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

Abstract

In Al-3 wt pct Mg/Al2O3p (or SiCp) composites fabricated by the pressureless infiltration method, the infiltration behavior of molten metal, the mechanical properties, and the interfacial reactions were investigated. The spontaneous infiltration of the molten Al-3 wt pct Mg alloy into the powder bed occurred at a relatively low temperature (700 °C for 1 hour under a nitrogen atmosphere). Spontaneous infiltration of the molten metal is related to the formation of Mg3N2 by the reaction of Mg and nitrogen. The tensile strength and 0.2 pct offset yield strength and elongation tend to decrease with increasing infiltration temperature and time, because of an increased interfacial reaction. In Al-3Mg/Al2O3 composites, MgAl2O4 was observed at 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 Al2O3 and the matrix. On the other hand, Al4C3 was formed at interfaces between SiC and the matrix in Al-3Mg/SiC composites. In addition, MgAl2O4 was observed as a reaction product at the interfaces between oxide films of SiC and the matrix, as well as at oxide films of the Al powder surface. Since the Si released as a result of the interfacial reaction is combined with Mg, age hardening can occur by the precipitation of Mg2Si via T6 treatment.