LAUSR

Abstract The application of Mg–6Al–1Zn (wt.%, AZ61) alloy as biodegradable bone implant material is limited due to its too rapid degradation, which is largely related to the microgalvanic corrosion induced by the coarse island second phase in the alloy. In this study, cerium (Ce) was alloyed in AZ61 alloy by selective laser melting, aiming to enhance its degradation resistance. The microstructure characteristics were investigated by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The degradation behavior was studied by the electrochemical test and weight loss test. Besides, the mechanical properties and cytocompatibility of the alloy were also assessed. The results showed that Al preferentially reacted with Ce in the AZ61-Ce alloy because of the high electronegativity difference between Al and Ce and formed acicular Al4Ce phase due to the oriented crystal growth. Meanwhile, the consumption of Al in forming Al4Ce phase inevitably reduced the precipitation of island Mg17Al12 phase. Compared with island Mg17Al12 phase, the acicular Al4Ce phase possessed much larger ratio of length to the cross-sectional area, leading to a higher electrical resistance. As a consequence, the island-to-acicular alteration of second phase greatly decreased the corrosion current density, thereby enhancing the degradation resistance by about 7 times. In addition, the AZ61-Ce alloy presented improved compressive strength owing to the strengthening effect of the acicular second phase, as well as favorable biocompatibility. The island-to-acicular alteration of second phase may provide a method for the development of high performance biomedical Mg alloys.