It is shown for the low-plasticity ferritic-pearlitic steel 15Kh2NMFA (2Cr, 1Ni, 0.5Mn, 0.5Mo), subjected to severe rolling deformation at 90 K, that the treatment by the alternating magnetic field results in a substantial decrease of the yield strength and an increase of fracture stress, total elongation, necking and dynamic shear modulus. This is accompanied by reduction of the internal friction background and coercive force. The changes in the physical-mechanical properties and the structure are related to magnetic-and electrical-nature processes giving rise to stress relaxation in the microvolumes with a high density of deformation defects.

The effect of low temperature (77 K) deformation by drawing (80%) on the superconducting properties and structure of vanadium is studied. The structural elements (fragment boundaries) responsible for the observed changes of critical parameters are isolated. The electron-phonon coupling constant and the electron mean free path undergo most significant changes in these regions of rotational deformation localization, which have a high density of defects and are powerful sources of internal stresses. The dislocation density at the fragment boundaries is estimated.

A. V. Mats, V. M. Netesov, UDC 621.789 and V. I. Sokolenko 1The paper addresses the influence of high-temperature ultrasonic treatment on the structure and impact toughness of steel 15Kh2NMFA. The observed increase of impact toughness and decrease of ductile-brittle transition temperature for the steel upon ultrasonic treatment of various durations are due to the formation of a uniform defect structure. Introduction.A study of the influence of ultrasound treatment on metals and alloys, which causes no form changes, but affects their strength characteristics is of considerable interest, insofar as material structure in this case differ from that generated through intensive plastic strains or during static deformation [1]. Such investigations are lucrative for getting deeper insight into physical processes of structural self-organization under external actions. Furthermore, their findings may facilitate the industrial application of ultrasound for treating the steels which are used, for example, in the nuclear reactor industry.Considering that dynamic bending impact tests make it possible to reveal a material susceptibility to brittle fracture, the objective of the present work was to clarify interrelation between the impact toughness behavior and the structural state of the reactor pressure vessel steel 15Kh2NMFA subjected to ultrasonic treatment (UST).Experimental. The investigation was carried out on a reactor pressure vessel steel 15Kh2NMFA which is of ferrite-pearlite type. Billets for test specimens were cut from a segment of a mill forged piece upon the standard mechanical and thermal treatment as involved in the manufacture of a reactor pressure vessel. For impact tests to be performed using a pendulum-type testing machine in the temperature range from -100 to 100°C we have prepared Charpy V-notched bars of rectangular cross section (10 10 mm) and 55 mm long. The UST procedure and methods for determination of the range of ultrasonic stresses s us in the test specimens are detailed in [2]. In this particular case, it was the specimen central portion which was subjected to UST (Fig. 1).With this end in view, the side surface of the specimen was tightly pressed, by a special captive nut, to the tip of the ultrasonic waveform concentrator. The UST frequency was 20 kHz. During the treatment the specimens were cooled with running water. Microhardness was measured using a Mod. PMT-3 tester. Structure investigations were performed by means of a Mod. ÉMV-100BR electron microscope. Foils for electron microscopic observations were cut from the Charpy specimens at a fixed distance from the V-notch, in the UST zone produced under various UST conditions. The density of dislocations and the angle of disorientation of neighbor microvolumes were determined by the procedures detailed in [3].Results and Discussion. Some researchers [4,5] have demonstrated that structural alterations in a crystal lattice under the action of ultrasonic vibrations at a fixed temperature depend on the nature of the initial structure and the range...

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The structural-phase aspects of the behavior of the critical current under load in the superconductive alloy Nb–48.5 wt% Ti are studied. It is shown that the optimum preliminary strain at T=77 K with subsequent annealing suppresses the tendency of the β matrix of the alloy to undergo phase transformations according to martensitic kinetics under uniaxial tension at T=4.2 K, and this is manifested in the reduction of the critical-current degradation effect when loaded to σ=0.9σfr in a transverse magnetic field of H=5 T. The paper discusses possible critical-current degradation mechanisms under mechanical loading in the niobium-titanium alloy, based on models of critical current flow in the β matrix reinforced with martensitic interlayers.