Eutectic decomposition in the goldsilicon system

Abstract

Using a gravity segregation technique it has been shown that the eutectic composition in the goldsilicon system occurs at 17.9 at. % silicon. When an alloy of the eutectic composition is quenched from the liquid phase a mixture of gold and a metastable phase designated "δ" is formed. The δ phase, which has a composition near Au3Si, has an orthorhombic structure with a = 7.82 A ̊, b = 5.55 A ̊ and c = 11.16 A ̊. At room temperature a thin surface layer of the δ phase dissociates over a period of a few hours, but the rest of the specimen remains undissociated even after a period of one year. Complete dissociation in a few hours was observed with filings at 150°C, and with bulk specimens at 340°C. © 1971.