Abstract

Solute segregating to grain boundary can stabilize the microstructure of nanocrystalline materials, but a lot of solutes also cause embrittlement effect on interfacial strength. Therefore, uncovering the solute effect on grain boundary strength is very important for nanocrystalline alloys design. In this work, we have systematically studied the effects of various solutes on the strength of a Σ5 (310) grain boundary in Cu by first-principle calculations. The solute effects are closely related to the atomic radius of solutes and electronic interactions between solutes and Cu. The solute with a larger atomic radius is easier to segregate the grain boundary but causes more significant grain boundary embrittlement. The weak electronic interactions between the s- and p-block solutes and Cu play a very limited role in enhancing grain boundary strength. While the strong d-states electronic interactions between transition metallic solutes and Cu can counteract embrittlement caused by size mismatch and significantly improve the grain boundary strength. This work deepens our understanding of solute effects on grain boundary strength based on atomic size and electronic interactions.

Highlights

  • Solute segregating to grain boundary can stabilize the microstructure of nanocrystalline materials, but a lot of solutes cause embrittlement effect on interfacial strength

  • The results indicate that solutes with a smaller or similar atomic size of Cu have no or very limited segregation ability to the grain boundary, while solutes with a larger size than Cu prefer to segregate to the interface

  • The strengthening/embrittlement effect is closely related to the atomic radius of solute and electronic interaction between the solute and Cu

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Summary

Introduction

Solute segregating to grain boundary can stabilize the microstructure of nanocrystalline materials, but a lot of solutes cause embrittlement effect on interfacial strength. While the strong d-states electronic interactions between transition metallic solutes and Cu can counteract embrittlement caused by size mismatch and significantly improve the grain boundary strength. This work deepens our understanding of solute effects on grain boundary strength based on atomic size and electronic interactions. Experimental works have shown that ­Zr12,13, ­Nb14, ­Mo15, and ­Ta16 can enhance the mechanical strength but B­ i17,18 causes brittle fracture of nanocrystalline Cu. One important objective of grain boundary segregation engineering is to find suitable solutes which can improve the thermal stability of materials while avoiding embrittling e­ ffects[1,2,19]. The results indicate that both the atomic radius of solutes and electronic interactions between solutes and Cu have important roles in altering the grain boundary strength

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