On Mon, 04 Apr 2005 11:30:47 +0100, The Natural Philosopher
wrote:

Actually, they are. Heating and slow cooling anneals. Heating and fast
cooling re-hardens.

NONONO! Not with Al!

Yes, with Al.


Baz wrote (and you followed up):
"Annealing ally is easy. Wipe it with soap - the sort you clean your face
with - and heat it 'till the soap turns black. Then quench in water."


That's the one!


So which is it ? Does heating and quenching harden aluminium or
soften it ?


The answer is of course both. There _are_ quenching processes for
aluminium that strengthen it, and coincidentally make it less ductile.
They're not useful "hardening" processes though.

If your bike frame is in 6065-T6 alloy, then that "T6" refers to just
such a process.


But for all practical home workshop processes, any heating of
aluminium anneals, normalises and softens it - whether you quench it
afterwards or not.