Phase Diagram Investigation And Thermodynamic Assessment Of Fe-Zr-Y-O Partial System

Oxide dispersion strengthened(ODS)alloys have many excellent properties,such as good thermal stability,outstanding hightemperature mechanical properties,excellent radiation swelling resistance and so on.Therefore,ODS alloys are considered to have great potential in the field of nuclear industry and superalloys.Both Y and Zr can combine with O to form a dispersed oxidation phase,so as to improve the radiation resistance and high-temperature mechanical properties of iron and steel materials.It is considered to be the main elements to improve the alloy properties.ODS alloy is usually prepared by mechanical alloying(MA),which has high cost,low efficiency and is unable to be produced in large quantities.In order to further understand the interaction between the main elements in ODS steel to improve the preparation process and increase the production efficiency,it is very necessary to study the phase equilibrium relationship of relevant systems.In this paper,the phase equilibrium relationship of some systems in Fe-Zr-Y-O is studied by the combination of equilibrium alloy method and thermodynamic calculation.The main research contents are as follows:(1)The phase equilibrium relationship of Fe-Zr-Y ternary system in the whole composition range at 973 K and 1073 K was determined by equilibrium alloy method,combined with SEM-EDS,EPMA-WDS and XRD.There are 12 three-phase regions,12 two-phase regions and 7 singlephase regions in the isothermal section at 973K;There are 13 three-phase regions,13 two-phase regions and 7 single-phase regions in the isothermal section at 1073 K.4 ternary compounds are detected in the above two isothermal sections,in which τ3-Fe3 Zr Y and τ4-Fe10Zr5Y2 are new ones.(2)According to the result of first principle calculation,combined with the latest experimental data and literature reports,the phase equilibrium of ZrY-O ternary system in the whole temperature and composition range is thermodynamically optimized by CALPHAD method,and a set of thermodynamic models and parameters describing the Gibbs free energy of each phase are obtained.The calculated result is basically consistent with the experimental data.