Refining of dispersion particles synsesized in molten aluminium by thermit reaction

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The particles dispersion composite aluminum alloy is excellent in wear resistance. The light wear resistant material has been required for the panic braking equipment of the transit system. Such materials have the difficulty in workability, and for the shaping, the casting seems to be an optimum. However, nonmetal particle dispersion to the molten metal maximizes the difficulty in production of composite slurry. It is getting harder, as the particle size is smaller and as total surface area of particles increase, because of the poor wettability.As simple and easy formation technique of the alumina particle dispersion aluminum alloy slurry, bulky silica particles was mixed into molten aluminium, then the thermit reaction was caused. Alumina phase was produced in molten aluminum silicon alloy. In spite of there being only 63vol% of alumina for material silica, the reacted particles maintained the size and shape of material silica. It became clear that the reacted large particle were polycrystal complex in which the alumina grain of about 200nm mixed with aluminium melt.The grain growth of the alumina phase is activated by the existence of the very high surface energy, while this slurry is retained at the stirring temperature. During the process of grain growth of alumina, isolated particles of about 5 μm in diameter were generated. Such a fine particles dispersed into molten matrix..By optimizing reaction temperature and agitation temperature, it was possible to get particle dispersion material in which alumina particles of averages particle size of 5 μm were made to disperse from the silica of 150 μm to about 15vol%. This material showed the excellent wear resistance which exceeded that of hypereutectic aluminium alloy used as abrasion resistant aluminum alloy.