A gold-copper alloy is an alloy that is made up of copper atoms and gold atoms. These alloys have less distinctive characteristics than those of the silver-copper series. But their brittleness is similar to the silver-copper series.
Copper-gold alloys are used in jewelry. Plating of a barrier layer between the two metals is necessary to prevent corrosion products from copper from covering the gold surface.
In addition, small amounts of copper are soluble in gold. However, the resulting alloy is not as easy to detect. The melting point of the alloy is much lower than the melting point of the pure elements.
It is possible to study the synthesis of colloidal gold-copper nanoparticles using time-resolved X-ray absorption spectroscopy. These results have led to a better understanding of the processes involved in alloy formation.
In the case of Au-Cu, the bulk has a melting point well below that of the pure metals. At temperatures above that, the alloy forms the crystalline phase of AuCu3 (L12).
Moreover, the alloy is characterized by a face-centred lattice. Gold atoms may segregate on any of the four lattices. Each crystal will have many nuclei and will follow a systematic scheme of order.
Assays of the alloy were performed on pieces cut from the plates. The limit of error was reduced to 0’02 per 1000 on a mean of three assays.
Compared with gold, copper has a larger shape parameter. It is also more soluble in gold. Consequently, the proportion of copper to gold in the alloy varies with region.