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Thanks for posting and comments!
(Tip for coarse checking what alloy you're just holding below)
Being a dabbler myself in this area, 2 friendly cents' worth:
-I guess your melt consisted of cast pulleys, probably press die-cast, but could've also be sand casted? 360 alloy perhaps?
These casting alloys are also containing mainly silicon between 8-12 percent, some copper, iron and perhaps magnesium,
which (supposedly) isn't heat treatable, just cold aging over 30 days.
I've done some different tests for casting my own aluminum over the last few years, and have come to like the die-casting AlSi9Cu3Fe alloy best,
for its good melting, casting and machining properties (but also that it's free and readily available at work, mostly from discarded office chair wheelstands).
For getting a real nice surface from this, I use shear tools for final turning and fly-cutting.
Drop-forged hard drive casings are also plentiful and free at work: casts and machines just excellent, though I haven't tried HT-ing it (yet).
Now, there's some intrepid Polish metallurgists that have tried HT for AlSi9Cu3Fe (that perhaps others might find interesting):
https://www.researchgate.net/publica...cal_properties
Other casted stuff I've found is different Zamac (ZnAl) alloys and even AlMg.
-Now, to make a rough check of what you've got:
1) Zero a digital scale and weigh the piece- note its dry weight.
2) Fill a container with water just to cover the piece completely.
3) Weigh that container (w/o the piece in it) - zero the scale, or note that weight.
4) Now, drop in the piece in, covered by water, but hanging free within the container by a supporting wire held by you. Note weight again.
5) If you couldn't zero the scale in 3): Subtract weight in 4) from the one in 3): you get the piece's "wet weight".
6) Divide "Dry weight" from 1) by "Wet weight" from 5), and you get the material's density- which could be checked against online alloy tables.
To avoid nit-pickers: "Wet weight" IS indeed a lousy word - replace with "Displaced Water Weight" then, if that floats your boat?
NOTE: -This is only a quick, rough method of separation: Zamac from, and in-between Al alloys, and to avoid getting unwanted Mg in your melts.
After a while you'll develop a certain feel for density, but also by distinguishing alloys' shine and surface when filed- a real fast method!
Personally, I don't use any pure aluminum, extrusions, beer cans or kitchenware in my melts,
'cos I don't dig streamers or gumminess when machining. I don't try machining low-Al content Zamac any longer for the same reason,
but have some 20 kgs of that crap for an upcoming casting mix: DIYSwede's Hi-Perf "Bronze Ersatz"
Just gotta get my electric 4 kW foundry together first.
Bonus for the Al alloy curious: https://www.mah.se/upload/_upload/Al...g%20alloys.pdf
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