Temperature and velocity dependence of the mechanical properties of intermetallic compound Ni3Al. II

This paper examines the retardation of superdislocations in LI₂ superstructure, due to the capture by superpartial dislocations (SPD) of atomic defects on the slip plane, and also resulting from diffusion of atomic defects in PD. When the jogs formed by the settling of defects on dislocations remain nondissociated, the sliding of superdislocations is accompanied by the generation of displaced rows of atoms the maximum linear energy of which in the L1₂ superstructure amounts to v/b (v is the ordering energy, b the interatomic distance). The maximum magnitude of retardation of superdislocations, dependent upon generation of displaced rows, is twice as high on cubic planes as on octahedral planes. The estimations presented indicate that the diffusion settling of atomic defects on the SPD of sliding superdislocations can be a cause of the anomalous temperature dependence of flow stresses under high temperatures. Some effects associated with the possible dissociability of jogs on SPD are examined.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii Fizika, No. 10, pp. 63–67, October, 1971.The authors express their thanks to É. V. Kozlov for helpful discussion.     

Temperature and velocity dependence of mechanical properties of the alloy Ni3Al. III

The temperatures and velocity dependence of the yield point and flow stress of the inter-metallic compound Ni₃Al was studied. It was established that, within the range of temperatures where the anomalous temperature dependence of flow stress is observed, an anomalous velocity dependence of these stresses also occurs. The increase of the yield point and flow stress of the alloy Ni₃Al with the increase of temperature is under the full control of thermally activated mechanisms of hardening. Three stages in the increase of resistance to deformation under increasing temperature were disclosed. It is assumed that two of these are associated with the deposition of atomic defects on sliding dislocations.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii Fizika, No. 11, pp. 107–113, November, 1971.     

Evolution of the dislocation structure and the hardening mechanisms of multiple slip oriented Ni3Ge single crystals

We studied the evolution of the dislocation structure of Ni₃Ge single crystals deformed by compression at room temperature. It is shown that the distribution of dislocations is spatially uniform in the studied alloy. The uniformity in the dislocation distribution is produced by relatively high amounts of the frictional stresses of the dislocations. On the basis of the obtained values of the dislocation structure parameters, the contributions of the various mechanisms in the dislocation drag are determined. It is shown that the resistance to deformation is determined primarily by overcoming reactive and unreactive forest dislocations, the total contribution of which is 0.9 of the applied stress.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 3, pp. 65–70, March, 1987.     

Mismatch and electron mobility in MBE GaxIn1−xas epitaxial layers on InP substrates

Composition inhomogeneity in nearly matched epilayers of the ternary semiconductor alloy Ga_xIn_1–xAs (x close to 0.47), grown by molecular beam epitaxy (MBE) on (001) InP substrates is correlated to variation of the lattice mismatch by x-ray imaging and local diffractometry. Misfit dislocations are shown to develop in areas of large misfit (above 2 × 10^–3) and are at the origin of a severe degradation of the electron mobility: an increase by a factor of about 4 in the intrinsic misfit (2.3 × 10^–3 compared to 0.6 × 10^–3) results in a 35 % reduction of the 77 K electron mobility.Part of this work has been done while this author was with Thomson-CSF Central Research Laboratory, Orsay, France     

Influence of copper solute on the creep rate sensitivities of aluminium

The presence of copper atoms as continuous networks at the grain boundaries of an aluminium-copper alloy has been considered not preventing the moving of dislocations during creep (or at least partially). The dislocations can bs absorbed by these boundaries and penetrate through them. That leads to changés of shape and structure of grains and also to the sliding of grains against each other. This was deduced from the accelerating increase in the sensitivity of the steady state creep rate to the applied stress of an aluminium 2·8 wt% copper alloy examined at wide range of temperatures (50–350 °C) and applied stresses (7–170 MPa). This rapid increase in the sensitivity parameter of the steady state creep rate occurs in Al-Cu alloys at quite higher ranges of applied stresses and may be attributed mainly to the contribution of the grain boundary movements to the creep strain.     

Study of diffusion creep accompanying superplastic deformation of the alloy ZhS6KP

The development of diffusion creep (DC) accompanying superplastic deformation (SPD) of the highly doped nickel alloy ZhS6KP is studied based on an investigation of the redistribution of dispersed intragrain deposits of the phase of Ni₃(Al, Ti). Deposit-free zones (DFZ) are formed in the alloy, held at the temperature of SPD and accompanying deformation at the grain boundaries. The contribution of DC to the deformation was determined from a comparative analysis of the width of the DFZ in the deformed and undeformed parts of the samples for different grain sizes and rates of DC taking into account diffusion accommodation. It was established that for the optimum rate of SPD the upper limit of the contribution of DC to deformation for 2-m grains does not exceed 11%. It is concluded, based on the distribution of DFZ, that the effect of DC accompanying SPD is determined by diffusion fluxes, associated with the local concentration of stress accompanying the development of grain-boundary slipping.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 6, pp. 40–45, June, 1986.In conclusion, we thank Yu. M. Mishin for a useful discussion of the results.     

