Nanodipoles of partial disclinations as carriers of non-crystallographic shear and crystal-lattice reorientation in nanocrystalline nickel and vanadium

Abstract

Using electron microscopy, an investigation is performed of microstructure features of re-orientation microbands formed in nickel and V–4Ti–4Cr alloys under severe plastic deformation in the Bridgman anvils. It is shown that their formation could be described within the framework of a quasi-elastic mechanism of motion of partial-disclination dipoles, which is controlled by the flows of non-equilibrium point defects in the fields of local gradients of normal stress-tensor components. Operation of this mechanism offers an additional advantage of nanostructuring the defect substructure during plastic deformation of metallic materials, followed by formation of the structure states wherein the nanocrystallites measure a few nanometers.