Structure and shear response of < 001 < tilt grain boundary in titanium nitride

The equilibrated structures and shear responses of < 001 > titanium nitride (TiN) symmetric tilt grain boundaries (GBs) are investigated using molecular dynamics simulation. The equilibrated GBs are only composed of the kite-shaped structures connected with edge dislocation cores. From the shear response analysis of TiN GBs, we find that there exist two major deformation modes, i.e., GB sliding and shear deformation coupled with GB motion (shear-coupling). GB sliding may finally lead to the GB fracture and the shuffling of GB atoms. The shear-coupling could be further divided into the ideal and non-ideal ones. For the ideal shear-coupling, the shear deformation coupling with GB motion can be exactly described by a factor solely dependent on the GB tilt angle. However, it is not if the additional shear deformations caused by GB sliding or vacancy emission occur during the shear-coupling. Based on the geometrical analysis of atomic deformation mechanism in GB, we propose two theoretical coupling factors to describe the shear-coupling with the additional GB shear deformations. In addition, the deformation mode of GBs could be changed by elevating the temperatures and adding vacancies into GBs.