cooled engines run at approx 400F so I didnt think 2011 would be a prob
But apparently it is

 

[123Cat]

Ken
I guess I should have asked at what temp does say,,,,,, aly 2011 start to lose its mechanical strength
That would be considerably lower than the annealing temp I guess
And thanks heaps
You guys are very impressive on my first post
Well done

By the by, con- rods in model engines are 2024 too

 

[kenvlach]

MIL-HDBK-5J METALLIC MATERIALS AND ELEMENTS FOR AEROSPACE VEHICLE STRUCTURES, a free (& huge) download at

http://assist2.daps.dla.mil/quicksearch/,

has data on the effect of temperature on the physical properties of Al 2024 but not 2011. For 1000 hours exposure, the yield strength of Al 2024 is down to ~87% at 300^oF and 80% at 400^oF.

For a comparison of the 2 alloys, the precipitation hardening temperature (to produce the T6 temper from solutionized alloy) is 320-340^oF for 2011 vs. 375^oF for 2024. Longer periods than the ~12 hour aging period (or higher temperatures) will cause overaging and loss of strength. Al 2024 has a significant advantage during long-term operation in the 300's^oF, consistent with your observations.

 

[123Cat]

Ken

You said for 1000 hours exposure the yield of 2024 aly is down to 80% at 400C

Does that mean its down to 80% yield immediatly the temp is 400C ????????

Thanks in advance

 

[kenvlach]

Not quite, yield stress = f(Temperature and time @ Temperature).
From MIL-HDBK-5J,
Figure 3.2.3.1.1(b). Effect of temperature on the tensile yield strength(Fty) of 2024-T3, T351, and 2024-T4 aluminum alloy (all products except extrusions).
[Curves are shown for 1/2, 10, 100, 1000 & 10,000 hours.]

At 400^oF, yield strength as % of room T value:
1/2 hr 78%
10 76
100 70
1000 60
10,000 46
Note: these values are more accurate than in previous post where I read off monitor; these are from a printout.

 

[123Cat]

Gee Thanks Ken

Well explained