Phase equilibria have been used to construct a simplified model of 14 karat (14K) yellow jewelry alloys. In this model, silicon has a reduced solubility in solid 14K (Au-Cu-Ag-Zn) alloys compared to its solubility in pure copper. This reduced solubility results in low values of the partition coefficient for silicon in these alloys. The microsegregation of silicon in 14K yellow gold jewelry casting alloys was evaluated based on the principles of non-equilibrium solidification. The dynamics of non-equilibrium freezing described by the Gulliver-Scheil equation predict the build-up of silicon in the liquid phase to such an extent that unexpected, silicon-rich phases and compounds may appear in the solidification structure. These phases can have deleterious effects on mechanical properties and limit the use of certain types of grain refiners in (Au-Cu-Ag-Zn) families of alloys. The practical limits of silicon levels in 14K yellow gold alloys which do not allow the formation of Cu-Si intermetallics are estimated.
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