Effects of backward extrusion on mechanical and degradation properties of Mg-Zn biomaterial.

Backward extrusion was used to improve the properties of Mg-based biomaterials. The microstructures, mechanical performance and corrosion properties of as-cast and backward extruded Mg-xZn (x=0.5, 1, 1.5, 2, wt.%) alloys were investigated. The secondary dendrite arm spacing of as-cast Mg-xZn alloys and the grain size of backward extruded Mg-xZn alloys were decreased with the increment of Zn content. Meanwhile, both strength and elongation were improved by backward extruded treatment. With increasing Zn addition, the corrosion properties of both as-cast and backward extruded Mg-xZn alloys were decreased. However, the corrosion performance of backward extruded sample was improved obviously compared to the corresponding as-cast one. More importantly, the degradation rate of the backward extruded alloy was stable, which was mainly associated with the fine second precipitates and the homogeneous microstructure. It was demonstrated that backward extrusion was an effective approach to manufacture high performance Mg-based biomaterials.