Earlier, (Lou Parker) wrote:

Can anyone tell me what the difference
is between 6061 T6 and 2024 T3 and
6063 T5 is?

All that stuff is in the Aircraft Spruce and Specialty catalog,
probably in the Wicks catalog, and certainly in Machinery's Handbook.
I think that everyone who messes around with airplanes should have a
copy of Machinery's.

In short:

The 4-digit number specifies an alloy. The 2000-series aluminums are
principally alloyed with copper, and the 6000-series with magnesium
and silicon.

The T-number specifies a recipe for heat treatment. T3 means solution
heat treated, T5 means artificially aged only, and T6 means solution
heat treated and then artifically aged.

Probably the most important difference between those materials is in
the strength properties. For example, the tensile strength properties
shown in Machinery's Handbook a

yield psi ultimate psi
6063-T5 21,000 27,000
6061-T6 40,000 45,000
2024-T3 45,000 65,000
7075-T6 73,000 83,000

Note that there are many other differences between the alloys such as
notch sensitivity, susceptibility to corrosion, machinability,
weldability, and such like. Be careful.

Thanks, and best regards to all

Bob K.
http://www.hpaircraft.com