Vacancy diffusion mechanism in K-state formation of NiCrAlFe alloy

Abstract

To address the challenge of determining the atomic occupancy of the K-state, the diffusion and migration behavior of vacancies in the NiCrAlFe alloy was investigated using first-principles calculations based on the climbing image nudged elastic band method (CI-NEB). The results indicate that Nickel (Ni) and Chromium (Cr) atoms tend to diffuse via a nearest-neighbor mechanism facilitated by vacancies. Ni atoms exhibit uphill diffusion, resulting in the formation of an enriched region on the (111) plane with the highest diffusion rate. Cr atoms diffuse along the [110] direction, leading to the formation of short-range ordered (SRO) structures characterized by alternating arrangements of Ni and Cr atoms or aggregation regions centered on Cr atoms with neighboring Ni atoms. Additionally, the presence of a small amount of aluminum (Al) promotes the formation of SRO structures. During the K-state formation process, the arrangement of atoms in the solid solution evolves from disorder to segregation and ultimately to order. This study elucidates the diffusion formation mechanism in the K-state of nichrome at the atomic level and provides new insights for investigating the precipitation mechanism of SRO structures in solid solutions.