Interfacial reactions in Al-Mg (5083)/SiCp composites during fabrication and remelting

The interfaces of aluminum alloy composites (5083) reinforced by SiC particles (as-received, oxidized 3.04 wt.% and 14.06 wt.%) were studied. The composites were fabricated by compocasting and certain samples were also remelted at 800 deg C for 30 min. The reaction mechanisms between SiCp and liquid Al and between the SiO sub 2 layer and Al(Mg) are discussed. The crystal boundaries of the MgO (or MgAl sub 2 O sub 4 ) reaction products are believed to be the diffusion paths (or channels) during the interfacial reactions. A SiO sub 2 layer, formed by oxidation of the SiC particles prior to their incorporation into the melt, plays an important role in preventing the SiCp from being attacked by the matrix. The interfacial reaction products are affected by both the alloy composition and the thickness of the initial SiO sub 2 layer.