Atomic scale modeling of {110} twist grain boundaries in α-iron: Structure and energy properties

Abstract

Atomic scale modeling was used to study the structure and energy of {110} twist grain boundaries (TWGBs) with various coincidence-site-lattice misorientations in α-iron. The small angle {110} TWGB contains a hexagonal dislocation network of two sets of 1/2⟨111⟩ and one set of ⟨001⟩ dislocation segments. The ⟨001⟩ segments are almost pure screw dislocations and the angle between the two 1/2⟨111⟩ segments varies from 83 to 109° for the rotation angle from 0.25 to 5.40°. This TWGB dislocation structure agrees well with an experimental observation that was not explained adequately so far. The large-angle TWGBs consist of periodic patterns rather than a dislocation network. The variation of the boundary energy with the rotation angle can be well fitted to the Read–Shockley equation in the low-angle range. An apparent cusp in the curve of the boundary energy against the rotation angle has been found and discussed.

Keywords:

• misfit dislocation
• boundary energy
• dislocation theory
• grain boundary structure

Acknowledgements

The authors gratefully acknowledge SR11000 supercomputing resources from the Center for Computational Materials Science of the Institute for Materials Research, Tohoku University. This work was partially supported by Grant-in-Aids for Scientific Research of the Ministry of Education, Science and Culture (Nos. 17002009, 18686077 and 15106015) and by the Division of Materials Sciences and Engineering, US Department of Energy with UT-Battelle, LLC.