Microstructural refinement and homogenization of Mg–SiC nanocomposites by cyclic extrusion compression

An as-extruded Mg–1 wt%SiC nanocomposite was processed by cyclic extrusion compression (CEC) at 350 °C. The homogeneity of grain and SiC nanoparticle (∼50 nm average diameter) distribution during the processing was investigated. With the increasing number of CEC passes, a finer grain size and more uniform particle distribution are obtained along with significant improvement in hardness. The matrix grain size is reduced remarkably from ∼27.6 μm to ∼6.5 μm after 8 passes of CEC. Nanoparticle declustering occurs through a mechanism of kneading caused by the intense turbulent flow of the Mg matrix during CEC, and the SiC nanoparticles are dispersed into the original particle-free regions. The property improvement is mainly attributed to Orowan strengthening and the Hall–Petch effect.