Vacancy surface migration mechanisms in dilute nickel-chromium alloys

SCRIPTA MATERIALIA

卷:202

Article

Startt, Jacob^1,2  Deo, Chaitanya^2,3  Dingreville, Remi^1,2 

[1] Sandia Natl Labs, Ctr Integrated Nanotechnol, POB 5800, Albuquerque, NM 87185 USA

[2] Georgia Inst Technol, George Woodruff Sch Mech Engn, Atlanta, GA 30332 USA

[3] Georgia Inst Technol, Sch Mat Sci & Engn, Atlanta, GA 30332 USA

关键词: Surface segregation;    Atomic migration;    Vacancy;    Ni-Cr;    Density functional theory;   

DOI  :  10.1016/j.scriptamat.2021.113998

来源: Elsevier

【 摘 要 】

We investigate the unitary mechanisms related to the surface migration of vacancies in dilute Ni-Cr al-loys via first-principle calculations. We survey a complete set of surface and sub-surface migration paths for vacancies near the (100) free surface and calculate the corresponding migration barriers. Our results show that a vacancy migrating towards the free surface will face lower energy barriers to migrate via atomic exchange with a neighboring Cr atom rather than with a Ni atom. Once a vacancy reaches the free surface, it will be trapped there. Our results also reveal that, when a Cr atom sits in the atomic plane just below the free surface, any in-plane vacancy hopping jump that would result in the vacancy sitting on top a subsurface Cr atom is energetically unfavorable. Taken together, these fundamental unitary sur -face migration mechanisms offer insights into the complex interactions between surface segregation and vacancy migration phenomena in Ni-Cr-based alloys. (c) 2021 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

【 授权许可】

Free