Internal friction in Al bicrystals with ⟨111⟩ tilt and twist grain boundaries

Abstract

Internal friction measurements were performed on various ⟨111⟩ tilt and twist grain boundaries in high-purity Al bicrystals. The temperature dependence of the grain boundary internal friction peak was determined, and the activation parameters of grain boundary relaxation were obtained. These parameters were found to change in a wide range depending on boundary geometry. The activation enthalpy of boundary relaxation and the pre-exponential factor of the relaxation time are related according to the compensation effect. The results are discussed in terms of the model of correlated relaxations. Bicrystals with vicinal Σ3 boundaries were observed to behave like single crystals, i.e. an internal friction peak did not appear. This evidences that both coherent and incoherent (60° ⟨111⟩ tilt) twins possess a high mechanical resistance.

Keywords:

• internal friction
• grain boundary
• bicrystal

Acknowledgements

The authors express their gratitude to the Deutsche Forschungsgemeinschaft and National Natural Science Foundation of China (Grants 10674136 and 10804108) for financial support and for their cooperation. The help of Bing Bing Zhao in bicrystal preparation is gratefully acknowledged.