An Ancient Bronze Ingot Smelted from Fahlore

Abstract:

A bronze bun ingot fragment, produced in an ancient furnace, was investigated. The original surface was craggy and covered by a dark green “layer” of corrosion products and at the intersection shrink holes are visible. X-ray fluorescence analysis confirms Cu as balance, up to 4 wt.% As respectively 2.5 wt.% S and smaller amounts of Sb, Ni, Fe, Ag were measured. This composition suggests that fahlores were processed. An inhomogeneous microstructure was observed over the cross section of the ingot caused by the alloying elements and their segregation during solidification of the melt. The microstructure is dominated by copper dendrites and the interdendritic regions are enriched with the residual alloying elements which form precipitates. Near the ingot surface large oxide crystals were observed indicating oxide formation during the solidification of the melt. Another kind of fine-grained oxides were identified which are formed potentially by corrosion. We can conclude that the ingot is arsenic bronze with quite a complex microstructure.

• Periodical: Materials Science Forum (Volume 891)
• Pages: 613-617
• DOI: https://doi.org/10.4028/www.scientific.net/MSF.891.613
• Online since: March 2017
• Authors: Florian Ertl, Susanne Strobl*, Roland Haubner
• Keywords: Arsenic Bronze, Bronze Ingot, Fahlore

References

[1] R. Krause, The beginning of metal ages, in: Archäologie in Württemberg, D. Plank (Ed. ), (1988) 111-139, Theiss, Stuttgart (in German).

[2] R.F. Tylecote, A History of Metallurgy, The Metals Society, Mid County Press London (1976) 5-28.

[3] M. Junk, Material properties of copper alloys containing arsenic, antimony, and bismuth - The material of Early Bronze Age ingot torques, Doctoral Thesis (2003) TU Bergakademie Freiberg.

[4] J. Konieczny, L. Kondziolka, I. Mlodkowska-Przepiórowska, The investigation of microstructure and hardness of archaeological alloys, J. of Achievements in Materials and Manufacturing Engineering 49 (2011) 166-179.

[5] P. Valério, A.M. Monge Soares, M.F. Araújo, R.J.C. Silva, E. Porfírio, M. Serra, Arsenical copper and bronze in Middle Bronze Age burial sites of southern Portugal: the first bronzes in Southwestern Iberia, Journal of Archaeological Science 42 (2014).

DOI: 10.1016/j.jas.2013.10.039

[6] G.F. Vander Voort: Metallography - Principles and Practice. ASM International, 3rd printing, (2004).

[7] T.B. Massalski, Binary Alloy Phase Diagrams, ASM International (1990) Metals Park OH.

[8] H. Schumann, Metallographie, VEB Deutscher Verlag für Grundstoffindustrie (1967) Leipzig.