Composition and microstructure of Roman metallic artefacts of Southwestern Iberian Peninsula (original) (raw)
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Materials Science Forum, 2010
This study concerns the elemental and microstructural characterization of proto-historic bronze rings from the southwestern Iberian Peninsula. Micro-EDXRF analyses demonstrate that the artifacts are binary bronze alloys (8-13% Sn) with arsenic and lead as the major impurities. Optical microscopy and SEM-EDS allowed the identification of common inclusions (e.g. copper sulphides) and alteration processes (redeposited copper, intergranular and intragranular corrosion). Microstructures consisting of fine dendrites, coarse and/or equiaxial grains were also identified, as well as the presence of (α+δ) eutectoid, deformed inclusions, twinned grains and/or slip bands. The combination of these characteristics allowed establishing the metallurgical procedures (casting, forging and annealing) used in the production of the bronze rings. The identification of different thermomechanical operational sequences indicates that the metallurgical knowledge was well established in the southwestern Iberian Peninsula during those ancient times.
Early technologies for metal production in the Iberian Peninsula
Materials and Manufacturing Processes, 2017
This paper focuses on the characterization of technological processes used for producing copper, tin-bronze and silver in the Prehistory and Protohistory of the Iberian Peninsula. To this purpose, slags and slaggy materials have been analyzed by optical microscopy (OM) and scanning electron microscopy (SEM-EDS). In particular, the results obtained allow us to characterize the main technological features for smelting copper ores since the 3 rd millennium BCE, a process that was performed in simple fire structures by using a non-slagging process. Regarding tin-bronze, the analytical data suggest that prehistoric bronzes were obtained by co-smelting copper and tin oxidic ores or by cementation of copper with cassiterite. Finally, some metallurgical debris dated to the Phoenician time, in the early 1 st millennium BCE, points to the extraction of silver from argentiferous copper ores employing a method similar to the 15 th century liquation process. This is a unique discovery up to now as this type of materials is unknown in any other Mediterranean region settled by the Phoenicians.
Journal of Archaeological Science, 2013
Archaeological works at Entre Águas 5 (Portugal) uncovered a seasonal LBA settlement with significant metallurgical remains (crucibles, moulds, prills and a tuyere) related to bronze production. Radiocarbon dating ascribes an occupation period (10the9th century BC) previous to Phoenician establishment in Southwestern Iberia. In spite of the proliferation of metal artefacts during LBA, the production of bronze alloys is still poorly understood. An integrated analytical approach (EDXRF, optical microscopy, SEMeEDS, micro-EDXRF and Vickers microhardness) was used to characterise this metallurgy. Crucibles show immature slags with copious copper nodules, displaying variable tin content (c. 0e26 wt.%), low iron amount (<0.05 wt.%) and different cooling rates. Certain evidences point to direct reduction of oxide copper ores with cassiterite. Scorched moulds with residues of copper and tin indicate local casting of artefacts. Finished artefacts also recovered at the site have an analogous composition (bronze with w10 wt.% Sn and low amounts of Pb, As and Fe) typical of coeval metallurgy in SW Iberia. Some artefacts reveal a relationship between typology and composition or manufacture: a higher tin content for a golden coloured ring or absence of the final hammering for a bracelet. An uncommon gilded nail (gold foil c. 140 mm thick; 11.6 wt.% Ag; w1 wt.% Cu) attests the existence of evolved prestige typologies. This LBA settlement discloses a domestic metallurgy whose main features are typical in Iberian Peninsula. Finally, it should be emphasized that a collection as comprehensive and representative of a single workshop has rarely been studied, enabling a deeper understanding of the various operations involving the bronze production and manufacture of artefacts.
Heritage, weathering …, 2006
atice metal was recognized as a new material in prehistorical times metallic artifacts began to be made and the metallurgical skills started to develop. Metallurgical scraps found in archaeological sites normally evidence metallurgical production of artifacts in situo Studies of metal scraps can reveal the different stages ofthenno-mechanical treatments that the artifacts were subjected to in arder to obtain a selected shape and hardness. While for metal artifacts sample taking can be problematic, sample taking in metallurgical scraps can be easier since scraps have nonnally no artistic/esthetical display value. Additionally, corrosion phenomena can be evaluated in scraps that frequently have not been subjected to any conservation treatment. This paper deals with metallographic (optical and electron microscopy), EDS-SEM and EDXRF studies that have been undertaken in correr based metallurgical bars of circular and square sections from Santa Luzia site, in central Portugal.
