[Jewelry making - Article 00514] - Re: [Orchid] Granulation Chemistry?

[James Binnion]

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    It is not really eutectic bonding it is liquid phase diffusion
    welding. The presence of a eutectic alloy is not required for
    granulation. You can granulate fine gold, and  gold and copper do
    not form a eutectic alloy. All that is happening is a small amount
    of copper is diffusing into the surface of the gold and for a brief
    moment the surfaces become liquid due to the high local
    concentration of copper which creates a lower melting point alloy on
    the surface as compared to the bulk metal. This local melting fuses
    the granules to the surface. 

    Keum-boo is not the same thing at all in that no melting occurs.  It
    is a form of solid state diffusion welding. Because there are no (or
    very few) oxides present when you burnish the gold foil onto the
    fine silver surface the molecules actually diffuse together into new
    crystals due to the application of heat and pressure. If the
    surfaces were absolutely clean and oxide free you could make them
    stick together at room temperature with only pressure from the
    burnisher. 


Jim
James Binnion Metal Arts
Phone (360) 756-6550
Toll Free (877) 408 7287
Fax (360) 756-2160
http://www.mokume-gane.com
jbin AT mokume-gane.com
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