Melting aluminium / magnesium alloy

In pyrotechnics we use an alloy of 50:50 magnesium / aluminium called magnalium, this is a very brittle material that is very useful in fireworks
manufacture. I would like to attempt to manufacture some and wondered what might the best way to go about it.
My idea is to take a cast iron pot with lid, place equal amounts of metal within, and then put the pot on an enclosed kettle bbq with a good charcoal fire built around it. To increase airflow I was thinking perhaps something along the lines of a leaf blower or hair dryer connected to the bbq air vent. I'm confident that the metals should mix sufficiently by themselves assuming they reach melting point. Accuracy is not too important for these purposes.
Reckon this sounds viable on a backgarden scale with limited budget?
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Richard H
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Molten magnesium in a air atmosphere is quite exciting to say the least, the alloy you desire requires smelting the two metals in a oxygen free enviroment, a bbq will not meet these requirements. I suggest you purchase the alloy ready made from a metals supplier, far to dangerous to attempt to cook up some at home without the proper equiptment.
Best Regards Tom.
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The metals will be contained in a cast iron pot with a heavy lid, I suspect that only a limited amount of oxygen is going to get in, and even then an oxidised layer on the top of the melt should stop any further oxidation. My theory anyway! I've read of pyrotechnists trying this without incident, so my main concern is generating the heat to melt the metals sufficiently.
Obviously I will be taking precautions just in case something happens, I'm well aware of the reactive nature of magnesium and aluminium, afterall this is why we use them in fireworks :-)
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Richard H
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snipped-for-privacy@aol.com (AZOTIC) wrote in message

Bah. I have a photo from a friend here showing a pool of shiny metal inside a crucible inside a furnace, written on the back is "1.5 lbs of freshly skimmed MagNESIUM (4Al) @ 1250F" (his capitalization :P ).
I've heard of making magnalium before. I would guess either the aluminum forms a protective skin, preventing the mag from burning, or it just can't get enough air to burn particularly hot.
The secret commercially is either a gas or flux cover. The latter would be a salt 'alloy', such as equal parts sodium and potassium chloride (can be had at the grocery store as "lite salt"; has to be fused (mmm, salt ingots!) before use), with other select ingredients to lower the melting point and improve fluxing action. For gas, either an inert gas must be used (as lit Mg will continue burning between two blocks of dry ice quite nicely) or sulfur dioxide works fine, a bit of elemental sulfur dropped in the crucible holds it I'm told. Stay out of the fumes...
Tim
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I'd say melt the Al, add a flux cover, and then dissolve the Mg into the Al most safely, in chunks not overflowing, to your rough 50:50. And have dry sand available at the very least. Preferable ground coal to soak up oxygen should you experience ignition. It's a delicate balance between heat input, molten temperature, and time spent dissolving MG into Al.
The more time at idle, the more Zn will fume out of your Al, if there's any. Zinc chills. Brr. And other compositional elements will boil out, but mostly ingot Al is pretty stable.
Then, as it cools, you stir it as it freezes to break it up, like making ice cream. You get a coarse powder that way.
Don't stir it vigorously while it's real hot!

And when he poured it, did it go actinic?

Love the stuff. Love frozen dinners, too, but what a wallop of sodium.
Maybe try 1/4 your smallest crucible one day, then upgrade....
I tolerance everything and tolerate everyone. I love: Dona, Jeff, Kim, Kimmie, Mom, Neelix, Tasha, and Teri, alphabetically. I drive: A double-step Thunderbolt with 657% range. I fight terrorism by: Using less gasoline.
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Natural gas or propane could be used as the gas. Obviously if you are going to do this, you are going to have to be careful. But natural gas plumbed into the iron pot will burn as it escapes from the pot, but will not burn inside the pot as there will not be any oxygen there.
Be careful and let us know how it turns out.
Dan
snipped-for-privacy@charter.net (Tim) wrote in message

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Richard wrote:

On your head be it ...
I have sucessfully melted aluminium on a ceramic electric kitchen cooker hob in a stainless steel cooking pan with a glass lid. IIRC magnesium has a similar mp.
I'm in the UK though, and we have proper electricity (240V) here.
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Peter Fairbrother


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I am also based in the UK, I never gave thought to an electric element based setup, obviously outside and well away from anyone or anything! I still reckon a charcoal fire would be the cheapest and quickest option.
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Richard H
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Richard wrote:

Saw your sig. Were you at K-Lob? I'm the turbopump guy.
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Peter

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We did the big firework display on the Saturday night :-)
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Richard H
UKRA#1172 L2 Cert
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snip-
I'm confident that the metals should mix sufficiently by themselves

It doesn't sound viable to me. My experience with molten metals over the years tells me that the metals, assuming you achieve success in melting them without a fire, are unlikely to become a homogeneous alloy. They have little reason to unless you give them some type of stirring action. When melted by induction in an inert atmosphere, the heating method serves that purpose. Unlike gasses, metals do not always distribute themselves evenly when combined, although they will do so when assisted. Some metal combinations will stratify given the opportunity. Silver and iron, for example. You're also going to have to come to terms with the fact that iron will be absorbed by the molten metal. Dunno what affect it will have on the purpose, but it's not a good idea when melting aluminum for casting.
Harold
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