Materials Science Forum Vols. 473-474

Abstract: The mechanism of lithium electrochemical reduction from its molten chloride at two different electrodes – glassy carbon and graphite – has been investigated by the cyclic voltammetry method in terms of so-called ‘thermodynamic’ or ‘material balance’ reversibility. It has been shown that the adsorption of lithium on glassy carbon and graphite plays an important role in the overall process of reduction, especially at polarization rates below 1 V/s. Lithium intercalation, probably due to small lithium atomic radius, practically does not have influence on the reversibility at these polarization rates. The process of lithium deposition on the electrodes used may be complicated by the dissolution of lithium in the melt in the whole range of polarization rates applied.

Abstract: The paper presents the study of the microstructure and ultrasound measurments by proeminent part of the nodular iron castings. The experiment has been made in the Havy Machine Factory in Clausenburg. The crossing speed of the ultasound increases near the edge of the castings. Analising the nodular iron microstructure by smoler castings, there occurs no graphite change. By bigger mouldings the shape of the graphite can change to a vermicular graphite near the edges. The thickness of the transformed stratum is of 0,1-0,3 mm. In the nodular graphite iron are acting the forces in the frontier-surface. After casting the evaporation of the magnezium increases near the edge of the castings. The changes of forces on frontier surface can be caused by the changes of the innere tension, and also by the interacting of moulding materials. Opinions regarding these two effects are contardictory in the technical literature. Our experiments have been made in the Heavy Machine Combinat (C.U.G) in Kolozsvar, on nodular iron containing different ferrit-pearlite proportions. The weight of castings varried between 0,5 kg and 8000 kg. The metalic melt necessary to nodulisation was produced inductive furnaces of 6,3 and 12 tons. Before treatment by magnezium alloy, the chemical composition of the iron melt varried between the following parameters, according to the different types of irons: 3,7-3.9% C, 0,2-1,4% Si, 0,1-1,0% Mn, max. 0,025% S, max. 0,05% P, 0,1-1,4% Cr,%, 0,05-0,3% Mo, 0,2-0,8% Cu, 0,2-2,0% Ni. The globularisation has been made in the Tundich-pot. The work-temperature was between 1450 and 1600 C. We used 1,8 – 2,2% FeSiMg and 0,4-1,6% FeSi for the nodulisation. Our target was the examination of the surface strata on the castings, using for mould mixtures with different chemical effect.

Abstract: The central problem of producing of Al/SiCP composites is to avoid the forming of brittle Al4C3, which leads to a poor corrosion resistance and degraded mechanical properties [Mingyuan, 1999]. The possible way is the covering of the SiC particles. This paper deals with the covering of SiC. The coated particles will be applied for producing aluminium matrix composites. We have covered three different grain sizes of particles. We have applied the nonelectrolytic method of deposition from solution for coating. Before the covering the surface needs to be catalysed. We have compared the effects of different type of catalysators, then we have analysed the effects of plating time by means of the scanning electron microscopy.

Abstract: The paper analyses via hydraulic modelling the retaining mechanisms of solid non-metal inclusions in the filtration process of aluminium melts through pressed sheets. Experimental determinations via hydraulic modelling show that the variation of filter thickness influences significantly the retaining mechanism of solid non-metal inclusions and implicitly its productivity.

Abstract: The Heusler alloy is a ferromagnetic compound (Cu2MnAl), that is suitable for the simultaneous monochromatization and polarization of the neutron beam in the form of singlecrystal. The prespecimen were cast in shell-sand or permanent steel moulds, then they were resolidified in crucibles of different size and material in the Universal Multi-zone Crystallizer (UMC) developed in the Institute of Material Sciences of Miskolc University. The solidified samples were investigated by means of a light microscope, electron microscope, energy disperse microprobe, X-ray diffraction as well as neutron scattering experiments.

Abstract: E-glass fibre reinforced polyester matrix composite was investigated, which was made by pullwinding process. Round three point bending (RTPB) specimens were tested under quasi-static and mode I cyclic loading conditions. Load vs. displacement (F-f), load vs. crack opening displacement (F-v) and crack opening displacement range vs. number of cycles (ΔCOD-N) curves were registered and analysed. Interfacial cracks were caused the final longitudinal fracture of the specimens under quasi-static and cyclic loading conditions.