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Author: Subject: Magnalium powdering process
Antiswat
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[*] posted on 17-12-2020 at 08:27
Magnalium powdering process


im gonna post my recent findings in messing around with MgAl 50:50 as i dont think anyone else has done this before and a few other observations and ideas

so first thing first, i casted my own from the respective metals on a kitchen stove, but i was having some of the magnesium burning up as it was melting down (i melted down the aluminium first)
but even despite major magnesium loss, ending up at maybe 40:60 Mg:Al it has intermetallic properties (crumbles into dust when smashed with a hammer, brittle)
however when i added more magnesium to counter the nitrogen/oxygen reacting with it, i got an alloy that more readily turned into dust, didnt need as hard a blow from a hammer
this is interesting as it makes me wonder - what is the exact ratio for the most brittle alloy?? i have given up looking into data for this realizing that this is a very very specific question, but this also could be very interesting to mess around with how much aluminium you can put in there and still have it working intermetallic, aluminium is also useful as a fuel- aluminium is very cheap compared to magnesium

anyways so main reason im making thread here, i found a small piece of MgAl on my table after i was done casting, i decided to chuck it into a 100 tonne press, it was squashed into a little disc maybe 2mm thick, i didnt keep an eye on what exact pressure i reached
it was brittle and yet not, it seemed like it was quite solid until i started rubbing a hammer around in it, then it fragmented into what seemed to be around 300 mesh metal dust, you wouldnt get that in first go smashing it with a hammer for sure, and seeing that you can get 50 tonne presses that are operated with a lever, making a steel frame stand and mounting a press overhead this is very doable at home, i did also think of using a paver sand vibrator for smashing the alloy up in bulk amounts, but pressing it to really stress the alloys crystal structure, compacting it into something that falls apart very easily makes this so much easier, combine this with a coffee grinder and you would have pyrotechnics grade metal dust with very low effort.

looking around i found it that they produce magnesium lithium alloys, so maybe one could make magnesium lithium aluminium alloy that would be intermetallic and brittle? it would be only for very specialty pyrotechnics and spooky for an amateur to handle- and really lithium powder is already totally doable, so it would only be niche, but the boundaries of intermetallic alloys is still very interesting

ontop of that, i poured some of the MgAl into water to form "popcorn" MgAl, it basically uses the steam pressure from the water to create this hollow kind of cake, and it doesnt appear to have much less magnesium content in it, theyre both equally reactive compared to MgAl cast into a bar shape

im also wondering- how can one easily test what magnesium content there is in the alloy? acetic acid reacts with magnesium, but if its very fine aluminium it should also react with that, and if you react all the magnesium then you would possibly end up with nano aluminium powder or around that? that in itself is also very interesting, especially if you would be casting some high aluminium content MgAl intermetallic, simply using the magnesium to make the metal brittle and then removing the magnesium with acids to produce super fine aluminium powder, boric acid prevents aluminium reacting with water- but theres probably a limit to what particle size aluminium it will prevent from reacting with water.




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RustyShackleford
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[*] posted on 17-12-2020 at 09:08


pouring it into water isnt the best idea, atleast use something like oil.
as for determining Mg, perhaps this is of use
"The Determination of Magnesium in Aluminium
Alloys BY F. PTTTS, M.A., A.I.C. "
i inserted the PDF here

Attachment: pitts1943.pdf (945kB)
This file has been downloaded 65 times

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[*] posted on 17-12-2020 at 10:38


why would you think its not a good idea to pour it into water exactly? i would say maybe some alcoholic solution would be more ideal as it would create even more cavities due to higher vapor pressure at the given temperature, and really a grown man shouldnt be afraid of a gallon of burning alcohol

reading the PDF i realize one could react the metals and turn it into hydroxide and then turn that into oxide, aluminium oxide doesnt react very well with acids but magnesium oxide does iirc. ill give the PDF some reading




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[*] posted on 17-12-2020 at 11:12


It's been 20years since I made any MgAl, but IIRC the two intermetallic eutectics are Mg2Al3 And Mg3Al2. The Al/Mg phase diagram should confirm this.

