Bone fractures and critical-size bone defects are significant public health issues, and clinical treatment outcomes are closely related to the intrinsic properties of the utilized implant materials. Zinc (Zn)-based biodegradable metals (BMs) have emerged as promising bioactive materials because of their exceptional biocompatibility, appropriate mechanical properties, and controllable biodegradation. This review summarizes the state of the art in terms of Zn-based metals for bone repair and regeneration, focusing on bridging the gap between biological mechanism and required bioactivity. The molecular mechanism underlying the release of Zn ions from Zn-based BMs in the improvement of bone repair and regeneration is elucidated. By integrating clinical considerations and the specific bioactivity required for implant materials, this review summarizes the current research status of Zn-based internal fixation materials for promoting fracture healing, Zn-based scaffolds for regenerating critical-size bone defects, and Zn-based barrier membranes for reconstituting alveolar bone defects. Considering the significant progress made in the research on Zn-based BMs for potential clinical applications, the challenges and promising research directions are proposed and discussed.

As for metal matrix composites (MMCs), the selection and application of reinforcements play a vital role in their comprehensive properties. In this work, the CrCoNi medium entropy alloy (MEA) was selected as reinforcement for Al matrix composites, and the effects of the content of the CrCoNi MEA on the mechanical properties and friction resistance were systematically investigated. It was found that the CrCoNi MEA can effectively improve the mechanical properties of the Al matrix composites, especially the 5 wt.% CrCoNi/Al composite can achieve a high strength without the sacrifice of ductility, due to the strengthened interfacial bonding between the Al matrix and the CrCoNi reinforcements caused by the element interdiffusion and the high mechanical performance of the CrCoNi MEA itself. In addition, the wear resistance of the composites can be enhanced by the inclusion of the CrCoNi MEA reinforcement, because the CrCoNi MEA can substantially improve the hardness of the composites and promote the formation of the oxidative protection film during the friction process. This work paves a new route for preparing Al matrix composites with high mechanical properties and friction resistance.