Refining of dispersion particles synsesized in molten aluminium by thermit reaction

颗粒分散复合铝合金具有优异的耐磨性。交通系统紧急制动装置要求使用轻质耐磨材料。这类材料在加工性上有困难，对于成型来说，铸造似乎是最佳选择。然而，非金属颗粒在金属液中的分散使复合料浆的制备难度增大。由于润湿性差，随着颗粒尺寸变小和颗粒总表面积的增加，它变得越来越硬。氧化铝颗粒分散铝合金浆料是一种简单易行的制备工艺，将体积较大的硅颗粒混入铝液中，引起铝热反应。在铝硅合金熔液中生成氧化铝相。尽管二氧化硅材料中只有63vol%的氧化铝，但反应后的颗粒保持了二氧化硅材料的大小和形状。结果表明，反应的大颗粒是由约200nm的氧化铝颗粒与铝熔体混合而成的多晶复合物。高表面能的存在激活了氧化铝相的晶粒生长，而浆料在搅拌温度下保持不变。在氧化铝晶粒生长过程中，形成了直径约为5 μm的孤立颗粒。通过优化反应温度和搅拌温度，可以得到平均粒径为5 μm的氧化铝颗粒从150 μm的二氧化硅中分散到15vol%左右的颗粒分散材料。该材料具有优异的耐磨性，超过了过共晶铝合金作为耐磨铝合金的耐磨性。

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.