Influence of the Iron Anisothermal Sintering on the Characteristic of the Hollow Cathode Discharge

SINTERING of steels and ceramics is conventionallycarried out in a furnace in a controlled atmosphere.Several alternative techniques have been developedsince 1966, as mentioned by Johnson et al. [1], toobtain components with improved properties, resultingin new applications for powder technology. Plasmasgenerated in microwave cavities, in hollow cathodedevices and microwave or RF-inductively coupleddischarges have all been used for sintering ceramics[2-5]. In the above mentioned papers it …     

Influence of the β-phase morphology on the corrosion of the Mg alloy AZ91

The influence of the microstructure, particularly the morphology of the β-phase, on the corrosion of Mg alloys has been studied using AZ91 as a model Mg alloy. The corrosion behaviour was characterized for five different types of microstructure produced by heat treatment of as-cast AZ91. The influence of microstructure can be understood from the interaction of the following three factors: (i) the surface films can be more or less effective in hindering corrosion and more or less effective in controlling the form of corrosion as uniform corrosion or localised corrosion, (ii) the second phase (the β-phase in AZ91) can cause micro-galvanic acceleration of corrosion and (iii) the second phase can act as a corrosion barrier and hinder corrosion propagation in the matrix, if the second phase is in the form of a continuous network. It is expected that these factors are important for all multi-phase Mg alloys because all known second phases have corrosion potentials more positive than that of the α-phase. A particular example of the corrosion barrier effect is provided by the fine (α + β) lamellar micro-constituent; when a β-phase plate nucleates this micro-constituent, the β-phase plate acts as a corrosion barrier. In contrast, nano-sized β precipitates, produced by aging, caused micro-galvanic corrosion acceleration of the adjacent α-phase. However, it is an important finding that the corrosion rate of the α-phase was decreased by the aging treatments that caused the precipitation of the nano-sized β particles.     

Recrystallization and the possibility of the realization of the α-γ diffusionless transformation during the ultrarapid laser heating of steels

Analysis is given of phase and structural transformations occurring upon ultrarapid laser heating in steels with different initial structures, namely, after annealing, after preliminary quenching, quenching and tempering, and after quenching with subsequent deformation and tempering. It is shown that a significant suppression of diffusion processes occurs during laser heating; this circumstance substantially affects the nature of the phase and structural transformations proceeding during laser processing. Special attention is given to studying the process of recrystallization and to the phenomenon of structural heredity during laser heating. The process of recrystallization during laser heating is considered as consisting of two stages, namely, an ordered lattice rearrangement (α-γ transformation) and the recrystallization of austenite that suffered phase-transformation-induced hardening (“phase naklep”). The effect of tempering and plastic deformation on the recrystallization of a preliminarily quenched steel consists in the intensification of the second stage, i.e., of the recrystallization of the transformation-hardened austenite. It is shown that the α-γ transformation during the laser heating of steels with the initial structure of lath martensite occurs by the “mechanism of recovery,” i.e., via the formation and growth of austenite nuclei. In steels with the initial structure of pearlite, the nucleation of austenite during laser heating can occur by a shear martensite-like diffusionless mechanism with the observance of characteristic orientation relationships between the initial ferrite and the newly formed austenite.     

Effect of the structure of the oxidized titanium surface on the particle size and properties of the deposited copper–molybdate catalyst

The parameters of wetting of oxide coatings on titanium formed by the method of plasma electrolytic oxidation (PEO) in an aqueous silicate electrolyte with subsequent deposition of a layer of TiO₂ nanoparticles and ultrasonic treatment by a polymer–salt gel including copper and molybdenum compounds have been investigated. The effect of the oxidized surface microrelief, TiO₂ nanoparticle layer, and pore shape and size on impregnation solution spreading and the structure of the copper–molybdenum catalytic coating formed at further thermal treatment has been demonstrated. Complex oxide composites with ultradispersed catalyst particle sizes characterized with high activity in oxidation of carbon black particles have been obtained.     

Refining the macromolecular model – achieving the best agreement with the data from X-ray diffraction experiment

ABSTRACT

Refinement of macromolecular X-ray crystal structures involves using complex software with hundreds of different settings. The complexity of underlying concepts and the sheer amount of instructions may make it difficult for less experienced crystallographers to achieve optimal results in their refinements. This tutorial review offers guidelines for choosing the best settings for the reciprocal-space refinement of macromolecular models and provides practical tips for manual model correction. To help aspiring crystallographers navigate the process, some of the most practically important concepts of protein structure refinement are described. Among the topics covered are the use and purpose of R-free, geometrical restraints, restraints on atomic displacement parameters (ADPs), refinement weights, various parametrizations of ADPs (full anisotropic refinement and TLS), and omit maps. We also give practical tips for manual model correction in Coot, modelling of side-chains with poor or missing density, and ligand identification, fitting, and refinement.     

