What the other guys said for the short answer. For the REALLY LONG
answer, download a copy of the
"METALLIC MATERIALS AND ELEMENTS FOR
AEROSPACE VEHICLE STRUCTURES"

http://assist.daps.dla.mil/docimages...1/MILHBK5J.PD5

All 1700 pages of it. Shows all the common aluminum alloys with
substaital writeups on the popular ones. 6061 rates about 30 pages IIRC.

pogo wrote:

What does it mean when I see something like " lot of 6061 aluminum tubes" ?
I mean what does the number mean and how can I make sense of it ?

Thanks !