Materials Science Forum Vol. 782

Abstract: At the late second and early third century coin copies, termed subferrata, were produced in the provinces Noricum and Pannonia of the Roman Empire. Subferrata consist of an iron core, which was plated with a copper alloy. To get information about the manufacturing process and the materials used, coins were cut and investigated after metallographic preparation by light optical microscope (LOM). Scanning electron microscopy (SEM) and energy disperse X-ray analysis (EDX) were used to get information about the local chemical compositions. The general composition was determined by X-ray fluorescence analysis (RFA). The Cu alloy coatings consist of Cu, Pb, Sn, Zn and small amounts of Ag. This alloy is a variant of gunmetal, known as leaded red brass. The coatings show mainly differences in the Pb and Sn content and moreover the intermetallic phase Cu₄₁Sn₁₁ was found. Inside the red brass coating droplet-shaped iron inclusions were observed. Near the interface, between coating and iron core, Cu and Pb were detected at the grain boundaries (liquid metal embrittlement). Probably, the iron flan was plated by immersing in a molten copper alloy. In the ferritic-pearlitic iron core, slag inclusions and regions with various carbon contents were observed. Furthermore, deformation twins (Neumann lines) were found in the Fe core ́s microstructure, leading to the suggestion that coining was performed after cooling the flan.

Abstract: Slags from three iron smelting and processing sites were investigated. The composition of the slags is connected to the metallurgical processes and the investigation should provide an indication of the process conditions.A slag from a small bloomery furnace at the archaeological site Waschenberg (Hallstatt period) was investigated. Slags from the medieval period were found near Eisenerz and at this time iron was produced in developed bloomery furnaces (Stuckofen). These slags are termed fayalitic slags and they consist of wustite (FeO), fayalite (Fe₂SiO₄) and glass-phase (amorphous silicates) in various concentrations. Three solidification-types were described and correlated with the microstructures and the FeO-SiO₂-CaO₂ phase diagram.During the 19^th century steel was produced in puddling furnaces by remelting iron products from Eisenerz. Such slags, from this process, found in the surroundings of Palfau, were investigated and contain FeO and Ca rich glass-phase, but no fayalite.Due to the different compositions of the slags the solidification and the microstructures are different.

Abstract: Bloomery furnaces were the first units for iron smelting. In the Hallstatt period small bowl-type furnaces were used and until the medieval period the size of such furnaces was increasing continuously. Experimental archaeologists reconstruct bloomery furnaces to study the processes of bloom production. In a small bowl-type furnace (Hallstatt period) at Asparn and in a larger shaft-type furnace (medieval period) at Ybbsitz smelting experiments were performed, The samples contained metallic iron and slag. Various amounts of iron in different stages of conglomeration up to larger iron pieces were found. The slag belongs to a fayalitic-type, consisting of wustite (FeO), fayalite (Fe₂SiO₄) and glass-phase (amorphous Ca-, Al-silicates) in various concentrations. The yield of metallic iron was highly different for the various experiments. In general, more metallic iron was formed in the larger shaft-type furnaces. A large bloom was not obtained.

Abstract: The study deals with a material survey and determination of the corrosion character of a Roman bronze vessel from an early Tiberian period. The ancient technology of the bronze vessel production was determined based on the evaluation of structural properties of the material using the prepared metallographic sections. The vessel was produced by combining the technologies of beating and metal embossing in a pre-cast bronze piece, side ornaments were cast from bronze. Chloride anions were identified along the material grains. It was identified that the mixture of corrosion products covering the surface of the vessel contained, in addition to other elements, basic copper chloride. The presence of chloride anions, atmospheric humidity and mechanical stress lead to corrosion of the bronze vessel called the bronze disease. The material in the upper part of the vessels lost cohesion completely and the neck of the vessel broke as a result of the corrosion process. The vessel was desalinated and reconstructed in a relatively unique way. At present, the vessel is a property of the National Museum in Prague.