Structural transformations in high-nitrogen austenitic steel

Results are reported from a study of the structure of steel aged after quenching and subsequent rolling at 20, 400, and 1000°C. It is shown that cold and warm rolling with low and moderate degrees of deformation intensifies the reaction which results in the discontinuous precipitation of chromium nitride. With high degrees of deformation, this reaction does not take place, and heterogeneous precipitation of nitrides occurs. Discontinuous and heterogeneous nitride precipitation take place during hot rolling. During subsequent aging, the processes of spheroidization, coalescence, and recrystallization result in the formation of a microduplex structure.Deceased.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 6, pp. 32–36, June, 1988.     

Change of dislocation substructures upon high-cycle fatigue of stainless steel

Methods of transmission electron microscopy of thin foils are used to study the evolution of dislocation substructures in Fe–0.1C–1.7Mn–0.92Ti–18.2Cr–10.4Ni–0.71Si corrosion-proof austenitic steel subject to high-cycle fatigue loading to destruction. Quantitative dependences of the dislocation substructure parameters on the number of loading cycles and distances to the sample surface are established. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 3, pp. 42–45, March, 2009.     

Structural properties of austenitic stainless steel in the initial state and after rf plasma nitriding

Mössbauer spectroscopy, TEM, electrical resistivity and magnetic measurements are used for investigation of structural changes of X5CrNi189 austenitic stainless steel sheet induced by rf plasma nitriding carried out at 400°C for 24 h. The initial structure formed by small grains of austenite and α′-martensite changes after nitriding into expanded austenite close to the surface and austenite with minor contents of ferrite/CrN in the bulk.     

Formation of an ultrafine structure in an austenitic steel stable against pressure-induced phase transformation

The effect of shear γ-? transformation on the hardness, size of structural elements, and transition to the submicrocrystalline stage of the structure during deformation of the austenitic steel 4Kh14N14V2M, whose phase stability depends on the pressure applied, has been revealed.     

Evolution of the phase composition and defect substructure of rail steel subjected to high-intensity electron-beam treatment

The morphology, structure-phase states, and defect substructure of annealed rail steel subjected to electron-beam treatment in the surface-layer melting mode are studied by scanning and transmission electron microscopy methods. The formation of the lath martensite structure, as well as cellular and dendritelike structures, containing nanoscale martensite crystals, is revealed.     

Carbon redistribution in austenitic steel weldments

In parts I and II of our papers (Czech. J. Phys.35 (1985) 1355 and36 (1986) 514) concerning carbon redistribution in austenitic steel weldments the stationary (SM) and quasistationary (QSM) models have been developed and applied in the analysis of Darken's and our own data. It was necessary, in deriving the quoted SM and QSM, to introduce some simplifying presumptions. The present part III gives the general solution (GS) of the problem. It is based on the theory of thermodynamics irreversible processes, and the resulting system of differential equations is integrated numerically. The properties and chances of the GS are demonstrated in comparison with experimental data and by different examples of the prediction of carbon redistribution. The events of the non-zero thermodynamic (skCi) and diffusion (skCi) interaction coefficients, of the Kirkendall effect, of the non-constant atomic volume effect and of the different Wagner's and Zupp-Stevenson expressions of carbon activity coefficient _C are discussed.     

Geometric phase in a composite system subjected to decoherence

In this paper, we investigate the geometric phase of a composite system which is composed of two spin- particles driven by a time-varying magnetic field. Firstly, we consider the special case that only one subsystem driven by time-varying magnetic field. Using the quantum jump approach, we calculate the geometric phase associated with the adiabatic evolution of the system subjected to decoherence. The results show that the lowest order corrections to the phase in the no-jump trajectory is only quadratic in decoherence coefficient. Then, both subsystem driven by time-varying magnetic field is considered, we show that the geometric phase is related to the exchange-interaction coefficient and polar angle of the magnetic field.     

Coherent states,phase states,and condensed states

We study phase properties of generalized coherent states obtained from usual Fock coherent states by adapting classical methods of statistical mechanics, in particular, the well-known procedure of thermodynamical limit. Moreover, we show that there exists a close connection between these states and the states describing boson systems with condensation properties.     

Structural and phase changes in metals during formation of the fatigue fracture surface in metals and alloys

The mechanisms of deformation-induced structural and phase changes, which accompany crack nucleation and growth during fatigue fracture of metals and alloys, are considered. It is shown that the crack steady growth phase is determined by the processes of local melting of the material in extension phase, and melt crystallization processes with formation of shrinkage pores in front of the crack tip in the unloading phases and crack narrowing.     

