Tarnish resistant low gold and low palladium yellow jewelry alloys with enhanced castability

Abstract

A boron-free, low-gold, and low-palladium metal alloy composition formulated to provide an alloy with an attractive yellow color, improved tarnish resistance, and enhanced castability. In certain implementations, the alloy contains gold, silver, copper, palladium and indium. The alloy preferably contains less than 25% by weight gold and the weight percent ratio of silver to copper is between 0.65 and 2.65 and the weight percent ratio of palladium to indium is between 1 and 5.

1 . An alloy composition consisting essentially of about 1%-25% by weight gold, about 15%-51% by weight silver, about 2%-9% by weight palladium, about 0.5%-7% by weight indium, about 0.5%-10% by weight zinc, about 0.1%-10% by weight tin, about 0.1%-5% by weight gallium, about 0%-5% by weight platinum, about 0%-1% by weight silicon, and balance copper, wherein said alloy composition has a copper to silver ratio of between 0.65 and 2.65 and a palladium to indium ratio of between 1 and 5. 
   
   
       2 . The alloy composition of  claim 1 , wherein the composition consists essentially of about 5% by weight gold, about 51% by weight silver, about 4% by weight palladium, about 1.4% by weight indium, about 0.1% by weight platinum, about 0.5% by weight zinc, about 34.13% by weight copper, about 3.75% by weight tin, about 0.02% by weight silicon, and about 0.1% by weight gallium. 
   
   
       3 . The alloy composition of  claim 1 , wherein the composition consists essentially of about 5% by weight gold, about 30% by weight silver, about 7% by weight palladium, about 1.4% by weight indium, about 0.1% by weight platinum, about 0.85% by weight zinc, about 50.78% weight copper, about 4.75% by weight tin, about 0.02% weight silicon, and about 0.1% by weight gallium. 
   
   
       4 . The alloy composition of  claim 1 , wherein the composition consists essentially of about 10% by weight gold, about 35% by weight silver, about 7% by weight palladium, about 7% by weight indium, about 7% by weight zinc, about 33.8% by weight copper, about 0.1% by weight tin, and about 0.1% by weight gallium. 
   
   
       5 . The alloy composition of  claim 1 , wherein the composition consisting essentially of about 15% by weight gold, about 22% by weight silver, about 7% by weight palladium, about 5% by weight indium, about 5.5% by weight zinc, about 45.1% by weight copper, about 0.1% by weight tin, and about 0.3% by weight gallium. 
   
   
       6 . The alloy composition of  claim 1 , wherein the composition consists essentially of about 19% by weight gold, about 17% by weight silver, about 8% by weight palladium, about 5% by weight indium, about 5.5% by weight zinc, about 44.9% by weight copper, about 0.1 % by weight tin, and about 0.5% by weight gallium. 
   
   
       7 . The alloy composition of  claim 1 , wherein the composition consists essentially of about 20% by weight gold, about 25% by weight silver, about 6.5% by weight palladium, about 3.75% by weight indium, about 1.25% by weight zinc, about 38.4% by weight copper, about 5% by weight tin, and about 0.1% by weight gallium. 
   
   
       8 . An alloy composition consisting essentially of about 1%-25% by weight gold, about 15%-51% by weight silver, about 2%-9% by weight palladium, about 0.5%-7% by weight indium, about 0.5%-10% by weight zinc, about 0.1%-10% by weight tin, about 0.1%-5% by weight gallium, about 0.1%-5% by weight platinum, about 0.1%-1% by weight silicon, and balance copper. 
   
   
       9 . A boron-free alloy composition, said composition comprises gold, silver, copper, palladium, and indium, wherein the weight percent ratio of copper to silver is between 0.65 and 2.65 and the weight percent ratio of palladium to indium is between 1 and 5.