The effect of Ag, Pb and Bi impurities on grain boundary sliding and intergranular decohesion in Copper

Abstract

We investigate the changes in grain boundary sliding (GBS) and intergranular decohesion in copper (Cu), due to the inclusion of bismuth (Bi), lead (Pb) and silver (Ag) substitutional impurity atoms at a symmetric tilt grain boundary (GB), using a first-principles concurrent multiscale approach. We first study the segregation behavior of the impurities by determining the impurity segregation energy in the vicinity of the GB. We find that the energetically preferred sites are on the GB plane. We investigate the intergranular decohesion of Cu by Bi and Pb impurities and compare this to the effect of Ag impurities by considering the work of separation, and the tensile strength, . Both and decrease in the presence of Bi and Pb impurities, indicating their great propensity for intergranular embrittlement, whilst the presence of Ag impurities has only a small effect. We consider GBS to assess the mechanical properties in nanocrystalline metals and find that all three impurities strongly inhibit GBS, with Ag having the biggest effect. This suggests that Ag has a strong effect on the mechanical properties of nanocrystalline Cu, even though its effect on the intergranular decohesion properties of coarse-grained Cu is not significant.

Keywords:

• Grain boundaries
• grain boundary sliding
• intergranular decohesion
• density functional theory

Acknowledgements

We thank the Academic Computing Group of the School of Engineering and Applied Sciences and the FAS Research Computing Group for computational resources. We gratefully acknowledge discussions with Frans Spaepen.

Notes

No potential conflict of interest was reported by the authors.

Additional information

Funding

This work was supported in part by the Department of Energy, SciDac [grant number ER-25788], and a gift from Intel Corporation. TDK acknowledges financial support from the Graduate School of Excellence MAINZ and the IDEE project of the Carl Zeiss Foundation.