Predicting and understanding vacancy-modified oxygen diffusion in dilute Ni-based alloys by first-principles calculations

Abstract

Controlling oxygen (O) diffusion is critical to materials synthesis, materials degradation, and their oxidation and hot corrosion protection. Herein we investigate O diffusion in dilute Ni-based alloys Ni₃₀VaXO by density functional theory (DFT) based transition state theory using a vacancy (Va) modified mechanism, where X represents 22 alloying elements. The diffusion jump rates are predicted by DFT-based phonon calculations and the quasiharmoinc approach (QHA). It is found that the reactive elements (e.g., Y, Hf, Al, and Cr) that form oxides easily increase O diffusivity while the noble Pt-group elements (e.g., Pt, Pd, Ir, and Rh) that are difficult to oxidize decrease O diffusivity in Ni-based alloys. These results indicate that the bonding strength between X and O, determinable by Ellingham diagram, plays a critical role in affecting O diffusion in Ni. Correlation analysis by means of linear fitting, sequential feature selection, and Shapley value indicates that O diffusivity in Ni₃₀VaXO connects closely to the electronic structures of alloying elements X, such as work function, electronegativity, and valence electrons. In addition, the identified outliers by correlation analysis are mainly alloying elements Y and Mn to correlate O diffusion in Ni₃₀VaXO.