Roles of Y2Zr2O7 Nano-Oxides in Helium Management in ODS Ferritic Alloys: A First-Principles Study

Y–Zr–O nano-oxide dispersion-strengthened (ODS) ferritic alloys have attracted increasing research efforts in recent years, for the enhanced nucleation and refinement of nano-oxides. Here, we report a first-principles exploration on the possible roles of Y₂Zr₂O₇ in helium management in Y + Zr and Y + Ti + Zr co-alloyed ODS ferritic alloys. Bulk phase calculations suggested that similarly as Y₂Ti₂O₇, Y₂Zr₂O₇ has a comparably strong capability for trapping helium at its interstitial sites. The equilibrium Fe/Y₂Zr₂O₇ interface structure was further predicted as the top-coordinated O-rich at the temperature range of interest. Vacancy and helium both segregate to the Y₂Zr₂O₇ interface, in preference to the Y₂Ti₂O₇ interface, the bulk interior of Y₂Zr₂O₇ and the grain boundaries. In this regard, Y₂Zr₂O₇ can be more effective than Y₂Ti₂O₇ in preventing vacancies and helium from reaching GBs. Based on these results, the profound implications for the helium tolerance of Zr-alloyed ODS ferritic alloys were discussed.