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solubility of zinc in molten aluminum
Is aluminum soluble in molten zinc?
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12AX7
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Completely.
Tim
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Zinc
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Thank you for your ansewr.
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JohnWW
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Of course, although there is an eutectic mixture of Zn and Al consisting of 95% Zn and 5% Al, see http://search.globalspec.com/Industrial/Zinc_and_Zinc_Alloys . Mixtures of Zn and Al, usually having much more Al than in the eutectic mixture,
are used for hot-dip galvanizing of mild steels with "galvalume", which is superior to and has a brighter appearance than plating with pure molten
Zn. Standard "Galvalume" usually has a composition of 55% Al, 1.5% Si, 43.5% Zn , see http://www.iza.com/zwo_org/Applications/General_Galv/030802.... and http://www.kingspan.info/first.php?page=1105958410&idsub... . However, the eutectic mixture is also used, see http://www.bekaert.com/na/Strand/Bezinal%20Coating.htm and http://www.freepatentsonline.com/4812371.html . The ASTM specifications are given at http://www.bg.agh.edu.pl/add-ons/02-04.doc .
This is plating to prevent corrosion, due to cathodic "sacrificial corrosion" of the Zn and Al, which are higher in the electrochemical series and
also resist corrosion themselves through forming thin oxide layers which unlike Fe2O3 or FeO(OH) are impervious to further attack by atmospheric O2.
See http://www.key-to-metals.com/Article21.htm
Mg may also be used in the mixture in small amounts, see http://library.aist.org/ISSStore/PDF.nsf/OnePage_by_Name/PR-... and http://natt.pnl.gov/tech/mg.pdf , and http://www.firw.ugent.be/doctoraat/doctoraten/documenten/sam... and http://www.edpsciences.org/articles/metal/abs/2005/07/P543/P... , usually added to the eutectic mixture. Small amounts of Si in the mixture, to
produce a harder surface, are also used. However, impurities impair the protection of the coating, see United States Patent 4056657 at http://patft1.uspto.gov/netacgi/nph-Parser?Sect2=PTO1&Se... , and http://www.ingentaconnect.com/content/maney/cest/2003/000000... .
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urbs
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Zamak
If I recall correctly, there are a number of zinc/aluminum alloys, many of which are known as pot metal or white metal, think carburetor or metal toy.
Zamak is the name of at least one of them that also has magnesium and copper http://en.wikipedia.org/wiki/Zamak
[Edited on 16-5-2006 by urbs]
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Eclectic
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The more modern ZA-8, ZA-12, ZA-27, Have better strengh and bearing properties. The number is the aluminum content:
http://www.a-m.de/englisch/lexikon/legierung-zn.htm
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unionised
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Is it my imagination, or did the second post answer the question allready?
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12AX7
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If you'd like to get more particular about how completely you can check this:
http://web.met.kth.se/dct/pd/element/Al-Zn.html
-They aren't very soluble solids much under the melting point, but the liquids are infinitely soluble.
Tim
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enhzflep
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| Quote: |
-They aren't very soluble solids much under the melting point, but the liquids are infinitely soluble.
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Infinitely miscible?
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12AX7
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..Whatever...
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Zinc
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A little OT but does molten zinc dissolve steel?
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not_important
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| Quote: | Originally posted by Zinc
A little OT but does molten zinc dissolve steel? |
Very little. You would need t oworry if your are building factilities that will have those conditions day in and day out, for months or years.
Otherwise it's not really a problem, remember that galvanised iron/steel is a zinc coating on the ferrous metal, often put on by passing the iron
through a bath of molten zinc.
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12AX7
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No, actually it dissolves quite a bit. Let me dreg up a phase diagram here...ah.
http://www.crct.polymtl.ca/fact/phase_diagram.php?file=Fe-Zn...
Galvanizing consists of a layer of zinc on top of several extremely thin layers of intermetallics (as shown), depending on process. Hot dip
galvanized steel is going to have a thicker diffusion/dissolution layer and an equilibrium amount of zeta phase in the zinc coating, while
electroplated stock may have a diffusion region of, I would SWAG, a few hundred nanometers (more if heated at some point in processing).
It is very easy to dissolve through tin cans, even with a layer of iron oxide, when melting zinc.
Interesting to note that zinc is so soluble in alpha iron (ferrite). I wonder what the characteristics of such a "steel brass" would be; probably
harder than ferrite, and able to be precipitation hardened much the same as aluminum (indeed, about the same temperature even). Large amounts of Zn
reduces gamma-Fe (austenite), which should reduce the influence of carbon, as martensite can't(?) form on quenching the absent austenite. (Something
this rich in Zn is probably uselessly hard and/or brittle though. Maybe some nickel would mellow it out.)
Tim
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not_important
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Interesting. I based my comments on two things.
The first was when I was trying to grow metal whiskers. I'd used junk bits of pipe to make a J shape, with the short arm capped and with a small tube
for feeding in N2, the longer arm had a close fitting ceramic tube insert and a small vent. It was held in verted, with zinc in the short arm which
was in a small furnace; the long arm was just out in the air. When I was done I'd unscrew the short arm, invert it in a large clay pot, and heat it in
the furnace to melt the zinc, then use tongs to remove the pipe from the zinc.
