Effect of reinforcement spatial distribution on mechanical properties of MgO/ZK60 nanocomposites by powder metallurgy

Abstract 0.5 vol% MgO/ZK60 nanocomposites with two reinforcement arrays were successfully fabricated by a conventional powder metallurgy technique. Specifically, the combination of powder oxidization and extrusion consolidation was used to obtain a composite microstructure that was characterized by fiber-like MgO rich bands embedded in an ultrafine-grained Mg matrix. Meanwhile, a homogeneous microstructure containing MgO nanodispersoids throughout the matrix was also achieved by introducing an extra high-energy ball milling. Compared with the unreinforced matrix alloy, both nanocomposites exhibited improved strength and marginally reduced elongations. Furthermore, the homogeneous nanocomposite showed a higher strength than that of inhomogeneous counterpart. Quantitative analysis indicated that fiber-like MgO rich bands only acted as load-carrying units and nanodispersoids activated multiple strengthening mechanisms which involved grain refinement, Orowan and dislocation strengthening.