Effect of atomic order/disorder on vacancy clustering in concentrated NiFe alloys

D Chakraborty and A Harms and MW Ullah and WJ Weber and DS Aidhy, COMPUTATIONAL MATERIALS SCIENCE, 147, 194-203 (2018).

DOI: 10.1016/j.commatsci.2018.02.011

Using molecular dynamics simulations, we elucidate the effect of atomic structure on vacancy clustering in ordered (L1(0)) and random NiFe. Based on our simulations, we predict the vacancy evolution to be in complete contrast between the two systems. While large vacancy clusters, i.e., stacking fault tetrahedra (SFT) are formed in the random structure, no clustering is observed in the ordered-L1(0) structure. Similar simulations are performed on L1(0)-CuAu and L1(0)-TiAl to understand whether SFT formation is generic in L1(0) structures, or is specific to NiFe. Both materials show SFT formation, thereby highlighting specific defect energetics in L1(0) NiFe that lead to the lack of vacancy clustering. We elucidate that L1(0)-NiFe has unique thermodynamic and kinetic defect energetics, i.e., antisite energies, vacancy sublattice preference, and directional migration energy barriers that collectively lead to the lack of vacancy clustering. Understanding such defect energetics could open avenues to prevent defect clustering in the vision towards development of radiation-tolerant concentrated alloys for nuclear reactor applications. (C) 2018 Elsevier B.V. All rights reserved.

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