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 pct and 14.06 wt pct) were studied. The composites were fabricated by compocasting and certain samples were also remelted at 800 °C for 30 minutes. The reaction mechanisms between SiC _p and liquid Al and between the SiO₂ layer and Al(Mg) are discussed. The crystal boundaries of the MgO (or MgAl₂O₄) reaction products are believed to be the diffusion paths (or channels) during the interfacial reactions. A SiO₂ layer, formed by oxidation of the SiC particles prior to their incorporation into the melt, plays an important role in preventing the SiC _p from being attacked by the matrix. The interfacial reaction products are affected by both the alloy composition and the thickness of the initial SiO₂ layer.