Assessment of Experimental Data and Thermodynamic Modeling in the Zr-Fe-O System
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INTRODUCTION
THE interaction of iron with a ZrO2 ceramic presents an issue of practical interest. The system Zr-O-Fe must be understood to aid in preventing refractories from reacting with metallurgical slag.[1] The system under investigation was part of a corium system (U-Zr-Fe-O). Thermodynamic modeling of the Zr-Fe-O system is essential for understanding the possible reactions of a melt in the active zone of a nuclear reactor, including the housing materials and reactions occurring during a severe nuclear accident.[1] The system is also of interest for deoxidation and inclusion shape control in steel.[2] ZrO2 that was partially stabilized by 10 mass pct MgO was proposed as a reinforcement component of the TRIP-matrix composite.[3] Therefore, the Zr-Fe-O system is a key subsystem for simulation of interfacial reactions between steels and ceramic materials. Experimental data for the Zr-Fe-O system are quite scarce due to difficulties in conducting such experiments.[3] It should be stressed that the phase equilibria in this system depends on oxygen partial pressures and therefore control of oxygen partial pressures in the experiments is very important. Substantial experimental difficulty is the reaction of samples with crucible material.[3] However, phase diagrams are available for the ZrO2-FeO system.[1,4,5] The difference between[4] and[1,5] is mainly in the composition of the eutectic reaction L = FeO (wustite) + tetragonal-ZrO2. The solubility of FeO in a ZrO2 fluorite phase was found to be 12, and 2.2 mol pct in the tetragonal phase.[1,5] The phase diagram of the ZrO2-Fe3O4 system in an air OLGA FABRICHNAYA, Principal Researcher, and DMYTRO PAVLYUCHKOV, Postdoctoral Researcher, are with the Institute of Materials Science, TU Bergakademie Freiberg, Gustav-Zeuner-Str. 5, 09599 Freiberg, Germany. Contact e-mail: [email protected] Manuscript submitted August 5, 2014. METALLURGICAL AND MATERIALS TRANSACTIONS A
atmosphere was investigated by different authors.[6,7] The low solubility of ZrO2 in the Fe3O4 magnetite phase (spinel structure) and Fe2O3 hematite phase (corundum structure) was found. On the other hand, the ZrO2based phases with tetragonal and cubic fluorite structures were found to dissolve only a small portion of the Fe3O4. Phase relations in the ZrO2-Fe3O4 system were investigated by[8] at an oxygen partial pressure of 2.1 9 103 bar. The isothermal section of a ZrO2-FeO-Fe2O3 system at 1473 K (1200 C) is presented in (Reference 9) based on experimental data at a measured oxygen partial pressure. Determination of the liquidus temperature in the ZrO2FeO-Fe2O3 system was based on a combination of experiments in an air atmosphere and calculations, and is presented by (Reference 10). Immiscibility in the liquid phase was indicated in the range of 34 to 82 mass pct of ZrO2 based on the results of X-ray diffraction (XRD) and scanning electron microscopy combined with wavelengthdispersive X-ray spectroscopy (SEM/WDS) investigation of quenched samples. Fruehan[11] investigated the equilibrium of a metallic li
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