Effect of compaction method on the structure and properties of bulk Cu + Cr<Subscript>3</Subscript>C<Subscript>2</Subscript> composites

Cu + Cr₃C₂ composites have been produced using the mechanical alloying of the elemental components, followed by severe plastic deformation by torsion, magnetic-pulse pressing, and electric-pulse plasma sintering. The composites are studied using X-ray diffraction and light and electron microscopy, as well as measurements of the hardness, density, and electric conductivity. Magnetic-pulse pressing at a temperature of 500°C makes it possible to produce volume nanocomposites with a homogeneous distribution of dispersed carbides over the copper matrix, which has a density of 96%, a Vickers microhardness of 4.6 GPa, a Rockwell hardness of 69 HRA, and an electric conductivity of 19% IACS units. Using electric-pulse plasma sintering at a temperature of 700°C, composites with the nanostructured copper matrix, which contains carbide inclusions and consists of domains surrounded by a layer of nearly pure copper, have been produced. These composites have a density of 88%, a Vickers microhardness of 4.0 GPa, a Rockwell hardness of 58 HRA, and electric conductivity of 26% IACS units.     

Sovol as an inducer of procarcinogen activating microsomal enzymes

The commercial mixture of polychlorinated biphenyls (Sovol) studied by biochemical and immunochemical methods was found to be an inducer of a wide range of cytochrome P-450 isoenzymes. The induced enzymes activated in the Ames test a series of procarcinogens differing both in structure and in target organs: benz(a)pyrene, 3-methylcholanthrene, nitrosomorpholine, dimethylnitrosamine, aflatoxin B1, orthoaminoazotoluene, 2-acetylaminofluorene, cyclophosphamide and benzidine. According to the parameters the studied Sovol is similar to Aroclor 1254 and may be recommended to be used as an inducer of microsomal enzymes in routine tests for carcinogen screening.     

Effect of hydrogen on the formation of the structure and phase composition in the Ti2AlNb-based alloy

Methods of X-ray diffraction, electron microprobe analysis, electron microscopy, differential thermal analysis, and microdurometry were used to study the effect of alloying with 5.2 and 8.5 at % hydrogen on the occurrence of phase and structural transformations in the intermetallic alloy Ti—24.3 Al—24.8 Nb—1.0 Zr—1.4 V—0.6 Mo—0.3 Si (at %) upon heating in the temperature range of 700-1050°C. It has been established that hydrogen favors the stabilization of the ? solid solution, the suppression of the formation of the α ₂ phase, and the reduction of the temperature of heating for quenching, starting with which the formation of an ordered a phase is possible in the alloy structure. Procedures of calculation of the electron concentration in the alloys with hydrogen have been proposed. By the method of the differential scanning calorimetry, the temperatures of disordering have been determined in the alloys.     

A diagram of isothermal decomposition of the β-phase in Ti-22Al-26Nb-0.5Zr-0.4Mo alloy

Using the methods of scanning electron microscopy and X-ray phase and durometric analysis, we constructed a diagram of isothermal decomposition of the metastable β-phase in Ti-22Al-26Nb-0.5Zr-0.4Mo alloy in the temperature range from 600 to 900°C in the course of its holding for up to 64 min. We also analyzed the morphologic features of the phases being formed. Translated from Fizyko-Khimichna Mekhanika Materialiv, Vol. 44, No. 3, pp. 62–66, May–June, 2008.     

Effect of the strain rate on the properties of electrical copper

The effect of the strain rate on the texture and strength characteristics of electrical copper is analyzed using an industrial experiment on low- and high-speed wire drawing. The mechanical properties of the product are determined. The strength of the wire drawn at a high speed is found to be about 20 MPa higher than that of the wire drawn at a low speed. Metallographic analysis shows no differences in the wire structures, and texture analysis reveals differences in the behavior of dominant texture components. The directions of the dominant texture components are found to rotate near the periphery of the workpiece (i.e., at the workpiece surface). The solution of the drawing problem by the finite element method demonstrates an analogous rotation of the principal elongation directions.     

Object-oriented description of graph data structures

A solution method for problems of processing graph data structures is presented. This method is based on the use of the specialized language TreeDL and on its extendable compiler. The capabilities of the language and of the compiler exceed the existing solutions, which makes the proposed method more efficient than its analogs.     

Effect of vibromechanical treatment on the structure of copper in cold reduction of long-length pipes

The microstructure and the texture of vibromechanically treated long-length copper pipes are studied by metallographic and x-ray diffraction methods. The degree of nonuniformity of strain of the material over the wall thickness is evaluated. Parallel studies of pipes subjected to the same degree of reduction by direct pressing are performed for comparison. Changes in the geometrical characteristics (the external and internal diameters, the wall thickness) with increase in the number of passes are analyzed.     

Interaction of a copper oxide particle with copper in drawing

The forming of copper near a copper oxide particle is determined during multiple-pass drawing. The interaction of the copper oxide particle with copper is studied by the calculation of the state of stress in a finite element formulation and using scanning electron microscopy data. The results obtained demonstrate that pores appear around copper oxide particles when strain accumulates in multiple-pass drawing machines. The pore length increases with the accumulated strain, which can result in breaks of a wire in a highly cold-worked state.     

Phase and structural transformations in the alloy on the basis of the orthorhombic titanium aluminide

Phase and structural transformations in the Ti-24.3 Al-24.8 Nb-1.0 Zr-1.4 V-0.6 Mo-0.3 Si (at %) alloy that take place during heating in the temperature range of 700–1050°C have been investigated. The temperature ranges of existence of the O + β, O + β + α₂, β + α₂, and β phase fields have been established. A scheme of the relationships between the volume fractions of the O, β, and α₂ phases depending on the temperature of heating of the alloy have been investigated. The formation of an ordered incommensurate ω (V _ω) phase has been revealed in the alloy during quenching from 900°C. The existence of a correlation between the hardness properties and changes in the phase composition and morphology of particles precipitating in the alloy has been shown.