Microscopic and microstructural study of arsenic copper from Spidej of Bazman (original) (raw)

Undoubtedly, one of the most important man-made objects in history is copper objects and their alloys, and in this regard, according to the available evidence, its oldest alloy, as copper-arsenic, has an important role in history. The existence of these works in various sites, especially in southeastern Iran since the Early Bronze Age, confirms this claim. One of the most significant strategic sites is located in the southeastern of Iran, is Spidezh. It is one of the most important settlement centers belonging to the third and second millennium BC, which is located 40 km southwest of Bazman. The site is located 3 km from Makhsan village and about 160 km from Iranshahr. Significant artifacts were brought to light from Spidezh cemetery such as stamps, ornaments (beads, pins, kohl holder pin, mirrors), agricultural tools, different types of weapons, etc. Spidezh registered under the number 6745 in the list of national monuments of Iran. In this study, a number of metal objects in Spidezh cemetery were examined to identify copper-arsenic compounds and the properties of this alloy. To study these objects, the SEM-EDS method was used to identify the microstructure of the metal matrix and the chemical composition of the elements, as well as the metallographic method to study the fabrication technique and phases studies. SEM-EDX analysis shows that some objects are made of Cu-As-Zn alloy and others are made of Cu-As alloy by casting and are considered as arsenic-containing bronze alloys. Arsenic acts as an excellent oxidant element in metal, reducing the porosity of the alloy and significantly increasing its hardness. Deliberate addition of low levels of arsenic can act as a dioxin in the samples. Also, the presence of sulfide in the impurities of these objects can be due to the use of sulfide ores. The amount of calcium and potassium in the EDS spot analysis of the inclusions indicates that this amount of elements is owing to coal fuel. These elements are considered as flux charge melt and eventually absorb the slag. The SEM images suggest that the impurities in the whole matrix of the metal in a point and elongated from can be the reason for the presence of unrefined copper with spiess in the process of making these works. This discarded waste contains sulfide, arsenide and iron-like compounds. The uniform and high percentage of 5% arsenic in these works shows that the manufacturing process of these alloys has been done by Co-Smelting method. Metallographic studies show that the physical operation on these works was a repetition of a cycle of cold work and annealing (irradiation) to further shape these works.