The effects of solution treatment on the corrosion resistance and cytocompatibility of micro-arc oxidation (MAO) coating on biodegradable Mg-2Zn-1Gd-0.5Zr alloy were studied in this work. Microstructural characterization, coating adhesion, electrochemical, immersion and cytocompatibility tests were carried out. The results demonstrated that the MAO coating was much more uniform after solution treatment with coating adhesion enhanced by about 30% compared with the as-extruded + MAO coated. Moreover, the corrosion resistance of the solution treated + MAO coated samples was respectively improved by more than 20% and twice, compared with as-extruded + MAO coated and as-extruded samples. In addition, solution treatment further improved the cell viability of the MAO coating of the alloy with the RGR exceeding 90% during the entire culture period with MG63 cells. Consequently, solution treatment is recommended as a preferred pretreatment for improving the corrosion resistance and cytocompatibity of MAO-coated Mg alloys.

Severe plastic deformation such as equal channel angular pressing (ECAP) could change the mechanical and corrosion resistance of Mg alloys. The effects of ECAP extrusion on the mechanical and biodegradable properties of an extruded Mg-1.5Zn-0.5Y-0.5Zr alloy were studied in this work. After two passes and four passes ECAP extrusion, the microstructure, mechanical properties and degradation behaviours were investigated. It showed that with increase of the extrusion pass, the average grain size of the alloy decreased greatly. After four passes extrusion, the grain size was about 1.37 +/- 0.22 mu m. The ECAP extrusion was beneficial to the ductility of the alloy. With increase of the extrusion pass, the elongation increased from 17% to 27%. However, the ultra-fine grains formation was detrimental to corrosion resistance. For the corrosion rate, compared with the without ECAP extruded samples, the corrosion resistance of the ECAP extruded samples obviously decreased.