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How to make 14K gold alloy less brittle?


#1

I made a 14K gold alloy with:

60% gold
22% silver
15% copper
3% brass

It gives the desired color, but the alloy is too brittle.
What can be done to make it less brittle while preserving the color?

Thanks,
Chung


#2

Why put the brass in? You are, in effect, adding more copper and
then some zinc. I’d wager that the zinc is making things brittle.
In my limited knowledge of metalurgy, zinc is usually added to lower
the melting point of an alloy (consider solder). Try leaving it out.

Other problems might have to do with the WAY that you’re pouring or
casting it, rather than the ingredients themselves. Good luck.

Andy cooperman


#3

Replace the brass with zinc. Jeffrey Everett


#4
 Replace the brass with zinc. 

Jeffery, brass is copper plus zinc, unless you’re talking about a
leaded free machining brass (which certainly would make for brittle
gold). If you simply replace the brass with zinc, you’re reducing
copper and increasing zinc. That won’t improve problems with
brittleness, as the zinc doesn’t particularly reduce brittleness.
it’s there as a deoxidizer, reducing oxides and porosity, but more
than the small amount needed to do that just makes the gold alloy
paler in color, lower melting, and not quite as ductile/malleable.
And because of the dramatic differences in melting point between gold
alloys and zinc, the easiest way to add zinc as a deoxidizer to gold
alloys is to add it in the form of a copper/zinc alloy, which of
course is brass. (I’m repeating myself, I know… :slight_smile: )

So I’d guess the problem is not with brass itself, but perhaps with
the TYPE of brass, or with some other contaminating factor.

Now, if the brass in question is actually a bronze, copper and tin,
then getting rid of that would make the metal dramatically better,
since tin is not so good for gold alloys…

cheers
Peter


#5
    Why put the brass in?  You are, in effect, adding more copper
and then some zinc.  I'd wager that the zinc is making things
brittle. In my limited knowledge of metalurgy, zinc is usually
added to lower the melting point of an alloy (consider solder). 
Try leaving it out. 

Zinc is added as a deoxidizer because copper absorbs oxygen like
crazy in its molten state.

Jeffrey Everett