Phase diagram and melting curve of Fe-alloys

State-of-the-art x-ray diffraction in combination with laser heated diamond anvil cell allows probing the crystal structure of solids up to the P-T conditions of the Earth’s inner core. Although more challenging, melting curves can be experientially determined as well. The systematic investigation of the phase diagram of binary (Fe-S, Fe-Si, Fe-C) and ternary (Fe-S-Si and Fe-S-C) systems, including the so-far neglected light-element rich side, will be carried by in situ synchrotron x-ray diffraction and absorption experiments combined with electron microscopy analysis on recovered samples. Furthermore, picosecond acoustics can be used as further independent technique to probe the melting curves, as even a small fraction of melting highly affects the acoustic waves propagation. Data on the stable crystal structures and stoichiometry of solid Fe-alloys, phase relations, eutectic composition and melting curves, will all be integrated into a consistent thermodynamic model that will be at the base of the structural models of planetary cores. Melting temperature determination at the solid-liquid core interface will provide the fundamental anchor point for core temperature profiles. Comparison of liquidus and core temperature profiles will allow discriminating amongst the different core crystallization regimes.

Photo of ID27 at ESRF © Daniele Antonangeli