INTERFACIAL REACTIONS IN AL-MG (5083) SICP COMPOSITES DURING FABRICATION AND REMELTING/

The interfaces of aluminum alloy composites (5083) reinforced by SiC p articles (as-received, oxidized 3.04 wt pet and 14.06 wt pet) were stu died. The composites were fabricated by compocasting and certain sampl es were also remelted at 800 degrees C for 30 minutes. The reaction me chanisms between SiCp and liquid Al and between the SiO2 layer and Al( Mg) are discussed. The crystal boundaries of the MgO (or MgAl2O4) reac tion products are believed to be the diffusion paths (or channels) dur ing the interfacial reactions. A SiO2 layer, formed by oxidation of th e SiC particles prior to their incorporation into the melt, plays an i mportant role in preventing the SiCp from being attacked by the matrix . The interfacial reaction products are affected by both the alloy com position and the thickness of the initial SiO2 layer.