Micro-structural and micro-chemical investigation of Samnite high-tin bronze cuirass discs: ancient metallurgy in central Italy

Abstract

In the present study, micro-structural and micro-chemical investigation of archaeological bronze artefacts provided new insight about the metallurgical manufacture of defensive weapons by the Samnite’s metalsmiths in central Italy from the archaic necropolis of Barrea (AQ) and Torrebruna (CH). In particular, the metallurgical features, the chemical composition and the manufacturing process of Cu-based high-tin alloys used to produce cuirass discs were investigated. These artifacts were used to protect the warrior’s heart (i.e. the kardiophylaches) but were also and more importantly a distinctive sign of rank and role of warriors of the archaic age (VI BC). The Samnite cuirass discs are multi-material artifacts made of a decorated bronze central part with a complex metallurgical structure, due to the presence of different Cu-Sn phases, and a surrounding iron cladding to support the disk. These discs were studied by different surface and bulk techniques, namely Optical Microscopy (OM), Field Emission Scanning Electron Microscopy coupled with energy dispersive X-ray microanalysis (FE-SEM-EDS), X-ray Diffraction (XRD) and Infrared Spectroscopy (FTIR). The combined use of these techniques proved the high technological level of the Samnite metallurgists. In fact, their particular composition, having an uncommon high content of tin, made their manufacturing process difficult because of the intrinsic brittleness of the alloy. This work disclose the ability of Samnites people to successfully manipulate fragile high tin bronze alloys by inducing temporary phase changes and, thus, facilitating the mechanical shaping of the artifact.