Thermodynamic Assessment of Mo-Ce and Mo-Y Systems

Abstract

Molybdenum is a refractory metal that is typically used for high-temperature applications due to its high melting point (2615°C), high-temperature strength, low thermal-expansion coefficient, and high thermal conductivity. The alloying of rare earth elements to molybdenum can help improve oxidation resistance as well as strengthening the alloy via dispersion strengthening due to formation of rare earth oxides. In this study, two binary systems, Mo-Ce and Mo-Y, were thermodynamically assessed based on limited phase equilibria information available in the literature. Self-consistent thermodynamic descriptions for both systems were obtained using the CALPHAD method.

Studies on calcium reduction of yttrium fluoride

“…Attainment of equilibrium in systems involving liquids is usually fast. Subsequent to slag–metal separation carried out ∼1600°C, ∼18 wt-% molybdenum should have dissolved in liquid yttrium according to the phase diagram of Mo–Y (Chan et al , 2010 b ). This would have precipitated as pure molybdenum stringers once the liquid yttrium solidified, as the solubility of molybdenum in solid yttrium is negligible (Chan et al , 2010 b ).…”

“…Subsequent to slag–metal separation carried out ∼1600°C, ∼18 wt-% molybdenum should have dissolved in liquid yttrium according to the phase diagram of Mo–Y (Chan et al , 2010 b ). This would have precipitated as pure molybdenum stringers once the liquid yttrium solidified, as the solubility of molybdenum in solid yttrium is negligible (Chan et al , 2010 b ). However, substantially lower concentration of molybdenum and its wide range as observed by ICP-AES indicates that the overall equilibrium was not reached during the present studies.…”