This paper focuses on the study of a group of metal artefacts recently recovered during the archaeological excavations in Vila do Touro (Central Portugal), i.e., 19 artefacts and a small metallic inclusion embedded in a pottery sherd. The objects have been analysed by an X-Ray Fluorescence spectrometer to characterise the elemental composition of metal artefacts. A Scanning Electron Microscope with X-ray Microanalysis System and an optical microscope were used to observe and chemically characterise the metal inclusion in the pottery. The fragment of an ingot was also analysed by a multicollector Inductively coupled plasma mass spectrometer to address issues bound to the provenance of raw material. The results revealed different compositional patterns (pure copper, binary bronze, i.e., Cu+Sn, leaded bronzes, i.e., Cu+Sn+Pb, and gold), while pointing out the Ossa Morena region (Southwest of the Iberian Peninsula) as likely source of copper used to produce the ingot.
STAR: Science & Technology of Archaeological Research
An analytical study is presented, aimed to determine the elemental composition of copperbased artefacts dated back from Copper Age to Early Iron Age (mid-fourth millennium to the VIIIth century B.C.), found on the Tyrrhenian side of the peninsula, corresponding to the Lazio region. The objects belong to different archaeological contexts and had various functions. They were analysed by the X-ray fluorescence technique. The results highlight the experimental character of Copper Age metallurgy, which will later evolve in the established use of copper-tin alloys. Regarding the Bronze Age, despite the typological and functional heterogeneity of the artefacts and the wide chronological range, the alloys are relatively homogeneous in composition, with regular changes that appear related to chronology, according to what is already known for the Italian peninsula. Such changes are supposedly due to variations in the availability of tin, which was not locally mined. Early Iron Age metallurgy is represented by the Selvicciola Hoard solely, which restricts the possibility of generalizing the conclusions. A striking feature of the alloys is the great compositional difference between the complete and the fragmented artefacts. The formers are made of tin bronze, whereas in the latter tin is replaced by antimony and/or lead. The use of such unusual alloys is unlikely due to lack of metallurgical knowledge. Considering the urbanized communities that arose in the Middle-Tyrrhenian area during the Early Iron Age, we suppose that such variability in a single context might be related to a production system capable of using alloys of different quality and value to satisfy a diversified demand.
Journal of Archaeological Science: Reports, 2016
The hoard from Coles de Samuel is one of the largest Cu-based metal collections from the Late Bronze Age (LBA) (13th-8th centuries BC) ever found in Central Portugal, consisting of 18 artefacts which typologically display a strong regional identity. In the present study, an integrated multi-analytical approach combining Energy Dispersive X-Ray Fluorescence (EDXRF) analysis, Optical Microscopy (OM) and Scanning Electron Microscopy with Energy Dispersive X-ray spectroscopy (SEM-EDS) has been used to characterise the artefacts both from a chemical and microstructural point of view with the aim to unravel their elemental composition and technological features. Results show that all artefacts are made of binary bronze (Cu-Sn) alloys, with a Sn content in the range of 8.7 ± 0.9 and 13.0 ± 1.0 wt%, with minor elements (Pb, As and Fe) never exceeding 1.1 wt% in total. The microstructure of the vast majority of the metal objects (13 out of 18) shows the presence of equiaxial α-copper grains with annealing twins and slip bands suggesting that, in the manufacturing process, they were subjected to forging plus annealing cycles. The remains of the objects present an as-cast microstructure constituted by dendritic structures, suggesting that metals did not suffer any thermo-mechanical operation after being removed from the mould. Pb, Ag and Au-rich globules together with Cu-S and unalloyed Cu-inclusions have been observed as well, resulting from impurities from ores. The typological characterisation of these metals and their archaeometallurgical data are consistent with an indigenous LBA Iberian metallurgical production supporting the hypothesis of a regional/local production and use of the artefacts from Coles de Samuel.