Peculiarities of reoriented bands formation in crystals

Abstract

The peculiarities of the formation and the development of reorientated bands in crystals are considered. Reorientated bands are investigated experimentally in MgO single crystals under the compression testing. It is shown that the misorientation between the material in the band interior and the surrounding volume can reach some degrees. The data of electron microscopy investigations of dislocation structure of such bands are performed. The disclination model is proposed for the propogation of the reorientated bands. This model permits to explain the laws of the band development, for example, the formation of discrete areas with reoriented crystal lattice ahead the terminated band.

Thermal evolution of deformation zones around microindentations in different types of crystal

“…The ductile/plastic stage; (0.7±0.9)T ml (for ionic and covalent crystals) (®gure 6) The present stage, together with the sharp increase in dislocation mobility, includes, in the process of deformation, new mechanisms of movement and interaction between the dislocations: simultaneous participation of conservative and nonconservative dislocation moving, processes of polygonization, etc. All this results in the superplastic behaviour of crystals under loading: the localization of plastic¯ow, the appearance of superplasticity, the formation of circular dislocation rows like the lines of equal shear stresses observed under deformation of isotropic solids (Frocht 1948, Gragert and Meyer 1967, Berezhkova et al 1983, Boyarskaya et al 1986. No hardening near the contact area arises in these conditions.…”

Elasticity Boundary-Value Problems for Straight Wedge Disclinations. A Review on Methods and Results

“…An important result was the explanation of the development of so-called reorientation bands in crystals based on the model of disclination dipole motion [5,76,77]. This model with modifications was successfully used in the analysis of kink band nucleation and propagation in materials [54,58,78,79] including those with layer or fiber structure [80][81][82][83].…”

Disclination Models of Misorientation Band Generation and Propagation

“…Misorientation bands (MBs) represent one of the typical elements of such substructures. They are observed as long straight strips of material having a crystallographic orientation different from that of neighbouring areas of the material [1,2,[4][5][6][7][8][9][10]. The boundaries of such MBs (i.e., the misorientation boundaries) are often illustrated as low-angle dislocation tilt boundaries, although they have a finite thickness of about 0.1-0.5 mm depending on the deformation magnitude [1], and consist in fact of high-density dislocation arrangements.…”