Effects of niobium on the resistance to abrasive wear in manganese-rich austenitic steel

Russian Physics Journal -     

Donor impurity states in elliptical quantum rings subjected to a magnetic field

Within the effective-mass approximation we calculate the energies of a donor impurity in an elliptical quantum ring subjected to a magnetic field. The energies are found to exhibit Aharonov-Bohm oscillations depending on the magnetic field and the eccentricity. As the eccentricity increases, the energies decrease and the period increases.     

Scattering-induced attenuation of an ultrasonic beam in austenitic steel

The scattering-induced attenuation coefficient of a beam of longitudinal waves propagating through an austenitic steel plate is measured as a function of the texture angle. The experimental data were obtained by mapping the incident and the transmitted ultrasonic field, and by evaluating the energy loss experienced by each plane wave component of the beam. Contrary to the behavior of data obtained by means of conventional techniques, that of the data reported in this work agrees qualitatively with the theoretical predictions. The reasons for the disagreement between theory and data obtained by means of conventional techniques are also discussed.     

Stationary and quasistationary models of carbon redistribution in austenitic steel weldments

In this paper models describing carbon redistribution in austenitic steel weldments are presented. The stationary model (SM) is based on the assumption that the substitutional atoms do not diffuse, they are stationary. The quasistationary model (QSM) describes the C-redistribution even in the case in which the substitutional atoms diffuse in a narrow interval which is situated in the neighbourhood of the weldment interface. In developing the models the following assumptions were used: The driving force of carbon diffusion is the gradient of the chemical potential in which the C-C interaction is not taken into account ( _C ^C = 0); the molar volumes of the solid solutions under consideration are the same and constant in both parts of the weldment; the Kirkendall effect does not occur.     

Stationary and quasistationary models of carbon redistribution in austenitic steel weldments

In this IInd part of our paper (Czech. J. Phys. B35 (1985) 1355) the analysis of carbon uphill diffusion data is presented. The analysed data were measured in the polycomponent steel weldments. All of the data satisfy well the conditions for stationary model application. On the basis of the present analysis the carbon diffusivities (D ₁ ^* ) appertaining to a non-alloyed austenite, the activity ( _C ^s ) and diffusion ( _C ^s ) interaction coefficients are evaluated. A Si anomaly in Darken's experiments is observed and discussed. On the contrary to the other substitutional elements Mn, Cr and Mo, which decrease simultaneously C-activity and C-diffusivity, silicon increases the carbon activity and, at the same time, decreases its diffusivity in the Fe-C-X_s austenitic solid solutions.     

Structural and morphological transformations of diamond-like coatings subjected to energy treatment

The impact of microwave radiation and heat treatment on the structure, morphology, and physical and mechanical properties of diamond-like coatings is studied; recrystallization of the coating structure is revealed. It is ascertained that microwave irradiation of diamond-like coatings changes their physical and mechanical properties.     

Structural changes in nickel alloys subjected to gamma irradiation in a gaseous medium

The structuring action of rays from⁶⁰Co and⁵⁷Co sources on dilute nickel alloys containing elements with a high affinity for oxygen was studied. It was shown that after irradiation in the alloys at room temperature there is a prolonged redistribution of the elements which is accompanied by the precipitation of dispersed oxides.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 2, pp. 75–82, February, 1996.     

Berry phase correction to electron density of states in solids

Liouville's theorem on the conservation of phase-space volume is violated by Berry phase in the semiclassical dynamics of Bloch electrons. This leads to a modification of the phase-space density of states, whose significance is discussed in a number of examples: field modification of the Fermi-sea volume, connection to the anomalous Hall effect, and a general formula for orbital magnetization. The effective quantum mechanics of Bloch electrons is also sketched, where the modified density of states plays an essential role.     

Structural ordering upon annealing of europium molybdate subjected to pressure treatment

It has been found that treatment of europium molybdate single crystals under high uniform pressure leads to radical changes of the IR reflectance spectra of the samples. Instead of a series of narrow lines, which are characteristic of the spectrum of the initial crystal, the spectrum of the sample subjected to pressure treatment exhibits broad bands. As follows from the results of X-ray diffraction measurements, this transformation of the IR spectra is associated with the fact that, after pressure treatment, the sample represents an amorphous matrix with inclusions of nanocrystals of the high-pressure phase. In the IR spectra, the high-pressure phase manifests itself in the form of a new line at approximately 600 cm⁻¹. After annealing of the sample with an increase of the temperature from 100 to 400°C, the high-pressure phase disappears. A further increase of the annealing temperature to 550°C leads to the recovery of the crystal structure of the initial β′ phase of europium molybdate and to the appearance of lines corresponding to the α phase.