Corrosion behavior of silicon nitride bonding silicon carbide in molten magnesium and AZ91 magnesium alloy

The corrosion behaviors of silicon nitride bonding silicon carbide (Si3N4/SiC) composites in molten magnesium and AZ91 magnesium alloy were investigated through immersion tests. The microstructure and the component of the surface layer of the composites were characterized by scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS) and X-ray diffraction (XRD). The experimental results show that there were slight corrosion phenomena on the surface of the composites when it contacted the liquid metals at initial stage. With increasing time, the reaction went to equilibrium gradually between the interface of composites and magnesium alloy. After about 7 h, the composites did not further react with liquid magnesium because of forming a resistant layer on the composites surface. The corrosion mechanism of the composites in molten magnesium and AZ91 magnesium alloy was also discussed.