For analysis you could try dissolving the metal in sodium hydroxide. Al should form sodium aluminate, I don't think Mg will.




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[*] posted on 18-12-2020 at 06:41


yes but then i would end up with magnesium hydroxide, hydroxides are usually a hell to deal with, either very low density, or even gel like
i think i could maybe react MgAl with HCl and then react that with Na2CO3, the aluminium carbonate breaks down into Al2O3 iirc- then i just have to dry it all out, discard the NaCl and excess Na2CO3, dissolve the magnesium oxide/hydroxide and weigh the Al2O3, i rather dont wanna make sodium aluminate, it always seems to turn into some nasty black solution, i could also try to submerge one bar into water- having a jug of water filled 100%, then weight it before/after to get accurate data on how much water it expelled and then weight the bar to get pretty accurate shot at density, luckily aluminium and magnesium isnt alloyed with much else but each other

now the question is, is the Mg2Al3 more brittle than the Mg3Al2 laves phase? and how far can you go with the alloys before they stop being brittle, at least in a practical sense brittle

Mg3Al2 appears to be 57.5%Mg + 42.5%Al - this might be the most brittle alloy. but Mg2Al3 is Mg37.5% + Al62.5%
so, im wondering ... it seems you can mess around with like 7.5+12.5% of aluminium, like 10% deviation in aluminium from 50% aluminium- maybe 20%? i recall water anodes are frequently made in 75-25% MgAl, i dont think that alloy is considered brittle- im speaking to one producer of MgAl alloys thats willing to sell me bulk quantities of MgAl50, maybe they have some alloy expert willing to share some knowledge/experience?

[Edited on 18-12-2020 by Antiswat]




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[*] posted on 18-12-2020 at 07:19


ball milling with little mineral oil added is get you a paste. otherwise (unless you have inert glove box) it is dangerous to work with fine flammable metal dust.



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[*] posted on 18-12-2020 at 07:35


i think the dangers of milling metal powders are well exaggerated, i was adviced charcoal to be added when ballmilling metal powders, with aluminium it will start clumping together before 1000mesh if you dont add charcoal or something similar, i recall one chemist put MgAl in a ballmill for 2 days and achieved almost completely black MgAl, i have myself in the past used coffee grinder for processing 2kg MgAl, and despite the whole mix being very hot, and also having extreme loads of friction when grinding, removing the lid to expose super fine MgAl dust didnt cause it to catch fire, if this even does happen i think i know what the real issue is- during ballmilling the dust isnt knocked up in the internal atmosphere a whole lot, but when you take it off the machine and turn it 90 degrees it will form a thick cloud of metal dust- and this is where you decide to open the thing, i have one friend who ran into this issue with aluminium multiple times, and managed to dunk the whole lot into a toilet with water twice, blowing up the toilet in both instances
ideally with long milling time you would wanna let the dust settle for a whole before opening it

but ive had black MgAl dust that would selfconfine with perchlorate, regretfully loud.

could it maybe be a question about humidity? metal fuels can and will react with water to use it as oxidizer as well as forming hydrogen gas

on a sidenote the MgAl i produced with coffee grinder came out as black MgAl by just passing it through 150 mesh sieve, not even once did it catch fire when i cracked off the lid




