Abstract: Modelling the constitutive behaviour of metallic materials based on their microstructural features and the micromechanical mechanisms in the framework of continuum mechanics is addressed. Deformation at the lengthscale of grains is described by crystal plasticity. The macroscopic behaviour is obtained either by a homogenisation process yielding phenomenological equations or by a submodel technique. The modelling processes for two light-weight materials, namely magnesium and titanium aluminides are presented.
Abstract: The optimization of CFC/Cu-interfaces for plasma facing divertor components in thermo-nuclear fusion reactors is proposed and demonstrated via an integrative numerical-experimental approach mainly comprising a macro-scale to micro-scale finite element modeling technique together with fracture mechanics tests. Results obtained by finite element analyses of real-scale CFC flat tile divertor components under high heat flux loading conditions are verified by the findings of tests in an ion beam high heat flux facility. From the macro-scale FE models of the full component the loading conditions are derived for micro-scale FE models that incorporate principal details of the micro-structured CFC/Cu-interface thus allowing to capture explicitly locally acting dissipative mechanisms which in turn at the macro-scale in fracture mechanics experiments increase the fracture toughness of the CFC/Cu-interface.
Abstract: A special ceramic material with specific performances for some extreme environments can be elaborated using basaltic-andesite as raw material. The volcanic rocks presents specific compositions, a complex structure and properties, so some of them, such as basaltic-andesite, may have multiple utilization. The elaborated basaltic-andesite compound ceramic material, in mixture with porcelain-clay and alumina was characterized with SEM (scanning electron microscopy), EDS (energy dispersive spectroscopy), X-ray diffraction and thermo-gravimetric analysis. Many of the properties of this sort of ceramic material surpass the electric insulator porcelain type KER 110 ceramic, and in some approximate the high alumina-content ceramic materials.
Abstract: Deuterium retention in single crystal and polycrystalline tungsten and molybdenum exposed to low-energy (38200 eV/D), high ion flux (10211022 D/m2s) deuterium plasmas at various temperatures were examined with the D(3He,p)4He nuclear reaction at a 3He energy varied from 0.69 to 4.0 MeV, and with thermal desorption spectroscopy. The surface morphology was examined by scanning electron microscope. Blisters formed on the Mo surfaces under plasma exposure are significantly larger in size than those for W. The D retention in the W and Mo samples increases with the exposure temperature, reaching its maximum at about 500 and 530 K (for ion fluxes of 1021 and 1022 D/m2/s), respectively, and then decreases as the temperature grows further. For polycrystalline W and Mo exposed at temperatures above 400 K, the D retention in the bulk (far beyond the ion implanted zone) is dominant. Plastic deformation caused by deuterium super-saturation within the near-surface layer is suggested as a mechanism for blister formation and creation of defects responsible for deuterium trapping at depths up to several micrometers.
Abstract: A process of friction plating was developed for modification of the surface of metal items by strain hardening combined with application of protective coatings aimed to improve corrosion resistance, hardness, wear resistance and other functional properties. Friction plating is performed by means of a metal wire brush rotating at high speed. Coating material in the form of a rod or strip is pressed with a certain force to the rotary wire brush. In the contact zone, coating material is heated up to a high temperature. Particles of coating material are picked up by the ends of brush wires and transferred onto the treated surface. At the same time, the surface of the product is conditioned and heated. Investigations of friction plating have shown that plastic deformation of the surface layer combined with application of coating material particles ensures their strong adhesion to the substrate.
Abstract: A growing demand for fibre-reinforced ceramics necessitates effective ways for machining these materials. In this paper, different tool concepts are presented for an efficient machining of carbon fibre-reinforced silicon carbide. Drill hole machining, slot machining and first investigations of free-form surface machining are presented.
Abstract: In the present work, laser surface alloying of H13 tool steel by using TiC has been performed by means of DHPDL (Direct high power diode laser). Different layers were produced by varying laser beam power and powder feeding rate. Several alloying degrees were obtained depending on the laser parameters employed. Laser surface alloyed layers were analyzed by using optical and scanning electron microscopy. Wear resistance was evaluated through pin-on-disk tests at room temperature. In general, it was observed that dilution of TiC powders into the molten H13 substrate decreased as the powder-feeding rate increased and particles size of the titanium carbide precipitates was larger for the higher feeding rates. Wear measurements showed lower values for the wear resistance coefficient of laser alloying layers produced at higher values of the powder injection (feeding) rate. Analysis of the wear surface track was conducted and the specific contribution of the microstructural features on the wear coefficient was assessed. Thus, it was found that larger particles sizes and particle contents protected the martensitic and dendritic steel matrix from being deeply worn. Lower TiC contents in the alloyed layer gave rise to a higher contribution of the plastic deformation in the wear track.
Abstract: The physico-chemical fundamentals (thermodynamics, kinetics) of tungsten carbides crystallization process are presented. Chemically vapor deposited coatings composed of tungsten carbides, metallic tungsten matrix with nanoparticles of tungsten carbides are synthesized from gaseous mixture of tungsten hexafluoride, hydrogen and propane at temperatures ranging from 623 to 923 K and can be used as materials for extreme environments. The physical and mechanical characteristics of these CVD coatings are discussed.