No abstract available

[en] The influence of conjoined action of tensile loading and ultrasonic oscillations on deformation behaviour and structural state of the polycrystalline vanadium is investigated. The instability of deformation on the yield plateau of the stress-strain curves is due to local structure changes dependent on amplitude of an ultrasonic stress

[en] Niobium and vanadium are considered for the change in their microhardness after quasihydroextrusion with 11, 29, 43 and 65 % reduction area at 77 and 300 K and subsequent annealings within the temperature range of 300...830 K, which corresponds to the third stage of recovery. Results of electron microscopic studies show that growth of the dislocation density and formation of the cellular structure in the process of hydroextrusion account for a ''deformation'' gain of the microhardness. Annealing gain of the microhardness is controlled by a redistribution of point defects and their complexes whose concentration monotonously increases with reduction in area under quasihydroextrusion

[en] Polycrystalline niobium was studied with the use of electron microscopy after quasihydroextrusion with deformation degree of 98.0 and 99.7% at 77 K. Nitride and oxynitride particles were found to precipitate out under severe deformation whereas at lower strains the metal remained single phase. All volume of deformed material was fragmented. Boundaries of misorientation and aggregated of dislocations of eformation origin were main structural elements. Possible reasons for anomalously intensi mass transfer of interstitials at the given thermal activation are considered. 12 refs., 1 fig

[en] Changes of structure, electrical resistivity and creep characteristics of annealed niobium and niobium preliminary strained by drawing on 80 % at 77 K are investigated at 77 and 300 K. It is shown that in the process of low temperature creep of metal with heavily distorted fragmentation structures the transition from logarithmic creep to recovery creep is observed. Deformation of preliminary strained niobium on a stage of logarithmic creep at strengths above yield stress is carried out by the processes, characteristic for mechanisms of an exhaustion of dislocation. Change of the mechanism of plastic deformation does not depend on highly distorted structure formation. The main contribution is due to formation of ensembles of the same dislocations. As a result of its collective interaction and movement at various stages of plastic deformation the borders of dislocation and disclination types are formed

[en] It was investigated the influence of ultrasonic action on nanostructure of deformation origin in the alloy of Zr-2.5% Nb. The nanostructure state was obtained by the combined rolling at 300 and 100 K on 96%. By means of electronic microscopy there were evaluated density of dislocations in the body of nanograins and volume concentration of grain phase, the level of stresses of 2-nd kind, and also change of these characteristics as a result of action of ultrasonic vibrations with stresses amplitude 85 and 200 MPa. The looked after effects are due to microshear relaxation in area of stress concentrators at relative low amplitudes of ultrasonic vibrations and by destruction of initial nanostructure and forming the new, more equilibrium, as a result of intensification of interaction of the fields of internal stresses, at large amplitudes. It is marked that ultrasonic deformation of nanostructure results, in the total, in realization of dynamic recovery processes with maintenance of nanostructure morphology. Thus there are a decrease of internal stresses level and smoothing of its spectrum, and also increase of structure homogeneity.

[en] Mechanical properties of polycrystalline GFE-1 hafnium strained by rolling at 300 K with ? degrees e=18...70 % were studied. The non-monotone dependence of proportional limit, yield strength and ultimate strength from the degree of rolling was found out. As a result of ultrasonic action with amplitudes of stresses, comparable with the yield strength, the effects of work-hardening of material are discovered in an anneal state and softening - in deformed, that caused by generation of defects and relaxation of internal stresses, accordingly.

[en] The changes in the structure and mechanical properties of polycrystalline vanadium after drawing deformation (including ultrasound superposition) up to 98% at 77 and 300 K are studied and analyzed. A decrease in the deformation temperature is found to lead to retardation of mass fragmentation processes in the material, along with a considerable growth of the degree of the structure imperfection. As a result, the regions of uniform dislocation distribution can be observed up to 90% compression. Possible evolution of this type of structure is considered. It is assumed that even in the most favorable situation for the structure to persist, the highest dislocation density achievable on deformation is two orders of magnitude lower than theory predicts. The continuous disorientations in this structure induced by smeared piles of dislocations having the same sign do not exceed 5 degree. The correlation between the structure characteristics and the features of the mechanical properties is analyzed

No abstract available

[en] The changes in the structure, resistivity and plastic deformation characteristics of the polycrystalline niobium, annealed and also preliminary deformed by drawing to 80%, were studied at 77 and 300 K. It is shown that during the low-temperature creep of highly defect systems, the dislocation exhaustion mechanism is working even at stresses above the yield stress as the processes of linear defect generation under these conditions are strongly hindered. The development of low-temperature creep processes in the highly distorted fragmented structures cannot be described by the classical representations. A transition from the logarithmic creep to the power law creep, characteristic for much higher temperatures is observed, at the same time the total level of internal stresses being decreased. The variation of the law of plastic flow in the given stage of niobium creep at low temperatures does not depend on the method of highly distorted structure formation. The formation of new structures, which are steadier to tensile stresses, plays a determining role.