Research methods of structural and phase transformations in nanomaterials deformed under pressure

The comparative analysis is given on the main research methods of the structural and phase transformations proceeding in nanostructures of metals and alloys during plastic deformation under pressure. It is shown that an adequate description of changes in structure of compressed materials under deformation is impossible without the use of continual models of the linear, planar and dot defects making a basis of any nanostructure. Within the theory of irreversible deformations based on the continual model of Debye and Gryunayzen's approach volume properties of dislocations, their congestions and intercrystalline borders are investigated. It is shown that dislocations have to have the excess volume which size is defined by the asymmetry of potentials of interatomic interactions in relation to stretching and compression of materials. The data confirming a considerable influence of an excess volume on the speed of processes of a diffusive mass transfer along dislocation lines are provided. Also it is shown that the excess volume of dislocation congestions significantly depends not only on volume properties of individual dislocations but also on a structure of congestions. The received results are applied to the analysis of the problems arising at a research of effects of increase in plasticity of materials under pressure. It is shown that the squeezing pressure can promote increase in speed of processes of a relaxation of internal tension and suppress processes of concentration of tension in places of origin of the centers of destruction of materials. However, it does not interfere with developments of a lack of adhesion, and at rather low temperatures a condition of hydrostatic compression can lead to acceleration of processes of cavitation. The methods describing the deformation interaction of dot defects in chemically non-uniform materials are considered. The analysis is given regarding shortcomings of the existing microscopic and continual theories applied to the description of volume properties of dot defects in the non-uniform environments corresponding to nanostructures of metals and alloys. The models describe not local deformation interaction of dot defects in continual environments with any properties of anisotropy.