Features of structural rearrangements at onset of plasticity in bcc iron with free surfaces of different orientation

Abstract

The features of structural rearrangements in nanosized body-centered cubic single crystals of iron with different crystallographic orientation under uniaxial tension, which lead to formation and propagation of structural defects, were investigated on the basis of the molecular dynamics method. It is shown that, when the elastic limit is reached, either twins or dislocations arise in the crystals. The mechanisms of their formation and motion differ substantially for the considered orientations of the crystals. At stretching along the. direction, the evolution of plastic deformation is determined by the nucleation and growth of one twin. Dislocations originate and slide only in the twin body. When the crystal is stretched along the. direction, a number of twins nucleate, at the front of which representative regions with face-centered cubic and hexagonal close packed lattices are formed. The nucleation of plasticity upon stretching a crystal along Y [111] is dislocation nature.