[SY-G5] Dynamic behaviors of dislocations and grain boundaries induced by phonon scattering in nanoscale
Conventional dislocation dynamics based on continuum theory is limited in its ability to describe motion of dislocations in nanoscale. This is because discrete characteristics are no longer ignored in nanoscale unlike in micro- or macroscales. Especially, the discreteness becomes a significant factor to describe core region of dislocation so that it contributes to nonlinear properties of the core. In a sense that the core determines mobility of dislocations and concerns interactions among them, the discrete approach must be carefully considered in nanoscale dislocation dynamics. To reflect the discrete characteristics in nanoscale, computer simulations and discrete lattice dynamics approach have been used to quantify properties of the dislocation core.
In our work, we carried out molecular dynamics simulation to study motion of the dislocation in nanoscale and found surprising behavior that internal stress of system where dislocation is inserted is dropped when the dislocation is in motion by externally applied stress. By using discrete lattice dynamics, we proved that this behavior occurs due to scattering of the wave emitted from breaking of atomic bond in the core [1].
Furthermore, we extended our approach to grain boundary since it can be assumed as a collection of dislocations if its misorientation angle is small enough. We simulated the grain boundaries for various misorentation angles under external stress. As a result, dropping of internal stress is also observed as in dislocation case. Not only the stress-drop, but the grain boundaries were curved during their motion and magnitude of the curvature and speed were inversely proportional to the misorientation angle. We analyzed these behaviors by using the discrete lattice dynamics and concluded that these are able to be appeared only in nanoscale materials.
References
[1] S. Kim, D. T. Ho, K. Kang, and S. Y. Kim, Acta. Mater, 115 (2016), p143-154.
In our work, we carried out molecular dynamics simulation to study motion of the dislocation in nanoscale and found surprising behavior that internal stress of system where dislocation is inserted is dropped when the dislocation is in motion by externally applied stress. By using discrete lattice dynamics, we proved that this behavior occurs due to scattering of the wave emitted from breaking of atomic bond in the core [1].
Furthermore, we extended our approach to grain boundary since it can be assumed as a collection of dislocations if its misorientation angle is small enough. We simulated the grain boundaries for various misorentation angles under external stress. As a result, dropping of internal stress is also observed as in dislocation case. Not only the stress-drop, but the grain boundaries were curved during their motion and magnitude of the curvature and speed were inversely proportional to the misorientation angle. We analyzed these behaviors by using the discrete lattice dynamics and concluded that these are able to be appeared only in nanoscale materials.
References
[1] S. Kim, D. T. Ho, K. Kang, and S. Y. Kim, Acta. Mater, 115 (2016), p143-154.