Subject: [Q] Want silver alloy other than Ag-Cu : how to make ?

From: C++ Freak <[email-masked]>
Date: 29 Apr 1996 11:59:44 GMT

As a hobby silversmith I have strong problems with the polishing of sterling
silver. This is due to the reddish firescale which is hard to remove.
So the alternative is another alloy. Pure silver is no option as it is too
soft.
Looking in the Degussa "Handbuch der Edelmetalle" (1967) (in German) I saw some
phase diagrams of which Ag-Si was the best (99% Ag, 1% Si) I made a sample
(pure Si alloy grade (99%) is hard to obtain) which turned out to be good:
easy to roll, etc. But the Si is hard to obtain.
Are there other elements suitable for alloying with silver ?
Tin is no option as it does not harden it. Zinc makes it too brittle and
oxidizes too easy.

Can somebody help me ?

Klaas

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From: C++ Freak <[email-masked]>
Date: 1 May 1996 09:00:35 GMT

Put 9 parts of fine silver with one part of a crushed small amorphous
solar panel of a broken solar penlite battery charger and melted it together
in an open flame using an oxypropane torch, heating it to 1450 C allowing the
Si to melt too. I melted it together on a piece of chamotte.
The flame should be *reducing* otherwise the Si oxidizes easily.
I diluted this brittle alloy with 9 parts of fine silver in a graphite
crucible in a propane-air furnace until 1000 C and I poured it into an L-shaped
iron bar.
The casting I rolled to sheet of 0.5 mm thich with three intermediate 
annealings. No cracks occurred during rolling or quenching and it's 
*firescale-free*.
When you have access to a vacuum of inert gas furnace which reaches 1450 C
you'ld rather use that, but I don't have such exotic and $$$ equipment.
Commercial alloys are normally made on that basis.

Klaas

BTW, aren't you nicknamed as a relative of Bill Gates (I am a software engineer
in daily life developing software for Bill's Windows too) ?

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From: John B <[email-masked]>
Date: Mon, 29 Apr 1996 19:58:17 +0100

In article <[email-masked]>, C++ Freak <[email-masked]>
writes
>Tin is no option as it does not harden it. Zinc makes it too brittle and
I am intrigued by the colour of your firescale. It is usually grey.
However. There are a number of ways to remove it or avoid it. You could
use Brittania grade silver which is of a higher quality than sterling
and does not oxidise so easily. Or pickle out the firestain with ten
percent sulfuric acid. 
-- 
John B

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From: [email-masked] (Peter Brooks)
Date: 1 May 1996 17:00:47 GMT

C++ Freak ([email-masked]) wrote:
: phase diagrams of which Ag-Si was the best (99% Ag, 1% Si) I made a sample
: (pure Si alloy grade (99%) is hard to obtain) which turned out to be good:
: easy to roll, etc. But the Si is hard to obtain.

Actually, if you can deal with very pure silicon, you might try to see
if a semiconductor manufacturer is around.  (Your address says "nl".  Perhaps
Phillips?)  Semiconductor manufacturerers use a *lot* of silicon wafers, but
a large percentage of those are used strictly for tests and monitors.  
We'll (yeah, I build them too) recycle them as much as possible, but after
a while they are too thin or are otherwise unusable.  At that point we
toss them.  Sometimes the surplus houses will get some wafers, but a lot of
them end up as landfill after a while.  Typically, at worst case, the wafers
should have an oxide and possibly aluminum on them.  The oxide would be a
dross.  I'd etch the aluminum away with phosphoric acid.  BTW, if you get
wafers with titanium/tungsten, the normal etchant is pure hydrogen peroxide.
You'd have a slow time using home-type peroxide, but it whould probably do
the job.

It's harder, but also possible to get reject product wafers.  The problem is
the additional junk that gets on a wafer--you could probably deal with the
silicon dioxide, but any metalization would make a bit of a mess.  The
fastest strip is by no means safe; I have a *lot* of respect for 
hydrofluoric acid, no matter what the concentration.  However, if there is
no 'passivation layer' (glass, or silicon nitride, or even a polyamide),
you could get rid of aluminum with a phosphoric acid dip and a bit of
patience.  The more exotic metals (like Ti, Tungstan, even Ni or Mo) 
probably wouldn't do too much.  They're very thin to begin with and tend
to be pretty refractory.

