Papers by Author: M. Grekhov

Abstract: Distinctive structure features of rods produced by hot and cold radial forging of a Zr- 2.5%Nb alloy were revealed. Most experimental data were obtained by X-ray methods. Among considered aspects, connected with the undulatory mechanism of energy transfer, there are the uniformity of bulk deformation, structure perfection under hot radial forging, the demolition of secondary phases and the oversaturation of α-Zr with Nb under cold radial forging, the role of phase transformations in deformation, and the suppression of recrystallization by annealing. Structure, texture and properties of products, produced by radial forging from Zr-based alloys, allow to consider this technology as an acceptable alternative to that usable nowadays.

Abstract: By taking into account an interconnection between substructure non-uniformity and substructure anisotropy, a new approach to study the substructure non-uniformity is developed as applied to metal rods, subjected to Equal-Channel Angular Pressing (ECAP). The X-ray method of Generalized Pole Figures (GPF) was used for construction of distributions of substructure parameters. Some experimental data are presented, illustrating possibilities and efficiency of the used approach.

Abstract: The texture of Ti and Zr rods, subjected to equal-channel angular pressing (ECAP) by routes C and BC, is considered as a source of information about the actual loading scheme, operating mechanisms of plastic deformation, the structure condition of material. Processes of grain reorientation under rolling and ECAP are compared and distinguishing features of the latter are revealed. Effects of grain fragmentation and dynamic recrystallization on the texture are discussed.

Abstract: A detailed X-ray study of Zr rods, subjected to ECAP at 350oC by routes C and BC, was conducted by the new X-ray method of Generalized Pole Figures, combining texture measurement with registration of X-ray line profiles. The data analysis is based on conceptions of the texture formation theory, connecting features of grain reorientation with activated deformation mechanisms. A degree of reproduction of the same distinctive texture by successive ECAP passes with antecedent rotation of the rod reflects attendant structure changes in material.

Abstract: New data on structure and texture features of Cu and Ti rods, subjected to ECAP at 20oC and 400oC respectively, were obtained by means of advanced X-ray diffractometric methods. A deformation inhomogeneity through rod’s cross-section was studied by reduced cubic samples 3x3x3 mm, cut out from different regions of rods. The inhomogeneity of ECAP rods is characterized by distributions of texture and substructure parameters. Main tendencies in structure formation by ECAP are revealed.

Abstract: Texture analysis and the new X-ray method of Generalized Pole Figures (GPF) were used by the study of texture and substructure inhomogeneity of Ti rods, submitted to Equal-Channel Angular Pressing (ECAP) at 400oC. Local texture features testify about gradual rotation of loading axes by ~15o when crossing the rod’s section. As a result of second pass (route C), the specific ECAP texture weakens and the textureless component intensifies. Observed substructure changes are connected with development of dynamic recovery and dynamic recrystallization.

Abstract: Irradiation of metal materials with low-energy ions is accompanied by the long-range effect, consisting in distinct texture and structure changes at the depth, exceeding, at least, by 104 times the thickness of the layer of ion retardation. In order to ascertain mechanisms of this effect, a layer-by-layer X-ray study was carried out as applied to ion-plasma treated cladding tubes of Zr- 1%Nb alloy for nuclear reactors. Impacts of pulse treatments with helium plasma by two different regimes and the ion energy of ~ 1 keV were compared. It was found, that only by minimal surface melting the ion-plasma treatment causes unpredictable bulk texture changes, consisting in arising of the axial texture component. The melted surface layer suppresses shock waves, associated with braking of ions and supposedly responsible for stimulation of dislocation processes at long distances from the surface.