Strengthening Aluminum (casting mix)

Curl

I want to cast a part out of Aluminum (from scraps). Is there anything I can throw into the melt mix to make it come out stronger (not as gummy and soft) ??

Some sort of ceramic I'm thinking? Very fine sand-like stuff (e.g. CaCO3)?

Any suggestions for heat treatment too? The part will be a shell-type housing, needs to be strong and stiff.

Astronuc

See - Aluminum Alloys – Effects of Alloying Elements
http://www.keytometals.com/page.aspx...site=ktn&NM=55

See also -
http://www.keytometals.com/page.aspx...icles&LN=EN#p2

Look under +The Basics of Nonferrous Metallurgy

There's a number of articles on Al and alloys.

Curl

Good stuff.

So if I add some Iron to the mix, how should I cool in order to keep a homogeneous (as close as I can) mixture after hardening. I don't want to form a distinct two phase composite, as I suspect it will lead to crack formation.

What is it talking about here:
"The solubility of iron in the solid state is very low (~0.04%) and therefore, most of the iron present in aluminum over this amount appears as an intermetallic second phase in combination with aluminum and often other elements."

Mech_Engineer

What kind of aluminum scraps are you using? If it's pure aluminum, you can add the components necessary to form a higher-strength alloy like 6061 or 7075. Then after casting, you can apply a heat treat like -T6 or -T651 to get the most stength you can out of it.

If its a mix of different aluminum alloys you don't know, well you'll basically be stuck with what you get...

Curl

It is most likely going to be 6061 heat treated aluminum scraps.

And how should the heat treatment go in order to get highest strength? I remember doing this in a lab at some point but I forgot it completely.

cloa513

Solution heat treat at 990 F for adequate time to allow for thorough heating and then water quench. Precipitation hardening is done at 320 F for 18 hours and air cool, followed by 350 F for 8 hours and air cooling.

Its easy to find by googling 6061 heat treatment.