High temperature thermodynamics of solutions of oxygen in zirconium and hafnium

The Tian-Calvet microcalorimetric method has been applied to the determination at 1323 Kelvin of ΔH(O2), the partial molar enthalpy of mixing of oxygen in zirconium and in hafnium. No measurable departure from Henry's law has been found for dilute solutions (ratio oxygen over metal smaller than 0.1). For concentrated solutions repulsive interactions are found in agreement with the existence of ordered structures at lower temperatures. The domain of homogeneity of zirconium has been found larger than previously assumed. (author)