Nano cerium oxide addition enhancing the degradation resistance of biomedical Mg alloy produced by selective laser melting

Magnesium (Mg) alloys are one of the promising bone implant materials on account of their excellent biocompatibilities, suitable mechanical properties and a distinctive degradability. However, their clinical application is hindered by their too rapid degradation rate under physiological conditions. In this study, nano cerium oxide (CeO2) was incorporated into AZ61 (Mg-6Al-1Zn, wt.%) via selective laser melting to improve the degradation behavior. The results indicated that the degradation rate of AZ61 was slowed down by about 64%, with CeO2 containing up to 2 wt %. This was mainly attributed to: 1) in the selective laser melting process of AZ61-CeO2, a part of CeO2 was reduced to cerium (Ce), and Ce reacted with aluminum (Al) in AZ61 to form acicular Al4Ce phase and hinder island Mg17Al12 phase precipitation, which caused the reduction of galvanic corrosion; 2) the other part of CeO2 was uniformly dispersed in the Mg matrix. It could enter the degradation product film as the matrix degraded, which was conducive to increasing the relative density and positive charge quantity of the degradation product film, then improving the degradation product film resistance against corrosive solution penetration. Meanwhile, the compression strength of AZ61-CeO2 increased with increasing CeO2 content and reached the maximum value of 241 +/- 12.0 MPa when CeO2 content was 2 wt%, which was principally put down to the refined crystalline strengthening and nano CeO2 dispersion strengthening. In addition, the results of cytocompatibility assessment showed that the AZ61-2CeO2 exhibited the best cytocompatibility. These results showed that the AZ61-2CeO2 produced by selective laser melting was a promising bone implant biomaterial.