Fabrication of In-Situ Intermetallic Compound Dispersed Aluminum Matrix Composites by Addition of Metal Powders

摘要

A new process was proposed to fabricate intermetallic compound reinforced Al matrix composites by the reaction between metal powders and molten Al. The Ni powders were added gradually onto the surface of the molten pure Al by stirring. The Al_3Ni particles, which are smaller than the added Ni powder, were in situ formed and homogeneously dispersed in the Al. The processing temperature was lower and the stirring time was shorter than those of the conventional vortex method for fabricating non-metal (Al_2O_3, SiC etc) reinforced Al matrix composites. The effects of the processing variables, such as processing temperature, size of the Ni powder, and stirring time, on the formation and dispersion behavior of Al_3Ni were investigated. It was found that the size of the Al_3Ni decreased with the decreasing processing temperature and stirring time. The process was also applied to Ti, Zr, Cr, Mo, W and Fe powders. Al_3Ti, Al_3Zr, Al_7Cr and Al_(12)M0 were formed and homogeneously dispersed, but the others failed. The size of the intermetallic compounds significantly depended on the specific elemental metal powder. The dispersion of the intermetallic compounds was affected by the oxidation of the metal powders. This process was applicable to the JIS AC8A alloy for forming the AC8A-Al_3Ni composite.