Say I have a sheet of Al 3'x3'x1". It is 6061 Al. I take this 6061 Al, solution heat treat it, quench it, then artificially age it. I follow the T6 specs for doing this (solution heat treat at 985F, quench, age at 320F for 18 hr). Will the entire sheet be considered T6. Or do the properties change throughout the thickness of the sheet?
It would be like putting a frozen turkey in the oven. You could cook the outside but the middle would still be frozen. The properties wouldn't be uniform throughout the turkey. This has to do with thermal conductivity, heat transfer, etc.
Is there anywhere in text (perhaps a chart or some equations) that say "for a sheet of Aluminum X" thick, there will be a T6 gradient of y = mx + b beginning from the surface? Or something similar? Thank you.
At the risk of repeating myself, 6061T6 will have nearly uniform mechanical properties throughout the piece. Your turkey analogy shows the problems of arguing via analogy without fully understanding all the relevant processes. (Whenever some argues by analogy a voice in your head should scream, "Danger Will Robinson!") The aluminum in homogenous, the turkey is not. The heat soak is long relative to aluminum's heat transfer coefficient as is the aging. If the turkey is frozen in the middle, the heat soak was too short.
If you want to stick with your analogy (this isn't really analogous either) think of the solution heating as thawing the turkey overnight and the aging as baking at 350 for several hours. Uniform doneness and a happy crowd at dinner. No stresses left in the turkey, nor any in the diners.
Any reasonably well set up consulting metalurgist will be able to advise you "off the cuff" & then take a sample, cut sections & hardness test. Such a simple routine should cost no more than $200. The alternative is to phone a local aluninium foundry, they produce lots of castings which eventually end up "T6" treated & they should have a good idea of the effects. Alternative 2 get a book out, there's no difficulty sourcing info on T6 treatment of aluminium.
My recollection is that the ASTM spec. has a plate thickness cutoff for 6061-T6(I believe it is 4 in. or 6 in.). The rule of thumb I have heard is that plates or sections greater than 7 or 8 in. in thickness will not heat treat uniformly to T6.