Archaeometallurgical characterization of a late Iron Age helmet

V magistrskem delu so predstavljene raziskave čelade, ki je najdena bila v novoodkritem pokopališču Pezdirčeva njiva, v kraju Podzemelj. Pokopališče sega v pozno Halštatsko obdobje oziroma pozno železno dobo (500–200 let pr. n. št.). Za čelado lahko menimo, da je ena najpomembnejših arheoloških najdb zadnjih let v Sloveniji, v svetu pa je najdenih le okoli 120 čelad. Namen dela je bila karakterizacija mikrostrukture, podrobna analiza kemijske sestave vzorcev iz različnih delov čelade in ugotovitev predvidene poti izdelave. Pri takih najdbah morajo biti vzorci vzeti z veliko previdnosti in na čim manj opaznih mestih. Vzorce se je analiziralo na vrstičnem elektronskem mikroskopu (SEM), Kemijska analiza pa je bila opravljena s pomočjo energijsko disperzijske spektroskopije (EDS). Preiskave so potekale tako na območju kovinske osnove kot območju na robu, kjer je prisotna oksidna plast. Dodatno se je izvedla še analiza z uklonom povratno sipanih elektronov (EBSD) za ugotavljanje orientacije in velikosti zrn. V drugem delu smo na podlagi rezultatov kemijske sestave delcev čelade izdelali zlitino, ki smo jo nato ročno kovali po različnih protokolih. Vzorce kovanja se je analiziralo s svetlobnim mikroskopom. Rezultati kažejo, da je kovinska osnova bronaste čelade sestavljena iz ena faze bakra in kositra, prisotni pa so tudi podolgovati vključki PbS. V mikrostrukturi opazimo dvojčične meje in drsne pasove, kar skupaj z vključki nakazuje na precejšno deformacijo pri izdelavi. Oksidna plast je neenakomerna in je debelejša na zunanji strani, kjer je prisotna tudi zemlja. Iz primerjave rezultatov kovanja z analizo najdene čelade, lahko sklepamo, da se je ta izdelala z izmeničnim hladnim kovanjem in žarjenjem.The master\u27s thesis presents the research of a helmet found in the newly discovered cemetery of Pezdirčeva njiva, in Podzemelj. The cemetery dates to the Late Hallstatt period or the Late Iron Age (500–200 years BC). The helmet can be considered one of the most important archaeological finds of recent years in Slovenia, while only about 120 helmets have been found in the world. The aim of the work was to characterise the microstructure, to analyse in detail the chemical composition of the samples from different parts of the helmet and to identify the intended manufacturing route. In such finds, samples must be taken with great care and in the least conspicuous places possible. The samples were imaged on a scanning electron microscope (SEM) and chemical analysis was carried out by energy dispersive spectroscopy (EDS). Investigations were carried out both in the metallic base area and in the area at the edge where the oxide layer is present. In addition, electron backscatter diffraction (EBSD) was carried out to determine grain orientation and size. In the second part, results of the chemical composition of the helmet particles were used to produce an alloy, which was then hand forged using different protocols. The forged bar samples were imaged using a light microscope. The results show that the metallic base of the bronze helmet consists of a single phase of copper and tin, with elongated PbS inclusions. The microstructure shows twin boundaries and slip lines, which, together with the inclusions, indicate significant deformation during manufacturing. The oxide layer is uneven and is thicker on the outside, where soil is also present. Comparing the results of the forging with the analysis of the helmet found, it can be concluded that the helmet was made by alternating cold forging and annealing