Investigations of microstructural changes in tin bronzes during cremation

Abstract

For many centuries, cremations were common and the ashes were buried in urns. During the late Bronze Age (ca. 1300–800 BC), cremations took place in Inzersdorf ob der Traisen as well. Thus, bronze artefacts in the urns were heat-treated. By experimental archaeology, cremations could be recreated and various microstructural changes in the bronze could be identified. For comparison, ancient bronze artefacts from Inzersdorf ob der Traisen were examined and similar structural changes to those found in experimental cremations were detected. In order to obtain more precise information about the effects of heat treatment, bronze sheets containing 10 wt.% Sn were annealed in a laboratory furnace at different temperatures and for different times. The heat-treated sheets were examined by metallography, light optical microscope (LOM) and scanning electron microscope (SEM) with energy-dispersive X-ray analysis (EDX). The newly formed microstructures, produced by these experiments, will be compared with those of ancient artefacts as well as those from the experimental archaeology samples. It was found that up to 500 °C no visible changes in the bronze structure occurred. At about 800 °C recrystallization of the bronze occurred. First melting occurred at 950 °C, which was even more pronounced at 1000 °C.