Solid state deoxidation of zirconium-oxygen solid solution using a combination of metallic Ca and Y in CaCl2 flux.

Aiming at the deficiencies of the three typical "external gettering" systems: metal-oxide equilibrium deoxidation (MED), halide flux deoxidation (HFD) and electrochemical deoxidation (ECD), a novel deoxidation method based on the combination of oxytropic rare earth metal Y and Ca for in-depth deoxidation of Zr-O solid solution was proposed. The thermodynamic properties of the deoxidation method were analyzed, and it was found that the addition of metallic Y could significantly improve the deoxidation ability of the Ca-CaCl 2 system, because Y could form Y-Y 2 O 3 equilibrium to "anchor" the activity of CaO (a CaO) at a very low level. When the activity of Y 2 O 3 (a Y2O3) and a CaO in the flux conforms to a Y2O3 < 18.9 a 3 CaO at 1173 K, the deoxidation mode is thermodynamically feasible. Experiments were conducted to verify the method. The results showed that even if CaO was saturated in CaCl 2 flux, the oxygen content of Zr-O solid solution could still be controlled at the level of less than 100 ppm, thus the "anchoring effect" of Y on a CaO was verified. The oxygen content, phase and microstructure of the reacted Y specimens were analyzed, which suggested that when the ratio of CaO was less than 40 % of its solubility in CaCl 2 flux, the oxygen potential of the system was controlled by Y-O solid solution, and when it was greater than 40 %, the oxygen potential of the system was controlled by Y-Y 2 O 3 equilibrium. [Display omitted] • A novel in-depth deoxidationmethod based on the combination of oxytropic metals Y and Ca was proposed. • The formation of Y-O solid solution and Y-Y 2 O 3 equilibrium can "anchor" a CaO at an extremely low level. • The oxygen content of zirconium can be stably reduced to less than 100 ppm using this deoxidation model. [ABSTRACT FROM AUTHOR]