The role of rare earth elements in biodegradable metals: A review

Compared with non-degradable metals, biodegradable metals, as a new generation of medical metallic materials, do not require secondary, which reduces the pain and economic burden of patients. However, currently developed biodegradable metals, including iron-based alloys, magnesium-based alloys, and zinc-based alloys, have deficiencies in their corrosion rates and mechanical properties, which have severely restricted the clinical application of biodegradable metals. So there is an urgent need to improve their mechanical properties, degradation behaviors and biocompatibility. Alloying is an important way to modify biodegradable metal materials. Rare earth elements (REEs) as alloying elements in biodegradable metals have attracted a great deal of attention due to their unique atomic structure and properties. The present review summarizes the effects of rare earth elements on the mechanical properties, degradation behaviors, and biocompatibility of biodegradable metals. Moreover, future research directions of rare earth elements alloying biodegradable metals are also prospected. STATEMENT OF SIGNIFICANCE: As a new generation of biomedical metallic materials, biodegradable metals have become a hot research topic in recent years as they can degrade completely in human body and thus avoid further secondary surgery. However, these biodegradable metal systems have drawbacks in clinical applications. Alloying is an important method to improve the properties of biodegradable metals. Among the various alloying elements, Rare Earth alloying elements are usually considered due to their unique atomic structure and properties. The present review summarizes the recent research progress of Rare Earth alloying elements in biodegradable metals. The effects of the Rare Earth alloying elements on mechanical properties, biodegradation behavior and biocompatibility of biodegradable metals are presented and discussed in detail.