6061 vs 2024 plate

Hello
I have a part that is is effectively a shim plate, we are holding it in a customer provides vacuum chuck. The part is 14" in x by 4 in in y. it is cut out of an 1/8" plate that gets cut down to 0.110 basically the problem is that since we are cutting on one side the plate bows once the vacuum is turned off.

cutting both sides in not an attractive option because getting the parts to seal again is not an easy thing.

The material provided by the customer is 6061-t6 while the print calls for 2024-t4. In the function of the part the lower strength of 6061 is not an issue.

the thickness is consistent so i don't think it will be a problem but i haven't heard back form the customer.

so my question is: do you think that 2024 tend to bow less than the 6061?
what else do you think? we could cut both sides .....

thank you for your time, link

Don't think you'll see any measurable difference in something that thin by just changing alloys. How about some kind of plastic snubber in the middle to keep it from sagging? If you can prevent the deflection from the vacuum, it should solve the problem, right?

You might try over-aging the alloy a bit to get some of the residual stress out. You could over-age (i.e., heat) 2024-T4 sheet and arrive at the same strength as 6061-T6.

Any material that has enough internal stress to banana on you would benefit from taking equal amounts off each side if you can. I know cast aluminum tooling plate would be more stable, but the thinnest I think you can get that material is 1/4", so it would be more machining to use.

Back in the days of 14 in. OD x .150 in. thick aluminum computer disks (~30 years ago) that were diamond faced for size, surface finish, flatness, runout and acceleration this was a basic process problem. Both sides were faced and no commercially available aluminum sheet would stay flat enough after facing. Incidently, all facing was also done with vacuum chucks.

The solution was to clean and stack the roughed out disks, clamp them tightly and put them through a lengthy (about 24 hours) thermal process to reduce internal stresses. It amounted to the over-aging suggested above but was done slowly to minimize themal gradients and used mechanical constraint (clamping) to prevent warping.

After the thermal treatment the material was very stable.