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The aim of this paper is to briefly analyze different methodologies for development of novel materials systems and coatings for use in extreme environments, with a focus on high-temperature applications in aerospace and aeronautics. The approach is based on a comparative analysis of selected major thermal stability properties of different material systems (mainly transition-metal oxides and carbides)...
Light-weight and high-strength polymer composites have attracted the special attention of automotive and aerospace sectors since they offer advantages such as less fuel consumption and higher fuel efficiency. In the present study, an effort has been made to prepare such polymer composites using natural fiber and very low-density hollow inorganic particles. The use of hollow glass microspheres (HGM)...
The cavity oscillation and splash characteristics dominate the operational stability and refining efficiency in converter steelmaking processes. These characteristics under excitation by bottom gas blowing in a steelmaking converter were evaluated using a developed filter-based multifluid model. The cavity oscillation mechanism was examined by reference to cavity surface flows, and its characteristics...
Flow forming is a metal-forming process for producing axisymmetric hollowed tubes starting from cylindrical workpieces. In cases where the preformed tube includes defects, impurities or inconsistencies, the final product may not withstand the required standard. In this work, the preformed tubes were produced by metal wires melted into the desired geometry using a gas-metal arc-welding robot. Two geometries...
The possible effect of Zr on the microstructural evolution of second- and third-generation body-centered cubic high-entropy alloys with increasing temperature was investigated by comparing two pairs of alloys differing from one another only by the presence of Zr in one of them. The experimental procedure comprised alloying in an arc furnace with subsequent thermal treatments at 1000°C and 1300°C,...
Welds in heavy haul rails are usually associated with accelerated wear and are a common source of defects, justifying a careful study of their characteristics. Heat-affected zones usually present hardness loss, corresponding to a spheroidized cementite region. The literature acknowledges that this is a consequence of the welding heat input but without further explanations. However, in order to control...
This article presents some recent results from fusion welding of titanium alloys with interlayers. Without an interlayer, the CP Ti weld typically results in comparable hardness across the weld and base material (BM). However, for α alloys, near-α alloys and α + β alloys, the fusion zone (FZ) and heat-affected zone (HAZ) show high hardness compared with the BM. Inversely, β alloys have FZ and HAZ...
With the aim of developing a novel aluminothermic reduction method for preparation of low-oxygen low-aluminum ferrotitanium by multistage deep reduction we studied the effects of the ratio of reductant Al on the occurrence and distribution of Al and O residuals. The results indicated that Al residual was present in the form of Ti3Al and Al2O3 inclusions. O residual in ferrotitanium with Ti content...
The structure and temperature stability of high-temperature permanent magnets Sm(Co0.796−xFe0.177CuxZr0.027)6.63 (x = 0.117 and 0.130) were studied using x-ray diffraction analysis, thermomagnetic analysis, and scanning and transmission electron microscopy. The magnets have a nanocrystalline cellular structure composed of the R2:17 cell phase, 1:5 boundary phase (27–28% by volume), and Z-phase platelets...
To reveal the effects of microwave irradiation on the structure, morphology, and supercapacitor performance of p-phenylenediamine (PPD)-functionalized graphene materials (FG), FG was synthesized by using PPD as a functional modifier with the combination of hydrothermal reflux and microwave irradiation. The results showed that microwave irradiation could realize rapid reduction of functionalized graphene...
Wire and arc additive manufacturing (WAAM) is becoming an increasingly important process for manufacture of components with complex geometry, being used for products made for products made from expensive metals such as Inconel 625. The shielding gas used to protect the molten metal is one of the key process parameters due to its significant impact on the structure and mechanical properties of the...
This work focuses on the localized forms of corrosion caused by microbiological activity, which have seldom been considered for long-term alteration processes of copper-based alloys. To reproduce a seldom-documented corrosion morphology found in some archaeological objects, called ‘tentacle like’, a Pseudomonas fluorescens strain was used on analogues of known composition in a solution containing...
In recent years, the production of customized medical implants through additive manufacturing by the Centre for Rapid Prototyping and Manufacturing in South Africa has grown significantly. While satisfactory results have been obtained and the quality of life of many patients has been improved, further research is required to enable the production of qualified components. This paper shares the growing...
The quest to consistently develop improved materials for direct application in automotive, aerospace, and other industries has led to the synthesis of titanium-based composites—with current research efforts being directed toward the utilization of carbon nanotubes (CNTs) as reinforcement. CNTs constitute an outstanding reinforcement for titanium-based matrixes, owing to their extraordinary physical,...
A computational fluid dynamics (CFD) model for a supersonic oxygen jet has been developed with detailed consideration of compressible flow properties and ambient temperature conditions. The model was validated by comparison of the axial velocity of the supersonic jet predicted by the CFD model with experimental measurements under different ambient temperatures. The effects of the turbulence model...
Additive manufacturing techniques for fabricating bonded magnets have the potential to reduce manufacturing cost and time-to-market of products and address the criticality of rare-earth elements (REEs), which is a concern for economic design of dependent applications such as permanent magnet machines. We investigated the magnetic alignment of anisotropic bonded magnet material comprising 65 vol.%...
A supersonic oxygen jet impinging onto the slag–metal interface is studied using computational fluid dynamics modeling with the aim of obtaining a better understanding of the multiphase interaction behavior in a converter. The dynamic interaction behavior as well as the effects of the slag thickness, viscosity, and surface tension are studied numerically. The results show that the geometrical dimensions...
Uniform and spherical LiAl0.075Mn1.925O4 particles have been successfully synthesized by the high-pressure spray-drying method. The structures and electrochemical properties of the particles were characterized by various techniques. Benefiting from the sphere-like morphology and Al-doping, LiAl0.075Mn1.925O4 delivers a capacity retention of 81.6% after 1000 cycles at 2°C, while LiMn2O4 exhibits a...
The carbochlorination kinetics of high-alumina fly ash was investigated. The influence of reaction temperature, time, carbon content, pellet diameter, and Cl2 flow rate on the reaction was analyzed. The morphological changes of the samples during the reaction showed that different sizes of spherical particles disappeared entirely after the carbochlorination process. For carbochlorination of alumina,...
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