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https://en.wikipedia.org/wiki/Solubility_table
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[*] posted on 15-5-2021 at 01:06


so, i have been messing around with different methods of cracking MgAl into smaller pieces, and it seems using a hammer drill is the go to, but you need to weld a steel plate on the end, preferably something like 10mm thickness and it has to be a strong weld, then you need a similarily sturdy pot to smash up the MgAl in, pieces of 50x50mm are doable to smash up with the hammer drill but larger than that and you wanna mount chisel head or similar sharp end to the hammer drill
in roughly 30 minutes i was able to crack down 1kg of MgAl chunks and have it pass through a sieve with 1mm holes
you may continue to grind it but it becomes a dust hazard, so maybe if a piece of cloth is attached to the pot and the drill (mind you, it doesnt spin around its just on hammer mode) one could probably acquire some quite fine MgAl
we didnt bother with this, instead we just take the first 100+mesh fraction and run it into a ~100mesh sieve
then we load that into a ballmill, even with the first crude fraction that is up to maybe 800 mesh in just an hour we got some very dark MgAl after it was run through a 150 mesh sieve

i also did construct some metal plates that hold 2 moving gears that are cranked by hand, but it seems the gears are not big enough to really get you where you want to go, sure it can work well if you pour in 400-800 mesh fraction but thats around the range it prefers
maybe having a set of different grinding gears can work, ive seen larger gears used for chewing up big chunks of MgAl, im quite sure if some smaller gears were automated and could maybe be adjusted with distance it could be used to produce some very fine MgAl, but its imperative that the gears are adjustable and the gear sizes are adequate to the mesh fraction you feed it / want out of it
the grooves on the gears i used was maybe 3mm and getting it into place was quite a hell, to make it moving you would probably need some lathe/milling machine action to get the right fit for all the parts, should be doable by mounting the gears on a rod which features on one rod a hole, a threaded rod going through, then this first rod secured by some nuts and then entering the second rod holding the second gear featuring a threaded hole
may be feasible to only control the distance on one end, but the gears needs to be gripping onto each other and thats the true menace of making this thing work

a coffee grinder is also possible to use but you end up with maybe 400 mesh fraction after it has been run through a 150 mesh sieve (the finest particles pass through faster, thus larger mesh can get you much finer mesh powder)
a coffee grinder can take quite large pieces, up to 20x20mm but ideally you want smaller chunks, the particle sizes are best when you do this, once the powder becomes closer to 100 mesh it just doesnt grind it that well anymore, supposedly splitting the pieces up is what gives you powder and the smaller pieces are less likely to be split by the coffee grinder, very useful for preparing the MgAl for ballmill

the sifting thing can be automated by mounting a vibrator

as for ballmilling MgAl, it can be dangerous as it can create a pyrophoric metal fume, my thesis is that people really just crack open the jar too fast right after turning it 90 degrees, even with long milling time it should be possible to open the jar if you slam it into table and give it a days rest, slamming it so that it doesnt dislodge super fine powder when youre opening it. maybe its because it tends to be very warm after ballmilling and that makes it more pyrophoric? burning metal is a gross situation and water really wont help you, CO2 neither when youre dealing with magnesium alloys as it just acts like oxygen, all i can think of is butane or argon, but then you risk the butane starting to burn also
aluminium foil would probably be the handiest for shutting out air, i managed to make airproof caps for erlenmeyer flasks a couple times

charcoal should be added when ballmilling, it can coat the metal particles so they dont ignite so easily with air

im gonna be messing more around with the hammer drill, trying with a finer fraction and sealing it up so i can experiment with making actual metal dust out of it without using coffee grinder or ball mill, with an automated sieve you get a lot more time on your hands.




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https://en.wikipedia.org/wiki/Solubility_table
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Fyndium
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[*] posted on 15-5-2021 at 01:56


Are the cheap plug-in ball mills of any good in eBay?

Why the drum can be plastic, while the media is super-hard ceramic? Why it doesn't destroy the drum as well as the agent?
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[*] posted on 16-5-2021 at 01:20


well hard plastic would cause greater risk of igniting the content through static so i can see the idea in that
you can also use lead but you will end up contaminating whatever you dump in there
for larger milling material i think its best to use irregularily shaped pieces that will tumble more, but for finer particles it makes more sense to have less tumbling, but ball bearings instead, if the media tumbles its unlikely to hit small particles effectively

i bet you can mill MgAl without even using any media




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https://en.wikipedia.org/wiki/Solubility_table
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