Influence of megaplastic deformation on the structure and hardness of Al–Cu–Mg alloy after aging

Methods of electron microscopy and X-ray diffraction have been used to investigate structural and phase transformations in the aluminum alloy of grade A2024 (Al–4.5 Cu–1.37 Mg–0.61 Mn–0.07 Si–0.27 Fe–0.02 Zn–0.02 Ti (wt %)) after aging and deformation by shear under high quasi-static pressure. It has been shown that the combination of two-stage aging with megaplastic deformation leads to the refinement of the structure to a nanolevel and to strengthening of the alloy (to an increase in the microhardness to 3000 MPa). The values of true deformation at which the deformation-induced dissolution of the particles of the strengthening S phase occurs have been determined.     

Active monitoring systems in the machining of discontinuous surfaces

A machine-tool system for active monitoring by vibrocontact measurement is proposed. This equipment increases the machining precision and productivity and also the technological margin of precision.     

The T-125/150-12.8 cogeneration steam turbine

The article presents the design, the economic indicators, and the main solutions on the thermal process circuit and layout of the T-125/150-12.8 turbine, a new design version of the T-100-12.8 turbine, which is one of the best known, unique and widely used cogeneration turbines in Russia and abroad. The project of the new turbine is supposed to be used both for renovating and upgrading already installed turbines of the T-100 family and for supplying it as a full set for replacing obsolete equipment or constructing new one.     

Electron-microscopic examination of the transition zone of aluminum-tantalum bimetallic joints (explosion welding)

A study of the structure of an aluminum-tantalum joint and a comparison of this structure with the structures of iron-silver and copper-tantalum joints have revealed the following processes of the interpenetration of the materials that occur during explosion welding: the formation of protrusions, the injection of particles of one material into the other, and the formation of zones of local melting. Regardless of the mutual solubility of the metals being welded, two types of fragmentation occur, i.e., (1) a granulating fragmentation (GF), which includes the formation, explosion-governed (EG) dispersion, and partial consolidation of particles, and (2) the fragmentation that is usually observed during severe plastic deformation. It is important that this traditional fragmentation is not accompanied by the formation and EG dispersion of particles. This feature allows one to easily distinguish these types of fragmentation (traditional and GF fragmentation).     

Laboratory criteria of crack resistance of high-strength steels for gas main pipelines

Low-carbon ferrite-bainite pipe steels of the K65 (Kh80) strength grade produced by two manufacturing companies have been studied using different mechanical tests and fractographic analysis of fractured surfaces. The results demonstrate that the energy capacity a (a _c) and the true relative reduction at fracture φ_f upon tensile tests, as well as the level of KCV ⁻⁴⁰ ≥ 250 J/cm² and the relative width of the zone of homogeneous ductile fracture L _C/B at the fracture surface of Charpy samples upon impact bending tests, can be used as the laboratory criteria of crack resistance.     

An intrinsic luminescence in binary lead silicate glasses

The low-temperature photoluminescence (PL) of xPbO · (1 − x)SiO₂ glasses (x = 0.20-0.75) was studied at Т = 10 K. The recorded PL-spectra are a superposition of three spectral components with maxima located at 1.8 eV (identified as Pb 6p → metal-bridging O2p radiative electron transition, the “R”-band), 2.0 eV (Pb 6p → non-bridging O2p, the “O”-band) and 2.55 eV (Pb 6p → Pb 6s, the “B”-band), respectively. It was found the essential link for “R”, “O” and “B” PL-bands with chemical composition x of the glasses under study. These concentration dependences are expressed as mutual PL-intensity variations for each recorded luminescence band that allowed to determine their origin. The shape of established dependences well coincides with numerical data on NBO- and MBO-density of chemical bonding, reported previously.The overall PL-manner within the temperature range of 10-295 K is described by an empirical Street’s law. It was shown that experimental photoluminescence quenching curves may be precisely approximated as a superposition of Mott relationships for nonequivalent luminescence centers. The obtained distribution of PL-centers on the activation energy for luminescence quenching reflects the essential donation of the low-energy states into the overall PL-process. The width of this energy distribution affects by the type of PL-emission band and the disordering degree in the arrangement of local PL-centers of a certain kind.     

Web technology in automated information and modeling systems for metallurgical processes

The software in information systems used by engineering personnel at metallurgical enterprises is considered. Such software operates automated workstations, support systems for decision making, information and modeling systems, expert systems, and so on. Typically, the software takes the form of desktop applications written in high-level programming languages (Visual C#, Visual Basic, etc.). The analysis of technological information from the enterprise’s database-management server entails the solution of programming problems, systems of differential equations, and mathematical-physics problems, for example. Such problems are unsolvable by the standard general-purpose programming languages. Therefore, the development of information and modeling systems requires access to outside software, such as Microsoft Excel and MATLAB. Interaction with Microsoft Excel depends on COM Interop technology, which requires the installation of Microsoft Office on each client computer. Interaction with MATLAB requires the preliminary assembly of a library in MATLAB Compiler and its connection to the program. MATLAB Runtime freeware must be installed on the client computer. However, desktop applications using Windows Forms do not meet the requirements of industrial information systems in terms of functionality, accessibility, and cross-platform compatibility. Accordingly, new technologies must be found for the creation of information systems. The best approach is the construction of web applications based on the ASP.NET MVC framework, which permits the transfer of mathematical libraries and modules for interaction with Microsoft Excel and MATLAB from Windows Forms, without modification. The structure of the web application employed in the development of information-system software is described. The web page employed has the following functional regions: the logo and title of the current page, the session-status menu, the function menu, group operations, notifications, and the working area.     

The impact of porosity,pH2 and pH2O on the polarisation resistance of Ni–BaZr0.85Y0.15O3−δ cermet anodes for Protonic Ceramic Fuel Cells (PCFCs)

The effect of porosity and atmosphere on the polarisation resistance of Ni-BZY cermet anodes for protonic ceramic fuel cells (PCFCs) was investigated using electrochemical impedance spectroscopy (EIS) and scanning electron microscopy (SEM). The level of porosity was adjusted by the use of differing amounts of starch porogen. The total polarisation resistance of the cermet anode (Rp) generally showed an increase with increasing porosity. The high frequency polarisation resistance (R2) was shown to have low atmosphere dependence but presented a strong correlation to microstructural variations. In contrast, the low frequency polarisation resistance (R3) was shown to have a low dependence on humidity but demonstrated a strong negative dependence on pH₂ with a value of unity. Subsequent discussion relates the lower frequency response to the dissociative adsorption of H₂ on the anode surface. The present study highlights that porogens are not required for peak performance in PCFC anodes under standard operating conditions, a result contrary to that of their oxide-ion conducting cermet counterparts.