Atomistic evaluation of the dislocation transmission across tilt and twist low-angle grain boundaries in body-centered cubic iron

Abstract

This study systematically and qualitatively evaluates the resistance for dislocation transmission across tilt/twist low-angle grain boundaries (LAGBs), which mainly consist of edge/screw dislocations (“GB dislocations”). The motion of the incident lattice edge dislocation is disturbed by the LAGBs, while the edge dislocation is transmitted to the adjacent grain by applying large shear stress if the tilt and twist angles are sufficiently low. It was observed that the twist LAGB is a stronger obstacle compared to the tilt LAGB for the incident lattice edge segment even though the misorientation angle of both tilt and twist LAGBs is the same because of the reconstruction of the GB-dislocation structures at the twist LAGB owing to the incident lattice dislocation. When we compare the incident lattice edge and screw components, the barrier effect of the GB on the transmission is stronger for the screw component than for the edge component. The stronger barrier effect can be explained mainly by the higher line tension of the screw component based on the dislocation bow-out model. Accordingly, the dominant factors of the GB-strengthening effect in LAGB are the incident lattice dislocation type, the structure of GB dislocations, and dislocation–dislocation reactions. These results indicate that the GB-strengthening factors are dominated by the type of incident lattice dislocation and the GB-dislocation character in addition to the macroscopic misorientation of the GB.