THE SPECIAL GRAIN BOUNDARIES FORMATION IN BCC METALS DURING STRONG UNIAXIAL DEFORMATION

Abstract

The texture of strongly deformed metal polycrystals was represented
by a set of stable grain orientations, which were preserved during the subsequent deformation (texture fi bers). A possible set
of stable orientations was determined by the deformation symmetry. For this reason, the stable orientations were bound by specifi c crystallographic relations, i.e. they might be superimposed by a set of discrete rotations. Some rotations in this set were close to special misorientation. Texture of bcc metal after strong uniaxial deformation (extrusion) was investigated by the orientation microscopy (EBSD). Special grain boundaries Σ33a, Σ19a, Σ27a, Σ9, Σ11 were observed between some deformed grains. The orientations of these grains formed the main of deformation texture fi bers. The probability of appearance of special misorientation – of a certain type of special boundaries within a local area was inversely proportional to the angle of rotation about the common axis <110> of the crystal lattice of adjacent grains.