Role of Zr in strengthening MoSi2 from density functional theory calculations.

MoSi 2 is an important intermetallic with excellent oxidation resistance at high temperatures above 1000 °C. However, its application at lower temperatures is limited by oxygen embrittlement, a phenomenon known as “pesting”. In this work, we comprehensively investigate the role of Zr in mitigating pesting in MoSi 2 using density functional theory calculations. We show that Zr dopants reduce the embrittling effects of oxygen interstitials at MoSi 2 grain boundaries by being a charge donor to oxygen. However, a more substantial effect is observed when Zr is present as a secondary getter nanoparticle phase. Oxygen interstitials have a strong thermodynamic driving force to migrate into the Zr subsurface at the Zr/MoSi 2 interface, and the work of separation of the clean and oxygen-contaminated Zr/MoSi 2 interfaces are much higher than that of MoSi 2 grain boundaries. Finally, we present an efficient screening approach to identify other potential getter elements using simple thermodynamic descriptors, which can be extended to other alloy systems of interest. These findings provide crucial fundamental insights and further avenues to optimize Mo and other alloys. [ABSTRACT FROM AUTHOR]