Effects of MgO nano particles on the mechanical properties and corrosion behavior of Mg-Zn-Ca alloy

An as-extruded Mg-3Zn-0.2Ca-0.3MgO (wt.%, ZX0.3) composite with good mechanical properties and high corrosion resistance was designed and fabricated by hot extrusion based on the requirements of biodegradable Mg alloys. The results revealed that the average grain size was reduced about 50% to 1.9 mu m and the yield stress was increased about 34%-269 MPa after adding MgO to Mg-3Zn-0.2Ca (wt.%, ZX) alloy. Theoretical calculation and experimental results showed that the grain boundary strengthening and Orowan strengthening were the main strengthening mechanisms (>95%) of the composite, while the addition of MgO NPs and the increasing of basal texture were harmful to the plastic of ZX0.3 composite. However, the activation of prismatic dislo-cations and pyramidal dislocations would reduce the negative impact of them. The corrosion test results revealed that in ZX0.3 composite, MgO nanoparticles (NPs) not only promoted the formation of the Mg(OH)2 layer, but also effectively barricaded the cracks extension in corrosion products layer, making the corrosion product layer much denser and durable. The corrosion rate of ZX0.3 composite was reduced by 30% to 0.79 mm/yr compared with that of ZX alloy. In addition, the reduced corrosion rate of matrix could provide a more suitable environment for cell adhesion and differentiation, which results in better cytocompatibility of the ZX0.3 compared with ZX alloy.