Study of the crystallography of slip in the alloy Ni3Al

It has been established that cubic slip is an effective mechanism for the strain of the Ni₃A1 alloy even at room temperature. Traces of cubic slip were observed in an electron microscope for all degrees of strain. The critical spalling stress in the plane of the cube is small and approximately 2.5 kg/mm². In a two-phase alloy consisting of segregations, '-phase (Ni₃Al) and a disordered matrix (-phase), the traces of cubic slip generated in the ordered phase which have reached the phase boundary, are even continued into the segregations of the disordered phase.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii Fizika, No. 7, pp. 42–47, July, 1971.     

Investigation of the magnetic anisotropy of yttrium-samarium ferrogarnets

The temperature dependence of the cubic and induced anisotropies of singlecrystal garnets Y_3–xSm_xFe₅O₁₂ (x = 0.2, 0.3, 1.1, 1.8) is studied by the method of ferromagnetic resonance in the 3-cm band.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 1, pp. 32–37, January, 1978.The authors are grateful to E. P. Naiden for performing the x-ray measurements.     

Screw dislocation mediated growth of sputtered and laser-ablated YBa2Cu3O7-δ films

By imaging the as-grown surfaces of sputtered and laserablated YBa₂Cu₃O_7– films with scanning tunneling microscopy (STM), we have directly observed spiral-shaped growth terraces which emanate from screw dislocations. The density of screw dislocations was observed to decrease with increasing growth temperature and substrate misorientation. The surface structures observed by STM together with cross-sectional transmission electron microscope (TEM) images provide insights into the mechanisms of crystal growth operative during the formation of YBa₂Cu₃O_7– films grown using these two widespread techniques.     

Influence of supersaturation by point defects on the shear modulus of nickel and nickel-boron alloy

The influences of supersaturation of samples by point defects on the shear modulus is investigated by the internal-friction method. It is found that, in the temperature range 0.25–0.5T_m, the shear modulus of such samples is less. A mechanism associated with increase in mobility of the dislocations on account of diffusional influx of the point defects formed on irradiation is proposed, and an expression is obtained for estimating the magnitude of the effect.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 1, pp. 53–56, January, 1984.     

Interaction of dislocations and deformation hardening of the ordered CuAu alloy

The critical configurations of combinations of various types of dislocations in ordered alloys with L1₀ superstructure are analyzed numerically. The characteristics of the dislocation combinations, as well as the partial resistance to motion of dislocations, owing to interaction of dislocations, are calculated for polycrystals and single crystals with different orientations of the ordered alloy CuAu.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 8, pp. 21–26, August, 1982.We thank V. I. Syutkina for her constant interest in this work and for valuable discussions.     

Generalization of the Bethe method to the case of a ternary alloy of A2BC type

The known Bethe and Cowley methods are extended to the case of ternary alloys with body centered cubic (BCC) lattice and three kinds of sites. The system of equations to determine the Curie point of an A₂BC type alloy is obtained.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 3, pp. 41–45, March, 1974.     

Effect of oxidation on the magnetic properties of Ni3Cr alloy

The effect of oxidation on magnetic susceptibility and electrical resistance was studied in samples of Ni₃Cr alloy which had been prehardened from 1066, 1190, and 1250°C. X-radio-graphic analysis of the samples was carried out. It was shown that the observed increase of the magnetic susceptibility of the alloy after oxidation in the temperature range 750–1050°C is related to the formation on the surface of the sample of a layer with a variable nickel content in the range Ni₃Cr to pure nickel.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 5, pp. 38–41, May, 1972.     

Martensitic transformation in La1−x Yb x Ag1−y In y

The structural phase transformation of La_1–x Yb _x Ag_1–y In _y has been studied on single crystals by low temperature Laue-technique. The martensitic transformation in this pseudobinary intermetallic alloy has to be characterized as a weak orthorhtombic distortion of a single I centered unit cell (c/a1.04;a/b1.006) and a collective slipping or twinning of these cells that gives a fixed orientation between the remaining cubic room temperature structure and the martensitic phase. Above room temperature exists an order-disorder transformation from the CsCl-B2 structure to an at room temperature metastable W-A2 structure. There is no dramatic change in the physical properties of this alloy by substituting La by Yb, so we may approximate our results to LaAg_1–y In _y .This paper is dedicated to Prof. Dr. S. Methfessel on the occasion of his 60^th birthday     

Thermally activated deformation processes in monocrystals of an ordered Ni3Fe alloy

The temperature dependence of the flow stresses of monocrystals of an ordered Ni₃Fe alloy is studied. The mechanisms determining the temperature dependence are deduced from experiments on the variation of the deformation temperature and stress relaxation. A theoretical estimate is given for the contribution of the thermal component of the flow stresses, and is found to be in good agreement with experiment.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 5, pp. 86–91, 1979.     

