Improving corrosion resistance and biocompatibility of AZ31 magnesium alloy by ultrasonic cold forging and micro-arc oxidation.

Corrosion resistant and biocompatible AZ31 magnesium alloy surfaces were successfully prepared by ultrasonic cold forging and subsequent micro-arc oxidation. The properties of these ultrasonic cold forging pretreated (UCFT)AZ31 magnesium alloy surfaces containing Sr-Ca-P micro-arc oxide coating (MAO/UCFT/AZ31) were studied. Results showed that surface grain refinement of AZ31 Mg alloy in the depth of 400 μm owing to the ultrasonic cold forging pretreatment was verified, and which provides more discharge channels for subsequent micro-arc oxidation. Comparing with the AZ31 magnesium alloy (AZ31) and ultrasonic cold forging technology treated AZ31 magnesium alloy samples (UCFT/AZ31), the corrosion resistance of MAO/UCFT/AZ31 significantly improved, which is also supported by the immersion experiments and electrochemical tests in simulated body fluid. Meanwhile, the MAO/UCFT/AZ31 samples also had excellent cytocompatibility as well as MAO/AZ31 samples. These results may beneficial to the developing of biodegradable medical materials in future.