The pipe interior was well galvanized, but didn't seem to be really chewed up, although I wasn't paying much attention to that area. The zinc didn't
look odd, and it melted about where expected, but it was just cheap alloy grade metal.
I never ran much above the melting point of zinc, furnace limitations. It is likely I was below the melting points of most if not all of the mixed
phases. But there were runs where pure zinc should have been molten, and if it were a good solvent for iron and the mixed phases I would expect some
visable damage to be done to the pipe. Could some ofthe mixed phases be less soluble in zinc, and formed a protecting layer? The pipe was much
thicker than a tin can, but if it were really soluble I'd expect to have seen the inner surface chewed up.
The second item behind my comments is that zinc's cousin mercury is a very poor solvent for iron. Mercury is shipped in iron flasks, power plants
boiled mercury in ferrou alloy tubing. So I extrapolated from that and my experience with zinc.
There might be a practical problem with iron-zinc alloys. Given the high vapour pressure of zinc, the lost of it during melting, casting, and working,
might make it difficult to maintain tight control of the alloy composition, and to uneven product quality.
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12AX7
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Ah, understandable.
Metallurgically, zinc resembles aluminum quite a bit. They are completely miscible, and completely soluble in solid solution just below the melting
point (the phases seperate at lower temperature however). They do not form an intermetallic.
Zinc also resembles metals in its row, such as gallium, copper, nickel and iron; however, because it's so much more like aluminum (probably due to the
behavior of its electrons, being seated at the end of the d-block), it tends to fit in less well. Brass, for instance, is a solid solution up until
about 25% zinc, where a beta phase starts to form because the alpha phase can't tolerate any more stress (since Zn atoms are a little larger(?)).
This is explained nicely here.
I once attempted to produce zinc oxide by boiling zinc in the end of a pipe. I took a piece of 1.5" pipe and welded a plate to the bottom. I melted
zinc in it in the furnace and attempted to blow combustion air in, but I got little more than aerosol out. Afterwards, I noticed that the zinc was
rather well caked on. In fact, that caking survived quite well even having cut off the end of the pipe to use the sealed portion as a crucible with
my induction heater. Eventually, I cleaned that crucible with HCl, revealing a craggy surface (in part due to Zn intermetallics and also due to
scaling from generally being orange hot in a pure air atmosphere).
Tim
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Zinc
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A little OT but is copper soluble in molten Al?
Also what is the melting point of a mixture containing 60% Al and 40% Cu?
Does it still have a golden collor?
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12AX7
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http://www.crct.polymtl.ca/fact/phase_diagram.php?file=Al-Cu...
10%wt Al, 90%wt Cu looks like a light brass. I would imagine pure gamma is silver.
Theta is about 50/50 by weight (Al2Cu) and has about the same melting point as aluminum. Aside from the nature of it obviously being an intermetallic
(with all its appearance, habit and mechanical properties), it looks about like aluminum.
Tim
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Zinc
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What is the melting point of the 10% Al and 90% Cu?
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12AX7
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Not much below Cu's.
If you want to cut the amount of copper to make it cheaper or lower-melting, the best you can do is yellow brass circa 35% (on the verge of white
(beta) brass), melting point about 1600F (870C).
Tim
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Zinc
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Would lead brass have a lower melting point than the aluminum version?
Also what would be the minimum amount of copper that it should contain to remain golden collored?
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12AX7
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Lead does not dissolve very well in copper. With processing and technique, you might end up with what would be better called a composite, copper
particles soldered together by lead. If the surface has a smooth layer of copper (perhaps produced by etching (with dilute HNO3) and burnishing), you
could get a copper color with a low softening point (that is, a "mushy" state, not actually molten).
What's it matter, anyway? Copper and bronze are easy to melt in a furnace.
Tim
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Zinc
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| Quote: | Originally posted by 12AX7
What's it matter, anyway? Copper and bronze are easy to melt in a furnace.
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I don't have a furnace and I still don't have all the materials and equipment to build one.
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12AX7
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Geesh, even African natives have the materials, just where are you? The Moon? Wait, no...
Tim
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Zinc
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How about a mixture of Zn and Mg instead of Al and Mg? Would it be also very brittle? Also in the ratio 50:50.
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12AX7
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Yes. The Zn-Mg system contains the brittle laves intermetallic, Zn2Mg, which is 15.7% Mg by weight.
http://www.crct.polymtl.ca/fact/phase_diagram.php?file=Mg-Zn...
As I recall, most of the other intermetallics aren't as brittle, and the regions containing pure metal are varying degrees of hardness and strength
(ranging from malleable pure metal to strong, hard alloy to brittle intermetallic-rich compositions). It is similar to the Al-Mg system's behavior,
but contains more intermetallics and in different ratios.
View it as an easy way to pulverize zinc that has slightly more reactivity.
Tim
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