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For my KITH knife this year I have been considering adding a theme of found wood and scrap metal on top of the 1 cubic once requirement and have been looking for potential ways to get some non-ferrous material to increase my options. I managed to get ahold of a rusted outa alternator that may be ~60 years old pictured below:

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The end of the housing is some kind of non ferrous casting and I was wondering if anyone had tips on how to potentially ID the alloy/if it would be safe or effective to try and make some kind of bronze or brass with pieces of the pot metal and windings. If I ask nicely I may be able to get XRF data, but that would still miss the presence of some lighter metals (notably Al) even if I can get the test done. 
 

On the safety side, it seems I want to look out for zinc, lead, and magnesium, is there anything else? And any low-tech ways to test this? If it’s too fraught I can also just not touch the pot metal and make pure Cu, but I thought it might be nice to have to have the option of alloying. 

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I would expect the end bells of an alternator to be an aluminum alloy rather than zinc or magnesium.  However, I can't say that I have any direct expertise with one that old.  

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I'd guess a zinc alloy, myself.  Possibly Zamak, (zinc-aluminum-magnesium), but maybe another alloy of zinc.  Pure zinc isn't strong enough.

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Aluminum and zinc were my first guesses as well. Is there a significant risk melting it if it is zinc? I’ve generally shied away from brass in casting to avoid that can of worms, but I’m sure it is possible to do safely. Also, not sure if it helps at all, but here is a picture of the grain in the break (made

with a hammer and cold chisel). I also scraped down to clean metal and put on a drop of vinegar which doesn’t seem to be doing much. Whatever this is, it’s pretty soft. 

 

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My understanding is that zinc is pretty dang safe to melt down by itself, because then you keep it cool enough to not put off fumes.  Only when you start going up to brass temps do you have to worry about it flashing off and spitting out the bad stuff.  If it were me, I would try getting a small chunk and heating it with a plumbers torch.  If it melts really quickly then pot metal, if not then aluminum.  Helps if you have some known pot metal and/or known aluminum on hand for comparison.  

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Posted (edited)

The melting point difference is a good idea. I don't have access to a torch at the moment unfortunately, however I have so far failed to melt a small shaving of it with a heat gun or a lighter. Not a definitive answer, but perhaps leaning towards aluminum. I do have a kitchen scale, so it I can get a piece with regular geometry I could try using the density as well.

Edited by Aiden CC
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I was able to pierce out a piece of fairly uniform thickness my scale said it was 1 g, so probably ~0.5-1.5 g assuming the scale can be trusted for low values like this. I calculated the volume of the piece, and the expected mass would be ~1.4 g for aluminum, ~3.5 g for zinc, and ~0.9 for magnesium alloy. It seems like it's definitely not zinc, and I think that magnesium would have reacted to the vinegar/flame so it seems like it's aluminum. From doing a bit of reading it seems like aluminum bronzes can have hardness and tensile strength in the range of some steels, can be heat treated if there is enough aluminum, and can forged hot. Pretty much all of the plans I have for this involve hammering it out into a sheet, which for so strong of an alloy could be a pain (though the potential for hot forging could speed things up). I won't be able to work on this for a month and a half or so, but maybe then I'll play around with some different compositions (that is, if I can get it to cast at all) and see what I can come up with. 

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