Neutron scattering material analysis of Bronze Age metal artefacts

Non-destructive characterization of bronze artefacts from archaeological finds of the 'Terramare'dwellings near Modena, Italy, was carried out by time-of-flight neutron scattering at the ISIS spallation neutron source of the Rutherford Appleton Laboratory, UK. This provides information on ancient metal technology and its development through the Bronze Age in that region. Six pieces from three different classes as to use and manufacture, from the Middle to Late Bronze Age, were investigated on the ROTAX and GEM beam lines at ISIS, providing a comparison between results from the two instruments. A comparison is also made with three axes of the same area of provenance (Emilia, Terramare culture) from the Early, Middle and Late Bronze Age respectively, analysed previously. Data collected provide stable refinements of the phase fractions and lattice parameters by the Rietveld method, allowing determination of Sn contents from the unit cell expansion due to the incorporation of Sn into the Cu-type alpha-phase. Notably, two of the objects exhibit a range of Sn contents in the bulk as is evident from broad diffraction peaks (4-8 and 10-14 wt% Sn), while the other four artefacts have more defined Sn contents of 8, 9, 10 and 14.5 wt% respectively. The higher Sn weight fractions are associated with the presence of pure unalloyed Cu, interestingly coexisting in one case with two bronze phases (alpha and the eutectoid delta). One sample shows the presence of 2-3 wt% Pb. Varying amounts of oxidation products such as cuprite were identified. Texture information extracted from the diffraction data provided some indications of different working treatments of the analysed objects.