Origin of differences in the excess volume of copper and nickel grain boundaries

Jonathan J Bean,Keith P Mckenna

doi:10.1016/j.actamat.2016.02.040

Jonathan J Bean, Keith P Mckenna

Open Access

https://doi.org/10.1016/j.actamat.2016.02.040

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Journal: Acta Materialia	Publication Date: Mar 23, 2016
Citations: 70	License type: cc-by

Affiliation: Science City York (United Kingdom)

Abstract

The excess volume associated with grain boundaries is one of the primary factors driving defect segregation and diffusion which controls the electronic, mechanical and chemical properties of many polycrystalline materials. Experimental measurements of the grain boundary excess volume of fcc metals Cu and Ni have shown a difference of over 40%. The difference in lattice constant between Cu and Ni is only 3%, therefore this substantial difference is currently lacking explanation. In this article we employ a high throughput computational approach to determine the atomic structure, formation energy and excess volume of a large number of tilt grain boundaries in Cu and Ni. By considering 400 distinct grain boundary orientations we confirm that theoretically there is a systematic difference between the excess volumes in the two materials and we provide atomistic insight into the origin of the effect.

Highlights

Grain boundaries play a decisive role in determining the properties and functionality of polycrystalline materials relevant to wide ranging technological applications [1e5]
The increased computational power available has allowed simulation of over 400 unique tilt grain boundary (GB) structures for Cu and Ni which span a wide range of orientations
Through analysis of these structures we have shown that there is a systematic difference between the excess volumes of Cu and Ni GBs of up to 0.2 Å which is consistent with experiment but not fully explained by the relatively small lattice constant difference of 3%

Summary

Introduction

Grain boundaries play a decisive role in determining the properties and functionality of polycrystalline materials relevant to wide ranging technological applications [1e5]. GBs are almost always associated with an excess volume relative to the corresponding bulk crystal. This additional ‘free space’ is thought to be one of the main factors responsible for the preferential segregation of defects and impurities towards GBs, which affects key materials properties, such as mechanical strength and electrical resistivity [6e8]. It helps explain the phenomena of enhanced impurity diffusion along GBs that has been observed in a diverse range of materials [9e11].

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Conclusion