Composition of tantalum nitride thin films grown by low-energy nitrogen implantation: a factor analysis study of the Ta 4 f XPS core level

Tantalum nitride thin films have been grown by in situ nitrogen implantation of metallic tantalum at room temperature over the energy range of 0.5–5 keV. X-ray photoelectron spectroscopy and factor analysis (FA) have been used to characterize the chemical composition of the films. The number of the different Ta–N phases formed during nitrogen implantation, as well as their spectral shapes and concentrations, have been obtained using principal component analysis and iterative target transformation factor analysis, without any prior assumptions. According to FA results, the composition of the tantalum nitride films depends on both the ion dose and the ion energy, and is mainly formed by a mixture of metallic tantalum, β-TaN_0.05 , γ-Ta₂N and cubic/hexagonal TaN phases. The kinetics of tantalum nitridation is characterized by two stages. In the first stage, the formation of β-TaN_0.05 species leads to a strong attenuation of the metallic tantalum signal. During the second stage, β-TaN_0.05 transforms into γ-Ta₂N and cubic/hexagonal TaN species. For intermediate ion doses, the concentration of γ-Ta₂N reaches a maximum, subsequently decreasing because of its transformation into cubic/hexagonal TaN phases with increasing ion dose up to saturation. At saturation, the films are mainly composed of a mixture of γ-Ta₂N and cubic/hexagonal TaN phases, but small Ta⁰ and β-TaN_0.05 signals are also observed. They should be attributed to preferential sputtering of nitrogen and/or to the limited thickness of the film. Comparison of the experimental nitrogen concentration with that obtained using TRIDYN simulations suggests that, in addition to nitrogen implantation and atomic mixing, other mechanisms, like ion beam enhanced diffusion or the chemical reactivity of the tantalum substrate towards nitrogen, should also be taken into account at higher ion-beam energies. PACS 68.49.Uv; 68.55.Nq; 81.05.Je; 81.70.Jb     

Phase transitions in TiNi(Rh) alloys

In this paper we report the results of x-ray structure analysis of how gamma rays and slight plastic strain affect phase transitions in the alloy Ti₅₀Ni₄₈Rh₂. Analysis of the published data on the temperature dependences of the rhombohedral angle in the R phase during the B2-R phase transition showed that not a single rhombohedral angle curve reflects the distortion relative to the cubic lattice of the B2 phase from the reduced temperature in the alloys TiNi and Ti₅₀Ni_50–xMe_x (Me=Fe, Co, Rh).Tomsk State Architectural-Construction Academy. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 10, pp. 67–75, October, 1995.     

Retardation of dislocations by the Cherenkov mechanism in crystals with a soft mode

The retardation mechanism of dislocations in crystals with a soft mode on account of Cherenkov emission of soft optical phonons is considered in the present work. The conditions in which this retardation mechanism appears are examined for various orientations of the wave vector q_c characterizing structural phase transition. It is shown that the threshold velocity of the retardation mechanism in the case where q_c¦V (V is the velocity of motion of the dislocations) decreases on approaching the phase-transition temperature T_c in proportion to ¦t_c–T_c¦. The dependence of the dynamic retardation coefficient B on the velocity V and the closeness to the point of structural phase transition is obtained.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 12, pp. 59–64, December, 1988.     

Strain hardening and characteristics of the dislocation structure of the alloy Ni3Mn with a different order state

The strain hardening, dislocation structure, and shear localization in slip traces are studied in this paper, as a function of the state of order in a Ni₃Mn alloy. The existence of a correlation between the strain-hardening characteristics, the interdislocation parameter , the number of single dislocations, and the shear localization magnitude in slip traces is established in the alloy under investigation.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 2, pp. 94–98, February, 1982.     

Effect of Hydrolysis Conditions on the Direct Formation of Nanoparticles of Ceria–Zirconia Solid Solutions from Acidic Aqueous Solutions

The effect of the cation concentration, hydrolysis temperature, and composition in the CeO₂–ZrO₂ system on the direct precipitation of ceria–zirconia solid solutions and the structure of the precipitates from acidic aqueous solutions of (NH₄)₂Ce(NO₃)₆ and ZrOCl₂ by hydrolysis under hydrothermal conditions were investigated. Nanometer-sized (8–10 nm) ceria–zirconia solid solution particles in a composition range of 0 to 60 mol% ZrO₂ were directly precipitated from the solutions with total metal cation concentration less than 0.2 mol/dm³ by simultaneous thermal hydrolysis at 150–240°C. The crystalline phase of the precipitates gradually changed from cubic and/or tetragonal to monoclinic with increasing the cation concentration of the solution from 0.2 to 0.8 mol/dm³ at the starting composition of 50 mol% ZrO₂ under hydrolysis condition of 150°C for 48 h, which was attributed to decrease in the supply of hydrolyzed Ce component caused by decrease in the hydrolysis ratio of (NH₄)₂Ce(NO₃)₆. Ceria–zirconia solid solutions containing large amount of ZrO₂ maintained high specific surface area and small-sized crystallite after heat-treatment at 900–1000°C for 1 h.