South American pre hispanic Au-Pt alloys from the metallurgical science and engineering

Abstract

The gold-platinum alloys, used to make sacred objects, found in the Tumaco-La Tolita cultural area and manufactured between 300 BC. and 500 A.D., have drawn the attention of archeology, metallurgy and archaeometallurgy professionals. Although there is general consensus as to the existence of a diversity of processes to explain their microstructures, there are still discrepancies about their interpretation and implications. In this work a critical review of most of the published studies on manufacturing by sintering -the production of metal alloy parts by heating, without reaching the melting temperature, modeled by pressure- gold conglomerates with platinum flakes or sand (between 2 and 0,044 mm approximately) is made from the point of view of the paradigm of Metallurgical Science and Engineering (MSE). Some concepts of this discipline are introduced that help to better understand the structures, processing (manufacturing methods), properties and behaviors of these alloys and indicate the contributions that, according to the authors themselves, each presented research group has made. By analyzing the involved phase diagrams, the authors of this work provide a possible explanation regarding the observation of the fragility of platinum particles and the hardness of the pieces.