Molecular Dynamics Simulation of Effects of Lattice Orientation on Crack Propagation in Alpha-Iron when the Primary Slip Direction is in the Plane of Tensile Stress

Molecular dynamics simulation was performed on bcc α-iron having two different lattice orientations which both included a primary slip direction (111) in the plane of applied tensile stress. Cracks on the (100) and on the (011) plane with crack growthedge direction [011] were studied. For cracks on the (100) plane, no nucleation of dislocations was observed, and the cracks propagated in both low- and high-temperature environments. For those on the (011) plane, brittle fractures without nucleation of dislocations occurred at low-temperature, but at high-temperature nucleation of [111] dislocation from the crack tip was observed. Local stress on the cleavage plane and on the slip plane are discussed from the viewpoint of the fracture mechanism.