Enhancing mechanical properties of squeeze-cast AZ91 magnesium alloy by combined additions of Sb and SiC nanoparticles

Abstract

The microstructure, compression, and creep responses of the squeeze-cast AZ91 alloy; the AZ91 alloy with 0.6Sb (wt.%) addition; and the AZ91 alloy with 0.6Sb (wt.%) + 2.0SiC (wt.%) (1.2 vol%) nanoparticles addition have been evaluated. The additions of 0.6Sb and 0.6Sb+2.0SiC to the AZ91 alloy reduce the grain size and decrease the β-Mg17Al12 phase, and result in improved compression and creep responses. The AZ91 + 0.6Sb+2.0SiCnp nanocomposite exhibits the best compression properties and the highest creep resistance. The dislocation climb controlled by pipe diffusion is the dominant creep mechanism in the alloys and nanocomposite. The superior compression responses are attributed to the reduction in grain size, and the improved creep resistance is attributed to the decrease in the β-Mg17Al12 phase for both the AZ91 + 0.6Sb alloy and AZ91 + 0.6Sb+2.0SiCnp nanocomposite. The strengthening due to CTE mismatch between the alloy and SiC nanoparticles, as well as the Orowan strengthening for the nanocomposite additionally contributed to the improved compression and creep responses.