An analysis of the dynamic resistance and the instantaneous energy of the CO2 arc welding process

A self-developed welding dynamic arc wavelet analyzer was adopted to analyze and assess the welding process of two CO2 arc welding machines. The experimental results indicate that the instantaneous energy can reflect the influence of the welding current and voltage on dynamic arc characteristic synthetically. Through calculating and analyzing the instantaneous energy, the energy during arc ignition and short circuit in CO2 welding process can be confirmed rationally, thus the foundation for the accurate design and control of the welding current and voltage can be provided. By reducing the ripple disturbance of the dynamic resistance, avoiding peak current and voltage waveform,and enhancing the transition frequency of short circuit suitably, the stability of the welding arc and the weld appearance can be improved.     

Dependence of the surface charge and the fluorine adsorption by γ-aluminum oxide on the solution temperature

The dependence of the surface charge of the γ-aluminum oxide and the fluorine adsorption on the solution temperature (20, 30, and 40°C), the pH (3.5–10), and the equilibrium concentration of fluorine in the solution (from 1.0 × 10⁻³ to 1.5 × 10⁻¹ M/l) is studied by the method of potentiometric titration and adsorption variations with the view to elucidate the nature of the processes that take place upon the removal of fluorine with the use of ECDM sludge of an aluminum alloy that was calcined at a temperature of 800 °C. The adsorption isotherms were processed using the Freundlich, Langmuir, and BET equations. The best coincidence with the experimental data is obtained with the use of the Langmuir equation. It is shown that both the solution temperature increase and the amount of fluorine adsorbed by the sample surface shift the pH_PZC to a more acid range. The fluoride adsorption occurs due to the exchange of the OH⁻-groups of the hydrated oxide surface for fluorine ions due to the interaction of the charged AlOH₂⁺ centers of the surface with F⁻ ions and due to the formation of hydrogen bonds of F⁻ and uncharged AlOH centers.     

‘Road map’ of the development of the technological component of the strategy of national security

This article is devoted to the development of guidelines for road mapping in planning the development of the technological component of structures of national security. Making the ‘road map’ is reduced to the method of conventional optimization i.e. achievement of the target in conditions of severe limitations of existing resources taking into account the effect of controlled and uncontrolled factors. Such a result can be regarded as a scientific novelty.     

Numerical Methods for Safeguarding the Performance of the Quenching Process

A new numerical technique for testing and evaluation of quenching media and quenching systems is outlined. The measured time-temperature samples as a result of cooling curve test are analyzed by the new software developed, in order to characterize quantitatively the quenchants. The method applied is based on Fourier analysis. Examples for evaluation and comparison of cooling performance of quenchants are presented the applicability of the computational technique.     

Thermodynamic database of the phase diagrams in the Mg-Al-Zn-Y-Ce system

The Mg-Al-Zn-Y-Ce system is one of the key systems for designing high-strength Mg alloys. The purpose of the present article is to develop a thermodynamic database for the Mg-Al-Zn-Y-Ce multicomponent system to design Mg alloys using the calculation of phase diagrams （CALPHAD） method, where the Gibbs energies of solution phases such as liquid, fcc, bcc, and hcp phases were described by the subregular solution model, whereas those of all the compounds were described by the sublattice model. The thermodynamic parameters describing Gibbs energies of the different phases in this database were evaluated by fitting the experimental data for phase equilibria and thermodynamic properties. On the basis of this database, a lot of information concerning stable and metastable phase equilibria of isothermal and vertical sections, molar fractions of constituent phases, the liquidus projection, etc., can be predicted. This database is expected to play an important role in the design of Mg alloys.     

Influence of the Anion Nature and the Metal-to-Additive Ratio on the Effectiveness of ε-Caprolactam during Cadmium Electrodeposition

The rate and mechanism of cadmium(II) electroreduction from electrolytes containing -caprolactam were found to significantly depend on the metal-to-additive ratio. Whatever the anion nature, the process sharply accelerates in the presence of an excess of cadmium cations, which form activated surface complexes with adsorbed -caprolactam molecules as bridging ligands. With an excess of the additive, metal depolarization due to the "-effect still persists in perchlorate media; in iodide solutions, -caprolactam inhibits this process. The formation of a dense adsorbed film composed of -caprolactam molecules and I^– anions at the electrode ensures a high throwing power of the electrolyte and makes it possible to obtain uniform elastic organocadmium plating.     

Numerical simulation of the welding deformation for the side sill of the bogie frame based on local-global method

Considering the limitation of computational capacity, a new finite element solution is used to simulate the welding deformation of the side sill of railroad car＇ s bogie frame based on the local-global method. Firstly, a volumetric heat source defined by a double ellipsoid is adopted to simulate the thermal distributions of the arc welding process. And then, the local models extracted from the global model are computed with refined meshes. On these bases, the global distortions of the subject studied are ascertained by transferring the inner forces of computed local models to the global model. It indicates that the local-global method is feasible for simulating the large welded structures by comparing the computed results with the corresponding actual measured values. The work provides basis for optimizing the welding sequence and clamping conditions, and has theoretical values and engineering significance in the integral design, manufacturing technique selection of the bogie frame, as well as other kinds of large welded structures.     

