Review of degradation behaviour biodegradable magnesium MgZnCa alloys

Metals such as stainless steel and titanium have long been used in orthopedics due to their strength and wear resistance. However, magnesium-based alloys, with mechanical properties closer to those of bone, are gaining increasing attention for biomedical applications. Magnesium implants are biodegradable, lightweight and offer advantages such as reduced stress shielding and the elimination of secondary surgery. Despite the above-mentioned advantages, Mg-based biomaterials have poor corrosion resistance in physiological environments. This study focuses on biodegradable Mg-Zn-Ca alloys, which are characterized by high biocompatibility and satisfactory mechanical properties. The degradation process is influenced by various factors such as the qualitative and quantitative composition, heat treatment method, microstructure, grain size, phase presence, and other parameters. Alloying with elements such as Zn and Ca helps improve the mechanical and corrosion properties; however, it should be noted that at certain concentrations can reduce ductility and accelerate degradation. The corrosion process results in the formation of magnesium hydroxide, magnesium chloride, hydrogen gas, and other compound groups. Although the presence of hydroxyl, calcium, and phosphate ions can promote the formation of protective layers that slow down corrosion, the formation of magnesium chloride further accelerates the degradation process. The article discusses the degradation process of magnesium alloys, emphasizing the importance of optimizing their chemical composition and the choice of heat treatment method, as well as the influence of these factors on microstructural and phase characteristics.