Activity of Chromium in Liquid Iron-Chromium System (Thermodynamics of Iron-Chromium System, 1st Report)

The activities of chromium in the liquid systems of iron-chromium and iron-chromium saturated with carbon were determined by a vaporization method using radioactive Cr51. The experiments were carried out at 1630°C up to about 40 at. pct chromium. It was found that iron-chromium system is a regular solution, showing negative deviation from the Raoult’s law. The interchange energy w was found to be about −10 kcal/mole. The value of w calculated from the phase diagram is also negative, but is not in good agreement with the above. It is theoretically inferred that the deviation from the Raoult’s law is larger in iron-chromium system than in iron-nickel system. The addition of carbon lowers the activities of chromium and the interaction parameter εCrC in carbon-saturated system is −12∼−16 over the composition range 0∼10 at. pct chromium.