EFFECTS OF SILICON CARBIDE NANOPARTICLES ON MECHANICAL PROPERTIES AND MICROSTRUCTURE OF AS-CAST Mg-12wt.% Al-0.2wt.% Mn NANOCOMPOSITES

Microstructure and tensile properties of as-cast Mg-12Al-0.2Mn alloys with SiC nanoparticles were studied. SiC nanoparticles were dispersed into Mg-12Al-0.2Mn melts through an ultrasonic based nanoparticle-dispersion method. The content of SiC nanoparticles varied from 0 to 2 wt.%. The microstructural analysis with optical and scanning electron microscopy (SEM) showed that the massive brittle intermetallic phase (beta-Mg17Al12) as well as alpha-Mg grain was significantly refined, enhancing both strengths and ductility of as-cast Mg-12Al-0.2Mn alloys. Transmission electron microscopy (TEM) showed that there were SiC nanoparticles in both a-Mg and beta-Mg17Al12 phases of the Mg12Al-0.2Mn nanocomposites. It was found that there was a partial reaction between Mg/Al and SiC nanoparticles, producing Mg2Si intermetallic phases. X-ray diffraction (XRD) analysis confirmed also that the content of Mg2Si phases increased with increasing SiC content, limiting a further ductility enhancement for Mg12Al-0.2Mn-SiC nanocomposite.