Contribution of EBSD for the Microstructural Study of Archaeological Iron Alloy Artefacts from the Archaeological Site of Loiola (Biscay, Northern Spain)
Céline Rémazeilles,
Maria Cruz Zuluaga,
Haizea Portillo-Blanco,
Egle Conforto,
Abdelali Oudriss,
Luis Àngel Ortega,
Ainhoa Alonso-Olazabal,
Juan José Cepeda-Ocampo
Affiliations
Céline Rémazeilles
Laboratory of Engineering Sciences for the Environment (LaSIE), UMR 7356 CNRS, La Rochelle University, Avenue Michel Crépeau, F-17042 La Rochelle Cedex 01, France
Maria Cruz Zuluaga
Department of Geology, Faculty of Science and Technology, University of the Basque Country (UPV/EHU), Sarriena s/n, E-48940 Leioa, Spain
Haizea Portillo-Blanco
Department of Geology, Faculty of Science and Technology, University of the Basque Country (UPV/EHU), Sarriena s/n, E-48940 Leioa, Spain
Egle Conforto
Laboratory of Engineering Sciences for the Environment (LaSIE), UMR 7356 CNRS, La Rochelle University, Avenue Michel Crépeau, F-17042 La Rochelle Cedex 01, France
Abdelali Oudriss
Laboratory of Engineering Sciences for the Environment (LaSIE), UMR 7356 CNRS, La Rochelle University, Avenue Michel Crépeau, F-17042 La Rochelle Cedex 01, France
Luis Àngel Ortega
Department of Geology, Faculty of Science and Technology, University of the Basque Country (UPV/EHU), Sarriena s/n, E-48940 Leioa, Spain
Ainhoa Alonso-Olazabal
Department of Geology, Faculty of Science and Technology, University of the Basque Country (UPV/EHU), Sarriena s/n, E-48940 Leioa, Spain
Juan José Cepeda-Ocampo
Department of Historical Sciences, Faculty of Philosophy and Letters, University of Cantabria, E-39005 Santander, Spain
Iron palaeometallurgy was carried out on three artefacts, classified as nails and excavated from the archaeological site of Loiola (La Arboleda, Biscay, northern Spain), to investigate Roman manufacturing techniques. Energy Dispersive Spectroscopy (EDS) coupled with Environmental Scanning Electron Microscopy (ESEM) and micro-Raman spectroscopy were used to obtain elemental composition and structural characterization of mineral phases. Metallurgical properties and crystallographic texture were studied by combining microscopic methods such as optical microscopy (OM), Electron Backscatter Diffraction realized in environmental mode (EBSD) and measurements of local Vickers microhardness. The three artefacts had different microstructures, distinguished by a large gradient of carbon content, although important segregations (inclusions) were observed in all of them. Two pearlite-rich artefacts showed a high density of structural defects (geometrically necessary dislocations and large crystallographic orientation gradients in pearlitic ferrite, curved pearlitic cementite) resulting from a high level of plastic deformation that occurred during the manufacturing process. The third artefact consisted of pure ferrite without structural defects. This one was clearly manufactured differently from the two others, so it probably had another functionality.
