Author Topic: Aluminum Copper Alloy Experiment (Read 91678 times)

Will_D · « **Reply #25 on:** May 25, 2015, 05:30:10 AM »

As the melting points are widely different the only way to get Cu and Al to alloy is by disolution.

The molten aluminium will alloy with the copper at the surface of the copper and create a eutectic. Given time and agitation the copper will sloooowly disolve into the aluminium.

The way to speed things up would be to increase the surface area a LOT so cut the copper wire into short (say = to the diameter) lengths and then see how quickly they disolve also stirring the pot will help.

PS: This is only my theory!

mattinker · « **Reply #26 on:** May 25, 2015, 07:57:48 AM »

It's not only your theory! That's how it works. I used fine stranded wire when dissolving Cu into Al to make ZA12. 1%Cu, 11% Al 88% Zn by weight. 10%Cu will dissolve easily into Al.

Regards, Matthew.

vtsteam · « **Reply #27 on:** May 25, 2015, 09:56:19 AM »

re. ZA-12:

Matt what were your feelings/results of the ZA-12 that you made? Did you make any castings with it?

The ZA-2 and ZA-3 I tried were purchased virgin alloy ingots. ZA-12 is not available easily here, and I have some pure zinc coming shortly to try different shop mized ZA numbers. But would be curious re. your results w/ZA-12.

re. al/cu:

I don't have fine copper wire, but didn't have any problem melting the copper tubing I used, folded into a couple of pellets (first photo at start of thread).

Perhaps as Ironman says it was the pre-heating that helped. I'll give here the exact procedure I followed in case it makes any difference:

First tried melting the copper, and I think it was 20+ minutes from placing cold crucible and pellets in the furnace. The crucible and pellet were glowing orange when I added a few small pieces of the 6061 to start a heel. I noticed that it immediately wetted the copper when melted (like solder). I gradually added more pieces of 6061 (low silicon Al) as it melted, then finally stuck the piston (high silicon Al) on top. It took awhile to heat up and melt -- probably 5 minutes. When I stirred it all there was no evidence of the copper pellets left, and I poured.

I wonder if preheating the copper pellets with a torch would allow them to be added after the aluminum, and still combine easily. That would save a lot of time and fuel and allow heavier section copper to be added (if they are a problem unheated). Even a mapp gas portable torch should bring a small pellet of copper up to red heat.

I also wonder if the cleanliness of the copper is a factor in getting the aluminum to wet it out initially -- like solder. Mine was clean copper tubing, and folding it with hammer also exposed bright areas.

mattinker · « **Reply #28 on:** May 25, 2015, 10:10:52 AM »

I was very pleased with the ZA12 I made, it casts well in sand and machines beautifully! It has good bearing qualities. I am very lucky as here in France A lot of roofs are covered with pure zinc sheet so good quality pure stuff is available, and having done roofing work, I've been saving off cuts (drops) and scrap from dismantled roofs for years. My stash is probably worth quit a lot as scrap alone! ZA12 is supposed to have similar bearing and vibration dampening characteristics to cast Iron.

Regards, Matthew

ironman · « **Reply #29 on:** May 26, 2015, 01:53:54 AM »

I did do a lot of stirring to get the copper to dissolve quicker but made no difference. My thoughts were that to heat the copper up would create an oxide coating and make it difficult to dissolve copper in aluminium. It could be that I will have wait longer for the copper to dissolve. As I pour mostly iron I have not gotten back to this experiment but will give it a try in the near future.

vtsteam · « **Reply #30 on:** May 26, 2015, 11:34:18 AM »

Thinking about it, Ironman, I bet the copper pellets were oxidized by 20+ minutes of furnace heating in an empty crucible, so my statement about clean copper probably doesn't hold water, so to speak.

I'm going to have to try a few experiments to see what gives re. dissolving copper in Al.

vtsteam · « **Reply #31 on:** May 26, 2015, 11:42:38 AM »

Thank you Matt. I will probably try some ZA-12 from purchased zinc ingot. I liked what I saw from the published specs, of ZA-12 but wasn't able to buy it, or I'd have probably used that on the lathe parts. What did you sand cast with the ZA-12?

mattinker · « **Reply #32 on:** May 26, 2015, 01:00:46 PM »

Quote from: vtsteam on May 26, 2015, 11:42:38 AM

What did you sand cast with the ZA-12?

I cast blocks for a "Tinker" T&G, that I didn't finish because I bought a Clarkson Mk I T&G, on which I used one of the castings for tooling.

It's very nice to work!

Regards, Matthew

vtsteam · « **Reply #33 on:** May 26, 2015, 07:37:02 PM »

Looking forward to trying it.

vtsteam · « **Reply #34 on:** May 26, 2015, 07:44:59 PM »

re. my own copper in aluminum melt. I didn't stir it while gradualy melting the aluminum around it -- probably 10 minutes.

Are we sure that stirring actually helps?

Here's an alternate theory:

Stirring removes the highly alloyed al-cu mix adjacent to the copper -- which may have a greater affinity and actually be more active in dissolving the remainder than the unalloyed aluminum is. Stirring would remove this surrounding layer.

Just a theory.

ironman · « **Reply #35 on:** May 28, 2015, 02:39:52 AM »

For me Stirring did not help, you may be right better to leave it go and do it's own thing instead of trying to speed it up.

