New Measurements of Fe Solubility in Liquid Mg up to 1450 °C and Reassessment of the Fe-Mg System

To investigate the MgLiq ↔ FeSol (Bcc and Fcc) equilibrium up to high temperatures, a suitable protocol for the thermodynamic study of volatile elements was developed. Pure magnesium was melted between 700 and 1450 °C (973 and 1723K) in a low-carbon steel sealed crucible (C35), itself sealed in a tantalum crucible to prevent magnesium leakage. The concentration of iron was characterised by inductively coupled plasma–atomic emission spectroscopy (ICP-AES) and the distribution of iron precipitates was examined by x-Ray tomography. The liquidus composition was measured up to 1450 °C and the results obtained confirm the trend in the literature with, however, significant differences above 1000 °C where a lower Fe solubility is measured in comparison with previous thermodynamic descriptions and the scarce available experimental data in this temperature domain. The existing Calphad model of the binary system was then re-evaluated.