"John B." wrote in message
...
On Tue, 5 Nov 2013 14:20:45 -0700, "Bob La Londe"
wrote:

From what I have read slow cooling of aluminum allows minerals to
precipitate out rather than remain in a more uniform suspension and or
solution when you cast aluminum. This is why a cast aluminum part is
usually not considered to be as good (and certainly not as strong) as a
forged part where the metal is only heated up enough to be shaped by the
press.

With that thought in mind would a process to rapidly cool the mold causing
the aluminum to freeze off quicker make a better quality part? Maybe not
as
good as a forged part, but better than a slow cooled cast part? I am not
sure where I am really going with this, but there are plastics that are
injected into water jacketed molds for rapid cooling and freeze off. The
differences in temperature for those plastics and water at cooling
temperatures are much lower than that of aluminum and water, but the
potential for a steam explosion in the event of a failure is still there.

Or you could simply heat treat the casting after it was removed from
the mold.
http://www.thebloughs.net/hobbies/me...uminum7075.pdf
refers to this.
--
Cheers,

John B.

Heat treating the casting sounds like a good option, but your link just
teases and taunts me.

"Oops! It's Not HERE!

We've searched everywhere, and we can't find the document you were looking
for. In techno-babel, the document you requested was called
/hobbies/metalworking/.../Aluminum7075.pdf

We're sorry. We called everyone we could think of to help us find it, but
it's just not here.

So, we've notified the Webmaster with all the information so he can fix it.
He's slow, so wait a day or so, and then try again"


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