Strengthening and Toughening Mechanisms of Cnts/Mg-Al Composites Prepared Via Powder Metallurgy Combined with Hot Extrusion

Abstract

The low absolute strength and room temperature ductility are the important reasons that limit the wider application of magnesium (Mg) alloys. In this work, 1 vol.% CNTs/Mg-xAl (x=0.5, 1, 2 wt.%) composites were prepared by powder metallurgy combined with hot extrusion to improve the comprehensive mechanical properties of Mg alloys. The ultimate tensile strength and elongation of as-extruded CNTs/Mg-2Al were 307 MPa and 10.5%, respectively, exhibiting strength-ductility synergy. Results further revealed that good interfacial bonding was formed between CNTs and Mg matrix, and high dislocation density was formed during extrusion due to the incompatibility of CNTs and matrix. Besides, CNTs induced the in-situ generation of the nano-Mg17Al12 phase, and the Al elements and CNTs promoted grain refinement and the activation of non-basal slips, which contributed to the synergistic enhancement of strength and plasticity.

Keywords: Mg matrix composites, Carbon nanotubes, microstructure, mechanical property, Strengthening mechanisms