Fabrication of biodegradable HA/Mg-Zn-Ca composites and the impact of heterogeneous microstructure on mechanical properties, in vitro degradation and cytocompatibility

Due to their desirable elastic modulus and density that are similar to natural bone, non-toxic element containing magnesium alloys are regarded as promising bio-degradable materials. A biodegradable HA-particle-reinforced magnesium-matrix composite Mg-3Zn-0.2Ca-1HA (wt%)was fabricated for biomedical application by a combination of high shear solidification (HSS)and hot extrusion technology. The microstructure, mechanical properties, corrosion resistance and cell biocompatibility of the composite were subsequently investigated. In comparison with the matrix alloy, the as-cast Mg-3Zn-0.2Ca-1HA composite obtained by HSS technology exhibited a uniform and fine grained structure, further refined after a hot extrusion ratio of 36:1. The yield strength (0.2%YS), ultimate tensile strength and elongation of the extruded composite were 322 MPa, 341 MPa and 7.6%, respectively. The corrosion rate of the as-extruded Mg-3Zn-0.2Ca-1HA composite was measured to be 1.52 mm/y. Electrochemical and immersion tests showed that the corrosion resistance of the composite is slightly improved comparing to that of the matrix alloy.