Nanoscale additions of aluminium oxide and copper to strengthen AZ91/ZK60A hybrid magnesium alloy

Abstract

Nanoscale additions of oxide (Al2O3) and reactive transition metal (Cu) were used to strengthen hybrid magnesium alloy AZ91/ZK60A after hot extrusion. In tension, the strength of AZ91/ZK60A was increased by up to +12% while the ductility was maintained near 10%. Co-existence of fine nanoparticles around coarse nanoparticles in the alloy matrix after nanoscale additions of Al2O3 and Cu was observed. The observation of mainly non-basal slip in the high strain zone (HSZ) adjacent to: (1) sharp points of the coarse nanoparticle or (2) near-spherical fine nanoparticles (after room temperature tensile deformation) contributed to strengthening of the alloy matrix. In comparison, mainly basal slip was observed in the HSZ around curved surfaces of the coarse nanoparticle, this being responsible for localized ductility enhancement. The observed synergistic ability of coarse nanoparticles surrounded by fine nanoparticles (having effectively > 100 nm or submicron size) to break up approaching HSZs also contributed to localised ductility enhancement. In compression, nanoscale additions of Al2O3 and Cu increased strength (by up to +51%) while the ductility was maintained near 12%. Here, these collective additions to AZ91/ZK60A enabled the strain hardening rate to be higher, resulting in ductility loss. © 2013 by American Scientific Publishers All rights reserved.