Materials Science Forum Vol. 946

Abstract: The Ni-Fe thin films were produced via electrodeposition in four different modes - direct current, and three types of pulse-modes with different pulse duration onto Au sublayer. The correlation between technological parameters of the electrodeposition and microstructure was demonstrated. Analysis of microstructure evolution revealed an un-expected changing of the film growth mechanism from “island” to “layer-by-layer” with the decreasing of the grain size less than 10 nm. Explanation was found in binding energies competition, that has been defined using the unique AFM method, based on recording the angle of the cantilever twist, when scanning in contact with the surface.

Abstract: Through-pores alumina membranes of 50 μm thickness and 70 × 70 mm size have been fabricated to deposit Ni nanowires by electrochemical processing. Due to highly ordered microstructure of the membranes, the pores were filled by nanowires almost to 100%. The membrane nanowires composite morphology; structure and chemical features have been studied by scanning electron microscopy, atomic-force microscopy and X-ray structural analysis. To measure the specific magnetization σ as a function of temperature in the range of 77–1400 K, the pondero-motive method was used.

Abstract: Drawing is the basic operation of wire manufacturing. At drawing a wire contacts with a die resulting in decrease of its diameter. During this interaction wire microstructure changes, especially on the contact area between a die and a wire. Specificity of microstructure changing on outer surface of carbon steel wire at drawing and its combination with torsion is presented in the paper. Using optical microscopy, it was found out that in the outer surface of carbon steel wire a narrow layer of highly deformed grains is formed. It is shown that thickness of this layer depends on the deformational processing intensity and is very specific depending on carbon content of the wire.

Abstract: Reasons for breakage of welding rod and wire at drawing are analyzed. It is shown that the basic reason for breakage is microphysical tree-like segregation which is caused by irrational addition of boron-containing material at after-furnace treatment, low effectiveness of steel continuous casting process, unproven technology of metal electromagnetic agitation in a mold at continuous casting. Peculiarities of alloyed elements liquation, both in welding rod and wire are studied. It is shown that non-uniformity of boron, manganese and silicon distributions in the longitudinal and transversal welding rod cross sections will become the main reason for increasing wire breakage during further drawing.

Abstract: Drawing is characterized by non-uniform character of plastic deformation, which is transferred from the die to the processed wire. Such impact causes specific change of wire microstructure. In the surface area the thin layer with highly deformed grains is observed. It is important to measure the thickness of this thin layer. For this purpose it is proposed in this paper to use the value of coefficient of anisotropy, which is calculated as the ratio of mean quantity of phase particles, crossed by secant line perpendicular to deformation axis on the unit of secant line length to the mean quantity of phase particles, crossed by secant line parallel to deformation axis on the unit of secant line length. Distribution of coefficient of anisotropy, both for low and high carbon steel wire after drawing, was obtained by Thixomet PRO software. It made it possible to calculate the thickness of highly deformed area automatically taking into consideration the difference of steels microstructure.

Abstract: We consider the problems of the complex application of the aluminium-yttrium binder in the fabrication of high-temperature resistant melting crucibles and investment molds thermoschemically resistant to titanium melts. The results of the contact interaction investigations of a molten titanium alloy with a material of aluminum-yttrium ceramics are presented. The usage of ceramic products of α-Al₂O₃–Y₃Al₅O₁₂∙α-Al₂O₃ composition under conditions of high-temperature melting and pouring under vacuum minimizes the physicochemical interaction and significantly reduces the alpha case layer on cast products, thereby improving their operational properties.

Abstract: The Raman spectroscopy is used to identify and determine the content of the components of a GdOCl − GdCl₃ • 6H₂O mixture. It can be used for analytical control of the composition and detection of undesirable oxygen-containing impurities in chloride reaction media in the preparation of rare-earth metals.

Abstract: This paper presents the results of the analysis of acoustic emission signals registered by using fiber-optic sensors during the propagation of ultrasonic waves in a polymer composite material. Fiber-optical sensors for acoustic emission were constructed according to the scheme of an adaptive holographic interferometer. Unlike piezoelectric sensors, fiber-optic sensors are distributed type sensors. This imposes certain features on the detection of signals in plates in which fiber-optic sensors are embedded. It is established that the difference of the spectrum of acoustic emission signals is registered in different directions of wave propagation. The local maximums of the spectrum are determined by the mode of wave propagation in the plate in different directions and the location of fiber-optic sensors.

Abstract: Physical theory of reliability is based on research into degradation processes of various origins which take place in a material of a stressed construction. Experimental evaluation of parameters carried out for such processes is a practically important problem by itself. One of the approaches to solving this problem is related to the studies into the stage of material softening due to deformation. This paper analyzes the issues of experimental validation of material softening properties in terms of a phenomenological approach to the problem of structural fracture. Results of deformation analysis for the “machine – model specimen” system, using catastrophe theory are used to form requirements for carrying out experiments which investigate the softening stage of materials. The success of such experiments – which should include recording a branch descending to zero on a computer diagram – is possible when small specimen, made from structurally heterogeneous materials, are strained in a sufficiently rigid testing machine. Thus, the conditions for manifestation of the softening stage connect properties of the material with properties of the load-applying system. Therefore, the material's limiting state – preceding the fractured – also depends on the conditions of loading, and the criteria of that fracture would be nonlocal. In consideration of the results of diagrams plotted from various bases for deformation measurement, a necessity of utilizing local material characteristics for calculation purposes is discussed. As an example of using the complete diagrams for determining kinetics of material degradation from external load, the results of specimen testing, which follows a cyclic training, are cited.

Abstract: Copper alloys are widely used in mechanical engineering. In the article it is shown that the requirements of consumers to properties of alloys are constantly increasing. Complex alloyed brasses have a high wear resistance and corrosion resistance. The wear resistance is a basic property of an alloy. This characteristic determines the operating life of parts working in the wear conditions. The wear resistance is supported by phase composition of alloy, uniformity of distribution of phase in the structure of alloy, their volume fraction, their morphology and their dimensions. At present time the technology of continuous casting of ingots of alloys Cu59Zn34.6Mn3.5Al2.5Fe0.5Ni0.4, Cu70Zn13Mn7Al5Fe2Si2Pb1, Cu58Zn36Mn2Pb2Si1Al1 and Cu58Zn35Mn3Si1.5Ni1.5Pb1 is developed. However, the need to use new alloys for manufacturing of critical parts requires the development of technology for their production, taking into account the composition of alloy and the features of formation of structure. Therefore, it is necessary to establish well-founded technological parameters of melting and casting of ingots of complex alloyed brass Cu62Zn31.6Mn3Al2Si0.8Ni0.4Cr0.2. For determination of temperatures of phase transformations in the structure of alloy, the differential thermal analysis was carried out. Liquidus and solidus temperatures of alloy were determined. The crystallization range of alloy was established. This brass in a solid state undergoes two phase transformations. The temperature of the first phase transformation is 750 oC. The temperature of the second phase transformation is 515 oC. The obtained experimental data make it possible to describe the proposed mechanism of phase transformations in alloy Cu62Zn31.6Mn3Al2Si0.8Ni0.4Cr0.2 during crystallization and following cooling.