Microtexture of pre-Columbian Platinum Alloys

MARTINA AVALOS; JAIRO ESCOBAR GUTIÉRREZ; NOHORA BUSTAMANTE SALAZAR; VANINA TARTALINI; PABLO RISSO; R.E. BOLMARO

Cancún

Congreso; XXV International Materials Research Congress; 2001

MRS

The metallurgy of platinum appeared in Europe in the eighteenth century, based mainly on powder metallurgy technology because of the high melting point of platinum (~1760 °C). However, ornamental objects made on Pt-Au alloys, and dated at about pre-hispanic times, were found in southern Colombia and northern Ecuador. These objects exhibit different geometries, colors, brightness and finishes that were obtained as a function of alloy composition and thermomechanical treatments. It is surprising how these pre-Columbian cultures managed Pt alloys when there was no evidence of a high temperature technology in the region. The goal of the present study is to analyze the microstructure and microtexture of pre-Columbian pieces made of Pt based alloys to support or reject the hypothesis about the manufacture of these pieces. Sometimes the archaeological pieces are obtained out of their original context, so the use of advanced characterization techniques is essential to reconstruct the history and context of the piece in the culture of origin. The study of antiquities and pieces of cultural value require non-destructive analysis techniques to preserve the sample of interest. In this context, the use of Electron Backscatter Diffraction EBSD technique together with EDS is suitable for the development of crystallographic and composition analysis of unknown alloys. The current samples were taken from some ornamental pieces from Museo del Oro, Bogotá, Colombia. They are mainly constituted of Au, Ag, Fe, and Pt with small traces of Ir and Pd, stemming from alluvial powder minerals. The research infers relative low temperature AuAg fluency simultaneous with diffusion mechanisms, to allow sintering between grains, mainly due to the presence of Fe that helps on bonding processes induced by hammering and intermittent heat treatments.