Effect of SiC nanoparticles addition on the microstructures and mechanical properties of ECAPed Mg9Al-1Si alloy

This study investigated the effects of 1 wt% SiC nanoparticles addition on the microstructures and mechanical properties of Mg9Al-1Si (wt%) alloy subjected to equal channel angular pressing (ECAP). Results showed that addition of SiC nanoparticles could refine matrix grain, Mg17Al12 and Mg2Si phase of as-cast alloy, but the Mg17Al12 phase still exhibited network structure and the morphology of Mg2Si phase was still Chinese-script type. During the ECAP process, network Mg17Al12 and Chinese-script shaped Mg2Si phases were partially broken down into fine particles (similar to 10 mu m) and much finer particles (similar to 2 mu m) respectively. In particular, these Mg17Al12 and Mg2Si particles were uniform distribution in ECAPed Mg9Al-1Si-1SiC composite. The well-distributed particles and the existence of SiC nanoparticles could promote the formation of fine DRXed grains through enhanced grain boundary pinning. During tensile testing at room temperature, ECAPed Mg9Al-1Si-1SiC composite exhibit optimal mechanical properties, the ultimate tensile strength and elongation to failure were reached to 255 MPa and 7.9%, respectively. Furthermore, at elevated temperature of 150 degrees C, the tensile strength and elongation to failure were considerably increased compared to an ECAPed, SiC-free Mg9Al-1Si alloy.