Biomedical magnesium (Mg) alloys have garnered significant attention because of their unique biodegradability, favorable biocompatibility, and suitable mechanical properties. The incorporation of rare earth (RE) elements, with their distinct physical and chemical properties, has greatly contributed to enhancing the mechanical performance, degradation behavior, and biological performance of biomedical Mg alloys. Currently, a series of RE-Mg alloys are being designed and investigated for orthopedic implants and cardiovascular stents, achieving substantial and encouraging research progress. In this work, a comprehensive summary of the state-of-the-art in biomedical RE-Mg alloys is provided. The physiological effects and design standards of RE elements in biomedical Mg alloys are discussed. Particularly, the degradation behavior and mechanical properties, including their underlying action are studied in-depth. Furthermore, the preparation techniques and current application status of RE-Mg alloys are reviewed. Finally, we address the ongoing challenges and propose future prospects to guide the development of high-performance biomedical Mg-RE alloys.

Magnesium (Mg) alloys are considered to be a new generation of revolutionary medical metals. Laser-beam powder bed fusion (PBF-LB) is suitable for fabricating metal implants with personalized and complicated structures. However, the as-built part usually exhibits undesirable microstructure and unsatisfactory performance. In this work, WE43 parts were firstly fabricated by PBF-LB and then subjected to heat treatment. Although a high densification rate of 99.91% was achieved using suitable processes, the as-built parts exhibited anisotropic and layered microstructure with heterogeneously precipitated Nd-rich intermetallic. After heat treatment, fine and nano-scaled Mg₂₄Y₅ particles were precipitated. Meanwhile, the α-Mg grains underwent recrystallization and turned coarsened slightly, which effectively weakened the texture intensity and reduced the anisotropy. As a consequence, the yield strength and ultimate tensile strength were significantly improved to (250.2 ± 3.5) MPa and (312 ± 3.7) MPa, respectively, while the elongation was still maintained at a high level of 15.2%. Furthermore, the homogenized microstructure reduced the tendency of localized corrosion and favored the development of uniform passivation film. Thus, the degradation rate of WE43 parts was decreased by an order of magnitude. Besides, in-vitro cell experiments proved their favorable biocompatibility.