Twin Nucleation Mechanism from a Screw Dislocation in BCC-Fe

Twinning is a predominant deformation mechanism in nanocrystalline materials. The present study uses molecular dynamics simulations to address the feasibility of forming a twin in BCC-Fe via the three-fold dissociation of a screw dislocation, as proposed by Sleeswyk. Gliding of the screw dislocation at lower shear strain rates and formation of the twin at higher shear strain rate via two-fold dissociation was observed. The gliding of the screw dislocation occurred through the kink-pair-assisted mechanism. Three-fold dissociation on three co-zonal {110} planes with the trailing stacking faults was noticed only at temperatures below or equal to 50 K. However, this dissociation failed to support Sleeswyk’s reaction explicitly. Sleeswyk’s reaction may occur through a spontaneous collapsing of the three-fold dissociation at the time of dissociation and proceeds with twinning. Interatomic potentials, which can predict the three-fold dissociation, were presented.