Tailored analytical strategies for theinvestigation of metallic artefacts from theAyanis Fortress in Turkey

A noteworthy number of metallic artefacts dating back to 673-645 BC have been found during excavations in the Ayanis Fortress, near the lake of Van. They are large bronze shields, quivers, helmets, arrows and plates, some of which are decorated with cuneiform inscriptions, and demonstrate a high-level quality of technological competence reached by the ancient craftsmen of Ayanis during the reign of King Rusa II. The artefacts have been studied from a microchemical, micromorphological and microstructural point of view by means of different techniques, from optical microscopy to scanning electron microscopy (SEM), to X-ray diffraction. Microchemical and microstructural investigations showed metallurgical features of the bronze artefacts and of the corrosion products' layered structures that can be explained in terms of manufacturing processes (repeated cycles of mechanical work and annealing thermal treatments) and environmental context (presence of high amounts of chlorides in the soil that preferentially attack the bronze along the grain boundaries). In particular, the repeated cycles of mechanical work and annealing thermal treatments were carried out to restore the ductility and the malleability of the alloy, thus inducing the crystallisation and the growth of flattened grains as well as impurities segregation phenomena along grain boundaries