Abstract

ABSTRACT The solute atoms and point defects at the nanocrystalline material grain boundary (GB) have a significant impact on their macroscopic properties. This study utilised first-principles calculations to investigate the impact of the single Ag solute atom and N vacancy defect on the properties of CrAlN Σ5 (012) [100] GB. The results indicate that Ag atoms preferentially segregate in the gap between two grains, increases the probability of N vacancies formed at GB. The volume effect of Ag atom causes GB expansion and reduces the tensile strength. N vacancy decrease tensile strength by causing GB contraction and increasing regions with low charge density. Ag atom and N vacancy increase the mobility of GB. During the sliding process of a clean GB, it initially transitions to a Kingery type GB and eventually to an unstable Duffy-Tasker type GB. The peak value of the sliding energy barrier for the Ag atom segregation GB is attributed to the separation of grains during the sliding process. Finally, the bonding mechanism of atoms at the GB interface was analysed using density of states (DOS) analysis. The research results provide a fundamental understanding of using GB segregation to change the mechanical properties of materials.

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