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Defect structure evolution and mechanical properties in irradiated crystal systems

Work number - M 23 FILED

Presented Institute of Applied Physics of NAS of Ukraine

Shchokotova O.M., Bashtova A.I.

The main goal of work is a development of theoretical approaches concerning the study of the structure formation processes of the point defects ensemble, of the formation processes of defects and voids and the influence of point and line defects on the processes of rearrangement of the composition of irradiated systems, and also the study of mechanical properties changes of crystalline systems under irradiation and mechanical loading.

The conditions for the passage of the processes of the formation of point defects as a result of the action of irradiation and the appearance of deformation instabilities are established when stochastic defect generation is taken into account. Dynamic regimes of growth of vacancy-type clusters and dislocation loops in pure metals are revealed on the example of nickel. In the framework of developed approaches, it is shown that the characteristic size of the vacancy clusters is several nanometers, depending on the rate of damage and the temperature of irradiation. Taking into account the elastic properties of the medium in the presence of defects and the dynamics of sinks density, the spatial self-organization of an ensemble of point defects in irradiated α-zirconium and the influence of the formed vacancy complexes on the elastic fields of deformation were studied. The conditions and properties of the passage of the selection processes of structures upon irradiation of thin metallic films are revealed. It is established that the stochastic process of defect generation does not lead to a disruption of the self-similar void growth regime, increasing only the void size. It is found that when the intensity of dislocations increases, a crossover of dynamic regimes of void size growth takes place with a decrease in the dynamic index from 1/2 to 1/3. The processes of nonequilibrium vacancies rearrangement during spinodal decomposition of the irradiated binary solid solution are studied in details. It was revealed that with increasing the rates of defect formation processes of spinodal decomposition are replaced by processes formation of spatial vacancy structures. It was established that the formation clusters of vacancies is accompanied by the selection of structures. In the framework of development of the phase field theory, taking into account elastic contribution at the mechanical loads, a physical picture of the local redistribution of microscopic deformations and stress fields was established, and the influence of irradiation on the plastic and strength characteristics of the studied materials and alloys was determined. For binary alloy Zr-Nb it was shown, that yield strength and ultimate strength increase with dose rate and decrease with temperature growth. The analytical solutions of plane contact problems for elastic wedge were built, that may be used for determening of characteristics of the stress-strain state of the grain-like components of a piecewise inhomogeneous structure of structural materials. The practical meaning of the conducted studies is that the obtained results can be applied to the prediction of changes in the properties of structural materials under irradiation.

Number of publications: 40, including 15 articles (10 - in English-language journals with an impact factor). The total number of times cited to authors publications /h-index of work, according to databases is, respectively: Web of Science –54/ 3, Scopus–60/ 3, GoogleShcolar –58/ 1.