Casting Simulations of Arsenical Copper: New Insights into Prehistoric Metal Production and Materials
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https://doi.org/10.1007/s11837-020-04210-8 Ó 2020 The Minerals, Metals & Materials Society
ARCHAEOMATERIALS
Casting Simulations of Arsenical Copper: New Insights into Prehistoric Metal Production and Materials BENJAMIN J. SABATINI,1,2 ANDREAS CZIEGLER,3 ¨ DLINGER 4,5 and MARIANNE MO 1.—Department of Mechanical Engineering, College of Science and Engineering, Ritsumeikan University Biwako-Kusatsu Campus (BKC), E62 1-1-1, Nojihigashi, Kusatsu, Shiga 5258577, Japan. 2.—Department of Materials Science and Engineering, Massachusetts Institute of Technology, 13-5065, 77 Massachusetts Avenue, Cambridge, MA 02139-4307, USA. 3.—Lehrstuhl fu¨r Gießereikunde, Montanuniversita¨t Leoben, Franz-Josef-Strasse 18, 8700 Leoben, Austria. 4.—Dipartimento di Chimica e Chimica Industriale (DCCI), Universita` degli Studi di Genova, Genoa, Italy. 5.—e-mail: [email protected]
To improve our understanding of prehistoric casting methods and materials, simulations for copper arsenic (As-Cu) alloys with up to 15 wt.% As were calculated. Cooling curves and the secondary dendritic arm spacings (SDAS) for the alloy were plotted and calculated, respectively, under non-steady-state conditions with a time-stepping procedure for prehistoric mold materials (e.g., quartz sand, sandstone, terracotta, and steatite). The cooling and microstructure of the alloy was also simulated in iron molds for immediate comparison with as-cast microstructure. The microstructure and SDAS of the as-cast alloys were studied and measured in polished samples with a metallographic microscope. The purpose of this research was to improve our ability to retroactively evaluate the influence of mold materials on as-cast microstructures and determine their materials. This article focuses on As-Cu alloy microstructure and SDAS values, and also discusses the phenomenon of ‘‘inverse segregation’’ and its relation to cooling rate and As concentration.
A a c cm c0 cl D h k k0 fs m n t tf T T0 v
List of Symbols Mold metal interface (m2) Overall heat transmission coefficient (W m2 K1) Specific heat of the mold (J kg1 K1) Specific heat of the metal (J kg1 K1) Alloy concentration (wt.%) Concentration of the liquid phase (wt.%) Diffusion coefficient (m2 s1) Heat transfer coefficient (W m2 K1) Thermal conductivity of the mold (W m1 K1) Partition coefficient Mass fraction of solid phase Slope of the liquidus line (K wt.%1) Time-step sequence (103 s) Time (s) Local solidification time (s) Temperature of the metal (K) Ambient temperature of the mold (K) Volume of casting (m3)
DT DHf q qm C k
Solidification interval (K) Latent heat of fusion (J mol1) Density of the mold (kg m3) Density of the metal (kg m3) Gibbs–Thomson coefficient (K m) Secondary dendritic arm spacing (lm)
INTRODUCTION Arsenic-copper alloys have limited application, having long since been replaced by safer and more capable alloys beginning in antiquity. Despite their early obsolescence, however, the alloys have great historical and archaeological importance, being the first produced by human
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