The Study On The Biodegradable Mg-Zn-Zr Alloys Used For Bone Fixation

Magnesium (Mg) alloys provide potential advantages for use as degradable implants in orthopedic applications due to the good mechanical properties, biocompatibility and degradability. However, the corrosion resistance of commercial Mg alloys should be improved before it can be employed as bone fixation materials.In this work, we fabricated the Mg-2.5wt%Zn and Mg-xwt%Zn-0.5wt%Zr alloys (x=2.5, 3.5, 4.5). The effects of alloying elements Zr and Zn on the mechanical properties and corrosion behavior of Mg-Zn-Zr alloys were investigated. Thereafter, we also studied the influence of surface treatment and addingβ-TCP particles on the Mg-2.5wt%Zn-0.5wt%Zr alloy. The results are listed as follows:1. The addition of Zr could significantly refine the grains of Mg-Zn alloy and improve its mechanical properties and corrosion resistance markedly.2. The tensile strength and hardness of Mg-xwt%Zn-0.5wt%Zr alloys (x=2.5, 3.5, 4.5) were improved with the increase of Zn content, but the elongation and corrosion resistance would decrease. The ultimate tensile strength (UTS) and elongation of Mg-2.5wt%Zn-0.5wt%Zr alloy are 305 MPa and 21.0% respectively. And its corrosion current density was caculated to be 2.10μA/cm~2, which is lower than other Mg-Zn-Zr alloys in the study.3. The MgF2 conversion coating of 0.5μm and theβ-TCP coating of 5μm were respectively synthesized on the surface of Mg-Zn-Zr alloy. The corrosion resistance of Mg alloy was markedly improved with the protective coating.4. 1wt%β-TCP particles adding into Mg-2.5wt%Zn-0.5wt%Zr alloy evenly distributed in the substrate. The mechanical and corrosive properties were improved by refining the grains of Mg alloy.