Dislocation induced stress drop in cubic metals

Abstract

Dislocation core has nonlinear properties which cannot be explained with linear elasticity theory. In respect that dislocation core is responsible for determining dislocation mobility, there have been many efforts to understand the core structures of dislocations. In this work, we firstly report that stress applied on free surfaces of nanoplate is dropped to certain value inside the plate when dislocation starts to move. We insist that phonon scattering induced by anharmonic strain field near the dislocation core reduces the applied stress during dislocation motion and derived relation between the applied stress and the amount of stress drop based on the model. We simulated edge dislocation in iron and aluminum by using molecular dynamics simulation and measured the amount of stress drop. Also, we observed that screw dislocation induces stress drop whose amount is much smaller than the edge dislocation. There was a good agreement between the model and simulation results when kink is not formed on dislocation line for both cases. Furthermore, our model predicts that the amount of stress drop decreases as temperature increases, which coincides with simulation result.