Dependence of the titanium structure formed under high-rate loading on its initial state

The structure of titanium specimens with different grain sizes and initial defect density that were subjected to large high-rate strains is studied, and the critical parameters of the onset of an unstable plastic flow in the specimens are determined. It is established that the formation of a titanium structure and the critical parameters governed by this structure are determined mainly by twinning. Twinning in shock-loaded titanium is the mechanism of plastic deformation that ensures the minimum change in the internal energy. Twinning in titanium under high-rate strain develops at the earlier stages over all admissible twinning systems and results in fragmentation of the structure. The twins are not the structural elements that contribute to the evolution of a uniform plastic strain. Fragmentation of the structure in the formation of twins decreases the critical parameters of the onset of an unstable plastic flow. It is found that as the strain increases, the twins fill the material up to a certain limit level, after which energy relaxation occurs owing to the formation of adiabatic-shear bands and/or cracking. The titanium structure formed in the deformation is highly stable. Translated fromFizika Goreniya i Vzryva, Vol. 36, No. 2, pp. 110–121, March–April, 2000.     

The chromium-nickel-carbon (Cr-Ni-C) phase diagram

Phase equilibria of the Cr-Ni-C system in the melting (crystallization) range were investigated by means of metallography, microprobe analysis, powder x-ray diffraction, differential thermal analysis, and melting point technique (Pirani and Alterthum method). On the basis of received results and assessment of available literary data, the phase diagram was presented as projections of solidus, liquidus, and melting (crystallization) diagram, reaction scheme at crystallization (melting), a number of vertical and isothermal sections. No ternary compounds were found in the system. The Ni-base phase forms equilibria with all others. The character of solid-phase equilibria does not change in the temperature range under investigation, from solidus to 800 °C.     

Excited-state absorption and anisotropy properties of two-photon absorbing fluorene derivatives

The electronic structure of fluorene derivatives N-(7-benzothiazol-2-yl-9,9-bis-decyl-9H-fluoren-2-yl)-acetamide (1); 9,9-didecyl-2,7-bis-(N,N-benzothiazoyl)fluorene (2); 4,4'-{[9,9-bis(ethyl)-9H-fluorene-2,7-diyl]di-2,1-ethenediyl}bis(N,N-diphenyl)benzeneamine (3); and 4,4',4"{[9,9-bis(ethyl)-9H-fluorene-2,4,7-triyl]tri-2,1-ethenediyl}tris(N,N-diphenyl)benzeneamine (4) were investigated by a steady-state spectral technique, quantum-chemical calculations, and a picosecond pump-probe method. These derivatives are of interest for their relatively high two-photon absorption. The steady-state excitation anisotropy spectra reveal the nature of the ground-state absorption bands. Semiempirical quantum-chemical calculations of the fluorene derivatives (AM1, ZINDO/S) show good agreement with experimental data. The spectral positions and alignment of various electronic transitions of derivatives 1-4 were estimated from their excited-state absorption and anisotropy spectra.     

High-temperature thermodynamic properties of the Al<Subscript>2</Subscript>O<Subscript>3</Subscript>-SiO<Subscript>2</Subscript> system

High-temperature mass spectrometry is used to investigate vaporization processes and determine SiO₂ activity in the Al₂O₃-SiO₂ system between 1850 and 1970 K. The results are consistent with the known phase equilibria in this system.__________Translated from Neorganicheskie Materialy, Vol. 41, No. 4, 2005, pp. 434–441.Original Russian Text Copyright © 2005 by Bondar, Lopatin, Stolyarova.     

Efficiency of measures aimed at decreasing the contamination of agricultural products in areas contaminated by the Chernobyl NPP accident.

The sequence of agricultural countermeasures taken in the Polessye area of the Ukraine contaminated by radionuclides as a result of the Chernobyl NPP accident is discussed. The efficiency of these countermeasures has been analysed. The concentration of 137Cs in crops has been shown to vary 10-100-fold, depending on the biological features of the plant species and on soil properties. Liming and mineral fertilizing of meadows increase the yield of grass and reduce 137Cs transfer to cows' milk up to 3.5-fold.     

Phase equilibria in the Cr-Ni-C system and their use for developing physicochemical principles for design of hard alloys based on chromium carbide

The Cr—Ni—C phase diagram at the melting point was plotted by a combination of procedures (metallography, x-ray, microprobe, differential thermal analysis, Pirani—Alterthum method, etc.). A general feature of this system is the existence of equilibria between the nickel-based phase and all the other phases. The temperature of the quasibinary (Ni)+(Cr₇C₃) eutectic was determined to be 1324±6°C. Based on both the phase diagram of the Cr—Ni—C system and the bending strength and Rockwell hardness of the alloys, the optimal composition of the initial carbide ingredient for production of hard alloys based on Cr₃C₂ with nickel—phosphorus binder was estimated as 13.0–13.3 at.%, substoichiometric with respect to Cr₃C₂. Institute of Problems in Materials Science, National Academy of Sciences of Ukraine, Kiev. Translated from Poroshkovaya Metallurgiya. No. 5/6(395), pp. 13–24, May–June, 1997.     

Rare-earth silicates

Binary systems of the type Ln₂O₃SiO₂ were studied. Three types of compounds were established for them: Ln₂O, SiO₄ (1:1) diorthosilicate, Ln₂Si₂O₇ (1:2), and the apatite-like silicate, Ln_4.67O [SiO₄]₃ (7:9), the latter being stable for the large cations. Systematization of the physical-chemical properties of rare-earth silicates was made. Based on the model of ideal solutions the liquidus curves were calculated for several Ln₂O₃  Ln₂O₃SiO₂ systems. The solid solution limits were determined for complex systems formed by rare-earth and alkaline-earth silicates. A series of rare-earth single crystals of simple and complex composition were grown by crystallization from molten solutions. Classification of the same type compounds into structural groups (morphotropic series) was made and partecipation of the 4f-orbitals in bondings was considered. The spectral-luminiscence characteristics of the rare-earth silicates are given.     

Modern cutting line in a plate-finishing section

Providing cutting lines with new-generation shears that have an arcuate top blade and employ a so-called “rolling cut” ensures plates’ geometric and dimensional accuracy (by narrowing the width and length tolerances, preventing oblique cuts, forming clean edges, reducing plate curvature, etc.). Plate production costs are reduced through the use of an efficient cutting method and dual trimmers, a reduction in the amount of production space and staff required, and combination of the trimmers and cross-cutting shears into one unit. The equipment designed for new plate-cutting lines at the Novokramatorskii Mashinostroitel’nyi Zavod meets all of these requirements.     

Comparison of tribological characteristics of nanostructured TiN,MoN, and TiN/MoN Arc-PVD coatings

The tribological properties of TiN, MoN, and TiN/MoN coatings have been investigated. It has been shown that, for multilayer (alternate) TiN/MoN coatings, a maximum hardness reaches 29–31 GPa that is significantly less than the hardness of MoN coatings (36.0–40.2 GPa) when changing the deposition conditions. MoN coatings possess lower coefficients of friction compared to TiN coatings, in particular at the initial stages of a scratch test. Two mechanisms of destruction are revealed by the adhesion tests, i.e., a cohesive failure with a minimum critical loading L _C1 and an adhesive test (plastic abrasion) with the appearance of a first crack L _C2. The resistance of multilayer (nanoscale) nanostructured TiN/MoN coatings with a total thickness of up to 8 μm is greater than that of TiN coatings.