Producing gold nugget simulants using copper alloys

Abstract

Today the imitations of gold nuggets are highly promising materials in conceptual jewelry design. The manufacturing technology of these materials is based on melted brass casting in a cooling liquid. The purpose of this research is to identify the most favorable technological processes to obtaining high-quality simulants of gold nuggets. The article presents the results of the experimental studies of CW508L brass. The most favorable technological parameters have been identified. They include the melt temperature up to 970±5 °C and use of water with the temperature not higher than 20–25 °C as a cooling liquid. Adherence to the specifications allows to obtain the casts, which superficially resemble natural gold nuggets found in alluvial gold deposits. The casts’ intricate shape and uneven relief providing this resemblance are due to the specific crystallization conditions of brass that differ from the crystallization conditions under conventional casting. The research involved the analysis of the chemical composition of the alloy samples before tests and the samples obtained after casting. After processing the alloy has featured an insignificant decrease in the zinc percentage, and an increase in the impurity content (silica, sulfur, iron, and chrome). The metallographic analysis of the initial sample of CW508L brass has shown a single-phase microstructure that is a solid solution of zinc substitution by copper. The similar study of the casts obtained in the experiment has shown the presence of a β-phase in their structure (along with an α solid solution) that is a CuZn-based solid solution having a positive effect on brass mechanical properties. This microstructure is typical of the alloys undergone accelerated cooling that qualitatively changes the process of melt converting into a solid substance.