Effect of alloying elements on the characteristics of metallic biodegradable materials: A review

Biomedical applications necessitate natural or synthetic biomaterials that can maintain, improve, or even replace damaged tissue or a biological function, facilitating healing for people who have suffered from an injury or disease. Metallic biomaterials show superior mechanical properties with greater service life than other materials. Biodegradable materials can avoid the inevitable second operation of removing the implant in the case of temporary implantation, reducing the risk of infections, medical complications, healing time, and cost. Magnesium (Mg), zinc (Zn), iron (Fe), and their alloys are potential biodegradable metallic materials. The characteristics of biodegradable metallic materials are variable and depend on many factors, such as alloying elements, microstructure, existing phases, and thermomechanical treatment. The current review emphasizes the impact of alloying element addition on the characteristics of metallic biodegradable materials, with particular attention to the relationships between alloying elements, microstructure, mechanical performance, corrosion, and biocompatibility. Mg alloys show good mechanical and corrosion properties with excellent biocompatibility. Using biocompatible alloying elements can improve Mg alloy mechanical and corrosion properties without affecting their biocompatibility. However, critical limitations are still maintained, like rapid degradation and gas bubble formation. Zn alloys could overcome the limitations of Mg alloys with appropriate degradation rates, ease of casting and processing, and good biocompatibility. Alloying, particularly with Mg, Li, and Cu, combined with thermomechanical treatment, can significantly affect the microstructure and mechanical performance of Zn alloys and overcome the problem of unsuitable mechanical properties. Fe alloys have excellent mechanical performance, formability, and biocompatibility with a low degradation rate. Applying surface treatment, using novel structures, alloying with the appropriate amount of alloying elements, and using advanced manufacturing techniques may present a way to solve the problems associated with biodegradable metallic materials, which could open new horizons and increase their applicability in biomedical applications.