role of zr in strengthening mosi2 grain boundaries from dft calculations
Name: Hui Zheng
Grad Year: 2021
MoSi2 is a promising intermetallic for ultrahigh-temperature applications due to its high melting point and excellent oxidation resistance at high temperatures (> 1000 C)1. However, its application is limited due to oxygen embrittlement at the grain boundaries (GBs) under low temperatures (400-600˚C), an effect also known as "pesting"2. In this work, we comprehensively investigate the role of Zr in mitigating pesting in MoSi2 using Density Functional Theory (DFT) calculations. We show that Zr dopants reduce the embrittling effect of interstitial oxygen at MoSi2 GBs by donating electrons to oxygen. A more significant effect is observed when Zr is present as a secondary getter nanoparticle phase. Interstitial oxygen has a strong thermodynamic driving force to migrate from MoSi2 to the Zr sub-surface region, and the work of separation of the Zr/MoSi2 interface, with or without oxygen interstitials, are much higher than that of MoSi2 GBs. Finally, we will also 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. 1 Y. Suzuki, P.E.D. Morgan, K. Niihara, T. Pavelkova, J. Ba, M. Nikl, and I. Jakubec, J. Am. Ceram. Soc. 81, 3141 (1998). 2 T.C. Chou and T.G. Nieh, JOM 45, 15 (1993).
Industry Application Area(s)
Aerospace, Defense, Security | Civil/Structural Engineering | Materials