Abstract:The effect of Mg content on the microstructures and properties of SiC_p/Al composites prepared by vacuum pressure infiltration was investigated by optical microscopy, X-ray diffractometer and electronic universal testing machine. The results reveal that the addition of Mg enhances the infiltration ability of Al matrix, leading to the increase of relative densities of composites. The addition of Mg promotes the SiC/Al interface reactions, no obvious reaction products are observed when Mg content is 0-6% (mass fraction), while both Mg₂Si and Al₄C₃ form at Mg content of 8%. The strength of composites increases with the increasing content of Mg when Mg content is among 0-6%, due to the increase of relative densities and strengthening of Al matrix by solid solution hardening. When Mg content is 8%, the formation of Al₄C₃ leads to the decrease the bonding strength of SiC/Al interfaces, undermining the bonding strength of composites. The thermal conductivity of composites increases with the increasing Mg content when Mg content is 0-4%, because of the increases of relative densities. When Mg content is 4-8%, the thermal conductivity of composites decreases as Mg content increases. It is explained by the combined action of excessive Mg undermining the thermal conductivity of Al matrix and Al₄C₃ weakening the heat transfer of interfaces.

Key words: SiC_p/Al composite; vacuum pressure infiltration; microstructure; phase; mechanical property; thermal conductivity