Dissolved Zn with nanoscale Cu and Al2O3 particles in Mg-Zn alloy: Nanocomposite with synergistically increased strength and ductility

Abstract

Nanocomposite technology (i.e., dissolved zinc with nanoscale Cu and Al2O3 particles) was used to synergistically increase strength and ductility of ZK60A after hot extrusion. In tension, the strength and ductility of ZK60A were significantly increased by up to +20% and +166%, respectively. There was no significant grain refinement or crystallographic texture change due to the addition of dissolved Zn with nanoscale Cu and Al2O3 particles. However, the addition of Zn enabled the formation of Mg-Zn nanorods responsible for strengthening during tensile deformation. The observation of mainly non-basal slip in the high strain zone (HSZ) adjacent to the nanorod (after room temperature tensile deformation) indicated the sufficiently robust nature of the interface between the nanorod and the alloy matrix. In comparison, mainly basal slip was observed in the HSZ around near-nanospheres (or non-nanorods) of Cu, Al2O3 or Mg-Cu origin, responsible for ductility enhancement. In compression, the addition of dissolved Zn with nanoscale Cu and Al2O3 particles increased strength (by up to +54%) but at the expense of ductility (decreased by -32%). Here, these collective additions to ZK60A enabled the strain hardening rate to be overall higher, resulting in ductility loss. The tensile/compressive yield stress anisotropy reduction after addition of dissolved Zn with nanoscale Cu and Al2O3 particles can be attributed to overall weak interface at nanoscale between the alloy matrix and near-nanospheres (or non-nanorods) of Cu, Al2O3 or Mg-Cu origin. © 2014 by American Scientific Publishers.