The effect of pressure on the eutectic in the system Fe-FeS

Abstract

The eutectic temperature in the system Fe-FeS is 988°C at 1 atm, and the eutectic composition is 31 wt percent sulfur. The temperature of the eutectic rises to a broad maximum of 1015°C in the 30 to 40 kb region and declines to about 1005°C at 60 kb. The composition of the eutectic shifts with pressure in the iron- rich direction. The eutectic composition contains 25 ± 1 wt percent S at 40 kb and 22 ± 2 wt percent S at 60 kb. It is clear that if this trend continues, the melting temperature of the eutectic must increase as pressures are increased until the melting tempel'ature of pure iron is reached. Thus the curve of the minimum melting tempera- ture in the Fe-S system, which appears to show a broad maximum at 30 to 40 kb, should show a broad minimum at some higher pressure.