Copper Test Melts with Additions of Pb, Bi, As, Sb and Sn

Abstract

Archaeometallurgical copper-artefacts contain a wide variety of metal admixtures (e.g. Pb, Bi, As, Sb, Sn) which either originate from the ores or were intentionally added. When the melt solidifies, these elements can accumulate in different structural areas and form special phases. The different alloying elements also interact with each other. In order to be able to examine these interactions, model alloys with different elements (Pb, Bi, As, Sb, Sn) and concentrations (5 or 10 wt.% each) were produced. More simple alloys show a dendritic microstructure and the added elements accumulate in the interdendritic areas. This is clearly visible for Pb and Bi additions, as both metals are not soluble in copper. As and Sb form compounds with Cu which precipitate mainly in the interdendritic regions. Sn is soluble in Cu at lower concentrations and Cu-Sn phases are formed only at higher concentrations. The resulting microstructures become very complex if more elements are involved. Finally, they enable us to have a better understanding for microstructures of ancient copper alloys.