Formation and Evolution of Dislocation Structures in Fe-3%Si Single Crystals Under Monotonous and Sequential Loading

Abstract

Tensile tests are performed on Fe-3%Si single crystals in a multiple slip orientation, namely the [110] axis, to promote the development of a cell structure. At low strains (ε<15%) , the resulting dislocation arrangement is composed of tangles distributed at random. This pattern evolves toward two families of dislocation sheets which constitute a mosaic like structure at higher levels of deformation. The sheets are composed of elementary tangles aligned in directions which are approximatively parallel to the trace of the active slip planes. When the deformed samples are further sheared at 90° from the tensile axis, the observed pattern is homogeneous only at low prestrains. For tensile deformations higher than 25%, microbands are formed and appear superimposed to the prestrain cell structure. The flow localization related to microband formation results from the destabilisation of the dislocation arrangement pertaining to the tensile deformation.