Fabrication of Al-3 wt pct Mg matrix composites reinforced with Al2O3 and SiC particulates by the pressureless infiltration technique

In Al-3 wt pet Mg/Al2O3p (or SiCp) composites fabricated by the pressureles s infiltration method, the infiltration behavior of molten metal, the mecha nical properties, and the interfacial reactions were investigated. The spon taneous infiltration of the molten Al-3 wt pet Mg alloy into the powder bed occurred at a relatively low temperature (700 degrees C for 1 hour under a nitrogen atmosphere). Spontaneous infiltration of the molten metal is rela ted to the formation of Mg3N2 by the reaction of Mg and nitrogen. The tensi le strength and 0.2 pet offset yield strength and elongation tend to decrea se with increasing infiltration temperature and time, because of an increas ed interfacial reaction. In Al-3Mg/Al2O3 composites, MgAl2O3 was observed a t interfaces between Al2O3 and the matrix, as well as at oxide films of the Al powder surface. In addition, MgO was observed at interfaces between Al2 O3 and the matrix. On the other hand, Al4C3, was formed at interfaces betwe en SiC and the matrix in Al-3Mg/SiC composites. In addition, MgAl2O4 was ob served as a reaction product at the interfaces between oxide films of SiC a nd the matrix, as well as at oxide films of the Al powder surface. Since th e Si released as a result of the interfacial reaction is combined with Mg, age hardening can occur by the precipitation of Mg,Si via T6 treatment.