Atomic size effect in impurity indued grain boundary embrittlement

TL;DR

This paper investigates how impurity atoms like Bi and Pb weaken copper grain boundaries, emphasizing the importance of distinguishing atomic size effects from chemical contributions using a new theoretical approach.

Contribution

It introduces a first-principles based phenomenological theory that separates atomic size effects from chemical effects in grain boundary embrittlement.

Findings

Atomic size effects significantly contribute to grain boundary weakening.

Chemical effects are distinguished from size effects using the new theory.

Previous conclusions about Bi and Pb effects are challenged by the new analysis.

Abstract

Bismuth segregated to the grain boundary in Cu is known to promote brittle fracture of this material. Recently, Schweinfest et al. reported first-principles quantum mechanical calculations on the electronic and structural properties of a Cu grain boundary with and without segregated Bi and argue that the grain boundary weakening induced by Bi is a simple atomic size effect. But their conclusion is invalid for both Bi and Pb because it fails to distinguish the chemical and mechanical (atomic size) contributions, as obtained with our recently developed first-principles based phenomenological theory.