Manxmodder · « **Reply #36 on:** May 28, 2015, 08:00:30 AM »

Steve,ironman, this is a very interesting topic indeed. I can see the logic in Steve's theory that stirring may be interfering with the eutectic process,but I also wonder if adding a flux after the aluminium has melted would speed up the alloying process.....OZ.

mattinker · « **Reply #37 on:** May 28, 2015, 08:10:47 AM »

When I made my ZA12, I used fine stranded wire, a coincidence, but I didn't need much by weigh as it was about 1% of the finished alloy. It just disappeared into the Al. I would support Steves theory about the stirring. this is a dissolving process in a corrosive environment.

Regards, Matthew.

vtsteam · « **Reply #38 on:** May 28, 2015, 08:37:52 AM »

Any chemists out there could probably correct my ancient high school memory of how the periodic table works, left to right, but I'm guessing Alumin(i)um would beat the pants off of Copper in a fair fight for the hand of Oxygen. That is, if it wasn't already married!

So if that's true (highly suspect) I imagine happily oxidized copper surrounded by a vat of molten aluminum is in for a rapid divorce, flux or no. Or to put it another way, aluminum would be a flux for copper, among other things.

Please notice I'm drifting off into hated theory, and experimenting less......

S. Heslop · « **Reply #39 on:** May 28, 2015, 03:00:14 PM »

I'd say it depends on what the activation energy is. It's pretty much the classic thermite reaction but that famously needs a damn hot flame to get it going.

Some day i'm going to go through my old notes because i've forgotten almost all the stuff I learned at university... it makes me a pretty lousy chemist.

bertie_bassett · « **Reply #40 on:** May 28, 2015, 03:35:13 PM »

Quote from: vtsteam on May 28, 2015, 08:37:52 AM

Please notice I'm drifting off into hated theory, and experimenting less......

best get off the computer and into the workshop then!

vtsteam · « **Reply #41 on:** May 28, 2015, 10:40:59 PM »

Afraid when I'm off the computer, I'm necessarily on the tractor now. Will try to sneak some experiments in if possible.

awemawson · « **Reply #42 on:** May 29, 2015, 07:12:23 AM »

Sounds familiar Steve - seems I'm only in the workshop to mend something or make adaptors etc. Half way through another double run of stock fencing at the moment to allow me to plant another 70 metres of native species hedging at the back end of the year.

awemawson · « **Reply #43 on:** May 29, 2015, 08:00:55 AM »

Here's the alloy that you should be shooting for Steve:

http://www.bbc.co.uk/news/science-environment-32886000

vtsteam · « **Reply #44 on:** June 03, 2015, 08:28:59 PM »

Missed that one Andrew!

I took a break after attacking a really tough stump with the Ford (and axe when I couldn't cut through some of the more hidden roots with the backhoe) and cast another piece for the lathe. This time in aluminum, because it isn't heavily loaded, but does mount the stepper motor under the ways, and it always helps to give them a nice massive aluminum plate as a heat sink to mout on.

And since I'd made some aluminum/copper alloy, I decided I might as well use that. Turned out I didn't quite have enough for the part plus sprue plus a little extra, and needed another 8 oz.

Good excuse to try another experiment in dissolving the copper in aluminum.

Last time I tried to melt the copper first, and got it and the crucibe red hot before giving up and adding small amounst of aluminum letting them melt and adding more until the full charge was in the crucible. I'd flattened the copper tubing and rolled it up to reduce oxidation when I was hoping to melt it.

This time I just tossed the piece of copper tubing into the bottom of the pot (no flattening or bending), and filled up the crucible with aluminum-copper alloy ingots plus the half 6061 and half piston aluminum to make up the 8 oz additional I thought I'd need. This was done cold,, then placed in the furnace.

There was no problem dissolving the copper at all, though I did notice that the 6061 took longer to melt than any of the other aluminum.

I didn't stir, except just before pouring to check for any undissolved copper and to skim the dross. There was no copper tube left, and little dross. The pour went normally.

So it looks to me like:

Aluminum will readily dissolve 3/8" copper tubing without stirring, and without preheating the copper. This melt took half the time of the first one.

Manxmodder · « **Reply #45 on:** June 04, 2015, 08:22:32 AM »

Very interesting, Steve. It's great to see this works so easily.

Alloying your own metals is a really useful discipline to learn,I've noted this for some future trials of my own.

.....OZ.

vtsteam · « **Reply #46 on:** June 04, 2015, 09:51:36 PM »

Thanks Oz!

NormanV · « **Reply #47 on:** May 16, 2017, 10:21:23 AM »

I followed this post with interest and filed it away in my memory for later use.
Now is the time! I require some material that is harder wearing than the normal alloy that I get from old wheels and thought that adding copper might do the trick. Today I melted one of my 2kg ingots and as it started to melt I added 100grammes of 20g copper wire. It took about 15 mins for the copper to completely melt and I poured it into a metal mould to produce a stick of alloy 50x25x300mm.
I read of Steve's tests of heat treating and that appears the way to go. Should I heat treat it before machining or after? I will be using HSS tools.
Norman

NormanV · « **Reply #48 on:** May 16, 2017, 10:45:52 AM »

I've just removed it from the mould. I have to say I was quite worried about how easily it would come out as my welding isn't up to much. I did make sure that there was draft on it but there were small gaps in the corners. I was worried that the aluminium would mould itself into it and be impossible to remove. I used polyfilla to seal the corners and much to my delight it worked perfectly. The metal fell out of the mould when I inverted it.

awemawson · « **Reply #49 on:** May 16, 2017, 10:48:12 AM »

You will find that it is a bit 'gummy' to machine annealed. Be aware that it will age harden as well as work harden.

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Author Topic: Aluminum Copper Alloy Experiment (Read 91678 times)