In situ investigation of high-pressure melting behavior in the Fe-S system using synchrotron X-ray radiography

We studied the high-pressure melting behavior of Fe-S mixtures containing 9wt% sulfur using the synchrotron X-ray radiographic method in a large volume press. By opening two graphite windows along the X-ray path and using boron nitride capsules, we were able to observe segregation of sulfur-rich liquid and iron-rich solid upon initial melting and determine the eutectic temperature of the Fe-S system at pressures between 13 and 16 GPa. Our results are in excellent agreement with the existing data from quench experiments, and are further supported by in situ X-ray diffraction measurements. The liquidus temperatures of this composition, determined on the basis of the disappearance of the solid phase on the radiographs, are also consistent with literature values. By observing radiographic changes with time, we monitored the approach to equilibrium and obtained preliminary data on the kinetics of the melting process.