Chemical environment and magnetic moment effects on point defect formations in CoCrNi-based concentrated solid-solution alloys

Abstract

Atomic investigation of point defects is the basis for exploring the mechanisms underlying the macro performance of materials under irradiation. Owing to the complex local disordered chemical environments and unique site-to-site lattice distortions, there have been few related studies on high-entropy alloys (HEAs). In this work, we applied ab initio calculations to systemically characterize the chemical environment and magnetic moment effects on point defect formations in three equimolar alloys, namely: CoCrNi, CoCrNiFe, and CoCrNiFeMn. These calculations were based on investigations of a large number of statistical atomic sites. An appropriate method applying similar atomic environments (SAEs) and an efficient approach using Widom-type substitution techniques were employed to achieve results that were reliable. It was found that the vacancy formation energies (VFEs) were conspicuously larger in the CoCrNiFeMn HEA than in the CoCrNi or CoCrNiFe alloys. The local chemical environment—in particular, the number of first-nearest neighbor (1nn) Ni and Cr atoms—is the key factor affecting the VFE, as vacancies prefered Ni-rich and Cr-poor environments. Interstitial defects were primarily dominated by Co and Mn. Finally, the point defect formation energies were found to be negatively correlated with the anti-magnetic moment changes in 1nn atoms. Our results indicate that the low vacancy generation in HEAs is important for their enhanced irradiation resistance and that the local anti-magnetic moments influences of the constituent elements on the VFEs provide guidance for the design of advanced radiation-resistant HEAs.