The doping impurities will be in really low concentrations.  Even at the 
surface, they don't get much above the ppm level, so I wouldn't be worried
about Arsenic.  By the time you got a whole wafer, you'd be in the ppb range
or lower.

Pete Brooks

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From: [email-masked] (James W. Swonger)
Date: 2 May 1996 13:12:40 GMT

While processed wafers are a source of silicon, there's a question
that needs to be answered first - is silicon at all soluble in silver
at temperatures you can achieve? Si is pretty soluble in aluminum,
somewhat in iron, but if you're looking for appreciable precipitation
hardening then you need a lot of dissolved silicon I think. A good
metallurgy reference might have solubility curves and phase diagrams
for Ag-Si, or not.

 Automobile pistons are typically a eutectic Al-Si mixture. If you
don't mind some aluminum in there, you can melt these easily, well
below the melting point of pure silver. The silicon is not the major 
component but at least it's already dissolved.

 Another option is using finely divided hard materials (e.g. 
silica (glass), alumina, silicon carbide, etc.) and loading the
melt with these and then cooling such that you form an ingot of
well-distributed metal matrix composite material, in this case
a silver body with included high-hardness material. You can obtain
these fillers in plate, whisker or simple granule form (all 
microscopic) and they will impart varying degrees of hardness and
toughness to the material. Of course, you will then have a much
more difficult time working the material, and subsequent heat
treatments (like flame soldering) may do unexpected things like
causing the included particles to come out to the surface, changing
the properties of the material near the joint.

 Finally, there are other alloyable metals which might produce
interesting hardness effects. Iron, platinum, other silvery or
white metals of native hardness higher than silver should raise
the hardness of the composition. How about chromium? Again, you'll
probably have a hard time getting to melt temperature on some 
of these, so look to solubility diagrams to see if you can get any
alloying.
-- 
##########################################################################
#Irresponsible rantings of the author alone. Any resemblance to persons  #
#living or dead then yer bummin. May cause drowsiness. Alcohol may inten-#
#sify this effect. Pay no attention to the man behind the curtain. Billy!#

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From: [email-masked] (Brian Adam)
Date: Sat, 11 May 1996 18:33:26 GMT

On 2 May 1996 13:12:40 GMT, [email-masked] (James W.
Swonger) said:

>at temperatures you can achieve?

Sure. But get the silicon from a metals supplier. Like someone who
makes silicon bronze. A foundry. What's all this talk about melting
down computer silicon chips to alloy with silver! Who knows what
exactly is in them!

I add silicon to silver when i'm casting high detail. Got to put in
the right amount. I guess it - about 0.5%. It's  brittle if I put in
too much. 

Tagline = virus

--
Brian Adam    - on RiscPC -     <[email-masked]>

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From: [email-masked] (Peter Brooks)
Date: 15 May 1996 00:40:30 GMT

: Sure. But get the silicon from a metals supplier. Like someone who
: makes silicon bronze. A foundry. What's all this talk about melting
: down computer silicon chips to alloy with silver! Who knows what
: exactly is in them!

Well, a fair number of us....  The base is *very* pure silicon,
while the dopants (which make the transistors) are in the ppb to ppm
range.  With the topside stuff (the metals that make it look like a
chip), you'd get:  silicon dioxide, some silicon nitride (occasionally
some polyamide, which would burn out), and some metals.. at a rough 
estimate, there would be about 0.5% 'gunk' in place, most of which
would be silicon dioxide and aluminum.  (Roughly equal proportions.  BTW,
the exotic metals would show up as a trace.  Might be some Pt, some
Ta, W, Ti, etc, but this shouldn't be a factor.)

The raw silicon wafers are *extremely* pure, and unfortunately,
extremely expensive.  OTOH, the industry scraps a fair amount of wafers,
and if you can get hold of scraps without metal on it, you've got a good
source of pure silicon.

Pete Brooks

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From: [email-masked] (PeterWRowe)
Date: 16 May 1996 01:37:35 -0400

In article <[email-masked]>, [email-masked] (Peter

>and if you can get hold of scraps without metal on it, you've got a good

And if the dopants and "junk" on top of the wafer bother you, then for
heavens sakes sand it off.  It's only a thin layer, and the material isn't
hard enough to bother a piece of wet/dry silicon carbide sanding paper. 
Just lay a sheet of perhaps 320 paper on a flat surface,  rub that chunk
of wafer across it a few times, and voila.  Your junked up surface is now
pretty cleared off...  Unlike the electronics boys, for adding silicon to
an alloy, you don't need a precision surface to the wafer...

       ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 
       Peter W. Rowe   M.F.A., G.G.
           Commercial and custom jeweler and metalsmith
                   Graduate Gemologist and Lapidary

Opinions expressed here are solely my own....... and subject to change    
according to my mood and the state of  my art ....

     No extra charge for smiles and friendship to those who return it
 'Cause life's too short and if we're not having fun, then why be here?
   ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

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From: "John R. Johnson" <[email-masked]>
Date: Thu, 16 May 1996 14:01:01 -0500

> an alloy, you don't need a precision surface to the wafer...

For what it is worth, even the heavily doped silicon after the process is
complete and the chip is scrapped as flawed, is closer to pure silicon 
that it was possible to measure 50  years ago!  I would love to go back in
time to 1948 and give Albert Einstein a $3.00 solar pocket type credit 
card sized calculator.  He would go CRAZY because all that stuff is 
happening in a piece of PURE SAND!  It HAS to be MAGIC.
(Note: the standard Science Fiction definition of Magic is "Technology
we don't yet understand!"
John

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From: [email-masked] (Kurt Rieder)
Date: 17 May 1996 01:39:20 GMT

PeterWRowe ([email-masked]) wrote:
: In article <[email-masked]>, [email-masked] (Peter
: Brooks) writes:
: >: Sure. But get the silicon from a metals supplier. Like someone who
: >: makes silicon bronze. A foundry. What's all this talk about melting
: >: down computer silicon chips to alloy with silver! Who knows what
: >: exactly is in them!
: >The raw silicon wafers are *extremely* pure, and unfortunately,
: >extremely expensive.  OTOH, the industry scraps a fair amount of wafers,
: >and if you can get hold of scraps without metal on it, you've got a good
: >source of pure silicon.
: >Pete Brooks

: And if the dopants and "junk" on top of the wafer bother you, then for
: heavens sakes sand it off.  It's only a thin layer, and the material isn't
: hard enough to bother a piece of wet/dry silicon carbide sanding paper. 
: Just lay a sheet of perhaps 320 paper on a flat surface,  rub that chunk
: of wafer across it a few times, and voila.  Your junked up surface is now
: pretty cleared off...  Unlike the electronics boys, for adding silicon to
: an alloy, you don't need a precision surface to the wafer...

Nobody has yet said what this exotic silicon wafer scrap costs.  You should
be able to buy virgin silicon metal for well under $1 per lb.  Why fool with
expensive electronic scrap ?  The guy who was making the silver alloy is
only adding 1%... purity is not at all an issue.

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From: [email-masked] (Peter Brooks)
Date: 20 May 1996 20:33:05 GMT

Kurt Rieder ([email-masked]) wrote:

: Nobody has yet said what this exotic silicon wafer scrap costs.  You should
: be able to buy virgin silicon metal for well under $1 per lb.  Why fool with
: expensive electronic scrap ?  The guy who was making the silver alloy is
: only adding 1%... purity is not at all an issue.

Well, we ordinarily never sell our scrap--it goes to the dumpster.  If
you are willing to do a bit of dumpster-diving, *or* if you have some
friends in the industry, you should be able to beat $1 per pound, especially if
all you need is 1% of your silver stock.  

Note that in the local (silicon valley) area, some outfits tend to be
pretty testy about dumpster divers.  OTOH, if you know an engineer or
low level manager/supervisor type, you can probably get a small stash for
the asking.  However, *don't* ask for junk wafers by product type....

Pete Brooks

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From: [email-masked] (Brian Adam)
Date: Mon, 20 May 1996 05:05:40 GMT

On 15 May 1996 00:40:30 GMT, [email-masked] (Peter Brooks) said:

>:...What's all this talk about melting

>range.  

Thanks. It's starting to make sense, then. Stiil, my source is a
foundry and the silicon I get from them is in chunk form, easily
broken up with a hammer to get small pieces. $14/kilo does me for a
while. I've saved the comments on this thread in case I ever need to
know. Thanks.
Brian

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From: [email-masked] (Neal E. Winters)
Date: Tue, 21 May 1996 03:38:45 GMT

A Little Zinc  helps the flow and leeps it white.