Research of the Plasma Sulfide Layer Formed on the Nitrocarburizing Layer

Low-temperature sulfurizing after nitrocarburizing are compared with only low-temperature sulfurizing on the surface of CrMoCu alloyed cast iron, the surface morphologies and microstructures are investigated by SEM and EDS.Results show that under proper treatment parameters, there are sulfide layer on both of the surfaces, and can more easily obtain sulfide layers on the surface of nitrocarburizing. Forming mechanism of sulfides were also studied elementarily.     

Coatings – the basis of the UK’s manufacturing economy

In 2015/16 the surface coatings industry contributed an estimated £13.5bn to the UK economy. By improving surface characteristics and performances, it is estimated to have positively impacted products valued at about £173bn, directly adding value to about 50% of the UK’s £358bn total manufacturing sales.     

Shortening the Duration of Heat Treatment in the Lower Bainitic Range

In many cases an isothermal treatment of throughhardenlng beating grades in the lower bainitic range allows to adjust the mechanical properties of machine components to the later application, similar to those of martensitic hardening.The achieved microstructure contains only a negligible amount of retained austenite, so a dimensional change of components during application can be reduced. One disadvantage of the isothermal bainitic treatment in salt bath is that the duration of the treatment is much longer than that of the martensitic hardening and this causes higher costs. Therefore it would be desirable to be able to shorten the transformation duration in the lower bainitic range. The aim of the present work is to determine the parameters, by which the process could be greatly shortened in comparison with the conventional transformation process in the lower bainitic range. Therefore the bainitic transformation behavior of the steel 100 Cr6 (SAE 52100) and the relevant influence factors were investigated by means of dilatometry, in which the heat treatments were carried out with different process variants including pre-quenching or post-quenching. The amount of retained austenite in the microstructure and the hardness of the steel after the shortened heat treatments were measured. Finally the possibility to use these processes in industrial production is discussed.     

Effect of Annealing on the Magnetism of the Sintered NdFeB Magnet

This paper deals with the effect of annealing on the magnetism of the sintered NdFeB magnet with a composition of Nd30B5.1Dy1.2Al0.6Nb0.7Fe62.4. Microstructural investigations of the grain size and grain boundaries with SEM were carried out. Microstructural investigations showed the presence of some Nd-rich phase in grain boundaries and main phase.The results of magnetic properties analysis shows that this non-magnetic Nd-rich phase, produced in annealing process,can increase or decrease the magnetism of the sintered NdFeB-type permanent magnet. Appropriate amount of Nd-rich phase will strengthen the pinning field and elevated the coercive force of magnet, but too many these non-magnetism phases in Nd2Fe14B main phase will decrease it. When the sintered NdFeB magnet was annealed at 3Pa and 492℃ for an hour the coercive force would raise from 915.6kA/m to l164.SkA/m, and the (BH)max from 277.7kJ/m to 349.5kJ/m. However, annealing at a non-optimized temperature at 542℃, microstructure changes in some main phase will leading the decrease of properties.     

Study on the Free-Surface Flow of Silicon Melt in the Crucible

The flowing of the free-surface-layer melt in the crucible has been studied by means of observing the movement ofthe mark particle on the free-surface of silicon melt.A new view on the transportation of the impurities in the melt hasbeen presented.The experimental results verify the effect of the free-surface-layer mew's flow on the distribution of theimpurities in the as-grown crystal.     

Research for the method of image acquisition of the molten pool in the TIG welding of aluminum alloy

Obtaining the image of molten pool aluminum alloy‘ s tungsten inert gas (TIG) welding becomes a challenging problem in the welding field. In this paper, a bran-new optical sensor based analyzing the light spectrum was designed, and the clear image of the molten pool during the aluminum alloy‘ s welding using the common industrial CCD camera was obtained. And with the new algorithm provided by myself, the desirable characteristic parameters of the molten pool of aluminum alloy‘ s welding were obtained, and it provides a good base for advanced monitor welding quality.     

Influence of the rotation frequency of the magnetic field on the dynamics of the domain structure of thin Fe–3% Si crystals

Some specific features of the reconstruction of the domain structure of thin (0.10 mm) Fe–3% Si single crystals have been investigated depending on the frequency of the magnetization reversal in rotating magnetic fields. The studies have been carried out in the range of frequencies of 60–300 Hz and induction amplitudes of 0.5–1.6 T. It has been established that the magnetization reversal of the samples of this thickness occurs via the displacements of 180° domain walls of the stripe domain structure without the participation of the C-domain walls. A qualitative explanation to the revealed features of the behavior of the domain structure has been given, and their possible contribution to the magnetic losses of the investigated samples has been evaluated.