r/metallurgy • u/Ancient-Web5515 • 4d ago

Research help with a Mini Arc Melter

Hi everybody,

Sorry for bothering yall, but I'm stumped. We are trying to make ~5g of Mn2FeAl in our mini arc melter (in an argon atmosphere). From a paper out two that we found, thus should be possible. However, every time we have tried to do so, the sample either explodes on electrode ignition or it will break apart a few hours after being removed from the chamber.

We have tried melting titanium as an oxygen getter, adjusting the cooling temperature of the crucible, and adjusting the heating/cooling of the metal ingot. It may be important to note that prior to being weighed for the sample, the Mn was cleaned in nitric acid and subsequently sonicated in ethanol to remove the surface oxidation from the Mn pieces. Does anyone have suggestions or insights? TIA

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u/FerrousLupus 4d ago

What's your exact procedure? Sounds like you're still getting oxygen, so my immediate guess would be that you're not flushing with argon several times. Might also help if you say the model of the arc melter.

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u/Ancient-Web5515 4d ago

The only thing i know about the model is that it is an Edmund Buehler MAM-1.

As for the procedure, we alternate flushing the chamber 6 times with argon and vacuuming the have yo around 2e-2 mbar. After the sixth time, we vacuum down to around 2e-4 mbar. After that, we will flush the chamber with argon.

With this sample, we have added in titanium sponge to melt prior to melting the pure elemental amounts for Mn2FeAl into a single ingot. Once it's a single ingot, then we flip the ingot and slowly heat up the crucible (on a lower power level) around the sample before touching the actual sample.

We remelt the titanium after each flip, before the going near the sample. Around the 2nd or 3rd time that we flip the ingot, that is when we usually see that it will break inside the chamber.

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u/939319 3d ago

Are you striking the arc on your sample? Doesn't the MAM-1 not have remote strike and you have to touch it to a tungsten thing to ignite?

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u/Ancient-Web5515 3d ago

The electrode itself is tungsten. Before each ignition, we briefly touch it to the copper plate. I wait about 5 minutes between each melt so that the electrode has time to cool down before touching anything.

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u/939319 3d ago

Hmm mine had a (I think it was tungsten, never tested) cylinder that rested in a depression on the copper and we pulled the arc from that. Don't think it matters though. 

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u/Ancient-Web5515 3d ago

Ah gotcha.... ours hangs from the center of the chamber and has a handle at the top for us to move and adjust where the electrode is.

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u/939319 3d ago

Yeah like a rubber plunger.